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THE 


CYCLOPADIA 


ANATOMY anv PHYSIOLOGY. 


VOL. III. 


eg a LONDON: e- 
ae ae ; " 
é x ~~ 


* 


n . - 


THE 


CYCLOPADIA 


ANATOMY ann PHYSIOLOGY. 


EDITED BY 


ROBERT B. TODD, M.D. F.RS. 


FELLOW OF THE ROYAL COLLEGE OF PHYSICIANS; 
PHYSICIAN TO KING’S COLLEGE HOSPITAL; AND 


PROFESSOR OF PHYSIOLOGY AND OF GENERAL AND MORBID ANATOMY IN KING’S COLLEGE, 


LONDON, ETC. ETC. 


LONDON: 
SHERWOOD, GILBERT, AND PIPER, 


PATERNOSTER- ROW. 


1847, 


ROBERT ADAMS, Ese. 
Surgeon to the Richmond Hospital, and Lecturer on 
Anatomy and Surgery, Dublin. 
. ALCOCK, M.B. Dublin. 
W.P. ALISON, M.D. F.R.S.E. 
Prof, of the Pract. of Med. in the Univ. of Edin. &c. 
_ JOHN ANDERSON, Esq. M.E.S. Richmond. 
J. APJOHN, M.D. M.R.1.A. 
Prof, of Chem. to the Royal Coll. of Surgeons, Ireland. 
“VICTOR AUDOUIN, M.D. Paris. 
Professeur-Administrateur au Musee d’ Histoire Naturelle. 
B. G. BABINGTON, M.D. F.R.S. 
Physician to Guy’s Hospital. 
THOMAS BELL, F.R.S. 
_ Professor of Zoology in King’s College, London. 
HARLES BENSON, M.D. M.R.1.A. 
_ Prof. of Med. to the Royal Col.of Surgeons, Ireland. 
_ J. BISHOP, F-R.S. London. 
JOHN BOSTOCK, M.D. V.P.R.S. London. 
_ W. BOWMAN, F.R.S. 
4 ‘ % Assistant-Surgeon to the King’s College Hospital and 


e Royal Ophthalmic Hospital, Moorfields, and De- 
onstrator of Anatomy, King’s College, London. 


J. E. BOWMAN, Esa. 
____ Demonstrator of Chemistry in King’s College, London. 
_ W.T. BRANDE, F.R.S. 
Professor of Chemistry to the Royal Institution, &c. 
J.E. BRENAN, M.D. 
_ G.BRESCHET, M.D. 
___ Surgeon to the Hotel-Dieu, Paris. 
W. BRINTON, Esa. 
_ Demonstrator of Anatomy in King’s College, London. 
_W. B. CARPENTER, M.D. F.R:S. 
p Lect. on Physiology at the London Hospital, &c. 
_ JOHN COLDSTREAM, M.D. Leith. 
___ Memb. of theWernerian Nat. Hist. Soc. of Edinb. &c. 
DAVID CRAIGIE, M.D. F.R.S.E. 
____ Fellow of the RoyalCollege of Physicians,Edinburgh, &c. 
‘T. BLIZARD CURLING, Esq. 
____ Lect, on Surg. and Assist. Surg. to the Lond. Hospital, 
_G.P. DESHAYES, M.D. Paris. 
A.T.S. DODD, Eso. 
_ HB. DUTROCHET, M.D. 
_W.F.EDWARDS, M.D. F.RS. 
_H. MILNE EDWARDS, M.D. 


Prof. of Nat. History to the College of Henry 1V., and 
_ tothe Central School of Arts and iniaiectaten, Paris. 


ARTHUR FARRE, M.D. F.R.S. 

___ Professor of Midwifery in King’s College and Physician 

Accoucheur to King’s College Hospital. 

R. D. GRAINGER, F.R.S. 

Lect, on Anat. and Phys. at St. Thomas’s Hospital. 

RR. E. GRANT, M.D. F.R.S. L.& E. 

___ Fell. of the Roy. Coll. of Physicians, Edinb. and Prof. of 

__ Comp. Anatomy and Zoology in Univ. College, &c. &c. 
'.A. GUY, M.D. : 

_ Prof. For. Med. King’s College, London, and Physician 

King’s College Hospital. 

HALL, M.D. F.R.S. L. & E. London. 

RY HANCOCK, Esa. 


Lect. on Anat. and Physiology at, and Surgeon to the 
haring-Cross Hospital. " 
ROBERT HARRISON, M.D. M.R.1.A. 
___ Prof. of Anat. and Surg. in the Univ. of Dublin. 
JOHN HART, M.D. M.R.1.A. 
Prof. of Anat. in the Royal Coll. of Surg. Dublin, 
2 * HIGGINSON, Esa. Liverpool. 
A BoUR JACOB, M.D. M.R.I.A. 
essor of Anatomy and Physiol to the Royal 
College of Surgeons in fretana. «iNeed a 
GEORGE JOHNSON, M.D. 
Assistant Physician to King’s College Hospital, and 
resident Medical Tutor in King’s College, London. . 


_ T.RYMER JONES, F.RS. 


Prof. of Comp. Anat.,in King’s College, London, 


CONTRIBUTORS. 


T. WHARTON JONES, F.R.S. London. 
T. WILKINSON KING, Esa. 
SAMUEL LANE, Esa. 

Lecturer on Anatomy, St. George’s Hospital, London. 
F.T. MACDOUGALL, Esa. 
JOHN MALYN, Esq. 
C. MATTEUCCI. 

Professor of Physics in the University of Pisa. 
ROBERT MAYNE, M.D. 

Lect. on Anat, & Phys. Richmond Hospital, Dublin. 
W.A. MILLER, M.D. F.R:S. 


Professor of Chemistry in King’s College, London. 


W. F. MONTGOMERY, M.D. M.R.I.A. 


Fellow of and Professor of Midwifery to the King 
and Queen’s College of Physiciansin Ireland. 


GEORGE NEWPORT, F.R.S. 
Vice-Pres. of the Entomological Society of London. 


R. OWEN, F.R.S. F.GS. 


Hunterian Professor of Comparative Anatomy and 
Physiology to the Royal College of Surgeons in London, 


JAMES PAGET, Ese. 
Lect. on Anat. & Phys. St. Bartholomew’s Hospital. 
RICHARD PARTRIDGE, F.R:S. 
Prof.of Descrip. and Surg. Anat. in King’s Coll.Lond. 
BENJAMIN PHILLIPS, F.R.S. London. 
Surgeon to the Westminster Hospital. 
SIMON ROOD PITTARD, Esq. London. 
W.H. PORTER, Esa. 
Prof. of Surgery to the Royal Coll. of Surg. in Ireland. 
J.C. PRICHARD, M.D. F.RS. 


Corresponding Member of the Institute of France, 
Member of the Royal Academy of Medicine of Paris. 


G. O. REES, M.D. F.R.S. 
Assistant Physician to Guy’s Hospital. 
J. REID, M.D 


Prof. of Medicine in the University of St. Andrews. 
EDWARD RIGBY, M.D. F.LS.. 

Lect. on Midwifery at St. Bartholomew’s Hospital. 
J. FORBES ROYLE, M.D. F.RS. F.G:S. 

Professor of Materia Medicain King’s College, Lundon. 

HENRY SEARLE, Ese. London. 
W. SHARPEY, M.D. F.R.S. . 

Prof, of Anat. and Physiol. in Univ, Coll. London. 
JOHN SIMON, F.R.S. 

Lecturer on Pathology, St. Thomas’s Hospital. 


J. Y: SIMPSON, M.D. 


Fellow of the Royal College of Physicians, and Pro- 
fessor of Midwifery in the University of Ediuburgh. 


SAMUEL SOLLY, F.R.S. 


Assistant Surgeon to St. Thomas’s' Hospital. 
GABRIEL STOKES, M.D. 
J. A. SYMONDS, M.D. 


Physician to the Bristol General Hospital, and Lectu- 
rer on the Theory and Practice of Medicine at the 
Bristol Medical School. 


ALLEN THOMSON, M.D. 


Fellow of the Royal College of Surgeons, and Professor 
of the Institutes of Medicine in the University of 
Edinburgh. 


JOHN TOMES, Esa. 


Surgeon- Dentist to the Middlesex Hospital. 


WM. TREW, Eso. 
W. VROLIK, 


Prof. Anat. and Phys. at the Atheneum of Amsterdam. 


RUDOLPH WAGNER, M.D. 
Prof.of Med.& of Comp. Anat.in theRoy.Uni.Erlangen. 


W.H. WALSHE, M.D. 


Physician to University College Hospital. 


R. WILLIS, M.D. 
W. J. ERASMUS WILSON, F.RS. 


Consulting Surgeon to the St. Pancras Infirmary. 


2 iihe AL 


sae | 


“? 


—— 
fd 


=o, 


p 


CONTENTS 


OF THE THIRD 


VOLUME. 


Instinct .........+.- Dr. Alison 


” Irritability .......... Dr. Marshall Hall 


A. Higginson, Esq. 
Anatomy ........ s : 


Knee-Joint, Abnormal 
Anatomy of the .. 
Lacrymal Organs .... T. W. Jones, Esq. 


| Larynx, Normal Ana- J. Bishop, Esq... 


_ Knee-Joint, ce} 


R. Adams, Esq... 


tomy eseeeeeeeeaeeee 
Larynx, Abnormal 


Anatomy eseceses W. H. Porter, Esq. 


Leg, Regions of...... A.T.S. Dodd; Esq. 


: 


I 


_ Lymphatic 


ale Po 


a 


# 
G 
} 


Leg, Muscles of .... A.T.S. Dodd, Esq. 
Life ...cceeeceeeeee+ Dr. Carpenter... 
Liver .......0...2.. E. Wilson, Esq... 
Luminousness, Animal Dr. Coldstream .. 
Lymphatic & Lacteal } S. Lane, Eaq..-.. 

BR SYSCEM 2..cccccce 
System, i pr. Medic ckevcus 

Abnormal Anatomy 
_ Mammalia .......... Professor Owen .. 
_ Mammary Glands.... S. Solly, Esq..... 
-Marsupialia ........ Professor Owen .. 
' Membrane .......... Dr. Todd........ 
"Meninges .......... Dr. Todd.....++ 
_Microscope.......... Dr. Carpenter.... 
MT cecescsccccess Dr. G.O. Rees .. 
Mollusca............ Professor Owen .. 
Monotremata ........ Professor Owen .. 
Motion, Animal, in- bu. Bishop, Esq... 

___ cluding Locomotion 
MUMEMICUS sc ccsccccceee. Dr. G. O. Rees .. 
_ Mucous Membrane .. W. Bowman, Esq. 
Muscle ............ W. Bowman, Esq. 
_ Muscular Motion .... W. Bowman, Esq. 


Page 
1 
29 


44 


48 


126 
137 
141 
160 
197 


205 


232 


234 
245 
257 
331 
331 
331 
358 
363 
366 


407 


481 
484 
506 
519 


Page 


Muscular System, Professor R. Jones... 530 


Comp. Anatomy 
Myriapoda .......- 
Neck, Muscles and 


Professor R. Jones.. 545 


Je Si E. . eeee 561 
Regions of the.. ; beac Bama: 


Nervous System... Dr. Todd.....+--«+ 585 
Nerve wecccccccces Dr. Todd..ccccrece 591 
se ag respi a. Anderson, Esq... 601 
Nervous Centres, 2 
Normal Anatomy $§ 
Nervous Centres, } 
Abnormal Anat. 
Nervous System, 
Physiology of the 
Ninth Pair of Nerves G. Stokes, Esq..... 721 
Nose .eccccses--» Je Paget, Esq. ...- 723 
Nutrition......... . Dr. Carpenter...... 741 
Csophagus........ Dr. G. Johnson .... 758 
Optic Nerves ...... Dr. Mayne ........ 762 
Orbit: 6... escecece Dr. G. Johnson <... 782 
Organic Analysis .. Dr. Miller ........ 792 
Osseous System, t Professor R. Jones.. 820 
Comp. Anatomy 
Osseous Tissue .... J. Tomes, Esq. .... 
Pachydermata .... Professor R. Jones.. 
Pacinian Bodies .. W. Bowman, Esq... 
Par Vagam.,. ..06.+ Droid. Reids. css oe 
Parotid Region .... Dr. G. Johnson .... 
Parturition........ Dr. Rigby ........ 
Penis cccescciaces- E. Wilson, Esq..... 
Perineum ........ Dr. Mayne ........ 
Peritoneum ..... . S. R. Pittard, Esq... 
Pharynx ...ccocsos. We Trew, Esq. ..0 
Pisces... 0. eeraces Professor R. Jones.. 


Dr. VOEE Sicéciaede 626 
Dr. Todds..... cose 712 


tr. Todd. .se.+++++720G 


847 
858 
876 
881 
902 
904 
909 
919 
935 
945 
955 


708, ey Bie ce read “ exist.” ate per : 
711, col. 1 59 “ optic thalami read “ hemispheres. Por 
712, col. 2) Whe 40, Se Sees” cond “Steinruch.” Cy . bs 
line 41, for “Hermann, Nasse,” read “ Nasse.” 
At page 902, see a list 0 Errata in the article Pan Vacum. “(+ orate 


ee ~agcdhaiade 


THE 


CYCLOPADIA. 


OF 


ANATOMY AND PHYSIOLOGY. 


Pi INSTINCT.—This word is often applied to 
~ the mental acts of the lower animals, as if it 
"were truly applicable to the whole of these 
acts 5 but a little consideration will shew, 
; t, that this word, in its more approved and 
t acceptation, is applicable only to a 
art of the mental operations, which may be 
ferred from the observation of the actions and 
habits of animals; and secondly, that in this 
‘Testricted sense, the term is applicable to a 
part of the operations of the human mind itself; 
and that the subject of instinct cannot be tho- 
‘roughly understood, unless information regard- 
ay it is sought in the consciousness of our 
Own minds, as well as in the observation of 
_ Other living beings. The study of this subject 
‘is therefore equally important as a part of 
“natural history, of mental philosophy, and of 
physiology ; and is a good illustration 
the necessity of this latter science being 
ased on the observation and generalization of 
the laws and conditions of vital action through- 
ut the whole extent of the animal creation. 
It is obvious, indeed, that various mental 
acts, of which we are conscious in ourselves, 
nay be inferred, with perfect confidence, to 
take place throughout the whole range of the 
imal kingdom, and even that some of them 
be performed with greater energy and 
sion in some of the lower tribes than in 
a. The different external senses attain their 
highest perfection in different animals ; that of 
‘smell, for example, probably in the predaceous 
immialia, that of touch in the antenne of 
, and that of sight in the predaceous 
‘birds ; it is not likely that any one is enjoyed 
in its highest perfection by man; and what 
have been accurately distinguished from mere 


; a Ill. 


sensations as the perceptions of external things, 
i.e. the notions as to the qualities of these, 
which naturally present themselves to our minds 
in consequence of sensations being felt, would 
seem in various instances to follow the sensa- 
tions more quickly and more surely in other 
animals than in us; for it is generally allowed 
that what appear to be acquired perceptions of 
the eye to us, i.e. the notions of the distance, 
size, and form of visible objects, are instanta- 
neously made known to many of the lower 
animals the very first time that those objects 
make impressions on their retine; the faculty 
of Intuition, which we must admit as part of 
the source of our own knowledge, appears to 
exist in greater perfection in other animals, and 
the notions of external things which they thus 
acquire are amply sufficient to regulate their 
muscular motions. 

It is equally plain that many of the strictly 
mental acts, of which our complex trains of 
thought are composed, are habitually performed 
by animals ; that they have a perfect recollec- 
tion of past sensations, implying the exercise of 
the powers of memory and of conception ; that 
the emotions of fear, of joy, of affection, of 
anger, even of jealousy, are as distinctly indi- 
cated by their actions as by those of man; that 
under the influence of these emotions their 
mental operations are excited or depressed, and 
their attention fixed or distracted, and their 
volition excited, as in our own case ; and that 
their actions are habitually guided by a clear 
perception, or rather, we should say, by conti- 
nual correct applications, of a first principle 
of belief, which is generally admitted to 
be an ultimate fact in the constitution of the 
human mind, and onwhich much stress has been 

B 


2 INSTINCT. 


laid by our ablest metaphysicians, “ the belief 
of the permanence of the order of nature,” or 
the conviction, “ that what has been as an an- 
tecedent, will be followed by what has been as 
a consequent ;” otherwise the lessons of expe- 
rience would be lost upon them, and no change 
could be effected in their habits by education. 
Under the influence of this mental law, it is 
certain that their recollections of past sensations 
excite in them various desires, and afford mo- 
_ tives to action, which prompt many of their 

movements exactly on the same principle by 
which the greater number of what are strictly 
called voluntary human actions are determined ; 
the object in view, in both cases, being simply 
to procure known pleasure or to avoid known 
pain, and the same metaphysical question pre- 
senting itself to the speculative inquirer as to 
both, viz. the question whether the voluntary 
power is really to will what we please, or is 
only to do what we will. Further, the various 
muscular movements required for any such 
actions, and the sensations and emotions which 
excite them, are gradually linked together by 
the mental principle of the association of ideas, 
so as to become obedient to the law of Habit in 
animals equally as in man. 

It has been generally admitted, since the 
time of Locke, that the essential inferiority of 
the intellect of animals, as com with that 
of man, lies in their very limited enjoyment of 
the faculty of abstraction, by which the mind 
is enabled to single out the different qualities 
or relations of the individual objects of sense, 
and make them the subject of abstract thought, 
and thereby form general notions, which are at 
once perceived to be equally applicable to 
many individual cases; and by help of which 
it continually elevates itself above the contem- 
plation of individuals, and classifies and me- 
thodizes its knowledge, and fits it for useful 
application,—for the deduction of inferences in 
reasoning, for the formation of fancied scenes 
in works of imagination, and for the adapta- 
tion of means to ends in practice. 

It is obvious, also, that none of those still. 
more general or abstract notions which conti-~ 
nually suggest themselves to the human mind 
in the course of the operations that are excited 
by the senses, such, for example, as space, time, 
number, power, &c. are indicated by any mani- 
festations that we see of the mental acts of the 
lower animals; and it may be stated, in general, 
that the limitation of their minds to particulars, 
and the want of the power of raising the 
thoughts to general ideas, and dwelling on the 
contemplation of these, is the grand obstacle to 
their adapting means to ends, drawing infe- 
rences from premises, or enjoying the use of 
language. The objections that have been started 
to this doctrine do not appear of much weight. 
Darwin, while he set aside the statement of 
Locke, endeavoured to distinguish instincts as 
* actions excited by sensations,” employed 
about the possession of pleasurable objects, or 
the avoiding of painful ones, already in our 
power, while voluntary (i.e. rational) actions 
are, employed “ about the means to acquire 
such objects.” But this distinction appears, 


on reflection, to be substantially the same. The — 
two noblest and most characteristic of the facul- — 
ties of the human mind, as defined by logi- 
cians, those of Reasoning and of Imagination, ~ 
(the latter of which is truly applicable to every 
kind of contrivance or adaptation of means to 
ends, of which we are capable,) evidently im- 
ply the existence of a mental power of forming 
and dwelling on general ideas, which are eq 
applicable to many individual cases; and if 
animals possessed this latter power, we might 
confidently expect to see them exhibit indica- 
tions of the two former. eae gs 
Why is it, for example, that Aptis 
who Gove been Fie St to assemble about the — 
fires which savages have made in the forests, — 
and been gratified by the warmth, have never 
been seen to gather sticks, and rekindle them 
when expiring? Not, certainly, because they 
are incapable of understanding that the fire — 
which warmed them formerly will do so again, 
but because they are incapable of a’ i 
and reflecting on that guality of wood, and that — 
relation of wood to fires already existing, which 
must be comprehended, in order that the action 
of renewing the fire may be suggested Fi 
is properly called an effort of Reason. Or why 
is it, that the different classes of predaceous — 
animals, although surrounded hy the materials — 
out of which the human race has manufactured 
so many implements of warfare, have never 
been able to avail themselves of any of them 
in aid of the instruments of destruction with 
which nature has agitate Arpeeatey 
because they are incapable of forming , 
general Bess i of the qualities and relations of 
external things, as are essential to the processes. 
of imagination and reasoning, by which men 
are led to the contrivance, and guided in the 
use, of artificial weapons. ee 
Again, although many of them are suscepti-. | 
ble of the emotions of joy, and to a certain 
degree of gratitude and attachment, founded 
on the sense and recollection of benefits, none — 
of them’ seem capable of forming the slightest — 
notion of that Divine Power, which has sug- 
gested itself to the human intellect in all ages, 
and even in the rudest conditions ha ‘| 
existence; we should regard any act of praise 
or prayer as an infallible indication of a mental 
capacity of the same rank as ourowM. 


Exceptions to this principle, to a certain ex. 


} 


f 


| 
a 
4 


| 


ia 


tent, must be admitted, as will eee 
pear, and the explanation of some of them 

certainly obscure; but the general fact un- 
doubtedly is, that those operations of the 
human intellect which imply the formation of 
general or abstract notions, or in the language: 
of Dr. Brown, the suggestion of relations, are. 
beyond the power of the lower animals. In- 
deed reflection on the nature of language, on: 
the small number of words (only substantive 
nouns, and only part of these) which apply to, 
individual objects, and on the necessity of the 
power of forming some kind of abstract or 
general notion, as indispensable to the use of 
every other kind of word, is sufficient to esta- 
blish, and is aig the simplest way of dis- 
tinctly conceiving, the essential difference be- 


___ tween the constitution of the mind of man and 
of that of the dumb animals. 

_. But it has nevertheless been long observed, 
_ that while animals are thus incapable of com- 

peepee the importance or devising means 
__ for the attainment of objects which we perceive 
to be within their reach, and clearly and imme- 
diately important to them, they habitually per- 
i form many actions which are admirably adapted 
_ to the attainment of certain ends, and these 
_ often remote and obscure, and known to us 
_ only by means of repeated observation and re- 
_ flection, and strictly inductive reasoning. No 
_ animals, for example, are capable of such ob- 
Servation and comprehension of the laws of 
_ fature, as to procure for themselves at pleasure 
artificial heat or regular and uniform supplies 
_ Of food; but many are seen to form nests or 
burrows, and lay up magazines of provisions, 
early in the autumn, which are to protect them 
+ omg cold and famine during the winter ; 


ow ile others, even while the temperature is still 
mild, undertake long and painful aerial voy- 
_ ages, whereby they escape from the rigours of 
‘a northern climate, and enjoy the warmth and 
abundance of the tropical regions. Such pro- 
olga for future contingencies are within the 
_ power of man, but in him they are clearly de- 
pendent on the power of forming and applying 
_ general notions ; and if the lower animals pos- 
_ Sessed that power, we can see nothing to hinder 
their enjoying the use of language, and might 
_ confidently expect to see many indications of 

varied contrivance for their own immediate 
convenience, which never present themselves 


sence of intelligence in the other actions of 
inimals, corresponding to that which ap- 
bears manifestly to regulate certain actions 
_ which accomplish certain definite purposes, is 
_ Our first reason for believing that, while nature 

-vouchsafed to man alone the enjoyment of 
vhat we call Reason,—the power of compre- 
ding her laws, and so adapting means to 
nds as to turn these laws to his own advan- 
age,—she has provided for the maintenance 
Mf other animals, not only by the circumstances 
m which she has placed them in the world, but 
0 by imparting to them, on certain occasions, 
peculiar mental impulse, urging them to the 

formance of certain actions which are useful 
D themselves or to their kind, but the use of 
hich they do not themselves perceive, and 
t performance of which is a necessary con- 
ence of their being placed in certain cir- 
mstances, and often, more particularly, of 
ir feeling certain sensations. And this is 
‘general notion which we attach to the term 
stinct. 


sition, not to the will, but to the reason of 
- The most correct expression of the 
ence between an action prompted by in- 
and one prompted by reason is, that 
the first case the will acts in obedience to 
impulse which is directly consequent on 
certain sensations or emotions, felt or re- 
Membered; in the last it acts in obedience 
to an impulse which results from acts of 


to any observer of their habits. The utter ab-. 


INSTINCT. 3 


reasoning and imagination. It is incorrect to 
say, that all the actions of animals differ from 
those of man in being performed without 
anticipation of their effects. Many of the 
most familiar actions of animals are guided by 
a perfectly correct anticipation of their conse- 
quences, (otherwise they would not be suscep- 
tible of training); but it is such an anticipation 
as implies the exercise only of the faculty of 
memory. The term Reason is properly applied 
to the anticipation of those consequences of 
actions, of which we can be informed only 
by processes of reasoning and imagination, im- 
plying the exercise of the faculty of abstraction, 
and the formation of general notions or ideas. 

In some instances, the instinctive impulse, 
consequent on a particular sensation or suc- 
cession of sensations being felt, acts im- 
mediately on certain nerves and muscles; and 
no experience is necessary, in order that the: 
action required, although a complex and dif- 
ficult one, may be performed with perfect pre- 
cision, as in the case of the winking of the eye, 
or shrinking of the arm from injury, or of 
suction and deglutition following certain im- 
pressions on the mouth and throat. These 
actions seem to be very nearly if uot precisely 
on the same footing as those which have been 
described by Whytt and others as the natural 
effects of sensation, and by Dr. Marshall Hall 
as indications of what he terms the reflex func- 
tion of the spinal cord,—such as the actions of 
breathing, coughing, sneezing, vomiting, &c. ; 
and in which the intervention of sensation, al- 
though strongly indicated, is not universally 
admitted. 

But in the greater number of cases, the in- 
Stinctive determination appears to act not di- 
rectly on the nerves and muscles, but on the 
train of mental changes which serves as the 
motive to the exertion of the will; it extends 
to a long succession of actions, performed by 
individuals or by societies, each of which takes 
place under the influence of a mental deter- 
mination of a permanent character, and is often 
effected by a succession of voluntary efforts, 
which may require some habit and experience 
in order that they may be performed with pre- 
cision. Thus many animals require some 
length of experience before they acquire the 
use of their limbs or of their wings; but 
having acquired that power, they are taught by 
instinct to use them for the purpose of flight 
immediately on feeling certain sensations and 
emotions. In all such cases the actions are 
strictly voluntary, although the will acts, as 
we believe, in obedience to instinct, not to 
reason; and this seems to be the proper view 
to be taken of such long-continued and ad- 
mirably combined actions as we see in the for- 
mation of the nests of birds, or of the houses of 
beavers, or in other instances to be afterwards 
mentioned. The sensations of these animals, 
at particular seasons, excite a variety of mental 
operations, but these operations are all con- 
trolled and directed by the desire or propensity 
to the performance of certain definite actions, 
whether by the individual alone or in concert 
with others. In the performance of these ae- 

B 2 


4 ; INSTINCT. 


tions, the sensations, the voluntary powers, the 
memory and instinct of the animals are all 
brought into play; but we have no reason to 
believe that, the animals performing them are 
on of anticipating their ultimate result. 

n all cases, those actions which are en- 
titled to the appellation of Instinctive are ge- 
nerally understood to be characterized by two 
marks, quite sufficient to distinguish them from 
the effects of voluntary power guided by rea- 
son: 1. That, although in many cases expe- 
rience is required to give the will command 
over the muscles concerned in them, yet the 
will, when under the influence of the instinc- 
tive determination, acts equally well the first 
time as the last; no experience or education is 
required, in order that the different voluntary 
efforts requisite for these actions may follow 
one another with unerring precision; and 2. 
That they are always performed by the same 
species of animal nearly, if not exactly, in the 
same manner; presenting no such variation of 
the means applied to the object in view, and 
admitting of no such improvements in the pro- 
gress of life or in the succession of ages, as 
we observe in the habits of individual men, or 
in the manners and customs of nations, adapted 
to the attainment of any particular ends by 
those voluntary efforts which are guided by 
Reason. “ The manufactures of animals,” says 
Dr. Reid, “ differ from those of men in many 
striking particulars. No animal of the species 
can claim the invention. No animal ever in- 
troduced any new improvement, or variation 
from the former practice. Every one has equal 
skill from the beginning, without teaching, 
without experience or habits. Every one has 
its art by a kind of inspiration, i. e. the ability 
and inclination of working in it without any 
knowledge of its principles.” A third distinc- 
tive mark, naturally resulting from the last, 
is at least equally characteristic, although much 
less generally observable,—that these instinc- 
tive actions are seen to be performed in cir- 
cumstances which reason informs us to be such 
as to render them nugatory for the ends which 
are usually accomplished by them, and for 
which they are obviously designed. The 
efforts made by migratory birds, even when 
confined, at their usual period of migration,— 
the mistake of the flesh-fly who deposits her 
eggs on the carrion-plant instead of a piece of 
meat,* or of the hen who sits on a pebble in- 
stead of an egg, or of the mule which remains 
immoveably fixed by terror instead of escaping 
from the flood which threatens to overwhelm it, 
(as exemplified in the inundation of the valley 
of Luisnes in Savoy in 1818,) or of the bee 
which gathers and stores up honey even in 
a climate where there is no winter,} are so 
many proofs, that an instinctive action is 

mpted by an impulse, which results merely 

m a particular sensation or emotion being 
felt, not by anticipation of the effect which the 
action will produce. 


* Kirby. 
t See Kirby enn sigs Introduction to Ento- 
mology, vol. ii. p, 469. 


But, in order to have demonstrative proof 
of the essential difference between instinct and 
reason, and of the correctness of the view 
which we take of the nature of that mental 
impulse which prompts what we call the in- — 
stinctive actions of animals, it is only neces- 
sary to reflect on what passes within ourselves 
on occasion of certain actions of the very” 
same class being performed by us. It is dif- 
ficult, indeed, in adult age, to distinguish — 
those actions which we perform instinctively — 
from those which we have learnt by 
efforts to perform habitually; bat in the case — 
of infants we see complex actions, useful or — 
necessary to the system, performed with per- — 
fect precision at a time when we are certain 
that the human intellect is quite incompetent 
to comprehend their importance or antici 
their effects yet we cannot doubt that it is by 
a mental impulse that they are excited, 
we perform the same actions in the same cir- 
cumstances in adult age, and are then con- — 
scious of the impulse which prompts them. — 
“ Tt is an instinct,” says Bichat, “ which I do 
not understand, and of which I cannot give 
the smallest account, which makes the i 
at the moment of birth, draw together its Pd 
to commence the action of sucking,” to be fo 
lowed by the still more complex act of deglu- 
tition. “ This cannot be wae to the mere 
novelty of the sensations which it experiences 
from snietial objects, for the general effect of 
such sensations is to determine various agita- 
tions or irregular movements indeed, but not 
an uniform movement, directed to a deter- 
minate end. If we examine different animals — 
at the moment of birth, we shall see that the — 
special instinct of each directs the execution — 
of peculiar movements. Young gee | 

of 
{ 


* 


' 


seek the mamme of their mothers, bi 
the order Gallinacee seize immediately the 
grain which is their appropriate nourishment, 
while the young of the Carnivorous birds 
merely open their mouths to receive the food 
which their parents bring to their nests. In 
general, it is very important to distinguish the 
irregular or varied movements which, at pe Tt 
moment of birth, are produced simply 
new sensations and excitements which the body — 
receives, from those definite actions which are 
the effect of instinct, a cause of which we can 
give no further explanation.” 

In fact, when we attend to the simple action 
of deglutition,* as performed in our mature | 
years, we may be conscious that it results from 
the same instinctive impulse which guided it 
with unerring precision in the new-born infant, 
long before the voluntary power of simply 
raising the hand to the mouth had been ac- 
quired. If we were to consult only the grati- 
fication of our sensations, we should Bae 
grateful food in the mouth; for when it is swe 
lowed the gratification immediately resulting 
from it is atan end, and there is no peculiar 
pleasure attached, in other circumstances, to 
the mere act of deglutition; but all we can 

* [I. e. that part of the act which is dependent 


on the voluntary movement of the — to pass 
on the food to the isthmus faucium.—ED.] 


i 


INSTINCT. 5. 


observe by attention to our own feelings on 
such occasions is, that while we feel the sen- 
_ sations of hunger and thirst, we feel also a pro- 
pensity, all but irresistible, to swallow what- 
ever grateful food or drink is in the mouth. 
This propensity is not only Ds to reason, 
but stronger than reason, and prompts us to 
action more surely and more energetically than 
the mere recollection of the effects previously 
resulting from food or drink taken into the sto- 
mach could have done. 

If we reflect further, we shall find that there 
are various other sensations, with which we 
_ €an feel, in our own persons, that an instinctive 
__ impulse is naturally linked. The term Appe- 
tite does not express the whole of these, 

although it is only by referring to the action 
_ which it uniformly prompts that an appetite 
___€an be distinguished from another sensation. 
__ Sympathetic movements, such as_ breathing, 
 coug ing, sneezing, vomiting, &c. are ascribed 
by Whytt and others to sensations ; and laugh- 
____ ter, weeping, the expression of feeling in the 
+ countenance and features, &c. are strictly refer- 
_ able to emotions of mind, and in the perform- 
ance of all these actions, a propensity which 
may be called strictly instinctive, because 
_ prior to experience, and independent of reason- 

_ ing, may be frequently and distinctly felt, and 
__is from the first equally effectual in exciting very 

_ complex muscular movements, as the impulse 
_ to swallow food in the mouth. We may 
_ Specify several other kinds or modes of action, 
_ which we are all conscious of frequently per- 
_ forming, and which we perform on many oc- 
_ €asions in obedience, not to any effort of 
reason, but to a truly instinctive impulse, natu- 
ally consequent on certain sensations or 
emotions, and felt even in adult age to be inde- 
pendent of, as they are in the infant prior to, 

__ any anticipation of remote consequences,—viz. 
1. those which are prompted by the instinct of 
____Self-preservation, (as the winking of the eye- 
lids when the eyes are threatened with injury, 
_ the shrinking of any limb or part of the body 
which is struck, the projection of the arms 
when we ate about to fall forwards on the 
face,* the act of crying ‘from pain or from 
fear) ; 2. those which are prompted by the 

_ Instinct of shame, as when the saliva escapes 

from the mouth, when the sphincters fail in 

_ their office, or the sense of modesty is out- 

_ faged; 3. those which are prompted by the 
instinct of imitation, existing more or less in 
the early stage of all human existence, and 
_ whereby we are all led to fashion our language, 
- Inanners, and habits, on the model of those 
_ around us, and particularly of those persons with 
_ whom we have either the most frequent inter- 
course, or the intercourse which is most fitted 
to make an impression on our minds; 4. those 
_ _ which are prompted by the emotions of affec- 


__*™ Let any one try the experiment of attempting 
: to fall forward on his face, with his arms extended 
at his sides, and he will be immediately conscious 
the instinctive impulse which urges him to 
throw forward his arms; and which he feels dis- 
tinetly and resists with difficulty, even when he 
knows that he is about to fall only on soft matter 
which cannot injure him. 


tion and pity, or still more decidedly by the 
impulse of maternal love, on witnessing the 
helpless condition of young infants.* We do 
not enter into details on these subjects at pre- 
sent, but merely mention them as examples, in 


‘which we may safely and legitimately avail 


ourselves of the evidence of consciousness to 
assure ourselves of the essential peculiarity, 
and of the paramount authority, of the in- 
stinctive impulse, as distinguished from the 
voluntary effort, which results from a train of 
reasoning. 

It has been often said that the nature of 
instinct is absolutely mysterious and inscru- 
table; but if what has now been stated be 
correct, this can be said of instinct only in the 
same sense in which it may be said of all 
mental acts without exception; the essence of 
mind, like that of matter, being wholly in- 
scrutable. The characters of the instinctive 
impulse may be distinguished as clearly as 
those of any other mental act, in the only 
way in which any such act can be distin- 
guished, viz. by attention to our own conscious- 
ness; although we never could have antici- 
pated d priori that this kind of mental impulse 
could have extended to so long continued and 
complex actions, and to the concerted ope- 
rations of so many individuals, as the operations 
of some animals indicate. 

Having satisfied ourselves of the existence 
of certain instinctive impulses, both in the 
lower animals and in ourselves, essentially dis- 
tinct from those voluntary efforts which are 
guided by reason, we need not be perplexed 
at finding that there is much difficulty in some 
individual instances, in determining to which 
class of mental acts particular actions ought to be 
referred. However difficult it may be in any in- 
dividual instance, to decide whether an action, 
of man or of animals, is the effect of a blind in- 
stinct, or of reason, anticipating and desiring 
its consequences, there can be no doubt or 
difficulty as to the fact, that these two distinct 
kinds of mental determination to the perform- 
ance of actions exist. 

Neither do we consider it of any import- 
ance to enter on the metaphysical speculations 
which ingenious men have hazarded at different 
times as to the nature of the agent, by which 
the instinctive actions may be supposed to be 
immediately excited. Some philosophers have 
been so strongly impressed with the admirable 
adaptation of means to ends which these phe- 
nomena present, in animals manifestly devoid 
of reason, that they have believed them to be 
in all cases the immediate offspring of the 
divine intelligence, and have expressed their 
theory in the form of an axiom, “ Deus anima 
brutorum,” which, it is humbly conceived, is 
admissible only in the same sense in which we 
assent to the more general assertion, “ Deus 
anima mundi.” 

Mr. Kirby, in his very learned and elaborate 
Bridgewater Treatise on the History, Habits, 
and Instincts of Animals, seems to favour the 


[* The greater number of the actions enumerated 
may, however, be accounted for on the principle of 
reflux nervous action, now so generally admitted by 
physiologists. —ED. | 


6 INSTINCT. 


idea which other philosophers have maintained, 
of intermediate agents between the Divine will 
and the living beings on earth, by which the 
actions of the latter are guided ;* but in pro- 
secuting this idea he is disposed to regard the 
proximate cause of instinct, as he expresses it, 
not as metaphysical, but merely as physical, 
and to suppose that “light, heat, and air, or 
any modihestion of them” may be the inter- 
mediate agents “ employed by the Deity to 
excite and direct animals, when their intellect 
cannot, in their instinctive operations ;” and 
that “ the organization of the brain and nervous 
tem may be so varied and formed by the 
reator as to respond in the way that he wills, 
to pulses upon them from the physical powers 
of nature.”+ 

On this it may be observed that this last 
sentence expresses no more than the truth, 
whatever opinion we may form as to the mode, 
in which the response of the nervous system 
of an animal to the impressions made on it by 
ay, aigp agents takes place; but if it be meant 

y the expression, that the proximate cause of 
instinct is probably not metaphysical but 
physical, to exclude all mental operation, and 
all consciousness of effort, from the instinctive 
actions of animals, we can regard the theory 
only as a denial of al! mental acts or affections in 
any of the lower animals, and as easily con- 
tradicted by the whole analogies of their struc- 
ture, by observation of their habits, and by 
the evidence of our own consciousness in the 
performance of those precisely similar instinc- 
tive actions which have been noticed above. 

It seems quite unreasonable to doubt that 
the immediate cause of all the actions that we 
call instinctive, is a strictly mental effort, but 
the occurrence of that effort in every case 
when it is required must in all probability be 
always held as an ultimate fact in the animal 
ceconomy ; and all speculations as to its inti- 
mate nature or proximate cause may be re- 
garded as mere conjectures, on a subject which 
is beyond the reach of the human faculties. 
Nor would any thing be gained, in the infer- 
ence as to final causes, from establishing any one 
of these conjectures ; for the mental constitution 
of man himself, and of the whole lower ani- 
mals, is equally a part of the contrivance of 
the Divine Artificer of the world, as the laws 
of motion or the properties of light. He who 
could make man after his own image could 
assuredly impart such mental propensities to 
other beings, as well as to man, as were ne- 
cessary for the ends for which the creation was 
designed. And when we attempt, in all hu- 
mility, but at the same time in confident re- 
liance on the mental powers which He has 
vouchsafed to us, to draw inferences as to His 
existence and attributes from the study of 
created things, we do so, not by vainly hag 
ing to comprehend the nature of the energy by 
which any of the changes (physical or mental) 
occurring around us are effected, but simply by 
observing the adaptation of means to ends in 
those regular and uniform laws which we are 


* See vol. ii. p. 243-4. 
t+ Vol. ii. p. 255-6. 


enabled to infer from the observation of such 
changes,—which we ascribe to His authority, 
and beyond which we feel that it is not yet 
given us, by any exercise of our minds, to 
ascend. In enabling us to draw those in= 
riaemes the instincts of animals, as we shall 
afterwards state, are of uliar importance 5 
but the inferences are She scien whatever o ‘ 
nion we may adopt as to the mode in which 
the Divine Intelligence so indicated rules the” 
wills of the animal creation. ih 

Having said so much of the yyeripenie 
of this class of phenomena, and —- 
to set them in the proper point of view, we 
shall next offer a very rapid sketch of the 
fr daa instincts exhibited in the different i 
of animals, arranging them simply ing to 
the purposes which they seem pit 
serve, and shall conclude with a few general 
reflections. bs 

It may be premised that it certainly seems 


— 


reasonable @ priori to suppose, that the strac- 
ture of the nervous system, and ially of 
the brain, of different animals, will some 


relation to the kind of instinctive 
which they exhibit. In the size of the sen- 
sitive and motor nerves, and portions of the 
cerebro-spinal axis whence these originate, par- 
ticularly the spinal cord, medulla 4 
and optic lobes (or corpora quadrigemina), in the 
higher animals, this relation may be distinetly | 
perceived; and it has been further confidently | 
stated by some phrenologists, that strong evi- — 
dence of sur of their peculiar doctrines — 
may be deduced from observation of the size 
andi form of the brains of animals, as pm 2 | 
with their instincts; but this last speculation — 
certainly cannot be carried further than the 
vertebrated animals, which form but a small 
part of the living beings that are continualh 
guided and ruled by the laws of instinct; , 
even in them no such relation of the size and 
form of the brain, or of any part of the brain, to the 
general intelligence of an animal, or to any par- 
ticular instinct, has been fully ascertained. In- 
deed, until some such essential difference shall — 
be observed between the habits and instincts of 
the dolphin, or other cetaceous animals, and the 
predaceous fishes, as may correspond to the 
extraordinary difference of the size and struc- 
ture of their brains, (that of the former bein 
much larger in proportion to the spinal : 
than the human brain, and of complex struc- 
ture, while that of the latter is not larger than 
the optic lobes or corpora quadrigemina of the 
same animal, and of very simple 
such speculations may be safely distrusted.* 
Mr. Kirby has stated that the principal in- 
stincts of animals may be referred to three 
heads; those relating to their food, those re- 
lating to their propagation and the care of their 
offspring, and those relating to their hybernation. 
But this enumeration is certainly defective, 
and indeed will hardly include several which 


* We cannot suppose this difference to be con- 
nected with the difference in the mode of 
ration of these animals, because we know that 
only part of the central masses of the nervous system 
of either, concerned in that function, is the medulla 
oblongata. 


has himself accurately described. The fol- 
ing ears a more comprehensive enume- 
ration. ree great classes of instinctive ac- 
tions may be distinguished; the first designed 
for the preservation of individuals; the second 
for the propagation and support of their off- 
spring; and the third for various purposes im- 
‘portant either to the race of animals exhibiting 
them, or to other animals, but not distinctly 
referable to either of the former heads. 
_ Each of these classes admits of obvious sub- 
_ I. Of instincts designed for the preservation 
of the individuals exhibiting them, we may 
enumerate the following :— 
1. All animals are endowed with instincts 
ag them to some means of escaping or 
lling injury or violence, but these are ex- 

-eeedingly various, both as to the kind and as 
to the degree of complexity of the actions 
which they excite; from the simple retraction 
‘of the tentacula of the infusory Vorticella, or 
the Medusa, Polype, or Actinia, up to the 
ve and formidable resistance of the ele- 
phant or the tiger. The most common instinct 
of self-preservation excited by the emotion of 
fear, is that which prompts to flight, an in- 
‘Stinct so obviously existing in the human 
species, that the effort by which it is resisted 
has inal] ages been regarded with respect; and 
another very common propensity in animals is 
that which prompts to concealment. This is 
often combined with flight, as in most of the 
Carnivorous Mammalia, the Rodentia, the Ce- 
tacea, the diving birds, reptiles, insects, &c.; 
‘but some of the higher animals, and many of 
‘the Mollusca and insects, and others of the 
lower tribes, remain quite motionless and 
counterfeit death when under the influence of 
ar;* and it is remarkable that when the cir- 
ances of the animals render this mode of 
ence the most effectual, it is that adopted, 

a preference to flight, even by single species 

_ of families, the other members of sich oka 
no such instinct, as in the case of the ptarmi- 
yan, which so frequently cowers among the 
grey lichen, or the snow on the mountain- 
tops, instead of taking wing like the moor fowl, 
or in that of the hedge-hog, which on occasion 
of any imminent danger makes no effort but 
that of coiling itself into a ball. 

_ In many instances the instinct either of flight 
or concealment is aided by very various special 
‘contrivances, equally instinctive, fitted either 
_ to deceive, or to alarm, or injure an assailant. 
4 even of the Mollusca, and some of the 
Teptiles, as the toad, squirt water on him; 
“many reptiles and some lower animals, as 
the scorpion, bee, wasp, &c., even some of the 
_ gelatinous radiata,t have the power of emit- 


_ * * Tn this situation, spiders will suffer them- 
“selves to be pierced with pins and torn to pieces, 
‘without discovering the smallest sign of pain. 
‘This simulation of death has been ascribed toa 
strong convulsion or stupor occasioned by terror ; 
wm: Ay is solution of the phenomenon is erroneous. 
If the object of terror is removed, in a few se- 
__ conds the animal runs off with great rapidity.”— 
leg on Instinct. 
i” + Kirby, vol. i. p. 198. 


INSTINCT. 7 


ting irritating matter of greater or less inten- 
sity; the electrical animals, as the gymnotus 
and torpedo, use their appointed weapons ; the 
hedge-hog and porcupine oppose their sharp 
thorns to any one who attempts to molest them ; 
many insects and some reptiles protect them- 
selves by emitting peculiarly fetid effluvia; the 
cuttle-fish tribe have the remarkable power of 
emitting an inky fluid which darkens the wa- 
ter and hides them; and on the other hand 
there is reason to believe that the phosphores- 
cent light which so many marine animals ex- 
hibit, may be suddenly augmented on occa- 
sion of any threatening of injury, and serve as 
a means of defence.* (See Lumrnousness.) 
The means of defence, and the instincts guid- 
ing them, in the case, not only of the higher 
Carnivorous animals, but many of the stronger 
of the Herbivorous classes, the elephant, the 
hog, the horse, the buffalo, the deer, &e. re- 
quire no illustration. 

The instinct which prompts many animals to 
utter cries when injured or threatened, (as well 
as on other occasions and for other purposes,) 
deserves notice as a means of protection, parti- 
cularly on this account, that as it is one of the 
instincts which most clearly extends to the 
human race, so we may perceive in man, as 
well as in some of the lower animals, that its 
use is not merely to frighten assailants, but 
especially to procure assistance and protection 
for the young animal from its parents. 

2. The most conspicuous and most remark- 
ably varied of the instincts under this head 
are those by which the food of different ani- 
mals is procured. With the exception of the 
sponges, and some others of the lowest Zoo- 
phyta, in which the nourishment is supplied by 
currents, all animals have organs corresponding 
to a mouth and stomach, into which aliments 
are taken by a process of deglutition, imply- 
ing sensations and instinctive efforts conse- 
quent on these; and in the Articulata and 
Mollusca, the most important central organ of 
the nervous system seems to be the nervous 
collar surrounding the cesophagus, which in 
the vertebrated animals seems to be developed 
and subdivided into the first, fifth, and part of 
the eighth pairs of nerves, with the corres- 
ponding portions of the cerebro-spinal axis, by 
which the sensation of hunger is felt, the 
suitable nourishment discriminated, and the 
instinctive effort, whether of deglutition only, 
or of mastication more or less powerful ac- 
cording to the food, is excited. 

In some instances subsidiary instincts are 
also implanted in certain animals, which are 
essential to their digestion and nutrition. The 
art of cookery, as universally practised by the 
human race, may be said to be the result of 
experience ; but this cannot be said of the pro- 
cy of many animals to swallow salt, still 

ess of the swallowing of gravel or pebbles by 
the graminivorous birds, or of the copious 
draughts of water, sufficient to store the nu- 
merous and peculiar cells of their first and 
second stomachs, which are taken by the camel 


* Ibid, vol. i. p. 178. 


8 INSTINCT. 


or llama before they enter on the deserts, and 
which enable them subsequently to subsist 
without water for many days. 

But the instincts by which animals are en- 
abled to search for and obtain food may be 
easily sup to be much more numerous 
and varied than those by which they merely 
seize and swallow it, and in fact furnish the 
conditions by which the varieties of the whole 
Structure of animals are chiefly determined. 
Probably the greatest number of animals are 
nourished by the vegetable world ‘in the living 
or dead state, and are continually guided by 
sensations, to which instinctive efforts are at- 


tached,—i. e. by appetites,—in the selection of. 


food, which may in general be found and 
seized without much difficulty. But through- 
out the whole animal kingdom, from the mi- 
croscopic animalcules up to the largest of 
the Mammalia, a very great number of carni- 
vorous animals are found, who subsist on, and 
continually repress the numbers of, the herbi- 
vorous tribes; and. it may easily be supposed 
that the instincts implanted in these animals, 
which oppose and counteract the varying efforts 
at self-preservation already mentioned, will be 
more varied, and bear more marks of contri- 
vance and ingenuity. Accordingly, from the 
numerous Vorticelle, or other animalcules, of 
the order Rotatoria, which excite currents in 
the water around them, and so attract into 
their stomachs many of the smaller ani- 
malcules, up to the lion, the whale, or the 
eagle, we find an infinite number of con- 
trivances and instinctive me aC served 
by organs, by which the predaceous animals, 
of all the orders, are enabled to prey on the 
others. The Polype, Echinus, and Actinia, for 
example, among the Zoophyta, seize their 
prey, as it is brought to them by the waves, 
with their numerous tentacula; the Entozoa, 
and the leech and other of the Annelides, have 
the faculty and the necessary instinct of attach- 
ing themselves to the larger animals in the 
situations which suit them, as the Cirrhipedes 
or barnacles do to vegetable substances. The 
cuttle-fish and other predaceous Mollusca have 
legs furnished with admirably constructed 
suckers and powerful jaws, and most of the 
Crustacea have claws and mandibles, suf- 
ficient to enable them to seize and destroy ma- 
rine animals of very considerable size ; and it 
is unnecessary to enlarge on the powerful 
means of destruction, or on the instincts guid- 
ing their use, which are seen in many genera 
of each of the classes of vertebrated animals. 
There is often a peculiar instinct guiding 
each of the Carnivorous Mammalia to the 
part of the body of its victim where it can 
most easily inflict a mortal wound, to the 
throat in the case of a large animal, to the head 
in that of a small one, of which the cranium 
may be pierced. In the greater number of 
them, however, the instinctive actions by which 
their prey is obtained are distinguished only by 
power and violence ; and although much con- 
trivance is employed for adapting the different 
parts of the structure to the habits and des- 
tination of the animals, there is little apparent 


ingenuity in the modes in which the animals 
perform their office in creation. The attitud 
and gesture of the cat, the pointer, or the tiger, — 
slow stealing with crouched shoulders on — 
his prey,” is an example of instinctive con-— 
trivance preliminary to the act of violence. — 
The aspect and expression of many camivo- ~ 
rous animals,—not only of the Mammalia and ~ 
birds, but of the shark, the cuttle-fish, the 
scorpion, the tiger-beetle, &c., are so adapted 
to the feelings and instincts of the animals on 
which they feed, as often to deprive them of 
the power of flight or resistance; and it is” 
maintained by many, that some of the predace-— 
ous animals have the power of fascinating 
Rr by merely fixing their eyes on them. 
any have ascribed this power to the 
and Mr. Kirby asserts it with confidence of — 
the fox.* A few only of the predaceous ani- 
mals, as the dog and wolf, have the instinct — 
of associating together for pages their prey. | 
It has been stated that the pelican the — 
dog-fish have a similar instinct.+ o 
But the more striking indications of con- 
trivance in the actions prompted by in- 
stinct are to be found in some of pow- 
— of the carnivorous sale ius 
iscatorius or fishing-frog, al a 
fish, having no strength or speed, obtains its — 
prey by stratagem, plunging itself in mud, or 
covering itself with sea-weed: “ it lets no part 
of it be perceived except the extremity of the 


g 


pear like worms. The fishes, attracted by this — 
apparent prey, approach and are seized bya 
single movement of the fishing-frog, and swal- 
lowed by his enormous throat, and retained by — 
the innumerable teeth by which it is armed.” f _ 
A still more singular art is practised by the 
Cheetodon rostratus, which feeds on pili, 
as Sir Charles Bell states, actually takes aim 
at them, and shoots them with a drop of water.§ 
The instinct of the myrmecophaga or ant-eater, — 
which protrudes the tongue to allure flies to 
settle on it, and then suddenly retracts it to 
devour them, also deserves notice. A more — 
complex art is practised by the ant-lion, which — 
digs a pitfall in the track usually followed by — 
ants, and conceals itself in the bottom of it, — 
waiting for its prey. But of all contrivances - 
in the animal creation for procuring food, the 
most complex and artificial are those of the — 
different genera of spiders, equally curious on — 
account of the peculiar organs by which they — 
spin their webs, as of the peculiar and varied — 
instincts by which they are guided in» “4 
them.|| For example, “ any common black — 
and white spider (Salticus Scenicus), which — 
may always be seen in summer on sunny rails, — 
&c., when it spies a fly at a distance, ap- — 
proaches softly, step by step, and seems to 
measure his distance from it by the eye; then 

if he judges that he is within reach, first fixing 


* Vol. ii. p. 269. 

t See Darwin’s Zoon. vol. i. p. 229, 249. 
¢ See Kirby, vol. ii. p. 406, and pl. xiii. 
i Bridgewater Treatise, p. 200. 

| See Kirby, vol. ii. p, 184 and 286. 


thread to the spot on which he is stationed, 
by means of his fore feet, which are much 
arger and longer than the others, he darts on 
lis victim with such rapidity, and so true an 
lim, that he seldom misses it. He is pre- 
ented from falling by the thread just men- 
joned, which acts as a kind of anchor, and 
bles him to recover his station.”’"* Again, 
the kind of spider that has received the name 
f Geometric, “ having Jaid the foundation of 
x net, and drawn the skeleton of it, by 
ming a number of rays, converging to a 
ntre, next proceeds, setting out from that 
unt, to spin a spiral line of unadhesive web, 
e that of the rays, which it intersects, and 
sr numerous circumyolutions finishes this at 
e circumference. This line, in conjunction 
th the rays, serves as a scaffolding for her to 
alk over, and also keeps the rays properly 
fetched. Her next labour is to spin a spiral 
yrinthiform line from the circumference 
ards the centre, but which stops somewhat 
lort of it; this line is the most important part 
‘the snare. It consists of a fine thread, stud- 
‘ith minute viscid globules, like dew,which 
ir viscid quality retain the insects which 
the net. The snare being thus finished, 
@ geometrician selects a concealed spot 
h the vicinity, where she constructs a cell, in 
hich she may hide herself and watch for 
me; of the capture of which she is informed 
he vibrations of a line of communication, 
rawn between her cell and the centre of her 
3. Many animals are guided by instinct to 
or habitations for themselves, of very various 
inds, for protection against injury and against 
old, from the simple contrivance of the earth- 
brm, which closes the orifice of its hole with 
es or straw, up to the elaborate structures 
the bee, the ant, or the beaver. Here we 
ybserve a singular but easily understood diffe- 
ace between the inhabitants of water and air. 
the greater number of the more delicate animals 
lat inhabit the sea, chiefly of the Mollusca and 
fustacea, are provided by nature with shells, 
 Oryery firm integuments, evidently for protec- 
_ tion against the violence of the waves, in the 
_ formation of which instinct has little or no 
; but there are some of the Annelides 
habiting water, as the Sabella and Terebella, 
id the larvee of some moths, which have a sin- 
instinct enabling them to form habitations 
cient for their own protection, “ by collect- 
ing grains of sand ad fragments ot decayed 
_ Shells, &c. which they agglutinate together by 
| neans of a viscid exudation, so as to form a 
fm defensive covering, like a coat of mail.” 
his may be stated as the intermediate link be- 
veen the habitations given to the Mollusca and 
ea by nature, and those which many 
animals have organs and instincts enabling 
to form for themselves. 
manceeuvres of the terebella are best 
ved by taking it out of its tube and placing 


fg 


__* Kirby, vol. ii. p. 298. 
___ ¢ Ibid. p. 295. See also Darwin’s Zoon, vol. i. 


fae 


ee 


- 


INSTINCT. 


9 


it under water upon sand. It is then seen to 
unfold all the coils of its body, to extend its 
tentacula in every direction, often to a length. 
exceeding an inch and a half, and to catch, by 
their means, small fragments of shells and the 
larger particles of sand. These it drags to- 
wards its head, carrying them behind the scales 
which project from the anterior and lower part 
of the head, where they are immediately ce- 
mented by the glutinous matter which exudes 
from that part of the surface. Bending the 
head alternately from side to side, while it con- 
tinues to apply the materials of its tube, the 
terebella has very soon formed a complete 
collar, which it sedulously employs itself to 
lengthen at.every part of the circumference 
with an activity and perseverance highly inte- 
resting. For the purpose of fixing the different 
fragments compactly, it presses them into their 
places with the erected scales, at the same time 
retracting the body. Hence the fragments, 
being raised by the scales, are generally fixed 
by their posterior edges, and thus, overlaying 
each other, often give the tube an imbricated 
appearance. 

“‘ Having formed a tube of half an inch or an 
inch in length, the terebella proceeds to burrow ; 
for which purpose it directs its head against the 
sand, and contracting some of the posterior 
rings, effects a slight extension of the head, 
which thus slowly makes its way through the 
mass before it, availing itself of the materials 
which it meets with in its course, and so con- 
tinues to advance tili the whole tube is com- 
pleted. After this has been accomplished, the 
animal turns itself within the tube, so that its 
head is next the surface, ready to receive the 
water which brings it food, and is instrumental 
in its respiration. In summer the whole task 
is completed in four or five hours; but in cold 
weather, when the worm is more sluggish, and 
the gluten is secreted more scantily, its progress 
is considerably slower.’”’* 

The habitation formed by the water-spider, 
which is not exposed to the violence of the sea, 
shews much greater delicacy of workmanship, 
as well as greater variety of instinct. 

“ The insects that frequent the waters,” says 
Kirby, “ require, as well as those that inhabit 
the earth, predaceous animals to keep them 
within due limits, and the water-spider is one 
of the most remarkable on whom that office is 
imposed by the Creator. To this end her in- 
stinct instructs her to fabricate a kind of diving- 
bell, for which purpose she usually selects still 
waters. Her house is an oval cocoon filled 
with air, and lined with silk, from which 
threads issue in every direction, and are fast- 
ened to the surrounding plants ; in this cocoon, 
which is open below, she watches for her prey, 
and even appears to pass the winter, when she 
closes the opening. It is most commonly en- 
tirely under water, but its inhabitant has filled 
it with air for respiration, by which she is ena- 
bled to live in it. She conveys the air in the 
following manner: she usually swims upon her 
back, when her abdomen is enveloped in a 


* Roget’s Bridgewater Treatise, vol. i. p. 279. 


10 


bubble of air, and appears like a globe of quick- 
silver; with this she enters her cocoon, and 
displacing an equal mass of water, again 
ascends fora second lading, till she has suffi- 
ciently filled her house with it, so as to expel 
all the water. The males construct similar 
habitations by the same maneuvres. How 
these little animals can envelope their abdomen 
with an air-bubble, and retain it till they enter 
their cells, is still one of Nature’s mysteries 
that have not been’ explained.” 

We need say nothing of the habitations 
formed by solitary animals of the higher tribes, 
chiefly by burrowing under ground, for their 
own protection and comfort; but the most curi- 
ous of such solitary habitations on the earth’s 
surface are also furnished by the tribe of 
spiders. 

“ Some species of spiders, M. Audouin re- 
marks, are gifted with a particular talent for 
building: they hollow out dens; they bore 
galleries ; they elevate vaults ; they build, as it 
were, subterranean bridges ; they construct also 
entrances to their habitations, and adapt doors 
to them, which want nothing but bolts, for 
without any exaggeration, they work upon 
a_ hinge saa are fitted to a frame. The 
interior of these habitations is not less 
remarkable for the extreme neatness which 
reigns there; whatever be the humidity of the 
soil in which they are constructed, water never 
penetrates them ; the walls are nicely covered 
with a tapestry of silk, having usually the lustre 
of satin, and almost always of a dazzling white- 
ness. 

“ The habitations of the species in question 
are found in an argillaceous kind of red earth, 
in which they bore tubes about three inches in 
depth and ten lines in width. The walls of 
these tubes are not left just as they are bored, 
but are covered with a kind of mortar, suffi- 
ciently solid to be easily separated from the 
mass that surrounds it.” “ The door that closes 
the apartment is still more remarkable in its 
structure. If the well were always open, the 
spider would sometimes be subject to the intru- 
sion of dangerous guests. Providence has there- 
fore instructed her to fabricate a very secure 
trap-door which closes the mouth of it. To 
judge of this door by its outward appearance, 
te pada to be formed of a mass of earth 
coarsely worked, and covered internally by a 
solid web, which would be sufficiently wonder- 
ful for an animal that seems to have no special 
organ for constructing it; but when divided 
vertically, it is found to be a much more com- 
plicated fabric than its outward ap ce in- 
dicates, it being formed of more than thirty 
alternate layers of earth and web emboxed, as 
it were, in each other, like a set of weights for 
small scales. 

“ If these layers of web are examined, it will 
be seen that they all terminate in the hinge, so 
that the greater the volume of the door the more 
powerful is the hinge. The frame in which the 
tube terminates above, and to which the door 
is adapted, is thick, arising from the number 
of layers of which it consists, and which seem 
to correspond with those of the door; hence 


INSTINCT. 


the formation of the door, the hinge, and the © 
frame, seem to be a simultaneous operation ;— 
except that in fabricating the first, the animal 
has to knead the earth as well as to spin the 
layers of web. By this admirable arrange 
these always co! d with each 
and the strength of the hinge and the thi 
of the frame will always be proportioned 
weight of the door. : 
“* The interior surface of the cover to the 


and remarkable for a series of minute or ‘ 
placed in the side opposite the hi r 
ranged in a semicircle; there are 
of these orifices, the object of which, M. Au- 
douin conjectures, is to enable the animal to 
hold her door down in any case of emergency — 
against external force, by the insertion of her 
claws into some of them.” * , 
But the most extraordinary habitations formed — 
by the instincts of animals are those which are 
the joint result of the labours of communities; 
and here we observe the same difference as has” 
been already noticed, between the inhabitants 
of the air and of the ocean. Many of the ani+ 
mals that inhabit the latter are formed by na- 
ture, as Mr. Kirby expresses it, (and evi 


with a view to the rude shocks to which they _ 


consisting | 


are exposed,) “ into a body politic, : 
of many individuals, and distinct as 
inhabiting different cells, but still ing a 
body in common, and many of them receiving 


benefit from the systole and diastole of a com- _ 


mon organ ; thus by a natural union is sy 
lized what in terrestrial animal communities re- 
sults from numerous wills uniting to effect a_ 
eon object. The vane as far as I recol- 
ect, exhibits no instance 0 PE aye l, 
nor the ocean of one which, like the beaver, — 
lemming, bee, wasp, &c. forms associations to 
build and inhabit a common house.” + | 

And there is a curious family, named Salpa, 
in which the individuals are attached to each 
other almost like bees in their cells at birth, 
and are afterwards separated when they have 
acquired strength; thus forming the link be- 
tween the aggregated sea animals (such as Co- 
rals, Madrepores, Sertularia, Fluswa, &c.) and 
the associated land animals. | 

The habitations that are formed by animals 


} 


of the latter description, although in very diffe- | 


rent parts of the scale of beings, afford Al 


curious evidence of skill and contrivance, and | 
of the wills of numerous individuals, bound _ 


together by a common instinct, as surely as the 
materials of which the aggregate animals are 


& 


composed. Take, for example, the houses of — 


| 
A 


beavers. 


« Beavers set about building some timer | 


the month of August: those that erect their — 


habitations in small rivers or creeks in which 
the water is liable to be drained off, with won- 
derful sagacity provide against that evil by 


* Kirby, vol. ii. p. 287, et seq. 
t Kirby, vol. i. p. 222, f 


ming a dike across the stream, almost straight 
ere the current is weak, but where it is more 
id, curving more or less, with the convex 
opposed to the stream. They construct 
these dikes or dams of the same materials as 
hey do their lodges, viz. of pieces of wood of 
kind, of stones, mud, and sand. These 
Shag oppose a sufficient barrier to the 
eboth of water and ice; and as the willows, 
yoplars, &c. &c. employed in constructing them 
‘often strike root in it, it becomes in time a 
green hedge in which the birds build their 


_« By means of these erections the water is 
ept at a sufficient height, for it is absolutely 
ecessary that there should be at least three 
set of water above the extremity of the entry 
into their lodges, without which, in the hard 
frosts, it would be entirely closed. This entry 
§ not on the land side, because such an open- 
ng might let in wild animals, but towards the 


_ © They begin to excavate under water at the 
ise of the bank, which they enlarge upwards 
sraduaily, and so as to form a declivity, till 
hey reach the surface ; and of the earth which 
omes out of this cavity they form a hillock, 
with which they mix small pieces of wood and 
ven stones; they give this hillock the form of 
adome from four to seven feet high, from ten 
to twelve long, and from eight to nine wide. 
As they proceed in heightening, they hollow it 
ut below, sb as to form the lodge which is to 
receive the family. At the anterior part of this 
dwelling, they form a gentle declivity termina- 
_ fing at the water, so that they enter and go out 
under water, 
_ © The interior forms only a single chamber 
‘Tesembling an oven. Ata little distance is the 
azine for provisions. Here they keep in 
the roots of the yellow water-lily, and the 
nches of the black spruce, the aspin, and 
birch, which they are careful to plant in the 
These form their subsistence. Their 
gazines sometimes contain a cart-load of 
e articles, and the beavers are so industrious 
at they are always adding to their store.” * 
The nests so admirably constructed by what 
ave been called the perfect societies of insects, 
white ants or termites, the ants or formice, 
@ bees, wasps, and humble bees, are well 
mown, and have been often described. The 
terials used by the two first genera are chiefly 
» with bits of straw or wood, cemented by 
himal secretions ; the bees manufacture wax 
or the purpose. 
___ “ The wasps and hornets are remarkable for 
the well-known curious papier-maché edifices, 
_ inthe construction of which they employ fila- 
hents of wood, scraped from posts and rails 
h their own jaws, mixed with saliva, of 
ich the hexagonal cells in which they rear 
T young are formed, and often their combs 
Separated and supported by pillars of. the 
_ Same material ; and the external walls of their 
_ Rests are formed by foliaceous layers of their 
ligneous paper.” + 
* Kirby, vol. ii, p. 510. 
t Kirby, loe. cit, p. 335. 


Dl ee el 


INSTINCT. 


‘11 


“ The tree-ants, again, are remarkable for 
forming their nests on the boughs of trees of 
different kinds; and their construction is sin- 
gular, both for the material and the architec- 
ture, and is indicative of admirable foresight 
and contrivance ; in shape they vary from glo- 
bular to oblong, the longest diameter being 
about ten inches, and the shortest eight. The 
nests consist of a multitude of thin leaves of 
cow-dung, imbricated like tiles upon a house, 
the upper leaf formed of one unbroken sheet 
covering the summit like a skull-cap. The 
leaves are placed one upon another in a wavy 
or scalloped manner, so that numerous little 
arched entrances are left, and yet the interior is 
perfectly secured from rain. They are usually 
attached near the extremity of a branch, and 
some of the twigs pass through the nest. A 
vertical section presents a number of irregular 
cells, formed by the same process as the exte- 
rior. Towards the interior the cells are more 
capacious than those removed from the centre, 
and an occasional dried leaf is taken advantage 
of to assist in their formation. The nurseries 
for the young broods in different stages of 
developement are in different parts of the 
nest.””* 

What is most peculiar in the habitations of 
all these “ perfect societies of insects,” is the 
formation, by the same working members of 
these societies, of cells of different size and form, 
suited for the different classes or ranks of indi- 
viduals which, as we shall afterwards state, 
each of these associations comprises ; and the 
occasional alteration of the size and form of the 
cells, when circumstances occur, which will 
be afterwards mentioned, to make an alteration 
of their destination advisable. 

There are other examples among insects, of 
imperfect societies or associations, found tempo- 
rarily and during the larva state only, which 
unite in forming tents under which they feed, 
and which shelter them from sun and rain. 
This is done by the larve of several species of 
butterfly and moth.+ 

4. The next instincts which may be noticed 
under this head are those connected with the 
hybernation of animals ; for in almost every case 
in which this faculty (which is found so gene- 
rally in the lower tribes, particularly reptiles and 
insects, as well as in the order Cheiroptera and 
several others of the higher animals,) exists, there 
is attached to it some instinctive propensity, 
prompting the animal, even although it be not 
one of those which form houses for themselves, 
at least to search for some suitable residence in 
which it may be sheltered during the winter, 
whether under ground, under stones or timber, 
under the bark of trees, &c.; and it is very re- 
markable that their hiding places are often 
found, or formed, long before the weather has 
become very cold. “ I am led to believe from 
my own observation,” says Mr. Spence, “ that 
the days which the majority of coleopterous 
insects select for retiring to their hybernacula are 
some of the warmest days of autumn, when 


* Ibid. p. 340. 
¢ Spence and Kirby, vol. ii. p- 21. 


12 


they may be seen in great numbers alighting on 
walls, rails, path-ways, &c.”* Some insects, 
and many larve (as the silk-worm) approaching 
to the state of pupa, form a covering for them- 
selves by exudations from their own bodies, 
likewise at some distance of time before the 
frosts set in. Many hybernating animals ex- 
hibit so little of any vital action as to require 
little or no nourishment during the winter, ex- 
cepting the product of absorption of their own 
fat; but it is also well known that many of 
different orders (as the beaver, the hedgehog, 
the squirrel, the dormouse, the bee, which are 
seldom or never quite torpid,) are guided b 
instinct to lay up stores of provisions, on whic 
they subsist during the winter. Some of these, 
as the lemming, have been observed to spread 
out their stores to dry in fine weather. me 
of the most curious of the provisions of this 
kind are the following :— 

“ There is an animal, the rat-hare, which is 
gifted by its Creator with a very singular in- 
stinct, on account of which it ought rather to be 
called the hay-maker, since man may or might 
have learned that part of the business of the 
agriculturist, which consists in providing a store 
of winter provender for his cattle, from this 
industrious animal. Professor Pallas was the 
first who described the quadruped exercising 
this remarkable function, and gave an account 
of it. The Tungusians, who inhabit the countr 
beyond the lake of Baikal, call it Pika, whic 
has been adopted as its trivial name. 

* About the middle of the month of August 
these little animals collect their winter’s pro- 
vender, formed of select herbs, which they bring 
near their habitations and spread out to dry 
like hay. In September they form heaps or 
stacks of the fodder they have collected under 
places sheltered from rain or snow. Where 
many of them have laboured together, their stacks 
are sometimes as high as a man, and more than 
eight feet in diameter. A subterranean gallery 
leads from the burrow below the mass of hay, 
so that neither frost nor snow can intercept their 
communication with it. Pallas had the pa- 
tience to examine their provision of hay piece by 
piece, and found it to consist chiefly of the 
choicest grasses and the sweetest herbs, all cut 
when most vigorous, and dried so slowly as to 
form a green and succulent fodder; he found 
in it scarcely any ears or blossoms, or hard and 
woody stems, but some mixture of bitter herbs, 
probably useful to render the rest more whole- 
some.”’+ 

“ Although,” says Kirby, “ ants during the 
cold winters in this country remain in a state of 
torpidity, and have no need of food, yet in 
warmer regions during the rainy seasons, when 
they are probably confined to their nests, a store 
of provisions may be necessary for them. Now 
although the rainy season, at least in America, 
is a season in which insects are full of life, yet 
the observation that ants may store up provi- 
sions in warm countries is confirm y an 
account sent me by Colonel Sykes, with respect 


* Introduction to Entomology, vol. ii, p. 438. 
t Ib. p. 507. 


INSTINCT. 


to another species which appears to belong to 
the same genus as the colsbeuted ants of visi- | 
tation, by which the houses of the inhabitants 
of Surinam were said to be cleared periodical) 


present species has been named by Mr. Hop 
the provident ant. These ants, after long-co 
tinued rains during the monsoon, were fe 
to bring up and lay upon the earth ona fi 
day, their stores of grass seeds and grains 
Guinea corn, for the purpose of drying them 
Many scores of these hoards were frequentl 
observable on the extensive parade at Poona! 
The great and important instinct of 
is another means by which the lives 
animals are preserved during winter. ~ 
number of species of birds, which pas 
summer to bring forth their young m 1 
country, but disappear from it im autumn, and” 
are known to spend the winter in the south ¢ 
Europe or Africa, has been stated at not less 
than five-sixths of the whole number ( 


here during the summer, and these are dese | 
by many other species, chiefly i 


waders, but likewise the field IgS, 
starlings, &c. which have brought forth 
young in the colder climates, and return 

for the winter. There are others, as the crane 
and stork, which perform similar mi ; 
but are rarely seen in this country. The 
tions of the larger birds from the 
regions are chiefly performed in large bodi 
forming angular lines, very high in the air 
those of the smaller birds of passage, lows, 
singing birds, &c. that go southwards from 
hence, seem to take place less regularly, and 
have been less accurately observed. ‘There are 
also many annual migrations from one part of 
this country to another, in spring and autumn, 
as of the plovers and lapwings, curlews, ring 
ouzels, &e. It is still doubtful with wh: 
sensations the propensity to perform these peri 
odical migrations is chiefly con whether 
with changes of temperature, or iency of 
food, or with the changes of the sexual desire 
(as maintained by Jenner.+) But it is certain 
that the migrations take place while the tem- 
perature is still such as is well borne by th 
animals; indeed of most of the ies 
birds of passage some individuals are ‘ 
observed not to migrate;{ and it is ly 
certain that most of the birds of passage do ne 
gradually withdraw, as if following the li 
changes of the food on which they live, but 
go off suddenly, and perform their voyages, p 
ticularly in autumn, so rapidly, as to be much 
exhausted and emaciated at the end of then 
so that it is certainly not under the influence 
sensations gradually changing and g to 
partial and successive changes of place, bu 
under that of a strong determination, overe 

ing the motives to action which are 
predominant, and commanding strenuous and 
painful exertion at a time when no great incon- 
venience is felt, that these voyages are per- 


* Vol. ii. p. 344, 
7 Phil. Trans. 1824, 
¢ See Darwin, Zoonomia, sect. xvi. 12, 


med. And if, with Darwin and some others, 
ve doubt of the existence of a blind instinctive 
opensity as the cause of these movements, we 
ave no resource but to ascribe them to a very 
gh degree of intelligence, combined with 
ach mental resolution, and extending toall or 
most all the individuals of thespecies, enabling 
em to foresee evils that are still remote, and 
termining them to undergo labour, fatigue, 
danger in order to avoid them. It has also 
sn repeatedly ascertained that the same indi- 
juals return after their six months of absence 
d long voyages, to the very spots where they 
d been brought forth, implying a power of 
cernment and recollection which appear to 
‘quite inconceivable. Of such high qua- 
ies of mind we see no indications in the other 
of these birds, excepting only in their 
parations for the nurture of their young ; and 
hey really possessed these qualities, we might 
pect with perfect confidence to see them 
ise many contrivances for their comfort and 
ience, and to witness variations and im- 
ents in habits, which we know from the 
itings of the ancient naturalists to have been 
rfectly uniform and stationary at least since 
e time of Aristotle. 
There are some of the Mammalia, chiefly of 
der Ruminantia, which likewise perform 
iodical migrations in the natural state, as has 
en particularly noticed in America, of the 
on, the musk-ox, and rein-deer. A similar 
has been observed in the quaggas in 
and a singular observation, as shewing 
ation of instinct according to varying cir- 
lances, was made by Dr. Richardson, that 
American black bear, when lean, and from 
hat cause unfitted for hybernation, migrates in 
winters from the northward into the 
nited States. 
The periodical migrations of fishes appear to 
e designed for the benefit of their offspring, 
ot for their own preservation; and there are 
her migrations, in immense numbers, of various 
tinds of animals which are not periodical, and 
of which the object is still obscure, but which 
do not fall under the present head. 
Of instincts for the propagation and 
of offspring —Of the very curiously 
ied instincts of animals connected with 
the propagation and support of their off- 
mr . ie heed not dwell on those which 
ust necessarily attend the very various 
inds of organs (so well arranged and de- 
scribed by Cuvier), by which the impreg- 
hation of the ova in the different tribes of 
mals is effected—the instincts, e.g. which 
r most male fishes to impregnate eggs 
dy laid, and many reptiles to impregnate 
hem at the moment of their emission from 
le body of the female, or which guide the 
ifferent warm-blooded animals in the different 
s of their sexual intercourse. The in- 
cts which enable animals to anticipate and 
vide for the wants of their young are still 
nore varied, and imply mental processes of 
ater complexity. The most important of 
hese may he referred to the following heads. 
1. This is probably one object of the migra- 


a 
; 
+ 


INSTINCT. 


13 


tions of birds above-mentioned, and certainly 
the main object of the migrations of great 
swarms of fishes, both in the sea, and of those 
which ascend the rivers; to which the same 
observations, as to the return to the same spot 
whence they had formerly departed, and as to 
the labours and hazard which the instinct im- 
pels them to incur, are in many instances appli- 
cable. 

“ The cod-fish makes for the coast at spawn- 
ing time, going northward; this takes place 
towards the end of winter, or the beginning of 
spring. 

“The mackarel hybernates in the: Arctic, 
Antarctic, and Mediterranean Seas, where it is 
stated to select certain depths of the sea called 
by the natives Barachouas, which are so land- 
locked, that the water is as calm at all times as 
in the most sheltered pools. 

“ It is in these that the mackarel, directed by 
instinct, pass the winter. In the spring they 
emerge in infinite shoals from their hiding 
places, and proceed southward for the purposes 
of depositing their eggs in more genial seas. 

“What the mackarel is to the north of 
Europe, the thunny is to the south. It de- 
posits its eggs in May and June, when it enters 
the Mediterranean, seeking the shores in shoals 
arranged in the form of a parallelogram, or as 
some say, a triangle, and making a great noise 
and stir. 

“The herring may be said to inhabit the 
arctic seas of Europe, Asia, and America, from 
whence they annually migrate at different times 
in search of food, and to deposit their spawn. 
Their shoals consist of millions of myriads, 
and are many leagues in width, many fathoms 
in thickness, and so dense that the fishes touch 
each other.” ‘The largest and strongest are 
said to lead the shoals, which seem to move in 
a certain order, and to divide into bands as 
they proceed, visiting the shores of various 
islands and countries, and enriching their in- 
habitants.” ‘ They seek places for spawning 
where stones and marine plants abound, against 
which they rub themselves. alternately on each 
side, all the while moving their fins with great 
rapidity.” 

“ In temperate climates the salmon quits the _ 
sea early in the spring, when the waves are 
driven by a strong wind against the river 
currents.” “They leave the sea in numerous 
bands formed with great regularity. The 
largest individual, which is usually a female, 
takes the lead, and is followed by others of the 
same sex, two and two, each pair being at 
the distance of from three to six feet from the 
preceding one; next come the old, and after 
them the young males in the same order.” 
“ They employ only three months in ascending 
to the sources of the Maraguon, the current of 
which is remarkably rapid, which is at the 
rate of nearly forty miles a day; in a smooth 
stream or lake their progress would increase in 
a four-fold ratio. Their tail is a very powerful 
organ, and its muscles have wonderful efiergy ; 
by placing it in their mouth, they make of it 
a very elastic spring, for, letting it go with 
violence, they raise themselves in the air to the 


14 


height of from twelve to fifteen feet, and so 
clear the cataract that impedes their course ; 
if they fail in their first attempt, they continue 
their efforts till they have accomplished it. 
The female is stated to hollow out a long and 
deep excavation in the gravelly bed of the river 
to receive her spawn.” * 

A similar periodical emigration has been ob- 
served in other animals, particularly in some of 
the Crustacea. 

“ Several of the crabs forsake the waters for 
a time, and return to them to cast their spawn ; 
but the most celebrated of all is that known 
by the name of land-crab, and alluded to by 
Dr. Paley as the violet-crab, and which is 
called by the French the ¢ourlourou. They are 
natives of the West Indies and South Ame- 
rica. In the rainy season, in May and June, 
their instinct impels them to seek the sea, that 
they may fulfil Ee great law of their Creator, 
and cast their spawn. They descend the moun- 
tains, which are their usual abode, in such 
numbers that the roads and woods are covered 
with them.” “They are said to halt twice every 
day, and to travel chiefly in the night. Arrived 
at the sea-shore, they are there reported to 
bathe three or four times, when retiring to the 
neighbouring plains or woods, they repose for 
some time, and then the females return to the 
water, and commit their eggs to the waves. 
This business dispatched, they endeavour to 
regain, in the same order, the country they had 
left, and by the same route, but only the most 
vigorous can reach the mountains.” + 

The object of all these migrations is, that the 
female animals may have an opportunity of de- 
positing their eggs where they will be in cireum- 
stances suited to their development, particularly 
as to the essential requisites, exposure to heat 
and to air. 

2. The same object, the choice of a suitable 
place for depositing their eggs, is accomplished 
in other instances by very different instincts im- 
planted in female animals. “ Reptiles,” says 
Kirby, “ and Fishes do not feel the instinctive 
love for their young, after birth, which is ex- 
hibited by quadrupeds and birds, but are in- 
variably instructed by the Creator to select a 
ag in which their eggs can be hatched either 

y artificial or solar heat.” Many of them 
likewise, as the salmon, dig holes before 
depositing them, for their protection. Those 
of the serpents which are not ovo-viviparous, 
bury their eggs in sand, or in heaps of fer- 
menting matter. The Saurians also select a 

TO lace for their » the crocodile, e.g. 
sagan beside IS species of sale 
mander commits a single egg to a leaf of 
Persicaria, protects it by carefully doubling the 
leaf, and then proceeding to another, repeats 
the maneuvre till her oviposition is finished. 
Toads and frogs lay their eggs in water, sur- 
rounded by a gelatinous envelope which forms 
the first nourishment of the embryo,” corres- 
ponding to the albumen of the bird’s egg. 

In iike manner every insect is directed by 
nature to place its eggs in situations where its 


* Kirby, vol. i. t Ibid. 


INSTINCT. oq 


young, when disclosed, will find its appro- 
priate nourishment; some burrowing in the 
earth for this purpose; many flies in dead 
animal matter about to putrefy; many in dif 
ferent parts of living vegetables;* bees and ants 
in the cells where they are to be fed by the 
working members of their hives, &e. A spe= 
cies of the ichneumon fly and some of the 
wasps have been observed to bury caterpi 
along with their eggs, on which their |. 
are to feed, and another fly to deposit its eggs 
on the back of a caterpillar, when the larvay 
feed on the secretion by which the covering of 
the pupa is to be formed.+ (veil 
3. The instincts called into action in the 
nidification, particularly of birds, are so nume~ 
rous, varied, and admirably adapted to 
purpose, as to have called forth admiration in all 
ages. The pairing of the parent birds at th 
beginning of spring, when the labour is to 
begin ; the choice of a: place suited to the 
habits of the species, on the ground, under 
ground, in rocks, on the edge of lakes or of 
the sea, in marshes, in bushes, on trees, on 
buildings of all descriptions; the choice of the 
materials, and the labour exerted for com- 
pleting the work ; some using clay, some sa 
some moss, some leaves, some straw or twigs : 
some moss or lichen; many forming a roug 
outside of materials hardly to be distinguishes 
from the surrounding objects, while the inside 
is warm and smooth ; some building in very pe= 
culiar forms to impede the access to their young; 
the tailor-bird sewing leaves together wit e€ 
distinct stitches, and the Java swallows forming 
their gelatinous nests, as the bees manufacture - 
their waxen cells, from the contents and secre- 
tions of their own stomachs ;—all furnish pr a 


g 


al 


of contrivance too obvious and too nez 1- 
justed to varying circumstances, to have es- 
caped the attention even of careless observers. — 
Many of the Mammalia make some kind of 
provision, although less artificial, for the re~ — 
ception of their progeny. ‘“ Cats search about 
inguisitively for a concealed situation; bur- 
rowing animals retire to the bottom of their 
burrows, and several of the Rodentia make — 
beds of their own hair to receive their young ;” — 
all beasts of prey, whose progeny come into 
the world blind and helpless, have some kind — 
of retreat in which they supply them at once 
with warmth and nourishment. Many i j 
also, besides those which associate in: hives, — 
use various precautions for the covering and pr 
tection of their eggs. 

4. The instinct of incubation, which forms: 
the next part of the provisions for the repro= 
duction of birds, the extraordinary change then 
effected in the habits of the female bird, par 
ticularly when attended and cheered, as hap= 

ns in so many cases, by the equally tempore 
foatinet of song of the vale biaeall Be 
natural phenomenon too striking and interesting’ 
to have escaped observation ; and the objectof 


* In this choice insects seem to be guided by the 
sense of smell, at least in the case where the food 
of the larve to be brought forth is different from — 
that of the parent. nen 

+ Darwin. 


via 


INSTINCT. 


this provision of nature has been fully elucidated 
by the observations of Reaumur and many 
others as to the efficacy of artificial heat in 
_ procuring the development of the chick. : 
___ 5. The instincts of many parent animals are 
_ likewise the means adopted by nature for pro- 
/ curing nourishment for the young. This is 
_ observed as to those of the lower orders whose 
N., ng are brought forth in circumstances ren- 
e od it impossible for them to procure their 
_ own food (as the bee and wasp), and also as to 
_ the carnivorous tribes, both of birds and quad- 
-rupeds; the exertion requisite for procurmg 
their prey being beyond the power of the young 
animal, the instinct of the parent supplies the 
defect. In most cases fresh supplies of food 
are daily or even hourly brought to the young 
animals, but in some instances stores of nou- 
bi rishment are provided for the young of the 
higher animals, equally as for those of the bee 
_ or ant; the pelican brings a large supply in 
__ his pouch from a single fishing; and according 
_ to the observations of an author in the Magazine 
of Natural History, some of the carnivorous 
animals have the curious instinct of storing up 
_ with this view animals not dead, but stupified 
by injury of the brain. “I dug out,” says he, 
“ five young pole-cats, comfortably imbedded 
in dry withered grass; and in a side hole, of 
proper dimensions for such a larder, I poked 
out forty large frogs and two toads, all alive, 
but merely capable of sprawling a little. On 
examination I found that the whole number, 
toads and all, had been purposely and dex- 
_ trously bitten through the brain.” * 

Lastly, the young of all warm-blooded 
animals being unable for some time after they 
come into the world to maintain their own 
temperature, would soon perish of cold, even 

_ if capable of procuring their own food, 
but for the protection they receive from their 

a. This seems to be the most general 

al cause of the erogyn or maternal affection 

so strongly implanted in all these animals, and 
to which so much of the first period of the 
existence of their offspring is intrusted, but of 
which there is little trace in the lower tribes. 

As, however, the dangers to which these young. 

_ animals are exposed are numerous and varied, 
; so nature has provided against them, not by a 
| 
4 


propensity to the performance of one kind of 
action only, but by a vigilant and permanent 
feeling which controls all the habits of the 
parent animal, and prompts many actions, some 
_ of which are strictly instinctive, while others 

Ought rather to be called voluntary, but are 
! quite at variance with the ordinary habits of 
the animals. Every one must be aware of the 
increased ferocity given to the female carnivo- 
rous animals during the time that they are 
occupied with the care of their young, and of 


the resolution with which birds, at other seasons 
pacific and even timid, will resent any intrusion 
on their nests or young broods; of the provi- 
dent care of the cat or the lioness, which carries 
her young in her mouth, and of almost all fe- 
male warm-blooded animals, which gather them 


* Magazine, &c. vol. vi. p. 206. 


15 


close to their bodies for protection from cold ; 
of the anxiety of the hen which has sat on 
duck’s eggs, when the ducklings take to the 
water; of the resolution and ingenuity with 
which the lapwing fixes on herself the attention * 
of passengers who may come near her nest, &c. 
But what most distinctly indicates that all this 
care and anxiety are unconnected with any such 
anticipation of the results as would be acquired 
by a process of reasoning, is the absolute indif- 
ference which succeeds, when the parent animal 
at length sees her offspring independent of her 
assistance— 


«« And once rejoicing, never knows them more.” 


III. Various instinctive propensities may be 
observed in animals, the object of which is the 
advantage of the race or of the animal creation 
generally, rather than of the individual or his) 
progeny, and some the object of which is still 
obscure. Some of these are, like the maternal 
affection last mentioned, obviously partaken by: 
the human race, or even chiefly perceptible 
in those animals which have much con- 
nexion with man. The instinctive attachments 
not only of dogs but various domestic animals 
to their masters or attendants, of cats to houses, 
of sheep to particular hills or pastures, might 
be illustrated by many curious anecdotes, and 
seem to be very similar to the feelings which, 
after being fully developed in the human race, 
and strengthened and extended by the reflective 
powers of the human mind, obtain the names 
of family affection, of local attachment, of 
patriotism, &c. If the instinct of modesty 
exists in hardly any animals, the desire of clean- 
liness may be observed in many. The instinct 
of imitation, formerly noticed, and which is of 
so essential importance to all human enterprises 
in which the cooperation of numbers is re- 
quired, is perhaps more distinctly observable 
in individual monkeys than in any other ani- 
mals, although it is probable that a similar 
feeling may be part of the bond of association 
by which many animals are congregated toge- 
ther in the mode to be presently noticed. The 
intuitive perception of the signs of emotion 
or passion in the countenance and gestures 
which precedes and excites the tendency to 
imitation in man, is obviously common to us 
with many other animals. 

In fact, although we rigidly maintain the 
essential superiority of the intellect of man 
over that of all other animals, we have already 
stated that the greater number of the active 
powers of the human mind which furnish the 
chief motives to action are on the same footing 
with those which operate on the lower animals. 
Not only are our appetites similar to theirs, 
but the greater number of the desires of which 
we are conscious are either shared with, us by 
them, or at least would seem to belong to the 
same class as their instincts. Thus the desire of 
approbation is quite obvious at least in some 
of the domestic animals, and the desire of 
society, as observed: by Stewart, seems to act 
very generally, although variously, in the ani- 
mal creation. The desire of power may be 
thought to be more peculiar to man, and we 


16 


have every reason to believe that no other ani- 
mal can reflect on the possession of power in 
the abstract, or indulge in the imagination of 
scenes in which it is to be exerted, or rejoice 
in the acquisition of wealth of any kind, as 
the means of exercising power and procuring 
pleasure, independently of the actual enjoy- 
ment of them; but many of the practical 
exemplifications of this desire come into direct 
comparison with, and probably involve feelings 
very similar to, the instincts of animals. Thus 
the pleasure which men feel in exerting power 
over the elements around them may be seen, in 
the case of children, to be prior to the expe- 
rience of any practical advantage from the arts 
of architecture, of mechanics, or of navigation ; 
and it may be confidently asserted, that but for 
this pleasure attending the exercise of those arts 
(and which may be supposed to be very similar 
to that which animates the beaver, the bird, or 
the ant in their respective labours,) they could 
never have been prosecuted with success. So 
also the pleasure which man in all ages has felt 
both in hunting and destroying animals, and 
also in acquiring dominion over them and sub- 
jecting them to his power, is clearly quite 
different from the anticipation of the useful 
purposes to which, whether dead or living, they 
may be applied, and appears precisely similar, 
both in its nature and in its object or final 
cause, to some of the instincts of animals. 

Indeed, in conformity to what has been 
already said of the essential peculiarities of the 
human intellect, it is only those motives to 
action which imply the previous formation of 
general notions or abstract ideas, that we can 
regard as liar to man ; and we may accord- 
ingly state that the desire of knowledge (we 
may even say more specifically, of scientific 
knowledge, ‘ rerum cognoscere causas’ ) and the 
sense of obligation religious and moral, are 
the motives to action which we believe to be 
_— peculiar to the human race. 

he most important instinct of animals refer- 
able to this head, clearly and strongly felt like- 
wise by man, (although combined in his case 
with many other feelings,) is the instinct of 
congregation. More or less of the desire of 
society is seen in a great majority of animals; 
but we may refer to this head many actions of 
animals, wherein many individuals of the same 
species cooperate, of which the object is in 
many instances still obscure, -but to which the 
animals are impelled with an energy, and fre- 
quently a self-devotion, attesting the strength 
of the mental feeling, and completely super- 
seding their usual habits. Messrs. Spence and 
Kirby enumerate not less than five kinds of 
association of insects to form what they term 
imperfect societies. 

“ The first of these associations (for the sake 
of company only) consists chiefly of insects in 
their perfect state. The little beetles called 
whirlwigs,—which may be seen clustering in 
groups under warm banks in every river and 
every pool, wheeling round and round with 
great velocity, at your approach dispersing 
and diving under water, but as soon as you 
retire resuming their accustomed movements,— 


INSTINCT. 


Am 
= 


seem to be under the influence of the sociai 
principle, and to form their assemblies for no 
other purpose than to enjoy together in the sun- 
beam the mazy dance. Impelled by the same 
feeling, in the very depth of winter, even whe: 
the earth is covered with snow, the tribes of 
Tipulide (usually but improperly called | mats) 
assemble in sheltered situations at mid- 
where the sun shines, and form themselves into 
choirs that alternately rise and fall with rap 
evolutions. , - ~f 

“ Another association is that of males during 
the season of pairing. Of this nature seems 
to be that of the cockchafer and 
which, at certain periods of the year and hours 
of the day, hover over the summits of the trees 
and hedges like swarms of bees. > al 

“ The males of another rogt-devouring beetle 
( Hoplia argentea, F.) assemble by myriad: 
before noon in the meadows, when in th se 
infinite hosts you will not find a single female. 

** The next description of insect associations - 
is of those that congregate for the purpose of 
travelling or emigrating together. De Geer has 
given an account of the larve of certain gnats” 
(Tipule, L.) which assemble in considerable 
numbers for this purpose, so as to form a band 
of a finger’s breadth, and of one or two yards 
in length. And what is remarkable, while 
upon their march, which is very slow, they 
adhere to each other by a kind of glutine 
secretion. 

“ Kuhn mentions another of the 
the larve of which live in society and emigrate 
in files. 1 

“ But of insect emigrants none are 
celebrated than the locusts, which, when arrived 
at their perfect state, assemble in such numbers” 
as in their flight to intercept the sun-beams and — 
to darken whole countries, passing from one 
region to another, and laying waste kingdom 


after kingdom. 
their quarters 
indigenous: 


fernch 


“ The same tendency to shift 
has been observed in our little 
devourers, the Aphides. Pe 

“ It is the general opinion in Norfolk, — 
Mr. Marshall informs us, that the saw-fly 
( Tenthredo ) comes from over sea. A farmer 
declared he saw them arrive in clouds so as to 
darken the air; the fishermen asserted that 
they had repeatedly seen flights of them pass — 
over their heads when they were at a distance — 
from land, and on the beach and cliffs they 
were in such quantities that they might have 
been taken up by shovels full. Three miles in- 
land they were described as resembling swarms 
of bees. 

“ It is remarkable that of the emigratin 
insects here enumerated, the majority, for in- 
stance the Libellule, the Coccinelle, Carabi, 
Cicade, &c. are not usually social insects, but 
seem to congregate, like swallows, merely for 
the purpose of emigration. 7 

“ The next order of imperfect associations - 
is that of those insects which feed together. 

“« Two populous tribes, the great devastators _ 
of the vegetable world, the one in warm and 
the other in cold climates, to which I have 
already alluded under the head of emigrations, — 


Pa 


INSTINCT. 


—I mean Aphides and Locusts,—are the best 

examples of this order. 

4 much as the world has suffered from 

_ these animals, it is extraordinary that so few 
_ observations have been made upon their history, 
_ economy, and mode of proceeding. 
_ The egys of the locusts were no sooner 
: hatched in June,” says Dr. Shaw, “ than each 
_ of the broods collected itself into a compact 
body, of a furlong or more in square, and then 
_ marching directly forwards towards the sea, they 
_ let nothing escape them; they kept their ranks 
| _ dike men of war, climbing over as they advanced 
_ every tree or wall that was in their way; nay, 
| ‘they entered into our very houses and bed- 
_ chambers like so many thieves. A day or two 
i after one of these hordes was in motion, others 
_ were already hatched to march and glean after 
2 - Having lived near a month in this 
_ manner they arrived at their full growth, and 
threw off their nympha state by casting their 
outward skin.” “ The transformation was per- 
formed in seven or eight minutes, after which 
they lay for a short time in a torpid and seem- 
ingly languishing condition ; but as soon as the 
sun and the air had hardened their wings by dry- 
ing up the moisture that remained on them after 
casting their sloughs, they re-assumed their 
former voracity with an addition of strength 
and agility.” 

“ According to Jackson they have a govern- 
ment amongst themselves similar to that of the 
bees and ants; and when the king of the locusts 
rises, the whole body follow him, not one soli- 
fary straggler bemg left behind. But that 
locusts have leaders like the bees or ants, dis- 
tinguished from the rest by the size and splen- 
dour of their wings, is a circumstance that has 
not yet been established by any satisfactory 
evidence; indeed, very strong reasons may be 
urged against it.” 

“ The last order of imperfect associations 

_ approaches nearer to perfect societies, and is 
that of those insects which the social principle 
_ urges to unite in some common work for the 
benefit of the community. 
“ Many larve of Lepidoptera associate 
_ with this view, some of which are social only 
_ during part of their existence, and others during 
the whole of it. 

“ A still more singular and pleasing spectacle 
when their regiments march out to forage, is 
exhibited by the Processionary Bombyx. This 
moth, which is a native of France and has not 
yet been found in this country, inhabits the 
vak. Each family consists of from 600 to 800 
individuals. When young, they have no fixed 
habitation, but encamp sometimes in one place 
and sometimes in another under the shelter of 
_ their web; but when they have attained two- 
thirds of their growth, they weave for themselves 
acommon tent. About sun-set the regiment 
leaves its quarters; or, to make the metaphor 
harmonize with the trivial name of the animal, 
the monks their cenobium. At their head is a 
chief, by whose movements their procession is 
regulated. When he stops all stop, and pro- 
ceed when he proceeds; three or four of his 
immediate followers succeed in the same line, 

VOL. IIT. 


17 


the head of the second touching the tail of the 
first; then comes an equal series of pairs, next 
of threes, and so on as far as fifteen or twenty. 
The whole procession moves regularly on with 
an even pace, each file treading on the steps of 
those that precede it. If the leader, arnving 
at a particular point, pursues a different direc- 
tion, all march to that point before they turn.”* 

Examples of occasional associations, more 
or less resembling all these, and of which the 
object is in many instances still obscure, may 
be found in all the classes of the higher ani- 
mals, as is obvious, when we consider to how 
many tribes of animals the term gregarious is 
usually applied, e. g. to almost all the Rumi- 
nantia, some of the Pachydermata, and a few of 
the Rodentia. Some of the genus Muride (rats 
and mice) have been long known to migrate, 
occasionally, in a manner resembling the 
locusts. ‘ The general residence of the lem- 
ming,” says Pallas, “is in the mountainous 
parts of Lapland and Norway, from which 
tracts at uncertain periods it descends in im- 
mense troops, and by its incredible numbers 
becomes a temporary scourge to the country, 
devouring the grain and herbage, and com- 
mitting devastations equal to those of an army 
of locusts.” “It is observable that their chief 
emigrations are made in the autumns of such 
years as are followed by severe winters.” ‘The 
ground over which they have passed appears 
at a distance as if it had been ploughed, the 
grass being devoured to the roots in numerous 
stripes or parallel paths, of one or two spans 
broad, and at the distance of some yards from 
each other.” “ The army moves chiefly at night, 
or early in the morning. No obstacles that 
they meet in their way have any effect in 
altering their route, neither fires, nor deep 
ravines, nor torrents, nor marshes, nor lakes ; 
they proceed obstinately in a straight line, and 
hence many thousands perish in the waters.” 
“ If disturbed, in swimming over a lake, by oars 
or poles, they will not recede, but keep swim- 
ming directly on, and soon get into regular 
order again.” “In their passage over land, if 
attacked by men, they will raise themselves up, 
uttering a kind of barking sound, and fly at 
the legs of their invaders, and will fasten so 
fiercely on the end of a stick, as to suffer them- 
selves to be swung about without quitting their 
hold, and are with great difficulty put to flight.” 
‘“‘ The major part of these hosts is destroyed by 
various enemies, as owls, hawks, weasels, ex- 
clusively of the number that perish in the 
waters, so that but a small part survive to 
return, as they are sometimes observed to do, 
to their native mountains.” The campagnol, 
or short-tailed rat, has been known to com- 
mit similar ravages in France. It is obvious 
here, that under the influence of this instinct, 
and of the excitement of numbers (in which, 
as in our own race, the principle of imitation 
is probably much concerned) the usual motives 
to action of these animals are superseded, and 
their usual habits changed. 

We are still uncertain as to the use, or final 


* Introduction to Entomology, letter xvi. 
c 


18 


cause, of the various congregations of birds 
that we daily witness, and of the varying 
habits which they then exhibit—crows, e. g. 
herons, and many water birds, roosting and 
bringing forth their young in large irregular 
societies; the crows, besides, assembling at 
particular hours of the day, at all seasons ; 
some of the genus Parus, leptagagd the 
great and long-tailed titmouse, feeding in small 
flocks at all seasons ;—plovers and lapwings 
keeping separate during bs season of hatching 
and rearing their offspring, but assembling in 
flocks after their young have attained matu- 
rity ;—most of the birds of this country in the 
depth of winter associating in flocks much 
greater than can be necessary for the sake of 
warmth ;—the hen chaffinches, and perhaps the 
' females of other birds, congregating separately ; 
—many of these flocks consisting of multi- 
tudes moving quite irregularly, but all of them 
having apparently some means of intercom- 
munication or agreement;—some of them, as 
the starlings, performing very singular evo- 
lutions in concert; and many, as wild geese 
_ and other water-birds, always showing the dis- 
position to fly in regular lines. 

‘The greatest of all the congregations of birds 
are those of the migrating pigeons in America, 
described by Audubon, as forming clouds 
which pass over the whole extent of a town for 
several hours together, and as settling on ex- 
tensive districts of the woods in such multi- 
tudes as to cause much devastation among the 
branches. 

But the most extraordinary of all the asso- 
ciations of animals are those which have re- 
ceived the title of the perfect societies of in- 
sects,—the bees, wasps, hornets and ants in 
the order of Hymenoptera, and the white ants 
or termites, in that of Neuroptera. The most 
important facts as to them seem to have been 
ascertained, partly by numerous former ob- 
servers, but chiefly by the [lubers, Latreille, 
and others in the present age. 

The essential peculiarity of these associations 
of insects appears to be the complete sepa- 
ration of the males and females, on whom the 
propagation of the species depends, from the 
working members of the communities, by whom 
the habitations are constructed, and who pro- 
cure food both for the young and for the more 
perfect insects. In the case of the bees, the 
only prolific female is the queen-bee; the males 
are the drones; the working bees, constituting 
the mass of the community, are sterile females, 
and the larve and pupe are confined to the 
cells and helpless; the ants appear to differ 
from these only in the perfect females being 
much more numerous (only a few, however, 
being retained in each ant-hill); but the 
termites differ, in the larve and even the pupe 
being working members, the males and females, 
when brought to perfection, always wandering 
abroad, and one of each sex in the perfect 
state only existing in each nest, being in fact 
forcibly detained there. 

Among these animals there is also a separate 
class, believed to be analogous to the working 
bees, i. e. to be sterile females, larger than the 


INSTINCT. 


labourers, and which are thought to act exclu- 
sively as the soldiers of the community,—the 
smaller working ants (larve) always disap- 
pearing, and these larger and fiercer animals 
shewing themselves, when any of the 
are attacked.* 
These associations differ from all other 
existing among animals, in the extraordinar 
instinct of respect and devotion shewn by tl 
working members to the impregnated female, 
single in each swarm of ag and in 
nest of termites, and few in number in ea 
nest of ants,—and with this instinct most 
their other peculiarities seem to be connected. 
But it is justly observed by Mr. Spence, that 
if we suppose all the labours of the bees a 
the ants to be guided by instincts, we must ne- 
cessarily attribute to these animals a much 
greater number and variety of instinctive 
pensities, and more extraordinary modifications 
of them to suit varying circumstances of their 
condition, than to any of what are usually 
called the higher animals. i 
“In the common duck, one instinct lead: 
it at its birth from the egg to rush to the water 
another to seek its proper food; a third to pair 
with its mate; a fourth to form a nest; a ifth 
to sit upon its eggs till hatched; a sixth to 
assist the young ducklings.in extricating them 
selves from the shell ; odd seventh to defend 
them when in danger until able to provide for 
themselves: and it would not be easy as far 
as my knowledge extends, to add many more 
instinctive actions to the enumeration, or t 
adduce many specimens of the superior classes 
of animals endowed with a greater number. _ 
“ But how vastly more manifold are the 
instincts of the majority of insects! 
“ As the most striking example of the whole 
I shall select the hive-bee,—begging you te 
bear in mind that I do not mean to include 
those exhibited by the queen, the drones, or 
even those of the workers, termed by Huber 
ciriéres (wax-makers); but only to enumerate 
those Leg by that portion of the workers, 
termed by Huber nourrices or petites abeilles, 
upon whom, with the exception of making wax, 
laying the foundation of the cells, col 
lecting honey for being stored, the principal 
labours of the hive devolve. a 
‘By one instinct bees are directed to send 
out scouts previously to their swarming in 
search of a suitable abode; and by another to 
rush out of the hive after the queen that leads 
forth the swarm, and follow wherever she 
bends her course. Having taken possess f 
their new abode, whether of their own se 
or prepared for them by the hand of man, 
instinct teaches them to cleanse it from 
purities ; a fourth to collect propolis, and y 
it to stop up every crevice except the entrar 
a fifth to ventilate the hive for ing the 
purity of the air; and a sixth to keep a con-— 
stant guard at the door. 7 
“In constructing the houses and streets of © 
their new city, or the cells and combs, there are - 
probably several distinct instincts exercised 5 


. 


ay oe 


at ¥ 
all ime 


i 
he 


* Sce Spence und Kirby, vol. ii. p. 39, 


INSTINCT. 


but not to leave room for objection, 1 shall 


regard them as the result of one only: yet 


_ the operations of polishing the interior of the 
cells, and soldering their angles and orifices 
_ with propolis, which are sometimes not under- 

_ taken for weeks after the cells are built; and 


} 


: 


i 
i] 


‘ 


&! 


EEE ee 


5 


‘the obscure but still more curious one of var- 
nishing them with the yellow tinge observable 
in old combs, seem clearly referable to at 
least two distinct instincts. 

« In their out-of-door operations several dis- 


tinct instincts are concerned. By one they are 


to extract honey from the nectaries of 


_ flowers; by another to collect pollen after a 
_ process involving very complicated manipu- 
lations, and requiring a singular apparatus of 
brushes and baskets ; and that must surely be 
_ considered a third which so remarkably and 
_ beneficially restricts each gathering to the same 
plant. It is clearly a distinct instinct which 


‘Inspires bees with such dread of rain, that 
even if a cloud pass before the sun, they return 
to the hive in the greatest haste. 

“ Several distinct instincts, again, are called 
‘into action in the important business of feeding 
the young brood. One teaches them to swal- 
low pollen, not to satisfy the calls of hunger, 
but that it may undergo in their stomach an 


elaboration fitting it for the food of the grubs ; 


and another to regurgitate it when duly con- 
cocted, and to administer it to their charge, 
proportioning the supply to the age and con- 
dition of the recipients. A third informs them 
when the young grubs have attained their full 
growth, and directs them to cover their cells 
with a waxen lid, convex in the male cells, but 
nearly flat in those of workers, and by a fourth, 
as soon as the young bees have burst into day, 
they are impelled to clean out the deserted 
tenements and make them ready for new oc- 
cupants. 

“ Numerous as are the instincts already 
mentioned, the list must yet include those 
connected with that mysterious principle which 
binds the working bees of a hive to their 
queen :—the singular imprisonment in which 
they retain the young queens that are to lead 
off a swarm, until their wings be sufficiently 
expanded to enable them to fly the moment 
they are at liberty, gradually paring away the 
waxen wall that confines them to an extreme 
thinness, and only suffering it to be broken 
down at the precise moment required ;—the. 


attention with which in these circumstances 
they feed the imprisoned queen by frequently 


putting honey on her proboscis, protruded from 
a small orifice in the lid of her cell ;—the 
watchfulness with which, when at the period 
of swarming more queens than one are re- 
eet they place a guard over the cells of 

ose undisclosed, to preserve them from the 


jealous fury of their excluded rivals ;—the 


exquisite calculation with which they inva- 
riably release the oldest queens the first from 
their confinement ;—the singular love of mo- 
narchical dominion, by which, when two queens 
in other circumstances are produced, they are 
led to impel them to combat until one is de- 
stroyed;—the ardent devotion which binds 


19 


them to the fate and fortune of the survivor;— 
the distraction which they manifest at her 
loss, and their resolute determination not to 
accept of any stranger until an interval has 
elapsed sufficiently long to allow of no chance 
of the return of their rightful sovereign ;—and 
(to omit a further enumeration) the obedience 
which in the utmost noise and confusion they 
shew to her well-known hum. 

“ T have now instanced at least thirty dis- 
tinct instincts with which every individual of 
the nurses amongst the working-bees is en- 
dowed; and if to the account be added their 
care to carry from the hive the dead bodies of 
any of the community; their pertinacity in. 
their battles, in directing their sting at those 
parts only of the bodies of their adversaries 
which are penetrable by it; their annual autum-_ 
nal murder of the drones, &c. &c.— it is cer- 
tain that this number might be very consider- 
ably increased, perhaps doubled.”* 

To these instincts, in the case of some species 
of ants we shall certainly have to add those by 
which they are guided in carrying on a regular 
system of warfare, either with other hives of the 
same species or with other species, in subjuga- 
ting and bringing up as workers or slaves those 
that they have subdued, and likewise in sub- 
jecting to their dominion tribes of Aphides.+ 

But all this becomes still more surprising, 
because more at variance with the usual in- 
stincts of animals, when we consider the power 
of adapting their operations to changes in their 
circumstances, which such associations of in- 
sects possess. 

“ Tt is,” says Mr. Spence, “ in the deviations 
of the instincts of insects and their accommoda- 
tion to circumstances, that the exquisiteness of 
these faculties is most decidedly manifested. 
The instincts of the larger animals seem capable 
of but slight modification. They are either ex- 
ercised in their full extent or not at all. A 
bird, when its nest is pulled out of a bush, 
though it should be laid uninjured close by, 
never attempts to replace it in its situation ; it 
contents itself with building another. But in- 
sects in similar contingencies often exhibit the 
most ingenious resources, their instincts surpri- 
singly accommodating themselves to the new 
circumstances in which they are placed, in a 
manner more wonderful and incomprehensible 
than the existence of the faculties themselves.” 

This observation we support by various in- 
stances taken from the history of different in- 
sects ; but the most extraordinary are from the 
societies of insects of which we now speak ; 
and of these the following are only a specimen. 

“ The combs of bees are always at an uniform 
distance from each other, namely, about one- 
third of an inch, which is just wide enough to 
allow them to pass easily, and have access to 
the young brood. On the approach of winter, 
when their honey-cells are not sufficient in 
number to contain all the stock, they elongate 
them considerably, and thus increase their capa- 


* Introduction to Entomology, vol. ii. p. 498 
et seq. } 
t Introd, to Entomology, letter xvii. 
c 2 


20 


city. By this extension the intervals between 
the combs are unavoidably contracted; but in 
winter well-stored magazines are essential, while 
from their state ot comparative inactivity spa- 
cious communications are less necessary. On 
the return of spring, however, when the cells 
are wanted for the reception of eggs, the bees 
contract the elongated cells to their former 
dimensions, and thus re-establish the just dis- 
tances between the combs which the care of 
their brood requires. But this is not all. Not 
only do they elongate the cells of the old combs 
when there is an extraordinary harvest of honey, 
but they actually give to the new cells which 
they construct on this emergency, a much 
greater diameter as well as a greater depth. 

“ The queen-bee, in ordinary circumstances, 

laces each egg in the centre of the pyramidal 

ttom of the cell, where it remains fixed by 
its natural gluten: but in an experiment of 
Huber, one whose fecundation had been re- 
tarded, had the first segments of her abdomen 
so swelled that she was unable to reach the 
bottom of the cells. She therefore attached her 
eggs (which were those of males) to their lower 
side, two lines from the mouth. As the larve 
always pass that state in the place where they 
are deposited, those hatched from the eggs in 

uestion remained in the situation assigned 

them. But the working bees, as if aware that 
in these circumstances the cells would be too 
short to contain the larve when fully grown, 
extended their length, even before the eggs 
were hatched. 

“ The working bees, in closing up the cells 
containing larve, invariably give a convex lid 
to the large cells of drones, and one nearly flat 
to the smaller cells of workers; but in an ex- 
periment instituted by Huber to ascertain the 
influence of the size of the cells on that of the 
included larve, he transferred the larve of 
workers to the cells of drones. What was the 
result? Did the bees still continue blindly to 
exercise their ordinary instinct? On the con- 
trary, they now placed a nearly flat lid upon 
these large cells, as if well aware of their being 
occupied by a different race of inhabitants.” 

But the most extraordinary of all these varia- 
tions of the operations of bees are seen in two 
cases which have been ofien produced for the 
sake of experiment, and of which the result 
appears to have been repeatedly and carefully 
observed. — 

“ If a hive be in possession of a queen duly 
fertilized, and consequently sure, the next sea- 
son, of a succession of males, all the drones, 
towards the approach of winter, are massacred 
by the workers with the most unrelenting fero- 
city. This would seem to be an impulse as 
naturally connected with the organization and 
very existence of the workers, as that which 
leads them to build cells or store up honey. 
But however certain the doom of the drones if 
the hive be furnished with a duly fertilized 
queen, their undisturbed existence through the 
winter is equally certain if the hive has lost 
its sovereign, or if her impregnation has been 
so retarded as to make a succession of males in 
the spring doubtful ; in such a hive the workers 


INSTINCT. 


do not destroy a single drone, though the hot 
test persecution rages in all the hives around 
them.” 
Again, “ in a hive which no untoward event 
has deprived of its queen, the workers take no 
other active steps in the education of her su 
cessors,—those of which one is to a el 
place when she has flown off at the of a 
new swarm in spring,—than to prepare a certam 
number of cells of extraordinary capacity fe 
their reception while in the egg, and to feed 
them when become grubs with a peculiar food 
until they have attained maturity. ‘This, th 
fore, is their ordinary instinct ; and it may hap 
pen that the workers of a hive may have no neces= 
sity, for a long series of successive generations, 
to exercise any other. But suppose them tol 
their queen. Far from sinking into that imac 
tive despair which was formerly attributed t 
them, after the commotion which the rapidly- 
circulated news of their calamity gave birth to 
has subsided, they betake themselves with an 
alacrity from which man, when under misfe 
tune, might deign to take a lesson, to the repa- 
ration of their loss. Several ordinary cells are 
without delay pulled down and converted into 
a variable number of royal cells, capacic 
enough for the education of one or more queen 
grubs selected out of the unhoused working 
grubs—which in this pressing et y are 
mercilessly sacrificed—and fed with ppre 
priate royal food to maturity. Thus sure of 
once more acquiring a head, the hive return te 
their ordinary labours, and in about sixte 
days one or more queens are produced, one 
which steps into day and assumes the reins of 
state.” if 
There can be no doubt that the perfect order 
and regularity seen in all the operations ¢ 
these societies of insects could not be main- 
tained without some mode of communication 
among the different individuals concerned in~ 
these operations ; and it appears di hi 
such means of communication exist, that 
it is in consequence of their being exercised, 
for example, that a swarm of bees, when it 
leaves a hive, takes the direction to a spot pre~ 
viously fixed on, and carefully examined, oy a 
small number of scouts, as 0 by I 


Knight.* \ ht} 
duly considered, we 


When such rig eh cons te 
cannot be surprised to find so intelligent a na- 
turalist as Mt. Spence acknowledging that he 
had at one time arranged them as indications 
of reason in these Peper on further 
consideration, we shall probably see cause to 
acquiesce in ‘his later and more matured judg 
ment, which cere reg to strictly ix oa 
tive, although singularly varying propensities; — 
chiefly on foo grounds, which exactly corre-— 
sean to what was stated in the beginning of 
this paper as the most distinctive characters of — 
instinct: 1. that although various contrivances 
are fallen on by all bees to enable them to con- — 
tinue their usual operations under varying ex- — 
ternal circumstances, yet there is no such v: 4 
observed either in the conduct of individuals © 


» +18 


* Phil. Trans. 1807. 


INSTINCT. 


of the species or in the conduct of different 
communities, as we cannot doubt must occur 
if the inhabitants of every hive were guided, on 
‘such unusual occasions, by processes of reason- 
ing, by observation of the laws of nature, by 
experience, and anticipation of the effects of 
their actions. If such mental processes were 
their guide, we should certainly observe a diffe- 
rence in the conduct of experienced workers, 
and of those just emerged from their pupe ; 
and we should observe some variety in the ex- 
 pedients adopted in different hives for meeting 
- such accidents or difficulties. 2. While the 
“Varying operations of these animals for one 
§ vu: end, the preservation of their own 
lives and the perpetuation of their species, are 
‘planned and combined in such a manner as to 
“Indicate consummate intelligence as to what is 
essential for that purpose, all these indications 
of instinct are limited to that object, and we 
“see no evidence of the exercise of their senses 
“suggesting to them any other trains of thought, 
or exciting them to the prosecution of other 
objects, such as a number of human intellects 
capable of planning and executing such works 
would certainly, sooner or later, attempt to 
accomplish. The degree of uniformity seen in 
their operations, and the limitation of the ob- 
jects on which their faculties are exerted, are 
therefore our reason for thinking (although we 
do not wish to express ourselves with absolute 
confidence on the subject) that the mental pro- 
cesses concerned, even in those the most elabo- 
ae and artificial of the works of animals, be- 
long to the same class as those notions of man 
“aa are prompted by his instinctive propen- 
sities as distinguished from his reason. 
_ At the same time it ought to be stated, that 
‘erga are many acts of individual animals, or 
: 


of particular communities, in which we must 
admit that, although instinct is concerned, it 
‘must be guided by mental operations, in which 
“short processes of reasoning, involving certain 
general ideas, must have been concerned. 
Several instances, quoted by Mr. Spence, seem 
hardly to admit of any other interpretation, 
e.g. the following from Huber. The bees of 
‘some of his neighbours protected themselves 
‘against the attacks of the death’s-head moth, 
Sphinx atropos,) by so closing the entrance of 
‘the hive with walls, arcades, &c. built of a 
ixture of wax and propolis, that these ma- 
uders could no longer intrude themselves. 
ure instinct would have taught “ the bees 
fortify themselves on the first attack ; if the 
ccupants of a hive had been taken unawares 
by these gigantic aggressors one night, on the 
“second at least the entrance should have been 
barricadoed. But it appears clear, from the 
“statement of Huber, that it was not until the 
ives had been repeatedly attacked, and robbed 
of nearly their whole stock of honey, that the 
dees betook themselves to the plan so success- 
fully adopted for the security of their remaining 
treasures; so that reason, taught by experience, 
seems to have called into action their dormant 
instinct.” 
_ Again, “a German artist, a man of strict vera- 
city, states that in his journey through Italy he 


. 


21 


was an eye-witness to the following occurrence. 
He observed a species of Scarabeus busily en- 
gaged in making, for the reception of its egg, a 
pellet of dung, which when finished it rolled to 
the summit of a small hillock, and repeatedly 
suffered to tumble down its side, apparently 
for the sake of consolidating it by the earth 
which each time adhered to it. During this 
process the pellet unluckily fell into an adjoin- 
ing hole, out of which all the efforts of the 
beetle to extricate it were in vain. After several 
ineffectual trials, the insect repaired to an ad- 
joining heap of dung, and soon returned with 
three of his companions. All four now applied 
their united strength to the pellet, and at length 
succeeded in pushing it out; which being 
done, the three assistant beetles left the spot 
and returned to their own quarters.””* 

A number of other instances have been col- 
lected by Mr. Duncan. 

“ Professor Fischer has published an account 
of a hen, which hen made use of the artificial 
heat of a hotbed to hatch her eggs.” 

“A fact is stated by Reaumur of some ants, 
which, finding they could derive heat from a 
bee-hive, contrived to avail themselves of it by 
placing their larve between the hive and an 
exterior covering.” 

“ Dr. Darwin observed a wasp with a large 
fly nearly as big as itself; finding it too heavy, 
it cut off the head and the abdomen, and then 
carried off the remainder, with the wings at- 
tached to it, into the air: but again finding the 
breeze act on the wings, and impede its pro- 
gress, it descended, and deliberately cut off the 
wings. Instinct might have taught it to cut off 
the wings of all insects previous to flying away 
with them ; but here it attempted to fly with 
the wings on, was impeded by a certain cause, 
discovered what that cause was, and alighted 
to remove it. Is not this a comparison of 
ideas, and deducing consequences from. pre- 
mises ?” 

“ M. de la Loubitre, in his relation of Siam, 
Says, that in a part of that kingdom which 
lies open to great inundations, all the ants make 
their settlements on trees; no ants’ nests are to 
be seen any where else. Whereas in our 
country the ground is their only habitation.” 

“ We sometimes kill a cockroach,” says 
Ligon in his history of Barbadoes, quoted by 
Spence, “and throw him on the ground, and 
mark what the ants will do with him; his body 
is bigger than a hundred of them, and yet 
they will find the means to lay hold of him 
and lift him up; and having him above 
ground, away they carry him; and some go 
by as ready assistants if any be weary, and 
some are officers that lead and shew the way ; 
and if the van-couriers perceive that the body 
of the cockroach lies across, and will not pass 
through the hole or arch through which they 
mean to carry him, order is given, and the body 
turned endways, and this is done a foot before 
they come to the hole, and without stop or 


stay.” + 


* Introd. to Entomology, vol. ii. p.525. 
t History of Barbadoes, p. 63. 


22 


Colonel Sykes communicated to Mr. Kirby 
a singular anecdote of some of the black ants 
in India, which had been prevented, for some 
time, from getting to some sweatmeats, by 
having the legs of the table on which they 
stood immersed in basins filled with water, and 
besides painted with turpentine. After a time, 
however, the ants again reached the sweatmeats ; 
and it was found that they did so by letting 
themselves drop from the wall, above the table, 
on the cloth which covered it.* 

“ In Senegal, where the heat is great, the 
ostrich neglects her eggs during the day, but 
sits on them at night. At the Cape of Good 
Hope, however, where the degree of heat is 
less, the ostrich, like other birds, sits upon her 
eggs both day and night.” 

“ Rabbits dig holes in the ground for warmth 
and protection; but after contmuing long in a 
domestic state, that resource being unnecessary, 
they seldom burrow.” 

“ A dog in a monastery, perceiving that the 
monks received their meals by rapping at a 
buttery-door, contrived to do so likewise, and 
when the allowance was pushed through, and 
the door shut, ran off with it. This was re- 
peated till the theft was detected.” 

“ A dog belonging to Mr. Taylor, a clergy- 
man, who lived at Colton, near Wolseley 
Bridge, was accused of killing many sheep. 
Complaints were made to his master, who as- 
pore. that the thing was impossible, because 
he was muzzled every night. The neighbours 
persisting in the charge, the dog one night was 
watched, and he was seen to draw his neck out 
of the muzzle, then to go into a field, and eat 
as much of a sheep as satisfied his appetite. 
He next went into the river to wash his mouth, 
and returned afterwards to his kennel, put his 
head into the muzzle again, and lay very qui- 
etly down to sleep.” 

“ T observed,” says the Rev. J. Hall in his 
Travels in Scotland, “two magpies hopping 
round a gooseberry bush, in a small garden 
near a poor-looking house, in a peculiar manner, 
and flying in and out of the bush. I stepped 
aside to see what they were doing, and found 
from the poor man and his wife, that as there 
are no trees all around, these magpies several 
succeeding years had built their nest, and 
brought up their young, in this bush; and that 
foxes, cats, hawks, &c. might not interrupt 
them, they had barricadoed not only their nest, 
but had encircled the bush with briers and 
thorns in a formidable manner; nay, so com- 
pletely, that it would have cost even a fox, 
cunning as he is, some days’ labour to get into 
that nest. 

“ The materials in the inside of the nest 
were soft, warm, and comfortable; but all on 
the outside, so rough, so strong, and firmly en- 
twined with the bush, that without a hedge- 
knife, hatch-bill, or something of the kind, 
even a man could not, without much pain and 
trouble, get at their young; as from the outside 
to the inside of the nest extended as long as my 
arm. 


* Bridgewater Treatise, vol. ii. p. 342. 


INSTINCT. 


“ These magpies had been faithful to ong 
another for several summers, and drove of 
their young, as well as every one else who at 
tempted to take possession of their nest. Thi 
they carefully repaired and fortified in~ 
spring with strong rough prickly sticks, th 
they sometimes brought to it by uniting the 
force, one at each end, pulling it along, whe 
they were not able to lift it from the ground.” 

uch examples leave no reasonable gro 
for doubt, that on certain subjects at lea 
some animals are capable of short and simp! 
processes of reasoning or of paar r 
ap to imply the tion of genera 
cathe. and the’ formation OF certain gene 
ideas, and that the difference, formerly st 
between the operations of their minds am 


ours, in that respect, is one of degree only, no 
absolutely of kind. But this admission, 


must be remembered, does by no means di 
minish the force of the considerations former 
adduced to establish the essential distinctior 
between the instinctive determinations promp 

ing the usual actions of animals, and some 
those of men, and those volitions, whether ii 
animals or men, which are consequent on th 


exercise of reason, and on such anticipation 0 
their consequences as a process of reasonin 
only can afford. 

It is worth while to mention that in se 
instances animals have been thought to be pos 
sessed of a faculty resembling reason, on ai 
count of actions, very wonderful indeed, t 
which the possession of reason would not have 
enabled them to perform. Thus there are 
many instances of animals finding their way t 
their usual place of residence, being re 
moved from it in such a way as to the 
mere act of recollection guiding n bac 
Mr. Duncan+ mentions having seen a pig 
which had been brought from London, k 
loose on Magdalen Bridge, in Oxford. “: 
flew first towards the north, but after se 
gyrations in the air, it flew directly east, 
reached London within the appointed time 
which was, I believe, three hours.” And Mr 
Spence gives an anecdote, well authenticated 
of an ass from Gibraltar, thrown overboard fror 
a vessel at a distance of 200 miles, ( 
swam ashore, and in a few days 
sented himself for admission when the ga 
the fortress was opened in the morning. Ty 
instances, equally extraordinary, have bet 
stated on unexceptionable authority to the pre 
sent writer; one of a pointer which had bee 
sent from Durham to the neighbourhood « 
Edinburgh by sea, and made his way back in 
few days by land, to his master’s house in th 
former county ;—the other of a kitten, whit 
had been brought in a carriage a distance | 
above forty miles, to Edinburgh, and made’ 
way back in a few days to its place of nativit 
in Stirlingshire, in doing which it must hav 
crossed several bridges. Similar facts h 
been ascertained in several instances as t 
sheep ; and the cases of the swallow and of t 


iv 
~ _ 


A ze 


- 44 
* Duncan’s Lectures on Instinct. al 
+ Ibid. 


cen 


a a in, 


INSTINCT. 


salmon, returring to the spots where they were 
bred after their long migrations, are clearly 
analogous. 

But in such cases it is obvious that the pos- 
Session of reason could not have enabled these 


animals, alone and unassisted, to find their 


way; neither was the result properly referable 
to instinct, this term being properly applicable 
only to the feeling of attachment which 
rompted the return home, not to the know- 
ledge which the animals somehow acquired 
where their home was to be found. The only 
term properly applicable to the acquisition of 
this knowledge is intuition, and they should be 
added to other facts, which shew that in va- 
rious instances animals acquire, by the exercise 
of their senses, information as to external 
things, more obviously distinct from the sensa- 
tions themselves, than those perceptions which 
Dr. Reid has so clearly shewn to be strictly 
intuitive inferences, drawn by the human in- 
tellect from the intimations of the senses. 
There is yet another fact well ascertained of 
late years regarding the instincts of animals, 
which we must not omit to state, because it is 
the only one which gives plausibility to the 
notion of Darwin, that sensations and experi- 
ence would explain the whole phenomena of 
instinct. This is the fact, which seems well 
ascertained as to certain animals at least,— 
which is very probably true of man, and sus- 
ceptible of important practical application in 
his case,—that the acquired habits of one gene- 
ration may become instinctive propensities in 
the next. Thus it has been often observed 
that the progeny of well-trained pointers learn 
to point with very little instruction. It is 
stated by Darwin that dogs in the wild state, 
both in Africa and America, have been observed 
not to bark, that they gradually acquire that 
note from European dogs ; and that the latter, 
when turned loose, retain it for three or four 
generations, and gradually lose it ; and it has 
been ascertained that in South America, when 
horses which had been taught to amble had 
been allowed to run wild, their progeny for two 
or three generations continued to practice that 
pace, and then lost it.* Of the existence of 
such acquired instincts, therefore, there can be 
no doubt; but it need hardly be said that it is 
quite incompetent to explain the perfect uni- 
formity and the skilful contrivance observed in 
the instincts of animals; both because its ope- 
ration seems too limited, and because that sup- 
position would only remove the difficulty as to 
the continuance of the instinctive operations 
from: the present to the early generations of 
animals. 
In reviewing the varied phenomena of which 
we have given this hasty sketch, it is impos- 
sible not to be struck with the very important 
share which they occupy in the provisions by 
which the earth’s surface is made a scene of 
continual activity and change. It is interest- 
ing to reflect on the different powers, to the 


__* This principle has been lately investigated and 
illustrated by Mr. Knight, in a paper read before 
the Royal Society of London. 


23 


operation of which we can trace the unceasing 
changes continually taking place around us, 
and particularly on the gradation, and very 
gradual transition that may be observed, from 
those by which inanimate matter is continually 
moved and changed, up to those which ema- 
nate from the intellect of man. By the ori- 
ginal impulse given to the world, and by the 
laws of gravitation and of motion impressed 
on al! matter, the greater and more striking 
movements of the inanimate world around us 
are continually determined ; and by the laws 
of chemistry, these movements are made sub- 
servient to constant changes in the composition 
of the inanimate world. Again, by the laws 
which were impressed on the lower class of 
living beings at the time of their introduction 
into the world, and by the consequently in- 
cessant reproduction of vital affinities, which 
it is in vain to attempt to resolve into the che- 
mistry of dead matter, a constant succession 
of living vegetable structures is determined, 
merely by the agency of air and water, heat 
and light, on those already existing. By the 
peculiar chemical operation of these living 
structures, the air, the water, and all the ma- 
terials of the earth’s surface are subjected to 
pee and continual changes, implying slow 
ut incessant movements, which seem clearly 
to indicate attractions and repulsions, peculiar 
to the state of vitality. It is still perhaps 
doubtful whether in the case of vegetables a 
property of vital contraction is to be added to 
the active powers of nature. In immediate 
but still obscure connection with the lowest of 
the vegetable creation are the lowest of the 
animals, where we see the first and slightest 
indications of sensations, and the feeblest mo- 
tions consequent on sensations, which we judge 
to be similar to those that we ourselves ex- 
perience and excite; and here also the vital 
power of contraction, on which the whole life 
and- activity of animals essentially depends, 
first clearly manifests itself. Then tracing the 
animal creation upwards, we find that the 
world contains an infinite number and variety 
of sentient beings, the provisions for whose 
enjoyment we may well believe to have been 
the main object of Providence in all the ar- 
rangements on the surface of the earth; and to 
which are granted, in a pretty uniform grada- 
tion, more and more of the sensations and 
mental faculties by which nature is made 
known, and of the powers by which she may 
be controlled, until we arrive at the intellect 
and the capacity of Man. 

It appears farther that the maintenance, and 
reproduction, and the very existence of these 
animal structures are entrusted in part to the 
sensations of which they are made susceptible, 
and to the voluntary powers with which they 
are invested; but that the introduction of these 
spontaneous powers into the regulation of their 
ceconomy is so very gradual, that it is hardly 
possible to say where the movements which 
result only from physical (although vital) 
causes terminate, and those which are excited 
by mental acts begin;— hardly possible, for 
example, to say, at least as to many animals, 


24 


whether the reflex function of Dr. Mar- 
shall Hall, on which respiration, degluti- 
tion, the evacuation of the bowels and blad- 
der, &c. depend, is to be regarded as the re- 
sult of a merely physical impression on the 
nerves and spinal cord, like the impression of 
blood on the heart; or whether the sensations 
which naturally accompany these actions are, 
in the natural state, of the cause which 
excites them. But that even when the volun- 

wers of animals are certainly the means 
employed for the ends of their creation, they 
are still very generally guided by the superior 
intelligence which has framed both theirphy- 
sical and mental constitution, and which rules 
the mental but instinctive efforts consequent 
on the sensations that are felt, as surely as the 
laws of muscular contraction rule the move- 
ments of the heart; and it is into the hands of 
man alone that the reins of voluntary power 
are absolutely resigned. 

And when we thus pass in review the sen- 
sorial and voluntary powers of animals, we 
are naturally led to the question, whether there 
is really in our Own case so great an exception 
to those laws of nature which regulate all the 
other members of the animal creation; whe- 
ther, admitting the essential superiority of the 
intellect or reason of man, the different desires 
and motives to action, which are implanted in 
him, are not equally subject to the control of 
the power that gives them, and whether their 
consequences are not as exactly ruled by laws 
and as fully anticipated, as those of the in- 
stincts of animals. 

Without entering fully on this abstruse ques- 
tion, we would take the liberty of remarking, 
in the view of placing it in its simplest form 
before our readers, that as the intimations of 
our own consciousness are the ultimate foun- 
dation of all the knowledge that we have or 
ean have of our own minds, and as certain of 
the intuitive principles of belief which our 
minds naturally suggest to us must be trusted, 
if we are to inquire into the subject at all ; 
so the only question that can be reasonably 


proposed on this point is, whether there is any - 


good reason for suspecting that the belief of 
our own free-will, which naturally attends cer- 
tain of the operations of our minds, is a de- 
ception; and that the analogy of other ani- 
mals is only applicable to the subject in so 
far as it can throw light on that question. 

Now, we find that the works of man, which 
we ascribe to his reason, and in the execution 
of which the consciousness of his free-will 
intervenes, are essentially different from those 
which we ascribe to the blind instincts of ani- 
mals, in the total absence (already noticed) of 
that uniformity which is so leading a charac- 
teristic of the effects of the latter; and we may 
reasonably assert that this is just the difference 
to be expected between the works of man and 
of other animals, on the supposition that the 
power concerned in the former is not subject 
to the direct influence and control of that 
higher intellect, by which the Jaws and limits 
of that concerned in the latter are irrevocably 
set; and therefore, that there exists no such 


INSTINCT. 


analogy between the works of man and of other 
animals as need induce us to suspect, that thi 
evidence of his consciousness on the point it 
question is not to be trusted. “ 
At the same time it ought to be observer 
and perhaps has not been duly remarked, ne 
only that the desires which are the principé 
motives to human action, are analogous to 
sometimes identical with, the instincts of ar 
mals, (many of them having been eviden 
given him with the same intention, and ith 3 
clear perception of their general result on fi 
condition,)—but also that the constitution 
the human mind appears from the intimation 
of our own consciousness to be such, as to 
allow of interposition of a superior power 
controlling in a certain degree the will ¢ 
without making itself obvious to his min 
For it is admitted by the soundest metaphy 
sicians, that the only truly voluntary po 
which we are conscious of ing over t 
train of thought in our minds, and therefore 
ultimately over many of our actions, operate 
only indirectly.* We have no power of de 
termining the thoughts that succeed one an 
ther or regulating the order of their succes 
sion ; and although various laws of association 
have been laid down, by which many of the 
component parts of the train appear to be con- 
nected, yet it will hardly appear to any om 
who reflects on the operations of his mind, 
that a// the thoughts which succeed one ano- 
ther can be ascertained to have such bonds o 
connection with one another. At all events, 
the only strictly voluntary power which we 
are conscious that we possess, is that of singlin; 
out and detaining any particular portion of the 
train, whereby it may be made to predominate 
in the mind, and to produce practical results 
which might not otherwise have followed; and 
even this kind of influence over the train of 
thought is not exercised exclusively by volition, 
but is produced in a great measure also by 
other causes, physical and moral. Nowif this” 
be so, how can we deny the possibility of a 
superior intelligence retaining a power of con- 
trolling the acts of any individual human mind, 
or of any number of minds, either by suggest- 
ing particular thoughts, or by causing the mind 
to dwell upon particular thoughts in preference 
to others, without its sense of its own volun- 
tary power being interrupted or withdrawn,—= 
nay, without the spontaneous voluntary power 
being really suspended, the only difference 
being in the degree of influence which it exerts 
over the train of thought and consequent 
litions ? nak. 
It has been said that the expression in Pope’s 
Universal Prayer— Raat 


az 


* «« So completely is the current of th in 
the mind,” says Stewart, ‘‘ subjected to physical 
laws, that it has been justly by Lor 
Kames that we cannot, by an effort of our will, 
call up any one thought, and that the train of our 
ideas depends on causes which operate in a man- 
ner inexplicable by us, ‘This observation, although 
it has been censured as paradoxical, is almost self- 
evident ; for to call up any particular thought sup- 
poses it to be already in the mind.” — Elements, 
ch, v. sect, 3. af 


INSTINCT. 


« And binding nature fast in fate, 
Left free the human will,” ‘ 
is inconsistent with a striking passage in the 
Essay on Man :-— 
*« Who knows but He whose hand the lightning 
forms, 
Who heaves old ocean, and who wings the 
storms, 
Pours fierce ambition in a Czsar’s mind, 
Or turns young Ammon loose to scourge man- 
.- kind?’ 
But if the foregoing statement of the mode 


3 action of the only voluntary power which we 


_ are conscious of possessing over the train of our 
thoughts is correct, it does not appear possible 
_ to deny that ambition or any other passion may 
be infused into any human mind, without de- 
_ stroying the consciousness, or suspending the 
action of that voluntary power. And if we 
_ reflect on the characteristics of many nations 
that have appeared on the earth’s surface—on 
the taste and genius of the Greeks, the mili- 
_ tary spirit of the Romans, the restless energy 
__ of the northern nations, the maritime adven- 
ture and commercial enterprise of Britain and 
America—and contrast these with the stationary 
civilization of China, or the languid, if not re- 
trograde condition of Italy, Spain, or Greece— 
is it unreasonable to suppose that the designs of 
Providence as to the progress of the human 
race are sometimes carried into effect by an oc- 
casional infusion into many mdividuals of our 
species, of feelings and desires, of the ultimate 
_ object of which they have as little perception. 
_ as animals have of the purposes of their in- 
stincts? But to prosecute this speculation 
farther would be foreign to the object of this 
_ paper. 
~ It is still to be remarked, in regard to in- 
stincts, that they have been long and justly 
} regarded as among the most important pheno- 


_ mena in nature, in reference to the doctrine of 
_ final causes, or the inferences of design, and of 
__ the adaptation of means to ends in the arrange- 
_ ment of the universe; and it is important to 
set in as clear a view as possible the proper use 
to be made of them in that enquiry. 

Tn fact, the whole plan of the construction of 
_ all the different classes of animals bears refe- 
rence to the instincts with which they are en- 
dowed, and would be useless without them. 
If the fangs and claws of the lion, the jaws 
and stomachs of the ox or the camel, or the bill 
and gizzard of the turkey, are admirably 
adapted for the prehension and subdivision of 
their respective aliments, as well as their organs 
of digestion for the assimilation of their food, 
all these provisions would have been useless, 
_ but for the instincts-which nature has im- 
; planted in these animals, by which their proper 


nourishment is sought, and the first part of the 
process of its assimilation is directed. 

The mutual adaptation of instincts to struc- 
ture, of structure to instincts, and of both to 
the ends of their creation throughout every 
part and function of an animal, and throughout 
every grade of the animal creation, has been 
illustrated by many authors, but perhaps most 
efficiently by Paley, as the most satisfactory of 
all the indications of the adaptation of means 


25 


to ends which the study of the universe pre- 
sents. 

It is indeed so clearly the fact that all the 
arrangements of the structure of an animal are 
subordinate to the instincts with which it is 
endowed, that the whole study of Comparative 
Anatomy, and the whole classification of ani- 
mals in so far as it is founded on their varieties 
of structure, require to be regulated by this 
consideration. The general principle by which 
the details of these sciences are held together 
may be stated to be this:—that while nature 
has observed a certain unity of plan in the con- 
struction, certainly of all the vertebrated, per- 
haps to a certain degree of all, animals, she has 
likewise introduced in all parts of the scale 
just such modifications of that plan as the si- 
tuation in which each animal is placed, and the 
office it has to perform, or as the French ex- 
press it, as the conditions of its existence, 
demand ; and then has implanted in it pre- 
cisely such instincts as are required to enable it 
to maintain itself—to turn those provisions to 
account—to enjoy its allotted portion of sen- 
sitive pleasure, and to fulfil the other objects of 
its creation, under those conditions. 

The study of the instincts of animals may 
be said, therefore, to hold a necessary interme- 
diate place between the study of their struc- 
ture, and that of the ends or objects of their 
creation—the structure being subordinate to 
the instincts, as these are subordinate to the 
objects of existence ; and it is by attending to 
them that the immense extent and infinite va- 
riety of the adaptation of means to ends in the 
animal creation is perhaps most distinctly per- 
ceived. 

It is stated by Mr. Whewell, that although 
the study of Final Causes has been often re- 
jected from the science of Physiology, yet 
it has been found impossible to keep them se- 
parate. ‘The assumption of final causes in 
this branch of science is so far from being ste- 
rile, that it has had a large share in every disco- 
very which is included in the existing mass of 
knowledge. The doctrine of the circulation of 
the blood was clearly and professedly due to 
the persuasion of a purpose in the circulatory 
apparatus.”* But there appears to be some 
ambiguity in this statement. The term 
physiology is properly applied to the in- 
vestigation of the physical causes of the 
phenomena of life—of the powers which 
are in operation, and the conditions under 
which they operate, in producing these phe- 
nomena. It is true that the different func- 
tions of life are dependent on one another in 
any individual animal ; and the science of phy- 
siology is most conveniently taught by arrang- 
ing their functions in the order of their de- 
pendence, and assigning, therefore, the final 
cause of each, after explaining the manner in 
which it is carried on. It is true, also, that the 
study of the uses to which the different func- 
tions are subservient, i. e. the study of final 
causes, has often led to the detection of phy- 
sical causes in this as in other sciences.. But 


* Hist. of the Inductive Sciences, vol. iii. p. 467, 


26 


the final cause cannot be substituted for the 
physical in physiology any more than in other 
sciences; and this is what was meant by the 
assertion of Bacon, that the doctrine of final 
causes is sterile. The object of physiology is 
to explain, not why, but how, the various func- 
tions of life are carried on. But when the laws 
of life are even partially ascertained, and their 
application understood, i. e. when physiolo- 
gical facts are referred to their physical causes, 
they afford many proofs of design and con- 
trivance, and so furnish a most important ad- 
dition to the general science of final causes. 

The science, relative to living bodies, which 
may truly be said to have its foundations laid in 
the study of final causes, is the science of Com- 
parative Anatomy, or of animal morphology; 
1. e. the exposition of the modifications which 
the general type of animal structure, and the 
plan of the functions carried on in that structure, 
undergo in the different classes of animals, and 
by means of which the objects of the animal cre- 
ation are accomplished by the laws of physio- 
logy throughout the whole extent of creation. 
These modifications are determined by the cir- 
cumstances in which animals are placed on the 
one hand, and by the purposes which they are 
to serve in the creation on the other. Every 
variation of structure has its use, in reference to 
one or other of these objects, and the branch of 
natural history which consists in the descrip- 
tion and arrangement of these varieties cannot 
be properly treated otherwise than by keeping 
their uses constantly in view. 

Thus, in regard to the function of digestion 
in the higher animals, its physiology, properly 
speaking, consists in reference to the laws of 
sensation, of instinct, of muscular motion, of 
secretion, as modified by changes in the condi- 
tion of the nervous system, of absorption, and 
of vital affinities and assimilation so far as 
they are known, by which the reception of 
aliment, and the changes on the aliment re- 
ceived into the body are effected; in this en- 
quiry our object is explanation, and however 
useful the observation of the purpose served by 
the organs of digestion may be, in suggesting 
enquiries or experiments by which the laws of 
which we are in quest may be made out, it is 
an interruption, not an assistance, to refer to 
these purposes, or to the importance of the 
function in the animal economy, as if we thus 
obtained an explanation of the phenomena : 
but when these different laws of vital action 
are explained, their adaptation to the object in 
view is properly stated as a branch of the doc- 
trine of final causes. And when we trace the 
modifications which the organs and function of 
digestion undergo in the different tribes of ani- 
mals, in the carnivorous, the herbivorous, and 
the graminivorous,—in the quadruped, the 
bird, the fish, the insect, the polype, &c., and 
compare these with the provisions for assimila- 
tion and nutrition in vegetables, our object 
is merely description, and the arrangement by 
which we must be guided in this department of 
natural history is clearly laid down by atten- 
tion to the purposes which these modifications 
are ipunded to serve, as adapted to the circum- 


INSTINCT. 


stances and to the offices of animals, i.e. to 
their final causes. : al 
As, in this science of morphology, or 
tracing the varieties of “ metamorphosed sym- 
metry,” we do not seek to assign the physics 
causes of any phenomena, it is no abuse of the 
doctrine of final causes to assume it as the 
basis of our arrangements; and that the prin. 
ciple of the unity of plan in the animal ere 
tion, without the study of the conditions o 
existence of the different tribes of animals, by 
which it is modified, and of the instincts ac 
companying each modification, is truly steri 
was clearly shewn by Cuvier, and has 
ably illustrated by Mr. Whewell.* ; 
is observation is strictly applicable to the 
instincts of animals, considered as an essenti 
element in their physiology. We obtain no 
explanation of the phenomena of instinet by 
referring to their use, or final cause; but th 
inferences drawn from the study of instine 
as to the existence and attributes of the 
Author of the universe, and the insight 
thus acquire into the arrangements of the 
animal creation, are not, on that account, the 
less certain or the less important. ‘ 
In order to perceive the extent and impor 
ance of these inferences, it is necessary to co 
sider, as has been stated above, not only the 
mutual adaptation of structure and instincts 
each other, but also the adaptation of both, 
the case of every animal, first, to the purpe 
of its own economy, and secondly, to the 
purposes which it is fitted to serve in the 
general economy of nature. ra 
Assuming, as we may safely do, that one 
great object, if not the most essential object, 
of all the arrangements of organized beings i 
to secure the greatest possible amount of sen- 
tient enjoyment throughout the world, the 
varying instincts and powers by which animals” 
provide themselves with food will appear on 
consideration to be better adapted to the attain- 
ment of this end than they could have been on — 
any other plan, consistently with the general 
laws, that animal enjoyment depends on the 
maintenance of organized animal structure, and 
this on the continual appropriation and assimi- 
lation of previously organized matter. The 
different races of animals are widely diffused 
over the globe by the powers which ae De 
granted them of indefinite reproduction. Those 
of them which are immediately dependent on 
vegetables for subsistence are naturally limited 
by the extent of surface over which v i 
is spread ; and when this limit has been at-— 
tained, the only expedient that can increase the 
number of animals (and it may be added, one 
which at the same time varies and multiplies — 
the kinds of animal enjoyments) is to make 
animals prey on one another, either in the 
living or dead state. “ Such is the command 
given,” says Dr. Roget, “ to countless hosts 
of living beings which people the vast 
of ocean ; to unnumbered tribes ofinsects which — 
every spot of earth discloses; to the greater — 
number of the feathered race, and also to a 


ye 


* Ib. p. 472, et seq. , 


a ae 


Ee So 


ESSE 


——9 -~ 


INSTINCT. 


more restricted order of terrestrial animals. To 
many has the commission been given to ravage 
and slaughter by open violence ; others are 
taught more insidious, though not less certain arts 


of destruction ; and some appear to be created 


chiefly for the purpose of quickly clearing the 
earth of all decomposing animal or vegetable 
materials (e.g. among the larger beasts of prey, 
the hyena, the jackall, the crow, and the vulture; 
among marine animals the crustacea and nume- 
rous mollusca, and among the lower orders, 
innumerable tribes of insects.) 

“ That a large portion of evil is the direct 
consequence of this system of extensive war- 


fare, it is in vainto deny. But although our 


_ sensibility may revolt at the wide scene of car- 


nage, our more sober judgment should place in 
the other scale the great preponderating amount 
of gratification which is the result. We must 


take into account the vast accession that accrues 
to the mass of animal enjoyment from the ex- 


ercise of those powers and faculties which are 
called forth by this state of constant activity ; 
and when this consideration is combined with 
that of the immense multiplication of life, 
which is admissible on this system alone, we 
shall find ample reason for acknowledging the 
wisdom and benevolent intentions of the Crea- 
tor, who, for the sake of a vastly superior good, 
has permitted the existence of a minor‘evil.” * 
This consideration is forcibly stated by Mr. 
Kirby in relation to one very numerous class of 
animals. “The object of the creation of the 
Arachnidans seems to have been to assist in 
keeping within due bounds the insect popula- 
tion of the globe. The members of this great 
and interesting class are so given to multiply 
beyond all bounds, that were it not for the 
various animals that are directed by the law of 
their Creator to make them their food, the 
whole creation, at least the organized part of it, 
would suffer great injury, if not total destruc- 
tion, from the myriad forms that would invest 
the face of universal nature with a living veil of 
animal and plant devourers. To prevent this 
sad catastrophe, it was given in charge to the 
spiders, to set traps every where, and to weave 
their pensile toils from branch to branch and 
from tree to tree, and even to dive beneath the 
waters.” “ The Scorpions and other Pedipalps 
are found only in warm climates, where they 
are often very numerous. Insects multiply be- 
yond conception in such climates, and unless 


_ Providence had reinforced his army of insecti- 


vorous animals, it would have been impossible 
to exist in tropical regions. The animals we 
are speaking of not only destroy all kinds of 
beetles, grasshoppers, and other insects, but 
also their larvee and eggs.”+ 

Without going into further details as to the 
adaptation of the instincts and powers of 
animals to their office in the world, we may 


‘remark, that there are two peculiarities attend- 


ing many of the phenomena of Instinct, which 
make them perhaps more important than any 
others, as indications of Design in the universe. 


* Bridgewater Treatise, vol. i. p. 46. 
+ Bridgewater Treatise, vol. ii, p. 302. 


27 


1. The evidence of design and of intellect 
which is drawn from the instinctive actions of 
animals, is precisely similar to, and comes into 
strict comparison with, that by which each of us 
is informed of the mental qualities, and even 
of the mental existence of every human being 
except himself. What evidence have we of the 
existence of reason in any of our fellow-men? 
Only this, that their actions and their words, 
which are a set of definite muscular actions, 
appear obviously to be directed to certain ends, 
and fitted for the attainment of these ends. 
Therefore, we say, they indicate design or con- 
trivance, i.e. reason or understanding, in the 
agents. The adaptation of means to ends is 
the indication of intellect, to which we yield 
practical assent every hour of our lives, and it 
would be a proof of deficiency of our own in- 
tellect if we failed todo so. Now, when we 
survey many of the instincts of animals, es 
cially many of those which are directed to the 
preservation of their lives or the reproduction 
of their species—when we see birds of all 
kinds building nests for their future progeny, 
and afterwards vivifying their eggs by incuba- 
tion,—the salmon ascending rivers to deposit 
their eggs in contact with the atmosphere,— 
beavers constructing their houses,—bees or ants 
piling together their cells and collecting their 
stores,—the migratory birds repairing to warm 
climates before winter,—the reptiles excavating 
their winter retreats,—the squirrel, the dor- 
mouse, or the pika, laying up their winter store 
of provisions,—the snail closing its shell and se- 
curing its magazine of air for the return of spring, 
—the spider spinning its web, and preparing its 
cell and trap-door,—the ant-lion digging his pit- 
fall,—the fishing-frog spreading his lines,—the 
camel storing his stomach with water for con- 
sumption in the desert,—the pelican filling her 
pouch with food for her young, and an infinity 
of other contrivances which the organs of ani- 
mals enable them to execute, which they do 
execute day after day and year after year with 
perfect precision, and without which they could 
neither maintain their own existence nor perpe- 
tuate their species; it is plain that we are con- 
templating a set of living muscular actions, 
equally adapted to certain definite ends, and 
equally efficient for the attainment of those 
ends, as the words or actions of any human 
being; and we cannot, without obvious and 
gross inconsistency, decline to draw from them 
the same inference that we habitually deduce 
from the adaptation of means to ends by the 
muscular actions of human beings. And if 
we are satisfied by the considerations stated in 
the beginning of this paper, and, in the case of 
our own instinctive propensities, by the evidence 
of our own consciousness, that the reason and 
intelligence, and anticipation of consequences, 
which are concerned in, and may be inferred 
from, these instinctive actions of animals, are 
not the mental attributes of the animals them- 
selves, we have no resource but to attribute 
their mental qualities to a superior Being, who 
gave to the first individual of each species of 
animals, and perpetuated to each race, its 
organic structure, its sensations, its muscular 


28 
powers, and its instinctive propensities. Ei- 
ther directly or indirectly a Mind, and that 
not the mind of any living animal, must rule, 
according to general laws, the instinctive ac- 
tions of all. 

It is true that there have been, in all ages, 
some resolute sceptics, who do not assent to 
the proposition that design can be traced from 
its effects, or that the observed adaptation of 
means to ends authorizes us to infer the exist- 
ence of an intelligent agent; but such a sceptic, 
if he be consistent, must also refuse his assent 
to the evidence of the existence of any sentient 
or intelligent being but himself. “ How do I 
know,” says Dr. Reid, “ that any man of my 
aeeeance has understanding? I never saw his 
understanding. I see only certain effects, which 
my judgment leads me to conclude to be marks 
and tokens of it. But, says a sceptical philo- 
sopher, you can conclude nothing from these, 
unless past experience has informed you that 
such tokens are always joined with understand- 
ing. Alas, it is impossible I can have this ex- 

rience. The understanding of another man 
is no immediate object of sight, nor of any 
other faculty which God has given me; and 
unless I can conclude its existence from tokens 
that are visible, I can have no evidence that 
there is understanding in any man.” 

In fact, the sceptical reasoner who refuses 
his assent to the intuitive judgment by which 
we infer design from its effects, can only be 
truly and thoroughly consistent if he place no 
faith in any intuitive truth, or first principle of 
belief, and therefore disbelieves the suggestions 
of his own consciousness. ‘ To such a scep- 
tic,” says Dr. Reid, “ I have nothing to say ; 
but of the semi-sceptics, I should beg to know, 
why they believe in the existence of their own 
impressions and ideas. The true reason I be- 
lieve to be, because’ they cannot help it; and 
the same reason will make them believe many 
other things.” * 

2. The evidence of design, which we deduce 
from the instinctive actions of man himself, has 
this striking peculiarity, that we are actually 
conscious of the propensities which excite them, 
and at the same time know that the purpose or 
design of these actions is not of our own con- 
trivance. We may be said actually to feed the 
adaptation, designed by Nature, not by our- 
selves, of the constitution of our minds to the 
laws of external nature and to the wants of our 
bodily organization. The very same machinery, 
consisting of efforts of volition, of actions pro- 
pagated along nerves, and of contractions of 
muscles, which we put in motion to accom- 

lish any of those objects which our own intel- 
igence and foresight enable us to understand, we 
here put in motion in obedience to propensi- 
ties implanted in us by nature, with as little 
knowledge of the purpose which it is to serve, 
and in the first instance with as little knowledge 
of the pleasure it is to procure, as the heart 
that beats within us has of the nature and uses 
of the circulation which it supports. In the 
performance of every one of these actions, we 


* Essays on Intellectua) Powers, p. 621 et seq. 


INSTINCT. 


may truly say that the intelligent mind of man 
bows to the superior wisdom of the Author o 
Nature. ’ s 
The speculations of Darwin on this subjee 
seem intended to weaken the evidence as to tl 
divine existence and attributes drawn from thi 
phenomena of instinct, first, by prey 
explain the instinctive movements : 
animals on the principle of irregular mov 
ments being first produced by uneasy a 
tions, and then those motions being selectet 
and voluntarily performed, which are found b 
experience to appease these sensations or pro- 
cure pleasure ; and secondly, by referring to 
fact formerly stated, that most instinctive pro- 


pensities are linked to, and, as he ‘it, 
* under the conduct of sensations pe desires * 
(as 


The first of these assertions is quite inconsi 
with what has been observed by others 
already remarked) in regard to the commenc 
ment of the instinctive actions in young ani. 
mals.* As tothe second, it is quite plain that the 
inference, which is drawn from the observed 
adaptation of means to ends in the phenome 
of instinct, does not require that there shall be r 
mental antecedent exciting the instinctive pro~ 
pensity, but only that the mental antecedent 
shall not be an anticipation, grounded on 
soning, of the effect which the action will pro- 
duce. ‘Even if the immediate antecedent of 
every instinctive effort were a pleasing ser 
tion, it would still be a fact, in the constitution 
of animals, that certain of their sensations, and 
not others, are naturally followed by certain 
definite muscular contractions, varying in the 
different tribes, and each adapted to a determi- 
nate end, known neither by experience nor by 
the reason of the aniinal exhibiting it; and this 
is the fact which justifies the conclusion in 
question. This has been already explained, 
and is so fully illustrated by Mr. Stewart in the 
answer, contained in his Life of Dr. Reid, to’ 
the criticisms of Darwin, that it is unnecessary 
to dwell upon it. ?* 
But although it is clearly no objection to the — 
evidence of design and benevolence in the Au-— 
thor of Nature, drawn from the phenomena of 
instinct, that the instinctive propensities are- 
often linked to and excited by certain pleasur- 
able sensations, yet it is a strong indication of 
the superior power by which they are implanted 
in the different orders of animals, that when 
they are in full force, and the object to be 
accomplished by them is important, they have 
frequently power to supersede and subvert the 
motives, by which the ordinary actions of the 
same animals are regulated, and suspend the 
ordinary laws of their mental constitution, so — 
as to induce an animal to persevere in actions” 
attended with privation and fatigue and positive 
suffering. “It ought not to be forgotten,” sa 
Paley, “ how much the instinct often costs the — 
animal that feels it; how much (e.g.) a bird — 
gives up by sitting on her nest,—how repug- 
nant it is to her organization, her habits, and 
her pleasures. An animal formed for liberty 


* See Kirby and Spence, Introd. to Entomology, 
vol. ii, p. 468. 


7 


IRRITABILITY. 


submits to confinement at the very season when 
‘every thing invites her abroad ; an animal de- 
lighting in motion, made for motion, all whose 
motions are so easy and so free,—hardly a mo- 
" ment at other times at rest,—is for many hours 
‘of many days together fixed to her nest as 
closely as if her limbs were tied down by pins 
‘and wires. For my part, I never see a bird in 
that position, but I recognize an invisible hand, 
‘detaining the contented prisoner from her fields 
and groves, for a purpose, as the event proves, 
_ the most worthy of the sacrifice.” 
> (W. P. Alison.) 
ss, 
_ INTESTINAL CANAL. See Sromacu 
AND InTesTINaL CaNaAL. 


4 


; 


IRRITABILITY; etym. irrito, to irritate, 
_ stimulate, excite; Syn. contractility, Dr. Bos- 
tock ; the vis insita, as distinguished from the 
vis nervosa, of Haller; Germ. Reizbarkeit ; 
that — vital power in the muscular fibre 
_ by which it contracts on being stimulated. 
The term irritability is certainly not the 
best which might have been devised to express 
this vital power, for it only expresses the suscep- 
tibility of being irritated ; the term contractility 
is equally inadequate, for it only expresses the 
result or effect of irritation in peculiar textures; 
the designation irrito-contractility, if not ob- 
jectionable by its length, would in my opinion 
Sayer the fulness of this property in the mus- 
_ cular fibre of animal bodies. 

The term irritability was employed by 
_ Glisson, and some of its phenomena were not 
unknown to Harvey, Peyer, Baglivi, and other 
early physiologists; but it is to Haller that we 
owe the accurate distinction of this principle 
from other principles in the animal economy, 
its full development, and its application to 
| Physiology. Many were the disputes in his 
own time as to the degree of his originality 
; and merit in this mattter, and Whytt proved a 
" steady and persevering opponent to his claims ; 
_ but posterity has done him the justice which 
“ contemporaries pertinaciously withheld ; 


and now whenever there is a doubt as to the 
meaning or acceptation of the term irritability, 
that doubt is at once dispelled by adding the 
epithet Hallerian. 

The best test of the Hallerian irritability 
is the electric influence. It is by means of this 
agent that we detect the presence and the per- 
sistence of this vital power. Generally the 
parts which are originally most irritable pre- 
serve their irritability longest; but we are not 
prepared to say that this is an invariable rule. 

galvanism is the best test of irritability, 
soa muscle, endowed with a high degree of 


pesabilicy, becomes in its turn an excellent - 


test of electricity ; and it was by the irritability 
in the muscles of the frog that Galvani first 
‘detected that form of electricity which has 

since borne his name, or that of galvanism. 

It is an important question, whether the 
property of irritability belongs to the pure and 
isolated muscular fibre, or whether it belongs to 
this, combined with the nerves—the nervo-mus- 
cular fibre. The two textures cannot be separa- 


29 


ted, the muscular fibres cannot be isolated from 
the fine fibrille of the muscular nerves, and 
therefore the question cannot be determined by 
distinct experiment. But many facts, anatomi- 
cal and analogical, would lead us to attach 
the term irrito-contractility, at least, to the 
compound texture ; the nervous portion receiving 
the stimulus, the muscular undergoing the 
contraction. 

Why are the muscles which perform 
involuntary functions so richly endowed with 
nerves? Some of the disciples of Haller, and 
especially Behrens, contended, indeed, that the 
muscular structure of the heart, for example, 
was not supplied with nerves. The anatomist 
whom I have just quoted wrote a treatise 
entitled, “ Dissertatio qué demonstratur Cor 
Nervis carere,” in which he asserted that the 
cardiac nerves were distributed entirely to the 
bloodvessels; to this the celebrated Scarpa 
triumphantly replied in his “ Tabulz Neurolo- 
gice Cardiacorum Nervorum,” &c. 

Dr. A. P. W. Philip ‘has placed himself 
at the head of the Hallerian school of the 
present day: Legallois had asserted that the 
spinal marrow was the constant and essential 
source of the action of the heart, which accord- 
ingly ceased when the influence of the spinal 
marrow was removed. But Dr. Philip de- 
tected a source of fallacy in Legallois’ experi- 
ments, and discovered that although to crush 
the spinal marrow suddenly, as in those 
experiments, suspended the action of the heart, 
yet that the spinal marrow might be slowly and 
gradually destroyed, and the action of the 
heart still remain uninterrupted. Similar ex- 
periments were afterwards made with similar 
results by M. Flourens, and published in his 
admirable “ Recherches sur le Systeme Ner- 
veux,” p.18. But though Dr. Philip has the 
merit of detecting the error of Legallois and of 
establishing the fact that the circulation may 
continue after the destruction of the spinal 
marrow, he has totally failed in proving that 
the action of the heart is independent of the 
nervous system, and that the irritability of 
Haller is exclusively a muscular power. It 
should be remembered that, after the removal of 
the brain and spinal marrow, the grand centres of 
the nervous system, the ganglionic or subsidiary 
nervous centres, remain, and that even after the 
removal of the heart from the animal body 
altogether,—in which case I have proved that its 
power of maintaining the circulation remains,—* 
there are still probably as many nervous as" 
muscular fibres ; and we know that the nerves 
themselves possess, independently of the ner- 
vous centres, the vis nervosa, or power of 
exciting under the influence of stimuli, the 
muscular fibre to contraction. 

I have also positively ascertained that 
after the destruction of the brain and spinal 
marrow in the eel, the heart is susceptible of 
being impressed through the medium of the 
ganglionic system. “ In an eel, in which the 
brain had been carefully removed, and the 


nue my Essay on the Circulation of the Blood, 
Pp» : : 


30 


spinal marrow destroyed, the stomach was 
violently crushed with a hammer. The heart, 
which previously beat vigorously sixty times in 
a minute, stopped suddenly and remained 
motionless for many seconds. It then con- 
tracted;—after a long interval it contracted 
again, and slowly and gradually recovered an 
action of considerable frequency and vigour.’”* 

Dr. W.C. Henry has added an argument in 
favour of the theory of neuromyic action of ano- 
ther kind. It is known that certain narcotics, 
applied to nerves, destroy the vis nervosa of 
that part. Dr. Henry found that “ a solution 
of opium injected into the cavities of the heart, 
or introduced into the intestine, immediate] 
arrested the actions of these organs.”+ it 
seems difficult to imagine that this effect of 
the narcotic was not produced through the 
medium of the nervous fibrille, the muscular 
being defended by the internal lining of these 
organs respectively, in the latter organ,a mucous 
membrane. 

After much consideration given to this 
subject, we should be disposed to conclude 
that in the phenomena of muscular action, the 
stimulus acts upon the nervous fibre, and that 
the contraction is an effect and the property of 
the muscular fibre. 

If this view be correct, we are necessarily 
led to consider the vis insita, or muscular 

wer, in connection with the vis nervosa. 

is latter power is peculiar to certain of 
the nervous system. It is not possessed by the 
cerebrum or cerebellum, or by the ganglia; but 
it exists in the tubercula quadrigemina, the me- 
dulla oblongata, the medulla spinalis, and the 
muscular nerves. The heart itself has recently 
been observed by Burdach to contract on sti- 
mulating the ceatiea nerves by galvanism. 

We owe the discovery of the distinct limita- 
tion of the vis nervosa, or, as he terms it, the 
“ excitabilité,” to M. Flourens.} 

The following were the supposed Jaws 
of action of the vis nervosa by Haller, Bichat, 
and Professor Miiller, before I began my own 
researches on this subject: 

Haller observes, “ Irritato nervo, convulsio 
in musculo oritur, qui ab eo nervoramoshabet.” 
“ Trritato nervo, multis musculis communi, 
totive artui, omnes ii musculi convelluntur, qui 
ab eo nervo nervos habent, sub sede irritationis 
ortos. Denique medulla spinali irritata, omnes 
artus convelluntur, qui infra eam sedem nervos 
accipiunt; megue contra artus, qui supra 
sedem irritationis ponuntur.” He concludes, 
“ conditio illa in nervo, que motum in muscu- 
lis ciet, desuper advenit, sive a cerebro et me- 
dulla spinali, deorsum, versus extremos nervo- 
rum fines propagatur.” And—“ ut adpareat 
causam motus a trunco nervi in ramos, non a 
ramis in truncum venire.”’§ 

Bichat observes, “ l’influence nerveuse ne 
se propage que de la partie supérieure a |’in- 
férieure, et jamais en sens inverse. Coupez un 


* Op. cit. p. 160. 

t Abstracts of a tread before the Royal 
Society, vol. iii. p. 60. 

t Op. cit. p. 16, &e. 

§ Elementa Physiologie, Lausanne, t. iv. p, 335. 


IRRITABILITY. 


nerf en deux, sa partie inférieure irritée fera” 
contracter les muscles subjacens; on a beau 
exciter l’autre, elle ne détermine aucune con- 
traction dans les muscles supérieurs ; de méme 
la moélle, divisée transversalement et agacé€ 
en haut et en bas, ne produit un effet ser 
que dans le second sens. Jamais l’infl 
nerveuse ne remonte pour le mouven 
comme elle le fait pour le sentiment.” * 

Lastly, Professor Miiller observes, “ the 
motor power acts only in the direction of the 
primitive nervous fibres going to muscles, ori 
the direction of the branches of the nerves ; and 
never backwards ;’ and “ all nervous fibre: 
act in an isolated manner from the trunk of @ 
nerve to its ultimate branches.” + .@ 

It is a singular circumstance, that an esta- 
blished fact in experimental research, an esta- 
lished principle of muscular action in t 
animal economy, should be without a) tion 
to physiology. Yet such has been case. 
For what is the application of the vis nervosa 
to the explanation of the functions of the ani 
ceconomy ? 

Before any such application could be made 
it was n that other modes of action 
this power should beascertained. I have, by a 
series of experiments, determined new laws of 
action of the vis nervosa, and have thus t 
enabled to make an extensive application © 
the principle to the functions of like ' 

The head of a river tortoise being separates 
between the third and fourth vertebra : 

1. The dorsal portion of the spinal marrow 
was laid bare to the extent of one inch below 
the origin of the brachial nerves; the spin 
marrow was then excited by means of th 
probe and by galvanism; both anterior 
posterior extremities, with the tail, were mover 

2. A lateral intercostal nerve was then laid 
bare, and stimulated in the same manner ; the 
same effects were produced as in the former 
experiment. 

These experiments have been Yr 
times, and I performed them in the presence 
of M. Serres and other gentlemen at Paris, in 
the month of August, 1839. They establish 
the following new laws of action of the v 
nervosa :— > *’ 

1. That it does act in the direction 
branch to trunk ; " 

2. That it is in a retrograde direction in th 
spinal marrow. “ 

The application of these new laws to ph; 
siology—the first application of the vis nerve 
to physiology—is very extensive, co-extens 
indeed with all the acts of ingestion ar 
egestion in the animal economy. But it doe 
not belong to our present article to treat of th 
important and extensive subject. We no 
return to that of irritability in general. 

The degree of irritability is not the same i 
every organ of the body. Haller and Nysten 
have investigated this subject, and the follow. 
ing are their statements respectively : 

Haller observes, “ Tenacissima virium in 

* Anatomie Générale, 2de ie, t. iii, p. 277. 
278, éd. 1801. ee ae , 

t Handbuch der Physiologie, i. 656. 


3 


« 


IRRITABILITY. 31 


farum intestina sunt, que et evulsa pergunt se 

contrahere et frigida demum; etiam his tena- 

cius cor, si omnia conputaveris, in pullo etiam 

evidentissime et in frigidis animalibus.” * 

The observations of Nysten are more exten- 
sive, and his inferences were deduced from expe- 
riments made upon the human subject imme- 
diately after decapitation. They areas follow: 

“1. La contractilité du ventricule aortique 
était éteinte 49 minutes apres la mort; 

“2. L’aorte n’a offert aucun mouvement de 
contraction ; 

_ 3. Cinquante-six mimutes apres la mort, 
la contractilité de l’estomac, des intestins et de 
ta vessie était éteinte ; mais ces organes n’ont 

u étre soumis assez promptement au galvan- 

isme pour connaitre la durée rélative de leur 

force contractile ; 

“ 4. Le ventricule pulmonaire perdit sa con- 
tactilité une heure 58 minutes apres la mort ; 

** 5. Deux heures 2 minutes apres la mort, 
le diaphragme ne se contractait plus; les mus- 
cles de l'appareil locomoteur perdirent succes- 

_sivement leur contractilité & mesure que le 
contact de l’air agissait sur eux ; mais ceux qui 
ne furent exposés a l’air que tard, par exemple 
au bout d’environ 4 heures, ne cessérent de se 
_ mouvoir que 4 heures 15 minutes aprés la mort ; 
6. Les oreilletes du ceeur, qui étaient 
_ exposées a l’air depuis le commencement de 
lexpérience, ne cessérent de se contracter que 

_ 4heures 40 minutes apres la mort.” + 
But if there be a difference in the irritability 
_ of different organs in the same animal, there is 

a still greater difference in the different animals 
_ themselves of the zoological scale. It may be 
_ Stated in general terms, that the degree of the 
_ irritability in the different parts of the animal 
_ series, as tested by galvanism, is inversely as the 
_ quantity of the respiration; so that in the 

reptile tribes, in which the respiration is exceed- 
_ ingly low, the irritability of the muscular fibre 
is such as to afford a delicate test of galvanism ; 
and in birds, in which the respiration is at its 
maximum, the irritability exists in its lowest 
degree. 

This important subject deserves the fullest 
development. We shall here, therefore, insert 
some observations which were read to the 
_ Royal Society, and published in the Philoso- 

phical Transactions in 1832. 
The due actions of life, in any part of the 
zoological series, appear to depend upon the 
_ due ratio between the quantity of atmospheric 
_ change induced by the respiration, and the 
_ degree of irritability of the heart: if either be 
unduly augmented, a destructive state of the 
_ functions is induced ; if either be unduly di- 
_Minished, the vital functions languish and 
_ eventually cease. If the bird possessed the 

_ degree of irritability of the reptile tribes, or 

_ the latter the quantity of respiration of the 

former, the animal frame would soon wear out. 

If, on the contrary, the bird were reduced to 

the quantity of respiration appropriate to the 


ie i — See * 


* Haller, Prime Linez, 1767, p. 207. 
+ Recherches de Physiologic, {gn, p- 312, 


reptile, or the latter to the degree of irritability 
which obtains in the former, the functions of 
life would speedily become extinct. Various 
deviations from the usual proportion between 
the respiration and the irritability, however, 
occur, but there is an immediate tendency to 
restore that proportion ; increased stimulus ex- 
hausts or lowers the degree of irritability, 
whilst diminished stimulus allows of its aug- 
mentation. The alternations between activity 
and sleep afford illustrations of these facts. 

Changes in anatomical form in the animal 
kingdom present other illustrations of the law 
of the inverse proportion of the respiration 
and irritability. The egg, the foetus, the tad- 
pole, the larva, &c. are respectively animals of 
lower respiration, and of higher irritability, 
than the same animals in their mature and per- 
fect state. Changes in physiological condition 
also illustrate the same law. The conditions 
of lethargy, and of torpor, present examples 
of lower respiration, and of higher irritability, 
than the state of activity. 

It may be remarked that whilst changes in 
anatomical form are always from lower to higher 
conditions of existence, changes in the phy- 
siological condition are invariably from higher 
to lower. 

These views are further illustrated by a re- 
ference to the quantity of stimulus and the 
degree of irritability of each of the parts and 
organs of the animal system. The oxygen of 
the atmospheric air is the more immediate and 
essential stimulus of this organ. Taken up in 
respiration, it is brought into contact with the 
heart, by means of the blood, which may be 
considered as the carrier of this stimulus, as 
it is of temperature and nutriment, to the 
various parts of the system. As oxygen is 
the principal stimulus, the heart is the prin- 
cipal organ of irritability, in all the verte- 
brated animals; if the contact of oxygen be 
interrupted, all perish in a greater or less pe- 
riod of time. 

The extraordinary differences which exist in 
animals which occupy different stations in the 
zoological scale, have long excited the atten- 
tion of naturalists. Nor have the differences 
which obtain in the various ages and states of 
its existence, in the same animal, escaped the 
attention of the physiologist. A similar re- 
mark applies to that singular state of existence 
and of the functions of life, designated hyber- 
nation. But it appears to me that a sufficiently 
comprehensive view has not been taken of the 
subject, and that many facts, with their mul- 
titudinous relations, still require to be deter- 
mined. 

I. Of the pneumatometer.— The principal 
of these facts is that of the quantity of respi- 
ration. ‘This is greater in proportion as the 
animal occupies a higher station in the zoolo- 
gical scale, being, among the vertebrated 
animals, greatest of all in birds, and lowest 
in fishes ; the mammalia, the reptiles, and the 
amphibia occupy intermediate stations. The 
quantity of respiration is also remarkably low 
in the very young of certain birds which are 


32 


hatched without feathers, and of certain animals 
which are born blind; and in hybernation it is 
almost extinct. 

To ascertain the quantity of respiration in 
apy given animal, with extreme minuteness, 
was a task of great difficulty. It was still 
more difficult to determine this problem, so as 
to represent the quantities of respiration in the 
different kinds, ages, and states of animals, in 
an accurate series of numbers. The changes 
induced in a given volume of air made the 
subject of experiment, by changes in the tem- 

ature and pressure of the atmosphere, and 

y variations in the height of the fluid of a 
pneumatic trough, which it is so difficult to 
appreciate minutely; the similar changes in- 
duced by the humidity of expired air, and by 
the heat of the animal itself, were so many 
and complicated, that it appeared almost im- 
man to arrive at a precise result. These 

ifficulties, in fine, were such as to lead one of 
the first chemists of the present day to give up 
some similar inquiries in despair. 

Fortunately I have been enabled to devise 
an apparatus which reduces this complex pro- 
blem to the utmost degree of simplicity. I 
now beg the indulgence of the reader whilst 
I give a detailed description of its construction 
and mode of operation. 


Fig. 1. 


(ara 


IRRITABILITY. 


This apparatus, which I shall designate th 
pneumatometer, consists of a glass jar (fig. * 
a, b,) inverted in a mercurial trough (c, d,) s 
grooved and excavated, as accurately to receiv 
the lower rim of the jar and the lowest pai 
the tube (e, f, g,) and also to admit of the an 
mal which is made the subject of experimer 
being withdrawn through the mercury. Th 
jar communicates, by means of the bent tub 
(e,f, g,h,) with the gauge (i, j,) which is i 
serted into a larger tube (k, /,) containing wate 
A free communication between the jar and t 
external air is effected and cut off, at a 
by introducing and withdrawing the little be 
tube (m,n,) placing the finger upon the € 
tremity (m,) whilst the extremity (m) is passet 
through the mercury. . 

If the jar be of the capacity of one hy 
dred cubic inches, the gauge is to contain t 
and to be graduated into cubic inches a 
tenths of a cubic inch; so that each smalles 
division shall be the thousandth part of th 
whole contents of the jar. x 

Attached to the same vray Hl 

laced a little apparatus (0, p, al 
poseaven and conaisiiat of a glass ball ( 
of the capacity of ten cubie inches, comm 
nicating with a tube (p,g,) bent at its uppé 
part, of the capacity of one cubic inch, ¢ 


GS I’ 


a 


> 


PERU LITTTTTTPE Terry rrr ryt 
° 


IRRITABILITY. 


vided. into tenths and hundredths, and in- 
Serted into a wider tube containing water, 
‘precisely in the manner of the gauge (2, 7.) 
Boric. to secure the exact proportion between 
capacity of the pneumatometer and that of 
‘the aérometer, it is only necessary to add more 
or less of mercury to the trough. 
_ The whole apparatus is inclosed in a glazed 
frame so as entirely to obviate the influence of 
artial currents of air. It is plain that changes 
im external temperature and pressure will affect 
both these parts of the apparatus equally ; and 
that the fluids in the gauge (i,j,) and in the 
tube (p, g,) will move pari passu. It is there- 
pre Only necessary to compare them, and to 
ake the difference, for the real alteration in the 
quantity of the gas in the jar. 
Previously to noticing this difference, the 
fluids in the outer and inner tubes are to be 
Drought accurately to the same level, by raising 
‘or depressing the outer tube (A, /,) and the 
inner one (p, 9.) 
In order that the air within the jar and that 
in the aérometer may be in the same state of 
humidity, a little water is introduced into the 
glass ball (0) of the latter. 

When the animal is to be removed, the 
fuid in the inner and outer tubes of the gauge 
@ to be brought to a precise level; the animal 
is then to be withdrawn through the mercury, 
by a cord attached to the little net or box in 
which it is secured; a quantity of fluid will 
immediately rise in the inner tube, (i, 7,) equal 
to the bulk of the animal; the bent tube (m, n) 
is now to be passed through the mercury into 
the jar so as to effect a communication with 
the atmospheric air; a portion of air equal to 
the bulk of the animal rushes into the jar, 
whilst the fluids in the gauge regain their 
evel. 

To avoid the error which would arise from 
e influence of the temperature of the animal 
pon the air within the jar of the pneumato- 
meter, the first observation of the degree upon 
he gauge must be made the instant the ex- 
Deriment is begun, and before the tempera- 
ure of the animal can have been communi- 
tated to it; and the last, so long after the 
inimal has been withdrawn as to allow of its 
estoration to the temperature of the atmos- 
here. 
In this way all calculations for the varied 
emperature and pressure of the external air, 
br augmented humidity and temperature of 
1e air of the pneumatometer, and for the 
thanges in the Freight of the fluid of the 
rough, are at once disposed of in a manner 
he most accurate and simple. 

It now remains to determine the quantity of 
ange induced upon the air of the pneumato- 
feter, by the respiration of the animal. Two 
lews may be taken of this change; that of 
Messrs. Allen and Pepys, that the oxygen 
yhich disappears is replaced by a precisely 
qual bulk of carbonic acid; or that of M. 
uiwards, that there is generally an excess of 
ve oxygen which disappears over that of the 
arbonic acid evolved. In either case the 
uantity of respiration is ascertained by the 
VOL. If. 


33 


gauge of the pneumatometer in the following 
manner. A frame made of glass rods (r,s) 
is placed within the jar (a, 6) suspending por- 
tions of calico, imbued with a strong solution 
of pure potassa, and provided with a small 
dish of wood, so as to prevent the caustic 
liquid from dropping upon the animal beneath. 
By this means the carbonic acid is removed as 
it is evolved, or after the animal is with- 
drawn. The rise of the fluid in the gauge of 
the pneumatometer gives the quantity of oxygen 
which disappears,—whether this be entirely ex- 
changed for carbonic acid, or only partly ex- 
changed for carbonic acid, and partly absorbed, 
—and denotes the precise quantity of the respi- 
ration. 

The question itself, of thé entire or partial 
exchange of the oxygen gas which disappears, 
for carbonic acid gas evolved, is at once de- 
termined by employing the same apparatus 
without the solution of potassa: in the entire 
exchange, there is no alteration in the bulk of 
the air of the pneumatometer; in the case of a 
partial exchange, the alteration in the bulk of 
the air gives the precise excess of oxygen gas 
which disappears, over the quantity of carbonic 
acid evolved. 

But this question, and that of the absorption 
and evolution of nitrogen, with the influence 
of night and day, of season, &c. are reserved 
for a future stage of this inquiry. 

It is important that the animal should be 
left for a considerable time in the very situation 
in which it is to remain during the experiment, 
before that experiment is begun, and before the 
jar is placed over it. In this manner the effect 
of timidity or restlessness is allowed to subside, 
and prevented from mingling with that of the 
natural state of the respiration. <A bit of cork 
must also be attached to the mercurial trough, 
so as to float upon the mercury at é, and pre- 
vent the disturbing effect of the contact of this 
fluid with the animal. 

It is also well, after having placed the jar 
in the groove of the mercurial trough, to pour 
a little water over the mercury exterior to the 
jar. The apparatus is thus rendered perfectly 
air-tight, which is not always effected by the 
mercury alone. 

By means of this apparatus we readily and 
accurately determine the quantity of the re- 
spiration of any given animal, in any given 
circumstances. 

II. Of the measure of the irritability. — 
The problem to be next determined is that of 
the degree of irritability of the muscular fibre, 
and especially of the heart. The question is 
beset with scarcely fewer or less difficulties 
than that of the quantity of respiration, whilst 
it involves far greater errors and more. dis- 
crepancy of opinion on the part of physio- 
logists. 

Even Baron Cuvier has fallen into these 
errors. It will be shortly demonstrated that 
the degree of irritability is, in every instance, 
inversely as the quantity of respiration. Yet 
M. Cuvier, in a remarkable paragraph, states 
the very contrary, and even speaks of that 
which is the exhauster, as the repairer, of the 

D 


34 


irritability; whilst, on the other hand, he 
makes statements which appear to me at va- 
riance with this very opimon. In the Ana- 
tomie Comparée (tome i. p. 49,) this cele- 
brated writer observes, “ Les expériences 
modernes ont montré qu’un des principaux 
usages de la respiration est de ranimer la force 
musculaire, en rendant a la fibre son irrita- 
bilité epuisée.” See also tome iv. p. 301. 
Similar observations are made in M. Cuvier’s 
more recent work, the Régne Animal: “ C’est 
de la respiration que les fibres musculaires 
tirent l'énergie de leur irritabilité,” (tome i. 
p- 57, 2me edit.) “ C’est la respiration qui 
donne au sang sa chaleur, et a la fibre la sus- 
ceptibilité pour l’irritation nerveuse,” (tome ii. 
p-1.) On the other hand, a’ of the 
mollusca, (tome iii. P; 3,) M. Cuvier observes 
of those animals of low respiration, * L’irri- 
tabilité est extreme dans la plupart.” The 
same term is, in fact, used in two distinct 
senses, in these paragraphs. 

No further proof can be necessary of the 
extreme vagueness and incorrectness of the 

revailing notions and expressions of physio- 
Aaiate in regard to this subject. All this will 
appear still more extraordinary, when the 
law, that the quantity of respiration and the 
degree of the irritability are, in fact, inverse 
throughout all the series, stages, and states of 
animated being, is clearly established. 

It is well known that the irritability of the 
heart and of the muscular fibre in general is 
greater in the mammalia than in birds, and in 
reptiles and amphibia than in the mammalia, 
whether we judge of it by the force and dura- 
tion of the beat of the heart, exposed to the 
stimulus of the atmospheric air, or by the con- 
tractions of the other parts of the muscular 
system. Now this is precisely the order of the 
quantity of respiration in these animals, as 
ascertained by the pneumatomer, inverted. It 
is essential, in accurately determining the ques- 
tion of the irritability of the muscular fibre, to 
compare animals of the same class inter se; 
birds and the mammalia, reptiles and amphibia, 
fishes, the mollusca, &c. must be compared 
with each other, both generically and specifi- 
cally. It is especially necessary to compare 
the warm-blooded, the cold-blooded, the air- 
breathers, and the water-breathers, in this man- 
ner. However the different classes may differ 
from each other, there are differences in some 
of the species of the same class, and especially 
that of fishes, scarcely less remarkable. 

Great differences in the duration of the beat 
of the heart are observed in feetal, early, and 
adult states of the higher animals; this dura- 
tion being greater in the first, and least in the 
last of these conditions. The order of the 
quantity of respiration is inverse. 

The law of the irritability being inversely as 
the respiration, obtains even in the two sides of 
the heart itself, in the higher classes of animals. 
The beat of the heart removed from the body 
does not cease at the same time in the wall of 
all its cavities, or of its two sides: but, as 
Harvey observes, “ primus desinit pulsare 
sinister ventriculus ; deinde ejus auricula; de- 


IRRITABILITY. 


mum dexter ventriculus ; ultimo (quod etiam 
notavit Galenus) reliquis omnibus cessantibt 
et mortuis, pulsat usque dextra auricula.”* — 
Even in this case the irritability is greatest i 
the part in which the respiration is least. _ 
It was shown by Hook, in the early days o 
the Royal Society,t that if, the iration 
being suspended, an animal appeared to 
dying, the beat of the heart and the signs 
life were speedily restored, on performing art 
ficial respiration, or even by forcing air throu 
the trachea, bronchia, and pulmonary ait-e 
and allowing it to escape through incision 
made through the pleura. ‘ 
It was, in the next place, clearly shown b 
Goodwyn, in one of the most beautiful spe 
cimens of physiological inquiry in any lan 
guage,} that in suspended respiration, it is th 
left side of the heart which first ceases t 
contract, the right side still continuing it 
function for several minutes, until the suppl, 
of blood may be supposed to fail. 
The facts detailed by Harvey had shown tha 
the left side of the heart was endued with le: 
irritability than the right; the experiment ¢ 
Hook, that respiration restored the action ¢ 
the heart, if it had previously ceased ; that 
Goodwyn, that this cessation and restorati 
of functions were observed in the left side ¢ 
the heart. It was obvious, on the other ham 
that the respiration belongs, as it were, to th 
left side of the heart. ‘ 
It appears plainly deducible from these fact 
that in circumstances and structures the mos 
similar, the respiration is accurately inve 
as the irritability. 7 
For the sake of a comparison with the hy 
bernating animal, the object of which will 
explained hereafter, I thought it right to repe 
this experiment. : 
Before I proceed to detail the result, I ma 
just describe an easy method o 
that part of it which consists of artificial res: 
ration. A quill is firmly fixed in the divide 
trachea: a small hole is then cut into that pat 
of the quill which is external; Read’s syring 
is then adapted to the other end of the qi 
At each motion of the piston downwards, - 
lungs are distended ; whilst the piston is raise 
the air escapes through the opening in the qu 
peasneing expiration. The experiment, thei 
ore, only requires the common action ¢ 
syringe. 
The experiment itself answered my expe 
tion. During the cessation of respiration, | 
left ventricle ceased to beat, the right ventr 
retaining its function; on renewing its respi 
tion, nee ventricle resumed its beat. 
appears from this experiment, that from ¥ 
of a degree of irritabality equal to that of t 
right ventricle, and its own proper stimulus 
arterial blood, the left ventricle ceased its 
tractions. The function of the right ventri 


PSL) ’ 


DeCriory 


* Opera Omnia, Collegio Medicoram Londine 
edita, 1766, p. 28. -— 

+ Phil. Trans. vol. ii. : 

t On the Connexion of Life with Respira 
London, 1788, p. 72, 82 note, al 


IRRITABILITY. 


must soon cease in consequence, from want of 
a supply of blood. 

_ These facts prove that arterial blood is the 
‘necessary stimulus of the left side of the heart, 
‘its irritability being low ; but that venous blood 
isa sufficient stimulus of the right, from its 
higher irritability : the phenomena plainly flow 
‘from the law, that the quantity of respiration 
and the degree of irritability observe an in- 
verse ratio to each other, and from the facts on 
which that law is founded. In this double 
‘sense, besides that of distinct cavities, the 
“Mammalia have, therefore, two hearts; and as 
‘the highly aerated blood of the left is the pecu- 
liar property of birds and the mammalia, so 
the highly irritable fibre of the right may be 
ae to that of the heart of reptiles and 
the fishes. 

Except for the objection to new terms, the 
left side of the heart might be termed arterio- 
contractile, and the right veno-contractile ; the 

first being stimulated by arterial, the second 
by venous blood. 
It is quite obvious that the heart will bear a 
‘suspended respiration better, the more nearly 
‘its irritability approaches to that which may be 
‘designated veno-contractile. The power of 
bearing a suspended respiration thus becomes 
a@ measure of the irritability. It is expressed, 
numerically indeed, by the length of time 
during which the animal can support a sus- 
pended respiration ; a conclusion of the highest 
degree of importance in the present inquiry. 
' Birds die almost instantly on being sub- 
‘merged in water ; the mammalia survive about 
three minutes, the reptiles and the batrachia a 
“much greater length of time. 
_ The unborn fetus, the young animal born 
‘with the foramen ovale open, the reptile, the 
‘ollusca, having all a state of the heart ap- 
‘proaching to the veno-contractile, bear a long- 
‘continued suspension of the respiration, com- 
‘pared with the mature animal of the higher 
classes. 
_ But the most remarkable fact deducible from 
this reasoning is the following: if such a case 
isted as that of the left side of the heart 
being nearly or absolutely veno-contractile, such 
‘an animal would bear the indefinite suspension 
of respiration ; such an animal would not drown 
though immersed in water. Now there is pre- 
‘cisely such a case. It is that of the hyberna- 
‘ting animal. It may be shown that in the 
state of perfect hybernation the respiration 
is nearly suspended ; the blood must, there- 
fore, be venous. See Hysernation. Yet the 
heart continues to contract, although with a 
‘reptile slowness. The left ventricle is, there- 
fore, veno-contractile, and in this sense, in fact, 
‘sub-reptile. The case forms a solitary excep- 
‘tion to the law pointed out by Harvey, that the 
left ventricle ceases to contract sooner than the 
‘right. If in the hybernating animal the left 
_Ventricle does cease to beat sooner than the 
right, it is only in so slight a degree as to be 
referred to the greater thickness of its parietes, 
_and the slight degree in which respiration still 
remains. It is obvious that the foregoing state- 
ment must be taken with its due limitations. 


35 


Venous blood is unfit for the other animal pur- 
poses, even though it should stimulate the 
heart to contraction. 

Another mode of determining the degree of 
irritability, is the application of stimuli, as 
galvanism. A muscular fibre endued with 
high irritability, as that of the frog, and the 
galvanic agency are mutually tests of each 
other.* 

A third criterion and measure of the irrita- 
bility is afforded by the influence of water at 
temperatures more or less elevated, in in- 
ducing permanent contraction of the muscular 
fibre. 

There are two other properties of animals 
which depend upon the varied forms of the 
inverse ratio which exists between the respira- 
tion and the irritability. The first is activity, 
the second, tenacity of life. 

The activity, which, I believe, M. Cuvier 
has confounded with the irritability, is generally 
directly proportionate to the respiration, and 
intimately depends upon the condition of the 
nervous system resulting from the impression 
of a highly arterial blood upon its masses, and 
not upon the degree of irritability of the muscu- 
lar fibre. It is the pure effect of high stimulus. 

To show that M. Cuvier has blended the 
idea of the irritability of the muscular fibre 
with that of the activity of the animal, it is 
only necessary to recur to the passages already 
quoted from that author, and to adduce the 
observations with which they are connected. 
“ On vient de voir a quel point les animaux 
vertébrés se ressemblent entre eux; ils offrent 
cependant quatre grandes subdivisions ou 
classes, caractérisées par l’espece ou la force 
de leurs mouvements, qui dépendent elles- 
mémes de la quantité de leur respiration, at- 
tendu que c’est de la respiration que les fibres 
musculaires tirent l’énergie de leur irritabilite.”’+ 
“ Comme c’est la respiration qui donne au 
sang sa chaleur, et a la fibre la susceptibilité 
pour l’irritation nerveuse, les reptiles ont le 
sang froid, et les forces musculaires moindres 
en totalité que les quadrupédes, et a plus forte 
raison que les oiseaux; aussi n’exercent-ils 
guére que les mouvements du ramper et du 
nager ; et, quoique plusieurs sautent et courent 
fort vite en certains moments, leurs habitudes 
sont généralement paresseuses, leur digestion 
excessivement lente, leurs sensations obtuses, 
et dans les pays froids ou tempérés, ils passent 
presque tous l’hiver en léthargie.” { 

It is extraordinary that M. Cuvier should 
have associated the elevated temperature of the 
blood with a high irritability of the muscular 
fibre, when they are uniformly separated in 
nature, and are, indeed, absolutely incompa- 
tible in themselves. The muscular fibre of the 
frog is so irritable, that it would instantly pass 
into a state of rigid contraction, if bathed with 
a fluid of the temperature of the blood of birds.§ 


* Bostock on Galvanism, pp. 4, 14. 
+ Le Régne Animal, tome i, pp. 56, 57, 2de 
edit. 
t Ibid. tome ii. pp. 1, 2. 2de edit. 
§ See an Essay on the Circulation, chap. vii. 
pp. 180, 181. 
D2 


36 


The same confusion of ideas on the subject 
of the activity of the animal and the irritability 
of the muscular fibre prevails, I believe, 
amongst our own physiologists; at least, in 
conversation with two, who may rank amongst 
the first, I found that they had uniformly con- 
sidered the respiration and the irritability to be 
directly, instead of inversely, proportionate to 
each other. 

That singular and interesting property of the 
lower orders of animals termed tenacity of life 
is, on the other hand, distinctly associated 
with a high degree of irritability of the mus- 
cular fibre. The property may be defined as 
consisting of the power of sustaining the pri- 
vation of respiration, the privation of food, 
various mutilations, divisions, &e. It is greater 
as we descend in the zoological scale. As 
activity depends upon the presence and condi- 
tion of the spino-cerebral masses acted upon 
by arterial blood, tenacity of life depends upon 
the diminution or absence of these masses and 
of this highly arterialized blood, being greatest 
of all in those animals which approach a mere 
muscular structure. Almost the sole vital pro- 
perty then remaining is the irritability; and 
this property does not immediately suffer from 
division. 

It is possible to reduce some of the reptile 
tribes to a state approaching that of animals 
still lower in the scale, by removing, by very 
slow degrees, successive portions of the ner- 
vous masses. This is most readily done in 
animals in which the respiration is already low, 
and the irritability high, as in the feetus, in the 
very young animal, in the reptile, &c., as in 
the experiments of Leyallois,* M. Serres, 
myself, &c. 

There is, even in animals most tenacious of 
life, one kind of mutilation—one kind of in- 
jury not well borne. As the blood is in its 
lowest condition of stimulus, it cannot be 
withdrawn with impunity; even frogs soon 
perish if their blood be allowed to flow. As the 
irritability, on the other hand, is high, certain 
stimuli, as galvanism, slightly elevated tem- 
peratures, &c. are speedily fatal. The batra- 
chia are promptly destroyed by immersion in 
water of a temperature of 108° of Fahr., and 
some fish and crustacea perish in great num- 
bers under the influence of a thunder-storm. 
It is a singular fact, that the fish alone, whose 
food is found amongst animals of a high irrita- 
bility, should possess an electrical organ for 
the destruction of its prey. 

The application of stimulus has uniformly a 
tendency to reduce the degree of irritability. 
The exclusion of all stimuli allows its augmen- 
tation. During active exercise the irritability 
is diminished ; during sleep it is proportionally 
augmented. 

Weare nowled to take another view of this sub- 
ject ofirritability. Whatisitssource? How is it 
renewed when it has been exhausted? These ques- 
tionslead us totake up another of greatinterest, to 


* Experiences sur le Principe de la Vie. 
+ Anatomie Comparée du Cerveau, tome ii. p, 224, 
¢ Essay on the Circulation, chap. iii. § 1. 


IRRITABILITY. 


physicians especially, viz. what is the condition 
of the muscular irritability in those cases it 
which the influence of the cerebrum, or of th 
spinal marrow, or both, isremoved respectively 
e cannot discuss this subject more clear 
than by adducing the following observatior 
read before the Royal Medico-Chirurgic 
Society and published in its Transactions, 
the year 1839. 
The utmost discrepancy of opinion prevai 
amongst physiologists and medical writers wpt 
this subject. Prochaska, Nysten, and Legalloe 
state, that the irritability of the muscular fibi 
remains in paralytic limbs; whilst Profess 
Miiller and Dr. Sticker assert the contrary. 1 
attempt has been made to reconcile a contr 
diction not very honourable to our science. 1 
explain this discrepancy of opinion is one 
the objects of this communication. Te 
The authors to whom I have referred, mish 
by the generic term and idea of paralysis, ha 
not sufficiently distinguished between its d 
ferent species. Yet it will be found, as we pre 
ceed, that this distinction is of the utmost in 
seg aay in the explanation of the phenomer 
n fact, cerebral paralysis, or that which n 
moves the influence of the brain, and spin 
paralysis, or that which removes the influen 
of the spinal marrow, are in totally ; 
conditions in reference to the irritability of @ 
rouscular fibre in the limbs severally affecte 
facts equally obvious in experiments and i 
clinical observations. I must make quot 
tions of some length, for these are necessar 
show the present state of the science. I sha 
then proceed to the detail of my own in 
gations. 
The first distinct notice of this subject whic 
I think it necessary to adduce, is contained” 
the following extract from the Opera Minora ‘4 
Prochaska:* “ Vis nervosa que in nervis 
commercio cum cerebro separatis superest, t 
una alterave musculi contractione, quam im 
tati cient, exhauritur, sed millenis plane coi 
vulsionibus excitandis par est; quod expert 
sum in rana, cui medullam spinalem in dot 
abscidi. Supervixit huic vulneri aliquot « 
bus; interim irritando medulle spinalis pa 
eam, que erat infra sectionem, convulsiones - 
artubus inferioribus excitavi toto tempore, ¢ 
supervixit, plane innumeras; neque extret 
tates inferiores prius mortue sunt, quam fe 
rana; Dein quod vis nervosa in nervis ¢ 
persistere possit citra cerebri auxilium proba 
videntur musculi paralytici, in quorum ner 
ob compressionem aliquam preternaturaler 
tum commercium cum cerebro sublatum € 
nihilominus tamen a stimulo electrice scintil 
longo jam tempore paralytici musculi conv 
Juntur.” 
More detailed remarks were made by Ny; 
and these, from being founded upon very ¢ 
tinct post-mostem experiments on the huma 
subject, have excited more attention. This ce 
lebrated physiologist observes, “ Chez deux 


e 


apoplectiques qui avaient succombé au bout d 


ODD 


Z 


"v 


* Ed. 1800, p. 84. 


IRRITABILITY. 


quelques jours, l’un a la premiere attaque et 
_Fautre a la seconde, le galvanisme a déterminé 

_ des contractions aussi fortes dans les muscles 
du coté sain que dans ceux du coté paralysé: 
__ les iris des deux cétés sont également contrac- 
_ tées.”” “ Cette propriété n’a été completement 
_ anéantie dans les organes musculaires des deux 
‘Sujets qu’environ 12 heures apres Ja mort; et 
on n’a observé aucune difference dans les mus- 
cles paralysés.”* 

__Legallois makes similar remarks, founded 
_ upon experiments made upon animals. He 
‘observes, “ M. Nysten a montré que dans 
les paralysies les plus completes, lirritabilité 
"Se conserve dans les membres paralysés tout 
aussi bien que dans ceux qui ne le sont pas. 
ai obtenu un résultat semblable d’un expéri- 
: que j'ai souvent répétée. Elle consiste 
@ détruire la moélle lombaire dans un lapin 
Phy de moins de dix jours ; il faut le choisir de 
_ eet Age, pour que la circulation ne soit pas ar- 
rétée, et qu’il puisse continuer de vivre. Quoi- 
_ que dans cette expérience, le train de derritre 
_ soit frappe de mort, et que ses nerfs ne puis- 
_ sent plus recevoir aucune influence de la mo- 
élle épiniére, Virritabilité s’y conserve, et l’on 
oa pendant fort long-temps, faire contracter 

es cuisses, en irritant les nerfs sciatiques. Il 
_ parait donc qu’il se fait dans toute l’étendue des 
_ nerfs une sécrétion d’un principe particu- 
lier.” + 
__ From these quotations from Nysten and Le- 
_ gallois we should be led to the conclusion that 
_ the muscles of paralytic limbs, in all cases of 
_ hemiplegia and of paraplegia, simply retain 

their irritability. From another series of ob- 
_ servations, made by philosophers equally worthy 
_ of our confidence, we should be led to an op- 
| posite conclusion. 

_ Some interesting experiments on this point 
_ have been recently performed by Professor 
_ Miller and Dr. Sticker. The former cele- 
_ brated physiologist observes,t “ It was known 
_ that, after the division of a nerve, the portion 
cut off from communication with the brain 
_ retains, for a certain time, its excitability; but 
_ the question, how far the continuance of the 
_ connection with the brain and spinal marrow is 
_ necessary for the longer preservation of the irri- 
_ tability of the nerves, and whether the muscles 
retain their irritability when their nerves no 


| seldom mooted. WNysten had asserted that the 
ia muscles of patients who died a short time after 
an apoplectic seizure preserved their irratibility, 
and contracted under the influence of the gal- 
i vanic stimulus, although the functions of the 
brain had been paralyzed. 

_ Thad good reasons, however, for believing 


_ * Recherches Physiologiques, 1811, p. 369; com- 
_ pare p. 377 and 419; and Cuvier, Histoire des 
a Beietnes Naturelles, tome i. p. 213. 
+ CBuvres de Legallois, éd. 1824, p. 23 and 24. 

_ $ See the excellent translation of the ‘‘ Handbuch 

der Physiologie,” by William Baly, M.D., vol. i., 
_ p- 631—633; and compare p. 663, 724, 727, 898, 
&c. and Grainger on the Spinal Cord, p. 96, 97. 


q 


37 


that, in such cases, the nerves retain their power 
only for a short time, losing it entirely after a 
longer interval; for, in experiments on the re- 
production of the nervous tissue in a rabbit, I 
had once observed, that the lower portion of 
the nervus ischiadicus, which I had divided 
some months previously, had lost all its exci- 
tability; and a similar fact had been before ob- 
served by Fowler. I have since performed, in 
conjunction with Dr. Sticker, new experiments, 
which have completely confirmed that suppo- 
sition. To prevent the regeneration of the 
nerves, and to withdraw more effectually the 
lower portion from the influence of the brain 
and spinal cord, a portion of the nerve (the 
ischiadic) was entirely removed. The experi- 
ments were made only on two rabbits and a 
dog; yet the results were so constant, that they 
are quite worthy of dependence. 

“ Eleven weeks after the division of the 
nerve in the first rabbit, it was laid bare in its 
course between the biceps and semitendinosus 
muscles. Contrary to expectation, and to our 
mortification, the continuity of the nerve was 
found to be restored. It was divided anew 
below the cicatrix ; and it is remarkable that, 
although the animal uttered a loud cry, the 
section excited no contraction of the muscles. 
The lower portion of the nerve was now ex- 
posed to the galvanic stimulus of a single pair 
of plates, was cut and pulled in every possible 
way, but not the slightest muscular contraction 
was excited. 

“* For the sake of comparison, the nerve of 
the opposite side was divided, when the animal 
showed signs of suffering the most severe pain, 
and violent muscular spasms took place; and, 
after the division, very slight irritation of the 
nerve itself, that is to say, of the lower portion 
of it, or merely of the muscles, excited strong 
twitchings, even after death. 

“« Ten weeks after the division of the nerve 
in the dog, the ends were found to be reunited. 
The experiment was performed exactly as in the 
rabbit, and the result, as to the effect on the 
nerve, was entirely similar: it had lost all its 
excitability; but the muscles still contracted 
slightly when stimuli were applied directly to 
them immediately after death: however, this 
remaining irritability was gone, while, in the 
muscles of the opposite leg, the strongest con- 
tractions could be excited. 

“« Five weeks after the nerve had been di- 
vided in the second rabbit, we proceeded to 
examine its state, and were the more interested 
on account of the short time that had elapsed 
since its division. The ends were not united ; 
they were somewhat swollen, and connected 
with the surrounding cellular tissue. In the 
other instances, the portion of nerve removed 
measured about four lines only; here its length 
was eight lines. No contraction of the muscles 
could be excited by irritating the nerve either 
mechanically or by a chemical stimulus, caustic 
potash, or by galvanism ; nor by irritating the 
muscle itself, aithough the rabbit had plenty of 
vital power. Qn the left side the muscles were 
found irritable, as in the other cases, both before 
and after death. 


38 


“ The foregoing experiments prove, at least, 
that when the va Detainee Tf the nerves 
with the brain is wholly cut off, they gradually 
lose the power of exciting the muscles to con- 
traction, while the muscles lose their irritability. 
The result would, however, have been still 
more decisive if, in place of a single pair of 
plates, a small galvanic battery had been em- 
a to stimulate the nerves and muscles. 

t, and that alone, would have enabled us 
to determine with certainty whether all the 
ete! of the muscles, in two of the cases, had 

an lost. The experiments as they were made, 
however, prove distinctly enough the necessity 
of communication with the brain for the pre- 
servation of nervous and muscular power. We 
may from them conclude also that if, after the 
division of a nerve, the excitability of the lower 
portion, and the irritability of the muscles are 
restored, the nerve has itself been completely 
reproduced ; and that this has not been the 
case if the nerve and muscle do not retain 
their vital properties.” 

I may here observe, that an experiment, si- 
milar to those of Professor Miller and Dr. 
Sticker, in which Sir Astley Cooper assisted 
the late Dr. Haighton, was made in this coun- 
try many years ago, but never published. The 
sciatic nerve was divided ina dog. In a few 
days the lower portion had lost its power of 
exciting muscular contraction. 

These statements appear, then, sufficiently 
opposed to each other ; how shall we explain or 
reconcile them? Before I proceed to discuss 
this question, I must beg the attention of the 
reader to a third series of observations and 
experiments, in a certain sense at variance with 
both those which have been detailed. 

My own attention was first drawn to this 
interesting point by the fact, well known to 
physicians, that if we administer strychnine to 
patients affected with paralysis, it is frequently 
the paralytic limbs which first manifest the 
culiar influence of this powerful remedy. . 
Fouquier has, I believe, too hastily generalized 
this effect of strychnine on the muscles of pa- 
ralytic limbs. And how well do I remember 
the same remark being made by M. Louis, as, 
in our visit round his wards at La Pitié, we 
came to a case in point. From that moment I 
did not cease to revolve the question in my 
mind, and to devise modes of observation and 
experiment to solve it. Certainly the conclu- 
sion of M. Ségalas d’Etchepare, in regard to it, 
is any thing but satisfactory. M. Ségalas ob- 
serves :— 

“ Ces expériences réunies autorisent donc a 
conclure que le tétanos produit par la noix vo- 
mique a pour condition premiere de son déve- 
loppement la présence du poison dans le sang, 
et que les phénoménes qui l’accompagnent sont 
dus a l’action anormale de ce fluide sur le sys- 
teme nerveux. 

“« Cette manitre de considerer l’action de la 
noix vomique donue un moyen simple d’expli- 
quer les effets de cette substance chez l’homme, 
et particulitrement ce fait si remarquable de la 
contraction des muscles paralysés plus prompte 
et plus énergique que celle des muscles sains, 


IRRITABILITY. 


fait observé d’abord par M. Fouquier,* et con: 
staté depuis par tant de praticiens du premie 
ordre. II est facile, en effet, de concevoir qu 
les muscles sains, soumis a la fois 4 l’empi 
du cerveau et a l’action du poison, résisten 
celle-ci plus que les muscles paral qu 
soustraits a influence cérébrale, ne sont ph 
commandés que par le poison.” 
Upon these observations of M. Ségalas, 3 
Ollivier remarks—* Mais s’il en est ainsi, con 
ment se rendre raison d’un fait observé ¢ 
long-temps par tous les praticiens, et sur lequ 
je viens d’appeler l’attention, c'est que la ne 
vomique cause souvent de violentes douleu 
dans les membres paralysés, sans ap port 
aucun trouble dans les ies saines? Pow 
quoi cette action spéciale sur les seuls organ 
paralysés? et, d’un autre cété, la douler 
percue ne prouve-t-elle pas que les partic 
paralysées ne sont point isolées entitrement 
centre nerveux, et qu’ainsi ce ne peut étre 
cette inconstance qu’on doive attribuer la local 
sation singuliére des effets de la strychnine ?”” 
It will soon be seen that this view, like ; 
former one, is far too general, far too indiser 
minate—that it is not in every case of paralysi 
that the strychnine would first display its it 
fluence on the paralytic limbs. Meantim 
however, I figured to myself the fact of 
strychnine acting on the spinal marrow, an 
diffusing its power equally along the nerves, 
the right hand and to the left, to the muscles | 
which they proceed respectively: and I ask 
myself the question—lIs the difference observe 
in its ultimate effects on those muscles, th 
power being obviously the same, owing to 
difference in the degree of the irritability of 
muscular fibre itself? Is the irritability of the 
fibre actually angmented? If so, the pheno 
menon would be explained ! . 
I waited with anxiety for opportunities 
submitting this question to the decision of 
periment. This I entrusted, in the first in 
stance, to my young friend and intellige 
pupil, Mr. Dolman. The result was as I an 
ticipated. A little child, aged two years, wa 
perfectly paralytic of the left arm. i 
est shock of galvanism was directed to be ap 
lied which should produce an obvious effec 
t was uniformly observed that the paralyt 
limb was agitated bv a degree of galva 
energy which produced no effect on the healt 
imb. 
A similar patient, with lysis of one le 
was creel to the came’ eisai by m 
friend and former pupil Mr. W. F. Barlow, an 
with the same result. zl 
I repeated the trial on several patients af 
fected vith hemiplegia, at my own house, uni 
formly with the same event: the paralytic limbs 
were always moved by an influence which 
lower than that required to affect the health 
limb, or if both limbs were agitated, it wa 
uniformly the paralytic limb which was mor 
shaken than the other. , 


i= 
yy = 


a 


‘an 


* Memoire sur l’emploi de la noix vomique dan 
les paralysies, par M. Fouquier, 1815. 
+ Traité de la Moélle Epiniére, 1827, p. 841. 


IRRITABILITY. 


_ I next repeated my observations upon a more 
extensive scale, at the St. Mary-le-bone and St. 
Pancras Infirmaries. There were two exceptions 
to the rule; whilst the numbers in which the 
phenomena as already described were observed 

_ were considerable. 

a These exceptional cases I shall notice parti- 

_ cularly hereafter. I must now remark that 

these observations seem, even more than those 

_ of Prochaska, Nysten, and Legallois, at vari- 

ance with the experiments of Professor Miiller 

_and Dr. Sticker. Before I proceed to discuss 

- this question, I must, however, detail some ex- 

_ periments of my own. 

| They were made on six frogs. I divided the 

_ Spinal marrow immediately below the origin of 

_ the brachial plexus ; and I removed a portion 

_ of the ischiatic nerve of the right posterior ex- 

_tremity. I had immediately, or more remotely, 

the following interesting phenomena. 

ist. The anterior extremities alone were 
moved spontaneously; both posterior extremi- 
ties remaining entirely motionless, when the 
animal, placed on its back, made ineffectual 
efforts to turn on the abdomen. 

_ 2d. Although perfectly paralytic in regard to 

Spontaneous motion, the left posterior extre- 

mity, that still in connexion with the spinal 

_ Marrow, moved very energetically when sti- 

_ mulated by pinching the toes with the forceps. 

_ 3d. The right posterior extremity, or that of 

_ which the ischiatic nerve was divided, was en- 

_tirely paralytic, both in reference to sponta- 

_ neous and excited motions. 

__ 4th. After the lapse of several weeks, whilst 

_ the muscular irritability of the left posterior ex- 
tremity was gradually augmented, that of the 

_ right was gradually diminished, phenomena ob- 

_ served when the animal was placed in water, 

through which a slight galvanic shock was 

_ passed accurately in the direction of the mesial 

plane. 

___In this interesting experiment we have, then, 
first the phenomena of loss of spontaneous mo- 

_ tion on removing the influence of the brain, the 

_ excited or reflex actions remaining; and the 

loss of these on removing the influence of the 

spinal marrow; secondly, in the case of mere 
cerebral paralysis, we have augmented irritabi- 
lity, and in that of the spinal marrow we have 

_ the gradual diminution of this property. 

] 5th. Strychnine being now administered, the 

_ anterior extremities and the left posterior extre- 

' mity, or that still in connexion with the spinal 

_ marrow, became affected with tetanus ; but the 

right posterior extremity, or that severed from 

_all nervous connexion with the spinal marrow, 

_Temained perfectly flaccid. 

__ 6th. Lastly, the difference in the degree of 

"irritability in the muscular fibre of the two 

_ limbs was observed when these were entirely 

_ separated from the rest of the animal. 

__ In a word, the muscles of the limb para- 
lysed by its separation from both cerebrum and 
spinal marrow, had lost their irritability; whilst 
those of the limb separated from its connexion 
with the cerebrum only, but left in its con- 
nexion with the spinal marrow, not only re- 
tained their irritability, but probably possessed 


ett 


39 


it in an augmented degree. The next question 
came to be,—Do these phenomena obtain in 
the human frame? _I visited a patient affected 
with hemiplegia, including paralysis of the face, 
and I passed a slight galvanic shock through 
two pieces of metal, of which one was placed 
over each cheek. The muscles of the paralytic 
side were most affected. 1 repeated the expe- 
riment with the same result. I now compared 
with these, two cases of injury of the facial 
nerve, passing the galvanic shock in the same 
manner, through the fibres of the orbicularis : 
it was now the muscle of the healthy side which 
was affected by the galvanism, the eyelid of 
that side being closed, whilst that of the para- 
lytic side gaped as before. I next compared 
the effect of galvanism in two cases of complete 
paralysis of the arm, one hemiplegic, the other 
the result of dislocation of the shoulder. The 
muscles of the former were more, those of the 
latter less, irritable than those of the healthy 
arm respectively, as were also those of the arm 
of a patient affected with the paralysis induced 
by lead. Lastly, I compared the cases of pa- 
ralysis of the lower extremities, one arising 
after pertussis, and therefore cerebral, the other, 
I think, from disease within the lumbar verte- 
bre: in the former there was augmented, in 
the latter, diminished irritability. 

By means of these experiments and observa- 
tions we are enabled, I believe, to explain all 
the apparent discrepancies between the state- 
ments of former authors, and between each of 
them and my own. 

The observations of Nysten and others deter- 
mined that the irritability of the muscular fibre 
still existed in ordinary hemiplegia; but they 
did not extend far enongh to determine the 
comparative degree of irritability of the para- 
lytic and of the healthy limbs, or the question 
whether, in the former, the irritability was dimi- 


. nished—the event probably expected—or aug- 


mented, a result, I believe, never anticipated. 

Prochaska and Nysten and Legallois failed 
in their experiments, too, by not allowing time 
for the change in the condition of the irritability 
of the muscular fibre to take place. 

Professor Miller and Dr. Sticker, on the 
other hand, did not distinguish between para- 
lysis arising from separation from the cerebrum 
merely, and paralysis arising from separation 
from the spinal marrow, a distinction of the 
utmost importance in every point of view, and 
that which explains the phenomenon under 
discussion. The term paralysis has been used 
by all the authors whom I have quoted in too 
general a sense. This is so true that I may 
affirm that in one kind of paralysis, that which 
removes the influence of the cerebrum, and 
which is therefore paralysis of spontaneous or 
voluntary motion, there is augmented irrita- 
bility; whereas in the other, that which severs 
the influence of the spinal marrow, the irrita- 
bility is diminished or even annibilated. 

We may conclude that in cerebral paralysis 
the irritability of the muscular fibre becomes 
augmented from want of the application of the 
stimulus of volition; in paralysis arising from 
disease of the spinal marrow and its nerves this 


40 


irritability is diminished, and at length becomes 
extinct, from its source being cut off. 

We may further deduce, from the facts whith 
have been detailed, that the spinal marrow and 
not the cerebrum is the special source of the 
power in the nerves of exciting muscular con- 
traction, and of the irritability of the muscular 
fibre; that the cerebrum is, on the contrary, 
the exhauster, through its acts of volition, of 
the muscular irritability. 

As a further deduction from the same facts, 
we may infer the diagnosis between cerebral 
and ci paralysis: mere cerebral paralysis is 
attended by augmented irritability, w 
spinal paralysis is that which is attended by 
diminished irritability. This fact will prove 
useful in many obscure cases. 

Having thus cleared up the physiological 
question, I proceed to the application of the 
principle to pathology ; and I may here observe 
that there is a whole series of phenomena which 
admit of explanation by its aid. 

And, first, the exception to the rule of aug- 
mented muscular irritability in paralytic limbs, is 
obviously dependent upon its existing in the 
cases of paralysis from the severed influence of 
the spinal marrow, as distinguished from those 
arising from the severed influence of the cere- 
brum merely. 

Secondly, we understand at once why the 
influence of strychnine is first and most seen in 
cerebral paralysis in the paralytic limbs. 

But there are still some other points which I 
must bring before the notice of the reader. 

The first of these is the influence of emotion 
in | pe limbs. 

he second is the similar influence of certain 
acts of respiration; as yawning, sneezing, 
coughing, &c. 

The third, the similar influence of the tonic 
power. 

It must have occurred to us all to observe 
the influence of surprise or agitation on the arm 
and hand, and perhaps on the leg, of a patient 
long affected by hemiplegia, whilst the limbs 
of the healthy side remained unaffected. In 
this case the influence of the emotion is, like 
that of strychnine in the case formerly discussed, 
exerted equally upon the limbs of both sides; 
but it is the muscles of the paralytic limbs 
which are most irritable, most susceptible of 
the stimulus ; it is, therefore, these limbs which 
are most convulsively affected. 

The same phenomenon is not observed in 

plegia, because the influence of the emotion 
is cut off from the affected limbs. 

Case 1.—I was called to a patient a short 
time ago, affected at that moment with bron- 
chitis. He was forty-three years of age, and at 
the age of twenty-four had been seized with 
hemiplegia. Recovering from the immediate 
danger of the attack, he remained hemiplegic, 
searcely regaining the use of the hand and arm 
at all, and only partially that of the leg. 

Whenever this patient is excited by meeting 
an acquaintance, or in any similar way, he has 
a little strabismus, and the hand and arm are 
contracted and convulsed in the most extraor- 
dinary manner: whenever he coughs, the leg 


IRRITABILITY. 


is thrown involuntarily upwards. The arm i 
severed, as it were, from volition, but affeete 
by emotion. 

Similar facts have been observed in t 
to the influence of certain respiratory acts, 
especially those of yawning, sneezing, &c. 

Dr. Abercrombie details the following int 
resting case in a note to the late Mr. Shaw. 

“ T think the following case will be interes 
ing to you and Mr. Bell. I had some tim 
ago under my care, a man affected with hemi 
plegia of the left side; the palsy complete, will 
out the least attempt at motion, except um 
the following circumstances : he was very muc 
affected with yawning, and e time — 
yawned the paralytic arm was raised up, with 
firm steady motion, until it was at right angle 
with his body (as he lay in bed on his back 
the fore-arm a little bent inwards, so that hi 
hand was above his forehead at its great 
elevation. The arm was raised steadily dui 
the inspiration, and when the expiration bega 
seemed to drop down by its own weight, wit 
considerable force. He continued liable to 
affection for a considerable time, and it cease 
gradually as he began to recover the natura 
motion of the limb.”—That is, as I concludi 
as the state of augmented irritability was te 
moved by the returning acts of volition, ~~ 

Not less interesting are the effects of 
tonic power. In cases of hemiplegia of lon 
duration, the paralytic limbs, but especially 
arms and hands, are drawn into a state 0 
chronic, rigid, contraction. This phenomeno 
is owing to the principle of tone constantl 
acting upon muscles now ing augmentet 
irritability, whilst they are never, or rare 
relaxed by acts of volition. . 

A similar effect is seen in idiots born with 
atrophied cerebrum: the influence of voli 
is wanting; that of the spinal marrow, the 
source, at once, of the tone and of the irrita 
bility of the muscular system, is in constan 
action, and induces chronic contraction, a 
effect which must, however, be distinguisher 
from that of spasm, which is excited imme 
diately by some disease of the spinal marrot 
itself. ta 

I may now resume the subject of the actio 
of strychnine on paralytic limbs. It is obviot 
that the generalization of M. Fouquier, M. Sé 
galas, and others, that the chnine atta 
the paralytic rather than the healthy limbs, wa 
too hasty. This is only true in those cases « 
paralysis in which the muscles still remain i 
nervous connexion with the spinal marrow; tl 
opposite result is observed in those other case 
in which such connection between the musel 
and the spinal marrow is intercepted. : 

I would here make another observation. The 
arms and hands, generally speaking, are mor 
under the influence of the cerebrum than th 
lower extremities; and these, on the othe 
hand, are more under the influence of th 
spinal marrow than the arms and hands. TI 
superior extremities are more and more fre: 
quently affected by hemiplegia than the infer 
these are more influenced by tetanus, b 
strychnine, &c. than the former, a fact whit 


ia 


IRRITABILITY. 


I have observed, in regard to strychnine, in 
_ Some cases of hemiplegia. These facts must 
_ be borne in mind in making our observations. 

__ Another circumstance must also be noticed. 

‘The more perfect the paralysis, generally 
_ Speaking, the more the irritability of the mus- 
(Salar fibre is augmented. In hemiplegia, the 

nn is generally at once more paralytic and 
“More irritable than the leg. In chronic cases, 
however, the irritability becomes impaired, 
together with the nutrition. 

_ Iwill now adduce a few cases which, how- 
‘ever succinctly detailed, will exemplify and 
substantiate the preceding observations. 
' Case 2—On January the 16th, 1839, I 
Visited a patient who had been seized with 
hemiplegia nine months before: the arm was 
perfectly paralytic, the leg less so, the face less 
so still. On passing the galvanic influence 
_ through the arms, the left or paralytic arm was 
- much more affected than the right, and dis- 
_ tinetly affected by a force which induced no 
_ effect whatever on the right, the tendons start- 
' ing on each completion of the galvanic circle ; 
the contraction of the muscles of the left side 
_ of the face was seen in its effect on the features ; 
_ and that of the left gastrocnemius, in its effect 
_0n the tendo Achillis, when no effect was per- 
_ ceptible on the right side of the face, or in the 
right leg. 
In this patient other and very interesting 
_ phenomena were observed : 
_ 1st. The arm has, from the beginning, been 
' much more paralytic than the leg or the face: 
_ 2d. The influence of strychnine was observed 
in the paralytic arm and leg only, in the latter 
_ more than in the former: 
_ 8d. Any sudden noise, or other causes of 
emotion, affect the paralytic side only—the leg, 
however, more than the arm: 
__ 4th. Yawning and sneezing move the para- 
_ lytic limbs; the former the arm, the latter the 
_ leg, principally : 
_ 5th. The act of stretching, and the act of 
“raising the right arm above the head, induce 
unconscious movements of the left or paralytic 


"7 


_ 6th. During sleep, the left or paralytic arm 
and hand are greatly contracted and painfully 
_ pressed to the side: 

; 7th. The paralytic arm shrinks from the 
application of cold, as the sudden contact of a 


hemiplegia : 
_ 8th. Lastly, the paralytic hand and arm are 
a constantly in a state of contraction. 

_ I repeated the trials with the galvanic shock, 
_ with the same results, on February the 14th. 

__ Case 3.—On January the 15th and 22d, 1839, 
_ I passed a slight galvanic shock through the 
_ orbicularis of each side of the face, in a patient 
_ affected with paralysis of the left facial nerve 
_ from exposure to cold, of six weeks’ duration. 

Here the right eyelid was forcibly closed, the 
left or paralytic eyelid being totally unaffected. 
Case 4.—On February the 13th, I passed 
the galvanic shock through the two orbiculares 
in a patient whom I visited with Mr. Burford, 
and in whom the facial nerve was partially 


cold hand; an example of the reflex action in\ 


41 


paralyzed by the removal of a considerable 
branch of the nerve, together with a tumour 
which had formed in its course along the cheek. 

The muscle of the paralytic side was un- 
affected, whilst that of the healthy side closed 
the eyelids on every application of the galvanic 
influence. 

Case 5.—I have more recently performed the 
same experiment on a patient affected with 
paralysis of the facial nerve, from otitis and 
disease of the temporal bone, with precisely 
the same result. 

Case 6.—On February the 9th, I compared 
the galvanic influence in two patients at 
the St. Pancras Infirmary: both were affected 
with complete muscular paralysis of the arm ; 
the first case was cerebral, being hemiplegia; the 
second was an injury of the brachial plexus, 
having resulted from dislocation of the shoulder ; 
the results were what I had anticipated ; in the 
case of hemiplegia, the irritability of the 
muscles of the paralytic limbs was greater than 
that of the muscles of the healthy limb; in the 
case of injured brachial plexus, the opposite 
state of things was observed, the irritability of 
the muscles of the paralytic hand and fore-arm 
being greatly diminished. 

Cause 7.—On January the 23d, 1839, I passed 
the galvanic shock through the hands of a 
patient who had been gradually affected with 
paralysis of the right, from handling leaden 
types, as a compositor. Here, again, the para- 
lytic muscles were unaffected by a degree of 
galvanism, which induced an evident effect on 
the muscles of the healthy limb. 

Cases 8 and 9.—On January the 10th, 1839, 
I galvanized a little boy with paralysis of the 
left leg; the muscles were more irritable than 
those of the healthy leg; the affection had fol- 
lowed pertussis, and I concluded that it was 
cerebral. This conclusion was confirmed by a 
fact which I learnt afterwards, viz. that in the 
commencement there was imperfect closure of 
the eyelids during sleep. On the same day I 
tried the galvanic influence in a case of partial 
paraplegia in a little girl, a patient of Mr. Bur- 
ford; in this case the muscles of the paralytic 
limbs were less irritable than those of the 
healthy limbs; I concluded that the disease 
was seated in the course of the nerves, and 
probably within the lumbar vertebre. 

Case 10.—It has been suggested to me that 
the loss of irritability in the cases of spinal 
paralysis might be owing to the defective nutri- 
tion of the muscles. I therefore tried the effect 
of galvanism in a case of chronic cerebral 
paralysis, or hemiplegia, with much emaciation 
of the paralytic muscles. I found these muscles, 
as before, much more irritable than those of the 
unaffected limb. 

I must repeat, that I am perfectly aware of 
the sketchy manner in which these notes of 
cases are given; but I have thought it better to 
leave the further details for another form of 
communication. 

In the meantime we may conclude, that by 
the test afforded by the galvanic trough, we are 
enabled to effect a diagnosis between the cases 
to which I nowallude. Disease of the cere- 


42 


brum itself,—disease of the dorsal portion of 
the spinal marrow,—induces cerebral paralysis, 
hemiplegia, or paraplegia ; disease compressing 
or destroying the facial nerve, or the cauda 
equina in the lumbar region, induces both 
cerebral and spinal paralysis. In the former 
case we shall i augmented, in the latter 
diminished irritability of the muscular fibre. 

I may now resume the points of this article, 
and observe, 

ist. That the spinal marrow, exclusive of 
the cerebrum, is the source of the muscular 
irritability : 

2d. That the cerebrum is, in its acts of voli- 
tion, an exhauster of that irritability : 

3d. That in muscles separated from their 
nervous cunnexion with the brain we have 
augmented irritability : 

4th. That in muscles separated from their 
nervous connexion with the spinal marrow we 
have, on the contrary, diminished irritability : 

5th. That the degree of the irritability of the 
muscular fibre of paralytic limbs, com 
with that of the muscles of the healthy limbs, 
will afford us a source of diagnosis between 
cerebral and spinal paralysis, and especially 
between 
- Hemiplegia of the face, and 
. Paralysis of the facial nerve ; 

. Hemiplegia of the arm or leg, and 
. Disease of the nerves of these limbs ; * 
. Disease of the spinal marrow in the 
dorsal region, and 
6. Disease of the cauda equina in the 
lumbar region; &c. 

6th. That the greater influence of emotion, 
of certain respiratory acts, of the principle of 
tone, kc. on the muscles of certain paralytic 
limbs than on those of healthy limbs, depends 
on their augmented irritability : 

7th. That the same principle explains the 
greater susceptibility of the muscles in certain 
cases of paralytic limbs, to the influence of 
strychnine : 

8th. That, in the conclusions of M. Fouquier, 
Professor Miiller, &c., a sufficient distinction 
was not made between the influence of the 
cerebrum and of the spinal marrow, which in 
this, as in so many other respects, have such 
different properties : 

9th. From these and other experiments and 
observations, I conclude, too, that sleep restores 
the irritability of the muscular system, by 
arresting the acts of volition which exhaust or 
diminish it; muscular efforts, on the other 
hand, diminish the irritability and induce 
fatigue. 

Before I conclude, I must beg my reader’s 
attention to some experiments of that able phy- 
siologist, Dr. J. Reid, of Edinburgh, which 
appear, at first sight, to be contradictory to 
those which I have just detailed. 

Dr. J. Reid’s paper is published in the 


Or won 


* In disease of the cervical vertebre the arms 
are sometimes paralyzed without paralysis of the 
legs; this probably arises from compression of the 
brachial plexus. See Sir B. Brodie’s paper in the 
Medico-chirurgical Transactions, vol. xx. p. 130; 
the galvanic trough would determine the question. 


IRRITABILITY. 


of the British Associs ‘ion 


Fourth Report 
the Advancement of Science, p. 671. I 
follows :— ry 
* Although prseloyen are still divided 
opinion as to the question whether nerves f 
nish a condition necessary to the irritation 
muscles, (i.e. whether every stimulus 
excites a muscle to contraction acts 0 
through the intervention of nervous filamen 
they have now very generally abandoned 
once prevalent theory, that the irritability 
muscles is derived from the brain or sp 
cord, i. e. that muscles are continually 
ceiving, through their nerves, from — 
larger masses of the nervous system, supp 
of a certain influence or energy, which e 
them to contract; and that some of the 
ments of Dr. Wilson Philip, in particular, ; 
seuerslly regarded as decisive against | 
eory. 
E Dr. Wilson Philip found by experi 
that the irritability of a muscle of which 
nerves were entire, was exhausted by applyi 
a stimulus directly to the muscular fik 
(sprinkling salt on them) even more quick 
than that of a muscle of which the nerves h 
been cut, and where all communication wi 
the yg source of nervous influence | 
energy had been cut off; and he states gem 
rally that a muscle of voluntary motion, if « 
hausted by stimulation, will recover its irri 
lity by rest, although all its nerves have 
divided. ¥ 
** But in opposition to this statement, at 
in support of the old theory of nervous ii 
ence continually flowing through certain of t 
nerves into the muscles, it has lately been state 
by Mr. J. W. Earle, that when nerves | 
the limb of a frog were cut, the skin strip 
off, and the muscles irritated by sprinkling sé 
on their fibres, until they had lost their pows 
of contraction, although they did not lose th 
power much more quickly than when the nervs 
were entire, yet they did not regain their pow 
although left undisturbed for five weeks; wh 
the muscles of the limbs of another frog, sim 
larly treated, but of which the nerves were le 
entire, completely recovered their irritabilit 
* Tt occurred as a fundamental objection 
the experiment of Mr. Earle, that in the ea: 
where the nerves had been divided, the m 
cles had become inflamed ; being found at # 
end of the five weeks ‘ softer in their 
than natural, a good deal injected with b 
and with some interstitial deposition of fluid 
them ;’ while in the limb to which the salt 
been applied, but of which the nerves 
entire, and where the irritability was recovere 
‘ although the colour.of the muscles was rath 
darker than natural, their texture remained u 
changed, and there was no interstitial depos 
tion of fluid in them.’ cntll 
* In these circumstances it might eviden 
be supposed that it was the inflammation an 
disorganization of the muscles, not the sectior 
of the nerves, which prevented the recovery 
the irritability in the case where the nerves hai 
been cut; and it became important to have th 
experiment repeated, with care to avoid suc 


7 
+ 
; 


injury of the limb of the animal as should 
‘cause inflammation to succeed the section of 
the nerves. 

_ “With this view, Dr. Reid performed a num- 
ber of experiments on frogs, in which the irrita- 
bility of the muscles of both hind legs was ex- 

_hausted or greatly diminished by galvanism, 
afer the nerves of one leg had been divided, 
_ and the lower part of the limb rendered per- 
" fectly insensible and incapable of voluntary 
- motion, (but without stripping off the skin,) 
_ while the nerves of the other had been left 
entire. The state of the muscles of both limbs 
Was examined after some days. The results of 
experiments were not uniform; but in 
several, where every attention to accuracy seems 
_ to have been paid, the irritability of the mus- 
eles in the palsied limbs appeared to be re- 
stored as perfectly as in others ; contractions 
_ being excited in them, in several instances, by 
the galvanism from four or even two plates, 
_ whereas they had formerly been irritated until 
_ they were no longer excitable by that from 
fe fourteen plates. 
ae That the muscles which thus recovered 
their irritability had lost all nervous connexion 
with the brain or spinal cord was proved, not 
only by their obvious insensibility, but by after- 
wards cutting off the heads of the animals and 
forcing a probe along the spinal canal, which 
excited forcible contractions in all parts, ex- 
cepting the palsied limbs. 
__ Dr. Alison’s paper contained the details 
of several of these experiments ; and he stated, 
if in conclusion, that as a positive result in such 
an inquiry must always outweigh a negative 
_ one, (particularly where a source of fallacy at- 
_ tending the latter can be pointed out,) these 
experiments appear fully to justify the assertion 
of Dr. Wilson Philip, that a muscle of volun- 
ay motion may recover its irritability by rest, 
_ although all its nerves be divided; 
§ that they afford, perhaps, more direct evidence 
_ than any others in support of the doctrine of 
_ Haller, now generally admitted in this country, 
that the property of irritability in muscles is 
independent of any influence or energy con- 
 tinually flowing from the nervous system, 
although, like every other endowment of living 
_ animals, it is subjected to the control of causes 
which act primarily on that part of the living 
frame. 
4 “ Dr. Allen Thomson expressed a doubt 
__ whether these experiments warranted the con- 
clusion drawn from them, not because he ac- 
_ quiesced in the theory to which they are op- 
posed, nor because he called in question the 
accuracy of the results described to have been 
_ obtained, but because he knew that former ex- 
_ periments had failed in producing such dimi- 
bution or exhaustion of the irritability of mus- 
__ cles as had been found by Dr. Reid; and con- 
ceived it possible that some of the numerous 
fallacies to which such experiments are liable 
might not have been sufficiently guarded 
against. 
“ The accuracy of Dr. Reid’s statement as 
to the great diminution or apparent exhaustion 
of the irritability of the muscles under the in- 


fe 


Vu 


IRRITABILITY. 


and, 


43 


fluence of galvanism, and the subsequent reco- 
very of the power, notwithstanding the division 
of all their nerves, was satisfactorily established. 
It is to be remarked, however, that in these 
experiments, as usual in such cases, the limbs 
to which the galvanism was applied were kept 
moist by the same saline solution with which 
the galvanic trough was charged; and Dr. 
Thomson has observed, that when they are 
moistened with pure water, the diminution of 
the irritability under the excitement by galva- 
nism is much less obvious. Hence he was led 
to suspect that the apparent loss of power in 
the muscles under that process might depend, 
not on the circumstance of repeated excitement, 
but on a degree, however slight, of injury to 
their texture by the action of the salt. This 
inquiry he proposes to prosecute further; but 
in the meantime it is certain that by the usual 
process of galvanizing a living muscle moist- 
ened by a saline solution, a very great diminu- 
tion of its irritability may be effected, which 
may subsequently be regained, notwithstanding 
the division of all its nerves; and as the fact 
of its recovery, not the cause of its diminution 
or exhaustion, is the point on which the infe- 
rence drawn from these experiments rests, that 
inference may be held to be sufficiently justi- 
fied.” 

The first question is,—what is the nature of 
that effect produced upon the nervous and mus- 
cular system by such agents as those employed 
in these experiments temporarily to diminish or 
suspend their powers? The immediate effect of 
an attack of hemiplegia,the immediate effect of 
an injury done to the spinal column, by acci- 
dent, or in an experiment, the immediate effect 
of galvanism, or other stimuli, applied to the 
nerves or muscles, is to suspend, for a time, the 
phenomena of the excito-motory power of the 
nerves, and of the irritability of the muscles, 
respectively ; which, however, repose renews. 
What is the nature of these changes? Do they 
not consist in the sudden reduction and more 
gradual removal of some physical effect, diffe- 
rent from the diminution and restoration of a 
purely vital property of these textures, widely 
different from the slowly induced loss of irrita- 
bility resulting from the removal of its source, 
the natural physical condition remaining un- 
changed? At any rate we must agree with 
Legallois. ‘Il faut se souvenir que deux faits 
bien constatés ne peuvent jamais s’exclure l’un 
l’autre, et que la contradiction qu’on croit y 
remarquer tient ace qu’il y a entre eux quelque 
intermédiaire, quelque point de contact qui 
nous échappe.” * 

I must here adduce two experiments of my 
own, performed and published many years ago.+ 

“ In an eel, in which the brain had been 
carefully removed, and the spinal marrow de- 
stroyed, the stomach was violently crushed with 
ahammer. The heart, which previously beat 
vigorously sixty times in a minute, stopped 
suddenly and remained motionless for many 
seconds. It then contracted ; after a long in- 


* CEuvres, Paris, 1824, t.i. p. 21. 
+ See my Essay on the Circulation of the Blood, 
1831, p. 160, 188. 


a’ 


terval it contracted again, and slowly and gra- 
dually recovered an action of considerable fre- 
quency and vigour.” 

“ A frog was made perfectly insensible by 
the application of laudanum or alcohol. Its 
respiration ceased. It did not move on the 
application of any irritant. The circulation in 
the web was carefully observed. When it had 
long continued in the same enfeebled state 
without change, the thigh was crushed. The 
circulation in the minute and capillary vessels 
ceased at once, and never returned. The sto- 
mach was now crushed in the same manner. 
The heart ceased to beat for many seconds. 
Its beat then returned, but never regained its 
former force.” 

In these experiments we have the sudden 
influence of shock and its gradual subsidence. 
The experiment is peculiarly interesting in 
many points of view :— 1. it is the only one on 
record of the effects of shock induced solely 
and exclusively through the medium of the 
ganglionic system ; 2. it exemplifies the. effect 
of shock or excessive stimulus on the heart, 
with its gradual though incomplete subsidence. 

The connexion of the ganglionic system with 
the irritability of the visceral muscles,—the 
heart, the stomach, the intestines, &c. forms the 
subject of an experimental investigation, in 
which I am at this moment engaged, and the 
results of which I purpose to give under the 
head of vis nervosa and vis insita. It is pro- 
bable that the ganglia are to thé internal mus- 
cular organs what the spinal marrow is to the 
muscles of the limbs, viz. the power of irritabi- 
lity, &c. This inquiry is founded on a fact 
first ascertained by myself, that, in spring, we 
may, by portions at a time with considerable 
intervals, totally destroy the brain and spinal 
marrow in the frog, eel, &c. leaving the circula- 
tion in the web or the fins and tail.* Wehave 
thus isolated the ganglionic from the rest of the 
nervous system, on which we may therefore 
proceed to experiment, watching the effect of 
various agents on the circulation and on the 
action of the heart, the stomach, the intestines. 

We have thus passed in review in its anato- 
mical, physiological, zoological, pathological, 
and those peculiar relations, the question of the 
irritability of the muscular fibre. It only 
remains for us to advert, once more, to the ex- 
treme importance of this principle in physiology : 
all physiology is involved, indeed, in the topic 
of the nervous system and the vascular system, 
and the principle of irritability seems, with its 
various and appropriate stimuli, to be placed 


between those two. 
(Marshall Hail.) 
JOINT.—See Articutation, and the arti- 
cles under the headings of the several joints for 
both the normal and abnormal anatomy. 
KIDNEY .—See Ren. 


KNEE-JOINT (normal anatomy of the). 
Gr. yév; Lat. genu; Fr. genou; Germ. 


* Op. cit, p. 136, 


NORMAL ANATOMY OF THE KNEE-JOINT. 


. pelvis in women gives, ceteris paribus, — 


Kniegelenk ; Ital. ginocchio. The knee-joi 
the largest joint in the body, results from t 
articulation of the os femoris with the tk 
below and the patella anteriorly. It admits 
extensive motion as a ginglymus, to which 
added an arthrodial motion, or a small degre 
rotation of the leg and foot, when the jon 
partly flexed. The articular surfaces are lai 
and complicated, the ligaments numerous, a 
the joint chiefly superficial; circumstam 
necessary to the freedom, stability, and sy 
metry of the limb, but exposing this import 
articulation to frequent accident and disea 
It is intended here to describe so much of 
the bones entering into the formation oj 
joint, and, 6, the cartilages, ligaments, &e., 
may be necessary to the elucidation of, ¢, | 
mechanical functions. 
(a.) Bones. The shaft of the os femor 
which in the middle of the thigh is triangul: 
becomes of a four-sided form as it approach 
the knee, in consequence of the bifurcatic 
the linea aspera. This rough ridge, whic 
the middle of the bone forms a prominent px 
terior angle, divides on entering its inferior hi 
into two diverging lines which terminate at 
convex articulating eminences called condyle 
a flat triangular surface of bone is thus 
where the popliteal vessels lie. The outer lit 
is most strongly marked, and gives origin to 
vastus externus and short head of the bice 
flexor cruris: the inner line is deficient ne; 
the upper part, over which the femoral 
pass into the ham; it gives attachment bek 
to the vastus internus and adductor magn 
The internal condyle is narrower and more pr 
jecting behind than the external; and in rel 
tion to the shaft of the bone, it appears to exten 
further downwards; but the natural obliqt 
pesition of the os femoris brings the condyh 
nearly horizontal. The greater width of th 


na 


greater obliquity to the os femoris than in m 
The condyles are separated behind by a d 
fossa, out of which the crucial ligaments t 
their origin ; their articulating surfaces are con 
vex both in the transverse and in the anter 
posterior directions, until in front they coales 
into ove pulley-like surface over which — 
patella plays in the motions of the joint: thi 
trochlea is convex from above downwards, br 
concave from side to side ; its outer half is me 
prominent than the inner, and extends high 
up the corresponding condyle. Above th 
trochlea there is a flattened or slightly depres 

surface, upon which the patella partly resi 
during complete extension of the joint, T 
thickness of the os femoris from front to b 
undergoes little change till the condyles sui 
denly jut out behind, and the edges of t 
trochlea rise up in front ; but from side to sid 
the shaft of the bone increases in breadth as: 
approaches the knee, the two postero-late: 
surfaces winding gradually round to beco 
antero-lateral, at the same time diverging ra 
pidly to form a smooth slope on the side of each 
condyle. Towards the posterior part of each 
of these sloping surfaces, there is an irregul 
prominence called the tuberosity, for the attach 


NORMAL ANATOMY OF THE KNEE-JOINT. 


ment of the lateral ligaments ; below which, on 
the outer condyle, there is a pit for the origin 
of the popliteus tendon, and a fossa leading 
“upwards and backwards from it which lodges 
the tendon when the joint is fully flexed. In 
the lateral aspect of the bone we best see the 
— curvature of the articulating surface. 
_ In two adult, but rather small, specimens before 
me the inferior part of the outer condyle is a 
Segment of a circle of fourteen lines radius, 
while the radius of the posterior portion is only 
_ Seven lines; similar measurements of the curves 
“of the internal condyle give radii of six and 
“twelve lines respectively: the centre of the 
‘smaller circle coincides precisely with the point 
of attachment of the lateral ligament on each 
side, and the advantages of this arrangement 
will appear when we come to consider the 
functions of the joint. The smooth articulating 
Surface of the trochlea and condyles is, in the 
 Tecent state, covered with cartilage. Above 
_ this surface and in the fossa between the con- 
dyles are numerous foramina for the transmis- 
sion of the nutrient vessels of the bone, the 
internal structure of which is here made up of 
Minute cancelli. The lower extremity of the 
08 femoris is cartilaginous at birth, becomes 
ossified from a separate centre, and long conti- 
_ hues to form an epiphysis ; but it is ultimately 
_ Joined to the shaft by perfect bony union. 
The thigh-bone exposes the largest extent of 
surface in the knee-joint; that of the tibia is 
_ the next in size. Its superior extremity is ex- 
panded into the same kind of cancellated struc- 
ture as the os femoris possesses at its lower 
_ part; and the width from side to side equals 
that of the condyles, which rest upon its upper 
Surface. That surface is nearly horizontal, in 
the erect position of the body ; ‘it is irregularly 
_ oval, the long axis passing from side to side, 
_ and is marked in the centre by a rough promi- 
_ hence or spine, in front of which is a depression, 
_ and at the back part a notch. On each side of 
_ these inequalities there is a smooth articular 
surface; the inner one the larger, especially 
from before backwards, and slightly concave ; 
while the outer one is flat round the margin 
_ and raised at the inner side by the base of the 
Spine. Viewing the bone in its anterior aspect 
we observe that below the articular surface it 
_ slopes downwards and forwards to the tubercle 
| which stands out at the upper part of the shin 
_ Or crest of the tibia; this tubercle gives insertion 
_ at its lower part to the strong ligament of the 
_ patella, a bursa being interposed between that 
ligament and its upper smooth portion. Nu- 
_ merous foramina are to be observed round the 
head of the bone for the purposes of its nutri- 
tion. Below the tubercle a section of the tibia 
shows it much reduced in size and somewhat 
_ triangular in shape; the outer side forming, in 
conjunction with the fibula, a large fossa for the 
tibialis anticus and other muscles; and the 
inner, facing also anteriorly, being a portion of 
that surface of bone which is covered only by 
skin and periosteum ; except at its upper part, 
where three flat tendons pass upon it to be 
inserted by the side of the tubercle in the follow- 
ing order; that of the semitendinosus lowest, 


45 


the gracilis next above, and the sartorius the 
highest up and most anteriorly. The posterior 
surface of the tibia at the supposed place of 
section has advanced considerably forwards, so 
as to leave a hollow for the popliteus muscle 
which lies obliquely on this part of the bone. 
A few lines below the great articulating surface 
on the head of the tibia there are two things to 
be noticed on its posterior aspect; at the outer 
side a small articular surface for the head of the 
fibula, and at the inner side a shallow pit 
where the tendon of the semimembranosus is 
inserted. } 

The patella is a flat disk of bone placed in 
front of the knee-joint; it equals in width the 
trochlea of the os femoris to which it is applied, 
the posterior surface being for that purpose 
covered with cartilage and divided into two 
slight cavities by a prominent vertical line ; the 
articular surface is oval from side to side and 
does not reach to the lower edge of the bone. 
Anteriorly, the patella is convex, and its hori- 
zontal slightly exceeds its vertical measure- 
ment, particularly in the female ; into its upper 
edge are inserted the united tendons of the 
rectus, cruralis, and vasti muscles; into its 
lower edge the strong ligamentum patelle 
which joins it to the tubercle of the tibia; it is 
covered only by skin, fascia, and some ten- 
dinous fibres, to which latter may be attributed 
the appearance of vertical strie observable on 
the bone. 

(b.) Cartilages, ligaments, §c.—-The whole 
of the bony surfaces which come into contact 
with each other or with the interarticular carti- 
lages during the movements of the knee-joint 
are covered with “ cartilages of incrustation ” 
(see ARTICULATION); and the extent of these 
on the condyles and trochlea of the os femoris, 
on the head of the tibia and the posterior sur- 
face of the patella, is well marked even in the 
dry bones by their smooth and compact ap- 
pearance and the total absence of foramina on 
the parts so covered. Besides these pure car- 
tilages there are two fibro-cartilages of a semi- 
lunar form lying upon the head of the tibia, 
which serve to deepen the articulating surfaces 
for the reception of the condyles. These semi- 
Innar cartilages, (cartilagines falcata, s. lu- 
nate) as they are named, are thickest at their 
convex edges which are attached rather loosely 
to the circumference of the head of the tibia ; 
the concave edges are thin and sharp, and lie 
unattached between the condyles and the tibia. 
The two semilunar cartilages differ slightly 
from each other in the two following points ; 
the inner one is falciform, decreasing in breadth 
from behind forwards; the greatest width being 


“at the inner and back part, five-eighths of an 


inch, whilst in front it is hardly more than one 
quarter of an inch; the anterior and posterior 
cornua are separated to the distance of an inch, 
whilst those of the outer semilunar cartilage 
approach to within three-eighths of an inch of 
each other; and, besides that the ring is thus 
more nearly completed, the breadth of the outer 
one is more uniform, being about three-eighths 
of an inch throughout the greater part. The 
thickness of either of them barely exceeds one- 


46 


sixth of an inch, at the outer margin or thickest 
~ They are both com of concentric 

bres, the extremities of which are fixed to the 
central parts of the head of the tibia, before and 
behind the crucial ligaments, with whose fibres 
they intermingle; the anterior extremities are 
usually joined together by a transverse liga- 
ment, but this is sometimes wanting. 

The ligamentum patelle, of vast importance 
in the actions of the knee-joint, is yet the most 
distant from its articular surfaces; it extends, 
broad and flat, from the lower somewhat point- 
ed portion of the patella to the inferior part of 
the tubercle of the tibia, being in the adult 
about two inches in length. It forms a strong 
inelastic but inflexible bond of union of the 
— with the tibia, and may with propriety 

looked upon as a continuation of the ex- 
tensor tendons which are inserted into the 
upper and lateral margins of the former bone; 
some fibres indeed pass over its anterior sur- 
face, but it is only through this bone and its 
ligament that the extensor muscles can act 
upon the leg. The patella is thus seen to be 
placed in a situation analogous to that of the 
sesamoid bones, in the tendons which play 
over bony surfaces, in the hands and feet. The 
ligament of the patella is covered anteriorly by 
dense integument, and the fascia of the leg: 
posteriorly a cushion of fat is interposed be- 
tween it and the joint at the upper part, while 
below it is separated from the bene by a bursa, 
whose situation was pointed out in the descrip- 
tion of the tibia. (See fig. 111, 6, vol. i. p. 252.) 
More closely applied to the joint are the lateral 
ligaments, the posterior and the crucial liga- 
ments ;and port 3 of the synovialcapsule which 
are described by some anatomists as alar and 
mucous ligaments. The lateral ligaments have 
a vertical direction at each side of the knee, and 
are placed nearer to the posterior than the ante- 
rior boundary of the joint; the upper attach- 
ment is in fact to the tuberosity at the centre 
of the smaller curve which the articular sur- 
faces of the condyles form at their back part. 
The internal lateral ligament descends from 
the tuberosity of the internal condyle of the os 
femoris to beneath the head of the tibia; it is 
nearly three inches in length, of a flattened 
form, narrow at its commencement, but en- 
larging considerably opposite the joint, to the 
synovial membrane of which as well as to the 
internal semilunar cartilage it adheres; infe- 
riorly it again contracts in width. Its upper 
attachment is covered by the fascia lata; below, 
it is inserted into the shaft of the tibia just 
beneath the head of the bone, and anterior to 
its inner angle; and the tendons of the sarto- 
rius, gracilis, and semitendinosus cross over it. 

The external lateral ligament (lig. laterale 
externum ) arises from the tuberosity on the 
external condyle of the femur, and descends, 
inclining backwards, partly covered by the 
tendon of the biceps, to be inserted with it 
into the head of the fibula; the attachment of 
its upper extremity is immediately above the 
origin of the popliteus tendon, which it crosses 
in its descent, so that this tendon enveloped by 
its synovial sheath is situated between the liga- 


NORMAL ANATOMY OF THE KNEE-JOINT. 4 


ment and the joint. The deviation of t 
ligament from the perpendicular direction” 
perceived most distinctly in the state of exte 
sion ; when the joint is flexed, the upper: 
tachment of the hgament is brought more it 
the perpendicular over its fibular attachme’ 
the ligament is relaxed and assumes the pi 
pendicular direction ; hence, in the flexed ee 
dition of the joint, the external condyle of 
femur, or the tibia on it, admits of a more fi 
motion. This ligament is contrasted by il 
less length and more rounded form with | 
internal lateral, and is composed like it 
shining tendinous fibres; a still shorter 
fibres sometimes passes more posteriorly fro 
the condyle to the head of the fibula, 
from the sheath of the popliteus tendon, at 
has been called the short external lateral lig 
ment. ‘y 
The posterior ligament (lig. posticum Wi 
slowii i a irtian of the eae of the semi 
membranosus muscle which is given off nea 
its insertion at the posterior and inner margt 
of the head of the tibia; the portion under co 
sideration forms a flat and dense fascia whi¢ 
passes upwards and outwards to the extern 
condyle, where it becomes adherent to the s) 
novial capsule and mingling with the tendine 
origin of the outer head of the gastrocnemius: 
posterior to it lie the popliteal vessels, and it 
front of it there is a quantity of firm granulates 
fat, into which some of its fibres penetrate. 
When the posterior ligament and the fat ju 
spoken of are removed, and the joint is ex- 
tended, the two crucial ligaments (ligament 
cruciata* ) are brought into view ; they may b 
seen on the anterior aspect by dissecting dow! 
the patella from the fore part of the na and 
putting it in a state of flexion; in the forme 
view, the posterior crucial ligament is be: 
seen; in the latter, the anterior: the uppe 
extremities of both are fixed in the fossa be 
tween the condyles of the os femoris; thei 
lower extremities are attached to the head « 
the tibia between the two articular surfaces. 
The anterior crucial ligament passes fre 
the inner and back part of the outer condyle 
downwards and forwards to the depression ii 
frontof the spine of the tibia, where some portion 
becomes continuous with the anterior extr 
mity of the internal semilunar cartilage. Th 
posterior extends from the fore and outer. par 
of the internal condyle downwards and back 
wards to the notch at the posterior margin 6 
the head of the tibia, where it becomes like 
wise attached to the posterior extremity of thi 
external semilunar cartilage. The crucial liga 
ments thus derive their name from decussatin 
one another like the strokes of the letter X; 
the crossing is, however, considerably abov 
their centre: the anterior passes to the oute 
side of the posterior. 7 
The synovial capsulet entirely surrounds t 


* [It is useful to bear in mind that these ligaments 
are called anterior and posterior with reference 
their insertions into the tibia, the one in front o 
the other behind, the spine of that bone.— Ed.] 

+ [Weber recommends as a good way of deme 
strating the full extent and connexions of the 


NORMAL ANATOMY OF THE KNEE-JOINT. 


joint, and there are good reasons for affirming 
that it is continued in a highly attenuated state 
over all the interarticular and incrusting carti- 
lages, giving them their smooth and secreting 
_ (See Anticotation.) The remain- 
_ der of its extent may be traced in the following 
manner: from the upper edge of the patella 
ascends behind the common extensor tendon, 
‘and is loosely reflected upon the thigh-bone 
‘two or three inches above the trochlea in the 
extended position of the limb; from each side 
of the patella it passes backwards in a broad 
Sheet, whose lower margin is attached to the 
edge of the semilunar cartilage, and thence goes 
to the tibia, while above it is loosely reflected 
on to the condyles of the os femoris, at the 
distance of nearly an inch from their cartila- 
-ginous surfaces; from the back part of the con- 
dyles these two lateral portions pass into the 


- 


_ fossa and join to cover the anterior surface of 
_ the crucial ligaments. From the lower edge of 


4 the patella the synovial membrane descends to 
i 


cover the fatty body which is placed in that 
part of the joint, and it accompanies a small 
prolongation from that body which frequently 
across the joint to the lowest portion of 
the trochlea of the os femoris, forming what 
has been named the mucous ligament; this 
Structure however is not always present. 
There is some discrepancy in the descrip- 

tions of different anatomists as to the alar 

ligaments, which are described as folds at the 
sides of the patella, and it seems altogether 
unnecessary to distinguish these lateral portions 
by name from the other parts of the synovial 
capsule. They are simply folds of the syno- 
vial membrane projecting into the articular 
cavity, and obviously destined to increase the 
extent of synovial surface for a greater amount 
of secretion. This membrane has a dense cel- 
lular tissue on its outer surface, by which it is 
_ connected -firmly to the posterior surface of the 
extensor tendons and fascia lata. It possesses 
_ some degree of elasticity, but its chief power 
_ of accommodation to the motions of the joint 
is derived from its lax connection with sur- 
rounding parts. 

(c.) The mechanical functions of this joint, 
or the movements of which it is capable within 
certain limits, and the resistance which it op- 
poses to motion beyond those limits, are plainly 
deducible from a knowledge of the parts of 
which it is composed. To say that the knee is 
a hinge-joint with a slight arthrodial or sliding 
motion, gives a very faint idea of the complex 
__ problem which has been solved in its construc- 

tion: to procure firmness without the aid of 
iA bony processes interlocking with one another 
@ (as in the ankle and elbow); and yet to com- 
bine free power of flexion with impossibility 
_ of over-extension; to oppose large surfaces of 
bone to one another, so as to ensure stability 
in the erect posture, without making the joint 


{ 


4 


synovial membrane of the knee-joint, to distend it 
by injecting some coagulating fluid, as size, through 
a hole bored through the centre of the patella.— 
Mechanik der menschlichen Gehwerkzeuge, p. 195, 


47 


unsightly by its size, are some of the indica- 
tions most admirably fulfilled. 

In the straight or extended position of the 
leg, the joint is firmly locked so as to admit 
of no lateral or rotatory motion; the pointing 
of the toes in and out in this position is effected 
by moving the hip-joint. The portions of the 
condyles forming the segments of large circles 
are, during complete extension, applied to the 
tibia and form a broad surface of support; the 
patella is drawn to the upper or deepest part 
of the trochlea; and the lateral and crucial 
ligaments, being attached nearer to the poste- 
rior than to the anterior surface of the thigh- 
bone, are together with the posterior ligament 
put upon the stretch. If the curve of the arti- 
cular surfaces of the condyles had been uni- 
form, with the lateral and crucial ligaments 
fixed to the centre of that curve, the posterior 
ligament only could have acted to restrain the 
leg from being flexed forwards upon the thigh, 
and it would be quite insufficient for that pur- 
pose: whereas, by the present arrangement, the 
centre of motion being placed nearer to the 
posterior surface of the condyles, the lateral 
and crucial ligaments cooperate with the pos- 
terior in opposing a strong check to over- 
extension. In flexion the joint admits of mo- 
tion to the extent of about 140 degrees, when 
it is arrested by the crucial ligaments. During 
this movement the condyles offer a diminishing 
surface to the head of the tibia, and the semi- 
lunar cartilages have their ends brought closer 
together, so as to deepen the cavities for their 
reception: in extension, the reverse takes place, 
the semilunar cartilages are pressed out from 
betwixt the bones to their greatest extent. The 
adjustment of these fibro-cartilages during 
flexion is effected partly by their elastic power 
of resuming their shape when pressure is re- 
moved, and in some degree by the atmospheric 
pressure urging these moveable parts between 
the ends of the bones, to prevent the formation 
of a vacuity in the joint. During the motions 
of the knee, the patella undergoes important 
changes of relative position both with regard 
to the os femoris and the tibia; it plays over 
the whole extent of the trochlea, being drawn 
in extreme extension half its diameter above 
that pulley, whilst in extreme flexion it has 
moved through a quarter of a circle and is 
found at right angles with the os femoris, 
forming in that situation the surface which 
comes to the ground in kneeling, and so de- 
fends the joint from injury. In relation to the 
tibia, the patella always keeps the same dis- 
tance from the tubercle, being joined thereto 
by the ligamentum patelle; but as the con- 
dyles recede during flexion, the patella follows 
them; so that a line passing over its anterior 
surface and that of the tubercle will, if pro- 
longed, reach the point of the great toe, though 
a similar line in the extended position will fall 
through the ankle-joint. The necessity for this 
advancing and receding movement of the pa- 
tella explains why it is a separate bone instead 
of forming a process of the tibia, as in the 
elbow-joint the olecranon forms a part of the 
ulna; and may also suggest the use of the 


48 


bursa behind its ligament. It has been said 
above that besides its ginglymoid motion, the 
knee-joint has a slight arthrodial motion in the 
bent position: this is strictly a rotation of the 
tibia on its axis, and the effect is to point the 
toes more or less to the outer side, rotation in- 
wardly to any great extent being prevented by 
the crucial ligaments. During this movement 
of rotation, the inner articulating surface on 
the head of the tibia advances forwards, while 
at the same time the outer one recedes; the 
lateral ligaments allow of this motion, in con- 
sequence of their inferior attachments being a 
good deal below the margin of the joints and 
the crucial ligaments permit the successive, 
though not the simultaneous, advance or re- 
cession of the cavities on the head of the tibia. 
In all positions of the joint the arrangement is 
such that the attempt to thrust forwards the 
whole head of the tibia is resisted by the ante- 
rior crucial ligament, whilst the posterior pre- 
vents it from being driven backward.* Ihe 


* [The following experiments, which may easily 
be tried, illustrate the respective offices of the se- 
veral ligaments. 

If the external fibrous investment of the joint 
be completely removed, taking care that the lateral 
and crucial ligaments shall be free from injury, 
the motions of the joint will be in no degree af- 
fected; but if the opposite experiment be tried, 
and the lateral and crucial ligaments be cut, leav- 
ing the external fibrous investment uninjured, 
excepting a small hole made for getting at the ligu- 
ments, it will be found that the integrity of the 
joint is completely destroyed, the bones are but 
loosely connected to each other, their apposition is 
destroyed, and they move about indifferently in 
every direction. 

Again, if after dissecting off the external fibrous 
investment both crucial ligaments be cut, leaving 
the lateral ligaments as the only bonds of con- 
nection between the two bones, it is found that 
during extension, the fixedness of the joint is un- 
impaired, but if flexion be made gradually, the 
bones becomes less in apposition and more move- 
able, and in the completely bent state of the limb, 
they become quite loosely connected and may rea- 
dily be moved from side to side, and the only limit 
to flexion is from the tibia coming against the 
femur, 

’ If the lateral ligaments be cut, leaving the cru- 
cial uninjured, the bones remain firmly connected 
when the joint is in the state of complete flexion, 
and the crucial ligaments still, as in the natural 
state, oppose any further flexion. In the gradual 
diminution of the flexion, the junction of the bones 
becomes less complete, and when the extension 
has been carried to its full extent, the bones may 
be separated from each other, and admit of lateral 
motion; and if the joint be held‘up so as to allow 
the tibia to hang from it, the foot will become 
everted by its own weight, and the two crucial liga- 
ments, instead of their crossed and oblique position, 
will assume a parallel and vertical direction. These 
experiments are described by Weber, but there are 
few anatomists in this country, for many years back, 
who have not frequently tried them. 

The office of the semilunar cartilages is three- 
fold: 1. filling up the empty space which the arti- 
cular surfaces leave around their point of contact, 
they distribute the pressure over a greater surface ; 
2. they serve to distribute the tension of the liga- 
ments in the movements of the joint more uni- 
formly, and thereby to oppose any jarring of the 
bones against each other; and, thirdly, theydeaden 
the vibrations which in the various movements of 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. a 


- branches, viz.two superior articular, which 


mucous ligament and fatty body of the jo 
change their situation in some degree duri 
its motions and may serve to fill spaces 1 
which would otherwise be left vacant: th 
that they are peculiarly concerned in secreti 
the synovia has been satisfactorily refuted 1 
der “ AnticuLaTiIon.” Z- 
The burse in the neighbourhood of the kn 
joint are numerous and not unimportant, ff 
the circumstance that some of them often 
into the joint itself. In the layers of fas 
anterior to the patella, one or more exist, 1 
perfectly formed and very liable to inflam 
suppurate. The situations in which the m 
pe ect specimens are found are as folle 
hind the ligament of the patella; ' 
the cruralis and fore-part of the os femo 
beneath the internal lateral ligament; at | 
insertion of the semitendinosus, gracilis, 2 
sartorius ; underneath each head of the gem 
oe ; and around the tendons of the s a an 
ranosus and liteus respectively ; 
named bursa PL ps ares on et distan 
between the popliteus and the tibia, and 
often communicates below with the supe 
tibio-fibular articulation, as well as with 
knee-joint above. This joint is supplied wi 
blood from the popliteal artery by five differ 


round the lower part of the os femoris; one mi 
dle articular which passes through the posteri¢ 
ligament to the central parts of the joint; am 
two inferior articular, which take their cour 
round the head of the tibia, and anastor 
freely with each other, and with the two upp 
the returning veins go to the popliteal. ss 
The comparative anatomy of the knee-joit 
gives for the most part the same essential. struc 
ture as we have described in man, ‘though va 
riously modified. ; 
In most animals, when in a standing pos 
ture, the knee maintains habitually a state 
flexion, and this arrangement conduces muc 
to fleetness and agility of motion. In the ele 
phant, however, the bones of the hind leg fort 
an upright pillar of support, and the knee is @ 
tended as in the human subject. The elephai 
also resembles man in the circumstance of th 
knee being brought to the ground in kneeling 
whereas, in most genera, the true knee is plac 
much nearer to the body of the animal. 


(Alfred Higginson.) 


KNEE-JOINT, asnormaL CONDITION 
or.—The abnormal conditions of the kne 
joint may be arranged under those which resu 
from disease and accident. The deviations 0 
casionally met with as the consequence of cor 
genital malformation are fortunately rare. _ 

DisEase.—The abnormal appearances in t 
knee-joint resulting from disease are those whi 
spring from some specific irritation, such 4 
struma, gout, rheumatism, syphilis, or malig 
nant disease, or from direct violence. Most 0 


these irritations affect all the structures of the 


the limbs, especially in standing, walking, or un- 
ning, are propagated along the bones,—VideWebe 
Mechanik, &c. p. 193. Ep.] a 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


articulation, and are associated with some form 
of inflammatory action, either acute or chronic. 
Simple acute inflammation of the knee-joint, 
or acute arthritis genu, may be the result of a 
contusion, a sprain, or a wound; or there may 
be no assignable cause. In the latter case it 
may have been preceded by rheumatic fever, 
_ erysipelas, or diffuse inflammation, which had 
| previously engaged distant organs and other 
_ Structures. The symptoms are usually strongly 
marked. Considerable pain, which comes on 
_ very suddenly, is felt in the knee; the leg in 
_ Most cases soon becomes flexed and reposes on 
its outside; and the patient cannot bear the 
_ slightest movement to be communicated to the 
_knee-joint. There is considerable increase of 
_ temperature in the skin over the affected arti- 
 Culation, together with tension of it from in- 
_ Ordinate effusion of synovial fluid into the 
joint. Although the usual phenomena of red- 
ness as anaccompaniment of phlogosis may not 
be observed externally, there can be but little 
doubt that the capillary vessels pervading the 
different structures of the interior of the joint 
are in a state of hyperemia. The patient'has 
but little sleep, and this is frequently inter- 
rupted by unpleasant dreams and painful spas- 
_ modic startings of the affected extremity. Cde- 
ma of the lower part of the limb now occurs, 
_ and in severe cases sometimes extends up the 
whole leg and thigh, even to the groin. The 
, Para refnetio fever may run so high, and the 
swelling and other local symptoms proceed so 
_ rapidly as to deprive the surgeon of any oppor- 
tunity of proposing or performing amputation 
_ to save the patient’s life. 
_ The fever in well-marked cases of acute ar- 
_thritis genu is sometimes symptomatic of the 
local disease ; sometimes it has preceded the 
“local affection, and has been ushered in bya 
_ very severe rigour followed by profuse perspi- 
‘tation. Like the disease, the fever will vary in 
its character. Erysipelas, rheumatic fever, and 
diffuse inflammation, as has been mentioned, 
will each occasionally present in their progress 
‘pnt of the disease of the knee-joint now 


under consideration, and the accompanying 
fever will bear the character of the disease with 
which the inflammatory affection of the joint is 
“associated. The local phenomena presented 
by an acute arthritis genu do not, however, 
Vary so much, except in degree and severity. 

_ Acute arthritis genu may supervene as 
4 consequence of wounds. Sometimes these 
wounds are very small. We have known one 
“tase in which a puncture made with a fine sew- 
ig needle, which was accidentally driven with 
force into the knee-joint, at the inside of the 
‘patella, was the cause of a fatal inflammation 
‘of the joint: the point of the needle probably 
penetrated the bone. The patient, a young 
‘Woman, was under the care of Mr. Colles 
Many years ago, in Steevens’s Hospital. In 
Some instances we have known inflammation of 
the synovial membrane of the knee to have 
been the result of a wound of the subcrureal 
bursa. A countryman had received a trans- 
verse wound by the cut of a broadsword 
just above the patella, and fatal inflammation 

VOL. III. 


49 


extended from this bursa, which was opened, to 
the synovial sac of the knee-joint. 

Acute inflammation of the knee-joint has 
been the result of surgical operations, such, for 
instance, as that occasionally undertaken for the 
extraction of moveable bodies which form in 
the joint and interfere with the due perform- 
ance of its functions. This operation, we be- 
lieve, is now very seldom recommended. We 
have heard and read of many cases in which 
it has been performed with complete success ; 
on the other hand, we have reason to know 
that many have died of the inflammation con- 
sequent on it, and that others have narrowly 
cacaped with their lives, having ever after- 
wards an anchylosed knee-joint. It is rather 
singular, but we believe it to be true, that 
the inflammation resulting from a valvular 
opening having been made in the knee-joint 
has not come on for six or seven days after the 
moveable cartilage has been extracted ; bat in- 
flammation being once set up, its course is ge- 
nerally acute and dangerous. 

We consider the observations and experience 
of Mr. Guthrie on the subject of wounds of 
the knee-joint to be too valuable to be here 
passed over. ‘ Wounds of the knee-joint,” he 
remarks, “ however simple, should always be 
considered of a dangerous nature, infinitely 
more so than of the shoulder, the elbow, or the 
ankle.” ‘TI could,” he adds, “ relate an infi- 
nite number of cases on these points, termi- 
nating fatally or in amputation, where the in- 
jury was severe, or apparently at first but slight, 
and but few cases where the capsular ligament 
was opened ‘into by a musket-ball, where the 
patient has preserved the use of the limb. In 
every case where the wound was known to be 
serious, I have invariably been disappointed in 
the hope of saving the limb.” He then adduces 
the following case as an instance of apparent 
simple injury that frequently occurs. “ This 
case,” he adds, “ will shew the danger of all 
these wounds, and the very great care and at- 
tention that are necessary for their cure. Co- 
lonel Donellan, of the forty-eighth regiment, 
was wounded at the battle of Talavera in the 
knee-joint by a musket-ball, which gave him so 
little uneasiness, that when a roller had been 
put on his leg, with some simple dressing, he 
could scarcely be persuaded to proceed to the 
rear. Ata little distance from the fire of the 
enemy we talked over the affairs of the mo- 
ment, when, tossing his leg about on the 
saddle, he declared he felt no inconvenience 
from the wound, and would go back, as he saw 
his corps was very much exposed. I explained 
to him the dangerous nature of the wounds of 
the knee-joint, and after he had staid with me 
a couple of hours, I persuaded him to go into 
the town. This injury, although at first to all 
appearance so trifling, and under the best sur- 
gical care, caused the death of this officer in a 
very short time, and proceeded so rapidly as to 
prevent any relief at last being obtained by 
amputation.” 

Some years ago MM. Larrey and Garriques, 
in France, recommended the amputation of the 
leg immediately below the tuberosity of the 

E 


50 


head of the tibia, instead of amputation of the 
thigh, where it was found impracticable to re- 
move the leg at the ordinary place of election— 
four inches below the knee-joint. But Larrey 
made an addition to this operation, namely, the 
extraction of the head of the fibula. He says, 
“‘ when the fibula is left short, which is usually 
the case, it is to be extirpated as useless, and 
troublesome in the application of the artificial 
leg, and the skin is to be left as long as pos- 
sible, to cover the stump.” Mr. Guthrie gives 
Larrey much praise for drawing the attention 
of the profession to this “ great improve- 
ment,” and adds the weight of his high autho- 
rity by recommending the removal of the head 
of the fibula. In alluding to this subject we 
may appear to be departing from the proper 
object of this article,—the abnormal appear- 
ances presented by the knee-joint; but having 
known some melancholy examples of acute in- 
flammation of the knee-joint to follow the 
operation here recommended, we take this op- 

rtunity of warning the profession against it. 

r. Guthrie himself says, it is possible, how- 
ever, that a case may occur (perhaps one in a 
thousand) in which the head of the fibula com- 
municates with the general cavity of the knee- 
joint; in such a case amputation must be done 
above the knee.” Independently of this com- 
munication between these two contiguous joints 
which Mr. Guthrie considers so rare, we have 
found, by repeated anatomical examinations of 
the relation existing between the synovial sacs 
of the knee-joint and that of the superior tibio- 
fibular articulation, that these two sacs are so 
close as to have but a thin transparent wall 
separating them. We consider it, not abso- 
lutely, but very nearly impracticable to cut out 
the head of the fibula in the living subject 
without making a communication with the pos- 
terior and back part of the synovial membrane 
of the knee-joint, so delicate is the thin trans- 
parent membrane which is interposed between 
the synovial sac of the knee-joint and the little 
synovial sac which partially envelopes the head 
of the fibula. Besides, in the living subject 
it must always prove to be a difficult matter 
to remove the head of the fibula without in- 


terfering with the tendon of the popliteus’ 


muscle, as we know the tendon to be enve- 
loped by a synovial production sent down 
along it, like that which in the shoulder-joint 
invests the tendon of the biceps. This synovial 
production is not confined to the tendon of 
the popliteus, but is also reflected over the 
groove formed for the reception of this tendon, 
and must be in danger of being opened in 
every operation which we can devise for the 
removal of the head of the fibula; and conse- 
quently, although there may be many cases in 
which it may be advisable to amputate the leg 
a little below the tubercle of the tibia, in no 
case, in our opinion, should the surgeon attempt 
to extirpate the head of the fibula. The idea 
that this small portion of bone, when left, is 
“useless and troublesome in the application of 
the artificial leg,” may be true, but it is not the 
less true that in the-majority of cases acute 
arthritis of the knee-joint wil! be very likely to 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


succeed to this operation ; and we feel satis! re 
that, as soon as these anatomical relations | 
tween the synovial sac of the knee-joint an 
that of the superior tibio-fibular articulation a 
“eri on, this modern proposal will be 
jected. : 

Among the causes of acute arthritis gen 
exposure to cold is very frequently referred 
4 the patient, and apparently with 

he knee-joints being less covered by mu: 
parts than any other of the large articulation 
are more subjected to the influences of 
and on this account are perhaps more gene a 
affected by acute and chronic inflammation th 
other articulations. It must be admitted, ho 
ever, that we have met with cases of 
inflammation of the knee-joint for the origin 
which we could assign no cause, having cor 
on, as we are accustomed to say, spontaneous 
Acute arthritis genu sometimes arises as 
symptom in the course of different disease 

us in diffuse inflammation and in phlebit 
it is quite usual to find the joints visited | 
most severe attacks of inflammation. We ha 
seen examples of acute arthritis supe 
suddenly in the course of a severe attack 
erysipelas ;* and in rheumatic fever and put 

ral rheumatism we can see little else than ; 
inflammation of the joints, the nature of the: 
flammation in these cases, however, being vé 
different. 

Although we have here spoken of th 
different forms of disease, diffuse inflammati 
phlebitis, and puerperal rheumatism, we 
ourselves long entertained the opinion expres 
by Mr. Arnott, Velpeau, Dance, Cruveilhi 
our friend Dr. Beatty, and others,+ that 
three forms of disease in which the acute arth 
tis we are here treating of occurs, are the sam 
and that the arthritis in all three is similar, a 
proceeds from the same common cause, 
phlebitis and its consequences. a 

The peculiar form of acute arthritis” 
adv to has in almost all cases been fou 
to have been preceded by phlebitis. This m 
have come on spontaneously, or in consequet 
of a wound, or of the vessel having been 
cluded in a ligature. The form of acute ar 
tis which has been called puerperal rheum 
has also been found, in many cases, coinei 
with or preceded by phlebitis of the veins ¢ ; 
uterine system, or of some other veins.[ 

We have seen many cases which we con 
dered to be examples of diffuse inflan 
in very young subjects, engaging the peric 
of the em and tibia, and terminating im 
complete destruction of the bone, in the sl 
space of three days. Sometimes the perioste 
of the femur, for example, formed a comp 
cylindrical sac containing the detached shaft 
the bone. 

The symptoms of acute arthritis which 0 
in the course of a case of diffuse inflam 


fe. 


@ 


* See Dublin Journ. vol. xvii. p. 336, and in 
article p. 55. a 
+ See Dublin Journ., and Mr. Arnott’s valu 
observations in the Med. Chir. Trans, 4 
t See Dance’s, Beatty’s, and Mr, Harrison’s¢ 
Dublin Journ. > 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


are usually ushered in by a severe rigor followed 
by perspiration. The patient is remarkably 
restless and depressed in mind. If the phle- 

_ bitis be external, as in that occasionally succeed- 
_ing to venesection, which has preceded the acute 
arthritis, the inflammation along the course of 
the wounded vein will be observed for several 
days before the attack of arthritis shall come on. 
_ Whatever may have been the cause of the 
inflammation of the joints, the disease does not, 
as in rheumatic fever, pass successively from 
_ joint to joint, completely leaving one joint 
to visit another. Although varieties may of 
_ eourse be noticed in the local symptoms which 
this dangerous disease presents, it very con- 
stantly happens that a joint once visited by it 
_ Seldom or never completely recovers its effects. 
Usually many joints are successively or simul- 
_ taneously affected, and we very generally dis- 
_ over that one or more of the internal organs is 
also implicated. Whatever joint is attacked in 
the course of the disease, it presents the ordinary 
_ characters of an acute arthritis. The integu- 
_ Ments covering the articulation sometimes wear 
a pink hue, and always have an elevated 
_ temperature. The affected limb is powerless. 
_ The patient complains of very considerable 
_ pain, more particularly, as it appears to us, in 
_ puerperal arthritis than in the affections of the 
_ joints which attend on the ordinary forms of 
_ diffuse inflammation. The swelling, when first 
_ examined, is soft and fluctuating. After a time 
_ the effusion of synovial fluid and pus increases, 
' iving rise to the distension of the synovial sac. 
_ If at this advanced period we carefully examine 
_ the parts immediately surrounding the inflamed 
joint, we can discover that the integuments and 
Subjacent parts feel somewhat indurated and 
‘edematous, reminding us of the hardened basis 
which we find circumscribing an abscess. It is 
_ probable that this condition of the surrounding 
erie arises from diffuse inflammation and the 
“infiltration of its digested purulent matter. 
The arthritis in these cases is seldom the cause 
of death ; either some internal vital organ be- 
comes violently inflamed by which the death of 
the patient is accelerated, or abscesses form in 
the subcutaneous or intermuscular cellular 
“membrane in various parts of the body, which, 
although more slowly, as certainly lead to a 
- fatal issue, for when the evacuation of the pus 
takes place, the quantity of matter which is dis- 
“charged and continues to be secreted is so 
“excessive as greatly to reduce the patient’s 
Strength, and the exhaustion from this source 
and from the diarrhea which usually attends are 
‘Sufficient to prostrate the powers of the youngest 
and strongest individuals. Most writers indeed 
have observed that in the majority of cases the 
Subjects of this disease had been in a bad state 
of health at the time the exciting cause came 
‘into action,—a cachectic condition produced by 
Over-exertion of mind or body, and that from 
these circumstances the susceptibility or pre- 
disposition to this disease most probably 
arose.* These observations are, we believe, 
fully borne out by experience, and it may not 


i * See Dr. Beatty, Dublin Journal, &c. 


51 


perhaps be uninteresting to adduce some 
remarks published by an author nearly forty 
years ago, which prove that he was practically 
acquainted with the complaint denominated by 
the moderns puerperal rheumatism or puerperal 
arthritis, and that he took a similar view of the 
predisposing causes of this disease. Mr. 
Russell in his work on the knee-joint, in treat- 
ing of acute cases of what he calls white 
swelling, says: “in those cases which proceed 
most rapidly, the disease will reach its acmé in 
the course of a few weeks.” The very rapid 
and acute cases seem to be connected with some 
state of great relaxation and weakness. He 
adds, “ the most remarkable instances of this 
variety which have fallen under my observation, 
have occurred in the cases of women in child- 
bed.” In the Richmond Hospital (Dublin) 
we had had many cases of this form of acute 
arthritis, from which we select the two following 
as serving to illustrate some of the foregoing 
observations. Both these individuals were in a 
delicate state of health when the disease attacked 
them, and the swelling of the knee-joints and 
other articulations formed a very small part of 
their diseases. 

Andrew Turner, 28 years of age, was ad- 
mitted into the Richmond Hospital on the 
7th of May, 1836. He had much abused his 
health and constitution. Five days after having 
been bled in the right arm to relieve the con- 
sequences of a severe beating, a superficial dif- 
fused redness appeared on the skin of the fore- 
arm ; the venesection wound was swelled and 
inflamed ; a severe rigor occurred, followed by 
profuse perspiration and fever ; erratic erysipelas 
characterized by a faint red mottling of the skin 
in patches appeared ; a blush of inflammation 
in the form of a patch showed itself on the 
shoulder, but not continuous with that on the 
fore-arm ; a pink patch next appeared over the 
right knee, then on the left arm, and afterwards 
on the left lower extremity ; and while this dis- 
ease invaded the body part after part, those 
once occupied remained engaged as before. 
On the 15th May, the ninth day from his ad- 
mission, there was observed effusion into the 
right knee and into the bursa which is subjacent 
to the crureus muscle. Although considerable, 
this effusion escaped the patient’s attention ; he 
complained of no pain, and to our enquiries 
always replied that he was going on “ gaily.” 
On the 18th the left knee-joint was tumefied, 
but not to the same extent as the right. He 
died on the 26th, his death being preceded 
by the ordinary symptoms of pneumonia, pleu- 
ritis, &c. On the post-mortem examination the 
anatomical appearances of pneumouia, pleuritis, 
and bronchitis were seen ; there was also effu- 
sion into the cavities of the pericardium and 
peritoneum. In the right knee-joint and sub- 
cutaneous bursa, which freely communicated 
with it, there was a large quantity of yellowish 
green fluid, which seemed to be formed of the 
mixture of purulent matter with the synovial 
fluid : flakes of lymph floated in it. The syno- 
vial lining of the subcrurceus bursa was very 
red, as was also that of the joint itself. The 
synovial membrane was elevated above the level 

E 2 


52 


of the cartilages by subsynovial infiltration. 
The ligamentum mucosum, as it is called, was 
very vascular. The capillary system of the 
semilunar cartilages was injected with minute 
red vessels. The left knee-joint, which had 
been but lately attacked, contained an inordinate 
quantity of synovial fluid, of a greenish-yellow 
hue, and of a thicker consistence and a deeper 
colour than natural. The synovial membrane 
was pale, and there was no infiltration in its 
subsynovial structure. The vein in which 
venesection had been performed was contracted 
in the neighbourhood of the wound, and lymph 
adhered to its lining membrane. Above the 
right elbow-joint and internal to the course of 
the vein, there was a small collection of matter 
between the skin and fascia. 

Susan Brett, et. 24, was brought into the 
Richmond hospital on 26th February in great 
distress and pain. On the 14th February she 
was suddenly seized with convulsions, being 
seven months pregnant. She was bled in the 
right arm and her head shaved. Two days 
after the operation the arm became very painful 
and swollen. The pain increased, and on the 
2ist labour-pains came on and continued 
during the day. In the evening she was again 
attacked with convulsions, and blood was 
drawn from the left arm. The child (her first) 
was not expelled until early the next morn- 
ing; the evening of the same day she had a 
severe rigour, which lasted half an hour, and 
was succeeded by profuse perspiration; this 
soon went off, but she remained cold and 
chilly for the remainder of the night. On the 
following morning (23d) she was seized with 
what she called severe rheumatic pains in her 
hips and right shoulder, which left her “all 
sore” and completely powerless. On the 24th 
the pain in the right shoulder-joint became 
most intense, and a severe stitch seized her in 
the same side, which prevented her drawing 
her breath. The pain in the arm also was now 
very severe, extending upwards from where ve- 
nesection was originally ier: The wound 
was found not yet healed. 

When brought to the hospital, the fifth day 
from her lying-in, she was in great distress and 

ain. Her pulse was 140, with some fulness, 

ut still compressible. She preferred lying on 
her right side bent forwards, with her knees 
drawn up- Her respirations were fifty-two in a 
minute, and greatly oppressed. At each effort 
of inspiration the ale nasi were much dilated. 
Her countenance was anxious, and there was a 
bright circumscribed flush on each malar emi- 
nence. For the last week she has raved con- 
stantly at night, and has been more ill at cer- 
tain hours of the day, very early in the morn- 


ing, and again at half-past five, p.m. At the . 


latter hour she was generally found perspiring 
copiously. Her bowels were too free. She 
complained of pain chiefly in the right shoulder 
and the lower part of the back; also in both 
her knees and metacarpal joint of the index- 
finger of the left hand. She also complained 
of her left hip. The right arm was swollen 
but not discoloured, «dematous, and pitting on 
pressure. The original wound made for vene- 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


section was ing, with unhealthy everted 
edges ; no ise coddel from it. She kept 
the arm in the flexed position ; to herself it fel 
quite powerless, and when the least movemer 
was communicated to it, she suffered great tor 
ment. There was a hard line up the arm 
responding to the course of the basilic ve 
and when even the slightest pressure was 1 
in this line, she suffered pain. Immediate 
above the elbow-joint the skin was hard 5 
subcutaneous cellular structure seemed more 
less edematous as if infiltrated with fluid ; 1 
skin and subjacent seemed to be matte 
together and somewhat edematous, and 
sure here also gave the patient much uneasine 
There was a suffused pink blush on the 8 
covering the metacarpal joint of the indi 
finger; the joint was much swollen, and sl 
complained of much pain in it. Her p 
pal suffering was from dyspnea. An exat 
nation of the chest by auscultation and pe 
sion furnished all the evidence of extrem 
bronchitis in both lungs, pleuritis with ine 
pient pneumonia: it was also inferred th 
effusion had taken place into the right side 
the thorax. q 
On the 28th February brs nol those decei 
ful appearances of amendment unusu 
the anikas of acute disease discovered th 
selves. It was reported that she had p 
better night ; her pulse fell to 1285 her res 
ration was reduced to forty in the minute; 
in the evening a pain, which she referred 
the situation of the diaphragm, came on” 
great severity. Her cough was trouble 
and in paroxysms ; she expressed great 
about herself, inquiring whether _were an 
hopes for her, and complained of pain in hi 
left elbow, where, however, there was 
swelling. The original wound made in” 
right arm for the first venesection was : 
open, but there was no inflammation about 
e wounds made in the left arm for two 
sequent bleedings healed perfectly. She no 
had pain in all her joints, Laren h 
metacarpal joint of the index finger 
hand. e shoulder-joints were 
she could not bear the slightest movement: 
them. Her knees were very 1, ch 
the left, which was greatly swollen, but its1 
teguments were not discoloured. Diarrh 
was very troublesome. . 
On the 2d of March profuse perspiratic 
broke out over the whole body, and cx 
of the feet came on. The next morning” 
pulse was 128; respiration was jerking a 
very much hurried ; and her countenance DB 
trayed great internal distress. She had rav 
all night. There was complete orthopneea, ai 
the swelling of the knees increased. She | 
at four o'clock. — 
On an examination of the body twenty-t 
hours after death, the shoulder-joints we 
found to contain a viscid greenish impe 
formed pus. Matter of the same appearance 
but less viscid, was met with on cutting dow 
to the right shoulder-joint among the musel 
external to it. The cartilages in both the 
articulations had lost their colour and seeme 


nx) 
cs 


ie 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


thinner than. natural, but were not ulcerated. 

e elbow-joints were in a normal condition. 
‘The joint of the index finger contained a thin 
greyish coloured matter, which was not con- 
fined to the joint, being also found in the mus- 
cles external to it. The cartilages on the head 
of the metacarpal bone and corresponding sur- 
face of the index finger were much ulcerated 


and partially removed. The knee-joints con- ’ 
tained a 


large quantity of a viscid greenish 
matter like lime-water and oil. Behind the 
right knee-joint, and extending down to the 
gastrocnemii muscles, matter of somewhat a 
similar character, except that no synovial fluid 
was mixed with it, occupied the interstices of 
the muscles and the cellular tissue of the lower 
- of the popliteal region. The hip-joint 
did not contain any matter. 

The basilic vein of the right arm was plugged 
up with a dense coagulum, which closely ad- 
hered to its internal tunic, and was not easily 
separable from it. There was no pus in the 
a 3 its exterior presented an unusual red co- 
our. 

On opening the cavity of the chest a quan- 
tity of serum escaped. There was a great 
quantity of a very yellow lymph effused on the 
surface of the pleura of both lungs, principally 
the right. In many places it was very thick, 
rough, and consistent. On the diaphragm and 
in the right side of the chest the lymph was 
soft, of a greenish colour, being in shreds 
easily removed, and leaving the subjacent mem- 
brane highly vascular. There were also evi- 
dences of interlobular pleuritis having existed : 
all division into lobes had been effaced. The 
lungs presented specimens of pneumonia in its 
three stages. A very small portion of the apex 

of the left lung alone seemed healthy, but 
even here the bronchial membrane was en- 
gaged and presented evidences of bronchitis 
having existed. In the substance of the lungs 
_ there were also found small abscesses present- 
_ing near their surface like little gangrenous 
_ abscesses surrounded by ecchymosed red spots ; 
_ these contained some grumous dark-coloured 
_ fluid, which, however, was inodorous. In others 
_ was found an ill-digested purulent matter ; and 
_ leading to one of these disorganized portions 
of the right lung near its apex, the minute 
veins on very careful dissection were found 
_ thickened, with yellow parietes; and many of 
_ those present at the examination satisfied them- 
_ Selves that these minute veins contained puru- 
lent matter. The heart and pericardium were 
natural. The most careful examination could 
_ discover nothing abnormal in the uterus. The 
_ large intestines throughout presented numerous 
RB slcerations on their mucous surface ; the neigh- 
_ bourhood of the ileo-ccecal valve being most 
_ beset by them. The mucous membrane was in 
_ astate of hyperemia. 
prognosis in cases of acute arthritis genu 
isin general very unfavourable except when the 
disease accompanies what has been usually 
termed rheumatic fever. In this case the syno- 
vial system of all the articulations is visited in 
succession, until the inflammatory disease ex- 
hausts itself as it were in three or four weeks, 


53 


often leaving no trace behind. It is, however, 
well known to medical men that in the course 
of these fevers fatal metastasis may occur from 
the synovial membrane of the knee or other 
joint to the pericardium or peritoneum.* In 
some few cases, after the general rheumatic 
fever and acute specific arthritis had subsided, 
we have known the chronic rheumatism, or 
nodosity of the joints, to set in, remaining 
permanently to interrupt the patient’s health. 
Not long ago there was a young woman in the 
Richmond Hospital, under the care of Dr. 
Hutton, having acute arthritis of the right 
knee-joint, which had remained after a severe 
attack ofsgeneral rheumatic fever. All the 
joints in succession had been visited by in- 
flammation. The fever, with its debilitating 
accompaniments, profuse perspirations, &c. 
subsided, but the local symptoms of acute 
arthritis of the right knee-joint continued, and 
increased even to suppuration, nor did ampu- 
tation of the limb save the patient’s life. These 
unfavourable results of acute arthritis, of the 
rheumatic form, may be considered as excep- 
tions. In general the form of inflammation of 
the joints, commonly called rheumatic fever, 
terminates favourably ; on the contrary, in cases 
where the knee-joints and other articulations 
are engaged during an attack of diffuse inflam- 
mation, puerperal arthritis, or phlebitis, the 
prognosis is most unfavourable, the disease in 
all these cases being generally fatal whether 
the joints be implicated or not. 

Anatomical characters of the acute arthritis 
of the knee——On examining the interior of a 
knee-joint which had recently been the seat of 
acute inflammation, we find that the synovial 
fluid has accumulated in the cavity of the 
joint, and that it is mixed with purulent 
matter; when this is removed, we perceive 
that the synovial sac has been widened and 
enlarged, and that the subsynovial tissue is 
much infiltrated, causing the synovial mem- 
brane to be raised up above the level of the 
articular cartilages. We have seen the syno- 
vial membrane or subsynovial tissue as red as 
the conjunctiva eculi in acute purulent ophthal- 
mia. In these cases the articular cartilages 
lose much of their natural white silvery lustre, 
become yellowish, and are found softened at 
their edges or circumference, where the ele- 
vated and inflamed synovial membrane is in 
contact with them. We have found the carti- 
lage of the patella softened and partially de- 
tached from the bone, even in very recent 
cases. In cutting down to the joint we have 
noticed an alteration in the natural colour of 
the muscles ; and outside the synovial sac we 
often encounter abscesses containing true pus. 
Generally speaking this sac is of an intensely 
red colour, and covered here and there with a 
green but not very consistent layer of organi- 
zable lymph. Some fragments of thinned 
shreds of exfoliated articular cartilage, with 
serrated edges, hang into the cavity of the 
joint, and some portions are altogether free, 


* See Dublin Hosp. Rep. vol. ii. p. 321. vol. iv. 
p- 368. © ; 


54 


and float about loose in the interior. We have 
found the minute capillary vessels of the car- 
tilages faintly traced in red lines, and have also 
discovered that these vessels admit the colour- 
ing matter of our injections. The vascularity 
of the cartilages under the influence of acute 
inflammation seems to be fully proved. We 
have it on the authority of Sir B. Brodie that 
he had been able to detect with the naked eye 
vessels in articular cartilage filled by blood ; 
and it is fresh in the recollection of the profes- 
sion that Mr. Liston has lately laid before the 
Medico-Chirurgical Society important obser- 
vations on this subject——The periosteum of 
the bones in the immediate vicinity of the knee 
is usually found to be of a red colour, thicker 
than natural, and easily detached from the 
bone ; the bones themselves occasionally pre- 
sent a reddish or pink hue externally, and a 
section of them shews, by its bright red colour, 
an increase in the number or size of the capil- 
— vessels, admitting red blood, which per- 
vade their medullary membrane and cancellated 
structure. 

Example of acute arthritis genu.—Michael 
Roche, twenty-seven years of age, was admitted 
into the Richmond Hospital in April 1832. He 
had an emaciated appearance, a dry tongue, 
and some fever. He complained of severe 
pain in the left knee, which completely inter- 
rupted sleep, and of frequent spasmodic start- 
ings of the limb. The limb was so much 
swollen that measurement of it showed an in- 
crease of six inches in its circumference over 
the sound one. The superficial veins were di- 
lated, the patella was thrown much forwards, 
and the leg and foot were cedematous ; the in- 
teguments were red and thinned, and a fluctu- 
ation of matter in the joint was very evident. 
He stated this violent attack to be of five weeks’ 
duration, having commenced with a very severe 
rigor, and attributed it to his having lain for 
some hours on wet grass. Three years previ- 
ously he had had an attack of acute inflamma- 
tion of the knee, which, however, quickly sub- 
sided, but leaving a stiffness of the joint. An 
opening was made with a lancet into the part 
of the knee-joint which was red and thinned, 
and eight ounces of purulent matter were let 
out, but no relief was afforded. Some super- 
ficial inflammation was observed, in the course 
of the lymphatics to the groin, from the wound, 
as also swelling of the inguinal glands. The 
spasmodic startings of the limb became more 
urgent, and the cdema increased. On the 
17th of April Dr. M‘Dowel amputated the 
limb. The incision passed through a sinus 
which he thought it necessary to dissect out. 
The muscles did not retract. On the following 
day the report from the man was that he rested 
well at night. But on the fourth day after 
the operation his countenance was flushed, his 
pulse feeble—96, and he complained much of 
the pain of the stump. On the 22d of April, 
the fifth day after the amputation, he had a 
rigor followed by a hot and sweating stage: 
his pulse amounted to 144. For some days 
‘subsequently he had frequent rigors. The 
stump was not doing well; the muscles were 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


of the Richmond Hospital. 


shrinking away daily and leaving the bone un 
covered. The edges of the wound had a 
sloughy appearance, and towards the end of 
the month he was attacked with diarrhea whie 
in a few days proved fatal. “a 
On an examination of the knee-joint all th 
structures entering into its composition exhi 
bited evidence of their having been the seat o 
recent high inflammatory action. The bon 
and synovial membrane presented a very gre 
degree of vascularity and redness; puruler 
matter and flakes of lymph were contained i 
the interior of the joint; a fragment of one: 
the semilunar cartilages alone remained, am 
the articular cartilages were in many place 
removed altogether; in other situations thes 
latter were thinned very much, and in one ¢ 
two places a number of minute perforation 
were seen in the articular cartilage investir 
the lower end of the outer condyle of the 
femur. The minute vessels of the joint wer 
rendered evident by a previous i on 0 
fluid size coloured by vermillion. yno 
vial membrane was much thickened and raise 
above the level of the ert it presente 
a red pulpy appearance, and uctions fron 
it piano eben te side of the femoral condyle 
and were loosely folded over the articular car 
lages ; and wherever this loose membrane wa 
in contact with the articular cartilages, these 
seemed to have been absorbed. Depressio 
in the cartilages exactly rac ee in forn 
with this vascular membrane, which was lodge 
in these superficial depressions. The articulz 
cartilages were thinned, and when elevated fro 
the bone a red ulpy membrane, very similar it 
appearance to the free surface which the syna 
membrane presented, was seen. The minut 
pores and perforations in the articular cartilag 
already noticed were evidently formed by th 
action of a pulpy membrane subjacent to the 
and causing their absorption, evidently in th 
same manner, it appears to us, as we find as 
exfoliation from a flat bone of the cranium t 
be perforated by the absorbing powers of t 
gtanulations proceeding from the bone beneat 
it. In examining this preparation, and reflec 
ing on the history of the case, it would appeai 
that when the limb was amputated, the com 
plete destruction of the articular cartilage w: 
in progress. On the free surface towards th 
cavity of the joint, the cartilage was evident 
absorbed by the villous productions from th 
inflamed synovial membrane; on the ossec 
surface the cartilage was acted i by a pulp 
membrane, which existed here also, and it wa 
this membrane which was produced from th 
bone and caused the number of minute perf 
rations already alluded to, having partial 
removed the articular cartilage.* e bone 
were in a condition of hyperemia. This newl, 
formed membrane seems to be endowed with 
power of absorbing, by its villi, the cartilag 
with which it comes in contact; for we mus 
agree with Mr. Key that these vascular fimbris 
or tufts are often buried into excavations in the 


* The preparation is preserved in the muse 1 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


cartilage, and the convexity of the villous mem- 
brane seems sunk into fovee formed in the 
cartilage, so as to leave no doubt of the vital 
mechanism, if we can so say, of the process, 
_ which seems quite analogous to the absorption 
_ of the sequestrum of a cylindrical bone, or the 
_ exfoliating piece of a flat bone. The writer 
os eed to the Pathological Society of Dub- 
in a recent specimen and a drawing of the 
knee-joint of a man aged seventy, William 
Walsh, who died the day previously (13th Dec. 
1839) in the House of Industry, of an attack of 
cute arthritis genu which had supervened on a 
chronic disease of the joint of long standing. 
‘The synovial sac of the joint had been much 
_ distended and was more capacious than usual. 
it was greatly thickened, and presented on its 
internal surface an intense scarlet colour. Ex- 
tensive deposits of a yellowish green lymph 
‘Were noticed over the entire of the synovial 
‘Sac: the strong contrast in colour between the 
peeen lymph and the red villous synovial mem- 
_ brane is well seen in the preparation. The cru- 
_ cial ligaments were partially removed, and it 
was found on dissection that the internal and 
external lateral ligaments had lost all their dis- 
_tinctness as fibrous bands; both seemed to be 
_ tesolved and spread out into thin membranes 
_ or fasciz, which but little restrained the move- 
ments of the knee, and allowed of a motion of 
rotation being communicated to the joint. The 
articular and semilunar cartilages were removed, 
and the denuded porous surfaces of the bones 
of the tibia, femur, and patella presented nu- 
merous small red spots, as if they had been 
sprinkled with red sand. An abscess contain- 
ing about two ounces of yellowish green pus, 
of a laudable consistence, was found under the 
_ crureeus muscle, just above the synovial sac of 
_ the joint: this abscess was isolated, and had no 
_ communication whatever with the interior of 
the sac of the joint. The fluid in the interior 
_ Of the articulation was more of a thin sanies 
_ than pus, but was abundant in quantity, and 
_ had made its way externally by a large sloughy- 
looking opening in front of the leg, about two 
inches below the knee. . 
_ Michael Smith, 58 years of age, was admitted 
_ into the Richmond Hospital in 1838, labouring 
under erysipelas of the head. During the 
_ course of the disease, one of his knee-joints 
became hot and swollen, the patella seemed to 
float, and on each side of it a fluctuation be- 
came evident. He was more or less insensible 
_ from the erysipelas of the head, but when the 
Knee-joint was moved, he exhibited signs of 
_ Suffering. On the eighth day after the knee- 
joint was first affected, he died of the erysipelas 
| of the head. The knee-joint was carefully 
_ Inspected, fine red injection having been previ- 
_ ously thrown into the femoral artery. The 
_ synovial sac of the articulation was distended 
_ by a turbid yellowish-green fluid, apparently 
composed of a mixture of pus and synovia. 
When this was washed away, the synovial 
membrane was found not so much thickened as 
in the former case, nor had it so much of the 
vivid scarlet colour as the last specimen alluded 
to; and reminded those who examined it of the 


| 


55 


appearance which the conjunctiva presents in 
subacute conjunctivitis. This membrane ap- 
peared to be thickened and pulpy where it had 
already advanced somewhat over the external 
condyle of the femur. The subsynovial tissues 
were more or less infiltrated. The cartilages 
had lost their normal whiteness and _brilliancy, 
and were of a murky yellowish hue; they were 
somewhat softened in their substance, and the 
cartilaginous covering of the patella was slightly 
elevated, in patches, and one spot of ulceration 
was seen at the circumference of its external 
edge. The cartilage covering this bone was so 
soft that the blunt probe easily penetrated into 
its structure. Many would call this a case of 
simple-synovitis genu, but it is manifest that, 
although the acute disease in the knee originated 
in the synovial membrane, the other structures 
of the joint very soon became implicated, and 
that, at the period of the patient’s death, which 
was only a few days after the first attack of the 
joint, the term of synovitis of the knee-joint 
was not sufficiently comprehensive. We have 
had many opportunities of examining the knee- 
joints of those who have died of diffuse inflam- 
mation, which has occurred. in females some 
short time after parturition, and in those cases 
denominated puerperal rheumatism, and in 
cases where the arthritis of the knee or other 
joints was concurrent with phlebitis; and in 
such cases we have found the most remarkable 
phenomena to be,—great effusion into the knee- 
joint of a fluid which would seem to be com- 

osed of equal parts of pus and synovial fluid. 

his was viscid, of a sea-green colour, and of 
the consistence of honey. In cutting down to 
the joint in these cases we frequently met with 
ill-digested matter in and amongst the muscles 
surrounding the affected articulation. The 
synovial membrane was of a pink colour. The 
articular cartilages presented an appearance 
which was rather peculiar. We have found 
them generally to preserve their normal adhesion 
to bone, to be smooth on their surface, but to 
be evidently thinned, and so reduced as to 
form a stratum covering the condyles of the 
femur scarcely half a line in thickness. The 
inter-articular cartilages externally preserve their 
normal appearance, but we can occasionally 
discover that after an attack of acute arthritis of 
the description now under consideration, these 
structures shew that they are permeated inter- 
nally by capillary vessels containing red blood. 
We have had many,—too many examples lately 
verifying the above description of the anatomical 
appearances presented on the examination of 
the knee-joints of those who have died of dif- 
fuse inflammation. 

Simple chronic arthritis of the knee-——The 
symptoms which denote the existence of simple 
chronic inflammation of the knee-joint are very 
similar to those belonging to the acute affection 
of this articulation, being only slower in the 
different stages of their developement and 
milder in their character. 

The simple chronic arthritis genu commences 
with a pain which the patient usually refers to 
the inner side of the joint. -This pain is not. 
sufficient to prevent him from following his 


56 


ordinary ion, and is at first usually un- 
accompanied by swelling, or if swelling exist 
at this early period, it is inconsiderable. There 
18 more pain and less swelling than in the ordi- 
nary case of scrofulous white swelling. The 
swelling, too, is different, that in the strumous 
being more elastic, more of a globular form, 
and situated at first more at the lower and ante- 
rior of the joint around the ligamentum 
ae #: in the strumous also the ham is sooner 
led up. Moreover, the simple chronic ar- 
thritis of the knee is a disease of adult life, and 
the strumous of the younger subject. As the 
— chronic arthritis of the knee proceeds, 
the limb wastes somewhat, a preternatural effu- 
sion of synovial fluid into the joint takes place, 
and pain on motion becomes so severe as to 
confine the patient to the house ; he complains 
of a constant, deep, boring pain, which is usu- 
ally referred to the inner condyle of the femur 
or tibia, and is accompanied by some spasmodic 
starting of the muscles of the limb, by which 
his “ri is disturbed. When pressure is made 
on the knee over the situation where uneasiness 
is experienced, the pain is increased; and the 
integuments of the affected articulation have a 
higher temperature than natural. In the early 
stage of the disease the popliteal space is not 
filled up. As the inflammatoryaction proceeds, 
the patient’s strength and spirits become ex- 
hausted by continued pain and confinement; 
the constitution becomes engaged, suppuration 
occurs in the interior of the joint, and matter 
makes its way to the surface, edema of the 
instep manifests itself, and the disease now runs 
very much the same course as does the chronic 
strumous white swelling, partial dislocation of 
the tibia outwards or backwards occurring, and 
amputation becoming necessary to save life. 

e two following cases may serve as exam- 
ples of the simple chronic arthritis genu. The 
first haere us a rare opportunity of witness- 
ing the anatomical characters of the disease ia a 
very early stage ; the second in the advanced 
form, as amputation could no longer be deferred 
with safety. 

J. M‘Cann was admitted into the Richmond 
Surgical Hospital on the 13th Dec. 1836, for an 
affection of his left knee-joint. The attack 
was about six weeks coming on, but he remem- 
bered that about.ten years previously he had 
fever, and that the left knee-joint was at that 
time severely visited by inflammation. Since 
that period, however, he remained well until 
he got cold, which ended in the present attack 
of the knee, and at this time no other joint was 
affected. The joint appeared to be much en- 
larged when compared with the right and 
healthy knee; the prominences of the bones 
were no longer evident ; the swelling was soft 
and fluctuating, and extended up the front of 
the thigh, but the ham was not in the least filled 
up; the knee was slightly flexed, and the ten- 
dons of the hamstring muscles were remarkably 
tense; he referred the pain to the internal side 
of the joint. Hoping to be released of these 
symptoms he sought admission into the hospi- 
tal. He was ordered twenty-four leeches 
and fomentations to the knee-joint, and to take 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


three times a day a pill containing two grail 
of calomel and half a grain of opium. On th 
fourth day of this treatment he complained ¢ 
scalding when passing urine, and of acid ere 
tations from his stomach. For the latter may 
—_ and lime-water were ae On the fifi 
ay diarrhea, probably mercurial, set in, whit 
was very sive’ and did not yield to the tre 
ment, which consisted in the administration 
an emollient enema containing forty d 
tincture of opium, and of a pill every 
hour, containing two grains of acetate of 
and one grain of opium ; and warm fom 
tions with turpentine to the abdomen. 
the fourth pill had been taken the diarrh 
ceased. Itis proper to mention that the fo 
going symptoms were accompanied at the con 
mencement by a good of fever of | 
sthenic type; the patient’s face was g 
flushed, his eyes glistened, the lips were vi 
million red, the pulse was one hundred an 
strong, and there was much increase of heat 
the surface. When the diarrhea ceased, a ne 
phenomenon, hematuria, presented itself, accon 
panied by great pain across the lumbar regio 
along the course of the ureters, and in the testi 
cles. The calls to pass water occurred hourly 
and half a pint of urine and blood mixed 
pass, which had not any urinous odour. Th 
calls became less frequent, but the fluid pas: 
became more and more pei countenan 
changed, and he had the ge 
loss arg ee) Added to this his romana 
in a continued state of erethism; he had urge 
desire for cold drinks, but nothing, not evi 
cold water, would for one moment remain 0 
his stomach. His countenance was sunken 
exsangueous ; his pulse, one hundred and forts 
could scarcely be counted. His surface becam 
cold, and he complained of the greatest sens 
of exhaustion. At this period m 
singultus set in and added much to his othe 
sufferings. The hematuria continued, the sto 
mach rejected every species of nutriment, and 
medicine failed altogether to relieve his sym 
toms. He died exhausted on the fourth di 
from the diarrhea setting in, and on the sevent 
from his admission into hospital. It is remar 
able that during the last three days of his illne: 
he did not feel any uneasiness in his. knee, an 
the swelling of the joint had greatly ¢ 
nished. 3 
On a post-mortem examination the kidr 
were found much enlarged and friable, 
some purpuric spots (petechia hemorrhagic 
on their surface. The spleen was very smi 
and of a healthy consistence. On openin 
the bursa beneath the rectus and vasti, it ¥ 
found to be distended with synovial fluid 
the ordinary character; no communicati 
existed hetween this bursa and the knee-jo 
When the proper synovial membrane 
joint itself was opened, the quantity of syno’ 
fluid was found to be very scanty. The sem 
lunar cartilages were normal, but the articular 
cartilages which invest the tibia and femur we 
of a yellowish hue, and here and there appeare¢ 
softer than natural. In one spot the ca 
covering the convexity of the internal cond 


OT 
og 


m7 


rs 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


of the femur was superficially removed for the 

size of a sixpence. To this softened, ulcerated, 

or abraded point the principal pain was referred, 

by the patient during life. There were not any 

loose and vascular synovial fringes hanging into 
_ the interior of the joint, but examining at the 

‘circumference of the cartilage, where it invests 
_ the external condyle of the femur, this mem- 
_ brane and its subsynovial tissue were very red, 
B wascular, and villous-looking. The outer edge 

of the cartilaginous covering of the femoral 
_ condyle was thin and minutely serrated, and the 

eye of the probe could be placed under this edge. 
John “esi et. 19, was admitted into the 
Richmond Hospital, January, 1839. He had 
_ been under treatment in the country for six 
months for a disease of the left knee-joimt which 
originated in a blow on the joint from the handle 
_ of aprinting-press. He fainted at the time of 
_ the accident, and the pain never ceased from that 
_ day up to this period of his admission. He 
_ was reduced a good deal in flesh. He had 
_ Occasional perspirations during the night, parti- 
_ ¢cularly about the head, and starting pain shoot- 
_ ing up and down the leg. He could not bear 
_ the joint to be moved but kept it semiflexed, 
and the limb lying on the outside. He stated 
_ that before his admission he had never been 
_ altogether confined for the complaint. There 
_ was some little swelling of the knee, which was 
tender on pressure. There was no swelling in 
_ the ham, nor enlargement of the inguinal glands. 
_ The calf of the leg was wasted, and the thigh 
__ also was less than the other by an inch in the 
_ measure of its circumference above the knee. 
_ He remaimed much in thisstate until March 14th, 
_ when he complained of suffering a constant 
_ dead pain” across the joint below the patella ; 
_ besides this there was occasionally a throbbing 
sensation which was more distressing to him 
_ than any other, even than the spasmodic starting 
of the limb. On the 2nd of April a valvular 
_ opening was made with caution into an abscess 
on the inside below the articulation; thin curdy 
' matter came away. This gave him some relief. 
_ On the 4th another opening was made in the 
outside above the joint, where also the abscess 
_ showed itself: matter of a similar description 
‘came away. Previous to these punctures hav- 
_ ing been made, amputation was proposed to 
_ the man as the only means of escape from this 
_ disease, but he preferred to have the abscesses 
_ opened. Fever did not follow upon this first 
or second operation, but subsequently it set in, 
and ran very high for four days, during which 
he perspired largely and had much pain and 
- starting of the limb, with head-ache and anxiety 
_ of manner, and for two days he was in a con- 
_ fused state bordering on delirium. Nor did the 
_ evacuation of the purulent matter prevent the 
enlargement of+the cavities of the abscesses 
_ connected with the diseased joint, as appears 
by the following report, dated May 10th, made 
by our clinical clerk, Dr. Bradshaw. “ The 
abscess has ascended up the thigh, running 
high up the popliteal region. The hectic fever 
is severe; his pulse in general 120, small and 
compressible ; emaciation had advanced and is 
still advancing; his strength is giving way 


57 


under the disease, and he must soon sink if 
amputation be not consented to.” On the 
10th May the report was, “ Diarrhea still con- 
tinues, but without abdominal pain or teoder- 
ness. The emaciation is very great. Pulse 120, 
small, and compressible. Tongue red, moist, 
and morbidly clean. The flexion of the leg on 
the thigh becomes every day more and more 
considerable, so that the angle becomes daily 
more acute.” On the following day amputation 
high up was performed. The disease of the 
knee had much affected the cartilaginous struc- 
tures of the joint, the absorption of which seemed 
to have been effected by a vascular pulpy mem- 
brane. The parts that had suffered most were 
the external condyle of the femur, the inver 
head of the tibia, and the inner and posterior 
surface of the patella. Along the trochlea of 
the femur there existed longitudinal grooves or 
furrows in the cartilage, which was not removed. 
A highly vascular and pulpy membrane was 
found filling the parts wherever the cartilage 
had been absorbed, and this membrane could 
be traced insinuating itself beneath the edge of 
the remaining portions of the cartilage, by which 
means the process of absorption seemed to have 
been effected. In the interior of the joint there 
were much pus and flakes of lymph, and where 
the. cartilages had been removed the porous 
surface of the bones had been covered by soft 
layers of lymph of very recent formation. 
Chronic rheumatic arthritis of the knee.— 
Tn the articles Hann, Hip, Etzow, &c. in this 
work we have treated of a chronic disease 
affecting other articulations, which we have 
denominated chronic rheumatic arthritis ; we 
shall now give an account of the symptoms 
and anatomical characters of this disease as we 
have found it in the knee-joint.. When this 
articulation is affected with it, other joints in 
the same individual will also be found more or 
less implicated. The commencement of this 
disease of the knee is marked by evidences of 
subacute inflammation, such as pain, heat, con- 
siderable swelling. This is followed by a 
second period, in which the heat and swelling 
diminish, but the pain continues. This pain 
is usually referred to the inner condyle of the 
femur and tibia. The patient may for a long 
period be able to walk, but every movement 
produces considerable pain, and at length he 
becomes incapable of walking or even of stand- 
ing. The limbs diminish in size, but become 
remarkably firm to the feel. The patient having 
at last lost the power of flexing or extending the 
Jimb, the hamstring muscles gradually become 
more tense. The knee-joints from the com- 
mencement incline slightly inwards, and the 
tibia outwards, and this bone is at the same 
time rotated in this last direction, so that the 
foot is everted ; if the limb then be kept in 
the semi-flexed position, and the tibia be thus 
rotated outward, carrying with it the ligamentum 
patellz, it is easy to account for the circumstance 
which we have in some examples witnessed in 
the disease,—viz. that the patella leans towards 
the outer condyle, and further, that it is then 
sometimes thrown completely over it, so as to 
represent the external dislocation of this bone. 


58 


When the distension of the synovial sac of 
the articulation is at its maximum, we usually 
notice in this disease a prominent tumour about 
the size of a small hen’s egg projecting into 
the popliteal space (fig. 3). is tumour 
leans towards the inner head of the gastro- 
cnemius ; it disappears when the knee is flexed, 
and becomes more tense and hard when the 
limb is in the extended posture, as when the 
patient stands erect. We have known several 
cases of this disease of the knee-joint, where 
the synovial sacs of the knees have been much 
distended, and have on these occasions almost 
uniformly observed this popliteal tumour formed. 
From its situation, and from negative evidence, 
we can readily infer that the swelling consists 
of synovial fluid contained in a bursa, which 
has a communication with the interior of the 
knee-joint. 

We have witnessed very many cases of this 
chronic rheumatic arthritis of the knee, in which 
this dropsical condition of the popliteal bursa 
existed, and some of these having had this 
chronic disease in both knee-joints, the burse 
were seen in both popliteal spaces,—presenting 
in these cases on a superficial inspection the 
resemblance to a case of double popliteal 
aneurism. 

We have also enjoyed an opportunity of 
ascertaining by anatomical examination the real 
condition of this synovial sac in this disease, 
and its relation to the synovial membrane of 
the joint itself, to which we shall have occasion 
just now to revert. 

When the palm of the hand is applied over 
the patella in the early stages of the affection, 
a sensation of a preternatural degree of heat is 
felt; and when pressure is made on the patella, 
and a lateral movement across the condyles is 
communicated to it, a very evident roughness 
is perceived, either on the articular surface of 
the patella itself, or the corresponding surface 
of the trochlea of the femur; and when the 
knee-joint is fully flexed, a charactenstic arti- 
cular crepitus becomes manifest. In the later 
stages of the disease, the subacute inflamma- 
tion, with the phenomena which it presents, 
subsides, the synovial fluid becomes absorbed, 
and the patella falls down on the trochlea of 
the femur; the popliteal bursa also disappears, 
and the grating produced by rubbing surfaces 
is perceived by the patient himself in all his 
movements, and can even be heard by the by- 
standers. If the joint be now examined care- 
fully by the surgeon, he feels satisfied that the 
smooth cartilage has been removed, either par- 
tially or completely, from the articular surfaces. 
Crests of ossific deposit may even be per- 
ceived, and, almost invariably, foreign bodies 
may be felt in the interior of the joint. Some 
of these are superficial, small, and moveable ; 
others are evidently situated more deeply in 
the interior of the joint. Some are small, 
some , and we have known one case, 
which we learned to be of forty years standing, 
in which numerous bodies* of this description 


* The case mentioned by Morgagni in which he 
Saw twenty-five of these bodies in the left knee- 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


could be felt, some literally as as the 
a floating about in the interior of the 
nee-joint, and which, we doubt not, we 
exactly of the same nature as those we k 
described in the elbow-joint. ; 
The osis in this disease must be w 
favourable, as it seldom yields to medicine, t 
it does not appear to us to shorten life. W 
have seen an example in which the knee-jon 
had been affected with this disease, as | 
patient herself reported, for forty years. 
are not prepared to say, however, that medic 
and proper treatment may not i 
short the disease, and we are sure the sufferin 
of the patient may be palliated at least I 
appropriate treatment. e following case | 
good example of this disease. 
Case of chronic rheumatic arthritis.—Patri 
Donohoe, 38, a carter, admitted into tl 
Richmond Hospital, (Dublin,) Nov. 24, 18 
complained of chronic pains in all his jon 
but the principal source of his uneasiness 
the diseased condition of his knee-joints, 
pecs his earning his livelihood. 
nee-joints were greatly swollen; he co 
plained of stiffness of them, and of some pa 
at the inner condyle of the tibia, which in 
creased when he stood up; yet he was able t 
walk a considerable distance. The limbs cou 
be fully extended, and when in bed he key 
them pretty constantly in this position. H 
could not fully flex them backwards. 
swelling of the knees differs from that of a 
ordinary white swelling, although it might 
respond much to the characters which a cas 
of chronic synovitis of the knee might pre 
or to a case which the older writers denomin 
hydrops articuli. The swelling viewed in 
is of an irregular globular form, involving th 
patella, its ligament, and the hamstring | 
dons in one uniform tumour; on the contra 
the ligamentum patella can be felt, with if 
edges as yet sharp and well defined, when th 
patient is desired to exert the extensor muscle 
of the leg. The tibia at the side of the li 
ment, as far as the insertion of the intern 
lateral ligament, can be plainly felt th 
the skin to be rough and scabrous, and it 
be ived that this part of the bone is be 
with bony vegetations. The breadth of # 
head of the tibia is increased; the synovi 
membrane contains a redundant secretion, whit 
elevates the vastus internus and forms a swell 
here which measures about seven inches in | 
vertical diameter, and which seems to be som: 
whatconstricted transversely in its centre (fig. 
The swelling of the knee on the outside is evide: 
enough, but is not so well marked as that: 
the inner side. 1t presents no transverse b 
subdividing it into two tumours. The ou 
line of the hamstring tendons is seen, whi 
the joint is viewed in profile, either fro 
without or within, and a very well defined ove 
projection from the popliteal space is observes 
(fig. 3). Its centre is on a level with the P 


joint of an old woman who died of apoplexy, we 
think must have been a case of the chronic disea 
we are now describing. 


Fig. 2. 


! i 
Well fifi 


Left knee-joint, front view. 
The prominent swelling on the left, A, is from the en- 
wf head of the tibia; that on the right, B, is the 


Hi 


_ soft globular swelling resulting from the effusion into 
___ the synovial membrane. 

per and projecting margin of the inner condyle 
of the tibia: it leans to the inner hamstring 
muscle. The rest of the popliteal space pre- 
sents a normal appearance. hen the limb is 
| fully extended, and the muscles are allowed to 
‘remain in a passive state, the patella may be 
| moved from side to side with much freedom. It 
‘appears to float as it were on the surface of an 
‘accumulated quantity of synovial fluid. When 
pressed against the trochlea of the femur, this 
fluid is moved laterally, and the patella strikes 
against the femur, and if a lateral movement be 
‘ow communicated to this bone, a grating of 
‘rough surfaces may be perceived. If we grasp 
‘the leg and flex it on the thigh, we find we can 
elicit a peculiar articular crepitus. . In this case 
‘it is quite audible, and resembles much the 
noises which electric sparks make when dis- 
‘charged in quick succession from an electrical 
apparatus. When the limb is much flexed, 
‘the swelling of course feels remarkably hard 
and solid, but when the limb is again brought 
back to its ordinary state of extension, fluctua- 
‘tion may be felt very evidently in it over its 
whole surface. The popliteal bursa, however, 
is felt very tense in the extended position of 
the joint, as when the patient stands and throws 
his weight on the limb. If we feel this bursa, 
and then cause the patient’s limb to be flexed, 
we can follow the fluid, as it were, with our 
fingers into the articulation. As the patient 
lies in bed, the limb left in the extended posi- 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


59 


Left knee-joint, side view, shewing the enlarged bursa 
._ in the popliteal space. 


tion, and the synovial sac as flaccid as possible, 
moveable bodies may be detected in its interior. 
Some appear to be adherent, and situated more 
particularly in the upper portion of the sub- 
crural bursa. When we elevate the leg, and 
preserve it still in the fully extended position, 
the patient, without any apprehension of pain, 
will permit us to press it firmly against the 
femur, and does not experience the least suf- 
fering even if we strike the heel forcibly. (See 
HIP, ABNORMAL CONDITION OF.) 

Both knee-joints in this case are affected 
with this disease, but the left is more distended 
by fluid than the right. The inner condyles of 
the femur and tibia of this limb are thrown 
somewhat inwards, and form a salient angle in 
this direction, which, the patient says, is cer- 
tainly the result of disease, as his limbs were 
perfectly straight before he was visited by his 
present illness. 

Although his knee-joints are more affected 
with this chronic disease, his other joints pre- 
sent very evident traces of this afflicting malady. 
The disease in him followed a rheumatic fever, 
which was brought on in consequence of his 
having lain a whole night asleep on a wet road, 
having fallen unobserved from fis cart when in 
a State of intoxication. 

Although this is not the place to speak of 
treatment, we may be permitted to say that 
under the influence of rest in bed and a mild 
mercurial course, followed by a long-continued 
use of sarsaparilla with large doses of the 
hydriodate of potass, this man left the hospital, 
by no means cured, but much improved and 
tolerably well able to follow his occupation. 


60 


He found it necessary, however, after the lapse 
of three years, to seek re-admission into the 
hospital, where he now is. The right knee- 
joint is now enlarged, and in a condition simi- 
lar to that of the left on his first admission. 
The latter, on the contrary, has nearly resumed 
its normal condition; the dropsical effusion of 
synovia has disappeared; he does not com- 
plain of pain in it; but if the joint be accu- 
rately examined, the bony irregularities which 
were noticed on the head of the tibia will be 
found, as might be expected, still to exist. If 
we move the patella transversely, an articular 
crepitus is perceived, plainly shewing that the 
cartilages have been removed from the patella 
and corresponding trochlea of the femur. The 
edges of the trochlea can also be felt through 
the skin to be elevated into rising crests. The 
peculiar crackling noise which is elicited when 
the joint is flexed and extended is infinitely 
more remarkable in the left knee-joint now, 
when it is comparatively well, than formerly, 
when it was much swollen, and when the syno- 
vial membrane was in what has been called a 
dropsical condition. 

Anatomical characters—When we have an 
opportunity of making an anatomical examina- 
tion of a knee in which the disease had been 
fully established, we find the synovial fluid 
increased in quantity, and but little altered in 
its sensible qualities. The membrane is thicker 
than natural, and opaque. Sometimes vascular 
synovial fimbriz are formed, and hang into the 
synovial sac.* We also find moveable carti- 
laginous bodies in the interior, similar to those 
noticed in the elbow-joint.t (See Exzow, 
ABNORMAL CONDITIONS OF.) 

In the line of flexion and extension we 
observe narrow sulci formed by the removal of 
the cartilages. On examining the popliteal 
tumour, we find it to be, what we might have 
surmised, an enlargement and dropsical condi- 
tion of the bursa, which naturally exists at the 
point of decussation of the semi-membranosus 
tendon with the tendon of the internal head of 
the gastrocnemius. This bursa communicates 
normally with the synovial sac of the knee- 
joint by a very small circular aperture. It is 
not an uniform ovoid sac, but evidently has 
semilunar septa irregularly thrown across its 
interior, making the bursa a small multilocular 
cavity. When the joint is much distended by 
synovial fluid, the bursa admits some of this 
fluid, and takes upon itself the same morbid 

rocess which affects the proper synovial mem- 
lieias of the joint itself. As we examine the 
disease when it has existed for some time, we 
find that the cartilage has been removed in 
grooves, and its place supplied by a porcelain- 
ous or ivory deposit. e bones of the knee- 
joint, however, present appearances charac- 
teristic enough: they generally appear to be 
enl This is obviously the case with the 
patella: it is broader than natural, excavated, 
and grooved vertically. All the bones seem 
enlarged and porous on all those parts of the 


* See Cruveilhier, liv. 9. pl. 6. 
t See Morgagni's case, in note above, 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


articular surfaces which have not been worn | 
use into porcelainous polished surfaces and st 
The cavities of the head of the tibia for dl 
reception of the condyles of the femur ; 
much deepened, and exuberant nodules 
vegetations of bone are thrown out around f 
circumference of this head. When we exan 
the femur, we find here also bony vegetati 
arranged along the lateral margins of the 
dyles, similar to those which we noticed aro 
the corona of the head of the femur.* © 
on Ped bone called the trochlea, u 
which the patella moves, is also grooved ye 
cally, and Che trochlea has rising edges t 
oa — which will be found to correspon 
the lateral margins of the la when 
bone is laid stock the troctlon of tie em 
The anatomical characters of this disease w 
it has existed long, will of course be still 
strongly marked. However, the dropsi 
effusion into the synovial sae will be found 
be much less as the disease is of longer dui 
tion. The joint becomes more and more flex 
the tibia has a tendency to be partially 
placed outwards, and the toe is everted: | 
patella under such circumstances is disloca 
on the external condyle, giving us ane 
example of this luxation from disease. Int 
interior of the joint foreign bodies are fout 
while the articular and semilunar cartilage 
altogether absorbed. . 
White swelling, or chronic strumous arthr 
of the knee—The knee-joint is more liab 
e disease commonly called white swe 
than any other articulation. This disea 
though utterly insidious in its attack and s 
in its progress, nevertheless presents some 
the characters of an inflammatory compl 
during its whole course. The first ; 
generally is reported as a deep-seated dt 
heavy pain unattended by swelling and 
increased by motion, but in children the swe 
ing is often the first symptom noticed. This 
followed by pain, which, although it ec 
only occasionally, is severe, and is re’ 
almost uniformly to the inside of the kn 
Some increase of temperature of the affect 
joint on comparison with the other knee, ¢ 
be ceiertiined 7 
The swelling does not at first encompass t 
whole joint, but first appears on the anteri 
and lower of the knee, occupying 
general the two little hollows on the differ 
sides of the ligament which joins the patella 
the tibia. This swelling is elastic, and 
examination by the finger conveys a sense 
softness and fluctuation, as if it containe 
fluid, although no fluid to any amount tea 
exists. The skin over the knee becomes p 
and shining, as if thinned. The subcutanes 
veins dilate and become very evident. 1 
muscles of the ret waste, so that the volu 
of this portion of the affected extremity is e 
widerihdpstekincdd: and the inferior part of 
thigh just over the knee suffers a characterist 
diminution in the measure of its circumference 
W 


+ 


* See HIP, ABNORMAL CONDITION OF, ff 
also Cruveilhier, liv. 9. pl. 6. fig- 2. 


¥ 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


Patients under an incipient attack of white 
swelling first experience inconvenience in walk- 
ing from weakness of the joint, a symptom 
which is more especially troublesome after 
exercise. But as soon as the pain becomes 
constant, the patient is no longer able to rest 
the weight of his body upon the affected limb 
without a great increase of uneasiness. On 

_ this account he is willing to save the limb as 

‘much as possible; he touches the ground, 

_ therefore, merely with his toes, trusting the 

_ support of his body chiefly to the other limb. 

_ In walking in this way the knee necessarily 

_ becomes bent, and what is thus begun becomes 

_ permanent from other causes; so that after a 

_ certain period the joint continues permanently 

in a state of flexion. 

___ Although we occasionally see cases in which 

the leg remains extended on the thigh, they 

_ must be considered rare, for in general the leg 
is in a more or less forced state of flexion on 
the thigh, and such is the patient’s apprehen- 

sion of pain he will not on any account extend 

‘the leg voluntarily, nor allow it to be extended 
by others. 

_. The earlier period of the disease is succeeded 

by a second stage,* in which the patient usually 

_ submits to the adoption of active and energetic 

_ treatment. The pain now not unfrequently 

diminishes, but the swelling continues in- 

creasing, the ham becomes fully occupied by 
it, the extremities of the bones appear to 
enlarge, and become more prominent as the 
flexion increases. Attacks of inflammation 

* ensue, accompanied by pain starting up and 
down the limb, by which sleep is interrupted. 

_ These attacks are usually succeeded by effusion 

of fluid into the synovial sac of the joint and 

_ cellular interstices around : abscesses form, and 

some fluctuation may now be discovered in 

different parts of the swelling. If at this 
period, which may be called the third or sup- 
purative stage of the disease, the bones be 

_ moved laterally, it will be perceived that the 
ligaments permit an unnatural degree of motion 

‘between them, and now, as in other articula- 

tions, ial or complete luxation may occur. 

Such, however, is the breadth of the surfaces of 

‘contact of the bones of the knee-joint, that 
‘complete luxation seldom happens. The limb 

at this period is usually found lying powerless 

_ On its outer side and in the semiflexed position ; 

and after some time a partial displacement of 

the leg outwards on the femur occurs: under 

_ other circumstances a partial or complete luxa- 

_ tion backwards happens. Although the disease, 

_ arrived at this stage, seldom terminates favour- 
ably, still instances do occur of unexpected 

improvement of the general health, of the 

_ Tesdlution of the swelling, of the absorption of 
‘Matter, and of one of the forms of anchylosis 

taking place. But usually the matter formed 
in and around the joint goes on accumulating, 


_ ™ Mr. Lloyd divides scrofulous white swellings 
into three stages ; the first being that in which the 
affection is confined to the bone; the second that 
in which the external parts become thickened and 
swelled; and the third what he denominates the 
sub-acute stage.—Lloyd on scrofula. 


61 


the tension of the knee-joint increases, and 
now in most cases an accompanying cedema of 
the foot is observed, a symptom than which 
there can be none more unfavourable. The 
nocturnal startings of the limb, disturbing the 
patient’s rest, become more painful and urgent, 
and abscesses communicating with the interior 
of the articulation open externally by one or 
more orifices, and give exit to a quantity of 
matter, which rarely has the quality of laud- 
able pus; on the contrary, it is for the most 
part a sero-purulent liquid, of a yellowish 
green colour, like whey, in which curdy mat- 
ters are found floating. It is remarkable that 
little diminution in the size of the swelling 
follows the escape of this matter. 

We have stated that the pus is seldom lau- 
dable. On some few occasions, however, its 
consistence may be that of good pus; but even 
then it soon degenerates into a thin fetid sa- 
nies of bad quality. The openings giving exit 
to the discharge sometimes close very speedily, 
and new collections form in different parts of 
the tumour. This, however, is unfortunately 
rare, for generally the openings degenerate into 
fistule. A probe introduced into one of these 
penetrates, if the route be not long and cir- 
cuitous, into the interior of the joint, and dis- 
covers the internal parts to be carious and dis- 
organised ; and if the bones of the articulation 
be now pressed together, a crepitation, arising 
from the friction of the carious and ulcerated 
surfaces, is perceived, furnishing unequivocal 
evidence of the last stage of disorganization of 
all the structures of the articulation. This is 
the most common course of the disease, but in 
some cases there are varieties to be observed. 
For example, the suppuration of the soft parts 
and ‘of the cartilages, and even caries of the 
bones, may occasionally precede the displace- 
ment of the bones; and all the parts of the 
articulation may be destroyed without the oc- 
currence of any displacement; but if, in this 
case, we move the bones of the articulation in 
opposite directions, we easily ascertain the re- 
laxation of the uniting ligaments, and that 
many of the conditions necessary to the dis- 
placement exist, although, from some cause not 
easily explained, it has not occurred. 

As to our prognosis we should remember 
that the age and constitution of the patient 
have considerable influence on the ulterior pro- 
gress of the disease, and our knowledge of this 
must control our anticipations as to the result 
to be expected, ceteris paribus. The disease 
in the truly strumous subject is very rebellious, 
and has a disposition to terminate in suppu- 
ration which it is difficult to baffle. In young 
subjects it is in general more acute, or the suc- 
cession of the different orders of symptoms is 
more rapid; but in young persons there is 
much more hope of cure than in the old and 
exhausted. We agree with Mr. Russell in 
opinion that it is in the cases of infants that 
the formation of anchylosis may be expected as 
the termination of a case of white swelling, 
though even with these true bony anchylosis 
must be considered as a very rare occurrence. 

In the beginning the disease has but little 


62 


influence on the constitution: it is not until it 
arrives at the second or third stage that it pro- 
duces any very remarkable alteration in the 
health ; but the pain about the commencement 
of the third stage is sometimes so violent as 
to deprive the patient of sleep and appetite. 
When the part is distended by abscesses, the 
pain is increased, but when these open or are 
opened, although temporary relief follows, 
slow fever supervenes, the discharge becomes 
Sanious and fcetid, and nocturnal sweats and 
colliquative diarrhoea shew themselves, together 
or alternately. 

Anatomical characters of the chronic stru- 
mous arthritis of the knee——The anatomical 
examination of a limb which has been ampu- 
tated on account of a white swelling, or after 
the death of the patient, demonstrates different 
alterations which disease produces in the struc- 
ture of the soft parts surrounding the diseased 
articulation, and in that of the bones, synovial 
membranes, and cartilages which compose it. 
The skin and subcutaneous cellular tissue are 
not greatly altered from their natural condition, 
except that the latter is usually infiltrated with 
a gelatinous matter, as is also the cellular struc- 
ture, which lies deeper, viz. that which unites 
the femur with the inferior part of the crureus 
muscle, as well as that behind the ligament of 
the patella, and that also which occupies the 
intervals between the condyles of the femur 
behind the crucial ligaments. These parts are 
equally infiltrated by a gelatinous fluid, of 
more or less density. The whole of this cel- 
lular structure presents the appearance of a 
soft, spongy, homogeneous mass. The liga- 
ments which secure the junction of the bones 
of the joint seem themselves involved in this 
morbid change of the surrounding cellular 
Structure, so that the tumefied ligaments and 
other structures seem to be confounded toge- 
ther, and to present an appearance almost like 
a fibro-cartilaginous mass. “ Thus have we 
seen,” says Boyer,* “ the fatty cellular tissue 
which is placed behind the ligamentum patella, 
so dense and thickened that it formed Dat one 
mass in which ligament and cellular tissue 
seem confounded together.” All these ap- 
Pees are present even before suppuration 

as occurred. If the disease had existed for 
any length of time so as to have arrived at the 
period of suppuration, we find, among the 
Structures thus altered, that symptomatic chro- 
nic abscesses have been formed. One extre- 
mity of them we observe usually communicat- 
ing with the knee-joint, while the other reaches 
the surface, and presents one or more openings 
which had become fistulous. These abscesses 
and fistulous canals we find always lined by a 
false membrane. The muscles which surround 
the diseased joint are pale and wasted, and the 
cellular tissue which is found in their thickness 
is ordinarily more or less infiltrated with the 
peculiar glairy matter above alluded to. The 
tendons of the flexor muscles are generally re- 
tracted and preserve their normal ap ce. 
The nerves we have had occasion to observe to 


* Maladies Chirurgicales, 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


be thicker than natural. These are the alte 
tions which are noticed in the soft , as. 
—_ an anatomical examination down to’ 
nes and ultimate structures of the joint 
self. It is probable, however, that the 
changes will not be found to have occur 
unless the disease has existed for some t 
previously in the centre of the bones thi 
selves. Sir B. Brodie, Lloyd, and othe Ss 
of opinion that this strumous disease be gins 
the centre of the heads of the bones of 
knee-joint, in the cancellous structure ; 
Rust has satisfied himself that the memk 
nous tissue which lines the cancellous str 
ture of the bones is the seat of the first mor 
action. They have found the interior of 1 
spongy tissue of the bones more vascular tl 
natural, and with much apparent justice 6 
ceive them to be inflamed. These char 
then, in the interior of the bone they belie 
to constitute the anatomical charaeters of f 
first period of the disease, and that when 
arts external to the joint become swelled a 
infiltrated by the gelatinous matter above allu 
to, the second period is fully established. — 
When the second period has commence 
and the soft parts are excited into irritat 
if opportunities occur of examining the in 
rior of the bones, they will be found to be st 
tened and easily penetrated by a knife. T 
synovial membrane contains an unusual qua 
tity of fluid, and the bones will undergo fi 
ther changes as the disease grows worse. Th 
structures become still softer, their eancelle 
structure is found filled with a yellowish chee: 
like matter. The bones, which in the first) 
riod were in an hyperemic condition, a 
now found to be less vascular, and _portiol 
even become necrosed, so that it is not 1 
common in advanced cases to find in the 
terior of the joint portions of dead bone. ~ 
these cases the spongy portion of the be 
seems so altered in structure as to appear hi 
dissolved, and to contain a sanious and feetit 
matter in its substance. The periosteum | 
vesting the bones in the neighbourhood of t 
diseased knee is very much thickened a 
easily detached. It is surprising to what 
extent this strumous disease may have ¢ 
vanced in the bones and in the external p 
around the joints while the synovial structu 
and cartilages remain but partially engag 
The wniter has lately been compelled to am 
tate a thigh for this disease of the knee in et 
sequence of the constitutional symptoms 
it excited in the system. In this case he ¢ 
covered that while the bones and soft p. 
externally were far advanced in the sect 
stage of the disease, the synovial membr 
and cartilages were perfectly natural. 
however, the disease has advanced far, 
the fistulous orifices are found to commit 
cate with the interior of the joint, we 
that the synovial membrane presents appe 
ances of morbid action having gone on imi 
and when the puriform fluid contained in it 
wiped away, that the surface of this m 


* Russel entirely differs from them. | 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


brane, instead of being white, is red and vil- 

lous, and much like mucous membrane in a 

high state of inflammation. We can frequently 
ascertain that this membrane has superadded 

to it layers of newly deposited lymph, which 
have become highly organized. Mr. Russell 
“says, that in his dissections of white swelling 
of the knee, he has found the inside of the 
synovial membrane covered with a layer of a soft 
_ substance, of a pale yellowish colour, and semi- 
transparent; that this substance was nearly 
one-eighth of an inch in thickness, softer in its 
‘inner concave surface, and firmer on the outer 
"convex part, where it adhered to the inside of 
the synovial capsule of the joint with a con- 
siderable degree of firmness. In many places 
observed on it avery beautiful plexus of 
_ vessels; and at the interstices between the sur- 
- face of the femur and tibia, he states that he 
generally found an appendage full of blood. 
vessels which had insinuated itself to the dis- 
tance of nearly half an inch. It very fre- 
quently happens that the cartilages and crucial 
ligaments are completely concealed from our 
view by a membrane, in some places of one- 
quarter or even one-half of an inch in thick- 
“hess, presenting a loose cellular structure, 
highly vascular, occupying the intervals be- 
tween the condyles, and hanging into the in- 
terior of the joint; and we have usually found 
this newly-formed structure to be superadded 
to the original synovial membrane, and to 
establish adhesions between the bones of the 
articulation, and we find bands of organized 
lymph stretching from the femur to the tibia. 
When this condition of the synovial membrane 
existed, we have usually found the cartilages 
remaining; but in other cases the synovial 
membrane itself has been found to be but little 
altered; and yet the cartilages have been re- 
‘moved partially or completely, the porous sub- 
Stance of the bone having been found exposed, 
; 4 covered by recent deposits of soft pultaceous 
lymph. 

Such are the organic changes which usu- 

ally produce white swellings. These changes 
present numerous varieties, but it is sufficient 
to notice the principal ones, and to observe 
‘that there are scarcely two patients in whom 
they are perfectly alike. 
__ Sir Benjamin Brodie, in his work on the 
joints, has remarked that when acute inflam- 
mation attacks the shaft of a cylindrical bone 
and the periosteum covering it, the disease is 
usually limited by the epiphysis, so that, not- 
withstanding the extensive abscesses and exfo- 
Tiations which frequently ensue, the neighbour- 
ing joints are not affected by it. Although we 
have seen numerous specimens proving the ge- 
neral truth of this observation, yet on the other 
hand we have witnessed exceptions to it: in- 
deed Sir Benjamin Brodie has further observed 
‘that a few instances occur in which acute in- 
flammation attacks the epiphysis itself, termi- 
nating also in exfoliations, &c. more or less ex- 
tensive. 

In very young subjects we occasionally see 
examples of diffuse inflammation which has 
engaged the periosteum of the femur or tibia, 


63 


and the epiphysis of one or both of these bones, 
the inflammation extending to the knee-joint. 
These cases are usually rapid in their course, 
and too frequently terminate fatally, the ordi- 
nary symptoms of diffuse inflammation being 
exhibited in their progress. In the post-mortem 
investigations of these cases we find that the 
periosteum is extensively separated from the 
bones by purulent matter; that the epiphyses, 
detached from the shafts of their respective 
bones, are loose in the interior of the joint; 
and that the synovial membrane is dis- 
tended by matter. In the serous and mu- 
cous membranes of the chest also we generally 
find evidences of acute inflammation having 
existed. The origin of these violent attacks is 
sometimes referred to a fall or other accidental 
injury, sometimes to a cold which commenced 
with a rigour. We have sometimes known 
this severe form of disease to succeed imme- 
diately to attacks of small-pox, and also of 
scarlatina. Dr. M‘Dowel, in the third and 
fourth volumes of the Dublin Journal, has de- 
scribed this disease under the heads Periostitis 
and Synovitis; and the museum of the Rich- 
mond hospital contains many specimens of 
these unhappy results of diffuse inflammation. 

Cases of diffuse inflammation are not the 
only ones in which we have seen matter, 
formed beneath the periosteum of the tibia, 
passing the epiphysis and getting into the 
cavity of the knee-joint; we have known in- 
stances of such occurrences in cases of acute 
necrosis of the tibia, in which the disease in its 
commencement had been exclusively confined 
to the one bone. Mr. Smyly, one of the sur- 
geons to the Meath Hospital, presented to the 
museum of the College of Surgeons in Dublin, 
a specimen, the result of an acute necrosis of 
the tibia. The following is the history of this 
case, which he kindly communicated to the 
writer. James Jarman, et. 9, was admitted 
into the Meath Hospital the 5th October, 1837. 
Sixteen days previously he had suffered a very 
severe contusion on the front of the left tibia 
by the accidental falling of an iron bar; there 
was, however, no breach of the skin, and the 
boy was able to walk about as usual for two 
days, when acute inflammation attacked the 
contused part, and daily increased for a fort- 
night. On the 4th of October he applied for 
relief at the dispensary. At this time a large 
and tense swelling extended from above the 
knee to the instep; a fluctuation was evident 
the whole way down the front of the leg. An 
incision was made into this swelling, which 
gave exit to a considerable quantity of thin 
discoloured pus, and the tibia was found quite 
denuded of periosteum. Great relief followed 
the opening of the abscess, but on the 10th of 
October there was much tumefaction observa- 
ble at each side of the patella, and redness, as 
if the joint were in a state of suppuration. 
The boy suffered much from irritative fever and 
occasional diarrhea: his pulse became very 
frequent, and his tongue red and dry. The ope- 
ration of amputation at the lower third of the 
thigh was now the only resource, and it was 
accordingly performed. 


64 


On examination, the knee-joint was found 
distended with purulent matter. The syno- 
vial membrane was covered in patches by a 
vascular pulpy membrane ; the cartilages were 
removed in several places. An opening was 
found in the wner condyle of the tibia, which 
perforated the spongy substance of this bone, 
and thus established a communication between 
the interior of the knee-joint and a large 
abscess as it were which had formed under 
the periosteum of the tibia. The shaft of the 
tibia was detached from the epiphysis and the 

riostieum, and was surrounded by matter. 

@ periosteum was thickened, vascular, rough, 
and gritty from minute particles of bone depo- 
sited in it. The ankle-joint was free—The boy 
recovered his health. 

Acute arthritis of the knee may be com- 
bined with acute osteitis of the bones of this 
articulation, and without any discoverable com- 
munication between the cavity of the arti- 
culation and the interior of the bones. On the 
2ist March, 1840, Mr. Smith presented to the 
Pathological Society the following case. Susan 
Christie, zt. 56, an inmate of the House of In- 
dustry, and for along period disabled by the 
affection of the knee-joints which we have 
described as chronic rheumatic arthritis, was 
removed to the Whitworth Hospital, where she 
died of a most acute attack of inflammation of 
the right knee-joint. On the post-mortem exa- 
mination old adhesions were observed in the 
chest. The right knee-joint presented the ex- 
ternal appearances noticed as belonging to the 
chronic rheumatic arthritis in a somewhat ad- 
vanced stage ; moreover, it was greatly swollen, 
and when the synovial membrane was opened 

rulent matter escaped; organizable lymph 
Fined this membrane and the cartilages generally. 
These structures, however, were in some places 
removed altogether, their place being supplied 
by a porcelainous deposit, grooved in the line 
of flexion and extension. From the condyles 
of the tibia the cartilage was raised up from the 
bone, apparently stretched out, and converted 
into a thin, flexible, and soft yellow membrane, 
difficult to be distinguished, except by its si- 
tuation, from a deposit of lymph the produce 
of recent inflammation. 

But the interior of the head of the tibia, 
its cancellated structure, the medullary mem- 
brane lining these cancelli, and the membrane 
of the medullary canal itself, all presented evi- 
dences of their having been the seat of acute 
inflammation. The purulent matter was dif- 
fused through the cancelli of the tibia, from 
the knee-joint, for one-third of its extent, but 
was nowhere collected into any isolated cavity 
or abscess, nor was there any communication 
between the purulent matter which occupied 
the synovial sac of the knee-joint, and that 
which pervaded the medullary structure and 
cancellated tissue of the tibia. In a word, the 
anatomical characters of a true acute osteitis 
of the bones entering into the formation of 
the knee-joint coexisted in an advanced stage 
with those of acute inflammation of all the 
other structures of the articulation. 

The osteitis of the lower extremity of the 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


femur or upper portion of the tibia sometim 
presents more of a chronic character. T 

flammation of the interior of the bone 3 
proceed to cause the death of a portion, wh 
is converted into a sequestrum, the presences 
which becomes a source of irritation and — 
flammation of the surrounding bone and 
formation of an abscess. The following ¢ 
came under the writer’s observation while un 
the care of his colleague Dr. Hutton in 
Richmond Hospital. Thomas Conolly, et. 
was admitted in May, 1838, for a disease 
the lower extremity of the left femur, of mi 
years’ duration. He had long suffered from 
deep boring pain in the interior of the bo 
At length an abscess formed, matter made 
way to the surface and was evacuated, a 


two small fistulous openings remained, throu: 
which a probe could be antsy deep into 1 
interior of the enlarged femur. The man w 
greatly exhausted by the quantity of the dis 
charge, by confinement, and heetie fever, a 
amputation was performed in the femur jus 
above the diseased part. The femur was four 
much enlarged near the knee-joint, and cover 
by wasted muscles, which had undergor 
considerable degree of fatty degeneration. Whe 
these were removed, the periosteum was foun 
thickened. A vertical cut from. before back 
wards was made through the femur, kn 
joint, and tibia, by which section the cavity : 
an abscess capable of containing a hen’s eg 
was exposed, which was placed transverse 
between the condyles, having two open fists 
lous orifices, one on the inner, the py on th 
external condyle. This abscess was lined by 
thick membrane which by a fine injections va 
proved to have been highly vascular; vil 
flocculi hung from it into the interior of the ea 
vity ; a dark-looking sequestrum of a cylin 
drical form, an inch and a half long and ha 
an inch thick, occupied the superior half of th 
cavity; one end of the sequestrum was fixe 
into the bony tissue of the femur, as if 
were on its way to present itself at the oute 
fistulous orifice ; the remainder of it lay dia. 
gonally across the cavity of the , th 
front wall of which was principally constitutec 
of soft parts, the femur having been absorbe 
in this situation. In the vicinity of the ab 
scess, particularly above it, the bone was greatly 
thickened, its cancellated structure solidifies 
and rendered apparently as dense as ivor 
The interior of the joint was quite unconnecte 
with the cavity of the abscess, but the joint 
self presented evidence of its having been ; 
one time the seat of some form of inflam 
matory action, because the shape of the con 
dyles of the femur was somewhat altered, am 
at the same time thetibia was partially displace 
backwards, and ligamentous anchylosis 
taken place. The cartilage had been remoy 
somewhat from the ends of the bones, and i 
place supplied in patches by a membrane like 
periosteum, and in other situations by a dense 
polished enamel. It was to be inferred fro 
the appearances which the bones and cont 
guous structures presented, that the knee-join 
had latterly been quite useless. > 


14 


_____ Abscess may, however, form in the interior 
__ f the heads of the tibia or lower extremity of 
le femur without being preceded by the death 
f any portion of the bone, as is proved by a 
ecimen in the museum of the Richmond 
ospital. A child, aged about twelve, had 
mg suffered from chronic disease of the upper 
rtion of the tibia. A chronic symptomatic 
scess pointed and opened spontaneously in 
le popliteal space, and here a fistulous open- 
ig remained discharging a quantity of thin 
pious pus. While under treatment for this 
ic disease, a sudden attack of acute ar- 
is set in, which threatened the patient’s 
_and amputation was immediately per- 
d. Upon examination of the knee-joint 
1 of the interior of the bones, which were 
posed by a vertical section made from before 
ards, an abscess was discovered in the 
ntre of the head of the tibia, capable of con- 
ining a walnut. This communicated with 
B popliteal abscess, which had long had a 
tulous opening in the ham ; but the abscess 
he interior of the tibia was now found to 
another opening into the cavity of the 
joint, which had all the appearance of 
g been quite recent. The matter of the 
ss of the tibia having suddenly made 
its way into the cavity of the knee-joint was the 
immediate exciting cause of the acute arthritis 
au, evidences of which were seen in a layer 
lymph which invested the synovial mem- 
we and the cartilages. The patient ulti- 
mately recovered. 
_ When the chronic form of necrosis affects 
he tibia and the epiphysis is included in the 
lisease, the knee-jojnt sometimes remains but 
altered, but in other cases remarkable 
S in its form take place. The leg is 
imes fully extended, and is even in ad- 
ce of the natural line, but it is more gene- 
ally flexed on the femur, and the tibia is at 
same time somewhat curved into the form 
fan arch, the concavity looking forwards. We 
have frequently known displacement of the su- 
erior head of the tibia, where it enters into the 
ormation of the knee-joint, to take place back- 
bards towards the popliteal space. This dis- 
lacement is usually incomplete. We have 
xamined many living examples of this defor- 
hity, and have had a few opportunities of inves- 
gating the anatomical changes the joint has 
een subjected to. 
Many circumstances tend to influence the 
rection in which the luxation may take place. 
he position in which the limb is preserved 
the attack ofinflammation of the tibia is 
f the most influential. As the limb is 
ly flexed during the first stage of the 
e, the partial luxation backwards will be 
ne most likely to occur. In these cases, 
ther the femur or tibia close to the knee be 
@ seat of the necrosis, more or less of effusion 
8 place into the synovial sac of the knee- 
joint; all the ligaments, of the joint become 
softened and relaxed; and the action of the 
Hamstring muscles overcomes the resistance of 
any remaining structures, and the tibia is dis- 
tocated partially backwards. 
VOL, 11k 
: 


4 ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


65 


Mr. West, surgeon to the Longford Infir- 
mary, sent to the writer of this article the leg 
and knee-joint of a man who had long con- 
tended against the consequences of a chronic 
necrosis of the tibia. There were from time to 
time exfoliations of bone, and a continual dis- 
charge of a thin sanious matter which so re- 
duced the strength of the patient as to render 
amputation necessary. <A cast of the limb, taken 
by Mr. Smith, and the bone are preserved in 
the museum of the Richmond Hospital, (figs. 
4 and 5,) from whichit will be observed that the 


fi 


\ 
\ 


Displacement of the tibia backwards from necrosis. 


displacement of the head of the tibia was par- 
tially backwards. This bone was drawn also 
somewhat upwards, passing inferiorly so far 
round the condyles of the femur that the arti- 
cular surfaces were almost abandoned. This 
is the simplest form of displacement of the 
tibia at the knee-joint from disease which we 
have noticed as the result of a chronic process 
of necrosis. We have seen some instances of 
necrosis in which the whole leg and foot were 
greatly rotated outwards on the femur, so that 
the innet ankle was placed directly forwards, 
and the outer malleolus directly backwards. In 
these cases the patella is completely dislocated 
on the outer condyle of the femur (fig. 6), be- 
cause the tubercle of the tibia, in its movement of 
rotation outwards, carries with it the ligamentum 
F 


66 ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


Fig. 5. 


Same as fig. 4, the soft parts removed. 
1, right femur displaced forwards; 2, tibia back- 
wards; 3, rough scabrous surface of tibia; 4, 
line of junction of the epiphysis. 


Partial displacement 
of femur inwards ; 
wards, 


Fig. 7. 


Left knee-joint. 


patel, and consequently gradually draws th 
ne outwards completely over the outer 

of the trochlea of the femur. We have si 
at the Richmond Hospital two similar ¢ 
this very curious result of necrosis of the t 
In these examples the knee-joint had p 
pated in the inflammation of the conti 
structure, and great deformity of bon ho 
was the consequence (fig. 7). 
one of these cases (Christopher Bec at. 
died of erysipelas, which was 

had no connexion with the deformity. Thek 
joint was examined, and the was fc 
dislocated outwards, and anchylosed to the o: 
surface of the external condyle of the fi 
(fig. 8.) The superior extremity of thet 
partially displaced backwards, and was gre 
deformed and enlarged, particularly the. 
condyle of this bone, the anterior half of. 
was deeply excavated to receive the condy! 
the femur; the posterior half of this cone 
was free and had no bone in contact wi 
but this portion of the tibia and the head 
fibula were so much rotated or twisted © 
wards and backwards as to form a v; 
cuous elevation in the lower part of the p 
teal space. The fibula was placed ¢ 
behind the tibia. The lateral ligament did 1 
exist. The ligamentum patelle was gre 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 
Fig. 8. 


i. | 

BY 

Femur displaced inwards. Patella anchylosed. 
ae 

" elongated and was directed backwards. The 
_ ctucial ligaments were also elongated, and 
_ instead of crossing each other were untwisted 


as it were and lay side by side. The carti- 
_ Tages were altogether removed, and when the 
_ femur was forcibly separated from the tibia, 
_ there were corresponding elevations and de- 
‘pressions which marked the several points of 
_ contact between the bones, in which a species 
‘of anchylosis had occurred. The body of the 
‘tibia was greatly enlarged and hypertrophied, 
‘and round perforations existed in its head, 
om which sequestra had been discharged. 


_ Af. Asnormat conpitrons OF THE KNEE- 
‘JOINT RESULTING FROM accrDENT.— Frac- 
| tures and dislocations are the principal acci- 
| dents to which the bones of the knee-joint are 
hal The muscular and tendinous fibres 
‘common to the rectus, crurceus, and vasti are 
Occasionally torn from the patella, and the 
higament of this bone is also sometimes rup- 
} tured. The proper ligaments, too, and other 
‘Structures of the knee-joint, suffer from sudden 
‘injuries, which we must here advert to as 
| briefly as we can. 
| _ Fractures of the shaft of the femur near to 

the knee-joint may be transverse or oblique, 

or one or both of the condyles may be broken 
off from this joint. 

_ 1. When a transverse fracture is situate 
| immediately above the condyles-of the femur, 


; 
} 


67 


Fig. 9. 


Displacement backwards of the superior extremity of 
the lower fragment. 


it is the inferior fragment which is displaced, 
its superior extremity being directed backwards 
towards the popliteal space (see fig. 9) ; the an- 
terior part of the condyles and trochlea have 
their aspect directed upwards, and form a 
swelling above the patella, giving to the joint 
a singular appearance. This direction back- 
wards of the superior extremity of the lower 
fragment is the result of the action of the 
gastrocnemii, the plantaris, and _popliteus 
muscles. 

2. Oblique fractures of the lower extremity of 
the femur near the knee-joint are more serious — 
and embarrassing than transverse fractures, not 
only on account of the immediate danger of 
the penetration of the skin by the upper frag- 
ment, and of the accident being thus rendered 
compound, but also on account of the great 
difficulty which is always experienced in main- 
taining the bones in apposition during the 
treatment of the case. 

Sir A. Cooper says the appearances presented 
by the usual oblique fracture of the lower ex- 
tremity of the femur are the following :—* The 


‘lower and broken extremity of the shaft of the 


femur projects, and forms a sharp point, which 

pierces the rectus muscle, just above the pa- 

tella, threatens to tear the skin, and sometimes 
F2 


68 


does so, whilst the patella, tibia, and condyles 
of the femur sink towards the ham, and are 
drawn upwards behind the broken extremity 
of the shaft of the os femoris, which is thrown 
forwards.” He adds that falls from a great 
height on the feet or knees have been the usual 
sources of this accident.* In most of the cases 
already met with, and described, of oblique 
fracture of the lower extremity of the shaft of 
the femur, the direction of the obliquity was 
from above downwards, and from behind for- 
wards, and the pointed extremity of the broken 
bone was consequently directed downwards and 
forwards ; but the pointed extremity has been 
seen towards the popliteal space. In Sir 
Charles Bell’s lectures on the thigh-bone which 
he has published, there is an engraving of a 
very remarkable case, which appears to us to 
have been an oblique facture of the femur near 
the knee-joint, in which the pointed extremity 
of the superior fragment presented towards the 
sae space.t About twenty years after the 

ne had been fractured, the patient, in jump- 
ing down from a chair, felt something snap, 
and very soon after a pulsating tumour formed, 
which was discovered to bea popliteal aneurism. 
The direction of the course of an oblique frac- 
ture may be various ; that downwards and out- 
wards is the least likely to be followed by 
dangerous consequences. 

3. Oblique fractures of the os femoris into the 
knee-joint, detaching laterally the condyles, are 
not very uncommon accidents; they may be 
known by the great and sudden swelling of the 
joint by which they are accompanied, by the 
great degree of lateral motion which can be 
communicated to the limb, by the crepitus 
which can be felt, and by the obvious deformity 
with which they are attended. 

It is sometimes the inner condyle, and some- 
times the outer, which is detached from the 
shaft; and in these cases the cavity of the 
synovial membrane of the knee-joint is always 
opened into by the fracture. The following 
case presents a good example of an oblique 
simple fracture, which detached the outer con- 
dyle of the femur from the shaft of this bone. 

Ganet Doyle, xt. 45, was admitted into the 
Richmond Hospital under the care of Dr. Hut- 
ton on the 27th March, 1839. He stated that 
about ten minutes before his admission he was 
Standing ona double ladder about four feet from 
the ground ; the ladder gave way under him 
suddenly, and he fell with it, the right limb 
having been engaged between two of the steps. 
During the fall he was sensible of being bruised 
below the knee by the steps, and of something 
“ cringing” in the lower part of the thigh; im- 
mediately after the fall he found the limb quite 

werless and was unable to put it under him, 

umefaction of the knee and lower part of the 
thigh took place instantly and to a great extent. 
On examination the outer condyle was found 
to move and grate against the inner through the 
centre of the joint; no breach of continuity 


* Sir A. Cooper on Dislocations, 8th edition, 
plate xv. 
t Fig. 3, plate iy. 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


edge obliquely by the callus which had un 


could be detected between the inner cond; 
and shaft of the bone. The femur, as the 
tient endeavoured to stand, was directed do 
wards and inwards, and the tibia downw 
and outwards, so that the junction of # 
two bones at the knee-joint formed an ok 
angle salient internally. There was consider 
enlargement of the femur in the situat 
the fractare for several inches above the k 
joint, and on measurement there was shortel 
of the injured limb for half an inch. By mak 
extension, and by pressing the condyles tow 
each other, the natural form of the limt 
restored. No fever nor constitutional di 
ance arose, and at the end of the fifth w 
passive motion was recommended. W 
man leh the hospital the external app 
of the joint was very nearly natural, 
that thé peaalla had been elevated! whittal 
the fracture. When this bone was moved aen 
the trochlea of the femur, a roughness was 
ceived to exist on the corresponding surfe 
and a sensation of something grating was ¢ 
veyed to the fingers of the examiner. 
was some shortening of the limb, which « 
still remained more inclined inwards towa 
the knee-joint than natural, and the movem 
of flexion was limited. . 
Sometimes an oblique fracture occ 
through the lower part of the femur into” 
joint, which detaches the inner condyle. 
prognosis in these cases of simple oblit 
fractures of the inner and of the outer o 
dyle of the femur, so far as life is concer 
does not appear, from what we have seen 
them, unfavourable ; but we Oe ae I 
examples of what may be a Ss 
fiaceacti of the lower enirebilag the femu 
that is to say, a transverse fracture of the lo 
extremity of this bone, combined with a y 
tical split from the transverse fracture do 
through the trochlea into the outercondyloid fos 
of the femur, in which the is is gener: 
unfavourable, even when the fracture is uneo 
bined with any wound in the integume 
Mr. Chelius, of Heidelberg, shewed — 
Smith and the writer, in August 1837, 
specimens of T fracture of the lower extrei 
of the femur. In the first case, the en 
nature of the accident was unknown to Mr. C 
lius. Violent inflammation set in in the ki 
joint and the whole limb, causing the death 
the patient. In the second case be ecogni 
the nature of the injury early, and amputa 
in the thigh saved the patient In such ca 
to decide at once whether amputation s| 
immediately resorted to or not, becomes a 
critical and often a very urgent question. 
the first opportunity be lost, the constituti 
symptoms attendant on the local inflammat 
set in so speedily, and ran to such a heii 
that a second seldom offers ; the two follow 
examples, however, should caution. us agai 
deciding hastily on immediate Mp 
cases of simple fracture, in which the cavity 
the knee-joint is implicated, because, altho 
in the first case the femur was broken in 
great number of fragments, the inflammé 


i 


at 


100 


followed was inconsiderable, and in the 
dan opporiunity for “secondary ampu- 

tion” was afforded even after acute inflam- 
ation of the joint had taken place. 
A healthy labourer, about 30 years of age, 
admitted into Jervis-street Hospital about 
ght years ago, under the care of the late Mr. 
llace, for a comminuted, but still a simple 
re of the lower extremity of the femur, 
ere it entered into the formation of the 
ee-joint. The accident was attended with 
rmous effusion, and there was a degree of 
dbility of the limb in the seat of the commi- 
fracture truly astonishing ; but little in- 
gation followed, and under the simplest 
ent the man ultimately recovered with a 
knee-joint. The second case was that of 
ged 13 years, who had received a simple 
ure of the lowest part of the shaft of the 
The condyles of this bone were de- 
id at their normal line of junction with the 
ft, and where they are covered with syno- 
| membrane ; the posterior and anterior cru- 
cial ligaments were separated from the femur, 
[had carried with them small portions of 
is bone. The result of the operation is not 
ded, but the specimen, preserved in our 
um at the Richmond School of Medicine, 
its, besides the injury the bones received, 
s of the very acute inflammation which 
wed, particularly on the surface of the sy- 
] membrane, which is covered with lymph. 
periosteum of the femur in the vicinity of 
fracture is much thickened and detached all 
nd from the femur. 
ong the valuable preparations presented 
Mr. Kirby to the College of Surgeons in 
lin is a specimen of one of these transverse 
res of the lower extremity of the femur, 
h was combined with a vertical split of 
bone down through the trochlea and outer 
yloid fossa. Although the fracture was a 
le one, it was followed by enormous effu- 
1, succeeded hy acute inflammation of the 
tructures of the joint; and Mr. Kirby in- 
ms me that amputation was successfully re- 
sorted to. The synovial membrane was much 
hickened, and evidences of acute inflammation 
if the structures of the knee-joint are still to be 
een in the preparation. 
Fractures of the tibia close to the knee-joint 
| may be transverse, or through the line of junc- 
tion of the epiphysis with the rest of the tibia 
€ young subject, or in the situation and 
ion of this line in the adult. In this case 
broad surfaces of the broken tibia nearly 
haintain their relations with each other. If 
there be any displacement, it will be that of 
the superior fragment, which will be drawn 
backwards towards the popliteal space, as the 
inner hamstring muscles will draw the bone in 
this direction. 
Oblique fractures of the upper extremity of 
the tibia which run into the knee-joint are 
‘accompanied with symptoms not very dissi- 
} milar from those belonging to oblique fractures 
of the internal condyle of the femur, except 
€ situation of the pain, and the crepitus which 
ean be elicited on motion being communicated 


eli ee elie el 


ey Te er ee le res 


a a 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


69 


to the broken portion of bone. There is the 
same sudden effusion into the knee-joint, and 
a very great degree of lateral motion is allowed, 
which is a movement the knee-joint does not 
normally possess. 

We learn from Blandin that Beclard had 
very frequently observed elderly females to be 
the subjects of fractures of the upper portion 
of the tibia, produced by the contraction of 
the flexor muscles of the leg, which muscles 
also he observed uniformly pulled the supe- 
rior fragment into the hollow of the ham. The 
explanation of the fracture occurring from such 
a cause must be referred to the atrophy which 
the head of the tibia undergoes in elderly 
people, in consequence of which the tibia he- 
comes thin in its shell, and the interior os- 
seous structure reduced to a thin reticular 
tissue, which in the dead subject we notice to 
yield to the slightest pressure of the fingers. 
We have known this,atrophy of the tibia to 
exist in adults as well ‘as in old subjects, and 
when present, it of course renders the bone 
liable to be broken by slight causes. More- 
over, we have usually found the species of 
reunion of the broken bone which can be 
effected under such circumstances to have been 
very imperfect; the patient after a long period 
endeavours to move about with the assistance 
of crutches; and effusion takes place into the 
knee-joint, the functions of which hecome 
greatly impaired for the rest of life. 

Fracture of the patella— This fracture oc- 
curs almost always in the transverse direction ; 
it is rarely oblique, and still more rarely longi- 
tudinal ; sometimes a fracture divides this bone 
into three or four pieces, or is what is called 
comminuted. The longitudinal fracture is rare, 
and this and the comminuted are generally the 
result of direct violence; and, although the 
transverse fracture may depend on a similar 
cause, still the violent contraction of the ex- 
tensor muscles of the leg is the most frequent 
source of this accident. When a fall occurs 
directly on the front of the knee, this joint 
being at the moment in a state of semiflexion, 
if a fracture take place it will no doubt be 
considered as the result of the fall directly on 
the bone, by which it is broken; certainly 
muscular action may lend its assistance to the 
external violence even in producing the frac- 
ture, and after this has occurred, to cause the 
separation of the fragments. 

This fracture cannot so readily be effected 
by muscular action when the limb is in a state 
of complete extension as when it is in a com- 
mencing state of flexion, because in complete 
extension the muscles act in the direction of the 
long axis of the bone; but in flexion at the 
knee to the first degree the patella is in a par- 
ticular condition, which is favourable to the 
production of fracture; it only applies itself 
to the condyles of the femur by its middle 
point. The base and summit of this bone are 
unsupported ; the extensor muscles of the leg 
.on one side, and the tendon or ligament of the 
patella on the other, are; in this position of 
the joint, oblique with relation to the long 
axis of the patella; the muscles then bend the 


70 


patella backwards, and it breaks Schelpe 
—according to Boyer and Malgaigne, “ a 
méme mecanisme que nous cassons un baton 
placé en travers le genou ; en agissant avec les 
deux mains sur ses deux extremités.” In 
transverse, oblique, and comminuted fractures of 
the patella there is almost always more or less 
separation of the fragments, and the signs of 
the accident are easily recognized. In some 
cases of fracture of the patella the fibrous and 
aponeurotic layer which immediately invests it 
anteriorly is broken ; in other cases, eed 
those from external violence, the fibrous layer 
remains entire; it is in these latter cases, as 
the fragments are preserved in complete appo- 
sition, that bony consolidation may be ex- 

ted. The following case, which it lately 

ll to our lot to attend in the Richmond Hos- 
pital, appears to possess some interest as a fact, 
tending to throw light on some of the disputed 
questions here adverted to relative to this ac- 
cident. 

A man, xt. 18, on the evening of 16th Fe- 
bruary, 1839, fell from the height of twenty 
feet to the ground, and fractured two of the 
cervical vertebre, of which injury and its con- 
sequences on the spinal marrow he died in 
forty hours. His lower limbs were paralyzed. 
It was noticed that the integuments over the 
patella were much bruised, and that there was 
some effusion into the cavity of the knee- 
joint. On the post-mortem investigation, the 
patella was found traversed by a perfect frac- 
ture of the bone; but the fragments were not 
separated from each other. On examining the 
patella anteriorly, its fibrous and aponeurotic 
coverings were in a perfect condition. Upon 
looking at the posterior articular surface of the 
patella, the cartilage was broken correspond- 
ing to the line of the transverse fracture of 
the patella, but only half-way across the trans- 
verse extent of the fracture was entirely through 
the bone. We regarded this accident to the 
patella to be the result of direct violence, com- 
plete paralysis of the lower limb having oc- 
curred as the immediate effect of the lesion of 
the spinal marrow; the usual source of dis- 
placement arising from muscular contraction 
was here destroyed. When we bear in mind 
the complete apposition existing in the frag- 
ments of this patella, we cannot for our parts 
question but that if life had been preserved, 
complete consolidation should have taken place. 
Although but few doubts are now entertained 
that the transverse fracture of the patella is in 
general a real rupture of the bone transversely, 
owing to the powerful action of muscles, it 
may not perhaps be amiss to adduce as an ex- 
ample of it, the following case of a patient 
who many years ago was under the care of the 
late Mr. Todd in the Richmond Hospital. A 
remarkably muscular man, a lamp-lighter in 
this city (Dublin), was on the top of his ladder 
when it slipped from the lamp-post, and he fell 
with it to the ground, making at the moment 
vain but violent efforts to save himself. The 
whole muscular system, according to his 
own account, seemed to be suddenly thrown 
into energetic and involuntary effort, to resist 


ABNORMAL CONDITIONS OF THE KNEE-JOINT, 


the fall; when he was lifted up, he was ung 
to stand. Mr. Todd, having examined I 
found both olecrana and both patelle 
transversely. We have often heard the 
named professor mention this case in his” 
tures, and the treatment of the 
also witnessed by Dr, Hutton. sa 
It was for a long time greatly doubted 
bony union of the broken pieces of the 
tella could occur, but it is now fully pr 
that the fractured patella does not want te 
any of the conditions necessary to the r 
and consolidation of broken bones. The sp 
structure of the patella and the 
of bloodvessels entering into its 
ought to favour the inflammatory turgese 
(Boyer) which seems necessary in = 
stage of ossification, and would do so but 
the continual contraction of the muscles fee 
resisted by the bandages s ed by surge 
keeps the fragments from each o 
and hence union has been so rare in th 
cases that the possibility of it under any 
cumstances was for a long time question 
Pibrae, one of the most distingui mem! 
of the ancient Academy of Surgery of Fra 
defied all the surgeons of to 
specimen of the fracture of the i 
solidly by bone, and no example was at | 
time produced. Among many cases pub 
since that time in various works, proving 
possibility of bony consolidation of the bro! 
patella, we adduce the following.* 
Louis Manilla, aged 36 years, of a 
vigorous constitution, being a veteran soldie 
the Salpetritre, on the 7th of April, 1797, 
thrown down by a comrade, with whom he’ 
struggling. One of his knees su i 
effect of this fall, and the patient suffered in 
part a sensation of crackling and 
and a pain which was extremely severe. 
could not rise without assistance, and M.1] 
lement recognised a transverse fracture of | 
patella. The interval between the two ff 
ments was very perceptible, but at 
of the two pieces was easily accomplished w 
the leg wasextended. The patient having 6 
brought to the infirmary, the fracture was 
duced by M. Lallement, and retained by mi 
of the apparatus of Desault. This bane 
was kept on for two months, at the end of wi 
time the fracture appeared to be united. 1 
ing one year the patient walked with the as 
ance of a cane and then returned to his 4 
The movements of the knee were nearly pe’ 
with the exception of flexion of the leg, w 
was still a little confined on the 18th Aug. 1f 
Manilla died of an attack of apoplexy, 
M. Lallement having examined the knee 
came satisfied that the two fragments of 
patella were solidly united. This bone b 
submitted to ebullition for ten hours was 
prived of the articular cartilage which covered 
posterior surface, and of the tendinous 
aponeurotic fibres which enveloped it. It) 
now evident that the total height of the p 


' 


. 
aCccid 


* See Boyer’s Surgery, vol. iii. p. 358. E 
Paris, 1818. ‘ . 


i ; 


t 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


which had been broken exceeded by about six 
times the same diameter of that of the opposite 
side. The fracture did not represent a straight 
nsverse line, but was somewhat undulated. 
it the two extremities of the line of junction of 
the fracture it was quite evident that the union 
of the broken bone was immediate, and by the 
tervention of a true bony callus. Lallement 
esented Boyer with the patella thus solidly 
ited, and he has given an engraving of it in 
his valuable work. 
Inthe collection of Dr. William Hunter, there 
sa well-marked instance of bony union of a 
transverse fracture of the patella, and other 
xamples have been seen in the dead subject 
by Mr. Wilson. In Sir Charles Bell’s museum 
were likewise similar specimens, one or two of 
which ae now in the Museum of University 
Vollege. 
_ Dislocations of the femur from the tibia at 
the knee-joint.—The articular surfaces of the 
_ head of the tibia for the reception of the femoral 
condyles are very superficial ; and although the 
Semilunar cartilages are superadded to them 
_ for the reception of the condyles of the femur, 
they have no direct tendency to resist luxations 
of the femur at the knee-joint. On the other 
_ hand it is to be recollected that the surfaces by 
hich the tibia and femur are articulated 
together are broad, and that the number and 
Strength of the ligaments which unite these 
_ bones is considerable. The solidity of the arti- 
i ulation is further augmented by numerous and 
‘powerful tendons which surround the joint. 
_ Although therefore the knee-joint from its situa- 
_tion and functions must be subjected to nume- 
Tous injuries, dislocations are very seldom wit- 
_ nessed as the result of accident. Dislocations, 
however, occur in four different directions ; two 
of them are incomplete and lateral while the 
‘others are perfect luxations, the femur being 
thrown either backwards or forwards. The 
Tateral luxations are the rarest. 
__._ The lower extremity of the femur is now and 
_ then dislocated backwards: the signs of the 
accident are the following. The thigh-bone is 
_ somewhat displaced to the side as well as back- 
_ wards, and the tibia is advanced before the 
_ condyles of the femur. The lower dislocated 
| extremity of the os femoris makes such pressure 
on the pean artery as to prevent the pulsa- 
tion of the anterior tibial artery on the foot. 
The patella and tibia are drawn by the rectus 
_ muscle forwards; such, Sir A. Cooper tells us, 
_ are the appearances the knee-joint presented in 
_ aman brought into St. George’s Hospital in the 
_ year 1802. The limb in this case was easily 
_ reduced by extending the thigh from above the 
__ knee, and by drawing the leg from the thigh and 
inclining the tibia a little backwards. As soon 
_ as it was reduced, the popliteal artery ceased to 
__ be compressed, and the pulsation in the anterior 
_ tibial artery was restored. We will quote the 
| following abstract. of a case of dislocation of the 
: 4 lower extremity of the femur backwards ;+ the 
‘ 


y 


* Prof. Cooper. 
+ London Medical Gazette, May 14, 1836, given 
| by Mr. Thomas Brittan, House Surgeon, Chester 
| Infirmary. 


: 
W 
: 


71 
subject of the accident, besides other injuries, 
was brought into the Chester Infirmary with a 
very complete dislocation of the lower extremity 
of the femur backwards. The whole limb was 
shortened four or five inches, and the condyles 
of the femur could be felt plainly among the 
muscles of the calf of the leg, while the tibia 
was in advance of the femur and drawn up- 
wards on the anterior part of this bone. The 
leg and foot were swollen and cold; all cireu- 
lation below the knee was stopped; there were 
no marks of external contusion. It appears 
that although the pulleys were used to reduce 
the luxation, it was easily effected by gradual 
extension of the limb. It became necessary 
after about five weeks had passed from the time 
of the accident, to amputate the limb in conse- 
quence of an extensive abscess which formed in 
the ham and calf of the leg. Upon examining 
the amputated limb, jit was found that the pop- 
liteal abscess was wy extensive and commu- 
nicated with the knee-joint. On tracing the 
course of the artery, which had been previously 
injected, it was found to be obliterated from 
just below the point where it gives off the 
superior articular artery, exactly to its bifurcation 
into the anterior and posterior tibial arteries. 
The nerve also for this distance was slightly 
enlarged and firmer than natural, having a cord- 
like feel; the whole being so closely connected 
by dense cellular tissue as to be scarcely sepa- 
rable. The attachments of the muscles were all 
perfect and did not appear to have been lace- 
rated. With respect to the joint the lateral 
ligaments on both sides were perfect; the ante- 
rior crucial ligament had been absorbed, but 
the posterior crucial ligament and the posterior 
ligament of Winslow were united into one 
band ; the synovial membrane was healthy or 
but very little altered; the semilunar cartilages, 
as well as those on the ends of the bones, were 
sound; there was no fluid in the joint. 

Case of dislocation of the femur backwards 
from the tibia—Sir A. Cooper remarks that 
cases of dislocation of the knee-joint are so 
rare that every instance of this accident is 
worthy of recita!. He adduces the following 
example from the experience of Mr. Too- 
good, of Bridgewater. Francis Newton, a 
strong athletic man thirty years old, fell from 
the fore part of a waggon, and was dragged a 
great distance betore he was disentangled from 
the framework of the shafts. In two hours 
after the accident the left knee was observed to 
be very much swollen; the os femoris was dis- 
located backwards, and its lower extremity 
occupied the upper part of the calf of the leg, 
the internal condyle of the femur being nearly 
through the skin; the tibia, fibula; and patella 
were driven up in front of the thigh. The 
appearances of the limb were so dreadful that 
Mr. Toogood despaired at first sight of being 
able to reduce it, but to his surprise the reduc- 
tion was easy. The limb was placed in splints; 
the strictest antiphlogistic treatment with rest 
was prescribed ; the symptoms were mild, and 
he suffered little from pain or inflammation. 

Malgaigne, in a letter to Velpeau in the Ar- 
chives Medicales, June 1837, upon the subject 


72 


of dislocation of the knee, to which we refer 
for many observations we have not space for, 
gives a case of luxation of the femur backwards 
and of the tibia forward, which in some re- 
spects differed from those adverted to by Sir 
A. Coo He informs us that M. Lavalette 
was called. on the 6th of April, 1815, to visit a 
man who had just before met with the accident 
we are now describing under the denomination 
of dislocation of the femur backwards and of 
the tibia forwards at the knee-jomt. The limb 
was in a state of extension, somewhat inverted, 
and much shortened; it could, however, be 
flexed and extended, although with much pain. 
The extensor muscles of the leg were in a 
relaxed condition, as were also the hamstring 
muscles from the shortening of the whole limb, 
A depression existed where the condyles of the 
femur ought to present themselves anteriorly, 
and below this space the superior extremity of 
the condyles of the tibia could be felt. e 
patella was placed horizontally on the upper 
articular surface of these condyles; its point, 
which is normally placed downwards, was now 
directed forwards, and its superior margin back- 
wards; its anterior or cutaneous surface was 
placed directly upwards, and its articular facet 
downwards, resting, as already mentioned, on 
the flat surface of the upper extremity of the 
condyles of the tibia. Tactic here knew 
that he had to deal with a complete luxation, 
which we have called a luxation of the femur 
backwards and of the tibia forwards; and he 
was finally convinced of the real nature of the 
case by placing his hand in the popliteal re- 
gion, where he distinctly felt the two condyles 
of the femur. 

Luxation of the lower extremity of the 
Jemur jorward.—The lower extremity of the 
femur is sometimes thrown forwards off the 
condyles of the tibia, while the latter bone is 
thrown backwards behind the condyles of the 
femur, producing the following appearances: 
the limb is shortened, the condyles of the os 
femoris are seen projecting, the ligament of the 
patella is depressed, and the leg is bent for- 
wards. Sir A. Cooper gives a case in which 
the condyles of the femur were completely dis- 
located forwards, and the head of the tibia 
passed so far backwards behind the condyles 
as to fill up completely the popliteal space. 
The tendinous connexion of the patella to the 
rectus muscle was ruptured ; the external con- 
dyle of the os femoris was very protuberant; 
the leg was bent forward and shortened, and a 
depression existed just above the patella. The 
patient felt most excruciating pain when the 
limb was moved, but when at rest theré was 
not any considerable suffering; the luxation 
was reduced, and in five months recovery was 
complete. 

Lateral luxation of the femur at the knee- 
joint.—Although from the structure of the parts 
it might at first be supposed that complete la- 
teral luxation should be less resisted than the 
luxation of the femur either forwards or back- 
wards, still there is no case on record with 
which we are acquainted of complete lateral 
luxation of the femur from the tibia as the 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


result of accident. We commonly see 
one of the condyles of the femur abandon 
tibia, while the-other remains in the ca 
first had left. The luxation is then wh 
called incomplete. The reduction of this It 
ation is easy in consequence of the rupt 
the ligaments.* 
Dislocation outwards of the femur ai 
knee-joint.—In the dislocation ou 
femur at the knee-joint, this bone is thr 
off the external condyle of the tibia, 
latter bone projects on the inner side of 
joint so as at once to disclose the nature 0 
injury. Sir A. Cooper once saw a case of 
kind at St. Thomas's Hospital, and 
was struck with three circumstances. The f 
was the great deformity of the knee from 
projection of the tibia inwards; the seco 
the ease with which the bone was reduce 
gradual extension ; and the third, the * 
tlammation which followed upon what 4 
So serious an injury. The man was di peas 
after a few weeks, having suffered little loca 
constitutional irritation. 
Example of dislocation of the mur 
wards.—Mr. Bovill was thrown from a 
the femur projected much externally ee tl 
knee, and the tibia much (below the situati 
of the inner condyle of the femur) to the i 
side of the condyle of the os femoris. © 
limb was extended from the thigh-bone, 
bent position ; the extension was a long ti 
continued, and force was employed by: 
persons for half an hour re the 
was reduced. Sir A. Cooper saw him ei 
months after the accident; the 
not then bend the limb at right angles witht 
thigh ; there was also an unnatural lateral m 
tion of the joint from the injury which 
ligaments had sustained. ola 
Incomplete dislocation of the femur i 
at the knee-joint—The femur is sometim 
thrown on the inner side of the knee-joint, ¢ 
condyles of the tibia being carried outwar 
The under surface of the inner condyle o 
femur may be felt through the skin, while 
outer condyle of this bone rests on the ¢ 
cavity hollowed on the u per casa 
inner condyle of the tibia, or rather b 
A deformity is produced analogous to t 
the external dislocation, and may be: pal D 
ceived. From the little experience had of su u 
cases, the reduction of the limb is stated to 
equally easy with the former, and the 
recovers with little diminution of the p owe 
the part. Sir A. Cooper states as his opini 
that in these cases the condyle of the os. femc 
with respect to the tibia is thrown somew 
backwards as well as outwards or ae 
alderman fell from his horse and partial! 
located the condyle of the os fomectaie ar 
and the tibia outwards; the femur wend - 
replaced. He was perfectly recovered am \ 
months. a 
To whichever side the tibia is lu 
always pulls with it the patella, which » 
* Blandin says : “ Je 1 ‘ai eprouvé m ! a 
fois 4 ’Hépital de la Charité,” Trae 
Topog. Paris, 1826, p. 617. 


also a displacement more or less considerable 
ecording to the degree of displacement of the 
tibia. In these incomplete dislocations of the 
nee-joint, the patella, it is said, suffers but 
ittle displacement, its long axis only becoming 
blique, and the lower point of the patella being 
directed either outwards or inwards, towards 
he tubercle of the tibia, according to the nature 
nd direction of the dislocation. These are 
he opinions of Boyer, who evidently has not 
fitnessed many cases of either complete or 
acomplete dislocations of the knee-joint. From 
hat we ourselves have noticed of the situation 
he patella takes when the bones are displaced 
nder the influence of disease, we should be 
ed to believe that even in partial luxa- 
on of these bones laterally—particularly in 
ie dislocation of the femur inwards and of the 
bia outwards—in this case the patella would 
s thrown completely over the trochlea and lie 
m the outer side of the external condyle, as in 
e.6and 8. If the limb be flexed and at the 
ame time the tibia everted, such an event 
s almost inevitable. 
locations of the patella—Although the 
atella is not articulated with the tibia, never- 
heless it is so strongly attached to this bone 
by ligament that the leg cannot be luxated 
“from the femur without the patella necessarily 
_ undergoing a change of place ; but the patella 
“may be luxated independently of the tibia. 
juthors speak of luxations of the patella in 
the directions upwards, downwards, inwards, 
and outwards ; but of these the two last alone 
deserve the name of luxations. The patella 
“annot descend beneath its usual place unless 
the extensor muscles of the leg be torn from 
cir attachment to its upper margin ; nor can 
is bone be elevated above its usual situation 
unless the ligamentum patella be ruptured. 
-Luxations of the patella then may take place 
‘im the direction inwards or outwards. The 
‘Tatter is decidedly the more common. Either 
_ luxation may be complete or incomplete. 
(Boyer. 
Da lCoapicte luxation of the patella outwards.— 
In this accident the patella is thrown com- 
Bletely off the articular trochlea of the femur. 
The internal edge of the bone is directed for- 
wards, its external edge backwards; its pos- 
terior cartilaginous surface is applied to the 
Outer surface of the external condyle of the 
0s femoris, and its anterior or subcutaneous 
gi is turned completely outwards. In 
is case the ligamentum patelle is somewhat 
twisted on itself, and its direction rendered 
oblique. ’ 
We recognize the complete luxation out- 
wards by the extended condition of the pa- 
tient’s limb, by his inability to flex it, by the 
| Severity of the pain when he attempts to do so, 
_ and by the depression which is observed to 
 €xist in the place the patella had abandoned, 
_ (at the bottom of which depression we can 
easily distinguish the articular pulley of the 
femur); finally, by the tumour formed by the 
_ Patella on the anterior part of the tuberosity of 
the external condyle of this bone. The acci- 
_ dent usually occurs to a person who, while 
‘¢ 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


73 


walking or running, falls with the knee turned 
inwards and foot outwards, and thus by the 
violent action of the extensor muscles instinc- 
tively exerted to prevent the fall the patella is 
drawn over the external condyle of the os fe- 
moris. When the person rises he finds him- 
self unable to bend or extend his leg, and the 
muscles and ligaments of the patella are on 
the stretch. This accident is generally the 
effect of muscular action, but the dislocation 
may result from accidental force acting on the 
patella. 

In the greatest possible flexion of the leg the 
patella is too much sunk between the condyles 
of the femur, and is too strongly applied 
against these eminences by its ligament and by 
the tendon of the extensor muscles, to permit 
it to yield to the action of external force. But, 
on the contrary, when the leg is moderately 
extended, these attychments are relaxed; the 
bone projects more, and enjoys greater mo- 
bility, which renders it susceptible of yielding 
and of being displaced either outwards or in- 
wards according to the direction of the impelling 
force. The luxation outwards, more easy and 
more frequent than that inwards, is ordinarily, as 
we have stated, the effect of a force acting upon 
the internal edge of the patella, by which this 
bone is pushed outwards, the leg being at the 
time either extended or moderately flexed. 
The natural prominence of the internal border 
of the patella renders it liable to be acted upon 
by blows, &c., and to be from this cause fre- 
quently thrown outwards over the external con- 
dyle of the femur. 

The patella is sometimes dislocated spon- 
taneously in persons of weak habit and of lax 
fibre, as it is denominated. If a person of this 
constitution be so malformed that the knees 
are directed too much inwards, the patella are 
from this cause still more predisposed to spon- 
taneous luxation. The mere circumstance of 
the existence of a faulty inclination of the 
knees inwards is not sufficient in itself to pre- 
dispose a patient strongly to a dislocation of the 
patella outwards; but when such a malforma- 
tion coincides with an habitual state of mus- 
cular relaxation, this spontaneous luxation is 
likely to occur. 

Luxation of the patella inwards.—This lux- 
ation is much less frequent than that outwards. 
It happens from falls against a projecting body, 
by which the patella is struck upon its outer 
side, the leg being at the time of the fall turned 
inwards. We require no other signs to enable 
us to recognize this accident than the cavity we 
notice in the place the bone has left, and the 
eminence it forms in the place to which it has 
been transferred, namely, on the internal side 
of the inner condyle of the femur. 

Incomplete luxation of the patella— The 
signs of this incomplete luxation are so evi- 
dent* that it is impossible to mistake them. 
The leg is extended, and if we endeavour to 
flex it, the pain the patient suffers is conside- 
rably increased. The natural form of the knee 
is altered; we perceive through the skin the 


* Boyer. 


74 


salient internal border of the articular pulle 
of the femur, which the patella has aban fee 
This last bone forms in front of the external 
border of the pulley a very remarkable tumour, 
upon which the finger may easily distinguish 
the external border of the patella. We can 
also easily recognize through the skin and the 

ular ligament the posterior articular surface 
of the patella, which has passed beyond the 
edge of the trochlea of the femur. 

“ In the course of a long practice,” says 
Boyer, “ I have met with but one case of dis- 
location of the patella,” (and this, it appears, 
was an incomplete luxation.) ‘“ A young man, 
wt. 16 to 18, very tall, fell, running along a 
corridor. The internal part of the knee in 
passing struck violently against the corner of a 
trunk, which produced an incomplete luxation 
of the patella outwards. The surgeon in ordi- 
nary of the family was called; but whether it 
was that he did not recognize the luxation or 
that he did not consider he could reduce it, 
he did not wish to undertake it without having 
the assistance of Sabatier. This celebrated 
professor was at first uncertain as to the species 
of dislocation which the patella had suffered ; 
but having carefully examined it and reflected 
on the phenomena the accident presented, he 
recognized the true nature of the case. He 
then attempted the reduction of the luxation, 
but failed in replacing the bone.” 

When Boyer arrived, he states that the pa- 
tient was lying on his bed, the limb being ex- 
tended and raised by pillows. The ordinary form 
of the knee was altered; the patella formed a 
tumour, which was sensible on the front of the 
external border of the articular pulley of the 
femur; in front of the internal border of the 
same pulley there was a depression, in the bot- 
tom of which could be perceived with the 
finger the same border of this pulley. The 
direction of the patella was changed in such a 
manner that its anterior surface was inclined 
inwards, and its external border forwards; 
finally, the external articular facet of the pa- 
tella could be felt by the touch through the in- 
teguments which covered it. By these signs it 
was easy to recognize the incomplete luxation 
outwards. 

Luxation of the patella on its edge—Some 
very eminent surgeons have doubted the possi- 
bility of such an occurrence as a dislocation of 
the patella on its edge. ‘ Some,” says Boyer, 
“have imagined that the patella could be 
luxated turning half round on its vertical or long 
axis so as to rest on one of its edges on the 
articular trochlea of the femur. e cannot 
conceive,” he proceeds, “ how the tendon of the 
extensor muscles of the leg and the ligament of 
the patella could lend themselves to such a 
rotation of the bone on its long axis; much less 
can we understand how these parts can admit 
of a total reversion of the bone, as authors pre- 
tend to have observed.” Notwithstanding these 
observations, it seems fully proved, that the 

tella can really be dislocated on its edge, and 
if we once admit the possibility of the partial 
rotation of the bone on its long axis, so as to 
constitute what is called a dislocation of the 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


patella on its edge, we can imagine that a more _ 
complete rotation of the eS ee ya 
might , constituting the com reve 
sion of peso ht of the surfaces and dges 
this bone spoken of by some writers. 
It does not appear that Sir A. Cooper hi 
seen the dislocation of the patella on its” 
but he states that he was informed by | 
Willing, formerly of Hastings, that he» 
called to a case in which the patella was dis 
cated on its edge. The nature of the acei 
was very obvious, as the edge of the bone for 
up the integuments to a considerable hei 
between the condyles on the fore part of 
joint. Mr. Willing reduced the dislocat 
but with considerable difficulty, by pressing: 
edges of the bone in opposite directions. 
The following case of dislocation of the patel 
on one of its edges occurred lately in the pra 
tice of Mr. Pentland, surgeon to the Droghet 
Infirmary, and is very interesting and important 
coming as it does from an acute and expel 
enced observer. J. M‘Greene, et, 25, of mide 
stature, was struggling to get down a stron 
man in play. He succeeded so far as to ge 
him on his knees, when the fallen man too 
hold of both his legs with his arms ele 
embraced round them, and when M‘Green 
struggling to disengage himself, he heard am 
felt his right knee give a loud snap. This 
attended with the most excruciating pain, an 
he fell to the ground to the left side; he felt tha 
he had lost all power over the right leg. 
was carried to bed, and Mr. Pentland saw 
in a few minutes after the accident. The 
was in a flexed state, presenting a most extrac 
dinary appearance, but which was readily seet 
to proceed from the patella having been dislo 
cated on its edge. Mr. Pentland stated tha 
he had some difficulty in ascertaining whi 
side was turned out, but he soon cone! 
that it was the under or articular surface. 
man could not move the limb atall, “and ne 
says Mr. Pentland, “ did I witness more dread- 
ful suffering. You would suppose,” he adds 
“ that the patella would force out through th 
integuments.” After repeated attempts he 
length succeeded in getting it into its place 
the reduction was attended with a loud noist 
and during the operation the man seemed 16 
suffer frightful torture. Immediately on th 
reduction, all pain ceased, and in a yr 
time he recovered the perfect use of the limb. 
A case of dislocation of the it 
edge is recorded by Dr. Watson in the Ney 
York Journal of Medicine and ger} 
October, 1839. He calls the accident a disle 
cation of the patella on its axis, and says, “ i 
poy I have bapa: bs Bory. b 
slightly flexed ; no of the pu xcep 
its devnek border eed petro of the fem 
could be felt. The patella was drawn upwards 
and twisted nearly at right angles with its proper 
position, so that its anterior face was directet 
mwards, and its outer edge was thrown Cot 
pletely forwards, forming an uneven and very 
rominent line beneath the skin in front of t 
joint. The reduction of the bone to its norm 
position was not effected without difficulty.” 


Surger 


Internal derangement of the knee——* The 
___ knee-joint,” says Mr. Hey, “is not unfrequently 
affected with an internal derangement of its 
“component parts, and this sometimes in conse~ 
quence of trifling accidents. The defect is, 
_ indeed, now and then removed as suddenly as 
it is produced, by the natural motions of the 
_ joint without surgical assistance; but it may 
remain for weeks or months, and will then be- 
_ come a serious misfortune, as a considerable 
degree of lameness may remain. This disorder 
‘may happen either with or without contusion. 
_ In the latter case the accident is easily distin- 
_ guished from all others. The joint, with respect 
_ to external form, seems perfect; if there be any 
_ difference from its natural appearance, it is, that 
_ the ligament of the patella appears rather more 
telaxed than in the sound limb. The leg is 
readily bent and extended by the hands of the 
surgeon, and without pain to the patient; at 
_ most the degree of uneasiness caused by this 
_ flexion and extension is trifling ; but the patient 
himself cannot freely bend, or perfectly extend 
_ the limb in walking; he is compelled to walk 
_ with an invariable and small degree of flexion. 
_ Though the patient is obliged to keep the leg 
_ thus stiff in walking, yet in sitting down the 
__ affected joint will move like the other.” 
_ Thecomplaint, Mr. Hey apprehends, may be 
__ brought on by any such alteration in the state 
_ of the joint as will prevent the condyles of the 
0s femoris front moving truly in the hollow 
_ formed by the semilunar cartilages and articular 
_ depressions of the tibia. According to him, an 
8g tension of the lateral or cross ligaments 
of joint, or some slight derangement of 
the semilunar cartilages, may probably be suffi- 
cient to predispose any one to this accident. 
Sir A Cooper, in alluding to the internal de- 
rangement of the knee-joint described by Hey, 
calls the accident a “ partial luxation of the 
thigh-bone from the semilunar cartilages ;” but 
it does not appear to us that he had any oppor- 
tunity of ascertaining the anatomy of such an 
accident. Sir A. Cooper has observed it to 
occur most frequently, when a person in walking 
strikes his toe, the foot being at the time everted, 
against any projecting body, as the fold of a 
carpet, after which the patient feels pain in the 
knee, which cannot be extended. He has also 
seen this accident happen from a person having 
suddenly turned in iis bed, when, the clothes 
not suffering the foot to turn with the body, the 
_ thigh-bone has slipped from its semilunar carti- 
He also states that he has known it occur 
from a sudden twist of the knee inwards when 
the foot was turned out. He says, “ under ex- 
treme degrees of relaxation, or in cases in which 
there has been increased secretion into the joint, 
the ligaments become so much lengthened as to 
allow the cartilages to glide upon the surface of 
the tibia, and particularly when pressure is 
_ made by the thigh-bone on the edge of the car- 
 tilage. The cartilages which receive the con- 
: dyles of the os femoris are united to the tibia 
__ by ligaments; and when these ligaments become 
extremely relaxed and elongated, the cartilages 
are easily pushed from their situations by the 
| condyles of the os femoris, which are then 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


75 


brought into contact with the head of the tibia; 
and when the limb is attempted to be extended, 
the edges of the semilunar cartilages prevent 
it.” It may be inferred from his observations 
that the accident may occur either at the internal 
condyle, which is the more common, or at the 
external, and that the position of the foot at the 
time of the occurrence of the accident has much 
influence in determining which of the semilunar 
cartilages is to be displaced. Thus, if the toe 
be everted, the displacement of the internal 
cartilage will occur; on the contrary, if the foot 
be fixed and inverted at the moment of the 
accident, the subluxation of the external con- 
dyle of the femur from the external semilunar 
cartilage will be the accident. Sir A. Cooper 
adduces the following case. Mr. Henry Dob- 
ley, et. 37, has often dislocated his knee, turning 
the foot inwards, and the thigh-bone outwards, 
by accidentally slipping on uneven ground, or 
by sudden ae of the limb. Considerable 
pain was immediately produced, accompanied 
with a great deal of swelling. His mode of 
reducing it is as follows. He sits upon the 
ground, and then bending the thigh inwards, 
and pulling the foot outwards, the subluxation 
of the os femoris being external, the natural 
position of the limb becomes restored. 

Mr. L. a well-formed gentleman, et. 29, 
has consulted me twice or thrice these last 
two years concerning this internal derangement 
of the knee-joint so well described by Hey. 
Mr. L. complains that, whenever he un- 
guardedly flexes the knee suddenly, the toe at 
the time being much inverted, he is instanta- 
neously seized with very disagreeable sensa- 
tions in the knee-joint, not amounting to pain. 
There is a sudden sense of weakness across 
the front of the joint, the limb is semiflexed, 
and a great feeling of tightness and stiffness 
exists behind, along the course and about the 
insertion of the biceps tendon. All these 
symptoms come on suddenly from some awk- 
ward movement or false step, such as, in walk- 
ing, putting his foot into some unexpected 
hole, but so very suddenly does the internal 
derangement occur, that, if walking at the mo- 
ment, he generally falls to the ground. After 
a little time, though lame, he is able to walk, 
and to place the heel to the ground, and though 
he usually keeps the limb slightly flexed, he 
can at will extend it. These accidents are 
usually followed by some effusion of synovial 
fluid into the joint. I have practised with 
success the extension and sudden flexion of the 
limb advised by Hey, and my patient has him- 
self occasionally, and with success, directed 
this maneeuvre to be practised on him by his 
servant, or by any one who happened to be at 
hand when the accident occurred. He attri- 
butes the first cause of this liability to the 
sudden derangement of the articulation to a 
violent sprain of the knee-joint he got while 
ringing a young and powerful horse; the latter 
pulled away from him with such violence, that 
Mr. L. fell to the ground, and during the 
fall he felt as if something at the internal 
side of the knee-joint had been broken: the 
thigh and tibia were bent in such a manner as 


76 


to form an obstuse angle internally, and it is 
not improbable, that by the sprain the internal 
lateral ligament or other structures in the in- 
terior of the joint were injured. The sprain 
was followed by swelling, &c., and it was six 
weeks before he recovered so as to be able 
to walk. Mr. L. remained well for eight 
months, when, in crossing over a ditch, the 
sudden derangement recurred. The moment 
the displacement of some part of the interior 
of the joint occurred, he dropped suddenly to 
the ground. Another day, while practising 
some gymnastic exercise, it occurred. Again, 
it happened while in bed, the bed-clothes em- 
barrassing the motion of the foot while he was 
turning his body round. On the last oceasion 
on which the displacement happened, he was 
on horseback ; he had just mounted, and was, 
while his knee was flexed, seeking with the in- 
verted foot for the off-stirrup, when the dis- 
a area happened. On all these occasions 
e has without loss of time sought to replace 
the deranged parts, and sometimes has suc- 
ceeded instantaneously, and sometimes weeks 
have passed without the adjustment of the 
arts in the interior of the joint occurring. 
he restoration of the use of the joint has al- 
ways been as sudden as the derangement, and 
the replacement has invariably been accom- 
panied by a sudden snap, as if something at 
that moment changed its place, and this to him 
was always the signal of recovery of the uses 
of the joint. When the extension and flexion 
of the limb in the manner recommended by 
Hey has been the means of restoration, he has 
on some occasions not only felt the sudden 
movement of what he considers the dislocated 
ae in the interior of the joint, but he thinks 
e could distinctly hear the crack the part 
gave in resuming its ordinary place. The writer 
of this has lately seen a examined Mr. 
L.’s knee-joint, and compared it with the 
opposite one, and cannot perceive the slightest 
difference on a simple inspection of both arti- 
culations either before or behind. The patella 
and the ligament which connects it to the tibia 
are just as firmly applied in front of the joint 
as usual, and there is now no effusion into the 
joint of any unnatural quantity of synovial 
fluid. He habitually wears a laced knee-cap, 
and finds only a difficulty in flexing as fully 
the affected knee-joint as the other, and he has 
an habitual fear of any movement of the leg in 
which this is at the same time flexed, and the 
foot inverted. This is a well-marked example 
of the internal derangement of the knee de- 
scribed by Hey; but what are the true ana- 
tomical characters of the accident, or what 
really is the structure, whether normal or ab- 
normal, which slips in and out with a noise? 
Nothing positive, in our opinion, has been added 
to the knowledge of the nature of the accident 
given to us by Hey, who has the merit not only 
of first describing the injury, but of also 
pointing out a simple and generally successful 
remedy. 
Many surgeons have considered that the in- 
ternal derangement of the knee described hy 
Hey, and considered by Sir A. Cooper as a 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


“ partial luxation of the femur from the semi- 
lunar cartilages,” is a dislocation of these fibr 
cartilages. Malgaigne justly criticises the vaga 
ness of the lan used by authors relative t 
this matter. M. Velpeau, according to Ma 
gaigne, in one place treats of this luxation as 
luxation of the semilunar fibro-cartilages, and | 
another work he seems so uncertain of the mi 
ture of the accident as to demand wheth 
the phenomena may not be owing to th 
istence, in the interior of the joint, of some ¢ 
those cartilages which we call foreign bodie 
Malgaigne himself seems to fall into the op 
nion of Sir A. Cooper upon this subject, a 
though he does not use the pei in 
considers the accident to be a simple par 
tial luxation of the femur from the tibia, the 
consequence of the relaxation of all the liga 
ments, but adduces no anatomical evidence ol 
the truth of his hypothesis. He iders the 
accident, “ Une simple luxation incomplete d 
femur sur le tibia, produite par un relachement 
de tous les ligamens, et tout-d-fait analog 
aux deplacemens occasionés par la méme 
dans les autres articulations.” Sir A. 
is of opinion that Mr. Hey’s plan is gene’ 
but not invariably successful, and adduces the 
case of a lieutenant in the army who sufferer 
this accident repeatedly, and the limb was 
often reduced by the above-mentioned means 
but at length, turning in bed, from the pre 
sure of the bed-clothes on his foot, the acciden! 
recurred. He came to London, but bendin 
the limb had now no effect in enabling him t 
extend the joint. Sir A. Cooper, therefore, ac 
vised him to visit Mr. Hey, but he learnec 
that in this case the dislocation was never | 
duced. In an obstinate case of this internal 
derangement of the knee-joint, which resistes 
all the ordinary means of surgical treatmen 
the writer succeeded (in Jervis-street Hospit 
by using the pulleys. Under exactly simi 
te cveutiiatshbels is lamented friend, Dr. 
M‘Dowel, subsequently succeeded by having 
recourse to the pulleys when all other me 
had failed. 
The knee-joint is seldom affected by sprains 
When, however, there is an undue inclinatior 
of the knee inwards, the internal lateral liga 
ment is occasionally, by an accidental fals 
step or twist, sprained, and sudden lamenes 
comes on followed by swelling, and more ot 
less inflammation of the synovial membrane 
the articulation. It has not been ascertain 
whether in such cases the fibres of the inter 
lateral ligament have given way, or whethe 
they are detached from the bone or not; but 
is not improbable that some such lesion hi 
occurred as that we have already noticed unde 
the head of Sprains in another articulatio 
(see ANKLE.) When sprains of the knee tak 
lace, it is almost invariably the inner side of the 
Joint to which the patient refers as the prin 
i seat of tenderness and pain. The join 
admitting of motion unaccompanied by any 
ps meses (although the act may be painfull 
ily distinguishes a sprain from any frat 
ture of the bones of the articulation. It 
not improbable that in sprains of the 


(v4 
le 


yt: 


+x. 
athe) 


+ 


joint, the interior of the articulation is occa- 
‘sionally injured ; that the crucial ligaments are 
stretched ; and that some of their fibres give 
way occasionally, breaking in their centres, or 
detached by their extremities from the bone. 
We lately had an example of a severe injury 
‘of the knee-joint, in which the anterior crucial 
ligament must have suffered great violence. 
‘The fibres of this structure did not give way, 
bat the portion of the tibia to which they were 
urally connected was torn up with the cru- 
ligament. We are not aware that such an 
cident as this has been before noticed, al- 
though it is probable that all complete luxa- 
jons of the knee-joint must be preceded by- 
such a lesion. 

_ A young man, aged 25, was admitted into 
‘the Richmond Hospital under the care of Dr. 
tton, on the 11th of December, 1837, with 
njury of the left knee-joint, which occurred 
hen wrestling. Being intoxicated at the time 
is account of the manner in which the acci- 
t occurred could not be depended upon. 
joint was much swollen, very tense, and 
inful; no fracture, and no other deformity 

that occasioned by the general swelling of 
the joint could be detected. The limb was 
jaintained in the semiflexed position and on 
ie outside. Inflammation and symptomatic 
r ran very high, and the pain was excessive, 
ecially on the least motion of the joint. 
in the eleventh day the pain and swelling had 
diminished. He could then raise the limb 
fiom the bed, but could not increase the 
‘amount of flexion. On the seventeenth day 
symptoms of diffuse inflammation set in; these 
_Tapidly increased, and on the twenty-fourth 

‘day from the receipt of the injury he died. 
The knee-joint was found to contain eight 
ounces of purulent matter, in which flakes of 
lymph floated ; the synovial membrane was 
soft, pulpy, and vascular ; the circumference of 
the cartilages covering the condyles of the femur 
was in a slight degree absorbed. On flexing 
the joint, the spine and central portion of the 
head of the tibia, with a considerable portion 

_ of its left articulating surface, were found torn 
| up from the rest of the bone in one piece, 
(fig. 10,) and remained attached to the ante- 
nor crucial ligament. 
Rupture of the quadriceps extensor tendon 
_ from its attachment to the superior border of 
the patella—The muscles and tendons around 
the knee-joint are very seldom the subject of 
accident. We have never heard of any acci- 
dental rupture of the tendons of the hamstring 
muscles ; we have, however, known some in- 
stances of rupture from the upper edge of the 
patella of the muscular and tendinous structure 
attached to the superior edge of this bone, con- 
sisting of the combined muscular and tendinous 
attachments, of the rectus, crureus, and vasti 
muscles. A person who has met with this 
_ accident cannot rise from the ground, nor can 
} he stand when raised without being sustained 
by two persons; when he attempts to lean his 
weight on the affected limb, it yields and 
_ bends forwards. On examining the knee we 
_ observe between the superior border of the 


roe eee a 


ABNORMAL CONDITIONS OF THE KNEE-JOINT. 


77 
Fig. 10. 


patella and broken tendon a separation of one 
inch, which is diminished when we extend the 
leg, and increased much when we flex it. If 
we introduce our fingers into the bottom of 
this depression, we feel plainly the trochlea of 
the femur. In this case, as may be expected 
in all analogous accidents, there is much effu- 
sion of synovial fluid, which distends the inte- 
rior of the joint; and it is probable that the 
synovial membrane does not escape laceration. 

Patrick Dignam, xt. 69, was admitted into 
the Richmond Surgical Hospital on the 15th 
of December, 1839, for a rupture of the tendon 
of the rectus cruris. He»stated that about a 
week previously, while carrying on his back a 
load of about two hundred weight, he slipped 
and fell backwards, and in making a violent 
muscular effort to recover himself, he felt some- 
thing snap about his knee. He fell backwards, 
and was unable to rise without assistance. 
When placed on his sound limb, he found he 
could not elevate the affected one; he could 
only flex it. Whenever he attempted to put 
the limb under him, it quite failed. him, his 
knee giving way and becoming instantly flexed 
against his will. It was found that consider- 
able effusion had taken place into the knee- 
joint: the patella was raised up and seemed to 
float as it were on the synovial fluid and was 
very moveable; its entire outline could be 
easily ascertained ; and when the leg was fully 
flexed, the patella was still quite moveable in 
the lateral directions. Above the margin of 
the patella a considerable depression existed 


78 


into which the fingers could be sunk, and the 

terior articular surface of the patella could 

felt and the condyles of the femur also could 
be recognised through the skin. The liga- 
mentum patelle seemed to be of its natural 
length. tient, when standing on the 
sound limb, could easily flex the affected one, 
but could not elevate it nor advance it in the 
least. When supported under each arm and 
desired to throw his weight on the injured limb, 
it instantly gave way under him, becoming 
suddenly flexed ; and if the man were not my 
ported, he would instantly fall forwards. It 
is now five months since he met with the acci- 
dent, and being unable to earn his living he is 
obliged to seek a shelter in the poor-house. 
The upper edge of the patella can now be 
plainly felt, and the muscular fibres normally 
attached to this margin are separated from it 
fully one inch, this interval being increased in 
flexion. The surface of the trochlea and the 
condyles of the femur can be plainly felt. The 
man is obliged to use crutches in moving about. 
The result has been unfavourable, but it is to 
be recollected that the man was of a weak and 
debilitated frame and neglected to seek assis- 
tance for many days. A dignitary of the esta- 
blished church in this country, aged 70 years, 
who had met with this accident, was more for- 
tunate; he was under the care of Mr. Wilmot, 
Professor of Surgery at the College of Surgeons, 
who informs me that his recovery from this 
accident took about a year, but that he 
could walk without lameness, and that the 
recovery was perfect. 

The tendon or ligament which connects the 
lower extremity or front of the patella to the 
tibia is sometimes broken transversely. This 
rupture sometimes takes place across the fibres 
of the ligament, and sometimes one or other of 
the extremities of the tendon is detached from 
the bone to which it is naturally connected. 
This rupture usually takes place in a fall upon 
the knee, the leg being at the time carried sud- 
denly in the greatest possible degree of flexion 
while the — is drawn upwards by the con- 
traction of the extensor muscles. We recog- 
nize this rupture by the following signs: the 
patient cannot raise himself from the ground ; 
the leg has a singular tendency to flex itself, 
and cannot voluntarily be extended. If we 
examine the knee immediately after the acci- 
dent and before any swelling has supervened, 
we observe that the patella is elevated, that its 
lowest point is now directed forwards, that a 
great degree of lateral movement can be com- 
municated to it, and that its ligament is preter- 
naturally relaxed. We observe underneath 
the skin at the place of the rupture a depres- 
sion or considerable vacuum. If we push the 
finger from below upwards undemeath the 
apex of the patella, we can elevate this bone so 
as to distinguish by the touch the eminence 
which se the two articular surfaces of 
the tibia from each other. Such signs leave no: 
doubt of the rupture of the ligament of the 
patella; but as. this rupture takes place as a 
consequence of a fall upon the knee, and as 
this. part: is more or less contused, there fol- 


LACRYMAL ORGANS. 


lows sometimes so considerable a 

it is impossible to recognize the rupture. It is 

not until after the disappearance of the swelling 

that we can often assure ourselves of the tn 

nature of the accident, Undercareful manage 

ment complete recovery takes place. . 
( Robert Adams.) — 


LACRYMAL ORGANS, or lacrymal 
sages, organa lacrymalia s. vie lac 
Fr. Les organes ou voies lac: 
Ital. Gli organi spettanti alle lagrime ; 
Die Thranenorgane. 

Under this head it is proposed to deser 
not only the lacrymal organs properly so ¢ 
but also the eyelids and conjunctiva. 
article therefore comprehends all the accessory 
or protecting parts of the eye ( tutamina oculi 
Haller) exceptthe orbit and muscles of the eye- 
ball, for which see the articles Face and Oxxrr 
Those parts of the orbit directly connected with 
the lacrymal organs are however noticed here. 

I. The eyelids.—P * Fr. Les paw 
we Ital. Le palpebre; Germ. Die Augen- 

ieder. “ 


The eyeball is invested in front by a mucous 
membrane called conjunctiva. Towards the 
margin of the orbit, this membrane leaves the 
eyeball and forms together with the skin, with 
which it is continuous, two horizontal fol 
an upper and a lower, intended i 
cover and so to protect the delicate and trans- 
poses front of the eyeball. The folds thus 
ormed by the application against each other 
of a layer of mucous membrane and a layer of 
skin are eyelids. 

Such is the simplest idea of eyelids, and 
are they found in the salamander and axole 
among reptiles, and so far as in certain 
stances they exist among fishes; such even 
is their state in man and the higher animals at 
the commencement of development. But, as 
in the perfect condition of the of vision, 
it is essential that the eyelids should admit of 
being readily drawn over the front of the eye~ 
ball, and as readily retracted in order again to 
permit the access of light, so something e 
than a mere tegumentary fold was required to” 
constitute a perfect eyelid. There was, in fact, 

uired something to impart firmness, espe- 
cially to the margins of the folds,—a structure 
which, oe. served See an ad une 1S 

int on which the muscles necessary he 
Saoneaans of the eyelids might exert their 
action, should cause no undue re on th 
eyeball, but rather give it an equable suppor 
and shield it from that irregular compression 
which might otherwise have been produced 
All these desiderata we find > pee bos i 
fibro-cartilaginous lamina, called ; 
lage, contained in either eyelid, within the fold 
formed by the skin and conjunctiva. « 

The tarsal cartilages do not oceupy the whole 
of the folds, but only a part at their free mar= 
gins. Between the upper edge of the carti- 


1 


* Palpebra, a palpitando, quod palpitare 
tremere videantur, propter citissimum et frequen- 
tissimum motum. 


a. 4 


LACRYMAL ORGANS. 


age of the upper eyelid and the lower edge of 
that of the lower, respectively, and the cor- 
“responding edges of the orbit, there intervenes 
é : 
__acellulo-membraneous expansion. This (and 
_ im the upper eyelid, the expansion of the le- 
yator palpebre superioris,) together with the 
: conjunctiva on its inside and the skin on its 
_ outside, serves as it were the office of a loose 
} hinge for the firm part of the eyelid. But the 


_ pivots on which the motions of the eyelids, 
__ especially of the upper, more immediately take 
| place, are the angles of the eye. The upper 
eyelid, indeed, moves somewhat in the manner 
{ _ of the visor of a helmet, its firm part, when 
| the eye is open, being drawn up and retracted 
_ within the margin of the orbit whilst its loose 
he: art is thrown into folds. 
____ External conformation of the eyelids.—The 
_ extent and form of the eyelids are best seen 


¥ 
f 


when they are closed in sleep. The convexity 
_ of their external surface then bespeaks a cor- 
_ responding concavity of the internal adapted 
_ to the prominent front of the eyeball. The 
_ Opening between the two eyelids is called the 
‘palpebral fissure, rima palpebrarum. In the 


z 
‘ 


closed state of the eye, this fissure represents a 
Mere curved’ line with the convexity down- 


q h 2 eyelids are moved, it is, in the open state, 
a wide elliptical aperture. 


Me 

Be 

1 s; but on account of the way in which 
It is chiefly by the motions of the upper 
i 

4 


eyelid that the open or closed state of the eye 
is commonly produced. The upper eyelid 
larger than the lower, and in the closed 
State of the eye from relaxation simply, as 
during sleep or in death, it covers much more 
of the front of the eyeball than the lower. 
But in forced closure of the eye by the action 
of the orbicularis palpebrarum muscle, the 
lower eyelid is drawn up, being impressed at 

_ the same time with a horizontal movement to- 
wards the inner angle, and meets the upper 
half-way, so that the latter cannot descend so 
_ far as it does during sleep. Hence, in active 
_ closure of the eye the skin of the upper eyelid 
__ is thrown into folds, whereas, in passive clo- 
_ Sure, it is smoothly extended in a convex form 
over the eyeball. The lower eyelid is capable 
__ of pretty extensive motion. It can of itself 
_ alone cover almost entirely the whole front of 
the eyeball, either when the upper eyelid is 
- held immoveably retracted under the edge of 
a the orbit, or in that morbid shortening or re- 
_ traction of the sane eyelid known by the 
" name of lagophthalmos. But as the covering 
of the eye by the lower eyelid is always the 
__ effect of a muscular exertion, the eye in lagoph- 
__thalmos will not be covered during sleep, 
hence the lower can never serve as a substitute 

_ for the upper eyelid. 

_ Sir Charles Bell* says, “ Anatomists have 
_ Sought for a depressor of the inferior eyelid, 
seeing that it is depressed, but such a muscle 
has no existence and is quite unnecessary. 
The levator palpebre superioris opens wide the 
eyelids, depressing the lower eyelid at the same 


Yar" Nervous System of the Human Body, 
Pp. . 


a i 


79 


time it elevates the upper one. If we put the 
finger upon the lower eyelid so as to feel the 
eyeball when the eye is shut and then open the 
eye, we shall feel that during this action the 
eyeball is pushed outwards. Now the lower 
eyelid is so adapted as to slip off the convex 
surface of the ball in this action and to be 
depressed, whilst the upper eyelid is elevated.” 
I believe the following to be what is usually 
observable in regard to the motions of the 
lower eyelid: the lower eyelid is drawn up 
over the eye by a muscular exertion; when 
that exertion is discontinued it falls back into 
its former state simply by its own elasticity 
and that of the integuments of the cheek. It 
is only in the forced state of looking down- 
wards that the prominence of the cornea forces 
down the lower eyelid, in the manner described 
by Sir Charles Bell. It is to be remembered, 
however, that in the act of looking downwards, 
whilst the prominence of the cornea forces 
down the lower eyelid, the upper, contrary to 
what might be inferred from Sir C. Bell’s state- 
ment as quoted above, is depressed, instead of 
being elevated. 

In winking the upper eyelid falls and the 
lower rises considerably. 

The free margins of the eyelids are broad 
surfaces. That of the upper eyelid is about 
one-twelfth of an inch broad; that of the 
lower about one-fifteenth. The edge bound- 
ing the margin anteriorly corresponds to the 
insertion of the eyelashes and is round. The 
posterior edge is much sharper and more de- 
fined than the preceding, and is the place where 
the delicate integument of the margin of the 
eyelid is continued into the palpebral con- 
junctiva. 

On the margin of either eyelid between the 
two edges or boundaries just described, but 
nearer the posterior than the anterior, and 
parallel to them, there is observable, on close 
inspection, a row of minute pores—the excre- 
tory mouths of the Meibomian follicles. 

The margins of the eyelids have been said 
to present a slope towards the eyeball, so that 
their outer edges only meet, when the eye is 
closed; and hence is produced a sort of chan- 
nel between them and the eyeball of a triangu- 
lar prismatic shape, which serves to lead the 
tears to the inner corner of the eye. Sucha 
conformation, if it exists in the upper eyelid, 
is very slight and is amply compensated for 
by the slope in the opposite direction of the 
margin of the lower eyelid. The fact thus ap- 
pears. to be that when the eyelids are closed, 
their. margins, as has been remarked by Ma- 
gendie, meet each other surface to surface as 
nearly as may be. 

The inner and outer. corners of the eye 
where the eyelids join are called canthi. The 
outer canthus, generally speaking, forms an 
acute angle; but on. close examination, it is 
observed that the apex is rounded off, some- 
what prolonged and turned slightly down- 
wards. The conformation of the inner canthus 
is altogether peculiar and rather complicated. 
At the inner canthus the palpebral fissure is 
prolonged into a sort of secondary fissure ; 


80 


hence, when the eye is open, the apex of the 
angle formed by the inner canthus is broader 
and toa much greater degree prolonged than 
the outer; it is also rounded ‘on turned down- 
wards, but likewise in a much greater degree. 
The margins bounding the secondary fissure 
being destitute of cartilage are not firm and 
square but soft and rounded. 

Where the margin of either eyelid is con- 
tinued into the margins bounding the secon- 
dary fissure in question, there is observed on 
slightly everting the eyelids a small promi- 
nence, and in the apex of it a minute aperture, 
larger however than those above mentioned of 
the Meibomian follicles. The eminence is 
called lacrymal papilla and the aperture lacry- 
mal point. 

The fissure is closed by the action of the 

orbicularis muscle at the same time as the eye- 
lids ; but its margins, especially at the lacrymal 
papilla, come completely into contact before 
they do. The space within the inner or nasal 
canthus is called lacus lacrymalis. The lacry- 
mal papille and their points are turned in 
towards it, ready to take up the tears as they 
collect. 
’ At the bottom of the lacus lacrymalis, there 
is seen a small reddish glandular body, the 
dacrymal caruncle, and between the latter and 
the white of the eye a semilunar fold of pink- 
coloured conjunctiva. 

Eyelashes, Cilia,* Fr. Cils; Ital. Le ciglia; 
Germ. Die Augenwim; Every one knows 
the conformation of the eyelashes. How that 
they are stiff compressed hairs, increasing at 
first in thickness from their root, then gradu- 
ally tapering to their free and slender extre- 
mity ; how that they spring from the anterior 
edge of the palpebral margins ; how that those 
of the upper eyelid are stronger and more nu- 
merous than those of the lower; how that those 
in the middle are longer than those towards 
the corners of the eyelids; and how that those 
of the upper eyelid are curved upwards and 
those of the lower eyelid downwards, so that 
their convexities regard each other. In regard 
to the curvature it is to be remarked that it is 
not gradually throughout the whole hair but is 
betwixt the thickest and the root. There 
is another slight but variable curvature towards 
the extremity. 

The skin of the eyelids is continuous with 
and similar to that of the face, only some- 
what more delicate. The skin of the upper 
eyelid is more delicate than that of the lower. 

The eyebrows, supercilia, Fr. Les sourcals ; 
Ital. Le sopraciglia; Germ. Die Augenbraunen 
(fig. 11). The external appearance of the eye- 
brows is too well known to require any particu- 
lar description. Their prominence is produced 
pady by the superciliary arches of the frontal 

ne over which they lie, but principally bya 
cushion of cellular and adi 
neath the skin, together with the roots of the 
hairs and muscular substance. The hairs of 
the eyebrow are, generally speaking, directed 
from within outwards, but internally, especi- 


se tissue under- 


* Cilia, quia oculos celent ac tueantur, 


LACRYMAL ORGANS. 


ally where they exist over the root of the no 
they are inclined in the opposite directic 
Those immediately over the root of the n 
indeed cross each other. Besides the gen 
direction from within outwards of the major 
of the hairs of the eyebrows, it is to be~ 
marked that the uppermost ones are inclin 
downwards and the lowermost ones upwat 
so that they are raised into a kind of ri 
along the middle line of the eyebrow, an 
rangement which presents a pleasing app 
ance of regularity. The eyebrows are cap 
of very free motions, and these are in ek 
connexion with the affections of the mit 
hence the eyebrows have always been ¢oi 
sidered a very important physiognomoni 
feature. The movements of the eyebro 
are effected by muscles inserted into their 
These muscles are: the frontalis, which 
the eyebrows ; the upper and outer fik 
the orbicularis palpe m, which depre 
them, and the conupitoreupseely aa draw 
them inwards. or their description, sé 
article Face. l, 
The eyelids act in conjunction with the ir 
on many occasions; thus, in a weak light an 
in the act of looking at distant objects, 
eyelids are widely opened at the same time the 
the pupil is dilated; when the eye is expo: 
to a strong light, on the contrary, or in lookin 
at near objects, the palpebral fissure is ec 
tracted along with the pupil. In sleep con 
plete closure of the aa is associated wit 
very great contraction of the pupil.* 


Fig. 11. 


SSS 


i 
THe lien at, (From Seaman 


aa, The broad free margins of the eyelids, w 
the mouths of the Meibomian follicles. 
4, Outer canthus. ius 
c, Inner canthus. > pial 
d, tones papilla and lacrymal point of ap 
eyelid. . 
e, The same of the lower eyelid. o 
Jf, Lacrymal caruncle, and g, semilunar fold, at th 
bottom of the lacus lacrymalis, which is 
space within the fissure of the inner cant as. 
hh, The orifices whence the eyelashes have beet 
plucked out. 
i, Eyebrow. 


* See farther on this subject, Tourtnal, Ueb rd 
Function der gg beim Sehen. in Miill 
Archiv, No, iii, 1838, a 


| Internal structure of the eyelids.—The tar- 
_ §al cartilages may be looked upon as the skele- 
on of the eyelids, and the membraneous ex- 
nsion intervening between them and the mar- 
fins of the orbits as connecting ligaments. The 
itter, indeed, are called the tarsal ligaments, 
_ although they do not in reality possess a liga- 
» Mentous structure, but consist merely of dense 
“laminar cellular membrane. On the inner sur- 
ice of the tarsal cartilages and tarsal ligaments 
le palpebral conjunctiva adheres. On the 
uter surface are the palpebral and ciliary por- 
ons of the orbicularis palpebrarum muscle, over 
lich is the skin. Moreover, incorporated 
th the superior tarsal ligament is the expan- 
in of the tendon of the levator palpebre supe- 
bris muscle. Imbedded in the substance of 
he tarsal cartilages lie the Meibomian follicles. 
nderneath the skin and the ciliary portion of 
ordicularis palpebrarum muscle, the roots of 
meyels shes lie close on the tarsal cartilages. 
Tarsal* cartilages —Tarsi; Fr., Les Tarses; 
41 tarsi; Germ., Der Augenliedknorpel. 
se are thin plates of fibro-cartilage, convex 
the outer surface, concave on the inner, to 
_ be adapted to the front of the eyeball. The 
pper is the larger. One of their margins is 
and straight, the other thin and curved, 
pecially so in the upper, which therefore re- 
nts in some degree a segment of a circle, 
ilst the lower is little more than a narrow 
- The thick and straight margin, called 
the ciliary, forms the margin of the eyelid; the 
hin and curved margin, called orbital, degene- 
es into the membraneous expansion already 
mentioned under the name of tarsal ligaments. 
rowards the outer canthus the orbital margins 
of the tarsal cartilages run into the ciliary ones 
tan acute angle, whilst towards the inner can- 
thus they form an obtuse angle by their junc- 
ion. The transverse length of the tarsal carti- 
lages is somewhere about an inch, the breadth 
of the upper cartilage at its broadest part about 
one-third of an inch, the breadth of the lower 
cartilage only half as much. At the inner can- 
thus the tarsal cartilages extend no farther than 
the lacrymal points, and at the outer canthus 
hey stop close to the commissure of the two 


: 
t 
} 
‘ 


if 
a 


Pe oe ee eae 


Sa 


As to the intimate composition of the tarsal 
Cartilages, they consist of what is called fibro- 
age, a microscopically fibrous substance, 
hout any of the corpuscles of common carti- 


a 


fee 


is substance is inconsiderable, and its con- 
istence not so great as in the upper. In the 
ower animals itis in the same state in both 
yelids. This is what has led Zeiss+ to say 
hat he never found a real cartilaginous tarsus 
in the human lower eyelid, nor among the lower 
mammifera in the upper eyelid either. “In 


‘In the human lower eyelid, the thickness of 


. 
__ * Tarsus, propter siccitatem quod carnis sit ex- 


togie. Bad. iv. p. 249, 
i VOL. ITI. 


i 


LACRYMAL ORGANS. 


81 


the sow only,” says he, “there isa nearer ap- 
proach to a tarsal cartilage than is to be found 
in apy other of the lower animals.” Miiller* 
has very well explained away all this difference 
of opinion, by showing that the dense cellular 
tissue which, according to Zeiss, occupies the 
place of tarsal cartilage in the human lower 
eyelid, and in both those of the inferior mammi- 
fera, is the same tissue, as the more consistent 
fibro-cartilage of the human upper eyelid, only 
in a less condensed state. 

The Meibomian glands are commonly de- 
scribed as being situate between the palpebral 
conjunctiva and tarsal cartilage. Winslow, 
Haller, and Zinn describe them as lying in 
grooves on the posterior surface of the tarsal 
cartilages. The Meibomian glands are seen 
very distinctly from the inside of the eyelids, as 
if they were immediately underneath the con- 
junctiva. But if the skin and orbicularis muscle 
be removed from the outside, these glands be- 
come equally viSible there.. “‘ Where, then,” 
asks Zeiss,t “do they lie,—before or behind 
the tarsal cartilage?” Examination of sections 
of the cartilage shows that the Meibomian glands 
lie in the substance of the tarsal cartilage itself ; 
and in the human lower eyelid and in both 
those of the lower animals, in the less consistent 
fibrous structure which there composes the 
tarsus. 

At the outer canthus the cellulo-membra- 
neous expansions called tarsal ligaments are 
stronger, and form bands which decussate and 
thus tie the tarsal cartilages to each other and 
to the outer margin of the orbit. These bands 
compose what is called the external palpebral 
ligament. 

The internal palpebral ligament is the tendon 
of the orbicularis palpebrarum muscle,—tendo 
oculi, or tendo palpebrarum. This, to adopt 
the description of Professor Harrison of Dub- 
lin, “is a small horizontal tendon, nearly one 
quarter of an inch in length. It is inserted in- 
ternally into the upper end of the nasal process 
of the superior maxillary bone ; thence it passes 
outwards and backwards to the internal com- 
missure of the eyelids, where it forks into two 
slips which enclose the caruncula lacrymalis, 
and are then inserted each into the tarsal carti- 
lage and the lacrymal duct.’’f 

Orbicularis palpebrarum muscle.—This is de- 
scribed in the article Face, vol.ii. p. 221. Here 
we shall only advert to some particular. points 
in its history. The fibres of the. orbicularis 
pertaining to the upper eyelid arise from the 
Internal angular process of the frontal bone, and 
from the upper edge of the tendo palpebrarum, 
and proceed, forming a curve, at first upwards 
and outwards, and then downwards and out- 
wards, within the upper eyelid and along and 
over the upper edge of the orbit towards the 
temple and outer angle of the eye. Here they 
meet those of the lower eyelid which have come 
from the nasal process of the upper jaw-bone, 


* Archiv, 1836. Jahresbericht, p. xxxviii. 

t L.c. p. 240, and op. cit. Bd. v. S. 216. See 
also Sichel in Lancette Franeaise, Gazette des Ho-~ 
pitaux, No. 53, 55, and 57. Paris, 1833, 

$ Dublin Dissector, 4th ed. p. 6. 

G 


82 


and from the lower edge of the palpebral ten- 
don, curvjng at first downwards Lit oaneeshes 

en upwards and outwards, within the lower 
eyelid and along the edge of the orbit, extend- 
ing some way down over the cheek. The part 
of the orbicularis more immediately contained 
within the eyelids, sometimes called the palpe- 
bral and ciliary portions, in contradistinction to 
the outermost fibres, which are without the eye- 
lids, and encircle the base of the orbit, therefore 
called the orbital portion, consists of pale thin 
fibres, of which those at the margin of the eye- 
lids are collected into a considerable fasciculus, 
having interposed between them and the tarsal 
cartilage the roots of the cilia. At the outer 
canthus the upper and lower fibres intercross 
and adhere to the external palpebral ligament. 
That many of the fibres of the orbicularis are 
inserted into and exert their action in a great 
degree on the skin of the eyelids, may be easily 
ascertained in the living person, by observing, 
during the action of closing the eye, the traction 
of the skin of the eyelids towards the nasal can- 
thus. By this traction, the skin, especially in 
the lower eyelid, is very much corrugated. This 
corrugation of the skin of the lower eyelid by 
the action of the orbicularis is greatest right 
over the lower part of the lacrymal sac,—that 
part which we commonly press upon when we 
want to evacuate any accumulation of mucus or 
tears,—that part where abscess of the sac gene- 
rally bursts and leaves a fistulous opening,— 
that part which we open in the operation for so- 
called fistula lacrymalis. This part of the 
lacrymal sac must therefore be immediately 
affected by the contraction of the muscle, and 
the pressure thus produced, together with that 
on the upper blind end of the sac by the supe- 
rior fibres, will promote the transmission of the 
tears and conjunctival mucus into the nasal 
duct. 

The great use of the orbicularis palpebrarum 
is to close the eyelids; but in effecting this it 
acts at a disadvantage, inasmuch as its action 
on the eyelids is not direct, but oblique ; there- 
fore they are brought together only by being 
drawn horizontally inwards, though it is the 
lower eyelid alone which yields to this latter 
movement. We may imitate in some degree 
the mode of action of the orbicularis, but in an 
opposite direction, by pressing the skin imme- 
diately outside the outer canthus, towards the 


seer mt 

vator palpebre superioris muscle.-—This is 
the antagonist of the upper part of the orbicu- 
laris. It is a weak slender muscle, but then it 
has the advantage of exerting its action in a di- 
rect manner. It extends from the bottom of the 
orbit to the superior tarsal cartilage, lying im- 
mediately underneath the roof of the orbit. It 
is the longest of all the muscles of the orbit. 
Thin and triangular, it rises by its apex, which 
is a short tendon, from the upper edge of the 
optic foramen. The fleshy body of the muscle 
gradually increases in breadth as it proceeds 
forwards ; then bending downwards over the 
eyeball, its insertion takes place by a broad thin 
tendinous expansion, the of the triangle, 
into the upper margin and anterior surface of 


_ LACRYMAL ORGANS. 


the superior targal cartilage, being i 
at the same time witb the ed il | 
ment. It is by the action of this muscle tl 
the upper eyelid is drawn up and retract 
within the orbit. ag 
Having thus described the skeleton and 
cles of the eyelids, it remains to consider #l 
investments and appendages. The investm 
of their inner surface, the palpebral conjuncti 
will be described farther on, along with 
rest of the conjunctiva. The skin of the eyel 
lies over the fibres of the orbicularis palpel 
rum. It is very fine and destitute of hairs, 
contains minute sebaceous follicles. The la 
are sometimes, especially in the lower eyel 
enlarged, and give out a morbid secretion, w. 
is hard, and forms those horny excresce 
occasionally met with in old . 
Cellular tissue of the eyelids —The conjut 
tiva investing the inner surface of the tar 
tilages adheres without the intermedium of at 
cellular tissue. The connection between t 
two structures is immediate and intimate, 
the compound membranes called fibro-m 
The rest of the palpebral conjunctiva ac 
by cellular tissue. The palpebral and ci 
portions of the orbicularis muscle are con 
on the one hand to the tarsal cartilages 
other subjacent parts, and on the other to 
superjacent skin, by a laminar cellular tissu 
which, like that in some other parts of t 
body, is not combined with the adi ssi 
Being rather loose, the cellular tissue of | 
eyelids becomes readily infiltrated by effust 
fluids, as in @dema and emphysema. It i 
unfrequently the seat of abscess. it 
Roots of the eyelashes. From the ante 
edge of the free margins of the eyelids, # 
eyelashes spring. They are inserted three 
four deep, especially in the middle. The ¢ 
sules of the bulbs of the eyelashes lie cle 
the tarsal cartilage under the ciliaris muse! 
skin, extending to the depth of about or 
eighth of an inch. One of the operations 
trichiasis is to extirpate the roots of the ey, 
lashes, but it is very difficult to remove the 
all, the oozing of blood is generally so gre 
When the part has healed the operati 
and the case seems doing well, a hair or 
will often be found here and there sprouti 
out again. . 
Connected with the roots of the eyelas 
as with other hairs, are small sebaceous glan 
consisting of minute but distinct lobules 
grains closely surrounding the capsule, ii 
which they send one or more excretory 
‘Maibconion glands. Glandule 
miane s. palpebrarum sebacee ; — Fr. 
glandes de Meibom ;—Ital. Le glandule 
bomiane ; -Germ. Die Meibomschen Dr 


ncorTr 
Tarsa 


7 = 


a 


* Gurlt, Vergleichende Untersuchungen tiber 
Haut des Menschen und der Haussiugethi 
besonders in Beziehung auf die Absonderun 
des Haut-talges und des Schweisses. In 
Archiv, 1835, p. 399. = 

t Zeiss. Fortgesetzte Untersuchungen wi 
Anatomie und Pathologie der A ider v 
E. Zeiss in Dresden. In Ammon’s Zeitschri 
B. 5, p. 216. 


These are elongated more or less compound 
_ follicles, secreting a peculiar sebaceous matter 
“intended as an ointment to protect the delicate 
gument of the margins of the eyelids from 
“any irritation which might result from friction, 
or the frequent contact of the tears, and also to 
eserve to it that peculiar degree of sensibility 
which, like all other transition structures from 
skin to mucous membrane, it possesses. The 
Meibomian glands lie imbedded in the sub- 
tance of the tarsal cartilages. They are ar- 
fanged close and parallel to each other, and ge- 
erally speaking in a direction at right angles to 
he ciliary margin of the eyelids, where they open 
that row of minute apertures already mention- 
d. There are between thirty and forty Meibomian 
ands in the upper eyelid, but not so many in 
1 lower, in which also they are shorter in 
onsequence of the difference in breadth be- 
veen the upper and lower tarsus. Sometimes 
> glands are united towards their orifice; 
jometimes, on the other hand, at their end. 
requently the tail of the gland bends laterally 
nd describes an arch. The structure of the 
feibomian glands consists essentially in a 
tral canal running from one extremity to the 
er, like the duct of the pancreas, and around 
that canal glandular loculi or crypte opening 
Into it directly, or through the medium of each 
} The duct suddenly contracts before 
jpening on the margin of the eyelid. In a 
transverse section of the Meibomian glands this 
f is seen, according to Zeiss, as a small 
hole around which are placed from five to six 
glandular grains. 
_ The Meibomian glands of the sow are small ; 
‘Tepresenting merely a short cyst subdivided 
into several loculi. The glands of the eye- 
ashes in the same animal are, on the contrary, 
arge. The Meibomian glands of the sheep, 
dog, and fox, are long very thick-walled bodies, 
im the middle of which there is a wide canal. 
Ranking next in complexity of structure are 
the human Meijbomian glands. Those of the 
horse, ox, goat, and cat; Zeiss found still more 
complex, consisting of lobes, lobules, and 
- granules.* J 
~ The secretion of the Meibomian glands is a 
mild, yellowish, unctuous substance, of the 
tonsistence of lard. Occasionally the external 
orifice of one or more of the Meibomian ducts 
_ becomes covered by a thin film, apparently of 
pidermis. This prevents the escape of the 
cretion, which accumulating raises up the 
' film into a small elevation, like a phlyctenula. 
this does not actually cause pain, but gives 
ise to uneasiness in the part when the eyelids 
re moved: the film is easily broken, and the 
cumulated secretion removed on the point of 


___ Hordeolum, or stye, according to some, is 
abscess of the Meibomian glands ; according 
to others, a small boil implicating the cellular 
tissue at the margin of the eyelid. Zeiss} sus- 
ects it has its seat in the capsule and glands 


__ * Zeiss’s papers in Ammon’s Zeitschrift, B. iv. 
and v., already quoted. 
IS + Locis citans. | 


+3] 


LACRYMAL ORGANS. 


83 


of the roots of the eyelashes. Abscess of the 
Meibomian glands does occur, and gives rise 
to a tumour on the edge of the eyelid like a 
stye, but the nature of the case is seen on 
everting the eyelid. There can be no doubt 
that the roots of the eyelashes are involved in 
the disease, because the hairs at the part affect- 
ed generally fall out at the end. Dr. Zeiss 
proposes to anticipate this result by plucking 
them out at once, and he says that by this pro- 
cedure the progress of the complaint is arrested, 
a thing, certainly, occasionally very desirable. 
In a small inflammatory tumour at the root of 
a hair on the cheek, I have obtained such a 
result from plucking out the hair. 


Fig. 12. 


The eyelids of the right side seen from within. 
( Modified from Soemmerring. ) 

a,a, Inner surface of orbicularis palpebrarum 
muscle. 

b, Palpebral fissure. 

c, c, c, Upper mass of lacrymal gland. 

d, Lower mass of lacrymal gland. . , 

e, e, Conjunctiva. The palpebral portion is 
smoothly spread on the inner surface of the eyelids. 
The portion which has been dissected from off the 
eyeball is in folds. J 

Ff, Hairs inserted into the orifices of the ducts of 
the lacrymal gland. These orifices are on the 
conjunctival surface of the upper eyelids towards 
its temporal extremity. : 

9> gs Meibomian glands of both eyelids seen 
shining through the conjunctiva and the thin layer 
of tarsal cartilage covering them on the inside of 
the eyelids. : 

h, Lacrymal papilla and point of the upper 
eyelid. i 

i, The same of the lower eyelid. 

k, Lacrymal caruncle. : 

l, Semilunar fold pressed aside to show the 
caruncle. 


II. The conjunctiva, semilunar fold, and 
lacrymal caruncle. 

The conjunctiva in general.—Tunica con- 
junctiva seu adnata. Fr. La Conjonctive. 
Ital. La Congiuntiva. Germ. Die Bindhaut. 
The conjunctiva is that membrane which lines 
the posterior surface of the eyelids, and covers 
the front of the eyeball to the extent of about a 
third of its whole periphery. This disposition 
has given rise to the distinction of a palpebral 
and ocular conjunctiva. Towards the margin 
of the orbit, all round the circumference of the 
eyeball, a cul-de-sac is formed by - reflection 

G 


84 


and continvation with each other of these two 
portions of the membrane. It is by this conti- 
nuity that the eyelids and eyeball are held in 
connexion, hence the name conjunctiva, and 
that the orbit is closed in and cut off from 
all communication with the space between the 
eyeball and eyelids. - 

The space between the eyelids and eyeball we 
shall distinguish by the name of oculo-palpebral 

€ of the conjunctiva, a name, the necessity 
or which appears from this, that in common 
language, when it is said a foreign body has 
got into the eye, it is only meant that it has got 
into the oculo-palpebral space of the con- 
Junctiva. The propriety of the name moreover 
will become more evident when the space in 
Serpents and Geckoes comes under considera- 
tion, for in them it is a closed cavity, (in ser- 
pents already designated by Jules Cloquet* 
oculo-palpebral sac of the conjunttiva,) re- 
ceiving the lacrymal secretion and communi- 
cating with the exterior only by the connexion 
it has with the nose through the nasal duct. 

What are called the superior and inferior 
palpebral sinuses of the conjunctiva are those 
parts of the oculo-palpebral space under the 
upper and lower eyelids respectively, where 
the ocular and paipebral portions of the con- 
junctiva are reflected and continued into each 
other, forming a cul-de-sac. The conjunctiva 
is here loosely attached to the subjacent cellular 
and adipose tissue, &c. of the orbit, and forms 
folds constantly varying with the motions of the 
eyeball and eyelids. The superior palpebral 
sinus of the conjunctiva is deeper than the 
lower, the reflection of the conjunctiva from the 
eyelids upon the eyeball being when the eyelids 
are passively closed: above, at the distance of 
about seven-tenths of an inch from the margin 
of the upper eyelid, and below, at about three- 
tenths of an inch from the margin of the lower. 
The cul-de-sac formed by the reflection of the 
conjunctiva does not lie very deep within the 
outer canthus, speaking in reference to it alone, 
though as near the edge of the orbit as above or 
below. 

The looseness of the folds formed by the 
conjunctiva at the upper and lower palpebral 
sinuses and within the outer canthus, together 
with the peculiar nature of its disposition at 
the inner canthus, presently to be noticed, allows 
of the free motions of the eyeball in all direc- 
tions. These folds may be readily seen on 
everting either eyelid, as also the continuity of 
the conjunctiva from the eyelid to the eyeball 
by requesting the person to look upwards, if it 
is the lower eyelid which is everted, downwards 
in the contrary case. 

In operations on the eyeball when the eyelids 
are held apart unskilfully, the folds are thrust 
out between the eyelids by the action of the 
orbicularis muscle, so that they almost bury 
the front of the eyeball and consequently im- 
pede the operator. 

By long-continued catarrhal ophthalmia and 
the abuse of blue stone and similar escharotics, 


* Memoire sur |’existence et la disposition des 
yoies lacrymales dans les serpens. Peris, 1821. 


LACRYMAL ORGANS. 


the conjunctiva is apt to become contracted an 
thickened, and to a i at the same time 
callous articular su In such cases th 
contraction tells very much upon the looser 
of the folds of the conjunctiva at the upper at 
lower palpebral sinuses, which may indeed 
said to be obliterated. The consequence 
this is great restriction in all the movements 
the eyeball. 
Foreign bodies which may have ente 
oculo-palpebral space sometimes get lod 
in Shasal bral posal of the conjunet 
especially the upper, and may be retained th 
for a length of time without causing much 
any irritation, the conjunctiva bei re 
loose and the adjacent cellular adi 
tissue of the orbit so soft that the body is - 
much pressed upon by the opposing surfac 
The contrary is the case when the foreign bo 
lies between the eyeball and the firm part 
the eyelid, for here its irritation excites t 
orbicularis muscle to stronger action wh 
serves but to aggravate the distress. 
Disposition of the conjunctiva at the inn 
canthus.—Under this head falls to be co 
dered the semilunar fold, the notice of whi 
it will be advantageous to premise by a deseri 
tion of the lacrymal caruncle. In consequen 
of the prolongation of the palpebral fissure 
the inner canthus into a secon one, | 
lacrymal caruncle and semilunar fold are $ 
exposed that their external con ion ¢ 
be readily and indeed best studied in the liv 
eye. ; ‘ 
“taal caruncle, caruncula la li 
Fr. La caroncule lacrymale. Ital. La caru 
cula lagrimale. Germ. Die Thranenkarunk 
This is a small reddish yellow eminence haviz 
a slightly tuberculated surface, beset with ve 
delicate scarcely visible hairs. It is situate 
as has been said, within the secon fissu 
of the inner canthus, and inclosed between t 
two slips of the tendo palpebrarum. To 
the lacrymal caruncle in its whole extent, it; 
necessary to evert slightly the lower eyeli 
when it 1s observed running into a point dow 
wards and outwards. The lacrymal carul 
consists of a mass of loose fibro-cartilagino: 
tissue, similar to that of the tarsal cartilages, 
which are imbedded follicles, secreting a fit 
of the same nature as that of the Meibomiz 
glands, and pouring it out by twelve or fif 
excretory orifices on its $ which is — 
vested by the conjunctiva. Anciently the 
crymal caruncle was thought to be the secret 
organ of the tears, and the lacrymal points 
excretory orifices. 1a 
Semilunar fold, plica semilunaris. 
repli semilunaire. Ital. La piega 
Germ. Die halbmondformigen Failte. In pass 
from the caruncle to the eyeball, the conjune 
forms a vertical semilunar fold which enclo 
at its free edge a minute cartilage of a na 
similar to the tarsal cartilages. This part 
the conjunctiva is distinguished from the 
portion by its reddish colour and greater th 
ness, indeed it resembles more the palpe 
conjunctiva than the ocular. The concavit 
the crescent, which is also the free edge of 7 


oo 


a 


“- 
(i 


a 


+ 7 
a6 


fold, is towards the cornea. The rolling of the 
___ eyeball outwards has a tendency to undo the 
_ fold, which on the contrary is rendered more 
distinct when the cornea is turned towards the 
“nose. In quadrupeds the semilunar fold is 
_ much more developed, and contains within it 
__ amore distinct cartilaginous plate. It consti- 
tutes what in them is called membrana nictitans. 
_ The third eyelid in birds is the same structure 
carried to its highest pitch of development. In 
“man, in whom it is very small, its component 
_ Structures are readily developed to a consider- 
able size by inflammation. According to Soem- 
Terring the semilunar fold is larger in the 
We shall have occasion to recur to 
the membrana nictitans of quadrupeds and the 
third eyelid of birds. 
___ The intimate nature of the connexion between 
the tarsal cartilages and the conjunctiva which 
Tines them has been already noticed. Beyond 
the tarsal cartilages the adhesion of the palpe- 
conjunctiva becomes looser and looser 
until its transition into the ocular conjunctiva. 
The ocular conjuictiva is smoothly spread 
the front. of the sclerotica, where it first 
s on the latter. The interposed cellular 
tissue is loose enough to allow it to slide upon 
‘the sclerotica, or even to be raised up in wrin- 
_kles according to the motions of the eyeball, 
‘which are thus facilitated. But as the con- 
_ Junctiva approaches the cornea it is more and 
more closely applied to the sclerotica and con- 
_ sequently less readily falls into wrinkles. The 
‘debated question of a conjunctival covering of 
the cornea will be considered when speaking 
of the intimate structure of the conjunctiva. 
The cellular tissue between the conjunctiva 
_ and sclerotica is sometimes the seat of extrava- 
Sations of blood, subconjunctival ecchymosis, 
Sometimes the seat of an accumulation of se- 
_ Tous fluid, as in the edema attending erysipela- 
| tous ophthalmia. It is sometimes the seat of a 
ity more serious form of cdema, that known by 
i _ the name of chemosis, and common in the 
| purulent inflammation of the conjunctiva. It 
_ may also be the seat of emphysema, and is 
_ occasionally so of phlegmon. 
Nature of the conjunctiva.—The conjunctiva 
forms part of that membraneous system, conti- 


heegroes. 


| nuous with the skin at all the natural apertures 
of the body, which lines the interior of the 
| tespiratory and digestive canals, and to which, 
i as to that lining the genito-urinary passages, 
} 
f 


_ the generic name of mucous membrane is given. 
_ Ofcourse different parts of this system present 
Specific peculiarities in structure and function, 
and this is the case even in regard to the palpe- 
bral and ocular parts of the conjunctiva, though 

So neareach other. Some of the Germans have 
_ unnecessarily involved this subject. Thus 
_ Walther viewed the conjunctiva as mucous in 
the eyelids, tegumentary over the sclerotica, 
ind serous over the cornea. Whence we some- 
times meet in their ophthalmological works such 
expressions as “ the conjunctiva considered as 
a mucous membrane,” and “ the conjunctiva 
considered as a serous membrane.” In refe- 
Tence to these opinions of his countrymen, 


<x 
1 = 


ee 


——_ 


LACRYMAL ORGANS. 


85 


Miiller* has thought it necessary to remark 
that the conjunctiva is as certainly a mucous 
membrane as any other of which the character 
has not been doubted. * * * On the other 
hand it has nothing in common with the serous 
membranes either in secretion, for the limpid 
secretion of the eyes is derived from the lacry- 
mal gland, or in its form, which is not that of a 
shut sac. 

Within the upper eyelid towards the outer 
canthus (fig. 12,f'), the conjunctiva presents the 
minute mouths, nine or twelve in number, of 
the ducts of the lacrymal gland. At the inner 
canthus the conjunctiva is continuous through 
the lacrymal points with the membrane lining 
the canalicules, and so through them, the la- 
crymal sac and nasal duct, with the mucous 
membrane of the nose. At the margin of the 
eyelids its continuity with the skin is seen. 

The oculdpalpebral space of the conjunc- 
tiva receives the tears much in the same way 
that the mouth receives the salivary secretions. 
Like other mucous membranes the conjunctiva 
secretes a mucous fluid which lubricates its 
surface and serves to protect it from the irri- 
tating action of external agents, and even from 
that of the lacrymal secretion which is naturally 
poured out on it. 

Intimate structure of the conjunctiva. 

Palpebral conjunctiva, conjunctiva palpe- 
brarum.—The conjunctiva lining the eyelids is 
thicker and more vascular than that which 
invests the sclerotica. On the posterior surface 
of the eyelids, about one-twelfth of an inch 
from and parallel with the posterior acute edge 
of the margin, there is a very slight groove. 
Between this and the edge of the eyelid the 
conjunctiva is sufficiently distinct by its moist 
shining surface and its vascularity, from the 
more integument-like though delicate invest- 
ment of the margin of the eyelids with which 
it is continuous. - But it is immediately in the 
groove and especially beyond it that the con- 
junctiva, as pointed out by Eble,+ first shows 
itself truly as a mucous membrane, that is, pre- 
sents all the characters commonly ascribed to 
mucous membranes. 

The palpebral conjunctiva consists of a 
chorion, the free surface of which presents 
papillz, constituting what is called the papillary 
body, and the whole is covered by anepithelium. 

The chorion of the palpebral conjunctiva is 
intimately incorporated with the tarsal fibro- 
cartilages, so that the latter and their investing 
conjunctiva might be considered together as 
constituting a compound or fibro-mucous struc- 
ture. Beyond the cartilages the chorion ap- 
pears in its independent and separable form as 
a felt-work composed of an interlacement of 
filamentous cellular tissue, and is the nidus for 
the ramification of the vessels and nerves. 

Papillary body—If the upper eyelid be 


* Handbuch der Physiologie des Menschen, 
Bd. i, S. 429, Coblenz, 1838, or Translation by 
Baly, p. 436. : , 

+ Ueber den Bau und die Krankheiten der Binde-~ 
haut des Anges,p. 9. Wien, 1828. 


86 


everted and examined, the moisture being first 
wiped off from its surface, under different direc- 
tions of the light, an appearance is observed as 
of a shining surface beset with small brilliant 
grains, as if minutely shagreened. This ap- 
ce is more or less distinct in different 
individuals and most so after death. 

The appearance described is produced by 
numerous papille, considered nervous b 
Ruysch,* and small glands by Miiller,+ and, 
after him, by most other authors. Eble} objects 
to this view of the matter, and asserts that the 
a are quite distinct from mucous glands, 

are the same as the papilla found on other 
mucous surfaces, and that they particularly 
resemble the papille of the mucous membrane 
of the gums ka inner surface of the al nasi. 
Eble, however, adds that these papille present 
themselves in all the mucous membranes in a 
Manner quite analogous to glands, and he 
thinks that the mucus of mucous membranes is 
the uct of the secretion of the papillary 
body. And this is equally applicable to the 
secretion of the palpebral conjunctiva, whence 
it would eg that Miller and Eble really 
_ do not differ in opinion, but only in the terms 
they employ to express it. 

The part where the papillary body appears 
least distinctly is between the edge of the eyelid 
and the groove on the posterior surface above 
mentioned. The palpebral conjunctiva all 
beyond the groove presents the papillary body 
in a more decided form, and the development 
of it goes on increasing to some distance beyond 
the orbital margin of the tarsus. The con- 
junctiva covering the lacrymal caruncle, as also 
the greatest part of the semilunar fold, present 
no papillary body. Towards the lacrymal 
points there is found a great number of pretty 
apparent papille. 

he illary body is very vascular. It is 
the morbid. development of it which constitutes 
the so-called granulations of the eyelids in the 
puro-mucous ophthalmiz ; of which indeed the 
papillary body appears to be the peculiar seat. 
An inflammation suddenly affecting a healthy 
conjunctiva from atmospherical causes is what 
is conventionally called a catarrhal ophthalmia. 
If this be allowed to fall into a chronic state, 
or if the conjunctiva has been affected by a less 
marked inflammatory action for a time, the 
papillary body becomes hypertrophied. In this 
state it forms as it were a new organ ready to 
be affected by a form of disease which a healthy 
conjunctiva is not all at once so prone to as- 
sume. Mere congestion caused by over- 
exertion of the eyes, or by heavy caps and high 
tight collars, as Dr. Vieminckx thinks, together 
with fatigue, exposure, want of cleanliness, 
abuse of stimulating liquors, &c., may give 


» a Thesaurus. 
¢ ahrungssatze iiber die contagidse oder 
agyptische Augenentziindung. Mainz, 1821. 


t Op. cit. p- 9, 29, pl. iand ii, Or the Belgian- 
French translation, ‘* De la Structure et des Mala- 
dies de la Conjonctive. &c. Traduit de l’ Allemand 
par Ed. de Losen de Seltenhoff, M.D. Publié par 
ordre du Ministre dela Guerre. Bruxelles, 1836. 


LACRYMAL ORGANS. 


- 
" 


2 


fe 


rise to this unnatural development of the 
lary body of the conjunctiva, and so predi 
in a particular manner, on the occurrence of ai 
atmospherical influence, to an attack of co 
junctivitis, and that rather of the form of 1 
Egyptian ophthalmia than of a simple ¢ 
sar pithel of the palpebral * 
ithelium of the conjunctiva 
“Tt ‘te extremely diffteult,” says Eble,* 
distinguish this on so fine a membrane, — 
though I have succeeded, by maceration 
boiling water, in detaching it in part fron 
eyelids of an ox, I have not again been able 
convince myself of the exactness of the obs 
vation as I could have wished.” J. F. 
doubted the existence of an epithelium. Et 
says again that he would, however, admit i 
presence on the conjunctiva rather from analo 
than from observation. Here is a good exam} 
of the assistance derivable from the microsec 
two such observers as Meckel and Eble 
with the naked eye to determine the existen 
of a structure which later observers with 
microscope have fully established. We sha 
return to the subject in speaking of the epith 
lium of the conjunctiva bulbi. é 
Sclerotic conjunctiva, conjunctiva sclerotic 
As far as vascularity goes, there is a decic¢ 
difference between this and the fp 
The sclerotic conjunctiva is composed of ; 
chorion or vascular basis of the membran 
covered by epithelium. Valentin} describe 
between the chorion and epithelium n 
structure which he calls papillary. 
The chorion of the sclerotic conjunctiva con- 
sists of irregularly stratified fibres of cellul 
tissue interwoven with bloodvessels — 
nerves. ' 
“ Do the conjunctiva sclerotice and the 
conjunctival pellicle of the cornea also presery 
a papillary body or not?” asks Eble,f in m 
ference to Valentin’s assertion of one. Eble 
admits the structure described by Valentin 
under the name of papillary y between 
the chorion and epithelium of the conjunc 
rtiva bulbi, but thinks, and correctly, that 1 
is a very different thing from the papillary DO 
of the palpebral conjunctiva as ibe 
himself. Valentin’s papillary body of the cot 
junctiva bulbi is a matter of the microscope= 
Eble’s papillary body of the palpebral con 
junctiva, though minute, is still in some de 
gree cognisable to the naked eye. Hypertre 
of the papillary body of the palpebral conjume 
tiva constitutes, as has been said, what is calle 
granular conjunctiva. We never see such a gr 
nular state of the sclerotic conjunctiva. = 
The following is Valentin’s description 
what he calls the papillary body of the conjun 
tiva bulbi:—It is best seen in the human e 
“ when, after several days’ maceration, 1 
loosened and swollen epithelium is careful 


Me 
eCen in 


* Loe. cit. 

+ Repertorium fiir die Anatomie &c, 
pp- 142—300. Berlin, 1837. E 
¢ In medicinischen Jahrbiicher des k. k, Oeste 
reichischen Staates, Neueste Folge, xvi. Band 


p. 73, 


. “Z 
Be 
“eo 


removed and the papillary body then separated 
by a shaving cut through the surface of the 
conjunctiva. The papille are seen under a 
microscope magnifying three hundred diame- 
s, as yellowish red corpuscles standing close 
ther, of an arched conical shape and pre- 
ing a round nucleus in their interior. 
any of the papille have short pedicles. Many 
resent at their extremity a small point or fila- 
tous prolongation which runs towards the 
thelium. Henle* thinks Valentin’s papille 
‘are nothing but the corpuscles of the epithe- 
um, presently to be noticed, distorted by the 
ction of the compressorium. Itappears to me 
lat Valentin’s papillary body constitutes a 
‘Structure of the same nature as the corpus 
Malpighianum of the skin. We know that 
‘$uch exists in the sclerotic conjunctiva from the 
tircumstance that in negroes and many of the 
Tower animals it is tinged of a black or brown 
~ colour, whilst in Isabella horses and in Swiss 
Taces among oxen it appears yellowish. 
Epithelium of the conjunctiva. The dis- 
covery of a characteristic structure in epithe- 
Tium enables us to determine its existence even 
en so delicate as not be separable as a dis- 
{ layer. It may appear merely as a tena- 
_ cious mucus little more than perceptible to the 
_ naked eye, but examined under the microscope 
it is found to consist of minute polygonal 
tells, flat and containing a central nucleus. 
ese corpuscles aggregated together more or 
less closely and in greater or less quantity con- 
stitute the substance of epithelium. The epi- 
dermis is essentially of the same structure ; as 
also the corpus Malpighianum, only when this 
is coloured, the cellules are found to contain 
colouring particles, as is remarkably the case 
im the black pigment of the eye, the small 
_ hexagonal bodies composing the membrane of 
| which belong to the same category as the cor- 
_ puscles of the epithelium or corpus Malpi- 
anum. 
__ According to Valentin the epithelium of 
the conjunctiva consists of rhomboidal or quad- 
e@ cells lying close together, the boundaries of 
yhich are formed by simple lines. In every 
there is found without exception a some- 
' 


what darker and more compact nucleus of a 
Tound or largish form. The average diameter 
‘of these cells, in the human eye, is about the 
two-thousandth of an inch. The nuclei are 
about half the size. 
Thickening of the epithelium takes place in 
opium and callous granulations. What is 
ee led cuticular conjunctiva is at the same time 
4 general contraction of the whole conjunctiva 
ith a thickened and dry state of the epi- 
_ thelium. 
_ _ Does the conjunctiva extend over the cornea ? 
Every one admits the existence of a layer on 
the anterior surface of the cornea, quite dif- 
ferent from its proper substance, and apparently 
a continuation of the conjunctiva covering the 
Sclerotica, but this layer on the anterior surface 
wal 


oD 


4. ™ Symbole ad Anatomiam Villorum intestina- 
um, imprimis eorum epithelii et vasoruam lac- 

teorum, p. 8. 4to, Berolini, 1837. - 

| i 


4 
; 


LACRYMAL ORGANS. 


87 


of the cornea does not present exactly the same, 
or at least all, the anatomical and chemical 
characters as the sclerotic conjunctiva. What 
of it can be raised is like epidermis or epithe- 
lium, coagulated and rendered white by the 
heat applied to separate it, and moreover it is 
not vascular, the vessels seen ramifying on the 
surface of the cornea in some inflammations 
being situated underneath it. 

What is the nature of the superficial layer of 
the cornea? It is composed of two lamelle. 
The more superficial constitutes a very fine but 
firm epithelium. According to Valentin, after 
sixteen or twenty-four hours’ maceration, the 
epithelium separates from the cornea. The 
cells have in this case lost a little in transpa- 
rency and are somewhat distended. The nuclei 
appear more or less swollen by the action of 
the water. The other lamella situated under- 
neath the epithelium is more loose in its co- 
hesion, and is What Valentin considers the 
same structure as the papillary layer described 
by him in the ocular conjunctiva. Valentin 
says that a chorion or fibrous layer does not 
exist in the conjunctival extension over the 
cornea. The bloodvessels derived from the 
sclerotic conjunctiva run merely betwixt the 
papillary body and the surface of the proper 
substance of the cornea. They are very deli- 
cate and extremely difficult to inject. 

Romer* has described the arteries of the con- 
junctiva corner from injections. The fine 
twigs of the arteries of the sclerotic conjunctiva 
unite together around the margin of the cornea 
into a vascular wreath or circle. From this 
there arise very numerous branches which run 
from the circumference towards the centre of 
the cornea, and in their course make two or 
three very fine subdivisions. Their ends bend 
distinctly inwards, and appear to penetrate the 
proper substance of the cornea. 

Having thus shown on the surface of the 
cornea the existence of an epithelium and a 
structure, called by Valentin a papillary body, 
similar to what is found on the surface of the 
sclerotic conjunctiva, as also a stratum of blood- 
vessels, we must admit a cellular support for 
those vessels, however delicate. If so, the 
bloodvessels and cellular tissue would consti- 
tute the essential elements of a chorion.t We 
can only explain the development of those ex- 
tensions of membrane like sclerotic conjunctiva, 
over the cornea by supposing an irregular and 
undue development or hypertrophy of these 
elements. 

The question, “ Does the conjunctiva’ ex- 
tend over the cornea?” may be considered as 
answered in the affirmative by the above ana- 
tomical demonstration. Morbid anatomy 
now comes in advantageously with its corro- 
borative evidence. ‘ Nothing is more in 
favour,”’ says Eble, “ of the existence of a con- 


* In Ammon’s Zeitschrift Bd. v- p- 2], Table I, 
Fig. 9 and 11. See also Miiller’s Archiv, 1836; 
Jahresbericht, p. 28; and Henle De Membrana 
Pupillari, &. Bonne, 1832. 

+ Medico-Chirurgical Transactions, vol. xxi. p. 
414, London, 1838; London Medical Gazette, vol. 


xxiil, pp. 571, 702, 815. 


junctival layer on the cornea than the microsco- 
pical structure of this membrane, for there is 
the greatest resemblance between the structure 
of the sclerotic conjunctiva and the investment 
of the cornea.”* Eble thus retracts the opinion 
he formerly expressed against the existence of a 
conjunctival layer of the cornea. 
xternally the sclerotica overlaps or en- 
croaches on, more or less, the edge of the 
cornea. In certain constitutions,and especially 
in old persons,t I have observed that the 
overlapping part of the sclerotica is thicker and 
more opaque than usual—perhaps also en- 
croaching more extensively on the cornea. The 
conjunctiva covering the overlapping sclerotica, 
especially when the latter is to any considerable 
extent, appears in its independent form with its 
chorion fully developed, and although it ad- 
heres to the subjacent overlapping part of the 
sclerotica very closely by cellular tissue, it by 
no means presents the same intimate union 
with the subjacent structure and the same rudi- 
mentary state which the conjunctival extension 
over the transparent cornea has. In an eye 
before me in which the overlapping sclerotica 
is to some considerable extent at the upper 
edge of the cornea, I easily raised up in a fold 
and then separated by dissection the perfectly 
developed conjunctiva from over the part. The 
conjunctiva covering the overlapping part of the 
sclerotica has a vascular connexion with the 
latter no otherwise than by the anastomoses of 
the proper vessels of each—a vascular con- 
nexion, which iadeed subsists between the scle- 
rotica and conjunctiva elsewhere. The dispo- 
sition just described is connected with a point 
in the pathology of the eye, viz. the bluish 
white ring which is observed to encircle the 
cornea more or less completely in certain inter- 
nal inflammations of the eye, and so frequently 
in what is called arthritic iritis that it has been 
considered a diagnostic of it, but certainly with- 
out just grounds. 

Before explaining the cause of the appear- 
ance, I would request it to be remembered that 
the insertion of the ciliary ligament is at some 
little distance from the apparent margin of the 
cornea; that the vessels which form the red zone 
of the sclerotica in the internal inflammations 
of the eye, and in inflammation of the proper 
substance of the cornea, are vessels which send 
branches inwards to the iris, opposite the ciliary 
ligament, branches outwards to anastomose 
with those of the conjunctiva, and lastly, 
branches which, following the original direc- 
tion, go to be distributed to the proper sub- 
Stance of the cornea. These vessels are not 
apparent in the healthy state, and one set of 
them only may become apparent in inflamma- 
tion. Thus in inflammation of the iris, they 
will be apparent only as far as opposite the in- 
sertion of the ciliary ligament. Between this 
and the clear part of the cornea is the opaque 
overlapping part of the sclerotica, which of 


* Medicinische Jahrbiicher des k. k. oester- 
reichischen Staates ; Neueste Folge. Band xvi. 

+ The arcus senilis, it is to be remembered, is not 
here the question. 


LACRYMAL ORGANS. 


course not being in the way of the progress 
the vessels towards the inflamed part, reme 
white as usual, and the cornea not be 
affected the minute branches to its proper s 
stance remain unenlarged and unseen. He 
the overlapping part of the sclerotica is see 
contrast between the abruptly terminatin 
sclerotic zone on the etter and the tr 
parent cornea (a ing on account 01 
dark phar 9.1 17 it) on the other, fort 
the bluish white ring. . " 
From this explanation the bluish 
round the cornea ought to exist more or | 
all internal inflammations of the eye, w 
obscured by vascularity of the conjuncti 
inflammation of the cornea. So itdoes; 
in persons of otherwise sound constitution” 
not of advanced age, the overlapping sclen 
is so transparent and sometimes also to so $1 
an extent, that it is not strongly contrasted” 
the transparent cornea. It is otherwise the ¢ 
however, in certain persons, especially sucl 
are advanced in life, in whom the encroa 
ment of the sclerotica and fully developed ¢ 
junctiva on the cornea exists to a great det 
and in a very opaque state, that the bb 
white ring appears in the exaggerated disti 
ness which has commonly attracted the n 
of surgeons. : m 
The condition of the eye mene for 
distinct appearance of the bluish-white Th 
round the cornea occurring principally in ¢ 
persons of bad constitution, and these be 
the very persons in whom an internal inflamm 
tion of the eye very often presents 
called the arthritic character, are 
which readily explain the error of sup 
the bluish white ring round the cornea diag) 


ae 
. “1 
CurmMsta 


III.—Lacrymal organs properly so called. 
Under this head are comprchentell 1. r 
secreting lacrymal organs, or the lacrymal gl 
and its excretory ducts. 2. The derivative I 
crymal organs, or the es by which t 
secretions of the lacrymal gland and of t 
conjunctival surface are drawn off é 
nose, viz. the lacrymal points, the lacryr 
canalicules, the lacrymal sac, and nasal duet 
The lacrymal gland and its ducts may 
considered as a branched diverticulum © 
conjunctiva ; the derivative lacrymal organs, 
use the expression of M. De Blainville, 
nothing but the continuation of the conjunet 
and its anastomoses with the olfactive mi 
brane. a 
1. Secreting lacrymal organs. i 
Lacrymal gland,— Glandula lacrymalis; 
La glande lacrymale ; Ital. La glandula t 
male; Germ. Die Thranendrise. ay 
When the lacrymal caruncle was supp 
to filtrate the succus lacrymalis, and the I 
mal points to excrete it, the lacrymal gl 
was called glandula innominata. re 
The lacrymal gland ( Fig. 13) consis 
of two masses, an upper and a lower. T 
upper mass, or glandula _ Su 
rior, lies in the lacrymal fossa, a depr 


* London Medical Gazette, vol. xxiii. p. 817. 


i 


r LACRYMAL ORGANS. 


% 
_ sion of a size sufficient to receive the point 
; the thumb, situated in the roof of the 
orbit at its upper and outer angle, just 
_ within the overhanging outer extremity of 

the superciliary arch. The superior lacrymal 
‘gland is’ of an oval or triangular shape about 
‘three-fourths of an inch in its longest diameter 
and about half an inch across. It is flattened 
from above downwards. Its upper surface is 
convex; its lower plane or concave. The 
thickest edge of the gland is turned outwards. 
The gland is of a reddish colour and is en- 
eloped in a thin but dense cellular coat. The 
dwer mass of the lacrymal gland, or glandula 
malis inferior, is a loosely connected ag- 
ation of lobules of the same glandular 
substance as the above. It was first described 
by the second Monro, who called the lobules, 
for distinction’s sake, glandule congregate.* 
_ The lower mass of the lacrymal gland is 
he smaller than the upper, with which it is in con- 
. t et above, whilst below it extends to the outer 
part of the upper margin of the tarsal cartilage of 
upper eyelid. It lies indeed in the substance 
of the upper eyelid at the outer part. It is seen 
‘shining through the conjunctiva in everting the 
ri per eyelid. 


mae! 


- Laerymal gland, left side. 


_@a, Superior mass; bb, inferior mass; c, part 
| of inferior mass lying towards the outer canthus. 


Intimate structure of the lacrymal gland.— 
_ The lacrymal gland is what is commonly called 
| conglomerate. It belongs to Miiller’s com- 
pound glands with canals of the ramified type. 
_ “Inthe arrangement of the secreting canals 
_ of the lacrymal glands,” says Miiller,+ “ two 
| principal forms are observed: the one is that 
which I discovered in the chelonian reptiles ; 
the other, that which prevails in birds and 
ammalia. In the chelonia, the gland is 
formed of a number of club-shaped lobes, 
“united together by means of the different ducts 
which run in their interior. The duct of each 
lobe is pretty uniform in diameter, and into it 
“Open an innumerable quantity of microscopical 
ts of coeca, which are arranged around it 


5. * Monro’s Observations, Anatomical and Phy- 
logical, wherein Dr. Hunter’s claim to some dis- 
Goveries is examined, p. 77. Edinburgh, p. 77. 
d senmuller, Partium Externarum oculi humani, 
‘Imprimis organorum lacrymalium descriptio anato- 
| mica, &c. § 109. Lipsie, 1810. 
_. + Handbuch der Physiologie des Menschen, 
Bd.1i. S. Or, Translation by Baly, p. 445. 
| See also ** De glandularum secernentium penitiori 


‘Structura, p. 51, 52, tab. v. figs. 3, 4, 5, & 8. 


4 

i 
iw 
fs 

a 


89 
at right angles like the foliage of a moss on its 
stem.” In birds, in which the lacrymal gland 
is very small and situate at the posterior angle 
of the eye, and Mammalia, the secreting ca- 
nals of the lacrymal gland are regularly 
branched and terminate in each acinus in a 
number of small cells. In birds these cells 
are very large; and in them, and likewise in 
the horse, the cells can be filled with mercury 
from the efferent duct. 

Efferent or excretory ducts of the lacrymal 
glands.—The lacrymal glands pour out their 
secretion by nine. or twelve very slender excre- 
tory ducts which proceed from above down- 
wards and open on the surface of the con- 
junctiva on the inside of the upper eyelid. 
The orifices of the ducts are placed at about 
one-twentieth of an inch apart from each other 
in a row extend\gg about half an inch from the 
outer canthus inwards, parallel to but a little 
above the outer part of the upper margin of 
the tarsal cartilage, that is, at the inferior boun- 
dary of the lower mass of the gland. 

The excretory ducts of the lacrymal gland 
were first discovered on the 11th of November, 
1665, by Nicolaus Steno,* in the eyelid of a 
sheep. He delineated them from the eye of 
the calf. Moreover it appears that Steno de- 
scribes vasa lacrymalia discovered in man, 
which opened in the membrane of the upper 
eyelid. 

Admitted by some and doubted by others 
from the time of Steno, the ducts of the lacry- 
mal gland became a subject of dispute between 
Dr. William Hunter{ and the second Monro,§ 
the one claiming to have observed them in the 
human eye before the other. 

The best way to demonstrate the ducts is to 
stretch the upper eyelid, turned inside out, 
upon the finger; then wipe clean the surface 
of the conjunctiva, and having by close in- 
spection at the place where the ducts open, 
as above described, discovered the orifices, 
take a short piece of human hair in the point 
of a forceps, and entering it at the orifice, 
push it on in the direction of the duct. From 
the orifices on the surface of the conjunctiva 
the ducts run nearly parallel with each other 
upwards. 

Of two eyes before me I have in this way 
inserted hairs into nine orifices of ducts in the 
one and into twelve orifices of the other, a 
work which did not occupy five minutes for 
each eye. In both eyes there is one orifice of 
a duct exactly within the external commissure, 


* Observationes Anatomice, quibus varia oris, 
oculorum et narium vasa describuntur, novique 
salive, lacrumarum et muci fontes deteguntur et 
novum Bilsii commentum rejicitur. Leide, 1662. 
See also Bibl. Anat. Clerici et Mangeti. Genev. 
1699. fol. tom. ii. p. 787. 

+ Thom. Bartholoni epistolarum medicinalium a 
doctis et ad doctos scriptarum centuria iii. & iv. 
Hafniez, 1667-8. Epist. 53. cent. iv. 

$ Monro’s Observations, Anatomical and Phy-_ 
siological, wherein Dr. Hunter’s claim to some 
discoveries is examined, p- 77. Edinburgh, 1758. 

§ Dr. William Hunter’s Medical Commentaries, 
p- 1, containing a plain answer to Professor Monro, 
London, 1762-4. 


90 


and another rather within the lower eyelid. 
See figs. 12 & 14. 


A left eye with the eyelids cut in the middle, and 
the outer halves everted to show the orifices of the 
ducts of the lacrymal gland, into which hairs are 
inserted, 


The preceding description of the lacrymal 
gland and its ducts shows that the latter and 
the lower mass at least of the former may be 
readily wounded along with the upper eyelid, 
and that in Crampton’s operation for entro- 
pium, the lower mass of the gland, together 
with some of the lacrymal ducts, must neces- 
sarily be wounded, if the eyelid be cut through 
near the outer angle and to any height. In 
cases in which I have performed the operation, 
however, I have not observed any lacrymal 
fistula or other bad consequence follow. 

Tears.—Lacryme, Fr. Les larmes; Ital. 
Le lagrime; Germ. Die Thrénen. The lacry- 
mal secretion like the salivary appears con- 
stantly to flow, though in no greater quantity 
than is sufficient to moisten the surfaces of the 
conjunctiva. The derivative lacrymal organs 
are in this case equal to the removal of it; but 
when the tears are poured out in unusual 
quantity, as they are, like the salivary or uri- 
nary secretion as well as that of the skin, in 
certain affections of the mind, they run over 
the margin of the lower eyelids and drop down 
the cheeks. 

According to Fourcroy and Vauquelin there 
remains after evaporating the tears, about one 
per cent. solid substance, which consists chiefly 
of common salt and a yellow extractive matter 
perfectly soluble in water. Before drying, this 
appears quite similar to mucus. 

2. Derivative lacrymal organs. 

Previously to describing the passages by 
which the tears are drawn off into the nose, it 
will be advantageous to take a glance at the 
cipal ps groove and canal in which the prin- 
ci t of those passages is lodged. 

Dhascest groove Por the lodgement of the 
lacrymal sac. The lacrymal groove, sulcus la- 
crymalis, is situated at the fore part of the 
inner wall of the orbit. It is directed from 
above downwards, extending from the junc- 
tion of the frontal bone with the nasal process 
of the superior maxillary and with the lacrymal 
bone, on the one hand, and to the inner and 
lower angle of the margin of the orbit on the 
other. Here it funs into the osseous canal for 
the nasal duct. The lacrymal groove is pretty 


LACRYMAL ORGANS. 


a 
deeply scooped out, and is about eight-tenth 
of weifoace a and five-twentieths broad, _ 

The outer aspect of the nasal Era ft 
superior mt bone is divided by an 
cending ridge, the continuation of that form 
the lower margin of the orbit, into two 
faces. The posterior surface, which is 1 
narrower, forms the anterior half of the lac 
mal groove. The posterior half of the gros 
is formed by that narrow grooved part 
orbital surface of the lacrymal bone in front 
its vertical crest. The line of junction (5 
dylesis ) between the posterior margin of 
nasal process of the superior maxillary be 
and the anterior margin of the lacrymalr 
down longitudinally in the bottom of © 
-groove. _* 

The anterior margin of the lacrymal gro¢ 
formed by the ascending ridge subdividing t 
outer surface of the nasal process of the sw 
rior maxillary bone, is thick and rounded. T 
posterior margin, formed by the crest whi 
subdivides vertically the orbital surface of t 
lacrymal bone, is thin and sharp. a 

Inferiorly the crest of the lacrymal bor 
forms a small curved prolongation directed fo 
wards and outwards, which serves to form t 
commencement of the posterior wall of ft 
osseous canal for the nasal duct. The proce: 
which is called hamulus ossis lacrym a 
culates with the orbital plate of the super 
maxillary.* _ 

The osseous canal for the nasal duct.—Th 
osseous nasal canal, about half an inch | 
length, extends from the lower extremity of # 
lacrymal groove to the lowest meatus of th 
nose, at the anterior of which it open 
Its orifice is overhung by the anterior extrem! 
of the lowest spongy bone. The osseous nas: 
canal is directed a little obliquely from befo 
backwards’ and from within outwards. It i 
somewhat narrower in the middle than at eith 
extremity. It is compressed from within o1 
wards, hence a horizontal section is rathe 
elliptical than circular. 

e anterior and outer walls of the osse 
canal are formed by a groove inclined dow 
wards and backwards on the inner surface 
the body of the superior maxillary bone, t 
continuation of that on the nasal process whi 
contributes to form the lacrymal ve. I 
posterior wall of the canal is im great pa 
formed above by the hamular process of # 
lacrymal bone, where it articulates with 
orbital plate of the superior maxillary. “ 
lowest part of the posterior wall is formed | 
the meeting together of the lacrymal proe 


* In man the lacrymal bone does not alwa 
form a single piece, ‘* In a great numberof cas: 
says M. Rousseau, ‘‘ the lacrymal bone is fo 
divided into two unequal parts, even in aged 8 
jects. The larger contributes to form the inj 
wall of the orbit, the smaller is situated be 
and outside the preceding on the floor of the orbi 
its exposed surface does not measure more thi 
two millimetres in extent, but it dips under t 
vertical crest of the first portion, and contribu 
to form the lacrymal canal.” See ‘* Descript 
d’un nouvel os de la face chez homme,” A 
nales des Sciences Naturelles. Paris, 1829. 


ts 


of the lowest spongy bone and the posterior 
margin of the groove in the superior maxillary, 
constituting the anterior and outer walls. The 
a al wall of the osseous nasal canal is 
formed superiorly by a continuation of the 
seous surfaces composing the lacrymal groove. 
Below, it is formed, in front, by a farther con- 
tinuation of one of these surfaces, viz. that of 
1e age maxillary bone, and behind by a 
thin plate of the lowest spongy bone, the nasal 
or lacrymal process of the lowest spongy bone, 
hich rises to join the inferior edge of the 
erymal. The anterior edge of this process 
f the spongy bone joins the posterior edge of 
le lower part of the lacrymal surface of the 
isal process of the superior maxillary. The 
ne of junction is thus the continuation of that 
it the bottom of the lacrymal groove. 

| Lacrymal papille, points and canalicules— 
"Fig. 15.) At the inner extremity of the ciliary 


ee 


4 Fig. 15. 


mtinuation of Figure 11, ing the relative situa- 
tion of the wpper mass of the lacrymal gland, and 
e exact 8 of the derivative lacrymal passages. 
( From Mote tng. ) 
a, b, c, d, superior and inferior lacrymal canali- 
i; a, a, lacrymal points; 6, 6, the small blind 
atations presented by the lacrymal canalicules, 
here they bend inwards to the lacrymal sac; ¢, ¢, 
ntinuation of the lacrymal canalicules; d, d, 
eir entrance into the lacrymal sac; e, f, g, lacry- 
sac ; é, blind end of the lacrymal sac ; f, middle 
rt of the lacrymal sac; g, its termination ; h, i, 
asal duct ; i, opening of the nasal duct into the 


Margin of each eyelid, where the fissure of the 
Nasal canthus begins, there has been already de- 
ibed a small papillary eminence, lacrymal 
alla, papilla lacrymalis, in the summit of 
hich is a small orifice, lacrymal point, of 
h a size as to admit athick bristle. The 
erymal points, puncta lacrymalia; Fr. Les 
ints lacrymaux; Ital. I punti lagrimali ; 
erm. Die Thranenpunkten ; are from their 
‘Size and situation sufficiently conspicuous as not 
to be confounded with one of the orifices of the 
Meibomian follicles. In the natural state the 
facrymal papillz are inclined towards the lacus 
rymalis. The lower papilla is somewhat more 
rominent than the upper, and situate some- 


¥. 
a 
\ hat more towards the temple. The dacrymal 


LACRYMAL ORGANS. 


91 


canalicules, canaliculi lacrymales, s. cornua 
limacum; Fr. Les conduits lacrymauzx ; Ital. 
I condotti lagrimali; Germ. Die Thrénen- 
kaniilchen ; lead from the lacrymal points into 
the lacrymal sac. From the superior lacrymal 
point the superior canalicule proceeds upwards 
ard outwards within the papilla a little way, 
then suddenly bending at an acute angle and 
forming at the same time a small dilatation, 
it runs downwards and inwards, inclosed in 
the fold of skin and conjunctiva forming the 
upper border of the fissure of the nasal can- 
thus, to the lacrymal sac. The course of the 
inferior canalicule is the counterpart of the 
above. From the lower point it runs a short 
way perpendicularly downwards and outwards 
within the corresponding papilla, then bend- 
ing abruptly apd\ike the upper forming a 
small dilatation, it proceeds upwards and in- 
wards, inclosed in the fold of skin and con- 
juuctiva forming the lower border of the fissure 
of the nasal canthus, to the lacrymal sac. 

The canalicules having met each other at the 
commissure of the fissure of the nasal canthus, 
pass under the tendon of the orbicularis mus- 
cle, and open by separate orifices, close to each 
other however, into the anterior and outer part 
of the lacrymal sac. These orifices indeed are 
separated merely by a duplicature of the mucous 
membrane composing their walls. 

The lacrymal canalicules have pretty firm 
walls of mucous membrane, which do not col- 
lapse, but when cut across are seen gaping 
open. The calibre of the canaliculi is about 
the thirtieth of an inch in diameter; that of the 
points is less, but these are capable of being 
dilated. 

The canaliculi are immediately surrounded 
by the fibres of the internal palpebral ligament, 
and those of the tensor tarsi muscle. 

Lacrymal sac ; saccuslacrymalis ; Fr., Le sac 
lacrymal ; Ital. Il sacco lagrimale; Germ., Der 
Thranensack.—( Fig. 16). This isa membra- 
neous reservoir of a vertically elongated form, 
and externally compressed, nine-twentieths of 
an inch long, and two-tenths broad externally, 


Fig. 16. 


Derivative lacrymal passages of the left side, seen from 
the side of the nasal cavity. 


Here it is seen that the nasal duct is much 
broader viewed from the side than from before. a, b, 
superior and inferior lacrymal canaliculi; ce, d, 
lacrymal sac; e, f, nasal duct; f, nasal orifice of 
the nasal duct, seen quite in its natural state. 


92 


It lies, by its inner and posterior surface, in 
the lacrymal groove, with the periosteum 
of which it is closely incorporated. Its an- 
terior and outer surface, which lies without 
the groove, is immediately covered by a 
strong aponeurosis derived from the upper 
and lower edge of the horizontal tendon of the 
orbicularis muscle, which passes across the la- 
crymal sac a little above the centre. This apo- 
neurosis adheres to the margins of the bony 
Site in which the sac is lodged, and there 

mes continuous with the periosteum. More 
superficially, the anterior and outer surface is 
covered by the muscular fibres of the orbicu- 
laris and by the skin. 

Above the lacrymal sac forms a cul-de-sac or 
blind end,—finis cecus sacci lacrymalis. Be- 
low it passes into the nasal duct. This transi- 
tion is marked by a slight contraction, some- 
times inside, by a circular fold of the mucous 
membrane, of which both are formed. 

At its anterior and outer part, a little below 
its upper blind end, and immediately behind 
the internal palpebral ligament, the lacrymal 
sac receives the canalicules. Overhanging the 
orifices of these there is a small semilunar fold 
of the mucous membrane of the sac.* 

The nasal duct; ductus nasalis; Fr., Le 
canal nasal ; Ital., Il condotto nasale ; Germ., 
Der Nasenkanal, is a laterally compressed 
canal, about three-quarters of an inch in length, 
and readily admitting the passage of a probe 
the fifteenth of an inch thick, continued from the 
lower part of the lacrymal sac. Itruns downwards, 
backwards, and a little outwards in the osseous 
canal already described, of which it is indeed 
nothing but the membraneous lining. The 
nasal duct is more contracted in its middle than 
at either extremity. It opens in the anterior 
and upper part of the lower meatus, at the 
lateral wall of the nasal cavity, and about one 
inch from the entrance of the nostril. Its ori- 
fice, which is overhung by the lower spongy 
bone, is a long fissure, oblique from above 
downwards and from within outwards. The 
obliquity of the orifice of the nasal duct is 
owing to the circumstance that the posterior or 
external wall of the membraneous part of the 
nasal duct descends farther than the osseous 
canal, and forms, by means of the folded pitui- 
tary membrane, a semi-canal, which descends 
in the external wall of the lower meatus, whilst 
the internal wall of the membraneous part of the 
nasal duct is shorter, and terminates where the 
osseous canal stops. 

The lacrymal sac and nasal duct are com- 
posed of a thick soft mucous membrane, which 
must be considered as productive of that of the 
nose. Externally, this mucous membrane is 
united with the periosteum of the osseous sur- 
faces in connection with the lacrymal sac and 
nasal duct, and as far as concerns that part of 
the lacrymal sac not in the osseous groove, by 
the aponeurosis derived from the tendo palpe- 
brarum. 

Internally, the mucous membrane of the la- 
crymal sac and nasal duct forms various small 


* Rosenmiiller, op. cit. § 125. 


LACRYMAL ORGANS. a 


plicee or ruge. Red and villous, it is q 
different from the white and smooth mu 
membrane of the canalicules. Like the j 
tary membrane of the nose, it secretes, in 
healthy state, a clear, mild, fluid mucus. — 
Lacrymal or tensor tarsi muscle —He¢ 
perhaps the proper place to notice a mi 
which was discovered many years ago 
Duverney,* delineated and described by] 
miller+ in 1805, and more recently re des 
by Dr. Horner,t an American anatomist, 
whose name it is now commonly associate 
To get a view of this muscle, Professor 
ner directs us to cut through the eyeli 
separate them from the ball, at the 
canthus ; then turn the lids over the nos 
move the semilunar fold and the conjunctit 
the neighbourhood, with the fatty matter, 1 
the muscle, such as it is represented in th 
lowing description, will be seen. “a 
“The tensor tarsi arises from the post 
superior part of the os unguis, just in ady 
of the vertical suture between the os planum 
the os unguis. Having advanced three lin 
bifurcates ; one bifurcation is inserted a 
the upper lacrymal canalicule, and termi 
at its punctum, or near it; and the lower b 
cation has the same relation to the lower 
mal canalicule. The base of the laer 
caruncle is placed in the angle of the bifurea 
The superior and the inferior margins of 
muscle touch the corresponding fibres of 
orbicularis palpebrarum, where the latte 
connected with the margin of the internal 
thus of the eye, but may be readily di 
guished by their horizontal course. The 
face of this muscle adheres very closely to 
portion of the sac which it covers, oe als 
the lacrymal canalicules. The lacrymal 
rises about a line above its superior margin, 
extends in the orbit four lines below its infe 
margin. The orbital face of the muse 
covered by a lamina of cellular membrane, 
between this lamina and the ball of the eye 
placed the semilunar fold of the conjun 
and a considerable quantity of adipose ma 
As the bifurcated extremities of the musel 
low the course of the canalicules, they are 
vered by the conjunctiva. The muscle i 
oblong body, half an inch in length, and a 
one quarter wide, bifurcated at one end; ai 
arises much deeper from the orbit than am) 
knowledged origin of the orbicularis. é 


i 


* Cuvres Anatomiques de M. Duverney, to 
4to., Paris, 1761. After speaking of the fib 
the orbicularis which lie over the lacrymal si 
said (tom. i. p. 130), “« Entre ces fibres, il ; 
petit muscle au dédans du grand angle qui) 
son origine de la partie anterieure de 1’os pla 
et s’insere a la partie interne du tendon mitoys 
commun 4 l’apposé de l’orbiculaire; c’est un 
muscle que j’ai observé il y a long-temps.” 

+t Rosenmiiller, Icones Chirurgico-An 
Wiemar, 1805. See also Mackenzie in 
Gazette, vol. xi, 

t Medical Repository for July, 1822. 
A Treatise on Special and General . 
William E. Horner, M. D., Professor of An 
in the University of Pennsylvania, &c, vol. 
498. Philadelphia, 1826. itn 


ra 


s LACRYMAL ORGANS. 


perior fork, however, has a few of its fibres 
ended with the ciliaris.” 

The action of the muscle appears to be to 
rect the lacrymal papille and points in to- 
ards the lacus lacrymalis, and to assist in 
eping the edges of the eyelids properly ad- 
_ justed to the eyeball. 

| WNerves.—The parts of the organ of vision 
which have been just described receive their 
ves from the fifth and seventh pairs; the 
her communicating sensibility, the latter the 
power to move. See articles, FirrH Pair oF 
PRVES, and SEVENTH PAIR OF NERVES. 
The first division of the fifth pair gives 
nerves not only to the accessory parts of the 

ye, but oo Ane also the eyeball ; hence it is 

illed ophthalmic. The second division of the 

th sends filaments to the lower eyelids. 
Nerves from the first division of the fifth 
| distributed to the accessory parts of the eye — 
' The first division of the fifth pair or the oph- 
thalmic divides into three nerves, the,fron- 
‘al, the nasal, the lacrymal. 
1. Frontal nerve. The supra-trochlear 
branch of this nerve gives filaments to the 
upper eyelid and inner canthus. The continu- 
ation of the frontal nerve sends filaments to the 
upper ary and external canthus. 

2. Nasal nerve. The infra-trochlear branch 
of this nerve supplies the parts at the inner 
panthus, the conjunctiva, the lacrymal caruncle 
and lacrymal sac ; it also gives filaments to 
the orbicularis palpebrarum. The tensor tarsi* 
eceives two twigs from it. The infra-trochlear 
sends branches upwards, which anastomose 
with those of the supra-trochlear. 

3. Lacrymal nerve—After supplying the 
lacrymal gland the branches of this nerve 
emerge from it, and ramify in the conjunctiva, 
rbicularis muscle, and skin of the eyelids. 
e lacrymal nerve forms anastomoses with 
ther branches of the fifth. 
Nerves from the second division of the fifth 
Pair distributed to the accessory parts of the 
é.—The principal of these is the inferior 
alpebral branch of the infra-orbital. The in- 
rior palpebral nerve divides into two branches, 
h external and an internal, which indeed 
"tay be separate from the first. 
The external branch runs in the substance of 
the lower eyelid, distributing branches in its 
Course, to the outer canthus, where it anasto- 
noses with the inferior palpebral filaments of 
the lacrymal nerve. 
|_ The internal branch supplies the part of the 
ower eyelid towards the nose, and terminates 

‘in the parts at the inner canthus, anastomosing 
_ with a branch of the infra-trochlear. 

The facial or portio dura of the seventh pair. 
Of the accessory parts of the eye, the orbi- 
tularis muscle is that which receives branches 
from the portio dura of the seventh pair; per- 
ier, also, the tensor tarsi muscle, as Mac- 
¥ 
2 * Rosenmiiller, Icones chirurgico-anatomice. 
eimar, 1805. 

Trasmondi, Intorno la Scoperta di due Nervi 

Il” Occhio umano ragguaglio. Estratto dal Gi- 
ale Arcadico, t. xix. p. T Roma, 1823, 


93 


kenzie conjectures. These branches of the 
portio dura freely anastomose with the branches 
of the fifth pair above described. 

To this superficial notice of the nerves of 
the accessory parts of the eye described in this 
article, all that requires to be added is, that the 
levator palpebre superioris receives its nervous 
filaments from the third pair. 

Bloodvessels.—1. Arteries.—The branches of 
the external carotid ramified on the face and 
the ophthalmic artery from the internal carotid 
are the sources from which the accessory parts 
of the eye receive their arteries. 

The branches of the external carotid in the 
face, viz. the facial, the infra-orbital of the in- 
ternal maxillary, the transverse artery of the 
face and the temporal send ramifications to the 
eyelids. Towards\the inner canthus the facial 
ends in the angular artery, which anastomoses 
with the nasal branch of the ophthalmic. The 
angular artery, or some one of its branches, is 
implicated in the operation for fistula lacry- 
malis as it is called. 

The ophthalmic artery gives off the acrymal, 
usually one of its first branches after its en- 
trance into the orbit. The lacrymal supplies 
the upper and lower masses of the lacrymal 
gland, besides other parts in the orbit, and at 
last issues from that cavity at the external 
angle of the eye. The muscular arteries of the 
ophthalmic, after supplying the recti muscles, 
are continued forward on the front of the eye- 
ball—one from the external rectus muscle, and 
two from each of the other recti. These arte- 
ries divide into two sets of branches, of which 
one set ramify in the ocular conjunctiva, and 
the other set supply the sclerotica. 

The ophthalmic, as it issues from the orbit at 
the internal canthus, gives off the palpebral 
arteries, superior and inferior. These ramify, 
in their respective eyelids, towards the external 
angle, where they meet and inosculate with the 
terminating branches of the lacrymal artery. 
The superior palpebral artery, moreover, inos- 
culates with the supra-orbital and anterior tem- 
poral ; the inferior palpebral artery with the 
nasal branch of the ophthalmic, the infra- 
orbital and transverse artery of the face, thus 
forming the tarsal or palpebral arches. 

The ramifications sent, from. the branches of 
the external carotid in the face, to the eyelids, 
and those from the ophthalmic, form by their 
inosculations a network, from which are sup- 
plied the different structures of the eyelids, the 
conjunctiva, the lacrymal caruncle, and ‘the 
lacrymal sac. 

Where the ocular and palpebral portions of 
the conjunctiva run into each other, bloodves- 
sels from the muscular enter and subdivide into 
two sets of branches—one set smaller, to the 
ocular conjunctiva, the other set larger, to the 
palpebral conjunctiva. The latter receives 
another and a still larger set, which enter it at 
the orbital margin of the tarsal cartilages, 
anastomose with the first set, and ramify for- 
wards to the free margin of the eyelids. 

The bloodvessels of the ocular conjunctiva 
are few and small in comparison to those of 
the palpebral. They atlect a reticular arrange- 


94 


ment, uced partly by the vessels crossi 

over RL ereirec sept, and partly by thoweis: 
lations. The latter is particularly the case 
around the cornea. It is only in the inflamed 
state—in catarrhal ophthalmia—that the vessels 
of the ocular conjunctiva can be well seen. 
In catarrhal opbthalmia, large superficial tor- 
tuous vessels are observed proceeding in a di- 
rection towards the cornea; a few of the same 
Size are seen crossing these, especially at a dis- 
tance from the cornea. Underneath the large 
vessels is a network of smaller ones, the 
branches of the larger. The arrangement of 
the vessels around the margin of the cornea 
has been already noticed. It can scarcely be 
doubted that the large dark-coloured varicose 
vessels, derived from the muscular, seen in the 
conjunctiva in the so-called arthritic states of 
the eye, are veins, as also the largest and most 
tortuous of those seen in catarrhal ophthalmia. 

Of the two sets of vessels distributed to the 
conjunctiva, one set supplies the conjunctiva 
ager the palpebral sinuses, the other that 
part of the conjunctiva which corresponds to 
the tarsal cartilages. Both sets give off nu- 
merous branches, which subdivide very mi- 
nutely in the papillary body. The second set, 

having given off their ramifications to the 
papillz, proceed towards the margins of the 
eyelids ; following, in the upper, a straighter 
and more parallel direction than in the lower. 

2. Veins.—The veins from the eyelids dis- 
charge their blood into the anterior and pos- 
terior facial veins. 

The blood from the other accessory parts of 
the eye is returned to the cavernous sinus by 
the ophthalmic veins, of which there are two 
to each eye:—one called the cerebral oph- 
thalmic, and the other the facial ophthalmic 
vein. 

Cerebral ophthalmic vein.—Larger than the 
facial ophthalmic vein, this begins at the inner 
angle of the eye, from the upper end of the an- 
terior facial vein. From this it passes back- 
wards through the orbit to the inner part of the 
superior orbital fissure, by which it enters the 
cranium, where it empties itself into the caver- 
nous sinus—seldom into the circular sinus. 
In this course it has several communications 
with the facial ophthalmic. The cerebral oph- 
thalmic vein receives directly or indirectly, 
besides the veins from the different parts of the 
eyeball and its muscles, a vein from the lacry- 
mal sac, and from the parts lying at the inner 
canthus ; the anterior nasal vein, the lacrymal 
yein, and the posterior nasal vein. 

Facial ophthalmic vein.—This receives the 
infra-orbital and some other deep veins of 
the face, besides some veins from the eyeball. 
The deep branch of the anterior facial vein 
takes one of its origins from it. The facial 
ophthalmic vein leaves the orbit by the supe- 
rior orbital fissure, and opens into the cavernous 
sinus below the cerebral ophthalmic. 

Comparative anatomy and development.— 
In ‘the description just given of the accessory 
parts of the human eye, allusion has been occa- 
sionally made to their structure in the lower 
animals; here such further observatjens will be 


LACRYMAL ORGANS. 


offered as may tend to illustrate_their physic 
gical importance in the animal series, 
And first, it may perhaps be well to’ ee] 
mind that, although generally speaking, or 
traced from the higher to the lower animals 
observed to become depreciated in dey 
ment; still that this is by no means ali 
the case in a ratio corresponding to 
tion of the animal in our classifications. 
the circumstances connected with the me 
life of an animal, be it mammal, bird, rep 
or fish, may be such as to call for a great 
less development of some pear 0 
Thus, though in the mammifera we find 
eyelids very perfectly developed, and in 1 
in an extremely imperfect state, or ent 
wanting, and though we find gradatior 
tween these two extremes in the 
ing an intermediate place, still there ¢ 
mammiferous animals in which the in gull 
passes right over the eyeball without form 
any palpebral fold; and there are fishes 
which there are not only palpebral folds, 
also an orbicular muscle, Again, the s 
lunar fold of man and the higher quad: 
is enlarged in quadrupeds into the membr 
nictitans, and in birds forms the very artifict 
constructed third eyelid, which subsists, th 
in a less perfect state, in reptiles, but in fis 
where the structure does exist, it is found a 
reduced toasemilunar fold. In man thela 
mal gland is large. In the lower mammi 
generally, in birds, and in the higher 
lacrymal gland is also found, But it is si 
in proportion to another gland situated at 
nasal canthus of the eye, the glandule 
Harder, which is developed in a direct pro 
tion with the membrana nictitans, or third ¢ 
lid, and to which it therefore belongs. I 
and the quadrumana there is no trace of 
glandule of Harder. It is incorrect to view" 
lacrymal caruncle in that light, for both 4 
exist together. 
Besides these differences in the developmi 
of the accessory parts of the organ of vis 
observed in the animal series and capabl 
being generalised, there exist specific ar 
vidual differences which can only be notice: 
detail. 4 
1. Eyelids. 
In subterranean mammifera, as the blind 
the chrysochloris of the Cape, the comm 
mole ; among reptiles, in the pipa, which I 
in obscure places; and in perennibranehi 
batrachia, which inhabit subterranean I 
or marshes, as the proteus and syren; an 
fishes which burrow in the mud or sand. 
the anguilliform and certain cyclostoma 
fishes, the eyes are very small, and the comt 
integument passes right over them w. 
forming any palpebral fold. In the Ophi 
reptiles as first pointed out by Jules Cloc 
in Geckoes among the Saurian les, 
shewn by J. Miiller ; and even in the blind1 
according to the latter author, there is a €ol 
pounding of the simple continuation of thei 
teguments over the eyeball, as described ab 
with the existence of a conjunctiva undernea 
enclosing an oculo-palpebral space. Thiss 


“1... 
—3bi8 


Ppt 


F LACRYMAL ORGANS. 


we will be described in speaking of the con- 
junctiva. In birds there is no example of the 
eyeball being covered over in a similar manner 
bya continuation of the-skin. 
.) In man the upper eyelid is the more de- 
“yeloped and the more moveable. Descending 
n him the lower is found gradually to 
issume the superiority in this respect. In the 
eetacea the upper.and lower eyelids are tumid 
olds of skin enclosing fat, but no tarsus, and 
xe Meibomian glands are entirely wanting. 
Phere is no orbicularis palpebrarum muscle, 
ut muscular fibres proceed from the anterior 
and posterior end of the orbital process of the 
frontal bone to the eyelids in the region of the 
outer and inner canthi. Instead of the levator 
alpebree superioris there is a hollow conical 
muscle which arises from the circumference of 
he foramen opticum and terminates in the eye- 
ids. A similar in four divisions occurs in the 
_ seal.* In the echidna there is a circular eye- 
In birds the lower eyelid is in general 
much larger and more moveable than the 
yper. In the ostrich and some parrots both 
elids are equally moveable. 
In birds the eyelids are closed in death. In 
the gallinaceous birds which I have examined 
_ this appears to be owing to an expansion of 
 @lastic membrane attached to the margin of the 
orbit and interlaced round the eyelids. During 
life the lower eyelid is opened by muscular 
ction by a proper depressor muscle. The 
ipper eyelid retains its levator. There is a 
tarsal cartilage in the lower eyelid; in the 
ipper eyelid there is a less dense fibrous struc- 
ure. The skin of the lower eyelid is naked 
md finer than that of the upper in accordance 
with its greater mobility. 
In chelonian reptiles the lower eyelid is, as 
n birds, the larger and more moveable ; and as 
_ the more moveable the eyelid the finer the 
integument, so in them the lower eyelid is naked 
as in birds. 
Tn lizards the eyelids form a sort of sheet 
stretched before the eyeball with a horizontal 
fissure closed by a circular muscle and opened 
bya levator and depressor. In the chameleon 
the palpebral fissure is represented by a small 
hole opposite the pupil. Tracing the eyelids 
in a general way from batrachian reptiles to 
fishes, we find a gradual depreciation of struc- 
| ture; thus salamanders have two folds of skin, 
‘upper and under, for eyelids, but not sufficient 
to cover the eyeball, whilst the pipa has none. 
_ In fishes generally, the skin before passing over 
he front of the eye becomes finer and forms a 
| slight circular fold, often only well-marked 
me bove Sometimes there is an anterior and a 


sterior semilunar fold, as in the herring, 
lmon, but especially in several of the shark 
It is the Orthagoriscus mola which has 
“circular folds for eyelids, and an orbicular mus- 
ele for closing them. The eyelids are again 
opened by five radiating muscles. 


| *Rapp, Die Cetaceen Zoologisch-anatomisch 
; t, Stuttgardt and Tubingen, 1837, quoted 
oe Miller’s Jahresbericht, p. cxx. in Archiv, 


i 
a 
4 
— 
i 


95 


Among the invertebrata some of the cepha- 
lopoda have large palpebral folds. In the 
octopus “the eyes are small in proportion, and 
the skin is drawn over them so as to cover them 
entirely at the will of the animal.”* There are 
no eyelids in the sepia officinalis, but a con- 
tinuation of the integuments passes over the 
eye. 

rycen and eyelashes occur only in a few 

mammalia. Eyelashes exist in the pachyder- 
mata, ruminants, &c. but are wanting especi- 
ally in small mammals. Meibomian glands 
are commonly found. 

In birds the eyelids sometimes present cilia. 
This is the case only in some birds of prey, in 
some parrots, in the ostrich, &c. but seldom in 
other orders. Very small Meibomian follicles 
are said to exist imhe eyelids of birds. In the 
eyelids of a common fowl at present before me, 
there are small transverse fissures on the mar- 
gin of the lids filled with a sebaceous matter. 
They have the appearance of very small Mei- 
bomian glands, not closed as in the mammifera, 
but open along their whole length. 

In a preceding part of this article I remarked 
on some points of resemblance between the 
iris and eyelids, as regards functions, and sym- 
pathy in the performance of those functions. 
In some of the lower animals there are certain 
eee in which they even approximate in form. 

n connexion, therefore, with the subject of the 
eyelids it will not be out of place to allude to 
that flocculent growth of the uvea hanging 
from the upper margin of the iris over the trans- 
versely elongated pupil in the horse, &c. and 
which appears to serve the purpose, if it may 
be so expressed, of an internal eyelid. An 
analogous but more curiously and highly deve- 
loped structure—a blending as it were of the 
iris with some remains of the structure of the 
eyelids—exists in the eyes of several fishes ; 
among others in the skate. 

The structure alluded to is a digitated exten- 
sion of the whole substance of the upper part of 
the iris, hanging over the pupil, which it is 
large enough entirely tocover. There being no 
intrinsic power of motion in the iris of fishes, 
the mechanism by which this digitated veil is 
drawn up from over the pupil is this :—Where 
the upper part of the ciliary margin of the iris 
is connected with the sclerotica, the latter is 
very flexible and is externally intimately con- 
nected with a fold or rudimentary eyelid which 
the integument forms before passing as con- 
junctiva over the eye. Muscular fibres are 
inserted into this fold at the point of connexion, 
and draw it upwards; the flexible part of the 
sclerotica of course follows this movement and 
the upper part of the iris, the sclerotica, so that 
the digitated veil is drawn up from over the 
pupil. In a young skate which I removed 
from the egg and preserved alive for some 
weeks, I observed that the digitated veil was 
kept down during the day, but was drawn up 
toward evening, and the large black pupil 
exposed. 


* Cuvier, Regne animal, vol. iii. p. 12, Paris, 


96 


2.—The conjunctiva.—Semilunar fold, mem- 
brana nictitans or third eyelid —Lacrymal 
caruncle and glandule of Harder. 

The existence of eyelids supposes a con- 
junctiva,—that is, the integument modified 
into a mucous membrane lining the posterior 
surface of the eyelids, covering the front of the 
eyeball, and thus connecting these two parts 
together. In those animals in which there is 
no palpebral covering either in the usual form 
of eyelids, or in that anomalous form in which 
there is no palpebral opening, there is, properly 
speaking, no conjunctiva: at the most, the com- 
mon integument may be softer, thinner, and 
more transparent where it covers the eye. 

The points deserving particular notice in the 
comparative anatomy of the conjunctiva are, 

1. The oculo-palpebral space of the con- 
junctiva. 

2. The membrana nictitans and third eyelid, 
with the glandule of Harder. 

In most animals the oculo-palpebral space of 
the conjunctiva is as it has been described in 
man. on as have been generally regarded 
as being without eyelids and vie lacrymales. 
The eye, indeed, has been commonly described 
as covered by a transparent lamella of epider- 
mis, which is cast with the rest of the epider- 
mis; and this has been often adduced as an ar- 
gument in favour of the extension of the con- 
junctiva over the cornea in other animals. Ser- 
pents have a palpebral covering, a conjunctiva 
and vie lacrymales; but the conformation of 
these parts is quite peculiar. For the first true 
exposition of the point we are indebted to Jules 
Cloquet.* 

In the article Heartnc, Orcan or, at the 
end of the section on the parallel between 
the ear and the eye, it is said, “ A part in 
the composition of the appendages of the 
eye analogous to the membrana tympani is 
only to be conceived by supposing the exist- 
ence of a mediate anchylo-blepharon, that is, 
an irregular membrane stretched between the 
edges of the eyelids, uniting them together, and 
closing in the space lined by the conjunctiva, 
which space would now communicate with the 
exterior only by the lacrymal canalicules and 
nasal duct, in the same way that the tympanic 
psig communicates with the exterior only by 
the Eustachian tube.” The mediate anchylo-ble- 
pharon here supposed is the actual and regular 
structure in serpents, and is the sole cause of 
the apparent anomaly in the conformation of 
their eye repenaem. The structure is this:— 

Around the margin of the orbit the skin ap- 
pears as if it formed a palpebral fold, covered 
with scales, and representing a sort of frame, in 
which is set, as it were, a transparent continua- 
tion of the skin before the front of the eye. But 
this is not the conjunctiva; it is a natural me- 
diate anchylo-blepharon, or a palpebral covering 
without palpebral fissure. It is, however, 
transparent, and was therefore formerly con- 
founded with the cornea. A conjunctiva lines 
the inner surface of this palpebral covering 


* Memoire sur 1’Existence et la Dis 


ition des 
Voies Lacrymales dans les Serpens. i 


aris, 1821, 


LACRYMAL ORGANS. 


without bral fissure, and invests the, 
part of » P bital, cavity, peeps 


flected on the sclerotica, and is from | 
continued over the cornea, closely adheri 
it. oe 

The conjunctiva thus forms a sac fe ut 
Jules Cloquet oculo-palpebral sac of the 
junctiva), confining a X Sg (which may ii 
manner be called oculo-palpebral) into} 
open the excretory ducts of the lacrymal g 

rom it the tears are drawn off by a cane 
tween the jaw and palate bone into the mx 
of which more will be said fartheron. 


Vertical section of the eye of the common viper, to 
rs disposition of the conjunctiva. ( 


a, the eyeball; 5, the optic nerve; ¢, the eye 
d,d, the scales surrounding the eyelid, ar 
which it appears as if at ae e, e, f 
culs-de-sac formed by the oculo-palpebral conj 
tiva on being reflected from the orbital cavity | 
the eyeball; f, cavity of the oculo-palpebral s 


the conjunctiva, 


‘ 


From the above description it will be reat 
understood how it is from the palpebral 
sion of the skin that the epidermis falls 
the skin is said to be cast, and not from th 
junctiva. 2 

Muller* has found the above structure in 
true serpents, even in the amphisbeenz, wh 
eyes are covered with thick skin. I do 
know if it has been observed in ccecilize ¢ 
He has found a similar structure among 
saurian reptiles in the geckoes, even in 
genus phyllurus. He has even found it | 
mammal, spalax typhlus,t the ore of wh 
appear to be covered by the thick hairy s 
underneath which, however, there is a su 
sac of conjunctiva. In the chameleon: 
follow the family of the geckoes, in Cu 
arrangement, there is a near approach t 
same structure, the palpebral covering pre 
ing only a very small palpebral opening © 
site the pupil. _ 

The membrana nictitans and third eyeli 
In the quadrumana, as in man, the conj 
tiva forms at the nasal canthus a simple : 
lunar fold, but larger. In the. other 
fera, including the herbivorous cetacea, and 


* Ueber eine Merkwiirdige Eigenthiimlichk 
Bau der Augen und Threnence e bei 
Geckonen. In Ammon's Zeitschrift, Bd, i. py 

+ Handbuch der Physiologie des Mens 
Zweiten Bandes Zweite Abtheilung, S, 313. 
blentz, 1838. 


4 


ae 
+4 


LACRYMAL ORGANS. 


cerns only the true cetacea, this fold is deve- 
_ loped into the membrana nictitans, which is 
disposed vertically within the horizontal eyelids 
__ at the nasal canthus, and is capable of being 
“pushed more or less towards the temporal can- 
thus, over the front of the eyeball. 

___ The membrana nictitans derives firmness 
_ from a thin plate of cartilage, which has some- 
$s asort of pedicle passing backwards by 
* 


he inner side of the eyeball. In the sheep, for 
xamp!e, the cartilage of the membrana nicti- 
ns is of the shape of the letter T. The cross 
p forms the margin of the membrane; and the 
eg, closely embraced by the glandule of Har- 
er, extends backwards between the eyeball 
ind inner wall of the orbit. -The cartilage of 
1 Membrana nictitans, unlike the tarsal car- 
lages, is true cartilage, with nucleated cor- 


In the elephant it is said there is a muscular 
rangement for carrying the membrana nictitans 
jutwards over the front of the eyeball. I think 
_ Ihave observed in the rabbit that the mem- 
_ brana nictitans receives part of the expansion of 
e levator of the upper eyelid. The membrana 
ctitans has not, however, like the third eyelid 
ds, any proper muscular apparatus; and 
an it is moveable, the motion is produced by 
eyeball, on its being retracted deeper into 
‘orbit by the retractor muscle, which dis- 
es and presses forwards the cartilaginous 
pedicle above described. 

_ The structure called semilunar fold in man, 
d membrana nictitans in quadruped mam- 
mifera, has attained its greatest development 
in birds, in which it is called the third 
It is transparent and capable of 
ing the whole front of the eyeball. En- 
ed in the conjunctival reduplication there is 
a fibro-cartilaginous structure, very thin and 
membranous. Of a triangular form, the third 
; elid has its free margin oblique from above 
downwards, and from without inwards. In the 
State of repose it is retracted and folded verti- 
) cally in the nasal angle of the eye. The third 
slid is drawn over the front of the eye by a 
very peculiar mechanism consisting of two 
Thuscles, the slender tendon of one of which 
funs through an elongated loop in the broad 
free end of the other. This muscular apparatus 
is supplied by the nervus abducens. 


lt! 


a a ae stad me 


The guadratus is a broad thin trapezoidal 
scle. It arises from the upper and posterior 
part of the eyeball, behind the prominence of 
ats largest circumference. From this point its 
fibres, which form a thin but broad fleshy belly, 
cend towards the optic nerve, converging 
Somewhat. It then terminates abruptly in a 
nee tendinous margin, close to the upper part 
of the optic nerve. In this free tendinons mar- 
in, which is considerably narrower than the 
n, there is an elongated loop or canal, in 
hich the tendon of the other muscle plays. 
_ Pyramidalis muscle-—The fleshy part of 
his muscle is comparatively smaller. It arises 
»y a broad curved base from the lower part of 
jhe eyeball, opposite the preceding. In its 
}scent towards the optic nerve, the muscle be- 
jomes contracted, and at last ends in a slender 
VOL. III. 
i 


97 


tendon on the nasal side of the optic nerve- 
The tendon immediately enters the pulley-canal 
in the extreme margin of the quadratus, and in 
traversing it turns round the upper part of the 
optic nerve. Thus changing its original direc- 
tion, it passes downwards on the temporal side 
of the optic nerve to the lower part of the eye- 
ball, round the prominent circumference of 
which it turns to get to the front of it, 
when it immediately enters the lower angle 
of the third eyelid. Having entered, it di- 
vides into two parts, one of which expands 
and runs between the layers of conjunctiva, 
forming the third eyelid, to the nasal angle of 
the eye ; the other passes along and forms the 
pretty firm free margin of the eyelid in question. 
Having traversed the whole margin of this and 
arrived at the upper part of the eyeball, it is 
inserted into the sclerotica just at the middle of 
the line whence the guadratus derives its origin. 
It is by this arrangement that the superior angle 
of the third eyelid is attached to the sclerotica, 
and consequently rendered immoveable. 

By its own elasticity the third eyelid remains 
retracted at the nasal angle of the eye. In this 
state its tendinous margin is relaxed ; but when 
the two muscles just described contract, the 
tendon of the pyramidalis is drawn straight, 
and the third eyelid is thus stretched over the 
front of the eye. 

“ From this curious disposition of the 
muscles,” says Dr. Porterfield,* ‘it is easy to 
conceive, how this internal eyelid is extended 
over the cornea far enough to cover all the 
pupil, though the muscles themselves are con- 
tained in a small space. Every body knows, 
that the contraction of all muscles is only in a 
certain given proportion to their length; and 
therefore that the eyelid might be drawn far 
enough over the cornea, nature was obliged to 
make use of a long muscle, which could not 
be contained in so small a place as the orbit, 
without being bent or inflected ; and therefore 
the one muscle is bent upwards near the optic 
nerve, making an acute angle, where it passes 
through the perforated end of the other 
muscle, by which means its action is greatly 
increased. But its action is yet more increased 
by the contraction of the square muscle itself, 
which must draw the cord or tendon of the py- 
ramidal muscle which passes through it, through 
a space double of what it moves itself; and 
thus the membrana nictitans is extended far 
enough to cover the whole cornea though its 
muscles are contained in a small space.” 

In Owls Nitzsch discovered a small bone on 
the lower surface of the bony ring of the 
sclerotica, ossiculum tuberculare, for the support 
of the long tendon of the pyramidalis. In par- 
rots the third eyelid is small. 

Among reptiles there is in chelonia and 
lizards a third eyelid much the same as in 
birds, but smaller and less moveable. It is 
moved only by a single muscle analogous to 
the pyramidalis of birds. “ An allied struc- 
ture,” says Miiller, “ is a spectacle-like trans- 
parent part in the lower eyelid of some lizards, 


* ‘On the Eye, vol. i. p. 34. Edinburgh, 1759, 
H 


98 


as several scinci, which may be drawn over the 
eye without interrupting vision, the cornea cor- 
responding to it.” This is the structure in the 
frog ; for what Cuvier admitted as a third eye- 
lid is horizontal instead of vertical, and, as 
Carus has shown, nothing more than the lower 
eyelid. In the frog the upper eyelid follows 
the motions of the eyeball. e lower eyelid 
has independent motion; admitting of being 
drawn over the eye and falling into a fold when 
this is open. 

The anterior and posterior semilunar folds in 
certain fishes have been already alluded to. 

The glandule of Harder—The glandule of 
Harder belongs peculiarly to the membrana 
nictitans or third eyelid ; it therefore does not 
exist in man and the quadrumana. The lacry- 
mal caruncle is not the representative of it, as is 
asserted in Dr. Grant’s Treatise on Compara- 
tive Anatomy, for both may exist together. I do 
not even know if it is correct to say that the 
two structures are developed in an inverse 
ratio, for in the sheep, in which the glandule of 
Harder is of considerable size, the caruncula is 
absolutely as great, if not greater, than that of 
man. Even among the hare kind, which have 
the membrana nictitans and glandule of 
Harder much developed, 1 find, particularly 
in the rabbit, a trace of lacrymal caruncle as 
scattered follicular grains along with small 
hairs at the inner canthus. It is only in birds 
that we lose all trace of the lacrymal caruncle. 

The glandule of Harder is situated in the 
orbit between its inner wall and the globe of 
the eye. Inthe sheep, for instance, the glan- 
dular substance is collected around the cartila- 
ginous pedicle of the membrana nictitans, 
on the inner surface of which it opens by two 
or three small ducts. In the elephant, in which 
the lacrymal gland is said to be wanting, or 
very small, the glandule of Harder is said to 
be very large. It opens between the membrana 
nictitans and the eyeball by an opening the 
size of a quill. Inthe hare kind, as has been 
said, the glandule of Harder is immense. It 
presents two lobes, and its duct opens in a 
wide lacuna within the membrana nictitans. 
According to Miiller,* the elementary particles 
or ends of the ducts are minute vesicles every- 
where equal and joining in the manner of 
branches into irregular oblong lobes. The 
excretory duct at the external surface of the 
gland opposite the eye is divided in the bi- 
lobated glandular mass into a great number of 
smaller ducts, which divaricating are joined 
each to a branch of the lobules. 

In birds the glandule of Harder is commonly 
much more considerable than the lacrymal 
gland. It lies as usual at the nasal canthus 
and opens within the third eyelid towards the 
eyeball. There is never any caruncle. Miiller 
tells us the glandule of Harder in birds is 
easily injected with mercury after its secretion 
has been all pressed out. The surface of the 
organ is divided into many smaller lobes. The 
internal ramification of the ducts does not ap- 
pear to be complicated. 


* De glandularum secernentium penitiori struc- 
tara, p. 5 tab. v. fig. 6 and 7. 


LACRYMAL ORGANS. 


In reptiles the glandule of Harder is smal 
than the lacrymal gland. = 

The secretion of the glandule of Harder 
thick transparent viscid matter. . 

Ill. reting and derivative laer. 
anpatuia Tia Gevdocaae of the laer 
gland and of that of Harder is generally m 
inverse ratio. It would appear that the ¢ 


9 


tive lacrymal apparatus is more in relation 
the lacrymal gland than with the glandt 
Harder, as it is much develo in man 
whom there is no glandule of Harder, and, 
reported, it is wanting in the elephant, in y 
the glandule of Harder is said to be 
large. The lacrymal gland exists in man, 
sapajous, and snakes, but no glandul 
Harder. In all other mammifera there is 
a lacrymal gland and a glandule of Hai 
proportion as the latter enlarges the forme: 
comes smaller. Among the cetacea, the 
phin possesses a lacrymal gland which 
rounds the eyeball likea ring. Its exer 
ducts, which are numerous, open on the’ 
surface of both upper and lower eyelids. 
derivative lacrymal apparatus is wantin 
this respect, seals and walrusses agree wit 
cetacea.* Other mammals, as moles and s 
mice, are said to present no trace of laet 
apparatus. In the elephant, small gl 
grains the size of a are said to represen 
lacrymal gland. Camper says the hip 
tamus has no puncta, from which mi 
ferred the absence of any lacrymal passage 
the nose. The elephant is also said to 
the derivative lacrymal apparatus. “s 
In birds the lacrymal gland is small, at 
at the posterior angle of the eye, either to 
the roof or the floor of the orbit. The der 
lacrymal organs in the common fowl, — 
stance, consist of two large lacrymal p 
upper the larger, and a membraneous 
leading into the nose. = 
In reptiles, the lacrymal gland lies behin 
eyeball, and is of considerable size, espec 
in harmless serpents. According to Duve 
the lacrymal gland in one species of ty; 
is six times larger than the extremely di 
tive eyeball; but even in rg 
the viper for instance, it is large. 
The sauria and chelonia have for th 
part both a lacrymal gland and a glan¢ 
Harder, the former the larger. Batrachia 
the lacrymal apparatus. 
In serpents the secretion of the lac 
gland is poured into the oculo-palpebi al 
from which a lacrymal duct leads. — 
colubri there is, in the fore and lowe 
the oculo-palpebral space, a hole © 
pore, in some individuals seen with di 
very distinct on the con in @ 
which may admit a bristle. is is th 
mal point; it is single and is continue 
a very slender membranous duct, 
tet pg which forms the lacrymal 
is, in harmless serpents, opens into @ 
pouch commaniodtiaged with the mouth im 
* Rapp. l.c. Rapp describes, in the t 
scattered grains of lacrymal gland, which 
the conjunctiva near the eyeball. ‘ 


a 
. 
= 


‘of the 


oquet® calls this pouch intermaxillary sinus 
or sac. In venomous serpents, the lacrymal 
canal opens, as in the mammifera, in the ex- 
ternal wall of the nasal foss:e. 
_ There is no lacrymal apparatus in fishes. 
In the description of the lacrymal gland in 
man, the intimate structure of it in the lower 
mals has been already alluded to. The re- 
of Miiller may be repeated here, that 
glands have often a perfectly different 
ure in different animals; of which the 
erymal gland examined in the chelonia, birds, 
id mammifera affords an example. 
‘The lacrymal bone contributes to separate the 
tbit from the cavity of the nose. It is wanting 
certain mammifera, as the phoce and most 
facea. It is enormously developed, on the 
y, in certain others, as the giraffe, stag, 
e. It exists also in birds, and forms in them 
fien the greatest part of the inferior margin of 
the orbit. In reptiles, its existence is variable. 
It is found in crocodiles. It is absent in the 
elonia, ophidia, and batrachia. It is also 
nting in fishes, unless the first infra-orbital 
‘assumed as analogous to it. 
ruminating animals, remarkably so in deers 
and antelopes, the infra-orbital fossa of the su- 
perior maxillary bone is very large, and is lined 
y areflection of the skin, more or less in the 
wm of asac. Theskin, which has assumed 
characters of a mucous membrane, contains 
substance numerous follicles,which secrete 
k blackish unctuous humour—a secretion 
h appears to have some relation with the 
function. This matter has been impro- 
called tears, hence the French name 
ers of the infra-orbital glandular sacs of 
minants. In the sheep these organs are re- 
presented by a mere fissure extending on the 
de of the nose from the nasal canthus. 
-Meckel compares to this structure the fovee 
in the face, behind the nostrils, of several poi- 
onous serpents, such as the rattle-snake; but 


Palatine branch of the upper jaw. 
bs 
Ps 


+ 


ars to secrete anything. The temporal gland 
bf the elephant seems to be of the same nature 
s the infra-orbital glandular sacs of rumi- 


nants. 

Development of the accessory parts of the 
eye.+—The accessory parts of the eye appear 
bsequently to the eyeball, and, as is the case 
ith the accessory parts of the organ of hearing 
n reference to the labyrinth or ear-bulb, have 
“quite a separate and distinct origin from it. 
That the development of the accessory parts of 
he eye is independent of that of the eyeball is 
_ confirmed by the anomalous conformation which 
| the organ has been sometimes found to present; 
' thus Malacarne relates a case in which the eye- 
_ balls, their nerves and muscles were wanting, 
f whilst the lacrymal apparatus and eyelids were 
regularly developed. 

_ Up to the eighth week the external integu- 

. 
ca 
| * Op. cit. 

_ + Burdach, Die Physiologie, als Erfahrungs- 
) wissenschaft, &c. and Valentin, Entwickelungs- 
-geschichte. 


LACRYMAL ORGANS. 


¢ membrane lining these parts scarcely ap- 


99 


ment passes quite smoothly over the eyeball. 
The conjunctiva is then partitioned off by the 
formation of a linear fold, which, in the ninth 
week, surrounds the anterior surface of the 
eyeball like a small ring. The upper and lower 
parts of the fold progressively enlarge until 
they meet each other over the eyeball, which 
takes place about the twelfth week. 

The progress of the development of the eye- 
lids is sometimes arrested, so that mere folds of 
skin have been found occupying their places, or, 
development having proceeded a little further, 
the eyelids have been found presenting their 
regular conformation indeed, but too short to 
cover the eyeball and incapable of motion. 

Having met, the edges of the eyelids ad- 
here by the extension of the epidermis from 
the one to the eter. In the human embryo 
the adhesion between the eyelids by the exten- 
sion of the skin ceases towards the latter 
months, but the edges continue sticking together 
by the Meibomian secretion until the period of 
birth. In the young of several of the mammi- 
fera, as the carnivora and rodents, the eyelids 
continue closed for some time after, birth— 
from one to two weeks. In birds, even in the 
embryo state, the eyelids never unite. 

Sometimes adhesion between the eyelids in 
the human subject is found at birth, constitut- 
ing what is called congenital anchyloblepharon ; 
and this may be either immediate or by the 
intervention of a membranous structure. 

The closure of the pupil by the pupillary 
membrane in the fcetus corresponds to the ad- 
hesion of the eyelids to each other at that period. 
According to Meckel the pupillary membrane 
continues entire in animals born blind, as it is 
expressed, as long as the eyelids remain closed. 

The tarsal cartilages first appear distinctly in 
the fifth month; and at birth, that of the up- 
per is perfectly developed. The eyelashes first 
appear free about the sixth month. 

The lacrymal gland is already evident in the 
last half of the fourth month. 

The inner canthus of the eye is at first more 
elongated than it is afterwards. 

On the ‘first appearance of the eyelids, 
Burdach tells us, the lacrymal caruncle presents 
itself; and at the inner angle a diverticulum of 
the conjunctiva sinks down to the oro-nasal 
cavity as the commencement of. the lacrymal 
sac and nasal duct. The lacrymal points 
project very much in the fifth month, and in 
the seventh are somewhat more retracted. The 
lacrymal apparatus in general, as also the 
Meibomian follicles, are proportionably much 
developed at an early period. 


BIBLIOGRAPHY.—See that of article Eye and 
the several works referred to in the course of 
this. The most complete, indeed, so far as 1 
know, the ony monography, is that of John Chris- 
tian Rosenmiiller, ** Partium externarum oculi ha- 
mani imprimis organorum lacrymalium descriptio 
anatomica, iconibus illustrata.” Lipsie, 1810. In 
this will be found a catalogue raisonné of all pre- 
ceding works bearing on the subject. 


(T. Wharton Jones.) 


H 2 


100 


LARYNX. Syn. Gr. aaevyé, from Ca 
(clamo); Fr. aor per bert sb ey 
Laringe.—The larynx is a complex piece of 
mechanism resembling a kind of box, (pixis 
cava, ) composed of an assemblage of carti- 
lages, the density and elasticity of which serve 
to protect its more delicate tissues, and to 
allow the free transmission of air for respira- 
tion. It is also exquisitely adapted for the 
production of voice. 

The larynx is situated in the mesial line, 
and opens superiorly into the pharynx, and 
inferiorly into the trachea. It occupies the 
anterior superior part of the neck, immediately 
below the os hyoides, and before the pharynx, 
which lies between it and the vertebral column. 
In front it is very superficial, being covered 
only by the sub-hyoidean muscles, and the 
common integuments. 

It admits of various kinds of motion: 1, 
those of elevation and depression parallel to 
the long axis of the body; 2, those complex 
movements within it which take place during 
respiration and the production of vocal sounds. 

The larynx considered with reference to the 
trachea, presents an enlargement denominated 


Fig. 18. 


The anterior transverse section of the larynx and 
trachea. a, the epiglottis; 6, 6, the horns of the 
os hyoides ; ¢, ¢, the inferior thyro-arytenoid liga- 
ments (chorde vocales); d, d, the thyro-arytenoid 
muscles; e, e, section of the thyroid cartilage ; 
Sf, f. the superior boundaries of the ventricles , g,9, 
section of the cricoid; h, the trachea; J, l, the 
ventricles. 


NORMAL ANATOMY OF THE LARYNX. 


the cuput asper@ asteria, or the head of th 
trachea. The absolute volume of the laryn 
varies with the age and sex of the indivic ua 
its magnitude is much more considerable 
men than in women ; in the former it ace u 
an extraordinary developement at the 
puberty. In eunuchs, however, this en 
ment does not take place. i 

The larynx does not represent any regt 
geometrical figure; it may be defined as 
irregular, inverted, truncated cone, whose 
tions at the apex and base are elliptical, 
approaching nearly to a circle at its june 
with the trachea. - 

This organ is perfectly symmetrical, wh 
however, applies to one of its sections 6 
viz. that of its mesial plane, or axis me 
consequently, all the others must be uns 
metrical: the section made at right angle 
it, or in its axis minor, gives the relative sit 
tion of its internal mechanism, as in figs. 
and 19, which should be carefully studied, v 
reference to the physiology of this organ. 


Fig. 19. 


The posterior view. The letters e, d, é, g, 
resent corresponding sections of the sam 
B b, the arytenoid cartilages invested by n 
membrane ; , the pharynx laid open. _ 


The larynx is composed of several stru 
which may be classed as follows: 1, 
tilages ; 2, the ligaments; 3, the mus 
4, the mucous membrane; 5, the mu 
glands; 6, the arteries-and veins; @ 
lastly, the nerves. a 

The cartilages of the larynx are ni 


NORMAL ANATOMY OF THE LARYNX. 


number,* of which three are single and un- 
‘symmetrical, the epiglottis, thyroid, and cri- 

goid ; two are placed laterally, and form a pair, 
ed the arytenoids. Upon the summits 
these are found two minute cartilaginous 
bodies, termed cornicula; the remaining 
0 (which, however, are not always present) 
fe situated anterior to the arytenoids, and in- 
volved in the aryteno-epiglottic folds, named 
_ the cuneiform cartilages. 

The cricoid cartilage. Gr. xeiKog, a ring, 
#100 3 Lat. Cartilago annuliformis ; Fr. Cri- 
edide ou annulaire ; Germ. Ringknorpel ; Ltal. 

ricoide.—This cartilage, situated at the base 
of the larynx, which it supports, is the thickest 
_ stron 


st of the whole assemblage of car- 
t is connected to the first ring of the 
a by elastic ligaments and mucous memn- 
its form, that of a ring, is not quite 
 Gireular, but approaching to an elliptical figure. 

t is shallow in front, at c, e, (fig. 20,) but it 
thicker and deeper than the first ring of the 
_ trachea; and, posteriorly, it is considerably 
_ deeper than at its anterior part, in the propor- 
ion of eight to two and a-half. 


Fig. 20. 


A, an anterior, B, the side view of the cricoid 
) Cartilage; a, the posterior superior margin; 5, b, 
‘the crico-arytenoid articulating surface; 6, 9, f, e, 
the superior descending margin ; d, e, the tracheal 
ure of the cricoid ; a, d, the greatest, a, c, the 
‘ depth of surface; a, e, the obliquity of the 
‘superior section to the axis; A, the left surface 
‘articulating with the inferior cornua of the thyroid 
| cartilage. 
_ The anterior external surface gives attach- 
ment to the crico-thyroid muscles (see fig. 26); 
more posteriorly we find an apophysis for the 
iculation of the thyroid (fh, fig. 20, B). Its 
osterior surface is divided into two equal por- 
tions by a vertical ridge along its middle line, 
a, d, fig. 20, B. This ridge, which was first 
noticed by Galen, gives attachment to some 
longitudinal fibres of the esophagus. On each 
side of it a concave surface is observed, which 
Bives origin to the crico-arytenoidei postici, 
9 €y fig 27. 
cee internal surface is smooth, and lined by 
the mucous membrane of the larynx. The 


| inferior margin is horizontal, and nearly circu- 


| 
: 


af 


- Galen describes only three, yov3pog bupecesdns, 
KovBpoc Dewrepos, xovdpos a-uTasvoesdnc. 


101 


lar; but the superior, which is bevelled 
obliquely inwards and upwards, about ec, e, 
(fig. 20,) ascends backwards in the direction 
of e, fig, 6, (fig. 20,) being slightly curved 
downwards between f° and g. The anterior 
superior outline of this cartilage presents that 
of the section of a cylinder, whose obliquity to 
its axis is in the direction a, e, and therefore is 
elliptical. It recedes anteriorly from the lower 
margin of the thyroid cartilage in the direction 
of g, f; e, (fig. 20,) leaving an interval called 
the crico-thyroid space, a, (fig. 20, B,) which is 
occupied by the crico-thyroid ligament ; on each 
side, in the lines e, f, g, by the lateral liga- 
ments, and more posteriorly by the crico- 
arytenoidei lateralgs, in the space f, g, to the 
external side of 6 (fig. 20). 

The posterior superior margin is horizontal 
on each side of a, (fig. 20,) and parallel to the 
inferior at d, having at 6 and 6 an oblong, 
oblique, and slightly cylindrical surface, in- 
clined upwards and outwards for the articu- 
lation of the arytenoid cartilages. These sur- 
faces are considered by Willis as “ portions of 
cylinders, whose axes are inclined both with 
respect to the horizontal and vertical sections.” 
In the vertical section, the projection of this 
articulating axis is in the position G, C, (fig. 
28,) and in the horizontal, in the line O, P, 
(fig. 30.) Between these surfaces is a slight 
depre:sion for the insertion of the arytenoid 
muscles. 

The thyroid cartilage. Syn. Lat. Cartilago 
scutiformis ; Fr. Thyroide ; Germ. Schildknor- 
pel.—This cartilage derives its name from Queeos, 
a shield, and edocs, form. It embraces the 
cricoid in a manner analogous to the carapax 
of the tortoise. It is formed to protect the 
internal mechanism of the larynx, both in front 
and at both sides, but is open behind. It serves 


Fig. 21. 


An angular view of the thyroid cartilage. a, the 
notch ; 6, b, the superior cornua ; c,c, the inferior 
cornua ; g, g, the superior tubercles ; h, h, the in- 
ferior tubercles; e, e, the wings of the thyroid ; 
i,a,i, the superior margin; h, d, h, the inferior 
margin ; a, d, the mesial line; f, the pomum. 


as a fulcrum and lever for the action of several 
muscles. It is composed of two quadrilateral 
lamine uniting in front at the mesial line (a, d, 


102 


Jig. 21): the angle of union becomes more acute 

as it approaches towards d. The prominence 

of this angle on the mesial line constitutes 

what is called the pomum Adami, which is 

more developed in the male than in the female 

sex, and becomes more conspicuous after the 

age of puberty; it may be readily felt in the 

living subject. On the four posterior angles 

of the thyroid are situated four cornua, or 

horns ; two superior, 6, b, and two inferior, 

ec, (fig. 21); they appear mere prolong- 

ations of the posterior margins; the superior 
being longer than the inferior are called the 

pt horns; they are articulated to the os 

yoides by ligaments, which allow a motion 

for the approximation and recession of the la-' 
rynx to and from the os hyoides. The inferior 
horns are shorter, curved forwards, and arti- 
culated at their extremities to the cricoid by 
oblique planes, directed forwards and inwards. 

On each wing of the thyroid there are two 

tubercles, one on the superior, and the other on 
the inferior margin (g, g, and h, h, fig 21). 
The superior tubercles are the largest. A small 
ridge passes obliquely across the external sur- 
face of the wings from g to /, extending from 
the base of one tubercle to the other, dividing 
each wing into two unequal segments, of which 
three-fourths are anterior and superior, and 
one-fourth posterior and inferior to the ridge. 
The anterior margin of the ridge gives attach- 
ment to the hyo-thyroid, and lies under the 
sterno-hyoid muscles, and the posterior to the 
inferior constrictor of the pharynx and sterno- 
thyroid muscles. 

The posterior or hollow surface of the angle 
formed by the junction of the ale of the thy- 
roid gives attachment on each side of the me- 
sial line to the thyro-arytenoid ligaments 
(chorde vocales) and muscles. The wings 
are concave internally for the lodgement of the 
thyro-arytenoidei and crico-aryteno.dei laterales 
muscles, and give attachment at their poste- 
rior margins to the membrane of the pharynx. 

The superior margin of each wing is curved 
in the line i, a, i, (fig. 21,) and gives at- 
tachment in its whole length to the thyro- 
hyoid membrane: it is deeply notched at a, 
immediately above the pomum Adami. It is 
less deep, and more broad and round in 
women than in men. 

Near the superior tubercles there is a notch, 
sometimes a foramen for the transmission of 
the superior laryngeal nerve. The inferior 
margin of the thyroid is nearly horizontal, and 
is shorter than the superior: there is a slight 
prominence at a, (fig. 21,) to which is attached 
the crico-thyroid ligament. Between the in- 
ferior tubercles at A, 4, (fig. 21,) and the in- 
ferior cornua, the lower margin is arched rather 
deeply. The posterior surface and margin of 
the wings of the thyroid are ridged, and give 
attachment to several muscles ; it rests against 
the vertebral column, which forms a base to 
the are of the thyroid, and protects the internal 
structure of the larynx. 

The arytenoid cartilages. Syn.: Gr. 
agurasvotsdys, Galen; Lat. Cartilagines ary- 


NORMAL ANATOMY OF THE LARYNX. 


tenoidea ; Fr. Cartilages arytenoides ; Ge 
Giessbeckenknorpel.—The arytenoid cartilay 
are two very irregularly formed bodies, situ 

on the articulating surface of the poste 
inner, and upper margin of the cricoid, (1 
Jig. 20,) in such a manner as to resemb 
mouth of an ewer; hence their name. — 
may be considered of a triangular or py! 

figure, having their bases spread out, (; 
Jig. 22,) and presenting surfaces for the a 
ment of ligaments and the action of mu 
We observe, 1, on their poe as 
triangular concave surfaces, between f a 
(fig. 22,) occupied by the oblique and 1 


“fa 
‘9 


verse arytenoid muscles. 2. Anteriorly, 
vex, triangular surfaces, d, b, (fig. 22,) 
Fig. 22. 


- 


eS 


A side view of the arytenoid carvings 2 
base and position of the crico-arytenoid articu 
oves; b, e, the posterior concave surface ; 


ateral prominence ; f, the corniculum lary 
g, the vertical portion of the cuneiform cartil 


ridges, (6, fig. 27,) for the me 
the superior thyro-arytenoid ligaments. | 
terally, cavities for the insertion of the 
arytenoid muscles, and lodgment of the 
form cartilages, (, g, Jig: rm 4. Inte 
surfaces reciprocally lel, lined with 
cous membrane, which permit their clos 
proximation. 5. Bases, on which are 
curved, oval grooves, a and a, . 22, 
responding to the articulating surfaces ¢ 
cricoid ; there are also on of these 
two prominences, one lateral, (c, jig, 
which gives attachment (/, fig. 27,) t 
crico-arytenoideus lateralis and posticus 
cles; the other anterior, giving atta 
(V, fig. 29) to the inferior thyro-aryt 
ligament. The latter prominence projec 
the vocal tube one-fifth of an inch in the 
and one-seventh in the female. On the) 
mit of the vertical prominences (f, f, fig 
is situated a small appendage called cornic 
laryngis. The arytenoid cartilages hav 
tensive freedom of motion, consisting ¢ re 
tory, round the articulating axis of the ¢ 
O, P (fig. 30); anda sliding motion, 
verse to their axis of articulation < 
int B (fig. 30). : 
P The fs. Shr laryngis—Syn. Capitul 
torini ; tubercles of Santorini ; carti 
corniculis ; Santorinischer Knorpel, 
These are two very small cartilaginous b 
first described by Santorini, from whom the 
rive their name. Their figure is nearly triangt 
with a flat smooth surface at their bases, | 
culated with some freedom of motion 
apices of the arytenoid cartilages. — 


attach! 


a» 
ei) 
rast 


NORMAL ANATOMY OF THE LARYNX. 


lengthen the arm of the vertical lever of the 
arytenoid, and yield to any oblique force 
cted upon them. 
The cuneiform cartilages, (Syn. cartilagines 
eiformes, seu Wrisbergiane,) are two small 
indrical cartilaginous bodies, situated im- 
diately in front of the vertical prominence 
f the arytenoid cartilages in the fold of mu- 
ous membrane g, (fig. 22.) They present a 
ical and horizontal prominence in the shape 
_ of the letter L, and partake of the form of the 
arytenoid cartilages. They are not always pre- 
ent, and their existence in man is denied by 
Sruveilhier:* this however is an error. Both 
viert and Wolff{ have confounded them 
the cornicula or cartilages of Santorini. 
the Quadrumana they are conspicuous, 
ing the superior vocal ligaments attached to 
ir bases, and they appear afterwards to con- 
t them with the arytenoid cartilages. The 
eiform cartilages are sometimes described 
Cruveilhier and other writers (though inac- 
ately) as the arytenoid glands. They serve 
as a link of connection between the arytenoid 
cartilages and superior ligaments. 
The epiglottis, from emt, upon, yAwrre, the 
gue. Syn. xAndgor, Hipp§ Ligula, Gal. 
um, Cic.|| Cartilago epiglottidis. 
iglotte, Fr. Kehldeckel,Germ. The epi- 
tis is a cartilaginous valve, situated at 
base of the tongue, and covering the 
ing of the larynx. The direction of the 
glottis is vertical, except during the act of 
utition, when it becomes horizontal. In 
it has been compared to a cordate leaf, 
g.23,) or that of the artichoke. The di- 
asions vary with the volume of the larynx. 
@ anterior aspect of the epiglottis is convex, 
the posterior concave; it is partly free and 
partly connected: the free portion projects 
above the level of the base of the tongue. It 
is lined by the mucous membrane: the centre 
Mf its superior margin is very slightly notched. 
| Inferiorly it terminates by a kind of pedicle, 
_ yery thin and delicate, which is attached to the 
angle of the thyroid immediately above the 
plane of the thyro-arytenoid ligaments. Nu- 
; merous foramina are observed, perforating its 
Substance (ff, fig. 23), rendering the struc- 
ture of this cartilage less dense than that of 
the thyroid or cricoid cartilage. It is consi- 
_ dered to be more brittle, in consequence of 
_ the cohesion of its particles being affected by 
' these perforations. Its elasticity, however, is 
augmented by each perforation admitting some 
fasciculi of the yellow elastic ligament which is 
_ expanded, and, as it were, rivetted on its an- 
_ terioraspect. In the larger Ruminantia, such 
_ as the ox, this structure is very conspicuous, 
the thickness of the elastic tissue being nearly 
equal to that of the epiglottis itself. This 
_ ligament is disposed so as to secure perma- 
_ nently the return of the epiglottis after its de- 


t 


he *® Anat. Descript. 

3 t Legons Anat. Comp. 

De organo vocis Mammalium. 
In Lib. Morb. 1. 

De Nat. Deor. ii. p. 54. 


103 
Fig. 23. 


i) 


ca 
@ 


A posterior angular view of the cartilages of the 
larynx, exposing the rugged and perforated structure 
of the epiglottis after the removal of the mucous 
membrane and the yellow elastic ligamentous tissues. 
(Drawn from a preparation in the Museum of 
King’s College, London. ) 


aa, the arytenoid cartilages; 6 6, the superior 
cornua; c, the right inferior cornu; d, the posterior 
surface of the cricoid catilage; e, the foramen for 
the transit of the superior laryngeal nerve; ff, 
the perforation of the epiglottis; i, the superior 
margin of the thyroid; ¢, the trachea; h, the right 
inferior tubercle. 


pression in the act of deglutition, indepen- 
dently of any muscular fibres. Its perforations 
have been described as giving lodgement to 
“ muciparous follicles,” but their office seems 
not to have been hitherto thoroughly investi- 
gated. 

Articulations and ligaments of the larynz.— 
The articulations are divided, first, into those 
connecting the larynx with surrounding struc- 
tures, called extrinsic articulations ; and, se- 
condly, those peculiar to the larynx itself, 
termed intrinsic articulations. 

Extrinsic articulations. — The hyo-thyreid 


104 


articulation. The thyroid cartilage is united 
to the os hyoides by three ligaments: the mid- 
dle and two lateral. 1st. The ligamentum 
thyro-hyoideum medium isa lax yellow tissue 
arising from the superior margin of the thyroid, 
and inserted into the inner margin of the os 
hyoides: it is thicker and denser at its middle 
part; its lateral borders are involved with the 
surrounding cellular membrane. The anterior 
surface in its middle is situated immediately 
under the integuments, having its sides co- 
vered by the thyro-hyoidei muscles, (g, fig. 25) 
and its posterior surface corresponding with the 
form of the epiglottis. 2d. The ligamenta 
hyo-thyroidea lateralia are small round liga- 
ments on each side of the larynx, connecting 
the tubercles of the great horns of the os hy- 
oides with the extremities of the superior cor- 
nua of the thyroid cartilage (cc, fig. 24). In 
the substance of these ligaments there are often 
found small osseous or cartilaginous bodies. 
The articulations of the thyroid cartilage 


Fig. 24. 


A mesial section of the larynx, from Lauth, The 
mucous ane and muscles are removed to expose 


the elastic ligaments. 


a, the epiglottis, b, the hyo-epiglottic ligaments; 
c ¢, the lateral thyro-hyoid ligaments ; e, a portion 
of the glosso-epiglottic ligament ; f, the crico-thy- 
roid ligament; gi, the junction of the crico-thy- 
roid, and lateral crico-thyroid ligament; n’, the 
attachment of the lateral crjco-thyroid ii aments 
to the base of the arytenoid cartilage ; n, the elas- 
tic ligament lining the bottom of the ventricles ; 0, 
the superior inner margin of the cricoid cartilage ; 
the lateral ligamentous connection with the inferior 
vocal cord; /, the superjor vocal cord; the right 
arytenoid cartilage, 


NORMAL ANATOMY OF THE LARYNX. 


with the os hyoides are furnished with sy 
vial membranes. “a 

The ligaments of the epiglottis—The 
glottis gives attachment to three ligams 
which contribute to its elasticity and the | 


lity of its position. a 
1. The ligamenticn th iglottideum j 
from the mesial line tae e notch « 
superior angle of the thyroid, and is im: 
into the base of the epiglottis. It bing 
epiglottis to the thyroid cartilage. 2d. 
ligamentum hyo-epiglottideum arises fron 
inner surface of the base of the os hyoi 
fibres passing horizontally are inserted 
the anterior surface of the epiglottis ; its; 
tends to keep the position of the epiglottis 
manently vertical. 3d. The ligamentum gl 
epiglottideum arises from the base of 
tongue ; it lies in the median mucous folds 
tween the tongue and epiglottis, and is inser 
into the anterior surface of the epiglotti: 
mediately above the Higamedtenal laa i 
tideum. Its action is nearly the same ast 
of the last-named ligament, but it is also 
nected with the motions of the base of 
tongue. ; 

Lhe tracheo-cricoidean articulation. — 
lower margin of the cricoid cartilage is 
culated with the first ring of the trachea b 
series of the same ligamentous fibres wh 
connect the rings of the trachea with each ot 
At the anterior mesial base of the cricoid th 
are found additional ligamentous fibres. — 
elastic tissue which connects the larynx 
the trachea permits considerable freedom 
multiplied movements of the neck with 
peding the regular transmission of the atm 
phere. In these movements the first rin 
the trachea passes within the inferior mar, 
the cricoid cartilage. 

The intrinsic articulations of the larynx 
Ist, the crico-thyroid ; 2d, the crico-aryten 
Besides these may be included the articula 
of the arytenoid with the cartilages of Santorii 
The cuneiform cartilages are generally unarti 
lated in man. 

The crico-thyroid articulation.—The i 
cornua of the thyroid are curved forwards 
inwards. Their extremities present oblit 
planes directed inwards and downwards, wi 
are firmly attached by a capsular ligameni 
the oblique discs on the sides of the 
directed upwards and outwards. § 

The ligament of this joint is of an orbic 
form, radiating in oblique fasciculi, the 
terior fibres of which extend nearly to the en 
arytenoid articulation. 4 

The crico-thyroid ligament. Syn. Pyr 
dal, or conoid ligament. Lat. Ligamen 
crico-thyroideum. Fr. Membrane, ou | 
ment thyro-cricoidien moyen. The ¢ 
thyroid ligament is a very thick, sti 
yellow elastic ligament, arising from 
mesial line of the inferior margin of 
thyroid; it then crosses the crico-thyroi 
space, and is inserted into the superior ma 
gin of the cricoid. This ligament supp 
the anterior part of the cricoid cartilage, a 


ey 


el 
= 


~ 
>* 


we 


“aa 
UE 
> 


_ trachea in conjunction with the crico-thyroid 
muscle. The nature and position of the arti- 
bulation of the thyroid, with the cricoid, render 
he force of this ligament of great utility and 
pportance. 
The lateral crico-thyroid ligament, lig. crico- 
hyroid laterale, arises immediately at the side 
“of the crico-arytenoid articulation. Some fas- 
iculi, according to Cruveilhier and Lauth, are 
tiached to the bases of the arytenoids, others 
we reflected horizontally forwards to the in- 
srior margin of the cricoid. It is bounded 
sternally by the thyro-arytenoideus and crico- 
rytenoideus lateralis, and lined internally by 
é mucous membrane of the larynx. 
The crico-arytenoid articulation—The ob- 
ue articulating convex surface of the cricoid 
48 received in a corresponding channel or 
groove at the base of the arytenoid cartilage. 
‘The ligament arises from the cricoid, and ra- 
jates both anteriorly and posteriorly round the 
ase of the arytenoid cartilage; a fasciculus is 
reflected along the base of its anterior mem- 
brane behind the attachment of the thyro-ary- 
tenoid ligament. The crico-arytenoid liga- 
ment is thick and strong, yet sufficiently loose 
9 permit a diversity of motion. Some anato- 
mists divide the ligament into anterior and 
terior. The articulation is lined and lubri- 
ed by a synovial membrane. 
The thyro-arytenoid ligaments. Syn. Chor- 
de vocales, Ferrein. Stimmbander, Germ. 
| These ligaments, as their name implies, con- 
lect the thyroid with the arytenoid cartilages, 
ad are instrumental in the production of voice. 
There are on each side two vocal cords, a su- 
berior and an inferior; the cavities between these 
igaments are termed the ventricles of the 
wynx. The inferior thyro-arytenoid ligaments, 
r,as they are often denominated, “ the true 
igaments of the glottis,” are much thicker and 
stronger than the superior: they present the 
form of nearly rectangular parallelograms, 
and are stretched horizontally across the long 
axis of the larynx, from the anterior horizontal 
"tubercle of the arytenoids, to the angle formed 
by the junction of the wings of the thyroid (c, 
g. 27). On their outer side these ligaments 
@ connected with the thyro-arytenoid mus- 
les; their anterior extremities are inserted into 
the thyroid, the posterior to the arytenoid car- 


lages ; the internal margins are free to vibrate. 
On exposing them by the removal of the mu- 
ous membrane they are found less than their 
ipparent volume. Immediately after death 
hey are semi-transparent, very elastic, and 
‘Composed of parallel fibres. They are con- 
nected with, and form a continuation of the 
ligamentum crico-thyroideum lateralis (k, fig. 
24). The length of the vocal ligaments varies 
with the general dimensions of the larynx: in 
‘the adult male they are much longer than in 
the female. In infancy they are very short, 
and increase from that period to the age of 
puberty in an arithmetical ratio. Thus, if at 

} One year old their length in parts of an inch 
is 0,2500, at five years they will be 0,3333, 
at nine 0,4166, and at fourteen 0,4999: these 
close approximations. 


2 


Pa Si: 


NORMAL ANATOMY OF THE LARYNX. 


105 


The superior thyro-arytenoid ligaments or 
superior vocal cords are, in contra-distinction 
to the inferior, denominated (though incorrectly) 
the false ligaments: they are of less thickness 
and strength than the inferior ligaments, and 
are further removed from the axis of the larynx 
(4, fig. 24). They arise from the internal 
angle of the thyroid, and are inserted into the 
middle of the anterior superior prominence of 
the arytenoid cartilages (fig. £4); they are 
composed of a few slender fasciculi of elastic 
fibres, approaching less nearly the mesial 
plane than the inferior ligaments; they appear 
more prominent, in consequence of their form- 
ing the roof of the ventricles. They are in the 
same plane as the aryteno-epiglottic muscle, 
and are connected with the fibres of the lateral 
crico-thyroid ligefhents. 

According to M. Lauth there is a connexion 
between the crico-thyroid, the lateral crico- 
thyroid, and thyro-arytenoid ligaments by three 
—e one of which is vertical, one hori- 
zontal, and one ascending (yg, k, n . 24 
the first of these being the ee A at 
second the lateral ; the third connects the thyro- 
arytenoid with the superior thyro-arytenoid 
ligaments, and lines the bottom of the ventricles. 
M. Lauth considers also that the thyro-epi- 
glottic, the hyo-epiglottic, and glosso-epiglottic 
ligaments are composed of the same elastic 
tissue. Muller and Cruveilhier concur in these 
views. They certainly appear of the same 
colour and texture under the microscope, and 
undergo the same change by exposure to the 
atmosphere: they also possess the same cohe- 
sive elastic properties. The strength of the 
inferior thyro-arytenoid ligaments is so great 
that they will tear away the cartilage to which 
they are attached without being injured, and 
will support the force of many pounds weight. 

Muscles—The motions of the larynx are 
exceedingly complex, and are performed by 
two sets of muscles, which are divided into two 
classes :—1, the extrinsic; and, 2, the intrin- 
sic muscles. The muscles which elevate the 
larynx are the digastrici, stylo-hyoidei, mylo- 
hyoidei, genio-hyoidei, and hyo-glossi, and 
those pharyngeal muscles which are inserted 
into the cricoid and thyroid cartilages. The 
muscles which antagonize these and lower the 
larynx are the sterno-hyoidei, the omo-hyoidei, 
the sterno-thyroidei, and the thyro-hyoidei. The 


os hyoides is the centre of motion for the action 


of these muscles. (See Necx, Muscies or 
THE.) We shall here confine our description 
to the 

Intrinsic muscles of the larynx, Syn.; mus- 
cles intrinsiques, Cruveilhier—The muscles of 
this division comprise those acting exclusively 
on the larynx itself. There are four pairs and 
one single: 1, the crico-thyroidei; 2, the 
crico-arytenoidei postici; 3, crico-arytenvidei 
laterales ; 4, thyro-arytenoidei ; and, 5, aryte- 
noideus, which, from a difference in the direc- 
tion of certain of its fibres, is divided into the 
oblique and transverse. Independently of these, 
there are some muscular fasciculi, named the 
thyro-epiglottidei and the aryteno-epiglottidei. 

The crico-thyrvidei.—These are very short, 


106 


thick, almost quadrangular-shaped muscles, 
situated on each side of the anterior part of 
the larynx: they arise from the anterior and 
inferior surface of the cricoid cartilage, on each 
side of the median line. The fibres are fleshy : 
the most internal directed obliquely upwards 
and outwards (m, fig. 25), the central very 


Fig. 25. 


A side view of the larynx with peta gape attached. 

a, the ih o-hyoideus muscle; 6, the middle 
thyro-hyoid ligament; e, the pomum; d, the crico- 
thyroid ligament; m, the crico-thyroid muscle ; 
ON, the direction of the inferior fibres of the crico- 
thyroid lying nearly perpendicular to the axis of 
the crico-thyroid articulation; f, the trachea; nn, 
the insertion of the thyro-hyoid muscle and mem- 
brane to the inner margin of the os hyoides. 


obliquely, and the inferior almost horizontally 
to the inferior margin of the thyroid and to the 
inferior horn: others are inserted into the pos- 
terior surface of the thyroid. A portion of this 
muscle is prolonged to the inferior constrictor 
of the pharynx. 

Each crico-thyroid muscle is covered by the 
sterno-thyroideus, and lies external to the crico- 
arytenoid lateralis and the thyro-arytenoideus. 
The triangular space between the crico-thyroidei 
is occupied by the crico-thyroid membrane. 

The action of the crico-thyroidei is to rotate 
the cricoid on the thyroid. The superior and 
middle fibres are at the greatest distance from 
the axis of rotation (N, fig. 26), and conse- 

uently acting as if at the arm of a long lever. 

n this action the anterior superior margin of 
the cricoid is elevated towards the inferior 
edge of the thyroid from f to f” (fig. 26), by 
which the posterior upper margin of the cricoid 
is carried backwards from B to B’ indicated by 
the dotted line 1, 2, 3, 4, 5, (fig. 26), and as 
the space is greater trom A B' than A B, it is 
manifest that the space in the mesial plane 


NORMAL ANATOMY OF THE LARYNX. 


Fig. 26. 


A view of the left side of the larynx to ill 
functions of the thyro-arytenoid, the st 
and crico-thyroid muscles, 

The dotted line 1, 2, 3, 4, 5, shows the 
of the cricoid cartilage when the crico-thyroid 1 
cles have closed the crico-thyroid > Mm, 
crico-thyroid muscle; N, the crico- at 
lating axis; A B and BA, the directions o 
force of the thyro-arytenoideus muscle; R S, 
direction of the force of the sterno-thyr 
muscle meeting that of the thyro-arytenc 
R; RN, the resaltant of the combined m 
forces R P and RS; ON and P N are } 
cular lines drawn from the directions of the f 
of the thyro-arytenoideus and sterno-th roi 
muscles to the common axis of rotation; they 
also the cosines of the angles R N O, RN P, 
B N P, and show the amount of force on the; 
of the sterno-thyroideus and thyro-ary 
muscles respectively; R’ and A’ are the p 
which R and A mu&t pass through when the 
roid is rotated forwards on the cricoid; A, 
point opposite which the thyro-arytenoideus is 
serted into the posterior angle of the thy 
lage; B, the point on which the thyro 
acts in rotating B towards A; ff’, 
roid space; A, the trachea. 


must be enlarged to an amount equal to 
difference of the distance A Band A B’ (fig. 
The action of this muscle, therefore, i: 
stretch the thyro-arytenoid ligaments. — 
direction of the force of the inferior horiz 
fibres of the crico-thyroid which are }j 
parallel to the line O N (fig. 25 and 26) b 
nearly perpendicular to the axis of rotation, 
have, consequently, little or no effect, ur 

superior fibres have (by raising the cricoid) 
duced an angle with the axis N (fig. 25); 1 
assist only when the crico-thyroid spa 
diminished. It has been commonly sw 

that it is the thyroid which is drawn for 
on the cricoid, and Cruveilhier adopts this : 
position ; but it has been refuted by Magen 
and not only do we observe that the atta 
ments of the crico-thyroidei are mechanic 
directed to produce a rotatory motion ¢ 
cricoid, but the latter has no fixed point 


Fig. 27. 


ae 


A\\ mpl 


A side view of the larynx, the left wing of the thyroid 
and the mucous membrane removed, and the fibres of 

the arytenoid muscle depressed to expose the liga- 
ments and chink of the glottis. 


__ @, the internal surface of the right wing of the 
thyroid ; 6 b, the arytenoid cartilages ; c, the thyro- 
arytenoid ligament; d, the thyro-arytenoideus 
muscle; d’, the thyro-arytenoideus superior vel 
_ minor; ee, the crico-arytenoidei postici; f, the 
_ crico-arytenoideus Seearal; m, the cricoid carti- 
lage; h, the trachea; J, the external prominence 
of the arytenoid cartilage. 


_ attachment or muscles appropriated to fix it as 
a fulcrum for motions in an opposite sense. 
The crico-arytenoideus lateralis is an irregu- 
Tar quadrilateral muscle, arising from the supe- 
_ ‘ior margin of the cricoid, from thence passing 
_ upwards and backwards, (/; fig. 28). . It is in- 
Serted into the posterior surface of the external 
prominence of the arytenoid cartilage by a tendon 
common to it and the thyro-arytenoid muscle. It 
__ is deeply seated under cover of the thyroid car- 
__ tilage and crico-thyroid muscle. The action of 
4 this muscle has caused much diversity of opi- 
4 nion. Cowper, Haller, Magendie, and others 
consider that it opens the glottis; but Bichat 
; and Sdemmering that it closes it. Its action 
has, however, been mechanically solved in the 
\ following manner by Willis. The arytenoid 
| 


cartilage is loosely fixed to the cricoid by liga- 
_ ments already described at B (figs. 28 and 29). 
The direction of the force of this muscle is 
represented by the line N X (fig. 30), having 
_ its point of insertion into the cricoid about X. 
_ The fibres in passing thence to the arytenoid 
(A, fig. 28) lie nearly parallel to the projection 


_ of the axis of motion, G C; the tension of this 
muscle in the direction N X (jigs. 29 and 30) 


4 
i 


4 
: 


NORMAL ANATOMY OF THE LARYNX. 
Fig. 28. 


107 


iit bh 

he pus! ua 
QZ i 

TT 


te 


wd 


A section of the larynx similar to that of fig. 27, with 
the thyro-arytenvid le 1 d to give a full 
view of the thyro-arytenoid ligaments, and the rima 
glottidis lying in the direction of A and B. 

The line G C is the vertical projection of the crico- 
arytenoid articulating axis; cc, f, g,h, represent 

the same parts as in fig. 27. 


tends to bring N X B into the same straight 
line and approximate the point V to the mesial 
plane; and as N is above the line joining B X, 
it will depress N and still more V, because the 
cartilage turns on the articulating surface be- 
neath Q. The action, therefore, of this muscle 
is to approximate the anterior arytenoid promi- 
nences and depress them. 

The arytenoideus (obliquus and transversus). 
Modern anatomists consider this as one 
muscle, but owing to the obliquity of the fibres 
of one of its fasciculi with respect to the other, 
some have made a division of it into arytenoideus 
obliquus and a transversus. It is a very short 
thick muscle, occupying the concavities on the 
posterior surface of the arytenoid cartilages and 
the interval between them. It consists of two 
layers; the superficial layer, which is composed 
of the oblique fibres, which arise from the base 
of the right arytenoid, and crossing the fibres 
of the deep-seated layer, are inserted into the 
summit of the left arytenoid cartilage: this is 
the arytenoideus obliquus of Albinus. The 
deep-seated layer is thicker and stfonger than 
the superficial; its fibres, which are directed 
transversely from one arytenoid to the other, 
constitute the arytenoideus transversus of Albi- 
nus. The arytenoid muscle is covered pos- 
teriorly with mucous membrane, which is con- 
nected to it by loose cellular substance, in which 
some mucous follicles are found ; anteriorly it 


108 


corresponds with the posterior surfaces of the 
arytenoid cartilages, and is connected by some 
muscular fibres and membrane with the supe- 
rior margin of the cricoid cartilage and with 
the whole length of the internal margins of the 
arytenoid cartilages. The immediate effect of 
the contraction of the arytenoid muscles is to 
approximate the posterior internal surfaces of 
the arytenoid cartilages, but their action, at the 
same time, tends to separate the anterior pro- 
minences, and to open the chink of the glottis. 
To counteract this effect the action of the crico- 
arytenoideus lateralis is called simultaneously 
into play, and the joint effect of these two 
muscular forces, represented by the lines N X 
and NY (fig. 30,) produce a resultant in the 
direction of W N ; hence the crico-arytenoideus 
lateralis and the arytenoideus muscle acting 
together tend to close the glottis posteriorly. 
Lhe thyro-arytenvideus.— This is one of 
the most important, most complicated, and 
perhaps least understood of any of the muscles 
of the larynx. It arises from the side of the 
angle of the thyroid cartilage, occupying about 
two-thirds of its height, and reaches within 
two or three lines of its superior margin. The 
central fibres are directed horizontally back- 
wards and outwards, slightly inclined upwards, 
and inserted into the prominence and concavity 
on the lateral surface of the arytenoid(/, fig. 27). 
The superior fibres terminate in the external 
ridge of the arytenoid; some of them pass 
round the arytenoid, and enclose the arytenoid 
muscle like a sphincter.* The inferior fibres 
which arise near the median plane (k, 29) 
are inserted, at a greater distance from it, into 
the arytenoid cartilages (f, fig. 30); some ex- 
ternal fibres are directed more eccentrically 


Fig. 29. 


A view of the larynx from above. ( From Mr. Willis. ) 


The mucous membrane is removed to shew the 
ligaments and muscles of the glottis. NF, NF, 
the arytenoid cartilages; T V, the vocal ligaments ; 
N X, the right crico-arytenoideus lateralis, the left 
is removed ; Xv L, the ring of the cricoid capable 
of rotating on the axis RS; ee, the crico-aryte- 
noidei postici ; E, the junction of the wings of the 
thyroid. 


* Lauth, Mem. de l’Acad. de Méd. 1835. 


NORMAL ANATOMY OF THE LARYNX. 


‘ligaments consist of nothing more than th 


Fig. 30. 


A portion of Sig. 29 ed to demonstrate ti 
ae and result of the forces of the 
OP, the horizontal projection of the ax 
articulation; TV, the vocal ligament; gh, 

direction of the force of the thyro-aryte: 
N X, of the crico-arytenoideus lotrel 
? 


of the crico-arytenoideus posticus; N 
arytenoideus transversus. 
upwards and backward, coreeponeay 
superior ligaments and ventricles, 
cording to Lauth, they terminate 
reaching the arytenoid. Some fibres « 
thyro-arytenoid take an oblique direction 
wards and downwards, arising immed 
below the superior internal margin of the ai 
of the thyroid, and are inserted into the ve 
tical prominence of the arytenoid cartila 
they are sometimes detached from those pass' 
horizontally, as in d, (fig 28,) constituting i 
thyro-arytenoidei —— of Albinus, t 
they are sometimes described as one muscle 
‘he thyro-arytenoideus corresponds to 
internal surface of the thyroid cartilage, fre 
which it is separated by some loose cellu 
and adipose tissue. Internally it is in conte 
with the inferior vocal ligament, which li 
contact with the thickest part of this mu 
the bulk of which causes the vocal ligame! 
on each side to project towards the mesial 
and contracts the aperture of the larynx. Son 
anatomists consider that the thyro-aryt 


tendons of these muscles; it is not diffie 
however, to prove the contrary by dissecti 

The functions of the thyro-arytenoidei, eo 
cerning which there has been much diversity 
opinion, produce several changes in the re 
tive position of the internal mechanism of 
larynx, and therefore they require rigid in 
tigation. The effects of these muscles m 
be considered, first, with respect to the 
of the vocal ligaments; secondly, to the ap 
ture of the glottis. We observe that the poi 
of attachment (at dd’ J, fig. 27) of the th 

tenoid are situated within those 
(fig.28); and, as the arytenoid cartilage is 1 
by ligamentous fibres to the point B, it follo 
that the contraction of this muscle will dra’ 
the point B, through the interposed aryten 
cartilage: if A be made the fixed point, 
contraction of this muscle will draw the poi 
B towards A by rotating the cricoid on the’ 
roid. If, on the contrary, B be fixed, then 
will approach B by the rotation of the thyroi 
on the cricoid. In both these cases the d 
tance from A to B is diminished, and as @ 
vocal ligaments are situated in a direct Iii 


NORMAL ANATOMY OF THE LARYNX. 


passing through A and B, this muscle must 
consequently relax them. 
The closing of the anterior and central por- 
tion of the glottis by these muscles, or that part 
lying between T and V (fig. 29), is effected, 
according to Mr. Willis, partly by the approach 
of the point V of the arytenoids towards T 
" arising from the obliquity of the axis of rota- 
tion, and partly by the swelling of the muscle 
“whilst contracting to approximate the arytenoid 
cartilages tending to fill the space TN X V 
(fig. 29), and to close tightly the sides of the 
passage below the vocal ligaments; thus clos- 
the anterior and central portions of the 


_ The question as to how A is made a fixed 
point, in the above demonstration, remains 
tobe solved. Mr. Willis remarks that while 
ull writers agree that the crico-thyroidei 
serve to approximate the cricoid cartilage to 
he thyroid, either by raising the cricoid or 
by depressing the thyroid, none of them have 
shown how the cartilages ate to be separated 
. Let us investigate this proposition. 

In order that the motions necessary to dilate 
_ the crico-thyroid space be effected by mus- 
cular motion, it is obvious that A must be 
made a fixed point, so that B’ may be drawn 
2 as (fig. 26), by which f’ ascends to f; the 
object in question (fig. 26). It is clear that 

the crico-thyroid muscle cannot be employed 
in this instance, as it has heen already shewn 
that its action is to force B to B’ and f tof’; 
whereas we have now to reverse the direction, 
_and to bring back B’ to B, so that f’ may de- 
_ seend to f. The sterno-thyroidei are the only 
muscles, which by their origin, insertion, and 
direction of force are calculated to effect this 

P| se; the insertion of one of these muscles 
itis about the point R at an angle with the 
_ axis R N (fig. 26), its force in the line ROS 
(fg. 26) cutting the right line O N at O; the 

_ efiect of which will be to draw forwards and 
_ downwards the thyroid cartilage from A to A’, 
and the point R I’; these muscles have the 

advantage of acting on the extremities of a 
lever equal to the line O N. When any force 
equal to that in RS is acting simultaneously 
with that of the thyro-arytenoideus, in the di- 
rection ARP B perpendicular to RS, the 
- composition of these forces RS and ARP B 
will produce a resultant in the diagonal R N, 
feats will cut the axis N; and as by hypo- 
thesis the forces RO and RP are equals, R 

and consequently A will be fixed points; but 
the attachment of the thyro-arytenoid at B 

makes an angle with the axis in the line BN, 

and the perpendicular cutting the direction of 

the force of this muscle produced to the axis is 
PN; thus whilst the sterno-thyroid has, by 
‘its action on the lever O N, fixed the points A 
and R, the thyro-arytenoid may act with an 
equal force at the point B on the lever P N ; 

but as the force P N is produced on the cricoid 

(which is free to move by the relaxing of the 

crico-thyroid), the result will be to rotate the 

point B towards A, and depress the point f” to 

J; and thus the question is solved. In the 
preceding demonstration it must be remem- 


109 


bered that the point R is assumed to be that 
in which the whole of the sterno-thyroid is in- 
serted, whereas it is expanded upon the surface 
around the oblique ridge, but any of its fibres 
below R will have the same effect as if at 
R, provided they are in the line OS. It 
must also be borne in mind that the thyro- 
hyoid prolongs the action of the ste:no-thyroid 
to the os hyoides; but in this instance the os 
hyoides itself descends simultaneously with 
the expansion of the crico-thyroid space, and 
we know that the sterno-thyroid is always in 
action during the descent of the larynx. There 
is, however, very little muscular force required 
for rotating the cricoid in the direction in ques- 
tion. It is therefore evident that the sterno- 
thyroid is the antagonist to the thyro-arytenoid, 
and that, in this instance, during the rotation 
of 'the cricoid on the thyroid in the direction 
BBPA must the antagonist to the crico- 
thyroid. 

From the preceding demonstrations we con- 
clude that when the crico-thyroidei, the thyro- 
arytenoidei, the crico-arytenoidei laterales, and 
the arytenoid muscles are acting simultane- 
ously, the chink of the glottis is entirely closed. 
Another function of the thyro-arytenoidei re- 
lates to their effects during the production of 
vocal sounds, which will be considered in the 
article Vorce. In order that the glottis may 
be closed in the manner just described, it is 
necessary that the crico-thyroid assisted by the 
sterno-thyroid should have fixed the fulcrum 
for the play of these muscular motions. 

The crico-arytenvidei postici.—The intrinsic 
muscles of the larynx already described tend, 
more or less, to affect the antero-posterior di- 
ameter of the laryx, the tension of the thyro- 
arytenoid ligaments, or the contraction of the 
chink of the glottis. The crico-arytenoidei 
postici have altozether a different tendency. 
They are a pair of muscles arising at the pos- 
terior surface of the cricoid (e e, figs. 27 & 28); 
the superior and middle fibres ascend obliquely, 
the inferior nearly vertical'y to be inserted into 
the lateral prominences at the bases of the ary- 
tenoid cartilazes, anterior to the crico-aryte- 
noidei laterales. 

These muscles lie under the mucous mem- 
brane of the pharynx, and upon the posterior 
surface of the cricoid. 

The contraction of these muscles is gene- 
rally said to draw the arytenoids backwards, 
outwards, and downwards, and to open the 
glottis posteriorly. This view is in a great 
degree, but not strictly, accurate. ‘The crico- 
arytenoideus posticus being inserted into the 
arytenoid cartilage at N has the effect of acting 
as on the arm of a short lever at N, and of 
rotating it upon the axis O P, in the direction of 
NW, which is directly opposed to the direc- 
tion of the force of the crico-arytenoideus late- 
ralis, which is represented by W N, therefore 
the effect of this muscle is to separate the vocal 
ligameuts, and consequently to open the chink 
of the glottis. Mr. Willis remarks that the 
thyro-arytenoidei postici do not draw the ary- 
tenoids backwards, as described by anatomists, 
which implies that the posterior fasciculi of the 


110 
ligamentous fibres of the crico-arytenoid arti- 
culation at B (fig. 30) are relaxed; for, al- 
though some fibres lying nearest the mesial 
plane are directed to draw the arytenoids to- 
wards B, they are counteracted by the fibres 
lying furthest from it, and by assuming the 
whole to act together, the resultant will be as 
nearly as possible "est gona jo to the axis of 
articulation O P, which would open the glottis ; 
and therefore he concludes that the force of the 
thyro-arytenoidei postici in a direction back- 
wards may be neglected. _Bichat erroneously 
considered that they assist the thyro-aryte- 
noidei and crico-arytenoidei in drawing the 
thyro-arytenoid ligaments very tense.* 

The thyro-epiglottidei—These are a pair of 
small muscles situated between the anterior sur- 
face of the thyroid cartilage and epiglottis ; they 
arise from the internal surface of the thyroid 
near its middle, and not far from the origin of 
the thyro-arytenoidei ; their fibres are directed 
upwards and forwards to the base of the epi- 
glottis, to which they are inserted behind the 
ligamenta thyro-epiglottidea. 

Their action is to depress the epiglottis. 

The aryteno-epiglottidei are two small mus- 
cles, arising from the superior pyramid of the 
arytenoid cartilages posterior to the arytenoid 
muscles, or from the fibrous raphé situated 
vertically behind them ; they pass upwards and 
forwards to the sides of the epiglottis, and upon 
the terior border of the thyro-epiglottic 
membrane. 

Action Owing to the direction of their 
fibres, the thyro-and aryteno-epiglottidei tend 
to depress the epiglottis, or rather to effect the 
tension of the aryteno-epiglottic mucous folds. 

The action of the intrinsic muscles of the 
larynx may be briefly recapitulated as follows : 

The crico-arytenoidei postici open the glottis ; 
all the other muscles close it. 

The arytenoideus obliquus and arytenoideus 
transversus approximate the arytenoid cartilages 
posteriorly. The crico-arytenoidei laterales 
and the thyro-arytenoidei bring them in Contact 
anteriorly, The thyro-arytenoidei close the 
centre of the glottis, and with the crico-thyroidei, 
assisted by the sterno-thyroidei, regulate the 
tension, position, and vibrating length of the 
chorde vocales. 

The crico-thyroidei and sterno-thyroidei an- 
tagonise the thyro-arytenoidei, and in stretch- 
ing the crico-thyroid ligament, the sterno-thy- 
roidei with the thyro-arytenoidei antagonise the 
crico-thyroidei. 

The crico-arytenoidei laterales, and thyro- 
arytenoidei, and the arytenoideus obliquus and 
transversus antagonise the crico-arytenoidei 
postici. These last-named muscles likewise 
may be said to antagonize all the muscles which 
close the glottis. 

The genio-glossi, the linguales, the stylo- 
pharyngei, and crico-pharyngei, and hyo-glossi, 
are muscles associated in common with the mo- 


* Qnand les thyro-arytenoidiens et crico-aryte- 
noidiens lateraux d’une part, et les crico-arytenoi- 
diens posterieurs d’une autre part agissent simul- 
tanément, les ligamens thyro-aryténoidiens sont 
fortement tendus. 


NORMAL ANATOMY OF THE LARYNX. 


and larynx, 
belong rather to the structure and functions « 
the two former of these organs than to # 
larynx, and consequently are considered ¢ 
as auxiliary. a 
The motions of the internal mechanis 
the larynx being effected by muse 
forces are directed, with respect to 
in various degrees of obliquity, and in diff 
planes, and producing by their combim 
results which can only be demonstrated on 
chanical principles, it has been deemed des 
ble to introduce them into the preceding it 
tigations to insure greater precision la 
and accuracy of result, and the more espe 
as we find in the works of our best anat 
writers the most discordant opinions, b 
parently upon mere hypothesis or 
observation, and without reference to any ¢ 
or principle from whence their conclusions 
drawn. . 
The perusal of the works of Albinus,* I 
ler,t Cowper,t Séemmering,§ Meckel,|j | 
chat, Magendie,** and Bell,++ confirm : 
remarks ; exceptions to these observations 
found in the works of Borelli,t{ Bart 
and W. Weber,|i|| Bernouilli,{{ 
and Willis;+++ from the invaluable in 
tions of the latter much assistance has b 
rived. 
Bloodvessels.—The arteries of the lai ynx 
derived from the superior thyroid, a branch o 
external carotid and from the inferior thy; 
branch of the subclavian. Small veins 
pany the arteries and empty themselves int 
neighbouring trunks. 4 
Structures called glands—The a 
gland. Syn. Glandule arytenoidee, 
gagni, Bichat, Cloquet; cartilago 
Jormis, Wrisberg, Bandt. The te 
gland is an inappropriate designation gi 
to the cuneiform cartilage by Morgagn 
whose views of the structure of this body 
adopted by Bichat,$§§ Cloquet,|jjj|| and C 


* Historia Musculorum, lib. ii. chap. 2. 
+ Elem. Phys. tom. iii. 

Anat. of the human body. 

De Corporis Hum. Struct. 


tions of the tongue, pharynx, 


Traité Générale, tom. x. 
Traité d’Anat. desc. tom, ii. 

** Physiol. 

tt Anat. of the human body. a 

tt De motu animalium. Lost Batav. 1 

§ Nouvelle mechanique des mouvem 
l’Homme et des Animaux, 1798. 

||| Mechanik der Menschlichen Geh 
mit xvii Taf. Gott. 1836-8. 

44 De motu musculorum. 

*** The muscular motions of the human b 

ttt Cambridge Phil. Trans. 1833. a 

tt} Constant glandule arytenoidee ex g 
substantia é livido albescente, de qua utilem ob 
endo laryngi succum maximé inter ede 
vociferandum, appressa epiglottis; vel 
vicini musculi exprimunt. 

§$§ Il apparoit que les deux glandes a 
ne sont que des glandes muqueuses plus pront 
que celles qui entourent le reste de la 
laryngée, mais qu’elles ont absolument le 


usage. Op. cit. p. 386. 
wil Les glandes sont formées de petits gr 
a assez consistans, d’une cout ris 
p- cit. 


NORMAL ANATOMY OF THE LARYNX. 


veilhier.* The description given of it by 

Morgagni is, that it consists of a granular sub- 

stance of a livid whitish colour, from which 

under the pressure of the epiglottic or neigh- 
bouring muscles a fluid is poured out. Wris- 
_ bergt described it as a cartilage under the name 
of cuneiform. Cuvier and Wolff, as before 
stated, have confounded it with the cartilage of 
Santorini. Morgagni appears to have mistaken 
for glandular the yellow elastic tissue pene- 
trating its body. Lauth describes some mucous 
‘follicles about its base and internal surface, 
jut he opposes the views of Morgagni on the 
constitution of this body. This body is some- 
jmes absent in the human subject, but scarcely 
erin the quadrumana. Its structure is de- 
cidedly cartilaginous. 
The epiglottic gland. — Syn. glandula epi- 
ploitidis, Fab. Cass. Morg. The epiglottic 
_ gland is a name given to a mass of yellow 
‘ligamentous adipose and cellular substance, 
‘situated in the triangular space between 
e anterior surface of the epiglottis and the 
ngle of the thyroid cartilage; it is bounded 
nteriorly by the thyro-hyoid membrane, above 
by the thyro-epiglottic mucous membrane and 
ligament ; below, by the union of the epiglottis 
®, th the thyroid cartilage, and on each side by 
_ the mucous membrane passing from the thyroid 
tothe epiglottis. Berengarius speaks of it as a 
fleshy gland: Steno and many others as com- 
_ posed of granules, whose ducts perforate the 
 epiglottis and open on its posterior surface. 
_ Fabricius, Casserius, and Morgagni{ have de- 
scribed and figured these supposed granules 
_ and ducts. Bichat,§ Cloquet,|| Quain,{/ and 
* most modern anatomists adopt the same views. 
_ Morgagni, upon the same supposition as he 
4 had formed of the nature of the elastic tissue, 
_ considers the composition of the epiglottis to 
ij be chiefly glandular. Cloquet and Bichat 
_ admit the difficulty of detecting any follicular 
_ structure, nor could we discover any under the 
_ microscope ; and from what has been already 
_ stated on the structure of the epiglottis, we 
conclude, as of the arytenoid, that the structure 
_ which enjoys the name of epiglottic gland is 
not glandular. 

Mucous membrane.—The mucous membrane 
of the larynx is continuous with that which 
covers the mouth and pharynx. The posterior 
_ Surface of the larynx is bounded by the pharynx, 

and is lined by mucous membrane both on its 


De 


i 


* Traité d’Anat. 
+ Prime linex phys. anat. ade Haller, ed. Wris- 
berg. Gotting. 1780-8. p. 157. 
Morg. advers. anat. om. tab. ii. p. 48. 
§ ** Cet espace est occupé par un corps manifeste- 
_ ment celluleux, et graisseux, dans sa plus grande 
_ partie, mais qui est inferieurement recouvré de 
petits grains glanduleux, tantot agglommérés, tantot 
isolés, lesquels envoient sensiblement des prolonge- 
mens dans les trous dont est percée l’epiglotte : les 
en emens paroissent s’ouvrir sur sa surface 
aryngée, aux orifices qu’on y distingue. Quelque- 
fois les petits corps ylanduleux sont tellement 
Masqués par cette graisse jaunatre, qu’on ne peut 
les distinguer.” Traité d’Anat. descript. tom. ii. 


p- 385. 
Anat. descript. p. 245. 
Elem. of Anat. p, 858. 


111 


anterior and posterior surfaces. If the state- 
ment of Cruveilhier be correct, this singular 
duplication is not to be found elsewhere in the 
animal economy; afterwards it is reflected over 
the surface of the base of the tongue, and lines 
the interior surface of the epiglottis; in this 
space it forms three folds, called glosso-epiglottic, 
often described as the middle, and two lateral, 
which adhere closely to the surface of the epi- 
glottis. The mucous membrane being reflected 
over the free part of the epiglottis, to which it 
rather closely adheres, then lines its posterior 
surface and dips into the larynx. 

A duplication called the aryteno-epiglottic 
fold passes from each side of the lateral mar- 
gin of the epiglottis to the vertical apophysis of 
the arytenoid cartilage. This membrane is 
connected posteriorly with the mucous coat of 
the pharynx, anélines the posterior surface of 
the larynx; it is reflected over the arytenoid 
cartilages, and with the aryteno-epiglottic fold 
forms the posterior and lateral superior margin 
of the larynx ; covers the superior thyro-aryte- 
noid ligaments, penetrates to the bottom of the 
ventricles; from thence, after lining the inferior 
thyro-arytenoid ligaments, it passes through the 
chink of the glottis, covers the thyro and crico- 
arytenoideus lateralis muscles, and the internal 
surface of the cricoid cartilages, and becomes 
the investing membrane of the trachea. 

The laryngeal membrane is perforated by 
numerous mucous orifices of a peculiar pale 
rose-colour, and is remarkable for its great sen- 
sibility, more especially in the region above the 
rima glottidis. 

Lhe rima glottidis. Syn. cavum seu sinus la- 
ryngis The chink of the larynx is an aperture 
directed horizontally, connecting the supra and 
infra-laryngeal regions, and allowing the free 
transmission of air in respiration. It is bound- 
ed posteriorly by the arytenoid cartilages, ary- 
tenoid muscle and mucous membrane; laterally 
by the arytenoid cartilages and the thyro-aryte- 
noid ligaments, which, with the mucous mem- 
brane reflected over them, present nearly rect- 
angular-shaped valves, attached on three sides, 
leaving one, bounding the glottis, free; ante- 
riorly by the angle of the thyroid. Immedi- 
ately above it are the ventricles, one on each 
side. The intrinsic muscles of the larynx not 
only contribute to its functions in the produc- 
tion of voice, but determine its form. The form 
of the chink of the glottis is variable; in the 
state of repose, or that of ordinary respiration, 
it is triangular, the aperture dilating during 
inspiration and contracting during expiration. 
When the arytenoids are separated to the great- 
est extent by the crico-arytenoidei postici, it 
assumes a lozenge form ; if the posterior bases 
of the arytenoids are closed by the arytenoid 
muscles it becomes an ellipse; if the anterior 
apophyses of the arytenoids meet by the action 
of the crico-arytenoidei laterales, the chink may 
be divided into two parts. The length of the 
chink of the glottis is very variable, and bears a 
relation to that of the thyro-arytenoid ligaments ; 
like the latter, it increases with age in an arith- 
metical proportion until the period of puberty ; 
at that time its length in the male sex under- 


112 


goes a sudden development, whilst in the female 
it remains stationary. The comparative length of 
the chink in the male and female is proportional 
to the relative lengths of the vocal ligaments 
already detailed. The length of the rima glot- 
tidis bears no relation to the stature of the indi- 
vidual. In the adult male it is about eleven 
lines, of which the boundaries formed by the 
arytenoid cartilages are four, and the thyro-ary- 
tenoid ligaments seven lines. In the male and 
female it is on a mean average as three in the 
former to two in the latter. In a female, M. 
Lauth however found the rima glottidis to mea- 
sure from ten to eleven lines, whilst that of a 
tall male extended only from eight to nine lines ; 
but this is a rare instance. 

The pomum Adami on the thyroid has a 
corresponding concavity within, which affords 
a greater length in the mesial section of the 
larynx, and which tends to increase the longi- 
tudinal dimensions of the glottis. In several 
of the ruminantia the concavity is very con- 
spicuous.* The breadth of the glottis is much 
less than its length. In a state of repose its 
transverse section is not more in the adult than 
about two or three lines, or with respect to its 
length as two to eleven, but the diameter varies 
with the intensity of the forces of the intrinsic 
muscles of the larynx. 

The ventricles. Ventricule ou sinus du laryne. 
Cruv.— These are oval or elliptical cavities 
directed from before backwards, between the 
superior and inferior ligaments. The depths of 
the ventricles are effected by the distance from 
the free margin of the vocal ligaments to the 
internal surface of the thyroid, or rather to the 
thyro-arytenoid muscles, which constitute the 
bottom of the ventricles. The internal part of 
the posterior cavity of the ventricles is enlarged 
and deepened by a duplicature of the mucous 
membrane passing external to the arytenoid 
cartilage, which has been described by Mor- 
gagni, and recently more particularly by Mr. 
Hiltont under the name sacculus laryngis, 
The ventricles are prolonged anteriorly, extend- 
ing along the vocal cords on each side of the 
epiglottis. In size the ventricles vary with the 
general dimensions of the larynx; they are 
each divided into an interior and posterior 
cavity by a transverse ridge. The ventricles 
afford greater freedom of motion to the inferior 
thyro-arytenoid ligaments. 

Nerves.—The larynx is exquisitely sensible, 
and, as we have seen, combines complex and 
delicate motions with secreting surfaces. These 
properties result from its nervous endowment, 
which is derived from two branches of the 
pneumo-gastric nerve, namely, the superior 
and the inferior laryngeal nerves. 

It will be unnecessary to enter into any de- 
tailed description of these nerves here. Their 
distribution will be found fully described in 
the article Par vaGuM, to which we refer. 
Let it suffice to mention, that the superior la- 
ryngeal nerve by its external branch gives fila- 
ments, 1, to the inferior constrictor of the pha- 


* Vide Pallas Spicil. Zool. Trans. xii, 
t Guy’s Hosp. Reports, No. v. 


NORMAL ANATOMY OF TILE LARYNX. 


A view, from Mr. Swan, of the superior @ 
inferior la nerves. a, a portion of 
tongue ; b, the epiglottis ; c, the thyroid cartila 
d, the posterior arytenoid muscle divided for s) 
ing a branch of the recurrent nerve passing to | 
oblique and transverse muscles; e, the late 
crico arytenoid muscle; f, the thyro- 101 
muscle ; g, the arytenoideus obliquus ; A, the ar 
tenoideus transversus ; i, the crico-thyroid 5 j, 

1, the superior laryngeal nerve; 2, a branch 
this nerve to the membrane connected with tl 
covering the epiglottis ; 3, a branch of the 
laryngeal to the membrane placed between 
superior extremities of the arytenoid ¢ 
4, the recurrent nerve; 5, a branch of the rm 
rent given off to the membrane lying betwee; 
larynx and pharynx; 6,a hence of th pcur 
nerve to communicate with a branch of the 
rior laryngeal nerve ; 7, a branch of the recurre 
to the posterior crico-arytenoid muscle ; 8, a bram 
to the crico-thyroid and crico-arytenoid le 
9, abranch giving filaments to the posterior 
arytenoid, and passing between this m 
the arytenoid cartilage, to terminate in the obliqa 
and transverse arytenoid muscles. 


rynx; 2, to the thyro-hyoid muscle and 
brane ; 3, to the laryngeal plexus; 4, to 1 
crico-thyroid muscle ; 5, to the thyroid glan 
The internal branch of the superior ynge 
nerve supplies filaments, 1, to the epiglottis 
2, to the adipose and mucous membrane 
4, to the arytenoid muscles; 4, to the thyro- 
arytenoideus; 5, to the crico-arytenoideus late 
ralis; 6,a descending anastomotic branch to th 


ecurrent; and, 7, to the aryteno-epiglottic 
ucous folds and muscles. 
The inferior laryngeal or recurrent nerve 
es filaments, 1, to the pneumo-gastric and 
diac plexus; 2, to the pharynx; 3, to the 
achea ; 4, to the esophagus; 5, to the crico- 
ytenoideus posticus; 6, to the arytenoideus 
liquus and transversus; 7, to the crico- 
jtenoideus lateralis and thyro-arytenoideus ; 
an anastomosing branch to the superior 
Our knowledge of the anatomical distribu- 
1 of the laryngeal nerves, and of the func- 
is of the intrinsic muscles of the larynx, 
sufficient, independently of experiment, to 
onstrate the inaccuracy of the well known 
n of M. Magendie, supported by Clo- 
Pinel, Percy, and several others, that the 
urrent nerve presides over those actions 
th open the glottis, whilst the superior la- 
geal influences those muscles which close 
glottis. The principal facts opposed to 
rt y of M. Magendie may be briefly 
ed as follows. 1. It was well known long 
re the promulgation of Magendie’s views 
the inferior laryngeal nerve gave to the 
muscle a filament which had been 
sribed by Andersch,* Bichat,t and Mec- 
and subsequently by Schlemm Bischoff, 
, Cruveilhier, Dr. Reid, and others, there- 
it has been sufficiently demonstrated that 
he recurrent nerve supplies the muscles that 
se, as well as those which open the glottis. 
-M. Magendie has stated that the crico- 
ytenoideus lateralis and thyro-arytenoideus 
yened the glottis, whereas in the preceding 
fails it has been proved that these muscles 
€ it. 3. The loss of voice which follows 
section of the recurrent nerves results from 
walysis of all the muscles (except the 
co-thyroid) which both open and close the 
a fact proved by the experiments of 
lois and Dr. Reid. The limited space 
d to this article will only permit us to 
the conclusions to which recent expe- 
s have arrived respecting the functions 
laryngeal nerves. ‘The external branch 
superior laryngeal is composed chiefly 
motor fibres, and it controls the action of 
2 crico-thyroid and the other muscles to 
ich it gives filaments. The internal branch 
the superior laryngeal is composed of sensi- 
ive fibres, which confer the most exquisite 
sibility on the mucous membrane of the 
yNx, more especially in its supra-glottideal 
ion. It is therefore the sensitive and the 
itor nerve of the larynx. The inferior la- 
geal supplies the muscles that hoth open 
| close the glottis, and is chiefly a nerve of 
Motion when it reaches the larynx, but a few 
if its fibres go to the mucous membrane. The 
mion of the superior with the inferior laryngeal 
ranch by an anastomosing filament, preserves 
-Teciprocal play in the functions of these 


; 


— theo 


b 


* 
enolc 


Fragmentum descr. nervor. 
+ Traité d’Anat. tom. iii, p. 216. 


¢ Man. d’Anat. tom. iii. p. 66, 


NORMAL ANATOMY OF THE LARYNX. 


113 


nerves: whilst the branches anastomosing with 
the sympathetic, connect the larynx with the 
ganglionic system ; the pulmonary and cardiac 
branches connect it with the respiratory and 
circulating systems, and thus associate the 
larynx with those vital functions. The laryn- 
geal nerves also belonging to the reflex system, 
Impressions made on the sensitive filaments of 
the larynx are reflected to the medulla ob- 
longata, and propagated. by a circuitous route 
to the motor filaments of the recurrent, so that 
a long interval is traversed in circulating an 
impression from the sensitive to the motor 
nerves of the larynx; but according to the esti- 
mate made of the speed with which an impulse 
is propagated along a nerve, which is assumed 
to be equal to that of electricity, the time occu- 
pied to transmit an impression from the fila- 
ments of sensation to,those of motion must be 
inappreciable to our senses. Other important 
physiological considerations result from recent 
experimental researches, those of Le Gallois 
and Dr. Reid in particular. 1. With respect 
to the motions of the glottis during respiration, 
the dilatation during inspiration, and contrac- 
tion during expiration, are the effects of the 
play of muscular force in opposition to the 
direction of the current of air in its passage 
to and from the lungs, the tendency of which is 
to produce the reverse action.* There is a 
constant periodical oscillatory motion of the 
arytenoid cartilages, revolving upon the axis of 
articulation, O P, (fig. 30,) at every expiration 
and inspiration ; hence the necessity of a syno- 
vial membrane to lubricate the crico-arytenoid 
articulation. 2. When the recurrent nerves 
are diseased, compressed, or cut, so as to para- 
lyse the crico-arytenoideus.posticus, the power 
of muscular action in opposition to the direction 
of the inspired air is lost. The valves of the 
glottis are drawn downwards with the air, the 
anterior apophysis of the arytenoid cartilages 
rotated inwards, the chink closes, symptoms of 
suffocation supervene, and asphyxia results. 

When spasmodic closure of the chink of the 
glottis occurs, the obstacle to the ingress of air 
is increased by convulsive attempts to draw in 
the breath, which causes a rarefaction of the 
air below the glottis, and augments the atmos- 
pheric pressure above it; and the chest thus, 
says Dr. Ley, ‘* becomes hermetically sealed.” 
If the aperture of the glottis be partially open, 
the air rushing through it causes a stridulous 
sound (/aryngismus stridulus ), whilst in ano- 
ther position of the glottis the crowing inspi- 
ration is produced ; this effect arises (accord- 
ing to Dr. Ley) from the chink of the glottis 
being partially open for the admission of air, 
and remaining so until an explosive expiration, 
such as screaming, coughing, or belching, me~ 
chanically bursts open the floodgates, and 
terminates the paroxysm. 


* In the production of these periodical mover 
ments, the action of the muscles is involuntary, but 
in their action for the purposes of voice, they be- 
come subordinate to the will, and therefore belong 
also to the voluntary system. 

I 


114 

Asphyxia is often delayed by the posterior 
chink of the glottis being seiniuelh t artially 
Open, in consequence of the coincident para- 
lysed force of the arytenoid muscles, and by the 
ona inclination of the crico-arytenoid articu- 

ting axis, with respect to its vertical section, 
preventing the approximation of the arytenoid 
cartilages by which the posterior part only of 
the chink can be closed. When any irritation 
is produced on the exquisitely sensitive mucous 
membrane of the larynx, it transmits a reflex 
action to the motor filaments of the recurrent, 
and the glottis is spasmodically closed, without 
any such morbid condition of the recurrent 
nerve as Dr. Ley supposed necessary. 

The larynx, when dissected out, and cleared 
of its extrinsic structures, presents on its ante- 
rior aspect the free margin of the epiglottis, the 
notch of the thyroid, the pomum Adami, its 
mesial line, the crico-thyroid space, and liga- 
ment, and the anterior border of the cricoid 
cartilage. 

On each side of the larynx are observable a 
portion of the wings of the thyroid, the crico- 
thyroid muscle, the great and lesser cornu, the 
oo and inferior tubercles, the oblique 
ridge, the superior and inferior margins of the 
thyroid, the side of the cricoid, with a portion 
of the lateral crico-thyroid ligament, and the 
superior, inferior, and posterior margins of the 
cricoid. 

On the posterior aspect are observable, the 
posterior free surface of the epiglottis, the ary- 
tenoid cartilages and muscles, the aryteno- 
epiglottic mucous folds, the crico-arytenoidei 
postici muscles, the vertical ridge of the cricoid, 
the posterior margins of the thyroid, and the 
posterior surface of the cricoid cartilages. 

In the internal surface, from above, we ob- 
serve the superior margin of the thyroid carti- 
lage and great cornua, forming the superior 
boundary of the larynx, the superior margin 
and notch of the epiglottis, the cornicula la- 
ryngis, the arytenoid and cuneiform cartilages, 
the aryteno-epiglottic mucous folds, the supe- 
rior and inferior vocal ligaments, the ventricles, 
the rima glottidis, and the mucous membrane. 

Looking from below upwards, we perceive 
the inferior circular margin of the cricoid, the 
membrane lining its internal surface, the infe- 
rior aspect of the thyro-arytenoid ligaments, 
and the rima glottidis. 

The preceding outline of thegeneral anatomy 
of the larynx will give the reader an idea of its 
manifold structures, its exquisite sensibility, 
its complex motions, its connection with the 
process of deglutition, and its admirable adapt- 
ation for the production of sound, and may 
serve to impress a conviction that it is one of 
the most elaborate and perfect specimens of 
mechanism in the human body. 


BIBLIOGRAPHY.— Galeni Opera, de locis affectis, 
lib, i. cap. 6, p. 6. Vesalius, De corp. humani 
fabrica, Basilie, fol. 1555. J. Casserius, de org. vocis 
et auditu, Ferrara, 1600, Riolanus, Opera. Anat. 
Paris, fol. 1649. Bidloo, Anat. Humani Corp. 


* For the description of the vocal functions, see 
the Article VOICE. 


ABNORMAL ANATOMY OF THE LARYNX. 


eg ha 1685. Malpighi, Opera = omnia, b 
ol. . otomia i 
Bvo. 1694, p. 80. ‘Dodart, Mem, de I? Acad. 1 
des Sciences, 1700. Morgagni, Adve ; 
omnia, Lugd. 1718. Santorini, O 
Anat. Venice, 4to. 1724. Albinus, Hist. 
Hominis, Leidz Batavorum, 4to., 1734. _ 
Mem. de l’Acad. Royale, 1741, p. 400. — 
ini, Anat. Int. Veronz, fol. 1754, » . 
45, 53. , Ouvres Anat. Paris, 8vo. 
p- 91. Winslow, Anat. Edinb. 8vo. 1763. Vieg d’. 
Mem. de l’Acad. Royale, 1779. Haller, El. Pl 
Soemmering, De corp. humani stract. vol.’ 
jecti ad Menum, 8vo. 1801. Savart, 
Chimie et de Physique, Paris, 8vo. 1825. 
nati, Recherches sur la Mechanisme de la 
8vo. Paris, 1832. Willis, Camb. Phil. 
vol. iv. p. 323, Camb. 1832. Cloquet, ' 
d’Anat. descrip. Paris, 8vo. 1834. Laut! hy 
de l’Acad. Royale de Med, 1835. P. Broe, 
d’Anat. descrip. Paris, 1837, p. 527. The 
cipal systems of anatomy. fe 
(J. Bisho 
LARYNX. (Morsip ANATOMY AND PA 
LoGy.)}—The importance of this organ t 
and even when existence is not actual! 
dangered, to the comfort and well-being 
individual, must render any deviation | 
healthy and normal condition in the highs 
gree interesting to the pathologist: ne 
that interest be diminished by reflecting ¢ 
paramount value of a knowledge of th 
viations to every practical physician. 5 
size and composed of few and appare 
ple structures—its functions so obviou 
any imperfection in their performance co 
quickly perceived and readily understoc 
would appear only reasonable to suppo: 
its various pathological conditions shoul 
been observed, and the symptoms con 
with them Jong since collected and arn 
Yet, such is not the history of the pathol 
the larynx: on the contrary, it presents 
to us with all the interest of a new dise 
and whatever is known on the subject 
result of investigations made within he I 
years. We have the opinion of the lal 
Cheyne, (no mean authority on 
that in the year 1800, “ vada ere 
in Britain more than one individual, | 
Monro, who was acquainted with the: 
ture of the disease of which General 
ington died—acute laryngitis ;” and the 
writer goes on to shew that in ten years 
quent to that general’s death, Dr. Bailli 
at the head of the medical profession: 
land, admitted that he was ignore 
nature of the same malady. But 
reverting so far back, I may be permi 
state, that within a comparatively rec 
I can personally remember the 
ledge that obtained amongst medical 
tioners in this particular, and the de 
results that too frequently ensued 
though it may be gratifying to reflec 
altered condition of things at preset 
must be obvious that a subject so shor 
under investigation cannot be expected 
been thoroughly worked out. 


‘ ry 
‘ 


: 


been brought forward—perhaps more 
behind, and any person now attempting 


an exact and adequate description of the pa- 
logy of this organ, may probably find it ne- 
sary to bespeak a very considerable degree 
indulgence. 
Accustomed to consider laryngeal disease 
actically, and more particularly with refe- 
nce to operation, I find it difficult to bind 
_ myself down to mere pathological arrangement, 
or to attempt a satisfactory classification. True, 
ke other organs, the larynx is composed of 
dit t structures, in each of which disease 
fill assume the character peculiar to itself, and 
xhibit the appropriate appearances in an exa-. 
ination after Neath, but it rarely happens that 
rbid actions are so limited in extent, as to 
tist and produce their proper results in one 
Ssue without the participation more or less of 
the others. This will produce confusion, and 
fender it a matter of difficulty to connect symp- 
ns with the existing pathological conditions 
hat Occasion them, and may be adduced as an 
jection to any attempt at arrangement 
junded upon structure alone: yet there really 
an be no classification altogether exempt from 
1 Same or a similar observation, and there- 
_ fore I shall adopt this one as having the merit 
“of the greatest simplicity. Following this 
iew then, I find the larynx to be composed of 
he following structures, viz. :— 
_ 1. Mucous membrane, exhibiting all the va- 
eties of inflammation that are observed in that 
ue when situated in other organs. Thus 
lammation here may be acute or chronic, 
egmonous or erysipelatous, idiopathic or 
mptomatic, and attended by fever of a ty- 
phoid or an inflammatory type. And these 
varieties eompanid different effects or results. 
nus we have examples of acute idiopathic in- 
ammation with fever of a sthenic kind in the 
troup of children, producing the adventitious 
membrane, and in the laryngitis of adults, that 
terminates so frequently in edema; and of the 
same local disease with asthenic fever in the 
diphtherite and in erysipelas: whilst accident 
furnishes numerous instances of the results of 
ymptomatic inflammation in the consequences 
of burns, scalds, penetrating wounds, and the 
allowing of caustic poisons. As happens 
© constantly in other structures, chronic in- 
mmation is here best known by the changes 
, induces, and furnishes us with abundant 
yecimens of hypertrophy or thickening of the 
membrane, and of the different forms of ul- 
meer fon. 
2. Submucous tissue, which is the seat of 
edematous effusions, and of the sloughy and pu- 
trid matter produced by diffuse inflammation. 
3. Cartilage, in which we remark great and 
ant varieties of disease, such as inflam- 
mation, ulceration, mortification, degeneration 
into an earthy unorganized material, atrophy, 
pertrophy, and some alterations of shape 
aid structure probably depending on scrofula 
or other constitutional taint. 
__ 4. Muscle, the seat of those spasmodic ac- 
| tions so frequent and so perilous in laryngeal 
© one and perhaps occasionally of gout 
x 


SS 


se cee 


ape DOT 


Sook taeda 


3 


|< 


=. 


" im DO 


nd rheumatism also. 


ni} 
iif 


| 
a 


ABNORMAL ANATOMY OF THE LARYNX. 


113 


5. Ligaments. I know not whether disease 
ever originates in these structures, but there can 
be no doubt that they are sometimes removed 
by ulceration, and there is reason to believe 
that great inconvenience and even danger may 
be occasioned by a preternatural relaxation of 
some of them. 

1. Acute inflammation of the mucous mem- 
brane is always in the first instance attended 
by a change of colour more or less intense ac- 
cording to its situation, being comparatively 
pale where it is closely attached to a subjacent 
cartilage, but of a deep and concentrated red 
tint, verging on purple, where it is more loosely 
connected by the intervention of cellular tissue 
er muscle. The membrane is also swollen, 
soft and pulpy, these characters being likewise 
influenced by the“nature of its connection to 
subjacent parts, and I believe the usual 
symptom of inflammation, “ pain,” is not ab- 
sent, although the mental agony attendant on 
obstructed respiration renders this a secondary 
consideration to the patient: certainly in the 
laryngitis of the adult, pressure on the pomum 
Adami is verv sensibly felt. In connexion with 
these changes the functions of the organ are 
interrupted and impaired. The usual secretion 
of the membrane is diminished in quantity, or 
perhaps ceases altogether, and hence the sen- 
sation of dryness or huskiness in the throat, 


_and the peculiar solitary ringing cough that 


uniformly is present. The voice is also in- 
jured, being occasionally nearly if not altoge- 
ther lost, and there is difficulty of breathing 
accompanied by a harsh stridulous sound ; this 
latter being caused by the mechanical obstruc- 
tion to the passage of air produced either by 
tumefaction or by spasm. Having continued a 
given time,—and the first stage of inflammation 
of the larynx if very acute is usually but short,— 
certain results or effects are developed, which, 
differing in the child and the adult, require a 
brief separate notice for each. 

The acute laryngitis of the child, or croup, 
although generally commencing in the larynx 
alone, and sometimes altogether confined to it, 
is by no means uniformly so: on the contrary, 
it not only may commence in or extend to the 
trachea, but possibly have its origin in the 
bronchial cells, and pass thence upwards along 
the tubes. It may also perhaps not be strictly 
correct to arrange croup amongst the diseases 
that are preceded or accompanied by inflam- 
matory fever, for occasionally it makes its at- 
tack without any previous warning whatever, 
and a child that had retired in apparently per- 
fect health may arouse and alarm its attendants 
in the middle of the night with the sounds of 
that dry, harsh, and incessant cough, and that 
loud and stridulous respiration which afford to 
the practised ear the painful but unerring evi- 
dence of the nature of the mischief present. 
In either case, however, the disease hastens to 
its second pathological state, in which the evi- 
dences of increased vascularity begin to disap- 
pear, and are succeeded by the secretion or 
effusion of a viscid tenacious lymph, which, 
assuming the form of a membrane, has ob- 

1-2 


116 


tained the namie of the false or adventitious 
membrane of croup. This substance is of a 
pale yellow colour, viscid and tenacious ; more 
generally found in the larynx than the trachea ; 
seldom occupying the entire circumference of 
the tube ; unorganized ; incapable of becoming 
the medium of union between opposing sur- 
faces, and with a strong disposition to separate 
from the surface on which it was originally 
formed. It usually commences in the larynx, 
and travels downwards along the trachea; more 
rarely it seems to beyin in the ramifications of 
the bronchial cells; and again, still more sel- 
dom is the entire of the mucous membrane 
attacked at once, and the adventitious mem- 
brane thrown out over its whole extent. Con- 
sidered as a pathological production, this false 
membrane of croup presents some curious and 
interesting subjects for observation, for although 
so generally met with that by some it has been 
regarded as the essential characteristic of the 
disease, yet perhaps it is not invariably or ne- 
cessarily so; at least I have seen cases so far 
resembling croup in all their stages, that they 
could not be distinguished from it during life, 
in which dissection subsequently shewed the 
mucous membrane swollen, and soft, and 
pulpy, with copious submucous effusion, yet 
without the formation of a single flake of 
lymph. Possibly in the few cases of this de- 
scription that came under my observation, the 
disease had proceeded with a rapidity which 
roved fatal before the membrane had time to 
ave been formed. Again, it is the only* 
instance of lymph being produced ona mucous 
surface as the result of active acute inflamma- 
tion. In chronic affections membranous layers 
of lymph are often formed, and in different 
situations, as in the bronchial cells and the 
mucous coat of the intestines, but the acute 
produces it alone in the structures that are the 
seat of croup. And lastly, it appears that this 
effect of inflammation is restricted to patients 
under twelve years of age. Mr. Ryland, in his 
excellent treatise on the larynx, has published 
atable from Bricheteau, by which it is shewn 
from the experience of fourteen distinguished 
authors, that croup “has never occurred at a 
later age than twelve years, and very rarely at 
that age.” My friend, Dr. W. Stokes, con- 
siders the cases published as examples of croup 
occurring in the adult as not being inflamma- 
tory croup at all, but analogous to the diphthe- 
rite of Bretonneau, which will be shewn to be 
avery different disease indeed. 
Such is the pathological condition of the 
rts in the second stage of croup—a condition 
indicated by the increased difficulty of breath- 
ing—the pale and swollen countenance—the 
straining eye—the dilated nostril and the purple 
lip; by the occasional expectoration off some 
portions of the false membrane; and (as hap- 
pens in every affection of the larynx) by severe 
and protracted spasms of the glottis. If the 
patient still continues unrelieved, the third and 
* For an apparent exception to this rule, see a 


case published in the Dub. Journ. of Med, Science, 
September 1838, No. 40, vol. 14. 


ABNORMAL ANATOMY OF THE LARYNX. 


last stage supervenes. The child still breath 
with difficulty, but with increasing lang 
its countenance is pale; its lip b 
there are generally convulsions, in — 
which the fatal event may take place; 01 
he sinks gradually, exhausted and worn 
and dies comatose. And we are to hk 
the actual and immediate cause of des 
the larynx but to the lungs and br 
matter how much the membrane may 
swollen, or how extensively the false mi 
brane may have been formed, the rima 1s 
completely closed, and the patient dies, 
because there is an absolute insufficiency of 
to provide for the arterialization of the b 
but because some change has taken plat 
the organ by which this most important 
tion is performed. When the thorax is op 
the lung does not collapse under the infla 
of atmospheric pressure : when the lung is 
into, it is found to be loaded with dark b 
and with frothy serum, the effusion of ¥ 
latter is often so abundant as nearly to fil 
trachea. The brain, if examined, is ft 
congested, and not unfrequently is there 
effusion of serous fluid into its ventricles. 
The acute inflammation of the mucous 0 
brane of the larynx bears no resemblan 
the adult to that in the child, excepting on 
the agonizing difficulty of respiration a1 
fatality of the result, but the pathological 
ditions are different, and therefore is the di 
in the adult far more manageable. I 
scarcely conceive, much less describe the 
istence of acute laryngitis to any dange 
extent in the membrane alone withe 
participation of the submucous tissue, in 5 
the perilous tumefaction is generally, | ‘no 
ways, seated; I shall, therefore, as I has 
therto done, consider this affection in e d 
tion with its principal pathological result— 
formation of an cedematous effusion. — 
Mucous membranes in every situation $€ 
to be connected to the adjacent tissues by 
species of cellular membrane termed reticul 
as a provision that the courses of the can 
which they form so important a part shoul 
be impeded by any accumulation of fat 
this reticular membrane is more or les 
according to the nature and consistence ¢ 
subjacent structure. Where mucous 
brane is attached to bone, the nature of 
connecting medium is so short and close, 
in many instances it is scarcely obs 
and the membrane, in addition to its 
tions, appears to perform that of a periost 
whilst in other situations, as in the intest 
is so lax as to allow the organ to become 
tended to an almost unlimited extent. 
usual effect of inflammation on this ret 
tissue is an effusion of a serous fluid wit 
cells, and the production of edema; bi 
is of little consequence where the | 
dense and close, and perhaps of sti 
where the organ is widely distensib 
larynx, however, presents an organ of 
character—the mucous membrane is 
tached to muscle and to ligament, 


ee 


~ 


ain are supported and restrained by resisting 
cartilages externally, so that if the submucous 
‘tissue which is here so loose as to allow the 
nembrane to be thrown into natural folds, 
‘should become the seat of infiltration, the 
swelling so pees cannot take a direction 
' outwards, but must tend to compress and 
’ close the aperture of the glottis. This is the 
__ @dema of the glottis, a formidable and too 
i often a fatal affection, but nevertheless present- 
. very considerable pathological varieties. 
us it is sometimes attended by fever, and 
ms only part of a more extended infamma- 
on, involving tonsils and fauces, pharynx and 
arynx: again, it is purely local, confined to 
e larynx alone, and so entirely free from any 
ecompanying fever, that the patient only com- 
s of the difficulty of breathing and the 
. It is often idiopathic, but may be 
roduced by injury, and is a common result of 
wallowing caustic poisons and boiling water ; 
or is it in this latter respect confined to the 
dult, for I have thus seen the superior aper- 
re of the glottis, in a very young child, 
marsed up and closed as if by the drawing of 
running string. It may be situated only in a 
of the larynx, the rest remaining free ; thus 
t is no uncommon occurrence to see only one 
ide of the glottis puffed and swollen, and the 
slit-like aperture thus converted into a curve; 
but the most interesting because the most prac- 
tical illustrations of partial edema will be 
found in cases published by Sir Henry Marsh, 
‘im which the disease appeared to be confined 
‘to the epiglottis alone.* Lastly, I believe it is 
ssible to have this eedema produced without 
external evidence of inflammation. In 
Museum of the School of Park-street there 
preparation shewing it as apparently occa- 
} the vicinity of a large carcinomatous 


she 


ned 


mour. 
_ Considering the pathology of this affection, 
the degrees of inconvenience and of danger 
likely to result from it will be easily under- 
stood. The symptoms will be, a loss or imper- 
ection of voice, which is generally very well 
narked, the utmost effort at articulation amount- 
ing to no more than an indistinct whisper ; and 
difticulty of respiration, including cough and 
ther signs of local irritation. The danger will 
robably be in proportion to the rapidity with 
ich the effusicn is formed, for life may be 
“Mnaintained with a wonderfully diminished 
supply of air to the lungs, provided the dimi- 
ution takes place gradually and slowly: but 
“it may not arise solely from this cause, for here, 
as in every other form of laryngeal disease, spas- 
odie exacerbations are painfully frequent, and 
ace the patient’s life in momentary danger. 
; ion; therefore, developes three different 
causes of death. 


™ 
ny) 


glottis, although swollen, is still pervious— 
perhaps apparently sufficiently so for the ordi- 


_* See Dub. Journ. of Med. Science, March 
1838, v. 13, no. 37. This excellent paper of Sir 
H. =. contains many illustrations of the 
‘Same fact. 


«| 


ABNORMAL ANATOMY OF THE LARYNX. 


117 


nary purposes of respiration; but in order to 
observe the relaxation after spasm, several hours 
must be allowed to elapse between death and 
the post-mortem examination, for the bodies of 
those who die of laryngeal disease become ex- 
tremely rigid, and remain in this state a consi- 
derable time. A second, in which the effusion 
having been poured out with great rapidity, the 
rima is found mechanically blocked up, and 
immediate suffocation occasioned: in this case 
neither the lungs nor brain are engaged, at least 
not necessarily. The third is, where the dis- 
ease has lasted three or four days or more, the 
cedema has been developed but slowly, and 
the diminution of the supply of air been less 
sudden: in these cases, besides the symptoms 
of strangulation;-6thers, indicative of a con- 
gested condition of the lung and brain, are 
observed during the latter periods of existence, 
and corresponding morbid appearances are dis- 
coverable after death. 

Very severe inflammatory affections of the 
mucous membrane of the larynx are unfortu- 
nately too frequent to admit of doubt or to 
create difficulty; but a good deal of confusion 
has arisen from an attempt to identify them, or 
some of them, with croup, because an exuda- 
tion takes place from the surface in some re- 
spects resembling the adventitious membrane 
formed in the latter disease. One of these has 
been described with graphic accuracy by M. 
Bretonneau of Tours, by him supposed to be 
the same with croup, and named Diphtherite : 
but although the differences between these af- 
fections have been observed and pointed out, 
the name is still frequently applied (I fear) 
without very precise ideas attached to it. The 
exact disease described by Bretonneau I do not 
profess to have ever seen, neither have I heard 
of it, unless in one instance in a family in this 
country which lost four of its young and inte- 
resting members by a visitation at least bearing 
some resemblance to it. In hospital I have 
heard the name applied to some throats which 
I never should have thought of identifying 
with that described by the French writer, and 
I feel satisfied that the attempt to mix up 
different and it may be opposite diseases 
under one generic name has done anything but 
simplify the study of pathology. If, however, 
by asthenic croup or diphtherite is meant the 
peculiar local disease which accompanies the 
eruption of scarlatina anginosa, or which is 
frequently met with without any cutaneous 
eruption, especially in adults—which is ac- 
companied throughout by low and typhoid 
fever, and is often propagable by contagion— 
then is the affection well known and its de- 
scription easy: but it bears no similitude what- 
ever to inflammatory croup. For besides that 
the constitutional affections are totally oppo- 
site, a circumstance of the greatest importance 
as influencing the progress of the respective 
cases, the local symptoms and appearances have 
marked and distinct characters. Thus the as- 
thenic angina is always ushered in by shivering 
and other precursors of fever; the soreness of 
the throat is intense from the very commence- 


448 


ment, and the part is even painful on pressure 
externally; every attempt to swallow is so 
dreadfully distressing that patients will suffer 
to be half-famished rather than attempt to get 
down a spoonful of fluid. In attempting to 
examine the throat there is often great diffi- 
culty, because the patient either cannot, or 
from the pain it occasions, will not open his 
mouth; but if it can be seen, it is observed 
to be of a deep red colour, verging on purple, 
sometimes diffused over the surface, sometimes 
in patches, and even from an early period 
abundantly covered by a thick glairy tena¢ious 
mucus that it is difficult to wipe from it. If 
the disease is severe, the membrane soon be- 
comes sloughy: “ the colour of the slough is 
prey or ashey: in some few instances it appears 
rown; its edges are abrupt and well defined, 
and it is surrounded by inflammation of an 
intensely deep red colour. The slough is in 
general slow in separating, and when thrown 
off it appears to resemble a membrane of viscid 
ta not unlike the adventitious substance 
‘ormed in croup, and the surface underneath 
looks of a bright red colour, is nearly level 
with the adjoining parts of the membrane, and 
seems more like the blush of erythema than 
the relic of mortification. I believe that wher- 
ever croup has appeared to have been conta- 
gious it will be found that malignant scarla- 
tina has prevailed also; and that the occur- 
rence of the laryngeal or tracheal disease was 
eecasioned by the spreading of the inflamma- 
tion from the fauces to the windpipe, or per- 
haps by the actual presence of one of these 
sloughing ulcers in the immediate neighbour- 
hood of the glottis.”* 

Such is the description of the effects of an- 
gina maligna on the mucous membrane written 
in the year 1825, but without any suspicion on 
the part of the writer that it could ever be 
ranged by the side of the affection termed 
eroup: for besides the essentially opposite 
characters of the feyer in each, which by them- 
selves would be all-sufficient, there are the 
following differences. The angina maligna, 
diphtherite, or by what other appellation it is 
to be known,—for with respect to it we enjoy a 
most happy abundance of nomenclature,—com- 
mences always in the fauces, and when it at- 
tacks the windpipe, which is by no means very 

uent, it does so secondarily by spreading 
to it; whereas croup seldom or never com- 
mences in the fauces unless when it appears as 
the sequela of some serious injury, such as the 
swallowing of boiling water. cosinchs ma- 
ligna even locally is not confined to the mucous 
membrane, as is evidenced by the intense pain 
in swallowing, the difficulty of opening the 
mouth, the enlargement, suppuration, and even 
gangrene of some of the adjacent glands; and 
it occasionally exhibits something like a me- 
tastatic transfer of disease to some important 
organ, such as the brain or liver. And even 
when recovery takes place, the difference is 
still remarkable: it is slow, often imperfect, 


* Potter on the larynx and trachea, p. 17. 


ABNORMAL ANATOMY OF THE LARYNX. 


and followed by anasarca or some similar 
dence of a broken and cachectie habi: L 
is not the place to enter more fully into 
examination of these two diseases, whic 
reader will fmd admirably contrasted it 
W. Stokes’ work on diseases of the ¢ 
where the angina is spoken of under the 
of secondary croup. we 
There ons other on 
nx to be noticed accompanied by ai 
aa, in both of which eta he eal 
dition of the submucous tissue is of gre 
portance, viz. erysipelas and diffuse infla 
tion. I believe the larynx is very seldot 
primary or original seat of an erysips 
attack, at least such has not come und 
observation ; but I have not infrequently 
it seized either by the spreading of the di 
from the head and face, or by some speci 
metastasis. The constitutional symptoms d 
life are of a low and typhoid character: 
local, those of painful and difficult degly 
and respiration, and the termination (as 
I know) always fatal. Nor are the a 
ances after death always satisfactory, for, 
other cases of erysipelas, the tumefaction 
subsides and the colour fades very soon 
death. In most instances, however, we 
the mucous membrane of a pees low 
and apparently greatly thickened: the 
mucous tissue filled sometimes with s¢ 
sometimes with a gelatinous lymph, and si 
times with a sloughy and putrid matter; 
natural folds of the organ obliterated, an 
rima more or less blocked up and closed b 
thickening and tumefaction of the adjacent 
But one of the most curious affectio 
which the larynx is liable is that of diffs 
flammation. I say “ curious,” because iti 
necessary that the mucous membrane 
be inflamed or thickened or otherwise enga 
or that there should be any remarkable s 
ling of the parts, and yet the breathing is I 
sibilous, or eroupy, as if from the 
some mechanical obstruction. In these ¢ 
which are always fatal, the cellular tissue” 
seat of the disease, and is found filled 
offensive purulent matter and flakes of wi 
ganized lymph, sometimes around the lar 
trachea, and esophagus, sometimes at the’ 
of the throat, and not infrequently exte 
to a considerable distance down into the | 
rior mediastinum. a 
Chronic inflammation of the mucous 1 
brane of the larynx resembles in its ef 
similar form of disease in other structures, 
cept that as the aperture of the glottis is 
and its functions essential to life, the sam 
gree of alteration or of disorganization ¢ 
have place here that may occur in others 
tions without the patient generally experie 
a degree of distress that will at least dire 
attention to the subject. Still is this af 
sufficiently insidious, and its progress in| 
instances so slow, that often irremed 2 
chief is produced before assistance is s¢ 
for: and thus it happens that we are oblig 
speak of chronic inflammation, not will 


ference to its commencement or the early pe- 
riods of its progress, but to its effects or pro- 
ducts, which, exhibiting various forms of de- 
rangement and disorganization, shew to the 
morbid anatomist the length of time the work 
f destruction must have been in operation, 
and the extraordinary changes of shape and 
orm and structure that may occasionally be 
ndured consistently with the maintenance of a 
miserable existence. 

_ The simplest form of altered structure in the 
_ Mucous membrane that I am aware of is that 
ed by a slow but progressive deposit (pro- 
ibly of lymph) within its substance, which 
enders it firmer, thicker, and more solid ; and 
though this must occasion inconvenience and 
ifficulty of respiration to a certain extent, and 
ublesome from the dry cough and occa- 
al spasmodic exacerbations that accompany 
» yet perhaps, whilst restricted to this stage, 
{is seldom perilous to life. But these altera- 
ions of structure, particularly if neglected, are 
eldom quiescent, and however slow in their 
progress have a tendency to move forward 
ither to a morbid or perhaps malignant change 
of the tissues, or to the partial removal of these 
by the process of ulceration. Thus, ulcers of 
e 
he larynx, however heretofore overlooked by 
pathologists, are now found to be extremely 
common, and I| know of nothing more diffi- 
sult than to subject the numerous varieties of 
them to any form of classification. They cannot 
be arranged according to structure, for they are 
very seldom so superficial or so insulated as to 
engage the mucous membrane alone ; neither 
ean they be classed according to the symptoms 
they occasion, for the suffering of the patient 
even his ultimate danger does not seem 
entirely to depend on their extent or character. 
The most practically useful division of these 
ulcers would be as to their exciting cause if it 
could always be discovered; yet even here 
there is so much uncertainty of symptom 
during life and such diversity of appearance 
after death as to render the subject obscure and 
unsatisfactory. 
In some instances the larynx becomes the 
seat of idiopathic ulceration, that is, the dis- 
ease seems to have been occasioned by cold or 
other causes of local irritation—at least such is 
he only explanation to be offered. “ Thus the 
laryngeal surface of the epiglottis and the in- 
ernal parts of the organ itself may be studded 
over with numerous minute aphthous ulcera- 
tions ; sometimes the edges are marked bya 
ellow line of superficial excoriation, bordered 
by a deep blush of inflammation; and in these 
cases I have always observed, during life, that 
great pain and difficulty of deglutition accom- 
per the symptoms of dyspnea, and often 
ormed the most prominent feature of the case. 
_ Occasionally the ulceration is deep and foul, 
and spreads with an almost phagedenic de- 
 Structiveness: these sporadic sores, usually 
ommencing above, either in the soft palate or 
_ the back of the pharynx and spreading down- 
_ wards, too often involve the destruction of the 
‘patient. Occurring as they constantly do in 
_ bad and cachectic habits, they are little under 


} 
om 
ia 

b 


te. 


ABNORMAL ANATOMY OF THE LARYNX. 


1192 


the control of medicine, and operation, how- 
ever it may prolong existence, scarcely holds 
out a hope of ultimate recovery.” 

In other cases the ulceration seems to be 
sympathetic, and either precedes or follows 
certain affections of the lung. Thus in cases 
of tubercular consumption, aphonia is often a 
very distressing symptom, sometimes accom- 
panied by difficult respiration, and occasionally 
by painful deglutition. In these instances not 
only is the larynx studded over with specks of 
ulceration, but the trachea and bronchial tubes 
leading to the cavity in the lung present a 
similar appearance, as if the matter possessed 
some corrosive quality and its passage over the 
mucous membrane became the cause of its 
ulceration. These appearances have been too 
frequently observed not to have attracted the 
notice of the morbid“mnatomist, but still it is 
extremely difficult to connect them with dis- 
ease of the lung in the relation of cause and 
effect, for sometimes the loss or imperfection 
of voice precedes or at least is amongst the 
earliest symptoms of consumption, and in other 
instances it only becomes manifest in the very 
latest stages. It is easy to conceive that the 
presence of an ulcer in the larynx, by pro- 
ducing difficult breathing and occasioning a 
diminution of the supply of air, may deter- 
mine the development of an abscess in a scro- 
fulous lung already well disposed to such dis- 
ease; but when the ulceration has occurred at 
a late period, and the difficulty of swallowing, 
the aphonia, and stridulous breathing appear 
among the closing symptoms of consumption, 
it will be difficult to account for the appear- 
ances observed, unless by supposing them to 
be sympathetically produced. 

But of all the causes from which ulcerations 
of the larynx are known to proceed, some 
specific or constitutional taint seems to be the 
most influential, such as syphilis, scrofula, mer- 
cury, or a combination of two or more of these. 
As far as my own observation extends, I cannot 
say I have ever seen the larynx engaged ina 
case of venereal where no mercury had been 
used, but on the other hand there is scarcely any 
organ more likely to be attacked where the me- 
dicine has been imperfectly or improperly used, 
or in which the attack is more perilous and 
unmanageable. Sometimes the larynx becomes 
ulcerated in consequence of phagedena or other 
destructive form of the disease spreading down- 
wards from the throat or fauces, but more fre- 
quently is it engaged alone. The ulcers here 
are seldom solitary, but present several spots of 
ulceration, and in some cases are so extensive 
that the whole configuration of the organ is 
spoiled and lost, the epiglottis being partially 
or entirely removed, and the chorde vocales and 
ventricles carried away. The surface of this 
extensive ulceration is irregular, warty, and 
gives the appearance of uneven granulation, 
and there are chaps and fissures that pass 
deeply into the substance of the subjacent car- 
tilage, portions of which are removed. When 
.the ulcers are more superficial they very often 
exhibit the herpetic appearance and the ten- 
dency to spread observed in mercurial sores, 


420 


healing in one situation whilst fresh ones break 
out in the neighbourhood, and cicatrizing with 
a depressed surface and evident loss of sub- 
stance. With respect to symptoms, the loss or 
imperfection of voice will very much depend 
on the situation of the ulcers; but the diffi- 
culty of breathing and general distress are by 
no means criteria by which the extent of de- 
struction of parts can be estimated, for some- 
times there is uncommon sufiering where the 
ulceration is extremely limited. Very fre- 
quently these ulcers (particularly if the epi- 
glottis is engaged) a er symptoms of diffi- 
cult deglutition, exactly resembling those of 
Stricture of the esophagus: but this is only 
during the time the sores are actually open, 
for, when healed, swallowing is performed 
with astonishing facility, even although the 
greater part of the epiglottis may have been 
carried away. 

But the most interesting fact in connexion 
with these ulcers is, that by rest and proper 
treatment they are susceptible of cure, and for- 
tunate it is that by means of operation we are 
enabled to afford this important organ the requi- 
s.ite degree of repose. Mr. Carmichael ia 
published two most interesting cases illustrative 
of this fact ; in which the patients recovered, and 
in which we have consequently a right to infer 
that the ulcerations healed. In the summer of 
1838 I operated on a woman in the Meath 
Hospital, who had symptoms of such extensive 
destruction of parts as must have proved fatal, 
but who nevertheless recovered with a complete 
capability of breathing through the rima, but 
with nearly a total loss of voice. The healing 
of this kind of ulceration may be inferred from 
that case also, but it is proved by the following 
observation : “In the Museum of the School 
of Park-street, Dublin, is a preparation taken 
from a poor woman who had been an inmate 
of the Meath Hospital ten or eleven different 
times for venereal ulceration of the larynx, and 
finally died there quite suddenly, as if from the 
effects of spasm. It shews where a large por- 
tion of the epiglottis had been removed, the 
ulcer having healed by a puckered cicatrix. 
From below the left ventricle a longitudinal 
scar extended a full inch and a half down into 
the trachea, the contraction of which had di- 
minished the calibre of that part of the tube 
very sensibly. The right ventricle was totally 
obliterated, and on different spots about the 
superior part of the trachea there were several 
small pale depressed cicatrices, evidently the 
results of former sores that had been open at 
different periods at which she had been in the 
hospital. The only ulcer that existed at the 
time of her death was a very small one, with 
ragged irregular edges, situated midway be- 
tween the natural position of the right ventricle 
and the root of the epiglottis.” 

The softer tissues of the larynx are also occa- 
sionally liable to gangrene, cireumscribed—con- 
fined to the organ itself and not exhibiting any 
tendency to spread. Of this I have as yet seen 
but one example, and that one under circum- 
stances that rendered it doubtful whether the 
disease should not be considered as sympathetic 


ABNORMAL ANATOMY OF THE LARYNX. 


with a similar affection of the lung. It" 
the case of a man who died in hospital of 
grene of the lung supervening on acute pr 
monia. Seven days before his death he 
attacked with symptoms of Tabi 
hoarseness, with ditficult and laborious 
ing, which gradually increased until 
was nearly lost and respiration quite stridu 
After death, besides the gangrene of th 
a gangrenous ulcer was found, inve 
chord vocales at the left side: its 
about the size of a shilling, and of 
green colour ; its edges quite stough Ys 
centre excavated to a considerable 
mucous membrane around highly 
covered with a pellicle of lymph. 
3. The peter of the larynx are 
very important diseases, some of 
to be peculiar to fibro-cartitage in this par 
situation, and all of which are attende wi 
convenience ‘and danger by reason of | 
interfering with the function of the orga 
shall commence with that which I belie 
be the most frequent, the most importa 
the most fatal ; indeed, when allowed tor 
own course it is always destructive, 5 
the patient’s life is preserved by art, it is 
the alternative of breathing for ever af 
through an artificial aperture. In cor 
of the similarity of symptoms between 
phthisis pulmonalis, it has obtained the né 
phthisis laryngea. { 
The exact manner in which this dise 
mences and the causes that lead to its prot 
tion have not yet been so accurately ascerta 
as to admit of no farther doubt or question: 
instance, Mr. Ryland seems to think that 
most instances it is secondary to some if 
matory affection of the laryngeal mucous 
brane or its subjacent tisssue,” whereas I 
ventured to believe that the original mo 
action was set up in the cartilage itself and” 
proper and peculiar to it; at the same til 
toust be confessed that I have seen it appare 
produced by the presence of an abscess in 
immediate vicinity, and I believe there 
no doubt of its being an occasional sequel 
typhus fever. Theessence of thedisease seem 
be a change of structure in some of thee 
followed by the death and disorganizati 
the newly formed material, and an atte 
its removal by abscess and ulceration. — 
on a post-mortem examination of one of 1 
cases an abscess is always found in the situa 
of some of the cartilages—very generally 0 
broad posterior part of the cricoid: and 
abscess has burst by one or more openit 
of them being very frequently just behind 
above the rima. On cutting into the cay 
the abscess, besides the matter, which is g 
ish, putrid, and abominably fetid, partiel 
a grey or white earthy material are foun 
there are always portions of bone, thin, 1 
at the edges, white and perfectly dead. — 
the disease has so far progressed, there is alw 
other and more extensive mischief; the extel 
parts in the neighbourood are swelled and thi 
ened, the mucous membrane ulcerated; 
arytenoid cartilages often detached; and 


7 
a 


, os 


Ye 
Py 
© 


- 


epiglottis, in every case that I have seen, more 
__ or less removed by ulceration. The who!e con- 
ation of the organ is lost or spoiled, and 
searcely bears a resemblance to the natural 
shape and appearance ofa healthy larynx. We 
aannot even form a conjecture of the causes 
that oceasion this formidable disease, or of the 
mstances that dispose to its production. 
_At some time beyond the middle period of life 
the cartilages of the larynx, except the epiglottis, 
d often of the trachea also, become converted 
into bone, and from the circumstance of carious 
ne being so constantly found in these ab- 
besses, it would appear that it is either during 
ocess of ossification or immediately after- 
yards that the disease commences. I have 
lways imagined that it was at the former of 
lese periods, and that the affection was pro- 
ced by some imperfection or irregularity in, 
deviation from, the ordinary and natural pro- 
-in a word, that this earthy unorganized 
material was formed instead of healthy bone. I 
had once an opportunity of seeing a case which I 
Tegarded as an example of the commencement of 
disease, in the person of a man who, having 
ed from laryngeal symptoms for some 
months, suddenly died in the Meath Hospital, ap- 
parently from the effects of spasm. “ Onslitting 
up the larynx, the cricoid cartilage appeared to 
highly vascular and organised. Its substance 
was internally as red as blood, and in three or 
fo places there were specks of an earthy white 
ubstance that crackled under the knife, and was 
dently of the same nature with that usually 
ound in caries of the laryngeal cartilages.” [ 
aware that one case can prove but little, 
articularly in pathological science, but oppor- 
nities of seeing the incipient stages of such 
n affection as this must be very rare, and every 
e ought to be recorded that will in any man- 
tend to throw light on a disease the etiology 
of which is so extremely obscure. 
_ However occasioned, this earthy degeneration 
Of the laryngeal cartilages is an extremely in- 
Sidious disease, its approach being so gradual 
S scarcely to alarm the patient, and its progress 
low. There is usually sore throat and difficulty 
swallowing, although this latter is not neces- 
Sarily a constant symptom; hoarseness, and at 
but triflingly impeded respiration. These 
‘inconveniences in the commencement are not 
Such as to produce much distress; for I have 
Known one patient suffer for three months and 
 anothernearlynine, beforeeitherapplied for relief, 
and in both the disease had a fatal termination. 
Afterwards, however, the symptoms become 
Thuch more aggravated, the difficulty of breath- 
F ig is exceedingly distressing, and there are exa- 
c rbations that bring the patient to the point of 


£ 


h by suffocation. I have already noticed 
One case in which dissolution took place at a 
very early period, and when .the occurrence 
could only be explained by the suddenness and 
Severity of the spasm. At length, as the dys- 
Ppnoea becomes extreme, the patient suddenly 
eat some partial relief; bis cough, which 
was before teasing and troublesome, now becomes 
$0! ter, and the expectoration free and copious. 
This latter has all the characters of purulent 


= 


of 


ABNORMAL ANATOMY OF THE LARYNX. 


121 


matter, and there are, mixed with it, particles 
of that white, gritty, earthy substance already 
described. Occasionally, pieces of the size of 
a pea of this unorganised substance are coughed 
up, and when they appear they leave very little 
doubt of the nature of the complaint. Towards 
the latter end of the disease the breathing be- 
comes loud and sonorous, with a whistling 
noise, so as to be heard at a considerable dis- 
tance. The cough is incessant ; the expectora- 
tion copious, with a peculiarly fetid gangrenous 
smell; the patient’s breath has this odour also, 
which may also be regarded as an unfavourable 
symptom. There is at all times convulsive 
struggling for breath, with occasional exacerba- 
tions. In most cases, but not in all, the chest 
becomes affected; thereis pain in some one 
part of it or other, with a Sensation of tightness 
round the thorax as if the patient could not 
draw a full inspiration. His strength seems to 
give way rapidly under these symptoms ; his 
body becomes emaciated ; he has night sweats 
accompanied with excessive restlessness ; and 
at last he sinks exhausted in the struggle and 
dies. 

Throughout the entire progress of the dis- 
ease there is seldom any well-marked paroxysm 
of fever, although the pulse is never much 
under 100; however, this may be attributed to 
the constant irritation under which the patient 
labours. The tongue is usually clean; the ap- 
petite cood—in some instances ravenous ; and 
the general functions of the body, with the 
exception of respiration, seem to suffer but 
little. The countenance is always pale, with 
that sickly dirty hue that characterises hectic 
fever. ‘The expression evinces great anxiety ; 
and this is so remarkable that patients suffering 
under this species of cynanche often seem to 
bear a strong resemblance to each other. 

It is now familiarly known to surgeons that 
even this dreadful condition is not utterly di- 
vested of hope, and patients in whom this dis- 
ease had wrought such ravages as to render the 
larynx quite unfit for the performance of its 
functions, nevertheless survived for years after 
an artificial opening had _ been practised in the 
trachea. Some of these patients have since 
died, and thus in a limited degree afforded op- 
portunity for examining the extent of destruc- 
tion produced, as well as proving the all-im- 
portant practical fact, that ulcerations here, how- 
ever extensive, are capable of being cicatrized 
if the organ is only left ina state of repose. In 
the Museum of the Royal College of Surgeons 
in Ireland is the larynx of a patient who lived 
for more than two years after having been o 
rated on by Mr. Purdon of Belfast, and the 
following are the appearances exhibited by the 
easy ae About half the epiglottis had 

en carried away, and the edge of the remnant 
is cicatrized. The space between the root of 
the epiglottis and the rima, rough on its sur- 
face, irregular and warty. The ventricles 
altered in shape, diminished in size, but not ob- 
literated. The dimensions of the rima greatly 
diminished. The canal of the larynx is not 
more than one-third of its natural size, and is 
lined by a thick uneven membrane, evidently 


122 


the product of cicatrization, and the place which 
should have been occupied by the broad por- 
tion of the cricoid cartilage exhibits an empty 
cavity, as if that structure had been removed 
by absorption or some other process, and 
nothing deposited in its room. One of the pa- 
tients on whom I operated in the year 1829 
died about a year sincein the Fever Hospital, 
and the larynx was examined by the surgeon of 
that institution, Mr. Trant; it presented ap- 
pearances so nearly similar to the above as not 
to require particular detail, and quite sufficient 
to shew that the original destruction had been 
such as totally to preclude the possibility 
of the organ ever being capable subsequently 
of performing the ordinary function of respi- 
ration. 

The cartilages of the larynx are also liable to 
mortification following on inflammation, and 
apparently produced by the causes that induce 
gangrene in other structures. I suppose this 
affection to be extremely rare, as I have met with 
but two cases, and have not heard of its being 
observed by others. In one of these cases a 
large abscess existed in front of the larynx and 
upper part of the trachea, in which the thyroid 
cartilage lay like a foreign substance entirely 
denuded, mortified, and abominably offensive, 
its appearance resembling that of wetted rotten 
leather. The front of the cricoid cartilage and 
of the two upper rings of the trachea had been 
removed by mortification also. The lining 
membrane of the larynx was thickened, corru- 
gated, and had a granular appearance ;_ part of 
it was ulcerated, through which the abscess had 
communicated with the pharynx.. The remnant 
of this larynx is preserved in the pathological 
collection of the School in Park-street, and 
shews that at least five-eighths of the organ had 
been totally and entirely destroyed. It proves 
that such a disease must be utterly hopeless and 
irremediable, and that, quite independent of the 
constitutional derangement that must lead to 
its formation and accompany its progress, no 
chance could exist of cicatrization and subse- 
quent recovery. 

Occasionally, although I should suppose very 
rarely, the cartilages of the larynx are the sub- 
jects of an alteration of structure strongly re- 
sembling the ordinary product of scrofula. Of 
this I have seen but one specimen, for which I 
am indebted to the kindness of my friend Dr. 
Benson. December, 1838. A man, et. 39, 
was received into the City of Dublin Hospital, 
under the care of Dr. B. for the treatment of 
what was considered to be chronic rheumatism. 
It was soon discovered that the pains were not 
rheumatic, but most probably depended on 
cerebral disease. The larynx presented a firm 
tumour externally, and there was an almost 
total loss of voice. He died, and after death 
scrofulous tubercles were discovered in the 
brain. The larynx was of a healthy structure 
in every part except in the thyroid cartilage, the 
ale of which were converted into a firm scrofu- 
lous mass, about the size of a large chesnut on 
each side. The nag OM or tubercular matter 
appeared to have been deposited originally in 
the centre of each ala. The margins and Ae 


ABNORMAL ANATOMY OF THE LARYNX. 


nua of the cartilage were unaltered, 
cartilaginous structure seemed to lose | 
sensibly on the surface of the tumour. — 
This very interesting preparation is p 
in the Museum of the Royal College of 
geons in Ireland. - 
Besides these deviations from the ord 
healthy conditions of the cartilages of | 
rynx, it is certain that one at least of the 
sents ap ces of abnormal changes b 
size and shape. Morbid thickening or 
trophy of the epiglottis, as well as its op 
state of contraction or shrivelling, hav 
spoken of by authors, but I have never 
fully satisfied that the former of these w 
rather the result of a thickened cond 
mucous membrane than of the cartilage 
and I believe the latter never is seen unle 
the consequence of previous ulceration. 
viation from its usual shape is by no i 
very uncommon in this cartilage, most inst 
of which are ‘trivial and unimportant, ai 
probably congenital ; but in some few inst 
the change is more remarkable. One of 
has been noticed by Dr. Stokes in the ¢ 
of his work which treats of diseases of | 
rynx and trachea, and by him it is terme 
leaf-like expansion of the epiglottis. 
scribes it thus : “ This has not been deserib 
any author, but a most remarkable prepa 
of the disease exists in the Museum 
School of Anatomy and Medicine nS 
street. The epiglottis is thinned and si 
elongated, and its form so altered as 
sent the shape of a battledore, the narro 
tremity being next the glottis. In the pr 
tion alluded to it is fully two inches in } 
and coincides with double perforating ule 
the ventricles. Nothing is known as | 
history of the case, but I have seen me 
less of a similar alteration in other cases | 
ryngeal disease.” a 
In a paper professedly devoted to abn 
anatomy, I know not whether I am warr 
in noticing derangements of function, — 
tended by any lesion of structure dise 
by dissection, yet there are some of thes 
hibited by the epiglottis which seem des 
of the attention of the physiologist. Th 
ascribed-to this cartilage of protecting | 
rynx during the process of deglutition is 
known, yet observation has furnished u 
examples of exceptions to this use, both 
tively and negatively ; for, as when this va 
structure is altogether removed (by expe 
in animals and by disease in man), the 1 
is nevertheless often found able to protect 
and the subject to swallow both liquidsand 
without much, and occasionally without @ 
convenience, so, on the other hand,it is 
which cannot be controverted, that the ep 
sometimes seems to be deprived of its 
tive sensibility, and permits the free introd 
into the windpipe of substances attemp 
be swallowed. This latter fact I first noti 
the case of a Wapiti deer which was brone 
mized by Sir Philip Crampton: it freq) 
discharged portions of its food 
wound, and yet after death the larynx in 


NADLEe 


BE ei’ 
nrou 


ABNORMAL ANATOMY OF THE LARYNX. 


_ parts wa found apparently perfect in its orga- 
nization. But not to rely on observations made 
on the inferior animal, a case soon afterwards 
becurred in the Richmond Surgical Hospital, of 
a young female wounded in the trachea rather 
w down in the neck. From this wound por- 
tions of the ingesta frequently escaped, and 
yet after death the larynx was found healthy, 
is Organization complete, and no. unnatural 
mmunication whatever between the cesophagus 
d windpipe in any part or situation what- 
ever. I have since had a precisely similar case 
“under my care in the Meath Hospital. These 
we instances in which the epiglottis seems inert, 
and the larynx is left patulous and unprotected ; 
there are other cases in which it appears to be 
orbidly active, although it is difficult to ex- 
_ Plain the agency by which such activity is pro- 
_ duced. In prosecuting some experiments on 
_ the subject of asphyxia, a stout middle-sized 

‘dog was let down into a brewing ‘vat that had 
_ been emptied of the fermenting liquor about 
ten minutes previously ; he was to all appear- 
ince perfectly dead in two minutes. After al- 
wing the body to remain thus for twenty 


Minutes, it was examined: the glottis was 
found to be of a very pale colour, and the rima 
‘eompletely shut up by the close approximation 
| Of the arytenoid cartilages. The epiglottis was 
shut down like a lid upon a box, so us perfectly 
__ to close the superior aperture of the larynz: 
| this latter was a curious appearance, and I 
Know not what muscles could produce the 
effect, but the fact was witnessed by Dr. Hart, 
now one of the professors of practical anatomy 
in the College of Surgeons, by Dr. Young, and 
others. I am also ignorant as to whether a 
similar condition of the epiglottis obtains in 
men who have been suffocated by carbonic 
| acid ; human subjects are seldom examined so 
_ soon after falling into a state of asphyxia as to 
allow of the immediate appearances being ob- 
served, and yet information on this point 
would be of great value in determining the 
| suitable means for attempting resuscitation. 
The most difficult part of the pathology of 
the larynx to contend with is that which has 
_teference to muscular organization, and unfor- 
tunately it is that which has been least ex- 
“amined, or on which examination has thrown 
the faintest and most unsatisfactory light. 
Furnished with an exquisitely delicate and 
beautiful arrangement of muscle, the normal 
etions of which are exemplified in the pro- 
uction of the different sounds of the voice, 
nd in giving force to the exit of the air in 
oughing, sneezing, &c. it would appear only 
. nable to suppose that the functional de- 
_angements of the larynx should be accom- 
anied by some appreciable corresponding le- 
10n of its muscular apparatus ; yet such does 
“hot seem to be the case, at least not invariably, 
and we sometimes find the voice impaired or 
, ote lost, the muscles of the organ ex- 
hibiting their ordinary appearance, and again 
remarkable and seemingly important lesions 
without much injury to voice or respiration. 
Under these circumstances we must speak of 
the morbid appearances that have been ob- 


. 
} 


| 
fi 
i 
“3 


123 


served in the first instance, and consider the 
irregularities of function afterwards. 

The muscles of the larynx are sometimes 
found in a state of extraordinary develope- 
Ment amounting almost to hypertrophy. I 
know not how far this may be considered to be 
an abnormal condition, or whether it may not 
be the natural result of great and constant em- 
ployment of the organ: reasoning from ana- 
logy this latter seems more probable, but dis- 
section has hitherto thrown no light upon the 
subject. 

They are likewise subject to atrophy or 
wasting, the fibres appearing thin, pale, and 
attenuated. Andral mentions cases of loss of 
voice in which he sometimes found the fibres 
of the thyro-arytenoid muscle wonderfully atro- 
phied, and sometimes separated from each 
other by some morbid secretion, either of pus 
or tubercular matter. I have been informed by 
Sir P. Crampton that he has seen in the Mu- 
seum of the Veterinary College in London, 
several preparations illustrative of the disease 
termed “ roaring” in the horse, which seems to 
be produced by an atrophy of the arytenoid 
muscles. A relaxation is thus effected which 
allows to the arytenoid cartilages an unnatural 
degree of mobility. Whilst the animal is at 
rest or moving slowly, the current of air passes 
gently, and there is no “ roaring ;” but when he 
is put to greater speed and respiration becomes 
more hurried or more forced, the little valves 
are acted on, the rima is proportionably closed, 
the breathing becomes stridulous, and that pe- 
culiar noise so well known to persons conver- 
sant with horses is produced. 

Lesion of function in the muscles of the la- 
rynx exhibits itself in the opposite conditions 
of atony and spasm. Examples of the former 
are to be found in some cases of partial pa- 
ralysis where the patients become totally in- 
capable of uttering any sound, however in- 
distinct and inarticulate; in the hoarseness and 
sometimes loss of voice that suddenly attacks 
young persons, particularly females, from ex- 
posure to cold and damp; and perhaps fre- 
quently inthe sympathetic aphonia that precedes 
or attends on phthisis. On the pathology of 
these affections morbid anatomy has thrown but 
little light, nor is it surprising that the subject 
has attracted a minor degree of attention, when 
it is recollected that the more severe laryngeal 
symptom, that of difficult respiration, is seldom 
or never present. I have had two cases of 
aphonia attended with pain and soreness in the 
larynx, which, under an idea that the disease 
was either gout or rheumatism, I treated with 
colchicum with apparently favourable results. 
I know not whether the supposition that the la- 
rynx may be the seat of either of these painful 
affections is correct or not, but I see no reason 
why it should enjoy so fortunate an exemption. 
However, although atony of the muscles of the 
larynx may not be attended with much peril, a 
spasmodic action of them is always eminently 
perilous, sometimes destroying life with a ra- 
pidity that almost precludes the possibility of 
assistance. There can, therefore,” be few sub- 
jects more interesting to the practitioner, and 


124 


although, as might be expected, the causes that 
produce these terrific affections have not been 
explained, yet it may be desirable to examine 
into the symptoms and some of the circum- 
roe that occasionally precede or accompany 
them. 

Spasm of the glottis is either idiopathic or 
symptomatic. 

The idiopathic occurs, as far as 1 know, only 
in children, as in the “spasmodic croup,” or 
laryngismus stridulus, unless we also choose to 
include within this class the hysteric dyspnea 
that occurs in young females. ' 

The symptomatic occurs as indicative of, or 
in connexion with, 

1. The application of some deleterious sub- 
stance to the larynx, as carbonic acid, boiling- 
water, or steam. 

2. The application of some irritating mate- 
rial, as a particle of salt. 

3. The presence of a foreign body within the 
trachea or bronchial tubes. 

4. The presence of a foreign body in the 
cesophagus. 

5. The existence (occasionally) of an aneur- 
ism of the aorta. 

6. The existence of. any other disease within 
the larynx or trachea. Any of these latter may 
be present in the adult or the child indif- 
ferently. 

Few diseases have attracted more attention 
than the spasmodic croup of children ; few 
have been more accurately described as to 
symptoms, and in none is our pathological in- 
formation more deficient; a fact that may al- 
most be proved by the number of different 
names by which it has been designated. It is 
the asthma of infants of Millar; the cerebral 
croup of Pretty; the spasm of the glottis of 
Marsh ; the spasmodic croup of other writers ; 
and the laryngismus stridulus of Mason Good 
and Ley. It occurs in very young children, 
with a peculiar difficulty of breathing, attack- 
ing for the most part suddenly, accompanied 
by a crowing sound, and oftentimes with a sus- 

nsion of respiration for several seconds. 

is difficulty of respiration varies in intensity 
from a single crow to a more prolonged paro- 
xysm threatening suffocation, and terminates 
when in recovery by a long deep-drawn respi- 
ration, with a peculiar stridulous noise; when 
in death, by such convulsive struggles as might 
lead, and indeed have led, to a belief that the 
cerebrum was engaged. Pallid and exhausted, 
the child falls lifeless upon the nurse’s arm, 
and is then generally said to have died in a 
fit. In these cases there is no cough; no 
raucal sound of voice; no continued stridulous 
breathing, except an occasional mucous rattle 
heard only while the infant sleeps be con- 
sidered as such; there is no fever; and on ex- 
amination after death no trace of inflammation, 
nor indeed any deviation from the ordinary 
healthy appearance of the organ, can be disco- 
vered. Under these circumstances, patholo- 
gists had no method of explaining the pheno- 
mena but by spasm, an irregular and invo- 
luntary contraction of the muscles of the larynx 
closing up the rima glottidis to a greater or less 


ABNORMAL ANATOMY OF TILE LARYNX. 


extent, and in a omer to such Closm 
terfering with and obstructing respiration 
But what is the cause of this spasm 
have supposed it to have an intin 
nexion with an hydrocephalic ; 
cause it has been sometimes seen in chil 
with large heads and sluggish dispositions 
because signs of cerebral congestion hay 
discovered after death ; but I have se 
sease prove fatal to the liveliest and 


Prd 


a 


most healthy children, and the congestiol 
just as well be the consequence as the 
of the closure of the glottis. Others aga 
referred it to the general constitution 
tation that proceeds from painful dentition 
doubtless cases have occurred in whit 
crowing respiration was relieved by suet 
scarifications of the gums, according as” 
tooth became prominent underneath; but 
although teaching an important practical Ie 
leaves the pathological connexion betw 
facts in as much obscurity as ever. Ac 
ing to others there is a constitutional tent 
to thi§ disease in some children, a fact wh 
must be conceded has been painfully exen 
fied in more families than one; but this 
ditary disposition to disease, al 1 
dantly obvious, is too imperfectly under 
to be discussed with any thing approach 
pathological accuracy. Lastly, improper oF 
wholesome food, indifferent clothing, a ¢ 
and tainted atmosphere, and exposure to ¥ 
situdes of climate, have been regarded as 
fluential exciting causes, and change of ei 
stances in these respects has often produce 
almost magical amendment in the conditi 
our little patients ; but still we are at a lo 
discover the immediate modus operandi ¢ ft 
pernicious iofluences, or why they show 
determined to the larynx in the form of an 
voluntary spastic contraction of its museles. 
Other causes have been assigned for the j 
duction of this disease, some of whic 
eminently deserving of attention; at the sai 
time it may be observed that its being ¢ 
buted to such a number of influences § 
that its real exciting cause is probably 
unknown. For instance, either this dise: 
an affection bearing a strong resemblance 
has been described by Dr. Kopp, and _ 
wards by Dr. Hirsch of Konigsberg, unde 
name of thymic asthma, and by them | 
buted to an hypertrophied condition o 
thymus gland, which by its weight and voh 
presses on the heart, the lungs, the large 
rial and venous vessels, and prevents the | 
exercise of their functions. Dr. Me ntgo' 
has published an interesting paper on this 
ject, in which he attributes the sudden ¢ 
to an enlargement of this gland, whether 
arises from hypertrophy of its substance 
alteration of its structure from scrofula or 
disease ; and explains how agitation or @ 
ment may suddenly distend and increase 
size of the organ in such a manner as to 4 
materially the condition of the surrour 
parts. Again, in the work by Dr. Ley alve 
referred to, a different explanation has | 
offered. Apparently relying on the ex{ 


tal researches of Magendie and Le Gallois, 
supposes that, if the recurrent nerves are 
ompressed to such an extent as to have their 
functions impaired, the glottis, under the in- 
fluence of the superior laryngeal branches, 
‘ould become and continue fast closed. The 
@ause of the disease then, according to him, 
will be found in some tumour, scrofulous or 
otherwise, so situated as to create an injurious 
degree of compression on the recurrent nerves. 
Phat an enlargement of the thymus gland may, 
rom its situation, produce great and serious in- 
convenience, it would be absurd to question, 
‘and perhaps there is sufficient evidence to shew 
lat it may occasion the symptoms and results 
f this very disease: but it is far from being 
roved that spasm of the glottis may not occur, 
md even prove fatal in cases where no such 
nlargement existed. Alterations of size, shape, 
and structure, even if rapid, take place gradu- 
. ally ,and their results should be gradual also, 
_ whereas this disease has been known to destroy 
3 Victim in its first and only paroxysm; and 
moreover, if structural change in the gland was 
its sole exciting cause, it would be difficult to 
account for its sudden disappearance on the 
— PP rit 
removal of the child to the country and its diet 
being changed. Whilst therefore it may not 
be denied that hypertrophy of the thymus can 
| oceasion the phenomena by others attributed 
to spasm of the glottis, there is not sufficient 
proof of its;being the general or even frequent 
cause of this peculiar disease. I shall have 
bccasion to notice the supposed consequences 
| of pressure on the recurrent nerves hereafter. 
t is questionable how far spasm occasioned 
by the contact of noxious or irritating sub- 
tances can justly be termed sympathetic, for 
| they are the results of an application of a di- 
"rect stimulus: it is immediate in its effects, 
and more or less complete according to the 
nature or quality of the exciting cause. Death 
om total submersion in carbonic acid gas 
becurs so quickly as almost to seem instan- 
| taneous, and the spasm entirely occludes the 
glottis. The mildest form of spasm seems to 
_ be that occasioned by the accidental admission 
of some particle of food which is usually 
expelled again very quickly by a cough suf- 
ciently distressing but seldom dangerous: yet 
“instances have been known of the apparently 
| trifling occurrence of the introduction of a par- 
ticle of salt being attended by a fatal result. 
_ However, when spasm is, or appears to be 
) produced by the presence of a foreign body in 
| the esophagus or the trachea, or by the pres- 
Sure of an aneurismal tumour, it is evidently 
Sympathetic, and it may be interesting to in- 
_ quire into the evidence by which such relation 
_of cause and effect is established. 
__ I had formerly entertained the opinion that 
spasm of the glottis should be the consequence 
of some irritation applied to the larynx itself, 
and not external to or at a distance from it, and 
therefore that the presence of a foreign body 
in the esophagus ought not to hold a place 
amongst its exciting causes. I have since, 
however, altered my views on the subject, and 
indeed, when we consider the number of cir- 


ABNORMAL ANATOMY OF THE LARYNX. 


125 


cumstances under which this morbid action 
may occur, we cannot be justified in denying it 
in this case in opposition to most respectable 
testimony. Mr. Kirby bas published a case in 
the Dublin Hospital Reports, in which death 
was apparently produced by spasm of the glot- 
tis in consequence of the lodgment of pieces 
of meat and bone in the esophagus: and Dr. 
Stokes saw an instance in which a piece of 
money was lodged in the esophagus and where 
croupy breathing and other laryngeal sym- 
ptoms were manifestly the result. In this lat- 
ter instance the foreign body was not lodged in 
the fauces or pharynx. I have myself seen 
cases to corroborate the above, but it is need- 
less to swell this article with proofs of a patho- 
logical fact that will probably not be called in 
question. Sait 

It is probably a new observation—at all 
events it is one of great pathological interest, 
that spasm of the glottis may be produced by 
the presence of a foreign body lodged within 
the bronchi. In the month of May, 1836, 
a child was brought from the country and 
placed under the care of my friend Mr. Cu- 
sack; his father’s account of the case was that 
he had swallowed a small pebble, was instantly 
seized with a violent paroxysm of cough, had 
croupy or sonorous breathing ever since the 
accident with occasional remissions and exacer- 
bations, but was sometimes brought to the 
verge of suffocation. The stethoscopie indi- 
cations were that the foreign body was loose 
and mobile within the trachea. I assisted Mr. 
C. in performing the operation of tracheotomy 
on this child; but, although the aperture in the 
windpipe was made very large, no stone was 
expelled, and the size of the organ did not 
admit of the employment of any forceps with 
which we were furnished. Immediately on 
the opening into the windpipe being perfected 
the croupy breathing disappeared, neither was 
there a severe paroxysm of cough experienced 
afterwards, and the father, either doubting that 
the foreign body had ever obtained admittance, 
or dissatisfied at its not being removed, car- 
ned him off to the country contrary to the 
wishes and advice of his medical attendants. 
We afterwards heard that the little pebble had 
been coughed up in about three weeks after he 
left town, but have not been informed as to the 
ultimate termination of the case. —< 

On the 13th of September, 1839, a child, 
aged three years and a half, was brought to the 
Meath Hospital: he had, half an hour pre- 
viously, swallowed a small stone, and was in- 
stantly seized with a violent cough which con- 
tinued up to the period of admission. His 
breathing was quite stridulous—countenance 
expressive of great distress—face and lips 
lived—efforts at respiration hurried and gasp- 
ing. The left side of the chest heaved vio- 
lently, the right was comparatively quiet: re- 
spiration very weak and interrupted in the 
right lung, in the left loud and puerile: no 
dulness over either lung on percussion. I per- 
formed the operation of tracheotomy, but no 
foreign body was expelled, and yet the little 
patient experienced the greatest relief. The 


126 


trachea was too small to allow of the intro- 
duction of any instrument for the extraction 
of the offending substance if such was there, 
so J merely satisfied myself with keeping the 
wound open, in the hope of its being coughed 
up. Whenever from any accident the wound 
in the throat became obstructed, the breathing 
became dreadfully oppressed, but he obtained 
instant relief when it was opened again and 
cleaned. Such were the phenomena of the 
case generally up to the 6th of October, when 
it was found that the wound had gradually 
closed and healed so as to leave the artificial 
opening very small, and on that day, in ¢on- 
sequence of the increased difficulty of breath- 
ing, I was obliged to open up the whole wound 
anew. This second operation afforded im- 
mediate relief. On the 6th of December the 
wound being again nearly healed, in a despe- 
rate fit of coughing he expelled a small stone 
about half an inch long by about two lines 
broad, through the rima glottidis. 

There were many other interesting facts con- 
nected with this case, which I omit here, my 
object being only to show that the difficult re- 
Spiration which rendered the operation neces- 
Sary was not caused by the mechanical ecclu- 
sion of the bronchi by the presence of the 
stone, but had ‘its seat in the larynx. The 
child had always repose when not called upon 
to employ the rima in respiration, although the 
stone was present in one or other of the bron- 
chi, and in this case it was remarkable that 
it shifted its position, as proved by stethoscopic 
evidence. 

It is sufficiently well known that the pres- 
sure of an aneurism, and of course of any 
other tumour, on the trachea or bronchi will 
produce difficult respiration to such an extent 
as to simulate laryngitis and to place the pa- 
tient’s life in imminent peril. is has been 
supposed to proceed from the mechanical ob- 
struction given to the passage of the air by the 
compression of the tumour, and I shall not 
deny that this cause may occasion inconveni- 
ence, but still may be allowed to doubt that it 

roduces the stridulous breathing and other 
aryngeal symptoms—at least in the majority 
of cases. In the month of July, 1837, I was 
requested by another practitioner to see a case 
of acute laryngitis and to operate if I deemed 
it necessary. The case appeared to be seriously 
urgent: the man oon to be on the point of 
suffocation; and having made some inquiries 
as to the history, and particularly as to the con- 
dition of the chest as ascertained by auscul- 
tation, I operated immediately. The relief was 
as marked and as decided as I had ever seen 
in any laryngeal affection ; and, after allowing 
the patient two or three hours’ repose, I had 
him removed to the Meath Hospital, in order 
to be under my own immediate care. He died 
on the fourth day afterwards from the bursting 
of an aneurism of the aorta within the chest, 
and on examination the larynx was found in a 
perfectly healthy and normal condition; yet 
was it evident, from the relief experienced on 
the opening being made below it, that the ob- 
struction to respiration that existed during life 


REGIONS OF THE LEG. 


had been caused within this organ. Th 
who, with Le Gallois and Magendie, exp 
spasm of the glottis by a compression e: 
cised on the recurrent nerves, may possi 
consider that the aneurism in this case | 
duced such pressure, and I am not ina‘ 
dition to deny it, because the sac was collap 
and empty, and I could not say what pres 
it might have created directly or indir 
when tense and full of blood. But the sa 
no situation lay in contact with the nervy 
seemed to hold any relation to it that ¥ 
lead to such a conclusion. I may add, 
dentally, that I have seen aneurismal tum 
which must have implicated this nerve 
which the spasmodic difficulty of bre 
did not exist, and therefore whilst I be 
that spasm of the glottis may be prod 
consequence of, or in connexion with, the 
istence of some tumour compressing the trael 
or bronchi, I cannot (in the present stat 
our knowledge) yield to the opinion t 
it so entirely to a compression of the 
nerve, . 
The ligaments of the larynx are, of e 
liable to disease. Thus, during life, we a 
on the possibility of an abnormal state af 
sion or relaxation, from observing certain 
rations of the tone of voice which are” 
supposed to be capable of being explai 
but the most frequent morbid appearance ft 
after death is ulceration, although here i 
evidence of its ever commencing in these s 
tures. In all cases of phthisis laryngea, 1 
ligaments suffer severely and in some are ¢ 
ally destroyed ; for the expulsion of the 
tenoid cartilages by coughing is no infre 
symptom of that disease, and it could not o 
wise occur. I have often imagined that 
ulceration of the ligaments was one caus 
the difficult respiration, particularly im ‘ 
where there is a marked difference between 
Spiration and expiration, by allowing to 
arytenoid cartilages too great a degree of 
bility, and permitting them to be thrown ¢ 
on the rima. When the connexions bet 
the cricoid and arytenoid cartilages are 
across posteriorly, it is easy to lay the ] 
down in such a manner as nearly to oblit 
the rima; and if a similar division be eff 
by disease, why may not these little b 
become loose, be acted on by the curre 
air and shut like a valve in every act of 


spiration ? ' 
( W. H. Porte 


LEG (Recrons or THE).—If the impor 
of a part, and the interest connected wit 
study of its structure and its diseases, be 
sured by the general amount of s 
through it entailed upon mankind, by 
treme liability to accident and injury, ai 
its value in the general movements ant 
being of the body, certainly the 
possess claims to our consideration gre: 
any other portion of the system of 
extent. From the integument to the bone 
from the knee to the ankle, every part of 
the frequent subject of disease, more or 


eh 
Pi 


interfering with the comfort, if not with the 
health, of the entire system. 

_ It is composed of two bones, the tibia and 
4 la, with accompanying masses of muscles 
before and behind, which act upon the 


If we divide the leg into anterior, external, 
and posterior regions, we find in the anterior 
‘the tibialis anticus muscle, the extensor com- 
munis digitorum, extensor proprius pollicis, 
and peroneus tertius; in the external region, 
the peroneus longus and brevis; and poste- 
, the two gastrocnemii, popliteus, plantaris, 
is posticus, flexor longus digitorum, and 
exor longus pollicis. Among these are run- 
ag the anterior and posterior tibial and pero- 
arteries, with their accompanying veins, 
lerves, and absorbents; all these bound toge- 
her, and supported by strong fascial coverings, 

d enveloped in the general integument. Be- 
_ tween this and the fasciz just mentioned, is an 

‘important layer of cellular tissue, (fascia super- 
 ficialis,) enclosing the two saphene veins, major 

and minor, and the superficial nerves and ab- 
sorbents. 
It may be well to make some few obser- 
Pitone upon the external form and characters 
_ of the leg, before describing the deeper seated 
parts. The leg, comprising all that part of the 
er extremity between the knee above and 
the ankle below, is somewhat of a conoidal 
tapering figure, rather flattened on its anterior 
and outer aspect, full and round posteriorly. 
This shape renders permanent compression by 
means of a bandage very difficult. The con- 
traction of the gastrocnemii, especially during 
walking, rarely fails in a short time to separate 
the turns of the bandage below, causing the 
_ lower ones to overlap each other, and producing 
constriction, irritation, and excoriation of the 
_ skin, above the malleoli. If this difficulty 
| were more considered, and the importance of 
the bandage in diseases of the leg duly appre- 
ciated, we should see more pains taken in ac- 
_ quiring the art of its application than is now 
common ; though we are happy to find that the 
minor operations of surgery are now beginning 
9 receive much more attention than formerly, 
and to form a part of the general system of 
demonstrative instruction. Assuredly the ag- 
gregate amount of suffering relieved would be 
far greater by attention to these minutie of 
_ surgery, than by the more striking, though not 
more important details of operations, which to 
__ the mass of practitioners can occur but seldom, 
| ifatall. 

_ The projection of the muscles at the back 
part of the leg, produced by the two gastro- 
_ enemii, and known under the name of the calf, 
forms a characteristic peculiar to man. No 
_ inferior animal possesses it, not even the ourang 

outang ; and the feeble and uncertain gait of 
_ these animals, when in the erect position, at 

once demonstrates the value of the muscles of 
the calf of the leg, and that this position is 
natural only to man himself. The form and 
expression of this part of the leg varies much 
_ according to age, sex, and general habit. In 

Seafancy the gastrocnemii, in common with the 

ef 


= 
| 


REGIONS OF THE LEG. 


127 


developement of the whole lower extremity, 
are small and feeble. The upper extremities 
are, in early infancy, even larger than the lower; 
these latter do not acquire their full growth 
and proportions till adult age. In the female, 
the general form of the leg is less marked and 
prominent, and more rounded than in the male, 
while, in this last, the leg presents every pos- 
sible variety of proportion, according as habits 
of exercise on foot, robust health, or long conti- 
nued sickness, has invigorated or enfeebled the 
muscular system at large, or this portion of it 
in particular. The broad and rounded surface 
of the calf of the leg is contracting as it de- 
scends, and at the lower part projects like a 
kind of cord, representing the tendo Achillis. 
In contraction, the calf shows two portions, 
marked out by a double fissure, which indi- 
cates the situation wher the gastrocnemius 
join the soleus, the lower elevation being 
formed by this last muscle, which extends 
lower down the leg than the gastrocnemius. 
This projection of the soleus is in some much 
more marked than in others, and is indicative of 
considerable power when it reaches lower down, 
much more so than when the whole prominence. 
of the calf is high up. In persons celebrated 
for pedestrian powers we have observed this 
projection of the soleus in a marked degree. 

In the anterior region of the leg, the form is 
considerably flatter than in the posterior, and 
narrows as we proceed downwards, at the 
lower part becoming almost round. During 
extension of the foot, this region is marked by 
longitudinal elevations and depressions, indi- 
cative of the situations of the, muscles, and: of 
the connecting portions of aponeurosis. An 
examination of these points will assist us in 
cutting down upon the arteries here, as the 
depressions mark the exact boundaries of the 
muscles, being produced by the aponeurotic 
processes, which dip between them. 

The integument of the anterior region, gene- 
rally covered with hair in man, and of a some- 
what dense structure, enjoys sufficient mobility 
to admit of wounds being united by the first 
intention, provided the loss of substance be 
not great. Not being very extensible, abscesses, 
tumours, &c., have great difficulty in projecting 
externally in front of the limb, and consequently 
for the most part remain more or less flattened. 
The posterior part of the leg has an integument 
more soft and elastic, and possessing fewer 
hairs than the anterior, particularly on the inner 
side. The position of the skin, with relation 
to the parts which it covers, occasions a marked 
difference in the mode of repaizing the ravages 
of extensive ulcerations or sloughings. On 
the front and outer part of the leg, where the 
skin is somewhat stretched over the tibia and 
fibula, the process of cicatrization can only 
draw together the sound parts to ‘a small de- 
gree. In consequence the healing process is 
slower in completion, and the cicatrix less de- 
pressed in proportion than when it is situated 
posteriorly. On the contrary, in this latter 
situation, the skin being stretched only over 
soft parts, when a considerable portion of it has 
been destroyed, the contractile force of the new 


128 


skin has full opportumity to exert itself, and 
this it does sometimes to a degree that is re- 
markable, acting as a sort of ligature upon the 
back part of the leg. We have seen a case 
where, by the cicatrization of an old and very 
extensive ulcer, the lower part of the calf of 
the leg, viewed in profile, had an appearance 
as if more than halt the entire leg ha en cut 
away.* The most dense and strong part of the 
integument of the leg is over the inner side of 
the tibia where this forms the only covering of 
the bone, while at the upper and back part of 
the leg the skin is exceedingly thin and deli- 
cate, and devoid of hairs. We may here’ re- 
mark, in illustration of the properties of the 
integuments of the leg, important in relation to 
Surgery, that the contractile property of the 
skin is usefully exemplified in amputation, 
when, should the flap of the integument be more 
extensive than we desire, even to a great de- 
gree, we always find that in the progress of the 
case it contracts so much as to exhibit no re- 
dundance in the end; in fact that a large 
uantity of integument, however unsightly, is 
less to be dreaded than the opposite defect. 
It is not our intention here to enter minutely 
upon the diseases of the parts we are now de- 
scribing, but we cannot refrain from alluding 
to a state of disease of the integuments which 
we have never seen but in the leg, and of which 
we have met with no account in books. It 
consists in a soft elastic swelling, generally 
occupying the entire circumference of the leg, 
for the lower third or fourth of its length, 
though often much less. The skin over it is 
considerably redder than natural, and of a 
somewhat dark colour. It is not at all tender 
to the touch, but is exceedingly painful when 
the foot is down and in exercise ; on pressing 
the finger firmly upon it no pit is left, but the 
skin is very white until the capillaries fill again, 
which they do slowly. Should the skin ulce- 
rate, the sore is very slow in healing, and gene- 
rally has a brownish unhealthy look, but the 
State in question often lasts for years without 
any ulceration occurring. The disease is very 
indolent, neither increasing nor diminishing in 
extent for many years. We have not been able 
to trace it satisfactorily to any cause more than too 
much standing. All the cases observed by us 
have occurred in females between the ages of 
twenty and forty, whose employment kept 
them very much on foot. It appears to us to 
consist in a varicose state of the capillaries of 
the cellular tissue and inner side of the cutis. 
No treatment that we have employed has had 
anything more than a temporary effect. Pres- 
sure, as long as it is continued, relieves it ; but 
all the morbid symptoms return upon the 
remedy being omitted. 

Immediately under the skin lies the cellular 
tissue, which is a part of the general cellular 
investment of the body, and is here known as 
the superficial fascia of the leg. It is gene- 
rally pretty thick, and is easily dissected back 
in amputations. Placed between two solid 
layers, the aponeurosis and skin, it easily in- 


* See article CICATRIX,. 


REGIONS OF THE LEG. 


flames and may become the seat of ex 
inflammation and abscess. When the in 
mation has terminated in gangrene, the slot 
ing process in this cellular tissue is r 
and often very uncontroulable ; and ¥ 
destruction has occurred to conside 
tent, in the after process of reparation 
cellular web is so short, close, and in 
to materially impede the freedom of mover 
in the limb. When pus has. been form 
facility which the loose texture of the s 
ficial fascia offers for its spreading in all ¢ 
tions, points out the necessity for early an 
incisions through the integuments; and 
before this stage of the inflammation, and ' 
it is in its most active state, the same 
practice offers us the best means of arresti 
progress. This cellular layer is the seat« 
effusion in phlegmonous_ erysipelas, ¢ 
phlegmasia dolens, and partially so 
phantiasis. The distension which th 
and the integument over it undergo in the) 
eases just mentioned, is occasionally e 
and affords a striking contrast between 
elastic properties of the natural and adventit 
structures. When anasarca distends a leg u 
which an old cicatrix exists, the newly for 
cellular web of this part is so little elastic 
so little admits the fluid into its cells 
considerable depression is seen here in 
midst of the general swelling. a 
Imbedded in this superficial fascia we 
a number of veins which are various in} 
none very large in the natural state, nun 
and here possessed of more surgical 
and importance than in any other superf 
region of the body. They are principal 
ranged in two sets; one commencing @ 
the inner ankle, and running along the i 
side of the calf, terminates just below the 
by one trunk called the internal or 
saphena. The other set form the sap 
minor, by coming from the outer ankle, ak 
the outer and back part of the leg, and tert 
nating in the popliteal vein in the midd 
the ham. This vein is superficial only im 
lower two-thirds of the leg ; after this, it; 
through the layers of the aponeurosis, and 
under it till its termination. This is the m 
ordinary course of them, but no part of 
circulating system is more various than t 
superficial veins in their divisions and arr 
ment. These veins, by becoming yari¢ 
frequently occasion great suffering to the 
tient, and annoyance to the surgeon, by 
difficulty of their cure. The saphena ma 
more liable to this state of disease than 
minor; indeed few persons whose habits a 
be much in the erect posture appear to a 
ag age without being more or less trot 
y it. 4 
The deeper seated veins, which accom 
the arteries, lie imbedded among the mu 
and from them receive considerable p 
support, in sustaining the weight of the coh 
of blood above them, and still more in ana 
sense, when, in contracting, the muscles: 
and press against their sides, and thus 
forcing onwards their contents. & 


« 


ae 


Pa eee ee ee ee er eee 


aq REGIONS OF THE LEG. 


Se agen veins are without this important 
p- Their sides are supported, on one hand, 
by the yielding layer of the fascia and muscles, 
and, on the other, by the integument. When, 
_ therefore, any impediment presents itself to 
the free transmission of the blood through the 
femoral, popliteal, or iliac veins, or even by 
the mere weight of the ascending column of 
lood, in persons who stand much, it is the 
uperficial veins that suffer most, and a perma- 
“nently dilated state is the frequent result. 
__ The pathology of varicose veins has not re- 
‘ceived the attention which it deserves, and 
hence the conflicting opinions as to the precise 
‘nature of their origin; we must even now con- 
ss with Delpech that the nature and causes 
the disease are unknown. It is quite clear 
at that state of disease of the veins commonly 
ermed varicose comprehends more than one 
lathological condition, and probably has more 
than one mode of origin. Every instance of 
an enlarged vein cannot be considered as a 
varix, unless we confound under the same 
denomination a condition of the vessel natural 
and healthy except in regard to its size, neither 
originating nor terminating in a morbid condi- 
on, with every variety and degree of disease 
iecompanied with enlarged capacity of the vein. 
We have seen the veins of the abdomen en- 
arged so as to fulfil the office of the vena cava 
‘inferior, which was obliterated. But there was 
ot the slightest mark of disease in these super- 
tial vessels. The uterine veins, also, in preg- 
ancy become enlarged in a similar manner, 
hus answering to the call for the increased 
reulation of blood in the uterus. This state 
the vessels has been aptly termed hyper- 
tophy, and the term varix has been restricted 
© permanently dilated states of the veins, at- 
nded with the accumulation of dark blood, 
hich more or less generally becomes coagu- 
ed and adherent to the parietes of the vessels. 
this latter species Andral enumerates six 
rieties: ist, simple dilatation without any 
change, such dilatation affecting either 
whole length, or occurring at intervals ; 
d, dilatation, either uniform or at intervals, 
th a thinned state of the veins at the dilated 
ints; 3d, uniform dilatation with thickening 
Of the venous coats; 4th, dilatation at inter- 
vals with thickening of the dilated points ; 5th, 
dilatation, with the addition of septa within the 
vein, whereby the cavity is divided into little 
cells in which the blood lodges and coagulates ; 
6th, a similar disposition combined with per- 
forations in the parietes of the veins, which 
communicate with the surrounding cellular 
issue in a more or less diseased state by nume- 
small apertures. From repeated observa- 
of its practical importance we should be 
ned to add to this list one other variety, 
via when the varicose state had extended into, 
r existed distinctly in, the capillaries of the 
We believe that in those troublesome 
ilcers known as varicose we shall frequently, 
f not generally, find this state of the minuter 
eins and capillaries, and we are more inclined 
© attribute the pain and the obstinate character 
f these ulcers to the pathological condition now 
“VOL, III. 


: i 


pi 
, he 
- 


a. 
neli 


KIN, 


129 


mentioned than to the mere vicinity of an en- 
larged vein as it passes through the superficial 
fascia. The causes of the diseased state in 
question have been variously stated, nor do 
Opinions yet agree upon it, some attributing it 
to mechanical influence, and others supposing 
a morbid tendency. Both these causes pro- 
bably act in different instances, or even co- 
operate in the same case; we shall now only 


“mention in illustration of the effect produce- 


able by the mechanical influence of too much 
standing, that it is not necessary to suppose 
that the valves are either destroyed or even 
materially injured in structure to nullify their 
agency in supporting the column of blood 
above them, since ever so small a communi- 
cation between the two columns, the upper 
and the under, is sufficiept to destroy all the 
beneficial agency of the salves as supporters of 
the gravitating fluid in the veins. ‘Therefore © 
a dilatation of the vein merely enough to draw 
the opposed edges of the’ valve ever so little 
apart, or even a thickening of the valves pre- 
venting the accurate coaptation of their edges, 
will be sufficient to prevent their power of 
support to the superincumbent column, and 
as far through the vein as this defective state 
of the valves may exist, so far will the gravi- 
tating column of blood be virtually unbroken 
and entire, and in the same proportion will the 
tendency to the varicose state be increased. 
This reasoning will explain many, probably 
the majority of cases where the eabid dila- 
tation having once begun goes on to increase 
rapidly by the continued operation of this ex- 
citing cause. That there are other causes 
capable of producing this state of the veins 
cannot be disputed ; indeed the occurrence of 
it in parts not likely to be affected by the up- 
right position, and even in several different 
parts of the body of the same subject, shews 
that there is occasionally a morbid tendency in 
the venous system to this particular state, 
which acts independently of any mechanical 
cause; but we believe that this predisposing 
cause is not necessary to the production of the 
disease, and that the morbid tendency, when it 
is met with, should be regarded rather as the 
exception than as the rule. 

In considering the causes of the disease in 
question, we should not lose sight of the rela- 
tive proportion of the deep and superficial 
venous circulations of the lower extremities, a 
preperrien varying in. almost every individual. 

n one, the superficial veins are large and nu- 
merous, and lie immediately under the skin; 
in another, they are few and small. Tt is ob- 
vious, that in the first case the blood retained 
by this route bears a large proportion to that 
passing through the deep set, much larger than 
it would in the latter case. In the first in- 
stance, therefore, these vessels will have a 
greater proportional weight of blood to sustain 
and transmit, than in the second ; while, in 
those individuals who have the superficial cir- 
culation small, the blood is chiefly returned by 
the deep set, which, from circumstances before 
mentioned, are more equal to the task, and in 
such persons the diseased state in question 

K 


130 


rarely occurs. This we conceive to be a ratio- 
nal and practical explanation of phenomena 
which are otherwise obscure. 

It seems probable that that most troublesome 
ulcer, the varicose, is kept up, and the difficulty 
of its healing produced not by the irritation 
occasioned by the mere vicinity of the enlarged 
veins, but from the actually varicose state of 
the capillaries of the skin at that part; at least 
we have found such a state of the vessels fre- 
quently, if not generally, to co-exist with this 
species of ulcer. The depth of the cellular 
layer (superficial fascia) in which these_veins 
lie should be accurately understood and borne 
in mind iv performing the operation of passing 
a needle under the vein for the cure of varices, 
according to Velpeau’s plan (a method which 
we have shekeed with considerable success.) 
Should the needle be passed so deep as to 
reach the fascia, the inflammation would pro- 
bably be severe, at any rate sufficient to com- 
plicate needlessly the operation. The thickness 
of the cellular layer varies in different subjects, 
according as it is distended more or less with 
fat or with accidental effusion; it is rarely, 
however, less than two lines in depth, thus 
affording abundance of room for the transmis- 
sion of the needle, 

The size of these veins of the leg in the 
healthy state is at the most not larger than a small 
goose-quill, but when varicose they sometimes 
swell to the size of the finger, and we lately 
saw a varicose enlargement of the saphena 
major a little below the knee, of the size of a 
large hen’s egg ; the quantity of blood that may 
in a short time be lost from them may hence be 
conceived. On the anterior region the veins 
are few, and varices but rarely occur compara- 
tively. On the inner region the saphena major 
lies close upon the bone in part of its course, 
and even indents it deeply when distention has 
continued long. In cutting upon the vein in 
this situation, we must bear in mind the conti- 
guity of the internal saphenus nerve, whose 
situation, with relation to the vein, varies much, 
sometimes being before, sometimes behind it. 
We cannot, therefore, lay down any rule for its 
avoidance, unless it be to open the vein parallel 
to its length. The saphena minor has a nerve 
running with it, which in phlebotomy must be 
avoided with the same precaution as the nerve 
on the inner side. 

The two nerves found imbedded in this su- 
perficial layer of the leg are, ist, the internal 
saphenus, which is the largest, and is passing 
from the inner side of the knee to the inner 
side of the foot, accompanying the saphena 
major vein; 2d, the external saphenus or com- 
municans tibialis from the tibial nerve, which 
runs near the saphena minor through the lower 
part of its course. 

Imbedded in the superficial fascia, we also 
find a set of lymphatics, principally on the 
inner side of the leg, receiving part of those 
from the sole and dorsum of the foot, while 
those absorbents which accompany the sa- 
phena minor are receiving their commence- 
ment entirely from the sole of the foot. All 

of these superficial lymphatics ascend to the 


REGIONS OF THE LEG. 


inner side of the thigh, and terminate in | 
inguinal glands. Hence diseases of the st 
cutaneous cellular tissue of the leg exert t 
influence upon the superficial glands of 
groin, and are not unfrequently the caus 
disease in them, which, without due ing 
might erroneously be attributed to di 
the genital organs. ; 
The aponeurosis of the leg forms an im: 
part of its economy. It is a dense tend 
structure, which immediately invests the 
cles, and partly affords them origin. 
quence of its strength and want of e! 
prevents swelling in deep-seated i 
tions, and we are consequently oblig 
divide it early and freely, particularly 
suppuration already exists, and when 
ter would otherwise burrow among the mi 
On the anterior region it is strong, ve 
tinct, and tense. In its superior fifth, it” 
attachment to the fibres of the tibialis a 
extensor communis digitorum, and pe 
longus. Below, it is pierced by the a 
tibial and musculo-cutaneous nerves. 
attached above to the heads of the tibiz 
fibula, and along the crest of the 
stretching from this to the anterior edge 
fibula. At the upper third of the leg, 
processes backwards between the mus 
be attached to the bones, thus forming s 
for the muscles, and affording to their fi 
greater extent of origin. At the lower 
thirds of the leg, the fascia is closely att 
to the intermuscular tissue, but has hen 
septa from its own structure. At th 
third, it binds the tendons firmly de 
places, and by its transverse fibres oppos 
ankle forms the anterior annular 
that part.* From the anterior edge + 
fibula, this fascia passes over the two pen 
muscles, and is again inserted on the po: 
border of the bone, forming a sheath for 
muscles, and dividing them from the 
The observations made above on the } 
treatment of purulent collections 
ally to this anterior portion of the fascia 
leg, on account of its greater strength, di 
and inelasticity. r 
At the back part of the leg, the apor 
is a continuation of that of the ham. — 
consider it as formed of two princi 
one superficial, and the other Pe . 
to the posterior border of the fibula xt 
and to the inner margin of the tibia in! 
the first appears to arise from the exp 
the tendons of the sartorius, gracilis, am 
tendinosus. Applied over the posterior 
of the calf, it is lost below in the fibro- 
tissue surrounding the heel. Thisp ortio 
thin and yielding, it allows deep-seat 
scesses to become superficial with great 
The second layer is a continuation of 
neurosis of the popliteal cavity, and 
between the two layers of muscles; bu 
ting into two, at the point where the sole 
taches itself from the deep parts, on 
divisions follows the anterior surface’ 


Ss 


* See ANKLE-JOINT, REGIONS OF. 


e 
tendo Achillis, of which it completes the 
fibrous canal, formed posteriorly by the super- 
ficial layer; the other remains applied over the 
osterior surface of the deep muscles, and both 
arrive at the heel. 
In its inferior third, this aponeurosis thus 
ircumscribes three spaces. One is filled by 
tendon of the muscles of the calf. The se- 
ond incloses the flexor muscles of the toes, 
ad the vessels. The third, which separates 
e two others, lies between the tendo Achillis 
nd the posterior surface of the last-named 
Muscles. The latter is remarkable, from being 
filled with fat and fibrous filaments, interlaced 
| various directions.* 
‘We have, for convenience of description, de- 
failed the anatomy of the superficial parts of 
le leg, without particular reference to the re- 
gional divisions, which become more defined, 
listinet, and practical as we investigate the re- 
ations of the deeper seated parts, and to which 
é shall therefore now limit ourselves. 
In the anterior region, comprising all those 
nuscles which rest upon the tibio-fibular fossa, 
ve find, on dissecting the fascia from the upper 
art, only two muscles exposed, viz. the tibialis 
nticus and extensor communis digitorum. 
ower down, we see in addition the extensor 
roprius pollicis coming out between the two 
fast, and the peroneus tertius a slip of the outer 
ide of the extensor communis. These four 
e, as it were, bound down in a canal, formed 
nteriorly by the aponeurosis, posteriorly by 
e tibia, fibula, and interosseous ligament. 
e direction of the tibialis anticus, its size, 
d boundaries should be borne in mind, as 
ese form the surest guide for cutting down 
on the anterior tibial artery. This muscle is 
a prismatic form, tapering downwards, and 
outer edge is indicated externally by a 
cus in the integuments made more apparent 
y extension of the foot. It is found more ac- 
rately by tracing a line from the middle of 
space between the crest of the tibia 
id the fibula to the middle of the instep ; and 
e, between this muscle and the extensor 
mmunis, the arteryruns. The external mus- 
sare the peronei longus and brevis; they 
enveloped in a sheath of the aponeurosis, 
d are applied, for some extent, to the exter- 
surface of the fibula. They are completely 
arated from the extensors and from all the 
nuscles of the posterior region by the two apo- 
neurotic septa attached to the anterior and 
sterior edges of the bone. The adherence of 
ié muscular fibres continuing until just above 
he outer malleolus, a transverse section, in the 
Wo superior thirds, does not entirely destroy 
heir action upon the foot, while, lower down, 
t would render abduction almost impossible. 
Ve have not heard of an instance of the entire 
upture of any of these muscles, nor is it an 
ccident likely to occur, as they are not, from 
neir Situation, likely to be called upon for any 
ery great exertion of power; but these muscles 
€ occasionally liable to the accidental rupture 


i 
i 
| 
} 


= 


; 

* See Velpeau’s Anatomy of Regions, translated 
dancock. 

ps 


4 


REGIONS OF THE LEG. 


131 


of some of their fibres, a circumstance attended 
with much more pain and distress in moving 
than the apparently slight nature of the accident 
might lead us to expect. We have had lately 
a case of this kind under our care, where the 
suffering and the injury to the movements of 
the foot were so great as at first to lead us to 
suspect a much more serious extent of injury 
than really existed. It was occasioned by at- 
tempting to push along a sack of corn with 
both knees, both feet being on the ground, and 
the heels raised, while the upper part of the 
sack was held in the arms. 

The only artery of importance in this region 
is the anterior tibial. It commences from the 
trunk of the popliteal nearly at right angles, 
traverses the opening in_the upper part of the 
interosseous ligament, cl®Se to the neck of the 
fibula, and below the head of the tibia. The 
angular curve which the artery makes at this 
part of its course, according to M. Ribes, ac- 
counts for the great retraction of it after ampu- 
tation of the leg.* It descends upon the inter- 
osseous ligament, in the direction of a line 
drawn from the middle of the space between 
the head of the fibula and the crest of the 
tibia, to the middle of the instep. Through 
the upper part of its course it lies upon the in- 
terosseous ligament; as it descends it gradually 
advances upon the tibia, and runs upon the 
anterior surface of this bone through its lower 
third. It is found at the upper third of the 
leg, between the tibialis anticus and extensor 
communis digitorum; in the middle third, its 
course is between the tibialis anticus and the 
extensor longus pollicis, and about four inches 
above the ankle-joint it passes obliquely under 
the tendon of this last muscle, and then is 
found between its tendon and that of the ex- 
tensor communis. It runs between two veins 
through its whole course. The nerve is on its 
outer side above ; in front in the middle; and 
internal below. An extensible but resistant 
cellular sheath unites the whole. It is evident, 
that in the upper part of its course the artery 
will be found much deeper than at the lower, 
when it is lying among the tendons, but in the 
living subject the natural state of tension of the 
muscles keeps these tendons more elevated 
than after death, and we shall consequently find 
the artery, even in this situation, deeper than 
from dissection we might have heen led to an- 
ticipate. The surgeon will find little difficulty 
in discovering this artery when it is required to 
be tied. The marks for his guidance are clear, 
and the situation of the vessel on the whole 
pretty uniform ; but owing to the depth of its 
situation above, and to the immediate vicinity 
of the veins and nerve, some difficulty will be 
experienced in excluding these from the liga- 
ture. The only branch from it of any surgical 
importance is the recurrent tibial. This arises 
just after the trunk has passed through the in- 
terosseous ligament, and passes upwaids in nu- 
merous branches to the ‘parts below and to the 
outer side of the knee-joint, anastomosing freely 
with the inferior external articular artery. These 


* See Velpeau’s Anatomy of Regions, p. 473, 
K 2 


132 


anastomoses form an important part of that 
system of collateral circulation by which the 
Stream of blood is continued to the leg and 
foot, after the obliteration of the popliteal 


aie 
he anterior tibial artery may require to be 
tied in case of wound or aneurism. In wounds 
of the dorsal artery of the foot, it may be advi- 
sable to put a ligature at the lower third of the 
leg, when the anterior tibial is running between 
the tendons. Its course may be here ascer- 
tained by feeling its pulsation, or by observing 
the liue of the tendon of the extensor proprius 
gai on the fibular side of which it here lies. 
hen about to tie it higher up, the incision in 
the integuments and fascia must be the more 
free in proportion as it is nearer the knee; and 
it may sometimes be advisable even to divide 
some of the fibres of the fascia transversely, to 
rmit more freely the retraction of the muscu- 
far sides of the cut. In dissection, we so easily 
separate the muscles and expose the artery, 
that we may underrate the difficulty attending 
the operation of tying it. The depth at which 
it lies in this part, the constant contraction of 
the muscles, and the difficulty of retracting the 
sides of the incision, occasioned by the strong 
aponeuroses, all constitute considerable obsta- 
cles to the operation. This artery was subcu- 
taneous in a case related by Pelletan, and is 
occasionally very small indeed, or even abso- 
lutely wanting. The first anomaly we have se- 
veral times seen in dissection, and an instance 
of the latter is related by Huguier.* In these 
cases a large branch of the peroneal, which had 
passed through the interosseous ligament a 
little above the ankle-joint, supplied the place 
of the lower part of the artery. In a case 
which was met with by Velpeau, he found this 
artery not perforating the interosseous ligament 
at all, but winding round the fibula just below 
the head of this bone, and in company with the 
musculo-cutaneous nerve.t 

The artery is accompanied by two veins, one 

laced on each side, throughout its course. 

e anterior tibial nerve, which is a branch 
from the peroneal, runs on the fibular side of 
the artery first, and then obliquely crosses it, 
sometimes again passing outwards, towards the 
lower part of the leg. The deep-seated lym- 
phatics following the course of the vessels, 
deep-seated disease of the front of the leg may 
produce alteration of the glands of the ham. 
A lymphatic gland is found in front of the an- 
terior tibial vessels, a little below the opening 
of the interosseous ligament through which 
the vessels pass. 

In the posterior region of the leg the mus- 
cles are arranged in two distinct layers, the 
superficial, composed of the gastrocnemius, 
soleus, and plantaris; the deep, of the popli- 
teus, the tibialis posticus, the flexor communis 
digitorum, and flexor longus pollicis. The 
gastrocnemius becomes tendinous, considerably 
higher in the calf than the soleus, sending off 


* See Velpeau’s Anatomy of Regions, p. 474. 
- Sce Velpeau’s Médécine Operatoire, tom. iii. 
137. 


REGIONS OF THE LEG. 


its broad thin tendon about the middle of th 
leg, to unite with that of the soleus, about @ 
junction of its middle and lower thirds. 
soleus, beginning its origin lower than ~ 
last muscle, from the bones of the leg, ¢ 
tinues its muscular fibres lower in proport 
in this respect varying considerably in di 
subjects. 

ese two muscles, arising above 
distinct heads, and having but one msé 
below, form in fact but one muscle, 4 
Meckel has named the triceps ‘ 
common tendon is of a strength propor 
to that of the muscles themselves, ai 
therefore exceedingly powerful. Ne 
ing, the combined action of the muscles is 
sionally too much for the tendon, and in 
ing, dancing, or other similar move 8, 
sometimes ruptured. After this ace 
difficulty of cure results, not so much 
injury done to the tendon itself, as from 
difficulty of bringing the two ends into a 
tion. In fact, complete union neve 
the utmost extension of the foot never bri 
the lower portion so high as the upper 
tracted by the muscles. The union, hi 
which is of a cellular structure, becomes 
ciently strong to be perfectly servic 
Boyer speaks of a partial rupture of the 
Achillis, and describes with precision the s 
toms, but we apprehend this form of the” 
dent is very rare.* The pathol of 
foot, which has only of late years 
understood, shows that permanent retr 
the muscles of the calf, either prima 
condary, is its most frequent cause, 
division of the tendo Achillis and the 
tendons of this has in co uer 
resorted to with ere success. iain Pp 
operating which our experience leads 1 
prefer, is to insert a sharp-pointed 
through the skin, and pass it behind the te 
with its flat side towards it, till having re: 
its farther side, the edge is turned, at 
tendon is divided in the withdrawal, w 
more division of the skin than the me 
ture. If the tendon is kept tense durin 
operation by the forcible flexion of th 
and is not quite divided at one c 
undivided tendinous fibres are pu 
stretched, and partially torn from their 
attachments, which occasions a sort of 
noise, which is not heard when the foree 
applied, till after the entire division 6 
tendon. The union here takes place i 
same manner as in rupture of the tendon 
the treatment proceeds upon a somewhat 
rent principle, since it is in this latter ¢ 
intention to keep the divided ends apart 
the foot is therefore placed at ight a 
while, in the ruptured tendon, the i 
tended, in order to approximate the @ 
much as possible. The extreme contrac 
the muscle, in club-foot, leaves no poss 
of further retraction of the upper part 


er 
oe 


— Boyer’s Maladies Chirurgicales, tom. 
p. 95. “ 
+ See Liston’s Practical Surgery, p. 16 


‘ 


tendon, therefore the whole separation, after the 

_ division, is performed by the moving of the 
_ dower part. 
The powerful muscles, now described, are 
never known to be ruptured themselves, the 
tendon, as we have seen, yielding first, but 
partial rupture of their fibres is not very 
uncommon, and is indicated by the same pain- 
symptoms as were alluded to in speaking 
of the anterior muscles. It is worth remarking, 
on the great power of these muscles, that, great 
is is the force required, to elevate the whole 
dy, by acting upon the heel, yet the muscles 
the calf are not nearly so soon fatigued in 
alking as those on the front of the leg, whose 
Tabour is merely the elevation of the foot and 
toes, and of this every one must be sensible 
Le fter unusually long exercise on foot. 

_ Between the gastrocnemius and the soleus 
is the plantaris tendon, a long slender slip, 
which, after crossing between the muscles, runs 
| onthe inner side of the tendo Achillis, to its 
nsertion. The belly of this little muscle is 
under the outer head of the gastrocnemius, 
slose to the origin of which it arises. Authors 

scribe the symptoms attendant upon rupture 
of this tendon, Put the diagnosis of injury to 
o small and deep-seated an organ must be so 
ncertain, that we should be much more in- 
clined to refer them to an injury of some of 
he fibres of the great muscles of the calf, es- 
pecially when we compare the power of the 
plantaris with that of its tendon, the passive 
ength of the latter appearing greatly superior 
0 the active force of the former.* Between 
he lower part of the tendo Achillis and the 
endons of the deep layer of muscles, there is 

considerable layer of cellular tissue, con- 
aining fat, and this is often the seat of trouble- 
ome chronic inflammation ; and if suppuration 
ollows, the abscess is often very difficult of 
ealing, from the constant movement of the 
endon, and the result is a troublesome sinuous 
leer, which can only be healed by keeping 
“the foot entirely at rest. 

The deep muscles, bound down in the pos- 
erior interosseal space, by the inter-muscular 
ayer of the aponeurosis, are found lying in this 
rder; the flexor digitorum communis, placed 
hnermost, upon the back of the tibia; the 
exor longus pollicis, on the fibula, and the 
bialis posticus between them, and partly con- 
eealed by them. Upon this last muscle are 
‘Situated the posterior tibial vessels and nerves. 
As they all of them have to pass nearly behind 
e inner ankle, the two outermost are gradu- 
ally approaching to the flexor communis, as 
they descend, till they are nearly in contact one 
With the other. As all these tendons, either 
| Primarily or secondarily, act upon the ankle- 
Joint, their action is retained after rupture or 
d vision of the tendo Achillis, so that the 
power of extension of the foot still remains, 
though in a feeble degree. 

Sal and pr of this region are the posterior 


e 


pe 


- 


r 


bial and peroneal, and are given off from the 
termination of the popliteal. The anterior ti- 


ie, ae ; : / 
__* See Dictionnaire des Sciences Medicales, ar- 
ticle Jambe. 


° 


REGIONS OF THE LEG. 


133 
bial also has here a course of a few lines, from 
its origin, till it perforates the interosseous liga- 
ment. The posterior tibial may be considered as 
the continuation of the trunk of the popliteal. 
It commences about an inch below the origin 
of the anterior tibial, and where the popliteal 
divides into this artery and the peroneal. The 
course of the posterior tibial may be defined 
by a line drawn from the middle of the ham, 
to a spot half an inch behind the inner mal- 
leolus. In this course it is accompanied by 
two veins, one on either side, also by the poste- 
rior tibial nerve ; in the upper part of the leg, 
this nerve lies to the inner or tibial side of the 
artery ; it soon, however, passes over it, and 
inferiorly it lies to its outer or fidular side. 

The posterior tibial artery is covered, in the 
upper and middle thirds of the leg, by the gas- 
trocnemius and soleus imrscles, but in the lower 
third only by the integuments, and by the su- 
perficial and deep fascie of the leg. In the 
upper third of its course, this artery rests upon 
the tibialis posticus muscle, in the middle 
third upon the flexor digitorum communis, 
and in the inferior third some fat and cellular 
membrane separate it from the tibia, and from 
the internal lateral ligament of the ankle-joint. 

In the inferior third of the leg, the posterior 
tibial artery runs nearly parallel to the inner 
edge of the tendo Achillis; between the os 
calcis and malleolus internus, it lies nearly in 
contact with the sheath of the flexor digitorum 
communis.* The only branch of surgical in- 
terest given off by this artery in the leg is the 
nutritious artery of the tibia, which comes off 
about its upper third, and in amputation at 
this part sometimes bleeds freely. 

In putting a ligature upon this artery, the 
difficulties attendant upon the operation vary 
according to the situation at which we seek for 
it. Itis favourably circumstanced for opera- 
tion in the inferior third of its course, being 
covered in the two upper thirds by the muscles 
of the calf. It may require to be tied fora 
wound in the sole of the foot, or for one behind 
the inner ankle. In either of these cases the 
artery may be found and tied with facility be- 
hind the inner malleolus. (See ANKLE-Jornt, 
Recion or.) When, however, itis deemed de- 
sirable to tie it at the lower third of the leg, it 
will be readily found by an incision of from 
two to three inches in length, performed mid- 
way between the inner border of the tibia and 
the tendo Achillis. After the division of the 
integuments, the superficial fascia, and the 
deep fascia, the artery will be met with di- 
rectly under the incision. Its accompanying 
veins sometimes completely conceal it; the 
nerve is here on the fibular side of it. 

In case of secondary hemorrhage after this 
operation, or in case of aneurism of the pos- 
terior tibial artery, forming in consequence of a 
wound of the artery in this situation, it may be 
necessary either to tie this vessel higher up in 
the leg, or to tie the popliteal femoral artery 
itself; it has been deemed prudent to give the 
patient the chance of success from the former 


* Sce article ANKLE-JOINT, REGION OF, 


134 


operation, before having recourse to so severe 
and hazardous a measure as that of tying the 
femoral or popliteal artery. 

The operation of tying the posterior tibial 
artery in the middle of the leg will be found 
much more difficult than either of the other 
situations mentioned, as this vessel here 
lies at such a depth from the surface, and is 
covered by the gastrocnemius and internal 
head of the soleus, which in this situation is 
attached to the tibia. To expose the arte 
here, the leg should be bent, the foot extended, 
and both laid on the outer side. The incision 
must be of considerable length, not less than 
four inches, along the inner edge of the tibia. 
The integuments and fascia being divided, 
(care being at the same time taken to avoid the 
saphena vein,) the edge of the gastrocnemius 
muscle will be exposed; this will be easily 
raised and drawn to one side. The soleus 
must next be divided from its attachment to 
the tibia, and at the bottom of this incision 
will be discovered some dense aponeurotic 
fibres, which are part of the deep fascia of the 
leg. The muscular fibres in the incision must 
now be held wide apart, and carefully sepa- 
rated from this deep fascia preparatory to its 
division, and immediately underneath this 
fascia lies the artery, with its accompanying 
veins, one on each side, with the nerve on its 
inner or tibial side, and here situated about an 
inch from the edge of the tibia. 

On the dead subject this operation is not 
attended with much difficulty; in the living, 
however, the case is very different; the mus- 
cles are then rigid and unyielding, and when 
the fascia which covers them is divided, they 
leave their natural situation, and become much 
elevated, so as to make the situation of the 
artery appear as a deep cavity, at the bottom of 
which the vessel is placed. The contraction of 
the muscles has been found in some cases so 
great an impediment to the operation, as to 
require the transverse division of part of the 
muscle. The operation of cutting directly 
from behind, through the fibres of the gas- 
trocnemius, is obviously still more objection- 
able, from the cause just mentioned. 

The second terminating branch of the pop- 
liteal artery is the peroneal. This is situated 
deeply, along the posterior part of the leg, 
taking the direction of the fibula ; hence it is 
sometimes called fibular. It commences about 
an inch or two below the lower border of the 
popliteus muscle, after perforating the tibialis 
posticus at the commencement of its course, 
and descends, almost perpendicularly, towards 
the outer ankle. In this course, it lies close 
upon the fibula, between the flexor proprius 
pollicis and flexor digitorum communis. On 
reaching the lower extremity of the interos- 
seous ligament, it divides into two branches, 
the anterior and posterior peroneal, the first of 
which passes through the aperture at this part 
of the interosseous ligament, and both of these 
run to the outer side of the foot. This artery 
is so small and so deeply seated, that its 
wounds are rare and unimportant. Hence 
but little has been said of its ligature, which 


REGIONS OF THE LEG. 


would be very difficult, and could be pe 
formed at the middle of the external side of 
leg. We should then divide the same parts 
for the tibial, but on the opposite side, a 
it is enveloped in the fibres of the flexor lor 
pollicis, we must also detach this muscle 
the fibula. - 
Each of these arteries of the posterior re 
is accompanied by two veins, which 
uently overlap the artery so as to conce 
rom view, in the operation of ‘inj 
they are also so adherent to its coats as to © 
sion some difficulty in separating dy | 
to avoid including them in the ligature, 
cularly where the artery, as in the f 
stance, is deep-seated. best 
accomplishing this is to insinuate the 
rismal needle first on one side, and t nA 
the other, not attempting to bring it outs 
opposite side of the artery, till, by this 
the lateral attachments are se .. 
The deep nerve which accompa 
posterior tibial artery is the tibial, 
considerable size, being the continu: 
the trunk of the popliteal. It is sit 
first, to the outer side of the 5 
down it runs nearly behind it, and so clo: 
it, that without care it may be injured, inelu 
in the same ligature, or even tied 
vessel. J 
It may not be amiss here to observe of 
distinctive marks by which the nerve m 
recognized, when passing the ligature 
the artery, that besides the most essentia 
absence of pulsation, which may occur 
the artery itself from accidental cau 
inexperienced operator will find conside 
assistance from the following, viz. the 
round, cord-like feel of the nerve, while 
artery has a flattened yielding feel 1 
pressed between the finger and thumb, 
the whitish, somewhat glistening, and pr 
nent round appearance of the nerve, thea 
haying a scammed reddish colour, 
tened, thick, and riband-like appearance, 
is raised upon the aneurism needle. 
the cut extremities of the two are sé 
ther, after an amputation, of course the 
open mouth of the one, and the pr 
stump of the other, like a tight p 
thread cut across, are readily recogniz: 
The lymphatics of these deep parts ac 
the bloodvessels, and pass to the gl 
of the ham; hence diseases occurring ™ 
parts beneath the aponeurosis of the 
their influence on the glands of the f 
space. a 
The two bones of the leg united bj 
interosseous ligament form an elongated 
in front which is closed in by the aponewt 
and is larger at the union of its two suf 
thirds than at its extremities. The 
being imbedded here are difficult 
circular amputations, at the same time th 
depth prevents the formation of a goot 
Posteriorly, they form a gutter, or fossa, la 
than the preceding, but also much more 
low, excepting at the lower part. enc 
deep muscles are easily comprehended it 


7 


flap in amputation. In the circular operation 
he section of the flesh, which can only be 
effected by passing the point of the knife 
transversely over the bottom of the interosseous 


ones and the posterior relative situation of the 
jula renders some precaution necessary in 
dividing them with the saw. The foot must 
be turned in, so as to bring the fibula a little 
mward, and care must be taken to commence 
@ section upon the tibia as being the longest 
“and strongest, but to finish the section of the 

bula first, since it is too thin and mobile to 
UP ort the movements of the saw without 
weaking at the termination. In amputation 
ve the tubercle of the tibia, it has been held 
able to remove the head of the fibula 
its joit, since this small portion of the 
bone is of no advantage to the stump and by 
its mobility may be some hindrance in the 
after treatment. (See Knes-Jornr-) 

The small size and moveable nature of the 
fibula constitutes some difficulty in the treat- 
ment of fractures of the leg, since the appli- 
cation of the ordinary bandages, &c., would 
have a tendency to press the bone’ inwards 
against the tibia, and we not unfrequently see, 
n old united fractures of these bones, this 
deformity to have been produced, in all proba- 
bility, from want of due precaution in the ap- 
lication of bandages. The defect may be 
obviated by proper care, that neither the splints 
1or the cushions should take any bearing upon 
the fibula itself except at its two extremities, 
nd great assistance may be derived from 
proper pressure, before and behind, upon the 
nuscles, gently forcing them against the inter- 
ysseous ligament and bearing outwards the 
Jone attached to it. 

After amputation of the leg, the tibia pre- 
sents a triangular surface, having the apex for- 
yards. As the skin covering it is hereby in- 
vested with the subcutaneous layer, it may, by 
ressure against this projection, ulcerate, or 
ough, and thus expose the bone. The great 
heans for obviating this accident is to have a 
300d supply of integument in the flap, so that, 
bringing the parts together afterwards, they 
hay not be drawn too tight over the bone. 
While this rule is attended to all will go on 
ell, whereas when the integument is left scanty, 
hothing can prevent unpleasant consequences. 
may often, however, be advisable to remove 
ith the saw the projecting angle of bone, and 
$a matter of precaution we generally do this, 
hough not attaching much importance to it.* 

In amputating above the tuberosity of the 
ibia, we run the risk of opening into the knee- 
‘Joint, as the synovial membrane is sometimes 
prolonged thus far. According to M. Lenoir 
@ synovial cavity of the knee is continuous 
with that of the superior tibio-fibular articu- 
ation, once in four times.t There are always 
< ™ See Bell’s Operative Surgery, vol. ii. p. 22. 

_ +t See Velpeau’s Anatomy of Regions, p. 484. 
Ke 


REGIONS OF THE LEG. 


135 


three principal vessels to be tied in this ope- 
ration: first, the anterior tibial, which is found, 
with its collateral nerve, close upon the inter- 
osseous ligament; secondly, the posterior ti- 
bial, in contact with the deep layer of the 
aponeurosis, and having its nerve to its outer 
side; and, thirdly, the peroneal, which is 
found imbedded in the flexor longus pollicis 
muscle, and may be readily tied without fear 
of injuring any nerve. These three arteries 
sometimes retract so far into the flesh after 
amputation, that to secure the anterior tibial 
it is necessary to cut through the interosseous 
ligament to the extent of some lines. This 
probably arises principally from the attachment 
of the muscles to the whole parietes of the 
interosseous fossa, while the vessels, enveloped 
by elastic cellular tisswes retract considerably. 

It must be borne in mind, that in whatever 
situation the amputation may be performed, if 
it be the flap operation the arteries of the flap 
are much more difficult to be found and se- 
cured, owing to the oblique nature of the sec- 
tion, than where, as in the circular operation, 
the muscles and vessels are cut transversely 
through. 

When the amputation is just below the tu- 
berosity of the tibia, the nutritious artery has 
here sometimes a volume sufficient to require 
a ligature. With the exception of this last, 
the arteries to be tied will be nearly the same, 
in whatever part of the length of the leg the 
amputation is performed. The muscular 
branches seldom occasion much inconvenience 
from hemorrhage. 

It may not be out of place here to remark 
on the subject of amputations of the leg, that 
the division of the bones high up may often 
save the knee, and thus give a good bearing 
for a wooden leg, but that we are too often apt 
to act upon the principle that, in amputations 
below the knee, this joint must necessarily be 
the bearing point; whereas we are convinced 
that a much more useful stump is gained by 
saving as much as possible of the leg, at least 
as far as half of its length, with the view of 
applying the wooden leg to the stump itself, 
and so preserving entirely the use of the knee- 
joint. We have now adopted this plan, with 
the most perfect success, in several instances, 
and always to the great comfort and satisfaction 
of the patient. Indeed, the loss of the limb, 
which is thus remedied, is really little felt, 
when compared with the great inconvenience 
of making the knee the bearing point, and thus 
taking away all the benefit of it as a joint. 
The reason why this mode of operating has 
not been more generally adopted, appears to 
us to consist in the fear that the cicatrix of the 
stump is ill able to bear the weight of the body 
in walking, when pressed between the ends of 
the two bones and the artificial leg. But be- 
sides that by the flap amputation in the middle 
of the leg, (the best possible situation for this 
operation, when practicable,) a soft cushion of 
muscle can be added to the integumental 
covering to obviate the effects of pressure, the 
fact is that in the application of the artificial 
leg to this stump, the bearing is not entirely 


136 


upon the stump itself, but it is divided between 
this and some part of the anterior surface of 
the leg, generally falling most powerfully 
about the tubercle of the tibia, The bearing 
on the anterior part of the leg is so strong, 
that unless the precaution is taken of well 
padding that — of the wooden box, the 
pain occasioned by the pressure entirely pre- 
vents the use of the wooden leg; but by the 
use of this precaution all inconvenience is ob- 
viated, and by this support to the weight of 
the body a valuable help is found for the pre- 
vention of injury to the cicatrix of the stump. 

The French surgeons used to recommend 
this mode of applying the artificial leg, but 
only in cases of conical stump, or at least 
where the integuments were from excess of 
inflammation after the amputation closely ad- 
herent to the bones.* But we have found it 
applicable to every case of amputation below 
the knee. The superiority which this wooden 
leg gives to amputations below the knee over 
all those at the ankle and through the joints 
of the foot is obvious. Besides saving the 
extra pain and risk of inflammation, it affords 
a much better point of support than the muti- 
lated foot can form. 

The anterior surface of the tibia being sub- 
cutaneous, and not covered by any artery of 
importance, indicates the region which should 
be chosen for exposing, when we would re- 
move a portion, trephine, extract sequestra, 
balls, &c. Superiorly, as its external region is 
only covered by the origin of the tibialis anticus 
muscle, it is favourable to the same operation. 
This consideration is the more important since 
the publication of the very valuable observa- 
tions of Sir B. Brodie on abscess in the can- 
cellated structure of the tibia, a disease which 
till then was little understood and scarcely at 
all described, and which, from our own expe- 
rience, we are inclined to think has not unfre- 
guently cost the patient a limb, which by a 
more correct knowledge of the disease might 
have been saved.t 

The periosteum of this anterior surface is the 
subject of troublesome inflammation more fre- 
quently than that of the other parts of the bone, 
in consequence of its greater exposure. Com- 
mon inflammation of it is often productive of 
abscess, necrosis, &e., or in a scrofulous dia- 
thesis, of caries ; while syphilitic inflammation 
is here showing itself in the form of nodes, 
occasioning great trouble to the surgeon and 
suffering to the patient, and generally leaving 
some permanent thickening. These nodes, 
which, as we have said, generally occur on the 
anterior surface of the bone, are sometimes 
thrown out upon the external and posterior 
parts, and when they do thus occur are 
doubly embarrassing to the surgeon from their 
deep situation among the muscles, and fiom 
the general similarity of the symptoms to mus- 
cular rheumatism; the extreme tenderness of 


* Sec Dictionnaire des Sciences Médicales, Art. 
Jambe. 

+ See also some excellent practical observations 
on the subject in Liston’s Elements of Practical 
Surgery, p. 95. 


REGIONS OF THE LEG. 


the periosteal inflammation, much me 
than that of rheumatism, and the more cireut 
scribed nature of this tenderness, are sigt 
which will facilitate the diagnosis, a subjec 
however, upon which it is not here the p 
to dilate. a 
In the foetus, the tibia presents me 
slight curve anteriorly, which appears 
augmented in the adult by the weight of 
body. The posterior muscles, stronger 
more numerous, acting on the flexible 
concur to the same end. Thus, in f 
rticularly from indirect causes, the al 
ormed by the fragments of the tibia is alm 
always in front, and the limb bends in 
situation of the fracture. a 
Experience proves that the two bones 0 
leg are more frequently broken togeti 
singly, a fact ascribed by Boyer to th n 
of the knee and ankle-joints. The directio 
an oblique fracture of the tibia is g 
from below upwards and from withi 
wards, a circumstance due to the form of 
bone. The end of the upper fragment 
presents itself under the skin, at the front : 
main part of the leg. The most frequent 
tion of fracture of either of the bones of | 
leg is at the lower third; this, in the tibia 
readily accounted for by its being here m 
exposed to injury and being smaller and we 
than elsewhere ; in the fibula, on the cont 
this part is not weaker, but is here placed n 
superticial, the upper part being complet 
covered and much defended by a cushior 
muscle. Fractures of the tibia at its a 
part are less liable to displacement thar 
down on account of the greater thi 
the bone, but the vicinity to the knee- 
here increases the danger of a fracture e¢ 
derably. In consequence of the thickne 
the bone at this point, fractures here are 01 
narily transverse, while the abundance 
spongy tissue causes them to unite quickh 
easily. The tibia is more frequentl 
by itself than the fibula because it 2 
tains the whole weight of the body, 
fibula has nothing to support. In fae 
fibula is generally broken at the same tf 
with the tibia, the injury to the fibula is 
subsequent to the other, and takes place 
cause this slender bone is not capable ¢ 
ing the weight of the body, the impulse 
ternal violence, or even the action of the 
cles, after the tibia has given way.* " 
There is rarely much displacement, ¢ 
gards the length of the bones, at what 
point their fractures may have oc 1, ut 
the cause has continued to act after thes 
tion of continuity. This appears to 1 
from the muscles being inserted over the w 
of the bony surfaces. -¥ 
When the fibula alone has been bro 
there is very little deformity resulting, ai 
principal support of the limb still rem 
particularly if the injury has resulted 
external violence. When however the ¢a 


v 


J 


CK! 
‘ 


* See Cooper's Surgical Dictionary, article Ft 
ture, a 


MUSCLES OF THE LEG. 


of the fracture is found in a violent twist of 
the ankle with dislocation, the deformity occa- 
_ sioned by this state of the joint is more or less 
considerable, according to the degree of this 


_ displacement. 
Ve (A. T. S. Dodd.) 
__ MUSCLES OF THE LEG.—The muscles 
lying on the bones of the leg, both before and 
behind, are, with the exception of one, pro- 
perly muscles of the ankle-joint and foot, since 
ir primary action is exclusively upon these 
. (See article Foor, Muscres or.) For 
convenience, however, of description they 
_ will here be demonstrated according to their si- 
 tuation. 
_ The muscles of the leg may be classed into 
mterior, external, and posterior. The anterior 
_ lying in the space between the tibia and fi- 
 bula are four in number, consisting of tibialis 
_ anticus, extensor proprius pollicis, | extensor 
longus digitorum, and peroneus tertius. The 
tibialis anticus and extensor longus alone are 
seen at the upper part of the leg on removing 
the deep fascia; the extensor proprius pol- 
licis emerging from between these muscles 
about one-third down the leg, and the peroneus 
ertius shewing itself as a separate slip of the 
axtensor longus, about the same height, and at 
‘its fibular side. 
1. Tibialis anticus lies upon the fibular and 
‘anterior surface of the tibia; arises, principally 
muscular, from the fibular side of the tibia, 
hrough its two upper thirds, from its tuber- 
osity and spine, and from a small portion of 
the interosseous ligament, from the fascia of 
he leg, and from an aponeurotic septum placed 
between it and the extensor digitorum longus. 
e muscle is larger above than below; its 
fleshy fibres converge to a strong tendon which 
osses from the outside to the fore part of the 
tibia, passes through a distinct ring of the 
annular ligament near the ankle, runs over the 
astragalus and os naviculare, and is inserted 
into the upper part of the os cuneiforme in- 
lernum, and base of the metatarsal bone of the 
great toe. The insertion of the tendon is con- 
“cealed in part by the adductor and flexor brevis 
of the great toe. Between the tendon of this 
‘muscle and the os cuneiforme we find a small 
bursa mucosa. This muscle is covered in front 
hy the fascia of the leg, to which it adheres 
superiorly ; behind it is in contact with the 
“tibia and interosseous ligament, on the fibular 
side with the extensor digitorum communis, 
and extensor proprius pollicis. Its action is to 
flex the foot upon the leg by elevating the an- 
terior part of the foot. 
_ 2. Extensor longus digitorum—This mus- 
cle occupies the fibular side of the tibio-fi- 
bular fossa, as the last filled the inner side. 
This is a tapering muscle also; it arises ten- 
dinous and muscular from the fibular or 
outer part of the head of the tibia, from the 
head of the fibula, and from the anterior angle 
of that bone almost its whole length, and from 
part of the tibial side of it also; it also takes 
origin from the interosseous ligament, from the 
fascia of the leg, and from the aponeurotic 


ne eee 
’ Pere ee 


aie acti 


| 


137 


septum situated between this muscle and the 
last. Below the middle of the leg it splits 
into four tendons. These pass under the ante- 
rior annular ligament in one common sheath 
with the peroneus tertius. They then run along 
the dorsum of the foot, spreading as they go, 
and are inserted into the root of the first pha- 
lanx of each of the four smaller toes. To- 
wards their termination each of the tendons ex- 
pands into an aponeurosis, covering the upper 
surface of the phalanges, and this is strengthened 
by the tendons of the extensor brevis and gives 
attachment to the lumbricales and interossei. 

This muscle is covered in front by the fascia 
of the leg, the annular ligament and the in- 
tegument; posteriorly it rests upon the fibula, 
the interosseous ligament, and the tibia; exter- 
nally it is in relation with the peronei muscles, 
internally with the tibiatts anticus, and extensor 
proprius pollicis; along its lower and fibular 
border lies the peroneus tertius. On the dor- 
sum of the foot its four tendons cross obliquely 
over those of the flexor brevis digitorum. 

Action. To extend all the joints of the four 
smaller toes, and to bend the ankle-joint. 

3. Extensor proprius pollicis lies between 
the two last muscles. Its origin is hidden by 
them. It commences about one-third down 
the leg, from the smooth surface of the fibula, 
between the anterior and tibial angles of that 
bone, of which surface it occupies part, through 
the middle third of its length, also from the 
lower two-thirds of the interosseous ligament. 
The fleshy fibres run obliquely forward into a 
tendon placed at the anterior border of the 
muscle, which after passing beneath the an- 
terior annular ligament, and along the dorsum 
of the foot, is inserted into the bases of the 
first and second phalanges of the great toe. 

Action. To extend the great toe, and to 
bend the ankle. 

By its fibular side this muscle is in relation 
with the extensor digitorum communis ; by its 
inner side with the tibialis anticus and anterior 
tibial vessels. The anterior border is covered 
by these two muscles, as low as about the 
middle of the leg, and inferiorly by the anterior 
annular ligament, under which it passes in a 
separate groove, and by the integuments. The 
posterior border rests upon the fibula and in- 
terosseous ligament, and it crosses in its course 
over the lower end of the tibia the ankle-joint, 
the anterior tibial vessels, and dorsum of the 
foot. 

4. Peroneus tertius——This, which is in fact 
a mere slip of the extensor digitorum com- 
munis, and is situated on its fibular side, is so 
closely connected with it at its origin that it 
can with difficulty be separated. It arises 
from the lower third of the fibula, being at- 
tached to the anterior border and inner surface 
of the bone; also from the interosseous liga- 
ment, and from an aponeurosis which connects 
it on the outer side with the peroneus brevis. 
It is inserted by a flat tendon into the fibular 
side of the base of the metatarsal bone of the 
little toe. Its action is to assist in flexing the 
foot upon the leg. 

It. is in contact with the fascia of the leg 


138 


anteriorly, with the fibula and _ interosseous 
ligament posteriorly, with the peroneus brevis 
on the fibular side, and with the extensor com- 
munis on the tibial side. Its tendon passes in 
the same sheath with that of the common ex- 
tensor, under the annular ligament. 

A very slight effort of the extensor com- 
munis and extensor proprius pollicis extends 
the digital pales and, if their action be 
continued, they will be made to bend the foot 
upon the leg. This they are enabled to do by 
the manner in which their line of direction is 
altered by the annular ligament of the ankle- 
joint, as it gives them all the mechanical ad- 
vantage of a pulley. The tibialis anticus and 
the peroneus tertius are the direct flexors of the 
foot on the leg, and if either act separately, it 
will give a’slight inclination towards the cor- 
responding side, and thus the last-named 
muscle forms one of that important set whose 
action is, by elevating the outer side of the 
foot, to throw the weight of the body on the 
inner side.* In the erect position these muscles 
take their fixed point below, and, by drawing 
on the bones of the leg, keep them perpen- 
dicular on the foot. 

The external muscles of the leg are two, the 
peroneus longus and brevis. They ye the 
whole length of the outer side of the fibula, and 
are placed between the extensors and flexors. 

1. Peroneus longus is a long powerful muscle, 
arising from a small portion of the fibular side 
of the head of the tibia, from the upper third 
of the outer side of the fibula, and from the 
fascia of the leg and its intermuscular pro- 
cesses. Proceeding obliquely downwards, the 
fibres are attached to a strong tendon, which 
passes, in contact with the peroneus brevis, 
along a groove at the back of the outer mal- 
leolus, enclosed in a synovial sheath. The 
tendon then passes through a rst | suleus in 
the cuboid bone, behind the base of the meta- 
tarsal bone of the little toe, winding obliquely 
across the sole of the foot, covered by the 
muscles of this part, till it is inserted into the 
internal cuneiform bone and base of the meta- 
tarsal bone of the great toe. In the tendon 
opposite the cuboid bone, is usually found a 
sesamoid bone. A bursal sheath encloses it in 
its passage across the foot. The action of this 
important muscle is to assist in extending the 
foot upon the leg, but principally to elevate 
the outer side of the foot, and thus regulate 
the bearing of the leg so as to throw the prin- 
cipal part of the weight upon the great toe.t 

This muscle is in contact on its outer side 
with the fascia of the leg. Indeed this apo- 
neurosis almost invests it, dipping between it 
and the flexor behind and extensors before. 
The peroneus is in contact with the fibula on 
its inner side above, lower down it rests upon 
the peroneus brevis. When passing across the 
foot it lies close to the bones, and conse- 
quently is covered by all the muscles of the 
sole. ; 

2. Peroneus brevis is situated at the outer 


* For further observations upon the action of the 
peronei muscles, see article FOOT, MUSCLES OF, 
+ See also Quain’s Manual of Anatomy. 


MUSCLES OF THE LEG. 


side of the leg, but lower down as to 
tachments than the preceding muscle. It a 
fleshy from the lower half of the outer side 
the fibula to near the outer malleolus, © 
sends offa roundish strong tendon, which pa: 
in the same groove behind the outer m 
lus, and in the same synovial sheath as the 
ceding muscle, but after passing the mal 
it has a sheath proper to itself. It is ins 
into the base of the metatarsal bone o 
little toe. Connected on its outer si 
peroneus longus, on the inner side to 
anteriorly to the common extensor and 
neus tertius, and posteriorly to the fi 
pollicis. : 
The action of these two muscles is f 
By the change in their direction, after tu 
behind the outer ankle, they are enabl 
ara the foot back, and so extend it o1 
eg. . 
The penoneus tertius is on the ec 
flexor ; it lies before the fibula, and ¢ 
in this action with the tibialis anticus to¢ 
the flexor. When, however, the three pe 
act together, and without the other flexors, 
combined action is to evert the sole of the 
and thus counterbalance the effect of the: 
ness of the outer side of the foot by t 
ferring the superincumbent weight to the | 
side. This action is particularly exemp 
in skaiting, but it is essential to every m 
ment of ordinary progression. (See a 
Foor, Muscies or.) When the foot is 
fixed point, the peronei act by keepin 
fibula and the whole leg steady, and — 
in the act of standing on one foot, cou 
acting the tendency of the body to fal 
wards. wall 
The posterior region of the leg com 
seven muscles, six of which are acting on 
foot and toes, and one is proper tot 
joint. We shall examine them as they ai 
with in dissection, and shall therefore dese 
them as forming two layers, superficial 
deep. The tirst contains three muscles: 1, 
trocnemius ; 2. soleus; 3. plantaris, __ 
1. Gastrocnemius.—This is situated it 
diately under the aponeurosis, and is a pt 
ful muscle, broad and flat anteriorly, and 
vex posteriorly, and forming the gre: 
of what is called the calf. It arises 
distinct heads from the back and upp 
of the two condyles of the femur, of 
the inner is the longer, and somewhat la 
These heads have between them a bi 
sulcus, which forms the lower of 
liteal space. They unite a little b 
knee-joint, in a middle tendinous line 
below the middle of the tibia send off g 
tendon which unites with the tendon 
soleus, a little above the ankle. ‘ 
The posterior surface is covered by the 
of the leg ; anteriorly it rests upon the 
teus, soleus, and plantaris, and poy 
vessels. When its heads pass over the ¢ 
dyles of the femur, they are guarded by sy 
burse. te 
2. Soleus.— This is the second porti 
that great muscle of the leg which has 


. 


“named by Meckel the friceps sure. It is 
seen immediately on raising the last muscle. 
It arises from two distinct situations ; first, from 
the upper and back part of the head of the 
fibula, and from the posterior surface and outer 
\dge of that bone for some way down. Se- 
cond, from the oblique ridge on the posterior 
' surface of the tibia, just below the popliteus, 
“and from the inner edge of that bone during 
‘the middle third of its length. From these 
two attachments the muscle almost imme- 
diately forms a thick fleshy belly, which de- 
sends lower than the gastrocnemius before it 
ends off its tendon. This, which is flat and 
ong, soon unites to the tendon of the gastro- 
“enemius to form the tendo Achillis,and is then 
passing to be inserted into the upper and 
back part of the projecting portion of the 
os calcis. At its insertion there is a small 
bursa between the upper part of the bone and 
the tendon. 
_ The soleus is in contact with the gastro- 
cnemius posteriorly ; below its fleshy fibres ap- 
— on each side of the tendon of that muscle. 
tween its two origins the posterior tibial 
vessels and nerve are passing, defended from 
pressure by the tendinous expansion which is 
on the under side of the muscle, and which 
spreads across from tibiato fibula. This muscle 
| is also in contact with the plantaris, the tendon 
of which crosses it obliquely from without 
| to within. In front it rests upon the deep 
layer of muscles and upon the posterior tibial 
vessels. 
_ The tendo Achillis is the thickest and 
strongest tendon in the body; it tapers down- 
wards nearly to the heel, and _ before its 
‘attachment expands again a little. It lies 
| immediately under the skin, and between it 
and the bones is a considerable layer of cel- 
lular tissue containing fat. 
The action of the two last described muscles 
_ is to elevate the os calcis, and thereby to lift 
p the whole body. When this is done on 
_ one foot in the act of progression, the other is 
‘capable of being carried forward unimpeded 
| by the irregularities of the surface. When the 
foot is the fixed point, the soleus by acting on 
the tibia and fibula fixes the leg, while the 
| gastrocnemius: fixes the femur, or by acting 
| further, draws it backward so as to bend the 
_ knee and lower the body. 
| 3. Plantaris—This little muscle is entirely 
covered by the outer head of the gastro- 
| cnemius. It arises from the upper part of the 
external condyle of the femur, and from the 
" posterior ligament of the knee-joint. Its mus- 
a ular structure is only about two inches in 
‘length, and it sends its long slender tendon 
_ downwards and inwards, between the two great 
0 uscles of the calf, emerging from between 
them just where their two tendons unite; it 
then passes down in contact with the edge of 
‘the tendo Achillis, to be inserted into the heel 
at the inner side of that tendon. 
_ The action of the plantaris is to assist the 
great extensors of the foot, and to draw upon 
the capsule of the knee-joint, so as to prevent 
any ill effects upon that ligament from the 


; 


| 


4 
i 
{ 


SL 


MUSCLES OF THE LEG. 


139 


motions of the knee-joint. It is occasionally 
deficient. 

The deep layer of muscles consists of four : 
1. popliteus; 2. flexor longus digitorum; 3. 
flexor longus pollicis; 4. tibialis posticus. 
They lie in close contact with the bones, and 
the last three of them are covered by the deep 
fascia of the leg. 

This membrane is a thin expansion, dense 
in structure, connected on each side with the 
borders of the bones, and towards the ankles 
with the sheaths of the tendons ; and if traced 
along the interval between the inner ankle and 
the heel, it will be found to cover the vessels 
and to terminate at the internal annular liga- 
ment. Immediately underneath it we find 
the deep layer of muscles now under consi- 
deration. ~ 

1. Popliteus is situated below and behind 
the knee-joint, is flat and somewhat triangular, 
being broader below than above.  Arises 
within the capsular ligament of the knee-joint, 
by a round tendon, from the under and back 
part of the outer condyle of the femur; ad- 
heres to the posterior and outer surface of the 
external semilunar cartilage; perforates the 
back part of the capsular ligament, and forms 
a fleshy belly which runs obliquely downwards 
and inwards. It is covered by a thin tendi- 
nous fascia from the tendon of the semi-membra- 
nosus ; inserted broad, thin, and fleshy into an 
oblique ridge on the posterior surface of the 
tibia, a little below its head, and into the trian- 
gular space above that ridge. Action, to bend 
the knee-joint, and when bent, to roll it so as 
to turn the toes inwards. 

2. Flexor longus digitorum is thin and 
pointed at its commencement, but gradually 
increases, and then diminishes again as its 
fibres end in a tendon. Arises fleshy from 
the posterior flattened surface of the tibia, be- 
tween its internal and external angles, be- 
low the attachment of the soleus, and con- 
tinues to arise from the bone to within two or 
three inches of the ankle. The fibres run 
obliquely into a tendon, which is situated on 
the posterior edge of the muscle. This tendon 
runs in a groove of the tibia, behind the inner 
ankle, and then passing obliquely forwards 
into the sole of the foot, receives in its passage 
a strong slip from the tendon of the flexor longus 
pollicis. It then divides into four tendons, 
which pass through the slits in the tendons of the 
flexor brevis digitorum, and as they run along 
the under surface of the toes they are bound 
down by strong fibrous sheaths, within which 
there are also little accessory ligaments assist- 
ing in fixingthem. They are inserted into the 
bases of the extreme phalanges of the four 
lesser toes. The action of this muscle is to 
flex all the four smaller toes, and to assist in 
elevating the foot upon the toes. 

Previously to its division, the tendon of the 
flexor longus gives insertion to an accessory 
muscle of considerable power (flexor acces- 
sorius ), which connects it to the calcaneum, 
and materially modifies the direction of its 
action upon the toes. Close to the point of 
division, the tendons give origin to four small 


140 


muscles (lumbricales), which may also be con- 
sidered as accessories to the flexor longus. 

When passing behind the inner malleolus, 
this tendon isin contact with that of the tibialis 
posticus, which lies close to the bone. They are 
inclosed in separate sheaths of synovial mem- 
brane. In the leg this muscle is bound down 
by the deep fascia, and covered partly by the 
posterior tibial vessels which separate it from 
the soleus; its anterior surface rests against 
the tibia, and overlaps the tibialis posticus 
muscle; in the foot, its tendon lies between 
those of the flexor longus pollicis which,are 
above it, and the flexor brevis digitorum which 
lies beneath it. 

3. Flexor longus pollicis is shorter but 
stronger than the former muscle. It is si- 
tuated the outermost of the three deep muscles 
of the leg, in contact with the fibula. It arises 
tendinous and fleshy from the lower half of 
the posterior surface and outer edge of the 
fibula, with the exception of the undermost 
portion. The fleshy fibres terminate in a 
tendon which passes behind the inner ankle, 
through a groove in the tibia; next through a 
groove in the astragalus ; crosses in the sole of 
the foot the tendon of the flexor longus digi- 
torum, to which it gives a slip of tendon; 

ses between the two heads of the flexor 

revis pollicis, and then runs in a sheath of 
tendinous structure which binds it to the under 
surface of the phalanx, and is inserted into the 
base of the last phalanx of ‘the great toe. The 
relations of this muscle in the leg are, pos- 
teriorly it is covered by the deep fascia, 
which separates it from the soleus; anteriorly it 
is in contact with the fibula, and overlaps the 
tibialis posticus muscle and the peroneal ar- 
tery. Its connections in the foot have been 
explained above. The action of the flexor 
longus pollicis is not confined to the great toe ; 
by means of the slip of tendon, which it gives 
to the flexor longus digitorum, it acts also 
upon all the toes, and secondarily upon the 
foot itself, assisting powerfully in the elevation 
of the heel in progression. But the mode of 
action of this muscle, and its complicated rela- 
tions with the other muscles of the foot, are 
too curious to be passed over with a slight ex- 
amination; in fact, we think it may clearly be 
shewn that there is here one of the most curious 
and beautiful arrangements and successions 
of muscular action to be met with in the whole 
system. We have elsewhere shewn that, from 
the peculiar form of the foot, the action of the 

roneus longus is essential to transmit the 

urden of progression from the weaker to the 
stronger side of the foot. (See article Feor, 
MUSCLES OF.) Let us now follow on the pro- 
gress of the foot in the act of walking, and we 
shall readily perceive the succession of action 
of its different parts, and the functions which 
each muscle performs. It is evident that the 
smaller toes being shorter than the large one, 
and nearer to the heel, they will, in the act of 
elevating the heel and propelling forward the 
body, come to their bearing on the ground 
somewhat before the great toe, their action 
being, in fact, by the breadth of base which 


MUSCLES OF THE LEG. 


they give to steady the onward progress of the 
y, and to deliver over accurately and ; 
curely the weight to the great toe, the ma 
organ of ulsion of the body. In 
accomplish this to the best effect, it is nee 
sary that the succession of actions shot 
accurate and complete, and that the musel 
the smaller toes should exert themselves 
fore that of the great toe. To this em 
flexor longus pollicis gives a slip to the fk 
of the toes, and by the commencement o} 
action, which merely firmly plants the 
toe against the ground, rouses the musel 
the other toes, assisting them to com 
their part of the process, while its own lal 
continues and is at its height when t 
necessarily accomplished and at an end. 1] 
by a beautiful combination and series of ac 
the powerful effort of the great extensors 
foot is controlled and guided to its proper 
first by the peronei, next by the flexors of 
smaller toes, assisted by the long flexor o 
great toe; and the body propelled onwa 
and balanced on this toe, the action is 
leted by the further effort of this one po’ 
ul muscle. The economy of muscular pé 
is here not less striking than the combina 
of action, for the flexor longus pollicis b 
inserted into the last phalanx of the grea 
its own proper action is not called for till af 
the muscles of the other toes have perfor 
their part; this muscle, therefore, consid 
the most powerful of all this deep layer, ¥ 
it not for the simple a of the slip 
communication to the other flexors, woul 
comparatively useless until the last moment 
the propulsion onwards of the body. But 
it lends its powerful assistance to the weal 
muscles previous to its own peculiar effort, 
when all its power is called for, the collate 
demand has ceased. 
4. Tibialis posticus is situated on the b 
of the leg between the last-named musel 
It arises fleshy from the posterior surface b 
of the tibia and fibula, immediately bele 
upper articulations of these bones with 
other. Between the two portions of this 
tachment is an angular opening through wi 
the anterior tibial vessels are transmitted. — 
muscle also arises from the whole inter¢ 
ligament; from the angles of the bor 
which that ligament is attached, and ' 
thirds of the flat posterior surface of the 
bula. The fibres run obliquely toward 
round tendon, which passes behind the i 
ankle, through a groove in the tibia. It is 
situated close to the bone enclosed in 
rate synovial sheath. It is inserted into” 
tubercle on the plantar surface of the os na 
culare, sending tendinous filaments to 1 
the other bones of the tarsus, and to the m 
tarsal bones of the second and middle t 
This muscle is covered at the lower part 
origin by the flexor longus digitorum and 
longus pollicis, and cannot be seen till th 
muscles are separated. But superiorly — 
covered by the soleus only, and here the post 
rior tibial, vessels rest upon it. Its 1 
surface is in contact with the interosseous liga 


ne, 


eal 


o> 


are 
. 


Se | 


¥ 


7 


LIFE. 


ment, the tibia and fibula. Its tendon runs 
close to the inner ankle and tarsal bones, and 
_ where it slides under the astragalus, is thick- 
ened by a cartilaginous or bony deposit within 
its fibres, analogous in force and use to the 
sesamoid bones in other situations. Its action 


__ is to extend the foot upon the leg, and to turn 


: the sole of the foot inwards. 
-_; 


(A. T. 8. Dodd.) 


LIFE.—Few abstract terms have been em- 
ployed in a greater variety of significations, or 


_ more frequently without any definite meaning 


at all, than the one now to be considered. 


_ And there is none regarding which it is more 
_ €ssential to possess correct ideas, in order to 
attain the fundamental truths of physiological 
science. 

_ very erroneous notions on this subject, will 


The prevalence of what we deem 


oblige us to follow a different plan in its treat- 
Ment, from that which we should have adopted 


_ if our duty had been merely to give an expo- 


sition of the present state of our knowledge 
Tespecting it. We shall commence by offering 


| a short statement of our own views, in order 
_ that we may, in the brief historical summary 
_ which it will be proper to include in this ar- 


ticle, more concisely indicate what we regard 
as the errors and inconsistencies of the prin- 
cipal theories which have obtained credit at 
various times. We shall subsequently con- 


_ sider more in detail some of the questions 
_ which require fuller discussion. 


I. Genera views.—We shall define Lire 
to be the state of action peculiar to an or- 
_ganised body or organism. This state com- 
-Mences with the first production of the germ; 


_ itis manifested in the phenomena of growth 


and reproduction; and it terminates in the 


_ death of the organised structure, when its 


component parts are disintegrated, more or less 
. completely, by the operation of the com- 


mon laws of matter. This definition differs 


_ but little from that given in many physiological 


_ works—* Life is the sum of the actions of an 


' organised being;” and we apprehend that we 
are more in accordance with the common usage 


_ of the term, in employing it to designate rather 


_ the state or condition of the being exhibiting 
_ those actions, than the actions themselves. 
_ this sense alone it is properly contrary to Death, 


In 


the condition of an organised body in which 
not only have its peculiar actions ceased, but 
its distinguishing properties been abolished 
(see Deatu); and it is then also contradistin- 
guished from dormant vitality, a state fre- 
quently observed, in which living actions are 
suspended, but the vital properties of the or- 
-ganism retained, so as to be capable of again 
exhibiting them when the requisite conditions 
are supplied. 

Life or vital activity, then, manifests itself to 
us in a great variety of ways,—in all those phe- 
nomena, in short, which it is the province of 

_the physiologist to consider. The changes ex- 
hibited by any one living being, in its normal 
condition at least, have one manifest tendency, 


, 


141 


the preservation of its existence as a perfect 
structure; by these it is enabled to counteract 
the ever-operating influence of chemical and 
physical laws, and to resist, to a greater or less 
extent, the injurious effects of external agen- 
cies. The first inquiry, then, which we have 
to make, in the inductive study of physiology, 
is into the conditions of these phenomena; and 
as in this process we follow precisely the same 
track as that over which the physical philo- 
sopher has already passed, we may advantage- 
ously avail ourselves of his guidance in it. 

In seeking to establish the laws by which 
the universe is governed, or, in other words, 
to obtain general expressions of the conditions 
under which its changes take place, the en- 
quirer first collects, by observation or expe- 
riment,* a sufficient number of instances having 
an obvious relation“to one another, with the 
view of determining the circumstances com- 
mon to all. The facility with which this pro- 
cess is performed will obviously depend upon 
the simplicity of the phenomena, and the rea- 
diness with which they admit of comparison. 
Where their antecedents are uniformly the 
same, they only need to be associated a suf- 
ficient number of times, for the mind to be 
satisfied of the constancy of the relation; and 
the general law of the effects is easily deduced. 
Thus, the law of gravitation is ascertained by 
the comparison of a number of corresponding 
but not identical phenomena; and the nume- 
rical ratio is established which governs the 
attracting force. To extend the application of 
this law, however, to phenomena that seemed 
beyond its pale, required the almost super- 
human genius of a Newton; but the idea, once 
conceived, was easily carried out when the re- 
quisite data were attained. But what is the 
nature of the aw of which we have just spo- 
ken as regulating the attractive force? It is 
simply an expression of the property with 
which the Creator has endowed all forms of 
matter, that its masses shall attract or tend to 
approach each other in a degree which varies 
in a certain ratio to their mass and distance. 
This property, it must be recollected, is only 
assumed to exist, as the common cause of the 
actions constantly occurring under our notice. 
If none of these actions were witnessed by 
man,—if, for example, but one mass of matter 
existed in the universe,—it might be endowed 
with this and every other property which we 
are accustomed to regard as essential to matter; 
and yet, from gravitation never being called 
into action, the mind would remain ignorant 
of the attribute. 

Such a common cause, the conditions of 
whose action are so simple and uniform that 
we can account for, and even predict, by a 
process of deduction, all the phenomena which 
It can operate to produce, may be regarded for 
a time as an ultimate fact. It may still, how- 
ever, be capable of union with other facts of a 


* For the proper distinction between these modes 
of research, and their respective applications to 
physiology, see Brit. and For. Med. Review, 
April 1838, pp. 320 et seq. 


142 


similar order, under a still more comprehen- 
Sive expression.* But it is not in every de- 
partment of science that the same facility in 
the attainment of general laws exists. Where 
the phenomena are of such a complex nature 
that the operation of the real cause is, as it 
were, masked by the influence of concurrent 
conditions, or where (as ofien happens in phy- 
Siology) the effects of the same apparent cause 
are totally different according to the instru- 
ments through which it operates, it is obvious 
that there will be great difficulty in the first 
stage of the inductive process—that of the clas- 
sification of phenomena,—so great, indeed, 
that it may be regarded as one of the principal 
obstacles to the advancement of those branches 
of science in which it presents itself. Of all 
the branches of physical science, that of me- 
teorology is the most obscure and apparently 
uncertain, and bears most resemblance to phy- 
siology. The changes which it concerns 
are daily and hourly occurring under our 
observation; and the general laws which 
govern them are tolerably well ascertained ; 
yet the mode in which their actions are com- 
bined is so peculiar, as hitherto to have baffled 
the most persevering and penetrating enquirers, 
in their attempts to explain or predict their 
operation. But no one thence feels justified 
in assuming the existence of any new or un- 
known cause, capable of controlling or sub- 
verting the influence of the rest; and sucha 
proceeding would not be justifiable, until all 
their possible modes of action have been ascer- 
tained: and put aside, leaving certain residual 
phenomena not otherwise to be accounted for. 
The peculiar difficulties which beset the in- 
vestigation of the laws of vital action have 
greatly retarded our acquaintance with them, 
and have even led to the belief that the induc- 
tive process is not applicable to them. These 
difficulties have arisen, in the first place, from 
the obstacles in the way of the collection of 
phenomena; secondly, from the peculiarly com- 
plex nature of these phenomena ; and, thirdly, 
from the vague hypotheses which have pre- 
vented them from being classed as simple facts 
on which generalisations are to be erected, or 
effects whose sources are to be ascertained, but 
which have clothed them in the delusive aspect 
of laws or causes. Until, therefore, the prin- 
ciples of philosophical induction are thoroughly 
understood, the peculiar combinations in which 
vital phenomena present themselves to our 
notice, their apparent dissimilarity from the 
changes which we witness in the world around, 
and their obvious adaptation to particular ends, 
might lead us astray into the labyrinth of un- 
profitable speculation with regard to the pre- 
siding agencies by which they are governed ; 
and the retrospective view which we shall pre- 
sently take will afford many examples of this 
error, even in recent times, and will in fact 
show that the legitimate objects of investiga- 


* Such would seem to be the tendency of certain 
recent speculations in regard to gravitation, mole- 
cular and electrical attraction, and chemical affinity. 


LIFE. 


tion, and the true mode of ing the 
are only now beginning to be understood. — 
When we observe the circumstances und 
which vital actions occur, we perceive that 
least two conditions are required for their p 
duction. The first is a structure in that pe 
liar state which is termed organised (see € 
GaNIsaTIon); the second is a stimulus 
some kind fitted to act upon it. Now thi 
no more than what we observe in the wo 
around, where every action involves two 
ditions of a corresponding character. W 
water is changed into steam, for example, i 
by the stimulus of heat. When a stone ff 
to the ground, it is by the attraction which 
mass of the earth exercises over its own. 7 
difference consists in the peculiarity of t 
actions exhibited by living beings, which a 
not identical with those elsewhere presented 
us, and which we cannot imitate by any p 
sical or chemical operations. Whilst 
chanical philosopher, then, refers to the p 
perty of gravitation as the cause of the effe 
just mentioned, the physiologist refers to 
capability of exhibiting vital actions, whi 
excited by certain stimuli, as the property 
the tissue which manifests them, us, wh 
he witnesses the contraction of a muscle, un 
the stimulus of innervation or of galvanis 
&c. he regards the effect as due to a propet 
of contractility inherent in the muscle, ¢ 
standing in precisely the same relation to 
organic structure, as gravity to matter in | 
neral. So far, however, the advance in our it 
quiry is more apparent than real; since it F 
fairly be said that, to speak of contractility 
the character of a body exhibiting contractior 
is merely a change in words without absolu 
gain. But, having done this, we are led 
inquire the conditions under which this cor 
tractility operates; and to analyse a number 
phenomena apparently dissimilar, so as to: 
tain the general law of its action. In this ma 
ner we proceed in regard to other classes of 
phenomena; and we shall thus acquire er 
our data are sufficiently precise and extensiy 
a knowledge of the properties of all the tiss 
or organised structures which compose t 
living body, and of the phenomena whi 
their single or combined operation will pi 
duce, under the influence of their respec! 
stimuli. re 
But the physiologist will not stop here. 
will seek to inquire to what these proper 
are due, which are so different from anyth 
exhibited by the same matter before it had 
come a part of the organised system. A 
if he consider the matter in all its be 
with a total dismissal of prejudice, he will 
unable, we think, to arrive at any other cone 
sion than that they are due to the act of orga 
sation, which, in combining the inorganie é 
ments into new compounds, and giv 
a peculiar structure, calls out or devel 
them properties which had previously exi 
in a dormant state, but required these ci 
stances for their manifestation. To this qu 
tion, however, we shall presently return, wh 


» 


idering other views which have been en- 
ertained respecting it. We shall now take a 
retrospective glance at the 


II. History or oprntons.—In the earlier 
ages of the world, before the true method of 
hilosophising on any subject was under- 
ood, it was considered as a sufficient ex- 
planation of any phenomenon to apply to it 
some abstract term, expressing a vague idea 
of a property inherent in the body which ex- 
hibited it, without attempting to ascertain the 
conditions of its operation.* Thus, all the 
‘phenomena of the movements of the heavenly 
‘bodies were attributed to the agency of a 
** principle of motion,” the laws of which were 
‘Searcely even sought for. In like manner, the 
simple optical fact—that, when the sun’s 
light passes through a hole, the bright image, 
if formed at a considerable distance from 
‘it, is always round, instead of imitating the 
figure of the aperture,—was attributed by 
Aristotle to the “ circular nature” of the sun’s 
light; whilst the mere consideration that the 
rays of light trave! in straight lines, would, if 
properly applied, have explained this pheno- 
menon, not only as regards the sun, but in the 
case of any other round Juminous body placed 
at a sufficient distance. It is not wonderful, 
then, that the still more intricate nature of the 
| phenomena exhibited by living beings, the 
obvious tendency of those presented by each 
" individual towards the same end, and the se- 
ductive simplicity of the hypothesis, should 
have induced the philosophers of that age to 
regard all vital actions as the immediate results 
| of one common cause; but that such a belief 
should have maintained its ground, with but 
| little alteration, to the present day, can only 
e regarded as a proof of the lamentable de- 
ficiency in truly philosophical views among the 
| cultivators of physiology. 

To the supposed cause of vital phenomena 
the term Life was applied by the older philo- 


_* This mode of philosophising has been very 
happily ridiculed by Fontenelle. ‘* Let us ima- 
gine,” he says, “all the sages collected at an 
( > age Pythagorases, Platos, Aristotles, and 
all those great names which now-a-days make such 
@ noise in our ears—let us suppose that they see 
the flight of Phaeton as he is represented carried 
ff by the Winds ; that they cannot perceive the 
rds to which he is attached, and that they are 
quite ignorant of everything behind the scenes. 
It is a secret virtue, says one of them, that carries 
off Phacton,—Phacton, says another, is composed 

certain numbers which cause him to ascend. 
A third says, Phaeton has a certain affection for 
‘the top of the stage; he does not feel at his ease 
when he is not there.—Phaeton, says a fourth, is 
not formed to fly ; but he likes better to fly than to 


leave the stage empty; and a hundred other ab- 
i 


Surdities of this kind, that would have ruined the 
reputation of antiquity, if the reputation of anti- 
At last 
me Descartes and some other moderns, who say, 
haeton ascends because he is drawn by cords, and 
because a weight more heavy than he is descending 
as acounterpoise. Thus to see nature as it really 
is, is to see the back of the stage at the opera.”— 
Quoted in Brown’s Lectures on Mental Philosophy, 
ct. Ve 


‘quity for wisdom could have been ruined. 


a 


LIFE. 


143 


sophers, who regarded it as a distinct entity or 

substance, material or immaterial, residing in 

certain forms of matter; and the cause, both 

of their organisation, and of the peculiar actions 

exhibited by them.* Every sect had its own 

notion of the origin and nature of this entity ; 

some regarding it as a kind of fire; others as a 

kind of air, ether, or spirit; and others, again, 

merely as a kind of water. The fable of Pro- 
metheus embodies this doctrine in a mytho- 

logical form, the artist being described as vivi- 
fying his clay statues by fire stolen from the 
chariot of the sun. Whatever was the idea 
entertained as’ to the character of this agent, 
all regarded it as universally pervading the 
world, and as actuating all its operations in 
the capacity of a life or soul; whilst a special 
division of it—a diyine particula aure—regu- 
lated the concerns of @ach individual organism. 
The opinions of Aristotle on this subject are 
very interesting, as presenting evidence of the 
tendency of his powerful mind to elevate itself 
above the level of his age, and as showing 
how completely even he was bound down by 
the prevalent tendency to hypothetical specu- 
lation, which seemed to offer so easy a solu- 
tion to all the mysteries of Nature. “ In con- 
sidering what holds the fabric of the universe 
together, and forms out of the discordant ele- 
ments a harmonious whole, he infers from 
analogy that it must be something similar in 
kind to that which forms and holds together 
an organised body, namely, a principle of life ; 
and that this principle, from the appearance 
of order and design displayed in the universe, 
must also have intelligence.” ‘ Besides this 
supreme animating principle (®ugts), the au- 
thor and preserver of all, there are many others 
which, by delegated powers, organise the bo- 
dies of animals and plants, so that all organised 
bodies whatever are to be considered as con- 
structed by and constructed for their animating 
principles, which, like the great animating 
principle, from being invisible to mortal eyes, 
indicate their existence, their energies, and 
their species, only through the medium of the 
structures which they form. Now, of these 
structures they are not only the efficient causes 
but, in his opinion, the formal and the final ; 
the causes of their motions, growth, and nu- 
trition ; the causes which give them a character 
and form; the causes on whose account they 
exist ; and even the causes of their being after- 
wards liable to corruption, as nothing is cor- 
rupted but what has been nourished, and has 
some time or other partaken of life. But, 
besides being causes of organised structures in 
these different senses, they are subordinate to a 
higher power, which prescribes their operations, 
not merely with reference to their separate and 
individual plans, but with a reference at the 
same time to that general and comprehensive 


* The term ¥vux" was applied by the Grecian 
philosophers to designate this animating prin- 
ciple, which included, with what is now known as 
the vital principle, the sensory and intellectual 
faculties. To the series of vital actions which, by 
many modern physiologists, is spoken of as Life, 
the term Zw» was given by the Greeks. 


144 


lan on which the universe itself is constructed. 
Te is under the influence of such a power that 
every particular species of soul regularly con- 
structs a system of organs adapted to its func- 
tions ; at every species of soul appears uni- 
formly to have its own species of body.” * 
Now it is a little singular that, whilst the ten- 
dency of modern philosophy has been to ex- 
plode the idea of any secondary existence 
acting beneath the Creator on the constitution 
and actions of the universe, but to refer all 
its phenomena to the continued operation of 
the has which He first impressed on matter, 
hysiologists, neglecting the obvious analogy 
Garon the actions of the universe and those 
of any single organised being (the Macrocosm 
and Miercoes) inted out by Aristotle, 
should have rained, with but little modifica- 
tion, his opinion regarding the second ; and 
should still attribute the phenomena of life to 
a secondary agency existing in each being and 
modifying the ordinary laws of matter to its 
purposes. This subject, however, we shall 
dismiss for the present, to return to it here- 
after. 

The mode of explaining vital phenomena 
which has been adduced as an example of 
early speculation on the subject, appears to 
have resulted from two tendencies that may be 
observed to characterise the unenlightened mind 
both in past ages, and at the present time. The 
first is that which may be considered as natural 
to man in the infancy of philosophy,—to regard 
all matter, at least the grosser forms of it, as 
essentially inert, and therefore to attribute all 
spontaneous motion to a union of the thing 
moved with some substantial moving cause. 
Now, although modern science has given a 
more correct explanation of the causes of mo- 
tion in the inorganic world, and has shown 
that, so far from being inert, every particle of 
matter is capable of exhibiting actions of va- 
rious kinds when placed in certain relations to 
others,—the superficial enquirer still regards 
matter as inert guoad vital actions, and is un- 
willing to attribute them to any possible ope- 
ration of its properties. And in this mode of 
reasoning he would seem borne out by the 
peculiar history of organised beings,—the phe- 
nomena of their origin, growth, decline, dis- 
solytion, and decay,— the contemplation of 
which, with the desire of accounting for them, 
oceasions the second tendency to which we 
have alluded; that, namely, to infer from this 
history the existence of an unknown something, 
which during the living state preserves the in- 
tegrity of the body, and the loss of which 
occasions the disintegration of the fabric. 
Thus it has happened that the doctrine of the 
animating principle has retained its hold over 
the public mind from the earliest ages of the 
world to the present day; and the vestiges of 
the opinions of the early Greek philosophers 
may be traced in the expressions, vital spark, 
vital spirit, breath of life, and others which 
are still prevalent. 


* Barclay on Life and Organisation, pp. 429- 
433. 


LIFE. 


The chief modification which these doctrit 

have undergone, in their transit to mod 
physiologists, has been the separation of 
vital principle—the entity which is supp 
to effect the organisation of the body, 
employ that organism as the instrument ¢ 
operations—from the soul or mental prine 
which is concerned in a series of actions 
tirely distinct. It is somewhat singular, | 
ever, that even Aristotle regarded the sot 
reasoning faculties as separable from th 
mainder of the ¥uyn, and as capable of 
isting independently of the body; and aj 
division of this kind was adopted by 
Roman philosophers, who designated the 
and sensitive principles by the term Ay 
whilst to the rational they applied the nat 
Animus. We shall not follow these doet 
through all the modifications which resi 
from the unfathomable profundity of s 
systems of philosophy, and the prete 
shallowness of others; but shall procee 
once to the more modern opinions, whic 
either openly professed at the present tin 
lurk in the unillumined corners in whieh 
heterogeneous relics of former systems fi 
hiding place, whose darkness is congeni 
their disunited formlessness. 

The ancient doctrine of the identi 
vital with the mental principle was revive 
Stahl in a somewhat altered form. This pI 
sopher maintained that the rational soul is 
primum movens of organisation; that it 
ultimate and sole cause of ic activ 
and that by its operation, according to 
fixed laws, it preserves the bod d 
and cures the effects of disease. Still, now 
a distinction was drawn by him between the 
of the animus and the anima, which was 
served by his followers, who have regarded 
as wishing to identify them. He looked 1 
them as the common effects of one princi 
and his great error was in supposing tl 
analogy or parallelism existed between 
Now it is necessary to bear this doctri 
stantly in mind when reading the 
many of the physiologists of the last ¢ 
otherwise their meaning will be grea 
understood. In the writings of Wh 
example, we constantly find actions re ern 
the soul as their cause, when it is 
evident that the author did not mean tha 
mind (as it is now termed) was at all conce 
in them. This was the case with his ¥ 
class of vital and involun motions, tt 
production of which, he pi tates, 
Sciousness is not always necessary. 
there are few if any Thilasghall ho W 
avow such a doctrine as that of Stahl a 
present time, we trace its effects very evid 
exerted upon popular opinion. We have ki 
it maintained by many well-informed per 
that the phenomena of life and 
obviously so closely connected, that, to 
one class to the operation of the properti 
matter without an independent control 
entity,—in other words, to set aside the 
trine of a vital principle,—necessarily i 
the relinquishment of the idea of mind ; 


ys 


istinct existence. Nothing, however, can be 
more absurd than such a dogma. The two 
es of phenomena are not connected other- 
se than by a very remote analogy. All the 
bhenomena of Life (putting aside, of course, 
ose psychical changes with which we are 
contrasting them) concern matter only, and 
‘consist in its actions and reactions, and there 
is nothing in them related to feeling or con- 
iciousness ; it is but reasonable, then, to refer 
hem to the laws of matter if we can do so. 
the phenomena of mind are universally 
allowed to be of a very different character ; 
there is nothing tangible or material about 
them; and, whether we regard them as causes 
i results of material changes, our reasons must 
ave a very different basis than the existence or 
non-existence of a vital principie. On this 
point all the most intelligent of modern writers 
we fully agreed.* 
The doctrine of “ the vital principle,” which is 
“at present very commonly received under some 
‘form or other, may be regarded as having been 
rst put forth in a distinct form by Barthez, 
ho invented this term to signify something 
stinct from either mind or body, but never- 
ieless capable of existing by itself. The vis 
edicatrix nature, which figures so promi- 
ently in the theories of Hoffmann and Cullen, 
‘nothing more than the same hypothetical 
gent under a different name ; for by this term 
as denoted a “ sort of in-dwelling guardian 
the body,” which “ presides over its func- 
ons in the state of health; and, when any 

ecidental cause of disturbance has given rise 
to a temporary disorder in the system, exerts 
elf to the best of its ability, with a sort of 
stinctive effort, often well directed, though 
pmetimes liable to mistake, to restore the 
healthful and regular condition.”+ No one 
have observed the phenomena of Life in 
orbid conditions of the body without witness- 
ing examples of the tendency to reparation in 
the various parts which have suffered from the 
ravages of disease or injury ; but this tendency 
Its, like their ordinary operations, from 
tir Original constitution as parts of an or- 
nised system, and not from any independent 
ent whose existence can be demonstrated ; 
that if the common phrase, “ the healing 
wer of Nature,” be i at all, it should 


Thus Mr. Abernethy, in his Exposition of 
nter’s Theory of Life, contended against con- 
nding perception and intelligence with mere 
lity. Dr. Prichard rematks (Review of the 
trine of a Vital Principle, p. 71,) that the con- 
cious principle or mind and the vital principle, 
pposing for a moment that both really exist, 
entirely distinct in their nature and attributes.” 
ind Dr. Alison’s anthority fully coincides with 
lose already qnoted. ‘* Whatever notion we may 
ntertain respecting the existence of a vital prin- 
“iple, it has no connexion with our notion respect- 
ng the existence of mind.” Seemed of Physio- 
logy, p. 3.) These three physiologists may be 
reg rded as fairly representing three different 
‘lasses of opinions regarding the vital principle ; 
che first being 4 zealous partizan of its claim to be 
sonsidered a distinct entity, the second as zealous 
nm opponent of the doctrine, and the third taking 
vn ntermediate position. 

+ Prichard, op. cit. p. 17. 

‘VOL. IIT. 


LIFE. 


145 


only be used as a general term for the expres- 
sion of this tendency. Precisely the same may 
be said of the “ Nisus Formativus,” or Bil- 
dungstrieb of Blumenbach. If it be employed 
merely as a general expression of phenomena 
evidently directed by their unknown cause or 
causes towards the same end, it is unobjection- 
able; but care must be taken lest it be sup- 
posed that something has been gained by such 
a generalisation, which, in fact, merely refers 
to the final cause and not to the efficient cause, 
and does not, therefore, carry us forward one 
step in the inquiry into the latter. If, on the 
other hand, it is intended thus to designate an 
agent whose operations produce these pheno- 
mena, it cannot be distinguished in any way 
from that commonly spoken of as the vital 
principle. Of a sitailar character would seem 
to be the “organic agent” of Dr. Prout, the 
“organic force” of Muller and other German 
physiologists. If by them are intended any 
entities separate from matter, or any forces 
distinct from those which the action of its 
properties creates, they evidently come under 
the same category.* 

We arrive, then, at last at the doctrine of 
the vital principle, which, since the time of 
Hunter, has prevailed in Britain, especially 
amongst his disciples, until a comparatively 
recent period, when its unphilosophical charac- 
ter, its inability to explain the phenomena of 
Life, and the absence of any valid evidence 
for such an hypothesis, have been made appa- 
rent. It is not easy to discover, however, from 
his writings, what were the precise opinions of 
Hunter upon this topic; for the inquirer is 
constantly perplexed by the peculiar vagueness 
of his expressions, which, if taken in a rigid 
sense, would indicate ideas quite opposed to 
one another. Thus, we find him at one time 
speaking of the brain as itself the materia vite 
in a concentrated state, and speculating that 
“ something similar to the materials of the 
brain is diffused through the body, and even 
contained in the blood.” But he elsewhere 
intimates his opinion that the principle of life 
is independent of organisation, a something 
superadded to the organised structure, as mag- 
netism to iron, or electricity to various sub- 
stances with which it may be connected. This 
view was warmly espoused by Mr. Abernethy ; 
so warmly, indeed, that he almost transforms 
the analogy into identity, maintaining that 
“ if the vital principle of Mr. Hunter be not 


* Such expressions, says Rudolphi, (Translation 
by How, p. 216,) may be approved of ‘* when it is 
wished briefly to mention the unknown cause of 
life ; but it is extremely objectionable to presume 
that they have thereby explained anything. - Au- 
thors generally commence at first with the modest 
declaration that they mean, by the word vital power, 
no more than the unknown origin of life; but this 
mask of modesty is presently thrown aside, and 
they proceed as if the thing had been quite clearly 
proved. It is now become a something which is 
imparted to the body ina certain quantum; and 
they talk of increased and diminished, exalted and 
fallen vital power, &c., and thus they have a Deus 
ex machiné which must help them through all 
obstacles. In such a case was Brown with his 
Excitability.” 

L 


146 


electricity, at least we have reason to believe it 
is of a similar nature, and has the power of 
regulating electrical operations.” 

We shall now inquire into the precise import 
attached to the term by those who continue to 
employ it. It has been well remarked by 
Mr. Mayo that the word principle, “ charac- 
teristic of a less advanced state of science, has 
been generally employed (as the final letters of 
the alphabet are used by algebraists) to denote 
an unknown element, which, when thus ex- 

, is more conveniently analysed.” Thus, 
it has been customary to speak of the pringiple 
of gravity, of electricity, or of magnetism, as 
the unknown causes of certain phenomena, 
whilst these are imperfectly comprehended. In 
so far, however, as the laws of these pheno- 
mena are understood, they terminate in referring 
all the results to simple properties of matter, 
from which they may be deduced by demon- 
strative reasoning, just as geometrical theorems 
from the postulates on which they are founded. 
But in the science of physiology the term has 
been employed in a less justifiable sense. It 
must be admitted on all hands, that the condi- 
tions of vital phenomena are not yet determined 
with sufficient precision to enable us to refer 
all observed facts, through the medium of 
general laws, to ee vital properties ; and 
there would be no objection, save the proba- 
bility of its abuse, to the employment of the 
term “ Vital Principle,” like “ Nisus formati- 
vus” or “ Organic Force,” as a convenient ex- 
pression for the sum of the unknown Le ae 
which are developed by the action of these 
ak ain But to this limit physiologists 

ave unfortunately not restricted themselves. 
They have regarded it as a distinct entity en- 
dowed with properties of its own, in virtue of 
which it acts upon matter,—removing its par- 
ticles from the pale of physical and chemical 
laws,—transforming them into organised tis- 
sues,—endowing these tissues with new pro- 
perties,—prompting their actions,—preserving 
their composition in defiance of external in- 
fluences which would tend to disintegrate them, 
—and finally quitting them, or being itself 
worn out with them, so as to leave the frame- 
work without its protecting influence, deprived 
of which it speedily falls to decay. 

Of the character of this principle, its expo- 
sitors leave us very much in the dark. Of all 
modern writers, Dr. Prout is probably the one 
who has most plainly expressed himself on it. 
In his Gulstonian Lectures* he informs us that, 
“ In all cases it must be considered an ultimate 

rinciple, endowed by the Creator with a 

culty little short of intelligence, by means of 
which it is enabled to construct such a mecha- 
nism, from natural elements, and by the aid of 
natural agencies, as to render it capable of 
taking further advantage of their properties, 
and of making them subservient to its use.” 
The fallacies involved in this supposition have 
been elsewhere so ably exposed+ that we shall 
not here stop to discuss it; but in our survey 


* Medical Gazette, vol. viii. p. 261. 
+ Roberton on Life and Mind, p. 36 et seq. 


LIFE. 


of the nature and causes of vital actio 
shall take occasion to inquire whether any st 
hypothesis is called for, or whether it is. 
worse than useless by complicating what 
otherwise readily explicable on simple and 
losophical principles. 
III. Narure AND CAUSES OF VITAL At 
It has been already pointed out that a 
changes in the external world are the rest 
the properties of inorganic matter, calle 
exercise by the means appropriate to ex 
stimulate each to activity; and we may 
observe that these means are different fo 
property. Thus, to develope the da 
perty of gravitation in any mass of maj 
should only have to bring it within thesp 
attraction of any other mass. But to de 
the dormant electrical property of a loa 
a mass of iron alone would serve. 
operation in chemistry is founded 
same principle, each substance 
being capable of responding, in a | 
io to itself, to the influence o 
rought to bear upon it. Now, he 
liar this idea may seem, it has been too 
neglected in the investigation of vital 
mena; and notwithstanding that we 
find a similarity of action, when the or 
structure, on the one hand, and the 
which call its oe tte into activity, 
other, are identical—and a difference m 
of these conditions always producing @ 
rence in the result,—physiologists have & 
the habit of looking to some other age 
the cause of the variation. It is tru 
occasionally meet with instances in 
result is different, without our being a 
detect any change in either of the co 
but, knowing as we do how very 
alteration in the structure of a tissue 6 
will at once destroy or entirely cha nge 
properties, we cannot wonder that they: 
undergo important modifications withe 
sources being perceptible to our prese 
of research; and, as will h 
fully shown, every extension of our po} 
observation renders this doctrine more pr 
When we analyse the mass of phet 
which are presented to us by the vital 
of the organised world, we find that t 
susceptible of reduction into distine 
by which the study of them is much 
Thus, all living beings introduce 
own structure alimentary materials deriy 
external sources; and all likewise subm 
fluid ingredients to the influence of thee 
they inhabit, in such a manner that a ret 
change occurs between them. In this 
we arrive at the notion of the distinct fu 
of living beings, each of which @ 
regarded (in its simplest form) as a g 
phenomena of similar character and 
to the same causes. Thus, the funt 
respiration, when stripped of all the ac 
times associated with it, is essentially th 
throughout the whole organized world: 
the simplicity of the changes involved 


* See Prin, of Gen, and Comp. Phys. ¢ * 


il 


4 


together with the facility with which it may be 
made the subject of experiment, render our 
_ knowlege of its character and conditions nearly 
complete. 
_ When we have analysed these groups of 
ital phenomena and satisfied ourselves of the 
onditions under which they occur, we are 
rought to the conclusion that for each a parti- 
| cular organ or species of structure is appro- 
7 lated in the organized system, and that its 
ih on is dependent upon the excitation of its 
properties by agents external to it, just as in 
the inorganic world. This dependence of life 
upon external stimuli has been completely 
erlooked by the advocates of the vital prin- 
le ; and it is probably to Brown, with all his 
ults and absurdities, that we owe the first 
rominent enunciation of the fact. When these 
imuli are withdrawn, vital action ceases ; 
jough, under favourable conditions, vitality 
or the vital properties of the organism may be 
retained. (Sect. VI.) 

} Every class of organs in the living body may 
be said to require its particular stimulus for the 
play of its properties. Thus, regarding the 
; structure as a series of assimilating 
sans—capable of converting nutrient mate- 
into structures like their own, and of thus 
using them to exhibit vital properties—we 
ay say that the supply of these nutrient ma- 
rials in a fluid state is the stimulus to their 
on. Again, to the excretory organs the 
ired stimulus is the presence of certain 
aperabundant and therefore injurious elements 
1 the nutritious fluid. To the action of the 
uscular system the excitement of innervation, 
the application of a physical stimulus, is 
scessary. In all classes of living beings we 
ind these functional changes performed under 
onditions which are essentially the same; and 
ence we are enabled to arrive at the laws 
yhich regulate each. 
These are not the only conditions required, 
however; for others of a still more general 
ure are constantly, and therefore impercepti- 
ly, operating. All vital actions, for example, 
equite a certain amount of heat for their per- 
mance, and the amount varies in different 
This is ro more, however, than what 
meet with in the inorganic world ; for many 
‘chemical and physical operations can only take 
place within certain limits of temperature, and 
these sometimes very circumscribed. The pre- 
ence of light, again, is essential to many others, 
pecially in the vegetable kingdom; but this, 
Zain, finds its parallel in the inorganic world, 
ay chemical decompositions (which indeed 
a remarkable analogy with the changes 
thich this agent produces in the green parts of 
slants when exposed to an atmosphere contain- 
ing carbonic acid) being due to its influence. 
nd although, with regard to electricity asa 
Vital stimulus, our absolute knowledge is still 
less, what we do know leads to the belief that 
‘it is an agent of at least as much importance 
1 the vital economy as in the operations of in- 
organic nature. 
tien is nothing, then, in the nature or con- 


Ll 

te 

a 
ae 


z 


tions of vital actions considered individually, 


LIFE. 


147 


which need cause us to reason upon them in 
any other way than we do. upon the phenomena 
of the inorganic world; and it is obviously- 
unphilosophical to asswme an agency which is 
not required to account for them. It must be 
recollected, too, that the onus probandi rests 
with those who make the assumption, and not 
with those who maintain the analogy in the 
character of vital phenomena to those of the 
universe at large. ‘The assumption may be 
easily shown to be not only useless, but insuffi- 
cient to explain phenomena without calling to 
its aid the very principles. which have been 
shown to be themselves competent. Thus, the 
physiologist who traces the operation of the 
vital principle in the function of secretion, is 
compelled to allow that, as by one principle so 
great a variety of préducts are eliminated by 
the various glands from one material, the diffe- 
rence in the results must be due to some 
difference in the structure of the organs respec- 
tively concerned. And it may then be fairly 
inquired of him, “If the difference in the 
glandular structure and action is capable of 
giving rise to so great a variety in the products, 
with the cooperation of this one vital principle, 
how can it be proved that this difference in the 
glandular structure and action may not be capa- 
ble of giving rise to the same result by itself, and 
without the aid of any such adjunct at all?”* 
A similar question might be put with regard to 
any other class of actions, in which, under the 
same general conditions, the results are modified 
by the peculiar characters of the instruments or 
organs respectively employed ; and, as a nega- 
tive reply must be given equally to all, it may 
be safely affirmed that no reasoning can deduce 
the doctrine of a vital principle from the phe- 
nomena of life separately considered. 

But the advocates of the doctrine rely much 
upon the peculiar adaptation of the various 
changes taking place in each being to the pur- 
poses of its existence ; and assume that this 
adaptation can only result from the control 
of a subordinate presiding agent constantly 
exercised over each. Here, again, we find 
such a doctrine not only unsupported by, but 
manifestly inconsistent with, the analogies of 
nature. No reflecting mind has any doubt 
that this earth and its inhabitants form a system, 
of which every part is perfectly adapted to the 
rest, (so that we might almost call it an or- 
ganised one, if the idea of a particular struc- 
ture were not involved in the term,) and of 
which all the actions and changes, however in 
appearance contrary, have one common ten- 
dency—the ultimate happiness of the creatures 
of Infinite Benevolence. The same may be 
said of it in regard to its relations with the 
system of which it forms a part; and probably 
of that system with regard to the universe in 
which it is but a speck. So far as we can un- 
derstand the working of the laws by which that 
universe is governed, we see them all mutu- 
ally adapted to the same ends, whether we 
consider the welfare of the whole system, or of 
our own comparatively insignificant planet, with 


* Prichard on the Vital Principle, p. 100. 
L 2 


148 


its countless living inhabitants. Have we, then, 
any more reason to assume that a vital prin- 
ciple or organic agent governs the concerns of 
each of these beings, than to sup that the 
Creator has delegated to a subordinate the care 
of each individual globe? Or is it not more 
consistent to suppose that upon the elements 
of all He impressed those simple properties, 
from whose mutual actions, foreseen and pro- 
vided for in the laws according to which they 
operate, all the varieties of change which it 
was His intention to produce, should necessa- 
rily result ? 

By another illustration of a different cha- 
racter we hope to set this point in a sull 
clearer light, and to be able to dismiss the 
subject without entering upon it as an abstract 
question. We shall suppose a young physio- 
logist, entirely ignorant of physical science, but 
educated in implicit faith in the vital principle, 
witnessing for the first time the action of a 
steam-engine. Here he would perceive a ma- 
chine composed of a number of dissimilar 
parts connected together, and moving by some 
secret agency which he desires to unveil. We 
may imagine him trying various experiments 
upon its functions,—such as shutting off the 
communication between the boiler and the cy- 
linder, or between the cylinder and the con- 
denser,—or applying cold where heat should 
be, and kindling a fire under the cold-water 
cisteru.. Hence he may arrive at the just con- 
clusion that the actions performed by each 

, when the machine was in regular opera- 
tion, have all a tendency towards one common 
object—the maintenance of its moving power. 
He will also perceive that these actions are as 
dissimilar as the structure of the exhi- 
biting them ; and he will not escape being sur- 
prised that the opposite influences of heat and 
cold should be essential to their production. 
Hence he may safely conclude that the whole 
series of phenomena is due to one presiding 
agency—a ‘steam-engine principle,”—by the 
operation of which upon the material structure, 
its actions are produced, and made to har- 
monize with each other, and with their ultimate 
object. And this conviction would be very 
much strengthened if he saw the machine en- 
dowed (as we may, for illustration, imagine 
quite possible) with the means of supplying 
its own wants,—regularly adding fuel to its fire, 
and cold water to its condensing cistern,—and 
even repairing for itself the loss it sustains by 
wear of material. Would such a person, en- 
tirely unacquainted with the properties of 
steam, be acting more unphilosophically in en- 
tertaining this notion, than in attributing the 
actions exhibited by living beings to the opera- 
tion of a vital principle? We think not. In 
each case the machine or organism is framed 
to take advantage of the properties with which 
the Creator first endowed matter; and the dif- 
ference is that, while the design of man con- 
structed the first to bring into operation those 
properties which alone he can control, the de- 
sign of Omnipotence constructed the second, 
and adapted it to develope properties of matter, 
which can only be exercised under the condi- 


LIFE. 


tions which a living being suppli 
which man, therefore, cannot avail him 
We may conclude, then, that if we c 
vital actions to the properties of the or 
which exhibit them, called into of on 
their appropriate stimuli, we do not re 
any other explanation of their mutual 
tion and dependence than the original d 
of the Creator. “No agent,” it has 
remarked, “can be required to adjust 
gulate the actions which ensue from this 
tual adaptation, since they are, like all 
phenomena in the universe, under the e 
of laws inseparable from their very existe 
But the question next arises, by wh 
have organised bodies become posse 
peculiar properties? It is, as we 4 
a a mere verbal alteration to attr 
e vital actions of an 0 to its peculiz 
perties; since we wade by hese pr 
ties only the capability of giving rise & 
changes which we witness, and we only 
of their existence by the observation ¢ 
changes. The real causes of the fF 
must be sought for in the events 
concerned in the formation of the 
and its first endowment with the 
which it exhibits ; and this leads us to co 
IV. THE coNNECTION BETWEEN — 
LITY AND ORGANISATION.—When Our 
quiry into the laws of Physics terminé 
referring any of its phenomena to the actic 
one of the universal properties of matt 
feel satisfied that we can trace the operatic 
second causes no higher; and that the ex 
of this property as inseparable from m 
and therefore as essential to our idea of 
the immediate result of the will of t 
Butin a great variety of instances we 
so; and we observe properties 
and inseparable from certain forms of m 
the laws of whose action, however, are 
finite as in the first case. Such pro 
therefore, form a ye of our notion of 
particular forms of matter; thus, the ma 
properties of iron, or the energetic attr 
which potassium has for oxygen, are ¢ 
ristics of these substances, which 
with others to distinguish them in our 4 
from other forms of matter possessing: 
properties in common with them. & 
properties will not be manifested exe 
peculiar conditions ; and according 
rity of the occurrence of those conditio 
be the probability of our remaining | 
of the property. We are obliged 
therefore, that every form of matter wit 
we are acquainted may have properti 
which we know nothing, simply bec 
not been placed in the circu 
to call them into activity; since it isonh 
action of some kind that the mind ¢ 
cognisant of their existence. We 
that it is very possible that all mati 
least all those forms of it capable of be 
organised, may be possessed of f 
which shall give rise to the action 
vital, when they are placed in ce 
tions; and that the mere absence of 


ert. 


a 


iz 


ed 


sstation of these, while the substance remains 
1 the condition of inorganic matter, is no 
proof that they do not appertain to it. 
_ We find nothing, then, in our fundamental 
ideas of matter, to oppose the doctrine that 
vital properties are developed in it by the very 
act of organisation. But we shall consider the 
estion in another point of view. We are 
stantly witnessing examples of the total 
hange effected upon the properties of certain 
forms of matter by their entrance into new 
sombinations. Thus, how completely different 
e the properties of a salt from those of the 
acid and alkali which unite to form it. And we 
re not obliged to have recourse to chemical 
on for cases of such a change; since there are 
_ examples in which mere mechanical admixture 
of the particles of different bodies will produce 
How different, for instance, are the 
erties of gunpowder from those of any of 
S ingredients. ey are all combustible it is 
true; but ina manner as unlike it as each 
other. Does any one think of assigning any 
Other cause to these changes than the act of 
ombination or admixture? Does he seek for 
it in the operation of a saline property super- 
idded to the compound of acid and alkali; or 
of a combustible principle presiding over the 
sombined actions of the nitre, sulphur, and 
harcoal, and directing them to one common 
rbject ? If not, why should he adopt a 
iifferent course in regard to vital properties ? 
In our investigation of natural phenomena, 
never observe a substance endowed with 
properties, without it has undergone some 
hange in its own condition, of which altered 
tate these properties are the necessary attend- 
mts. Unless, therefore, an instance could be 
roduced in which the same form of matter 
all at one time evince properties of which it 
proved to be destitute at another, we have no 
ght to speak of any property as distinct from 
ne matter which exhibits it, or as capable of 
Being superadded to it or subtracted from it. It 
“May be desirable for us to pause here, in order 
examine a case in which it has been alleged 
hat such an addition takes place, and which 
s been used as an analogical argument in 
pport of the doctrine of a vital principle. 
has been commonly said that a living body, 
‘assimilating and organising the nutrient 
atter by which the changes essential to its ex- 
istence are maintained, superadds or communi- 
fates to it by a separate act, those vital proper- 
ties of which it was itself previously possessed ; 
and there is no more difficulty, it has been 


gued, in conceiving how vital properties may 


derstanding how magnetic properties may be 
Superinduced upon iron. But the analogy is 

lased upon a false conception of the latter 
? cess, which is really conformable in cha- 

acter to those by which gravitation or any 
‘other properties of matter are brought into ac- 
tion. For the so-called communication of 
Magnetic properties to iron is nothing more 
than the production of a change in the condi- 
tions of the metal, by which its electric proper- 
nes ave manifested in a manner peculiar to 
tself, and caused to give rise to magnetic 


i 


LIFE. 


be communicated to organised matter, than in ~ 


afi 
powers. If, then, an analogy exists between 
the two processes, (which can scareely be de- 
nied,) it leads us to the belief that, just as mag- 
netic powers are developed in iron, when the 
metallic mass is placed in a condition to mani- 
fest them, so the very act of organization deve- 
lopes vital powers in the tissues which it 
constructs. Forno one can assert that there 
does not exist in every uncombined particle of 
matter which is capable of being assimilated, 
the ability to exhibit vital actions when placed 
in the requisite conditions; in other words, 
when made a part of a living system by the 
process of organisation. It is only the com- 
plexity of the conditions required to manifest 
it, which prevents our recognising this capabi- 
lity as acommon property of matter, or at least 
of those forms of Ei we know by expe- 
rience to enter into the composition of organised 
structures. 

Such are the conclusions to which we are led 
by the general comparison of vital phenomena 
with those of the external world ; and it would 
be difficult, we might say impossible, to prove 
that there is anything in the former which re- 
moves them from the pale of such reasoning. 
In fact, it appears to us that observation of 
them alone would lead to similar inferences. 
We perceive organisation and vital properties 
simultaneously communicated to the germ by 
the structures of its pareat; those vital proper- 
ties confer upon it the means of itself assimi- 
lating, and thereby endowing with vitality, the 
materials supplied by the inorganic world. It 
is very true that in this germ we cannot per- 
ceive a single trace of the future being, the 
various organs and structures of which are 
evolved during its development. But these 
are not evolved in any other way than by the 
progressive extension and complication of the 
parts of the original germ. If we witnessed 
the aggregation of inorganic matter to form a 
head in one place, a trunk in another, and 
limbs in a third, and the subsequent union of 
these, we might be disposed to suspect the 
existence of some invisible agent which di- 
rected and controlled the operation; but we 
can trace nothing in the real process but the 
effect of the properties with which the struc- 
ture of the germ is endowed at the same 
time and by the same act that it is organised 
by the parent. Nor is there anything in 
the subsequent life of the being that op- 
poses such a view; on the contrary, much 
that confirms it. As longas each tissue retains 
its normal constitution, renovated by the ac- 
tions of absorption and deposition by which 
that constitution is preserved, and surrounded 
by those concurrent conditions which a living 
system alone can afford, so long, we have 
reason to believe, it will retain its vital proper- 
ties, and no longer. And just as we have no 
evidence of the existence of vital properties in 
any other form of matter than that denomi- 
nated organised, so have we no reason to be- 
lieve that organised matter can retain its regular 
constitution, and be subjected to its appro- 
priate stimuli, without exhibiting vital actions. 
The advance of pathological science renders it 
every day more probable that derangement in 


139 
function always results, either from some struc- 
tural alteration (although this may be ofa kind 
imperceptible to our senses), or from some 
change in the character of the stimuli by which 
the properties of the organ are called into action. 
There is no difficulty, therefore, in accounting 
on this view for the death of the whole system 
on the cessation of any one function ; since any 
perturbation in the train of vital actions will 
not merely disturb the regularity of all, but, if 
sufficiently serious, will check those nutrient 
processes on the uninterrupted continuance of 
which the vital properties of the several parts 
depend; the degree of that dependence being 
proportioned to their respective tendencies 
to spontaneous decomposition if not thus 
renewed. Still, the vital properties of in- 
dividual parts may be retained for a consi- 
derable period after general or somatic death 
(see Deatu) has taken place; and vital actions 
may continue, as already stated, so long as the 
conditions which they require in the living 
body are supplied. So far from a dead body 
having “all the organization it ever had whilst 
alive,” as has been often maintained by the 
upholders of a separate vital principle, it 
will be found, on a more minute survey, that 
no single portion of it is existing under the 
same circumstances in these two states;* and 
there is good reason to believe that those agents 
which destroy life with the least apparent or- 
ganic change, produce structural alterations 
which are not the less important because more 
minute. Some instances of this kind will be 
presently noticed (Sect. V.). We must confess 
ourselves at a loss to understand how the gra- 
dual death of individual parts of the body can 
be explained upon the doctrine of the vital 
principle, without supposing that it may be 
split into as many individual existences as there 
are organs in the system ; such an idea would 
then coincide with that of the swperadded pro- 
perties of which we have endeavoured to show 
the fallacy, and all the arguments derived from 
the unity of its operations would fall to the 
ground. 

One often repeated objection to the doctrine 
that vitality results from organisation may, we 
think, be easily disposed of, as it is more spe- 
cious than real. It is considered by some to 
be a sufficient disproof of this doctrine, to refer 
to the universally-admitted fact, that the exist- 
ence of organisation implies a previous exist- 
ence of life; and thence to infer that life 
cannot be at the same time the cause and the 
consequence. But this is a sort of dox 
which reminds us of the question that puzzled 
the profound casuists of yore—* Whether does 
the bird spring from the egg or the egg from the 
bird?” It is evident that the life of any indi- 
vidual being may be the consequence of the 
action of stimuli upon its organism, just as the 
bird is produced by warmth from the egg ; and 
yet that the organisation of its structure may 
be the result of the previous existence of life 
in the parent, just as the egg is produced by a 
bird. We are only referred backwards, there- 
fore, in our enquiry into the efficient cause of 


* See Prichard on the Vital Principle, p. 117. 


LIFE. 


Sas 


the a of vital p to the. 
creation of each organism. Here some we 
maintain that the Creator formed a vital p 
ciple or organic agent, and then set it te 
ganise the body. But we appear hat 
is an assumption which we have no rig 
make; and that itis more philosophic: 
cause more consistent with what we else: 
witness, to suppose that the Creator, i 
forming matter, endowed it with prop 
virtue of which it became capab 
biting vital actions or life, when first cor 
by Him into an organised structure; 4 
the Parent of all thus impressed uw 
elements of which each created 
composed, the spirit® of the laws , 
in future govern its growth and 
just as He impressed upon the bodies 
posing the planetary system that mo 
action whose subsequent continuance has 
us the notion of the laws of gravitati 
motion. To account for the perpet 
the race, we require nothing but the cont 
operation of those laws; in other 
continuance of the same mode of 
which particles of inorganic matter 
sively organised, and, gud organised, b 
pable of performing vital actions, a_ 
which consists in the production of corr 
ing changes on other materials. 

The actions performed by living b 
not all, however, immediately depend 
the operation of the vital properti 
organs ; since many are evidently con 
to physical laws, and the properties 
gans by which they are performed are ¢ 
to them with many kinds of inorganic 1 
and are exhibited by dead as well as b 
organised substances, as long as ne o 
change takes place in their composition. 
this kind are the property of elasticity 
rious tissues, especially certain of a ligame 
character; and that by which endosmose 
place through certain membranes. 1 
observed, however, that the existence 0 
properties in the tissues of the living 
obviously depends upon a certain 
of their ultimate molecules, which can 6 
maintained by the exercise of their m 
functions; and that any irregularity y i 
latter, still more their entire cessatior 
speedily impair the properties, by 
course to the constant tendency to decor 
tion in the tissues which exhibit them, 
further, it may be remarked that in | 
stances these properties are dependent fe 
excitement to action in the livi 
those truly vital processes whi 
nical contrivances or chemical ope 
produce or imitate. 

Between these two extreme classes ¢ 
nomena,—the purely physical, and 
vital—there is a third, of a very pect 
perplexing character. We allude 
tions concerned in preparing the 
organisation out of the aliment 
the system. Many are dis to 
as of a vital character, and to 


<i 


. 
ONSIG 


* Horschel’s Preliminary Discourse, p. 87. 


‘soon as the living body has begun to change the 
composition of the substances upon which it 
A acts, it endows them with a new set of affinities, 
contrary to those which it before possessed 
When subject to the operations of chemistry. 
Others, again, are content to refer the opera- 
ions in question at once to the ever-ready vital 
principle, which, according to them, produces 
a directs these changes in the organism, and, 
! long as it resides there, keeps in check the 
ural tendency of its structure to decay. We 
e inclined to believe, on the other hand, that 
€ operations in question are immediately due 
0 the agency of the same laws as those which 
eside over inorganic matter, operating, how- 
ever, under conditions which the living or- 
“ganism alone can supply. We shall now 
amine what evidence may be produced in 
your of this opinion, and how far it is con- 
istent with the general phenomena of life. 
V. Cuances 1n composit1on.—The ali- 
entary materials which serve as the food of 
@ living organism, cannot be appropriated by 
Several tissues, and rendered like themselves 
in structure and properties, until they have un- 
ergone certain changes in composition, by 
nich the proximate principles ave produced. 
It is by the organisation of these compounds, 
that the constant disintegration of the elemen- 
tary parts of the living system is compensated, 
and those vital properties maintained, the exer- 
cise of which forms an essential part of the 
circle of actions involved in life. Another 
class of changes in composition consists in the 
production, from the same materials, of the 
peculiar ingredients which characterise each se- 
creted product; some of these may be regarded 
as directly eliminated from the nutritious in- 
gredients of the blood, in the same manner as 
are the solid tissues themselves; whilst others 
_ would rather seem to result from the new com- 
bination of the disintegrated elements, which 
are taken up and removed by the current of the 
Circulation, and carried to organs destined to 
_ separate them entirely from the living portions 
_ of the system. All these changes are frequently 
said to be effected by a vital chemistry ; or (to 
Speak in more precise language) to result from 
_ the operation of vital affinities, of a different 
character from those ordinary chemical affinities 
_ which produce the well-known changes in the 
_ inorganic world. In conformity with the New- 
tonian direction to avoid unnecessarily multi- 
| plying causes, we shall briefly examine the 
_ grounds upon which this hypothesis is based, 
_ and enquire whether it is requisite for the ex- 
planation of phenomena, or even gives us any 
_ assistance in our researches. 
The chief ground for the assumption of a 
distinct set of vital affinities appears to be, 
_ that the mode of union of the elements of the 
4 organic compounds is essentially different from 
that which prevails in the inorganic world; 
and that the chemist, who has the power of 
| effecting or controlling those changes which are 
| produced by physical laws, and can therefore 
_ imitate to a great extent the immense variety of 
| combinations which the mineral kingdom af- 


_ fords, is unable to effect or control the action of 
"| 


- Se 


= 


LIFE. 


- properties it has a binary character. 


151 


similar materials, so as to produce any of the 
class of organic compounds or proximate prin- 
ciples. It has, until very recently, been re- 
garded as a distinctive character of organic 
compounds, that their elements are combined 
in ¢ernary or quaternary arrangements of com- 


plex nature, in which each ingredient is equally 


united with all the rest; whilst all inorganic 
substances admit of being ultimately resolved 
into simple binary combinations. Thus fibrin 
is regarded as composed of 6 parts of carbon, 
2 of oxygen, 5 of hydrogen, and 1 of nitrogen ; 
and these elements are imagined to form a qua- 
ternary compound, all having a mutual attraction 
for each other; whilst carbonate of ammonia, 
which consists of 1 carbon, 2 oxygen, 3 hy- 
drogen, and 1 nitrogen, is a binary combination 
of two other binary compounds, carbonic acid 
and ammonia. Bef‘on this it may be remarked, 
that there are undoubtedly some proximate 
principles, (that is to say, the simplest forms to 
which organic compounds can be reduced, 
without altogether disuniting them into their 
ultimate elements,) which consist of two ele- 
ments alone, and which exist in this simple 
form in living bodies. Such are some of the 
compounds of carbon and hydrogen. Further, 
the rapid progress of analytic research is leading 
to the belief that the complex arrangements 
just referred to may be resolved into those of a 
binary character; so that most organic com- 
pounds may be regarded as resulting from the 
union of others of simpler nature, just as a salt 
is formed by the union of an acid and an alkali. 
The discovery of cyanogen, and of its capabi- 
lity of acting as a compound radical,—uniting, 
like chlorine or iodine, with hydrogen to form 
an acid, and even occasionally serving, like 
oxygen or sulphur, im combination with some 
metals, as the base or alkali to such an acid,— 
was the first step in a career of brilliant disco- 
veries, which, even at the present day, may be 
regarded as scarcely commenced. When cy- 
anogen combines with a metal, the combination 
is in reality a ¢ernary one, although in all its 
Thus, the 
cyanuret of silver (whose ultimate composition 
is 1 part of the metal, with 2 carbon, and 1 
nitrogen,) will form a salt, in which it acts as 
the acid or negative ingredient, with the cya- 
nuret of potassium; and the soluble cyanurets 
will form salts with the chlorides or iodides of 
the metals, thus establishing their claim to a 
binary character. _ But still further ;—cyanogen 
in combination with iron appears itself to act 
as a compound radical, combining as a simple 
body with other elementary substances.* From 
the analogy afforded by this and other in- 
stances, many chemists are now disposed to 
look upon the combination of the oxy-salts in 
a new light. It is suspected that, when sul- 
phuric acid and soda are brought together, the 
resulting compound is not formed by the union 
of an atom of the acid with an atom of the 
alkali, but by the generation of a new com- 
pound radicai, sulphatorygen, consisting of 1 
part of sulphur with 4 of oxygen, which unites 


* Liebig, in Turner’s Chemistry, 6th ed. p. 776. 


152 


as a simple body, like chlorine, iodine, or cya- 
nogen, with the metal sodium.* 

It will be seen, then, that the tendency of 
modern researches in inorganic chemistry is to 
prove, that the mode of combination which 
characterises the union of its elements, is not 
by any means so simple as it has been usually 
supposed; but that a binary, a ternary, and 
perhaps even a quaternary compound, may 
perform the part of an element, combining 
with other elements which are really simple, to 
form what are regarded as simple aes com- 
pounds. We shall now enquire what reason 
there is for believing that the compounds with 
which organic chemistry supplies us, have a 
Similar constitution. We must be content, 
however, with selecting one or two examples 
from among the vast number which the in- 
dustry of analytic chemists is constantly bring- 
ing to light. The vegetable a/kaloids have been 
generally regarded as proximate principles, not 
to be separated into simple compounds without 
an entire disunion of their elements. They all 
contain one equivalent of nitrogen ; and there 
is good reason to suspect that this element is 
not equally combined with all the rest, but 
exists in union with hydrogen in the form of 
ammonia, to which the alkaline power of these 
substances is due. Again, camphor was long 
considered a proximate principle of ternary 
composition; but it is now found to be an 
oxide of camphene,—a compound radical con- 
sisting of carbon and hydrogen, which will 
unite, like cyanogen, with simple bodies ; form- 
ing camphoric acid with another equivalent of 
oxygen, and entering with chlorine, &c. into 
other compounds. Lastly, urea may be men- 
tioned, in which the four elements that com- 
pose it may be regarded as existing in several 
forms of binary combination. It contains these 
elements in the following proportions :—2 oxy- 
gen, 4 hydrogen, 2 carbon, and 2 nitrogen. 
These may be considered as existing in the 
form of cyanic acid, ammonia, and water; one 
equivalent of each of these forming cyanate of 
ammonia; and, in fact, by the artificial union 
of these compounds, urea has actually been 
produced. It is by no means certain, however, 
that these compounds exist as such in urea ; 
and various ideas of its composition are enter- 
tained by chemists, on which this is not the 
place to comment. Our object is simply to 
show the analogy in the composition of the 
products of vital chemistry with that of the ar- 
tificial compounds whose formation is subject 
to none but physical laws. Why the chemist 
is not more successful in imitating in his labo- 
ratory the operations of the living economy, 
will presently become subject for consideration. 

An argument employed by many physiolo- 
gists for the existence of a distinct set of vital 
affinities, is founded upon the evident truth, 
that the tissues and fluids which maintain a 
certain composition when possessed of vitality, 
speedily resolve themselves into new combina- 
tions when this has become extinct. Hence it 
is inferred that the affinities which hold toge- 


* See Graham’s Chemistry, p. 158 et seq. 


LIFE. 


ther the elements during life, are of a d 
nature from those which operate in fp 
their subsequent separation. Now, 7 
objected to this inference, that no solid or fi 
compounds which have a disposition to : 
taneous decay after death, can continue 
without change during life ; that the 
the processes of interstitial absorption anc 
position seems to bear a pretty cor 
in every case, with the natural tendency 
composition; and that the maintenance oj 
original combination is not so much ow 
anything peculiar in the affinities 
together its elements, as to the constant re 
of particles in a state of incipient decay 
their replacement by others freshly ui 
Thus, we find that all the most permaner 
of the animal frame, such as the ma: 
tons of the polypifera, the calcareous 
of the mollusca, or the bony scales of fi 
to the possible duration of which geok 
scarcely dare to assign a limit, are extr 
in the living animal, undergoing sear 
interstitial change when once form 
to these in order of durability are the 
structures of animals, and the woody 
plants, whose connection with the circu 
system appears rather adapted to meet 
gencies of growth, injury, or disease, thar 
maintain a constant change es by th 
dency to decomposition. hen we ex 
the softer tissues, on the other hand, 
that the rapidity of interstitial chan 
compensates for the increased tenden 
cay; and that the perfect exercise t 
respective functions imperatively demant 
constant maintenance of their normal ¢ 
tion. Moreover, there are many orgar 
ounds which are as permanentas those 
in the laboratory of the chemist; of th 
are gum, sugar, and many other proximatep 
ciples, which simply require for their pr 
tion such external conditions as are 
to prevent the spontaneous decompos' 
many inorganic bodies. The degree in ¥ 
these are subject to ordinary chemical 
tions will be presently mentioned. It app 
then, to be an inference better founded 
than that first mentioned, that the pre 1 
of the normal constitution of organie 
pounds in the living body, is dependent on’ 
continuance of the vital actions of the € 
nomy, rather than due to its mere possessi 
the property of vitality. In fact, that 
reasonably maintained as an infe 
these phenomena, which we have a 
tempted to prove on other grounds; 
vitality of each tissue, that is to say, its f 
sion of vital properties, is dependent on 
perfect condition of its organisation, and tt 
so far from preserving the organism from dec 
it merely remains until decay has comm 
These inferences are, we think, fully borne 
by the two following facts. When life is’ 
extinguished by starvation, the whole body 
hales a putrid odour even before the o 
of death, and rapidly into putrefactit 
afterwards : here it would seem that the proc 
of spontaneous decomposition, which we ha) 


ie 


A 


represented as constantly occurring in the tis- 
sues, has been unbalanced by the reposition of 
nutrient materials; and that it has therefore 
‘manifested itself in the body even during life. 
Again, when spontaneous gangrene occurs 
from obstruction to the circulation, decomposi- 
tion slowly supervenes in the part from which 
he ie supply of nutrient fluid is cut off; and 
_ coincident with its progress is the extinction of 
the vital properties, constituting molecular 
[ eath. (See vol. i. p. 791.) Corresponding 
changes may result in the whole body when 
the nutritive functions are interrupted, not by 
obs action to the motion of the circulating 
fi id, but by depravation of its character ; and 
we then perceive the vital properties of each 
t ssue impaired in a degree correspondent to 
the dependence of the integrity of its structure 
upon the constant renewal of its elements. 
_ The presumed impossibility of forming, by 
chemical combination of their elements, 
iy of the class of organic compounds or prox- 
principles, is regarded by many physiolo- 
gists as in itself a sufficient ground for the as- 
mption that the affinities which act in the 
living body are different from those which we 
‘recognize in the inorganic world. The fact, 
however, which we have already noticed re- 
arding the artificial production of urea is one 
ich powerfully opposes such an assump- 
tion.* This is slurred over by Miller, with 
ie remark that it can scarcely be considered 
as organic matter, being rather an excretion 
han a component of the body—a distinction 
which does not remove it from the pale of the 
tion of the supposed laws of vital affi- 
ity. Seeing the vast progress which organic 
chemistry has made during the last few years, 
d the rapid increase of our knowledge re- 
arding not merely the composition but the 
‘mutual relations of the class of bodies under 
consideration, we cannot but think it premature 
to assert that other compounds may not be pro- 
‘duced in a similar manner. Be it observed, 
however, that the doctrine for which we are 
ow arguing only concerns the production of 
compounds which are destined either to 
thrown off from the system, or to undergo 
Subsequent organisation ; and cannot apply to 
those in which the process of organisation, and 
@ consequent development of vital properties 
ve already commenced. This distinction is 
a yery important one, and may, we think, 
by being kept steadily in view, save much un- 
Successful because mis-directed labour. If, for 
aay our view be correct, it may be pos- 
ible for the chemist to produce the gum or 
Sugar which he finds in the ascending sap of 
. a: but he can never hope to imitate the 
atex or elaborated sap, which already shows 
) traces of organisation and of the possession of 
vital properties. In like manner the formation 
} of albumen may be a worthy object of his 
) endeavours, whilst these would be totally fruit- 
less if directed to the production of fibrin, 


- 

| 

_* We do not quote any others reported to possess 
| the same character, such as the production of fatty 
| matter by Berard and Hatchett, because they still 
| require confirmation. 


hers tlt, tN 


*™ 


an 


E LIFE. 


153 


which differs from it but little if at all in che- 
mical constitution, but which is endowed in 
its fluid state with properties that nothing but 
the influence of a living system can generate. 

But quitting these speculations, we shall in- 
quire what positive evidence may be produced 
of the operation of chemical affinities in the 
changes of composition that form so important 
a part of vital action. Many facts might be 
collected which favour such a belief; but the 
following must here suffice. In the progress 
of vegetation we have frequent oceasion to 
observe the conversion of gum and of fecula, 
which consists of gum enclosed in vesicles, 
into sugar. This takes place in germination, 
in the budding of the potato and other fleshy 
stems, in flowering, in the ripening of fruit, as 
well as in many other instances ; in alt these in 
which fecula is the subject of the change, it 
would seem that this product, having been 
stored away out of the current of the circu- 
lation against the time of need, is to be again 
brought into use, and to supply the pabulum 
of young or rapidly-growing parts by conver- 
sion into sugar. These changes are effected in 
various modes. Where gum is the subject of 
the conversion, we commonly find an acid 
employed to produce it, as in the ripening of 
fruits, where lignin as well as gum seems to 
undergo this change. The chemist can pro- 
duce the same effect by digesting gum or lignin 
with an acid at a certain temperature. Again, 
where the conversion of fecula into sugar takes 
place as one of the ordinary processes of the 
vegetable economy, it is effected by the pro- 
duction of a secretion termed diastase, which 
occasions both the rupture of the starch-vesicles 
and the change of their contained gum into 
sugar. This diastase, which is abundantly 
stored up in the neighbourhood of the eyes or 
buds of the potato, may be separately obtained 
by the chemist; and it acts as effectually in his 
laboratory as in that of the vegetable organism. 
Further, he can imitate its effects by other che- 
mical agents; for, by the joint operation of 
heat and acid, he can produce the same trans- 
formation. 

These are among the remarkable instances 
of the catalytic action recently described by 
Berzelius,* which is common to organie and 
inorganic operations, and which is not yet 
found to ke comprehensible within the known 
laws of chemical affinity. The peculiarity of 
the action consists in the production by one 
body, A, of a change in the composition of 
another, B C, without itself undergoing any 
alteration. Thus, the peroxide of hydrogen, 
which is readily decomposed by any substance 
having an affinity for oxygen, is also decom- 
posed by some which themselves undergo no 
change, such as the metals and the fibrin of the 
blood ; these produce in it a state analogous to 
fermentation, oxygen escaping and water being 
left. Again, not only decompositions but new 
combinations may be effected in this manner. 
Thus, most metals at high temperatures, and 
platinum in a state of minute division at low 
temperatures, as well as various porous sub- 


* Edinb. Phil. Journal, vol, xxi. 


154 


stances slightly heated, produce the union of 
oxygen and hydrogen in an explosive mixture. 
The action of sulphuric acid on alcohol in pro- 
ducing ether, without itself undergoing change, 
appears referable to the same class along with 
those just described. We may consider it 
proved, then, that many substances possess 
the power of exercising upon compound bodies 
an influence essentially distinct from what is 
known as chemical affinity—an influence which 
consists in the production of a displacement 
and new arrangement of their elements, without 
themselves directly participating in it. Assu- 
redly such a power, which is capable of effect- 
ing chemical reactions in inorganic substances 
as well as in organised bodies, though still too 
little known to be accurately explained, must 
play a far more important part throughout na- 
ture than we have hitherto been led to suppose. 
“ In defining it a new power,” says Berzelius 
with philosophic caution, “ I am far from 
wishing to deny that some connexion exists 
between its influences and the electro-chemical 
ones with which we are familiar. On the con- 
trary, I am very much disposed to recognize 
it as a peculiar manifestation of these same 
influences.”* 

Another interesting series of facts, which 
seem to confirm the theory of the operation 
of chemical affinity in the living body, is that 
which relates to the evolution of electricity 
during the ordinary processes of growth both 
in plants and animals. The late researches of 
Dr. Faraday have fully proved the identity of 
electrical attraction with chemical affinity, and 
have shown that all chemical changes are at- 
tended with a disturbance of electric equili- 
brium. If, therefore, the changes occasioned 
by the growth of organised systems are imme- 
diately governed by laws similar to those which 
preside over inorganic matter, we should ex- 
pect to find that electricity is constantly being 
developed by them in the same manner as we 
obtain it by chemical decomposition or recom- 
position. There is no deficiency of evidence that 
such is the case, as the results of late inquiries 
most abundantly testify.+ 

That chemists have not been more successful 
in imitating the operations of vital chemistry, 
by the artificial production of organic com- 
pounds, is due not only to their ignorance of 
the composition of such bodies, but to their 
want of acquaintance with the form or con- 
dition in which they must be brought together, 
in order to enter into the desired union. Every 
one conversant with chemical operations is well 
aware of the important influence thus exerted. 
A slight change of temperature, for example, 
often reverses the affinities of a body; and many 
elements are susceptible of particular actions 
when in a nascent state (i.e. when in the act 


* This eminent chemist has been quoted as an 
advocate of the doctrine of vital affinities. If such 
was formerly held by him, it is evident, from the 
tenor of the communication here referred to, that 
he has abandoned it. 

+ See the Author’s essay on the laws regulating 
vital and physical phenomena, in Edinb. Philos. 
Journal for April 1838; and Principles of General 
and Comparative Physiology, p. 379 et seq. 


LIFE. 


of being freed from some other combinatic 
which in their ordinary condition could not 
so affected. When it is considered, 
how little we know of the operation 
conditions in the laboratory of life, no 
will be felt that its results should often ap 
contrary to what might have been anti 
No reasonable ground has yet been 
for supposing that, if we had the pow 
bringing together the elements of any o1 
compound in their requisite states and p 
tions, the result would be any other 
which it is found to be in the living 
the agency of vitality, as Dr. Prout 
marks, “ does not change the prope 
elements, but simply combines them in 
which we cannot imitate.” : 
It is hoped that the foregoing statemen 
have established the probability (which 
that the present state of our kne le 
these subjects will allow us to assert) th 
affinities which hold together the eleme 
living bodies, and which govern the elabo 
of organic products, are the same as 
stantly operating in the world aro 
would seem, at any rate, premature te 
that the operations of vital chemistry a 
rected by distinct laws and due tor 
The designations organic and vital @ 
seem to have been employed by some ¥ 
to express only the peculiarities of the ¢ 
stances and conditions under which these 
usually operate, rather than any real 
in the nature of the powers themselves 
others appear to use them as provisional 
only, referring those effects to the operat 
vitality which chemistry is not yet im ac 
tion to explain. In the former sens¢ 
nifest that such employment of the ¢ 
jurious as leading to misconception. . 
latter it is petiahenn if it do not check i 
and create a prejudice against the recepti 
new facts. The period when all difficulty 
have vanished from the application of che 
laws to the phenomena of the vital ect 
may be very far distant; and in the 
“ we must be content with gathering a} 
dications which occasionally break out fro 
clouds of mystery in which the subject 
scured.” But it must not be left out 
that every fresh discovery adds to the | 
of these indications, and that they 
the same direction ; so that the probab 
the universal operation of chemical a 
the living body mes every day more 
and the difficulty in proving the existen 
distinct set of vital affinities is constan 
coming less easily surmounted. 
VI. Vita tity IN A DORMANT OR INA 
CONDITION.—There are many organised 
at particular periods of whose existen 
vital action seems to be suspended ; al 
may result either from the absence of 
muli necessary to maintain it, or fro 
change in the organism itself, by whieh 
comes for a time less capable of respon 
these stimuli. When vital action is suspé 
from the deficiency of external stimuli, | 
two things must happen ; either the vita 
the organism will be destroyed by the | 


= 


tegration of its tissues; or it may be preserved 
| consequence of the absence of those agents 
_ which ordinarily excite decomposition. The 
Occasional suspension of vital action from a 
shange in the organism itself, appears usually 
to result from a general law of periodicity, 
ich affects, more or less, all organised 
beings, producing the phenomena of sleep, 
“hybernation, &c.; but it may also arise from 
_ particular causes operating within the system, 
‘aSin syncope. Each of these cases will now 
be separately considered. 
— Dormant vitality of seeds, eggs, &c.—The 
condition of organised beings of which we have 
to treat—that in which vital action is sus- 
ed from the absence of the stimuli ne- 
ry to maintain it, and vitality never- 
heless preserved—is manifested in the most 
 rema able manner by the reproductive germs 
which are periodically separated from plants 
it id animals, and which are endowed with the 
| power of developing themselves into new indi- 
_ viduals when the requisite conditions are sup- 
plied to them. In the lowest classes of each 
Kingdom, it would appear that these germs are 
liberated from the parent unprovided with any 
means for the continuance of their development ; 
|_and that from the first, therefore, they rely upon 
| the surrounding elements for al/ the conditions 
of their active existence. It is beautifully pro- 
vided that, in proportion to the probable defi- 
ciency of some of these, should be the tenacity 
with which the apparently lifeless germs re- 
tain their vitality. The sporules of the fungi, 
which can only subsist on decaying organised 
Matter, seem universally diffused through the 
atmosphere, and ready to vegetate with the 
most extraordinary rapidity whenever a fitting 
nidus is afforded for their development. This, 
at least, appears the only feasible mode of ex- 
plaining their appearance in the forms of mould, 
mildew, &c. on all decaying surfaces; and 
that there is no improbability in the suppo- 
sition itself is shown by the estimate of Fries, 
who states that a single individual of reti- 
ularia maxima will emit above 10,000,000 of 
these germs, so minute as when collected to 
be scarcely visible to the naked eye, rather re- 
sembling thin smoke, and so light as to be 
wafted by every movement of the atmosphere, 
so that, he remarks, “ it is difficult to conceive 
a place from which they can be excluded.” 
Itseems more than probable that in a similar 
Manner is to be explained the appearance of 
_ infusorial animalcules in all situations adapted 
_ to their existence; and that their germs are 
_ constantly and universally diffused through the 
_ air, ready to commence the active exercise of 
ieir dormant properties whenever they meet 
— the stimuli to their development afforded 
_ by warmth, moisture, and decomposing organic 
atter.* 
We have no means of ascertaining the 
length of time during which this dormant vi- 
_ tality may be preserved. It would be difficult 
-. assign a limit to it, since it is scarcely con- 
eivable that any change can occur in the struc- 


* For an important experiment on this subject 
} reeently performed by Schultz, sce Edinburgh Phi- 
_losophical Journal, Oct, 1837. 


LIFE. 


155 


ture of these minute desiccated points which 
they do not undergo during ihe first few 
hours of their aerial residence; and we have 
no reason to believe that vitality can be de- 
stroyed without change of structure. With re- 
gard to the seeds of phanerogamic plants, we 
have more certain evidence, and this of a very 
interesting character. It is to be remarked, 
however, that in them, as in the eggs of 
higher animals, there is, besides the germ it- 
self, a reservoir of nutriment supplied by the 
parent, which enables the germ to ¢ontinue its 
development up to the point at which it be- 
comes fit to maintain its own existence, with- 
out any other than the ordinary assistance of 
vital stimuli. The germination of a seed, for 
example, requires only warmth, moisture, and 
the access of air, and is further accelerated by 
the absence of light?“and the hatching of an 
egg is dependent only on a temperature more or 
less elevated and the presence of air. Hence 
the necessity for so great a tenacity of vitality 
as that possessed by the germs of the simpler 
classes does not exist, and although under 
favourable circumstances the vitality of seeds 
may be prolonged for an almost indefinite 
period, they are more susceptible of the inju- 
rious influence of external agents, and their 
fertility is destroyed by changes of condition 
which would have no effect in the former case ; 
whilst the eggs of animals appear still less tena- 
cious of vitality, although in a few instances 
capable of retaining it for some time, even under 
considerable disadvantages, as will be presently 
noticed. 

The seeds of most plants which inhabit tem- 
perate climates are adapted to remain dormant 
during the winter, and may be preserved in 
dry airand moderate temperature for a consi- 
derable time. Some of those which had been 
kept in the Herbarium of Tournefort for up- 
wards of a century were found to have pre- 
served their fertility. But with regard to those 
which are brought from tropical climates there 
is greater uncertainty, and unless they have 
been carefully excluded from the contact of air 
and from variations of temperature, a large pro- 
portion are usually unproductive. Cases are of 
no unfrequent occurrence in which ground that 
has been turned up spontaneously produces 
plants dissimilar to any in their neighbourhood. 
There is no doubt that in some of these the 
seed is conveyed by the wind, and becomes 
developed in spots .which afford congenial 
soil, in the same manner as the germs of 
fungi and infusoria. Thus itis commonly ob- 
served that clover is ready to spring up on 
soils which have been rendered alkaline by the 
strewing of wood-ashes, or the burning of 
weeds ; and it is stated by Professor Graham 
that after any hill-pasture in Scotland has been 
laid dry and limed and the surface broken, 
white clover always makes its appearance. 
But there are many authentic facts which can 
only be explained on the supposition that the 
seeds of the newly-appearing plants have lain 
for a long period imbedded in the soil, at such 
a distance from the surface as to prevent the 
access of air and moisture, and that, retaining 
their vitality under these circumstances, they 


156 


have been excited to germination when at last 
exposed to the requisite conditions.* 

Most physiologists, at least, are content to 
adopt this explanation, seeing that it is con- 
formable to what is otherwise known of the 
persistence of vitality in seeds ; but it has been 
recently maintained that in such instances a 
— production takes places, similar to 
that which many philosophers have supposed 
to occur among the lower tribes of organised 
beings.t This is not the place to discuss such 
a theory, of which it would not perhaps be 
very difficult to show the absurdity; but the 
following case furnishes, we apprehend, a very 
satisfactory proof that seeds may preserve their 
vitality for an unlimited time, when the ex- 
ternal conditions are such as to prevent either 
the active exercise of their properties or the 
disorganisation of their structure. “ 1 have now 
before me,” says Professor Lindley,f “ three 
plants of raspberries whichhave been raised in the 
gardens of the Horticultural Society, from seeds 
taken from the stomach of a man, whose skele- 
ton was found thirty feet below the surface of 
the earth, at the bottom of a barrow which was 
opened near Dorchester. He had been buried 
with some coins of the Emperor Hadrian, and 
it is probable, therefore, that the seeds were six- 
teen or seventeen hundred years old.” 

In regard to eggs, no such examples are, we 
believe, on record ; nevertheless, there are some 
tribes of animals whose eggs are capable of 
being preserved for a considerable length of 
time, and of undergoing very severe treatment 
without loss of their vitality. Most insects de- 
posit their eggs sufficiently early in the summer 
for the larve to be hatched and attain their 
full growth before the autumn deprives them 
of their supply of food, and these pass the 
winter in the pupa state. But there are some 
which do not begin to lay until the activity of 
vegetation has nearly ceased, and their eggs 
remain undeveloped until the ensuing spring 
arouses both the animal and vegetable creation 
into life. The curious instincts which lead 
these insects to choose secure places for the de- 
position of their eggs, and to use other means 
of protecting them against cold and moisture, 
are described by Mr. Kirby ;§ and the same 
author points out the beautiful correspondence 
between the temperature required for the de- 
velopment of the buds of the plant and of the 
larve that prey upon them. It has been men- 
tioned in a former article|| that the eggs of the 
slug are capable of enduring a temperature of 
40°, and of being completely desiccated, with- 
out losing their fertility ; and it can scarcely be 
doubted, therefore, that these might preserve 
their vitality like the seeds of plants for an un- 


* For several cases of this kind related on the 
authority of Professor Graham, see Dr. Prichard’s 
Physical History of Man, third edit. vol. i. p. 39, 
&c.; and for a very curious instance communicated 
to the author of this article, see his Principles of 
General and Comparative Physiology, p. 141. 

t+ See Dr. Weissenborn’s papers in the Philo- 
sophical Magazine for 1838. 

¢ Introduction to Botany, p. 298. 

Kirby and — Entomology, vol. ii. p. 443. 
Voi. ii. p. 402. 


LIFE. 


— str if a aroused into 
nor disorganised by decomposing ager 
It will par to denied that the ag 
which are known to destroy the vitality 
seeds and eggs are such as are calculate 
produce important changes in their strue 
and composition, even though these be 
kind inappreciable by our present means « 
search. Thus most seeds are killed by a 
perature of 160°, which is that at whie 
ture of the vesicles of fecula takes plac 
the application of heat sufficient to dest 
Vitality of an egg coagulates its albumen 
electric shock is well known to be a po 
means of instantaneously extinguishi ng th 
properties of eggs or seeds; and althou 
precise alterations which it effects in the” 
ture or composition of their parts is not 
stood, it cannot be doubted that importa 
ganic changes are produced by so power 
agent. Cold, in like manner, probabl 
injuriously on most eggs and seeds as” 
plants, by causing the rupture of the cel 
their tissues through the expansion of the 
tained fluids in the act of freezing. — 
not mean to say that other changes are ne 
produced by such agents, but we 
these as evidences of the position with y¥ 
we started—that vitality is not destroyed b 
influence of external agents without a struc 
change of some kind being induced by 
operation. - 
But it is not during their emb 
merely, that the vital actions of living bei 
may be suspended by the deficiency of ext 
stimuli, and yet their vitality be preser 
Both the vegetable and animal kingdoms: 
numerous examples of such an occurrer 
all periods of existence, especially among 
lower tribes. Mosses, for instance, ofter 


ye 


pear completely desiccated in dry weather 
seem as if dead; whilst, on the applicatic 
moisture, they revive in all their pristine be: 
The curious Lycopodium of Peru exhibits 
torpor in a still more remarkable mat 
When desiccated by drought, it folds i 
leaves and contracts its roots so as to fot 
ball, which, apparently quite devoid of ani 
tion, is driven hither and thither by the 
as soon, however, as it reaches a moist § 
tion, it sends down its roots into the soil, 
unfolds to the atmosphere its leaves, wl 
from a dingy brown, speedily change to 
bright green of active vegetation. 
of Jericho is the subject of similar trans’ 
tions. Instances exactly parallel are furnis! 
by the animal kingdom. The common W 

animalcule is one of the most remark 
being capable of desiccation so complete: 
splinter if touched with the point of a 
and still preserving its vitality so as to 1 
when moistened.* In animals reduced 


a ee ee” ec ee ~~ ce. ee 


* This fact has been denied by some natur 
but the author can positively assert it n his 
experience. See Principles of Gen. and Cor 
Physiology, p. 90, note. From es ents | 
quent to the one there related, he is inclined 
believe that of two species of Rotéfer, s 
allied as to be usually considered the sam 
thus revivifiable, and the other not. 


a. 
“y 


LIFE. 


state of torpidity by cold, some vital action 
usually continues; and such cases cannot 
_ therefore be adduced under the present head. 
_ But instances are by no means rare in which 
the whole body has been frozen, and vital action 
has of course been completely suspended, yet 


Tg te the destruction of the power of renew- 


“ing them under more favourable circumstances. 
- Lister first noticed that he had found caterpil- 
lars so frozen, that when dropped into a glass 
they chinked like stones, but nevertheless re- 
_vived ; and this statement has been confirmed 
_ by Bonnet and others. The Papilio Brassice 
has been produced from a larva which had been 
" exposed to a frost of 0° Fahr., and which had 
become a lump of ice. Fishes are occasion- 
‘ally found imbedded in the ice of arctic seas ; 
and some of these revive when thawed. This 
tenacity of life appears greater, however, in the 
“Species which are confined to shallow lakes or 
age and which have not the power, there- 
fore, of escaping from the effects of cold. This 
is perhaps the proper place to mention those 
“undoubted cases in which insects have been 
ently killed by immersion in water or 
irit, continued for along period, and have 
_ yet revived on exposure to the air and sun. 
_ Without multiplying facts, then, it may be 
‘atl affirmed that many organised beings 
‘may retain their vital properties, in some in- 
“stances to an unlimited duration, while all vital 
activity or life is completely suspended, through 
absence of the stimuli necessary to main- 
in it; and that this preservation of vitality 
so close a relation to the resistance offered, 
y the structure and composition of the sub- 
“Stance possessing it, to the influence of disin- 
tegrating agents, that it may reasonably be 
msidered as a result of the maintenance of 
its normal constitution. The physiologist is 
‘hot yet in a condition to explain those diffe- 
a in strueture and composition which 
-enablesome organisms to offer a much greater re- 
‘sistance to such injurious influences than others ; 
but he considers himself entitled to assume that 
such exist in all, since there are many instances 
in which he is able to detect them. 
_ Suspension of vital action under other cir- 
cumstances.—We have next to consider those 
eases in which vitality is rendered for a time 
dormant, by causes originating in the system 
itself, rather than by the withdrawal of external 
Stimuli. Under this head we may place all 
those phenomena to which the name of hyber- 
nation is usually given; but which, as will 
presently be seen, cannot be appropriately de- 
Signated by that term. The greater number of 
hog indigenous to temperate climates un- 
ergo an annual series of phases, in which 
their vegetative processes exhibit every grada- 
tion from a torpor apparently complete to the 
most surprising activity. In many, indeed, 
is series of phases constitutes the whole of 
life; the individual ceasing to exist as soon as 
it has been once performed, and a new genera- 
tion called into existence.. In many more, a 
total suspension of activity appears to take 
place, as may be observed in plants whose 
Stems die annually, whilst the roots retain their 


157 


vitality. This condition exactly resembles that 
of certain animals which pass the winter ina 
state of profound torpor. In those, however, 
whose stems are woody and persistent, vital 
action does not seem to be completely checked 
even by a frosty atmosphere ; as late experi- 
ments show that a movement of sap takes 
place, though to a trifling degree, in the depth 
of winter. And, lastly, in evergreen plants, 
these changes of condition are less complete ; 
the activity of the vegetative processes being 
diminished by the partial withdrawal of their 
appropriate stimuli, but not being altogether 
suspended. Now although it is unquestion- 
able that this series of changes is greatly influ- 
enced by the successive alterations in the ex- 
ternal conditions of the beings, which the 
revolution of the seasons induces, it does not 
admit of doubt that itjs originally dependent 
on the peculiar constitution of the organism, 
by which a periodical diminution of its activity 
is occasioned. For nothing will prevent a 
plant from shedding its leaves nearly at its 
usual time ; and although by artificial heat, or 
by removal toa warmer climate, a new crop may 
be brought out within a short interval, this can 
only be effected by keeping in a state of activity 
the processes which ought to be at rest, so that 
an injurious influence is exerted on the general 
system like that which results from artificially- 
prolonged watchfulness in animals. Whena 
plant is reduced, by the periodical decay of its 
stem and leaves, to the state of a bulb or root, 
it seems almost to revert to that remarkable 
condition already described as peculiar to seeds ; 
the vitality of the structure being capable of 
remaining dormant for a considerable time, and 
of being then aroused into full activity by the 
appropriate stimuli. We are not aware of any 
authentic facts which fix the limit to the dura- 
tion of this condition. Instances have been 
related of the growth of bulbs unrolled from 
the envelopes of Egyptian mummies; but 
there is reason to believe that deception has 
been practised on this point upon the too-ready 
credulity of travellers. However, there can be 
no doubt that, under favourable circumstances, 
bulbsand roots may be preserved for many years ; 
the conditions necessary for this object being such 
as neither excite the vitality of the structure to 
action, nor occasion the disintegration of the 
latter and the consequent loss of its properties. 
The animal kingdom presents us with condi- 
tions very analogous to those just alluded to. 
In a large proportion of those inhabiting tem- 
perate climates, there is a periodic diminution 
of vital activity during the colder part of the 
year; but this, in the higher tribes at least, 
scarcely amounts to an absolute suspension, 
since the circulation, and the functions of nu- 
trition and secretion which depend on it, are 
carried on,though feebly. (See HyBERNATION.) 
It is easy to understand why this must be the 
case. The softer portions of the animal frame, 
which are most concerned in the processes of 
organic life, are not periodically cast off and 
renewed like the corresponding parts of plants ; 
and, if their integrity were not maintained by 
the circulation of nutritious fluid during their 


158 


inactive state, their normal constitution would 
be soon affected by their proneness to de- 
. composition, and their peculiar properties be 
bn nd lost. Amongst cold-blooded ani- 
mals, however, we find instances of more com- 
plete suspension of vital actions, which may 
even be prolonged for a considerable period. 
Thus, Spallanzani kept frogs, salamanders, and 
snakes, in a torpid state, in an ice-house, where 
they remained three years and a half, and rea- 
dily revived when again exposed to the influ- 
ence of a warm atmosphere. Insects, in their 
pupa state, may be regarded as analogous to 
plants reduced to bulbs. Although the dura- 
tion of this torpid condition is ordinarily deter- 
minate for each species, and although some 
changes occur during its continuance which 
scarcely warrant us in characterising the state 
as one of entire inactivity, there are some in- 
stances which prove that it may be prolonged 
for an almost indefinite period, under particular 
circumstances. The degree of temperature to 
which pupe are exposed seems to have the 
same kind of influence over them as on the 
eggs of insects. Thus Reaumur found that 
pupe, which would not naturally have been 
disclosed until May, might be caused to un- 
dergo their metamorphosis in a fortnight during 
the depth of winter, by the influence of artifi- 
cial heat; and, on the other hand, that their 
change might be delayed a whole year beyond 
its usual time, by the prolonged influence of a 
cold atmosphere. We can scarcely imagine, 
however, that temperature is the so/e agent in 
accelerating or retarding the final metamor- 
phosis. If the caterpillar of Papilio Macha- 
on, one of those which has annually a double 
brood, becomes a pupa in July, the butterfly 
will appear in thirteen days; if not until Sep- 
tember, it will not make its appearance until 
the June following, that is, not in less than 
nine or ten months. Here it is evident that the 
torpor has been prolonged from some cause in- 
herent in the system itself, for the purpose of 
preventing the disclosure of the butterfly at too 
early a period of the season. A still more cu- 
rious proof of this tendency to prolonged tor- 

idity during the pupa state is the following. 
Tt a number of the pupez of the Eriogaster 
lanestris, a moth whose lJarve are common on 
the blackthorn in June, be selected at the 
same time, and placed in the same circum- 
stances, the greater number of them will dis- 
cluse the perfect insect in the February follow- 
ing; some not until the February of the year 
ensuing ; and the remainder not before the same 
month in the third year. The same has been 
observed of the <Arclea mendica, of which 
thirty-six pupa, grown from eggs laid by the 
same parent, produced twelve perfect insects in 
each of the three following seasons.* The final 
cause of this curious tendency may be, as sur- 
mised by Mr. Kirby, to secure the race from 
being cut off by unfavourable seasons, or by 
some extraordinary increase of its natural ene- 
mies. But its efficient cause can only be looked 
for in some modification of the properties of 


* Kirby and Spence’s Entomology, vol, iii. p. 266. 


LIFE. 


a 0 _—— 7 rs ” 


nee Oe 


the organism analogous to that wl 
he phenomena of hylan inc her ani 
e same periodicity, manifesting itself, n 
dallas eo diminished temperatu 
the season of greatest heat, is obse i 
pical climates. Many tribes of insects i 
torrid zone seem to retire to places of re 
during the parching droughts of summe 
make their appearance again during the 
season, when vegetation is in the highes' 
riance. We here trace the e 
adaptation of the phases of animal an 
table life as in the former instances; 
efficient cause which induces these ¢€ 
must be different. 
Our limits do not allow us to dilat 
one very interesting department of this § 
—the prolongation of dormant vitality 
particular circumstances in frogs and 
reptiles. Many marvellous stories of thi 
are on record ;—such as the inclosure 0 
animals in solid blocks of granite or 
igneous rocks, which no well-informe 1 
can credit. There are, however, a sufi 
number of authentic cases to prove, in th 
mation of those who have fairly exan 
them, that toads and other reptiles may] 
closed in masses of rock apparently so 
in the substance of the trunks e 
that they may preserve their vitality unde 
circumstances for a very long period. J 
former instances, it would appear hat th 
mal has fallen into a chink or crevice, 
has been gradually filled up by the wash 
of gravel or other materials disposed t¢ 
dify ; and that thus the a ce of | 
mass has been given, when in reality son 
munication has existed between the cavil 
the external air. It is by no means impos 
moreover, that these animals might be 
imbedded in the sandstones at prese 
course of formation in many localiti 
rocks possessing considerable hardn 
being at the same time sufficiently fp 
allow of the slow passage of air th roug 
substance. Where toads have becom 
bedded in crevices of trees, and bee 
rounded by new layers of wood, it is¢ 
that a direct communication with the a 
phere will probably exist by means 
ginal crevice, although it may be mue 
rowed ; but even if this be not the eas 
porosity of the wood will furnish the re 
condition. Some amount of access — 
would seem, from the experiments of 4 
wards and Dr. Buckland, to be essential 
prolonged vitality of toads enclosed in 
masses ; and this will probably maintain ¢ 
feeble respiratory action upon the blood th 
the general surface, just sufficient to p 
the decomposition of the body. Vital | 
cannot, therefore, be regarded as so comy 
extinct under these circumstances as 1 
of the cases formerly mentioned, where 1 
plication of cold has not only comp! 
checked it, but has also done away wi 
necessity for it, by completely subduit 
tendency to decomposition. ia 


In the human economy, as in that of 
ite 


be 


My, 


_. 
Se 
. 


on-hybernating animals, it is only occasion- 
ly that anything approaching to this suspen- 
on of vital action can occur. That which 
akes place during sleep only relates to the 
sorial functions; the organic changes expe- 
cing but little diminution in activity. The 
eness of the connection hetween their vital 
ations, and the immediate dependence of 
hese upon external stimuli, involve the de- 
struction of life when they are totally with- 
drawn ; and it is only under peculiar conditions 
of the organism itself, that we ever witness a 
uspension of vital action without the speedy 
supervention of death. Indeed it may be 
‘fairly questioned whether such suspension can 
er completely take place; and whether the 
nges which occur in the periphery of the 
‘culation are not continuing, however feebly, 
when no action can be detected at the 
‘centre. This condition is termed syncope ; and 
| its phenomena will be more fully detailed here- 
after. (See Syncope.) We are inclined to think 
that, where a state of apparent death has conti- 
ued for some days, vital action was never 
mtirely suspended ; though perhaps its cessa- 
tion may be more complete where the syncope 
‘is but transient. Such would seem to be the 
ge where individuals have recovered from a 
ubmersion under water, which has been pro- 
onged beyond the few minutes that suffice to 
oduce asphyxia. It is generally supposed, 
ind we think with reason, that the mental emo- 
tion experienced at the moment of submersion 
oduces a state of syncope; and that the or- 
anism, being in that state less dependent on 
| external stimuli than when in a more active 
‘condition, can bear privations which would be 
Otherwise fatal, just as is known to be the case 
vith hybernating animals, the pupe of insects, 
ce. The well-known case of Col. Townsend 
appears to us to prove that an apparent cessa- 
tion of vital action does not imply its entire 
‘€xtinction ; since when no changes could be 
| etected by his medical attendants, he was vo- 


= Re ee Me 


Tuntarily acting on his system both to retard and 
Tenew its usual functions. Dr. Cleghorn of 
Glasgow knew an individual who could control 
the action of his heart, so as to be able to feign 
death at pleasure. . 
_ Although in these cases we may be disin- 
clined to admit the ¢ofal suspension of vital 
action, there can be no doubt that it may occur 
in portions of the human body under the influ- 
nce of cold, and that, if carefully treated, it 
‘May be again renewed. Nay more ;—there is 
undoubted evidence that portions of the body, 
fier being totally separated from it, may be 
Teunited and made again to form integrant parts 
of the structure, if no disorganisation has taken 
place in the interval. That such an occurrence 
Is perfectly consonant with the doctrines which 
we have maintained regarding the connection 
between vitality and organisation—will be at 
Once evident; but we do not see how it can be 
satisfactorily explained by the advocates of the 
loctrine of a separate life or vital principle. 
Does the finger or nose which has been cut off 
a with it a chip or off-shoot of the parent 
ital principle or organic agent? If so, when 
does that quit ifs material tenement? There 


| 


& 


LIFE. 


159 


is no evidence of its existence in the separated 
part, which is completely dead to the general 
structure, and which nothing prevents from 
speedy decay, if its vital actions be not soon 
renewed. And if it be supposed to remain, it 
must again become merged in its parent prin- 
ciple, when re-union of the divided parts has 
taken place, or must submit to it like a dutiful 
child. There is no end to the absurdities in 
which those may be involved, who adhere with 
pertinacity to a doctrine so useless and so un- 
philosophical as that of a single controlling 
agent or power, presiding over the affairs of 
each organism. 

It is with much satisfaction that the author 
of the foregoing article (which was written 
above a year ago) refers his readers to the re- 
cently published Supplement on the Atomic 
Lheory, by Dr. Daubeny, for a full discussion 
of the question briefly cpnsidered in§ V. The 
conclusions at which The learned Professor has 
arrived are of precisely the same character as 
those for which the author has here argued, and 
are expressed in almost the same language. 
The following passages may be extracted from 
among many of great interest. 

“ There is little doubt that it will eventually 
appear, that all the secretions or excretions of 
animals and vegetables are only so far de- 
pendent upon life, inasmuch as, in consequence 
of the favourable temperature which it sustains, 
the constant circulation of the fluids it occasions, 
and their exposure to external agents in vessels 
of different shapes and dimensions, a mechani- 
cal separation of the ingredients of the blood is 
effected in some instances, and a chemical 
change produced in its composition by catalytic 
action in others.” ‘The putrefaction of vege- 
tableand animal matters appears to be produced, 
not by any sudden cessation of those affinities 
which had previously bound their respective 
elements together, but by the predominance 
over them of the natural forces, which we may 
without much difficulty conceive to have been 
controlled under the circumstances in which the 
living body is placed; nor does there seem any 
sufficient reason for calling in the intervention 
of an occult principle to explain that, to the 
solution of which by known causes, every fresh 
advance in chemical knowledge seems to bring 
us into closer approximation.” ‘ [tis now cer- 
tain that the same simple laws of composition 
pervade the whole creation; and that, if the 
organic chemist only takes the requisite pre- 
cautions to avoid resolving into their ultimate 
elements the proximate principles upon which 
he operates, the results of his analysis will show 
that they were combined ‘precisely according to 
the same plan as the elements of the mineral 
bodies are known to be.” 


BIBLIOGRAPHY.—Besides the systematic Trea- 
tises on physiological science by Haller, Cullen, 
Blumenbach, Dumas, Richerand, Treviranus, Ru- 
dolph, Magendie, Bostock, Tiedemann, Mayo, Ade- 
lon, Burdach, Alison, Roget, Fletcher, Dunglison, 
Arnold, Miiller, Carpenter, and others,—the fol- 
lowing, among the almost innumerable writings on 
the subject, may be advantageously consulted. 

Aristotle, Opera. Cicero, Quest. Tusc. lib. i. 
Idem, De nat. deorum. Lucretius, De rerum na- 
turd. Bacon, Historia vite et mortis, Harvey, 


160 


De generatione animalium, Lond. 1651. Glisson, 
De viti naturali, Lond. 1672. Stahl, De vita, 
Halle, 1701. De Gorter, De actione viventium 
particulari, Amstel. 1748. Hoffman, Dissertatio 
vite animalis, Halle, 1731. Bonnet, sur les corps 
organisés, Amst. 1776. Brown, Elementa medi- 
cine, Edinb. 1780. Priestley, On matter and spirit, 
Birm. 1782. Hunter, On the animal economy, 
Lond. 1786. Darwin, Zoonomia, Lond. 1794. Cu- 
vier, Lecons d’ anat. comp., Paris, 1799. Bichat, 
Sur la vie et la mort, Paris, 1802. Oken, Abriss 
des Systems der Biologie, Goett. 1805. Wolff, 
Ideen iiber Lebenskraft, Altona, 1806. Abernethy, 
On Hunter’s Theory of Life, Lond. 1814. Law- 
rence, Lectures on physiology, &c. Lond. 1816. 
Philip, On the laws of the vital functions, Lond. 
1817. Pring, On the laws of organic life, Lond. 
1819. Barclay, On life and organisation, Edinb. 
1822. Good, Study of medicine, Lond. 1825. 
Prichard, On the vital principle, Lond, 1829. Bell, 
Bridgwater treatise, Lond. 1833. Prout, Bridg- 
water treatise, Lond. 1834. Roberton, On life and 
mind, Lond. 1836. Clark, Report on physiology to 
Brit. Assoc. 1834. Reél, Von der Lebenskraft, in 


Archiv. I. B. 
( W. B. Carpenter.) 


LIVER, Normat Anatomy.—Syn. Gr. 
umae; Lat. jecur, hepar; Fran. foie; Germ. 
Leber ; Ital. fegato. The liver is a conglo- 
merate gland of large size, appended to the 
alimentary canal, and performing the double 
office of separating certain impurities from the 
venous blood of the chylopoietic viscera, pre- 
viously to its return into the general circulation, 
and of secreting a fluid necessary to digestion— 
the bile. 

It is situated in the abdomen, in the right 
hypochondriac region, and extends across the 
epigastrium into the left hypochondriac region. 
Superiorly it ascends to a level with the sixth 
or seventh rib, diminishing the cavity of the 
chest on the right side, and inferiorly it ap- 
proaches by its anterior border, the lower mar- 
gin of the thorax. 

The general form of the liver is flattened, 
being broad and thick towards the right ex- 
tremity, and narrow and thin towards the left. 
Glisson compared its shape to the segment of 
an ovoid cut obliquely in the direction of its 
length, and Dr. Alexander Monro to the hoof 
of an ox rounded superiorly. [ts superior 
surface is convex ; the inferior irregularly con- 
cave ; the posterior border is thick and rounded, 
and the anterior thin and sharp. 

Its position in the abdomen is oblique, the 
convex surface, in the erect posture of the body, 
being directed upwards and forwards, and the 
concave downwards and backwards. The broad 
border is posterior and superior, and the thin 
margin anterior and inferior. If the trunk be 
inclined forwards the free edge of the liver 
may be felt, extending below the margin of the 
thorax. 

It is in relation by its convex surface, su- 
periorly with the diaphragm, which separates it 
from the under surface of the right lung and 
from the heart ; anteriorly with the diaphragm 
and transversalis muscle, and with the sheath 
of the rectus and linea alba at the epigastrium ; 
and on the right side with the diaphragm and 
transversalis muscle, which are interposed be- 
tween it and the seven or eight lower ribs, 
Its inferior or concave surface. is in relation 


—e 


NORMAL ANATOMY OF THE LIVER. 


2 =. 


with the anterior aspect of the sto 
ascending portion of the duodenum, 
verse colon, the right supra-renal ca 
the right kidney, and sometimes 
extremity with the upper end of the sp 
The posterior border rests against the 
phragm, which intervenes between it at 
vertebral column, and is in contact w 
inferior vena cava, cesophagus, and ri 
mogastric nerve. The anterior bo 
and in relation with the transverss 
which separates it from the cartil 
lower ribs, with the round ligament 
notch, and with the sheath of the ree 
linea alba at the epigastrium. @ 

The liver is retained in its place by « 
tures of peritoneum which pass bet 
convex surface and posterior border 
diaphragm, and by a fibrous cord — 
crosses from the linea alba to the inferio 
cava. These are the ligaments of the 
they are five in number, the broad, tl 
lateral, the coronary, and the round lig: 


Se.>77 
6 


The upper or convex surface of the li er. 


No 1, the right lobe ; 2, the left lobe; 3. 
of the lobus Spigelii seen projecting bey 
eerie border; 4, 4, the anterior or 
order ; 5, the notch in the anterior borde 
gives passage to the round ligament 12; 6, 
posterior or rounded bord r; 7, the broa 
ment; 8, the left lateral ligament; 9, t 
lateral ligament; 10, the point of sep 
of the layers of the right lateral ligament 
close the oval space, 11,11; 12, the rom 
ment; 13, the fundus of the gall-blad 
jecting beyond the anterior margin of the 
The notch upon the anterior margin corres} 
with the gall-bladder is also seen ; 14, the i 
vena cava emerging from the liver in the ¢ 
the oval space of the coronary ligament, 
small vessels seen ramifying upon the sv 
the organ are superficial lymphatics, 


The broad ligament, (fig. 32, 7) 
form, longitudinal, 1. latum, 1. susper 
hepatis) is an antero-posterior duplica 
peritoneum which extends from the ne 
the anterior margin of the liver to the § 
part of its posterior border. It is bi 
front where it incloses the round ligamet 
becomes narrow as it passes backy 
its synonym, falciform. It serves to” 
the convex surface of the liver with 
alba and diaphragm. “ 

The luteral ligaments (fig. 32, € 


NORMAL ANATOMY OF THE LIVER. 


peels) are two triangular folds of peri- 
‘toneum which commence at each extremity of 


the posterior border of the liver and converge 
towards the termination of the broad ligament. 


They are broad near the extremities of the or- 
fan, and permit of a certain degree of motion 
in the right and left lobes, but become narrow 
is they approach the middle line. The two 
“layers which compose the right lateral ligament 
separate as they pass inwards, and partly inclose 
in oval space (11, 11) of variable size, which 
4s uncovered by peritoneum and in close con- 
act with the diaphragm; the remainder of the 
Space is bounded by the division of the layers 
of the broad and left lateral ligaments. The 
peritoneum surrounding this space, with the 
contained cellular tissue, which is large in quan- 
tity and connects the posterior border of the 
liver firmly with the right leaflet of the central 
tendon of the diaphragm, constitutes the co- 
ligament. The inferior vena cava (14) 
srges from the liver at about the middle of 
his space previously to its passage through the 
“quadrilateral opening in the tendon of the dia- 
“phragm. The left lateral ligament, near to its 
extremity, advances a little upon the upper sur- 
face of the left lobe. 
The round ligament, (fig. 33, 12) (ligamen- 
im teres, umbilicale) is a rounded fibrous 
i rd resulting from the obliteration of the um- 
bilical vein of the foetus. It is contained in 
the anterior margin of the broad ligament, and 
nay be traced forwards along the linea alba to 
he umbilicus, and backwards through the notch 
im the anterior border of the liver and along 
tl i longitudinal fissure to the posterior border, 
Where it is connected with the coats of the 
inferior vena cava. 
_ Turning to the under surface of the liver we 
have to examine certain jissures which divide 
his aspect of the organ into lobes; the fissures 
ue five in number ; the longitudinal, the fis- 
re for the ductus venosus, the transverse, the 
sure for the gall-bladder, and the fissure for 
e vena cava. 
_ The longitudinal fissure, (fig. 33, 4, 4) (sul- 
cus longitudinalis, umbilicalis, horizontalis) 
extends, as it name implies, longitudinally 
across the concave surface of the liver from the 
notch on the free margin of the organ to its 
posterior border. At about two-thirds from 
ihe anterior border it is met by a short fissure, 
the transverse, which joins it at right angles. 
the longitudinal fissure up to this pomt is 
deep and is generally covered in by an arch of 
val lable breadth (pons hepatis, fig. 33, 19) 
vhich connects the adjoining sides of the right 
left lobes ; beyond this point it is shallow 
nd takes the name of fissure for the ductus 
eno (5) from containing the fibrous cord 
nto which the ductus venosus is converted 
ter the cessation of fetal circulation. The 
ongitudinal fissure marks the division of the 
yer upon its under surface into a right and 
eft lobe, and contains the fibious cord of the 
found ligament, which is the degenerated um- 
jilical vein of the foetus. Opposite the ex- 
ity of the transverse fissure the fibrous 
jord is often partially dilated and communi- 
| VOL. Trr. ‘ 


: 
‘ 
: 


161 
Fig. 33. 


The under or concaypfsurface of the liver. 


Nos. 1, 1, the anterior border ; 2, 2, the posterior 
border; 3, the notch upon the anterior border; 
4, 4, the longitudinal fissure containing the fibrous 
cord of the round ligament ; 5, the fissure for the 
ductus venosus ; 6, the transverse fissure; 7, the 
point of union of the three fissures, the longitudinal, 
the transverse, and that for the ductus venosus ; 
9, the portal vein in the transverse fissure, the 
hepatic artery, and the trunk of the ductus commu- 
nis choledochus ; 11, the cystic duct; 12, the gall- 
bladder; 13, 13, the inferior vena cava passing 
through its fissure; 14, the cord of the ductus 
venosus, joining the inferior cava as that vessel 
emerges from the substance of the liver; 15, part 
of the oval space on the posterior border of the 
liver; 16, the right lobe; 17, the left lobe; 18, 
the lobulus quadratus; 19, the pons hepatis; 20, 
the lobus Spigelii ; 21, the lobus caudatus. 


cates with the portal vein. This is an indica- 
tion of the natural inosculation subsisting 
between these two vessels during intra-uterine 
existence. 

The transverse fissure (fig. 33, 6) (sulcus 
transversus, sulcus vene porte) is short and 
deep and about two inches in length; it com- 
mences near the middle of the under surface 
of the right lobe and passes transversely in- 
wards to join the longitudinal fissure. It is 
the hilus of admission to the vessels of the 
liver, and gives passage to the hepatic artery, 
portal vein, and hepatic ducts, as well as to the 
lymphatics and nerves. The transverse fissure 
is bounded before and behind by the elevated 
borders of the lobus  quadratus and lobus 
Spigelii. These lobes were named by the older 
anatomists the portal eminences, and were con- 
sidered as the pillars which flanked the en- 
trance to this great portal of the liver. 

The fissure or rather the fossa for the gall- 
bladder 1s the shallow angular depression which 
lodges the biliary sac. It is broad in front and 
generally marked by a notch upon the anterior 
border of the liver, and narrows as it passes 
backwards. It is situated in the right lobe 
and runs parallel with the jongitudinal fissure, 
while posteriorly it opens into the commence- 
ment of the transverse fissure. 

The fissure for the vena cava (fig. 33) is 
situated in the same longitudinal line with the 
preceding, but upon the posterior border of 
the liver. It commences at the under surface 
of the organ and terminates upon the upper 
part of the posterior border at about the middle 

M 


162 


of the oval space inclosed by the coronary liga- 
ment. This fissure is always very deep and 
surrounds the vena cava for two-thirds or three- 
‘fourths of its cylinder. Sometimes it is con- 
verted into a canal by a thin layer which is 
stretched across it from the lobus Spigelii to 
the contiguous border of the right lobe. The 
hepatic veins pour their blood into this portion 
of the vena cava. 

These five fissures taken collectively, namely, 
the longitudinal fissure and fissure for the 
ductus venosus on the left, the fissures for the 

|-bladder and vena cava on the right, with 
e transverse fissure passing between them, are 
represented by Meckel as resembling the letter 
H, whereof the transverse bar is placed nearer 
to the posterior than to the anterior extremity. 
Viewing them in this way the two anterior 
branches are, the longitudinal fissure on the 
left and the fossa for the gall-bladder on the 
right; and the two posterior are, the fissure 
for the ductus venosus on the left, and the 
fissure for the vena cava on the right. 
The existence of these five fissures upon 
the under surface of the liver causes its division 
into as many portions, which are named lobes, 
viz. the right, the left, the lobus quadratus, 
the lobus Spigelii, and the lobus caudatus. 
The right lobe, (fig. 32, 1, fig. 33, 
16,) (lobus major) is the largest division 
of the liver, and forms the whole of the bulky 
right extremity of the organ. It is convex 
upon its upper surface and irregularly con- 
cave below; at its right extremity and be- 
hind it is thick and rounded, and thin and 
sharp in front. It is separated from the left 
lobe on its convex surface by the broad liga- 
ment; beneath by the longitudinal fissure and 
fissure for the ductus venosus, and in front by 
the notch on the free margin of the liver. The 
transverse fissure and the fissures for the vena 
cava and gall-bladder are situated on the under 
surface of this lobe and serve to limit the 
boundaries of the three minor lobes ; the lobus 
yar Spigelii, and caudatus. Upon 

is surface it is marked by three depressions, 
one in front, of large size, for the right ex- 
tremity of the transverse colon, and two behind, 
one for the right supra-renal capsule and ano- 
ther for the right kidney. 

The left lobe (fig. 32, 2, fig. 33, 17,) 
(lobus minor) is four or six times smaller than 
the right; flattened in form, and thinned to- 
wards its circumference into a sharp margin. 
It is divided from the right lobe by the broad 
ligament above, by the notch in the anterior 
margin of the liver in front, and by the longi- 
tudinal fissure and fissure for the ductus ve- 
nosus below. seperti it is convex and in 
relation with the diaphragm, to which it is con- 
nected by the left lateral ligament, and infe- 
riorly it is concave, and presents a broad and 
shallow depression which rests upon the ante- 
rior surface of the stomach. By its extremity 
it sometimes touches the spleen, and by its 
posterior border corresponds with the termina- 
tion of the esophagus and with the right pneu- 
mogastric nerve, 

he lobus quadratus (fig. 33, 18,) (ante- 


NORMAL ANATOMY OF THE LIVER. 


rior | eminence) is a quadrilateral a 
slightly elevated division situated upon 
under surface of the right lobe near to- 
middle line of the liver. It is bounded a 
riorly by the free margin of the organ, po 
riorly by the transverse fissure, to the le! 
the longitudinal fissure, and on the right b 
fossa for the gall-bladder. ‘. 

The lobus Spigelii (fig. 33, 20,) (po: 
portal eminence) is a prominent conic 
smaller than the preceding, and sit 
the posterior border of the liver, b 
two layers of the lesser omentum. Its b 
triangular, and bounded in front by the 
verse fissure ; on the left side by the f 
the ductus venosus, and on the right 
fissure for the vena cava and lobus 
which last connects it with the under su 
the right lobe. By its anterior border} 
relation with the portal vein, by its left 
with the fibrous cord of the ductus ve 
and by the right with the venacava. It 
terior extremity is received into the at 
communication between the fibrous core 
ductus venosus and the vena cava. 

The lobus caudatus (fig. 33, 21,) is | 
like appendage to the lobus he ‘Tt 
tremely diversified in form, bei om 
well developed and a distinct lobe; at 
times a mere vestige recognisible only t 
eye of the experienced anatomist. 1 
it is a slight ridge, merging into the sur 
the liver on either side, and at other t 
marked by a fissure on one side or @ 
both. Ordinarily it is an angular pro 
two or three inches in length; comm 
by a narrow isthmus from the lobus 
passing obliquely outwards and 
the side of the gall-bladder, and subsic 
its extremity into the surface of the right 
The depression on the under surface ¢ 
right lobe, in front of this process, is for 
ception of the curve of the ascending 
and the posterior depressions for the 
renal capsule and right kidney. 

The coverings of the liver are twofold, a: 
investment, which is obtained from the 
neum, and a proper fibrous capsule 
from the capsule of Glisson. The per 
encloses the whole of the liver with the’ 
tion of that part of the rior borde 
constitutes the oval space (fig. 32, 1 
33, 15,) and is surrounded by the ec 
ligament, of the fossa for the gall-blade 
fissure for the vena cava, and the tr 
fissure. The proper capsule is most 
upon those parts of the organ which : 
uncovered by the peritoneum, particu 
the oval space upon its posterior border. 

The alse of the liver varies consid 
both with the period of life and ¥ 
greater or smaller proportion of bloo 
contained within its vessels. Thus in 
it presents a light red colour, which ¢ 
into a reddish brown in the adult, and in 
in depth of shade with the age of the § 
If the individual have died from hemor 
the liver appears bleached and presents 
lowish grey tint; if from general conge 


it may assume a chocolate or purplish brown 
or a slate colour, and if from obstruction to the 
“bile-ducts, a variable shade of yellow. Its 
texture is firm and dense, but extremely fra- 
foc: the fracture presenting a granular appear- 


__ The dimensions of the liver are very consi- 
derable, as may be inferred by recollecting that 

his is the largest organ in the body. Through 
the longest diameter from the extremity of the 
Tight to the edge of the left lobe, it measures 
‘about twelve inches; from before backwards, 
through the transverse diameter of the right 
e, about seven inches, and through the thick- 
st part of the right lobe, in a vertical di- 
ion, about four inches. These measure- 
mts, however, can only be received as an 
oximation to the average, for the size of 
1 Organ varies in different individuals ; thus it 
larger in males than in females, and is more 
ky in persons of sedentary habits than in 
se who are robust and active. Its weight is 
bout five pounds; its relative weight to the 
entire body, as 1 to 36; and the specific gra- 
one half heavier than water. 


ewn that in 100 parts, there are, of 
BONE ae ess ti davies s'.s0e 61.79 
Solid matters ............ 
Of 100 parts of the solid matters, 
71.18 are soluble in water, hot or cold, or 
alcohol; and consist of, osmazome, 
stearine, elaine, resin, oleic and 
margaric acids, gelatine, and sali- 
vine. 
_ 28.72 are insoluble. 
2.034 are salts; viz. chloruret, phosphate of 
potash, phosphate of lime, and 
: oxide of iron. 
Bullocks’ liver, analysed by Braconnot, is, 
according to Berzelius, analogous to the pre- 
seding, the differences being dependent solely 
upon a difference of manipulation. 100 parts 
contain, 
55.50 water. 
_ 44.50 solid matters, composed of, 
Vessels and membranes . .18.94 
Soluble matters 
100 parts of the pulp of liver contained, 
58.64 water. 
20.19 dry albumen. 
6.07 matter very soluble in water ; slight- 
we ly in alcohol ; containing little 
Mt nitrogen. 
- 3.89 fat. 
0.64 chloruret of potash. 
0.47 phosphate of lime containing iron. 
0.10 salt of potash combined with a 
he combustible acid. 
Varieties in the liver may be referred to one 
ftwo heads—varieties in form, and varieties in 
sition. 
Varieties in form occasionally occur, but 
hey are more rare in the liver than in almost 
in} other organ of the body. I have seen the 
eft lobe so small as to appear but a mere ap- 
yendage to the right, being connected to it only 
ya thin and narrow isthmus. Cruveilhier re- 
ords an instance in which the left lobe was 


NORMAL ANATOMY OF THE LIVER. 


163 


attached to the right merely by a vascular pe- 
dicle about half an inch in length; the extre- 
mity of the lobe being adherent to the upper 
pait of the spleen. Deep and narrow grooves 
are occasionally seen upon the convex surface 
of the right lobe running in an antero-posterior 
direction ; they correspond with projecting fasci- 
culi of the diaphragm, and occur generally in 
women who have laced tightly. This surface . 
is also marked frequently in females with deep 
channels, which are formed by the pressure of 
the ribs, and are also the result of tight lacing. 
The liver is sometimes’ constricted in the 
middle from this causg,and a dense fibrous 
band, produced by thickening of the fibrous 
capsule, extends around it like a belt. The 
lobes are occasionally divided by deep fissures 
into several additional lobes ; the liver in this 
case presents a character which is normal 
amongst the lower animals. In a few in- 
stances the fossa for the gall-bladder has been 
found excavated so deeply as to render the 
fundus of the sac apparent through an open- 
ing on the upper surface of the liver, a pecu- 
liarity which is also normal amongst some of 
the lower tribes of animals. 

Varieties of position are more frequent than 
those of diversity of form. During utero-gesta- 
tion the liver is usually pressed considerably 
above its ordinary plane, so as to impede more 
or less the action of the diaphragm and pro- 
duce embarrassed respiration. In an extremely 
fat subject I once saw the diaphragm raised by 
the liver to a level with the fourth intercostal 
space, measured near to the sternum. In its 
natural position the thin margin of the liver 
scarcely reaches the border of the thorax, but 
in women who have laced tightly during youth 
nothing is more common than to find this edge 
forced several inches below the base of the 
thorax, and altered in its form. In these cases 
the direction of the aspects of the organ are 
likewise changed ; the convex surface looks di- 
rectly forwards, instead of upwards and for- 
wards, and lies in contact with the abdomina 
parietes. The concave surface is directed back - 
wards in place of downwards and backwards, 
and the posterior border is forced upwards. 
In a sketch from the subject, now before me, 
the greater part of the convex surface of the 
organ is in contact with the abdominal pa- 
rietes, and the free margin extends into the 
umbilical and lumbar regions. In another 
sketch, as a result of the enormous magnitude 
of the stomach from the same cause, the liver 
is raised almost perpendicularly, the extremity 
of the left lobe being in contact with the dia- 
phragm, and the right lobe in the right iliac 
fossa. A part of the liver has been found in 
the sac* of inguinal and umbilical hernia. 
Various peculiar appearances are observed in 
the liver of the foetus arising from arrest of 
development. Thus, for instance, the entire 
organ, or a part of it, may be situated in the 
chest, or from absence of development of the 
abdominal parietes the liver may form part of 


* Gunzius de Herniis, in Portal’s Anatomie Mé- 


dicale, 
M 2 


164 


an exabdominal tumour, and be uncovered ex- 
cepting by the membranes of the ovum. But 
the most interesting and unexplained form of 
‘altered position is that in which the whole of 
the viscera of the body are trans , and the 
liver becomes placed on the left instead of the 
right side. These cases are generally perfect, 
and the peculiarity does not seem to interfere 
with the life or functions of the subject. The 
liver presents its natural form and size, and 
with the simple exception of left for right, pre- 
cisely the same relations. The aorta, of course, 
occupies the right side, and the vene cave the 
left, while the stomach is transferred to the 
right. Sir Astley Cooper has preserved the 
viscera of an adult who was the subject of 
this transposition. And a few years since I 
had the opportunity of examining a similar 
case in the body of Smithers, a man who 
was executed for committing arson accom- 
panied with loss of life in Oxford-street. The 
viscera of this man were eghen: healthy, the 
liver finely formed, and the general fabric ro- 


bust. 

The gall-bladder (fig. 33, 12,) (cystis 
fellea) is a membranous sac of a pyriform 
shape, situated in the shallow fossa upon the 
under surface of the right lobe, and lying pa- 
rallel with the longitudinal fissure. For con- 
venience of description it has been customary 
to divide it into a body, fundus, and neck 
(cervix), although no precise mark of division 
subsists between these parts. The body is the 
middle portion ; the fundus the expanded ex- 
tremity, which approaches the notch in the free 
border of the liver, and frequently extends be- 

ond it; and the neck the narrow and taper- 
ing portion of the sac which enters the right 
extremity of the transverse fissure and forms 
the cystic duct. 

The sac is in relation by its upper surface 
with the substance of the liver, and by the 
under part with the pylorus and ascending 
duodenum. The fundus corresponds with the 
right border of the rectus muscle, and may be 
felt in that situation when filled with gall- 
stones. 

The coats of the gall-bladder are three :—1. 
an external or serous covering derived from the 
peritoneum, which covers all that portion of 
the sac which is not in contact with the sub- 
stance of the liver. The gall-bladder is some- 
times completely surrounded by the peritoneum, 
and hangs loosely connected with the liver by a 
duplicature of that membrane. 2. A fibrous 
layer* (nervous) composed of cellulo-fibrous 
tissue intermingled with tendinous fibres; and, 
3..a mucous coat which lines the interior of the 
sac, and is continuous through the cystic and 
hepatic ducts with the mucous lining of the 
biliary structure of the liver, and through the 
ductus communis choledochus with the mu- 
cous membrane of the duodenum and ali- 
mentary canal. The internal surface of the 
mucous layer is raised into innumerable small 
ridges and folds (ruge) by the ramifications of 
the cystic artery and its capillaries, which give 


* In the ox, according to Monro, this coat is 
distinctly muscular. 


NORMAL ANATOMY OF THE LIVER. 


to it a peculiarly reticulated appearance, an 
the fl rece of the ruge are jepresiet il 
numerous small muciparous follicles. In th 
neck of the sac the mucous membrane is 
duced into from six to twelve small f{ 
forming a kind of spiral valve b Pans 
which the bile is regulated in its descent i 
the duodenum, and assisted in its entrance j 
the gall-bladder. The existence of this pe 
liar valvular apparatus gives to the neck ¢ 
gall-bladder a sacculated appearance. - 
cous membrane is but loosely connected 
the fibrous coat, and the cystic artery wi 
branches ramify hetween them. ‘ 
The excretory duct of the gall-bladd 
cystic, (fig. 33, 11); it is about 
and a half in length, and in diame 
equal to the cylinder of a crow’s quill. 
generally somewhat tortuous in its coursi 
appears sacculated from the continuatiot 
it of the spiral valve. Upon enterit 
transverse fissure it unites with the 
duct of the liver, the hepatic duct, 
junction of the two constitutes the d 
communis choledochus. The ductus ec 
choledochus, about three inches in h 
cends through the right border of the 
err lying in front of the portal ve 
to the right of the hepatic > a 
into the duodenum by TE ing or n 
tance obliquely between its coats. Itis 
to the other vessels in its course by the ¢e 
tissue of Glisson’s capsule, and near 
mination is considerably constricted. 
The excretory ducts of the liver and 
bladder have three coats, an external or 
coat, a reo or fibrous, and an intern 
cous. A question exists among physi 
as to the probable muscularity ¢ he 
coat in man; it is undoubtedly contractil 
in some few instances of obstruction ha 
sented an appearance very closely resem 
muscular fibres. Cruveilhier thinks the 
ture analogous to the dartos. In some 
as in the horse and dog, this coat is ¢ 
muscular, 
Varieties in the gall-bladder.— 
sometimes enormously dilated without a 
parent obstruction in its ducts. Occ 
in acephalous and anencephalous feetuse 
altogether absent. In a preparation now! 
me of the liver of a foetus at the full p 
which lived for several hours after b 
which presented, in anatomical s 
peculiarities dependent upon 2 
velopment, the most careful di 
failed to discover the slightest ind) 
gall-bladder. Among the lower mai 
in cats, a double or accesso 
by no means uncommon. Kierna' 
served several instances of this variety. — 
self have seen two, and have one 
before me. In the kinkaju an ac 
bladder is the normal character, 
liver of a small animal 
in the Museum of the College of & 
there are three gall-bladders. 
Structure of the liver.—The liver ; 
posed of lobules, of a connecting 


ture, | 
Ie 
; 


| 


NORMAL ANATOMY OF THE LIVER. 


called Glisson’s capsule, of the ramifications 
of the portal vein, hepatic duct, hepatic 
artery, hepatic veins, lymphatics and nerves. 
_ For an accurate knowledge of these different 
‘Structures, anatomy is indebted to the labours 
. of Mr. Kiernan, to whose paper on “ The 
enaromy and Physiology of the Liver,” con- 
tained in the Philosophical Transactions for 
_ 1833, I shall have constant occasion to refer. 
The small bodies (lobules, acini, corpuscula, 
glandular grains, granulations) of which the 
liver is composed were discovered by Wepfer 
im the liver of the pig, about two years pre- 
viously to the appearance of Malpighi’s cele- 
brated work, “ De Viscerum Structura Ex- 
ercitatio Anatomica.” Malpighi, unacquainted 
with Wepfer’s discovery, examined and des- 
tibed these bodies, both in animals and in 
man, under the name of /obules; and the lo- 
ules he found to consist of smaller bodies, 
ich he named acini. From some want of 
ecision in Malpighi’s descriptions, these two 
lames have been confounded by the majority 
succeeding anatomists; the term /obules, 
with its distinctive application, has been disre- 
parded and forgotten, and the term acini has 
ie een applied to those minute bodies of which 
. liver appears to be formed when examined 


oye 


Heneath the microscope with a moderate power, 
the acini of Malpighi. So great, indeed, is 
the confusion of terms even in 1838, that we 
find a justly celebrated authority in minute 
'anatomy, Miiller, in speaking of Kiernan’s 
discovery, using the following words. “ He” 
(Kiernan) “describes the lobules of the liver 
(which by other anatomists are termed acini),” 
and further on he observes: “ his description 
their form is indeed similar to that which 
we have given above of the acini of the mace- 
‘tated liver of the polar bear.” Now, setting 
‘aside the anachronism of discovery contained 
‘in the above quotation, which, as it appears to 
‘te, should have been, our description of the 
adcini of the polar bear is similar to his des- 

iption of the form of the lobules, inasmuch 
as Kiernan’s discovery was published in 1833, 
¥ Miiller’s description of the macerated liver 
of the polar bear in 1835, I cannot but feel 
‘somewhat surprised in observing that Miiller 
‘draws no line of distinction between the lo- 
‘bules and their supposed constituents the 

ini. Nay, that he would seem to imply that 
all anatomists were acquainted with the lo- 
bules, but that they assigned to them a dif- 
nt name. To prove that this is not the 
e, I quote a passage from his work upon 
the glands, published in 1830, in which he ex- 
ia himself unable to distinguish the ele- 
mentary structure of the liver either in man or 
in numerous other mammalia, for he says, “In 
homine, ut in plurimis mammalibus, in he- 
patis superficie certa quedam particularuam 

mentarium sive acinorum conformatio con- 
Spici non potest.” Now the question to be de- 
cided, is the meaning which he assigns in this 
quotation to the word acinorum ; does he mean 
by that word the lobules or the acini of Mal- 
vighi? The solution is simple; we have it in 
‘his own words, and exhibited in a figure in 


ra 


165 


which his peculiar views of the anatomy of 
the organ are clearly illustrated. In this fizure, 
(fig.217, page 485,) he says, “ Observantur 
fines ductuum biliferorum elongati, seu cylin- 
driformes acini, in fizuris ramosis et foliatis 
varie dispositi.”” So that the acini of Miiller 


- in 1830 are the terminations of the biliferous 


ducts, corresponding therefore with the acini of 
Malpighi, and the lobular biliary plexus of 
Kiernan. In 1835, as instanced in the “ ma- 
cerated liver of the polar bear,” the acini 
of Miiller are the lobules-of Malpighi and 
Kiernan. 

Now seeing this indecision of opiaion upon 
a subject of so great importance in relation to 
the proper understanding of the minute anatomy 
of the liver, I have deemed it my duty, in the 
service of anatomy, to place before my readers 
this cursory sketch of the history of the anatomy 
of the organ, and to establish the meaning of 
the terms I shall have occasion to use in des- 
cribing its intimate structure. By the word 
lobules I shall mean, not the acini of anato- 
mists, “ which are anything or everything or 
nothing as the case may be,” but the lobules of 
Malpighi and of Kiernan ;—by the word acini 
I shall indicate the smaller bodies of which 
the lobules appear to be composed (acini of 
Malpighi and of all writers); but which have 
been shewn by Kiernan to be the meshes of a 
plexus of biliary ducts, the “ lobular biliary 
plexus.” 

The lobules are small granular bodies of 
about the size of a millet-seed, of an irregular « 
form, and presenting a number of rounded pro- 
jecting processes upon their surface. When 
divided longitudinally (fig. 34) they have a 
foliated appearance, and transversely (fig. 35) 


A longitudinal section of a-sub-lobular vein. 

Nos. 1, 1, longitudinal sections of lobules, pre- 
senting a foliated appearance. 2, 2, superficial lo- 
bules terminating by a flat extremity upon the 
surface of the liver ; 3,3, the capsular surface of 
a lobule; 4, the bases of the lobules seen through 
the coats of the vein and forming the canal in which 
the sub-lobular vein is contained; 5, the intra-lo- 
bular vein commencing by minute venules at ashort 
distance from the nike surface of the lobule ; 
6, the intra-lobular vein of a superficial lobule com- 
mencing directly from the surface ; 7, the open- 
ings of the intra-lobular veins which issue from the 
centre of the base of each lobule; 8, the interlo~ 
bular fissures seen through the coats of the sub-lo- 
bular vein; 9, interlobular spaces. 


166 


an irregularly pentagonal or hexagonal outline 
with sharp or rounded angles in proportion to 
‘the van or greater quantity of Glisson’s 
capsule contained within the liver. Each 
lobule is divided upon its exterior into a 
base and a capsular surface. The base 
(fig. 34, 4) corresponds with one extremity 
of the lobule, is flattened and rests upon an 
hepatic vein, which is thence named sub-lobular, 
The capsular surface (fig. 34, 3, 3) includes 
the rest of the periphery of the lobule, and has 
received its designation from being inclosed in 
a cellular capsule derived from the capsule of 
Glisson. In the centre of each lobule is a 
small vein, the intra-lobular (fig. 34, 5, 6, 
Jig. 35, 3.) which is formed by the conver- 
gence of six or eight minute venules from the 
rounded processes situated upon the surface of 
the lobule. The intra-lobular vein thus con- 
stituted takes its course through the centre of 
the longitudinal axis of the lobule, pierces the 
middle of its base, and opens into the sub-lo- 
bular vein. The circumference of the lobule 
with the exception of its base, which is always 
closely attached to a sub-lobular vein, is con- 
nected by means of its cellular capsule withthe 
capsular surfaces of surrounding lobules. The 
cellular interval between the lobules is the in- 
terlobular fissure (fig. 34, 8, fig. 35, 2), and 
the angular interstices formed by the appo- 
sition of several lobules are the interlobular 


spaces (fig. 34, 9, fig. 35, 1). 


Angular lobules in a state of anemia. From Kiernan’s 


‘ . Sree AG 
No. 1, interlobular spaces, containing the larger 
interlobular branches of the portal vein, hepatic 
artery and duct ; 2, interlobular fissures ; 3, intra- 
lobular veins formed by minute venules which con- 
verge towards the centre of the lobules, 


The lobules present considerable variety of 
form dependent upon their situation and upon 
the manner in which they are examined. For 
instance, the section of a lobule divided trans- 
versely has an irregularly pentagonal or hexa- 
gonal figure, and longitudinally a foliated a 

rance. The lobules of the centre of the 
Fiver are angular and smaller than those of the 
surface, on account of the pressure to which, 
from their position, they are submitted by sur- 
rounding lobules. They are also more an- 
gular in some animals than in man. The sur- 
face of the liver of the cat, in which the portal 
vein is injected, has a beautiful reticulated ap- 
pearance produced by angular meshes of an 
hexagonal figure; the hexagonal outline being 


NORMAL ANATOMY OF THE LIVER. 


formed by the interlobular fissures, reddenex 
the injection in the minute branches of 
a vein, and the included area by the 

ule viewed upon its transverse diameter, 
a section of the liver made from the free ma 
to the posterior border in the direction of 
hepatic veins, the lobules are found te 
larger than in a section made transverse 
those vessels. The lobules of the exterior 
ticularly on the concave side and px 
border, are for the same reason lar 
lying obliquely to the surface and corr 
ing in direction with the course of the 
lobular veins. They are also more x 
from the absence of compression b 


ing lobules. But one appearance deseril 
Kiernan is peculiarly cheractoristigill 
bules which form the surface of the livi 
superficial lobules. The word surface 
instance does not refer simply to the p 
of the organ, but also to the various 
channelled through its interior for t 
of the portal vein, hepatic ducts, and 
artery, and also for the main trunks of 
patie vein, “ all these canals beiog si 
“tubular inflections inwards e 
= of the 7 ; The superficial - 
- 34, 2, . 35) are not terminat 
a rounded jah ane like those of the 
but are flat and apparently incomp 
though cut across by a transverse ine’ 
peculiar form gives to the anatomist a— 
surface which affords all the advantages 
servation of a transverse section, and @ 
him to detect by external examination tl 
tive condition of both the central port 
surface of the lobule. In these é 
the intra-lobular hepati¢ vein, instead of 
entirely concealed within the lobule, comm 
directly from the flat surface. A knowle 
this structure, says Kiernan, “ enables us 
jecting the hepatic veins to limit the in 
to this system of vessels, which is effec 
withdrawing the syringe when the ir 
pons in minute points upon the sw . 
iver.”” Occasionally double lobules, or 
having two coerce veins, are seel 
the surface. ; 
“ Each lobule,” according to Kierna 
composed of a plexus of bili cts 
venous plexus formed by candi of the 
vein, of a branch (intra-lobular) of an _ 
vein, and of minute arteries ; nerves anda 
ents, it is to be presumed, also enter int 
formation, but cannot be traced into 
“ Examined with ~ microettiias alo 
a ntly com of numerous” 
bodies of a valent colour, and of | 
forms, connected with each other by ¥ 
These minute bodies are the acini of M: 
“If an uninjected lobule be examine 
contrasted with an injected lobule, it} 
found that the acini of Mal ini he: 
are identical with the inj obular p 
the latter, and the bloodvessels in both 1 
easily distinguished from the ducts.” 
Guisson’s capsuLeE is the web of e 
tissue which envelopes the hopes rtery, 
vein, and ductus communis choledochus d 
their passage through the right border of the! 


we. 


NORMAL ANATOMY OF THE LIVER. 


omentum, and which accompanies them along 
the portal canals and interlobular fissures to 
their ultimate distribution in the substance of 
the lobules. It forms for each of the lobules a 
_ distinct capsule. which invests it on all sides 
_with the exception of its base, and is then ex- 
panded over the whole of the exterior of the 
» constituting the proper capsule of the 
liver. Glisson’s capsule serves to maintain the 
_ portal vein, hepatic artery, and hepatic ducts in 
‘connection with each other, and attaches them 
_also to the surface of the portal canals; it con- 
hects the trunks of the hepatic veins to the 
_ Surface of the canals in which they run ; it sup- 
j the lobules and binds them together, and 
its exterior expansion it invests and protects 
entire organ. But Glisson’s capsule, ob- 
es Kiernan, “ is not mere cellular tissue ; 
“it is to the liver what the pia mater is to the 
brain; it is a cellulo-vascular membrane, in 
which the vessels divide and subdivide to an 
"extreme degree of minuteness ; which lines the 
portal canals, forming sheaths for the larger ves- 
Sels contained in them, anda web in which the 
smaller vessels ramify; which enters the inter- 
Tobular fissures, and with the vessels forms the 
apsules of the lobules, and which finally enters 
@ lobules, and with the bloodvessels expands 
itself over the secreting biliary ducts. Hence 
arises a natural division of the capsule into three 
portions, a vaginal, an interlobular, and a lobu- 
rtion.”’ 
e vaginal portion of the capsule is loose 
d abundant; it occupies the portal canals 
and incloses the portal vein, hepatic duct, and 
epatic artery. In the larger canals (fig. 36, 
8,) it completely surrounds these vessels, but 
in the smaller ones (fig. 37,) is situated only 
On that side of the portal vein upon which 
he duct and artery are placed, the opposite side 
Of the vein being in contact with the capsular 
Surfaces of the lobules. It constitutes a me- 
dium for the ramification of the vaginal plexus 
rmed by the vein, artery, and duct, previously 
their entrance into the cellular interval of the 
terlobular fissures. 
_ The interlobular portion forms the cellular 
capsule for each of the lobules and the bond of 
ion between their contiguous surfaces. It 
pports the plexiform ramifications of the por- 
al vein, hepatic artery, and duct, and is the 
medium of vascular communication between 
all the lobules of the liver. 
_ The lobular portion forms sheaths for the 
Minute vessels which enter the lobules, and a 
oie parenchyma for the substance of those 
ies. 
_ The portal vein is formed by the union of the 
ie trunks which return the blood from the 
ylopoietic viscera, viz., the superior and in- 
ior mesenteric, the splenic, and gastric veins. 
Bp mencing behind the pancreas where all 
ese veins converge, the portal trunk ascends 
along the right border of the lesser omentum, 
lying behind the hepatic artery and ductus com- 
munis choledochus to the transverse fissure. 
At the transverse fissure it bifurcates into two 
tunks which enter the right and left lobes, 
and divide and subdivide as they take their 


167 


course through the portal canals, until they are 
ultimately lost in the substance of the lobules. 
The branches of the portal vein are accompanied 
throughout their course by branches of the hepatic 
duct and hepatic artery, and they are inclosed 
and connected to the capsular surfaces of the 
lobules forming the portal canals, by Glisson’s 
capsule. The branches of the portal vein are 
divisible into vaginal, interlobular, and lobular. 

The vaginal branches (fig 36, 3, fig. 38, f') 
are the small veins which ase-given off by the 
portal trunks during their passage through the 
portal canals, and which are intended to convey 


AN y "S\ 


“> 


~ 
‘ 


e) 


A transverse section of a large portal canal and its 
vessels. The lobules are in a state of general con- 
gestion, their central portions being more congested 
than their marginal portions. — From Kiernan’s 

japer. 

No. 1, Superficial lobules forming the parietes of 
the canal. In some the intra-lobular vein does not 
extend to the surface of the canal; this appearance 
depends upon the direction in which the incision is 
made. 2, The portal vein. 3, Vaginal branches 
arising from the vein and dividing into interlobular 
branches which enter the interlobular spaces. 
4, Hepatic duct. It is seen to give off vaginal 
branches which divide into interlobular ducts, the 
latter enter the interlobular spaces. 5, The hepatic 
artery ; itis seen giving off vaginal branches which 
divide into interlobular branches, and the latter 
enter the spaces with the branches of the portal 
vein and hepatic duct, 6, Three interlobular ves- 
sels, a duct, vein, and artery, entering each inter- 
lobular space. 7, A part of the vaginal plexus. 
8,8, Glisson’s capsule, which completely surrounds 
the vessels. 


their blood into the substance of the lobules. 
In the cellular sheath of Glisson’s capsule which 
surrounds the portal vein, they inosculate freely 
with each other and form, together with the va- 
ginal branches of the duct and artery, a vascu- 
lar plexus, named from its situation the vaginal 
plexus. This vaginal plexus establishes a com- 
munication between the vaginal veins through- 
out the portal canals, and serves to equalise the 
supply of blood to the lobules. Opposite each 
interlobular space an interlobular vein is given 
off, which enters between the lobules and rami- 
fies in the interlobular fissures. In the larger 
portal canals (fig. 36,) the vaginal plexus com- 
pletely surrounds the portal vein, hepatic duct 


168 


and hepaticartery, and the interlobular spaces are 
pecker 29 solely with branches which are derived 
fiom its ramifications. But in the smaller por- 
tal canals (fig. 37, fig. 38) the capsule of Glis- 
son, upon which the plexus chiefly depends, is 


WSS 
A transverse section of a small portal canal and its ves- 
sels, The lobules are in a state of general congestion. 

From Kiernan’s paper. 

No. 1, The portal vein; the greater part of its 
cylinder is in contact with the portal canal. 2, In- 
terlobular branches of the vein entering directly the 
interlobular spaces, with branches of the artery and 
duct, without ramifying in the canal. 3, Two vagi- 
nal branches arising from the vein, and forming a 
vaginal plexus on that side of the vein, which is 
separated from the canal by Glisson’s capsule. 
From the plexus the interlobular branches arise. 
4, The hepatic duct giving off vaginal branches. 5, 
The artery giving off vaginal branches. Glisson’s 
capsule is situated on one side only of the canal, 


situated only upon that side of the vein, on 
which the duct and artery are placed, and the 
vaginal plexus consequently follows the same 
disposition. On the opposite side the portal 
vein being in contact with the lobules, gives off 
interlobular branches directly to the spaces. If 
the portal vein (fig. 38) be laid open in this 
situation, the form of the lobules bounded by 
the interlobular fissures will be distinctly a 
parent through its coats, and the openings of the 
interlobular veins will be found to correspond 
with the interlobular spaces. 

The interlobular veins enter the intervals of 
the lobules through the interlobular spaces and 
divide into numerous minute branches, which 
ramify in the capsules of the lobules and then 
enter their substance. They cover with their ra- 
mifications the whole external surface of the lo- 
bules with the exception of their bases, and of 
those extremities of the superficial lobules which 
appear upon the surfaces of the liver. The 
interlobular veins communicate freely with each 
other and with the corresponding branches of 
adjoining lobules, and establish a general 
portal anastomosis of the freest kind through- 
out the entire liver. When the portal vein is 
well injected, these veins form a series of inos- 
culations which surround all the lobules and 
give to the surface of the organ the appearance 
of a vascular network composed of irregularly 
pentagonal and hexagonal meshes. If the vein 
be only partially injected the interlobular vein 
in the jnterlobaiar space is alone filled, and the 
branches which it sends off into the neighbour- 


Longheren section of a small portal vein 


he lobules are in a state of anewmia,—After 


nan. Ay 

a, Portions of the canal from which the 
removed to show that it is formed by lobules’ 
present the same appearance with those up 
external surface of the liver. 6, The side o 
portal vein which is in contact with the c al. 
side of the vein which is separated he 
by the hepatic artery and duct, by the Glis 
capsule surrounding them,and by the vaginal p) 
d, The internal surface of the portal vein, 
which is seen the outline of the lobules, at 
openings of the interlobular veins which corre 
with the ee acai Upon the oj 
side (c ), the portal vein being se fro 
rand dike A ite are no pa Fo pi é 
openings of smaller portal veins. f, Vaginal 
giving off branches in the portal canal and fo 
a plexus. g, The hepatic artery giving off ) 
branches. A, The hepatic duct giving off y 
branches, " 


ing interlobular fissures not proceeding 
as to inosculate and form meshes, ha 
radiated appearance and resemble a num 
minute stelle; these are the stellated ves 
anatomists. e 

The lobular veins are derived from the’ 
lobular veins; they form a plexus ¥ 
the lobule, and converge from the et 
ference towards the centre, where they term 
in the minute branches of the intralobular 
“This plexus, interposed h 


ews “cas coe 


between th 
lobular portal veins and the intralobularh 
vein, constitutes the venous part of the I 
and may be called the lobular venous pt 
‘fig. 39). The irregular islets of the sub 
of the lobules seen between the meshes 0} 
plexus by means of the microscope an 
acini of Malpighi, and are shown by & 
to be portions of the lobular biliary ph 

The portal vein collects the ve 
from the chylopoietic viscera, and 
lates it through the lobules ; it likewise rec 
the venous blood which results from the 
bution of the hepatic artery to the structt 
the liver; these two sources of supply cons 
the two origins of the portal vein, the abdon 
origin and the hepatic origin. 


ee oe ee ar se ee 


lobules, in which the portal venous plexus is seen. 
After Kiernan. 
££ a, Interlobular veins. The appearance of venous 
circles formed by these veins is that which is 
afforded by a common lens; when examined with 
higher power the interlobular fissure is seen to be 
filled by a vascular plexus. 6, The lobular venous 
‘plexus. ‘he circular and ovoid spaces seen be- 
een the branches of the plexuses are occupied by 
rtions of the biliary plexus: they are the acini 
Malpighi. c, The intralobular vein in the centre 
each lobule, collecting the blood from the lobu- 
ar venous plexus. 


_ The hepatic duct bifurcates in the transverse 
fissure into two branches, which enter the right 
d left lobes of the liver and subdivide into 
aller branches, and the smaller branches 
mpany the divisions of the portal vein and 
patic artery through the portal canals to their 
timate distribution in the lobules. The 
nches of the hepatic duct, like those of the 
rial vein, are divisible into the vaginal, inter- 
bular, and lobular ducts. 
The vaginal ducts pass transversely through 
the capsule of Glisson, by which they are enve- 
loped in common with the portal vein and 
lepatic artery, and divide into numerous small 
nches which assist in forming the vaginal 
From the plexus of ducts two kinds 
branches are given off, the interlobular, 
which run along the margins of the interlobular 
ures and enter the interlobular spaces to be 
stributed upon the capsular surfaces of the 
lobules ; and the lobular, which enter the sub- 
stance of those lobules which form the parietes 
of the portal canals. In the smaller portal 
als the vaginal branches and plexus are 
situated only on the sgh side of the canal, 
th es, on the side nearest 
the duct, passing directly into the interlobular 
es. “The transverse branches and those 
hich arise immediately from them do not 
anastomose with each other, but the smaller 
spre sometimes appear to do so; I cannot, 
owever,” says Kiernan, “ from dissection, 
affirm that they do, for those which appear to 
anastomose are exceedingly small vessels and 
meet each other at the spaces, hence it is diffi- 
cult to ascertain whether they really anastomose 
or enter the spaces together without anasto- 
mosing.” ; 


NORMAL ANATOMY OF THE LIVER. 


169 


The interlobular ducts ramify upon the cap- 
sular surface of the lobules with the branches 
of the portal vein and hepatic artery. Kiernan 
finds these ducts to communicate freely with 
each other, for he says, “ If the left hepatic 
duct be injected with size or mercury, the injec- 
tion will return by the right duct without extra- 
vasation and without passing into other vessels, 
and the injection will be found in the inter- 
lobular and vaginal ducts as well as in the 
trunks. This communication between the two 
ducts does not take place like that which exists 
between the right and lefffrteries through the 
medium of the vaginal branches of the trans- 
verse fissure, the injection being found in inter- 
lobular branches arising from the right duct. 
From this experiment, which I have frequently 
repeated with the same result, it appears that 
the right and left duct anastomose with each 
other through the medium of the interlobular 
ducts. This experiment does not always suc- 
ceed, which probably arises from the quantity 
of bile contained in the ducts.” 

The lobular ducts entering the*lobule by its 
circumference divide and subdivide into minute 
branches which anastomose with each other 
and form a “ reticulated plexus,” the lobular 
biliary plexus (fig. 40). ‘This plexus consti- 


Fig. 40. 


aa, Interlobular ducts giving off branches which 
form the plexus within the lobules. The central 
portion of the lobules is uninjected. 5b, The rami- 
fications of the intralobular veins. With regard to 
this figure Kiernan observes, ‘‘ No such view of 
the ducts as that represented in this figure can be 
obtained in the liver. The interlobular ducts are 
in the figure seen anastomosing with each other. 1 
have never seen these anastomoses, but I have 
seen the anastomoses of the ducts in the left lateral 
ligament, and from the results of experiments re- 
lated in this paper, I believe the interlobular ducts 
anastomose. 1 have never injected the lobular 
biliary plexuses to the extent represented in the 
figure.” 


tutes the principal part of the substance of the 
lobule, and seen through the meshes of the 
portal venous plexus, gives rise to the appear- 
ance of acini or of cecal terminations of ducts. 
The ultimate terminations of the ducts have 
not yet been seen; they are imagined by 
Miiller to end in “ short pannicle-like tufts 
closely interwoven together,” and he supports 
his opinion by citing the circumstance of the 
ducts in the embryo of the fowl and larva of 


170 


the frog ending in twig-like terminations. 
Kiernan inclines to the apts that they termi- 
nate in loops, although he says nothing which 
could lead us to suppose that he rejects the 
paaieg of their terminations being ccecal. 

authors agree that they end by closed 
extremities. It is this plexus which constitutes 
the true glandular portion of the liver. 

Miiller, in reference to the terminations of 
the ducts in anastomosing plexuses, states, that 
the history of the development of the organ is 
opposed to the belief in the existence of anas- 
tomoses. Certainly, if we are to creditsthe 
principle which he himself has established for 
the development of glands, viz. that “ however 
various the form of the elementary parts, all 
secreting glands without exception follow the 
same law of conformation,” the same process 
must take place in all; and analogy would lead 
us to infer that a plexiform anastomosis would 
be the arrangement of the terminal ducts in so 
complicated a gland as the liver of the adult, 
whatsoever it may happen to be in the unde- 
veloped organ of the embryo. That there is 
nothing irrational in this opinion we would 
turn for proof to another page of his Physiology, 
where he observes, “ in the scorpion, as I have 
discovered, the tubes (of the testis) anastomose, 
forming loops.” Again, he says, “ Lauth has 
but once seen a seminal canal ending with a 
free extremity in the human testis. Krause has 
seen such free ends of the tubuli seminiferi 
frequently, and confirms the ppinien of their 
terminating in that way as well as by anasto- 
mosis. Lauth attributes the circumstance of 
free extremities of the tubes being so seldom 
seen to their uniting with each other so as to 
form loops. He describes the division and 
reunion of the tubes to be so frequent that in a 
small portion which he spread out, and in 
which there were about forty-nine inches of 
tube, he found about fifteen anastomoses. It 
is, however, only towards their extremities that 
the seminal tubes anastomose thus freely. The 
discovery of the anastomoses of the seminal 
tubes is ectly original.” Krause observes 
the same fact also with regard to the uriniferous 
ducts. Now I would ask why, if the ducts 
of the seminal gland and uriniferous gland 
anastomose so freely, the ducts of the biliary 
gland should not do the same? And why, if 
the anastomoses of the seminal ducts be a dis- 
covery so original, the less easily demonstrable 
fact of the anastomoses of the biliary ducts, 
discovered ‘by Kiernan, may not be equally 
original? I speak from laborious research upon 
this subject, and surely there cannot be a com- 
parison between the difficulty of unravelling 
the simple ducts of the testis and the compli- 
cated and minute masses of the biliary ducts, 
an tion so intricate that Miiller acknow- 
ledges it “ difficult to decide the question.” 
The above facts of the anastomoses of the 
seminal and uriniferous ducts would, in my 
mind, were other evidence wanting, be a cir- 
cumstance powerfully aiding my belief in the 
anastomoses of the biliary ducts; but the sub- 
ject is not without its proofs, and these, as it 
appears to me, from careful examination, incon- 


NORMAL ANATOMY OF THE LIVER. 


testible. “ The left lateral li . 
Kiernan, “ may be considered as a rudin 
liver, in which this organ presents itself to 
examination in its simplest form. From t 
edge of the liver connected to the ligame 
numerous ducts emerge, which ramify eth 
the two layers of peritoneum of which 
ligament is composed.” “ These ducts, 
smallest of which are very tortuous in 
course, divide, subdivide, and anastomose 
each other. They are sometimes excee 
numerous, two or three of them in 
being of considerable size; some of the 
Ferrein” (by whom they were discos 
“ says, frequently extend to the diaphragt 
ramify on its inferior surface. ome 
extend only half way up the ligament, ¥ 
they divide into branches, which formin 5 ar 
(fig. 41,) return and descend towards the li 


ea - 
SS 


The left lateral ligament, in which ave 
jected biliary ducts with their anasto 
Kiernan,* 


anastomosing or being continuous 
ducts issuing from it. The spaces bi 
the larger or excreting ducts are oc 
by plexuses of minute or ing @ 
“ Branches of the portal and hepatic 
with arteries and absorbents, also ramify 
ligament, which, including between its | 
a plexus of secreting and excreting ducts 
bloodvessels ramifying on their pariete 
mirably displays the structure of the — 
The same appearances are seen in th 
which sometimes arch over the vena ca 
longitudinal fissure, when they are st 
thin. — 
The hepatic ducts are extremely va 
and ina Prell-injected liver are always 
pletely covered with the ramifications ‘ 
epatic artery. The ruge upon their in 
surface are formed by large vessels, “ a 
as well as veins,” which are distributed be 
the mucous membrane. This membr 
beneath the microscope, appears pla 
every part of its tori by innumerab) 
nated papille of a semilunar form. The 
distributed upon these papill 
artery which ascends upon each side 
lamina, and divides into a beautiful 
of capillaries which are collected after 
distribution into a small vein and return 
the portal vein. “It is,” says Kiernan 
the rupture of the delicate vessels forming 


consist 


* I have carefully examined this 
and pledge myself to its accuracy. 


NORMAL ANATOMY OF THE LIVER. 


papille that is to be attributed the facility with 
which Scemmering and other anatomists in- 
jected the ducts from the arteries and veins, 
_and not to any direct communication between 
the vessels and the ducts.” 
The mucous lining of the ducts is provided 
vith a considerable number of muciparous 
follicles which mingle their secretion with the 
bile during its passage along the excretory 
‘tubes. These follicles have been described by 
ll anatomists as existing in the larger ducts, 
it they were not known to be present in the 
smaller branches until they were discovered and 
igured by Kiernan. In the larger ducts they 
irregularly dispersed, but in the smaller 
es are found arranged in two longitudinal 
WS upon opposite sides of the ducts. Hence 
e vascularity of the hepatic ducts is intended 
fo perform a higher function than the mere 
nutrition of those tubes; it provides an im- 
portant secretion as an auxiliary to the compo- 
sition of the bile. ; 
_ The hepatic artery arises from the celiac 
axis and ascends through the right border of 
the lesser omentum to the transverse fissure of 
the liver, where it bifurcates into two branches 
for the right and left lobes. The right and left 
epatic arteries ramify in the portal canals, and 
give off branches which accompany each twig 
of the portal vein and hepatic duct. Their 
Branches, like those of the vein and duct, are 
‘the vaginal, the interlobular, and the lobular. 
__ The vaginal arteries arise from the hepatic 
Bteries in the portal canals, and assist in form- 
ing the vaginal plexus in the capsule of Glisson, 
om which the interlobular branches are given 
off to accompany the interlobular portal veins 
and ducts. In the larger canals the plexus 
completely surrounds the portal vessels, but in 
he smaller canals the plexus is situated only 
On the side opposite to the cylinder of the 
artery, and in the tissue of Glisson’s capsule. 
This vaginal plexus has the effect of supplying 
the lobules which are the most distant from the 
vessel to which they belong, as certainly, as those 
which are in immediate contact with its cylin- 
ler. The vaginal arteries anastomose so freely 
with each other, that if the hepatic artery of 
one side be injected, the injection will return by 
that of the opposite side. 
_ The interlobular arteries enter the intervals 
of the lobules through the interlobular spaces 
and ramify upon the capsular surface of the 
obules. ey are distributed principally to 
the interlobular ducts, around which they form 
a vascular net-work. The question of the 
mosculation of these vessels is very difficult to 
lecide by dissection on account of their ex- 
treme minuteness; but analogy would lead us 
to infer that they must communicate. 
_ The lobular arteries, “ exceedinuly minute 
and few in number,” so as to be demonstrable 
with much difficulty in the structure of the lo- 
bules, enter the circumference of these bodies 
with the lobular ducts upon which they are 
distributed. They are the nutrient vessels of 
he lobules, and termivate in the lobular venous 
plexus formed by the portal vein. 
_ The mode of distribution of the hepatic ar- 


; 


171 


tery is a subject upon which some difference 
of opinion subsists between Miiller and Kier- 
nan. Kiernan states that the hepatic artery is 
distributed chiefly upon the coats of the ducts 
and gall-bladder, upon the coats of the other 
vessels to which it forms the vasa vasorum, and 
to the substance of the lobules. The ducts are 
highly vascular, and are abundantly supplied, 
the lobules sparingly, but ‘“ few” vessels, and 
those “ exceedingly minute,” being traceable 
into them. From the capillavies of the ducts 
and vessels, the blood having become venous 
during its circulation is returned into the portal 
vein, and thence conveyed onwards to the lo- 
bules, where it is distributed through the lobular 
venous plexus. The blood of the terminal 
lobular arteries also becomes venous in the 
substance of the lobules, and is likewise poured 
into the lobular venous plexus. So that, ac- 
cording to this author, the whole of the blood 
distributed through the hepatie artery is re- 
ceived by the portal vein, either in the course 
of that vessel, or at its termination in the lo- 
bular venous plexus, and therefore, that all the 
blood circulating through the plexus must ne- 
cessarily be venous. He likewise affirms that 
no part of the blood of the artery is poured 
directly into the hepatic vein. “The intra- 
lobular veins,” he says, “convey the blood 
from the lobular venous plexus, and not from 
the arteries.” These views are the results of 
the evidence of numerous experimental injec- 
tions. With regard to the vascularity of the 
lobules, he observes, “‘ These bodies cannot be 
coloured with injection from the artery, even in 
the young subject; in the adult, after the most 
successful injection, when the arteries of the 
cellular capsule, those of the excreting ducts 
and gall-bladder, and the vasa vasorum are mi- 
nutely injected, a few injected vessels only are 
detected entering the lobules. I have fre- 
quently tied the thoracic aorta in living animals, 
thereby cutting off all supply of blood from 
the abdominal viscera; and in these animals, 
when injected from the aorta below the ligature 
forty-eight hours after death, the integuments, 
the secreting portions of the kidneys, the spleen, 
pancreas, intestines, and pelvic viscera were co- 
loured in a remarkable degree by the injection ; 
on the surface of the liver a few vessels only 
could be discovered, this organ presenting a 
curious contrast with the surrounding coloured 
viscera. The gall-bladder and ducts were, how- 
ever, equally well injected with the intestines ; 
the vasa vasorum were also well injected.” 
Perceiving in the progress of his experiments 
that the injection thrown into the artery passed 
freely into the portal vein by means of the ca- 
pillary communication existing between these 
two vessels on the coats of the ducts, and 
through the vasa vasorum of the vessels, he 
imagined that the injected fluid might in this 
way be diverted from the lobules, and that this 
must be the cause of his want of success in 
filling the lobular arteries. To ascertain if such 
were the case, he injected the portal vein in the 
first instance with blue, and then the arteries 
with red. ‘“ On dissection, branches of the two 
sets of vessels were found in the coats of the 


172 


vessels, and in those of the excreting ducts and 
gall-bladder; the lobules were coloured with 
the blue injection; the red was confined to 
their circumference, and appeared in points 
only. This experiment was varied by inject- 
ing the portal vein and its branches as far only 
as the entrance of the latter into the lobules, 
the lobules thus remaining uninjected. The 
injection propelled through the arteries had 
now free access to the uninjected lobules, and 
no exit by the injected portal vein; and the 
artery having no communication with the he- 
patic veins, the injection had no exit by these 
vessels: the lobules however were not better 
injected in this than in the preceding experi- 
ments. From these experiments I conclude, 
that the secreting part of the liver” “is supplied 
with arterial bl for nutrition only. As all 
the branches of the artery of which we can 
ascertain the termination, end in branches of 
the portal vein, it is probable that the lobular 
arteries terminate in the lobular venous plex- 
uses formed by that vein, and not in the intra- 
lobular branches of the hepatic veins, which 
cannot be injected from the artery.” Miiller, 
who published upon this subject previously to 
the discoveries of Kiernan, and was therefore 
not aware of the exact distribution of the ves- 
sels, was deceived by this free communication 
between the hepatic artery and portal vein. 
He conceived, with the older anatomists, that 
the arterial blood was mixed with the venous 
blood of the vena porte, ina capillary network, 
“vascula ultima reticulata,” common to the 
three bloodvessels of the liver, the hepatic ar- 
tery, portal vein and hepatic veins. Observing, 
moreover, in the injected preparations of Lie- 
berkiihn,* that the “ vascula ultima reticulata,” 
the lobular venous plexus of Kiernan, appeared 
as well filled when the injected fluid was 
forced into the hepatic artery, as when intro- 
duced through the portal or hepatic vein, he at 
once decided that the artery must pour its blood 
directly into this plexus. Hence he writes, 
* Vascula ultima reticulata sanguinem tam ab 
arteriis quam a vend portarum accipere, ve- 
nisque hepaticis reddere, ex hisce argumentis 
concludo: Post injectionem in arteriam hepa- 
ticam non minus quam in venam portarum aut 
venas hepaticas factam, eadem communia vas- 
culorum minimorum retia replentur, quod ex 
injectionibus exsiccatis Lieberkiihnianis, Bero- 
lini asservatis, facile quisquis sibi persuadebit.” 
Having recourse himself to an extremely im- 
perfect experiment, the injection of water into 
the hepatic artery, and finding that this fluid 
returned by the portal vein, and possibly by the 
hepatic vein, he became convinced of the com- 
munications of all the vessels in the “ vascula 
ultima reticulata,” and added another argument 
to the injections of Lieberkiihn in favour of 
his opinion; for he says, “ Injecti liquores co- 


* Having, through the kindness of Mr. Liston, 
had an opportunity of examining with the micro- 
scope some of the injections of Lieberkiihn of dif- 
ferent tissues, I can bear testimony to their beauty 
and wonderful minuteness, and can fully appre- 
ciate the deservedly high estimation in which they 
are held among the physiologists of Germany. 


NORMAL ANATOMY OF THE LIVER. 


lorati ex alio vasorum ordine facile in al 
transeunt, qualis frequens Halleri veteram 
Walteri, denique et Rudolphi cel. extat e 
rientia. I equidem transitum 
pide et colorate sepius observari.” Noy 
regard to the injections of Lieberkiihn, I 
only repeat with Kiernan, that if the lob 
venous plexus or “ vascula ultima 
were filled, actually, from the 
only route which the injection could 
taken must have been through the capil: 
the excretory ducts and vasa vasoram, and 
through the portal vein. But with re; 
the water experiment, I am quite 
its utter inadequacy to elucidate so delic 
pot as that under discussion. In 
experiments, made with a view of assuri 
self of the nature of these plexuses, I hay 
been content with my injection unless I 
distinctly trace with the aid of the mi 
each capillary vessel from the interlobulat 
to the intralobular vein, and this I have 
failed to do in a successful injection 
abet vein; or in the opposite course whe 
epatic veins have been filled. But in 
most successful injection from the artery, 
the capsular arteries have been beautife ly 
I have never observed more than a 
are in the circumference of ok 
here is, however, in the consideration 
question, one circumstance which apps 
have been altogether overlooked by 
but which seems to me to be fatal to the o 
which he entertains with regard to the dis 
tion of the arterial blood. e ducts at 
dantly supplied with blood from the 
indeed to so great an extent, that in a 
injected liver their coats appear to consist ¢ 
wholly of the ramifications of minute ve 
Now if the aggregate of the surface form 
the ducts, which is thus covered with ¥ 
supplied from the artery, be considered, it 
be evident that very httle can be left for 
“vascula ultima reticulata.” And if 
jointly with this fact, the difficulty of inje 
the lobules from the artery be consid 
must be admitted that Miiller carries hisd 
somewhat too far, in asserting without li 
tion “that the arterial blood of the he 
artery and the venous blood of the port 
come mixed in the minute vessels of the 
The hepatic veins return the whole of t 
nous blood from the liver to the general 
circulation. They commence in the cei 
each lobule by means of a small vein 
intralobular, which collects the blood 
circulation through the lobular venous p 
The intralobular veins pour their curren! 
the sublobular veins, and these latter ur 
form the hepatic trunks, which 
inferior vena cava. The hepatic differ fro 
portal veins in being more immedi 
tact, and more closely connected with the 
stance of the lobules. Thus the intralo 
veins are embedded in the substance of ¢ 
lobule, and the sublobular inclosed in ¢ 
formed by the bases of the lobules, and th 
fore by that part which is uninvested b 
lobular capsule. The hepatic trunks 


= 


ol 


nig 


rhe 


* 
PTTInNALe 


NORMAL ANATOMY OF THE LIVER. 


from the preceding in being lodged in canals 
_ formed by the capsular surface of the lobules, 

the hepatic venous canals, which are analogous 
_to the portal canals excepting in the absence 
_ of a proper investment of Glisson’s capsule. 
It follows from this circumstance, that there 
are no vessels in connection with the hepatic 
veins at all resembling the vaginal branches 
_ and plexuses of the portal vein. The general 
course of the hepatic veins is from the two 
_ surfaces and free margin of the liver towards 
_ the vena cava in the posterior border; that of 
_ the portal vein radiates from the transverse fis- 
sure in the centre of the under surface to all 
_ parts of the circumference; hence the two 
veins cross each other in their course, the 
_ former proceeding from before backwards, and 
the latter from the centre towards the circum- 
ference. In examining either of these sets of 
vessels, we should, therefore, be guided in the 
direction of our section by this peculiar ar- 
“rangement. There is another mode by which 
_we arrive at a knowledge of the means of dis- 
_criminating between the two veins in a section. 
The hepatic vein being closely adherent to the 
lobules forming the canal in which it is lodged, 
“remains open, and retains the form of its cy- 
linder upon the face of a section ; it may also 
be recognised by being solitary. The portal 
yein, on the contrary, being surrounded by the 
loose, vasculo-cellular web of Glisson’s cap- 
Sule, is permitted to collapse; it is also charac- 
terised by being associated with a branch of the 
hepatic artery and duct. In the consideration 
of the hepatic veins | shall describe, first, the 
‘intralobular, next the sublobular, and then the 
hepatic trunks. 
_ In the centre of each lobule is situated an 
intralobular vein (fig. 34, 5,) which is 
formed by the convergence of from “ four to 
‘six or eight” minute venules, from the processes 
‘upon the surface of the lobule. In the super- 
ficial lobules, the intralobular vein commences 
directly from the surface, and the minute ve- 
mules by which itis formed may be seen in an 


freee injection converging from the circum- 


nce towards the centre. The vein then 
akes its course through the centre of the longi- 
tudinal axis of the lobule, and piercing the 
middle of its base opens into the sublobular 
vein. The intralobular veins have no direct 
communication with the portal vein or with 
the hepatic artery, and they simply serve to 
‘collect the blood which has circulated through 
the lobular venous plexus, and convey it into 
the general current of the hepatic veins. 
The sublobular veins (fig. 34) are named from 
their position at the base of the lobules. They 
are lodged in canals which are formed by the 
bases of all the lobules of the liver. They are 
extremely thin and “delicate in texture,” and 
lie in close contact with the substance of the 
lobules, so that upon laying open one of these 
veins, the bases of the lobules may be seen 
distinctly through its coats. In the centre of 
the base of each of the lobules will be ob- 
served the opening of the intralobular vein, so 
that the whole internal surface of the vein is 
Pierced by these minute openings. In the 


173 


smaller portal veins, on the other hand, where a 
number of small foramina were seen upon the’ 
internal surface of that side of the vessel 
which lay in contact with the canal, and where 
the outline of the lobules was also perceptible, 
it was observed that the small openings cor- 
responded with the interlobular spaces, and were 
the entrances of the interlobular veins. 

The hepatic trunks receiving the blood from 
the sublobular veins take their course along the 
“hepatic venous canals,” andterminate by 
two large openings corresponding with the 
right and left lobes in the inferior cava, at the 

oint where that vessel is lying deeply im- 

dded in the posterior border of the liver. A 
number of minor hepatic veins also terminate 
in the cava at this part of its course. The he- 
patic venous canals resemble the portal canals 
in being formed by the capsular surfaces of the 
lobules, lined by a prolongation of the proper 
capsule. The hepatic trunks are thick and 
dense in their structure, and their external coat 
is composed of “longitudinal bands,” From 
the thickness of their texture the outline of the 
lobules is not apparent through their coats, nor 
have they any intralobular veins opening into 
them. 

The coats of the hepatic veins are supplied 
with blood by the hepatic artery, and the venous 
blood is returned to the ramifications of the 
portal vein. 

The lymphatic vessels of the liver are divi- 
sible into the deep and superficial. The former 
take their course through the portal canals, and 
through the right border of the lesser omentum, 
to the lymphatic glands situate in the course 
of the hepatic artery, and along the lesser curve 
of the stomach. They are easily injected (by 
rupture of course) from the hepatic ducts, and 
Kiernan remarks, that “ injection sometimes 
passes from the arteries and portal veins into 
the lymphatics. I have frequently seen them 
in the right border of the lesser omentum, 
when distended with injection, as large as small 
veins. The superficial lymphatics, (figs. 32 and 
33,) are situated in the cellular structure of the 
proper capsule, over the whole surface of the 
liver. Those of the convex surface are divided 
into two sets; 1st, those which pass from be- 
fore backwards ; and 2d, those which advance 
from behind forwards. The former unite to 
form trunks, which enter between the folds of 
the lateral ligaments at the right and left extre- 
mities of the organ, and of the coronary liga- 
ment in the middle. Some of them pierce the 
diaphragm, and join the posterior mediastinal 
glands; others converge to the lymphatic 
glands situated around the inferior cava. Those 
which pass from behind forwards consist of two 
groupe: one ascends between the folds of the 
broad ligament, and perforates the diaphragm 
to terminate in the anterior mediastinal glands ; 
the other Curves around the anterior margin of 
the liver to its concave surface, and from thence 
to the glands in the right border of the lesser 
omentum. The lymphatic vessels of the con- 
cave surface are variously distributed according 
to their position ; those from the right lobe 
terminate in the lumbar glands ;—those from 


174 


the gall-bladder, which are large and form a 
remarkable plexus, enter the glands in the 
right border of the lesser omentum ; and those 
from the left lobe converge to the lymphatic 
glands situated along the lesser curve of the 
stomach. 

The nerves which supply the liver are de- 
rived from the systems both of animal and 
organic life; the former are filaments of the 
right phrenic and two pneumo-gastric nerves, 
and the latter of the solar plexus. The branches 
from the right phrenic nerve descend by the side 
of the inferior cava, to unite with the hepatic 
plexus in the right border of the lesser omen- 
tum. Swan describes a small ganglion, to 
which filaments converge from the right semi- 
lunar ganglion and right phrenic nerve, as being 
the medium of communication between the 
fe teeth nerve and the hepatic plexus. The 

ranches of the pneumo-gastric nerves pass 
between the two layers of the lesser omentum 
to its right border, and pursuing the course 
of the hepatic artery are distributed with 
the hepatic plexus to the gall-bladder and 
along the portal canals. The hepatic plexus 
proceeds from the solar plexus and surrounds 
the hepatic artery to the transverse fissure ; its 
filaments then accompany the branches of that 
vessel to their ultimate termination, and some 
few are observed to ramify upon the portal 
vein. 

Progressive development of the liver in the 
animal series.—The liver in its simplest condi- 
tion is a mere inflection of the mucous lining 
of the alimentary canal, forming a small cecal 
recess or follicle. The capillary vessels rami- 
fying upon the parietes of this follicle pour 
their secretion upon its internal surface, and it 
is thence conveyed to the alimentary canal to 
be mingled with the ingesta. In this its most 
rudimentary form the liver would appear to be 
present in the Laginella, a small cilio-brachiate 

lypus described and figured by Dr. Arthur 

arre.* Upon the stomach of the Laginella 
are seen several minute cceca which open into 
its cavity; they are usually empty when the 
animal has been for some time without food, 
but become filled with a brownish fluid after a 
meal. The next most elementary form of the 
hepatic coecum is seen in the single lengthened 
follicle discovered by Owen in the ascaris ha- 
licoris. This follicle opens into the alimentary 
canal at about calottiedl Wom its oral extremity. 
Among the Annelida, as in the medicinal leech 
(fig. 69, vol. i.) the liver is represented by 
numerous simple ceecal pouches appended to 
each side of the digestive canal. The next 
step in the complication of the organ is ob- 
served in the lengthened filiform tubuli which 
are connected with the sides of the canal in the 
Aphrodita. These are narrow and constricted 
at their commencement, dilating gradually as 
they proceed farther from the intestine, and 
terminating by a small oval sac. In other 
species of the same genus and in the Areni- 
cola (fig. 70, vol. i.) they pons 7H a_ tendency 
to ramify, by developing small ccecal pouches 


* Philosophical Transactions, 1837, 


NORMAL ANATOMY OF THE LIVER. 


from their sides. In these terminal saece 
Pallas discovered a “ bitter fluid, of an oliy 
brown or greenish-black colour,” which 
conceived to be the juices of marine pla 
which had gained admission into the tub 
through their openings of communication ¥ 
the intestine, but which, it is more than : 
bable, was the proper biliary secretion ¢ 
tubes themselves. In the class ects 
hepatic cceca vary in ive ¢ 
from the simple vesicular dilatations ¢ 
upon the digestive canal of the 
splendidula, or the simple cecal tubu 
carnivorous Cicindela, to the numerous ¢ 
follicles of the Dytiscus, or to the more I 
ened tubuli of the Blatta orientalis. Thr 
out the whole of the class the charaeter | 
roe is tubular, the developrens aa 
the tubuli depending upon iarities 
food or habits of the ema Arac 
the cecal follicles are short, and 
at their extremities in a cluster of 
rounded vesicles, which give’ to the ¢ 
lobulated appearance. They are seer 
Scorpion, in fig. 83, c, c, page 204, 
In the class Crustacea, the hepatic organ as 
a higher and more complicated charact 
simple ccecal follicle of Insecta bee 
branched and ramified, of which we © 
good example in the Argulus foliaceus, 
neated by Miiller. In the a ’ 
(fig. 214, 483, vol. i.) the hep 
(te is more branched than’ ini 
and in the Pagurus striatus (fig. 215, pa 
vol. i.) the liver is composed of an extra 
assemblage of ramified follicles. Int 
organ of the Squilla mantis we perceivea re 
able transition from the simple branched a 
mified follicle of the lower Crustacea to t 
forms of the organ in the molluscous” 
Upon the exterior it is lobulated, and 
lobe is composed of a congeries of mit 
bules which appear like granulations upi 
surface. Examined in its interior it prest 
primary dilated sae of considerable size, 
which branch off a number of secondar 
of smaller dimensions, and these le 
studded over every part of their sui 
minute cecal follicles of a rounded form 
the subregnum Mollusca the liver is of 
size, and approaches in external form & 
solid and if ulated organ of vertebrate 
internal conformation we may still trace 
the lower classes a close analogy with the 
fied tubuli of Articulata. Thus im the” 
Gasteropoda the gland is composed of 
pouches, which divide and subdivide 
smaller and smaller follicles and termin 
small dilated sacs. They may be com 
in their disposition to the stem, bra 
twigs, and fruit of a cluster of gra 
liver of this kind is seen in the Helix p 
In the Murex triton the follicular 3 
the organ would appear to be lost. T 
ternal surface presents a lobulated form 
the interior is composed of a delicate sp 
tissue, consisting of larger and smaller 
which may all be inflated from the exer 
duct. This seeming difference in the 


~2 


ea 


=} 


NORMAL ANATOMY OF THE LIVER. 


of the organ is, however, more apparent than 
real, for the numerous cells may be considered 
as so many follicles from which smaller fol- 
licles are developed. The cellular character of 
the organ depends upon the more extensive 
‘subdivision of the follicles, their assemblage 
in greater numbers, their consequent compres- 
sion, and the adhesion of their parietes. In 
he Sepia family the spongy structure of the 
epatic organ is still more distinct. It is chan- 
elled into numerous canals, from which smaller 
nals branch off in various directions; from 
branches cells are developed, and the 
ietes of the cells are every where surrounded 
smaller and smaller cells, the entire texture 
ing very similar in arrangement to the cel- 
ular lung of the higher reptilia. 

The liver in Vertebrata is more close and 
complex in its structure and less amenable to 
@ observations of the anatomist than in the 
inferior series. We observe nothing, even in 
the lowest fishes, which bears any direct com- 
arison with the cellular structure of the liver 
of Cephalopoda. The general character of the 
an in fishes is loose: and flabby, shewing 
at, although difficult to demonstrate, its in- 
ternal texture evidently contains numerous tu- 
buli. If the efferent duct of the liver of a 
fish be inflated, the whole organ appears dis- 
tended ; hence we might infer that the primi- 
hs structure of the organ is precisely the 
‘Same, consisting in the ramifications of the 
hepatic tubuli or ducts, the increased wants 
= higher position of the animal demanding 


augmented extension of surface. This is 
e great principle in the development of all 
andular organs—extension of surface. The 
mple follicle is sufficient for an animal so low 
a the scale as a cavitary entozoon, but as the 
functions of the animal increase, its simple fol- 
le must be extended to a greater length, or 
ched or ramified; and as high in the ani- 
mal scale as the Vertebrata these subdivisions 
fave attained so great a degree of minuteness 
that they are demonstrable to the practised eye 
nly through the aid of the highest microscopic 
wers. 

Miiller arranges the glandular system into 
simple and compound glands. The former he 
vides into two groups: 1. “ simplest glands,” 
which “are mere recesses of greater or less 
mension in the surface of a membrane ;”” and 
2. “more complicated forms,’ in which se- 
1 of the recesses are assembled together 
and open by so many distinct mouths, or they 
unite and form a common duct which termi- 
Mates bya single opening. The “ compound 
gana’ he likewise subdivides into two groups: 
1. those which “ ramify with a certain degree 
of regularity, the principal trunk giving off 
branches laterally at certain intervals, these 
sending out in the same way side branches, 
which in their turn afford a third set.” This 
disposition constitutes lobulated glands, and is 
the type of conformation of the liver in Inver- 
tebrata. 2. “ The second group of the glands 
with ramified secreting tubes consists of those 
in which the ramification is irregular, and in 
vhich there is no division and subdivision of 


175 


the gland into” secreting “lobules. The liver 
of Mammalia belongs to this group.” 

The form of the liver in Fishes corresponds 
with the direction of the long axis of the body ; 
thus, for instance, it is elongated, and con- 
sists of a single lobe in the eel, while in the 
skate it is broad and extends into each lateral 
half of the abdominal cavity. In other fishes 
it is variously divided into lobes, and is often 
placed altogether on the left side of the body. 
In the class Amphibia, the liveretso corresponds 
with the form of the body of the animal: in the 
frog it is short and divided into two primary lobes 
and several lobules; in the lengthened forms it 
is long and less divided. In the class Reptilia 
the liver is large, and bears an equal relation to 
the form of the visceral cavity. It is long and 
undivided in Ophidia, and short and divided 
into a right and a left lobe in Sauria and Che- 
lonia, the two lobes being spread out over the 
intestines. In Birds there is great uniformity 
in the form and size of the liver. It is smaller 
in proportion to the bulk of the body than in 
Reptilia and Fishes, and larger than in Mam- 
malia. It is situated in the middle line of the 
visceral cavity, and receives the heart into a 
depression upon its under surface. In the 
class Mammalia the liver is very much reduced 
in size, and is more compact and firm than in 
the lower vertebrata. In animals with simple 
stomachs it is situated in the middle line of the 
abdomen. In others, with large or compound 
stomachs, it is pressed towards the right side. 
The number of lobes does not depend upon a 
greater or less division of the liver into parts 
in accordance with the activity and mobility of 
the animal, but obeys a law in the animal 
economy, by which new parts are superadded 
in proportion to the increase of the wants of 
the creature. Man is placed at the foot of the 
scale in the progressive complication in exter- 
nal form of the liver of vertebrata; the entire 
organ may be considered in him as a central 
lobe, the lobus Spigelii being the rudiment of 
a second or right lobe. The liver of the ourang 
offers the same character. Ruminants have 
also a liver which presents the most rudimen- 
tary form of division. The liver of man is the 
type of the central or principal lobe, to which 
are added upon each side, in the animal scale, 
a right and a left lobe, and from these latter 
are developed a right lobule and a left lobule. 
This most complicated form of liver, consisting 
of five lobes, is met with among Carnivora and 
Rodentia; and throughout Mammalia, the suc- 
cessive additions and subtractions from this 
normal type form a constant and generic eha- 
racter. Besides this real division of the liver 
into five lobes, fissures of various depth are 
constantly met with, as in man, which give 
the appearance of a much greater subdivision. 
These secondary portions are to be looked upon 
as the mere results of separation, and have no 
relation with the primitive type. A most ex- 
traordinary form of liver is met with in a small 
rodent animal from Cuba, the Capromys, in 
which the whole surface is divided by deep 
fissures into small masses of a triangular and 
quadrangular form, like the kidney of a bear. 


176 


A similar arrangement is seen upon the visceral 
surface of the liver in the Llama. 

- The gall-bladder is absent in all invertebrata, 
the efferent ducts of the biliary organ termina- 
ting for the most part by several openings in 
the digestive stomach. In Fishes the gall- 
bladder is observed for the first time in the 
animal series, but it is not by any means con- 
Stant in its existence. It is absent in many 
genera, and in these cases is frequently re- 
placed by a dilatation upon the hepatic duct 
and by several efferent tubes. In the class 
Reptilia it is invariably ae and _ varies 
considerably in form, in the different genera. 
In serpents it is placed at the extremity or 
even beyond the liver, and occupies the space 
formed by the pyloric contraction of the sto- 
mach. The cystic duct is consequently ex- 
tremely long. Among the Chelonia the gall- 
bladder is enclosed within the substance of the 
liver, and receives its secretion through the 
medium of cyst-hepatic ducts. Some of these 
ducts unite also with the cystic duct and con- 
stitute a ductus communis choledochus. In 
Birds the gall-bladder is occasionally absent, 
as in Pigeons, Toucans, &c. without supplying 
to the comparative anatomist a sufficient reason 
for the peculiarity; being present and absent 
in the same natural genera and under precisely 
the same circumstances of food and climate. 
The bile is brought from the liver by two ducts, 
a cyst-hepatic duct which opens into the gall- 
bladder, and an hepatic duct which terminates 
in the duodenum near to the cystic duct. 
When the gall-bladder is absent, both hepatic 
ducts terminate in the duodenum. There is no 
instance in the whole class of a ductus com- 
munis choledochus. In Mammalia, the gall- 
bladder is by no means constant; it is deficient 
as a general rule, to which there are several 
exceptions, in herbivorous animals, as in the 
horse, stag, elephant, peccary, tapir, whilst it 
is present in the ox, sheep, goat, antelope, &c. 
In the first giraffe examined in this country by 
Owen it was absent; in the next he found two. 
Upon the hepatic duct in the elephant, near to 
the duodenum, there is a remarkable dilata- 
tion. In the cat and seal the ductus communis 
choledochus is dilated in the same situation. It 
is not uncommon to find a double gall-bladder 
or two gall-bladders in the cat; in the kinkaju 
this is supposed to be the normal condition ; 
on in the Museum of the Royal College of 

urgeons there is a preparation, preserved b 
Hunter, of the liver A a seiaeal in whic 
are three gall-bladders. 

Throughout Invertebrata the bile is secreted 
from arterial blood. In Fishes the portal vein 
is formed by veins returning from the tail and 
occasionally from the air-bladder and genital 
organs. In Reptiles a part of the blood from 
the lower extremities unites with that from the 
alimentary canal to constitute the portal circu- 
lation. In Birds the portal vein also receives 
a part of its blood from the tail and lower 
extremities by means of its communication 
with the pelvic veins. ( Fig. 171, u, v, z, page 
338, vol. i.) Injections of the portal vein 
carefully conducted, as well as injections from 


NORMAL ANATOMY OF THE LIVER. 


the internal iliac vein, have shewn that a venc 
communication subsists between the small 
branches of the two systems in the e in- 
testines, even in man. In su 
communication Miiller, in his Ph 
uotes the observations of Retzius: 
essor Retzius, of Stockholm, however, has it 
formed me that he has discovered in man so 
minute communications between the veins 
the intestines and the branches of the ve 
cava. When he injected the vena cava and 
pores with fine injection of different color 
é found that the whole meso-colon and co 
sinistrum were injected with both colours, a 
veins belonging to the two systems at seve 
places formed anastomoses. The veins of 
colon and meso-colon, which belonged to tl 
system of the vena cava and entered the 
renal vein, lay superficially, while those wh 
belonged to the vena porte lay for the mo: 
part nearer the mucous membrane. The € 
ternal surface of the duodenum also had 
ceived injection from the vena cava. 
Breschet too has filled the inferior mesente 
vein from branches of the inferior cava, a 
Schlemm has discovered distinct ce 
munications of the inferior mesenteric ve 
with branches of the inferior cava about t 
anus.” Besides these communications bt 
tween the two systems occurring in the pelvis 
Kiernan points to another most important com 
munication upon the surface of the liy 
“ The capsular veins,” he says, “ are branch 
of the portal vein; these vessels communicat 
freely with branches of the phrenic veins. | 
some cases of atrophy of the liver, and 
cases in which the circulation through the live 
has been for some time obstructed, a collater 
circulation is established by means of th 
communications which take place between t 
capsular branches of the hepatic artery 
portal vein and those of the hans artery and 
vein.” In diving animals, as in the otter an & 
seal, in which large venous reservoirs exis 
upon the inferior cava, for collecting the re- 
turning blood during submersion, the hepatic 
veins are muscular. Kiernan observes with 
regard to the hepatic veins of the seal that they 
“differ in many respects from those of any 
other animal I have examined. The intra- 
lobular veins at their exit from the lobules do 
not as in other animals terminate immediately 
in the hepatic veins: these vessels enter the 
hepatic venous canals, where they unite into 
branches, which, like the vaginal branches of 
the portal vein, are connected by a fine cellular 
tissue, with which they form around the he- 
patic veins a cellulo-vascular sheath precisely 
similar to that surrounding the branches of the — 
portal vein. i 


Vee : 
1010 


“« py, 
vo. 


The structure of the two sheaths 
is similar, but their uses are different. That 
of Glisson’s capsule has been explained; 
the capsule of the hepatic veins in the seal 
appears destined to admit of the muscular con- — 
tractions of these vessels.” “ The external 
coat of the hepatic veins is composed of cireu- 
lar fibres which in the larger vessels form a 
complete tunic. In the smaller vessels the — 
fibres are arranged in the form of circular fas- 


— 
| i 


NORMAL ANATOMY OF THE LIVER. 


ciculi, which are connected with each other 
by oblique intermediate fibres. All the fas- 
ciculi do not extend completely round the 
veins ; some, dividing into two portions, unite 
with fibres from those above and below, and 
form other fasciculi.” “ In the porpoise the 
hepatic veins are connected to their canals; 
no circular fibres are seen in their coats. Their 
external surface is reticulated, the ridges cor- 
responding to the interlobular fissures, where 
the interlobular cellular tissue is continuous 
with the cellular coat of the veins. The mouth 
of an intra-lobular vein occupies the centre of 
each space circumscribed by the ridges.” 

The distribution of the vessels in the liver 
in the three great classes, Reptilia, Aves, and 
Mammalia, has been ascertained to be the same 
with that which has been so completely illus- 
trated in the discoveries of Kiernan. In 
Fishes but few observations have been made, 


but analogy would lead us to infer that the ge- 


neral arrangement must be the same. 

Development of the liver in the embryo.— 
The development of the liver in the embryo 
commences so early in Mammiferous animals, 
hurries so rapidly through its different phases, 
and is completed so soon, that it has hitherto 
been impossible to obtain any connected and 

recise information with regard to its progress. 

he observations of eminent physiologists made 
from time to time have, however, shewn that 
the mode of its development is in all respects 
similar to the development of the liver in the 
chick. Indeed, the egg of the bird is in the 
highest degree favourable to anatomical exa- 
mination, both on account of its large size and 
the facility with which the incubated egg may 
be obtained from hour to hour, and from day 
to day. The principle of development there- 
fore being the same in the ovum of the bird as 
in Mammifera, I shall here trace the progress 
of the liver in the chick according to the most 
recent researches of Baer. 

In the embryo of the fowl at the commence- 
ment of the third day, the common vein of the 
body is embraced by two pyramidal cecal 
pouches which communicate by their bases 
with the intestinal canal, and which shoot for- 
wards so as to carry before them a fold of the 
vascular layer of the germinal membrane, in 
which they begin to ramify by giving off cecal 
branches from their sides and extremities. 
These two cecal tubuli with their correspond- 
ing ramifications form two flattened processes, 
which represent the two lateral lobes of the 
liver. By the end of the third day the two 
processes resemble -folds of the vascular layer 
in which the tubuli are seen ramifying; they 
have increased in size and almost surround the 
vein. On the fourth day the liver has the appear- 
ance of two flattened processes which enclose 
the vena porte. The hepatic tubuli have be- 
come lengthened and further removed from the 
intestine, and have ramified more freely in the 
vascular layer. By their bases the hepatic 
tubuli approach nearer to each other, and at 
the end of the fourth day they coalesce and 
form a common tube. On the fifth day the 
liver has attained considerable size; its two 

VOL. III. 


177 


lobes have become thick and appear to possess 
a spongy texture in their interior. The hepatic 
ducts are connected with the intestine by a 
common duct, the ductus communis chole- 
dochus ; and the portal vein gives off large 
branches which are distributed among the ra- 
mifications of the ducts. On the sixth and 
seventh days the liver receives an abundance 
of blood and is nearly as red as the auricle of 
the heart. The left lobe is sensibly smaller 
than the right. On the eighth>ninth, and 
tenth days the liver has lost its great redness 
and presents a yellowish brown tint; the vessels 
have diminished in calibre, while the paren- 
chyma has increased, and the gall-bladder has 
become apparent. The succeeding days aug- 
ment the size of the organ, and mould it to 
the form which it possesses after the escape of 
the chick from the egg; it begins to secrete 
bile; and the gall-bladder assumes the pyri- 
form shape which it retains in after-life. 

In the human ovum the formation of the 
embryo commences visibly at about the third 
week of intra-uterine existence; the parietes 
which separate the embryo from the ovum begin 
to be developed, and rudiments of the intestinal 
canal, the liver, and the heart soon become 
distinctly visible. Upon its earliest appearance 
the liver is of large size, and between the third 
and the fifth week is one-half the weight of 
the entire body, divided into several lobes of 
a reddish grey colour, and receives a large pro- 
portion of blood from the omphalo-mesenteric 
vein. From the fifth to the eighth week the 
liver extends as low as the margin of the 
pelvis; it is soft, almost pulpy, and greyish in 
colour. The gall-bladder is developed in the 
form of a lengthened filiform cord, having an 
extremely minute canal through its centre. By 
the third lunar month the liver extends nearly 
to the pelvis and almost fills the abdomen, and 
the right lobe has increased somewhat beyond 
the left. The texture is more firm and of a 
redder colour, and the gall-bladder is long and 
conical. At the fourth lunar month the liver 
is still prolonged nearly to the margin of the 
pelvis, but the left lobe is evidently shorter 
than the right. The gall-bladder is elongated, 
straight, and vertical in direction, and contains 
a little mucus. Upon its internal surface a 
few ruge begin to be perceived ; it receives no 
bile, although a small quantity of that fluid is 
secreted by the liver and poured into the in- 
testine. By the fifth lunar month the liver has 
acquired an increased consistence and deeper 
colour. It no longer descends so low as the 
pelvis, but appears to have diminished in bulk 
in proportion with the size of the abdomen. 
The gall-bladder assumes a more: horizontal 
direction, and the contained mucus has a yel- 
lowish green tint. The openings of the ductus 
choledochus and pancreatic duct, at first placed 
at a considerable distance from each other, 
approximate and produce less projection of 
the mucous membrane. By the sixth lunar 
month the descent of the liver is still more 
curtailed, the fcetus increases in development 
from before backwards, and the organ becomes 
more horizontal. By the seventh lunar month 

N 


178 


the gall- bladder contains bile, and the mucous 

membrane becomes rugous and reticulated. 

At the eighth month, and during the ninth and 

tenth months, the liver becomes still more ho- 

rizontal in position and of a deep red colour. 

The bile is more abundant and of a clear green 

tint. Atthe tenth month, that is, at birth, the 
relative proportion of the liver to the rest of 
the body is as 1 1018 or 20; the average in 

the adult being as 1 to 36. After birth the 
size and weight of the liver diminish until the 
end of the first year, for, according to Meckel, 
the liver of the newly born infant weighs one- 
fourth heavier than at the age of eight or ten 
months. The borders of the liver are rounded 
in the foetus, and the inferior surface is convex. 
The lobes are nearly equal until birth, after 
which the left diminishes in size, the right re- 
maining stationary or growing but little, and 
at the age of one year the left lobe is scarcely 
one-half so large as at birth. The texture of 
the liver in the fetus is soft and fragile and 
apparently homogeneous in structure; during 
the earlier periods its colour is a light brownish 
grey; at about the mid-period it becomes 
deeply red, and after birth loses a portion of 
its colour from a diminution of the quantity of 
blood circulating through it. 

Uses of the liver—The liver performs two 
most important functions in the animal eco- 
nomy :—1, it separates from the venous blood 
of the chylopoietic viscera certain elements 
which are needful to digestion ; and, 2, it de- 
purates the venous blood. The first of these 
fur.ctions constitutes the secretion of bile. 
The second is evinced in a comparative exami- 
nation of two of the great depurating organs, 
the lungs and the liver, in the various classes 
of animals, where the latter will be constantly 
found in exact relation with the development 
of the respiratory organ, and with the neces- 
sity for the removal of a larger quantity of 
hydrogen and carbon from the blood. Thus, 
in herbivorous animals, the liver is small ; it is 
small also in monkeys and in man. It is large, 
and has reached its highest development 
amongst Mammiferous animals in Carnivora. 
In birds it is larger in proportion than in Car- 
nivora, from the greater necessity of a highly 
oxygenated blood in that class of animals. 
In Reptiles, with cold blood and a low degree 
of respiration, it is large; it is large also and 
for the same reason in Fishes; and very large 
among the Invertebrata. 

Secretion of bile—The bile, which would 
appear, from the existence of follicular recesses 
in the alimentary canal, to be produced in all 
animals from the lowest to the highest, is 
secreted in man and in vertebrata from the 
blood during its circulation through the lobu- 
lar venous plexus in the lobules of the liver. 
Hence it becomes a question of importance to 
physiology to decide from what kind of blood 
it is elimmated. If, according to Kiernan, all 
the arterial blood of the hepatic artery become 
venous previously to its passage into the lo- 
bular venous plexus, the 
from venous blood ; that venous blood being 


NORMAL ANATOMY OF THE LIVER. 


ile must be secreted ~ 


derived from the capillaries of the ch 
organs, and from the capillaries of the 
artery. I have given Kiernan’s reasons 
belief that this is the truth; and in corrobo- 
rating the results of his injections I mustalso 
add my own testimony to his view of the ; 
cretion of the biliary fluid. Miiller, ente 
taining, as I have already shewn, a differei 
opinion with regard to the distribution of th 
vessels of the liver, believes that the bile 
secreted from a mixed arterial and ven 
blood, resulting from the termination of be 
the hepatic artery and portal vein in the “y 
cula ultima reticulata,” or lobular ven 
a From the undecided manner in wi 
e expresses this opinion, I am temp 
give the quotation in which it is con 
that my readers may judge how far he be re 
in earnest in his assertion. “ It is known tha 
injection thrown either into the hepatic art 
or into the portal vien, fills the same capil 
net-work, from which, on the other hand, 
hepatic veins likewise arise.” : 
Since reading the above paragraph I hi 
injected twelve livers for the purpose of : 
ciding the question, in my own mind, of 
ultimate termination of the hepatic 
I have in no instance succeeded in foremg 
jection into the lobular venous pas t 10 
every other of the organ has been beau 
fully injected. I have therefore been forces 
the conclusion that some ee must € 
with regard to this passage, and that, altho 
—— true ihibaectitinda to the portal ve 
iiller cannot mean that the capillary” 
work (lobular venous plexus) from which t 
hepatic veins arise, is actually filled fron t 
hepatic artery. But he continues, “ It 
ars, therefore, that the arterial blood of the 
epatic artery, and the venous blood of 
porta, become mixed in the minute vessé 
of the liver, and that the secretion of 
probably takes place from both.” Now, w 
deference to Miller’s judgment, the ky ic 
with our present knowledge upon t 
anatomy of the liver, ought not to be one 
serena or surmise ;—does it? or does it nt 
ut he appears far from satisfied, in relyi 
for the support of his argument upon his oF 
peculiar theory of the arrangement of the | 
patic vessels, and, as if distrusting its é 
ency, he exclaims in another page of his P 
siology, “ But the possibility of bile b 
secreted from arterial blood is demonstrat 
by the cases in which the vena porte enters 
vena cava directly instead of being distribut 
through the liver. Mr. Abernethy observed 
anomalous structure in a male child ten mon 
old; and Mr. Lawrence has detailed a case 
which the same malformation existed in a chil 
several years of age. In Mr. Abernethy’s ea 
however the umbilical vein was still 
and branched out in the substance of 
it is possible therefore, as Mr. Kiernan remarks, - 
that the arterial blood, after having nourished — 
the liver, was poured into the branches of the — 
umbilical vein, just as it is in the normal con= 
dition, according to his opinion, poured into— 


& 


"sy 


i 


NORMAL ANATOMY OF THE LIVER. 


branches of the portal vein, and the secretion 
of bile therefore might still have been derived 
from venous blood.” 

“ M. Simon and Mr. B. Phillipps have in- 
ferred from experiments which they performed, 
that the bile is secreted from the blood of the 
portal vein. But Mr. Phillips found that 
after the vena porte had been tied the secretion 
of the bile still continued, though in di- 
minished quantity; and he concludes, there- 
fore, that it is formed both from arterial 
and venous blood. He perceived no change 
in the biliary secretion when the hepatic artery 
was tied.” 

The cases recorded by Wilson, Abernethy, 
and Lawrence are interesting, but they do 
not appear to me to affect in the slightest de- 
gree the arguments on either side of the pre- 
sent question. It is true that it might be 
asserted in behalf of Miiller’s opinion, that the 
blood sent to and circulating in the liver was 
arterial, and that from this alone bile was 
secreted, for in both cases bile was found in 
the gall-bladder, while the vena porta emptied 
itself into the vena cava. On the other hand 
it was ascertained by Kiernan in the only one 
of the three cases in which the liver was pre- 
served, that the umbilical vein (hepatic portal) 
was pervious, of considerable size, and rami- 
fied as usual through the portal canals and 
terminated as usual in the lobular venous 
plexus. Now, although the hepatic portal 
vein (umbilical) did not obtain its accustomed 
supply of blood after the placental circulation 
was arrested, from the abdominal portal vein, 
yet there is no reason for supposing that it did 
not collect the venous blood from the capillaries 
of the arteries supplying the coats of the ex- 
cretory ducts and other vessels. Again, the 
transmission of the remaining portion of the 
arterial circulation through the vaginal, the 
interlobular, and lobular arteries must have 
seriously affected its arterial character if it have 
not indeed altogether converted it into venous 
blood. Although Mayo, who took part in the 


_ examination of this liver, observed upon this 


point that “ it cannot be supposed that the 
arterial blood, in its passage through the vasa 
vasorum into the branches of the umbilical 
(hepatic portal) vein underwent the usual 
change into venous blood ; and it was still, he 
contended, arterial blood, though less pure in 
character, which was conveyed through venous 
canals into the secreting part of the liver.” 
Now it may be fairly presumed that blood 
which is not arterial must be venous; but it 
must at the same time be admitted that the 
normal degrees of arterialisation are various in 
individuals, and different in different regions 
of the body at the same moment; so that no 
Satisfactory argument can be sustained"upon an 
assumption of the sub-arterial character of the 
blood. {would rather suggest another train 
of reasoning. The abdominal portal vein re- 
turning blood possessed of peculiar properties 
from the chylopoietic viscera terminates in a 
fare anomaly in the inferior cava, so that the 
portal blood is mingled with the general venous 


current of the system. The lungs receiving 


179 


this blood exert their appropriate influence in 
separating from it a portion of the noxious ele- 
ments with which it is combined ; but it cannot 
be supposed that this blood will return to the 
heart as pure in character as that which has 
circulated in the usual way through the other 
depurating organ, the liver. No; it still con- 
tains the elements from which bile may be 
secreted, and a larger portion than usual is 
therefore sent to the liver, that this secretion 
may be eliminated. Hence we cannot treat 
the blood thus flowing into the liver from the 
aorta in a much larger curreft than natural 
(“ in ordinary cases one principal artery is 
found in each canal; in this case two, and in 
some places three arteries of equal calibre were 
found in each canal’) as mere arterial blood 
destined for nutrition alone; but we must re- 
gard it as a fluid bearing in its course the ele- 
ments of the bile; and therefore, whether it be 
poured through the capillary channels of the 
lobular venous plexus, or through those of its 
own developing in the substance of the lobules, 
it is nevertheless an abnormal influence which 
cannot be tested by man’s decision, but is part 
of the compensating principle so admirably 
displayed by nature in all her operations. 
With regard to the evidence of experimental 
Operations upon living animals, this must at 
all times be unsatisfactory and inconclusive 
from the difficulty of observing and apprecia- 
ting the consequences of the experiment, and 
from the morbid condition impressed upon the 
animal by the serious nature of the operations 
themselves. Those which have been performed 
are favourable to the conclusion that the bile is 
separated from the blood of the portal vein. 
But I have little faith in such experiments ;— 
after the ligature of the portal vein, the animal 
lives but a short period ; the blood arrested in 
its current is conveyed through the medium of 
inosculations into the general venous circula- 


‘tion, and then, as I have above suggested, if 


the animal survive sufficiently long, the bile 
may be secreted from the fluid which contains 
it, viz. from the arterial blood. 

Cuvier entertains the opinion, that the bile 
is secreted from venous blood, as may be per- 
ceived in the following passages :—“ Le foie des 
animaux vertébrés a en effet un caractére qu’il 
he partage avec aucune autre glande ; c’est que 
sa sécrétion est alimentée par du sang veineux; 
par du sang qui a déja circulé, et qui n’est pas 
retourné au cceur, ni par conséquent au poumon. 
Cette circonstance a lieu, non-seulement dans 
des animaux 4 circulation double, od tout le 
sang doit repasser par le poumon, avant de se 
rendre aux parties, le foie excepté ; mais encore 
dans les animaux 4a circulation simple (les 
reptiles), oX une si grande portion du sang 
artériel n’a point retourné au poumon, et tient 
par conséquent de la nature veineuse ; c'est 
presque alors du sang deux fois veineux qui se 
rend dans le foie.’ May we not, therefore, 
from the powerful arguments afforded by anato- 
mical investigation, and from our knowledge of 
the compensating energies. aroused by nature 
in cases of anomaly,—may we not, at least 
until weightier reasons to the contrary shall be 

N 2 


180 
developed by the progressive discoveries of our 
‘sivas Predy conclude that the bile is 
secreted from venous blood ? 

The quantity of the bile is a question diffi- 
cult to decide accurately ; it would appear to 
be secreted most abundantly during digestion, 
when the augmented activity of the stomach 
would seem to be communicated to its neigh- 
bouring organ, the liver. Certainly it is eva- 
cuated from the gall-bladder into the digestive 
canal at that period. In animals which have 
been kept long fasting the gall-bladder is always 
greatly Sistenied. Schultz observed, in an ox 
which had been kept for some time without 
food, from twelve to sixteen ounces of bile in 
the gall-bladder, and in another, after digestion, 
from two to four ounces only. In a dog which 
had not eaten for some time he found five 
drachms, in another, after digestion, about two 
drachms. In a case of abscess of the liver 
communicating with the gall-bladder and 
lung, recorded by Dr. Monro, the whole 
of the bile flowed through the fistulous canal 
and was discharged by coughing, “ in proof of 
which,” he says, “ the feeces were of the same 
whitish colour and had as little smell as those 
of a person deeply jaundiced. The quantity 
of bile discharged by coughing was different at 
different times. It was always greater after 
meals, and especially for an hour or two after 
dinner. The quantity expectorated could not 
be measured with great accuracy from being 
mixed with mucus and saliva. The whole 
yori in twenty-four hours was from ten to 

fteen ounces; and, in this case, I had an 
opportunity of observing the effects of certain 
articles of food, and in particular of acids, of 
wine, and of different fruits, in increasing the 
quantity of bile.” 

Expulsion of the bile-—This process 1 have 
just shewn takes place more abundantly during 
digestion than at any other period. In all 
carnivorous and in most herbivorous animals 
there exists a peculiar provision for the col- 
lection of the bile during the period of ab- 
stinence, in a membranous reservoir, the gall- 
bladder. Some herbivorous animals, deprived 
of a distinct gall-bladder, have a compensating 
dilatation upon the hepatic duct. The use of 
this organ is to retain the bile until digestion 
demands its excretion. Those animals, there- 
fore, that are provided with it are such as 

rform the function of digestion at variable 
intervals. But in those whose digestion is con- 
tinuous, as is the case in many herbivora, the 
bile flows as it is secreted into the alimentary 
canal; being very probably provided more 
abundantly under the stimulus of a full sto- 
mach than during the abstinence from food or 
during sleep. In the contracted state of the 
duodenum the small and oblique opening of 
the ductus communis choledochus is closed to 

the passage of the fluid; it therefore regurgitates 
along the cystic duct into the gall-bladder. In 
the slight ascent along this tube it is facilitated 
by the spiral valve, which also serves to restrain 
its too sudden emission during spasmodic ac- 
tion of the abdominal muscles. As soon as 
the duodenum becomes filled with the chyme 
from the stomach, the opening of the ductus 


NORMAL ANATOMY OF THE LIVER. 


communis choledochus is less compressed. The — 
rears, of the a but more a 
arly the passage of the chyme along the py- 
lorus into the upper part of the duodenum, 
causes a gentle pressure upon the coats of th 
gall-bladder which favours its emission; | 
contents are gradually expressed, and flowin 
along the ductus communis choledochus 
mingled with the pulpy mass in the duodenum 
This explanation of the rocess seems to ha 
been entertained by Haller, and to have aris 
in his mind from the consideration of ana 
tomy of the serpent, where the gall-bl e 
far removed from the liver and is situated 
the space formed by the contraction of the p 
lorus and its termination in the small i 
tine. Neither do I consider its truth inys 
dated by those cases in which the gall-bh 
is partly imbedded in the liver, for in st 
instances that portion of the liver is compress 
which immediately covers the fundus of 
gall-bladder, or a of the gall-bladder 
exposed against which the duodenum m 
exert an Fe compression. Miill 
that the efferent ducts of glands are surroun 
by “ an extremely thin layer of muscular sul 
stance,” which, although not demonstrable an 
tomically, he thinks to be placed beyond dispu 
by physiological observations. “ contract 
power of the ductus choledochus in birds 
known to Rudolphi. By irritating mechaniea 
or by galvanism the ductus choledochus of 
bird just dead, I have frequently produc 
very strong contraction of it, which cont 
some minutes, after which the duct 
its previous state. I have often excited stre 
local contractions of the ureters likewise, b 
in birds and rabbits, by the application of 
powerful galvanic stimulus. Tiedemann 
has seen motions of the vas deferens of a horse 
eusue on the et of a stimulus. I 
appears indeed that periodic vermicular motio 
are performed by the efferent ducts, at le 
the ductus choledochus, in birds; for I hha 
once observed in a bird just killed, contraction 
of the duct occurring regularly in pauses € 
several minutes, the tube dilating again in t 
intervals ; and what was remarkable, the ¢o 
tractions took place in an ascending direction 
namely, from the intestine towards the liver: 
and this seems to throw some light on th 
mode in which the bile at certain times, it 
stead of being expelled into the intestines, i 
retained and driven into the diverticulum 0 
the duct, namely, the gall-bladder ; the con 
lete closure of the mouth of the duct cont 
utes perhaps to this effect. The discharge 
the bike frots the gall-bladder during dige stion 
results probably from the mere * ure of the 
surrounding parts, and the action of the ab- 
dominal muscles, while the mouth of the due 
is open: for I doubt if the gall-bladder is con- 
tractile ; I could produce no contraction ¢ 
in mammalia and birds even with the most 
werful stimulus of a galvanic Aad 
onro considers the middle coat of the gall- 
bladder in man to contain muscular fibres ; the» 
muscular coat in the gall-ducts of the dog and — 
horse are, he observes, quite distinct, and upon — 
irritation he has seen the gall-bladder contract 


por 


Con 


a 


NORMAL ANATOMY OF THE LIVER. 


in a living animal so as to resemble an hour- 
glass. Andral thinks that he has perceived 
muscular fibres in the hypertrophied coats of 
the gall-bladder, and Ferrus records a case as 
occurring to Amussat where, in obstruction to 
the ductus choledochus by a gall-stone, the 
middle coat of the gall-bladder and ducts above 
the impediment was evidently muscular. This 
preparation was seen by Kiernan at the time 
that it occurred. The bile during its stay in 
the gall-bladder becomes inspissated by the 
removal of the tluid part of the secretion, which 
is Most probably taken up by the numerous 
lymphatics which cover its suriace. 

he uses of the bile are threefold; 1. it acts 
chemically upon the chyme and produces the 
Separation of the chyle; 2. it combines with 
the residuum and forms the fecal matter ; 3. 
it stimulates the mucous surface of the canal 
and promotes its secretion, and the contractile 
action of the muscular coat. 

_Red and yellow substances of Ferrein.— 
Since the period when anatomists were di- 
vided in their considerations of the liver by the 
two great contending opinions of Malpighi 
and Ruysch, the former maintaining its com- 
position of glands, and the latter of mi- 
nute vessels, the majority of observers have 
adopted the views proposed by Ferrein, who 
was the first to vindicate the existence of two 
distinct substances, which he named cortical 
and medullary. It was reserved for Kiernan 
im Our own day to prove that “ the structure 
of all the lobules is similar;” that “each lo- 
bule is the same throughout ; ” that “ one part 
of a lobule is not more vascular than another ;” 
and that “there is, therefore, no. distinction 
of red and yellow substances in the liver; the 
red colour results from congestion only.” This 
doctrine being now established as an undis- 
puted truth, it is not surprising to observe that 
anatomists and pathologists differed in opinion 
with regard to the relative position and appear- 
ance which these two imaginary substances 
occupied in the respective livers which they 
chanced to examine, and upon which they 
established their decision. Thus we find that 
Ferrein described the medullary substance as 
being red in colour, and of a pulpy con- 
Sistence, and the cortical as friable in its struc- 
ture, and of a yellowish red colour. Auten- 
rieth, on the contrary, found the red substance 
to be cortical and the yellow medullary. 
Mappes having obtained a liver in a different 
State of congestion, conceives that the yellow 
substance might be named granulated ; he de- 
cribes it as forming convolutions, one while 
like intestines, and another while branched, 
flat, or rounded; and the spaces between the 
convolutions as being rounded, or resem- 
bling oblong fissures filled with a brownish 
and loose substance. Meckel coincides with 
Mappes in the relative position of these parts ; 
they are not, he says, placed as in the brain, 
One on the exterior, the other in the interior, 
but they alternate throughout the entire organ, 
the yellow substance forming the mass of the 
liver, and the byown filling the interspaces. 


Rudolphi objects to the terms medullary and 


181 
cortical. Bouillaud asserts that the yellow sub- 
Stance presents itself in the form of granu- 
lations having the figure, colour, and arrange- 
ment of the secreting granules of the bile 
known, as he remarks, under the name of 
acini. These granules, he says, are surrounded 
by the brown substance, which therefore as- 
sumes an angular appearance; it is composed 
of a vascular net-work, and may be compared 
to erectile tissue. Andral, in his Anatomie 
Pathologique, says, “ Lorsqu’on examine avec 
quelque soin un certain nombre ge foies, l’on 
y reconnait l’existence de deux substances: 
l'une rougeatre, od se ramifie surtout le sys- 
teme capillaire de l’organe ; l’autre blanche ou 
jaunatre, qui semble surtout destinée a l’accom- 
plissement de la sécrétion biliare. Dans l'état 
normal ces deux substances sont distinctes.” 
The opinion of Ferrein is opposed by Portal 
and Cruveilhier: the former anatomist, after 
reproving certain modern authors who wished 
to combine the views of Malpighi and Ruysch 
by admitting that the liver was formed both of 
glands and of a prodigious number of vessels, 
contents himself by asserting that Ferrein’s idea 
of the composition of the glands of the liver 
of two substances was gratuitous. To Cruveil- 
hier the distinction of two substances appears ill 
founded, for he observes that the two colours 
when they exist, which is not constantly the 
case, do not belong to two distinct granula- 
tions, but to one and the same, which is yel- 
lowish in the centre where the bile predo- 
minates, and of a brownish red in the circum- 
ference where the blood is situated. Kiernan 
ranks Miiller among the authors who entertain 
an opposite opinion to that of Ferrein, but 
I find upon referring to his work upon the 
glands, that he distinctly admits a kind of 
double substance although he objects to its de- 
signation, medullary and cortical ; hence he ob- 
serves :—“ Diversam substantiam hepatis, ut- 
pote medullarem et corticalem, que per hepar 
totum undique obveniunt, qualem Autenrieth, 
Bichat, Cloquet, Mappes, atque etiam J. Fr. 
Meckel admittunt, equidem neque in historia 
evolutionis amphibiorum et avium, neque in 
hepate adultorum microscopice observato con- 
spexi. Historia evolutionis hanc questionem 
evidentissime illustrat. Systema nimirum duc- 
tuum biliferoram in embryone amphibiorum et 
avium liberis finibus in superficie hepatis pro- 
minulis conspicuum. Sarmentula illa foliatim 
et paniculatim divaricata, colore e gilvo can- 
dido nitent, magnopere ab interstitiis sanguino- 
lentis distincta. Hine sane duplicis substantie 
species exoritur, quoniam circum ductuum bi- 
liferorum a tela conjunctiva expleantur, que 
ex subtilissimis fere constat vasculorum sangui- 
ferorum retibus, in quibus arteriz et venule 
advehentes in revehentes venas transeunt. 
Atque hee sola est utriusque substantie notio. 
Sed in omnibus organis glandulosis fere idem 
obvenit.” In his Physiology he is disposed to 
modify his previous idea of two substances, 
for he says, “ From my researches, however, it 
results that there is but one kind of real he- 
patic substance, formed of agglomerated biliary 
canals; but the ramified divisions of this sub- 


182 


tance being connected by a vascular cellular 
tissue, which is often of a dark colour, a con- 
trast between this and the yellow substance of 
the acini is produced. A similar relation of 
the constituent parts of the liver exists in the 
embryo of the bird; in it the yellowish twig- 
like ramifications of the biliary canals are seen 
on the surface of the organ rising out of a 
reddish vascular tissue.” 

M. Dujardin, in an article entitled, “ Re- 
cherches Anatomiques et Microscopiques sur 
le Foie des Mammiferes,”* has advanced some 
opinions which he conceives will throw a doubt 
over the labours of Kiernan. . My space will 
not permit an analysis of his paper, but it 
will be obvious to all who may be disposed to 
read it, that he has not advanced a single new 
fact, but on the contrary has confessed the 
most imperfect and inadequate means of ex- 
amination. Thus, he observes, “ with an in- 
jection sufficiently fine we can inject the portal 
vein as far as the capillaries which surround 
the lobules.” Therefore, according to him, the 
interlobular veins are capillaries, and we need 
not wonder that with such injection he gets no 
further, but denies the existence of vessels in 
the lobules altogether. The lobules, he says, 
are composed of glutinous corpuscules or glo- 
bules, which leave channels between them, 
through which the corpuscules of the blood 
pass without alteration ; at the same time by an 
action analogous to the phenomena of absorp- 
tion and assimilation in the lower animals, 
these lobules separate from the serum the excre- 
mentitious particles which are excreted upon 
the surface of the lobule. The blood of the 
“ite vein is transmitted through the lobule 

y a kind of “ filtration organique,” and from 
it the resinous matters of the bile are elimi- 
nated ; the arteries, on the contrary, secrete the 
alkaline substances, which in the first instance 
dissolve the resinous substance, and afterwards 
constitute the true agents of digestion. M. 
Dujardin concludes his theoretical but inge- 
nious speculations with an excuse for being 
obliged to give them to the world in their pre- 
sent imperfect state, and promises to renew his 
researches with perseverance. I feel pleasure 
in recording his promise, and have no doubt 
that by better directed injections in the human 
liver, using size and vermilion in place of oils 
and varnish, he will be induced to modify 
his views with regard to this most interesting 
organ. 

PATHOLOGICAL ANATOMY OF THE LIVER.— 
If we consult the works of pathological writers 
upon this subject, we shall o e at every ste 
of our progress the greatest ambiguity and dif- 
ference of opinion to exist. The reasons for 
this want of consent upon the true nature of 
the diseases of so important an organ are not 
to be ascribed either to want of talented ob- 
servers or of excellent observations, but solely 
to the ignorance which has hitherto prevailed 
with regard to the exact anatomy of the organ. 
I have shewn that the most celebrated authors 
found it necessary in starting with their in- 


* Annales Frangaises et Etrangéres d’Ana- 
tomie et Physiologie, 1838. 


ABNORMAL ANATOMY OF THE LIVER. 


quiries to establish for their guidance a theory 
of the structure of the liver; sen theory was 
based upon imagination or upou - 
poe ay mm upon art frail” taniy he 
crumbling superstructure of their pathological 
deductions is supported. The hype or 
atrophy of the white or of the red subst 
and the wild speculations of pathe 
theorists, have now fallen into the shade bet 
the light which recent discoveries have throt 
upon the anatomy of the liver. Intimate 
associated with that anatomy, and with 
knowledge of the distribution of the 
the explanation of the mode in which 
circulation is performed, and the elucidation | 
the causes which may give rise to impedime 
in its course ; in other words, the pring ples 
congestion. Indeed, so closely allied is 
condition with the natural circulation, th 
Kiernan, in his paper upon the Anatomy: 
Physiology of the Liver, has deemed it a part” 
of the subject to explain the various conge 
tions to which the organ is liable, t 
manner in which they may be imitated ar 
ficially. Upon this point we have, therefé 
precise information, and the history of ¢o 
gestion we may regard with a feeling of sati 
faction. The same observations, with the exé 
anatomy of the liver as a basis, have not 
et been extended to its diseases; our knc 
edge of these is therefore pt impe 
fect. Kiernan concludes his paper with a par 
graph of much importance to this brane 
pathology :—“ While engaged in the 
nation of the natural structure of the liver, 
have not been inattentive to the changes pr 
duced in it by disease; and, with the pern 
sion of the Society, I propose submitting to it 
consideration a paper on the morbid anato 
of this organ.” Now this was written in 183: 
and I trust that the time is not far di : 
when the additional labours of that exe 
observer will be placed in the hands of the 
fession. 

In the arrangement of the diseases of 
liver I have adopted a physiological order, ; 
shall consider its morbid conditions under 
seven following heads :— , 
. Diseases of the serous membrane. 

. Diseases of the mucous membrane. 
. Disorders of the venous circulation. 
. Disorders of biliary excretion. 

. Diseases of the parenchyma. 

. Disorders of function. = 
. Entozoa. iy. 
. Diseases of the serous membrane.—The 
serous covering of the liver, like serous me 
branes in other parts of the body, is liabl 
acute inflammation. The effects of this inflam 
mation are also similar; the capillary vessels 
become over-distended and lose their power of 
contraction ; coagulable lymph is effused upon — 


Mt 


the surface of the organ, and causes its me@- — 
chanical cohesion to the contiguous serous 
membrane; the coagulable lymph becomes 
organised by the development of new capillary — 
vessels from the meshes of the old, and th % 
adhesions are traversed by vessels of larger 
size, and constitute a permanent bond of 


tts 


ropny | 


Pr. 


ry 
- 


iz 


it 


KF NOGC RON 


3 : 


a 


j 
| 


“ABNORMAL ANATOMY OF THE LIVER. 


-union between the peritoneum proprium and 


the peritoneum reflexum. In this state, adhe- 
sions are not uncommonly met with upon the 
convex surface of the liver, but not so fre- 
quently upon its concave side. The inflam- 
matory action is confined to the peritoneum of 
the organ itself, and that of the parietes of the 
abdomen immediately in contact with it, and 
seldom extends to the serous membrane of 
neighbouring viscera. This is the membranous 
hepatitis of pathological writers, and is accom- 
panied by considerable local uneasiness, and 
by sympathetic pains in various parts of the 
body, dependent upon the communication of 
its proper nerves with the nerves of other re- 
gions, as with the phrenic nerve, giving rise to 
pain in the right shoulder and chest, with 
cough; with the pneumogastric nerve, producing 
uneasiness at the cardia, pain along the cesopha- 
gus, dysphagia and nausea ; and with the solar 
plexus and lesser splanchnic nerve, causing 
pain in the right kidney, &c. This disease is 
usually associated with chronic congestion of 
the substance of the liver, but exists, some- 
times, quite independently of any internal 
morbid action. 

As a consequence of chronic inflammation, 
the serous membrane is sometimes thickened 
and opaque and dense in its consistence ; at 
other times it is less resisting than natural and 
easily broken. 

Depositions are occasionally found in the 


‘subserous tissue of the liver as a result of 


chronic inflammation of the serous membrane. 
They consist most frequently of an athero- 
matous substance, and orcasionally of thin 
plates, having a cartilaginous density and appear- 
ance. The gall-bladder is not unfrequently 
thickened in its coats by the deposition of fat, 
of tuberculous, or of calcareous substance. 
The latter has been described as ossified gall- 
bladder. 

2. Diseases of the mucous membrane.—In- 
flammation of the mucous membrane of the 
liver is acute or chronic, and is more frequent 
than that occurring in the serous membrane. 
Being continuous with the mucous membrane 
of the duodenum, the lining of the biliary 
ducts and gall-bladder is constantly subject to 
sources of irritation from disorders of diges- 
tion, improper aliment, and stimulating sub- 
stances taken into the alimentary canal, or from 
any cause giving rise to undue action in the 
intestinal mucous surface. Almost all the 
chronic diseases of the liver are to be referred 
to this prolific source, and it is also hy means 
of this direct continuity that many of the thera- 

utic remedies exert their alterative influence. 

e effects of inflammation on the mucous 
membrane, are 
5 a. Thickening. 
b. Softening. 

c. Hemorrhage. 
d. Suppuration. 
e. Deposition. 

a. Thickening of the submucous tissue is 
the most frequent consequence of irritation of 
the mucous membrane ; the calibre of the ducts 
is in this way diminished ; actual stricture and 


183 


obliteration of the tubes occurs, and the bile, 
at first but partially impeded, becomes alto- 
gether obstructed. The gall-bladder is some- 
times enormously thickened, particularly where 
the irritation is kept up by the presence of se- 
veral or a single large gall-stone. The coats 
are usually very much condensed and con- 
tracted, and their structure appears lost ; occa- 
sionally they are dilated. In a case which 
occurred to Amussat,* wherein the ductus com- 
munis choledochus was obliterated, and the 
gall-bladder and ducts were very much distend- 
ed, the middle coat presented atthe characters 
of muscular fibres. 

b. Softening of the mucous membrane may 
occur in the biliary ducts, but more particularly 
in the gall-bladder, and from the same causes 
which produce it in other mucous surfaces. 
I have seen two instances in the gall- 
bladder in which patches of the surface were 
converted into a softened pulp, which gave 
way upon the distension of the sac with air. 

c. Hemorrhage.—The gall-bladder has been 
observed filled with blood, having its source in 
the capillaries of the mucous membrane. In 
these cases intestinal hemorrhage had occurred 
before death, and upon examination, no conges- 
tion or lesion could be found in the mucous 
membrane other than that which was seen in 
the gall-bladder. 

d. Pus has likewise been found in the gall- 
bladder, and in the larger hepatic ducts, some- 
time pure, but generally mingled with the bile. 

e. Abnormal deposits in the submucous cel- 
lular tissue are occasionally seen. They are 
most frequent in the gall-bladder, and consist 
generally of calcareous accretions. 

3. Disorders of the venous circulation 
Under this head I have to describe the various 
forms of congestion of the liver. It has been 
customary hitherto to consider hepatic con- 
gestion as a pathological condition, and in 
compliance with that custom I have given it a 
place under the above title, although I shall 
have occasion to shew that it is not in itself a 
disease, but the mere result of diseased actions 
occurring in other parts, and wholly dependent 
upon the peculiar anatomical structure of the 
organ. Andral, in his excellent work on pa- 
thological anatomy, observes, “ L’hyperémie du 
foie est un des états morbides que présente le 
plus fréquemment cet organe. Tantdt cette 
hyperémie est générale, alors le foie est partout 
d’un rouge uniforme; son volume est aug- 
menté et sa consistance peu changée, lorsque 
V’hyperémie est simple. Cette hyperémie est 
souvent partielle; alors, en un certain nombre 
de points, on trouve comme des taches rouges 
variables en forme et en grandeur, qu’entoure 
un parenchyme plus pale. _ 

“Trois espéces d’hyperémie du foie doivent 
étre admises, relativement aux conditions de 
l’économie dans lesquelles elles surviennent. 

“ Une premiere espece d’hyperémie est celle 


* Dictionnaire de Médecine, article Foie. Mr. 
Kiernan was the pupil of Amussat at this period, 
and saw this interesting case. He informs me 
that the appearance was distinctly muscular, 


184 


gui résulte d’un travail d'irritation dont le foie 
est devenu le siége. Cette irritation est tantét 
idiopathique, et tantdt elle est la suite d’une 
Irritation primitivement fixée sur le tube di- 


“ Une seconde espéce d’hyperémie, dont le 
foie me parait susceptible, est celle dans la- 
quelle le sang s'accumule d’une manitre toute 
passive au sein du parenchyme hépatique, 
comme il s’accumule dans les gencives des 
scorbutiques. : 

“ Enfin le troisitme espéce d’hyperémie du 
foie est purement mécanique; elle s’observe 
dans les cas od un obstacle quelconque s’oppose 
a la libre entrée du sang dans les cavités droites 
du ceeur; le sang stagne alors dans les veines 
sus-hépatiques, et engorge le foie.” 

Now the researches of Kiernan have proved 
that “ in consequence of its double circulation, 
the liver is naturally in a state of sanguineous 
congestion” afier death, and that author has 
also pointed out the various forms of conges- 
tion which are observed in the organ. “ San- 
guineous congestion of the liver,” he observes, 
‘is either general or partial.”’ 

a. General congestion affects the whole of the 
substance of the liver, which presents a gene- 
rally diffused red colour; the central portions 
of the lobules having usually a deeper hue than 
the marginal portions. 

Partial congestion is of two kinds, 

Hepatic venous congestion. 
Portal venous congestion. 

b. Hepatic venous congestion may exist in 
two stages. “In the first and most common 
stage (fig. 42) the hepatic veins, their intra- 
lobular branches, and the central portions of the 
lobular venous plexuses are congested. The 
congested substance is in small isolated patches 
of a red colour, and occupying the centres of 
the lobules is medullary; the non-congested 
substance is of a yellowish white, yellow, or 
greenish colour, according to the quantity and 
quality of the bile it contains; it is conti- 
nuous throughout the liver, and forming the 
marginal portions of the lobules is cortical.” 


Fig. 42. 


Rounded lobules in the first stage of ic venous con- 
gestion, as seen upon the surface of the liver. After 
Kiernan, 


“This is the usual and natural state of the 
organ afier death,” and arises from arrest in the 
eirculation of the hepatic veins, while the cur- 


ABNORMAL ANATOMY OF THE LIVER. 


rent of blood in the minute branches 
portal vein is still in motion. 
“Tn the second stage (fig. 43) the con 
extends through the lobular venous plexuses t 
those branches of the portal vein situated it 
the interlobular fissures, but not to those in tl 
spaces, which being larger there and giv 
origin to those in the fissures, are the last t 
congested ; when these vessels contain bl 
the congestion is general, and the > liv 
red. In this second stage the non-cc ges 
substance appears in isolated circular and 
mous patches, in the centres of which the spa 


and fissures are seen. This form of congest 
“very commonly attends disease of the h 
and acute:disease of the lungs or pleura; 
liver is larger than usual in consequence of” 
quantity of blood it contains, and is frequet 
at the same time in a state of biliary cong 
tion, which probably arises from the 
neous congestion. Although in the first s 
the central portions of the plexuses, aud in| 
second the greater portion of each plexus, a 
those branches of the portal vein occupying t 
fissures are congested, and although the ple 
are formed by the portal vein, yet as this 
of congestion commences in the hepatic 
and extends towards the portal vein, and 
is necessary to distinguish this form fre 
commencing:in the portal vein, the term of hi 
patic-venous congestion will not probably | 
deemed inapplicable to it.” The second sta 
of hepatic venous congestion, generally © 
bined with biliary congestion, gives rise to thos 
various appearances which are called drat 
drinkers’ or nutmeg liver. 
c. “ Portal venous congestion is of very rare 
occurrence ; I have seen it in children only 
In this form, the congested substance never as- 
sumes the deep red colour which characteri eS 
hepatic-venous congestion ; the interlobular fis- 
sures and spaces and the marginal ions of 
the lobules are of a deeper colour usual 5 
the congested substance is continuous and cor- 
tical, the non-congested substance being me-— 


re 


ABNORMAL ANATOMY OF THE LIVER. 
Fig. 44. 


Lobules in a state of portal venous congestion, as seen 
on the surface of the liver. The congested part oc- 

' cupies the margins of the lobules, the uncongested 
portion their centres. After Kiernan. 


dullary and occupying the centres of the lo- 
bules.” 

The causes of congestion are all such as tend 
to interfere with the circulation in the liver 
or with the general circulation; for in- 
stance, impediment to the circulation of the 
blood through the capillaries of the lungs, 
diseases of the valves of the heart, aneurism, 
&e. A slighter degree of obstacle produces 
congestion of the hepatic veinsonly, the venous 
turgescence being limited by the lobular ve- 
nous plexus. If the obstruction be greater, the 
lobular venous plexus itself is congested ; if 
the cause continue, the congestion extends 
through the interlobular fissures into the neigh- 
bouring lobules, and in a more advanced de- 
gree the congestion spreads itself throughout 
the whole of the lobules, and becomes general. 
From the liver the congestion extends to the 
alimentary canal, and gives rise to intestinal 
hemorrhages, hemorrhoids, ascites, &c. : 

The variety of appearance in the vascularity 


of the lobules in congestion, and the constancy 


i i 


of its occurrence, have deceived those patholo- 
gists who maintain the existence of two sub- 
stances, and the difference of position and form 
of the congested and uncongested portions has 
given cause for the diversity of opinion with 
regard to its situation. For a perfect elucida- 
tion of these difficulties, physiology is indebted 
to the genius and perseverance of Kiernan. 
The mode in which the attention of this author 
was drawn to the subject forms part of the his- 
tory of hepatic congestion, and deserves to be 
detailed in his own words. “ My attention,” 
he observes, “ was first directed to the anatomy 
of the liver by the study of the admirable works 
of M. Andral. In the first organs I examined 
I found the small branches of the hepatic veins 
ramifying exclusively in the red,j and those of 
the portal vein in the yellow substance. I 
concluded that the liver was composed of two 
venous trees, a portal and an hepatic tree, the 
former having a cortex of yellow, the latter of 
red substance ; and with M. Bouillaud, I thought 
it probable that the red substance was the organ 


185 


of the function imagined by Bichat. I next 
ascertained the lobular structure, and concluded 
with Ferrein, that the red substance was me- 
dullary and the yellow cortical. Subsequent 
dissections, in which I found branches of both 
the portal and hepatic veins ramifying in the 
red substance, tended to unsettle the opinions I 
had formed respecting the anatomy and physio- 
logy of the two substances, and these opinions 
were finally overturned by the examination of 
a liver in which I found the branches of the 
portal vein alone ramifying in the red, and 
those of the hepatic veins in the yellow sub- 
stance. The only conclusion ttt could be 
drawn was, that the red colour resulted from 
congestion ; that it was medullary, occupying 
the centre of each lobule, when the hepatic, 
and cortical forming the circumference, when 
the portal vein was congested.” 

Miiller, in the eleventh figure of plate 11 of 
his admirable work on the glands, has made a 
singular error with regard to the structure of 
the liver, and the arrangement of the ultimate 
biliary ducts. In the description of this figure 
he says, “Segmentum hepatis Sciuri junioris, 
microscopio simplici visum. Observantur fines 
ductuum biliferorum elongati, seu cylindri- 


Fig. 45. 


A part of Miiller’s \\th figure of plate 11, which he 
considers to represent the distribution and arrange- 
ment of the ultimate biliary ducts. The liver in 
this section isin a state of hepatic venous conges- 
tion in the second stage. The congested portion 
corre: generally with the central or hepatic part 
of the lobules, and the uncongested portion with the 
interlobular fissures, in which are situated the 
branches of the portal vein. 


a, A small branch of the portal vein giving off 
twigs to the various interlobular spaces. If these 
twigs be continued so as to unite with each other, 
the form of the lobules will be apparent; as at b, b. 
The angles formed by the giving off of the twigs 
from the portal vein are the interlobular spaces. 
ce, Irregularly oval patches of uncongested lobules ; 
the dark spot in the centre is an interlobular space, 
from which the portal vein radiates in various di- 
rections, so as to surround the various lobules by 
whose conjunction the space is formed. d,d, Lo- 
bules entirely congested. Inthe centre of the lo- 
bules of this section I have marked the situation of 
the intralobular vein, although it may not be appa- 
rent, or but slightly so, in the congested liver. The 
small spaces, e, e, generally mistaken for intralo- 
bular veins in this form of congested liver, are in- 
terlobular spaces. 


186 


formes acini, in figuris ramosis et foliatis varié 
dispositis.” Now the truth is, that this section 
is im the second stage of hepatic venous con- 
gestion, and the “figuris ramosis et foliatis” 
are simply the uncongested portions of the 
lobules, of a lighter colour than the rest, and 
presenting the foliated and ramous appearance 
which is common to this form of congestion. 
The “fines ductuum biliferorum elongati seu 
cylindriformes acini” are obviously imaginary. 
e dark lines in the centre of the foliated ra- 
mifications are small branches of the portal 
vein lodged in interlobular fissures. If the 
twigs given off by these branches be made to 
unite with each other, we shall then have the 
true form of the lobules. This has been done 
in fig. 45, upon a part of Miiller’s drawing, for 
the purpose of shewing how the error has 
arisen, and how the form of the lobules may be 
restored. This appearance of the congested 
liver is by no means unfrequent in occurrence, 
and I subjoin a careful and accurate drawing 
of a similar arrangement in the human liver, 
fig. 46,) for the purpose of comparison with 
that of Miiller. 


Fig. 46. 
» 


= 


= 
y 8 


Section of a portion of liver exhibiting ic venous 
pals Sa an the ond sage cardi dence 
from nature by Bagg, and to be compared 
with Miiller’s figure. 

a, The portal vein in an interlobular fissure, giv- 
ing off small twigs to adjoining fissures, and sur- 
rounded by the uncongested portion of the liver. 
b, The form of a few of the lobules is shewn. c, Ir- 
regular patches of uncongested liver, as in Miiller’s 
figure; the space in the centre of each being an 
interlobular space. d, Interlobularspaces. e, The 
congested portion of the liver. 


Coming from so high an authority.as Miiller, 
this figure has been copied without hesitation 
by several writers, together with the explanation 
given of it by the author. Mr. Grainger has 
introduced it into his article upon the glands in 
this Cyclopedia, fig. 217, page 485, and Mr. 
Carpenter has also given it a place in his recent 
excellent work * on physiology. In his text, 


* — of General and Comparative Phy- 
siology, 1839. 


ABNORMAL ANATOMY OF THE LIVER. 


the latter gentleman observes with to 
figure :—‘‘In the squirrel indeed’ teens al 
longations may be distinctly seen, the 
sacs being cylindrical in form, and clos 
packed together.” + 
Hepatic venous congestion in its most con 
mon form, viz., in the second stage, is t 
stumbling-block of all anatomists whe 
engaged in the investigation of the mi 
anatomy of the liver; and it is under 
head that I must now consider the view 
Cruveilhier with regard to the suppe 
mal anatomy of this organ. Isolated 
distribution of the vessels in the liver, h 
described the form and arrangement 
lobules with sufficient accuracy; but the 
must be remembered that his description 
written subsequently to the publication ¢ 
researches of Kiernan. But his concept 
the structure of the lobules is comp 
neous, for after combating the com 
of the existence of two distinct subst 
says :—“ Les deux couleurs jaune et | 
quand elles existent, n’appartient pas a¢ 
granulations distinctes, mais bien a la n 
granulation qui est jaune au centre, of 
trouve le bile, et rouge-brun a la circonférer 
ov se trouve le sang.” Now Kiernan has 
tinctly proved that the structure of the lob 
is the same throughout, and their colom 
also uniform. Craveilhier must therefore 
founded his opinion and his description uj 
a liver in the second stage of hepatic | 
as, in which there exists a paw lice 
of lobules having the appearance of sma 
and variously shaped chem of a yellov 
colour, situated at regular intervals, and § 
rounded by a reddish brown substance. T 
tah spots are seen in figs. 43, 45 & 
ey are the clusters-of terminal bilia y du 
of Miiller,—the central portions of the lobi 
of the liver of Cruveilhier; but if they b 
amined carefully, their true nature will becor 
clearly apparent. They are actually the 
congested portions of the lobules of a liver 
the state of hepatic venous congestion at 
second stage, and have each an inte 
space fora centre. In the next passage C 
veilhier observes :—‘ Le foie humain, excey 
dans les cas de dévelopment considérable 
granulations, se prete difficilement a leur etu 
vu leur petitesse.” Here again in the wor 
“ dévelopment considérable,” we perceive ; 
idea founded upon the same erroneous if 
pee with regard to the structure of | 
obules. The real lobules are as nearly as p 
sible of the same size in the liver of ever 
individual, but these imagi ob 
Cruveilhier, having mic 
the hepatic substance for centres, necessari 
vary in size and form with the degree of « 
gestion, and hence have given rise to the ide 
of an increased development of the lobules 
Again, the true lobules are not so small in the” 
human liver as to render their examination 
difficult ; they may be seen distinctly with the 
naked eye, and with the commonest lens may be 
examined accurately. But in the congested 


. 
porto 


r 
‘. 


ABNORMAL ANATOMY OF THE LIVER. 


state of the organ they are more obscure, as 
may easily be inferred when we perceive such 
distinguished authorities as Miller and Cru- 
veilhier, from want of making the liver the 
_ subject of especial investigation, deceived by 
_ such appearances. That Cruveilhier has actu- 
ally mistaken the uncongested patches seen on 
_ the surface of a congested liver for the lobules, 
_ isclearly proved by a succeeding paragraph :— 
_ “Du reste, le volume des grains glanduleux 
_ présente beaucoup de variétés suivant les indi- 
_ vidus, et ce volume est tout-a-fait indépendant 
' du volume du foie lui-méme. Les médecins 
| quis’occupent d’anatomie pathologique ont sou- 
| vent noté ce dévelopment, sous le titre d’hepar 
_ acinosum. II est une maladie caractérisée par 
_ la coincidence de l’atrophie du foie, qui est 
 réduit 4 la moietié, au tiers de son volume, et 
_ du dévelopment considérable des grains glan- 
_ duleux.” Now the hepar acinosum is without 
question a liver in the second stage of hepatic 
_ venous congestion, and presents several varie- 
ties in the precise form of the uncongested 
_ patches. 
_. Starting with erroneous data such as these, 
_ what can be expected as the result of an expe- 
_ rimental injection of the liver made by Cru- 
_ veilhier, those who are thoroughly informed 
_ upon the exact anatomy of this organ will have 
no difficulty in anticipating; but to those who 
_ areonly imperfectly acquainted with it, his con- 
clusions must appear startling :—“ Le foie ainsi 
_injecté soumis a divers agens chimiques a pré- 
senté les resultats suivans: 1, l’injection bleue, 
c’est-a-dire celle de la veine cave, avait péné- 
tré dans la partie centrale des grains yglandu- 
leux, partie qu’on appelle substance jaune du 
foie. Au milieu de la partie centrale était 
Yinjection jaune, c’est-a-dire l’injection du 
canal biliare. Autour de l’injection bleue, 
etait Vinjection rouge, c’est-a-dire, linjection 
de la veine porte, et de l’artére hépatique, 
ui occupait toute la substance dite rouge 
Za foie. ll suit de la que chaque grain 
glanduleux présente un appareil vasculaire 
ainsi disposé: 1, au centre, un canal biliare ; 
2, sur un plan plus excentrique, un cercle vas- 
culaire formé par les ramifications de la veine 
hepatique; 3, un cercle vasculaire concen- 
trique au précédent, formé par les ramifications 
de la veine porte et de |’artere hepatique.” 
Thus in the centre of his lobule, Cruveilhier* 
found the yellow colour of the ducts, most 
probably effused and colouring the whole of the 
yellow portion of his lobule. Next came a 
circle of blue, and then a circle of red, formed 
conjointly by the portal vein and hepatic ar- 
Now we have shewn that the centre of 
Cruveilhier’s lobule is an uncongested patch 
formed by the contiguous margins of several 
adjoining hepatic lobules, and having an inter- 
_ lobular space for a centre ;—where, therefore, 


* These injections were not made by Cruveilhier 
himself, but by his assistant M. Bonami, as we are 
informed b M. Dujardin, in his paper ‘‘sur le 
foie, &c.”” The material used for the purpose was 
Spirit varnish, and the results were not alway’ suc- 
cessful, 


187 


could we expect to find the yellow but in the 
interlobular space, and diffused immediately 
around it, so that the colouring matter would 
obscure the red injection of the portal vein and 
artery of that immediate point. Around the 
uncongested patch and in the congested sub- 
stance we should find the intralobular veins of 
three or four or five surrounding hepatic lo- 
bules, (hence the vatiable size of Cruveilhier’s 
lobules,) embracing by a kind of zone the 
yellow centre ; and externally to the vein, the 
surrounding iuterlobular fissures would display 
the red injection of the portal vein and hepatic 
artery. 

4. Disorders of biliary excretion— Bil- 
iary congestion may be produced by various 
causes; the most frequent is temporary thick- 
ening of the mucous lining of the ducts from 
inflammation or capillary congestion ; this will 
simply diminish the calibre of the ducts or 
produce a complete stricture. The obstruction 
may endure for a shorter or longer period ; 
the swelling of the membrane may subside 
and the tube be restored to its original dimen- 
sions, or it may become chronic and be a per- 
manent impediment to the free current of the 
bile. Another cause of congestion of the bile- 
ducts is hepatic venous congestion, which acts 
by producing pressure upon the lobular biliary 
plexus and interlobular ducts. This is usually 
a chronic cause. Congestion of the bile-ducts 
may likewise depend upon the impaction of a 
gall-stone in the larger biliary ducts or ductus 
choledochus, obliteration of one of the ducts 
by the pressure of a tumour, disease of the 
pancreas, or thickening of the mucous mem- 
brane of the duodenum. In each of these 
cases the ducts are loaded with bile, which 
gives a yellowish or greenish hue to the whole 
substance of the liver. Biliary congestion in a 
chronic form is usually accompanied with more 
or less of hepatic venous congestion. 

When one of the bile-ducts is obliterated or 
obstructed by a biliary concretion, the ducts 
become dilated above the constriction, and 
considerable reservoirs are formed in the sub- 
stance of the organ. If the impediment exist 
in the ductus choledochus, the gall-bladder 
becomes greatly distended as well as the biliary 
ducts. The irritation caused by the pressure 
of the bile has given rise to inflammation and 
ulceration of the coats of the gall-bladder or 
of the ducts, and the bile has been effused into 
the peritoneal cavity and produced death. 
When the cause of the obstruction is a biliary 
calculus of moderate size, the pressure of the 
column of the bile will sometimes force it on- 
wards into the duodenum, and thus remove 
the impediment. In other cases, when the 
obstruction occurs in the cystic duct, the bile 
ceases to enter the gall-bladder, the sac be- 
comes thickened and diminished in size, and 
filled with a colourless viscid mucus. 

5. Diseases of the parenchyma. — The 
diseases of the substance or parenchyma of the 
liver may be referred to the following heads :— 
a, inflammation ; 6, hypertrophy ; c, atrophy ; 
d, softening; e, induration; f, fatty degene- 


188 


ration ; g, pus ; h,tubercle ; i, scirrhus ; k, medul- 
lary sarcoma ; /, fungus hematodes; m, melanosis. 

a. Inflammation.—The tissue of the liver is 
liable to inflammation,—hepatitis, or the lobular 
hepatitis of some writers. The symptoms, like 
those detailed in the consideration of inflam- 
mation of the serous membrane, are severe and 
prominent, and clearly indicative of the nature 
of the disease. The pathologic appearances 
are deep redness, softness, general congestion, 
and enlargement of the organ from distension 
with blood. This condition is but rarely ob- 
served, from the circumstance of inflamma- 
tion of the liver having no direct tendency to 
cause death, but being rather the precursor of 
the various other forms of disease which affect 
the organ. All the changes which occur in 
the liver are preceded or accompanied by in- 
flammation acute or chronic, but more fre- 
quently by the latter, and in most instances by de- 
rangement of the venous circulation, and, occa- 
sionally, of the biliary excretion, giving rise to a 
complication of venous and biliary congestion. 

b. Hypertrophy of the liver is increase of 
bulk of the organ, not depending, as in con- 
gestion, upon the quantity of blood circulating 
through it, but upon actual augmentation of 
the tissues of which it is composed. This 
state of enlargement of the liver may be gene- 
ral, or it may be confined to a part, as to a 
single lobe. Its predisposing cause is proba- 
bly irritation of the mucous membrane of the 
ducts which gives rise in the first instance to 
retarded circulation and venous congestion, or 
it may be impediment either in the circulation 
through the heart, or through the rest of the 
venous system ; or, again, it may depend upon 
diminution of the general powers of the system, 
as in a scrofulous constitution. The lobules 
are always in a state of partial congestion, re- 
sembling the second stage of hepatic venous 
congestion ; the congested portion presents a 
deep red tint, and the uncongested part is 
ramose or convoluted in appearance, of a dirty 
white, greyish, yellowish, or greenish hue, in 
proportion to the condition of the biliary ap- 
paratus and to the quantity of bile contained 
within the liver. Sometimes the organ is pale, 
and appears deficient in its supply of blood ; 
at other times it has a generally diffused red- 
ness, or the congestion may be greater in some 
situations than in others. The consistence of 
the liver in hypertrophy is equally variable 
with its colour: sometimes it is softer than 
natural, at other times it is dense and appa- 
rently granulated, the uncongested part pro- 
jecting from the surface, and the congested 
portion sinking beneath its level. Hyper- 
trophy of the liver is generally associated with 
chronic disease of the lungs, scrofula, and 
rickets, and often exists as a cause in ascites. It 
has been observed fifteen, eighteen, thirty-five, 
and even forty pounds in weight, and to have 
produced the displacement of the other abdo- 
minal viscera by its enormous size. 

c. Atrophy of the liver is a condition of the 
nutritive functions of the organ which may 
succeed chronic inflammation or even hyper- 


ABNORMAL ANATOMY OF HE LIVER. 


trophy ; it occurs more rarely than hypertre 
to which its comparative frequency has bee 
estimated by Portal as 5to95. The substa 
of the liver diminishes in bulk, the 
become indistinct and variously congest 
they appear intermingled we 
by the cellular structure with which th 
surrounded. Sometimes the proper 
of the liver is entirely removed and 
by a loose or condensed cellular ti 
other times the entire substance of th 
is to have been absorbed by an er 
abscess, which has evacuated its cont 
the intestinal canal, and the parietes 
terwards contracted and degenerated i 
atrophied mass. Lieutaud gives an 
of a liver that was shrivelled into a on 
larger than his fist. Portal found the liver | 
a case of ascites not bigger than an apple. 
ordinary size. Partial atrophy of the li 
conjoined with hepatic venous ion is n 
an te consequence of the practice 
lacing. I have before mea very interesting spe 
men of this affection. The surface of the live 
marked by deep fissures into irregular pe 
gonal divisions resembling very strikingly 
lobulated appearance of the foetal kidney. — 
One situation the stages of this change are’ 
tinctly apparent ; a certain portion of the or 
about half an inch in breadth, has beco: 
partially atrophied from the pressure of 
adjoining and protuberant portions of the 1 
and in the lobulated portion the ie su 
stance of this atrophied mass has col 
pletely removed by absorption, leaving a 
of condensed cellular cicatrix extending like 
septum for some distance into the organ, 
is in this way that many of the grooves at 
fissures upon the convex surface of the liv 
are raat 

But the most interesting form of atro 
the liver is that which was named by 
cirrhosis. In cirrhosis, the liver is diminish 
in volume to the extent of one-half or on 
third of its natural bulk, the relative si 
the right and left lobes is destroyed, ar 
surface is rendered shapeless by the projec 
of a number of ridges or granular points. — 
entire organ appears wrinkled and shri 
and ofa yellow or greenish colour, varying i 
tint from a bright chrome to a yellowish 
greenish brown. Upon dividing it with 
knife it is observed to be more dense the 
usual, and the surface of the section present 
number of patches of variable size and of 
roundish form, which resemble granules; hen 
this condition of the organ is named by 
French authors “ foie granuleux.” In an a 
vanced stage it is accompanied with jaune 
and ascites, and is frequently preceded by som 
disease, either of the lungs or heart. 

Kiernan is, I believe, the first pathologi 
who distinguished the true nature of cirrhosis, 
which he called atrophy of the liver. A very 
interesting case of this disease occurred in St. 
Bartholomew’s Hospital, under the care | 
Dr. Latham, in 1832, an account of which ws 
published in the Lancet in November of thi 


Fal 


= 


-! 


a 


hen 


»~ 


i 


ABNORMAL ANATOMY OF THB LIVER. 


year. The patient died with jaundice and 
ascites. The liver, a portion of which I pos- 
sess, presented a fine specimen of granulated 
cirrhosis; it “ was diminished to one-half its 
natural size, and Mr. Kiernan on injecting it, 
discovered that a collateral venous circulation 
had been established by way of the diaphragm.” 
In another case in a woman who had been 
tapped ninety times, Kiernan upon injecting 
the liver found that the same kind of collateral 
circulation had been formed. The circulation 
through the liver had been impeded by the 
developement of condensed cellular tissue, and 
the greater part of the blood of the portal vein 
had made its way through dilated vessels upon 
the surface of the organ to the diaphragm, and 
from thence into the general venous circulation. 
Tn this case there were numerous bands of ad- 
hesion between the liver and diaphragm, and 
between the intestines and the walls of the 
abdomen, and these also were traversed by 
large veins conveying blood from the portal 
vein into the genera! venous current. 

With regard to the pathological nature of 
the disease many opinions have been enter- 
tained by different writers. Laennec, dazzled 
by an ingenious theory deduced from his ob- 
Servations upon the nature and progress of 
scrofulous tubercle, saw in the mottled and 
granular section of cirrhosis only a “ morbid 
deposit,” a special accidental tissue existing in 
the two states of crudity and softening. But 
I quote the words of this author as detailed by 
Ferrus,* for while he errs in his speculations 
with regard to the nature of the disease, he 
draws an excellent picture of its general cha- 
racters and appearance. “ Les cirrhons ex- 
istent dans l’état de crudité et de ramollisse- 
ment. Dans le premier de ces états elles 
présentent un tissu d’une couleur fauve plus 
au moins foncée, qui quelquefois tire un peu 
sur le verdatre; on ne peut s’en faire une 
meilleure idée qu’en la comparant a celle 

u’offrent les capsules surrénales chez l’adulte. 

e tissu, quoique fort consistant, a une sorte de 
flaccidité que je ne puis mieux comparer qu’ a 
celle de certains fongus, ou d’un cuir mou. 
Le tissu des cyrrhoses est d’ailleurs compact, 
assez humide et trés-délié. On n’y distingue 
aucune trace de fibres, quoiqu’il presente en 
certains cas des divisions en forme de squames. 
Les cyrrhoses prennent en se ramollissant une 
couleur plus brunatre.” 

«M. Laennec admet trois sortes de cyrrhoses: 
1°. cyrrhoses en masses; 2°. en plaques; 
3°. en kystes. Lorsqu’il existe, dit-il, des 
cyrrhoses dans le foie, elles forment ordinaire- 
ment de petites masses dont le volume ne 
Surpasse jamais celui d’un noyau de cerise, et 
quelquefois égale 4 peine celui d’un gros grain 
de millet. Ces masses sont toujours extréme- 
ment nombreuses, et tout le tissu du foie en 
est par-emé. Leur petitesse fait que lorsqu’on 
incise un foie dans lequel il en existe un grand 
nombre, son tissu parait au premier coup d’eil 
homogeéne et d’une couleur jaune fauve. Mais 
si on examine plus attentivement le tissu hepa- 
tique, on s’apercoit facilement qu’il est rempli 

* Dictionnaire de Médecine, Art. Foie. 


189 


d’une innombrable quantité de corpuscules 
assez semblables, pour l’aspect 4 ces lobules 
de graisse durcie et rousse&tre que l’on trouve 
communément dans le tissu cellulaire sous- 
cutané de la cuisse et de la jambe des sujets 
attaqués d’anasarque. Ces petites masses sont 
que!quefois unies trés-intimement au tissu du 
foie ; mais assex souvent elles en sont separées 
par une couche mince de tissu cellulaire qui 
leur forme une enveloppe tenue, et alors ils se 
détachent assez facilement. La surface exté- 
rieure du foie devient flétrie, rugueuse, et ratatinée 
a-peu-pres de la méme maniére qu’umé pomme 
flétrie.” 

Bouillaud* considers this condition of the 
liver a dissociation of the two natural elements 
of the organ: “ les masses jaunes fauves con- 
stituant le tissu accidentel, appelé cirrhose, ne 
sont autres chose que les granulations secre- 
toires se desorganisant graduellement par l’effet 
de l’obliteration du lacis vasculaire, et de 
Vobstacle a la circulation hepatique qui en 
resulte.” We have already combatted the ex- 
istence of two substances, and further remark 
upon this subject must be quite unnecessary. 

Andral + sees, in the cirrhosis, atrophy of the 
red substance and hypertrophy of the yellow 
substance. Of all modern authors, Cruveilhier 
approaches nearest to the true condition of the 
organ, but from his misapprehension of the 
exact nature of the lobules, even his opinion 
cannot be accepted without limitation. Chetia: 
sis, says this author,} is “atrophie du plus 
grand nombre des grains glanduleux, et hyper- 
trophie avec coloration jaune des grains glandu- 
leux restans.” Now cirrhosis is undoubtedly 
a partial atrophy of the liver with hypertrophy 
of the cellular structure; complete atrophy of 
some of the lobules, partial atrophy of others, 
and biliary congestion without atrophy or hy- 
pertrophy of the rest. Those small yellow 
grains varying in size from a millet-seed to a 
pea or to a hazel-nut, are not distinct lobules 
in a variable state of hypertrophy, but small 
uncongested patches eomipoaedl of parts of 
several adjoining lobules, and having a single 
or several interlobular spaces for a centre. 
Hence it is, as we have before shown, that Cru- 
veilhier§ has observed the “ partie centrale de 
chaque granulation repond au radicule biliare, 
et consequemment est souvent teinte en jaune 
et que la partie excentrique repond & l’element 
vasculaire et consequemment est plus rouge 
que la partie centrale.” 

d. Softening of the liver may accompany any 
of the changes resulting from acute inflamma- 
tion. The degree of softening is very variable, 
the organ having at one timea simple abnormal 
degree of friability when pressed by the hand, and 
at others constituting a pulpy mass scarcely re- 
tained in its form by the cellular framework of its 
vessels and Glisson’s capsule. Softening may be 
unaccompanied by any marked change in the 
bulk of the organ, but is always associated with a 
variable intensity of venous congestion. Biliary 


* Mémoire de la Societé Médicale d’Emulation, 
+ Anatomie Pathologique, vol. ii. p. 

${ Anatomie Descriptive, vol. ii, p. 568. 
§ Anatomie Pathologique, livraison 12. 


190 


congestion is also frequently present, and tinges 
the substance of tg Tith a variable hue 
of yellow, green, &c. Portal observes that the 
liver of patients who have died of scurvy is 
often so much softened that it appears in a 
State of decomposition, has a reddish brown 
colour, and resembles the lees of red wine. 
Baillie remarks that sofiening of the liver is 
not uncommon in old persons, that it a 
proaches in consistence to the texture of the 
spleen, and is ofa brownish red colour. 

e. Induration of the liver is occasionally 
attendant upon hypertrophy or atrophy of the 
organ, but it may also exist with a normal size 
of the liver without other rs agers change than 
the brownish red tint which it receives from 
venous congestion, or the various shades of 
yellow, green, or brown induced by biliary 
congestion. The density and hardness acquired 
by the liver in a state of atrophy are sometimes 
truly astonishing. In a case detailed by Mor- 
gagni the organ resisted the knife, and several 
such instances are to be met with among the 
writings of the older pathologists. 

J. Fatty degeneration of the liver—Upon 
referring to the section upon the chemical 
analysis of the liver, it will be observed that a 
certain proportion of oily matter is one of its 
natural constituents. Under the influence of 
diseased action this quantity is greatly aug- 
mented, and increases to such an extent as 
completely to take the place of the normal 
structures. Vauquelin has published an analy- 
sis of a fatty liver, from which the quantity of 
oily matter present may be fairly estimated 
thus; in 100 parts he found, 


| eeeoeee seed ee 45 
Parenchyma ........ 19 
Water or eee sere eeeee 36 

100 


The fatty matter is usually distributed equally 
through the organ, being apparently infiltrated 
into the cellular texture of the parenchyma. At 
other times it is deposited in a mass or forms se- 
veral collections in different parts of theliver. The 
fatty liver 1s greasy upon the surface, and when 
cut into has the appearance of a section of 
yellow soap. The vessels seem pressed upon 
and are scarcely perceptible, while the 
deposition is divided into angular masses by a 
coarse and compressed cellular tissue. 

Fatty liver is generally consistent and solid 
in its texture, but sometimes the fat exists 
almost in a fluid state. Portal has observed 
the liver quite white and softened almost to the 
fluidity of melted fat, where no hepatic sym- 
ptoms existed during life; and he particularly 
records the case of a woman suffering under a 
severe form of syphilis in which this condition 
of the liver existed. 

From the name which has been given to this 
disease by pathologists, fatty degeneration, we 
might be led to infer that the texture of the 
organ was actually converted into this oily sub- 
stance. This, however, is quite inconsistent 
with our knowledge of pathological phenomena. 
The fatty deposition is obviously an undue 


ABNORMAL ANATOMY OF THE LIVER. 


secretion of a normal constituent, but wheth 
resulting from irritation from whatever causi 
or from absence of vital energy, is a quest 
upon which I am unwilling, without furtl 
investigation, to hazard an opinion. f 
regard to the causes of fatty liver Am 
observes, “ Les causes sous |’influer 
phe eae le foie devient le siége d’une 

e matiére grasse sont encore inconnues. ( 

émis qu’une hypothése lorsq’on a dit que 
dégénération graisseuse du foie était le pro 
d’une irritation de cet organe. Car on po 
tout aussi bien soutenir que cette dégénéra 
graisseuse, loin d’avoir été précédée par un 
dirritation du foie, est survenue parcequt 
nutrition de cet organe est devenue mo 
active; et cette derniére hypothése serait d% 
tant plus soutenable, qu’elle se déduirait d’ 
grande loi de l’économie en vertu de laqué 
toutes les fois qu’un organe tend a s’atro 
une matiére grasse vient & se sécréter autour’ 
cet organe ou ala place méme de ses mo 
cules.”’* 

Fatty liver is most frequently observed” 
persons who have died from scrofulous tuber 
in the lungs; in those, says Andral, in 
the blood has not been efficiently arterial 
and in whom the pulmonary exhalatic 
greatly diminished. Can it be, he inqui 
from the absence of the due separation 
hydrogen from the lungs that this compoune 
hydrogen, fat, becomes deposited in the pare 
chyma of the liver? ‘This question is wi 
deserving the attention of pathologists, 
solution might lead to important inform: 
The disease has also been observed in 
cancerous disorders and in dartrous dise 
of the skin. 

g- Pus. Abscess in the liver occurs in 
rincipal forms, either as a single abscess + 
arge size inclosed in a cyst, or as numero 

small collections of matter, bounded by 
substance of the liver or diffused amongst 
lobules. In the first form it constitutes idi 
pathic abscess of the liver, a disease of tropi 
countries, and rare in our tem te 
Abscess is generally preceded by acute inflai 
mation and more rarely by chronic inflam 
tion, and attains an enormous size, engrossi 
the whole of the right lobe and sometimes ¢¢ 
verting the entire organ into one huge cy; 
The cyst may be thin or thick, and more or! 

organised. Andral and Louis conceive th 
its internal surface is analogous to at 
membrane. The quantity of pus contained 
one of these abscesses varies from a few ow 

to several pints. My friend Dr, Macna 
who has seen much practice in the West 
during a residence of twenty-two y 
Jamaica, has observed that abscess in the liv 
occurs more rarely in the West than in the EB 

and, moreover, that this disease affects the Bur 
peans and not the Negroes. During the who 
of his experience he never saw a single case of 
abscess in the liver in the Negro, and among the © 
white population of his district only four well 
aienanaial 


* Anatomie Pathologique, vol. ii. p. 597 


ZZ 


ABNORMAL ANATOMY OF THE LIVER. 


__ The irritation of abscess causes the effusion 
_ of lymph and adhesion to the abdominal pa- 
rietes or to the adjoining viscera ; ulceration fol- 
_ lows, and the contents of the cyst are discharged 
_ through the artificial opening. The situations in 
which the matter escapes from the cavity of the 

abscess are various. 1. It may burst externally, 
_ making its way either between the ribs or up- 
wards towards the axilla. In a case observed 
by Dr. Macnaught the abscess pointed at the 
epigastrium and was opened by the surgeon in 
attendance. 2. It may become adherent to the 
diaphragm and burst into the pleura. 3. It may 
cause adhesion between the serous membrane 
_ of the liver and of the diaphragm, and between 
_ the latter and the pleura pulmonalis, and the 
matter may escape into the lung and be 
coughed up, as in the case already detailed, 
which occurred to Dr. Munro. 4. In rare cases 
_ the pus has been effused into the cavity of the 
_ peritoneum. 5. The abscess may become adhe- 
rent to the stomach, duodenum, or colon, and 
the matter be discharged into the alimentary 
canal. A well-marked case of abscess dis- 
charging its contents into the stomach occurred 
to myself in the case of a woman who has 
Since perfectly recovered. About two pints of 
matter were vomited by the patient. In a simi- 
lar case observed by Dr. Macnaught the patient 
recovered. In two other cases, where the 
matter was poured into the intestines, the 
patients died. 6. Abscess has been seen to 
Open into the gall-bladder, and the pus to be 
conveyed thence through the ductus communis 
choledochus into the duodenum. 7. In one 
case the matter was discharged into the vena 
cava; and in another, 8, described by Dr. 
Smith, into the pericardium; and in a case 
detailed by Dr. Graves,* the abscess opened 
both into the stomach and pericardium. 

Besides the preceding form of abscess, which 
is idiopathic in its origin, abscess may occur in 
the liver from external injury, as from a blow. 
The inflammation attending upon this injury is 
much slighter than that which gives rise to 
idiopathic abscess; the collection of matter is 
generally smaller, and terminates either by dis- 
charging its contents or by absorption. 

The second variety of abscess in the liver, 
that in which numerous purulent collections 
exist, depends for its cause upon the occurrence 
of wounds or, of surgical operations. The suc- 
cession of abscesses in the liver from wounds, 
particularly of the head, has long since been 
admitted as a well-established fact, for the 
explanation of which numerous theories have 
been invented. Theory, however, has now 
5 yielded before facts,—facts, too, of the most 
interesting and satisfactory kind, for which 
= 
4 


? 


pathology is indebted to the genius and indus- 
try of Cruveilhier. The experimental re- 
searches + of this excellent author, published 
in 1826, enabled him to establish a law of the 
utmost importance in the consideration of the 
phenomena of disease, viz. that “ tout corps 


* Dublin Medical Journal, January 1839. 
+ Recherches sur la siege immed, de ]’inflamma- 
tion. Nouv, Bibl. Med. vol. iy. 


191 


etranger introduit en nature dans le systeme 
veineux determine lorsque son elimination par 
les emonctoires est impossible des abscés viscé- 
raux entitrement semblables 4 ceux qui suc- 
cédent aux plaies et aux opérations chirurgicales, 
et ces abscés sont le resultat d’une phlebite 
capillaire de ces mémes visceres.”* These 
experiments consisted in the introduction of 
metallic mercury into the veins of an animal, 
say of the lower extremity. In the course of 
twelve, eighteen, or twenty-four hours the animal 
experienced much difficulty of breathipg, and 
soon expired. Upon inspection globules of the 
mercury were found in the lungs. Ifa smaller 
quantity of mercury were introduced the animal 
would live for several days or weeks, and upon 
examining the lungs at different periods the 
globules were at first seen to be surrounded by 
a red induration and afterwards by pus. This 
experiment was varied by pouring the mercury 
into the medullary cavity of a bone with pre- 
cisely the same results; in one instance he 
placed a single globule in the medullary cavity 
and found it again at the end of a month in 
the lungs, divided into several minute globules, 
each of which formed the centre of a small 
tuberculous abscess. Cruveilhier then injected 
a small quantity of mercury into one of the 
omental veins of a dog—the subject of umbili- 
cal hernia; the dog was killed in the third 
month after the operation, being reduced toa 
state of marasmus. Upon inspection the liver 
was found filled with small abscesses, each 
surrounding a small globule of mercury. Having 
by means of these experiments satisfied himself 
that the lungs were the barrier to all foreign 
matters introduced into the general circulation, 
as was the liver of those admitted into the 
abdominal circulation, he proceeded to another 
series of experiments. Opening a vein in the 
hinder extremity of a dog he introduced into it 
a long piece of stick, which gave rise to 
phlebitis aud the secretion of pus. The pus 
thus produced being carried into the circulation 
excited, in the first instance, abscesses in the 
lungs, and, secondly, in the liver. Upon 
these facts and upon a multitude of excellent 
observations Cruveilhier founds his opinion that 
abscess in the liver from wounds and surgical 
operations is always preceded or accompanied 
by purulent collections in the lungs, and 
always results from the same cause, viz. from 
capillary phlebitis, consecutive upon phlebitis 
in the neighbourhood of the wound, and im- 
mediately produced by the irritative action of 
globules of pus brought from the diseased veins 
to the capillaries of the structures in which the 
secondary suppuration is developed. 

In every case of secondary abscess in the 
liver, following wounds of the head, or after 
amputation or operations upon bones, Cruveil- 
hier has found phlebitis of the vessels situated 
in the structure of the bones. Hence he esta- 
blishes an important general proposition, that 
“ le phlébite des os est une des causes les 
plus fréquentes des abscés viscéraux suite des 
plaies et des opérations chirurgicales dans 


* Anatomie Pathologique, liv. xi. 


192 


lesquelles ces os ont été intéressés.” The re- 
moval of hemorrhoids and operations upon the 
uterus are sometimes followed by abscess of 
the liver, a circumstance which is easily expli- 
cable upon the principles so clearly demon- 
strated by this author. 

An excellent instance of secondary abscess 
of larger size than usual has been kindly fur- 
nished to me by my frend and colleague Mr, 
Rutherford Alcock, who, from his official posi- 
tion in Spain and Portugal during the recent 
struggles, has had much experience in injuries 
to the head. A man received a bayonet wound 
in the scalp, and died upon the fourteenth day 
after his admission into the hospital. Upon 
inspection there was observed thickening of the 
dura mater and a small quantity of matter 
upon the pia mater. No pus was discovered 
in the lungs, but a large abscess was found 
occupying the greater part of the right lobe. 
A statistical report from a work upon gun-shot 
wounds by the same author is also interesting. 
“ Of scalp wounds, with and without abrasion, 
there were sixty-one; two only died, and one 
only presented disease of the liver; the other 
died from an attack of erysipelas.”’ 

The pathological changes which take place 
in the liver in these cases are, in the first 
instance, effusion of blood and lymph and 
induration around the inflamed vein ; secondly, 
a.secretion of a yellow concrete pus into the 
ninute veins and among the lobules, giving to 
the liver, as Cruveilhier remarks, a granite-like 
appearance. In the next place the pus collects 
into small abscesses lodged in irregular cells, 
which increase in size by continued secretion 
and by communication with other cells. All 
these collections of matter are surrounded by a 
congested circle, which gives them a peculiar 
and characteristic appearance. After having 
existed for some time Cruveilhier has observed 
that the pus becomes converted into a concrete 
mass, very closely resembling the matter of 
scrofulous tubercle. 

h. Tubercle in the liver is a disease of rare 
occurrence, and has seldom been observed 
independently of the existence of similar depo- 
sitions in the lungs and other organs of the 
body, and of general indications of a scrofulous 
diathesis. When present, it exists in the form 
of small rounded tubercles, generally numerous, 
and varying in size from that of a millet-seed to 
a hazel-nut. They are composed of the soft 
cheesy or curdy deposit which is characteristic 
of this disease, and have a tendency to a 
brownish colour. The tuberculous matter is 
deposited in the tissue of the lobules by infil- 
tration, and the lobules immediately surround- 
ing the tumours are compressed nt § congested. 
The obstruction to the circulation in the organ 
being general on account of the number of the 
tubercles, the entire liver is more or less con- 


i. Scirrhus.—Carcinoma affects the liver 
under a variety of forms, but appears most 
frequently as tubercles of different size and 
consistence. These tubercles are more fre- 
quent than those of scrofulous origin, and are 
generally accompanied by symptoms denoting 


ABNORMAL ANATOMY OF THE LIVER. 


a cancerous diathesis, and by the existenes 
the same time of similar tumours in other par 
of the body. In their earliest development 
the liver nearly all carcinomatous tumours pr 
— - same chara! resembling sma 
whitish, semi-opaque es,,occupying t 
tissue of one 6 pe mito g of the loblead 
they increase in size they put on certain peculij 
ap ces, which have gained for t 
subdivision into species and varieties. 
not intend in this place to enter into the 
rangements proposed by authors, but will bri 
describe the most striking varieties that hi 
fallen beneath my own examination. The s 
plest of these tumours has been termed 8 
rhous tubercle, a name which appears parti 
larly applicable from its resemblance in ¢h 
racters and structure to the same form of t 
mour occurring in other parts of the bo 
Commencing like the carcinomatous tume 
generally in a semi-opaque patch, the outl 
the lobules is for some time distinctly perce 
tible through its area, but at a later perid 
centre of the patch becomes quite opaque, 
presents a cartilaginous hardness .nd creakit 
sound when divided with the knife. Thee 
cumference is gradually diffused in the su 
rounding textures, and the progressive inerea 
of the tumour seems to take place by the 
cretion of a milky albuminous fluid into 
meshes of the lobular venous plexuses. 1 
circulation in these plexuses is at first uni 
peded, but by the increase and induration 
the secretion it is gradually arrested, and 
vessels obliterated. The obliterated 
give rise to the appearance of small cells, i 
which the carcinomatous matter is deposi 
and the larger are are produced by the tissu 
of the capsules of the lobules variously dis 
torted from their original form by the inere 
deposition. As the tumours become more an 
more large, white lines, formed by compresse 
cellular tissue, are observed radiating from tl 
centre towards the circumference. When 
upon the surface of the liver, the scirr 
tubercle appears flat, or very slightly depresse 
towards the centre. In a preparation of thi 
form of tubercle now before me, the 
tumour is slightly raised above the surface 
presents no central depression, is cartilaginou 
in appearance, and has an irregular outlit 
Its section is dense and hard like cartilagi 
with no appearance of vessels, and of th 
tly and semitransparent whiteness whi 
is generally observed, in scirrhous tube 
particularly in the variety which this prepa 
tion illustrates. Sometimes these tubera a 
small and very numerous, of a yelloy 
brownish colour, and have a great activity: 
increase ; the cells in which they are cont: 
are thick and of larger size, and the albun 
nous secretion less firm than in the precedin 
variety. Occasionally they are reddened in th 
centre by the effusion of blood, from the con- 
gestion of unobliterated vessels, and some- 
times by the continuation, through the tumour 
of dilated vessels, which supply them 
nutrition. In their enlarged state 
quently coalesce and give rise to an i 


mort) Ls 


ABNORMAL ANATOMY OF THE LIVER. 


- compound mass, which assumes the form of 
_ the particular part of the organ in which it is 
placed, and is divided into compartments, 
marking its original multiple form by septa of 
condensed Glisson’s capsule supporting dilated 
vessels. It would appear to be this form of 
tumour which has been described by Farre as 
the first variety of his tubera diffusa; he gives 
them the following character. ‘‘ Tubera, ele- 
vated at the surface of the organ, but not uni- 
form in their figure, some rising with a regular 
Swell into a round form, others acquiring a 
margin by being gradually depressed towards 
the centre, forming tumours without cysts, 
almost pulpy in their consistence, cellular in 
their structure, and containing an opaque white 
fluid.” 

_ Another form of the albuminous carcinoma- 
tous tumour is the “ large white tubercle” of 
_ Baillie, the tubera circumscripta of Farre, by 
whom they are thus admirably described : 
Their colour inclines to a yellowish white, 
and their projecting surfaces, slightly variegated 
with red vessels, deviate from a regular swell 
by a peculiar indentation at or near their cen- 
tres, which are perfectly white and opaque. 
They vary much in size, which depends on the 
duration of each tuber, for at its first appear- 
ance it is very minute, but during its growth it 
assumes the character above described, and at 
its maturity exceeds an inch in its diameter. 
They adhere intimately to the liver, and their 
figure is well defined. They commonly remain 
distinct at the surface of the liver, but inter- 
nally they ultimately coalesce and form im- 
mense morbid masses which pervade its sub- 
stance. They possess so close a cellular struc- 
ture that the section of them at first view 
appears solid and inorganic; but on the edge 
of the knife, by which they have been disse- 
vered, an opaque white fluid of the consistence 
_ of cream is left, and a fresh portion of this 
fluid is gathered on it at each time that it is 
repassed over the surface of the section. Their 
cellular structure becomes more apparent after 
long maceration.” 

The depression in the centre of carcinoma- 
tous tumours, although generally met with, is 
not a necessary character of cancer. Its mode 
of formation has been ably pointed out by Dr. 
Carswell, in his beautiful work on pathological 
anatomy: “ The depression is not observed 
_ unless when the tumour is divided or is situ- 
ated on the surface of an organ, as the liver, 
_ where tumours of this kind are generally met 

with. In the former case the depression arises 
_ from the softer substance, after the division of 
the tumour raising itself by its elasticity above 
the unyielding nucleus; in the latter it is pro- 
duced hy the peritoneum adhering to the sur- 
face of the tumour when small, and preventing 
its development in that direction. If the tu- 
mour does not come in contact with the peri- 
_ toneum until it has acquired a considerable size, 
it presents no such depression, or only a very 
small one. Hence the reason why, in carci- 
noma of the liver, we meet with some tumours 
having a smooth globular surface, and others with 
a central depression of greater or less extent.” 

VOL. IIT. ; 


193 


Another variety of carcinomatous tumour is 
named the gelatiniform cancer, from the exis- 
tence of a firm and jelly-like deposit which oc- 
cupies the cells of the tumour in place of the 
albuminous secretion common to the preceding 
forms. I have before me an interesting speci- 
men of gelatiniform tubercle. The liver con- 
tains a considerable number of these tumours 
of variable size, and dispersed through every 
part of its structure. The smallest resemble 
the small patches described above as the inci- 
pient stage of carcinomatous tumour generally ; 
the largest are equal in size to a walnut. They 
are distinctly circumscribed, and the lobules 
immediately surrounding them are flattened 
and compressed. In the smaller tubercles the 
form of the lobules is quite distinct, but in the 
larger the lobules have yielded to the peculiar 
characters of the disease. On the surface the 
centre of the tubercle presents an oval or cir- 
cularly indented ring, around which the tumour 
swells suddenly and then subsides to the cir- 
cumference. On making a section of one of 
these tumours, 1 found a central area of about 
two lines in diameter, transparent, dense, and 
apparently gelatinous, and distinctly bounded 
by a white marginal line; the marginal portion 
of the section forming the bulk of the tumour 
was elastic, and rose above the central area to 
subside gradually in the marginal line of the 
circumference. The whole section bore a stri- 
king resemblance to the conjunctiva affected 
with chemosis, only that it was paler in its 
colour, or to a beautiful flower with a single 
large and expanded circle of petals. On exa- 
mining a thin section with a lens of low power 
a number of minute parallel injected capillaries 
were seen traversing the marginal portion of 
the tubercle towards the boundary line of the 
area, but no vessels could be traced beyond 
that line into the central portion. The resem- 
blance to the petals of a flower was produced 
by white lines which radiated from the boun- 
dary line of the area to the circumference, and 
divided the marginal portion of the tumour 
into six or eight compartments. From careful 
examination it appeared to me that the central 
area was a single lobule expanded by the gela- 
tinous deposition with which its tissue was in- 
filtrated, and the marginal compartments pre- 
sented a similar character. 

k. Medullary sarcoma.—Another form of tu- 
bercle, associated with the cancerous diathesis 
and belonging to the carcinomatous family, is 
medullary sarcoma, or encephalosis. The tu- 
mours produced by this disease are larger than 
scrofulous tubercles, and more regular in form 
and fewer in number than scirrhous tumours, 
Developed originally in the same way with 
scirrhus, by infiltration into the tissue of the 
lobules, or into the vessels themselves, of the 
peculiar greyish white and opaque substance of 
which they are composed, they increase in size 
and obstruct the circulation in the surrounding 
lobules. Their internal structure is a loose 
cellular base, filled with a soft and brain-like 
matter, frequently coloured with blood, or 
containing coagula in various stages of soften- 
ing, resulting from hemorrhagic extravasation, 

cs) 


194 


Sometimes these tumours present a certain de- 
gree of consistence, but as they increase in 
size they become more and more softened and 

M Baillie describes a large tumour in 
the liver which he considers scrofulous from 
being softened in the centre, and containing a 
fluid resembling pus; this is most probably 
a tumour of the kind I am now describing. 
Another tumour, of which he expresses himself 
at a loss to understand the nature, soft, of a 
brownish colour, and of about the size of a 
nut, appears to be also referable to the same 


es. 

The second and third varieties of the tubera 
diffusa of Farre present characters resembling this 
disease. V. 2. “ Tubera, elevated at the surfaces 
of the affected organ, encysted, or having dis- 
tinct cells, formed by the growth of a fungus, 
which separates in flakes, and is composed of 
a fine reticular texture, containing an opaque 
white fluid.” V. 3. “ Tumours rising with a 
regular swell from the surfaces of the affected 
parts and yielding to the touch, composed of a 
very delicate reticular texture, pulpy in its 
consistence, varying in its colour even in the 
same subject, charged with an opaque fluid, 
and growing from cysts or cells.” 

Cruveilhier considers the venous capillary 

stem as the seat of origin of carcinoma, par- 
ticularly of the form which I am now consi- 
dering ; hence he observes, “ Ayant exprimé 
d’une coupe faite 4 un foie cancéreux une ma- 
titre d’un blanc-rougeatre, encéphaloide qui 
se moulait 4 la maniére du vermicelle, et qui 
pouvait acquérir en se tordant une grande lon- 
gueur, j’apercus sur cette coupe un orifice plus 
considérable que les autres ; j'incisai cet orifice 
et je parvins dans un vaisseau tres volumineux 
qui me parut étre une des ramifications de la 
veine porte. Alors je disséquai avec beaucoup 
d’attention cette veine, et je ne fus pas peu 
€tonné de voir que cette veine, depuis les plus 
grandes jusq’aux plus petites divisions, était 
remplie par cette matiere encéphaloide, adhé- 
rente aux parois et tout-a-fait semblable a celle 
or exprimait par les coupes faites au foie. 

1 me fut facile de suivre les ramifications ex- 
tremement dilatées de la veine jusque dans 
l’areoles des coupes. L/altération était bornée 
a la veine porte, les veines hépatiques et leurs 
ramifications étaient parfaitement saines.’’* 

l. Fungus hematodes is the term applied to 
all carcinomatous tumours which have a ten- 
dency to the unnatural development of new 
vessels and to effusions of blood into their tissue. 
In the same organ, hard and cartilaginous 
scirrhous tumours may exist with those of a 
softer texture, and of a medullary form, and 
both of these may be mingled together in the 
soft, elastic, and bleeding mass which consti- 
tutes fungus hematodes. The tumours of 
fungus hematodes are often of very large size, 
and by their frequent hemorrhagies give rise to 
extreme eee and the speedy death of the 
patient. Farre arranges this form of carcinoma 
among his tubera diffusa, of which it forms the 
fourth variety, which he thus defines: “ Tu- 


* Anatomie Pathologique, liv. 12. 


“ABNORMAL ANATOMY OF THE LIVER. 


mours elevated at the surfaces of the liver and 
inclining to a round figure ; pulpy in their con- 
sistence, being charged with a thick and opaque 
fluid, variegated in their colour, chiefly hite 
mingled with red, the former prevailing in thei 
incipient, the latter in their advanced stage 
composed of a very vascular and reticular te 
ture, attached either to distinct pouches or 
the substance of the liver, and so unlim 
and rapid in its growth as to burst or destn 
the peritoneal tunic of this organ and to 
trude in the form of a bleeding fungus.” 
_m. Melanosis.—Melanosis exists in the li 
as in other structures of the body, 1st, as 
melanic secretion infiltrating the cellular str 
ture of the organ, and giving a diffused gene 
blackness to the substance of the lobules; 2 
as a morbid tissue com of an areolar: 
lular network, in which the black carbonace¢ 
matter is deposited; or 3dly, as a mela 
pigment accompanying carcinoma or tuber 
and imbuing the abnormal tissue with its’ 
culiar colour. The colour of melanosis in t 
liver varies from a deep chocolate-brown t 
rich black. Sometimes it is diffused in patel 
through the substance of the organ, at oth 
times it exists in the form of rounded cireut 
scribed tubercles of variable size and numb 
Laennec considers melanosis as an 
tissue without analogue among the animal t 
sues ; he classes it with cancerous deger 
tions, and describes it as existing in his tt 
favourite conditions of crudity and soften 
But the researches of Cruveilhier have shey 
that in many instances melanosis is to be t 
ceived as a mere pigment, resembling the p 
mentum nigrum of the choroid, which impress 
its peculiar colour upon natural and mor 
tissues, and he has also proved, in oppositi 
to the view entertained by Laennec, that 1 
softened state or state of infiltration 
que? recedes the more dense and en 
orm. Melanosis rarely exists in the liver 
out being at the same time found in vario 
other structures of the body, as in the brat 
eye, lungs, heart, spleen, kidney, mucous m 
brane, muscles, skin, &e. 
6. DisorpERs or FruNcTION.—The princi 
function of the liver being the secretion of b 
we shall have to consider under this head ¢ 
changes which may occur in the secretion” 
this fluid and in the fluid itself, in consequei 
of derangement of function in the organ. The 
disorders may be divided into three kinds: 
a. Suppression of the bile. " 
b. Alterations in the physical properties 
the bile. ‘ 
c. Alterations in the chemical qualities” 
the bile. ; 
a. Suppression of secretion of the bile, 
suppression of urine, occasionally occurs — 
the liver. This disease appears to have be 
known to Darwin,* who calls it “ ps 
the secretory vessels” of the liver; the patients, 
he says, “ lose their appetite, then their fles 
and strength diminish in consequence, the 
appears no bile in their stools nor in their urine 


. 
Aaccide 


ull 


* Zoonomia, vol. ii, p. 5, 


x 


_ its physical properties. 
ts prop 


ABNORMAL ANATOMY OF THE LIVER. 


nor is any hardness or swelling perceptible in 
the region of the liver.” Kiernan, who has 
observed several cases of this disease, informs 
me that the symptoms are sudden jaundice, 
depression of the powers of the system, and 
speedy dissolution ; upon dissection he found 
complete absence of bile in the biliary ducts, 
the mucous membrane of which appeared 
bleached. 

b. Alterations in the physical properties of 
the bile-——The changes to which the bile is 
liable are in no wise referable to any particular 
alteration in the liver. In cases where this 
organ has been considerably diseased, the se- 
cretion of the bile has been found natural and 
healthy; and in other cases, where a slight de- 
gree of congestion was all the apparent patho- 
logical derangement, the secretion has assumed 


_ a morbid epEerance, or has been deficient or 


Superabundant in quantity. Gall-stones are 
sometimes found in the gall-bladder without 
any admonitory symptoms during life, and 
icterus may be a frequent and even a fatal 
malady without any obstruction appearing in 
the course of the biliary tubes after death, or 
without any satisfactory indications of diseased 
action in the liver. “I have been sometimes 
astonished,” says Andral, “ on seeing the 
enormous quantity of bile which distended the 
alimentary canal in cases where the slightest 
degree of congestion existed in its coats, and 
when the liver appeared in no wise altered.” 
Nay, it has been proved both by observation 
and experiment that the bile is materially 
changed in appearance, quantity, and consist- 
ence by the mere alteration of diet. Experi- 
ments made upon living animals have long 
since shewn that bile taken from different indi- 
viduals is capable of producing very different 
effects upon the animals into whose bodies it 
has been introduced; thus some will give rise 
to a trifling irritation, while others will occasion 
more or less serious symptoms and even rapid 
death. Some bile may be touched and even 
tasted without inconvenience, while other bile, 
precisely similar in appearance, will produce 
pustular eruptions and ulcerations upon the 
tongue and upon the lips. “ Here then,” says 
Andral, “ are serious changes in the bile which 
are wholly imperceptible to the investigation 
of anatomy.” 

The colour of the bile differs very consi- 
derably, being sometimes hardly distinguish- 
able from serum, and at other times presenting 
a variable tint of amber, orange, green, brown, 
olive, and even black. In consistence it is 
equally various, being one while limpid and 
diffluent, and another while black, viscous, and 
grumous. 

b. Alterations in the chemical properties of 
the bile —In chemical composition, the altera- 
tions in the bile are not less numerous than in 
In fatty liver the bile 

been found composed almost wholly of 
albumen and water. Under other circum- 
stances the natural constituents are greatly 
altered in their relative proportion. 

The formation of biliary calculi may be re- 
ferred to disproportionate secretion of the na- 


195 


tural elements of the bile, the increased quantity 
of certain of its constituents giving rise to the 
deposition and accretion of these substances in 
a form corresponding with the cavities in which 
they are produced. Gall-stones have been 
found in the smaller biliary ducts in the sub- 
stance of the liver, in the excretory ducts both 
within and external to the organ, and in the 
gall-bladder. They have also been me rith 
inclosed in a cyst, formed most probably by 
the obliteration of one of the hepatic ducts, 
and adherent to the organ or suspended from it 
by a pedicle. Malpighi found gall-stones in 
the small biliary ducts and considered them as 
petrified lobules. The size of biliary concre- 
tions is very various, being sometimes exceed- 
ingly small, and at other times of considerable 
bulk. When small they are generally numerous ; 
I have counted upwards of a hundred, and in- 
stances are recorded where more than a thousand 
were found in the gall-bladder. When they 
are large they are few in number, and frequently 
single. I have seen the gall-bladder filled with 
three, two, and even one large calculus. A 
large oval gall-stone now before me equal in 
size to a pigeon’s egg I removed from the 
ductus choledochus. Their form is equally 
various with their size and other physical cha- 
racters. I have now before me gall-stones with 
a flattened shape, triangular, and tuberculated 
on the angles and on the surface; others have 
three equal facettes with sharp or flattened or 
rounded angles; others again are irregular in 
their outline and would seem to be moulded 
to the canals and cavities from which they have 
been withdrawn. Being stained by the colour- 
ing matter of the bile, their colour varies with 
the predominant tint of the secretion in which 
they have been formed, hence some are reddish 
brown or black; others are yellow, and others 
again white; some are mottled yellow and 
black, or white and black with various shades 
of green. 

In chemical composition there are, according 
to Andral, five principal varieties of biliary 
concretions ; they are, 1. of yellow colouring 
matter; 2. of resin; 3. of cholesterine; 4. of 
picromel; 5. of phosphate of lime. The first 
kind appears very ill founded, for yellow is a 
prevailing tint among gall-stones, and is the 
mere pigment by which cholesterine and the 
other substances are coloured. By far the 
largest proportion of gall-stones are formed of 
cholesterine, either pure, when it presents a 
white semitransparent mass beautifully cystal- 
lized in its interior, or variously tinted with 
brown, yellow, or orange, and radiating from 
the centre towards the circumference or from 
a small central nucleus. The smaller calculi 
also exhibit upon fracture the same radiated 
appearance. The gall-stones of resin and 
picromel may be classed together and consi- 
dered as biliary concretions formed of inspis- 
sated bile probably accreted through the agency 
of cholesterine. The calculi of salts of lime 
are less frequent ; they are found in the gall- 
bladder or in the ductus communis choledochus. 
I have observed them to present two varieties, 
firstly, incrustations of phosphate of lime upon 

02 


196 


the surface of calculi of cholesterine; and 
secondly, laminated calculi composed of con- 
centric layers of sng. and carbonate of 
lime variously coloured and having a central 
nucleus. The latter form is, I believe, rare; 
I possess but one specimen; itis of large size, 
and rough and irregular upon the surface.* 

7. Entozou-~—The Entozoa met with in the 
human liver are hydatids or acephalocysts ; 
they are inclosed in a fibrous cyst and are con- 
tained in a single parent hydatid vesicle. The 
internal surface of the vesicle is soft and often 
pulpy, and covered by minute hydatids which 
are adherent to its sides. Besides these the 
parent vesicle is usually filled with a great 
number of smaller vesicles of variable size. 
The hydatid cyst generally occupies the right 
lobe of the liver and increases to a prodigious 
size, producing absorption of the structure of 
the organ, and forming adhesions with the 
neighbouring viscera. The existence of ace- 
phalocysts may sometimes be detected during 
life by the presence of a large tumour in the 
region of the liver, which forms a projection of 
the abdominal parietes, is soft and yielding to 
examination by the hand, and unaccompanied 
with symptoms denoting cancerous disease. 
Occasionally the cyst is hardened by deposits 
of cartilaginous or bony plates. Contiacting 
adhesions with surrounding parts, the hydatid 
cyst has discharged its contents externally 
through the abdominal parietes; more fre- 
quently, however, it opens into the alimentary 
canal, as into the stomach or colon. Occa- 
sionally it bursts into the cavity of the abdo- 
men, and in one case opened into the lungs, 
and many of the smaller hydatid sacs were 
ejected by coughing. 

Some small cysts have sometimes been ob- 
served in the liver containing a calcareous 
deposit, mingled with membranous substance 
resembling fragments of hydatid sacs. These 
cysts are supposed to result from the spon- 
taneous cure of acephalocysts. 

Small intestinal worms have now and then 
been found in the biliary ducts; these are 
imagined to have gained admission into those 
tubes from the duodenum through the ductus 
communis choledochus. 


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1793. Soemmering, De concrementis biliariis cor- 
poris humani, Francfort, 1795. Baillie, Morbid 
anatomy of the human body, Lond. 1797. Gibson, 
A treatise on bilious diseases, indigestion, &c. 
Lond. 1799: Powel, Observations on the bile and 
its diseases, Lond. 1801. Schwarze, Diss. de sym- 
a inter cerebrum et hepate, Lips. 181]. Furre, 
orbid anatomy of the liver, Lond. 1812. Portal, 
Observations sur la nature et le traitement des 
maladies du foie, Paris, 1813. Ballingall, Pract. 
obs. on fever, dysentery, and liver complaints as 
they occur amongst European troops in India, 
Edinburg, 1818. Mahlendorf, De ictero, Berlin, 
1818. Mills, Enquiry into the effects produced on 
the brain, lungs, &c. by diseases of the liver, 
Lond. 1819. Thilenius, Ueber Leberentzundung 
und ibre Behandlung, &c. Hufeland’s Journal, 
vol, xviii. Ackermann, Von Entzundung der Leber 
und deren Endigung in Vereiterung, Ackermann’s 
Bemerkungen, vol. vi. Vater, Reply to Schimmer, 
De calculi in vesicula fellea generatione ; in Haller 
Disp. Path. vol. vii. Betzold, De cholelitho; in 
Haller Disp. Path. vol. iii. Haller, De calculis 
felleis, Opusc. Path. Morgagni, De calculis felleis, 
in Opusc. Misc. Percival, ‘On a new means of de- 
composing gall-stones. Beitrag, Zur Geschicte der 
Gallensteine vonEisfeld; in Isenflamms und Rosen- 
miillers Beytrag, vol. i. Pemberton, A practical 
treatise on the diseases of the abdominal viscera, 
md. Chestons, Pathological enquiries; abscess 
in the liver. Pouteau, Des ulceres de la foie a la 
snite de blessures de la téte, Cuvres, vol. ii. 
Loffier, Ueber die Leberentzundung bei Schwangern 
und Wochnerinnen. Bichat, Anatomie patho- 
Hope, Princi- 
q es and illustrations of morbid anatomy, &c. 
nd. 1834. Mayo, Outlines of human pathology, 

. Carswell, Pathological Anatomy. Cruveil- 


t, i hier, Anatomie pathologique du corps humain.* 


(W.J. Erasmus Wilson.) 


* [See also Dr. Bright’s admirable paper on 
Abdominal Tumours and Intumescence, in Guy’s 
Hosp. Reports, No, xi.—ED.] 


197 


LUMINOUSNESS, ANIMAL. (Phos- 
phorescence.) An evolution of light from the 
bodies of living animals, independent of the re- 
flection of incident light. 

The animals which possess the property of 
thus emitting light are almost entirely inverte- 
brate, and chiefly marine. We have accayats 
from several naturalists of certain fishes having 
been seen to give out light while in their native 
element, and some have conjectured,—but on 
insufficient grounds,—that all fishes doso. The 
turtle and a species of toad inhabiting Surinam 
have been reported to have the same property ; 
and the eyes of some carnivorous mammals 
appear to emit flashes of light. But we find 
this function constantly and distinctly mani- 
fested only by certain mollusca, insects, crabs, 
annelida, acalephe, and zoophytes. These are 
the following :— 

Mottusca 
Pholas dactylus 
Salpa zonaria 
telesii, Sc. 
Pyrosoma atlanticum 
giganteum, §c. 
Crustacea 
Cyclops brevicornis 
Gammarus pulex 
Cancer fulgens, $c. 
Scyllarus ? 
InsEcTa 
Lampyris noctiluca 
splendidula 
italica 
ignita 
phosphorea 
nitidula 
lucida 
hemiptera 
japonica 
Elater noctilucus 
ignitus 
phosphoreus- 
lampadion 
retrospiciens 
lucidulus 
lucernula 
speculator 
janus 
pyrophanus 
Luminosus 
lucens 
extinctus 
cucujus 
lucifer 
Bupestris ocellata ; 
Chiroscelis bifenestrata 
Scarabeus phosphoricus 
Pausus spherocerus 
Fulgora laternaria* 
serrata 


® Doubts have been expressed by several observers 
with regard to the luminousness of this insect. In 
travelling in the countries of South America where 
it occurs, they have never seen it shine ; but the 
testimony of other naturalists is so decided in 
favour of it being luminous, that we are constrained 
to suppose that the animal may give out light in 
certain seasons of the yearand not in others. There 
can be no doubt, at least, that its congeners above- 
named are tiuly luminous. 


~ 


198 


Fulgora pyrrhorhyncus 
candelaria 
Pyralis minor 
Acheta gryllotalpa? 
Myniapopa 
Scolopendra electrica 
phosphorea 
morsitans 
Julus ————? 
ANNELIDA 
Nereis phosphorans 
noctiluca 
cirrigera 
mucronata 
Planaria retusa 
EcnuinopERMATA 
Asterias —————? 
Ophiura telactes 
hosphorea 
Acactepuz. Almostall the species of Medusa, 
Beroe, Physalia, Rhizophora, Stephanomia, 


and Physophora. 
ZooPpuyta 
Pennatula phosphorea 
grisea 
rubra 


argentia 
Inrusorta. Many species belonging to the 
pe Cercaria, Volvox, Vibrio, Trichoda, 
incophea. 

With regard to fishes, the statements of 
naturalists are so contradictory that we still 
hesitate to admit any of them on the list of 
truly luminous animals. The sharks, more fre- 
quently than other fishes, are reported as lumi- 
nous. The light given out by them is said to 

roceed from their abdominal surface. When 
arge shoals of fishes are swimming rapidly, 
flashes of light, broad and deep, are sometimes 
seen about them and are supposed to be 
emitted by the fishes themselves. ese appear 
‘occasionally at very great depths. They have 
been traced in the British seas to shoals of 
herrings and the coal-fish ; and Dr. M‘Culloch 
enumerates also the pollack, the pilchard, the 
sardine, the whiting, the mackarel, and the gar, 
as being sometimes accompanied by these 
lights.* 

The common earth-worm is not included in 
the above list, although several observers have 
reported it as luminous, because the fact of its 
being so is not sufficiently determined. It is 
said to give out light only during the period of 
propagation. 

me voyagers, as Peron, have stated that they 
have seen sertularia, gorgonie, alcyonia, and 
sponges gre out light immediately after being 
redged from the bottom of the sea ; but we sus- 
pect that in most of these instances the light 
proceeded not from the zoophytes, but from 
some light-giving annelids itical upon them. 
This is frequently met with in the British seas, 
II. Characters and properties of animal light. 
—lIt is only in its most obvious qualities that 
animal light has hitherto been the object of 
scientific research. In colour and intensity it 
varies very much at different times in the same 
animal, and still more in different animals. 


_ * Edin. Encycl. art. Phosphorescence. 


ANIMAL LUMINOUSNESS. 


With regard to colour the following variet 
occur. In pholas dactylus the light is bluis 
white ; in lampyris noctiluca it is greenish 4 
a shade of blue ; in /. italica, bright blue; | 
Elater noctilucus, brilliant green, with 
“« the most beautiful golden blue ;” in 
pyrrhorynchus, deep purple and se 
marine animals generally it is white with var 
shades of blue. Doubtless these differen 
depend chiefly upon the various colours of 
integuments through which the light is seen. 
In lampyris italica, there are alternate | 
sions and extinctions of the light, wh 
place with some degree of regularity 
to be synchronous with the pulses of | 
culating current, visible in the wing-cases 
this beetle.* - 
The fire-fly (Elater) shews two kind: 
light ; one constant, like that of the glow-we 
but more feeble; the other a vivid white ] 
suddenly intermitted. Its illuminating po 
seems to be greater than that possessed by 
other animal ; the light emitted from its t 
thoracic tubercles is so great that the smal 
— may be read with it; and in the W 
ndies, (particularly in St. Domingo, wh 
they are abundant,) the natives use ther 7 
stead of candles in their houses. They alse 
them to their feet and heads in trave ing 
night to give light to their path through 
forest. The intermitting of the light in” 
insect is such as to give an observer the ides 
a membranous veil being suddenly drawn 
the source of light, and then as suddenly w 
drawn. -@ 
In a_ species of cancer seen by Smith 
the Gulf of Guinea, the light (which seemed 
be emitted by the brain) was of a deep 
colour when the animal was at rest; but wi 
it moved, bright coruscations of silve' de 
were darted from it in all directions. The lis 
of some centipedes inhabiting the islands 
the Pacific is of a beautiful emerald-g 
colour. It is connected with a mucous ma 
covering the animal, which may be rubbed 
by the fingers, and communicates to then 
smell not unlike that of muriatic acid. __ 
Sometimes the light proceeding from the. 
is so white and dull as to give effect « 
sea of milk. This is frequently seen in 
Gulf of Guinea, and seems to be caused so 
times by the presence of numerous Salpa 
Scyllari, at other times by the admixture o 
debris of fishes and other marine animals 
cently dead. a 
An extraordinary series of phenomena — 
nected with a particular display of the © 
nousness of the sea, is reported by Mr. E 
derson as having occurred in the Atlat 
(lat. 2° long. 21° 20’ W.) on the 5th Ma 
1821. About 9 pe. the sea appeared 
ally luminous. Every person who kept 
fixed upon it for but a short time was it 
ately affected with giddiness, headache, 
the eyeballs, and slight sickness. u 
these symptoms varied in intensity amongst 


hed 
‘ 


* A species of lampyris lately found in New 
land is said also to china rhythmical pulses, | 
vol, ii. p. 245. : 


- ~ 


~~ 


vi 


oe 


ANIMAL LUMINOUSNESS. 


hie yet there was not one on board who 
id not feel some degree of them; and all im- 
puted them to the effect of the light proceeding 
from the surface of the ocean. Mr. Henderson 
remarks; “ For my own part, the headach, &c. 
which followed immediately my looking at the 
water, was particularly severe, nor did it go off 
until morning. The effects I experienced were 
like those produced by smoking too much 
tobacco.”* 

There have been recorded some accounts of 
very intense light produced over a great extent 
of the ocean’s surface by luminous animals, but 
it does not appear that any other voyagers have 
experienced physical effects from the light such 
as are described by Mr. Henderson. The great 
intensity with which it is occasionally produced 
by marine animals, however, is well illustrated 
by the descriptions that are given of the moral 
emotions with which it inspires the beholders. 
Witness, for instance, Mr. Bonnycastle’s descrip- 
tion of a scene which he met with in the Gulf 
of St. Lawrence, (7th Sept. 1826.) While it 
was very dark, a brilliant light, like that of the 
Aurora, was seen to shoot suddenly from the sea, 
in a particular quarter. It spread thence over 
the whole surface of the water between the two 
shores of the Gulf; and shortly there was pre- 
sented “one blazing sheet of awful and most 
brilliant light.” << Long tortuous lines of light 
showed many large fishes darting about as if in 
consternation at the scene.” ‘The light was suf- 
ficient to enable one to see the most minute 
objects on the ship’s deck. On drawing upa 
bucketful of the water, and stirring it with the 
hand, it presented “ one mass of light, not in 
sparkles as usual, but in actual coruscations.”+ 

Messrs. Quoy and Gaimard state that in 
handling luminous marine animals while alive, 
they have always been sensible of an odour pro- 
ceeding from them similar to that which is per- 
ceived around a highly charged electrical appa- 
Tatus. © 

The only observation with which we are ac- 
quainted that seems to indicate the evolution of 
heat in connexion with the light of animals, is 
that reported by Macartney, who states that he 
found the thermometer raised by two or three 
degrees when placed in contact with a group of 
living glow-worms shining, or even with their 
light-giving sacs cut off. The repetition of this 
experiment, however, has not produced the 


-Same result in the hands of others: they saw no 


rise of the thermometer. 

TIT. Circumstances in which light is given 
out, and by which its intensity is affected — 
It is not known whether there be any lumi- 
nous animals that give out light in all circum- 
Stances, and at every period of their existence, 
in their natural situations. So far as observa- 
tion extends, certain mollusca, and some of the 
Species of elater appear to shine without inter- 
mission. But most of the other light-giving 
animals with which we are acquainted use their 
ag function only occasionally, and that, 
or the most part, under some kind of excite- 
Ment or irritation, natural or artificial. In the 
* Trans. Med. and Phys. Soc. of Calcutta, i. 107. 
+ Trans. of Lit. and Hist. Soc. of Quebec, 


199 


absence of more direct means of investigation, 
we may, perhaps, attain to some measure of 
acquaintance with the nature and analogies of 
animal light by inquiring into those sources of 
irritation under which it is given out. Here, 
however, we are met by the difficulty of finding 
contradictory statements of facts made by dif- 
ferent observers. So that our exact knowledge 
on the subject is still insufficient to admit 
of any satisfactory conclusions being drawn. 
What is known on this point may be conveni- 
ently considered under the two following heads. 

I. Circumstances essentially connected with 
the state of nature in which the animals are 
placed when they give out light. 

II. Circumstances artificially produced af- 
fecting the emission of light. 

I. Natural circumstances in which light is 
emitted by living animals. The luminousness 
of animals in their natural state is affected by, 
1. Changes in the state of the medium in 
which they live, whether air or water, in regard 
to its temperature and electricity. 2. By solar 
light. 3. By abrupt collision with other bodies. 
4. By loud noises. 5. By the internal move~ 
ments of the animals themselves, amongst 
which may be included the exercise of the ani- 
mal’s will. 

1. Temperature, §c—By far the greater 
number of luminous animals with which we 
are acquainted are riatives of warm climates ; 
but those inhabiting the ocean are seen in 
almost all latitudes, even in the coldest; al- 
though in these they are not so numerous, and 
give less light. No aérial insects give out 
light, in ordinary circumstances, excepting at a 
temperature of about 50° Fahr. and upwards ; 
and the higher the natural temperature, the 
brighter is the light emitted. 

In temperate climates the cmap ieee shine 
only in summer and autumn. L. noctiluca 
appears in this country between June and Sep- 
tember; L. splendidula, in Germany, is lumi- 
nous in May; and L. hemiptera so early as in 
the end of April. 

The light of pholas dactylus is strongest in 
summer; and that of marine animals in ge- 
neral is increased before storms. 

2. Solar light.—It is said that Scolopendra 
does not shine at night excepting it has been 
exposed during the day to solar light. A short 
time of exposure to the sun’s rays seems to be 
sufficient to refresh its luminous power, as (like 
all other light-giving animals) it secretes itself 
as much as possible during the day. It is 
stated by Burmeister,* with regard to the Lam- 
pyris Italica, that if it be kept some days in 
the dark it entirely loses its luminousness, but 
regains it on being again placed in the sunshine. 

8. Lunar light—Macartney remarked that 
luminous meduse generally retreat from the 
surface of the water at moon-rise. 

4. Abrupt collision with other bodies.— 
Marine luminous animals very readily emi 
their light on being struck by any moving body; 
so that one of the most commonly observed 
phenomena connected with this subject is the 


* Manual of Entomology, transl. by Shuckhard, 
p. 494, 


200 


sparkling of the minute meduse and other 
animals, swimming on the surface of the sea, 
when they are dashed against the sides of a 
ship, struck by an oar, or tossed on the foamy 
crests of the waves; and this even while no 
other light is seen excepting just at the points 
where the water is agitated. In experimenting 
with Meduse, Macariney found that, when 
kept in a glass vessel in a state of perfect rest, 
they gave out no light, but that, on the slightest 
movemeni of the vessel, a brilliant flash was 
emitted, which was brightest when the animals 
swam near the surface. Macculloch remarks, 
“* Very often we have found the water crowded, 
even with the largest meduse, yet scarcely be- 
traying themselves by an occasional twinkle, 
when the dash of an oar or any accidental agi- 
tation was sufficient to involve the whole water 
in a blaze of light.” 

5. Loud noises——When any loud noise is 
made near a luminous insect while shining, it 
frequently ceases to give out its light. 

6. Internal movements of the animals them- 
selves,—will, §c.—With regard to insects, we 
have many concurreut testimonies to the fact 
that more light is emitted during the season of 
procreation by most of the species than at other 
times. Sostrikingly is this the case in the Lam- 
pyrides, that the light given out by the female 
has been generally regarded, (although without 
sufficient reasons,) as deStined only to attract 
the attention of her mate. After the eggs are 
deposited, the light gradually decreases in in- 
tensity. 

While it is obvious that, for the most part, 
the emission of light is altogether independent 
of any voluntary effort on the part of the animal 
itself, yet it appears probable that, through 
some means or other, the animal has the power 
of varying the intensity of the light at pleasure. 
We cannot, for instance, imagine that sound 
can have any direct effect on the light-giving 
organs themselves, so as to cause them to shine 
less brightly when loud noises are made near 
them. Such effect must be communicated 
through the animal’s sensorium. It is sup- 
posed by some physiologists that variations in 
the intensity of the light given out by insects 
depend on the quantities of air admitted through 
the trachez in respiration, over which quantities 
the animal’s will seems to exercise some con- 
trol. In observing the luminousness of the 
elater, Spix concluded that this control is so 
perfect, as to admit of the light being wholly 
extinguished by the animal’s preventing the ad- 
mission of air ; and this view is adopted also 
by Treviranus. These changes, however, are 
explained by others, (as by Miiller and Mur- 
ray,) by supposing that, when the light seems 
to fade, the organs are merely withdrawn be- 
hind opaque parts, or, as it were, veiled by a 
curtain. 

In general the light is increased when the 
animal is in motion; and in insects, parti- 
cularly during flight. Macartney observed of 
the beroé, that when it swam slowly near the 
surface of the water, its whole body became 
occasionally illuminated in a slight degree; but 
that, during its contractions, a stronger light 
jssued from the ribs, and that when a sudden 


ANIMAL LUMINOUSNESS. 


shock was communicated to the water in 
it was swimming, a vivid flash was given out. 

That the luminous function is in many an 
mals directly under the control of their 
seems to be proved by the fact, that whil 
under any sudden irritation calculated to alar 
them, they, at first, emit light strongly, yet ¢ 
the frequent repetition or continuance of 
same kind of irritation, they extinguish the 
light, and cannot be excited to shew it agai 
for a considerable time. ‘| 

Il. Artificial circumstances in which light’ 
emitted by living animals, or by which 
emission of it is affected. 

Light-giving animals being removed fix 
their natural situations, and subjected to art 
ficial processes and agents, are found to have 
their lamannennie affected by being exposes 
to, 1. the effects of accumulated elect 
and electrical currents; 2. immersion 
rious fluid and gaseous media; 3. pressure 
their bodies; 4. removal of their lami 
organs, and mutilation of these and of o 
organs ; 5. exposure to various degrees of hi 
and moisture; 6. immersion in vacuo; 7. ¥ 
moval from all foreign sources of light. ¢ 

1. The effects of accumulated electricity @ 
electrical currents. In experimenting on m 
rine luminous animals, Macartney pa 
shock through water in which they were 
ming ; immediately their light was exting 
for an instant, but afterwards became bri 
than before. In reporting the result of a § 
milar experiment, Humboldt merely says th 
the luminousness of the animals was increaset 
after the shock. Macaire subjected glow 
worms to the action of galvanism, and foun 
that when one wire was forced 
body of the insect as far as the luminot 
organs, while the other was applied to the sui 
face slightly moistened, the light became bi 
liant. One galvanic pole produced no effec 
but when insects not shining at the time wer 
placed ina galvanic circle they always beg 
to give out light. This result was not ol 
tained in vacuo, but whenever the air 
admitted, the light reappeared. No effect 
ever seemed to be produced by common 
tricity, howsoever applied. 

2. Immersion in various fluid and gasea 
media.— Luminous marine animals, when 
moved from their native element, and plu 
into fresh water, give out their light fora 
more vividly and more steadily, but afte 
it gradually fades and becomes extinct. Miner 
and vegetable acids, alcohol, and sol 
tions of corrosive sublimate, and the salts, 
produce nearly the same effect; only 
these the light-giving property is more spees 
destroyed. Observers differ in their accom 
of the effects produced by immersion in 
rious gases. Most of those who have eri 
mented in this way have seen the ben of the 

low-worm very rapidly extinguis in hy- 
angen gas ; zr fe s sulphuretted and car 
buretted hydrogen, carbonic acid, chlorine 
nitrogen gases; but Sir H. Davy found tha 
hydrogen gas produced little or no change in 
the state of the light; the same was the result 
of Murray's experiments, who also found 


ANIMAL LUMINOUSNESS. 


the glow-worm continue to shine in carbonic 
acid gas. Immersion in oils of all kinds de- 
stroys the light-giving property in most of the 
Insects endowed with it; but in Lampyris 
italica, Carradori found that the light conti- 
nued to be emitted when the luminous part 
of the body was plunged into oil. 

3. Pressure of their bodies—It has been 
observed that shortly after the death of the in- 
Sect, the light-giving organs of elater emit light 
freely when the body is bruised, and in general 
mechanical irritations of all kinds cause a cer- 
tain degree of increase in the intensity of the 
light given out. Some animals, as pennatula, 
seem to emit their light rarely, excepting in 
such circumstances. 

4. Removal of the luminous organs, and mu- 
tilation of these and of other organs.—The 
luminous organs may be cut out from the 
bodies of glow-worms and fire-flies without the 
peculiar property of the organs being imme- 
diately destroyed. The emission of light can 
for some time be re-excited by slight me- 
chanical irritations ; as by touching the organs 
with the point of a pin. Those of the glow- 
worm have been seen to shine for two or three 
days after excision, when slightly moistened. 
with water, heated or electrified. In experi- 
menting on the same insect, Todd found that 
the light was extinguished within six minutes 
after the head was cut off; as also when the 
luminous rings were cut into, but was renew- 
able by the application of heat. Sheppard 
removed the luminous matter from a glow- 
worm; the wounds healed within two days, 
and the body became again filled with new 
light-giving substance.* 

5. Exposure to various degrees of heat and 
moisture.—Light-giving insects in general do 
not shine at any temperature below that of 
53° Fahr. Macaire took some glow-worms 
that had been kept for some time at a tem- 
perature of 50° Fahr., plunged them into water 
at 55°, and gradually raised the temperature. 
Light was emitted for the first time at 77°, 
and increased in intensity until the water was 
at 105°. At this temperature the animals died, 
but the light continued until the temperature 
had reached 134° 5, when it wholly disap- 

red. When glow-worms are thrown alive 
into water heated to 110° and upwards, they 
die instantly, but at the moment emit a brilliant 
light. When they are exposed to an artificial 
cold suddenly, they perish at any degree below 
the freezing point of water; but the light ma 
be partially restored by a temperature of 70°, 
although the animals shew no other sign of 
vitality. When the insects are dried artificially, 
the light is extinguished, but it may be restored 
by their being again moistened. 

6. Immersion in vacuo.—W hen glow-worms 
are placed in vacuo, their light fades, but re- 
appears on admission of air. ; 

7. Removal from all foreign sources of light. 
—lIf luminous insects be confined in a dark 
place, they shine little in the early part of the 
day, but long before night they begin to do so; 


* Kirby and Spence’s Entomology, ii. 426. 


201 


although generally, in their native situations, 
they do not emit light until the twilight. If 
the confinement in a dark place be protracted, 
they do not shine so brightly as after having 
seen the sun during the day. 

1V. Seat of luminousness in different animals. 
—In most of the luminous animals that infobit 
the ocean, a great part of their surface seems 
to be endowed with the property of forming, 
and pouring out, a mucous fluid, which contains 
the luminous matter, and is frequently mis- 
cible with water and other fluids. This some- 
times so entirely covers the whole animal as 
to cause it to emit light from every point of its 
surface; but more generally when the animal 
is swimming, the light is seen to proceed only 
from certain regions. Some of the meduse, 
even of the largest size, emit light from a very 
small point, particularly when the luminous 
organ is placed in the central parts of the body. 
When the light is vivid, it seems to be larger 
than it really is, from the refracting power of 
the gelatinous tissues through which it passes. 
Occasionally the luminous point has not a 
diameter equal to the 1-200th of that of the 
animal itself. In cydippe pileus and oceania 
pileata of the Baltic, Ehrenberg finds that the 
light issues solely from the vicinity of the 
ovaries, and in oceania hemispherica, from the 
bases of the cirri. Pholas dactylus gives out 
light most strongly from the internal surface 
of its respiratory tubes. The luminous mucus 
is sometimes poured out even by very small 
animals in such quantity as to leave a lumi- 
nous wake behind them, as in an instance 
mentioned by Quoy and Gaimard. These ob- 
servers saw such luminous lines formed in the 
paths of certain extremely small creatures, so 
transparent that their forms could not be dis- 
tinctly made out. The positions of their bodies 
were marked in the water by bright spots, 
which were followed in their course by lumi- 
nous wakes, at first about an inch in breadth, 
but afterwards by the movements of the water 
spread out to the breadth of two or three 
inches. This luminous mucus is supposed to 
be the seat also of the remarkable stinging 

roperty possessed by many of the acalephe. 
t retains its luminousness in some instances 
for a day or two after being emitted by the 
animal, but loses it whenever putrefaction 
commences. 

But although this luminous mucus be so ge- 
nerally secreted and emitted by marine ani- 
mals, it is evident that the light given out by 
many of them has its seat in certain organs 
more or less internal, whence it proceeds in 
gleams and momentary flashes that seem to 
depend only on the movements of some im- 
ponderable agent. The exact position and re- 
lations of these organs can seldom be satis- 
factorily discovered, but in some crabs and mi- 
nute crustaceous animals that emit light, it is 
observed to proceed from the central organs of 
the nervous system. In other crustacea the 
whole body seems to be full of light, which is 
emitted, as at so many windows, through the 
translucent membranes interposed between the 
segments of the crust. Dr. Macculloch con- 


202 


cludes from his numerous observations on this 
subject, that, in marine animals generally, the 
coats of the stomach and intestines are the 
light-giving organs. 

In insects the seat of luminousness is more 
satisfactorily ascertained, and is found to vary 
very much in different species and tribes. 
The eggs of the lampyrides are said to be fre- 
quently seen luminous, and to continue so for 
several days after being deposited. In the 
states of larva and chrysalis also, the same in- 
sects emit light most vividly when touched, 
chiefly from the posterior segments of the 
body. On being much irritated, the whole of 
the chrysalis seems to shine in a slight degree, 
and for a short time. 

In the perfect female glow-worm of this 
country, the light is emitted chiefly from the 
inferior and lateral surfaces of the two or 
three last segments of the abdomen. The 
male of the same species presents only two 
small luminous points on the sides of one of 
the segments. hen the light-giving surfaces 
of the female lampyris noctiluca are narrowly 
examined, it may be seen that, on the penul- 
timate and antepenultimate segments, they pre- 
sent bands of a bright greenish-yellow light, 
which are abruptly terminated towards the 
trunk by an irregularly waved line; and that 
from the rest of the same segments there 
issues a fainter light of a pale green colour. 
There is also a little light given out by the 
posterior extremity of the dorsal line. In 
L. italica, the two last segments are wholly 
and nearly equally luminous. Most of the 
glow-worms in displaying their light recurve 
their tails upon their backs, so as to bring their 
luminous surfaces into view. 

Elater noctilucus gives out light principally 
from two points of the thorax, which are some- 
what raised, and of an oval shape; but it has 
also two light-giving organs situated beneath 
the wing-cases, which are not seen except 
when the insect is flying. Light is also 
emitted from the internal parts through the 
interstices between the abdominal segments. 

In bupestris ocellata, the light is emitted 
from certain yellow spots upon the elytra: in 
scarabeus phosphoricus from the belly: in 
chiroscelis bifenestrata, (a New Holland insect) 
from two oval, hairy, reddish spots on its 
second ventral segment; while, in pausus sphe- 
rococcus, a dim phosphoric light issues from 
its singular hollow globular antenne. 

Macartney says that he always observed the 
shining of scolopendra electrica to be accom- 
pee? by the appearance of an effusion of a 

uminous fluid upon the surface of the animal, 
perler'y about the head. On touching this, 

is finger and other bodies received on their 
surface a phosphoric light, which continued to 
shine for a few seconds, and then died away ; 
and yet he could not see any actual moisture, 
even upon smooth glass, although examined 
immediately and attentively. 

The researches of Treviranus have led him 
to conclude that there is no special luminous 
organ in insects; but that the generally dif- 
fused fatty matter is the seat of the function, 


ANIMAL LUMINOUSNESS. 


by which the luminousness is produced. He 
concludes, therefore, that, when the air has ree 
access to the interior of the body through the 
respiratory tubes, the whole of the internal 
organs give out light; and that this is not seen, 
excepting at certain points of the surface 
merely because the integuments are not trans- 
lucent. ,.* 
V. Anatomy of light-giving organs.—T| 
accounts of examinations of these organs 
have hitherto been published are rather imp 
fect. This appears to be owing chiefly tot 
fact that the organs themselves are of ¥ 
simple structure and furnish no materi 
lengthened description. So much so a’ 
in insects, that one would be inclined 
to conclude with Treviranus, that they a 
nothing but the common fatty or inter 
substance which fills up the bodies of i 
slightly modified by the presence of so 
phosphoric matter, were it not for the fa 
particularly observed by Macartney, 
the glow-worm, the luciferous organs are: 
sorbed after the season for their use is p 
and their places supplied by the u 
stance. The following are the results ob 
by this naturalist and by Spix from their ¢ 
sections of the glow-worm, the fire-fly, a 
the lantern-fly. : 
In the glow-worm, there is spread over t 
internal surface of the segments of the 
men a yellowish substance of the consi 
of ponte, which is thickest in the middle 
each segment, and terminates near each m 
by a wavy outline. It is of a closer 
than the fatty matter, but otherwise re 
it. Besides this substance, the last segn 
furnished internally, just beneath the mo: 
transparent part of its integument, with twe 
small round bodies, lodged in depression: 
which contain yellow matter of more close 
homogeneous texture. Miiller and 
describe these round bodies as “ two small 
ovate sacs, composed of thready membranes 
and filled with a soft yellow pasty matters 
Under the microscope, they appeared to Macait 
to be composed of numerous branching fila 
ments, with minute granules adhering to them 
It is from points of the surface correspondin 
to the situation of these round bodies that th 
light is most constantly and most bright 
emitted. When dry, these luminous organ 
have somewhat of the appearance of gum 
The dried matter is translucent and yellowis 
becomes darker on being kept, and appears 
be granular in its structure. Itss gl 
vity is a little greater than that of water. 
In the fire-fly, the internal concavities of the 
yellow spots of the corselet, whence the 
proceeds, are filled with a soft yellow sul 
stance, oval in shape, and of ee uniforn 
consistence and density. This, under the 
croscope, appears to be formed of a 
number of very minute parts or lobules, closely 
pressed together. Around these oval bodies, 
the fatty matter of the corselet is arranged | 
a radiated manner. Spix describes the sam 
organs as “ yellowish glandular masses, into 
which many branches of the trachea enter.” 


2 


rod 


ae 


4 


te. 


> 
#2. 


— 


> ss 


“ae er 


ANIMAL LUMINOUSNESS. 


In elater ignitus the masses of luminous sub- 
stance are extremely irregular in their figure ; 
they are situated close to the posterior angles 
of the corselet, and are more loose in their 
structure than the same parts in elator noctilucus. 

The luminous proboscis or snout of the 
Julgora is hollow, and has a free communica- 
tion with the external air by a narrow slit 
situated near the base of the organ. Its cavity 
is lined with a fine membrane, between which 
and the outer translucent corneous crust, there 
is interposed a soft tissue of a pale reddish 
colour, arranged in lines longitudinally, which 
is supposed to be the seat of luminousness in 
this insect. 

In several instances it has been found that 
the light-giving substance has continued to 
shine for a considerable time after being re- 
moved from the body of the insect. In such 
cases it has been observed that there appeared 
to he no diminution either in the weight or the 
bulk of the luminous organs, excepting what 
was obviously produced by evaporation of the 
fluids. 

VI. Geographical distribution of luminous 
animals.—In almost all seas, in every latitude 
from 60° S. to 80° N., have light-giving ani- 
mals been seen; but they are more abundant, 
and shine with greater brilliancy, in the tropical 
than in the colder climates. In general, it is 
observed by voyagers, the luminous mollusca 
and acalephe occur in greatest numbers not far 
from land ; and that they are particularly plen- 
tiful in the seas surrounding groups of small 
islands within the tropics. 

The luminous insects are met with chiefly 
in the warmer climates of the temperate zones 
and within the tropics. We are not aware of 
any having been met with beyond the latitude 
of 58°. 

VIL. Theories of animal luminousness.— 
Very numerous have been the theories formed 
by philosophers with regard to the nature of 
the luminous matter which produces the phe- 
nomena now under review. From the facts 
Stated above, it appears that we are not yet in 
a position to determine with certainty whether 
or not animal luminousness has its source in 
the operations of any agent already known. 
At least it appears to us that facts enough have 
been accumulated to set aside the assumption 
of most of the theories hitherto promulgated. 
The following are some of these. 

1. That light is imbibed from the sun’s rays 
by luminous animals and given out in the 
dark. (Beccaria, Mayer, &c.) 

2. That the light is owing to a kind of com- 
bustion maintained by the oxygen of the air. 
(Spallanzani.) 

3. That light is swallowed with the food, 
oy disengaged by peculiar organs. (Brugna- 
telh. 


4. That the light-giving matter is composed 
of phosphorus and albumen; and that the 
variations in the intensity of the light depend 
on the more or less complete coagulation of the 
albumen, by some internal means placed under 
the control of the animal’s will. (Macaire.) 


203 


5. That a fluid containing phosphorus is 
secreted by the luminous organs, and shines 
on its being exposed to the oxygen of the air 
introduced by respiration. (Darwin, H. Davy, 
Heinrich, Treviranus, and Burmeister.) 

6. That the luminous organs concentrate 
and modify the nervous influence so as to form 
it into light; so that, according to this theory, 
animal luminousness is an effect solely of vital 
power. (Macartney and Todd.) 

7. Tiedemann thus expresses his opinion: 
“ Animal luminousness would seem to depend 
on a matter, the product of the changes of 
composition accompanying life, and, to all ap- 

earance, secreted from the mass of humours 

y particular organs. This liquid probably 
contains phosphorus or an analogous combus- 
tible substance, which combines with the oxy- 
gen of the air or of aérated water at a medium 
temperature, and thus produces the disengage- 
ment of light. The preparation and secretion 
of this substance are acts of life, which change, 
augment, or decrease by the influence of ex- 
ternal stimulants, whose action on the animals 
modifies their manifestations of life. But the 
phosphorescence itself depends on the com- 
position of the secreted matter and cannot be 
regarded as a vital act; because, on certain 
occasions, it continues for whole days and even 
after the death of the animal.” * 

This opinion seems to coincide pretty nearly 
with that of Darwin, Heinrich, and others, 
stated above (5); and we must admit that it ap- 
pears toharmonize the facts better than any of the 
other theories that have been propounded. But, 
while it seems satisfactorily to assimilate many 
of the phenomena to others more familiar to us, 
and more within the reach of our investigations, 
and thus appears to furnish future inquirers 
with a key to the elucidation of what yet re- 
mains obscure, it is obvious that it leaves some 
of the phenomena unexplained, and that se- 
veral of these seem to be quite irreconcilable 
with the theory of the phosphorescence being 
essentially dependent on the composition of 
secreted fluids. In some of the extremely 
delicate acalephe, for instance, from which the 
brightest radiance is so frequently emitted in 
momentary fitful flashes, it is difficult to con- 
ceive why, if the light mainly depended on 
the nature of some matter poured out by cer- 
tain organs at the instant of the flash, the light 
should not continue for at least a few seconds. 
The circumstance of its doing so in some in- 
stances, and even mixing gradually with the 
surrounding sea-water, certainly proves that 
there is such a fluid as this theory supposes in 
certain animals; but does not remove the dif- 
ficulty presented by the facts we have al- 
luded to. 

We feel ourselves constrained by these and 
other such facts to believe (with Macartney 
and Todd) that in many, perhaps in all, lumi- 
nous animals, both terrestrial and marine, the 
light emitted is the consequence of an evolu- 


* Comparative Physiology, translated by Drs. 
Gully and Lane, i. 270. 


204 


tion of an imponderable agent by the nervous 
systems of the animals, just as the electrical 
fishes give their shock without the interposition 
of any visible or ponderable secretion. In this 
view we may regard the luminous organs as 
laying the same part in relation to the evo- 
ution of light as the electrical organs of the 
torpedo do to the production of the shock. 
The single fact of luminousuess continuing in 
the organs or in their effused fluids, after they 
have been removed from the body of the ani- 
mal, seems to point to a great difference ex- 
isting between the two classes of phenomena 
which we have just compared, in certain ani- 
mals; but it may be that the difference is 
more ap nt than real; for this fact may be 
explained by supposing that a phosphoric sub- 
stance really does enter into the composition 
of the light-giving organs; and yet we may 
with great probability conjecture that it is not 
the chief agent in causing the phenomena of 
luminousness. It remains, then, for future in- 
quirers to determine the chemical composition 
of the luminous organs, and the fluids emitted 
by the animals, the phenomena of whose lu- 
minousness seem to be irreconcileable with the 
idea of their being dependent on the nature 
of these fluids; if they be found to contain 
phosphoric matter, it may be concluded that, 
as this does not appear to be essential in them 
to the production of the phenomena of lu- 
minousness, so neither may it be in other ani- 
mals, in which it is believed to be the chief 
agent in the manifestation of their light-giving 
function. 

To this theory, (which is only a combination 
of the two most generally received in modern 
times,) we do not, in the facts which have 
come under our notice, see any serious objec- 
tion. The only argument adduced against 
Macartney’s theory by Tiedemann and other 
physiologists, who have carefully considered 
the facts of the case, is founded on the circum- 
stance of the light continuing, in a certain 
degree, for some time after the death of the 
animals, which, of course, cannot be supposed 
to be owing to the continued operations of the 
nervous system. This posthumous light, how- 
ever, may depend on the phosphorescence of 
the luminous organs or their effused fluids in 
virtue of their composition, while the full evo- 
lution of light during life may be produced 
chiefly by the play of imponderable agents in 
and from the nervous system, independently, 
in some cases, of the chemistry of the fluids ; 
in other cases, aided and modified by the nature 
of these and by the structure of peculiar organs. 

It is scarcely necessary to take particular 
notice of the various other theories that have 
been suggested, as the facts stated in the pre- 
ceding part of the article are sufficient to set 
them aside. 

VIII. Uses of animal luminousness—We 
know nothing certainly with regard to the 
uses of the light-giving function ; but as almost 
all observers have remarked that male insects 
seem to be attracted towards their mates by the 
brilliancy of the light emitted by the latter, it 


ANIMAL LUMINOUSNESS. 


has been generally supposed that the lumin 
ness is subservient to the generative function 
Although it may be so to a certain extent, it i 
obviously not essentially connected with i 
even in the glow-worm ; for the light endure 
long after the season of love is past. Sor 
have conjectured that the light may sometim 
be the means of preserving its i 
the destructive attacks of enemies. Thus Shy 
pard observed a large beetle running rount 
shining scolopendra, as if wishing to attack 
but seeming to be scared by the light. 
may imagine, also, that the light enab! 
possessors to see surrounding objects at 
and so to thread their way in safety through 1 
darkest places. te 
Considering that, in the ocean, there is ab: 
lute darkness at the depth of 800 or 1000 f 
at least that, at such depths, the li 4 
sun ceases to be transmitted, Maccu , 
suggested* that, in marine animals, theirlum 
nousness may be “a substitute for the light 
the sun,” and may be the means of enab 
them to discover one another, as well as th 
prey. He remarks, “It seems to be partic 
cularly brilliant in those inferior animals whi 
from their astonishing powers of reproducti 
and from a state of feeling apparently Iii 
superior to that of vegetables, appear to 
been in a great measure created for the sup 
and food of the more perfect kinds.” 
IX. Luminousness of animals not innat 
and other allied phenomena.—We have + 
counts of the surface of the human body aj 
pearing luminous in consequence of ph 
phoric matter being largely mixed with t 
sweat in the course of various diseases. T 
urine also both of men and several of t 
lower animals is occasionally luminous und 
similar circumstances. It is said that the urit 
of Viverra mephitis and V. putorius is 
ways so.t 
The eyes of human albinoes, almost all 
mammalia which possess a tapetum lucidu 
as also those of some birds of prey, serpent 
and insects, seem to shine in a feeble ligi 
from the reflexion and concentration of th 
rays falling upon them from external object 
Pallas thought that this light was developed 
the retina, and regarded it as an electrical f 
nomenon. But it has been plainly prove ib 
Prevost, Gruithuisen, and Esser,{ that # 
shining of the eye depends, in most cases, 0 
reflexion of light. They found that there wa 
no appearance of luminousness in absolw 
darkness; and that the eyes of dead anim: 
gave the same effect as those of the livin 
when placed in similar circumstances. 
It would appear, however, from some obser 
vations made by Rengger on the eyes of | 
certain South American ape, ( Nyctipithecus 
trivirgatus, ) that there is reason to believe im 


3 


% 


ps 


* ro 
* Edin. Encycl. art. ‘¢ Phosphorescence.” pe 
+ Langsdorff, Reise. ii. 184. : 
t Edin. New Phil. Jour. ii. 164. i 
§ See also Hessenstein, de Luce ex quorund 
animal. oculis prodeunte, atque de Tapeto lucido, 
Jenz, 1836. 


eae ee eee 


ene 1 


LYMPHATIC AND 


the emission of light from the eyes of some 
animals, independently of the reflexion of in- 
cident light. The ape in question is nocturnal. 
The luminousness of the eye was seen by 
Rengger only when there was total darkness ; 
and then the light was so brilliant that objects 
at the distance of a foot and a half from the 
eye were distinctly seen.* In commenting on 
this statement by Rengger, Treviranus remarks,+ 
“that the intensity of light may be increased 
by the brilliant tapetum of the eye, while it is 
concentrated as in a concave mirror, cannot be 
doubted. But it is impossible that a feeble 
light so concentrated should illuminate objects 
placed at the distance of a foot and a half from 
the eye of this ape, in a dark place.” The 
same physiologist seems to be satisfied that 
some dogs also have a similar power of gene- 
rating light within their eyes. In these, he 
States, the light is seen only when an impres- 
sion on the sight or hearing arouses the ani- 
mal’s attention, or when he is excited by the 
operation pf some instinct or passion. 

We are, therefore, constrained to conclude 
that this subject is still open for elucidation by 
future inquirers. If it should be proved that 
some of the higher animals really do emit 
light from their eyes, independently of the in- 
cidence and reflexion of that from without, it 
will go far to render it probable that, in lumi- 
nous animals generally, the development of 
light depends more upon the movements of 
some imponderable agent in and from their 
nervous system, than upon the nature of the 
composition of the fluids poured out by the 
luminous organs. 

Another series of phenomena, intimately 
connected with, and illustrative of, those previ- 
ously considered, demands notice here, namely, 
the shining of fishes, and other animal bodies 
shortly after death. The luminousness of dead 
fishes isa very common subject of observation, 
but not on that account the less worthy of par- 
ticular attention. It has been ascertained that 
the light is given out from every part of the 
body, external and internal, that is exposed to 
the air ; and that on the surface of the luminous 
parts there is a slight moisture, or solution of 
the tissues of the animal, which can be scraped 
off, or diffused in water, and continues lumi- 
nous for a short time after being so removed. 
When pieces of the skin or muscle of a fish 
are placed ina little water, the luminousness 
appears only on the surface when the water is 
at rest; but whenever it is agitated the light is 
diffused through the whole body of water. 

In some fishes, as the whiting, this lumi- 
nousness appears within a very short time after 
death ; in others, not for some days; but in 
all it ceases before the truly putrefactive process 
has commenced. It is observed that those 
fishes which most quickly putrefy, are also 
those which give out light the soonest. 

From the circumstance mentioned above, 
that this luminous fluid formed on the bodies 
of dead fishes is miscible with water, and re- 

* Rengger’s 


Paraguay, s.3 
+ Biologie, i, 439, 


os oe der Saugthiere von 


LACTEAL SYSTEM. 205 


tains its luminousness fora short time after 
being so mixed, it has been concluded that the 
beautiful phenomenon of the phosphorescence 
of the sea may be frequently owing to the pre- 
sence, in great quantity, of the remains of fishes 
recently dead. It is certain that the magst 
careful observers sometimes fail to detect any 
entire living animals in sea water taken up 
from a brilliantly luminous sea; and find only 
abundance of small fibres and shreds of what 
seem to be broken-down animal tissues. Pro- 
fessor Smith* concluded from his own obser- 
vations made in the Atlantic, that, while the 
bright sparkling light of the surface of the 
ocean is always emitted by living animals, that 
duller diffused luminousness, which is fre- 
quently seen over a vast extent of the sea, 
giving it the appearance of milk, is given out 
by “a dissolved slimy matter, which spreads 
its light like that proceeding from phosphorus.” 
Under the most powerful microscope, Smith 
saw nothing in such water but “the most mi- 
nute glittering particles, having the appearance 
of solid spherules.” Humboldt saw a great 
extent of the surface of the sea rendered almost 
gelatinous by the admixture of numbers of 
dead dagyse and meduse. 

It may, therefore, be regarded as probable, 
at least, that the luminousness of the ocean is 
sometimes caused by dead matter; but it is 
certain that, in the great majority of instances, 
it is entirely owing to the presence of living 
animals, possessed of the light-giving property.+ 
In attempting to examine these, so as to deter- 
mine their forms and habits, it is important to 
keep in mind that they are sometimes ex- 
tremely small, so as to be distinguished with 
considerable difficulty, even with the aid of the 
best microscopes. And when they are larger, 
they are frequently so transparent as to elude 
notice. 


BIBLIOGRAPHY.—Canton, Phil. Trans. 1769. 
446. Macartney, Phil. Trans. 1810. 2. Spallan- 
zani, Mem. della Soc. Ital. vii. 271. Macaire, 
Mem. sur les Lampyres, in Jour. de Physique, 
xciii. 46. Humboldt, Reise i. 109. Todd, Jour- 
nal of Science, 1826. 241. Murray, Experimental 
researches, 1826, Kirby and Spence, Introd. to en~ 
tomol. ii. 256. Quoy and Gaimard, Ann. des Sc. 
Nat. iv. 1, Tiedemann, Comp. physiol. i. 257. 
Macculloch, Phosphorescence, in Edin. Encycl. xvi. 
1823. Burmeister, Manual of entomol. by Shuck- 
hard, 494. Muller, Physiology, by Baly, vol. i. 
ed. 2, 1839. 


LUNG.—See Putmonary OrGans. 


LYMPHATIC AND LACTEAL SYS- 
TEM, —(Fr. Systéme lymphatique; Germ. 
Saugadersystem oder Lymphgef dsssystem. 


* Tuckey’s Voyage, 258. 

+ Martin, Canton, Hulme, and others supposed 
the luminousness of the sea to be caased bya phos- 
phorescent oil, generated during the putrefaction of 
animals. Silberschlag regarded it as phosphoric. 
Mayer, Beccaria, Monti, Brugnatelli, and others, 
believed it to be owing to the giving out of light 
imbibed from the sun’s rays. Bajon, Delaperriere, 
and Gentil imputed it to electrical agency, because 
it is excited by friction. Foster supposed it to be 
sometimes electric, and sometimes putrefactive. 


206 


Syn. Absorbent system.)—The lymphatic sys- 
tem is com ad in the first place, of the 
vessels which collect and convey the lymph 
from all parts of the body and the chyle from 
the intestines, and ultimately deposit them in 
the veins. Secondly, of the small fleshy bo- 
dies called conglobate, lymphatic, or absorbent 
glands, which are found connected with this 
system of vessels in various parts of their 
course. 

The lymphatic system is confined to the 
class Vertebrata. It is the least complicated 
in Fishes, and consists in them simply of pel- 
lucid valveless vessels. In Reptiles, also, it 
is composed of these vessels only, but which 
are armed with more or less perfect valves. In 
the two higher orders of Vertebrata, Birds and 
Mammalia, to the vessels containing very nu- 
merous and perfect valves, the conglobate 
glands are superadded : in all, however, the ter- 
mination of the system is in the veins, and its 
origin and general arrangements are probably 
in all essentially the same. 

The different parts of the lymphatic system 
had escaped the notice of anatomists until the 
middle of the sixteenth century, and the entire 
system was not discovered till the middle of 
the seventeenth. I must here except the lym- 
“soe glands, which from their large size must 

ave been observed by the earliest anatomists, 
and we accordingly find them alluded to by 
Hippocrates, who classed them with the other 
glandular organs. 

The first isolated discovery in the vascular 
part of this system was made by Eustachius in 
1563, who saw and described accurately the 
thoracic duct in a horse. He called it the 
vena alba thoracis, and traced it downwards 
from the left subclavian vein to the lumbar ver- 
tebre, where he noticed the dilatation now 
called the receptaculum chyli ; he however had 
no conception that it formed the trunk of a se- 
parate system of vessels, but conceived it to be 
a vein of apeculiar kind. Fifty-nine years af- 
terwards, in the year 1622, Asellius was fortu- 
nate enough to discover the lacteal vessels on 
the mesentery of a dog; and although on the 
following day he was much disappointed in not 
being able to see them in another dog in- 
spected for the purpose, by continuing his re- 
searches he soon convinced himself of their ex- 
istence in most animals. He also attributed to 
them their proper function, having remarked 
that whenever there was chyle in the intestines, 
these vessels also contained a white fluid, and 
could then only be seen. He failed, however, 
to connect the vena alba thoracis, the discovery 
of Eustachius, which had probably been for- 
gotten, with his own, and mistaking the lym- 
phatics of the under surface of the liver for the 
continuation of his vessels, was led into the 
error of supposing them to terminate in the 
liver. Asellius, who died in 1626, had not 
seen the lacteals in man, but inferred and as- 
serted their existence. According to Haller, 
Veslingius was the first who saw these vessels 
in the human subject, in the year 1634; but 
Breschet informs us, in his Systéme Lympha- 
tique, page 4, that, “en 1628, les lympha- 


LYMPHATIC AND LACTEAL SYSTEM. 


s pour la p - 


Sen 


tiques du mésenttre furent aperou 
mitre fois chez homme. Peirese, ur 
d’Aix, informé par Gassendi de la découvert 
qu’ avait faite Aselli, distribua plusieurs exem 
plaires de l’ouvrage de ce proffesseur aux n 
decins de sa connoissance, et leur abandonna 
criminel condamné a mort, pour verifier le fi 
sur son cadavre. On fit bien ( 
homme avant de le conduire au supplice, 
une heure et demie aprés sa mort, louvertu 
du bas ventre montra le mésent®re tout cor 
vert de vaisseaux lactés pleins de chyle.” 
The thoracic duct was rediscovered in t 
year 1649, by Pecquet, who published ad 
scription of it in 1651. Haller ascribes 
discovery to Veslingius: “Idem Veslingiu: 
nisi plurimum fallor, primus post Eustachiom 
contra omnes coetaneos, rectius anno 1649 
vidit vas lacteum grande, in pectus adscender 
cum reliqui incisores, partim ab Asellio pr 
suasi, et partim a lymphaticis vasis hepatis 
ducti, chyliferos ductus ad hepar ducerent.” — 
It now became evident that the thoracie di 
was the trunk of the vasa lactea, and that th 
chyle was not conveyed to the liver, as : 
supposed, but was poured into the venous sy 
tem at the union of the subclavian and interr 
jugular veins of the left side. The lymphat 
of the under surface of the liver were soon aft 
shewn by Glisson and Veslingius to have t 
valves so arranged as to convey their cont 
from, and not to this organ. 
In the two or three following years the 
of the lymphatic system was discovered 
Rudbeck in Sweden, by Bartholin in Den 
mark, and by Jolyffe in this country ; nor wa 
it long before the function of absorption wi 
ascribed to it by Glisson, in 1654, and b 
Hoffmann. Since this period, we have been it 
debted for various details of the arrangement © 
this system of vessels in man and other Mam 
malia, in Birds, in Reptiles, and Fishes, 
numerous investigators, Nuck, Ruysch, A 
nus, Meckel, Hunter, Monro, Hewson, Cruiel 
shank, Semmerring, Mascagni ; and in the pre 
sent day to Fohmanu, Lauth, Lippi, 
Panizza, and other continental anatomists. 
The lymphatic vessels in the human sub ec 
are exceedingly delicate and transparent tub 
numerous but small, existing in most if me 
in every part of the organism, cro 
with valves, and terminating, after pass 
through the glandular bodies, in two prine 
pal trunks, through which the contents of th 
whole system are emptied into the circulatii 
venous blood at two corresponding Sie 
far distant from the heart, viz. at or close te 
angles of union between the subclavian am 
internal jugular veins. The two trunks of tl 
lymphatic system are by no means 
trical. That which enters the veins on the I 
side measures as much as sixteen or eightei 
inches in length in the adult human sub 
It commences in the abdominal cavity by 
a slightly marked dilatation, the recepta em 
chyli, into which the chyliferous vessels pour their 
contents ; it then passes through the thorax to 
reach its termination in the neck. This trunk 
is usually termed the thoracic duct ; it may 


Loe 


= 


CC 


LYMPHATIC AND 


be said to receive the lymph of three-fourths of 
the body, together with the whole of the chyle. 
The right lymphatic trunk is about two lines 
in diameter, very short, corresponding in situa- 
tion and length to the last half-inch of the left 
trunk ; consequently it will only be found at 
the root of the neck, close to the point of its 
termination. This trunk receives the remaining 
fourth of the lymph, viz. that collected from the 
right upper fourth of the body. Professor 
Lippi published a work on the lymphatic 
system in the year 1825, in which he described 
in the human subject many terminations of the 
lymphatics in other parts of the venous sys- 
tem, especially in the vena cava inferior, the 
vena porte, and the principal branches by 
which these vessels are formed, but subsequent 
observers have not corroborated his views. The 
vessels which Professor Lippi saw joining 


_ other large venous trunks were evidently the 


returning veins of the conglobate glands, into 
which the injection received by the lymphatics 
had passed during its transit through the glands : 
—a fact of extreme interest, and to which we 
must recur in speaking of the structure of the 
glands, but which has been observed by every 
anatomist who has had much practical experi- 
ence in injecting the lymphatic system. Lippi 
would have been perfectly correct, how- 
ever, had he confined his statement to what 
takes place in Birds, Reptiles, and Fishes. 

The lymphatic vessels resemble the veins in 
possessing valves, and in conveying their 
contents from branch to trunk ; moreover their 
internal tunics are continuous where the one 
set of vessels joins the other. In their mode 
of distribution also throughout the body the 
analogy between the two systems is consi- 
derable. Eustachius, when he first saw the prin- 
cipal trunk of the lymphatics, from its being 
filled with chyle, at once described it under 
the name of the vena alba thoracis, and many 
have considered the lymphatic vessels as an 
appendage to the venous system, rendering it 
more perfect. Although we are warranted in 
saying that the lymphatic vessels convey their 
contents from branch to trunk, by which is 
generally understood from smaller and more 
numerous to larger and less numerous vessels, 
as is the case with the veins; yet is there~an- 
other principle apparently of an opposite kind 
observed in their distribution, by which the in- 
fluence of capillary attraction is engaged in the 
important service of moving onward their con- 
tents, at the same time that these are ex- 
posed to a larger surface of the containing 
vessels, from which in all probability they derive 
some essential modification. This admirable 
and simple provision is especially evident in 
the lower extremities, where the greatest resis- 
tance from gravity is to be overcome. A vessel 
on the instep, for instance, of half a line in 
diameter, instead of emptying itself into a 
larger one as it proceeds upwards, bifurcates 
into vessels of equal diameter with itself; each 
of these again will in a similar manner sub- 
divide, until at length bya series of dicho- 
tomous divisions, although some reunions may 
take place, this single vessel has multiplied 


LACTEAL SYSTEM. 207 


itself by the time it reaches the inguinal region 
into as many as fifteen or more branches, each 
of the same diameter or nearly so as the ori- 
ginal branch on the instep. Indeed, through- 
out the lymphatic system, we scarcely find a 
branch of more than an inch in length whese 
diameter is not within the range requisite for 
the production of capillary attraction. The 
thoracic duct itself, which is two or three lines 
in diameter, may be said to form an exception, 
but the onward progress of its contents is 
specially provided for by its juxta-position to 
the aorta, from which circumstance it is sub- 
jected during life to an alternating pressure of 
considerable force, and fully competent in a 
vessel provided with valves to ensure the ad- 
vance of its contents. 

The principal lymphatics in any part of the 
body may be said, taken collectively, to equal 
the capacity of the arteries or veins of the same 
part ; thus, in the inguinal region the sum of 
the diameters of the lymphatic vessels may 
equal the diameter of the main channel by 
which the venous blood is returned from the 
lower extremity ; but by this simple subdivision 
of the outlet for the lymph into numerous 
branches, that almost universal, and, in its 
effects, wonderful power, by which the nutrient 
fluid throughout the vegetable creation is car- 
ried from the lowest fibril of the root to the 
highest living point in vegetable existence, is 
made available in the progression of the lymph in 
animals towards the centres of the system. This 
disposition of the lymphatic vessels throughout 
their course necessitates a greater uniformity in 
point of size, than we find to hold good with 
the artery or vein, and indeed constitutes their 
chief peculiarity in distribution when com- 
pared with the other divisions of the vascular 
system. The arborescent appearance, except 
on the surface of the liver and spleen, is 
scarcely to be met with in the lymphatics ; they 
almost always form a net-work of vessels, the 
meshes of which vary both in form and size 
in the different organs and in different parts 
of the body; as a general rule, when the 
vessels have a short course to run, the spaces 
they enclose are small and more nearly equi- 
lateral; but when the contrary is the case, as 
occurs in the extremities, the meshes are very 
large and much elongated, so that the vessels 
run nearly parallel with each other, and the 
net-work arrangement is scarcely perceptible ; 
there is, however, still less appearance of arbor - 
escence. 

In this respect the lymphatics may be said 
to resemble more the capillary bloodvessels, 
which in the web of the frog’s foot, or in the 
vesicular lungs of the salamander, toad, or frog, 
are so plainly seen to form a net-work of nearly 
equal-sized vessels, and, indeed, to cease to be 
capillaries when they become arborescent. 

Another peculiarity in the disposition of the 
lymphatic vessels occurs at their approach to a 
conglobate gland, through which their contents 
‘are to be conveyed. The vessels leading to a 
gland which are termed the vasa inferentia or 
afferentia of the gland, vary in number, being 
seldom less than two, and rarely amounting to 


208 


more than five orsix. They maintain their ordi- 
nary size and appearance to within a quarter of 
an inch of the gland, where they suddenly branch 
out, artery-like, into several Rapr RSE Va 4 minute 
vessels which plunge into the gland, thus con- 
veying the lymph,in a minutely divided state 
through this organ to emerge again from it by 
a converse arrangement of equally small vessels, 
which at a quarter of an inch from the gland, 
are collected like so many small veins into one 
or more trunks, called the vasa efferentia of the 
gland ; not unfrequently there is but one of 
these vessels passing from a gland, and rarely 
more than two or three; they are, however, 
generally larger than the vasa inferentia, and often 
double theirsize. ( Fig. 52.) A similararrange- 
ment in the bloodvessels before entering or 
passing from their agen glandular organs 
may be noticed in the spleen and kidney, but 
the only instance in which a bloodvessel col- 
lecting its contents from branches assumes 
the opposite function of distributing them 
into narrow streams occurs in the vena porta, 
‘where the blood is to be passed through 
the liver to be subjected to its action. The 
same object, it is true, is effected at the heart 
with the blood of the vene cave, together with 
the lymph and chyle, when conveyed in capil- 
lary streams through the lungs to be converted 
into arterial blood; the right side of the heart, 
however, here intervenes between the collect- 
ing vessels and those which have to redistribute 
the blood ; the latter also are called arteries 
though they convey the same venous blood to 
the lungs which the former vessels brought to 
the heart. 

The vasa inferentia are by most authors des- 
cribed as entering that edge of the gland which 
is farthest removed from the trunks of the 
system, and the vasa efferentia that nearest 
tothem. This I find not to be the case; the 
vessels usually plunge into and emerge from 
the broadest surfaces of the gland; sometimes 
it is the deeper surface, sometimes the more 
superficial, and frequently both. The vasa in- 
ferentia may enter one surface, and the vasa 
efferentia pass from the same or the opposite 
surface of the gland. The vasa efferentia, as 
they proceed onward, become the vasa infe- 
rentia of succeeding glands; thus the lymph is 
often made to traverse several glands before it 
is received by the trunks of the system. This 
is so much the case in the neighbourhood of 
the thoracic duct, especially in the pelvic and 
abdominal cavities, that the lymphatic system 
assumes altogether a different aspect; the net- 
work appearance, the uniformity in point of size, 
are lost sight of in the numerous large short 
vasa efferentia and inferentia, intervening be- 
tween the closely set glands. The appropriate 
lymphatic vessels of the viscera and walls of 
these cavities, nevertheless maintain the ordi- 
nary disposition, the appareut irregularity de- 

nding upon the circumstance, that the large 
ymphatics of the lower extremities, are inter- 
rupted by numerous glands in their passage to 
the thoracic duct. 

The lymphatic vessels are distributed through- 
out the body on two planes, one superficial, the 


LYMPHATIC AND LACTEAL SYSTEM. 


other deeply seated. The vessels of the t 
planes where they approach each other cc - 
nicate freely. A similar arrangement takes p 
partially in the venous system ; and it is inter 
ing to remark that where this occurs, the. 
like the lymphatics, are armed with valves. We 
cannot fail to recognize here a double pr 
vision to facilitate the progress of the cont 
of a vessel towards their proper destinati 
while the valves prevent effectually any retro. 
grade movement, the double plane of vessel: 
by increasing the number of channels, le ser 
the liability to arrest from the various cau 
of obstruction. The superficial lymphatis 
accompany more or less the superficial vein 
where these occur, but in other parts of @ 
body they assume various appearances pecul 
to each viscus or organ ; the superficial lymph 
tics, of the liver, spleen, kidney, and lung 
instance, differ materially from each oth 
arrangement and appearance. The deep 
lymphatics every where follow the course of 
large bloodvessels. They are fewer in 
and perhaps rather larger than the superficia 
The superficial and deep lymphatics commu 
nicate with each other in the lymphatic glas 
as well as in different parts of their course. 

The chief peculiarity of the coats of 
lymphatic vessels is their remarkable thinne 
and transparency ; in other amps they be: 
considerable resemblance to the coats of tl 
veins ; indeed in some of the lower animals 
veins are nearly as thin, and when empt 
blood, as transparent as the lymphatics. A 
anatomists admit the existence of two coats 
the lymphatics, an internal serous lining, 
at intervals is thrown into folds to form thy 
valves, and an external thicker fibrous covering; 
to these is added by some anatomists, with whor 
I am disposed to coincide, a third, anale 
to the cellular tunic of the bloodvessels, . 
conveys to them their vasa vasorum, and by 
which they are connected to the surrounding 
Structures. 

The inner tunic is extremely fine and delic 
probably less elastic and extensible than is 
nerally imagined, and is the first to give 
under distention from forced injections. — 
appears to possess a much closer texture th 
the fibrous tunic, to which it is firmly adhe: 
and whose contractions and dilatations i 
compelled to follow. The epithelium 
are distinguished with difficulty on the inne 
surface of this tunic, but I have satisfied my 
self of their existence. On placing an open 
lymphatic in the field of the microscope 
the bloodvessels have been minutely injec 
the vasa vasorum may be very distinctly seen 
but it is difficult, from the perfect trans 
parency, of this tunic, to say whether t 
vessels reach it, or are only seen through 
The vasa vasorum of the lymphatics do 
appear to affect any constant or fixed arr 
ment; they are by no means numerous, and [ 
have never been able to detect any on the val- 
vular folds. | 

The fibrous tunic, like the internal, 1s trans 
parent; it is very elastic, and admits of consi- 
derable distention without rupture. There is 


4 
Be? 


it 


LYMPHATIC AND LACTEAL SYSTEM. 


great variety of opinion with respect to the na- 
ture of its tissue. Breschet and many other 
anatomists describe this tunic as resembling 
the cellular coat of the bloodvessels, and are 
under the impression that the lymphatics are 
altogether deficient in that which is analogous 
to the middle or fibrous coat of the arteries and 
veins. Mascagni and Rudophi have not been 
able to detect muscular fibres in it. Cruveilhier 
conceives it to be composed of the tissu jaune 
elastique, or tissu dartoide. Schreger thinks he 
has seen circular muscular fibres in the thoracic 
duct of manand of large animals, and Sheldon 
States that he has distinctly seen muscular 
fibres in the thoracic duct of the horse. By 
lacing a portion of the thoracic duct or large 
ymphatic laid open with the lining membrane 
uppermost, on a piece of glass, and by scra- 
ping off the internal membrane, the fibrous 
tunic will be exposed ; if it be now moistened 
with a drop of water, and a piece of tale placed 
over it, it may be readily examined under the 
microscope. I have several times examined 
rtions of the thoracic duct and of the larger 
ymphatics taken from the horse, and from the 
human subject, and have invariably found the 
tunic exposed on’ removing the lining mem- 
brane, to be composed of fibres passing princi- 
pally in the longitudinal direction ; these fibres 
are uniform and cylindrical, and resemble in 
these respects the organic muscular fibre as de- 
scribed by Schwann ; they lie for the most part 
parallel with each other, and are occasionally 
seen to form a large fasciculus, somewhat analo- 
gous to the longitudinal muscular bands of the 
large intestine. These fibres measure from 
1-5000th to 1-6000th of an inch in diameter, 
_ and present at intervals, a sudden zigzag inflec- 
tion ; several fibres collected together into a sort 
of primitive fasciculus are bent together at the 
same points. These abrupt deviations from 
the straight line do not occur at equidistant 
points ; the intervals between them differ 
greatly 5 they average 1-400th of an inch in 
ength. Under the lining membrane some few 
fibres may be distinguished taking a transverse 
course, others may be seen in an oblique direc- 
tion, but the great majority are arranged longi- 
tudinally. The primitive fibre of cellular 
tissue is freely mixed with the peculiar fibres 
just described. The physiological fact that the 
lymphatics have the power of contracting and 
emptying themselves of their contents, has not 
been disputed ; but with respect to the nature 
and form of the fibre in virtue of which they 
possess this faculty, there has been and still 
exists great uncertainty. No one can have ex- 
amined the lacteal or lymphatic vessels in a 
recently killed animal without having observed 
the rapidity with which this system will empty 
itself of the fluid it contains ; and if the trunk 
of the system be ligatured, it will be found 
that this power remains for an hour or more 
after death, as may be proved by puncturing 
the duct within this period below the ligature, 
or by puncturing a distended lymphatic, which 
will be instantly evacuated of its contents, and 
will refill again and again when pressure is 
made below the orifice. 
Lymph hearts——I must not here omit to al- 
VOL. III. 


209 


lude to the pulsatile sacs or hearts belonging to 
the lymphatic system, discovered by Miller in 
frogs, toads, salamanders, and lizards, and by 
Panizza in serpents. In frogs, Miiller describes 
two pairs, one situated just under the skin in 
the ischiadic region, the other more deepty 
seated over the third cervical vertebra. Their 
pulsations he describes as about 60 in a 
minute and not synchronous with those of the 
heart. The lower pair propel the lymph into 
the ischiadic vein ; the upper, into the internal 
jugular.* Ihave seen these transparent pul- 
sating bodies in the frog, where they may be 
easily exposed by removing the skin from 
either side of the rudimentary tail, but have 
not examined them sufficiently to pass any opi- 
nion upon them. 

External to the fibrous tunic is situated a 
delicate and loose cellular tissue, which per- 
forms the same offices for the lymphatic, which 
the cellular tunic does for the artery and vein, 
viz. it conveys to it the vasa vasorum for its nu- 
trition, and connects it to the surrounding tis- 
sues. The supply of nerve to the lymphatic 
has not hitherto been detected ; there can how- 
ever be no doubt but that it possesses its proper 
degree of sensibility, and its contractile power 
is in all probability regulated by nerve. 


Fig. 47. 


a and b, lymphatics laid open longitudinally to shew 
the arrangement of the valves in their intericrs. 
( After Breschet. ) 


The valves of the lymphatics resemble in 
their mode of formation and in their appear- 
ance the same structures in the veins; they are 
however more frequent and more universal in 
the lymphatic system ; indeed, in the more per- 
fect animals they are found every where except 
in the incipient networks of this system. It 
has already been stated that in fishes and in 
some amphibious animals the lymphatic system 
is either entirely deficient in valves, or is only 
supplied with them in a partially developed 
state. The valve is composed of two semi- 
lunar flaps, so arranged that the reflux of 
the fluid within, forces them away from the 
sides of the vessel towards its centre, where 
the two flaps meet and completely close it, 
while the fluid passing in its proper direction 


* Professor Weber has described one of these 
hearts in a large serpent, the pithon bivitatus. It 
measured nine lines in length, and four in breadth ; 
it had an external cellular, a middle muscular, and 
an internal serous tunic. See Phil. Trans 1833, 
Miiller’s Archiv. for 1835, and Valentin’s Reper- 
torium, Bd: 1, p. 294. [Miiller has subsequently 
described similar lymphatic hearts in the Chelonian 
Reptiles, Archiv. 1840, p. 1-4.—ED.] 

Pp 


210 


simply presses the flaps back against the sides 
of the vessel, and thus no obstruction is offered 
to its onward course. The flap of a valve con- 
sists of a fold of the inner coat of the vessel, 
which, where a valve is to be formed, ceases to 


a, b, and c, lymphatic vessels inverted, giving three 
different views of the valves formed by the lining 
membrane. (After Breschet. ) 


line the vessel, and is reflected towards its inte- 
rior; having reached half-way across, it 1s 
doubled upon itself, and returns to the side of 
the vessel, which it continues to line as if it 
had never been interrupted. The two layers 
of this fold adhere very firmly together so as to 
form a very delicate transparent semilunar flap. 
It presents a convex attached, and a straight or 
slightly concave unattached edge; the former 
corresponds to a semilunar line on the interior 
of the vessel, the horns of which look towards 
the trunks of the system, where the lining mem- 
brane was reflected from and returned to the side 
of the vessel; the latter to the line of doubling 


Fig. 49. 


a, afront view of a valvular flap. 5, a profile 
view of a lymphatic vessel and valvular fap; the 
lower half of the flap, or that nearest the base, 


is represented thicker than the rest. According 
to Lauth and Breschet, this thicker portion is 
formed of all the coats of the vessels ; the thinner 


ortion, of the lining membrane only. (From 


eschet. ) 


of the membrane upon itself; thus a little pouch 
is formed between the flap and the side of the 
vessel, which can only be filled by the fluid 
passing in one direction ; and as a valve is 
constituted of two such pouches, when they are 
filled the vessel is completely closed. Some 
anatomists conceive that a lamina of fibrous 
tissue intervenes between the layers of the fold. 
Breschet, in his “Systéme Lymphatique,” 
adopts Lauth’s view of the structure of the 
valve. He describes the flap of a valve as 
composed of two parts, one thicker and situated 
at the base of the fold, the other forming the 
rest of the flap more thin and delicate. It is 
this latter part which he conceives is formed by 


LYMPHATIC AND LACTEAL SYSTEM. 


a doubling of the lining membrane only, whil 
7 thicker part, vay Me e base, he has assured 
imself is produced a prolongati tich 
the Shrous coat anak inwards betwen he 
folds of the innertunic. TI have not been able 
to — this description of the structare of the 
valve, but I have distinctly observed circulat 
constrictions in the more bead-like lymphatic 
seen in the neighbourhood of some of the 
K bynes glands, into the formation of whic 
the fibrous coat does appear to enter. Of 


laying open one of these vessels previous 
distended with quicksilver and dried, opposit 
the external constrictions, which were numerow 


and not more than a line apart, valvular fo 
differing from those hitherto described, wer 
seen to project into the interior of the vessel 
they did not completely close its cavity, bw 
left a circular or oval opening, through whie 
the contents of the vessel might pass in eith 
direction. These valvular constrictions 1 
sembled much the dried pyloric valve (fig. 5 
B); and I am inclined to believe, from th 
thickness, that they contain circular fibres de 
rived from the middle coat, by which durin 
life they may be able to close their vessels” 
perfectly as the pyloric valve closes the cot 
munication between the stomach and duc 
num. In very many places there occur t 
semilunar folds (fig. 50, A), mI fer orm: 
of the lining intial only, like the flaps 
the ordinary valves, from which they differ, hoy 
ever, in having their attached and unattach 
edges, as well as the flaps themselves, on 
same plane, consequently not forming pouches 
but a transverse though incomplete septt 
across the vessel. Each of these flaps extem 
only one-third across the vessel, and terminat 
by a crescentic edge, by which arrangement a 
elliptical opening is left in the central third 
a vessel, between the two folds. This fort 
of valve would appear to offer a partial obstrue 
tion to the tr of the lymph in either din 
tion, as no provision is manifest by which th 
flaps would be made to fall against the sid 
of the vessel, either by the onward or retrogr 
course of its contents. I have 
ticed a combination of the circular constrict 
with the semilunar flaps here described (fig-5 
C), by which mechanism, supposing the form 
to be endowed with a vital contractility, t 
latter might be brought in contact, so as Ci 
pletely to close the elliptical opening that wo 
otherwise be left in the centre of the vessel. 
At the entrance of the lateral branches i 
the thoracic duct, or of one lymphatic into ar 
ther, a valve will be found, of a somewhat dif 
rent form to those already described. It is con 
posed oftwo semilunar flaps, seldom of equal 
arranged somewhat like the ilio-ceecal 
One flap is occasionally so slightly devele 
that there appears but one large semilunar fo 
at the entrance of the vessel. At the uniono 
some of these vessels with others, especially o 
those which lie nearly = with each other 
no valve will be found, but simply a defini 
curved line, marking the orifice of commu 
tion. The valves in the lymphatic system 
very closely set together. The distane 
tween them varies much. In vessels of a line 


equently nD 


LYMPHATIC AND LACTEAL SYSTEM. 
Fig. 50. 


Exhibits three forms of valves of very frequent occur- 
rence in the lymphatics, especially in the neighbour- 
hood of glands, and which are not described in 
works on Anatomy. ( Taken from specimens pre- 
pared for the microscope.) Magnified ten diameters. 
A. a, the interior of the vessel. 06, b, the 

valvular flaps composed of the lining membrane 

only. The attached, the unattached edges, as well 
as the surface of these flaps, are on the same plane ; 
they do not perfectly close the vessel. 

B. a, the interior of the vessel. 6, the valvu- 
lar flap of a circular form, resembling the dried 
pyloric valve of the stomach; apparently com- 
posed of the fibrous as well as the inner tunic. 

C represents 4 combination of the two former. 
a, the interior of the vessel. 6. valvular flaps re- 
sembling those of A. c, a third fold resembling 
the circular fold of B. 


in diameter they are frequently not more than a 
line apart, while in others of half that magni- 
tude there may be an interval of an inch between 
them. It has been observed that they are more 
frequent and closer together in the larger lym- 
phatics than in the smaller; this is not always 
the case; for instance, the lymphatics of the 


_ upper extremity, which are much smaller than 


those of the lower, have less intervals between 
their valves ; and in the neck, where the vessels 
are still smaller, the valves are less distant apart. 
It appears to me that the valves are much more 
approximated to each other in the neighbour- 
hood of the glands, and this observation-applies 
to the vasa afferentia as well as to the vasa effe- 
rentia, but especially to the latter; from which 
circumstance the notion may have arisen, that 
the valves are more frequent the larger the 
vessel. The valves recur less frequently in the 
thoracic duct than in any other part of the 
system. It is not uncommon to find in this 
vessel an interval of two or three inches in 
extent without a valvular fold. 


Mode of origin of the lymphatics—The- 
‘plan I have hitherto adopted in describing 
‘the lymphatic vessels has been to present to 


the reader, first, that which is most readily 


211 


understood, because easily recognizable by our 
senses, and about which there could be little 
difference of opinion; but I have now to direct 
attention to a part of our subject which has 
hitherto baffled the efforts of all inquirers, viz. 
the mode of origin of the anise vessels, 
concerning which the sight, aided by the most 
powerful glasses, has failed to supply us with 
satisfactory and demonstrable information. The 
numerous opinions and conjectures on this sub- 
ject, only present us with so many instances, of 
the vain struggles of the human mind, to ad- 
vance in a strict science of observation, beyond 
the limits assigned to our senses, and of the 
unwillingness, even in the philosopher and man 
of science, to acknowledge the weakness and 
limited range of his faculties. 

When we consider the transparency of the 
coats of the lymphatic vessels, as well as of their 
contents, the small size of their secondary 
branches, and the numerous valves they every 
where present, we cannot feel surprised that 
their precise origin should be involved in 
much obscurity. From the opaque nature of 
the chyle, it might be imagined that while the 
vessels were distended with this fluid, the 
anatomist would be enabled to trace them to 
their commencing branches, but unfortunately, 
it is almost impossible to prevent the onward 
motion of the chyle in the vessels first re- 
ceiving it, while the valves offer a complete 
harrier to any retrograde movement. Added to 
which, the opacity of the coats of the intestine 
renders it extremely difficult to follow these 
vessels from the peritoneal surface of the outer, 
to the villous surface of the inner tunic, even 
when distended with chyle. Transparency of 
the coats of the intestine may be obtained by 
drying, but the chyle becomes transparent at 
the same time. Various modes of investigation 
have been adopted by anatomists to overcome 
these difficulties, the principal of which it may 
be necessary here to mention. Injections of 
quicksilver ot coloured fluids have been thrown 
into the arteries, by which means the injection 
has occasionally made its appearance in the 
lymphatic vessels: this result occurs, accord- 
ing to Panizza, in a particular organ in an 
animal of one species, while in another the 
experiment will succeed, not in the same, but 
in some other organ. Thus he succeeded in 
filling the lymphatics from the arteries, in the 
intestines of the dog and pig; in the liver of 
man, the horse, and dog ; in the testicle of the 
dog and bull; in the penis and spleen of the 
horse. He was unsuccessful in the intestines 
of man, the horse, birds, the salamander, and 
the tortoise; in the liver of reptiles; in the 
spleen of man, the dog, and the pig; in the 
kidneys of mammalia and birds; in the penis 
of man and the dog. 

Breschet is of opinion that injections by the 
veins pass more readily into the lymphatic sys- 
tem. Ihave now in my possession two prepa- 
rations where the lymphatics have been acci- 
dentally injected from the veins; one in the 
mesentery of the turtle, the other in the kidney 
of. man; and I have undoubtedly observed 
this occurrence much more frequently after in- 

P 


212 


jections by the veins than by the arteries. 
Every anatomist who has had much experience 
in stew | the "ig ft ON vessels has been in- 
commoded by the injection passing unex- 

tedly into some large vein, and on looking 
‘or the communication, he has found the veins 
from a lymphatic gland conveying the injection 
into one of the nearest large venous trunks. 
This has occurred to me frequently in the 
human subject, where the common iliac veins 
and the cava inferior have received the quick- 
silver from the veins of the neighbouring 
lymphatic glands. I have also seen the same 
occurrence lately in the horse, and have the 
specimen shewing the fact now in my museum, 
It was these veins conveying the imjection from 
the lymphatics into the venous trunks, which 
Lippi mistook for the vasa efferentia of the 
glands, and which induced him to publish his 
work describing many terminations to the 
lymphatic system in mammalia, hitherto un- 
known to anatomists. This error was the more 
excusable, inasmuch as his opinion appeared 
to be confirmed on the investigation being 
pursued by himself and others in the remain- 
ing classes of vertebrate animals, where various 
communications do actually take place between 
the lymphatic trunks and the veins. 

Coloured fluids have been thrown into the ca- 
vity of the pleura and peritoneum in living ani- 
mals for the purpose of bringing the lymphatic 
vessels into view, and of tracing if possible their 
extreme branches after absorption had taken 
place. In this way it is said that minute vessels 
anastomosing with each other, and forming a 
delicate net-work, may be made apparent on the 
surface of the serous membrane, and that the 
trunks of the neighbouring lymphatics may be 
seen filled with the coloured fluid. In post- 
mortem examinations also, the absorbent vessels 
have been observed distended with a fluid of a 
yellow or red colour, where effusions of pus 
or blood had taken place during life. Inall these 
instances we probably first notice the injection 
in the larger lymphatic vessels which are easily 
recognized by their numerous valves, and on 
tracing these back to their commencing branches 
we only discover an intricate net-work of mi- 
nute vessels apparently continuous with each 
other. It is exceedingly difficult to distin- 
guish these from equally small branches of 
artery and vein, filled probably with the same 
coloured injection. You look in vain for the 
channel by which the injection has entered 
these vessels ; no continuity of lymphatic with 
the minute twigs of the other sets of vessels 
can be detected ; no open orifice belonging to 
either can be distinguished. Many anatom- 
ists have endeavoured to fill the commencing 


branches of the lymphatic system by forcing’ 


the injection, thrown into them, in a retrograde 
direction, and in fishes where there are no 
valves, with the effect of shewing very nume- 
rous lymphatic vessels destitute of orifices, but 
‘not so universally distributed as has been 
imagined. 

Fohmann, Breschet, and others have simply 
made a puncture in the tissues, and by forcing 
quicksilver into the wound, have occasionally 


LYMPHATIC AND LACTEAL SYSTEM, 


succeeded in filling a minute net-work of lympha- 
tics. Cruickshank and Hewson employes iga- 
tures to the thoracic duct, to the larger lymph: 
tics, or simply round the limb immediately pre- 
vious or subsequent to the death of the anima 
for the purpose of distending the radicles of th 
system. Taaay: the microscope has been hai 
recourse to by most observers. But the pr 
vailing physiological opinions of the day ha 
more influence than all our anatomical in 
vestigations in determining our notions of th 
mode of origin of the lymphatic vessels. I 
deed, so much has this been the case, that I sha 
find it convenient, in treating the subject of 
origin of these vessels, to refer to the physi 
logical views of the periods during which th 
successive opinions have been broached. Th 
only other observation I shall make on enterit 
upon this difficult and still obscure subject i 
that the chyle seen on the coats of in 
testine, contained in its proper vessels, so near 
to the villous tunic, has tempted anatomists t 
confine their observations perhaps too muec 
to this one-absorbing surface, with the fixe 
intention of applying the information thu 
gained, to the whole system ; whereas the fluic 
contained in the chyliferous vessels differs 
much from that of the rest of the system, tha 
it is not very improbable that the former which 
admit particles of matter should posSess ori- 
fices, while the latter should receive its con- 
tents by imbibition without peoweeer orifices, 
which, in fact, is the opinion held by two em 
nent physiologists, who have paid considerak 
attention to the subject, Magendie and Cruveil- 
hier. The first opinion with respect to the 
mode of origin of the lymphatic vessels which 
I shall consider is that by open orifices. aq 
Many investigators at various peri nave 
attributed open orifices to the radicles of th 
lymphatic vessels; indeed, this has been the 
prevailing opinion till within the last few 
years. Asellius, the discoverer of that part of — 
the system which is connected with the intes- 
tines, imagined that his “ vasa lactea”’ com 
menced by open mouths from the interior o 
the intestine. His words are, “ ad intesti 
instar hiant spongiosis capitulis.” The first dis 
coverers of the rest of the system, the ** va: 
lymphatica,” did not attribute to them the fum 
tion of absorption, but regarded them as destine 
to assist the veins in returning the cireulat 
fluids to the heart. They supposed them, the 
fore, to be continuous with those arteries whic 
admitted a colourless fluid only, while th 
veins in a similar way received their conten 
from the arteries conveying the red blood. Th 
lymphatics properly so called were not con: 
dered to possess open orifices at their orig: 
until they were generally recognized as shar 
with the lacteals, the important office of abst 
ing fluids, as well as conveying them towar 
the heart. It was not fairly established antil 
the time of the Hunters, that these vessels 
formed part of the absorbent system, alth 
Glisson and Hoffmann had expressed thi 
opinion to this effect, a few years after the dis 
covery of the lymphatic vessels. But to + 
justice to this part of our subject, it will b 


LYMPHATIC AND LACTEAL SYSTEM. 


necessary to enter more fully into the Hun- 
terian theory of absorption. 

The Hunters, Monro, and their followers 
Cruickshank, Elewson, and Sheldon, conceived 
that the lacteals and lymphatics formed one 
great system of vessels by which alone absorp- 
tion was effected in the living body, either for 
the purpose of collecting new materials, or for 
the removal of the old ; consequently, that these 
vessels were essential agents in the growth and 
habitual nutrition of the structures ;— that 
whenever any of the solid or fluid components 
of the body, whether of a healthy or morbid 
character, disappeared, their removal was 
effected by the lymphatic vessels; this in- 
cluded the ulcerative process, which they 
considered as exclusively carried on by these 
vessels. Many ingenious experiments were 
eee to disprove absorption by the veins. 

uids of various colours impregnated with 
musk and other odours were thrown into the 
intestines of living animals, and were after- 
wards detected in the lacteals, but not in the 
veins, and imbibition was considered impos- 
sible in the living structures. These views 
were generally received throughout Europe, 
and have been acquiesced in almost to the 
present day. Our phraseology, written or 
oral, whether in reference to Pathology, 
Physiology, or Anatomy, is evidently still 
imbued with them. This theory of the func- 
tions of the lymphatic system necessitated a 
corresponding anatomical disposition in the 
mode of origin, as well as in the general ar- 
rangement of these vessels. They were re- 
quired to be universal for the purposes of 
growth and nutrition ; wherever there was the 
artery to deposit, there must be lymphatic to 
absorb; and as imbibition was inadmissible, 
they were endowed, as a matter of necessity, 
it open mouths, by which they were said to 
commence from all serous and from all mucous 
surfaces, including the interior of all the visceral 
cavities, the serous linings of the arteries, veins, 
and even of the lymphatics themselves, the 
synovial surfaces of the joints; the surface of 
the skin, the mucous linings of the alimentary 
canal, of the aerial, urinary, and other pas- 
sages, of the excretory ducts, and from the in- 
terstitial cellular tissue of the whole organism. 
It was admitted that the orifices of the lymph- 
atic vessels could not be shewn; that they 
eluded our senses by their transparency and 
extreme minuteness ; but on the villi of the in- 
testine, the commencing lacteals were supposed 
to be detected, turgid with chyle, and their 
mode of origin by patent orifices was described 
by more than one anatomist. An analogous 
arrangement at their commencement was ad- 
judged to the lymphatics, without any further 
investigation directed specially to these vessels. 
Cruickshank thus describes the appearance 
of the supposed lacteal orifices on the villi, 
seen in a female who died suddenly seven or 
eight hours after a full meal. “ In some hun- 
dred villi, I saw a trunk of a lacteal forming 
or beginning by radiated branches, The ori- 
fices of these radii were very distinct on the 
_ surface of the villus, as well as the radii them- 


213 


selves, seen through the external surface pass- 
ing into the trunk of the lacteal; they were 
full of a white fluid. There was but one of 
these trunks in each villus.” He en also 
that Dr. Hunter examined them under the 
microscope, and counted as many as fifteen to 
twenty orifices to each villus. According to 
Lieberkuhn, the lacteal commences on the 
apex of each villus by one or more orifices 
leading to an ampullula situated near the apex 
of the villus, from whence one lacteal branch 
proceeds through the centre to the base of the 
villus. The ampullula, he states, is lined by 
a spongy cellular tissue, which he conceives is 
subservient to absorption. With respect to the 
orifices, his words are: “ Quod autem unum 
saltem adsit foraminulum in cujusvis ampul- 
lula apice, certo examine mihi constat: in- 
terdum tamen, licet rarissime, plura ut in pa- 
pillis mammarum, vidisse memini.” Sheldon 
admits Lieberkuhn’s description of the orifice 
of the lacteal vessel, and of the ampullated ap- 
pearance of its commencement from the villus ; 
but it appears to me, on looking at Shel- 
don’s plates, and reading his description of the 
ampullule, that he as well as Lieberkuhn, 
whose plates he has copied, have mistaken the 
mucous follicles of the intestines for the am- 
pullated villi. Speaking of the ampullule, Shel- 
don says, “ I have seen them of different forms, 
most commonly bulbous, as represented by 
Lieberkuhn. I have also seen a number of 
ampullule filled with chyle, sometimes form- 
ing clusters, as represented in plate I., while 
in other parts of the small intestines [ have 
found them solitary, and projecting beyond the 
villi, as may be seen in several of the figures 
in plate I.” Hewson has seen a net-work of 
lacteals as well as of bloodvessels on the 
villus, but no ampullule; he states that the 
orifices of the lacteals can only be discerned 
when the villus is rendered turgid and erect 
by the fullness of the bloodvessels. In refer- 
ence to these orifices, he says: “ It might be 
here objected that these were only lacerations 
of the villi, but I am persuaded they were not, 
from having, on repeatedly examining them, 
observed the pores or orifices very distinct and 
empty ; whereas, were they lacerations, I think 
I shots have seen the injection in them, as 
the villi were so much injected by it.” These 
are the data upon which has been founded the 
opinion that the lacteals and lymphatics arise 
every where by open mouths. I have myself 
examined under the microscope the villi of 
various animals destroyed at different periods 
after a meal, for the purpose of detecting the 
mode of origin of the lacteal vessels. I have 
looked at them for hours together before and 
after the bloodvessels had been filled to great 
minuteness, but have never been enabled to 
discover orifices on the apices, or on any 
other part of the villus, and I can adduce the 
names of a host of modern observers of consi- 
derable celebrity, Rudolphi, Panizza, Haasse, 
Lauth, Fohmann, Breschet, Miller, Treviranus, 
and others, who deny the existence of any such 
orifices. Magendie and Cruveilhier conceive 
that the chyle must enter the lacteals by ori- 


214 


fices on account of the material particles of 
which this fluid is composed; the lymph the 
suppose enters the vessels by imbibition throug 
their coats. 

Before alluding to the other opinions on the 
subject of the origin of the lymphatic vessels, 
it may be as well to premise the changes 
which have taken place in our physiological 
notions with respect to the function of ab- 
sorption since the time of the Hunters and 
their immediate successors. Magendie has 
proved by numerous convincing experiments, 
that imbibition does take place in the living 
as well as in the dead body, not only through 
the coats of the lymphatics and bloodvessels, 
but through all the tissues. 1t has been equally 
well established by Magendie, Delille, Segalas, 
Mayer, Emmert, and other physiologists, that 
we can no longer exclude the veins from _parti- 
cipation in the important function of admitting 
new and foreign matters into the animal sys- 
tem. With respect to imbibition, I will select 
one of many experiments instituted by M. 
Magendie. He exposed the external jugular 
vein in a dog, and having separated it from its 
cellular attachments, placed a piece of card 
underneath the vessel so as to isolate it from 
the surrounding parts. He now applied to the 
centre of the vein a watery solution of the 
Spirituous extract of nux vomica. In four mi- 
nutes the ges oe of poisoning made their 
appearance. If then it be admitted that imbibi- 
tion takes place in the living textures, there can 
be no longer an absolute necessity for open 
mouths to the origins of the absorbing vessels, 
and it follows that the lymphatics cannot be the 
sole agents in the process of absorption. 

I will now adduce some experiments con- 
ducted by different physiologists, proving the en- 
trance of varioussubstancesinto the livinganimal 
system by other channels than the lymphatics. 
Magendie divided all the structures of the 
hind leg of a living dog, with the exception of 
the femoral artery and vein, through which the 
circulation was carried on. He then inserted 
the upas tieuté poison into the foot of the 
mutilated limb. The animal was poisoned in 
the usual space of time required for this sub- 
stance to take effect. He repeated the same 
experiment with the additional precaution of 
placing inert tubes into the artery and vein, 
and afterwards dividing these vessels, leaving 
the limb connected to the trunk by the tubes 
only, through which the blood passed to and 
from the limb; the same effect followed on the 
introduction of the poison. 

Mayer injected a solution of prussiate of pot- 
ash into the lungs of an ammal: in from two 
to five minutes after the injection, the serum 
of the blood, tested by a salt of iron, gave 
evidence of the presence of the prussiate of 

tash by the usual green or blue precipitate. 

t was detected in the blood long before it 
could be perceived in the contents of the tho- 
racic duct, and in the left side of the heart be- 
fore it appeared in the right. It was therefore 
evident that the pulmonary veins and not the 
lymphatics had first received the prussiate of 
‘potash and conveyed it to the heart. Segalas 


LYMPHATIC AND LACTEAL SYSTEM. 


included a piece of intestine between two lig 
tures in a living animal, and tied all the blood- 
vessels leading to it excepting one artery; the 
lacteals were ‘eft aninored and pervious ; an 
aqueous solution of nux vomica was no 
jected into the peor of intestine and th 
secured for an hour without producing ¢ 
symptoms, but on removing the ligature fro 
one of the veins, the poison took effect in 
minutes. The converse of this experiment ¥ 
performed by Magendie and Delille. Ap 
tion of intestine of a living animal was 
cluded between two ligatures ; the lacteals p 
ceeding from it were ligatured and divi 
the bloodvessels being left pervious. A § 
lution of nux vomica thrown into this piece 
intestine destroyed the animal in six ming 
Emmert applied a ligature to the abdom 
aorta in a dog, and afterwards inserted pi 
acid into the foot of one of the hind legs; _ 
ill effects followed in seventy hours; the 
ture was then removed, and in half an & 
symptoms of poisoning appeared. 
ua addition & ‘ini Pe bibition, Dr. D 
chet has shewn that fluids situated in contact 
animal membranes permeate them in obedi¢ 
to certain laws. When two fluids of differ 
densities are in contact with the opposite 
of a membranous septum, y both pe 


. 


to the denser fluid; to this he applies the t 
of Endosmosis : the slower current from 
denser to the rarer fluid he calls Exosmo: 
These remarkable powers must be continu 
in action in the animal machine, compose 
it is of solids and fluids, and cannot for th 
future be lost sight of in considering the s 
ject of the absorption and deposition of ft 
in a living animal, or the arrangement of 
structures by which these important function: 
areaccomplished. Taking these facts into con 
sideration, and bearing in mind the exper 
ments above detailed, we are led to thee 
clusion, that the capillary bloodvessel 
even other tissues imbibe indiscriming 
fluids brought in contact with them, and ay 
rently in obedience to the physical or mec 
nical laws regulating imbibition, rather thar 
virtue of any new and essential 3 
which they may be endowed as living st 
tures ; while the lymphatic system is” 
possession of a higher grade of n 
companied with an elective power (espec 
manifest in the lacteals) existing only with 
and if not entirely independent of mechan 
or physical laws, at any rate ently 
variance with them; by this elective pe 
they are enabled, to a great extent, to re 
materials injurious to the economy of 
animal, and to select those alone which ni 
be made subservient to the nutrition of th 
system. (ar. 
These physiological considerations will 

pare us better for the examination of thet 
maining theories on the mode of commen 
ment of the lymphatic vessels. We shall n 
enter upon that which ascribes to them 
origin from the cellular tissue. Fohmann ha 


- 


LYMPHATIC AND LACTEAL SYSTEM: 


injected the lymphatic vessels from the cellular 
tissue, and most anatomists have remarked that 
when an injection thrown into the bloodvessels 
has extravasated into the cellular membrane, it 
has occasionally entered the lymphatic vessels. 
I have several times injected Fohmann’s so 
called lymphatic cells of the umbilical cord, 
and have preserved a specimen shewing them, 
but cannot acquiesce in the opinion that they 
form a part of the lymphatic system. These 
cells, which readily receive the quicksilver in- 
troduced into a puncture made in the cord, 
vary in diameter from 1-100th to 1-250th 
of an inch, and communicate freely with 
each other; they have a very regular and 
organized appearance, but can only be injected 
after putrefaction has commenced. Fohmann 
describes them as situated between the lym- 
phatics of the placenta, which terminate in them, 
and those of the fcetus, which commence from 
them. I have never succeeded in pressing the 
injection from the cells of the cord into the 
lymphatics of the fetus or of the placenta. 
Treviranus conceives that the lymphatics every- 
where commence by elementary cylinders of 
cellular tissue, and that in the villi of the intes- 
tines these elementary cylinders are so arranged 
as to have one of their extremities terminating in 
a lacteal vessel situated in the centre of each 
villus, while the other reaches the periphery of 


_ the villus, on the surface of which they present 


little vesicular projections, in whose centre he 
thinks he perceives a minute orifice. Arnold 
also observed a similar arrangement of the cel- 
lular tissue of the orbit into minute cylinders, 
which he supposed to be an incipient net-work 
of lymphatic vessels. Cruveilhier considers it 
probable that the cellular tissue and the serous 
membranes are formed of lymphatic vessels; 
and Mascagni makes a more sweeping assertion 
that all the white textures and the whole cel- 
lular web of the body is composed of these 
vessels. 

The opinion that the lymphatic system com- 
mences by a plexus or net-work of vessels 
larger than the capillary bloodvessels, and 
which can always be seen by the unassisted 
eye when injected, appears to be the best 
supported by evidence, and to be that more 
generally received by modern investigators. 
These incipient plexuses are considered to 
be destitute of orifices either on the villi or 
elsewhere, and in this respect to resemble 
the peripheral branches of the arteries, veins, 
and excretory ducts, which, according to 
the more recent views in minute anatomy, no 
where present open mouths. The splendid 
injections of Mascagni, Fohmann, Lauth, and 
Panizza, shewing these vessels in various parts 
of the body, on the interior of mucous mem- 
branes, on the surface of particular portions of 
the skin, on the serous membranes, especially 
that part covering the solid viscera, on the 
lining membrane of the heart and blood- 
vessels, and of the excretory ducts of the 
glandular viscera, offer a body of evidence 
which can scarcely be resisted. In none of 
these situations can open orifices be discovered 
by the aid of the microscope or by means of 


215 


urging on the injection. On the surface of the 
liver, where the lymphatics may be injected 
with great facility, by pressing in a retrograde 
direction the injection may be forced beyond 
the valves, and by continuing the force some 
extremely minute globules of mercury may be 
made apparently to pass through the coats of 
the vessels. Haase has also, by the same pro- 
cedure, forced the mercury through a net-work 
of lymphatics on the surface of the skin; but 
these circumstances can hardly warrant the 
supposition of lateral organized pores. These 
primary networks of lymphatic vessels are said 
to be deficient in valves in some situations. 
The meshes of the networks are of various 
forms and sizes: sometimes they are nearly 
equal-sided, at others oblong or irregular; in 
some places the vessels are so closely set that 
the spaces between them can scarcely be seen ; 
in others they are larger and very distinct. 
The plan adopted by Fohmann to display these 
vessels, though liable to some objections, ap- 


Fig. 51. 


Shews an incipient plexus of lymphatic vessels. 
( From Breschet. ) 

a, the more superficial plexus formed of very 
minute valveless vessels. 06, a deeper plexus 
formed of larger valveless vessels, which receive 
the contents of the former, and which terminate in 
lymphatic vessels armed with valves. 


pears to be the most successful. He pierces 
the part to be injected with a sharp-pointed 
lancet, held nearly horizontally, so as to pro- 
duce a very superficial wound, the lymphatic 
net-work being generally nearer the surface 
than the capillary bloodvessels ; into the wound 
thus effected the pipe of the mercurial injecting 
tube is inserted, and the quicksilver is made to 
enter some of the vessels opened in the in- 
cision, either by the weight of the column of the 
mercury or by urging it on with the handle ofa 
scalpel. On the glans penis this method scarcely 
ever fails to fill the lymphatics, which are of 
large size. In the skin of the scrotum, and in 
the neighbourhood of the nipple, success will 
occasionally attend the attempt to shew these 
vessels; but in other parts of the integument , 
the endeavour has with me always been fruit- 
less, so much so that I cannot help doubting 
their universal existence on the surface of the 
true skin. Breschet’s description of a net- 
work of lymphatics brought into view by 
piercing the cuticle only, with a capillary tube 
of glass connected with.a column of mercury, 
I am convinced is deceptive: his words are-— 


216 LYMPHATIC AND 


** I] consiste (ce procédé) & percer superficielle- 
ment le tissu cutané avec l’extremité d’un tube 
capillaire en verre ou en acier, de fagon a 
n'intéresser que |'épiderme, pour arriver au 
réseau vasculaire situé entre cet épiderme et le 
chorion. On obtient ainsi l’injection de réseaux 
admirables de vaisseaux lymphatiques.” I 
have frequently produced the appearance here 
alluded to in all parts of the body: a fetus 
answers best for the purpose, but the proper 
lymphatics are never filled from these supposed 
net-works of lymphatic vessels. They are 
clearly nothing more than the spaces around 
the bases of the papille of the skin, from which, 
as putrefaction commences, the cuticle sepa- 
rates more readily than from their apices, con- 
sequently little canals are left around the pa- 

illa, which communicate with each other and 
orm a pretty exact resemblance to vessels fill- 
ing rapidly as the mercury runs around the 
bases of the papilla. ‘The appearance:can only 
be produced at a certain stage of putrefaction 
when the cuticle is about to separate. On 
removing the cuticle, the pretended vessels im- 
mediately disappear; but on the glans penis, 
on the scrotum, and on the skin of the nipple 
the removal of the cuticle will not disturb the 
net-works of vessels which may be there in- 
jected; moreover from these the lymphatic 
trunks can always be filled. I am also dis- 
posed to think, contrary to the received opinion, 
that the serous membranes do not universally 
present this superficial network of lymphatics ; 
there are at any rate parts of these membranes 
where I have never seen these vessels injected, 
while there are others in which anatomists in- 
variably succeed in shewing them; and for the 
mere purpose of absorbing the fluid secreted 
by the serous sacs, there appears to me nothing 
extraordinary in the supposition, that those por- 
tions of the membrane only which are most 
conveniently situated for the purpose should be 
endowed with the proper organization to effect it. 
The mode of procedure, however, adopted by 
Fohmann and others to display the incipient 
lymphatic net-works is open to serious abjee* 
tions, and calculated without great circumspec- 
tion to lead into error. The capillary blood- 
vessels will often be implicated in the wound 
required to pierce the lymphatic net- work, con- 
sequently the injection may be found in the 
arterial and venous as well as in the larger 
lymphatic branches leading from the part. To 
succeed to any extent many punctures may be 
required, and in all probability some of these 
will conduct the injection into the three sets of 
vessels; but I have several times by the first 
puncture succeeded in injecting a net-work of 
vessels on the glans penis, which has conveyed 
the injection at once into the lymphatic 
branches on the body of the penis, and into 
these vessels only. The cellular tissue will 
also readily receive the injection, and where 
the cells are very small and uniform, as is the 
case with the umbilical cord, they resemble 
very much a net-work of vessels distended 
with quicksilver; and although Fohmann ad- 
mits these to be cells, yet from their regularity 
he has been led to consider them a part of the 


LACTEAL SYSTEM. 


lymphatic system. In the same cat . 
be classed the supposed lymphatic cells of the 
cornea observed by Arnold and by Miiller. 
The submucous cellular tissue also is fre 
quently arranged in little cylindrical cells whiel 
communicate with each other, and these cells 
on receiving the mercury put on the appearane 
pretty exactly of a net-work of put 
lymphatic vessels are not found conveying th 
injection away from them to the nearest lym 
phatic glands, which I imagine should be the 
proof required before we admit any vessels: 
cells to belong to the lymphatic system, ho 
ever beautifully displayed by our injection 
The subserous tissue is open to the same 
mark, and I can hardly offer a better instance 
of what appears to me to be an error ari 
from this source, than by quoting Fohman 
own words in reference to what he deseribe: 
the lymphatics of the brain. Les vaisse 
lymphatiques des enveloppes des masses 
trales du systéme nerveux sont tres faciles” 
démontrer, surtout au cerveau et au cervel 
Lorsqu’on enfonce une lancette entre la pit 
mére et l’arachnoide, et qu’on insuffle le canal 
que l’on vient de pratiquer, on voit paraitre un 
réseau lymphatique interposé entre ses 
tuniques, réseau formé de rameaux d'un calibr 
plus considérable que dans les autres tissus dt 
corps; cependant leurs parois sont si foible 
qu'elles se déchirent presque aussitot qu’on 
introduit le mercure.” With respect to 
universal net-work of lymphatics attributed t 
the lining membrane of the heart, and to th 
of the arteries and veins, I cannot admit, 
the injections of a few minute canals 
quicksilver on the lining membrane of the 
heart in the horse, by Lauth, and similar it 
jections by Cruveilhier and Bonamy, can 
received as demonstrative: the injection 
not traced from them to a distinct lymp 
vessel, armed with valves and no ‘its 
course towards a lymphatic gland; these mie 
nute canals might have been capillary blood- 
vessels, or, as Breschet observes in his exph 
nation of the plate which he gives from 
of these supposed vessels, “ Nous pensons 
qu'ils sont uniquement constitués par des la 
cunes du tissu cellulaire.” om 
In concluding what I had to say of the 
origin of the lymphatic vessels, a subject 
inextricably mixed up with our preconcei 
physiological notions, I ought, to 
offer some apology for advancing im an art 
of this nature any opinion peculiar to mys€ 
I mean in reference to curtailing the e t 
which the lymphatic system will be found t 
exist inthe organism. My own mind has beet 
forced to this conclusion after some s 
attention to the subject, both from anatomic 
and physiological considerations. ua) 
It has appeared to me in the first place, that 
anatomists who have especially devoted their 
time to this interesting subject of late years, 
have not yet fairly freed themselves from the 
influence of the Hunterian views with resp 
to the part performed by the lymphatic vessel 
as well as by the arterial capillaries, in eff 
ing the growth and habitual nutrition of the 


i 


oy 


LYMPHATIC AND LACTEAL SYSTEM. 


structures. To support the Hunterian theory 
the lymphatic was required to be present with 
every molecule of the organization, there with 
open mouth (for imbibition in the living body 
was not admitted as possible) to remove the 
old material in order to make room for the new, 
which was supposed to be deposited by the open 
mouths of capillary arteries. Now, although 
physiologists no longer admit that the arteries 
any where terminate by open mouths, but 
consider all nutrition to take place by the 
transudation of the liquor sanguinis through 
the delicate tunics of the capillary blood- 
vessels, and although venous absorption, as wel! 
as lymphatic, is acknowledged to take place, 
consequently that the ubiquity of the lym- 
hatic ceases to be a matter of necessity, still 
it appears to me that physiologists have not 
yet shaken off the old impression, that every 
icle of the organization must have its lym- 
phatic vessel, and I cannot help thinking that 
the continuance of this impression is mislead- 
ing us in our notions of the arrangement of 
the system. 

There are also some additional anatomical 
considerations which have had their weight in 
leading me to the opinion that the lymphatic 
system is less extensive than is generally sup- 
posed. It is not, I believe, known to anato- 
mists that the lymphatic vessels admit readily 
of dissection in their uninjected state; these 
vessels do not easily give way under traction, 
and by using the forceps to hold them, and a 
blunt but pointed instrument to detach them 
from the surrounding cellular membrane, to 
which they are but loosely attached, they may 
be dissected with equal facility as the cuta- 
neous nerves, for which they are not unfre- 
quently mistaken by the young dissector. I 
have in this way several times dissected the 
lymphatics of the upper extremity, from the 
glands in the axilla to the fingers, and in the 
lower, from the inguinal glands to the toes. 
In proceeding thus to trace these vessels, scarcely 
a single lateral branch can be detected in the 
leg and thigh, by which the supposed universal 
net-work of the surface of the skin could have 
been connected with the rest of the system. 
When the subcutaneous lymphatic vessels are 
injected with quicksilver, every anatomist must 
have remarked the absence of lateral branches ; 
this has always been accounted for by sup- 
posing a valve at the termination of each late- 
ral branch into the larger longitudinal vessels ; 
but in dissecting these vessels in their unin- 
jected state, the lateral branches if present 
ought to be met with, which is not thecase. I 
am fully aware that Haase, and other inves- 
tigators, have succeeded in getting the injection 


_to pass in a retrograde direction from the sub- 


cutaneous lymphatics of the lower extremity 
into a net-work of vessels of small extent situ- 
ated close to the surface of the skin: this has 
occurred to myself on two occasions, in the 
skin over the tibia, and in the inguinal region, 
but in both these instances it was in a portion 
of skin presenting a cicatrix; the net-work was 
circumscribed, and left the impression on my 
mind of an abnormal rather than of a normal 


217 


condition of these vessels. The entire pro- 
fession have adopted the notion that the pro- 
cess of ulceration is effected by the lymphatic 
vessels, consequently that, as every steycture 
may ulcerate, so it must have its lymphatic 
vessel. But I may be permitted to ask patho- 
logists to consider, whether they are not still 
influenced by the Hunterian theory, viz. that 
the countless open mouths of the lymphatics 
(which modern anatomists do not allow them 
to possess) effect the removal of the textures 
disappearing by ulceration, rather than by the 
few facts and observations bearing upon this 
important question. I would ask whether the 
occasional instances, of inflamed lymphatics 
containing pus, being found leading from an 
ulcerated surface, are sufficient to establish the 
opinion, that the whole process is effected by 
this set of vessels; or whether the occurrence 
is not more satisfactorily accounted for, by the 
supposition that the ulcerative process has im- 
plicated a lymphatic vessel, and that the pus 
has entered the vessel by an opening thus 
effected in its paries, or that the pus has been 
formed in the lymphatic itself, as the result of 
inflammation affecting its interior; more par- 
ticularly when it is borne in mind, that the pus 
globule is much too large to have entered these 
vessels by imbibition, and that open mouths are 
denied to them. The parts of the body in 
which I have seen pus in the lymphatics, have 
been on the surface of the lung, on the mu- 
cous membrane of the intestines, on the penis 
when ulcers had occurred in these organs, also 
in the subcutaneous lymphatics after suppura- 
tion and sloughing of the cellular tissue,—situ- 
ations in which every anatomist has seen lym- 
phatics, and where the ulcerative or sloughing 
processes might readily have effected an open- 
ing into them. 

The lymphatic or absorbent glands, called 
also conglobate glands by Sylvius, and lym- 
phatic ganglia by Chaussier, are small fleshy 
bodies of a flattened form, rounded or oval in 
outline, varying from the size of a millet-seed 
to that of an almond; so situated in various 
parts of the body as to intercept the lymphatic 
vessels in their course towards the trunks of the 
system. They are generally clustered together, 
but occasionally are found single or isolated. 
The isolated glands are usually very small; 
the large ones clustered together. .The lym- 
phatic glands are well protected from pressure. 
In the limbs they are principally situated in 
the cellular spaces at the flexures of the joints, 
and enjoy the same protection as the main 
bloodvessels, close to which they are generally 
located. The loose cellu!ar tissue in which they 
are for the most part imbedded, allows them 
great freedom of motion, by which they are 
enabled to elude pressure. 

The lymphatic glands are most developed in 
childhood, least so in old age, and are interme- 
diate in this respect in adult life. They are 
not found in Amphibia and Fishes, and in 
Birds only in the cervical region: intricate 
plexuses of large lymphatic vessels occur fre- 
quently in those animals which are destitute of 
lymphatic glands. 


218 LYMPHATIC AND 


_ The colour of the lymphatic gland, a ane ing 
apparently on the contents of its bloodvessels, 
is of a pale rose — resembling in this re- 
spect the colour of the salivary glands or of the 
cineritious matter of the brain; the exceptions 
to this observation will be found in the mesen- 
teric glands while the chyle is passing through 
them, when they assume a whitish colour; the 
lymphatic glands in the neighbourhood of the 
liver and gall-bladder have been pepsi to 
possess a slight yellow tinge, but this is to be con- 
sidered a si dear appearance. The black 
colour of the bronchial glands is remarkable and 
not easily accounted for; the lymph passing 
from the lung to them being always perfectly 
transparent and colourless. 

The lymphatic gland has a capsule of con- 
densed cellular tissue, which surrounds it and 
firmly adheres to it, appearing to send cellular 
prolongations into its substance ; the outer sur- 
face of this capsule is connected to the surround- 
ing textures by a loose cellular tissue. The 
capsule appears to serve the purposes of convey- 
ing the bloodvessels to the interior of the gland, 
of isolating it from the surrounding parts, and 
of preventing its over-distension by the lymph 
conveyed to it. 

The bloodvessels of the lymphatic glands are 
large and distinct; frequently more than one 
artery is traced to a gland; the returning veins 
do not generally correspond either in direction 
or‘number with the arteries. The veins are 
much larger, but have appeared to me fewer in 
number than the arteries. 

Nerves of considerable size pass to the lym- 
-phatic glands and can generally be traced 
through them, from which circumstance it has 
been doubted whether any filaments are left in 
the gland; but if acute sensibility to pain from 
undue pressure or from disease be adinitted as 
dependent upon a proper supply of nerve, un- 
doubtedly they possess it. a e exact mode of 
arrangement of the bloodvessels in the interior 
of the gland is not well known. Aftera success- 
ful injection of these vessels the gland assumes 
the same colour as the injection itself. 

Our knowledge of the structure of the ab- 
sorbent glands rests mainly upon the informa- 
tion obtained by throwing injections of mercury 
or coloured wax into the lymphatic vessels. In 
this mode of investigating their texture, the walls 
of the canals or cavities containing the injection, 
which appear, as in the kidney and testicle, to 
form the parenchyma of the organ, are com- 

ressed, and when dry become transparent. 
he arrangement of the minute bloodvessels on 
the lining membrane of these canals has not 
been sufficiently investigated, and until this 
has been effected, our knowledge of the structure 
and function of the lymphatic gland must be 
considered very unsatisfactory, and as consist- 
ing of little more than conjecture. The great 
point of controversy has been, whether the in- 
jection thrown into the gland by the afferent 
ymphatic vessels was contained in cells or in 
convoluted vessels, which if decided would 
throw but little light upon the office performed 
by the gland—a desideratum in physiology of 
considerable importance, and without which 


LACTEAL SYSTEM. 


we are left in the dark at the very thresho 
of our investigations with respect to 
changes effected in the lymph and chyle 
advance towards sanguification. On examinin 
Fig. 52. eo 


oT 


Lymphatic glands iajones with mercury. 


( After ™ 
A, gland injected and dried. a@, a, vasa a 
rentia. b, vasa efferentia. 9 
B, gland injected and laid open to show the 
rent cells. i, apparent cells; e, vas efferens; 
vasa afferentia., 


the glands thus distended with injections, ¢ 
vasa inferentia are seen reaching the g 
from various sources, and on their appre 
it they may be observed to subdivide in 
tremely minute branches, which disapp 
plunging into its substance: equally mina 
vessels may be observed emerging from 
opposite side or surface, which soon unite 
form the vasa efferentia of the gland ; the gla 
itself, which is intermediate in position betwe 
these vessels, when injected, presents a gi 
nular surface, and at first sight an obse 
would generally conclude that he was lo 
ing upon minute cells filled by the injec 
in making a section also into the substa 
of the gland and allowing the mercury — 
escape, the appearance on a supe 
spection is still that of cells; proceedit 
however, with more attention to examine 
supposed cells, especially after making a sect 
as close to the surface of the gland as possib 
by the aid of the microscope it will be evide 
that tubes closely set together and adherent 
each other, have been laid open, passin 
various directions, and in their interior ma 
valvular constrictions and thread-like inters 
tions may be seen; in fact the gland appea 
to be entirely composed of a convoluted 
the sides of which as they come in contact are 
firmly held together by cellular membrane 
derived from the capsule. — 
This convoluted tube forming the gland is no 
always cyl'ndrical, but is occasionally dilated 
and looks fattened near the surface where 
pressed by the capsule; the size of this tub 


. 
iCclal 


——————— 


SE ———————— 


ee ee 


ee ie 


LYMPHATIC AND LACTEAL SYSTEM. 


is much larger than that of the branches of the 
vasa afferentia and efferentia, a fact that has 
been too much overlooked by anatomists, and 
which leads me to conjecture that these vessels 
enter and arise from its convolutions by open 
mouths; be this as it may, we know that the 
injection conveyed into the gland by the vasa 
afferentia readily passes from it by the vasa 
efferentia. I should not here omit to mention 
a circumstance already adverted to of consi- 
derable interest, viz. that the injection conveyed 
to a gland by an afferent vessel is occasionally 
teceived by the veins of that gland, and to all 
appearance without rupture or extravasation. 
The occurrence itself is admitted by all; but 
physiologists differ much in their explanations 
of the channel by which the injection has en- 
tered the vein. Some explain it by an extrava- 
sation into the cellular tissue from an injury 
by which both sets of vessels have been opened ; 
others, who conceive that a minute net-work of 
lymphatics exists on the interior of the veins 
and arteries, will have no difficulty in ima- 
gining a rupture of this net-work; the vasa 
vasorum of the lymphatics, which may be dis- 
tinctly seen on their interior after a minute in- 
jection, may be supposed to have given way 
and to have admitted the injection from the 
interior of the lymphatics. . But these opinions 
will not explain. -why this communication 
should take place within the gland only, and 
invariably with the vein, never with the artery. 
The general opinion is that this communi- 
cation takes place accidentally, and not by 
any real continuity of canal. Johmann stands 
almost alone in asserting thata natural commu- 
nication does exist between the lymphatics and 
veins within the glands, especially in those 
Situations where in birds, reptiles, and fishes, 
the lymphatics have been proved to terminate 
directly in the veins. Fohmann even ventures 
an opinion as to the mode in which the lym- 
phatic joins the vein ; not, he conceives, by con- 
tinuity of peripheral branches, but by an effer- 
ent lymphatic opening into the side of a vein 
before the latter emerges from the gland. 
Without committing myself to the exact mode 
of union, I must confess I agree with Fohmann 
that a natural communication does exist in 
some of the glands between the lymphatics and 
the veins. It has been observed hundreds of 
times. It has occurred to every anatomist who 
has engaged himself with the injection of these 
vessels; I have met with at least twenty such 
instances myself, while a similar communica- 
tion between a lymphatic and artery within a 
gland has never been observed. I am entirely 
ata loss, therefore, to account for these occur- 
Tences without admitting a natural channel to 
exist between the one set of vessels and the other. 

I have before observed that the exact arrange- 
ment of the bloodvessels in the interior of the 
canals of which the glands are constituted, is 
not known ; but we are equally in the dark with 
respect to the vascular supply received by other 
minute tubes, such as the seminiferous, urini- 
ferous, and lactiferous tubes, from the capilla- 
ries of whose lining membranes, however, we 
admit that their appropriate secretions are de- 


219 


rived. As far, then, as organisation is con- 
cerned, there is nothing to forbid our ascribing 
a secreting function to the interior of the 
canals of the lymphatic glands, or of theNym- 
phatic vessels generally. There can be little 
doubt but that the lymph and chyle undergo 
modifications in their passage through the ab- 
sorbent glands, although we are not at present 
prepared to state the nature of that modification. 
It has been observed that the chyle included 
between two ligatures in its own vessel before 
it has reached a gland will not coagulate, 
although after it has passed the gland coagula- 
tion readily takes place. Miiller remarks 
from this circumstance that the glands of the 
mesentery appear to have the power of changing 
part of the albumen of the chyle into fibrin. 
At any rate we are warranted, from the little we 
do know ofthe structure of the absorbent gland, 
in asserting, that the chyle and lymph collected _ 
from various sources must be mingled together 
in the glands, that they must be divided into 
extremely minute streams on their entrance 
into or exit from a gland, that they must be 
submitted to a great extent of surface of their 
containing vessels, and subjected to considera- 
ble delay in their passage through the gland. 
Mr. Gulliver’s observations on the fluid con- 
tained in the absorbent glands would almost 
lead us to conclude that their proper office was 
to fabricate the peculiar globule of the lymph 
and chyle; my own observations on these fluids 
before and after reaching the glands would 
not bear out this opinion; but as I have next 
to consider the characters, physical, microsco- 
pical, and chemical, of these fluids, I shall 
shortly enter more fully into this subject. 
Lymph is a transparent fluid, slightly opa- 
line, of a light straw colour ; its specific gravity 
is 1022°28, water being 1000°00; its odour, 
which is slight, varies, and is peculiar to each 
animal ; it is alkaline, and has a saline taste. I 
collected in an ounce-phial about three drachms 
of lymph from a large lymphatic in the axilla 
of a horse, by inserting a small silver tube into 
it. In about ten minutes the whole had coa- 
gulated into a jelly-like mass ; in half an hour 
a separation had taken place into a fluid and 
solid part: the latter formed a soft tremulous 
clot modelled to the form of the phial. A 
drop of this lymph placed on a piece of glass, 
and covered by talc, was submitted to inspec- 
tion under the microscope, immediately after its 
removal from the vessel. A number of colourless 
spherical globules were observed in it havinga 
granular surface, and precisely resembling those 
described by Mr. Gulliver as belonging to the 
mesenteric, lymphatic, and thymus glands. I 
am not aware whether Mr. Gulliver considers 
these globules as belonging exclusively to the 
glands, or whether he thinks them distinct 
from or identical with the lymph and chyle 
globule. My own observations lead me to 
state that they are found in the lymph or chyle 
before and after passing the glands, as well as 
in their transit through them. Iam also dis- 
posed to assert that these globules remain co- 
lourless, and that whenever the lymph possesses 
a slightly red tint, it obtains that tint from the 


220 


presence of blood corpuscules which have ac- 
cidentally entered it. After coagulation had 
taken place, the lymph was again examined 
under the microscope, the globules were all 
found entangled in the clot; scarcely one re- 
mained in the transparent fluid. The clot, when 
disturbed, torn, and pressed, contracted to less 
than one-twentieth of its original bulk, and the 
few blood corpuscules it contained, being now 
approximated closely together in the contracted 
pi gave it a slightly red tint. On examining 
the serum of this lymph under the micro- 
pe a week afterwards, when putrefaction 

commenced, numerous exceedingly minute 
animaicules were seen diffused through it in 
active motion. 

Miiller gives an account of a fluid which 
makes its appearance after a portion of the skin 
of a frog is removed from the muscles; this 
fluid he considers to be pure lymph; he de- 
scribes it as perfectly transparent and colourless, 
having a saline taste, but void of smell. Under 
the microscope he detected in it a number of 
colourless and spherical globules, about one- 
fourth of the magnitude of the elliptical blood 
corpuscule of the same animal, a few of which 
were unavoidably mixed with this lymph. 
Miiller also describes what he considers to be 
human lymph, obtained from a small fistulous 
opening on a man’s foot, the remains of a wound 
received on the instep; by pressure from the 
great toe towards the opening a transparent 
fluid could be made to transude; this fluid also 
contained colourless spherical globules, much 
smaller than the blood corpuscules. It, as 
well as that obtained from the frog, coagulated 
spontaneously, and appeared to possess the 
other properties of lymph. After coagulation 
had taken place in the fluid obtained from the 
man’s foot, he observed that the globules were 
partly found in the clot, while some remained 
in the fluid surrounding the clot. In the horse’s 
lymph examined by myself, all the globules 
were entangled in the clot. 

The red colour of the contents of the tho- 
racic duct, especially in the horse, has been 
remarked by most observers, but the cause 
of this redness has not been well ascer- 
tained. Breschet says, in his Systeme Lym- 
phatique, page 160: “Ce qu'il efit été in- 
téressant surtout de déterminer, c’est si la ma- 
titre colorante qui teint quelquefois le chyle, 
et méme la lymphe, y est dissoute, ou si elle 
affecte soit toujours, soit au moins quelque- 
fois, la méme disposition que celle des globules 
du sang.” I have frequently examined micro- 
“so ore this reddish fluid of the thoracic duct, 
and have invariably found it to depend upon 
the presence of red corpuscules pe 4 the 
form and size of those of the blood. I believe 
_ that these red corpuscules are extraneous to the 
lymph, that their presence is accidental, and 
should be considered as a post-mortem occur- 
rence. I would attribute their existence in the 
contents of the thoracic duct to the circum- 
stance that very many lymphatics must be di- 
vided with the other structures, before the tho- 
racic duct or indeed any large lymphatic can 
be exposed; these divided lymphatics must 


LYMPHATIC AND LACTEAL SYSTEM. 


necessarily have blood applied to their ¢ 
extremities ; the vessels being ceive t! 
blood corpuscules, and convey them from ¢ 
parts to the thoracic duct. is is not mer 
conjecture. I have seen the blood enter th 
divided vessels ia the following experime 
made for the purpose. On the under sur 
of the liver of a horse recently killed I 
served some large lymphatics filled wit 
beautifully transparent fluid. I made an i 
sion into dalivet over these vessels, of course 
viding them, and ina few seconds saw ro 
veying a reddish fluid towards the thoracie di 
The lymph bears great resemblance to 
liquor sanguinis both in its re ad 
mical characters. Miiller, who had obsery 
that the blood of frogs will not coagulate ¥ 
they are kept out of water in summer for e 
or ten days, mentions the coincidence ¢ 
when this is the case, the transp fi 
which he obtained by removing a piece of 
from a living frog, ma which he co ceiver 
be the lymph of the animal, was also incap: 
of spontaneous coagulation. aA 
Leuret and Lassaigne give the follow 
analysis of lymph obtained from the lymp 
tics of the neck in a horse :-— ' a 
Water seis sacs. eweece 
Albumen .... .... 
Fibrine cs ..2<s +2 eoee 
Chloride of sodium... .. } 


2 


Chloride of potassium ... 
Sod eee eee eee eee e ee 


a 
Phosphate of lime... .. .. 


Salivary matter, ozmazome, 
phates, muriates, and acetates of soda ai 
potash, with phosphate of potash, have in ade 
tion been detected in the lymph by i 
and Gmelin. . a 
Chevreul analysed some lymph procured 1 
Magendie from the thoracic duct of a hoi 
after five days’ abstinence. Its compositio 
was as follows :— 


- 
PUe 


Wallet ives s'. tse eee econ 9296 
Filtine ss ssa<e5 wes ee 42 
Albumen scidcseiww meee 61:0 | 
Muriate of soda...... Per 61 
Carbonate of soda........ 1°83 


Phosphate of lime........ 2? 
Carbonate of magnesia .... 5 
Carbonate of lime..... eee 5 


10000 


M. Magendie and M. Collard de Martign 
have examined the lymph in animals, after 
priving them altogether of sustenance; w Po 
the tenth or twelfth day the lymph was fou 
in greater abundance, ph: to have more 0! 
the red tinge, and to be more consistent; but 
after this period it diminished in quantity, be- 
came more watery and had less of the rose tint. 
The latter physiologist rejects altogether the 
opinion entertained by some, that the lymp 
would assume a redder colour the longer the 
animal fasted. “a 


LYMPHATIC AND LACTEAL SYSTEM 


The lymph is said to coagulate more readily 
after passing through the lymphatic glands, and 
the nearer it approaches the thoracic duct. I 
have not found this to be the case in so marked 
a degree as has been stated. I have collected 
lymph from the lymphatics of the intestines 
before they reached the glands, and from va- 
rious parts of the body in which no glands are 
situated, and have invariably found the fluid to 
coagulate spontaneously, although if in small 
quantity it may shortly return to the liquid 
State. 

The fluid contained in the lacteal vessels in 
Mammalia is of a white colour like milk, and 
is called chyle ; it has a marked saline taste, is 
slightly alkaline, and has no perceptible odour. 
I have now before me several specimens of 
recent chyle collected carefully from the lacteal 
vessels, before they reach the glands, from the 
glands themselves, from the vasa efferentia of 
the glands, and from the thoracic duct. These 
specimens were taken from a donkey killed for 
the purpose, seven hours after a full meal of oats 
and beans. About half a drachm was obtained 
from the vasa inferentia, and a drachm from the 
mesenteric glands themselves in watch-glasses; 
from the vasa efferentia about three drachms 
were procured in a test-tube, and from the 
thoracie duct in a phial nearly an ounce. All 
were of a pure mi!k-white colour except that 
from the thoracic duct, which had a slight pink 
tint. They all jellied spontaneously in from 
five to ten minutes; that from the vasa infe- 
rentia again liquified in about half an hour, 
and remained in this state; on other occasions 
I have known it retain its solidity, I have also 
seen the chyle from the glands, and from the 
vasa efferentia, return to the liquid state after 
having been coagulated for a short period. I 
haye observed the same occurrence in lymph 
before and after it had traversed a gland. In 

_ about half an hour, with the exception already 
noticed, these specimens of chyle separated 
_ into a kind of serum and clot, the latter form- 
_ ing by far the greater portion, at least four-fifths 
of the whole. This clot, however, ou being 
broken up and pressed, contracted to one- 
twentieth part of its former bulk; both the 
_ serum and the clot retaining their white colour. 
_ In the specimen obtained from the thoracic 
_ duct the pink tint was confined to the clot, and 
the serum was whitish or whey-coloured. It 
ought here to be stated that chyle, before it has 
reached the receptaculum, will not always se- 
parate into a fluid and solid portion, but will 
remain of the consistency of a soft white jelly, 
from which, however, by breaking it up, a white 
fluid may be obtained. 

I find great error and confusion in the 
descriptions hitherto given of the microsco- 
pical appearances of the chyle. Miiller and 

_ Breschet both state, that the white colour of 
the chyle depends upon its globules, which 
they then proceed to describe; they both 
quote Prevost and Dumas as estimating the 
diameter of the chyle globule at 1-7199th of 
an inch, or about half that of the blood glo- 
bule in man. Miiller says that in the cat he 

_ finds them of the same size as the blood cor- 


221 


uscules, and in the rabbit some of them were 

arger; in the calf, the dog, and the goat he 
found them much smaller than the blood cor- 
puscules of the same animal. Breschet, This 
work on the lymphatic system, published in 
1836, acknowledges the unsatisfactory state of 
our knowledge with respect to the globules of 
the chyle and lymph. Tiedemann and Gmelin, 
in their elaborate work on digestion, distinctly 
state they consider the white colour of the chyle 
to depend upon fatty particles, which form a sort 
of emulsion with the serous portion of the 
chyle. Mr. Gulliver has given by far the most 
correct description of the microscopical appear- 
ances of the chyle that I have met with; he is 
the first who has noticed the extremely minute 
particles which constitute the characteristic 
microscopical appearance of the chyle, for the 
larger globules, noticed by most observers, are 
found also inthe lymph. Mr. Gulliver has not, 
however, corrected the statement of Miiller, Bre- 
schet, and others that the white colour of the 
chyle depends upon these larger globules; but 
I doubt not he would acquiesce with me in 
opinion that the white colouf depends alto- 
gether upon the more minute particles. With 
these preliminary remarks I shall proceed to 
describe the microscopic characters of the chyle 
from my own obervations. 

Every one is aware that the lacteals, when 
not conveying chyle, contain a transparent 
fluid not to be distinguished by the eye from 
the lymph of other parts of the system; to 
this fluid is added, during the digestion of 
a meal, myriads of extremely minute parti- 
cles, twenty or thirty times less in size than 
the lymph or blood globules of the same 
animal, and which can scarcely be distin- 
guished by aglass of less power than one- 
eighth of an inch focus, upon which un- 
doubtedly the white colour of the chyle de- 
pends; when these particles are very numerous, 
the chyle is perfectly white and opaque; when 
less so, it will be whey-coloured or semitrans- 
parent. These particles are peculiar to the 
chyle, and I have been in the habit, for the 
last two years, of calling them the chyle gra- 
nules, in contradistinction to the globules of 
different kinds which are also found in this 
fluid. The chyle granules, when allowed to 
dry on a piece of glass, measure from 1-20,000th 
to 1-10,000th of an inch in diameter, and are 
larger and more distinct in carnivorous than in 
graminivorous animals. The most remarkable 
peculiarity, which I believe I am the first to 
notice, of these chyle granules, is their con- 
tinual vibratory or oscillatory motions. On 
viewing under the microscope a drop of chyle 
taken from the lacteal of a carnivorous animal 
and placed between a piece of glass and 
tale, the motions of the chyle granules 
will be seen to be so constant and ceaseless 
that the observer would ai first sight be led to 
consider the chyle as a moving mass of restless 
animalcules; but on noticing the limited range, 
as well as the sameness, and apparent want of 
object, in these to and fro movements, he will 
probably feel inclined to attribute them to 
some unknown attraction and repulsion, influ- 


222 


encing inert and unorganized particles. It is 
assuredly a striking fact, and one fraught with 
great interest, that the new molecules on their 
first introduction into the living system, should 
possess one of the most conspicuous attributes 
of vitality, viz. motion.* Mr. Ancell, who has 
_ great attention to the animal fluids, has 
uently examined these moveable granules 
with me, and is inclined to consider their mo- 
tions, as indicating the first obvious impress of 
Vitality which the new material has received 
from its association with living matter. Be- 
sides the granules, there exist in the chyle 
numerous spherical globules colourless and 
granular on the surface, averaging 1-5000th, 
but ranging between 1-3000th and 1-7000th of 
an inch in diameter, resembling in every par- 
ticular the lymph globule, with which they are 
probably identical. ‘These globules I conceive 
are not derived from the interior of the intes- 
tine as some have supposed, nor from the 
glands, as I presume is Mr. Gulliver's opinion, 
but I would rather say are formed in the chyle 
and lymph by the aggregation of similar par- 
ticles, probably fibrinous. Globules of oily 
or fatty matter are also found in the gs Pr 
these may be readily distinguished by their 
circular and even outline, by their smooth and 
apparently flat surfaces, and by the great variety 
of their size, some being as small as the chyle 
granule, while others exceed the globule in 
diameter ; in many respects they resemble the 
milk globule in appearance. Blood corpuscules 
will of course be frequently seen mixed with 
the chyle, as it is exceedingly difficult to collect 
it free from them. In the chyle the blood cor- 
puscule loses its circular outline, its ordinary 
flattened form, its concave or cupped surface, 
and assumes a corrugated or wrinkled appear- 
ance, a spiked or serrated edge; the blood 
corpuscules, when thus corrugated, are less in 
diameter than the surrounding chyle globules, 
and have frequently been mistaken for them. 
On examining the blood taken from a living 
animal after a recent flow of chyle into it, this 
appearance of the blood corpuscule will also 
be readily distinguished. The corrugations 
alluded to on the blood corpuscule may be 
mistaken for spots on it; and when the corpus- 
cule is revolving or vibrating, they may even 
appear like particles moving within it. I was 
for a short time misled by this deceptive ap- 
pearance into the belief that the chyle granule, 
when received into the blood, entered the 
envelope of the blood corpuscule to form its 
nucleus. This erroneous notion, however, was 
soon corrected on finding that other fluids pro- 
duced the same appearance in the blood cor- 
uscules. It will be observed then, that I am 
induced to think that the chyle is never per- 
fectly free from lymph; that in fact the lymph 
is termed chyle when it is rendered white by 
the addition of the moveable chyle granules 
from the interior of the intestine, to which are 


* [Wagner has depicted in his Icones Physiolo- 
gice minute granules, which he designates ‘‘ Mole- 
cule minores, cujusmodi in liquore chyli natant, 
procul dubio chyli granala futura.” Tab. xiii. 
fig. 11.—Ep.] 


LYMPHATIC AND LACTEAL SYSTEM. 


added from the same source the oily or fatty 
icles. sag 
If the clot and serum of the chyle be ex: 
mined separately under the microscope, the 
will both be found to contain the chyle granu 
in sufficient quantity to render them whit 
the chyle globule, or any blood corpusei 
that the specimen may have contained, will 
entangled in the clot, while the oily partiel 
will be principally found in the serum. If 
coagulation has been incomplete, or the s 
cimen has been agitated, some chyle glob 
and blood corpuscules will of course be 
with the serum. ” 
The chyle has been analyzed by B 
Emmert, by Vauquelin, by Marcet, 
and Brande, by Leuret and i an 
Tiedemann and Gmelin, but in a science 801 
pidly progressive as chemistry it is desirak 
adduce the most recent information bear 
the subject. I shall therefore select the 
lysis given by Berzelius, (taken from the 
lation of his treatise on Chemistry by Mi 
linger, published at Paris in 1833,) who ado 
some of the opinions of ‘Tiedemann and G 
lin, and with whose analysis of the chyle 
pretty exactly agrees. “7 
In 100 parts of chyle, taken from tl 
racic duct of a horse during the digestio 
meal of oats, he obtained, after breaking 
and pressing the clot, 96°99 parts by 
serum and 3°01 of clot: the former was 
duced by desiccation to 7°39 parts and 
latter to 0°78 ; consequently, after evaporati 
the proportions in 100 parts stood thus— 
Desiccated clot rere ceses ere ee 


- a 
xs 


err 


Water 


© 


The dry clot softened when digested in 
tilled vinegar, but without being dissol 
it to any perceptible extent. A small qua 
of a brownish-yellow oil was obtained fron 
by the action of boiling alcohol. a 

One hundred parts of the desiccated 
contained— 6 
Brown fatty matter 
Yellow fatty matter... re VFe esdecoun 
Osmazome, lactate of soda, and chlo-) ,, 

ride of sodium ..........0yseeugne 
Extractive matter soluble in water, in- 

soluble in alcohol, with carbonate > 2 

and a little phosphate of soda ....) | 
Albumen ee Pee errr eee eereeseseeee ., | 
Carbonate with traces of phosphate es r | 


lime.. 


It has been generally stated and belie 
that a sufficient quantity of chyle for chemic 
analysis could not be obtained from the lacte: 
before they reached the thoracic duct, cor 
quently, that which has hitherto been submit 
to chemical examination has been t fi 
the trunk of the system, where it must of n 
cessity have been mixed with a greater or 


: 


a < 


LYMPHATIC AND LACTEAL SYSTEM. 


quantity of lymph; the comparison therefore 
between chyle and lymph has never been fairly 
instituted. Regretting with others the defici- 
ency in our knowledge of the relative compo- 
sitions of these important fluids, which, though 
derived from such different sources, enter in 
combination the already circulating blood, I 
a some experiments, which need not 
ere be described in detail, for the purpose of 
ascertaining the quantity of chyle that might 
be procured from the vasa efferentia of the 
mesenteric glands, and found that by a little 
care and contrivance as much as half an ounce 
of perfectly pure chyle might be procured from 
a horse after a full meal. I now applied to 
Dr. G. O. Rees, well known to me as an able 
and zealous investigator of the too much 
neglected science of animal chemistry, and re- 
quested him to undertake the analysis of 
the unmixed chyle and lymph, and to institute 
the desired comparison between them. Dr. 
Rees kindly acquiesced in my proposal, and 
has published the result of his inquiry in one 
of the late numbers of the London Medical 
Gazette, from which I transcribe his analysis 
with some of his observations, the whole of 
which are well worthy of perusal. The fluids 
in question were procured from a donkey, 
killed seven hours after a full meal of oats and 
beans. 

Analysis of chyle and lymph before reaching 
the thoracic duct, by Dr. G. O. Rees— 


Chyle. Lymph. 
MON ae tess. .2ees 90237 .. 96°536 
Albuminous matter ...... 3°516 . 1-200 
Fibrinous matter ...... eo “Ooo .. O'420 
Animal extractive matter so- 2 ,, : 
luble in water and alcohol . O83: -. 0240 
Animal extractive matter so- ,. . 
luble in water only .... $§ Aes Soko 
Fatty matter............  3°601 .. a trace. 


Alkaline chloride, 
sulphate and carbo- 


Salts.< nate, with traces of }0°711 .. 0°585 
alkaline phosphate, 
oxide of iron .... 
100-000 100°00 


Dr. Rees describes the albuminous matter of 
chyle as possessing a dead-white colour, which 
he attributes to the admixture of a substance 
of a peculiar character, and upon which he 
conceives it probable that the white colour of 
the chyle depends. Will further investigation 
prove this peculiar substance to be derived from 
the chyle granule? or is the chyle granule 
formed of a combination of this substance with 
fatty matter ? 

This peculiar matter, Dr. Rees states, is 
readily obtained by agitating chyle with ether, 
when the mixture speedily separates into three 
distinct strata, the centre stratum being the 
substance in question; a similar matter, he 
observes, may be obtained from saliva by 
treating it in the same way. He found it to 
Teact as follows :— 

“ It was insoluble in alcohol, both hot and 
cold—insoluble in «ther—miscible with water, 


223 


and soluble in liquor potasse. When it had 
been dried on platinum foil, the addition of 
water made it pulpy, and it was found. gtill to 
be miscible with that fluid, from which, how- 
ever, it separated in flakes on the addition of 
diacetate of lead.” 

I have now examined each part of the lym- 
phatic system in detail, and on reviewing it 
as a whole, with the mind fully emancipated 
from the old erroneous views in physiology, 
and with a full conviction of the truth of the 
modern discoveries with respect to imbibition, 
endosmosis, and exosmosis, including venous 
absorption, as established by Magendie, Du- 
trochet, Segalas, Delille, and others, and ad- 
mitted by Miiller, Panizza, Fohmann, Lauth, 
Breschet, and all the modern investigators in 
this interesting and intricate field of inquiry, 
in which I regret not to be able to mention 
the name of one of our own countrymen since 
the time of Cruickshank, Hewson, and Sheldon 
—in bringing, I say, with our present improved 
state of knowledge in physics and physiology, 
the mind to bear upon the subject of the lym- 
phatic system, it appears to me that we are 
justified in materially modifying our opinions, 
both with respect to the functions exercised by 
this system of vessels, as well as with regard to 
its anatomical arrangement, which has been 
made to depend so much upon the precon- 
ceived physiological notions respecting it. Ff 
venture then to suggest that we are going too 
far in attributing to the lymphatic (since the 


‘veins also absorb) the important and universal 


function of interstitial absorption of the old 
material, previous to the deposition of the new, 
in the process of growth and nutrition; that it 
is without sufficient proof that we admit the 
ulcerative process to be carried on solely 
through the agency of the lymphatic system, 
or that the removal of all morbid growths or 
depositions is effected by the one order of ab- 
sorbent vessels unassisted by the other; and 
indeed that there would be nothing repugnant 
to sound reasoning, or at variance with the pre- 
sent improved state of our knowledge, were we 
to confine the functions of the lymphatic system 
more within the bounds ascribed to the lacteat 
vessels during the process of digestion, viz. to 
select and prepare nutritious materials for the 
purpose of sanguification, and to deposit them 
in the already circulating current. 

Descriptive anatomy.—I1 now proceed to 
describe the exact course which the lymphatic 
vessels take in the different parts of the body, 
the position and number of the absorbent 
glands which they traverse, and the precise 
direction, mode of commencement, and termi- 
nation of the two principal trunks, into which. 
they pour their contents. 

This part of our subject, the descriptive 
anatomy, neither requires nor admits of that 
rigid exactness which is absolutely necessary in 
tracing out the ramifications of the blood- 
vessels. In the first place, the surgeon, in the 
performance of his operations and in the treat- 
ment of wounds, scarcely finds it necessary to 
take the lymphatic vessels into consideration. 
To relieve the stricture in strangulated femoral 


224 LYMPHATIC AND LACTEAL SYSTEM: 


hernia, he unsparingly divides the principal 
lymphatics and glands in the inguinal region. 
In the next place these vessels vary so 
much in number, and consequently in position 
in different individuals, while there exist so 
many where their presence is rather 
presumed than demonstrated, that a general 
outline of their course is all that can be re- 
quired or depended upon. In the distribution 
of these vessels two principal objects are spe- 
cially provided for; the conveyance of the 
lymph to its appropriate glands, and after- 
i from them to the two trunks of the sys- 
tem. We, consequently, first notice an evident 
tendency of the vessels from the structures in 
which they take origin towards the glands 
which intervene between them and the trunks 
of the system; secondly, their necessary course 
from these glands to the trunks themselves. 

With this key to the distribution of these 
vessels, I propose to describe, first, the posi- 
tion of the glands, then to treat of the trunks 
of the system; and, lastly, having these two 
fixed points, to trace the vessels throughout their 
course. 

In the lower extremities the conglobate glands 
are chiefly found in the inguinal region, where 
they are divided into a superficial and deeper 
seated cluster; a few small glands are situated 
in the popliteal space surrounding the bloodves- 
sels. We rarely meet with one between the 
popliteal space and the inguinal region, and they 
are only occasionally met with below the knee, 
and then isolated and extremely small. In the 
eppes extremity the large and clustered lym- 
phatic glands are only found in the axillary 
space; a single gland is generally located just 
above the internal condyle of the humerus; 
below this point a distinct gland is rarely met 
with, 

In the cervical region the principal lympha- 
tic glands are situated in two cellular intervals, 
found at the upper part between the omo-hyoid 
and lecenie cloves mamterl muscles, and below 
between the latter muscle and the trapezius. 
The glands in these positions are ranged in a 
line so as to form a sort of chain of glands, 
hence the term glandule concatenate as applied 
to them. 

On the head and face the glands are few, 
small, and isolated. One may be pretty con- 
stantly met with behind the ear over the mas- 
toid process of the temporal bone, another in 
front of the ear in the neighbourhood of the 
parotid gland. One or two will be found 
under the margin of the lower jaw, both in the 
median line and also more laterally situated. 
A small lymphatic gland will usually be distin- 
guished amonst the numerous but small buccal 
and labial glands. 

In the cavity of the cranium no lymphatic 
glands have been discovered, but in the abdo- 
minal and thoracic cavities they are very nume- 
rous. In the abdomen they are chiefly situated 
in the neighbourhood of the larger bloodvessels. 
In the pelvic region they form clusters, or rather 
chains of glands accompanying the external, in- 
ternal, and common iliac vessels, and in the 
lumbar region they are similarly arranged on 


either side of the aorta, as high as the pe Fe 
origin of the superior mesenteric artery. . 

The absorbent glands which intercept 
lacteals in their course towards the receptacu 
chyli are large and numerous; they are s 
ated between the folds of the mesentery, ; 
accompany the trunk and some of the t 


of the superior mesenteric 3 th 
usually semed mesenteric glands. he 
ing lymphatic glands of the abdominal viseer 
though numerous, are smaller and more isolat 
they will generally be found one ee ‘ter 
of the viscera to which they belong, n 
quently between the folds of the peritonet 
Of this description may be considered the 
accompanying the hepatic and splenic vess 
the coronary and gastro-epiploic arteries of th 
stomach, the small glands of the mesocolon ¢ 
epiploon, those associated with the renal ¢ 
spermatic arteries. 7” 
The largest absorbent glands of the thora 
cavity are those which receive the lymphati 
from the lungs; they are situated at the roo 
of the lungs, pretty closely attached to | 
bronchi; they are generally of a dark cok 
and are called bronchial glands. Those 
ciated with the lymphatic vessels of the he: 
are few and small ; two or three may general 
be noticed of the size of millet-seeds on 
aorta and pulmonary artery, where these vs 
are invested by the pericardium. In the post 
rior mediastinum close to the thoracie duc 
three or four large lymphatic glands are usu: 
met with, as well as several smaller ones in 
intercostal spaces, not far from the thor 
duct. In the anterior mediastinum also son 
small glands may be observed imbedded — 
loose cellular tissue in the neighbourhood — 
the internal mammary vessels. Occasioua 
a small gland may be seen on the convex su 
face of the diaphragm. a 
In the substance or parenchyma of the 
ferent organs no lymphatic glands have b 
detected. They have never been seen in 
brain, spinal marrow, in the lungs, liver, splee 
kidney, or testicles, in nerve, muscle, or bom 
Having given this general outline of 
position of the lymphatic glands, I shall no 
proceed to describe the trunks of the system. 
The thoracic duct, (fig. 53,) or pri 
trunk of the lymphatic system, generally e 
mences on the body of the second lu: 
vertebra pretty exactly in the median li 
concealed behind the root of the right em 
gent artery, bounded on the right by ther 
crus of the diaphragm, and to the left by 
aorta, to which it is connected by cellular t 
It may be said to be formed by the union 
the lymphatics of the lower extremities w 
the trunks of the lacteals proceeding from 
intestines. At the conflux of the p inci; 
vessels from these three sources,—and here 
be more than one from each,—a dilatation 
sometimes found, which has been called th 
receptaculum chyli. From the body of the se= 
cond lumbar vertebra the thoracic duct ascen 
into the thorax between the aorta and ve 
azygos. In the thorax it is situated behi 
the right pleural fold of the posterior medias: 


7 


: 


LYMPIIATIC AND LACTEAL SYSTEM. 


The thoracic duct and right lymphatic trunk. 
After Mascagni. 
a, Thoracic duct. 1 
b, The right lymphatic trunk. ’ 4 
e, The trunk of the cervical lymphatics entering 
separately the internal jugular vein. 
8, Subclavian vein. 
9, Internal jugular vein. 
_ #, Vena azygos. 
tinum, having the aorta to its left, the vena 
_ azygos to its right, and the esophagus in front. 
In this position it ascends as high as the fourth 
_ or third dorsal vertebra, at which level, con- 
_ tinuing its course upwards, it turns from right 
_ to left, passing behind the descending portion 
_ of the arch of the aorta, above which it ap- 
_ pears a little external to the root of the left 
subclavian artery, from whence continuing to 
ascend it passes between the latter and the 
left common carotid artery, lying on the 
longus colli muscle; it now mounts into the 
tvical region in front of the vertebral artery 
and vein to the level of the seventh cervical 
_ vertebra, opposite to which it begins to form a 
curve, first Aetads and outwards, then down- 
s and inwards, striding over the subclavian 
artery to reach the angle of union between 
_ the subclavian and internal jugular veins, at 
‘which point it empties itself into the venous 
‘system either by one or more branches. 
__ The thoracic duct is not uniform in diameter 
throughout its course ; besides the occasional 
dilatation at its commencement, it generally 
presents another on the fourth dorsal vertebra 
just below its passage behind the descending 
thoracic aorta. Its narrowest part usually cor- 
responds to the sixth or seventh dorsal vertebra. 
The duct is frequently tortuous and rarely 
Single throughout. It often splits into two or 
more branches, which after a longer or shorter 
course reunite; this division and reunion may 
be two or three times repeated, and it may ul- 
timately terminate by two or three branches 
Instead of one. 
VOL. 111. 


we 


225 

The principal irregularities in the arrange- 
ment of the thoracic duct, which have been 
recorded by anatomists, are—a doublé@ duct, 
one terminating in the left, the other in the right 
side of the neck ; a bifurcation of the duct at 
a higher or lower level, one branch terminating 
in the angle of union of the subclavian and 
internal jugular veins of the left side, the other 
emptying itself either into the corresponding 
point on the right side or joining the right 
lymphatic trunk, close to its termination; a 
single trunk terminating altogether on the right 
side of the conflux of the internal jugular and 
subclavian veins, in which case a short lym- 
phatic trunk is found on the left side similar 
to that which usually exists on the right, con- 
stituting a partial lateral inversion or trans- 
position confined to the trunks of the lymphatic 
system. 

Besides the lymphatics of the lower extre- 
mities and the lacteals, the thoracic duct re- 
ceives directly or indirectly the lymphatics of 
the remaining abdominal viscera (except a few 
from the right lobe of the liver), those from the 
exterior and interior of the lower half of the 
trunk ; also the lymphatics of the left upper 
extremity, and left side of the head and neck, 
those from the left lung, the left side of the 
heart, and from the exterior and interior of the 
left upper half of the body. 

The right lymphatic trunk nearly equals the 
thoracic duct in diameter; it is, however, not 
more than half an inch in length. Its situation 
is in the neck at the level of the lower edge of 
the seventh cervical vertebra, where it will be 
found lying upon of the subclavian vessels close 
to the inner edge of the scalenus anticus muscle, 
and opposite to the union of the subclavian and 
internal jugular veins, at which point it termi- 
nates in the venous system. 

The right lymphatic trunk receives the lym- 
phatics of the right upper extremity and of the 
right side of the head and neck, those from the 
right lung and right side of the heart, some few 
from the right lobe of the liver, and from the 
exterior and interior of the right upper half of 
the body. 

Some of the principal branches which ordi- 
narily empty themselves into the right lym- 
phatic trunk occasionally terminate separately 
in the internal jugular or subclavian veins close 
to their junction. When these vessels all enter 
the veins separately, then the right lymphatic 
trunk is said to be deficient. 

Having described the position of the trunks 
of the lymphatic system as well as the situa- 
tions of the conglobate glands in the various 
parts of the body, I now proceed to trace the 
vessels themselves. 

I shall commence with the description of the 
yop of the lower extremities, as being 
the most remote from the trunks of the system. 
They are divided, as in all other parts of the 
body, into a superficial and deep-seated set, 
which latter accompany the principal bloodves- 
sels. They are associated successively with the 
digital arteries, the internal, external plantar, 
and dorsal arteries of the foot ; in the leg with 
the anterior, posterior tibial, and fibular vessels, 
q 


Fig, 54. 


Superficial lymphatics of the lower extremity. 
( After Mascagni. ) 
a, Saphena major vein. 
6, Inguinal glands. 
e, Commencing branches. z 
d, e, f, g, The continuations of the vessels simi- 
larly marked in the former wood-cut. 


At least two lymphatics, which are united 
frequently by short branches crossing from one 
to the other, accompany each of these arteries, 
and all are ultimately conducted by the blood- 
vessels to the popliteal glands, in which they 
terminate. The vasa efferentia of these glands, 
from two to six in number, entwine around the 


LYMPHATIC AND LACTEAL SYSTEM. 


liteal and femoral vessels, having uent 
Camuinoncassiea with each other by = OSS 
branches, until they reach the inguinal region 
where they terminate for the pee in 
deep-seated cluster of se yey glands; one 
more, however, may reach the superficial glam 
or even those accompanying the e t 
artery above Poupart’s ligament. The 
seated lymphatics in their course are joined 
branches which have accompanied the prine 
ramifications of the bloodvessels; they also 
various points form communications with | 
superficial lymphatic vessels. ~ 
e superficial lymphatics of the lower extt 
mities may be divided into two Pe ) 
sisting of numerous vessels which fo! more ¢ 
less the course of the saphena major vein al 
terminate in the inguinal glands; the other cot 
posed of but few vessels, which, accompany 
the saphena minor vein, join the popliteal g! 
The latter take origin from the dorsal surfa 
of the little toe and from the outer edge of @ 
dorsum and sole of the foot ; they proceed wil 
the branches of the saphena minor vein in 
direction of the xine malleolus, from then 
to the outer edge of the tendo Achillis, whi 
they glide with the vein under the fascia of t 
leg to reach the centre of the gastrocnem 
muscle, between the heads of which they ¢ 
to join the popliteal glands. The super 
lymphatics which accompany the saphena 
jor vein commence on the dorsal su of | 
toes, where they communicate with the di 
lymphatics. On the dorsum .of the foot th 
ascend in from three to six branches; the mo 
internal mount over the internal malleolus w 
the branches of the saphena major vein to tl 
inside of the knee; the most external pass ov 
the external malleolus and outer side of the le 
at a higher or lower level however, they a 
directed inwards and pass over the spine 
inner surface of the tibia to join the former, 
the inner side of the knee; those from | 
centre part of the dorsum of the foot ascend” 
front of the tibia ; these also soon tend in 
to be associated with the rest. 

Another set take origin from the sole of ¢ 
foot and proceed upwards on the back of © 
leg superficial to the fascia, having commu 
cated freely with the lymphatics accompany 
the saphena minor vein. These also soc 
later turn inwards to gain the inside of 
knee. From these sources some twelve or 
teen branches may be enumerated, which 
tinue to ascend on the inside of the thigh 
the saphena major vein. Some few pass un 
the fascia lata to join the deep-seated vess 
From the back of the leg and thigh they rece 
an accession to their numbers of several vesst 
the mest of these reach them from the insic 
some few from the outside of the limb. 4 
ultimately terminate in the superficial clus 
of glands in the groin. Some few, howeve 
may dip down to join the deep-seated glar 
and to unite with the deep-seated lymphatic 
One may occasionally be seen to pass the } 
guinal te to reach those accompanying 
external iliac artery. " 

The inguinal glands also receive the supe 


: | 
= 


cS 


LYMPHATIC AND LACTEAL SYSTEM. 


q 
“ y Superficial lymphatics of the lower extremity. 
a bie (After Mascagni.) ~ 
5 ¢, ¢, Commencing branches. 
___d, Lymphatic vessels passing from the outer to 


e posterior part of the leg to gain its inner surface. 


z 
4 
5 e, Vessels passing from the outer to the posterior 


‘part of the thigh to gain its inner surface. 
| Ff, Vessels passing from the outer to the anterior 
“part of the leg to gain its inner surface. 
g» Vessels passing from the outer to the anterior 
part of the thigh to gain its inner surface. 


ficial lymphatics from the genitals, from the 
lower half of the anterior and posterior part of 
the trunk, from the perineal and gluteal re- 
gions. The lymphatics of the scrotum collect 


_ Into one or two branches, which take their 
_ course with the superficial pudic veins to reach 


the glands in the groin. Those of the penis 
commencing on the glans and prepuce pro- 
ceed generally in three principal branches on 
the body of the organ, two of which are si- 
tuated laterally, and the third on the centre of 
its dorsal surface. These three vessels not un- 
frequently unite near the root of the penis 


_ into one vessel, which immediately divides 


right and left into branches, which also accom- 


227 


pany the superficial pudic veins to the inguinal 
glands. In the direction of the superficial 
epigastric and circumflexa ilii vejhs there are 
several lymphatics derived from the anterior 
and lateral parts of the abdomen, which empty 
themselves in the inguinal glands. The super- 
ficial lymphatics from the perineal and gluteal 
regions, some from the loins and posterior and 
upper part of the thigh, stream round the 
outer part of the limb in the neighbourhood of 
the trochanter major to terminate in the same 
glands. 

The vasa efferentia of the inguinal glands, 
three or four in number, are much larger thar 
the vasa inferentia; they receive the contents of 
all the lymphatics hitherto described, and pass 
under Poupart’s ligament with the femoral ar- 
tery and vein to become the vasa inferentia of 
the glands associated with the external iliac 
artery. From the anterior and lateral muscular 
paries of the abdomen, the lymphatics accom- 
pany the epigastric and circumflexa ilii arteries, 
and terminate in the external iliac glands. 
The external iliac glands are also joined by the 
vasa efferentia from the glands accompanying 
the internal iliac artery. These latter receive 
the lymphatics, associated with the gluteal, 
ischiatic, and obturatrix arteries, which enter 
the pelvis by the same openings as the arteries 
which they accompany. The lymphatics from 
the prostate gland and vesicule seminales, from” 
the bladder and rectum, from the vagina and 
uterus, those accompanying the internal pudie 
vessels derived from the interior of the penis 
and clitoris, and those from the walls of 
the pelvis, all terminate in the internal iliac 
glands. 

The glands accompanying the common iliac 
artery, on the one hand, receive their efferent 
vessels from the internal and external iliac 
glands, and on the other give their efferent 
vessels to those, associated with the aorta, which 
constitute the lumbar glands. 

The lymphatics of the testicle, of the kid- 
neys, and renal capsules, those accompanying 
the lumbar arteries, the lymphatics of the 
rectum, sigmoid flexure and descending por- 
tion of the colon, all terminate in the lumbar 
glands. Those from the testicle are derived 
from the interior as well as from the surface of 
the organ; they take their course upwards 
with the spermatic arteries and veins in several 
branches, to reach the renal and lumbar glands. 

The lymphatics of the kidneys emerge from 
its substance at the fissure of the organ, having 
taken their course with its bloodvessels, where 
they are joined by the superficial vessels; they 
pass through the small renal glands, and ulti- 
mately reach the Jumbar glands. 

The lymphatics of the renal capsules unite 
chiefly with those of the kidneys, but also on 
the left side with those of the spleen, and on 
the right with those of the liver. They are at 
length conducted to the lumbar glands. The 
lymphatics accompanying the lumbar arteries 
receive their branches from the structures sup- 
plied by those arteries, and empty themselves 
into the lumbar glands. The lymphatics from 
the descending colon, from its sigmoid flexure, 

Q 2 


228 LYMPHATIC AND 


and from the rectum, take somewhat the 
course of the inferior mesenteric artery and its 
branches; they pass through their appropriate 
glands, and are ultimately received by the 
lumbar glands. 

The vasa efferentia of the lumbar glands 
cannot be said to receive the contents of all the 
vessels and glands hitherto described; they, 
in fact, empty themselves into the principal 
lymphatics by whose union the thoracic duct 
is formed, or into the duct itself soon after its 
formation. The principal lymphatics above 
alluded to may be traced more or less dis- 
tinctly from Poupart’s ligament to the second 
lumbar vertebra, where they usually unite to 
form the thoracic duct, the vessels of opposite 
sides communicating freely with each other. 

Their position and arrangement will be well 
understood by the accompanying wood-cut. 


Fig. 56. 


ere 


Ne 


nny 
er 


In the dissection from which this wood-cut was 
taken, the injection did not pass freely into the 
glands, from which circumstance the vessels are 
more distinctly seen, as it permitted the glands 
which partly concealed them to be removed with- 
out causing extravasation. These vessels, after 
taking somewhat the course of the external, in- 
ternal, and common iliac arteries, may be seen 
to ascend pretty close to the inner edges of the 


LACTEAL SYSTEM. 


muscles, to communicate freely by cross 
ranches, and opposite to about the third 
lumbar vertebra to pass inwards, on the right 
side behind the cava, on the left behind the aorta. 
to unite into one vessel on the body of the = 
cond lumbar vertebra, behind the root of the 
right renal artery, and thus to form the com- 
mencement of the thoracic duct. Inthe su je t 
from which the drawing was taken the branches 
did not unite in the abdominal cavity. Ts 
nearly equal-sized vessels ascended into 

thorax, which, however, soon coalesced. 
union generally takes place opposite the ab 
dilatation malle No. 41, ant eiadl would | 
termed the receptaculum chyli, although th 
lacteals generally enter above this point. 
The lacteals, properly so called, take origi 
from the small intestines. During the proce 
of digestion they contain a white fluid, 
chyle, but at other times their contents are 
colourless like those of the rest of the lympha- 


incipal * 
ening So preeee ee 
into which the vasa efferentia 
glands of these regions empty the 
and the convergence and 
bese: the bodys duct is 
‘ormed on the 
Shewing 


. 


Fig. 56. Shewing the 


. 


of the second lum 
vertebra. ing also in this insta 
owing ae 


: g ; 
double ; Factbes i tact py 4 


a, The body of the second 
vertebra. 

b, The right crus of the diaphrag 

ec, The left crus of the diaphragm. — 

d, The abdominal aorta displaced. — 

e, The diaphragm. 

J, Psoas muscle. 

1, Vasa efferentia of the 

glands. 

2, Their vasa efferentia. 

3, The rincipal branches cia 
with the internal inguinal glands 

4, Those accompanying the extert 
and common iliac glands. 

5, Those accompanying the 

lands. 
6, The convergence of the 


opposite sides, 
10, The trunks from the 1 


* 


7 and 
right sides, which in this instat 
did not unite (as is usually © 
case) to form the thoracic 
but passed separately into t 
vity of the thorax. 

8, Transverse communications - 
tween the vessels of opposite sid 

9, A communication between — 
transverse branches in the 
direction. 

11, The receptaculum chyli, in 
instance remarkably abrupt, ~ 
of a globular form, 


tic system; they are joined by the lymphat 
of the caput coli, the ascending and transver 
colon; they also communicate with the lym: 
phatics of the liver, spleen, pancreas, ane 
stumach. The more modern opinion is, thi 
the lacteals commence from the villi and fre 
the spaces between the villi in the small inte 
tines, not by open mouths, but by a delicate net- 
work of vessels, through the coats of whi 


LYMPHATIC AND 


_ the chyle is supposed to enter by imbibition. 


This incipient net-work of lacteals terminates at 
the roots of the villiin branches, which perforate 
the muscular coats of the intestines, the trunks 
of which may be easily distinguished under 
the serous coat, taking a transverse course to 
gain the cellular interval between the layers of 
the mesentery. These are what may be termed 
the deep-seated lymphatics of the intestines 
which alone contain the chyle, but there are 
superficial lymphatics belonging to the intes- 
tines situated immediately under the peritoneal 
coat, which take a longitudinal course and 
join the deep-seated vessels. From the intes- 
tine the principal branches pass in nearly 
straight lines between the layers of the mesen- 


_tery, where they traverse the mesenteric glands 


to accumulate from every portion of the small 
intestine around the trunk of the superior 
mesenteric artery. The lymphatics from the 
cecum, the ascending and transverse colon, 
which have passed through their appropriate 
glands and have accompanied more or less the 
ilio-colic and colic arteries between the layers 
of the meso-colon, now join the lacteal vessels. 
The vasa efferentia from the mesenteric glands 
form two or more trunks, which, conducted 
by the root of the superior mesenteric artery, 
reach the thoracic duct, into which they empty 
their contents just above its commencement. 
The lymphatics of the stomach chiefly 
accompany the bloodvessels. ‘Those associated 
with the vasa brevia and with the left gastro- 
epiploic vessels, having passed through their 
glands unite with the lymphatics from the 
spleen. Those accompanying the right gastro- 
epiploic vessels having traversed their glands 


communicate behind the pyloric extremity of 


SEieeel 


the stomach and at the commencement of the 
duodenum, with the lacteals, and with the 
lymphatics from the liver. At the upper cur- 


vature of the stomach, the lymphatics take their 


course from the cardiac to the pyloric orifice 


accompanying the branches of the coronaria 


yentriculi arteries, they pass through the glands 


there situated, and join the lymphatics descend- 
ing from the liver in the capsule of Glisson. 


The lymphatics of the pancreas near the 


head of the organ communicate with the lacteal 


vessels from the duodenum; the rest empty 
themselves into the lymphatics coming from 
the spleen. 
_ Atthe hilum of the spleen the deep-seated 
lymphatics which have accompanied the blood- 
vessels in the substance of the organ are joined 
by the superficial vessels. The principal 
branches having in their course received lym- 
citi from the stomach and pancreas, and 
aving traversed the splenic glands, accompany 
the trunks of the splenic artery and vein, and 
unite with the lymphatics of the liver in their 
course to the thoracic duct. 

The deep-seated lymphatics of the liver 
accompany the ramifications of the portal 
vessels throughout the substance of the organ ; 
they emerge with the hepatic ducts at the 


_ transverse fissure of the liver, where they are 
_ joined by the lymphatics of the gall-bladder 


and by the superficial lymphatics from the 


LACTEAL SYSTEM. 229 


under surface of the liver. They pass through 
the glands situated in the capsuleyof Glisson, 
receive free communications front the splenic 
and gastric lymphatics, and ultimately termi- 
nate in the thoracic duct either separately or 
in conjunction with the lacteal trunks. 

The superficial lymphatics of the upper 
surface of the liver form three or four fasciculi, 
which enter the thorax without joining the 
trunks of the deep-seated vessels. One set 
streams from the upper surface of the right, 
another from that of the left lobe to gain the 
suspensory ligament of the liver, between the 
folds of which the larger branches, six or eight 
in number, pass upwards and enter the thorax 
between the attachment of the diaphragm and 
the ensiform cartilage to gain the anterior 
mediastinum, where they join the large lym- 
phatic vessels accompanying the arterize mam- 
marie interne. From the right and left lobes 
in the neighbourhood of the lateral ligaments, 
and chiefly, though not entirely, from the 
upper surface of the organ, two other streams 
of superficial lymphatics tend towards the 
lateral ligaments, between the layers of which 
the principal branches pass. They perforate 
the diaphragm to gain its upper surface, some 
of them passing backwards to reach the thoracic 
duct in the posterior mediastinum, while others 
form a large vessel which creeps upon the 
thoracic surface of the’ diaphragm under the 
pleura and near the margin of the ribs, to gain 
the anterior mediastinum, where on each side 
it unites and terminates with those vessels 
which have arrived at the same point from 
between the folds of the suspensory ligament. 
The lymphatics of the left lateral ligament 
often, however, pass downwards to the abdo- 
minal cavity, joining the lymphatics of the 
under surface of the liver or of the cardiac 
extremity of the stomach. 

The thoracic duct receives but four branches 
during its passage through the thorax; the 
lymphatics of the lungs and of the heart, as well 
as the large branches accompanying the mamma- 
riz interne vessels, make their exit from the 
thoracic cavity, to empty themselves into the 
two lymphatic trunks in the cervical region. The 
intercostal lymphatics accompanying the inter- 
costal bloodvessels, traverse the little glands si- 
tuated near the necks of the ribs, take their 
course to and enter the larger glands in the pos- 
terior mediastinum. These same glands also 
receive the cesophageal lymphatics, and even 
some communications from the bronchial 
glands ; their vasa efferentia, four or five in 
number, enter the thoracic duct at different 
levels. 

The large lymphatics accompanying the mam- 
marie interne arteries collect their branches 
from various sources; those from the liver have 
been already noticed ; some pass through the in- 
tercostal spaces close to the edges of the ster- 
num: some have accompanied the intercostal 
branches of the mammariz interne vessels; 
others are received from the thymus gland and 
pericardium and pleura. The greater part of 
these vessels pass through the little glands si- 
tuated in the anterior mediastinum before they 


230 


are received into the principal branches. These 
latter pass upwards in front of the transverse 
vein, to empty themselves on the left side into 
the termination of the thoracic duct; on the 
right, into the right lymphatic trunk, or they 
join the large veins separately, close to the en- 
trance of the two trunks of the system. 

The lymphatics of the lungs are of large 
size, and are divided, as in other parts of 
the body, into a superficial and deep-seated 
set. The latter accompany the ramifications 
of the bloodvessels and air-tubes throughout 
the texture of the organ, and communicate at 
various points with the superficial vessels. The 
principal branches escape from the lung at its 
root, where they are joined by the superficial 
vessels, and pass with them through the large 
bronchial glands. The superficial lymphatics 
of the lung are larger than those of any other 
viscus; they are situated in the interlobular 
fissures immediately under the pleura, and are 
injected with greater facility than the lymphatics 
of other parts of the body; their principal 
branches pass from the surface of the lung 
towards the inner edge and root of the organ, 
where they unite with the deep-seated ves- 
sels, and pass with them through the bron- 
chial glands. The vasa efferentia of these 
glands having communicated with the glands 
in the posterior mediastinum pass upwards on 
the trachea, where they meet with other glands 
with which they interchange branches; having 
entered the cervical region with the trachea, 
they unite freely with other lymphatics, espe- 
cially with those of the thyroid gland, and 
ultimately terminate, on the left side, in the 
thoracic duct; on the right, in the right lym- 
phatic trunk, or separately in the large veins. 

The lymphatics of the heart are neither large 
nor numerous; they proceed both from the sub- 
stance and from the surface of the organ ac- 
companying the principal bloodvessels; their 
appropriate glands are chiefly situated on the 
ascending thoracic aorta and trunk of the pul- 
monary artery; where these vessels are covered 
by the pericardium, they ascend in front of the 
arch of the aorta, pass between the sternum 
and transverse veins, communicate freely with 
the large vessels of the anterior mediastinum, 
and terminate with them on either side in the 
trunks of the system, the greater number, 
however, passing on the left sides to the tho- 
racic duct. 

The deep-seated lymphatics of the upper ex- 
tremity successively accompany the digital arte- 
ries, the superficial and deep palmar arches, 
the radial, ulnar, and interosseous arteries. At 
least two lymphatic vessels accompany each ar- 
tery; they communicate by short transverse 
branches with each other, and also at different 
sara with the superficial lymphatics. At the 

nd of the elbows they unite into three or four 
vessels which pass up the arm with the bra- 
chial artery to gain the axillary glands, into 
which they empty themselves. The small 
glands which not unfrequently may be found 
accompanying the brachial artery, and even, 
but more rarely, the ulnar or radial vessels do 
not generally intercept the deep lymphatic 


LYMPHATIC AND LACTEAL SYSTEM. 


Fig. 57. 


Superficial lymphatics of the 
( After Mascagni. 
a, a, Commencing lymphatic vessels ascend 
in the forearm with branches of the median vi 
b, c, d, The continuations of the vessels simi 
marked in the former woodcut. 
e, A vessel passing from the posterior to the ai 
terior surface of the arm over its outer edge. 
Ff, Branches of the basilic vein. 7 
» Cephalic vein. 
z Axillary glands. 
i, Two small glands situated above the int 
condyle. 


vessels, but the latter rather receive the eff 
vessels from these glands, they having collectet 
their afferent vessels from the surrounding tex- 
tures. 


LYMPHATIC AND LACTEAL SYSTEM. 
Fig. 58. 


Super ficial lymphatics of the upper extremity. 
( After Secs. 

a,a, Commencing lymphatic vessels which ac- 
company the branches of the cephalic and basilic 
veins. 

b, Lymphatic vessels passing from the posterior 


_ to the anterior surface of the forearm over its inner 


edge, with branches of the basilic vein. 

d, Lymphatic vessels passing from the posterior 
to the anterior surface of the forearm over its outer 
edge, with branches of the cephalic vein. 

c, Lymphatic vessels passing from the posterior 
to the anterior surface of the arm over its inner 
edge. 


The superficial lymphatics of the upper ex- 
tremity in their passage to the axillary glands 
follow more or less the course of the subcuta- 
neous veins. Those which accompany the ce- 
phalic and basilic veins commence on the 
dorsal surface of the fingers, where they com- 


-Municate with the digital lymphatics; from 


thence they proceed over the metacarpus to the 


_ posterior surface of the forearm, tending with their 
accompanying veins towards its ulnar and ra- 


231 


dial edges, over which, sooner or later, they 
pew to gain the anterior surface, and at the 

end of the elbow they have all collected in 
the neighbourhood of the internal condyle. 
The lymphatics accompanying _ median 
vein take origin from the palmar/Surface of 
the fingers, where they communicate with the 
digital lymphatics ; they take their course up- 
wards first on the palm of the hand, then on 
the anterior surface of the forearm, and at the 
bend of the elbow join those already traced to 
the same point. The great majority of these 
vessels now continue their course upwards 
over the internal condyle to the inner side of 
the arm, some of them traversing the little - 
gland or glands situated just above the internal 
condyle; from thence they take the nearest 
route to gain the axillary glands, of which they . 
form the principal vasa inferentia. Some three 
or four of the lymphatics, which in the forearm 
were associated with the branches of the ce- 
phalic vein as far as the bend of the elbow, 
separate themselves from the rest, and ascend 
with this accompanying vein on the outer side 
of the biceps, and in the interval between the 
deltoid and pectoralis major muscles, where 
they meet with a gland which they traverse and 
ultimately pass with the vein over the pectoralis 
minor muscle to gain the deep-seated lympha- 
tics accompanying the axillary artery. 

The axillary glands collect their vasa infe- 
rentia also from the upper half of the anterior, 
posterior, and lateral surfaces of the trunk. 
From the anterior surface those on the ab- 
domen above the umbilicus ascend; those on 
the upper part of the chest, joined by some 
from the cervical region, descend; those on a 
level with the axilla from the pectoral muscles 
and the glands of the breast take a transverse 
direction—all in short converging towards the 
axilla, where the glands in which they termi- 
nate are situated. From the posterior surface 
of the trunk in a similar way they concentrate 
from the lumbar, cervical, and dorsal regions 
to pass over the posterior border of the axilla 
to reach the same glands. 

The vasa efferentia of the axillary glands, 
four or five only in number, but of large size, 
receive the lymph conveyed to these glands 
from the various sources just described; they 
pass associated with the axillary vessels under 
the subclavius muscle, unite into one or two 
branches, which usually pass over the subcla- 
vian vein, to,terminate either separately in 
this vein, close to its union with the internal 
jugular, or else join the lymphatic trunks. 

The lymphatics of the head and face may be 
divided as in other parts of the body into the 
superficial and the deep-seated. They all have 
to pass through the glands situated in the cer- 
vical region. The superficial accompany prin- 
cipally the veins of the head and face. Those 
from the head form two groups: one anterior 
associated with the temporal veins, descends 
in front of the ear, joins the small glands 
situated at the root of the zygoma, and in 
the substance of the parotid gland; it passes 
with the temporal vein through that gland 
and below the angle of the jaw continues to 


232 


follow the course of the vein over the digastric 
and stylo-hyoid muscles, where it meets 
with lymphatic glands which it enters; the 
posterior group aecompanies the occipital and 
ee auricular veins, traverses the glands 

hind the mastoid process, and afterwards 
those situated at the back and me part of 
the neck. The facial lymphatics, like the facial 
veins, receive branches from the forehead and 
a pass from the inner canthus of the eye 
along the side of the nose and over the bucci- 
nator muscle, where they meet with one or two 
small glands ; they then gain the anterior edge 
of the masseter, from whence they pass be- 
low the margin of the jaw, to traverse the 
glands there situated. ‘These three groups of 
vessels communicate freely with each other 
in the cervical glands, and are joined by some 
of the deep-seated lymphatics. These latter 
may be divided into those of the cranium 
and those of the face; the former as well as 
the lymphatics of the interior of the orbit are 
not sufficiently known to admit of our stating 
the exact course which they take. Fohmann 
and Mascagni both conceive that they have 
discovered the lymphatics of the brain and its 
membranes and have had them delineated in 
their published plates; but they differ so ma- 
terially from each other, and their descriptions 
are so far from satisfactory that we must be 
content to say that we are ignorant not only of 
the course they take but even of their existence. 
Fohmann represents them to be very large and 
numerous, situated principally between the 
arachnoid membrane and pia mater, while 
Mascagni figures them on the pia mater as 
exceedingly small and as accompanying some 
of the veins; others are also depicted as asso- 
ciated with the meningeal vessels ; the trunks 
of these vessels are supposed to descend with 
the carotid, vertebral, and meningeal arteries 
and with the internal jugular veins; while 
Fohmann throws out a hint that they may ter- 
minate in the venous system within the cra- 
nium. 

The deep-seated lymphatics of the face are 
associated with the bloodvessels; those accom- 
panying the internal maxillary arteries enter 
the gland or glands in the substance of the pa- 
rotid, and join the temporal lymphatics. The 
rest accompanying their bloodvessels reach the 
upper cervical glands, and communicate freely 
with the superficial lymphatics already traced 
to the same glands ; the further progress of the 
lymphatics in the neck is regulated by the 
position of the glands, which it will be re- 
membered form two groups, one situated be- 
tween the stetto-siesbsld muscle and the 
trachea, and associated more with the internal 
jugular vein, the other located in the cellular 
interval between the sterno-mastoid and tra- 
pezius muscles in the neighbourhood of the 
external jugular. The former receives the lym- 
phatics from the tongue, pharynx, and larynx, 
and lower down from the thyroid gland, 
trachea, and esophagus; while the latter col- 
lects them from the muscles of the posterior 
recion of the neck and of the shoulder. The 
afferent and efferent vessels of these two 


ABNORMAL ANATOMY OF THE LYMPHATIC SYSTEM. 


series of glands have uent communica- 
tions with each other. At the root of the neck 
they unite freely with the lymphatics emerging 
from the chest and with those of the uppel 
extremities, until ultimately one large ve ol is 
formed on either side, which receives the con- 
tents of the whole, and which terminates eit 
by opening separately into the internal ju sul 
vein close to the entrance of the lymphat 
trunk, or into that trunk itself. @ 
(S. Lane.) 


LYMPHATIC SYSTEM, ABNO 
ANATOMY.—The congenital variations fro 
the normal distribution of the lymphatic syste 
which have naturally most attracted attentio 
are those of the thoracic duct, or of the rig 
lymphatic trunk; the remainder of the sj 
lying too minute for general investigation, am 
the mode of its examination being within | 
“a of only a few. a 

he thoracic duct frequently varies as to t 
precise point at which it opens into the venou 
system, sometimes opening into the subclayia 
vein, at others into the jugular. A ve 
striking departure of it from its usual arrange 
ment is when it is found opening into the veil 
on the right side, just as it ordinarily does | 
the left. I saw an instance of this duril 
the winter of 1834, in the body of a child di 
sected by Mr. Skey. The duct folle it 
usual course as high as the fifth dorsal vertebr 
it then inclined to the right side, and opene 
into the angle between the right jugular an 
subclavian veins. It was remarkable that— 
this subject the right subclavian artery w; 
abnormal in its mode of origin; it arose fro 
the extreme left portion of the arch of the aort 
and passed to its destination behind the e 
and cesophagus. A similar transposition of th 
thoracic duct occurs in cases of general t 
position of the viscera. 

The thoracic ducts have been found somi 
times both terminating on the same side, som 
times on opposite sides. It has also be 
found dividing into two large trunks which pas 
upwards parallel to each other for a conside 
able distance, and then unite again. Variet 
have been observed as regards its mode 
opening into the jugular and subclavian vei 
Instead of terminating as a single trunk, it! 
been found to subdivide into two or thn 
branches, which open separately into the su 
clavian or jugular veins. At its termina 
the duct experiences generally some degree 
dilatation—in some instances I have seen’ 
so considerable as to have the ap nee of: 
aneurismal enlargement. The duct has f 
wise been found to empty itself into the vel 
azygos. In the pig, according to Panizza, 
communication between the duct and this ¥ 
is constant and normal. = 

The varieties in the course and distribution 
of the lymphatic vessels and in the number 
and position of the glands are doubtless as 
numerous as those of the veins. y! 

The diseased states of this system may bi 
examined, first, as regards the lymphatic and 
lacteal vessels ; secondly, with reference to the 


a 


ABNORMAL ANATOMY OF THE LYMPHATIC SYSTEM. 


absorbent glands; and, thirdly, with respect to 
the nature of the contents of the system. 
Inflammation of the absorbent vessels has 
long been known to practical men. A number of 
red lines appearing through the skin, and giving 
to the touch the sensation of round and hard 
cords immediately underneath the skin, taking 


_ the direction and occupying the position of the 


superficial lymphatics, are seen to proceed from 
some point of irritation, as a poisoned wound 
or a syphilitic sore, towards the nearest set of 
absorbent glands. There are much tenderness 
and pain on the least pressure in the whole 
course of these lines, and the glands to which 
they go are more or less swollen, and the skin 
over them is of a reddish colour. These lines 
correspond to the inflamed absorbents, which, 
at first isolated, soon excite inflammation in 
the surrounding cellular tissue, and the hard 
cords above described are lost in the thickened 
and infiltrated subcutaneous tissue. When an 
Incision is made into such an inflamed surface, 
the lymphatics, according to Gendrin, are seen 
upon the margins of the incision as red fibres, 
having the irregular, knotted appearance which 
those vessels exhibit when injected with mer- 
cury and converging towards the inflamed 
tissue of a gland. 

It may be fairly presumed that the anatomi- 
cal characters of these vessels in a state of 
inflammation are the same as those of the 
inflamed thoracic duct, examples of which 
have occurred to Gendrin and Andral. The 
vessels of its coats (vasa vasorum_) are much 
injected, and the coats themselves thickened 
and rendered friable—the inner coat red, soft, 
and swollen—sometimes with lymph poured 
Out upon it, which tends to obstruct and 
obliterate the canal, giving rise to dilatation 
below the obstructed point, or with pus effused, 
which also occasions the vessels to be dilated. 
Sir A. Cooper found adhesion and ulceration 
of the valves of the thoracic duct in a body in 
which he could not succeed in injecting that 
vessel. 

In the body of a phthisical patient Andral 
found the lacteal vessels on the surface of the 
intestine, corresponding to the situation of an 
ulceration of the mucous membrane, remark- 
ably white and hard, and so dilated at intervals 
as to resemble a string of rounded nodules. 
On examination these nodules were found to 
be caused by thickening of the coats of the 
lacteal vessels. 

Irregular dilatations or varicosities of the 
absorbent vessels, but especially of the thoracic 
duct, have been very frequently observed. 
These most frequently arise from some pres- 
sure impeding the circulation of the fluid in 
them, as a tumour or aneurism pressing on 
the thoracic duct in some part of its course. 
Mr. Cruikshank delineates a thoracic duct, 
remarkable for its great size. It was found in 
a man 40 years of age, but the cause of the 
dilatation was not apparent, as no obstruction 
existed either at the entrance of the vessel into 
the veins or in any part of its course. The 
great trunks of the absorbents accompanying 
the large arteries in the extremities were en- 


233 


4 ’ 
larged also, but the cutaneous absorbents were 
of their usual size. The case referred to by 
Dr. Baillie, in which the duct is said to be as 
large as the vena azygos, is probably the same. 

The morbid changes of the absorbgnt glands 
are much more familiar to us than those of the 
lymphatics themselves, as being more appreci- 
able if not of more frequent occurrence. In- 
flammatory states of these bodies are very often 
met with, either in conjunction with inflamed 
lymphatic vessels or alone. In inflammation 
the absorbent glands become enlarged, very 
vascular, and painful to the touch, and the 
surrounding cellular tissue participates in the 
inflammation, so that if several glands be 
inflamed a tumour of some size and hardness 
will be formed. The tissue of the absorbent 
glands themselves is not prone to run into sup- 
puration, but pus will often speedily form in 
the surrounding and connecting cellular tissue, 
which by-and-bye accumulates, forms an ab- 
scess, is discharged, and leaves the glands, 
with the intervening cellular tissue, dissected 
away by the suppurative and sloughing process. 
It is thus that a bubo will originate from one 
or more inflamed inguinal or axillary glands, 
and when the constitution is enfeebled and fa- 
vourable to a phagedenic action, we frequently 
find these glands exposed by the destruction of 
the skin and cellular tissue. Sometimes, how- 
ever, little collections of pus form in the glands 
themselves, and, according to Gendrin, the 
fluid in the glands differs remarkably from that 
in the cellular tissue, the latter being thick, 
opaque, viscid, and of a greenish hue, whilst 
the former is clear, transparent, and almost 
colourless. Gendrin infers from his observa- 
tions that the lymphatics which permeate the 
inflamed glands become obliterated ; but Dr. 
Bocher, a German anatomist, quoted by Andral, 
affirms that he repeatedly injected with mercury 
lymphatic ganglions presenting different forms 
of morbid alteration, and that he invariably 
found the injection pass freely through all the 
convolutions of vessels, whence he concludes 
that in diseases of these ganglions the lesion is, 
at least in the great majority of cases, confined 
to the cellular tissue that unites the convolu- 
tions of the vessels, or to the coats of the ves- 
sels, but that there is no obstruction of their 
cavity. The lymphatic glands are also liable to 
be chronically inflamed, or to be hypertrophied, 
and under both conditions put on the same 
anatomical characters, viz. redness, increased 
size, induration. In children, of both sexes, 
the glands at the angle of the jaw and those of 
the neck frequently afford examples of these 
morbid states. The bronchial and mesenteric 
glands likewise present similar enlargements. 
Atrophy of the absorbents occurs very com- 
monly in old persons. 

Various deposits are met with in the absor- 
bent glands. Of these the most frequent is 
tubercle, or a cheesy curdy matter of a yel- 
lowish hue, which bears much resemblance to 
tubercle. This matter is deposited in isolated 
spots in the glands, or else appears to be infil- 
trated throughout their substance. In phthisical 
subjects, in scrofulous patients, these deposits 


234 


are usually met with. The cervical, bronchial, 
and mesenteric glands are those most frequently 
affected, but all the absorbent glands are very 
often engaged. Louis states that in phthisis* 
the relative frequency of tuberculization of these 
glands is as follows,—the mesenteric, meso- 
cecal, meso-colic, cervical, lumbar, and axil- 
lary glands, and that the bronchial glands are 
as often affected as the mesenteric. 

The glands affected in children observe pretty 
nearly the same order as regards the relative 
frequency of the affection. They are always 
much enlarged, and frequently closely adherent 
to each other or neighbouring textures ; and the 
cheesy matter either infiltrates the tissue or is 
deposited in small portions in the glands. In 
an infant, which I had lately under my care in 
conjunction witn Mr. Holt, it was found, upon 
post-mortem inspection, that the severe cough 
with remittent dyspnea, under which the child 
sunk, was owing to a mass of enlarged bron- 
chial glands, of the size of a hen’s egg, filled 
with cheesy matter, pressing on the primary 
bronchi and on the pulmonary plexus of 
nerves. 

Cancer, melanosis, and encephaloid matter 
ate frequently found in these bodies, especiall 
when other organs have been similarly affected. 
Deposits of calcareous matter are likewise often 
met with in them, and, as far as my experience 
goes, in none more frequently than in the bron- 
chial glands ; these deposits occur generally in 
old subjects; they consist of phosphate of lime. 
It has been suggested that this calcareous phos- 
phate might be derived from the earthy matter 
of the bones ; and Andral relates two remark- 
able cases in which there was a coincidence 
between the deficiency of a certain quantity 
of osseous matter where it should naturally be 
deposited and its deposition in the lymphatic 
system. In one, a boy et. 16, the bronchial, 
mesenteric, and pelvic glands were occupied 
by calcareous concretions, and his lungs also 
contained them ; there was also an abscess in 
one of the iliac fosse, with erosion and de- 
struction of the os ilii. In a second case, a 
woman, et. 33, who died of acute pleuritis, 
supervening upon a chronic pulmonary affec- 
tion, the bodies of six vertebrx, the last dorsal 
and five lumbar, were found destroyed, and cal- 
careous concretions were found in the cervical, 
thoracic, bronchial, abdominal, pelvic, axillary, 
and inguinal glands. 

The black matter which is so often found in 
the bronchial glands must not be confounded 
with melanoid matter. We seldom examine a 
body that has passed adult age without finding 
more or less of this matter in the bronchial 

lands, derived doubtless from the pulmonary 
lack matter, which is conveyed to these glands 
by the pulmonary lymphatics. 

The changes which occur in the lymph itself 
have not as yet received any attention from pa- 
thologists. This fluid is, however, occasionally 
either mixed with or replaced by others in the 
lymphatic vessels. Cases are on record (Ma- 
jendie, Dupuytren) in which it is stated that 


_ * Dr. Cowan’s translation, p. 73. 


MAMMALIA. 


‘neum have been filled with blood, and that 


the lymphatics in the neighbourhood of san- 
guineous effusions into the pleura and perito- 
pus had been absorbed into them from a neigh- 
bouring abscess. Such cases require confirma 
tion with our present improved means of ob- 
servation, as it is difficult to understand hoy 
particles so large as the blood corpuscles 
the globules of pus, could have permeated t 
coats of the absorbent vessels. In future th 
microscope must be brought to our aid in 

examination of such cases. Authors rel 
likewise that bile has beeu found in the] 

phatics of the liver and in its neighbourho 
in cases where the flow of that fluid has be 

obstructed, (Mascagni, Saunders ;) and Tiede 
mann states that in dogs, in which he had ti 

the hepatic duct, the biliary secretion kev 
made its way into the lymphatics. Ear 
matter, as in the glands, has also been fou 
in the vessels themselves, and the tubereula 
encephaloid, or cancerous matter has likew 
been met with stopping up these vessels. 


$ 


For Bibliography, see that of ABSORPTIC 1. 
(R. B. Todd.) 


MAMMALIA.—(Lat. Mamma, a teat ; Ge 
Saiigethiere ; Fr. Mammiféres; Eng. Me 
mals.)\—The most highly organized class” 
animals, distinguished out ly by a total 
pores covering of hair, and generally | 

aving external teats or mamme, whence 
name. Mammals always possess mamma 
glands, and suckle their young; the fetus 
developed in the womb ; their leading at 
mical character is to have lungs com 
highly vascular and minutely cellular struet 
throughout, and suspended freely in a thora¢ 
cavity, separated by a muscular and tendiz 
septum or diaphragm from the abdomen. 

Mammals, like birds, have a heart compos 
of two ventricles and two auricles: they resp 
quickly, and have warm blood ; inspirat 
is performed chiefly by the agency of th 
phragm : the right auriculo-ventricular 
membranous, at least never entirely fle 
and the aorta bends over the left, never over! 
right bronchial tube. The primary branches 
the aorta are given off, not immediately ai 
but at a little distance from its a 
there is less constancy in the order of th 
origin than in birds: the phrenic arterie 
the ceeliac axis, and the superior mesenteric 
tery are always branches of the abdomina 
aorta, which terminates by dividing beyond tt 
kidneys into the iliac arteries, from whi 
spring both the femoral and ischiadie brat 

he caudal or sacro-median artery, which | 
some long-tailed Mammals assumes the ¢ 
racter of the continued trunk of the aor 
never distributes arteries to the kidneys or legs 
as in birds. The kidneys are nourished, and — 
derive the material of their secretion, exclusively — 
from the arterial system: their veins are sim 
ple, commencing by minute capillaries in the 
parenchyma, and terminating gonecaly by a 
single trunk on each side, in the abdominal 


ep, 


d 


MAMMALIA. 


vena cava: they never anastomose with the me- 
senteric veins. 

The kidneys are relatively smaller, and 
present a more compact figure than in the 
other vertebrate classes; their parenchyma 
is divided into a cortical and medullary por- 
tion, and the secerning tubuli terminate in 
a dilatation of the excretory duct called the 

elvis. The tbuli uriniferi are — slightly 

ranched, and the ramification takes place in 
the dichotomous, and not pinnatifid manner: 
they are convoluted in the cortical, and straight 
in the medullary portions of the kidney, and 
with a few exceptions terminate upon valvular 
prominences, called mammille. The vreters 
convey the urine toa urinary bladder situated 
anterior to the rectum, and to the genital tubes 
or cavities. The liver is generally divided into 
a greater number of lobes than in birds. The 
portal system is formed by veins derived ex- 
clusively from the spleen and chylopoietic 
viscera. The cystic duct, when it exists, 
always joins the hepatic, and does not enter 
the duodenum separately. The pancreatic duct 
is commonly single. 

The mouth is closed by soft flexible mus- 
cular lips. The upper jaw is composed of 
palatine, maxillary, and intermaxillary bones, 
and is fixed ; the lower jaw consists of two 
rami, which are simple, or formed by one 
bony piece, and are articulated by a convex or 
flat condyle to the base of the zygomatic pro- 
cess, and not to the tympanic element of the 
temporal bone; the base of the coronoid pro- 
cess generally extends along the space between 
the condyloid and the alveolar processes. The 
jaws of Mammals, with few exceptions, are 
provided with teeth, which are arranged in a 
single row; they are always lodged in sockets, 
and never anchylosed with the substance of 
the jaw; in most cases they present dif- 
ferent forms in the same individual, and the 
molars have two or more fangs. Never more 
than two teeth succeed each other in the ver- 
tical direction, and in this case the fang of the 
deciduous tooth is always completed before it is 
shed. The tongue is fleshy, well developed, 
with the apex more or less free. The posterior 
nares are protected by a soft palate, and the 
larynx by an epiglottis ; the rings of the trachea 
are generally cartilaginous and incomplete be- 
hind : there is no inferior larynx. The cso- 
phagus is continued without partial dilatations 
to the stomach, which varies in its structure 
according to the nature of the food, or the 
quantity of nutriment to be extracted therefrom. 
An epiploon of greater or less extent is conti- 
nued from the great curvature of the stomach. 
The termination of the duodenum is generally 
tied closely to the apo’ above the root of the 
mesentery. The colon is suspended generally 
by a distinct duplicature of peritoneum, called 
the meso-colon : the cacum coli when present is 
usually single. The rectum commonly termi- 
nates by an aperture distinct from that of the 
urinary or genital canals. 

The female generative organs consist of two 
ovaries, which with very few exceptions are 
equally developed ; there are always two ovi- 


235 


duets or Fallopian tubes, a simple or more or 
less completely bifid uterus, a vagina, which 
is commonly single, and a clitoris. The es- 
sential element of the ovum, the germinal vesi- 
cle, acquires a surrounding granu} stratum 
(tunica granulosa), a small vitelline mass, and 
a vitelline membrane, before it quits the ovisac. 
The ovisacs or Graafian vesicles, consisting of 
an ovarian vesicle and a vascular layer of the 
condensed cellular tissue, or stroma of the ovary, 
are never pendent, and rarely racemose. 

The male organs consist of two equally de- 
veloped testes, commonly situated in an ex- 
ternal tegumentary pouch or scrotum : the vasa 
deferentia form an epididymis at their com- 
mencement, and frequently communicate with 
the ducts of vesicule seminales at their termi- 
nation, and the semen is conveyed outwardly 
along a complete urethral canal, where it is 
mingled with the secretion of certain accessory 
glands, of which those called “ Cowperian,” or 
‘¢ preprostatic,” are constant ; there are also ge- 
nerally prostatic and in many cases vesicular 
glands. The penis is always perforated by an 
urethral canal, along which, with very few ex- 
ceptions, the urine as well as the semen is con- 
ducted from the body. 

The true vertebre of Mammalia have their 
bodies ossified from three centres, and present 
for a longer or shorter period of life a com- 
pressed epiphysis at each extremity. They are 
articulated by concentric ligaments with inter- 
posed glairy fluid, forming what are called the 
intervertebral substances ; the articulating sur- 
faces are generally flattened, but sometimes, as 
in the neck of certain Ruminants, they are 
concave at one end and convex at the other; 
such a vertebra, however, may be distinguished 
from a vertebra of a Reptile, with a similar 
ball-and-socket structure of the articular sur- 
faces, even when found in a fossil state, and 
when the test of the articulating medium can- 
not be applied, by the constant anchylosis or 
confluence of the annular with the central part 
orbody. The cervical vertebre, with one or 
two exceptions, are seven in number, neither 
more nor less ; the Monotremes, which are the 
instances commonly opposed to other generaliza- 
tions, form no exception to this rule. The 
lumbar vertebre are more constant and more 
numerous than in other classes of vertebrate 
animals. The atlas is articulated by concave 
articular processes to two convex condyles, 
which are developed from the ex-occipital ele- 
ments of the last cranial vertebra. The tym- 
panic element of the temporal bone is re- 
stricted in function to a subserviency to the 
organ of hearing, and never enters into the 
articulation of the lower jaw. The frontal 
bones are developed each from a single centre ; 
there are no anterior or posterior frontals. The 
olfactory nerves escape from the cranial cavity 
through numerous foramina of a cribriform 
plate. The optic foramina are always distinct 
from one a and generally from the fis- 
sure lacere anteriores, and consequently give 
passage only to the optic nerves and ophthalmic 
arteries. The carotid canals do not intercom- 
municate. The cranial bones, in regard to the 


236 


number and persistency of their sutures, are 
intermediate in character to those of Birds and 
Reptiles. The anterior extremity of the skull 
is always formed by both the upper and lower 
jaws. The scapula is generally an expanded 
plate of bone; the coracoid, with two excep- 
tions, appears as a small process of the scapula : 
the clavicle is inconstant as to its presence ; the 
sternum consists of a narrow and usually simple 
series of bones; the sternal portions of the ribs 
are generally cartilaginous, and fixed to the 
vertebral portions without the interposition of 
a distinct articulation ; there are no abdominal 
ribs or abdominal sternum. The pubic and 
ischial arches are generally complete, and 
united together by bony confluence on the 
sternal aspect, so that the interspace of the two 
bony pelvic arches is converted into two holes, 
called foramina obturatoria, or thyroidea. 

The brain in Mammalia consists of cerebral 
and optic lobes, cerebellum and medulla ob- 
longata, but the optic lobes are placed on the 
upper part of the crura cerebri, are solid, are 
always divided by a transverse fissure, and are 
generally concealed by the cerebral lobes, in 
consequence of the large relative size of these 
masses; the decussation of the corpora pyrami- 
dalia is always distinctly marked: the tuber 
annulare and lateral lobes of the cerebellum 
have a correspondingly conspicuous develop- 
ment; the ventricles of the cerebrum are large, 
and contain a corpus striatum and cornu am- 
monis; the fornix is always well developed, 
but the following aphorisms in Cuvier’s cele- 
brated abstract or condensation of M. Serres’ 

rize essay are applicable only to the placental 

ammalia, viz. “ The corpus callosum as well 
as the pons Varolii are peculiar to Mammalia. 
The corpus callosum is developed in direct 
proportion to the size of the corpora striata 
and hemispheres. It increases progressively 
from Rodentia to Man. The corpus collosum 
is developed in direct proportion to the de- 
velopment of the tuber annulare.” 

In the Marsupial Order, as in the Kangaroo 
and Wombat, the cerebral hemispheres are 
relatively larger and more complicated with 
convolutions than in any Rodent, yet the trans- 
verse commissure which represents the rudi- 
ment of the corpus callosum connects only the 
hippocampi majores ; it is not separated from 
the fornix by any septum lucidum ; and, upon 
divaricating the cerebral hemispheres, the la- 
teral ventricles are as much exposed as when, 
in placental Mammalia, the corpus callosum 
has been removed. The tuber annulare, how- 
ever, exists in the Marsupial as in the Placental 
Mammalia, and illustrates its correlation with 
the lateral lobes of the cerebellum. The class 
Mammalia is the only one in which the cere- 
bral hemispheres are observed to have their 
vascular superficies multiplied or increased by 
convolutions, which arrive at ther maximum 
of development in Man. 

The olfactory nerves of mammals are soft, 
and divide into numerous branches in the 
cranium, which out by the orifices of the 
cribriform plate of the «thmoid. 

Themervi vagi principally supply the larynx, 


MAMMALIA. 


form a plexus around the cesophagus, and do 
not wie into a single trunk eons x to 
the stomach. The left recurrent ot 
the right, bends round the trunk of the aorta. _ 
The cervical portion of the sympathetic nerve 
passes along the neck on the sternal aspect 
the transverse processes of the vertebra; ai 
its trunk in the thorax and abdomen is m 
immediately connected with the ganglia of tl 
spinal nerves. The splanchnic nerves fo 
large ganglia before giving off the 
plexuses. 
The sclerotic coat of the eye is a fibr 
membrane, and never contains bony pl 
In the quantity of aqueous humour and th 
convexity of the lens, Mammals are gene 
intermediate to Birds and Fishes; b 
have no marsupium or pecten, nor any ¢l 
roid gland. 
The organ of hearing is characterized 
Mammalia by the full development of © 
cochlea with a lamina spiralis ; there are th 
distinct ossicles in the tympanum ; the met 
brana tympani is generally concave external! 
and the meatus auditorius externus often & 
mences with a complicated external ear, havit 
a distinct cartilaginous basis. ~~ 
The external apertures of the of sm 
are provided in Mammalia wit ub 
cartilages and muscles, and the extent of 1 
internal organ is increased by accessary cavill 
or sinuses which communicate with the p: 
sages including the turbinated bones, 
The tongue is always soft and fleshy, ai 
gustatory surface is provided with conical, fo 
sulate, and fungiform papille; it is suppl 
by a large proportion of the third division 
the fifth pair of nerves, as well as by the ninth 
and glosso-pharyngeal. “ 
Classification —The Mammalia were first 
separated from other four-footed animals and 
distinguished as a class or particular group — 
(genos) by Aristotle, the founder of natural 
history, by whom they were denominate 
Sootoka, or Viviparous animals. The Greek 
philosopher divided the Zootoka, according to 
the nature of their locomotive organs, into 
three sections: 1st, Dipoda, or bipeds; 2d, 
Tetrapoda, or quadrupeds ; and 3d, A pode 
or impeds, which comprehends the Whale- 
tribe. The second of these primary division 
—the quadrupeds,—which includes by far the 
largest proportion of the class, and in common 
parlance is considered as the class itself, is 
subdivided by Aristotle into two great natural 
groups, according to the modifications of the 
organs of touch. In the first of these groups, 
the extremities of the digits are left free for 
the exercise of the tactile sense, the nail or 
claw being placed on one side only (Ungui- 
culata of Ray); in the second group, the 
digits are inclosed in hoofs (Ungulata of Ra’ y)- 
For the convenience of treating of the different 
forms of the Unguiculate quadrupeds, Aristot 
employs for their further subdivision anothe 
system of organs, viz. the teeth. His first ya 
or family is composed of those Unguicu 
which have the front teeth trenchant, or termi- 
nating in a cutting edge, and the back teeth 


= 


-_ 


MAMMALIA. 


triturant, or with a flattened surface, as the Apes 
( Pithecoida) and the Bats ( Dermoptera): 
his second family includes the Unguiculate 
quadrupeds with acuminated, canine, or car- 
nivorous teeth, and is called Karcharodonta, 
or Gampsonucha; whilst the quadrupeds cor- 
responding with the Rodent order of modern 
naturalists are grouped together and indicated 
by a negative dental character, viz. the absence 
of canine teeth. 

With respect to the hoofed or Ungulate 
quadrupeds, Aristotle continues to employ the 
organs of progressive motion for the subordi- 
nate characters, and divides them into, 1st, 
Polyschide, or multungulates, as the Elephant, 
&e.; 2d, the Dischide, or bisulcates, including 
the Ruminants ( Merykozonta ), and the Hog- 
tribe; 3d, the Aschide, or solidungulate quad- 
rupeds, as the Horse and Ass. 

he Apodal Zootoka, which form the third 
of Aristotle’s more comprehensive groups, un- 
derwent no corresponding subdivision in his 
system. It embraces the modern Cetacea, 
under the name of Kefoda. Thus the natural 
class of animals, now universally recognized 
under the Linnean epithet Mammalia, although 
it comprehends creatures the most diverse in 


237, 


their forms and habits, some, e. g. skimming 
along the air with wings like birds, others ha- 
bitually dwelling on, the ocean disguised as 
fishes, was clearly appreciated and first indi- 
cated by Aristotle, who included thereip the Bat 
and theWhale,with the ordinary hairy dead ruped 
and the naked biped, according to principles 
acknowledged as consisting with the soundest 
philosophy by the best-informed physiological 
naturalists of the present day. 

During the two thousand years which have 
elapsed since Aristotle wrote and lectured on 
natural history, the ideas of learned men re- 
garding the nature and classification of Mam- 
mals received no improvement, and any 
change which they underwent was for the 
worse. Our great countryman Ray was the 
first to introduce any amelioration of Aristotle’s 
arrangement. ‘This arises chiefly from the 
tabular form in which he expressed his ideas, 
and in which the subordination of the charac- 
ters and groups is more definitely set forth 
than in the existing compendium of Aristotle’s 
History of Animals. Ray’s improvements of 
classification relate, however, only to the Te- 
trapodous Mammals. It is as follows: — 


“A Table of Viviparous Four-footed Animals, 


“ Viviparous hairy animals or quadrupeds are,— 


if Ungulate, and these either 


Bisulcaie, which are 


ae 


| Unguiculate, whose feet are either 
Bifid, as in the CaMEL, or 
} Multifid, which are 


{ Solidipedous, as the Horse, Ass, ZEBRA. 


Ruminants with horns, that are 
Persistent, as in the Ox, Sueep, Goat, 
or ; or . 
Deciduous, as in the Srac. 
Not Ruminants, as the Hoe. 
| Quadrisulcate, as the Rurnoceros, Hippopotamus. 


ment, so that the extremities alone are visible at the margin of the 


J With digits adhering together, and covered with a common integu- 


foot, and are covered with obtuse nails, as in the ELepwanr. 
With digits in some measure distinct and separable from each other, 


the nails being 


§ Depressed, as in APEs, 
or 


d Compressed, where the incisor teeth are 
( Many, in which group all the animals are carni- 


L 


©The anomalous species,” Ray afterwards 
observes, “‘ among the viviparous quadrupeds 
with a multifid foot are the Hedge-hog, the 


vorous and rapacious, or at least insectivorous, 
or subsist on insects with vegetable matter : 
{ The larger ones with the 
Muzzle short, and head rounded, 
; as the Feline tribe; or with the 
Muzzle long, as the Canine tribe ; 
The smaller ones with a long slender 
body, and short extremities, as the 
Weasel or Vermine* tribe ; 


or < 


Two very large, of which tribe all the species are 


phytivorous, as the Hare.” 


Armadillo, the Mole, the Shrew, the Taman- 
dua, the Bat, and the Sloth. The first five of 
these species agree with the canine and vermine 


* Genus Verminewm, from their worm-like form, 


238 


a in their elongated muzzle, but differ 
rom them in the form and disposition of the 
teeth: the Tamandua, indeed, is altogether 
destitute of teeth: the remaining two anoma- 
lous species have the muzzle shortened.” 


Linneus defines the Class Mammalia, as 
follows :— 

Heart, with two auricles and two ventricles. . 

Blood, warm. 

Lurgs, respiring reciprocally (“ Pulmones re- 
spirantes reciproce.”’ ) 
_ Jaws, incumbent, covered ; armed with teeth 
in most. 

Penis intrans. 

Generation, viviparous ; lactiferous. 


= 
a 


MAMMALIA. 


4 tongue, nostrils, eyes, ears, tactile p: 
ille. s 
R Covering, hairs; few in tropical; ve 
sparing in aquatic mammals. Te 

Support, four feet, except in those 
entirely aquatic, in which the posteri 
are bound together in the fin of the tz 
tail in most. ea 

Wih res to classification, Linneus, 
Aristotle and Ray, founds his primary divis 
of the Class Mammalia on locomotive ong: 
but his secondary divisions or orders are tal 
chiefly from modifications of the dentary syst 
The following is the scheme of his ar 
ment :-— 


Front teeth, none in either jaw .........seeee = avandia he 
S°0 Unirniculate Front teeth, cutters 2, laniaries 0. .... cess eeseereves . GLIRES. 
= s **** ) Front teeth, cutters 4, laniaries 1. ........0eeeeeeeeees Pai 
| Front teeth, piercers (6, 2, 10), laniaries 1....... connie om 
= 4) Uneulate ...,., § Eront teeth, in both upper and lower jaw ...... awe-enen oa 
= Bs Waly soe ( Front teeth, none in the upper jaw ........++.- ops vhmas 
7h A Maticate s.0s.06.;, TOM VOID Oxsi0iccis'. do usis ee oss capsids 20 pene . 
(From the ‘ Systema Natura,’ ed. xvi. Holmiz, p. 24.) : 
d 
On comparing the three preceding systems, mense; esophagus and alimentary canal wi 


it will be found that the most important errors 
of arrangement have been committed, not by 
Aristotle, but by the modern naturalists. Both 
Ray and Linneus have mistaken the character 
of the horny parts enveloping the toes of the 
elephant, wach do not defend the upper part 
merely, as is the case with claws, but embrace 
the under parts also, forming a complete case 
or hoof. 

With respect to Linneus, however, it must 
be observed, that although he has followed 
Ray in — the elephant in the unguiculate 
group of quadrupeds, he has not overlooked the 
great natural divisions which the latter natural- 
ist adopted from Aristotle, as is evident from 
the Table above quoted. He erred, perhaps, 
in not giving names to those primary divisions. 

From the manner in which Linneus has ar- 
ranged his Orders in this Table, it would seem 
that he had the circular progression of affini- 
ties in view. The Walrus among Bruta con- 
nects the commencement of the chain with 
Cete, which forms the last link; but whether 
or not he had perceived the affinity of Elephas 
to the Glires, and intended it as a transi- 
tional genus to that Order, as Cuvier has sub- 

uently shown it to be, is less certain. 
allas* divides the Class Mammalia into 
seven Orders, viz. 

I. Ferz. II. Semirerz. 

IV. Rumivantia. V. ANoMALOPoDa. 
VI. Betituz. VII. Ceracea. 


Order I. FERZ. ! 

The Fer are characterized by incisors, 
small ; /aniaries very powerful; molars tren- 
chant and tricuspid, (Jlacero - tricuspidatos ) ; 
clavicles minute suspended in the fi + almost 
obsolete and functionless; vertebral column 
elongated and flexible; ‘muscular force im- 


* Zoographia Rosso-Asiatica, 1831. 


Til. Gurres. 


short, with a very short cecum and cok 
digestive power so active as to reduce € 
bones to chyme; penis supported by a bon 
prolific virtue not very great; young born 
skin pretty flexible, and fat os, sometimes ¢ 

The genera included in the Order thus pl 
losophically characterized are 


1. Felis. 2. Canis. 3. Ursus. 4. Mek 
5. Viverra. 6. Mustela. 7. Phoca. 


Order II. SEMIFERZ. “ 
“ All preconceived opinion being laid asic 

the following genera,” says Pallas, “ seem 
be linked together by an uninterrupted series” 
of affinities and to constitute a strictly natu 
family, viz. Simia, Lemur, Vespertilio, grow 
together by Linneus under the name of Pi 
mates—with these, Didelphys, Talpa, Sore 
and Erinaceus, which he classed without a 
stable character with the Fere. These dit 
from the Order Fere in the continuity of : 
dental series, generally also in the number of i 
cisors and in the less elongated canines; in t 
multifarious and singular structure of the pe 
tadactyle feet, the perfect clavicles, and in sho 
in their habit, food, and general nature.” 


Order III. GLIRES. 
“ This Order,” says Pallas, “ is so natur 
and clear in its characters that it did not esea 
the older Zoologists. All the genera co 
posing it agree in their bifid or hare-lip, th 
rosorial incisors generally two in number, | 
perfect clavicles, sub-bipartite large 
cecum, and great apparatus of the male gene- 
rative organs, exceeding that of any other 
order. ey produce a blind offspring, as 
the Fere and Semifere.” It must be observ 
however, that the perfect clavicles and lar 
cecum are not, as Pallas states, constant chi 
racters of the Glires. 


[-¥ 


MAMMALIA. 


Order 1V. RUMINANTIA. 

1¢ Ruminantia, or the natural Order re- 
cognized by Aristotle under the name of 
MnpuxdQovra, subsequently adopted by all Zoo- 
logists, have their external and internal cha- 
racters alike conspicuous and cogent. These, 
according to Pallas are, incisors wanting in 
the upper jaw ; hoofs bifid ; habit of the whole 
body ; stomach quadruple; intestines very long 
with aceecum ; suet for fat; cotyledons in place 
of placenta. The genera included in this order 
are Camelus, Moschus, Cervus, A:goceros, Bos, 
Antilope. 


Order V. ANOMALOPODA. 

The genera grouped together by Pallas under 
this name differ, he observes, from each other 
in their dental apparatus and the structure of 
their feet, yet nevertheless are linked together 
by natural affinity (“ sed amen inter se naturali 
affinitate coherent’’). Thus Hippopotamus is 
allied to Equus, the horse to Rhinoceros and 
its congener Hydrecherus, and these to the 
genus Sus. The following characters are com- 
mon to the whole order: molares truncate, tritu- 
rating ; feet ungulate, supported on the digits ; 
stomach a macerator, with enormous colon and 
cecum; clavicles wanting; produce perfect ; 
Jood vegetable. 

The genera which Pallas exemplifies in this 
Order, which corresponds with the Pachyderma 
of Cuvier (the Proboscidians being excepted), 
are Equus, Sus, Rhinoceros, Hippopotamus. 


Order VI. BELLU. 

In this Order,— characterized by incisors 
none; canines projecting from the upper jaw 
only, composed of ivory ; molars few; mamme 
pectoral (in which the Bellue mainly differ 
from the Anomalopoda); feet; with connate 
digits forming a shapeless sole ;—Pallas in- 
cludes the genera Elephas and Rosmarus, re- 
jecting therefrom the T'richecus or Manatee, 
as having the hind-feet coalescing with the tail, 
and therefore more rightly to be referred to the 
Cetaceous Order. In this latter view Cuvier 
agrees with Pallas. As to the rest it is scarcely 
necessary to say that the tusks of the Elephant 
differ from those of the Walrus in being im- 
planted in the inter-maxillary bones instead of 
the maxillaries, and are therefore regarded as 
incisors. 


Order VII. CETACEA, 

Pallas observes that since the Cetacea differ 
from the other Lactantia chiefly in having 
their boneless posterior extremities blended 
with the cartilaginous tail (“ quod artus posticos 
exosses, in caudam cartilaginibus fultam co- 
adunatos obtinent’’), the Manatus and Trichechus 
rightly fall under this Order, although they ap- 
proach more to the nature of Quadrupeds. 
Both the Manatus proper and the Rytina, 
which is the Manatus Borealis of Pallas, agree, 
however, with the true Cetacea in having no 
other rudiments of posterior extremities than 
some small pelvic bones. 


We shall now proceed to the arrangement 


$39 


of the Mammalia proposed. by Cuvier in the 
last edition (1829) of the ‘ Régne Animal ;’ 
and this is the more interesting, as, in giving 
the outline of his method, he ae the 
principles on which the divisions ofthe class 
are founded. 

“ The characters by which Mammalia differ 
most essentially one from another are derived 
from the organs of touch, from which results 
their degree of dexterity, and from the organs 
of mastication, which determine the nature of 
their food; and, as a corollary to these, de- 
pends not only every thing which is connected 
with the digestive functions, but a variety of 
other circumstances relative even to their de- 
grees of intelligence. 

“ The perfection of the organs of touch is 
estimated by the number and mobility of the 
digits, and the extent to which they are inclosed 
in aclaw or in a hoof. A hoof which com- 
pletely incloses that part of the digit which 
touches the ground, precludes the exercise of 
it as an organ of touch or of prehension. The 
opposite extreme is where the nail, in the form 
of a simple lamina, covers only one side of the 
end of the digit, leaving the other side in pos- 
session of all its delicacy of tact. 

“The kind of food is indicated by the 
molar teeth, to the form of which the arti- 
culation of the jaws invariably corresponds. 

“ For cutting flesh, the molar teeth must be 
trenchant and serrated; and the jaws fitted to- 
gether, so as to move like the blades of a pair of 
scissors, simply opening and closing in the 
vertical direction. 

“ For bruising grains and roots, the molar 
teeth must have flattened crowns, and the jaws 
a horizontal motion : and further, that the grind- 
ing surface may be always unequal, like a 
millstone, the teeth must be composed of sub- 
stances of different degrees of density, and con- 
sequently wearing down in different proportions, 

“The ungulate quadrupeds are all of neces- 
sity herbivorous, or with flat-crowned molars 
(fig. 59), because the conformation of their feet 
does not permit them to seize living prey. 


Lower jaw, African Elephant. 


“ The unguiculate animals are susceptible of 
more variety. They are not limited to one kind 
of food ; and, besides the consequent variation 
in the form of their molars, they differ ma- 
terially from each other in the mobility and 
sensibility of their digits. There 1s, more- 
over, a characteristic which prodigiously. in- 


240 


Fig. 60. 


Skull of a Rodent, 


Hind leg, Antelope. 


fluences their dexterity, and gives variety to 
their modes of action: it is the faculty of 
opposing a thumb to the other fingers, so as 
to seize the smallest objects, which constitutes 
a hand, properly so called. This faculty is 
carried to its highest degree of perfection in 
man, in whom the whole anterior extremity is 
free, and can be exclusively employed in pre- 
hension. These different combinations, which 
strictly determine the nature of the several mam- 
miferous animals, have formed the grounds for 
their distribution into the following Orders. 

“ Amongst the Unguiculate animals, the 
first is Man, who, in addition to his peculiar 
privileges in every other respect, is distinguished 
zoologically by possessing hands on the ante- 
rior extremities alone ; the posterior extremities 
being destined to sustain him in the erect 
position. ( Fig. 60.) 

“The Order which comes nearest to Man, 
—that termed Quadrumana,—has hands on the 
four extremities. ( Fig. 61.) 

“ Another Order, termed Carnivora, has not 
the thumb free and opposable on either the 
anterior or posterior extremities. ( Fig. 62.) 

“ These three Orders likewise seve- 
rally the three kinds of teeth, viz. molars, lani- 
aries, and incisors. 

“ The quadrupeds of the fourth Order, viz. 
the Rodentia, have the digits differing little from 
those of the Carnivora; but they want the 
laniary teeth, and have the incisors of a form 
and Supedtion altogether peculiar to them- 
selves. ( Fig. 63.) 

«“ To these succeed the animals whose digits 
now become much cramped, being sunk deep 
in large and, most commonly, crooked claws. 
They are further defective in the absence of 


MAMMALIA. 
Fig. 61. 


if w 


Hind extremity, Ape. 
Fig. 64. 


Shall of the Giraffe. 


incisor teeth; some of them even want th 
laniaries, and others are altogether destitute o 
dentary organs. We shall com he 
under the term Edentata. (See fig. 33, vol. ii 
. 49.) - 
Pe This distribution of unguiculate 
would be perfect, and would form a 4 
lar chain, if New Holland had not latel 
furnished us with a small collateral chai 
composed of the Marsupial animals, all th 
genera of which, while they are connected by 
a general similarity of organization, at the sal 
time correspond in their dentition* and die’ 
some to the Carnivora, others to the Rodenti 
and a third tribe to the Edentata. “al 
“ The Ungulate animals are less numerou 
and present fewer variations of form. 
“ The Ruminantia, by their cloven feet 
(Fg 64,) their want of upper incisors, (fig. 65. 
and their complicated stomach, form a ver: 
distinct Order. ae 
“ All the other quadrupeds with hoofs migl 
be united into a single Order, which I woul 
call Pachydermata or Jumenta, (fig. 66,) th 
elephant excepted, which might form an Orde 
of itself, having some remote affinities to t 
Order Rodentia. The Pachyderms have com: 
monly incisors in the upper as well as the low 
jaw.  ( Fig. 67.) ‘a 
“ Last of all come the Mammalia whic 
have no hinder extremities, and whose fish-liki 
form and aquatic life would induce us to form 
them into a separate Class, if their economy 


* In the article MARSUPIALTIA it will be shown how 
much more essential are the points of resemblance 
between the dentition of the different Marsupié 
animals than between any of these and the pla 
cental genera, with which they correspond in iet 


MAMMALIA. 241 
12. Canis. 13. Fenis. 14. Viverra. 15° 
Musteta. 16. Ursus. 17. DipELpPHIs. 
18. Tatpa. 19. Sorex. 20. Erinaceus. 


a i 


Fig. 67. 


i 8 ee eee eee 


p 1S 
«95056 cel Wg 


weit I Lt 


Skull of the Rhinoceros. 


"was not in every other respect the same as in 
the Class in which we shall leave them. They 


“ing sustained upon the watery element, include 
‘the most gigantic forms to be found in the 
‘whole animal creation.”—Regne Animal, 2nd 


Having thus given a brief exposition of the 
‘principles which have guided five of the most 
‘original writers on Natural History in their 
‘ptimary arrangement of Mammalia, we shall 
next subjoin a short tabular view of the genera 
or minor groups included by Linneus and 
Cuvier in their respective Orders. 


The System of Mammalia of Linnaeus, from 
the 12th edition of the ‘ Systema Nature.’ 
* A. Unguiculata. 

fs I. Primates. 

__ Fore teeth cutting; upper ones parallel, four; 
_laniaries solitary. Teats pectoral, two. Food, 
fruits, except a few which use animal food. 
1.Homo. 2.Simia. 3.Lemur. 4. Vezs- 
-PERTILIO. 

4 Il. Brora. 

_ Fore teeth none in either jaw. Feet with 
large nails. Food mostly vegetables. 5. Exx- 
| *PHAS. 6. Tricuecus. 7. Brapvypus. 8. Myr- 

MercopHaca. 9. Manis. 10. Dasypus. 

.. Ill. Ferra. 

_ Fore teeth conical, usually six in each jaw; 
taniaries long; molaries pointed, conical. 

Hood, carcasses and living prey. 11. Puoca. 

B VOL. 111. 


IV. Guires. y, 
Front teeth cutting, two in each jaW. Food, 
bark, roots, vegetables, which they erode or 


gnaw. 21.Hysrrix. 22. Lepus. 23. Cas- 
TOR. 24. Mus. 25. Scrurus. 26. Noc- 
TILIO. 


B. Ungulata. 
V. Pecora. 4 
Fore teeth cutting, many in the lower jaw, 
none inthe upper jaw. Feet bisulcate. Four sto- 
machs. Food, herbs, which they pluck, and 
afterwards ruminate. 27. CAMELUS. 28. 
Moscuus. 29. Cervus. 30. Capra. 31. 
Ovis. 32, Bos. 
VI. BELLUE. 
Fore teeth obtuse. Tread heavy. Food, 


vegetables. 33. Equus. 34. HiproporaMus. 
35. Sus. 36. Rarnoceros. 

C. Mautica. 

Vil. Crre. 


Teeth in some horny, in others bony. In 
place of Feet they have pectoral fins without 
claws ; and a horizontal flattened tail. Nostrils 
terminating in one or two fistulous apertures at 
the anterior and upper part of the head. Food, 
mollusca and fish. 37. Monovon. 38. Ba- 
LENA. 39. PuysererR. 40. DELPHINUS. 


The System of Mammalia of Cuvier, ac- 
cording to the 2nd Edition of the < Régne 
Animal.’ 

A. Unguiculata. 

With three kinds of teeth. 

I. Brmana. 


Sect. a. 


1. Homo. 
II. QuaDRUMANA. 
1. Simie, incisors four in each jaw, erect ; 
nails flattened. 


Fig. 68. 


a, Incisors; 6, canine or laniary ; c, false molars, 
premolars, or bicuspids ; d, true molars. 


a. Inhabiting the Old World; molars five 
on either side of each jaw. Puruecus, &c. 

f. Inhabiting the New World; molars six 
on either side of each jaw. Cersus, &c. 

2. Lemurini, incisors more than four either 
in the upper or lower jaw, procumbent. Ler- 
muR, &c. 

III. Carnivora. 

1. Cheiroptera, with membranous expansions 
between the fingers, and laterally between the 
extremities. 

a. Vespertiliones, with the bones of the an- 
terior extremity disproportionately elongated. 
Preropvs, ke. 

R 


“Srv a * 
’ 


242 MAMMALIA. 
B. Seieted, with the fingers and toes of 
the same | GaLEoPITHeEces. 


2. Insectivora, without lateral membranous 
expansions ; molars cuspidated. 
“a. With two long anterior incisors, the rest 
short, the laniaries sinall. Erinaceus, &e. 

8. With the incisors small, the laniaries 
large. Cenreres, &c. 

3. Carnivora, incisors six in each jaw; mo- 
lars, some of them sectorial or trenchant. 


Fig. 69. 


Dentition of Bear. 
a, Incisors ; 5, laniary ; c, false molars ; d, secto- 
= molar or ‘carnassial ; e, tuberculate or true mo- 
ars, 


a. Plantigrada. Ursus, &c. 
fp. Digitigrada. Canis, Fexis, &e. 
y- Pinnigrada. Puoca, &c. 


Fig. 70. 


Hind extremities, Seal. 


IV. Marsupiatia. 

1. Incisors small; laniaries long; posterior 
molars cuspidated. Divetpuis, &e. 

2. Lower incisors two, long ; upper ones six. 
Upper laniaries long and pointed ; lower ones 
small. Puataneista, &c. 

8. Lower laniaries wanting; no thumb on 
the hind feet. Hypstprymnus. 

4. No laniaries. Macropus. 

« 5. Lower incisors two, no laniaries: upper 
incisors six; two small laniaries. PHasco- 
ARCTOS. 

6. Two long incisors in each jaw; no lania- 
ries. Puascotomys. 

Sect.b. Without laniaries ; two large incisors 
distant from the molaries. 
. Roventia. 

1. With clavicles. 

a. Sciuride, anterior digits four, posterior 
five ; tail cylindrical and bushy. 

B. Muride, tail cylindrical, not bushy. 

: y- Pedetide, anterior digits five, posterior 
our. 


i 
fie 
Bk: he 

Ns 

‘ 


— Spalacide, anterior digits five, p 
iD 


t. "s. Castoride, tail flat and scaly, 
2. With imperfect clavicles, or none. 
a. Hystricide, body covered with si pines 
B. Leporide, "two small incisors behind 
ree superior large ones. uy 
aviade, no character in common, ; 
Sect. c. Without incisor teeth. — 
VI. Epentata. 
1. Tardigrada ; with a short muzzle. 
pypus, &c. 
2. Typical LEdentata; with an elon; 
muzzle. Dasypus, &c. ' 
3. Monotremata ; with marsupi 
acloaca. ORNITHORHYNCHUS, 
B. Ungulata. 
a. Not Ruminants. 
VII. Pacnypermata. 
1. Proboscidea ; with a proboscis: iei 
projecting ; feet pentadactyle. Er : 
2. Typical Pachydermata ; feet t 
or di-dactyle. Hippopotamus, &e. 
3. Solipeda; feet monodactyle. 
b. Ruminants. 
VIII. Ruminantia. 
. Without antlers or horns. Cametu 
. With antlers. Cervus, &e. 
. With horns. Awntirope, &e. 
C. Mutica. 
IX. Ceracka. 
1. Herbivora; teeth fitted for n 
Manatvus, &e. 
2. Typical Cetacea ; teeth unfitted f 
tication, or wanting. Derxtpuinvs, &e. — 


The ideas that have been broached respe 
the attinities and classification of the Mami 
after Cuvier, and which are most 
for their novelty and boldness, are the 
have emanated from the naturalists of t 
lish Quinary school. The founder ant 
most talented of this sect—Mr. W. 8. . 
—thus enunciates his views of the ar og i 
servable between the principal groups 0 
malia, and those into which the class o 
resolvable. Every Mammiferous 
he says, “ may be reduced to these five or 
that is, may be assimilated, in a greate! 
degree, to one or other of the followir g. 
forms ; viz. Man, the Lion, the Horse, th 
and the Mouse. I shall show hereafter 
these five orders form a continued se; 
ing into itself, so as to be a natural ¢ 
the mean time, I must recall to thea 
the reader the orders of Birds as defi 
ranged by Mr. Vigors; and to whieh dl 
and arrangement I have just soplied a0 
a test, only to corroborate their accurac’ 
to make them display additional harmony 
“ When we have heard the Parrot or 1 
ate speaking; when we have witness¢ 
former feeding itself as it were with | 
when, in short, we have reflected on the rer 
ent of © 


be 


wre 


able intelligence and developm 
throughout the whole order of Insessor 
which both birds belong,—there has bee 
one, perhaps, dull enough not t 
to Primates....1 allow indeed, that it ' 


rom pare 


{ 
| 


MAMMALIA. 


cult to follow the opinion of the great naturalist 
of France, who, ignorant of the true nature of 
relations of analogy, imagined that the Psitta- 
ceous tribe of Birds ought to occupy the first 
step in the scale of nature below Man ; but we 
cannot help adopting the notion of Linnzus in 
the‘ Systema Nature,’ that although not near 
him in construction, they are yet analogous to 
him in various important respects. And, adopt- 
ing this notion, we must place the whole order 
of Insessores, to which Psittacus belongs, op- 
posite to the Primates, of which Man forms the 
type. 
ie The analogies existing between birds of 
prey and carnivorous quadrupeds having been 
noticed by Aristotle, who called both groups 
Gampsonucha, were enlarged upon by Plu- 
tarch. Among a host of moderns who have 
been struck with the resemblance, [ may par- 
ticularly mention Linneus, who in his ‘ Sys- 
tema Nature’ has expressly called his Acci- 
pitres ‘ Feris analogi ;’ and Buffon, who has 
treated the subject at length and with his usual 
eloquence. I conceive, therefore, that no one 
can object to the oy of my placing the 
Fere opposite to the Raptores. 

“ The analogy between Aquatic Birds and 
Aquatic Mammalia scarcely requires the men- 
tion of the authority of Linnzus to make it be 
granted. It is indeed so evident, that Her- 
mann, according to his custom, takes it for a 
relation of affinity. In both orders the ante- 
rior appendages of the vertebral axis dwindling 
into fins, and the two undivided posterior ap- 
pendages being placed so far behind on the 
axis as to show that both were intended for 
motion in the water rather than on land, are 
circumstances of themselves sufficient to autho- 
rize the placing of the Cetacea opposite to the 
Natatores. 

* Two orders still remain in each class to be 
considered : the Glires and Ungulata among 
the Mammalia; and among Birds, the Rasores 
and Grallatores. The relations of analogy 
pointed out by Linnezus between Mammalia 
and Birds are, as Hermann has observed, not 
always correct ; and his errors have arisen from 
the misfortune of his not detecting the natural 
group of Aristotle and Ray, which the latter 
has called Ungulata.* Having only been able 
to seize Aristotle’s subdivisions of this group, 
he lost the parallelism of analogy, and fell, as 
I shall hereafter show, into very glaring mis- 
takes. In the ‘ Systema Nature,’ however, he 
has mentioned that very striking analogy which 
appears between his groups of Gralle and 

ruta ; that is, according to the parallelism of 
analogy, between the orders of Grallatores and 
Ungulata, since the Bruta, as we have seen, 
do not form an order, but only a natural subdi- 


* In making this assertion, Mr. Macleay ap- 
pears to have overlooked the tabular arrangement 
prefixed by Linnzus to the more extended charac« 
ters of his orders of Mammalia. The only fault in 
the construction of his Ungulata is the exclusion of 
the elephant from that division ; for with respect to 
the edentate Bruta, Linneus and Cuvier correctly 
interpreted nature in placing them among the Un- 
guiculate Mammalia, 


243 


vision of the Ungulata. That this analogy is 
demonstrably true, I deduce from the following 
facts. Of their respective classes, tha orders of 
Ungulata and Grallatores contain eacine of 
the longest legs in proportion to the body,— 
witness Camelopardalis and Hamantopus. Both 
orders present us, in groups not exactly aquatic, 
with instances of the toes soldered together, as 
in the Horse ; or connected together by a web, 
as in the Flamingo. Both orders present us 
with the greatest elongation of muzzle or facies, 
—witness Myrmecophaga, or Antilope (particu- 
larly A. Bubalus L.), and Scolopaz ; and also 
with the most depressed form of muzzle,— 
witness Hippopotamus and Platalea, which 
genera also afford us the truest specimens of 
Wading Vertebrata. In both orders we have 
the most elongated claws,—witness Megalonyx 
and Parra. Both orders afford us the swiftest 
animals in running,—as the Horse and Tachy- 
dromus ; and the most pugnacious on account 
of love,—as the Bull and Machetes. The Bull 
moreover and the Butor Yor Bostaurus, for 
hence comes the bird’s name,) afford us the 
loudest and hoarsest voice of their respective 
orders : where we have also the most remark- 
able instances of the upper and under mandi- 
bles touching each other merely at their base 
and point ; as Myrmecophaga, or the whole of 
the ra pev ovx apQodovra of Aristotle, and 
Anastomus Illig. Both orders exhibit orna- 
mental appendages to the head,—as the antlers 
of the Stag and the crown of the Crane; and 
both orders afford us the only instances of true 
horns,—as Bos or Rhinoceros, and Palamedea 
L. To see a hundred instances of resemblance, 
it is only necessary to walk intoa museum. I 
shall therefore only further say, that both orders 
contain polygamous animals, are generally gre- 
garious, and more graminivorous than granivo- 
rous, being essentially inhabitants of marshes 
and savannahs. Thus then, with Linneus, I 
place the Bruta, or rather the whole order of 
Ungulata to which they belong, opposite to the 
Grallatores. 

“ Four orders in each class being now dis- 
posed of, it follows by parallelism of analogy, 
that the Glires ought to be placed opposite to 
the Rasores. But setting theory aside,—is this 
position true in fact ?* 

“ Linneus, from the above-mentioned error 
in his series of affinity, considered the Rasores 
to be analogous to his group of Pecora. But 
this group, according to Aristotle and Ray, is 
only a subdivision of Ungulata, which have, I 
consider, been now proved to be analogous to 
the Grallatores. If, therefore, Linneus be 
right in making his Bruta analogous to the 
order of Wading Birds, it follows that his Pecora 
must be so also. 


* <The ancient name of Struthio Camelus, as 
well as the form and habits of the Ostrich, show in- 
deed arelation of analogy to the Camel; but then 
we are to recollect, in the first place, that the Os- 
trich is at the osculant point or confines of the 
orders of Gralle and Rasores; and secondly, that 
such slight variations of the parallelism of analogy 
often appear, although I think it possible that even 
these are subject to rule.” 

R 2 


244 


“The analogy of the Rasores to the Rumi- 
nating Animals was first, I believe, mentioned 
by Linneus in the ‘ Systema Nature.’ It has 
since his days been copied and copied, until 
now it almost becomes a sort of heresy to in- 
quire into its accuracy. I am not, however, 
aware that any reason for this analogy has ever 
been assigned, beyond the fact,—that one order 
affords the principal part of those birds which 
are domesticated by man for purposes of food ; 
and the other, the principal part of sbseag sain 
which are destined to the same purpose. Now, 
granting even this domestication not to be the 
work of art, but to be an analogy really existing 
in nature, | would observe,—setting the whole 
family of Anatide aside,—that the Glires 
afford us many eatable or domesticated animals, 
suchasthe Capromys and Rabbit ; and the Gral- 
latores afford us similar instances in the igor a 
and Psophia. If some Rasores be said, like 
the Pecora, to have ornamental appendages to 
the head, so it must be remembered has the 
Crowned Crane; whereas no rasorial bird is 
truly horned, like the Palamedea. But it may 
be worth while to take into consideration suc- 
cessively the grand characteristics of the Ra- 
sores, as given by ornithologists to distinguish 
them from all other birds. 

“The Rasores are, properly speaking, frugi- 
vorous birds; by which I do not mean eating 
fruits only, but all manner of seeds or grain. 
Now this character of being frugivorous applies 
much more to the Glires than the Ungulata, 
which are truly herbivorous, and only feed on 
grain in an artificial or domesticated state. To 
begin, then, with the rasorial or scratching 
powers of gallinaceous fowls; these are cer- 
tainly the most burrowing of frugivorous birds: 
now the most burrowing of frugivorous quad- 
rupeds are certainly not the Ungulata, but the 
Glires. These birds are characterised by the 
shortness of their wings and the weakness of 
their pectoral muscles. Now if we inquire 
whether it is among the Glires or Ungulata 
that we find the corresponding fae of 
the vertebral axis,—that is, the fore-feet most 
shortened,—the answer will be, certainly not 
among the Ungulata; where, on the contrary, 


Animals typically. 
2. VERB Sics cecovses Carnivorous .........06- cece eet RAPTORES 
2. PRiMATES’.......-Ommivorous ........0.5..+++00+-2+ [NSESSORES. 
3) GLIRES! ov0056 55's Frugivorous .......... Sinla V6 nls Wit 3. Rasores. = 
4. UNGuLATA........ Frequenting the vicinity of water ....4. GRALLATORES. — 
5S. CRracka. 2... sds IRIE SAGO ss ba 0:0 Sak ees ea 5. NaTaToREs.” 


The additional knowledge of the organization 
of the Mammalia, and especially of the Mar- 
supialia, which has been acquired since the 
time of Cuvier, has led to corresponding im- 

rovements in their classification. A primary 

inary division of the class based on modifica- 
tions of the generative function has been esta- 
blished chiefly by the proofs that have been 
adduced of their co-existence with characteristic 
conditions of the nervous and vascular systems, 
as well as of the generative organs themselves. 
These primary groups or sub-classes I have 
named Pracentatia and ImpLacentatia, 


MAMMALIA. 


the Giraffe has them extraordinarily lengthened : 
but among the Glires we have the Jechaal f 
this respect almost a bird. In more= 
over, this latter order is distinguished, like the 
Rasores, by the strength of those muscles of 
the two posterior appendages of the ral 
axis or hind-feet, that contribute to locomotion 
Gregarious habits distinguish the most of 
Rasores ; so they do ina still more extraordi. 
nary manner the Glires. Many are insec 
vorous in both orders, and some are omni 
rous. The muzzle or facies of Glires is 
and round, very like that of Fere, there b 
a direct relation between the two orders. Th 
facies of Rasores is also short and round, ver 
like that of Raptores (the order analogous t 
that of Fere ); and there is also a direct rela. 
tion between these two orders. Many Ras 
perch and nestle on trees; so do many of th 
Glires. The Rasores generally feed on han 
grain, which they pick up with their hook 
beak, and masticate in a triturating giz: 
the Glires feed also on hard substances, 
they gnaw with their strong hooked incisor 
and masticate with their grinders. In bot 
orders the thumb is very often rudimer 
In both orders the tail varies from an extraor 
nary length, as in the Squirrel and Pheasant 
to being very short, as in the Hare and Par 
tridge,.......No orders in their respective 
classes present the tail so spread out am 
flattened as the Glires and Rasores,—witne: 
the Beaver and Peacock. In both orders t 
sense of hearing is much developed. In be 
orders we find animals, such as Squirrels at 
Pigeons, with their toes perfectly free; a 
others, as Hydromys and Phasianus, w 
have them united at the base by a membran 
Castor is an aquatic animal, having some 
tion to Cetacea ; Struthio is a terrestrial anim 
approaching to the Natatores. And so on reli 
tion comes so fast upon relation, that I know not 
how we can for a moment hesitate to place 
Glires opposite to the Rasores. 
“ 1 conceive it now to be demonstrated, - 
so far as relates to the analogies existin 
nature between the orders of Mammalia 
Aves, we ought to place them thus :— 


re 


ro 


indicative of the adherence of the ovum 
uterus in the one, and its non-adhe , a 
the ovo-viviparous reptiles, in the other gro 
Taking the orders as they are defined 
characterised by Cuvier, the progression 
their affinities, so far as they can be gi 
linear series, seems to be as follows :* ; 
Class —-MAM MALIA. “ 
Sub-Class—PLACENTALIA, 

Orders. — I. Bimana. II. Quadruman 


* See the excellent Catalogue of the 
in the Museum of the Zoological S 
George Waterhouse, Esq. Curator. 


PLC 


be 


MAMMARY GLANDS. 


III. Cheiroptera. 1V. Insectivora. V. Car- 
nivora. WI. Cetacea. VII. Pachyder- 
ma. VIII. Ruminantia. 1X. Edentata. 
X. Rodentia. 5 
Sub-Class—IMPLACENTALIA. 
XI. Marsupialia. XII. Monotremata. 
The aim of the subjoined table is to express 


245 


the mutual affinities and inter-dependencies of 
the several orders of Mammalia, rei points 
at which they are most nearly related to the 
inferior classes of the vertebrate animals. The 
annectant genera, some of which are extinct, 
are printed in italics, the orders and classes in 
Roman capitals. 


BIMaNa. 
QuADRUMANA. 
i] | 4 | | | 
Galeopithecus. Lemur. : Cheiromys. : 
Bradypus. Didelph YS. 
-CHEIROPTERA........ CARNIVORA........ | .......- RODENTIA...... MARSUPIALIA. 
Cu ie 


INSECTIVORA.... 
Otaria. 
CETACEA... 


Pterodactylus. — Ichthyosaurus. 
| 


AVES. PISCEs. 


MAMMARY GLANDS.—Syn. Les glandes 
mammaires, Fr., Die Milch, die Brust-drisen, 
Germ. These important organs of secretion 
are the peculiar characteristic of the highest 
division of the animal kingdom, Mammalia. 
Tn a physiological point of view they should 
be regarded as uterine appendages, as a por- 
tion of that series of instruments which Na- 
ture has provided in greater or less number, 
according to the ultimate perfection of the 
animal, for its gradual development. Their 
close proximity to the ovarian apparatus in 
some Mammalia, the cetacea for instance, and 
their peculiar structure and function in the 
Marsupiata, confirm this view of their phy- 
sidlogical character. It is interesting to trace 
how gradually they have been removed from 
their caudal position to the atlantal portion of 
the body, so that in the human species, where 
the instincts are subjugated to the control of 
reason, and the helplessness of the infant has 


_ been made the means of moral training to the 
_ mother, these organs are brought towards the 


anterior, the nobler portion of the body. 
_ _ It must not, however, be supposed that this 
_ change of position is sudden, any more than 


« 


_ any other step in the scale of progressive deve- 


lopment of organized beings. Formerly it was 
supposed that the re-connection of the ovum to 
the mother through the medium of bloodvessels 
collected into a placenta was as universal 
throughout the class Mammalia as the presence 
_ of these glands; but the careful researches of 
Professor Owen have proved that the Marsu- 
_ piata and most probably some of the Mono- 
_ tremata form an exception to this rule. The 
_ fact is interesting in reference to the present 
| Subject from the greater importance which is 


ra 


np © si MENTMEM SS coco s 
| aren 
Glyptodon. Toxodon. Moschus. 
e —J 


wes. .PACHYDERMATA,... RUMINANTIA. 


.. MonorREMA, 


eee ee eee 


RepTiLia. 


(R. Owen.) 


given to the mamma in consequence of the ab- 
sence of this vascular connection, and the addi- 
tion of accessory structures which are absent in 
the more perfect mammalia. 

The arrangement of the secreting membrane 
of mammary glands has been universally found 
to be vesiculated, the only difference in differ- 
ent classes of animals consisting in the extent 
of secreting surface, owing to differences in the 
size of the cells, and their greater or less concen- 
tration within a circumscribed space. This 
vesiculated structure was described in 1751 by 
Duvernoi* in the hedgehog (Trans. of the 
Petersburg Academy), and in the human spe- 
cies it was discovered by Cruikshank, and de- 
scribed in his work on the absorbent glands, the 
second edition of which was published in 1790. 
At page 209 his words are, “ The acini are 
small vesicles like Florence flasks in miniature ; 
in these, the arteries secreting the milk termi- 
nate ; and from these the excretory ducts, or the 
tubes carrying off the milk take their origin. 
The existence of such vesicles has been doubted ; 
Dr. Hunter doubted till my injections con- 
vinced him of the fact.” He then goes on to 
explain his ‘method of injecting, and concludes 
by saying that preparations exhibiting this fact 
may be seen in the anatomical collection in 
Great Windmill-street, which he had made 
fifteen years previously. 

Miiller, to whom the above fact was known, 
states that Mascagni recognised and demon- 
strated the vesicular ends of the lactiferous 
tubes and the absence of all direct commu- 
nication .with the bloodvessels, in his Pro- 
dromo della Grande Anatomia, Firenze, 1819. 


* Miller de gland. &c. 


246 


He refers also to*the observations of Buffon 
on the vesicles of the mamma of the horse, 
ox, and goat; to those of Von Baer on the 
vesicles in the mamma of the Delphinus Pho- 
cena, to those of Van Hoeven and Vrolik in 
the same, and in the Balena rostrata, and of 
Meckel in the Ornithorhynchus, adding ori- 
ginal observations and illustrations of his own, 
which demonstrate the same vesiculated struc- 
ture in the hedgehog and rabbit. 

During the course of the present year, 1840, 
the anatomy of the human breast has been des- 
cribed in a manner by Sir A. Cooper that leaves 
us nothing to desire, and the minuteness and 
accuracy of his descriptions are only equalled 
by the beauty and fidelity of the plates which 
represent the interesting results of his labours. 
In our description, therefore, of the human 
breast we shall do little more than draw from 
this deep well of instruction. 

Human mamma.— The position of the human 
mamme upon the pectoral muscles is too well 
known to require any detailed account. 

The nipples project forwards and outwards 
with a slight turn upwards, a direction which 
is beautifully adapted to the position of the 
infant when lying in its mother’s arms; and the 
abundance of the lactiferous tubes at the lower 
“paiey of the breast, as will be more particu- 
arly described hereafter, forms a soft cushion 
for the head of the child to rest upon. 

“ The margins of the breast,” ae Sir Astley 
Cooper,* “do not form a regular disc, but the 
secreting structure often projects into the sur- 
rounding fibrous and adipose tissue so as to 

roduce radii from the nipple of very unequal 
engths, and a circular sweep of the knife cuts 
off many of its projections, spoils the breast 
for dissection, and in surgical operations leaves 
much of the disease unremoved.” 

At the age of puberty and for some time 
after, if the breasts are not called upon to per- 
form their office, they present to the touch a 
dense, compact, smooth, and equal surface ; 
but the distension of the cells in lactation 
stretches and relaxes the uniting cellular and 
fibrous membrane, and separates it into “ small 
bodies with indentations around them.” This 
lobulated character does, however, supervene 
even in childless women upon the cessation 
of the sexual secretion. 

Following the arrangement of Sir A. Cooper, 
we shall consider the individual parts of the 
breast from without inwards. 

The nipple is not placed in the centre of the 
breast, but nearer the abdominal margiu of the 
gland. In the virgin it is a rounded cone and 
nearly smooth until puberty, but in the lactating 
woman forms a flat surface, cribriform with the 
lactiferous tubes in the centre. “ At 16 years 
it is slightly wrinkled; at 17 it has small 
papilla upon its surface; from 20 to 40 years 
the papille are large; from 40 to 50 the nipple 
becomes wrinkled; from 50 to 60 the nipple 
is elongated ; and in old age it usually has a 


warty appearance.” 
This alteration in form during lactation, the 


* Page 13. 


MAMMARY GLANDS. 


extremity becoming the broadest bes nders- 
the adhesion of the child’s mouth firmer and 
more complete. F. 

The nipple or mammilla consists of the com= 
mon integuments, fascia, milk-tubes, od- 
vessels, nerves, and connecting cellular mem- 
brane. re 

The cuticle offers no peculiarities except t 
processes which it sends into the lactifero 
tubes, which may be drawn out after continus 
maceration. Its extreme delicacy is well kno 
to the medical practitioner. 

Sir A. Cooper states that the rete muco; 
“enters with the cuticle into the lactife 
tubes.” This may be better seen in the lat 
quadrupeds, where they terminate a few ling 
from the extremities of the tubes, forming 
fringed edge. “a 

“ Cutis of the nipple—This forms a consit 
able portion of the mammilla, and it is divi 
into two surfaces when the breast is ima s 
of lactation. 

“The first forms the dise or circumfer 
of the nipple, and the second its bro 1, 
truncated apex, in which the nat 
of the milk-tubes may be seen in numel 
orifices. ee 

“ The disc is composed of a numb 
papille, which produce a vascular and s 
surface, and which form its erectile and h 
sensitive tissue. 

“ The direction of these Loge is fro 
base towards the apex of the nipple, so 
they are pushed back as the mammilla 
the mouth of the child, and thus gre 
ment is produced. 

“ They lap over be truncated extrem 
nipple, forming a foliage upon its apex. 
folinted charéete is one of the me 
of gestation. 

“ They form in their arrangement upon 
nipple broken portions of circles, but # 
the nipple is elongated and dried they ap 
to be spiral. 

“They form flaps, which are at their ec 
divided into numerous projections, with ser 
depressions between them. } 

“ They are directed forwards towards the 
of the nipple, and the papille of the chil 
lips passing from within outwards, meet th 
in sucking, are received between them, in 
mix with them, and produce conside 
adhesion and sensation. : 

‘“ They are very numerous and large foi 
size of the part, and rather spongy at 
extremities. a 

“ They are very vascular bodies, and I 
given a figure of them injected. The mi 
arteries which pass from the base towards” 
apex of the nipple send numerous branch 
the papille cutis, which divide into little bus 
of vessels in each papilla and te 
veins. 
“ The veins also are very numerous, a 
will be seen injected, forming bushes 
to the extremities of the arteries. 

“ The application of the child’s lips, the dra 
ing of the nipple in the motions of the child’ 
head, and the suction produced by its moutl 


ity: 
ban 


erm. 


MAMMARY GLANDS. 


produce so much excitement as to occasion 
erection of the nipple.” 

The nipple is carefully connected with the 
gland by means of a firm fascia encircling the 
lactiferous tubes derived from the general 
fibrous tissue of the breast and thorax. 

The areola.—This term has been applied to 
the coloured circle which surrounds the nipple. 
It is smooth until the period of puberty, when 
it becomes slightly tuberculated. Its diameter 
inachild is about half an inch; at puberty 
and in young women double that size, and 
during lactation is as much as two inches or 
more, not again changing except in very old 
age, when it almost disappears. 

The change of the colour of the areola from 
a reddish tint to a dark brown as the result of 
impregnation is well known to the practitioner. 
The cuticle is thin as in the nipple. Speaking 
of the cutis of the areola Sir A. Cooper 
observes, that “ when the areola is examined 
with attention after the separation of the cuticle 


A front view of the nipple and areola} shewing the 
foliated appearance of the papille and the numerous 
but smaller papille of the areola. 
This and the following figures are all taken from 
Sir A. Cooper’s work. 


247 


and rete mucosum, its surface is found to be 
covered with papille like those ofthe nipple, 
but of smaller size, although stiil extremely 
distinct. They are smallest at the circumference 
of the areola, but gradually increase in size as 
they approach the nipple. They are disposed 
in circles, their bases fixed in the cutis, and 
the apex of each is directed towards the nipple, 
so that they are opposed to the papille of the 
lips of the child. They are very vascular and 
sensitive bodies”. (See fig.71.) The whole 
structure of the areola points to it as a continu- 
ation of the nipple. 

The nipple and areola are lubricated by the 
secretion of especial mucous follicles which 
surround them, called by Sir A. Cooper the 
tubercles of the areola. “ These glands are 


extremely vascular, lobulated, and cellular. 
Each orifice opens into an arborescent vessel or 
vessels.” (See fig. 72). 


A tubercle filled with yellow injection and twenty-three 
times magnified. These are the tubercles which 
have been supposed by anatomists to produce milk, 
and to have communication with the lactiferous tubes, 
From which, however, they are separate and dis- 
tinct. They secrete a mucous fluid, which has 
more the appearance of gruel than milk, 


A section of the mammary gland through the nipple, shewing the ducts over a bristle unravelled, and pro- 


ceeding to the posterior part of the gland. Th 


e ligamenta suspensoria may be seen passing from the 
anterior surface of the gland to the skin, supporting the folds or processes of the former, 
considerable cavities between them, in which the fat is contained in its proper membrane. 


and leaving 
The fascia 


may be observed passing to each extremity of the gland and dividing into two portions; the anterior 


oceedi the surface of the gland to form the | 
a ae. or rctoes which a ole quantity of fat is contained; and both these layers 
assist in producing the fibrous tissue of the gland. 


gland, sending 


ia; the posterior behind the 


It also sends processes of fascia backwards to join 


the aponeurosis of the pectoral muscle, b, b, forming the line from one extremity of the gland to the other. 
The section, mente, clearly shews the. various cords by means of which the breast is slung and 


‘sustained, a, a, the fascia. 


248 MAMMARY 


We must next direct our attention to the 
internal structure of the breast, first as regards 
the protective arrangements. 

e fascia enveloping the breast, like the 
tunica albuginea of the testicle, sends in pro- 
cesses to support and protect the secreting 
membrane of the gland and suspend it in its 
Situation. These processes are all denomi- 
nated by Sir Astley the ligamenta suspensoria, 
(fig. 73). The ends of these ligaments are 
spread out and incorporated with the posterior 
surface of the skin, and give it whiteness and 
firmness.” 

The secerning portion of the gland con- 
sists of the minute cells which were referred to 
at the commencement of this article, and we 
learn from Sir A. Cooper that “ their size in 
full lactation is that of a hole pricked in paper 
by the point of a very fine pin; so that 
the Gallles, when distended with quicksilver 
or milk, are just visible to the naked eye. 
( Fig. 74.) They are rather oval than round, 


Fig. 74. 


Shews the origin of the ducts 
from the milk cells, (injected 
with quicksilver and magnified 
four times. ) 


being slightly elongated where the bunch of 
the lactiferous tubes springs from them; but 
they appear more rounded to quicksilver, and 


Fig. 


A view of the preparation of six milk tubes 


c, c, ec, the branches of the mammary ducts. 
d, d, d, d, their glandules. 


injected from the nipple. 
a, a, a, the straight or mammillary Sabon, f Hy 
b, b, b, the reservoirs or dilatations of the du 


GLANDS. 


when distended with milk than when filled” 
with wax.” 
These minute cells or cellules are bound up — 
together so compactly as to form little bodies” 
or “ glandules,” varying in size from a pin 
head to that of a small tare. When se ed | 
from the rest of the gland but attached to the 
mammary duct, which originates in se » 
branches from its cellules, it presents a 
mose appearance. 
From the cedlules the milk-tubes originate i 
a radiate form by small and numerous branches, 
They increase in size by repeated unions, an 
terminate by five or six branches in dilatations 
the “ reservoirs” of Sir Astley. “ These re 
tacles are of a conical form (see fig. 75) 
the mammillary tubes, and they begin fre 
the extremities of the larger branches of the 
milk-tubes and terminate in the straight du 
of the nipple.” ' 
In most other classes of the Mammalia th 
reservoirs are much larger than in man, wher 
they hardly deserve the title, and in the cow 
they are so capacious as to be capable of cone 
taining at least a quart. d 
The different ducts of these reservoirs take 
straight course, diminishing in size, 
the nipple to its extremity, where they te: 
in a cribriform manner, with very con 
orifices, varying in size from those of a k 
to a common pin. Their number is 
twenty. w 
Arteries—The mamma receives its — 
ply of blood from branches of the internal 
mammary, axillary, and intercostal eries. 
Sir Astley divides them into anterior and pos- 
terior, the former passing from the axillary 
artery and the latter from the internal mame 


t 


nrouw 


75. 


proceeding from the apex of the nipple, 
cts. 


MAMMARY GLANDS. 


mary, and there is generally a large vessel 
entering the pectoral or costal surface of the 
_ breast and sending its branches through the 
gland to meet the others upon the surface of 
the organ. The branches from the axillary are 
given off by the superior and long thoracic 
_ arteries; those from the internal mammary are 
_ either derived directly from that vessel or from 
_ its intercostal branches. “ The arteries upon 
_ the cutaneous surface of the breast are lodged 
in the festoons formed by the ligamenta sus- 
_ pensoria, and proceed to the nipple. There 
their extreme branches pass each other at the 
_ base of the nipple. They send branches for- 
_ wards from the base to the apex of the nipple, 
_ which are parallel to each other and divide into 
_ Yery minute branches which supply the papille 
: and the ducts. They also send branches from 
_ the base of the nipple backwards into the 
_ gland at its centre, and they freely anastomose 
_ with those arteries which enter the back of the 
gland, and they then distribute their ramifica- 
_ tions to its substance.” 
__ Veins.—“ The branches of the veins arising 
_ from the nipple pass from its papille in parallel 
_ branches to its’ base, and then form radii to an 
_ ellipse behind the areola at its margin.” Their 
minute divisions in the papille with the cor- 
responding divisions of the artery constitute 
the erectile tissues. From the ellipsis of veins 
four principal branches proceed, beside others 
which are less important: these are distri- 
_ buted on the fore part of the breast, forming a 
_ net-work by their free anastomoses. 
4 They terminate, 1st, by two large branches 
in the axillary vein, and by several branches in 
_ the vein accompanying the arteria thoracica 
_ longa; 2d, in the cephalic; 3d, in the internal 
-Mammary vein by branches which pass between 
g cither the first and second or the second and 
_ third ribs; 4th, by a deep-seated vein which 
_ enters the fourth mammary intercostal vein ; 
_ 5th, a plexus of veins passes over the clavicle 
to terminate in the external jugular and sub- 
clayian veins. 

Nerves.—These are derived from the dorsal 

_ division of the spinal cord. The third dorsal 

nerve descends upon the vessels which are distri- 
_ buted to the nipple and gland, the fourth and 
fifth are distributed directly to the breast, and 
_ the sixth sends some filaments upon the extre- 
_Mities of those arteries which have passed the 
_ nipple, but which send branches into the gland. 
_ It also receives a supply from the grand sym- 
_ pathetic nerve. 

Absorbents.—These vessels are described by 
Sir Astley Cooper as follows :— 

“ These vessels always exist in great numbers 
in the breast, and when the gland is in a state 
of lactation they are readily injected and 
demonstrated. 

“They are divided into a superficial and 
deep-seated order. The first are cutaneous 
and are most connected with the nipple and 
the mucous glands of the skin, and the second 
arise from the interior of the glandular and 
secretory structure of the mamma. 

“The superficial arise from the nipple, 


249 


and they pass principally upon the surface of 
the gland, behind the skin, Opts axillary 
side. 

“ In my injections I find them as follows :— 

“ First, they pass upon and then under the 
superficial fascia, and between it and the 
aponeurosis of the pectoral muscle. They are 
next continued over the intercostal muscles. 

“ Here they enter the absorbent or cribriform 
Opening, or sometimes there are two openings 
in the fascia axilla, as it there passes from the 
edge of the pectoralis major to that of the teres 
major and latissimus dorsi muscles, and which 
fascia shuts up and forms the floor of the 
axilla. 

“« Having passed through this fascia into the 
axilla they enter the first set of axillary absorb- 
ent glands, and form a considerable plexus of 
absorbent vessels between them. 

“‘ They then rather descend to the third and 
fourth ribs to enter another set of absorbent 
glands, which are placed between the third and 
fourth ribs and second and third intercostal 
spaces, and they then ascend to the second 
rib. 

“ Here they form a large and elaborate 
plexus upon the axillary vein, from one to two 
inches below the clavicle, and reaching the first 
rib they again enter absorbent glands. 

“« From these glands, situated upon the first 
rib, an absorbent trunk is formed, of the size of 
a large crow-quill, which is placed close to the 
inner side of the axillary vein and between the 
first rib and the clavicle, and this absorbent 
trunk terminates at the angle formed between 
the right jugular and right subclavian vein, 
where the absorbents of the right arm and those 
of the right side of the neck also end in the 
veins. 

“ There is an opening formed for this vessel 
under the costo-clavicular ligament with a 
distinct margin on each side. 

“ The place of termination of the absorbents 
in the vein is a little above and behind a line 
drawn from the middle of the clavicle above 
the first rib. 

“On the left side the absorbents of the 
breast form a similar absorbent trunk, which 
terminates at the angle of the left jugular and 
subclavian veins, at which angle the thoracic 
duct also ends. 

“ Besides this course of the absorbents from 
the breast and through the axilla there are 
other absorbent vessels which pass behind the 
axillary vein, artery, and axillary plexus of 
nerves to join the absorbents of the arm. They 
also pass through several absorbent glands, and 
ascending before the axillary plexus of nerves, 
they mount behind the clavicle and before the 
axillary bloodvessels, to terminate on each side 
at the angle of the jugular and subclavian 
veins. 8 

“« Thus there are two courses of the absorbents 
from the breast through the axilla; one internal 
to the bloodvessels and between them and the 
ribs ; the other, which is more external, joins 
the absorbents of the arm, and passing behind 
the vessels and nerves of the arm, then crosses 


250 


the nerves and the axillary artery to enter the 
angle of the jugular and subclavian veins. 

“Tf, therefore, the absorbent glands in the 
axilla are obstructed by disease of the breast, 
other absorbent vessels carry their fluid into the 
absorbents from the arm, and when their glands 
are obstructed other absorbent or lymphatic 
vessels are found to pass behind the scapula 
from the axilla to enter the cervical glands 
above and behind the clavicle. 

“ The absorbents of the sternal side of the 
nipple principally take two courses. 

‘The first accompany the vein and the 
artery to the second intercostal space between 
the second and third cartilages of the ribs, and 
penetrating the intercostal muscles, they pass 
to the anterior mediastinum, where they accom- 
pany the internal mammary artery and vein, 
and enter some absorbent glands. 

« A set of absorbent vessels from the sternal 
side of the breast, placed lower down, enter 
the intercostal muscles between the fourth and 
fifth cartilages of the ribs, and join the former 
in the anterior mediastinum. 

« After entering the anterior mediastinum a 

of those which pass from the right breast 
join some vessels from the convex surface of 
the liver, and are continued into the angle of 
the right jugular and subclavian veins, whilst 
those absorbents of the left breast which enter 
the anterior mediastinum pass to the angle of 
the left jugular and subclavian veins. 

“The deep-seated absorbent vessels which 
can be best injected from the ducts and milk cel- 
lules whilst the breast is in a state of lactation, 
arise from the mucous membrane of the lacti- 
ferous tubes and milk-cells, and form a plexus 
of great beauty in the interior of the gland. 

«“ These numerous absorbents, as seen in the 
preparation, unite into two principal vessels, 
which pass into the axilla, and there enter the 
same absorbent glands as those which receive 
the superficial absorbents. 

Those on the sternal side of the nipple pass 
into the anterior mediastinum, though some 
of them turn round above the nipple and enter 
the axillary glands. 

“« The deep-seated absorbents, many of them, 
join the superficial upon the convex or cuta- 
neous surface of the breast, and after passing 
through the glands in the axilla terminate with 
them at the angle of the jugular and subclavian 
veins. 

«“ But the absorbents of the concave or costal 
surface of the breast take a different course. 
They penetrate the intercostal muscles behind 
the breast and enter absorbent vessels which 
accompany the aortic intercostal arteries on the 
axillary side of the breast, but on the sternal 
side they join the internal mammary inter- 
costals ; the former pass into the thoracic duct 
in the posterior mediastinum ; the latter enter 
those vessels in the anterior mediastinum which 
I have already described.” 

The effect of age upon the mamma is to 
absorb its glandular structure, to load the ducts 
with mucus, to obliterate the milk cells, to 
excessively ossify the arteries, and to thin and 


MAMMARY GLANDS. 


wrinkle the nipple, and at length in a great 
degree to absorb it. But the deposition of fat 
occupying the place of the glandular structure, 
the general contour of the breasts in fat pe 
is maintained. 

On the mammary glands in the m 
credit of discovering the intimate structure 
this gland in the male is entirely due to Si 
Astley Cooper; nothing, we believe, wha 
ever having been known on the subjec 
vious to his researches. Its size 
different individuals; it is largest in 
light complexion and effeminate app 
‘“« The largest male glands which I have see 
says this author, “ were found in a man 
testes were remarkably small.” 

In some persons it is no bigger than a larg 
pea, in others an inch and a half or even 
inches. There are papilla on the nipple 
in the areola of the male as in the female, 0 
they are more minute and much less 
The cutaneous glands and tubercles are y 
similar in both sexes. ‘ 

“ The gland is constituted of two parts: 
first, of very minute cells, and, second) 
small conical ducts which divide into: 
rous branches in the glands, and termi: 
straight ducts which end in very minute orifi 
atthe nipple. In their form, in their 
sions, and in their course through the 
they all form a miniature resemblance 
gland and vessels of the mammary glan 
the female.” (Fig. 76.) The whole is § 
ported by a firm fascia, as in the female. 


Fig. 76. 


a 


Five ducts of the male gland, injected with | 
silver, exhibiting its ramifications and cells. 
ducts divide much in the same manner as those 


Semale. a 


Murat and Patissier, in the article 
refer to a case related by Dr. Renault of 
individual whose mamme were equal in siz 
those of the female and emitted a serous 
having the appearance of milk. The org 
generation were diminutive, the testicles a 
the size of a small nut, and his penis” 
mere tubercle, and, even in a state of ere 
only an inch and a half in length. Nev 
less he was given to venereal imtercourse 
all the usual habits of men. M 

This discovery of the glandular strz 
the male breast explains, most satisfac 
the cases which are on record of the sustena 
of the infant by the male parent after the dea 
of the female, the most authentic of whi 
is related by Humboldt in his travels. 


* Dict. des Sciences Méd. 
+ Vol. iii, p, 58. 


MAMMARY GLANDS. 


Although the usual number of mamme in 
human species is only two, still there 
are exceptions and instances on record of 
more having been developed. One of the 
best authenticated and most recent of these 
cases is related by Dr. Lee, in the Transac- 
tions of the Medical and Chirurgical Society 
for 1837.* 

In this instance “ the inferior or pectoral 
mamme were fully developed and in the na- 
tural situation, and their nipples, areole, and 
glands presented nothing unusual in their ap- 
pearance. Near the anterior margin of the 
axilla, a little higher up on each side, was si- 
tuated another mamma, about one-sixth of the 
size of the others. The nipples of these were 
small and flat, but when gently pressed, a 
milky fluid which had all the external cha- 
racters of the milk secreted by the other breasts, 
flowed copiously and readily from several ducts 
which opened on their extremities. When 
milk was drawn from the lower breasts, a small 
< preiel usually escaped from the nipples of 

e superior breasts, and when the draught 
came into the former, the latter invariably be- 
came hard and distended.” The flatness of 
the nipples prevented her suckling her children 
by them. Dr. Lee, inthe above paper, quotes 
five other cases from foreign authors of qua- 
druple mamme, also stating that “ in some 
women only one breast has been developed ; 
others have had two nipples placed on one 
mamma; and a few individuals have had three 
breasts, two in the natural situation and a third 
situated in the middle of the two others. Only 
one case has been recorded of five mamme in 
the human subject.” + 

Comparative anatomy.—In considering this 
division of our subject we shall especially di- 
rect our attention to those points in the anatomy 
of the mammz of animals which possess a phy- 
siological interest, omitting minute anatomical 
details unless they bear upon general principles. 
These organs in the Kangaroo, one of the Mar- 
supiata, as we have already hinted at, are 
peculiarly formed, for the young of these ani- 


_ mals, when first removed from the uterine cavity 


of its parent, is more like an earth-worm in its 
appearance than the active animal by which 
it is produced. So helpless is the condition of 


_ this young animal that it has not been inap- 


propriately called a mammary fetus, for the 


_ Mamme, in this instance, act at first like a true 


_ placenta as a permanent conductor of nutri- 


ment, and not, as in the higher Mammalia, 
a mere storehouse to be resorted to occasionally. 
Indeed, so close is the union between the pa- 
rent and its offspring, and so imperfect the 
power of the foetus to abstract nourishment by 
suction, that Geoffroy St. Hilaire had recourse 


_ to the hypothesis that there was some vascular 


connexion. But the imperfect power of the 
feetus is compensated by the addition to the 
breast of a muscular apparatus, which propels 
forwards the nutritious juices of the mother 
into the alimentary cavity of the helpless 


* Page 266. 
¥ Dict. des Sciences Méd. tom. xxxiv. p. 529. 


251 


young one. From the interesting account 
which Mr. Morgan has given of these glands* 
in the Kangaroo, we shall extratt the following 
particulars. 

In this animal there are four teats, two of 
which, in the virgin state, are at the bottom of 
a narrow pouch in which they lie hid. It is to 
one of these teats that the marsupial fcetus is 
attached immediately after its removal from the 
uterus, and their size, at first small in accord- 
ance with the minute mouth of the animal, in- 
creases with its growth. The muscular appa- 
ratus above alluded to embraces both the teat 
and the gland, and acts from the marsupial as 
its fixed point. The teat is further provided 
with a true vascular erectile tissue. 

The upper or smaller gland is perfectly 
similar in its organization to the larger, and, 
notwithstanding the doubts which Mr. Morgan 
expresses regarding its use, Mr. Owen observed 
in the instance which he has so carefully re- 
corded in the Philosophical Transactions for 
1834, that the fwetus was attached to the upper 
and not the lower nipples, and “ that the 
nipple in use by the young one of the previous 
year was the right superior or anterior one.” 
With regard to their minute structure it would 
appear from the figures of Mr. Morgan that the 
lacteal tubes originate in plexuses and not in 
cells, but the text is not very precise on this 
point. 

The consideration of the existence of these 
organs in those bird-like Mammalia, the Orni- 
thorhynchi, or duck-billed moles of Australia, 
is interesting. For the beak-bearing mouth of 
the adult would not lead us to expect the ex- 
istence of a gland, the secretion of which is 
usually obtained by the action of a soft mouth 
convertible into a sucking apparatus. 

Nevertheless a distinct mammary gland was 
described and figured by Meckel in 1826; and 
an organization of the lips and tongue of the 
young animal to correspond with it was sub- 
sequently described by Professor Owen in the 
Trans. Zool. Society, vol. i. p. 228, 1834. 

According to Meckel this gland is placed 
on the side of the abdomen between the pan- 
niculus carnosus, to which it adheres loosely, 
and the obliquus descendens abdominis, stretch- 
ing from the anterior and external margin of 
the pectoral muscle and inferior extremity of 
the sternum to the thigh. Its great size is 
merely one among the many instances which 
we meet of the comparative want of con- 
centration of individual organs in the lower 
as contrasted with the higher animals, for the 
secreting surface itself is much less extensive 
than in those animals in whom the whole organ 
is much less. 

The mammary glands of the Ornithorhyn- 
chus are peculiar for the absence of the nipple, 
a deficiency which is not met in any other 
class.. In the Cetacea it is so completely bu- 
ried and concealed that it has been described 
as absent, but it exists perfectly formed, 
buried in its protecting fissure. The defi- 
ciency in the first and concealment in the last 


* Linn. Trans. vol. xvii. 1828. 


252 


has a relation to the aquatic mode of 
life, the whole surface of the body 
being constructed with the view of 
avoiding friction. The mammary gland 
in the Ornythorhynchus consists inter- 
nally of pyriform cocal pouches, with 
their bases turned towards the skin, 
their apices communicating with short 
excretory ducts; the walls of these 
pouches are thick and the cavities nar- 
row. As regards simplicity of the in- 
ternal arrangement of the gland, that in 
the common porpoise, where the cells 
and milk tubes are large and diffused, 
may be placed next in order to the 
Ornithorhyrchus. 

There is no reason for supposing 
that there is any essential departure 
from this kind of arrangement of the 
secreting portion of the gland in dif- 


Fig. 78. 


One of the clefts a little open, to shew the end of the 
mamill@ buried in it. 


Fig. 79. 


Shews the cleft more open, exhibiting the nipple and 
its orifice poh iors into it. These clefts are placed 
tn their natural direction in the long axis of the 
animal, but fig. 77 is not. 


ferent animals, the cellular or vesicular having 
been met with in all instances where this 
gland has been carefully injected and un- 
ravelled. But the efferent ducts vary con- 
siderably. We learn from Sir A. Cooper that 
the cow, the ewe, the goat, the guinea-pig, and 
the porpoise, have only one tube in each 
teat. The pig has two, the rhinoceros has 
twelve, and the hare and rabbit and the cat 
and bitch several. “ In the Graminivora the 
reservoirs are enormously large, in the Carni- 
vora comparatively small. In the pig there is 
scarely any reservoir; in the porpoise the great 
enlargement of the milk-tube is a substitute for 
the reservoir.” 


MAMMARY GLANDS. 


3 the situation of the clefts in the skin of 
which contain the mamilla, and which are placed on each 
of the anus and os externum vaginge. They are ¢ 
smaller than nature in this drawing, but figs. 78 and 79.4 
the natural size. 


Fig. 77. 


= me ary 
So 


Pe oe 5 Fo SS = 


ss 


Morbid anatomy.—It must be clearly un 
stood by our readers that we do not intend te 
more than a mere outline of its diseases, ¢ 
must refer them for more ample information 
the admirable works of Sir A. Cooper 3 
others. The diseases of the breast have be 
divided by Sir A. Cooper into three class 
“‘ first, those which are the result of comm 
inflammation, whether it be acute or chron 
Secondly, into complaints which arise fro 
peculiar or specific action, but which are 1 
malignant, and do not contaminate other 
tures. Thirdly, into those which are not 
founded on local, malignant, and specific a 
tions, but which are connected with a pecu 
and unhealthy state of the constitution. a 

Simple inflammation of the breast, like 
flammation in every organ where its progre 
would rapidly prove destructive to its essen 
structure, is attended with excessive and ii 
ordinate pain, and thys gives such warnin 
the danger that it cannot be disregarded by 
sufferer. The fibrous protective covering of 
gland, like that of the testicle, prevents inordii 
swelling, but occasions greater hardness to: 
touch. This inflammatory action, usually 4 
unequivocal in its appearance, very rapidly ¢ 
velopes pus ; the abscess following is troul 
some and extremely obstinate in cure ; chro 
abscess does, however, occasionally oceur, 
absence of all the usual symptoms of infla 
mation masks the character of the disease 
gives rise to the suspicion that it is a ma 
tumour requiring extirpation. Sir Astle; 
lates some cases which came under his 
in which the sense of fluctuation indicate 
him the true character of the disease, 
others in which the extirpating knife of 
surgeon was only arrested by the flow of p 
This same author describes such occasi 
distension of one of the lactiferous tubes cau 
by chronic inflammation and obliteration of 
aperture as to simulate chronic abscess. T 
breast is liable to what has been called hyda 
disease, of which there are four kinds, one 
a malignant nature; the other three are not) 
The first has been designated by Sir A. Coope 
cellulous hydatids; the second is the sera i 
tumour of Sir B. Brodie; the third is the ani 


Ag 


MAMMARY GLANDS. 


mal or globular. Cellulous hydatids are sim- 
ple bags containing fluid. ‘The breast gra- 
dually swells,” says Sir A. Cooper,* “and in 
the beginning is entirely free from pain or 


tenderness; it becomes hard, and no fluctu- 
ation can then be discovered in it; it con- 


tinues slowly growing for months and even 
years, sometimes acquiring very considerable 
magnitude, the largest I, have seen having 
weighed nine pounds; but in other cases, al- 
though the bosom was quite filled with these 
bags, yet it never exceeded twice the size of 
the other breast.” After a time fluctuation 


Tay be felt and the cutaneous veins enlarge, 


—————————e 


but the breast continues free from pain and the 
constitution does not suffer. The tumour is 
moveable and pendulous, in some cases in- 
volving the whole gland, in others only a small 
portion. 

** When the swelling,+ and the breast in 
which it is situated, are examined, it is found, 
upon a careful dissection, that the interstices 


_of the glandular structure itself, and the ten- 


_ dinous and cellular tissue connecting it, are in 


cll ie 


a great measure filled with fibrous matter, 
poured out by a peculiar species of chronic 
inflammation, but in some instances a bag is 
formed into which a serous, or glairy, or some- 
times a mucous fluid is secreted, according to 
the degree of inflammation attending it, and 
this fluid, from its viscidity and from the solid 
effusion which surrounds, as well as from the 
cyst being a perfect bag, cannot escape into 
the surrounding tissues; but by its quantity, 
its pressure, and by the gradual yielding of the 
bag, it becomes of a very considerable size ; 
and yast numbers of these cysts are found to 


_ occupy each part of the breast, producing and 
_ Supporting a continued but slow irritation, and 


occasioning an effusion of fibrous matter, by 
which the breast forms an immense tumour 


_ consisting of solid and fluid matter. Within 


these bags of fluid, hydatids hang by small 
stalks.” ‘The size of these cells varies from 
the head of a pin to that of a musket-ball.” 
“ When the tumour requires removal for this 
disease, it is necessary to take away all the 
hardened and swollen parts of the breast, for 
they have cysts, or cells, formed in them; and 


_ if any cyst be suffered to remain, it will still 


_ continue to grow, and the remaining part of 
the breast to form an hydatid tumour. The 


_ great solace to the patient in this disease is, 


i 
2 
. 


that as it does not contaminate other structures, 
there is no danger of its extending by absorp- 
tion, of its producing any complaint beyond 
the breast, or of its affecting other parts of the 


_ body; nor have I seen it seated in both breasts 


at the same time.” 

Sir B. Brodie} has pointed out an important 
feature in the development of certain cysts in 
the breast, which are different from the true 
hydatid. This consists in the generation of a 
morbid growth or excrescence from their in- 
terior, which becoming organized sometimes 


__.™ Iilustrations of the Diseases of the Breast, by 
Sir A. Cooper, 1829. Part i. p. 21. 


+ Page 22, op. cit. 
_ £ Medical Gazette, Feb. 21, 1840. 


253 


entirely fills the cyst so as to convert it into a 
solid tumour, which ultimately protrudes ex- 
ternally as a fungous growth, afid presents a 
new and formidable appearance. “ In this 
last stage of the disease,* it is evident that 
spreading ulceration, sloughing and hemor- 
rhage, the usual results of an ulcer occurring 
in a diseased structure, must ensue, and that 
no remedy is likely to be ofany service to the 
patient, except the removal of the affected 
parts by surgical operation.” The operation is 
not recommended in the early stages of the 
disease, as these cysts sometimes become ab- 
sorbed previously to the development of the 
fibrous tissue. As the disease is merely local 
the operation is wholly unattended with danger. 
The term by which Sir B. Brodie designates 
these tumours is that of “ sero cystic tumour 
of the breast.”’ It appears probable that the 
bladder scirrhus of Dr. Benedict is nothing 
more than this form of hydatid disease. 

“ The third species of hydatidt+ which is 
found in the breast is the animal or globular, 
and which consists of a bag containing a fluid, 
which has no vascular connection with the 
surrounding parts; and it produces within its 
interior a multitude of bags similar. to itself. 
It is in fact a true entozoon similar in every 
respect to that found in the brain of sheep and 
in many other organs of the human frame.” 

“* When one of these hydatids,”} says Sir 
A. Cooper, “ is produced in the breast, an in- 
flammation is excited by it, and a wall of 
fibrine surrounds it, it feels hard, and from the 
small size of the hydatid a fluctuation cannot 
be discovered; but as the hydatid grows, 
although the quantity of solid matter increases, 
yet as the fluid in the hydatid becomes more 
abundant, a fluctuation in the centre of the 
tumour may be ultimately perceived.” 

The disease is not malignant, and if a sim- 
ple puncture and evacuation of its contents 
should not prove effectual in dispersing it, may 
be removed without danger. 

The chronic mammary tumour occurs early 
in life and unconnected with any diseased state 
of constitution. ‘ It grows,” according to 
Cooper, “ from the surface of the breast rather 
than from its interior, and it therefore generally 
appears to be very superficial, excepting if it 
spring from the posterior surface of the breast, 
when it is deep-seated and its peculiar features 
are less easily discriminated.” These tumours 
are unconnected with the glandular structure of 
the breast. Dr. Warren§ relates a case in which 
he removed one of these tumours from a young 
woman, who four years after the operation 
nursed an infant from the same breast. They 
are extremely moveable, frequently begin with- 
out pain, and continue many years without 
exciting any uneasiness. They vary in size, 
have a lobulated character, and are invested in 
a fibrous membrane. “ Although these tumours 
are not in their commencement malignant, and 


* Page 842, loc. cit. 
+ Page 45, op. cit. 
t Loc. cit. page 48. 
Surgical Observations on Tumours, Boston, 
1837, p. 211. 


254 


they continue for many years free from the 
disposition to become so, yet if they remain 
until the period of the cessation of menstruation 
they sometimes assume a new and malignant 
action.” The breast is not exempted from the 
deposit of either cartilaginous or ossific matter, 
and tumours of this character are occasionally 
developed in its substance. 

The breast is oceasionally enlarged by hyper- 
ae of the adipose tissue. A tumour of 
this kind, removed by Sir Astley Cooper, is 

reserved in the Museum of St. Thomas’s 

ospital, which weighed 14 lbs.100z. The 
whole structure of the mamma also has been 
found hypertrophied and the breasts enormously 
increased in dimensions without being appa- 
rently the subject of any disease. That all- 
pervading poison of some constitutions—the 
scrofulous tubercular matter—does not leave 
the mamma exempt from its influence. Sir 
Astley says that these tumours “ can only be 
distinguished from the simple chronic inflam- 
mation of the breast by the absence of tender- 
ness, and by the existence of other diseases of 
a similar kind in the absorbent glands of other 
parts of the body.” They produce no danger- 
ous effects, and do not degenerate into malig- 
nancy. 

“The breast is liable to become irritable 
without any distinct or perceptible swelling, as 
well as to form an irritable tumour composed 
of a structure unlike that of the gland itself, 
and which therefore appears to be of a specific 
growth.” When the complaint affects the 
glandular structure of the breast, there is scarcely 
any perceptible swelling, but one or more of 
its lobes becomes exquisitely tender to the 
touch, and if it be handled the pain sometimes 
continues for several hours.” ‘ There is no 
external mark of inflammation, as the skin 
remains undiscoloured.” Besides this irrita- 
ble and painful state of a whole or part of the 
breast, a tumour sometimes is found distinctly 
circumscribed, highly sensitive to the touch, 
acutely painful at intervals, more especially 

rior to menstruation, very moveable, often not 
arger than a pea, seldom exceeding the size of 
a marble; generally one only exists, but in 
other cases there are several similar swellings.” 

“ Although they continue for years they vary 
but little in size. I have never seen them 
suppurate. kw sometimes spontaneously 
cease to be painful, and sometimes disappear 
without any obvious cause. Upon dissection 
they are found to be composed of a solid and 
semi-transparent substance, with fibres inter- 
woven with it, but without any regular distri- 
bution, and I have not been able to trace any 
large filament of a nerve into them.” “The 
pain with which this tumour is accompanied, its 
tenderness to the slightest touch or to pressure 
of any kind, the suffering which succeeds ex- 
amination, distinguish it from the hydatic, the 
chronic mammary tumour, and the scirrhous 
and fungous tubercle.” 

The malignant or incurable diseases of the 
breast may be classed under two heads, scirrhous 
carcinoma or cancer, and fungus hematodes. 

Scirrhus has been again subdivided into 


MAMMARY GLANDS. 


genera by different authors, some in relation te 
their external ap ces and situation, other 
in accordance with their internal structun 
Dr. Benedict, Professor in the Universit, y 
Breslau,* in giving the following arrangeme 
has rather pursued the former plan :—1st. © 
taneous cancer. 2d. True scirrhus; co 
ing of—1. Nodulated scirrhus; 2. 
scirrhus; 3. Bladder scirrhus. 
Miiller, in his late work on cancer, which’ 
been translated by Dr. West, describes” 
different kinds of carcinoma to which the bre 
in common with other organs, is liable, not 
reference to their seat whether cutaneous 
glandular, but in accordance with their intin 
structure; and to scirrhus, medullary saree 
carcinoma alveolare, and carcinoma melano 
of former authors, has added carcinoma reti 
lare and fasciculatum. To these we shall ret 
a little further on, dwelling previously o1 
form of cancer which is not very common 
highly important in a practical point of 
to the surgeon. 
“ Cutaneous cancer of the breast,” says 
Benedict, p. 39, “ deserves to be particuli 
noticed, because most surgeons frequently | 
found it with the common cancer, from 
it, however, materially differs. It never s 
in the substance of the organ, but al 
solely in the surface of the skin, n 
probably from fat and adipose glands of 
same. Its form is similar to that of cam 
the face and eyelids, and arises in the : 
way. At first there is nothing but a little 
wart, or hard little spot somewhere upon 
skin of the breast. This place begins grad 
to redden and then passes into a stage of 
tion. The swelling which has edges | 
a hard base spreads out, increasing bol 
depth and width so as to advance from the s 
into the substance of the gland, not pas: 
far, and only very gradually destroying 
breast. The glands of the axilla are 
attacked so early as in carcinoma of the g 
itself, and the hectic fever which ulti 
destroys the patient developes itself 
much longer period. . 
Mr. Travers (Med. Chir. Trans. vol. x 
also describes this cutaneous cancer in the 
lowing words: “ There is a cancerous tu 
of the skin which appears upon the 
in other parts, connected with a 
change in the texture of the skin. The 
of the skin is, I believe, primary. It 
of a brawning induration with extension of 
areole, a coarseness such as this 
sents when viewed through a ry 
which gives it a resemblance to pig's § 
Isolated tubercles of various sizes appear at 
siderable distances apart: the texture of 
subjacent cellular membrane is enormo 
thickened and has a cartilaginous hardness; 
the’ breast when the skin undergoes this chat 
upon that organ is early and immoveably fi 
the chest.” I have drawings of two cases of 
kind: one which occurred in the practic 


“ 


’ 
Ae 


or 
~ 


oe 


¥ 


* Bemerkungen iiber die Krankheiten der rust 
und Achsel-Driisen. Breslau, 1825, 4to. p. 4 


MAMMARY GLANDS. 


_ Mr. Travers, at St. Thomas’s Hospital, the other 


in the private practice of Mr. South; the for- 
mer I inspected in company with that gentle- 
man. The post-mortem appearances were 
interesting from the immense crop of white hard 


~ tubercles which were found studding the pleura 


costalis. 
Dr. Benedict considers that “ the primary 
skin disease can be removed almost always with 


_ a favourable result if the operation is performed 


- 
i 
: 


4 
; 


previous to enlargement of the neighbouring 
glands, disease of the parenchyma of the mam- 
ma, or constitutional fever.” 

The ordinary scirrhus of the mamma in its 
early stages usually presents itself to the sur- 
geon as a hard tumour, situated in not on the 
glandular substance of the breast. At first it 
is comparatively moveable, but it cannot be 
moved independent of the structure which sur- 


_ rounds it, and in the progress of development it 


soon contracts adhesions by means of root-like 
prolongations with the whole mamma. Its 


_ surface varies, not decidedly nodulated nor yet 


uniformly smooth; not tender to the touch, 


though it may be the seat of sharp lancinating 


_ pains. As the tumour increases, its adhesions 


extending on all sides, the nipple becomes 
drawn in, and its most prominent surface as- 
sumes a dusky hue. The constitution now 
begins to suffer, the glands in the axilla enlarge, 
and at this period there is no difficulty in dis- 
tinguishing the nature of the disease. In its 
early stage it might be confounded -with a 
tumour which Mr. Travers in his paper just 


referred to has thus described: “ There is a 


tumour met with in the breasts of young women, 
more like a shelled walnut in point of size and 


_ nodosity than any thing to which I can com- 


_ pare it. 


It is of a stony hardness, and it is not 


_ reduced by regulated equal compression, mer- 
_ tury, iodine, or blisters. It is an enlargement 


pi 


mae 


SS 
thee 


and partial cohesion of the lactiferous-tubes in 
a cluster, in one or more places, and which dis- 
position in a less degree pervades the ducts 
throughout the organ.” The absence of lanci- 
nating pains, constitutional disturbance, and 
the peculiar countenance attendant on malig- 
nant disease, assist the surgeon in his diagnosis. 
The earlier period of life at which it makes its 
appearance is also a circumstance worthy of 

attention. 
Miiller describes scirrhus, or carcinoma, sim- 
_~ (syn. carcinoma fibrosum) as “irregular in 
»* not lobulated, hard and resisting the 


knife, and presenting, when divided, a greyish 


appearance which has but very little similarity 
to cartilage. Whitish bands are not invariably 


_ present. Scirrhus of the mammary gland oc- 


casionally shews, here and there, whitish fila- 
ments, some of which are hollow, and contain a 
colourless, whitish or yellowish matter. Pro- 
bably this appearance of white filaments is the 
result of thickening of the walls of the lacti- 
ferous tubes and lymphatics, and this idea is 
confirmed by the absence of these filaments 
from scirrhus of non-glandular parts. The 
mass of scirrhus is composed of two substances, 


* West’s Translation, 41. 


255 


the one fibrous, and the other grey and granu- 
lar.” The fibrous substratum is composed of a 
very irregular net-work of firm bu nde of fibres. 
The grey consists of microscopic, formative 
globules, but slightly adherent to each other ; 
they are transparent hollow cellules, from 
0.0048 to 0.00166 or 0.00130 of an English 
inch in diameter, some of them exhibiting a 
distinct nucleus. They have no connection 
with the fibrous structure.” 

Carcinoma reticulare, Miiller says,* “ occurs 
more frequently than carcinoma simplex. On 
making a section of it, it may be immediately 
distinguished from the latter by the white reti- 
culated figures intersecting the grey mass, which 
are perfectly evident to the naked eye. It ac- 
quires a large size more readily than carcinoma 
simplex, and is further distinguished from its 
tendency to assume alobulated form. It some- 
times approaches the consistence of scirrhus, 
at other times it is softer and more nearly re- 
sembles fungus medullaris.” Though its con- 
sistence varies, its structure always remains the 
same, and with the exception of cancer alveo- 
laris, no form of carcinoma can be so readily 
distinguished. 

Carcinoma alveolare, though usually found in 
the stomach, occasionally attacks the breast, and 
a very good specimen of it is deposited in the 
museum of St. Thomas’s Hospital. This dis- 
ease, like the former one, consists of innumera- 
ble white fibres and lamina crossing each other 
in all directions, and having their interspaces 
occupied by cells which vary in size from that 
of a grain of sand to that of a large pea. For 
the history of the development of this and other 
forms of cancer see Propucts, Morsrp. 

Soft cancer, fungus hematodes,and medullary 
carcinoma, are oneand the same disease. It forms 
a soft elastic swelling, giving something of the 
sensation to the fingers of deep-seated fluid, 
increases rapidly, and is seldom confined to any 
single organ in the body. It occurs earlier in 
life than scirrhus, and is more decidedly a con- 
stitutional disease. “ The tumour with which 
alone this is liable to be confounded,” says Mr. 
Travers, “is the hydatid breast, as it is called, 
and there is sufficient resemblance in the 
rounded outline, the elastic resistance, the ab- 
sence of glandular affection, the distressing in- 
conveniences of size, weight, and distension, 
the turgid veins and livid discoloration of the 
surface, to create some hesitation. But in the 
medullary disease it seldom happens that the 
health is not affected, whereas in the hydatid 
breast it is undisturbed ; the figure of the me- 
dullary tumour is less uniform, being marked 
by dark tuberous elevations and immovably 
fixed to the side by the prolongations of the 
diseased growth in one or more parts of its cir- 
cumference ; whereas the hydatid tumour, not- 
withstanding its oftentimes enormous bulk, is 
globular and remains perfectly detached and 
pendulous. The main distinction is that the 
mammary gland is not, in my experience at 
least, the seat of the medullary or fungoid dis- 
ease as it is of the hydatid. 


* Page 45, loc. cit. 


256 


“In proportion as the malignant fungus is 
recent and of small din:ensions, is the diffi- 
culty of diagnosis from the hydatid cyst, for 
the fungus, as I have before said, ordinarily 
commences on the interior of a cyst containing 
a fluid, from the vascular lining of which it 
hangs like a fringe, and it is common to find 
more than one, often several contiguous cysts, 
in the early stage of the disease. As the fungi 
grow, the cysts burst and are blended in the 
same mass. From this account it will appear 
that there is sufficient analogy between the 
hydatid and fungoid disease in its incipient 
state to require more aids to diagnosis than 
those derived from manual examination. We 
sometimes meet with puzzling analogies in 
these diseases.” 

“ The relation of medullary sarcoma,” says 
Miiller, “ to scirrhus or carcinoma simplex is 
displayed by the fact that after amputation of a 
scirrhous breast, real fungoid tumours may oc- 
cur in other parts, as many observations of Zaup- 
taft, Cruveilhier, and others abundantly shew. 
This affinity is further illustrated by microscopic 
examination, which shews that many structures 
comprehended under the generic term of fungus 
medullaris differ greatly from each other, and 
have nothing in common but the softness of 
their texture.” Miiller therefore employs the 
term fungus medullaris “ as a collective name 
for different forms or stages of developement 
of soft cancer, which undergo imperceptible 
transitions into each other.” The following are 
the varieties for a knowledge of the minutize 
of which we must refer our readers to the 
original. 

“1. Carcinoma medullare, abounding in 
roundish formative globules which make u 
the greater part of the medullary mass, chesigh 
intersected by a delicate fibrous net-work. 

“ 2. Carcinoma medullare, with an exceed- 
ingly soft cerebriform base composed of pale 
elliptical bodies without caudate appendages. 

* 3. Carcinoma medullare, with caudate or 
spindle-shaped corpuscules. 

“ Carcinoma fasciculatum (syn. hyacinum.) 
—Among the structures commonly included 
under the name fungus medullaris, are some 
altogether fibrous in their texture, and which 
correspond with other forms of that disease 
only in the softness of their tissue. The 
fibrous structure of these growths is immedi- 
ately evident on breaking or dividing them ; 
when torn they do not crumble, but are readily 
rent in the direction of the fibres. If ex- 
amined under a microscope they display nei- 
ther the cellular globules of other varieties of 
carcinoma, nor the caudate corpuscules, which 
give a fibrous appearance to some forms of fun- 
gus medullaris.” 

Mr. Travers, in the paper previously referred 
to, says that “ certain anomalous morbid 
changes, as large fungous excrescences and 
deep cavernous fetid ulcers, are now and then 
the sequele of tumours in the female breast 
which are in a loose and slovenly classification 
termed cancerous. They are not so; but they 
are almost as incapable of being conducted 
to a curative termination as if they were; their 


MAMMARY GLANDS. 


ferns said to affect the 
ing remarkable for its slowness and fr 
from pain.” He also describes an excor 
of the integument around the nipple g ul 
extending over the breast, accompanied by 
ichorous exudation which remains in the sai 
incurable state many years, and ultimate 
throws up a broad toad-stool fungus exquis 
irritable and much disposed to bleed. 
neither the glands nor health.” mm 

Melanosis or black cancer has been met ¥ 
in the breast, but we believe never as a prim 
disease, the breast having been attacked s 
sequently to other tissues. Breschet, in 
treatise on this disease, gives a representa 


7 


of it in this organ. There is a preparation 
it in the museum of Bartholomew's He 
It is considered by Miiller as “ merely a 
of cancerous degeneration, and termin: 
the same way as other forms of carcinoma.” 
“« Microscopic examination,” says Mil 
“ detects two forms of melanotic st 
In both instances the basis of the structure 
formed of a fibrous network, the stroma of 
lanosis, within the meshes of which the m 
noid matter is deposited. This matter is gt 
rally composed of cells, filled with 
or blackish green granules. These cells 
and always continue to be free, never becom 
coherent. Their forms are very various. Mi 
indeed most, are round, oval, or i 
some are elongated; a few actually caud 
terminating at one or both extremities m 
point or ina fibril. Still more rarely the 
present several points. They are real pigm 
cells.” This author discovered in one of 
larger cells a nucleus with its nucleolus, | 
dependently of the pigment granules. 
cannot conclude this article more satisfactor 
than by quoting from the same accurate ¢ 
server, Mr. Travers, of whose observatior 
have already so fully availed ourselves. 
“ No description can comprehend all 
varieties of tumour to which this organ is li 
nor does any share of experience enable 
nicest observation to suggest an infallib 
to their nature. We have sometimes 6 
manipulation to depend upon, which is an 
imperfectly cultivated by scientific surge 
Cases now and then arise about which 
most accurate observers are liable to er 
True it is this does not frequently hap 
the distinction between innocent and malig 
growths. The several species of innocent 
mours already enumerated may all be di 
guished from scirrhus with comparatively 
difficulty; but if any doubt exists we m 
consider the age, habits, and circumstance 
the patient. For example, we should asee 
if marks of scrofula are present; if the uter 
functions are regular and healthy; if the 
mour can be referred to violence in the ee 
mencement, which from the exposed situatt 
of the organ is far from uncommon; if m 
than one lump exists in the same breast; 
both breasts are infected; if painful, the ch 
racter of the pain; if any absorbent glands 
altered in the neighbourhood and how. 
many cases of breast tumour are in the recol- 


. 


te 


F 
f 


MARSUPIALIA. 


lection of experienced surgeons which have 
been dispersed by some one or other of the 
remedies in ordinary use, local or constitu- 
tional; and how many that have resisted all 
and remained stationary for years, the patient’s 
mind having been tranquillized by the assur- 
ance of their innocency. Doubtless on- the 
other hand a fatal result has sometimes ad- 
ministered a silent but painfully intelligible 
reproof to the over-confidence of the surgeon.” 
(Samuel Solly.) 


MARSUPIALIA, ( Marsupium, a pouch,) 
Eng. Marsupials; Fr. Marsupiaux ; Ger. Beu- 
telthiere. 

Essential external character— Mammalian 
quadrupeds, distinguished by a peculiar pouch 
or duplicature of the abdominal integument, 
which, in the males, is everted and contains the 

_ testes; in the females is inverted, covering the 


_ mamme, and generally sheltering the young for 
_ a certain period after their birth. 


 centa. 


BO 


Essential internal character —In both sexes 
two supplementary trochlear bones are articu- 
lated to the anterior part of the brim of the 
steed around which play the muscles em- 

racing and supporting the testes in the male, 
and the mammary glands in the female; these 
bones, from their connexion with the pouch, 
are called “ marsupial.” 

The quadrupeds associated together by the 
common external and osteological characters 
above defined, are ovo-viviparous or impla- 
cental,* the vascular layer of the allantois not 

_ being developed, so as to organize the villi of 
_the chorion, or to form cotyledons or a pla- 
The marsupial also differ from the 
placental Mammalia in other important parts 
of internal organization, as in the structure of 
the brain and of the heart, and in the con- 
dition of the sanguiferous and absorbent sys- 
tems; and they present remarkable modifica- 
tions of the genital apparatus in both sexes. 
Classification —The Marsupial animals are 
generally of small size; some, as the Pigmy 
m (Petaurus pygmaeus), and Dwarf 


_ Phalanger ( Phalangista nana), are less than 


_ the common mouse : the largest known existing 
“species is the common or Great Kangaroo 
Peleropus major). With the exception of 
‘the Virginian Opossum, all the Marsupialia 
are confined to the southern hemisphere of the 
globe, and they are pe y natives of Aus- 
tralasia, to which part of the world several 
remarkable genera are peculiar, and where, with 
a few exceptions, as certain Cheiroptera and a 
few Rodent genera, as Hydromys, Hapalotis, 
and Pseudomys, all the known aboriginal 
mammals are Marsupial or Monotrematous.+ 
It is in the Australian continent that we per- 
ceive the Marsupial quadrupeds typifying, so 
to say, or playing corresponding parts with 
those allotted to the placental Mammalia ina 
larger theatre of the habitable surface of the 


* On the Generation of the Marsupialia, Philos. 
Trans. 1834, p. 333. 

+ The Dingo or Wild Dog is without doubt a 
comparatively recent and accidental introduction. 


VOL. III. 


257 


earth. The carnivorous Thylacines*_and Da- 
syures,+ for example, are the pigiffy destruc- 
tives of the country, committing occasional 
ravages among the sheep and poultry, but not 
disdaining dead animal matter or garbage. 

The species of Phascogale, Myrmecobius, 
and Perameles represent the placental Insec- 
tivora. Many Murstiiols which live in trees 
have an omnivorous or vegetable diet ; these in 
their prehensile tail and hinder thumb typify 
the Quadrumana ; and one species, the tailless 
Koala, seems to represent the American sloths 
or the arboreal sun-bears of the Indian Archi- 
pelago. 

Another species of Marsupial, the Wom- 
bat, presents the dentition which characterizes 
the placental Rodentia; and the Petaurists, 
like the flying squirrels, have a parachute 
formed by broad duplications of the skin ex- 
tending laterally between the fore and hind legs. 

The Kangaroos are the true herbivorous 
Marsupialia, and many interesting physiolo- 
gical conditions present themselves to the mind 
in contemplating the singular construction and 
proportions of these animals. It would ap- 
pear that the peculiarities of their gestation 
rendered indispensably necessary the posses- 
sion of a certain prehensile faculty of the 
anterior extremities, with a free movement of 
the digits and a rotatory power of the fore-arm, 
in relation to the manipulations of the pouch 
and of the embryo therein protected and ma- 
tured. At the same time an herbivorous quad- 
ruped must possess great powers of locomo- 
tion in order to pass from pasture to pasture, 
and to avoid its enemies by flight. These 

owers, as is well known, are secured to the 
erbivorous species of the placental Mammalia 
by an ungulate structure of four pretty equally 
developed members. Such a structure, how- 
ever, would have been incompatible with the 
procreative economy of the Kangaroo. It is, 
therefore, organized for a rapid course by an 
excessive development of the hinder extre- 
mities, and these alone serve the animal in 
flight, which is performed by a succession of 
extensive bounds. The tail, also, is of great 
power and length, and, in the stationary po- 
sition, the body is supported erect on the tripod 
formed by the tail and hind legs, while in easy 
progression the tail serves as a crutch, upon 
which and the fore feet the body is sustained 
while the hind legs are swung forwards. 

‘As the Australian Continent, the great me- 
tropolis of the Marsupial quadrupeds, still 
remains but very partially explored, and as 
new species and even genera of Marsupials 
continue at each expedition to reward the re- 
searches of the scientific traveller; and as, more- 
over, the recovery of two lost but distinct 
genera from the ruins of a former world makes 
it reasouable to suppose that other types of 
Marsupials remain still hidden in the crust of 
the earth, it can hardly be expected that the 
zoologist should be able to arrange in a natural 
series, with easy transitions according to the 


* The Hyzna of the Colonists. 
+ The Devil, Native Cat, &c. of the Colonists. 
Ss 


258 MARSUPIALIA. — 
order of their affinities, the few and diversified © The incisors are of equal and re 
forms of this implacental group which are at larly arranged in the segment of a circle wi 


present known. 

In the subjoined classification the modifica- 
tions of the digestive system have been taken as 
the guide to the formation of the primary groups 
of the Marsupialia. 

The Continent, however, in which the Mar- 
Supials exist in greatest number and variety, 
is characterized by the paucity of organized 
matter upon its surface, and consequently few 
of the species are nourished by a well-defined 
diet. Re dncpe carnivorous quadruped could 
without much difficulty have found subsistence 
in the wilds of Australia, prior to the intro- 
duction of civilised man and his attendant 
herds; and we find, in fact, that the native 
genera which are the most decidedly carnivo- 
rous do not include species larger than the dog. 
We can only reckon among these strictly car- 
nivorous species the Thylacines and the Da- 
syures ; and, on the other hand, not more than 
two or three Marsupial genera feed exclusively 
on vegetable substances. The remainder de- 
rive a promiscuous nutriment from dead or 
decaying animal and vegetable matter, crus- 
tacea, and the refuse of the sea-shore, insects 
in their perfect and larva states, live birds, 
young and succulent sprouts, leaves, fruits, 

The terms, therefore, which will be given 
to the different primary subdivisions in the 
present classification of the Marsupialia must 
not be understood to indicate strictly or ex- 
clusively the nature of the food of the species 
severally included in these groups, but rather 
their general tendency to select for their support 
the substances implied by those designations. 


Classification of the Marsupialia.* 
Tribe I. SARCOP HAGA. 
The genera in this tribe are characterized by 
an important anatomical condition, viz. the ab- 
sence of an intestinum cecum. 


Genus 1. THYLACINUS. ( Fig. 80.) 
Fig. 80. 


Thylacinus Harrisii, one-third natural size. 


ie 48 : a 
Incisors 3—9 canines 7—;° 
3—3 / 4—4 
3-3; molars asa 


™ Proceedings of the Zoological Society, Jan. 8, 


premolars 


* = 46. 


an interspace in the middle of the 
both jaws. The external incisor on e 
is the strongest. The laniary or canine t 
are long, strong, curved, and pointed, hi 
those of the dog tribe. The spurious mol 
in this as in all other Marsupials have t 
roots; their crown presents a simple co 
pressed conical form, with a posterior tuber 
which is most developed on the hindn 
The true molars in the upper jaw are unequé 
triangular, the last being much smaller than 
rest; the exterior part of the crown is rai 
into one large pointed middle cusp and 1 
lateral smaller cusps obscurely developec 
small strong obtuse cusp ga om 
inner side of the crown. molars of | 
lower jaw are compressed, tricuspidate, 
middle cusp being the longest, especially 
the two last molars, which resemble closely t 
sectorial teeth (dents carnassiérs) of the 
and cat. 

The fore feet are 5-digitate, the hind 
4-digitate. On the fore foot the middle 
is the longest, the internal one or pollex| 
shortest; but the difference is slight. On 
hind foot the two middle toes are of n 
equal length and longer than the two lat 
toes, which are equal. All the toes are arn 
with strong, blunt, and almost straight claw: 

The only known species of this genus,= 
Thylacine ( Thylacinus Harrisii, Temm.,, - 
delphys Cynocephalus, Harris,) is a native 
Van Dieman’s Land, and is called by 1 
Colonists the “ Hyena.” It is es largest 
the carnivorous Marsupials, equalling in | 
the shepherd's dog, ay is of a tron bui 
and stands lower on its legs. Its head is 
disproportionate magnitude. The prinej 
characteristic of its colour is the trans 
black bands which traverse the back. It dwi 
in caverns and holes in the rocks, and seeks 
prey by night, devouring the smaller n 
quadrupeds, and at the present 
committing destructive ravag 
the numerous flocks of sheep ¥ 
have been introduced by the E 
pean settlers into the island, 
the spines of the Echidna seen 
be no defence against the des 
tive and voracious propensitie 
the powerful Thylacine, for the} 
digested remains of one of t 
monotremes have been found ij 
stomach. ve 

In confinement the Thylat 
utters from time to time a 
guttural cry, and appears in the 
time exceedingly inactive and 
pid, presenting an almost cont 
movement of the nictitating n 
brane of the eye. = 


J 
n 


af 
1839. The series of skulls carefully preparec 
Mr. Waterhouse at the Zoologi Society © 
afforded me the chief materials for the illustra 
of the dental formule of the different Mars 
genera. : 


MARSUPIALIA. 
Genus DASYURUS. (Fig. 81.) 


Dasyurus Ursinus, one-third natural size. 


4 4—4 . 1—1 
Incisors 5—Z; canines 7 ; premolars 
2—2 4—4 
ino? molars any = 42. 


The eight incisors of the upper jaw are of 
the same length and simple structure, and are 
arranged in a regular semicircle without any 
median interval. The six incisors of the lower 
jaw are similarly arranged, but have thicker 
‘crowns than the upper ones. The canines 
__ present the same or even a greater relative de- 
velopment than in the Thylacine: in an extinct 
species of Dasyurus* they had the same form 
and relative proportions as in the Leopard. 
The spurious molars have a pointed com- 

ressed triangular crown with a rudimental tu- 
_bercle at the anterior and posterior part of its 
base. The grinding surface of the true molars 
_in the upper jaw is triangular; the first presents 
four sharp cusps, the second and third each 
‘five, the fourth, which is the smallest, only 
_ three. In the lower jaw the last molar is 
nearly of equal size with the penultimate one, 
__and is bristled with four cusps, the external one 
being the longest : the second and third molars 
have five cusps, three on the inner and two on 
the outer side; the first molar has four cusps: 
these are all sharply pointed in the young 
animal, in which the posterior tubercle of the 
posterior molar in the lower jaw is divided 
_ into two small cusps. 

The carnivorous character of the above den- 
tition is most strongly marked in the Ursine 
_ Dasyure or Devil of the Tasmanian Colonists, 
_ the largest existing species of the genus, and 
_ a most pestilent animal in the poultry-yard or 
: er. 

‘Genus PHASCOGALE. ( Fig. 82.) 


Phascogale penicillata. 


* Dasyurus laniarius, Owen: the fossil remains 
of this species were discovered with those of two 
tic species of Kangaroo in the bone-caves of 
ellington Valley, Australia, by Major, now Sir 
Thomas, Mitchell. 


wees, ee 


259 
4—4 1—1 

Incisors 323; canines =: premolars 
3—3 — 
3—3 5 4—4 ° 

In the present dental formula may be dis- 
cerned a step in the transition from the Da- 
syures to the Opossums, not only in the in- 
creased number of spurious molars, but also 
in the shape and proportions of the incisors. In 
the upper jaw the two middle incisors are 
longer than the rest, and separated from them 
by a brief interval ; they are more curved and 
project more forward. The three lateral in- 
cisors diminish in size to the outermost. The 
middle incisors of the lower jaw also exceed 
the lateral ones in size, and project beyond 
them but not in the same degree, nor are they 
separated from them by an interval, as in the 
upper jaw. The canines are relatively smaller 
than in the Dasyures. The spurious molars 
present a similar form, but the third in the 
lower jaw is smaller and simpler than the two 
preceding ones. The true molars resemble 
those of the Dasyures. 

The general character of the dentition of 
these small predatory Marsupials approximates 
to the insectivorous type, as exemplified in 
the Shrew, Hedgehog, &c. among the placental. 
Mammalia, and corresponds with the food and 
habits of the species which thus lead from the 
Sarcophagous to the Entomophagous tribes. 

The interval is further diminished by a 
lost marsupial genus which forms one of the 
ancient Mammalia that have rendered the 
oolitic formations at Stonesfield so celebrated. 
This genus, which I have called Phascolothe- 
rium, presents the same numerical dental formula 
as in Phascogale, viz. 


— 46. 


molars 


. 1? . 2. 
Incisors 33 or 44; Canines qj ° 
1? —? 
premolars §3? molars 7—7- 


But the incisors and canines are separated by 
vacant interspaces, and occupy a large pro- 
portional space in the dental series: the true 
molars resemble those of Thylacine. ; 


Tribe II. ENTOMOPHAGA. 

This is the most extensive and varied of the 
primary groups of the Marsupial order. In 
the system of Cuvier, the species of this tribe 
are united with those of the preceding to form 
a single group characterized by the presence of 
long canines and small incisors in both jaws: 
but in most of the Entomophagous genera of 
the present classification, the canines present a 
marked inferiority of development, and the 
species are consequently unable to cope with 
animals of their own size and grade of organ- 
ization, but prey, for the most part, upon the 
smaller and weaker classes of invertebrate 
animals. Their intestinal canal is complicated 
by a moderately long and large cecum; and 
while, in the Sarcophaga, the feet are con- 
structed upon the plan of those of the ordinary 
placental Digitigrades, they offer in the pre- 
sent tribe a variety of well-marked modi- 

s.2 


260 MARSUPIALIA. ¥ 
fications, according to which the species may general external form and bushy tail, it off 
be arranged into gressorial, saltatory, and scan- an especial approximation to the genus Ph 


sorial groups. 
a. Gressoria. 
Genus MYRMECOBIUS. 

The only known existing representative of 
this family is the animal described by Mr. 
Waterhouse, which constitutes the type of his 

nus Myrmecobius, and of which the following 
is the remarkable dental formula. ( Fig. 83.) 


Fig. 83. 


, 4—4 . 1 
Incisors 3g? Canines [—7; premolars 


3—3 


=——s; molars >= 54. 


6—6 
a3? 6—6 
From this formula it will be seen that the 
number of molars, eighteen in both jaws, ex- 
ceeds that of any other known existing mar- 
‘supial, and nearly approaches the peculiar 
dental formula of the extinct Thylacotherium,* 
and that which characterizes some of the ex- 
isting Armadillos. The resemblance to the 
genus Dasypus is further carried out in the 
small size of the molar teeth, their separation 
from each other by slight interspaces, and their 
implantation in sockets, which are not formed 
= eg a well-developed alveolar ridge or process. 
The molars, however, present a distinct multi- 
cuspidate structure, and both the true and 
false ones possess two separate fangs, as in 
other Marsupials. The inferior molars are 
directed obliquely inwards, and the whole 
dental series describes a slight sigmoid curve, 
(fig. 97.) The false molars present the 
usual eorprenred triangular form with the 
‘apex slightly recurved; and the base more or 
less obscurely notched before and behind. The 
canines are very little longer than the false 
molars; the incisors are minute, slightly com- 
pressed and pointed; they are separated from 
each other and the canines by wide intervals. 
The Myrmecobians are insectivorous,+ and 
shelter themselves in the hollows of trees, fre- 
uenting most, it is said, those situations where 
the Port-Jackson willow abounds. In the 
structure and proportions of its hinder feet, 
_Myrmecobius resembles the Dasyurine family ; 
and in the slightly develo canines, the 
smooth external surface of the skull, the 
breadth between the zygomata, and the absence 
of the interparietal ridges, as well as in its 


* This small Insectivore, of which the marsu- 
pial character is doubtful, had twenty-four molars 
in each jaw.—See Geol. Trans. New Series, vol.vi. 


art 1. 
i + Mr. Gould informs me that they feed exclu- 
sively on ants. 


cogale. 
Genus PERAMELES. (Bandicoot 


« 


B. Saltatoria. 


Pea: 


pee 


: VOLE OIA A“ 


Ae 


ae 


Ince Se 
neisors 3-3; canines 7—75 Ff 
3—3 . 4—4 . 
3_3 3 molars 74" == 48. 
This dental formula characterizes a num 
of Marsupials commonly known in Aust 
by the name of Bandicoots; the hind legs) 
longer and stronger than the fore, and exhi 
in a well-marked manner the feeble and slen 
conditions of the second and third ¢ 
counting from the inside, and the sudden 
crease in length and strength of the fourth ¢ 
fifth, or two outer toes, which are chiefly 
servient to locomotion. In consequence of 
inequality of length in their extremities 
mode of p ion in the Bandicoots is 
bounds, the hind feet being moved t 
ther, and alternately with the fore 
as in the hare and rabbit, and the cruppe 
raised higher than the fore-quarter. 
which offer the greatest range of on 
the present genus are the external or poste 
incisors and the canines: the molars, a 
which originally are quinque-cuspidate, ha 
their points worn away, and present a smo 
and oblique grinding surface in some spe 
sooner than in others. 
The Bandicoots which approach nearest 
the Myrmecobius in the condition of th 
cisive and canine teeth, are the Perameles « 
sula and P. Gunnii. There is a slight inte 
between the first and second incisor, ¢ 
outer or fifth incisor of the upper jaw is se 
rated from the rest by an interspace equ 
twice its own breadth, and moreover pr 
the triangular pointed canine-like crown wW 
characterizes all the incisors of Mi ) 
but the four anterior incisors are placed 
together and have compressed, quadrate 
incisive crowns. From these incisors the cai 
is very remote, the interspace being equ 
divided by the fifth pointed incisor, which 
canine very slightly exceeds in size. In Per 
nasuta the incisor presents the same gene 
condition, but the canines are relatively 
In Per. Gunnii, the outer incisor is ele 
the others, which it also more nearly resemb 
in form than in the preceding species; but 
Per. Lagotis, it is not separated from the: 
by a wider interval than that which interve 
between the first and second incisor. In b 


Phe 


oe 


Ee 


MARSUPIALIA. 


the preceding Bandicoots the canines are long 
and well i but the true molars have 
the grinding surface worn down flat in the full- 
grown specimens which I have, had the oppor- 
tunity of examining. 

The marsupial pouch in the Bandicoots, at 
least in the falbipeoten females of Per. nasuta, 
Per. obesula, and Per. Lagotis, has its orifice 
directed downwards or towards the cloaca, con- 
trariwise to its ordinary disposition in the 
Marsupials ; this direction of the pouch evi- 
dently relates to the procumbent position of 
the trunk when supported on the short fore 
and long hind legs. In the stomach and in- 
testines of a Perameles obesula I found only 
the remains of insects; and in the examination 
of the alimentary canal of a Per. nasuta, Dr. 
Grant obtained the same results. Nevertheless 
the Perumeles Lagotis, lately living at the Zoo- 
logical Gardens, refused meat and meal-worms, 
and subsisted on vegetable food exclusively. 

Genus CHG@ROPUS. 

_ The singular animal on which Mr. Ogilby 
has founded this genus, is briefly noticed and 
figured in Major Mitchell’s Australia, (Vol. ii. 
pl. 38, p. 131,) and the individual described 
is preserved in the Colonial Museum, at Syd- 
ney, N.S. Wales, (No. 35 of Mr. Geo. Ben- 
nett’s Catalogue.) 

It would appear that the two outer toes of 
the fore foot, which are always very small in 
the true Bandicoots, are entirely deficient in 
the Cheropus, unless some rudiments should 
exist beneath the skin ; at all events only two 
toes are apparent externally; but they are so 
developed and armed as to be serviceable for 
burrowing or progression. The inner toe is 
wanting on the hind-foot. Dental formula : 
1—1 
1—1’ 
—4. = 46. 


 Incisors, 
3s— 


. 
3 > 


= 3 canines, pre- 
—3 


molars, molars, 


’ All the teeth are of small size; the canines 
resemble the spurious molars in size and shape, 
and these are separated by intervals, as in Myr- 
mecobius. The marsupium opens downwards 
in the Cheropus, asin the true Bandicoots. The 
species described has no tail. The genus 


_ would seem by its dentition to rank between 


Myrmecobius and Perameles. Its digital cha- 


_ Yacters are anomalous and unique among the 


Marsupialia, but are evidently a degeneration 
from the Saltatorial or Bandicoot type. 
y. Scansoria. 

Genus DIDELPHYS, (Opossums, fig. 85.) 

These Marsupials are now exclusively con- 
fined to the American Continents, although 
the fossil remains of a small species attest their 
former existence in Europe contemporaheously 


_ with the Paleothere, Anoplothere, and other 


extinct Pachyderms, whose fossil remains cha- 
racterize the Eocene strata of the Paris Basin. 
The dental formula of the Genus Didelphys is,— 
5—5 —1 

oe, Ser ae oad 


7 3 1 
Incisors, canines, 


4 


<=: = 50. 


molars, ab 3; molars, 
3—3 


The Opossums resemble in their dentition the 


261 


Didelphys Virginiana. 


Bandicoots more than the Dasyures: but they 
closely resemble the latter in the tuberculous 
structure of the molars. The two middle in- 
cisors of the upper jaw are more produced than 
the others, from which they are also separated 
by a short interspace. The canines are well de- 
veloped ; the upper being always stronger than 
the lower. The false molars are simply conical, 
but are more compressed than in the Carnivo- 
rous Marsupials. The posterior false molar 
is the largest in the upper jaw ; the middle one 
is the largest in the lower jaw; the anterior 
one is the smallest in both jaws. The true 
molars are beset with sharp cusps which wear 
down into tubercles as the animal advances in 
age. The crowns of the upper molars present 
a triangular horizontal section: the base of the 
triangle is turned forward in the posterior mo- 
lar ; and obliquely inwards and outwards in 
the rest. In the lower jaw the true molars are 
narrower and of more equal size than in the 
upper jaw: there are five tubercles on each, 
four placed in two transverse pairs, the anterior 
being the highest, and a fifth forming the 
anterior and internal angle of the tooth: the 
anterior and external angle seems as if it were 
vertically cut off. 

The smaller species of Didelphis, which are 
the most numerous, fulfil in South America 
the office of the insectivorous Shrews of the 
old Continent. Their external resemblance is 
so close that some have been described as spe- 
cies of Sorex, but no true representative of 
this placental genus has hitherto been disco- 
vered in South America. The larger Opossums 
resemble in their habits, as in their dentition, 
the Carnivorous Dasyures, and prey upon the 
smaller quadrupeds and birds, but they have 
a more omnivorous diet, feeding on reptiles 
and insects and even fruit. One large species, 
(Did. cancrivora) prowls about the sea- 
shore and lives, as its name implies, on crabs 
and other crustaceous animals. Another spe- 
cies, the Yapock, frequents the fresh waters, 
and preys almost exclusively on fish. It has 
all the habits of an Otter ; and, in consequence 
of the modifications of its feet, forms the type 
of the sub-genus Cheironectes, Ill. Besides 
being web-footed the anterior extremities pre- 
sent an unusual development of the pisiform 
bone, which supports a fold of the skin, like 
a sixth digit; it has indeed been described, as 
such, by M. Temminck : this process has not, of 
course, any nail. The dentition of the Yapock 
resembles that of the ordinary Didelphis. All 
the Opossums have the inner digit of the hind 
foot converted by its position and development 


262 


into a thumb, but without a claw. The hinder 
d is associated in almost all the species 
with a scaly prehensile tail. 

In some of the smaller Opossums the sub- 
abdominal tegumentary folds are rudimental, 
or merely serve to conceal the nipples, and are 
not developed into a pouch: the young in 
these species adhere to the mother by entwining 
their little prehensile tails around her's; and 
they cling to the fur of the back, hence the 
term dorsigera applied to one of these Opos- 
sums.* 


Tribe 1II. CARPOPHAGA. 

Stomach simple ; caecum very long. 

In this family the teeth, especially those at 
the anterior part of the mouth, present consider- 
able deviations from the previously described 
formule ; the chief of which is a predomi- 
nating size of the two anterior incisors, both 
in the upper and lower jaws. Hitherto we 
have seen that the dentition in every marsupial 
genus has participated more or less in a carni- 
vorous character ; henceforth it will manifest a 
tendency to the Rodent type. 

Genus PHALANGISTA. 

The Phalangers, so called from the phalanges 
of the second and third digits of the hinder ex- 
tremity being inclosed in a common sheath of 
integument, have the innermost digit modi- 
fied to answer the purposes of a thumb; and 
this hinder hand being associated in many of 
the species with a prehensile tail, they evidently, 
of all Frugivora, come nearest to the arboreal 
Species of the preceding section. In a system 
flamed on locomotive characters they would 
rank in the same section with the Opossums. 
We shall see, however, that they differ from 
those Entomophagous Marsupials in the con- 
dition of the intestinal tube. Let us examine 
to what extent the dental characters deviate 
from those of the Opossums. 


Fig. 86. 


In the skull of a Phalangista Cookii, of 
which the dental formula is accurately given 
in fig. 86, there are both in the upper and 
lower jaws four true molars on each side, each 


* Few facts would be more interesting in the 
present branch of zoology than the condition of 
the new-born young, and their degree and mode of 
uterine development in these Opossums. Since 
the marsupial bones serve, not as is usually de- 
scribed to support a pouch, but to aid in the func- 
tion of the mammary glands and testes, they of 
course are present in the skeleton of these small 
pouchless Opossums as in the more typical Mar- 
supials. 


MARSUPIALIA. 


beset with four three-sided pyramidal sharp 
pointed cusps; thus these essential and mos 
constant teeth correspond in number with tho 
of the Opossum: but in the opps jaw t 
differ in the absence of the internal cusp, whi 
gives a triangular figure to the grinding surface 
of the molars in the Opossum; and the ; 
terior single cusp is wanting in the true mola 
of the lower jaw. Anterior to the upp 
grinders in this Phalanger there are two pi 
molars of similar shape and proportions — 
those in the Opossum; then a third premok 
too small to be of much functional importan 
separated also, like the corresponding ante 
premolar in the Opossum, by a short inter 
from those behind. 4 
The canine tooth but slightly exceeds in siz 
the above false molar, and consequently he 
occurs the first great difference between 
Phalangers and Opossums; it is, howe’ 
but a difference in degree of development ; ai 
in the Ursine and other Phalangers, as well 
in the Petaurists, the corresponding tooth pi 
sents more of the proportions and form o 
true canine. é 
The incisors, which we have seen to be n 
variable in number in the Carnivorous 
are here three instead of five on each 
the upper jaw, but their size, especially th at 
the first, compensates for their fewness. 
In the lower jaw there is the same n 
of molars and functional premolars as in | 
Opossums ; the two very minute ard funeti 
less molars, which form part of the same 
tinuous series, represent the small premolar 
canine of the upper jaw; and anterior ‘o th 
there is one very small and one bee’ rge 
procumbent incisor on each side. Now if | 
comparison be just and natural, the differ 
in the number of teeth between the Phalar 
and the Opossum will resolve itself into 
former being minus certain incisors in the 
per and lower jaws: in the latter, the g 
development of the middle incisors as 
produce an atrophy of all the rest. 
The interspace between the functionals 
veloped incisors and molars in both jaws als 
contains in the Phalangers teeth of small 
and little functional importance, and vai 
not only in their proportions but their nu 
The constant teeth in the Phalangers are 
4—4 3—3 . 


—- —_—— JNCISG 


a 


true molars, and the 


— ve 


Fig. 87. 


a 


El, Oe 


1. _ 


NSB ee ~ 


accor 


MARSUPIALIA. 


The canines (c. fig. 86 and 87,) are constant 
in regard to their presence, but variable in size ; 
they are always very small in the lower jaw. 

With respect to the functional premolars 
1—1 
1—1 
molars, and their crowns reach to the same 

inding level; sometimes a second premolar 
is similarly developed in the upper jaw, 
as in the Phal. Cookii, and as in the great 
flying Phalangers, (Petaurus Taguanoides, 
fe. 88) but it is commonly absent, or re- 
placed by a very minute tooth, shaped like a 
canine ; so that in the upper jaw, between the 
posterior or functional premolar and the in- 
cisors, we may find three teeth, of which the 
posterior is the largest, as in Phal. Cookii, or 
the smallest as in Phal. cavifrons; or there 
may be only two teeth as in Phal. ursina and 


these are always in contact with the 


Phat. vulpina, and the species, whatever that 


may be, which M. Fr. Cuvier has selected as 
the type of the dentition of the Genus. 

In the lower jaw similar varieties occur in 
these small and unimportant teeth; e. g. there 
may be between the procumbent incisors and 
the posterior premolar, either three teeth as in 
Phal. Cookii and Phal. cavifrons, or two, as 
in Phal. ursina, Phal. maculata, Phal. chry- 
sorrhoos ; or finally one, as in Phal. vulpina 
and Phal. fuliginosa. The most important 
modification is presented by the little Phal. 
gliriformis of Bell, which has only three true 
molars on each side of each jaw. As these 
modifications of the teeth are unaccompanied 
by any change of general structure or of habit, 
whilst those teeth which most influence the diet 
are constant, it is obvious that these differences 
of dentition are unimportant, and afford no 
just grounds for subgeneric distinctions. 

The Phalangers, being provided with hinder 
hands and prehensile tails, are strictly arboreal 
animals, and have a close external resemblance 
to the Opossums, by which name they are 
generally known in Australia and the Islands 
of the Indian Archipelago, where alone they 
have hitherto been found. They differ from 
the Opossums chiefly in their dentition; and in 

esce with this difference their diet is 
more decidedly of a vegetable kind.* The 
Australian Phalangers feed chiefly on the ten- 
der buds and the leaves of Eucalypti: but 
according to Temminck,+ the Indian Phalan- 
ers are omnivorous, and combine insects with 
its and leaves. Mr. Ogilbyt states that 
both “ the Phalangers and Petaurists display 
so decided a tt Sess for live birds, as to 
make it probable that these constitute a main 

rtion of their food in a state of nature.” I 

nd, however, that the intestinal canal, and 
especially the caecum, offers so great an addi- 
tional development in length, as, with the cor- 
responding predominance of the incisors, and 
atrophy of the canines, to indicate clearly a 


* In the stomach and intestines of specimens 
sent to me in spirits from Australia, I have never 
fonnd any other alimentary substances but those of 
a vegetable nature. 

+ Monographies de Mammalogie, p. 3. 

$ Mag. Hist. Nat. 1837, p. 458. 


263 


natural and constant tendency in the Phalangers 
to a vegetable diet. Guided theyefore by the 
totality of their organization, I am led to place 
them in a distinct section from that which con- 
tains the Opossums, but, in that section, they 
come the nearest to the true Opossums. The 
Phalangers of the Indian Isles have short ears 
and the greater part of the tail naked. To this 
group have been applied the names Ceonyz, 
Cuscus, and Balantia ; the Australasian Pha- 
langers have moderately long ears, and the 
greater part, or else the whole of the tail is 
covered with hair. All the species possess 
considerable freedom of lateral movement in 
the anterior digits, and in some small species, 
as Phal. gliriformis, Bell, they appear to be 
naturally divided into two groups, the two 
outer being opposed to the three inner fingers. 
To the hairy-tailed Phalangers exhibiting this 
character, Mr, Ogilby gives the subgeneric 
name Pseudocheirus, restricting the term Phalan- 
gista to the remaining species. With reference 
to the subgenera Cuscus, Bualantia, Pseudo- 
cheirus, &c. I heartily concur in the opinion 
of the experienced and judicious Temminck,* 
that these numerous sections are perfectly use- 
less, and a burthensome charge to the memory. 
Genus PETAURUS. 

There are many species of Marsupialia limi- 
ted to Australia and closely resembling, or 
identical with, the true Phalangers in their den- 
tal characters and the structure of the feet. I 
allude to the Petaurists or Flying Opossums : 
these, however, present an external character 
so easily recognizable, and influencing so ma- 
terially the locomotive faculties, as to claim 
for it more consideration than the modifica- 
tions of the digits or spurious molars which 
we have just been considering in the Pha- 
langers. A fold of the skin is extended on 
each side of the body between the fore and 
hind legs, which, when outstretched, forms a 
lateral wing or parachute ; but which, when the 
legs are in the position for ordinary support or 
progression, is drawn close to the side of the 
animal by the elasticity of the subcutaneous 
cellular membrane, and there forms a mere te- 
gumentary ridge. These delicate and beautiful 
Marsupials have been separated generically from 
the Phalangers under the name of Petaurus: 
they further differ from the Phalangers in want- 
ing the prehensile character of the tail, which, 
in some species of Petaurus, has a general 
clothing of long and soft hairs, whilst in others 
the hairs are arranged in two lateral series. 

Now in the Petaurists there is as little con- 
stancy in the exact formula of the dentition as 
among the Phalangers. The largest species of 
Petaurus (Pet. Tuguanoides) for example, is 
almost identical in this respect with the Pha- 
langista Cookii, which M. Fr. Cuvier has 
therefore classed with the Petauri. Those 
teeth of Pet. Taguanoides which are sufficiently 
developed, and so equal in length, as to exer- 
cise the function of grinders, or in other words, 
the functional series of molars, includes six 
teeth on each side of the upper jaw, and five 


* Loc. cit. p. 10. 


‘ix 


264 


teeth on each side of the lower jaw. The four 
ee molars in each row are true, and bear 
jour pyramidal cusps, excepting the last tooth 
in the upper jaw, which, as in Ph. Cookii, has 
only three cusps. In the upper jaw the space 
between the functional false molars and the in- 
cisors is occupied by two simple rudimentary 
teeth, the anterior representing the canine ; but 
being relatively smaller than in Ph. Cookii, 
the crowns of the two anterior incisors are rela- 
tively larger. In the lower jaw the sloping 
alveolar surface between the functional molars 
and large procumbent incisors is occupied, ac- 
cording to M. Fr. Cuvier, by two rudimentary 
minute teeth, as represented in the figure 
(fig. 88). I have not found any trace of these 


Fig. 88. 


Petaurus Taguanoides. 


in the two skulls of Pet. Taguanoides examined 
by me. In Ph. Cookii we have seen that 
there are three minute teeth in the correspond- 
ing space ; but these differences would not be 
sufficient ground to separate generically the 
two species if they were unaccompanied by 
modifications of other parts of the body. 

In Petaurus sciureus and Petaurus flaviventer 
the dentition more nearly resembles that of 
Phalangista vulpina. In the upper jaw the 
functional molar series consists of five teeth on 
each side; the four hinder ones being, as in 
Pet. Taguanoides, true tuberculate molars, but 
diminishing more rapidly in size as they are 
placed further back in the jaw; the hinder 
tooth has three tubercles, the rest four; the 
apices seem to be naturally blunter than in Pet. 

aguanoides. 

tween the functional premolar and the 
incisors there are three teeth, of which the 


Fig. 89. 


2 
> 


Petaurus flaviventer. 


representative of the canine is relatively much 
larger than in the Pet. Taguanoides; the first 
false molar is also larger and has two roots; the 
second, which is functional in Pet. ‘laguanoides, 
is here very small. The canine is more deve- 
loped ; the first incisor is also relatively larger 
and more produced. In the lower jaw the 
functional series of grinders consists of the four 
true tuberculate molars only, of which the last 


MARSUPIALIA. 


is relatively smaller, and the first of a mo: 
triangular form than in Pet. ides. Tt 
space between the tuberculate molars and 
procumbent incisor is occupied by four smal 
teeth, of which the one immediately rior t 
the molars is large, compressed, pointed, a 
has two roots; the remaining three are rm 
mentary and have a single fang; the anter 
of these corresponds to the one regarded 
canine in the upper jaw. ’ 
Among the species exhibiting this der 
formula, viz. 


Incisors 2—3; canines =: pre 
lars s—3., molars 4—* = 40, 
3—3 4—4 


are Pet. sciureus, Pet. flaviventer, 
macrurus. 

The Pigmy Petaurist differs from the } 
ceding and larger species, in having 
hairs of the tail distichous, or oranges 2 
regular lateral series like the barbs of a fea’ 
and in having the spurious molars large: 
sharp-pointed; and the true molars bris 
each with four acute cusps. This tendene 
the dentition to the insectivorous cha 
with the modification of the tail, induced 
Desmarest to separate the Pigmy 
from the rest of the species, and const 
new sub-genus for its reception under the 
of Acrobates.* » 

To Mr. Waterhouse, however, is due 
credit of having first pointed out that the Pi, 
Petaurist had but three true molars on each 
of each jaw instead of four. There seems, t 
fore, to be better reason for accepting this s 
generic section, although we evidently peree 
a transition to this condition in the sm 
of the hinder or fourth molars in the Se 
Petaurist and its congeners. 

The description of the dentition of the Pig 
Petaurist in the Régne Animal, besides be 
defective in this remarkable particular, is” 
quite exact in other respects. In four ai 
specimens, two of which were males, and 
females with young in the pouch, I find the 
lowing dental formula to be constant (fig. § 

3— 1—1 id 


ieee a pr 
> > 


re 


ja 


Incisors canines 


lars 


The three quadricuspidate grinders of thew 
jaw are preceded by three large premol. 
of which has two fangs, and a com 
triangular sharp-pointed crown, slightly bu 


* Axpog, summus, Bawo, gradior, as frequent 
the summits of trees. . 


MARSUPIALIA. 


gressively increasing in length as they are 
placed forward. An interspace occurs between 
these and the canine, which is long, slender, 
sharp-pointed, and recurved. The first incisor 
is longer than the two behind, but is much 
shorter than the canine. In the lower jaw the 
true molars are preceded by two functional 
false ones, similar in size and shape to the 
three above the anterior false molar, and the 
canine are represented by minute rudimental 
simple teeth; the single incisor is long and 
procumbent as in the other Petaurists. 

With these differences of dentition approach- 
ing more or less to one or other of the modifi- 
cations of the dentition in the group of Phalan- 
gers, the Petaurists may nevertheless be readily 
discriminated from those Phalangers which 
_ they most resemble ; for example, the Petaurus 
Taguanoides may be distinguished from the 
_Phalangista Cookii by the greater relative 
length in the latter of the nasal and maxillary 
_ portion of the skull; while in most of the other 
ies of Petaurus, the facial part of the skull 
_ is relatively shorter than in the Pet. Tugua- 
 noides. 

Genus PHASCOLARCTUS. 

The absence of anomalous or functionless 
premolars and of inferior canines appears to be 
constant in the only known species of this 
genus. The dental formula in three examples 
of this species ( Phasc. fuscus, Desm.) is 


3—3 . int 
Gags INS omy 5... Premo- 


EE ———— “<_< — 


dd ee 


Incisors 


Sy... 1—1 4—4, ; 
; lars ei molars — 30. ( Fig. 95.) 
The true molars are larger in proportion than 
in the Phalangers; each is beset with four 
_ three-sided pyramids, the cusps of which wear 
down in age, the outer series in the upper teeth 
being the first to give way; those of the lower 
_ jaw are narrower than those of the upper. The 
“spurious molars are compressed and terminate 
in a cutting edge; in those of the upper jaw 
_ there is a small parallel ridge along the inner 
side of the base. The canines slightly exceed 
‘in size the posterior incisors; they terminate in 
an oblique cutting edge rather than a point ; 
their fang is closed at the extremity: they are 
situated as in the Phalangers close to the inter- 
maxillary suture. The lateral incisors of the 
upper jaw are small and obtuse; the two ante- 
rior or middle incisors are twice as long, broad, 
and thick as the posterior incisors; they are 
conical, slightly curved, sub-compressed, be- 
velled off obliquely to an anterior cutting edge, 
but differing essentially from the dentes scal- 
prari of the Rodentia in being closed at the 
extremity of the fang. The two incisors of the 
lower jaw resemble those of the upper, but are 
larger and more compressed; they are also 
formed by a temporary pulp, and its absorption 
is accompanied by a closure of the aperture of 
the pulp cavity, as in the upper incisors. The 
Koala, therefore, in regard to the number, kind, 
and conformation of its teeth, closely resembles 
the Phalangers, with which it also agrees in its 
long cecum and the general conformation of 
its digestive organs. It has also the extremities 


aa 


265 


similarly organised for prehension iftach is ter- 
minated by five digits; the hind feet are provided 
witha large thumb, and have the two contiguous 
digits enveloped in the same tegumentary fold ; 
the anterior digits are divided into two groups 
the thumb and index being opposed to the 
other three fingers. We have already noticed 
a structure approaching to this in some of the 
small Phalangers. The Koala, however, differs 
from the Phalangers and Petaurists in the ex- 
treme shortness of its tail, and in its more com- 
pact and heavy general form. It is only known 
to feed on the buds and leaves of the trees in 
which it habitually resides. 


Tribe IV. POEPHAGA. 

The present tribe includes the most strictly 
vegetable feeders; all the species have a com- 
plex sacculated stomach, and a long simple 
cecum. 

Genus HYPSIPRYMNUS. Potoroos. 

Guided by the modifications of the teeth 
we pass from the Koala to the Potoroos 
and Kangaroos—animals of widely different 
general form. The Potoroos, however, present 


Hypsiprymnus murinus. 


absolutely the same dentition as does the Koala, 
some slight modifications in the form of certain 
teeth excepted. The premolars in their longi- 
tudinal extent, compressed form, and cutting 
edge, would chiefly distinguish the dentition of 
the Potoroo; but the Koala evidently offers 
the transitional structure between the Phalangers 
and Potoroos in the condition of these teeth, of 
which one only is retained on each side of each 
Jaw in the Potoroos as in the Koala. 

The dental formula of Hypsiprymnus, the 
generic name of the Potoroos, is : 


Tncisors 


3 eee 
ot canines 


As molars — 30. 


—t1 
5% Premo- 


lars 


The two anterior incisors are longer and more 
curved, the lateral incisors relatively smaller 
than in the Koala. The pulps of the anterior 
incisors are persistent. The canines are larger 
than in the Koala; they always project from 
the line of the intermaxillary suture; and, 
while the fang is lodged in the maxillary bone, 
the crown projects almost wholly from the in- 
termaxillary. In the large Hypsiprymnus ursi- 
mus the canines are relatively smaller than in 
the other Potoroos, a structure which indicates 
the transition from the Potoroo to the Kangaroo 
genus. In the skeleton of this species in the 


266 


Leyden Museum, the canines have a longitu- 
dinal groove on the outer side. 

The characteristic form of the trenchant pre- 
molar has just been alluded to: its maximum 
of development is attained in the arboreal Po- 
toroos of New Guinea ( Hypsiprymnus ursinus 
and Hyps. dorcocephalus ), in the latter of which 
its antero-posterior extent nearly equals that 
of the three succeeding molar teeth. In all the 
Potoroos the trenchant spurious molar is sculp- 
tured, especially on the outer side, and in 

oung teeth, by many small vertical grooves. 

e true molars each present four three-sided 
pyramidal cusps; but the internal angles of 
the two opposite cusps are continued into each 
other across the tooth, forming two angular or 
concave transverse ridges. In the old animal 
these cusps and ridges disappear, and the grind- 
ing surface is worn quite flat, as in fig. 91, 
which represents the dentition of the original 
Potoroo, described in White’s Voyage. 

Genus MACROPUS. Kangaroos. 

In the genus Macropus (fig. 92) the normal 

condition of the permanent teeth may be ex- 


pressed as follows :-— 
P 3—3 ss o0—oO 
Incisors, — 3 canines, poe. ; premo- 
lars, emake ; molars, ee. a8, 
1—1 4—4 


The main difference, as compared with Hyp- 
siprymnus, lies in the absence of the upper 
canines as functional teeth; the germs, how- 
ever, of these teeth are always to be found in 
the young mammary fcetus of the Macropus 
major, and I have seen them a but of 
very small size, and concealed by the gum, in 
the adults of some small species of kangaroos, 


Macropus major, one-third nat. size. 


as Macropus rufiventer, Ogilby, and Macr. 
psilopus, Gould. This, however, is a rare ex- 
ception ; while the constant presence and con- 
spicuous size of the canines will always serve to 


istinguish the Potoroo from the Kangaroo. 
But ‘there are also other differences in the form 
and proportions of certain teeth. The upper 
incisors of the Macropi have their cutting 
margins in the same line, the anterior ones not 
being produced beyond thatline, as in the Hyp- 
siprymni: the third or external incisor is also 
broader in the kangaroos, and is grooved and 
complicated by one or two folds of the enamel, 
continued from the outer side of the tooth ob- 


MARSUPIALIA. 


liquely forward and inward. Tn most 
the anterior fold is re ted by a 
groove: the relative size of the outer 
the extent and position of the i 
enamel, and consequently the proportions | 
the part of the tooth in front or behind it, va 
more or less in every species of Macrom 
there are two folds of enamel near the ante 
part of the tooth in Macr. major, and 
terior portion is of the greatest extent, ai 
entire crown of the tooth is relatively br 
in this species. The middle incisor is 
also complicated by a posterior notch 
an external groove. ese modifications of 
external incisors of the kangaroos were first 
ticed by Mr. Jourdan, and subgeneric disti 
tions, with names often sufficiently unmean 
if not absurd,* have been subsequently b 
upon them; but such dental characters pos 
neither sufficient constancy nor physiole 
eae to justify such an application. 
. Fr. Cuvier has propel a binary 
sion of the genus Macropus, as here defit 
founded on the absence of permanent 
molars, and a supposed difference in the” 
of succession of the true molars in certair 
cies of Kangaroo, combined with modifical 
of the muzzle or upper lip, and of the tail. 
The dental formula which I have ass 
to the genus Macropus is restricted in its 
plication by that naturalist to some small; 
cies of Kangaroo, grouped together under 
term Halmaturus, originally applied by I 
to the Kangaroos generally.+ The rest 
Kangaroos, under the generic tem M 
pus, are characterised by the following « 
molars, — 
The truth, however, is 
both the Halmaturi | 
Macropi of M. Fr. Cu 
have their teeth deve 
in precisely the same 
ber and manner: they 
differ in the length of 
during which certain of 
teeth are retained.{ I 
great Kangaroo, 
ple, the permanent pret 
which suceeeds the e 
ponding deciduous or 
the vertical direction, 
pushed out of place 
shed by the time the 


Sern 


ex 


formula :—lIncisors, = 


* E.g. ia, Gray, Petrogale, Gray, 
signifies ‘ rock weasel.’ 
t Prodromus Systematis Mammalium et . 
8vo. 1811. The dental character which 
cellent naturalist gives, accurately expi 
condition of the canine or laniary teeth, * 
niarii aut nulli, aut superiores 2 ambigui, 
in medio inter primores et molares ce 
80; but there are never more than five mola 
place on each side of each jaw in the Kangar 
¢ M. Fr. Cuvier was aware that a deciduous” 
rious molar existed in the great indo} 
species of his subgenus Macropus, but he belli 
that it was peculiar to an early period of life, 
then existed only in a rudimental state 


ee 
— as 


germeé,” and that instead of being disp 


MARSUPIALIA. f 


true molar has cut the gum: the succeeding 
true molar is soon afterwards extruded; and 
T have seen a skull of an old Macropus major 
in the Museum at Leyden, in which the 
_ grinders were reduced to two on each side of 
 €ach jaw by this yielding of the anterior ones 
to the vis a tergo of their successors. 
_ The general form of the body in the Ma- 
_ cropodide is that of an elongated cone, the 
broad and stout haunches forming the base, 
and the produced tapering muzzle the apex. 
_ The proportions of the body are, however, re- 
duced by so elegant a gradation that they are 
_ justly considered as among the most picturesque 
of quadrupeds. The hinder extremities are al- 
ways longerand stronger than the fore ones, but 
_ in various proportions ; the difference being least 
" in the arboreal Potoroos, and in that section of 
the genus = hegctaa by the Hypsiprymnus 
_ myosurus of Van Dieman’s Land. The tail is 
_ very long in all the species, but is strongest in 
_ the great kangaroos, which make use of it as a 
_ kind of crutch or fifth extremity in their slower 
modes of progression. In the Potoroos the 
tail is more slender, and in these and some of 
_ the smaller species of kangaroo it is bent be- 
neath the body when the animal reposes. 


Tribe V. RHIZOPHAGA. 

In this tribe, the stomach is simple in out- 
ward form, but complicated within by a large 
cardiac gland ; and the ceecum, which is short 
and wide, with a vermiform appendage. 

Genus PHASCOLOMYS, (jig. 93.) 
In its heavy shapeless figure, large trunk, 
and short equably developed legs, the Wom- 
_ bat offers as great a contrast to the Kangaroos as 


Fig. 93. 


Phascolomys fusca, Geoff’. one-half nat, size. 


does the Koala, which it most nearly resembles 
in its general outward form and want of tail. 
But in the more important characters afforded 
by the teeth and intestinal ¢anal, the Wombat 


succeeded in the vertical direction by a permanent 
Spree molar, as in the Halmaturi, it was dis- 
aced by the true molars, which are developed 
rom behind forwards. 1 have however detected the 
crown of thepermanent spurious molar in the jaws 
of the Macropus major in a concealed alveolus, and 
have observed it completely formed and in place 
in an individual which had nearly attained its full 
_ size.—See F, Cuvier’s account of the Halmaturus 
_ Thetis in the “« Histoire des Mammiféres,”’ folio. 
4 


267 


differs more from the Koala than the latter does 
from either the Phalangers or Kangaroos. 

The dental system presents the extreme de- 
gree of that degradation of the teeth, interme- 
diate between the front incisors and true molars, 
which we have been tracing from the Opossum 
to the Kangaroos: not only have the function- 
less premolars and canines now totally disap- 
peared, but also the posterior incisors of the 
upper jaw, which we have seen in the Potoroos 
to exhibit a feeble degree of development as 
compared with the anterior pair; these in fact 
are alone retained in the dentition of the present 
group, the representative of which possesses 
the fewest teeth of any Marsupial animal. The 
dental formula of the Wombat is thus reduced 
both in number and kind to that of the true 
Rodentia.* 


S349 ee ce. 1524 
Incisors, z 5 canines, 3: premolars, nee 
—A4 
molars, = 24. 
—4 


The incisors moreover are true dentes scalpra- 
rii, with persistent pulps, but are inferior, espe- 
cially in the lower jaw, in their relative length 
and curvature to those of the placental Glires; 
they presenta subtriedral figure, and are traversed 
by a shallow groove on their mesial surfaces. 

The spurious molars present no trace of that 
compressed structure which characterizes them 
in the Koala and Kangaroos, but have a wide 
oval transverse section ; those of the upper jaw 
being transversed on the inner side with a 
slight longitudinal groove. The true molars 
are double the size of the premolars: the su- 
perior ones are also traversed by an internal 
longitudinal groove, but this is so deep and 
wide that it divides the whole tooth into two 
prismatic portions, with one of the angles 
directed inwards. The inferior molars are 
in like manner divided into two triedral 
portions, but the intervening groove is here 
external, and one of the facets of each 
prism is turned inwards. All the grinders 
are curved, and describe about a quarter 
of a circle: in the upper jaw the con- 
cavity of the curve is directed outwards ; 
in the lower jaw, inwards. The false and 
true molars, like the incisors, have per- 
sistent pulps, and are consequently devoid 
of true fangs, in which respect the Wom- 
bat differs from all other Marsupials, and 
resembles the extinct Toxvodon, the denti- 
gerous Bruta, and herbivorous Rodentia. 

I may add that the Wombat deviates from 
the other Marsupials in the number of its ribs ; 
as these are very constant in the rest of the order, 
the difference in the Wombat, which has 15 
pairs, instead of 13 or 12, is the more deserving 


* In all the placental Rodents, which have more 
than three molars in each lateral series, the addi- 
tional ones are placed at the anterior part of the 
row, and are subject to displacement by a perma~ 
nent successor in the vertical direction, and conse- 
quently are essentially ‘‘ premolars,’”’ or spurious 
molars; the Wombat strikingly manifests its mar- 
supial character in having four true molars on each 
side of both jaws. 


268 


of notice. The Koala, like the P and 
Kangaroos, has 13 pairs of ribs ; but this class 
of characters will form the subject of the fol- 
lowing section. 


OsreoLocy or tae Marsupratta. 

Of the Skull—The form of the skull 
varies much in different Marsupial animals, 
but it may be said, in general terms, to re- 
semble an elongated cone, being terminated by 
a vertical plane surface behind, and in most 
of the species converging towards a point ante- 
riorly: it is also generally more depressed or 
flattened than in the placental Mammalia. The 
skull is also remarkable in all the Marsupial 
genera for the small proportion which is de- 
voted to the protection of the brain, and for the 
great expansion of the nasal cavity immediately 
anterior to the cranial cavity. 

In the stronger carnivorous Marsupials the 
exterior of the cranium is characterized by bony 
ridges and muscular impressions, but in the 
smaller herbivorous and insectivorous species, 
as the Petaurists, Potoroos, and Myrmecobius, 
the cranium presents a smooth convex surface 
as in Birds, corresponding with the smooth un- 
convoluted surface of the simple brain con- 
tained within. 

The breadth of the skull in relation to its 
length is greatest in the Wombat,* Ursine Da- 
syuret and Petaurists, in which it equals three- 
fourths of the length, and is least in the Pera- 
meles lagotis, in which it is less than one-half. 

The occipital region, which is generally plane, 
and vertical in position, forms a right angle 
with the upper surface of the skull, from which 
it is separated by an occipital or lambdoidal 

-crista. is crista is least developed in the 
Myrmecobius, Petaurists, and Kangaroos, and 
most so in the Thylacine and larger Opossums, 
in which, as also in the Koala, the crest curves 
slightly backwards, and thus changes the occipi- 
tal plane into a concavity for the firm implanta- 
tion of the strong muscles from theneck and back. 

The upper surface of the skull presents great 
diversity of character, which relates to the dif- 
ferent development of the temporal muscles, and 
the varieties of dentition in the different genera. 

In the Wombat the coronal surface offers an 
almost flattened tract bounded by two slightly 
elevated temporal ridges, which are upwards of 
an inch apart posteriorly, and slightly diverge, 
as they extend forwards to the anterior part of 
the orbit. 

The skull of the Virginian Opossum pre- 
sents the greatest contrast to that condition, for 
the sides of the cranium meet above at an acute 
angle, and send upwards from the line of their 
union a remarkably elevated sagittal crest, which, 
in mature skulls, is 6 gag a at more deve- 
loped& than in any of the placental Carnivora, 
not even excepting the strong-jawed Hyena. 

The Thylacine and Dasyures, especially the 
Ursine Dasyure, exhibit the sagittal crest in a 
somewhat less degree of development. It is 
again smaller, but yet well marked in the Koala 
and Perameles. e temporal ridges meet at 


* As 15 to 20. +t As 10 to 14. 


MARSUPIALIA. 


the lambdoidal suture in the larger Ph 
and in the Hypsiprymni, but the size 
muscles in these does not require the de 
lopment of a bony crest. we 

In the Kangaroo, the temporal ri wh 
are very slightly raised, are y 


interspace of the third of an inch. al 
They are separated for a proportion: 
greater extent in the Petaurists, est 
Petaurus flaviventer ; and in the smoot 
convex upper surface of the skull of Peta 
sciureus, Pet. pigmeus, Myrmecobius, thi 
pressions of the feeble temporal muscles 
cease to be discernible. 2 
The zygomatic arches are, however, com 
in these as in all the other genera: the 
usually, indeed, wnat pr ; but 
variations do not indicate the nature o 
food so clearly, or correspond with the. 
rences of animal and vegetable diet in the 
degree as in the placental Mammalia. 
this is not surprising when we recollect thi 
Marsupial animal is devoid of incisors it 
upper jaw, like the ordinary Ruminants o 
placental series : accordingly the more — 
pete dental system with which the herbiyo 
angaroos, Potoroos, Phal &c. are 
vided, and which appears to be in relatic 
the scantier pasturage and the dry and 
character of the herbage or foliage on 
they browse, requires a stronger apparatt 
bone and muscle for the action of the jaws 
especially for the working of the tert 
teeth. There are, however, well marked ¢ 
rences in this part of the Marsupial skull. 
the weakest zygomatic arches are those 
Insectivorous Perameles and é 
which structure we may discern a corres 
dence with the Edentate Anteaters of the 
cental series. Still the difference in the ¢ 
lopment of the zygomata is greatly in favo 
the Marsupial Insectivora. q 
The Hypsiprymni come next in the ore 
development of the zygomatic arches; wi 
again are proportionally much stronger 
true Senescona The vength of the zygo 
in relation to the entire skull is greatest in 
Koala and Wombat. In the former 
they are remarkable for their depth and 
and parallel course, as well as for their 
tudinal extent. In the Wombat they ha 
considerable curve outwards, so as gre 
diminish the resemblance which otherwise 
ists in the form of the skull between this } 
supial and the Herbivorous Rodentia of 
placental series, as, e.g. the Viscaccia. _ 
In the carnivorous Marsupials the out 
sweep of the zygomatic arch, which is grez 
in the Thylacine und Ursine ‘a 
accompanied by a slight curve up : 
this curvature is chiefly expressed by the 
cavity of the lower margin of the zygoma 
is by no means so well marked as in 
placental Carnivora. It is remarkable that th 
upward curvature is greater in the ( 
zygomata of the Perameles than in the stror 
zygomata of the Dasyures and Opossums. | 
the Koala and Phalangers there is also a sligl 
tendency to the upward curvature; in th 


, 


Wombat the outwardly expanded arch is per- 
fectly horizontal. In the Kangaroo the lower 
margin of the zygoma describes a slightly undu- 
lating curve, the middle part of which is con- 
vex downwards. 
_ In many of the Marsupials, as the Kangaroo, 
_ the Koala, some of the p 
and Opossums, the superior margin of the 
_ zygoma begins immediately to rise above the 
_ posterior origin of the arch. In the Wombat 
an external ridge of bone commences at the 
_ middle of the lower margin of the zygoma, and 
gradually extends outwards as it advances for- 
wards, and being joined by the upper margin 
of the zygoma, forms the lower boundary of 
‘the orbit, and ultimately curves downwards in 
front of the ant-orbital foramen, below which 
it bifurcates and is lost. This ridge results, as 
it were, from the flattening of the anterior part 
of the zygoma, which thus forms a smooth and 
slightly concave horizontal platform for the eye 
_ to rest upon. 
__ The same structure obtains, but in a slighter 
degree, in the Koala. 
_ In the Kangaroo the anterior and infenor 
part of the zygoma is extended downwards in 
‘the form of a conical process, which reaches 
below the level of the grinding-teeth. A much 
shorter and more obtuse process is observable 
in the corresponding situation in the Phalangers 
and Opossums. 
The relative length of the facial part of the 
skull anterior to the zygomatic arches varies re. 
‘markably in the different Marsupial genera. In 
the Wombat it is as six to nineteen; in 
the Koala as five to fourteen; in the Pe- 
_ taurus sciureus and Petaurus Bennettii it forms 
‘about one-fourth of the entire skull; in the 
_ Phalangers about one-third ; in the carnivorous 
Dasyures and Opossums more than one-third ; 
in the Thylacine nearly one-half; in Perameles, 
Macropus, and Hypsiprymnus murinus, I]. the 
length of the skull anterior to the orbit is equal 
to the remaining posterior part ; but in a species 
Hypsiprymnus from Van Dieman’s Land 

_( Aypsiprymnus myosurus, Ogilb.), the facial 
part of the skull anterior to the orbit exceeds 
that of the remainder, and the arboreal Hypsi- 
ag from New Guinea present a still greater 
length of muzzle. In most Marsupials the 
skull gradually converges towards the anterior 
extremity; the convergence is more sudden 
in the Petaurists, especially Pet. Bennettii ; 
but in the Perameles lagotis the skull is re- 
markable for the sudden narrowing of the face 
anterior to the orbits, and the prolongation of 
the attennated snout, preserving the same 
diameter for upwards of an inch before it finally 
tapers to the extremity of the nose. In the 
Koala the corresponding part of the skull is 
as remarkable for its shortness, as it is in the 
Per. lagotis for its length, but it is bounded 
laterally by parallel lines through its whole 
extent. Before concluding this account of the 
general form of the skull, I may observe that 
in nearly all the Marsupials two long processes 
project downwards from the inferior angles of 
the occipital region ; they correspond in func- 


Vy 


MARSUPIALIA. 


halangers, Petaurists,’ 


269 


tion with, and have been desfribed as the 
mastoids, but they are developed from the 
ex-occipital bones. These processes are longest 
in the Kangaroos and Koala; in the Wombat 
they co-exist with the true mastoid pro- 
cesses, which are of larger size. In the Opos- 
sums and Dasyures the exoccipital processes 
are short and obtuse; in Acrobates they cease 
to exist, but they are present in the larger 
Petaurists. 

Of the composition of the cranium.—The 
occipital bone is developed, as in the placental 
Mammalia, from four centres or elements,—the 
basilar below, the supra-occipital above, and 
the ex-occipitals at the sides; but these ele- 
ments remain longer separate, and in some 
genera do not become at any period of life 
united by continuous ossification. 

In the skull of an aged Virginian Opossum, 
I found the supra-occipital still distinct from 
the ex-occipitals, and these not joined together, 
though anchylosed to the basilar element. I 
say not joined together, because in this Mar- 
supial animal they meet above the foramen 
occipitale and complete its boundaries, as the 
corresponding superior vertebral lamine com- 
plete the medullary canal in the region of the 
spine. I find the same structure and condition 
of the occipital bone of an adult Dasyurus 
Ursinus, and it is exhibited in the plate of 
the cranium of this species given by M. 
Temminck.* 

In the skull of the mature Wombat, of which 
a reduced representation is given at fig. 94, the 
ex-occipitals were still unanchylosed ; the left 
is figured separate at a. 

In the skull of a Perameles nasuta the ex- 
occipitals are separated by an interspace, so 
that a fissure is continued from the upper part 
of the foramen magnum to the supra-occipital 
element. The same structure may be observe: 
in the great Kangaroo, and it is very re- 
markable in the young skulls of this species ; I 
found this superior notch wide and well marked 
in Macropus Bennettiit. In the Wombat the 
corresponding fissure is very wide, and the 
lower margin of the supra-occipital is notched, 
so that the shape of the foramen magnum 
somewhat resembles that of the trefoil leaf. In 
the Koala, the Phalanger, Petaurists, Hypsi- 
prymni, and Dasyurus Maugei, the elements of 
the occipital bone present the usual state of bony 
confluence. 

The temporal bone generally presents a per- 
manent separation of the squamous, petrous, 
and tympanic elements. I have observed this 
reptilian-like condition of the bone in the ma- 
ture skulls of an Ursine Dasyure, a Virginian 
Opossum, a Perameles, in different species of 
Potoroo and Kangaroo, in the Wombat, and in 
the Koala. The petrous and mastoid elements 
are commonly anchylosed together. So loose 
indeed is the connexion of the tympanic bone, 
that without due care it is very liable to be lost 
in preparing the skulls of the Marsupials. In 
the Kangaroo and Wombat (fig. 94, 6) it 


* Monographies de Mammalogie, pl. viii. 


270 


Phascolomys. 


forms a complete bony tube, about half an 
inch in length, with an irregular exterior ; 
it is wedged in between the mastoid and 
articular processes of the temporal bone. In 
the Potoroo the bony circle is incomplete at 
the upper part; in the Perameles and Da- 
syures the tympanic bone forms a semicircle, 
the posterior part being deficient, and the tym- 
panic membrane being there attached toa des- 
cending process of the squamous element of 
the temporal bone. Here we have a near ap- 
ingen to the form of tympanic bone in Birds, 

ut we have a still closer resemblance to its 
condition both in Birds and Reptiles, in its 
want of union with and relations to the petrous 
element of the temporal bone. In the Rodent 
quadrupeds the tympanic, petrous, and mas- 
toid elements of the temporal bone are always 
anchylosed together; this condition is well 
shewn in the skull of the Porcupine and 
Beaver, in which the mastoid element sends 
down a thin obtuse preares behind the petro- 
Ppa portion. It is to the expansion of 

e petro-tympanic, and not of the mastoid 
portion of the temporal bone, that the enlarge- 
ment of the tympanic cavity is due in the 
Rodentia, and this expansion forms in that 


MARSUPIALIA. 


‘the auditory cavity ; but, with one single 


order, as is well known, a bulla osse 
which is situated anterior and internal tot 
mastoid process. In many of the Marsupi: 
as the Dasyures, Petaurists, Perameles, F 
toroos, and Koala, there is also a large bu 
ossea for the purpose of increasing the exter 


ception, the Wombat, this bulla is not fon 
by the tympanic or any other element of 
temporal bone, but by the expansion 
base of the great ala of the sphenoid be 
Acrobates and Perameles lagotis, in addi 
to the preceding bulla there is also an ext 
dilatation of the petrous element of the 
poral bone, which thus forms a second 
smaller bulla on each side, behind t 
bulla ossea formed by the sphenoid. r 
Marsupials the petrous bone is of smalls: 

rally limited to the office of protecting the pp 
of the internal ear, and sometimes, as 
Koala, is barely visible at the exterior of 
of the skull. The petrous and mastoid elem 
are usually anchylosed together in the Mi 
pials, and the mastoid portion appears 

occipital region of the skull of the Ke 
between the ex-occipital bones and squan 
portion of the temporal. The petrous elen 
of the temporal bone ap external 
the corresponding part of the skull of a yo 
Emeu. In the Kangaroos and Womk 
petro-mastoid bone presents a larger size, 
is visible in two situations on the outsid 
the skull, viz. at the usual place at the 
where the petrous portion is wedged in 
tween the basilar bone, ex-occipital and s 
noid, and again at the side of the cra 
where the mastoid portion appears between 
squamous, ex-occipital, and supra-oee 
bones. In the Wombat it sends outwards 
strong compressed process which 
the lateral boundaries of the occipital pla 
the cranium ; but this process is entirely 
to the ex-occipitals in the Koala and « 
Marsupials. 

The auditory chamber of the ear is | 
mented in the Phalangers, the Koala, the’ 
garoos, and Potoroo, by a continuation ¢ 
cells into the base or origin of the 
haga de but the extent of the bony air-el 

ers communicating with the tympanu 
proportionally greatest in the Flying Oposs 
where, besides the phen bulla, the m 
element and the whole of the zygom 
cess of the temporal bone are expandé 
form air-cells with very thin and smooth ¥ 
thus presenting an interesting anal r 
structure of the cranium to the class of bir 

The direction of the bony canal of 
of hearing corresponds, as in the pla 
Mammalia, with the habits of the sp 
The meatus is directed outwards and a 
forwards in the carnivorous Dasyures, 
wards and a little backwards in the Peram 
and Phalangers; outwards, backwaré 
upright in the Kangaroos, and directly 
wards in the Petaurists and Wombat; but 
differences of direction are but slightly mai 

The squamous element of the tempe 


_ generally reaches half-way from the root of the 
zygoma to the sagittal ridge or suture; it is 
most developed in the Wombat, in which its 
_ superior margin describes a remarkably straight 
line. The zygomatic process of the temporal 
bone is generally compressed and much ex- 
_ tended in the vertical direction in the Opossum, 
_ Dasyure, Phalanger, Koala, and Kangaroo. 
| In the Wombat it curves outwards from the 
_ side of the head in the form of a compressed 
and almost horizontal plate; it is then sud- 
_ denly twisted into the vertical position, to be 
_ Feceived into the notch of the malar portion of 
the arch. 
| _ The cavity corresponding to the sphenoidal 
bulla ossea in other Marsupials is in this 
| Species excavated in the lower part of the 
_ Squamous element of the temporal bone at the 
_ inner side of the articular surface for the lower 
‘ er This articular surface, situated at the 
__ base of the zygomatic process, presents in the 
| Marsupial, as in the placental Mammalia, 
_ various forms, each manifesting a physiological 
_ Telation to the structure of the teeth and adapted 
| to the required movement of the jaws in the 
_ Various genera. In the herbivorous Kangaroo 
_ the glenoid cavity forms a broad and slightly 
_ convex surface, as in the Ruminants, affording 
freedom of rotation to the lower jaw in every 
direction. In the Phalangers and Potoroos 
the articular surface is quite plane. In the 
_ Perameles it is slightly convex from side to 
_ side, and concave from behind forwards. In 
_ the Wombat it is formed by a narrow convex 
_ ridge considerably extended, and slightly con- 
_ Cave, in the transverse direction. This ridge is 
| not bounded by any descending process pos- 
| teriorly, so that the jaw is left free for the 
“movements of protraction and retraction. But 
‘this structure is widely different from that 
which facilitates similar movements in the Ro- 
dentia. In these there is a longitudinal groove 
on each side, in which the condyle of the lower 
_ jaw plays backwards and forwards, but is im- 
_ peded in its lateral movements; these, on the 
contrary, are freely allowed to the Wombat, 
| and the oblique disposition of, the lines of 
enamel upon the molar teeth correspond with 


the various movements of which the lower jaw 
of the Wombat is thus susceptible. In the 
Koala the glenoid cavity is a transversely ob- 
_ long depression with a slight convex rising at 
the bottom, indicating rotatory movements of 
the jaw. In the carnivorous Dasyures it forms 
4 concavity still more elongated transversely, 
tess deep than in the placental Carnivora, but 
adapted, as in them, toa ginglymoid motion of 
_ the lower jaw. In all the genera, save in the 
i, Wombat, retraction of the lower jaw is opposed 
_ bya descending process of the temporal bone 
_ immediately anterior to the meatus auditorius 
and tympanic bone. 

_ The glenoid cavity presents a characteristic 
tructure in most of the Marsupialia in not 
ing exclusively formed by the temporal bone. 
ith the exception of the Petaurists, the malar 
one forms the outer part of the articular sur- 
ce for the lower jaw, and in the Thylacinus, 
lasyurus Maugei, Dasyurus ursinus, Pera- 


MARSUPIALIA. 


f 271 


meles, Hypsiprymnus, and Macropus the sphe- 
noid ala forms the inner boundary of the same 
surface; but this.ala does not extend so far out- 
wards and backwards in the Wombat or Koala. 

The sphenoid bone has the same general 
form and relative position as in the ordinary 
Mammalia, but in many Marsupials it presents 
a similarity to that in the Ovipara in the per- 
sistence of the pterygoid processes as separate 
bones, as shown in the Wombat (fig. 94, c). 
It is only in the Koala that I have observed 
a complete obliteration of the suture joining 
the basilar element of the sphenoid with 
that of the occipital bone. In the Thylacine 
a narrow straight bridge of bone is continued 
from the auditory sphenoidal bulla forwards to 
the base of the pterygoid process, resembling 
the condition of the pterygoids in Birds. 

The chief peculiarity in the sphenoid bone 
is the dilatation of the root of the great ala 
already alluded to. This dilatation communi- 
cates and is filled with air from the tympanum. 
It forms the hemispherical bulla ossea on each 
side of the basis cranii in the Dasyures and 
Phascogales, and the large semi-ovate bull in 
the Myrmecobius, Cook’s Phalanger, &c.; but 
in the Koala the bulle (6, fig. 95,) are still 


( iN AIT x 


Phascolarcius. 

more developed, and are produced downwards 
to an extent equal with the ex-occipital pro- 
cesses (a, fig. 95); they are somewhat com- 
pressed laterally, and instead of the smooth 
and polished surface which characterizes them 
in the preceding genera, terminate here in a 
rough ridge. The dilated air-chambers or 
bull of the sphenoid are very small in the 
Thylacine; in the Phalangers and Potoroos 
they are relatively smaller than in the Dasyures, 
and they are incomplete posteriorly in the Kan- 
garoos and Wombat. In the Brush-Kangaroo 
the above process from the sphenoid joins the 
base of the large descending process of the 
ex-occipital. The pterygoid processes are 
relatively largest in the Kangaroo, Wombat, 
and Koala, and present in each of these species 
distinct hamular processes. In the Potoroo, 
Kangaroo, and Wombat the sphenoid ala com- 
bines with the pterygoid process to form a 
large and deep depression opening externally. 
In the Kangaroo, Dasyures, Koala, and Wom- 
bat the great ale of the sphenoid articulate 
with the parietal bones, but by a very small 
portion in the two latter species: in the Pera- 


272 


meles and Potoroos the sphenoid ale do not 
reach the parietals. 

There is little to notice in the parietal bones 
except the obliteration of the sagittal suture in 
those species in which a bony crista is deve- 
loped in the corresponding place. They pre- 
Sent a singularly flattened form in the Wombat, 
in an aged skull of which, and in a similar one 
in the Kangaroo, I observe a like obliteration 
of the sagittal suture. In the Kangaroo, 
Potoroo, Petaurus, Phalanger, and Myrme- 
cobius there is a triangular inter-parietal bone. 
The corresponding bone I find in three pieces 
in the skull of a Wombat. 

The frontal bones are chiefly remarkable for 
their anterior expansion and the great share 
which they take in the formation of the nasal 
cavity. In the Thylacine the part of the cranium 
occupied by the frontal sinuses exceeds in 
breadth the cerebral cavity, from which it is 
divided by a constriction. The coronal suture 
presents in most of the Marsupials an irregular 
angular course, forming a notch in the frontals 
on each side which receives a corresponding 
triangular process of each, parietal bone: this 
form of the suture is least pronounced in the 
Acrobates and Myrmecobius. A process cor- 
responding to the posterior frontal augments 
the bony boundary of the orbit in the Thylacine, 
the Ursine Dasyure, and in a slighter degree 
in the Virginian Opossum ; it is relatively most 
developed in the skull of the Myrmecobius 
Jasciatus, where the orbit. is large; but the 
bony boundary of the orbit is not complete in 
any of the Marsupials. In the Myrmecobius 
there is a deep notch at the middle of the 
supra-orbital ridge. A corresponding but 
shallower notch is present in the skull of 
Petaurus sciureus. have found the frontal 
suture obliterated in old specimens of the 
Thylacine, the Virginian Opossum, Cook’s Pha- 
langer, the taguanoid, and yellow-bellied Pe- 
taurists; but the frontal suture exists in Petaurus 
Sciureus, Acrobates, and other Marsupials. 
The inter-orbital space is concave in the Pha- 
langers and in the Petaurus Taguanoides, but 
is quite flat in the other Petaurists. 

e lachrymal bones vary in their relative 
size in different Marsupialia. In the Koala 
they extend upon the face about a line beyond 
the anterior boundary of the orbit, and at this 
part they present a groove with one large and 
two or three small perforations. In the Wom- 
bat their extent upon the face is slightly in- 
creased; it is proportionally greater in the 
Kangaroos, Potoroos, Phalangers, Petaurists, 
and Dasyures, in which this part of the 
lachrymal bone presents two perforations close 
to the orbit. In the Thylacine, besides the 
two external holes there is a large perforation 
within the orbital margin. This carnivorous 
Marsupial, as compared with the Wolf, pre- 
sents a greater extent of the facial portion of 
the lachrymal bone, and thus indicates its 
inferior type. In the Myrmecobius the lachry- 
mal bone exhibits its greatest relative develop- 
ment. 

The malar bones are very strong and of great 
extent in almost all the Marsupialia. They 


MARSUPIALIA. 


are least developed in Acrobates, 1] 
cobius, and Perameles lagotis. In the latt 
the malar bone presents a singular form, b 
bifurcate at both extremities: the proces 
zygomaticus maxille superioris is wedged 
the cleft of the anterior fork; the correspor 
ing process of the temporal bone fills up 
sterior notch; the lower division of — 
ifurcation is the longest, and in all the ¥ 
supialia enters into the composition of 
articular surface for the a 
the Petaurists, where it just 
The anterior bifurcation of the & 
one is not present in the Marsupials ger 
the external malo-maxillary suture fe 
oblique and almost straight line in the Wom 
Phalanger, Opossum, Dasyures, and Kangar 
Owing to the inferior development of the zy; 
matic process of the superior maxillary in | 
Wombat, the malar bone is not suspen 
the zygomatic arch in this Marsupial as in 
placental Rodentia. It is also of ’ 
much larger size and of a prismatic 
arising from the development of the ¢ 
external ridge above described. In the 
garoos, Potoroos, Great Petaurus, and — 
langers it is traversed externally by a & 
showing the extent of attachment of 
masseter; in the Koala the ridge extends al 
the malar bone near the upper margin, — 
surface below presents a well-marked exes 
tion. 4 
The nasal bones vary in their form and 
tive size in the different genera ; they are lor 
and narrowest in the Perameles, short 
broadest in the Koala. Their most 
teristic structure is the expansion of their 
and posterior extremity, which is well mai 
in the Wombat, Myrmecobius, " 
Phalangers, Opossums and Dasyures. 
In the Potoroos the anterior extremitie: 
the nasal bones converge to a point which } 
jects beyond the inter-maxillaries. In s§ 
Petaurists and Perameles the correspon¢ 
ints reach as far as the inter-maxillaries, 
in a skull of the Perameles lagotis I have fe 
the bony case of the nasal passages to be fu 
increased by the presence of two small ros 
bones, resulting, as in the Hog, from os 
of the nasal cartilage. 
The inter-mazillary bones always ec 
teeth, and the ratio of the development of t 
bones corresponds with the bulk of the de 
apparatus which they a They are 
sequently largest in the Wombat, where 
extend far upon the side of the face and 
articulated to a considerable proportion of 
nasal bones, but do not, as in the plac 
Rodentia, reach the frontal or divide 
maxillary bone from the nasal. yD 
sent a somewhat lower degree of develop 
in the Koala, but both in this species 
in the Wombat they bulge outwards and - 
remarkably increase the transverse diam 
of the osseous cavity of the nose. Ne 
in Hypsiprymnus nor Macropus do I f 
the incisive palatal foramina entirely im 
intermaxillary bones, as is descri t 
author of the text in Pander and D’Alto1 


Skelete der Beutelthicre ; a small proportion of 
their bony circumference is due to the anterior 
extremity of the palatal process of the maxil- 
lary: the same structure cbtains in the Wom- 
_ bat, Koala, and Opossums. In the Dasyures 
and Phalangers a greater proportion of the 
posterior boundary of the incisive or anterior 
palatal foramina is formed by the maxillaries ; 
in the Petaurists they are entirely surrounded 
by the maxillary bones, while in the Perameles 
_ they are, on the contrary, entirely included in 
_ the intermaxillaries. They always present the 
form of two longitudinal fissures: the Myrme- 
_cobius agrees with the other Marsupials in this 
_ Structure. 
__ The superior mavillary bone in the Wom- 
_ bat sends upwards a long, narrow, irregular 
_hasal process, which joins the frontal and 
nasal bones, separating them from the inter- 
_ maxillaries; the part of the maxillary bone 
_ which projects into the temporal fossa behind 
the orbit presents two or three smooth tuberosi- 
_ ties, formed by the thin plate of bone covering 
_ the pulps of the large curved posterior grinders. 
_ The corresponding part in the Perameles lagotis 
is perforated by numerous minute apertures 
like a cribriform plate, and this structure is 
presented in a-slighter degree in the Potoroos 
and Ursine Dasyure. The antorbital foramen 
does not present any marked variety of size, 
which is generally moderate. It is much 
closer to the orbit in the carnivorous Marsu- 
pialia than in the corresponding placental 
_quadrupeds. It is relatively largest in the 
_Ursine Dasyure. It presents the form of a 
_ vertical oblique fissure in the Wombat. I have 
observed it double in the Kangaroo. The chief 
differences in the maxillary bones, indepen- 
| dently of the teeth and their alveoli, are pre- 
_ sented by the palatal processes, the modifica- 
_ tions of which we shall consider in conjunction 
with those presented by the palatal processes 
f the palatal bones. The perforations and 
acuities of the bony palate deserve, indeed, 
icular attention, as they are often specific 
d of consequence in the determination both 
f recent and fossil species. 

In Phalangista Cookii, in Petaurus flaviven- 
ter, and Petaurus sciureus, in Macropus major, 
nd. some other great Kangaroos the bony 
palate is of great extent and presents a smooth 
Surface, concave in every direction towards the 
mouth ; it is pierced by the two posterior palatine 
‘foramina at the anterior external angles of the 
| palatine bones, either within or close to the 
transverse palato-maxillary sutures. Behind 

ese foramina, in the Kangaroo, there are a 
few small irregular perforations. The bony 
palate is similarly entire in the Hypsiprymnus 
ursinus. In Macropus Bennettii there are four 
orifices at the posterior part of the bony palate. 
the two anterior ones are situated upon the 

ato-maxillary suture, and are of an ovate 
form with the small end forwards. The two 
‘posterior foramina are of a less regular form 
and smaller size. In the Brush Kangaroo 

Macropus Brunii, Cuv.) the posterior palatal 
foramina present the form of two large fissures 
placed obliquely and converging posteriorly. 

VOL. WI, 


MARSUPIALIA. 273 


They encroach upon the posterior borders of 
the maxillary plate. Anterior to these vacancies 
there are two smaller foramina, and posterior 
to them are one or two similar foramina. 

In the Australian Potoroos, Wombat, and 
Koala, the posterior palatal openings are large. 
and oval, and situated entirely in the poet 
bones. In Hyps. setosus they extend as far for- 
wards as the interspace between the first and 
second true molars; in Hyps.-murinus they 
reach to that between the second and third 
true molars. Posterior and external to these 
large vacuities there are two small perforations. 
In the Phalangers, with the exception of Ph. 
Cookii, the palatal openings are proportionally 
larger; they extend into the palatal process of 
the maxillaries, and the thin bridge of bone 
which divides the openings in the Potoroo, &c., 
is wanting ; the two perforations at the pos- 
terior external angles of the palatine bones are 
also present. In the Virginian Opossum the 
bony palate presents eight distinct perforations, 
besides the incisive foramina; the palatal pro- 
cesses of the palatine bone extend as far for- 
wards in the median line as the third molars : 
a long and narrow fissure extends for an equal 
distance (three lines) into the palatal processes 
both of the palatines and maxillaries: behind 
these fissures and nearer the median line are 
two smaller oblong fissures; external and a 
little posterior to these are two similar fissures, 
situated in the palato-maxillary suture ; lastly, 
there are two round perforations close to the 
posterior margin of the bony palate. 

In the Ursine Dasyure a large transversely 
oblong aperture is situated at the posterior part 
of the palatal processes of the maxillary bones, 
and encroaches a little upon the palatines ; 
this aperture is partly,* perhaps in young 
skulls wholly, bisected by a narrow longitu- 
dinal osseous bridge. In Mauge’s Dasyure there 
are two large ovate apertures crossing the palato- 
maxillary sutures separated from each other 
by a broad plate of bone; posterior to these 
are two apertures of similar size and form, 
which, being situated nearer the mesial line,.are 
divided by a narrower osseous bridge; each 
posterior external angle of the bony palate is 
also perforated by an oval aperture. In the 
Viverrine Dasyure the two vacancies which 
cross the palato-maxillary suture are in the 
form of longitudinal fissures, corresponding to 
the fourth and fifth grinders; the posterior 
margin of the bony palate has four small aper- 
tures on the same transverse line. 

Now there is no carnivorous quadruped in the 
placental series which has a bony palate cha- 
racterized by perforations and vacuities of this 
kind. Inthe Dog, the Cat, and the Weasel-tribe 
the bony palate is only perforated by two 
small oblique canals which open in or near the 
palato-maxillary suture. The very great in- 
terest which is attached to the fossil remains of 
the Stonesfield Marsupials, the only mammi- 


* The large aperture in the skull of the Da- 
urus ursinus figured by Temminck is the result 
of accidental injury to the bony palate. Mono- 
graphies de Mammalogie, pl, viii. 
T 


274 


ferous remains hitherto discovered in the se- 
condary formations, will justify the minuteness, 
perhaps tediousness, with which I have dwelt 
on characters that, inclusive of the teeth, serve 
to distinguish the cranium of the Marsupial 
from that of any Placental quadruped. e 
structure of the bony palate in the Marsupials 
is interesting in other respects. Since the de- 
fective condition of this part of the cranium is 
one of the characteristics of the skull of the 
Bird, it might be expected that some approx- 
imation would be made to that structure in the 
animals which form the transition between the 
Placental and Oviparous Classes. We have 
already noticed the large vacuities which occur 
in the bony palate of nearly all the Marsupials ; 
but this imperfectly ossified condition is most 
remarkable in the great Perameles lagotis and 
Acrobates. In the former (fig. 96) the bony 


Fig. 96. 


= Perameles lagotis. 


roof of the mouth is perforated by a wide 
oval space extending from the second pre- 
molars to the penultimate molars, exposing to 
view the vomer and the convolutions of the 
inferior spongy bones in the nasal cavity. Be- 
hind this space there are six small perforations, 
two in a transverse line midway batween the 
great vacancy and the posterior margin of the 
bony palate, and four in a transverse line close 
to that margin. In Acrobates a still larger pro- 

rtion of the posterior part of the palate is 
ormed by membrane. 


MARSUPIALIA. 


Cavity of the cranium.—The Ferg: 
cranial cavity are remarkable for their thickne: 
in some of the Marsupial genera. In th 
Wombat the two tables of the parietal bone: 
are separated posteriorly for the extent of mor 
than Fait an inch, the insters being lle 
with a coarse cellular diploé ; the frontal bone 
are about two and a half lines thick. In | 
Ursine Dasyure the cranial bones havea 
milar texture and relative thickness. ' 
Koala the texture of the cranial bones is der 
and their thickness varies from two lines toh 
a line. In the Kangaroo the thicknes 
considerably in different parts of the 
the parietes are generally so thin as tot 
sar which is the case with the 
arsupials, as the Potoroos and Petaw: 
The union of the body of the second : 
of the third cranial vertebra takes place in| 
marsupial as in the placental Mammalia at 
sella turcica, which is overarched by the b 
ward extension of the lesser ale of the sphen 
The optic foramina and the fissure las 
anteriores are all blended together, so thi 
wide opening leads outwards from each sid 
the sella. Immediately posterior and 
to this opening are the foramina rotunda, 1 
each of which in the Kangaroo a remar 
groove leads to the fossa Gasseriana at the e¢ 
mencement of the foramen ovale ; s 
groove is indicated in a slight degree 
Dasyures and Phalangers, but is almost 
solete in the Wombat and Koala. The c 
canals pierce the body of the sphenoid, a 
Birds, and terminate in the skull 
together behind the sella turcica, which is 
bounded bya _ posterior clinoid process. — 
sphenoidal bulla, which forms the chief pa 
the tympanic cavity in the Perameles la 
forms a large convex protuberance on each 
of the floor of the cranial cavity in that spe 
The petrous bone in the Kangaroo, Koala, 
Phalangers is impressed above the 1 
auditorius by a deep, smooth, round pit, 1 
lodges the lateral appendage of the cereb 
The corresponding pit is shallower in the 
syuri, and is almost obsolete in the Wor 
The middle and posterior fissure lacera 
the usual relative position, but the latter 
small. The condyles are each perforated 
norly by two foramina in most of 
cops, the Thylacinus forming the exeeé 
Of the composition and form of the for 
magnum we have already spoken: it 
great size in relation to the capacity © 
cranium ; the aspect of its plane is back 
and slightly downwards. " 
In the Kangaroo and Phalancer a thin 
of bone extends for the distance of one oF 
lines into the periphery of the tentorial p 
of the dura mater, and two sharp spine 
sent down into it from the upper part 0 
cranium in the Phalangista on ina. ne 
torium is supported by a thick ridge of bo 
in the Thylacine; but it is not comple 
ossified in any of the Marsupials: in 
species, indeed, as the Dasyures, the K 
and the Wombat, the bony crista above ¢ 
scribed does not exist. There is no ossif 


or 


= 


of the falciform ligament as in the Ornitho- 
rhynchus. 

___ The anterior depression or olfactory division 
_ of the cavity of the cranium, as it may be 
termed from its large size, is separated in a 
_ well-marked manner from the proper cerebral 
_ division of the cavity. It is relatively smallest 
_ in the Koala. In all Marsupials it is bounded 
_ anteriorly by the cribriform plate of the eth- 
moid bone, which is converted into an osseous 
reticulation by the number and size of the 
_ olfactory apertures. The cavity of the nose, 
from its great size and the complication of 
the turbinated bones, forms an important part 
of the skull. It is divided by a complete 
| bony septum to within one-fourth of the an- 
| terior aperture; the anterior margin of the 
| septum is slightly concave in the Koala; de- 
| scribes a slight convex line in the Wombat, 
| Kangaroo, and Phalanger, and a_ sigmoid 
| flexure in the Dasyure. A longitudinal ridge 
i projects downwards from the inside of each of 
; 

) 


_ the nasal bones, and is continued posteriorly 
_ into the superior turbinated bone; this bone 
| extends into the dilated space anterior to the 
cranial cavity, which corresponds with the 
frontal sinuses. The convolutions of the middle 
spongy bone are extended chiefly in the axis of 
the skull; the processes of the anterior con- 
voluted bone are arranged obliquely from 
below upwards and forwards. They are ex- 
tremely delicate and numerous in the Da- 
_syures and Phalangers; they consist of thin 
_lamine of bone beautifully arranged on the 
“convex surface of the os turbinatum, and 
placed vertically to that surface in the Po- 
 toroo; but the bone becomes very simple in 
the Kangaroo, Koala, and Wombat. The 
“nasal cavity communicates freely with large 
maxillary sinuses, and finally terminates by 
_ wide apertures behind the bony palate. In the 
‘skull the nasal cavity communicates with the 
‘mouth, as before mentioned, by means of the 
ious large vacuities in the palatal processes. 
Mazxilla inferior—The lower jaw of the 
arsupials is a part of their osseous structure 
vich claims more than ordinary attention in 
consequence of the discussions to which the 
| fossil specimens of this bone discovered in 
the oolitic strata of Stonesfield have given rise. 
‘These specimens, which are well known to the 
English reader by the figures of them published 
‘in the Bridgewater Treatise of Dr. Buckland, 
and in the Elements of Geology of Mr. Lyell, 
_were regarded by Cuvier as appertaining to 
the Marsupial series of Mammalia, and to be 
nearly allied to the genus Didelphis. 
_ This opinion of the great founder of Oryc- 
tological Science has been called in question 
by other naturalists, and has been more espe- 
cially opposed by Professor De Blainville, who 
oie it to be more probable that they be- 
ng to a genus of Saurian Reptiles than to 
the Didelphis or any genus of insectivorous 
Mammals. I have examined the two speci- 
Mens in the possession of Dr. Buckland, the 
— formerly in the collection of Mr. 
roderip and now in the British Museum, and 
‘that which is preserved in the Museum at York. 


MARSUPIALIA. 


273 


The composition of the lower jaw, each ramus 
of which consists of one piece of bone, the 
convex condyle, broad and high coronoid pro- 
cess, and the structure and mode of implan- 
tation of the molar teeth, sufficiently attest the 
mammiferous character of these remains: the 
size, elevation, and form of the coronoid pro- 
cess of the lower jaw, the process continued 
from the angle of the ramus, with the tubercular 
crowns of the molar teeth, indicate the carni- 
vorous and insectivorous character of the spe- 
cies in question. In the presence of canines 
and the number of the incisors and molars, 
one of these small Insectivora (Phascolotherium) 
approaches most nearly to the smaller species 
of the modern genus Didelphis; while in the 
structure of the molar teeth, and in the form 
of the coronoid process, it very closely re- 
sembles the Thylacinus. The number of the 
molars in the other genus ( Thylacotherium ) 
exceeds that of any known ferine Insectivore, 
placental or marsupial. We have seen, how- 
ever, that the marsupial Myrmecobius possesses 
nine molars on each side of both upper and 
lower jaws. Besides the osteological charac- 
ters above alluded to, there is a peculiarity in 
the lower jaw of the Marsupial animals, which 
was first indicated by Cuvier in the genus 
Didelphys, but which is not restricted to that 
genus. In the carnivorous Marsupials, as the 
Thylacine, the lower maxillary bone resembles 
in general form that of the corresponding spe- 
cies in the placental series, as the Dog: a 
similar transverse condyle is placed low down 
near the angle of the jaw, on a level with the 
series of molar teeth; a broad and strong 
coronoid process rises high above the condyle, 
and is slightly curved backwards; there is the 
same well-marked depression on the exterior 
of the ascending ramus for the firm implantation 
of the temporal muscle, and the lower boun- 
dary of this depression is formed by a strong 
ridge extended downwards and forwards from 
the outside of the condyle. But in the Dog 
and other placental Carnivora (the seals ex- 
cepted), a process, representing the angle of 
the jaw, extends directly backwards from the 
middle of the above ridge, which process gives 
precision and force to the articulation of the 
jaw, and increases the power by which the 
masseter acts upon the jaw. Now, although 
the same curved ridge of bone bounds the 
lower part of the external muscular depression 
of the ascending ramus in all the Marsupials, 
it does not in any of them send backwards, 
or in any other direction, a process correspond- 
ing to that just described in the Dog and other 
placental Carnivora. The angle of the jaw 
itself, in the Marsupials, is as if it were bent 
inwards in the form of a process encroaching 
in various shapes, and various degrees of deve- 
lopment in the different Marsupial genera upon 
the interspace of the rami of the lower jaw. 
In looking directly upon the lower margin of 
the jaw, we see, therefore, in place of the mar- 
gin of a vertical plate of bone, a more or less 
flattened triangular surface extended between 
the external ridge, and the internal process or 
inflected angle. This characteristic structure is 
T 2 


276 


elearly exemplified in the fossil jaw from the 
Stonesfield oolite, in the British Museum, re- 
presenting the extinct Marsupial which I have 
termed Phascolotherium Bucklandii. In the 
Opossums the internal angular process is tri- 
angular and triedral, directed inwards, with 
the point slightly curved upwards, and more 
uced in the small than in the large species. 

n the Dasyures it has a similar form, but the 
apex is extended into an obtuse process. In 
the Thylacine the base of the inverted angle*is 
proportionally more extended, and a similar 
structure is presented by the fossil Phascolo- 
there. In the Perameles the angle of the jaw 
forms a still longer process; it is of a flat- 
tened form extended obliquely inwards and 
backwards and slightly curved upwards. It 
presents a triangular, slightly incurved, and 
pointed form in the Petaurists, in which it is 
longest and weakest in the pigmy species, 
(Acrobates, Desm.) It is shorter and stronger 
in the Myrmecobius (fig.97). In the Po- 
toroos and Phalangers the process 
is broad with the apex slightly de- 
veloped; it is bent inwards and 
bounds the lower part of a wide 
and deep depression in the inside 
of the ascending ramus. In the 
great Kangaroo the internal margin 
of this process is curved upwards, 
so as to augment the depth of the 
internal depression above men- 
tioned. The internal angular pro- 
cess arrives at its maximum of 
development in the Wombat, 
(fig. 94,) and the breadth of the 
base of the ascending ramus very 
nearly equals the height of the 
same part. This broad base also 
inclines downwards and outwards 
from the inflected angle, and the 
2 same uliarity occurs in the 
geew soi, JAW of the Phascolothere. In 
7 “the Koala the size of the process 
in question is also considerable, but it 
is compressed, and directed backwards with 
the obtuse apex only bending inwards, so 
that the characteristic flattening of the base 
of the ascending ramus is least marked in 
this species. There is no depression on the 
inner side of the ramus of the jaw in the Koala, 
but its smooth surface is simply pierced near 
its middle by the dental artery. The surface 
of the external muscular depression bounded 
below by a broad angular ridge, as above de- 
scribed, is entire in the Dasyures, Opossums, 
Bandfeoots, Petaurists, and Phalangers; but 
in the Wombat the outer surface of the as- 
cending ramus is directly perforated by a round 
aperture immediately posterior to the com- 
mencement of the dental canal:* the corres- 
ponding aperture is of larger size in the Kan- 
garoo. But in the Potoroos both the external 
and internal depressions of the ascending ramus 
lead to wide canals, or continuations of the 
wide depressions which pass forwards into the 


Fig. 97. 


* A bristle is represented passing through this 
aperture in fig. 94, 


MARSUPIALIA. 


substance of the horizontal ramus, and so 
uniting into one passage, leave a vacant spa 
in the intervening bony ee Pe is stru 
ture, if it had been observed only in the jaw 
a fossil Marsupial, would have supported ; 
argument for its Saurian nature, more cogs 
than any that have been adduced in the ¢ 
cussion of the Stonesfield fossils, on account 
the analogous vacuity in the jaw of the C 
codile. 
The commencement of the dental cana! 
the Potoroos and Wombat is parallel with 
beginning of the molar series, and it ha 
same relative position in the Stonesfield | 
supials; but in the other carnivorous and 
sectivorous species the dental foramen is pla 
further back. In the Wombat a vascular groc 
is continued from the foramen along the in 
side of the ramus of the jaw as in the Ste 
field fossils; and a corresponding but w 
groove is present in the lower jaw of the WV 
mecobius. In the Thylacine and Ursine 
syures and their fossil congener the Phase 
there, the condyle of the lower jaw is pla 
low down, on a level with the molar ser 
it is raised a little above that level in the su 
ler Dasyures and Opossums, and ascen¢ 
proportion to the vegetable diet of the s 
cies. J 
In all those Marsupials which have fi 
very small incisors the horizontal rami of 
jaw converge towards a point at the symphi 
The angle of convergence is most in 
Wombat, and the gradual diminution in 
size of the rami as they approach this pa 
most marked and direct. The internal sur 
of the symphysis menti is almost horizor 
and is convex from side to side in the inte 
between the molars and incisors. The 
becomes obliterated in aged individuals. 
is also wholly obliterated in the skull | 
Koala now before me; in all the other Mi 
pial crania which I have examined, the | 
of the lower jaw are disjoined at the s 
physis ; and in the Opossum, both the rat 
the lower jaw and all the bones of the face 
remarkable for the loose nature of their 
nection. 3 
Vertebral column.—The vertebral colut 
divisible in all the Marsupials into the | 
classes of cervical, costal, lumbar, sacral, 
caudal vertebra. The cervical vertebrae | 
riably present the usual number, seven 
the usual character of the perforation of 
transverse process, or rather the presen¢ 
the upper and lower transverse processes, 
the union of their outer extremities with 
dimental rib. I found the cervical ribs ¢ 
dentata distinct and unanchylosed in a m 
Perameles. In the Dasyures, Opossums, 
dicoots, and Phalangers, the seventh ce 
vertebra has only the upper transverse pro 
and consequently wants the character ol 
perforation, as in many of the ordinary Mai 
malia. In the Petaurists, Koala, ” yom 
Potoroos, and Kangaroos, the seventh vert 
is perforated like the rest. But in 
garoo both the dentata and atlas have the tt 


> 


verse processes grooved merely by the ¥ arte 


_ arteries; and in the Koala and Wombat the 
atlas presents only the perforation on each side 
of the superior arch. In the Perameles and 
some other Marsupials, as the Cayopollin, an 
affinity to the cold-blooded Ovipara is mani- 
_ fested in the structure of the atlas (fig. 98), 
which exhibits a permanent se- 
paration of the neurapophyses 
or superior lamine from the 
centre or body below. In the 
Koala and Wombat the body 
of the atlas remains perma- 
nently cartilaginous, and the 
lower part of the vertebral ring 
‘is completed by dried gristly substance 
(fig. 99). In the Petaurists, Kangaroos, 


Fig. 99. 


Atlas of Pera- 
meles lagotis. 


Atlas, axis, and third cervical vertebra, Koala. 


_ and Potoroos, the atlas is completed below 
by an extension of ossification from the 
_ heurapophyses into the cartilaginous nucleus 
' representing the body, and the ring of the 
' vertebra is for a long time interrupted by a 
" longitudinal fissure in the middle line, the 
_ breadth of which diminishes with age. This 
_ fissure is represented in figures of the atlas of 
a Potoroo and Kangaroo, given by Pander and 
D’Alton, ( Beutelthiere, fig. c, plates iii. & vii.); 
but in some of the skeletons of these Marsu- 
pials examined by me I find the ring com- 
“taba and the fissure obliterated. In all the 

upials the spine of the dentata is well 
developed both in the vertical and longitudinal 
directions, but most so in the Virginian and 
Crab-eating Opossums, (fig. 100), where it 
increases in thickness posteriorly; in these 
_ Species also the third, fourth, and fifth cervical 
_ vertebre have their spines remarkably long and 
_ thick, but progressively diminishing from the 


Ht 


pythird (fig. 101), which equals in height and 


be Fig. 100. 


be] 
“y 


a; Vertebra dentata, 
bs idelphys Virginiana. 


Third cervical vertebra, 
Didelphys Virginiana. 


MARSUPIALIA. 


277 


thickness, but not in longitudinal extent, the 
spine of the dentata. These spines are four- 
sided, and being closely impacted together, 
one behind another, must add greatly to the 
strength, while they diminish the mobility of 
this part of the spine. I know of no other 
mammiferous genus which presents the same 
Structure: in the Armadillos the corresponding 
Spines are largely developed, but they are 
anchylosed together. In the Orang the cervical 
Spines are very long and strong, but have the 
ordinary sub-cylindrical rounded form. Tyson, 
who has described and figured the above struc- 
ture of the cervical vertebree in his anatomy of 
the Opossum, conjectures that it is given to 
this arboreal animal in order “that there might 
be no danger of its breaking its neck should it 
happen to fall to the ground by chance or de- 
sign:” but this teleological conjecture is inva- 
lidated by the fact that the Phalangers, Petau- 
rists, Koala, and other arboreal Marsupials 
present the usual structure of the five posterior 
cervical vertebrz, the spines of which are much 
smaller and weaker than that of the dentata, 
and in the Phalangers and Petaurists almost 
obsolete. These do not require the neck to be 
strengthened to aid in overcoming the struggles 
of a resisting prey. I observe in the Pha- 
langista Cookii that the superior flattened 
arches of the five last cervical vertebre bear 
a ridge on each side of the spine having 
the same direction and form, and nearly the 
same size. The structure of the transverse 
processes of the cervical vertebra, in the Opos- 
sum, is adapted to the strengthening and fix- 
ation of this part of the vertebral column: 
they are expanded nearly in the axis of the 
spine, but obliquely, so that the posterior part 
of one transverse process overlaps the anterior 
part of the succeeding. This structure is ex- 
ibited in a slighter degree in the cervical ver- 
tebre of the Dasyures, Phalangers, and Great 
Kangaroo. In the Petaurists, Potoroos, Wom- 
bat, and Koala, the direction and simpler form 
of the transverse processes allows of greater 
freedom of lateral motion. In the Koala and 
Wombat a short obtuse process is given off 
from the under part of the transverse process 
of the sixth cervical vertebra. In the Poto- 
roos, Kangaroos, Petaurists, Phalangers, Opos- 
sums, and Dasyures, this process 1s remarkably 
expanded in the direction of the axis of the 
spine. In the Bandicoots corresponding pro- 
cesses are observed progressively increasing in 
size, on the fourth, fifth, and sixth cervical 
vertebre. 

The number of the dorsal vertebrz is greatest 
in the Wombat, where it is fifteen, correspond- 
ing with the number of pairs of ribs: it is 
least in the Petaurists, which have twelve 
dorsal vertebre.* In all the other genera there 


* In the skeletons both of the Pet. macrurus and 
Pet. sciureus in the Museum of the College of Sur- 
geons there are twelve pairs of ribs; but in the 
Pet. macrurus the succeeding vertebra has a short 
transverse process on each side, the extremity of 
which has the appearance of having supported a 
costal appendage. Cuvier, however, assigns but 
twelve dorsal vertebre to this species in his table. 
Leg. d’Anat, Comp, 2d edit. p. 180, 


278 MARSUPIALIA. 


tebre both by anchylosis and partial ju netic 
with the ossa innominata. 


are thirteen dorsal vertebre and thirteen pairs 
of ribs.* 

In the Koala the length of the spine of the 
first dorsal hardly exceeds that of the last 
cervical, but in all other Marsupials the diffe- 
rence is considerable, the first dorsal spine 
being much longer: those of the remaining 
dorsal vertebra progressively diminish in length 
and increase in breadth and thickness. They 
slope backwards towards the centre of motion, 
which in Mauge’s Dasyure is shown to be at 
the ninth dorsal vertebra, by the verticality of 
its spine, towards which both the preceding 
and succeeding spines incline. In the Pera- 
meles the centre of motion is at the eleventh 
dorsal vertebra, in the Potoroo and Kangaroo 
at the twelfth, in the Petaurists at the thir- 
teenth vertebra. In the Phalangers, Opossum, 
Koala, and Wombat the flexibility of the spine 
is much diminished, and the centre of motion 
is not defined by the convergence of the spinous 

rocess towards a single vertebra, but they all 
incline slightly backwards. 

The lumbar vertebre are four in number in 
the Wombat, seven in the Petaurists, and six 
im other Marsupialia; the total number of true 
vertebre being thus the same in all the genera. 

The pressure which the trunk of the Wombat 
must occasionally have to resist in its extensive 
subterranean burrows, is probably the condition 
of the development of the additional pairs of 
ribs in that species. 

The anterior oblique processes, which begin 
to increase in length in the three posterior dorsal 
vertebra, attain a great size in the lumbar ver- 
tebre, and are locked into the interspace of the 
posterior oblique processes which are double on 
each side, except in the Perameles, and in the 
last lumbar vertebre of all the other genera. 
The transverse processes of the lumbar vertebrae 
oe increase in length as the verte- 

rz approach the sacrum ; they are most deve- 
loped in the Wombat, where they are directed 
obliquely forwards. In the Kangaroos, Poto- 
roos, and Perameles, they are curved forwards 
and obliquely downwards. The length of these 
and of the anterior oblique processes is rela- 
tively least in the Petaurists, Phalangers, and 
Opossums. 

Sacrum.—The numberof vertebra succeeding 
the lumbar which are anchylosed together in 
the sacral region of the spine, amounts in the 
Wombat to seven (fig. 102), but if we regard 
those vertebre only as sacral which join the ossa 
innominata, then there are but three. In the 
Phalangers there are generally two sacral ver- 
tebre, but in the Phalangista Cookii the last 
lumbar assumes the character of the sacral ver- 


* Cuvier assigns only twelve dorsal vertebre to 
the Kangaroo Rat, but in two different species of 
i in the Mus. Coll. Surgeons, there 

are thirteen dorsal and six lumbar vertebra, and 
Fo aad the same number in the skeletons of 
ypsiprymnus ursinus and dorcocephalus in the 
Leyden Museum. Pander and D’Alton figure 
thirteen dorsal vertebre in the Hypsiprymnus mu- 


remus. 

+ In Phal. Cookii the sixth lumbar vertebra is 
joined by a part of its transverse processes to the 
ossa innominata, 


of the powerful hinder extremities is trans’ 
to two anchylosed vertebra. 
there is only a single sacral vertebra, the s 
of which is shorter and thicker than those ¢ 
lumbar vertebra, and is turned in the cont 
direction, viz. backwards. 


vertebra by anchylosis, two of which join 

ilia. In Mauge’s Dasyure, two sacral ve 
tebre are anchylosed, but it is to the expand 
transverse processes of the anterior one 
that the ossa innominata are joined. The sat 
kind of union exists in the Viverrine Da 
syure, but three vertebre are anchylose 
gether in this species. 
and Petaurists there are two sacral vert 
In Petaurus macrurus three are 
together, though only two join the ilium. 
the Wombat (fig. 102) the transverse 

cesses of the numerous anchylosed vertebrae 
remarkable for their length and flatness, tht 
of the first four are directed outwards and 
confluent at their extremities; the remai 
ones are turned in a slight degree backwat 
and very nearly reach the tuberosities of ” 
ischia, behind which they Sipe ir 
in size and disappear in the three ca 
vertebra. The transition from the sacral to 
caudal vertebre is very obscure in the Wor 
If we limit the sacral to the three v 
the ilium, then there remain twelve 
for the tail. The spinal canal is com 
all but the last three, which consist only © 
body. There are no inferior spines, anc 
the six posterior vertebrae, which progre: 
diminish i 
aperture of the pelvis, the tail is scarcely vi 
in the living animal. In the Koala (fig. 1 
the tail is also very short. In the Chen 
it seems to be wanting. 
Perameles I find eighteen caudal 


~ (OL, 


Pelvis of the Wombat. 
In the Kangaroos and Potoroos the im peti 
In the Pera nel 
r 


In the Myrmecobius there are four 


In the 


a 


ae 


in length, extend beyond the poste 


In one specie 


another twenty-three. In two species of Po- 
_ toroo there are twenty-four caudal vertebra, 
but the relative length of the tail differs in 
_ these by one-third, in consequence of the 
_ different length of the bodies of the vertebrae. 
In Hypsiprymnus ursinus there are more than 
_ twenty-six caudal vertebre. In the great Kan- 
roo there are twenty-two caudal vertebre. 

n Bennett’s Kangaroo there are twenty-four 

_ caudal vertebra, which are remarkable for their 
size and strength. In the Phalangista vulpina, 
there are twenty-one caudal vertebre. In the 
Petaurus macrurus 1 find twenty-eight caudal 
_ vertebra, while in the Pet. sciureus there are but 
_ twenty ; the bodies of the middle caudal vertebra 
_ in both these species are remarkably long and 
_ slender. The Myrmecobius has twenty-three 
caudal vertebre. In the Dasyurus Maugei I 
' find twenty caudal vertebre ; in Didelphis can- 
_ erivora there are thirty-one; in the Virginian 
Opossum there are twenty-two caudal vertebre. 
In the latter species the spinal canal is con- 
‘tinued along the first six; beyond these the 
_ Superiorspinous processes cease to be developed, 
and the body gives off, above, only the two 
anterior and two posterior oblique processes, 
which are rudimental, and no longer subservient 
to the mutual articulation ofthe vertebre. The 
transverse processes are single on the first five 
caudal vertebre, and are nearly the breadth of 
the body, but diminish in length from the 
second caudal, in which vertebre they are gene- 
rally the longest. In the other vertebre a short 
| obtuse process is developed at both extremities 
of the body on either side, so that the dilated 

"articular surfaces of the posterior caudal ver- 

tebre present a quadrate figure. 

In most of the Marsupials which have a long 
tail, this appendage is subject to pressure on 
some part of the under surface. In the Kanga- 
roo (fig. 103,) this must obviously take place 
_ toa considerable degree when the tail is used 
as a fifth extremity, to aid in supporting or pro- 

pelling the body. In the Potoroos and Bandi- 

' €oots the tail also transmits to the ground 
_ part of the superincumbent pressure of the 
_ body by its under surface, when the animal 
is erect, but it is not used as a crutch in 
locomotion as in the Kangaroos. In the 
-Phalangers and Opossums the tail is pre- 
hensile, and the vessels situated at the 
under surface are liable to compression 
when the animal hangs suspended by the 
tail. To protect these vessels, therefore, as 
well as to afford additional attachment to 
‘the muscles which execute the various 
| movements for which the tail is adapted in 
_ the above mentioned Marsupials, V-shaped 
bones, or inferior arches (hzemapophyses) 
_ are developed, of various forms and sizes, 
and are placed opposite the articulations 
' of the vertebrae, a situation which is analo- 


—, 


Fig. 103. 


bn igs ae alii > 


MARSUPIALIA. | 


279 


gous to that of the superior arches in the 
sacral region of the spine in Birds, and in 
the dorsal region of the spine in the Chelonian 
Reptiles. The two crura of the sub-vertebral 
arch embrace and defend the bloodvessels, and 
the spinous process continued from their point 
of union presents a variety of forms in different 
genera. 
: In Cook’s Phalanger I find the 
Fig. 104. hemapophyses commence between 
oun the second and third caudal ver- 
tebre, increase in length to the 
fourth, and then progressively 
diminish to the end of the tail; 
the penultimate and anteepnulti- 
mate presenting a permanent sepa- 
ration of the lateral moieties, and 
an absence of the spine (fig. 104.) 
In the Virginian Opossum and 
Vulpine Phalanger they are sim- 
ple, about a quarter of an inch in 
length where longest, and directed 
obliquely forwards, and diminish 
in size as they approach the extre- 
mity of the tail. In the Potoroos 
the extremity of the long anterior 
spines is dilated and produced 
both backwards and forwards; the 
posterior smaller ones become ex- 
panded laterally, and give off 
similar but shorter processes from 
each side, whereby the base of 
support is extended. In the Great 
Kangaroo the spine of the first 
subvertebral arch only is simple 
and elongated, the extremities of 
the others are expanded, and in 
some jut out into four obtuse pro- 
cesses, two at the sides, and two 
at the anterior and posterior sur- 
Terminal cau. *°°S- In a_ carefully prepared 
dal vertebra, Skeleton. of Macropus Bennettii 
in the Museum of the Zoological 
Society, I found these inferior spines want- 


280 


ing between the last nine vertebre of the 
tail, In the Petaurists, Phascogales, and Da- 
syures, where the tail acts as a balancing pole, 
or serves, from the long and thick hair with 
which it is clothed, as a portable blanket to keep 
the nose and extremities warm during sleep, 
the subvertebral arches are also present, but in 
less number and of smal'er relative size. They 
are here principally subservient to the attach- 
ment of muscles, their more mechanical office 
of defending the caudal vessels from pressure 
not being required. 

Thorax.—The ribs consist of thirteen pairs, 
except in the Wombat, which has fifteen, and 
Petaurists, which have twelve; the first is the 
shortest, and, except in some of the Petau- 
rists, the broadest. In the Pet. macrurus the 
fifth, sixth, or seventh are the broadest, and 
the ribs generally have, both in this species and 


The sternum consists of a succession of elon- 
gated bones, generally six in number, but in 
the Petaurus Taguanoides five, and in the 
Wombat four. 

The first bone, or manubrium sterni, is the 
largest, and presents in many species a triangu- 
lar shape from the expansion of its anterior part, 
and sometimes a rhomboidal figure. A strong 
keel or longitudinal process is given off in many 
species from the middle of its inferior or outer 
surface; the side next the cavity of the chest 
is smooth and slightly concave. In the Wom- 
bat, Phalangers, and others, the keel is pro- 
duced anteriorly into a strong process, against 
the Sides of which the clavicles abut: the first 
pair of ribs join the produced anterior angles of 
the manubrium, 

In the Dasyures, Opossums, Phalangers, 
and Petaurists, the manubrium is compressed 
and elongated, and the clavicles are joined to 
a process continued from its anterior extremity ; 
the small clavicles of the Kangaroo have a 
similar connexion. 

The cartilages of the true ribs (which fre- 
quently become ossified in old Marsupials) are 
articulated as usual to the interspaces of the 
sternal bones; the last of these supports a broad 
flat cartilage. 


MARSUPIALIA. 


Phascolomys fusca. 


in Pet. sciureus, a tore compressed form thi 
in the other Marsupials; but this ch 
does not exist in Petaurus Tuguanoides. Int 
Great Kangaroo they are very slender g 
rounded, except at the sternal extremities, wh 
are flattened for the attachment of the cartila 
In this species and the Bush Kangaroo, 
seven anterior pairs of ribs articulate dire 
with the sternum. The cartilages of the 
false pairs are long and bent towards the : 
num, but do not join it, nor are they cor 
but have a gliding motion one over the other. 
In the Myrmecobius there are eight pairs 
true ribs; the two last pairs are floating F 
In the Opossum there are seven pairs of © 
ribs, and six which may be regarded as cosi 
nothe. In the Petaurist six pairs out of f 
twelve, and in the Wombat six pairs only ¢ 
of the fifteen, reach the sternum (fig. 105). 


‘ 


Kes 
WAZ KE 
\ = 


Of the Pectoral Extremities—The seap 
varies in form in the different Marsupk 
In the Petaurists it forms a scalene trian 
with the glenoid cavity at the converger 
the two longest sides. 

In the Wombat it presents a remarkabl 
gular oblong quadrate figure, the neck be 
produced from the lower half of the an 
margin, and the outer surface being tray 
diagonally by the spine, which in this spe 
gradually rises to a full inch above the p 
the scapula, and terminates in a long nai 
compressed acromion arching over the nec 
reach the clavicle. r 

In the Koala (fig. 106), the superior 
does not run parallel with the inferior, bt 
cedes from it as it advances forwards, and 
passes down, forming an obtuse angle, and 
a gentle concave curvature to the neck ¢ 
scapula ; a small process extends fre 
middle of this curvature. In the Potor 
upper costa is at first parallel with the lower 
this parallel part is much shorter ; the remain 
describes a sigmoid flexure as it approach 
neck of the scapula. Pein 

In the Great Kangaroo, the Perameles, F 
langers, Opossums, and Dasyures, the wh 
upper costa of the scapula describes a sigmol 


i= 
ie 


MARSUPIALIA. 


curve, the convex pos- 
terior position of which 
varies as to its degree and 
extent. 

The subscapular sur- 
face is remarkable in the 
Perameles for its flatness, 
but presents a shallow 
groove near the inferior 
costa. In most other 
Marsupials it is more or 
less convex or undulat- 
ing. 

In the Great Kangaroo 
the supra-spinal fossa is of 
less extent than the space 
below the spine, and 
the spine is inclined up- 
In the Perameles and Dasyures the 


Scapula of Koala. 
wards. 


Prono of the supra and infraspinal sur- 


ces are reserved, and the whole spine is 
bent downwards over the infraspinal surface. 
In the Potoroos and Phalangers the acromion 
is, as it were, bent downwards so as to 

resent a flattened surface to the observer. 
le the Potoroos and Opossums this appear- 
ance is produced by a true expansion of the 
acromion. In the Perameles the coracoid 
process is merely represented by a slight pro- 
duction of the superior part of the glenoid ca- 
vity. In the Kangaroo and Potoroo it forms a 
protuberance on the upper part of the head of 
the scapula. In the other Marsupials it as- 
sumes the character of a distinct process from 
the same part, and attains its greatest develop- 
ment in the Wombat and Koala, in the latter 
of which it is forcibly curved downwards and 
inwards. 

The clavicles are present in all the Marsu- 
pials, with the exception of the genus Pera- 
meles, and probably also the Cheropus. In 
the claviculate Marsupials they are relatively 
strongest and longest in the burrowing Wom- 
bat, weakest and shortest in the Great Kanga- 
roo. In the latter they are simply curved with 


the convexity forwards, and measure only two 


inches in length. In the Wombat they are 
upwards of three inches in length, and have 
a double curvature; they are expanded and 


obliquely truncate at the sternal extremity, 


where the articular surface presents a remark- 
ably deep notch: they become compressed as 
they approach the acromion, to which they are 
attached by an extended narrow articular surface. 
In the Koala the clavicles are also very 
strong, but more compressed than in the Wom- 
bat, bent outwards in their whole extent, and 
the convex margin formed, not by a continuous 
curve, but by three almost straight lines, with 
intervening angles; progressively diminishing 
in extent to the outermost line which forms the 
articular surface with the acromion. In the 
Myrmecobius the clavicles are subcompressed 
and more curved at the acromial than at the 
sternal end. In most of the other Marsupials 
the clavicle is a simple compressed elongated 
boue, with one general outward curvature. 


_.. The humerus in the Dasyures and Thyla- 
_ cines resembles that of the Dog-tribe in the 


281 


imperforate condition of the inner condyle, but 
difiers in the more marked development of the 
muscular ridges, especially of that which ex- 
tends upwards from the outer condyle for the 
origin of the great supinator muscle. This ridge 
is terminated abruptly by the smooth tract for 
the passage of the musculo-spiral nerve. 

In all the other genera of Marsupials that I 
have examined the internal condyle of the hu- 
merus is perforated. But in some species of 
Petaurus, as Petaurus sciureus, the foramen is 
represented by a deep notch; and in the Pha- 
langista Cookii, both foramen and notch are 
wanting.* The ridge above the external condyle 
is much developed in the Petaurus macrurus 
and sciureus, and notched at its upper part, but 
this notch does not exist in Pet. taguanoides. I 
find similar differences in the development of 
the supinator, or outer ridge, in the genus 
Perameles ; in the Per. lagutts it is bounded 
above by a groove; in Per. Gunnii it is less 
developed and less defined. In the Kanga- 
roos, Potoroos, Wombat, and Koala (fig. 107), 
the outer condyloid ridge extends in the form 
of a hooked process above the groove of the 
radial nerve. In all these, and especially in 
the Wombat, the deltoid process of the hu- 
merus is strongly developed; it is continued 
from the external tuberosity down the upper 
half of the humerus; except in the Petaurists, 
where, from the greater relative length of the 
humerus, it is limited to the upper third. 

The interspace of the condyles is occasion- 
ally perforated, as in the Perameles lagotis and 
Wombat. The articular surfaces at both ex- 
tremities of the humerus have the usual form; 
but it may be observed in some 
Marsupials, as the Koala, that 
at the distal articulation the 
| externalconvexity forthe radius 
has a greater relative extent 
than usual, and the ulnar con- 
cavity is less deep. 

The bones of the fore-arm 
present little to detain our 
notice. They are always dis- 
tinct and well developed, and 
their adaption to pronation and 
supination is complete. The 
prehensile faculty and ungui- 
culate structure of the anterior 
extremities appear to have 
been indispensable to animals 
where various manipulations 
were required in the economy 
ofthe marsupial pouch. When, 
therefore, such an animal is 
destined like the ruminant to 


Humerus of the 


Koala. range the wilderness in quest 
of pasturage, the requisite 
powers of the anterior members are re- 


tained and secured to it, as has been already 
observed, by an enormous developement of the 
hinder extremities, to which the function of 
locomotion is restricted. 


* In the other species of Phalangista, and in the 
Petawrus taguanoides and macrurus, the internal con- 
dyle of the humerus is perforated, _ 


282 - 


We find, therefore, that the bones of the fore- 
arm of the Kan differ little from those of 
the burrowing Wombat, the climbing Koala, or 
be eee hear we, save in ror =~. 

present the greatest proportional strengt 

in the Wombat, and the soiree proportional 
length and slenderness in the Petaurists or Fly- 
ing Opossums, in which the radius and ulna are 
in close contact through a great portion of their 
extent, and thus lend a firmer support to the out- 
stretched dermal parachute. They are also long 
and slender inthe Koala. In general the radius 
and ulna run nearly parallel, and the interos- 
seous space is very trifling. It is widest in the 
Potoroos. The olecranon is well developed in 
all the Marsupials. Inthe Virginian Opossum 
and Petaurists we find it more bent forwards 
upon the rest of the ulna, than in the other Mar- 
supials. Inthe Wombat, where the acromion is 
the strongest, and rises an inch and a half above 
the articular cavity of the ulna, it is extended 
in the axis of the bone. The distal end of the 
radius in this animal is articulated to a bone 
representing the os scaphoides and os lunare. 

The ulna, which in the same animal con- 
verges towards a point at its distal end, has that 
point received in a depression formed by the 
cuneiform and pisiform bones ; these are bound 
together by strong ligaments, and the pisiform 
then extends downwards and backwards for 
two-thirds of an inch. The second row of the 
carpus consists of five bones. The trapezium 
supports the inner digit, and has a small sesa- 
moid bone articulated to its radial surface. 
The trapezoides is articulated to the index digit, 
and is wedged between the scapho-lunar bone 
and os magnum; this forms an oblique articu- 
lar surface for the middle digit; but the largest 
of the second series of carpal bones is cuneiform, 
which sends downwards an obtuse rounded 
process, and receives the articular surface of 
the fifth, and the outer half of that of the 
fourth digit, the remainder of which abuts 
against the oblique proximal extremity of the 
middle metatarsal bone. 

The five metacarpal bones are all thick and 
short, but chiefly so the outermost. The inner- 
most digit, or pollex, has two phalanges, the 
remainder three ; the ungueal phalanx of all the 
digits is conical, curved, convex above, ex- 
panded at the base, and simple at the opposite 
extremity. 

In the-Perameles the ungueal phalanx of the 
three Thiddle digits of the hand, and of the 
two outer digits of the foot, are split at the 
extremity by a longitudinal fissure commencing 
at the upper part of the base. This structure, 
which characterizes the ungueal phalanges in 
the Placental Anteaters, has not been hitherto 
met with in other Marsupial genera.* 

The terminal phalanges of the Koala are 
large, much compressed and curved ; the con- 
cave articular surface is not situated, as in the 
cats, on the lower part of the proximal end, 
but, as in the sloths, at the upper. The claws 
which they support are long. 


* It would be interesting to examine the skeleton 
of the Cheropus, with reference to this structure. ~ 


MARSUPIALIA. 


In the Great Kangaroo the first row of the 
carpus is composed, as in the Wombat, of thr 
bones, but the apex of the ulna rotates in a 
vity formed exclusively by the cuneiforme 
There are four bones in the second row; of 
which the unciform is by far the largest, and 
supports a part of the middle, as well as th 
two outer digits. Inthe Potoroos I find t 
three bones in the distal series of the carpus 
the trapezoides being wanting, and its place in 
one species being occupied by the proximal en 
of the second metacarpal bone, which articulates 
with the os magnum. In the Perameles there 
are four bones in thesecond carpal row, although 
the hand is less perfect in this than in any other 
Marsupial genus, Cheropus excepted, the three — 
middle toes only being fully developed. 

In the Petaurists the carpus is chiefly re 
markable for the length of the os pisiforme. — 

It would be tedious to dwell on the minor 
differences observable in the bony structure of 
the hand in other Marsupials. I shall there- 
fore only observe that though the inner digit 
is not situated like a thumb, yet that the fingers 
enjoy much lateral motion, and that those at 
the outer can be opposed to those at the inner 
side so as to grasp an object and perform, ina 
secondary degree, the function of a hand. In 
the Koala the two inner digits are more deci- 
dedly opposed to the three outer ones than in — 
any other climbing Marsupial. But some of — 
the Phalangers, as the Ph. Cookit and Ph. 
gliriformis of Bell, present in a slighter de- 
gree the same disposition of the fingers, by — 
which two out of the five have the opposable — 
properties of a thumb. I have observed a 
similar disposition of the digits in the act of 
climbing in the Dormouse, and it probably is 
not uncommon in other placental Mammalia of — 
similar habits and which have long, slender, — 
and freely moveable fingers. As a permanent 
disposition of the digits, the opposition of 
three to two is most conspicuous in the pre- 
hensile extremities of the Chameleon. ‘ 

Of the Pelvic Extremities—The pelvis ( 
109) in the mature Marsupials is com f 
the os sacrum, the two ossa innominata, and the — 
characteristic supplemental bones, attached to — 
the pubis, called by Tyson the ossa marsupialia 
or Janitores Marsupii. ‘ 

We seek in vain for any relationship be- 
tween the size of the pelvis and that of the 
new-born young, the minuteness of which is 
so characteristic of the present tribe of animals. 
The diameters both of the area and apertures 
of the pelvic canal are always considerable, 
but more especially so in those Marsupialia — 
which have the hinder extremities dispro: 
tionately large ; as also in the Wombat, where — 
the pelvis is remarkable for its width. The 

elvis is relatively smallest in the Petaurists; 
at even here the diameter of the outlet is at 


Hiss 


foramina by an osseous bridge continued from — 


MARSUPIALIA. 


the pubis to the ischium on each side of the 
symphysis. 

In the Kangaroos, Potoroos, Phalangers, and 
Opossums the ilia offer an elongated pris- 
matic form. They are straight in the Opossum, 
but gently curved outwards in the other Mar- 
supial genera. In the Dasyures there is a lon- 
gitudinal groove widening upwards in place of 
the angle at the middle of the exterior surface 
of the ilium. The ilia in the Petaurists are 
simply compressed, with an almost trenchant 
anterior margin. They are broader and flatter 
in the Perameles, and their plane is turned 
outwards. But the most remarkable form 
of the iliais seen in the Wombat, in which 
they are considerably bent outwards at their 
anterior extremity. In the Kangaroos and 
Potoroos the eye is arrested by a strong pro- 
cess given off from near the middle of the 
ileo-pubic ridge, and this process may be ob- 
served less developed in the other Marsupialia. 
The tuberosity of the ischia inclines outwards 
in a very slight degree in the Dasyures, Opos- 
sums, Phalangers, Petaurists, and Perameles, 
in a greater degree in the Kangaroos and Poto- 
roos, and gives off a distinct and strong obtuse 
process in the Wombat, (fig. 108,) which 


Right os innominatum and marsupial bone, 
Wombat. 


not only extends outwards but is curved for- 
wards. In the Potoroos the symphysis of the 
ischia, or the lower part of what is commonly 
called the symphysis pubis, is produced ante- 
riorly. The length of this symphysis, and the 
straight line formed by the lower margin of the 
ischia is a characteristic structure of the pelvis 
in most of the Marsupials. 


283 
The Marsupial bones (a, a, fig. 109) are 
Fig. 109. 


(Mp 
ip 


Pelvis and marsupial bones of the Koala. 


elongated, flattened, and more or less curved, 
expanded at the proximal extremity, which 
sometimes, as in the Wombat, is articulated 
to the pubis by two points; they are relatively 
straightest and most slender in the Perameles ; 
shortest in the Myrmecobius, where they do 
not exceed half an inch in length; longest, 
flattest, broadest, and most curved in the 
Koala, where they nearly equal the iliac bones 
in size. They are always so long that the 
cremaster muscle winds round them in its 
passage to the testicle or mammary gland, and 
the uses of these bones will be described in 
treating of that muscle. 

With reference to the interesting question— 
What is the homology or essential nature of 
the ossa marsupialia? I entirely concur in the 
opinion first advanced by the able anatomist, 
M. Laurent,* viz. that they belong to the 
category of the trochlear ossicles, commonly 
called sesamoid, and are developed in the 
tendon of the external oblique which forms the 
mesial pillar of the abdominal ring, as the pa- 
tella is developed in the tendon of the rectus 
Jemoris. I had arrived at this conclusion from 
independent researches, and unaware of any 
prior announcement of this view when I dis- 
cussed the question before the Zoological So- 
ciety in 1835.+ I cannot, however, participate 
in the opinion of M. Laurent and the celebrated 
De Blainville, that the marsupial bones are 
superadded to the abdominal muscles to aid in 
an unusually energetic compression required to 
expel the uterine foetus. It is notin the females 
of those animals which give birth to the smallest 


* See his note inserted in the ‘Bulletin des Sci- 
ences Médicales’ of Férussac, 1827, No. 77, p. 112, 
and the Annales d’Anat. et de Physiologie, 1839, 

. 240. 
R + See the abstract of a paper on the anatomy of 
the Dasyurus, Proc. Zool, Soc., January, 1835. 


284 


foetuses that we ought to find auxiliary parts 
for increasing the tg of the muscles engaged 
in parturition, e bones in question are, 
moreover, equally developed in both sexes: 
and they are so situated and attached that they 
add to the power of the muscles which wind 
round them, and not of those implanted in 
them. They are not, however, merely sub- 
servient to add force to the action of the “ cre- 
masteres,” but give origin to a great proportion 
of the so-called “ pyramidales.” 

The osteogenesis of the marsupial pelvis de- 
rives some extrinsic interest from the not yet 
forgotten speculations which have been broached 
regarding the analogies of the marsupial bones. 
These have been conjectured to exist in many 
of the placental Mammalia, with a certain la- 
titude of altered place and form, disguised, 
€. g. as the bone of the penis in the Carnivora, 
or appearing as the supplemental ossicles of 
the acetabulum, which exist in the young of 
many of the Rodentia. In the os innomina- 
tum of the immature Potoroo the curved pris- 
matic ilium contributes to form, by the outer 
part of its base, the upper or anterior third of 
the acetabulum; the rest of the circumference 
of this cavity is completed by the ischium and 
pubis, excepting a small part of the under or 
mesial margin, which is formed by a distinct 
ossicle or epiphysis of the ilium, (a, fig. 110,) 
analogous to that de- 
scribed by Geoffroy St. 
Hilaireas the rudimen- 
tal marsupial bone in 
the rabbit. Now here 
there is a co-existing 
marsupial bone: but 
besides the five sepa- 
rate bones just men- 
tioned, there is a sixth 
distinct triangular ossi- 
cle, which is wedged 
into the posterior in- 
terspace of the ischio- 
pubic symphysis. How 
easy were it to suggest 
that this single sym- 
metrical bone may be 
the representative of 
the os penis removed 
from the glans to the 

‘2 root of the intromittent 
; organ! I regard it as 
a mere epiphysis of the 
ischium: The circumference of the acetabulum 
is always interrupted by a deep notch opposite 
the obturator foramen, which is traversed by 
a ligamentous bridge, and gives passage to 
the vessels of the Harderian gland lodged in 
the wide and deep acetabular fossa. 

The penial like the marsupial bone is essen- 
tially an ossification of the fibrous or sclerous 
tissue. 

The femur is a straight, or nearly straight, 
long, cylindrical bone, having a hemispherical 
head supported on a very short neck, espe- 
cially in the Petaurists, and situated here 
almost in the axis of the shaft, above and 
between the two trochanters, which are nearly 


Fig. 110. 


MARSUPIALIA. 


of equal size. In the Kangaroos and Potoroos 
the head of the thigh-bone is turned more 
inwards, and the outer or greater ter 
rises above it. In other Maes the great 
trochanter is less developed. In most of the 
species a strong ridge is continued down 
to within a short distance from the trochanter, 
and this ridge is so produced at the lower pai 
in the Wombat as almost to merit the name 
of a third trochanter. In the Wombat ; 
Koala there is no depression for a ligamentu 
teres. The shaft of the bone presents no ding 
aspere. ¥, 
The canal for the nutrient artery commences - 
at the upper third and posterior part of the 
bone in the Koala, and extends downward: 
contrariwise to that in most other ma 
and placental Mammalia. a 
At the distal extremity of the femur the 
external condyle 1s the largest, the internal 
rather the longest. The intermediate anterio 
groove for the patella is well marked in the 
Perameles, where the patella is fully developed, 
but is broad and very shallow in the Phalai 
gers and Dasyures, where the tendon of t 
rectus muscle is merely thickened or offers 
only a few irregular specks of ossification ; | 
the corresponding surface in the Petaurists 
Wombat, and Koala is almost plane from side 
to side; in these Marsupials and in the Myrme- 
cobius the patella is wanting. 1 find adistinet 
but small bouy patella in the Macropus E 
nettii. There is a sesamoid bone above and 
behind the external condyle of the femur in the 
Myrmecobius and some other Marsupials. J 
In the knee-joint, besides the two crucial 
ligaments continued from the posterior angles — 
or cresses of the semilunar cartilages—one to” 
the outer side of the inner condyle, the other 
to the interspace of the condyles—there isa 
strong ligament which passes from the anterior 
part of the tibial protuberance backwards 
the inner side of the fibular condyle, and a 
second continued from the same point along 
the outer margin of the outer semilunar ¢ 
tilage to the head of the tibia. 
The tibia (a, fig.111) presents the usual dis- 
position of the articular surface for the condyles 
of the femur, but in some genera, as the Wombat 
and Koala, the outer articular surface is continu- 
ous with that forthe head of the fibula. In the 
Kangaroos and Potoroos the anterior part of 
the head is much produced, and in the young 
animal its ossification conmmences by a centre 
distinct from the ordinary proximal epiphysis 
of the bone. A strong ridge is continu 
down from this protuberance for about or 
sixth the length of the tibia. In the Koalaa 
strong tuberosity projects from the anterior part 
of the tibia at the junction of the upper with — 
the middle third. In this species and in the — 
Wombat, as also in the Opossums, Dasyures, — 
Phalangers, and Petaurists, the shaft of the — 
tibia is somewhat compressed and twisted; 
but in the Kangaroos, Potoroos, and Pera-— 
meles the tibia is prismatic above and sub- 
cylindrical below. The internal malleolus is — 
very slightly produced in any Marsupial, but 
most so in the Wombat. : 


OCnDAl 


ei = 


se 


MARSUPIALIA. 


The fibula is complete, and forms the ex- 
ternal malleolus in all the Marsupials. In one 
species of Hypsiprymnus and in one species of 

erameles (P. lagotis ) it is firmly united to the 
the lower part of the tibia, though the line of 
Separation be manifest externally. In a second 
species of each of the above genera it is in close 
contact with the corresponding part of the tibia, 
but can be easily separated from that bone. 
In the Great Kangaroo the fibula is also a 
distinct bone throughout, but it is remarkably 
thinned and concave at its lower half, so as to 
be adapted to the convexity of the tibia, with 
which it is in close contact and attachment. 
In each of these genera, therefore, in which 


locomotion is principally performed by the - 


hinder extremities, we perceive that their osseous 
structure is so moditied as to ensure a due 
degree of fixity and strength; while in the 
other marsupial genera, as Phascolarctos, Phas- 
colomys, Phalangista, Petaurus, Didelphis, 
and Dasyurus, the tibia and fibula are so loosely 
connected together and with the tarsus, that 
the foot enjoys a movement of rotation analo- 
gous to the pronation and supination of the 
hand. This property is especially advantageous 
in the Petaurists, Phalangers, Opossums, and 
Koala, because in these the inner toe is so 
placed and organized as to perform the office 
of an opposable thumb, whence these Marsu- 
= have been termed Pedimana or foot- 
anded (fig. 111). 

It is to this prehensile power that the modi- 
fications of the fibula chiefly relate. In the 
Wombat, Koala, Petaurists, and Phalangers 
it expands to nearly an equal size with the tibia 
at the distal extremity, and takes a large share 
in the formation of the tarsal joint; but the 
articular surface is slightly convex, while that 
of the tibia is slightly concave. The proximal 
extremity of the fibula is also much enlarged, 
but compressed and obliquely truncated, and 
giving off two tuberosities from its exterior 
surface ; to the superior of these a large sesa- 
moid bone (c, fig. 111) is articulated; I have 
observed the same sesamoid attached to the 
upper end of the fibula in a Dasyurus macru- 
rus and Petaurus taguanoides. M.'Temminck 
figures it in the Didelphys ursina and Didel- 
phys Philander. This sesamoid and the ex- 
panded process to which it is attached form the 
analogue of the olecranon; and the corres- 
pondence of the fibula with the ulna is very 
remarkably maintained in the Pet. taguanoides, 
in which the proximal articular surface of the 
fibula is divided into two facets, one playing 
upon the outer condyle of the femur, the other 
concave, vertical, and receiving an adapted con- 
vexity on the outer side of the head of the tibia, 
which rotates thereupon exactly like the radius 
in the lesser sigmoid cavity of the ulna. 

In the scansorial and gradatorial Marsupials 
the bones of the hinder and fore extremities 
are of nearly equal length, but in the saltatory 
species the disproportion in the development of 
the bones of the hind leg is very great, especi- 
ally in the Kangaroos and Potoroos (fig. 103). 
However, in those singular species of Huypsi- 
prymnus which inhabit New Guinea and take 


285 


Bones of the leg and foot, Phalangista. 


refuge in trees, the organization of the Kangaroo 
is modified and adapted so as to make climb- 
ing a possible and easy action. The fore and 
hind legs are here more equally developed, 
and the claws on the two larger toes of the 
hind feet are curved instead of straight. Ina 
skeleton of one of these scansorial Potoroos, 
the Hypsiprymnus ursinus, in the Museum at 
Leyden, in which the humerus is three inches 
and a half long, the femur does not quite equal 
five inches in length: the ulna is nearly four 
inches, the fibula nearly five inches in length. 
The fibula is also less firmly connected with 
the tibia than in the great Kangaroo. 

The following is the structure of the tarsus 
in the Wombat. The astragalus is connected 
as usual with the tibia, fibula, caleaneum, and 
scaphoides. The upper articular surface for 
the tibia is as usual concavo-convex, the inter- 
nal surface for the inner malleolus flattened and 
at right angles with the preceding, but the 
outer articular surface presents a triangular 
flattened form, and instead of being bent down 
parallel with the inner articular surface, slopes 
away at a very open angle from the upper 
surface, and receives the articular surface of 
the fibula so as to sustain its vertical pressure. 
A very small proportion of the outer part of 
the inferior surface of the astragalus rests upon 


286 


the calcaneum; a greater part of the super- 
incumbent pressure is transmitted by a trans- 
versely extended convex anterior surface to the 
scaphoid and cuboid bones. This form of 
the astragalus is also characteristic of the Koala, 
Petaurists, Dasyures, and the Pedimanous 
Marsupials (d, fig.111). In the Kangaroos, 
Potoroos, and Perameles which have the pedes 
saltatorii, the fibular articular surface of the 
astragalus is bent down as usual at nearly right 
angles with the upper tibial surface. 

The calcaneum in the Wombat presents a 
ridge on the outer surface which serves to sus- 
tain the pressure of the external malleolus which 
is not articulated to the side of the astragalus. 
The internal surface which joins the astraga- 
lus. is continuous with the anterior slightly 
concave surface which articulates with the 
cuboides. The posterior part of the bone is 
compressed, it projects backwards for nearly 
an inch, and is slightly bent downwards and 
inwards. This part is relatively shorter in the 
Koala, Phalangers, Opossums, and Petaurists, 
but it is as strongly developed in the Dasyuri 
as in the Wombat. The anterior part of the 
calcaneum of the Phalangers is shown at e, 
Sig. 111. 

In the Dasyurus macrurus I observe a small 
sesamoid bone wedged in between the astragalus, 
tibia, and fibula at the back part of the ankle- 
joint. In the Petaurus taguanoides there is a 
supplemental tarsal bone wedged in between 
the naviculare and cuboides on the plantar sur- 
face. Inthe hand-like foot of the Phalanger 
the structure of the tarsus is shown in fig. 111: 
J is the naviculare, g the internal cuneiform, and 
h the os cuboides. In the Wombat the sca- 
phoid, cuboid, and three cuneiform bones have 
the ordinary uses and relative positions. 

The analogy of the carpal and tarsal bones 
is very clearly illustrated in this animal. The 
anchylosed naviculare and lunare of the hand 
correspond with the astragalus and navicu- 
lare of the foot, transferring the pressure of 
the facile majus upon the three innermost 
bones of the second series. The long, back- 
ward-projecting pisiform bone of the wrist 
closely resembles the posterior process of the 
os calcis; the articular portion or body of 
the os calcis corresponds with the cuneiforme 
of the carpus; the large carpal unciform re- 
presents the tarsal cuboides, and performs the 
same function, supporting the two outer digits ; 
the three cuneiform bones of the foot are obvi- 
ously analogous to the trapezium, trapezoides, 
and os magnum. The internal cuneiform bone 
is the largest of the three in the Wombat, al- 
though it supports the smallest of the toes. It 
is of course more developed in the Pedimanous 
Marsupials, where it supports a large and op- 

ble thumb. 

In the Wombat the metatarsals progressively 
increase in length and breadth from the inner- 
most to the fourth ; the fifth or outermost meta- 
tarsal is somewhat shorter but twice as thick, 
and it sends off a strong obtuse process from 
the outside of its proximal end. A correspond- 
ing process exists in the Phalangers (fig. 111). 
The innermost metatarsal of the Wombat (fig. 


MARSUPIALIA. 


105) supports only a single phalanx ; the rest 
are succeeded by three phalanges each, pro- 
gressively increasing in thickness to the outer- 
most; the ungueal phalanges are elongated, 
gently curved downwards, and gradually dimi- 
nish to a point. 
In the Myrmecobius the tibial or 
most toe is represented by a short rudim 
metatarsal bone concealed under the ski 
In the Dasyures the innermost toe has 
phalanges, but it is the most slender and does 
not exceed in length the metatarsal bone of th 
second toe. In the Petaurists it is rathe 
shorter than the other digits but is the strongest, 
and in Petaurus taguanoides the terminal 
phalanx is flattened and expanded ; the te 
set wide apart in this genus. In the Opossums 
and Phalangers the innermost metatarsal b 
is directed inwards apart from the rest, am 
together with the first phalanx is broad and flat. 
The second phalanx in the Opossums support 
a claw, but in the Phalangers is short, trans 
verse, unarmed, singularly expanded in 
Cookii, but almost obsolete in Ph. ursin 
(fig. 111,1). Inall the preceding genera there 
are two small staan bones on the under 
side of the joints of the toes, both in the fore 
and hind feet. -< 
The commencement of a degeneration of the 
foot which is peculiar to and highly che 1 
istic of the Marsupial animals may be discerned 
in the Petaurists, in the slender condition of 
the second and third toes, as com ith 
the fourth and fifth. In the Phalangers t 
diminution of size of the second and third te 
counting from the hallux, is more marked, 
They are, also, both of the same length and 
have no individual motion, being united 
gether in the same sheath of integument as far 
as the ungueal phalanges, whence the name of — 
Phalangista applied to this genus (fig. 111, 
2 and 3). - 
In the saltatorial genera of Marsupials 
degradation of the corresponding toes is ex= 
treme, but though reduced to almost fila- 
mentary slenderness they retain the usual num= 
ber of phalanges, and the terminal one of each 
is armed with a claw. These claws being the 
only pe of the rudimental digits which pro- 
ject freely beyond the integument, they 
like little appendages at the inner side of the 
foot for the purpose of scratching the skin 
dressing the fur, to which offices they ar 
exclusively designed. The removal of the i 
nermost toe, corresponding with our g 
toe and the hallux of the Pedimana, commenc 
in the Perameles. In one species I find t 
metatarsal bone of this toe supports only 
single rudimental phalanx which reaches to the ~ 
end of the next metatarsal bone, and the inter- 
nal cuneiform bone is elongated. In another 
species the internal toe is as long as the abortive 
second and third toes, and has two phalanges, 
the last of which is divided by the longitudinal 
fissure characteristic of the ungueal phalanges — 
in this genus. In the Perameles lagotis the — 
innermost toe is represented by a rudi 
metatarsal bone, about one-third the length of 
the adjoining metatarsal. 


Ref 


me, 


hee inal 


La 


MARSUPIALIA. 


In the Peophagous Marsupials no rudiment 
of the innermost toe exists. The power of the 
foot is concentrated in all these genera on the 
fourth and fifth or two outer toes, but especially 
the fourth, which, in the Great Kangaroo, is 
upwards of a foot in length, including the 
metatarsal bone and the claw. This formidable 
weapon resembles an elongated hoof, but is 
three-sided and sharp-pointed like a bayonet, 
and with it the Kangaroo stabs and rips open 
the abdomen of its assailant: with the ante- 
rior extremities it will hold a powerful dog 
firmly during the attack, and firmly supporting 
itself behind upon its powerful tail, deliver its 
thrusts with the whole force of the hinder 
extremities. 

The cuboid bone which supports the two 
outer metatarsals is proportionally developed. 
The internal cuneiform bone is present, though 
the toe which is usually articulated to it is 
wanting. It is also the largest of the three, 
and assists in supporting the second metatarsal ; 
posteriorly it is joined with the navicular and 
external cuneiform bones, the small middle 
cuneiform occupying the space between the 
external and internal wedge-bones and the 
proximal extremities of the two abortive meta- 
tarsals. The great or fourth metatarsal is straight 
and somewhat flattened; the external one is 
compressed and slightly bent outwards ; the toe 
which this supports is armed with a claw simi- 
lar to the large one, but the ungueal phalanx 
does not reach to the end of the second pha- 
lanx of the fourth toe, and the whole digit is 
proportionally weaker. 

In the climbing Potoroos, ( Hypsiprymnus 
ursinus and Hypsiprymnus dorcocephalus ), the 
two outer toes are proportionally shorter than 
in the leaping species, and are terminated by 
curved claws by which they gain a better hold 
on the branches and inequalities of trees. 

Myotocy.—To give a description of the 
muscular system with the same detail as of the 
osteology of the Marsupials would not be at- 
tended with the same advantages. Modified 
as this system necessarily is in conformity with 
the various modes of locomotion in the different 
Marsupial genera, as running, leaping, burrow- 
ing, swimming, even flying, we should here 
fail to detect in these modifications so many 
marks illustrative of the aberrant and inferior 
type of structure of our present group as we 
have witnessed in those of the skeleton. In 
addition, moreover, to their physiological rela- 
_ tions, the importance of the passive and endur- 
ing parts of the locomotive system to the 
zoology both of recent and extinct species, con- 
fers upon them a claim to our attention which 
the more perishable though more highly organ- 
ised and active parts of the same system do not 
possess, even if a detailed myology comported 
with the scope and extent of the present work. 
The present notice, therefore, of this depart- 
ment of the anatomy of the Marsupialia will 
be limited to a brief description of a few of the 
most striking peculiarities. 

Every one knows that the erect position is 
the most usual one in the Kangaroos; yet the 
conditions of this posture are very different from 


287 


those in the human subject. The trunk, in- 
stead of resting on two nearly vertical pillars 
so placed with reference to the superincumbent 
weight that it rather inclines to topple forwards, 
is here swung upon the femora as upon two 
springs, which descend from the knee-joints ob- 
liquely backwards to their points of attachment 
at the pelvis ; and the trunk is propped up be- 
hind by the long and powerful tail (fig. 103). 

In Man the massive and expanded muscles 
which find their attachment in the broad bones 
of the pelvis, especially at the posterior part, 
are the chief powers in maintaining the erect 
posture. But in the Kangaroo the glutai offer 
no corresponding predominance of size; the 
narrow prismatic ilia could not, in fact, afford 
them the requisite extent of fixed attachment. 

The chief modifications of the muscular sys- 
tem in relation to the erect position of the trunk 
in the Kangaroo are met with on the anterior 
part of the base of the spinal column. The 
psoe parve, for example, present proportions 
the very reverse of those which suggested their 
name in humananatomy. They form two thick, 
long, rounded masses, which take their origin, 
fleshy, from the sides of the bodies and base of 
the transverse processes of the lower dorsal and 
all the six lumbar vertebrz, and from the extre- 
mities of the three last ribs; the fibres converge 
penniformwise to a strong, round, middle 
tendon, inserted in the well-marked tubercle or 
spine of the pubis, already noticed. 

The disposition of the abdominal muscles, 
especially at the pubic and hypochondriac re- 
gions, has been described and figured by Mr. 
Morgan* and Professor Vrolik+ in the female 
Kangaroo. The principal modifications are 
seen first in the presence of a large muscle 
called the triangularis by Tyson, the anterior 
rectus abdominis by Mr. Morgan,t and con- 
sidered as the analogue of the pyramidalis - 
muscle by Meckel ; secondly, in the equal de- 
velopment of the cremaster in both sexes; and 
thirdly, in the formation of a moveable bone in 
the situation and, as it were, in the substance 
of the mesial or internal pillar of the abdominal 
ring, which bone serves as a trochlea or pulley 
for the cremaster, and affords an extensive 
attachment to the abnormally developed pyra- 
midalis. 

This part of the muscular system is here 
described as it exists in a male Phalanger (fig. 
112), that sex being chosen, because most of 
the peculiarities, as the extensive pyramidalis,§ 
the cremaster, and the ossified tendons of the 
external oblique abdominal muscle have been 
regarded as being essentially connected with the 
physiology of the marsupial pouch, whereas 
they are equally developed in both sexes. 

The external oblique (obliquus externus ), 
besides the usual origin by digitations from the 
ribs, also arises from the fascia lumborum ; it 
is inserted fleshy into the summit of the mar- 


* Linn. Trans. xvi. 1833. 

+ Tydschrift voor de Natural, 1837. 

$ A portion of the external oblique is included 
by Mr. Morgan with the triangularis under this term, 

§ Considered by Home as a sling by which the 
mammez were supported, 


Abdominal muscles, Phatangista vulpina. 


supial bone (a), over which its strong inner 
tendon is spread ; the external oblique becomes 
aponeurotic at a line continued from the mar- 
supial bone outwards, with a gentle curve, to- 
wards the anterior extremity of the ilium; and 
in the opposite direction, or inwards, the car- 
neous aes of the external oblique terminate 
in an aponeurosis along a line parallel with the 
oblique outer margin of the pyramidalis; the 
fascia continued from the latter boundary of the 
fleshy fibres passes over, or dermad of, the so- 
called pyramidalis, and meets its fellow at the 
linea alba ; it is strictly analogous to the anterior 
layer of the sheath of the rectus in ordinary Mam- 
malia. It is seen reflected from the pyramidalis, 
at b, fig.112. The aponeurosis continued from 
the external and inferior boundary of the car- 
neous fibres divides as usual into two distinct 
portions; one, tion S-RbDe to the internal or 
mesial pillar of the abdominal ring, spreads its 
glistening fibres, as above described, over the 
dermal surface of the marsupial bone (c), to 
which it closely adheres: the other column (d) 
contracts as it descends obliquely inwards, 
forms, like Poupart’s ligament, the upper boun- 
dary of the space through which the psoas and 
iliacus muscles and femoral vessels and nerves 
escape from the pelvis, and is finally inserted, 
thick and strong, into the outer end of the base 
of the marsupial bone. 

This bone is so connected with the pubis 
that its movements are almost limited to di- 
rections forwards and backwards, or those con- 
cerned with the dilatation and diminution of 
the abdominal space; the contraction of the 
abdominal muscles must draw the bones in- 
wards so as to compress the contents of the 
abdomen, and so far as the connections of the 
bone permit, which is to a very trifling degree, 
the external oblique may draw it outwards to- 
wards the ilium. 

In some Marsupials, as the Koala, the trice 
adductor femoris sends a slip of fibres to the 
external angle of the base of the marsupial 
bone, and would more directly tend to bend 
that bone outwards. 

The upper or anterior fibres of the internal 


MARSUPIALIA. 


A to the seer part of the acetabulum : these ear- 


oblique have the usual origin; the lower ones 
(e) arise fleshy from the outer and anterior — 
spine of the ilium, and for an inch along an 
aponeurotic chord extended from that process” 


neous fibres pass inwards, and slightly up 
and terminate close to the outer margin of the 
rectus, where they adhere very strongly to the” 
transversalis, but give off a separate sheet of 
thin aponeurosis which is lost m the cellular 
sheath of the posterior rectus. - # 

The fleshy fibres of the transversalis abdomi- 
nis (f)) are closely connected by dense cellular 
tissue with those of the internal oblique ; they” 
are arranged in finer fasciculi, and have, as 
usual, a more transverse direction; they - 
nate along the same line as those of the internal 
oblique in an aponeurosis (g), which is con 
tinued along the inner or central surface of th 
—_ rectus to the median line. The le 

oundary of the Heshy fibres of the transve 
is parallel with the line extended trans I 
between the anterior extremities of the ilia; 
fascia, less compact than an aponeurosis, is con- 
tinued downwards from this margin, ive- 
lopes the cremaster and the constituents of the’ 
spermatic chord, as they pass outwards and 
forwards beneath the lower edge of the inte 
oblique. 

The pyramidalis (h) arises from the 
inner or mesial margin of the marsupial bone; 
from which the fibres diverge, the lower ones 
passing transversely across the interspace of the 
bones, and meeting at a very fine raphé, or 
linea alba ; while those fibres from the anteri ie 
ends of the marsupial bones gradually exchang ez 
their transverse direction for one obliquely for-— 
wards. The breadth of each pyramidalis oppo-— 
site the upper end of the marsupial bone is 
more than an inch, the thickness of the muscle — 
one line. Ls 

The rectus abdominis or posterior re 
(i) comes off from the pubis along the inner 
pet of the strong ligamentous union of t 

road base of the marsupial bone, and 
pands as it ascends until it attains the level 
the ensiform cartilage, when the rectus dimi= 
nishes as it is inserted into the sternal extre= 
mities of the ribs reaching to the manubrium 
sterni and first rib in the Dasyures, as in the 
cats. 

The slight indications of tendinous inter> 
sections which were noticed in this dissection 
were confined to the posterior or central super 
ficies of the muscle; the first extended o 
half-way across from the outer margin. 

The cremaster (k), in the Phalanger and 
Opossum, is not a fasciculus of fibres simply 
detached from the lower margin of the interna 
oblique or transversalis, but arises by a narrow — 
though strong aponeurosis from the iliur > 
within and a little above the lower boun of 
the internal oblique, with the fibres of whi 4 
the course of the cremaster is not parallel; it 
might be considered as a part of the trans- — 
versalis, but it is separated by the fascia above 
mentioned from the carneous part of that mus= 
cle. Having emerged from beneath the margin” 
of the internal oblique, the cremaster escapes 


> a 


¢ . 
aes a 


* =a 
3 


+¥ 
‘td 


MARSUPIALIA. 


by the large elliptic abdominal ring (/), bends 
round the marsupial bone near its free ex- 
tremity, and expands upon the tunica vaginalis 
testis. In the female it has the same origin, 
course, and size, but spreads over the mam- 
mary glands at the back of the pouch. If the 
anterior fascicles of the diverging and em- 
bracing fibres be dissected from the posterior 
Ones, the appearance of the cremaster dividing 
into two layers is produced. 

The principal modifications of the muscles 
of the pectoral extremity are here described as 
ye: Seaore in the Perameles lagotis. 

trapezius is a broad and very thin mus- 
cle, having its origin extended from the skull, 
along the cervical and dorsal spines, to the 
fascia covering the lumbar portion of the latis- 
simus dorsi: its fibres converge to be inserted 
along the spine of the scapula, the anterior ones 
directly continued into the pectorales, whereby 
it becomes an extensor of the humerus and a 
protractor of the fore extremity. 

The Jatissimus dorsi arises chiefly from the 
broad aponeurosis covering the muscles of the 
lumbar region of the spine, and from the spines 
of the six posterior dorsal vertebre ; the fibres 
gradually converge, the muscle increasing in 
thickness as it diminishes in breadth, and 
terminating in a strong flattened tendon one 
inch before its insertion at the upper third of 
the humerus. 

The chief peculiarity of this muscle is its con- 
nection with an accessory extensor (omo-anco- 
neus) of the antibrachium. This extensor 
takes its principal origin by fleshy fibres from 
the terminal half inch of the fleshy part of the 
latissimus dorsi, and continues fleshy, slightly 
diminishing in size to its insertion at the apex 
of the olecranon; it may thus be considered as 
a slip detached from the latissimus dorsi, yet 
its fibres from their very origin run at right 
angles to those of that muscle, to which they are 
attached. To remedy the inconvenience of 
an origin from a yielding and flexible part, a 
thin aponeurotic slip, two lines in breadth and 
an inch in length, attaches a part of the base of 
the superadded muscle and the corresponding 
portion of the latissimus dorsi to the sheath of 
ihe teres major, and to the inferior costa of the 
scapula near its posterior angle. 

1e serratus magnus offers no peculiarity 
worthy of notice. 

The supra-spinatus, a strong penniform mus- 
cle, exceeds the infra-spinatus in breadth by as 
much as the supra-spinal fossa is broader than 
the infra-spinal one: it has a broad and strong 
insertion into the great outer tuberosity of the 
humerus. The infra-spinatus is inserted into 
the upper and posterior part of that tubero- 
sity. 

The deltoides is a comparatively small muscle ; 
it arises from the anterior half of the spine of the 
scapula and from a fine aponeurosis covering 
the infra-spinatus ; its fibres converge to be in- 
serted in the upper part of the deltoid ridge. 

A thin small strip of muscle arises from 
about the middle of the inferior costa of the 
scapula, beneath the infra-spinatus ; its fibres 
pass forwards and join the lower margin of the 

VOL. Ii. 


289 


small deltoid, thus bracing and enclosing the 
tendon of the infra-spinatus. 

The subscapularis offers no peculiarity. 

The teres major is a strong sub-compressed 
muscle arising from near the posterior half of 
the inferior costa of the scapula, and joining, as 
before stated, the tendon of the latissimus. 

The triceps extensor has its long portion 
arising from the anterior third of the inferior 
costa of the scapula; its second head comes 
from the posterior part of the proximal third of 
the humerus; the third portion takes its origin 
from the whole of the posterior part of the 
humerus ; in addition to these, the olecranon 
receives the above described fourth superadded 
slip from the latissimus dorsi. 

e pectoralis major is, as usual in the Mar- 
supial and many of the Placental quadrupeds, 
a very complicated muscle; it consists of an 
anterior or superficial, and a posterior or deeper 
portion ; the anterior portion receives the strip 
of fibres before mentioned from the trapezius, 
there being no clavicle or clavicular ossicle 
interposed in the Perameles: its fibres con- 
verge, increasing in thickness as they dimi- 
nish in breadth, and are inserted into the 
anterior .and outer part of the strongly deve- 
loped pectoral ridge. The second and main 
portion of; the pectoralis arises from the whole 
extent of the sternum; its fibres are twisted 
obliquely across each other as they converge 
to be inserted into the inner part of the pectoral 
ridge; some of the internal and posterior fibres 
of this portion of the twisted pen pass ob- 
liquely upwards and behind the anterior fasci- 
culi, and are inserted into the coracoid process, 
thus representing the pectoralis minor.* Be- 
neath this latter portion of the twisted pectoral, 
a long and slender muscle passes to be inserted 
into the anterior part of the tuberosity of the 
humerus; this may likewise be regarded asa 
dismemberment of the pectoralis major, but it 
arises from the fascia of the rectus abdominis, 
below the cartilages of the lower ribs. Thus 
the strong pectoral ridge of the humerus is 
acted upon by muscles having a range of origin 
from the occiput and cervical vertebre along 
the whole extent of the chest to the beginning 
of the abdomen. 

The biceps is a powerful muscle, although 
its short head from the coracoid process is sup- 
pressed. The long head has the usual origin 
and relation to the shoulder-joint; its tendon 
is very thick and short. The fleshy belly joins 
that of the strong brachialis internus, situated 
at the external side of the humerus, whence it 
takes its principal origin from the short deltoid 
ridge, closely connected there with the second 
portion of the triceps, and deriving some fleshy 
fibres from the lower and outer third of the 
humerus. The portion of the biceps arising 
by the long head soon resolves itself into two 
distinct penniform muscles ; the tendon of the 
outer one joins that of the brachialis, and this 
conjoined tendon simply bends the fore-arm, 


* Professor Vrolik found that the pectoralis 
minor in the Kangaroo was inserted not into the 
coracoid process, but into the humerus between the 
biceps and the tendon of the pectoralis major. 

U 


2°0 


while the other tendon bends and pronates; 
this, which is a direct though partial continua- 
tion of the biceps, is inserted into the ordinary 
tubercle of the radius ; whereas the other ten- 
don is attached to the fore part of the proximal 
end of the ulna. 

The muscles which arise from the internal 
condyle of the humerus are the pronator teres, 
which has the usual origin, insertion, and rela- 
tive proportions, and next the palmaris longus. 

There are, likewise, distinct and strong fas- 
ciculi of muscles corresponding to the flexor 
carpi ulnaris and radialis, and to the flexor 
sublimis digitorum. 

The strong ridge continued from the olecra- 
non to the posterior and inner part of the ulna 
gives origin to a great proportion of the oblique 
fibres of the flexor profundus; but both this 
and the flexor sublimis terminate in a single 
thick and strong tendon, which after passing 
the wrist divides into those corresponding with 
the perforating and perforated tendons here con- 
centrated upon the three long middle fingers. 

The pronator guadratus runs the whole length 
of the interosseous space, passing from the radius 
a little obliquely downwards to the ulna. 

The supinator longus, arising as usual from 
the upper part of the strongly developed ridge 
above the outer condyle, sends its tendon across 
the carpal joint, which tendon divides before it 
crosses, and is inserted by one of its divisions 
into the base of one of the metacarpal bones 
of the index finger, and the other to the adjoin- 
ing metacarpal bone. 

These are the principal muscles of the fore 
extremity which require notice in this place. 
Their modifications, in respect of number and 
Strength, relate to the act of digging up the 
soil, which is habitual in the Bandicoots, as it 
is for the purpose of obtaining food, and not for 
shelter. It is for this purpose that the three 
middle digits of the hand are developed at the 
expense of the other two, which are rudimental ; 
and we have seen that the whole powerof the deep 
and superficial flexors is concentrated upon the 
fossorial and well-armed fingers; and that by 
the single common tendon in which the fleshy 
fibres of these muscles terminate, they move 
them collectively and simultaneously. Thus 
variety of application, and especially the pre- 
hensile faculty, are sacrificed to the acquisition of 
force for the essential action. In no Marsupial 
is the hand so cramped as in the Perameles, 
sir a in the Charopus, where the functional 
and rial fingers are reduced from three to 
two. It is in relation to this condition, doubt- 
less, that the clavicles are wanting in these 

nera, while all other Marsupials possess them. 

e inverted position of the pouch in the Pera- 
meles might also be conceived to have relation 
to their imperfect hands, the mouth of the 
ney being thus brought nearer to the vulva ; 
but I am disposed to regard it as being more 
essentially connected with the habitually in- 
clined or procumbent position of the trunk in 
the Saltatorial Entomophaga. 

’ The muscles of the hinder, extremity are 
chiefly remarkable in the Kangaroo for their 
prodigious strength and unusual number: the 


MARSUPIALIA. 


“a muscle of very great strength; it termi 


accessory muscle of the biceps, e. g. is di 
into two strong fasciculi, which unite to 
inserted into the side of the lia ;* the 
riformis is also a double muscle.t 

The sartorius has its insertion so modified 
that it becomes an extensor instead of a flexor 
of the tibia: it is chiefly fixed to the tibial side 
of the patella, and by fascia into the capsular 
ligament of the knee-joint and the anter 
proximal tuberosity of the tibia. InaD 
( Das. macrurus) 1 found that the sartoriv 
had a similar disposition and office. In th 
ambulatory carnivorous Marsupial the external 
and middle glutei are so disposed as to extend 
the thigh, while the internal gluteus ini 
and rotates it inwards. 

In a Bandicoot ( Perameles lagotis ) the 
torius ran nearly parallel with and derr 
the rec/us, and was inserted into the upp 
of the patella. Besides this sesamoid, 
is rarely developed in other Marsupials, 
found a thick cartilage attached to its 
part and interposed between the common 
don of the recti and vasti, removing that te 
further from the centre of motion and ine n 
the power of the extensor muscles of the leg.” 

he rectus femoris has its two origins very 

distinct, and its analogy to the biceps of 
upper extremity is very close. f 
is a very thick and strong muscle. 

The biceps flexor cruris in the Peram 


7 


. oe 


in a strong and broad aponeurosis, which 
tends over the whole anterior part of the tik 
being attached to the rotular tuberosity of that 
bone, and terminating below in the sheath of — 
the tendo Achillis, whereby this muscle be- 
comes an extensor of the foot. 4 
It is a curious fact that all the eq nipeda 
Marsupials, whether burrowers as the Wom-— 
bat, climbers as the Koala, Phalangers, and 
Opossums, or simply gressorial, as the De 
syuride, have the tibia and fibula so connectet 
together as to allow of a certain degree of ro- 
tation upon each other, analogous to the pr 
natory and supinatory movements of the b 
of the antibrachium, and the muscles of — 
leg present corresponding modifications. 
not without interest in the question of 
affinities of the Marsupials to find that ‘ 
of the analogous carnivorous, pedimanous, 
rodent Placentals present this condition of 
hind leg. 
In the Dasyurus macrurus, the plantar 
instead of rising from the femur, has its fix 
point in the fibula, from the head to half-w 
down the bone, fleshy; its tendon passes of 
liquely inwards and glides behind the im 
malleolus to its insertion in the tar 
so that it rotates the tibia in beside 
tending the foot. The soleus has an extensive 
origin from the proximal to near the distal end — 
of the fibula. There are as usual three deep- — 
seated muscles at the back of the leg. Of 
these three the muscle analogous to the tibialis 
posticus is readily recognized; its tendon glides 


ae 


4 


* Cuvier, loc. cit. p. SOL. 
+ Ibid. p. 502. 


; 
} 


MARSUPIALIA. 


behind the inner malleolus, and is inserted 
into the inner or tibial cuneiform bone. 

The muscle which has the relative position 
and origins of the fleror longus pollicis, sends 
its tendon by the usual route to the sole of the 
foot, where it divides and distributes a flexor 
tendon to all the toes except the rudimental 
hallux; it has the same disposition in the 
Opossums, where the hinder thumb or great 
toe is fully developed; for this modification, 
however, the Comparative Anatomist is already 
prepared by meeting with it in the first step 
from man, viz. in the Chimpanzee and Orang.* 

The third deep-seated muscle, being situ- 
ated internal to the two preceding ones, may 
be the analogue of the flexor digitorum commu- 
nis longus ; it nevertheless sends no tendon to 
the toes nor even to the tarsus, but its fibres pass 
from the tibia obliquely outwards and down- 
wards between the preceding muscle and the 
interosseous ligament to the fibula, where they 
are exclusively inserted so as to oppose the 
plantaris and rotate the foot outwards. This 
muscle closely adheres to the interosseous 
fascia, and thus resembles in its attachments 
the pronator quadratus of the fore limb: it is 
most developed in the pedimanous climbing 
Marsupials, where the rotation of the foot is 
more extensive and more useful. 

The subjoined illustration (fig. 113) of this 
modification of the muscles of the hind-foot is 
taken from a dissection of the Phalangista vul- 
pina, which very closely accords with that 
above described in the Dasyurus macrurus: a, 
expanded tendon of the sartorius; b, gracilis ; 
c, semitendinosus ; and d, semi-membranosus ; 
both these muscles are inserted, as in many 
other quadrupeds, low down the tibia: e, gas- 
trocnemius; f, plantaris; g, the analogue of 
the fleror longus pollicis pedis ; h, tibialis posti- 
cus; this muscle divides and is inserted by two 
tendons, h’ and h”, into the internal and middle 
cuneiform bones: i, the rotator muscle of the 
tibia, probably a modification of the flexor 
digitorum communis pedis; its fibres descend 
obliquely from the fibula p to the tibia ¢. 

In the muscles on the anterior part of the 
leg I observed no peculiarity worthy of notice ; 
the extensor brevis digitorum has, however, its 
origin extended into this region and is attached 
to the outside of the fibula. There are three 
peronei ; the external one is inserted into the 
proximal end of the fifth metatarsal: the ten- 
don of the middle peroneus crosses the sole in 
a groove of the cuboid like the peroneus longus: 
the internal peroneus is an extensor of the 
outer or fifth toe. The Perameles lagotis, 
among the Saltatorial Marsupials, presents a 
different condition of the extensors of the foot 
from that above described. The gastrocnemit, 
soleus, and plantaris all arise above the knee- 
joint, and the tendon of the plantaris, after 
sheathing the tendo Achillis and traversing the 
long sole, is finally inserted into the base of 
the metatarsal bone of the fourth or largest 
toe; thus this muscle, which is strongly de- 
veloped, bends both this toe and the knee, 
while it extends the foot. 

* Zoolog. Proceedings, 1830, p. 59. 


204 


Muscles of ieg, Phalangista vulpina. 


Nervous System. 

The brain bears a smaller proportion to the 
body in the Marsupials than in any other order 
of Mammals: thus, in the Ursine Dasyure it 
is as 1 to 520, in the Wombat as 1 to 614, 
in the great Kangaroo as 1 to 800: it is 
relatively largest in the smaller species of 
Petaurists and Phalangers. 

The Marsupial brain is also the simplest as 
respects its external form in the Mammiferous 
class. The cerebral hemispheres do not ex- 
tend over the cerebellum in any of the species, 
and in some, as the Dasyures and Opossums, 
they leave the optic lobes exposed. The brain 
consists, as in other Mammalia, of a medulla 
oblongata with a pons Varolii, cerebellum 
(d, fig. 114), optic lobes, or bigeminal bodies, 
(c, fig. 114), cerebrum (b), to which may be 
added, on account of their large proportional 
size and distinct development, the olfactory 
lobes (a, a,). In the Phalangers and Petau- 
rists, the Opossums, Perameles, the insectivo- 
rous Phascogales, and the smaller Dasyures the 
surface of the cerebral hemispheres is smooth 
and unconvoluted. In the Dasyurus ursinus 
the complication of the cerebral surface is 
merely indicated by a few slight indentations ; 
it is in the strictly herbivorous species as the 
Kangaroo (fig. 115) and bf eee that the 

u 


292 


hemispheres are 
enetrated by an- 
ractuous fissures. 

In the Wombat 
a large longitudi- 
nal fissure bounds 
the outer side of 
the natiform pro- 
tuberance | ol- 
factory tract at the 
base of the brain ; 
from the anterior 
moiety of this fis- 
sure three or four 
smaller ones curve 
upwards upon the 
sides of the hemi- 
spheres. On the 
upper surface a 
short transverse 
fissure marks off 
what may be regarded as the anterior lobe 
of the cerebrum, and behind this each hemi- 
sphere exhibits a few detached shallow fissures. 
In the Kangaroo (fig. 115) these fissures be- 
come continuous and are deeper; a long 
and nearly transverse anfractuosity divides the 
upper surface of the hemisphere; behind the 
shorter fissure which marks off the anterior 
lobe, and between the two transverse fissures 
there is a longitudinal one bounding a con- 
volution that runs parallel with the median 
interspace of the hemispheres. The ante- 
rior lobes are also broken by small fissures; 
two or three long and moderately deep 
ones ascend upon the sides of the hemi- 
spheres (a), and the posterior portion (6) 
preter occasionally small detached fissures. 
o far therefore as the external surface is con- 


Brain of Dasyurus ursinus. 


Fig. 115. 


Brain of Macropus major. 


MARSUPIALIA. 


cerned, the brains of the herbivorous Marsu- _ 
pials are more complicated than those of any — 
of the Rodent Mammalia. The cerebellum 

llel, trans- _ 


presents the usual close-set, sub- 
verse convolutions: it is remarkable for ¢ 
large proportional size of the median or 
form lobe, as compared with the lateral le 
especially in the carnivorous and insecti 
Marsupials, where this condition is a: 
with a corresponding diminution of their com= 
missural band or ‘ pons Varolii,’ as is shown ii 
the view of the base of the brain of an Ope 
sum (fig. 116, 6). am 
(M8 ) In the Kangaroos, 
Perameles,Phalanger k 
and Koala the hemis- 
pheres or lateral lobes 
of the cerebellum at 
characterized by asm: 
subspherical late: 
process or apper 
(¢, ¢, fig. 115), 
is lodged in a pec 
fossa of the peti 
bone above the in 


me 


——— 


Opossums, but they 
Brain of Didelphys Vir- ate not developed” 
giniana. t . n the 
upper surface of the 
cerebellum the medullary substance appears 
superficially at a small tract between the ver= 
miform processes, marked with an asterisk in — 
figures 115 and 117. The simple disposi- 
tion of the arbor vite is shown in fig. 118, _ 
Behind the pons Varolii are seen the two 
trapezoid bodies (c, fig. 116); and the corpora — 
pyramidalia (d) are always pep in 
guishable from the corpora olivaria. 
cerebri, which, in the um (e, fe 116 r 
left exposed below, like the optic lobes abe 
by reason of the small proportional size of 
cerebrum, are more completely concealed in tl 
brain of the Kangaroo and Wombat. Then: 
form protuberances form a great 
the under part of the cerebral hemisphere 
all the Marsupials; their external bour 
which is basial in the Wombat and Kangaro 
runs along the side of the hemispheres t 
outer side of the olfactory lobe in the Ope 
be inner root of the olfactory =e orms: 
ulbous or lionic enlargement a 
* b). Behind the comnnienene of ie optic 
nerves is seen a broad and short infundibulum 
supporting the pituitary gland (d, fig. 1 
and posterior to this is the single corpus 
cans. The optic lobes are solid, and are each 
divided by a transverse fissure, as in the Pla- 
cental Mammalia; the anterior divisions or — 
‘nates ’ (B, fig.117) have a greater longitudinal 
diameter than the posterior ones or ‘ testes,’ 
which have a greater transverse development. _ 
The difference in the relative development of 
the nates and testes is much less in the herbi- 
vorous and carnivorous Marsupials than in the 
corresponding Placental quadrupeds. 


- 3 
HOTUOen | 


MARSUPIALIA. 


_ From the. fact that the cerebral organ is that 
which exhibits the most marked degradation of 
structure in the class of warm-blooded Verte- 
brate animals which are characterized by an 
oviparous generation, I was induced to sus- 
t, after having ascertained how closely the 
pialia approached Birds in their mode 
of generation, that the brain might present in 
them some corresponding inferiority of structure, 
as compared with the Placental Mammalia. 

The brain in the placental Mammalia is es- 
sentially characterized by the complexity and 
magnitude of the apparatus by which the he- 
mispheres are brought into communication 
with one another. With respect to size, the 
cerebrum is in many species proportionally 
inferior to that of Birds; and in most Insecti- 
vorous and Rodent Mammalia it presents an 
equally smooth and uniform external surface ; 
but notwithstanding the absence of convolu- 
tions and its diminished size, a large appa- 
ratus of medullary fibres is present, which 
connect together the opposite hemispheres, as 
well as the distant parts of the same hemi- 
sphere; and this apparatus, or great commis- 
sure, is superadded to the anterior, posterior, 
and soft commissures, which, with the excep- 
tion of a very slight rudiment of the fornix, 
are alone developed in Birds for the purpose 
of uniting the opposite sides of the brain. In 
the higher Mammalia, in which the cerebral 
hemispheres acquire superior size and increased 
extent of surface by means of convolutions, the 
superadded commissural apparatus presents a 
corresponding development and a highly com- 
plicated structure; its several parts being dis- 
tinguished as the corpus callosum, fornix, and 
their intercommunicating lamine, termed the 
septum lucidum. 

The corpus callosum is the principal bond of 
union between the opposite hemispheres; it 
extend$, as is well known, horizontally above 
the ventricles, its middle fibres passing trans- 
versely, while those of its extremities, which 

are more or less bent beneath its body, radiate, 
and all intermix, in apposition with the as- 
cending and diverging fibres of the peduncles 
of the cerebral hemispheres. It has hitherto 
been considered as the great characteristic of 

the brain in the Mammalia, and, taking the 
human brain as the term of comparison, to be 
developed in the ratio of the magnitude of the 
cerebral hemispheres. 

In the placental Mammalia this is a pretty 
accurate expression of the relations of the 
corpus callosum; and as the posterior lobes of 
the hemispheres are the first to disappear in 

_ the descending comparison, so the corpus cal- 
losum diminishes in longitudinal extent from 
behind forwards, and thus the corpora quadrige- 
mina, pineal gland, and posterior part of the optic 
thalami are successively brought into view on 
divaricating the cerebral hemispheres in the 
different Mammalia, as the Rodentia, Chei- 
roptera, and Edentata, which exhibit this pro- 
gressive degradation of the great commissure. 
An attentive study of the manners of dif- 
ferent Marsupials in confinement, and an in- 
spection of the exterior forms of the brain in 
some of the species, induced me to allude, in 


293 


my paper on the generation of the Kangaroo,* 
to an inferiority of intelligence and a low de- 
velopment of the cerebral organ, as being the 
circumstances in the habits and structure of 
these singular animals, which were most con- 
stantly associated with the peculiarities of their 
generative economy. I have since derived the 
most satisfactory confirmation of this coinci- 
dence from repeated dissections of the brains 
of Marsupials belonging to different genera ; 
and although unable to explain how a brief 
intra-uterine existence and the absence of a 
placental connexion between the mother and 
foetus can operate (if it be really effective and 
any thing more than a relation of simple co- 
existence) in arresting the development of the 
brain, yet it is a coincidence which has not 
been suspected, and is, in various points of 
view, perhaps the most interesting of the ana- 
tomical peculiarities of the quadrupeds here 
treated of. 

In order to obtain satisfactory proof of the 
difference in the structure of the brain in the 
marsupial and placental quadruped, I have 
dissected and compared together, step by step, 
the brains of a Wombat and Beaver. These 
animals are of nearly equal bulk, and manifest 
so many mutual affinities in their structure 
that they have been classed in the same order 
of Mammalia. The Wombat is, in fact, in all 
its exterior characters, save the marsupial and 
scrotal pouch, a Rodent; and in its internal 
anatomy, especially its digestive organs, more 
nearly resembles the Beaver than do many of 
the true Rodent animals. The brain of the 
Beaver was also preferred for this comparison 
of internal organization, because, on an out- 
ward inspection, it would be pronounced to 
be the less highly organized of the two; the 
hemispheres in the Wombat presenting a few 
convolutions, as before described, whilst in the 
Beaver they are perfectly smooth. 

Tn the Beaver, however, the cerebrum is ex- 
tended further backward, although it still leaves 
the cerebellum quite uncovered ; while in the 
Wombat a portion of the optic lobes (corpora 
quadrigemina) is also exposed. 

On divaricating the hemispheres of the brain 
in the Beaver we bring into view, about three 
lines below the surface, the corpus callosum ; 
and on removing the cerebral substance to a 
level with this body, its fibres are observed to 
diverge into the substance of each hemisphere 
in the usual manner, some bending upwards, 
but a greater proportion arching downwards 
and embracing the cerebral nuclei; the anterior 
fibres radiating into the anterior, the posterior 
fibres into the posterior extremities of the 
hemispheres. : 

The portions of the brain which are removed 
in thus tracing the extent of the corpus callo- 
sum, bring into view the corpora bigemina 
and the pineal gland; but the optic thalami 
are concealed by the great commissure above 
described. 

On separating the hemispheres of the brain 
of the Wombat, not only the bigeminal bodies 
(B, fig. 117,) and pineal gland (u, Jig. 117,) 


* Phil. Trans, 1334, p, 358. 


294 


but the optic thalami (¢, ¢, fig. 117) are im- 
mediately brought into view, and instead of a 


Fig. 117. 


Phascolomys fusca. 


broad corpus callosum, we perceive, situated 
deeply at the bottom of the longitudinal 
fissure, a small commissural medullary band, 
(m, fig. 117) passing in an arched form over 
the anterior part of the thalami, and extending 
beneath the overlapping internal or mesial sur- 
faces of the hemispheres, (9, fig. 117,) which 
are thus, as in the Bird, disconnected with 
each other. 

On gently raising the hemispheres from 
above the commissure and pressing them out- 
wards with the handle of a scalpel, the instru- 
ment passes into the fissure upon which the 


hippocampus (n, fig. 117) is folded; and, on. 


continuing the pressure, the hippocampus is 
torn through, and the lateral ventricle is ex- 
posed, The mesial wall of the hemisphere is 
continued from the superior and internal border 
of the hippocampus, and is composed in the 
Wombat, as in the Bird, of a thin lamina of 
medullary substance analogous to a detached 
layer of the septum lucidum. In the Kan- 
garoo the mesial parietes of the lateral ventricles 
are stronger, being about two lines in thickness. 

The posterior transverse fibres of the com- 
missure are continued outwards and backwards 
beneath the more longitudinal fibres, which 
overlap them as they pass from the tenie 
hippocampi (0, fig. 117) forwards to the 
anterior cerebral lobes. All the fibres of the 
commissure pass along the floor of the lateral 
ventricles into the substance of the hippocampi 
majores, which are of proportionally very large 
size. Thus the commissure, which is brought 
into view on divaricating the cerebral hemi- 
spheres in the Wombat, is seen to be partly 
the bond of union of the two hippocampi 
majores in the transverse direction, and eahie 
of the hippocampus and anterior lobe of the 
same hemisphere in the longitudinal direction, 
Tt also fulfils the other function of the fornix 


MARSUPIALIA. 


by sending down from the inferior surface two — 
small nerve-like processes, which extend ver 
cally, hehind the anterior commissure, thre 
the substance of the optic thalami, near t 
mesial surfaces, to the corpus albicans, at t 
base of the brain. 
The superior view of the connexions of the 
hippocampal commissure of the Wombat is” 
given at m, n, 0, fig. 117. lp 
If in the Beaver's brain the posterior thie 
ened margin of the corpus callosum be raist 
it is observed at the middle of its inferia 
face to be closely connected with the cent 
a commissural band of fibres, arching over the” 
anterior part of the optic thalami, and passing” 
outwards and backwards along the floor of t 
Jateral ventricles into the substance of the hip- 
pocampi, which are as largely developed as ii 
the Wombat. The anterior part of the corp 
callosum is bent downwards, and is attache 
along the middle line of its inferior surface by 
a uniting medium of medullary substance, r 
presenting the septum lucidum, to the hippo- 
campal commissure or fornix ; the teniz hip- 
pocampi extend forwards, as in the Wombat 
into the anterior lobes. “Ss 
The corpus callosum being removed, and t 
commissural fibres of the hippocampi bei 
left behind, the view of the Beaver’s brain now 
corresponds with that obtained in the previot 
dissection of the brain of the Wombat, 
we regard, therefore, as wanting the principal 
mass of the corpus callosum, theseptum lucidum, 
and consequently the fifth ventricle. The ar- 
tery of the plexus choroides, (p, fig. 117,) im ~ 
both the Beaver and Wombat, enters the lateral 
ventricle, where the hippocampus commences 
at the base of the hemisphere, and the plext 
is continued along the under surface of the — 
tenia hippocampi, and passes beneath the 
fornix, through the usual foramen, to gommu- 
nicate with its fellow in the third ventricle im- 
mediately behind the anterior crura of the 
fornix, which are sent down in the Beaver, as 
in the Wombat, from the centre of the inferio 
surface of the hippocampal commissure. 
If we expose the lateral ventricle by removit 
its outer parietes in a marsupial an pee: ta 
quadruped, as, for example, in the garoo 
and Ass, the hippocampus major, the teni 
hippocampi, the plexus choroides, and th 
foramen Monroianum are brought into view. | 
a style be thrust transversely through the inter 
nal wall of the ventricle, immediately aboy 
the hippocampus, in the placental quadrape 
it perforates the septum lucidum and enter 
the opposite ventricle below the corpus callo=— 
sum. If the same be done in the marsupia 
brain the style passes into the opposite ventricle, 
but is immediately brought into view from ~ 
above by divaricating the hemispheres, and is — 
seen lying above the fornix or commissure of — 
the hippocampi. 


is commissure may, nevertheless, be re- 
garded as representing, besides the fornix, the — 
rudimental commencement of the corpus callo- 
sum ; but this determination does not invalid 
the fact that the great commissure which unites 
the supra-ventricular masses in the Beaver, 


the Bat, and all other placentally develo 


y 
$ 


tia 
> 


MARSUPIALIA. 


Mammalia, and which ‘exists in addition to the 
hippocampal commissure, is wanting in the 
brain of the Wombat; and as the same defi- 
ciency exists in the brain of the Great and Bush 
Kangaroos, the Vulpine Phalanger, the Pera- 
meles lagotis, the Ursine and Mauge’s Dasy- 
ures, and the Virginian Opossum, it is most 
probably the cerebral characteristic of the mar- 
as ip division of Mammalia. 

n the modification of the commissural ap- 
paratus above described, the Marsupialia pre- 
sent a structure of brain which is intermediate 
between that of the placental Mammalia and 
Birds; as in the latterclass the great commissure 
is wholly wanting, and the hemispheres, though 
comparatively larger than in many of the Mam- 
malia, are brought into communication only by 
means of the anterior, posterior, and soft com- 
missures, and by a slight trace of the fornix or 
pacereepel commissure. 

_ Of the other peculiarities of the marsupial 
brain, the relatively large size of the anterior 
commissure (c, fig. 118) is most worthy of 
notice; its development corresponds with 
the large size of the cerebral ganglion, which 


a 
Didelphys Virginiuna, 


forms the chief origin of the olfactory nerve, 
and some of the anterior fibres of this com- 
missure arch forwards, and are directly con- 
tinued into those nerves. 

In the position, superficial transverse fissure, 
and solidity of the bigeminal bodies, the mar- 
supial brain adheres to the Mammiferous type, 
as also in the exterior transverse fibres of the 
commissure of the cerebellum, forming the 
pons Varolii, the presence of which relates to 
the development of the lateral lobes of the 
cerebellum. 

In one of the latest published treatises on 
comparative anatomy, the Lehrbuch der Ver- 
gleichenden Zootomie, zweite auflage, 1834, 
of Carus, the first and chief structural charac- 
teristic of the brain in Mammalia is stated, as 
in the Legons d’Anatomie Comparée of Cuvier, 
to be the presence of the corpus callosum.* 
The brain of the Rodentia is cited as the 
example of the transitional condition of this 
organ from Mammalia to Birds.¢ Besides tlie 


* <Theils und vorziizglich werden sie in den 
durch eine neue grosse Commissur vereinigten,’ 

122, B.i. p. 77. ‘* Die einzelnen Hirnmassen 

etreffend, so aiissert sich, wie schon bemerkt, das 
Eigenthiimliche der ersten, der Hemispharen, vor- 
ziiglich durch die Erscheinung des Balkens (corpus 
callosum) und des Gewolbes (fornix).” 

+ ‘Im allgemeinen bildet zur Hirnform dieser 
Klasse von der der vorigen (der Vogel) dice Gehirn- 
bildung, wie sie in den Nagethieren (Rodentia) 
ae wird, dendeutlichsten Uecbergang.” Ibid. 
| 


295 


Rodentia, Carus afterwards states that the 
Monotremata, Marsupialia, and Insectivora 
(shrews, moles, and bats) also present the more 
simple form of brain among the Mammalia, 
“ the hemispheres being of an ovate form con- 
tracted anteriorly, and their surface perfectly 
smooth, as in Birds, not extending over the 
cerebellum, and sometimes not over the corpora 
quadrigemina. Internally the great commissure 
is generally very short (in the Bats and Kan- 
garoo hardly so long as the corpora quadrige- 
mina, a structure which reminds one of that in 
Birds). The fold of the corpus callosum and 
the cornua ammonis (which Carus terms the 
processes of the corpus callosum in the ven- 
tricles) are commonly broad and large.”’* In 
illustration of this simple structure of the 
mammiferous brain Carus gives a figure of the 
brain of a Rodent, and from the whole descrip- 
tion the reader is led to infer that the Rodent 
and Insectivorous placental Mammalia partici- 
pate with the marsupial Mammalia in all the 
characters of the cerebral organization which 
approximate to those in Birds. Rudolph 
Wagner also describes the brain in the Roden- 
tia, Cheiroptera, Edentata, and Marsupialia as 
being characterised by the small size of the 
corpus callosum,t which does not extend far 
back. It must not be supposed that the pre- 
ceding quotations are adduced to detract from 
the merit of works whose reputation deservedly 
stands high. The position of the accomplished 
and indefatigable authors in a central town of 
Germany is unfavourable to the acquisition of 
specimens of animals which, like the Marsu- 
pialia, are almost confined to one of our most 
distant colonies; but it would be unpardonable 
in an English Comparative Anatomist, pos- 
sessing the requisite opportunities of consult- 
ing nature, to content himself with copying 
the generalizations of foreign systematic writers, 
which, as regards the marsupial Mammalia, 
are liable to repose on so limited and imperfect 
an induction. 

The Spinal Chord.—The spinal chord mani- 
fests all the usual Mammalian characters; the 
brachial and pelvic enlargements correspond 
with the relative size and muscularity of the ex- 
tremities to which they furnish the nerves, the 
lumbar or pelvic enlargement is consequently 
most marked in the Kangaroo (fig. 119) and 
Potoroos, but does not exhibit the rhomboidal 
sinus which characterises this part of the 
chord in Birds. The disposition of the layer of 


* <« Die aussere gestalt der hemispharen ist in 
den Nagera, so wie in den Schnabel-und Beutel- 
thieren, Spitzmausen, Maulwiirfen und Fleder- 
miusen ein vorwarts sich verschma‘erndes Eirund, 
und ihre Oberflache, wie in Vogel volikommen 
glatt; hinterwarts werden dadurch weder kleines 
Hirn, ja oft nicht einmal die Vierhugel bedeckt ; 
innerlich ist die grosse Commissur (corpus callosum ) 
gewohnlich noch sehr kurz (bei den Fiedermausen 
und dem Kinguruh kaum so lang als die Vierhiigel, 
eine Bildung, so an die Vogel erinnert) der Ums- 
chlag des Balkens und Forsetzung desselben in die 
Seitenhohlen (cornua Ammonis) vorziiglich breit 
und gros (f. v.e. g.)” Ibid. § 124, p. 79. 

j Der Balken ist noch schmal bei den Nagern, 
Fledermausen, Edentaten und Bentelthieren und 
geht nicht weit nach hinten.—LZehrbwch der Ver- 


. gleichenden Anatomie, p. G09, 1835, 


Fig. 119. 


Brain and spinal chord, Mapropus penicillatus. 


grey matter enveloping the central medullary 
tract in each lateral moiety of the chord is 
shewn in the three situations marked 1, 2, and 
3 (fig. 119); the superior expansion and com- 
plexity of the grey matter in the anterior 
columns of the pelvic enlargement accords 
with the predominance of the locomotive over 
the sensitive function* in the strong saltatory 
hind legs of the Kangaroo. 

Organs of Sense —The olfactory nerves and 
the osseous cavities and lamine destined for 
the protection and support of the pituitary 
membrane offer a remarkable proportional 
development in all the Marsupials, and more 
especially in the Insectivorous and Carnivorous 
tribes. e outer root of the olfactory nerve 
appears as a continuation of the whole nati- 
form protruberance ; a corresponding accumu- 
lation of nervous matter,“ protuberantia py- 
riformis,” + at the base of the inner root of 
the olfactory nerve has already been noticed ; 
both these broad tracts consist externally of 
grey matter: the middle or medullary root of 
the nerve is the smallest. It is very con~ 
spicuous in the Wombat, where it emerges 
from a longitudinal fissure at the anterior and 
inner of the “ protuberantia natiformis.” 
The ol nerves or rather lobes are hollow, 
and contain, as in most Mammalia, the ante- 


* Mayo, Outlines of Physiol p. 238, 
Phil. Trans. 1837, p. 95.” 


MARSUPIALIA. g 


rior continuation or extremity of the lateral 
ventricles (0, fig. 118). The filaments pass 
from the skull through several foramina of a 
cribriform plate. Certain species of Kangaroo, 
of the subgenus Osphranter, Gould, remarkabl 
for theiracuteness of ae urbinated 
bones so large that the lateral expansion of th 
nasal cavity forms a marked feature in the skul 

The chief deviation from the Mam 
type in the orgun of hearing presents itse 
the form of the stapes, the body of ‘ 
a simple elongated style either entirely, a 
the saad ‘is for seo its : as 
the Kangaroo (fig. 120), where it divides int 
two short crura, before ter- 
minating in the base ; it us 


i 


Fig. 120. 
more or less approximates 
Ne 3 _ the form of the col nella in 
€@& the bird. 
The largest proporti 
Stapes of the Kan- external ears are those of the 
Free Perameles lagotis, the short 


est those of the Wombat. The internal struc- 
ture of the ear is not less strikingly develope: 
in the Perameles than the oa appendages 
The tympanic cavity is very extensive, but is 
formed, as in other Marsupials, by the sph 
noid and petrous bones; the tympanic bong 
is limited to the function of supporting the 
ear-drum, and forming the inte 
ment of the meatus auditorius externus. Th 
internal extremity of the tympanic cylinder 
projects obliquely into the posterior and outer 
part of the sphenoidal bulla. The membrana 
tympari is a delicate transparent tissu 
slightly concave internally, and having the 
long handle of the malleus (a, fig. 121) at- 
tached to it. This pro- 
cess of the malleus is bent 
upon itself at a right an 
a the inner portion is 
broader and thicker than 
that which is attached to 
the membrana tympani, 
and it is anchylosed at i 
internal extremity by < 
thin and tran it plate 
of bone (6) to the si 
of the incus (ce). T 
little ossicle, which here 
appears as a process - 
che malleus, presents 
notched articular surface for the orbicular end 
of the stapes. This portion of the stapes gives 
off a short slender process for the attachment of 
the stapedius (d ), and then is continued in the 
form of a moderately long and slender colamel- 
liform shaft to the elliptical and slightly ex- 
panded base which closes the foramen ovale. — 
Organ of Vision—The anatomy of the eye 
offers no peculiarity illustrative of the affinities _ 
of the Marsupialia or of any other speciality in 
their economy save the nocturnal habits of the 
majority of the order. It is in relation to these — 
habits that the lens is large and convex, the 
iris broad, the pupil round and generally wide, 
and the cornea pega 9 pare large. Cy 
The Harderian gland and the retractor oculi 
co-exist, as vrenat in Mammalia, with the — 
nictitating eyelid. This is always largely de~ 


COULD 


Fig, 121. 


rs 


Auditory ossicles, 
Perumeles. 


‘ MARSUPIALIA. 


veloped, and the conjunctiva covering its free 
margin is stained black. 

In the Kangaroo I found the dark pigment 
on both the inside and outside of the choroid, 
and the ciliary processes very well developed. 
The lens is proportionally large. In the dead 
Kangaroo the radiated muscle of the iris is 
much contracted, and the pupil widely open. 
Beneath the upper eyelid in the Kangaroo 
there is a cartilaginous ridge having the con- 
junctiva reflected over it. 

Organ of taste—The tongue is well deve- 
loped and freely moveable in all the Marsu- 
pialia, and the epithelium covering the simple 
papille of its dorsum is never condensed into 
spines. In the carnivorous species, as the 

lasyuri, the conical papille are minute and 
soft, but directed backwards so as to givea 
slight roughness to the tongue when stroked in 
the opposite direction. Under a lens they 
appear like fine shagreen. Near the base of 
the tongue in Dasyurus viverrinus there are 
three fossulate papille, in triangle, with the 
apex towards the epiglottis. There is a small 
lyita beneath the tip of the tongue. 

In the Perameles, besides the minute and 
generally diffused simple papille, there are 
others of larger size, placed at distances of 
nearly a line apart, and raised about a third of 
a line above the surface of the dorsum. The 
fossulate or glandular papille correspond in 
number and arrangement with those of the 
Dasyures, but the entire tongue is relatively 
longer and more slender, especially in Per. 
lagotis. 

In some species of Opossum, as Didelphys 
Philander, the margin of the tongue is fringed 
with a series of fine long papille. 

In the Phalangers there is a thickening at 
the edge of the frenum lingue, but no true 
lytta. The dorsal papille resemble those of 
the Dasyures, but are somewhat more obtuse. 

In the Kangaroo there is a callous ridge 
along the middle of the under surface of the 
free extremity of the tongue, and a corresponding 
furrow along the dorsum; the latter is common 
to all the Marsupials. In the Wombat and 
Koala the dorsum of the tongue rises some- 
what abruptly from a furrow surrounding its 
base; its form is narrow, moderately deep, 
diminishing in this respect to the tip, which is 
rounded. In both the Kangaroo and Koala 
there is a single large fossulate papilla near 
the base of the tongue. ‘ 

The palate is sculptured in most Marsupials 
with transverse ridges. These are most nume- 
rous in the Bandicoots, being fourteen in the 
Perameles nasuta, and are slightly curved for- 
wards. The roughness thus produced must aid 
the tongue in retaining small insects. 


Dicestive System. 

Mouth.—The various modes of locomotion, 
resulting from the different modifications of the 
osseous and muscular systems observable in the 
several families of Marsupialia, relate to the 
acquisition of as various kinds of alimentary 
substances, which necessarily require for their 
assimilation as many adaptations of the diges- 
tive organs, 


297 


Food,—means of obtaining it,—instruments 
for preparing and mechanically dividing it,— 
cavities, canals and glands for chemically 
reducing and animalizing it,—form a closely 
connected chain of relationships and interde- 
pendencies. The usual sequence of anatomical 
description has here been followed in com- 
mencing with the consideration of the passive 
and active organs whose office it is to carry the 
stomach to the food and the food tothe mouth, 
and we have now to describe the preparatory 
mechanical instruments in digestion, and the 
modifications and appendages of the alimentary 
canal. 

Thejaws of the Marsupialiaare covered by well- 
developed fleshy lips ; the upper lip is partially 
cleft in the Kangaroos, as in some of the Ro- 
dents; the muzzle is clad with hair in the 
Great Kangaroo and a few other species of 
Macropus, but in other Marsupialia it is naked 
and generally red from the vascularity of the 
integument. 

The masticatory muscles of the jaws consist 
in the Marsupial, as in other Mammalia, of the 
temporal, the masseter, the external and in- 
ternal pterygoids, and the digastricus. They 
are chiefly remarkable for the large proportional 
size of the masseter and internal pterygoid; the 
great developement of the latter muscle is con- 
stant in all the Marsupials, and is the condi- 
tion of the peculiarly large and inflected angle 
of the lower jaw. The relative size of the 
masseter, as compared with the temporal mus- 
cle is greater in the herbivorous than in the 
carnivorous species, but this difference is 
much less in the Marsupial than in the cor- 
responding placental genera. The extent of 
origin of the temporal muscle is indicated by 
the various conditions of the temporal and pa- 
rietal crests ; the inner surface of the zygomatic 
arch always affords origin to a portion of the 
fibres of this muscle, and in some species, as 
in the Koala, to all that portion of it which is 
inserted into the external fossa of the coronoid 
process and ascending ramus of the jaw, the 
fibres from the temporal and parietal bones 
being implanted on the inner side of the coro- 
noid process. The masseter takes its origin by 
a strong band of tendinous and carneous fibres 
from the inferior and anterior part of the zy- 
goma ; the muscle expands as it is directed 
backwards, and is inserted into the ridge which 
bounds the external temporal fossa of the as- 
cending ramus, and into the outer side of the 
inflected angle of the outer jaw. The erternal 
pterygoid takes its origin from the temporal 
plate of the sphenoid and the base of the 
pterygoid plate anterior to the sphenoidal 
bulla; the fibres converge to be implanted 
into the inner projecting side of the condyle 
of the jaw. The internal pterygoid arises 
from the outer depression of the longitudi- 
nally extended pterygoid plate already men- 
tioned as characterizing the cranial structure 
of the Marsupials, and is implanted along the 
inner surface of the inflected angle of the jaw. 
The digastricus arises from the ex-occipital 
process ; its fibres expand, and are inserted 
into the lower margin of the maxillary ramus, 
anterior to the commencement of the inflected 


298 


angle of the jaw. The preceding description is 
taken from a dissection of the Koala. The 
masticatory muscles of the Wombat differ only 
in their relative proportions ; the masseter in 
this gliriform Marsupial is single, nting no 
trace of that subdivision and modified attach- 
ments which adapt it to the protraction of the 
lower jaw in the true Rodents, and accordingly 
the structure of the joint of the lower jaw of 
the Wombat exhibits, as already described, a 
corresponding difference from the Rodent 
type. 
vihere is no toothless genus among the true 
Marsupials, unless the Monotremes which re- 
present the Edentate order of the Placental 
Mammalia be regarded as modified Marsupials. 
Molar and incisor teeth are present in both 
jaws in every true Marsupial species ; the ca- 
nines are but feebly represented in many, as the 
Phalangers, Petaurists, &c. are wanting in the 
lower jaw in the Potoroos and Koala, and in 
both jaws in the Kangaroos and Wombat. The 
grinders, on the other hand, present their most 
complicated structure in these last cited herbi- 
vorous genera. 

The Dasyures and Thylacine offer the carni- 
vorous type of the dental system, but differ 
from the corresponding group of the Placental 
Mammalia in having the molars of a more 
uniform and simple structure, and the incisors 
in greater number; which number, however, is 
different in the different Marsupial carnivorous 
genera, as is expressed in the dental formule 
already given. 

The canines are as formidable for their size, 
shape, and strength in the Thylacine and Ur- 
sine Dasyure, as in the Dog or Cat, and in a 
fossil species of the latter genus ( Dasyurus 
laniarius ),* which co-existed, in ancient Aus- 
tralia, with herbivorous Marsupials of greater 
size than now inhabit that continent, these 
teeth were as large as in the Leopard. In 
the Thylacine the points of the lower ca- 
nines are received in hollows of the intermaxil- 
lary palatal plate when the mouth is closed, 
and do not project, as in the carnivorous pla- 
centals, beyond the margins of the intermaxil- 
laries. 

In some of the smaller species of the carni- 
vorous group, as the Phascogales, the canines 
lose their great relative size, and the molar 
teeth present a surface more cuspidated than 
sectorial: there is also an increased number of 
teeth, and as a consequence of their more equa- 
ble development they have fewer and shorter 
interspaces. Thus the Phascogale penicillata 
has, as Mr. Hunter observed, “a mouth full of 
teeth,” and these are adapted for the capture 
and mastication of insects and other small and 
low organized animals. 

In the Opossums the canines still exhibit a 
superior development in both jaws adapted for 
the destruction of living prey, but the molars 
have a conformation different from that which 
characterises the true flesh-feeders, and they 
consequently subsist ona mixed diet or lower 
organized animals; some, as the web-footed 
Cheironectes, betake themselves to the water, 


* See Major Mitcheli’s Australia, vol. ii. 


MARSUPIALIA. 


and prey, like the otter, on fish; others 5 
about the sea-shore and subsist on crust 
as the Didelphys cancrivora. 
The Perameles are for the most part in: 
vorous ; the incisors are always very small, 
molars generally multicuspidate; some species, 
as Per. nasuta, have the canines not more dé 
veloped than the premolars, which they clos 
resemble ; but in others, as the Per. lagoti 
they are proportionally as large as in 
Opossums, and the inferior ones are cor ; 
in the same position when the mouth is closes 
as in the Thylacine. But the Per. lagotis, im- 
stead of exhibiting a corresponding approac¢ 
in the structure of the molars to a carni 
diet, have these unerring indicators of the na 
ture of the food terminated by a broad oblique 
flattened surface, adapted to the trituration 6 
farinaceous vegetable roots, the destruction: 
which is confidently attributed to this specie 
of Bandicoot by the colonists of Swan River 
The interesting genus Myrmecobius 
in the small size and scattered dis 
tion of its teeth, the nearest approach amon 
the Marsupials to the edentate group of th 
Placental Mammalia ; the multicuspidate strue 
ture of the molar teeth, and their small | 
indicates that the Myrmecobius feeds 
on the weaker insects which are implied b 
its generic name. It is important to notice 
that in many of the Marsupials there is a 
inconstancy in the number of teeth in 
of the same genus, and sometimes even in 
individuals in the same species; this at least 
appears to be the case in the Myrmecobius, in 
which, of three specimens examined, identical 
in all other respects, one had forty-eight, the 
other fifty-two, and the third fifty teeth. We 
have already pointed out the variety which 
tains in the spurious and true molars of 
Phalangers and Petaurists. The prominent 
feature in the change from the carnivorous to 
the herbivorous type of dentition is the ine 
nate development of the two middle inciso1 
the lower jaw, at the expense, as it would se 
ofthe posterior ones. In the Phalangista 
e. g. six incisors are always present in the le 
jaw, but only the first two have any functi 
character: the canine tooth again offers neit! 
a form nor size by which it can be distinguis 
from the spurious molars; in the other 
supials with the same characteristic modi 
tion of the hinder feet, including the Petauri 
with the Phalangers, the small posterior incis¢ 
are wanting wholly or in part; the canines seem 
also to be lost, and the spurious molars are 
fewer, but variable in number. This incon 
stancy is not to be wondered at in teeth whi 
have too simple a form and too insignificant a 
size to exercise any influence on the habits and 
economy of the species; and it would seem to— 
be lost labour in the zoologist to attempt to 
found generic distinctions, and invent new — 
names for the species in which these insignifi- 
cant varieties are presented. The six incisors 
of the upper jaw and the two anterior ones in 
the lower jaw, with the true molars in both 
jaws, present a constancy of character and a 
functional importance in their development in 
all the Phalangers and Petaurists. These teeth 


ro 


r 


MARSUPIALIA. 


are adapted, the first for cropping the foliage of 
the gum-trees ( Eucalypti) and similar trees, 
and the others for bruising and masticating the 
same. The grinding surface of the molars ge- 
nerally presents four blunt tubercles. 

The Koala resembles in its dentition and in 
its diet and arboreal life the Phalangers and 
Petaurists. In the lower jaw the absence of 
teeth between the two large procumbent incisors 
and the false molars is constant ; in the upper 
jaw, however, the lateral or posterior incisors 
begin to exhibit the same diminution of size as 
the corresponding teeth in the lower jaw of 
some of the Phalangers, while the two anterior 
upper incisors present a proportional increase ; 
the canines correspond in feebleness and form 
with the small incisors. In the Wombat, the 
defective development to which the teeth be- 
tween the incisors and molars are subject in 
the Marsupial tribe, has reduced the dental for- 
mula of both jaws to the rodent type ; but the 
shape, comparative shortness, and procumbent 
position of the two large inferior incisors, and 
the three-sided figure of the opposing pair 
above, bespeak the marsupial character of which 
this genus offers so extreme a modification. 
The grinders, however, agree with those of the 
herbivorous rodents in the absence of fangs, 
arising from the uninterrupted growth and ossi- 
fication of their formative pulps; they offer 
also in both jaws an extreme degree of the cur- 
vature which characterises the molars of some 
herbivorous Rodents, as the Guinea-pig, and 
the great extinct gliriform Pachyderm, called 
Toxodon; but their chief distinctive peculi- 
arity is the marsupial excess of number already 
mentioned. 

With respect to the modifications of the 
teeth of the herbivorous Marsupials, it need 
only here be observed that the grinding surface 
of the true molars in the Kangaroos most re- 
sembles that which characterizes the same teeth 
in the Tapir, Dinothere, and Manatee. 

No Marsupial pessesses teeth composed of 
an intermixture of layers of dentine, enamel 
and cement throughout the crown, but the ex- 
ternal layer of coronal cement is very conspi- 
cuous in transverse sections of the teeth of the 
Marsupials, viewed with the microscope, and 
forms a thick layer on the outside of the crowns 
of the teeth in the genera Macropus, Phascol- 
arctus, and Phascolomys. 

The modifications of the tongue and soft 
palate have already been noticed. In two 
species of Marsupials I have detected cheek- 
pouches. In the Koala they are wide and 
shallow, situated one on each side of the upper 
lip; the orifice is opposite the first superior 
premolar, and leads forwards above a horizontal 
fold of the mucous membrane which attaches 
the upper lip to the side of the intermaxillary 
bone, separating this part of the cheek-pouch 
from the mouth. In the Perameles lagotis 
there are also two small fossze, one on the in- 


side of each cheek, about four lines in diameter, . 


and lined by a very distinct white epithelium. 
The fauces are wide in the Zoophagous, but 
narrow in the Entomophagous and Phytopha- 
gous Marsupials. 
Alimentary canal.—The esophagus in passing 


299 


through the chest recedes from the spine as it 
approaches the diaphragm, and is loosely con- 
nected with the bodies of the dorsal verte- 
bre by a broad duplicature of the serous 
membrane of the posterior mediastinum. In 
the Phalangers the esophagus terminates in the 
stomach almost as soon as it has pierced the 
diaphragm ; in the Opossums it is continued 
some way into the abdomen; in the Didelphys 
Virginiana, for example, for the extent of an 
inch and a half; in Did. brachyura, for half 
an inch. In the Kangaroos the abdominal 
portion of the esophagus is of still greater 
extent ; I have observed it five inches long in 
a male Macropus major. 

The inner surface of the cesophagus is gene- 
rally smooth, or disposed in fine longitudinal 
plaits ; but in the Virginian Opossum the ter- 


‘minal part of the cesophagus presents many 


transverse folds of the lining membrane analo- 
gous to, but relatively larger than those in the 
Lion and other Felines. I have not met with 
a like structure in the Phalangers nor in any 
other genus of Marsupials; what is more re- 
markable is that the transverse cesophageal rugze 
are not developed in the carnivorous Dasyures 
or Phascogales, where analogy would lead one 
to expect them, rather than in the insectivorous 
Opossums. 

The stomach presents three leading modifica- 
tions of structure in the Marsupialia; it is either 
simple, as in the Zoophagous, Entomophagous, 
and Carpophagous tribes; or is provided with a 
cardiac glandular apparatus, as in the Koala and 
Wombat; or is complicated by sacculi, as in the 
Poephagans. 

It might have been expected that the stomach 
would have exhibited some modifications in 
the development of the left or cardiac extremity 
comin with the differences of food and 
dentition observable in the large proportion of 
the Marsupial order, in which this viscus pre- 
sents its simple condition ; but this is not the 
case: the form of the stomach is essentially the 
same in the carnivorous Dasyure, the insecti- 
vorous Bandicoot, and the leaf-eating Phalan- 
gers. It presents a full, round, ovate, or 
sub-triangular figure, with the nght extremity 
projecting beyond and below the pylorus; the 
longitudinal diameter seldom exceeds the ver- 
tical or transverse by more than one-third ; often, 
as in Phascogale and Dasyurus viverrinus, by 
only one-fourth of its own extent; and the 
cesophagus enters at the middle of the lesser 
curvature, or sometimes nearer the pylorus, but 
always leaves a large hemispherical cul-de-sac 
on the left side. Daubenton has given illustra- 
tions of this characteristic form of the stomach 
in different species of Didelphys; it is here 
figured as it exists in the Phascogale (fig. 122). 
The stomach is relatively much more capacious 
in the carnivorous Marsupials than in the car- 
nivorous Placentals. Some slight modifica- 
tions occur in the disposition of the lining 
membrane; thus in the Phascogale I observed 
a series of very thick ruge radiating from the 
middle of the upper part of the ccecal end of 
the stomach, some of which were continued 
along the lesser curvature to the pylorus. Dr. 
Grant found, in the Perameles nasuta, that “ the 


300 


Alimentary canal, Phascogale flavipes. 


internal surface of the left cul-de-sac was quite 
smooth and villous (?), while the right half of 
the stomach was entirely covered internally with 
ruge, running chiefly in a longitudinal direc- 
tion, and particularly numerous towards the 
pylorus.””* 

The stomach in the Wombat and Koala does 
not materially differ in external figure from that 
of the above-cited Marsupials ; the esophagus 
terminates nearly midway between the right and 
leftextremities, but further from the pylorus in the 
Wombat than in the Koala. The conglomerate 
gastric gland is of a flattened ovate form, rela- 
tively larger in the Wombat than in the Koala, 
situated to the left of the cardiac orifice, at the 
lesser curvature of the stomach (fig. 123). 
The gastric gland has a similar position in the 


Fig. 123. 


NIV 


Hh 
Hit I! hy 


N) 
yyy 


Stomach of the Wombat, inverted. 


* Wernerian Transactions, vol. vi. p. 199. 


MARSUPIALIA, 


Beaver, but in this animal the excretory orifices — 
of the gland are arranged in three longitudinal 
rows, while in the Wombat and Koala 
are scattered irregularly ; in the Wombat they — 
are about thirty in number, and the bottoms of 
the larger depressions are subdivided into 
smaller cells. In the partially contracted state 
the inner membrane of the stomach of the — 
Wombat, as represented in the figure, is dis- 
posed in pretty regular longitudinal rugm, 
which gradually subside towards the pylorus; 
but when the stomach is distended these folds” 
disappear, and the left extremity presents a full 
globular form. In the Wombat dissected by 
me the esophagus terminated nearer the 7 
lorus than is represented in the figure 
given from the Comparative Anatomy of 
Everard Home. 
The sacculated stomach of the Kangaroo, 
which offers the extreme modification of 
organ in the Marsupial order, resembles the 
human colon both in its longitudinal extent, — 
Structure, and disposition in the abdon 
The natural relative position of this singu 
viscus is, however, very different from 
described by Sir Everard Home,* who eyi- 
dently has taken his account from the drawin 
by Mr. Clift, from which our fig. 124 is taken: 
the object of this drawing, however, being to 
pourtray the modifications of the inner surface 
of the Kangaroo’s stomach, it is artificially dis-_ 
a accordingly. In a full-grown female 
angaroo (Macropus major), I found the 
abdominal cesophagus four inches long, and — 
terminating at six inches distance from the left” 
extremity of the stomach: this extremity was 
folded forwards and to the right in front of the 
cesophagus ; from the basis of the left cul-de-— 
sac the stomach continued to expand, and ~ 
descended into the left lumbar and iliac regions, 
whence it stretched upwards and to the right 
side obliquely across the abdomen, to the right — 
hypochondrium, where it became contracted 


Fig. 124. 


sent JA Mite yy), 
M, 


we ", 


Se eceenen se 


Stomach of the Kangaroo. - 


and finally bent downwards and backwards to 
terminate in the duodenum. The whole length 
of the stomach, following its curvatures, was 
three feet six inches, equalling that of the ani- 
mal itself from the muzzle to the vent. ; 


* Lectures on Comp. Anatomy, i. p. 156. 


MARSUPIALIA. 


The stomach of the Kangaroo may be re- 
garded as consisting of a left, a middle, and a 
right or pyloric division. The left extremity of 
the stomach is bifid, and terminates in two 
round cul-de-sacs. The sacculi of the stomach 
are produced, like those of the colon, by three 
narrow longitudinal bands of muscular fibres, 
which gradually disappear, together with the 
sacculi at the pyloric division. One of the 
longitudinal bands runs along the greater cur- 
vature, at the line of attachment of the gastro- 
eolic omentum ; the others commence at the 
base of the left terminal pouches, and run, one 
along the anterior, the other along the posterior 
side of the stomach: the interspace, between 
these bands, forming the lesser curvature of 
the stomach, is not sacculated. The largest of 
the two terminal sacculi (d, fig. 124) is lined 
with an insulated patch of vascular mucous 
membrane, which is continued for the extent 
of five inches into the cardiac cavity; the epi- 
thelium is continued from the csophagus in 
one direction into the nearest and smallest sac- 
culus, and extends in a sharp-pointed form for 
a considerable distance in the opposite direction 
into a series of sacculi in the middle compart- 
ment of the stomach (c): this epithelium is quite 
smooth. The vascular mucous surface recom- 
mences by a point at the great curvature, near 
the beginning of the middle compartment, and 
gradually expands until it forms the lining of 
the whole inner surface of the right half of the 
stomach. Three rows of clusters of mucous fol- 
licles (g, g) are developed in the mucous mein- 
brane of the pyloric half of the middle com- 
partment; they are placed parallel with the lon- 
gitudinal muscular bands: about fifteen patches 
are situated along the greater curvature, and there 
are nine in each of the anterior and posterior 
rows. These glandular patches disappear alto- 
gether inthe pyloriccompartment of thestomach, 
where the lining membrane is thickened, and 
finely corrugated; but immediately beyond the 
pylorus there is a circular mucous gland three- 
fourths of an inch broad: the non-sacculated 
pyloric division of the stomach was five inches 
in length. 

In the smaller species of Kangaroo the 
stomach is less complicated than in the Macro- 
pus major ; the number of sacculi is fewer: in 
Macropus Parryi, Ben. the third longitudinal 
band at the great curvature of the stomach is 
almost obsolete: in the Brush-tailed or Rock 
Kangaroo, ( Macropus penicillatus, ) the cardiac 
extremity terminates in a single sub-clavate cul- 
_ de-sac. In all the species which I have exa- 
mined the esophagus terminates in the middle 
division of the stomach, close to the produced 
crescentic fold which separates it from the cardiac 
compartment. In the great Kangaroo a second 
slighter fold is continued from the right side of 
the cardiac orifice parailel with the preceding, 
and forming with it acanal, somewhat analogous 
to that in the true ruminating stomachs, and 
along which fluids, or solid food not requiring 
previous preparation in the cardiac cavity, might 
be conducted into the middle compartment. 


I have more than once observed the act of- 


rumination in the Kangaroos kept in the Viva- 


301 


rium of the Zoological Society. It does not 
take place while they are recumbent, but when 
the animal is erect upon the tripod of the hind 
legs and tail. The abdominal muscles are in 
violent action for a few seconds, the head is 
then a little depressed, and the cud is masti- 
cated by arapid rotatory motion of the jaws. This 
act is by no means repeated in the Kangaroos 
with the same frequency or regularity as in the 
true Ruminants. A fact may, however, be 
noticed as an additional analogy between them ; 
balls of hair, cemented by mucus, adpressed 
and arranged in the same direction, are occa- 
sionally formed in the stomach, of which I 
have met with two, of an oval shape, in the 
Macropus Parryi. 

In the genus Hypsiprymnus the stomach is 
as singularly complicated as in the Kangaroos, 
and the complication is essentially the same in 
both; arising from the sacculation of the pa- 
rietes of a very long canal by a partial dispo- 
sition of shorter bands of longitudinal fibres ; 
but in the Potoroos this sacculation is confined 
to that part of the stomach which lies to the 
left of the esophagus, while the right division 
of the cavity has the ordinary form and struc- 
ture of the pyloric moiety of a simple stomach. 
The left or cardiac division is enormously de- 
veloped ; in relative proportion, indeed, it is 
surpassed only by the true ruminant stomachs, 
in which both the rumen and reticulum are 
expansions of the corresponding or cardiac 
moiety of the stomach. The relation of the 
stomach of a Potoroo to that of a Kangaroo 
may be concisely expressed by stating that the 
termination of the cesophagus in the former is 
removed from the commencement of the middle 
sacculated compartment to its termination. 

When fluid is injected into the stomach of 
a dead Potoroo, it distends first the pyloric 
division; it is probably by a kind of anti- 

eristaltic action that the aliment is propelled 
into the long sacculated cecum to the left of 
the cesophagus. 

The moditications of the epiploon, as an ap- 
pendage to the stomach, may here be noticed. 

n the Kangaroo it is of very moderate size, 
being continued loosely from the stomach to 
the transverse colon, but not extended beyond 
that part. The posterior layer lies between the 
stomach and the intestines, and affords a good 
illustration of one of the uses of the epiploon, 
as it evidently prevents these parts from inter- 
fering with each other’s motions. The anterior 
layer generally contains more or less fat. In 
the Petaurus the great omentum is continued 
from the great curvature of the stomach, and 
the commencement of the duodenum. In the 
Phalangers it is of considerable extent, and 
is usually loaded with fat. In the Opossums I 
have found it generally devoid of fat, when 
this substance has been accumulated in other 
parts. In the Phascogales and Dasyures the 
epiploon is of moderate size, and contains 
little or no fat. 

Having seen that, with the exception of the 
Potoroos and Kangaroos, the stomach is simple 
in the Marsupialia, presenting only some addi- 
tional mucous glands in the Koala and Wom- 


202 


bat, it is to the succeeding parts of the ali- 
mentary canal that we have to look for those 
modifications which should co nd with a 
vegetable, a mixed, or an animal diet; and 
never perhaps was a physiological problem 
more clearly illustrated by comparative ana- 
tomy than is the use of the caecum coli by 
_ the varying conditions which it presents in the 
present group of Mammalia. 

In the most purely carnivorous group of the 
Marsupial order the stomach presents in the 
magnitude of the left cul-de-sac a structure 
better adapted for the retention of food than 
we find in the stomachs of the corresponding 
group in the placental series. In the most 
strictly carnivorous Fere, as the cat-tribe, there 
is a cecum, though it is simple and short; but 
in the Marsupial Zoophaga this part is entirely 
wanting, and the intestinal canal, short and 
wide,* is continued, like the intestine of a rep- 
tile, along the margin of a single and simple 
mesentery from the pylorus to the rectum. 

In the Entomophagous Marsupials, some of 
which are suspected with reason to have a 
mixed diet, the intestinal canal is relatively 
longer; the distinction of small and large in- 
testine is established; and the latter division 
commences with a simple, moderate-sized, sub- 
clavate cecum. 

In the Carpophagous Pha- 
langers, whose stomach resem- 
bles that of the predatory Da- 
syure, the compensation is made 
by a longer intestine, but prin- 
cipally by the extraordinary 
length of the cecum, which ir 
some species is twice that of 
the body itself. 

Lastly, in the Koala, which 
is, perhaps, a more strictly ve- 
getable feeder than the Petaurists or Pha- 
langers, the cecum is more than three times 
the length of the animal, and its essential 
part, the inner secreting membrane is farther 
augmented by about a dozen longitudinal 
parallel, or nearly parallel, plaits, which 
are continued from the colon three-fourths 


Fig. 126. 


Fig. 125. 


Ceecum of an 
Opossum. 


Cacum of the Koala. 


* The jejunum, in the Thylacine, has a dia- 
meter of two inches and a half. 


MARSUPIALIA. 


of the way towards the blind extremi 
When we reflect that the Sloth, which hi 
the same diet and connate habits | 
the Koala, has a singularly complica’ dd 
mach, but no cecum, the vicarious offic 
this lower blind production of the dige: 
tube as a subsidiary stomach is still m 
strikingly exemplified. What then, it may 
asked, is the condition of the cecum in 
Marsupials with enormous sacculated _ 
machs? It is in these species compar 

short and simple. In the Potoroos 
scratch up the soil in search of f 

roots, it is much shorter than in 
Kangaroos which browze on grass. Ther 
slight tendency to sacculation at the 
mencement of the cecum in the latter | 
supials, by the development of two longitud: 
bands (fig. 127). 

In the Wombat the cecum is 
extremely short, but wide; it is 
remarkable for being provided 
with a vermiform appendage. 

In this animal, however, the 
colon is relatively longer, larger, 
and it is puckered up into sacculi 
by two broad longitudinal bands. 
In the specimen dissected by 
me, one of these sacculi was so 
much longer than the rest as to 
almost merit special notice as a 
second cecum. 

The most interesting peculiarit 
which the Zoophagous Staracpiale 
exhibit in the disposition of their 
simple intestinal canal, consists in 
its being suspended from the very 
commencement of the duodenum 
on a simple and continuous me- 
sentery, like the intestine of 
a carnivorous reptile. The 
duodenum makes the ordi- 
nary fold on the right side, 
but it is not tied to the spine 
at its termination; the com- 
mencement of the jejunum 
may, however, be distin- 
guished by a slight twist of 
the mesentery, and a fold of 
peritoneum is continued from Wombat. 
the lowest curve of the loop of the duoder 
to the right iliac region, as in the Kangar 
The intestine is a little narrower at its mic 
part than at its two extremes; the tuni 
crease in thickness towards the rectum. u 
is a zone of glands at the commencement of 1 
duodenum. 7 

In the LEntomophaga the duodenum 
tightly connected to the spine, where it eros: 
to be continued into the jejunwm : from this pai 
the mesentery is continued uninterruptec 
along the small intestines and colon to t 
rectum; so that although the cecum is ge 
rally found on the right side, its connections 
are sufficiently loose to admit of a 
position. i 

In the Petaurus pygmaeus the duodenum is 
attached to the spine as in the Opossums, but 
it is not tied down to the right iliac region 


es" 
ae. 


Fig.1 8. 


Cacum 


MARSUPIALIA. 


a fold of peritoneum continued from the con- 
vexity of its depending curve. I found the 
cecum in this species disposed in a spiral 
curve in the left lumbar region: the colon 
ascended a little way in front of the stomach, 
receiving a branch of the superior mesenteric 
artery, and was then continued straight down 
to the anus; thus we are again reminded of the 
oviparous character by the shortness of the 
large intestine. ‘ 

In the Pet. taguanoides the duodenum is 
tied down to the iliac region, as in the Da- 
syure; the cecum is four inches long, and 
the colon is relatively longer than in the Acro- 
bates ; it makes the tour of the abdomen much 
as in man, but is continued into the rectum 
without forming a sigmoid flexure. 

In the Phalangers the duodenum winds round 
the root of the mesentery, descending pretty 
low down on the right side, and becoming a 
loose intestine or jejunum on the left side. 
The long cecum is suspended by a broad du- 
plicature of peritoneum continued from the 
mesocolon; and the colon is closely attached 
at its transverse arch to the duodenum and root 
of the mesentery. 

In the Koala the cecum and large intestines 
arrive at their maximum of development. The 
duodenum commences with a small pyriform 
sacculus nearly an inch in breadth, and soon 
contracts to a diameter of five lines, which is 
the general calibre of the small intestines. The 
large intestines, where the ilium terminates, 
have a diameter of two inches. The end of 
the ileum (a, fig. 129) protrudes for the extent 


Fig. 129. 


Tleo-ceecal valve, Koala. Half its natural size. 


of a quarter of an inch within the cecum, 
forming a very effectual valve: near this part 
there are two wide and deep glandular fosse : 
the longitudinal valvule conniventes of the 
large intestines have already been noticed. 

In the Potoroos the small intestines are dis- 
posed nearly as in the Phalangers: the short 
and wide ccecum lies in the right hypogastrium: 
the colon makes the usual tour of the abdomen, 


303 . 


but is disposed in long convolutions through 
its whole course, being suspended on a broad 
mesocolon. The diameter of both small and 
large intestines is nearly the same: in Hyps. 
setosus 1 found this to be half-an-inch. 

In the great Kangaroo the descending por- 
tion of the duodenum is attached posteriorly, 
by means of a thin peritoneal duplicature, to 
the spine, and anteriorly to the ascending co- 
lon: it makes an abrupt turn upon itself, and 
a fold of peritoneum is continued from the con- 
vexity of the curve to the right iliac region. 
The small intestines are strung in short folds 
on a rather narrow mesentery. The cecum is 
in part suspended from the same mesenteric 
fold. The colon, besides its posterior con- 
nexions with a mesocolon, is attached, as be- 
fore observed, to the duodenum ; and also, by 
means of the great omentum, pretty closely to 
the stomach, whence it passes down, forming 
many large and loose convolutions to the rec- 
tum, being attached by a broad mesocolon to 
the left hypochondriac region. 

The zone of glands at the commencement of 
the duodenum has been already noticed ; 
they are present in other Marsupials, even in 
the most carnivorous species; but [I have not 
met with a similar structure in the placental 
Mammalia. The villi of the small intestines 
in the Kangaroo are of moderate length, com- 
pressed and close-set. Glandule aggregate 
are arranged in narrow patches in the ileum. 
There are seven groups of siinilar follicles in 
the cecum; and a few long and narrow patches 
of glands occur in the colon intermingled with 
numerous glandule solitariz ; the surface of the 
rest of the lining membrane of the large intes- 
tine is disposed in a very fine net-work. 

Two faint longitudinal bands extend along 
the first ten inches of the colon and are con- 
tinued along two-thirds of the cecum: the 
sacculi produced by these bands are but very 
feebly marked. I have not met with any ex- 
ample in the Macropus major of a cecum, 
which, either naturally or when inflated and 
dried, presented the sacculated structure repre- 
sented by Cuvier in fig. 8, pl. xxxix. of the 
Lecons d’Anat. Comparée. 

The contents of the cecum in the great Kan 
garoo are of a pultaceous consistence, and the 
mass continues undivided along the first two feet 
of the colon, gradually becoming less fluid and 
then beginning to be separated into cubical 
feces about an inch square. The diameter of 
the large intestine in this species exceeds very 
little that of the small intestines. 

In all the Marsupials two sebaceous follicles 
open into the termination of the rectum. The 
anus has its proper sphincter, but is also sur- 
rounded, in common with the genital outlet, 
by a larger one. When the penis is retracted, 
the fecal, urinary, and genital canals all ter- 
minate within a common external outlet; so 
that in the literal sense the Marsupials are mo- 
notrematous. 

The following is a table of the length of the 
intestinal canal, and its parts in a few species 
of the different families of Marsupialia, 


304 


MARSUPIALIA. 
Tuble of the length of the intestinal canal as compared with the body. 


: Body from snout! Intestinal canal Small 
SPECIES. to vent. with cecum. intestines. intestines, 
Ft. Inch. | Ft. Inch. | Ft. Inch. | Ft. Inch. | Ft. 
Thalacynus Harrisii .| 3 4 9 8 
Phascogale flavipes. .| 0 5 o 14 
macrurus . 1 4 5 0 
Perameles nasuta...| 1 4 3 5 2 5 0 9 tt) 
Didelphys Philander} 0 9 3 5 4st: 8 1 23 | 0 
DPetaurus pygmaeus ..| 0 24 0 6% 0 5 0 0g | O 
Phalangistavulpina | 1 8 24 10 11 0 9 0 4 
MR GG 6-6) 0. 5 6.8 1 7 18 8 9 9 6 10 2 
Phascolarctos fuscus.} 1 11 24 0 7 8 10 5 6 
Hypsiprymnus setosus 1 0 5 0 2 5 2 6 (0) 
Macropus major .. 4 3 3 32 0 22 0 9 0 1 
Phascolomys i. ombatus; 2 6 25 6 11 3 14 2 0 4 


Salivary glands.—These glands in the Car- 
nivorous Dasyures consist of a small parotid 
and a large submaxillary gland on each side. 
I searched expressly, but in vain, for the zygo- 
matic gland; the Dasyures do not agree with 
the dogs in having these glands. They have no 
sublingual gland. The submaxillary gland is 
placed in front of the neck, so that its duct passes 
on the dermal side of the tendon of the biventer 
maxille, and terminates half an inch from the 
symphysis menti. There is a thick row of 
labial glands along the lower lip. The Opos- 
sums and Bandicoots present a similar salivary 
system. 

In the Phalangista vulpina there is a sub- 
lingual gland on each side of a firm texture, 
about one inch in length and three lines broad ; 
a roundish submaxillary gland about the size 
of a hazel-nut; and a broad and flat parotid, 
larger than in the Entomophagous or Sarco- 
phagous Marsupials. 

The parotid glands are relatively larger in 
the Koala, in which the duct takes the usual 
course over the masseter and enters the mouth 
opposite the third true molar, counting back- 

s. 

In the Wombat I found the parotid glands 
very thin, situated upon both the outer and 
inner side of the broad posterior portion of the 
lower jaw; the duct passed directly upwards 
and outwards to the insertion of the sterno- 
cleido-mastoideus ; here it was buried in the 
cellular substance anterior to that muscle, then 
turned over the ramus of the jaw, and, pur- 
suing a somewhat tortuous course over the 
masseter, entered the mouth just anterior to 
the edge of the buceinator. The submaxillary 
glands were each about the size of a walnut; 
their ducts terminated as usual on each side of 
the freenum lingue. 


* These admeasurements were obligingly com- 
municated to me by my friend Mr. Hobson, of 
Hobart Town, Van Dieman’s Land, and were taken 
from an animal killed in the wild state. I subjoin 
the admeasurements of an individual of the same 
species which died after a year’s confinement in the 
Zoological Gardens: there is a considerable diffe- 
rence in the length of the intestinal canal and 


= 
In the great Kangaroo the parotid is v 
large, extending from below the auditory me 
tus three or four inches down the woot | 
the Hypsiprymnus it reaches as far as the els 
vicle. In both cases this gland is separate 
from the submaxillary gland by the su 
lary vein. hy 
The tonsils are small in all the Marsupial: 
but are not represented in the carnivorous spi 
cies, as in the Placental Fere, by simple glan 
dular pouches at the sides of the fauces; for 
example, they consist of an oblong glandula 
body on each side in the Dasyurus macrurus. 
The liver—The liver is subdivided i 
many lobes in all the Marsupial genera. It is 
relatively largest in the burrowing Wombat 
and carnivorous Dasyure; relatively smallest 
in the graminivorous Kangaroo, in which it is 
situated, as in the placental Ruminants, en- 
tirely to the right of the mesial plane. The 
small or Spigelian lobe, which tis into 
lesser curve of the stomach, is given off 
the left lobe of the liver in the Kangaroos, but 
from the right in most other Marsupials ; the 
difference just noticed in the Kangaroo de 
on the peculiar disposition of its rem: 
stomach. > 
In the Koala the under surface of the liver 
(fig. 130) is singularly sculptured and subdi- 
vided into thirty or forty l-bules; this condition 
is presented in a minor degree in the liver of th 
Ursine Dasyure. a 
In a long-tailed Dasyure, which weigher 
3 Ibs. 8} 0z., the liver weighed 3} oz. avoir 


dnpeiee. ; 

he gall-bladder is present in all the Marsu- 
pials, and is generally of large size and loosely 
odged in a deep cleft of the cystic lobe. In 
the Opossum it generally perforates that lobe, 
and the fundus appears at a round opening on 


4h 


=. 
pence 

an 

Labl, 


“ha 


especially of the cecum; and it may be alle 
to speculate upon the influence which differ 
of diet and confinement may have had in prod 
this difference. Mr. Martin’s admeasurements of 
another Phal. Vulpina agree more nearly with mine. 
—See Zool. Proceedings, 1837. ‘ "sy 

; t bap vermiform process measures two inches in 
ength, 


MARSUPIALIA. 


Fig. 130. 


Liver of the Koala. 


the convex surface of the liver. The coats of 
the ductus choledochus are thickened towards 
its termination, and become the seat of nu- 
merous mucous cysts which open into the in- 
terior of the duct. 

In the Phalangers the terminal half-inch of 
the ductus choledochus is similarly enlarged 
and glandular. The biliary and pancreatic ducts 
generally unite together before perforating the 
duodenum. In the Virginian Opossum, the 

long-nosed Bandicoot, and the long-tailed 
_ Dasyure they pour their secretions into the gut 
an inch from the pylorus. In the great Kan- 
garoo the glandular ductus choledochus is 
joined by the pancreatic duct, and terminates 
in the duodenum five inches from the pylorus. 
_ The pancreas.—The pancreas extends as 
usual from the duodenum to the spleen, be- 
hind the stomach; it is characterized by a pro- 
cess sent off at right angles, or nearly so, to 
the main lobe at or near its left extremity. I 
have observed other small and thin processes 
_ branching out into the duodenal mesentery in 
a Phalanger; and similar but still more nu- 
merous processes, so as to give the organ a 
_ dendritic appearance in the Kangaroo; but the 
 first-named process is constant. 

The spleen.—It is interesting to observe that 
the spleen corresponds in this triangular or T- 
VOL. IIT. 


305 


shaped figure with the pancreas. In the great 
Kangaroo ( Macropus major ) 1 found the main 
body of the spleen ten inches long, and the 
rectangular process six inches ; both parts were 
narrow and thin. 

Absorbents.—The lacteal absorbents form, in 
the Dasyurus viverrinus, two thin, subelongate, 
dark-coloured mesenteric glands: one of these 
is situated near the pylorus, at the end of the 
pancreas. The plexiform cysterna chyli is si- 
tuated in the Kangaroo ( Macropus Parryi was 
the species from which the following descrip- 
tion is taken) upon the crura of the diaphragm, 
and extends upon the right side above the dia- 
phragm into the thorax. Two thoracic ducts are 
continued from the cysterna, one along the left, 
the other along the right side of the bodies of 
the dorsal vertebree. The right duct crosses the 
seventh vertebra and joins the left, which again 
divides and reunites, forming a slight plexus, 
before finally terminating at the confluence of 
the left subclavian and jugular veins. The 
double thoracic duct in the Kangaroo was first 
noticed by Dr. Hodgkin; it is interesting, on 
account of its resemblance to the characteristic 
condition of the great nutrient conduit in the 
Bird and Crocodile; in these, however, each 
division terminates in the vena innominata of 
its own side, which was not the case in the 
Kangaroo above described. 

Blood—¥rom the characteristic elliptical 
form of the blood-dises of Birds and Reptiles, 
and the rare occurrence of that form, as in the 
exceptional case of the Camel tribe, among the 
placental Mammalia, the examination of these 
particles of the circulating fluid in the Marsu- 
pial genera was attended with more than ordi- 
nary interest, and the results, derived from a 
comparison of species belonging to all the lead- 
ing groups, show that the different tribes of 
Marsupial animals correspond with the analo- 
gous placental Mammalia both in the circular 
or subcircular contour of the blood-discs, and 
very nearly also in their size.* 

Dasyurus viverrinus——The blood-dises of 
this small carnivorous Marsupial were sensibly 
larger than those of the analogous placental 
Mammalia, as the Cat. The ordinary or un- 
broken discs had their margin rounded off. 
The number of the granulated discs was con- 
siderable; many of them presented a well- 
defined margin, notched like a cog-wheel. The 
average diameter obtained by me was z)),th of 
an inch, 

Dasyurus ursinus.—The average diameter of 
the blood-discs is 34: observed extremes of 
Size sh, and 74,,. 

Perameles lagotis—The blood of this Mar- 
supial, which was examined while recently 
drawn from the living animal, and under the 
same circumstances as that of the two species 
of Dasyure, presented a still greater number of 
the granulated blood-discs mixed with others 
of the ordinary form. The descriptions of such 
altered blood-dises not only by Hewson and 
Falconer, and in recent times by Professor 

* See Medical Gazette, November 13, 1839, and 
Mr. Gulliver’s observations, London and Edinb. 
Philos, Magazine, February, 1840. 

x 


306 


Wagner, (Hecker’s Literarische Annalen, Fe- 
bruarheft, 1834,) but also in works in our own 
language, as in Hodgkin’s Translation of Ed- 
wards’s Influence of Physical Agents on Life, 
Appendix, p. 438, 1832, have rendered the fact 
sufficiently familiar. But the connection of 
this well-known appearance with the mode of 
formation or multiplication of the blood par- 
ticles had not before attracted the attention it 
seemed to deserve; on this subject I have else- 
where remarked : “ In some of the granulated 
blood-discs of the Perameles the subdivisions 
potdecing that appearance were fewer and 
arger, and were separated by deeper clefts 
than I had before observed ; they suggested to 
me the idea that the blood-disc was under- 
going a spontaneous subdivision into smaller 
vesicles, and, although my observations are not 
at present sufficiently numerous to warrant the 
pi tegen that the development of smaller ve- 
sicles within itself is a normal property of the 
ordinary coloured vesicle or blood-disc, yet the 
obscurity which still hangs over the origin and 
reproduction of the blood-discs, and the unex- 
pected constancy of the granulated form in a 
greater or less proportion of them while recent, 
and floating in the serum, in different species of 
animals examined by me, makes me unwilling 
to suppress any idea naturally arising out of 
such observations and likely to be suggestive 
of examination of the same appearances by 
other microscopical observers.”* The general 
form of the blood-vesicles of the Perameles is 
the usual circular flattened disc: they presented 
a greater variety of size than in the Daysurus, 
but upon the whole a larger average diameter, 
Viz. y,4;th of an English inch. 

Phalangista Vulpina.—Average diameter of 

blood-dise 5th inch, 

Petaurus sciureus.—Ditto ditto yyth inch. 

Macropus penicillatus—Do. do. z45th inch. 

Macropus major.—Ditto ditto 45th inch. 

Phascolomys Vombatus.—Do. do. ,t;3th inch. 

The results of the present observations on 
the blood of the Marsupial quadrupeds cor- 
respond generally with those obtained from the 
placental Mammalia, inasmuch as the blood- 
discs of the species which derives its nutriment 
from the greatest variety of organized substances, 
as the Perameles, which subsists on insects, 
worms, and the farinaceous and succulent ve- 
getables, are Jarger than those of the strictly 
carnivorous Dasyure, and of the herbivorous 
Kangaroo, the blood-discs of the latter, like 
those of the placental Ruminant, being the 
smallest, though not in the same proportion. 
In each natural group of Marsupialia there is 
a direct relation between the size of the blood- 
disc and that of the species, 

Heart.—The heart is inclosed in a pericar- 
dium, and situated in the same relation to the 
lungs, mediastinum, and thoracic cavity as in 
the Rodent and most other mammiferous quad- 


* Medical Gazette, 1839, l.c. My hypothesis 
has received a certain degree of confirmation by 
the subsequently published observations on the 
division of the corpuscles of the blood by Mr. 
Quekett, (Med. Gazette, January, 1840,) and by 
Dr, Martin Barry, Philos. Trans. 1840, p- 595. 


MARSUPIALIA. 


rupeds. It offers no peculiarity in its general 
oe form. The apex is less obtuse i 
some species, as the Phalanger and Wombat, 
than in others, as the Kangaroo. The serous 
layer of the pericardium is reflected upon thi 
large vessels near to the heart. The fibrouw 
layer of the pericardium adheres to the sternut 
in the Kangaroo. The appendix of the rig 
auricle is always divided into two r 
cesses, (a, a, figs. 131 and 132,) one in fre 
and the other behind the trunk of the a 


Fig. 131. 


¢ 
a 


Heart of the Kangaroo. 


Besides this characteristic modification of | 
external form, the right auricle presents som 
still more essentially marsupial conditio 
in its interior. There is no trace, for 
of a ‘ fossa ovalis’ or an ‘ annulus ovalis 
any marsupial animal;* and the absence 
these structures, which are present in the 

of all the placental Mammalia, doubtless” 
lates to the very brief period during which | 
auricles intercommunicate in the Marsupis 
and to the minute size, and in other resp 
incompletely developed state, at which 1 
young marsupial animal respires air by 
lungs, and has the mature condition of | 
pulmonary circulation established. The 

and left auricles intercommunicate by 
oblique fissure in the uterine embryo of 
Kangaroo, when two-thirds of the period | 
gestation is past, but every trace of this fost 
structure is obliterated in the subsequent gro 

of the heart; so that in the mature animal 
wide terminal orifice of the posterior cava 1 


* Physiological Catalogue, Mus. Royal Ce lege 
of Surgeons, 4to. vol. ii. p. 52. a 


MARSUPIALIA. 


rated from that of the anterior cava by a 
simple crescentic ridge (e, figs. 131 and 132), 
which forms a salient angle of the parietes of 
the auricle between these apertures. The an- 
terior cava (b ) returns the blood from the right 
side of the head and the right anterior extre- 
mity; the corresponding vein on the left side 
(¢) passes down in all the Marsupials, as in 
Birds and Reptiles, behind the left auricle, 
below the two pulmonary veins, and, after 
receiving the coronary vein, joins the inferior 
cava (d) immediately before its expansion 
into the auricle. 


Fig. 132. 


. Heast of the Wombat. 


Where the posterior extremities are less or 
not larger than the anterior ones, as in the 
Ursine Dasyure and Wombat, the posterior 
cava 1s somewhat less than the left vena 
mnominata (figs. 131 and 132), and they 
appear to terminate by separate apertures in 
the auricle; but in the Kangaroo (fig. 131) 
the proportions of the two veins are reversed, 
and the posterior cava more obvious! y receives 
the left vena innominata before it terminates: 
these two veins meet at a very acute angle, and 
are separated by a crescentic ridge similar to, 
but thinner than, that which divides their 
a orifice from the orifice of the anterior 

va. 

The right auriculo-ventricular valve is mem- 
branous, as in the placental Mammalia, and 
its free margin is attached by fine chorde ten- 
dine to three columnz carnez ; these in the 
Kangaroo (fig. 131) all arise from the septum 
of the ventricles, but in the Wombat (fig. 132) 


307 


the base of two of the columne is situated at 
the angle between the septum and the thin 
outer wall of the ventricle. 

The right ventricle extends nearly to the 
apex of the heart in the Wombat, but falls 
short of that part in the Kangaroo. The ven- 
tricle is continued in the form of a pyramidal 
process, somewhat resembling a budbus arte- 
riosus, to the origin of the pulmonary artery 
Cf; figs. 131 and 132), and projects beyond the 
general surface of the heart further than in 
ordinary Mammalia. 

The appendix of the left auricle is notched 
in the Kangaroo to receive the apex of this pro- 
cess, but not in the Wombat. Two pulmonary 
veins (, fig. 133) terminate close together, or by 
a single trunk, at the upper and dextral angle 
of this auricle. The mitral valve is regulated 
by two short and thick columne (k, k, fig. 133), 
which send their tendinous chords to the margin 
and ventricular surface of the valve. 


Fig. 133. 


Heart of the Wombat. 


The ventricles and auricles present the usual 
mammalian proportions and relative thickness 
of their parietes. Three sigmoid valves are 
situated at the origin of the pulmonary artery, 
and the same number at that of the aorta. 

After the coronary arteries, the primary 
branches from the arch of the aorta rise in 
some species by three, in others by two trunks. 
The broad-chested Marsupials, the Koala and 
Wombat for instance, are those in which the left 
carotid (g’, fig. 132) and subclavian (h’ ) arise 
separately from the arch; the arteria inno- 
minata dividing into the right subclavian and 
carotid (g, h, fig- 132), as in man. In most 
of the other Marsupials the innominata gives 
off both carotids (g, g, fig. 131) as well as the 
right subclavian (A); and the left subclavian 

x 


308 


(h) alone has a separate origin. The common 
carotid in the Kangaroo gives off the thyroid 
artery, and afterwards divides opposite the 
transverse process of the atlas into the external 
and internal carotids. The internal carotid 
describes a sharp curve at its origin, and passes 
along the groove between the occipital condyle 
and the exoccipital process to the foramen ca- 
roticum. The vertebral arteries are given off 
by the subclavians, and to the skull, as 
usual, through the vertebral foramina of the 
cervical transverse processes. They unite be- 
neath the medulla oblongata to form the basilar 
artery, which sends off at right angles to the 
cerebellum two branches as large as itself: it 
divides opposite the anterior margin of the 
pons Varolii, and the diverging branches are 
connected by two straight transverse canals, 
before they anastomose with the internal caro- 
tids to form the circle of Willis. No pecu- 
liarly marsupial condition occurs in the distri- 
bution of the other arteries of the head, or 
those of the neck, the chest, and anterior ex- 
tremities; but I may observe that in the Koala, 
Wombat, Kangaroos, Potoroos, most Phalan- 
gers, ( Phal. Cookii is an exception,) most Pe- 
taurists, ( Pet. Sciureus is an exception,) the 
Opossums, Bandicoots, and Phascogales, the 
brachial artery perforates the internal condyle 
of the humerus; it passes over that condyle, 
impressing it with a more or less deep groove 
in the Dasyures and Thylacine. 

In the abdomen, the primary branches of 
the aorta are sent off in the same order as in 
most of the ordinary Mammalia, with the ex- 
ception of the constant absence of an inferior 
mesenteric artery. This modification probably 
relates to the simplicity of the mesenteric at- 
tachment of the intestines above described. A 
still more marked example of the oviparous 
affinities of the Marsupialia, as exemplified in 
the arterial system, occurs in the mode of 
origin of the great arteries of the posterior 
extremities. In Man and the ordinary Mam- 
miulia these are derived, as is well known, from 
a single trunk on each side—the common iliac 
artery; in Birds from two primary branches of 
the aorta, one corresponding with the external 
iliac and femoral, the other with the internal 
iliac and ischiadic arteries. In the Kangaroo 
and Phalangista vulpina the aorta gives off, 
opposite the interspace of the two last lumbar 
vertebra, the iliac arteries ; but these are after- 
wards resolved into the ordinary branches of the 
external iliac of the placental Mammalia, with 
the addition of the ilio-lumbar artery. The 
trunk of the aorta, much diminished in size, 
maintains its usual course for a very short 
distance, and then gives off the two internal 
iliacs, and is continued as the ¢ arteria sacra 
media’ to the tail. The transitional cha- 
racter of this part of the marsupial sangui- 
ferous system between the oviparous and pla- 
cental types, is manifested in the large size of 
the external iliacs as compared with the internal 
iliaes, their greater share im the supply of blood 
to the hinder extremities, and the brevity of 
the aortic trunk between their origins. In 
most Birds the femorals or external iliacs are 


MARSUPIALIA. 


smaller than the ischiadic or internal iliac 
arteries subsequently given off. At the uppel 
part of the thigh the femoral divides into 
two equal branches; the one which corresponds 
with the radial artery in the fore leg (m, fig.134) 
principally supplies the foot in the Kangaroos 
it passes along the back of the radius, be! 
the gastrocnemius internus and tibialis posticu 
and divides a little above the internal malleolus. 
The smaller division (/, fig. 134), which folle 
the ordinary course of the femoral along the pe 
teal space, is lost upon the inner and ior F 
of the tarsus; the larger branch winds over th 
malleolus to the front of the tarsus, sends off 
the anterior tarsal artery, and is then continued 
along the inner and afterwards the under part of 
the metatarsal bone of the long-and strong toe. 

In fig.134, a is the trunk of the celiac artery 
b that of the superior and inferior mesenteri 
arteries; c is the capsular artery of the left side; 
d, d, the renal arteries; e the s tic artery, 
of which the left branch is shown continued to 
the left ovarium g, which, with the uterus 
vagina s, and bladder ¢, is drawn to the rightside; 
the spermatic arteries = — but 
separately in the male Vulpine cary i 
the diavel iliac, coreisnatiel with ré ! 
mon iliac in placental Mammalia, and wit 
the femoral artery in Birds, (see Vol. i. pe 33) 
Sigs. 170, 23 ;) below these are given off A, t 
arteries corresponding with the ischiadie ar. 
teries in Birds, (Vol. i. p: 337, fg. 170, 26,) 
and with the internal iliacs in nalia; 
[they are represented of too small a size in 
the cut]; & is the femoral artery; / the ex- 
ternal, m the internal branch; é is the saere 
median or caudal artery, which is protecte 
in its course along the tail by the hem. 
apophysial or chevron-like processes of the 
caudal vertebre. This artery of course cor- 
responds in size with the developement ane 
functional importance of the tail, and must b 


DOS | 
Es 


E 
' 
ya 


rudimentary in the tail-less or nearly tail-les; 
Marsupials, such as the Cheropus, Koala, an 
Wombat. . 


With respect to the veins of the Marsupi 
it may here be noticed that the iliac vei 
combine to form the trunk of the abdomin 
cava, as in the rest of the Mammalia, witho 
conveying any part of their blood to the kit 
neys: in the Kangaroo they both pass on 
central aspect of the iliac arteries. The re 
veins, in like manner, directly communie 
with the abdominal cava, and do not cont 
bute any share in the formation of the por 
vein. This great secerning trunk of the hepa 
organ presents the strictly mammalian con 
tion, being formed by the reunion of the gast 
intestinal, pancreatic, and splenic veins. Ti 
in the chest that we first meet with decie 
traces of the oviparous type of structure in 
venous system of the Marsupialia. The prim 
tive veins of the animal system of orga 
commonly called ‘ azygos,’ retain their orig git 
separation and symmetry; the left ‘ azyg 
bends over the left bronchus to com 
with the left anterior cava, and the rig 
gos over the right bronchus to join the rigi 
anterior cava. ‘The left anterior cava commol 


™ 


MARSUPIALIA. 209 
Fig. 134. 


LSS 


= i ) 


Hi <SRv 
| HOSS 
Wives 


ay 


# 
F 


Branches of the abdominal aorta, Kangaroo. 


the termination of this and the two other venous 
trunks in the right auricle has already been 
; noticed. 
_ Respiratory organs—In the condition and 
_ structure of the respiratory organs all the Mar- 
supial species adhere to the Mammalian type ; 
a 


. receives also the coronary vein of the heart: 
/ 


the only tendency to the Ovipara is in the 
_ entireness of the tracheal rings in certain spe- 
cies. In the Phalangista fuliginosa, where I 

counted twenty-nine rings, the first four-and- 
_ twenty were entire; below these they were 
_ divided posteriorly, the interspace growing 
_ wider to the twenty-ninth ring. In the Dasy- 
_urus macrurus the rings of the trachea are 
_ twenty-three in number, and are incomplete or 

rather ununited behind. In the Perameles the 
tracheal rings are divided posteriorly by a fis- 
sure. In no species have I found the trachea 
divided near the larynx into two long bronchiz, 


. 


as in the Rodent genus Helamys, nor convo- 
luted in the chest as in the Edentate Sloth, both 
of which modifications are more striking ap- 
proximations to the oviparous type of structure 
than the entire rings above-mentioned. 

The Jungs present the most simple form in 
the Wombat, in which they consist of a single 
lobe on both the right and left sides, with a 
small lobulus azygos extending from the right 
lung to the interspace between the heart and 
diaphragm. ; 

In the Macropus major I found the right 
lung with two notches on the anterior margin, 
and the left lung undivided. In the Macropus 
Parryi both lungs had one or two notches. 
In another Kangaroo I found the right lung 
divided into four lobes, the left intotwo. The 
azygos lobe is large in consequence of the 
length of the chest in the Kangaroos, and the 
distance of the heart from the diaphragm: it is 


310 


three-sided, one side convex, the second con- 
cave and applied to the pericardium, the third 
side concave, and in contact with the dia- 
phragm. 
In the Potoroo the left lung is unilobate with 
a fissure on the anterior or upper edge; the 
right lung has two or three deep alba. The 
azygos lobe is elongated, pointed, and triedral, 
as in the Kangaroo. 

In the Petaurists and Phalangers the right 
lung is trilobate, the left bilobate ; there is also 
a lobulus azygos. The Koala has the lungs 
similarly divided, and not simple as in the 
Wombat. 

In the Opossums, Dasyures, and Perameles 
the right lung is usually trilobate, (bilobate in 
Didelphys brachyura,) and with the usual 
azygos appendage: the left lung is commonly 
divided into two, but is sometimes entire, as in 
the Perameles and Didelph. brachyura. In all 
the Marsupials the right lung is the largest, 
owing to the oblique inclination of the heart to 
the left side. 

The thyroid glands are two disunited bodies 
n the Dasyures; they were each the size of a 
horse-bean in the Das. macrurus. They were 
of the same size in a Phalangista fuliginosa, 
but were united by a filamentary strip passing 
between their lower extremity, across the first 
tracheal ring. In the Koala, the thyroid gland 
is situated lower down extending from the 
fourth to the ninth or tenth tracheal ring. In 
the Wombat I found the thyroid glands two 
elongated bodies of a dark colour reaching 
from the thyroid cartilage to the seventh tracheal 
ring on each side. 

The larynx of the Marsupialia consists of a 
cricoid, thyroid, and arytenoid cartilages and 
an epiglottis. The latter is always remarkable 
for its large size, and generally for its emar- 
ginate apex. There is no muscle ing from 
the epiglottis to the tongue; its is con- 
nected in the Kangaroo by a triangular fascia 
to the body of the os hyoides and the greater 
cornua; and a small muscle passes from the 
middle part of the body of the os hyoides to 
the dorsum lingue. 

In the Phalangers the epiglottis is broad 
and short, and with a bifid apex. In the Pe- 
rameles and Phascogale the sides of the broad 
and short epiglottis are attached to the apices 
of the arytenoid cartilages, retaining thus much 
of its early condition, which will be adverted to 
in the account of the peculiarities of the mam- 
mary fcetus. 

In the Perameles lagotis I found on the base 
of the tongue in front of the epiglottis a 
small sacculus of mucous membrane, which 
communicated by a regular symmetrical cre- 
scentic aperture, situated between the body of 
the os hyoides and the thyroid cartilage, and 
continued down in front of the thyroid cartilage : 
the surface of the cavity was smooth and lubri- 
cated, and it seemed to be for the purpose of 
facilitating a hinge-like motion between the 
thyroid cartilage and the body of the os hy- 
oides. 

The thyroid cartilage is convex externally and 
protuberant in the Phalangers and Koala, but 


MARSUPIALIA. 


a 
offers no —— modification in other Mar- 
rah a e base of the arytenoid cartilage 
is broad in the antero-posterior direction, and 
the chordz vocales short and feebly developec 
The Marsupials have little or no voice: t 
Wombat emits a guttural hissing sound: th 
Dasyurus ursinus a snarling growl or whine 
the Thylacine is described as uttering a shor 
guttural cry. I have never heard a vocal m 
of any kind from the Kangaroos, Potoroos, F 
taurists, Phalangers, or Perameles. 4 
Renal system.—The kidneys present a simp 
conglobate external form in all the Marsupial 
as in fig. 134, 0, o,and in their structureand po= 
sition in the abdomen agree with the Mamma 
lian type of structure. - 
In the Macropus Parryi the kidneys at 
situated six inches above the brim of th 
pelvis, and lying in the same transverse line 
they have the same relative position in othe 
Poephaga. ¥ 
In the Koala the right kidney is higher by 
its whole length than the left. In the D 
uri macrurus and viverrinus, the right kidn 
lies half an inch higher or in advance of th 
left: in this carnivorous genus a few branch 
of the renal veins are distributed upon the su 
face of the kidney, but not in the same pre 
portion or with the beautiful arborescent di: 
poe characteristic of the kidneys of th 
ats, Suricates, and Hyena. In a Dasyuru 
macrurus weighing three pounds eight ounces 
the two kidneys weighed thirteen drachms. 
In a Phalangista vulpina, weighing five poun 
three ounces, the two kidneys weighed ; 
ten drachms. 
The substance of the kidney is divided int 
a cortical and medullary Boni the former i 
generally a thin layer. e tubuli urinifei 
terminate on a single mammilla which project 
into the commencement of the ureter in th 
Opossums, but does not extend beyond 
pelvis of the kidney in the Kangaroos. | 
the Kangaroos the medullary substance for 
several lateral abutments to the base of tl 
main mammilla. 
The supra-renal glands generally present th 
relative position ae proportions to the kidney 
represented in the Kangaroo, at fig. 13 
They are, asin most of the smaller quadre 
less flat than in man: the right body genera 
adheres to the coats of the vena cava, and t 
left to the renal vein. In the Dasyures the e: 
ternal stratum is light-coloured ; this surrounc 
a dark-coloured layer, and then there is a lig 
coloured central part, but no cavity. vy 
The ureters terminate at the back of the ne 
of a muscular and pendulous urinary blade 
(t), which only exhibits a trace of urachus | 
the middle of its anterior part in the youn 
marsupial, while in the maternal pouch, 
Male organs of generation— The testes, 


which are still abdominal at the time of b 
descend, soon after the feetus is } 
the pouch, into the external pedunculate pre- 
penial scrotum; the canal of communica- 
tion between the abdominal cavity and the tu- 
nica vaginalis is long and narrow, but always 
remains pervious, 


MARSUPIALIA. 


The tubuli testis are relatively sinaller than 
in the Rodentia, but are similarly arranged, the 
8 Highmorianum being near the surface 
and upper part, not at the centre, of the gland. 
The epididymis is large, and generally loosely 
attached to the testis: in a small species of 
Kangaroo I found the connecting fold of serous 
membrane half an inch broad. The vasa de- 
ferentia pass from the globus minor along the 
infandibular muscular sheath formed by the 
cremaster as far as the abdominal ring, then 
bend downwards and backwards, and termi- 
nate below and external to the ureters, at the 
commencement of the urethra (a, fig. 135), 
on each side a longitudinal verumontanal ridge. 
There are no vesicule seminales in any Mar- 
supial quadruped. 


Fig. 135. 


A, Hypsiprymnus. B, Phascolarctus. C, Phascolomys. 


311 


As the part of the urethral canal immediately 
succeeding the termination of the vasa defe- 
rentia is the analogue of the vagina, some mo- 
dification of this part might be anticipated in 
the male corresponding with the extraordinary 
form and developement which characterise the 
vagina in the female: accordingly we find that 
the combined prostatic and membranous or 
muscular tract of the urethra is proportionally 
longer and wider in the Marsupial than in any 
other Mammiferous quadrupeds (fig. 135, b). 
It swells out immediately beyond the neck of 
the bladder, and then gradually tapers to its 
Junction with the spongy part of the urethra : 
it is not, however, divided like the vagina. 
Its walls are thick, formed of an external thin 
stratum of nearly transverse muscular fibres ; 
and a thick glandular layer, the secretion of 
which exudes by innumerable pores upon the 
lining membrane of this part of the urethra. 
In a male Kangaroo I found that a glairy mucus 
followed compression of this musculo-prostatic 
tract of the urethra: the canal itself is here 
slightly dilated. 

Three pairs of Cowper’s glands (c, ¢, ¢, fig: 
135) pour their secretion into the bulbous 
part of the urethra: the upper or proximal 
pair are not half the size of the two other pairs 
in the Kangaroo, but are relatively larger in 
the Koala and other Marsupials: the two 
lower pairs are situated, one on each side the 
lateral division of the bulb of the urethra; 
their ducts meet and join, above this part, with 
the duct of the smaller gland: each gland is 
inclosed by a muscular capsule. 

The penis consists of a cavernous and a 
spongy portion, each of which commences by two 
distinct bodies. The separate origin of each late- 
ral half of the spongy body constitutes a double 
bulb of the urethra (e, e, fig. 135), and the ‘ ac- 
celerator urine,’ as it is termed, undergoes a 
similar division into two separate muscles, each 
of which is appropriated to compress its par- 
ticular bulb. The two bulbous processes of 
the corpus spongiosum soon unite to surround 
the urethra, but again bifurcate to form a dou- 
ble glans penis in the multiparous Marsupials, 
in which most of the ova are impregnated in 
both ovaria, as the Phalangers, Perameles, 
Opossums, &c. (6, b, fig. 136). 

This modification of the opposite extre- 
mities of the corpus spongiosum, called ‘ bulb’ 
and ‘glans,’ was detected by Cowper in his 
dissection of a male Opossum; and, in his 
account of the anatomy of that animal in 
the Philosophical Transactions for the year 
1704, he says, “ As the bulb of the urethra 
in man is framed for the use of the glans, to 
keep it sufficiently distended when required, 
so It seems it is necessary to have two of 
these bulbs, inclosed with their particular mus- 
cles in this animal, to maintain the turgescence 
of its double or forked glans when the penis is 
erected.” —Vol. xxiv. p. 1585. } 

The force of this ingenious ‘reasoning on the 
correlation of the bulb to the glans might seem 
to be invalidated by the fact thatin the uniparous 
Marsupials, as the Kangaroo, the glans penis 
Ch, fig. 135) is single, and yet the bulb double 


312 


but in this circumstance we may perceive an 
example of the retention of a typical structure 
at the deeper seated part of a system of organs, 
when not incompatible with a slight modifi- 
cation of a peripheral segment of the same 
system ; it being by no means obviously neces- 
sary to abrogate the division of the urethral 
bulb simply because the blood accumulated 
in each division was to be driven in a concen- 
trated current upon a single, instead of a dou- 
ble glans penis. 
e intermediate structures of the glans be- 
tween the two extremes above instanced are 
resented by the Ursine Dasyure, Koala, and 
ombat. In the Koala (fig.135, B) the glans 
penis terminates in two semicircular lobes, and 
the urethra is continued by a bifurcated groove 
along the mesial surface of each lobe. In the 
Wombat (fig. 135, C) there isasimilarexpansion 
ofthe urethra into two divergent terminal grooves, 
but the glans is larger, cylindrical, and par- 
tially divided into four lobes:* the chief’ struc- 
ture of interest in this part of the Wombat is 
the callous external membrane of the glans, 
and its armature of small recurved, scattered 
horny spines, which do not occur in any other 
Marsupial animal. The small retroverted pa- 
ille on the infundibuliform glans of the 
oala and on the bifurcate glans of the Phalan- 
gers and Petaurists are not horny. 

In the Perameles lagotis not only is the glans 
bifurcate, but each division is perforated, and 
the urethral canal is divided by a vertical 
septum for about half an inch before it reaches 
the forked glans. From theseptum tothe bladder 
the canal is simple, as in other Marsupials. 
The bifurcations of the glans in the Opossums 
and Phalangers are simply grooved. 

If the experiments of Haighton and the 
detection, by Drs. Bischoff and Barry, of sper- 
matozoa upon the ovary itself a coitus, 
had not rendered the question of the neces- 
sity of the contact of the semen with the 
ovarium for impregnation almost independent 
of the aid of Comparative Anatomy, the diffe- 
rences of structure above described in the 
urethra and glans penis of the Marsupial 
animals would have gone far to explode the 
once prevalent notion of an ‘ aura seminalis’ 
fertilizmg the ovum through the medium of 
the circulating fluid: for why, on such an 
hypothesis, should the impregnation of two 
ovaria, each communicating with a distinct 
oviduct, uterus, and vagina, as in the Opos- 
sum, require two conduits of the semen in the 
male, one for each vagina?—and wherefore, 
in the case of an uniparous Marsupial, in 
which the fecundating stream need ascend only 
to a single ovarium, as in the Kangaroos and 
ted ian is the penis terminated by a single 

Jans 
‘ The spermatozoa of the Perameles have a 
single barb at the base of the head, which is 
sub-elongate and compressed ; in other respects, 
as in size and proportion of the filamentary tail, 
they resemble the spermatozoa of the Rabbit. 


: Nan Legons d’Anat. Comparée, 1805, t. vy. 
p- 9i. 


MARSUPIALIA. 


Neither Je be Kangaroo, Phalanger, nor Da- 
ure did t NR present a spiral head 
ns any noticeable deviation from the char oters 
of the spermatozoa in the smaller placental 
quadrupeds: those of the Dasyure have 
node at the base of the head. oil 
The corpus cavernosum penis commences b 
two crura(d, d, figs. 135, 136), neither of whi 
have any immediate attachment tothe bony pelvis 
Cuvier correctly states, that in the Kangaroo the 
two crura of the corpus cavernosum, and the tw 
bulbs of the corpus spongiosum, soon unite to 
form a single cylindrical body, having a cana 
which nearly follows the direction of its axi 
whose parietes are equally strong and fibrous, 
and which contains the urethra; so that the 
transverse section of the corpus cavernosum 
resembles a ring; but the two lateral cavities 
are separated by two vertical septa which e: 
tend one from the central canal to the dorsum 
penis, the other from the central canal to the 
inferior wall of the penis.* 
In the Kangaroo and Potoroo, the erectores 
penis (fig. 135 d,d) arise by a thin fascia from 
near the lower part of the symphysis pubis, soon 
become fleshy, and increase in thickness as they 
pass outwards: each muscle then returns upor 
itself, atan acute bend, to grasp the crus pe 
and terminates in a strong tendinous expan 
at the junction of the cavernous with 
bous structure. 


Fig. 136. 


Male Organs, 

( Cowper, l. c.) 

The retractor penis (figs 135,136, g, g) arises 
in the pasta gp al middle ee the sa- 
crum, and divides into two muscles, behind 
rectum, opposite the dilated commencer 
of the musculo-prostatic part of the w 
each division diverges to the side of the ree 
then passes to the interspace between the 
tum and roots of the penis, and along the 


¢ 


oe 


_™ Legons d’Anat. Comp. 1805, t. v. p. 73. 


MARSUPIALIA. 


lateral and posterior part of the penis, until it 
is inserted with the opposite muscle at the 
base of the glans. 

In the Opossum and those Marsupials 
which, having a bifid glans, enjoy, as it were, 
a double coitus, there is a levator penis (f, f, 
fig. 136), which is not present in the Kangaroo. 
Each portion of this muscle takes its origin 
from the fascia covering the crus penis, con- 
verges towards its fellow above the dorsum 
penis, diminishing as it converges, and termi- 
nates in a common tendon inserted into the 
pe part of the base of the glans. 

here is another powerful muscle which, 
though not immediately attached to the penis, 
must exert, in all Marsupials, so important an 
influence upon its erection as to merit notice 
here. This is the external sphincter ani, or 
more properly ‘ sphincter cloace :’ it is an inch 
and a half in breadth in the Kangaroo and half 
an inch in thickness; from the back of the 
termination of the rectum it passes over the 
anal glands and sides of the base of the penis, 
inclosing the two bulbs with Cowper’s glands 
and their muscles, and terminates anteriorly in 
a strong fascia above the dorsum penis, so as 
to compress: against that part the vene dor- 
sales. 

This adjustment and function of the great 
sphincter did not escape the observation of 
Cowper. Speaking of the erectores penis of 
the Opossum, he says, “ the muscles of the 
cavernous bodies of the penis of this creature, 
having no connexion with the os pubis, cannot 
apply the dorsum penis to the last-named bone 
and compress the vein of the penis, whereby 
to retard the refluent blood and cause an erec- 
tion, as we have observed in other creatures ; 
but some large veins of the penis here take a 
different course, and pass through the middle 
parts of the bulb (crus), and are only liable to 
the compression made by the intumescence of 
the muscles (cc) that inclose them. But the 
chief agent in continuing the erection of the 
penis in this animal is the sphincter muscle of 
its anus, or rather cloaca; and not only the 
sphincter muscle of the cloaca of the male 

possum, but that of the female also, closely 
embraces the penis in coition, and effectually 
retards the refluent blood from its corpora caver- 
nosa, by compressing the veins of the penis.”* 
The penis is bent upon itself in a sigmoid 
form when retracted ; with the glans concealed 
just within the cloacal aperture, from which it 
emerges, as in the Ovipara, when the penis is 
turgid and erect. 

Female organs.—These consist of two ovaries, 
two oviducts or fallopian tubes, two uteri, two 
vagine, an uro-genital canal, a clitoris, mam- 
mary organs, and marsupial pouch. 

The ovaries are small and simple in the 
uniparous Kangaroos; tuberculate and rela- 
tively larger in the multiparous Opossums; 
but the largest size and most complicated 
form of these essential organs which I have 
met with in the Marsupial order were pre- 
sented by the Wombat (fig. 137). The 


* Phil. Trans. vol. xxiv. 1704, p. 1584, 


313 


ovaria are represented of their natural size in 
fig. 138, a a’, in the great Kangaroo, where they 
present an oval form and a smooth unbroken 
exterior, except after impregnation, when a 
large corpus luteum projects from the surface, 
as ata’. The ovaria are not inclosed by a cap- 
sular duplication of the peritoneum, but are 
lodged within the expanded orifice of the ovi- 
duct, or ‘pavilion,’ near the upper or anterior 
extremities of its two principal lobes or pro- 
cesses. These are of considerable extent, and 
their internal surface, which is highly vas- 
cular, is beset with ruge and papille. In 
the Dasyures and Petaurists the ovaries are 
elliptical, subcompressed, and smooth. In the 
Opossum the ovarium consists of a lax stroma 
remarkable for the number of ovisacs imbedded 
in it, the largest of which are the most super- 
ficial, and give rise to the tubercular projections 
on the surface of the ovary. 

In the Wombat (fig. 137) each ovary, be- 
sides being lodged in the pavilion, as in the 
Kangaroo, is inclosed with the pavilion in a 


Fig. 137. 


Ovarium and pavilion, Wombat. Natural size. 


eritoneal capsule. In the unimpregnated 
emale examined by me, the ovaries were six 
times as large as in the Kangaroo, and pre- 
sented a well-marked botryoidal form, resem- 
bling the ovarium of the bird. Numerous ovi- 
sacs in different stages of growth projected from 
the surface, the largest presenting a diameter of 
eight lines (fig. 137, a); the structure of these 
ovisacs, the character of the stroma in which they 
are imbedded, and the dense albugineous tunic 
by which they are inclosed, bespeak the strictly 
mammalian type of the ovaria of the Phascolo- 
mys as of every other genus of Marsupial; but 
the affinity of the Wombat to the Rodent order, 
in many species of which the ovaria are tu- 


314 MARSUPIALIA. 


Fig. 138. 


a, Right ovarium. 

a’, Left ovarium, with corpus 
luteum, 

hb, Oviducts, 

ec, Right uterus. 

ce’, Left uterus, impregnated. 

d, Os tince. 

e, Vaginal cul-de-sac. 


e, Vaginal canals. 

e”, Vaginal septum. ~ : 

f, Commencement of uro-ge- — 
nital canal. 

i, Chorion of foetus, 

k, Umbilical cord. ' 

**, Round ligaments of the 
uterus, 


Female organs, Kangaroo, 


MARSUPIALIA. 


berculate, is again. manifested in this part of 
its structure. The expanded orifices of the 
fallopian tubes present a greater development 
than in the Kangaroo, and are still more re- 
markable for the number, size, and variety of 
the fimbriated processes and folds which aug- 
ment the internal vascular surface of the pavi- 
lion. In both the Wombat and Kangaroo the 
lining membrane of the contracted portion of 
the oviduct is similarly complicated by minute 
and delicate reticular plications and processes. 
The oviducts are shorter and less sinuous in 
their course in the uniparous Kangaroo, fig. 
138, b, than in the multiparous Opossums (6, 
Sig. 139). 

In the above described essential parts of the 
female generative apparatus the mammalian 
type of structure is closely adhered to; the de- 
viations most characteristic of the implacental 
group begin to manifest themselves in the re- 
maining parts, and here under so irregular and 
complicated a form as to require a brief review 
of the analogous structures in other groups of 
animals for their intelligibility. 

The variations of structure which the female 
generative organs present in the oviparous 
classes of Vertebrata are fewer and of less de- 
gree than those observable in the different orders 
and genera of the Mammalia. The most pre- 
vailing characteristic of the oviparous type of 
the female generative organs is the absence of 
union in the mesial plane of the lateral efferent 
tubes, which consequently continue separate to 
their terminations in the excretory outlet. 

In Birds the genital apparatus is characterised 
by the higher, and, in the female, as far as 
function is concerned, exclusive development 
of the left moiety ; and the uniformity in the 
condition of the excluded ovum in this class 
corresponds with the sameness which po 
in the structure of the organs concerned in its 
production. 

In Reptiles the ovaries and efferent parts of 
the genital system are equally developed, or 
nearly so, on both sides. But although a con- 
siderable uniformity of structure is found to pre- 
vail in this system throughout the different 
orders of the class, the widest difference obtains 
both in the place of development of the ovum 
and the condition in which it quits its mother. 
No one, e. g., could have predicated from a 
comparison of the structure of the ovaries and 
oviducts in P ssaapcapet and innocuous Serpents 
that any difference existed in the structure and 
development of the ovum, much less that the for- 
mer were ovo-viviparous but the latter oviparous; 
or, froma comparison of the same organs in 
Lacerta crocea and Lacerta agilis, that a like 
difference should exist in the generative eco- 
nomy of species so nearly allied as for a long 
time to have been confounded together by 
naturalists. 

In Mammalia, however, in most of the orders 
of which the connexion of the ovum with the 
uterus is so much more intimate than in the 
preceding classes, the variations in the structure 
of the female sexual organs are more numerous 
and remarkable; and though it be admitted 
that the nature of the fetal coverings and ap- 


315 


pendages results from the original constitution 
and properties of the ovum, yet the modifica- 
tions of the uterus have evidently, in this class, 
a subordinate relation to those differences. 

In tracing the female generative apparatus 
from the human subject through the different 
orders of Mammalia, we find that it approxi- 
mates to the oviparous type of structure in two 
ways, viz., by an obliteration of the os tince, 
which is the characteristic limit between the 
uterus and the vagina in this class; and bya 
gradually increasing division of the uterus and 
vagina until they become two separate tubes 
throughout their entire extent. 

In no mammiferous genus do the female 
organs present that character of unity or con- 
centration, with distinction of parts, which is 
found in the human subject ; for in the lower 
orders, besides the more essential differences 
above-mentioned, there is always an elongation 
of the uterus, with a thinning of its parietes, and 
in general a blending together of the urethral 
and sexual passages. This latter deviation com- 
mences in the Simie, and in the Lemures the 
angles of the uterus begin to elongate and to 
assume the form of cornua. The mesial cleft 
increases, and the cornua preponderate in the 
Carnivora, the Cetacea, the Ruminantia, and 
the Pachydermata; but it is in the Rodentia, 
which present affinities to Birds in other 
parts of their structure, that the uterus is first 
found completely divided into two lateral halves. 
This structure is not, indeed, uniformly met 
with in all the genera of the order; but besides 
the Hare and Rabbit, in which the double 
uterus is allowed to exist by De Graaf and 
Cuvier, a similarly complete division of the 
organ obtains in the genera Sciurus, Arctomys, 
Spalax, Bathyergus, Echimys, Eretizon, (F. 
Cuvier) and Hydrocherus ; while in the genera 
Mus, Cavia, Caelogenys, and Dasyprocta, a 
portion of the true uterus still remains undi- 
vided ; though this part, to which alone the term 
‘ corpus uteri’ can be properly applied, is ex- 
tremely small or rudimental. Nevertheless, 
although the corpus uteri exists in these genera, 
the true vagina is as remarkable for its length 
and capacity as in those in which the corpus 
uteri has ceased to exist. 

Hitherto the vagina has presented itself un- 
der the form of a simple undivided canal, 
communicating with the urethro-sexual passage, 
at least after impregnation by a single aperture. 
But it is a remarkable and interesting fact that in 
the Sloth, in the Mare and Ass, in the Pig, and 
in the Cow, the vagina in the virgin state com- 
municates with the urethro-sexual passage by 
a double aperture, in consequence of being 
traversed by a narrow vertical septum or chord. 
This septum has been described by veterinary 
authors as a hymen in the Mare; the analo- 
gous part in the human subjectalso occasionally 
presents the same structure, and has even been 
observed in some cases to extend as a mesial 
partition inwards towards the uterus. j 

Inthe Marsupialia, where from the small size 
of the foetus at birth a similar conformation is 
permitted to remain as a permanent structure, 
the vagina is in some genera wholly, and in 


316 


others partially divided ; but the divided por- 
tion in the latter is always that which is nearest 
the urethro-sexual passage. 

The true uterus is completely divided in all 
the Marsupial genera, and each division is of a 
simple elongated form, as in the Rodentia. 

The superadded complications in the female 
generative organs of the Marsupials, as com- 

with other mammals, are not then rightly 
attributable to the uterus, but to the vagina; 
and they are of such a nature as to adapt the 
latter to detain the feetus, after it has been ex- 
pelled from the uterus, for a longer period than 
in other Mammalia. 

These complications vary considerably in the 
different marsupial genera. On a comparison 
of the female organs in Didelphys dorsigera, 
Petaurus pygmeus, and Petaurus taguanoides, 
in Dasyurus viverrinus, in Didelphys Virgi- 
niana, in Macropus major, and Hypsiprymnus 
murinus, I find that the relative capacity which 
the uteri bear to the vagine diminishes in the 
order in which the above-named a are follow, 
while the size of the external pouch increases in 
the same ratio. 

In Didelphys dorsigera the uteri (fig. 139, 
¢, ¢,) rather exceed the unfolded vagine in 


Fig. 139. 


Didelphys dorsigera. 


length. In most Marsupials the vagine at 
first descend as if S: commaeaicaleet directly 
with the urethro-sexual passage; but in this 
small Opossum, in which the abdominal pouch 
consists of two slight longitudinal folds, and 
the young, as is implied by its trivial name, 
are transported by the mother on her back, 
each vaginal tube (e, e, fig. 139,) after em- 
bracing the os tince (d), is immediately con- 
tinued upwards and outwards, then bends 
downwards and inwards, and, after a second 


MARSUPIALIA. 


bend upwards, descends by the side of the 
opposite tube to terminate re with th 

extremity _—_ wee in the commot 

or uro-genital passage (f'). 

In the Petauri, the vagina, when unfolk 
are a little longer than the uteri. On examinin 
a specimen of the Pigmy Petaurist which hai 
two very small young in the pouch, I fou 
both the true uteri of three times the di mete 
of the same in an unimpreguated specimer 
but the vagine were unaltered in size, it 
cating that the situation in which gestati 
takes place in this species is the same as in th 
Kangaroo. The vagine, after receiving th 
uteri, descend close together half-way toward: 
the commencement of the urethro-sexual pa 
sage, but do not communicate together in th 
part of their course. From the upper part | 
these culs-de-sac they are continued upware 
and outwards, forming a curve, like the ha 
dles of a vase, then descend, converge, am 
terminate close together, as in the precedin 
era sh i 

In rus viverrinus and Didelphys Vir 
Pee ey mesial culs-de-sac of a gin 
descend to the urethro-sexual passage, and ar 
connected to, but do not communicate with it 
The septum dividing them from each other is 
complete, being composed of two layers whic 
can be separated from each other, and which 
result indeed from the apposition and mutu 
cohesion of the vagine at this part. In ore 
to reach the common passage, each tube is con- 
tinued outwards from the upper end of the cul- 
de-sac, and forming the usual curve, terminates _ 
parallel to the orifice of the urethra. Th 
vagine in the Dasyures are smaller in propor- 
tion to the uteri than in the Virginian Opossum, 
but of a similar form. i. 


> 


ip 


of the mesial culs-de-sac of the vagine was im- 
perfect; but it is doubtful whether this inter- 
communication was not the result of parturition, 
or of an accidental rupture in the specimen ex- 
amined. If it should prove to be a specific 
difference of structure, it is an approximation 
to the condition of the female o in the 
Phalangers, the Wombat, and the Kangaroos. 

In the Macropus major the vagine (fig. 138, 
e, & ) preponderate in size greatly over the uter 
(c, c’); and, the 8 (e”) of the descending 
cul-de-sac being always more or less incom= 
plete, a single cavity (e) is thus formed, into 
which both uteri open ; but however imperfect 
the septum may be, it always intervenes and 
preserves its original relations to the uterine 
orifices (d, d). he. 

The foetus has been conjectured to pass into 
the urethro-sexual cavity by a direct aperture 
formed after impregnation at the lower blind — 
end of the cul-de-sac, but I have not been able — 
to discover any trace of such a foramen in two — 
kangaroos which had borne young; and be- — 
sides, I find that this part of ihe vagina is not | 
continuous by means of its proper tissue 


* Buffon, Hist. Nat. tom. x. p. 279. 


MARSUPIALIA. 


with the urethro-sexual passage, but is con- 
nected with it by cellular membrane only ; 
as might have been anticipated from the struc- 
ture presented in the simpler forms of the mar- 
supial uterus, as in Didelphys dorsigeraand the 
Petauri, in which the culs-de-sac do not come 
into contact with the urethro-sexual passage. 
The evidence of M. Rengger on the develop- 
ment of the young and the parturition of the 
Didelphys Azare is also directly opposed to 
the theory of a temporary orifice in the mesial 
cul-de-sac. 

_ The last form of the marsupial female organs 
which may be noticed is that which is found in 
one species at least of the Kangaroo Rat ( Hyp- 
siprymnus murinus). The type of construction 
is, however, the same as in the great Kangaroo, 
but the mesial cul-de-sac of the vagina attains 
a still greater development ; it not only reaches 
downwards to the uro-genital passage, but 
also expands upwards and outwards, dilating 
into a large chamber, which extends beyond 
the uteri in every direction. From the sides 
of this chamber the separated portions of the 
vagina continue downwards, to terminate, as 
usual, in the urethro-sexual canal.* 

In all the preceding geuera the structure of 
the uteri is as distinct from that of the vagine 
as in the Rodentia. The fibrous or proper 
tunic of the uteri is thicker than that of the 
vaginz, and the lining membrane is soft and 
vascular, and disposed in numerous irregular 
folds, which, in section, give apparently a still 
greater thickness to the uterine parietes. The 
whole extent of the vagine, on the contrary, is 
lined with a thin layer of cuticle, which is rea- 
dily detachable, even from the middle cul-de- 
sac, so generally considered as the corpus uteri 
in the Kangaroo. 

The inner surface of the culs-de-sac in the 
Opossum is smooth, but in the lower part of 
the single cavity in the Kangaroo and Potoroo 
it presents a reticulate structure. The lining 
membrane in the lateral canals in all the genera 
is disposed in regular longitudinal folds, a dis- 
position which characterizes the true vagina in 
most of the ordinary quadrupeds. In the 
Kangaroo, as in the other Marsupialia, the 
lateral canals communicate with the common 
er urethro-sexual cavity without making a pro- 
jection; but at the distance of three-fourths of an 
inch from their termination there isa sudden con- 
traction, with a small valvular projection in each 
(fig. 138). By those who consider the cul-de- 
sac and lateral canals as a modification of the 
corpus uteri, these projections will probably be 
regarded as severally representing an os tince ; 
but as they do not exist in the Opossums and 
Petaurists, in which there is simply a contrac- 
tion of the vaginal canals at the corresponding 
part, and as in both these and the Kan- 
garoo, the true uteri open in the characteristic 
valvular manner, as in the Rodentia, without 
the slightest appearance of a gradual blending 
with the median cul-de-sac, the valvular struc- 
ture in the lateral canals cannot be regarded as 


* See Philos. Trans., 1834, pl. vi. fig. 6. 


317 


invalidating the view here adopted of the 
vaginal nature of the median cul-de-sac, 
which is supported both by the general tex- 
ture and connexions of the part in question, 
as well as by what is now ascertained to be its 
limited function. Moreover, in the large single 
vagina of some of the Rodentia, as the Hare, 
Rabbit, and Paca, there are two corresponding 
valvular folds of membrane near its commence- 
ment, a little way above the urethral aperture. 

In endeavouring to trace the purposes an- 
swered by the different forms of the female 
marsupial organs above described, considerable 
difficulty arises from the want of the necessary 
evidence which would be afforded by the ex- 
amination of the pregnant uterus in each genus, 
and by the absence of information as to their 
respective periods of gestation, and the powers 
of the new-born foetus. As far, however, as a 
conclusion can be drawn from the relative pe- 
riods of gestation in the Kangaroo and Opos- 
sum, the proportionate capacities of the vagine 
to the uteri would appear to be greater as gesta- 
tion is shorter; the vagine being thus calculated 
to present fewer obstacles to the escape of the 
foetus in proportion to the duration of its uterine 
existence ; and, consequently, a less capacious 
and complete external pouch is requisite for its 
ultimate perfection. From Rengger’s descrip- 
tion of the connexion of the foetal Opossum to 
the uterus, it might be concluded that the gene- 
ration in that animal approximated to the true 
viviparous mode more nearly than it does in the 
Kangaroo; but the determination of this inte- 
resting question will require a more exact inves- 
tigation into the nature of the feetal vessels and 
membranes in the genus Didelphys. The im- 
pregnated uteri of the smaller pouchless Opos- 
sums of South America would be objects of 
peculiar interest and value in the present state 
of the inquiry. 

With respect to the variations of structure 
in the marsupial female organs, it may also be 
remarked, that though they are apparently 
most complicated in the Kangaroos and Pha- 
langers, yet in reality they deviate from the 
type of the normal Mammalia in a minor de- 
gree in these Marsupialia than in the Didel- 
phides and Petauri. For, the essential differ- 
ence being a division of the vagina into two 
canals, we find this bipartition to be most com- 
plete in the multiparous genera, while in the 
Kangarovs the division is only partial, and the 
complexity arises from augmented capacity and 
extent. It is to be observed, however, that the 
bipartition of the vaginal canal in the Kanga- 
roos is not continued from the uterus into the va- 
gina, leaving its distal extremity single, but com- 
mences at the urethro-sexual cavity, and is 
arrested near the uteri, the orifices of which thus 
open into a common canal. 

The situation of the rudimentary vaginal 
septum or hymen in the unimpregnated female 
organs of the placental Mammalia before men- 
tioned, corresponds with this formation in the 
Kangaroo; and in a case where this septum 
was preternaturally developed in the human 
subject, it was found to obey the same law of 


318 


formation, and at the same time to have been 
coincident with a completely divided uterus.* 

It is not unusual to find the vagine of the 
Kangaroo distended with a gelatino-mucous 
adhesive secretion containing hard irregularly 
shaped fibrous masses. One of these bodies, 
which was found in the mesial cul-de-sac of 
a Kangaroo, was described and figured by 
Sir Everard Homet as the vertebral column 
and occipital bone of a fetus; and peal a 
theory of marsupial generation appears to have 
Seaiendh Scene by this belief Professor 
Leuckart,} who found similar bodies in the 
vaginal tubes of a Kangaroo, compares them to 
a mola, or false conception, but observes that 
there was nothing in their structure that would 
permit him to form a conclusion that they were 
parts of a foetus. 

In the Wombat the lining membrane of 
the vaginal culs-de-sac is greatly increased by 
innumerable irregular ruge and papillae, the 
urethro-sexual canal is lined by a thick epi- 
thelium, and its surface is broken into count- 
less oblique ruge and coarse ay eg the 
surface immediately surrounding the urethral 
orifice, which in this as in other Marsupials 
is close to the vaginal orifices, is comparatively 
smooth. 

The clitoris is situated in a preputial recess 
near the outlet of the uro-genital passage : it is 
simple in those marsupials that have a simple 
glans penis, but is bifid in those which have 
the glans divided : and in the Opossum each 
division of the glans clitoridis is grooved. 

Development of the Marsupialia.—Before 
proceeding to detail the present received doc- 
trine of the generation and development of the 
Marsupialia, it may not be unprofitable to take 
a rapid glance at the different opinions that 
have prevailed at different periods respecting this 
interesting and difficult part of their economy. 

The minute size of the young of the Ameri- 
can Opossum when first received in the mar- 
supium, their pendulous attachment to the 
nipples, and perhaps the mode in which the 
nipples themselves are developed, gave rise, 
among the earlier observers, to a notion that 
the young were originally formed by and from 
those parts. 

‘And t this belief was not only current then, as 
now, among the unscientific settlers in the colo- 
nies where the marsupial animals are common, 
but was entertained likewise by the best in- 
formed Naturalists of those times. Thus the 
learned Marcgrave, in his account of the Opos- 
sum, says, when speaking of the marsupial 
pouch, “ Hac bursa ipse uterus est Animalis, 
nam alium non habet, uti ex sectione illius com- 
peri; in hac semen concipitur et catuli forman- 
tur.” § And Piso repeats the assertion more 
strongly. “ Ex reiteratis horum animalium 
sectionibus alium non invenimus uterum preter 


* Dr. Parcell, Philosophical Transactions, vol. 
lxiv. p. 478. 

t Philos. Trans. vol. Ixxxv. p. 228. 

Pi ngiag Archiv fur Physiologie, tom, viii. 


p- 442. 
§ Hist, Rerum Naturalium, Brasil. 1648, 


MARSUPIALIA. 


hanc bursam, in qua semen concipitur et catuli 
Jormantur. Quos deinde quinos vel senos simul — 
circumfert, mobiles, perfectos, sed depiles, adeo=— 
que pertinaciter uberibus affivos, ut a perpetua— 
suctu vix avellantur, antequam permittente — 
matre ad pastum ipsi egrediantur.” * ) 
The assertion that the young grow from the 
pipple was again repeated in to the 
Philander Opossum ( Didelphys Philander) by 
Valentin in his History of Amboyna, and has 
even been revived at a comparatively recent 
period.t Some glimpses of the truth were ob- 
tained, however, before the time of the authors 
who have been a a H 
example, speaks of the generation th 
ri ahhen in the same words in h 
Cuviert sums up the then existing - 
ledge of the subject in the second edition of 
his ‘ Régne Animal.’ “ eT quinosve — 
rit catulos, quos utero conceptos, editosque in 
Mies alvi capacitate quadam, dum adhuc par= 
vuli sunt, claudit ac servat.”§ And Mafieius — 
more particularly describes the attachment of 
the young to thenipple. “ Illud autem mi ; 
in Cerigonibus” (Opossums) “ ex ejus alvo dua 
dependent veluti mantice, in iis catulos cit 
cumfert, et quidem adeo pertinaciter suoquem=_ 
que uberi affixos, ut a perpetuo suctu non 
avellantur, antequam ad pastum ipsi per se 
progredi valeant.” || “ 
Nevertheless, as the uterine gestation is here 
simply alluded to without any detailed obser-_ 
vations in proof of it, the assertion was compara-_ 
tively of little value in a scientific point of vi i ? 
and the gemmiparous theory, sup . 
Macao and Biso, ps bore book a 
valent at the time when Dr. Tyson first turned 
his attention to this subject. 4 
The discovery of the true uterus, recorded 
by that learned and accurate anatomist in the — 
20th volume of the Philosophical Transactions, — 
p- 105, was the first step towards a corre ." 
theory of the generation of the marsupial ani~ 
mals. It necessarily caused him to reject the 
gemmiparous theory, but, as often happens in 
such cases, Tyson was led into the orpene me 
sceptical extreme ; and he was also induced 
doubt the really accurate statements of H 


* De Indie utriusque Re Naturali et Me 
lib. v. c. 24, 1658. * 

t See Geoff. St. Hilaire, in the Journal Ce e~ 
mentaire du Dict. des Sciences Médicales, tom. ii Ay 
p- 193 (1819) : « Si les animaux a bourse nai emt 
aux tétines de leur mére.” 

¢ ‘‘ La premiére de toutes leurs particulari 
est la production prématurée de leurs petits, qi 
naissent dans un état de développement a p pine 
comparable a celui auquel des foetus ordinaires par- 
viennent quelques jours aprés la conception. In- 
capables de mouvement, montrant a peine des — 
germes de membres et d’autres organes extérieures, — 
ces petits s’attachent aux mamelles de leur méreet _ 
y restent fixés jusqu’ace qu’ils se soient dével 
au degré auquels les animaux naissent ordinaire- 
ment. Presque toujours la peau de l’abdomen est 
disposée en forme de poche autour de ces mamelles, 
et ces petits si imparfaits y, sont préservés, comme — 
dans une seconde matrice.” Régne Animal, 1829, 
vol. i. p. 172. 

i Hist. Mexican. lib. ix. p. 330. 

| Joh. Petr, Maffeius, Hist. Indica, 


MARSUPIALIA. 


nandez and Maffeius respecting the function of 
the marsupial pouch; “ for,” says Tyson, 
“here I find they place the mammez or teats, 
and they tell very odd stories about it,” &c. 

The female Opossum which Tyson dissected 
appears to have been a young one, and there- 
fore, for a reason which has lately been clearly 
explained by Mr. Morgan, he was unable to 
detect thenipples within the pouch, and although 
he confesses that he was equally unable to find 
them upon the outer skin, he rejected the state- 
ments respecting the premature birth of the 
young and their pendulous attachment to the 
nipple, and, believing the generation of the 
Opossum not to deviate from that of ordinary 
quadrupeds, he limited the function of the 
marsupium to that of affording a temporary 
shelter to the young in time of danger. 

assertions of Hernandez and Maffeius 
were soon, however, corroborated by other ob- 
servers; and Daubenton* repeated and con- 
firmed the dissections of Tyson, so far as re- 
garded the existence and general form of the 
uterus; but no satisfactory explanation was 
offered as to the nature or precise period of the 
uterine development or of the passage of the 
young to the marsupium. 

The next really important advance towards 
the solution of this problem was made by 
John Hunter, who in the dissection of some 
marsupial foetuses of the Kangaroo detected 
evidences of a deviation from the ordinary 
mode of mammiferous development, fn the ab- 
sence of the usual traces of a placental organi- 
zation ; there being in these fetuses no per- 
ceptible remains either of an urachus, of umbi- 
lical arteries, or of an umbilical vein. The 
beautiful series of preparations+ exhibiting these 
and other interesting facts in the structure of 
the mammary t foetus of the Kangaroo are pre- 
served in the Museum of the Royal College of 
Surgeons, and afforded the principal materials 
for the paper on Marsupial Generation, pub- 
lished by Mr. (afterwards Sir Everard) Home, 
in the 85th vol. of the Philosophical-Transac- 
tions (1795). I have already shewn that one 
of the chief grounds of the theory of marsupial 
generation there | agree is untenable, the sup- 
posed remains of the foetus,§ described as being 
situated in the corpus uteri, (vaginal cul-de-sac,) 
being nothing more than a portion of the inspis- 
sated secretion commonly present both in this 
sac and the lateral canals. The temporary ori- 
fice by which the fcetus is stated to pass imme- 
diately from the so called corpus uteri into the 
vagina (uro-genital passage) does not exist. 

In the subsequent theory of marsupial gene- 


* Buffon, Hist. Naturelle, vol. x. 

+ See Nos. 3758-3777, Physiol. Catal. vol. v. 
¢ I adopt this termfrom M. de Blainville, in 
preference to the term ‘ marsupial’ previously pro- 
posed by Dr. Barton, to express the condition of the 
young of the Marsupialia from the time they enter 
the pouch to that of quitting the nipple, or to the 
close of the period of their uninterrupted attach- 
ment to the nipple. 

§ No. 3460 F. Physiol. Series, Mus, R. Coll. 
of Surgeons, 


319 


ration propounded by Sir Everard Home,* the 
‘ cornua uteri’ of Tyson are regarded as por- 
tions of the Fallopian tubes. These he believes 
to furnish the yelk of the ovum, while the lateral 
canals, ‘ uteri reduplicati’ of Tyson, secrete the 
albumen ; the ovum is supposed to be impreg- 
nated and incubated in the uterus, (middle cul- 
de-sac formed by the communication of the two 
vaginal canals,) out of which the young one is 
Stated to pass into the vagina (uro-genital pas- 
sage) by a particular opening, which prior to 
gestation does not exist. 

The only observations published by John 
Hunter himself relative to marsupial genera- 
tion are contained in the ‘ Zoological Appendix 
to White’s Voyage to New South Wales,’ 
where, in the introduction to his descriptions 
of the quadrupeds of that country, Mr. Hunter 
alludes to the American Opossum, and ob- 
serves, “there is something in the mode of 
propagation in this animal that deviates from 
all others ; and though known in some degree 
to be extraordinary, yet it has never been at- 
tempted, where opportunity offered, to com- 
plete the investigation. I have often endea- 
voured to breed them in England; I have 
bought a great many, and my friends have 
assisted me by bringing them or sending them 
alive, yet never could get them to breed; and 
although possessed of a great many facts re- 
specting them, I do not believe my information 
is sufficient to complete the system of propaga- 
tion in this class.” 

At this period, when it was admitted on all 
hands that some remarkable peculiarities were 
connected with the marsupial generation, and 
yet their precise nature and signification re- 
mained unelucidated by any direct and accu- 
rate observation or experiment, it is not sur- 
prising that the subject should have given rise 
to many curious hypotheses and speculations ; 
those of Sir Everard Home have already been 
noticed. I shall next briefly allude to the 
writings of M. Geoffroy St. Hilaire. 

The fruitful and discriminating labours of 
this talented Naturalist in advancing the zoolo- 
gical history of the Marsupialia cannot be too 
highly esteemed, but his attempts to elucidate 
their generative economy have been less suc- 
cessful. 

Placing an undue reliance on the relation of 
Count Aboville,t he first revived the gem- 
miparous doctrine,t meeting the objection 
afforded by Tyson’s discovery of an uterus, by 
the remark that the fetus of the marsupial 
animal has never been found there; but that 
the teats are developed in the ratio of the size 
and according to the number of the young: 
that mules equally possess a generative appa- 
ratus, which is stricken with sterility: that 
some plants with a perfect system of procrea- 
tive organs, nevertheless propagate by gemma- 


* Philos. Trans. 1819, p. 234, and Lectures on 
Comparative Anatomy, vol. iii. 

+ See the note at the end of the 2d volume of 
€ Chastelleux Voyage a l’Amerique Septentrionale, 
Paris, 1786.’ 4 

¢ Journal Complementaire du Dict. des Sciences 
Médicales, 1819. 


320 


tion, &e. This theory, however, was aban- 
doned, or at least considerably modified after 
the publication of Dr. Barton’s letters relative 
to the breeding of the Opossum. The product 
of marsupial generation is then stated by M. 
Geoffroy to quit the uterus in the condition ofa 
gelatinous ovulum, comparable toa Medusa, and 
to become organically connected with the nipple 
by cme of vessels. He sup , there- 
fore, that a flow of blood followed the detach- 
ment of the mammary foetus from the nipple,* 
and even speculates upon the signification of 
the thyroid gland, on the strength of this hypo- 
thetical confluence of the maternal and fetal 
vascular systems in the marsupial tribe. + 

In Sinother essay M. Geoffroy abandons this 

inion, it having been proved by repeated 
° tion that the adhesion of the foetus to 
the nipple is by simple contact merely ;{ and 
finally, he falls into the opposite extreme, and 
from some appearances of an urachus which 
were pointed out to him in a very small foetus 
of an American Opossum, he describes them 
as vestiges of a placental organization. 

Mr. Brocyui:t in his elaborate and excellent 
Memoirs on the Structure and Development of 
the Mammary Organs of the Kangaroo, bears 
testimony to the simply mechanical mode of 
attachment between the mammary fetus and 
the nipple in the Kangaroo, and was the first 
to show that the young animal, in its blind 
and naked condition, prior to the act of volun- 
tary detachment,—the birth ‘ a la manitre des 
Marsupiaux,’ as it is called by M. Geoffroy,— 
would bear a separation from the nipple for 
two hours, and voluntarily regain its hold. The 
mammary fetus of the Kangaroo on which Mr. 
Morgan experimented was nearly the size of a 
fully grown Norway rat. Mr. Collie, surgeon 
R.N. in a letter addressed from New South 
Wales, and published in the Zoological Journal, 
(No. xviir. p. 239,) obtained the same result 
in detaching from the nipple of a smaller 
species of Kangaroo (Macropus Brunii) a 
mammary foetus, not two inches in length: he 
says, “I gently pressed with the tip of my 
finger the head of the little one away fist the 
teat of which it had hold, and continuing press- 
ing a little more strongly for the space of a 
minute altogether, when the teat which had 
been stretched to more than an inch came out 
of the young one’s mouth, and showed a small 
circular enlargement at its tip, well adapting it 
for being retained by the mouth of the sucker.” 


- Gockvey St. Hilaire, in detailing some observa- 
tions on a Kangaroo in the ‘ Annales des Sciences,’ 
observes, “ car le sang apergu 4 la litiére est un 
indice qu’a ce moment le foetus s’est detaché de la 
tetine et qu’il est né définitivement ala maniére des 
marsupiaux.” Vol. ix. p.342, 1827. 

t “* Des vaisseaux nourriciers se repandroient-ils 
des parties du pharynx le long et entre les lames de 
la trachée artére pour entrer fe ceeur, et (conjectare 
de M. Serres) le gland thyroide seroit-il le point 
de lear reunion?” Geoff. St. Hilaire, Mémoires du 
Muséum, tom. xix. p. 406, 1822. 

¢ Art. Marsupiaux, Dict. des Sciences Nat. tom. 
xix. 1823. 

§ Transactions of the Linnwan Society, vol. xvi. 
pp. 61, 455, 


MARSUPIALIA. 


—* An hour afterwards the young was ob- 
served still unattached, but in about two hours 
it had hold of the teat, and was actively em- 
pit sucking.” : — 
r. Barton’s very interesting observations on 
the American Opossum are as follows : the: 
female Didelphis Woapink sometimes produces — 
sixteen young ones at a birth. I have actually 
seen this number attached to the teats, but 
never a greater number. When they are first 
excluded from the uterus, they are not only 
very small but very obscurely shaped. The 
place of the future eyes is merely marked b: 
two pale bluish specks; we see no ears; it 
short the animal is a mere mis-shaped embryon. 
Its mouth, which is afterwards to become ve 
large, is at first a minute hole, nearly of a trian- 
gular form, and just of a sufficient size to” 
receive the teat, to which the little creature 
adheres so firmly, that it is scarcely matter of 
surprise that Beverly* and other writers have 
asserted that the young grow fast to the teats. 

“ Tt is not true that the young cannot 
detached from the mother without the loss of 
blood ; I can assert the contrary from many ex- 
periments made upon embryons weighing nine 
grains and upwards. I have fully satisfied 
myself as to all the various circumstances, both 
in the structure and in the exertions of the — 
minute animal, which enable it, while yet a 
mere speck of living matter, to cling so firmly — 
to the fountain of its support. ‘ 

¥ The wonderful little Didelphis is 
by no means the inanimate or the passive being 


~ 


some physiologists and naturalists have repre- 
sented it.t ‘a 
“ The toes of the ne of ve new born 
embryon opossum are furnished with sharp and 
hard waite of claws, but this is not the case 
with the hind-feet. The latter are for some 
weeks of little use to the animal; but by means 
of the former it is enabled to cling most firmly 
to the teat, and especially to the hair in the 
marsupium immediately around the teat. 
An opossum-embryon, or fetus, which 
weighed sixty-seven grains, lived upwards of 
thirty hours after I had detached it from the 
teat. Another which weighed 116 lived thirty. 
eight hours, at which time I killed it by putting 
it in spirits. , 
“* Superfcetation (I should perhaps in st 
propriety say uterine superfcetation) is wholly 
incompatible with the established laws of the 
economy of the Didelphis. But Nature, always 
provident, wastes no time. While, therefore, 
the first litter of young opossums are fast ai 
proaching to their adult state, the mother ac 
cepts the ardour of the male; she is impreg 
nated ; and after a gestation which is not, — 
think, remarkably short, if we consider 
small size of the embryons when they are 
cluded from the uterus, the marsupium is d 
tined to perform the office of a second, I was 
going to say a more important, uterus; just at 
the time when the first litter have attained su 
a size that they are no longer (one or two 0 


* History of Virginia, p. 136, 1722. 
t Pennant, Arctic Zool, i, p. 84. 


MARSUPIALIA. 


them at the utmost) capable of taking refuge in 
her pouch.” * 

Besides the satisfactory evidence, thus afforded 
by different and independent observers, respect- 
ing the condition of the mammary foetus and its 
true relations to the nipple, the discovery of the 
uterine foetus was announced nearly at the 
same time by two naturalists in two different 
species of marsupial animals. Mr. Collie, 
whose experiment on the young mammary 
feetus of a Kangaroo has just been quoted, 
States in the same letter, “I have just now 
procured two gravid uteri, (of the Macro- 
pus Brunii,) in which fetuses seem to be 
arrived at, or very near to, the termination of 
the period of gestation. One of them, which 
is about the size of the smallest young already 
mentioned, which was about one-half larger 
than the body of the common wasp, as being 
in the abdominal sac, has protruded through 
an Opening inadvertently made in the uterus, 
and is distinctly seen through its transparent 
membranes and the liquor amnii.”+ About the 
same time Dr. Rengger, a naturalist who was 
detained several years by the Dictator Francia 
in Paraguay, gave the following account of the 
generation of a species of Opossum ( Didelphis 
Azare@) in his work on the Mammalia of that 
province. ‘ The foetuses are developed in the 
cornua uteri, and not in the lateral canals. 
Some days after impregnation they have the 
form of small round gelatinous corpuscles, 
which do not appear, even when examined 
with a lens, to have any communication with 
the mother, but a red line indicates the first 
commencement of development. Towards the 
end of gestation, when the foetuses have attained 
the length of six lines, they are seen to be en- 
veloped in a membrane and provided with an 
umbilical chord, which is united to the uterus 
by the medium of many filaments. The head, 
the four extremities, and tail are recognizable 
with the naked eye, but those foetuses which 
are nearest the Fallopian tubes are generally least 
advanced. “In gestation they make the circuit of 
the lateral canals, in which they are found to be 
deprived of their foetal envelopes, and to have 
no communication with the parent by means of 
the umbilical chord; whilst one foetus was 
found in this situation, two others were still in 
the body of the uterus (vaginal cul-de-sac), 
from which the umbilical chords were not yet 
detached, At this period a slight enlargement 
of the cul-de-sac and lateral canals was the 
only change perceptible in them.” f 

Thus, by the various observations derived 
from the different sources above indicated, the 
following propositions are satisfactorily esta- 
blished, viz. that the young of the Marsu- 
pialia are developed, primarily, as Tyson con- 
jectured, in the true uteri or cornua uteri; but 
that, contrary to Tyson’s opinion, they are, as 


* Barton, ‘ Facts, Observations, and Conjectures 
relative to the Generation of the Opossum.’ Annals 
of Philosophy, vol. vi. 1823, p. 349. 

+ Zoological Journal, vol. v. p. 240. 

t From the Analysis of Rengger’s “ Saugethiere 
von Paraguay” in the Bulletin des Sciences Nat. 
tom. xxi. p. 469. 

VOL, II}. 


321 


compared with other Mammalia, prematurely 
born; and that, nevertheless, the attachment 
of the immature young to the nipple is essen- 
tially the same as in ordinary mammals, the 
young marsupial being nourished by the lac- 
teal secretion, and its blood aerated by its own 
independent respiratory actions. 

Such, therefore, being the condition of the 
problem of marsupial generation in the year 
1830, there remained to be determined by exact 
experiment and observation the period of uterine 
gestation, the structure of the fetal envelopes 
and appendages, the nature of the connection, 
if any, between the uterine foetus and the 
womb, the manner of the uterine birth, and the 
condition and powers of the new-born young. 

With a view to the solution of these ques- 
tions, I applied for and obtained from the 
Council of the Zoological Society permission to 
perform the requisite experiments on the Kan- 
garoos in the menagerie in Regent’s Park. A 
healthy female ( Macropus major, Shaw) was 
separated from the rest; she had a young one 
which measured about one foot two inches from 
the nose to the root of the tail, and which 
continued to return to the pouch for the purpose 
of sucking and for shelter. The right superior 
nipple was the one in use; it was nearly two 
inches long, and one-third of an inch in dia- 
meter; the mammary gland formed a large 
swelling atits base. The other three nipples 
were everted, and about half-an-inch in length. 

A healthy full-grown male was admitted into 
the paddock with this female for a certain 
period each day, and watched, during that 
time, by the keeper or myself. In the course 
of a week the female seemed to be in a con- 
dition to excite the sexual ardour, and after 
a few days toying on the part of the male, she 
received his embrace on the 27th August, at 
1 p.m. The female stood with her fore-paws 
off the ground, the male mounted, ‘ more 
canino,’ embracing her neck with his fore-paws, 
and retained his hold during a full quarter of 
an hour; during this period the coitus was 
repeated three times, and on the second occas 
sion much fluid escaped from the vulva. The 
male was removed from the female in the 
evening of the same day, and was not after- 
wards admitted to her. On September the 2d, 
six days after the coitus, I examined the pouch 
of the female, and this scrutiny was repeated 
every morning and eyening until the birth of 
the young kangaroo had taken place. I select 
the following from the notes taken on those 
occasions ;— 

“ Sept. 6th.—10th day of gestation. The 
pouch is nearly free from its peculiar brown 
musky secretion. The right superior nipple 
retains its large size, and the young one that 
has left the pouch returns occasionally to suck. 

“ Sept. 11th—15th day of gestation. No 
appearance of a mammary fetus; nipples in 
the same condition ; the young kangaroo con 
tinues to suck and return to the pouch for 
shelter. c 

“ Sept, 30th—34th day. The nipple in 
use by the young kangaroo (which has died) is 
diminished in size, and the brown secretion 

¥ 


322 


has n to be formed. 5 the foetus 
seize the larger nipple as the readiest, or be 
directed to another more proportionate to the 
size of its mouth ? 

“ Oct. 4th.—38th day. The keeper has 
observed the female putting her nose into the 
pouch, and licking the entry. She was exa- 
mined at six in the evening ; there was a slight 
increase of the brown secretion; the nipple 
formerly in use has diminished one-third in 
size ; the other nipples indicate no appearance 
of approaching parturition. 

“ Oct. 5th.—39th day. The keeper exa- 
mined the pouch at seven this morning, and 
found there the young one attached to a — 
On being made acquainted with this fact I re- 
paired to the Zoological Gardens, and examined 
the pouch. The new-born kangaroo (fig. 140) 
was attached to the left superior nipple (fig. 140, 
a), to the point of which it adhered pretty 


Fig. 140. 


New-born fetus and left nipples, Macropus major. 
firmly. It measured one inch from the mouth 
to the root of the tail, was quite naked, and co- 
vered by a thin semitransparent vascular integu- 
ment; the place of attachment of the umbilical 
chord was obscurely indicated by a longitudinal 
linear cicatrix. The fore-legs were longer and 
stronger than the hind ones, and the digits were 
provided with claws; the toes were developed 
on the hind legs; the body was bent forward ; 
and the short tail tucked in between the hind 
legs. This little animal breathed strongly, 
but slowly ; no direct act of sucking could be 
perceived. Such, after a gestation of thirty- 
eight days, is the condition of the new-born 
young of a species of Kangaroo, of which the 
adult, when standing erect on his hind feet and 
tail, can reach to the height of seven feet. The 
birth having taken place in the night, the mode 
of transference of the young to the pouch and 
nipple was not observed. 

e hypothesis of an internal passage from 
‘the uterus to the pouch—countenanced by 
some 9K anatomical observations on the 
course of the round ligament to the abdominal 
ring, and the continuation thence of the cre- 
master to the posterior part of the mammary 
gland, together with the primitive inverted 
condition of the nipple—is wholly refuted by 
‘more exact observations of the conditions of 
these I was chagrined at the loss of so 
favourable an opportunity of determining, er 
visu, this interesting part of the problem ; for 
it had been my intention, if the symptoms of 
ap hing pregnancy had been more marked, 
to have established a night as well as day-watch 
ever the female; but by placing perhaps too 


MARSUPIALIA. 


much reliance on the observations on the preg- 
nant kangaroo recorded in the 9th volume of the 
Annales des Sciences, in which the duration 
of four months is assigned to the uterine gesta- 
tion of this species, 1 had not anticipated sc 
speedy a termination of that process as resulter 
from my experiment. ts 

In order, however, to remedy, as far as might 
be, this omission, it occurred to me that if the 
young kangaroo were detached from the nipple 
and deposited at the bottom of the pouch, any 
actions of the parent, by which its origin 
transference from the uterus to the nipple had 
been aided or effected, might be instinctively 
repeated, and thus an insight be gained into 
their nature. As, therefore, the experiments of 
Messrs, Morgan and Collie seemed to show tha 
this might be done without necessarily causin 
the death of the young one, I rmed_ the 
experiment with the sanction and assistance ¢ 
Mr. Bennett, then Secretary of the 
Society. 

“ Oct. 9th.—I examined the pouch of the 
female, and found the young one, now 
days old, evidently grown, and respiring vige 
rously ; it adhered more firmly to the nipple 
than was expected, requiring a ue 
gentle pressure to detach it: when that took 
place, a minute drop of whitish fluid, a kim 
of serous milk, was expressed from the nipple. 
No blood followed, nor anything to indicat 
a solution of organic continuity; the extremit 
of the nipple was small, not swollen as in Mr, 
Collie’s case. The young one moved its extre 
mities vigorously. It was deposited at the bo 
tom of the pouch, and the mother was left and - 
then carefully watched. Soon after this 
done she seemed uneasy, was often scratching 
the exterior of the pouch, and every now 
and then dilated the cavity with her two fo 
paws, grasping the sides of the aperture, an 
pulling them in contrary directions, just as it 
drawing open a bag; she then inserted he 
muzzle prey deeply into the pouch, movin 
her head about as if to lick off something fro 
the interior, or perhaps to move the little one 
She kept her nose in the pouch sometimes 
half-a-minute. I never observed her to pt 
~ fore-legs, or either of them, in the pouch 
they were always occupied in keeping open th 
mouth of the pouch, whale she 7 at wol 
with her mouth within it. She generally cor 
cluded by licking the mouth of the pouel 
and occasionally she stooped down to lick # 
cloaca, which she could reach with ea 
When she scratched the outside of the pouch 
seemed as if to push up something that was it 
side towards the aperture. hi 


pre. 
OOLOPgIC 


LOnUN 


These actions 
repeated at short intervals for about an hou 
she then lay down and appeared quiet. She 
had also lain down in the intervals of the abot 
operation, but during that time never med 
with the pouch ; when stimulated to do so b 
some uneasy sensation, she always rose upot 
her hind feet, and then inserted her muzzl 
alternately into the pouch and vulva. Observin 
the freedom with which she could reach both 
these parts, I was led to believe that the mode 
of removal of the young from. the vulva to th 
fi 


MARSUPIALIA. 


uch was by the mouth of the mother. Her 
fore-paws, in this case, would be used, not 
for the transport of the young, but for keeping 
the mouth of the pouch open for its reception, 
it being deposited therein by the mouth, and so 
held over a nipple until the mother had felt it 
grasping the sensitive extremity of the nipple. 

This means of removal is consistent with 
analogy ; dogs, cats, mice, all transport their 
young from place to place with the mouth. In 
the case of the kangaroo, it may be supposed 
that the foetus would be held by the lips only, 
not the teeth, on account of its delicate con- 
sistence. Whether this theory, suggested by 
witnessing the actions of the mother after an 
artificial separation of the Marsupial fetus, 
be correct, must be confirmed by actual obser- 
vation. There is no internal passage from the 
uterus to the pouch :—the mouth of the vagina 
cannot be brought into contact with that of the 
ian either by muscular contraction in the 
iving or by any force of stretching in the dead 
kangaroo :—as the young was proved by the 
result of this experiment not to have the power 
of itself to regain the nipple, @ fortiori we 
may conclude that it could not transfer itself 
from the vulva to the interior of the pouch and 
to the apex of the nipple :—the fore-paws of 
the Kangaroo would not so effectually protect 
the tender embryo from the external air as the 
mouth, nor so safely ensure its passage to the 
pouch, notwithstanding that they are adroitly 
used in grasping objects, being similar, in 
respect of the extent and freedom of motion of 
the digits, to the fore-paws of the Rodents. 

After the mother had rested quietly for a 
short time, we again examined her, but found 
the young one still detached, moving more 
vigorously than before. On an examination 
two days afterwards the marsupium was found 
empty: the young one had died and had pro- 
bably been removed by the mother. 

Thus the period of uterine gestation, the 
condition of the new-born young, and the pro- 
bable mode of its transference to the nipple 
being determined in the genus Macropus, it 
next remained to be determined how the embryo 
was nourished in utero. The means of giving 
the required solution were shortly after afforded 
by specimens of the impregnated uterus, trans- 
mitted to me by Mr. George Bennett, Captain 
Grey, and Dr. Sweatman. The first was of the 
Macropus major, nearly two-thirds of uterine 
gestation having been completed ; the second 
was of the Macropus penicillatus, at about the 
same or somewhat earlier period of gestation ; 
the third exhibited the uterine foetus at nearly 
the completion of that period of its existence. 

Before, however, giving the summary of what 
I have elsewhere* recorded respecting the 
uterine development of the Marsupialia, a de- 


scription of the ovarian ovum must be pre-. 


mised. 

In the Kangaroo this part agrees in all essen- 
tial points with the observed ovarian ova of 
placental Mammalia: the main moditication 


* Proceedings of the Zool. Society, 1833, Philos. 
Trans. 1834. 


323 


is the greater proportion of vitelline fluid and 
globules, and the smaller proportion of fluid 
between the external membrane of the ovum 
(vitelline membrane) and the ovarian vesicle, 
or lining membrane of the ovisac. 

Ina female Macropus Parryi, the ovum from 
the largest ovisac of the left ovarium measured 
wth of a line in diameter, the germinal vesicle 
risth of a line in diameter. 

We are at present ignorant of the changes that 
take place in the development of the ovum 
between the period of impregnation until about 
the twentieth day of uterine gestation. At this 
time, in the great Kangaroo ( Macropus major ), 
the uterine fetus (fig.138) measures eight 
lines from the mouth to the root of the tail; 
the mouth is widely open (fig. 141); the 
tongue large and protruded; the nostrils are 
small round apertures; the eyeball not yet 
wholly defended by the palpebral folds; the 
meatus auditorius externus is not provided with 
an auricle; the fore-extremities are the largest 
and strongest ; they are each terminated by five 
well-marked digits ; those of the hind legs are 
not yet developed; the cervical fold of the 
mucous layer or the branchial fissure is still 
unenclosed by the integument. The tail is 
two lines long, thick and strong at the com- 
mencement; impressions of the ribs are visi- 
ble at the sides of the body; the membranous 
tube of the spinal marrow may be traced 
along the back between the ununited elements 
of the vertebral arches ; posterior to the um- 
bilical chord there is a small projecting penis, 
and behind that, on the same prominence, 
is the anus. This foetus and its appen- 
dages were enveloped in a large chorion, 
puckered up into numerous folds, some of 
which were insinuated between folds of the 
vascular lining membrane of the uterus, but 
the greater portion was collected into a 
wrinkled mass. _ The entire ovum was re- 
moved without any opposition from a placental 
or villous adhesion to the uterus. The chorion 
(a, a, fig. 141) was extremely thin and lacera- 
ble; and upon carefully examining its whole 
outer surface, no trace of villi or of vessels 
could be perceived. Detached portions were 
then placed in the field of a microscope, but 
without the slightest evidence of vascularity 
being discernible. The next membrane, whose 
nature and limits will be presently described, 
was seen extending from the umbilicus to the 
inner surface of the chorion, and was highly 
vascular. The foetus was immediately enve- 
loped in a transparent amnios. 

On turning the chorion away from the foetus, 
it was found to adhere to the vascular mem- 
brane above-mentioned, into w the um- 
bilical stem suddenly expanded. With a slight 
effort, however, the two membranes could be 
separated from each other, without laceration, 
for the extent of an inch; but at this distance 
from the umbilicus the chorion gave way on 
every attempt to detach it from the internal 
vascular membrane, which here was plainly 
seen to terminate in a well-defined ridge, formed 
by the trunk of a bloodvessel. 

When the whole of the vascular membrane 

¥ 2 


324 


/ Wilplrr : 
"N . 
Mena) PAU? 


WG Sas 
~ 
SQ.“ 
ae a TP 
ANT 


Uterine fatus with chorion and foetal appendages, Macropus major. The foetus is magnified twice the 


b, fig. 141) was spread out, its figure a 

0, 46 to have Sank’ shit of a cone, oF which 
the apex was the umbilical chord, and the 
base the terminal vessel above-mentioned. 
Three vessels could be distinguished diverging 
from the umbilical chord and ramifying over it. 
Two of these trunks contained coagulated 
blood, and were the immediate continuations 
of the terminal or marginal vessel: the third 
was smaller, empty, and evidently the arterial 


trunk. ides the extremely numerous rami- 
fications diSpersed over this membrane, it dif- 
fered from chorion in being of a yellowish 


tint. Theamnios (c, 141) was reflected from 
the umbilical chord, and formed, as usual, the 
immediate investment of the foetus. 

The umbilical chord measured two lines in 
length and one in diameter. It was found to 
contain the three vessels above-mentioned, with 
a small loop of intestine; and from the ex- 
tremity of the latter a filamentary process was 
continued to the vascular membrane. The 


MARSUPIALIA. 


margins of the umbilicus or abdominal ope 
ing were very strong, offering much resistang 
to their division. On tracing the contents” 
the chord into the abdomen, the two le 
vessels with coagulated blood were found - 
unite; the common trunk then be 
wards beneath the duodenum, and after be 
joined by the mesenteric vein, went to t 
under surface of the liver, where it penetrat 
that viscus: this was consequently an omph 

mesenteric or vitelline vein. e artery | 
a branch of the mesenteric. The membra 
therefore, upon which they ramified, answer 
to the vitellicle, i. e. the vascular and m 
cous layers of the germinal membrane, whic 
spreads over the yolk in ovi nimi 
and which constitutes the umbilical vesicle 
the embryo of ordi Mammalia. The | 

mentary pedicle which connected this men 
brane to the intestine was given off near t 
end of the ileum, and not continued from | 
cecum, the rudiment of which was very e\ 


~ 


MARSUPIALIA. 


dent half a line below the origin of the pedicle. 
(See the foetus in fig. 141.) 

The small intestine above the pedicle was 
disposed in five folds. The first from the 
stomach or duodenum curved over the vitel- 
line vein, and the remaining folds were dis- 
posed around both the vitelline vessels. From 
the cecum, which was given off from the re- 
turning portion of the umbilical loop of the 
intestine, the large intestine passed backwards 
to the spine, and was then bent, at a right angle, 
togo straight down to the anus. The stomach did 
not present any appearance of the sacculated 
structure so remarkable in the adult, but had 
the simple form of a carnivorous stomach. 
The liver consisted of two equal and symme- 
trically disposed lobes. The vena porte was 
formed by the union of the vitelline with the 
mesenteric, and doubtless the other usual veins, 
which were, however, too small to be distinctly 
perceived. The diaphragm was perfectly 
formed. 

The vena cava inferior was joined, above 
the diaphragm, by the left superior cava, just 
at its termination in a large right auricle. The 
ventricles of the heart were completely joined 
together, and bore the same proportions to each 
other as in the adult,—a perfection of structure 
which is not observed in the embryos of ordi- 
nary Mammalia at a corresponding period of 
development. The pulmonary artery and 
aorta were of nearly the same proportionate 
size as in the adult: the divisions of the pul- 
monary artery to the lungs were at least double 
the size of those observable in the embryo of a 
sheep three inches in length. The ductus 
arteriosus, on the contrary, was remarkably 
small. The aorta, prior to forming the de- 
scending trunk, dilated intoa bulb, from which 
te carotid and subclavian arteries were given 
off. 

The lungs were of equal size with the heart, 
being about a line in length, and nearly the 
same in breadth: they were of a spongy tex- 
ture and of a red colour, like the veins, from 
the quantity of blood they contained. This 
precocious development of the thoracic viscera 
is an evident provision for the early or prema- 
ture exercise of the lungs as respiratory organs 
in this animal: and on account of the simple 
condition of the alimentary canal, the chest 
at this period exceeds the abdomen in size. 

The kidneys had the same form and situ- 
ation as in the adult. The supra-renal glands 
were half the size of the kidneys. 

The testes were situated below the kidneys, 
and were one-half larger than those glands, the 
superiority of size depending on their large 
epididymis, with the adherent remains of the 
Wolffian body. They continue within the ab- 
domen for six weeks after uterine birth. 

At a later period of uterine development, 
when the fetus, measured in a straight line 
from the mouth to the root of the tail, is ten 
lines in length, the urachus expands into a small 
allantois (d, fig. 141), of a flattened pyriform 
figure,and finely wrinkled external surface. This 
bag insinuates itself between the amnios and 
chorion, carrying along with it two small hypo- 


325 


gastric arteries and an umbilical vein, but not 
establishing by their means an organized and 
vascular surface of the chorion by which a 
placental attachment is formed between the 
ovum and the womb. The allantois depends 
freely from the end of the umbilical chord, 
and has no connexion at any part of its cir- 
cumference with the adjoining membrane. Its 
office is apparently that of a receptacle of 
urine. 

The vitellicle or umbilical sac presented the 
same large proportionate size and vascular 
structure as in the first described foetus. The 
chorion which enveloped this foetus and its 
appended sacs was adapted to the cavity of the 
uterus by being disposed in innumerable folds 
and wrinkles. It did not adhere at any part 
of its surface to the uterus, but presented a 
modification not present in the chorion of the 
earlier foetus, in being partially organized by the 
extension of the omphalo-mesenteric vessels 
upon it from the adherent vitellicle. The di- 
gits of the hind legs were distinctly formed in 
this embryo. 

The new-born foetus of the great Kangaroo 
does not exceed, as we have already shown, 
one inch in length; its external characters have 
been already described. Dr. Barton has given 
the following account of the Opossum ( Didel- 
phys Virginiana) at an analogous period. 
*¢ I have been so fortunate as to ascertain the 
size and weight of several embryos imme- 
diately after their exclusion from the uterus. 
One of them weighed only one grain! The 
weight of each of the six other young ones 
was but little more than this. The young 
opossums, unformed and perfectly sightless as 
they are at this period, find their way to the 
teats by the power of an invariable, a deter- 
minate instinct” (qu.?), In this new domi- 
cilium they continue for about fifty days, that 
is, until they attain the size of a common 
mouse (Mus musculus), when they begin to 
leave the teats occasionally, but return to them 
again until they are nearly the size of rats. 

“ At the end of about fifty or fifty-two days 
from its first reception in the pouch the eyes of 
the young begin to open. 

“ T have found that the same embryon has 
increased in weight 531 grains in sixty days, 
that is, at a rate of almost 9 grains daily. The 
animal attains to nearly its full growth in about 
five months; but never, I believe, (in our lati- 
tudes 1 mean,) procreates the first year of its 
existence. : 

-“ On the 21st of May, upon looking into 
the box which contained the female Opossum, 
I found that she had just excluded from her 
uterus seven embryons; the smallest of which 
scarcely weighed one grain, another barely two 
grains, and the remaining five (taken together) 
exactly seven grains.” * 

In the Kangaroo about ten months elapse 
before the mammary fetus quits the pouch: 
it has, prior to this period, quitted the nipple, 


* Barton, in Annals of Philosophy, vi. (1823), 
p. 349. <« Facts, Observations, and Conjectures relative 
to the Generation of the Opossum.” 


326 


and occasionally protrudes its head and changes 
its position in the pouch. 
anatomical condition and progressive 
development of the rm foetus of the 
Marsupialia offer a subject of highly interest- 
ing research, especially if com with the 
same circumstances in the uterine feetus of an 
se sized and analogous placental aa 
uch still remains to be done in this chapter 
of the history of Marsupial generation; at 
present J have to offer the following obser- 
vations, 

By comparing the new-born Kangaroo with 
a similarly sized foetus of a sheep, we find that, 
although, in the Kangaroo, the ordinary laws 
of development have been adhered to in the 
more advanced condition of the anterior part 
of the body and corresponding extremities, yet 
that the brain does not present so dispropor- 
tionate a size; and the same difference is ob- 
servable in the uterine fcetus of the Kangaroo, 
even when compared with the same sized em- 
bryo of an animal of an inferior class, as the 
bird. This difference, I apprehend, is owing 
to the rapidity with which the heart and lungs 
acquire their adult structure in the Kangaroo, 
whereby the passage of the purer and more 
nutritious blood through the foramen ovale and 
left auricle to the primary branches of the 
aorta and so to the brain is impeded. The 
brain, however, of the mammary fetus, though 
exhibiting a low degree of development, yet is 
of a firmer texture than in a similarly sized 
foetus of a sheep, and attains its ultimate pro- 
portion by a more gradual process of growth. 

In a mammary fetus, one inch and a half 
in length, the urinary bladder is largely deve- 
loped, and adheres by its apex to the perito- 
neum, exactly opposite that part of the abdo- 
minal integument where a small linear ridge 
indicated the previous attachment to the umbi- 
lical chord and appendage. There are also 
minute but distinct traces of umbilical arteries 
running up the sides of the bladder to this point 
of attachment. As the urinary bladder be- 
comes afterwards expanded in the abdomen, 
the peritoneum is gradually, as it were, drawn 
from this part of Ke wudowinal ietes, form- 
ing an anterior ligament of the bladder. Ina 
mammary fetus of the Kangaroo about a month 
older than the above, there was at the superior 
= of this duplicature a small projecting point 
rom the bladder, like the remains of a ura- 
chus; but the fundus, now developed con- 
siderably above this point, was covered with 
a perfectly smooth layer of peritoneum; and 
it is this modification, I apprehend, which 
led Hunter to suppose that there was no trace 
of urachus or umbilical arteries in the fetuses 
of the Marsupialia. In the Sloth, the Manis, 
and the Armadillo, the urachus is continued 
in the same manner from the middle of the 
anterior part of the bladder, and not from the 
fundus. 

In neither of the above foetuses of the Kan- 
garoo was there any corresponding trace of 
umbilical vein, although there was a distinct 
ligamentum suspensorium hepatis, formed by 
a duplicature of the peritoneum descending 


MARSUPIALIA. 


from the diaphragm to the notch lodging the 
gall-bladder, and not entering, as usual, th 
fissure to the left of that notch: the allantois is” 
too small, and its function too limited for the 
preservation of any permanent trace of its” 
peculiar vein. NES 
The small intestines in the mammary foetus, 
one inch and a half long, when compared 
with those of the uterine fetus above de- 
scribed, were found to have acquired several 
additional convolutions ; the fold to which the 
umbilical vesicle had been attached was still — 
distinct, but now drawn in to the back of the 
abdomen. The cecum was much elongated, — 
but the colon proportionately not more deve- 
loped than in the uterine fetus; the subse- 
quent modification, therefore, of the large in- 
testines seems evidently destined to com 
the digestion of the vegetable food. t 
The stomach was not sacculated, but the — 
division between the cardiac and middle com- — 
rtments was more marked than in the uterine 
cetus. The liver had now advanced in its 
development beyond the oviparous form which — 
it presented in the uterine fetus, the right lobe © 
being subdivided into three. The su L 
glands bore the same ionate size to the 
kidneys. The testes were still larger than the 
kidneys, and were situated below them, not — 
having yet passed out of the abdomen: this 
takes place when the mammary feetus is about — 
three inches long from the nose to the root of 
the tail. The ductus arteriosus was distinct in 
the small mammary feetus, but I could i 
perceive any trace of the thymus gland. Is — 
this gland unn on account of the pre~— 
cocious development of the lungs? or because 
of the small size and gradual growth of the 
brain? The latter appears the more probable — 
condition of its absence, as in the ovovivipa- 
rous classes with small and simple brains — 
the thymus gland is rudimental or of doubtful 
existence. ita 
Notwithstanding that the new-born Kanga- — 
roo possesses greater powers of action than the — 
same sized embryo of a sheep, and 
mates more nearly in this respect to the ne 
born young of the rat, yet it is evidently in- 
ferior to the latter. For, although it is enabled 
by the muscular power of its lips to grasp and 
adhere firmly to the nipple, it seems to be 
unable to draw sustenance therefrom by it 
own unaided efforts. The mother, as Profes 
Geoffroy and Mr. Morgan have shown, 
therefore provided with the peculiar adapta’ 
of a muscle (analogous to the cremaster) to 
mammary gland, for the evident pose of 
injecting the milk from the nipple into the 
mouth of the adherent fetus. Now it can 
scarcely be supposed that the feetal efforts of 
suction should always be coincident wi 
maternal act of injection; and if at a 
this should not be the case, a fatal ace 
might happen from the milk being foreit 
injected into the larynx, unless that u 
were guarded by some i 
Professor Geoffroy first described the 1 
fication by which this purpose is effected; and — 
Mr. Hunter appears to have anticipated the ne- 


COL 


oe 


MARSUPIALIA. 327 


cessity for such a structure, for he dissected 
two small mammary feetuses of the Kangaroo 
for the especial purpose of showing the rela- 
tion of the larynx to the posterior nares. The 
epiglottis and arytenoid cartilages are elongated 
and approximated, and the rima glottidis ‘is 
thus situated at the apex of a cone-shaped 
Jarynx, (fig. 142, c,) which projects, as in the 
Cetacea, into the posterior nares, where it is 
closely embraced by the muscles of the soft 
palate. The air-passage (6) is thus completely 
Separated from the fauces, and the injected 
milk passes in a divided stream on either side 
the larynx to the esophagus. 


Fig. 142. 


SZ litt 
Md, 


Népple, and head of Mammary Fostus, Kangaroo. 


Thus aided and protected by modifications 
of structure, both in the system of the mother 
and its own, designed with especial reference 
to each other’s peculiar condition, and afford- 
ing, therefore, the most irrefragable evidence 
of creative foresight, the small offspring of the 


‘Kangaroo continues to increase, from suste- 


nance exclusively derived from the mother, for 
a period of about eight months. During this 

iod the hind legs and tail assume a great 
part of their adult proportions; the muzzle 
elongates; the external ears and eyelids are 
completed ; the hair begins to be developed at 
about the sixth month. At the eighth month 
the young Kangaroo may be seen frequently 
to protrude its head from the mouth of the 
pouch, and to crop the grass at the same time 
that the mother is browsing. Having thus 
acquired additional strength, it quits the pouch 
and hops at first with a feeble and vacillating 
gait, but continues to return to the pouch for 
occasional shelter aad supplies of food till it has 
attained the weight of ten pounds. After this 
it will occasionally insert its head for the pur- 
pose of sucking, notwithstanding another fetus 
may have been deposited in the pouch; for the 
latter, as we have seen, attaches itself to a dif- 
ferent nipple from the one which had been pre- 
viously in use. 

Mammary Organs—In the young Marsu- 
pial, as Mr. Morgan was the first to observe 
in the Kangaroo, the nipples are not visible, 
but are indicated by the orifices of a kind 
of cutaneous preputial sheath in which they 
are concealed. M. Laurent has noticed a 
similar condition of the nipples in a mam- 
mary feetus of an Opossum and a Perameles. 
I have also observed it in the marpmary foetus 


of a Petaurist and Dasyure: it is doubtless, 
therefore, common to all Marsupials. 

Once naturally protruded and the preputial 
sheath everted, the nipples, in the Kangaroo 
at least, continue external. They are longer 
and more slender than in other quadrupeds, 
and when in use generally present a terminal 
expansion (fig. 142, d). This part lies in 
a deep longitudinal fossa on the dorsum of 
the tongue (a, fig. 142); and the originally 
wide mouth of the uterine fetus is changed 
to a long tubular cavity, with a terminal sub- 
circular or triangular aperture just large enough 
to admit the nipple, to which the young Mar- 
supial thus very firmly adheres. 

In the Phascogale, in which the nipples are 
relatively larger than usual, and of a subcom- 
pressed clavate form, the young, when grown 
too large to be carried in the pouch, are 
dragged along by,the mother, if she be pursued, 
hanging by the nipples. 

The number of nipples bears relation in 
the marsupial, as in the placental Mammalia, 
to that of the young brought forth ata birth; 
although from the circumstance of the produce 
of two gestations being for a short time suckled 
simultaneously, the nipples are never so few. 
Thus the uniparous Kangaroo has four nipples ; 
of which the two anterior are generally those 
in use: the Petaurists, which bring forth two 
young at a birth, have also four nipples: the 
Thalycine has four nipples: the multiparous 
Virginian Opossum has thirteen nipples, six on 
each side and the thirteenth in the middle. In 
the Didelphys Opossum there are nine nipples, 
four on each side and one in the middle. The 
Didelphys dorsigera has the same number of 
nipples, although six is the usual number of 
young at a birth (fig.143). In the Phas- 
cogale penicillata there are eight nipples ar- 
ranged inacircle. The Perameles nasuta has 
the same number of nipples arranged in two 
slightly curved longitudinal rows; this Mar- 
supial has three or four young at a birth. 

The nipple in all the Marsupials is imper- 
forate at the centre; the milk exudes from six 
to ten minute orifices arranged round the apex. 
It increases in size with the growth of the 
mammary foetus appended to it. 

The mammary gland has the same essential 
structure as in the ordinary Mammalia; it has 
no cavity or udder; its chief peculiarity arises 
from its being embraced by the muscle, already 
noticed, which has the same origin and course 
as the cremaster muscle in the male. 

Marsupial pouch.—The development of the 
pouch is in an inverse ratio to that of the uteri 
and directly as that of the complicated vagine : 
thus it is rudimental in the Dorsigerous Opos- 
sum, which has the longest uteri and the sim- 
plest vagine: we may conclude therefore that 
the young undergo a greater amount of deve- 
lopment in the womb in this and allied 
species.* 


* Is there any essential modification of the mem- 
branes of the ovum in these small Marsupials? The 
means of determining this question are most de- 
sirable. 


328 


Female Didelphys dorsigera, with young and pouch. 


In the Kangaroos and Potoroos, which have 
the shortest uteri and longest vaginal tubes and 
cul-de-sac, the marsupial pouch is wide and 
deep. It is composed of a duplicature of the 
integument, of which the external fold is sup- 
ported by longitudinal fasciculi of the panni- 
culus carnosus converging below to be im- 
planted in the symphysis pubis. The mouth 
of the sac is closed by a strong cutaneous 
sphincter muscle. The interior of the pouch 
is almost naked: a few hairs grow around the 
nipple: it is lubricated by a brown sebaceous 
secretion. The mouth of the pouch is directed 
forwards in most Marsupials: the reversed 
position in the Perameles and Cheropus, where 
the mouth is directed towards the vulva, has 
been already noticed. M. Laurent* has made 
the interesting observation of the presence of a 
rudimental pouch in the male mammary feetus 
of an Opossum: he could not discern equal 
traces of the nipples: that of the pouch is 


* Annales d’Anatomie et de Physiologie, 1839, 
p- 237. 


MARSUPIALIA. 


soon obliterated, as the scrotum increases in 


size. 

In the male Thylacine the rudimental mar- 
supium is retained, in the form of a broad 
triangular depression or shallow inverted fold 
of the abdominal integument, from the middle 
of which the peduncle of the scrotum is con- 
tinued. In the female the orifice of the 
cious pouch is situated nearer the ior than 
the anterior boundary of that receptacle. 4 


A few observations on the claims of the Mar- 
supialia to be regarded as a natural group of ani- 
mals may not inappropriately conclude this ar- 
ticle. Cuvier, in 1816, first separated the mar- 
supial from the other unguicu + 
to form a distinct group, which he describes as 
forming, with the Monotremes, a small collateral 
chain, all the genera of which, while they are 
connected together by the peculiarities of the 
generative system, at the same time correspond 
in their dentition and diet, some to the Car- 
nivora, others to the Rodentia, and a third 
tribe to the Edentata. M. de Blainville, in 
the tables of the Animal Kingdom which he 
published in the same year, 1816, constituted 
a distinct sub-class of Cuvier’s “ small col- 
lateral chain” of mammals, and gave to the 
sub-class the name of Didelphes in antithesis 
to that of Monodelphes, by which he distin- 
guished the Placental Mammalia. 

The class or sub-class ‘ Implacentalia,’ of 
which the Marsupialia form one order, also in- 
cludes a second order, the Monotremata, which 
can only be termed ‘ Didelphes’ in the sense 
in which the word is applicable to many of 
M. de Blainville’s ‘ Monodelphes,’ i. e, in re- 
ference to their having two distinct uterine 
tubes. But the merit of the primary division 
of the Mammalia into Pracentatia and Im- 
PLACENTALIA does not rest upon the appro- 
reer of the terms, but upon the esta- 

lishment, by a long series of anatomical re- 
searches, of a primary division of the Mam- 
miferous class, which before was a mere hy- 
pothesis. str 


Many acute and sound-thinking naturalists 


refused their assent to the views of Cuvier and 
De Blainville, which, as they were sw 
by a knowledge of the conformity of organiza- 
tion of only the generative system in the Mar- 
supials, were unquestionably defective in the 
evidence essential to enforce conviction. The 
best arguments for returning to the older views 
of classification, and for — the Mar- 
supial genera, according to the affinities aj 
rently indicated by their dental and praate: 
systems, among the different orders of the Placen- 
tal Mammalia, have been advanced by Mr. Ben- 
nett, the accomplished author of the Gardens 
and Menagerie of the Zoological Society de- 
lineated, (vol. i. p. 265); and these have been 
repeated with approbation, and adopted by 
later systematists, as by Mr. Swainson. 
The discovery of the true affinities of the 
Marsupialia could only flow from an insight 
into their whole organization, and the question 
which Mr. Bennett proposes with reference to 
the genus Phascolomys, “ What is there of im- 


ee 


MARSUPIALIA. 


portance. in the structure of the Wombat, 
except this solitary character of the Marsupium, 
to separate it from the Rodent order ?”—a ques - 
tion which he might in 1831 have asked with 
equal force in reference to any other Marsupial 
genus,—could only be answered satisfactorily 
by the submission of the Marsupialia in ques- 
tion to a thorough dissection. 

Although the Marsupials present modifica- 
tions of the dental system corresponding with 
the carnivorous, omnivorous, and herbivorous 
types, yet they agree with each other, and 
differ from the analogous Placental Mammalia 
in having four instead of three true molars, 
i.e. four molars which are not displaced and 
succeeded by others in the vertical direction. 
The incisor teeth, also, either exceed in number 
those of the analogous Placental classes, or are 
peculiarly arranged and opposed to each other. 

In the locomotive organs it is true that we 
see some of the Marsupials having a hinder 
thumb, like the Placental Quadrumana; others 
are digitigrade, with falculate claws, like the 
Placental Fere; a third, as the Wombat, has 
the feet adapted for burrowing; a fourth, like 
the Cheironectes, is aquatic, and has webbed 
feet ; yet all these Marsupials agree with each 
other in having a rotatory movement of the 
hind foot, analogous to the pronation and su- 
pination which, in the F pepo quadrupeds, 
are limited when enjoyed at all to the fore feet ; 
and they manifest moreover a peculiar modi- 
fication of the muscles of the hind leg and foot 
in relation to these rotatory movements. In 
those Marsupials, as the Kangaroos, Potoroos, 
and Perameles, in which the offices of support 
and locomotion are devolved exclusively or 
in great part upon the hind legs, these are 
strengthened at the expense of the loss of the 
rotatory movements of the feet; but in the 
‘enormous development of the two outer toes, 
and the conversion of the two inner ones into 
-unguiculate appendages, useful only in cleans~ 
ing the fur, these Marsupials differ from all 
Placentals, whilst the same peculiar condition 
‘of the toes may be traced through the Pedima- 
nous group of Marsupials. Thus the locomo- 
tive organs, notwithstanding their adaptation 
to different kinds of progression, testify to the 
unity of the Marsupial group in the two 
remarkable peculiarities of structure above 

The vascular system gives evidence to the 
same effect. We have seen that the Marsupials 
present the following peculiarities in the struc- 
ture of the heart: viz. the right auricle mani- 
fests no trace of either fossa ovalis or annulus 
ovalis, and receives the two vene cave supe- 
riores by two separate inlets. This genera- 
lization is, however, less urgent than the pre- 
ceding in the present question, because the 
modification, as regards the separate entry of 
the superior vene cave, obtains in a few pla- 
cental species, as in the elephant and certain 
Rodents; but as the first cited cardiac cha- 
racter is common and peculiar to the Mar- 
supial Mammalia, and as the second, while 
it is universal in the Marsupials, occurs only 
as an exceptional condition in fhe placental 


329 


series, the arguments which they afford to the 
unity of the Marsupial group cannot be over- 
looked ina philosophical consideration of the 
affinities of the Mammalia. 

With respect to the nervous system, it has 
been shown that in the structure of the brain, 
the Marsupialia exhibit a close correspondence 
with the Ovipara in the rudimental state of the 
corpus callosum ; the difference which the most 
closely analogous placental species offer in this 
respect is broadly marked. 

hese coincidences in the Marsupialia of 
important organic modifications of the dental, 
locomotive, vascular, cerebral, and reproductive 
systems, establish the fact, that they constitute, 
with the Monotremes, a natural group inferior 
on the whole in organization to the Placental 
Mammalia. 

The following is a tabular view* of the subor- 
dinate divisions in the Marsupialia regarded as 
an order of the Implacental sub-class of Mam- 
malia :— 


* Of the various forms of Marsupial animals 
attempted to be arranged in natural groups in the 
present classification, it may be asked which is the 
typical form? or in other words, which genus com- 
bines most of the points of organization peculiarly 
characterizing the Marsupialia ? 

We have seen that certain modifications of the 
nervous, circulating, and generative systems are 
common to all the genera. But the female gene- 
rative organs approach nearest to the Rodent 
type in the small dorsigerous Opossums, in which 
the characteristic external pouch becomes very 
nearly obsolete. It is not the genus Didelphys 
therefore that we should select as the type of the 
Marsupials. It appears to me that there is both 
a dental and a digital character which may be re 
garded as eminently marsupial; the former, be~ 
sides the number of true molar teeth, consists in 
the opposition of six vertical incisors above toa 
large procumbent single pair below; the latter is 
exemplified in the atrophied and coadunate con- 
dition of the second and third digits of the hinder 
foot. The Phalangers, Petaurists, Koalas, Kan- 
garoos, and Potoroos possess, in addition to the ordi- 
nary Marsupial characters, both these modifications 
of teeth and digits. It seems, therefore, that it is 
from one of these genera that we should select the 
Marsupial type par excellence. If we say the Pha- 
langers, it may be objected that the hinder hand 
and opposable prehensile thumb indicate in these 
a transition from the Marsupialia to the Quadru- 
mana. Should the Petauri be our choice, then 
again we perceive in the development of the lateral 
tegumentary folds, and their connection with the lo- 
comotive members, a tendency to the Flying Squir- 
rels, The tail-less Koala may be deemed to ex- 
hibit in its clumsy form and proportions a resem- 
blance to the tree-bears, The Kangaroos and 
Potoroos obviously typify the Rodent Jerboas, and 
they have lost the peculiar rotation of the hind leg 
and the muscular modification connected there- 
with. If, however, the type of a natural group of 
animals, and such I have proved the Marsupial 
group to be, is that which manifests the greatest 
number of the structural modifications peculiar to 
the group, and the smallest number of such as are 
common to other natural assemblages of Mammalia, 
then the Koala has the best claim to typical pre- 
eminence. The Marsupial bones might be readily 
supposed to afford a simple indication of the most 
peculiarly Marsupia! animal, if they offered different 
relative magnitudes in different genera: now the 
range of variety in this respect is, in fact, consi- 
derable, and the Marsupial bones present their 
greatest development in the Koala. 


330 


MARSUPIALIA. 


Classification of the Marsupialia. 


Tarses. 
1. Sarcoph 


both jaws; a simple stomach, no in- 
testinum cecum . 


aga. 
Three kinds of teeth, canines long in Thylacinus, 
2 Dasyuride ees ; 


ee eee eee ee aeeee 


Extinct transitional forms .\sceese re eee ee ee ee) ¢ Thylacotherium(?) § 


2. Entomophaga. 
Three kinds of teeth in both jaws; a 


simple stomach, a moderately long ¢ Ambulatoria. .- Myrmecobius. 


SRECSEIRUM CCUM. . cc cecseccccecs 


Saltatoria 


Scansoria...... Didelphys .... Tree 


FAMILIES, 


GENERA. Suns-GENERA. 


Dasyurus. 


Phascogale. 


§ Phascolotherium. } Fossil 


¢ Cheropus. 
? Perameles. 


3. Carpophaga. E Cuscus. 

Anterior incisors large and long in both Phalangista .... Peter 
jaws; canines inconstant; stomach 4: ‘apoa. 
simple, or with a special gland; a Phalangistide ; - Petaurista. 
very long intestinum cecum ....+. Petaurus ....++4 Belidia. 

Acrobata. 
Phascolarctide.. Phascolarctus. 
4. Poephaga. 

Anterior incisors large and long in both J Lagocheles. 
jaws; canines present in the upper € yy. 15 podide Br aS gre Halmaturus. 
jaw only, or wanting; a complex ** ¢ Macropus. Macropus. 
stomach, a long intestinum c@cum.. Osphranter. 

5. Rhizophaga. 

Two scalpriform incisors in both jaws; at is 
no canines; stomach with a special . § Phascolomys. 
gland; caecum short, wide, with a Phascolomyide . *UDiprotodon.,, Fossil. 
vermiform appendage ..seee.seees 
BIBLIOGRAPHY.—Marcgravius, G. Historia natu- Zoological Journal, No. xviii. 1828, Ueber 


ralis Brasiliz, _ ; Piso, De Indie utriusque re 
naturali, fol. Hernandez, Hist. Mexican. 
lib. ix. p. 330. Tyson, Philos. Trans. 1698, 
vol. xx. Cowper, Philos. Trans. 1704, vol. xaiv. 
Daubenton, Buffon, Hist. Nat. tom. x. p. 325, 
1750. Aboville, Count, in Chastelleux Voyage a 
l’ Amerique Septentrionale, 1786. Hunter, John, 
Appendix to White’s Journal of a Voyage to New 
South Wales, 1790. Home, Sir Everard, Philos. 
Trans. 1795, 1819; Lectures on Comparative 
Anatomy, 1814-1823,” Cuvier, G. Lecons d’ Anato- 
mie pares, Li san and 1836-1840 ; Annales 
du M 30 Fossiles, 1922, t. ili. 5 
Régne lt eiGand 1829. Geoffroy St. Hilaire, 
Annales du Muséum, 1803; Journal Complemen- 
taire du Dictionnaire des Sciences Médicales, t. iii. 
1819; Mémoires du Muséum, 1822; Anatomie 
Philosophique, tom. ii, 1822; Dictionnaire -_ 
Sciences Naturelles, art. Marsu iaux, 1823; 
nales des Sciences Naturelles, 1827. Meckel, 3 F. 
Abhandl. aus der menschl. & vergl. Anatomie und 
er ie, 1806; System der vergl. Anatomie, 
1821-1 Bulletin de la Soc. Philo- 
mathique, 1818; Comptes Rendus ry l’Acad. des 
Sciences, 1838.” Ti » Icones cerebri simia- 
ram, &c. 1821. Barton, Dr. Annals of Philosophy, 
vol. vi. 1823. Treviranus, Biologie, hap feo ar: 
Zeitschrift fiir Physiol. Bd. iii. 1827. 
Physiologie, Bd. i, pl. iv. 1828. Tester tate Lettre 
sur deux sujets d’Anatomie Comparée, Bulletin 
des Sciences Médicales, Juin 1827; Voyage de la 
Pareles Soe Annales jd’ Anatomie et - Fey 
siologie, Broderip, W.J. ournal, 
128° Grant, Dr. R. Wernerian Transactions, 
vol, vi., Anatomy of Perameles nasuta. Collie, Dr, 


einige Eigenthiimlichkeiten im Ban der Beutel- 
thiere, Zeitschrift fur organische Physik, pert 
1828. Leuckhart, Meckel’s Archiv. far Ph 

t. viii. Rengger, Dr. Saugethiere von 

8vo. 1829. Morgan, John, ' rans. Lemme Society, 
vol. xvi. 1829 “and and 1833, Mammary Organs of 
Kangaroo. Owen, R. Proceedings of 
Society—1831, Female Organs of angaroo; 
Uterine Gestation and Foetus of K ry 
Anatomy of Macropus Parryi; 1 Anat. of 
Dasyurus Macrurus; 1836, Anat. 0 of Wombat; 
1837, Allantois of Kangaroo ; Anat. of 
Koala, Osteology of Marceriatin 889, Classifi- 
cation of Marsupialia. Phil. Trans .—1834, Gene- 

ration of Marsupialia; 1837, Brain of Marsupialia 

Medical Gazette, 1839, Blood-discs of ae 


Animal (Economy, ed. 1834 ; Description of 

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Mayo, H. Outlines of Prince 1833, sat 
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Chord of ong BS 3605 
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“vol. x of the 


sactions, 1836; Marsu one 
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Kangaroo, in Van der Hoeven’s Natuur 

3 deel. 1 Temminck, Monographies de Mam- 
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Gould, Monograph on Kangaroos. 

(R. Owen.) 


MEMBRANE—MENINGES—MICROSCOPE. 


MEMBRANE, (in Anatomy,) Gr. penyiy€ 5 
Lat. Membrana; Fr. Membrane; Germ. die 
Haut. This term is commonly applied to 
designate those textures of the body which are 
disposed or arranged as lamine, destined to 
cover organs, to line the interior of cavities, or 
either singly or by their application one over the 
other, to constitute the walls of canals or tubes. 
Expansion with very slight thickness is the 
main morphological characteristic of mem- 
branes in their ordinary sense. 

I do not intend here to give any classifica- 
tion of the membranes: the term is extensively 
used in descriptive as well as in general ana- 
tomy ; and anatomists differ materially as to 
the degrees within which they limit its meaning. 
Anatomists hitherto have been content to adopt 
the gross anatomy of the textures as the basis 
of their classification, a circumstance which 
has given rise to much error, as well as to great 
variety of opinion. Now, aided as we are by 
excellent microscopes, and by the light which 
they have thrown upon the minute anatomy of 
the tissues, we should only admit that classifi- 
cation which is based on an ultimate or even 

roximate anatomical analysis. As these points 
will be all fully treated of in the article Tissue, 
' reference is made to it for the details respecting 
the membranes. 
(R. B. Todd.) 


MENINGES.— This word signifies mem- 
branes ; it is specifically applied to those mem- 
branous expansions which cover and more or 
less protect the brain and spinal cord, and in 
this sense is best interpreted by the German 
word Hirnhaut. The term is in common use 
on the continent, but not so frequently em- 
ployed by British anatomists, although always 
understood by them in the sense above given. 
It appears to have been thus applied first by 
Galen, who distinguished pnyuye waxyvrepn, 
or the dura mater, and pxviyé Acwrn, or the 
pia mater. 

The description of the membranes of the 
brain and spinal cord will be found in the 
article Nervous CenTREs. 

(R. B. Todd.) 


MICROSCOPE, (susxgos, small,and cxomsw, 
to look at,) an instrument for aiding the eye in 
the examination of minute objects. Although 
a description of the structure and uses of this 
instrument cannot be considered as strictly 
belonging to a work like the present, yet the 
knowledge of them is so closely connected with 
its general objects that it has been deemed ad- 
visable to make it an object of special attention. 
The applications of this instrument to the pur- 
poses of the anatomist and physiologist are so 
numerous, that a whole treatise might easily be 
written upon them alone. We are not aware, 
until we come to think on the subject, how 
much of our knowledge of what takes place 
within the living body is dependent upon its 
revelations. To take a familiar illustration,— 
the capillary circulation might be, in some 
degree, guessed at by tracing the ramifications 
of the bloodvessels as far as they could be dis- 


\ 


331 


cerned with the naked eye; but we shouldjhave 
known extremely little of it without the micro- 
scope. Our whole knowledge of the early 
processes of development in plants and animals 
is gained by the same assistance. Not only is 
much of that, which ranks as established ana- 
tomical or physiological truth, founded upon 
microscopic researches, but similar researches, 
which are being prosecuted at the present time, 
are yielding a harvest of discovery still richer in 
amount, whilst not less important in its cha- 
racter. 

We propose, in the present article, to take a 
general view of the principles, optical and me- 
chanical, which are concerned in the construc- 
tion of the microscope; and then to give an 
outline of the results of some of the most re- 
cent enquiries in which it has been profitably 
employed,—confining ourselves chiefly, how- 
ever, to those which concern the origin and 
formation of the principal organized structures. 
If it be thought that the former portion is too 
much extended, we have only to say, that we 
know of no single treatise to which we can 
refer our readers for a large part of the informa- 
tion which we desire to convey; and that we 
have therefore judged it desirable to make the 
article complete in itself. 


I. OpricaAL PRINCIPLES GOVERNING THE 
CONSTRUCTION OF MICROSCOPES. 


All microscopes, except those which operate 
by reflection (to be hereafter noticed), depend 
for their operation upon the influence of convex 
and concave lenses on the course of the rays of 
light passing through them. _ This influence is 
the result of the well-known laws of refraction 
—that a ray passing from a rare into a dense 
medium is refracted towards the perpendicular, 
and vice versa. When, therefore, a pencil of 
parallel rays passing through air impinges upon 
a convex surface of glass, the rays will be made 


Fig. 144. 


l 


a 


: 


G 


| 


: 


: 
A B, parallel a7 of light falling upon the convex 
> 


Qa 


Ss 
Q 


Qa 


[ 


l HI 
surface F, B, D the centre, D B, D B, radii, 
which are the perpendiculars to the curved sur- 
face at the several points ; BC, course of the 
rays if uninterrupted ; B E, their course in con- 
sequence of the refraction they have undergone, 
converging to a focus at E, 


to converge, for they will be bent towards the 
centre of the circle, since the radius is the per- 
pendicular to each point of curvature. The 
central ray, as it coincides with the perpendi- 
cular, will undergo no refraction; the others 
will be bent from their original course in an 
increasing degree in proportion as they fall ata 
distance from the centre of the lens; and the 
effect upon the whole will be such, that they 


332 


will be caused to meet at a point, called the 
Jocus, some distance beyond the centre of cur- 
vature, This effect will not be materially 
changed, by allowing the rays to into air 
again through a plane surface of glass, such as 
would be formed by a section of the glass in the 
vertical line ; a lens of this description is called 
a plano-conver lens ; and it will hereafter be 
shown to possess properties, which render it 
very useful in the construction of microscopes. 
But if, instead of passing through a plane sur- 
face, the rays re-enter the air through a corivex 
surface, they will be made to converge still more. 
This may be best understood by considering 
the course of parallel rays, as in the adjoining 


Fig. 145. 


F ra: 
NTS _ Le 

l eal = 
ALK ee 
Bai ee eC 
in ee 


aS 


a: § 


A B, parallel rays passing through glass and falling 
upon the convex surface FBG; BH, B :: 
radii prolonged, which are the perpendiculars to 
the curved surface at the several points; BC, 
course of the rays if unrefracted; B E, their 
course in consequence of refraction. 


figure (fig. 145). Here the radii pone will 
be the perpendiculars to the curved surface; and, 
according to the law of refraction just alluded to, 
the rays passing from the dense into the rare 
medium will be bent from the perpendicular, 
so as to be made to converge towards a focus, 
as in the former instance. It is easy to see, 
therefore, that the effect of the second convex 
surface will be precisely equivalent to that of 
the first; for the contrary direction of the sur- 
face is antagonized by the contrary direction of 
the refraction; so that the focus of a double 
convex lens will be at just half the distance 
from it, or (as commonly expressed) be half 
the length of the focus of a plano-convex lens. 
In fact, the focus of the former to parallel rays 
will be the centre of its sphere of curvature, and 
its focal length will therefore be the radius; 
whilst the focus of the latter will be in the op- 
posite side of the sphere, and its focal length 
will be the diameter. Now it is evident that 


Fig. 146. 


a falling on a double convex lens brought to 
focus ve paced “eg pres. che ca 


MICROSCOPE. 


Fig. 147. 


Parallel falling on a plano-convex lens brought to 
a Seed al che distance of ita diandter, aa 
versa. . 

if a double convex lens will bring parallel rays 

to a focus in the centre of its sphere of curva- 
ture, it will on the other hand cause rays to 
assume a parallel direction, which are diverging 
from its focus; so that if a luminous body were 
placed in that point, all its cone of rays, which 
fell upon the surface of the lens, would pass 
out in a cylindrical form. Again, if rays al- 
ready converging fall upon a convex lens, they 


Fig. 148. 


Rays already converging brought to a focus nearer than 
the centre; and rays di ing from such a point, 
still diverging in a diminished . 


Fig. 149. 


Rays divergi i distant than the 
nh y ip peta ry 
yond it, ; 
nearer to 


will be brought to a focus at a point 

it than the focus for parallel rays (which is 
called its principal focus); and, if they be di- 
verging from a distant point, their focus will be 
more distant than the principal focus. The 
further be the point from which they diverge, 
the more nearly will the rays approach the pa- 
rallel direction; until, at length, when the ob- 
jects are very distant, their rays in effect become 
parallel, and are brought to a focus in the 
centre of the sphere. If they diverge from the 
other extremity of the diameter of the sphere, 
they will be brought to a focus at a nd. 
ing distance on the other side of the lens. On 


= >" 


the other hand, if they be diverging from a point | 


within the principal focus, they will neither be 
brought to converge nor be rendered parallel, 
but will diverge in a diminished degree. The 
same principles apply equally to a_plano- 
convex lens, the distance of its principal focus 
being understood to be the diameter of the 
sphere. They also apply to a lens whose sur- 
faces have different curvatures; the principal 
focus of such a lens is found by multiplying the 
radius of one surface by the radius of the other, 
and dividing this product by half the sum of 
the same radii. For the rules by which the 
foci of convex lenses may be found for rays of 
different degrees of convergence and divergence, 
we must refer to works on optics. 

The influence of concave lenses will evidently 


Fig. 150. 


a 


Parallel rays falling on a plano-concave lens made to 
diverge as from its principal focus, and rays con- 
verging to that focus rendered parallel, 


be precisely the converse of that of convex. 
Rays which fall upon them in a parailel direc- 
tion will be made to diverge as if from the 


principal focus, which is here called the nega- 
tive focus. This will be, for a plano-concave 


Fig. 151. 


i 


a 
Ni! 
‘i 


WHA = 


— 


==35, 


———_— 


— 
= == 
= = 
=F 
E ; 


Parallel rays made to diverge as from the principal 
focus, and rays converging to that focus rendered 
parallel. 


Fig. 152. 


Rays greatly converging made to converge less, and 
rays slightly diverging made to diverge more. 


lens, at the distance of the diameter of the sphere 


_ of curvature; and for a double concave, in the 


centre of that sphere. In the same manner, 
Tays which are converging to such a degree that, 


MICROSCOPE. 


333 


Rays slightly converging made to diverge. 


if uninterrupted, they would have met in the 
principal focus, will be rendered parallel; if 
converging more, they will still meet, but ata 
greater distance ; and if converging less, they 
will diverge as from a negative focus at a greater 
distance than that for parallel rays. If already 
diverging, they will diverge still more, as from 
a negative focus nearer than the principal focus; 
but this will approach the principal focus, in 
proportion as the distance of the point of di- 
vergence is such, that the direction of the rays 
onions the parallel. 

f a lens be convex on one side and concave 
on the other, forming what is called a meniscus, 
its effect will depend upon the proportion be- 
tween the two curvatures. If they are equal, as 
in a watch-glass, no perceptible effect will be 
produced; if the convex curvature be the 
greater, the effect will be that of a less powerful 
convex lens; and if the concave curvature be 
the more considerable, it will be that of a less 
powerful concave lens. The focus of conver- 
gence for parallel rays in the first case, and of 
divergence in the second, may be found by 
dividing the product of the two radii by half 
their difference. 

Hitherto we have considered only the effects 
of lenses upon a pencil of rays issuing from a 
single luminous point, and that point situated 
in the line of its axis. If the point be situated 
above the line of its axis, the focus will be 
below it, and vice versi. The surface of every 
luminous body may be regarded as comprehend- 
ing an infinite number of such points, from 
every one of which a pencil of rays proceeds, 
and is refracted according to the laws already 
specified ; so that a perfect but inverted image 
or spies of the object is formed upon any 
surface placed in the focus, and adapted to re- 
ceive the rays. 


In optical diagrams it is usual, in order to 
avoid confusion, to mark out the course of the 
rays proceeding from two or three only of such 
points. By an inspection of the subjoined 
figures, it will be evident that, if the object be 
placed at twice the distance of the es 
focus, the image being formed at an equal dis- 


Fig. 155. 


Formation of images by convex lenses. 


tance on the other side of the lens, will be of 
the same dimensions with the object: whilst, 
on the other hand, if the object be nearer the 
lens, the image will be farther from it, and of 
larger dimensions ; and if the object be farther 
from the lens, the image will be nearer to it, and 
smaller than itself. Further, it is to be re- 
marked, that the larger the image in proportion 
to the object, the less bright it will be, because 
the same amount of light has to be spread over 
a greater surface ; whilst a smaller image will 
be much more brilliant, in the same proportion. 

The knowledge of these general facts will 
enable us readily to understand the ordinary 
operation of the microscope; but the instru- 
ment is subject to imperfections of various 
kinds, the mode of remedying which cannot be 
comprehended without an acquaintance with 
their nature. One of these imperfections re- 
sults from the spherical aberration of the rays 
which have passed through lenses, whose curva- 
tures are equal over their whole surfaces. Hf 
the course of the rays be carefully laid down, it 
will be found that they do not all meet exactly 


Fig. 156. 


AB, rays falling on the periphery of the lens; F, 
focus of these; a, b, rays falling nearer the 
centre ; f, more distant focus of these. 


in the foci already stated, but that the focus of 
the rays which have passed through the peri- 

heral portion of the lens is much closer to it 
than that of the rays which are nearer the line 
of its axis; so that, if a screen be held in the 
former, the rays which have passed through the 
central portion of the lens will be orpe by 
it before they have come to a focus; and if the 
screen be carried back into the focus of these, 
the rays which were most distant from the axis 
will have previously met and crossed, so that 
they will come to it in a state of divergence. 
In either case, therefore, the image will have a 
certain degree of indistinctness ; and there is 
no one point to which all the rays can be 
brought by a lens of spherical curvature. The 
difference between the focal points of the cen- 
tral and of the peripheral rays is termed the 
spherical aberration. It is obvious that, to 


MICROSCOPE. 
produce the desired effect, the curvature is re- 


uired to be increased around the centre of 
e lens, so as to bring the rays which pass 
through it more — to a focus, and to be 
diminished towards the circumference, so as to 
throw the focus of the rays influenced by it to 
a greater distance. The requisite conditions 


may be exactly fulfilled by a lens one of whose 


surfaces, instead of being spherical, is a 

of an ellipsoid or hyperboloid of certain pro- 
portions ; but the difficulties in the way of the 
mechanical execution of lenses of this ip- 
tion are such, that, for all practical purposes, 
they have been entirely abandoned in favour of 
lenses with spherical surfaces. Various means 
have been devised for diminishing the aber- 
ration of these. In microscopes of ordi 
construction, the method employed is to dimi- 
nish the aperture or working te? te of the lens, 
so as to employ only the rays that pass 

the central part, which, if sufficiently small in 
proportion to the whole sphere, will bring them 
all to nearly the same focus. The use of this 


may be particularly noticed in the object-glasses — 


of common microscopes ; where, although the 
lens itself be large, the greater portion of its 
surface is rendered inoperative by a stop, which 
is a plate with a circular aperture interposed 
between the lens and the rest of the instrument. 
If this aperture be gradually enlarged, it will 
be seen that, although the image becomes more 
and more illuminated, it is at the same time 
becoming more and more indistinct; and that, 
in order to gain defining , the aperture 
must be reduced again. Now this reduction is 
attended with two great inconveniences ; in 
first place, the loss of ieee of light, the de- 
gree of which will depend upon the quantity 
transmitted by the toon? and will vary therefore 
with its aperture; and, secondly, the diminu- 
tion of the number or quantity of rays, which 
will prevent the surfaces of objects from bei 
properly seen. Thus, for example, we shall 
suppose the observer to be looking at the scales 
of a butterfly’s wing with a microscope fur- 
nished with two object-glasses of the same 
focal length,—one corrected, the other not so. 
If, with the same illumination of the object, he 
apply to it the uncorrected objective, the aper- 
ture of which is necessarily small, after having 
looked at it with the corrected lens, he will, in 
the first place, perceive that the whole field is 
much darker; but if, by increasing his illumi- 
nation, he give the image an equal brightness, 
and see its outline with equal distinctness, he 
will be completely unable to see with the un- 
corrected lens a series of delicate lines upon 
the surface of the scale, which the other es. 
evident. The power of exhibiting these and 
similar objects 1s termed penetration; it de- 
pends upon the size of the conical pencils of 
light admitted by the lens, and therefore upon 
its aperture. ‘ 
The spherical aberration may be considerably 
diminished by making the most advantageous 
use of single nani Thus the aberration of a 
plano-convex lens, whose convex side is turned 
towards parallel rays, is only #4ths of its 


thickness, whilst, if the plane side be turned 


towards the object, the aberration is 44 times 
the thickness of the lens. Hence, when a plano- 
convex lens is employed, its convex surface 
should be turned towards a distant object, 
when it is used to form an image by bringing 
toa focus parallel or slightly-diverging rays ; 
but it should be turned towards the eye, when 
it is used to render parallel the rays which are 
diverging from a very near object. The single 
lens having the least spherical aberration is 
a double convex, whose radii are as 1 to 6. 
When the flattest face is turned toward parallel 
rays, the aberration is nearly 34 times its thick- 
ness; but when the most convex side receives 
or transmits them, the aberration is only ;i,ths 
of its thickness. The spherical aberration may 
be still further diminished, however, or even 
got rid of altogether, by making use of com- 
binations of lenses so disposed that their op- 
_ posite aberrations shall correct each other, 
whilst magnifying power is still gained. For 
_ it is easily seen that, as the aberration of a con- 
cave lens is just the opposite of that of a con- 
_ vex lens, the aberration of a convex lens placed 
in its most favourable position may be cor- 
rected by a concave lens of much less power 
in its most unfavourable position; so that, 
although the power of the convex lens is weak- 
_ ened, all the rays which pass through this com- 
bination will be brought to one focus. This is 
the pencil of the aplanatic doublet proposed 
by Sir J. F.W. Herschel, consist- 
_ ing of a double-convex lens of 
the most favourable form, and a 
meniscus with the concave of 
_ longer focus than the convex.* 
_A doublet of this kind may be 
made of great use in the mi- 
_eroscope, as we shall hereafter 
_ show. Herschel’s 
_ Butthesphericalaberration is not doublet. 
the only imperfection with which the optician 
has to contend in the construction of micro- 
_seopes. A difficulty equally serious arises from 
the unequal refrangibility of the different coloured 
rays, which together make up white or colour- 
_ Tess light,t so that they are not all brought to 
_ the same focus, even by a lens free from sphe- 
rical aberration. It is this difference in their 
tefrangibility which causes their complete sepa- 
ration by the prism into a spectrum; and it 
manifests itself, though in a less degree, in the 
image formed by a convex lens. For if pa- 
rallel rays of white light fall upon a convex 
surface, the most refrangible of its component 
Tays, namely, the violet, will be brought toa 
focus at a point somewhat nearer to the lens 
than the principal focus, which is the mean 
of the whole; and the converse will be true of 
_ the red rays, which are the least refrangible, 
_ and whose focus will therefore be more distant. 


* The exact curvatures to be given to these sur- 
faces will be found in the original memoir, Pbil. 
Trans. 1821. 

+ It has been deemed better to adhere to the 
ordinary phraseology, when speaking of this fact, 
as more generally intelligible than the language in 
which it might be more scientifically described, 
and at the same time leading to no practical error. 


4 
| 


MICROSCOPE. 


335 
Fig. 158. 


Diagram illustrative of ehromatic aberration, 
A B, rays of white light refracted by a convex 


lens; C, the focus of the violet rays, which then 
cross and diverge towards E F; D, the focus 
of the red rays which are crossed at the points 
E E, by the violet; the middle point of this 
line is the mean focus, or focus of least aber- 
ration. 


This is easily proved experimentally. Ifa 
lens be so fixed as to receive the solar rays, 
and to illuminate a white screen at any dis- 
tance between the lens and the mean focus, the 
luminous circle will have a red border, because 
the red rays will there form the exterior of the 
cone; but if it be removed beyond the mean 
focus, the circle will have a violet border, be- 
cause the violet rays will then be outermost. 
As the spherical aberration would be mixed up 
with the chromatic in such an experiment, the 
undisguised effect of the latter will be better 
seen by taking a large convex lens, and co- 
vering up its central part, so as to allow the 
light to pass only through a peripheral ring ; 
and since the greater the alteration in the course 
of the rays, the greater will be the separation 
of the colours, (or dispersion, as it is techni- 
cally called,) this ring will exhibit the pheno- 
menon much better than would be done by the 
central portion of the lens. Hence, in prac- 
tice, the chromatic aberration is partly obviated 
by the same means used to diminish the sphe- 
rical aberration,—the contraction of the aper- 
ture of the lens, so that a very small portion 
of the whole sphere is really employed. But 
this contraction is attended with so much in- 
jury to the performance of the microscope in 
other respects, that it becomes extremely de- 
sirable to avoid it. In no single lens can any 
correction for chromatic aberration be effected ; 
and it requires a very nice adjustment of two, 
three, or even more, to accomplish this with 
perfection. 

The correction is accomplished by bringing 
into use the different dispersive powers of va- . 
rious materials, which bear no relation to their 
simple refracting power. As the effects of con- 
cave lenses are in all respects the converse of 
convex, it is obvious that, if a concave lens of 
the same curvature be placed in apposition 
with the convex, in such an experiment as 
that just alluded to, the dispersion of the rays 
will be entirely prevented, but neither wi!l any 
change in the course of the rays take place. 
If, however, we can obtain a substance of 
higher dispersive power in proportion to its 
power of refraction, it is obvious that a con- 
cave lens of less curvature formed of it will - 
correct the dispersion occasioned by the convex 
lens, without altogether antagonising the re- 
fraction of the latter. This is accomplished 


336 


without any essential difficulty in practice ; for 
the dispersive power of flint-glass is so much 
aaa than that of crown-glass, that a convex 
ens of the former, the focal length of which 
is 73 inches, will produce the same degree of 
colour with a convex lens of crown-glass whose 
focal length is 4, inches. Hence a concave 
lens of the former material and curvature will 
fully correct the dispersion of a convex lens of 
the latter, and will yet diminish its refractive 

wer only to such an extent as to make its 

us ten inches. The correction for chromatic 
aberration in such a lens would be perfect, if 
it were not that, although the extreme rays, 
violet and red, are thus brought to the same 
focus, the dispersion of the rest is not equally 
compensated ; so that what is termed a secon- 
dary spectrum is produced, the images of ob- 
jects seen through such a lens being bordered 
on one side with a purple fringe, and on the 
other with a green fringe. Moreover such a 
lens is not corrected for spherical aberration ; 
and it must of course be rendered free from 
this, to be of any service, however complete 
may be its freedom from colour. 

eats have long since been able to effect 
the required corrections, with sufficient accu- 
racy for most practical purposes, in the con- 
struction of large object glasses for telescopes ; 
the size of which has been only limited by the 
impossibility of obtaining glasses of large di- 
mensions perfectly free from faults. But it 
has been only of late years, that the construc- 
tion of achromatic and aplanatic object-glasses 
for microscropes has been considered prac- 
ticable,—their extremely minute size appearing 
to forbid the employment of the necessary 
combinations, since a very high amount of 
accuracy is required in the several curvatures, 
in order to obtain any real improvement. About 
the year 1820, however, the attempt was first 
made in France by M. Selligues, who was fol- 
lowed by Frauenhofer at Munich, by Amici at 
Modena, and by Mr. Tulley of London; and 
with these attempts a new era in the history of 
the microscope may be said with truth to have 
commenced. The work has been prosecuted, 
both theoretically and practically, with the 
greatest zeal, and the result has been most 
successful. By combining two or three groups 
of double lenses, each corrected in a particular 
manner, so that the whole is quite free from 
aberration, a perfectly sharp and clearly- 
defined image may now be obtained through 
a lens of many times the aperture of those 
formerly in use; and the differences in the 
representation of the objects under enquiry, 
between such lenses and a good achromatic, 
are such as could not have been, a priori, sus- 
pected. One of the most pleasing results of 
this improvement has been the greatly-increased 
unanimity amongst microscopical observers, 
as to the appearances actually witnessed by 
them; for with the old and imperfect instru- 
ments, great uncertainty could not but exist in 

to many objects, of whose nature ever 

one formed his own opinion, frequently Fheviie! 4 
ing to preconceived ideas; but at present the 
objects are presented to the sight of each ob- 


MICROSCOPE. 


server 


that there is much less scope for the of 
his imagination as to their real character,— 
however much he may exercise it upon their 
history. It would be foreign to the purpose 
of this article to enter into scientific details 
upon the minutiz of the construction of achro- 
matic combinations; but it may not be amiss 
to state that, in the opinion of the author, 
English artists have far su foreigners in 
the construction of lenses of very short focus, 
whilst some foreign combinations which he has 
seen, of low magnifyin wer, possess an 
advantage over those of” ritish make,—the 
constructors of the latter having sometimes 
sacrificed what he deems adequate correctness 
in aiming at a very large aperture.” 
With these preliminary details as to the na- 
ture of the means by which mi ic power 
is obtained, we shall proceed to notice their 
chief applications to practice. Excluding for 
the present the solar and gas microscopes, in 
which an image visible to any number of 
sons at once is formed upon a screen, is 
viewed by them precisely as other surroundi 
objects would be, we shall consider the instru- 
ments (to which the term microscope is more 
commonly applied), whose effects are eke which 
by their influence on the rays of light which 
enter the eye of the observer, and which can 
be used, therefore, by but one at the same 
time. These are distinguished as single or 
simple, and compound microscopes. Each of 
these kinds has its peculiar advantages for the 
anatomist; and we shall, therefore, describe 
the construction and uses of both in some 


detail. Their essential difference consists in 
this,—that in the former the rays of light which 
enter the eye of the observer directly 


from the object itself, after having been subject 
only to a change in their course, whilst in the 
latter an inverted image of the object is formed 
by a lens, which image is viewed by the ob- 
server through a simple microscope, as if it 
were the object itself. The simple mi 

may consist of one lens, but (as will be pre- 
sently shown) it may be formed of ¢wo or even 
three ; but these are so disposed as to produce 
an action upon the rays of light commer 
to that of a single lens. For this kind of mi- 
croscope, therefore, we prefer the term simple 
to single. In the compound microscope, on 
the other hand, not less than two lenses must 
be employed, one to form the inverted image 
of the object, and this being nearest to itis 
called the object-glass, whilst the other . 
nifies that image, being interposed between it 
and the eye of the observer, and is hence 

the poate Both these may be 
of several lenses, as will be hereafter shown ; 
but they are so arranged as to have the func- 
tions of a single lens, and are only combined 


* Those who wish to study the principles which 
hoald” 


now guide opticians in their construction, U 

refer to Mr. J. J. Lister’s paper in the Phil. Trans, 
for 1829, and Mr. Ross’s Tiassa in the Trans. of 
the Society of Arts, vol. ii, ‘ 


of a good instrument, with so” 
much more clear and uniform an pape ws - 
play of 


| 


MICROSCOPE. 337 


for the purpose of correcting the defects inci- 
dental to it. 

In order to gain a clear notion of the mode 
in which a single lens serves to magnify minute 
objects, it is necessary to revert to the pheno- 
mena of ordinary vision. An eye free from 
any defect has a considerable power of ad- 
justing itself in such a manner as to gain a 
distinct view of objects placed at extremely 
varying distances; but the image formed upon 
the retina will of course vary in size with the 
distance of the object; and the amount of 
detail perceptible in it will follow the same 
proportion. To ordinary eyes, however, there 
is a limit within which no distinct image can 
be formed, on account of the too great diver- 
gence of the rays of the different pencils which 
then enter the eye; since the eye is usually 
adapted to receive and bring to a focus rays 
which are parallel or slightly divergent. This 
limit is variously stated at from five to ten 
inches ; we are inclined to think from our own 
observations, that the latter estimate is nearest 
the truth; that is, although a person with ordi- 
nary vision may see an object much nearer to 
his eye, he will see little if any more of its 
details, since what is gained in size will be 
lost in distinctness. Now the utility of a con- 
vex lens interposed between a near object and 
the eye consists in its reducing the divergence 
of the rays forming the several pencils which 
issue from it; so that they enter the eye ina 
State of moderate divergence, as if they had 
issued from an object beyond the nearest limit 
of distinct vision; and a well-defined picture 
is consequently formed upon the retina. But 
not only is the course of the several rays in 


Fig. 159. 


Diagram illustrating the use of the Simple Microscope. 


each pencil altered as regards the rest by this 
refracting process, but the course of the pencils 
themselves is changed, so that they enter the 
eye under an angle correspondent with that at 
which they would have arrived from a much 
larger object situated at a greater distance. 
The picture formed upon the retina, therefore, 
corresponds in all respects with one which would 
have been made by the same object, greatly 
increased in its dimensions, and viewed at the 
smallest ordinary distance of distinct vision. 
A short-sighted person, however, who can see 
objects distinctly at a distance of three or four 
inches, has the same power in his eye alone, 
by reason of its greater convexity, as that which 
the person of ordinary vision gains by the 
VOL. III. 


assistance of a convex lens which shall enable 
him to see at the same distance with equal 
distinctness. It is evident, therefore, that the 
magnifying power of a single lens, depending 
as it does upon the proportion between the 
distance at which it renders the object visible, 
and the nearest distance of unaided distinct 
vision, must be different to different eyes. It 
is ordinarily estimated, however, by finding 
how many times the focal length of the lens 
is contained in ten inches; since, in order to 
render the rays from the object nearly parallel, 
it must be placed very nearly in the focus of 
the Iens; and the picture is referred by the 
mind to an object at ten inches distance. Thus, 
if the focal length of a lens be one inch, its 
magnifying power for each dimension will be 
ten times, and consequently a hundred super- 
ficial; if its focal distance be only one-tenth 
of an inch, its magnifying power will be a 
hundred linear or ten thousand superficial. 
The use of the convex lens has the further ad- 
vantage of bringing to the eye a much greater 
amount of light than would have entered the 
pupil from the enlarged object at the ordinary 
distance, provided its own diameter be greater 
than that of the pupil. It is obviously neces- 
sary, especially when lenses of very high mag- 
nifying power are being employed, that their 
aperture should be as large as possible; since 
the light issuing from a minute object has then 
to be diffused over a large picture, and will be 
proportionally diminished in intensity. But 
the shorter the focus the less must be the dia- 
meter of the sphere of which the lens forms a 
part; and unless the aperture be proportionally 
diminished, the spherical and chromatic aber- 
rations will interfere so much with the distinct- 
ness of the picture, that the advantages which 
might be anticipated from the use of such 
lenses will be almost negatived. Nevertheless, 
the simple microscope has always been an in- 
strument of extreme value in anatomical re- 
search, owing to its freedom from those errors 
to which, as will hereafter appear, the com- 
pound microscope is subject; and the greater 
certainty of its indications is evident at once 
from the fact, that the eye of the observer 
receives the rays sent forth by the object itself, 
instead of those which. proceed from an image 
of that object. A detail of the means em- 
ployed by different individuals, for procuring 
lenses of extremely short focus, though pos- 
sessing much interest in itself, would be mis- 
placed here; since recent improvements, as 
will presently be shown, have superseded the 
necessity of all these. It may, however, be 
stated that Leeuwenhoeck, De la Torre, and 
others among the older microscopists, made 
great use of small globules procured by fusion 
of threads or particles of glass. The most im- 
portant suggestion for the improvement of the 
simple microscope composed of a single lens 
proceeded some years ago from Dr. Brewster, 
who proposed to substitute diamond, sapphire, 
garnet, and other precious stones of high re- 
fractive power, for glass, as the material of 
single lenses. A lens of much longer radius 
of curvature might thus be employed to gain 
Z 


338 


an equal magnifying power, and the aperture 
would admit of great extension without a pro- 
portional increase in the spherical and chro- 
matic aberrations. This suggestion has been 
carried into practice with complete success as 
regards the performance of lenses executed on 
this plan; but the difficulties of various-kinds 
in the way of their execution are such as to 
render them very expensive; and as they are 
not superior to the combination now to be de- 
scribed, they have latterly been quite super- 
seded by it. 

This combination was first proposed by Dr. 
Wollaston, and is known as his doublet. It 
consists of two plano-convex lenses, whose 
focal lengths are in the proportion of one to 
three, or nearly so, having their convex sides 
directed towards the eye, and the lens of 
shortest focal length nearest the object. In 
Dr. Wollaston’s original combination no stop 
was interposed, and the distance between the 
lenses was left to be determined by experiment 
in each case. A great improvement was subse- 
quently made, however, by the introduction 
of a stop between the lenses, and by the divi- 
sion of the power of the smaller lens between 
two; this is due to Mr. Holland.* By these 
means a combination may be produced, in 
which the errors are made to correct each other 
so nearly that all the advantages of a wide 
aperture with a very short focus may be gained. 

e general nature of the performance of a 
doublet or triplet may be understood from the 
adjoining figure, (fig.160,) in which LO L’ is 


Fig. 160. 


Diagram of the passage of rays through a doublet. 


the object, P a portion of the pupil, and D D 
the stop. The ager of light from the two 
extremities, L L’, of the object cross each 
other in the stop, and consequently pass 
through the two lenses on the opposite sides 


* Trans. of Soc. of Arts, vol. xlix. 


MICROSCOPE. 


of the axis O P; so that each becomes af- 
fected by opposite errors, which to a certain 
extent balance and correct one another. To 
take the pencil L, for instance, which enters 
the eye at RB, R B; it is bent to the right 
at the first lens, and to the left at the second; 
and as each refraction alters the direction of 
the blue rays more than of the red, and more- — 
over, as the blue rays fall nearer the margin 
of the second lens, where the increased power 
of the refraction, consequent upon the distance 
from the centre, compensates in some di 
for the greater focal length of the second lens, 
the blue and red rays will emerge very nearly 
parallel, and are therefore colourless to pede 
At the same time the spherical aberrati 
been diminished by the circumstance that the 
side of the pencil, which passes one lens 
nearest the axis, passes the other nearest the 
margin. This explanation applies only, how- 
ever, to the pencils near the extremities of the 
object. The central pencil, it is obvious, will 
pass through the same relative portions of the 
two lenses, and only an imperfect correction 
will therefore take place, and of those i 
from the intermediate points the eae 
correction will with their imity to 
er or to the ctcumferenee. "Hence dou- 
let is not a perfect magnifier; but it is 
much superior to a single lens, and may bees 
constructed as to show many of the usual test- 
objects,—especially those in which a moderate 
amount of penetration is sufficient, 
the definition be good,—in a very beautiful 
manner. Its angle of aperture, however, by 
which is meant the angle of the apex of the 
conical pencils of rays admitted by it, cannot 
be advantageously increased much 40° 
or 45°. But when the smaller lens is replaced 
by a combination of two others, so as to form 
a triplet, their joint aberration is so much less 


Fig. 161. 


Diagram to illustrate angle of aperture. 

A, lens with small opening, admitting onl peneila ; 
of rays diverting at pap of 15° " * 
with large opening, admitting pencils of 50°. : 

that it is more counterbalanced by the third — 

lens placed above the stop. In this manner 
the transmission of a still larger angular | 

a to 65°,—is ouial compati er 
istinctness; and great etrati i 

thus combined with perfect definition, "a 
well as with brilliancy of illumination. For 
the purposes of anatomical investi » as 
we shall hereafter state, we consider good 
doublets and triplets, where circumstances — 
admit of their employment, superior to any 
other kind of magnifying instrument. The 
principal disadvantages which the use of them — 
involves are the close poe’ to the object — 
required by their very short focus when a high 


MICROSCOPE, 


magnifying power is employed; and the strain- 
ing of the eye, which is occasioned by their 
very minute aperture. Thus a triplet in our 
possession, which will show the most difficult 
test-objects, has a focal distance of only about 
3th of an inch, and an aperture through which 
the smallest pin would scarcely pass. But the 
first of these disadvantages is more apparent 
than real. The object should be always co- 
yered with talc, (which may be easily split into 
lamine of the ,};th of an inch in thickness,) for 
the purpose of protecting both it and the lens 
from injury by accidental contact; and the 

ifier should not be screwed into the arm 


which carries it, but loosely fitted, so that, if the: 


observer should happen to bring the arm too 
near the stage, he may not force down his lens 
upon the object. As Mr. Holland justly ob- 
serves, “ Should the proximity of the object 


to the lowest lens of the triplet be urged as a 


material objection to its usefulness, it may be 
answered that the whole microscope is a mass 


_of delicacies; consequently, it cannot be al- 


lowed that a line be arbitrarily drawn, beyond 
which every thing is to be considered as too 
delicate.” The second of the above objections 
must be obviated by never continuing the use 
of deep powers in a simple microscope for any 
length of time at one sitting, and by taking 
care to adjust the instrument in such a manner 
that the head may be as little inclined forwards 
as possible. 

The only other form of simple microscope 
which we shall notice is one commonly known 
under the name of the Coddington lens. The 
first idea of it was given by Dr. Wollaston, 
who proposed to cement together two plano- 
convex, or hemispherical lenses, by their plane 
sides, with a stop interposed, the central aper- 


ture of which should be equal to th of the 
focal length. The great advantage of such a 


lens is that the oblique pencils pass, like the 


central ones, at right angles with the surface; 


and that they are consequently but little subject 
to aberration. The idea was further improved 
upon by Mr. Coddington, who pointed out 
that the same end would be much better an- 
swered by taking a sphere of glass, and grind- 


; ing away the equatorial parts, the groove being 


then filled with opaque matter, so as to limit 


_ the central aperture. Such a lens gives a large 


phere of view, admits a considerable amount 
of light, and is equally good in all directions; 
but its powers of definition are by no means 
to those of an achromatic lens, or even 
adoublet. This form is very useful, there- 
fore, as a hand lens, in which a high power is 
not required, but has no particular advantages 
for magnifiers of short focus, nor for the object- 
glasses of a compound microscope.* 
_ It may be desirable to mention that a magni- 
fier, now known under the name of the Stan- 


hope lens, and much praised by those interested 


_* We think it right to state that many of the 
Magnifiers sold as Coddington lenses are not really 
(as we have satisfied ourselves) portions of spheres, 
but are manufactured out of ordinary double-con- 
vex lenses, and will be destitute, ‘therefore, of 
many of the above advantages. 


339° 


in its sale, is nothing more than a double con- 
vex glass, much thicker than ordinary, so that 
an object in contact with one of its surfaces 
shall be in focus to the eye placed behind the 
other. This is an easy method of applying 
rather a high magnifying power to scales of 
butterflies’ wings and other similar flat and 
minute objects; but the instrument is totally 
destitute of value as a means of scientific re- 
search, and must be regarded as an ingenious 


hilosophical toy. 
r Ceaonnd ‘Micro- 
scope. — The com- 
pound microscope es- 
sentially consists, as 
already stated, of two 
lenses, which are so 
disposed that one of 
them receives the rays 
of light from the object, 
and forms an image by 
its refraction of them; 
and this image is seen 
by the eye through the 
second lens, which acts 
upon it as asimple mi- 
croscope. The princi- 
ple of such a micro- 
scope will be at once 
understood from the 
adjoining diagram (fig. 
162). According to the 
laws already stated, if 
the object be ata less 
distance from the lens 
than its diameter of cur- 
vature (supposing it to 
be a double - convex 
lens, or twice that dis- 
tance of a plano-con- 
vex) the image will be 
larger than the object; 
and this in proportion 
as the latter is brought 
nearer to the principal 
focus, at which it can 
give rise to no image, 
as its rays after refrac- 
tion become parallel. 
Hence, by the use of 
the same object-glass, 
a considerable variety 
of power might be ob- 
tained ; for, if the image 
be formed near the lens, 
it will be small; but if 
the object be caused to 
approach it, the image 
will be thrown to acon- 
siderable distance, and 
will be proportionably 
magnified. The eye- 
piece would of course 
require, however, a cor- 
responding re-adjust- 
ment; and, in fact, 
the construction of 
the whole instrument 
would need modifica- 


Fig. 162. 


A B, the object, of which 
an amplified image is 
formed by the object- 
glass C D, in the con- 
trary direction, at A’ B’, 
by the convergence of 
the rays of the several 
pencils to afocus. These 
again diverging are re- 
ceived by the eye-glass 
LM, which gives them 
the nearly parallel di- 
rection necessary for 
them to enter the eye, 
and causes the apparent 
size of the image tobe E, 


z2 


340 


tion. Further, the optical disadvantages of such 

a plan would be considerable, for the nearer to 
the principal focus of the lens the object is 
brought, the more obliquely will the rays fall 
upon its surface, and the greater, therefore, will 
be the errors of aberration. This method of 
augmenting the power of a microscope has 
been adopted in spite of these disadvantages,” 
but it is not found to answer. Nevertheless, it 
is capable of being made of great utility, as 
we shall presently show, to a limited extent. 
A much more generally convenient method of 
varying the power of the microscope 1s to 
employ, as object-glasses, lenses of different 
foci ; and thus, as the same distance between 
the image and the lens is constantly maintained, 
whilst that of the object varies, the number of 
times that the latter is amplified is changed in 
a like proportion. In whatever mode addi- 
tional amplification be obtained, two things 
must always result from the change; the por- 
tion of the surface of the object, of which an 
image can be formed, must be diminished, and 
the quantity of light spread over that image 
must be proportionably lessened. In the use 
of high magnifying powers, the compound 
microscope has the great advantage over the 
simple, that the object need not be brought to 
nearly the same proximity with the lens, and 
that much more of it can be seen with comfort 
at a time. The long focus and large ——— 
with which the eye-piece is usually made pre- 
vent even the prolonged use of the instrument 
from acting prejudicially on the visual powers, 
except in cases of peculiar tendency to nervous 
disorders of the eye. And as the power of the 
eye-piece as well as that of the object-glass 
can be raised, there are scarcely any limits to 
the magnifying power that may be obtained. 
Practically, however, there are limits, arising 
from the fact that, as the amplification is greater, 
the aberrations will be increased in even an 
augmented proportion; so that these com- 
pletely antagonise the benefit otherwise deri- 
vable from the employment of high powers. 
The aberrations can only be diminished by 
contracting the aperture of the object-glass ; 
and this renders the image so dark that no real 
advantage is gained. Moreover, the imperfec- 
tions necessary to the best compound micro- 
scope, in which ordinary lenses are employed, 
are further augmented by the slightest error in 
the centering of the lenses, so that their axes 
do not coincide. 

In addition to the two lenses of which the 
compound microscope has been stated essen- 
tially to consist, another is usually introduced 
between the object-glass and the image formed 
by it. The ordin urpose of this lens is to 

ange the course of the rays in such a manner 
that the image may be formed of dimensions 
not too great for the whole of it to come within 
the range of the eye-piece, and consequently 
to allow more of the object to be seen at once. 


* We have seen a microscope, constructed by 
Chevalier, in which the tube was capable of being 
drawn out to the length of between three and four 
feet! 


MICROSCOPE. 


ar 
*" 
i 
>? 
~— e 
va 
Fit ls #2) 
“si 
“ ; 
=y) 
fey 
ar 
o 
t 
ae 
sie 
‘ 
aut 
‘ 
a 
(st 
ity 
i 
| = . 
— ert 
= : 
t i é 
So ’ sa 


tint 

Section of Compound Microscope, with field-glass 
¥ introduced. bine 
A A, the image which would be formed by the — 
object-glass alone; B B, the — formed by — 
the interposition of the field-glass F F; the an 
of this image is within the range of vision of the 
eye-glass E E, and the field of view is therefore : 
increased. fee ; 
7 
Hence it is called the field-glass (fig. 163). 
It may be so adjusted, however, in regard — 
to the eye-glass, as to correct its errors mm 
almost a perfect d ; and it is now, therefore, — 
usually considered as belonging to the ocu- — 
lar end of the instrament,—the eye-glass and — 
the field-lens being together termed the eye- — 
piece. Various forms of this eye-piece have — 


been proposed by different opticians, and one 
or other will be preferred, according to the 
oe for which it be required. It may be 
id down as a general principle, however, that 
to give the highest effect to the microscope, in 
regard to clearness of view and penetrating 
power, no more than two lenses should be 
employed; and that when a certain amount 
of these may be sacrificed to gain a large flat 
field, three is the largest number which can 
be introduced with any benefit. This prin- 
ciple is founded on the fact that, whenever 
light impinges on the surface of even the most 
transparent body, a part of it only is trans- 
mitted, the remainder being reflected. In the 
e of light through ordinary lenses, there- 
_fore, a certain quantity is lost by reflection 
at each surface; and every multiplication in 
the number of lenses entails, therefore, a 
itive evil, which may or may not be 
_ counterbalanced by the good it effects. In 
the doublet or triplet already described, 
the correction of the aberrations is an advan- 
tage much greater than the injury resulting 
from the substitution of four or six surfaces for 
two; but this is by no means the case in the 
eye-piece, in which (from their low power) the 
aberrations are much less. Hence, when too 
many lenses are employed in it, although the 
field of view (that is, the circle within which 
the image is comprehended) may be very much 
enlarged and rendered flatter, the brilliancy 
and sharpness of the image are so much im- 
paired, and it is invested with so much false 
colour, that, for all scientific purposes, the 
instrument is rather deteriorated than im- 
proved. 
_ The eye-piece which may be most advan- 
_ tageously employed with achromatic object- 
glasses, to the performance of which it is 
“ desired to give the greatest possible effect in 


out the necessity of a large field, is that termed 
the Huyghenian, having been employed by 
Huyghens for his telescopes, although without 
the knowledge of all the advantages which its 
best construction rendered it capable of afford- 
ing. It consists of two plano-convex lenses 
with their plane sides towards the eye. These 
are placed at a distance equal to half the sum 
of cer focal lengths ; or, to speak with more 
precision, at half the sum of the focal length 
of the eye-glass, and of the distance from the 
field-glass at which an image of the object- 
glass would be formed by it. A stop or dia- 
______ phragm must be placed half-way between the 
two lenses. By Huyghens this arrangement 
Was intended merely to diminish the spherical 
aberration ; but it was subsequently shown by 
Boscovich that the chromatic dispersion was 
also in great part corrected by it. Since the 
___- introduction of achromatic object-glasses for 
compound microscopes, it has been further 
_____ shown that all error may be avoided by a slight 
-_—sover-correction of these, so that the blue and 

___ red rays may be caused to enter the eye in a 

: een direction, and thus to produce a colour- 
____lessimage, though not actually coincident (fig. 


MICROSCOPE. 


regard to defining and penetrating power, with- . 


—— 


ee arenes 


ase 


-— 
—ceme OS ee 


L mY a Nn 


Section of Huyghenian eye-piece, adapted to over- 
corrected achromatics. 


LMN, the two extreme rays of three pencils, 
which, without the field-glass, would form a blue 
image convex to the eye-glass at B B, and a red. 
one at RR. By the field-glass, however, a 
blue image, concave to the eye-glass, is formed 
at B’ B’, and ared one at R’R’. As the focus 
of the eye-glass is shorter for blue rays than for 
red rays, by just the difference in the place of 
these images, their rays, after refraction by it, 
enter the eye in a parallel direction, and produce 
a picture tree from false colour. If the object- 
glass had been rendered perfectly achromatic, 
the blue rays, after passing the field-glass, would 
have been brought to a focus at 6, and the red at 
r, so that an error would be produced, which 
would have been increased instead of antago- 
nised by the eye-glass. 


164). Further, the image produced: by the 
meeting of the rays after passing through the 
field-glass is by it rendered convex towards the 
eye-glass, instead of concave, so that every part 
of it may be in focus at the same time, and the 
field of view thereby rendered flat. Those who 
desire to gain more information upon this sub- 
ject than they can from the accompanying dia- 
gram and the explanation of it, may be re-. 
ferred to Mr. Varley’s investigation of the pro- 
perties of the Huyghenian eye-piece in the 
51st volume of the Transactions of the Society 
of Arts, and to the article “ Microscope” in 
the Penny Cyclopedia. 

By an achromatic object-glass for a com- 
pound microscope, therefore, is not meant one 
which simply contains within itself a perfect 
correction for its own errors, but one in which 
the usual order of dispersion is so far reversed 
that the light, after undergoing the series of 
changes effected by the eye-piece, shall come 
uncoloured to the eye. ‘ We can give no spe- 
cific rules,” says the writer of the article just 


342 


referred to, whom we believe to have had great 
practical experience in the matter, “ for pro- 
ducing these results. Close study of the for- 
mule for achromatism given by celebrated ma- 
thematicians will do much ; but the principles 
must be brought to the test of repeated expe- 
riment. Nor will the experiments be worth 
any thing, unless the curves be most accu- 
rately measured and worked, and the lenses 
centred and adjusted with a degree of preci- 
sion which, to those who are familiar only with 
telescopes, will be quite unprecedented.” We 
are not favourable to the use of a very high 
magnifying power in the eye-piece; and we 
believe that it will be discontinued in propor- 
tion to the perfection attained in object-glasses. 
We have seen microscopes of foreign construc- 
tion in which only object-glasses of compara- 
tively long focus were employed, and the re- 
quired power was made up by the great con- 
vexity in the eye-glass; but the performance of 
these was not to be compared to that of instru- 
ments of British manufacture. Our own expe- 
rience leads us to think that there are very few 
objects of which more can be made out with a 
deep than with a shallow eye-piece,—the dimi- 
nution in distinctness and loss of sight being 
nearly sufficient to counterbalance the gain 
derived from increased power. Hence the mag- 
nifying power of an instrument is by no means 
to be regarded as an indication of its excel- 
lence ; for that is to be considered as the best 
which, ceteris paribus, will show the most 
with the lowest power. It may be scarcely an 
exaggeration to affirm that there are few objects 
of which the details may not be as well made 
out by an achromatic microscope magnifying 
but 100 diameters, as by the best ordinary 
microscope magnifying 1000; and there are 
many objects shown with the greatest readi- 
ness by the former, which are totally inscru- 
table by the latter. 

Next in order of optical perfection to the 
achromatic microscope with the Huyghenian 
eye-piece, we are disposed to rank the doublet 
microscope, invented by Mr. Holland. This 
gentleman has proposed to adapt to his dou- 
blets and triplets a compound body, con- 
taining an eye-piece somewhat resembling the 
Huyghenian, but differing from it in having the 
lenses fixed at a distance equal to the whole 
sum of their foci. “ By this increase of dis- 
tance, light and defining power are gained, 
although the magnifying power and the field 
of view are diminished ; but at the same time 
the latter is rendered very perfect.” Having 
ourselves had a microscope constructed upon 
this principle, we can speak in very high terms 
of its performance. The field of view will 
appear very small to those accustomed to the 
use of eye-pieces of high power; but every 
part of it is brilliantly illuminated, and diffi- 
cult test-objects are exhibited by it with a 
sharpness and definition which we have seldom 
seen equalled. For objects which require to 
law alae surface in view at once, such a 
microscope is inappropriate ; but for the pur- 
pose of minute examination of those in which 


MICROSCOPE. 


the may be studied independently, we 
orl ng as the best substitute for the achro- 
matic microscope; and we can ly re- 
commend it to those who are debarred by the 
price of the latter instrument from possessing 
themselves of it. In employing doublets or 
triplets of high power as objectives in 

a microscope, care must of course be taken 
(as when they are used singly) to avoid injuring 
them by contact with the object. For the most 
difficult test-objects, a triplet of jth of an inch 
focus should be employed; and the 

should successively diminish down to a dou- 
blet of jth of an inch, which may be advanta- 
geously employed for opaque objects. It is 
necessary to state that the performance of this 


microscope will very much depend upon the . 


attention paid to the illumination of the 
object; on this we shall hereafter treat in 
detail. 

We shall next s of ieces which 
are intended to afl 7 the inner the field in 
the most advantageous manner, without 
to the perfection of minute details. This ob- 
ject is ordinarily attempted by the substitution 
of two plano-convex lenses, or double-convex 
lenses of low curvature, for the single lens of 
the eye-glass. It has been pro to make 
the same change in the field-glass ; but, in our 
opinion, the loss by reflexion from two addi- 


tional surfaces is by no means nee 
the diminution of. aberration. e are nie 
selves, however, in the habit of employing an 
pd gw which we regard as greatly superior 
to that in ordinary use. It consists of a me- 
niscus having the concave side next the eye, 
and a convex lens having the form of least 
aberration, with its flattest side next the ob- 
ject, nearly resembling, therefore, Herschel’s 
aplanatic doublet. The field-glass is a double- 
convex lens of the form of least aberration. 
With this eye-piece we are enabled to obtain a 
field of 14 inches diameter (measured at the 
usual distance—10 inches) equally distinet and 
well illuminated over every part, i 
rably adapted for the display of sections of 
wood, wings of insects, and objects of a simi- 
lar description, and also for opaque objects. 
When employing it for these purposes, we 
much prefer the use of ordinary double-convex 
objectives to achromatic lenses; for the | 
being adjusted for a much smaller field, pro- 
duce an image which is only distinct in the 
centre; and the former, being of low power, 
may have an aperture quite sufficient to admit 
the requisite amount of light. Even with 
deeper objectives, the performance of this eye- 
piece approaches much more closely to the 
effect of an achromatic microscope, than would 
be supposed by those who have only seen the 
ordinary one; and, when made on a small 
scale, it may be advantageously substituted for 
Mr. Holland’s for all but the most difficult 
objects. The two additional surfaces are of 
course disadvantageous, by reflecting some of 
the fainter rays proceeding from the more 
delicate markings; but the increased magnify- 


ing power is gained with so little aberration, 4 


j 


q 


a 


MICROSCOPE. 343 


‘that a considerable general advantage is hence 


derived. We can regard no microscope as 
complete, without an eye-piece of this kind, 
with a set of ordinary objectives of low powers; 
for it will certainly do what no other combi- 
nation with which we are acquainted can effect. 
The great improvements recently made in the 
construction of achromatic objectives, and the 
unquestionable fact that, for exhibiting the 
‘Minute details of objects, they are infinitely 
superior to all other kinds, have had, we think, 
atendency to blind microscopists to the ad- 
vantages afforded by other combinations, where 
it is desired to obtain a view of the general 
arrangement of the parts of a large object, 
rather than to investigate its minutiz. 

We should recommend, therefore, that every 
achromatic microscope should be fitted with at 
least two Huyghenian eye-pieces, adapted ex- 

ressly to the achromatic objectives; and that 
it should also have a meniscus eye-piece, with 


a set of ordinary object-glasses of long focus. 


And the best substitute for such a microscope, 
at least for the purposes of anatomical or phy- 
siological research, we believe will be found 
in Mr. Holland’s doublet microscope, which 
should be furnished with his eye-piece for 
doublets already described, and with a me- 
niscus eye-piece and ordinary object-glasses of 
low power. In this last form of compound 
microscope, there is the further advantage, 


that the high magnifying power of the doublets 


and triplets employed as objectives renders 
them available as simple microscopes; and 
this cannot be said of achromatic object-glasses, 
which have not yet been usually made of 
shorter focus than one-tenth of an inch, and 
which are not, therefore, of much use in them- 
selves. No one, however, can be regarded as 
entitled to form positive conclusions in regard 
to difficult questions of microscopic enquiry, 
until he has availed himself of the very best 
means of observation at his command; and 
these are certainly to be found only in achro- 
Matic microscopes of the highest class. 

For viewing large opaque objects, achromatic 
objectives of low power are often very useful, 
on account of the large quantity of light they 
admit, which supersedes the necessity of arti- 
ficial illumination ; this is a particular advan- 
tage in anatomical investigations, in which it 
is often especially necessary to avoid the re- 
flection of condensed light from the surface of 
the object, on account of the confusion which 
is thereby occasioned. 

The achromatic objectives at present usually 
made on the continent consist of sets of three 
or more, of which one, two, or three may be 
used at once. In this manner considerable 
variety of power may be gained; but the 
highest degree of perfection in the performance 
must be sacrificed to obtain it, since no single 
objective consisting of two lenses only can be 
thoroughly corrected, and each combination 
ought tobe corrected for itself alone. The 
best achromatics made by British artists consist 
of combinations of two or three compound 
lenses, which cannot be separated; and thus 


Fig. 165. 


° 
Section of the English achromatic combination. 


every required power must be furnished by a 
distinct combination. The expense of a mi- 
croscope fitted with the requisite number of 
these, however, is a great bar to its general 
employment. Other combinations have been 
constructed, therefore, in which the lens next 
the object may be removed, so as to diminish 
the magnifying power considerably ; and the 
corrections are so adjusted as to be nearly the 
same when the two or when three compound 
lenses are used together. The difference be- 
tween the performance of the best of these, 
and that of those most perfectly adjusted, is 
not, for general purposes, of much importance. 
Two sets of these separating lenses,—a high 
and a low one,—giving four powers, therefore, 
which may range from an inch and a half to 
one-eighth of an inch focus, will adapt the 
microscope, with the eye-pieces we have men- 
tioned, to a great variety of purposes. 

The power may be further varied by length- 
ening the body of the microscope, by drawing 
out the eye-piece, which should always be 
made capable of this kind of movement. This 
operates by increasing the distance from the 
object-glass of the image formed by it, and 
therefore augmenting the size of the image; 
the object must of course be brought some- 
what nearer on the other side. We have al- 
ready stated that the length of the body cannot 
be much increased with advantage; but a mo- 
derate variation will be found useful in many 
ways. It enables the magnifying power to be 


‘adjusted to almost any point intermediate 


between those given by the different objectives. 
Thus, one may give a power of 80 diameters, 
and another a power of 120; by using the first, 
and drawing out the eye-piece, the power may 
be increased to 100. Again, it is often very 
useful to make the object fill up the whole, or 
nearly the whole, of the field of view. This is 
especially the case, when it is itself not very 
transparent, and requires a strong light to 
render its details visible; in which condition 
a glare entering around its edges would very 
much interfere with its distinctness. When 
opaque objects, also, are being viewed by con- 
densed light, in the modes hereafter to be 
stated, it is often extremely desirable to make 
them, or the discs on which they are mounted, 
fill up the whole field. In either case the 


344 


drawing out of the eye-piece until the end is 
accomplished answers the object most simply 
and effectually. In the use of the micro- 
metric eye-piece, also, which will be presently 
described, the capability of adjusting the mag- 
nifying power to a certain definite amount will 
be found of very great utility. It is to be 
borne in mind, however, that for giving the 
highest effect to the achromatic objectives, a 
certain fixed distance of the eye-piece is neces- 
sary; this is usually adjusted by the maker; 
but it may be easily determined by trial, since 
at any other the want of correction of the chro- 
matic aberration will make itself apparent 
reaver slightly) by the presence of coloured 
inges around the images. 

The degree of perfection in the construction 
of the optical part of a microscope, whether 
simple or compound, is judged of by the dis- 
tinctness and comfort (by which we mean the 
freedom from strain or effort on the part of the 
observer) with which it exhibits certain objects, 
the details of which can only be made visible 
by combinations of lenses of high magnifying 
eg and a near approach to correctness. 

uch are called test objects. They are of 
various degrees of difficulty. For testing the 
penetrating powers of a microscope, the lined 
scales on the wings and bodies of certain in- 
sects are commonly employed. The scales 
from the wings of many Lepidoptera are so 
coarsely marked, that a good ordinary com- 
pound microscope, or deep single lens, will 
make the lines apparent. But there are many 
others, which, under such magnifying powers, 
only show a flat unmarked surface, requiring 
lenses of large angular aperture to make their 
lines visible. One of the most beautiful of 
these, and at the same time most easily re- 
solved, is the scale of the Menelaus butterfly ; 
its longitudinal strig may be seen in the best 
ordinary microscope, but they require a cor- 
rected object-glass to be well made out; and 
its transverse markings are only to be seen 
distinctly with a superior instrument. A scale 
with more delicate lines than these is the 
larger of those of the Lycena Argus; the smal- 
ler one will be presently noticed. The most 
difficult of the test-scales, however, is that of 
the Podura plumbea, or common spring-tail ; 
and a microscope which will distinctly exhibit 
its markings may be regarded as, for this class 
of objects, of the highest order. For defining 
power, however, another class of objects is 
needed. Among these one of the best is the 
small scale of the Lycena Argus (or battledore), 
which, with an inferior instrument, appears 
covered with coarse longitudinal lines; but 
these, when more perfectly defined, are found 
to be resolvable into separate circular or oval 
dots, arranged ina linear manner. The curi- 
ous hair of the Dermestes, and that of the 
Bat, require a microscope of good defining 
power to represent their forms with clearness 
and accuracy. We have ourselves been accus- 
tomed to employ the branching hairs of the 
common bee as tests of the correctness of a 
microscope of moderate power; for they have 


- . e * 


colour, under most of the ordinary 
illumination, unless there is a perfect freedom 
from chromatic aberration. The spiral fibres 
lining the trachee of many insects, also, will 
be found good tests of the defining powér, 
and freedom from aberration, of a mi e. 
For still lower powers, we consider the glan- 
dular dots in the peti = a =~ resinous 
trees (especially those of the order Conifers) 
as on veetcectten tests. They ought to be 
rendered distinctly visible with an object-glass 
of half an inch focus; and the depression in 
the centre should be clearly made out, with a 
perfect freedom from colour. We have seen 
objectives of English construction (in which a 
large aperture for showing opaque objects was 
the chief point aimed at) so defective in this 
respect, as to be far inferior in their exhibition 
of these and similar objects to French acro- 
matics of much smaller aperture. We may 
here repeat the general rule, that those micro- 
scopes are, ceteris paribus, the best, which will 
show the most with the lowest magni 
power. It will sometimes happen al- 
though the details of an object may be made 
out with tolerable clearness, there is a sort of 
thin fog or mist over the whole field. This 
fault may proceed from the too great enlarge- 
ment of the aperture of the objective, or from 
a faulty mode of illumination; or it may result 
from the imperfect extinction of the rays re- 
flected within the body of the microscope from 
the surfaces of the lenses of the iece, 
and from the interior of the tube itself;*— 
a fault which may be obviated by carefully 
coating the inner surface with a black ore 
adapted to absorb all the false light. B 
velvet may be advantageously used for this 
paiaens. If the aperture be too the 
ult may generally be corrected by the use of 
stops beneath the stage, by which it may be 
diminished as required. This plan, whieh will 
be presently described more in detail, will be 
found very much to increase the applicabi- 


lity of low-power achromatic lenses of that — 


large aperture which is desirable for opaque 
objects, ay 
II. Or THE MECHANICAL ARRANGEMENTS © 
OF MICROSCOPES. 

Having now described, with as much detail 
as the nature of this article permits, the prin- 


«3 ‘ 


ciples on which the operation of the micro= 


scope depends, we shall next proceed to con- 
sider the means of arranging the eae por- 
tion of the instrument, so as to confer upon it 
the best and most varied application, keepi 
especially in view, however, the wants of the 
anatomist and physiologist. 


We shall begin — 
by stating what, in any form of mi aa 
we regard as the essential conditions to be 


attained in its construction. : - 
1, Steadiness and firmness in all its parts, 


* [Or it arises, as suggested to the Editor by 
Mr. Powell, the eminent optician, from imperfection 
in the correction of the objectives.—ED. sie 


1 


j 
+ 
| 


MICROSCOPE..- 


‘so that it may be free from vibration. An 
amount of vibration, which is imperceptible 
when low powers are used, is-sufficient to 
render the most perfect optical arrangements 
-for high magnifying powers next to useless, 
That the whole instrument should be secured 
-as much as possible from vibration, by being 
placed upon a steady table, and this on a 
Steady floor, is of the first importance for its 
advantageous employment. But, as an entire 
freedom from this cause of vibration can rarely 
be obtained in an ordinarily-constructed house, 
the next point to be aimed at is such an ar- 
rangement of the optical portion of the instru- 
ment in regard to the object, that any vibra- 
tion which takes place may affect both alike, 
‘in which case it will be scarcely perceptible. 
In many microscopes of ordinary construction 
the stage is comparatively motionless, whilst 
the body (containing all the optical portion) 
is subject to tremor; and in such instruments, 
when a high magnifying power is employed, 
the object is seen to oscillate so rapidly upon 
the slightest cause of vibration (such as a per- 
son walking across the room or a carriage rol- 
ling by in the street) that it is frequently almost 
indistinguishable. Various modes have been 
devised for obviating this inconvenience, the 

chief of which we shall hereafter notice. 
2. Capability of accurate adjustment to 
_ every variety of focal distance, without move- 
ment of the object. It is now a principle 
almost universally recognised in the construc- 
tion of good microscopes, that the stage on 
which the object is placed should be a fixture; 
and that the movement by which the focus is 
to he adjusted should be effected in the body 
or optical portion. Several reasons concur to 
establish this principle, which was, we believe, 
first insisted upon by Dr. Goring.* Among 
the most important we consider to be that, if 
the stage is made the moveable part, the ad- 
justment of the illuminating apparatus must 
be made afresh for every change of magnify- 
ing power, whilst, if the stage is a fixture, the 
illumination having been once well adapted, 
the object may be examined under a great 
variety of magnifying powers, without its being 
changed in any respect. Moreover, if the 
stage is the moveable part, it can never have 
that firmness given to it, which it ought for 
Many purposes to possess. It is almost im- 
possible to make a moveable stage free from 
some degree of spring; so that, when the hands 
bear upon it in adjusting the position of an 
object, it yields to an amount which, however 
trifling, becomes apparent with high powers 
by the alteration of the focus. We might add 
many more reasons, but these will here suffice. 
it having been determined, then, that focal 
adjustment should take place in the optical 
portion of the microscope, the next point for 
consideration is the mode of effecting it. This 
should be such as to allow free range from a 
Minute fraction of an inch to three or four 


* See Pritchard and Goring*s Microscopic Illus- 
trations, 


focus. 


345. 


inches, with equal power of obtaining a deli- 
cate adjustment at any part. It should also 
be so accurate that the axis of the instrument 
should not be in the least altered by movement 
in a vertical direction ; so that, if an object be 
brought into the centre of the field with a low 
power, and a higher power be then substituted, 
it should be found in the centre of its field, 
notwithstanding the great alteration in the 
In this way much time may often be 
saved by employing a low power as a finder 
for an object to be examined by a higher one; 
and, when an object is being viewed by a suc- 
cession of powers, no readjustment of its place» 
on the stage is required, such as would other- 
wise be necessary for each. The best modes 
of securing these ends, also, will be considered 
in their proper place. 

3. The power of placing the instrument in 
either a vertical or a horizontal position, or at 
any angle with the horizon, without deranging 
the adjustment of its parts to each other, and 
without placing the eye-piece in such a posi- 
tion as to be inconvenient to the observer. It 
is certainly a matter of surprise that opticians 
should have so long neglected the very simple 
means which are at present so commonly em- 
ployed, of giving an inclined position to mi- 
croscopes ; since it is now universally acknow- 
ledged that the vertical position is, of all that 
can be adopted, the very worst. We do not 
ourselves consider the horizontal position of 
the body and its appendages at all an advan- 
tageous one, although it has been adopted in 
some of M. Chevalier’s latest and best instru- 
ments. In the first place it requires that the 
whole microscope should be raised so much 
above the level of an ordinary table, as to 
bring the eye-piece to the height of the eye of 
the observer when sitting upright at his ease; 
if this be not done, a constrained and conse- 
quently disadvantageous position of the head 
is required on his part; and if it be, all the 
manipulations must be executed at an elevation 
very inconvenient and fatiguing to the arms. 
Moreover either the stage must be rendered 
vertical, in which case all the objects must be 
so secured (to prevent their slipping) as to 
render the necessary movement of them very 
difficult; or, the stage being horizontal, the 
direction of the rays must be changed, after 
they have passed through the object-glass, by 
a prism ora mirror placed at an angle of 45° 
in their course, as in M. Chevalier’s construc- 
tion, which we think a decided disadvantage, 
as introducing another source of imperfection 
and error. We believe that it will be gene- 
rally acknowledged, that an inclination of about 
45° to the horizon is the most convenient for 
unconstrained observation ; and the instrument 
should be so arranged, that, at such an incli- 
nation, the stage may be so far elevated above 
the table, that, when the hands are employed 
at it, the elbows may rest upon the table. In 
this manner a degree of support is attained, 
which gives such free play to the muscles of 
the hands, that movements of the greatest 
nicety may be executed by them; and the 


346 


fatigue of long-continued observation is greatly 
diminished. Such minutia may appear too 
trivial to deserve mention; but no practised 
microscopist will be slow to acknowledge their 
value. At the inclination we have mentioned, 
the de of the stage from the horizontal 
position will not be such as to render it neces- 
sary to confine the objects with more than a 
slight force, and accordingly they may be 
moved by the hands with considerable free- 
dom ; and light objects may be placed upon a 
slip of glass without any confinement, or co- 
vered with talc if necessary, and yet be in 
little danger of falling off it. These are con- 
yeniences which are of more value in practice 
than they may appear in theory; for it will 
often be found that the saving of a little time 
in the adjustment of the microscope is of 
great importance in the observation of objects 
which are undergoing change. There are some 
objects, however, which can only be seen in a 
vertical microscope, as they require to be viewed 
in a position nearly or entirely horizontal ; such 
are dissections in water, saline solutions under- 
gving chrystallisation, &c. For other purposes, 
again, the microscope should be placed hori- 
zontally, as when the camera lucida is used 
for drawing or measuring. It ought, therefore, 
to be made capable of every such variety of 
ition. 

4. The last principle on which we shall 
here dwell is simplicity in the construction and 
adjustment of every part. Many ingenious 
mechanical devices have been invented and 
executed, for the purpose of overcoming dif- 
ficulties which we cannot but regard as trivial. 
If all these were combined in one instrument, 
a degree of complexity would be thereby 
engendered, which would prevent it from be- 
ing generally available. Our own experience 
leads us to the conclusion, that a moderate 
amount of dexterity in the use of the hands is 
sufficient to render most of these superfluous ; 
and without such dexterity, no one, even with 
the most complete mechanical facilities, will 
ever become a good microscopist. We shall 
hereafter describe, however, some of those 
which are in most general use ; premising that 
we cannot speak from much experience of 
their applicability, since we have ourselves 
found no difficulty in doing without them, as 
we recommend our readers to do. Although a 
large box, well filled with glittering brass im- 
Pravnonts of various shapes and sizes, may 
have a very inviting appearance, it will often 
be found that these are more for show than use, 
and add to the expense of the instrument in a 
proportion far exceeding their utility. Among 
the conveniences of simplicity, the practised 
peaevennptat will not fail to recognize the 
saving of time effected by being able quickly 
to set up and put away his instrument. Where 
a number of parts are to be screwed together 
before it can be brought into use, interesting 
objects as well as time are not unfrequently 
lost; and the same cause will often occasion 
the instrument to be left exposed to the air and 
dust, to its great detriment, because time is 


MICROSCOPE. 


required to put it away. With those who are 
not practised in mocha a i oe h 
is especially necessary ; in we have often 
Seen) a slight advantage on the side of sim- 
plicity of arrangement cause an inferior in- — 
strument to be preferred to a superior one, 
Yet there is, of course, a limit to this simpli- 
fication; and it ought never to interfere with 
due attention to the principles already spe-— 
cified. ty 

Before proceeding to notice any of the ordi- 
nary forms of stands for simple or 
microscopes, we shall make a few remarks on 
the best means of carrying on a dissection — 
under a magnifying power. The simplest of 
all means of effecting this, where the objectis 
large and opaque, and a low magnifying power 
only is requisite, is to fasten it down upona 
board, to any part of the edge of which may 
be afhxed, by means of a small clamp, a 
jointed stem, carrying a socket or cell, into 
which a lens mounted in the usual 
may be dropped. This stem, being 
of movement in every possible direction, but 
having also sufficient stiffness in its joints 
remain in any position in which it 
placed, appears to us preferable to any other 
pes of supporting the lens. The object 

e illuminated, if necessary, by light condensed 
through a convex lens, or reflected from a con-— 
cave mirror. Pe se tenant must pay 
on under fluid, the only variation necessary 
the use of a shallow trough, instead of a board, 
which may be filled with water, dilute spirit, 
or oil of turpentine, as the case requires; to — 
the edge of this trough the clamp me be fixed 
in the most convenient position ; the bot- 
tom of it (if of metal) may be covered with a 
piece of cork, or a layer of resin and 
wax, for the purpose of receiving the pins 
necessary to fix the object. Where the object 
is smaller, and the dissection may be carri 
on under a higher magnifying power, we 
strongly idee the use of -Mr. Slack's 
dissecting microscope, of which a description 
and figures may be found in the 49th volume 
of the Transactions of the Society of Arts.* 

Dissecting instruments.—The instruments 
employed in microscopic dissection must of — 
course vary with the nature and size of the 
object. The following will, we think, be found _ 
most generally useful. Small pointed scalpels. 
The iris-knife is a convenient size and form 
for many purposes. Scarpa’s curved catarac 
needle is an instrument which we have found 
extremely serviceable. Fine scissors, one leg 
of which should be fixed in a long handl 
and the other kept apart from it by a spriz 
so as to close by the pressure of the finger and 
to open of itself; the blades should both be — 
pointed and sharpened on a hone; these will 

* [Mr. Powell, the optician, Clarendon-strect, — 
Somers’ Town, has enlarged and improved con- 
siderably Slack’s dissecting microscope; and Mr. 
Ross, of Regent-street, has also on sale a conve- 
nient form of dissecting microscope, which is deli- 
neated in the Penny Cyclopedia, art. * Micio- 
scope.’—Ep.] oy 


i 


pais 


MICROSCOPE. 


be found much superior to any form of knives 
for cutting through delicate tissues without 
disturbing them. Swammerdam is said to 
have made great use of such implements, in 
his dissections of insect structures, which, 
from the accounts of them on record, seem 
almost to have surpassed any which have been 
since executed. The curved forceps recom- 
mended by Mr. Slack, we also have used with 
much advantage. For more minute dissection 
we can strongly recommend common needles, 
and cutting implements which may be easily 
manufactured from them, by grinding down 
their sides upon a hone. These may either be 
fixed in wooden handles, or, which is much 
better, held in little instruments resembling 
crayon-holders, specially constructed for their 
reception. The dissector is thus enabled to give 
to his needle the effect of a long elastic point or 
of a short stiff one, by simply altering the part 
at which it is held. In the ivory handles 
of these holders, also, there is a receptacle for 
the needles, which makes the whole of this 
useful little apparatus complete in itself.* 

Many microscopists, especially on the conti- 
nent, are in the habit of making great use of the 
compressorium, an instrument in which an ob- 
ject may be submitted to graduated pressure 

etween two plates of glass, the parallelism of 
which is perfectly maintained. The results 
obtained by such compression, however, must 
be accepted with great caution, and need to be 
corrected by those views of the object which 
are gained without that distortion of it to which 
itis liable in this method. The class of inves- 
tigations in which the compressorium is most 
valuable, is that in which such structures as the 
minute ovum need to be closely scrutinized, 
without any further change in their shape than 
may render their contents more distinctly visi- 
ble. For such purposes we believe that a 
steady hand and a well-made aquatic box will 
answer the purpose sufficiently; but to those 
who prefer relying on mechanical assistance, 
the compressorium will be a useful instru- 
ment. 

We shall now proceed to describe some of 
the modes of mounting and arranging simple 
and compound microscopes, which appear to 
us most convenient. The first that we shall 
notice is a form which has cheapness and sim- 
plicity to recommend it, and which, if well 
made, is capable of an adjustment sufficiently 
delicate for all ordinary purposes. It is a 
slight modification of one of Mr. Pritchard’s.+ 
A (fig. 166) is the stand, or basis, into which 
the pillar is screwed. This may be variously 
constructed, according to the purpose for which 
it is designed. If bulk be an object, it may be 
around disk of lead; but if weight must be 
avoided, a thick tablet of mahogany about six 
inches square, or five inches by seven, (the 
longest side being in the direction of the 
movement of the pillar,) is preferable. If great 


* Such needle-holders are sold by Mr. Pritchard, 
Fleet-street, London. 


+ Microscopic Illustrations, 2nd ed. p. 82. 


347 


eae” 


SoA 
Rs 


Elevation of ordinary compound or simple microscope, 

A, base; B, hollow pillar, with joint at bot- 
tom; C, triangular rack; D, nut by which it 
is moved; E, bar carrying compound body ; F, 
other end adapted for simple magnifiers; G, 
compound body; H, objective; I, spring fork ; 
M, mirror attached to sliding tube, tightened by 
the nut, N; S, stage. 


portability be desired, the pillar may be made 
to screw into the top of the box that holds the 
apparatus; but this plan should notbe adopted, 
unless all the smaller fittings be contained in a 
tray which may be lifted out, in order that 
there may be no necessity for opening the box 
when the instrument is in use. The pillar isa 
thick tube of brass about six inches long, with 
a large screw at the bottom for being attached 
to the stand, and a joint above this, for allow- 
ing it to be inclined at any angle. If this joint 
be well constructed, the instrument will remain 
in any position in which it is placed, without 
any steadying rod or perceptible vibration. 
Within the tube is a triangular bar, with a rack 
cut on its posterior edge; this may be raised 
or depressed from the top of the tube, by turn- 
ing the milled head, which carries a pinion 
working into the rack. Partieular attention 


348 


should be paid to the action of this rack; it 
should work through a triangular socket at the 
top of the pillar of at least an inch long, closely 
embracing the bar, so that it may be moved up 
and down without the least shake, or variation 
from its axis, or tendency to slip, when loaded 
with the full weight it has to carry; at the 
same time, it should be sufficiently sensitive to 
be moved by the slightest rotation of the pinion, 
which may be effected, not only by the milled 
head, but by a lever, as in Mr. Holland’s mi- 
croscope. Such a rack will afford the means 
of focal adjustment for doublets and triplets of 
high power, as well as for ordinary magnifiers. 
If it be considered desirable to vary the length 
of the pillar, and consequently the height of 
the stage, this may be effected by attaching the 
rack, stage, &c., to a piece of tube which shall 
slide within the one that is attached to the 
base ; if the top of the lower one is sprung, and 
surrounded by a clamping screw, the upper one 
may be firmly fixed at any elevation. This 
plan has been proposed by Dr. Goring for the 
pillar of his engiscope; but we consider it per- 
fectly inapplicable to a large instrument, of 
which the pillar should be solid, in order to 
avoid oscillation. The triangular bar carries at 
its top a double arm, attached to it with a 
screw and a small milled head, by which its 
movements may be rendered more or less free. 
This arm should be thick and well hammered, 
in order that, when it carries the compound 
body, it may not be subject to vibration. The 
object of the double bend in one side of it is to 
allow the nose of the body, which is screwed 
into the hole on that side, to project below it, so 
that the magnifiers may be attached on its un- 
der side ; by this means, the necessity for un- 
screwing the body every time that the magni- 
fier is to be changed (which is requisite where 
the magnifier is screwed into the arm and the 
body into it) is avoided, without any increase 
in the length of the rack, which would other- 
wise be necessary for low powers. The other 
side of the arm carries the magnifiers, when 
employed as single lenses ; the same set may 
be used as are fitted to the compound body, 
their interior being screwed for attachment to 
it, and their exterior being adapted to drop 
loosely into the hole of the second arm. For 
such a microscope, we should recommend a 
series of ordinary lenses from 24 or 2 inches 
focus to }th of an inch, and two or three dou- 
blets from jth to jth, with a triplet of sth. 
These may all be used as objectives with a 
meniscus eye-piece ; though, for the latter, Mr. 
Holland’s will, in most cases, be preferable. 
The stage of this microscope may be a simple 
plate, attached to the top of the pillar, as in 
Jig. 166, with a spring stage and other appurte- 
nances adapted to it. We are inclined to re- 
commend for such a microscope, however, for 
the sake of simplicity and facility of use, a 
stage in which the ordinary loam of fixity 
is in some degree departed from. The upper 
part of it consists of a thick and strong fork, 

rojecting about 2 inches and about 1} inch 
bivoud) of well-hammered brass, firmly attached 


MICROSCOPE. 


to the top of the pillar ; at about §thsofaninch — 
plate of similar dimensions, — 


with an aperture of about an inch. 
upon this lower plate by a spiral ‘pring, aa 7 


below this is a 


guided by vertical pins working 


through aper. 
tures in it, is a thin moveable plate, whic i i, 


constantly being pressed upwards by ing 
against the fork. This stage combines, in a 
degree which renders it an extremely conve- 


nient one, the advantages of the ordinary spring- 


stage, and the fork. The objects, 
ee in sliders, on slips of glass, or in aquati 
xes, are readily slid under the ; 
fork (which should be bevelled off on the under 
side so as to allow them to enter), and are held 
by the spring with sufficient firmness in any 
position, whilst ready movement is also 
mitted them. The fork may have a versal 
hole drilled in it on each side, for holding the 
stage forceps or other such instrument; and it 
may be made thick enough to allow of a la- 
teral hole for fixing the condenser, ou 
being too much weakened. The thickness 
of the fork will be of no kind of inconve- 
nience, as the nose of the microscope will have 
free play from side to side between its prongs. 
= the lower plate may be attached ground- 
glass, stops, condensers, polarising a paratus, 
or any other required fiednge. The dendiviakt 
tage of this stage is that it affords no firm sup- 
port to the object, which is in some instances 
of importance. This pp be obtained by sim- 
ply adapting a plate to the upper side of the 
fork, which may be received into grooves on its 
lower surface; and this plate may then be con- 
sidered as the stage. Whenever such an in- 
strument is being adapted to the purpose of 
dissection, all that is n is to raise up a 
support for the hands on each side of the stage, 
which may consist of books, or still better of 
blocks of wood cut to the form of the outside 
of Mr. Holland’s case; and the height of the 
stage being then adjustible by the sliding tube 
of the pillar, all the advantage of Mr. Holland’ 
microscope, except its self-containedness, may be 
secured. We have only further to mention 
the mirror, which should be at least two inches 
in diameter, and have one of its sides , 
and the other concave. Its stem should be 
attached to a short piece of sprung tube slidi 
over the pillar, at capable of Bo 
in any situation by a clamping screw. wm 


If a still more portable microscope be re- 


quired, combining considerable range of Lge 
with great exactness of adjustment, we ¢é 

strongly recommend an instrument constructed 
upon the plan of the large one subse 
be described, (fig. 167,) but upon about two- 


fifths of the scale. Its pillar may either be — 


screwed into the lid of the box con th 
apparatus, or mounted on a — similar to 
that which is used for portable telescopes,—the 
tripod being reversed, and the legs being folded 
round the stem, when it is packed in its bo: 
The delicate focal adjustment of which thi 
microscope is susceptible renders it more ad. 
vantageous than the one last described, when 
deep magnifying powers are being employed ; 


a 
4 


| 
, 
| 
| 


4 


rr 
4 
\ 


MICROSCOPE. 


and its portability is a great recommendation. 
The one in our own possession is packed, with 
its tripod, into a box whose outside dimensions 
are 7% inches by 5, and its depth only 2, and 
this also contains a short body with meniscus 
eye-piece, four ordinary magnifiers, and three 
doublets and triplets, which may be used 
singly or as objectives, illuminating lenses and 
Speculum, aquatic boxes, and other small ap- 
paratus,—the weight of the whole being no 
more than 2% lbs, although a magnifying power 
of 450 diameters, with sufficient penetration to 
exhibit the markings on the Podura, and with 
perfect steadiness, may easily be obtained by it. 
The instruments we shall now describe are 
not adapted for use in any other way than as 
compound microscopes. Their size and weight 
are such as would render them far less conve- 
nient than the smaller forms already described 
for use with simple lenses, although there is no 
other reason why they should not be thus em- 
sya Every constructor of microscopes has 
is own favourite model ; and there are few re- 
cently made instruments of the highest class 
which do not possess some particular recom- 
mendations. Amidst the numerous claimants 
to our notice, we shall select two; of which 
the first is the form adopted by one of the best 
constructors of achromatic objectives in this 
country ; and the second is the one which we 
have ourselves had in use for several years, 
and which we do not desire to lay aside for 
any we have seen. With respect to the former, 
our limited space compels us to refer to the 
article Microscope in the Penny Cyclopedia, 
where a delineation and full description of Mr. 
Ross’s Microscope will be found.* 
We shall now describe the microscope 


* [Without wishing in the least degree to detract 
from the merit of Mr. Ross’s microscope, (to 
which, on the contrary, he bears willing testi- 
mony,) the Editor deems it but justice to refer 
to a very beautiful instrument constructed by Mr. 
Powell, which he has employed for some time, and 
which is also used by several observers in this city. 
The body of the microscope moves on a triangular 
bar, having a bearing of three inches, which ren- 
ders it very steady. The coarse adjustment is ob- 
tained by a rack and pinion, attached to which are 
two large milled heads, which allow of the body 
being adjusted with either hand. The fine adjust- 
ment has also two milled heads, only two inches 
apart from the coarse one, and their axis being 
horizontal and parallel to each other, renders the 
motion of the hand from one to the other perfectly 
easy, withont removing the eye from the body of 
the microscope. The stage is seven inches square. 

e convenience of its being thus large is, that the 
hands do not interfere with the object when adjust- 
ing it. The heads that move the stage have their 
axis in the same line, and so placed that with the 
same hand the stage may be moved in all direc- 
tions ; this is convenient when viewing an object, 
the surface of which is very irregular; with the 
right hand you can move the stage, and there being 
two heads to the adjustments for the body, with 
the left the object can be adjusted into focus. There 
are likewise two milled heads to one motion of the 
stage, by which means both hands may be employed 
at the same time, which is sometimes requisite. 
On the same bar that the body rests, moves the 
‘* achromatic condenser,” by which arrangement it 
4s certain to move in the same line with the body, 


349 


which we have ourselves been accustomed to 
employ, and state what we regard as its advan- 
tages; not omitting to notice the objections 
which may be brought against it, and bearing 
in mind that every microscopist is naturally 
most partial to the form which he has himself 
adapted to his own ideas of convenience. It 
is principally constructed according to the 
plans of Mr. Pritchard and Dr. Goring ; and 
we may observe in limine, that the objections 
which have been brought against any form of 
construction in which the body is screwed by 
its lower extremity to a horizontal arm, as 
placing it in the most unfavourable position for 
vibration, independently of the stage, are ap- 
plicable only to instruments which are not 
made with sufficient solidity; for, having had 
an opportunity of comparing the quality in this 
respect, of Mr. Ross’s microscope, with our 
own, the two being placed in exactly the same 
circumstances, we could not find that there 
was any inferiority on the part of the latter. 
It must be borne in mind, that every increase 
in the size and power of a microscope must be 
accompanied by more than a corresponding 
increase in solidity, in order to guard effec- 
tually against oscillation. 

The stand or basement is a slab of solid 
mahogany 12 inches square and 14 inch thick, 
loaded with lead at the corners, aud having a 
strip of thick baize, about 1$ inch broad, glued 
round the edge of the under side; the whole 
weight bears upon the baize, which does not 
readily communicate vibrations; and the large 
surface over which the pressure is distributed 
gives the instrument a degree of imperturba- 
bility which would scarcely have been antici- 
pated. The slab is surrounded by a slightly 
elevated rim ; and it thus serves as a most con- 
venient little table, on which the various pieces 
of apparatus required for microscopical obser- 
vation may be carried about with the instru- 
ment without any danger. The pillar of the 
microscope carries at its lower extremity a 
screw, above which is a fange or shoulder of 
2 inches diameter; the screw is received into 
a socket let into the wooden foot, and firmly 
attached to it, and itself having a shoulder of 
equal size; so that, when the pillar is firmly 
screwed down upon it, there is not the least 
tendency to vibration between the two. The 
socket is not let into the middle of the base, 
however; but its centre is only 24 inches from 
one of the sides, and 9%, therefore, from the 
other; so that, in fact, when the microscope is 
placed vertically, the centre of the stage pretty 
nearly corresponds with the centre of the foot. 
The object of this is to give a decided prepon- 
derance in weight to the front of the foot in all 
positions of the microscope ; for we are inclined 
to think that much of the oscillation so fre- 
quently complained of in microscopes is to be 


which is most essential, for unless it did 80 when 
using different power object-glasses, the axis of the 
lenses would not coincide. There are many other 
conveniences and improvements to this microscope 
which cannot be mentioned in this, brief notice.— 
ED.], 


350 
Fig. 167. 


Superior Compound Microscope. 


A A, base; B, pillar with joint at the top; CC, 
stem, containing square tube D, which is moved 
by a fine screw turned by the nut E; within this 
tube slides the square bar F, carrying the arm G; 
into this isscrewed the tube H, within which the 
compound body slides; I, the objective; K, 
stage-fork ; L, sprung tube, tightened by the nat 
N, carrying the frame of the mirror M. 


attributed to the fact, that, when the instrument 
is much inclined, the hinder foot receives 
nearly the whole weight, and the portions of 
the mstrument on the two sides so nearly 
counterpoise each other, that a very slight cause 
will communicate an oscillation to the whole. 
We can strongly recommend to our readers a 
basis of this kind, having not only our own ex- 
peeeee of its benefit to guide us, but that of 

iends whom we have induced to adopt it, and 
whose previously unsteady microscopes have 
been greatly improved thereby. It certainly 
does not possess the merit of portability ; but 
this, in a large microscope for observations of 
the highest kind, ought not to be a considera- 
tion. Nothing is easier than to have a separate 
tripod of the ordinary kind for use when occa- 
sion requires. To such a tripod Mr. Ross* 
has recently applied a method of construction, 
which he states to be very effectual in obviating 
vibration; but we cannot speak from experi- 
ence in regard to its use; and being well satis- 


* Microscopic Journal, No. 2. 


MICROSCOPE. 


fied with our own much simpler and less ex- 
pensive plan, we do not see the necessity for it: 

The pillar is just an inch in diameter, and 
consists of a stout brass tube loaded with lead. 
On the firmness of this part much depends. 
It is 8 inches from the foot to the centre of the 
joint. The middle piece of the joint is th of an 
inch thick ; and to this is attached a tubular 
clamp with a binding screw, which closely em- 
braces the stem. This mode of construction 
we adopted in accordance with the recommen- 
dation of Dr. Goring and Mr. Pritchard ;* but 
we are doubtful if its advantages counterba- 
lance the disadvantage of a certain want of 
fixity which it imparts to the remainder of the 
instrument supported by it. The stem is a 
thick brass tube of about f,ths of an inch in 
diameter ; to the upper part of it is firmly at- 
tached the stage, which is composed of a simple 
plate of well-hammered brass, 4 of an inch 
thick ; its length from the front of the pillar is 
4 a its breadth 24 orig aa “re domes 
ter of its aperture 14 inch. e only —_ 
preg. eitached to it is Ne fork, of whi 

e two wires work through sockets projecting 
from the under side of the stage. This fork is 
made sufficiently thin to poo a certain de- 
gree of elasticity; and, being firmly held in 
any position by the friction of its wires, it is a 
very useful means of holding aquatic boxes, 
slips of glass, large sliders, &c., affording, by 
its wide opening, (2 inches,) considerable free~ 


_ dom of movement to the object. The utility 


of this fork will depend upon the goodness of 
its construction in the first instance; it ought 
to work easily, and yet hold tightly in any po-~ 
sition. The sockets through which its wires 
pass should be sprung, so that they may be 
tightened at pleasure, should they work loose. 
The stage has a slight rim projecting into the 
lower side of the aperture, in order to hold 
various fittings which are attached to it by a 
bayonet catch, and holes are drilled in various 
parts of the stage (the massiveness of which 
prevents its being weakened thereby) for the 
reception of the pins of the forceps, condenser, 
&e. The stem carries a sprung tube, to which 
the mirror is attached, in the manner to be 
presently noticed. 
From the top of the stem projects a square 
tube, a little more than {,ths of an inch each way, 
the upper end of which is sprung, so as to 
grasp with sufficient firmness a solid bar of half 
aninch square, which slides up and down within 
it. The upper end of this bar carries the arm 
to which the body of the microsco 
on the accuracy of its formation the truth of 
movement will of course depend ; but if well 
made, a rise and fall of 34 inches may be 


allowed to it, without the slightest alteration in 
the position of the axis of the body which it — 


carries. The advantages of this sli in 
ment over the rack commonly employed for the 
coarse adjustment we as considerable ; 
very much time is saved ; for the arm may be 
shifted from its greatest to its least distance 
from the stage, in scarcely more time than is 


* Op. cit. 


is attached; _ 


‘ 
alls tie a 1 


MICROSCOPE. 


required for making the slightest adjustment. 
The axis of the body is never changed in the 
least degree,—which we have rarely found in 
rack adjustments, owing to the pressure of the 
pinion against one side of the bar; and thus an 
object is always kept in the centre of the field, 
whatever change made be made in its focal 
distance by an alteration of the magnifiers. By 
alittle practice, the power of making adjust- 
ments of extreme minuteness may be obtained, 
if the bar have been originally filed so true 
that it works with perfect smoothness in every 
ai An additional adjustment, which may 

made of any required fineness, is provided 
for, however, by making the square tube or 
socket itself moveable, and connecting it with 
a micrometer screw worked by a large milled- 
head at the bottom of the stem. By turning 
this screw, the socket, and the bar which it 
carries, are raised or depressed in any minute 
degree; and the socket being made to work 
through stuffing- boxes closely packed with 
cork, all twisting on its axis by the action of 
the screw is avoided. On the fineness of the 
serew the delicacy of the adjustment will of 
course depend. That which we have employed 
has forty turns to the inch; and the milled- 
head being 1% inch in diameter, or about 44 
inches in circumference, a movement of one- 
fiftieth of its periphery, or something less than 
#th of an inch, will affect the arm to the amount 
of s)oth of an inch. We should recommend, 
however, a screw rather finer than this. By 
dividing a circle on the milled head, and affix- 
ing an index-point to the bottom of the stem, 
the amount of motion given may be known to 
a great nicety, and thus the thickness of a mi- 
nute object laid upon any surface may be mea- 
sured. If its upper side be brought exactly 
into focus, and it be then removed, and the 
Surface on which it has lain be brought into 
focus by the micrometer screw alone, the num- 
ber of divisions over which the index has passed 
will of course indicate the thickness. This me- 
thod, which was proposed by Mr. Valentine,* 
answers very well Er such objects as the vessels 
of plants, scales of insects, &c. which can be 
completely isolated, when a sufficiently high 
power is employed, so that distinctness can 
only be obtained at one point. We consider it 
a great advantage of this kind of adjustment, 
that it is effected at a considerable distance 
from the stage, and that the hand is therefore 
in no danger of deranging the position of ob- 
jects or apparatus connected with it. 

The arm which carries the body is attached 
to the top of the bar by a screw-pin passing 
through the former, by which it is enabled to 
traverse from side to side. This movement 
will often be found extremely useful, both in 
the examination of different parts of objects 
which it is desirable not to move, and in chan- 
ging magnifiers, &c. on the body; the want of 
it we consider one of the chief inconveniences 
in Mr. Ross’s form of construction. The arm 
is jths of an inch thick, and broad enough at 
the part farthest from the centre to receive the 


* Trans. of Soc. of Arts. 


351 


body, which is not made tapering in the usual 
manner, but is attached by a screw of 14 inch 
diameter, with a large shoulder above it. By 
this mode of attachment, and by the massive- 
ness of the arm itself, all vibration from the top 
of the bar is prevented ; at least we have not 
been inconvenienced by it. When the bar is 
pushed into its socket, so that the arm ap- 
proaches the stage, (as when high powers are 
used,) no oscillation can arise from its vibra- 
tions; and the socket itself works through an 
aperture in the stage-plate, to which it is so 
closely fitted that no oscillation can arise in 
that point; so that, both in theory and prac- 
tice, we find the form here proposed unobjec- 
tionable on this score. It is true that, when 
the bar is drawn out to its full extent, oscilla- 
tion may arise; but this is never the case, ex- 
cept when low powers are being employed, and 
then we altogether fail to perceive it. In the 
construction of the body there is nothing worthy 
of peculiar remark; and, as we have already de- 
scribed the various modes of magnifying the 
object, we shall therefore now pass on to con- 
sider the best means of illuminating it. 

The perfect illumination of the object is a 
matter of the utmost importance, especially 
when high magnifying powers are being em- 
ployed. There are many difficult objects which 
require to be viewed under a great variety of 
aspects, in order that their true characters may 
be determined ; and there are not a few whose 
structure cannot be understood at all, even with 
the most perfect arrangement of the optical 
portion of the microscope, unless similar atten- 
tion be bestowed on the concentration of the 
light by which they are viewed. We shall, 
therefore, bestow on this subject more attention 
than it has ordinarily received. 

For transparent objects of large size, which 
are being viewed with low powers, such as sec- 
tions of wood, wings of insects, &c. we find a 
concave mirror by far the most simple and, at 
the same time, effective means of illumination ; 
and the optical errors to which it gives rise are 
not such as to interpose any practical difficulty 
in its use. It should be, for such a microscope 
as we have described, of greater size than that 
ordinarily employed ; three inches may be re- 
garded as a good diameter. It should be set, 
by an universal joint, upon a piece of tube 
fitted to slide stiffly up and down the stem 
which descends from the stage. In this man- 
ner its distance from the object may be readily 
varied ; and the degree of concentration of light 
effected by it will thus be easily adapted to the 
character of the object to be viewed. Thus, if 
it be pushed near the stage, the pencil of con- 
vergent rays will not be nearly brought to a 
focus, and a large surface will be illuminated 
with a moderate light. But if it be drawn 
nearer the opposite end of its range, the rays 
will be more concentrated, so that a smaller 
surface will be illuminated, but with much 
greater brightness. By the former adaptation 
we are enabled to illuminate, with great equa- 
lity, and by means of the ordinary lamp-flame, 
an area of three-eighths of an inch in diameter, 
with sufficient intensity to produce a very bright 


352 


field of fourteen inches. In viewing large ob- 
jects for which great perfection is not required, 
we find it advantageous to interpose a ground- 
glass at about half or three quarters of an inch 
distance beneath them ; thisis easily adapted to 
the under side of the stage. It serves to pro- 
duce an extremely equable diffusion of the 
light over a large field, and to deaden the glare 
which is occasioned by the direct admission of 
so large a quantity ; but, if applied to objects 
which require to be seen with great distinct- 
ness, it will be found to produce a kind of, fog 
which seriously impese the power of the micro- 
scope; and with objects of any difficulty it is 
quite inadmissible. In viewing objects, how- 
ever, of the largest size that the microscope can 
receive, by a good diffused daylight, the ground- 
glass is never required. A bright cloud, oppo- 
site to the sun, is then the best source of illu- 
mination. For the purpose of effecting these 
and other adjustments of the mirror, we have 
found it convenient to have the tube which 
carries it sprung, so as to slide rather loosely on 
the stem, and to secure it in any particular 
situation by means of a large milled head which 
screws on one end of the tube, and clamps it 
upon the stem. 

The plane mirror, with a condensing lens 
between it and the stage, is preferred by many 
to a concave mirror; and for certain objects it 
is, without doubt, superior. For ordinary use, 
however, we prefer the concave mirror, for the 
following reasons :—Its effects are obtained by 
a single adjustment ; whereas, in the use of the 
plane mirror and lens, two adjustments are re- 
quired: and if (as we shall presently state to 
be often desirable) the mirror be thrown quite 
out of the axis of the optical part of the instru- 
ment, it is difficult to adjust the condenser 
with correctness.. Further, in order to obtain 
light enough for a field such as we have men- 
tioned, the condensing lens must be nearly 
three inches in diameter, and thus becomes 
very cumbrous and inconvenient. For objects 
of a high class the concave mirror should of 
course not be employed; but for these the 
common condenser is by no means adapted, 
and must be put aside for a superior one, such 
as we shall presently describe. The plane mir- 
ror and condenser enable the observer, how- 
ever, to obtain an additional variety of illumi- 
nation, which is often advantageous; and by a 
simple modification, proposed by Mr. Varley, 
the light of a bright cloud may be artificially 
imitated by them. The means of doing this 
consist in covering the surface of the plane 
mirror with carbonate of soda or pounded glass, 
by which the direct solar rays are reflected very 
much as by a white cloud. We have also seen 
a plaster of Paris mirror employed for the same 
purpose, and with good effect, where, on ac- 
count of the transparency of the object, it was 
necessary to reduce the amount of light sent 
through it, without interposing any screen that 
should produce indistinctness. 

It is often very desirable to throw the centre 
of the mirror a good deal to one side of the 
axis of the body of the microscope, so that the 
reflected rays may fall very obliquely upon the 


MICROSCOPE. 


object, and cause its prominences and ‘depres- 
maes to exhibit tales of much greater depth’ 
than can ever be seen with more direct light. 
No microscope, in which there is nota provision 
for this movement, can be edas having 
its resources properly developed ; and we have 
seldom seen one which comes * to our 
of the degree in which it should be permitted. — 
In general, the mirror-frame is im ; 
fixed to the sprung tube which carries it; and 
thus it can only be turned out of the axis at a 
angle which will evidently interfere with its u 
In our own microscope, the mirror-frame is 
connected with the tube by a stalk of an inch 
in length, so that the centre of the mirror is 
three inches from the stem. This, of . 
involves a lengthening of the stage, and of the 
arm which carries the body, in order that the 
centre of the apertures of all three may be in 
the same line; but the disadvantage hence 


resulting is easily avoided by increasing the 
strength of these nak: The riety of illaiite 
nation which may be given by a mirror fitted 
in the manner we have described, is very preat ; 
and some very curious and unexpected pheno- 
mena are not unfrequently disclosed by means 
of it. For example, the field may be rendered 
almost dark, by turning the centre of the mirror 
considerably out of the axis, so that none of tl 
rays reflected by it pass up the body of 
microscope; whilst objects of great delicac 
will frequently appear brilliantly illuminated, 
on account of their retention of ra ny the 
light which is passing obliquely through them. 
In this at be we die often Sen enabled | 
see an immense number of the minutest ani- 
malcules (monads) rapidly moving through 
water, in which, with direct light, none but the 
larger ones could be distinguished ; and the 
interest of the spectacle is heightened by the 
phosphorescent glow which the anima Ss 
appear to have when thus illuminated.* A 
similar effect may be produced without the 
use of the concave mirror, by causing a dire 
pencil of rays from a lamp or candle to be 
thrown very obliquely upon the object by 
means of a condensing lens. ij i>-tn 
In the examination of many. delicate objects 
with high powers, direct light will often 
found more advantageous than reflected. T 
may be obtained with facility, by placing a 
lamp or wax-candle behind the stage, irror 
being turned out of the way. In the me 
the direct light of a bright cloud will often be 
found to produce an extremely beautiful effect; 


+ 


but in order to attain this without an inconve- 
nient position of the head, the microscope § 
must agp etal to such a height, t whi 
the stem is horizontal, or even inclined in 
position contrary to the usual one, the eye-piece ~ 
may be at a convenient height for the eye. y 
different modes of illumination best suited to” 
different objects can only be found out by ex- 
perience, since achromatic objectives vary in 
their relative effects with each. 


pes 
* This method of viewing objects biel fo 
noticed, a few years since, as a new discovery; it — 
had long, however, been familiar to ourselves, — 
and, we belieye, to most other scientific observers, 


MICROSCOPE. 353 


When condensed light is employed with 
“4 powers, great care is necessary in order 
to bring out the best effects of a microscope, 
with difficult objects. These remarks apply to 
the simple as to the compound forms of the 
instrument. We do not ourselves consider the 
ordinary condenser as of much more value for 
the higher than for the lower class of trans- 
parent objects; and we think that it may be 
discarded from the instrument without dis- 
advantage. Great assistance may be obtained, 
however, from a well-constructed condenser, 
in the resolution of the more difficult class of 
microscopic objects. That which was pro- 
posed by Dr. Wollaston for use with his 
doublet consists of a tube about six inches 
long, having at the lower end a diaphragm 
with a circular perforation about three-tenths 
of an inch in diameter, through which light, 
proceeding from a radial point or surface, is 
reflected by a mirror below it. At the upper 
end of the tube is a plano-convex lens, about 
three-fourths of an inch focus, with its plane 
side next the observer; the object of which is 
to form a distinct image of the circular per- 
foration in the plane of the object, which 
should be at about eight-tenths of an inch 
from the lens. We consider this instrument 
to be theoretically faulty; inasmuch as the 
point from which the illuminating rays di- 
verge, and the limiting aperture are not co- 
incident, so that pencils brought to a focus for 
the former are not for the latter. The length 
of the tube, again, is an inconvenience, espe- 
cially in the case of small microscopes. Never- 
theless, it is much superior to the ordinary 
form of condenser. An improvement was 
suggested by Dr. Goring, which consisted in 
shortening the tube below the lens, and re- 
moving the stop from that end of it to the 
Other, so that it should be just beneath the 
object; in this manner the illuminating rays 
may be brought to a focus on the object, the 
ale ones being cut off by the stop. 

Ve have derived much advantage from the 
use of this condenser in the small doublet mi- 
croscope already noticed, and by a slight mo- 


dification of it we can obtain a variety of 


illumination, which is often very useful. ‘Our 


_ condenser consists of three tubes, one sliding 


within the other; the outer one is fixed to the 
under side of the stage; the second carries at 
its upper end the stop, the distance of which 
from the object may thus be changed, and the 
inner one carries the condensing lens. A stop 


_ may be screwed into the bottom of the latter, 


if it is desired to adopt Dr. Wollaston’s plan. 
ie have derived the greatest advantage from 
the use of this condenser, however, by using 


it with direct light from a radiant point at 
_ some distance,—a bright cloud, for instance, 


in the day-time,—and a lamp or candle on the 


_ Opposite end of the table at night. In either 


of these cases, the focus of the illuminating 
: may be made coincident with the plane 
of the object, without that glare which will 


_ almost certainly be produced if the source of 
_ light is nearer and more intense. When thus 


a 


" used, Dr. Goring’s condenser approaches in its 


VOL. III. 


character to that of Sir D. Brewster,* which 
we shall now describe, adding some ideas of 
our own in reference to its construction. 

The principle of illumination on which Sir 
D. Brewster lays great, and we think fully- 
deserved stress, is, that the focus of the illu- 
minating rays shall be coincident with the 
object, so that there shall not be two sets of 
rays at different angles, one proceeding from 
the luminous object and the other from the 
object to be magnified. This can only be 
attained in any degree by making the image 
of the illuminating body coincident with the 
object; and it will be perfectly accomplished, 
in proportion as the rays forming that image 
are themselves free from aberration. If, for 
example, the white rays have been separated 
into their component colours by the condenser, 
these colours will be imparted to the object, 
the appearance of which will also be rendered 
less distinct by the spherical aberration of the 
condensing lens. Hence an achromatic lens, 
or, if this be objected to on account of its 
expense, a Herschel’s aplanatic doublet, should 
be used as the condenser; the latter we have 
found to answer very well, as the centre of 
the circle illuminated by it is very nearly free 
from false colour. Further, if a mirror be 
employed to change the course of the rays, 
it should be of metal, in order to avoid the 
false rays reflected from the first surface of the 
glass. If day-light be employed, no other 

recaution is necessary; but if the illumination 
é obtained from a lamp or candle, it will be 
necessary to limit the amount of light ad- 
mitted. This must not be by a stop placed 
beneath the lens, for the reason already speci- 
fied ; but it should be accomplished by a stop 
or shade placed as near as possible to the flame, 
so that the image of that and of the flame 
may be brought—virtually if not exactly—to 
the same focus. We have found that the same 
end may be attained by removing the lamp or 
candle to a greater distance, so as to diminish 
the intensity of the light to the required 
amount, and only a very low flame will then 
be required, as the condensation of the rays 
is much more perfect than with the ordinary 
lens. The achromatic condenser is strongly 
recommended also by M. Dujardin, an eminent 
microscopist of France; and we know that it 
is now considered an indispensable addition to 
microscropes of the highest class, affording, 
as it does, the means of resolving objects, 
previously considered too difficult to admit of 
a clear view of their nature. We are disposed 
to think, however, that some improvement is 
necessary in order to develope the highest 
powers of this instrument. The rays of light 
proceeding from the radiant Ba or object, 
being brought to a focus by the condenser on 
its surface, cross each other there, and should 
proceed to the object-glass of the microscope, 
as if they came from the object itself. Now, 
unless they are made to converge upon the 
object at the same angle at which they diverge 


* Treatise on the Microscope, from the Ency- 
clopedia Britannica. ‘ 
A 


354 


to enter the objective, we cannot but think that 
a source of error still remains, and that the 
most perfect image possible, formed by an 
achromatic object-glass, of an object which is 
artificially illuminated, can only be produced 
when the rays from the source of light take 
exactly the same course as if they proceeded 
from the object itself. That they may have 
this course, they must be made to converge 
upon the object by a condensing lens, whose 
focus for parallel rays (if the illuminating point 
be very distant) shall be the same as the acting 
focus of the objective. A different condenser 
would thus be required for every objective ; 
but the ccpuate of these would be sufficient 
to preclude their general employment. The 
same condenser might be employed, however, 
for several low powers; the highest having 
their own expressly adapted to them. We 
may mention it as a fact for which we cannot 
very well account, that we have been able to 
obtain a very beautiful and distinct illumina- 
tion by the use of an aplanatic-doublet con- 
denser, receiving its rays from the ground glass 
globe of the common table-lamp, which would 
not seem to furnish any of the conditions that 
we have dwelt on as of theoretical impor- 
tance. 

Opaque objects may be illuminated in two 
principal ways, either by a light cast obliquely 
upon them by a condensing lens, or by rays 
thrown upon them perpendicularly by a silver 
speculum fixed to the object-end of the body, 
which receives them from the mirror below, 
Both these modes have their peculiar advan- 
tages, and will be found by experience to be 
applicable with advantage to different classes 
of objects. No general directions on the sub- 
ject can, however, be given. The condenser 
to be used by lamp-light for large opaque ob- 
jects should be a bull’s-eye or hemispherical 
lens of four inches in diameter; by this, 
even from a common candle or flat-wicked 
lamp, a sufficient light may be attained for 
almost any purpose, and with an Argand lamp 
a very powerful illumination is obtained. For 
the parallel rays of day-light, however, an 
ordinary double-convex lens of the focus of 
two inches or more may be employed; this 
may be mounted upon a separate stem and 
foot, as the bull’s-eye should always be, or it 
may be attached to some part of the micro- 
scope itself. We have seen foreign instru- 
ments in which it was fixed to the object-end 
or nose of the body; a construction which we 
deem essentially bad, inasmuch as it then re- 
rinse to be readjusted every time that the 
ocal distance is changed by the substitution of 
one objective for another. A better mode in 
our opinion is to attach it to the side of the 
stage by a jointed arm possessing a pin which 
may be fitted into one of three or more holes 
drilled in the side of the stage with sufficient 
tightness to remain in any position. If the 
wire to which the lens-frame is attached be 
made to through a sprung socket con- 
nected by a ball-and-socket-joint with the 
jointed arm, an immense variety in position 
may be readily given to the condensing lens, 


MICROSCOPE. 


which will render a separate mounting for it 
unnecessary. Ae 
The metallic speculum, or Lieberkuhn, for 
throwing down rays directly upon the obj 
is sometimes attached to the objective i 
sometimes to a tube which may be drawn down 
over it to the required amount. The former con- 
struction is the most perfect, each magnifier 


having its own speculum; but the latter is_ 


most economical, as one peraies serves for 
many objectives. When the latter \ 

tion is employed, the tube should be marked 
with the numbers of the magnifiers at the 


points at which it may be best adjusted for 


each, so that, when the object is in the focu: 

of the objective, it may be in full receipt of 
the rays reflected from the speculum. In this 
mode of illumination the size of the concave 
mirror will be found to have a considerable 
influence ; and the capability of adjusting also 
its distance from the s lum gives a 


variety to the mode of illumination. It can 
never be too fully kept in mind, that, in the 
examination of doubtful objects, no really satis- 


factory result can be attained, until they have 
been viewed in every possible way. When the 
object is not perfectly apaqiie, or does not fill 
up the whole of the field of view, it should 
always be placed on an opaque disc, which 
should be large enough to interrupt all the rays 
passing directly upwards from the mirror to the 
eye. The colour of this disc may be advan- 
tageously varied for certain objects, but in 
general we consider a dead black the best for 
giving them effect. Asa general rule it may 
be remarked, that the fewer the rays entering 
the eye except through the object, the more 
perfect will be the view of it; and if there be 
anything approaching to a glare around an 
opaque object, whether the light di- 
rectly from the mirror, or be reflected back 
from the too-bright surface of the dise, it is 
equally injurious, and will occasion a mis- 
tiness over the object itself. It is evident, how- 
ever, that the size of the disc must be governed 
by that of the field of the objective em d; 
for, if too large, it will interrupt too much of 
the light impinging on the speculum. A piece 


of black glass, mounted upon a long strip of — 


common window-glass, will be 

useful where the object is such that it 
be laid upon it when the microscope is 
clined. hen the object requires to be 
in the stage-forceps, however, a disc of 
card may be placed behind it, so as 

it a back-ground. And for some 
Opaque objects, it is most advantageous to em- 
ploy little concave discs or cups, with th 
interior blackened, in front of which the ol 
jects are to be placed. Similar dark back- 
grounds are useful when oblique light is em-— 
ployed. vy 


Pare 


E 


aE 


i 


be 


' - 


III. MacGniry1nG POWER OF MICRO- 
SCOPES. 


The next point to which we shall advert is 


8 


J. 
tg ss n 
an 


H 


] 


the mode of estimating the magnifying pow 
of microscopes, and of measuring the real — 
size of objects under examination, Our esti- — 


ee Ri 


MICROSCOPE. 


mate of the magnifying power of a microscope 
must depend upon the standard which we 
assume as the ordinary distance at which the 
object is seen with the naked eye; since, if 
brought within five inches, it is seen under 
double the angle, and therefore of double the 
size which it appears to possess at ten inches. 
Tf, therefore, the former distance were taken as 
astandard, the magnifying power of a lens or 
‘microscope will only be half that at which it 
‘would be estimated with reference to the other. 
Nearly all opticians, however, have agreed in 
‘considering ten inches as the standard of com- 
parison; and when, therefore, an object is 
figured as magnified 100 diameters, it is meant 
that this figure placed at ten inches distance 
from the eye is 100 times the dimension, each 
way, of the real object seen with the eye alone 
at a similar distance. The measurement of 
the magnifying power of simple or compound 
microscopes by this standard is attended with 
no difficulty. All that is requisite is to have 
a glass or thin slip of ivory accurately divided 
) a small fraction of an inch (;};th will usually 
answer very well), and a common foot-rule, 
divided to tenths of an inch. The glass or 
ivory micrometer being adjusted to the focus 
of the magnifier, the rule is held parallel with 
it, at the distance of ten inches from the eye. 
the second eye be then opened, whilst the 
other is looking at the object, the circle of light 
‘included within the field of view, and the 
object itself will be seen faintly projected upon 
_ the rule ; and it will be very easy to mark upon 
_ the latter the apparent distances of the divi- 
sions on the micrometer, and thence to ascer- 
| the magnifying power. Thus, supposing 
each of the divisions of ;,th of an inch 
sponded with 13 inch upon the rule, the 
linear magnifying power is 150 diameters; 
‘if it corresponded with half an inch, the mag- 
“nifying power would be 50 diameters. The 
erficial magnifying power is of course esti- 
mated by squaring the linear; but this isa 
mode of statement never adopted by scientific 
_ observers, although often employed to excite 
_ popular admiration or to attract customers by 
those whose interest is concerned in doing so. 

__When the magnifying powers of the several 
_ objectives of a microscope are known, it is easy 
_ to make a fair approximation to the real size of 
an object under examination, by projecting its 
_ Image, as before, upon a foot-scale held at ten 
_ Inches distance ; and the apparent dimensions 
it there exhibits, divided by the magnifying 
ig employed, will of course be its real size. 
_More accurate measurements are generally re- 
quired, however, although the foregoing may 
“serve as a sufficiently near approximation for 
_ ordinary purposes. Various methods of ob- 
taining these have been devised. The most 
perfect measurements are obtained by a fine 
_____micrometer-screw, by turning which either the 
_ object or the body will be made to execute a 
_ transverse movement; just as, in the fine ad- 

_ justment of the focus, the body is made to 

_ pproach or recede from the stage. This ap- 

_ paratus may be attached to the stage, if it be 


355 


thought preferable to move the object, or to 
the arm if the body be made to traverse. In 
proportion to the fineness of the screw, and to 
the size of the milled-head, will measurements 
be obtained of minute accuracy. In the focus 
of the eye-piece a very fine thread is placed ; 
and one edge of the image being brought 
against it, the position of the micrometer is 
noticed; and the other edge being then brought 
to the same line, the number of divisions of 
the micrometer-screw, which have passed over 
the index, will indicate its size. The expen- 
siveness of this micrometer, when made with 
sufficient accuracy and minuteness, is the only 
bar to its general employment. Other means 
have been devised, however, which are scarcely 
inferior; and the simplest of these requires 
only the use of an eye-piece of a construction 
different from the ordinary, with coarsely di- 
vided glasses. The micrometer eye-piece is 
made upon the principle of Ramsden’s. The 
optical part of it differs from that in common 
use, in having the plane side of the field-glass 
turned towards the object; and in the adjust- 
ment of the foci of its lenses in such a manner 
that the image to be viewed by it must be 
beneath the field-glass instead of being be- 
tween it and the eye-glass. In its focus there 
is placed a plane glass with divisions on it; 
these may be from ith to jth of an inch 
apart ; the latter will enable very minute mea- 
surements to be taken. By this arrangement, 
when the object is brought into focus, it ap- 
pears as if it were traversed by cross lines; 
since its image is coincident with the divided 
glass, and is, like it, viewed by the eye-piece 
as by a simple microscope. The value of these 
divisions will, of course, depend upon the 
degree in which the object is magnified in the 
image; and they must be ascertained for every 
objective, by the divided glass or ivory mi- 
crometer. This being brought into focus, and 
so placed that the direction of its two sets of 
lines shall correspond with those of the divided 
glass in the eye-piece, the number of divisions 
in the latter, corresponding to each division of 
the former, must be observed, and their value 
will be thus ascertained. Thus, if one divi- 
sion on the ;,th inch micrometer be found to 
coincide with eight on the eye-piece, these 
eight will together indicate a dimension of j;th 
of an inch upon the object; and each division 
of the eye-piece will of course be equivalent 
to the ith of an inch. If there is not an 
exact correspondence, or if it be desired to 
obtain a power which can be expressed in 
round numbers, a little alteration in the length 
of the body, made by drawing out his eye- 
piece, will enable the microscopist to effect 
this ; but the eye-piece should be marked, so 
as to be adjustible to the same point again, 
when the same magnifying power is employed, 
When the value of the divisions on the glass 
in the eye-piece is ascertained for every mag- 
nifier, the object-glass micrometer may be put 
aside altogether; since by the use of the eye- 
piece alone, a series of lines, the real distance 
corresponding to which is sae 4 projected 
A 


356 
upon the object; and, with a little practice, 
a very close estimate may be formed of the 


proportional size of the object, when it only 
extends over a part of a single division. This, 
for ordinary purposes, is by far the most con- 
venient mode of measurement. 

The camera lucida, however, which has been 
adapted to the microscope for the purpose of 
delineating representations of microscopic ob- 
jects, may be most advantageously applied 
also to micrometry. By this instrument (of 
the construction of which we shall presently 
speak) a highly magnified picture is projected 
upon a surface on which its outlines may be 
easily marked, and on which their size may, 
therefore, be determined with the greatest 
nicety. Here, as in former cases, the micro- 
meter object-glass must first be employed, in 
order to fix the standard. If one of these be 
placed in the focus of the microscope, and the 
camera lucida be so adjusted, that an image of 
its lines be thrown upon a piece of paper ata 
fixed distance from it, the distance of these 
may be marked with precision ; and subdivi- 
sion on the paper may be carried to any re- 
quired extent, so as to afford the means of at 
once ascertaining the size of an object placed 
in the field. Thus, if the magnifying power 
and the distance of the paper be so adjusted, 
that the lines which are really jth of an 
inch apart are projected upon it at five inches 
distance from each other, every inch on the 
paper will of course be equivalent to hth 
of an inch on the object. Lines of jth of 
an inch apart may easily be drawn on the 
paper; and the distance between each of these 
will represent y5J,5th of an inch on the ob- 
ject. In this manner the size of an object may 
be known with great nicety, and with less lia- 
bility to error than in the use of the screw mi- 
crometer. It is easy to increase the apparent 
size of the image thrown by the camera lucida 
to almost any required extent; so that even 
greater minuteness may be attained. The dis- 
tance between the eye-piece and the paper may 
be increased,—either vertically by placing the 
latter upon a chair or even on the floor,—or 
horizontally, by turning the prism or mirror 
a quarter round, and projecting the image in 
the direction of the side of the room, so that 
the range of distance is much increased. Such 
a plan is, of course, of no use in delineation ; 
but in micrometry it may be had recourse to 
with advantage, especially when comparing the 
relative sizes of similar objects, such as the 
blood-discs. For every magnifying power, 
whether gained by changing the objective or by 
increasing the distance of the screen, a determi- 
nate value must of course be ascertained for 
the divisions of the latter. 

The camera lucida of Dr. Wollaston is some- 
times applied to the eye-piece of the micro- 
scope for the purpose of delineation and micro- 
metry; but it is much inferior for these pur- 

to other plans which have been devised. 
Probably the best of these consists of a mirror 
composed of a thin piece of rather dark-coloured 
glass cemented on a piece of plate-glass, in- 


MICROSCOPE. 


clined at an angle of 45° in front of the 
glass. Of the light which passes out from 
latter, a sufficient quantity is reflected by 
mirror to give a distinct image; nade 
paper and pencil can be distinctly seen through 
the glass, though rather darkened co- 
loured glass, which thus serves to render the 
image more brilliant. A lens is placed below 
the reflector, which causes the rays from the 
paper and pencil to diverge at the same ans 
with those received from the eye-glass; 80 
both the object and the pencil are seen with 
equal distinctness. The use of a small 4 
polished steel mirror, fixed in the focus 
eye-piece, and inclined upwards towards the 
eye at an angle of 45°, is by some to 
this. The mirror being smaller than the pupil 
allows the rays from the paper to pass up into 
the eye around it; and thus the image is seen 
as upon the screw. In the use of either of 
these instruments, the chief difficulty (as in the 
use of the common camera lucida) is for t 
delineator to see both the i and 
with sufficient distinctness to enable him to 
make an accurate tracing of the former. Much 
will depend upon the advantageous adjustment 
of the amount of light upon the object and the 

per respectively. In drawing or m 

y lamp-light, we have found it useful to plac 

a small taper near the sereen, so that its dires 
rays may fall upon it, whilst the lamp is used 
for illuminating the object; and when the 
screen is illuminated by daylight it is prefer- 
able still to use the lamp for the other purpe 
The point of the pencil should be blackened. 
The micrometer eye-piece also may be em- 
ployed for drawing; its squares being repr 
sented by squares on the paper; and the por- 
tion of the object between each being delineated, 
in the manner commonly practised by artists. 
No assistance of this kind, however, can su 
that skill to the microscopic draughtsman whi 
is required for making finished delineations of 
any object. Accuracy of outline is all that 
they can ensure. ee 7 

Under this head it seems not inappropr 
to introduce a few remarks on the degree of 
minuteness in the structure of objects, which 
the magnifying power of the microscope ena- 
bles us to detect. ' th 

Much speculation has taken place amor 
philosophers at different times, relative to” 
possibility of detecting the ultimate riggs 
material, especially organic, substancé@s; 2 
saiesoscopists hase ocseulaaai hazarded state- 
ments in regard to their size, which an in-— 
creased knowledge has shown to be invalid. — 
It was a favourite theory about fifteen yee : 


He) 


since, that all organized bodies are made up of 
globules, which cannot be resolved into 

other kind of structure, the diameter of 4 
was stated at about gdgth of an inch. T { 
great improvements which have been recently 
made, however, in the microscope, and the 
general advance of knowledge on the Subject” 
of the ultimate constitution of organized st 
tures, have shown the erroneous nature of tl 
view, by proving that there is no body, 


minute, which is not capable of being resolved 
into smaller particles, as far as our means of 
observation can carry us; and the absurdity of 
the particular dimensions assumed is further 
shown by the fact, now well known, that there 
are very numerous species, and countless indi- 
viduals, among the Polygastric animalcules, 
whose whole bulk is susie less than that of one 
of the so-called ultimate particles, and which 
contain within this a considerable number of 
different organs. The following statements 
made some years since by Ehrenberg will give 
a very good idea of the mode in which the 
size of such organs and of their component 
parts may be approximately known, when they 
are themselves too minute for measurement. 
“T could plainly distinguish with a micro- 
er magnifying nearly 800 diameters, Mo- 
s, which were filled with colouring nutritive 
substances, and which possessed voluntary mo- 
tions, but the entire and greatest diameter of 
whose body only amounted to the ;,);th or 
spoth of a Parisian line. I could perceive 
in the largest individuals of this form as many 
as six, and in the smallest as many as four, in- 
_ ternal sacs coloured blue by indigo, which at 
_ times did not occupy half the internal dimen- 
sion of the animal. Such a sac, therefore, of 
an animalcule measuring ,A;th of a line, 
_and if we suppose only four sacs occupying the 
half of it, (therefore not one of the smallest,) 
4S qafpth of a line in size. Further, if we 
‘Suppose the single colouring particles, with 
which the stomachs are filled, not to be nume- 
Tous, it would be against all probability not to 
think that they were filled by several particles. 
_ Let us, however, only suppose each sac to 
_be filled with three colouring atoms,—which, 
from the roundness made perceptible by the 
“Motion communicated to them when diffused 
_ through the water, we may well admit,—this 
___ alone affords a proof of the existence of material 
colouring particles of red and dark blue moving 
freely in water, which measure sh,,th of a 
line, or jg3}gth part of an inch in diameter; 
and calculating these objects from the smallest 
__ Of the animalcules, which by actual observation 
were found to be 5th of a line in size, and 
which sometimes contained four coloured points 
in the hinder part of the body, these particles, 
which cannot be distinguished individually by 
By * the eye with a magnifying power of 800, but 
_ which are yet to be recognized as corporeal, 
_ would amount to gj,th of a line, or 
 gmdoth of an inch. Further, the smaller 
_ Monad-stomachs are seen isolated in the body, 
_ and with sharp outlines. In larger Infusoria, 
_ which are th of a line, or more, in diameter, 
___ these internal receptacles are recognized as evi- 
____ dent membranaceous sacs, which often make 
their appearance isolated, when the animalcule 
____ is pressed, or when it divides itself, and which 
¥. have been supposed to be separate infusoria, 
Internal monads. It can be distinctly seen 
that, when two such digestive sacs touch one 
another, the thickness of the partition between 
_ them is, in comparison with the diameter of the 
stomach, extremely small, so that the former is 
Searcely perceptible ; it may be reckoned as at 


MICROSCOPE. 


357 


the most sth of the latter, Granting, how- 
ever, the thickness of the partition to be as much 
as 7th the diameter of the sac, this would 
amount to yedggth of a line, or yahoo th 
of an inch, in monads g¢pth of a line in 
size, in which the stomachs measure but one- 
eighth of the whole length of the body, and 
are therefore jg/5;th of a line in diameter.” 
When similar views are extended to the young 
of the species on which this calculation is 
founded, or to smaller species in the existence 
of which there is good reason to believe, the 
minuteness of structure thus disclosed becomes 
still more wonderful. “ Let not these calcu- 
lations,” it is justly remarked by Ehrenberg, 
“be regarded as playful; they are so far in 
earnest, that they are founded on the contem- 
plation of nature, and are not to be considered 
as a groundless speculation. They plainly de- 
monstrate an unfathomableness of organic life 
in the direction of the smallest conceivable 
space; and if the word infinity be too much for 
what we know at present, let the word unfa- 
thomableness, which I have purposely em- 
ployed, avert from me the reproach of exagge- 
ration, and establish the direction which the 
physical, chemical, and physiological enquiries 
of our days, should they be rendered fruitful by 
new powers, have to take, and what deviations 
they have to avoid.” 

To these enquiries Ehrenberg has subjoined 
an attempt to calculate the power of vision for 
the human eye, and the ultimate power of the 
microscope. From his experiments on_ the 
smallest square magnitudes which are ordina- 
rily visible at any distance by the human eye, 
he finds that they vary in different cases from 
yth to yi,th of a line ; but when strongly il- 
luminated, much smaller bodies can be seen, 
metallic particles of y4th of an inch being 
visible in common daylight; and non-transpa- 
rent threads of 4),th of a line in thickness 
being distinguished, when held between the 
eye and the light. Hence the size of the mi- 
nutest objects visible with a given magnifying 
power of the microscope might be determined 
by dividing their apparent dimensions, as just 
stated, by the magnifying power; thus no 
square corpuscles of less dimension than 
sayoth or 4dath of a line could be seen with 
a magnifying power of 100 diameters. In 
practice, however, owing to the degree of im- 
sedate which must necessarily attend the 

est-constructed instruments, the minuteness of 
the smallest visible objects cannot be judged of 
entirely by this rule; since, in order that it 
should be correct, it is necessary that the 
object of yi,th or s4,th of a line in dia- 
meter, should be represented to the eye as 
clearly by a microscope magnifying 100 dia- 
meters, as a real object of Ath or pth of a 
line would be; this is very far from being the 
case, owing to the loss of light by reflection in 
passing through the lenses, as well as to the 
errors of the lenses themselves, which can never 
be perfectly corrected. With a magnifying 
power of 1000, which is perhaps the highest 
that has yet been employed to real advantage, 
the minutest particle which could possibly be. 


358 


distinguished would be ggdyth or ygdyth of 
a line square, and thus they would be much 
larger than those of whose existence a very 
simple process of reasoning is sufficient to con- 
vince us. 

BIBLIOGRAPHY.—The following works may be 
referred to.— Hooke, Micrographia, Lond. 1665. 
Baker, Of Microscopes, Lond, 1785 Adams, On 
the Microscope, Lond. 1787. Brewster, Treatise 
on the Microscope from Encyclopedia Britannica, 
also Treatise on new Philosophical Instruments. 
On Optics, Lardner’s Cyclopedia. Lister, in Phil, 
Trans, 1829. Chevalier, Des Microscopes, Par. 
1839, Mandl, Traité Pratique du Microscope, Par, 
1839. Pritchard and Goring, Micrographia ; also, 
by the same authors, Microscopic Illustrations and 
Micadacopie Cabinet. Slack, Holland, and Turrell, 
in Trans, Soc. Arts, vol. 49. Penny Cyclop. art. 
Microscope, Hildebrandt, Anatomie, Band. i. p. 128. 

( W. B. Carpenter.) 


MILK.—(Taaa, Gr.; lac, Lat.; le lait, 
Fr.; die Milch, Germ.; latte, Ital.) The 
secretion of the mammary gland. In treating 
of the milk it will perhaps be best, previous to 
entering upon its description as produced by 
the human subject, to give a general account 
of the secretion as obtained from the cow, such 
being the most familiar example afforded to us. 
Milk may be regarded as a serous fluid, hold- 
ing in suspension minute white globules com- 
ig of casein and fatty matter. These glo- 

ules have been microscopically examined by 
Raspail, who states them to have a diameter 
of .00039 inch, and to disappear on the 
addition of a solution of potassa. The most 
recent microscopic observations on the milk are 
those of Professor Nasse, of Marburg,* who 
gives the following as the constituents of the 
normal secretion of the mammary gland :—Ist, 
smooth, homogeneous, transparent oil globules 
and large oil globules, also the common milk 
globules; 2d, cream globules, distinguishable 
by their facette-like appearance; 3d, granu- 
lated yellow corpuscles; 4th, the lamelle of 
epithelium; 5th, the more or less turbid 
medium in which the four preceding kinds of 
a are suspended. 
he common milk globules are composed of 
fatty matter, which dissolves rapidly in ether. 
No membrane can be seen investing them. The 
first nine days after delivery the largest globules 
measure x};th of a line in diameter, but subse- 
quently become as large as y}gth, but they vary 
in size throughout lactation. The cream glo- 
bules are considered by Professor Nasse to be 
formed after the milk has been drawn or 
exposed to the air, for in fresh woman’s milk 
no globules but the common milk globules 
above described are discernible: the cream 
globules occur as large as Ath of a line in dia- 
meter. The yellow granulated corpuscles are 
culiar to the colostrum; their diameter is 

M q}oth to sisth of a line; some are found mea- 
suring Zsth of a line in length and jth in breadth. 
They are composed of fatty matter. The author 
considers them analogous to the mucus cells 
cast off from mucous membranes, and thinks 
that perhaps they come from the gland ducts. 
From my own observations I am inclined to 


* Miiller’s Archiv, 1840, Heft iii. p. 258. 


MILK. 


think that the cream globule of Nasse exists 
even in fresh milk, and may easily be seen in 
specimens containing but little fatty matter. I 
lately saw them in the milk of a woman who 
had suckled for seven months. I have not 
been able to rid the milk of globules by ether 
or liq. potasse. If milk be agitated with ether, 
then allowed to stand, and the lower stratum 
of fluid examined, we can detect distinct 
globules in it—globules of all sizes, and 

the appearance described by Nasse as i 

to the cream globule. From the variety in size 
which I have so constantly observed, I cannot 
understand how any author can have made 

his mind to give an admeasurement to the 
globule of milk; for my own part, after much 
careful observation, I feel convinced that the 
milk contains nothing which deserves the name 
of a true organic globule. That globules exist 
I do not deny, and these I believe to be what 
have been described by Nasse as cream ar 
bules, appearing when milk has creamed, 
cause the adhering fatty matter is separated ; 
but, notwithstanding, being very obvious before 
creaming occurs, in specimens of fresh milk 
containing a small proportion of fatty matter. 
The serum in which these particles float 
composed of water, holding in solution 
alkaline lactate and chloride with traces 
sulphate and phosphate, lactates of lime and 
magnesia, sugar of milk, and animal extractive. 
Oxide of iron and an earthy phosphate are to 
be detected in the ashes of milk, but these, in 
all probability, are derived from the casein of 
the secretion. When milk is allowed to remain 
at rest for some hours, a pellicle forms on its 
surface, varying with the nature of the milk: 
this is what is called the cream, and consists of 
the fatty or butyraceous matter of the milk in 
combination with a varying proportion of casein. 
It is from this tebe i butter is obtained by 
churning, by which operation the bu 

particles unite into a mass to the exclusion of 
the casein, which remains suspended in the 
serum, and thus forms a mixture known y the 
name of butter-milk or lait de beurre of the 
French. The whole of the casein, however, 
cannot be removed from the butter 
its minute particles being entangled 
cohering fatty globules, and it is in 
measure Owing to its presence that butter is 
more or less prone to me rancid and de- 
composed. Milk from which the cream has 
been removed still retains the greater of 
the casein, and when this is precipi from 
it by the action of rennet, we obtain a curd, 
which, being pressed and dried, constitutes 
cheese. The clear liquor se from this 
curd contains the more soluble matters of milk, — 
viz. the alkaline salts with the sugar of pre | 
and in Switzerland a considerable quantity of 
this sugar is manufactured from whey and used 
for household purposes. I have it it 
best to notice the various operations in domestic 


is 
an 
of 


ee ~ 


2S ae 


economy to which the milk is subjected, not 
only because by them several of its proximate 


elements are eliminated, but likewise that the 


reader may have some familiar object with — 


which to connect the following account of the 


butter 


- MILK. 


epee properties of the constituents of the 
fluid. 

The fatty matter of milk obtained by churn- 
ing cream, and which is known by the name 
of butter, differs from the other forms of animal 
fat in several particulars. It yields about 88.5 
per cent. of fixed acids on being saponified, for 
which purpose it requires no more than four- 
tenths of its weight of caustic potassa ; it there- 
fore unites with alkali very easily. Of these 
acids the margaric and oleic are in large propor- 
tion, the stearic existing as a mere trace. Glyce- 
rine, as is the case with other fats, is a constant 
el of the saponification of butter. The great 

istinguishing peculiarity of this form of fatty 
_ matter consists in the production of three volatile 
acids as results of saponification; these have 
been carefully examined and distinguished by 
Chevreul in his admirable work, “ Sur les 
Corps gras.” He has named them the butyric, 
caproic, and capric acids. The production of 
these acids by the action of alkali has been 
traced by Chevreul to the existence of a new 
form of fat which he detected in butter mixed 
_ with the stearine and elain, and to which he 
gave the name of butyrine: thus butter may 
be regarded as composed of three different 
kinds of fatty matter—stearine, elain,; and 
butyrine—the two former yielding by saponifi- 
_ Cation the margaric, oleic, and stearic acids, 
and the latter the three volatile acids above 
mentioned. The proportions of the three kinds 
of fat vary considerably in different specimens 
of butter. The solubility of butter in alcohol 
is stated by Chevreul to be 3.46 parts in 100 at 


_ a boiling temperature, the specific gravity of 


menstruum being 0.822. The stearine 
obtained from the alcohol by cooling is more 
_ ¢rystalline and of a more brilliant white than 
_ that obtained from common fat, and 1.45 parts 
_ require 100 parts of alcohol of specific gravity 
0.622 for its solution. The elain obtained from 
br possesses no peculiar characteristics. 
_ The butyrine when separated from it, which is 
only to be accomplished with difficulty, pos- 
Sesses the following qualities:—it is an oil 
ely of a yellow colour, but some speci- 
‘mens of butter yield it perfectly white; it con- 
Cretes at 32° Fahrenheit, and possesses the 
smell and taste of butter; it mixes with boiling 
alcohol in all proportions; it is soluble in 
anhydrous alcohol. Potassa and the other 
alkalies are not the only substances capable of 
producing the-volatile acids by acting on buty- 
tine. Alcohol if long digested produces a 
Similar effect, as does strong a ite acid, 
and if butyrine be allowed to putrify these 
_ acids are developed. 
_ The casein or cheesy matter of milk which is 
obtained with some slight admixture of the 
Y matter in the production of cheese from 
the skimmed milk has the following chemical 
operties. It is soluble in water after long 
gestion; but this is most likely owing to 
Some decomposition which occurs in it, and it 
1s certain that casein in its pure, undecomposed, 
and dry state is quite insoluble in water. 
Casein, as it exists dissolved in skim milk, is 
Precipitable by the mineral acids and also by 


359 


the acetic acid. The process which Berzelius 
recommends in order to obtain this substance 
is as follows :—Skim milk is to be mixed with 
a small proportion of dilute sulphuric acid, 
which unites with the casein and precipitates 
it in the form of a white clot. This is to be 
well washed with distilled water on a filter in 
order to separate the whey which it contains. 
After this carbonate of baryta and water are to 
be mixed up with the mass, by which means 
the acid is separated and the casein remains 
dissolved in the water, and may be separated 
from the carbonate and sulphate of baryta by 
filtration. Casein obtained by this process is 
more or less soluble in water, and is precipi- 
tated from its aqueous solution by the acids. 
It rapidly undergoes the putrefactive fer- 
mentation. It is soluble in the alkalies and 
in alcohol both boiling and cold, but far more 
so in the former, from which it rapidly deposits 
on cooling. Casein, when dissolved by the 
assistance of the acids, is precipitated by the 
ferro-cyanide of potassium. It is distinguished 
from albumen, with which it possesses many 
physical and chemical properties in common, 
by being precipitated from solution on the ad- 
dition of acetic acid, and the precipitate so 
formed being with difficulty soluble in an 
excess of the precipitant. It must not be 
imagined, however, that albumen under all 
circumstances cannot be precipitated from so- 
lution by the addition of acetic acid, for when 
dissolved in an alkaline solution, that proxi- 
mate principle is immediately thrown down on 
the addition of the acid. Casein, like albu- 
men, always contains some sulphur as a neces- 
sary element in its composition ; the presence 
of this body may be easily shown by boiling 
casein in a concentrated solution of potassa, 
when the liquor rapidly assumes a brown 
colour, and gives out ammonia, an alkaline 
hydro-sulphuret remaining dissolved, which 
may be proved by the solution becoming of a 
deep black colour on the addition of a salt of 
lead. The aqueous solution of casein is pre- 
cipitated by all the earthy and metallic salts 
which precipitate albumen in the dissolved 
state. Tannin precipitates it even from its 
solution in alcohol, notwithstanding that men- 
struum protects it from the precipitating action 
of the acids. The ultimate analysis of casein 
is, according to Thenard and Gay Lussac, 
carbon 59.781, nitrogen 21.381, hydrogen 
7.429, and oxygen 11.409. Caseous matter, 
as precipitated by rennet in making cheese, is 
liable to a peculiar kind of putrefaction, which 
has been investigated by Proust and Braconnot; 
the latter obtained as a product of putrefaction 
a peculiar crystalline substance, to which he 
gave the name of aposepedine, from ago and 
onwsdwv, indicative of its origin. Proust had 
before noticed this substance and called it 
caseous oxide. It may be prepared very easily 
by allowing cheese to putrify under water and 
evaporating the solution so obtained to dry- 
ness ; the dried mass is then to be treated with 
alcohol until that menstruum exerts no further 
solvent action ; the portion insoluble in alcohol, 
on being dissolved in water, and digested with 


360 


ammal charcoal, yields us by filtration and 
evaporation pure crystals of aposepedine. This 
substance has the following properties: it is 
somewhat bitter to the taste, very slightly so- 
luble in alcohol, soluble in water, and of 

ter specific gravity than that fluid. It sub- 
imes when heated strongly, but always un- 
dergoes a papers decomposition. It contains 
sulphur. In addition to aposepedine, cheese 
when decomposing has been found to contain 
acetic acid, acetates of ammonia and potassa, 
chloride of potassium, ammoniaco-phosphate 
of soda, margarate and phosphate of lime, and 
a peculiar extractive matter. 

I shall now proceed to consider the sugar of 
milk which is left in the whey after the sepa- 
ration of the cheese by rennet, and exists in 
solution with the salts of the milk, lactic acid, 
and animal extractive matter. 

Sugar of milk may be obtained from whey 
by evaporating it to the consistence of a syrup, 
and setting it aside for a length of time, when 
small granular crystals of the principle are 
observed to deposit. The following are the 
principal qualities of sugar of milk. It hasa 
Sweetish taste, the grains crushing with dif- 
ficulty between the teeth; its specific gravity 
is 1.543. It contains about 12 per cent. of 
water, which may be separated by carefull 
fusing it; when fused it is still quite white if 
the heat be not too strongly urged. It is solu- 
ble with difficulty in water, requiring three 
parts of boiling water and six of cold for that 
purpose. It is very slightly soluble in alcohol, 
and quite insoluble in ether. When acted on 
by concentrated nitric acid it becomes trans- 
formed into a mixture of oxalic, malic, and 
muric acids. By the action of caustic potassa 
it is changed to a brown-coloured bitter mass, 
which is insoluble in alcohol. 

Sugar of milk has been stated to be in- 
capable of undergoing the alcoholic fermen- 
tation; but late experiments by Hess (Poggen- 
dorff, Annalen der Physick) shew that such 
will occur, and an intoxicating liquor has been 
long known among the Tartars, which is pre- 
pared from the milk of the mare, and to which 
they give the name of Koumiss. Sugar of 
milk has been analysed by Berzelius: including 
its 12 per cent. of water, its composition is as 
follows : 

Carbon.... 40.125 or 1 atom, 
Hydrogen,. 6.762 or 2 atoms, 
Oxygen.... 53.113 or 1 atom: 
or deducting the 12 per cent. of water, 
Carbon,... 45.94 or 5 atoms, 
Hydrogen.. 6.00 or 8 atoms, 
Oxygen.... 48.06 or 4 atoms. 

It will be observed, on comparing the ana- 
lysis of hydrous sugar of milk with that of 
starch, that they accord very nearly, and sugar 
of milk is convertible, as is the case with starch, 
into true sugar, by the action of sulphuric acid ; 
these facts strongly point out the curious ap- 
proach to vegetable matter which is made by 
this constituent of an animal secretion. 

After the crystallization of the sugar of milk 
from the whey, we have left in solution, accord- 
ing to the experiments of Berzelius, lactic acid 


MILK. 


and lactates, chloride of potassium, an alkaline 
phosphate, phosphates of lime and magnesia, — 
and traces of oxide of iron, a 


I shall not here enter upon the question — 


whether or not lactic acid be the iar acid 


the 7th volume of the French edition 


zelius’ Chemistry. For my own part I can 


only wish that one quarter of the animal acids 
mentioned in our modern chemical works had 


the same right to be distinguished as peculiar — 


animal principles. Mons. Lassaigne, in his 
ee bearing date 1836, wae speaking of © 
actic acid, says, “ regardé pendant temps — 
comme de I’acide acétique modifié une 
matiére organique, M. Berzelius a établi d’une 


maniére incontestable sa véritable nature.” 
Anhydrous lactic acid has the following ulti- 
mate composition. 
Car Meceveocsssesessees 50.50 
Hydrogen Seen eeeertce 3.60 
Oxygen .ccc.svces sees 43.90 
Berzelius’ analysis of skimmed cow’s milk is 
as follows: 


- . 


Caseous matter with some butter 2.600 
Sugar of milk . cee s0ciosieeuee 3.500 ‘a 
Extractive, lactic acid, and lactates 0.600 
Chloride of potassium ........ 170 
Alkaline phosphate.... ....... 0.025 ~ 
Earthy phosphates, trace of oxide evs? 
of ITOD 0. c's oie pie ce ee 0.220 Ww 
Waters «0s: oe de daellicee ~~ 92.875 2) 
The cream from this milk yielded the follow- 
ing result: as 
Butter oso «sce sv.0.00eh wee 
Caseous matter ....ce0e-- 3.5 


Whey eee e ewe eee eee eeae 92.0 + 
The specific gravity of this milk was 1.0348, 
and that of the cream 1.0244. 

A specimen of cow’s milk which I lately 
examined was of sp. grav. 1.0338, and its solid’ 
contents 121.85 in 1000 pre t eed? 

The ashes of cow’s milk, according to Pfaff 
and Schwartz, are composed of phosphates of 
lime, magnesia, and iron, phos of soda, 


chloride of potassium, and soda, which, before — 


incineration, had existed in combination with 
lactic acid. They found 1000 parts of the 
milk yielded 3.742 parts of ash. 108 
According to the experiments of Van Stip- 
trian, Luiscius, and Bondt, the proportion of — 
cream which separates from cow’s milk is 
about 4 per cent. of its weight. They ob- 
tained from milk 2.68 per cent. of butter, 8.95 
of casein, and 3.60 per cent. of sugar of milk. — 
The first milk which is observed in the breast 
afier parturition has received the name of colos- 
trum ; it differs somewhat from ordinary milk.» 
It has been stated by some authorities that ~ 
scarcely any cream can be obtained from the 
colostrum, and that no butter can be obtained — 
by churning. According to Stiptrian, Luiscius, 
and Bondt, however, the colostrum from the 


cow yields 11.7 per cent. of cream, 3 of butter, 


and 18.75 of cheese. They state the specific — 
gravity of the colostrum at 1.072; dried and in= — 


cinerated it yielded 54 per cent. of ash. They 


ae Ss 


MILK. 


do not mention sugar of milk as a constituent, 
and in this respect agree with MM. Chevallier 
and Henry, who do not mention it in their 
analysis of the colostrum of the cow. 

Donné has observed a microscopic difference 
between the globules of the colostrum and those 
of milk. He states the colostrum globule to be 
made up of small granules united together, or 
enclosed in a transparent envelope. ‘They dis- 
appear in ether, and when the fluid is evapora- 
ted, small tufts of acicular crystals are observed. 
Donné traced these globules in milk secreted 
twenty days after parturition. M. Giiterbock 
has also observed these compound globules, and 
says he could detect the transparent membrane 
after the ether had dissolved the enclosed 

ules. M. Mandl has not been able to 
etect these compound globules, and believes 
_ them to be made up of agglomerated milk glo- 
bules. The following is the result of a com- 
tive analysis of colostrum and true milk by 

. Simon, 


Colostrum. Common milk. 
Casein .... 4 percent. 3.5 per cent. 
PAT S05 IT: a 5 AT: 5 
Putter 6.0. 5 5 2.3 


> 

I shall now proceed to the consideration of 
the milk of the human subject, which differs 
in some respects from that obtained from the 
cow; its general characters are, however, iden- 
tical. One of the principal differences to be 
observed consists in the caseous matter of 
human milk not being so universally preci- 
pitable by acids as that which exists in the 
secretion from the cow. Meggenhofen found 
but three out of fifteen specimens which he 
examined that could be precipitated by the hy- 
drochloric or acetic acids. Three specimens of 
human milk examined by myself were found 
not to be precipitable either by the muriatic, 
nitric, or sulphuric acids. Although human 
milk resists the coagulating power of the acids, 
it is, notwithstanding, easily precipitable by 
rennet; but the curd so formed is some time in 
collecting, owing to the minute size of the pre- 


_ Cipitating flocculi; thus there appears both a 


physical and chemical difference between the 
caseous matter from the human subject and 
that from the cow. The casein of human milk 
being incapable of forming insoluble combina- 
tions with the mineral acids, may be regarded 
as bearing chemically the same relation to the 
casein of cow’s milk that the albuminous matter 
of the chyle bears to that principle as it exists 
in the blood. The butyraceous matter of hu- 
man milk has been stated by some chemists to 
be too liquid to admit of the formation of 
butter by churning; this, however, has been 
proved incorrect by the experiments of Pleischl, © 
who succeeded in obtaining butter from the 
cream of human milk, which was similar in 
appearance to that from cow’s milk, and expe- 
riments into the nature of this form of butter 
have been made by Meggenhofen, who considers 
it as identical with that obtained from the cow. 
The specific gravity of human milk has been 
stated so low as from 1.020 to 1.025, but this is 
certainly far too low ; for out of six specimens 
_ which | examined the specific gravities varied 


361 


between 1.030 and 1.035. The proportion of 
solid matter contained in milk is, according to 
Meggenhofen, 11 to 12.5 per cent. and some- 
times more. I have had occasion to verify this 
result, having obtained 64.15 of solid matter 
from 500 grains of milk. The specific gravity 
of this specimen was, however, as high as 
1.0358. 

Human milk when fresh is either neutral 
or slightly alkaline. Its analysis, according to 
Meggenhofen, is as follows, being the results 
obtained from milk from three different sub- 
jects. 

No. 1. 
Alcoholic extractive, but- 

ter, lacticacid and lac- 

tates, chloride of sodi- 

um, traces of sugar of 


MES. Ais SOCAN 9.13.. 8.61,.17.12 
Aqueous extractive, sugar 
of milk, and salts .... 1.14.. 1.29.. 0.88 


Caseous matter (coagula- 

ted by rennet) ...... 2.41.. 1.47.. 2.88 
WaReP, Bis AScriene oils’. 87.25. .88.35. .78.93 

The specific gravity of the milk appears to 
increase as the woman continues suckling, this 
increase ceasing at some period which is as yet 
undetermined. Milk at three days after partu- 
rition I found of specific gravity 1.0310, at four 
days 1.0334, and at six weeks 1.0358. 

Payen has analysed three specimens of 
human milk with the following results :— 
Butter voles . 5.18... 5.16.. 
Caseous matter........ 0.24.. 
Residue of evaporated 

whey (containing the 

extractives, salts, and 

sugar of milk) ...... 7.86.. 7.62.. 7.93 
Water ........2.+---85.80. .86.00. .85.50 

Berzelius remarks upon these analysis, and 
says that a considerable portion of caseous 
matter remained in all probability in the whey, 
and was estimated in the residue obtained by 
evaporation. 

According to Meggenhofen the salts contained 
in milk amounted to from 0.5 to 1.25 parts in 
500 of the secretion. In an experiment made 
by myself, 500 grains of milk yielded 1.20 
grains of salts. 

Pfaff and Schwartz obtained 4.407 parts of 
ash from 1000 of milk, which they found to be 
composed as follows :— 

Phosphate of lime........+. 
Phosphate of magnesia...... 
Phosphate of iron.........- 
Phosphate of soda ........ 
Chloride of potassium ....., 
Soda from decomposed lactate 


5.20 
0.18... 0.25 


2.500 
0.500 
0.007 
0.400 
0.700 
0.300 


4.407 


Berzelius very naturally expresses surprise 
that no carbonate of lime, chloride of sodium, 
or alkaline sulphate, is mentioned in this ana- 
lysis, since casein always yields the earthy salt, 
and chloride of sodium is constantly present in 
animal matters which are intended for the nou- 
rishment of man. The absence of alkaline 
sulphate is quite inexplicable, as it is always a 


362 MILK. 


product of the combustion of animal substances 
containing an albuminous or caseous consti- 
tuent. € proportion of cream contained in 
milk from the human subject has been deter- 
mined by Sir Astley Cooper at from one-fifth 
to one-third by measure, varying with the 
health, the food, the habits, and state of mind 
of the mother. The colostrum or first milk 
which is observed in the human breasts has 
been examined by Meggenhofen. He states 
that it contains more saline matter than the 
after milk, and describes it as having the ap- 
pearance of a weak solution of soap containing 
oleaginous particles. It is very prone to be- 
come sour and decompose, and becomes viscid 
by exposure to the air, hence its name from 
xorAAwuas, to agglutinate. 

Several instances are on record of the exis- 
tence of milk in the male breasts, and the ana- 
lysis of a specimen lately | spigeree by Mayer 
in Schmidt's Jahrbucher, July 1837, is as fol- 
ows :— 

Fatty matter... ...... 1.234 

Alcoholic extractive .... 3.583 

Watery extractive ...... 1.500 

Insoluble matters ...... 1.183 

Total solid contents .... 7.500 in 100 
parts of the fluid. 

It was slightly alkaline. The following were 
the physical properties of this milk: when left at 
rest it quickly coagulated, and cream soon sepa- 
rated; after some hours butyraceous globules 
collected on the surface. Its specific gravity 
was 1024. 

Milk from several of the herbivorous Mam- 
malia has been examined by Stiptrian, Luiscius, 
and Bondt, with the following results :— 

The milk of the ass has a specific gravity of 
1.023 to 1.0355; it yields a white and light 
butter which is very apt to become rancid. 
The caseous matter does not separate so easily 
as in cow’s milk; the whey, however, can be 
obtained very clear, and is found to contain 
more sugar of milk than that from the cow. 
An analysis yielded the following result : 

reaM ...+.+e++- 2.9 per cent. 
ee Pe eee mare 
Sugar of milk .... 4.5 ,, 

The milk of the mare has a specific gravity 
of 1.0346 to 1.015; it yields but little cream, 
but contains a very large proportion of sugar; 
the analysis gave : 

0.8 percent. of cream, 
7) oe caseous matter, 
and 8.75 _,, of sugar of milk. 

The milk of the mare, as also that obtained 
from the ass, very rapidly commences the alco- 
holic fermentation, an effect which cannot be 
produced but with the greatest difficulty in 
cow’s milk. 

Goat’s milk has a specific gravity of 1.036; 
it possesses a very disagreeable odour of the 
animal, and the more strongly so if the goat 
be dark-coloured ; it yields a large quantity of 
cream and butter; the latter contains, in addi- 
tion to the usual acids of butter, a peculiar 
acid to which the name of hircic acid has been 
given; it is to this principle that goat’s milk 


owes its peculiar unpleasant odour. This milk 
contains also a large quantity of caseous matter 
of a firm dense character. Payen found goat’s 
milk composed as follows : i 
Butter .eccsescsecccecees 4.08 
Casein er eeeee eee ennee evree 4.52 
Sugar, salts, and extractives.. 5.86 
Water ...ccccccccssccess GOO” 

Stiptrian, Luiscius, and Bondt 
7.5 per cent. of cream, 4.56 of butter, 9.12 
casein, and 4.38 per cent. of sugar from the 
milk of a goat. 

The milk of the sheep has a specific gravity 
of 1.035 to 1.041; it yields a larger propor- 
tion of cream: the butter is semifluid and 
yellow in colour; it putrifies very easily. Thi 
milk yields 11.5 per cent. of cream, 5.8 of 
butter, 15.3 of caseous matter, and 4.2 per 
cent. of sugar of milk. 

The milk of the bitch and also of the por- 
poise have been lately examined by Dr. Bird; 
the former contained 15.8 per cent. of a 
and 7.2 of butter mixed with some sugar 
milk. That from the porpoise contained 23.00 
per cent. of oily matter, and a volatile ingre- 
dient supposed to be phocenic acid. The 
cific gravity of bitch’s milk is stated at 1.024. 

The milk is very prone to become contami- 
nated by various ingesta; that of the cow is 
frequently impregnated by the odours derived 
from particular pasturage, and if saffron or in- 
digo mixed with their diet the milk has 
been observed to assume more or less the 
colour of those pigments. 4 

Chevallier, Henry, and Peligot made expe- 
riments on the milk of asses to whom several 
different substances had been exhibited ; t 
were enabled to detect the oxides of iron . 
zinc, the trisnitrate of bismuth, common salt, 
and sesquicarbonate of soda with great ease ; 
sulphate of soda required to be administered in ~ 
very large doses before it could be detected in 
the milk, and sulphate of quinine could not be 
discovered, though large quantities were intro- 
duced into the stomach. These 
state likewise that the iodide of om 
cannot be detected in the milk unless exhibited 
in doses of upwards of a drachm. This rule, 
however, cannot apply to the human subject, 
as I lately very readily detected it in the milk 
of two of my patients, one of whom had taken’ 
only 45 grains of the iodide in divided doses 
of 5 grains each, administered three times a day 
for three days; and the other 105 grains in 21 
doses of 5 grains each, administered in like 
manner. It is probable that many substances 
enter the milk which the ype state of 
mistry does not admit of our detecting, and 
every practitioner is aware of the danger in- 


curred to the child by or any 7 
medicine to the mother during the period 
lactation. ae 
There is perhaps no animal secretion which 
bears so strongly-marked an analogy with the 
blood as the milk, and which promises us so 
fair a prospect of discovery in the mysteries 4 
of secretion, and we cannot but hope that as” 3 


animal chemistry advances we may be able to_ 4 
imitate those changes which occur in the minute _ 


parts of the mammary gland, where, though 
each constituent of the blood be changed in its 
character to form milk, yet each constituent of 
that secretion retains an obvious type in the 
fluid from which it was eliminated ; thus if we 
compare the blood and this secretion side by 


Blood separating 
into * 
¢ Fibrin 
Clot ? Red particles 
f Albumen 
and Alcoholic extractive, viz. 
lactates 
Serum << Aqueous extractive; albu- 


minate of soda 
Alkaline salts 
Fatty matter 


The similarity of reaction between fibrin, 
albumen, and casein is well known to chemists, 
and the derivation of the latter from the former 
can scarcely admit of a doubt; the only dif- 
ference acknowledged between fibrin and albu- 

men is a physical one, and it would be exceed- 
_ ingly interesting to ascertain whether or not the 
_ easein, which, like fibrin, separates on stand- 
ing, be not physically different from that por- 
tion of casein which remains in the fluid after 
the milk has creamed. The red particles of 
_ the blood certainly bear no analogy whatever to 
_the butyraceous matter of milk in its perfectly 
_ formed state; it is a curious fact, however, 
_ noticed by Sir Astley Cooper, that the colos- 
_ trum at its first appearance is occasionally of a 
ted colour, and the cream which separates is 

of a still deeper red tinge, thus rendering it 
_ probable that the fatty matters are in this in- 
Stance the colouring ingredient. I may men- 
tion, in addition, that it is not easy to obtain 

_hematosine quite free from fatty matter; there 
i ea to exist a natural affinity between 

em. 


The alcoholic extractives of blood and milk 
_ are too obviously analogous to need comment, 
as are the salts and likewise the fatty matters 
_ adherent to the casein of the milk and the 
albumen of the serum. The sugar of milk 
appears in all probability derived from the 
ueous extractive of the blood, an ingredient 
ich has scarcely attracted sufficient attention, 
and the development of whose chemical rela- 
tions may perhaps assist us greatly in obtaining 
a further insight into the true nature of those 
changes which are effected in the minute struc- 
ture of secreting glands. I have thought it 
right to mention the above resemblance, as I 
cannot help thinking that we may be greatly 
assisted hereafter in the physiology of secretion 
by attempting to reduce each proximate ele- 
ment of a secerned fluid to some type in the 
, and afterwards endeavouring artificially 

_ to produce those substances from their ana- 
___ logues in the circulating fluid; as nature may 
perhaps in this way form them for the various 
__-Secretions, by the so-called chemistry of vita- 
lity. Physiologists and chemists are, in the 
present day, too prone to attribute the forma- 
tion of those substances contained in secretions, 


MOLLUSCA. 


363 


side, we remark not only identical physical 
changes to occur, but also the existence of a 
set of proximate elements, which, though proper 
to each, still possess many chemical qualities 
in common ; for instance— 


Milk separating 


into 
Casein : Cain 
Butyraceous matter 
Casein a 
Alcoholic extractive, a i 
lactates and lactic aci : 
Aqueous extractive, with > aa Ik 
sugar of milk eet 
Alkaline salts 
Fatty matter 7 


and which cannot be detected in the blood, 
to changes occurring among the ultimate ele- 
ments of organic matter, changes of a character 
too intimate and obscure ever to be induced 
by those reagents which non-vital chemistry 
applies in effecting transformations. Such a 
conclusion is founded on the assumption that 
organic chemistry is not to make that progress 
which we now see in almost every branch of 
inquiry, a progress marked by the develop- 
ment of new laws which not only become 
valuable as indicators for the ascertainment of 
new facts, but which have a retrospective in- 
fluence on science, rearranging and altering the 
bearings and relations of previously ascertained 


phenomena. 
(G. O. Rees.) 


MOLLUSCA, (Lat. mollis,) Malakia and 
Ostracoderma of Aristotle; Mollusques, Fr. ; 
Weichthiere, Mollusken, Germ.; Mollusks, 
Engl.; invertebrated animals, distinguished by 
Bruguiere from insects by the negative cha- 
racters of the absence of bones, of stigmata, 
and of jointed feet; and first accurately de- 
fined by Cuvier as a ree division of the 
animal kingdom, with the following anatomical 
characters. The Mollusks are animals without 
an articulated skeleton or a vertebral column. 
Their nervous system is not concentrated in a 
spinal marrow, but merely in a certain number 
of medullary masses dispersed in different 
points of the body, the chief of which, termed 
the brain, is situated transversely above the 
cesophagus, and encompasses it with a nervous 
collar. Their organs of motion and of the 
sensations have not the same uniformity as to 
number and position as in the Vertebrata, and 
the irregularity is still more striking in the 
viscera, particularly as respects the position 
of the heart and respiratory organs, and even 
as regards the structure of the latter: for some 
of these respire elastic air, and others water, 
either fresh or of the sea. Their external 
organs, however, and those of locomotion are 
generally arranged symmetrically on the two 
sides of an axis. The circulation of the Mol- 
lusks is always double; that is, their pulmo- 
nary circulation describes a separate and dis- 
tinct circle. The blood of the Mollusks is white 


364 


or bluish, and it appears to contain a smaller 
proportionate quantity of fibrine than that of 
the Vertebrata. The veins probably fulfil the 
functions of absorbent vessels. Their muscles 
are attached to various points of their skin, 
forming more or less dense and complex tis- 
sues. Their motions consist of various con- 
tractions, which produce inflections and _pro- 
longations of their different parts, or a relax- 
ation of the same, by means of which they 
creep, swim, and seize upon various objects, 
just as the form of these parts may permit, 

ut as the limbs are not supported by articu- 
lated and solid levers they cannot advance 
rapidly. Nearly all Mollusks have the body 
enveloped by a duplicature of soft and usually 
muscular integument, which bears more or less 
resemblance to a mantle: it is sometimes nar- 
rowed into a simple disc, sometimes prolonged 
into one or more tubes, or is extended and 
divided in the form of fins. 

The Naked Mollusks are those in which the 
mantle is simply membranous or fleshy. In 
most of the species one or more plates, of a 
substance more or less hard, are a in 
its substance, usually in successive layers, 
which increase in extent as well as in thick- 
ness as they are successively formed. When 
this substance remains concealed in the thick- 
ness of the mantle, it is still customary to style 
the animals ‘ Naked Mollusks.’ Most com- 
monly, however, it becomes so much deve- 
loped that the contracted animal finds shelter 
beneath or within it, and it is then termed a 
shell, and the animal is called a Testaceous 
Mollusk. 

The mode of generation is too varied in the 
Mo!lusks to afford any common character to 
this sub-kingdom : but, being for the most part 
sluggish and feeble animals, with low and little 
varied instincts, they are preserved chiefly by 
their fecundity and vital tenacity. 

The nervous system of the Mollusks may 
consist of one or more ganglionic masses ; but 
these are scattered, often irregularly or unsym- 
metrically, through the body, and the inter- 
communicating chords never form a symme- 
trical knotted pair along the middle line of the 
ventral surface of the body; whence the term 
* Heterogangliata,’ expressive of the charac- 
teristic condition of the nervous system, with 
which the unshapely and often unsymmetrical 
figure of the whole body corresponds. 

The number of the ganglia follows closely 
the progressive development of the muscular 
system : the first is that which is found between 
the anal and respiratory tubes of the Ascidiz, 
and which regulates the elongator and sphincter 
muscles of these tubes. The development of 
a muscular heart and of a bivalve shell with 
its adductor muscle is accompanied with the 
appearance of a second ganglion or centre of 
the nerves which supply that muscle: a second 
adductor muscle, with the superaddition of a 
muscular foot and its retractors, produces an 
additional ganglion or ganglions, and the com- 
plication of the nervous system is further aug- 
mented when the breathing and anal siphons 


MOLLUSCA. 
are unusually prolonged, and provided with — 


strongly developed annular contractile muscles 
and with proportionately powerful retractors. 
The progressive development of the nervous 
system may be traced thus far in the tunicated 
and bivalve Mollusca without its reaching the 
stage which is marked by the ap 


z 
+ 


ove. 


distinct supra-cesophageal ganglion or brain. — 


the species have, in fact, no distinct head, and 
are termed Acephalous Mollusks. The first 
appearance of this important part with its 
appendages, which are usually subservient to 

e organs of special sense, is associated with 
- accumulation of nervous matter, in the form 
of a transverse chord, with a lion or gang- 
lions, above the paRebeesal co of the cso- 
Phagus, forming the brain; whence these Mol- 
usks are termed ‘ Encephalous.’ 

The development of the brain proceeds 
directly as the organs of the senses increase in 
number and complication, and consequently 
pnt its maximum in the pearask : alo 

s with highly complex eyes and disti 
organs of Nidal’ pa in these the beta 
protected by a cartilaginous cranium, pier 
the first representative of the true interna 
skeleton which is met with in the Invertebrate 
division of animals, and one of the main 
organic characters by which the higher Mol- 
lusks surpass Articulates in the ascent to the 
Vertebrate type. 

The nervous system of the Mollusks is re- 
markable for the peculiar and distinct colour 
of the ganglions in certain species, as the fresh- 
water Muscles and Unios; and for the contrast 
between the density of the cellular sheath of 
the nerves and the semifiluid pulp which it 
contains. This structure allows of an artificial 
injection of the nerves, which has led some 
anatomists to describe them as parts of an 
absorbent system. 

Although the bivalve Mollusks are headless 
and without brain, some of them have mani- 
fested signs of a perception of light, and in a 
few species simple ocelli have been detected on 
the verge of the mantle. we 

In the Encephalous Mollusks the eyes, 
when present, are small, never exceed two in 
number, and are usually supported on flexible 

uncles or tentacula; but in the Dibran- 
chiate Ay eatin: they are large, always ses- 
sile, and highly complicated. ae 

The organ of hearing is liar to the Ce- 
ras oy in the present division of the animal 


"theo special and cine 
e organ of smell, as a i cir- 
cumscribed part, has likewise been recognized 
only in the highest class: but Cuvier observes, 
that the skin of the Mollusks so clearly re- 
sembles in its softness and lubricity a pituitary 
membrane, that they probably may recognize 
odours at every point of their external surface. 
Professor De Blainville conjectures that in 
Gastropods the soft extremities of the first 
of cephalic tentacles may be the seat of 
organ of smell. An organ of taste has 
course been recognized only in the Encephalous - 
Mollusks, in many of which the tongue is large 


pair: 
of 


MOLLUSCA. 


‘and complex, and in the Cephalopods is evi- 
dently provided with gustatory papille. The 
sense of touch is in this as in other groups of 
animals the most generally possessed and the 
most widely diffused over the body. The mar- 

inal fringe of tentacles on the mantle of most 
valves: the branched processes of the skin 
in certain Pteropods and Gastropods ; the ce- 

halic tentacles or ‘ horns,’ as they are termed, 
in the Snail and allied Mollusks; the rich and 
varied apparatus of cephalic and labial ten- 
tacles—nearly one hundred in number—in the 
Nautilus; and the extremities of the acetabuli- 
ferous arms of the higher Cephalopods, may 
all be regarded as organs of delicate sensa- 
tion: the same opinion may reasonably be 
entertained of the highly vascular surface of 
the ventral locomotive disc or ‘ foot’ in the 
Slug, Snail, and other Gastropods. 

The voluntary muscular fibre of the Mollus- 
cous animals is distinguished from that of the 
Articulate and Vertebrate animals by the ab- 
‘sence of the transverse strie, and in most of 


the Acephalous Mollusks it is antagonized by a 


merely elastic gelatinous fibre. In the Tuni- 
caries the flexible outer coat obeys and opposes 
the change of form which the inner muscular 
envelope occasions. In the Bivalves, whose 
shell affords firm levers of attachment to the 
muscles, the antagonizing elastic force is im- 
planted at the hinge of the shell; and some of 
the species ( Mollusca subsilentia of Poli) can, 
by virtue of this mechanism of solid lever with 
its attached muscular and elastic fibre, execute 
short leaps. 
_ The Encephalous Mollusks with a cerebral 
centre of nervous influence antagonize one 
series of muscles by the regulated action of 
another series, and are no longer dependent on 
mere elastic fibres for their movements. The 
musculo-cutaneous mantle is propeced in the 
form of fins in the Pteropods, Heteropods, and 
some Cephalopods ; or there is an accumula- 
tion of longitudinal fibres, intersected by ob- 
ique or transverse ones on the ventral surface 
of the mantle, producing the thick contractile 
disc, which is termed the foot. This some- 
times extends the whole length of the body, as 
in the Gastropods, sometimes is developed onl 
from the region of the neck, as in the Trache- 
lipods. The attachment of the body to the shell 
in these Mollusks, the presence of, and power 
of retracting and elongating, a siphon or breath- 
ing tube, the movements of the head and its 
appendages, especially when these are deve- 
loped into instruments of progressive motion 
and prehension, as in the Cephalopods, are the 
Shic! conditions of the progressive advance- 
ment and complication of the muscular system 
in the Molluscous sub-kingdom. 
_ The heterogangliate type of the nervous sys- 
tem, with the correspondingly low condition of 
the muscular and other organs of relation, 
which, commencing in the Ciliobrachiate Po- 
lypes, is established in the Mollusks, is on the 
whole very inferior to the conditions and powers 
of the sensitive and motive systems in the Arti- 
culates: but, on the other hand, “ the organs 
of growth and reproduction become more 


365 


evolved ; and in the Mollusca we are presented 
with a perfecting of the internal organs, which 
is to prepare for and to be more fully deve- 
loped in the higher animals.”’* 

The alimentary canal is provided with a se- 
parate mouth and vent: the stomach may be 
distinguished from the csophagus and intes- 
tine, and a liver is present in all the Mollusks, 
and is remarkable in most for its large size and 
complicated lobular form. The bile is secreted 
from arterial blood. The mouth in the Ace- 
phalous Mollusks is generally concealed in the 
interior of the pallial cavity, but is always si- 
tuated at the anterior part of the body, or that 
which is opposite to the excrementory and re- 
Spiratory tubes or orifices. There are neither 
jaws nor salivary glands in this division. Amon 
the Encephala, however, in which the mouth 
is armed with horny plates representing in diffe- 
rent species the knife, the saw, the rasp, or the 
scissors, the salivary system attains an extraordi- 
nary degree of development, especially in the 
Cephalopods, in which the mandibles resemble 
those of the Raptorial bird, and sometimes have 
their margins armed with a calcareous dentated 
plate. In the Cephalopods the pancreas makes 
its first appearance. The special forms of the 
progressive complications of the digestive sys- 
tem in the present division of animals will be 
found amply illustated in the articles Tunt- 
cata, Concuirera, Preropopa, Gasrro- 
popa, CEPHALOPODA. 

The circulating system, which, as has been 
stated, is complete and double in all the 
Mollusks, is provided in all the species with 
a systemic heart, and in the highest organized 
species with a distinct heart for the lesser or 
branchial circulation, The systemic heart first 
appears in the sessile Tunicaries as a vasiform 
undivided ventricle, which, however, is in- 
closed in a distinct pericardium. It is concen- 
trated into a more compact muscular organ in 
the Conchifers, and divided into a venous and 
arterial chamber; but the auricle, and some- 
times also the ventricle, as in Arca, is sub- 
divided and segregated, according to the law 
of self-repetition, which is exemplified in all 
the systems of organs at their first appearance 
in the animal kingdom. The heart of the 
Gastropods exhibits the higher type of a single 
auricle and ventricle, both placed at the termi- 
nation of the lesser and the commencement of 
the greater circulation. In the highest Cepha- 
lopods the course of the blood is accelerated 
in both circulations by a muscular ventricle, 
but the superadded analogue of the pulmonic 
heart here, likewise, at its first appearance 
illustrates, by its separation into two distinct 
ventricles, the law above alluded to in reference 
to the systemic heart of the lower Mollusks. 

The respiratory organ is distinctly developed 
in all Mollusks, and is subject to the greatest 
variety of forms in this division of the animal 
kingdom; yet, with the exception of the small 
sessile order of Ascidians at the lowest extreme, 


* See the eloquent and ‘philosophic ‘ Recapitu- 
lary Lecture’ of Prof, Green, Vital Dynamics, 8vo. 
1840. 


366 


connecting the Mollusks with the Zoophytes, 
it affords perhaps the best positive character of 
this great primary group of the animal king- 
dom; for whereas, in the Articulate division, 
the breathing organs are lateral or open upon 
or towards the sides of the body, and in the 
Vertebrate division communicate with the oral 
extremity of the nutritive canal, in the Mollusca 
they are connected with the anal outlet. 

 uropoietic system, where traces of it are 
oo e, as in most Gastropods and in 
Cephalopods, likewise communicates withthe 
respiratory cavity. 

e rich endowment of vibratile cilia de- 
Serves to be noticed as characterizing the bran- 
chial organs, and constituting the chief mecha- 
nism 1 gebete in most Mollusca. The 
organs of vegetative life subservient to the pro- 
creation of the species are not less remarkable 
for bulk, variety, and complexity than are those 
which minister to the preservation and growth 
of the individual. Although comparatively 
simple and reduced to the essential formative 
organs in the Acephala, they are, with very 
few exceptions, placed in distinct individuals, 
that is to say, one Ascidian or Oyster possesses 
only the testicle, and is a male; another only 
the ovarium, and is a female. In the order 
Conchifera, the females have the gills modified 
to serve as a receptacle for the impregnated ova 
during foetal development. 

Among the Encephalous Mollusks are many 
hermaphroditical species, some with the male 
and female organs terminating sufficiently close 
together for independent or self-impregnation; 
others having the outlets of the two organs 
remote, and requiring the concourse of another 
individual in reciprocal fecundation ; or the 
same individual is impregnated by another and 
supeapuater a third, as is curiously exempli- 
fied in the nuptial chain thus formed by nu- 
merous individuals of the Marsh-snails ( Lym- 
n@a). The Trachelipods and Cephalopods 
are again diecious, like the lowest classes 
of Mollusks, but exhibit the generative organs 
under the highest stage of complication; and 
some of the latter class are remarkable for 
the expulsion not only of the ova aggregated 
in groups contained in special receptacles, but 
also of the spermatozoa in a similar state of 
aggregation in cylindrical cases, which, by the 
arrangement of their elastic tissue, manifest 
movements, prior to their rupture, which have 
long excited the surprise and admiration of the 
physiological observer. 

A large vitellus, among the numerous nucle- 
ated cells of which it is often difficult to recog- 
nize a single one as the centre of development, 
or as the germinal vesicle, characterizes the ovum 
of most Mollusks. In most species also the early 
formation of vibratile cilia on the surface of the 
germinal membrane, and the rotation of the 
embryo upon its axis produced by their action, 
are striking though not peculiar phenomena. The 
adherence to a uniform type in the earlier pe- 
riods of growth is singularly manifested in the 
rr of Tritonia, Doris, Aplysia, and other 
naked Mollusks, which are protected for a cer- 
tain period by an external spiral univalve shell. 


MONOTREMATA. 


The classification of the Molluscous vine 
has exercised the judgment and discrimination 
of some of the ablest Zoologists, and is a sub- 
ject too expanded for the limits assigned to the 
present article. The principles of a natural 
distribution into the larger groups according 
to general organization seem to be adhered to 
in the following system. ay ; 
Taking the nervous system as a guide to 
the divisions of highest value and extent, the 
Mollusca separate themselves, as already shown, 
into AcepHata and EycEPHALa. ‘ 
The Acephala may be divided to 
the nature of their external covering into Tu- 
nicaTa, where this is continuous, flexible, and 
elastic; and into Concutrera, where it is tes- 
taceous and divided into two or more valves, 
The Conchifera may be subdivided according 
to the modifications of the respiratory cet 
into Palliobranchians and 7 
Respiratory characters likewise mainly distin- 
guish the sessile Tunicaries or Ascidians, and 
the floating Tunicaries, or Salpaceans. — " 
The Encephalous Mollusks are classified ac- 
cording to their organs of locomotion, as Pre- 
ropops, Gasrropops, and CEPHALopops. 
The respiratory organs afford the best charaec- 
ters for the subdivisions or orders of these three 


classes. , 
( Richard Owen.) 


MONOTREMATA, Gr. novos, single, rence, 
hole, in reference to the single cl excre- 
mentory and generative outlet; Fr. Mono- 
trémes ; Ger. Monotremen ; Eng. 

An order or primary group of the Implacental 
subclass of Mamma ia, representin Eden- 
tata in that subclass; allied to the ialia 
by the absence of the corpus callosum and by 
the presence of the marsupial bones, but differ- 
ing in the absence of the abdominal pouch and 
scrotum, in the absence of teeth, in the sim- 
plicity of the bigeminal bodies, and in some 
remarkable modifications of the skeleton and 
generative organs. 

As the order Bruta or Edentata is that which 
exhibits the lowest modifications of the Pla- 
cental type of the Mammalian structure, and 
offers in some respects the nearest approach in 
that subclass to the Ovipara, so the Monotre- 
mata present the extreme modifications of the 
Implacental type, and make the last step in the 
transition from the Mammalian to the Oviparous — 
classes. 

The Monotremes are, however, trae Mam- 
malia in all essential points of structure: th 
possess functional mammary glands, which 
are largely developed at the breeding season ; 
their lungs consist of a spongy tissue, sub- 
divided throughout into very minute cells; 
they are suspended freely in a thoracic cavity, 
separated by a complete muscular and aponeu- 
rotic diaphragm from the abdomen: the arch 
of the aorta bends over the left bronchus: the 
larynx is superior, and is defended by a well- 
developed epiglottis : the kidneys are compact 
conglobate glands with distinct cortical and 
medullary substances, secreting the urine from 
arterial blood, and returning the blood to the 


MONOTREMATA. 


cava by a single large vein. The lower jaw 
articulates with the base of the zygomatic, and 
not with the tympanic element of the temporal 
bone, and the cranium articulates by two dis- 
tinct condyles with the atlas. 

The quadrupeds which combine these essen- 
tial mammalian characters with the oviparous 
modifications above-mentioned are peculiar to 
Australia and Van Dieman’s Land; they form 
three well-marked species, referable to two 
distinct genera. One of these genera, called 
Echidna by Cuvier, is characterized by an 
elongated slender muzzle, terminated. by a 
small mouth, and containing a long and exten- 
sible tongue like that of the Ant-eaters. The 
jaws are edentulous, but the palate is provided 
with many rows of small, sharp, hard, epidermal 
spines, which are directed backwards, and the 
base of the tongue is similarly armed. The 
feet are short, but remarkably broad and strong, 
and are each provided with five very long and 
strong claws. The upper part and sides of the 
body are defended by spines similar to but 
larger than those of the hedge-hog. The tail 
is very short. The genus Echidna contains two 
species, one ( Ech. hystrix) characterized by a 
more complete armour of spines, with a scantier 
admixture of darker coloured hair; the other 
( Ech. setosa), by being clothed with a greater 
proportion of lighter coloured hair, which half 
conceals the spines. These characters are 
constant in both sexes, and as well marked in 
the mature as in the young individuals. 

Both species of Echidna are terrestrial and 
fossorial ; they feed almost exclusively on ants, 
and abound in certain districts of both Australia 
and Tasmania, playing there the same part in 
the economy of Nature which is assigned to 
the Pangolins ( Manis ) in Asia and Africa, and 
to the Ant-eaters ( Myrmecophaga) in South 
America. 

The Ornithorhynchus—the second genus of 
the Monotrematous order—is an aquatic Insec- 
tivore,* but combines water-snails, worms, and 
other small Invertebrata with the insects that 
constitute the staple article of its food. These 
it obtains, not by its tongue, which is short 
and inextensible, but by its lips, which are 
largely developed, and supported by singularly 
modified intermaxillary and lower maxillary 
bones; the whole mouth presenting a close 
resemblance to the broad and flattened beak of 
a duck. The similarity is increased by the 
lateral lamelle of the lower jaw; but both 
jaws are provided with four horny teeth; the 
anterior one on each side, both above and 
below, is long, narrow, and trenchant; the 
posterior one is broad, flat, and shaped like a 
molar tooth. The feet are short, broad, armed 
each with five claws, but less robust than in 
the Echidna. The fore feet have a web, which 


* See No. 541, B. Physiological Series, Museum 
Royal College of Surgeons, London. ‘‘ Debris of 
Insects belonging to a genus of the Nawceride, 
which were found in the cheek-pouches of the 
Ornithorhynchus age Mr. Bennett (Zool. 
Trans. 1834, p. 239) found in the cheek-pouches 
of the Ornithorhynchns mud and gravel, with frag- 

ments of insects and shell-fish. 


367 


not only unites and fills the interspaces of the 
toes, but extends beyond the extremities of the 
claws; the web of the hind foot terminates at 
the base of the claws. With these swimming- 
feet is associated a strong, broad, horizontally 
flattened tail, which completes the organic 
locomotive machinery for the aquatic existence 
of an air-breathing and warm-blooded quadru- 
ped. The body is clothed with a dense coat 
of hair, which consists of a fine fur, intermixed 
with long, stiff, flattened, and sharp-pointed 
hairs, that seem to represent the spines of the 
Echidna. Only one species of Ornithorhynchus 
is as yet satisfactorily defined ; it occurs in the 
fresh-water rivers, ponds, and lakes of Australia 
and Van Dieman’s Land. 

As external ears and large eyes would be ill 
suited to the habits either of a burrowing or a 
swimming animal, both genera of Monotremes 
are characterized by the absence of the auricle 
and the small size of the visual organs. The 
male in both genera bears a horny pointed spur 
upon the heel, which is perforated, and trans- 
mits into the wound it inflicts the secretion of 
a peculiar gland. This singular repetition of 
an offensive mechanism, which, prior to the 
discovery of the monotrematous mammals, was 
known only in certain insects and serpents, 
completes the anomalous combinations in the 
external characters of the present order. 

Echidna hystrix and Ornithorhynchus para- 
dorus were first described and figured by Dr. 
Shaw ; the former as early as the year 1792 in 
the third volume of the Naturalists’ Miscellany, 
under the denomination of Myrmecophaga acu- 
leata ; the latter in the tenth volume of the 
same work in the year 1799, by the name of 
Platypus anatinus. 

In the following year this more extraordinary 
animal received a further description, together 
with its present zoological denomination from 
Professor Blumenbach, in “ Voigt’s Magazin 
fiir den neuesten Zustand der Naturkunde, 
Bd. ii, 1800;” and soon after Sir Everard 
Home gave an account of some of its ana- 
tomical peculiarities, which appeared in the 
Philosophical Transactions for the year 1800. 
As these observations, however, were limited 
to the head and beak, they rather tended to 
perplex than guide the naturalist in assigning 
the position of the animal in the natural 
system. 

Professor Blumenbach, in his Elements of 
Natural History, placed the Ornithorhynchus 
paradoxus among the Palmata of his mamma- 
logical system, between the otter and the 
walruss; while Dr. Shaw more naturally re- 
ferred it to the Bruta of Linneus; but being 
limited to such points of comparison as the exter- 
nal form alone presented, he merely discerned 
the affinities of the Platypus and the Echidna 
to the Myrmecophage. The real value and 
extent of these affinities could only be deter- 
mined by a deeper insight into their respective 
organizations. The important memoirs on the 
anatomical structure of both these animals read 
before the Royal Society by Sir Everard Home, 
and published in the Philosophical Transactions 
for 1802, drew the attention of the scientific 


368 


world more strongly towards their remarkable 
peculiarities and deviations from the ordinary 
structure of the Mammalia. In these investiga- 
tions the author having brought to light nume- 
rous instances of mutual aflinity, before con- 
cealed under very dissimilar exteriors, grouped 
the two animals together under the same generic 
appellation, adopting that of Ornithorhynchus, 
proposed by Blumenbach. He likewise ex- 
pressed his opinion that they differed consider- 
ably in their mode of generation from the true 
Mammalia, on the ground of the peculiarities 
of the organs themselves, and on the at 
of nipples in both species, and especially in 
the female of the Oriitherkyuchas pears Hi 
The opinion of Sir Everard Home was soon 
after adopted by Professor Geoffroy St. Hilaire, 
who, inthe Bulletin des Sciences Philomathiques, 
(tom. iii.), constituted a new order for these 
animals under the term ‘ Monotremata;’ having 
been led to believe, from an imperfect dissec- 
tion, that the genital products of both sexes as 
well as the urine and excrement, were voided 
by a single common outlet. Concluding, also, 
by inference that the mammary glands as well 
as nipples were wanting, and strengthened in 
his belief of the oviparous nature of the Mono- 
tremata by some accounts from New South 
Wales respecting the discovery of the eggs of 
the Ornithorhynchus,* he subsequently sepa- 
rated the Monotremata altogether from the 
Mammalia, and characterized them as a class 
intermediate to Mammalia, Birds, and Reptiles. 
This mode of viewing the Monotremata was 


Fig. 


MONOTREMATA. 


nerally assented to. The 
erie weit a 0 - one of his vig | 
separat e Myrmecophaga . 
Shaw Soon the true Anteaters san the ic 
term § Echidna,’ and who afterwards con- 
siderable additions to its anatomical history, 
as well as to that of the Ornithorhynchus para- 
doxus, in the Legons d’ Anatomie 
whilst he adopted the collective term * Mono 
tremata,’ admitted it in the‘ Regne Animal’ as 
indicative only of a tribe or family in his order 
Edentata. Spix, Oken, and Blainville 
more decidedly opposed the opinion of Geof- 
froy, and the latter naturalist in an dis- 
sertation on the place which the Ornithorhyn- 
chus and Echidna ought to hold in the animal 
kingdom, after adducing the numerous instances 
in which the structure of the Monotremes 
agrees pg that of Rye Mammals, ex- 
presses his opinion that the mammary organs 
will altimately be detected, and considers the 
animals themselves as most closely allied to 
the Marsupial order. 

The exact position of the Monotremata, their 
natural affinities, and the value of the group, 
could, however, be only a matter of speculation 
before their organization, and especially their 
cerebral structure, had been thoroughly eluci- 
dated; the consideration of these points will 
therefore be resumed after the requisite anato- 
mical and et bees res details have been given, 
for a knowledge of which, as the Orni- 
thorhynchus, science is chiefly indebted to the 
celebrated Meckel.+ 


168. 


not, however, 


Skeleton of the Echidna Hystriz, (Pander and D' Alton, corrected from Nature. ) 


int, so that the whole skull resembles 
the half of a pear split lengthwise. The facial 
angle of the Echidna is 36°, that of the Orni- 
thorhynchus 20°, being almost the lowest in the 
mammiferous class. The cranial bones and ~ 


OsTEoLocy. 

Of the skull—The skull in both genera of 
Monotremata is long and depressed, but is cha- 
racterized by a relatively larger cranium in pro- 
portion to the face than in the Marsupials. The 
parietes of the expanded cerebral cavity are 
rounded, and their outer surface is smooth. 
These characters are most conspicuous in the 
Echidna, in which the jaws are slender, elon- 
gated, and gradually diminish forwards to an 


* See Linn. Trans, xiii. p. 621. 


obtuse 


their constituent pieces continue | dis- 
tinct in the Echidna than in the Ornithorhyn- 
chus; and their relative position, their con- 


< ease Rene de aegeys ee 1797. ; 
t Sce his beautifal Monograph, ‘¢ Ornithorhynchi 
Paradoxi Descriptio Anatomica,” folio, 1826. — 


MONOTREMATA. 


‘nections, and the proportions in which they 
enter into the formation of the skull, have been 
in great measure determined and described in 
that genus.* 

I have had the opportunity of investigating 
the composition of the cranium, a point so im- 
a in regard to the natural affinities of the 

onotremata, in the young Ornithorhynchi 
transmitted to the Zoological Society of Lon- 
don by Dr. Weatherhead ; and the comparison 
of this part of their anatomy has enabled me 


_ Fig. 169. 


369 


better to appreciate and understand peculiarities 
of the same part in the Echidna, the skull of 
which is here also described from original spe- 
cimens. 

In the cranium of a young but full-grown 
specimen of Echidna setosa, (g, fig.169, 170, 
171,) the four elements of the occipital bone are 
unanchylosed and are joined together by smooth 
linear harmonize. The basi-occipital (fig. 170, a) 
presents a six-sided rhomboidal figure, with the 
posterior margin notched to complete the lower 


Occipital and sphenoidal cranial vertebra, Echidna 


setosa. (Original. ) 


boundary of the large vertical occipital foramen, 
and thickened and smoothly rounded to form the 
inferior extremities of the two occipital con- 
dyles. These condyles are principally deve- 
loped from the ex-occipital elements (figs. 169, 
171, 6, b), which are expanded superiorly 
and terminate in an angle wedged in between 
the supra-occipital and petrous bones; they 
extend, but do not meet, above the occipital 
foramen, being separated by a notch closed by 
membrane in the recent state. The supra- 
occipital element (figs. 169 & 171, c) isa 
transversely oblong quadrilateral plate of bone; 
its short lateral margin is joined by a linear 
harmonia with the upper part of the os petro- 
sum, on each side; the wide anterior mar- 
gin is similarly articulated with the single 
parietal bone, and is slightly overlapped by its 
posterior margin; this representative of the 
deltoid suture runs straight across the posterior 
and upper part of the skull. 


Fig. 171. 


Occipital region of skull, Echidna setosa. ( Original. ) 


In the specimen in which the preceding 
condition of the occipital vertebra was mani- 
fested there was no trace of sagittal suture ; 
the upper and middle region of the cra- 
nium was covered by a single broad, slightly 
convex, parietal bone, (fig. 169, d,) joined 
posteriorly, as above described, with the supra- 
occipital, laterally with the petrous and sphe~ 
noid bones, and anteriorly with the sphenoid 


* See Legons d’Anatomie Comparée, Ed. 1837. and frontal bones, which the agin overlaps 
B 


VOL. III. 


370 


by a squamous modification of the coronal 
sutures The part described in this Article 
as a lamelliform portion of the petrous bone, 
(fig. 169, e,) which exteuds upon the lateral 
an of the posterior region of the skull, is 
regarded by the Editors* of the Legons d’Ana- 
tomie Comparée, Ed. 1837, as the squamous 

rtion of the temporal; and the flat oblong 

ne, (fig. 169, B,) which forms Leek of the la- 
teral wall of the cranial cavity and the posterior 
half of the zygomatic arch, and which supports 
the articular surface for the lower jaw, is thought 
to be the malar bone. But when we consider 
the low development or total paeppennnce of 
the malar bone in the skull of the Insectivora 
generally, as in Echinops and Centetes among 
the Fere, and as in the edentate Manis and 
Myrmecophaga, it is unlikely that the malar 
bone should attain so superior a size and fulfil 
such important functions in the Monotrema- 
tous Edentata, in which its condition, according 
to the above views of the editors of the Lecons 
d’Anat. Comparée, would be unique in the 
mammiferous class. It appears to me to be 
more reasonable to regard the malar bone as 
either altogether absent in the Echidna, as it is 
in the Manis, and the zygomatic arch as being 
completed in the Echidna by a greater exten- 
sion of the zygomatic processes of the tem- 
poral and superior maxillary bones; or else to 
suppose that these are actually united, at an 
earlier period, by a separate imtervening jugal 
style, which, however, I have not been more 
successful in finding than the Continuators of 
Cuvier. With respect to the great develop- 
ment which the petrous bone, according to my 
view, must present in the Echidna, it may be 
observed that this bone forms part of the occi- 
pital region of the skull in most Marsupials, 
and also contributes as large a proportion to 
the lateral parietes of the skull in certain Ro- 
dents, as the Helamys, as it is here described 
to do in the Echidua. 

The side of the cranium is principally formed 
by the largely developed petrous bone (fig. 170, 
e) and the great ala of the sphenoid, which meet 
and are joined in the interspace separating the 
parietal from the squamo-temporal bone, by a 
nearly vertical harmonia half an inch long; 
this harmonia is crossed at nearly right angles 
by a deep groove, which in some parts sinks 
through the wall of the cranium and exposes 
its cavity. The groove or canal first runs be- 
tween the squamous and petrous elements of 
the temporal bone, and is a conspicuous fea- 
ture in the skull of the Ornithorhynchus. 

The lower part of the side of the skull of the 
Echidna is closed by the squamous element of 
the temporal, which overlaps a large portion 
of the petrous hone, and by a small portion of 
the sphenoid: it is represented detached from 
the skull at fig. 169, The lower boundary 
of the squamo-temporal forms a straight line, 
from which the glenoid surface for the lower 
jaw (f) is extended inwards at a right angle, 
upon the base of the skull; the anterior part 


* The very able anatomists, MM. Laurillard and 
Duvernoy. 


MONOTREMATA. 


is continued forwards, protecting the temporal * 


fossa by a thin vertical plate of bone, and then 


diminishes to a slender, straight, styliform, — 
zygomatic process which rests obliquely on a 
corresponding process of the superior 

lary bone. ee ania 

The tympanic cavity is shallow, exca- 
vated in ny basal test of the petrous bone, — 
where it is widely open in the macerated skull: 
it is figured closed by the tympanic bone and 
membrane at g, fig. 170, and exposed by their 
removal at ¢” fig. 170. The plane of the mem- 
brana tympani is horizontal, and its exter- 
nal parce looks nearly downwards. ee- 
fourths of its circumference are implanted in 
the groove of the very slender incomplete 
formed by the detached tympanic bone, whi 
is figured with the anchyl malleus at c, fig. 
169. The petrous bone is continued from 
tympanic fossa forwards and inwards, in the 
he ofa bev and nearly iat 
(fig. 170, ¢,) to the pterygoid plate sphe- 
ou (¥, i) which alot horkental. Ths pe- 
trous and pterygoid plates are joined by an 
oblique harmonia, and both contribute to extend 
the bony palate backwards. The pa pro- 
cess of the petrous bone is abruptly terminated 
behind by the Eustachian groove id -170*), 

The frontal bone (fig. 169, h) in the cranium 
here described was divided by a median frontal 
suture, toothless like the rest; the angle be- 
tween the superior and the orbital plates is 
rounded off; the orbital plate joins the great 
ala of the sphenoid by a deeply sinuous suture. 
The anterior part of the frontal is largely over- 
lapped by the bases of the nasal bones, which 
encroach upon the interorbital space. 

The nasal bones (fig. 169, n) receive the upper 
edge of the superior maxillary bone into a groove 
at their outer margin, and articulate anteriorh 
with the intermazillaries (fig. 169, 0); but these 
meet above the nasal canal in front of the nasal 
bones for an extent of about three lines, and 
thus exclusively form the boundary of the single, 
oval, and terminal external nostril. The lower 
or palatal process of the intermaxillary extends 
backwards in the form of a long and slender 
pointed process which is wedged into a fissure 
of the superior maxillary bone. 

The anterior palatal or incisive foramen is a 
single large elongated fissure extending from 
the narrow anterior symphysis of the inter- — 
maxillaries backwards, for some distance, be- 
tween the palatal processes of the maxillaries. 
At the back part of the bony palate a narrow 
fissure extends forwards between the id 
bones, and the intermediate extent of the 
bony palate is entire, or presents only a few 
minute perforations. The palatal bones, if — 
originally distinct, soon become confluent wi 
the maxillaries. There was no se osseous ~ 
style representing the malar bone between the 
zygomatic processes of the maxillary and tem- — 
poral bones in the skull here described.* if 

The zygomatic process of the superior mar-— 

ay 4 


ech 


* Cuvier v8 “« Entre ces deux a: 
un trés-petit filet qui represent le jugal.” 
Ossem. Foss, 4to., vol. v., p. le : 


illary bone (fig. 169, m_) extends backwards as 
far as the posterior boundary of the zygomatic 
_ ortemporal fossa; the palatal process extends 
along the floor of the orbit in a similar form 
and to nearly the same extent. The orbit is 
marked off from the temporal fossa by merely 
a slight ridge extending down and across the 
suture joining the frontal and sphenoid bones. 
The skull of the Echidna differs from that of 
the edentulous Manis and Myrmecophaga in 
_ the completion of the zygomatic arches, in the 
unclosed state of the tympanic cavity, in the 
_ large size of the foramen incisivum, and the 
“surrounding of the external nostrils by the 
rmaxillary bones alone: it differs also in 
smaller relative distance between the poste- 
or palatal fissure and the superior maxillary 
bones, and in the apparent absence of the pala- 
tine bones, the presence and interposition of 
_ which between the pterygoid and maxillary 
atal plates elongates the palate in the pla- 
al Anteaters at the part where it is rela- 
tively shorter in the Echidna. In the modi- 
_ fication of the pterygoid plates of the sphenoid 
_ to complete the posterior nasal canal, the 
_ Echidna manifests an interesting resemblance 
with the great Anteater; but it differs from 
this, as from every other mammiferous species, 
_ in the palatal plates contributed by the petrous 
bones to the broad posterior part of the roof of 
the mouth which supports the horny palatal 
h. Cuvier describes the posterior palatal 
re as extending between the palatine bones, 
__and therefore regards the plates, which are here 
affirmed to be developed from the petrous bone, 
____asbeing the pterygoid processes of the sphenoid ; 
and, according to this view, he truly observes 
_ that their horizontal position is very remark- 
e;* but he might have added, that their 
e in the formation of the tympanic cavity 
‘was not less so. The same determination of 
ie ie bones composing the posterior part of the 
osseous palate of the Echidna is repeated in 
_ the Lecons d’Anatomie Comparée, 1837, 
43 454. If, however, the sphenoid be sepa- 
_ tated from the occipital bone, which was easily 
_ done in the young skull of the Echidna repre- 
_ sented in figs. 169 and 170, the horizontal plates, 
described by Cuvier as pterygoids, are left 
behind, not as separate bones, but as conti- 
_ huous portions of the petrous elements of the 
__ temporal, which form, at the same time, part of 
_ the base of the cranial cavity, complete the 
_ inner wall of the tympanum, and the anterior 
part of the Eustachian groove. The palatines 
of Cuvier are developed from the sides of the 
_ basi-sphenoid, and almost immediately bend 
_ inwards and meet below the nasal canal, which 
_ they thus prolong posteriorly, as in the Myr- 
_ mecophaga; and they are separated poste- 
_ fiorly, also, as in that genus, by an acute fissure, 
_ Presenting unequivocally the same modifications 


‘ 
? 


x 
4 


_* Cuvier says, ‘‘ Une echancrure digne et pro- 
_fonde sépare les palatins en arriére. Le plan de 
_ chacun d’eux est continué en dessous par une apo- 
physe ptérygoide, qui ici, chose bien remarquable, 
_ €st horizontale ou a peu pres: elle contribue a 
____ former la cavité de la caisse.”’--Ossem. Fossiles, 

_ Le.p.146. Meckel is silent on this subject. 


MONOTREMATA. 


371 


which characterize the pterygoids in the pla- 
cental Anteaters, and in the Crocodile. The 
suture dividing the pterygoids from the pala- 
tines in the Echidna is obliterated, if it ever 
existed ; or the true palatines may be confluent 
with the palatine processes of the maxillary 
bones. 

Some of the Marsupials, as the Wombat,- 
resemble the Echidna in the open state of the 
tympanic cavity in the dry skull; but the most 
essential points of correspondence with the 
cranial anatomy of the Echidna are found, as 
might be expected, in the Ornithorhynchus. In 
this Monotreme the tympanic cavity (fig. 173, 
A, k) is a simple excavation at the under part of 
the petrous bone; the periphery of the opening, 
which looks almost directly downwards, is en- 
compassed by the tympanic and malleal bones, 
(fig-173, D, a, b,) the outer and anterior part of 
the circle being formed by the os tympanicum. 
The tympanic cavity is relatively smaller, but 
is defended posteriorly by a larger process sent 
downwards by the petrous bone near its outer 
side. The petrous bone here forms no palatal 
process, but the bony roof of the mouth is ter- 
minated by the pterygoid plates, (fig. 173, a, 
t, ) which meet below the nasal canal, as in the 
Echidna, but are not divided by any posterior 
fissure. Ina skull of the Ornithorhynchus, in 
which the suture dividing the palatine processes 
of the maxillary bones from the bony palate 
posterior to them remains, there is no trace of a 
division between the pterygoid and palatine 
bones, which contribute to complete the osseous 
palate (fig. 173, a, e). 

Lhe occipital bone of 
the young Ornithorhyn- 
chus corresponds with 
that of the Echidna in the 
relative size and position 
of its four component 
parts. The ex-occipitals 
are shown at fig. 172, 
b, 6, and the supra-occi- 
pital at c. The petrous 
element of the temporal 
(e) likewise sends a thin 
plate to form the poste- 
rior part of the side of the 
cranium, but it does not 
intervene between the pa- 
rietal bone and squamous 
part of the temporal, as 
in the Echidna. The 
middle of the upper mar- 
gin of the cranial plate Skull of young Ornitho- 
of the petrous bone is "hynchus. ( Original. ) 
notched, and a small vacuity here intervenes 
between the petrous and parietal bones, which is 
closed by the squamo-temporal (f), the upper 
margin of which overlaps the descending pos- 
terior angle of the parietal bone (d). The form 
of the squamous element of the temporal is 
very remarkable in the Ornithorhynchus: its 
ascending cranial or proper squamous portion 
is asmall sub-quadrilateral bony scale, narrower 
antero-posteriorly, but higher than the corres- 
ponding part in the Echidna; articulated by 
its squamous margin with the parietal and 

2B 2 


Fig. 172. 


MONOTREMATA. 


372 


Skeleton of the Ornithorhynchus, ( Mechel.) 


MONOTREMATA. 


trous, but separated from the latter, at its 
ower half, by a fissure analogous to but wider 
than the canal which traverses the squamous 
union of the same bones in the Echidna. The 
base of the squamous plate is contracted but 
thickened to form the origin of the zygomatic 
process : it sends inwards a thin plate, concave 
externally, which forms the glenoid cavity for 
the lower jaw, and is applied against the basal 
of the petrous bone. The glenoid plate 

is equal in size to the squamous process. They 
meet at aright angle, and, from the tubercle 
developed from their union, external to the 
glenoid cavity, the zygomatic process is con- 
tinued forwards to join that which is sent off 
by the superior maxillary bone. I could not 
find any distinct malar bone in the young 
Ornithorhynchus. The same arguments against 
considering the squamous bone to be the malar 
apply to this Monotreme as have been used in 


‘reference to the Echidna. 


The parietal bone (fig. 172, d) forms the 
chief part of the upper region of the skull; it 
is longer in proportion to its breadth than in 
the Echidna. Both the lambdoidal and co- 
ronal sutures are squamous, and the parietal 
overlaps the frontal bones. There is no trace 
of sagittal suture; the bony falx is developed 
from the line which that suture would occupy. 
The lateral connexions of the parietal differ 
from those in the Echidna by its union with the 
Squamous portion of the temporal bone, as 
above-mentioned. 

The frontal bones (h,h) are relatively smaller 
than even in the Echidna: they were divided 
by a suture in the specimen described. The 
form of their exposed surface is shown in 


fig. 172, h, h. 


The side of the skull anterior to the petrous 
bone is formed by the great ala of the sphenoid 


(he. 172, i), whichis joined by a well-defined 


linear harmonia to the parietal bone. 
The Ornithorhynchus differs from the Echidna 


- in the large vacuities in the floor of the skull 


behind and in front of the tympanic cavity, the 
one representing the combined jugular and 
condyloid foramen, the other the oval foramen, 
between which the body of the sphenoid also 
nts two membranous spaces. The skull 
iffers also in the larger size of the foramen 
rotundum, in the stronger zygomata, the more 
complete orbit, and the singular modification 


__ of the bones supporting the beak. The cranial 


cavity is proportionally smaller and shallower 
in the Ornithorhynchus. The sutures of the 


_ €ranial bones are much sooner obliterated, and 


the whole upper and lateral parietes then con- 
Sist of a thin continuous dense plate of bone 
without diploé. 

The resemblance which the Ornithorhynchus 
offers in this respect to the class of Birds is 
noticed by Meckel. 

_ The oblique canal, (fig. 173, c, c,) which 
traverses the squamous suture between the 

and squamous portions of the temporal 
in the Echidna, is so much shorter and wider 
in the Ornithorhynchus that it appears to de- 
tach from the side of the cranium a distinct 


373 


superior column or root (fig. 173, c, a) to the 
posterior commencement of the zygomatic arch. 
An analogous canal runs between the tym- 
panic and mastoid bones in the skull of the 
Crocodile, and is dilated to great width in the 
Lizards ; but the presence of a distinct tym- 
panic bone in the usual position in the Orni- 
thorhynchus nullifies the supposition that the 
ie root of the zygoma can be the analogue 
of the os quadratum in the Ovipara. 

The articular surface for the lower jaw 
(fig.173,c, b) is much more distinctly developed 
than in the Echidna; it occupies the base of 
the zygoma, is extended and concave trans- 
versely, narrower and slightly convex from 
before backwards: it is not defended by any 
posterior process. The zygoma is complete, 
and consists of a nearly vertical straight plate 
of bone, expanded at its anterior or maxillary 
extremity, where it sends upwards an angular 
process bounding the orbit posteriorly, and 
bends downwards to support the broad alve- 
olus of the horny molar tooth (fig.173, a, g, A). 
The orbits are small and directed obliquely 
upwards and outwards. The skull is more 
contracted between them than in the Echidna, 
but anterior to them it begins to expand, be- 
comes flattened horizontally, then bifurcates, 
and the two depressed branches, after slightly 
diverging, terminate each by an inwardly 
inflected process, the extremities of which 
are half an inch apart. The space inter- 
cepted by the facial fork is the external bony 
nostril (fig. 172, p), which is thus left incom- 
plete anteriorly. The forms and proportions 
in which the bones of the face enter into the 
formation of the external nasal aperture are 
illustrated in the figure of the cranium of 
the Ornithorhynchus given by Pander and 
D’Alton,* and I have verified the accuracy 
with which the sutures are there delineated. 
Cuviert supposed the facial forks to be formed 
by the intermaxillary bones, and describes a 
small bone in the middle of their interspace 
(fig. 172, p.) suspended in the cartilage of the 
upper mandible, and with an emargination on 
each side of its inferior plate, which he conjec- 
tured might represent the nasal bones and the 
palatine part of the intermaxillary bones. The 
true nasal bones (fig.172, n,n) are, however, 
as shown by Pander and D’Alton, analogous in 
situation to and more largely developed than 
those of the Echidna. They commence each by 
an angular process, which overlaps the frontal, 
and extends into the inter-orbital space. They 
are continued forward of equal breadth, and 
have their anterior extremity obliquely trun- 
cated and terminated in a fine point, which 
extends to the middle of the inner side of the 
facial fork. The nasal bones thus form the pos- 
terior half of the boundary of the bony nostril. 
The superior maxillary bone (fig. 172, m, m), 
after sending off a process (c), which curves 
over the ant-orbital at extends forwards 


* Skelete der zahnlosen Thiere, 1825, (tab. ii. 
fig. a.) . 
+ Legons d’Anat, Comp. 1837, ii. p. 459. 


374 


in a pointed form along the outer side of the 
facial fork as far as the nasal does on the inner 
side, and an angular fissure is intercepted 
between the anterior extremities of these bones 
into which the pointed posterior part of the inter- 
maxillary bone (fig. 172, 0,0) is inserted. The 
anterior half of the facial fork with its inflected 
end is wholly formed by the intermaxillary 
bones, which thus bound the anterior half of 
the wide external nasal aperture. The small 
detached intermediate bone (fig. 173, a,b) may 
be regarded as a separate centre of ossification 
of the palatine process of the intermaxillaries, 
and of the middle stem which divides the ante- 
rior nostrils in birds and lizards. 

The vomer forms a bony septum, dividing 
the whole extent of the nasal canal from the 
spine of the sphenoid forwards. 

There is a small lachrymal foramen (fig. 
169, 1) at the anterior and inner part of the 
orbit in both the genera of Monotremes; a 
little lower down is the commencement of the 
ant-orbital canal. This canal branches in the 
Echidna, and terminates on the outer side of 
the maxillary bone by a succession of small 
foramina; but in the Ornithorhynchus, where 
it transmits a much larger sensitive nerve, it 
divides into three canals, of which one emerges 
beneath the uncinated process of the maxillary 
above mentioned ; a second descends and opens 
upon the palate ; and the third passes forwards 
into the substance of the facial fork, and termi- 
nates by a large foramen at the outside of the 
intermaxillary bone. 

On the exterior of the cranium the ridges 
indicating the extent of the temporal muscles 
are clearly developed in the Ornithorhynchus, 
and correspond with the stronger zygomata and 
the more complete apparatus for mastication 
in this Monotreme. Four linear impressions 
upon the upper surface of the skull diverge 
from the middle of the lambdoidal ridge, and 
terminate at the temporal ridges. The occipital 
foramen (fig. 173, c) has a vertical plane, as in 
the Echidna, and has a similar rounded notch 
at its upper part. 

The interior of the skull offers many unusual 
modifications. The sella turcica is elongated 
and narrow in both Monotremes; it is bounded 
ge very distinct lateral walls in the Echidna. 

e posterior clinoid processes are chiefly 
remarkable for their height in the Ornitho- 
rhynchus. The semicircular canals stand out 
in high relief in this species, as in Birds. In 
the Echidna the ethmoid encroaches upon the 
anterior part of the cranial cavity in the form 
of a large convex protuberance made by the 
posterior wall of the olfactory cavity, and a 
very extensive cribriform plate is developed. 
In the Ornithorhynchus the olfactory tract is 
comparatively small, in the form of a depres- 
sion, and the nerve escapes by a single foramen 
at the anterior part of the ethmoidal plate. 
This is likewise an interesting mark of affinity 
to the bird and reptile; but the most remark- 
able and characteristic feature in the interior 
of the skull of the Ornithorhynchus is the bony 
falx (fig. 173, 8). This is not present in the 


MONOTREMATA. 


Echidna. The tentorium is membranous in 
both Monotremes. d 
The lower jaw consists in the Echidna of 
two long and slender styliform rami without a 
symphysial joint, but loosely connected together 
at their anterior extremities. An 
cess divides the horizontal from the 
ramus, which rises at an open angle and ter- 
minates in a small oblong convex condyle. A 
short obtuse coronoid process extends from the 
waper part of the horizontal ramus as far in 
advance of the angle as the condyle is behind 
it. The rest of the ramus is rounded likea rib, 


and diminishes to the anterior extremity. _ = h 


dental canal commences below the 
process and divides in its progress, one branch 
terminating near the middle of the smooth 
alveolar border, the other close to the end of the 
ramus. In no Mammiferous animal does .the 
lower jaw bear so small a proportion to the sk 
or to the rest of the skeleton as in the Echidna. 
In the Ornithorhynchus the lower jaw is 
much more developed (fig. 173, £). Each 
ramus commences teriorly by a ae sub- 
hemispherical condyle, the convexity of which, 
so characteristic of the Mammalian class, is 
strongly marked. The ascending ramus is 
nearly horizontal, flattened below, and con- 
tinued upwards in the form of a low vertical 
compressed plate, on each side of which there 
is a deep fossa. The ascending is continued 
by a gentle curve into the horizontal u 
and the angle of the jaw is very feebly indicated. 
The horizontal ramus suddenly expands and 
sends off above in the same transverse line 
two short obtuse processes, both of which 
might be termed ‘ coronoid;’ this structure is 
peculiar to the Ornithorhynchus. The oa 
most process (c), although the largest, is the 
superadded structure, as it affords insertion to 
the internal pterygoid. About two lines anterior 
to these processes the upper border of the 
horizontal ramus expands to form the shallow 
oblong alveolus (e) for the horny grinder. Its 
floor is perforated by several large foramina. 
The dental canal divides; one branch opens by 
a wide elliptical foramen on the outside of the 
ramus immediately anterior to the 
the other terminates at the lower part of the 
end of the ramus. The rami of the jaw con- 
verge and are united at a symphysis of more 
than half an inch in length; there they become 
expanded and flattened, then again disunite, 
and are continued forwards as two 
processes (b), which diverge from each other to 
their broad rounded terminations, and are 
situated just behind the inflected extremities of — 
the similarly separated inter-maxillaries (fig. 
173, a, c,c). On the outer sides of the upper — 
surface of the broad symphysis are the, ae 
and narrow sockets of the two anterior trenchant 
horny teeth. The Monotremes differ from the 
Marsupials in the absence of the inflected pr 
cess developed from the angle of the lower jaw. — 
Of the vertebral column.—Both Monotremes — 
have twenty-six true vertebre, of which the — 
seven first are cervical. In the Echidnasixteen, — 
and in the Ornithorhynchus seventeen, of the a 


ye 


\. 


following vertebre support long and functional 
ribs, so that there are three lumbar vertebre in 
the Echidna, and but two in the Ornithorhyn- 
chus, which thus resembles the Lizards in the 
great proportion of the trunk which is encom- 
d by the costal arches. Another approxi- 
mation to the Oviparous type is made by the 
long-continued separate state of the short 
cervical ribs in both Monotremes: these in a 
young but nearly full-grown Echidna are 
detached from all the cervical vertebra except 
the atlas. The vertebral end of the cervical 
_ rib is bifurcated; the lower branch, represent- 
ing the head, is articulated to the transverse 
_ process or tubercle developed from the body 
_ of the vertebra; the upper branch, represent- 
_ ing the costal tubercle, is articulated to a trans- 
‘verse process developed from the side of the 
age the neural arch. In the Ornitho- 
vhynchus the cervical ribs appear to become 
earlier anchylosed to the vertebra, except as 
_vegards the axis, in which the broad costal 
appendage retains its original independence 
. throughout life, and is slightly moveable 
upon the confluent extremities of the two 
‘transverse processes. In the succeeding ver- 
_tebre the space intercepted between the two 
_ transverse processes, the vertebra, and the cos- 
tal rib, forms the so-called ‘ perforation of the 
transverse process’ for the vertebral artery in 
_humananatomy. In the Echidna, above alluded 
‘to, the ‘ neurapophyses’ or vertebral plates of 
the atlas, which together form the neural or 
_ Spinal arch, were unanchylosed at their upper 
or spinal extremities. The atlas of the Orni- 
i trrnchus is chiefly distinguished from that 
of the Echidna by the continuation, from the 

Tower part of its slender body, of two long 
_ diverging processes which are developed in the 
_ strong tendons of the recti capitis antici 
_ muscles. The spine of the dentata is broad 
and high in both Monotremes; those of the 
other cervicals progressively diminish in size 
‘in the Ornithorhynchus, but become at once 
néarly obsolete in the Echidna. The transverse 
_ and spinous processes are of moderate size in 
_ the rest of the true vertebre, but are largest in 
the lumbar region. The posterior oblique 
‘processes are single in these vertebre. The 
articular surfaces of the vertebre, which are 

_ slightly concave, are joined together by a thick 
_ ¢ireular band of ligamentous fibres (fig. 174, a) 
_ attached to the circum- 
ference of the articular 
Surface, enclosing a cen- 
_ tral oblate spheroidal ca- , 
_ vity ) lined bya synovial “eee 
_ membrane and filled with 
fluid. 

The ribs are long and 
Slender in the Ornitho- 
_ thynchus, somewhat stron- 
es cee the Echidna. The 
a is flattened, the rest 
are cylindrical. Each rib 
is articulated by a single 
joint, uniting the head to 
the. vertebral. interspace, Intervertebral cavities, 
or to the side of the cen- Echidna. ( Original. ) 


Fig. 174. 


a} 
+ 


ee 


MONOTREMATA. 


375 
trum, as in the two last pairs: the tubercle, 
though small, is distinctly developed, and de- 
fines the neck of the rib, although it does not 
join the transverse process of the vertebra. 

Meckel’s statement, ‘ tuberculum adest nul- 
lum,’ is applicable only to the last three or 
four pairs of ribs. The first six pairs are joined 
to the sternum in both the Ornithorhynchus and 
the Echidna. Six pairs of ossified sternal ribs 
(hemapophyses*) are articulated to the ster- 
num in the Echidna; the first four are nearly 
straight and sub-cylindrical; the fifth and sixth 
are expanded. Five pairs of ossified sternal 
ribs are present in the Ornithorhynchus, to 
which the second to the sixth vertebral ribs 
inclusive are joined by shorter intervening 
cartilaginous pieces of a similar form. The 
first rib in the Ornithorhynchus is joined to the 
sternum by cartilage alone. The interposed 
cartilages, which thus form a third element in 
the costal arch, repeat a structure common in 
crocodiles, and may be regarded as the homo- 
logues of the costal appendages in the ribs of 
birds, which in this class are removed from the 
interspace of the vertebral and sternal rib, and 
articulated to the vertebral piece. 

The cartilages of the false ribs in both genera 
are singularly expanded and flattened, and 
present an imbricated arrangement, gliding 
upon each other with a slight yielding motion : 
the last vertebral rib, which is the shortest and 
straightest, is terminated by a short free carti- 
lage. Many bone-corpuscles are scattered 
through these cartilages. 

The ordinary sternum, to which the true ribs 
articulate, consists of four ossicles, and in the 
Echidna a fifth is developed in the base of the 
ensiform cartilage; the most anterior of these 
ossicles (fig. 173, a, s) has the usual expanded 
hexagonal form and large proportions of the 
manubrium sterni, and receives, besides the 
first and part of the second pair of ribs, the 
extremities also of the coracoid bones. The 
ensiform cartilage in the Echidna presents an 
elongated oval form with a central perforation. 
A large T-shaped episternal bone (fig. 173, , t) 
is articulated to the anterior surface of the 
manubrium sterni; it is the key-bone of the 
complicated scapular arch. 

The sacrum consists in the Ornithorhynchus, 
as in most Saurians, of two vertebra, distin- 
guished by the greater breadth and thickness 
of their transverse costal processes. In the 
Echidna there are three sacral vertebra. 

There are thirteen caudal vertebre in the 
Echidna (fig. 168). The first is the largest, 
with broad transverse processes, the rest pro- 
gressively diminishing, and reduced, in the six 
last, to the central element. The Ornithorhyn- 
chus (fig. 173, a) has twenty-one caudal ver- 
tebre, of which all but the last two have 


* In the complete vertebre which encompass 
the centre of the vascular system, the hemapo- 
physes or halves of the chevron-bone, or inferior 
vertebral laminz, are retained, together with the 
inferior or hemal spine. The series, sometimes 
anchylosed, as in Man, of these spines forms the 
* sternum :’ the inferior lamine or hemapophyses 
are the sternal ribs. wie 


376 


transverse processes, and the first eleven have 
also spinous and articular processes. The 
transverse processes are broad and depressed ; 
they gradually increase in length to the tenth 
caudal, then as gradually diminish to the twen- 
tieth; their extremities are expanded, and, 
from the fifth backwards, are thickened and 
tuberculate. The spinous processes progres- 
sively diminish in height from the first 
caudal. The first six caudal vertebre have 
both posterior and anterior oblique processes, 
and are joined together both by these and by 
the articular surfaces of the body: the anterior 
articular processes are present, but age 
sively diminish in size from the seventh to the 
sixteenth vertebre, and are not subservient to 
their reciprocal articulation. Inferior be seg 
processes are developed from the bodies of 
the third to the nineteenth caudal vertebra 
inclusive; but there are no hemapophyses 
articulated to the vertebral interspaces, as in 
many Marsupials and the Edentata. In the 
Echidna the inferior spinous processes are 
absent ; but rudiments of hemapophyses are 
connected with the interspaces of one or two 
of the middle vertebra of the tail. The cau- 
dal vertebre in the Ornithorhynchus are of 
nearly the same length to the two last; they 
progressively diminish in vertical diameter as 
they recede from the trunk, and are chiefly 
remarkable for their breadth and flatness; 
resembling in this respect, as Cuvier has ob- 
served, the caudal vertebre of the Beaver, and 
we might add those of the Cetacea; the hori- 
zontally extended tail having a similar relation 
to the frequent need which an aquatic animal 
with hot blood and a quick respiration of air 
has to ascend rapidly to the surface of the 
water. 

Of the pectoral extremities —Cuvier* justly 
observes that the most remarkable part of the 
osteology of the Monotremes is the organiza- 
tion of the shoulder; which corresponds with 
that of birds, and still more with that of 
lizards. 

Had these anomalous Mammals been ex- 
tinct, and their fossilized skeleton alone, as in 
the Ichthyosauri, been preserved for the con- 
templation of the naturalist, the perplexity 
which the combination of this structure with 
the mammalian conditions of the skull and 
vertebree would have occasioned may be readily 
conceived. 

The scapula (/) is represented detached, with 
the coracoid (0), at G, fig. 173; /* is the 
cartilage appended to the short convex base. 
The scapula is long, narrower than in most 
Mammalia, and has its posterior vertebral 
angle so much produced, as to give it a re- 
semblance to the scapula of the bird and 
saurian: this resemblance is farther increased 
by the origin of the spine close to the anterior 
costa, and by the spine being bent forwards 


so as to seem to form a continuation of the | 


external surface of the scapula, which is thus 
rendered concave in the Ornithorhynchus. 


* Ossem. Foss. v. pt. 1, p. 146. 


MONOTREMATA. 


The spine, however, terminates in a freely pro- 
jecting acromion. F 
The true anterior costa is, in this Monotreme, 
represented by a ridge which traverses ob- 
liquely the inner and convex side of the sca- 
pula, from the anterior vertebral angle to the 
neck of the bone. In the Echidna this ridge 
is nearly obsolete, and the spine of the sca- 
pula is bent so as to form a ments con- 
tinuation of body of the scapula wi 
of which it is nearly parallel : the sotonsie aa 
mination is slightly twisted. a 

Both Cuvier and Meckel describe the 
nous process of the scapula as the anterior 
margin, (superior costa in human ra 
and consequently consider the spine of th 
scapula as being absent. Cuvier says, “ Le 
bord antérieure descend presque droit jusqu’a 
Vendroit ou il se courbe en dedans pour former 
une apophyse, qui porte la fourchette.” Meckel 
recognises this process as the acromion : “ Margo 
anterior partis superioris versus inferiora ex- 
trorsum primo flexus, dein eminentiam, acro- 
mion, antrorsum et introrsum versam, emittit.” 
The ‘ margo anterior’ of Meckel, * bord anté- 
rieure’ of Cuvier, is, in fact, the true spine of 
the scapula, and the true ‘ margo anterior’ is 
the ridge above described. The proof of this 
is afforded by the origin of the supra-spinatus 
muscle which occupies the s between 
Meckel’s ‘ margo anterior’ and the ridge 
which I regard as the true anterior costa, and 
which is not noticed by either of the anato- 
mists above quoted. 

Since the scapula is peculiarly characterized 
in Mammalia by the presence of a spine and 
in Ovipara by its absence, its recognition in 
the Monotremes, under the modification 
which its apparent absence is occasioned, 
the transition to the oviparous type of this bone 
is effected, becomes a subject of especial in- 
terest. 

The whole scapula is broader, thicker, and 
less curved in the Echidna than in the Orni- 
thorhynchus. In both Monotremes, the pos- 
terior margin or costa is concave, most so in 
the Ornithorhynchus, and in both it is turned 
towards the trunk, so that the sub-scapular 
surface looks obliquely forwards and inwards. 
The articular surface is divided into two facets: 
the one, internal and flat, articulates with the 
coracoid; the other, external, is sligh’ 


the glenoid cavity for the humerus. meres 


The coracoid (fig. 173, G, 0) early coalesces 


with the scapula in the Ornithorhynchus; it main-= 
tains its independent condition to a later 
in the Echidna. In both it is a strong, su 


pressed, subelongate bone, expanded at both 


ends; one of these is articulated and anchylosed 


with the scapula, as above described; the other 


is joined to the anterior and external facet of the 
manubrium sterni. The posterior margin of 
the coracoid is concave and free; the anterior 
margin is straight and articulated with a thin’ 
broad irregularly quadrilateral jar of bone in 


the Ornithorhynchus, and a thicker and nar- 


tly con- 
cave, and contributes, with a similar but nar 
rower concave surface of the coracoid, to form 


MONOTREMATA. 


rower corresponding bone in the Echidna. 
These bones, which are called the ‘ epicoracoids’ 
(fig- 173, a,nn) are joined by their median 
margin to the stem of the episternal, and by 
their anterior margins to its transverse branches, 
which are overlapped by the epicoracoids. 

e true or acromial clavicle (fig. 173, 4, 
mm) is a long, slender, compressed, slightly 
bent bone, continued from the articular cavity 
at the end of the acromion to near the median 
line of the episternum, anterior to but parallel 
and in contact with the branches of the epi- 
sternum, with which the clavicles finally co- 
alesce, but at an earlier period in the Orni- 
thorhynchus than in the Echidna. These 
clavicles are the homologues of the os fur- 
catorium in the bird: the T-shaped episternum 
(fig. 173, a, t) is feebly represented in birds by 

e€ median process continued forwards be- 
tween the coracoid articular cavities from the 
fore part of the sternum. It is in Lizards, and 
especially in the extinct Ichthyosaur, that the 
episternum presents the same form, develop- 
ment, and relation to the clavicles, as in the 
Monotremes. The epicoracoids again are want- 
ing in the bird, but they are present in lizards, 
and the remarkable breadth of the coracoid in 
the Enaliosauria is due to their presence, al- 
though, singularly enough, they are anchylosed 
to the coracoids in these extinct reptiles, while 
in the warm-blooded Monotremes they remain 
separate. In the Echidna they are articulated 
with the coracoid bya true synovial joint. To 
Tender the resemblance between the Mono- 
‘treme and the Bird complete, in respect of the 
structure of the scapular arch, the episternum 
‘must be reduced to a short and simple process 
attached to the anterior part of the manubrium 
Sterni, the epicoracoids must be removed, and 
the clavicles anchylosed together at their mesial 
extremities.* 
_ The humerus is a short and strong bone, 
expanded at both extremities, and, as it were, 
twisted half round upon itself. The proximal 
expansion terminates by a broad thick convex 
border, the middle part of which is developed 
into the articular head, which is so adapted to 
the glenoid cavity, that the bone is maintained 
in a horizontal position, and the distal expan- 
sion is nearly vertical. The deltoid and pec- 
toral crests are strongly developed ; both con- 
dyles are remarkably produced, especially the 
internal one, which is perforated. ( Fig. 173, 
H, a.) The distal articular surface scarcely 
occupies a fourth part of that broad termination 
of the humerus: it presents, in the Echidna 
(fig. 168), a convex tubercle, which is broadest 
in front, for the articulation of the radius, nar- 
row behind, for that of the ulna. The articular 
surfaces of both anti-brachial bones are concave : 
so that the elbow-joint admits freely of flexion 
and extension, abduction and adduction, but is 
restricted in the movement of rotation. 


* For a full and elaborate discussion of the 
various opinions which have been offered respect: 
ing the homology or signification of the complicated 
apparatus of the shoulder in the Ornithorhynchus, 
the reader is referred to Meckel, ¢ De Orsithorhyn: 
cho,’ &c. pp. 12-15. 


377 


The radius and ulna are in contact and 
pretty firmly connected together through nearly 
their whole extent; the interosseous space 
being reduced to a slight fissure. The una is 
chiefly remarkable for the olecranon, (fig. 173, 
4, u,) which is bent forwards upon the humerus, 
and transversely expanded at its extremity, 
especially in the Ornithorhynchus, in which the 
lower or inner angle of the expanded ex- 
tremity is considerably produced. The shaft 
of the ulna is compressed, and increases in 
breadth, in the Echidna, as it approaches the 
broad carpus. In the Ornithorhynchus it is 
bent like the italic /, is more cylindrical, and 
more suddenly expanded at the distal end. 
The radius offers little worthy of notice, except 
that in the Ornithorhynchus it is flattened next 
the ulna, and so applied to that bone as to 
prevent altogether a rotation of the hand upon 
the ulna. In the Echidna the distal articular 
surface of the ulna (fig. 175, n) presents two 
convex trochlee separated by a median con- 
cavity; that of the radius (fig. 175, r) offers 
a reverse condition: here two concavities are 
divided by a median convex ridge ; all the four 
facets at the carpal joint of the antibrachium 
are in the same transverse line. The two 
radial concavities receive the two articular 
convexities of the broad scapho-lunar bone 
(fig. 176, a): the two: convex trochlee of the 
ulna play upon two concavities, one-half of 
each of which is contributed by the cuneiform 
(fig. 176, 6) and pisiform bones (c). This com- 
plicated joint limits the movement of the hand 
upon the fore-arm to flexion and extension. 


Fig. 175. 


Bones of fore-foot, palmar aspect, Echidna setosa. 
( Original. ) 


Notwithstanding the confluence of the sca- 
phoid with the lunar bone in the carpus of the 
Echidna, as in that of the Marsupials and 
Carnivora, it includes eight ossicles, a small sesa- 
moid bone (fig. 176,* ) being developed in the 
tendon of the flexor carpi radialis, and articu- 
lated with the scapho-lunar bone and radius. 
The distal series of the carpus includes the four 
normal bones, the trapezium. (fig. 176, h) 


378 


supporting the innermost digit or pollex, the 
trapezoides (g), the index, the os magnum (/’), 
which is almost the smallest, sustaining the 
medius, and the unciforme (e) the two outer 
digits: this description is taken from the 
Echidna: the only essential difference obser- 
vable in the Ornithorhynchus is the contribu- 
tion by the os magnum of a greater share to 
the articulation with the ring-finger. 

In the Echidna all the bones of the fore- 
extremity are relatively larger and stronger 
than in the Ornithorhynchus, but this dif- 
ference is especially remarkable in the meta- 

} bones and two first rows of phalanges 
Jig. 176, h, i, k), which are singularly short, 
broad, and thick. The palm is strengthened 
by two large sesamoids developed in the flexor 
tendons in the Echidna; these are sometimes 
confluent (fig. 175, 1). The number of pha- 
langes in both Monotremes is the same as in 
other Mammals, viz. two to the thumb and 
three to each of the fingers. This is not the 
case in any Saurian, and the retention of the 
Mammalian type at the peripheral segment of 
the limb, with the singular deviation from it at 
the central supporting arch, is not one of the 
least remarkable points in the osteology of the 
Monotremes. 

There is a sesamoid bone at the palmar 
aspect of each of the distal articulations of the 
phalanges in the Echidna (fig. 175), and at all 
the digital articulations in the Ornithorhynchus 


(fg. 173, u,d@). 


Fig. 176. 


Bones of the fore-foot, Echidna hystrix. 


The ungual phalanges are long, depressed, 
nearly straight, of great strength in the Echidna, 
in which each of them is perforated at the 
palmar aspect (fig. 175). 

Of the pelvic extremities.—The pelvis of the 
Monotremes bears a resemblance to that of 
Reptiles in the length of time during which 
the three components of each os innominatum 
remain distinct, especially in the Echidna; and 
in the great development of the ilio-pectineal 
spine, which equals in size that of the tortoise, 


MONOTREMATA. 


in the Ornithorhynchus; the pelvis of “ei 
Echidna resembles that of Birds in the we 


ration of the acetabulum (fig. 177, g), butthe 

pelvis in both Monotremes chiefly resembles 
that of the higher implacental Mammalia in 

the presence of the marsupial bones. see ; 

Fig. 177. . 

Re a es 

a oe 

a 

“ 


Internal view of pelvis, Echidna setosa. ; 
( Original. ) - 
The ilium (fig. 177, a) is a short, strong, 
trihedral bone, with the upper extremity ex- 
panded and everted in the Ornithorhynchus. 
he ischium (6) has its tuberosity prolonged 
backwards in an obtusely-pointed form in the 
Ornithorhynchus. The pubis in the same 
animal, besides having the spinous process 
directed forwards, gives off a second smaller 
process, which projects outwards; this s 
is present, but less developed in the Echidn 
(fig.177, f). The pubis (c) and ischium con- 
tribute an equal share to the formation of the 
foramen obturatorium (/) and to the symphysis 
which closes the pelvis below: the symphysis is 
relatively shorter in the Echidna (d) than in the 
Ornithorhynchus. mS 
The marsupial bones (fig. 173, A, 22, 177, €) { 
are relatively larger and score in the Mono- — 
tromes than in the ordinary Marsupialia, the 
Koala excepted; their base extends along the 
anterior margin of the pubis from the sy 
outwards to that of the spinous process 
177, f); they are relatively longer in the 
Echidna (e) than in the Ornithorhynehus; they — 
always remain moveably articulated with the 
brim of the pelvis. C2 a 
The femur is short, broad, and dane f 
head rises, like that of the humerus, from the — 
middle of a broad expanded proximal end, 
having on each side a strong process, the outer 
one representing the great, the inner one tl 
small trochanter. In the Echidna a project- 
ing ridge extends from the great or outer tro- 
chanter beyond the middle of the bone; the — 
whole of the inner part of the shaft is bounded — 
hy a trenchant edge; both outer and immer 
margins of the bone are trenchant in the 
Ornithorhynchus. The distal end of the femur — 
is expanded transversely, but com : 
before backwards. The rotular trochlea 


a 


transversely, convex vertically, in the Echidna ; 
it is hardly definable when the cartilage is 
separated from the bone; but the patella itself 
is well developed, and ossified in both Mono- 
tremes (fig. 173, a, p). 

The tibia is straight in the Echidna, but 
bent, with the convexity next the fibula, in 
the Ornithorhynchus; its criste are slightly 
marked. 

The fibula is slightly bent in the Echidna, 
but is straight in the Ornithorhynchus ; in both 
Monotremes it is longer than the tibia by the 
extent of a process which rises upwards beyond 
_ the proximal articulation of the fibula, and 
most strongly expresses the analogy of this 
bone with the ulna: this process (fig.173, a, v) 
reaches half way up the back of the femur in 
the Ornithorhynchus, and, like the olecranon, is 

tly expanded at its termination. Cuvier* 
_ Indicates the resemblance of this structure in 
the Monotremes with the fibula and the super- 
numerary bone imposed upon its enlarged prox- 
imal end in the pedimanous Marsupials. 

The tarsus (figs. 178, 179) consists of a 
seaphoid (a), astragalus (b), a calcaneum (c), 
three cuneiform bones (d,e, f’), and a cuboid (g’) 

inthe Echidna; but the cuboid in the Ornitho- 


Fig. 178. 


Bones of hind-foot, Echidna hystrix. ( Cuvier.) 


_ thynchus is divided into two bones, as in some 
_ Reptiles, one for the fourth and the other for 
the fifth metatarsal bones. In both Mono- 
_ tremes there is a sesamoid bone (fig. 178, *) 
placed at the interspace between the astragalus 
and the naviculare; a second supernumerary 
__ bone (**) is articulated to the posterior part of 
_ the astragalus, and supports the perforated spur 
en characterizes the male sex (fig. 173, 
‘ q K, . 
The calcaneum of the Ornithorhynchus ter- 
_ Minates by sending outwards a short obtuse 
tuberosity ; in the Echidna this part is more 
Slender, and is singularly directed inwards 


* Ossem. Foss. v. pt. i. p. 153. 


MONOTREMATA. 


379 


and forwards, nearly in a line with the digits 
(fig. 179, e). 

The astragalus in the 
Ornithorhynchus pre- 
sents a double trochlea 
above for the tibia and 
fibula, and a depres- 
sion on its inner side, 
which receives the in- 
curved malleolus of the 
tibia, almost as in the 
Sloths. The toes have 
the same number of 
bonesas in other Mam- 
malia; their size and 
form are more alike in 
the two Monotrema- 
tous genera than those /, 
of the fingers: the un- #7 
gual phalanges, like “ # 
the claws they support, 
are more curved than 
those on the fore foot, 
but like them they are 
perforated on their in- Bones of hind-foot, plantar 
ner and concave side aspect, Echidna setosa. 
(fig.179). ( Original. ) 


Fig. 179. 


OF THE MUSCULAR SYSTEM. 

The figure (180) here given from Meckel?* il- 
lustrates some of the most instructive peculiari- 
ties of the muscular system of the Ornithorhyn- 
chus. The animal is dissected from the ventral 
surface; the great cutaneous muscle, the ‘ pan- 
niculus carnosus’ (1), is reflected from the right 
side, and the deeper-seated muscles are shown 
on the left. The panniculus carnosus, which is 
remarkable for its thickness, encompasses nearly 
the whole body, adhering most firmly to the 
external skin, but separated from the subjacent 
muscles, especially where it covers the thorax, 
abdomen, the arm, and the thigh, by a copious 
and lax cellular tissue; and in the female, at 
the abdominal region, by the mammary glands. 
The fibres are chiefly longitudinal, but at the 
lower part of the neck become transverse. The 
obtuse posterior end of the muscle is attached 
by three or four fasciculi to the dorsal aspect 
of the transverse processes of the caudal 
vertebre. The legs and the arms protrude 
through oblique apertures in this muscular 
tunic; some of the anterior fasciculi are in- 
serted by a short tendon into the pectoral ridge 
of the humerus; and others, still more anterior, 
are attached to the cranium, the lower jaw, and 
lower lip. A strip of fibres, which is cut off 
at 1*, is attached to the os hyoides; another 
fasciculus (1’) spreads over the cheek-pouch, 
ah assists in emptying that receptacle of the 
ood. 

The trapezius (9) is divided into two muscles; 
the posterior portion is an oblong slender tri- 
angle arising by a broad tendon from the tenth 
and eleventh vertebre and ribs, and inserted by 
a short strong tendon in the anterior extremity 
of the spine of the scapula; the anterior portion 
is shorter, but broader, and is subquadrangular; 
it arises from the occiput and tendinous raphé 


* De Ornithorhyncho, &c. tab. v. 


380 


connecting it with its 
fellow of the opposite 
side (called ‘ ligamen- 
tum nuche’ by Meckel), 
and is inserted into the 
Spine (‘ margo anterior 
scapule,’ Meckel) and 
acromion process of the 
scapula, and into the 
outer half of the cla- 
vicle. 

The latissimus dorsi, 
a very long and broad 
muscle, arises from the 
spines of all the dorsal 
and lumbar vertebra, 
and from the eleven 
posterior ribs; it is in- 
serted by a broad and 
strong tendon into the 
distal half of the ulnar 
margin of the humerus. 
At its anterior part this 
muscle may be sepa- 
rated into a superficial 
and deep stratum. 

The rhomboideus is a 
single muscle, but thick 
and long, extending 
from the occiput to the 
narrow base of the sca- 
pula. 

The splenius is united 


by an intermediate ten- | 
don with the opposite | 


muscle, and is inserted 
into the mastoid pro- 
cess. 

The biventer cervicis 
and the complerus are 
distinct throughout their 
whole course, which ex- 
tends from the anterior 
dorsal and posterior cer- 
vical spines to the occi- 
put; the complexus is 
the longest and thickest 
muscle, and divides into 
an external, shorter, and 
deeper-seated portion, 
and an internal, longer, 
and superficial portion. 

The sacrolumbalis ari- 
ses from the dorsal ex- 
tremity of the ilium, is 
attached to the ribs, over 
which it passes in its 
course to its insertion 
into the transverse pro- 
cesses of the four or five 
pecgel cervical verte- 


The longissimus dorsi 
is a much thicker and 
narrower muscle, and 
extends from the dorsal 
aspect of the sacrum 
along the spine to the 
third or fourth cervical 
vertebra. 


MONOTREMATA. 
Fig. 180. 


} oF fo fp ‘Us 
| \ Lh AS | 
i ei 


Muscular system, ventral aspect. Ornithorhynchus paradoxus. ( Meckel. ) 


MONOTREMATA. 


The transversalis cervicis and trachelo-mas- 
toideus are blended into a single oblong muscle 
arising from the anterior dorsal and the trans- 
verse processes of the six lower cervical ver- 
tebre, and inserted into the mastoid process. 

The sterno-mastoid is a double muscle on 
both sides, one portion being superficial (8), 
the other deep-seated; each arises separately 
from the episternal bone, and is separately 
inserted into the mastoid tubercle, behind the 
tympanic cavity. The omo-hyoideus and mylo- 
“ppg (10, 10) have a common insertion into 

eos hyoides. A muscle (1”), arising from 
the hyoid bone and expanding to be inserted 
into the lower lip, serves to retract this part. 
The sterno-hyoideus (11) joins the hyo-glossus. 
The genio-hyoideus (12) and the stylo-hyoideus 
(13) have the normal relations: the biventer 
maxille (14) is a short thick muscle, inserted 
near the bend, representing the angle, of the 


aw. 

The caudal muscles are powerfully developed. 
The oblique fibres of the inferior or deflector 
muscles are shown at 53; they are removed on 
the other side to expose the anterior caudal 
nerves (i). The obliguus externus abdominis 
(3, 3) arises from all the vertebral ribs, except 
the first, and from the dilated extremity of the 
ilium; it is inserted by a strong tendon into 
the outer extremity of the marsupial bone (vr), 
then expands into an aponeurosis which is 
attached to the internal margin and base of the 
marsupial bone, and into the symphysis pubis, 
decussating with the tendinous Apres of the 
opposite muscle. 

e obliquus internus (6) arises from the 
anterior part of the ilium, expands, and is 
inserted into the broad cartilages of the seven 
posterior ribs (v, v). 

The ¢transversus abdominis (7) is a thicker 
muscle, and arises from both the ilium and the 
transverse processes of the lumbar vertebre ; 
its tendon passes behind the recti to blend with 


_ that of the opposite muscle, and with the 


aia of the obliqui externi, in the linea 


The pyramidalis, or superficial rectus (4), is 
here, as in the ordinary Marsupials, of very 
large size; it arises from the whole inner margin 
of the marsupial bone ; its fibres converge to- 
wards and are confluent at the linea alba with 
those of its fellow, and it gradually terminates 
in a point opposite the posterior part of the 
sternum. It depresses the ribs, shortens the 
abdomen, and protracts the marsupial bone. 

The rectus abdominis, or posterior rectus (5), 
arises from the posterior margin of the marsu- 
pial bone, and is inserted into the cartilage of 
the first rib, the manubrium sterni, and the 
coracoid bone. 

_ The diaphragm presents the structure which 
is characteristic of the true mammiferous ani- 
Mal. The lesser muscle arises from the first 
lumbar and four last dorsal vertebre, and ex- 
pands to be inserted into the central tendon, 
which chiefly receives the fibres of the greater 


‘Muscle arising from the cartilages of the eleven 


inferior pairs of ribs. 
The pectoralis (2) is of very striking dimen- 


381 


sions; the origin of the superficial portion 
extends from the acromion, along the sternum 
and linea alba, almost to the pubis; a deeper- 
seated portion arises from the six osseous 
sternal ribs; the fibres of both portions con- 
verge to be inserted into the largely-developed 
pectoral or anterior crest of the proximal half 
of the humerus. 2 

The pectoralis minor is attached to the cora- 
coid, and the subclavius is likewise inserted, 
as in some other quadrupeds, into this bone, 
which is no longer a subordinate process of the 
scapula in the Monotremes. 

e subscapularis is a narrow muscle, and 
narrower in reality than at first sight it appears 
to be, since the supra-spinatus, from the inflec- 
tion of the spine and acromion, arises from the 
same aspect of the scapula, and appears to 
form the anterior fasciculus of the subscapularis ; 
its distinct insertion into the anterior tubercle 
of the head of the humerus points out its true 
nature. 

The infra-spinatus (20) and the large teres 
major cover the whole external surface of the 
scapula. 

e deltoid is divided into an anterior and 
a posterior portion. The anterior portion (19) 
arises from the anterior extremity of the cora- 
coid, and is inserted into the summit of the 
deltoid crest of the humerus: the posterior 
part (21) arises from the anterior and superior 
apex of the scapula, and is inserted into the 
lower half of the deltoid crest. There are 
also two muscles to which the name coraco- 
brachialis may be applied, a superior one (22) 
and an inferior one (25). 

The biceps brachii arises by two heads ; one 
(23) arises from the sternal extremity of the 
coracoid, the other (24) also arises from the 
coracoid ; the common tendon is inserted into 
the middle of the radius. 

The other muscles of the anterior extremity 
adhere closely to the mammalian type. The 
extensor carpi radialis (30) sends three ten- 
dons, to be inserted respectively into the second, 
third, and fourth metacarpal bones. There is 
a single common flexor digitorum, as well as 
extensor digitorum (27). 

The extensor digiti minimi (26), the indica- 
tor (28), the extensor pollicis (29), the prona- 
tor teres (32), and the flexor carpi radialis (33) 
are all remarkable for their strength in the 
Ornithorhynchus, and are still more powerfully 
developed in the Echidna. 

The most remarkable muscle on the palmar 
aspect of the fore arm is the fleror carpi ulnaris, 
which arises by two separate heads, the longer 
one from the broad olecranon, the shorter one 
from the internal condyle of the humerus; the 
common tendon is attached to the os pisiforme 
and the metacarpals of the fourth and _ fifth 
digits. 

The psoas minor from its insertion into the 
pelvic arch should be regarded as a muscle of 
the pelvic extremity, and it is one of the largest 
of thes muscles. It arises from the sides of 
five dorsal vertebra, and its strong tendon is 
implanted in the remarkably-developed ilio- 
pectineal process. It depresses the pelvis, 


382 


and with it also the tail and the pelvic extre- 
mities. 

The psoas magnus and iliacus internus form 
a single muscle, having the usual origins, and 
inserted by a common tendon into the large 
internal condyle. 

The gluteus externus is larger than is usually 
the case with quadrupeds; its tendon is inserted 
into the plantar fascia and the bone which sup- 

the spur. The gluteus medius, gluteus 
internus, pectineus (45), biceps flexor cruris, 
gracilis (34), sartorius (35), rectus femoris (36), 
adductores femoris (46), semitendinosus (47), 
semimembranosus, vastus externus, offer no 
notable deviations from the usua! structure. A 
strip of fibres (49) descends from the gracilis to 
the sphincter cloace (H). A muscle, called by 
Meckel ‘ flexor accessorius a cauda ad tibiam 
tendens’ (54), arises from the transverse pro- 
cesses of the anterior caudal vertebra, and 
converges to be inserted into the tibia. Another 
peculiar adductor of the leg, which might be 
termed ‘ intertibialis’ (52), is attached by its 
extremities to both tibie; its fleshy belly passes 
across the sphincter cloacee (H), and is connected 
with a strip of the panniculus carnosus (#). 

The gastrocnemius (48) derives its largest 
origin from the produced and expanded head of 
the fibula, and its smaller belly trom the internal 
femoral condyle; its tendon is implanted in the 
caleaneum. The analogy between the gastro- 
cnemius and ulnaris internus is strikingly illus- 
trated in the Ornithorhynchus. 

The soleus arises from the head of the fibula 
and from a large proportion of the tibia; it is 
nowhere blended with the gastrocnemius, but 
is inserted by a thick and short tendon into the 
astragalus. 

The abductors of the outer digits of both 
the hand and foot are well developed for the 
purpose of expanding the web which connects 
the toes. 

In the figure the following muscles of the 
leg are shown, viz. 37, tibialis anticus, 38, ex- 
tensor hallucis longus, 39, peroneus longus, 
40, peroneus brevis, 41, extensor digitorum 
communis profundus, brevi analogus, 42, exten- 
sor digitorum communis sublimis, 43, a portion 
of the same muscle corresponding with the 
indicator of the fore leg, 44, ertensor digiti 
quinti accessorius. 

NERVOUS SYSTEM. 

Brain.—In the male Ornithorhynchus 
Meckel found that the brain weighed two 
drachms, German weight (about four drachms 
avoirdupoise), and bore a proportion to the 
weight of the body as 1 to 130. It was in- 
closed by a pretty strong dura mater, of which 
the fold corresponding with the bony falx ad- 
hered but slightly to that process. The cere- 
brum weighed one drachm and a half, German; 
neatly the whole of its superficies was smooth ; 
a few vascular impressions marked the side of 
the anterior lobe: its shape was triangular, 
depressed; the contracted anterior lobes form- 
ing the obtuse apex of the triangle: the pos- 
terior lobes are wide and cover the corpora 
bigemina. The surface of the cerebrum is 
smooth and unconvoluted (fig. 181). 


MONOTREMATA. 


Silo vou en have of bree cee 


In describing the structure of the cerebral 
hemispheres Meckel observes, with ence 
to the most characteristic part of this ! 
in the Mammalia, “ us callosum ade: 
quidem, sed breve, quam haud quatuor line 
longitudine equet, memorabilius etiam 
in dimidia duo lateralia, linea mediana h 
confluentia, esse disjunctum. Equidem : 
tem in faciebus sese spectantibts internis nul- 
dete ACRNCle ea invenire potui.”— 
-c. p. 33. o 
During my investigations of the structure of 
the brain in the Marsupial err 
in memory the apparent exception to the ! 
like condition ‘of the co of calls wh 
the Ornithorhynchus, according to the above — 
description, presented, but which each suc- 
cessive example of the brain of the Marsupial — 
uadruped served to establish more firmly as — 
rule of structure in the higher order of t 
Implacental sub-class. It was difficult t 
believe that in the lower or M atous 
group, the cerebral organ, which indicates so 
accurately the true affinities and natural posi- 
tion of the Vertebrate animal, and which fe 
lows so faithfully the degradation of the general 
organization of each species, should offer so 
abrupt an ascent to the cerebral condition of 
the placental Mammalia, as would be indi- 
eated by a corpus callosum of four limes long 
in a brain of which the hemispheres measure 
only fourteen lines in length (German se 
The strong suspicion of an error in the cel 
biated anatomist’s description justified a re= 
serve in acknowledging this exception until 
the opportunity of testing it by a disse 
of a brain of a Monotrematous qui 
should have presented itself; and my 
as to the great development of the ¢ 
callosum of the Ornithorhynchus were furt 
justified by the indication of its nearer 
proach to the Oviparous type afforded t 
simple bipartite condition of the tubere 


* Philos. Trans. 1837, p. 87. 


MONOTREMATA. 


called ‘quadrigemina.’ Well preserved speci- 
mens of Ornithorhynchus presented to me by Mr. 
Thomas Bell, surgeon R. N., in 1838, have ena- 
bled me to determine this question. There is 
neither corpus callosum nor septum lucidum 
in the Ornithorhynchus. 

The part described by Meckel as the corpus 
callosum corresponds with the fornix and 
hippocampal commissure, as it exists in the 
Marsupialia, excepting that the essential func- 
tion of the fornix, as a longitudinal commis- 
sure, uniting the Aippocampus major with the 
olfactory lobe of the same hemisphere, is more 
_ exclusively maintained in the Ornithorhynchus, 
in consequence of the smaller size of the trans- 
_ verse band of fibres uniting the opposite hip- 
-pocampi, and representing the first rudiment 
_ of the corpus callosum, as it appears in the 
_ development of the placental embryo. The 
_ thin internal and superior parietes of one 

lateral ventricle are wholly unconnected with 
_ those of the opposite ventricle. 
__ Meckel makes no mention of the fornix or 
hippocampus major: the latter forms a large 
pyramidal prominence at the outer and pos- 


terior of the ventricle, and is confluent 
_ with the inferior and external parietes of that 


-eavity. The corpus striatum is long and nar- 
_ row: the thalamus opticus small, and is united 
"with its fellow by a soft commissure, which 
es to the same level, whereby they appear 
form a continuous body. The anterior com- 
_ Missure is very large, as in the Marsupials. 

The posterior bigeminal body is much 
smaller than the anterior, and the trans- 
verse depression which divides them is very 
feebly marked: the longitudinal groove is 
‘equally feeble on the ‘ nates,’ and is alto- 
er absent in the ‘ testes,’ which thus form 
le small tubercle. It is in the condition 
ese parts, recognized, but too briefly no- 
d by Meckel, that the brain of the Orni- 
hynchus deviates most essentially from the 
arsupialia, and offers the most direct step in 
descent to the Oviparous type. 

e cerebellum is modeiately large, highest 
the middle, but with small lateral append- 
: the median or vermiform part is traversed 
transverse furrows; and its vertical section 

_ exhibits an ¢ arbor vite.’ 

_- The medulla oblongata is broad and de- 
essed : its inferior surface exhibits the corpora 
nidalia (fig. 181, a), the corpora olivaria 
), which expand as they advance forwards, 
arently in relation to the immense size of 
trigeminal nerve. Their anterior extremi- 
are crossed by large trapezoid bodies (6), 
ured by Meckel as the pons Varolii); and 
rior to those is the true ‘ nodus encephali’ 
which is narrow, in correspondence with 
small lateral lobes of the cerebellum; and 
n this there emerges on each side a large gan- 
id body (c’), from which the trigeminal nerve 
arises. The under surface of the medulla 
Ongata is traversed by a deep median lon- 
dinal groove. 

he brain of the Echidna is relatively larger, 
and its external surface is complicated by 


responding hemisphere. 


383 


conyolutions.* It weighs twelve drachms and 
thirty grains avoirdupoise, and bears a proportion 
to the weight of the body as 1 to 50. The 
cerebral hemispheres conceal the bigeminal 
bodies, but do not extend over the cerebellum. 
The broad posterior part of each hemisphere 
is disposed in three nearly parallel transverse 
convolutions, the outer extremities of which 


Fig. 182. 


Brain of the Echidna, right hemisphere dissected. 
( Original. ) 


incline forwards (fig. 182); anterior to these 
is a larger convolution bent upon itself ata 
right angle, one crus running transversely ; 
the other longitudinally, and forming the inner 
boundary ofthe anterior halfof each hemisphere : 
this convolution was not divided by a transverse 
anfractuosity, as in the figure in the ‘ Voyage 
de la Favorite,’ loc. cit. On the outside of 
the longitudinal convolution there are two or 
three oblique folds which converge towards 
the contracted anterior part of the brain, or 
descend to its under surface: besides these 
principal and more constant convolutions there 
are a few smaller and less regular ones at the 
lateral and inferior parts of the hemispheres, 
especially on the great natiform protuberances. 
The principal anfractuosities sink more than 
a line’s depth into the substance of the he- 
misphere: the posterior convolutions are con- 
tinued upon the median surface of the he- 
misphere, and interlock with those of the cor- 
The depth of the me- 
dian fissure of the hemispheres is from five 
to six lines: the hippocampal commissure (0). 
one line and a half in antero-posterior diameter 
is seen at the bottom of the fissure which 
divides the hemispheres. 

The dura mater in the Echidna is thin and 


* See the figures and description of the external 
characters of the brain of the Echidna, given by 
MM. Eydoux and Laurent in the ‘ Voyage de la 
Favorite,’ 8vo. 1839, tom. v. pl. 9, p. 161. 


384 


transparent; the membranous falx is less deep 
than the osseous one of the Ornithorhynchus. 
I found no bony plate between the hemi- 
spheres in the Echidna. The arachnoid is 
transparent, but relatively strong. The cere- 
bellum is traversed by several narrow trans- 
verse anfractuosities, disposed as in fig. 182. 
The vermiform or alien lobe, as in the 
Ornithorhynchus, is larger in proportion to 
the lateral lobes than in the Marsupialia, and 
the limits between them are much less dis- 


tinctly defined. 
(fg. 
os 


The base of the brain in the Echidna 
183) is remarkable for the deep and 
excavations at the under part of the anterior 


Fig. 183. 


Base of brain of Echidna. ( Original.) 


lobes, forming the base of the enormous 
olfactory nerves. The natiform rh gecesi 
are unusually large. The medulla oblongata 
is broad and flat, but contracted anteriorly to 
an angle; the pyramidal bodies (a) long and 
narrow ; the olivary bodies (6) broad, but flat. 
The pons Varolii (c) presents, as in the Orni- 
thorhynchus, a low development proportion- 
ally to the size of the brain: it is not raised 
beyond the level of the under surface of the 
medulla oblongata: it is of a triangular form 
with the obtuse apex turned forwards: the 
median longitudinal groove formed by the ba- 
silar artery is well marked : the trapezoid bodies 
are relatively narrower than in the Ornitho- 
rhynchus. 

The pituitary gland (p, fig. 183) is one line 
and a half in length and one line in breadth: 
its under surface adheres closely to the dura 
mater of the sella turcica. The corpus mam- 


MONOTREMATA. 


millare is single, broad, and but little ele- 


vated. : ¢ 
The internal, superior, and posterior walls 


of the lateral ventricle are from one line to two — 


lines in thickness ; the outer wall is between 
two and three lines; when the roof of the 
ventricle is removed, as in fig. 184, two 
elongated convex bodies exposed, as pe 


the marsupial brain: posterior 
largest (h) is the hip- i 
pocampus major: the Fig. 184. 
anterior body (s) is A 
the corpus striatum. “ye 


The whole internal 
wall of one ventricle 
is quite disunited from 
that of the opposite 
hemisphere.* 

The contracted an- 
terior parts of the hip- 
pocampi are connected 
together by the short 
transverse commissure 
above mentioned, 
which is the sole re- 
presentative of the cor- 
pus callosum and for- 
nix. Theseptum luci- Right lateral ventricle laid 
dum and fifth ventricle vO Echidna. 
are entirely absent. “— 

The pia mater, which accompanies the ven- 
tricular artery into the floor of the ventricle, 
at the base of the hippocampus, s over 
the optic thalami, and sends up a 
fold of membrane, one line and a half broad, 
between the hip pus and the —— 
striatum. The free margin of this fold is 
slightly thickened by the choroid artery. . 

t is necessary to remove the hippocampus 
re, in order 
i and bige~ 


and posterior of the hemis 
to bring into view the optic 
182, 2) and nates 


minal bodies. 
The optic thalami (fe. 

appear as one convex body slightly contracted 
laterally, and divided from each other by a si 
moid linear fissure: the testes are only half the 
breadth of the nates, and the median longiietians 
line of division, which is very faint in the larger 
bodies, is not visible in the smaller and pos- 
terior tubercle. The Echidna py in 
this characteristic modification with Orni- 
thorhynchus.t 


- 


* The internal structure of the hemi 


of 
the Echidna’s brain is not described in the* Voyage — 
~ 


de la Favorite.’ 


+ MM. Eydoux and Laurent have thrown into 


the following tabular form the published results 
of the dissections of the brains the 

cental Mammalia as compared with P. 
Mammals and Birds. 


pes MONODELPHEsS, DIDELPHES. OrniTHODELPHEs. | OISEAUX. | a) 
Corps calleuxr .... existe. manque. manque. manque. 
Pont de Varole . . existe. existe. existe. manque. 
Lobes optiques .. .| quadrijumeaux et | quadrijumeaux et bijumeaux et bijumeaux et 

supérieures. supérieures. supérieures, lateraux, =| 


They add: ‘‘ En indiquant ce résultat des ob- 
servations de M, R, Owen, aux-quelles nous avons 


joint les observations de Meckel en les 


nous devons faire remarquer que Stocks! 2 eopamen 


: 


| 


_ The medullary fibres of the optic thalami (fig. 
182, ¢) and bigeminal bodies (r, s) form a thin 
stratum above a third ventricle of unusual capa- 
city, the relative size of which appeared somewhat 
Jarger than was natural from the decomposition 
of the medullary matter of the soft commis- 
sure. The principal commissure of the he- 
mispheres is the anterior one, which is sub- 
cylindrical, and measured two lines thick verti- 
cally, and one anda half horizontally. The pos- 
terior commissure is a narrow strip of medullary 
matter, which thickens the upper part of the 
valvula Vieussenii. The ‘ iter’ or canal from 
the third to the fourth ventricle is proportion- 
ally wide. The arbor vite, as displayed by 
a vertical section of the vermiform process, 
sends off four principal and some minor 
medullary branches. 
The spinal chord in the Ornithorhynchus is 

long and slender, but fills closely the spinal 
canal: it is thickest at its commencement and 
at the lower two-thirds of the cervical region ; 
itis more slender in the dorsal region, espe- 
cially near the loins; it is slightly enlarged in 
the lumbar region, and gradually terminates in 
a point in the canal of the sacral vertebra : 
the cauda equina is very feebly represented. 
“In the Echidna the form and proportions of 
_the spinal chord (fig. 185) are strikingly dif- 
ferent: it is here nearly as short and thick, 
relatively, as in the hedge-hog, and terminates 
_ ina point, at d, before it has reached the middle 
of the dorsal region. Nevertheless, in this 
short tract the two usual enlargements, giving 
origins respectively to the nerves of the pec- 
__ toral and pelvic extremities, are clearly marked ; 
__ theslightly contracted intermediate portion being 
extremely short: the cauda equina is remark- 
_ able for its length. The nerves escape, as usual, 
from the intervertebral foramina, and have a 
longer course in the spinal canal, in proportion 
as they supply parts more distant from the chord. 
____ It is interesting to find the peculiar structure 
_ of so important a part as the spinal chord re- 
oe in two species, which, with the excep- 
tion of the dermal spines, and their common 
_ charactersas Mammalia, differ in other respects 
as widely from one another, and occupy such 
distant places in their class. Can the short- 
_ hess of the solid chord, and the great length 
of the nerves within the spinal canal, have 
any physiological relation with the habit, 
common to both the placental and monotre- 
- Matous hedgehogs, of rolling the body into a 
_ ball when torpid or asleep, or when the tegu- 
mentary armour is employed in self-defence ?* 
_ The olfactory nerves are large in the Orni- 
thorhynchus (fig. 181, 1,1). The external root 


de Meckel, et que les déterminations de 1’anato- 
_ -miste Anglais doivent etre adoptées.”” — Voyage de 
Favorite, p- 166. 
ce 


' “ Cet échidné passait Ia majeure partie de son 
_ temps dans une espéce d’engourdissement, blotti, 

' enroulé 4 la maniére des hérissons.”— Voyage de la 

Favorite, p. 159. 

| VOL. III. 


MONOTREMATA. 


385 


is remarkable for its 
length and relative size: 
it arises from the poste- 
rior surface of the cere- 
bral hemisphere imme- 
diately behind the bige- 
minal body ; bends round 
the crus cerebri to the 
inferior surface; and is 
continued forward to join 
the internal root which 
rises from the base of 
the anterior lobes of the 
brain. 

In the Echidna the 
olfactory nerves may be 
described as enormous. 
The external root (fig. 
183, 1a) arises from 
nearly the whole anterior 
part of the natiform pro- 
tuberance, which extends 
its origin, as in the Or- 
nithorhynchus, to the pos- 
terior part of the hemi- 
sphere. The internal root 
(183, 1 6) is also very 
large: the lateral ventri- 
cle is prolonged forwards 
into the olfactory nerve, 
which would appear like 
a continuation of the en- 
tire hemisphere, were it 
not that it is overlapped 
by the anterior convo- 
lution. 

The extent and. com- 
plications of the olfactory 
cavity are proportionate 
in the two Monotremes 
to the size of their respec- 
tive nerves. 

The optic nerve (fig. 
181, 183, 2) is small in 
both Monotremes, in ac- 
cordance with the dimi- 
nutive size of the eye: 
the two nerves are joined 
by a transversely oblong 
chiasma. 

The eye is protected, 
in the Ornithorhynchus, 
by a cartilaginous plate 
continued from the upper 
rgb of the orbit, which 

eckel compares with 
the bony palpebral plates 
Brain and spinal chord, in the Crocodile. Both 

Echidna, Half natural Monotremes have a well 
size. ( Original.) developed membrana nic- 
titans: there are also an upper and a lower 
eyelid, each of which has its proper apertor 
muscle. 

In the Ornithorhynchus the sclerotic is carti- 
laginous, the cornea flabby, the retina very 
thick: there is no trace of pecten or marsu- 
pium: the lens is very small, two lines in 
vertical and transverse diameter, one line in 
antero-posterior diameter ; the mes 2 surface 

c 


386 


is nearly flat, the posterior very convex. The 
choroid is black, without a tapetum lucidum : 
a np is circular. 

nerves of the third pair (fig. 183, 3) have 
the usual origin and destination, and are like- 
wise very small; the fourth nerve is still more 
minute. 

The fifth pair in the Ornithorhynchus ex- 
ceeds, in relative magnitude, that of any other 
animal; though large, also, in the Echidna, 
its size is much less remarkable in this Mono- 
treme. 

The trigeminal nerve in the Ornithorhynchus, 
(fig. 181, 5,) emerging from the ganglion an- 
terior to the pons, soon divides into three 
branches ; the first and second appearing as one. 
The first and smallest division divides into two 
equal branches: the superior or ethmoidal 
branch enters the nose, emerges from a canal 
in the upper part of that cavity, and supplies 
the skin at the upper part of the face; and, 
by a branch continued from between the nasal 
and intermaxillary bones, is distributed to the 
nostrils and contiguous integument. 

The second division of the fifth is two lines 
broad and one line and a half thick; it passes 
through the foramen rotundum, and the chief 
part of it passes into the ant-orbital canal. 
On its emergence it divides into two branches, 
distributed, the one to the nasal or upper pa- 
rietes of the face, the other to the lateral or 
labial integuments. The palatine branch di- 
vides into a posterior smaller nerve, which 
passes through the posterior palatine foramina : 
the anterior and larger branch emerges from 
the anterior palatine canal and supplies Jacob- 
son’s organ and the surrounding palatine mem- 
brane. 

Thethird division of the fifth (5’) is broader but 
thinner than the second; it leaves the cranium 
by the foramen ovale, and is distributed as 
usual, in part to the manducatory muscles, 
but mainly to the sensitive labial mtegument 
of the lower jaw (fig. 180, a a). 

The sixth nerve (fig. 183, 6) is as small as 
the third. The seventh and the acoustic pre- 
sent half a line in diameter. 

The acoustic nerve is expended upon a 
labyrinth remarkable for the small relative size 
of the semicircular canals, and their free pro- 
jection into the cavity of the cranium. 

The cochlea is wide, but not high; it is bent 
around a modiolus, and divided as usual into 

a superior and inferior scala. 

The foramen ovale is nearly circular, and 
opens into the wide but shallow tympanic 
cavity. It is naturally closed by the base of a 
small columelliform and imperforate stapes 
(fig. 173, p, d): the stem of this ossicle is 
articulated with a triangular plate of bone (c), 
representing, according to Meckel, the incus. 
This bone is connected with a small bent os- 
seous style (b), which serves to complete, with 
the similarly-shaped tympanic ossicle (a), the 
frame supporting the membrana tympani. 
This membrane is concave externally, and 
forms the inner extremity of a long and narrow 
meatus auditorius externus, which is strength- 
ened by a cartilagmous incomplete cylinder, 


MONOTREMATA. 


protected by a valve, but not provided with 
an external auricle. ‘4 
The auricle is equally wanting in the 
Echidna, in which the external aperture of the 
auditory canal presents the form of a vertical 
slit, shaped like the italic S, one inch anda 
half in length: the margins of the slit are 
tumid, and support a row of bristles which 
rotect and cover the orifice when recumbent. 
he meatus is remarkably long; the tube is — 
strengthened in this Monotreme by a series of 
incomplete cartilaginous hoops, connected to= —— 
gether by a aarrow longitudinal ilagi a. 
band, so that its structure closely resembles 
that of a trachea (fig. 188, a, a). The tym- 
panic fossa is almost entirely encircled with a 
slender hoop of bone (fig. 169, c) consisting of 
the anchylosed tympanic bone and malleus. 
The portion which represents the tympanic 
bone (a), and which can be separated from the 
malleus in the youngsubject, is a slender osseous 
filament bent into three-fourths of a cirele, 
and placed upon the inner margin of the tym- __ 
panic fossa, its concavity looking outwards: — 
this concavity is impressed with a fine groove 
ms the insertion of the membrana tympani : 
the posterior of the hoop passes across 
the eine of the Restneliiln 
and terminates in a free point upon the pos- 
terior wall of the tympanic fossa: the or 
end of the hoop is applied to and usually 
anchylosed with the longitudinal bar of the — 
malleus (b). ' 


Only a small portion of this ossicle is con- 


an 


tained within the cavity of the tympanum ; the 
principal portion forms the external and part 
of the posterior boundary of the bony meatus 
satneny and is then continued forwards in 
the form of a slender pointed process; 

bone slightly expands as Ly extends backwards, 
and its broadest part is abruptly bent inwards 
until it nearly meets the posterior end of the 
tympanic hoop. From the extremity of this in- 


fected portion a slender compressed red 


2 


w 


extends to the centre of the space encircled by — 
the bony hoop; it is attached by its whole 
length to the membrana tympani, and repre- 
sents the handle of the malleus, At the pos- 
terior margin of the broad incurved part of the 
malleus there are two minute tubercles 
a line apart: the short and simple columelliform 
stapes (d) ascends vertically from the inner- — 
most of these tubercles, with the upper surface 
of which it is articulated ; its ite ex- 
tremity closes the foramen ovale im the form — 
of an expanded plate. The membranetyai | 
pani is concave outwardly at its middle part. — 
The eighth and ninth pairs of nerves — 
have the usual origins and proportions. The 
pneumogastric nerve (fig. 180, d) is 
attached, at its origin, to the hy ' 
(fg. 180, 6), but is quite distinct from the © 
sympathetic (fig. 180, f): it gives off the 
superior laryngeal, and then long 
the neck to the chest: the right nerve here 
sends its recurrent branch, in the usual manner, 
round the arteria innominata; the left branch 
(fig. 187, k) winds round the aorta: the trunk 
of the pneumogastric is then expended in the 


‘ 


eeeepelmonic, cesophageal, and gastric 

nerves. The spinal accessory nerve (fig. 180, 

¢c) is thicker than the pneumogastric, and has 

the usual distribution. 

_ The brachial plexus is formed by the five 

terior cervical and the first dorsal nerves. 

‘he third cervical nerve is shown at g, fig. 180. 

_ The median nerve perforates the inner condyle 

of the humerus. 

_ The lumbar plexus is formed by the two 

_ posterior dorsal, the two lumbar, and the first 

_ sacral nerve. 

_. The great ischiadic nerve divides into the 
peroneal and tibial branches before it quits the 

elvis. The crural nerve is shown at h (fig. 


DIGESTIVE SYSTEM. 

Ornithorhynchus, which subsists on 
insects, larve, mollusks, and other 
invertebrates which conceal themselves 
the mud and banks of rivers, is provided 
‘with a mouth which most nearly resembles the 
flat and sensitive bill of a lamellirostral bird. 
singularly modified jaw-bones, already de- 
ibed, are invested byasmooth coriaceous inte- 
nent, (fig. 173, A, E,a,) devoid of hair, but 
forated by innumerable minute foramina. At 
base of the jaws this integument is produced 
a free fold, which overlaps the hairy covering 
the cranium immediately behind it. The 
ment covering the upper mandible ex- 
beyond the margins of the bone, and 
a tumid, smooth, and highly sensible 
the narrower and shorter under jaw is 
' closely invested: the oral or upper sur- 
of the lateral part of the under jaw sup- 
a series of about twenty nearly transverse 
‘increasing in breadth as they approach 
angle of the jaw: the corresponding sur- 
e of the upper jaw is smooth. 
The two anterior horny teeth in both jaws 
elongated, narrow, with their outer part 
d into a trenchant edge in the lower jaw. 
two posterior teeth (fig. 173, h, and F) in 
_ jaws are flat, with two broad and slight 
vations, corresponding with the two parts 
into which each molar may be divided in the 
young animal. 
_ Immediately on the outside of the posterior 
part of each molar in the lower jaw, is the orifice 
an oblong cheek-pouch (fig. 180, F, F), about 
two inches in length, and halfan inch in diame- 
ter: the pouch is continued backwards, and 
ned with a hard dry cuticle. 
The tongue (fig. 186) consists of two 
s, the normal, anterior, narrower portion 
and a broad, raised posterior lobe (/'), 
ogous to the intermolar eminence of the 
e in certain Rodents. This part is pro- 
ced anteriorly into a free projecting apex in 
the Ornithorhynchus, and is rendered still 
more remarkable in that animal by being 

armed with two short thick horny spines (g, g), 
- projecting forward. 
_ Theanterior part of the tongue is beset with 
Yather coarse papille, and extends into the 
_ posterior interspace of the incisive teeth, but 
with the apex more than an inch distant from 


pp) Toe 


» | 
hy 
4 


MONOTREMATA. 


the cloaca. 


387 


the anterior aperture of the 
mouth. The raised pos- 
terior lobe of the tongue 
must impede the passage 
of unmasticated food to 
the pharynx, and doubtless 
tends to direct it on each 
side into the cheek-pouch- 
es; whence the Ornitho- 
rhynchus may transfer its 
store at leisure to the mo- 
lar teeth, and complete its 
preparation for degluti- 
tion. An _ air-breathing 
warm - blooded animal, 
which obtains its food by 
the capture of small aqua- 
tic animals, while sub- 
merged, must derive great 
advantage from the struc- 
\ | ture which enables it to 
Q Suh 7 transfer them quickiy to 
EN a temporary receptacle, 
Nina whence they may be ex- 
i tracted and _ masticated 
i while the animal is floating 
a on the surface or at rest in 

Tongue and larynx of its burrow. 
the a The soft palate is thick, 
(Sat) broad, and divided poste- 

riorly into three fimbriated lobes. 

The pharynx is narrow, and is singularly en- 
compassed by two posterior processes of the 
thyroid cartilage (fig. 189, c,c). 

The cesophagus becomes slightly dilated near 
the diaphragm, below which it expands into a 
moderate-sized membranous stomach (fig. 187, 
1), which is chiefly remarkable for the close 
approximation of the cardiac and pyloric ori- 
fices. The intestinal canal is moderately wide, 
five feet three inches and a half in length, and 
provided, at a distance of four feet three inches 
from the pylorus, with a small and slender 
caecum (w). - 

The small intestines are chiefly remarkable 
for the extent of the mucous coat, which is 
disposed in numerous folds or valvule conni- 
ventes: these are transverse at the beginning 
of the duodenum, but are placed more or less 
obliquely in the rest of the small intestine ; 
they are about two lines broad, and placed 
very close together in the duodenum, but 
diminish in breadth and number as they ap- 
proach the coecum coli. There are about fif- 
teen longitudinal folds in the first half of the 
colon; the remainder of the intestine has a 
smooth inner surface. There is no valvula coli, 
The rectum (z) terminates at the anterior and 
dorsal part of the vestibular compartment of 
In fig. 191 a probe (6’) is passed 
through this termination. On each side of its 
termination there is an oblong glandular pro- 
minence, about four lines in length and two 
in breadth, on which there are about ten ori- 
fices of glands, which Meckel considers as 
‘analogous to the anal glands of other quadru- 

ds. 

The long, slender, tubular mouth -of the 
2c2 


Xi) i i 


= ZG : 
Thoracic and abdominal viscera, Ornithorhynchus. 
( Meckel. ) 


Echidna is unprovided with teeth; but the 
palate is armed with six or seven transverse 
rows of strong, sharp, but short retroverted 
spines. The tongue is long and slender as in 
the true Anteaters ; its dorsum is broad, flat, 
callous, and beset with hard papille, and the 
insects are doubtless part Gh and lacerated 
between these and the pa'atal spines. As, how- 
ever, the food undergoes less comminution in 
the mouth of this Monotreme than in that of the 
Ornithorhynchus, the pharynx and cesophagus 
are wider, and a dense epithelium lines the 
inner surface of the latter tube, and is conti- 
nued over the capacious stomach to the py- 
lorus, near which orifice it is ert ss into 
numerous horny and sharp papille. e sub- 
jacent mucous membrane is smooth; the tunics 
of the stomach are very thin, except at the 
pylorus, which forms a prominent protuberance 
in the duodenum. The intestinal canal of the 
Echidna is seven times the length of the body; 
the mugous membrane is not raised into val- 


MONOTREMATA. 


vular folds; a small vermiform and glandular 
cecum divides the small from the large intes- 
tines; the rectum terminates as in the Ornitho- 
rhynchus. 

Salivary glands ——There ap to be no 

rotid gland in the Echidna, and it is doubt- 
ul whether the thin flat stratum of glandular 
substance (fig. 180, E), which extends from 
the meatus auditorius to the check- in 
the Ornithorhynchus, can be so ed. The 
submaxillary gland (fig. 180, D) is a mode- 
rately-sized, oval, compact body, situated be- 
hind and below the meatus auditorius; it mea- 
sured five lines in the long diameter and four 
in the short diameter. The duct is very small, 
scarcely admitting an absorbent as ipe ; 
it passes under the omo-mylo-hyoi eus (10},and 
then, contrary to the usual mode, begins to be 
disposed in a series of about twelve close trans- 
verse folds, and terminates by a single aperture 
at the freenum lingue. 

The submaxillary gland (fig. 188, 5) is of 
unusual dimensions in the idna, in which 
it extends from the meatus auditorius along the 
neck, and upon the anterior part of the thorax: 
it is a broad, flat, oblong lobulated body, nar- 
rowest at its anterior extremity, from which the 
wide duct emerges. When the duct has reached 
the interspace of the lower jaw it dilates, and 
then divides into eight or ten undulating 
branches, which subdivide and ultimately ter- 
minate by numerous orifices upon the mem- 
branous floor of the mouth. This modificati 
which escaped the observation of Cuvier 
M. Duvernoy, appears to be unique. The 
large size of the glands and the mode in which 
the secretion is s over the floor of the 
mouth, relate to the lubrification of the 
slender, and extensible tongue, and to its fit- 
ness as an instrument for obtaining the insect 
food of the Echidna. 

The liver (fig. 187, r, 7) closely retains the 
mammalian type of the organ in Mono- 
tremes. Four lobes may be distinguished in 
the Echidna: the principal or cystic lobe re- 
ceives the suspensory ligament in a fissure; the 
large gall-bladder is placed a little to the right; 
the left lobe occupies the left hypochondrium ; 
the Spigelian lobule is of moderate size; it is 
an appendage of the ng lobe. The liver pre- 
sents nearly the same form in the Ornithorhyn- 
chus, which has likewise a large gall-bladder 


7. 187, ). 
a a are three hepatic duets in the Echidna 
which join the cystic, and the common canal 
terminates in the duodenum pen: more than 
an inch from the pylorus. In the Ornithorhyn- 
chus the two chief hepatic ducts join the cystic 4 
near the neck of the bladder; the third hepatic 
joins a more distant part of the cystic; t 
ductus choledochus receives the atic 
duct about nine lines before its termination, a: 
in the Marsupials, where its coats are thickened 
and glandular, and opens into the duodenum _ 
about eight lines from the pylorus. att 

The pancreas in the Ornithorhynchus is a thin _ 
lobulated gland bent upon itself; the leftand — 


larger portion descends by the side of the left 


ee 


f the spleen.* The pancreas is thicker 
the Echidna, and enlarges considerably to- 
ds the duodenum. 

The principal difference occurs in the place 
termination of the pancreatic duct, which, 
1¢ Ornithorhynchus, joins the ductus chole- 
us, but in the Echidna terminates sepa- 
ately in the duodenum and nearer the pylorus 
an does the ductus choledochus. 

he arrangement of the hepatic and pan- 
tic ducts is thus conformable to the Mam- 
an ype and the Ornithorhynchus, in the 
ee of the junction of these ducts near the 
mencement of the ductus choledochus, ma- 
Sts its affinity to the Marsupials, as the 
__ Same structure occurs in the Dasyure. 

. = The spleen (fig. 187, u, u) consists of two 


bent upon each other at an acute angle, 
* Meckel, loc. cit. p. 46. 


MONOTREMATA. 
Fig. 188. 


389 


Submaxillary glands, Echidna setosa. (Original. ) 


in which the Monotremes again resemble the 
Marsupials. In the Ornithorhynchus the ante- 
rior and right lobe is four inches long, the pos- 
terior and left lobe two inches and a half; the 
right lobe is bent upon itself. In the Echidna, 
besides the two lobes which are continued for- 
wards from the’left side, there is a third shorter 
descending appendage.* The lobes are thin and 
moderately broad in both Monotremes, and in 
structure, size, situation, and general figure, the 
spleen conforms to the Mammalian type, al- 
though this is exhibited under a more than usual 
complication of external form. 


CIRCULATING SYSTEM. 

Blood of the Ornithorhynchus—A Mammal 
presenting such striking resemblances in cer- 
tain parts of its organization to the oviparous 


* Cuvier, |. c. t. iv. p» 591s 


390 
modification of the Vertebrate type as does 
the Ornithorhynchus, is one of which it was 
obviously most interesting to ascertain the 
form of the blood-discs. I have made appli- 
cations to different professional and zoological 
correspondents in Australia on this subject, 
for the transmission of a portion of recently 
drawn blood thinly spread and dried on glass, 
or preserved in its fluid state in brine and 
other menstrua of the same density as serum, 
and for the results of observations on ‘the 
blood-discs of both the Ornithorhynchus and 
Echidna. Mr. Hobson, of Hobart Town, 
Van Diemen’s Land, an accomplished sur- 
geon and comparative anatomist, has made 
the required observations on the blood of 
the Ornithorhynchus, of which he has trans- 
mitted to me the following account :—* The 
globules of the blood of the Ornithorhyn- 
chus are discoid, and measured about the 
goth of an inch, calculating two-and-a-half 
millimetres to the line. The human blood- 
globules were placed side by side with those of 
the Ornithorhynchus, and both in shape and 
size so nearly resembled each other that it was 
impossible to say which was human and which 
was Ornithorhynchus. These examinations 
were made in the presence of Mr. Ronald 
Gunn, by means of one of Oberhauser’s mi- 
croscopes ; the powers used were 250, 400, and 
800. In order to be sure that there was no 
delusion, I placed the elliptical globules of a 
Lizard’s blood beside those of the Ornitho- 
rhynchus. The tenacity and high florid colour 
of the blood, together with the greater propor- 
tional number of globules in a given quantity” 
(in the Ornithorhynchus) “ is most interesting 
in an analogical point of view.” 

From the preceding highly valuable observa- 
tions we may infer that the Ornithorhynchus 
resembles the Mammalia in the circular form, 
the size, the proportional number, and florid 
colour of its blood-dises, which correspond in 
size with those of the only Edentate species 
yet examined, viz. the Armadillo,* and conse- 
quently with those of the Quadrumana and 
of Man. 

The blood-discs of the Echidna, according 
to the observations made by Dr. John Davy on 
a portion of blood of that animal, transmitted 
to Eng!and in brine, are likewise circular. 

Heart.—The heart of the Ornithorhynchus 
(fig. 187, a, b, c) presents a rounded oblong 
form ; it is situated in the middle of the ante- 
rior part of the chest, parallel with the axis of 
the cavity. It is inclosed ina thin subtrans- 
parent but strong pericardium. 

The right auricle (6) is larger and longer 
than the left; its appendix is free and is slightly 
bifid, as in the Marsupials. It receives the 
venous blood, also, as in that order, by three 
great veins; the left vena innominata (/') de- 
scending behind the left auricle to join the 
termination of the inferior cava (h). The coro- 
nary vein also terminates in the auricle to the 
right of the inferior cava. The right superior 


* See Medical Gazette, Nov. 18, 1840. 


MONOTREMATA. 


cava (e) is joined to the left by a transverse 
branch (g). Meckel found in the heart of 
both the Ornithorhynchi dissected by hima 
deep but closed fossa ovalis, near the upper 
extremity of the septum. This structure would 
indicate that the intra-uterine existence of the : 
oung .was of longer duration than in the 
Maservialia. < 
The right ventricle (a) is capacious, with thin 
parietes. The tricuspid valve I found to consist 
of two membranous and two fleshy portions: 
the smallest of the latter was situated nearest the 
origin of the pulmonary artery, and seemed to — 
correspond with the lesser fleshy valve obseryv- 
able in the heart of certain birds, as the Ostrich; 
it is attached to the whole of the side of the 
first or adjoining membranous portion. The 
second fleshy portion may be described as ana- 
logous to the muscular valve in the Bird’s heart, 
if the lateral margin of this were detached from 
the wall of the ventricle, and the connection of 
its two extremities was preserved, the one to” 
the angle between the fixed and moveable wall 
of the ventricle, the other to the auriculo-ven- 
tricular orifice. The two edges of the lower 
half of the second fleshy portion of the valve 
in the Ornithorhynchus are free ; but those of 
the upper half are attached to the two mem- — 
branous portions of the tricuspid valve; the 
margin of the membranous part of the valve is 
attached to the fixed wall of the ventricle by 
two small chorde tendinee; and the structure 
of the valve thus offers an interesting transi- 
tional state between that of the Mammaland 
age the Bird.* ** 
e origin of the pulmonary artery is pre 
Sided with the hase’ prae vile axe 
The left ventricle has thick parietes, 
which form the apex of the heart; the mitral 
valve is membranous; the larger flap is at- 
tached to two strong columne carner; the 
smaller flap to three smaller columne. 

The smal! left auricle (c) receives two pulmo- 
nary veins. 
In the Echidna the free appendix of the 
right auricle is slightly indented. The ter- — 
minal orifice of the superior cava is protected 
by a membranous semilunar valve, ng 

from its left side. The musculi 


inati d 

verge from a strong fasciculus, which exter 
from the appendix to the orifice of the in- — 
ferior cava; this fasciculus bounds the left — 
side of a wide fossa ovalis, which is imper- 
forate. The inferior cava is protected bya large _ 
membranous Eustachian valve; the left vena 
innominata terminates by a distinct aperture te 
the left of the preceding, and is also defende 
by a process of the Eustachian valve. 1 
inner surface of the right ventricle is more irre- 
gular than in the Ornithorhynchus; the f 

wall is attached to the fixed one by set 
columne carnez and short chorde tendinew; t ne 


tricuspid valve is membranous and consists of 


one principal portion attached to the exter 


* «© Similitudo quedam cum avium valvula: ve- 
nosa dextra et propter carnositatem et aera A. 
figuram minime pratervidenda adest.”—Meckel, 
lic, p. 3l. 


circumference, and a smaller portion closing the 
outer angle; the free margin of the valve is 
attached to the extremity of a large fleshy 
column, arising by different roots from both 
the fixed and the free walls of the ventricle; a 
short fleshy column is attached to the left ex- 
tremity of the valve; some chord tendinez are 
fixed to the right angle of the valve. The rest 
of the structure of the heart corresponds with 
that in the Ornithorhynchus. 

_ The aorta (fig. 187, d) bends, as in the 
Mammalia, over the left bronchus. The pri- 
mary branches come off from the arch, in 
both Monotremes, as in Man, viz. arteria in- 
ominata, left carotid, and left subclavian. 
; innominata divides, after a course of three 
" . into the right subclavian and carotid 
(fig. 187, i), the latter being the smallest 
nch. Both subclavians emerge from the 
tl above the first rib, and pass between 
it and the coracoid. 

The phrenic, celiac, and mesenteric arteries 
e given off from the abdominal aorta; the 
renal artery is short, wide, and single; there is 
0 inferior mesenteric artery, but the abdominal 
orta terminates by dividing into the two com- 
mon iliac and the caudal arteries, the arterial 
em agreeing in this and the other essential 
acters with the Mammalian type. The 
crural artery is shown at y, fig. 180. 

__ Each of the superior vene cave receives the 
_azygos vein of its respective side. The inferior 
has a long course in the thorax; it is 
, y dilated in the liver in the Ornithorhyn- 
 chus, as it is in the Placental divers, the Otter 
and Seal for instance.* 

___ The veins of the kidney are continued from 
renal artery, and communicate solely with 
inferior cava. The vena porte is consti- 
ed as in other Mammalia. 


oP inal 


RESPIRATORY SYSTEM. 


The Jungs of the Monotremata are con- 
to the thoracic cavity, and suspended 
ely in compartments partitioned off by du- 
tures of the pleura. The right lung is 
ided, in the Ornithorhynchus, into three 
lobes, of which the smallest (fig. 187, ») fills 
interspace between the heart and diaphragm : 
@ left lung (0) is undivided. The structure 
the whole is spongy, and divided into 
ute cells. 
e trachea (fig. 187, m) is wide, as in 
aquatic mammals: the cartilaginous 
‘Tings, fifteen in number, are broad and slightly 
_ overlap each other: the bronchial annuli are 
__ bony, and are continued of that texture through 
Bik, part of the lungs. 
_. Inthe Echidna the trachea is narrower than 
in the Ornithorhynchus: there are twenty-two 
__ tracheal hoops, which are disunited behind ; 
: firm cartilaginous annuli are continued 
_ along the larger branches of the bronchus for 
; eel way into the lung, but the smaller 
___ branches are membranous. 
There is no trace of inferior larynx in either 


_* Meckel, 1. c. p. 32. 


MONOTREMATA. 


Monotreme. The superior /a- 
rynx is conformable to the Mam- 
malian type, but presents some 
remarkable modifications in the 
Ornithorhynchus. The thyroid 
cartilage (fig. 189, c) in this 
animal is very broad; its middle 
part is prominentand acuminate: 
the lateral ale are bony,and each 
of them divides, and sends one 


of the processes to the posterior Larynx of 
part of the pharynx (fig.186,c), Ornithorhyn- 
where it becomes cartilaginous, chus. 

and is confluent with the corres- _ ( Meckel. ) 


ponding process of the opposite side. The cri- 
coid cartilage (fig. 189, d) is ossified at its 
middle anterior part. The arytenoid cartilages, 
(fig. 189, e, e) present the usual triangular 
form, and are of large size. The epiglottis 
(fig. 189, a) is remarkably broad, with an 
acuminated and notched apex. 

Besides a small thymus gland, Meckel found 
in the Ornithorhynchus two other lateral glands 
on the external part of the chest, extending be- 
tween the scapula and humerus, covered only 
by the panniculus carnosus and the trapezius. 
These presented a reddish colour, a lobulated 
structure, and pretty firm texture. 


RENAL SYSTEM. 

The suprarenal bodies (fig. 190, 6, 6) are of 
moderate size, of the usual structure, and have 
the ordinary situation internal to the anterior 
extremities of the kidneys. 

The kidneys (a, a), in both Monotremes, are 
smple, compact, conglobate glands, situated, 
as usual, far forwards on the loins, the right a lit- 
tle in advance of the left. The external surface, 
after the removal of the capsule, is smooth. 
The renal tissue consists of the two usual por- 
tions; the cortical, or softer and more vascular 
part, being easily distinguishable from the more 
compact medullary part. The tubuli uriniferi 
terminate on the concave surface of a sinall and 
simple pelvis. 

The ureter (fig. 190, c,c) takes the usual 
course to the contracted neck of the bladder, 
but terminates, in the male, in the urogenital 
canal, below the vasa deferentia; and, in the 
female, (fig. 191, /,/,) beyond the uterine orifice, 
which thus intervenes between the ureter and 
the orifice of the urinary bladder. 

In all respects, save the place of termination 
of the excretory ducts and their relation to the 
reservoir of the renal secretion, the Mono- 
tremes adhere closely, in regard to their urinary 
system, to the Mammalian type. The circum- 
stances in which they deviate from the higher 
mammals approximate them closely to the 
Reptilia, and especially the Chelonia ; and it 
is to be observed that the deviation commences 
where the urinary system begins to be connected 
with the generative organs, in which the ovipa- 
rous type of structure is especially manifested. 


ORGANS OF GENERATION. 

The male organs in both Monotremes con- 
sist of a testis, vas deferens, Cowper’s glands, 
and penis: there are neither prostatic glands 
nor vesicule seminales. 


392 


Male organs, Ornithorhynchus. (Mechel. ) 


The Monotremes are true testiconda, and in 
this respect differ from the Marsupial animals. 
In the Echidna each testicle is situated imme- 
diately below, or sacrad of, the kidney, and is 
suspended to that gland bya fold of peritoneum ; 
the same fold is continued to the neck of the 
bladder, inclosing the vas deferens, which is 
disposed in a szries of close transverse folds 
throughout its whole course. It corresponds 
closely, in these respects, with the Ornitho- 
rhynchus. In neither Monotreme is there any 
disparity of size between the right and left 
testicle : the latter is figured in situ at a’, fig.187. 
The vas deferens ( fig.190, f.) emerges from the 
upper or atlanta! extremity of the testis (e) ; 
aA, from its peculiarly extended, plicated, or 
folded course, seems to prolong the epididymis 
nearly to the neck of the bladder; the folds 
gradually diminish, and the duct itself enlarges, 
as it approaches its termination, which is in the 
beginning of the urogenital canal (g). This 
canal is continued through the pelvis and termi- 
nates in the vestibular passage, anterior to the 
orifice of the rectum (q). 

The vascular tissue of the penis com- 
mences at the termination of the urogenital 
canal; it is separated by a median septum 
into two lateral moieties, and both are in- 
closed by a common dense fibrous sheath. 
The whole penis in its collapsed and retracted 
state is about fifteen lines in length, and is con- 
cealed in a large preputial sheath. The ter- 
minal half of the penis is formed by the glans, 
which presents a quadrilateral form, and is 
traversed by a median longitudinal furrow upon 
both the upper and the under surface. Its ex- 
terior is beset with numerous short and hard 
epidermal spines: its extremity is bifurcated, 
and each lobe is directed outwards and termi- 


MONOTREMATA. 


nates in three or four spines, (k, k,) much 
larger, but softer, than the rest, and which are 
usually retracted in a depression. ; 
A fongitadinal azygos levator muscle runs 
along the upper surface of the penis; it arises 
by two lateral slips from the mternal stratum 
(n) of the protrusive sphincter. Another lon- 
gitudinal but longer and more slender muscle, 
the retractor penis, (fig. 190, p,) arises from 
the upper part of the of the tail, bends 
downwards over the caudal muscles and vessels, 
and is inserted into the origin of the penis near 
the termination of the urogenital canal. The 
true urethra or canal of the penis begins bya 
small orifice at the root of hs penis, — the 
termination of the urogenital passage, 
the combined action of the last described 
muscle with the sphincter cloace, it can be 
brought into closer approximation with the uro- 


genital It must be supposed that 
this temporary continuation of the urethra and 
urogenital takes place during the vigo- 


rous muscular and vascular actions of the parts 
in coitu, and that the semen is then propelled 
from the one along the other without i 
into the common vestibular compartment of the 
cloaca. Under ordinary circumstances, as 
when the urine is transmitted along the uro- 
genital passage, it must escape into the vesti- 
bule, and may there be blended, as in the Bird, 
with the rectal excrement. The true seminal 
urethra, commencing by the distinct ape 

as above described, is about a line in diameter, 
and continues single to the middle of the glans, 
where it divides into two canals; each branch 
runs along the middle of the bifurcation of the 
glans, and, when arrived at the base of the large 
papille, subdivides into smaller channels cor- 
responding with the number of the papille, 
and opening upon their apices. If the canal 
of the penis were slit open along its under part 
and thus converted into a groove, the male 
organs of the Ornithorhynchus would be then 
essentially like those of a Tortoise. The adhe- — 
sion to the Mammalian type is manifested ina 
highly interesting manner by the com 

of the urethral canal, whilst the affinity to the 
Marsupial order is evinced in its bifurcation ; 
corresponding with that of the glans itself. Had 
the penis been neither perforated nor } 
as Cuvier once believed, the structure wou 
have been extremely anomalous. That the 
existence of a penis is essentially and subordi- 
nately related to the sexual organs and not to the — 
renal, is beautifully illustrated by the complete — 
separation of the uro-urethral from the semino- — 
urethral passages in the Monotremata. 

The modifications by which the male 
in the Echidna din a ae of the Ornithor- 
hynchus, are confined to the glans penis, which 
divides into four mammiloid processes, rough- 
ened by minute papille, and terminated by a 
depression in which is the branch of the semi-— 
nal canal that traverses each process. o7 
glands (fig.180, k, k, and fig.190, A) are of larg 
relative size; they are situated between the be 
of the penis, the arch of the ischium, and intern 
= of the thigh: their secretion is ied 

y along and slender duct (fig. 190, m) into the 


MONOTREMATA. 393 


seminal urethra. The physiological relation of | The female organs of generation (fig. 191) 
these glands to such a canal is clearly illus- consist of two ovaria, the right much smaller 
trated by their presence in the Monotremes, than the left, two oviducts, two uteri, a clitoris, 
and their absence in the oviparous animals and mammary glands. 

which have merely a seminal groove. 


bat eee 
- = - * 


a, Cloacal outlet. 
. 6b, Common vestibule. 
*" c, Uro-genital canal. 


Ff, Left ovary. 
J’, Right ovary. 
i, Ovarian ligament. 


ce’, Its sphincter. k, Urinary bladder. 
d, Uterus. 1, Ureter. 
d’, Oviduct. m, Os uteri. 


e, Ovarian aperture. 


my Female organs of generation, natural size, Ornithorhynchus. (Owen, Philos. Trans. 1832. ) 


394 


The ovaria correspond in situation and sur- 
rounding attachments with the testes in the 
male; and the oviducts and uteri exhibit in 
their closely convoluted disposition an analogy 
with the long epididymis or vas deferens. 

The left ovary (fig.191, f) is an irregular, 
semi-elliptical, flattened body, with a wrinkled 
and slightly granulated surface in the unexcited 
state; but thicker, and with the surface studded 
by elevations formed by the ovisacs in different 
stages of development at the season of sexual 
excitement. At this period I have usually 
found two ovisacs, as in the figure, which are 
conspicuously larger than the rest, and present- 
ing each a diameter of about two lines. The 
right ovary (/”) is a narrow, thin, generally 
elongated y; sometimes broader, with a 
finely granulated surface. It is often scarcely 
to be distinguished from the ovarian ligament 
to which it is attached. This ligament (i, 2) 
arises from the posterior parietes of the abdo- 
men, behind and a little on the outer side of 
the kidney, and passes along the edge of the 
broad ligament to the fallopian extremity of the 
oviduct, where it divides into two; one portion 
is attached to the side of the ovary, the other to 
the posterior margin of the fallopian orifice: 
after a course of an inch they again unite, and 
the ligament is continued along the anterior 
part of the uterus to its cervix, where it is in- 
sensibly lost. The two separated portions of 
the ligament support a large pouch of perito- 
neum which forms the ovarian capsule; the 
wide anterior orifice of the oviduct is also, by 
means of this ligament, prevented from being 
drawn away from the ovary. 

The efferent tube of the ovarian products is 
present on both sides of the body, and is divi- 
sible into an oviduct, or fallopian tube, (d’,) 
and an uterus (d). The size of the latter is 
nearly equal on both sides, but the right ovi- 
duct is much shorter than the left, and corre- 
sponds with the abortive condition of the ovary. 

e external serous coat of the oviduct is 
loosely connected to the muscular coat by fila- 
mentary processes of cellular membrane, among 
which numerous tortuous vessels ramify. The 
muscular coat is thin and compact, and is most 
readily demonstrable in the uterus. The mu- 
cous coat is thin and smooth in the oviduct; 
it is thick, soft, plicated, but not villous, in 
the uterus. 

The left uterus in a female with a large 
ovary, shot in the month of September, was two 
inches long, from four to five lines in diameter, 
and about a line thick in its parietes ; it be- 
came suddenly contracted and thinner in its 
coats to form the oviduct, which presented a 
diameter of about two lines, slightly enlarging 
to within an inch of the extremity, which forms 
a wide membranous pouch, (d”,) opening into 
the capsule of the ovary by an oblong orifice or 
slit (e) of eight lines in extent. The edges of 
this orifice were entire,as in the oviducts of 
Reptiles, not indented as in the fimbriated ex- 
tremity of the Fallopian tube in ordinary qua- 
drupeds. The entire length of the oviduct 
and uterine tube, when detached from their con- 
nections with the mesometry, was nine inches. 


MONOTREMATA. 


The right uterus and oviduct of the same speci- 
men exhibited similar differences in diameter 
and structure, but was shorter, measuring only 
six inches in length. oi) 

In a specimen with a slightly developed 
ovary, killed by Mr. Bell in April, the uteri 
were not much wider than the oviducts, and not 
thicker in their coats; the entire tubes were 
much less in all their dimensions than those 
just described. 

In the specimen above described with the 
large ovary, the thickened parietes of the first — 
portion of the uterine tube depended chiefly on 
an increase of the inner membrane, which pre- 
sents in a high degree the character of a se- 
creting surface. This membrane at the cervix 
uteri presented in all the specimens many 
deep and close-set furrows, which, as the 
grew wider, were gradually lost, and the surface 
became more or less smooth in the different 
specimens, being most irregular in the i 
men with the largest ovary. In the oviduct, 
the inner surface is at first smooth after leaving 
the uterus, but beyond that becomes finely re- 
ticulate, and in the terminal dilated part be- 
comes again smooth. The cervix uteri makes 
a valvular projection analogous to an os tince 
on each side of the commencement of the uro- 
genital canal, just beyond the orifice of the 
urinary bladder. There are two orifices on 
each of these prominences; the lower one is the 
termination of the ureter, and a bristle is repre- 
sented as passing through it in fig. 191; the 
upper or anterior orifice is the os uteri, m. 

n young or virgin Ornithorhynchi this ori- 
fice forms scarcely any projection into the aro- 
genital canal, and it is divided by a narrow 
septum, or hymen.* a 

“The uro-genital canal ©) is one inch anda 
half long, and three or four lines in diameter, 
but capable of being dilated to as great an 
extent probably as the pelvis will admit of; 
the diameter of the bony passage being seven- 
tenths of an inch. It is invested with a mus-— 
cular coat, the external fibres of which are 
longitudinal, the internal circular. The inner — 
membrane of this part is disposed in longi- 
tudinal ruge more or less marked, but pre- 
sents as little the character of a secreting mem=- 
brane as that of the vestibule, being smooth 
and shining; the orifices of a few minute 
follicles are situated in the interstices of the 
ruge near the orifice of the urinary bladder. 

It is this division only of the rom 
the uterus which is situated within the pelvis, 
the vestibule being produced beyond it, a 
the common outlet being in consequence sit 
ated at a considerable distance from the @ 
of the pelvis.t 

If the Ornithorhynchus were oviparous, its 
eggs must be disproportionately small compared 
with those of birds, in order to pass through — 
the unyielding pelvis, unless the albumen and — 
shell were subsequently added to the yolk in 


sate TO 


4 


Ls AD 


a , . 
el ee 


+t In this structure, as well as in its aquatic life, 
the Ornithorhynchus resembles the Beaver. ‘ 


MONOTREMATA. 


vestibule. But, as has been before observed, 
neither the lining membrane of the vestibule nor 
that of the genito-urinary passage presents the 
characters of an active secreting membrane; and 
it is highly improbable that an almost callous 
surface daily traversed by the excrements, 
should be suddenly modified to contribute so 
important a share to the nutrient store of the 
embryo. 

The common vestibule (5) is about one inch 
four lines in length, and varies from half an 
inch to an inch in diameter. The muscular 
fibres immediately investing it are disposed as 
follows. A thin circular muscle arises from a 
dorsal raphé which extends the whole length 
of the canal. Of this muscle the sacral fibres, 
or those nearest the outlet, surround the whole 
vestibule; but the atlantal or more internal 
fibres pass obliquely upwards, and surround 
the termination of the rectum only, serving as 
a sphincter to it. On the sternal aspect of the 
vestibule there are a series of longitudinal 
fibres, which extend from its external orifice to 
that of the urogenital cavity, the office of which 
is to el elena these orifices; and in this 
action the oblique fibres above described would 
assist, while at the same time they clused the 
rectum. 

On the sternal aspect of the urogenital 


_ canal, and close to where it joins the vesti- 


bule, the clitoris is situated, which is conse- 


- about an inch and a half distant from 


the external orifice of the vestibule. It is 
inclosed in a sheath upwards of an inch in 
length, and about two lines in diameter, of a 


_ white fibrous texture, and with a smooth in- 


ternal surface, and this sheath communicates 


_ with the vestibule about a line from the ex- 
_ ternal aperture. The clitoris itself is a little 


flattened body shaped like a heart on playing 


_ Cards; it is about three lines long, and two 


lines in diameter at its dilated extremity, where 


_ the mesial notch indicates its correspondence 


of form with the bifurcated penis of the male. 
From the shortness of the clitoris, and the 
length of its sheath, it is obvious that no part 
of it can project into the vestibule in the ordi- 
“hary state of the parts, as stated by Sir Everard 
Home, its extremity being situated at least an 
inch distant from where its sheath communi- 
cates with that cavity. 

At the base of the clitoris are two small 
round flattened glands, the analogues of Cow- 
per’s glands in the male, which open into the 
sheath or preputium clitoridis. These glands 
were largest in the specimen whose uterine 
Organs were most developed. 

The vestibule is lined by a dark-coloured 
cuticular membrane, and has a tolerably uni- 
form surface. The rectum opens freely into it 
posteriorly, as indicated by the probe 6’, in 
Jig. 191; the line of distinction in the relaxed 
State of the sphincter above-mentioned being 
‘little more than a change in the character of 
the lining membrane. 

_ The urogenital canal, on the contrary, opens 
into the vestibule by a contracted orifice, and, 
1n one of the specimens examined, made a small 
circular and valvular projection into that cavity. 


395. 


On either side the termination of the rec- 
tum there are from six to eight small apertures 
of dark-coloured glands or follicles, about the 
size of a pin’s head, situated immediately. 
behind the proper membrane of the vestibule, 
and corresponding with the anal follicles of 
the Marsupial and other Quadrupeds. 

The female organs of the Echidna corres- 
pond in all essential points with those of the 
Ornithorhynchus. 

Products of generation.—The mode of ge- 
neration and course of development of the 
Monotremata, although elucidated in many 
essential points by the light of anatomy and 
analogy, still demand observation of the breed- 
ing animals, and of the impregnated uterus 
and embryo in several stages, before they can 
be fully determined. ; 

The close resemblance of the efferent tubes, 
in their complete separation and in their mode 
of termination, with the oviducts of Reptiles, 
and more especially of the Oviparous tortoises, 
added to the approach to the very peculiar 
condition of the female organs in Birds which 
the Monotremes offer in the unequal develop- 
ment of the ovaria and oviducts, have inclined 
several physiologists to a belief in the reports 
which from time to time have been published 
of the discovery of eggs in the nests of the 
Ornithorhynchus. But a comparison of the 
organs themselves with the conditions essential 
to the Oviparous generation of a warm-blooded 
animal offers almost insuperable difficulties to 
this view. The difference of structure and 
dimensions between the uterine and oviducal 
divisions of the efferent canal is greater in the 
Ornithorhynchus than in any bird, and so 
closely corresponds with that which charac- 
terizes the uterus and oviduct in the Kangaroo, 
that it is highly probable they perform similar 
functions in the completion and development 
of the ovum. 

But the experienced physiologist would seek 
to obtain a closer insight into the mode of 
generation of the Monotremes by a comparison 
of the more essential generative organ,—the 
ovary,—with that of the bird. Now it has been 
shown that this organ, at the period of sexual 
excitement, does not differ in size or form from 
that of the Rodent or Marsupial quadruped ; 
nay, that some of the latter tribe, as the 
Wombat, more nearly resemble the bird in the 
large size of the ovisacs or calyxes than the 
Monotremes are known to do. Avyolk of large 
size appears, however, to he an essential con- 
dition of an egg which is to be hatched by a 
warm-blooded animal out of the body; but 
the vitelline portion of the ripe or nearly ripe 
ovarian ovum of the Ornithorhynchus does not 
equal the twentieth part of the yolk of the 
egg of a bird of corresponding size: and it is 
scarcely necessary to observe that the yolk is 
always exclusively a product of the ovarium, 
and that the material added to it by the oviduct 
or uterus must be analogous to the albumen, 
chalaze, and cortical investments of the bird’s 


The unimpregnated ovarian ovum from an 
ovisac of two lines in diameter, of the Orni- 


396 


thorhynchus, is of a spherical form, 
and very nearly fills the ovisac. The 
diameter of the germinal vesicle is to 
that of the ovum as 1 to 38. The 
vitelline fluid is rich in the number 
of its nucleated cells or granules, 
and the intermixed, clear, colourless 
oil-globules. The vitelline membrane 
is moderately thick, smooth, and 
highly refracting. The ovum is se- 

ted from the ovarian vesicle, or 
ining membrane of the ovisac, by a 
very small quantity of fluid and a 
Stratum of granules or cells. The 
proper tunic of the ovisac consists of 
a dense and very vascular layer of 
the ‘ stroma’ or proper tissue of the 
ovary, which is rather thicker and 
more distinctly laminated than in 
most Mammalia, and in this re- 
spect widely differs from the lax 
stroma of the ovary of the bird. The 
most important difference to be noted in the 
present comparison with the bird is the small 
size of the ovarian ovum, depending on the 
relatively scanty amount of vitelline matter, 
superadded in the ovary to the essential part of 
the ovum, the vesicula germinativa. 

It may be objected that the impregnated 
ovarian ova in birds rapidly augment in bulk 
as the time of dehiscence approaches, and that, 
although the ovaria of the Ornithorhynchus 
may have been investigated within a few days 
of the reception of the impregnated ovum into 
the oviduct, the changes occurring in such a 
period might much more nearly approximate 
the ovarian ovum of the Ornithorhynchus to 
the size and other conditions of that of the bird 
than in the instances above described. 

The following observations on the impreg- 
nated ovum in the uterus itself prove, how- 
ever, that no such approximation to the bird 
in regard to the proportion of yolk added to 
the ovarian ovum, or as respects the size of 
the ovum prior to dehiscence, is made by the 
Ornithorhynchus. 

For the acquisition of this important evi- 
dence in the question of the generation of the 
Monotremata science is indebted to the ex- 
ertions of Mr.Geo. Bennett, F.L.S., a Member 
of the Royal College of Surgeons in London, 
and Colonial Zoologist at Sydney, New South 
Wales. Three uteri, containing undeveloped 
ova, were transmitted by that gentleman to the 
Museum of the Royal College of Surgeons, 
in 1834, and with the sanction of the Board of 
Curators, were described by me in the Philo- 
sophical Transactions of that year.* 

In these specimens the left ovary only had 
taken on the sexual actions, but did not ex- 
ceed in size the same parts in the unimpreg- 
nated specimens above described. The right 
ovary had, however, become enlarged ; it mea- 
sured half an inch in length, a third of an 
inch in breadth, and was about half a line in 


* See vol. cxxiv. p. 555, and Physiol. Catalogue 
of the Hunterian Museum, vol. v. p. 112, No. 
3460 A. 


MONOTREMATA. 


Left uterus i i 
(Owen, Phil. Trans. 1834. ) 


ted, Ornithorhynchus. 


thickness : a few ovisacs, about the size of a 
small pin’s head, projected from the surface. 
The left ovary in each of the specimens was 
concealed by the thin membrane forming the 
expanded orifice of the oviduct, to which it 
was agglutinated by a coagulated secretion. 
In two of the specimens the left ovary pre- 
sented two empty ovisacs, or corpora lutea 
(fig. 192, b 6), corresponding with the num- 
ber of ova found in the uterus. In the third 
specimen the left ovary presented two ovisacs 
still uncicatrized ; but only one ovum was con- 
tained in the uterus. In a fourth specimen 
three similar ovisacs were present, but the ova 
had been removed from the uterine cavity. 
The discharged ovisacs were of an elongated 
flask-shaped form about three lines in length, 
and two in diameter, with the margins of the 
orifice, through which the ovum and granular 
substance had passed, everted, with a slight 
contraction, resembling the neck of a flask, 
below the a pe On compressing these. 
ovisacs, small portions of coagulated sub- 
stance escaped. When longitudinally divided, 
they were found to consist of the same parts 
as the ovisac before impregnation, with the 
exception of the granular contents and gra- 
nular stratum; but the theca, or innermost 
parietes of the sac, was much thickened, and 
encroached irregularly upon the empty space, 
so as to leave only a cylindrical passage to the 
external opening. 

The impregnated Ornithorhynchus, in the 
uterus of which the two smallest sized ova 
were found, was shot on the evening of the 
6th of October, 1832, in the Yas river, Murray 
County, New South Wales. These ova were 
of a semitransparent white colour when 
but had lost that ap ce when exami 
at the Museum, to which they had been trans- 
mitted, in situ, with the uterus and surround- 
ing parts well preserved in spirits. The ova 
were situated at the upper part of the left 
uterus, and at the distance of about a line 
from each other. Each ovum was spherical in — 
form, and measured two lines and a half in 
diameter; they were of a deep yellow colour, 


MONOTREMATA. 


with asmooth and polished surface, and had 
not the slightest adherence to the uterine pa- 
rietes. 

The specimen containing the two ova next 
in size (fig. 192, cc) was shot in the same 
locality on the 7th of October. These ova 
Measured each three lines in diameter, and 
were situated a little below the middle of the 
left uterus: they were of a spherical form, 
but had evidently been slightly compressed in 
the uterine cavity. They were of a lighter 
colour than the preceding; a circumstance 
which was specially evident at the upper part, 
from the subsidence of the contained vitelline 
Mass. Externally they were sinooth and rolled 
freely out of the position where they were 
lodged, like those of the preceding specimen. 

The third specimen, in the uterus of which 
the largest ovum was contained, was shot on 
the evening on which the first specimen was 
obtained. This ovum had the same spherical 
form, smooth exterior surface, and freedom 
from connexion with the uterus, as in the pre- 
ceding; but was of a much lighter colour, 
Owing to the increased quantity of its fluid 
contents, to which its greater size was chiefly 
attributable. It measured three lines and a 
half in diameter, and had been situated ina 
depression or cell a little below the middle of 
the left uterus. The lining membrane of the 
uterus was highly vascular in the recent state 
in each of the above specimens. 

In all these ova the contents could be seen, 
through the cortical or outer membrane, to be 
of two kinds, viz. a greyish sub-transparent 
fluid, and a yellowish denser mass, which 
varied in their relative proportions as above- 
mentioned, the denser substance always sub- 
siding to the lowest part of the ovum, which- 
ever way it was turned. 

In the largest ovum, the yellow mass or 
yolk occupied about one-third of its cavity, 
while in the smallest it constituted four-fifths 
of the whole mass. 

The chorion or cortical membrane of these 
ova (fig. 193, a) offered a moderate degree 
of resistance when torn open with the forceps, 
and yielded equally in every direction when 
Separated from the yolk, the rent margins 


Fig. 193. 


Uterine Ovum, magnified and dissected, 
Ornithorhynchus. 
( Owen, Phil. Trans. 1834. ) 


397 


curling inwards like the coat of an hydatid. 
This membrane is of a dull greyish colour, 
inclining to brown, slightly transparent, and 
more polished upon its inner than upon its 
outer surface: it resembles the cortical mem- 
brane of the ovum of the Salamander, but is 
of a more delicate texture. The fluid contents 
occupied the space between the cortical and 
vitelline membranes, a situation analogous to 
that of the albumen in the egg of the fowl, 
but had not become coagulated by the action 
of the spirit in which it had been so long im- 
mersed. 

The yellow matter, or yolk, was seen to be 
invested by its proper —— (fig. 193, b), 
which, when reflected under the microscope, 
was found to consist of an extremely thin, 
smooth, and transparent outer layer, which 
I regard as the membrana vitelli (fig. 194, a), 
with a thicker granular membrane immediately 
lining it, analogous to the blastoderma or ger- 
minative stratum (fig. 194, 6). 

The contents of the 
above investments, or 
substance of the yolk, 
consisted of innume- 
rable minute opaque 
granules, similar in size 
and regularity of form 
to those contained in 
the ovarian follicles; 
and with these gra- 
nules were mingled 
larger transparent glo-| ee 
bules of oil. There was! ortion of the ee 
not the slightest trace sum, Ornithorhynchus. 
of chalazz attached to ( Owen, Phil. Trans.1384. ) 
the vitelline membrane, 
as from analogy we might have expected, had 
the ovum been destined to have been perfected 
by incubation. I was unable to detect any 
rudiments of the embryo: an opaque streak 
was discernible on one part of the yolk, but 
not sufficiently definite to be satisfactorily re- 
cognised as a cicatricula; it is indeed, proba- 
ble, from the observation of Lieutenant Maule,* 
that the ova attain a greater size by the im- 
bibition of the nutrient material before the 
lineaments of the foetus become visible. 

The changes which the impregnated uteri of 
the Ornithorhynchus had undergone, as com- 
pared with the same part in the quiescent state, 
were greater than those which have been ob- 
served to take place in the Kangaroo. The 
uterus containing the two smallest sized ova 
measured seven lines in diameter, but was 
much firmer and denser than in the unim- 
pregnated specimens; and having also in- 
creased in length, was thrown into more abrupt 
curves on either side of the ovarian ligament. 
The uterus which had contained the largest 
ovum measured an inch in diameter; and that 
containing those of the second size was of 


Fig. 194. 


* Proceedings of the Zoological Society, 1832. 
** In the insides of several female platypi which 
were shot, eggs were found of the size of a large 
musket-ball and downwards.” 


398 


nearly the same size (fig. 192). The right 
uterus in all the specimens had become sym- 
pathetically affected, being firmer in texture 
and thicker in its coats. 

The parietes of the impregnated uteri were 
from three to four lines in thickness; an in- 
crease which was principally occasioned by 
the extension of small vascular folds between 
the fibrous and internal coats, which were so 
placed at right angles to these tunics as to 
present an appearance very similar to that of 
the secoud cavity of the stomach of the Por- 
pesse. The fibrous coat was slightly thickened 
near the cervix, and the serous covering was 
separated from it by the ramifications of nu- 
merous large and tortuous uterine vessels. 

There was not the slightest trace of a deci- 
dual or adventitious membrane in the cavity of 
the womb ; and especial attention was directed 
to this circumstance, in consequence of the 
office assigned to it in a recent work,* as mi- 
nistering support to the ova in the higher 
Mammalia, at a period when, like those of the 
Ornithorhynchus, they have no attachment to 
the uterine parietes.+ 

It may, however, be said that the deciduous 
membrane is here represented by the cortical 
or outer covering of the ovum: but this mem- 
brane, though of a denser structure and with- 
out villi, is certainly analogous to the outer 
tunic of the uterine ovum of the Rabbit and 
Bitch, which in then is gradually separated 
from the vitelline membrane by the imbibition 
of albuminous fluid. Now the relative pro- 
portion of the fluid interposed between the 
cortical and vitelline membranes in the small 
and large ova of the Ornithorhynchus, shows 
that the mutual recedence of the two mem- 
branes is effected in the same way. 

If the form, the structure, and the detached 
condition of the ova of the Ornithorhynchus, 
should still be regarded by some as compatible 
with, and perhaps favourable to, the opinion 
that they are excluded as such, and that the 
embryo is developed out of the parent’s body, 
the following objections oppose themselves to 
such an opinion: the only part of the efferent 
tube of the generative apparatus which can be 
compared in structure or relative position. to 
the shell-secreting uterus of the Fowl, is the 
dilated terminal cavity in which, in all the 
specimens above described, the ova were situ- 
ated; and upon the oviparous theory it must 
be supposed either that the parietes of this 
cavity, after having secreted the requisite 
quantity of soft material, suddenly assume a 
new function and complete the ovum by pro- 
viding it with the calcareous covering neces- 
sary to enable it to sustain the superincumbent 
weight of the mother during incubation ; or, 
that this is effected by a rapid deposition of 
the same material from the cuticular surface of 
the external passages; or lastly, according to 
a more recent, but still more improbable sup- 


* Breschet, Etudes de l’Q2uf Humain. 
+ In the recent specimens Mr. Bennett noticed 
besides the ova only a “ mojsture” in the uterus. 


MONOTREMATA. 4 


ition, by a calcareous secretion of the ab- 
tt ie poured out upon the “my ' 
after its ee Me eh ‘ad 

But granting that the egg is provided in any 
of can pi Se the n external co= 
vering, yet from the evidence afforded by the | 
specimens under consideration, the ovum is 
still deficient in those parts of its organization — 
which appear to be essential to successful in= 
cubation, viz. a voluminous yolk to support — 
the germinal membrane, and the 2 
for bringing the cicatricula into contiguity with 
the body of the parent. Add to this, that such 
a mode of development of the foetus requires” 
that all the necessary nutritive material be 
accumulated in the ovum prior to its exclusion. 
Now the bony pelvis of the bird is 
modified to allow of the escape of an 
both large from the quantity of its 
and unyielding from its necessary 
covering ; but whatever affinities of structure 
may exist in other parts of the Ornithorhyn- 
chus, it is most important to the question of 
its generation to bear in mind that it manifests 
no resemblance to the bird in the condition of — 
the pubic bones. v9 

Again, as we have seen that the ova of the — 
Ornithorhynchus have attained a diameter of — 
little more than two lines after having traversed 
the whole of the Fallopian tube, the length of 
which is six inches, and the internal i b 
surface increased by numerous folds, it may — 
be reasonably inferred, from the analogy of the 
Rabbit and other Mammalia, that the ovum 
was of much smaller dimensions when first 4 


bad 


received into the oviduct. But the yolk in — 
Birds and Oviparous Reptiles is invariably the 
product of the ovary, and derives no e. 


ciable increase from the secretions the 

efferent tube, which supply only the albu- — 

minous part of the egg, or the material forthe 
4 


first formation of the chick. If, therefore, the 
gestation of the Ornithorhynchus terminates by 
the exclusion of an egg, as in the Bird or 
Tortoise, the preparatory steps in the formation — 
of the ovum are widely different, for the parts — 
concerned manifest the essential characters of 
the Mammiferous type, and the germ itself has" 
a corresponding structure. 
These facts, it is agreeable to find, are in 
exact accordance with the now ascertained — 
functions of the abdominal glands; for since 
the yolk in the Bird, besides its uses in the 
course of the fetal development, is intended 
as an after-substitute for a mam ion, 
remaining, as it does, but little diminished 
at the close of incubation, it might have been 
concluded, from @ priori physiological dedue- 
tion, that the Monotremes, in which no such sub- 
stitute is required, would approximate the other 
Mammalia in the small size of the ovarian ovam. 
The nature or amount of subsequent devia- 
tions from a true viviparous generation can be 
determined only by future examinations of more 
advanced ova. From the structure of the cor- 


* Geoffroy St. Hilaire, Gazette Medicale, z 
11, 1833, 23 


_ tical membrane it is probable that this does not 
_ become organized into a placenta, and that the 
_ Monotremata like the Marsupiata are essentially 
‘ovoviviparous. Since, however, the female Or- 
nithorhynchus has no tegumentary pouch to pro- 
tect a prematurely born offspring, it must be pre- 
sumed that the foetus acquires greater propor- 
tional bulk* and more mature strength by a 
longer continuance within the uterus. In this 
€ase it may be doubted whether the vitelline 
vesicle will suffice for nourishment and respi- 
‘ation through the whole period of develop- 
‘ment, and the allantois and umbilical vessels 
will probably be more expanded for that pur- 


t . 


_ pose 
__ The means of prosecuting this inquiry are 

‘the more likely to be afforded, since, through 

exertions of Mr. Bennett, the period when 

pregnant female may be procured is now 

ertained. Had not a specimen, supposed 

be in this condition, which my friend had 

ained alive, unfortunately escaped from its 

finement, he would, there is little doubt, 

ascertained the true nature of the gene- 

ye product, and the probable duration of 
ation. 

With reference to the latter point, Mr. Ben- 
‘nett observes, that two months after the cap- 
ture of the female specimen with the smallest 
viz. on the 8th of December, 1832, he 
eceeded in laying open one of the burrows 

he Ornithorhynchi on the banks of the Mur- 
bidgee River, in which three living young 
ss were found: they were naked, and mea- 
ed only one inch and seven-eighths in 
h, and he considers them to have been 
tly brought forth. Not having any means 
reserving these specimens, and being at a 
distance from Sydney, they were lost. 
nest was most carefully scrutinized by 
Bennett, but not the slightest trace of an 
hell could be perceived in it. 
he principal points, therefore, in the ge- 
‘ive economy of this paradoxical species 
which still remain to be determined by actual 
observation are— 

_ Ist. The manner of copulation. 
orem The season of copulation. (This is pro- 
_bably at the latter end of the month of Sep- 
_ tember or beginning of October.) 

__ 3d. The period of gestation. (This is pro- 
bab six weeks.) 

_ 4th. The nature and succession of the tem- 
_ porary structures developed for the support of 
_ the foetus during gestation. 

Sth. The exact size, condition, and powers 
_ of the young at the time of birth. 

- 6th. The act of suckling. 

_ @th. The period during which the young 

requires the lacteal nourishment. 

oe The age at which the animal attains its 

fall size. 

I have ascertained the following particulars 

“Wy 

__* In reference to this point it may be observed, 

that the kidneys are not lodged low down in the 

oe in the trae Ovipara, but occupy the posi- 
ion characteristic of the Mammiferous type of 

structure, which allows free space for the enlarge- 

__-‘™ment of the uterus during pregnancy. 
=. 


5] 


MONOTREMATA. 


399 


respecting the young Ornithorhynchus, pro- 
bably not long excluded from the foetal enve- 
lopes, by an examination of two specimens, 
obtained by Lieut. the Hon. Lauderdale Maule, 
from two different nests, discovered by him in 
the banks of the Fish River, Australia, and 
presented by Dr. Weatherhead to the Zoolo- 
gical Society of London. 

Subjoined is an outline of the smaller of 
these specimens of the natural size (fig. 195). 


Fig. 195. 


Young Ornithorhynchus. ( Original. ) 


The following are admeasurements of these 
two specimens :— 


Smaller Larger. 
Ornitho- Ornitho- 
rhynchus. thy eee 
In. Le n L. 


Length from the end of the 

upper jaw over the curve 

of the back to the end of 

the tal «uo eesee eee Oo ee 6 6 
Length from the same points 

in a straight line along the 

abdomiensce a. oo aca ce 2°41 4 0 
Greatest circumference of the 

Od sass cccsew ec dae 
Length of the head 
Length of the upper man- 

GIDIG SE Naveteicice cc asiet tess 
Breadth of the upper man- 

dible at the base 
Thickness of the upper man- 

dible at the anterior margin 0 0 
Length of the lower mandible 0 2 
Breadth of the lower man- 

dible at the base........ 0 
Length of the tail from the 

WBE or occa sieciesieietete ie 
Breadth of the tail at the root 
Length of the fore foot .... 
Breadth of the fore foot.... 
Length of the hind foot.... 
Breadth of the hind foot .. 
Distance between the eyes. . 
Distance between the nostrils 
From the exterior nostrils to 

the end of the mandible 0) 
From the tip of the tongue 

to the end of the lower 

mandible 


wo 
oz: sewowohww p> wo oO 
Nie tom CD Nim in 
o eoocece So S oo Sc o — > 


So 
°o 


400 


The circumstances which first attract atten- 
tion in these singular objects are the total ab- 
sence of hair,* the soft flexible condition of 
the mandibles, and the shortness of these parts 
in proportion to their breadth as compared with 
those of the adult. 

The integument 
with which the man- 
dibles are covered 
is thinner than that 
which covers the rest 
of the body, and 
smoother, present- 
ing under the lens a 
minutely granulated 
surface when the 
cuticle is removed, Head of young Ornithorhyn- 
which, however, is hus. (Owen, Zool. Trans. ) 
extremely thin, and has none of the horny 
character which the claws at this period present. 
The margins of the upper beak are rounded, 
smooth, thick, and fleshy; the whole of the 
under mandible (fig. 196, g) is flexible, and 
bends down upon the neck when the mouth 
is attempted to be opened. The tongue, 
(fig. 196, h,) which in the adult is lodged 
far back in the mouth, advances in the 
young animal close to the end of the lower 
mandible; all the increase of the jaws beyond 
the tip of the tongue, which in the adult gives 
rise to a form of the mouth so ill calculated for 
suction or application to a flattened surface, is 
peculiar to that period, and consequently forms 
no argument against the fitness of the animal 
to receive the mammary secretion at an earlier 
stage of existence. The breadth of the tongue 
in the larger of the young specimens was 3$ 
lines ; in the adult it is only one line broader ; 
and this disproportionate development is plainly 
indicative of the importance of the organ to the 
young animal, both in receiving and swallow- 
ing its food. The mandibles are surrounded 
at their base by a thin fold of integument, which 
extends the angle of the mouth from the base 
of the lower jaw to equal the breadth of the 
base of the upper one, and must increase the 
facility for receiving the milk ejected from the 
mammary areola of the mother. The oblique 
lines which characterize the sides of the lower 
mandible in the adult were faintly visible on 
the corresponding parts of the same jaw of the 
young animal: a minute ridge of the inner 
sides of these lines indicates the situations of 
the anterior horny teeth of the adult. 

The situation of the exterior nostrils (figs. 
195, 196, a) has already been given; they 
communicate with the mouth by the foramina 
incisiva, which are situated at nearly three lines 
distance from the end of the upper mandible, 
and are each guarded by a membranous fold 
extending from their anterior margin: the nasal 
cavity then extends backwards, and terminates 
immediately above the larynx, the tip of the 


Fig. 196. 
« b 


* This is not accidental, as in many of the adult 
specimens sent over in spirit, for the cuticle is 
entire. In the specimens which Mr. G. Sennett 
discovered, the skin had a slight downy appear- 
ance. 


MONOTREMATA. 


epiglottis extending into it, and resting upon 
the soft palate. 

On the middle line of the upper mandible 
and a little anterior to the ils there is a 
minute fleshy eminence lodged in a slight de- 
pression (fig.196, b). In the smaller specimen 
this is surrounded by a discontinuous margin 
of the epidermis, with which substance, there- 
fore, and probably (from the circumstance of 
its being shed) thickened or horny, the caruncle 
had been covered. It is a structure of which 
the upper mandible of the adult presents no 
trace, and is obviously analogous to tho heme 
knob which is observed on the upper 
in the foetus of aquatic and gallinaceous Birds. 
I do not, however, conceive that this structure 
is necessarily indicative of the mandible’s 
having been applied, under the same cireum- 


stances, to overcome a resistance of precisely the 
same kind as that for which it is desi in the 
young Birds which possess it. The shell-break- 


ing knob is found in only a part of the class; 
and although the similar caruncle in the Orni- 
thorhynchus affords a curious additional affinity 
to the Aves altrices, yet, as all the known history 
of the ovum points strongly to its ovo-vivipa- 
rous development, the balance of evi is 
still in favour of the young being brought forth 
alive. 

The situation of the eyes (fig. 195, b, 196, c) 
was indicated by the convergence of a few wrin- 
kles to one point; but when, even in the larger 
of the two specimens, these were ab ges upon the © 
stretch, the integument was found entire, and 
completely shrouding or covering the eyeball 
anteriorly. This fact is one of great im 
to the question of the mammiferous 
of the Ornithorhynchus. For on the supposition 
of the young animal ing locomotive 
faculties, which would enable it like the young 
gosling, immediately after birth or exclusion, 
to follow the parent in the water, and there 
to receive its nutriment, (whether mucous or 
otherwise,*) the sense of vision ought certainly 


* Geoffroy St. Hilaire ae in 1833, for 
the analogy of the abdominal glands of the Orni- 
thorhynchus with those‘of the S 7 ie 
** a mucus possessing a ve we , s, 
“‘T should not be sarees if this mucus, a 
abundant and more substantial in the M 

became the nutriment of the young after their 
hatching. The Monotremata would act, in this 
respect, like some aquatic birds which condact 
their young after hatching to the water, and assist 
them in their sustentation. The maternal instinct 
would lead the female Ornithorhynchus to effect 
the contraction of the gland, which is possible by 
the efforts of the panniculus carnosus and the great 
oblique muscle, between the fibres of which the 
gland is seated, and thus procure for the young, 
at several periods of the day, by wa of uate 
ment, an abundant supply of mucus. if this edu- 
cation is carried on in the water, where we know, 
by the history of the generation of frogs and the 
nutrition of their tadpoles, that the mucus com- 
bines with the ambient medium, becomes thick, 
and supplies an excellent nutriment for the early 
age ae these reptiles, we shall understand the 
utility of the ventral glands of the Ornithorhyn- 
chus, as furnishing a source of nutriment for the 
young of these animals,—for youn i newly 
hatched.””"— Gazette Médicale, Feb. 18th, 1833.— — 
Proceedings Zool, Society, March 1833, p. 29. 


to be granted to it in order to direct its move- 
ments. The privation of this sense, on the 
contrary, implies a confinement to the nest, 
and a reception on land of the mammary 
secretion of the parent. 

The auditory orifices (fig. 196, d) are situated 
-about a line behind the eyes. 

The general form of the body and the carti- 
laginous condition of the bones of the extre- 
_ mities equally militate against the young Orni- 
~ thorhynchus possessing, at this period of its 
_ existence, active powers of swimming or creep- 
ing. The head and tail are closely approxi- 
mated on the ventral aspect, requiring force to 
_ pull the body out into a straight line ; and the 
relative quantity of integument on the back and 
belly shows that the position necessary for the 
due progressive motions is unnatural at this 
_ stage of growth. 
____ The toes on each of the four feet were com- 
pletely formed, and terminated by curved, co- 
nical, horny claws; but the natatory fold of 
_ membrane of the fore foot had not the same 
proportional extent as in the adult, and the 
‘spur of the hind foot did not project beyond its 
_ socket in either specimen. In the smaller one, 
which was a male, it presented the form of an 
obtuse papilla; while in the larger specimen, 
_ although a female, it was more plainly developed 

ind more pointed (fig. 197,,f). This circum- 


—, 


oC 


Fig. 197. 


"Hina. fot and spur, young female Ornithorhynchus, 
=. magnified. ( Owen, Zool. Trans. ) 
te 
Stance is inexact accordance with the known laws 
_ of the development of sexual distinctions, espe- 
_ cially of those of secondary importance, such 
as beards, manes, plumes, horns, tusks, spurs, 
&e,, which do not avail in distinguishing the 
sexes till towards the period of puberty. As 
the spur is the only obvious distinction of the 
sexes in the full-grown Ornithorhynchus, I 
_ Was compelled to refer to the internal essential 
_ organs, in order to determine the sex of the 
_ Specimens here described. 
_ The ventral surface of the smaller specimen 
was carefully examined with a lens; but no 
trace of an umbilicus could be satisfactorily 
_ determined. In the very young or newly born 
_ Kangaroo, a longitudinal linear trace of the 
_ attachment of the umbilical vesicle is at that 
__ time apparent, but it is rapidly obliterated ; 
_ aS is probably also the case in the Omitho- 
By tynchus, , 
______In the smaller specimen the intromittent 
n projected a little way beyond the excre- 
VOL. III. 


-MONOTREMATA. 


401 


mentory orifice, as in the young Marsupialia ; 
but it was not continuous, as in them, with the 
anterior margin of that outlet. In the larger 
female specimen the corresponding organ was 
visible just within the verge of the opening ; 
but this clitoris, remaining stationary in its 
development, is afterwards, as 1 have shown in 
my paper on the Mammary Glands of the Mo- 
notremes,* removed to a distance from the 
preputial aperture by the elongation of the 
sheath, just as the minute spur of the female 
lies concealed at the bottom of the progres- 
sively elongated tegumentary socket, and as 
the tongue is left at the back of the oral cavity - 
by the growth of the jaws. 

The following anatomical appearances were 
noticed in these young Ornithorhynchi :— 

On laying open the abdomen in the larger 
specimen, the most prominent viscus was the 
stomach, which was almost as large as in the 
adult animal, deriving at this period no assist- 
ance from the preparatory digestive cavities, 
the cheek-pouches, which were not yet deve- 
loped. The stomach extended in a curved 
direction across the epigastric and down the 
left hypochondriac region to the left iliac re- 
gion. It was full of coagulated milk. 

In the smaller specimen the stomach was 
empty; when distended with air it exhibited 
a less disproportionate development. It was 
situated in the left hypochondriac and lumbar 
regions. The intestines contained air, with 
granular masses of a mucous chyme adhering 
to their internal surface. This condition of 
the digestive canal would seem to show that 
no long period had elapsed since the birth of 
the specimen, and that either lactation had not 
been in full action, or that the young one had 
been deserted by the parent for some time 
before it was taken. 

In both specimens the spleen bore a propor- 
tionate size with the stomach; and as the dif- 
ference in the development of the stomach was 
considerable, the correspondence between the 
condition of the spleen with that of the diges- 
tive cavity was made very obvious. 

The difference in the development of the 
liver was not greater than corresponded with 
the different size and age of the two specimens. 
But the pancreas in both bore the same ratio to 
the stomach as the spleen. This, therefore,would 
seem to afford some indication of the organs 
with which the function of the spleen is more 
immediately related. 

The intestinal canal in the larger specimen 
was situated almost entirely on the right side 
of the abdumen. The c@cum in both was very 
minute and filamentary. I examined the i/eum, 
and more especially in the usual situation above 
the cecum, but could not perceive any trace of © 
the pedicle of the umbilical or vitelline vesicle. 
The other vestiges of foetal organization were 
more obvious than in the ordinary marsupial 
or ovoviviparous Mammalia. 

In both specimens, but more especially im 
the smaller one, the umbilical vein was seen, 
extending from a linear cicatrix of the perito- 


* Phil. Trans. for 1832, p. 525. 
2» 


402 MONOTREMATA. a 


neum, opposite the middle of the abdomen, 
along the anterior margin of the suspensory 
ligament to the liver. It was reduced to a 
mere filamentary tube, filled with coagulum. 
From the same cicatrix the remains of the 
umbilical arteries extending downwards, and 
near the urinary bladder, were contained within 
a duplicature of peritoneum, having between 
them a small flattened oval vesicle, the re- 
mains of an allantois, which was attached by 
a contracted pedicle to the fundus of the 
bladder. 

As both the embryo of the Bird and that of 
the ovoviviparous Reptile have an allantois 
and umbilical vessels developed, no certain 
inference can be drawn from the above appear- 
ances as to the oviparous or viviparous na- 
ture of the generation of the Ornithorhynchus, 
But the structure of the ovary and that of the 
ovum, both before and after it has quitted the 
ovisac, afford the strongest analogical proof of 
the intra-uterine developement of the embryo, 
and at the same time accord with the ascer- 
tained fact of the mammary nourishment of the 
young animal. 

The kidneys were situated remote from th 
pelvis and high up in the lumbar region. 

The situation of the kidneys with respect to 
each other varied in the two specimens; in the 
larger one, the left was a little higher than the 
right; in the smaller one it was a little lower; 
the latter is the ordinary position in the adult. 
The supra-renal glands did not correspond with 
this arrangement, but in both instances the 
right was higher than the left, agreeing with the 
relative position of the testes in the male, and 
the ovaries in the female. In Man the large 
size of the supra-renal glands is noted as a 
foetal peculiarity, but in the Ornithorhynchus 
they are of minute size, their greatest diameter 
not exceeding one-eighth of a line in the smaller 
specimen here described ; and they increase in 
size progressively with the growth of the ani- 
mal, and in a greater proportion than the kid- 
neys, which increase would appear, therefore, 
to have relation to the development of the ge- 
nerative organs. There were no traces of the 
corpora Wolffiana. 

he testes in the small male specimen were 
situated a little below the kidneys: they were 
of an elongated form, pointed at both ends, with 
the epididymis folded down, as it were, upon 
their anterior surface. In the female, the ova- 
ries were freely suspended to the loins in a 
similar position, the right being at this period 
as large as the left: it is the persistence of the 
latter at an early stage of development which 
occasions the disproportionate size of the two 
glands in the adult. The still greater inequa- 
lity of size in the oviducts of the Bird arises, 
as is well known, from a similar arrest of the 
development of the one on the right side, but 
both are equal at an early stage of existence. 
The uteri were straight linear tubes, scarcely 
exceeding the size of the ovarian ligaments. 

The lungs were found amply developed in 
both specimens; the air-cells remarkably ob- 
vious, so as to give a reticulate appearance to 
the surface, and a resemblance to the lungs of 


ordinary Marsupialia in having the thymus 


a turtle. They had evidently been permeated — 
by air in the smaller specimen. “SI 

The heart, in both specimens, was of the — 
adult form, with the apex entire; but the left 
auricle was proportionately larger than in the 
adult heart. 


true viviparous Mammalia. Here also we * 
have the indication of a more prluestes bi 
existence than in the marsupial animals, there 

being no trace of a ductus arteriosus either in — 


The Ornithorhynchus also deviates from the — 


—_. 


gland. This is situated in front of the great 
vessels of the heart, and consists of two lobes, 
of which the right is the largest. The traces of 
foetal structures presented by these young Or- 
nithorhynchi, and especially the allantoic dila- 
tation of the urachus, indicate that the Mono- 
tremata differ from the Marsupialia ao 7 
continuance of the true fetal or im 


existence. ae 
Mammary organs.—In this section will be 
adduced the evidence in f of the ially 


Mammalian nature of the Monotremes which 
the presence and ascertained function of the — 
mammary glands have yielded. : 
The most important result of Professor Mec- _ 
kel’s anatomical investigations of the Ornitho- 
rhynchus was his discovery of the two large 
abdominal subcutaneous glands: these he con- 
cluded to be the mammary o which until 
that period had been sup to be absent in — 
the Ornithorhynchus. ’ 1 
Subjoined is the figure which Meckel has — 
given of one of these glands in its natural — 
relative position, fig. 198. It measured four — 
inches and a half in length, two inches in — 
breadth, and half an inch in thickness. j 
From this apparently conclusive evidence of — 
the affinity of the Ornithorhynchus to the Mam=- — 
malia, Professor Meckel, however, is far from 
drawing conclusions as to the identity of their 
mode of generation. For assuming that the 
difference between the bringing forth of living — 
young and of eggs is really very small and by 
no means of an essential nature, and remarking: 
that birds have accidentally hatched the eg 
within the abdomen and so produced a livit 
foetus,—an occurrence which has also beer 
duced by direct experiment, and that, las 
the generation of the Marsupial animals is very 
similar to the oviparous mode, he deems it 
very probable that as the Ornithorhynchus: 
proaches still nearer than the Marsupial ani 
mals to Birds and Reptiles, its mode of gene- 
ration may be in a prope degree analo- 
gous. For an animal possessing mammar 
glands he claims, however, the right to ra 
with the Mammalia, agreeing with Professor 
Geoffroy only so far as to consider the Mor 
tremata as a distinct order of quadrupe 
which he places, as Cuvier has done, next 
the Edentata. ae 
Against this conclusion, however, Profess 


MONOTREMATA. 


i fl WT | 
\ "AN |W 
yA 
Mammary gland, Ornithorhynchus, nearly arrived at 
full size. ( Mechel. ) 


i} 
‘ 


403 


Geoffroy has argued (Annales des Sciences 
Nat. ix. 1826, p.457) that the subcutaneous 
abdominal glands considered by Meckel as 
mammary, possess none of the characters of a 
true mammary gland ; he states that he exa- 
mined them with the greatest attention, com- 
paring them with the human mammary glands, 
and especially with those of Marsupial animals, 
and that they were of a totally different texture, 
consisting of a vast number of cacums placed 
side by side, all directed to the same point of 
the skin, where only two excretory orifices were 
to be perceived, and these orifices so small 
that the head of the smallest pin could not be 
made to enter them. That above all there was 
no trace of nipples; that in the specimen 


\\\ examined by him, which had the size and ap- 
} pearance of an adult female, the apparatus in 


question was not more than a fourth part the 
size of that observed by Meckel. But a mam- 
mary gland, Professor Geoffroy observes, when 
arrived at its full development, occasions an 
enlargement of all its constituent parts, the 
nipple acquiring additional bulk even before 
lactation commences, and that there was no 
appearance of this kind in the Ornitho- 
rhynchus. He considers, therefore, these ab- 
dominal glands as analogous to those which 
are situated along the flanks « Salamanders, 
and still more to the odoriferous glandular ap- 
paratus which is concentrated at the sides of 
the abdomen in the Shrews. 

In the absence of direct testimony of the 
nature of the secretion of the abdominal sub- 
cutaneous glands of the female Ornithorhyn- 
chus, the next obvious step was to test their 
disputed nature and office by an examination 
of their periods of increase and functional 
activity, as compared with those of the ovaria. 
If these glands had been analogous to the scent- 
glands of the flanks in the Shrews, and if their 
secretion had been destined to attract the male 
to the sexual intercourse, as suggested by Pro- 
fessor Geoffroy, their development ought to 


) have proceeded pari passu with that of the ova- 


ria, and the enlargement of both organs ought 
to have simultaneously reached its maximum. 
But in specimens in which the ovisacs were 
enlarged so as to indicate the ova to be ripe 
for development, I found* that the abdo- 
minal glands had madea comparatively slight 
progress to their full size (fig. 199). This 


pv ca NAFTA 
a 


Mammary gland, Ornithorhynchus, natural size at 
non-breeding season. 
(Owen, Phil. Trans. 1832.) 
* Philos. Trans. 1832, p. 525. 
2D2 


404 


condition was only manifested in the females 
with ovaria, large indeed, but without promi- 
nent ovisacs, and in which the recent corpora 
lutea were almost absorbed. These facts were 
established by the dissection of five female 
Ornithorhynchi. 

In each of these specimens the mammary 
gland was composed of between one hun- 
dred and two hundred elongated subcylin- 
drical lobes, forming an oblong flattened mass, 
and converging to a small oval areola in the 
abdominal integument, which areola is situated 
between three and four inches from the cloaca, 
and about one inch from the mesial line. The 
lobes in the fully developed glands are rounded 
and enlarged at their free extremities, and 
measured at that end three or four lines in 
breadth, and became narrower to about one-third 
from the point of insertion, where they end in 
slender ducts. Almost all the lobes are situated 
at the outer side of the areola, and remark mand 
converge towards the mesial line of the abdomen. 
Between the gland and the integument the 
panniculus carnosus (fig. 199, a) is interposed, 
closely adhering to the latter, but connected 
with thegland byloose cellular membrane. This 
muscle is here a line in thickness, its fibres are 
longitudinal, and, separating, leave an elliptical 
space for the passage of the ducts of the gland 
to the areola. On the external surface of the 
skin, when the hair is removed, this areola can 
ouly be distinguished by the larger size of the 
orifices of the lacteal ducts, compared with 
those for the transmission of the hairs. 


Mammary areola, Ornithorhynchus, natural size. 
(Owen, Phil. Trans. 1832.) 


The orifices of the ducts thus grouped together 
form an oval spot, which in the female with 
the largest glands measured five lines in the long 
and three in the short diameter. In none of 
the specimens was the surface on which the 
ducts terminated raised in the slightest degree 
beyond the level of the surrounding integument. 

eckel was disposed to believe that the 
ducts terminated on a small eminence about 
the size of a millet-seed, but did not succeed in 
demonstrating the fact by injection of the ducts.* 


* Meckel writes: ‘* Ductuli excretorii, maxime 
attenuati, in glandul# medio extrorsum aperiuntur. 
Quamvis neque setas, neque mercuriam per ductus,et 
per se, ut monui, angustissimos, et spiritu vini con- 


MONOTREMATA. 


Not any of the specimens of Ornithorh 
chus examined by me have presented a 
mammary eminence of any dimensions; on 
the contrary, I have succeeded in demonstrat- 
ing the termination of the lacteal duets on 
the flat areolar tract. Having in vain at- 
tempted to insert the smallest absorbent 
pipe into the mouths of these ducts, I thrust 
it into the extremity of one of the elongated 
lobes, and after a few unsuccessful efforts 
at length saw the mercury diffuse itself in mi- 
nute globules through the parenchyma of the 
lobe, and at a distance of an inch it had evi- 
dently entered a central duct, down which it 
freely ran to the areola, where it escaped exter- 
nally from one of the minute oritices just de- 
scribed. This was re on most 
of the lobes with similar results, the greater 
part of them terminated by a ange duct open- 
ing exteriorly and distinct from the rest, but in 
a few instances the ducts of two contiguous 
lobules united into one, and in these cases the 
mercury returned by the anastomosing duct 
and penetrated the substance of the other lobe 
as pi! as that into which the pipe had been 
inserted. 

Some of the lobes injected by the reflux of 
the mercury through the duct, and of which it 
was more certain that the glandular structure 
and not the cellular membrane was filled, were 
dried, and various sections were submitted to 
microscopical examination. At the greater 
extremity they are minutely cellular, the cells 
communicating with each other, and elongating 
as the lobule grows narrower, first at the centre, 
so as to form apparently minute tortuous tubes, 
which tend towards and terminate in a 
central canal, or receptacle, from which the ex- 
cretory duct is continued. On making a sec- 
tion of the corium through the middle of the 
areola the ducts are seen to converge sli 
to the external surface, but there is no inve 
or concealed nipple at this part, as in the Kan- 
garoo. ( Fig. 201 is a sketch of a magnified 
view of this section, with the section of one of 
the dried and injected lobules.) 2 

Thus, prior to and independently of any { 
direct observation of the secretion of theab- 
dominal glands, the anatomical facts f 
to bear upon their disputed function were in- 
dubitably more favourable to the opinion of — 
the German than of the French Drotensont 
for, 1st, the glands are confined to the 
and vary in degree of development at 
ferent periods in individuals of equal size, at- 
taining in some an enormous development; — 
2nd, the secretion is conveyed ow | 
means of numerous long and narrow ducts, — 


4 


4 


tractos, et fluido concreto repletos,trajicere nD, 
area tamen indicatur in cute. Quamvis pili hat par- 
tem tegant, apparet tamen, hos si abstuleris, plaga 
uinqgue circiter lineas longa, tres lata, foram : 
iis, e quibus pili egrediuntur, majoribus, nigris, 
circiter octoginta stipata, forsan ductuam excre- 
torium orificiis. Praterea in hujus medio j 
siancula duarum linearum diametri adest, . 
destituta, sed eminentiunculis inaequalis, inter quas- 
precipne una, milii granum haud aquans, reliqu 
antecellit. Hz sine dubio papille et dactuum ori- 
ficia sunt,” —Loc. cit. p. 54. ‘Cas 


Fig. 201. 


hi twice natural size. 
_ strongly implying its fluid nature, and most 
_ Contrary to the mode in which odorous sub- 
_Stances are excreted; 3rd, the excretory ori- 
fices are by no means extended over so wide a 
_ Space, in proportion, as in the Shrew, but col- 
lected into a point which we know to be not 
_ disproportionate to the size of the mouth of the 
_ young animal, and this point is situated in a 
_ part of the body convenient for the transmission 
_ of a lacteal secretion from the mother to her 


Be ve with an ordinary mammary gland 
that of the Gidithorhynchus differs chiefly in 
_ the absence of the nipple, and, consequently, of 
_ the surrounding vascular structure necessa 
for its erection. But the remarkable modifica- 
____ tion of the mouth in the young Ornithorhynchus 
_ Temoves much of the difficulty which previously 
attached itself to the idea of the possibility of 
an animal with a beak obtaining its nutriment 
_ bysuction. The width of the mouth in the 
_ smallest observed Ornithorhynchus — corres- 


~ 


MONOTREMATA. 


Terminal ducts, and lobe of mammary gland, injected ; 


405 


ponds with the size of the mammary areola; 
and the broad tongue, extending to the apices 
of the broad, short, and soft jaws, with the 
fold of integument continued across the angle 
of the mouth, are all modifications which pre- 
pare us to admit such a co-adaptation of the 
mouth of the young to the mammary outlet of 
the parent, as, with the combined actions of 
suction in the recipient, and compression of 
the gland in the expellent, to effect this essen- 
tially Mammalian mode of nourishment. 

We may presume that a corresponding mo- 
dification of the mouth of the new-born 
animal obtains in the Echidna, since the mam- 
mary glands in this Monotreme* correspond in 
structure, and mode of termination of the excre- 
tory ducts, with those of the Ornithorhynchus, 

As yet the secretion of the mammary glands 
of the Echidna has not been observed ; but that 
of the Ornithorhynchus has been detected not 
only in the stomach of the young (unfe p.401), 
but oozing from the lacteal pores of the female, 
and by more than one competent observer.+ 
Mr. George Bennett, describing his dissection 
of a female Ornithorbynchus shot at Mun- 
doona, New South Wales, on the 14th 
of November, the day before his arrival at 
that place, and which “ had evidently just 
produced her young,” and had very large 
mammary glands, thus records his obser- 
vation of their secretion. “The glands were 
very vascular on the surface, the mammary 
artery ramifying over them in a most beautiful 
and distinct manner. The fur still covered 
that portion of the integument on which the 
ducts terminated, and there was no appear- 
ance of a projecting nipple.” “ How different 
was the appearance in the recent state of this 
mammary gland from that which I had pre- 
viously seen at the Royal College of Sur- 


/ geons, in a specimen long preserved in spirits, 


in which I had the opportunity of witnessing 
the injection of the ducts with mercury by my 
friend Mr. Owen, the mercury exuding, as I 
have seen the milk from the similar ducts, 
upon the integuments.”—Zoological Trans- 
actions, vol. i. p. 251. In a female Ornitho- 
rhynchus, which with her two full-furred young 
were captured alive by Mr. Bennett on the 
28th of December, he says, “ The milk that 
could be expressed from the glands was but 
trifling in quantity; and, in the mother of these 
young animals, such would have been expected 
to be the case, for they were capable of feeding 
upon more substantial diet.” —Ibid. p. 254. 

Crural gland and spur.{—This remarkable 


* See Phil. Trans. 1832, p. 537, pl. xvii., figs. 
2 and 3. 

+ Hon. Lauderdale Maule, Proc. Zool. Society, 
0 ii. p. 145. G, Bennett, Esq. ib. part i. p. 82. 

art ii. p. 141-11. 

$ Meckel, loc. cit. p. 54, calls this peculiar 
sexual gland ‘ femoral,’ observing, ‘‘ ne ipso no-= 
mine de functione judicium proferam, forsan re« 
trahendam, hoc nomen 4 situ impono.” As, how- 
ever, the femoral position is peculiar to the Orni- 
thorhynchus, the gland being popliteal in the Echid- 
na, I prefer a name derived from the word ‘ crus, 
which has a more extended signification to the 
whole hinder extremity. : 


406 


apparatus in the Mo- 
notrematous quadru- 


peds must be classed 
with the accessory or- ~ 
gans of generation in 
the same category with 
the antlers of Deer, the 
spurs of the Cock, the 
claspers of the Shark, 
and other peculiar 
characteristics of the 
male sex. It has been 
already shown, in the 
description of the 
young Ornithorhyn- 
chus, that the external 
of thea tus 
ete so aeeened 
as to distinguish the 
sex at that immature 
period ; a small spur, 
concealed in a cavity 
or socket of the inte- 
pe covering the 
eel, the bottom of 
which closely adheres 
to the accessory tarsal 
ossicle, exists in both 
sexes; a magnified 
view of the part in the 
young female is given 
at fig. 197. As the 
young animal advances 
to maturity the cutane- 
ous socket increases in 


land and spur, 
ithorhynchus. 

( Mechel. ) 
width and depth in the female, but without 
any corresponding growth of the rudimentary 
spur, of which in aged female Ornithorhynchi 


sometimes no trace remains. In the male 
Omithorhynchus the tarsal spur soon begins to 
rise above the socket, and finally attains a 
length of ten lines with a basal breadth of 
five lines, apparently everting the tegumentary 
socket in the progress of its growth. The spur 
(fog. 173, K, e; fig. 202, e) consists of a firm 
semitransparent horn-like substance: it is coni- 
cal, slightly bent, and terminated by a sharp 
point; its base is expanded, and notched at 
the margin for the implantation of the ligaments 
which connect the spur with the accessory flat 
tarsal bone (os basilare, Meckel,) (fig. 173, k, 
d; fig. 202, d.) The base of the spur is co- 
vered by a thin vascular integument. The 
spur is traversed by a canal which commences 
at the centre of the base and terminate. by 
a fine longitudinal slit, about one line distant 
from the point, closely resembling in this 
respect the canal that traverses the poison 
fang of the venomous snake.* Like that canal 
also the spur of the male Monotreme is sub- 
servient to the transmission into the wounds it 
may inflict of the secretion of a peculiar gland. 

is gland (a, Je: 202) is situated in the 
Ornithoth nchus at the back part of the thigh, 
between the femur and the long process from 
the head of the fibula, covered by the integu- 


* De Blainville in Bulletin de la Société Philo- 
mathique, 1817, 


MONOTREMATA. 


ment and the cutaneous muscle. It is of a 
triangular or reniform figure, convex above, 
concave below, or towards the leg; from twelve 
to fourteen lines in length, seven or eight lines — 
broad, and three or four lines thick, with a — 
smooth exterior, invested by a thin capsule, — 
on the removal of which the gland may easil; S 
be divided into a number of small lobes. Its — 
intimate structure, as displayed by a successfu 
injection of mercury, is minutely cellular, like” 
that of the glandula Harderi of the hare or 
goose, but with the ultimate secerning cells” 
more minute; the excretory duct is conaaiay 
from the concave side of the gland, and — fs 
clusters of vesicles are developed from parts” 
of its expanded commencement.* The duct, 
(fig. 180, 1,) which is about a line in width 
sak with pretty strong tunics, descends pres) 
down the back of the leg, covered by the 
flexor muscles and posterior tibial nerve, to 
the posterior part of the tarsus, where it sud- 
denly expands into a vesicle (b, fig. b 
about three lines in diameter ; vesicle is — 
applied to the base of the spur, and a minute — 
duct (c, fig. 202) is continued from it into the 
canal which traverses the spur. 

The tarsal perforated spur and its j 
apparatus are both relatively smaller in the 
male Echidna than in the i = 
The gland is situated lower down, in the 
popliteal region, between the insertions of the — 
deep-seated fasciculi of the adductor femoris” 
and the origins of the gastrocnemius; it is of 
subspherical form, about the size of a pea, — 
with a smooth exterior; the excretory duct, 
wide at the commencement, soon contracts into 
a filamentary canal, which again enlarges to — 
form a small reservoir for the secretion just 
above the base of the spur. fe 

The true nature and use of this apparatus 
has not yet been determined. Its close ry 
with the poison apparatus in other ani 
obviously suggests the idea of a corresponding 
function, but no well. authenticated case of — 
symptoms of poisoning consequent upon a — 
wound inflicted by the spur has been d.: 3 
It seems on the contrary that the Ornithorhyn- 
chus possesses not the instinct of availing itself 
of a weapon so formidable, as upon this thee 
the spur must be, when attacked or ann: 
Mr. George Bennett tried the following experi- 
ment with a full grown wounded but lively 
male Ornithorhynchus :—“ I commenced by — 
placing my hands in such a manner, when 
seizing the animal, as to enable it, from th 
direction of its spurs, to use them with 
the result was that the animal made strer ; 
efforts to escape, and in these efforts scratched” 
my hands a little with the hind claws, and 
even, in consequence of the position in which 
I held it, with the spur also. But althoug 
seized so roughly, it neither darted the 
into my hand nor did it even make an att 
so to do. As, however, it had been sta 
that the creature throws itself on the back wh 
it uses this weapon, (a circumstance not very 


ecoraed. 
oat 


* Miller, De Glandularum 


it. Struct. Pp. 3, 
tab. ii. fig. 10. ee pl 


: MOTION. 


_ probable to those who have any knowledge of 
_ the animal,) I tried it also in that position ; 
but though it struggled to regain its former 
sture, no use was made of the hind claw. 
b tried several other methods of effecting the 
object I had in view; but as all proved futile, 
_ Iam convinced that some other use must be 
_ found for the spur than as an offensive weapon. 
_ Lhave had several subsequent opportunities of 
__ Yepeating the experiments with animals not in a 
_ wounded state, and the results have been the 
 same.”* 
____ Evidence to a like effect is given by the 
_ zoologists of the French expedition in the Astro- 
_ Tabe, in reference to the male Echidna.t An 
objection to the theory of the spur and gland 
_ being a defensive apparatus is their absence in 
the female. 
Since then this apparatus forms a sexual 
character, it may be presumed that its func- 
_ tio n is connected with that of generation. 
_ Whether the spur be a weapon for combat 
‘among the males,—or, like the spiculum amoris 
_ of the Snail, be used to excite the female, the 
_ injected secretion being an additional stimulus, 
_ or whether the spur be mechanically useful 
in retaining the female during the coitus,—are 
_ conjectures which must be verified or disproved 
_ by actual observation. 
. i : 
__BIBLIOGRAPHY.—Shaw, Naturalists’ Miscellany, 
8. General Zoology, vol. i. 1800. Blumenbach, 
ilos. Transactions, ié00 ; and Voigt’s Magazin 
‘den neuesten Zustand der Naturkunde, Band 2, 
Home, Philos. Transactions, 1802, pp. 67 
356. Ibid. 1819. Lectures on Comparative 
atomy, passim. Cuvier, Legons d’Anatomie 
arée, 1799-1805, passim. Ossemens Fossiles, 
tto. vol. vy. 1823. Peron and Lesueur, Voyage de 
decouvertes aux Terres Anstrales, 1807. Meckel, 
age zur Vergleichenden Anatomie, 1808. Fro- 
otizen, 1824. Ornithorhynchi paradoxi de- 


mathique, 1817. Nouvelles Annales du Mu- 
im, tom. ii. 1832. Geoffroy St. Hilaire, Ana~- 
nie Philosophique, tom. i. 1818. Mémoire sur 
~Glandes Abdominales des ts cat bh 

ement présumées mammaires, lesquelles se- 
nt, non du lait, mais du mucus, &c. Gazette 
cale de Paris, 1833. Sur des Glandes Abdo- 
hinales chez l’Ornithorhynque dont la determina- 
ion, comme mammaires, fut en Allemagne, et est 
uveau en Angleterre un sujet de controversie, 
1833. Rudolphi, Abhandlungen der Berliner 
emie der Wissenschaften, 1829. Jaffé, Thesis 
- de Ornithorhyncho paradoxo, Berolin, 1823, 
l, Edinburgh Philos. Journal, 1822. Hill, 
ean Transactions, vol. xiii, 1822. Knoz, 
rmerian Transactions, vol. v. Van der Hoeven, 
va Acta Physico-Medica, tom. xi. 1823. Pander 
D’ Alton, Skelete der zahnlosen Thiere, 1825. 
ant, (Dr. R.) Annales des Sciences Naturelles, 
29, tom. xviii. Miiller, De Glandularum Secernen- 
m Structura penitiori, fol. 1830. Owen, Philos. 

nsactions, 1932, 1834. Proceedings of the 


__* Zoological Transactions, vol. i. p. 236. 
_ + ** Nous n’avons point entendu parler d’accident 
asionné par cette piqfire, et nous-mémes nous 
" vons touché, irrité cet Echidné sans qu’il ait ja- 
_ mais cherché a se servir de son arme, pas méme 
4 - lorsque nous exercions sur elle une assez forte pres- 
Sion,” —Zoologie du Voyage de l’Astrolabe, p. 124. 


= 
¥ 


407 


Zoological Society, October, 1832, March, 1833. 
Zoological Transactions, vol. i. 1834. Bennett, G. 
Zoological Transactions, 1834. Kydoux & Laurent, 
Voyage de la Favorite, 1836, 8vo. 

. (R. Owen.) 


MONSTROSITY.—See Teratotccy. 


MOTION ANIMAL, ANIMAL DY- 
NAMICS, LOCO-MOTION, or PRO- 
GRESSIVE MOTION OF ANIMALS.— 
Amongst the infinite number of objects pre- 
sented by the Deity to our contemplation in 
the sublime spectacle of the universe, there are 
none, relating to the economy of animal life, 
more important in their consequences, more 
calculated to awaken inquiry, or deserving 
of more profound research, than the phe- 
nomena of progressive motion in man and 
animals. 

Life, in virtue of which animated beings 
possess sensation and exhibit the play of the 
vegetative functions, endows the muscular 
system with contractility, and is the funda- 
mental cause of all the motor power of 
animals. : 

The theory of the progressive motion of 
animals presents a most extensive field for 
anatomical and physiological inquiry, far too 
extensive indeed for the space here allotted to 
this subject; it will therefore be treated only in 
outline. The automatic, and several of the 
voluntary motions which belong to the vegetative 
functions of the animal economy, though de- 
rived from the same source as those of progres- 
sive motion, will not be included in this investi- 
gation. 

The theory of locomotion relates to those 
mechanical functions by which animals are 
capable of changing their relative positions 
or distances with respect to surrounding ob- 
jects supposed to be stationary or fixed. 

The locomotive organs of the higher animals 
are composed of a system of levers of various 
forins, orders, and dimensions, so united or ar- 
ticulated at the joints as to give them the re- 
quisite mobility as well as direction of motion. 
The fulcra to these levers are the earth, the 
air, or the water; the active agents of mo- 
tion are the muscles which constitute a 
complex system of contractile organs, firmly 
attached to the levers, whereof the points of 
connexion, amount of contraction, and direc- 
tion of force, communicate to the levers, to 
which they are firmly attached, all the move- 
ments necessary for progression. 

The progression of some animals, such as 
the Annelida and Ophidian Reptiles, is effected 
by the alternate contraction or flexion and 
elongation, or by undulatory movements of the 
body; in others, as Bipeds, Quadrupeds, 
Fishes, Birds, &c., by the alternate approxima- 
tion and angular separation of the levers which 
form the organs of progression. These prin- 
ciples apply to animals, whether their levers 
are represented by wings, fins, or legs, and 
whether the progression is effected on solids, 
in water, or in the air. 

The various modes of animal progression 


408 


are swimming, fying, crawling, climbing, 
leaping, running, walking, &c. The con- 
sideration of these diversified methods of 
progression involves the theory of the mo- 
tion of bodies in general, of the lever, the 
pulley, the centre of gravity, specific gravity, 
and the resistance of fluids, &c.; and, as 
we shall have occasion for constant refer- 
ence to the mechanical principles connected 
with these subjects, they will be first dis- 
cussed; but for the convenience of those 
who are unacquainted with the algebraic 
method of computation and analysis, the 
latter will generally be separated from the 
text. 

Fundamental Axioms. — First, every body 
continues ina state of rest or of uniform mo- 
tion in a right line until a change is effected by 
the agency of some mechanical force. Secondly, 
any change effected in the quiescence or mo- 
tion of a body is in the direction of the force 
impressed, and is proportional to it in quantity. 
Thirdly, reaction is always equal and con- 
trary to action, or the mutual actions of two 
bodies upon each other are always equal and 
in opposite directions. 

Thus if M (fig. 203) be a particle of matter 
free to move in any direction, and if the lines 
MA, MB, represent the intensity of two forces 


Fig. 203. 


Bhi=+ sseceeee eee 


M B 


acting on itin the direction MC, the particle M 
will move towards C by the combined action 
of the two forces, and it will require a force 
in the direction of CM, equal to MA+ 
MB to keep it ina state of rest; but if MA 
and MB (fig. 204) represent the intensities 
and directions of two forces acting on the par- 
ticle M in opposite directions, if MA be 


Fig. 204. 


A M 


MOTION. 


see gon of forces. 


which RN is the diagonal, — 
and consequently into an — 
indefinite number of such 
pairs.* This construction is — 
called the parallelogram of — 
forces. daa 
The resultant of any 
number of forces meeting — 
in acommon point may be — 
ascertained thus: first, let 
the resultant of any two 
forces be found as b . 
and substitute this one force 
for the two components pro- 
ducing it; then combine — 
this new force with one of 
the remaining forces, and continue this process 
until all the forces are reduced toa single foree, 
which is the resultant sought. The following 
geometrical solution will render the subject 
more apparent: let P, P’, P’, &e. (jig. 
represent a number of forces meeting in the 
common point A, and let A P, AP’, A P” be - 
proportional to these forces vely > 
through P draw PR equal and to 
AP’, and through R draw RR’ equal and 
parallel to AP”, and through R/ draw R’ R4 
equal and parallel to A P”’; join AR’, which 
represents the resultant of the four forces AP, — 
AP’, AP”, AP”. A similar opera- — 
tion will serve for any number of forces. 


Fig. 205. 


a 


This figure is denominated the poly- 
If the directions of 
three forces are rectangular, and in dif- 
ferent planes, the resultant may be L 
as follows: let PC, PC’, PC”, (fig. 207) be — 
the intensities and directions of three forces, — 
complete the lelopiped BD; then the — 
forces PC, PC’ have Pr for an eepen 
therefore P r may be substituted for teks ‘ 
forces; and by compounding the forces PC”,~ 
Pr, we get PR the diagonal of the parallelo- 
piped BDr for an equivalent to the three 
forces. This construction is called the 
parallelopipedon of forces.+ “7 
An equilibrium cannot subsist be- 


* 


greater than MB, the particle M will be 
moved towards A by the difference of these 
two forces, and it will require a farce equal to 
that difference to keep it at rest, 

The composition and resolution of forces — 
In the composition of forces it is proposed ta 
find the resultant, arising from any number or 
system of forces acting upon a given point. The 
resolution of forces, which is the converse of 
the former process, consists in discovering what 
forces acting in given directions would com- 
bine to produce a given resultant: Thus, if there 
be two forces F F* (fig. 205), whose directions 
and magnitudes are represented by F N, F’N, 
and if FR, F’R be drawn respectively parallel 
to FN, FN, then by the composition of forces 
we find the magnitude and direction of the 
equivalent or resultant of these two forces to 
be RN, and conversely it may be resolved 
into a pair of forces as RF, RF’ represented by 
the adjacent sides of any parallelogram, of 


~B tween any two forces acting a 
int of matter, if the lines represet t- 
ing the directions of the forees be inclined” 
to each other at any angle; but a third force 
equivalent to their resultant and jn an oppo- 


® Vide Gregory, vol. iii. ch. ii. p. 23. 

t From the same construction the resultant ¢ 
system of forces may be found, dis in diffe 
ier by the method of rectangular co-ordin 

etP Cuz, PC =y, PC’=z, (fig. 2 
by the 47 Euc, Lib. I. we have Pr? = PC*4> 
Cr? = x?-+y?, and PR? = Pr?+4rR? oe 
x? -+- y?-+- 2%, whence the resultant PR 
J/x?-+y?+2*. The position of the resultant 
is thus determined ; let r, r’,r” denote the mm 
known angles formed by the direction of the re~ 
sultant with each of the co-ordinates, and R cos. 
r, Ros. r’, R cos. r” willrepresent the equivalents — 
of the resultant in the several directions of theaxes, 
hence we have Ros. r = x, Reos. r’ 
K cos r” =z, .°- 


«ee 


} 5 
Cos. r= 7’ cos. 1 = Co. ae Re 


site direction toit, will produce an equilibrium. 
= Fig. 206. 
P 


“hipy 
Let N (fig. 205) be the point acted upon by 


any two forces N F, N F’, which form an angle 


FNF*,, and the line N R their resultant, which 
will draw the point in the direction NR. But 
if a third foree NR’, equal and opposite to NR, 
be applied, it will destroy the motion in 
NR, and the point N will remain at rest by 
the simultaneous action of the three forces 
NR, NF, NF’. 

i Fig. 207. 


RE a 
mak 


= 4 Pee © 


~. 
a oO 


_ Centre of gravity—The centre of gravity 
of any body is a point about which, if acted 
‘upon only by the force of gravity, it will ba- 
ve itself in all positions; or, it is a point 
which, if supported, the body will be sup- 
ported however it may be situated in other 
Tespects; and hence the effects produced by 
or upon any body are the same as if its whole 
_ ‘mass were collected into its centre of gravity. 
. To find the centre 
of gravity of any plane 
body mechanically, 
let the plane a e db 
(fig. 208) be sus- 
penced freely by a 
string from the point 
a, to which a plumb- 
line a6 is also at- 
tached — the latter 
will coincide with 
the vertical line a 6, 
which is to be marked 
with a pencil: then 
i gen the plane 
and plumb-line from 
| a second point e, 


_ Fig. 208. 


! when the plumb-line 

will hang vertically 

+ in the line ed, inter- 

 secting a b in c, the point c will be the centre 
of gravity of the plane. 


a 


i. 
7 


“w 
be 


MOTION. 


409 


To find the distance of the head and feet 
from the centre of gravity of the human body 
in a horizontal position; balance the body 
placed upon a plane a é on a triangular prism 
de,asin fig. 209 ; then draw a line on the plane 


Fig. 209. 


close to the edge of the prism; again balance 
the body in another position and draw a line 
as before, the vertical line passing through c, 
the intersection of these lines will pass through 
the centre of gravity. 

After the plan of Borelli, Weber balanced a 
plank across a horizontal edge, and stretched 
upon it the body of a living man: when the 
whole was in a state of equilibrium, in which 
the method of double weighing was adopted, 
by accurate measurements he found the total 
length of the body 

m.m. in. 
= 1669.2 = 65.30853 
the distance of the centre of gravity below the 
vertex == 721.5 = 28.406455 
above the sole of the foot 
= 947.7 = 37.310949 
above the trausverse axes of the hip-joints 
= 87.7 = 3.454729 
above the promontory of the sacrum 
= 847) 0(341519 


As the horizontal plane of the centre of gravity 
lies between three-tenths and four-tenths of an 
inch above the promontory of the sacrum, it 
must traverse the sacro-lumbar articulation 
which is intersected by the mesial plane, be- 
cause the body is symmetrical, and by the 
transverse vertical plane, the sacro-lumbar arti- 
culation must, therefore, contain the common 
point of intersection of all three planes, which 
coincides with the position of the centre of gra- 
vity of the body when standing; but this point 
varies in different individuals in proportion to 
the difference of the weight of the trunk to that 
of the legs, as well as by any change of the 
position of the limbs. 

The centres of gravity of particular figures 
may be found geometrically and analytically, 
as shewn in mechanical treatises; but these 
methods require computations too detailed for 
our limits. 

The attitudes and motions of every animal 
are regulated by the positions of their cen- 
tres of gravity, which, in a State of rest and 
not acted on by extraneous forces, must lie in 
vertical lines which pass through their bases 
of support. Thus, if g (fig. 210, a and B) be the 
common centre of gravity of two bodies whose re- 
spective centres of gravity are g, H, in A 


410 


the whole mass will be supported, whilst in 
B it will fall over on the side of H. 


A 


Fig.210.  B 


In most animals moving on solids, the centre 
is supported by variously adapted organs; 
during the flight of birds and insects it is 
suspended; but in fishes, which move in 
a fluid whose density is nearly equal to their 
specific gravity, the centre is acted upon 
equally in all directions. 

The lever —Levers are commonly divided 
into three kinds, according to the relative po- 
sitions of the prop or fulcrum, the power, and 
the resistance, or weight. The straight lever of 
each order is equally balanced when the power 
multiplied by its distance from the fulcrum 
equals the weight, multiplied by its distance, 
or P the power, and the weight, are in 
equilibrium when they are to each other in the 
inverse ratio of the arms of the lever, to which 
they are attached: the pressure on the fulcrum 
however varies. 

In straight levers of the first kind, the ful- 
crum is between the power and the resistance, 
as in fig. 211, where F is the fulcrum of the 


Fig. 211. 


lever AB; P is the power, and W the weight 
or resistance. We have P:W::BF:AF, 
hence P. AF =W. BF, and the pressure on the 
fulcrum is both the power and resistance, or 
P+W. 

In the second order of levers (fig. 212) the 
resistance is between the fulcrum and the 
power ; and, as before, P: W:: BF: AF, but 
the pressure of the fulcrum is equal to W—P, 
or the weight less the power. 


Fig. 212. 


MOTION. 


In the third order of lever the power | ts 
between the prop and the resistance (fig. 213), 


Fig. 213. 


nS 


where also P: W:: BF: AF, and the pressure 
on the fulcrum is P—W, or the power less the 
weight. . 

In the preceding computations the wees of 
the lever self is Teegleched for the sake n- 
plicity, but it obviously forms a part of the 
elements under consideration, especially with 
reference to the arms and legs of animals, 

To include the weight of the lever we have 


the following equations: P. AF+AF. } AF= 
W. BF-+BF.4 BF; in the first order where 
AF and BF represent the weights of 

portions of the lever respectively. Similarly, 


in the second order P. AF=W. BF+AF-: Fr 
and in the third order P. AF=W. BF-++BF. 


* In this outline of the theory of the lever, the 
forces have been considered as acting ver- 
tically, or parallel to the direction of the f 
of gravity. iy 
The head moving backwards and forwards 
on the atlas acts on the principle of the 
first kind of lever, the fulcrum being placed 
between the power and the resistance. The” 
tibia resting on the astragalus acts on the prin- 
ciple of the second order of lever, when the 
heel is raised by the tendo Achillis, the re 
sistance being between the power and the 
fulcrum, or between the heel and the toes. ny 
In lifting a weight by the hand and bendin 
the elbow-joint, as in fig. 214, in which p tl 
power, or biceps muscle is inserted at a betwee! 
the fulerum f, and the resistance w or b, ¥ 
act on the principle of the third order of lever 
In the latter case, however, the power, in 
stead of acting vertically, is applied obliquely 
and the lever, instead of simply resting on th 
fulcrum, turns upon a point at f, 
Instead, therefore, of estimating the } 
p and w as before, according to their reciproc 
distances from the fulcrum, we resolve 
them into two other forces by pe 
drawn from the fulcrum f to the directions 
the forces p and w. Thus, in fig. 214, | 
not be tow as b f to af, but as the pe 
diculars from fon the vertical line throt 
to that on ac the direction of the inserti 
the 1 ppt a é 
he pulley.—The principles of the si 
pulley are ieactbanedl into th mecha 
animals for the production of motion, 
change the directions of the motions of 
organs in reference to that of the + 


> a 
hMendic! 
~s 


MOTION. 


411 


Fig. 214. 


ing them. There are no examples of the 
ound pulley in animal structures. 
€ recognise the simple pulley in the trans- 
sion of the tendons of the peronei muscles 
gh the groove of the external malleolus of 
man ankle-joint, in the tendon of the obtu- 
‘internus gliding through the groove in the 
chii, in the tendon of the circumflexus 
i passing through the hamular process of 
phenoid bone, in the tendon of the obliquus 
erior gliding through the ring attached to 
frontal bone, and in several other instances 
2 a change of the directions of the limbs 
alts from tendons passing over joints, through 
Oves in bones, or under ligaments, by which 
-muscles are capable of producing effects 
‘distant organs without disturbing the sym- 
try of the body, an effect which, owing to 
mited power of contraction in the muscles, 
be accomplished in no other way. 
uniform motion.—If a body move 
stantly in the same manner, or if it pass 
ual spaces in equal periods of time, its 
is uniform. The velocity of a body 
uniformly is measured by the space 
h which it passes in a given time.* 
velocities generated or impressed on 
nt masses by the same force are reci- 
y as the masses.+ 
uniformly varied.—When the mo- 
of a body is uniformly accelerated, the 
it passes through during any time what- 
oy eh io the square of the time. 

e leaping, jumping, or springing, of 
in any direction, (except the vertical,) 
yaths they describe in their transit from one 
nt to another in the plane of motion are pa- 
lic curves. 
ie legs move by the force of gravity as a 


‘Thus if v be the space passed over by the bod 
1 unit of time, that space x by ¢, or ¢v will 
€ Space s passes over in ¢ units, that is, 
STV. ew eee te wee . 
If a force communicates a velocity » to a 
m, and a velocity v’ to a mass m’, then we 
te Ueno ©) ss 
lly, if f be the accelerating force, the space 
$= 


tv 


= eovveccecessesec(4), 


. - 
4LOttLO 


2, Peeesseeeesr re ). 


pendulum.—To the many instances already 
recognised of the connexions subsisting be- 
tween the functions of living animals and the 
physical sciences, another remarkable con- 
tribution has been recently added by the Pro- 
fessors Weber, whose experimental researches 
satisfactorily demonstrate that the swinging 
forwards of the legs of animals in progres- 
sive motion obeys the same laws as those 
of the periodic oscillations of the pendu- 
lum. In order to ascertain these relations, 
MM. Weber instituted a series of experi- 
ments upon legs of given lengths, both 
in the living and dead subject, and under 
variously modified circumstances. Having 
removed a leg from the trunk at the hip- 
joint, and suspended it by a short thread 
that it might move as if upon the axis of the 
head of the femur; upon giving it an im- 
pulse they found it oscillated nearly in the 
same time as in the living state. They next 
communicated a vibratory motion to a leg sus- 
pended to the acetabulum by the ligaments of 
the hip-joint only, the muscles having been 
previously cut through: in this experiment the 
oscillatory movements were rather less than in 
the preceding. The oscillations of the leg 
of a dead person after the rigidity of the muscles 
had subsided, were still further diminished. 
On comparing the durations of the vibrations 
of the legs in these several states with those of 
the living, they found their periods nearly equal 
or in the following proportions. 


Half 
Length| dura- 
of leg. | tion of 
No. in me- |oscilla- 
tres.* | tion. 
m “i 
1 | 0.831 | 0.370 |An exarticulated freely suspended leg. 
2 | 0.866 | 0.371 |The same. 
A leg suspended to the trunk by the 
3 | 0.831 | 0.355 } ligaments only, the muscles of the 
hip joint having been cut through. 
4 | 0.831 | 0.355 i Jes. of the dead body in its natural 
A living leg swinging uninfluenced 
5 | 0.860 | 0.346 { by the action of muscles. 
6 | 0.860 | 0.322 jA living leg walking on the het ; 
7 | 0.860 | 0.393 1S Beitr ck leg walking on the ball o: 


* A metre = 3.2808992 feet. 
A millimetre = 0,03937 inch. 


412 


From this table it appears conclusive that no 
muscular force is employed or required to pro- 
the leg forwards after it has been raised and 

nt by the flexor muscles, and that the force 
of the earth’s gravity alone on the leg is suffi- 
cient to Siiceaption that purpose. The diffe- 
rence found between the oscillation of the legs 
in the living and the dead body is very small, 
and is attributed by those authors to the elas- 
ticity of the ligaments connecting the leg to the 
trunk, and some trifling differences in the 
length of the legs, but decidedly not to muscu- 
Jar action. An application of the principles 
of the pendulum to the legs of animals mov- 
ing in a vertical plane shows that the durations 
of their periodic oscillations must be respec- 
tively as the square roots of their lengths,* 
estimated by the distance of the centre of 
oscillation ; or thetime of a complete oscillation 
of any leg from behind forwards when inu- 
fluenced only by gravity is to the time in 
which a heavy body would fall through half 
the length of the leg, considered as a com- 
pound pendulum, as the circumference of a 
circle is to its diameter. 

It further results from the periodic move- 
ments of the legs being subordinate to the 
force of gravity, that the same individual 
would necessarily walk slower as he ap- 
proached the equator, and quicker as he ap- 

roached the poles, all other circumstances 
foie equal. For example, let us suppose 
any two persons to be walking in different 
latitudes, whose legs are of unequal length, and 
acted on by unequal gravitating forces, then by 
the theory of the prema the time of the 
swinging forward of their legs respectively will 
be as the square roots of their lengths directly 
and as the square roots of the gravitating forces 
in those latitudes inversely.+ 

Mechanical effects of fluids on animals im- 
mersed in them.—When a body is immersed in 
any fluid whatever, it will lose as much of its 
weight relatively as is equal to the weight of 
the fluid it displaces. In order to ascertain 
whether an animal will sink or swim, or be sus- 
tained without the aid of muscular force, or to 
estimate the amount of force required that the 
animal may either sink or float in water, or fly 
in the air, it will be necessary to have recourse 
to the specific gravities both of the animal 
and of the fluid in which it is placed. 

The specific gravities or comparative weights 
of different substances are the respective weights 

* Let? and / equal the lengths of any two 
pendulums, ¢ ¢’ the times of vibrations, g the force 


of gravity, w tos the ratio of the circumference of 
a circle to its diameter, then 


t= a/ omits rt 
& & 
*. & 


* 22 3:3: Jt LIE x ws0) 00 CBs) 


+ Forasto=-r A/a mies a/> 
hence ¢: ¢’:: a/ =: IN pee 


MOTION, 


of equal volumes of those substances.* Wher 
any solid body is immersed in a fluid and left 
to itself, it will sink if its ific gravity is 
greater than that of the fluid; but if its specific 
gravity be less than that of the fluid, it will rise 
to the surface and be sustained there; and when 
the ppenite gravity of the solid and fluid ar 
equal, the body will remain stationary wherever 
it is placed. When the weight of any 
taken in a fluid is subtracted from its ’ 
out of the fluid, the difference is the weight o! 
a volume of the fluid equal to that of the solid; 
this is to its weight in air, as the specific gravity — 
of the fluid to that of the solid; so that generally 
the specific gravities of solid bodies are as their 
weights in the air directly, and their losses ix 
water or any other fluid inversely. > i 
The specific gravity of air, water, and m 
cury, when the barometer stands at 30 in. 
the thermometer at 55°, being to each other a: 
13, 1000, 13600, it results that all those ani- 
mals whose specific gravities approximat oO 
that of water are nearly 1000 times heavier 
than air, and more than thirteen times lighter 
than mercury, and consequently animals that 
would sink and perish in water could walk on 
ge surface of mercury. ra 
he human body in a healthy state, with 
the chest filled wih, air, is ek ighter 
than water, and its sinking generally depends 
upon the air in the lungs escaping ur der 
the pressure of water upon its immersion. Dr. 
Arnott remarks that if this truth were generally 
and familiarly understood, it would lead to the 
saving of more lives than all the mechanical 
life-preservers which man’s ingenuity will « 
contrive. ° pea 
Atmospheric pressure uces a great va~ 
riety of et Bal = proeetnpe res : 
If we estimate the surface of a man to be equal — 
to 2000 square inches, the pressure of the atmo- 
sphere on his body with the barometer at_ 
30 in. will amount to 30,000Ibs., or about 15 
tons; when the barometer falls from 30 to 27 
inches, the pressure is reduced from 15 to 13 
tons ; we need not, therefore, be surprised that 
variations of atmospheric pressure should be 
attended with corresponding sensations in living 
animals. hal 
The pressure of the atmosphere enables some 
animals (as we shall subsequently prove) to fix 
themselves to rocks with great force, to walk 
up the surfaces of glass windows, to sustait 
themselves in an inverted position on th 
* If W, w are the weights of two substance 
V, v their volumes, 8, —_ specific gravities 


then Sie:i oe aa 
> } 


Vv 

t Let W = the weight of the body in air, W" 

its weight in water or any other fluid, S = thi 

specific gravity of the solid, s = the specific gr 

vity of the fluid, then we shall have the followin 
proportions ; 

W — W’:W::s8:S8>3 


is 


» 
5 
« 


h w— Ww’ 
ence 6 =. Ww s teeter eeee 

w ag 
and s= Ty? sorceress CO 


> 


= 


_ ceilings of rooms in opposition to the force of 
_ gravity, and to hold the mechanism of the joints 
together with a force proportional to their respec- 
_ tive areas. 
_ The air being elastic, its density decreases as 
the elevations above the earth’s surface increase, 
and when the heights increase in an arithme- 
tical progression the densities decrease in a 
geometrical progression ; hence, in the flight 
of birds, the weight of air which they displace, 
and the effective force of their wings must 
oo vary with every change of eleva- 
on. 
_ Animals moving in water at various depths 
are not subjected to the same variations of den- 
sity that are experienced in air, since water, being 
nea So suffers no sensible change 
of volume at the greatest depths of the ocean ; 
but although the density remains nearly con- 
st the pressure increases with the depth, 
being equivalent to about one pound on the 
‘Square inch for every two feet. The specific 
‘Btavity of water being from 800 to 1000 times 
greater than air, its pressure becomes very great 
at the known depths to which many fishes and 
Cetaceous animals descend. 
Resistance of fluids—Animals moving in 
air and water experience in those media a 
sensible resistance, which is greater or less 
“proportion to the density and tenacity of 
fluid, and the figure, superficies, and ve- 
city of the animal. 
An inquiry into the amount and nature of the 
Stance of air and water to the progression of 
mals will also furnish the data for estimating 
; proportional values of those fluids acting as 
fulera to their lcsomotive organs, whether they 
be fins, wings, or other forms of lever. 
The motions of air and water, and their direc- 
exercise very important influences over 
ty resulting from muscular action. 
_ The resistance of a plane moving perpendi- 
eularly to itself in a fluid, equals the weight of a 
column of the fluid of which the base is equal to 
the plane, and the altitude to the depth through 
which a body would fall to acquire by gravity 
_ the velocity of the plane.* 
__ If the direction} of the motion, instead of 
_ being perpendicular to the plane, as before 
_ Supposed, be inclined to it at any angle, the 
__ * Leta represent the area of the plane, v the 
_ velocity, p the specific gravity of the fluid, then 


ae 2 
the height due to the velocity being, the whole 
Betis” 
resistance is . 
e 2 
a2 a p—. weet ceccccccccee( Me) 
___ hence, ceteris paribus, the resistance is as the 
_ square of the velocity. 
: <al Let 4B (fig. 215) be the plane, and x p the 
__ direction of its motion, a 8 pv the angle whose sine 
__ iss, the number of particles which strike the plane, 
_ as well as the force of each particle, will be dimi- 
__ hished in the ratio of 1 to s, therefore the whole 
_ Fesistance will be diminished in the ratio of 1 : s?, 
_ but the effective part of the resistance being per- 
_ pendicular to the plane, the whole resistance in 
_ the direction a £ is to the effective part in the 
on 8 Eperpendicular to a zB, as A £ and B g, 


ins 


f. 


MOTION. 


415 


resistance will be diminished in the triplicate 
ratio of the sine of the angle of inclination. 
When a body is termi- 
nated by a curved surface 
generated by the revolu- 
tion of a plane round its 
axis, and moves parallel 
to that axis, the amount 
of resistance may be ob- 
tained by the formule 
and analysis subjoined.* 


Fig. 215. 


b d 


Fig. 216. 


e 


d 


But the forms of animals, though symme- 
trical, can rarely be considered as mathemati- 
cally regular figures, and consequently many 
of the data for calculating the resistance to 
their movements must be derived from experi- 
ment. 

Passive organs of locomotion. Bones.—The 
solid framework, or skeleton of animals which 
supports and protects their more delicate tissues, 
whether chemically composed of entomoline, 
carbonate, or phosphate of lime; whether 
placed internally or externally; or whatever 
may be its form or dimensions, presents levers 
and fulcra for the action of the muscular system, 
in all animals furnished with earthy solids 
for their support, and possessing locomotive 
power. 

The form, strength, density, and elasticity 
of skeletons vary in relation to the bulk 
and locomotive power of the animal, and to 
the media in which it is destined to move. 


oras 1tos, Hence the whole resistance in the 
direction of the motion will be diminished in the 
ratio of 1 : s8, and will therefore be 


apy s eccccvecceces+(10.) 


2g. 

* Letbead (fig.216) be the section through the 
axis ca of the body whose motion is in the direction 
of ca, draw the tangent e g to any point of 
the curve meeting the axis produced in g, draw the 
ordinates e f and e’ f’ indefinitely near each other, 
also draw e’ a’ parallel to gc, then lete f= zx, 
e f=y,be=z, and s the sine of the angle g 
to the radius 1; then 2 w y is the circumference of 
the circle whose radius is ef and2@ yx ee’ or 
2 yd z is the surface described by e’ ¢ in its re- 
volution about the axis c a, which is the quantity 
represented by (a) in the preceding note, therefore 


ae a oles SEE PROT 5 


will be the resistance on that ring or the differen- 
tial of the resistance to the body whatever 
its figure may be.—(See Gregory’s Mechanics, 
chap. v. p- 521.) 


2uyd z, or 


414 MOTION. 
The number of moveable articulations ina joints, with ridges and protuberances for th 
skeleton determines the degree of its mobility tachment of muscles, and with levers adap 


within itself; and the kind and number of these 
articulations of the locomotive organs determine 
the number and disposition of the muscles act- 
ing upon them. See ArticuLaTION. 

The strength, density, and elasticity of the 
external skeleton of animals have been but 
very partially investigated or made an ob- 
ject of either physiological or mechanical en- 
quiry, notwithstanding their great importance 
in the animal economy generally, as well as 
their office in locomotion. 

A superficial inspection, however, is suffi- 
cient to detect that the shells of those animals 
which reside constantly at the bottom of the sea, 
as the Astrea triduina, Phombus, &c. are more 
dense, and contain a greater number of calca- 
reous lamine than those which swim or float, 
either by means of specific organs of progres- 
sion, such as the Ianthina vulgaris, the Lymne, 
and Hyalea, or upon hydrostatic principles, as 
in the Neutiios, assisted, it is believed, by the 
siphon. Shells are formed with a design to 
resist the greatest external pressure, consistent 
with the least expenditure of materials, and 
with regard to the habits of the animal. The 
bones of vertebrated animals, especially those 
which are entirely terrestrial, are much more 
elastic, hard, and calculated by their chemical 
elements to bear the shocks and strains incident 
to terrestrial progression than those of the 
aquatic vertebrata; the bones of the latter 
being more fibrous and spongy in their texture, 
the skeleton is more soft and yielding. 

The bones of the higher orders of vertebrata, 
such as the Mammalia, which are designed to 
afford large surfaces for the attachment of their 
powerful muscles of locomotion, are constructed 
in such a manner as to combine lightness with 
strength; therefore their surfaces are convex ex- 
ternally, concave within, and strengthened by 
ridges running across their discs: such are the 
forms of the scapular and iliac bones. 

The long bones of the legs and arms of 
Mammalia are piled on each other endwise, 
forming a series of moveable columns, which in 
the standing position are directed vertically ; 
these are designed to support the head, neck, 
and trunk, with all their contents and appen- 
dages, together with their own weight, and to 
elevate the trunk to some variable height above 
the plane of position. 

It would indeed be a problem of no small 
difficulty, if it were proposed to an artist to 
erect a moveable column, com of a de- 
finite number of rods, so united and inclined 
as to fulfil all the objects, for which the long 
bones of the extremities are designed when 
viewed only mechanically, and adapted to 
support the weight of the superincumbent or- 
gans, to present the lengthened dimensions ne- 

to raise the trunk often far above the 
plane of motion, the strength requisite to bear 
the shocks directed upon them both vertically 
and laterally, the symmetry of form and beauty 
of proportion corresponding to the outline and 
functions of other organs, their extremities being 
furnished with articulating surfaces for the 


to perform all the varied offices of locomotic 
n quadrapeds, which have four osseous 
columns to support the superincumbent orgar 
the pressure of the trunk on each leg is 
half that in bipeds; but owing to the he 
zontal inclination of the trunk and the proje € 
tion of the neck and head, the anterior osseous 
pedestals have to sustain the largest proportion” 
of the weight ; and we consequently find that the - 
angle formed by the bones of the anterior ex-— 
tremities at the joint are less, and the direetic 
of the bones nearer the vertical plane in these 
than in the posterior: this arrangement is most 
» 8 a8 pe in the larger Ruminantia d 
achydermata, especially in the Elephant, 
Horse, &e. We an. shecstdas readily per- 
ceive why the shafts of the long bones of — 
ia are pa “ 


the leas — arms of most Mam: 
tia ollow cylinders; the prismatic outlin 
peolossjualéa in the Elephant and Megatheriu: 
The weights which cylindrical or tic 
flexible columns will support perpendicularl 
when their bases and composition are equal 
is, according to Euler,* in the inverse ratio of — 
the squares of their lengths, therefore if we take 
any bones, of similar materials and thickness, — 
but of which the lengths are as 1, 2, 3, 4, 4 “ 
they will support weights without flexion rela- 
latively in the proportions 1, }, }, t 
whilst the lengths increase in an arithmetical 
progression, the weights will decrease in a 
geometrical | Pha omer= the necessity, there- 
fore, for dividing the columns which sustain the — 
trunk by means of the joints, independently of 
the use of the latter for locomotion, is obviou 
According to Galileo, the power of a beam 
or bar to resist a fracture by a force acting late- 
rally, is as the section of the beam, where the force 
is applied, multiplied into the distance of the — 
centre of gravity of the section from the point or 
line where the fracture will end. By applying — 
this principle to the case of bones, we deduce - 
the following propositions, which must, he 
be regarded only as approximations to the tre 
The lateral strength of two cylindrical bones 
of equal weight and length, of which one is’ 
hollow and the other solid, are to each other 
as the diameters of their transverse sections 
Thus, let a b, de (fig. 217, A, B,) be the: 
tion of the two bones: then the strength of 
tube d ¢ is to that of the solid a b as de to ab. 


: ae 
t , 
» 


oe 
Fig. 217. 3 
x ta 
a 
i 
sf 
y is 


* De curvis elasticis, No. 37. wo 


Fig. 217. 


7 e 

if 
‘Upon the principle of this proposition, it was 
long since observed by Galileo that nature 
‘greatly augments, in a thousand ways, the 
ngth of bodies without mcereasing their 
t, and that if a wheat straw which sup- 
is the ear, that is heavier than the whole 
k, were made of the same quantity of mat- 
but solid, it would bend or break with 
greater ease than it uow does. The feathers 
birds as well as the bones of animals pre- 
‘sent similar provision for the combination of 
‘strength, lightness, and economy of material. 
The strength of bones, however, cannot, as 
t possibly be inferred from the preceding 
roposition, be increased with the same quan- 
s of matter indefinitely, because when the 
neter of the tube exceeds certain dimensions 
will become so thin and fragile as to break 
most without offering any resistance. 

The lateral strengths of prismatic bones of 
he same materials are as the areas of their 
ons and the distances of their centres of 
vity directly; and their lengths and weights 


Po the deductions which may be drawn 
the preceding proposition Galileo very 
y concludes that “ there are limits set 

the magnitudes of the works of nature 

md art, and that the size of ships, palaces, 

ind temples, trees and animals, cannot surpass 

certain dimensions ; and he observes that large 
animals have neither the strength nor speed 

_ proportionate to their bulk, and if there were 

ny terrestrial animals much larger than those 
we know, they could hardly move, and would 

be much more subject to the most serious acci- 
dents: and also that it is impossible for nature 
to give bones to men, horses, or other animals, 

_ if they were enlarged to immense heights so as 

to perform their offices proportionally unless 

the structure of bones were composed of ma- 
terials much more firm and resisting, or that 

_ they were made of a thickness out of all 

‘proportion, which would render the figure and 

_ appearance of animals monstrous.” Mr. Banks 

has found that an oak rod one inch thick, sup- 
at each end, will break by its own 

_ weight at the length of 57.45 feet, and a similar 

_ one of iron at 38.223 feet; Emerson also found 

that the cohesive strength of bone is double 

a = of oak, whilst its specific gravity is only to 
Fork of the latter as 1656 to 1170, or as 92 to 


a 


, 


MOTION. 


A415 


65. In the Megatherium and Elephant the 
length of the bones of the legs is small com- 
pared with their diameters, and consequently 
they possess greater comparative strength as 
columns in supporting their ponderous super- 
structures. 

In the thigh bones of most animals an angle 
is formed by the head and neck of the bone 
with the axis of the body, which prevents the 
weight of the superstructure coming vertically 
upon the shaft, converts the bone into an elastic 
arch, and renders it capable of supporting the 
weight of the body in standing, leaping, and 
in falling from considerable altitudes. 

Joints —Where the limbs are designed to 
move to and fro simply in one plane, the gin- 
glymoid or hinge-joint is applied ; and where 
more extensive motions of the limbs are requi- 
site, the enarthrodial, or ball and socket joint, is 
introduced. These two kinds of joints predo- 
minate in the locomotive organs of the animal 
kingdom. Though the ginglymoid joint re- 
stricts the movements of the limbs to one 
plane, yet it secures that precision of direction 
and firmness of step recognized in their motions, 
as well as the steadiness with which they sup- 
port the trunk. The elbow, knee, and ankle- 
joints, in man more especially, though gingly- 
moid, are differently constituted and possess 
different degrees of mobility. The limbs re- 
volving upon the elbow-joint move in concen- 
tric planes, whilst those articulated at the knee 
allow, according to Weber, a rocking motion 
upon each other; the ankle has the greatest 
latitude of motion of these three ginglymoid 
joints. 

The enarthrodial joint has by far the most 
extensive power of motion, and is therefore 
selected for uniting the limbs to the trunk, 
as it is at the enarthrodial joints that the planes 
in which all the limbs move is determined. 

The enarthrodial joints permit of the several 
motions of the limbs termed pronation, supi- 
nation, flexion, extension, abduction, adduc- 
tion, and revolution upon the axis of the limb 
or bone about a conical area, whose apex is 
the axis of the head of the bone, and base cir- 
cumscribed by the distal extremity of the limb. 

In consequence of the structure of the ankle- 
joint, the foot may be directed out of the plane 
of the leg’s motion. 

The limbs, in moving upon or about the 
heads of bones, describe ares of circles, of 
which the centres of motion are the axes of the 
heads of the bones or the tubercles on which 
they revolve. 

eae: * The office of the ligaments 
with respect to locomotion is to restrict the 
degree of flexion, extension, and other motions 
of the limbs within definite limits. 

The strength, form, elasticity, and points of 
attachment of ligaments are sufficient to effect 
the objects above mentioned ; they are, how- 
ever, destined mechanically to limit the motions 
rather than to expend their forces in supporting 
the weight of the limbs suspended beneath the 
joints to which they severally belong. ; 

The. influence of atmospheric pressure in 
supporting the limbs was first noticed by Dr. 


416 


Arnott, though it has been erroneously ascribed 
by Professor Miiller to Weber. Subsequent 
experiments made by Dr. Todd, Mr. Wormald, 
and others, have fully established the mecha- 
nical influence of the air in keeping the mecha- 
nism of the joints together. The amount of 
atmospheric pressure on any joint depends upon 
the area or surface presented to its influence 
and the height of the barometer. The forces 
acting in opposition to the weight of the limb 
are the pressure of the air, and a force em- 
ployed by the ligaments and muscles equal to 
the excess of the weight of the limb, if any, 
above that of the pressure of the atmosphere. 
According to Weber the atmospheric pressure 
on the hip-joint of a man is about 26 pounds, 
The pressure on the knee-joint is estimated by 
Dr. Arnott at 60 pounds. This estimate agrees 
with our measurement of the area of the surface 
of the knee-joint in an adult female, but is too 
small for an adult male which is about 90 
pounds. In the Elephant and Megatherium, 
the pressure of the air upon the joints is 
greater in proportion to the increased bulk and 
weight of their limbs. In the latter the area 
of the plane bounded by the edge of the coty- 
loid cavity, is an ellipse whose diameters are 
seven and eight inches, and therefore present 
a plane surface exceeding 43.9824 square inches, 
which, being multiplied by fifteen, with the 
barometer at 30inches, will be =43.9824 x 15, 
or about six hundred and sixty pounds pres- 
sure upon the cotyloid joint of this greatest 
of terrestrial Mammalia. 

Muscles—The amount and effects of mus- 
cular contraction, the absolute and relative 
power of muscles in reference to their length, 
mass, and obliquity of direction, and the ex- 
penditure of their power to support given 
weights, will now be either simply noticed or 
briefly estimated. 

In the application of muscles to the purposes 
of locomotion we find them so arranged as to 
produce great velocity, and at the same time to 
admit a great extent of motion, still preserving 
the beauty of proportion. These objects are 
obtained, ist, from the oblique directions of 
their fibres towards the tendons; 2d, from the 
obliquity of the direction of the tendon to the 
bones on which they act ; 3d, from the proxi- 
mity of their points of insertion to the articu- 
lations of the bones, or axes of motion in the 
joints. 

The muscles are capable of «contracting (ac- 
cording to the researches of MM. Prevost and 
Dumas) about #, or nearly one-fourth their 
whole length, which, owing to the circumstances 
just mentioned, is sufficient to produce all the 
positions and motions observed in animals. 

It has been already determined by experi- 
ment that the volumes of muscles do not alter 
by contraction, their thickness only increasing 
as they decrease in length, and vice versa. 

The comparative power of muscles in the 
same animal, according to Borelli, may be 
thus estimated :— 

When two muscles are composed of an equal 
number of fibres, or are of equal thickness but 
of unequal lengths, they will suspend equal 


MOTION. 


weights, but their motor powers and the height 
to which they are capable of raising the weights 
will be as the lengths of the muscles. at 
2d. When the lengths of the muscles are 
equal and their thicknesses unequal, their rela~ 
tive powers will depend upon their thicknesses, — 
but they will raise weights to equal heights. 
3d. When the lengths and thicknesses a 
unequal, the weights they will raise will depend 
on their thicknesses, and the heights to whic 
they will raise them will be as their lengths. 
When the fleshy fibres of a muscle lie pa. 
rallel to the tendon, the s which 
they will draw it equals the contraction of the 
fleshy fibres; but when ae’ = are inserted ob- 
liquely into the tendon, space ugh 
which they will draw it will vary with hee vr 
clination. _ 
Thus, let two equal fleshy fibres, AC, B mi j 
Png. 


with 


and produce D C to meet it in P, 
Sp apiece to AB. Now if the poin 
be considered as fixed, and the angle A 
be such that radius : its sine : : AC ; 
length of A C when contracted, then the joint 
action of the fibres will draw the point C to P. 


Fig. 218. 


D 


For with A B, as centres describe the circular 
arcs P E, P F, touching each other at P, then 
it is evident that the point C will, after the _ 
contraction of C A, be somewhere in the are 
E P, because the radius of E P is the . 
of A C when contracted; for a similar a 
C will be somewhere in F P; therefore it 
will be at P, their point of contact. The 
same result becomes apparent from the consi- — 
deration that the forces in the direction C A 
C B are equivalent to forces in the direction 
C P, P Aand C P, P B respectively, of which 
the forces in the direction C P are not counter= 
acted, but gradually diminish and become 2 
when the fibres are at right angles to r 
tendon, that is, when C coincides with P. 
It is here assumed that there is no ob- 
stacle to the free motion of the tendon in 
the line C P, ey 
If the obliquity of the fibres be Jess than 
AC P, the arcs will intersect in some point 


contrary, the obliquity be greater than dl e - 
angle AC P, the arcs will not meet, but C 


will be drawn to P. In this case the contrac- 
tile force is more than sufficient for the object 
to be attained. All other things remaining 
the same, the space C P will be greatest 
when the obliquity is that which is stated in 
the proposition. If A P = $A C, the Z 
A CP is 48° 35’ nearly. 
From the researches of the Professors Weber 
_ we learn that the weight of the extensor muscles 
generally predominates over that of the flexors ; 
_ those of the leg being selected, their propor- 
_ tions in two well-formed healthy subjects were 


"found to be as (2403.2 +) : 810.3 


4} — == 2913.75 :1320.85,* or as 11 
a “* 
to 5 in favour of the extensors, the proportions 

are divided by 2, or halved, to allow for 

the double office which some muscles perform 
of both flexion and extension, according as 

_ either end becomes the fixed point. The pre- 
onderance of the weight of the extensors be- 

‘comes greater ifthe double action of each be 

omitted in the computation and the whole 

weight of each set be substituted; the pro- 

‘portion then becomes, 2403.2 : 810.3, or as 
8 to 1 nearly. 

_ The weight of the extensor muscles, when 

compared with that of the rest of the leg, is in 

_ the proportion of 5 to 9, and to the whole of 

the muscles, including the flexors, as 3 to 4, 

consequently the extensor muscles of the leg 

_ weigh three-fourths of the whole series. 

_Borelli has given approximate values for 
the powers of a great number of the muscles 

_ of the human body, from which we select a 

_ few computations which will convey an idea of 

the enormous amount of their absolute power 

_and the large proportion of it which is sacri- 

ficed in order to gain velocity. Borelli states 

_ that the whole force expended by the muscles 

of the arms, when stretched horizontally, is 

_ 209 times greater than that of any weight sus- 

at at its extremity, and that the force of 

"the biceps to that of the brachialis is as 3 to 2.6, 

_ or as 15 to 13, and their absolute forces as 300 

to 260. He estimates the force of the deltoid 

at 61600 pounds, the sum of the forces of the 
intercostal muscles at 32040 pounds, and of 
the glutei at 375420 pounds. The extensor 

_ muscles of the hip, knee, and ankle-joints 

have also a large proportion of their power 

Sacrificed to velocity; the amount of this inter- 

change has been estimated upon the following 

principles of Borelli. 

_ Let us suppose a porter carrying a weight to 

bein the act of stooping in order to enter a door- 

way with his load; his body is bent, with one leg 
raised from the ground, and the heel of the 


__ * 2403.2 = the weight of the muscles in 
___- grammest acting over one joint of the leg, viz. the 
_ glutei = 936.0, vasti and cruralis = 1092.0, so- 
. is == 375.2, and 1021.1 = the weight of those 
_ flexors and extensors of the leg acting over two 
eins, viz the rectus = 199.2, semitendinosus 
== 128.2, semimembranosus = 206.5, biceps 
== 129, gastrocnemius 358. 
_ + A grain = 0.067508 gramme. 
VOL. 111. 


MOTION. 


417 


other elevated, as in fig. 219; he is sustained in 
this position by the glutei (f), the quadratus 
femoris (y), and the gastrocnemius and soleus 
(2). Then if the weight r = 120lb., the weight 
of the porter 150lb., the line rs be the direc- 
tion of the force of gravity cutting the femur 
and tibia in c and a, the centre of gravity of 
the man be at 6, and the common centre of 
gravity of the man and his load be at a, then 
the weight of the man from the head to 6 will 
be = '3%lb. = 75lb., and of the section 4 
to c, by supposition, is = 47, therefore the 
weight of the are a b c = 75 +47 = 122, 
also by supposition the section c v = 20, 
and consequently the whole arc ¢ bv gr = 
142, also the distances of the directions of the 
muscles from the axes of the joints to the dis- 
tances of the line of gravity are, according 
to Borelli, in the following ratio: } the distance 
J 6 is to the distance m b as 1 is to 8; ov 
is tot vasito 6;}kdistopdas1 to 3; and 
t v to b m as 3 to 4; hence we derive these 
proportions ;— 

tv:bm::r-abvr:gz, 
or 3:4:: 120-4 122: 3223lb. = the pressure 
of the weight of man and load at the point z. 

ap:bm::r+abvdf:s, 
or 3:8::120 $- 150 : 720 = the force of the 
whole weight at s. 

Lb fi:mb::r+tabc:g, 

2E 


418 


or 1: 8:: 120 + 12%: 1936 : = the force re- 
sisted or employed by the glutei muscles. 
Rvostus:2:y, 
or 1: 6: : 23223: 1936 : =—* the power exerted 
by the quadratus femoris; 
Lkd:dp::s:1* 
or 1:33: 720: 2160. The last proportion gives 
the force exerted by the gastrocnemius and 
soleus muscles to sustain the weight of the man 
together with the weight r ; now as the sum of 
. the forces exerted by the muscles f-+- y + / 
= 2 x (1936) + 2160 = 6032, and the 
Weight supported being only 120lbs., it follows 
that the extensor muscles of the leg, to sustain 
this weight, exert a force = 6032lbs., being 
more than fifty times the weight. 

Force of muscles at various stages of their 
contraction.—The variations which the force 
of muscles undergoes in different states of their 
contraction have not yet been thoroughly in- 
vestigated; though it is a subject not only 
susceptible of being pretty accurately deter- 
mined, but also leads us to form a more cor- 
rect hypothesis of the laws which regulate the 
contraction of the muscular fibres, and of the 
physical operation of the vital agents which 
are the immediate causes of the contraction. 

The force of muscles, according to the ex- 

riments of Schwann, increases with their 
ength, and vice versd. His experiments were 
made on the gastrocnemius muscle of a frog. 
The apparatus which he employed consisted 
of a Saat. to which the frog was fixed, 
with the thigh in the horizontal position, the 
leg being raised so as to be perpendicular to 
the board, and the foot again flexed to the 
horizontal position, in which posture the limb 
was firmly fixed; a rod or beam was suspended 
over the board and made capable of turning 
upon it as its axis of oscillation. This balance 
beam was unequally divided with respect to its 
axis of motion, one arm being to the other as 
1 to 6. To the longest arm of the beam a 
scale was separated; to the other arm the tendo 
Achillis (which had been carefully exposed 
and detached from the heel) was attached by 
means of a thread; by this method a very 
small contraction of the muscle caused the 
other end of the beam to revolve through a 
much greater space, so that the slightest con- 
traction of the muscle became very apparent. 
The ischiatic nerve was then laid bare, cut 
through high up in the thigh, and drawn out, 
great care being taken not to injure the sur- 
rounding vessels. The nerve was then laid 
upon two wires, connected with a galvanic 
battery, consisting of a single pair of plates, 
one of the wires being connected with one pole 
of the battery, and the other made to commu- 
nicate with the opposite pole by using a slight 
pressure upon it. The skin was left entire, 
except where the tendon and nerve were ex- 
posed. By this simple apparatus, Schwann 
observed that the force of the muscle was at a 
maximum when at its greatest elongation, and 


* This computation differs from that in the 53d 
prop. of Borelli where he has substituted new 
and arbi values for s and z in the two last aa 
portions, which diminish the values of y and 


MOTION. 


at a minimum at its greatest contraction. In 

a series of five experiments, which were repeated 
at equal intervals, the forces of the muscles at 
different lengths were in the following propor- 
tions : — 


No. of Muscle. Comparative 
, uscle Difference 
Spotl in grains length of in 
ments. weight Muscle. length. . 
Ove sees e+. 14.1 
60 eereeee .17.1 ocebae ween 
a 120 eek oe mel Ger “eee eo 


180.. Pree. seokiit 
" 0 end of experiment. " 
©. cies cmadea kee 
2 ORE 
‘ 900.2 we oc 0020.4, eden 
0 end of exp. 14.4 
0... ccwdep sce Our 
*etee vcee 18-040 sane 
00 0:0 0208s cane n ee 
50 Saeevecca eke 
0 end of exp. 14.1 


0. ccccceese laws naan eee ‘Z 
4. ; 100. ceecceee IDL. cecccccncten 
200... eeeee ee 2de2 
100. ... ee0+--16.8 
0 eee eee ood kaeke ose age ae 
5 100 . + ec cee ohGsku soe See 
‘ 200...... 2000187 
100... .eesece 16.1 
Qeecseees » 11.17 


This table shows that twice the com ive 
length coincides with twice the force of the 
muscle, and that at its greatest contraction the 
force = 0. In the first two experiments the 
increase of force and length of muscle were 
uniform ; but in the last three the ratios of the . 
force and the length varied; the earliest ex- 
periment, however, was performed when the 
animal might be supposed to be nearest to 
its normal condition, and therefore when the re- 
sult approximated most nearly to the healthy 
play of the muscle. 

These experiments of Schwann are d 
to the hypotheses of Prevostand Dumas, as well 
as to those of Meissner, who the pheno- — 
mena of muscular contraction to be due to the 
force of electric attraction, but as the latter in- 
creases in force the more nearly the attracted bo- 
dies approach each other, and decreases as they 
recede in the inverse ratio of the square of the 
distance, and as the force of elastic bodies” 
varies in a ratio differing from that of muscles, 
when their length and force affecting them 
vary, we conclude that the contraction of — 
muscles does not depend upon any of the — 
known laws connected either with electro- 
dynamics or the forces regulating the molecules — 
of elastic matter. a 

If we conclude from the experiments of 
Bergolotti, Mayo, and Prevost and Dumas, 
that the contraction of muscles is unaccom-— 
panied by a diminution of bulk, and that the 
aggregate molecules present equal volumes ar 
are at equal distances from each other, 
ther contracted or not, the electric force would 
remain constant, whilst the muscular foree 
varied; or if with Professors Gruithuisen and 


MOTION. 


Ermann, that the molecules approximate during 
contraction, the magnetic force would increase 
at the same time, and the muscular force is 
observed to decrease, therefore both of these 
hypotheses are inconsistent with the theory 
of the identity of the magnetic and muscular 
forces. 

The power of muscles, however, rapidly 
decreases by exertion, especially in some of the 
lower animals, such as the Ophidian and Batra- 
chian reptiles; the ratio of decrease is in pro- 
portion to the energy of action, until, by con- 
tinued exertion, locomotion becomes impos- 
sible. It has now been sufficiently demonstrated 
that muscles are capable not only of moving 
the levers on which they act with great force 
and velocity, and of prolonging their action 
for a greater or less period, but that they arc 
endowed also with a surplus of force beyond 
what is necessary for locomotion, and which is 
peered to the various purposes of life. 

aving now given a brief statement of the 
mechanical principles applicable to the loco- 
motion of animals, we shall proceed to give an 
outline of their various modes of progression 
according as it is performed in air, in water, 
or on solids ; and in the first place, for example, 
we shall select those that move by means of an 
aeriform medium. 


Secr. II. Flying.—Flying depends on the 
power which animals pos of raising them- 
selves in the air, and of moving through it with 
considerable velocity in every direction. The 
power of flight is denied to a large proportion 
of the animal kingdom, and requires for its 
exercise a certain configuration of body, adjust- 
ment of parts, and modification of structure, 
based on the most profound principles of dyna- 
mics. In flying, as in swimming, the animal 
Moves in a medium which furnishes a suitable 
fulerum to its levers or locomotive organs, 
‘whatever may be their kind or form. Air sup- 
plies the medium to animals that fly as water 
to those that swim. Air, however, being more 
than eight hundred times lighter than water, 
gives a proportionably diminished support to 
the animals which move in it; consequently, 
instead of having the whole or nearly the whole 
weight of the body sustained, as when plunged 
in water, the same animal weighs as much 
More in air as corresponds to the difference in 
the specific gravities of the two fluids, or nearly 
as 1}to 1000. The weight of the volume of 
air displaced by the equal volume of any 
insect or bird indicates the amount of buoyancy 
or force acting vertically upwards, in opposition 
to the force of gravity on the mass of the body 
of the animal acting vertically downwards. The 
difference between the specific gravity of animals 
and that of the atmosphere represents the 
weight necessary to be overcome in flying by 
the action of their locomotive organs; or, in 
other words, whatever may be the amount of 
the force of gravity on the mass of particles 
composing the whole animal in a direction 
vertically downwards, and the resistance of 
the air on its surface due to its velocity, an 
equal force acting vertically upwards will be 


419 


required to sustain it in the air, and a still 
greater force to cause it to rise. It is the vast 
preponderance of the weight of most animals 
over that of the air they displace, which con- 
stitutes the chief obstacle to their flight, in 
addition to their inappropriate form and the 
unsuitable organization of their locomotive 
organs. 

Flight of insects.—The flight of insects 
depends on the same principles as that of 
birds, notwithstanding the dissimilar structure 
of their bodies and wings. The skeleton of 
insects is both light and dense, and, without 
greatly adding to their weight, affords the 
necessary fulcrum for the action of an elaborate 
muscular system. The mobility of the seg- 
ments of the abdomen upon the thorax enables 
the insect to bend upon itself, and to adjust 
the position of the centre of gravity, with 
respect to the articulation of the wings during 
flight. The attachment of the wings to the 
trunk lies above the centres of magnitude and 
gravity, so that the insect is kept steady whilst 
flying. Compared with their volume, the 
weight of insects is less than that of birds: the 
lightness of their skeletons and the diffusion 
through their bodies of trachee and air cavities, 
greatly tend to diminish their specific gravity 
and the quantity of muscular action em- 
presen during their flight. The form of their 

odies is very irregular, but being for the 
most part either cylindrical or ellipsoidal, is 
well adapted to pass through the air with little 
resistance. 

In the Diptera, the single pair of wings is 
articulated to the meso-thorax; in the other 
orders with two pairs of wings, the first pair 
is also articulated to the meso-thorax, and the 
second to the meta-thorax. The wings are 
composed of a duplicature of the common 
integuments continued from those parts of the 
body. In the Diptera and Hymenoptera the 
ratio of the areas of the wings to their weight 
is much less than in the Lepidoptera; and as 
this ratio decreases, the number of the vibrations 
of the wings in a given time proportionally 
increases. Hence it is vastly greater in the two 
former orders than in the latter. The neure 
when injected with air and fluid assist in giving 
expansion and tension to the wings; an office 
compared by Jurine to the support given toa 
sail by its cordage. Insects are capable of 
varying the area of their wings during their 
elevation and depression, by alternately filling 
and exhausting the tubes, which movements 
follow synchronously the expansion and con- 
traction of the thorax. The muscles which act 
indirectly on the wings at the same time effect 
changes in their surfaces, angular inclinations, 
and ratios of velocity during their ascent and 
descent. There is an elaborate mechanism pro- 
vided in the structure of insects relating to their 
flight. The surfaces of their wings, like those 
of birds, are in general slightly convex above 
and concave below. In the Strepsiptera, Or- 
thoptera, and Hemiptera their figure approaches 
that of the quadrant of a circle. In the Diptera, 
Coleoptera, and diurnal Sphinges it is ellip- 
soidal. The figure of the wings varies, how- 

2E2 


420 


Fig. 220. F 


MOTION. 


Areas of wings within the parallels, showing the ratio of increase with their distances from 


the axis of the body. 
1.228 1.07743 0.40631 


0.26 1.28° 


uv 


eee 


<7" 


en ae eS a coe 


‘ 
A 


> se . 


— 
—— 
e<J 


- 
me, 
~s < 


eee ee oO ee Te eee a | 


4 3 2 1 


Distances of parallels from the axis of the body in 0.4 of an inch. ( Morpho automedon, ) 


ever, considerably in different orders of insects, 
and they are here described rather in the 
language of geometry than in that of entomo- 
logy. The ratio of the area of the wings to 
the weight of the insect varies in each order, 
and approximates to a constant quantity only 
in the same order. The wings of insects dimi- 
nish in thickness from their base to their apex, 
and from their anterior to their posterior 
margin;* the strongest nervures traverse the 
anterior margin of the wing, and confer 
on that portion the greatest resisting power. 
The posterior margin being weaker is inclined 
upwards and backwards in reference to the 
direction of its stroke. The plane of the 
wing, as Straus has correctly remarked, is 
therefore inclined at a different angle to the 
horizon at every moment of its descent. By 
the composition of forces the obliquity of the 
wings backwards and downwards gives to the 
centre of gravity an impulse upwards and for- 
wards. The radial and cubital nervures in 
insects supply the place of the bones of the 
arm in birds; and though different in structure, 
they have the same mechanical effect. The 
anterior nervures being articulated to the apo- 


* See Chabrier sur le vole des insects, c. i, p. 424. 


im Pe, 


0 


physes of the wings, and being fixed at their 
extremities upon the two axillary first pieces, the 
latter, with the wings, form a /ever g the 
order, aud when the internal borders of the — 
two axillary pieces are lowered the wings are 
raised, and vice versi; or as the axillaries are 
articulated upon the border of the clypeus, — 
the movements of elevation and depression in 
these produce the contrary movements in the 
wings.* The wings of insects oscillate during 
flight through arcs of various lengths, which 
depend on the distances of the centres of the — 
wings from their axes of motion, and other dy= 
namic conditions. In the Lepidoptera they 
appear to describe an are of 180°,so as to — 
meet each other at each elevation and depres- 


sion, In some other orders the are of 7 
tion appears to be much less. Amongst the 
Coleoptera, in some of which the elytra assis 
the under wing in flight, according to Chabrier, 
the latter describe an are four times as great as — 
the former.t In estimating the number of — 


* See Straus-Diirckheim, loco cit. 212. ‘ 

+ Dans les hannetons chaque aile, en volant 
paroit décrire un arc de plus de 200° cent, tandis 
que celui tracé dans le méme temps les é 
est peut-étre au dessous de 509 cent. See Chabr 
sur le vole des insects, p. 31. 


MOTION. 


strokes made by the wings of insects as well as 
of birds during flight, it is necessary to take into 
‘the account the length of the are in which they 
oscillate. 

The oscillations of the wings of insects are 
too rapid to be numbered by common observa- 
tion. The principles of optics,* acoustics, and 
dynamics have been employed to determine 
them during their flight. According to Bur- 
meister the pitch of the sound made during 
flight varies with the number of strokes made 
by the wings, although the production of the 
sound is perfectly independent of them.t If 
the number of strokes is synchronous with 
the number of vibrations which produce the 
sound, we can ascertain the number of their 
oscillations very readily; but we are not yet 
furnishéd with sufficient evidence that each 
stroke of the wing is coincident with one 
musical semi-vibration to determine this ques- 
tion with precision. According to the analysis 
made on the flight of birds, if the same data 
may be considered applicable, we shall see by 
-Chabrier’s investigations when all other things 
remain the same, that the number of strokes 
made by the wings of insects will vary as the 
“square roots of the weight directly, and of the 
area of the wings inversely. 

In the Coleoptera, the ratio of the area of the 
wings to the weight of the insect is small in 
comparison with other orders. The elytra of 
the Coleoptera add to their weight and surface 
in passing through the air, without contributing 
either to the vertical elevation or horizontal 
velocity of the insect; on the contrary, as their 
surfaces are inclined to the axis of the body 
and the direction of motion, they retard the 
velocity of the beetle in moving against the 


wind. The centre of the forces lies posterior 


to the articulation of the wings, and as the 
angle of inclination of the elytra tends to ele- 
vate the head and depress the abdomen by its 
resistance to the wind, the axis of the body 
becomes inclined vertically during flight. In 
a stag beetle weighing forty grains, the area of 
each elytra measured 0.366364 of a square 
inch, and the true wings, calculated as the 
quarter of an ellipse, gave 0.6263565 of a 
Square inch each, or 1.2527126in. for both. The 
Same measured by a graduated scale gave 
0.62240 in. each, which shows how nearly the 
form of the trie wings approaches to a segment 
of perfect ellipse. Those Coleoptera in which 
the ratio of the surface of the wings is very small 
cannot fly against a strong wind. Olivier says, 
_ “ None of this class can fly in opposition to the 
wind,” but this assertion is opposed by Kirby, 
who states that the Melolonthe Hoplie fly in all 
directions ; others, as the Cicindelx, take short 
flights, and may be easily marked down by 


_ the entomologist. The Cetonie expand their 


Wings in flight without elevating their elytra, as 
is done by other Coleoptera. 

The Dermaptera, though generally on their 
legs, take flight towards evening. The wings 


* See Nicholson’s Journal, 4to. vol. iii. p. 38. 
_ + Remarks on the causes of sound produced by 
Insects in flying, by Dr. H. Burmeister. Taylor’s 
Scientific Memoirs, vol. i. p. 378, 1837. 


421 


of the earwigs are ample; the nervures radiate 
from a common centre to the external margin 
of the wings, which they expand like a fan. 
According to Ray, the tegmina of the Orthop- 
tera assist the wings in flight. The Grillus 
domesticus flies with an undulatory motion 
like the woodpecker, alternately making a few 
strokes with the wings in order to give a pro- 
jectile velocity to the body upwards, and then 
folding the wings to descend on the opposite 
side of the vertex of a parabolic curve. Owing 
to the analogous structure of their wings, the 
Gryllus campestris and Gryllotalpa are capa- 
ble of using them in a similar manner. The 
Hemiptera employ their hemi-elytra to assist 
the wings in flying.* By this means the area 
of the wing is increased, a greater surface is 
given to it for striking the air, the ratio of the 
surface of the wings to the weight of the body 
is augmented, the quantity of action and the 
number of vibrations necessary to sustain it in 
the air is diminished, and the power of flight ~ 
is consequently increased. 

The Lepidoptera are furnished with a far 
greater area of wing in proportion to the weight 
of their bodies than is observed in any other 
flying animal. The under wing approaches in 
figure to the quadrant of a circle, and in many 
species the two meet posteriorly and form a 
semicircle. The anterior and under wings are 
locked together during their descent so as to 
give them a synchronous action, and a compact 
surface to resist the air. The surfaces of the 
two wings on each side increase with the 
distances of their sections from the axes of 
motion; in the Morpho automedon (fig. 220), 
in which the areas of the sections of the wings 
lying between the parallels 1, 2, 3, 4, drawn at 
equal distances from the axis of the body, will 
he seen to increase (the last one excepted) as 
the distances from the centre of motion of the 
wings increase; the effect of which is, to throw 
the centre of resistance to a greater distance 
from the axis of motion, so that the muscles of 
the wing act at a mechanical disadvantage ; 
and the weight of the body being small in 
proportion to the area of the wing, the 
body oscillates considerably at each elevation 
and depression, and its flight is rendered un- 
steady. 

The surface of the anterior wing is less than 
that of the posterior, being as 2.08 : 2.4483471 
square inches, and the sum of the surfaces of 
the four wings is =9.0566942 inches. As the 
solid contents of the body are very small when 
compared to the surface of the wings, we 
naturally conclude that the Morpho has pro- 
longed powers of suspension. The great mag- 
nitude of the wings of the Lepidoptera are 
generally in proportion to the weight of their 
bodies, and the force of their muscular system 
endows them with great powers of flight; but 
it is most frequently accomplished in a zig-zag 
path. In the Pontia brassice the weight of 
the insect is found to be 1.525 gr.; the area 
of the anterior wing 0.6 square inch, the area 


* See Dr. Roget’s Bridgewater Treatise, third 
edition, vol. i. p. 313. 


422 


of the under wing 0.65; the sum of the areas 
of the two wings consequently is =1.25; but 
when placed in the position of flight, as the 
anterior wing lies partially over the under wing, 
the whole effective surface of the two wings 
measures 0.83, and that of the four 1.66 in. 
During re the dorsal planes of the wings 
of the diurnal Lepidoptera are directed verti- 


cally and brought into contact. 
octurnal Lepidoptera,—Many of this order 


have large organs of flight; their wings, which 
in repose lie in or beneath the horizontal plane, 
are triangular, their apices being the most dis- 
tant points from the body when the wings are 


Fig. 


0.208 


MOTION, 


extended, and their areas are in the inverse ratio 
of their velocities, and their distances from he 
centre of gravity. Thus in the Erebus Strix Sig. 
221) the wings are greatly expandedand of a form — 
the best calculated for rapid flight, the i 

of the sections of the wing being, for the r 
part, in the inverse ratio of their distances fr 
the axis of motion; ne the re 

of that of the Pontia, the Morpho, and 
of the diurnal Lepidoptera. The anterior 
is much larger than the posterior, being 
7.175 to 5.095 square inches. The area | 
four wings is therefore about 12.270 inches, 
which, being very considerable in f d 


221. 


0.419 


0.707 


0.8314 


0.987 


1 


1.3225 


Areas within the parallels. 


1.5834 


1,5534 
oh 


1.545 


1.2 


MOTION. 


to the cubic contents of the body, endows this 
insect with great powers of suspension in the 
air and with great velocity of motion. The 
triangular figure of the wings prevents the un- 
steady undulating progression observed in the 
diurnal Lepidoptera, and the flight is conse- 
quently more direct as well as more rapid. The 
wings of many of the moths are of considerable 
dimensions. The largest male Atlas moth in 
the collection at the British Museum measures 
5% inches on each side, estimated from their 
axes of motion to the apices of the wings, pre- 
_ senting a total area of 264 square inches. If 
the force of the muscles acting on the wings is 
proportional to their areas, they must possess 
the most extensive power of flight. The Bombyx 
mori, or silk-worm moth, is stated to travel 
more than a hundred miles a day.* 

The Neuroptera have a separate set of 
muscles appropriated to the movements of 
each wing, which being detached can be 
moved either synchronously or independently 
of each other: the muscles also are actually 
inserted into the wing, instead of moving 
them indirectly, as in other orders of insects, 
The surfaces of the four wings of the Libellule, 
or dragon-flies, are nearly equal in most species ; 
they are always expanded in repose, and ex- 
tended horizontally at right angles to the axis 
of the body, so that they take flight in an in- 
stant. Their figure is lanceolated. The ratio 
of the united areas of the four wings to the 
weight of the body is greater than in the Cole- 
optera and Hymenoptera, and the muscular 
power is proportionally augmented. ‘The arti- 
culation of the wings being situated above the 
centre of gravity keeps them steady in flight: 
their velocity is very great, exceeding that of 
the Swallow. Leeuwenhoek once observed one 
of this tribe in a menagerie 200 feet long, 
chased by a swallow ; the insect flew with such 
velocity, and turned to the right and left in all 
directions so instantaneously, that the swallow, 
with all its powers of flight and tact in chasing 
insects, was unable to capture it, the insect 
always keeping about six feet in advance of the 
bird. The great length and surface of the 
wings of the Libellule, and the power of the 
muscles acting on them, is such that they appear 
to be never tired of flying in quest of their prey. 

In a specimen of the Hshna maculatissima, 


____ which weighed fourteen grains, the area of the 


anterior wing was 0.7324 in. the posterior 
0.8988 in. and the area of the four wings 
3.26408 square inches. The preponderance of 
surface in the posterior wing enables the Libel- 
lulz to change the direction of their path of 
Motion with great facility, and to capture their 
prey on the wing. «Previously to taking flight, 
this Ashna exerts a vibratory movement with 
its wings; the oscillations are made in very 
minute ares, and with great rapidity, producing 
a faint though distinct sound. The pitch indi- 
cates that the wings perform ninety-six vibrations 
inasecond. On taking flight the wings oscil- 
late through larger arcs, with a less number of 
vibrations, the amount of which it is not easy 


* Lin. Trans. vol. iii. p. 40. 


423 


to determine, and does not depend, as some 
distinguished entomologists have supposed, on 
their mutual friction. 

In a Triphena pronuba, weighing 8.545 
grains, the area of the anterior wings measured 
0.6213, and that of the under wings 0.68 
square inches, making the sum of the areas of 
the four wings 2.6026 square inches. 

In the Hymenoptera the ratio of the areas 
of the four wings to the weight of the 
insect is less than in the Neuroptera, and 
they are consequently obliged to make a 
greater number of strokes in the same inter- 
val of time in order to suspend themselves 
in the aig. The areas of the upper are greater 
than those of the under wings. When ex- 
panded they are retained in the same place, 
and are linked together by means of small 
hooks, so that the upper and under wings act 
simultaneously and with greater power. A 
humble bee, which weighed 6.2 grains, had 
wings the sum of whose areas measured 0.366 
of a square inch, or rather more than sth of a 
square inch to each grain weight of the body. 
Bees are not only celebrated for the geo- 
metry displayed in the structure of their cells, 
but also for the precision with which they re- 
turn to their homes by the shortest path or in a 
straight line. The collectors of honey make 
use of this fact to discover their nests. Having 
captured two of these insects, they separate 
them some yards from each other, and on setting 
them free, ascertain with an instrument the 
angles respectively made by the lines of their 
flight with that between the points of their de- 
parture, then the point where the two lines of 
direction intersect each other indicates the posi- 
tion of the nest. The humble bee, wasp, and 
hornet fly with great force, but owing to the 
weight of their bodies, compared with the areas 
of their wings, cannot fly with much speed 
against a strong wind, so that a person might 
easily outstrip them by running in the same 
direction against the wind. When disturbed, or 
before leaving their abode, they wheel round the 
spot in a large circle, and then fly off at a tangent 
to some part of the curve. The Ichneumons are 
provided with a far greater expansion of wing, 
In proportion to their weight, than the Bees, 
and can consequently sustain themselves in the 
air with less expenditure of muscular action. 
In a species of ichneumon allied to Ophion 
luteus, which weighed 0.5 gr. the areas of the 
anterior wing measured 0.0832 in. the poste- 
rior 0.0480 in. the sum of the two wings 
0.1322 in. and that of the four = 0.2644 in. 

The Diptera are furnished with only two 
wings, which when in repose lie directed 
obliquely backwards upon the abdomen; their 
figure is nearly that of an ellipse, and their 
areas are ample when compared to the weight 
of their bodies. Three examples of Musce vo- 
mitoria for instance were found to weigh 2.4375 
grains, which gives for the mean weight of each 
0.8025 gr. and the mean areas of both wings 
were found to be from 7th to Ath of a square 
inch. Instead of posterior wings they have 
poisers, the articulation of which to the thorax 
is placed more posteriorly than in the four- 


424 


winged insects, so as to lie above the centre of 
gravity. According to Dr. Derham, if either 
a poiser or winglet be cut off, the insect flies as 
if one side overbalanced the other, till it falls 
to the ground ; and if both be removed, it flies 
unsteadily. Shelver states that the removal of 
either winglets or poisers deprived the insect of 
the power of flight altogether. The pneumatic 
pressure which retains them inverted to the 
ceilings of rooms, gives them a position favour 
able for flying off instantaneously, the centre of 
gravity being below the articulation of the 
wings, enabling them to regain the pendant 
position of the trunk in flight. 

In the crane fly the centre of gravity is ad- 
justed, and the direction of flight directed by 


MOTION. 


. a 
4 
its long legs ; the two fore legs being extended 
forwards, and the four hind legs backwards. — 
According to Kirby, the one nts the “*” 
prow, the other the stern of a ship. The velo- 
city of the house, and large flesh flies (Musca 
domestica et vomitoria) appears to be from 
five to six feet in a second, or about four miles 
in an hour ; but if favoured by the wind, they 
are seen flying round the ears of horses when tra- 
velling at the rate of from ten to twelvemilesin — 
an hour.* Lg 
The following table presents at one view the — 
proportions of the areas of the wings in square — 
inches to their weight in grains of various spe= — 


—<— ¢ 


cies of insects which have been alread 
scribed in the text. 


Order. ies, Area of Wings in Weight 
eas poh A iaake pay tA 
CoLeorrera .......| LucanuS cervuS....eo...+| 1.2527126...sccce] 40% ’ 
Hymenoprera .....| Bombus...... eeadiccecce| O:966)eFcb cutesy eee r 
Ophion luteus .......+++-| 0.2644......... ee] 0.5. " 
DiprTera ........++| Musca vomitoria .........| 0.083333 or 7,.....] 0.8025. i* 
LEPIDOPTERA ...... Pontia brassiee ...6.56060)] 2:50 2s cediic cc vet teen i 
Triphena pronuba........| 2.6026 ..+seesse..| 8.545. 
NevuropTera ......} A’shna maculatissima..... 3.26408 |... «eso oes) oaes 


By the help of this table we are enabled to 
compare the proportions of the area of the wing 
to the weight of the insect in d.fferent orders, 
and to estimate the relation between these pro- 
portions and the absolute powers of flight, 
when the latter have been ascertained by expe- 
riment. 

Ifthe velocity and power of suspension varied 
in insects precisely in the same ratio as the 
areas of the wings to the weight of their bodies, 
we should be enabled to compare with tolerable 
accuracy the relative powers of the flight of in- 
sects from data similar to the preceding, but 
there are several other mechanical and physio- 
logical conditions involved; such as the ratio 
of the force of the muscles to the areas of the 
wings, and the figure and structure of the latter. 
The Lepidoptera which have the greatest 
surface of wing in proportion to their weight, 
should surpass all other insects in power of 
flight, yet the diurnal section at least yield to 
the Libellule in velocity, if not in the duration 
of their suspension in the air. From the pre- 
ceding data we conclude, that to render a man, 
whose weight is 150 pounds, capable of sus- 
pending himself in the air by the assistance of 
artificial wings, with the same facility as in- 
sects, would require an extent of surface be- 
yond the control of his muscular force, and 
consequently that the act is impossible. 

Flight of Birds.—In the organization of 
birds, we observe that many parts common to 
other animals are modified, the power of the 
muscular system is increased, and new forms 
of matter are introduced to confer on them 
the power of flight. The bulk of birds is 
less than that of quadrupeds of equal strength, 
and owing to many of their bones being per- 
meated with air, and their skin clothed with 
feathers, their specific gravity, and conse- 
quently the demand on their muscular power 


are diminished.t Instead of the cylindrical — 
form observed in animals which move ex- — 
clusively on solids, the anterior extremity of — 
birds is expanded into a triangular surface, of 
which the apex is the distal, and the base is the 
proximal section of the wing in reference tothe 
axis of rotation. The arm is articulated to the — 
trunk by a ball and socket joint, permitting all the - 
freedom of motion necessary for flight, whilstin 
consequence of the axes of motion oe 

moid joints of the fore-arm being di ei 1 
perpendicularly or obliquely to the ascent and 

descent of the wing, it is prevented from yield- 

ing to the resistance of the air during elevation 

and depression, and is more conveniently folded — 
on itself during repose. The surface of the 
wings may be increased or diminished by — 
abduction and adduction, in consequence of — 
which the resistance of the air to their motion — 
may be proportionally varied in the up and 
down strokes. The amount of this resistance is 
also varied by the surface of the wing being © 
convex above, and concave below. The feathers — 
are moreover provided with a curious me- 
chanism by which the barbules lock into each 
other, so as to unite all the parts of the vane, 
and present a continuous surface to the air 
The ten primary and the secondary feathers, 
which have the greatest leverage, are inserted 
into the arm and fore-arm, and directed so 
as to produce the greatest surface of wing 


-- 


* See Kirby and Spence, vol. ii. p. 357. 

+ 1. The Pelicanus onocrotalus is five feet 
length, but its skeleton weighs only twenty-th 
ounces, whilst the whole animal weighs twenty- 
pounds. See Roget’s Bridg. Treat. vol. i. p. 4 

2. The skeleton of the Carrion Crow whi 
weighs only twenty-three grains, Jaquamin, 
Sci. Nat. series 2, 11, p, 2718. 

3. Many entire Humming Birds weigh only 
eighth of an ounce, or one drachm. 


MOTION. 


without very sensibly increasing its weight. 
The scapulars which have the least velocity 
are shorter and weaker. The length and 
strength of those feathers which contribute so 
largely to increase the area, vary directly with 
the velocities of that portion of the wing to 
which they belong. The ratio of the area of the 
wings of birds to their weight is by no means 
constant. It is least in the Cursores, such as 
the Ostrich, Cassiowary, and Emeu ; greater 


in the Insessores, as the Raven, Crow, and 


Humming-bird ; and greatest in the diurnal Rap- 
tores, as the Eagle, Falcons, and Vultures. The 
wer of flight in birds, provided the muscular 
rces vary in proportion, is as the areas of their 


wings directly, and as their specific gravities in- 


versely. Owing to the triangular figure of the 
expanded wing, the area of its sections dimi- 


 nishes as their distance from the centre of gra- 
_ yity increases,and from the same cause the areas 


are in the inverse ratio of the velocities corres- 
ponding to the distances of the sections from 
e axis of motion. The centre of resistance 


coincides very nearly with the middle of the 


length of the wing from the shoulder-joint to 
the tip. The wing is moved on the princi- 
ple of the third order of levers, and the power 
is applied sufficiently near the axis of motion 
to produce a considerable relative velocity. 
The power of the muscles acting on the wing 
is increased in proportion to their mass, being 
to those of the inferior extremity (according to 
Borelli) in the proportion of more than three to 
one, their absolute power in proportion to the 
weight of the bird being as 10000 to1. In 


_ order to give the osseous framework the surface 


and strength necessary for the attachment of the 


— pectoral muscles which act on the wing, 
the sternum is carinated, whereby its surface is 
increased in proportion to the mass of the mus- 


cular fibres which are inserted into it, and the 


_ shoulder-joints are strengthened by the elonga- 


tion of the coracoid processes, and the magni- 
tude of the clavicles. The fixed condition 


of the ribs and vertebral column tends also to 


strengthen the thoracic sections of the bird, and 


_ enables it to resist the enormous muscular force 


applied to it during flight.* This brief outline 


_ of the manifold adaptations necessary for aerial 
_ progression will give some idea of the number 
and complication of the elements which enter 


into the composition of so small a fabric, and of 


the enormous muscular power with which birds 


are endowed, compared with their bulk and 
weight. When a bird rises from the ground, 
and at the moment it begins its flight, the first 


_ impulse is communicated to its centre of gravity 


by the sudden extension of the legs, as in lea 

ing. During this action the humerus is raised ; 
the wings are unfolded and spread out hori- 
zontally by the extension of the fore-arm, and of 


* The position of the scapulo-humeral joint with 


425 


the carpal, metacarpal, and phalangeal bones. 
The force resulting from the sudden extension of 
the legs elevates the whole mass of the bird 
above the plane of position, and the body thus 
raised being deprived of the support previously 
afforded would begin again to fall by its own 
weight, as soon as the projectile force became 
insufficient to sustain it, but the wings having 
in the meantime been spread out to their fullest 
extent, are made to descend with great velocity 
by the contraction of the powerful pectoral 
muscles. In consequence of the planes of the 
wings being disposed either perpendicularly, or 
obliquely backwards to the direction of their 
motion, a corresponding impulse is given to the 
centre of gravity. The resistance of the air to the 
wings during their depression through a greater 
or less are of a circle becomes greater than the 
force of gravity on the mass of the bird, together 
with the resistance of the air on its body due to 
its velocity, and consequently the bird rises. 
During the ascent of the wing, the opposite 
effect takes place. The bird has not only to 
encounter the resistance which the air opposes 
to the motion of the wing during its back stroke, 
but also the resistance due to its figure when in 
motion, as well as the force of gravity. These 
are so many forces tending to neutralize the 
down stroke of the wing, and to produce an 
opposite effect, so that there will result a 
motion, the amount of which may be pretty 
nearly ascertained when the necessary data are 
obtained by experiment. 

The principal data required for computing 
the quantity of muscular action expended, the 
velocity of the centre of the wing, and the num- 
ber of its periodic oscillations necessary to sus- 
tain the bird in the air, may here be briefly 
stated. 1st. The area of the horizontal section 
of the body of the bird: 2d. The area of the 
two wings whilst they are lowered. 3rd. The 
area of the wings whilst they are raised. 4th. 
The velocity with which the bird is driven 
through the air. 5th. The velocity with which 
the wings are lowered. 6th. The velocity with 
which the wings are raised. 7th. The respec- 
tive durations of the elevation and depression of 
the wings. 8th. The weight of the whole bird. 
9th. The weight of an equal volume of air. 
10th. The resistance of the air due to the 
figure and velocity of the bird. 11th. The ratio 
of the resistance which the air opposes to the 
wings during their elevation and depression, 
12th. The ratio of the resistance of the air to 
the time of an elevation of the wings to that of 
a depression. 

These are the principal data which are deemed 
necessary for estimating by dynamics the amount 
of the force employed by birds during their 
flight.+ If the area of the wings of birds always 
preserved the same ratio to their weight, the 


respect to that of the great pectoral muscles throws 


the centres of gravity and figure below the axis of articulation of the wings,so that the animal is 
kept steady in flight, whilst its figure is such as to enable it to glide through the air with the least pos- 


sible resistance. 


+ Let us suppose the bird to endeavour to rise perpendicularly in the air by equal flappings of its 
wings in a vertical direction, and let s = the area of the transvere section of the bird, A = the area 


_of the wings whilst they are depressed, A’= the area of the wings whilst they are elevated, wu == 
the velocity with which the bird rises in the air, V = the velocity with which it depresses its 


426 MOTION. 


velocity of the centre of the wing would be the descent in the wing were constant, the nur ber 
same in all birds, and if the are of vibration of flappings would vary inversely as the dis- 
and the ratio of the time of ascent to that of tance of the centre of the wing from the axis of 


wings, V‘ = the velocity with which it elevates its wings,* ¢ = the time reckoned from the mo- 

ment when the wings begin to be depressed, + = the time of a depression, +‘ = the time of an 

elevation, W = the weight of the bird, r = the weight of a cubical foot of air, g = the velocity 

acquired by gravity in an unit of time, & = a constant coefficient, by which we multiply the product 
2 


=" in order to get the expression for the resistance of the air to the rising of the bird, 


is therefore wk s = K = asimilar coefficient for the expression of the resistance of the air to th 


& 
depression of the wings, K’ = a similar coefficient for the resistance of the air to its elevation. 
During the depression of the wing the bird is drawn downwards by the force W, arising from its own 


weight, and by the resistance of the air to its rising, namely, w k s but it is driven upwards | ; 
the resistance which the air opposes to the motion of the wing, that is, r nate, hence 


the equation to the motion will be 


Wok AsO? ets em 
g dt 2g 2g 


7 8 


rf 
2W ark A (V—u)?—m k 8 u2—2 W g..erccccccccessecsseees(la) ‘ 


These are approximative values. The motion of the wing being very quick, we may considers to 
be constant during a depression, and if u,, u, be the values of u, at the beginning and end of the 
depression, equation (12) will become Be 


4 WwW (u,—u,) = v{ T KA (V—tu,) 8 ane T ks 13 —2 W g}. os cokes lee ) 
Similarly if w,, u, be the values of u at the beginning and end of an elevation, the equation for he 
motion will be 7 


“}) 


2W(u,—u,) =—7{r KA’ CW + u,)*+wrksuZt+2 Wg}. ee eveeeere rd © is 
By adding the two latter equations together we have 


QW(uy—u,)==t{ mK A(V—uy)*—a ke 8 ug —2We}—r' {we K'A( V0, 2-9 ks u2+-2 W gece eens a5) 


Since, at the end of every flapping the wings are supposed to be in the same position as they wel 2 
at the beginning of it, we must have ; a 


Vr=V' Veveaccccccerssccccccersccneresesesecssel 


The two equations (15) and (16) express the conditions under which the bird may acquire a given 
motion, the nature of which is shown by the variation u, — u, which the velocity u undergoes in the 
time + + +. If we suppose the motion of the bird to be uniform during each flapping u, =u, = nt 
and if we take the value of V’ in equation (16), equation (15) will become : 


=tr er KA (V—u,)—aK' A’ (Ve+ ur’ P4417) 7 wk s u2—(7r +7) r 2Weg. .. 7) 


In order to fly, the bird must expend a quantity of force sufficient to overcome the resistance of hi 
air to the motion of the wings, and, considering the velocity of the bird to be constant during ea 
movement of the wings, the quantity of force expended in a depression will be 


V—un,)2 7 
) wK ace Ve, 
and in an elevation : 
wk AW +4) ye, 
2g 


If we now sup u, =u, as before, and substitute the value of V’, we shall have for the wh 
force expended in an unit of time oS 


erat KA(V—u,) + Ka (tery : . odbt ge 


, 

(1 

pie 
Let +’ = p+, and K’A’ = q KA, equation (17) then becomes r 


“Ts 


0 =P Vu) —4 (V +p —@ +P) ES g—@+e) ANH 


aKA —" 


* V and V’ are supposed constant during the times of clevation and depression, respecti and are referr 
to the centres of the wings. ; be f Sir 7 a 


"Ta 


MOTION. 427 


_ motion; but according to our experiments the whilst the areas of their wings are respectively 
weight of the Pigeon is 4347.344 grains; of 0.6198, 1.11, and 0.054 feet : hence, we see 
the Rook 4170.25; and of the Canary 229; that in these instances, as probably in other 


aud solving it with respect to V, we have ; 


Vapit! a/ prt 3 Axton EAL i abt SUP ee 
py taj (Cy eee (19) 


and supposing the same things in (18), it will become 
mKAV § 
2g (P+ Pe 


Here we may substitute for V its value found in equation (19). If the bird merely supports itself 
_ in the air without rising or falling, v, = 0, and the expressions for V and the force expended in an unit 
Of time, viz. (19) and (20) will become respectively ‘ 


PPV —uP+ a (V+ pu)? } eveeeeseeceeerseeee ee (20) 


\E gtr 208 
pP—q *wKA 


>) Cees eeeeeteoeecssecseseeeesse(al) 


wPtq, /Ptr 2Ws 
P-Pt’ eee ORS 


ee cccerccccccceccccccesseseers (2a) 


We may suppose q to be known from the figure of the bird and the power which it has of expanding 
the wing in a depression, and closing it during an elevation, so as to mcrease and diminish the surface 
‘and resistance alternately; and in order to find the least quantity of force necessary to sustain the 
bird, we must give to p such a value as will make the expression (22) a minimum. 
_ All other things being the same, we see that the quantity of force expended is proportional to the 
W%, and is alsoinversely asthe ./density of theair. Let us take, as an example, the data given by M. 

Chabrier with respect to the Swallow. W = 0.01526 kil. w= 1.25kil. A = 0.0086 met. car. g = 
9.80422 met., now from experiment it is found that a plane surface very nearly equal to the surface of a 
swallow’s wing will produce a resistance in air equal to the weight of a column of fluid, whose 
base is the plane and altitude between one and a half, and twice the height due to the velocity with 
which the plane is moving ; if, therefore, we suppose the resistance of the wing to be a little more on 
_ account of the concavity of its surface, and consider the altitude just twice the height due to the 
_ velocity, K will =2. It is also evident that p > 1 andq < 1, and by giving different values to g, we 
i = obtain the corresponding values of p. 

Let g=}, then when (22) is a minimum. 


p = 3.073 

V= 8,18 = 26.8304 feet. 
(22) = W 10.36 = 33.784 feet. 
2. Let g = Jeececccvccccccccscccccc ep = 1.866. 

V = 6,9] = 22.6648 feet. 

. (22)==:W 8m.39 = 27.5192 feet. 
De Oo LRt Joc cc ees cccccccvecccccvep = 1.6 
V = 6,81 = 20 3368 feet. 
(22) = W 7.95 = 26.0660 feet. 


We may observe that the several values assigned to g do not produce any great variations in the 
values of V and (22), we may, therefore, with tolerable accuracy conclude that a bird which just 
.'é rts itself in the air, expends as much force every second as would be sufficient to raise its own 
weight a height of 8 metres or 27.5192 feet. The mean velocity of the descending wing is about 
_ 7 metres or 22.96 feet per second, and the velocity of the ascending wing is about one-half of it. 
_ Let us now take the distance of the centre of the swallow’s wing, from its axis of motion, to be three 


- inches, and that it oscillates in an arc of 120°= sy then the length of this are will be found 


o by the following proportion 1 : 3 8s : 2% = 6.2832 inches; the velocity divided by this 

length is = 43.85, being the number of arcs which would be described by the descending wing in 

_ one second, but the ascending wing takes 1.866 seconds to describe the same number of arcs, conse- 

oe «sgt this number, divided by the sum of the times taken by each wing, namely, 2.866, gives 15.3, 
the number of flappings, each consisting of two arcs, per second. 


Such is the result by Chabrier’s formula. If we apply the same formula to the case of the Pigeon, 
el is 14.9, or nearly 15 flappings per second; but actual observation proves this to be 
ly three times the real number; a similar discrepancy is observed in the case of the Rook, 


; 
E 


A 


428 


dissimilar orders, the areas of the wings do not 
as the weights of the birds. 

e ratio of the times of the descent and as- 
cent of the wing will cause a corresponding 
difference in the ratio of the resistance of the 
air, which is not as the velocity simply, but as 
the square of the velocity. The velocity of the 
wing varies according to the celerity with which 
the bird moves, and it moves through a greater 
or less arc according as the bird merely sus- 
pends itself in the air or is in rapid motion, on 
the rational supposition that birds employ their 
locomotive organs in such a manner as to econo- 
mize as much as possible the expenditure of 
their muscular power. We find by the an- 
nexed analysis that for this purpose the ratio of 
the time of the descent of the wings to that of 
their ascent is nearly as one to two, and that the 
ratio of the resistance of the =p to that of the 
down stroke lies between one-half, one-fourth, 
and one-fifth. In the Swallow, for example, in 
order that the bird may merely sustain itself in 
the air, the centre of the wings, according to 
Chabrier, must descend with a velocity of about 
seven metres, or 22°9662944 feet per second, 
which, we find by the annexed analysis, gives 
15°3 for the number of vibrations, and for the 
minimum amount of action expended in the 
same time, a force which would raise its own 
weight to the height of 26°246 feet. 

The ratio of the time of the ascent and de- 
scent of the wing becomes much greater when 
the bird moves against the wind, suppose about 
forty-eight feet per second, or in rapid flight; 
and the velocity of the descent of the wings, 
and quantity of action expended, will augment 
in proportion. The great quantity of action ex- 
pended in flight tends to confirm the views of Bo- 
rellirespecting the vast power with which the pec- 
toral muscles of birds are endowed. In small 
birds the oscillations are performed with such 
great rapidity, that they cannot be numbered 
by the eye; but in the finches and humming- 
birds, the oscillations of which produce a musi- 
cal note, the pitch will enable us to determine 
with accuracy the number of oscillations in a 
given time. In large birds, the wings move 
through arcs of greater circles than in small 
ones, and the times of their periodic oscilla- 
tions decrease in the same ratio, and may thus 
be more easily numbered: the areas of their 
wings, and the resistance which they encounter, 


where the formula gives 7.38, and observation from 2 to 3 flappings per second. It is 
remark, that by supposing V to be equal to the cube root, instead of the square root of ? +P 3 
P-q # 


the number of fappings in each of the last two cases by the formula, agrees very closely 
by the mean of several observations. 2% 
The quantity of force expended would be greater if the density of the air were less, but 


number determin 


would only increase in the ratio of 1.4 to 1 if the air were but half as dense. We may, ther 
that the height to which a bird can raise itself is limited not so much by want of su 


conclude 


MOTION. 


bear some proportion to the greater weight o 
the body : bat adieeek theory ascribes to th 
wings a large number of oscillations, it by 
no means follows that they perform t 
exact number assigned at least for any leng! 
ened period. On the contrary, we observe 
that many birds, such as the Woodpecker,* 
and most Insessores, give a few strokes of the 
wings by which the body acquires a projec~ 
tile velocity sufficient to elevate it through a 
considerable space, and that when the im- 
pulse thus given is nearly expended, they re- 
peat this action, and again suspend it. If they 
ate moving horizontally, their is 
ek izes ina similar manner; the axis of the 
ird is inclined upwards at each impulse 
apa but the mean motion is horizontal. 
e curve described during each projection is — 

a parabola. After a few strokes, during th 
ascent, the wings are folded until the bird has 
passed the vertex of the curve, and has de 
scended to some distance on the opposite sid 
when they suddenly expand their wings again, 
and by a few strokes describe a new curve. — 
this mode of progression the velocity is ‘ 
variable, hiehae ual to that which a body 
would acquire by falling through one-fourth of 
the parameter of each point in the curve 
Many large birds, such as the Rooks, Pige 
&c. when descending from great heights 
iets their wings, and incline the axis of then 
ies obliquely downwards, as in fig. 222. 


“ 
Ls 


Fig. 222. 


\\ 


In this case the air opposes sufficient resistane 
in a vertical direction upwards to keep in equil 
brio the force of gravity acting upon the bad 
vertically downwards, so that the motion of th 
bird becomes uniform, without requiring an 
movement of the wings.+ Another mode of de 


‘ened 


ae 


support in the resistance of the air as by the difficulty of respiring in too rare an atmosphere. 


* The Rook appears to make from ten to fifteen, and the Pigeon from ten to twenty-three e! , 


strokes of the wing in five seconds. 


t+ The soft downy feathers which line the wings of the nocturnal rapacious birds, as the Owl, p 
the wings to perform its evolutions during flight in search of their prey without noise. On Y 
in the diurnal species of this order, which chase and capture thei 
secrecy would suffice, the feathers are strong, and their passage threugh the air is accompanied 


a rushing noise, 


a 
eir prey in open day, and where 


aj 


MOTION. 


scent is performed with greater celerity by ele- 
vating the wings at an angle of nearly 45° above 
the plane of the horizon, (asin fig.223,) by which 


Fig. 223. 


=>psd 
~- 


Fy eee: ee 
\ 

oy 
~~ 


_ the resistance of the air, compared with the re- 
“sistance to the wing when horizontal, is dimi- 
_nished in the ratio of radius to the cube of the 
sine of inclination, that is, as a b to d c3; con- 
‘sequently, a bird with its wings elevated at any 
angle to the horizontal plane will descend with 
greater velocity than when they are in the direc- 
tion of ab. We most frequently observe that 
Pigeons elevate their wings in this manner 
until they arrive within a foot or two of the 
‘ground, when, to prevent the shock they would 
_ otherwise receive, owing to the velocity ac- 
pipe during their descent, they suddenly turn 
their axis perpendicular, which had previously 
been parallel, to the direction of their motion, 
and by a few rapid strokes of the wing neu- 
 tralize their momentum, and thus reach the 
pound with ease and safety. In order to pro- 
duce lateral motion one wing oscillates more 
‘rapidly than the other, thereby causing the 
head to turn towards the side to which the 
_ latter wing is attached. 
The tail of the bird performs the office of a 
‘Tudder in steering its course; its plane being 
horizontal tends chiefly, as Borelli has demon- 
_ Strated, to elevate and depress the head, rather 
_ than to turn the axis of the bird laterally. Let 
__ us, for instance, suppose that a bird, flying in 
the direction of its axis g f, (fig. 224) elevates 


Fig. 224. 


its tail into the position b A parallel to on, 
the resistance of the air will depress b towards 
k, and causing the bird to rotate on its centre 
of gravity c will elevate the head from a to- 
wards /; on the other hand, if the tail be de- 
pressed into the position b 2, parallel to / k, by 
| the resistance of, the air, the point b will be 


Tien’. 


429 


raised towards m, and the head depressed to- 
wards 0, consequently the direction of the bird 
in its mesial plane is regulated by the tail.* 
In the Grallatores the tail is short and its sur- 
face very small, and the function of a rudder is 
transferred to the legs, which are projected back- 
wards in flight, to counterbalance the depressing 
weight of their long extended neck and head 
This fact was noticed by Aristotle.t The Swal- 
lows, which are almost always upon the wing, 
economise their muscular action by giving a few 
strokes with their wings, and by keeping them 
expanded, scud through the air with great velo- 
city in chace of their prey; this interval of 
comparative repose must be of great service to 
them during their annual migrations across the 
sea to other countries. The velocity of some 
birds is very great. The Eider-duck is said to 
fly 90 miles in an hour, the Hawk 150. The 
great Albatross wafts itself across the Pacific 
Ocean apparently with untiring energy, owing 
to the vast muscular power with which it is 
endowed. 

Flight of fish and other animals——Besides 
insects and birds, there are some other animals 
capable of sustaining themselves during a short 
period in the air by means of membranous ex- 
pansions or enlarged pectoral fins. The Dac- 
tilopterus and Exocetus, or flying fish, are en- 
abled to raise themselves above the surface of 
the water by the action of their enormous pec- 
toral fins; but Mr. Bennett, who appears to 
have particularly observed their motions; states 
that i has never seen these fishes sustain 
themselves for a longer period than thirty se- 
conds, nor ever witnessed any vibration in their 
pectoral fins. Captain Basil Hall estimates their 
longest flight at about two hundred yards, and 
they have been sometimes known to rise above 
the surface of the water as high as twenty feet. 
The projectile force with which they emerge 
from the water determines their elevation, and 
the expanded pectoral fins merely sustain them 
for a brief interval. 

The Draco Volans (fig.225) is provided 
with a broad disc on each side, extending from 
the fore to the hinderextremities. It is covered 
by the skin, supported by the first six false 
ribs, and directed horizontally. This membra- 
nous disc expands and closes like a fan, and is 
elevated and depressed like the wings of birds 
to break their fall in descending from trees, but 
notwithstanding the extent and mobility of 
their wings, they are said to be incapable of 
raising themselves in the air, since their arms 
are detached, and neither enter into the compo- 
sition of the wings, nor assist in their elevation 
or depression. 

The area of the wings of the Draco volans 
(fig. 225)} estimated from the mesial section of 
the body is nearly 5°052 square inches. Ano- 
ther Draco volans which is preserved in spirits 


* See Borelli, De motu Animal. c. 22, p. 235. 

+ See Taylor’s Aristotle’s Progressive Motion of 
Animals, c. x. p. 184. 

t In consequence of the specimen in the collec- 
tion of Professor Grant, from which the annexed 
outline was made, being dry, its weight in the 
living state could not be ascertained. 


430 


in the Hunterian Museum, weighs 120 grains, 
and has membraneous expansions which mea- 
sure about five square inches, or 24 grains 
weight to each square inch of wing: the area is 
as reat in proportion to the weight of the ani- 
mal as in many birds, and greater than in the 
Stag Beetle. The wings of the Volant Lacerta 
resemble in structure those of insects rather than 
of birds, the ribs supplying the place of neure 
in the former, and of the osseous framework of 
the anterior extremity in the latter. They have 
sufficient membraneous expansion for flight, 
provided the muscles which move them were 
so applied, and had sufficient force to elevate 
and depress them with the necessary velocity. 

The Galeopithecus, or flying Cat, and the 
Pteromys, or flying Pha'anger, are also fur- 
nished with lateral membranes extending from 
the atlantal to the sacral extremities, to both of 
which they are attached, but they are incapable 
of raising the animal in the air, and rather per- 
form the office of parachutes than of true organs 
of progression. 

e fossil remains of the Pterodactylus show 
that it was organized for flight; the pha- 
langes of the ulnar finger being greatly elon- 
gated, apparently for sipeens a membrane 
extending along the whole ulnar aspect of the 
arm and side of the body to the leg; a me- 


chanism which enabled these animals to mov 
through the air like birds. The four oth 
fingers are free to answer the purpose of pi 
hension, and are terminated by curved hoo 
like the thumb of the Bat. Pig 
The Cheiroptera are endowed with extensi 
powers of flight. The figure of the Bat p 
sents an outline closely resembling that 
birds, and calculated to offer the least resis 
ance in the direction of their motion dur 
flight. Their anterior extremities are ¢ 
structed like wings, and their whole organiza 
is adapted for aerial progression. The 
of the body com to the area of th 
— wings is very small, and hence the 
ave the power of raising and supporting ther 
> the 3¢ p 

the wings, and 
4 


reg 


selves in the air. The osseous 
but light, the sternum carin 
and clavicles fitted to support 


MOTION. 


furnish a large surface for the attachment of the 
muscles which move them. The fore-arm, con- 
sisting almost solely of the radius, does not 
possess the power of pronation and supina- 
tion, which would tend to lessen the resist- 
ance of the air to the wing in flight; the 
hand rotates on the radius by abduction and 
adduction, as in birds, so that, when folded, 
the little finger lies along the outside of the ra- 
dius: the fingers, which are of great length, 
contribute to the expansion of the wing in 
flight ; the thumb, which is not enclosed by the 
interdigital membrane, terminates by a strong 
hook for prehension, and for suspending the 
animal when in repose. The wing, taking its 
commencement from the neck, extends to the 
arm, feet, and tail. The interfemoral membrane, 
when developed, has its margin supported by 
an osseous extension from the calcanium; this 
membrane serves to elevate and depress the 
axis of the animal, its functions in this respect 
being analogous to that of the tail of birds. 
The elastic though delicate membrane of 
which the wings are composed, gives its stroke 
upon the air a great mechanical effect. 

The proportion of the area of the wings to 
the weight of the body is greater in Bats than 
_ inmany species of birds, and nearly approaches 

that in the Lepidopterous Insects, consequently 
their power of flight is very considerable. 

Bats are capable of increasing the area of 
their wings during their descent, and of con- 
tracting them during their ascent by the alter- 
nate flexion, extension, abduction, and adduc- 
tion of their elbows, fingers, and hands; and 
they can also vary their velocity, and conse- 
quently the resistance of the air during the 
elevation and depression of their wings in the 
Same manner as birds. The ratios of the times 
and of the resistances during these move- 
ments of the wings, as likewise the number 
of their oscillations in a given time, may be 

“computed very nearly by the formula appli- 
cable to the flight of birds, but owing to the 
extensive area of their wings compared with 
their weight, their oscillatory movements are 
comparatively slow. Their power of flight pre- 
ponderates greatly over the force of gravity and 
the mass of their bodies, so that they are ca- 
eit of flying with great ease, even when 

en with one or two young ones. Their 
centres of gravity and magnitude lie beneath 
the axes of the articulation of the wings with 
the trunk, an arrangement which keeps them 
Steady during flight. In repose they suspend 
themselves by their hind feet to some elevated 
object, from which on being alarmed they can 
fly off instantly. Their inferior extremities pos- 
sess neither the length necessary to raise the 
body sufficiently to expand their wings, nor the 
power to project it vertically, like birds on 
taking flight; but by dropping suddenly from 
the ment of suspension, they are enabled to ex- 
pand their wings instantaneously and without 
obstruction in the air. Their velocity is so great 
that they can overtake and capture their insect 
food on the wing. 

The amount of force requisite for aerial pro- 

gression is so enormous, owing to the rarity of 


431 


thé atmosphere, that it would be impossible for 
a man to sustain himself in the air by means of 
his muscular strength alone, in any manner 
he is capable of applying it. It is calculated 
that a man can raise 13 25 lbs. avoird. to a 
height of 3.25 feet per second, and can conti- 
nue this exertion for eight hours in the day, he 
will therefore exert a force capable of raising 
381600 Ibs. in the day to a height of 3.25 feet, 
or 47700 lbs. to a height of 26 feet, which, ac- 
cording to Chabrier, is the height to which a 
bird would raise itself in one second by the 
force it is obliged to exert in order to sustain 
itself in the air. Now, if we suppose the con- 
ditions necessary for flight in man to be the 
same as for birds, and that a man whose weight 
is 150 Ibs. could concentrate the muscular 
power of a day’s labour into as short a period 
as the ac¢omplishment of this object required, 
we might find the time ¢, during which he 
could support himself in the air, from the fol- 
lowing equation :— 
150 ¢ = 47700, 

hence ¢ = 318”, or about five minutes. 

It is, however, impossible that a man could 
concentrate the force of eight hours’ labour into 
the short interval in which he would have to 
expend it when supporting himself in the air. 
The opinions of Borrelli and Chabrier agree with 
these views, and we are not so sanguine as to 
suppose with Bishop Wilkins, Sir G. Cayley, 
and others, that with the assistance of some 
mechanical contrivance men will some day be 
enabled to fly by the force of their muscular 
system. Such hypotheses, like the ancient 
stories of Dedalus and Icarus, &c. serve only 
to deceive the ignorant, amuse the credulous, 
and misdirect the human mind to attempt the 
accomplishment of impossible objects. 

Sect. III. Swimming.—In swimming, as 
in flying, the fulcrum which affords the requi- 
site resistance to the action of the locomotive 
organs of animals is the fluid medium in which 
they move, and as this medium yields to the force 
impressed on it by the organs, it is evident that 
these modes of locomotion are regulated by 
different principles from those applicable to 
animals whose progression is performed upon 
solids. 

The reaction of the water in swimming is 
equal to theaction impressed on it by the impulse 
of the locomotive organs ; and if motion ensues, 
it results from a surplus force in the body in 
motion, equal to the difference between the 
force of the locomotive organs, and the resist- 
ance of the medium. The motion is accelerated 
as long as the force of the locomotive organs is 
greater than the resistance of the medium react- 
ing against the surface of theanimal. When the 
mean forces urging the animal forwards and the 
resisting force are in equilibrio, the motion be- 
comes uniform. When these forces are at the 
maximum, the velocity is also at a maximum. 
If the weight of the animal be equal to that of 
the water it displaces, there will be no ten- 
dency to rise or sink, as the vertical force of the 
water upwards will be equal to the force of 
gravity upon the animal vertically downwards, 
and forces need only be employed to urge the 


432 
centre of vity forwards, backwards, or ob- 
liquely. case is different with animals 


moving upon solids, where the weight of the 
body has to be supported as well as urged for- 
wards by the instruments of progression. When 
‘the weight of the water displaced is greater than 
that of the animal, the body floats upon the sur- 
face, as in the Palmipedes ; if, on the contrary, 
the weight of the animal be greater than that 
of the water displaced by its bulk, a verti- 
cal as well as a horizontal force is requisite, 
pe to the difference of the specific gravities 
of the animal and the water, to prevent its sink- 
ing during progression.* 
animal kingdom includes a vast number 

of species which are aquatic and constantly 
reside in ponds, lakes, rivers, and seas, having 
their general structures organized for inhabiting 
in these dense and resisting media, and their 
locomotive organs adapted for swimming. The 
number of these is far beyond the reach of 
calculation. Many of the larve of insects and 
the tadpoles of Amphibia, which in their adult 
state are either entirely or partially terrestrial, 
commence their career in water; in these not 
only the locomotive organs, but their respi- 
ratory systems undergo metamorphosis. 

Ciliograde animals.. -Under this denomina- 
tion are comprehended the polygastric and rota- 
tory animalcules, and many genera of the orders, 
such as the Porifera, Polypifera, and Acale- 
phe, whose locomotive organs are those minute, 
transparent, elastic, and very flexible conical 
filaments well known by the name of Cilia. 
The nature and structure of these organs have 
been fully detailed in the article C111, so as to 
render any further description here superfluous. 
The cilia act as levers, to which the water is 
the fulcrum. 

We may here referto the Volvox, as affording 
a familiar example of ciliary locomotion. The 
figure of this animalcule being spherical, the 
cilia placed on its surface are all equidistant 


MOTION. 


from its centre, but those possess the gre 
mechanical power which are placed at e 
distances from either pole of the animal’s 
of rotation. The volvox is capable of cham 
its axis of revolution, or varying its directic 
and appears to revolve across the field of tl 
microscope like a planet over that of the te 
scope. In the Rotifera, or whee’ 
the cilia are arranged in rows, around t 
margin of one or more circular dises, capab 
of being extended and retracted from the body.* 
When the tail of the animal is free, it moves” 


. 
animaic' 


retraction of the body, the head and tai 


selves by the two posterior exsertile bulbs. 
Porifera and Polypifera.—The comers 
Flustra are for a brief period capable of a cilio- 
grade mode of progression. In the gemmules” 
of sponges the cilia are spread over about two- 
thirds of the body. According to Grant, t 
zoophytes swim in a zigzag course, with the 
bous pre ae directed forwards . their fi 
is pyriform ; their migrations are ry 
duration, for after the lag of a few digs ¥ 
which are spent in seeking for some suit 
locality, they fix themselves during the rem 
der of their lives. ee 
The Actinie are capable of gliding upon 
the discs which form their bases of support. 
Reaumur asserts that they sometimes invert 
their position, and employ their tentacles as 
feet ; they also diminish theit specific gravity 
by augmenting their dimensions through the ab- 
sorption of water; when detaching es 
at the base, they suffer the current of the sea to” 
drift them from place to place. : 
Unlike most of the rhe which are fixed, 
the Hydra viridis is capable of moving in th 
liquid medium which it inhabits (fig. 226). 


226. mt 


tihemsel ve 


Fig. ~— 
ez .. : | Ma 
ATE 4 
Sor SE) | Y 


The Hydra viridis represented in its different stages of terrestrial locomotion, as figured by ' 


has three modes of progression ; the first is ac- 
complished by alternate flexions and extensions 
of the body ; thusthe head being fixed by the oral 
tentaclesat c (fig. 227), thelittle disc terminatin 
the anal extremity is drawn forwards from a, an 


* See theory of Specific Gravities. 


a 
fixed at b ; the head is then raised and carrie 
forwards, by the exension of the body, toward: 
d; these two actions of flexion and extensior 
complete a step, whose length is = ac — be. 
The second mode of progression is perfor 


| 
* See Ehrenberg’s Infus. Berlin, 1830, 


eg 
“a 


_ bya series of somersets, the tail being thrown 
over the head; if the head is first made the 
fixed point atc, as before, the tail will then 
_deseribe the semicircle a d, which is twice 
he length of a step, or ad — cd, in the second 
_ movement ; the tail being fixed at d, the head 
_ turns upon it as the centre of a new circle, 
and takes a position in advance of d, at a dis- 
tance equal to c d; in these two actions the 
animal travels over a space equal to a 6. 
In this manner the head and tail are ad- 
vanced alternately. The third mode of pro- 
gression is by far the most speedy. The Hydra 
i javing crawled to the surface of the water, lifts 
‘its tail above it to dry in the air, whereby it 
exerts a repulsive action on the water; this 
hydrostatic apparatus, acting as a float, is ca- 
pable of suspending the body at the surface of 
the water in an inverted position ; in this pos- 
ture it rows itself along, or is drifted by the 
_ winds from point to point without effort. 
_ In the Beroé Pileus, the motions are partly 
by cilia attached to rectangular lamine, which 
are arranged in rows along the eight coste 
died Jig. 32, vol. i.) of the elliptically- 
formed body. According to Dr. Grant, each 
Yow contains about forty lamine, whose 
trarisverse section presents literally the appear- 
ance of the floats upon the paddle-wheel of a 
steam-boat : when the whole of these lamine 
‘strike the water simultaneously, the resultant of 
their combined action is in the line of the pro- 
_ jection of the axis of the animal, which 
is usually directed vertically. ‘The direction, 
_ however, may be changed by the cilia acting 
partially, by which the inclination of the axis 
in the direction of the animal is determined. 
The Physalus has the power of rendering it- 
_ Self either specifically lighter or heavier than 
__ water, by means of the inflation or contraction 
of its air-bladder; with the assistance of 
i which the aniinal is enabled either to swim upon 


the surface, or sink, if alarmed, into the bosom 
% of the ocean. The swimming-bladder of the 
_ Physalus is of considerable dimensions, and 
nearly of an elliptical figure, its longest axis being 
_ directed horizontally. The top of this bladder 
is furnished with a membranous lamina or 
_ crest, serving to increase the surface presented 
_ to the wind, before which it sails with consi- 
_derable velocity. The Rhizophysa Melon, the 


id 


4 


_ Tifera, with most of the Acalephe, having al- 
-Teady been described and figured in the article 
Aca.epux, the reader is referred to them for 
further particulars, but it may be remarked that 
the progression of the Diphyes is performed 
upon the principle of the Syringogrades, merely 
by the reception and expulsion of water by 
VOL. Tt. 


MOTION. 


_ Agalma Okenii, and the Diphyes Campanu-— 


433 


their two truncated sections, which, taking place 
alternately, gives the animal a mean uniform 
motion of considerable velocity.* 

Cirrigrade animals.—Unkke the entirely soft 
gelatinous forms which compose the Pulmograde 
and Ciliograde Acalephe, the Cirrigrade group 
have an internal solid skeleton to support their 
soft and delicate exterior tissues. In the Por- 
pita this skeleton is composed of a flat, circular, 
semicartilaginous plate, which lies horizontally 
on the surface of the water; to this plate 
are appended numerous cirrhi which perform 
the office of oars in rowing the animal on the 
surface of the sea: the Porpita is permeated 
with pores, which being filled with air render 
it of less density than the water upon which 
it floats. The Velella Limbosa has a thin 
perpendicular crest resting obliquely upon 
the horizontal plate, which being elevated above 
the water, and presenting a considerable sur- 
face to the wind, serves as a sail. In the 
Rataria cordata,t the crest is furnished with 
muscular fibres, by which the sail can be ele- 
vated or lowered at pleasure; but this does 
not take place without altering at the same 
time the centre of gravity; for the position of 
the body is nearly reversed when the crest 
is lowered, but it recovers itself on the crest 
being elevated. 

Pulmograde animals.—The umbelliform or 
mushroom-shaped dise of the Rhizostoma being 
capable of expansion and contraction at the will 
of the animal, is employed not only to keep 
the body (which is specifically heavier than 
water) at its surface, but also to propel it 
along. When the plane of the disc lies hori- 
zontally, and its whole margin contracts simul- 
taneously, the percussion given to the water is 
perpendicular to the plane, or in a vertical di- 
rection, and the animal receives an ascending 
impulse equal to the force of the reaction 
caused by the displacement of the water. In 
moving horizontally, the centre of the dise is 
turned in that direction, and the animal can 
also accelerate its descent by the assistance of 
the disc. The contractions of the disc are iso- 
chronous, and repeated about fifteen times in a 
minute,} or 15 X 60 = 900 times in an hour. 
The convex surface of the Aurelia aurita is 
directed forwards in progression ; in this posi- 
tion the whole margin of the dise is called 
into action, by which the locomotive force is 
increased, and owing to the figure of the disc the 
resistance of the water is diminished, and the 
speed is consequently accelerated. 

Syringograde animals.— Under this denomi- 
nation we shall include the Holothuria, the Salpz, 
and the larve of those insects whose progres- 
sion is effected by the alternate reception and 
expulsion of water to and from their respiratory 
organs by an action similar to that of the syringe. 
Independently of moving upon solids by means 
of its tubular feet, the Holothuria, according to 
Muller, is capable of drawing water into its 
cloacal aperture, and by means of its muscular 
system, of expelling it from its respiratory 


* See vol. i. p. 35 et seq. 
+ Vide Art. ACALEPHA, vol.i. p. 40, fig. 12. 
t See Grant’s Lectures, Lancet, 1833. 

2F 


434 


organs with sufficient force to propel itself 
through the surrounding medium. e Ya 
gression of the Salpa cristata is effected by 
drawing water into its body, at an opening si- 
tuated in the posterior segment of the mantle, 
where a valve (fig. 228 c) is placed to pre- 


Salpa cristata. 


vent its returning by the same aperture; the 
mantle having been distended by the water, 
contracts upon it, by which action it is ex- 
pelled at an opening situated at the side of the 
mouth (a); its progression is retrograde, or in 
the direction of a 6, opposite to that of the 
fluid in 6 a. 

The larve of some Dragon Flies, such as the 
Ashna and Libellula, draw in and expel the 
water alternately at the anus, which they occa- 
sionally lift out of the water, and project a 
small stream at a distance above the level of 
its surface: the hydrodynamic effect of these 
actions is to give a locomotive impulse to the 
centre of gravity in a direction opposite to that 
of the ejected fluid. The reaction of the water, 
which is equal to the action of the ejected 
stream, is not only sufficient to overcome the 
resistance of the surrounding medium and the 
inertia of the body of the animal, but also to 
drive it along. The velocity of the Syringo- 

des is accelerated during the expulsion of 
the water, and retarded during its reception ; 
consequently the motion is never uniform. 

The Vermiform animals are for the most part 
destitute of distinct locomotive organs, yet,owing 
to the flexibility of their lengthened and usually 
cylindrical bodies, they swim with great faci- 
lity. They glide by a series of lateral undu- 
latory movements of the body, with which the 
strike the water obliquely backwards, and wit 
equal force on each side of the axis of motion, so 

- that the force impressed on the water is trans- 
lated to the centre of gravity of the animal in 
an opposite direction forwards; the com 
sition of all the forces giving a resultant the di- 


MOTION, 


rection of which coincides with the axis of motion. 
Many serpents whose habits are chiefly terres- 
trial, swim with the head elevated wk 
surface of the water; others glide enti “ e- 
neath it. Some of the Entozoa, as the Tenia, 
and, among the Annelides, the Planarie, when 
immersed in warm water, swim by similar un 
dulations of the body; the latter, however, wil 
the ventral aspect upwards. In the Ophi 
Hydrophyli, or water-snakes, the tail i 
tened ; and its planes being directed vertically. 
give it the properties of a powerful oar, im 
striking the water by lateral oscillations. TI 
many chetopod Annelides, the sete cirt 
form numerous and complex external or 
progression. The Terebella has four rows ¢ 
sete in tufts; the dorsal row projecting in 
horizontal, the ventral in the vertical plane. 
They extend along the whole of the elongate 
subquadrangular-shaped body. In the Eunice 
Gigantea, which grows to the length of mor 
than ten feet, each ring is furnished with tw 
lateral packets of bristles, and two cirrhi. I 
the Nereis nuntia the locomotive ns @ 
complex and greatly multiplied. @ cirr 
and sete may propel the y forwards, 
dependently of those undulatory moveme 
which are indispensable for the progress 
of the apodous Annelides. wa 
Aquatic insects —The perfect insects sw 
like quadrupeds and birds, by the a 
flexion and extension of their legs. A 
the aquatic insects the Dytiscus is one 
best organized for swimming ; its figure res¢ 
bling that of a boat, being calculated to gli 
through the water with little resistance. T 
posterior legs aregreatly developed, an 
moved by powerful muscles perfor 
office of oars, and are the principal in 
used in swimming. Their movements fo 
are made in a plane nearly horizontal. TI 
haunches being xed to the thorax, give firm 
ness and precision to these legs, which do t 
differ materially from those of other Co 
with the exception of the tarsi, which are m 
flattened, and present their broad surf 
the water. They are furnished with 1 
stiff hairs, which bend when the leg is 
forwards, and become straight when its mor 
ment is vigorously reversed, thus in 


Fig. 229. 


The Dytiscus, from Straus-Durchheim, sho 
various positions which the posterior legs t 
swimming, J pe 


effect of the stroke. In the back stroke, the 
thigh (d, fig. 229) moves first, describing an 
are of a circle about their iliac extremity, from 
_ dtod’ and d” successively. During this move- 
ment the legs e and tarsi 7 are flexed pas- 
_ sively, and carried forwards to e’, f’,s0 as to 
act with little effect on the water. The two 
thighs d” d” begin to approach their greatest 
- flexion forwards, the legs e’ ¢’ and the phalanges 
_ f@ f* extend in succession, so that the water 
“opposes resistance to only one of them ata 

1e. The tarsi (/”) having been completely 
tended outwards, the two legs are suddenly 
ied backwards, pressing on the water, with 
entire plane of the tarsi, and as the silky 
fringes which cover the phalanges are extended 
al the same instant, their surface is considerably 
‘augmented. The other parts of the two legs press- 
ing upon the tarsi, as in the walk or the leap, 
“projects the body forward in the direction of 
its axis. In walking, the two members of the 
me pair act alternately, in order to serve, 
ch in its turn, as a support to the centre 
gravity. In swimming, on the contrary, the 
dy being supported by the water, the two 
‘members move simultaneously, in order to give 
the greater impulse, and it is in this respect 
_ that swimming differs essentially from walking, 
d more nearly approaches leaping. The 
dle legs of the Dytiscus act in a manner 

“Similar to the posterior, but being shorter 
and weaker, contribute little towards accele- 

‘ating the movements of the animal; the an- 
terior pair appear to be used chiefly for the 
of altering the direction of its motion. 

€ motions of insects in the water may be 
‘thus explained : let a b (fig. 230,) be the axis 
of the body passing through the centre of gravity 
0; and let co be the excess of the specific gra- 
vity of the water over that of the insect, acting 
a vertical direction upwards; and do the re- 
ce of the water to the insect moving in a 
ection oblique to the axis of the body; this 


Fig. 230. 


atter force is decomposed into two forces, one 
in d g parallel, and the other in de or go 
perpendicular to the body, the former of which 
is lost, and the latter forces it obliquely down- 


MOTION. 


435 
wards and backwards; this force being com- 
bined with the force of the water c o produces 
a resultant in A 0, opposite to d o, which is 
the force by which the insect ascends passively. 
On the other hand, when the insect moves ho- 
rizontally with its axis inclined in a 6, and 
its centre of gravity in 0, (fig. 231,) let its 


Fig. 231. 


J 


A figure from Straus-Diirckheim, to illustrate the 
movements of insects swimming horizontally. 


velocity be represented by h 0, so that the force 
in this direction may be the resultant of the 
forces of the locomotive organs, of the water 
co, and of the resistance which it opposes to 
the motion of the body in the direction of d 0, 
opposite to h o. The resistance of the liquid 
in d 0, acting obliquely upon the plane of the 
body, a b, (which is known from the velocity 
of the body and the inclination of its axis to 
the horizontal plane,) may he decomposed into 
two forces, one in dg oreo parallel, and the 
other in d e or g o perpendicular to the body; 
the former is ineffective, and the latter tends 
to force the body backwards and downwards. 
The force g 0, being combined with that of 
the water c 0, produces the resultant i o, 
which, with the force of the oars, must give 
the two components of h o. Completing the 
parallelogram of forces, of which 4 o is the 
diagonal, we find that the legs must generate 
a force represented in magnitude and direction 
by f 0, and it is in the direction of this com- 
ponent, or, more correctly, in a line parallel 
to it, that the centre of force of the feet ought 
to act, which is in fact the case. 

The Hydrophilus has nearly the same form 
as the Dytiscus, but is not quite so well or- 
ganized for swimming. The Gyrinus also, as 
well as the Hydrophilus, swims in conformity 
with the same principles as the Dytiscus. The 
Nepa, being ill organized for swimming, usually 
walks in the water. The Hydrometra being so 
light, and having a little globule of air attached 
to its feet, has the power of swimming on the 
water without sinking. The Notonecta, in which 
the centre of gravity lies above the centre of 

2Fr2 


436 
magnitude, swims in an inverted position; it 
1s propelled exclusively by its posterior legs, 
which are lengthened, and move in a plaue 

lel to the axis of the body. The thighs, 
egs, and tarsi are nearly of equal length; 
the two phalanges, which are slightly flattened, 
are furnished with hairs to strike the water 
with greater force, arid to vary the surface pre- 
sented in the effective back strokes. When 
the insect is poised freely in the water, its 
centre of gravity lies in the vertical line, pass- 
ing downwards from the centre of the figure. 
From the singular circumstance of its swim- 
ming on its back, it has derived the appellation 
of Notonecta. 

Decapods.—In the Crustaceous Macrourous 
Decapods, such as the Lobster, Prawn, and 
Shrimp, the tail is prolonged, and equals 
the length of the body. It is the princi- 
pal organ of locomotion, and the seven seg- 
ments which compose it are nearly of a 
semi-elliptical form, the terminal being fur- 
nished on each side with laminz, which the 
animal spreads out transversely like a fan, in 
order to produce a greater surface in striking the 
water. At the dorsal aspect, the segments of the 
tail are locked before its extension is com- 
pleted, but on the abdominal aspect there is 
greater freedom of motion. The segments of 
the tail are articulated with each other on both 
sides by ginglymoid joints, of which the axes of 
rotationare directed perpendicularly to the plane 
of the mesial section, consequently their mo- 
tions are restricted to one plane. A slight 
eccentricity, however, in the direction of the 
articulating axes of the joints permits a li- 
mited obliquity of motion in the tail, but at 
the expense of muscular power. In swim- 
ming, the convex surface of the tail is pre- 
sented to the water during the back stroke, 
and the concave ventral surface in the effective 
stroke, by which the force translated to the 
centre of gravity in flexion is to that of exten- 
sion nearly as two to one.* During each 
flexion of the tail the animal is propelled 
backwards, and its velocity is accelerated, but 
during each extension it is retarded, so that its 
movement is retrograde and accomplished by 
a succession of impulses. In the swimming 
Decapods, the thoracic stemmata are laminated 
to assist in progression. 

The Cephalopods.—The Cephalopods swim 
according to the same principles as the Holo- 
thuria, by admitting water into the interior of 
the body and jetting it through the funnel with 
sufficient velocity to communicate a locomotive 
retrograde impulse to the animal, which enables 
it to traverse the sea with considerable speed. 
From the time of Aristotle to that of Cuvier, 
the Argonaut, or Paper-Nautilus, has been sup- 

to have its slight and delicate mono- 
thalamus shell designed for a boat, and the 
broad expanded membranes terminating the 
two dorsal feet organized for sails; but, what- 
ever poetry may have been associated with this 
view, must be abandoned by the Zoologist for 


* See Principles of Resistance of Curved Sur- 
faces moving in Fluids. 


MOTION. 


ug 
the more iodern and more physiological con- 
clusions to be deduced from the researches of 
M. Sander Rang* and Madame Power, ‘ho 
have discovered and assigned the true function 
of these expansions, the fabrication of the shell. 
Pteropoda.—Amongst Pteropods, the Clio 
Borealis presents a conical shaped body al 
an inch long; its locomotive organs cons 
two uniform expansions attached on each 
of the neck, the planes of which lie paral 
the axis of the body. According to Esch 
the fins are composed of one muscular fasei- 
culus, which passes through the neck, a 
this muscle acts in a manner resembling t 
principle of the double-paddled oar with wh 
the Greenlander steers his course on the 
surface of the same seas wherein the Clio is 
found. The inclination of the planes of the 
fins to that of the axis of the y determines 
the direction of the animal. The Clio, how- 
ever, is destitute of organs of prehension, 
consequently incapable of fixing itself to so 
it must therefore either remain at the botton 
of the sea or paddle its course upon the dense 
medium which it inhabits. 7” 
Pisces.—Amongst the great multitude of ani- 
mals moving in seas, rivers, and lakes, F 
next claim our attention. The medium in whit 
fishes move being nearly of the same speci! 
gravity as themselves, they are sustained by suc 
an amount of hydrostatic pressure as almost to 
neutralize the force of gravity upon their ma 
so that organs of progression, calculate ¥ 


support nearly their whole weight, such as occu 
in terrestrial animals moving on solids and in 
rarer medium, are unn . Weobservea 
that as they are sustained on all sides by gr 
hydrostatic pressure, they do not require the 
organs of support to be of that magnitude ami 
density which are requisite to  terrestri 
Mammalia for resisting the shocks of externa 
forces. In the osseous fishes the bones an 
therefore, light and elastic, and in the cart 
ginous fishes the organs of support are s 
more light and flexible. The specific gray 
of fishes, although small, is greater than un 
consequently we know, by hydrostatic prineig 
that without continued muscular effort, or s¢ 
provision for rendering themselves of equal or! 
specific gravity than the water, they musts 
to the bottom and remain there ;f but the: 
nomy of a great number of fishes requires 1 
they should sustain themselves pane 
above the solids forming the of ri 
lakes, and seas, and that they should be ena 
to rise to the surface, or sink into the depi 
the ocean in pursuit of their prey. As 
however, would otherwise require a vast” 
never-ceasing play of muscular action during 
Nature has provided them with an é 
which prevents this waste of muscular | 
the introduction into their system of t 
bladder. This hydrostatic apparatus 18 Of 
rious shapes, but always of sufficient dimensio! 
to contain, when it is distended, as mi 
inches of air as will render the fish s 


hy = 


* Vide Guerin’s Magazin de Zoologie. _ 4 , 
t See Theory of Specific Gravities, sect. du 


MOTION. 


lighter than water, and as the specific gravities of 
airand water are to each other nearly as 1 to 815, 
asmall bulk is sufficient to render the lesser 
fishes lighter than the medium they inhabit. 
The position of the air-bladder being immedi- 
ately under the spine and above the centre of 
gravity causes the fish to rise without the danger 
of turning over on its back. Those fishes which 
are furnished with an air-bladder are capable 
_ Of either renewing, expelling, compressing, or 
dilating its aerial contents, and of varying its 
area so as to rise, sink, or remain in equili- 
brio. The air-bladder becomes by this means 
an important auxiliary organ of locomotion, 
_ and affords an illustration of one of the many 
__ evidences of design in the primary formation of 
_ aquatic animals. 
_ The Diodons and Tetrodons render them- 
selves buoyant by swallowing air, which filling 
the first stomach becomes inflated like a bal- 
loon; but as the gastric reservoir lies below 
‘the centre of gravity, the bodies roll over in 
_ an inverted position, and are driven in the 
direction of the winds and tides without the 
abl of directing their course.* The forms of 
fishes are considerably diversified, being sphe- 
_ fical in the globe ¢tetrodon ; an elongated cy- 
linder in the Eel; compressed in the Dory and 
_ Spah ; flattened into planes parallel to the me- 
‘sial section in the Pleuronectide ; elliptical in 
the Salmonide, Scomberide, and Mugilide. 
‘In nearly all the orders of fishes the surface 
laa to the water by the head and shoul- 
ders inclines more or less to the vertebral axis 
_ of the fish, which coincides with the axis of 
_ Motion, and therefore is adapted to offer resist- 
‘ance, which varies with the angle of incli- 
‘nation. 

In the Salmon, Cod, and Mackerel the form 
of the body approximates to that which is con- 
_ sidered by mathematicians to offer the least re- 
_ Sistance to the surrounding medium. The 


_ Organs of support are developed principally in 
_ the plane of the mesial section, and consist 
_ of superior and inferior spinous, interspinous, 
dorsal, and ventral fin elements, the projections 
Of which prevent motion of the vertebral axis 
im the plane of the mesial section. The ver- 
tebre are short, numerous, and, towards the 
adal extremity, destitute of transverse pro- 
es, an arrangement which gives the tail 
‘considerable degree of lateral motion; 
ving to which it becomes the most essential 
can of locomotion. The locomotive or- 
ms of fishes are the fins and tail; the 
toral fins represent the anterior, and the 
entral the posterior extremities of the higher 
ers of Mammalia. In the Cod, the legs 
e absolutely in front of the arms, being sus- 
ded under the throat. The Percide, which 
_ are provided with two dorsal, two pectoral, and 
two ventral, as well as anal and caudal fins, 
“have the greatest number of locomotive organs. 
The planes of the dorsal and anal fins are in 
the mesial section of the fish, and being res- 
tricted in that plane by a kind of ginglymoid 
joint, are capable only of elevation and depres- 


_* See Dr. Roget’s Bridgewater Treatise. 


437 


sion. In the Cod, Halibut, and Gurnard, the 
action of these fins serves merely to increase 
or diminish the lateral surfaces of the fish, so 
as to prevent any tendency in the animal either 
to oscillate laterally, or turn upon its vertebral 
axis into an inverted position, which it would 
be inclined to do without some muscular 
effort, since in the erect posture the centre 
of gravity lies above the centre of figure.* 
The plane of each ventral fin is in general 
nearly horizontal, and perpendicular to that of 
the caudal ; their action serves to balance the 
body, to incline it on either side, when one fin 
only acts, and to elevate and depress the fish 
by their joint effort+ In many fishes the 
pectoral fins being at right angles to the tail 
and vertical, act horizontally, and communicate 
either a progressive or a retrograde impulse to 
the body, thus assisting the action of the tail ; 
if they are both retained in an extended position, 
they will retard the velocity of the fish; if one 
pectoral fin only is extended, it will turn the fish 
ma curve towards that side ; if the other only, it 
will turn it on the opposite side: they thus per- 
form the office of a rudder. When the planes 
of the pectoral fins are directed obliquely for- 
wards and upwards, they communicate an as- 
cending and a retarding impulse to the fish, but 
the amount of retardation is compensated by- 
the power which the fish acquires of ascending. 
When the caudal, ventral, and oblique pec- 
toral fins move simultaneously, there result 
three forces acting in different planes, whose 
intensities, estimated in directions perpendi- 
cular to those planes, are severally proportional 
to the products of their areas multiplied into 
the squares of their velocities ;{ the resultant of 
these forces may be obtained by the law of the 
parallelogram of forces.§ 

In the Rays, the pectoral fins are developed 
to an enormous extent, and being directed 
horizontally, their action is vertical, like the 
wings of a bird. They are furnished with a 
great number of joints, which endow them with 
considerable mobility ; they have the power to 
increase the surface of the fin during depression, 
and to diminish it during elevation. The disc 
of the ventral fins lies in the same plane as the 
pectoral, and acts in a similar manner, but the 
plane of the caudal fin is at right angles to 
them. The depression of the pectoral and 
ventral fins elevates the fish, whilst the lateral 
motions of the tail propel it forwards. The 
area of the pectoral fins in the Rays is very 
great Compared with that of the caudal; and 


* In Piscibus, pars gravissima ossium spine, 
copiosissima caro musculosa in dorso supremo 
posita est, vesica vero aerea in infimo ventre recon- 
ditur; ergo centrum gravitatis Piscium supra cen- 
trum magnitudinis eorum in supremo dorso repo- 
situm est; et ideo, dum in aqua innatant, naturali 
instinctu revolverentur ventre supino, qua positura 
cum natatui valdé iacommoda sit, cojuntur Pisces 
artificiosé se retinere situ erecto. Borelli, loco cit. 


+ Pinnz duplicate, que in duobus locis infimi 
ventris piscium existunt, non inserviunt ad motum, 
sed ad stationem eorum. Borelli, loco cit. p. 257, 

{ Sce resistance of fluids. 

§ See method of rectangular co-ordinates. 


438 


the intensity of their action (all other things re~ 
maining the same) must be proportional to their 
areas respectively. Sometimes the Rays glide 
sideways, in which motion the pectoral and 
caudal fins exchange their office, the former 
striking horizontally, and the latter vertically, 
the result of which may be obtained by the 
composition of forces, when their directions 
and intensities are given. The Rays, being 
destitute of an air-bladder, require a much 
greater force in the vertical direction upwards 
to sustain themselves in swimming ; hence the 
necessity for the power and mobility of the 
ral fins which we find conferred on them. 
e great lateral development of the surface of 
the Rays compared with their depth, and the 
great depth of the Pleuronectides compared 
with their breadth, entitle the former, rather 
than the latter, as Mr. Yarrell justly observes, 
to the appellation of flat fish. 

The first movement of a fish from a state of 
rest is usually produced by the flexion of its 
tail, as to a, fig. 232; during this action 
the centre of gravity (c) recedes slightly from 
its previous position ; the tail being flexed into 
the position a, is forcibly extended by the 
muscles on the opposite side, in the direction 
of the line a i, perpendicular to its plane. 
The force of its action upon the water in a i 
is translated to the body of the fish in ¢ a, 
causing the centre of gravity c to move obliquely 
forwards in the direction of ¢ A, parallel to i a. 
The tail having reached the mesial line c d, its 
power of urging the centre of gravity forwards 
not only ceases, but during its flexion in eo, 
it acts backwards in the direction of o e ; having 
reached the point 0, it is again forcibly ex- 
tended in the line o e, causing an impulse on 
the centre of gravity in c 6, parallel to oe; if 
the two forces c A and c 6 acted simulta- 
neously, we should obtain the resultant cf, but 
as they do not, the point c will not move ex- 
actly in the right line cf, but in a curved line, 
which lies evenly be- 
tween d c f and a 
line drawn parallel 
to it through k. The 
fish being in motion, 
the tail describes the 
arc of an ellipse,* 
whereas if it were 
stationary, it would 
describe the arc of a 
circle. If we sup- 
pose the force re- 
sulting from the flex- 
ion of the tail to be so 
great as to neutralise 
the velocity which the 
centre of gravity had 
acquired during its 
extension, the result 
would be a state of 
rest whenever the tail 
reached the points a 
and o, and a greater 
force than this would 


Fig. 232. 


* Borelli, loco cit. prop. 24, p. 259. 


MOTION. 


cause it to recede; which, i r Jol 
Lubbock,* is the case, although it pever 

been detected in the movements of the li 
animal. The minute investigation of this: 
ject, however, embraces a very complex 
lysis. There are several circumstances w 
militate against the hypothesis of Sir 
Lubbock ; first, the muscles which move th 
tail are capable of varying its surface during 
flexion and extension, and of contracting ii 

during the former and expanding it during the 
latter action, by which the resistance is propor= 
tionably varied. Secondly, the muscles of th 


tail incline its plane to the direction of its mo- 
tion during flexion, and present its plane 
pendicularly to that direction during extens 
which causes the effective resistances in the 
strokes to be to each other as 1 : s*, where 
is the sine of the inclination of the tail to th 
horizon. Thirdly, according to Dr. Roget, the 
water having been set in motion during the 
tension of the tail, in the same direction, a 
comparatively but little resistance in flexion 
on the contrary, when the motion of the tail 
is reversed, the water meeting it in an op 
direction produces a resistance proport 
the sum of the squares of the two 
These are so many causes which contrib: 
diminish the force of the tail during its flexio 
without producing a retrograde motion in the 
fish. e same demonstration serves whe 
the plane of the tail is directed horizontally, 
in the Cetacea and Flat Fishes, but # 
pulse given must be estimated in a vertical 
stead of a horizontal plane. The velo 
some fishes is very considerable, and 
maintained for lengthened periods. ord 
to Lacepede, that of the Salmon is eight r 
or 26°24 feet in a second; others are said 
to travel upwards of sixteen miles in an hb 
the Shark, for instance, will often Ly 
and gambol around a ship in full sail ae oss t 
Atlantic. In those fishes which have the gre 
est velocity the tail is forked, the area is 
inverse ratio of the distance from the centre | 
gravity; in these the centre of force is ¢ 
half the distance from the centre of motio 
When the tail presents a triangular surfa 
of which the apex is the centre of motion, 
centre of force is three-fourths the distances 
its base from the axis of oscillation. With 
form of tail the muscles act at a mechan 
disadvantage, and consequently the ani 
moves very slowly. ~ 
If we consider the density of the m 
in which these animals move, the 
which it opposes to their bodies, and # 
periods during which they will continue 
progression, we may form some idea of 
great energy with which their muscular sys 
is endowed. ie 
Aquatic Birds.—In the Aquatic 
thorax and abdominal regions present a fo 


* See Dr. Roget’s Bridgewater Treatise, 1 " 
369. 


~~) 


~ 


accom) 


= 


‘eS 


2 +t See Chabricr, Mém. de l’Acad. des 
tom. xi. In this paper formule are given: or 
ing the velocity of the centre of the tail 

quantity of action expended in swimming. — 


a4 
bid 
a 


resembling the keel of a boat. The feathers 
are furnished with an oleaginous secretion, 
which prevents the water from penetrating to 
the skin ; they also enlarge the bulk of the bird 
without very sensibly increasing its weight. In 
the Palmipedes, the osseous system, though 
more dense and less permeated with air than 
in birds destined for long and continued flight, 
is yet so light as to render their specific gravity 
considerably less than water, so that a large 
_ proportion of the body is sustained above its 
ay by hydrostatic pressure alone. The in- 
_ terdigital membranes which give an expanded 
surface to the feet of these birds, acting at the 
end of the long lever, formed by the metatarsal 
bone, enable them to strike the water with 
_ considerable force.* In the effective stroke pro- 
_ duced by the extension of the legs, the flat 
surface of the feet is presented to the water in 
the direction of motion, whilst in the back 
_ stroke they are drawn forwards very obliquely 
and with less force. In the former action, the 
centre of gravity is accelerated, but during the 
latter it is retarded, so that there results a 
succession of impulses and a variable motion. 
The Swan and other Palmipedes sometimes 
pend out their wings as a sail, upon which 
_ the wind acts with sutlicient force to propel 
them along without the expenditure of any 
muscular power. The specific gravity of birds, 
being much less than unity, enables them to 
glide upon the surface of the water without any 
_ expenditure of muscular action in the vertical, 
_ consequently it is required only in the horizontal 
direction. 

__ Quadrupeds—Many quadrupeds have their 
feet palmated to afford a larger surface for 
“striking the water in swimming. Many of the 
_ Saurian, Batrachian, and Chelonian tribes have 
their feet thus organized, though the Caymans 
_ are semipalmated. The lateral direction of the 
locomotive organs of the three former orders 
_ enables them to give an oblique stroke down- 
_ wards and backwards, so as to communicate 
__ an ascending as well as a horizontal impulse to 
_ the centre of gravity, and thus to prevent their 
sinking whilst they are urged forwards. In the 
‘common Otter the feet are also palmated, a 
construction which enables them to move in 
the water with surprising agility, and with suf- 
_ ficient velocity to overtake and capture the fish 
on which they prey. In a similar manner 
the feet of the Newfoundland Dog are also 
furnished with interdigital membranes, but 
__ Owing to the number of their respiratory move- 
id ‘ments in a minute they are incapable of re- 
maining below the surface of the water for 
lengthened periods. The Ruminantia, Carni- 
-vora, and Pachydermata, being all of less spe- 
cific gravity than water, can swim with facility, 
and their locomotive organs, acting as in ter- 
-restrial progression, render swimming a task of 
__€asy accomplishment. Quadrupeds swim by 
__ the alternate extension and flexion of their 
____ legs; the effective stroke is performed during 
_ €xtension, and the back stroke during flexion, 


* 
es 


‘ 


7 


Ss 


* See Principles of the Resistance of Fluids. 


MOTION. 


439 


presenting in the former a larger area to the 
water than in the latter. In consequence of 
the difference of their specific gravities, the 
Horse is capable of swimming even when 
loaded with the weight of a man, with a large 
proportion of its body above the surface of 
the water. The feet of the Solidunguli are well 
formed for striking the water, the flat portions 
of which are employed in the effective and the 
convex in the back stroke, so that the propor- 
tion of the resistance of the water in these 
two strokes, owing to the figure of the foot, 
are to each other nearly as two to one.* 
Man.—The figure of the human body, 
the position of the respiratory apertures, the 
number of respiratory movements made in a 
a minute, the different plane in which the loco- 
motive organs usually act in terrestrial progres- 
sion, and the small surfaces which the hand and 
feet present tothe water, contribute to render man 
the least adapted of almost all animals for swim- 
ming. The specific gravity varies in different indi- 
viduals ; it is rather greater than water when the 
chest is nearly exhausted, and less when well 
expanded with air; hence a man has alwaysan 
hydrostatic apparatus which will keep him 
floating, if he has the knowledge of this fact 
and sufficient presence of mind to employ it. 
The density and temperature of water produce 
at the moment of immersion an involuntary 
expulsion of air from the chest, added to which 
the consequent alarm and misdirected struggles 
facilitate the fatal catastrophe of drowning. In 
swimming, the hands and feet are employed so 
as to present the least surface to the water in 
the back and the greatest in the effective stroke ; 
in the former the hands are brought near the 
mesial plane, with the palmar surfaces parallel 
to each other ; they are then thrust forward by 
the extension of the arm, with the points of 
the fingers in advance to cut the water with the 
least resistance; when the hands have nearly 
reached their greatest distance from the centre 
of gravity, they are rotated by pronation, so 
that the palms are directed at an oblique angle 
outwards and downwards; they are then forced 
backwards by the abduction of the whole arm 
through a large arc of a circle, having the shoul- 
der-joint for its centre, and the length of the 
arm for its radius ; the fore-arm is then flexed, 
and carried into its former position preparatory 
to making another stroke. During the exten- 
sion of the arm, the feet are drawn towards 
the centre of gravity, with their convex surface 
directed obliquely backwards by the extension 
of the ankle and flexion of the hip and knee 
joints, and during the adduction of the arm 
the flat surfaces of the feet are driven forcibly 
backwards and downwards by the sudden ex- 
tension of the leg. From the ratio of the areas 
of the hands and feet, and the ratio of the dif- 
ference of their velocities in the two strokes, 
there results such a preponderance of the force 
iu the vertical direction upwards and in the hori- 
zontal direction forwards as is sufficient to keep 
the respiratory openings above the surface of the 


* See Resistance of Fiuids. 


440 
' water, and to overcome the resistance which 
the water o to the motion of the body, 
due to its figure and velocity. In resisting me- 
dia, both the facility with which bodies im- 
mersed are supported, and the difficulty of 
moving through them, increase with the density 
of the medium: this arises from the increased 
resistance which the particles oppose to their 
displacement; hence, according to Borelli, 
fishes expend, in order to acquire a given velo- 
city, nearly twice as much animal power as 
birds, but are supported in the fluid without 
any exertion, whereas birds, as we have seen, 
are obliged to use considerable force to sustain 
themselves in the air.* 

Secr.1V. Progression on solids—The pro- 
gressive motions of animals on solids are ac- 
complished with much less expenditure of mus- 
cular action than is employed by animals in 
swimming or flying. In the various movements 
of animals upon solids the reaction of the 
ground is always equal and opposite to the 
quantity of muscular action impressed on it.+ 
The velocity being equal, muscular action in- 
creases as the resistance of the solids decreases; 
hence the augmentation of labour in walking 
on a loamy or soft soil, such as the sands on 
the sea-shore. If an animal were projected 
into space, and moving in an unresisting me- 
dium, no effort of its limbs would ever enable 
it to change either the velocity or direction of 
the motion of its centre of gravity. From 
these dynamic considerations we perceive the 
importance of a surrounding resisting medium 
to animal progression. We shall now trace 
the modes of terrestrial progression from the 
lower forms of the animal kingdom succes- 
sively through the intermediate groups, to man. 

Radiata.—In the general outline of the 
Echinodermata we observe great diversity in 
the structure of the organs of support and 
locomotion. The Crinoidea belong most gene- 
rally to those forms of the Echinodermata 
which are permanently fixed. Amongst the 
Asterioidea, in the Comatula, the locomotive 
organs consist of long, complicated, flexible arms 
radiating from a common centre, and subdivid- 
ing into numerous filaments covered with spines, 
which perform the office of so many legs, 
enabling the animal to drag itself along 

_the bottom of the sea, or of so many tenta- 
cula to lay hold of surrounding solids or to 
seize their prey. In the Ophiura the rays are 
of considerable length, being composed of a 
great number of pieces curiously imbricated 
and connected together by ligaments; they are 
flexible and moveable in every direction, and 
act not only as legs for crawling on the ground 
but also as fins, which, by a kind of undula- 
tory movement, enable the animal to swim 
during short intervals. In the Asterias the 


* See Borelli, p. 260. 

+ Barthez, in opposition to Euler, Borelli, and 
others, denies that reaction is the cause of progres- 
sive motion on solids, but in the explanation which 
he gives of it it is difficult to understand his reason- 
ing, without taking into account the resistance of 
the ground, 


MOTION. 


five rays diverge at nearly five equal ar 
from the axis of revolution. In the Se 
each ray, according to Reaumur, is compe 
of seven hundred calcareous plates, of which 
there are about three thousand five hundred 
in the whole animal. The rays of the . 
terias do not possess the flexibility of the 
the Comatula or Gorgonia, and of themselve 
would be insufficient to propel the animal ale 
Nature has therefore substituted other org 
of progression in tubular, retractile, fi 
suckers, protruded from oblique ambala 
rations, by means of which the animal — 
Is dragged along the bottom of the sea or 
n the vertical surfaces of submarine rocks. 
If an Asterias left to all appearance mot 
less and inanimate by the retiring waves, — 
be picked up from the beach, and placed in” 
a large glass jar filled with sea-water, an asto- 
nishing spectacle will be observed. “ Slowly,” 
says Professor Rymer Jones, “ the rays ex- 
pand to their full stretch; hundreds of feet 
protrude through the ambulacral apertures, and 
each apparently possessed of independent ac- 
tion, fixes itself to the sides of the vessel; as 
the animal begins its march, the nu is 
suckers are all soon employed in fixing 
detaching themselves alternately, some remain- 
ing adherent, whilst others change their posi- 
tions; and thus by an equable gliding motion 
the star-fish climbs the side of the glass.” ‘The 
progression of the Asterias is laboured and 
exceedingly slow, and ill adapted for traversing 
such surfaces as the rough shingles of the sea~ 
shore. ‘ 
Echinida.—The Echinus Esculentus is one 
of the most complicated and elaborately formed 
species of the whole Echinodermata; its figare 
is spherical : the five pairs of arched ambulaeral, 
and five pairs of tubercular columns, are joined 
to each other by zigzag sutures. The nume- 
rous spines are connected to the tubercles by a 
ball and socket articulation. According to Dr, 
Grant, the skeleton is composed of more than 
ten thousand pieces, the spines acting as 30 
many inflexible levers, and the numero 
suckers protruding through the oblique ambu 
lacral foramina, as so many feet, form a ¢ 
set of organs for progression.» 3 
In the Echinus, the spines being perpen: 
dicular to the shell, elevate its centre of gravit 
(which, on account of its globular figure, is i 
the centre of the shell) far above the plam 
of motion, protect the shell from inte val i t 
jury, and increase the diameter of the whe 
sphere, with respect to that of the shell alor 
by twice the mean length of the spines. Fro 
the nature of their eepanne ss the spines ; 
capable of moving in every direction upon th 
saheroutce ceuchies but these alone ¥ o 
be insufficient to enable these animals to eli 
the sides of submarine rocks and vertical p 
cipices in search of shell-fish on which @ 
prey; but by the aid of their tubular feet, 
which they have the power of exten 
yond the spines, we behold in the 


> eh ini 

* Grant’s Outlines of Com. Anat, p. 18. _ 
a 

ity 


MOTION. 


curious spectacle of globular bodies moving 
in direct opposition to the force of gravity. 
The structure of this interesting animal in a 
mechanical point of view is worthy the pro- 
found attention of the mathematician, as well 
as of the anatomist and physiologist. 

Sect. IV. Annelida—tThe terrestrial An- 
nelides, such as the Lumbrici or Earth-worms, 
have the body cylindrical, and divided into up- 
wards of one hundred and twenty segments, 
which permit of extension and contraction, with 
the power also of curving the trunk vertically 
and horizontally, according to the play of the 
muscular system. The progression of the 
Lumbrici is aided by their retractile sete, or 
conical spines, eight of which are attached to 
each ring, consequently there are as many or 
more than 8 x 120 = 960 of these sete in 
a single worm, to assist its locomotion. As 
many of the Lumbrici attain the length of 
nearly twelve inches, there must be about twelve 
tings or segments in an inch of the body 
taken longitudinally ; now each ring being arti- 
culated with great freedom of motion, and the 
integuments being soft, flexible, and elastic, the 
trunk possesses very great mobility. 

The locomotion of the Lumbrici is simple, 
and performed in the following manner. When 
the animal is about to advance, the head is 
raised, and about fifteen or twenty of the an- 
terior segments are extended and placed firmly 
upon the plane of position ; the sete and rings 
assist in fixing the segment in advance ; this 
being effected, the next fifteen or twenty rings 
are drawn forwards, and the sete are again 
fixed in a similar manner; subsequently a third 
and fourth series successively complete the pro- 
gression of a step. The space taken at each ad- 
vance depends on the energy and magnitude 
of the animal, and the nature of the surface on 
which the movements are performed. Some 
Lumbrici, about six inches in length, having been 
placed upon a smooth surface, performed a 
distance equal to their own length at six or 
seven complete steps, taking about one inch at 
each advance; this occupied nearly one mi- 
nute of time, being a velocity of progression of 
about thirty feet per hour. ‘The smoothness of 
the surface retarded the celerity of their move- 


ments in consequence of the sete being inca- 


pable of fixing the segments against any points 
with sufficient power to enable them to draw 


the succeeding segments forward; under these 


circumstances the mouth was observed to be 
substituted, and to lay firm hold of the surface, 
whilst the anterior segments were drawn for- 
wards. The Lumbrici are capable of ascend- 
ing a plane inclined at an angle of 45° to the 
horizon, provided its surface presents suffi- 
cient irregularities for the application of the 
rings and sete. The centre of gravity of the 
‘Lumbrici is very near the middle of their 
length. The cylindrical form of the articulata, 
and the minute dimensions of the sete, render 
them (with such a limited basis of support) 
very liable to turn upon their axis, and roll 
over on their backs, but they readily recover 
the pendent position of the abdomen by bend- 
ing the trunk forwards into an arch, with its 


441 


convexity resting on the plane of motion, and 
the head and anus raised above it, but inclined 
to one side: the inclined direction of the raised 
segments causes the animal to revolve on its 
axis, and regain its natural position. 

When irritated, the Lumbrici contract and 
contort the body into curves resembling in 
form the letter S; they appear capable of con- 
tracting the body to one half of its entire length ; 
in which condition the integuments present a cor- 
rugated appearance. The Nais and Naiades are 
swimmers. The Hemocharis walks like the 
caterpillar of the Geometra. The Hirudines, 
or Leeches, are more developed in a transverse 
direction than the Lumbrici ; in these animals 
the mouth is surrounded by a lip, and the 
anal extremity is furnished with a flattened 
disc, each of which is capable of causing a 
vacuum, and the head and anus being fixed to 
the plane of position, whilst the body is elon- 
gated and contracted alternately, the locomo- 
tion is effected. Leeches are well known to be 
capable of thus ascending vertically upon the 
smooth surface of glass, to which they adhere 
with considerable force. 

Insecta. Apode larve of Insects —The num- 
ber of segments which compose the lengthened 
cylindrical form of the Apode larve and the dis- 
position of the muscular system permit the trunk 
to be moved in various directions ; to be elon- 
gated, contracted, curved upwards, downwards, 
or on either side, thus contributing to the pro- 
gression of the Apodes. The cephalic, thoracic, 
and abdominal sections, which may be consi- 
dered as merely auxiliary organs in animals 
furnished with arms and legs, are employed by 
the cylindrical Apodes as the sole instruments 
of locomotion. 

The progression of the Balaneus Nucium, the 
Maggot of the hazel-nut, is thus performed. 
Having first laid hold, with the mouth, of some 
point in the plane of position, the body is con- 
tracted and curved upon itself, and the anal 
extremity drawn forwards ; the latter then takes 
a fixed point for a fulcrum, and the segments 
which had previously approximated during the 
contraction, are again separated in succession 
from behind forwards, causing a slight undula- 
tion of the body in successive curves, vertical to 
the plane of motion. The head having been pro- 
jected forwards by the elongation of the trunk, 
repeats the same actions, recurring as before, 
in succession. Their progression is slow and 
laborious, each step not being more than from 
one-twelfth to one-fourteenth of aninch. The 
Cionus Scrofulariz, like the common Snail, 
secretes a slimy substance which enables it to 
walk on the leaves of the figwort, on which 
it feeds.* The larve of the Muscide are pro- 
vided with unguiform mandibles, with which 
they maintain a firm hold, whilst the body is 
contracted and dragged forwards. Other larve, 
as the Syrphus, use their mandibles for the 
same purpose.t 

Pedate Larve.—Many of the pedate larve 
of insects are furnished with six legs like the 


* De Geer, vol. v. p. 210. 
+ Kirby and Spence, vol. ii. p. 272. 


442 


perfect insect, which support the three 
first rings of the trunk. In many larve 
there are no organs of locomotion, whilst 
others are furnished with a variable num- 
berof rudimental legs, presenting differently 
constituted organs for progression. Most 
of the larve of the Lepidoptera have ten 


MOTION. 


pair of these pro-legs, respectively arti - 
culated to the sixth, seventh, eighth, ninth, 
and anal segments of the body. One 
family, the Lophyrus, has sixteen pro-legs. 
Others, as the Stylotoma, have fourteen, 
and the Tenthredo twelve. The perfect legs 
move (according to Kirby and Spence) in the 
same order as in the imago state; the pro- 
legs serve not only to raise and support the 
abdominal and caudal segments of the trunk, 
but also to assist in grasping objects in the 
plane of motion, and in urging the centre of 
gravity forwards. 

When the head and thoracie segments are 
fixed, the body and tail are drawn forwards ; 
the trunk is arched in the vertical plane; the 
tail being fixed, the pro-legs are advanced 
successively in pairs, beginning from the anal 
segment; the body is then extended, and 
the head advanced to take a new position; a 
conspicuous undulation of the body is produced, 
proceeding from the caudal to the cephalic seg- 
ments. The larva of the Ant-lion (Myrmeleon) 
moves in a backward direction, even after the 
removal of its legs. Many larve, such as the 
Caterpillar of the Hawk-moth, move with ex- 
treme slowness, whilst others possess consi- 
derable powers of locomotion, as the Apotela 
Leporina, which has received its appellation 
from the rapidity of its movements. But of all 
terrestrial larvee, the most remarkable for their 
attitudes and motions are the Geometre. The 
true Geometre have only two anal, and two in- 
termediate pro-legs ; with these they grasp any 
object so as to fix the anal extremity : the trunk, 
with the head, is then extended, elevated, and 
inclined from the horizontal towards the vertical 
position, and the animal appears to be in the 
act of surveying surrounding objects as repre- 
sented in fig. 233. In progression,thehead being 


Fig. 233. 


a4 


fixed on the surface of motion at ¢ (fig. 234) ; 
the anal extremity is drawn forwards to the 
thoracic segments, from a to b; the trunk is 
then again extended to d, and a series of the 
same alternate flexions and extensions is em- 
ployed to carry the larva onwards. During 
progression, the Geometre spin a silken cord, 
which they fix by the head on the plane of 
position at each step, thus measuring the dis- 
tance over which they pass. The use of this 
cord is to enable them to descend from the 


trees, however lofty, on which they feed, and 
to reascend by the same means, without th 
necessity of taking a circuitous route, an 
encountering the inequalities of the trunk am 
branches. In like manner the Caterpillars ©: 
the Cabbage-butterfly weave a ladder of silk 
on the plane of a glass-window, which serves 
as a fulcrum for its legs, and thus enables the 
animal to ascend. -*5 
Perfect Insects—The order in which the 

of the Hexapods move in walking or ranning has 
been accurately explained by Professor Muller. 
Whilst watching insects which move slowly, 
he observed that three of their legs were always 
moving at the same time; these were advance 
and put to the ground, whilst the other three 
ropelled the body of the insect forwards. 
The feet, which moved simultaneously, wei 
the fore and hindmost foot on one side, an 
the middle foot of the opposite side; the 


the fore and hind foot on this side, and th 
middle one of the other side, so that in two step 
all the six feet are set in motion.* In the 


movement, whilst the legs, 1, 2‘, 3, (fig. 


fom 
oy 
a 
A , 


Fig. 235. 
1 v r 
2 2’ 
8 3’ 


4 
™ 
= 


remain on some solid to support the body, 
project it forwards, the Ocha three le 
1,’ 2, 3, are raised and advanced ; then, wh 
the legs, 1’, 2, 3’ are, in their turn, support 
the body, 1, 2’, 3 are raised and advanced, ¢ 
so on alternately. It will be observed, 
the base of support in these movements i 
triangular plane, with the three feet p 
the three angles; the base and apex ol 
triangle alternating at each alternate moven 
of each set of legs; so that in the first m 
ment, the apex, which is at 2, takes the o 
re side at 2’ in the second step. The H 
s are supported by their three pairs of 
and the stability of the animal is z 
the horizontal direction of the legs ot 
this arrangement affording a larger tal 
support of the centre of gravity. Th 
pair of legs being articulated to the proth 
the second pair to the mesothorax, 
third to the metathorax, also gives to th 
axis an increased stability. The articul 


: 
* Miiller, by Dr. Baly, p, 970. 


oa 


ve 


the coxe to the trunk is by cotyloid joints, 
as in the Rhimophore, or by ginglymoid 
joints, as in the Lamellicornes; and between 
the trochanter and femur, the coxa and tro- 
_ chanter, the femur and tibia, the joints are 
usually ginglymoid : the axis of each of these 
joints is turned at right angles to the next, 
_ so that, as Dr. Roget remarks,* “ there results 
from the combination of both, a capability in 
the thigh of executing a circular motion, in a 
_ manner almost as perfect as if it had revolved 
‘in a spherical socket. The principle of this 
_ compound motion is the same as that employed 
_ on ship-board for the mariner’s compass and 
other instruments which require to be kept 
_ Steady during the motion of the ship. For this 
_ purpose, what are called gimbals are used, the 
_ parts of which have two axes of rotation at 
tight angles to each other, so as to enable the 
mpass to take its proper horizontal position, 
matever may be the inclination of the ship.” 
le remaining joints of the legs of insects are 
also ginglymoid. The tarsi, which vary in 
‘number from two to six, terminate by a double 
_ hook; those on the anterior pair of legs are 
_ directed backwards; those on the middle pair 
_ inwards ; and those on the tail-piece, forwards ; 
_ bywhich disposition the insect is enabled to 
"Tay hold of rough surfaces, and to walk up in- 
_ clined or vertical planes with security. 
' _In the progression of insects, the fore and 
middle legs are extended, and the hind legs 
flexed previously to urging the body forwards ; 
‘in doing which, the actions of these legs are 
_ feversed. The simple hook terminating the 
_ locomotive organs of most insects will not en- 
_ able them to walk on water, to climb vertically 
On glass, or stand inverted on ceilings, actions 
_ which many can perform, and for this purpose 
_ 4n additional apparatus is therefore provided. 
_ The common Gnat and some Coleoptera 
Which walk on the surface of water, have 
the tarsi furnished with a brush of fine hairs, 
_ which appear, when the surfaces are free from 
Moisture, to repel the fluid with sufficient 
_ force to sustain the weight of the animal, and 
in confirmation of this theory, it is found that 
if the legs are moistened with spirit of wine, 
he animal immediately sinks and is drowned. 
Ose insects which ascend vertically on the 
_ Surface of glass, or remain suspended in an 
& __ inverted position from the ceiling, are furnished 
with an additional apparatus. We have a 
familiar example in the House-fly, which has 
_ the extremities of its feet furnished with two 
_ funnel-shaped membranous suckers, moveable 
____ by muscles in every direction, by which they 
are capable of exhausting the air on very 
_ Smooth surfaces, thus causing the pressure of 
the atmosphere to sustain the weight of the 
___ body : the area of these suckers is so beautifully 
adjusted to the weight of the insect, that the 
__ pressure of the air alone is more than sufficient 
to sustain the weight of the insect without ex- 
___ értion, and to suspend its body to a ceiling in 
an inverted position. The centre of gravity is 
__ 4s thus suspended, instead of being supported, 


* Bridgewater Treatise, i. 294, 


MOTION. 


443 


the legs having merely to resist the force of 
gravity upon the body. In the Bluebottle-fly 
( Musca Vomitoria ) these suckers are conspi- 


cuous, and the edges being serrated enable 
them to apply the disc of this pneumatic 
apparatus to any kind of surface, 


Fig. 237. 


In the 
Fig. 236. 


Bibio febrilis (fig. 236), the foot is furnished 
with three suckers, in the Musca domestica 
with two (fig. 237), and in the Cymbex 
Lutea with five. Numerous other species, 
amongst which is the common Wasp, are fur- 
nished with cushions and analogous suckers, 
which enable them to ascend vertically on 
glass. 

The predaceous insects run with great velo- 
city in proportion to their height. Those which 
are furnished with very short legs must ad- 
vance them at intervals of time corresponding 
to the square roots of their length, on the 
supposition that their legs are subject to the 
same physical laws as those of the human 
race. Mr. Delisle observed a minute fly run 
three inches in half a second, making 540 
steps in the same time ; each of these steps 


0.0056 


of an inch in length. The great number of 
steps taken by these minute animals conveys 
to the mind of the observer an impression 
that the animal is running, whereas it is merely 
walking, the body not swinging freely in the 
air, as is necessary, according to the definition 
of Weber, to constitute the act of running. 
Myriapoda.—In the Myriapods, the great 
number of legs and the celerity of their move- 
ments, as for example, in the Scolopendra, 
render it difficult to detect the order of their 
motions. The numerous segments entering into 
the lengthened form of the trunk, each of 
which is furnished with a pair of legs, give to 
the body great flexibility, and enable the 
Myriapods to turn from a right line to any 
curved or angular path, or to pass over rough 
surfaces with facility. The legs, in number from 
fourteen to forty-two, are short, and directed 
laterally ; they are composed of four segments ; 
all the joints, except that by which they are 
attached to the trunk, are ginglymoid, and 
terminate in a sharp conical claw, which gives 
precision and security in climbing. The legs 
appear to move in a determinate order; every 


3 
t have been consequently —— 
mus q y Pats 


444 


alternate leg on one side supports the animal, 
and urges the centre of gravity forwards, 
whilst the corresponding leg on the other side 
is raised and advanced to take a new position 
on the plane of motion. Such, at least, seems 
to be the process employed, but there is very 
great difficulty in ascertaining their motions 
with perfect accuracy ; we therefore give the 
above in part practically, and in part hypothe- 
tically. The Myriapods move with considerable 
agility ; usually run, and if disturbed, continue 
that pace for a great length of time. They have 
the power of climbing with facility the per- 
pendicular surfaces of trees, walls, &c. 

Arachnida.—The Arachnida are furnished 
with four pairs of legs, which render their mode 
of progression more complex, and more diffi- 
cult of observation, than that of the Decapods.* 
Their coxe are articulated to the base of the 
cephalo-thorax by cotyloid joints arranged in 
an elliptical form, and directed horizontally 
outwards ; all the remaining articulations of the 
legs are ginglymoid, which is the best mode of 
articulation for the horizontal movements of the 
leg whilst urging the body forwards ; the tarsi, 
which are composed of a variable number of 
segments, terminate by a double or single hook, 
which affords to this tribe of animals the means 
of ascending vertically, whenever any surfaces 

resent minute irregularities adapted for pre- 

ension ; the legs, projecting from the cephalo- 
thorax horizontally, increase the base of support. 
The centre of gravity is that of an ellipse. 
The Arachnida cannot ascend vertically on 
glass, but are enabled to walk in an inverted 
position on ceilings or rough surfaces without 
the assistance of their web. 

The organs of motion in spiders, though 
nearly constant in number, differ exceedingly in 
length; the general principle is, however, the same. 
After long and repeated observation, I disco- 
vered the order in which the eight legs of these 
animals are putin motion. If we first attend 
to the manner in which the legs are moved 
on either side singly, they will be found to 
move first the fore leg, 
then the fourth, then 
the third, and lastly, the 
second leg; that is, in 
the order 1, 4, 3,2. On 
observing the motion of 
the legs on both sides of 
theanimalsimultaneous!y, g 
they are found to move the 
first right leg, then the 
fourth left; then the first 
left and the fourth right ; 
then the third right and 
the second left ; and lastly, 
the third left and the se- 4 4 
cond right (fig. 238). 

Of these, the first two sets are moved conse- 
cutively, like those of a quadruped, 1’, 4, 1, 4’; 
the last two in pairs simultaneously, that is, 
3’, 2, then 3, 2’; and whilst the legs of one 
side of the animal are moving consecutively 


Fig. 238. 


* The female is furnished with an additional 
pair, to enable her to carry her eggs. 


MOTION. 


in the order 1, 4, 3, 2, the legs of the ot 
side are moving in pairs in the inverted o 
4’, 1’, 2’, 3’. In descending vertically by m 
of a newly-spun thread, they hang by one o 
the hind legs; on ascending the same thread 
they employ three legs; the two first on one 
side, and the first or soon on the other; in 
running, the second pair of legs is placed im 
advanne of the first, ben choos Gf the! third be. 
fore the second, thus giving the feet a greater 
range of space at each step. The fourth pair 
or hind legs, are directed beck ward nearly pa- 
rallel to the line on which the animal is 
moving ; they seem to be chiefly used to support 
the posterior segments of the abdomen, but 
also exercise a limited action in propelling the 
body forwards. Four legs support the body 
almost, but not quite, simultaneously, as stated 
by Professor Miiller, whilst the other four 
are raised. The progression of the spider is 
usually rapid ; it can run upon its web with 
great facility ; it can leap many times its own 
length in chace of prey; it can float during a 
limited period on water; and the facility with 
which it can spin and throw a OSS 
cavities from one fixed point to another, at a 
considerable distance, endows it with a mode 
of transit across spaces which is denied to many 
other animals. a 

Decapoda.—The modes of progression 
ployed by the Deepa are both various 
singular. Organized either to swim in 1 
or seas, to walk and run on the dry la 
at the bottom of water, both fresh and 
they are furnished with organs of locomotion 
suitable for these different purposes. The five 
pairs of legs articulated at the base of 
cephalo-thorax have the whole of the ji 
articulated, and directed to move on sol; 
either laterally or directly backwards. The 
front legs are generally the most massive and 
powerful, throwing the centre of gravity for- 
wards nearly between the axes of ther articu- 
lations. 

The Brachyurous Decapods, as the Cancer 
Maia, §c., present either a quadrilateral or 
pyriform figure. They are generally destitute 
of the great elongations of the abdominal si 
ments and expansion of tail into fins for swim. 
ming, which we find in the Macrourous De. 
capods. The consolidated carapace of the di 
capod tribe deprives them of lateral flexibility 
in the thoracic section of the trunk. The lai 
species of Decapods, such as the Cancer cursu 
or land crabs, are capable of running with : 
velocity, that a man on horseback has difficul 
in keeping up with them. From their spee 
they were called by the more ancient natu 
ralists equi. In many species, such as 
Inachus thoracicus, the Leptopus longipes, at 
the Leptopodia sagittaria, the legs are grea 
elongated, and consequently exercise a locon 
tive office resembling that of the tipula among 
insects, differing however from it in the direc 
tion of the articulations, by which the pr 
gression of these different classes is 
Thus in the Leptopus longipes (fig. 
action resulting from the flexion anc 
tension of the legs in gf, g’ f’ will 


” 


acro 


239), t 


MOTION. 445 
Fig. 239. 
we A a Sf; A 
Z. “a é g 
: ] 
F, A 


Leptopus longipes. 


the centre of gravity c backwards in the 
direction of de, but by the elongation of one 
set of legs from f to h, and subsequent re- 
traction towards f, and the simultaneous con- 
traction of the other set from f” to A’, and 
subsequent extension towards f’, the centre c 
will be propelled laterally in the direction of 
ab, perpendicular to de. The lines a 6, de 
represent both the magnitude and direction 
resulting from the two movements of the legs, 
in g f, g’ f’ and h f, h’ f’ respectively, but, 
by changing the position of the legs, they may 
also move obliquely. 

The Macrourous Decapods, as the lobsters, 
are all organized for swimming ; and they have 
accordingly been considered under that section. 

Gasteropoda.—The motions of the Gastero- 
poda are proverbially slow; the situation and 
Structure of the muscular foot enable them to 
traverse surfaces vertically, as well as horizon- 
tally. The centre of gravity is supported within 
the base formed by the disc of the foot, which 
is organised to expand, contract, and curve in 
every direction; also to produce a vacuum, 
_ and to secrete an adhesive fluid for the pur- 
pose of securing the stability of their position 
on surfaces directed at any degree of obliquity, 
or on the ceilings of rooms, or roofs of buildings, 
in opposition to the force of gravity. 

The Limaces, or slugs, and Helices, snails, 
present in progression a crawling or gliding 
motion. When, for instance, the Helix pomatia 
prepares for moving, the head, neck, and foot 
are first protruded from the shell; the foot is 
next extended on the plane of position, with 
the shell raised upon it; the muscular fibres 
of the foot then produce an alternate contraction 
and elongation of the successive segments of 
its disc, commencing posteriorly and proceed- 
ing forwards by a visible undulatory motion. 
During these alternate elongations and contrac- 
tions, the animal glides perceptibly from point 


to point, though so slowly that many hours are 
required to traverse the distance of a few feet. 
As these animals crawl up the vertical planes 
of a glass window, the successive undulations 
of the foot are plainly visible when viewed 
from the opposite side. Miiller considers them 
capable of producing a vacuum at various por- 
tions of the dise of the foot, thus availing 
themselves of atmospheric pressure in addition 
to their adhesive mucilaginous secretions. The 
patella, or limpet, and similar Gasteropods are 
well known to produce between the foot 
and plane of motion, a vacuum so powerful 
that the shell may be broken rather than the 
animal will suffer itself to be detached from 
the surface to which it adheres. The minute 
dimensions of each undulation of the foot 
render the Gasteropods incapable of traversing 
loose ashes or sawdust placed in their path, and 


‘ these means are consequently often employed 


by gardeners to prevent slugs from destroying 
the young and tender plants. 
Cephalopoda.—The locomotive organs of the 
Cephalopodous Molluscs are adapted to serve 
the triple purpose of legs for terrestrial progres- 
sion, arms fur prehension, and oars for swim- 
ming ; the Loligo and Sepia are also furnished 
with fins, which are placed on each side the dorsal 
aspect of the trunk, and are the organs chiefly 
employed when swimming. Their terrestrial 
progression is performed by eight legs, leaving 
the two long tentacule free for prehension. . 
The fleshy legs of the Cephalopods are extremely 
flexible, of various lengths, and capable of 
moving in every direction, whilst the acetabule 
enable them to lay hold of bodies with great 
force. In walking, the head and trunk are 
inverted, the direction of motion is retrograde, 
and they move very slowly on solids (fig. 240). 
Ophidia.—The Ophidian Reptiles are desti- 
tute of organs capable of supporting and carry- 
ing the trunk in progression, and therefore they 


446 


require some organs modified to render them 
capable of reptation. For this purpose we 
find the spinal column is composed of a greater 
number of vertebre than is to be found in any 
other class of animals. The number of verte- 
bre varies in different species of Ophidia. In 
a large Python three vertebrae in their normal 

itions measured one inch, which in an ani- 
mal of six feet in length would give 216 verte- 
bre of equal dimensions ; towards the tail, how- 
ever, their bulk diminishes, by which the flexi- 
bility of that part is augmented ; the vertebre 
are most numerous in some of the smaller spe- 
cies of Ophidian Reptiles. The bodies of the 
vertebre are short, and are articulated together 
by a ball and socket joint which is situated at 
the inferior border of the body of the vertebra ; 
but as this kind of articulation permits of a ro- 
tatory motion in every direction, it would ren- 
der the whole spine exceedingly weak if the 
motion of the vertebre was not restricted in 
some other part; to attain this object, and to 
give steadiness and precision in their move- 
ments, the articulating processes are elongated 
and furnished with double articular surfaces; of 
these the inferior is horizontal, and the superior 
oblique. The horizontal articular surface of 
one vertebra projects backwards as far as the 
extreme convex head of the ball, whilst that of 
the next vertebra projects forward as far as the 
edge of the socket ; by this arrangement the ho- 
rizontal articular surfaces are in contact to the 


Fig. 


The Octopus vulgaris represented in the act of creeping on the shore, its back being turned towards t 
spectator, towards whom it is supposed to be advancing. ‘ 


MOTION. 


extent of the depth of the socket. The superior 
oblique articular surfaces of correspondin 

tions of the two vertebre are also locked into 
each other when the vertebral column is ex- 
tended ; all the articulating processes being 
cuneiform and fitting into cavities or upon cor- 
responding surfaces effectually prevents any 
twisting of the body around it. The areas of 
the planes of the articular surfaces are suffi- 
ciently extensive to enable the animal to rotate 
each vertebra laterally 15° without causing” 
them to slide from each other, consequently 
successive vertebre allow of a sufficient range 
of motion to render the animals capable of 
turning certain portions of its body atright angle 
to each other. Owing to the position of the ar 
throdial joint, a small amount of flexion on the 
abdominal aspect in the mesial plane is suffi- 
cient to produce a considerable space between 
the spinous processes, so that 


e motion of 
the spine in this direction is rather restricted, 
and from the same cause the spine cannot he 
but very slightly flexed on the dorsal 
in the mesial plane without dislocation. ‘ 
movements of the spine for the pu of 
locomotion are, therefore, chiefly lateral. The 
ribs which extend from the atlas to the anus 
are articulated to the short transverse : 
cesses of the vertebra, and in consequence of the 
absence of the sternum, scapula and pelvis, 
are endowed with great om of motion ; 
they act in pairs on the transverse a’ i 


240. 


oes | 


‘scuta (which take a variable number of fixed 
points in the surface of motion), and enable them 
to propel the body forwards and supply the 
place of so many legs. Their muscular sys- 
tem, though capable of exerting great power, 
acts at a mechanical disadvantage, and is 
quickly exhausted. Serpents move by diffe- 
rent methods, and upon different principles of 
progression. First, in a straight line, with the 
whole ventral aspect of the trunk in contact 
with the plane of motion. Secondly, in a 
curved line, with the trunk arched laterally, 
_and the ventral aspect also in contact with the 
_ ground. Thirdly, in a curved line, with the 
_ body moving by an undulatory alternate elon- 
a eg and contraction of small segments of the 

be he Fourthly, in a straight or curved line, 
with the trunk arched vertically in two or more 
curves. Fifthly, in a straight or curved line, 
_ with the trunk arched vertically in a single 
Curve, consisting of the greater part of the 
trunk. Serpents possess also the power of 
_ climbing, swimming, and springing. In the 
first order of locomotion, or that of a straight 
_ line, with the whole of the ventral aspect resting 
immediately on the ground, the serpent is urged 
_ onwards by the oscillation of the ribs acting on 
_ the abdominal scuta, at successive points of 


MOTION. 


447 


its length. The scuta of a segment or seg- 
ments having secured a fulcrum in the plane 
of motion, the ribs connected with the fixed 
seuta, acting in turns, rotate backwards; the 
next segments in advance perform a similar 
action, until the whole series have completed 
the step.” The length of the complete step 
depends on the arc through which the ribs 
oscillate, and the distances of the scuta from 
the axes of motion; and, as these are both 
small, and the motion has to be transmitted 
through the whole length of the reptile, this 
method of progression is, in consequence, very 
slow, presenting to the eye a tardy gliding 
movement. 

In the second order of motion, the progres- 
sion is performed in a curved line, with the ven- 
tral aspectalso in contact with the ground. The 
method of advancing in this order is similar to 
that in the first; but as the reptile passes 
through a larger space in order to reach a given 
point, the progression will, consequently, be 
slower. Thus, if the reptile be flexed as re- 
presented in fig. 241, its length, when extended 
being equal to the right line A 6, becomes 
by flexure only equal in the direction of 
motion to a e. 

In the third order of motion, the reptile 


‘is curved laterally, as in the second, but small 
segments of the trunk are successively flexed 
and extended, and the steps taken do not de- 
_ pend on the time or extent of the oscillations 
of the ribs, but on those of the retractions and 
___ élongations of the segments of the body; and 
_ asthe latter greatly exceed the former in celerity 
_ and amount, the progression in this order is 
vastly greater than in the preceding, which is 


Fig. 


Fig. 241. 
, IA 


the slowest. These modes of progression are 
practised by the common Snake, the collared 
Viper, and other Ophidians. 

n the fourth order, the trunk is arched into 
three or four vertical curves. This is an acce- 
lerated mode of locomotion ; first, the spaces 
taken at each step are large; and secondly, 
because the reptile moves in a straight line. 
When the head 6 is advanced from 6 to A, 


242, 


é h 


Fig.243. 


each point of application to the plane of 
motion will advance in equal spaces, either 
simultaneously or in succession ; in the former 
case, there will be a succession of leaps, with 
greater velocity and expenditure of muscular 
power than in the latter. Many serpents adopt 
this mode of progression, as the Coluber Escu- 
lapii, the Coluber Chersea, and others, (fig. 242.) 
In the fifth order, the progression is effected 


448 


by the flexion and elevation of the trunk in a 
single arc or curve, as seen in fig. 243. If 
during the extension of the reptile the tail be 
ata, it is by flexion advanced to e, during 
which motion the head is fixed at 6; the tail 
being then fixed at e, the body is suddenly ex- 
tended, and the head projected to h; so that 
in these two actions of flexion and extension 
the serpent has advanced through a space equal 
toaeorbh. The velocity of this mode is 
Great, but will manifestly depend on the num- 

r and magnitude of steps taken in a given 
time. This mode of progression is that used by 
the rattlesnake, when the greatest speed is ne- 
cessary in pursuit of prey, for instance, or 
in escaping from an enemy. When these 
flexions and extensions are performed with the 
greatest rapidity, the speed of the rattlesnake 
exceeds that of man. The principle of loco- 
motion in the fifth order is similar to that 
of the larve of the Geometre, and might, with 
equal propriety, bear the same designation 

The Amphisbena walks with equal facility 
either backwards or forwards; the lower jaw 
being supported by the tympanic bone, which 
is articulated to the cranium, is used by these 
serpents as a fulcrum for retrograde ;progres- 
sion. The Boa and the Python climb trees with 
great facility ; this they effect in a spiral curve, 
the scuta of various segments, through their 
enormous length, laying hold of the bark ; and 
aided by the great flexibility of their vertebral 
column, they are enabled to ascend in opposi- 
tion to the force of gravity. They select trees 
in the vicinity of streams and rivers, and sus- 

ending themselves from the branches in an 
inverted position by means of their prehensile 
tail (which is furnished with a corneous hook 
on each side the anus), seize and crush qua- 
drupeds even of large size as they approach to 
drink. 

Serpents are also capable of darting, either 
from the curved position or the spiral coil, by 
the sudden elevation of the body to an erect 

sture; such is the movement of the deadly 

obra de Capello in its attack on the uncon- 
scious traveller, and in the same manner the 
common Viper inflicts its less dangerous wound. 
The erection of the trunk, either from the ver- 
tical curve of the Rattlesnake or the horizontal 
coil of the Cobra, is said to generate a projec- 
tile force sufficient to raise the reptile above 
the plane of motion. Although destitute of 
the limbs with which the higher vertebrata are 
furnished, serpents are endowed with the power 
of transporting themselves from place to place 
with a velocity ter than many bipeds and 

uadrupeds. eir locomotive powers enable 
them to chase and capture their prey ; to stride 
across plains; to ascend and descend hills and 
precipices, inaccessible to most of the higher 
animals; to climb trees; to swim lakes, rivers, 
and seas; and thus not only to provide the 
means of subsistence, but also to choose those 
places of abode which are most suitable to their 
wants, pleasures, or habits. 

Amphibia —In consequence of the amphi- 
bious nature of many Batrachia their loco- 
motive organs are adapted both to terrestrial 


MOTION. 


and aquatic modes of progression. The earni~— 
vorous Caducibranchiates-in an adult state 
present an almost quadrilateral figure, and as_ 
many of the osseous elements’of the skele 
(which in fishes are separate) are anchy 
together, they give solidity to the framework 
and afford levers and fulera for muscular action 
to sustain the shocks necessarily connected with 
a terrestrial mode of locomotion. In the Frog 
the anterior extremities are short compa 
with the posterior; the toes are 
with a broad web, consisting of an expansio 
of the integuments, a structure which, with the — 
length and strength of the posterior extremities, 
renders them well adapted for leaping and — 
swimming. The eight vertebre have a ball 
and socket articulation, which gives them 
some degree of motion on each other. Their 
legs being directed horizontally prevent the — 
Amphibia from supporting their trunks above 
the plane of position. ws 
In a state of repose, the Frog assumes a 
sitting posture ; the thighs are flexed fo 
and outwards ; the legs are flexed backwards 
on the thighs; the lengthened feet and toes are 
again directed forwards; the trunk is inclined 
to the vertical plane at an angle of about 
45°, which brings the centre of gravity within 
the base formed by the pelvis and posteri 
extremities, leaving the anterior extremities 
either free or lightly touching the ground. 2 
legs, in a state of flexion, are ready on the 
least alarm to project the body forward by 


their sudden extension. 1 


’ Lill 


rae 


. 
The Bull-frog is said to project itself six or 
eight feet at each leap, and the leaps are re- 
peated so rapidly that it is captured with ¢ 
culty, unless chased at a great distance from 
the water. It will also spring over a wall five 
feet in height. The Hyla, or Tree-frog, has eae 
of its toes furnished with a concave disc, 
acts as a sucker to enable the animal to attach 
itself to branches of trees, amongst which it 
runs with great facility. The feet of the Rana 
esculenta and Rana pipa are palmated for 
swimming, those of the Rana bufo semi- 
Imated, and the Rana calomella and oth 
ave two osseous tubercles on the palms o 
the hands, which enable them to climb th 
planes of old walls in order to secrete them: 
selves in the crevices. ¥ 
The urodelous kinds of Caducibre 
are adapted for land and water; those adapte 
for terrestrial progression have the tail of 
cylindrical form, as in Salamandra, whilst tho 
adapted for the water, as the Triton, have 
pisciform tail, the planes of which are direc 
vertically. ss 
The perennibranchiate tribes of Amphib 
residing constantly in the water, and with 
rudimentary atlantal and sacral extremitit 
have the trunk elongated and pisciform, a 
the tail compressed laterally to give a greate 
impulse in swimming, as in the Proteus, th 
Axolotl, Siren, &e. = 
Saurian Reptiles.—The Sauria have co 
monly four legs, but a very few are restr 
to two. Of these, some are organized for 
gression on land, others for locomotion both 


os. 
Ci det) 


MOTION. 


land and water. The outline of the Sauria 
presents a lengthened form, having the atlanto- 
sacral axis much greater than the transverse ; 
they partake more of the figure of the Ophidian 
than of the Chelonian reptiles, but differ from 
the former in having legs for the support of 
the trunk and for locomotion, and also in having 
amore complex skeleton, including besides the 
vertebral and costal bones, scapule, clavicles,* 
Sternoid, pelvic, and sacral elements, as in 
‘Mammiferous quadrupeds. The acetabula of the 
Scapulz and ossa ilii are inclined horizontally 
Outwards; the humerus and femur, which are 
short, take the same direction; the ginglymoid 
articulations of the elbow and knee joints are 
inclined backwards eccentrically to those of the 
Shoulder and thigh. The effect of this is that 
the extension and flexion of the fore-arm and 
leg, being made in the plane of the trans- 
verse horizontal section of the body, are at the 
Same time movements of abduction and ad- 
duction; an arrangement which renders the ex- 
tremities ill adapted for rapid progression on 
land. Those Sauria which have the four legs 
nearly of an equal length may be considered 
the best adapted for locomotion; the vertebral 
column being in this case parallel to the plane 
of motion. When the legs are nearly of equal 
length, the bones of the anterior and posterior ex- 
tremities bear the following proportions : in the 
arm of the Crocodilus acutus the humerus is 
found to be 4.334, the ulna 3.083; and in the 
leg, the femur 4.666, the tibia 3.5 inches, so 
that 4.334 + 3.083 — 4.666 — 3.5 =—0.75 
inch for the difference of the length of these 
bones. The metatarsus and toes are longer 
and broader than the carpus and phalanges of 
the fingers, and present a large surface to strike 
the water in swimming.t The posterior extre- 
mities of the Biporcatus are palmated,{ those 
of the Cayman semipalmated. The legs of 
the Sauria are very short compared with the 
length of the animal, (which, in the Bipor- 
catus, is more than 10 feet,) and their hori- 
zontal inclination tends still more to depress 
the centre of gravity towards the plane of mo- 
tion. From the same cause the legs act on 
land at a great mechanical disadvantage. 

In the Crocodilean Sauria, the cervical ver- 
tebre have but a limited lateral motion owing 
to the projection and interposition of the false 
ribs; the dorsal vertebre have their transverse 

rocesses elongated and fixed to the ribs, which 

ve no tubercles, consequently there is but 
little lateral motion of the back ; the lengthened 
tail, however, admits of considerable lateral 
pray and is of great use in swimming. The 
rocodile cannot curve its trunk abruptly or 
turn it at an acute angle with facility; it runs, 
however, with considerable agility in a right 
line. The bones of the skeleton are of a 
fibrous spongy character, which diminishes the 
Specific gravity of the animal, and is a great 


* The Crocodile has no clavicle. 

+ Hunterian Museum. 

¢ The same remarks ap ly generally to the Alli- 
rs of America as to the Crocodiles of the Old 

orld, 

VOL, III. 


449 


advantage in its swiftest mode of progression, 
which is in a fluid medium. 

Lacert@.—The Lacertine Saurians are smaller 
in dimensions than the Crocodilean, and pos- 
sess much greater mobility of the vertebral 
column ; the prolongation of the animal in the 
axis of its mesial section is much greater than 
in its transverse section. As in the Cioco- 
dilean species, most of the Lizards are pro- 
vided with four legs, but a very few species 
have two only. In a few forms, such as the 
Chirotes and Bipes, the animal cannot support 
the body above the surface of motion, and 
consequently drags the thoracic and abdominal 
segments along upon the ground. In con- 
sequence of the construction of the hands, 
claws, and prehensile tail, many Lizards climb 
with facility. The Gecko is provided with a 
pneumatic apparatus which it employs in a 
Tanner similar to that of the house-fly; the 
under surface of each of the five toes, which 
(with the exception of the thumb) terminate 
in a sharp claw, is furnished both in the fore 
and hind feet with as many as sixteen trans- 
verse plicw, which open into as many cavities 
or sacs (fig. 244). The contraction of the 
muscles, acting upon these plice and sacs, 
erects the former and dilates the cavities of the 
latter ; the serrated edges being at the same 
time accurately applied to any smooth surface, 
a vacuum is produced, and by this structure 
the animal is enabled to climb up the vertical 
planes of walls, and to walk in an inverted 
position on the ceilings of rooms. The Anolis 
and Tupenambis, as well as the Gecko, run 
with considerable speed, and have the power 
of leaping a great distance; others propel them- 
selves either backwards or forwards by applying 
two or more parts to the 
ground as a fulcrum, and 
by the alternate flexion 
and extension of the body, 
aided by the long and 
flexible tail. 

In the Thecadactylus 
the toes are expanded and 
furnished at their lower ex- 
tremities with transverse 
folds; these folds are di- 
vided by a deep longitu- 
dinal groove, in which the 
claw can be entirely con- 
cealed ; by this provision 
the claws are preserved 
sharp for climbing. 

In the Ptyodactylus, 
the toes are flattened into 
So! plates, the lower parts of 

ie which are striated like a 
fan; the middle of the fold is cleft, and the 
claw is fixed in the fissure. All the toes have 
the claws very much curved. This peculiar 
organization of the feet enables the animal to 
climb with great facility. 

In order to allow of the more secure pre- 
hension of its insect food on the agitated 
branches of trees, the Cameleon has short, 
strong, muscular limbs ; a strong, flexible, and 
prehensile tail; two thumbs ad ot to three 

G 


Fig. 244. 


WAL 


lima cyst 


~ 


450 


fingers on the anterior extremity, and three 
thumbs opposite to two fingers on the posterior. 
Many of the climbing Lacertine Sauria have 
very elongated and flexible fingers, which give 
them great power of prehension and rapidity of 
motion, so that they are enabled to climb ra- 
pidly up the vertical surface of walls and 
trunks of trees. 

Chelonia—The Chelonian reptiles are en- 
closed in a ponderous case formed by the cara- 
— and plastrum, which they are destined to 

rag along with them in all their movements. 
In the terrestrial species, the dorsal, costal, 
sternal, and pelvic osseous elements are all 
fixed, leaving the neck and caudal extremities 
of the body alone free. The legs, which are 
short and curved, act in consequence of their 
horizontal inclination at a great mechanical 
disadvantage, rendering the progression of the 
Chelonia proverbially slow. The humerus is 
bent, and in pronation is locked against the 
plastrum ; the latter tends to assist it in sup- 
porting the animal. The same body also pre- 
vents the femur from exercising any great degree 
of flexion, but allows it more freedom of action 
in extension; from the relative position of the 
cotyloid articulation and the absence of that 
impediment in the direction of extension, the 
hinder extremities give altogether a more 
effective impulse in walking. The length of 
the arm and fore-arm equals that of the thigh 
and leg. 

In the Testudo elephantopus, the femur mea- 
sures five inches, the tibia five, the humerus 
six, the radius four; then as 5+ 5=6 + 4, 
the sum of the lengths of the anterior and 

sterior extremities is equal. The feet and 
ands of the Turtle are furnished with a mem- 
branous expansion between the toes and fin- 
gers, which enables them to act as fins. The 
anterior extremities in this species are much 
more developed than the posterior. The 
body is remarkably flattened and depressed 
so as to present the smallest amount of re- 
sistance in cleaving the water in quest of their 
vegetable food. In the Emydes, or fresh- 
water Chelonia, the feet are palmated, by which 
means they are enabled to move with’ greater 
facility and expedition on soft and yield- 
ing surfaces, such as muddy banks and 
rivers, as well as to swim in pursuit of their 
prey in the water. The Chelonia are re- 
markable for the great transverse extension of 
the trunk compared with their length; they 
differ in their mode of progression fiom the 
Ophidian reptiles in having legs, and from the 
Saurians in the immobility of the ribs. The 
Aquatic Chelonia are rendered of less specific 
gravity than their bulk would indicate, both 
by the spongy texture of their organs of support 
and by the great extent of their respiratory 
apparatus, which reduce their specific gravity 
to that of the medium in which they move, and 
admit of their sleeping motionless on the sur- 
face of the water. 

The structure of the arch-formed carapace 
and dense plastrum, and the more solid union 
of all the osseous elements surrounding the 
trunk of the Terrestrial Chelonia, enable them 


MOTION. 


to resist the external pressure to which, rom 
their partially burrowing habits, they are su < 
jected, and also to endure the trampling of 


lai uadrupeds. 
As qpa aey ia tribe traverse the sur- 
face of the earth as digitigrade bipeds. In 
standing, the trunk is elevated and supported at — 
various heights above the plane of position, k 
the legs through which its weight is transmitted 
to the ground. It is balanced and kept in equi- — 
librio on an axis passing through the centres of 
the heads of the femurs perpendicularly to the 
plane of the mesial section. i 
The inclination of the trunk lies between the 
vertical and horizontal planes; but its angle of © 
elevation depends on the position and weight — 
of its various elements and appendages, such 
as the head, neck, and anterior extremities, 
which determine the distance of the centre of — 
gravity to the cotyloid articulation. The ilio- — 
femoral articulations being placed more for- 
wards in the ossa innominata than in quadru- — 
peds, enables them to bring the centre of 
gravity within the base of support on their 
two feet with little elevation of the trunk 
Several methods are employed by birds to” 
alter the relative position of their centre of 
gravity in standing, namely, first, by curva-— 
ture of the neck; secondly, by folding the 
wing on each side; thirdly, by the elevation 
or depression of the trunk above or below the 
horizontal plane in which the cotyloid joints 
are situated. All these different positions of 
the trunk and its appendages throw the centre 
of gravity backwards towards the vertical line 
passing through the base of support, which may 
also be changed and thrown forwards by bend- 
ing the joints of the legs. ae 
The areas of the bases of support vary in 
different orders of birds according to the num-— 
ber, length, and direction of their toes. e 
action of the gracilis muscle, which enables 
birds to stand on one leg in repose, was 
monstrated by Borelli, and though his views 
were opposed by Vieq D’Azyr and Barthez 
they have been confirmed by Monro, Cuvier 
Miller, Roget, and Owen. In walking slowly 
the body rests a long time on both legs and 
short time on one ; during the former period t 
motion of the trunk is retarded, but during th 
latter itis accelerated. In these movements, 0 
leg is flexed, raised from the ground, and swut 
forwards to take a new position in advance, whil 
the other supports the trunk and propels it fe 
wards; and as soon as the foot of the raised 
arrives in a position 


rpendicular to the head 
the femur, the hind leg is lifted and repe ats 1 
like movements. The time during which the bo 
is supported on one leg, in proportion to th 
when it is resting on both, depends on- 
celerity of progression. The time of the 
lation of the swinging leg is governed by t 
length of the leg and the are through whie 
is suffered to oscillate.* In walking, the ee 


of gravity oscillates laterally; this motic 


* For further details on walking upon two! 
see those on human progression, many of W. 
are applicable to birds. 


ee ee 


MOTION. 


most conspicuous in some of the Natatores, as 
the Goose, Duck, &c., and in those birds 
which have the greatest space between the cotv- 
loid cavities and the least length of legs. Many 
birds depress and elevate the head, and ex- 
tend and retract the neck at each step, in order 
to preserve in equilibrio the forces acting on 
the centre of gravity; the Moor-hen and some 
others are also observed to spread out the tail 
like a fan, which is alternately elevated and de- 
pressed at each step; and these successive 
actions of the tail taking place at the extremity 
of that portion of the lever opposite to the 
head, tend to produce an equilibrium between 
those portions of the trunk lying on each side 
of the cotyloid articulations. 

In the progression of some of the long-legged 
Grallatores, such as the Crane and Stork, the 
Swinging leg describes a portion of a circular 
curve round the standing leg. Pliny appears 
to have observed this kind of movement, for, 
in his Hist. Nat., lib. x. c. 23, he says, “ Grues 
mansuefacte gyros quosdam indecoro cursu 
peragunt.” 

Alarge number of birds, suchas the Sparrows, 
Canaries, Blackbirds, &c., instead of moving the 
two feet alternately, move them simultaneously : 
in these movements the legs are first flexed and 


then suddenly extended in succession, by which 


means the trunk and both legs are elevated 
from the ground, and progression is effected 
by a series of short leaps. In running the 
Cursores outstrip all other birds, and per- 
haps all other animals. The osseous columns 
which support the trunk are of great length 
and size, and are acted on by powerful muscles. 
The femurs, though short, have a considerable 
diameter ; the tibia is long, but still longer is 
the tarso-metatarsal bone. The bones of the 
legs elevate the trunk to a great height, by 
which they are enabled to stride over a large 


_ Space at each step. Aided by its compa- 


Tatively diminutive wings, the Ostrich will out- 
Strip the fleetest Arabian horse in his flight 
across the desert, as will the Cassowary the 
swiftest Greyhound. Thus, though deprived by 
the comparative smallness of their wings of the 


__ power of aerial progression, these birds are fully 
_ compensated by the velocity of the terrestrial 
_ movements. 


_ The Scanscres, such as the Woodpecker, 
Parrot, Cuckoo, &c. have the internal toes and 


_ thumbs turned backwards, which enables them, 
_ with the assistance of the tail, to climb and to 
Suspend themselves to the upright trunks of 


trees; during which action, the legs, tail, and that 
portion of the tree against which they rest form 
the three sides of a triangle. 

Mammiferous Quadrupeds——The locomotive 
organs of the mammiferous quadrupeds are 
tore highly organized than those of the Ba- 
trachia and Chelonia. The bones of the skele- 


ton are more compact, hard, and dense, and 


contain a greater proportion of the calcareous 
hosphate; they are, therefore, better calcu- 
lated to resist the shocks incidental to terres- 
trial progression: the vertebral column, which 
is directed horizontally, is convex at its dorsal 
and concave at its ventral aspect. It forms a 


451 


single arch, extending from the pelvis: to the 
last cervical vertebra, as it is kept bent by 
strong ligaments. It constitutes a powerful 
elastic column, well adapted to support the 
weight of the abdominal viscera as also of extra- 
neous burdens which these animals are destined 
to bear. The spinal column of mammiferous 
quadrupeds is endowed with much greater 
mobility and elasticity than in the Saurian and 
Chelonian quadrupeds. The trunk is directed 
horizontally, resting on the four legs, which, 
like so many columns, support the centre 
of gravity. The scapule and pelvis have 
the power of rotating in a vertical plane 
through a large arc; the axes of the acetabula 
of the shoulder and hip-joints are directed 
vertically downwards to receive the heads 
of the ossa humeri and femoris, the shafts 
of which are directed vertically upwards. 
These ball-and-socket joints permit the several 
motions of flexion and extension, abduction 
and adduction, pronation and supination: 
the rest of the joints of each extremity are 
ginglymoid, a construction which, although 
it restricts the limbs thus articulated to move- 
ments in one plane, yet secures to these 
movements greater precision. The joints are 
lined and lubricated by synovial membranes, 
which, throughout the life of the animal, effec- 
tually secure them from injurious friction not- 
withstanding their varied and long-continued 
exertions. The elastic ligaments permit great 
freedom of action under all ordinary circum- 
stances without rupture. The osseous columns, 
which enter into the composition of the extre- 
mities, are piled upon each other endways, 
with their long axes either vertical or inclined ; 
and, in order to give them the power of sus- 
taining the greatest possible pressure with the 
least weight and expenditure of solid materials, 
the shafts of the long bones are formed into 
hollow cylinders, of which the height and base 
are adjusted to each other with the greatest 
mechanical precision. The bones of the extre- 
mities in most mammiferous quadrupeds are 
inclined to each other’s axes at a greater or 
less angle, the magnitude of which is in pro- 
portion to the bulk and speed of the animal. 
In those quadrupeds which have the greatest 
bulk and least velocity of locomotion, the bones 
approach nearest the vertical direction : such is 
the case with the elephant. On the contrary, 
in those animals which are remarkable for the 
greatest speed, the axes of the bones are in- 
clined to each other at the greatest angle. 
Although the angular disposition of the 
bones diminishes their power of sustaining 
great weight, and increases the expenditure of 
muscular effort, ‘yet it confers on the legs 
greater elasticity, and enables them, from the 
oblique transmission of the impulse, to sustain 
sudden shocks without fracture of the bones ; it 
also enlarges the range of motion, and gives 
the posterior extremities greater power of pro- 
jecting the body forwards during rapid loco- 
motion. The bones of the anterior extremity 
having to support the weight of the head and 
neck, as well as a large proportion of the trunk, 
are inclined nearer to a vertical direction than 
262 


452 


those of the posterior; this tends to throw 
the centre of gravity a little in advance of the 
middle of the quadrilateral figure described by 
the four legs of the quadruped on the plane 
of position. 

Although the bones of the posterior extre- 
mities are inclined to each other at a greater 
obliquity than those of the anterior, they have 
the calcaneum projecting considerably beyond 
the axis of the palowhondibial articulation, so 
that, acting with the advantage of a powerful le- 
ver, the waste of muscular force is diminished,and 
the disadvantage arising from their obliquity is 
partially compensated. The time and order in 
which the legs of quadrupeds succeed each 
other in motion determine the deno- 
minated the walk, the trot, the gallop, the 
amble, and the leap, or bound. 

In order to illustrate many of the general 

rinciples on which the progression of qua- 
io s is effected, we shall select the horse as 
an example. In standing, the animal rests its 
trunk on the legs which form the four columns 
of muppet. Let us suppose the legs to be 
placed on the ground at A B E D (fig. 245): 
if these points be joined, they form a rectangular 
parallelogram. , 

When the animal walks slowly with his 
right side in advance, the left hind leg moves 
first ; the right fore leg second ; the right hind 
leg third ; and the left fore leg fourth. During 
these four successive motions, the centre of 
gravity is propelled forwards over a space equal 
to the length of one step. Let us now investi- 
gate what takes place during these successive 
motions. The hind foot having been pre- 
viously extended, and having urged the centre 
of gravity forward, is first moved; it is then 
flexed, lifted from the ground, and advanced 
from E toe. Whilst the leg E is in the act of 
advancing to e, the trunk is supported on 
three legs, A B D, thus having the base 
of support transferred from the plane of a rec- 
tangular parallellogram to that of a right-angled 
triangle. 

In this movement, the centre of gravity G 
must fall within the plane A B D, which is 
effected by an oblique lateral movoment of the 
trunk towards B D. The foot E having taken 
a new position at e, the second foot B is set 
in motion, raised, and advanced to 6, and the 
base of support becomes transferred from the 
rectangular triangle, A B D, to the oblique- 
angled triangle, Ae D: by an oblique lateral 
motion of the trunk, the centre of gravity is 
propelled towards A a, within the new base of 
support, leaving the leg free to move without 
danger of the horse falling. The leg B having 
advanced and taken a new position at b, the 

Teg D is next raised and advanced to d, 
during which the base of support is transferred 
from the plane A e D, to that of A be, 
within which the centre of gravity is propelled ; 
lastly, the leg A is.advanced to a, and thie 
base of support is transferred from the plane 

A be to that of bed. When the leg A 

has reached the point a, the base of support 
becomes a new parallelogram a b e d, equal 
jn dimensions to thatof AB ED. In walk- 


MOTION. 


Fig. 245. 
am Fe 
is 
ii) 
i‘ 
whe f 
' \ 4 
i 4 4 
\ 4, 
\ 4 
\ Ff 
\, “ 
/ 
\ i 
\ if 
if 
\ A 
\ 4) 
sf 
’ 
x 
4 tA 
// 
bea 
// ‘ 
if ‘ 
fi 
ii 
Pine 
Ag 
/ yf 
if 
‘ 
// * 
Pie | 
‘ ‘ 
7s 
/ / 
AG 2 
e for Gc d 
Gh\-- 2 
‘ 
‘ 
‘ 
" 
. 
‘ 
‘ 
’ 
\ 
‘ 
\ 
‘ 
A} 
‘ 
‘ 
‘ 
‘ 
. 
‘ 
. 
\ 
\ 
\ 
x 
\ 
‘ 
\ 
‘ 
‘ 
‘ 
4 
‘ 
\ 
x 
Y 
\ 
i 
E (i D 


ing, the four legs move in the order above- 
mentioned successively. The time occupied it 
performing the series of movements to com- 
plete a step varies. In horses of large dimen- 
sious, one foot moves the length of a step ev 
second, and, therefore, each leg swings one qu 
ter, and rests on the ground three-quarters 0 
asecond. In walking at a more rapid pac 
each leg moves in rather a less period, and 
interval between the setting down of one 
and the rising of the next vanishes. 

The trot.—In the trot the — 
pairs diagonally. If the legs A D (fig. 2 
be first raised and advanced, then B Row 
generally be raised the instant that A D reac 
the ground ; on the other hand, when the le 
B E are raised before those of A D reach 
ground, the trot approximates to the gallop 0 
two beats, the four legs being at the same t 
for a minute interval, above the plane of m 
tion. The bases of support in the trot are’ 
lines A D and B E alternately. The san 


ot 


MOTION. 


leg moves rather oftener during the same pe- 
riod in trotting than in walking, or as 6 to 5. 
The velocity acquired by moving the legs in 
pairs, instead of consecutively, depends on the 
circumstance that in the trot each leg rests on 
the ground during a short interval, and swings 
during a long one, whilst in walking each leg 
swings a short, and rests a long period. The 
undulations arising from the projection of the 
trunk in the trot are chiefly in the vertical 
plane ; in the walk they are in the horizontal. 
In fig. 246, as designed by Bewick, and 
adapted to our purpose, we observe that the 
vertical line passing through the base of sup- 
port, lies not only behind the centre of gravity 
of the horse, but also of the centre of the mass 
of the rider, consequently the anterior legs 
will bear much the greatest proportion of the 
burthen. 

The gallop.—The gallop may be divided 
into three kinds, which may be distinguished 
by the number and order in which the feet 
happen to reach the ground. When the horse 
; ins the gallop on the right, the left hind leg 
_ reaches the ground first; the right hind and 
- left fore legs next, simultaneously, and the 
right fore leg last; this is termed the gallop of 
three beats. In the gallop where the four legs 
strike the ground successively, the left hind 
foot reaches the ground first, the right hind 
foot second, the left fore foot third, and the 
_ fight fore foot fourth ; ¢his is the gallop of four 
beats, but it is not the kind of movement 
adapted for great speed.* The gallop wherein 
the legs follow the same order as in the trot, 
—that is, the left hind and right fore feet reach 
the ground simultaneously, then the right hind 
and left fore feet ;—is the order in which horses 
_ move their feet in racing, where their greatest 
Speed is required, and is called the gallop of 
two beats.+ In the amble, the two legs on one 
_ Side rest on the ground, and _ propel the centre 

of gravity forwards, whilst those on the oppo- 
Site side are raised and advanced, and on 
taking a new position on the plane of motion, 
the former pair are raised and advanced in a 
Similar manner: these successive actions are 
accompanied by a considerable lateral motion. 
‘The amble is the pace peculiar to the Giraffe : 


* The gallop of four beats is often denominated 
“ the er.” i 


t See Sainbell. 


453 
in the horse it is only effected by artificial 
training. Borelli has erroneously described the 
order of the motions of the feet of the horse in 
walking; he states that the fore and hind feet 
on the same side move first, and then the fore 
and hind feet on the opposite side: these 
views, however, differ from the order as de- 
scribed by Aristotle,* and they have since 
been opposed by Barthez and Miiller, whose 
Opinions coincide with those which, after 
repeated observations, have been here intro- 
duced. In the gallop, the centre of gra- 
vity moves in a vertical plane, and describes the 
path of a projectile. The space passed over 
on the plane of motion is equal to the hori- 
zontal velocity of the centre of gravity multiplied 
by the time.t According to Sainbell, the cele- 
brated horse, Eclipse, when galloping at liberty, 
and with its greatest speed, passed over the 
space of twenty-five feet at each stride or leap, 
which he repeated 2} times in a second, being 
nearly four miles in six minutes and two se- 
conds. The race-horse, Flying Childers, was 
computed to have passed over eighty-two feet and 
a half in a second, or nearly a mile in a minute. 
Sainbell has given the geometrical proportions 
of Eclipse, together with the angles of in- 
clination and range of motion of the joints of 
the four extremities. He states that a consi- 
derable angle of inclination of the shoulder- 
joint, as well as an angular disposition of the 
limbs, are essentially necessary for great speed. 
Sir C. Bell,t however, states, “ that the speed 
of a horse depends on the strength of his loins 
and hind-quarters, and what is required in the 
fore-legs is strength in the extensor tendons ;” 
but surely this hypothesis cannot be correct, or 
the brewer’s dray-horse would be the fleetest. 
The horse is one of the most useful and most 
perfectly organized quadrupeds, combining 
great strength with speed. The length, strength, 
and angular disposition of the bones of the 
legs, the power of the muscles, the structure of 
the joints, the lengthened metatarsal and me- 
tacarpal bones, the consolidation of the pha- 
langes, and the structure of the expanded foot, all 
conspire to perfect the geometrical proportions 
of this valuable quadruped. 

Having now given in detail the various 
movements of the horse, we shall briefly pass 
to the other orders of Mammalia. 

Marsupialia.—In the Kangaroo, we observe 
a greater disproportion between the length of 
the anterior and posterior extremities than is 
found in any other quadruped, the length of the 
legs to that of the arms being as 383 to 174 
inches,§ or rather more than two to one. This 


* After the right of the fore feet they move the 
left of the hind feet. Afterwards they move the 
left of the fore feet and right of the hind feet. 
See Taylor’s Aristotle on the Progressive Motion of 
Animals, chap. xiv. 

+ See eq. 1. 

¢ Library of Useful Knowledge, Art. Animal 
Mechanics. . 

§ These measures are taken from a skeleton in 
the Hunterian Museum. Some variation will 
occur in the absolute length of the extremities, 
arising from the age and magnitude of the animal ;. 
but the ratio of the length of the extremities in the 


454 


difference arises chiefly from the great length of 
the tibia, which is nearly equal to that in the 
Giraffe, the former being to the latter as 16°5 
to 18 inches. In the Rodentia, as the Hare, 
Agouti, and Guinea-pig, we observe a similar 
disproportion in the length of the extremities. 
The Rabbit, in moving slowly, advances the 
anterior feet two or three steps alternately, the 
roa limbs remaining inactive. The body 
ving been elongated by this means, the 
anal legs are suddenly extended and drawn 
$ simultaneously ; thus, the rabbit walks 
with the fore, and leaps with the hinder pair 
of legs. Those quadrupeds in which the 
length of the posterior extremities much pre- 
dominates over that of the anterior, are ob- 
served to descend declivities in a straight line 
with difficulty, on account of the great inclina- 
tion of the axis of the trunk to the plane of 
motion, which puts the animal in constant 
danger of oversetting; they therefore take a 
zigzag course. In ascending a hill, however, 
their progression is greatly facilitated by the 
length of their posterior extremities. The speed 
of the Hare is well known to be greater than 
that of the fleetest horse or hound. 
Ruminantia.— Many of the Ruminantia, 
such as the Deer and Antelope, are beautifully 
and symmetrically organized for rapidity of loco- 
motion ; the Camel for prolonged power of tra- 
versing the arid desert; and the Ox for the 
strength and development of its muscularsystem. 
Amongst the Ruminantia some species have 
the neck of great length, and the head being 
surmounted with massive horns, or antlers, 
renders it necessary that the spinous processes 
of the lower cervical and superior dorsal verte- 
bra be lengthened, so as to form powerful 
levers for the attachment of muscles, and of 
that yellow elastic tissue, the ligamentum 
nuche, which is greatly developed in the Rumi- 
nantia, to support the head and its appendages ; 
the latter acting at the end of a long lever tends 
to throw the centre of gravity forwards nearly 
between the anterior extremities. The figure 
of the trunk is elliptical ; its transverse axis dimi- 
nishes as it approaches the anterior extremities ; 
there are no clavicles ; and from the small degree 
of curvature of the ribs, the arms are thrown 
almost together beneath the trunk, and nearly 
in the plane of the mesial section of the body. 
The Giraffe presents greater length of osseous 
columns for the support of its superstructure 
than is to be found in any other animal; the 
bones of the anterior extremity are directed 
more vertically than those of the posterior, 
which enable it to support, with less weight of 
bone and less expenditure of muscular force, 
its lengthened neck, upon which the head acts 
as at the end of a long lever. The metatarsal 
and metacarpal bones are of great length, and 
being directed vertically, as in the Pachy- 
dermata, the trunk is elevated to a great height. 
The three phalanges of each finger and toe are 
inclined forwards ; the extensor tendons act on 
them by means of a pulley, through the inter- 


same species of animals may be considered nearly 
constant for all ages, sexes, and magnitudes, 


MOTION. 


position of the sesamoid bones, which increase — 
the distance of the direction of the tendons — 
from the axes of the joints, and give them 
greater power. - 

The length of the arms to that of the bes 
in the Giraffe is as 71 to 67 inches, whicl 
gives a difference of four inches in favour of 
the length of the arms. This dispro 


furth the | tenet Coa ) 
er augmented by the len "d 
and by ie: inceeadl angular disposition of 
the posterior extremities. 
In the Camel, the length of the legs is more 
nearly equal than in the Giraffe, the anterior ~ 
being to the posterior limbs as 49 to 47 inches ; 
the spine is consequently directed more hori- — 
zontally than in the Giraffe. The order in which 
the movements of the legs succeed each other in 
the Camel is like that of other quadrupeds. 
The velocity of the camel at its common tra- 
velling pace is estimated at 2} miles an hour.* 
In Deer and Antelopes, the geometrical pro- — 
portions are such as to confer on them great 
speed. The lightness, elegance, and 
of their osseous fabric, the energy of their mus- 
cular system, the freedom of motion in the 
vertebral column, the large are described in tl 
greatest rotation of the ry and pelvis, the 
length and proportions of their extremities, the — 
length of bre olecranon and calcaneum, the 
vertical direction and my of the sal 
and meta bones, the inclined direction — 
and freedom of motion of the three phalanges 
of the fingers and toes, the number and relative 
distances of the joints,—all conspire to perfect 
the progression of these Ruminantia. They 
bound by the sudden flexion and extension of — 
all the legs, which are lifted from the ground 
simultaneously, and which, after projecting t ® 
centre of gravity in a vertical direction, appear 
to arrive agiin synchronously on the plane o 
motion. They walk or trot ier the prineip 
of other quadrupeds, as explained already in— 
the Horse. The Deer and Antelope, celebrated - 
for speed, bound over plains, ascend or des 
mountains, and also possess the power of 
ing across an abyss of great breadth, or dowr 
precipices twenty or thirty feet in a th- 
outsustaining the slightest injury from . 
Proboscidia——The enormous bulk of t 
head and body, and massive proportions of th 
osseous and muscular systems, are more largely 
developed in the ponderous Proboscidia than in 
any other known species of terrestrial quadru- 
peds. The dimensions of the bones of th 
extremities are proportional to the gravity 
the superincumbent weight; the scapula an 
pelvis, as well as the axes of the scapulo-humer 
and ilio-femoral cavities, are directed nearly pe 
pendicular to the plane of progression, and t 
whole column in each extremity presents a le 
angular disposition of the axes of the bon 
than is found in the lighter and more agi 
solidungulous Pachydermata. The olecrano 
and calcaneum, as well as the ers 
afford long and powerful levers for the applica 
tion of muscular action. The ginglymo 


P 


UCHaAal 


* Sce Rennel on the rate of travelling of cam € 
Phil. Trans, 1791, p. 129, ‘ 


MOTION. 


articulations of the carpal and tarsal bones 
allow a very limited motion. The axes of these 
bones are inclined almost vertically, but those 
of the metatarsal and metacarpal bones are 
directed rather more horizontally. The phalan- 
ges of the toes diverge from each other to give 
a broader base of support to these great digiti- 
grade quadrupeds: their walk is slow and heavy, 
and the order in which the legs move is the 
same as in the Solidungula. 

Carnivora.—tin the structure of carnivorous 
quadrupeds, such as the Lion and Tiger, we 
observe the strength of the more ponderous 
and slow-moving Ruminants, as the Ox, com- 
bined with the agility and speed of those 
lighter forms, as the Stag. ‘This union of 
strength with speed is due to the geometrical 
and physical relations of the elements that enter 
into the composition of these powerful digiti- 
grade Carnivora. The spine possesses greater 
mobility by the retraction of the spinous and 
transverse processes, and the trunk is of less 
weight and bulk compared to their mus- 
cular power than in the herbivorous rumi 
nants. In the Lion the scapula, which is 
directed very obliquely forwards, is unfettered 
in its motions by a clavicle; the humerus is 
long and cylindrical, and has its axis directed 
_ downwards and backwards, forming, with that 
of the scapula, an angle of 110°; the radius 
_ and ulna are articulated so as to allow of pro- 
Ration and supination; the olecranon projects 
several inches beyond the axis of rotation in 
the elbow-joint, and constitutes a powerful 
lever for the application of the tendons of the 
extensor muscles of the arm; the direction of 
__ the sacro-iliac articulation is eccentric to that of 
_ the sacrum, and the pelvis, which is inclined 
very obliquely backwards, forms, with the pro- 
_ jection of the vertebral column, an angle of 
_ about 110°; the femur is directed forwards in 
Standing at an angle with the pelvis of 84°; the 


tibia and fibula are distinct bones; the calca- 


neum is of great length; the tarsus and meta- 
tarsus inclined vertically, the phalanges horizon- 
tally; the last of which is elevated above the 
plane of motion.* In both the arms and legs 
the phalanges terminate in strong, curved, re- 
_ tractile claws for the prehens‘on and laceration 
of prey. The posterior extremities in both the 
~ lion and tiger are longer, and the bones in- 
_ ¢lined more obliquely to each other than the 
anterior, giving them greater elasticity and 
_ power in springing: they walk, trot, and 
gallop upon the same principle as the horse. 
Cheiroptera.—The bat being principally or- 
ganized for flight, is provided with compara- 
tively diminished powers of progression upon 
Solids; the legs are feeble and. incapable of 
Supporting the trunk, and they move by 
a crawling, and sometimes a small leaping 
motion, 
Quadrumana,—Of all Mammalia, the figure 
and organization of the Quadrumana approx- 
imates most nearly to man. They are destined 


* Itis in consequence of the direction which the 
tarsal, metatarsal, aud phalangeal bones take, 
that the Carnivora and other animals are digiti- 
grade, ; 


455 
to climb the trees of the forest; to leap from 
branch to branch; to walk, trot, or gallop as 
Lil iy upon plain surfaces, with the trunk 
directed either horizontally, or to walk as 
bipeds upon the posterior extremities alone, 
with the trunk directed vertically. For these 
several positions of the trunk and modes of 
progression they are furnished with a suitable 
geometrical conformation of their osseous frame- 
work, more especially in the Ourangs and 
Chimpanzee. In the Quadrumana the spinal 
column has greater freedom of motion than in 
the Pachydermata and Ruminantia. The sca- 
pula, which is directed forwards at an acute 
angle with the vertebral column, is supported 
byaclavicle; the ginglymoid cavity is deep, for 
the secure rotation of the head of the humerus ; 
the latter is long, but slender in the Hylobates 
or long-armed Gibbon; the radius and ulna 
are distinct and free from the motions of pro- 
nation and supination; the carpus is often 
composed of nine bones by the division of one 
in the second row, to give greater mobility to 
the hand; the metacarpus and phalanges are 
much lengthened, but the same in number as 
in man ; the iliac bones, which are long and 
narrow, are directed backwards nearly parallel 
to the vertebral column, but presenting with it 
posteriorly a very small angle; the tuberosities 
of the ischium incline outwards, giving a large 
base of support to the animal when resting on its 
callosities. In the Hylobates, the femur is curved 
and of less length than the humerus, but it is 
nearly of equal length in the Chimpanzee and 
Ourangs. The tibia and fibula are long and slen- 
der; the articulations of the astragalus, calcis, 
scaphoid, cuboid, and cuneiform bones are 
directed obliquely, which gives to the ankle- 
joint a motion eccentric to the axis of the leg, 
the effect of which is to throw the animal upon 
the outer edge of the hands and feet. The 
long metatarsal and phalangeal bones are in- 
clined upwards and inwards, by which they are 
adapted for prehension in climbing or standing 
on the branches of trees; the calcaneum is 
short, and its axis of motion is eccentric, 
with respect to the direction of the tendons of 
the gastrocnemius and soleus muscles ; which, 
though not very powerful, act at a mechanical 
disadvantage tending to diminish their effective 
force in a twofold manner. In many Quadru- 
mana, as the Cercopithecus and Semno- 
pithecus, the lengthened and flexible tail is 
employed as an organ of prehension, but in 
the Macacus and others the tail is pendent, 
and not employed in their movements. In the 
Mandrills the tail is very short; the Simia, 
Pithecus and Simia Innuus have merely a tuber- 
cle, whilst the Ourangs and Gibbons are desti- 
tute of this organ altogether; the deficiency of 
the mass of extensor muscles of the ankle- 
joint in the Gibbons and Jockos is alleged by 
Daubenton * as a reason why these apes cannot 
maintain themselves in the erect position. Per- 
rault is of opinion that the straightness of 
the ossa ilia prevents the extensor muscles 


* Encyclop. Méthodique Dictionnaire des Ani- 
maux, p. 20 


456 


from acting with sufficient mechanical advan- 
tage to extend the thigh as perfectly as in 
man. Vicq D’Azyr®* states, that in the Man- 
drills the flexors of the leg are inserted lower 
than the extensor muscles, and that they 
oppose the perfect extension of the leg upon 
the thigh, which renders it impossible for them 
to stand upright for any length of time without 
tottering. ‘The Chimpanzee, the Ourang-Outang, 
and some of the Gibbons, however, are ca- 
pable of walking upon their posterior extre- 
mities with the trunk nearly erect; but the 
poe being narrow, and the cotyloid cavities 
ing directed inwards so as to throw the soles 
of the feet very near each other, the base of 
support becomes very much contracted, and 
the animal stands very unsteadily. Of all the 
Quadrumana, the trunk of the Chimpanzee is 
directed nearest the vertical; in walking as 
well as in conformation he approaches nearest 
to the figure and gait of man. In the Hylo- 
bates and Laniscus the arms are of sufficient 
length to enable them to touch the plane of 
motion with the fingers and assist them in 
walking; this is resorted to whenever the 
centre of gravity falls anterior to the base of 
support formed by the hind extremities. 

I'he Lemurs are more decided!y quadrupeds ; 
the large are described by the spine, directed 
with its concavity downwards ; the lengthened 
horizontal direction of the face to the direc- 
tion of the scapular and cotyloid articulations, 
contribute to the prone position of the Lemurs. 
Some of the tribe, as the Lemur tardigradus, 
are denominated Sloths from their proverbially 
s'ow progression. Although the Ourangs have 
the advantage over other Quadrumana, of walk- 
ing erect, and having the hands and arms free 
for prehension and great variety of action, such 
as using a club for defence or assault ; yet the 
Gibbons outstrip the Ourangs in the velocity 
of their progression, and in their power of 
swinging and projecting themselves from tree 
to tree with extraordinary velocity. According 
to Duvaucel, the Hylobates agilis can launch 
itself from bough to bough at the distance of 
forty feet asunder, apparently without effort or 
fatigue. Martin relates, that “a live bird being 
set at liberty in the presence of a female Hylo- 
bates agilis, she marked its flight, made a 
long swing to a distant branch, caught the 
bird with one hand in her passage, and at- 
tained the branch with her other hand, her 
aim both at the bird and the branch being as 
successful as if one object only had gained 
her attention.” The addition of a long and 
flexible tail in the Cercopithecus, Semno- 
pithecus, and several other species, gives a fifth 
organ of prehension which is employed to as- 
sist them in a variety of motions. The walk, 
trot, and gallop of the Quadrumana are per- 
formed upon their four extremities on the same 

neiples as those of quadrupeds in general, 

ut as plantigrade bipeds their locomotion is 
accomplished like that of man. 

Secr. V. Man.—The locomotion of man 
is that of a plantigrade biped. When the 


* System Anat. des Animaux. 


MOTION. 


body is erect and the face inclined ata s! val 
angle above the horizontal plane, the head is 
exactly balanced on the atlas, and its weight is 
transferred to the latter with the least expen 
diture of muscular action: its axis of motion 
is bisected by a vertical line passing through its 
centre of gravity when it is in equilibrio upon 
the atlas: in every other position of the head 
the expenditure of muscularaction is increased. 
It has 5 a observed by Daubenton, that, vhe 
in the position of a quadruped, man is obliged 
to elevate the head above the axis of the ver- 
tebral column, in order to see directly for- 
wards; and in depressing the head to the 
earth, the position of the occipito-atlantal arti- 
culation prevents the jaws reaching the ground, 
The movements of the head on the atlas are — 
restricted to one plane, namely, the vertical 5 
but its articulation with the dentata permits 
a horizontal motion through a large are of a 
circle ; the head cannot turn without the atlas, 
nor the atlas without the head; on the con- 
trary, the atlas and dentata revolve upon each 
other in opposite directions. By means of 
these two joints, whose axes of motion are ¢ 
right angles to each other, the head enjoys a 
considerable range both in the vertica 
horizontal planes. a 
The vertebral column.—The office of this 
complex structure is purely mechanical. The 
flexibility of the spine 1s due to the twenty-foui 
joints which divide its length, and the interposi- 
tion of the elastic, intervertebral, fibrous tissues. 
It is upon the elasticity and quantity of the latte 
that the flexibility of the vertebral column de 
pends. The mean proportions of the heights of 
the cervical, dorsal, and lumbar intervertebral 
elastic tissues to that of the bodies of the ver- 
tebre are estimated by Weber as follows: _ 4 


Heights of cervical vertebrae .... 
Dorsal sal 


Lumbar ,, 


Heights of intervertebral tissues. . 


Cervical 3 oe 
Dorsal > a 
Lumbar a: o 
and their mean diameters, 


28.0 “| 
And, admitting their breadth to be equal 
their thickness, which is near the truth, # 
tranverse sections will be as the — f 
breadths, or as 225, 640, 784. Hence, if 


cervical, dorsal, and lumbar portions are cury 


with equal force, their angles of flexion ¢ 
their elasticity will be in the following 
portions : 4 
(2) : @) an 
2257 © \6407 ~ \7B4 " | 
846 : 297 ; 298 lam | 


that is, the angle of flexion of the dorsal a 

lumbar portions, notwithstanding their 

lengths, are nearly equa!, whilst the angle 

the cervical portion, though of much | | 
; 


& 
‘i 


oF ES eS ee ee 


MOTION. 


length, will be nearly three times greater. The 
greatest flexion of the trunk is in the plane of 
its mesial section, and results chiefly from the 
cervical and lumbar vertebre. According to 
Weber, its greatest twisting or torsion hori- 
zontally is derived from the dorsal region. The 
angles of flexion of the head and trunk in two 
cases were as follows: 
Crown of the head Sternum and Sum of the 
and sternum. sacrum. two. 
Beteriie tO! oecsee OS occas. 2300 
DUeMeadiet Oo 5.600 85° -..\c¢20 260° 


Mean.. 161° 84° ...... 2450 


Of these two cases nearly two-thirds of 245° are 
accomplished by the head and neck, and one- 
third only by the dorsal and lumbar vertebrz. 

The curved form of the spine, somewhat re- 
sembling an italic f, instead of being a cause 
of weakness, is, on the contrary, a source of 
strength and security; for forces acting verti- 
cally upon it are transmitted obliquely, thus 
diminishing their mechanical effect ; and the 
elasticity of the intervertebral tissue prevents 
the shock to which the bones would otherwise 
be subjected at every step in walking. With 
respect to the power of the vertebral column 
to sustain weight, if we regard it in conse- 
quence of its form and elastic intervertebral 
Substance as a spring with small flexures, it is 
capable of bearing a greater weight than if it 
were straight, in the proportion of the square 
of the number of curves plus one to unity ; 
that is, a weight sixteen times as great. Consi- 
dered as a whole, the vertebral column repre- 
sents a lever of the third order, of which the 
fulerum is in the axis of the articulation of 
the fifth lumbar vertebra with the sacrum: the 
power is the mass of muscles inserted into the 
sides of the vertebre; and the resistance, the 
weight of the head, soft parts of the neck, the 
thorax, and part of the abdomen.* 

In standing erect, the direction of the verte- 
bral column is perpendicular to the horizon. 
Weber found, by means of plumb-lines let fall 
on each side opposite the centre of the heads of 
the femurs on which the trunk is balanced in 
the erect position, that the transverse vertical 
plane intersected both ends of the spine, pass- 


- Ing through the atlanto-occipital articulation 


above and the sacro-lumbar below; he found 
also lying in the same plane the two mastoid 
processes and the centres of the ankle and knee 
joints. 

Viewed separately, each vertebra represents 
a lever of the first order, whose fulcrum is the 
next vertebra, on which it rests; the power and 
resistance are the muscles acting upon it in 
different points alternately. The spinal column 
of animals is a flexible lever, destined to move 


_ and support a multitude of organs, and to con- 
_ nect the more distant parts of the skeleton with 


each other. We have nothing in the structure 
of locomotive or other machines bearing the 
least resemblance to its mechanism; and if, 
with Sir C. Bell, we compare it to the mast of a 


* Vide Majendie Phys., by Dr. Milligan, p. 175. 


457 


ship, it will tend only (as Dr. Arnott has alrea- 
dy pointed out) to convey an erroneous impres- 
sion, both of its structure and its functions. 

In standing, the vertebral column transmits 
the weight of the organs appended to or sup- 
ported by it by means of the sacrum to the 
pelvis. The pelvis is a lever of the first order, 
having its fulcrum in the ilio-femoral articula- 
tions on the heads of the femurs; the power 
and resistance are the muscles acting anteriorly 
and posteriorly to the axis of rotation. 

In the erect position of the trunk the pelvis 
is inclined to the direction of the vertebral co- 
lumn. The angles, both of the superior and 
inferior margins, have been measured by Nae- 
gele and Weber. According to the former, the 
mean angle of inclination of the superior mar- 
gin to the horizon is 60°, and to the vertebral 
column 150°. The inclination of the inferior 
margin with the horizon 11°, and with the ver- 
tebral column 101°. The angle which the 
pelvis forms with the vertebral column permits 
the femurs to extend farther backwards, and to 
increase their range of oscillation. The magni- 
tude of the transverse diameter of the ring of 
the pelvis determines the distance of the heads 
of the femurs from each other, and throws the 
thighs sufficiently apart, to prevent their friction 
upon each otherin walking. The pelvis can ro- 
tate only on an axis perpendicular to the plane of 
the mesial section, when the body rests equally 
on both legs, but can turn horizontally upon 
the heads of either femur whilst the body rests 
on one leg. In standing, the pelvis is kept 
in equilibrio by several forces. The weight of 
the abdominal viscera, lying anterior to its axis 
of rotation upon the femur, tends to depress 
the pubes, and rotate the pelvis forward, while 
the weight of the vertebral column, acting pos- 
terior to that axis, tends to swing it back- 
wards. 

The weight of the vertebral column prepon- 
derates over the parts lying anterior to the axis 
on which the pelvis rotates, and consequently 
would require a considerable expenditure of 
muscular action to keep it in equilibrio on the 
femurs, but the obliquity of the vertical axis of 
the pelvis to that of the vertebral column 
throws the resultant of all the forces, acting 
downwards upon it, near the axis of rotation, 
which tends to preserve the balance; added 
to which, the muscles which draw the ver- 
tebral column backwards, having one of their 
points of insertion in the sacro-iliac section 
of the pelvis, tend to elevate it, and to neu- 
tralize their action on the vertebre in an 
Opposite direction. The principal agents in 
keeping the pelvis in equilibrio are the pow- 
erful muscles acting between it and the thigh. 

The pelvis receives the whole weight of the 
trunk and superposed organs, and transmits it 
to the heads of the femurs. It has two axes of 
motion, one of which is on the last vertebra, 
and the other in the ilio-femoral articulation ; 
in both cases it acts as a lever of the first order. 

The legs.—The leg moves by means of three 
joints, namely, the ilio-femoral, the knee, and 
the ankle. In the erect posture the first of 
these allows the leg to move only forwards, the 


- 


458 


second only backwards, and the third neither 
backwards nor forwards. 

The length of the legs, measured from the 
hip-joint to the ground when standing erect, 
preponderates slightly over that of the body 
when taken from the distance of the crown of 
the head to the axis of the hip joint, conse- 
quently the centre of gravity is raised above the 
plane of position rather higher than the semi- 
distance from the head to the ground when the 
entire sole of the foot is in contact with the 
earth.* In consequence of the lengths of the 
femur and tibia being nearly equal, and of the 
zigzag direction which the limbs take during 
flexion, and because the angle of the greatest 
flexion of the knee-joint is nearly equal to the 
sum of the angles of the hip and ankle, it 
results that in the simultaneous flexion of 
these three joints, (provided the angle of in- 
clination of the foot to the ground continues 
30°,) the trunk preserves its erect position as 
when standing, and therefore ascends and de- 
scends (by the flexion and extension of the legs) 
in the same vertical line. The greatest amount 
of elongation and contraction of the leg result- 
ing from the greatest extension and flexion of 
the hip, knee, and ankle-joints, may be easily 
ascertained by measuring with a line from the 
hip-joint to the head of the astragalus during 
such flexion and extension, and marking the 
difference in the length of the line in the two 
states. By this method the length is estimated 
by Weber as follows : 


m.m. 
In the greatest state of extension.. 924.26 
In the greatest state of flexion.... 404.74 


The actual lengths of the several portions of 
the leg are 


m.m. 

Head of the femur to the condyles. . 380.0 

From the condyles to the convex 

articular surface of astragalus .. 

Axis of articulation of the astragalus 

to centre of foot 136.0 

During the greatest extension the first three 
of these points of the leg formed an angle of 
148°8', and during the greatest flexion an angle 
of 40°. The second, third, and fourth points 
form in the greatest extension an angle of 
157° 4, and in greatest flexion 94° 6’. 

The proportion between the greatest and 
smallest length which the leg can assume varies 
but little. 

Figs. 247 and 248 from Weber show the 
greatest amount of extension and flexion which 
the leg can effect; the corresponding difference 
in length is as 14 to 5, but in walking and run- 
ning the flexion is less, and the difference of 
length as 11 to 9. 

In standing, the weight of the body is trans- 
mitted from the pelvis to the heads of the 
femurs; the oblique directions of the latter 
upwards and inwards keep in equilibrio the 
vertical forces downwards and outwards pro- 
duced by the weight of the body on the wedge- 
like sacrum. 

The femurs transmit the weight impressed 


420.0 


* See positions of the centre of gravity, sect. i, 
p. 409. 


MOTION, 


Fig. 247. 


on them by the trunk, together with their own 
weight and that of the soft parts to the tibie. 
The shafts of the latter are straight, and by thei 
rismatic form their solid contents are ver 
urther from the axis of the bone, which enable: 
them to support a greater weight with less ex- 
penditure of materials. 4 
The fibula adds likewise to the strength ¢ 
the tibia, both vertically and laterally; the 
latter transmits, in its turn, its own weight at 
that of its soft parts to the astragalus. 
The astragalus transmits the pressure made 
upon it partly to the calcaneum and partly 1 
the scaphoides; the calcaneum partly to t 
ground and partly to the cuboides; the se 
phoides transfers the force through the cune 
form bones; the toes to the ground, whe 
the base of support terminates, supposin 
the entire foot to rest on it. In the mechanist 
of the foot we discover an elastic arch, up¢ 
which the shock of the body is received, ar 
transmitted obliquely to the ground. This adm 
rable structure prevents the jar which the bor 
would otherwise sustain at each step by thes 
action of the ground in walking, running, le: 
ing, or falling; but an exact investigation 
the mechanism of the foot would occupy mi 
space than we have assigned to this subj 
The areas of the soles of the two feet and © 
space lying between them is the whole base 
support in standing on both legs; but w 
standing upon one only, this is diminish 
not only by the area of one foot, but also o 
space lying between them. In the latter: 
the base is so narrow that the act is not easi 
complished, but the difficulty of keep 
trunk in equilibrium is vastly increase 
the base of support is reduced to the area 0 
great toe, as is accomplished by opera dani 
or to the area of one-fifth or two-fifths 
square inch as in skating, or to one still le 
in rope dancing, wherein the base of sup 
oscillates laterally. In this latter case, the ¢ 
culty is increased by the necessity of keeping 
trunk in equilibrio, but the centre of gravi 
retained in the plane of the rope by ixin 
eye on some distant point in it. The- 
tion which the two feet ought to take, ¥ 
equally advanced and equally inclined, so 


Pili 


> 


MOTION. 


they may form the greatest base of support, has 
been mathematically investigated by Parent 
and Barthez. According to the latter, the tra- 
pezium which forms the base of support will 
be a maximum when the prolongations of the 
lines drawn through the central line of each 
foot and passing through the centre of each 
heel form an angle of 38° 56”. 

The calculation of Parent is defective, from 
its being based upon the hypothesis that the 
foot turns as upon a pivot about its articula- 
tion with the leg, instead of around the heel. 
When the body stands erect upon both legs, 
and presses equally on each, the legs will form 
equal angles with the vertical line passing 
through the centre of gravity; but if the two 
legs form different angles with that line, the 
pressure upon the legs will be unequal, and 
will vary with the angles of inclination, 
for example, in fig. 249, a d is perpendicular 
and g 7 parallel to the horizon; if a 


Fig. 249. 


and ag represent the entire force exerted by 
the legs to support the whole body, ad and ai 
will be the corresponding portion of these forces 
necessary to sustain the weight of the body, 
and will also together represent that weight ; 
and if a d and az be found by experiment, the 
absolute forces, a b, ag, will be found.* In 
standing, the limbs serve merely to support the 
body, and to preserve the centre of gravity at a 
certain height above the plane of position, 
within the base of support, which is a necessary 
condition to prevent it from falling. In addi- 
tion to these functions they translate the trunk, 
during progression, from point to point, and 
keep it in equilibrium, in all the varied move- 
ments and under the action of all the extra- 
neous forces incidental to locomotion.+ 


* See Borelli de motu animal. prop. 138, p. 173. 
+ When a man stands with his centre of gravity 
at a vertical height H, above the plane of the hori- 
zon, if his weight be P, then the amount of force 
which he expends in order to stand is, according 
to Poisson, equal to PH.—Traité de Mech. Paris, 


2 - 


459 


Walking.—In walking or running, the body 
may be divided into two portions, namely, the 
trunk, head, neck, and arms, which constitute 
the burden that is to be borne, and the legs 
which support and carry the burden along. 
The former cannot, however, be considered as a 
merely passive or dead weight, as the trunk 
and arms contribute to keep in equilibrio the 
forces acting on the centre of gravity during 
progression. In walking, the trunk is carried 
forwards with its major axis directed nearly 
perpendicularly to the horizon, like a rod poised 
endways on the hand. The power to keep the 
trunk thus poised whilst it is moved forwards 
is attained only after considerable experience 
during the earlier period of man’s career, when 
his unsteady gait, numerous trials, and frequent 
falls afford practical illustrations of the difficulty 
of the process. Every movement of the legs, 
arms, head, or trunk, as well as the bearing of 
burdens in various positions, requires a compen- 
sating movement of some other part, in confor- 
mity to the theory of parallel forces, to preserve 
the whole in equilibrio; therefore, in order to 
keép the supported parts poised on the rounded 
head of either femur, whilst the body is trans- 
ferred from one to the other, and carried forwards 
in the air, either against or in the same direc- 
tion as the wind, there must be a continued in- 
terchange of compensating movements, and 
these actions are placed under the controul of 
the excito-motory division of the nervous sys- 
tem. It is well known that when any portion 
of a rigid body receives motion from a neigh- 
bouring body, all the parts of the rigid body 
will partake of the same motion, only when 
the direction of the force passes from the point 
of contact through the centre of gravity. If this 
is not the case, as, for example, when the upper 
extremity of the propelling leg acts on the 
lower part of the trunk of the human body in 
the erect position, the lower part would be pro- 
pelled forwards and upwards, whilst the centre 
of gravity of the trunk would be left behind, 
and fall backwards; but if this centre be in- 
clined forwards at the beginning of the step, the 
weight of the body and its required momen- 
tum will propel it forwards and downwards ; 
hence the resultant of the several forces will be 
a force which propels the body forwards in a 
direction which, by experience, is found to be 
nearly horizontal: but there is also another 
force which affects the trunk, namely, the re- 
sistance of the air, which tends to turn the 
trunk backwards, and must be counteracted by 
the force of gravity, through the inclination of 
the trunk forwards. The amount of this con- 
stant inclination of the trunk must be estimated 
by the resistanceewhich it encounters from the 
air in walking and running. It must therefore 
be greater in rapid progression, because the 
resistance of the air is then more powerful than 
in more deliberate motion. Without this incli- 
nation it would still be possible to preserve a 
uniform position of the body in walking and 
running, not, however, by the force of its own 
gravity, but by means of the power of the mus- 
cles, which connect it with the limbs ; but this 


460 


would require a great expenditure of muscular 
force, which is aided b the inclination of 
the trunk. That this inclination really takes 
place is confirmed by experience, and its 
amount has been measured by Weber, both in 
walking and running with various degrees of 
velocity. In order to take these measures with 
accuracy, a given path was passed over, some- 
times in running and sometimes in walking, 
with various d of speed, the time being 
measured and the steps counted. By means 
of a telescope, placed sideways to this path, 
the difference of inclination in walking and 
running was ascertained, but as it was extremely 
difficult to find the actual position of the centre 
of gravity of the trunk in such varying posi- 
tions, a conspicuous line marked on the trunk 
was substituted for the vertical line passing 
from the axis of the femurs through the centre 
of gravity, and thus its slightest deviations 
were observed. The vertical position of the 
trunk when at rest may be exactly estimated by 
the angle which it makes with this marked line 
in walking to and fro, in running to and fro, 
and in standing in the two opposite positions. 
The last angle, deducted from each of the two 
first, gives the double inclination of the trunk 
from the vertical in walking and running. . The 
results of these measurements are given in the 
following Tables. 


TaBLeE 1. 


Measure of the inclination of the trunk in 
walking and running. 


Angle between the 
two a posi- 
tions of the marked 
line in standing. 

130 74 

130 74 

130 66 

15° 46 


14° 00 


TABLE 2. 


Measure of the inclination of the trunk in 
walking slowly. 


Angle be- 
tween the ° 
two oppo-| = | Double 
site posi-| §& inclina- 
a a Duration |tions of the 2 tion 
° of marked of the 
Step. Step. line. . trunk. 
0.629 0.833 0.755 
0.664 0.777 18° 9 | 0.855] 4°9 
0.699 0.848 18° 9 | 0.824] 4°9 
0.664 | 0.793 | 20°6 | 0.837! 6°6 
0.699 | 0.839 | 20°6 | 0.833| 6°6 
0.629 0.812 18° 9 | 0.774] 4°9 


MOTION. 


TabLe 3. = 
Measure of the inclination of the trunk in 
é quick walking. - 
0.838 0.452 1.85 
0.838 0.426 27° 8 1.97 
0.838 0.429 26° 1 1.95 
0.838 0.428 27° 5 1.96 
0.838 0.444 32°6 | 1.89 
0.816 0.438 31° 8 1.86 
0.838 0.431 24° 9 1.945 
0.838 0.419 29° 2 2.00 
0.838 0.439 27° 5 1.91 
0.888 9.436 29° 2 2.04 
0 838 0.432 30° 9 1.94 
0.888 0.438 32° 6 2.03 
0.888 0.456 31° 8 1.95 
TABLE 4. 
Measure of the inclination of the trunk — 
in running. 
1.372 0.325 4.22 
1.509 0.323 48°1 | 4.67 
1.509 0.337 49° 8 5.00 
1.509 0.302 55° 8 5.03 
1.509 0.300 56° 7 4.72 
1.509 0.320 53° 3 
1.509 0.320 


We therefore conclude that when we vai 
our steps, the velocity of the upees ends of tl 
legs, together with a corresponding inclination 
is communicated to the trunk. run 
then, as has been before observed, exactly re- 
sembles a rod balanced on the fi ar 
carried forward; the inclination in cas 
depending on the laws of mechanics. y 

he force of the muscles which keep 
trunk in a state of equilibrium is likewise ec 
nomized in walking and running by the regu’ 
oscillations of the arms. The distance of t 
scapulo-humeral articulation from the ax 
which the trunk freely moves, gives an 
applied at the shoulder-joint a considera 
mechanical effect on the trunk. In prog 
the arms and legs move simultaneou: 
the following order. Whilst the right | 
swings forwards, the trunk is turned round h 
zontally on the head of the left femur, 
would pres! the right shoulder before the 
but at the same time the right arm swings ba 
ward and the left forwards, and by generati 
force in an opposite direction neutralises ” 
tendency. A corresponding compensation fa 
place when the left leg swings forward, 
this is effected by a good walker, without ¢ 
sensible lateral twisting of the trunk. 
length of the arms is so adjusted to that of 
legs, that they oscillate with the latter in sr 
curves simultaneously. Weber has comp 
the duration of a single oscillation of 
hanging straight down, at 0”.63, and wh 
at right angles at 0’.53. The pace is | 
strained and less fatiguing when the arms 


_ progression. 
~ tension produces an increased velocity in the 


MOTION. 


allowed to accompany the movements of the 
legs without muscular effort. When the body 
is put in motion, the momentum generated re- 
quires an equal furce in the opposite direction 
to stop it, for which purpose the trunk is thrown 
back ; and this, with the resistance of the feet on 
the ground, will commonly suffice. When, 
however, this is not the case, the motion must 
be arrested gradually, or, as it often happens 
when the plane of position is composed of ice, 
the leg goes on without the trunk, and the cen- 
tre of gravity comes to the ground. 

In walking, the trunk is also elevated and 
depressed at each step vertically, as well as 
oscillated in other directions. By the assist- 
ance of a rod graduated into millimetres, which 
was carried at the head of the trochanter major 
by the ambulator, and viewed through a tele- 
scope, Weber was enabled to ascertain the 
amount of the elevation and depression of the 
trunk. He found that when the length of the 
steps treading on the whole sole of the foot 
measured 2.39 feet, the mean elevation and de- 
pression were 1.1 inches. The plane in which 
the rod vibrated, and the magnitude of the 
oscillations, did not appear to vary materially, 
whether the speed was accelerated or retarded. 
In walking on the ball of the great toe the 
mean elevation and depression of the trunk 
was 0.8 inch. 

Estimate of the forces employed in walking. 
The forces which we have to estimate in walk- 
ing are, first, that of the extension of the leg; 
secondly, the gravity of the body ; thirdly, the 
resistance which the body encounters in pro- 
gression. Of these, the first is that force which 
the leg exerts by its extension to bring it into 
a straight line, as if both of its extremities (viz. 
the head of the femur, and that part of the foot 
which is in contact with the ground) endeavoured 
to push each other away. The direction of this 
force depends on the position of the extremi- 
ties of the leg ; but whatever that direction may 
be, it is always resolvable, on the principle of 
the parallelogram of forces, into a vertical and a 
horizontal component. The vertical portion of 
the extension upwards is equal to the second 
force, or the gravity of the body acting vertically 
downwards ; in this case the centre of gravity 
remains at the same height above the plane of 
The horizontal portion of the ex- 


horizontal direction, the magnitude of which 
depends on the position of the supporting leg. 
By means of these forces the body is propelled 
forwards. At the moment the body receives the 
impulse of extension it is accelerated until the 
third force, namely, the resistance,* augmenting 
continually with the velocity, is equal to that 
of the acceleration ; when these two forces neu- 
tralize each other, the body will move forwards 
with an uniform velocity. 

Hitherto the forces which influence walking 


* The principal resistance is occasioned by the 
advanced leg when it reaches the ground. Other 
resistances are the frictions of the joints, of the sole 
of the foot upon the earth, of the air, &c., but these 
are very trifling when compared with the retard- 
ation caused by the advanced leg. 


461 
have been considered as if they were uniformly 
accelerating forces; but though they are not 
strictly such, yet as they recur at the end of 
each step, the mean velocity of the body will 
remain the same as if they actually were so.* 
Let us assume a common point of application 
of the forces, and consider this as the centre of 
the body, or the point of separation between the 
trunk and the legs. The three forces may be re- - 
presented (fig. 250) by three straight lines meet- 


Fig. 250. 


ad 


a 


ing at this point, thus: Let c be the centre of the 
body; draw ca in a vertical direction, c b 
in a horizontal, and c d in the direction of the 
prolongation of the leg on which the body is 
supported. These three lines will represent in 
magnitude and direction the forces which are 
in action during progression, if they be so taken 
that either of them equals the diagonal of the 
parallelogram formed by the other two, and 
will coincide in direction with that diagonal 
produced beyond c. Messrs. Weber do not 
consider those physiologists worth refuting who 
state that the forces which propel the body for- 
wards exceed those that drive it back, for in 
that case, from the continued preponderance of 
force in one direction, there would result, not 
an uniform, but a continually increasing velo- 
city. An uniform motion in a straight line 
can only take place either when no force what- 
ever is exerted on the moving body, or when all 
the forces by which it is affected are in equi- 
librium. 

In order to investigate with greater precision 
the laws which regulate the movement s of the 
body, the Messrs. Weber have considered the 
weight of the trunk to be collected at the point 
of junction of the legs, and the weight of each 
leg, supposed a straight line, to be collected in 
a point at a given distance from that junction. 
The movements of these points are supposed to 
take place in the same vertical plane. They 
have then applied the general equation for the 
motion of a system of material points,t and 
deduced by means of it that the raised leg, in 
walking, swings forward like a pendulum, the 
length of which is the above-mentioned given 
distance, but in consequence of the motion of 
the point of junction, which is supposed to 


* The three forces which influence walking are so 
related to each other, that each of them is equiva- 
lent and opposite to the resultant of the other two. 

+ See Poisson’s Traité de Mechanique, Paris, 
1833, vol. ii. § 531. 


462 


move uniformly in a horizontal line, it has a 
re € motion in its curve of oscillation, 
which, if measured from its lower extremity, is 
just equal to the velocity of the point of junc- 
tion, when estimated in the direction of the 
tangent of the curve at the commencement of 
the step. Hence, in quick walking, when the 
Swinging leg is supposed to come to the ground 
.In a vertical position, it describes half of the 
curve during each step. By following the 
same course of reasoning Messrs. Weber have 
ascertained the amount of the vis viva, or vital 
force, communicated to the swinging leg in 
any given time; the amount communicated to 
the body by the standing leg; the proportion 
which the time when the body is supported on 
one leg bears to the whole time of a step; and 
the height at which the centre of gravity is 
borne above the ground.* In order to verify 


* After an elaborate analysis the Messrs. We- 
ber have deduced the following equations, which 
express the general laws of walking. 
At pA = 2 ,... 2. eccccccesses 
(hk — 4 g 8) & 4 pt = 12... eee ee (24) 


< s1+n Cos iad @—«)} 


WN Bo Cabe B) Rives cs icvevesaceseses 


(bak titers tantiee IOS 


In which equations 
—a 
=a/i+r2 . 
" a/ x lg 


= 7 are (Cos = 
w 


). 


x!l- 


(eels 
k= 
(ip rar= sin qit—«) } sn 


The mass of the trunk is supposed to be con- 
centrated in a point m at the upper end of the 
leg, and the mass of the swinging leg in a point 
m’in the leg which is considered as a straight 


line. vy * ; 

lis the length of the hinder leg at the begin- 
ning of a step. . 

h is the height of m above the horizontal plane 
at that time. d 

is the distance between the hinder foot and 

the forward at that time, or the length ofa step. 

@ is the time during which m falls below its ho- 
rizontal line at the end of the time ¢. 

U is the length of the hinder leg at the end of 
the time before it is extended or becomes /, 

+ is the time of one ~~ F : 2 

t is that portion of it during which the leg is 
swinging. 


MOTION. 


the pendulous movements of the legs a person 
was placed upon a small block, and by sup- 
porting himself on one leg, suffered the other, 
measuring thirty inches, to swing, with relaxed 
muscles, as a pendulum. A vi mo 
having been communicated bya slight mov 
of the trunk backwards and forwards, the num 
ber of oscillations made in the time of a minut 
were found to be 84, consequently * 


o = 0”.714285 = time of one oscillation 
and since the lengths of pendulums*at th 
same place vary inversely as the squares of th 
numbers of oscillations in a given tim 
842: 607 :: 39}: 1 (the length of a pendulun 
which vibrates synchronously with the leg) 
602 x 39} _ 140850 _ 19 9¢. 
84? ae 
inches. Now as the whole length of the leg 
was 34 inches, the centre of oscillation must be 
less than two-thirds of that length from the 
point of suspension, and consequently les 
than in a prismatic rod, the length of which 
is such as will vibrate synchronously wit 
the leg. This accords with the known figure 
of the leg, the mass of which diminishes a: 
the distance from the axis of motion in- 
creases. The time of a half oscillation ¢ 
the freely suspended leg which we have found 
0”.714285 __ 0”.3571425 . ical 
aren aay » approximates ve 
closely to that found by the Webers, both m 
the living and the dead subject. 
The second experiment was made 
engraver, Mr. Vasey. In walking at the ra 
of four miles per hour he counted 2000 step: 
15 x_60 _ 0". 


hence / = 


every fifteen minutes; then 


the time of each step ; now as 2000 steps wer 
taken in one mile of 5280 feet, the length of e: ‘ 


oy 
ris the ratio of the distance between m 
m’ to I. 
P gis the accelerating force of gravity = 3% 
eet. 
m is the number 3.1416. 
T is the time of an oscillation of a pen¢ 
whose length is rl. 
w is the ratio of the mass‘of the trunk to 1 
mass of the swinging lege 
The quantities / T, ~ must be previt 
ascertained, and w and g being always the sa 
there will be nine equations for finding the vah 
of the ten remaining quantities; if therefore 
know any one of these ten, the rest may be fou 
In regular progression the force communics 
by the supporting leg to the trunk must e 
re imparted by the trunk to the swingin; 
that is 7 


mi(etrape sin} = (t—a) } ym : 


a Oe, tee 
h t 


SS 


? 


cr. 


from which, by substituting ? for ¢ 
v 


~ we get equation (26.) 


» saa 


MOTION. 


463 


Fig. 251. 


Pee Hee 


PAG aks. 1S 13-14 


15 1617 18 


Fig. 251 shows the tive positions 0 
the leg during two successsive steps. To 
render them more distinct they are divided 
into two groups, The 18 figures of the 
Jirst group show all the positions through 
which the leg passes while the toe rests 
upon the ground. The 10 of the second 
show the successive positions during the 
time the body is carried forward by the 
swinging leg. The positions from 1 to 4 
show that division of time of the first 
step, when both legs are on the ground ; 
the figures 5 to 14 give the portion of 
time of the first step when one leg rests 
on the ground while the other swings ; 
from 15 to 18, that division of the second 
step where both legs rest on the ground ; 
No. 19 to 28 show the portion of time 
when one leg swings while the other rests 
on the ground. 


ig. 90 Of. @ & 24 2 6 27 28 


5280 


~ step must have been 5 = 2.64 feet. In this 


case also the length of the leg was 34 inches, 
which gives 19.961 inches for the length of the 
synchronous pendulum, and for the time of 
each half oscillation 0.357; hence the time of 
taking each step was longer than the time in 
which the leg was susceptible of swinging 
without muscular effort, as a pendulum, by 
about 0”.093. 

The step is considered as commencing at the 


_ instant when the hindmost leg is raised from 


the ground. Let us then suppose the whole 
sole of the foot of the right leg, which is in 
advance of the left, to be in contact with the 
ground, upon which it acts as a fulcrum; the 
hip, knee, and ankle-joints to be in a state of 
partial flexion, and the line from the head of 


the femur to the ankle-joint to be vertical, as 
in fig. 251, No. 4. In this position, the right leg 
supports the whole weight of the trunk, and the 
left, being extended obliquely backwards, does 
not contribute to the support of the burthen. 
The flexed position of the right leg lowers the 
centre of gravity, and the effective portion of 
the force of extension, acting only in a vertical 
direction, produces no horizontal motion. At 
this moment, the left leg having previously 
communicated a slight horizontal impulse to the 
centre of gravity, and the trunk being inclined 
forwards, the head of the femur of the right 
leg is propelled from No. 4 towards No. 18. 
The leg, instead of being vertical, is now di- 
rected obliquely forwards and upwards. In 
order that the head of the femur with its load 
may be sustained at the same height above the 


464 


MOTION. 
Fig. 252. 


6&9 1011 


12 13 14 igs 


Fig. 252 shows the simultaneous positions of both legs during a step, dinided into four groups. 
4 to 7, gives the different positions which the legs simultaneously assume while both are on the ground ; 
second group, 8 to 11, shows the various positions of both legs at the time when the posterior p 
From the ground, but behind the supported one ; the third group, No. 12 to 14, shows the positions which 
legs assume when the swinging leg overtakes the standing one ; and the fourth group, 1 to 3, the p 
during the time when the swinging leg is propelled in advance of the resting one, 


plane of motion, whilst it moves forwards with 
the trunk, from No. 4 to 18, the distance from 
the head of the femur to the foot must be con- 
stantly increasing. To accomplish this the mus- 
cles which extend the hip, knee, and ankle- 
joints are gradually contracted, and the length 
of the leg sufficiently increased by its extension 
‘to reach from No. 18 to the ball of the foot 
(fig. 251). In these movements the sole of the 
foot rotates on the ground, and (independently 
of the angle formed by the legs) increases the 
length of the step by the length of the foot 
from the heel to the ball; because, when the 
head of the femur arrives at No. 18, fig. 251, 
the line from the ankle-joint to the ball is 
perpendicular to the ground. At the moment 
that the head of the femur of the left leg arrives 
at a position vertical to the foot, as No. 4, 
Sig. 251, the right leg is lifted from the 
ground,* and, from its oblique position and 
weight, swings forward like a pendulum, 
whose axis of motion is in the hip-joint, Nos. 
19 to 28, fig.251, and having passed by the sup- 
porting leg it touches the ground, with the 
ankle-joint in advance of the head of the femur, 
No. 1, fig. 251. The heel is first placed upon 
the earth, and by degrees every part of the 


* Measure of the elevation of the heel and toes 
in walking, the distance passed through 30 metres. 


Num- Elevation | Elevation 
ber of of the [of the point 
steps. | Time. heel. jof the toe.| Velocity. 
metre. metre. 
41 17.4 0.178 0.092 1.72 
39 12”.7 0.173 0.115 2.36 


The first g 


d 
4 

ry 

e 


leg is elevated 


~ 


sole, the hollow arch only excepted, is brou 
into contact with the ground, and the head ¢ 
the femur is again over the ankle-joint, as before, 
No. 4, fig. 251. The motion of the left leg ak 
ternates with that of the right in the same 
manner.* In the first period of the movement 
the left leg is seen in the rear of the right leg, 
No. 8 to 11, fig. 252. Having overtaken the 
latter, No. 12 to 14, fig. 252, it advances 
before it and comes to the ground in suffiel 
time to receive the weight of the body as s 
as the right leg ceases to act, No. 4, fig. 
so that the instant the weight of the tra 
is transferred to it from the right leg bem 
ing slightly and returning to its former posi 
tion, it acts like a spring, and prevents an 
sudden concussion arising in consequene 
of the translation of the burthen from on 
leg to the other. The weight of the tran 
being thus propelled, supported, and transfern 
from one leg to the other alternately, a consta 
and uniform movement in a horizontal dire 
is maintained. The right and left leg 
thus swung and supported the body altern 
and having been on the ground simulta 

a short, and separately a long, period, the h 
rizontal path of the centre of gravity, dur 
these two movements, is equal to the length 
a double step. In consequence of this mite 
change of offices the supporting leg is act 

whilst the swinging leg is comparatively f 


ae 
<-> 


* The Webers compare the action of the foot 
rolling of a wheel, with this difference, that 
tation of the wheel is uninterrupted, whi 
the foot is terminated and renewed at ev 
In walking on the ball of the foot, or on t 
the rotation is confined to the distance be 
ball of the foot and the point of the toes. 


we 


MOTION. 


sive; that is, it swings forwards by the force of 
gravity alone, independently of muscular ac- 
tion. The supporting leg is regarded by 
the Messrs. Weber as a substitute for the pro- 
pelling weight of a clock, and the swinging leg 
as the substitute for the pendulum, both ex- 
changing their offices alternately. The distance 
from the point where the ball of the foot of the 
Swinging leg quits to the point where it is again 
placed on the earth, is equal to the length of a 
double step. This outline of the action of the 
legs in walking depends on principles which we 
shall now proceed to investigate more strictly, 
in doing which we shall draw largely from 
the theoretical and experimental researches of 
the Messrs. Weber, whose labours have con- 
tributed so extensively to advance our know- 
ledge in this interesting branch of human phy- 
siology. 

The positions of the body in walking at va- 
rious instants of time have been described both 
by Borelli and Weber; it is thus represented 
by the latter. Let fig. 253 be the vertical, and 
Jig. 254 the ground plan, on planes in a straight 


Fig. 253. 


<A at ke 
a Bigu% “55, 
horizontal path. In fig. 253 the simultaneous 


positions of the two feet are represented at 
the moment when they reach the ground, 
also the position of the centre of gravity of the 
body in the vertical plane. The position of the 
right leg is shown by the continued lines, and 
that of the left leg by the dotted lines. The 
extremity of the right foot is designated by the 
‘letter a, that of the left by the letter b, and the 
centre of gravity by c, the contemporaneous 
positions of these points being denoted by the 
humerals annexed to these letters. In the 
horizontal projection, fig. 254 represents the si- 
multaneous position of both legs and of the cen- 
tre of gravity ; the letters and figures are the same 
as in the preceding diagram. At the instant when 
the hinder leg is raised from the ground at the 
commencement of each step, the extremity of the 
forward leg and the centre of gravity lie in the 
normal plane of the line of progression; for 
example, at the beginning of the first step, 6, 
and ¢,, of the second step a, and c,, and of 
the third step, b, and c,, lie in the normal 
plane of the direction of progression. 

In each step the extremity of one leg must 
VOL. III. 


465 


be advanced as far before the foot of the other 
as in the preceding or following steps the other 
leg was placed before the first, for example :— 
in the first step, the foot, a,,,, must ad- 
vance so far before b,,., as in the second 
step b, ,, ,must advance before a, . 5 ,- 

The time of each step, that is, the space of 
time between the raising of each foot in succes- 
sion, is subdivided by Borelli and the Webers 
into two parts, namely, one part in which 
one leg, and the other when both legs are 
on the ground: for instance, during the first 
step, while the centre of gravity advances 
from c, to c,, one leg, and, while it advances 
from c, to c, both are on the ground.’ In the 
second step, while the centre moves from c, to 
C3, one leg only, but while it advances from 
c, to c, both legs are again on the ground, and 
so on in succession. But there is no instant in 
walking in which the body moves freely through 
the air without either leg touching the ground, 
as in running. 

The sum of the squares of the elevation of the 
centre of the body above the horizontal plane, 
and the length of the step, is equal to the square 
of the length of the extended leg.* This pro- 
position depends on the circumstance that the 
forward leg stands vertical to the ground at the 
instant the hinder leg quits it; and that the 
two legs, with the horizontal distance between 
them, form, at this moment, a right-angled tri- 
angle. According to the Webers, the body, in 
walking, continues to be affected by the exten- 
sor power of one leg only, because the expen- 
diture of the extensor power of the legs to 
support the body is only just sufficient to sus- 
tain it; and this expenditure is at a minimum 
only when the forward leg bears the whole 
burden during that period in which they are 
both on the ground, for as the forward leg acts 
at a less angle than the hinder leg, it is capable 
of supporting the body at a much greater me- 
chanical advantage, which is at a maximum 
when it stands vertically. MM. Weber also 
find that the body is accelerated whilst one 
leg, and is retarded whilst both legs are on 
the ground; for, in slow walking, the forward 
leg being placed on the ground in advance of 
the centre of gravity, it tends for an instant to 
check the horizontal velocity of the body. 

We shall now take a brief view of the velo- 
city in walking, and of the principles on which 
it depends. MM. Weber have shewn that 
the velocity in walking varies with the height 
at which the head of the femur is carried from 
the ground; as this height increuses, the velo- 
city decreases.t The length of each step de- 
creases as the height of the centre of gravity in- 
creases; for the greater the elevation, the less 
will be the distance to which the leg will ex- 
tend ; therefore corpulent persons, and porters 
with heavy burdens on the shoulders, take steps 
of diminished length. The duration of a step, 


* Hence we get eq. 23. 


+ The velocity being uniform =? and 


7 
therefore increases as h decreases. 


2H 


466 MOTION. 


also, depends on this height. When the centre 
of gravity is most cx gree the swinging leg 
must be placed on the ground in the vertical 
position, instead of being suffered to pass be- 


Taste 7. 2% 

Measure of the time of vibration of the 
and of the shortest time of a step i 

ferent persons. os 


yond it, as it does in slow walking. In quick Duration of on 
walking the propelling leg acts more obliquely Persons. Swinging. Step. 
on the Sank, which is more inclined, and RY: 
forced forwards more rapidly than in slow s ‘ 
walking. The time when both legs are on the A. 0.730 0.375 
ground diminishes as the velocity increases, B. 0.662 0.337 | 
and it vanishes altogether when the velocity is Cc: 0.730 0.372 — 
ata maximum. D. 0.680 0.340 
0.696 0.348 © 
: 0 746 0.341 — 
‘hae ania G. 0.740 0.380 
Measure of the velocity in quickest walking. H. 0.690 0.370 
Space traversed 47 metres. z. 0.663 0.337 
K. 0.678 0.345 
E. 0.724 0 362. 
Number of Steps. Time. M. 0.743 0.374 
53 17.57 Mean. 0.7068 =| 
54 18.00 
55 18.20 Taste 8. 
54.5 18.18 Measure of the natural gait in 
55 18.42 with different velocities on the entire 
54.5 18.00 of the foot. 
se nas Space traversed 43.43 metres. 
a . . 
54 17.477 oe 5 a 4 
54 18.05 Steps. | Time. | Steps. | Steps. | Ve 
E s met. 
oe ie fe 51 | 18.12 | 0.335 | 0.851 
52 | 20.48 | 0.394] 0.835 | 2 
From this table we observe that the velocity 54 22.55 | 0.417 | 0.804 } 1. 
in quickest walking is at the rate of 2.608 54 24.83 | 0.460 | 0.804 
metres, or about 7.897 feet per second. In 55 26.38 | 0.480 | 0.790° 
conducting their experiments the MM. Weber 57 28.90 | 0.507 | 0.726 
found that the velocity was constant, whether 60 33.70 | 0.562 | 0.724 
the power of the muscular system had been 61 34.92 | 0.572 | 0.712 
renovated by repose, or exhausted by fatigue, 65 39.27 | 0.604 | 0.668 
and therefore they concluded “ that so long as 66 | 41.60 | 0.630 | 0.658 | 1. 
the muscles exert the general force necessary 69 45.72 | 0.663 | 0.629 
to execute locomotion, the velocity depends 69 46.07 | 0.668 | 0.624 
on the size of the legs and on external forces, 73 53.02 | 0.726 | 0.595 
but not on the strength of the muscles.” 76 57.72 | 0.760 | 0.572 | 0. 
82 | 69.40] 0.846 | 0.530 
80 68.78 | 0.860 | 0.543 | 
Taste 6. 88 | 79.67 | 0.908 | 0.493 
Measures of military marching. 97 93.67 | 0986) a 
Space traversed 43.43 metres 101 | 104.08 | 1.030 | Casey 
f vi 109 |114.40 | 1.050 | 0.390 
a gd hte Length. TABLE 9 — - 
o o in . . . - 2h 
Steps. | Time. Step. | Metres. | Velocity. Experiments on the time during which 
rests on the plane of position in 
degrees of velocity. za 
49.3 | 21.50 | 0436} 0881 | 2.020 Duration | Length i 
52.3 | 27.17 | 0.519 | 0.831 | 1.598 ° of ae 
54.7 | 32.35 | 0.592 | 0.794 | 1.342 Step. |. Step. | Velosea aim 
61.7 | 43.57 | 0.706 | 0.704 | 0.997 met. 
68.8 | 55.08 | 0.801 | 0.631 | 0.789 0.344 | 0.790 2.30 
74.2 | 64.02 | 0863 } 0585 | 0.678 0 376 0.804 214 0. 
87.1 83.72 | 0.961 | 0.499 | 0.519 0.429 0.755 1.76 
100.5 | 105.16 | 1.046 | 0.432 | 0.413 0.523 0.657 1.27 
111.5 | 124.00 |} 1.112 | 0.390 | 0.350 0.742 0.659 0.89 7) 


~ <a 


MOTION. 


Tasie 10. 

In the following table we find the proportion 
between the duration of the slep and the 
time of the leg resting and swinging 
during very diversified paces. 


Duration of Duration of Duration of 
Step. Standing. Swinging. 
“a “” “ 
. 0.344 0.341 0.347 
: 0.376 0.400 0.352 
: 0.429 0.484 0.374 
0.523 0.570 0.476 
0.742 0.817 0.667 


These experiments prove that the time in 
which the leg is swinging is least in the quickest 
, and is equal to half the whole time of 
_ oscillation of the leg ; that it increases in pro- 
portion as the step becomes slower; that, con- 
sequently, that division of time which the 
_ Swinging leg occupies in describing its entire 
curve is increased by one-half of the entire 
_ portion of time, and more in proportion as the 
_ pace becomes slower. ‘This gives rise to an- 
_ other range of experiments. which have been 
_ made by the Messrs. Weber with the same 
_ design, of which the following table is the 
~ result.* 


; TaBLeE 11. 
_ Experiments on the time in which the leg 
stands on the ground, with various degrees 
of velocity in walking. 
Duration | Length Duration 
of of of the Leg 
Step. Step. Velocity. | resting. 
“ q m. “a 
0.317 0.820 2.587 0.317 
0.430 0.741 1.721 0.513 
0.463 0.712 1.537 0.504 
0.582 0.621 1.067 0.692 
0.660 0.562 0.851 0.782 


Whence we deduce the following comparison 
between the duration of the leg standing and 
that of its swinging. 


Duration Duration Duration 
of of of 

Step. Standing. Swinging. 
0.317 0.317 0.317 
0.430 0.513 0.347 
0.463 0.504 0.422 
0.582 0.694 0°472 
0.660 0.782 0.538 


The number of steps which a person can take 
‘in a given time in walking depends, first, on 
_ the length of the leg, which, governed by the 
_ laws of the pendulum, swings from behind 


_ * In these experiments the footsteps were taken 
on the ball only. 


467 


forwards: secondly, on the earlier or later in- 
terruption which the leg experiences in its are 
of oscillation by being placed on the ground. 
When the hinder leg has quitted the ground, it 
swings forward by its own gravity, in conse- 
quence of its freedom of motion in the ilio- 
femoral articulation and its oblique position ; 
and, in order that the body may be supported, 
it must, at least, move so far forwards that the 
foot may arrive at a position vertically under 
the head of the femur; for in that direction 
the leg not only supports the body with least 
effort, but it is also in that position that it can 
most easily avoid any impediment in its path 
by transferring the point of support to any por- 
tion of the sole of the foot, particularly if the 
latter be turned outwards, which gives a greater 
security than when it is directed parallel to the 
line of motion. The weight of the swinging 
leg and the velocity of the trunk serve to give the 
impulse by which the foot attains a position 
vertical to the head of the thigh bone; but as 
the latter, according to the laws of the pendu- 
lum, requires, in the quickest walking, a given 
time to attain that position, or half its entire 
curve of oscillation, it follows that every person 
has a certain measure for his steps, and a cer- 
tain number of steps in a given time which in 
his natural gait in walking he cannot exceed. 
We can easily ascertain the time it requires to 
accomplish the quickest step in walking, which 
is equal to the half vibration of the leg made 
with relaxed muscles. In order to make the 
steps follow each other in much slower succes- 
sion, the foot isnot placed on the ground when 
it arrives in the perpendicular position, or the 
half oscillation from behind forwards as in the 
rapid pace, but we plant it on the ground 
somewhat later when the foot has described 
more than half the curve of vibration. From 
these principles we conclude that the man in 
Jig. 255 walks much faster than that in fig. 256; 
in fact the former makes steps 27.559 in. in 
length, whereas in the latter the steps are barely 
23.622 in. in length; and whereas the first 
makes a step in 0”.35, the second takes 0.422 
for a step, so that the velocity of fig. 255 is 
nearly double that of fig. 256. These figures 
are represented as walking on the toes, as if the 
foot always touched the ground in the same 
position, and their steps are shorter than when 
the entire sole is brought into action. Fig. 255 
shows the greatest step which it is possible to 
make with the toes. The steps are shortest in 
fig. 257, in which the difference of the heights 
of the centre of gravity, compared with that of 
Jig. 255, may be easily seen.* 

In, figs. 258, 259, and 260, the legs are of 


* These figures, with the others upon the same 
lan, reduced to ith the natural size, are drawn 
in accordance with the principles on which the 
theories of walking, running, and leaping are 
based. They are taken in the various instants of 
a step as seen through a revolving disc, con- 
structed upon the principles of the stroboscope in- 
vented by Dr. Faraday, and modified so as to 
apply to these purposes by Stampher.t These 


+ Vide Poggendorft’s Ann. vol. 22. p. 600. 
2 W<2 


468 


Fig. 255. 


MOTION. 


cSA2 


figures serve also to illustrate the following for- 
mulas. 


These three equations, which are deduced from 
the general formulas, are intended to express the 
principal data upon which the theory oft walking 
is based. If n = r = 1, and 6= 0, and we 
substitute for & its value as deduced from experi- 
ment in walking, and let (« + 1) g = 34.65,t 
T = 0”.7 and / = 0.95 met. by substituting these 


+ In this estimate ~ = 2.53, g — 9.811 metre. 


values in the equations above we get the 
results which accord very closely with ex 


No. + | t h 
“ “ m. 
1 0.350 | 0.350 | 0.642 
2 | 0.414 | 0.872 | 0.727 
3 | 0.422 | 0.875 | 0.736— 
4 | 0.432 | 0.378 | 0.749 
5 | 0.446 | 0.3882 | 0765 
6 | 0.465 | 0387 | 0786 
7 | 0.494 0395 | 0.817 | 04 
8 | 0.542 | 0.406 | 0.864 


Nos, 1 and 3 are represented in figs. ; bs 
and Nos. 1,3, 7, in figs. 258, 259, 260. 


MOTION. 


equal length, equally extended, and represented 
at the moment when the previously swinging 
leg is placed on the ground; but fig. 260, 
which is walking slowly, has the leg advanced 
far beyond the vertical. Fig. 259, which is 
walking quicker, has the leg less advanced, 
whilst fig. 258, which represents the greatest 
possible celerity, has the foot placed directly 
in the vertical line, passing through the head of 
the femur. We observe also that of the paths 


Fig. 


469 


described by the swinging leg of the three 
figures, that of fig. 260 has nearly completed 
the entire curve, that of fig. 259 a little more 
than half, and that of fig. 258 exactly half 
the curve; and that the dotted line which 
serves to indicate the path of the leg is least 
in fig. 260, greater in ‘he. 259, and greatest in 
Jig. 258. The time is greatest in fig. 260, less 
in fig. 259, and least in jig. 258; conse- 
quently, when the leg swings beyond the 


257. 


feet) 


470 


Fig. 260. 


vertical line, not only the time of swinging 
the leg has increased, but also the time in 
which both legs are resting on the earth; for 
the latter commences at the instant when the 
forward leg has reached the ground, and termi- 
nates when the head of the femur has arrived 
at the vertical line, passing through the point 
of support of the same foot. The time aug- 
ments in proportion to the distance which the 
swinging leg passes beyond the vertical posi- 
tion, or half oscillation. The time when both 
legs are resting is greatest in fig. 260, because 
it must be sufficiently great for the head of 
the femur, together with the whole trunk, to 
advance to a position directly over the foot, 
during which the head of the femur moves 
very slowly, and by the direction of the for- 
ward leg its action is to retard the horizontal 
advance of the centre of gravity. The time is 
less in fig. 259, because the head of the femur 
has to pass through a less space, and the sup- 
porting leg acts against the trunk ata less 
angle; but in fig. 258 the time of both legs 
resting at the same time, disappears altogether. 
The two legs complete the least portion possi- 
ble of the vibrating curve, and the duration of 
each step amounts only to the time of half an 
oscillation. In walking very slowly we may 
suffer the swinging leg to vibrate so long, that 
it partly returns to its former position before it 
reaches the ground. 

We have seen in quick walking that during 
the time both legs rest on the ground, the ad- 
vanced leg continually forms a smaller angle 
with the vertical than the hinder leg; but in 
very slow walking the forward leg may form a 
greater angle with the vertical than the hinder 
leg; the magnitude of this angle determines the 


MOTION. 


kind of gait the walker acquires. In order t 
accomplish this, the swinging leg is suff 
nearly to complete its curve of oscillation be- 
fore it is placed on the ground, and during this 
time the centre of Bravity moves so little, tha 

half the length of the step may not be at one 

described, and the entire duration of the step wil 
be about four times greater than in the quickest 
pace.* In this case the forward leg really 
makes a greater angle than the hinder as | 
reaches the ground, but during the time thal 
both legs are on the ground, the angle of th 


forward leg diminishes, whilst that of th 
hina augments, = there is an instan 
when both legs form equal angles. When the 
angle of the forward leg | bncatlad zero, or in othe’ 
words, when it is directed vertically, the hinde 
leg rises from the earth; for example, in fig 
261, where a c represents the right leg, be 
the left, in the beginnin 
of a step, or the instant the 
foot a is raised from the 
ground ; ¢ c” is the magni 
tude of the step, or tl 
space which the centre ¢ 
gravity passes through i 
the time of a step, e” bein 
the centre of that spac 
Now, if the foot a, wh 
was raised at the begi 
ning of the step, were placed again on tl 
ground at a’, at the instant when the centre: 
gravity reaches the middle point c”, then bo 
legs would form equal angles with the vertic 
or, the angle b c’ a=a c” a, in wh 
c” w is the vertical through c”; but if the an 
of the hinder leg to the vertical be less, wh 
the right leg is set down in a’, the cer 
gravity will not have arrived at the 1 
point c”, but at c’; however, whilst both legs 
on the ground, the centre of gaia D 
pelled from c’ to c”, after which angle be’, 
Increases and the angle a c” @ diminis 
(where c’ @ is the vertical through ¢’); w 
the centre of gravity is propelled onwards fr 
ce” to ce”, the angle a’ c’ « is less than 6 c” 
until the termination of the step. . 
In this slow method of walking a very m 
sured pace results, in which the body is carr 
very erect, and remains for a considerable ti 
in the rear of the forward leg after it first rea 
the earth; consequently the duration of 
step will be very considerable, nearly one 
cond and a half, the length of the step 
short, and the velocity of the centre of gra 
which is very little at the middle of thes 
varies considerably during each step, so 
there is an instant in which the body is n 
at rest. This is denominated by Weber 
grave or procession step.+ . 
A remarkable difference may be obsery 
the duration of the steps of two different 
sons, one of whom has long and the other 
legs. In quickest walking the duratio 


* That is, where T represents the entire dw 
of an oscillation of the legs the time ofa step 
quickest to that in the slowest walking will 
4T to 2T, or four times that of quickest walk 

t Vide Weber, loc. cit. sect. 199, p- 344, 

a. 


asin 


will rise again to its former level. 


MOTION. 


their steps will equal the time of oscillation, and 
the case is nearly the same in a slower pace. 
We observe, therefore, that when children and 
grown persons, or tall and little men, are walk- 
ing together in the pace most easy and natural 
to them, they move in a different time. It is 
true the movements of the legs, like those of 
any other member, may be accelerated by means 
of the muscular force and made to move 
quicker than when they are merely impelled 
by their own gravity in swinging from behind 
forward, but when so continued an exercise of 
muscular power is required, such an unnatural 
pace cannot long be sustained. 

In the estimate already given of the forces 
which have an influence in walking, it will be 
observed that as long as the force of the exten- 
sion of the legs in a vertical direction upwards, 


‘Is equal to that of gravity upon the body acting 


vertically downwards, the centre of gravity will 


“Move in a direction perfectly horizontal; but 
experience shows that as soon as the force of 


the extension of the supporting leg ceases, the 
centre of gravity falls below the horizontal path 


_im which it was previously moving; but the 


instant the other leg stands perpendicularly it 
The mathe- 
matical theory of walking proves that from the 


_ figure of the human machine there must of ne- 


cessity be a sinking of the centre of gravity in 
order that progression may be accomplished. 
By varying the time of the sinking of the body 


at the end of each step, the effect of the resist- 
ance of the air and other extraneous influences 


which would disturb the horizontal velocity of 
the trunk, are compensated. In a favourable 
wind, when it travels at a greater velocity than 
the walker, it is necessary he should increase 
the time of sinking to counteract its effect, and 
preserve a mean uniform motion. 

The application of mechanical principles 
does not accord with slow as it does with that 
of quick walking, for the former is too much 
under the control of the will of the walker, and 


the limbs are not suffered to swing freely by 
their own gravity as in quick walking, in which 


this volition diminishes, according to Weber, 
at least when the slightest exertion is continued 
for any length of time, and it is in this condition 
alone that theory and experiment nearly ap- 
proximate. We must, however, remember that 
‘the control exercised by the muscular system 
over the limbs in slow walking is a new force 


which animals are enabled to interpose in 


order to vary the effects which result from the 
eee! laws in operation during locomotion, 
and by no means refutes the theory of the 
influence of those forces which affect, not only 
the locomotion of animals, but the motion 
of matter universally. 

Running.—The laws which regulate running 
in many of the lower animals, such as qua- 
drupeds and birds, are nearly the same as in 
Man. It will therefore be necessary to enter 
into the details of this movement in reference 
to the latter only. 

The principles upon which walking and 
nning differ.—In running as in walking it 
may be considered as a fundamental law that 


471 


the same motions of the body recur after each 
double step; and that both legs exercise equal 
and alternate actions in these movements. In 
running the object is to acquire a greater velo- 
city in progression than can be attained in 
walking. In order to accomplish this, instead 
of the body being supported on each leg alter- 
nately, the action is divided into two periods, 
during one of which the body is supported 
on one leg, and during the other it is not sup- 
ported at all. The latter condition constitutes 
the principal difference between these two 
modes of progression. When the body is pro- 
jected upwards so as to swing freely in the 
air, the hinder leg must be raised from the 
ground before the advanced swinging leg has 
reached the vertical position; hence, in run- 
ning, the duration of the step is less than the 
half-duration of the oscillation of the leg, be- 
cause, when the advanced leg has reached the 
vertical position and is again placed on the 
ground, the hinder leg has already begun to 
describe a portion of its are of oscillation. By 
these means the duration of the step is di- 
minished, whilst the length is increased, both 
of which tend to augment the velocity. The 
length of the step is consequently greater than 
that side of a right-angled triangle, whose 
hypotheneuse is the extended leg, and the 
other side the elevation of the centre of gravity 
above the ground. In running the step may 
be divided into two periods; the first, the time 
t, during which the body is supported on one 
leg, and the second, the time +r — ¢, during 
which it is not supported at all. 

Forces employed in running. —The forces 
which act in running are the same as in walking; 
first, extension; secondly, gravity; thirdly, 
resistance. In running, a horizontal move- 
ment of the centre of gravity is not practicable 
as in walking, for afthough the extensor power 
might be so regulated that-the centre should 
continue at the same elevation so long as the 
body poised on one leg, it would evidently fall 
during the time it was left unsupported. Now, 
as it is found after the whole time of a step 
to have neither sunk nor risen, and since no 
instantaneous elevation of the centre of gravity 
takes place between the termination of the pre- 
ceding and the commencement of the following 
step; it follows that during the time ¢, it 
must ascend just as much as it sinks during 
the time +— ¢. The effects of gravity and 
resistance have been sufficiently explained in 
the theory of walking.* 

The conditions for regular progression in 


* By an analysis based on data similar to those 
for walking, Messrs. Weber have deduced the 
following equations which express the general 
laws of running. 


CB ise pe OFS Saas via cio hho ale miais CED 
(ks —4h 28)? be? P= I2......00- - (30) 
RE ie By Spr bb nado a's! 9: cole e siee COM) 


: $e LCT te eeerereeeerreeees (32) 


472 


running are fulfilled if the vital force which 
the body receives by the extension of the 
supported leg whilst it is on the ground, is 
equal to the vital force communicated to 
the swinging leg during the time of its oscil- 
lation.* 

The motions of walking and running tend 
continually to approximate, in proportion as the 
time in which both legs are on the ground in 
the former, and the time in which the body is not 
supported at all in the latter, is diminished, and 
the laws of both running and walking coincide, 
when the time that the body swings unsup- 
eg in the air in the former, and that where 

th legs are on the ground in the latter, 
vanishes. 

The resistance of the air to the trunk, when 
it is propelled with great velocity as in run- 
ning, requires to be compensated, in order to 
be kept in a state of equilibrium, either by 
the force of its own gravity, or by that of its 
muscular system. The former method is usually 
adopted to prevent an unnecessary expenditure 
of vital power. 

It will be seen in Table 4, that the angle of 
inclination of the trunk in running, is to that in 
quick walking, as 49°.8 to 31°.8, when the 


2s 
(4 +1) 8 (¢— 6" (1— 55) 


soe (33 
(ratty —(—ry GC 


ea eee eee weee 
<<" 


vise (96) 


(35) 


*eeeeeere 


In which equations, 


ee, 


Le = are (cos 
r 
rn= Vi) <b r(h — s)" 
lg t 

The other expressions being the same as those in 
walking, 

¢ .-.. isthe uniform velocity of the point m in 
a horizontal direction. 

$ se++ is the space through which the centre of 
gravity is raised in the time ¢. 

s'..+- 1s the space through which the same 
centre is raised in the time ¢ — 6. 

When + —¢ = 0, that is, in slowest running, 
the above equations become identical with those 
in quickest walking, where the time during 
which both legs are on the ground vanishes. 

* That is, when 


1 SE (¢— OY 2a _ 
(m + m’) rane ene ¢| 77) = 


m (l-brat yc —m(1— ry ct 


and as == by substituting «, we get equa- 


tion (33), from which the height of the centre 
of gravity is to be found. 


} 
MOTION. 


length of step in the former is to that in the 
latter as 1.509 to 0.888. ~ ete 
In order to find the amount of the 
undulations of the trunk in running, I. 
Weber viewed the runner through a tele cope, 
adapted for that purpose. They calculate the 
undulations to be from 3th to §th of an inch; 
they estimate the duration of the step to be 
jth to jth of a second, of which the bod) 
swings freely in the air jth of a second, and 
of this falls jth; now, by the law of falling 
bodies, the centre of gravity will descend in this 
time 22 mm. = 0°85614 in.; hence, the dod) 
falls through a less space in running than in 
walking. ‘nd 
The simultaneous positions of the centre 
of gravity and of the two feet atindividua 
instants of time, of which fig. 262 is a vertic 
and fig. 263 a horizontal representation. The 
right foot is marked a, the left b, and the centre 
of gravity c: 6,, signifies that during th 
time a is passing from atoa,, and ¢ fro 
c to ¢,, b remains standing on the point 6, , 
and soon. In order to sey the swing- 
ing from the supporting leg, in fig. 262, th 
Srnler is so sa that it does not reac 
the horizontal line ; and in fig. 263, the swin 
ing leg is represented as if it swerved from th 
path both on the right and left sides alter 
nately: ¢,, Cy = C3, Cs = Cy, Cz, indicate the 
length of the step =p, a, dy, = Gsy 
= 6b, » 6,6 = 2p. e time which elaps 
from the instant when 6 steps in 6, , toa, i 
a, 4, is the duration of astep vr. The time ii 
which ¢ epee vey frém c, to c, is the time 
when the body is suppates upon one le 
The time in which c adeincan fiom Cy 0 ¢, 
the time + — ¢, during which the body s' Dy 
in the air. The time in which ¢ advan ro 
c, to c,, is the time in which the left k 
swings, which is greater than +, in which 
merely sg from c, toc,. The instant wher 
the left leg steps in 6, or the night in a,, t 
leg must press against the ground with su 
force as to impede the accelerating force — 
gravity upon the body, and communicate to 
an ascending movement; to accomplish th 
the leg must be set down on the ‘?p 
pendicularly, therefore the lines ¢,, 6, €gy: 
&c. are vertical. a 
The length of the extended leg being 6, 
Jig. 262, at the end of the time ¢, ¢, d, = 
= c t,* the horizontal distance of the body 
the time ¢, and c, d = ¢, b, +o, a 
h +s, where / represents the distance of 
centre of gravity from the beginning of 
step, and s the height to which it is eley 
in the time ¢; now, if 6, dc, be a right-am 
triangle, then a 
(b, 2)? = (6, d)? + (c, dP . 
or, 

RP=COP +E AESP 
That is, the square of the length of the exter 
leg is equal to the sum of the squares of 


* The line cyd is vertical, and ¢, d, horia 
meeting c,d ind, ; the letter d and line ¢ 


omitted in the figure to prevent confusion. — 


3 


-, 


MOTION. 473 


path described by the centre 
of gravity in the time ¢, and the 
distance of the centre from the 
earth at the end of that time. 
The time occupied in running 
between the raising of the leg 
from the ground and the setting 
it down again is equal to the 
duration of the step, together 
with the portion of time during 
which the body swings in the 
air; or, it is the time in which 
¢ (fig. 262) advances from c, to 
¢;, being the time between the 
raising of the left leg and the 
setting it down again, but this 
time is divided into two por- 
tions, namely, that whilst c 


CTI 
ay 


oe 


. Figures designed by Weber, to illustrate the laws of running. 


moves from c, to c,, and that whilst it moves From these principles it is obvious that no 


from c, to c,; the latter portion is the duration man in the act of running could possibly be in 
of the step; the former the time in which the ; 
body swings freely in the air. Fig. 266. 


Fig. 265. na 


ie 


Preparing to run, and running, from designs by Flarman. In fig. 265 ¢ d falls behind the advanced foot, so 
‘that the posterior leq be ws only a small portion of the weight of the body, but is in a position to push the centre 
of gravity forwards before quitting the ground. Y 


474 


the attitude of the annexed design by Flaxman 
(fig. 266), in which it will be seen that the 
whole mass of the body lies posterior to the 
vertical line a c’ b, ing through the base of 
support, whereas the preceding theory shews 
that in quick walking and running the swinging 
leg never a beyond the vertical dc, which 
cuts the head of the femur. This figure has 
therefore been drawn upon false principles. 


TABLE 12. 
A Table of fifty-six experiments on running 
with various velocities. Space passed through 
43.43 met. = 142°2504 feet. 


MOTION, 


‘381 Mean Dura- 

5 = \Namber| __ tion | Length ; 
2) 0 Time. of in |Velocity. 

g | Steps. Step. | metres. 

zo 
6 | 28°17] 7°56 | 0°268]| 1°542| 5°753 
3 | 38°83| 9°91 | 0:293]| 1°284] 4°382 
6 | 35°92| 10°80 | 0°301| 1°209| 4:016 
7 | 38°17/ 11°99 | 0°314/ 1°138] 3°624 
3 | 42°67| 13°60 | 0319] 1°018| 3°194 
7 | 46°5 | 15°173] 0°326] 0°934] 2°865 
6 | 53° 16°81 | 0°317/ 0°819] 2°583 
8 | 60°5 | 18:35 | 0°303] 0°718] 2°369 
5 | 71:2 | 21°68 | 0°304| 0°640} 2°105 
4 | 83°75) 25°45 | 0°304|] 0°519]| 1°707 
3 }104°33| 31°84 | 0°305]| 0°416| 1°367 
3 |137°7 | 41°49 | 0°301| 0°315]| 1:046 


From this table we see that the length of 
step increases rapidly, whilst the duration va- 
ries but very little; and that the duration is 
always equal to a half oscillation of a pen- 
dulum. 

Duration of spring .. = 0°2618 dif 
Duration of half oscil- 2 __ 0°323 yr beke 
lation of pendulum § — 

Hence we perceive that the duration of the 
spring is less than the oscillation of the leg as a 

ndulum by a very small fraction only, which 
is probably due to muscular action. 

n quick running the length of step rapidly 
increases, whilst the duration slowly dimi- 
nishes ; but in slow running the length dimi- 
nishes rapidly, whilst the time remains nearly 
the same. The time of a step in quick run- 
ning, compared to that in quick walking, is 
nearly as two to three, whilst the lengths of the 
steps are as two to one, consequently a person 
can run in a given time three times as fast as 
he can walk. The velocity in running is usually 
at the rate of about ten miles in an hour, but 
there are many persons who for a limited period 
can exceed this velocity. 

In the human race, however, the velocity in 
running varies considerably, depending on 
a variety of physical conditions, such as age, 
sex, stature, muscular power, the nature of the 
surface on which the progression is performed, 
and the angle of elevation above, or depression 
below the plane of the horizon. Man is ex- 
ceeded in s by many of the lower animals, 
owing to differences in the structure of the 


locomotive organs, and the physical laws 


they obey. « 
j pen be or jumping.—This mode of pro 
gression is adopted by a great number of 
animals; some of which resort to it only 
the accomplishment of a particular object, 
others as a regular means of locomotion, =—=_— 
In most of the orders of the animal king- 
dom there are some species which transfe 
themselves from place to place by a succession 
of impulses, in air, in water, and on solids: it 
is to the latter we shall confine our on, 
having already briefly mentioned the former in 
the sections on flying and swimming. z 
In leaping, the object to be attained is to 
take the greatest length of step without refer 
ence to its duration ; and herein it differs fror 
running, in which the greatest steps are taken 
in the least possible time. 7 
The height to which animals of different 
orders are capable of springing* varies, but 
according to Straus-Durckheim, all those in 
the same order leap to equal elevations. i 
Amongst insects, the Grasshopper and Cricket, 
and in the order Felis, the Cat, the Leopard, 
and the Tiger, all rise to the same elevations 
above the positions of their respective centres of 
gravity at the instant when their feet quit the 
ground. ’ 
This appears at first to be inconsistent 
the computations made on the proportion + 
the force of muscles to the mass of animals of 
different dimensions. 


— 
aALLECDLION, 


If we select four diffe- 
rent animals of the same order, in which the 
dimensions of one kind are as 1, 2, 3, 4, 
their weights will be as the cubes of thes 
numbers, or, as 1, 8, 27, 64; but since the fore 
of a muscle depends on the number of its” 
fibres, and therefore increases in the ratio of ii 
transverse section ; that is, as the square of on 
of these dimensions, the muscular of th 
animals will be as 1, 4,9, 16, and the velocities 
(supposing the muscles to act instantaneously 
will be as the forces divided by the weights,ora 
1, }, 4, 4, and the heights of the leaps be 

as the squares of the velocities would | 
as 1,}, }, %- Now, as they are all found | 
arrive at the same height, this may be @ 
plained by supposing that the muscles do 
act instantaneously, but as constantly accel 
rating forces during the continuance of the spri 
The force on an unit of mass in the Cat i 
that on an unit in the Tiger, as 1 to 4; and si 


the dimensions of the latter are four times the 
of the former, the tiger passes through fo 
times the space the Cat over, reckor 
from the beginning to the end of the time | 
muscles act, until the animal quits the grou 
and therefore is elevated to the same height 
the cat.+ a 

From these principles we see the reason 


* The spring is that portion of the leap w 
takes place before the feet quit the ground, __ 

+ Thus :—Let s = the space passed thro 
during the spring of the cat, f = the muse 
force employed in the time ¢ of a spring, | : 
by equation (3), = 
s= ft. ¥ <7 ‘ 
Now, as the tiger vasses through a space ==" 


MOTION. 


Fig. 267. 


475 


Let f g (fig. 267) be the axis of the body, 
passing through the centre of gravity 0; a 6, 
the tarsus; bc, the leg; c d, the thigh, with 
the trochanter; and d e, the hip. All these 
articulations being flexed, the tarsal extremity 
b of the leg is advanced forwards under the 
centre of gravity 0, which is a little above it. 
In this state, if the tarsus a 6, which is di- 
rected backwards, become flexed, the angle 
a bc opens, and as the tarsus rests against the 
ground, the leg b ¢ begins to move, and 
raising its crural extremity, draws with it the 
whole body. Now, as the centre of gravity is 
placed before the point b, instead of being 
elevated, it is, on the contrary, urged forwards 
and downwards, describing an arc of a circle, 
of which the centre is b, and the action of the 
flexor muscle of the tarsus continuing during 
the whole time that the limb is resting against 
the ground, the direction of the motion which 
it impresses on the centre of gravity changes 
at each point of the are which the latter de- 
scribes in being always a tangent to this are. 
We might thus determine its action for each of 
these points, but for greater simplicity we 
shall select only three ; namely, the commence- 
ment, middle, and the end of the motion. 

During the flexion of the tarsus, the leg 
expands itself, and tends to open the angle 
bcd; but since it rests with its tarsal extre- 
mity upon the plane of 
position, the thigh ¢ d be- 


comes moveable, and is 
raised forwards, turning 
as aradius round itscruro- 
tibial articulation c, and 
carrying with it the whole 


body, in the samme manner 
’ asin the motion of the leg; 
the direction of the force 


many of the small insects leap a greater dis- 
tance in proportion to their masses than the 
larger animals; for example, if the Flea, which 
can leap two hundred times its own height, 
were as large as the Cricket, it could only leap 
as far as it does at present; but the latter can 
‘leap much higher than the former, and there- 
fore, of these two insects, the Cricket is the 
best organized for leaping. We shall now pro- 
ceed to investigate the effect of the extension of 
the legs of insects in leaping. 


and the muscular force equals } f, during the 
time ¢’ of its spring, 


ot. Asa 3% 0 Bere aah cast (BR) 


and, 
t = 46. eee eset eee eee eeeeseseenee (37) 
The velocity of the cat will be, 
v— /2fs 
hence, that of the tiger is, 


va VIF wa V 2h 


that is, the tiger and cat have the same velocity, 
_and therefore the same height of spring, reckoned 

from the positions of their centres of gravity at the 
instant of their quitting the ground. 


’ 


produced by the extensor 
muscle changes at each 
point of the curve which the centre of gra- 
vity describes; but this direction is always 
a tangent to the curve, and consequently per- 
pendicular to the radius c 0, passing through the 
cruro-tibial articulation and centre of gravity. 
The motion produced by the extensor muscle 
of the trochanter on the thigh c d, opens the 
angle c de, tending to depress it at its tibial 
extremity, but as it rests upon the leg, which 
by its own elevation resists it, the motion is 
wholly communicated to the hip de, which is 
flexed forward, and carries the body with it; 
the direction of the force of this muscle is 
perpendicular to the radius d 0, passing through 
d, the articulation of the hip with the tro- 
chanter and the centre of gravity. Lastly, the 
motion produced by the extension of the hip 
e d upon the body in a direction opposite to 
that of the thigh, is perpendicular to e 0, and 
impresses on the centre of gravity an oblique 
impulse downwardsand backwards. The forces 
resulting from the extension of the tarsus and 
the hip being very feeble, may be neglected. 
The muscular force expended in these mo- 
tions may be thus approximatively estimated. 
By the extension of the leg, the centre of gra- 
vity o will be acted on at the beginning of 


476 


motion by a force o m perpendicular to oc ; 
by the extension of the thigh at the same time 
the centre will be also urged by a force on, 
perpendicular to the radius o d; the resultant 
of these two forces is o o’, in the direction of 
which the centre of gravity is raised in the 
first instant of motion, and the body and foot 
will be in the position a, b,c, d, e,' o', J; g’. 
If the action of the muscles ceased after this 
first impulse, the body wouldarrive in the second 
instant at p, where o' p = 0 o’, but at the point o’ 
the centre of gravity receives two new impulses, 
one o' m' from the extensor of the leg, and 
another o’ n’ by the extensor of the trochanter ; 
the first is in a direction perpendicular to o' c’, 
the second perpendicular to o' d’, the former 
being combined with the motion o’ p, which is 
that of the centre of gravity ; in the second 
instant there arises a second resultant o’ q, 
which the body would pass through in the se- 
cond moment, if the action of the thigh did 
not take place, but this new force o' n’ being 
con:bined with o’ g, produces the ultimate re- 
sultant o’ o”, which the centre of gravity really 
"weng through in the second moment, and the 

ody takes the position a, b, c’, d’, €’, 0, f”, g”. 
In the moment which follows, the centre of 
gravity would arrive by the second impulse at 
p’, a distance equal o o”, but the forces of 
the muscles continuing to act, one of them 
o” m” produced by the extensor of the leg, 
and always perpendicular to o” c’, gives with 
the motion o” p'a resultant o” 9‘, which being 
combined in its turn with a force o” n” pro- 
duced by the extensor of the trochanter in a 
direction perpendicular to o” d’, gives a new 
ultimate resultant o” o”, which the centre of 
gravity passes through in the third instant. If 
the distance from the point o” to the point b is 
greater than the length of the leg, it is evident that 
the body of the insect will be elevated during 
the third instant, and the muscles being no 
longer able to produce any new impulses, be- 
cause the foot no longer furnishes them with 
points of support, the centre of gravity will in 
the succeeding intervals of time pass over spaces 
equal to o” o”. 

In this demonstration we have only consi- 
dered two forces as acting to produce the leap, but 
there are others which influence the motion of 
the body as above mentioned, the effect of which 
we must here notice. By the extension of the 
hip on the thigh, the body which we have sup- 
i not moveable on the hip would be flexed 
orwards from its horizontal ition; but this 
is corrected by the motion of the body on the hip 
coi by that of the leg on the tarsus, The extensor 
muscle of the tarsus opens the angle a b c, and 
tends to lower the extremity a of the tarsus ; 
but since that is supported the leg 6 c is moved 
and flexed up » giving to the centre of 
gravity a motion forwards and downwards, per- 
dicularly to the radius b 0. This new force 
ing combined with o o’, produces in the first 
instant a resultant more inclined forwards than 
oo. This oblique direction is afterwards cor- 
rected by the motion of the body on the hip. 
In short, if the body were only subject to the 
forces of the muscles of the tarsus, the leg, and 


MOTION. 


Fig. 268. 

im” 
d: } 
: ' 
_h! 
; a ' 
: Fog: wt y 

ty er 
ir 
og 7 a oO 


the thigh, it would take a direction more — 
oblique than f’ g’; but by the’ motion of the 
body on the hip, the centre of gravity receives — 
a new impulse backwards and downwards per= — 
pendicular to eo, and this new force combined 
with o’ 0” gives a resultant more vertical, and 
as it acts in an oblique direction downy 
it diminishes necessarily the velocity of t 
leap; but the body thereby regains its h 
zontal position. e other legs also contri- 
bute to the elevation of the body in leaping, but 
their action must be very feeble, because these 
limbs seldom present a greater size or 
in leaping insects than in other species. The 
middle pair of legs being always directed 
outwards and backwards, urge the body w 
wards and forwards. The anterior pair, on th 
contrary, being placed greatly in advance of 
the centre of gravity, and directed op posite 
to the others, move it upwards and back- 
wards; these limbs, however, being compara- 
tively very feeble, can produce but little effect 
on the direction which the body would take 
were it only impelled by the two hinder pairs. 
In almost all the perfect insects the legs are 
the instruments of leaping, but the Elater is” 
capable of jumping whilst on its back, in or 
der to recover its normal position, which owing 
to its figure it could not otherwise effect. 
this purpose, a mechanism not generally found 
in eo i insects is provided ; the pro-sternum 1s 
prolonged backwards, and terminates im @ 
strong conical spine, which in a state of r 
is lodged in a grooved cavity situated in the 
meso-sternum. ‘The insect having been tured 
on its back, is observed to curve the body 
forcibly backwards; during this movement thi 
spine of the sternum is drawn out of its 
sheath, and rests upon the edge of it, and th 
bases of the elytra are elevated above the plane 
of position. The flexor muscles, situated — 
the inferior aspect of the body, next contrac 
by which the spine is forcibly pressed | 
the edge of its sheath; the sternum is 
suddenly relaxed, the spine darts into its sh 
with great velocity, the head and thorax fly 
and the base of the elytra descends ups 
supporting surface with such force I 
insect by the reaction is propelled up 
the height of one or two inches, during 
the animal turns over upon its legs.” 
order to understand more clearly how this ak 
lace, let a b (fig. 268) be the axis of 
y; © its centre of gravity; # the 


pameie <.- 


MOTION. 


lation at which the trunk and thorax are flexed 
upon each other; fand g, the centres of force 
of the anterior and posterior parts of the body ; 
when the body is curved preparatory to the 
leap, it takes the position a’ x’ b’, and the centre 
of gravity will be at o’ ; when the body returns 
to its former position a x b, the two centres 
of force come in contact with the ground in 
J and g; the forces with which they strike the 
ground acting perpendicularly to a b, impart to 
the centre of gravity o a velocity in the same 
direction, but the reaction of the ground gives 
to the body two impulses equal and opposite 
to the forces d f and e g; the linesf dand ge 
not passing through the centre of gravity o, 
one part only of the force raises the body above 
the ground, the other part of the force pro- 
duces a rotation of the body around the centre 
of gravity ; the force g e being much nearer 
the centre than fd, and their velocity of rota- 
tion being in the direct ratio of their distances 
from the point 0, the motion produced by g e, 
being opposite to that of fd, is destroyed by 
a part of the latter, and the remainder of fd 
will give the body a rotatory motion in the 
direction of f.f'h: by means of this motion 
the insect is enabled to reverse its position.* 
The larve of insects are variously organized ; 
for example, that of the Tyrophaga casei, when 

reparing to leap, bends itself into a circle, 

ringing its head and tail in contact, and 
fixing its two mandibles in the cavities of its 
anal tubercles; it then contracts its body into 
an oblong figure, so that the two halves are 
parallel to each other. This being accom- 
plished, it suddenly unlocks its head, and ex- 
tends its body with such force, that the re- 
action of the surface on which it rests propels 
the body into the air to the distance of several 
inches. The leaping of fishes and serpents has 
been already mentioned in Section IV. Birds 
walk, run, and leap like Man. The Incessores 
and other short-legged Birds usually move on 
solids by a succession of leaps. 

In most quadrupeds the propelling force of 
the leap is produced by the extension of the 
posterior extremities alone. When a consi- 
derable elevation of the body is the object to be 
attained, the centre of gravity is, previously to 
the leap, thrown back and lowered by the 
flexion of the hip, knee, and ankle-joints of the 
hind legs; the fore-legs are then raised from 
the ground by the extensor muscles of the 
trunk, the axis of which, before parallel to 
the horizon, is now inclined at a considerable 
angle to it. At thismoment the extensor mus- 
cles of the posterior extremities are suddenly 


* According to Kirby and Spence (loco cit. vol. ii. 
p- 314), the elater makes a double movement pre- 
paratory to the leap, by first drawing out the spine 
from its sheath, making it re-enter, and then 
causing it to fly out with a spring in the moment of 
leaping. This, however, appears to be a very in- 
correct view of what takes place. Mr. Darwin 
does not consider that sufficient stress has been 
laid on the elasticity of the spine, and that the 
sudden spring of the elater could not have resulted 
from muscular contraction alone, without some me- 
chanical contrivance. Bs of the Voyage of 
the Beagle, vol. iii. p. 35.) 


477 


contracted, and the leg is extended with suffi- 
cient velocity to elevate the trunk of the animal 
above the ground. At the end of the leap, 
the anterior feet first reach the ground simul- 
taneously, and then the two hind feet in a 
similar manner; the head being brought be- 
tween the two fore-legs, in order to throw the 
centre of gravity as far back as possible. The 
direction of the force of propulsion depends on 
the position of the propelling legs, and on the 
angle of inclination of the trunk to the plane 
of motion ;—the intensity on the quantity of 
force impressed by the extension of the legs. 
In those quadrupeds which constantly move 
by a succession of leaps, the length of the 
posterior legs greatly exceeds that of the ante- 
rior; but in those wherein the length of the 
four legs is nearly equal, the leap is attended 
with so great an expenditure of muscular action 
that itis only resorted to on particular occasions. 

Borelli* is of opinion that the power of 
leaping is greatest in those animals in which 
the extremities of the bones of the legs de- 
scribe (in proportion to their masses) ares of 
greatest circles, because they must move with 
greater velocity in the same time; in other 
words, that those animals which have the 
greatest relative length of the posterior legs 
leap to the greatest height. Nor doves this mili- 
tate against the analysis of Straus, according to 
which we have seen that animals of the same 
kind which have the greatest length of leg 
occupy a proportionably long time in springing. 

In the Bull-frog amongst the Batrachia, in 
the Kangaroo amongst the Marsupialia, and in 
the Jerboa amongst the Rodentia, we find the 
greatest disproportion in the length of the ante- 
rior and posterior extremities ; the length of the 
latter predominating so greatly, that they walk 
and trot with difficulty; but when pursued, the 
Jerboa can leap nine feet at each step, and repeat 
these leaps so rapidly, that it is said the Cos- 
sacks, though mounted on the fleetest horses, 
cannot overtake them. The Kangaroo reposes on 
the hind legs and tail, which form a triangular 
base, leaving the arms free for prehension. In- 
dependently of the Jerboa, other Rodentia, 
such as the Hare and Rabbit, are also furnished 
with lengthened posterior extremities, by which 
they possess considerable power of springing. 
As the mass of animals increases in a greater 
ratio than the force of their muscular system, 
the large Proboscidie are almost incapable of 
leaping, but the solidungulous Pachydermata 
are well organized for leaping, as well as many 
of the Ruminantia, such as the Deer and Ante- 
lope. In these two orders the lengthened cal- 
caneum and metatarsal bones contribute chiefly 
to assist the muscles in the spring. In the 
Carnivora, we find the ankle-joint possessing the 
same structure as in the Ruminantia and Pa- 
chydermata. The geometrical relation of their 
osseous and muscular systems is such as to 
confer on them great power in making a 
spring; that of the Tiger is well known. The 
leaping of the Cheiroptera and Quadrumana 


* Quod longiores sunt vectes extremi crurum, saltus 
majores fiunt, See Part. prim. Prop. 176, p, 211. 


478 


has been briefly described in the last section, 
and our limits will not permit further illustra- 
tions. We shall therefore proceed to the in- 
vestigation of the leap in the human race. 


Fig. 269. 


Preparing to “eC ye ad legs, as designed 


In Man the leap is 
accomplished with con- 
siderable expenditure 
of muscular action, 
amounting, according 
to Borelli, to no less 
than 2900 times the 
weight of the body;* 
but since, notwith- 
standing the increased 
exertion, the velocity 
of this kind of motion 
is much less than in 
running, it is rarely 
adopted as a means of 
continued progression, 
but rather for passing 
over the greatest pos- 
sible space without re- 
gard to the time taken 
to accomplish each 
81 In leaping, either 
both legs are employed 
simultaneously to pro- 
ject the body, as in 
Jig. 269, or each leg is 
used alternately. Bo- 
relli has confined his 
seb e thes 5 

rmer case ; ut as neiti 
that mode of leaping ch eset. Betas i. 
merely consists of a both legs, 

* This estimate is calculated by Borelli in the 
same manner as the force of the muscles in Sec- 
tion I, On this, as on several other occasions, 
Barthez has chosen to deny without attempting to 
disprove the conclusion of Borelli. (See Barthes, 
Nouv. Mecan. p. 97,) 


Fig. 270. 


at the 
with 


MOTION. 


succession of isolated movements, there bein 
always a pause between each two, we shal 
vestigate the latter case as the only one w 
admits of a continued uniform progre 
the only one, therefore, which is proper 
the scope of the present article.* - 
In the alternate movement of the legs, th 
swinging leg is not placed on the ground ¢ 
soon as it has reached the vertical position, as’ 
quickest walking and running, but it is sufferet 
to swing beyond it, and the placing it on t 
ground is delayed until it comes a second tim 
to the vertical position, consequently the — 
swings freely in the air for a longer peri 
in running, whereby a longer step is é 
Fig. 271 represents the various is « 
the centre of gravity and of each leg im sue 
cessive instants of time: a is the right foot 
b the left, and ¢ the centre of gravity. a,,, 
signifies that while c moves a c, toc 
and c,, and b from 6, to 6, and by a Fe 
mains at the point a,,,. The spaces a, 
= &c. the lengths of the steps. 
body i J 


DC 


b = Co, C 
It ‘will be observed that whilst the 
advancing from c, to cy, it is su 
rojected by the right leg. From c, to ¢, 
egs are off the ground, from c, to c, the body i 
supported and projected by the left leg, anc 
from c, to c, both legs are again off the grount 
and so on successively. 
TaBLe 13. a 

Table shewing the length and duration of # 
steps in leaping with various velocities. a 


Doda Vv 


Length of on 
steps. Duration, Velocity. | 
1.243 0.460 2.702 
1.578 0.468 3.372" 
1.688 0.455 3:710/' = 
1.809 0.411 4.402 
1.977 0.404 4.894 


* In leaping, the equations (29) (32) (34) 
the same as in running. Equations (30) and (; 
are omitted, for @ = 0, since the centre of 
vity of the body does not sink, because at 
beginning of each step the leg is bent, and th 
is, therefore, no depression, as is necessarily 
case in walking and running. Instead of equat 
(31) and (33), we have, 


27 = TH+E+(1 +— 


dt 
T 
cos pRB 


2s 
1 2(1— — 
ais ide 3a «cececcunl 


r(2—~r) ‘ 
The condition for regular progression in leapi 


in walking and running, is that the Vital 
communicated by the supporting leg to the tr 
equals that communicated by the trunk to 
swinging leg. In the present case the 
force is, 


st 


m’ cr (2 _ r) eee Rr a 
and the former is the same as in running, 
y é 


MOTION. 


By table 13 we find that the 
duration of the step in leaping 
is less than in slow walking,* 
but greater than in running ;t+ 
the length of step is much 
greater than in walking, and 
may be made greater than in 
quickest running. As the 
body swings freely in the air 
a longer period, and rises to a 


479 


greater elevation in leaping 
than in running and walking, 
it is necessary that the projec- 
tile force should be made 


greater, but the time during 


which the extensor power of 


the leg acts, although very 
short, is of intense action; 


' wr, 
ay, 
Niner 


foe, 
ig 


Figures designed by Weber to illustrate the formulas for leaping. 


hence, it is not easy to regulate the amount 
of muscular action as in walking and run- 
ning, and consequently it may be too great or 
too little for the object in view. The vertical 
undulations also are much more considerable 
than in the other modes of locomotion. 

In descending rapidly the sides of steep hills 
it is much safer to do so by leaping than by 
running, as in the former mode of progression 
the foot is placed on the ground at the end of 
each step in a position favourable for stopping, 
which cannot be done in the latte. MM. 
Weber consider that the study of the laws 
which regulate the locomotion of man, and of 
the mechanism by which it is accomplished, 
will assist mankind in the construction of au- 
tomatic locomotive machines. Mr. G. Rennie 
has studied the construction of animals and the 
principles on which they move with a view of 
applying them to the locomotion of the steam- 
boat, on the supposition that animals move in 
air, in water, with the least expenditure of mus- 
cular force, an hypothesis which accords with 

* See Table 8. + See Table 12, 


our views as wellas those of M. Dumas, who 
considers that man is capable of moving and 
producing a greater mechanical effect, with 
less expenditure of fuel, than can be produced 
by any steam-engine hitherto invented. 

In every mode of progression there is a sen- 
sible increase of action in the circulating and 
respiratory systems ; but the effect produced on 
them is much greater in running and leaping 
than in walking. In the two former cases a vio- 
lent palpitation of the heart and hurried respira- 
tory movements are quickly produced, on which 
account they cannot be very long continued. 
In running, when four steps are taken in 
a second, the difficulty of breathing soon 
causes the pedestrian either to slacken his pace, 
or what may be most advantageously substi- 
tuted when it is desirable to continue nearly the 
same speed, and at the same time preserve the 
breath, to exchange the running for a leaping 
movement. In consequence of the deliberate 
manner in which the steps may be taken in 
leaping, the breath may be preserved for a longer 
period, and the action of the heart diminished ; 


480 


ee ee ere in leap- 
ing than in running, the velocity is not very sen- 
sibly diminished, although the duration of each 
step is increased; that is, for example, when we 
substitute three leaping, instead of four running, 
steps ina second. In Table 12 we find that the 
t length of step in running is 1™.542, and 
in Table 13 that the greatest length of step in 
leaping is 1™.977, consequently four of the for- 
mer exceed three in the latter mode of p 
sion in a second by 0.237, or 0.76736 feet 
only ; but this loss of space is compensated by 
the greater time the pedestrian employs in tak- 
ing each step in leaping, being = 0".136. 
MM. Weber consider that leaping stands in 
the same relation to running that the grave step 
in slow walking does to quick walking. The 
difference of the grave and quick step in walk- 
ing consists in this, that in the former the oscil- 
lation of the leg has nearly completed its curve 
of vibration before it is placed on the ground, 
and therefore forms a greater angle with the 
vertical than the hind leg. The same difference 
also exists between running and leaping, inde- 
pendently of which there is another important 
variation, which is that in leaping the swinging 
leg completes its entire arc of vibration before it 
is placed on the ground, and makes the greatest 
angle with the vertical it can possibly effect. 
In running, on the contrary, the leg is set per- 
pendicularly on the ground and consequently 
the angle with the vertical =o. In the grave 
step as well as in leaping the foot is brought 
into contact with the ground preparatory to 
resting upon it; and, lastly, the duration of the 
leaping step exceeds that of the ranning step 
in the same degree that the duration of the 
grave step exceeds that of the quick step. These 
are the principal differences which distinguish 
the four modes of locomotion most usually 
adopted by man. 
he study of the mechanism of which the lo- 
comotive organs of animals is composed, of the 
laws by which their progression is accomplished, 
and of the vital force which they expend in pro- 
pelling the body from one point in space to 
another with different velocities, serves to in- 
struct alike the anatomist and the physiologist, 
the artist and the mechanician. Ignorance of 
these laws has been productive of grotesque 
delineations of the human figure as well as of 
the lower animals when represented in motion. 
We have abundant evidence of this in the pro- 
ductions of painters and sculptors, both of 
the ancient and modern schools. Locomotion 
is not only a function indispensably necessary 
for the prolongation of the lives of a vast as- 
semblage of animals, but it is also applicable as 
a force to innumerable purposes in life. On 
account of the importance of this subject, we 
shall in conclusion briefly investigate the man- 
ner in which animal force is estimated, and 
under what circumstances it may be employed 
to the test advantage. Thus, let @ denote 
the whole force of an animal when at rest, and 
let us suppose it to be incapable of any effort 
when it is moving with the velocity V; let F 
be the effective force when its velocity is V’; 
then, if the action of the force be uniform, 


MOTION. 


which from the principles assigned we may 
der to be ae since it is the dif. 
ference only between the velocities V and V’ 
that is efficient, the effective force will vary a 
the square of the efficient velocity,that is = 


9:F::(V—of:(V—Vp 


hence F = @ (yao ~~ ° : 


Vi! ue 
WT Pe. VE " i 
or, the utmost velocity with which any 
not impeded moves, is to its velocity when im 
peded by a given resistance, as the square roo! 
of its absolute force to the difference of the 
square roots of its absolute and effective forces 
Let us now investigate the velocity with which 
an animal must move and what must be its 
load, that the work performed by it may be a 
maximum. Retaining the same notation, let 
V —V’ = u; then since F = @ “=F ie 
the product of the moving force into its velo 
city, or the momentum of impulse FV’ 


will = ox (V — u), and making this ; 


maximum, we find u = 3V, and V’ = 4V 
Therefore the effective work of an animal is 
maximum when itis so loaded, that with 
whole force in action its velocity amounts t 
one-third of the greatest velocity which it | 
capable of exerting without any load at al 
In a series of experiments made on men an 
horses, by drawing a lighter along a can: 
and working several days consecutively, th 
force was measured by the curvature and weig 
of a track rope, as well as by a spring stee 
yard 5 and the product of this force multiplies 
y the velocity per hour was considered a 
the momentum. By these experiments the 
forces of men were found very nearly as 
(V — V’, and those of horses, loaded so ¢ 
wv to oe able to trot, as (V — V’jr7 
— V’)'8, results which agree close 
with the theory. In the applieatieial of the 
formule let us suppose a man’s power to 
70 pounds, and his utmost s in walking 
be six feet per second, hence @ will equal 7 
and V equal 6, therefore F = $9 = 31j, 
is the greatest force a man can exert in walki 
and he will move at the rate of }V = 2 feet 
a second.t The strength of a horse ma 
easily computed in a similar manner—it 
generally reckoned to be six times that of n 
or about 420 pounds at a dead pull—the 


* ‘This is a formula of Euler’s, who has g 
another expression > (--F): by 


formula the greatest mechanical effect is ’ 
V’ = / $V, but it does not agree with the 
riments of Schulze and others as near as the 
in the text. See Schulze on the Strength of 
and Horses, Acad. Berl. 1783. ae 
+ According to Buchanen, the force ( 
pumping is 1742, by a winch 2856, in ringing 3 
and in rowin .—Buchanen on human lab 
Repert. 15, 319. et 


and V = 


re 


he : oe 


MUCUS. 


velocity being about 10 feet per second, its 
maximum action will be $ (420) = 1853, and it 
will move at the rate of P or 34rd feet per se- 
cond, being about 22 miles per hour. With 
the help of these formule the maximum forces 
of any other animals may be found. 


BIBLIOGRAPHY. —Aristotle, On the progressive 
motion of animals, by Taylor. Fabricius ab Aqua- 
pendente, De motu locali animalium, Opera ed. 
Bohnii, Lipsie, 1687, p. 332. %, De vi. 
motrice et motionibus animalium, Opera, tom. ii. 
lib. xi. Florentie. Borelli, De motu animalium, 
4to. Lugduni, 1685. Haller, Elementa physio- 
logiz, tom. iv. lib. xi. sect.1v. Barthez, Nouvelle 
mécanique des mouvemens de |’homme et des ani- 
maux, 4to. Par. 1798. Magendie, Precis élément. 
de physiol. tome i. Roulin, Recherches sur le 

isme des attitudes et des mouvemens de 
Vhomme, in Magendie’s Journal, tom. i. ii. 1821-2. 
Gerdy, Sur le mécanisme de la marche de l’homme, 
Magendie’s Journ. tom. ix, and Physiol. médicale 
didactique et critique, par P. N. Gerdy, Paris, 1833, 
tome i. partie 2. Krause, Handb. der menschl. 
Anat. Bd. 1. Poisson, Traité de mécanique, Paris, 
1833, tome ii. Weber, W. and E., Mechanik der 
menschl. Gehewerkzenge, Gott. 1836. Kirby and 
ate Introduction to entomology, 8vo. Miiller, 
lements of Physiology by Baly. Roget, Bridge- 
water Treatise. Paley, Natural theology, with notes 
by Brougham and Bell. Gregory, O., Treatise of 
mechanics. Chabrier, Mémoire de l’Acad. tom. ii. 
— Sur le vol des Insectes, et observations sur 
quelques parties de la mécanique des mouve- 
mens progressifs de l"homme et des animaux ver- 
tebrés, 4to. Paris, 1823. Straus Diirckheim, Con- 
_ sidérations générales sur l’anatomie comparée des 
animaux articulés, 4to.Paris, 1828. Cuvier, Régne 
Animal. Perrault, Mecanique des animaux. Pa- 
vent, On animal mechanics, A. P. 1702. Marian, 
On the position of the legs in walking, A. P 1721. 
, On the motions of the Horse. Bernou- 
illius, J. De motu musculorum, Lond. 4to. 1708. 
son’s Piinciples of mechanics, Lond. 4to. 
1800. Pinel, On animal mechanics, Roz. xxxi. 350, 
xxxiii. 12, xxxv. 457. Mayow, J. De motu mus- 
culari et spiritibus animalibus. 


(John Bishop.) 


MUCUS (from pvée, the secretion of the 
Schneiderian membrane). This word has been 
used in so very indefinite a sense by the 
members of the medical profession, that animal 
chemists have had great difficulty in fixing on 
any distinctive characters by which the sub- 
Stance might be identified. The great source 
of confusion appears to have been that phy- 
siologists and the profession generally have 
applied the adjective mucous or mucoid 
to certain forms of secreted matter; from 
which circumstance the term mucus has 
gradually advanced into substantive use as a 
medico-chemical word, embracing in its mean- 
ing the secretions from the mouth, nose, in- 
testines, &c. as though these were identical 
in their chemical characters. We shall pre- 
sently show, however, that such is not the case. 

In the Philosophical Transactions for 1800 

_ Mr. Hatchett published a paper, in which he 
_ endeavoured to show that such a principle 
__ as mucus really existed, characterised by pecu- 
| - Tiar properties; but considered it a modified 
form of gelatin. Dr. Bostock subsequently 
_ published a paper in Nicholson’s Journal, in 
_-which he showed that mucus differed from 
elatin; this he proved by demonstrating that 
VOL, III. 


481 


tanning did not precipitate mucus, though 
gelatin was immediately thrown down by it, 
whereas diacetate of lead precipitated mucus 
copiously, without affecting gelatin: bichloride 
of mercury and ferrocyanuret of potassa did 
not precipitate either mucus or gelatin. I shall 
show hereafter that these last-mentioned re- 
actions do not apply to every form of mucus: 
the ingenious experiments of Dr. Bostock can 
indeed no longer be considered pertinent, in- 
asmuch as the researches of modern chemists 
have gone far to prove that gelatin is rather 
a product than an educt of animal analysis. 
The experiments of Dr. Bostock were made 
on the saliva of the mouth, and some sub- 
sequent observations by Mr. Brande made on 
the same secretion showed that the precipitates 
obtained by the diacetate of lead and nitrate 
of silver consisted of the chlorides and phos- 
phates of those metals; a fact which inclined 
Mr. Brande to consider mucus as a compound 
substance rather than a proximate element, and 
induced him to apply electricity as a means of 
decomposition. From the results obtained 
in this inquiry, Mr. Brande was inclined to 
consider mucus as a compound of albumen 
either with pure soda or chloride of sodium. 
Dr. Marcet made some experiments on 
mucus which induced him to believe that 
several morbid secretions contained it as a 
constituent; he considered it to be present 
in dropsical effusions. Berzelius, though he 
allows the secretions of the mucous membranes 
to differ in chemical character, and to possess 
distinct properties according to the especial 
office they have to fulfil in lubricating par- 
ticular parts, still believes that such a proximate 
element as mucus really exists as one of the 
constituents of such secretions, and notices it 
in his analysis of mucus of the nose. In 
considering this subject it is, therefore, neces- 
sary to premise that the general term, as used 
by the medical profession, has no relation 
whatever to the chemistry of the question, 
the secretions of the different mucous mem- 
branes varying greatly in chemical composition, 
but, notwithstanding, presenting a physical 
character in common, in relation to which 
the term mucous has been applied to them. 
The inquiry of greatest interest consists in 
determining whether there exists a peculiar 
proximate element in virtue of which the 
mucous character is developed, or whether, on 
the other hand, the peculiar physical character 
can be traced to the presence of some combi- 
nation of albumen which is common to all 
mucous secretions, notwithstanding that they 
may differ greatly in other respects. We have 
already seen that the latter opinion is supported 
by Mr. Brande’s experiments, while Berzelius, 
on the contrary, seems to favour the former 
view of the case. Before entering upon this 
question I shall describe the chemical characters 
of several secretions from mucous surfaces, as 
the reader will then be better prepared for the 
inquiry. I shall commence with the secretion 
from the nose, since this may be regarded as 
the type of those viscous products to which 
the general name of mucus has been applied. 
21 


482 


The secretion of the Schneiderian membrane, 
according to the analysis of Berzelius, is com- 
sed as follows :— 
UCUS sesecsicces 5.33 
Alcoholic extractive and alkaline lactate 0.30 


Chlorides of potassium and sodium 0.56 

Aqueous extractive, traces of albumen, 
and a phosphate ........ses2e050. 0.35 
combined with the mucus...... 0.09 
Water ee ee eee eee teat eereerreeeeee 93.37 
100,00 


The chemical characters of the substance 
which Berzelius notices in this analysis as 
“mucus” are as follows. It is not soluble 
in water, but swells up and becomes transpa- 
rent. When dried it 1s again capable of being 
swelled by water; but after this experiment 
has been repeated several times it becomes 
of a yellow colour, and assumes somewhat 
the appearance of pus. When boiled in water 
it neither hardens nor contracts ; but after this 
treatment it is found, to a certain extent, to 
have lost its property of swelling. When dry 
it is of a yellow colour and transparent. By 
distillation it yields carbonate of ammonia and 
empyreumatic animal oil. ‘The ashes obtained 
from this substance yield phosphate and car- 
bonate of lime, with traces of carbonate of 
soda. This mucus is soluble in weak sulphuric 
acid ; the strong acid darkens its colour and even- 
tua!ly destroys its texture. Weak nitric acid co- 
agulates it superficially and renders it partially 
yellow: long digestion in this acid causes 
its solution. Acetic acid contracts it, but 
does not dissolve it even when assisted by 
heat. It dissolves from it, however, a portion 
of albumen, which renders the solution preci- 
pitable by the ferrocyanuret of potassium. 
Caustic potash renders this mucus more tena- 
cious, but by digestion it dissolves it. In- 
fusion of galls coagulates it when dissolved 
in acids or when swelled by water. These 
characters described by Berzelius may be re- 
ceived as the genera! properties of that substance 
to which mucous secretions owe their viscous 
character. 

Urinary mucus.—This form of mucus is 
best obtained by allowing recently voided urine 
to remain at rest in a tall glass vessel, when 
the mucus will subside after some hours, and 
may be collected by pouring off the super- 
natant fluid as nearly as possible without 
disturbing the precipitate, and throwing the 
remaining part of the secretion on a filter; 
the mucus will now be retained on the paper. 
Its properties are as follows :—when ined cn 
paper it exhibits a bright surface; on being 
moistened, however, it rapidly assumes its 
original appearance. It is insoluble in sul- 
phurie acid, but the nitric and acetic acids 
dissolve it in large proportion, and the solution 
is precipitable by ferrocyanuret of potassa: 
caustic potassa in solution dissolves it entirely. 

Sualivury mucus.—The saliva, as it passes 
from the mouth, contains, in all probability, 
two kinds of mucus; one derived from the 
pueous membrane lining the mouth, and the 


MUCUS. 


other from the internal membrane of the salivary 
ducts. When saliva is allowed to stan 
very soon separates into two parts; one @ 
supernatant liquor of a slightly milky hue, 
and the other a deposit of a white colour, 
which in this state does not exhibit the ordinary 
physical characteristics of mucus. On pouring 
off the liquor, however, and then agitating the 
deposit with water, it immediately assume 
the glairy character; indeed, without the addi. 
tion of water it will exhibit a mucoid tenacity 
if an attempt be made to raise it from the 
vessel in which it has collected. The liquo 
which has been poured off from this dens 
form of the principle still contains a portior 
of mucus in suspension, which may be 
tained by dilution with water, and may pre 
bably be a less coherent form of mucus secreted 
by the lining membrane of the salivary duets 
These two forms of mucus have much the 
same chemical characters, being insoluble iz 
water and coagulable, and rendered firme 
by the acetic, hydrochloric, and sulphuri 
acids. The liquors obtained by digesti nes 
acids on mucus are not precipitable = t 
addition of alkalies, which shows that th 
form of the secretion does not contain any 
free subphosphate of lime. It is dissolve 
by caustic alkalies and peels by th 
acids when thus dissolved: the solution it 
alkalies, however, is not Coney a residue 
being always obtained, which is soluble ia 
acid, but which cannot be precipitated fror 
the acid sulution by means of caustic alk 
and, therefore, is not an earthy sa!t. Notwit 
standing this, however, we can always obta 
evidence of the existence of phosphate — 
lime in considerable proportion by incinerati 
mucus ; and Berzelius considers the tart 
formed on the teeth to be derived from t 
source. This form of mucus is consider 
by Berzelius to approach very nearly to 
obta.ned from the stomach and intestines: | 
differs greatly from nasal mucus, which 
sulub!e in the sulphuric and nitric acids. 
Intestinal mucus—The mucus of the stom: 
and intestines can be best obtained by washi 
the mucous surfaces of those organs tal 
from an animal that has fasted some he 
it is occasionally observed adhering — 
crement. This mucus, when dried, 
longer capable of assuming the ter 
character on being moistened with wat 
according to an observation of Berzeli 
quires an alkaline solution for burps 
it is coagulable by the acids. The acetic 
acts powerfully upon it, solidifying it” 
pletely. None of the acids dissolve it; 
acetic acid seems, however, to have a | 
action, since the liquor obtained by dige 
it is precipitab'e by the addition of it 
of galls, but not always, by the ferrocys 
of potassa. ‘The caustic a!katies dissolve 
mucus, and the addition of acids preci 
it when thus brought into solution, 
Mucus of the gall-bladder has been exan 
and appears to resemble that last d 
it is insoluble in the acids and pr 
by them from solution in alkalies. 


Px 
a] 
> 
ae 


te 


MUCUS. 483 


From the descriptions which I have now 
given I think it will be allowed that, inasmuch 
as the mucus which is obtained by the chemical 
analysis of different secretions fails to show, 
when subjected to tests, those agreements in 
reaction which must be regarded as essential 
to prove identity, the question as to the 
existence of any substance to which the name 
of “ mucus” should be applied, as one of the 
proximate elementary animal bodies, should 
be regarded as concluded. ‘That there is 
always a matter present in the secretions of 
mucous membranes, which possesses a gluti- 
nous character, and to which the physical 
Bberies of the secretion are owing, is un- 

oubtedly true; but this is quite a distinct 
question from whether or not this tenacious 
constituent be entitled to the rank of a proxi- 
Mate element: and the fact of a difference 
being observed in the chemical reactions of 
this body. as obiained from various secretions, 
strongly opposes such an idea. In order to 
examine into this question I made, some time 
ago, at the suggestion of Dr. Bright, some 
ehemical observations on those effused fluids 
which partake more or less of the mucous 


character,* such as the effusions which occur 
in ovarian dropsy, and to compare the results 
obtained with similarly conducted experiments 
on other fluids of a more purely serous character, 
and also with seruin of blood, as it appeared 
probable that some point of difference might be 
detected to which the mucoid character could 
be traced, notwithstanding the total absence of 
any substance obtainable in a solid form and ex- 
hibiting physical characters like those of mucus. 
I subjoin the examination of five fluids effused 
in ovarian tumours, and one of a purely serous 
character drawn from a case of ascites ; the serum 
of blood is also offered for comparison ; the 
separation of these fluids being carried only 
so far as the division into free albumen, 
aqueous extractive, and alcoholic extractive. 
These analyses were made on equal weights, 
or nearly so, of solid matters, obtained by 
evaporating each fluid, as previous observation 
had convinced me that the viscous character 
into the nature of which I was examining 
was quite independent of the degree of con- 
centration of the effusions, the most tenacious 
generally possessing the lowest specific gravity. 


Ovarian effusions. Fluid Serum 


‘ of of 


— 
No. 1. No. 2. 


ee 
No. 3. No 4. No.5. Ascites. Blood. 


A Bara sisia's «ADO a oa AIOU. foe a Del Dis ois 40rd Vieis 6 v LAS jess GOD ies eee 
Aqueous extractive ......4.94....4.73....4.79....3.25....7.05.... 1.43... .0.35 
| Alcoholic extractive......0.54....0.70....1.45.... .57....1.79....2.11....0.87 


These analyses at once showed that the 
aqueous extractive existed in greater proportion 
in the tenacious fluids of ovarian cysts than 
in the more serous effusion of ascites and 
the serum of blood; but another difficulty 
remained to be solved, which was, that some 
of these viscous liquors which were less mucoid 
in character than others, did not indicate the 
cause of such difference when the examination 
had been extended only to the separation into 
the three parts above mentioned, viz. albumen, 
aqueous extractive, and alcoholic extractive. 
On incinerating the aqueous extractive, how- 
ever, so as to ascertain the proportion of 
animal matter and alkaline salts contained in 
it, I discovered that, while those specimens 
which showed the mucoid character in a more 
marked degree contained salts and animal 
matter in nearly equal proportions in their 
aqueous extractive, those in which the mucoid 
character did not greatly predominate either 
showed a deficiency or excess of salts; both 
conditions appearing more or less to interfere 
with the perfect development of the peculiar 
tenacious character of the secretion. I have 
now to notice the late ingenious and valuable 
observations of Dr. Babington, who has done 
more to assist this inquiry than any observer 
who has as yet examined into the subject. 
_In a paper published in the fifth number of 
__ the Guy’s Hospital Reports, Dr. Babington de- 
-seribed some experiments showing that various 
_albuminous matters were capable of assuming 
_the mucous character by mixture with the 
alkalies. Serum of blood, pus, milk, and 
~ of egg were all so affected; and the 


glairy mass so obtained was insoluble in water, 
precipitable by diacetate of lead, but not by 
bichloride of mercury or infusion of galls. 
It admitted of being washed with water till 
all traces of alkalinity were removed, but it 
still retained its mucous character. This syn- 
thetical formation of mucus is a most important 
fact; and I see no reason whatever to doubt 
that the artificially formed viscous mass differs 
from that secreted by membrane. It is true 
that the latter always contains microscopic 
globules, which of course are wanting in the 
artificial product; but these globules are, I 
believe, in no way connected with the viscous 
character of mucus, but are rather superadded 
to it, and frequently in very small proportion 
to the mass of the secretion. 

The experiment of Hunter, who consolidated 
albumen by the addition of hydrochlorate of 
ammonia,as also the observations of Dr. Pearson 
on the action of some others of the neutral 
salts on pus, are confirmed by Dr. Babington 
in the paper to which I have alluded. The 
microscopic history of mucus, or rather of 
those organic globules which accompany the 
secretion, is a matter of considerable interest: 
before entering upon it, however, I wish to state 
my reasons why these globules are not, according 
to my belief, the cause of the viscous character 
of mucus. In the first place we do not 
observe them in sufficient numbers to autho- 
rize such an opinion; and, secondly, some of 
the most viscous forms of the secretion do 
not become corrugated to any perceptible 


* See Guy’s Hospital Reports, April 1833, 
21.2 


484 


degree by the addition of concentrated saline 
solutions, whereas, by some experiments lately 
made with my friend Mr. Lane, I have been 
satisfied that the mucus globules are so affected, 
and may easily be observed, under a powerful 
microscope, to expand or contract according 
as water, or strong solutions are mixed with 
them. ‘The mucus globule admits, in fact, of 
the exudation or imbibition of fluids according 
to the laws of endosmose and exosmose, and 
were the greater part of a mass of mucus 
composed of these globules, we should observe 
it to corragate in concentrated solutions; but 
such is not the case, as I have before stated, 
with many of the most viscous forms of mucus, 
while the mucus of the bladder, on the con- 
trary, which (except in severe diseases) is one 
of the least coherent forms, shows a tendency 
to contract under such circumstances, and on 
microscopic examination proves to contain 
globules in large number in proportion to its 
mass. This reaction, I think, renders it very 
probable that the view I have mentioned is the 
correct one. Most forms of mucus swell when 
moistened by water or weak solutions; but 
this is no proof of action on organic globules 
unless the opposite experiment (contraction by 
strong solutions) can be successfully performed. 
The mucus globule varies greatly, as seen in 
different secretions; so much so that any one 
who has examined this subject microscopically 
must be familiar with a form of globule peculiar 
to each secretion. I shall first describe the 
globule generally, and then proceed to notice 
its varieties in appearance. The mucus globule 
is nearly transparent, and larger than the blood 
globule. As it exists in the saliva and urine 
it is of a very regularly circular form, with 
a well defined margin and a somewhat granular 
surface. In the more adhesive forms of ex- 
pectoration, however, it loses this well defined 
and rounded form, and its translucence is 
impaired ; the granular surface can always, 
however, be seen. In a portion of mucus 
taken from the back of the throat I lately 
had an opportunity of examining this last 
mentioned condition, and took occasion to 
examine whether or not it depended on a 
partially empty condition of the globule, 
which could be remedied by the addition of 
water. I found, by careful treatment, in this 
way under the microscope, that the bodies 
gradually assumed a more rounded form, 
and eventually exhibited an appearance almost 
identical with the more transparent globules 
observed in the saliva and urine. By sub- 
sequently adding a concentrated solution of 
sugar to them, however, the original appearance 
was speedily reinduced, owing to the endos- 
modic action of the sirop. is experiment 
has led me to a belief that the cause of 
difference in the microscopic appearance of the 
mucus globule, as seen in different secretions, 
is attributable rather to the circumstances 
under which it is placed than to any difference 
in organization. 

It would appear, from the facts collected 
up to the present moment on this subject, that 
we are justified in considering, 1st, that mucus 


MUCOUS MEMBRANE. 


is a compound of albumen in a state of close 
combination with alkaline salts, and probably 
free alkali; 2nd, that the artificial compound 
formed by the addition of alkalies and neutral 
salts to albuminous matter is essentially the 
same as mucus; 3rd, that the mucus ¢ 
is superadded to the viscous matter in 
secretions of mucous membranes, and is in 
no way concerned in imparting the peculia 
tenacious character to such fluids. y 

A great deal of trouble has been taken | 
devise chemical means of distinguishing be- 
tween pus and mucus, or to detect the presene 
of the former when existing combined i 
small proportion with the latter. No chemics 
method of inquiry can ever be applicable to 
this question: the microscope must be ha 
recourse to for the detection of the pus globule, 
if the mucus be suspected to contain it in 
quantity so small as to escape casual exami- 
nation. When pus is present, however, even 
in very small proportion to the mucus, if 
physical characters are so distinct that 
chemical or mic ical tests can possib 
be required. Considered as a means of prov 


Pe 
oDUuLe | 
a 


the folly of using chemical tests is at once 
apparent when we recollect that the questic 
as regards pus is entirely one of structur 
and we cannot in reason use chemical te 
to determine the presence or absence of 
globule. When pus exists as a deposit i 
urine, we may easily distinguish it he 
hosphates with which it is sometimes cor 
‘ounded by adding an alkali, as recommende 
by Dr. Babington, in whieh case the depos 
(which must be previously separated by | 
cantation from the urine) assumes the glair 
character of mucus, and thus shows its alb 
minous nature. As affording us a distinetij 
test, therefore, between these two substance: 
chemistry becomes useful; but inasmuch ; 
the addition of alkali to most forms of albi 


- 


minous matter developes a mucous ‘i 
the re-agent cannot correctly be called a t 
for pus. We become assured of the presi 
of pus by this reaction only, because previt 
experiment has shown that the 
and pus are the only two substances assu) 
a peculiar and similar appearance in the u 
G. Owen Rees. 


phosph: 
all 


MUCOUS MEMBRANE.—This term | 
been usually and properly restricted to th 
large expansions of membrane, in the int 
of the body, which are continuous ; 
external tegument: but it is impossible, in 
present state of knowledge, to treat of t 
apart from the true glands and the skin, w 
form with them a great system, to whicl 
generic term mucous will be applied im 
article. £ 

Many anatomists since the time of B 
have treated of the mucous membranes 
skin under the common title of tegume 
membranes ; and the opinion has been gi 

<< 


* Bonn, Specimen Anatomico-Medicum I 
&c. de continuationibus membranarum, &c. 
diforti Thesauro, tom, ii. p. 265. Roterod. 17 


MUCOUS MEMBRANE. 


ally gaining ground, that all the glands fur- 
nished with excretory ducts have a very close 
relation to the former, in which their ducts for 
the most part open. Still, it does not appear 
that the proofs of this alliance have been hi- 
therto, by any author, deemed sufficient to in- 
duce him to blend these several parts under a 
description common to themall. Even Miiller, 
in whose philosophical work on the glands is 
contained so much new and important evidence 
of this relation, continues thus to sever them 
in the late edition of his Physiology. But, in- 
deed, although much weight is to be granted 
to the arguments drawn from continuity and 
occasional convertibility of structure, course of 
developement, rough analogies of composition 
or of function, and sympathies under disease, it 
must be allowed that Pitherto that most im- 
portant of all proofs has been all but wanting, 
which, as I shall endeavour to show, is capable 
a being derived from minute anatomical ana- 
lysis. 

The researches which I have hitherto been 
able to make on this subject are still so incom- 
plete, that I should have gladly delayed their 
publication for some time longer, had the pro- 
gress of this work admitted of it. As itis, I 
shall state the conclusions to which I have 
been led, and the grounds they rest upon, 
{pointing out, as far as possible, where farther 
examination is demanded,) with the hope of 
thereby giving a clearer and more satisfactory 
view of the structure and relations of this im- 
portant class of tissues than could be otherwise 
accomplished. 

I shall point out that the skin, mucous mem- 
branes, and secreting glands, consist of certain 
elements, which the anatomist may detect and 
discriminate, some of which are essential to 
their tissue, others appended or superadded,— 
and that the broad characteristic distinctions 
between these structures, appreciable to ordi- 
nary sense, as well as the innumerable grada- 
tions by which they every where blend insensi- 
bly with one another, are solely due to various 
degrees and kinds of modifications wrought in 
the form, quantity, and properties of these re- 
spective elementary parts. 

The skin is the outer tegument of the body ; 
the mucous membranes form its internal invest- 
ment, and are continuous with the skin. The 
duets of all glands are continuous either with 
skin or mucous membrane, and their true 
secreting portion, as already described, (see 
Guanp,) is merely a further prolongation of 
the same tissue. These offsets, like the great 
mucous tracts, are in the direction of the inte- 
nor of the body ; they form follicles and tubes 
of infinite variety, and, however complicated, 
May still he regarded, in a certain sense, as ex- 

_ ternal to all other textures. Thus the mucous 
_ System may be described as a great and un- 
interrupted membrane, every where perfectly 
_ closed, in which the rest of the animal, or the 
_ parenchyma, is enclosed. This membrane has 
_ two surfaces, the one free, superficial or exter- 
hal, the other attached, deep, or parenchymal. 
It is on the parenchymal surface that the ap- 
pended structures (viz. blood- and lymphatic 


485 


vessels, nerves, and areolar tissue) are found 
in more or less profusion. 

The functions of the mucous system, nume- 
rous and diversified as they are, all bear a dis- 
tinct reference to its really external anatomical 
position, and by this circumstance they are 
associated together: the principal are sensation, 
absorption, secretion, excretion, and defence of 
the parts lined by it against the contact of 
foreign bodies. 

A glance at the opinions that have prevailed 
concerning the structure and relations of the 
mucous membranes, will exemplify, more clearly 
perenne than any other course, how imperfect 

ave been the means employed, until a very 
recent period, in researches into minute or 
structural anatomy. The distribution of their 
bloodvessels had indéed been studied with 
brilliant success by Ruysch, Lieberkiihn, and 
others, by the aid of injections, the admirable 
delicacy of which no modern art has surpassed ; 
and somewhat of their extensive connexions, 
general properties, and even of their texture, 
had been divined from rough dissection, mace- 
ration, and observations on the mode of their 
developement and on their morbid states. But 
the ignorance that really prevailed, as to their 
intimate structure, is abundantly evinced by the 
number of disputed questions, the absence of 
precision of detail, and the substitution of loose 
and unwarranted analogies in its stead. Within 
the last five years discoveries have been made 
which throw a new and most important light 
on the whole subject, and when viewed in con- 
nection with one another, must be considered 
to have greatly simplified our knowledge re- 
specting it. These discoveries, due chiefly to 
Boehm, Boyd, and Henle, result from exami- 
nations of recent specimens with the micro- 
scope, and those of the last observer, which are 
especially valuable, were made with high pow- 
ers employed upon a single tissue (the epithe- 
lium) in different forms and situations. It is 
this kind of research that promises the most 
enlarged and trustworthy results to any one 
who will follow it in a spirit of due caution 
against hasty generalization, and which has 
already done so much in the present day to- 
wards a complete remodelling of our ideas, 
both concerning the elements of organization 
and their union to form compound tissues. 

Before proceeding to a description of the 
anatomical elements of the mucous system, it 
is necessary to premise that a great portion of 
the membranes, usually termed mucous, are 
glands of a complicated structure, arranged in 
a membranous form, consisting of a closely 
packed mass of secreting tubules, which open 
on the general surface, and are essentially invo- 
lutions of it. The bloodvessels and other ap- 
pended tissues occupy the intervals of these 
tubules, and so approach the surface; but, ne- 
vertheless, they always remain on the deep or 
parenchymal aspect of the mucous tissue. So, 
the same membranes present projections, which 
are nothing more than hollow evolutions of the 
same mucous tissue, into which the appended 
tissues are extended. The same remarks apply 
strictly to many regions of the skin. Hence it 


486 


becomes necessary to guard against confound- 
ing such membranes with the simple 
mucous tissue, of which these and all other por- 
tions of the mucous system consist. 

Of the ultimate structure of the mucous 
system.—It has been already stated that the 
mucous tissue is essenti.lly an uninterrupted 
membrane in which the other tissues of the 
animal are contained. A very cursory attempt 
will serve to shew how much more easily it 
admits of being separated and examined ‘in 
certain situations rather than in others. This 
variety depends chiefly on the difference of its 
arrangementand connexions in different regions. 
In the testis and kidney, the capillary vascular 
rete, spread over its parenchymal surface, has 
no intimate attachment to it, and the appended 
areolar tissue is in very small quantity. In 
the testis especially, this latter may be said 
to be almost wanting as an investment to the 
individual tubules, being, as it were, disposed 
as a collective covering to the entire organ, 
sending partial septa itte its interior, and 
bearing the name of Tunica Albuginea. In 
the kidney, a more intricate vascular rete in 
a great measure supplies the place of areolar 
tissue. Hence, in these viscera, the simple 
mucous element allows of being isolated with 
remarkable facility. In the liver, its isolation 
is almost impracticable, owing to its lying in 
the interstices of a capillary plexus that may be 
termed solid, from its being extended uniformly 
in every direction. The intricacy of the inter- 
lacement of the mucous and vascular elements 
in this organ is sufficient to explain the total 
ignorance that prevails concerning the mode 
of termination of the biliary ducts, and con- 
cerning their size, shape, and connexions in the 
lobules of the gland. In many other true 
glands, the mucous tissue may be submitted to 
examination without much difficulty; examples 
of which may be seen in the pancreas and 
salivary glands, with those allied to them, such 
as the duodenal glands of Brunner, the buccal, 
palatal, arytenoid, tracheal, &c.; and in the 
sudorific glands of the skin. In the compound 
membranes also, as that of the alimentary 
canal below the cardia, and the more highly 
developed parts of the skin, the mucous ele- 
ment may be generally distinguished from the 
tissues in connexion with it in a satisfactory 
manner. But in the plane expansions of the 
simple membrane which line the bony cavities 
of the nose and ear, its isolation and the demon- 
stration of its structure are far more difficult, 
for reasons which will be afterwards explained, 
and our knowledge of it here still rests partially 
on the ground of analogy. 

In the mucous tissue there are two structures 
that require to be alee | described, viz. 
the busement membrane and the epithelium. 
The basement membrane is a simple homoge- 
neous expansion, transparent, colourless, and 
of extreme tenuity, situated on its parenchymal 
surface, and giving it shape and strength. This 
serves as a foundation on which the epithelium 
rests. The epithelium is a pavement composed 
of nucleated particles adhering together, and 
of various size, form, and number. The fol- 


MUCOUS MEMBRANE. 


lowing general observations on these element; c y 
rts will receive illustration as we advance. 
either the one nor the other is peculiar to the 

mucons tissue in the sense either of being 

invariably present in it, or of not being found 
elsewhere. There are certain situations of the 
mucous system where no basement membrane 
can be detected, and others from which the 
epithelium is absent. Both, however, are never 
absent together. Avain, a structure apparently 
identical with the basement membrane is met 
with in numerous textures besides the mucous. 
and all internal cavities, whether serous, 8} yno . 
vial, or vascular, or of anomalous kind, (as thost 
of the thymus, and thyroid body) are lined by 
an epithelium. Ss 
In the ensuing description these circum: 
stances will be enlarged upon, and the excep- 
tions and local peculiarities pointed out, as fa 
as I have been able to ascertain them. 
present, I would say that these two elem 

are generally present. The most in n 

questions in animal physiology are involved it 

the determination of the nature and offices 
these two elementary pes of the mucou 

tissue. The discovery of them is, however, t 

recent, and our knowledge of their history ; 

yet too incomplete, to allow of any ce 
conclusions on the subject. Both prese 
various modifications in different situatio 

the study of which is of great im w 

reference to their function. It will now be o 

business to descend to a particular account 

each. va 

Of the basement membrane.—-The basem¢ 

membrane of the mucous tissue, as displ 

in the kidney, is an extremely thin, transpare 
and homogeneous lamina, simple and entin 
without any aperture or appearance of structu 

(fig. 273, c). It forms the parenchymal wall” 

the uriniferous tubules; gives them their siz 

shape, and stability ; is in relation, on the one 
hand, with the vascular system of the org 
and on the other with the epithelial lini 

It is simply in contact with the capi 

plexus, which is fixed chiefly by their t 

tual interlacement; but the epithelium adh 

to it by an organic union. When detac 

from the vascular rete which it traverses, 4 

deprived of its epithelium, it readily wrn 

(fig. 273, c); and such is its tenuity, thi 

is sometimes only by the folds thus oceasi 

that it becomes visible at all. The epithe 
readily separates from it after a slight ma 
tion, and also in many diseased states 
organ, such as inflammation and Bright 
ease. Though this basement tissue is S¢ 
cate, its presence or absence in any fre 
of a separate tubule may always be ascer 
by the aspect of the marginal outline; 
be linear and well defined, the basement 
brane is present, but if irregular and br 
the epithelium only (fig. 273, a, b). Tt: 
times happens that when the epithelium 
seem to be altogether detached, the base 
membrane retains, scattered evenly Ov 
surface and at some distance apart, a nu 
of roundish marks, of the size and aspeé 
the nuclei of epithelium particles. 


MUCOUS MEMBRANE. 


A portion of a tubrile of the human 
kidney, magnijied -OU diameters, 


Ata, the basement membrane and 
epithelium are both seen in a iy 
natural state. At 6, the base- yl) 
ment membrane has been sepa-_ ff 
rated, and the epithelium is some- 
what s ollen, and its outline 
‘woolly.”? At ¢, the epithelium 
has been detached and the base- 
ment membrane is seen somewhat 
wrinkled: d,a detached epithe- 
lial particle seen in face; its 
minutely mottled texture is not © }) 
represented in the wood-cut. 


most probably the early condition of the new 


or advancing series of these particles. Its 
thickness in the kidney certainly does not ex- 
ceed the sgiggth of an English inch. I have dis- 
covered, that in the Malpighian bodies of the 
kidney, which are the dilated extremities of 
the urmiferous ducts, with an enclosed tuft of 
arterial capillaries, the basement membrare is 
ofien, to some extent, naturally bare, i.e. w.thout 
a covering of epithelium. This is the only situa- 
tion of the body in which such an arrangement 
is known. 

In the testis, the same membrane may be 
shewn without difficulty to be that which gives 
to its secreting tubules their peculiar strength ; 
and here, as might be expected, it is somewhat 
modified. The difference is principally as 
regards its thickness, which here reaches y,4,,th 
of an English inch, and in some animals 


Fig. 274. 


A portion of a tubule of the testis ( Guinea-pig, Co- 

baya), magnijied 300 diumeters. 

a@a, basement membrane; a’, corpuscle in its sub- 
stance ; b 6, epithelium in situ, consisting of par- 
ticles of different dimensions, with minute gra- 
nules in their interstices ; c, cavity of the tubule 
full of detached epithelium particles, of various 
size and appearance, and mingled with nume- 

 rous seminal animalcules; d, one of these semi- 
nal animalcules. 


even exceeds that amount, its essential charac- 
ters, however, remaining the same. In the 
larger tubes, emerging from the gland, this 
tunic becomes gradually invested by a delicate 
fibrous layer, by which the vascu'ar network is 
attached to it, aud which at first sight may 


487 


appear to form an integrant part of the wall 
of the canal. 


Terminal vesicles of the pancreas of the dog, magnified 
300 diameters. 
The basement membrane is seen ata a a, where the 
epithelium has been a little detached. 


In the salivary and all the allied glands, 
the basement membrane admits of being easily 
demonstrated. A very thin slice of the fresh 
organ should be torn by needles, gently washed, 
and inspected under a high power. The termi- 
nal vesicles of the duct will then be brought 
into view and their outline seen to be perfectly 
sharp and linear (fig. 275, a aa). In parts 
where the epithelium which they contain has 
been loosened, the basement membrane will be 
left in relief. It is of extreme delicacy ; and, as 
in all other situations, its capillary plexus (when 
well filled with coloured material) may he seen 
ramifying, not in its substance (for its tenuity 
renders such a disposition impossible), but on 
its parenchymal surface. 

have sought in vain for the basement mem- 
brane in the lobules of the liver, and I am in- 
clined to think that it does not exist in this 
gland, except in the excretory part of the bile 
ducts. 

In the air-cel!s of the lungs the basement 
membrane assumes a most interesting and re- 
markable developement, for it constitutes almost 
the entire thickness of their walls, the epithe- 
lium being of extreme delicacy. It appears to 
be here strengthened by interlacing arches of 
elastic fibrous tissue, but to be itself transpa- 
rent and homogeneous, as elsewhere. It is on 
its parenchymal surface that the close vascular 
web is spread out. (See Putmo.) 

But this membrane may be also detected in 
every part of the alimentary tube, which is 
more characteristically mucous, in that, viz. in- 
tervening between the cardia and the lower ex- 
tremity of the canal. Here it deserves an 
attentive study on account of the apparent com- 
plexity of its foldings, and because its exist- 
ence here offers the most unequivocal proof 
which we possess, of the anatomical identity of 
the true glands with the membranes usually 
called mucous. As it is more delicate in this 
part than any other, and difficult of detection 
by reason of the enormous preponderance of its 
epithelial investment, I shall describe the man- 
ner in which it may be best observed. The 
specimen should be as fresh and healthy as 
possible, or should have been immersed in 


488 


alcohol immediately on its removal from the 
body ; a fragment of the tubes of Lieberkiihn 
should then be scraped off, pulled to pieces, 
and examined in a fluid medium under a 
high power. The margins and rounded extre- 
mities of the tubes will then be seen to be 
sharply defined, as in the cases already men- 
tioned, and to be formed by a structure inde- 
pendent of the epithelium, which latter forms 
Aths of their thickness. This structure is the 
basement membrane. When masses of epithe- 
liam, escaped from the tubes and bearing their 
form, are met with floating around, their out- 
line is uniformly irregular, and, as it were, 
woolly. Sometimes, as in the kidney (fig. 273), 
the basement membrane is seen up to a certain 
point only, beyond which it has been detached ; 
and in less recent specimens a tube of basement 
membrane is sometimes seen, containing a mass 
of broken-down epithelium. 

If the part selected for examination be the 
stomach, the same precautions should be ob- 
served, for here this membrane is, if possible, 
more delicate than below the pylorus, and the 
epithelial particles are often so large as to bulge 
the tubes very irregularly, especially towards 
their blind extremities. It is between these 
bulges that the basement membrane may be 
best seen (fig. 276). 

Nothing is more difficult than to explore, in 
a satisfactory manner, the internal structure of 
the intestinal villi. Their thick epithelial caps 
and their abundant vascular rete are readily 
demonstrable, but the arrangement of the lac- 
teals, which undoubtedly exist in them, and 
of the structure on which the epithelium imme- 
diately rests, has hitherto almost entirely eluded 
our research. In vertical sections of the recent 
small intestine of the Car- 
nivora, I have several times 
seen the direct continuity 
of the epithelium covering 
the villi, with that lining the 
tubes which open at their 
base; and also a distinct 
continuity between the inte- 
rior of the villi, where the > Gym 
vessels are spread out, with a") a 
the vascular intervals be- 
tween the tubes, which con- 
tain the fine capillary web 
surrounding the tubes, and 
likewise give passage to the 
branches to and from the 
villi. It is then difficult to 
avoid the belief that the 
basement membrane of the 
tubes is continued under the Lower extremity of a 
epithelium wie villi, to the dog ( Cant > 
support it, and form a “awa : 
of / ose remarkable shea gr le a 
tions. Nevertheless I have 
not been able to see it in an 4t@¢, Nem basement 
isolated and distinct form, Cetien ee 
and do not therefore assert  pulging epithelial 
its positive existence ; only particles. 

I believe that the fact that 
the injected vessels of a villus, when seen in 
profile at its margin under a high power, and 


Fig. 276. 


MUCOUS MEMBRANE. 


when the epithelium has been removed, seldom _ 
come to the extreme edge, is attributable to the 
circumstance of the basement membrane still 
investing them. This membrane, if it really — 
exist here, adheres intimately to the part 
within the villus. 
It might seem at first sight a hopeless t 
to search in so dense and complicated a stru 
ture as the skin, for the analogue of a mem-— 
brane like that I have been describing, which, — 
in no situation where it can be u i 
brought into view, exceeds the 8000th of 
inch in thickness. But as it must exist, if at 
all, between the epidermis and the vessels i 
nerves of the cutis, in a position sufficientl 
determinate, much of the apparent difficult 
is removed. The most favourable situations 
for its detection are those in which the skin” 
is highly developed, presenting, like the small 
intestine, villi (termed papillz) on its free sur-— 
face. The close resemblance these 
pille and the villi of mucous membranes has 
observed by many anatomists. The dis- 
tribution of the vessels within pee: essentially 
the same. Here, then, under epidermic 
layer, we might expect to find the 
membrane. I have removed with great care 
the whole of the epidermis from a thin ver- 
tical section of such a specimen (and it is 
better to have previously steeped it in solu- 
tion of carbonate of potass), and have ther 
examined the outline of the bare papille with 
a power of 300 diameters. This outline 1 
sharply defined, and appears to be Lec 
by a homogeneous membrane, enclosing the 
vascular and nervous contents. This mem. 
brane I believe to be that which I am 
describing, though, as in the case of the intes- 
tinal villi, 1 have never been able to isolate 1 
and thus unequivocally prove its presence 
This is a part of the skin which has never been 
noticed by anatomists on account of its tenuity, 


, 
¢ 


Part of the tubule of a sudoriferous gland fron 
Ml sotila. aay 320 diameters, 
A, transverse section ; B, side view of the inte 
obtained by bringing the axis of the tubule 
focus; a a a, basement membrane; b b 3, ¢ 
thelium ; cc, cavity of the tubule; d, super 
epithelial particles; e, dee epithelial particle 
A a detached superficial epithelial par 
shewing the nucleus and pigmentary gi 
g, its detached nucleus, with a nucleolus. 


MUCOUS MEMBRANE. 


but which is quite distinct from the cuticle, 
and the great mass of that complicated struc- 
ture to which the terms ‘cutis’ and ‘ dermis’ 
are applied. 

A very strong reason for believing this mem- 
brane to be present in the skin, is the fact of 
its existence in those minute organs, so profusely 
scattered under the cutaneous surface, the se- 
baceous and sudoriferous glands. In fig. 277 
I have represented it in a portion of one of the 
latter, taken from the axilla, where they are 
very large. These glands are nothing more 
than involutions of the external tegument, and 
correspond closely with the labial and allied 
glands connected with the ordinary mucous 
membranes. It is impossible to suppose that 
a structure attaining so marked a developement 
in those parts, should be wanting in the general 
superficies, with which they are, at numberless 
points, directly continuous. ; 

In other situations, where a simple expanse 
of mucous membrane is spread out upon a 
surface of the body, as in the csophagus, 
ei mouth, nose and its sinuses, vagina, 

ladder, &c. (from all of which, however, 


_ there are numerous prolongations called follicles 


and glands, which shew this structure well,) 
a basement tissue such as that described has 
not been shown to exist. Its existence rests 
at present principally on analogy, and it is 
difficult to say whether it be not more or 
less modified. Certain of the peculiarities 
presented by these several parts depend on 
a modified form and greatly augmented mass 
of the epithelial element, but many also on 
varieties in the areolar and vascular tissues 
underlying the mucous tissue, and, properly 
speaking, forming no part of it. These will 
be treated of under the topographical descrip- 
tion of the membrane. 

Of the epithelium.—A very brief period has 
elapsed since it was universally held that most 
mucous membranes wanted epithelium, and 
their analogy with the skin was only maintained 
in this particular by a fancied resemblance 
drawn between epidermis and mucus. One of 
the principal results of microscopic observation, 
conducted with the improved modern instru- 
ments, is that of Henle, proving not only that 
this structure is present throughout the mucous 
System, but that in most situations it is so abun- 
dant as to constitute nearly the whole material of 
the tissue. This fact, as yet so novel, coupled 
with the discovery announced at the same time 
of the occurrence of a lining of analogous cha- 
racter on all internal cavities, makes the study 
of this structure under its varied forms pecu- 
liarly interesting and important. It will readily 
be conceived how wide a field is here opened 
to view, and how premature it would yet be to 


_ attempt to offer a general history of such a 


4 
4 


] 
| 


structure. The numerous questions presenting 
themselves on every side render this impossible; 
and if it were not so, the scope of the present 


_ article would oblige me to confine the descrip- 
_ tion to those forms of epithelium met with 
_ in the mucous system. In acknowledging the 


great obligations I am under to Henle’s admi- 
rable paper on this subject, I may state that 


489 


the following account has been written as much 
as possible from my own observations. 

By the term epithelium is now meant a layer 
of particles or modified cells, furnished with 
nuclei and nucleoli, lining an internal surface 
of an organized body, and by their apposition 
and union constituting a kind of pavement. 
A similar investment to an external surface is 
styled epidermis. Both these, m their ordinary 
forms, will be embraced by the following de- 
scription. 

Epithelium is an organized structure endowed 
with vitality. This is shewn by its form, the 
process of its growth, and the living properties 
it displays. Of these the most eminent is that 
of ciliary motion, which in all the higher 
animals is performed by cilia clothing the free 
surface of epithelial particles. But in very 
many situations, if not in all, the processes 
of nutrition carried on in the epithelial layer 
of the mucous system differ materially from 
those of other organic tissues ; the old elements, 
which in other cases are reconveyed into the 
blood, being here shed on the free surface of 
the membrane, and thus becoming at once 
eliminated from the system. 

The epithelial particles preserve a greater 
resemblance to the form of the development 
cell than most other tissues. In many parts 
they continue to be truly cells throughout their 
existence, and in no instance is the nucleus, 
from which they have proceeded, absorbed. 

In connection with a wide and varied range 
of function, these particles present numerous 
modifications of form, bulk, and texture, the 
leading features of which have been pourtrayed 
by Henle. The following arrangement, how- 
ever, differs in several respects from that pro- 
posed by him,* and is more in accordance with 
what I have myself observed. Founding it on 
the anatomical condition of the particles and 
on their office, I distinguish three varieties, — 
the /amelliform or scaly, the prismatic, and the 
spheroidal. These all run together by imper- 
ceptible gradations. The particles may be also 
divided into non-ciliated and ciliated, the scaly 
being always bald, the prismatic and sphe- 
roidal in some situations furnished with cilia. 

Of the lamelliform or scaly variety—This 
consists of broad flattened particles (or scales, 
properly so called), having an angular outline 
(caused by their lateral apposition) and a 
nucleus, which is generally eccentric. These 
scales form layers of extremely«variable thick- 
ness. They are generally, however, super- 
imposed in great numbers over one another, 
as in the mouth, fauces, and cesophagus of the 
human subject, where they constitute the 
Opaque defensive investment so visible to the 
eye in those parts. 

But the best-known example of this form is 
presented by the cuticle, which from its ex- 
posed position is thicker and denser than any 
internal epithelium. This variety, then, is the 
one which offers the most convincing proof of 


* He divides it into pavement epithelium (or 
the scaly), cylinder epithelium (or the prismatic), 
and ciliated epithelium. See Miiler’s Archiv. 


490 


Vertical section of the epithelium of the mouth, shew- 
ing its lamelle and the changes uf form which the 
particles successively undergo. 

a, superficial laminz, consisting of true scales ; 
b, c, particles in progress of flattening; d, deep 
layer of particles; a’, b’, c’, d’, separate particles 
in the several stages. Magnified 300 diameters. 


Fig. 279. 


A few scales detached from the surface of the uvula. 
Magnified 300 diameters, 


the homology of the mucous membranes with 
the skin. The term ‘ scales’ is only applicable 
to these particles in the last of the stages 
through which they pass. They first appear on 
the surface of the basement membrane as gra- 
nular dots, each of which soon becomes in- 
vested with a cell membrane. Both nucleus 
and cell increase in size up to a certain point, the 
cell being then more or less globular, and con- 
taining a material that appears transparent and 
almost entirely fluid. By this circumstance, 
chiefly, it is distinguished from the spheroidal 
form of particle, presently to be noticed. The 
cell now begins to flatten, loses its fluid con- 
tents, and is at the same time the seat of certain 
changes by which its chemical properties are 
modified. At length its opposite surfaces unite, 
except where the nucleus intervenes, and a 
lamella of extreme tenuity results, which being 
now arrived at the surface is loosened and 
shed. It appears to be by the continual pres- 
sure arising from the growth of newly-formed 
particles that the peculiar characters of this 
variety result. Accordingly, the scales are 
only found constituting the superficial layers of 
a series (fig. 278, aa’). Itis met with in those 
parts only where foreign pressure, or more pro- 
perly friction, has to be encountered. In such 
parts a thick coating of epithelium’is evidently 
desirable, and the hard and almost horny 
qualities which these particles at length assume 
where most to violence, admirably 
adapt them for their object. On such parts, 
moreover, cilia would not be needed, and it 
would even seem that this variety of epithelium 
when converted into true scales possesses 


MUCOUS MEMBRANE, 


neither ee substance nor vital power to 
develope and su these exquisite organs. 
The scaly epitietions is pease for the 
tenacity with which its icles adhere to one 
another, and to the su on which they rest. 
This adhesion is manifest at all the stage 
through which the particles pass. It is stronge 
between particles at the same ee than be 
tween those at different stages of growth, s 
that there is always a tendency to a separatior 
into successive lamine on maceration or othe 
wise. Hence have resulted the divisions 
the epidermis into two, three, or more layer 
and especially that remarkable fallacy of n 
garding the rete mucosum as a distinct structure 
How far this adhesion is owing to the presence 
of an intercellular substance in all instance 
it is difficult to decide; but it seems highly 
probable that, in the deepest layers, where th 
particles are small and rounded, such asubstanee 
must exist in considerable abundance, filling uj 
the interstices, and serving asa kind of blastem 
in which the nuclei (or cytoblasts) of fresh parti- 
cles originate. I have lately (Jan. 1842) ascer 
tained a very curious fact, giving evidence of 
adhesion. This is, that the delicate thread 
drawn out of the cutis when the cuticle | 
stripped from a gee of macerated skin, cor 
sist entirely of the epithelium of the sweat 
ducts, the particles of which are so intimatel 
united with one another, and with those of thi 
deeper layers of the epidermis, as to allow ¢ 
being thus dragged out of their tube of bas 
ment membrane, often for a length of an eigh 
of an inch. 4 
The scaly epithelium is subdivisible into tw 
forms, the regular and the irregular. In 
Jormer, the scales are united = to edge in 
regular manner, as in the skin of the Frog an 
other reptiles, and on many internal surfae 
especially in the lower animals. In this fo 
the particles do not become so thin as in the” 
other, and the superficial scales are cast off 
lamine consisting of a single series and 
uniform thickness. In the datier form, ° 
overlap one another without order, and presi 
no regular figure. This is the ordinary for 
and is that presented in the skin and oth 
parts of Mammalia and Birds. -= 
Of the prismatic variety.*—In this the 
ticles have the shape of small rods, dispe 
endwise on the basement membrane, in a sit 
layer, the thickness of which depends on 1 
length. These rods are united to one ano’ 
by their sides, which are flattened for that’ 
pose. They are, therefore, prisms and 
cylinders, as Henle terms them. are 
almost invariably of very unequal thickn 
different parts, being bulged somewhere - 
the middle by their nucleus, which is oval, 
its long axis parallel to that of the par 
Their deep or attached ity 6 also, u: 
tapers to a point, in order, probably, to a 
room for new particles to spring up in th 
tervals. This is more decidedly the case w 
they clothe a convex surface, (as hat 0 


* To this the very appropriate term ¢ 
been lately given by Professor Todd. 


MUCOUS MEMBRANE. 


intestinal villi,) and their sides tend to assume 
the direction of radii from a common centre. 
Hence they are sometimes even triangular in 
outline. Their opposite or free extremity is 
much thicker, often as thick as the part bulged 
by the nucleus, and near this extremity neigh- 
bouring particles are generally very intimately 
attached to one another, having often the ap- 
ted of being blended into a single mass. 

e best example of this is on the villi of the 
small intestine (fig. 280). The contiguous par- 
ticles, however, are fitted closely together in 
the greater portion of their length, and to effect 
this the bulging nuclei vary in the height at 
which they are placed. There can be no doubt, 
that, in certain situations at least, as will be 
afterwards shown, these particles are being con- 
tinually shed, and consequently are being per- 
petually renovated. But it is very difficult to 
ascertain their early condition and changes, and 
I am not aware of any satisfactory observations 
having been made for this end. From the 
great facility with which they become detached 
from the surface they invest, it is next to im- 
possible to examine them in situ on thin verti- 


Fig. 280. 


Villus of the intestinum ilium of the Dog, with the 
epithelium partially detached. 

@ a, solitary particles remaining attached ; 6, club- 
shaped extremity of the villus from which the 
epithelium has been detached; cc, epithelium 
at its base. Magnified 150 diameters. 

d, detached particles, shewing their close union, 

_ especially at the surface (at the letter); e, other 
detached particles, shewing their various shape, 
their nuclei and nucleoli. The letter is placed 
at their freeextremity. Magnified 350 diameters. 


Fig. 281. 


a, ciliated epithelial particle from the 
inner surface of the membrana tym- 
pani of the human subject ; 6, cili- 
ated epithelial particles from the 
bronchial mucous membrane of the 
human subject. All these shew the 
nuclei and nucleoli. Magnified 300 
diameters. 


491 


Epithelial particles from the cornu uteri of the Cow. 
The opposite cornu contained a foetus one inch and 
a half long. 

a, small particle, apparently in an early stage of 
development. ‘The nucleus is smaller than in the 
other specimens; b, another more advanced—the 
nucleus and surrounding substance are both 
larger, especially the latter, which presents a fine 
granular texture ; c, a particle made angular by 
pressure against others. It presents two nuclei, 
as though formed by fission; d, another of a dif- 
ferent shape; e, detached nucleus, showing its 
transparency and clear outline ; also two excen- 
tric dots, the nucleoli. Mugnified 300 diameters. 


cal sections. But there is no reason for sup- 
posing their mode of growth to be originally 
different from that of the scaly variety. Their 
nuclei probably appear first on the surface of 
the basement membrane, and around these a 
cell is developed (fig. 280, a). But this cell 
from its earliest period seems to contain an 
amorphous substance, which under high micro- 
scopic powers looks finely mottled, but not so 
definitely so as to allow of being called granu- 
lar. As the particle advances towards its full 
size, it loses its cell-membrane, and when com- 
plete is to be regarded rather as a solid mass of 
organic substance, surrounding a nucleus, than 
asacell. Here, then, is a striking difference 
between the scale and the prism: maturity 
being marked in the one by the disappearance 
of the substance of the cell; in the other, by 
that of the cell-membrane. 

Of the spheroidal variety (see figs. 273 to 
277).—In this the particles are of a rounded 


F ig 283. 

» Three epithelial particles from the 

Y human liver. 

a, nucleus ; 6, nucleolus ; ¢, fatty 
particle. 


Magnified 300 diameters, 


form, though generally somewhat flattened 
where they touch. They are always thick, 
from the substance they contain. It is this 
variety that constitutes the chief mass of the 
secreting glands, and hence it might not impro- 
perly be styled glandular. It corresponds with 
the prismatic variety, in its usually constitu- 
ting in the glands a single layer, and in the 
predominance, from the first, of its substance 
over its membrane. In the glands, indeed, the 
membrane can seldom be discerned at all, and 
the substance surrounding the nucleus, though 
more bulky, has the same finely mottled cha- 
racter already noticed in the prisms. In other 
situations the cell-membrane is persistent, but 
even then it never flattens into a scale. This 
variety presents in the different glands nume- 
rous modifications, which have not yet been 
studied with the accuracy they merit. It is 


492 


difficult to reject the belief that it is intimately 
concerned jn the glandular function, and varies 
in correspondence with it. 

To the preceding summary account of these 
three principal kinds of epithelium much might 
be added respecting the intermediate forms. 
This, however, does not appear to be required 
in so general a description. The spheroidal 
and the prismatic are seen blended in the speci- 
men I have figured from the human membrana 
bay fp (fig. 281). 

Mf the non-ciliated and ciliated epithelium.— 
The true scaly variety appears never to be 
clothed with cilia. The prismatic epithelium 
is that which most commonly bears these vibra- 
tile organs. They are placed on the free extre- 
mities of the prisms in the respiratory tract and 
in the uterus and Fallopian tubes. The true 
piped epithelium is always without cilia. 

is is a general fact, and one of great import- 
ance. But those varieties which seem iuterme- 
diate between the spheroidal and the other two 
forms are often furnished with cilia ; of which 
examples may be seen in the Malpighian bodies 
of the kidney, in the mucous membrane of the 
frog’s mouth, and in that of the human tympa- 
num (fig. 281). In all cases the cilia, when 


Fig. 284. 


Various particles of epithelium from the frog’s mouth. 

a, b,c, small particles that have not reached the 
surface. They appear to present three stages or 
periods, showing a subdivision of the nucleus and 
a formation of two cells out of one ; d, three fully 
developed particles, with cilia on their free sur- 
face; e, f,g, other complete particles, showing 
cilia on that part only which has formed a portion 
of the general surface of the membrane. 

Magni : 


‘agnified 400 diameters, 


they exist, are developed only on that aspect of 
the particles which forms a portion of the gene- 
ral surface of the membrane. 

It is as yet entirely unknown by what pro- 
cess the cilia are produced and nourished ; 
whether the particles, with their cilia, are shed 
from time to time, and are succeeded by others, 
(as is most probable,) or whether the same 
organs remain, and merely change their com- 
ponent elements. (On the subject of Crit in 
general the reader is referred to Dr. Sharpey’s 
excellent article.) 

Of the elementary tissues appended to the 
mucous system.—The two elementary tissues 
now described may be considered as the more 


MUCOUS MEMBRANE. 


essential constituents of the mucous system, or 
as forming the simple mucous membrane. 
simple mucous membrane envelopes the rest of 
the body. It contains within its own substance © 
neither vessels nor nerves, but is, strictly spea 
ing, extra-vascular. By modifications, chiefl 
of the epithelial element, it is in itself ca 8 
of presenting variety of appearance and 
properties in different situations, But in im-— 
mediate connection with its deep surface, tha 
is, with the basement membrane, there are cer- 
tain tissues common to almost ony eee of the 
frame, but here assuming a peculiar arrange. 
ment and office, and by their diversities ii 
various localities, occasioning the most compli- 
cated varieties of outward form, of structure, 
and of function. ” 
These appended tissues are minute blood- 
vessels, a lymphatic network, nerves, and - 
lar tissue. 
It has been already stated that in many parts 
the simple mucous membrane, by its innume- 
rable minute involutions over an extensive sur- 
face, is formed into a com brane. 
Into the composition of this (of which a good 
example is afforded by that of the stomach) the 
appended tissues enter more or less largely, but 
they are likewise, in addition, generally spread 
out in great abundance as a layer underneath 
the compound membrane. This layer has been 
commonly termed submucous cellular vane 
(sometimes tunica nervea,) in the case of in 
ternal surfaces, and cutis vera or dermis in the 
case of the skin. : J 
Bloodvessels. — These may be said to be 
universally present under the sim, mucous 
membrane, with the exception ps of th 
cornea, where vessels, in the normal state, have 
not yet been demonstrated. The capillaries, 
their simplest form, appear to be arranged as 
plane network, such as that of the rectum 0 
the frog (fig. 285). The interstices of th 
network vary much in size and shape in dii 
rent localities. The most copious supply ¢ 
blood distributed to any such membrane is t 
afforded to the air-cells of the lungs in all a 
mals. Here this plane capillary plexus hi 
areole scarcely exceeding the diameter of 
vessels themselves. Where the membrane th 
supply is folded, however irregularly, th 
follow its surface, and bence result many vai 
ties in their arrangement and inosculations. 
even seems to be for the purpose of gainin 
great freedom of inosculation between the 
illaries that the extraordinary complexity 
en given to many of the simple m 
brane, especially in the secreting glands. | 
many foldings from somewhat distant parts 
the membrane are there brought into imm 
diate proximity to one another, and are 
lied by the same or closely connected ves 
This is remarkably exemplified in the tes 
kidney, and liver. The capillary system of 
these, as well as of other solid glands, may 
styled a solid plerus, being extended in ey 
direction, and presenting areole of nearly eq 
size in whatever plane a section of it be 
The liver presents the most perfect instance: 
such a solid plexus, and in it the vessels ar 


aiilt 


MUCOUS MEMBRANE. 


Capillaries on the rectum of the Frog. 
a, a, arteries; 6, b, veins. 
unusual dimensions, apparently to allow of the 
more free transit of the blood, which is here 
propelled feebly by the vis a tergo acting through 
the capillaries that form the portal vein. Though 
it has not been so described, I believe, from 
injections that I have made, that the whole 
organ is one such plexus, and that if it were 
possible to abstract from it all vessels larger 
than capillaries, and to leave these entire, all 
the lobules would still be connected together 
by capillary channels identical with those of 
which they themselves principally consist. 
Hence the lobules of the liver are not definitely 
bounded on all sides by a capsule of any kind, 
but here and there blend by continuity of sub- 
stance with those adjoining them. The larger 
rtion of their contour is, however, well de- 
ned by the ultimate twigs of the portal vein, 
and of the ducts derived from the lobule, as so 
clearly proved by Mr. Kiernan in his well- 
known paper. 

The size of the capillaries varies much in 
different parts of the mucous system. In the 
liver they are very capacious, always one-third 
wider than the diameter of the blood globule, 
and sometimes nearly double. In the lungs 
they are almost equally great. In the intestinal 
villi also they are of large dimensions. In 
these organs they form a network on the inner 
surface of the basement membrane, and are 


_ Supplied by an artery that ascends in the axis 


of the villus. The veins from this network are 
generally two, one on each side. This plexus 
of the villi is strikingly contrasted by that 
clothing the tubes that open at their base. In 


_ this latter I have observed the diameter to be 


_ as small as that of the capillaries of the salivary 
glands, which do not exceed the width of a 


493 


blood globule. This disparity is another con- 
firmation of the opinion that the villi are chiefly 
absorbing, and the tubes secreting organs. 
Many other varieties might be enumerated, but 
these are among the most remarkable. 

Under most of the compound mucous mem- 
branes bloodvessels are spread out in great pro- 
fusion, and especially in certain localities. The 
arteries and veins respectively form plane ple- 
xuses, more or less close, more or less intricate, 
from which emerge branches that pass between 
the foldings of the simple membrane and com- 
municate with its capillaries, already described. 
There may even be a series of these arterial and 
venous plexuses situated one over another, and 
successively springing out of one another. The 
effect of this arrangement of an arterial network 
on one side of the capillaries and a venous net- 
work on the other side, is that the blood, be- 
sides being delayed in their neighbourhood, is 
most freely and equably distributed in the 
capillaries themselves : a condition which could 
scarcely be otherwise accomplished, since, in 
the case of a villous membrane at least, the 
capillaries form a series of isolated systems, of 
which one belongs to each villus. The arrange- 
ment now spoken of exists in the submucous 
areolar tissue of the stomach and intestinal 
canal, and in most parts of the skin. In the 
solid glands, where the capillaries form one 
continuous system, such arterial and venous 
networks are not found. At least such inoscu- 
lations, when they exist, are few and rare. In 
the stomach of many fishes there is a plexus of 
great thickness under the mucous membrane. 
In the nose also, chiefly on the spongy bones 
and septum, there is a plexus of very large 
veins, well known to anatomists, and also a less 
capacious arterial plexus; smaller ones are 
met with in other parts, as the cheeks and lips, 
the palate and pharynx. The use of these, 
especially that of the nose, may be to serve as 
a diverticulum for the blood in cerebral con- 
gestions. These are the vessels that give way 
in ordinary epistaxis. 

Of the lacteal and lymphatic vessels —The 
lacteals have their sole origin from a plexus 
underlying the simple mucous membrane of 
the alimentary canal, and it is probable that in 
every part of the skin a close network exists, 
such as has been described by several anato- 
mists (see Lympuatic System). Considering 
the means hitherto at command for ascertaining 
the precise position of this network, it is not 
wonderful that disputes should have arisen as 
to whether it lies in the rete Malpighii, or 
within the surface of the dermis. I would 
hazard the opinion that the real situation of 
this plexus is underneath the basement mem- 
brane which is everywhere present in the skin. 

Of the nerves.—These are numerous and 
varied, as might be expected from the position 
of the mucous system in regard to the rest of 
the body. They may all be styled afferent, 
and are divisible into three kinds, viz. the 
sensory, the excito-motory, and the sympathetic. 
The nerves of special sense distributed to this 
system are those of smell, taste, and touch. 
The nerves of common sensation and the excito- 


494 


motory nerves are almost exclusively found 
here. The tubules of the sympathetic nerves 
are chiefly given to the proper mucous metm- 
branes and to the glands. All these will be 
considered more at length under other heads, 
and they are therefore only referred to here. 
Of the arevlar tissue —Before describing 
the remarkable varieties presented by this 
tissue under different parts of the mucous 
system, I must advert to its constitution in 
Ose situations where its ordinary characters 
are well marked—as in subcutaneous fascia, 
in muscle, on the exterior of the pharynx, &c. 
Singular as it may appear, there is no correct 
account of this structure in any of the works on 
minute anatomy. [tin truth consists of two 
tissues, distinct from each other, and respec- 
tively allied to the white and to the yellow 


fibrous tissues. The white fibrous element of 


areolur tissue is chiefly in the form of bands of 
very unequal thickness, in which are to be 
seen numerous streaks taking the general direc- 
tion of the whole, but not parallel to the border, 
nor continuous from end to end. These streaks 
more resemble the creases of a longitudinal 
folding than intervals between separate fibrille, 
for which they have been mistaken. These 
bands split up without difficulty in the long 
direction, whence result fibrils of the most va- 
ried width, the finest being far too minute for 
measurement, even with the best instruments.* 
These bands interlace and cross one another in 
various directions, and their natural course is 
wavy. They frequently subdivide and join 
those near them. [esides these bands, com- 
monly called fasciculi, there are some finer 
filaments of the utmost tenuity which seem to 
take an uncertain course among the rest. The 
yellow fibrous element is everywhere in the 
form of solitary fibrilla, which correspond in 
their essential characters with the tissue of that 
name. They are disposed to curl, and are 
traly branched at intervals of variable length ; 
these branches (which usually retain the size of 
the fibril from which they spring) becoming 
continuous with others in the neighbourhood. 
They have higher refractive properties than the 
white element, and their borders are conse- 
quently darker. 

It is easy to overlook this twofold compo- 
sition of areolar tissue in specimens examined 
in water, but their discrimination is made easy 
by a trifling artifice. This consists in adding a 
drop of acetic acid, which instantly swells the 
white bands, and makes them transparent, but 
produces no change in the yellow fibrils. These 
effects of tle acid may be watched, if the agent 
be made tospread gradually over the specimen ; 
and there can scarcely be conceived a more 
beautiful example of the aid chemistry will 
afford anatomy than that presented in the 
course of this interesting process.t The change 


* The fibrille of true white fibrous tissue are 
almost precisely similar, and, as I believe, are only 
produced by he observer himself in opening out 
his specimen for inspection. 

+ In the case of the dartos, this procedure de- 
tects not only what has just been described, but a 
third element, hitherto in this situation quite con- 


MUCOUS MEMBRANE, 


produced in the white bands is such as to shew — 
very clearly that they are not truly fasciculi, or 
aggregations of fibrille. The action of the 
acid on these two elements is identical with 
that produced on the two tissues to which I~ 
have shewn them to be anatomically allied. 
To these two elements of areolar tissue are 
be attributed physical properties similar to the 
of white and yellow fibrous tissues, and 
will vary greatly in different situations, accord 
ing to the proportion and mode of arrangement 
under which the two elements coexist. 
Of the arcolar tissue of glands.—The 
appears to be a very prevalent misconception 
with to the quantity of this 
found in the interior of the large glands, as 
liver and kidney. It is imagined that it p 
trates into every interstice, mingles with 
capillary rete, and envelopes the ultimate 
secreting tubules. It is, however, impossible 
in the most recent specimen of these organs 
to discover anything answering to this deserip-— 
tion. All that can usually be detected is a 
small quantity accompanying the larger vessels 
in their course within the organ, and forming 
septa between its coarse subdivisions. And it 
would be difficult to suppose a purpose which 
more abundant supply could subserve. The ca- 
pillary network mo Y the secreting tubules by their 
mutual and intricate interlacement sufficiently 
sustain one another; no freedom of motion is 
required between them; there is no fore 
tending to separate them. I am far from 
saying, however, that the ultimate substance ¢ 
these glands consists only of simple mucoi 
membrane and bloodvessels. In the inter- 
stices of these there are probably nerves a 
lymphatics, of the mode of termination 
which we know nothing, but which seem much 
fewer than is commonly supposed. There 
also more or less of an interstitial amorphou 
substance, hereafter to be described, - a 
In these glands and in the substance of” 
many compound mucous membranes there are 
to be seen here and there small bodies up 
unlike cellular tissue in an early stage of 1 
development. They have a bulging nue! 
from which they taper to the extremities; ai 
they are much longer and slenderer than 
prismatic epithelium. With their nature a 
use I am at present quite unacquainted. 
The lungs seem mainly to owe their extrao 
nary elasticity to the yellow fibrous element 
their submucous areolar tissue. This is spre 
in great abundance under the whole 
and much predominates over the white. Int 
trachea ef bronchia it is besides largely ¢ 
loped in longitudinal bands visible through 
mucous membrane. In the whole of this 
gion its fibrils take a general longitudinal d 
tion, but branch and inosculate at very freq 
intervals, enclosing areole of small dimensi 
But this element does not cease with the tut 
it is prolonged in the form of branching, are! 
bands over the basement membrane of the @ 
cells, which it renders elastic and firmly suppor 
founded with areolar tissue. This is non-strial 
muscle, at once known by its beiny loaded wi 
coipuscles, v1 persistent cell-nuclei. See MUSC 


—- 


MUCOUS MEMBRANE. 


Where mucous membranes are not destined 
to move on the parts they cover, the areolar 
tissue beneath them is very scanty. This is 
the case in the nasal cavities, even in the por- 
tions furnished with a great substratum of 
bloodvessels. But where much motion is re- 
quired, as where a muscular lamina underlies 
the mucous, and the enclosed cavity is liable to 
vary in its dimensions, the areolar tissue is co- 
pious, and very similar in its elements and in 
the size of its interstices to the ordinary forms. 
Examples of this are seen in the whole alimen- 
tary tract. 

But it is under the cutaneous part of the mu- 
cous system that this tissue assumes its highest 
developement. Elsewhere its object is to pro- 
mote freedom of movement, or to confer elasti- 
city. Here it answers both these purposes, and 
in addition gives a great capacity of resistance 
against external pressure and violence. The 
former end is attained by the structure called 
Subcutaneous fascia, which is a large quantity 
of this tissue in its ordinary form. The two 
latter are effected by that more condensed part 
to which the term of cutis has been given. This 
last is the structure to which the submucous 
areolar tissue of the intestinal canal mainly cor- 
responds, as may be shown by an examinatioh 
of the submucous tissue of the mouth, pharynx, 
and esophagus, which holds an intermediate 
place. To describe its modifications in different 
Situations would be to encroach too much on 
the province of another article (see Skin), and 
a few general remarks must here suffice. 

The framework of the cutis may be said to 
consist entirely of a modified form of the areolar 
tissue. Both elements are enormously deve- 
loped, but especially the yellow fibrous one. 
The fibrille of this are thicker than elsewhere, 
and branch and inosculate with great freedom, 
enclosing interstices open on all sides, and 
giving passage to the wavy bands of the white 
fibrous element as well as to vessels, nerves, 
the ducts of the sweat-glands, the sebaceous 
glands, and the roots of the hairs. These in- 
terstices are in general very close, but they vary 
with the size of the parts which occupy them. 
On the deep surface of the cutis the yellow 
fibrous element changes gradually into that of 
the subcutaneous fascia, or that of ordinary 
areolar tissue. It cannot be doubted that the 
skin chiefly owes its elasticity and toughness to 
this remarkable developement of the yellow 
fibrous element. 

Lopographical view of the mucous system in 
man.— Referring the reader to the article Skin 
for a detailed description of that part of the 
mucous system, and its immediate dependen- 
cies, I shall now proceed to point out some of 
the more remarkable varieties of the internal 
tracts. These tracts have been usually com- 
prehended under two general divisions, the 
_ gastro-pulmonary, and the genito-urinary. The 
_ former is continuous with the skin at six points, 

the two eyelids, the two nostrils, the mouth, 
and the anus; the latter at a single one, the 
orifice of the urethra in the male, and the labia 
_ pudendi in the female. Besides these, there 
are two smaller tracts, the mammary, each of 


495 


which is subdivided into several, which open 
separately on the skin. 

The description of the gastro-pulmonary 
tract may be commenced at the lips. It covers 
their inner surface, the cheeks, gums, tongue, 
and palate, and extends into the labial, buccal, 
and larger salivary glands, of which it consti- 
tutes the chief mass. It passes over the arches 
of the palate, (where its involutions form the 
tonsils,)and lines the pharynx, Eustachian tubes, 
and the cavities of the tympana. Penetrating 
into the nose by the posterior nares, it lines 
all the passages and chambers of that organ, 
and advances along the nasal duct to the lachry- 
mal sac. Thence it may be traced along the 
canaliculi to the front of the eye, where it takes 
the name of tunica conjunctiva; covers the 
posterior surface of the eyelids, a certain por- 
tion of the sclerotic, and the cornea, and forms 
the caruncula, the Meibomian and lachrymal 
giands. In these complicated portions of its 
course, the membrane shares more or less in the 
construction of the five organs of special sense, 
and is the essential seat of two of them, taste 
and smell. From the pharynx it spreads in 
two directions; first, into the larynx, trachea, 
tracheal glands, and bronchial ramifications, 
until it terminates by forming the air-cells of 
the lungs; secondly, into the alimentary 
canal. Here it lines the esophagus, stomach, 
and intestinal tube, as far as the anus, and it 
penetrates along the excreting ducts of the liver 
and pancreas, into the inmost recesses of those 
glands, to form their secreting surface. 

The genito-urinary tract may be traced along 
the urethra into the bladder, ureters, and pelvis 
of the kidneys; and thence into the substance 
of those organs as far as the Malpighian bodies, 
the extremities of the uriniferous tubules.. In 
connection with the urethra, processes pass to 
the glands of Cowper; and, in the male, 
into the interior of the prostate, the vesicule 
seminales, vasa deferentia, and tubules of the 
testes. In the female, the vagina, uterus, and 
Fallopian tubes receive a lining from it, which, 
at the fimbriated extremity of those canals, be- 
comes continuous with the serous membrane of 
the abdomen.” 

The very remarkable differences presented to 
the eye by different parts of this system have 
been a source of great difficulty to anatomists, 
who, on other grounds, believed them to be 
nearly allied ; and it would appear that hitherto 
no satisfactory explanation has been given of 
the anatomical conditions on which this variety 
depends. This deficiency I shall now endea- 
vour in some degree to supply. From the ex- 
aminations I have made, I have been led to 
consider in a distinct and separate manner the 
several elementary tissues already mentioned, 
composing the simple mucous membrane, and 


* This remarkable exception to a general fact 
has long attracted attention. As a mere anatomi- 
cal difficulty, it has lately received curious illustra- 
tion from Henle’s discovery of the existence of an 
epithelium on serous and other allied surfaces. But 
its true explanation can_ probably only be attained 
by a study of its morphology, joined with that of its 
final cause. 


496 


lying underneath it; and am come to the con- 
clusion that the must complicated diversities 
that are met with, admit, when studied in this 
manner, of being explained and reconciled to 
a common type of structure. 


Peculiarities of the skin, mucous membranes, 
and glands. 

Of the skin.—This is chiefly peculiar in its 
epithelial element and its submucous areolar 
tissue. The epidermis is composed of a vast 
number of superimposed lamine of scales, 
which, in the earlier stages of their develope- 
ment, and especially in certain races of man- 
kind, contain minute pigment granules in their 
interior. The pigment disappears more or less 
completely as the particles attain the surface. 
It is continued for some distance down the hair 
follicles and sweat-ducts, and thus serves to mark 
the continuity of these parts with the general 
surface. Hairs, nails, hoofs, and other simi- 
lar appendages are all composed of modified 
epithelial particles, and are nearly peculiar to 
the skin. The sebaceous and _perspiratory 
glands, and the spiral ducts of the latter travers- 
ing the epidermis, are also among the most 
characteristic features of this part of the mucous 
system. The papille of the skin have their 
counterpart in the villi of the mucous mem- 
branes ; the cutis vera, as it is called, has also 
its analogue in the submucous areolar tissue, 
but it is so enormously developed that the re- 
semblance has escaped the notice of anatomists. 
Its characters have been already briefly de- 
scribed. It is a striking fact that the cutis, like 
the submucous areolar tissue, contains no fat, 
even in the most corpulent subjects. I have 
repeatedly made this remark. The cutis differs 
in this respect from the subcutaneous fascia, 
which is therefore, perhaps, to be regarded as 
less allied to the submucous areolar tissue. 

Of the mucous membranes—These hold an 
intermediate place between the skin and the 
true glands. They blend insensibly with the 
former at the different orifices of the body, and 
may, uuder favourable conditions, become so 
modified as to assume the appearance of skin. 
The change then wrought is nothing more, 
however, than an increased deposit of epithelial 
scales, with an absence of the natural moisture; 
and it may be doubted whether a transforma- 
tion of this kind could occur in a mucous 
membrane of which the epithelium was not of 
the scaly variety. On the other hand certain 
parts of the membranes usually termed mu- 
cous are nothing less than real glands arranged 
in a membranous form. 

The mouth, pharynx, wsophagus, the vagina 
and vaginal surface of the uterus, are the parts 
whose lining membrane most nearly resembles 
the skin. Their most remarkable feature is the 
thickness of their covering of epithelial scales, 
provided for their protection against foreign 
contact and pressure, and in connection with 
this the existence of numerous glands opening 
upon them for the lubrication of their surface. 

any of these glands correspond with the 
sweat-glands of the skin in being similarly 
scattered under the surface. Such are the 


MUCOUS MEMBRANE. 


buccal and all the small glands allied to them, 
which, in particular, resemble the ly deve- 
loped sweat-glands of the axilla. e only 
difference between them is in the mode of in- 
volution of the secreting membrane, which 
the former is cellulated, in the latter tubular. 
These portions of the mucous membranes a! 
a tm the skin by the denseness of th 
submucous areolar tissue. ‘w 

In the pharynx it is only that part of th 
lining membrane below the posterior arches of 
the palate, or that exposed to friction during 
deglutition, that has the dermoid characters 
now described: all above is more delicate, is 
clothed with ciliated epithelial prisms, and be- 
longs physiologically to the nasal or respirator 
tract. e lower or buccal surface of the soft 
palate differs in a similar way from the upper. — 

The lining membrane of the Eustachian 
tubes and tympana is very delicate, none of 
the elementary tissues i ne 


ao 
* 


redominating. Th 
epithelium is in a single layer of prisms clothed 
with cilia. The submucous areolar tissue is it 
very small quantity, and the vascular network 
consists of little more than a simple plane ex 
pansion. In the nose, the epithelium, accor 
ing to Henle, is scaly on the septum and ot 
the ale for some way within the nostrils. Here 
also there are hairs—an advance towards th 
characters of the skin; beyond this it is every- 
where ciliated, even within the bony sinuses 
The membrane covering these sinuses is ¢ 


extreme tenuity, and presents the elementat 
tissues all in a simple . That covering th 
pendulous parts of the spongy bones, on thi 
contrary, as long been noted for its gre 


thickness—a character due to neither of 
elements of the mucous tissue itself, but to # 
extraordinary size of the submucous sels 
Both arteries and veins are large, but especial 

the latter, which here form a plexus imme 
diately beneath the surface, and not separat 
from it by any considerable quantity of dens 
areolar tissue. Hence the facility with wh 

these vessels give ite Baier when 

tended with blood. The lining of the no 
has been sometimes called a fibro-mucous me 
brane, from its close connection with the } 
riosteum. The periosteum in the sinuses 
extremely delicate, in consequence of the 
nuity of the bony lamine it invests; a 
would perhaps be impossible to separat 
there from the submucous areolar tissue. “ 
globe and cornea are covered with scaly 
lium, of which the particles are smaller tow 
the folds of the eyelids,* where they gradu 
become prismatic, and along the tarsal bor 
clothed with cilia, so small as to be only rt 
nizable a short time after death. The conji 
tiva of the lower lid is very minutely vil 
At the pharyngeal orifice of the glottis, 
epithelium becomes ciliated and contin 
along the trachea and bronchial ramifiea 
as far as the air-cells, but, according to 
own observations, the cilia there cease, and 
epithelium changes its character to a rem 
able.variety of the glandular form. In the 


* Henle, loc. cit. 


MUCOUS MEMBRANE: 


passages, as formerly described, the submu- 
cous areolar tissue presents a remarkable mo- 
dification, and is closely joined to the peri- 
chondrium of the inner surface of the cartilages. 
It is worthy of remark that the glands with 
which the tracheal portion of the membrane is 
furnished, are not placed, like the buccal, 
duodenal, and other similar glands, immedi- 
ately subjacent to the mucous membrane, but 
on the posterior surface of the trachealis muscle, 
which is pierced by their ducts. This peculiar 
arrangement would seem to be accounted for 
by the deviation from the ordinary form which 
the submucous areolar tissue here presents, 
and which renders it ill adapted to give to these 
irregular-shaped bodies that loose investment 
which they everywhere possess, and which 
therefore appears necessary to them. 

The mucous lining of the whole alimentary 
canal below the cardia is the largest and best 
marked example cf what I have termed the 
compound mucous membrane, being com- 

_ posed of vertical tubes which are truly glands, 
_ Opening on the general surface. ‘That of the 
_ small intestine presents villi also. This entire 
membrane is very soft and easily torn, because 
its chief mass consists of an epithelium, the 
particles of which adhere but slightly either to 
one another or to the basement membrane, and 
are everywhere disposed in a single layer. 
There is moreover scarcely any areolar tissue 
between its involutions, which have, therefore, 
little besides the vascular web to sustain them. 
The submucous areolar tissue is in considerable 
abundance between the mucous and the muscular 
coats. (See Sromacu and InrestinaLCawnat.) 
The lining membrane of the hepatic and pan- 
creatic ducts is simple, and its epithelium of the 
prismatic variety. 
In the genito-urinary tract, the epithelium 
resents every variety. The fossa navicularis* 
is clothed with small, flat, or roundish scales, 
_ the rest of the urethra with a single series of 
' prismatic particles. The cells of the prostate 
| are lined with spheroidal epithelium, the vasa 
_ deferentia with prisms. In the vesicule semi- 
nales there is a pavement of somewhat flat- 
tened granules, and also in Cowper’s glands. 
In the bladder, ureters, and pelves of the kid- 
-neys, the epithelium is in the form of longish 
cells intermediate between the spheroidal and 
the prismatic varieties. The aymphe, clitoris, 
hymen, and vagina are covered with scaly epi- 
thelium, and this has been noticed by Henle in 
cases where the*hymen has been entire. Within 
| the neck of the uterus the epitheliuin becomes 
_ prismatic and clothed with cilia, and so con- 
_ tinues over the surface of the uterus and Fal- 
lopian tubes, and even for some distance over 
__ the outer surface of their fimbriated extremities. 
eyond this it merges gradually into the com- 
essed cells of the serous membrane. The 
_ lining membrane of the Fallopian tubes, as well 
_ as that of the uterus, is of a compound nature, 
especially during gestation, and consists of 
ules arranged vertically to the general sur- 
e. It is to be observed that the cilia only 


* Henle, loc. cit. 
) VOL. III. 


497 
clothe the general surface, and that the epithe- 


lium lining the tubules is spheroidal, or inter- 


mediate between that and the prismatic. It isa 
form of the glandular variety, and bears no cilia. 

Of the glands——The varieties apparent in 
these organs also may be explained by an ex- 
amination of the modifications and modes of 
aggregation of the elementary tissues already 
mentioned. It may be said, in general terms, 
that the glands are characterized by their solid 
form, by the great preponderance of their epi- 
thelial and vascular tissues, and by the small 
quantity of their areolar tissue. It is rare for 
this last to invest every individual involution 
of the mucous surface in the interior of a gland ; 
but it usually gives a common covering to the 
whole organ, as well as less complete ones to 
those subdivisions of it, termed lobes or lo- 
bules, which result from the mode of distri- 
bution of the bloodvessels and duct, and are 
designed for the purposes of package or pro- 
tection. 

Such an investment is usually termed the 
proper coat or capsule of a gland, and seems 
to correspond most nearly with the submucous 
areolar tissue of the compound mucous mem- 
brane, as, for example, that of the intestinal 
canal. 

The propriety of these remarks will appear, 
on a particular application of them. As I be- 
fore entered somewhat in detail into the internal 
composition of the liver, it may now be se- 
lected for illustration. The epithelium, which 
in the gall-bladder and larger ducts is of the 
prismatic kind, becomes bulky and of a flat- 
tened spheroidal form, in the lobules. It there 
also acquires a peculiar character, viz. nume- 
rous minute globules of an oily or fatty nature, 
disseminated within the substance of each par- 
ticle. The basement tissue seems to cease, 
and on an examination of a thin section of the 
lobule under a high power of the microscope, 
its chief bulk appears to consist of epithelium. 
There is scarcely a trace of areolar tissue to be 
anywhere detected. Even the coats of the 
capacious capillary bloodvessels, in the close 
meshes of which the ultimate ramifications of 
the bile ducts are situated, are with difficulty 
seen, and are of extreme delicacy. The sub- 
mucous areolar tissue of the hepatic ducts, 
with which the whole of the contiguous cap- 
sule of Glisson should be associated, cannot, 
when arrived at the lobules, be followed into 
their interior. It can only be distinguished in 
very slender quantity, giving them a partial in- 
vestment, on those aspects which share in form- 
ing the portal and hepatic-venous canals, and 
where, in the angles of union between three or 
more lobules, a terminal twig of the portal 
vein runs up to open on all sides into their 
capillary plexus. No lobule is isolated from 
the rest by a complete capsule, but commu- 
nicates immediately by its capillary network, 
with those near it. The intralobular vein has 
a similar want of areolar tissue around it; and 
thus the main mass of the lobule, and of the 
whole liver, consists of epithelium and a plexus 
of capillaries. Those lobules, however, whick 
contribute to form the general surface of the 

2K 


498 


organ have an additional and dense covering 
of areolar tissue on that surface: a covering, 
which has the same relation to the mucous 
element, as that on the portal aspect; which is 
continuous with the capsule of Glisson at nu- 
merous points; and which is here developed 
as a membrane of support, as a nidus fora 
lymphatic rete, and as a foundation for the 
peritoneal tunic, that it sustains. 

The nerves and lymphatic vessels of the in- 
terior of the liver, though but little known, are 
too inconsiderable in point of size to affect the 

eral accuracy of this description. Hence 
it evidently appears, on what modifications of 
the elements of the mucous tissue and of those 
appended to it, the peculiar friability, colour, 
and other properties of this organ depend. If 
the “ parenchymatous” areolar tissue abounded 
in this gland to the extent implied in the de- 
Scriptions of Bichat and some more recent 
authors, no doubt its toughness would be far 
greater than it really is. But where an organ 
is sufficiently screened from injury by its po- 
sition, where its different parts are so well 
connected by the continuity of a close network 
of capillary vessels, and are not required to 
move on one another, it would be difficult to 
imagine what purpose a greater development 
of areolar tissue would serve. 

In the kidney, the epithelial and vascular 
elements are in corresponding abundance, the 
areolar tissue in very small quantity. The 
general texture, however, is more tough than in 
the liver, from the universal presence of the 
basement membrane on thetubes. In the me- 
dullary portion, the tubes radiate from the 
apex towards the base of the cones, and are 
imbedded in a firm, granular substance, not 
hitherto described, but which resembles a 
blastema, and is probably composed of cells. 
In this substance is also imbedded the capil- 
lary plexus surrounding the tubes, as well as 
the vessels. that convey blood to and from this 
plexus, and take the same direction as the 
tubes. Hence the firmness and close texture 
of this part of the kidney as compared with 
the other, and the facility with which it tears 
from the apex to the base of the cones. At the 
base of the cones, the tubes enter the cortical 
substance and take a course, in sets, towards 
the surface. The central tubes of each set 
reach the surface and then recline inwards and 
become convoluted. But the others bend down 
one after another and become convoluted before 
reaching the surface. All at length terminate 
in the Malpighian bodies, which lie among the 
convolutions. The arteries and veins also take 
a general course from the hilus towards the 
surface. Hence, on tearing the cortical of 
the organ, there is a disposition for the lacera- 
tion to occur in lines continuous with the radii 
of the medullary cones, and this disposition is 
less evident as we aprerese the surface; but 
between these lines the torn surface is very 
uneven, where it is formed by the contorted 
tubes. The cortical part has less of the inter- 
tubular matrix than is met with in the medul- 


" cones. 
n the kidney there is a peculiarity of the 


MUCOUS MEMBRANE. 


highest interest in the relative situation of the 
vascular and mucous tissues, which seems to 
have reference to the peculiar function of the 
gland. There are two systems of capillary 
vessels, the former of which, or that in con- 
nection with the renal artery, perforates the mu= 
cous membrane at the extremity of each tube 
and lies on the outer surface of the membran 
that is, bare and loose within the dilated ex- 
tremities, which thus form the capsules of the 
Malpighian bodies.* (See Ren.) 7 
The common submucous areolar membran 
of the kidney, or that forming its capsule, 1 
in most animals chiefly composed of ordinay 
areolar tissue with close meshes. But where 
more resisting covering is required, as in th 
lion, this areolar tissue is modified ; the whi 
fibrous element predominates so much as 
give the capsule the glistening aspect of a 
aponeurosis. This is an admirable example ¢ 
the transition from areolar tissue into whi 
fibrous tissue, and helps to show the true natui 
and relations of the tunicaalbuginea of the testis 
The testis, compared with the liver and kit 
ney, presents several modifications of the elk 
mentary tissues. The basement membrane 
much stouter than in the latter gland, the tube 
are larger and their convolutions more loose 
joined by any intervening substance. There 
no appearance of an intertubular substant 
except towards the corpus Highmorianum, at 
the principal connecting medium between 
tubes seems to be the vessels, which are less n 
merous than in the glands already men 
and form a looser network. secreting t 
bules for these reasons admit of being ve 
easily separated from one another, and 
ravelled to great lengths. The epithelial e 
ment of the testis constitutes a lining of ec 
siderable thickness, and is highly remarkab 
(see fig. 274). Though no seminal animaleu! 
have been hitherto seen in the interior of 
particles while still attached to the basemen 
membrane of the tubes, yet from recent 
searches, and especially from those of Wagn 
on the phases of their development, it ist 
dered highly probable that these singu 
moving bodies originate in the epithe 
particles, as one of the results of their na 
evolution. The loose aggregation of the 
bules of the testis makes a firm external ¢ 
sule necessary, and where, as in man, t 
gland is much exposed to injury by its : 
ation, a further protection of this kind is 
requisite. Hence the firm unyie 
character of the tunica albuginea in— 
the contrast of which with the thin coveri 
the large but well protected testicle of the 
ise (for example), is well worthy of atte 
n many large animals, the tunica albug 
like the aponeurotic capsule of the lion’: 
ney, is traversed more or less comple 
large veins which it thus serves to su 
The tunica albuginea consists almost sol 
white fibrous tissue, and represents the 
mucous areolar tissue of the mucous syst 
The peculiarities of the salivary glan 


~~ 


. 
Lic 

ae 

ne 


* Phil. Trans. 1842, part I. 


‘ 


: 


MUCOUS MEMBRANE. 


sult from the predominance of their epithelial 
element over the others. The ducts terminate in 
vesicles, very similar in the figure they assume 
to those of the lungs, but nearly filled up 
with epithelial particles. The basement mem- 
brane is very delicate. The capillary vessels 
encircle the vesicles, and are comparatively few 
in number, whence the pale colour of these 
glands. The areolar tissue forms capsules for 
those aggregations of vesicles, termed lobules, 
but does not penetrate between the individual 
vesicles. 

_ The mammary glands derive their extreme 

denseness and toughness, as well as their white 

colour, principally from the areolar tissue, in 
which the proper glandular membrane is en- 
closed. This tissue penetrates more abundantly 
between the minuter subdivisions of the gland 
than is observed in any other instance. It 
thus affords support, at the same time that it 
permits and facilitates movement of one part 

of the organ on another. It is also of such a 

hature as to readily allow of distension during 
_ lactation. 

General outline of the functions of the mu- 
_ cous system.—By its external anatomical posi- 

tion, this system is subservient to four great 
_ functions: the reception of impressions from 
without, the defence of the body from external 
injurious influences, the absorption of foreign 
particles, and the separation of such as are for 
any reason to be eliminated. It may almost 
be said to be the peculiar seat of these func- 
tions, which, however, are distributed in a very 
* unequal manner over its different regions. 

Reception of external impressions—The skin 
and mucous membranes appear everywhere 
fitted by their nervous supply to receive im- 
pressions, which, being conveyed to the ner- 
yous centre, may there excite a reflexion of 
Stimulus along motor nerves, without the in- 
tervention of consciousness. Common sensa- 
tion, or that which in its most exalted form 
becomes touch, exists in all parts of the cuta- 
neous surface, within the mouth, for some dis- 
tance within the nostrils, and (with the excep- 
tion of the pharynx and esophagus) in general, 
wherever the epithelium is of the true scaly 
variety. Where the sense of touch is most 

ect, the simple membrane is observed to be 
involuted into the form of papillz for the pur. 
hae of crowding a larger number of nervous 

ps into a given space. Taste and smell, 
which are nearly allied to touch, are the other 
ea senses of which the mucous system is 

seat. The sensations of hunger and thirst 
seem also referrible to this tissue. 

Defence, from external influences—One chief 
division of the mucous system, viz. the skin, 
derives its main characteristics from its adap- 
tation to this function, and those parts of the 
Mucous membranes which are most exposed to 
_ the contact of irritating substances approach 
_ the most nearly to the skin in their structure. 
Their Seg is scaly and in thick lamine, 
their submucous areolar tissue abundant, dense, 

d resisting. The nervous endowments of 
_ Such surfaces, whether excito-motory or sen- 
sorial, mainly contribute to the protection of 


499 


the animal. And, on the external tegument, 
the developement of hairs, nails, &c. in their 
endless modifications of form, position, and 
structure, serve, with few exceptions, the same 
important purpose. In some parts of the mu- 
cous membrane peculiarly obnoxious to pres- 
sure, there are special glands for the lubrication 
of their free surface. 

Absorption of external material.— Every 
particle, entering the body from without, is ab- 
sorbed, in the first instance, through some por- 
tion or other of the mucous system. What is 
now known of the nature of this function in 
general, renders it certain that every part of the 
mucous system would form an absorbing sur- 
face, if favourably circumstanced for doing so. 
But as the extraneous material, to be absorbed, 
must be brought into contact with the absorb- 
ing surface, often by some special and com- 
plicated means, this function is chiefly limited 
to certain distinct districts of the system. With 
few exceptions the glands are not suited 
either by their position or structure to receive 
the contact of extraneous substances, and even 
many portions of the mucous membranes are 
incapacitated in the same manner, as, for ex- 
ample, most of those lining the excretory pas- 
sages of the glands. The secretions which, in 
a healthy state, are the only substances brought 
into contact with these surfaces, are, it is true, 
occasionally modified by a partial absorption 
of their constituents; but, generally speaking, 
this occurs to a very slight extent. Once 
formed, they usually traverse the channels, 
leading to the outlets of the body, unchanged. 

The simplest condition under which this 
function presents itself appears to be that ex- 
hibited by the respiratory surface, which, whe- 
ther it be arranged as lungs or gills, is con- 
cerned with aeriform particles, and absorbs and 
secretes through the self-same structure. The 
skin also is a very active absorbing surface, 
and appears, by the best observations, to be 
provided with a close net-work of lymphatics, 
which I have already stated to be most probably 
situated immediately under the basement mem- 
brane. It does not appear that the existence 
of the lymphatic pores, described by MM. 
Breschet and Roussel de Vauzéme as opening on 
the free surface of the cuticle, has been confirmed 
by any subsequent anatomist. I have sought 
in vain for any such system of vessels in the 
cuticle, and I believe those distinguished ob- 
servers must have been deceived by the irre- 
gular lines of union between the epidermic 
particles. It is true that the thickness and tex- 
ture of the layers of epidermic seales are little 
calculated to allow of their being permeated 
by foreign material, whether fluid or gaseous ; 
and, therefore, it is not likely that absorption is 
effected to any great extent either through their 
substance or interstices. It seems more con- 
sonant with facts to suppose, that this process, 
especially in respect to solid matters, is carried 
on by the simple membrane of the sudoriferous 
ducts, with which external particles would 
easily be brought into contact through their 
open extremities. But as these ducts traverse 
the thickness of the cuticle, and in that part of 

2K2 


500 


their course have not (in man) any proper wall, 
but are bounded only by the edges of the scales 
between which they pass, it is very probable 
that the deeper and softer lamine of epidermic 
particles may not merely be moistened by the 
secretion of the ducts, but, under favourable 
circumstances, may borrow extraneous matters 
from them, and thus become a part of the ab- 
sorbing medium. In reference to the question 
of absorption by the skin, it is interesting to 
notice the modification of this structure in those 
lower animals in which this function is mani- 
fested in much greater activity than in man. 
A better example cannot, perhaps, be selected 
for this purpose than that of the frog. Its epi- 
dermis consists of a single layer of scales, and 
in consequence they do not overlap, but join 
edge to edge. These scales are not reduced to 
mere membrane, but always contain a con- 
siderable quantity of fluid in their interior. 
The sweat-pores open here and there in the 
interstices between three scales, and have true 
walls, formed out of a pair of modified epi- 
dermic particles, adapted to one another, and 
elongated into the subcutaneous texture. They 
thus bear a very close resemblance to the 
stomata of leaves. I lately discovered this 
singular arrangement in the cast-off cuticle of 
the animal. It seems undeniable, that, here, 
absorption is effected by the whole series of 
epidermic scales, as well as by the pores. _ 

. But the most remarkable, and at the sametime 
the most recondite form, under which this func- 
tion is exhibited in the mucous system, is that 
met with in the alimentary tract. Here, indeed, 
water and aqueous solutions are imbibed, with 
great rapidity, into the vascular plexuses of the 
blood and lacteal systems, as the united testi- 
mony of many able experimenters abundantly 
shews. But from this merely physical process 
of imbibition is to be distinguished the more 
mysterious and elective function of chylous 
absorption, which is conducted by the lacteals 
alone, and is consequently limited to the region 
supplied with that system of vessels. For an 
account of the present state of knowledge on 
the highly important subject of the intimate 
nature of this function, the reader is referred 
to Apsorprion and Lympuartic System, in 
which he will find the chief of the conflicting 
statements and opinions of physiologists de- 
tailed and discussed. It has already been ex- 
plained in the present article, that the latest 
observations on the structure of the villi, and 
apparently the most exact ones, because con- 
ducted with the most improved lenses, and 
accordant with other collateral discoveries, make 
it highly probable that the opinion assigning 
open mouths to the lacteals is erroneous. In 
_ the description of those orifices, furnished by 
Treviranus, we may plainly discern his partial 
acquaintance with characters which we now 
know to be those of the prismatic epithelium 
investing the villi; and the less precise asser- 
tions of the same kind by several other excel- 
lent anatomists, we may now, perhaps, fairly 
consider to have been founded on deceptive 
appearances which, in their day, did not admit 
of secusie interpretation. If any such orifices 


MUCOUS MEMBRANE. 4a 


exist, their minuteness must be extreme, and — 
they? must lie in the intervals between pe 
prisms of epithelium. But even such attenu-— 
ated pores, the best microscopes fail to detect, 
and at least it may with certainty be affirmed, 
that none large enough to admit a chyle-globule — 
exist. The structure of the villi, no less than 
our knowledge of the absorbent function im 
eneral, seems to indicate that the chyle, when — 
rst taken up, is strictly a fluid, and only ac- 
quires its solid particles after it has entered Sh 
lacteal plexus. ee 
Of the separation of material from the body 
—This function appears to be carried on 
every part of the mucous system. One great 
division, that of the glands, is specially des- 
tined to it, as are likewise those portions of th 
compound mucous membranes, which ha 
been already described as coming prope: 
under the designation of glands. If, he 
the essential nature of the function of secretion 
be adequately considered, it will scarcely be 
doubted that even the simplest parte of the 
mucous membranes, and the whole cutaneous 
surface (as distinguished from its sebaceous 


— 


and perspiratory glandular offsets) share largely 
in this important office. It is true that in the 
skin this function holds a subordinate place to 
that of defence and protection, but its existen 
is only an example of what an attentive survey 
of nature everywhere discovers; the accom- 
plishment of various ends by means of the 
same simple instruments. p 
The notion that a secreted product must be 
fluid, is one that has arisen out of a partia 
and imperfect insight into the nature of the 
secreting process. Those matters which 
eliminated in the largest quantities and by th 
largest glands are for the most part so, in th 
shape under which they meet the eye, that is 
after their separation from the organ in whic 
thev are secerned. But in the case of the lung 
the secretion is gaseous as well as fluid, and in 
numerous instances, which have been recent 
brought to light, chiefly by the labours « 
Henle, it is found, when minutely seru 
nized, to consist of organic forms entitled t 
be styled solid. 
The problem which physiologists have ne 
to resolve, is how far these organic for 
which are more or less altered epithelial pr 
ticles, are necessarily concerned in the 
formance of the function, for epithelium is 
but universal in the mucous system. It wor 
be foreign to the province of this articl 
enter at length on the general question of se 
tion, and I shall confine myself to a few 
marks tending to show in what direction re 
researches point.* e 
When the secretion of a sebaceous follich 
the skin is minutely examined, it is foun 
consist entirely of epithelial particles co 
ing the sebaceous matter, and more or 
broken and compressed, These are simili 
the particles lining the follicle, and are m 
* Purkinje, Isis 1838, No. 7. Schwann, Fro1 
notiz. Feb. 1838. Henle, Miiller’s Archi 
P 104-8, 1839, p. 45; also Miiller’s Phys. 
aly, 2nd edit., vol. i., p. 503-4, ie 


ty 
*, 2 
£ 


4 


MUCOUS MEMBRANE. 


festly the same structures, detached and matted 
together. The secretion found in the tubules 
of the testis is chiefly composed of epithelial 
particles resembling those attached to the base- 
ment membrane of the tubules. Some of these 
are very perfect, others have undergone changes. 
It has been already stated that the seminal ani- 
malcules are most probably a developement of 
some of these particles, not altogether different 
in its nature from that of the cilia found upon 
them in other situations. The secretion of an 
ordinary mucous follicle is likewise made up 
of epithelial particles resembling those still 
attached to the membrane. The thick, semi- 
fluid mucus found in the stomach has been 
shown by Wasmann* to consist of rounded 
nucleated particles, which both in size and 
shape correspond with those of the stomach 
tubules. This mucus may be even seen pro- 
jecting from the cells into which these tubules 
discharge themselves, and no doubt can exist 
that the proper secretion of this organ is chiefly 
composed of the bulky epithelium thrown off 
by the tubules; a view corroborated by the 
fact,t that this mucous membrane, consisting 
almost solely of epithelium, when mixed with 
certain acids naturally existing in the gastric 
juice, evinces the same powers of dissolving 
alimentary substances as that wonderful men- 
struum itself. The same thing may be ob- 
served in the intestinal canal, where the adhe- 
_ Sive mucus is little else than the aggregated 
epithelial caps of the villi, together with that 
which has escaped from the vertical tubes of 
the membrane. These facts may be always 
verified in a healthy animal just killed, and 
may thus be shewn to be independent of any 
morbid action. The legitimate conclusion from 
them seems to be this: that the peculiar prin- 
ciples of these respective secretions are lodged 
in the epithelial particles ; having been depo- 
sited there from the blood, in the natural 
course of developement. In other words, the 
process of secretion in these cases consists in 
an assimilation of the material from the blood 
by an organized tissue, which, when fully de- 
veloped, is loosened and shed. 

This view, so captivating by its simplicity, 
has certainly much satisfactory evidence in its 
favour, and it may, at least, be regarded as 
‘sufficiently established to constitute a strong 
presumption in favour of the general position, 
that all secretion is primarily assimilation. 

That the epithelial particles, when their 
growth is completed, should detach themselves 
m a more or less entire state, in all cases, from 
the membrane to which they have adhered, 
cannot be supposed essential to this general 
position, and even the total absence of any 
vestiges of these particles from any particular 
secretion would scarcely form a valid argument 
against it. For at present we know of no reason 
_ why the assimilated material should not be 
_ gradually given up by a slow disintegration or 
p deliquescence of the particles, or even by a 
" - 
5 * De digestione nonnulla. Berol. 1839. 

_.t Miiller’s Archiv. 1836, page 90. Schwann, 
‘ uber das Wesen des Verdauungs prozesses. 


Pe 


501 


continual separation of it without a concomitant 
destruction of the particles themselves. 

But in numerous instances besides those that 
have been mentioned, there is more or less 
direct evidence of an actual shedding and con- 
tinual renovation of the epithelium. The scaly 
variety of this tissue, whether on skin or mu- 
cous membranes, is a wide-spread example of 
this: the particles may be observed to augment 
in size by the intus-susception of new material 
from the blood, afterwards to undergo a slow 
loss of substance, and, finally, to lose their 
connection with the body altogether. They 
retain their position till nothing but the nucleus 
and cell-membrane remain, till they are re- 
duced, as it were, to a mere skeleton. How 
the material thus separated from the body is to 
be distinguished from a secretion, it would not 
be easy to decide. In the saliva of the mouth, 
are present, not only detached scales, but globy- 
lar nucleated particles, of a very delicate aspect 
and regular character, which seem manifestly 
to come from the salivary glands. They differ 
in some respects from the epithelium of these 
organs, but appear most probably to be par- 
ticles of it altered by endosmose of the water 
of the secretion through the cell-membrane ; 
for the ultimate vesicles and ducts of these 
glands are not merely lined, but filled, with 
epithelial particles, which, being thrown off 
from the basement membrane, must in due 
time escape to make room for the advancing 
series: and yet none of them in an unaltered 
state are found in the saliva. 

I may in this place refer to an opinion 
recently entertained in Germany, that the 
secreting membrane of certain glands is arranged 
in the form of closed vesicles filled with nu- 
cleated particles, which, from time to time, 
are discharged, as the secretion, by the bursting 
of the cell in which they are contained. Henle* 
conceives that this arrangement exists in the 
mammary, salivary, and lachrymal glands, as 
well as in almost every mucous membrane, 
however apparently plain and simple. Was- 
mann + has described a similar structure in the 
middle part of the stomach of the pig. This 
view of the existence of closed vesicles is 
obviously at variance with the general view 
hefore given of the universal continuity of the 
simple membrane of the mucous system. I 
am familiar with many of the appearances on 
which it is founded, and without presuming to 
pronounce them very decidedly deceptive, I 
may state that hitherto my observations induce 
me to agree with Dr. Baly{ in his rejection of 
the interpretation put upon them by the Ger- 
man anatomists. A thin slice of a mass of the 
many-lobed terminal vesicles of one of these 
glands, especially if compressed, very readily 
assumes the aspect of a congeries of cells, each 
entirely surrounded by an envelope of base- 
ment membrane. But I have several times, in 
favourable sections, observed this membrane 
passing off into a neck, and becoming con- 


* Miiller’s Archiv. 1839, p. xlv. 
+ De digestione nonnulla. Berol. 1839. 
¢{ Translation of Miiller’s Physiology, p. 504. 


502 


tinuous with that of the duct. Such observa- 
tions seem to me in a great measure conclusive 
on this subject; and I am strengthened in this 
view b the fact, that the capsules of the 
Malpighian bodies of the kidney are now 
universally considered to be perfectly closed 
vesicles, whereas they are in reality the ex- 

ed wall of the duct, as I have lately 
shown by several kinds of proof.* But what- 
ever may be the real fact in the matter under 
“es an it is admitted by all that the epithelium 
is formed in enormous quantities, and is being 
continually thrown off; which is the circum- 
stance chiefly intended to be insisted on at 

resent. 

In the healthy bile also, in the urine, and in 
various other secretions Dr. Henle has met 
with particles of epithelium detached from the 
ery passages, and in different stages of 


Turning to those two great emunctories, the 
liver and kidneys, in the secretions of which 
no trace of the epithelium of the secreting part 
of the organs can be detected, we might be 
disposed, on a slight consideration, to conclude 
the evidence they furnish to be unfavourable to 
the general position here advanced. We must, 
indeed, be content for the present to acknow- 
ledge that it is less plain and direct, and 
shrouded in our great ignorance concerning the 
play of chemical affinities in living bodies; 

ut still it is too interesting and important to 
be passed over in silence. Though the epithe- 
lium of these organs be not detached entire, as 
in many other cases, there is much, in each 
instance, to explain the discrepancy consistently 
with the theory in question. 

I have described the lobules of the liver as 
consisting of a solid plexus of capillary blood- 
vessels, in the meshes of which is a congeries 
of epithelial particles. We possess no accurate 
account of the mode of termination of the 
biliary ducts; but it seems clear, from the 
small meshes of the vascular plexus being 
completely filled by the epithelium, that no 
true ducts, i. e. tubes, penetrate the substance 
of the lobules: the tubular ducts probably 
commence on the surface of the lobules. The 
epithelium of the lobules is doubtless conti- 
nuous with that of the ducts, but the cavity of 
the ducts and their basement membrane termi- 
nate at the surface of each lobule. Though the 
cavity of the ducts be not continued within the 
lobule, yet it is very possible that injection 
urged along the ducts might insinuate itself by 
the side of the epithelium into the interstices 
of the vascular plexus, and thus, like the 
epithelium itself, form a solid piceus within 

e lobule. This appearance probably led Mr. 
Kiernan to describe the termination of the ducts 
as forming a plexus within the lobule, the 
lobular biliary plexus. And this description 
must be allowed to be essentially correct; for 
although the cavity of the duct cease at the 
surface, the epithelium of the lobule is, in 
respect of function, its real continuation. I 
have further observed, that although the epithe- 


* Phil. Trans. 1842, Pt. I. p. 59. 


MUCOUS MEMBRANE. . 


-secretion, and to prevent the latter from 


lium of the lobule has, on the whole, a plexi>— 
form arrangement, yet its particles in some ‘ 
measure affect a radiating direction from the — 
central axis towards the circumference, a 
towards certain parts only; and when veneal 
is broken up by violence, the resulting frag- 
wont of opabenee are apt to consist of a 
inear series 0 icles. Many of the 4 
too, are eaten the erage ace aal 
appearance of having been recently formed and — 
as yet incompletely developed. It is ai 
remarkable that the particles should contain 
granules of oily matter in their interior; for 


although chemical analysis has detected di 
rences between this substance and cholesterine,* 
yet as the chief peculiar principles of the bile 
are forms of hydro-carbon, the coincidence — 
cannot be an accidental one. It is not con- 
tended that the contents of these particles are 
the finished secretion, but rather that their 
chemical constitution undergoes some modifi- 
cations during the disintegrating process. 
it is worthy of notice, that in many cases wher 
the decarbonizing function of the lungs is 
slowly but greatly interfered with, as in phthisis 
pulmonalis, and where the liver is consequently 
called into increased activity as a compensati ng 
organ, these oily globules exist in such abun. 
dance and size as to gorge and swell the parti 
cles (and therefore the whole viscus) to near 
double their natural bulk.+ But this is not al 
the evidence, that this epithelium is the souree 
of the bile. I am informed by my friend, Dr 
W. Budd, that Dr. Henle in his recent editio 
of Soemmering, of which I have not yet bee 
able to obtain a copy, describes the epithelic 
particles as appearing yellow or yellowi: 
in direct light, and as probably containing 
He also states that the presence of the fatt 
globules in the epithelium is inconstant, am 
corresponds with the varying fatty contents 6 
the bile. He is unable at present to determine 
in what manner the contents of the particles 
find their way into the ducts. 4q 
The foregoing facts, taken together, afford 
very strong presumption that the epithel 
particles of the lobules are the agent assimilatit 
the secretion from the blood. It would 
still more satisfactory if particles could be fe 
undergoing decay. Meanwhile it seems i 
possible to assign to them any other office 
it be granted that the sole function of 
is to secrete bile. For in the case of o 
glands, the only other use that can with 
degree of plausibility be attributed to the 
thelium is that of its serving to defend 
secreting membrane from the contact of 


a 


ss 
se 


entering the blood. And it cannot exist 
that purpose in the liver, because it is | 
the only structure besides the bloodvessels 
does not constitute a lining membrane. 
_The peculiarity in the minute structu 
the kidneys, which bears on the prese 
tion, is of a kind entirely different 
presented by the liver, and yet tends to 
a similar conclusion. It consists of a Sp 
* Kuehn, Kastner’s Archiv. xiii. p. 337, — 
+ Author in Lancet, Jan, 1842. da 


-§ 
~ 


MUCOUS MEMBRANE. 


apparatus at the extremity of each secreting 
tube, apparently designed to furnish a flow of 
water down the canal.* A large quantity of 
water is evidently required in this secretion as 
a menstruum for the salts and proximate prin- 
ciples it contains; and there is no doubt, from 
the analogy of other glands, that the walls of 
the tubes are the membrane secreting these 
substances. Now the epithelium constitutes at 
least 4%ths of their thickness, and is the only 

of them with which the water can come 
into contact. It therefore seems highly pro- 
bable that this fluid is provided in the manner 
described, in order to dissolve, out of the 
epithelial particles, the peculiar principles which 
they have previously assimilated from the 
blood. 

In support of this general position it may 
be observed, further, 1. That the epithelium, 
which constitutes so large a portion of the true 
glands, is solid and bulky, usually character- 
ized by its finely granular texture, and in this 
respect contrasts strongly with that lining the 
vascular system, which is of extreme delicacy 
and transparence. The exceptions to this re- 
mark contirm its importance. In the air-cells 
of the lungs, the secretions of which are ga- 
seous and not solid, the epithelium is of great 
tenuity, and in the Malpighian capsules of the 
kidney, which appear to serve principally as 
receptacles for the aqueous fluid that escapes 
from the bare capillaries within them, this 
Structure is either wanting or consists of per- 
fectly transparent particles. In many inter- 
mediate varieties, too, there appears traceable a 
correspondence between the bulk of the nu- 
cleated particles and the activity of the secreting 
function ; of which the scaly form in general 
may be mentioned as an instance. 2. That 
many peculiar substances are secreted into the 
interior of nucleated cells, although prevented, 
by the position of those cells, from escaping 
from the body. Such are various fats and fixed 
oils, colouring matters, &c. 3. That this func- 
tion of abstracting somewhat from the blood, 
and elaborating it, seems the most probable 
one that can be assigned to the thymus and 
thyroid bodies, the spleen, and supra-renal 
capsules, and specially to the nucleated par- 
ticles forming so large a portion of these several 
Structures. On the whole there seems much 
weight of evidence in favour of the proposi- 
tion “that secretion is a function very nearly 
allied to ordinary growth and nutrition: that 
whereas these are a combination of two func- 
tions, assimilation of new particles and rejection 
of old, the old being reconveyed into the blood, 
secretion consists in a corresponding assimila- 


_ tion and rejection, but the old particles are at 


Once thrown off from the system without re- 
entering the blood. According to this view, all 
effete material received into the blood, from the 


old substance of the various organs, must be 
_ Teassimilated by an organized tissue, specially 
_ designed for the purpose, viz. the epithelium, 
_ before it can be eliminated : and all substances 


* Phil. Trans. Pt. I. 


1842, p. 73. 
( article REN. as 


See also the 


503 


thrown off from the system, but designed for 
an ulterior purpose, must in like manner be 
assimilated in order to their separation.” It 
places in a strong light a principle of great im- 
portance in physiolugy, the subordination of 
the bloodvessels and their contents to the tis- 
sues among which they are distributed. 

The function of secretion may therefore be 
considered to be universal over the mucous 
system, and its different activity in various si- 
tuations to be dependent on, as it certainly is 
closely associated with, differences in the ar- 
rangement and structure of the epithelial ele- 
ment. The basement membrane, from being 
absent from the lobules of the liver, seems a 
tissue of inferior (perhaps of no) importance 
in respect of this function, and probably is 
chiefly subservient, wherever it exists, to the 
mechanical support of the epithelium. 

There are probably ¢hree ways in which the 
secretions are finally separated from the body : 
and these three ways appear to have a reference 
to the chemical qualities of the product, and to 
their effete or non-effete character. 1. The par- 
ticles assimilated into the nucleated cell may 
be thrown off by virtue of minute chemical 
changes occurring in it, without the cell itself 
being altered in form. In this case the nu- 
cleated cells will be permanent, or only very 
slowly renewed, and the secretion will be 
formed, or at least perfected, by the passage 
of its elements through the cells. 2. The nu- 
cleated cells, as they arrive at their full size, 
may undergo a slow change in the arrangement 
of their elements, and gradually disappear by 
a kind of solution or deliquescence, thus form- 
ing the secretion. 3. The nucleated cells, when 
mature, may be cast off at once, and entire, 
with their contents. The two last modes are 
attended with a continual formation of new 
cells. 

It would appear that, in general, where the 
secretion is formed by the rejected chemical 
elements of the cells (1), or by the destructive 
solution of the cells (2), it is effete; but that, 
when formed chiefly by the separation of cells 
that are mature and contain much organic 
matter (3), it is destined for ulterior purposes 
in the economy. Of the first the kidney seems 
to be an example, of the second the liver, of 
the third the lining membrane of the stomach. 

The varieties in the qualities of the products 
secerned by different portions of the mucous 
system are only referrible to varieties in the 
elective powers of the tracts which respectively 
furnish them, and admit of being most readily 
explained by the view of the nature of secre- 
tion already advanced. It is unnecessary, in 
this place, to enter on a particular description 
of the boundaries of these several tracts, and 
I shall only offer a few observations on the 
nature and extent of that secretion which has 
given its name to the structures here treated of. 

The term mucus, like so many others trans- 
mitted from an early period, was originally 
employed to denote an exaggerated and partial 
condition, was subsequently applied more 
loosely and widely in a generic sense, and 
now requires to be reduced to a more definite 


504 


application in accordance with that necessity 
for precision of thought and expression which 
characterizes modern science. The exposition 
contained in the article Mucus will render it 
superfluous for me to define its present accept- 
ation. It is denied by Dr. Gruby that the 
viscid form of mucus is a normal secretion 
from any membrane whatever, and he considers 
its existence as a certain mark of diseased ac- 
tion. This view, if less absolute, would be in 
@ great measure correct, since there is no doubt 
that in a state of perfect health most mucous 
surfaces are wholly unprovided with any pro- 
tection of this kind. If the nasal cavities, the 
trachea or bronchia, the intestinal or urino- 

nital tracts, be examined in a healthy animal 

illed for the purpose, we may search in vain 
for any slimy covering, such as they are com- 
monly imagined to possess. But in a state of 
disease, each of these surfaces will secrete great 
quantities ; and it is nota little remarkable, that, 
even when healthy, if moistened and allowed to 
undergo slight putrefaction, they will become 
coated with a viscid fluid, having the physical 
characters of mucus. Yet the slimy fluid of the 
mouth cannot with propriety be considered 
abnormal. The true saliva is not viscid, as it 
escapes from the ducts of the glands into the 
cavity of the mouth: it probably becomes so 
by dissolving the substance derived from the 
scales of epithelium lining the mouth, as they 
advance to the surface and flatten. The fluid 
of ranula is not merely the accumulation of a 
natural secretion, but seems gradually to ac- 
quire its great viscidity by receiving the debris 
of the epithelium lining the excreting channels, 
and by the partial reabsorption of its aqueous 
portion. 

In the intestinal canal, however, although 
there is no viscid mucus naturally present, yet 
there is a large amount of“ inspissated mucus” 
being continually separated from the villi and 
follicles of Lieberkuhn. This mucus, as already 
mentioned, is nothing more than the debris of 
epithelial particles. 

But chemists have detected, in most of the 
secretions, a small proportion of a substance 
nearly allied to mucus, and probably a form of 
it. There is good reason to believe this to be 
the product of the membrane lining the ex- 
cretory passages, and to represent the old epi- 
thelium of that membrane. Where the secre- 
tion of the gland is fluid and in considerable 
quantity, it seems to be sufficient to convey 
away this debris from the surface which it tra- 
verses on its way out of the system, as in the 
salivary and allied glands, the liver, kidney, 
&c. But where, from the absence of this 
means of carrying off the debris of the epithe- 
lium, it might be supposed to be liable to 
accumulate and clog the surface, cilia are de- 
veloped ; of which the best example is fur- 
nished by the respiratory tract, the nasal ca- 
vities, and the tympana. That this is the 
great office of these wonderful organs upon 
these extensive surfaces appears to be proved 
by the fact that the currents they produce are 
uniformly towards an outlet. Henle has ob- 
served this in several parts, and I have-ascer- 


MUCOUS MEMBRANE. 


tained it by experiment in the case of thetra~ — 
cheal and bronchial membrane. iv 
In this tract no secretion is visible with the 
naked eye, but with the aid of the microscope — 
I have found, in perfectly recent animals, mi- 
pute globules of —— tenuity and of va-— 
rious sizes, which had the pearance ie 
mucus oozing from the smadieahdon'el the epithe- — 
lial particles. It is impossible but that “, 
cilia should move these globules along the 
face,and discharge them into the pharynx ; 
it hardly admits of doubt that mucus, morbidly 
existing on the bronchial membrane, is gradu; 
ally lifted up by these untiring agents to t 
region where it excites coughing, and is foreibly 
expelled by the rush of air. The patient is 
often conscious of its slow motion upw 
when it is in the form of a pellet and proc 
from an isolated spot. This is remarkably 
case too in hemoptysis, and also in that rare 
disease the bronchial polypus, where branched 
tubes of lymph are brought up in this m 
This view of the use of cilia in the muc 
system of the higher animals appears to me te 
merit much attention. I had intended to have 
considered it under a separate head, but it b 
been introduced here both in corroboration: 
the general position as to the nature of 
tion, and in illustration of the nature and ex 
of the special secretion from the ordinary & 
cous membranes. . 
On the whole I think it may be concluded 
1. That every part of the mucous sy 
where epithelium exists, secretes. “ 
2. That the secretion differs, in different 
gions, according to the vital properties of th 
epithelia; and that these vital agree: ; 
usually attended with appreciable varieties of 
structure. That corresponding varieties of che- 
mical constitution coexist with these is highly 
probable, though only as yet proved ina few 
cases. x 
3. That mucus is the least peculiar of the 
secretions, yet by no means universal from t 
mucous membranes, but confined to tracts” 
comparatively limited fe pre extent, chi 
the excretory channels of the glands. : 
In the preceding summary account of th 
structure, relations, and offices of the mucow 
system, I have not been able (without inter 
— to the course of the description) 
refer sufficiently to the labours of those ar 
mists to whom we owe almost all our kno 
ledge of the subject. This deficiency, of 
I am very sensible, I shall endeavour in soi 
degree to supply by a brief review of the 
searches which have led to the more mode 
and general views on the subject. SI 
over the imperfect descriptions of the anc 
we find that when the microscope first beca 
an instrument of anatomical research, the se 
character of the cuticle was recognised by M 
pighi and Leeuwenhoeck ; and that the form 
of these great anatomists had a wonderfully ¢ 
insight, considering the period at which he I: 
into the close relation that subsists between f 
glands, mucous membranes, and skin. TI 
labours of the anatomists of the next age we 
spent with great success upon matters of det 


~ S 
= any 


MUCOUS MEMBRANE. 


particularly on the distribution of the blood- 
vessels, which Ruysch and Lieberkiihn particu- 
larly illustrated ; and, by the general advance 
of knowledge, the way was being gradually 
prepared towards that more philosophical ar- 
rangement of the tissues of the body, in con- 
formity with their intimate texture and con- 
nexions, of which the first example is to be 
found in the work of Bonn,* already alluded 
to. He here traces, with great accuracy, the 
continuity of the skin and mucous membranes 
at the different orifices of the body, and he 
clearly recognises their close structural rela- 
tion, considering the mucous membranes to be 
roductions of the skin. To our countryman, 
Dr. Carmichael Smith,+ we are indebted for 
the first application of this arrangement to the 
gd of pathological classification, and 
inel soon after followed in the same track.} 

But a new era dates from the remarkable 
works of Bichat,§ in which he delineated the 
structure, vital and other properties, and the 
relations of the different tissues of the body, 
and arranged them ona basis, which, though 
faulty in some of its details, has received no 
essential modification in its principles since his 
time, and entitles him to the praise of rare 
genius and sagacity. He seems to have clearly 
perceived the true connexion that exists between 
the skin, mucous membranes, and glands, al- 
though he failed to carry out his views into the 
subdivisions of his system, where he was still 
fettered by the crude notions of his predeces- 
sors. One of the most remarkable features in 
his work, bearing on the present subject, is the 
analogy he draws between the epidermis of the 
skin and the mucus of mucous membranes, an 
analogy which he discovered with the eye of 
the mind, which has been since often rejected, 
but which can now be shewn to be real by the 
eye of sense. 

Most writers of eminence since the time of 
Bichat have adopted the principal part. of his 
views, and some have advanced further towards 
a full recognition of the homology of the skin, 
mucous membranes, and glands, among whom 
must be mentioned, in particular, J. Miiller, 
whose classical work on the glands,|| published 
in 1830, placed him at once in the foremost 
rank among the anatomists of our own day. 

Subsequently to that date, the improve- 
ments in the construction of the microscope 
and the consequent employment of greater 
magnifying powers, have added an extraor- 
dinary stimulus to anatomical and physiolo- 


_ gical studies, and directed a host of inquirers 
_ into an almost unexplored field, from which 
the harvests already reaped give the most fa- 
 yourable earnest of future and rapid additions 
_ to the stores of knowledge. To the Germans 
_ is unequivocally due the merit of having far 
outstripped all other nations in the honourable 


* De continuationibus Membranarum. Roterod. 
+ Medical Communications, vol. ii. London, 


t Nosographie Philosophique, ‘Paris, 1798. 
Traité des Membranes, 1800. Anatomie Géné- 
7 e, 1801. 


_ _|| De Glandularam secernentium structura peni- 
tiori. Lipsiz, 1830, 


505 


path thus opened, and in no collateral path of 
inquiry which has been pursued to the same 
extent, has so much new, interesting, and im- 
portant information of an accurate and satis- 
factory character, been obtained, as in that 
which it has been my duty to treat of in the 
present article. The names of Purkinje, Va- 
lentin, Henle, and Schwann deserve primary 
honour in this place, and to these may be added 
those of Ehrenberg, Treviranus, R. Wagner, 
Boehm, Wasmann, Gruby, and Gerber. 
Among the French anatomists, MM. Turpin, 
Mandl, and Donné have contributed much, 
and our own countrymen have not been be- 
hind. Dr. Sharpey, Dr. Sprott Boyd, Dr. Todd, 
Mr. Nasmyth, Dr. Barry, and Mr. Toynbee, 
are all distinguished in this field of research.* 

In the present article J have endeavoured to 
combine with all the authentic information I 
could obtain from these sources, the results to 
which I have been brought by a two-years’ 
study of the anatomical characters of the whole 
mucous system. So rapid, however, are the 
daily advances of knowledge, that it is possible 
much has been omitted which is already in 
some shape before the public, and, on the other 
hand, that a few years may greatly modify the 
general views that are here set forth. As the 
anatomical details, however, have been all sub- 
stantiated by my own observations, except where 
otherwise stated, I am enabled to speak with 
more confidence of their correctness. 


BIBLIOGRAPHY.— (See also the list of works 
appended to the articles GLAND and SKIN. )—WMar- 
cellus Malpighius, De viscerum structura. Op. omnia, 
Lond. 1687. Peyer, De gland. intest. Amstel. 
1681. J.C. Brunner, De glandulis duodeni, Fran- 
cofurt. 1715. Lieberkiihn, De fabrica et act. vill. 
intest. hom. Lugd. Bat. 1744, 4to. Haller, Ele- 
menta Physiol. lib. xi. Bonn, Specimen Anato- 
mico-Medicum, &c. extat in Sandifort. Thesauro, 
vol. ii. Roterodami, 1769, xii. p.265. Carmichael 
Smith, In transactions of a Soc. for promoting 
Med, Knowl. vol. ii. Lond, 1790. Soemmering, 
Baue des Menschlichen korpers, Frankfurt a M. 
1791. R.A. Hedwig, Disquis. Ampull. Lieber- 
kuihnii physico-microse. Lipsiz, 1797, 4to. Pinel, 
Nosographie philosophique, Paris, 1798. X. Bi- 
chat, Traité des Membranes, Paris, 1800; Ana- 
tomie générale, 1801. K.A. Rudolphi, Progr. de 
humani corporis partibus simil. 4to. Gryph. 1809. 
J. F. Meckel, Handbuch der Menschlichen Ana- 
tomie, Bd. 1. Halle, 1815. C, Mayer, tiber His- 
tologie u. eine neue Eintheilung der Gewebe des 
Menschlichen Korpers, 8vo. Bonn, 1818. H. 
Buerger, Examen Microsc. vill. intest. Hale, 1819. 
fF, A. Béclard, Elémens d’anatomie générale, 8vo. 
Paris, 1825. Billard, De la membrane muqueuse 
gastro-intestinale, &c. 8vo. Paris, 1825. Craigie, 
Elements of general and pathological anatomy, 
Edinb. 1828. Doellinger, De vasis sanguiferis que 
villis intestinorum, &c. insunt, Monachii, 1828. 
E. H. Weber, Hildebrandt’s Anatomie, 1830. J. 
Miiller, De glandul. secernentium structura peni- 
tiori, Lipsie, 1830; and, in English, Mr. Solly’s 
i 9 translation. G. Breschet, Ann. des Sciences 
Nat. 1834. Purkinje & Valentin, Commentatio phy- 
siologica de phenom. motis vibratorii continui, 
&c. 4to. Wratislav. 1835. Isis, 1838, No.7. Boehm, 


* To these must now be added Mr. Goodsir, who, 
in a paper —~ which an abstract has been just pub- 
lished) read at the Royal Society of Edinburgh on 
the 30th March, supports the view of secretion_here 
given, with several new proofs. See Lond. and 
Edin. Monthly Journal of Med. Science, May, 1842. 


506 


De Gland. intest. struct. penitiori, Berol. 1835. Gurlt, 

Miiller’s Archiv, 1835, page 399,—1836, page 263. 

on Boyd, Loe ig Essay on the structure of 
m 


€ mucous membrane of the stomach, Edinb, 
1836. Krause, Miiller’s Archiv. 1837, p.8. Henle, 
Symbole ad anatomiam villorum intest. imprimis 
eorum epithelii et vasorum lacteorum, Berol. 1837, 
Hufeland’s Journal, 1838. Miiller’s Archiv. 1838, 
p- 103. Ibid. 1839. Heft iii. p. xxxi.—Heft iv. 
p- xlv. Valentin, Repertor. 1838, p. 310. Was- 
mann, De digestione nonnulla. Dissert. Inaug. 
Berol, 1839, and Froriep’s Notizen, April, 1839. 
Miiller’s Physiol by Baly, London, 1837-41, 
vol. i, 2d edit. 1839, p. 477-503, et seq. Schwann, 
Froriep’s Notiz. Feb. 1838: * Mikrosk. Unter- 
suchung. Berol. 1839. R. B, Todd, Lectures on 
the mucous membrane of the stomach and intes- 
tinal canal, Med. Gaz. 1839 and 1842. Gerber, 
General anatomy by Gulliver, Lond. 1841. A. Na- 
smyth, Three memoirs on the teeth and epithelium, 
Lond. 1841. 7' , On non-vascular animal 
tissues, Phil. Trans. 184], part ii. Martin Barry, 
On the corpuscles of the blood, Phil. Trans. 
part ii. 1840, partsi. & ii. 1841. Mandl, Anatomie 
microscopique, Paris, 1839-41. Gruby, Observ. 
microscopice, Viennz, 1841, 


( W. Bowman.) 


MUSCLE.—(Syn. Mis, Musculus, Mus- 
cular or Sarcous tissue; vulgo, Flesh, Meat.) 
This term is applied to certain fibrinous con- 
tractile organs, either elongated and fixed at 
their two extremities, or hollow and enclosing 
a cavity, which in all the higher animals are 
the seat of the power by which locomotion, 
circulation, the prehension and passage of 
food, the expulsion of many of the excretions 
and of the young, as well as other diversified 
functions, are performed. It is also used to 
denote the peculiar contractile material or 
tissue, constituting the principal and essential 
portion of such organs. This tissue is always 
arranged in the form of fibres, which in many 
minute animals occur singly, each serving the 
purpose of a perfect muscle. But they are 
usually aggregated in very great numbers, sur- 
rounded with a network of capillary vessels, and 
connected to one another by areolar tissue. The 
nervous tissue is universally associated with 
the muscular, however small may be the quan- 
tity of the latter; it is through this that the 
Stimulus to contract is ordinarily transmitted, 
and, when the mass is great, made to affect 
simultaneously many Contiguous fibres. A 
muscle is the organ resulting from the union of 
these several parts. 

Muscles are styled voluntary or involuntary, 
according as they are, or are not, subject to the 
influence of volition, and they have been usu- 
ally so classified. But, however convenient 
these terms may be in the ordinary language 
of physiology, they cannot be applied, in a 
strict sense, to the purposes of classification 
without obvious objections. Many muscles, 
especially those under the immediate domi- 
nance of reflex nervous action, (as the respi- 
ratory and sphincter muscles,) partake of both 
characters, since volition can interfere only 
temporarily with their contraction; and all 
muscles, even the most confessedly voluntary, 
are subject to emotional and instinctive influ- 
ences, in which the will has no share. The 
attempt to introduce an intermediate or mixed 
class, which has been generally sanctioned, 


MUSCLE. 


while it is an acknowledgment of the imper- 
fection of the arrangement, does not appe r te 
be ee poppers ym = ne 
or siological grounds. subjection ¢ 
pan ectlasiink to She influence of the pill | 
made the basis of classification, all muscle 
should be accounted voluntary on which 
can exercise a direct influence either in cav 
or controlling contraction, even though suc 
influence be but momentary, and capable « 
being exerted only while the stimulus exciti 
of involuntary action is in abeyance. o- 
The voluntary muscles are generally soli 
organs, while the involuntary are hollow; an 
on recurring to the minute structure of the 
respective elementary fibres, we detect ve 
striking differences between them, those of thi 
former being striped crosswise with very deli 
cate and close parallel lines, which, with som 
exceptions, are altogether absent from the la 
ter. But these exceptions are of so impo 
a kind as to demonstrate beyond doub 
there is no necessary connexion between 
minute conformation of the fibres and thei 
lation to the influence of the will. The mu 
cular coat of the esophagus often displays @ 
striped structure as far down as the stomae 
though the will has no power whatever ove 
movements ; and the heart itself is com post 
of striped fibres. As the structural difference 
between these two kinds of fibre are constan 
well-marked, and therefore easily ascertair 
and as they seem, moreover, to be rel 
varieties in the activity and mode of e: 
of their contractile power, they will be employ: 
as the ground of division in the present ¢ 
ticle. ‘ 
I shall first describe the minute anatomy 
these two kinds of elementary fibre, a 
steps of their development; and, secon 
shall advert to their mode of aggregation 
to the arrangement of the tissues found in 
nection with them. = 
a. Of the striped elementary fibres.—Th 
have received the name of Primitive Fasei 
on the erroneous supposition of their be 
bundles of finer filaments. They may be sé 
rated from the tissues associated wi 
the compound organ by a variety of me 
but as they always constitute the prince 
mass of the organ, they may be exami 
without any attempt at such separation. 
was a favourite plan with the older anator 
to obtain the fibres apart by submitting f 
to a long boiling, which destroys the textu: 
the vessels and filamentary tissue, but al 
same time considerably modifies the size, | 
and structure of the fibres. It is in general: 
requisite to take a small portion of a mt 
as fresh as possible, (but after its contrat 
has departed,) and to tear it, under water 
fine shreds, with needles. By these m 
elementary fibres will be separated f 
another, and being in parts irregularly 
and torn, can be submitted to inspectic 
a high power of the microscope, in such ace 
tion as to exhibit most of the im it poi 
their structure. Many sedulous examinati 
specimens from various sources are r% 
for the acquirement of a correct idea of | 


hen 
ae 


MUSCLE. 


organization and properties, but that this simple 
method of procedure is the one most likely to 
lead to a true insight and conclusion regarding 
the anatomy, not only of this but of all elemen- 
tary structures, becomes every day more evi- 
dent. Various subsidiary means may doubtless 
be employed with advantage, such as injections 
and physical and chemical agencies; but the 
method which of all others is the least liable to 
admit of erroneous interpretations by the ad- 
mixture of artificial elements in which the mind 
of the inquirer has had a share, is that of em- 
loying a power capable of reaching the utmost 
imits of organization, on examples the most 
ne approaching to their natural state during 
e. 

There is perhaps no one line of inquiry in 
the whole range of minute anatomy so beset 
with difficulties and sources of error, and 
therefore so much demanding a cautious study 
and sagacious discrimination between conflict- 
ing appearances, as this of the structure of the 
striped fibre. The following description is 
substantially the same as that published by me 
in the Philosophical Transactions, 1840, and 
which all my subsequent observations have 
tended to confirm. To that paper I would 
venture to refer those who may desire to enter 
at greater length upon the grounds of the view 
here summarily given. 

1. Length.—This varies exceedingly in dif- 
ferent muscles. The sartorius, the longest in 
the body, often surpasses two feet in length, 

_ and the individual fibres are as long, extending 
_ in parallel bundles from end to end. In many 
others they do not exceed a quarter of an inch ; 
_ thus their greatest variety is presented in their 
length. 
\ 2. Thickness—This should be examined in 
_ the uncontracted state of the fibre, which for 
this purpose should be removed from the body 
after all contractility has departed. I have 
elsewhere* given a table of numerous compa- 
tative measurements in various animals, and 
subjoin the following abstract : — 
Diameter of the elementary fibres of striped 
muscle in fractions of an English inch. 
From to 
Human ...... gts is, average of males 555 
» females 4, 


‘ 
y 


Other Mammalia phy ts, average ...... shy 
ds ..seeeee hp Meh xdeeres ahr 
Re CHES o> ois.e.s Toy hoe ” eeeeee ht 
ee as a ” cescee ah 
Insects cans aes ae cee Rais rns a5 


oe Dy ” 

I believe that the fs diameter of the 
fibres in the human female is upwards of a 
fourth less than in the male, and that the ave- 
= of both together is greater than that of 
other Mammalia; but a more extensive exami- 
nation is requisite to establish this. Fish have 
fibres nearly four times thicker than those of 
_ Birds, which have the smallest of all animals. 
_ Next to Fish come Insects, then Reptiles, then 
Mammalia. In each of these different classes, 
however, an extensive range of bulk is observ- 
able, not only in the different genera, but in the 
me animal and the same muscle, some fibres 
ing occasionally three, four, or more times 


* Philosophical Transactions, 1840, p. 460. 


507 


the width of others. In general the fibres of 
the heart are smaller than those of other striped 
muscles. The varieties in the average bulk in 
different classes have a close connection with 
differences of nutrition and of their irritability, 
which will be reverted to. 

3. Figure.—This is subject to some variety, 
depending on their number and manner of 
package. Sometimes, as in some parts of In- 
sects, they are flattened; but when they are 
isolated, or loosely aggregated, they are more 
or less cylindrical. In all the cases, however, 
where many fibres are arranged side by side, 
as in the Vertebrata, the larger Insects, and 
Crustacea, they are irregularly polygonal, the 
contiguous sides being flattened, evidently from 
the effect of package. Yet some interspaces 
are always left for the passage of bloodvessels, 
nerves, and areolar tissue among and _be- 
tween them. Their form may be most readily 
displayed by a transverse section of a muscle 
that has been dried en masse, as long ago shown 
by Leeuwenhoeck (fig. 286). 

4. Colour——The colour of muscle depends 
partly on the colour of its elementary fibres, 
partly on the blood contained in its vessels, 
and there is strong reason to believe that the 
colouring matter of both is the same, or nearly 
so. That the fibres have always a colour of 
their own is at once evident on inspection 
under the microscope. It is generally more or 
less of a reddish-brown, but varies much in 
different animals and in different muscles, and 
even in the same muscle according to its state 
of development and activity. In Reptiles and 
Fish generally, and in Crustacea, the flesh is 
white, sometimes pinkish, but in some fishes, 
as the Gurnard, the gill-muscles are red. These 
varieties of colourare attended with none of struc- 
ture. In Birds the colour varies much, being 
often white and deep red in the same animal, but 
generally the pectoral muscles are very dark. 


Transverse sections of striped muscle that had been 
injected and dried, magnified 70 diameters. 

A, from the Frog. 

B, from the Dog. ; 

a, a, section of elementary fibres, shewing their 
angular form and various s:ze. 

b, b, sections of the injected capillaries, shewing 
the position they occupy among the fibres. 

These figures shew th greater vascularity of the 
muscle with the narrower elementary fibres. 


508 


The most deeply coloured muscle I have seen 
was the great pectoral muscle of the Teal 
( Querquedula crecca), killed after migration. 
n Mammalia the colour is ordinarily red, 
being deeper in the Carnivora than in the vege- 
table feeders. Among the domestic animals 
many varieties exist, which need not be spe- 
cially enumerated. A considerable part of the 
colouring matter is extracted by repeated wash- 
ing of a muscle, which then becomes pale, but 
not quite colourless; some part of the loss of 
colour here sustained is doubtless owing to the 
solution of the hematosine of the blood con- 
tained in it. A muscle, if hypertrophied, 
grows redder, and vice versi; and probably 
the practice of bleeding calves some days 
before they are killed, makes their flesh more 
pale and tender, by causing the absorption of a 
rtion of the proper colouring matter of the 
bres, as well as by abstracting the blood 
circulating among them. 

5. Internal structure.—Though the elemen- 
tary fibres of all animals are visible to the 
naked eye, and in some animals, as the Skate 
(Raia Batus), are often as thick as a small pin, 
nothing of their internal organization can be 
distinguished without the aid of a powerful 
lens. There is indeed, in certain lights, a 
splendid pearly iridescence, resulting from 

e arrangement of their structure, and quite 
characteristic among the soft tissues; but this is 
not explained till a high power of the micro- 
scope is brought to bear upon the fibres. They 
are then seen, when viewed on the side, to be 
marked by innumerable alternate light and dark 
lines, whose delicacy and regularity nothing can 
surpass, and which take a rallel direction 
across them; and if the focus be altered so as 
to penetrate the fibre, they are found to be pre- 
sent within it just as on its surface, thus differ- 
ing from those on the trachee of insects, which 
exist only at the surface. At the extreme border 
of the fibre the light lines are sometimes seen to 
project a trifling degree more than the dark 
ones, thus giving a slight scallop, or regular 
indentation, to the edge. If often happens, in 
tearing the fibres roughly with needles before 
examination, that they crack across, or give way 
entirely, along one or several of these dark lines, 
the line of fracture or cleavage running more or 
less completely through the fibre in a plane at 
right angles with its axis; and occasionally two 
or more of such complete cleavages will occur 
close together, the result of which is the separa- 
tion of so many plates or discs (fig. 287, B), of 
which the light lines at the surface are the edges, 
and the corresponding light lines seen within 
are what may be termed the focal sections. 
Thus it is evident that there is a tendency in 
the mass of the fibre to separate, when torn or 
pulled after death, along the transverse planes, of 
which the dark transverse stripes are the edges. 
When such a separation takes place, a series 
of discs result, but to say that the fibre is a 
mere pile of discs is incorrect, for the discs are 
only formed by its disintegration. Neverthe- 
less they are marked out, and their number 
and form are imprinted, in the very structure 
of the fibre, in its perfect state. ( Figs. 287 
and 288.) 


MUSCLE. 


Fragments of. stri elementary fibres ng 
camange in cnt dimieaal magnified 300 


A, longitudinal cleavage. 

At a the longitudinal and transverse lines 
both seen, Some longitudinal lines are darker 
wider than the rest, and are not continuous fro 
end to end, 

b, primitive fibrille, separated from one 
by violence at the broken end of the fibre, a1 
marked by transverse lines equal in width to tho 
at a. 

¢ represents two appearances commonly present 
by the separated single fibrilla. On the upper on 


bs 


the borders and transverse lines are all pe: 
rectilinear, and the included spaces perfect] 
angular. In the lower the borders are scallope 
the spaces bead-like. When most distinct and 

finite, the fibrilla presents the former of these a 


pearances. 
B, transverse cleavage. The longitudinal li 
are scarcely visible. 
a, incomplete fracture following the opp 
surfaces of a disc, which stretches across the in 
val and retains the two f. ents in connexi 
The edge and surface of this disc are seen | 
minutely granular, the granules pond; 
size to the thickness of the disc and to th 


between the faint longitudinal lines. 
6, another disc nearly detached. 


But again, it always happens that de 
dinal lines, more or less continuous and 
rallel, according to the integrity of the” 
and the strength and distinctness of the tre 
verse lines, are also to be discerned ; and 1 
the transverse ones, not on the surface only, 
throughout the whole of its interior. 
found that there is a remarkable pronenes 
the fibre to split in the direction indicate: 
these lines also; by which splitting it is re 
into a great number of fibrilla. These br 
like the discs, do not exist as such in th 1 
and to obtain them its structure must be 
sarily broken up to a certain extent, fo 
union which naturally subsists between 
parts must be destroyed. It is therefore 
correct to say that there is an indication i 
entire state of the fibre of a longitudina 
rangement of its parts, occasioning a cle 
in that direction on the application of vio 
( Fig. 287.) " 

Sometimes the fibre will split into ; 
only, more often into fibrille only, but 
are always present in it the transverse and 
longitudinal lines which mark the two 
ages. It is the most common to find a ch 
or fracture taking both directions irregulal 
running partly in the transverse dark lin 


MUSCLE. 


partly in the longitudinal dark lines, some- 
times being crosswise on the exterior, more or 
less lengthwise within. These cracks are often 
short, even, well defined; at other times the 
parts near them are much stretched, or quite 
disorganized, — differences depending on the 
brittleness or toughness of the particular fibre, 
which qualities vary very much in different 
specimens, according to the state of nutrition, 
period of examination, and other circumstances. 

Hence it is clear that the discs and fibrille 
consist of the same parts, and merely result 
from the different direction in which the mass 
breaks up. To detach a fibrilla entire is to 
remove a particle from every disc, and to take 
away a disc is to abstract a particle of every 
fibrilla. Thus, every disc consists of a 
particle of every fibrilla, and every fibrilla 
of a particle of every disc. Therefore every 
fibrilla of the same fibre has the same number 
of particles, and every disc in like manner is 
composed of the same number of particles. 

If, now, isolated discs and fibrillz be examined 
under a high magnifying power, they will be 
found to bear out, in the fullest manner, the 
description that has been given. The discs are 
marked on the edge by the fragments of the 
longitudinal lines, and if regarded on their flat 
Surface, present a finely granular appearance, 
the granules being equal in diameter with the 
fibrille (fig. 288). In fact, the dark lines be- 

i Surface of a dise separated from an ele- 
Pe: ith coadiod JSibre fe timed which had 

lain long ao iapirtin It Hs aap 

ly granular structure spoken of in 
is The granules pam intended 
to be represented equal in size. Mag- 

nified 300 


diam, 


_ tween the granules are the fragments of the 
longitudinal lines of the interior of the fibre. 
_ Again, the fibrille, whether taken from the 
surface or from the interior, are always found 
to be marked at intervals by transverse dark 
lines, which are nothing more than the frag- 
_ ments of the transverse lines seen on and in the 
' fibre. They uniformly correspond with them in 
. distance and force (fig. 287, c). Thus, whether 
_ the fibre cleave crosswise or lengthwise, the 
_ resulting fragments bear in their structure their 
_ respective portions of the lines, taking an op- 
_ posite course, and evincing a co-existent ar- 
rangement in the opposite direction; and when 
a detached disc or fibrilla is itself broken, the 
fracture follows the lines thus imprinted in its 
_ Structure. 
It remains to inquire, what is the nature 
and meaning of the dark lines so often men- 
tioned ? 

They can be best examined in the separated 
dises or fibrille; and they appear to be un- 
doubtedly the results of an unequal refraction 
of the light transmitted through the object. 
The light spaces intercepted between them, 
and which by their union constitute the discs 
and fibrille, have the aspect of small lenses or 
_ particles of higher refractive power than the 
_ connecting material, which consequently is in 

_darkness when the inclosed spaces are in focus. 

By placing the object out of focus, however, 


a 


, 
A 
“3 


q 


509 


the light and dark parts are reversed, which is 
precisely what occurs with true lenses. I have 
had a series of beaded rods of glass con- 
structed, which have exactly the same ap- 
pearance as the fibrille; and when two of these 
are regarded between the observer and the 
window, one being in front of the other, and 
their beads corresponding, the dark circum- 
ferences, visible round the beads of each rod 
when seen separately, are found to be converted 
into transverse bars, crossing the rods at right 
angles in the interval of the beads; or, in other 
words, forming the elements of the transverse 
stripes. 

My friend, Dr. Gruby, of Vienna, informed 
me that he had had spiral rods of glass con- 
structed, which, when placed in front of one 
another, have the same appearance as that often 
met with in the fibres, and he conceives the 
fibrill to be, consequently, spiral threads: an 
opinion advanced by Muys, to explain the 
phenomenon of contraction, but unnecessary 
for that purpose, and which is quite at variance 
with all I have observed on the subject. Such 
spiral rods, however apposed, can never pre- 
sent lines absolutely transverse, such as always 
exist on the unmutilated fibre, and generally 
on the detached fibrille ; and the minute zig- 
gags the stripes so often form, and which might, 
if constant, be possibly explained by the 
notion of spiral rods, are the mere result of a 
stretching and disturbance of the direction of 
the axes of the particles composing the discs 
and fibrille. But the cleavage of the fibre 
into discs is especially opposed to the idea of a 
spiral form of each fibrilla. 

I think it is clear that the dark lines in both 
directions are not occasioned by a difference 
of colour, but solely by a variety in refraction ; 
but on what this difference in refraction de- 
pends it is more difficult to explain. Is the 
connecting material of a different refractive 
power, or of the same nature as the particles it 
unites? If of the same nature, it must be of 
smaller dimensions, and minute interspaces 
must be left; but of the existence of such in- 
terspaces there is no conclusive evidence. It 
seems more probable that the connecting ma- 
terial is less dense, and fills up every interval ; 
but I do not pretend to determine what may 
be its nature, or whether it differs chemically 
from the parts it serves to join. 

It is remarkable that the direction of the 
cieavage should vary so much in different spe- 
cimens, without it being possible to say on 
what the variety depends: and the question 
has still to be determined, whether the trans- 
verse and longitudinal modes of union between 
the particles are the same. It is most likely 
that they are, and the differences in the regu- 
larity and breadth of the transverse and longi- 
tudinal lines are easily explained on that sup- 
position. 

The transverse dark intervals between the 
particles, being all ranged on the same plane, 
the edge of which is directed to the observer, 
when he looks on the side of a fibre, appear 
as a sharp line, while the longitudinal dark 
intervals not being on a plane, are seen irre- 


510 


gularly one in front of the other, as a little 
Somalia will shew. Hence the latter 
seldom seem so definite or regular as the 
former. Nevertheless their union, seen on the 
surface of a detached disc, often presents much 
regularity, and forms curved or straight lines, 
such as result when a number of balls of equal 
size are huddled together on a level. 

It may be concluded from what has now 
been advanced, that the discs and fibrille, (or, 
in other words, the general mass of the fibre,) 
are made up of a number of particles, which 
I have termed primitive particles, or sarcous 
elements, and which would be obtained ina 
detached form by a general separation occur- 
ring along the transverse and longitudinal lines 
visible in the fibre. The existence of these 
particles, as well as their form and size, is in- 
dicated in the structure of the fibre, while yet 
entire; but they are united together, and have 
no independent existence, each being by its 
very nature a part of the mass, which is ren- 
dered incomplete by the removal of a single 
element. It results also from this descrip- 
tion that these particles have no definite 
outline on all their aspects, being united 
together; and that they only obtain such an 
outline on being severed; on which account 
it is perhaps impossible to say whether, in 
the perfect fibre, they be rounded, square, or 
polygonal. 

An example of the strong lateral union of 
these particles to one another was presented b 
the specimen from which the following skete 
was taken. It consisted of two or three ele- 


mentary fibres from the leg of a newly-born 
rabbit, which had been kept for some months 
in weak spirit. They were lying in a curved 
form on the field of the microscope, and pre- 
sented on the convex edge transverse series of 

Fig. 289. 


the particles, which, hav- 
ing lost their longitudinal 
while they retained their 
lateral union, stood out in 
relief, as represented in 
fig. 289, a, a, a. 

It sometimes happens 
that a linear series of them 
(a fibrilla) is separated, 
which has the appearance 
of a necklace of beads, 
with constricted intervals, 
while at other times the 
intervals, though dark, are 
of equal width with the 
light or highly refracting 
particles. Again, it is pos- 
sible, by steeping in acid 
a transverse section of a 
dried muscle, to separate 


cles, , oe ies the particles considerably 
come from one another, and to 


see that they are granules 
acting as lenses, being much more refractive 
than the material connecting them. Such 
transverse sections are an artificial division 
into discs, and the intervals between the Pe 
ticles widen out most in specimens taken from 
birds (fig. 290). 


MUSCLE. 


sepa from an 
ther. The cut edge of th 
tubular sheath of each fibre 
is also seen, : 


It is in these sarcous elements that the ¢ 
tractile power resides, and, as they are apt 
retain after death the varying effects of the con- 
traction they have undergone during the rigo 
mortis, it is not easy to give an exact measu 
ment of their size or shape. An average dr 
from very numerous observations shews, how 
ever, that they are very nearly alike in thes 
respects in all animals and at all periods of lif 
Their diameter in the longitudinal directior 
the fibre, as indicated by the distance bet 
the transverse lines, is thus shown to be :* — 


No. 
Eng.Inch. Obse 


In the Human subject.. shy +. 27 
In Mammalia generally qbgy - ‘ 
In Binds. 6) 040i 590% Wis +e ? 
In Reptiles..... cocee tikes | ee 
In Fish. .....<+000 » yee s ee 
In Insects .....006.- gdp oe f 
Their diameter in the opposite directic 
that marked by the distance between the lo 


itudinal lines is less, often by a half, | 
liable to variety from the cause already sf 
cified. 2 
In a paper, entitled “ On Fibre,” read be 
the Royal Society, on the 16th December 
the 6th January last,+ Dr. Barry describes” 
Jibrilla to be a flat filament rounded at 
edges, and deeply grooved along the m 
line on both its surfaces. He states that | 
flat filament consists of two spiral th 
placed side by side, with their coils interlacé 
that it “ is so situated in the fasciculus ( 
mentary fibre) of voluntary muscle, as to] 
sent its edge to the observer;” and tha 
curves of the spiral thread, then seen, 
have been the appearance that “ suggeste 
idea of longitudinal bead-like enlarg 
producing the strie.” In Dr. Barry’s op 
“the dark longitudinal strie are spaces | 
bably occupied by a lubricating fluid) be 
the edges of flat filaments, and the dark t 
verse strie, rows of spaces between the ci 
of the spiral threads,” of which each fla 
ment consists. ‘“ In a postscript, the a 
observes, that there are states of vol 
muscle in which the” (doubly-spiral, flat,) 
gitudinal filaments have no concern in 
peosucyes of the transverse strie, these 
ing occasioned by the windings of sp 


within which very minute bundles of k 


eS 
* Auct. loc. cit. p. 474. ae 
+ Proceedings of the Royal Society, No. 


MUSCLE. 


tudinal” (doubly-spiral, flat,) “ filaments are con- 

tained and have their origin.” 

This description, so entirely opposed to the 
more simple view above given (and which was 
already in type when the paper “ On Fibre” 
was read) demands a brief notice. The paper 
of which it forms part, might perhaps have 
been more explicitly entitled, ‘‘ On the double 
spiral structure of the organic world;” for, 
in it, the doubly-spiral flat filament, giving the 
appearance of transverse strie to voluntary 
muscle, is discovered to exist in the interior 
of the blood-corpuscles of all animals, and 
* apparently in every tissue in the body. The 
author enumerates a great variety of organs in 
which he has observed the same kind of fila- 
ments.” “ And if the author’s view of iden- 
tity in structure between the larger and the 
smaller filaments be correct, it follows that 
spirals are much more general in plants them- 
selves than has been hitherto supposed ; spirals 
would thus appear, in fact, to be as universal 
as a fibrous structure.” “ Valentin had pre- 
viously stated, that in plants all secondary de- 
posits take place in spiral lines. In the in- 
ternal structure of animals, spirals have here- 
tofore seemed to be wanting, or very nearly so. 
Should the facts recorded in this memoir, how- 
ever, be established by the researches of other 
investigators, the author thinks the question in 
future may perhaps be, where is the ‘ secon- 
dary deposit’ in animal structure, which is not 
connected with the spiral form? The spiral in 
animals, as he conceives he has shown, is in 

_ strictness not a secondary formation, but the 
_ Most primary of all; and the question now is, 
_ whether it is not precisely so in plants.” 

As these speculations profess to be grounded 
solely on observations of particular structures, 
of which muscle is one, I shall make no apo- 
logy for applying my few remarks solely to the 
_ account of this structure, which is all that can 
_ properly be considered here. A renewed ex- 
amination of this tissue has confirmed, fully 
and decisively to my own mind, the account 
I gave of it in 1840, and which was the result 
of two years’ study. 1.1 find that when the 
natural and ready cleavage happens to be into 
fibrillee (and I do not pretend to explain why 
_ this cleavage should be at one time into fibrillz 
_and at another time into discs, I only know 
the fact,) these solitary and isolated fibrille do 
not present any such central longitudinal 
groove, as Dr. Barry describes, to indicate 
their double nature: that the cross lines are usu- 
ally transverse, and not oblique, by which I 
mean that the spaces they bound have a rectan- 
gular outline, so sharp and definite, that the 
tnind rests entirely satisfied that there cannot 
_ be two opinions concerning them, between 
any who have examined the object in one of 
owell’s best microscopes, and with the use of 
admirable definer and clarifier of the 

the achromatic condenser. That right 
a can be produced by a spiral, whether 
_ double or single, however distorted by accident 
_ or violence,’ it is impossible to conceive. That 
these transverse lines may sometimes become 
‘oblique by irregular traction, such as is almost 


511 


necessarily applied in preparing the object, is 
most easy to understand, if we bear in mind, 
that the substance in the different spaces which 
they cireumscribe is one united mass. 2. The 
transverse cleavage of the elementary fibre, 
which I first showed to be occasionally so com- 
plete as to separate it into discs, cannot be 
reconciled with Dr. Barry’s statement. For 
the surfaces of such discs present, as in fig. 
288, a fine granular aspect, and no ends of 
doubly spiral threads. And the definite and 
beautiful appearance presented by a transverse 
section of the fibre in all animals, but espe- 
cially in Birds (fig. 290), is totally at variance 
with his views: for the particles there dis- 
played are highly refracting, round, and not 
aggregated in pairs. The condition repre- 
sented in fig. 289 is not less opposed to them. 
Other proofs might be adduced, but they 
would lead to greater detail than is compatible 
with the form of the present publication; and 
perhaps they will be allowed to be unneces- 
sary. 

6. Of the corpuscles of the elementary fibre. 
The elementary fibres always contain, among 
their primitive particles, a number of corpuscles, 
which either are, or are analogous to, the nuclei 
of the cells of development, of which this 
and other structures have originally consisted. 
These corpuscles are visible in the early stages 
of growth (fig. 291), but disappear towards 
the close of fcetal life, as the lines resulting 
from the deposit of the contractile particles 


Fig. 291. 
a 


= pepe et 
iss 


Elementary fibres from the pectoral muscle of a fetal 
calf about two ths after conception, shewing the 
corpuscles at a, a, a. Magnified 300 diam. 


Fig. 292. 


Fig. 293. 


Elementary fibre from the leg of the large Meat-fly 
( Musca vomitoria ), 

a, a, line of termination of the fibre, along which 
the tendon (6) is attached to it. 

¢, central series of corpuscles. 

Along the margin the sarcolemma is elevated by 
water, (which has been absorbed, ) and is thereby 
shown to be adherent to the margin of the dises, 


512 


grow dark, The addition of a little acid, how- 
ever, swells the fibre, obliterates the cross lines, 
and brings the corpuscles into view, not only 
at this early ati but at every subsequent 
one, even to old age. In insects, the nuclei 
in the earliest stage are a single or double 
series in the axis of the fibre, and in the per- 
fect fibre they hold the same position (figs. 
292 and 293, c). In the Vertebrate classes 
they have a like correspondence, being scat- 
tered equally throughout the mass, in both 
foetal and adult states. Where the fibre is 
small, however, they usually abound more 
towards the surface. They are oval and flat, 
and of so little substance, that though many 
times larger than the primitive particles, and 
lying amongst them, they do not interfere 
with their mutual apposition and _ union. 
These corpuscles are frequently the cause of 
irregular dark longitudinal streaks, seen in the 
fibre by transmitted light. They usually contain 
some central granules or nucleoli (fig. 295). 
It is doubtful whether the corpuscles or nuclei 
originally present remain through life, or whe- 
ther successive crops advance and decay during 
the progress of growth and nutrition. But it 
is certain, that, as development proceeds, fresh 
corpuscles are deposited, since their absolute 
number is far greater in the adult than in the 
fetus, while their number, relatively to the 
bulk of the fibre, at these two epochs, remains 
nearly the same. 

7. Of the sarcolemma, or tunic of the ele- 
mentary fibre.—This is a simple transparent 
homogeneous membrane of extreme tenuity, 
but very tough and elastic, which, in the form 
of a perfect tube, invests every elementary fibre, 
adheres to its surface, and isolates it from sur- 
rounding parts. It is universally present in vo- 
luntary muscles, and may be demonstrated in a 
variety of ways. When the fibres have been im- 
mersed in alcohol, which causes them to shrink, 
it is often seen wrinkled on their surface; or 
when they are cracked or broken across, it fre- 
quently remains entire and connects the severed 
fragments (fig. 294). This method of showing 


Fig. 294. 


Fragments of an elementary fibre of the Skate, held together 


by the untorn but twisted sarcolemma. 
a, Sarcolemma. 


it is best followed in the case of the large and 
brittle fibres of the Skate; or, it may be seen 
cutacross in a general transverse section of a 
dried muscle (fig. 290). When the texture 
of the fibre is destroyed by maceration, the 
broken mass is sometimes retained hy the 
sheath, which thus becomes visible. hen 
the fibre swells by acid, this tunic resists, and 


MUSCLE. 


b, b, opposite fragments of the fibre. 


the swollen mass emerges at its broken a 
open end : but, if this is not effected with 
ficient celerity, the sarcolemma may give 
at different points, being burst by the n 
which thus forms hernie. Such 
masses being unequally stretched have the 
transverse and longitudinal lines distorted fro: 
their true direction and thrown into v 

gant curves (fig.295), Again, if a fibre st 


Part of an elementary fibre from the human 
ject, treated with ic acid, 
a, point at which the sarcolemma is burst. 
b, hernia of the sarcous mass, with di 
of the longitudinal and transverse lines. 
c, a smaller hernia. 
les are seen scattered throughout the 
and some detached ones, d, are represented below. T 
average diameter is one-thousandth of an English 


_ 


retaining its irritability, be immersed in wate 
this fluid, on being absorbed, excites cor 
tion, by which it is immediately expelled 
among the primitive particles. hen tl 
forced out it usually collects between 
fibre and its sheath, raising the latter 
form of bulle (figs. 301 and 302, an¢ 
Muscutar Morton). The progress of t 
teresting phenomenon evinces the adhesio 
exists between the fibre and its sheath. 
bulla immediately subside, by 
transudation of their fluid, when 
part is placed in thick syrup. 
met with a singular demonstratit 
the existence and properties 0 
colemma, in finding it filled 
merous trichine (fig. 296), whi 
taken the place of the contractil 
terial, the sheath preserving all its 
racteristic beauty and transparen 
I discovered this remarkab 
brane in Insects, Crustacea, a 
the tribes of Vertebrata, in 18; 
knowing that Professor Schwann had 
viously described it in connection with the 
velopment of muscle in Insects and * 
He believes it to be a persistent po 
the membrane of the original ce 


oh 


* Auct. loc. cit. p. 480, 


1. xvii 41-5 
t Mikros. Untersuch. p. Yes, Ph 


MUSCLE. 


Trichine within the sarcolemma, from which all the 
contractile material had disappeared, 
From an Eel, 
a, ovum. 
%, worms in slow motion. 


velopment, united to form a single tube, the 
septa at first resulting from their apposition 
having been absorbed. This opinion is un- 
-doubtedly ingenious; but, as | have yet no 
data from which to judge of its correctness, 
I neither admit nor deny it. I have seen 
the sarcolemma in human muscle as early 
as the period of birth, and have traced it at 
all epochs, to old age, when the atrophy of 
its contents has often seemed to render it 
more easy of detection. It also remains in 
muscles wasted by disease or accident at other 
periods of life, and no difference appears to 
occur in it whether the specimens examined 
are pale or dark-coloured, firm or flaccid. It 
is thickest in those classes that possess the 
thickest elementary fibres, viz. in Crustacea 
and Fish, and so thin in Birds, whose fibres 
are the smallest, that it is often difficult to 
detect it at all. 

With regard to the use which this singular 
structure may serve in the economy of the 
organ, our present ignorance of the manner in 
which motion is excited renders any explana- 
tion that might be offered of doubtful value. 
But it has appeared probable to me, first, that 
it may act as a mechanical protector and iso- 
lator of the contractile tissue enclosed within it; 
secondly, that its exquisitely smooth exteraal 
‘surface may facilitate those rapid minute 
motions of neighbouring fibres, one against 
another, which may be shown to og¢cur in 
contracting muscle (see Muscutar Motion); 
and, thirdly, that from its apparent similarity 
in structure to the membrane of the neryous 
tubules, which run among the fibres, and be- 
tween which and the proper contractile tissue 
it seems certainly to intervene, as well as 
from its extensive contact and union with 
the surface of the contractile tissue, it may be 
the conducting medium of that influence, 
“whose mode of propagation the late disco- 
_very of the loop-like termination of the nerves 
in muscle has hitherto only seemed to render 
more inexplicable than ever. 
fir Of the extremities of the elementary 


res, and their attachment to other struc- 
ures.—Every fibre is fixed to fibrous tissue, or 
to something analogous to it; but an accurate 
€xamination of this difficult subject gives no 
‘countenance to the ordinarily received opinion 
‘that this tissue is prolonged over the whole fibre 
from end to end, as its cellular sheath; nor is 
this view reconcileable with the physical require- 
ments of the case. After many trials I have 
hever succeeded in isolating a muscular fibre 
with the tendinous fibrille pertaining to it, in 
ther Mammalia or Birds; but this may be 
VOL, III. : 


513 


oceasionally accomplished in Fishes, and in 
certain muscles of insects. In these examples 
the minute detachment of the fibrous tissue 
may be seen to pass and become attached to 
the truncated extremity of the fibre. The fibre 
ends by a perfect disc, and with the whole 
surface of this disc the tendon is connected 
and continuous (fig. 297). The sarcolemma 


Fig. 297. 


Extremity of an elementary fibre, from the Skate 
( Raia Batus), shewing its attachment to tendon. 
a, a, line of union between the two structures, 
b, tendon. ! 
ec, muscle. 


ceases abruptly at the circumference of the 
terminal disc, and here some small part of the 
tendinous material appears to ‘be joined to it. 
The same disposition may be well seen in the 
legs of certain insects (fig. 293). In other 
cases, where the muscle is fixed obliquely to 
a membranous surface, each fibre is obliquely 
truncated at its extremity, at an angle deter- 
mined by the inclination of its axis, instances 
of which may be seen in the limbs of Crus- 
tacea, and elsewhere. 

9. Development.—The researches of Valentin 
and Schwann have shewn that a muscle con- 
sists in the earliest stage of a mass of nu- 
cleated cells, which first arrange themselves in 
a linear series, with more or less regularity, 
and then unite to constitute the elementary 
fibres. As this process of agglutination of the 
cells is going forward, a deposit of contractile 
material gradually takes place within them, 
commencing on the inner surface and ad- 
vancing towards the centre, till the whole is 
solidified. The deposition occurs in granules, 
which, as they come into view, are seen to be 
disposed in the utmost order, according to the 
two directions already so often mentioned. 
These granules are the sarcous elements, and 
being of the same size as in the perfect muscle, 
the transverse stripes resulting from their appo- 
sition are of the same width as in the adult; 
but as they are very few in number, the fibres. 
which they compose are of corresponding 
tenuity. From the very first period of their for- 
mation these granules are parts of a mass and 
not independent of one another, for as soon 
as solid matter is depgsited in the cells, faint 

2k 


S14 


indications of a regular arrangement in gra- 
nules are usually to be met with. It is com- 
mon for the longitudinal lines to become well- 
defined before the transverse ones. When 
both are strongly marked, as is always the case 
at birth, the nuclei of the cells, which were 
before visible, disappear, being shrouded from 
view by the dark shadows caused by the mul- 
titudinous refractions of the light transmitted 
through the mass of granules; but, as before 
stated, they can still be shown to exist by im- 
mersion ina weak acid, which, while it swells 
the fibrinous material of the granules and 
obliterates their intervening lines, has no action 
upon the nuclei. 

6. Of the unstriped elementary fibres.—This 
variety possesses far less interest than the other 
in consequence of its apparent simplicity of 
structure. The fibres consist of flattened bands, 
generally of a pale colour, bulged at frequent 
intervals by elongated corpuscles similar to 
those of striped muscle, and capable of being 
displayed by the same process (fig. 298). The 
texture of these fibres seems to be homoge- 
neous. By transmitted light they have usually 
a soft, very finely mottled aspect, and without 
a darkly-shaded border. Sometimes the mot- 
tling is so decided as to appear granular, and 
occasionally these granules are arranged ina 
linear series for some distance. This condition 
is probably an approximation towards the struc- 
ture of the striped fibre, for I have observed 
the granules to be about the size of the sarcous 
elements already described. It is generally to 


be seen more or less distinctly in the gizzard 
of Birds, and I have now and then met with it in 
the fresh muscle of the stomach, intestinal 
canal, urinary bladder, and uterus of Mam- 
malia. The ordinary diameter of the unstriped 


Fig. 298. 


nstriped bres the human colon. 
a, treated with acetic acid, and shewing the cor- 


puscles. 
b, fragment of a detached fibre, not touched with 
acid. ; 


MUSCLE. 


fibre is from gpsoth to gahsth of an inch. m 
this account oie appearance of these fibre: 
might be expected that their discrimination 
from ane tissues would be often difficult. 
And, in fact, it is so to an inexperienced eye. 
The peculiar texture, however, the size, the oft 
margin, and, above all, the presence of nume: 
rous elongated oval corpuscles, with two 
three granules in their centre, are characters 
which, taken together, L believe to be decisive 
As a number of fibres usually take a paral 
course together, the bulgings occasioned 
the corpuscles give rise to partial longitud 
shadows, extending for some way it 
corpuscles, in the intervals of the fibres. Aj 
these irregular longitudinal shadows occ 
ec uniformly throughout an g 
bres, and as some are necessarily out ¢ 
while others are in focus, the whole mass co 
monly presents a very confused reticul: 
pearance, which has given rise to an alm 
universal notion that these fibres do, in reali 
interlace one with another, and do not r 
parallel. This notion, however, is, in @ 
cases, erroneous. It is doubtful whether 
fibres are invested in a sarcolemma: none 
hitherto been detected in an unequivocal n 
ner. It is also still a matter of specu 
how they terminate, or whether they in 
instances have a termination. In the cas 
the more or less circular set of fibres, in lc 
the small intestine, for example, it is uncet 
whether each fibre surrounds the ca 
returning into itself as a ring, or, me 
once, as a spiral, or whether it only 
tially pts § it, the rest of the circle b 
completed by others. Whether the are 
tissue (the representative of the fibrous) 
is always found in connection with these 
serves to give them an attachment by u 
with their extremities, or by involving the 
its meshes, 1s also altogether unknown. 
the gizzard of Birds the ends of the fibres 
united to white fibrous tissue, thus m : 
approximation to the striped fibre, as th 
in colour. But I have not been able, 
diligent search, to detect the true trans 
stripes, which Ficinus describes to exist i 
organ. 1 
Of the mode of aggregation of the 
tary fibres—The two kinds of fibre 
structure has now been described, are 
gated into masses of very various sh 
bulk, and supplied with areolar tissue, 
and nerves, so as together to form the 
termed muscles. But if we trace these 
downwards through the animal scale, we 
to examples in which solitary fibres exi: 
out any such appendages, and yet e€ 
performing the office of, and truly con: 
a perfect muscle. And even many f 
found, so far smaller than the usual 
sions as to consist of only one or tw 
series of sarcous elements, and these 
only visibly present near the centre of th 
where developement is most advai e 
the contractile energy greatest. In sucht 
and simple forms we may ea tr 
from the striped towards the unstr 


Vic 


iverecalic 


iF 


= 


\ ad 


eae 


MUSCLE. 


the transverse lines being often irregular, 
broken, or faintly marked. And we may also 
discern a clue to the meaning of the structural 
condition which is found in the complicated 
muscles of the higher animals. The essential 
contractile material is the fibre, and its mass 
is accurately proportioned to the power de- 
manded. If this is below that of a single 
elementary fibre, the fibre is reduced in pro- 
portion ; if more is required than one fibre can 
Supply, the size of this is not increased but its 
number multiplied. The point at which an 
increase in number supersedes one in size, is 
that which has been already stated to be the 
average bulk of the fibre. This differs in the 
different classes of animals, and corresponds 
with the demand there may be in each class 
for vascular and nervous supply. For by the 
very constitution of the contractile materal, it 
can receive neither vessels nor nerves into its 
interior substance, and therefore it must be 
itself subdivided further and further in pro- 
portion to the amount of these which are to be 
im contact with its surface. 

In the compound organs termed muscles, 
the fibres are usually disposed in parallel sets 
of 10, 20, 30, or more, surrounded and held 
together by a delicate areolar tissue, which 
penetrates more or less among the individual 
fibres, but does not necessarily invest each one 
of them from end to end, as it is frequently 
described to do. Where the fibres are not very 
large, it is often difficult to discern any areolar 
tissue at all in connexion with them. ‘These 
first sets admit of considerable motion on 
one another, in consequence of the looseness 
of their areolar sheath. Like the elementary 
fibres themselves their figure is polygonal, for 
= in their turn are arranged (if the muscle 
be large enough) into secondary sets, and are 
flattened by being pressed together. These 
= are aggregated into tertiary sets, and 

se into still larger ones, according to the 
size of the particular organ. All these sets 
partake of the polygonal figure of the elemen- 
tary fibres; except the portion that forms a part 
of the general exterior of the muscle, which is 
usually more or less rounded. As the packets 

of fibres are larger, so their angles are more 
rounded, and their surface covered with a more 
abundant areolar sheath, and they approach, 
in fact, to the condition of a perfect muscle, 
which is itself included in an envelope of 
areolar tissue. Their angles are thus rounded 
in consequence of the greater quantity of areo- 
lar tissue, and of the larger size of the vessels 
and nerves that occupy their intervals. For the 
same reason the elementary fibres themselves 
* are less sharply angular, when very small, as in 
Birds, because the vessels accompanying them 
are proportionally more abundant, and occupy 
more space in their intervals. 
‘ arrangement of the elementary fibres 
into these packets has received more attention 
than its importance deserves, and anatomists 
have endeavoured to afhx definite names (fasci- 
culi, lacerti, &e.) to certain sizes of them. 
But no division of this kind is to be found in 
nature. It may be safely said that packets of 


' 


315 


every possible bulk exist from the simple set of 
two or three fibres, to those of many thou- 
sands, these last being subdivided with the 
greatest irregularity. And it is only in muscles 
possessed of some thickness that any such 
package in sets is to be met with. The ab- 
dominal plane muscles, which contain such an 
arrangement in the larger animals, are, in the 
smallest, composed of a single unbroken layer 
of elementary fibres. A similar diversity exists 
between rnuscles of different size and shape in 
the same animal. In the gluteus maximus, 
which is liable to pressure and change of 
position from its peculiar situation, the fibres 
are made up into lacerti, about one-quarter of 
an inch thick, surrounded with a dense areolar 
sheath, and attached loosely to one another ; 
while the glutei situated underneath are, like 
the psoas, unprovided with such dense septa 
of areolar tissue, and seem more uniform 
throughout. 

From these and many other considerations 
which might be adduced, it may be clearly 
seen that the mere aggregation of the elemen- 
tary fibres in a muscle into larger or smaller sets, 
is determined solely by its own peculiar cir- 
cumstances and exigencies, and is not of a 
nature to demand particular description in so 
general an account as the present. 

The direction of the elementary fibres of vo- 
luntary muscles is usually straight, between 
their points of attachment, which are always 
some form of the fibrous tissue. This tissue 
may be so arranged as that the sets of mus- 
cular fibres passing from it, may be either 
ers or oblique to one another, but the fibres 
orming any one set are generally placed in a 

arallel series. If the fibrous tissue form a 
aminar expansion on the surface of a muscle, 
the muscular fibres pass off from it obliquely, 
either to a similar expansion on the opposite 
surface or to atendon. If they arise from an 
extensive surface of bone (i. e. of periosteum) 
they conduct themselves in a similar fashion, 
and also if they pass from a line of tendon or 
of bone. In all these cases the muscle may 
be styled penniform. If a thread or sheet of 
fibrous tissue dip into the interior of a muscle, it 
gives origin to the muscular fibres on both 
sides, and they diverge from it obliquely: 
such a muscle is styled doubly penmiform. 
When several such sheets enter the muscle at 
both extremities, and give attachment to the 
fibres obliquely placed in the intervals, the 
muscle is styled compound penniform, as the 
deltoid. 

One result of the varied arrangement of the 
tendinous fibres with regard to the muscular, 
is the production of symmetry and beauty of 
form ; a second is convenient package; a third 
is the adaptation of the particular muscle to the 
kind and amount of exercise which is required 
of it. Where a great mass of fibrous tissue runs 
into a muscle, the number of fibres and their ob- 
liquity is very much increased, while the length 
of each is diminished ; and, as a general result, 
the power of such a muscle is augmented 
while the extent of its contractions is limited. 
The same mass of contractile material may be 

212 


516 


arranged as a few long fibres (as in the sar- 
torius), or as many short ones (as in the 
_Tasseter). In the former case its con- 
tractions would be characterized by their ex- 
tent, in the latter by their power; for, ceteris 
paribus, the extent is as the length, the power 
as the thickness. 

The terms origin and insertion are employed 
with great convenience in ordinary anatomical 
Janguage to denote the more fixed and the more 
moveable attachments of muscles. In human 
anatomy general consent has sanctioned their 
use, and even, with few exceptions, their par- 
ticular application to each muscle in the body, 
although this assignment is in many cases arbi- 
trary, in consequence of its being impossible to 
determine which attachment is the more fre- 
quently the fixed one. 

The arrangement of the fibres in the heart 
has been already fully treated of in this work. 
(See Heart, Fibres of.) 

In the muscular coat of the alimentary canal, 
of the bladder, and uterus, the unstriped fibres 
are disposed, as in the heart, so as to enclose 
a cavity, but without having, as in that organ, 
any point at which they can be said to com- 
mence or terminate. In the alimentary tube 
they are arranged in two laminee, the respective 
fibres of which take a course at right angles to 
each other. In the bladder the arrangement is 
reticulate. The elementary fibres form sets 
of variable thickness, which at numerous 

ints send off detachments to join neigh- 
-bouring bundles, whence has sprung the notion 
that the fibres are heanghell. it is mani- 
festly, however, the sets of them only that are 
branched, the unstriped like the striped fibres 
being invariably simple from end toend. In 
the uterus the disposition of the fibres is essen- 
tially similar, calculated to allow of great 
variety in the capacity of the cavity they 
encircle. 

Of the areolar tissue of muscles-—This tissue 
is much more abundant in the voluntary than 
in the involuntary muscles. In the former it 
forms an external investment, which sends 
septa into the intervals between the larger and 
smaller packets of fibres, and thus enables 
them to move in some degree independently 
of one another. The density of these general 
and partial sheaths is proportioned to the 
amount of pressure to which the organ may be 
subject, as is exemplified in the superficial 
muscles of their back, and in those superficial 
muscles generally where a fibrous aponeurusis 
does not perform the same office. e areolar 
tissue does not usually clothe every individual 
fibre from end to end, giving it a cellular 
sheath, except in cases where the elementary 
fibres are of large dimensions. Besides the 

tection the areolar tissue affords to the mus- 
cular fibres, it admits of motions between 
them. But it must also serve the important 
office of limiting undue motions of one part 
of a muscle on another part, by its form- 
ing a connecting bond between neighbouring 
bundles. But a principal use of it appears to 
he that of furnishing a resisting nidus in which 
the delicate vessels and nerves can traverse¢ the 


MUSCLE. 


interstices of the fibres, and by which they 
can be protected from hurtful dragging during 
the unequal and oscillating movements of the 
fibres of a voluntary muscle during its state of 
activity. This idea is su ed by the fact 
that searcely any areolar tissue exists in the 
heart or in the unstriped muscles generally. — 
In the heart, though the contraction is power-— 
ful, it is instantaneous or nearly so, and there+ 
fore probably more uniformly diffased, so that 
neighbouring fibres must be less moved on one 
another than in the more sustained contraction — 
of a voluntary muscle. Moreover the mutual 
intertwining of even the elementary fibres in 
this organ is, in many parts of it, so intricate, — 
as to contribute much to their mutual support. — 
And in the other mvoluntary muscles, the con-_ 
tractions are 98 baer evenly progressive - 
along the fibres of the same set. 7 
Of the bloodvessels of muscles—The arteries 
and veins of muscles commonly run together, 
and most of the arterial branches, to within 
two removes from the capillaries, are accom- 
panied by two vene comites. invariably 
more or less across the direction of the 
fibres, divide and subdivide, first in the in- 
tervals between the larger sets, then between t 
smaller sets, till the ultimate twigs insinu 
themselves between the fibres composing the 
smallest bundles, and break up into their capil- 
lary terminations. In this course the vessel 
supply the areolar tissue, their own coats, and 
the attendant nerves. The capillary plexus of 
the areolar membrane consists of irregular 
pretty equal-sized meshes, and contrasts strong! 
with that of the muscular tissue itself. The 
proper capillaries of muscle are quite chara 
teristic in their arrangement, so that a per 
who has once seen them can never afterw: 
mistake them, They consist of longitud) 
and transverse vessels, the longitudinal alway 
following the course of the el ib 
and lying in the intervals between them, th 
transverse being short communications pla 
at nearly equal distances between the longit 
dinal ones, and crossing nearly or quite 
versely over or under the fibres. mann 
in which the longitudinal vessels are 7 
in relation to the fibres, is seen in fig. 
where I have represented them as : 
seen on a transverse section. ue 
occupy the iuterstice between three or m 
fibres, but sometimes also the space bet 
the contiguous surfaces of two fibres. “ 
length of the longitudinal vessels does 
usually exceed the twentieth of an inch; ino 
words the terminal twigs of the artery and : 
pertaining to the same aa are se 
further than that apart. length of 
transverse anastomosing capillaries neces: 
varies with the thickness of the fibres” 
which they pass (fig. 299). The diamet 
the capillaries of muscle varies like tha : 
others with the size of the blood- particles 
the animal. It is, however, only just suffiel 
to allow of the particles to pass. If a 1 ij 
ment of a frog’s oe ae fresh, | 
examined, series of blood-particles will 
seen in the longitudinal - capillaries. 


ee eee 


MUSCLE. 


—- 


View of the capillaries of muscle (part of the latis- 
simus dorsi of u mouse, where it consists of a single 
sheet of fibres ), 

4@, a, terminal twig of the artery. 
6, b, terminal twigs of two neighbouring venous 

Beeches, anastomosing, and carrying off blood 

the same capillary net-work c, c. 
¢, an elementary fibre, to show the relative size 
and direction of those to which the capillaries here 
represented are distributed. 


particles are compressed and elongated, some- 
times to a great extent, evidently by the nar- 
rowness of the canal which contains them. 
It may seem at first sight not doubtful that in 
the living creature these elastic blood-discs are 
similarly elongated in their passage through 
the vessels of muscle, but the admirable re- 
searches of Poiseuille will perhaps serve to 
explain this appearance without our being 
driven to suppose the presence of so formid- 
able an obstacle to the capillary circulation 
} et these organs. It is more probable 
that the contraction of the vessels and the com- 
pression of the blood-discs occur, on some of 
the contents of the vessels being permitted to 
escape by the severing of the fragment for 
microscopic examination. The coats of the 
capillaries of muscle consist of a simple diapha- 
nous membrane, in which a few irregular-shaped 
eytoblasts occur at infrequent intervals. 
or the nerves of muscle-—The distribution 
f the nerves through muscular structures has 
always been a subject of great interest with 
those who looked to this line of inquiry for 
some clue to the explanation, either of that 
wonderful active connexion subsisting between 
them, or of the nature of the contractile act 
itself. But though the anatomical results ac- 
cruing from this inquiry are of a highly satis- 
factory kind, considered in themselves alone, 


517 


= they cannot be said to have hitherto contri- 
uted, in any great degree, to the elucidation of 
these mysterious questions. The best mode of 
inspecting the arrangement of the ultimate ner-' 
vous twigs, is to select a very thin muscle, (as 
one of the abdominal muscles of any small 
animal, or one of the muscles of the eye of a 
small bird,) to steep it in weak acetic acid, and 
then thin it out under the compressorium. The 
primitive tubules of the nerve may then be 
readily distinguished with a power of 100 to” 
200 linear. They separate from one another, at 
first in sets, afterwards in twos, threes, or fours, 
and if these be followed they will be found 
ultimately separating from one another, form- 
ing arches, and returning either to the same 
bundle from which they set out or to some 
neighbouring one (fig. 300). In this loop- 
like course they accompany to some extent the 
minute bloodvessels, but do not accurately 
follow them in their last windings, since their 
distribution is in a different figure. They pass 
among the fibres of the muscle, and touch the 
sarcolemma as they pass; but as far as present 
researches have informed us, they are entirely 
precluded by this structure from all contact 
with the contractile material, and from all im- 
mediate intercourse with it. How then shall 
we explain the transmission of the nervous in- 
fluence to a material thus enclosed? If it 
were wise or safe to go a single step in advance 
of pure observation on so abstruse a question, 
we might suggest, resting on the seemingly 
sure ground of exact anatomy, that this in- 
fluence must be of a nature capable of ema- 
nating beyond the limits of the organ which 
furnishes it. But further than this, as to how, 


or to what extent this influence may so emanate, 


Fig. 300. 


L 


Loop-like termination of the nerves in voluntary muscle. 
After Burdach. 


or as to what may be its nature, it would, per- 
haps, in the present state of knowledge, be 
hardly warrantable even to speculate. 

d. Of the distribution of the striped and 
unstriped fibre in the body.—The striped fibre 
is met with in all the voluntary muscles, and 
in a few involuntary, as the constrictors of the. 


518 


pharynx aud the museular coat of the cso- 
phagus, and the heart. In the cesophagus it 
appears to be mingled with the other variety to 
a somewhat uncertain extent. In some speci- 
mens from the human subject I have been un- 
able to detect any striped fibres in the lower 
half of that tube, either in the circular or 
longitudinal layer, but in other examples they 
have been traceable to within an inch of the 
stomach. Among the lower animals consider- 
able differences occur, as has been well pointed 
out by Mr. Gulliver,* who observes that in 
general “the muscular fibre of animal life 
(striped) extended further towards the stomach 
in the outer than in the inner layer of the eso- 
Phageal muscular sheath.” In several animals 
this gentleman found the striped fibres even on 
the stomach (as in the Rabbit, Lepus cuniculus, 
Linn., the Sheep, Ovis aries, Desm., the Sloth 
Bear, Ursus labiatus, Blainv.) while in many 
others he met with them to within a very short 
distance of that cavity. Dr. Todd has also 
shewn them to me on the glandular pouch at 
the cardiac extremity of the stomach in the 
Dormouse. It is stil] unknown in what manner 
the two varieties of fibre are arranged at this 
point of junction, some supposing that they 
are simply intermixed, others that they pass 
into one another by imperceptible gradations. 
The former of these views is that which appears 
Most consonant with my own observations. 
Mr. Skey considers + that the fibres of the heart 
“‘ possess a somewhat compound character of 
texture,” and this opinion seems highly pro- 
bable. They possess, it is true, the transverse 
Stripes indicative of an arrangement of particles 
in parallel series, but there is frequently a want 
of that uniformity and precision in this appear- 
ance which so remarkably characterize voluntary 
muscle. The cross lines are apt to be broken 
and interrupted, and are sometimes difficult to 
discover at all. This condition is well repre- 
sented by Mr. Skey in fig. 5 of his second te 
In some of the smaller and lower animals the 
particles never form transverse stripes. These 
fibres, as explained by him, are smaller than 
the average diameter of the voluntary muscles 
of the same subject by two-thirds, and in most 
parts of the heart they are not aggregated in 
parallel sets, but twine and change their relative 

ition. Striped fibres have been found in the 
iris, in the small muscles of the ear, and in 
those muscular fasciculi that surround the ure- 
thra immediately in front of the prostate. They 
are also found in the sphincters of the anus and 
vagina. 

e unstriped fibre is met with in the ali- 
mentary canal from the middle of the ceso- 
ong to the rectum, and constitutes the double 
ayer investing that tube. It also forms the 
muscular coat of the bladder and that of the 
uterus. The dartos owes its contractility to the 
presence of fibres of this variety, which, in con- 
sequence of the abundant admixture of areolar 


* Proceedings of the Zoological Sociéty of Lon- 
don, No. 81, Sept. 1839. 
+ Phil. Transactions, 1837, p. 381. 


MUSCLE. 


statement. They appear to me to have all t 


tissue, has not hitherto been clearly recognized; 
but it may be detected by the addition of acetic © 
acid, which, by bringing into view the peculiar — 
corpuscles it contains, distinguishes it from both 
the white and yellow fibrous elements of the 
areolar — But even without this pees 
test, to which some may object, it is ible 
to discover this form of becsecii fibre in the 
dartos, by the characteristic ap ces 

have been already attributed to it. Since satis- 
fying myself of the real existence of this fibre — 
in the dartos, | have on many occasions de- — 
tected a very decisive ee action advan- 
cing from one side of the scrotum to the other, 
and continued for a considerable period, yet of 
a kind which it was impossible to refer, with — 
any degree of probability, to the cremaster. 
In one case particularly, occurring in the prac-— 
tice of Mr. Fergusson, where the tunica dartos — 
was much hypertrophied, in connection wit 
an old stricture of the urethra, we observed thi 
peristaltic contraction of a very vigorous 
scription. The fibres which have been ¢ 
scribed as peculiar to the dartos seem to be 
nothing more than a certain modification of the 
areolar tissue in that region. In the 
cavernosa penis of the horse there is a large 
quantity of this kind of fibre, as may be ascer- 
tained by microscopic examination, although 
Professor Miiller* seems indisposed to consid 
it really muscular. He states that “ viewed 
the microscope these fibres do not n 
resemblance to muscular fibres,” but my ow 
examinations of them have not confirmed 


OTDO 


characteristics of this variety, and by t 
acid are seen to contain a great number of : 
puscles. Moreover they appear to consist che 
mically of fibrine. Professor Miiller has fail 
in exciting contraction in them in the 
horse, but this is not a conclusive fact as 
their nature, for it may be and probably a he 
case that they do not act unless strete 

erection of the organ. In the quiescent co 
tion of the part they may be considered to 
in a contracted state, like the muscular co 
an empty intestine, and so would natu 
appear to be unaffected by the stimul 
galvanism. The erection of the penis § 
with great probability to be attributab 
pressure exercised on the superficial ve 
the organ by a continuation of a structure 
logous to the dartos, and certainly con! 
the unstriped muscle, which is continues 
the base of the penis under the skin. 
erection of the nipple also occurs, on an 
chanical irritation, with a motion so very 
resembling the peristaltic action of imu 
fibres, that I have little doubt such wou 
found, constituting a layer, under the skin 
region. And it may be matter of ing 
far the general contractility of the skin 
pendent on a diffusion of this tissue, — 
quantities, throughout its areolar s : 
excretory ducts of all the larger glands a 
to possess a covering of fibre belonging 


d ive 


hy 
oy 


ens 
* Physiology, by Baly, second edition, p.' 


MUSCULAR MOTION. 


variety. Such is the case with thé ductus cho- 
ledochus in Birds, and probably in Mammals, 
and in the ureters and vasa deferentia. The 
bronchial tubes may be mentioned under this 


head as the best marked example of this ar-_ 


rangement. The trachealis muscle consists evi- 
dently and entirely of the unstriped fibres, and 
the same may be traced down the brorchial 
ramifications as far as the air-cells themselves, 
though not into them. The distinctive charac- 
ters of this form of muscle may here be une- 
quivocally discerned, and if anatomists had 
been better acquainted with them, there would 
not have been room for those disputes regarding 
the muscularity of the bronchial tubes which 
have so long attracted the interest of practical 
physicians. Recently, indeed, there has been 
added to the satisfactory evidence of anatomy 
the well proved fact that these fibres may be 
excited to contraction by the galvanic stimulus.* 
In the case of other glands it is still unknown 
how far the muscular coat invests the ramifica- 
tions of the duct; it is most likely that it gra- 
dually ceases a short way within the organ, 
and at least it seems clear that no portion 
of the secreting membrane itself is ever in- 
vested by it. 

e. Of the distribution of the striped and 
wnstriped fibres in the animal kingdom.— 
The striped fibres have been found in all ver- 
tebrated animals, and in Insects, Crustacea, 
Cirropods, and Arachnida. Future researches 
will probably discover them even more exten- 
sively diffused. But in the lower animals, 
especially when they are of small size, we find, 
as formerly mentioned, that the distinctive cha- 
racters of the two varieties begin to merge into 
one another and be lost. The transverse stripes 
grow irregular, not parallel, interrupted ; a fibre 
at one part will possess them, at another part 
wili be without them; and even the peculi- 
arities of the unstriped fibres are sometimes no 
longer to be met with in parts which are un- 
doubtedly muscular, as the alimentary canal 
of small insects. It is evident that here the 
elementary fibres, if of their usual bulk, would 
be greatly disproportioned to the requirements 
of the case, and consequently even the minute 
ultimate fibre seems to be reduced within 
limits which remove from it those anatomical 
characters by which alone we can positively 
aver its existence. Considering, however, the 
circumstances which have been already ad- 
verted to in this article, as determining the size 
of the elementary fiore in all animals, we 
Should not be justified in denying the same 
_ muscular tissue to exist here which in the higher 
and larger forms of life assumes the figure 
and bulk of the elementary fibre; and by the 
same mode of reasoning it may be concluded, 
that a tissue having the same properties as the 
Striped fibre, and indeed essentially identical 
with that of which they consist, may possibly 
be the effective agent to which are due those 
wonderfully vivacious movements witnessed in 
the bodies of many of the minutest infusoria, 
where the best microscope can hardly do more 


* Dr. Williams, on Discases of the Chest, last. 


edition, Appendix. 


519 


than discern the organs thus put in motion. 
And it seems far from an unphilosophical view 
of the nature of ciliary motion, to refer it to 
the contractions of a ‘tissue not entirely dif- 
ferent in kind from the muscular. The ele- 
mentary fibres of muscle, diminutive though 
they be, and hardly discernible with the eye, 
are yet gross organs in comparison with those 
which the microscope enables us to conceive 
capable of being formed out of them, without 
any necessary destruction or even injury of 
their contractile power. 

J. Chemical constitution —There is little to 
add on this subject to what will be found under 
the head of Fisrine. By the aid of the mi- 
croscope, however, our knowledge has been 
rendered somewhat more precise, as to the 
chemical properties of the elementary struc- 
tures existing in the fibres. If any substance 
capable of dissolving fibrine (as liq. ammoniz) 
be added to the muscular fibre, this is seen to 
swell, to lose more or less completely its trans- 
verse and longitudinal markings, and to exhibit 
at once those corpuscles or cytoblasts, which 
before lay concealed among the sarcous ele- 
ments. ‘These corpuscles and the sarcolemma 
are not affected, but the sarcous elements are 
almost entirely taken up. But for however 
long atime the fibre be exposed to the alka- 
line menstruum, there will always remain a 
kind of web, of extreme tenuity and trans- 
parency, from which the sarcous elements ap- 
pear to have been withdrawn. This may be 
seen in a transverse section of a muscle that 
has been thus treated, then washed and dried. 
I have not been able to detect in it any sort of 
structure.* 

( W. Bowman. ) 


MUSCULAR MOTION.— Under this 
head it is intended to consider the contractility 
of muscle, its source, the stimuli that excite 
it, and the nature of the minute movements 
occurring during the act of contraction. 

a. Of the contractility of muscle—This 
subject having already been ably discussed in 
this work (see Contractitity), I shall here 
confine myself to such a brief statement as 
may appear to be required by the advance of 
knowledge since the publication of the article 
in question. 

1. Is it a property inherent in the muscular 

bre? Are we to believe in the ‘ vis insila’ of 
Haller?—The supporters of this opinion have 
always been exposed to the objection that in 
the cases of contraction adduced by them as 
the effect of a topical or immediate stimulus, 
the isolation of the muscle from all connexion 
with nervous fibrils has not been demonstrated. 
Moreover, what has generally been regarded as 
their strongest ground, viz. the statement that 
involuntary muscles are not capable of being 
excited to contraction by irritation of their 
nerves, has lately been shown by the numerous 


(* The principal facts relating to the morbid 
states of Muscle will be found in the articles 
HEART, Morbid States of, and HYPERTROPHY and 
ATROPHY. An historical sketch of the subject 
concludes the article MUSCULAR MoTIon.—ED. ]} 


9 


520 


experiments of Mittlers Valentin, and others, 
to be erroneous amd unworthy of credit. But 
I have elsewhere* adduced the evidence of 
direet microscopical observations made on living 

ments of the elementary fibre of voluntary 
muscle, entirely isolated from every extraneous 
tissue, whether nerve or vessel, to shew that 
this is a property inherent in this tissue, and 
that, whatever be its source, it is capable of 
being brought into action by a stimulus topi- 
cally applied. Thus, when such a fragment is 
examined, contraction is found to occur first 
at its broken extremities, and if water (which 
has long been known to be a rapid exhauster 
of muscular irritability) be brought into con- 
tact with it, it is seen to absorb the fluid 
and to’be excited to contractions, which com- 
mence at the surface. The same thing is fre- 
gently to be met with under a different form. 

particle of foreign matter, as a hair or piece 
of dust, may be included by design or accident 
in the field so as to touch the side of the fibre 
at a single point. When this happens, the fibre 
will often exhibit a contraction so plain and so 
limited to the point touched, as to give un- 
equivocal proof of its being the result of the 
irritation of pressure. 

Theseinteresting phenomena may be observed 
more or less satisfactorily in all animals whose 
fibres retain their irritability for a sufficient 
length of time after removal from the body, 
and the crab and lobster will be found the most 
favourably adapted for the purpose. In many 
reptiles and fishes, also, the steps occur slowly 
enough to be adequately scrutinized. 

The facts in question can admit only of one 
explanation if it be conceded that the mus- 
cular element has been here separated from 
the nervous; and certainly that separation 
has been effected unless the nervous tubules 
send off from their terminal loops a set of 
fibrils which penetrate the sarcolemma and 
diffuse themselves through the contractile ma- 
terial within; a supposition for which there 
exists at present no foundation in the obser- 
vations of the most diligent investigators of 
this subject. 

They will, therefore, probably, be regarded 
as conclusive proof that contractility is a pro- 
perty inherent in the very structure of muscle, 
and capable of being excited to action inde- 
pendently of the immediate instrumentality of 
nerves. 

The determination of this point must have 
a very important bearing on the question of 
the nature and cause of contraction, into which 
no small confusion has been introduced by 
the attempts to account for that phenomenon 
by various hypotheses of electrical action. That 
one, especially, which aims at establishing an 
attraction between distant points of the fibres 
where the nerye crosses them, (the ‘ zig-zag 
hypothesis’ of Prevost and Dumas,) and which, 
with the wrongly interpreted facts on which it 
principally rests, has had an immense, though 
sometimes unperceived influence, ever since it 
was broached, on the whole question of con- 
traction, is entirely refuted by the facts above- 


* Phil. Trans, 1840, p. 487, 


MUSCULAR MOTION. 


_Thiy important question, like the last, is de- 


mentioned. There are some others, sprung out, 
of this, which do not here require more than a 
passing allusion. ae 

2. Suurce of contractility: whence derived? 


bated up to the present day, but seems 
length to have become disenthralled of 
loose hypotheses which have long in 
with its settlement, The discussion may be 
limited to such particulars as seem to be the 
most conclusive. 
It may be observed that the contractility and — 
development of muscle, other things being t iy 
same, are always proportionate to one another, 
Allcauses interfering with development diminis 
contractility. Thus muscles become atrophied — 
and weak by disuse, by lessening their supply” 
of blood, by cutting off their connexion 
the central part of the nervous system. he 
are, on the contrary, augmented both in size 
and power by active use, during which both 
the vascularand nervous parts supplied to them 
are no doubt urged to increased activity. Tow 
is it to be decided whether these changes Of — 
contractility depend on changes of nutriti¢ 
or whether both be not a common 
changes in the amount of nervous power broug! 
to act upon the muscles. Dr. Marshall Mall 
has remarked that in paralysis from disease 
involving the spinal cord or nerves, asting 
of the muscles is far more rapid and complete 
than in paralysis from affection of the bra 
wherein the spinal cord and its connection Wi 
the muscles remains in a normal state; and 
deduction seems at first sight plain and inevi 
able, that it is from the spinal cord that @ 
contractility is derived, or at least that t 
integrity of the spinal system is essential to 
maintenance of that property in the muscle 
An ingenious experiment of Dr. John Reid’ 
however, proves that this is not the case, 
explains the part which the spinal system play 
in respect of this property in the insta 
referred to. ‘“ The spinal nerves were € 
across, as they lie in the lower part 
spinal canal, in four frozs, and both pos 
extremities were thus insulated from their 
vous connexions with the spinal cord. T 
muscles of one of the paralyzed limbs 
daily exercised by a weak galvanic bai 
while the muscles of the other limb ° 
allowed to remain quiescent. This was 
tinued for two months, and at the end of 
time the muscles of the exercised limb ret 
their original size and firmness and conu 
vigorously, while those of the quiescent 
had shrunk to at least one-half of their’ 
bulk, and presented a marked contrast 
those of the exercised limb. The muse 
the quiescent limb still retained their cor 
tility, even at the end of two months; 
there can be little doubt (adds Dr. I 
from the imperfect nutrition of the 
and the progressing changes in their 
structure, this would in no long time have 
appeared had circumstances itted me 
prolong the experiment.” It is clear from” 


td 


PSU! 


iS 
' 


r 


* Edinb. Monthly Journal of Medical Sei 
May 1841, p. 327. ; 


———————— 


MUSCULAR MOTION. 


description that though contractility remained, 
it was diminished proportionally to the wasting, 
in the limbs that had not been exercised. 

The results of this admirably devised experi- 
ment cannot possibly be reconciled with the 
opinion that the spinal cord has any necessary 
or immediate influence in conferring contracti- 
lity on muscles—that it is the source whence 
that property is derived. On the contrary, they 
show in a manner that admits of no dispute 
that both coutractility and nutrition have been 
preserved together by the continued activity of 
the property existing in the fully developed 
organ at the period when the experiment was 
begun ; and hence it is plain, and conformable 
to all analogy, that contractility is a property 
depending for its integrity on a healthy state of 
nutrition, which in its turn requires for its 
support the due exercise of the property it 


_ coniers. 


It might, perhaps, be argued by one dis- 


‘posed to uphold the electrical hypothesis of 


the nervous influence and muscular power, 
that in the foregoing experiments the galvanism 
supplied the place of the intercepted nervous 
communication, by directly furnishing the 
muscles with the endowment of contractility ; 
and it is not easy to meet the objection by any 
decided proof to the contrary. It would be 
very difficult to induce oft-repeated contractions 
in a paraly-ed muscle by any other than elec- 
trical agency; but the refutation of this view 
will be found in the general arguments against 
the identity of the nervous influence with any 
form of electricity. 

Viewed by the light of this and other allied 
experiments, the variation found in the state of 
nutrition of paralyzed limbs is easily accounted 
for. In cerebral paralysis: the muscles are still 
subject to contraction in obedience to reflected 


‘Stimuli through the spinal cord, while in the 


complete spinal palsy and that arising from 
disease of the nerves, they are never excited to 
action; whence their firmness in the former 
compared with their impoverishment in the 
latter case. In the paralysis of the lower limbs 
So graphically described by Pott, and resulting 
from disease propagated to the cord from the 
vertebre, the early symptoms are those of 
irritation, and consist rather of irregular con- 
tractions, probably in part reflex, and which 
the patient is unable to control, than of any 
diminution of actual power in the limbs; and 
it is constantly remarked that in this stage there 
is no loss of size in the affected parts, but 
rather that in the midst of a general emaciation 
consequent on the patient’s confinement, these 
limbs retain their fullness, and even appear 
hypertrophied. Should the malady advance to 
disorganization of the cord, the muscles cease 
to be excited. They become dead to all stimuli 


_ except such as are topically applied, and being 


hever so stimulated, soon become flabby and 
wasted. Thus it would appear that the spinal 
cord in cerebral paralysis serves to ree up 
contractility in the muscles, not by supplying 
them with it, as from a source, but by exhaust- 
ing them through the contractions it excites. 
It is not a charger but an exhauster through its 


521 


nerves ; and as exhaustion alternating with re- 
accumulation is necessary for healthy nutrition, 
and healthy nutrition induces contractility, it 
becomes in such cases an important though 
indirect agent in the maintenance of that pro- 
perty in the muscles. ‘There can be little doubt 
that if muscles completely cut off from the 
nervous centres were submitted to galvanic 
agency at frequent intervals, they would not 
decrease in size, and might, if already atrophied, 
be even augmented in bulk and power; and 
ds some of the vaunted successes obtained 

y galvanism and electricity may be explained 
in this manner. 

There appears to be no argument nor esta- 
blished fact on the other side which invalidates 
the experiment of Dr. Reid, or which does not 
admit of being explained on the ground which 
that experiment substantiates; and the whole 
question 1s still further cleared by the singular 
circumstance that has been often adduced, that 
foetuses born without brain or cord may have 
their muscular system developed and active. 

If, to what has now been advanced, there 
be added the evidence before adduced, that 
this is a property inherent in the very structure 
of muscle, and that it is capable of being 
exerted therein independently of all communi- 
cation with other tissues, it will probably no 
longer remain doubtful that it is a property 
belonging to muscle as a tissue, and that it 
only requires for its perfection that nutrition 
should be perfect. Whatever interrupts nutri- 
tion interferes with it, and it matters little 
whether such interruption arise from the want 
of its own exercise or from deficiency of arterial 
supply, arising from causes either local or 
general. Inertness of a muscle, whether the 
consequence of diseased nerves or otherwise, 
will be attended with more or less atrophy and 
weakness, according to its degree, and to that 
alone. 

For full information concerning the varieties 
in the intensity of this power, and in its dura- 
bility in muscles after systemic death or after 
their removal from connexion with the nervous 
and vascular systems, the reader is referred to 
the article InRITaBILiTyY. 

I would merely remark in corroboration of 
the views there maintained, that in the animal 
series the size of the elementary fibres and the 
consequent amount of their vascular supply, 
independently of the more or less arterial 
quality of the blood, is accurately proportioned 
to their irritability. Thus Birds, whose irrita- 
bility is most exalted and most evanescent, 
have the smallest fibres and the most richly 
supplied with blood, while Reptiles, Fish, and 
Crustacea, in which the irr.tability is most 
enduring, have fibres of large dimensions and 
provided with a vascular web of small com- 
parative size (fig. 286, art. Muscre). The 
same is true as regards the heart compared 
with the voluntary muscles. 

b. Of the stimuli of muscle—The stimuli 
which induce contraction have been classed 
into remote and immediate. Properly speaking, 
the remote stimuli are stimuli to the nerves and 
not to the muscles: they cause a change in the 


522 


motor nerves, which are thus made to excite 
contraction by their immediate and topical 
action on the muscles. Of these the chief are 
volition, emotion, and impreasions carried by 
the afferent nerves to the nervous centres and 
involuntarily reflected thence; but various 
diseases and injuries of the motor nerves, either 
at their origin or in their course, and pressure, 
heat, chemical substances, electricity, gal- 
vanism, &c. applied to their texture, are to be 
ranged under the same head. 

The nature of the change thus induced in 
the motor nerves is entirely unknown. There 
seems, however, no ground for believing that 
it differs with the particular stimulus which 
induces it, and certainly a clear distinction 
ought ever to be drawn between it and its 
exciting cause. The nerves, when this change 
is induced in them, occasion the muscles to 
which they are distributed to contract. The 
stimulus they give is an immediate one, and is 
termed the vis nervosa or the nervous stimulus 
of muscle. It acts topically on the muscular 
fibre. The other immediate stimuli are physi- 
cal and chemical; they are rarely exerted in 
the living body, except in the case of the 
hollow muscles. It has already been stated 
that trustworthy experiments have lately shown 
these to be under the influence of motor nerves 
derived from the spinal marrow, but it seems 
probable that some at least are norma!ly excited 
to contract by direct stimulation, to one form 
of which, that of stretching or distension, they 
are peculiarly liable from their arrangement as 
investments to cavities. All muscles, however, 
may be made to contract by physical and 
chemical stimuli applied to their fibres. 

The effects of water and mechanical pressure 
as immediate stimuli have been already alluded 
to. Chemical substances may be seen to act 
similarly, if they be not so powerful as to 
destroy the texture of the part; and it is pro- 
bable that electrical forces have a like agency. 
An interesting phenomenon has been pointed 
out by Dr. Stokes,* which seems to show very 
clearly that contractions of voluntary muscles 
may be excited by an immediate stimulus in 
the living body. In various cases of phthisis, 
and in others, particularly those attended with 
emaciation, a sharp tap with the fingers on any 
muscular part is instantly followed by a con- 
traction, evidenced by the rise of a defined 
firm swelling at the point struck, enduring 
several seconds before it gradually subsides. 
This is often so prominent as to throw a shadow 
along the skin, and for the moment it might 
almost be mistaken fora solid tumour. That 
it is limited to the point struck is full proof of 
its being a direct effect of the irritation, and 
not produced through the intervention of 
nerves; for a contraction excited in the latter 
mode would be diffused over the part to which 
the nervous twigs irritated were supplied, and 
would therefore frequently extend to some dis- 


tance. 
c. On the visible changes occurring in muscle 


* On Diseases of the Chest, p.397. See also 
Dr. Guy, in the new edition of Hooper’s Phy- 
sician’s Vade Mecum, p. 92. 


MUSCULAR MOTION. 


during contraction.—1. Of the changes essential — 
to ceeetasal muscle in action becomes short _ 
and thicker, and it is well ascertained by 
experiments often repeated that these changes 
in its relative dimensions are accurately pros — 
portioned to one another. The whole organ — 
neither gains nor loses in bulk. oe 
What is true of the organ is true of the 
tissue—in contraction it increases in diar 1 
ter and shortens in a corresponding degree. 
This is all that can be said in general respect- 
ing the visible features of this rem cable 
Ehepeensice. Late investigations, instead of — 
explaining the manner in which contraction 
is effected, by shewing its dependence on 
forces previously understood, have only served — 
to point out the inadequacy of the coarse and 
mechanical hypotheses whi ysiologi ». 
been so prone to confide in, and to make it 
more than probable that they must ever be — 
content to repose upon the fact above stated 
the simplest which the most refined microseo- 
pical analysis can ever disclose. mg 
The intimate connexion between the nerves 
and muscles, both in rest and action, and the 
exquisite organization displayed in the structure 
of those muscles which are most quick and 
energetic in their movements, have powerfully 
contributed to excite the hope that a clue to the 
discovery of the physical mechanism of con- 
traction would one day be found. It mayb 
thought, therefore, a subject of disappointment 
that when at length a close insight into it: 
visible characters has been obtained, and the 
minutest particles which the best instrument 
can discern have been brought under observa- 
tion during their state of activity, the only 
change that can be appreciated in them is th 
which was long ago known by accurate exper : 
ment to occur in the aggregate mass, viz. th | 
they become shorter and thicker. 4 . 
All muscle, after systemic death or ¢ 
removal from the body, undergoes a con 
termed the rigor mortis, which has 
much attention in all that relates to the 


¥ 


zo 


of its approach, its course and duration, at 
the practical bearings it presents. (See Deat 
This phenomenon may be varied by the apy 
cation of stimuli, and is eminently suited 
the display of the minute changes occurt 
in muscle during its active state. _ 
The muscle with stri fibres is peeulis 
adapted for the display of these changes; 
its texture not being homogeneous, but mar 
throughout with perfect regularity into spé 
or particles so minute as to require to bet 
highly magnified before they can be even see 
all, the anatomist is provided with the m 
of detecting movements, which, without 
circumstance, must have remained conces 
It is accordingly by the study of this ¥ 
of the tissue that the results just alluds 
have been obtained. ee 
When a fragment retaining its contracti 
is torn up into its elementary fibres, these 
seen to undergo a slow movement at cert 
points, especially where they have suff 
violence, as at their broken extremities. 1 
movement consists of a shortening and thick 


MUSCULAR MOTION. 


ing of the material composing the fibre, as is 
shown by the general outline of the part, but 
especially by the appearances visible in its 
interior. The transverse stripes, both light and 
dark, become longer and thinner; in other 
words, the discs expand in circumference, 
flatten and approximate to one another; or to 
use another form of expression, the fibrillz 
become shorter and thicker, both in the par- 
ticles composing them and the material con- 
necting those particles (fig. 301). 


Fig. 301. 


¢ 
tary fibre (from the eel ) partiall: 


Frag t of an elem 
contracted in water, 

@, uncontracted part. 
 b, contracted part, along the border of which, at 
' ¢, ¢, the sarcolemma is raised from the surface 
by the water that has been absorbed, that has 
thereby caused the contraction, and by it has been 
expelled from the contractile mass. 

These changes are always local, or partial, 
and it is most evident from the characters they 
constantly present, that they are not limited to 
any determinate regions, points, or segments, 
but occur indifferently wherever the exciting 
cause may chance to be exerted. Neither discs 
nor fibrille appear to have the smallest share, 
as aggregations of particles bearing those par- 
ticular forms, in producing the phenomena of 
contraction. A contraction is never bounded 
to a particular number of discs or fibrille, and 
is never accurately limited by the interval 
between two discs. It constantly happens that 
at the edge of the contracted part several discs 
are only partially engaged in it. A contraction 
generally, when commencing at the broken 
end of a fibre, occupies its whole width there; 
but when it commences at the border of the 
fibre it may be confined to a portion of many 
discs. And, further, a contraction never occu- 
pies the whole length of a fibre or fibrilla at 
once. A contraction excited in an elementary 
fibre by the contact of a hair extends into the 
Mass equally in all directions, as we might 
Suppose it would do, if the mass were homo- 
geneous. 

In a word, an attentive study of these inte- 
resting phenomena has convinced me that in 
the bare fact of contraction the build of the 
fibre is an item of no importance whatever: the 
exquisite symmetry displayed in the apposition 
of its component particles is, as it were, dis- 
regarded and overlooked, while the whole pro- 
cess is to be referred to the material itself, the 
ultimate tissue, whose property is contractility. 
This property appears to reside both in the par- 
ticles and the substance connecting them. 

The ultimate movements, therefore, on which 
contraction depends, whatever they may con- 


sist in, are molecular, and far beyond the reach 
of sense. 


Magnified 300 diam, . 


523 

It will be perceived that this view of the 
subject is the only one which can harmonize 
the fact of contraction in voluntary muscle 
with the same phenomenon in structures which 
have no complicated internal arrangement of 
particles. In regarding contractility, therefore, 
as a property of the living muscular fibre in 
general, it is meant that it resides in it asa 
property without which it would not be muscle, 
and in such a manner that no particle, how- 
ever microscopic, can be detached from muscle 
which does not of itself, and independently of 
the rest, possess this property, as long as it 
possesses vitality. 

It follows from what has been advanced that 
those hypotheses which refer contraction to a 
force exerted between determinate but distant 
points of the fibre, as where the nervous fibrille 
cross it, or at intervals such as Miiller* has 
sometimes seen in insects, must fall to the 
ground. They are so entirely incompatible 
with the facts above stated that it can scarcely 
be necessary to dwell at length on the other 
reasons for rejecting them, or on the explana- 
tion of the phenomena adduced in their support. 
The main fact on which they have been built 
is that long ago mentioned by Hales, and more 
recently studied with minute care by Prevost 
and Dumas, viz. that in the abdominal muscles 
of the frog detached and excited by galvanism, 
the elementary fibres are seen to be thrown 
more or less into a zig-zag form. It is evident 
that in interpreting what they saw these eminent 
physiologists mistook the relaxed fibres for 
contracted ones. In conducting such experi- 
ments many precautions are required, and at 
the best, nothing of the real process of contrac- 
tion can be witnessed. As Miiller correctly 
remarks, the muscle is too thick to be seen 
under a high power. Besides, the shock of 
galvanism causes only an instantaneous con- 
traction, during which the muscle is so agitated 
that it is in vain to attempt to.examine its con- 
dition. It gets out of the focus of the instru- 
ment. What is seen afterwards is not the 
contraction but its result, viz. an approximation 
of the extremities of the fibres. If the galvanic 
shock has acted uniformly on all the fibres 
(which is rare), they all remain straight; but if 
on a part only, those which have escaped con- 
traction are thrown into zig-zags by having their 
ends brought nearer through their cellular con- 
nexion with neighbouring contracted fibres. It 
is most natural that the precise point of such 
flexures should often be determined by the 
passage of nerves or vessels across the fibres. 
This is corroborated by the circumstance that 
relaxed fibres fall at once into zig-zags when 
their ends are made to approach by mechanical 
means. 

MM. Prevost and Dumas have themselves 
drawn attention to an example of shortening 
without zig-zags in the case of the distended 
abdominal muscles of the female frog before 
spawning. They found that the fibres of those 
muscles when cut across remained straight, 
after shortening from 145 to 107 millimetres. 


* Physiology by Baly, p. 889. 


524 


Independently of the immense disadvantage 
at which the hypothesis in question supposes 
the force to act, (viz. either’ between the par- 
ticles at the retiring angles only of the zig-zags, 
or between the distant angles themselves,) it 
seems quite inconsistent with the able experi- 
ments of Schwann, which show that the power 
of a muscle diminishes in a direct ratio with 
the degree of its contraction. With these 
experiments, indeed, any hypothesis is at 
variance which is based on the idea ofan 
attraction between isolated and separate points 
or particles, as, for example, the sarcous ele- 
ments, for it cannot be conceived but that such 
an attractive force would augment in a multi- 
plying ratio with the proximity of the points 
attracted. 

2. On passive and active contraction. Pas- 
sive contraction.—Passive contraction is that 
which every muscle is continually prone to 
undergo, independently of stimuli, and by the 
mere quality of its tissue. The muscles are 
ever kept on the stretch by the nature of their 
position and attachments, and cannot have their 
ends so approximated by attitude or other- 
wise, as that their tendency to shorten them- 
selves shall cease. If, for example, the rectus 
muscle of the thigh have its extremities brought 
as near together as can be effected artificially 
by posture, they would yet be found to ap- 
proach still nearer on being freed from their 
attachment to the bones. This tendency to 
contract has been distinguished by the term 
retractility, from its being manifested by the 
retraction that occurs when the belly of a mus- 
cle is cut across. But, in this instance, the 
retraction would appear to be in part caused by 
an active contraction excited by the stimulus of 
the injury. It has also been styled tonicity. 
The ive contraction of muscles continually 
opposes their elongation by the action of anta- 
gonists, and restores them when that action 
ceases. It is that which accommodates them 
to an attitude artificially given, when no mus- 
cular effort is required to maintain it. When 
no active contraction is present in a limb, the 
passive contraction remains, and being brought 
to a state of equilibrium in all the muscles by 
their mutual antagonism, the limb is said to be 
at rest. This is the general condition during 
sleep. The passive contractility of muscles, 
therefore, is being ever exerted, without being 
attended by fatigue; there seems no good rea- 
son for supposing it to be a property different 
from active contractility ; it is rather the neces- 
sary condition of that property, in its passive 
or unstimulated state. Passive contraction is a 
vital act, for it ceases with the rigor mortis. 

Active contraction.—This is the form of con- 
traction which is attended with those manifes- 
tations of power or force that specially charac- 
terize muscle. It is always excited by a sti- 
mulus, and is always exerted in opposition to 
another force within the body, which it is able 
more or less completely to master. The op 
sing force is generally the passive covtmatity 
of antagonist muscles, but it may be the elasti- 
city of parts, or, in the case of hollow muscles, 
the resistance of their own contents. Active 


MUSCULAR MOTION, 


contraction is ial in extent and duration, 
It requires uitereelassb-ey being attended with 
exhaustion of the power which produces it, 
which exhaustion in the voluntary muscles is 
attended with the sensation termed muscular 
Satigue. bd 
3. Of the differences between the minute — 
movements of muscle in passive and active con- 
traction. In passive contraction.—It is, per- 
haps, impossible in the higher animals to ob- 
serve the nature of the microscopic movements 
occurring during the passive shortening of a — 
muscle; but in the lower and smaller forms of 
life ite may omgres accompa It 
may always a oubtful, however, whether, 
any contraction that may be one witnessed be 
entirely of the ive kind, and consequently — 
the noceianuntins noticed are not worthy of 
implicit reliance. But it is more easy and quite 
as satisfactory to bring a muscle under i 
tion, which is still in situ and in equilibrium 
with its antagonists ; in such, contractile force 
is still present, though its effects are neutralized. 
This may be done in various small animals; per-_ 
haps the tail of small fish or of the tadpole of the 
common frog is the best adapted for the 
In the latter, when deprived of its thick } 
ment, I have succeeded in gaining such a ae 
and have found the contraction to be quite uni- 4 
form throughout, the transverse stripes bei 
tionary oat equidistant. This is nothing mo 
than might have been expected on @ priori 
grounds. The contraction being the effect of the - 
pee exercise of the property shared equally — 
y all parts of the tissue, would be equal in equal - 
masses, and as the elementary fibres are of pre-— 
cisely equal width and substance from end to 
end, no part of them could predominate in ac-— 
tion, as long as no special stimulus was applied: 
It may be concluded, therefore, that passis 
coutraction is attended by a movement abso 
lutely uniform throughout the whole mass of 
an elementary fibre or of a muscle. ie? 
In active contraction.—The case is far othe 
wise in active contraction, as may now be cor 
sidered proved by a considerable body of e 
dence. ‘y 
It might be argued, prior to direct pre 
that active contraction, being the answer to 
stimulus, must be partial, at least at its 
mencement, since no stimulus can be ap 


at the same instant to every particle of 


¥ 


muscle. i. 
Certain features of the contractions 
in fragments removed from the body, and 
amined in water under the microscope, hav 
close bearing on the present question. Ti 
been already said that such contractions 
uniformly partial; but they t two fur 
varieties, either remaining in the part wi 
they first occur, or leaving it as they en 
others in the neighbourhood. The accidt 
circumstances under which the fragmé 
placed explain these varieties. In the forn 
case the fragments are free to move; their ent 
approach in proportion to the amount of o 
traction, and as there is no force to extend th 
again when the contractile force ceases to” 
manifested in them, and advances to fresh par 


. 
an 
“ 


<9 


J ha 


MUSCULAR MOTION. 


the contraction has the appearance of being 
permanent. In the latter case, certain parts of 
the fibre (as its broken extremities) are fixed 
more or less firmly, so as to offer a resist- 


ance to the contraction that takes place, this - 


resistance enabling the contractile force ad- 
vancing to new parts to obliterate the traces 
of contraction in the parts in which it is sub- 
siding, by stretching them. The ends usually 
become fixed in consequence of their being 
the first to thicken from contraction and from 
their thus receiving the pressure of the la- 
mina of mica or glass with which it is requi- 
site to cover the object, and they are the first to 
contract, because irritated both by being broken 
and also by the water, which is absorbed soonest 
where the sheath is deficient. This fixing of 
the ends brings the fibres in question nearly 
into the condition under which they exist 
in the living body, where it has already been 
explained that there is always a resistance to be 
Overcome in active contraction. This particular 
variety of the phenomenon, therefore, deserves 
special study. Those animals whose muscles 
are most tenacious of their contractility are the 
best suited for examination, and among these 
the young crab or lobster may be most easily 
obtained. In an elementary fibre from the 
claw, laid out on glass, and then covered with 
a wet lamina of mica, the following phenomena 
are always to be observed. ‘The ends become 
_ first contracted and fixed. Then contractions 
_ commence at isolated spots along the margin of 
the fibre, which they cause to bulge. At first 
they only engage a very limited amount of the 
Mass, spreading into its interior equally in all 
directions, and being marked by a close approx- 
imation of the transverse stripes. These contrac- 
tions pull upon the remainder of the fibre only 
in the direction of its length, so that along its edge 
the transverse stripes in the intervals are very 
much widened and distorted. These contrac- 
tions are never stationary, but oscillate from 
end to end, relinquishing on the one hand what 
they gain on the other. When they are nume- 
rous along the same margin they interfere most 
irregularly with one another, dragging one ano- 
ther as though striving for the mastery, the 
larger ones continually overcoming the smaller, 
then subsiding as though spent, stretched again 
by new spots of contraction, and again, after a 
short period of repose, engaged in their turn 
by some advancing wave: this is the first stage 
of the phenomenon. ( Fig. 302.) The con- 
tractions increase in number and extent, and 
gradually engage the whole substance of the 
fibre. There is still the same struggle, the same 
alternate action and repose in individual parts, 
but as the contractions by degrees predominate, 
the ends of the fibre are drawn more and more 
near, (intermediate portions by their contrac- 
tion receiving some of the pressure.) until at 
last the whole fragment is reduced to a third of 
its original length, and stiffened with the rigor 
mortis. 

The muscular tissue in these animals is very 
tough, but where it is more fragile, as in the 
Frog, it may give way in the intervals between 
spots of contraction, and become ruptured and 


525 


Border of an elementary fibre of a young Crab, shew~- 
ing a spot of contraction (b) and the sarcolemma 


elevated in the form of bulle by the expressed 


water (a). Magnified 300 diam, 


disorganized in various degrees.* In fishes I 
have seen a succession of phenomena similar to 
what has been described in the Crab; waves of 
contraction advancing and receding, but gradu- 
ally augmenting in bulk, till the whole fibre 
was finally contracted. (Fig. 303.) 


Fig. 303. 


Stages of contraction seen on one in an el: 

tary fibre of the Skate. The uppermost state is that 

previous to the commencement of contraction. 

a, a, a@, successive ‘ waves’ of*contraction seen 
moving along one margin of the fibre, marked by a 
bulging of the margin, by an approximation of the 
tranverse stripes, and by a consequent darkening 
of the spots. 

b, b, b, similar ‘ waves” still moving along the 
fibre, bnt engaging its whole thickness. 


In all these examples, as long as the ends of 
the fragment are fixed, and will not yield to 
the convellent force, that force is seen to be 
exerted in a momentary manner in successive 
portions of the mass. In proportion as they 
yield to it, the resistance which enabled the 
contraction of new parts to stretch those from 
which it was receding is removed, and the ap- 
pearances of contraction remain. A distinction 
is required between the contractile force and 
the contraction resulting from its exercise. The 
latter will be permanent, if no force from with- 
out be exerted to obliterate it by stretching, for 
a contracted muscle has no power of extending 
itself; there is no repellent force between its 
molecules. From these phenomena, therefore, 
it is possible to eliminate the appearances re- 
sulting from a subsided force, and to judge of 


* Phil. Trans. 1840, p. 490, pl. xix. -fig. 75. 


526 


the mode and duration of action of the force 
itself. Thus sifted, they prove that, even when 
directly stimulated by water after removal from 
the body, a muscle contracts in successive por- 
tions, never in its totality at once, and that no 
particle of it is capable of exhibiting an active 
contraction for more than agen of age 

The appearances presen y muscle that 
has Gao va tured “4 its own inordinate con- 
traction in fatal tetanus in the human subject 
will supply the link wanting to connect the 
foregoing phenomena with those occurring in 
healthy contraction during life: for tetanic 
spasm differs from sustained voluntary contrac- 
tion only in its amountand protracted duration, 
and in its being independent of the will; none 
of which circumstances are of essential import- 
ance in regard to the nature of the act of con- 
traction itself. 

The muscles are so arranged in the body 
that no amount of contraction which the me- 
chanism of the bony and ligamentous frame- 
work will permit one of them to undergo, can 
by possibility occasion the rupture of a relaxed 
antagonist: to be ruptured the antagonist must 
be itself contracted. But a muscle, if contract- 
ing beyond its natural amount, may be so re- 
sisted by mechanical powers, in or out of the 
body, as to rupture itself. Hence, the contrac- 
tion of a muscle is a necessary condition, and 

enerally the essential cause of its own rupture: 
the other condition being a force greater than 
the tenacity of the ruptured part, holding its 
ends asunder; this latter may be either the 
active or ive contraction of antagonists, or 
mere mechanical resistance. But it is evident 
that for a muscle to be ruptured by its own 
contraction, that contraction must be partial, as 
is shewn in the case of the Frog’s muscle 
already mentioned. An examination of muscle 
ruptured in tetanus is found to bear out these 
observations in the fullest manner.* The ele- 
mentary fibres present numerous bulges of a 
fusiform shape, in which the transverse stripes 
are very close. These swellings or contracted 
parts are separated from one another by inter- 
vals of various lengths, in which the fibre has 
either entirely given si or is more or less 
stretched and disorganized. These appearances 
are met with after all contractility has departed ; 
they are the vestiges of the spasm during life. 
Yet in other muscles, which have been likewise 
convulsed, but not ruptured, they are not 
found. Their presence is, therefore, the result 
of the rupture. They admit only of the follow- 
ing explanation: the contractile force has o 
rated at the points contracted, and by its excess 
the intermediate portions have been stretched to 
laceration. Having once given way, the con- 
tracted parts have become isolated, and can no 
longer have been extended after the subsidence of 
their contractile force ; they consequently retain 
the form and appearances they possessed, when 
surprised, as it were, by the rupture they have 
themselves produced of the intervening parts. 

Supposing, for a moment, that active con- 
traction were a universal and equable act, and 


* Phil. Trans. 1841, p. 69. 


MUSCULAR MOTION. 


that by the superior power of an i: a 
weak muscle been ruptured, the appear- 
ances resulting would manifestly be entirely — 
different from those now detailed. The fibres — 
beyond their ruptured point would have pe 
transverse stripes uniformly approximated. ; 
From the preceding facts I conclude, 
that active contraction never occurs in the 
mass of a muscle at once, nor in the 
any one elementary fibre, but is always parti 
at any one instant of time; 2dly, that no active 
contraction of a muscle, however appa 
ge ge is more than instantaneous i 
one of its parts or particles; and therefore, 
3dly, that the sustained active contraction of a 
muscle is an act compounded of an 
number of partial and momentary contractic 
incessantly changing their place, and engaging 
new parts in succession; for every ae ee ts 
the Ans must take its due share in the act. 
Ar phenomena yet remain to be mentic 
which, by admitting of a satisfactory xplana- 
tion on this view of the subject, give stre : 
testimony to its correctness. The first he 
muscular sound heard on applying the ear to a 
muscle in action. It resembles, acce to 
Dr. Wollaston’s apt simile,* the distant ramb= 
ling of carriage wheels, or an exceedingly rapid 
and faint tremulous vibration, which, when well 
marked, has a metallic tone. It is the sound of 
friction, and appears to be occasioned by those 
movements of the neighbouring fibres upon one 
another, with which the partial contraction 
must be attended in their incessant oscil oni 
The other phenomenon is one, the existences 
which has been recently ascertained by MM. 
Becquerel and Breschet,t viz. that a 
during contraction augments in temperature. 
They have found this increase to be usually 
more than 1° Fahr., but sometimes, when 
exertion has been continued for five minut 
as in sawing a piece of wood, it has been double 
that amount. is development of heat ‘ 
to be in a great measure attributable to, a 
even a necessary consequence of, the frictic 
just alluded to. 
Thus it would appear that active contract 
consists in a disturbance of that state of equ 
brium ordinarily existing in muscles 
rest; that their different portions suce 
undergo momentary contractions, and that #l 
is always a considerable part of each fibre u 
contracted. This will account for the rema 
able fact that detached fragments of the ¥ 
tary fibre will contract by t irds of | 
length, though an entire muscle, in its ne 
situation, cannot shorten by more than 
third. This great capacity of contraction imt 
tissue would be without a purpose, if ity 
not that it only admits of momentary exer 
and therefore requires that in the ongan sui 
sive parts should take up the act, and by 
doing, render it, as a whole, continuous. Tn 
active fibre the contracting parts are conti ual 


Hing 


“ 


”* Phil. Trans. 1811. 
+ Recherches sur la chaleur animale, 
des appareils thermo-electriques ; par ' 
uerel et Breschet, Membres de I’Institut. Archiv 
u Museum, tom. i. p. 4U2. a 


x me 


dragging on those in which the contractile force 
has just subsided, and which intervene between 
them and the extremities of the fibre. These 
are thereby instantly stretched, and come to 
serve the temporary purpose of a tendon; but 
one which resists extension more by its passive 
contractility than by its mere tenacity. It is 
these parts which in tetanic spasm suffer lace- 
ration; which happens in consequence of the 
contraction excited by the vis nervosa, being 
then too powerful to be resisted by the passive 
contractility. 

The preceding account of the minute changes 
oceurring during contraction rests on data fur- 
nished by the striped form of muscular fibre ; 
but there is nothing contained in it, which 
seems at variance with the little that is posi- 
tively known regarding the contractions of the 
other form. The differences between the con- 
tractions of the two varieties are almost cer- 
tainly confined to the manner of exercise, and 
do not extend to the essential nature of the act. 
Though the unstriped fibre has not been stu- 
died by the microscope during its active state, 
with the same success as the other, yet the 
‘similarity of the gross changes observed in it 
by the naked eye, to those seen in voluntary 
‘muscle, forbid us to doubt the identity of the 
phenomenon, in all that essentially constitutes 
‘it an act of contraction. 

From the knowledge we possess, we are per- 
haps entitled to hazard some further conjec- 
‘tures respecting the differences in the mode of 
exercise of the contractile power in different 
‘eases. In whatever that mysterious power may 
consist, it would appear that the structural 
modifications of the two kinds of fibres are 
intimately connected with the manner in which 
it is capable of being exerted. Wherever the 
striped structure occurs, we witness an apti- 
tude for quick, energetic, and rapidly repeated 
‘movements, while, where it is deficient, they 
are sluggish, progressive, and more sustained. 
The varieties in the character of contractions 
performed by striped muscles are very strik- 
ing, especially that of the heart, as compared 
‘with the prolonged action of the voluntary 
muscles. In both there is an alternate mo- 
‘mentary action and repose of every contractile 
particle, but in the heart the contraction is 
universal at one instant, and the repose equally 
“universal at the next, while, in the prolonged 
action of the voluntary muscles, contractions 
-of certain parts of each fibre always co-exist 
“with repose of other parts.* 

The contractions of voluntary muscles differ 
“greatly from one another in duration, energy, 
and extent. Nothing is more wonderful, if it 
be well considered, than the power the will 
“possesses of regulating the amount of stimulus 
which it is able to give to the muscles, and 
that of transmitting it with uniformity during 
-agiven period. Dr. Wollaston+ was of opi- 


* By the expression ‘ universal at one instant,’ 
T do not mean absolutely so, for observation and the 
. presence of the muscular sound both declare that 
the contraction, even of the heart, though so ap- 
parently momentary, is progressive. 
| + Philos. Trans, 1811. 


ain 


MUSCULAR MOTION. 


527 


nion, that the phenomenon of the muscular 
sound affords a proof that the duration of a 
muscle’s contraction depends on the application 
to it of a succession of distinct impulses; and 
this idea, according very nearly, as it does, with 
the later evidence of observation, appears, on the 
whole, the most satisfactory that has been ad- 
vanced on this abstruse subject. He also 
thought that the intensity of a contraction cor- 
responds with the rapidity with which these 
impulses are transmitted to it, and this like- 
wise may be, in part, true. But there is, in 
addition to this, in all probability, a difference 
in the intensity of the stimulus itself in dif- 
ferent cases, producing a difference in the size 
of each wave, a difference in the amount of 
coutractile energy exerted in each, and a dif- 
ference in the rapidity with which the waves 
oscillate along the fibre. The extent of the 
contraction (the duration and intensity being 
the same) will manifestly depend on the 
amount of the length of the fibre which 
is contracted at once. But we are ignorant 
whether this variation in amount is effected 
by a variety in the number of waves, or in the 
extent of the fibre engaged by each of them. 
The ancients appear to have been quite ig- 
norant of the nature of muscles. Plato and 
Aristotle attributed to them so trivial an use, 
as to think that, like fat, or a kind of clothing, 
they kept out heat in summer and cold in 
winter.* The nerves and tendons were con- 
founded with the muscles, as they commonly 
are at this day, by the vulgar. Borelli, in his 
elaborate work, De motu animalium,+ thinks 
it requisite (in 1734) to adduce arguments 
against the doctrine that muscle and flesh 
are different, the former composed of an ag- 
gregation of tendinous fibres, the latter a cer- 
tain villous substance incrusted by the blood 
upon their exterior, a fact showing the ex- 
tremely loose notions that prevailed on this 
subject even up to a comparatively recent pe- 
riod. The fibres so obviously composing the 
essential part of muscle have been the subject 
of the most extraordinary speculations, pro- 
bably ever since it was discovered that they 
were endowed with contractility, the property 
which, on a superficial aspect, seemed the 
most closely associated with life. And it is by 
no means surprising, that when the micro- 
scope began to open a new world to view, it 
was applied with ardour to the investigation of 
this tissue. It is not easy to appreciate justly 
the accounts given of it by some of the earlier 
micrographers, in consequence of the indeter- 
minate meaning of many of the terms they 
employed, and the imperfection of the means 
at their disposal for accurate definition and 
measurement of the objects they describe. 
Robert Hooke, however, had probably a cor- 
rect general knowledge of the elementary fibres 
of voluntary muscle, and possibly even saw 
the fibrille into which they often split; for we 
find him in 1678 speaking of the “ fibres which 
seemed like a necklace of pearl in the micro- 


* Vesalius, vol. i. p. 182. 
+ Propos. ii. 


528 


scope.”* Previous to him no author appears 
to have examined them. But Leeuwenhoek,+ 
his friend and correspondent, makes continual 
mention of his examinations of the muscular 
fibre of various animals. This acute and en- 
thusiastic observer clearly recognized the im- 
portant fact, that each elementary fibre is a 

and separate organ in itself; he was 
astonished to find that in all animals, the 
largest as well as the smallest, these fibres are 
excessively minute; he discovered the manner 
in which they are aggregated, and invested by 
areolar tissue; and by boiling and drying a 
muscle and then making tranverse sections of 
it, he ascertained those of voluntary muscle to 
be polygonal and solid. He described the cross 
lines, which he conceived to be on the surface 
only and to be the coils of a spiral thread. 
To this structure he attributed the active power 
of the fibre, comparing it to an elastic coil of 
wire. Ie further saw the longitudinal lines 
visible on the elementary fibre, and considered 
them to be an evidence of a still minuter com- 
position by fibrille. All these points are well 
illustrated by figures, which leave no doubt of 
his meaning; but, as his results are scattered 
through a great number of letters, much of 
what he accomplished seems to have been over- 
looked by later writers. Leeuwenhoek con- 
cluded that in contraction the cross markings 
approximate, but I cannot discover that he 
speaks of having seen this. He confounded 
the cross markings seen on tendon with those 
of muscle, and fell into the prevalent error of 
attributing contractility to the tendons. Mal- 
pighi incidentally mentions the minute structure 
of muscle in only one passage of his works.t He 
appears to have seen the transverse stripes of the 
elementary fibre,and tohave alsolikened them to 
those of tendon. Contemporary with Leeuwen- 
hoek was de Heide,§ who, in 1698, published 
some observations on muscular fibre, describ- 
ing and figuring the transverse markings. In 
1741, Muys,|| in a voluminous work, with 
good plates, gave all that was previously known, 
and added many observations of hisown. His 
book, however, is learned rather than profound. 
He separates the elementary fibres into the 
simple and reticulated, and seems to have con- 
sidered the stripes to be the effect either of mi- 
nute zigzags during contraction or of a spiral 
form of the fibrille. 

Prochaska§[ next produced an excellent trea- 
tise on muscle, in which he explained, with 
great clearness, the figure, size,and solidity of 
the elementary fibre, and the appearances of 
the fibrille into which it divides. He fell into 
the error, however, of confounding the trans- 
verse markings in the intervals of the discs, 
with other creasings or flexuosities which never 


* Posthumous Works by Waller, 1707,—Life, 


p- XX. 6 : 
+ Epist. Physiologice, passim. 
t De enslbyah, p- 9, 10, written before the 
year 1687. : Peas 
§ Experimenta circa conguims missionem, fibras 
motrices, &c. Amstel. 1698. 
Investigatio fabrice, &c, Lugd, Bat. 1741, 
De carne musculari. Vienne, 1778. 


MUSCULAR MOTION. r 


4 


exist in the living body, but continually pre- 
sent themselves, in ao dead fibre, ra eee 
chanical causes. All these he attributed to — 
lateral pressure made on the fibre and fibrille 
by vessels, nerves, and areolar tissue, which 
he erroneously imagined to penetrate the inte- 
rior of the fibre. Prochaska injected muscle 
with great success,* and found the vessels so _ 
numerous that he was induced to believe con-— 
traction to depend on distension of the vessels, 
throwing the fibrille into zigzags. a 
Fontana,t a few years afte gave a 
ape more accurate meyer of the fibre than 
ad previously appeared, one remark: 
for its sim licity.. According to him the ele- 
mentary fibre cousists of fibrille, marked at 
equal distances by dark lines, which by their 
lateral apposition occasion the ance — 
of cross strie. Hence he styled the fibre a — 
primitive fasciculus. By this term, which has 
been generally adopted, undue importance is 
attributed to the longitudinal cleavage, for the — 
elementary fibre may as justly be called a pi 
as a bundle. It is not, however, in strictnes: 
either one or the other. , 
In the period that has elapsed since For 
tana’s description was published, up to the 
last few years, no real addition has been made 
to our knowledge, and so discredited or for- 
gotten, at least in this country, were the labours 
of the authors already enumerated, that th 
anatomy of the muscular fibre was taken u 
as a new inquiry in 1818 by Sir Everard He 
and Mr. Bauer.} The latter very exceller 
observer must have been deceived by the im 
—, of his glasses, which do not see 
ave been adapted to so minute a structur 
for his results, as published by Sir E. Home 
have had the effect of retarding rather than 
advancing our knowledge, by raising doubts a: 
to the credibility of any conclusions found 
on microscopical research. In 1832, LE 
Hodgkin and Mr. Lister§ re-discovered the 
transverse markings on the elementary fibre: 
voluntary muscle and of the heart, and point 
out, as Muys and Fontana had done, th 
their presence was a character by which th 
could be distinguished from the fibre of 1 
uterus, bladder, &c., which latter they o 
sequently denied to be muscular. Since the 
many inquirers, both in this country a 
abroad, have taken up the subject with ii 
proved instruments. oy 
Among those who have arrived at cone 
sions similar to those of Fontana may be m 
tioned the names of Lauth, Miiller, Schwa 
and Henle. Others, however, have entertai 
very opposite and, as I believe, erroneous ¥ 
of the composition of the fibre. Mandl e 
ceives the cross markings to be produced — 


Lh ak 


“J 
» OP 


- 


me by Baron Larrey, to whom they were pr 
wy Prochaska himself, during the occupation 
ienna by the French. ~s 
+ Sur le Venin de la Vipére, &. 1781. 
¢ Phil. Trans. 1818 & 1826. one 
$ Appendix to Translation of Dr. Edwards’s we 
Ne l’Influence des Agens Physiques sur la Vie. 
TF ecaoa pratique du Microscope, p. 7: L 


* Some of these preparations were y s 


. 


MUSCULAR MOTION. 


_ 6piral thread of areolar tissue investing the 
fibre, and Mr. Skey* describes them as an 
external structure, independent of the fibrille, 
which he believes to be arranged in band-like 
Sets around a glutinous substance in the axis 
of the fibre. Ficinust falls into the old error 
of Prochaska, of imagining the striz to be the 
_ tesult of minute flexures of the fibrille, and, 
_ ke him, he confounds with them the secondary 
_ flexures of the whole fibre. Hence, says he, 
_ the appearance of globules or particles is false, 
and only exists during contraction. Other 
“opinions still I have had occasion to allude to 
‘in the course of the article Musctr, which, as 
_ before remarked, is founded on observations 
which have been now two years before the 
public.t 
All the best observers are agreed as to the 
existence of certain appearances, and the dis- 
‘repancies we encounter in the interpretation 
them ought not to bring discredit on all 
arches of this sort. They place, indeed, 
}a strong lizht the difficulty of the inquiry, 
and the necessity for repeated, varied, and un- 
biassed observation, with the best instruments 
“We can command But we are too familiar 
With conflicting and even opposite statements 
concerning visible facts, occurring daily under 
eyes of every one, to suppose it possible 
any kind of investigation wi!l ever be free 
om those causes of error, which lie in man’s 
ature, in his own microcosm, and the effects of 
ich can only be neutralized by the common 
consent of numerous Gndepebdent observers. 
As for those difficulties, whatever they may be, 
ch are inherent in the nature of the subject, 
cannot doubt that they will be, in due time, 
ppreciated and overcome. 
ome of the opinions concerning the nature 
contraction. entertained by the earlier ob- 
ervers, have been already mentioned; another, 
ich seems to have been grafted on the doc- 
trine of the vital spirits, was, that these spirits 
were directed into the fibres and distended 
em, thus causing them to tumify and shorten. 
Accordingly, some (as Robert Hooke and 
wper) considered each fibre or fibrilla to be 
hollow; which need not excite surprise, when 
e find the great Mascagni§ believing each to 
a lymphatic vessel. The first hint of another 
noted hypothesis is to be found in the 
Memoirs of the French Academy. 1724:— 
L’Abbé de Moheres there says,|| “ Les fibres 
? pues qui s’étendent selon la longueur du 
muscle, et dont le raccourcissement fait son 
action, se divisent en un grand nombre de 
tes fibres de méme nature longitudinales 
- aussi, et qui sont liées les unes aux autres par 
des filets nerveux transversaux disposés le long 
des fibres de distance en distance. De plus, 
____ Hes petites fibres charnues ne sont pas droites, 
Mais pli¢es en zigszags, dont les angles se 
* Phil. Trans. 1837. 
t De Fibre Muscularis Forma et Structura. Lip- 


5 4 
t Phil. Trans. 1840, 
Prodromo della grande Anatomia—da Franc. 
Automarchi, Firenze, 1819. 
|| Malgaigne, Anat. Chirurgicale, vol. i. p. 102. 
‘aris, 
-¥OL. 111. 


= 


529 


trouvent aux endroits, ot sont les filets trans- 
versaux.” Hules* examined the abdominal 
muscles of small living frogs, and saw them 
thrown into zigzags during contraction, as he 
imagined ; but he inistook the uncontracted for 
contracted fibres, as I have explained.t Pre- 
vost and Dumas, at a later period,t described 
the same zigzag flexure of the fibres during 
contraction, and further imagined it to be an 
electrical effect produced by the passage of the 
nerves across them at their angles of flexure. 
This doctrine was too captivating not to obtain 
very general credence, especially as it seemed 
to fall in with a notion, at that time very cur- 
rent among speculative physiologists, that the 
nervous influence is a form of electricity. But 
its validity has of late begun to be questioned ; 
Professor Owen,§ in small filariz and in a spe- 
cies of vesicularia, observed a fact opposed to 
it, viz. the bulging of the (unstriped) fibres near 
their centre, without their falling out of the 
Straight line, in contraction. A similar fact 
was observed in the case of the (unstriped) 
muscles of the Polypifera, by Dr. A. Farre;|| 
and Dr. Allen Thomson,{[ on repeating the 
experiment of Hales and Prevost on the Frog, 
“ observed single fibres continuing in contrac- 
tion, and being simp'y shortened, and not fall- 
ing into zigzag plice ; and he was led to sus- 
pect, from this and other circumstances, that 
the zigzag arrangement was not produced until 
after the act of contraction had ceased.” M. 
Lauth, after a careful investigation, concludes** 
that a fibre may shorten with or without zigzag 
inflection. Such, I believe, was the state of 
this question in 1840, when I published the 
observations,t+ on part of which the account 
of the nature of contraction, given in the pre- 
sent article, is principally based. In the fol- 
lowing year I addedf{t a note, on the appear- 
ances met with in human muscle ruptured by 
tetanic spasm, and which seemed to me to 
prove that the conclusions I had previously 
drawn from the phenomena of the rigor mortis 
were true as regards the act of contraction, as 
it occurs in the living body. 


BIBLIOGRAPHY.— To the following works may be 
added the several systematic treatises on descriptive 
anatomy, and on general anatomy and physiology. 
Hooke, Posth. Works, by Waller, 1707. Experi- 
ments and Observations of Robert Hooke, &c. by 
W. Derham, 1726. Malpighi, De Bombycibus, 

. 9, 10. Leeuwenhoek, Phil. Transact. 1674, 
677, 1683, &c. Epist. Physiolog. passim. De 
Heide, Experimenta circa sanguinis missionem, 
fibras motrices, urticam marinam, &c. Amstelod. 
1686 and 1698. Croone, De ratione motis mus- 
culorum, Lond. 1664. Muys, An account of se- 
veral observations concerning the frame and tex- 
ture of the muscles, Phil. Trans. 1714. De car- 


* Hemastatics, R; 59. 
¢ Phil. Trans. 1840. 
¢ Majendie’s Journal, 1825. : 
§ Hunter’s Works by Palmer, vol. iv. p. 261—2, 
note. 
Ht Phil. Trans. 1838, pp. 394 and 396. 
Quoted by Owen, loc. citat. i ‘ ‘ 
** L’Institut. No. 73, quoted by Miiller in his 
Physiology, Baly’s Transl., p. 888. 
tt Phil. Trans. 1840, pt. ii. 
tt Phil. Trans. 1841, pt. ii. . 
M 


530 


nis musculose strncturé, Lugd. Bat. 1730, In- 
vestigatio fabrice, uz in partibus musculos 
component. extat. Lugd. Bat. 1741. Borelli, 
De motu animaliam. Ed. Neapoli, 1734. i 
Myotomia Reformata. Introduct. Haller, Ele- 
ment. Phys. lib. xi. Hales, Statical Essays, Lond. 
1741. Prochaska, De carne musculari, Vindobon. 
1778. Fontana, Traité sur le venin de la vipére, 
Flor. 1781. J. Hunter, Croonian Lectures, 1781, 
Works by Palmer, vol. iv., notes by Owen, Lond. 
1838. G. R. Treviranus, Vermischte Schriften, Gott. 
1816, Beitrage zur Aufklarung, &c. P. Mascagni, 
Prodromo della grande anatomia, Firenze, 1819. 
Home and Bauer, Phil. Trans. 1818 and 1826. 
Milne Edwards, Mémoire sur la struct. element. 
&c. Paris, 1823; Ann. des Sciences, 1826. Pre- 
vost & Dumas, Majendie Journal de Physiologie, 
1825. Hodgkin and Lister, Appendix to a Trans- 
lation of W. F. Edwards ‘* on the Influence of Phy- 
sical Agents on Life; and Annals of Philosophy, 
1827. Valentin, Histor. evolutionis syst. musc. 
prolusio. Wratislav. 1832 ; Ueber den Verlauf und 
die letzten Enden der Nerven. F. C. Emmert, 
Ueber Endigungsweise der Nerven in den Muskela, 
Bern. 1836. E. Burdach, Beitrag zur Mikrosko- 
pisch. Anatomie der Nerven, Konigsburg, 1837. 
Roulin, Majendie Journal, vol. i. H. Meyer, 


Diss. Inaug. de Muscul. in duct. efferent. gland.. 


Berol. 1837. Krohn, Miiller’s Archiv. Jahrg. 1837 ; 
Heft. 3, 4; Brit. and For. Med. Rev. Ap. 1838. 
Ficinus, De fibre muscularis forma et structura, 
Lipsiz, 1836. Schwann, in Miiller’s Physiology 
by Baly, Lond. 1837-41. Baly, in the same, pt. iv. 
description of plate. auth, 1’Institut, No 73. 
Skey, Phil. Trans. 1837. Malgaigne, Anatomie 
Chirurg. vol. i. Mandl, Anatomie Microscopique ; 
Traité Pratique du Microscope, Paris, 1839. Gul- 
liver, Observations on the muse. fibres of the 
esoph. and heart, &c. Zoolog. Proceed. No. 81, 
1839. Henle, Allgemeine Anatomie, Soemmering, 
6ter Band. 1841. Palicki, De musculosa cordis 
structura, Wratisl. 1839. Barry, Phil Trans. 
1839-40-41-42. Bowman, Phil. Trans. 1840-41. 


( W. Bowman. ) 


MUSCULAR SYSTEM, (Comparative 
Anatomy oF).—The muscular system of ani- 
mals, as the term is generally understood, is 
composed of masses or fasciculi of highly irri- 
table filaments, by the contractions of which 
the movements of the body, whether voluntary 
or involuntary, are effected, and the arrange- 
ment of these moving powers, their size and 
strength, forms and general disposition, must 
of course vary ad infinitum in the different 
classes of animals, in conformity with the varie- 
ties of their external form, or the innumerable 
kinds of apparatus conferred, for special pur- 

es, upon particular tribes or even species of 
iving beings. Of these detailed accounts are 
elsewhere given in those articles which treat of 
the structure and anatomy of each class entering 
into the composition of the animal kingdom. 
Nevertheless, it has been deemed advisable, 
upon the present occasion, to collect together 
in one view the principal facts connected with 
general myology, and to state, as briefly and 
concisely as the nature of the subject will 
allow, those grand physiological points which 
an extended review of the comparative organi- 
zation and development of the muscular system 
reveals to the anatomical observer, in order to 
concatenate the leading facts recorded in other 

of this work. 
It may be laid down as an axiom universal 


_are developed to such an extent as to 


MUSCULAR SYSTEM. 


in its application, that the condition of the 
musculur system in any race of animals must 
dependent upon, or at least in strict conforma 
with, the development of the nervous apparatus, — 
by the influence of which muscular mov 
are excited, controlled, directed, and associated 
Thus, as we advance from lower to more — 
elevated forms of living creatures, it is easy | > 
perceive that in exact proportion as the nervous 
system makes its appearance, and = 
gressively more clahoranshy organized, the m 1S- 
cles themselves become developed and assume — 
a perfection of structure and precision of move= 
ment adapted to the increasing exigencies of the 
animal economy; nay,it has now satisfacto- 
rily established that even among the highest race 
of the animal creation, during the progress of 
embryo development, the most intimate relation 
is observable between the state of the ne 
centres and the condition of the nascent mu 
as they become gradually formed and perfee 
In the lowest Zoophytes where nervous fibr 
of any kind are not perceptible, even under the 
most rigid microscopical examination, the con 
tractile tissue of the body is equally diffuse 
and devoid of aggregation into filaments ¢ 
fasciculi of mascular fibre, and precisely um 
the same conditions the first radiment of the 
vertebrate embryo, being as yet entirely deve 
of nerves, is also destitute of distinet mi 
cles, the movements of which could only 
associated and rendered efficacious by means 
nervous intercommunication; and this ¢ 
plete want of aggregation of the elements 
muscular tissue is as remarkable throughow 
the Acrite division of the animal world as it 
in the nervous matter entering into the comy 
sition of their bodies, which, although its 
sence is not to be detected by our senses, is f 
sonably supposed to exist in a diffused s 
even in the lowest tribes of animated bein 
As soon as nervous threads become appart 
and long before ganglionic masses of neur 


= 


~ 


hoa 
oe 


SF # 


them to be regarded as centres of inn 
the muscular tissue, in like manner, assum 
different and far more perfect character. 
elementary molecules composing muscular 
are then distinctly visible, and assuming a 
nite arrangement become grouped in lo 
dinal series, exhibiting contractile bai 
fascicles placed in precise directions, and 
ble of effecting movements of a more dee 
character than could possibly be exerci 
creatures deprived of nervous cords, wl 
the contractions of numerous muscular 
might be associated and made to coope! 
the accomplishment of a given purpose. 
Moreover, it must be obvious that, | 
great division of the animal creation W 
characterized by the existence of nervo 
ments, the ganglionic centres bei 


imperceptible, or at least where any have 
detected, in a very rudimentary state 0 
velopment (the Nematoneura of F 
Owen); such a condition of the nervol 
ratus involves, as a necessary COr 
important circumstances connected 
general economy of the beings so © 


regards their means of relation with the external 
world. Having as yet no ganglia developed 
sufficiently important, from their size or situa- 
tion, to merit the title of brains, or fit to be 
regarded as const.tuting a common sensorium, 
whereunto information derived from remote 

rts of the body may be conveyed, localized 
instruments of sensation would be as yet super- 
fluous, and consequently, with the exception 
of the generally diffused sense of touch which, 
from its extreme delicacy, seems in these 
lowest forms of existence to supply to a 
 €ertain extent the deficiency of other means of 
_ perception, instruments of sensation are not 
_ as yet conferred. The presence of a localized 
‘organ of sense, analogous to an eye or an ear, 
‘must obviously be useless to a creature pos- 
sessed of no sensorial centre. to which informa- 
tion, derived through the medium of that sense, 
_ may be transmitted, and organs of the higher 
‘Senses are, therefore, as yet entirely wanting 
throughout the Nematonerurose division of 
the animal kingdom,* as, @ fortiori, they are 


glasses. In like manner the existence of 
ternal locomotive members, moved by any 
‘powerful or elaborately constructed muscular 
_ apparatus, is not to be expected in animals that 
possess not ganglia capable of presiding over 
_.., muscular motion. Limbs, there- 
fore, properly so called, are not as yet de- 
_ Yeloped; and, if in some of the most perfect 
_ Epizoa, the rudiments of such structures be- 
_ come apparent, it is only because the animals 


ein them are so nearly allied to the 
_ Articulata, in their general structure, that the 
‘ervous ganglia in them are beginning to be 
developed, and thus they can only be looked 
bon as the transition steps leading by an 
almost imperceptible gradation from one great 
_ type of animal organism to another of a more 
_ @levated character. 
Im the Arricurata (Iomocancirata, 
Owen), brains, or ruling ganglionic centres, for 
___ the first time make their appearance in a suffi- 
_Gient state of development to correspond with 
_ rgans of sense of a localized character, or to 
_ Allimate systems of muscles adapted to wield 
_ locomotive limbs, and combine complex ac- 
tions now essentially connected with the more 
_ perfect attributes bestowed on forms of life 
__ €apable of more extensive re'ations with sur- 
“Pounding objects. Still, however, an exact 
correspondence exists between the progressive 
_ €xpansion of the nervous centres and the gradual 


ix 
- 
~ 


__* In laying this down as an important physiolo- 
cal axiom, a few words of explanation will be 
equired by those, who, adopting Ehrenberg’s 

views, regard the red spots observable upon nume- 
ia Animalcules and Zoophytes as being the eyes 
of those creatures. ‘That many species of such 
animals possess red spots occupying definite posi- 
‘fons upon different parts of their bodies, no one 
will be disposed to deny who has paid the slightest 
attention to their economy and organization; but 
that these red spots are eyes, we think, for the 
feasons above stated, may reasonably be doubted, 
more especially as it has not even been proved by 
| observation or experiment that they possess either 
the Stracture, or the functions of any visual appa- 
fatus, with which we are acquainted. 


MUSCULAR SYSTEM. 


necessarily deficient throughout the AcriTE - 


531 


appearance of limbs moved by a distinct mus- 
cular apparatus, which become progressively 
superadded to the annulose body or trunk of 
the articulated animal, and in precisely the 
same manner does the advancement of the 
nervous system from a less perfect to a more 
concentrated condition evidently precede the 
appearance of external appendages, subservient 
to the exercise of more exalted powers of sen- 
sation, or increased capabilities of locomotion. 
The humb!estannulose forms, as for example the 
Leech and the Earthworm, possessing, as they 
do, a nervous system consisting of an extended 
series of numerous pairs of feeble ganglia, none 
of which are as yet sufficiently potent to con- 
trol any complex muscular apparatus, or to 
appreciate impressions derived from without with 
much nicety or precision,are necessarily deprived 
of outward limbs, or complicated instruments 
of sense ; their soft and flexible integument is 
unequal to sustain any jointed members what- 
ever, and the first rude vestiges of simple eyes, 
ocelli, are all that can be allowed for the pur- 
poses of vision. By degrees the nervous gan- 
glia becoming fewer in number as they coalesce 
into larger and proportionately more energetic 
masses, the moving organs of the body become 
perfected in the same ratio; limbs, almost 
impotent as yet, but sti!l sketching out the arti- 
culated legs hereafter to be perfected, make their 
appearance, and the apodous Annelidan, the 
humble inhabitant of the water, is promoted 
to a terrestrial existence ; jointed feet at length 
become appended to the segments of the still 
worm-like body, small and feeble at first, as in 
the Iudlus terrestris and the other vegetable- 
eating Myrrapops, but speedily, in proportion 
as the individual segments of the body become 
enlarged and strengthened, and the motor gan- 
glia accuire increased energy, assuming larger 
dimensions and greater perfection of structure, 
until the annulose anima! attains the strength 
and activity of the carnivorous Scolopendra, 
and becomes fitted for a life of rapme and 
destruction. 

Advancing from the Scolopendra, which as 
yet is only able to creep upon the surface of 
the ground, we are at length conducted to the 
far more active and highly gifted races of 
Insects, properly so called, in which the de- 
velopment and perfection of the muscular sys- 
tem is advanced to a condition adapting these 
wonderful little beings to an aerial existence, 
and in making the transition from Myriapod 
to the Insect the carrying out of the same 
great law is most obviously and conspicuously 
illustrated. The nervous ganglia, still nume- 
rous and proportionately feeble even in the 
Scolopendra, become in the aerial insect reduced 
in number until they are collected into a few 
large and potent masses; senses of a wonder- 
fully exalted description, correspondent with 
the increased size of the encephalic ganglia, 
replace the simpler organs of the less exalted 
Articulata ; those segments of the body where- 
unto locomotive members are appended coalesce 
and become fused together into a dense and 
strong thoracic armour able to sustain the vio- 
lent efforts of the powerful muscles now re- 

2M 2 


532 


quired for flight; the corresponding ganglia 
contained within the thorax exhibit a size and 
development proportioned to that of the mus- 
cles they are destined to animate; and the 
winged Insect becomes thus competent to the 
exhibition of feats of strength and activity not 
bess paralleled in any other race of living 
ings. 

On taking a survey of the molluscous or of 
the vertebrate divisions of the animal creation, 
the same great law is every where apparent, 
and we are reminded, on all hands, that a strict 

rallelism exists between the condition of the 

Ocomotive system, whatever may be its cha- 
racter, and the perfection of the nervous appa- 
ratus, whereby muscular movements are con- 
trolled and directed. As a necessary conse- 
quence of the above intimate and inseparable 
relation, which invariably exists between the 
organs of motion and those of innervation ; 
and allowing, as modern Zoologists all admit, 
that the nervous system, whatever may be its 
condition, is to be regarded as the ruling pri- 
mary portion of the animal economy, we are 
naturally led, therefore, in reviewing the mus- 
cular system generally, to take this great phy- 
siological axiom as our guide, and beginning 
with the simplest forms of life to trace the first 
appearances and successive complication of 
the motor organs as we advance through the. 
different classes of animated beings. 

In the Cuvierian classification of the Régne 
Animal a!l the lower animals, originally con- 
founded under the general name of Zoophytes, 
are included in one great division, called 
Raprata, from the circumstance that many 
forms of these animals exhibit more or less of 
a radiated arrangement in the general outline 
of their bodies. For the term Raprata, in 
the article Anima Kincpom of this Cyclo- 
pedia, Dr. Grant has substituted that of 
“ Cyctoneura,” acknowledging, at the 
same time, that the name selected by him 
was of equally partial application, and conse- 
quently unsatisfactory; inasmuch as, in the 
great majority of the animals ranged under it, 
so far from any nerves being visible, “ disposed 
in a circular manner around the oral extremity 
of the body,” not a trace or vestige of nervous 
fibre is by any means discoverable; and, 
moreover, many of the animals thus grouped 
under one denomination are so remote and 
dissimilar from each other in every feature of 
their economy, that it is impossible to regard 
them even as being organized according to the 
same type. As regards the condition of their 
muscular system, the most striking differences 
are at once perceptible; the Sponges, the 
Polyps properly so called,* the Polygastrica, 
and the Acalepha, have the texture of their 
bodies so soft and gelatinous, that not a mus- 


* In the article referred to, polypiform animals, 
with ciliated tentacula around the mouth, ure 
classed with the Polypifera. Recent observations 
made by Lister, Milne Edwards, Ehrenberg, and 
Dr. pie Ke Farre, have, however, since shewn such 
creatures to be so far removed in their general 
organization from the true Polyps, that they now 
constitute a distinct class under the title of Bryozoa, 


MUSCULAR SYSTEM. 


cular fibre is by any means apparent in any of 
them ; while, = e oer. eae the chen ae 
derms have muscular systems constructed u pom 
exceedingly elaborate and complex principles. 
Taking the nervous system for our guide, itis 
at once evident that the presence of nervesand . 
of muscles goes hand in hand,andthe RapiaTA 
of Cuvier or the Cycroneura of Grant is at 

once separable into two great groups, one divi- 
sion being without either visible nerves or mus- 
cles, while the other is found to possess b a 
Classifying them, therefore, according to 

principle, and adding to the list o a 
animals some which, in the article ANtMaAt 
Kincpom, have, as we think, been erroneously — 
included in the Diploneurose (articulated) sub- — 
kingdom, they readily range themselves under 
the following denominations :— 7 


Acrita. ' 
Anima!s with neithcr nerves nor muscles. 
Agastrica. 
Polypiphera. 
Polygastrica. 
Acalephe. 
Sterelmintha. 


* 


‘af 
Nematongeura — Animals both 
of nerves and muscles, either without percep 
tible ganglionic centres of innervation, or wher 
these do exist, they are extremely radimentary, 
and not arranged in any parallel series. Thi 
division will include ae 
Celelmintha, | 
Bryozoa, a. 
Rotifera, * 
Epizoa, ‘i 
Echinodermata. ee 
The term Agastrica is here proposed te i 
clude those ad forms of peta existen 
which obviously form the transition from th 
Vegetable to the Animal Kingdom; many « 
them indeed seeming rather to belong to t 
former than to the latter division of the or 
nized world. Such are, for example, the coi 
fervoid animalcules, which, in their structu 
and mode of reproduction, are evidently nes 
allied to vegetables, although from the see 
ingly spontaneous movements of which si 
the Oscillatoriw, &e. are capable, they have! 
claimed by Zoologists as belonging to theit 
partment. The Sponges ( Porifera, Grant) 
equally allied to vegetables in the nature 
living parenchyma that invests and forms 
porous or reticulated skeletons; and mo: 
mately related to these,notwithstanding the 
rent texture of their framework, are many ¢ 
lithophytous Corallines and Fungia, th 
portions of their skeleton being in like n 
deposited in an organized soft tissue, the 
nature of which is by no meansas yet ¢ 
blished. All the above plant-like fe 
however, in one grand and striking 
stance,—they are devoid of any stom: 
digestive cavity, a feature of their 
which of itself would be sufficient 
doubt whether they are strictly entitled — 
regarded as animals or classed with the ¥ 
ble creation. ’ 


' 


— 


We need scarcely say that in the Agastrica 
no muscular system whatever can be detected, 
the living portions of their bodies being entirely 
made up of a soft granular parenchyma which 
only dubiously exhibits contractile movements 
under any circumstances. 


group of animals naturally allied to each other 
in the general details of their economy, but 
offering very great diversity of structure and 
external form. In the simplest or gelatinous 
Polyps ( Hydride) the acrite condition of the 
nervous and muscular tissues is most conspicu- 
‘ously exemplified. Examined under the mi- 
‘eroscope, the entire substance of the minute 
gelatinous bag composing the body of the 
Hydra seems to consist of a glairy material, 
_ wherein are suspended coloured globules that 
constantly change their relative pesitions, and 
_ move about from place to place as the creature 
contracts, or extends different parts of its sub- 
Stance, but not a fibre or filament is discernible 
Passing in any direction, nevertheless the move- 
‘ments of the Hydra appear to be performed 
with facility, and its powers of locomotion are 
considerable. 

__ In the Alcyonide and other compound cor- 
tical Polyps, muscles of any kind are equally 
invisible, and the contractions observable either 
in the substance of the common body or in the 
numerous hydriform mouths that minister to 
the support of the general mass, seem to be 
entirely due to the approximation of molecules 
diffused through the entire substance of the 
animal, rather than dependent upon any thing 
ike muscular structure ; nevertheless it has been 
Stated, though erhaps erroneously, that some 
families (the Pennatulide) are able to swim 
from place to place by consentaneous move- 
“ments of the polyps and polyp-bearing arms 
with which many species are provided. 
The tubular Polyps are equally devoid of 
so thing like muscular fibre, nevertheless the 
\ and uncalcified membrane that connects 
the Polyps to the cells wherein they are lodged, 
_ and the Hydriform Polyps themselves, are en- 
“dowed with the capability of performing all the 
_ Movements required to protrude the flower-like 
bodies from the cups that contain them, and to 


te and swallow the materials required for 
ir support. 


____ But in every group of animals, as we ap- 
= ope the most highly organized members of 
~ ‘that group, we find the characters of a more 
~ exalted type of organization beginning to ma- 
 -nifest themselves, and thus in the Actiniade, 
_ which are obviously osculent between the 
_ Aecrite Polyps and animals possessing a true 
_ Muscular system, a fibrous arrangement of the 
_ €ontracting portions of the body becomes very 
“distinctly recognisable, and a nervous filament 
‘May be displayed under favourable circum- 
_Stances passing round the oral extremity of the 
creature, and thus closely approximating the 
- hematoneurose type of structure. The infuso- 
rial animalcules ( Polygastrica, Ehren.) seem, as 
far as relates to their muscular system at least, 
to be strictly acrite animals, but such is their 
extreme minuteness, that much uncertainty 


MUSCULAR SYSTEM. 


In the Polypiphera we find a very extensive 


533 
still necessarily exists concerning their intimate 
organization. Their locomotive apparatus most 
frequently consists of fringes of vibratile cilia 
variously disposed, the movements of which 
are most probably dependent upon the exist- 
ence of a peculiar vital tissue distinct from 
muscle. In many species, e.g. the Proteus 
(Ameba diffluens), the contractions of the 
body are extensive, so that even the outward 
form of the animalcule is perpetually changing, 
and some, the Vorticelle, are attached to highly 
irritable pedicles of exquisite tenuity, that 
may be straightened or suddenly thrown into 
close spiral coils by some inherent power, the 
nature of which is as yet quite incompre- 
hensible. In some, as for instance Chilodon 
urcinatus, moveable hooks are found to be ap- 
pended to the surface of the animalcule, and 
some ( Nassula) are provided with a peculiar 
dental apparatus, consisting of a minute cylin- 
der of horny filaments; nevertheless no appear- 
ance of muscular or nervous fibre has as yet 
been detected even in the largest and most 
conspicuous species. 

The AcaLepn# next claim our notice as 
members of the Acrite division of the animal 
creation, and in every point of their economy 
they strictly conform to the general characters 
belonging to this type of organization. (See 
Acrira.) Their bodies are soft, pe'lucid, and 
gelatinous, without any trace of muscular fibre 
being perceptible in their composition ; their 
digestive canals are excavated in the paren- 
chyma of the body, not contained in any abde- 
minal cavity, and the canals through which 
nutrimentis conveyed to different parts of thesys- 
tem are entirely devoid of proper external coats ; 
neither, as'we believe, do nerves exist in any 
of the class, although, as we are well aware, 
two eminent observers have entertained a con- 
trary opinion. Professor Grant,* in his account 
of the anatomy of Cydippe pileus, describes a 
double ring of nervous fibre as surrounding 
one end of the alimentary canal of that beau- 
tiful little Acaleph, and has even figured ganglia 
distributed at intervals upon these circular 
cords, from which secondary nerves are de- 
scribed as emanating. Such a circumstance as 
the existence of nerves and ganglia in an ani- 
mal confessedly acrite, and presenting no traces 
of that type of structure which, in all other 
cases, invariably accompanies so elevated a 
condition of the nervous system, from its very 
singularity was well calculated to attract the 
notice of the physiologist, and we are ourselves 
quite satisfied that the distinguished professor 
has been led into error upon this point, most 
probably from having mistaken the circular 
canals, described by Delle Chiaje and others, 
as surrounding the ora! extremity of the Beroes, 
and which are indeed frequently filled with an 
opaline fluid, for nervous fibre.t 


* Vide Transact. of the Zoological Society of 
London, vol. i. and the figure at p. 109, vol. i. of 
this work. 

+ At the Birmingham meeting of the British 
Association, during a very interesting discussion 
npon this point, it was agreed by Mr. Forbes and 
Mr. Thompson, whose qualifications for such re~ 


534 


Professor Ehrenberg has more recently an- 
nounced that he had detected a nervous fila- 
ment encircling the margin of the dise in one 
of the pulmonigrade Acalephz, and connecting 
the red spots, which he is pleased, as we think 
without sufficient reason, to call eyes, with each 
other. Such a nervous system would, at least, 
be anomalous ; and, notwithstanding the justly 
high reputation of the eminent professor of 
Berlin, we cannot but think that the interests 
of physiology require us to pause before we 
assent to the views of Professor Ehrenberg,as re- 
lates to the nature of the filament in question. 

In the Sterelmintha or parenchymatous En- 


_ _ tozoa of Cuvier, the same acrite condition, both 


of the nervous and muscular systems, is still 
observable in the lower forms belonging to this 
group of internal parasites, which being, for the 
most » in their natural situations either en- 
closed in cells or closely imbedded in the sub- 
Stance of the viscera of other animals, could 
not be expected to have any power of locomo- 
tion conferred upon them; their bodies are, 
therefore, in the simplest species (such as the 
Hydatids, Cysticerci_) mere membranous bags 
of homogeneous texture, and without a trace 
of fibre in their composition: their powers of 
moving are proportionately feeble, and are 
limited in fact to slight contractions, which are 
but indistinctly perceptible on the application 
of stimuli to the surface of the living animal. 

In the Tape-worms ( Tenia) the presence 
either of nerve or muscle is equally impercep- 
tible, and the whole structure strictly conform- 
able to the Acrite type. As, however, we 
mount higher in the scale of organization 
among these parasites, we again find how 
nearly succeeding types of structure are made 
to approximate, and even to a certain extent to 
become blended, as it were, with each other. 
In the Flukes ( Distoma ) and kindred genera, 
and in many of the Acanthocephalous Sterel- 
mintha, although their structure is evidently 
parenchymatous, the skin, without presenting 
any decided appearance of muscular fibre, be- 
comes more coriaceous and contractile, and at 
the same time nervous filaments become dubi- 
ously perceptible : a transition is obviously in 
progress, and thus we are gradually introduced 
to another and a more elevated series of 
animals. 

The NematToneura, as is obvious from 
every part of their economy, are gifted with 
higher attributes, and permitted to enjoy a 
more extended intercourse with external ob- 
jects than any creatures comprehended under 
the preceding division. They are no longer 
rooted to one spot or imprisoned in enclosed 
cavities, but, on the contrary, are for the most 
part erratic in their habits, and in many of them 
the locomotive system is so efficiently con- 
structed that their movements, exhibiting con- 
siderable activity and energy, argue the posses- 
sion of distinct and precise!y arranged muscles, 


searches are well known, that, although they had 
examined several hundred specimens of the Beroe 
in question, for the purpose of ascertaining this im- 
portant fact, their endeavours to detect the nervous 
systzm referred to had been entirely unsuccessful, 


MUSCULAR SYSTEM. 


and display such combination and consentane- 
ous action of different parts of the body ¢o- 
operating to produce a given result, that the 
existence of an intercommunication throughot 
the system by means of nerves might read 
be predicated, even had not anatomy reve: 
to us that such animals actually possess a ner- 
vous apparatus. It would seem indeed to be 
clearly indicated by the physiological relations 
that exist between the two systems, that . 
possession of muscular fibre arranged in dis- — 
tinct fasciculi involves, as a matter of course, 
the co-existence of nervous threads, wh 
the actions of distinct and distant muscles 
be associated for the attainment of a common 
object ; and accordingly we find that these two — 
important additions to the animal eco a 
make their appearance sincera No- 
large ganglionic masses are as yet developed 
sufficient importance to be d as consti- 
tuting a common sensorium, to which the per- 
ceptions derived from external senses must b 
referred, and from whence mandates of volit 
can be supposed to emanate. Senses, th 
fore, that 1s, localized and special senses, can 
not as yet be given; the traces of individuality 
are but feebly recognizable ; the vital power 
are still, to a great extent, diffused throug! 
the different tissues of the body, and not | 
lected and concentrated, as in animals — 
sessed of brains, that is, of centralized — 
dominant aggregations of neurine; and, as 
consequence of this important circumstane 
some of the most striking characters commo 
to the Zoornyres still linger in this divisi 
of creation ; the radiated form is yet extensive 
met with, multiplication by mechanical div 
sion of the body is still, to a certain ext 
possible, and severed portions of the body 4 
found to be reproduced by growth from t 
mutilated part. : 
The C@LeELMINTHA or Cavi 
worms, living in the interior of other anit 
differ in so many points from the Acrite Ento; 
that Cuvier, although in the Regne Anima 
was content to group them together in the: 
class, was obliged to separate ‘hem into _ 
distinct orders, calling the SrerELMIN' 
“ intestinaux parenchymateux,” while the f 
highly organized are designated “ intestin 
cavitaires.” The Ceelelmintha, in fact, are 
ganized in accordance with quite a diff 
type of structure, as must be at once ev! 
upon the slightest comparison between 1 
The digestive apparatus is now no longer 
posed of tubes excavated out of the § 
mass of the body, and presenting no outt 
the escape of egesta, but a distinct alim 
canal now makes its appearance, suspen 
a capacious abdominal cavity, wherein, 
over, are lodged the male and femal 
generation, which in the Celelmintha are 
rally found in different individuals. The 
rietes of the body are in these worms obv: 
muscular, and are composed of © 
fibres arranged in superposed strata and @ 
ing different directions. Towards the ext 
of the body they are disposed longitudina 
but the inner layers assume a circular or spi 


> 

i: 
id 
ensive 


_ organs 0 
Ce@termintua. The Bryozoa which, while 


arrangement ; such a disposition providing for 
the extension or shortening or lateral inflexions 
of the worm, and enabling the animals so con- 
structed to move about with facility in the cavi- 
ties wherein they reside. 

Nevertheless, at this, its first appearance in 
the animal series, muscular fibre has not as yet 
attained to the perfection of structure that it 
offers in the higher classes. The fibres are as 
yet indistinct, soft, and gelatinous; they ap- 
pear to be deficient in fibrin; neither do they, 
when examined with the microscope, present 
the transverse strie that are so characteristic of 
the muscular tissue in a more advanced condi- 
tion. The little fascicles are, moreover, ex- 
tremely short, and run but a little distance 
before they disappear, and are succeeded by 
others. Their whole appearance, in fact, is 
that of muscle in a rudimentary condition, and 
very accurately resembles the nascent muscular 
tissue when it first becomes apparent in the 
embryo of the vertebrate animal. The nervous 
System accompanying this condition of the 


Muscles is extremely simple; a delicate ring 


surrounds the commencement of the cesopha- 
gus, by which, perhaps, the muscles of the 
mouth are associated during the act of imbibing 
nourishment, and prolonged from this ring are 
two long and thread-like nerves, one running 
along the dorsal and the other along the ventral 


" aspect of the body, and passing quite from one 


extremity to the other, but without any percep- 
tible ganglionic enlargements in their course.* 
Having, therefore, no brains or central masses 
to which sang could be referred, localized 

sense are likewise wanting in all the 


naturalists were ignorant of their more compli- 


cated organization, were, until a recent period, 


confounded with the Polyps, are, from their 
€ntire structure, very justly entitled to a much 
higher position in the scale of animals, and un- 


_ doubtedly belong to the Nematoneurose type. 


‘These little beings inhabit transparent cells of 
very elaborate and delicate construction, from 
the mouth of which they protrude the anterior 
portion of their bodies when in search of food. 
Although from their general appearance the 
Bryozoa might easily be, and in fact have been 
until recently, erroneously regarded as Polyps, 
the differences between the two classes are ex- 


ceedingly striking and important. The Bryo- 


zoa, instead of having the tentacula that sur- 


found the oral aperture quite simple and fila- 


mentary, as the Polyps have, are furnished 
with ciliated tentacula, and from the rapid 


_ ciliary movement which is incessantly going 


on, while the arms are expanded, strong cur- 
Tents are formed in the surrounding water, 
all of which impinging upon the oral orifice 
bring to the mouth such nutritive materials as 
are necessary for the support of the creature. 
The digestive apparatus is no longer a closed 


* The dorsal nervous cord of the Ascaris, first 
described by Cloquet, (Anatomie des vers intesti- 
naux, ) seems to have been overlooked by the learned 
writer of the article <‘ Animal Kingdom,” who has 


arranged the Entozoa as being diploneurose ani- 
mals. 


MUSCULAR SYSTEM. 


535 


sacculus, as in the Polyps, but, on the contrary, 
presents a very elaborate structure, consisting 
of a gizzard, stomach, and distinct intestinal 
canal, terminated by an anal aperture, though 
which the feces are ejected; and, more- 
over, the whole of the digestive viscera float 
loosely in a visceral cavity wherein they are 
suspended. In addition to this, the mouth of 
the cell occupied by the Bryozoon is defended 
by a most delicate and complicated opercular 
apparatus, requiring a very perfect set of mus- 
cles to perform all the required movements 
connected with the protrusion and retraction of 
the body, so that there is abundant reason for 
separating the animals in question from the 
Acrite Zoophytes. 

As relates to their muscular system, rudi- 
mentary in its development as it must still ne- 
cessarily be, many circumstances of great inte- 
rest have been brought to light by the patient 
investigations of Dr. Arthur Farre, to whose 
valuable memoir* we are indebted for the fol- 
lowing particulars, which we give at some 
length, more especially as they will serve not 
only to elucidate this part of our subject, but to 
correct several important errors that have been 
promulgated relative to the Rorirera, an 
important class of animals next to be noticed, 
of very analogous structure. 

For the purpose of drawing the protruded 
Bryozoon into its retreat two distinct sets of 
muscles are provided, one set acting upon the 
animal and the other upon the flexible opercu- 
lum that closes the cell. The muscles for the 
retraction of the animal are contained in the 
visceral cavity, and consist of two bundles of 
delicate thread-like cords, the one set arising 


‘from the bottom of the cell to be inserted about 


the base of the stomach, the other also arising 
from the bottom of the cell and passing up free 
by the sides of the pharynx to be inserted around 
the line of junction between this organ and 
the tentacula. 

The muscles provided for the retraction of 
the operculum consist of six flattened bundles 
of fibres, which act upon the flexible portion 
of the cell and a delicate circle of sete placed 
around its orifice. It is at once evident there- 
fore that the muscular system in the Bryozoa is 
capable of great precision of action, and the 
fasciculiare most accurately adjusted. Neverthe- 
less if the intimate structure of this form of 
muscle be investigated, it is found not to have 
attained to full perfection. ‘ It would appear,” 
says Dr. Arthur Farre, “ as if muscular fibre 
were here reduced to its simplest condition. 
The filaments are totally disconnected, and are 
arranged one above the other in a single series. 
They pass straight and parallel from their ori- 
gin to their insertion, and have a uniform dia- 
meter throughout their course, except that each 
filament generally presents a small knot upon 
its centre, which is most apparent when it 
is in a state of contracticn, at which time the 
whole filament also is obviously thicker than 
when relaxed. The filaments have a watery 


* Dr. A. Farre, on the structure of Ciliobra- 
chiate Polypi. Phil. Trans. part 2 for 1837, 


536 


transparency and smooth surface, and under 
the highest powers of the microscope present 
neither an appearance of cross markings nor 
of a linear arrangement of globules.” Besides 
the retractor muscles in the Bryozoa there like- 
wise exists a muscular membrane which lines 
the cell, and forms the parietes of the body, 
in which fibres are distinctly apparent, running 
transversely: these by their contraction com- 
ing the visceral cavity and the fluid which 
it contains will tend to elougate the body of 
the Bryozoon, and assist in effecting its protru- 
sion; although, as Dr. Farre supposes, this 
process is principally accomplished by the 
cooperation of the alimentary canal, which has 
the power of straightening itself from the sig- 
moid flexure, into which it is thrown when the 
animal is retracted. 

The condition of the nervous system in the 
Bryozoa has not been as yet made out, a cir- 
cumstance at which no one will be surprised 
who considers the extreme difficulty of micro- 
scopic researches concerning the structure of 
animals so minute as these ; but from the close 
affinity that there decidedly is between these 
animals and the Rotifera, there can be little 
doubt that a similar arrangement exists in 
both. 

Inthe Rorrrera or Wheel Animalcules, the 
nervous system, according to Ehrenberg, con- 
sists of several filaments communicating with 
minute ganglia dispersed in different parts of 
the body, although without any obvious arrange- 
ment or symmetrical disposition, so that the 
muscular apparatus in these beautiful animals 
dienes itself in a very perfect state of deve- 
opement. The ciliated organs around the 
mouth, which are apparently the representatives 
of the ciliated arms in the Bryozoa, are retracted 
by a special set of muscles derived from the in- 
terior of the membrane that lines the shel! and 
circumscribes the visceral cavity, and the antago- 
nists to these are the delicate parietes of the 
visceral cavity itself, which acting upon the fluid 
therein contained, causes the extrusion of the 
ciliated lobes, whenever the wheel-like organs 
are required to be put in motion.* 

But besides the muscular bands, that, in 
the Rotifera, are appropriated to the protrusion 
and retraction of the wheel-bearing organs, 
others are connected with a peculiar prehensile 
apparatus placed at the hinder extremity of the 
body, and forming an instrument of very great 
importance in the economy of these creatures. 
It consists of a prehensile forceps, the blades 
of which are worked by distinct muscles; and 
by the assistance of this organ the action of the 
wheel-like cilia is at once changed from that of 
a locomotive power into a means of procuring 
and seizing food. If these forceps are not 


* It seems more than probable that the tranverse 
muscular fibres that occur in the parie.al membrane 
of the Rotifera have been mistaken by Ehrenberg 
for vascular canals, described by tha. observer as 
emanating from a dorsal vessel; such at least is 
the opinion of Dr. Arthur Farre in the memoir 
above referred to, an opinion which quite coincides 
with the result of our own observations upon this 
subject. 


MUSCULAR SYSTEM. 


employed, the apparent! ee ae = 
pe the little weit rapid through the water; 

t does it choose to take hold of some foreign 
body by means of its forceps, and thus anc 
itself in a given spot, the use of the whee 
entirely changed, their rotation merely 
ducing currents or rather a powerful whirlpool 
in the water, which sucks from a distance every 
thing within its influence, and thus brings food — 
into the mouth. ~ 

The next class of animals, the Ep1zoa, pre=_ 
sent us with a beautiful series of gradation 
development, clearly demonstrating the insepara 
ble relation that must exist between the nervot 
and locomotive systems. The Epizoa see 
indeed, to be the osculant group interpe 
between the Intestinal worms ps the vt 
lated classes, and exhibit in a permanent con-— 
dition the progressively improving external 
articulated limbs, which are we permitted to 
attain their full development in higher races of 
the animal creation. The Epizoa, like the 
Ceelelmintha, are parasitic in their habits, livin: 
however, upon the external surface, and not in 
the interior of other animals. They are prin= 
cipally found fixed to the eyes, the skin, the 
gills, or even the inside of the mouth of fishes 
or to the branchial organs of various forms of 
aquatic animals, from which they suck thi 
materials necessary for their support, and at | 
same time are freely ex to the influences 
of the surrounding medium for the purpose 
respiration. In the humblest of these parasite 
the structure of the body is scarcely supe! 
to that of many Ceelelmintha, suckers and pre 
hensile organs placed in the vicinity of th 
mouth being their only means of adhering to th 
surface upon which they live; but in the Le 
neans the first appearance of outward liml 
begins to be perceptible, not as yet recognisabl 
as legs or locomotive agents, but not the I 
on that account the first rude sproutings ¢ 
members that are to be by degrees perfected” 
more highly privileged genera. Some of the 
Lerneans, indeed, present most grotesq) 
shapes, and a!most exactly resemble the e 
bryos of Vertebrate animals at the period wh 
the first buddings of limbs begin to pro, 
from the sides of the body. This resemblat 
indeed, is far more real than it would at 1 
appear, inasmuch as there is a parallelism 
be established between the permanent coi 
tion of the Lernean and the transitory stat 
the embryo at the corresponding 0 
development that is strictly physiological. — 
condition of the nervous system in them 
is precisely similar, exhibiting in both ¢ 
the nematoneurose type; the same rudi 
tary condition of the muscular system is 
sequently equally met with in the embry 
in the Lernean, but as the nervous syste 
the former is rapidly advancing to a | 
exalted state of development, so do the 
and the muscles appertaining to them impr 
in the same ratio. = 

In the higher genera of Ep1zzoa mi 
ganglia exist in connexion with the ner 
filaments, and in such the limbs are of e¢ 
more exactly formed and begin to sketel 


MUSCULAR SYSTEM. 


as it were the limbs of Crustaceans and other 
 Articulata. 
_ The study of the muscular system in the 
extensive class Ecurnopecmata, the last of 
the nematoneurose division of the animal world, 
is invested with considerable interest on account 
of the very different kinds of locomotive appa- 
ratus that successively make their appearance ; 
for as the outward form of these elaborately con- 
_ structed creatures changes through all the phases 
represented by the Encrinite, the Sturfishes, 
the Echinus, the Holothuria, and the worm- 
like Siponculus, the muscles successively assume 
a different arrangement. 
The Encrinite in its outward form might be 
_ mistaken for a polyp, the jointed calcareous 
“stem whereby it is fixed to the rock, the body 
‘and rays around the mouth, as well as the 
appendages to the stem, being all in their essen- 
al structure exactly comparable to those cor- 
_tieal polyps, that have an internal jointed cal- 
areous basis of support. The numerous 
‘pieces that compose the skeleton of the Encri- 
nite are all invested with a living contractile 
crust, whereby, in fact, they were secreted, 
d which forms the bond that connects them 
her. The living crust that covers the 
nerinite can scarcely, indeed, as yet be looked 
90n as being muscular, so soft and acrite 
does its composition appear to be; nevertheless 
in these Echinoderms it seems to be the only 
oving power employed, and by its slow con- 
actions bends the arms, or rays, or stem in 
given direction. 
_ In the long-armed Starfishes, such as the 
“Comatule, Gorgonocephali, and Ophiuri, the 
slender and flexible rays around the body are 
1 like manner covered with a living contracting 
, more dense and coriaceous than that of 
Encrinite, but still presenting very dubious 
earances of muscular fibre, whereby the 
ovements of the rays are effected. The rays 
emselves constitute the instruments of pro- 
sion, and by their aid these Polyp-like 
ures crawl at the bottom of the sea, or by 
itwining them around the sea-weed that covers 
the rocks climb in search of food. 
In Asterias and kindred forms the exterior 
of the hody is still encrusted with the same 
contractile covering, and can be bent to a 
certain extent; but in these short-armed Star- 
es the rays have become so short and devo.d 
f flexibility that they can no longer be useful 
the purposes of locomotion: an additional 
cular apparatus is therefore now conferred 
the extraordinary system of protrusible 
sers, that become the chief agents in walk- 
}, Or in seizing prey. 
_ As we advance from the Asteride we find 
the rays at length totally disappear: the 
y assumes a pentagonal form ( Pulmipes ), 
en circular ( Scutella ), and at last is enclosed 
ee ovoid or globular shell, as in Echinus, 
_ Cidaris, &c. In these spherical Echinoderms 
the external soft and living crust that still 
covers the exterior of the shell presents obvious 
claims to muscularity, more especially where 
‘it passes on to the articulated spines that are 
‘attached to the surface of the shell and now 


L 
tx 


537 


become the principal means of prozression. 
The suckers, however, that formed the only 
locomotive organs in the Asteride still are met 
with in the Echinide,—these and the spines 
constituting an apparatus for locomotion, which, 
for its complexity, is unparalleled in the ani- 
mal creation. In the Echinide, moreover, a 
strangely constructed set of dental organs are 
developed, and for these likewise special muscles 
are appointed, for a description of which the 
reader is referred elsewhere. (See Ecuino- 
DERMATA.) 

In the Holothuride the shell of the Echinus 
is no longer secreted, and the living integument 
itself constitutes the whole parietes of the body, 
which now becomes quite soft and flexible, 
clearly commencing that transition which is to 
connect the Echinodermata with the Annulose 
division of the animal kingdom. The suckers 
of the last family are, however, still persistent 
and form the principal means of moving from 
place to place. The texture of the fleshy skin 
of the [olothuria is dense and coriaceous, and 
strong bands of muscular fibre arranged in five 
divisions pass in a longitudinal direction, from 
one end of the body to the other, between 
which circular and transverse fasciculi are dis- 
tinctly perceptible. Imbedded in the muscular 
walls that enclose the visceral sac of the Holo- 
thuride, delicate nervous filaments are to be de- 
tected passing along the body froraend to end, and 
most probably these are connected together by 
a circular filament surrounding the esophagus. 
Ganglia, if they exist at all, have, from their 
minute size, hitherto esciped observation; and, 
as might be expected from such a condition of 
the nervous system, the muscular contractions 
of the fibrous integument, although associated 
through the medium of the nerves, and con- 
sequently far stronger and more energetic than in 
the lower asteroid Echinoderms, are still almost 
entirely uncontrolled by the influence of volition ; 
nay, so remarkably is this the case, that in 
most species of Holothuria, npon the applica- 
tion of the slightest stimulus to the exterior of 
the body, or even by simply taking them out 
of the water in which they live, such violent 
and general contraction; of the whole integu- 
ment are excited that the intestines and other 
viscera are forced extensively through the anal 
orifice, and it is almost impossible for the 
anatomist to procure a specimen of these crea- 
tures without finding it more or ‘less spoiled 
from this circumstance. 

Lastly, in the Siponculi the vermiform ap- 
pearance is completely established, the longi- 
tudinal and circular muscles that bound the 
visceral cavity are strongly and distinctly deve- 
loped, the complicated apparatus of foot-like 
suckers has disappeared, minute ganglia are 
visible towards the anterior end of the body, 
and we arrive at the annulose condition, that 
characterizes the next great division of the 
animal creation, which now offers itself to our 
contemplation. 

Homocancurata (Owen).—The third great 
natural group of living beings consists of crea- 
tures having the exterior of their bodies divided 
into rings or segments arranged behind each 


538 


other in a longitudinal series, and generally 
furnished with lateral appendages of different 
kinds symmetrically disposed, which are sub- 
servient to many and very various purposes. 
The nervous system, moreover, throughout the 
entire range of this extensive series assumes a 
new and constant arrangement in itself, quite 
sufficient to characterize this sub-kingdom of 
animated nature, and with the different modifi- 
cations of this portion of their economy are 
intimately connected the progressive changes 
observable in the structure and habits of the 
different classes included therein. 

In the simplest conceivable condition under 
which a Homogangliate animal could exist, and 
doubtless among the lowest of the red-blooded 
worms and most imperfect forms of insect 
larve such a condition might be pointed out, 
the body would consist of a long succession of 
similar rings, each of which would contain an 
appropriate nervous apparatus consisting of a 
pair of ganglia symmetrically disposed on each 
side of the mesian line, from which nerves 
proceed for the innervation of the segment in 
which the brains or ganglia were placed. These 
ganglia in each segment communicate with each 
other and likewise with the pairs that precede 
and follow them by inter-communicating ner- 
vous filaments, and thus the entire series of 
individual brains or ganglia is united into one 
system made up of as many pairs as there 
would be rings entering into the composition 
of the body. There is, however, a remarkable 
difference between the anterior pair of ganglia 
and those placed in the succeeding segments. 
The first pair is invariably situated above the 
cesophagus on its dorsal aspect, while all the 
rest are arranged beneath the alimentary canal 
along the ventral region of the animal, so that 
the nervous cords that join the first and second 

airs of ganglia embrace the esophageal tube. 
The supra-esophageal pair of brains invariably 
communicates with the instruments of the 
senses whenever such exist, and therefore is 
very justly comparable to the encephalon of 
higher animals; while the succeeding chain of 
sub-cesophageal ganglia animate the muscles of 
the different segments of the body, and may 
therefore be looked upon with great reason as 
representing the spinal cord of the Vertebrata. 

But while the ganglia either of the head or 
of the ventral cord are thus numerous, as we 
have supposed them to be, in the lowest worm, 
they are as yet by far too small and devoid of 
energy in such a dispersed condition to corres- 
pond with organs connected with the higher 
senses, or even to wield muscles of sufficient 
power to support the weight of the body raised 
on articulated limbs. Therefore, before senses 
can be given or active limbs bestowed, a pro- 
cess of concentration must be gone through, the 
encephalic masses must be enlarged and thus 
rendered more perfect, the ganglionic centres 
that influence muscular movements reduced in 
number and made proportionately more ener- 
getic, and exactly in the ratio in which this 
improvement is effected in the nervous system, 
do the muscles become by degrees stronger and 
more efficient, and the limbs appended to the 


MUSCULAR SYSTEM. 


body more active and useful 1 ‘i 
agents. This, however, will be best i- 
fied by a rapid survey of the principal classes 
that compose the division of animals we 
now considering. a 
In the lowest Annelidans, as for example the 
Gordius or hair-worm, so impotent are the 
minute ganglia bestowed, that even the rings 
upon the exterior of the body are scarcely 
indicated, and not the least vestiges either o 
limbs, tentacula, or eyes are to be detec 
In the Leeches even, although the number o 
ganglia is in them considerably diminished, and 
rings of the body more strongly marked, extei 
nal limbs cannot as yet be given, their pl } 
being supplied by the suctorial dises of the 
head and tail; nevertheless, even in : 
aquatic Annelides, the encephalic masses are 
sufficiently advanced to permit organs of vision 
to be granted, and accordingly for the first time 
in the animal series (as far as our own belie 
goes) are real eyes met with. The muse 
system in these humble worms consists exelt 
sively of the contractile walls of the body, 
fibres of which are arranged in three stra 
superposed one upon the other, and pass 
different directions, one stratum being ce 
posed of longitudinal, another of oblige 
spiral, and another of annular fibres surrour 
ing the body of the animal; but these 
sufficient for progression, all the movements: 
contraction, elongation, or flexure of the bot 
being provided for by this simple arrangeme 
In the Nereis, Aphrodite, and other erra 
worms, external appendages become develop 
from the lateral aspects of the different 
ments, in the shape of bundles of seta, mor 
by muscles appropriated to each set, and th 
constitute the first rudiments of locomot 
limbs. The senses are at the same time — 
proved in their condition, tentacula or fet 
are found appended to the head, and the ey 
become larger and more conspicuous, althe 
still presenting the form of simple sg 
ocelli. 
In the Myrrapopa the limbs becon 
culated, and of sufficient strength to pern 
a terrestrial existence, each one of the f 
legs having a distinct set of muscles a 
priated to its movements, in addition 
muscular apparatus, whereby the 
the as yet flexible and elongated bo 
Iie Bre § with motion, and which of « 
represent the strata of the muscular cover 
the Leech, strengthened and endowed wi 
capability of more precise action, in pr 
as the cuticular skeleton has become 
dense and distinctly jointed. Anten 
moreover, now placed upon the head 
bling those of Toons no doubt cons 
organs of sense of a similar nature, a 
eyes in Scolopendre are found to be ve 
tinct and perfectly organized, but still 
ocelli resembling the simple eyes of Inst 
In the admirably constructed class ¢ 
SECTS, Creatures adapted to an aerial exis 
and consequently requiring the utmost é: 
of muscular power to sustain their bodi 
the air, the muscular system of the locon 


articulated appendages, the legs and wings, 
must undergo a still further improvement, and 
the means whereby this is accomplished are 
sufficiently manifest. The nervous ganglia are 
accumulated into a few large and powerful 
centres of innervation; the rings of the body, 
to which the locomotive organs are attached, 
are dilated and strengthened in proportion to 
the force of the muscles placed within, and 
constitute three thoracic rings of such firmness 
and inflexibility that they may well be looked 
upon as forming a distinct division of the exo- 
skeleton, and give rise to the distinction laid 
down by entomologists betweeen the head, the 
thoracic, and the abdominal segments that enter 
_ into the composition of an insect’s body. But 
_ the same concentration of the nervous system, 
which permits an Insect to possess the extraor- 
dinary powers of flight with which it is gifted, 
allows by the increased perfection given to 
the brain, the possession of elaborately con- 
Structed senses. The eyes assume a complexity 
of structure that is truly wonderful, the sense 
_of touch attains extreme delicacy, and indubita- 
bly the means of smelling, of tasting, and of 
hearing are now conferred, however incapab'e 
we may be of pointing out the mode in which 
_ they are exercised ; nay, it is extremely proba- 
ble that capabilities of perception of which we 
_ can form no idea, are bestowed upon the Insect 
‘Faces commensurate with the activity of their 
movements and the wide range of duties they 
are appointed to perform. 
_ During the metamorphosis to which Insects 
are subject, that is to say during the advance- 
ment of these creatures from an embryo condi- 
m to their mature or perfect state, changes 
are constantly in progress, both in the nature 
and arrangement of the locomotive organs, and 
of course as these changes are effected, the 
entire disposition and even the vital properties 
of the muscular system oa elghats to their 
movements undergo a considerable modification. 
larvee of many genera have externally the 
_ appearance of the simplest worm, being pro- 
_ vided with not even any vestiges of the loco- 
Motive apparatus that subsequently is to be 
Mevelopet : even the rings or segments of the 
_ body are entirely soft, the cuticular covering 
__ being of extreme tenuity, and the tegumentary 
_ muscles, as a natural consequence, propor- 
__ tionally rudimentary in their structure. In 
‘| _ Such larve the nervous system exhibits the 
____ lowest condition found among the apodous An- 
__helidans, and the eyes and external senses are, 
if they exist at all, of the humblest possible 
character. This is the case, for example, in 
the maggots of many Dipterous and Hymenop- 
terous Insects. 
__In others, as for instance in the caterpillars 
of the Lepidoptera, the locomotive powers are 
of a slightly ameliorated description : the larva 
Possesses a distinct head, and to the succeeding 
‘Segments, rudely constructed limbs named legs, 
and others bearing still less resemblance to the 
locomotive members of the future insect, to 
which the name of pro-legs has been appro- 
elie are the only instruments of progression, 
ven in the most perfect larve, as in those of 


rh, ol 


MUSCULAR SYSTEM. 


539 
the aquatic Beetles, the form is elongated and 
resembles that of an Annelidan; the legs are 
comparatively feeble and of small size, and 
simple ocelli replace the compound eyes that 
afterwards become developed in the perfect 
Insect. 

During the progress of the metamorphosis, 
the nervous system within is undergoing a pro- 
cess of concentration precisely comparable to 
that which has been noticed in advancing from 
the lower to the higher classes of ArTICULATA. 
The ganglia coalesce and become less numerous, 
the encephalic pair attain a higher development, 
and as this is accomplished the legs and wings 
of the mature being sprout from the sides of 
the segments appropriated to sustain them, 
enclosed in and defended by cases of cuticle 
temporarily provided, which constitute the 
covering of the pupa or chrysalis, until at 
length, the aggregation of the previously sepa- . 
rated ganglia being completed and the brain 
perfected to the extent required, the pupa-case 
is thrown off, the newly-formed limbs expand, 
and the insect, with its newly-acquired limbs, pos- 
sesses an additional system of muscles, which 
have been developed with their growth, and 
only arrive at their full state of perfection when 
the body has ceased to grow, and the genera- 
tive system, having attained its complete pro 
portions, proclaims the animal mature and able 
to propagate its species. 

The addition of wings, indeed, to the body 
of flying insects would seem to be a provision 
specially connected with the distribution of the 
progeny to which they are to give birth, and all 
the phenomena connected with their develop- 
ment and that of the muscular appar itus pro- 
vided for their movements to have relation to 
this great and closing act of the insect’s exist- 
ence. The period of time during which these 
animals live in their imperfect or wingless state, 
during which many of them have important 
offices assigned to them, constitutes, in most 
cases, by far the longest portion of their lives, 
and some aquatic larve, indeed, reside for 
months or even years in the water under their 
immature or wingless form, which perish in a 
few hours after they have been gifted with the 
means of aerial locomotion. Had they never 
been furnished with wings, it is abundantly 
evident that the species of such insects could 
never have been dispersed beyond the precincts 
of the pond or the ditch in which the parent 
had passed her existence, but the brief space 
allowed them to enjoy life in the winged con- 
dition is sufficient for the achievement of the 
great object in view, and the Ephemeron and 
the little Gnat, while they appear to be only 
sporting out their evening’s life amid the sun- 
beams, are, in fact, disseminating their offspring 
through different localities. 

The next class of HomoGanGLiaTe animals 
comprises the ARacHNIDANS, the Scorpions 
and the Spiders, animals visibly intended 
to be destroyers, appointed to keep within 
due limits the different races of the Insect 
world, and by assisting in the great work 
of destruction that is on all sides in progress 
against them, to prevent their fertility from 


540 


becoming prejudicial to the other members of 
the animal creation. The tyrant must neces- 
sarily be stronger and more sagacious than the 
victims intended to be subdued, and accord- 
ingly, in the Arachnida, the great law that has 
hitherto been our guide in tracing the develop- 
ment of the muscular system is carried out one 
step further. The coalescence of the nervous 
ganglia and consequent concentration of the 
skeleton is found in these creatures to be more 
conspicuous than even among the Insects the n- 
selves: even the head and thorax, which in the 
last class were distinct from each other, now 
become fused into one piece, forming the 
cephalo-thorax of the creatures under considera- 
tion. The limbs and the jaws are thus rendered 
stronger and more formidable, and the muscles 
whereby they are wielded attan the fullest 
development permitted amongst articulated 
animals. Among the Crustacea forming the 
last class of this important sub-kingdom of 
creation, we find a series of aquatic Articulata 
running parallel as relates to the condition of 
their muscular system with the terrestrial Arti- 
culata, and exhibiting precisely the same rela- 
tions between the state of concentration of the 
nervous system, and the degree of efficiency 
conferred upon their locomotive apparatus. 
The humblest forms of Crustaceans have all 
the segments of the body distinct and move- 
able, and, moreover, in their elongated sha 
resemble the larve of aquatic Insects. Tn 
these the articulated limbs appended to the 
different segments of the body are extremely 
feeble, and only adapted to natation ; but pro- 
ceeding upwards in the scale the locomotive 
members assume a more effective appearance, 
and the segments supporting them run together, 
and become consolidated. Whilst the muscles 
of the trunk preponderate in their development, 
as in the Shrimps and Macrourous Decapods, 
the limbs are of secondary importance as 
instruments of locomotion, and the largely 
developed tail forms a strong and powerful oar, 
a means of propulsion best fitted to their nata- 
torial habits; but as we approach the shore and 
meet with Crustaceans, adapted to a littoral 
existence, the muscles of the trunk become 
diminished in importance in proportion as the 
legs acquire additional strength. The concen- 
tration of the segments of the trunk is carried 
out to the greatest possible extent in the Bra- 
chyurous Decapods, and the Crabs are thus 
enabled to leave the sea and prowl about upon 
the beach, or even to exchange an aquatic for 
a terrestrial existence; and, as in the case of 
the Land Crabs, to reside during a greater part 
of the year at a distance from their native 
element. 

It is, however, interesting to observe that in 
the most highly organized of the Crustaceans, 
the Brauchyura, the complete centralization of 
the body and nervous ganglia is effected, as in 
the case of Insects, in a slow and gradual 
manner, and that their muscular system under- 
goes a metamorphosis scarcely less remarkable 
than that observed among the Insects them- 
selves. The Crab on first leaving the egg is 
almost in the conditiou of a long-tailed Shrimp, 


MUSCULAR SYSTEM. 


and the locomotive limbs scarcely to be 
nised as being worthy of such a ttle, being not 
only rudimentary in their size but exclusive 
adapted for swimming; and it is only 
several times casting its shell and p 
through distinct sere, ee of form, 
muscles of the less attain the preponde: 
over those of the trunk and become st 
enough for progression on land. a 
The fourth grand division of the ani 
kingdom, comprising the MOLLUSCA © 
Cuvier, is characterized by the he ap vi 
dition of the nervous ganglia, which, throu 
out the extensive series of creatures construct 
according to this type, are distributed witl 
any symmetrical arrangement in different pat 
of the body, whence the Mollusca have 
nained by Professor Grant CycLo-GaNGLIAT 
and more recently by Professor Owen HrrEr 
GaNGLtaTA, the latter term being, as we ¢ 
ceive, the preferable of the two. In the Me 
lusea the general outline of the body parti 
pates, more or less, in the want of syinmel 
that is so conspicuous in the disposition ¢ 
ganglia composing the nervous system, and # 
muscular apparatus does not exhibit that 
cision and regularity which is visible among 
the Articulata. There is no longer, in f 
any trame-work, but when a shell is presi 
as, for exainple, in the Snails and kindred fort 
both terrestrial and marine, it is on'y in th 
parts of the body that are protrusible from 1 
testaceous covering that the tegument exhi 
this decided muscularity, the mantle lining 
shell being constantly thin and membranou: 
But the most strongly developed part of 
muscular covering of a gasteropod is the br 
fleshy disc attached to the ventral surface 
the body which constitutes the appa 
locomotion, and gives the name conferred 
zoologists upon the entire class. This dise, 
foot, as it 1s likewise called, is entirely m 
up of contractile fibres, disposed in va 
directions, so as to confer all the capabi 
of movement necessary for securi Og 
sion along the plane surfaces over which t 
sluggish animals are destined to crawl. — 
Having, as yet, no internal skeleton ¢ 
loped, and being equally destitute of anyt 
like an external articulated frame-work, it 
be evident that if creatures of this de 
are to be provided with organs requiring 
moved by subordinate sets of mu 4 
that there is no firm point of attachment 
found, as is the case among Insects 
Vertebrata, recourse must be had to 
plan, and accordingly few more a 
deviations from what is generally met 
other animals can be pointed out than W 
with in the extensive class under conside} 
The parts of the mouth, the tentacles, th 
and those parts of the male generative § 
needed for copulation, are in many inst 
so constructed that they may, when not! 
be completely retracted into the general ¢ 
of the body and packed up amongst the v 
by means of a mechanism quite peculiar 
of which a particular account is 
given. (See GasTiropopa.). 


In the Preropop Mo tusca, we likewise 
find the entire body enclosed in a muscular 
bag, forming what is called the visceral sac, 
but the locomotive organs present themselves 
under a different aspect. These consist of two 
muscular flaps or wings, appended to the op- 
posite sides of the neck, which form, in fact, 
two oars or paddles, wherewith the little Ptero- 
pods row themselves about from place to place, 
or gambol gaily among the waves, which some- 
times, in the northern oceans, swarm with count- 
less multitudes of them. The lateral fins in ques- 
tion were regarded by Cuvier as being likewise 
subservient to respiration, an opinion, however, 
which Eschricht satisfactorily confutes. The lat- 
ter writer, moreover, points out a little circum- 
Stance worth recording, namely, that the wings 
are not distinct and separate organs as at first 
they would appear, but that the muscles mov- 
ing them pass continuously in a crucial di- 
rection through the neck of the animal from 
one wing to the opposite, so as to convert the 
whole apparatus into an exact representation of 
the double paddle used by the Greenlander, in 
rowing his Bisi. or canoe, over the very seas 
frequented by the Pteropods, in such abun- 
dance. 
~ In the Carnivorous Cepuatopopa the mus- 
cular sac composing the body, the parietes of 
the head, and the long and flexible arms with 
their curiously constructed sucking cups ap- 
pended, are all made up of variously disposed 
‘contractile fibres; but these are too fully and 
“well described in another place to require more 
than a passing notice in this general survey. 
(See Cepuaropopa.) 

_ Arrived at the vertebrate division of the ani- 
_ tal series, we at once find the moving powers 
‘assuming a complexity of arrangement and 
Precision of action, proportional to the elabo- 
rate construction of the internal osseous, or car- 
__tilaginous skeleton, which now forms the frame- 
work of the body, and must be regarded as 
entering into the composition of several dis- 
_ tinet systems of organs appointed to different 
_ offices, and physiologically independent of 
each other. Each of these systems, or sets of 
muscles, indeed, is developed for special pur- 
goses, and so far are they from_ progres- 
sively presenting themselves, in a gradually 
‘Improving condition, as we rise from’ lower to 

‘more elevated orders of Vertebrate animals, 
_ that the physiologist must be prepared to ex- 
‘pect every irregularity in this respect ; impor- 
_ tant organs, or sets of organs, that in the lowest 

‘Vertebrata are found to be most elaborate and 
_ complex in their structure, are not unfre- 
“quently either wholly or partia!ly obliterated, as 
Be ascend the scale of animal life, and others 


_ equally important to the animals possessed of 
ben, are only met with in certain races, that 
are endowed with peculiar habits or capabi- 
ities. 
_ But, what is still more startling to the ana- 
tomist, who has confined his dissections to the 
‘examination of the muscular system as it exists 
in mature or complete animals, and has con- 
sequently been accustomed to describe as being 
permanent and invariable the origins and in- 


MUSCULAR SYSTEM. 


541 


sertions of every muscle, that he meets with, 
the study of embryogeny reveals to the philo- 
sophical enquirer a series of changes in pro- 
gress, as relates to the arrangement or even the 
existence of various parts of the animal eco- 
nomy, involving changes as remarkable, in all 
the muscular apparatus connected therewith. 

In order, therefore, fully to lay before the 
reader, with as much brevity as perspicuity 
will allow, phenomena so important as those 
which next offer themselves to our notice, it 
will be advisable, first, to enumerate the prin- 
cipal systems of muscles that enter into the 
composition of a completely formed Vertebrate 
creature, premising that each may be but feebly 
developed in proportion to the rest, and many 
of them, indeed, absolutely wanting in a given 
animal, and afterwards to examine separately 
the varieties of arrangement met with in the 
animal series in relation to each, and likewise 
the metamorphoses that accompany embryonic 
developmeut. 

Without overburdening with detail this in- 
teresting enquiry, or unnecessarily multiplying 
divisions of the muscular apparatus, we shall 
content ourselves with grouping all the muscles 
of a Vertebrate animal, as belonging to one or 
other of the following systems, each of which 
will demand separate examination. 

1. Vertebral system, muscles directly acting 
upon the spine and cranial vertebra. 

2. Cos‘al system, muscles moving the ribs 
and parietes of the thorax and abdomen. 

3. Hyvid system, muscles acting upon the 
os hyoides and branchial arches. 

4. Opercular system, muscles moving the 
operculum of fishes. 

5. Muscles of the limbs. 

6: Muscles acting upon the lower jaw and 
serving for mastication. 

7. Tegumentary system, muscles acting upon 
the skin and its appendages. 

8. Vocal system, muscles of the voice. 

9. Diaphragm. 

10. Lingual system. 

11. Ocular system, muscles moving the eye- 
ball and its appendages. 

12. Aural system, muscles acting upon the 
ossicles of hearing and moving the external ear. 

13. Nasal system, muscles acting upon 
moveable parts of the nose. 

14. Generative system, muscles attached to 
the apparatus of generation. 

1, The muscular apparatus peculiarly appro- 
priated to the movements of the vertebral chain 
of bones presents its maximum of developement 
in the osseous fishes, in which animals loco- 
motion being principally accomplished by the 
lateral sweepings of the broadly expanded ver- 
tical tail, every arrangement has been made to 
increase the depth of the spinal column and to 
extend the surface presented by the superior 
and inferior spinous processes to the greatest 
possible degree, not only by lengthening inor- 
dinately those processes themselves, but like- 
wise by appending to their extremities addi- 
tional pieces derived apparently from the 
exo-skeleton. The muscles destined to act 
upon the dexible spine of the fish are propor- 


542 


tionate to the violence of the impulse required 
in rath the tail, and occupying the lateral 
regions of the body, extend quite from the head 
to the caudal fin, constituting almost the entire 
bulk of the animal, and possessing sufficient 
strength from their combined contractions to 
scull the fish through the water with surpris.ng 
velocity, or even to enable the salmon to throw 
itself up the cataract, that bars its progress up 
the river, where it is commissioned to lay its 


During the changes that accompany the de- 
velopement of the tadpole, which by its meta- 
morphosis into a frog is literally converted from 
the condition of a fish into that of a reptile, the 
transmutation observable in the pi Se of 
the muscles acting upon the spine are not less 
remarkable, than those witnessed in the verte- 
bral column itself. Whilst in its tadpole state 
the frog is, as regards its powers of locomotion, 
strictly a fish, and rows itself about entirely by 
the movements of its expanded vertical tail 
exactly as fishes do, but as the limbs of the 
reptile gradually make their appearance the 
lateral muscles of the spine that previously 
formed the bulk of the creature are absorbed 
and disappear, the hitherto flexible and elon- 
gated vertebral column becomes short and but 
little gifted with motion, and its muscles in 
the same ratio grow feeble and unimporta: t, 

In the other forms of Rept.les, as well as in 
Birds and Mammalia, the muscular system 
acting upon the vertebral chain presents great 
uniformity of character, the number and strength 
of the muscular fasciculi being exaggerated, or 
diminished in different regions in proportion as 
mobility is permitted, the movements of the 
spine being generally diminished, and tram- 
melled in exactly the same ratio as the loco- 
motive limbs become more perfect and efficient. 

2. The costal muscles form a system apart, 
quite independent of those connected with the 
vertebral column, and exactly keeping pace 
with the developement of the skeleton of the 
thorax. In Fishes a thoracic cavity cannot be 
said to exist, inasmuch as the ribs that enclose 
the viscera seem rather processes fixed to the 
spine, in order to give a greater extent of sur- 
face for the attachment of muscles destined to 
act upon the tail, than properly the representa- 
tives of the costal elements of the skeleton ; 
neither do ribs exist in the tadpole, or even in 
the perfect frog. Even in those Batrachia that 
are most gifted in this particular, minute corni- 
cula appended to the apices of the transverse 
processes of the vertebra are the only rudi- 
ments of a costal system of bones, and these 
muscles are vainly looked for. 

In the Tortoises and Turtles likewise, al- 
though both vertebral and sternal ribs are 
present, and so hugely developed that they con- 
stitute the great bulk of the earapax covering 
these strange reptiles, such is the immobility 
of the dorsal shield, and so securely are the 
ribs conjoined by suture, that any muscular 
apparatus destined to act upon them would 
have been obviously superfluous. 

In Serpents, however, the case is widely 
different ; for in these lithe and limbless crea- 


MUSCULAR SYSTEM. 


tures the ribs are made to serve as most impor-_ 
tant locomotive agents, and their movements — 
must be proportionably free. Dorsal ribs only 
are here met with, but these being now move-_ 
ably articulated to the sides of the spinal co- 
lumn, and moreover acting at their opposit 
extremity upon the ventral scuta, perform th 
duties of internal legs, and being continued 
an unbroken series from the very atlas neal 
to the termination of the tail, it is not diffieu 
to imagine the numbers and complexity of th 
additional muscles now provided, to wield oj 
gans so numerous and important. 

In Lizards and in Birds the thorax assume 
its most complete state of developement, at 
exhibits both dorsal and sternal ribs articu 
to each other and capable of extensive move. 
ments ; muscles are therefore given to act upe 
both the dorsal and the sternal series. 

Lastly, in the mammiferous races the 
rior costal bones are once more removed, the 
place be.ng oncupted by elastic cartilages, 
resiliency of which to some extent antagoniz 
those muscles which act upon the mo 
portions of the thorax. 

The sternum, or rather the sternal syste 
bones, althouzh frequently found to ef 
largely into the composition of a thoracic | 
vity, seems rather to be in relation with 
anterior extremity, and the muscles der 
from it principa!ly subservient to the moti 
of those limbs. Thus in the frog and toad 
have a largely developed sternum without ei 
ribs or thorax; and in the case of Birds, 
strict correspondence between the conditic 
the sternum and the powers of flight is 
strikingly exemplified. a 

3. Perhaps the most interesting lesson to 
derived from such a survey of the museu 
system of vertebrate animals as this, is tat 
by an examination of the hyoid apparatus, 
of the musc'es connected with it, in the di 
rent members of the vertebrate series, and al: 
during the different phases of embryonic 
lopement, in any of, the air-breathing or | 
elevated classes. It is in Fishes that thi 
of the ske!etoa exhibits the greatest comph 
of structure, and forms a most elaborate ff 
work of branchial arches, destined to st 
the gills, which some writers have been tel 
erroneously to consider identical with the t 
of the air-breathing races. The branch 
hyoid organs are in fact substitutes for t 
racic or pulmonary portion of the sk 
and in exact proportion as the latter | 
more complete, and better adapted te 
respiration, does the former shrink in its 
sions and become simplified by the a 
of successive portions, which previously 
into its composition, and a consequent ret 
ling, as it were, of the muscles connected | 
with. Thus during the metamorphosis” 
tadpole, the branchial arches that before 
largely developed, are progressively foul 
disappear as the lungs assume their offic 
the whole hyoid system of bones and mi 
changed so as to become adapted to the 
formance of totally different functions. 

The permanent or adult condition of 


* 


hyoid apparatus likewise undergoes a progres- 
sive simplification as we examine it in the more 
elevated forms of Vertebrata. Thus, in the 
bird it still consists of elements, that in the 
mammiferous animal may be dispensed with. 
The cornua, the last remnants of the branchial 
arches, are still largely developed in many qua- 
drapeds, and in fact it is only when we arrive 
at the human species that we see the pieces 
composing the byoid portion of the skeleton 
reduced to their simplest condition, and the 
muscles appended thereto correspondently re- 
duced in their number and modified as regards 
the functions they perform. 

4. The muscles that act upon the opercular 
Openings in Fishes are, of course, peculiar to 
_ animals possessed of a branchial respiratory 
system. 

5. The muscles of the limbs exhibit perhaps 
greater varieties than any others belonging to 
the animal economy, their existence and rela- 
tive size being entirely dependent upon the 
kind of progression conferred on any given race 
or family of the vertebrate creation. It would 
‘seem indeed that an inverse proportion always 
_ €xists between the condition of this system of 
“muscles and those that act upon the trank— 
_ the large developement of the one set rendering 
the other of secondary importance. Thus in 
the generality of the osseous Fishes the enor- 
mous bulk of the lateral muscles of the trunk 
renders any great strength of limb unnecessary, 
“and the muscles moving the pectoral and ven- 
tral fins, the representatives of the arms and 
legs, are proportionately small and feeble; but 
in the Plagiostome Cartilaginous Fishes, the 
_ Skates and Rays, the conditions are precisely 
reversed ; the muscles of the trunk shrink into 
“comparative insignificance, and the enormously 
‘developed hands, which here form the great 
__ bulk of the body, moved as they are by muscles 
__ 0f corresponding power, form the great agents 
__ in locomotion, and by their vigorous flappings 
_ Taise these creatures from the bottom of the 
_ Sea, their usual resting-place. 

___The phenomena attendant upon the growth 
of the limbs in Amphibious Reptiles beautifully 
exemplify the same circumstances. In the 
 Lepido-siren, that possesses still the form an‘ 
the Scales of a fish, although it breathes both 
ae gills and lungs, the legs or fins, for it is 
_ difficult to say to which appellation they are 
‘best entitled, are of the simplest possible struc- 
ture, each consisting but of a simple, tapering 
_ Stem, so flexible and feeble that it can scarcely 
be deemed at all useful for the purposes of 1o- 
comotion. 
____ Inthe Siren lacertina we have still the long 
and flexible body of an eel, the tail obviously 
\ forming the chief, or, indeed, the only effective 
__-4gentin progression. Nevertheless, seeing that 
is Amphibian being possessed of lungs can 
breathe the air, the first sproutings of legs are 
here manifest. Two rudimentary limbs corres- 
ponding with the anterior pair of other reptiles, 
and terminated by four extremely imperfect 
toes, are appended to a feeble scapulary appa- 
is, and thus the Siren is allowed to raise its 
head at least out of the, marsh where it re- 


i esl ee 


MUSCULAR SYSTEM. 


543 


sides, and obtain a supply of the atmospheric 
fluid. 

The Proteus is, in form, almost as fish-like 
as the Siren, and its tail is still a strong and 
muscular oar; the limbs nevertheless are slightly 
more developed ; and besides the imperfectante- 
rior extremities, each of which is terminated 
by three toes, a rudimentary pelvis and pelvic 
extremity are now sketched out, the latter pre- 
senting two little toes, but hardly as yet suffi- 
ciently complete to be useful as locomotive 
organs. 

Equally striking examples of the gradual de- 
velopement of locomotive extremities are found 
in those reptiles whereby the transition is effect- 
ed, between the Ophidian and Saurian types of 
structure ; thus in the genus Anguis, as for ex- 
ample, in the common English blind-worm 
( Anguis fragilis ), although externally it would 
appear to be as strictly apodous as the gene- 
rality of other serpents, yet on stripping off the 
skin, these reptiles are found to possess the first 
rudiments of limbs, that are afterwards to be 
made efficient in more highly gifted genera; a 
little pelvis 1s distinctly discermble, imbedded 
in the muscles towards the hinder part of the 
body ; and, in front, a sternum, scapula, and 
clavicle, may all be perceived hidden beneath 
the integument, although no traces of legs or 
feet are as yet to be detected. 

In other serpents more nearly approximated 
to the quadrupedal Saurians, as in the genus 
named Bimanes ( Chirotes, Cuv.) in additiou 
to the scapulary apparatus, two short anterior 
extremities armed with toes, moved by tole- 
rably complete muscles, are met with, whilst 
the hinder legs are wanting. In Bipes, on the 
contrary, it is the pelvic pair of legs that are 
developed, the place of the anterior being only 
indicated by the existence of the frame-work 
and muscles of the shoulder. Lastly, in the 
Saurians and Tortoises the quadrupedal type is 
fully adopted, and the muscles of the limbs 
assume an importance proportionate to the 
duties they have to perform. 

Still more interesting is it to watch the daily 
growth of the muscles that make their ap- 
pearance, as the legs of the Frog are slowly 
formed, budding, as it were, from the sides of 
the Tadpole, and vicariously taking the office 
of those, that previously constituted the loco- 
motive apparatus ; the vertebral system of mus- 
cles, whereby the tail of the aquatic animal 
is moved, being entirely obliterated as the limbs 
advance to maturity. 

6. The masticatory muscles, or those con- 
nected with those movements of the lower 
jaw that are concerned in the preparation of 
food, present great uniformity of arrangement 
throughout all the Vertebral orders, and ob- 
viously constitute a distinct and isolated group, 
the development of which is in exact relation 
with that of the rest of the manducatory ap- 
paratus. 

7. The tegumentary system of muscles, al- 
though only represented in the human body by 
a few detached and isolated remnants, con- 
stitutes among many of the lower animals a 


very important part of their economy, either 


544 


destined to act upon the skin itself or upon 
cuticular structures of very diversified shape, 
which are occasionally developed in different 
regions of the body, and not unfrequently ap- 
propriated to the performance of important 
duties. In those quadrupeds that have their 
backs covered with strong spines, such as the 
Echidna, the Porcupine, and the Hedgehog, 
the cutaneous muscles, usually named panni- 
culus carnosus, are met with in their most com- 
plete form, since in these creatures every quill 
or spine is moved by muscular bands con- 
nected with its base, that serve to erect or de- 
press it at pleasure. The crests and other 
moveable appendages tu the skin met with 
among Birds, are equally furnished with the 
means of motion by strengthening particular 
parts of the muscular apparatus in question. 

In Reptiles, on account of the nature of their 
corneous integument, the muscles of the skin 
are but slightly developed, or indeed most 
generally are not to be detected. - But in Fishes 
they once more present themselves, under a 
novel and most important aspect. The azygos 
fins in these aquatic Vertebrata are, as is else- 
where shewn (vide Pisces), derivations from the 
exo-skeleton, and consequently all the slips of 
muscle, that act upon the individual rays of 
the dorsa!, caudal, or anal fins, however ano- 
malous their nature may appear without such 
a key to their real character, are obviously 
merely portions of the tegumentary system of 
muscles here elevated into an importance not 
witnessed .in other animals, where the exo- 
skeleton is less decidedly appropriated to the 
purposes of locomotion. 

8. The muscles whereby vocal sounds are 
modulated, are equally entitled to be looked 
upon as a distinct and superadded system only 
conferred upon certain races of Vertebrata, and 
that under very various conditions. In Fishes 
these muscles are of course absolutely wanting, 
and even amongst the air-breathing Reptiles 
they are so imperfectly developed as scarcely 
to be regarded as vocal organs. But in Birds 
and Mammalia they assume a higher form, and 
are variously located and more or less nume- 
rous in exact proportion as the voice is per- 
fected. In Birds, indeed, the vocal muscles 
are principally se at the thoracic extremity 
of the trachea, but in Quadrupeds and in Man, 
at the opposite end, the whole machinery being 
thus so completely altered that even analogies 
between the different sets of muscles are not 
easily pointed out. 

9. The diaphragm is an apparatus exclu- 
sively conferred upon the Mammiferous Ver- 
tebrata, since in these only is the thoracic 
cavity separated from the abdomen by a mus- 
cular septum. 

10. The muscles of the tongue must like- 
wise be regarded as forming a distinct group, 
increasing in complexity and extent of motion, 
in proportion as the organ to which they belong 
assumes ter importance, either as an in- 
strument for the prehension of food, or as an 
agent in mastication. 

11. The ocular system of muscles may be 
divided into those which act on the eyeball, 


MYRIAPODA. 


and those employed in moving the palpebral 
appendages. The former when complete con- 
sist of four recti, two obliqui, and the choano 
or suspensary muscle, which not unfrequen 
is distinctly divided into four. The reedi ; 
invariably met with and present few variat 
worthy of notice. The obliquus superior 
Mammals passes through a pulley, 
not the case in other Vensbedtl while 
choanvid muscle is principally met w 
Quadrupeds. 
The muscles of the eyelids are mos 
fectly developed in Birds, in which dis 
muscles are appropriated to the movemen 
the upper and lower eyelid as well as to 
nictitating membrane, which in the f 
races has a proper set of muscles appoi 
to draw it over the eye not met with in ot 
classes. > 
12. The muscles of the auditory ppa 
become fully developed only in the mamm 
rous ear, where four little muscles are in 
riably found connected with the ossicula 
tus, as in the human subject. The mu 
appointed for the movements of the exte 
ear are, however, in many Quadru 0 
more numerous than in Man; in iy 
human ear they merely exist, in a radimen 
condition. 2 
13. The nasal apparatus has likewise a 
tem of muscles of its own, although th 
stances in which it is met with in any 
like a complete state of developement are ¢ 
paratively rare. In Fishes, Reptiles, and — 
these muscles, indeed, can hardly be sa 
exist; and even in the generality of Man 
they are feeb!e and unimportant. It is o 
the proboscidean species, that the nasal mi 
assume their full complexity, and the tr 
the elephant is in modern times the oi 
ample, wherein the anatomist can cont 
them. 
14. The muscles of the generative § 
are only found to exist, as a distinct set, | 
Mammalia, as in these alone is the 
canal complete, and a perfect ejaculat 
paratus given. y 
Thus, therefore, we may learn from thi 
survey, that so far from finding in the: 
frame the fullest and most elaboratel 
structed examples of the various divis 
the muscular system, or, in other word 
pical condition of that part of the 
economy, the human anatomist, in mai 
stances, has only an opportunity of ex: 
the vestiges or rudiments of organs, the 
lower animals attain to a far more e0 


developement. 
(T. Rymer J 


MYRIAPODA, (from the Greek 
ten thousand, i. e. numerous, and groug,. 
the name of an important and highly i 
ing class of articulated animals, mtern 
in their structure and ap ce b 
the Annelidans and the Insecta, pr 
so called; approximating the former in 
worm-like form of their bodies, which 
composed of a great number of rings or 


ments, and likewise allied to the latter by the 
construction of their jointed locomotive legs ; 
these, however, instead of being only six in 
number, as in the true Insects, are, in the 
Myriapoda, always at least twelve, and fre- 
quently extremely numerous, being appended 
to all the segments of the elongated body, 
whence the names “ Centipedes” and “ Mille- 
pedes,” by which these creatures are commonly 
_ designated. All the members of the class are 
apterous ; they exhibit externally a succession 
of cylindrical or compressed rings, each of 
which sustains one or more, frequently two 
_ pairs of jointed feet, all of very similar con- 
_ Struction, being generally terminated by a 
‘single sharp claw. There is no consolidation of 
the anterior segments into a thorax resembling 
that of the Insecta, although many celebrated 
- Entomologists are disposed to regard the three 
"anterior rings as the representatives of the tho- 
racic segments. Upon the head are placed 
‘two antenne or feelers, which, in one large 
‘group, are short, stunted, and composed of 
“seven articulations, whilst in others these organs 
are long and setaceous, presenting a much 
greater number of distinct joints. Compound 
or simple eyes, allied in their structure to those 
of Insects, are generally, but not always, pre- 
Sent. The mouth is formidable, and, in many 
ts, resembles that of Insects, being fur- 
ed with strong mandibles, adapted to de- 
ir either animal or vegetable substances. 
the species breathe air by means of lateral 
mata and tracheal tubes, a circumstance 
reby they are at once distinguishable from 
Crustacea. Their jointed legs remove 
m from the Annevipa, while they differ 
from the Insecta in many important particulars, 
pat more especially in the progressive growth 
f their bodies, by the production of new seg- 
nts, and the development of additional loco- 
“motive limbs, the number of which increases 
With the age of the animal, while, on the con- 
‘y, in Insects, the segments that existed at 
h are found to coalesce into a smaller 
mber, and the prolegs of the larve become 
iterated when the Insect attains its complete 
hexapod condition. 


aa 


All the Myriapoda are terrestrial in their 


_ habits, lurking beneath stones or in the crevices 
of houses. Many of them inhabit decaying 
_ timber, or are found beneath the bark of trees, 
Ss they devour such vegetable substances 
_ as are adapted to their support; or, in the 
_ ease of the more highly organized species, 


_ Wage war against other animals, upon which 
t 1 aaa : . : 
e classification of the Myriapoda has hi- 
_ therto been and still is exceedingly imperfect 
_ and unsatisfactory, apparently in consequence 
of their very wide distribution and the general 
similarity of their appearance. Our country- 
man, Dr. Leach, in his zoological miscel- 
lany, was one of the first who gave a general 
arrangement of these animals, which was 
o by Latreille; but he appears only 
to have examined the European species. In 
Griffiths’ Translation of Cuvier’s Animal King- 
_ dom, Mr. J. E. Gray, of the British Museum, 
VOL. III. 


MYRIAPODA. 


545 


gave the figures of some exotic genera; but of 
these the Editor left the descriptions very im- 
perfect, and only made slight references to 
them in the explanations of the plates. Since 
that time Dr. J. F. Brandt published a mono- 
graph of the Myriapoda chilognatha,* in 
which he pointed out several new genera and 
re-named many, previously established by Mr. 
Gray. More recently M. P. Gervais has pub- 
lished his studies on Myriapods,+ consisting 
of a revision of the class and a list of the 
species, but having overlooked the slight notes 
given of Mr. Gray’s genera, has in one or two 
instances been led into error. Under these 
circumstances it is, with very great satisfaction, 
that we are able, by the permission of Mr. 
Gray, who has kindly placed his manuscript 
at our disposal, to lay before our readers the 
following review of the entire class. 


Order I. CHILOGNATHA, Latr. 
* (Julus, Linn.) 

Antenne seven jointed; rings of the body fur- 
nished with two pairs of legs. 

Fam.1. Juxip. Body cylindrical, smooth, 
rolling up into a spiral form and composed 
of many joints. Each segment formed of 
three imbricated parts, the upper part co- 
vering the body and sides of the abdomen. 
Antenne short, thick. Eyes many in a 
group. 

Gen.1. Jutus. ( Fig. 304, 1, 2, 3.) 

2d, 3d, 4th, and 5th joint of antenna elon- 
gated, attenuated; 2d longest, 5th and 6th 
longer than the rest. 


Fig. 304. 


Julus. 


* Bull. Soc. Imp. Moscow. 
+ Annales des Sciences Naturelles for 1837. 
2Nn 


546 


Gen. 2. Spnaroxotus. Brandt. 
2d, 3d, 4th, and Sth joint of antenna short, 
roundish, equal; the 2d rather longer than 
the rest, the 5th and 6th nearly equal. 
Gen. 3. Sperostrertus. Brandt. 
Lower lip with a semilunar pit in the middle 
and without any tubercles. Eyes many, in 
lunate tubercles. 
Gen. 4. Sperora@vs. Brandt. 
Lower lip with two transverse oblong tubercles 
separated by a transverse groove. 
Gen. 5. Sprrocycuistus. Brandt. 
Lower lip flat, with tubercles placed in an im- 
pression in the centre of its : 


Fam. 2. CraspEpOSOMADZ. 

Body cylindrical (striated), consisting of many 
joints, each formed by a single piece, an- 
tenne slender. Legs 48 pairs or more. 
Eyes many, in a linear series or triangular 
patch. 

Gen, 1. Craspeposoma. Leach. 

Body elongate, depressed. Rings with a com- 
pees lateral edge. Eyes in a triangular 

teh. . 
ee Gen. 2. Cytinprosoma. Gray. 

Body elongate, quite cylindrical, with very in- 
distinct longitudinal strie. Eyes in a small 
oblong, kidney-shaped patch. 

Gen. 3. Reasta. Gray. 

Body subcylindrical, striated longitudinally. 
Eyes in a nearly linear patch. 

Gen. 4. Campata. Gray. Platyulus, 
Gervaise. 

Body rather depressed. Eyes in a double line 

on each side of the back of the head. 


Fam. 3. PotypEsMIp2. 

Legs 31 pairs. Eyes none or only single tu- 
bercles, situated just on the outer side of the 
tentacles. 

Gen. 1. Potypesmus. Latr: 

Body elongate, depressed : rings slightly edged 
at the sides, forming an interrupted margin. 
Antenne with rather long joints. 

Gen. 2. Fonraria. Gray. 

Like Polydesmus, but the margin of the body 

is rude, and forms a continuous edge. 
Gen. 3. Srenonra. Gray: 

The body slender, the rings subquadrate, with 

toothed extended lateral edges. 
Gen. 4. Srosarea. Gray. 

Body slender, subcylindrical ; the lateral mar- 

gin forming a very slight ridge. 


Fig. 305. 
Fam. 4. GLomerip2. 

Body depressed; rings 11; semi- 4 
lunar. Eyes 8, placed in an 
arched line on each side of 
the head. Antennz inserted 
on the upper front part of the 
head. , 

Gen. 1. Gromeris. Latr. 

The first dorsal ring striated in 
the middle of the side. (Fig. 
305.) ar 


MYRIAPODA. 


Gen. 2. Lamisca. Gray. G 
Brandt. 


Fam. 5. ZepHRONIADA. a 

Body depressed ; rings 12; semilunar. 1 
many in a circular group. Antenne on 
side of the head. ( Fig. 306, abcd.) 


Fig. 306. . 
Se . 
e@ f eS RB 

ED 


Gen. 1. ZepHronia. Gray. 
Brandt. ‘ ' 

Antenne 6-jointed, penultimate joints : 
last largest, oblong, rounded at he 
( Fig. 306.) ie 
Gen. 2. Spuozrotuerra. Brandt. Seph 
part. is. iwi 

Antenna 7-jointed, 6th joint nearly « 
last joint smallest, truncate at the tip. — 


Fam. 6. Potyxenipz. 

Body depressed; rings 6; soft, s 

with a tuft of scales on each side; feet 

Eyes many in a group. ie 
Gen. 1. Potyxenus. Latr. ( Fig. é 


Fig. 307. 


Polyxenus lagurus, 


Order II. CHILOPODA. L. 
Antenne of 14 joints or more. §& 
the body flattened, each bearing 
pair of feet. + 


Fam. 1. Scuricermpz. “ 

Antenne filiform, very long. eg V 

Eyes reticulate. +" 

. Gen. 1. eee I k 

eet 15 pairs or more. - 308, OX 
livida C 7 


MYRIAPODA. ; 5AT 


Fig 308. Gen. 2. ScoLOPENDRa. 

Eyes 4-4. Stemmatiform. Antenne setaceous, 
17 or 20 jointed. Body of 23 depressed 
rings. Feet 21 pairs, hinder longest, with 
the first joint spinulose (Fig. 310.) 


Fig. 310. 


Scutigera livida. 
Fam. 2. ScoLoPENDRIDZ. 
e tapering, moniliform, moderate. Legs 


rous, moderate. Eyes numerous in 
» or wanting. 

Gen. 1. Lirnosivus. 

s of the body 17, imbricate. Eyes 
gregarious. Antenne 20 to 40 jointed. 
309, Lithobius forficatus.) 


Gen. 3. Cryprops. 

Eyes inconspicuous, Antenne setaceous, 17 
jointed. Feet 21 pairs, hinder longest, not 
spinous. 

en. 4. Srricamra. Gray. ( Geophilus. ) 

Eyes none. Antenne 14 jointed, moniliform, 
rather elongate. Body linear, depressed. 
Feet very numerous, fifty pairs or more. 


The whole body of a Myriapod consists of 

a succession of similar rings or segments of 

various form and consistency, the number of 

which would seem to be constant in the mature 
2N2 


Lithobius. 


548 


or adult animal, but subject to important and 
very remarkable varieties ——— the progress 
of its growth. In the lower forms, such as 
Julus (fig. 304), the texture of the segments 
is hard, crustaceous, and brittle; but in the 
Scolopendroid races, the rings are flattened 
and covered above and below with tough and 
coriaceous scute, In all the Chilopoda each 
segment supports only a single pair of ambu- 
latory legs, which resemble in many respects 
those of insects, but terminate invariably in 
a simple claw. In the Chilognatha, on the 
contrary, witii the exception of a few of the 
most anterior, and likewise of the terminal 
or anal segments, each ring has two pairs 
of feet attached to its under surface, con- 
sisting apparently of two half segments con- 
joined; and this view of their composition is 
further strengthened by the fact, that a deep 
transverse indentation or groove is always visi- 
ble upon the dorsal surface, dividing the other- 
wise apparently single ring into an anterior 
and a posterior moiety, to each of which is 
fixed a pair of short and very feeble legs, com- 
posed of several distinct articulations. The 
three first segments in Julus form exceptions, 
however, to this arrangement, each of these 
supporting only a single pair of ambulatory 
feet, and these segments have been supposed 
by some authors to represent the thoracic seg- 
ments of the true insects. The seventh ring, 
likewise, in the female, has one pair deficient, 
they being replaced by the orifices leading to 
the sexual organs. The anal and penultimate 
segments are completely apodal in the Julide, 
whilst, on the contrary, in some of the Chi- 
lognatha, the size of the locomotive limbs in- 
creases progressively as we approach the caudal 
extremity, the last segment supporting the 
longest pair, which are directed backwards, so 
as to have in some measure the appearance of a 
furcate tail. 

In the Scolopendride ( Chilopoda, Latr.), a 
family which embraces those forms of Myria- 
“oaty that are most nearly allied to Insects, we 

ave a race of carnivorous Myriapods, pos- 
sessed of strong and active limbs, varying in 
number in different genera from fifteen to 
twenty-one pairs, by the aid of which they can 
run with considerable rapidity, and are able, 
owing to the flexibility of their long and 
jointed bodies, to wind their way with facility 
among the lurking places of Insects, against 
which they on an unrelenting warfare, 
All of them are found carefully to avoid the 
light, and generally to frequent damp situations, 
more especially where decaying animal or vege- 
table oo ma abound. ey lurk, therefore, 
under stones or pieces of old wood, or are met 
with beneath the bark of trees, localities which 
from their structure they are peculiarly adapted 
to occ . 

In the following account of the anatomy 
of these creatures we shall select the Scolo- 
pendre, properly so called, for particular de- 
scription, as being the largest and, conse- 
quently, most commonly met with in our 
collections, noticing, however, as we proceed, 


MYRIAPODA. 


such peculiarities as may be worthy of notice — 
in other genera. : 
The Scolopendre have their bodies com- 
posse of twenty-one segments exclusive of the — 
ead, to each of which is attached a pair of 
jointed legs. The segments are all o 
more or less quadrilateral in their s th 
transverse diameter being generally the longes 
but their size is very variable and irreg: 
The whole body is depressed, each segmer 
consisting of a dorsal and a ventral slate | 
soft but corneous consistency, formed by 
thickening of the cuticle in those regions of t 
body, while the sides to which the legs a 
appended, and where, moreover, the respirato 
spiracles are situated, are soft and of a coris 
ceous texture. ‘ 
The legs are all five-jointed and terminat 
in a simple sharp horny claw: those appends 
to the segments in the neighbourhood of t 
head are comparatively small, but as they ap 
proximate the hinder part of the body 
increase in size and strength, the last pair be 
turned backwards so as scarcely to ' 
as locomotive agents. 
The head, and more especially the ps 
entering into the construction of the oral; 
paratus of these Myriapoda, present 
difficult inquiries to the scientific entor 
who would attempt to identify them 
parently corresponding structures met witl 
the organization of the mouth of insects, < 
accordingly we are not at all surpri 
that no two authors agree as to the names | 
are most applicable to the different pieces 
longing to this portion of their economy. 1 
Myriapoda, be it remembered, are obviot 
an osculant or transition group allied 
to the Annelidans, to the Insecta, to the Ai 
nidans, and to the Crustacea. It is by 
meaus surprising, therefore, that, in the 
struction of almost every part of their bo 
we find an organization intermediate t 
these important divisions of articulated a 
as we shall again and again have occasic 
tice. But, perhaps, in no part of their eco 
is this intermediate structure better exemi 
than in the mouth of the Scolopendra, t 
different portions of which all writers ap 
to have given names rather in conformity 
their own preconceptions than with ani 
affinities that have been pointed out, o 
general view of the real nature of such 
dages. With all respect for the opinic 
preceding writers, we shall, on this ac 
endeavour, in the following deseriptio 
avoid as much as possible technicalities 
liar to the orismology of any particular 
of zoological science. ‘ 
The head of a Scolopendra, or that 
of the creature which supports the instr 
of sensation and the organs employed for 
prehension of food, appears, when ¥ 
superficially, to consist of two segments 
a circular shield-like plate, constituting tl 
head, that exists only upon the dorsal ¢ 
of the body, in which are i 
and which, moreover, coutains the eyes 


* 
- 


v 


ih ape 


as 
7 


Pa a a 


a _ 


overlaps the greater number of the pieces 
belonging to the mouth. The second segment, 
by far the larger and the stronger of the two, 


envelope, the strongest segment of the whole 
body, is entirely devoted to the support and 
movement of a pair of sharp bi-articulate and 
hooked fangs resembling jaws, that move trans- 
versely like the (so-called) mandibles of a 
_ Spider, but which are in reality only modifica- 
tions of the ambulatory feet converted into 
‘instruments for killing prey, each being per- 
_forated near its sharp termination with a long 
oval slit, through which venom is said to be 
instilled into the wound inflicted by this 
rmidable weapon. 


| ___ The head properly so called, namely the 


ular shield-like plate seen upon the dorsal 
irface at the anterior extremity of the body, 
although apparently consisting of a simple 
horny disc, is doubtless composed of several 
nents conjoined superiorly ; indeed, these are 
pletely confused, and inferiorly are too soft 
membranous to be distinguished, except 
the presence of those articulated appendages, 
hich, although forming parts of the mouth, 
still merely repetitions of the jointed legs 
ed to the other segments of the~ body. 
the most superficial plate, with its articu- 
appendage, the /abium and labial palpus of 
mologists, is but an incomplete ventral 
um, with its articulated limb in a rudimen- 
condition’ as compared with those of the 
dy, and is even armed with a distinct claw, 

e the locomotive legs. In like manner the 
nd pair, the mazille of authors, are legs 
one step further removed from their normal 
n, but not more so than are the poison- 
s already described. In the third pair or 
dibles we have a leg reduced to its terminal 
» and that is broad and serrated so as to 
ome useful in manducation. Lastly, the 
corneous and serrated piece (the Jabrum_) seems 
to be the last vestige left of limbs of this 
€scription, the two horny remnants of legs 
ing become consojidated with each other 
with the dorsal head-plate, so as to form 
anterior boundary of the mouth. 

imentary canal.—The alimentary canal in 
the Myriapoda is of extremely simple con- 
ion, and both in its form and general 
ngement, very nearly resembles that of the 
2 of Lepidopterous Insects. In Julus ter- 
is (fig. 311) the esophagus (h) is seen to 
f considerable capacity, in accordance with 
ature of the coarse food upon which these 
etable-eating species live. The stomach is 
and bowel-like, extending from the termi- 
of the esophagus to the insertion of the 
ic vessels. To this succeeds a wide and 
lated colon, which passes directly to the 
Aap of the body, where it terminates. 

the Scolopendroid genera the same con- 
rmation of the alimentary apparatus is met 
th, the stomach and intestine passing straight 
om the mouth to the anus without any pecu- 
Harities of structure worthy of notice. 
In Lithobius forficatus, which we may take 
asa Speciinen of one of the Chilopod Myria- 


MYRIAPODA. 


and, in fact, from the density of its corneous — 


549 


poda, a very similar arrangement exists; the 
Fig. 311. esophagus, which is pro- 
portionately narrow, ends 
in a_ simple stomachal 
enlargement of an oblong 
“shape, and this termi- 
nates in a straight bowel, 
the point of separation be- 
tween the one and the 
other being only indicated 
by the entrance of the 
biliary vessels. 

The glands connected 
with the alimentary ap- 
paratus closely resemble 
those of the insect larva. 
Two convoluted salivary 
tubes are seen folded up 
at the sides of the cso- 
phagus, where their con- 
volutions are intervolved 
into a species of ravel 
(fig. 311, i) with the 
origins of the hepatic ves- 
sels (4), which latter, after 
a tortuous course, are in- 
serted, as in Insects, at 
the termination of the sto- 
machal portion of the di- 
gestive tube. 

Respiratory System.— 
The Mirdanets respire in 
the same manner as In- 
sects by means of late- 
ral spiracles and tracheal 
tubes. The spiracular ori- 
fices are, in the Scolo- 
pendride, very conspi- 
cuous, as, for example, 
in Lithobius, (fig. 312,) 
where the corneous lips 
of the apertures leading 
to the trachee (s, s, s, s) 
are seen situated behind 
the origins of the legs, 
upon the sides of the 2d, 
4th, 6th, 9th, 11th, 13th, 
and 15th segments, occur- 
ring upon the alternate 
segments, except in the 
case of the 8th, where 
there is one missed. The 
trachez derived from these 
spiracles pass inwards to 
be disbributed upon all 
the viscera, ramifying in 
every partof the body, 
and thus conveying air 
throughout the system. In 
structure these air-vessels exactly resemble those 
of true Insects, and are equally characterized by 
the existence of a spiral fibre in their interior, 
whereby they are always kept permeable. , 

Circulatory system.—In the nature of their 
circulatory apparatus the Myriapoda are closely 
related to the Insects properly so called. A 
long dorsal vessel passes from the tail towards 
the head along the mesial line of the body. 
The sides of this vessel, on clearing away the 


SFA 
a 


ae 


SS 
ee a 


fats —<— 


o—l 
<a 


i 


550 MYRIAPODA. 


fat Nags on ype it on ‘all sides, are seen 
to rated at intervals . 

with papa valvular ori- Fig. 312. 
fices, through which the cir- 
culating fluid gains free admis- 
sion from the general cavity 
of the body, and by the un- 
dulatory contractions of the 
dorsal heart thus constructed 
is forced forward toward the 
head. Arrived in the neigh- 
bourhood: of the csophagus, 
the dorsal heart is seen to give 
off several vessels, and ac- 
cording to the opinion of Mr. 
Newportand Mr. Lord,* there 
is reason to suppose that a 
vascular system more com- 
plete than has as yet been 
proved to exist in any of the 
true Insects may be pointed 
out in this region of the body. 
The dorsal vessel itself, when 
examined under a microscope, 
is distinctly muscular, being 
formed of circular flat bands 
that surround the cavity of the 
tube, so that doubtless the 
action of this heart, in the 
larger species at least, is suffi- 
ciently energetic. 

Foramina repugnatoria.—These are a series 
of orifices which in the Julide are seen upon 
the lateral aspect of every segment of the body, 
and communicate with as many minute mem- 
branous sacculi placed within the body. These 
sacculi, both from their position and relations, 
forcibly remind us of the series of respiratory 
sacs met with in the Leech and other air- 
breathing Annelidans, but in Julus they are 
supposed to be merely organs of secretion from 
which some offensive fluid is poured for the 
protection of the animal. 

Nervous system.—The nervous system of the 
Myriapoda, as in all the Articulata, exhibits a 
double series of ganglia connected by cords of 
inter-communication. The supra-cesophageal 
ganglion, situated within the cephalic segment 
of the body as relates to its development, 
seems to hold a place intermediate between 
that of the Annelida and of Insects, or perhaps 
more strictly speaking, corresponds with the 
larva condition of the latter. The ventral chain 
of ganglia is numerous in proportion to the 
nutaber of segments which enter into the com- 
position of the body, their number decreasing 
as the locomotive limbs over which they preside 
become more fully nererepes and capable of 
more vigorous action. hus in Julus and 
Geophilus, where the limbs are extremely 
numerous and feeble, the ganglia in their num- 
ber and small size a ener the condition 
they exhibit in the Nereis or more elevated 
Annelides, but in Scolopendra (fig. 313) the 
more powerful limbs and stronger muscles 
required by their carnivorous habits demand 
greater developement of the centres of the ner- 
vous system. 

* Vide Med. Gazette for 1837. 


“il 


Senses.—In the structure of their or 
sensation likewise, the Myriapoda so 1 


resemble Insect larve that little can be said 
concerning them in addition to what the reader 
will find elsewhere stated. (See articles An- 
NELIDA, Crustacea, Aracunipa, LNsEcrTa.) 
The antenne upon the head, which are in- 
variably two in number, correspond in all 
essential circumstances with those met with in 
Insects, and doubtless perform the same func- 
tions. The eyes when present, which is not 
the case in all the genera, exhibit the form of 
_ simple ocelli congregated upon the head, and 
arranged in lines or triangular patches ; but in 
no case do they exhibit the appearance of a 
really compound eye, such as is possessed by 
ey of Insects in their perfect state. 
_ With respect to the other. senses, touch, taste, 
and smell, but little is known except by conjec- 
ture, and presuming them to exist we can only 
suppose them to be conferred in the same 
Manner as in the real Insect. 
_ Generative system.—A remarkable difference 
_ exists between the Chilognatha and the Scolo- 
‘pendroid Centipedes with respect to the posi- 
_ tion of the organs of generation. In the former 
the external openings, both of the male and 
female genitals, are situated near the anterior 
extremity of the body, as is the case among 
the Annelida; whilst in the Chilopodous 
‘genera, which exhibit a higher grade of organi- 
gation, the generative apertures are found in 
_ the caudal segment as in the Insects. 
_ In Lithobius the structure of these parts is 
in both sexes very simple. In the male there 
_ are three long and convoluted secreting tubes 
_ resembling the simplest form of the testis in 
___ Insects, wherein, doubtless, the seminal fluid 
_ iselaborated. These are united at their termi- 
‘nations so as to form a kind of common recep- 
tacle, from which two tubes proceed to the 
root of the intromittent organ, at which point 
___ theyare joined by four smaller auxiliary vessels, 
__ which seem to take their origin in masses of 


_ fatty substance. The penis is a horny cylin- 
_ drical tube that can be protruded from beneath 
_ avalvular plate which covers the anal orifice 
(fig. 309, “ss 
_ he female apparatus consists of a single 
_ Sacculated ovarium, occupying the mesian line 
of the body. From this proceeds a narrow 
_ €xeretory duct, which, however, prior to its 
termination beneath the anal segment becomes 
_ considerably dilated into a cavity that has been 
_ improperly named uterus. Here it receives 
bo bead 
__ two sets of supplementary vessels, the one a 
t of wide ceca, the other composed of four 
_ €onvoluted vessels apparently destined to secrete 
bo og additional covering to the eggs before 
their extrusion. The female generative orifice, 
ituated in the anal segment, is covered with a 
late and furnished with a pair of small 
ny forceps calculated to assist in copulation. 
_4the male generative organs of Scolopendra 
‘present a very peculiar structure; but these 
we have already described elsewhere (see Gr- 
| NERATION, ORGANS OF). 
_ The male generative organs of Julus (fig. 314, 
A) are two elongated and partially convoluted 
tubes placed side by side beneath the alimentary 
‘canal immediately above the nervous system. 


MYRIAPODA. 


551 


The excretory ducts or terminations of these 
tubes run towards the anterior part of the body, 
where. they terminate in two organs of intro- 
mission (a), which pass out at the under surface 


Fig. 314. B 


A 


of the seventh sec- 
ment by distinct ori- 
fices behind the se- 
venth pair of legs. 
Posteriorly they ex- 
tend backwards as far 
as the middle of the 
colon. In the ante- 
rior third of their 
course they lie close 
A» together, but after- 

wards separate, be- 

come smaller, and have developed from their 
sides at short distances a number of minute 
glandular ceeca, or transparent vesicles (c), which 
doubtless constitute the secreting portions of 
the apparatus or proper testes of the animal. 
The two efferent ducts, whereby the secretion 
of these ceca is conveyed out of the body, 
inter-communicate freely by short transverse 


j 


canals (fig. 13, dd), and from the sacculated 


552 


nation appear in some species 
to perform likewise the office 
of reserveirs for the seminal 
fluid. In a large African species 
Mr. Newport found the double 
bine intromission to be 

ensile (fig. 314, B, a), 
each part ls the form of a 
distinct claw between the move- 
able joints, of which passes out 
the elongated half corneous 
penis. These are co- 
vered in anteriorly by a horny 
valve somewhat of a trian- 
gular form, and the whole oc- 
cupies an oval space on the 
under surface of the seventh 
segment, corresponding to that 
usually occupied by the legs. 
“ With regard to the product of 
secretion in these organs,” ob- 
serves Mr. Newport,* “ I have 
never yet found any thing but 
a granulous fluid in the ceca, 
eeperonty similar to the gra- 
nules in the higher animals 
from which Spermatozoa are 
produced, but this might have 
arisen from the immature re- 
cent specimens I was alone 
able to obtain. It would be 
interesting to ascertain whether 
these germs of Spermatozoa are 
produced in the ceca as there 
seems reason to believe, as we 
shall presently find that the ova 
in the female are secreted in 
sacs which appear to be ana- 
logous to these ceca in the 
male organs. I am inclined to 
think that the Spermatozoa are 
not iste x he until the granu- 
lous fluid has passed into the 
efferential ducts at the season of 
impregnation.” 

e female organs of the 
Julide (fig. 315) are described 
with equal minuteness in the 
paper above referred to, from 
which we extract the following 
exceedingly valuable observa- 
tions, as nearly as possible in 
the words of Mr. Newport him- 
self, to whom we are also in- 
debted for the illustrative fi- 
gures. In the female Julus, the 
organs of reproduction are as 
simple as those of the male. 
They consist of a single elon- 
gated bag or oviduct, covered 
on its exterior surface with a 
very great number of ovisacs 
or coeca of various sizes, each 
of which secretes but a single 
ovum. This oviduct extends . 
backwards beneath the alimentary canal, from its 


Fig. 315. 


* Phil. Trans, for 1841. 


MYRIAPODA. | 
appearance that they present towards their termi- double vaginal outlet (a a), which is 


Aa 


in the fourth segment behind the second pait 
of legs, as far as the posterior part of | 
rectum close to the anus, where it ends in a — 
cul-de-sac (d). It is most nearly in contact with 
the alimentary canal on its upper surface, but 
is separated from it by adipose tissue; 
the pregnant female it is smooth, and 
tended with ova that have passed into it 
from the ovisacs, and are ready to be 
posited immediately after intercourse with 
male. The ova at the anal extremity, | 
is, at the commencement, of the duct 
as perfect as those near the vaginal outle 
The oviduct contains within its cavity, at le 
from seventy to eighty of these perfect ees 
awaiting ienpeegiianes, Sean in two or mot 
irregular rows, and greatly distending its sides 
In some of the larger species of the ge 
there are four and in others five rows of eggs, 
number of which is much greater than in our | 
tive species. The ovisacs (fig.315 and 316,¢ 


% 
are little sacculi, distributed thickly to the n 
ber of many hundreds over the whole 
of the oviduct, from its posterior or eax 
tremity to within a short distance of its vag 
outlets. Each ovisac, whatever be its 
developement, contains but a single ©) 
every part of which is produced in it, for 
germinal vesicle in the most rudimentary 
to the yelk, albuminous fluid, and shell. — 
fact deserves particular consideration. A 
proportion of the ova in the ovisaes ” 
arrive at maturity, but are re n 
growth by the more rapid developeme 
others that are near them, so that on exalt 
an oviduct partially distended with 
greater number of ovisacs in different 
developement, are at the sides and oP 
under-surface of the duct, in parts which ¢ 
nd to the interstices between the fully. 
oped eggs, that have passed into the ovi¢ 
or are still forming on its exterior. One re 
ovisacs usually exists on each side of the: 
near its upper part, but most of the ovisaes } 
the course of developement are at IS 5 


ioe 


4 


> ar =” 


MYRIAPODA. 


The structure of the duct and of its numerous 
ovisacs is best seen in those specimens that 
have not yet arrived at maturity, or in those 
which have just deposited one laying of eggs. 
In these individuals the oviduct, to within a 
short distance of its division into two outlets, 
is studded with minute ovisacs, each filled with 
the rudiments of its minute ovum. Its ge- 
heral appearance in a female, that has recently 
deposited its eggs, is completely botruoidal, 
very like the ovary of Birds, some ova being 
always fully developed, and ready to pass into 
the oviduct, while others are in various stages 
of developement, many of which are imper- 
oe except with the aid of a powerful 
ens. 

But the most remarkable condition of the 


female organs in the Julide is their double 


vaginal outlet, as in Crustacea, although the 
oviduct itself is a single tube until near its 
termination, where it is divided into two short 
canals, which from a slight opacity at their 
base, where they join the single duct, appear, 
when seen by transmitted light, to be separated 
from it by a valve or duplicature of the lining 
mucous membrane. The vaginal orifices are 
simply two nipple-shaped portions of the tegu- 
ment, with somewhat oval apertures sur- 
rounded by a corneous ring, from which is 
developed a circle of minute hairs. They are 
Situated on the under surface of the fourth 
segment of the body, and correspond in posi- 
tion to the insertion of the legs in the third 
segment. 

Ova.—We have already seen from Mr. New- 
port’s description of the female generative 
system of Julus, that the ova are formed in 
Separate ovisacs, from which they issue com- 
pletely constituted eggs, into the cavity of the 
ovarium or common duct, through which they 
are expelled from the body after impregnation ; 
and we now proceed to lay before the reader 
the important results of the investigations of that 
distinguished anatomist relative to the struc- 
ture of the ova themselves, and the progress 
of embryonic developement. The existence 
of the ovisacs in Julus as single isolated cap- 
Sules on the exterior of the oviduct, in each 
of which a single egg is produced, is, Mr. 


Newport observes, a circumstance particularly 


favourable to a minute examination of the 


©vum in all its states, especially as ova are 


found at the same time in every stage of de- 
velopement. The smallest ovisacs appeared 
like very minute glandiform bodies, developed, 
as it were, immediately from the structure of 
the duct itself, and in these the rudiments of 
the future egg had already begun to be pro- 
duced. The smallest rudiments of eggs ex- 
amined were of an elongated shape, and as yet 
not more than three, or at most four blood- 
globules in diameter. They appeared already 
to have distinct parietes, and to be filled with 
very minute graniform cells of a uniform size, 
slightly opaque, and of a yellow colour. The 
diameter of these cells, as nearly as could be 
ascertained by direct comparison, was equal to 
about one-third of that of a blood-globule. 


In the midst of these cells there was a larger 


but much more delicate structure of a circular 


553 


form and equal in size to about two of the cells, 
but whether this was the germinal vesicle or its 
macula could not be determined. Other ovi- 
sacs twice the size of the foregoing were filled 
with similar contents, and from the opacity 
and yellow colour of the graniform cells, it 
was evident that they constituted the yelk in 
one of its earliest stages. At a later period 
both the yelk and its including vesicle are in- 
closed in a distinct membrane—the membrana 
vitelli, and before its escape into the oviduct 
all the parts of a perfect egg, namely, the yelk, 
the germinal vesicle with its macula, the mem- 
brana vitelli, the albumen, and likewise the 
shell lined by the membrana externa or chorion, 
are completely formed. 

Evolution of the embryo—The develope- 
ment of the young Julus Mr. Newport di- 
vides into several distinct and well-marked pe- 
riods, during each of which phenomena are pre- 
sented of the utmost interest, both to the phy- 
siologist and in an entomological point of view. 

The first period extends from the deposition 
of the ezg to the gradual bursting of the shell, 
and exposure of the embryo within it, occu- 
pying the space of twenty-five entire days, 
during which the egg acquires a sensible in- 
crease of bulk. 

On the nineteenth day there was a complete 
alteration in its form; it was more obtuse at 
both ends, and had become much larger, and 
the outline of the embryo, coiled up within the 
shell and nearly filling the whole interior, was 
very distinct, although, as yet, there were no 
rudiments of limbs or even of a division of 
the body into distinct segments. On the fol- 


lowing day, the twentieth, the outline of the 
embryo was more apparent, and on its concave 
or ventral surface there were faint traces of a di- 
vision of the body into six segments (fig. 31 reel 


Fig. 317. 


Up to this period Mr. Newport 
was unable to detect any funis 
or umbilical cord attached to 
the embryo, although, in conse- 
quence of Rathke’s observations 
in Crustacea, such a structure 
was particularly sought for, the 
whole body still appearing to be 
formed of cells of different sizes. 

From this time the egg be- 
came every day larger until the twenty-fifth 
day, when it was greatly distended and began 
to assume a kidney-shaped appearance, and 
commenced bursting longitudinally in the me- 
dian line of the dorsal surface, the back of 
the soft and perfectly white embryo gradually 
pressing through the opening. 

In the second period of developement the 
embryo is exposed to a new medium, and 
perhaps derives the means of its further growth 
from external sources, although it is still enve- 
loped in the foetal membranes and retains its 
connection with the shell. 

The liberation of the embryo is a remarkably 
slow process as compared with the escape of 
other animals from the egg. In Mr. New- 
port’s observations, from ten to twelve hours 


* This and the succeeding figures are copicd 
from Mr. Newport’s paper, before quoted. The 
objects have been magnified twenty-five diameters. 


554 


elapsed before the body of the young my- 
riapod was so far liberated as to remain only 
partially enclosed between the two halves of the 
shell, as represented in fig. 318, being still at- 
tached to its interior by a pe- : 
dicle or funis (fig. 319, d). Fig. 318. 
So remarkable is its condi- 
tion at this period that it 
strongly resembles the ex- 
pansion of the germ in the 
seed of a plant, rather than 
the evolution of a living 
animal. The embryo is per- 
fectly motionless, and the 
bursting of its shell appears 
to be effected not by any 
direct effort of its own, since, up to this time, it 
has acquired only the form and external sem- 
Dlance ofa living animal ; but, by the force of ex- 
pansion of the growing body, the development 
of which being greatest along the dorsal or larger 
curvature, exerts, in consequence, a greater de- 
gree of force against the middle of the dorsal 
than the corresponding part of the ventral sur- 
face; the head and tail of the embryo acting 
as a fulcrum against the ventral surface only at 
the ends of the shell, and thus bending it into 
the kidney-shaped form it assumes, while the 
dorsal surface of the embryo is gradually 
pressed through the opening. From the com- 
parative rapidity of its enlargement imme- 
diately afier the shell is fissured, Mr. Newport 
observes, that it seems as if the stimulus given 
to it by exposure to a new medium, atmo- 
spheric air, were the great means of exciting its 
evolution. 

The embryo is now formed of eight distinct 
segments (fig. 319), including the head, the 
ninth or anal segment being still indistinct. 
The head is more 
defined in its out- 
line, and firmer in 
texture than other 
parts of the body, 
and is __ inflected 
against the under } 
surface of the pro- 
thorax (2) or second 
egment, from which 
it is divided on the 
upper part bya deep 
transverse line: at 
its sides it exhibits 
a faint trace of the future antenne. The four tho- 
racic segments also exhibit on their ventral sur- 
face little nipple-shaped extensions, three of 
which on each side are the rudiments of future 
legs. When viewed from above, the body of the 
embryo appears compressed and wedge-shaped, 
its greatest diameter being in the second and 
third segments, while each succeeding segment 
is more and more contracted. Mr. Newport 
was unable at this period to detect any separate 
internal organs, the whole embryo being still a 
congeries of vesicles or cells, in the midst of 
which there seemed to be some faint traces of 
the commencement of an alimentary canal. 

« At the end of the first day,” continues Mr. 
Newport, “ I carefully removed the embryo and 
shell into diluted spirits of wine, and, on ex- 


Fig. 319. 


MYRIAPODA. 


amination beneath the microscope, found the — 
body of the embryo covered with an exceed. 
ingly delicate cuticle, through which the cells 
it was formed of were distinctly visible. It 
was also completely enclosed in a smooth an 
perfectly transparent membrane (fig. 319, ©) 
which seemed to contain a clear fluid, inte 
between it and the embryo. This men 
rane I regard as the analogue of the amni 
the vitelline or investing membrane of ft 
embryo in the higher animals, and ide 
with the membrana vitelli, before described, 
the proper membrane of the yelk in the e 
Julus. It is a shut sac that completely inves 
the embryo, except at its funnel-shaped %& 
mination at the extremity of the body (fig. 31 
d), where it is constricted, and together wii 
another membrane (e), which in yu 
egg is external to this and lines the interior 
the shell, assists to form the cord or pro 
funis (d). aa 

“The funis enters the body of the embryo 
the posterior part of the dorsal surface of 1 
future penultimate segment, where the mit 
or spine exists in the adult animal, and not 
the dorsal surface of the thoracic region, as § 
by Rathke in the Crustacea. The proper a 
or terminal segment is, as yet, but 
perfectly developed. In the funis @) 
also observed some exceedingly delicate st 
tures that exhibited all the appearane 
vessels. They seemed to enter the body 
two sets, that were spread over and enti 
lost in the membrane (e). Whether these 
indeed vessels, or merely folds of the m 
brane I am not certain. The membrane (¢ 
which they appeared adheres closely to 
shell and retains the embryo in connet 
with it by means of the funis. In the unl 
egg, this is also a shut sac like the am 
and forms the membrana externa or chorion 
the second or outer investing membrane 
ovum lining the interior of the shell. 
: “ The bran: of re two investing 

ranes of the embryo in iapoda may,” 
Mr. Newport, “ be regarded with some int 
in reference to the analogies which they 
to similar structures in Vertebrata, sim 
shew the persistence of one universal lawi 
mode of vise ment of the germ.” 

On the third day the embryo had ¢ 
ably increased in size, but was still per 
motionless and attached:to the shell b 
funis. This attachment continues for | 
days, during which the embryo remains 
tially protected by the two halves of the : 
When examined at this period in thet 
State, all the parts of its body are still” 
tinct, but in specimens that have been 
time in ‘spirits of wine, the divisions! 
the segments are well marked. The ru 
of the legs are more developed, but t 


he uni 


ae 


the second and third segments less tha 
fifth, so that not only at the bursting © 
shell, as noticed by Savi, but also for s¢ 
days afterwards the embryo is competely 
dal, the future limbs existing only in@ 1 
mentary state. Posteriorly to the fifth segm 
the body is more soft and delicate, and the s 
ments less clearly defined. This results fit 


A 


the circumstance that it is at this part of the 
body that the future new segments are to be 
produced. 

On the fourth day, Mr. Newport first ob- 
served some faint traces of a single eye, or 
ocellus, on each side of the head. The embryo 
had now further increased in size, and the ru- 
diments of its future legs had become larger 
and more obtuse, an appearance which the 
newly-formed limbs of the Articulata often 
exhibit previously to their further elongation. 
Traces of the formation of internal organs were 
now evident through the tegument at the pos- 


terior part of the body, and the funis was con- 
tracted as if about to separate. Internally the 


body was still formed of cells aggregated toge- 
ther, but differing more in size than at any 
revious period, as if they were becoming 
used into separate tissues, and in the midst 
of them and closely surrounded on all sides 
was the newly-formed alimentary canal. The 
canal was now more opaque, and when pressed 

‘out of the body more firmly adhered together 
_ than any other internal structure, and was dis- 
_ tinetly composed of an aggregation of very 
minute cells. Around the sides of the body 
muscular structure was also in the course of 
development, but as yet was exceedingly in- 
distinct, insomuch that Mr. Newport could 
discover no perfect fibre, a fact that sufficiently 
accounts for the entire absence of spontaneous 
_ Motion in the embryo up to this period. 

A new process was now about to commence 
—the development of new segments. On the 
third day, as has been already stated, the pos- 
terior part of the body is less distinctly divided 
into segments than the anterior, the first five 
Segments being most distinctly marked. The 
sixth and seventh are now more defined. It is 
in the membrane f, fig. 321, that connects the 
seventh with the eighth segment at the posterior 
‘Margin of which last the funis (d) enters, and 
which segment is permanent as the penultimate 
throughout the life of the animal, that the for- 
mation of new segments is taking pas At 
this period it is only a little ill-defined space 
that unites the seventh and eighth segments 
into one mass, but in proportion as the anterior 
parts of the body become developed, this part 
__ ts also enlarged, not as a single structure, but 

as a multiplication or repetition of separate si- 
“milar structures. 

On the ninth day the changes have advanced 
much further (fig. 320) ; 
‘not only have the future 
hew segments become 
‘more distinct, but trans- 

verse depressions are also 
Seen on the dorsal surface 
of the original segments, 
shewing their division into 
‘double ones, as in the 
“perfect animal. The rudi- 
ments of the legs are now 
further developed, and 
their transparent distal 
extremities are seen through the investing mem- 
brane applied closely together and extended 
along the ventral surface of the body, as in the 


MYRIAPODA. 


555 


nymphs or pupz of true Insects. The an- 
tenne and ocelli are more apparent, and the 
embryo itself has increased at least one-third 
of its original dimensions. It is still attached 
by the funis to the shell, but this attachment is 
daily becoming more fragile, and is now sepa- 
rated by very slight causes. The embryo has 
thus continued to grow through nine succeed- 
ing days, since the bursting of its shell, without 
any visible means of nourishment, the nutri- 
ment supplied by the yelk having been ex- 
hausted before that occurrence. Hence it be- 
comes a matter of inquiry from whence it now 
derives its means of growth? Whether it has 
already sufficient materials derived from the 
egg, and stored up within itself for its future 
development, or whether the external inclosing 
membrane may not still contribute to the func- 
tion of nutrition by absorbing fluid condensed 
from the air of the humid locality in which it re- 
sides. The probability of this last supposition, 
says Mr. Newport, is somewhat countenanced 
by the fact that I have constantly observed the 
membranes of the embryo at this period co- 
vered with microscopic drops of fluid, but 
whether this is fluid condensed on the mem- 
branes from the atmosphere of the dwelling, 
or whether it results from the transudation of 
that which was contained in the amnion, re- 
mains for future inquiry. 

Up to this period the embryo gives not the 
slightest evidence of spontaneous or voluntary 
motion. Internally it is still composed of cells 
of different sizes that are now in the course of 
producing muscular and other structures. In 
some parts of its body no arrangement of them 
seems as yet to have taken place, the cells 
being merely aggregated together. Cells of 
three very distinct sizes now exist. The dia- 
meter of the largest of these is nearly three 
times that of the second size, and the second 
again are nearly twice and a half the size of the 
smallest. The smallest sized cells fill up the 
interspaces between the others, and appear as 
if breaking down to form interstitial or cellular 
substance, while the second sized cells are 
arranged in rows to form particular structures. 

In the midst of these cells the alimentary 
canal is now nearly complete, but Mr. Newport 
was unable to observe its connexion with the 
funis. At its anal extremity it is a little dilated, 
and extends forward as a short straight intestine, 
the rectum, until it arrives at a part where a 
valve seems about to be formed. The diameter 
of the canal is there enlarged, and on its surface 
are three distinct longitudinal muscular bands. 
The so-called hepatic vessels also exist as dis- 
tinct tubes inserted one on each side into the 
alimentary canal at the constricted or valve-like 
part above noticed. The canal is then conti- 
nued forwards until it is again dilated into the 
proper stomach, and terminates or rather com- 
mences in a narrow cesophagus. It is much 
longer than the body of the embryo, being con- 
voluted or folded upon itself in its lower por- 
tion, to adapt it to the changes that the body 
undergoes in the enlargement and elongation 
of its segments. It is not yet separated from 
the now forming structures by any distinct 


556 


investment, either adipose or peritoneal, except 
only what belongs to itse!f; but is closely sur- 
rounded by cells of the second and third size 

On the tenth day the great circulatory or 
dorsal vessel was distinctly seen through the 
amnion and skin. This doubtless had existed 
much earlier, although not observed. It was 
exceedingly well marked, but Mr. Newport was 
as yet unable to detect any motion in it. The 
head of the embryo had now begun to assume 
the poe corneous appearance common to 
the larve of true insects; its body had much 
increased in size, and the amnion was still co- 
vered with microscopic drops of fluid. 

On the eleventh day the head was more dis- 
tinct, and the antenne appeared at its sides 
like short crescent-shaped clubs, with their 
terminations directed forwards. Above them 
the single ocelli were distinctly seen. All 
the segments, posterior to the third, exhibited 
the transverse line that indicated the division 
into double segments, and the posterior seg- 
ments were much increased in size. 

On the morning of the seventeenth day (fig. 
321) Mr. Newport found all the embryos ready 
to leave the amnion. ; 

Some of them were al- Fig. 321. 
ready detached from the — 
shell ; others were still 
connected to it. Their 
increase of bulk within 
the last few hours had 
been very great. The 
body was now more 
straightened, the head 
less inflected under the 
thorax, and the eye was 
a dark-coloured spot 
above and behind the wae 
antenne. The segments of the body were di- 
vided by distinct reduplicatures of the proper 
tegument, and the legs folded side by side 
against the ventral surface were much further 
extended beneath the amnion (b, a). The trans- 
verse divisions of the first six segments strongly 
marked the original segments, and the amnion, 
now about to burst, was tightly extended over 
the dorsal surface, and by the elongation of the 
body was rendered more distinct on the ventral. 
The great increase in the length of the animal 
was mainly occasioned by the growth of the 
posterior segments, more especially those in 
the antepenultimate space, the proper germinal 
space or membrane (f°), the faint divisions of 
which into new segments were now distinctly 
seen through the amnion. The seven anterior 
segments, including the head, were greatly en- 
larged, and the hitherto minute anal an 
nultimate segments (8, 9), in the first of which 
the remains of the funis (d) forms a rudimen- 
tary spine, had also become enlarged, and were 
now fast acquiring the form they afterwards 
retain throughout the life of the animal. Some 
of the specimens soon threw off their covering 
and entered the third period of development. 

The animal was now shang omar and 
possessed three pairs of legs, but it still la 
with these Seiktp ‘davaloped legs coiled wid 
without voluntary motion. The amnion had 


MYRIAPODA. 


been fissured at its anterior dorsal surface, and 
slipped off backwards from the i g- 
ments, and Jay at the anal extremity, while 
animal itself, with its limbs coiled up, app 
as if exhausted with these its first spontar ous 
efforts. No other signs of anima enc 
were given than occasional slight moven 
of the antenne. The embryos thus passe 
from their apparently inanimate to an animat 
state of existence, from a condition in whic 
they appeared merely to vegetate, endoy 
with no voluntary or instinctive p 
like the vegetable formed entirely of an agg 
gation of cells, totally incapable of spontaneot 
motion, to one in which they became activ 
beings, gradually acquiring voluntary and it 
stinctive faculties both as regards ‘mean: 
of precuring nourishment and of f i 
themselves from injury. 
In about an hour after leaving the amnik 
the young Julus exhibited a marked che 
Its head was elongated on the prothorax (2 
the parts of the mouth were distinctly mov 
able, and the eye, a single ocellus on each Si 
of the head, acquired a darker colour. The 
whole body had been increased at least on 
fourth in bu!k since leaving the amnion. — 
now measured about a line in length, and € 
hibited very distinctly the nine a é 
ments. e seven anterior of these we 
strongly marked. In the germinal space, ( 
321, /;) between the original seventh 
segments, six new segments were now develo 
These were still very small, the length of t 
whole being equal only to that of one of t 
original segments. At the present time t 
did not form independent divisions of the be 
ate were covered by the common tegument, 4 
thus appeared like supplementary f t 
serena dapeiont scdenaa from mi 
membrane and interposed between the sever 
and the penultimate segment (8), which, as 
fore stated, is a permanent segment througl 
the life of the animal. This latter fact shews 
it is not merely by an elongation and divi: 
of the terminal segment that the body of 
Julus is developed, but that it arrives at 
fect state by an actual production of 
new segments; that these are new growths 
formations which are in progress long bt 
they are apparent to the eye, and that 
original segments of the ovum into whic 
animal is first moulded are permanent segi 
throughout its whole life. ; 
But still more curious is it that not only 
new segments been formed as described, 
that the common tegument by which the 
now covered and which also invests the ¥ 
body as the true skin, has already begun 
detached preparatory to its being thrown 
is shewn in the fact that the new segment 
now seen beneath it; and it is further ren 
able that this deciduation of the first skit 
the animal had actually commenced befor 
bursting of the amnion. These cireums 
explain the cause of the very quiescent sta 
the young Julus, and its almost and perh 
entire abstinence from food whilst this” 
remains on its body. It is not until 


- 


ee 


pe 


— one 


organs find their out- 
let, a circumstance 


lier changes of the 


_ duction of new seg- 


the segment imme- 


from: the fact that 


MYRIAPODA. 


is thrown off that the new segments become 
elongated, and the Julus then appears suddenly 
to have acquired six new divisions to its body. 

The production of new legs is equally cu- 
rious. Up to the present period the animal 
has but six legs (fig. 322, 6 a), but four addi- 
tional pairs are nevertheless in the course of 
formation. These at present exist only as eight 
minute nipple-shaped prominences on the under 
surface of the sixth and seventh segments (0 ¢ ), 
four on each, covered by the common tegu- 
ment, which, we have seen, is becoming deci- 
duous. The three single pairs of legs that now 
exist as the only locomotive organs are attached, 
pair to the prothorax or second segment, 
one to the third and one to the fifth segment. 
The fourth, or segment intermediate between 
these last, never possesses any legs, but in the 
female contains the outlets of the organs of ge- 


 neration. The general appearance of the ani- 
_ mal has now become less delicate, the head has 


uired a darker colour, and a faint broad 
patch (fig. 322, p) is now making its appear- 


ance at the anterior partof the seventh seg- 


ment. This patch, 
which is permanent 
through all the ear- 


Fig. 322. 


animal, is of the 


greatest utility in de- 
termining the pro- 


ments. It is in 


diatel sterior to 
this a. the male 


the more remarkable 


this outlet is in the anterior part of the 
Original germinal space, and at the bursting 


of the egg this is very near the termination 


of the body. Such was the condition of 
the young Julus one hour after leaving the 
amnion. It soon began to exhibit its animal 
powers, to shew the instincts peculiarto its 
Species, and to be sensibly affected by ex- 


_ ternal causes. In less than six hours from the 


very slowly but with instinctive care. 


bursting of the amnion the little creatures were 
in motion. 


At first the antenne were the or- 
gans employed. They were moved slowly to 
and fro, and seemed to gain power by use. 


‘Tn a short time the limbs began to be extended, 


and the animal slowly raised itself upon them 
for the first time. Its first efforts at locomotion 
were exceedingly feeble, but it gradually gained 


‘Strength. At the end of twelve hours the em- 
bryos crawled slowly about, but moving the an- 


tenne briskly. On exposing them to a strong 
light a marked effect was produced in their 
movements. They evidently were greatly af- 
Te by it, and seemed instinctively to shun 
it. This was the first marked exhibition of 
instinct. Locomotion was at first performed 


The 
anal segment, previously to each step, was 


expanded like the anal leg of the larva of an 


insect, and being first attached like a true pro- 


557 


leg, and its step, as it were, measured, its body 
was carried forwards by at. effort that extended, 
as in insects, from segment to segment. 

At twenty-four hours after escaping from 
the amnion the young animals were lying toge- 
ther in a heap, but when disturbed seemed to 
have acquired more power of moving: they 
remained quiet except when aroused, and had 
not yet taken food. The only marked diffe- 
rence in their appearance, excepting that they 
had still further increased in size, was in the 
nipple-shaped protuberances on the sixth and 
seventh segments, the rudiments of future legs. 
These were now more distinct and mammiform. 
Ten hours later in the day they assumed still 
more the appearance of nipples projecting from 
the under surface of the segments. When 
examined in specimens that had been placed in 
spirits of wine, it became evident that these 
projections were occasioned by the develope- 
ment under the deciduous tegument of four 
new, but exceedingly minute legs, complete in 
all their parts, each covered by its proper skin. 
The claws to the legs of the other segments 
were also more strongly marked. The new 
segments (f) were more developed, although 
still covered by the common tegument, and, as 
in the preceding state, forming only one divi- 
sion of the body, while a small space behind 
them indicated the point from which other new 
segments were to be produced. 

On the nineteenth day, Mr. Newport found 
that the animals had acquired a little darker 
colour, but were still remaining quiet in their 
cells, and did not appear to have taken food. 
The enlargement of the body had not extended 
to the prothorax, which did not increase in size 
in proportion to the rest. The double pairs of 
new legs to the sixth and seventh segments 
were now distinctly visible through the exter- 
nal tegument, which had begun to be separated 
from the under surface of the old segments, to 
which up to this period it had closely adhered. 
The patch on the side of the seventh segment 
had become darker, and the new segments 
were further advanced. 

On the twenty-first day (fig. 323) the young 
Juli still remamed coiled up and _ perfectly 
quiescent, with their 
legs disposed side by 
~, side along the under 
YA surface of the body, like 
/ the pupe of Lepi- 
J dopterous Insects. The 
new legs had consider- 
ably increased in size, 
as well as the whole 
animal, although it had 
not taken food. The ani- 
mal was still. partially 
coiled up, but the skin 
that covered its body 
was greatly distended, 
more especially along 
the ventral surface. It 
was less able to move 
than before, the period 
of throwing off this skin being fast approach- 
ing: the double legs of the sixth and seventh 


558 
segments, inclosed in their proper skin, were 
now more elongated and very much en- 
larged, and the new segments were further 
developed as well as the germinal membrane. 
The external tegument was more extensively 
separated from the whole body, especially at 
the erior and the head was retracted 
within it “and bent on the under part of the 
thorax. It was thus evident that this tegu- 
ment was not of recent formation, that it 
simply enclosed the animal as the whole had 
been previously enclosed in the amnion, as is 
proved by the circumstance that it extended 
smoothly over the whole body, antenne and 
legs, and did not follow the inflection or redu- 

lication of the proper surface of the animal 
ike the true skin beneath it, but passed di- 
rectly over the segments, and was simply pro- 
truded or distended by the growth of parts be- 
neath, as in the instance of the new legs (6). 
Up to this period, therefore, observes Mr. New- 
port, the young Julus must still be regarded as 
in the embryo condition, although for a day or 
two after bursting the amnion, it possessed 
the power of locomotion and evinced some 
developement of instinct. At its next change 
of skin, when it enters what Mr. Newport 
regards as the fourth period of its developement, 
and when it has acquired fourteen pairs of 
legs, it assumes for the first time a condition 
analogous to the larva state of true insects on 
bursting from the ovum; the difference be- 
tween the two being that the analogue of this 
tegument of the embryo in insects is slipped off 
at the bursting of the amnion on leaving the 
shell, while that of the Myriapod is not thrown 
off until some days after it has entirely left the 
ovum. This embryo condition of the animal 
will therefore explain the circumstance of its 
first acquiring a pind ete] of locomotion, and 
then remaining perfectly quiescent without 
taking food to prepare for this change—the 
third period of its embryo life. 

The lower portion of the alimentary canal is 
at this time distinctly visible through the new 
segments, exhibiting a corrugated or folded ap- 

ce, an arrangement doubtless intended to 
allow of its sudden extension at the period of 
throwing off the skin and elongation of the seg- 
ments. The colon is of a very dark colour and 
exhibits its thickened peculiar structure with 
its longitudinal muscular bands. Around its 
posterior part, Mr. Newport observed an 

tion of what app: to be globular cells. 

ey seemed to be part of the organs of gene- 
ration in the course of developement. At first 
they were regarded as hepatic vessels, but this 
Mr. Newport considers could hardly be the 
case from the fact that each of these organs 
directly enters the canal as a straight vessel, but 
they might be vessels folded up to be unfolded 
suddenly, as in the case of the alimentary canal. 

By the twenty-sixth day the young Julus 
casts off the covering in which it had hitherto 
been infolded, and enters the fourth period of 
deve , having now seven pairs of legs 
and fi segments to its body (, Ae. 324). 

In this condition the antennz were found to 
have become elongated by at least one-third of 


MYRIAPODA. 


joints. 


their original length, and exhibited six distinet 

e eye still consisted ofa single ocel- 
lus, but this was now surrounded bya darker 
coloured portion of the tegument. The new 


I ¢ 
legs (bc) were equal in size and length to # 
original ones, but were evidently more fe 
The transverse markings on the seven 
segments (2-7) were very distinct, and t 
brown patch on the seventh segment was mt 


darker in colour. The whole body of thea 
mal was considerably elongated. This ° 
produced chiefly by the extension of thet 
segments (7 g) formed by the germinal m 
brane at the p agese>: part of the sevent »t 
which, in the early part of the last peri 
seemed to form a single distinct segment 
vered by the common tegument. ; 
anterior of these segments (8), now the 
of the whole body, had uired an @ 
equal on its upper surface to the p ; 
ment, but was shorter on its ventral suri 
Like the preceding original segments it 
divided into two regions by a transve' 
pressed line. The next segment in 
to this, the ninth, had also become enlar 
about one-third of the size of the eighth, 
was, like it, marked transversely. The 
four segments were each more developed 
in the preceding state, but not to so gt 
extent as the others. The two 1g 
ments (14 15), the penultimate and anal 
undergone no change. They had simp 
quired a little extension at the apex of the 
ment, and were now covered with a fes 
tered hairs. It is thus proved that the be 
elongated, not by the division of the” 
formed segments into others, but always t 
formation of new ones in the 
brane that extends from the posterior 
the antipenultimate segment to the per 
which last segment, with the anal, underg 
change. That segment is always furthe 
vanced in growth which is immediately 
rior to the last segment that possesses 
then the next in succession, until we 
the terminal ones—the penultimate 
anal—that never possess legs. = 
By the forty-fifth day more new segm 
had evidently been developed by the gern 


- 
PCedaIn 


oe 


y4 
PINnain 


o © ae 
PeLitiitidi 


om ~ 


‘membrane, soon to be exposed by another 
change of skin that was about to take place. 
The Julus ceased to eat, became torpid, 
and lay coiled up in a spiral form. The 
ment of the body began to assume a 
whitish crustaceous appearance, and the ani- 
mals secreted themselves beneath any dry co- 
vering, but avoided parts too wet. The princi- 
oq changes in their general appearance were in 
_ the eyes, each ocellus being much more dis- 
tinct, and in the germinal space, which was 
developed to its greatest extent, and distinctly 
exhibited the six new segments. 
_ The change of skin, according to Mr. New- 
is effected in the following manner. The 
_ young Julus, when about to cast its integu- 
_ ment, bends its body in a semicircular form, 
with its head inflected against the under sur- 
face of the second segment. In this condition 
‘it remains for several hours with its legs widely 
arated and the dorsal surface of the segments 
ended. The head is then more forcibly 
bent on the sternum, and a longitudinal fissure 
takes place in the middle of the epicranium, 
_and is immediately extended outwards on each 
‘Side posteriorly to the antennz in the course of 
other sutures, the analogues of which Mr. 
Newport has described as the triangular and 
picranial sutures. Through the opening thus 
rmed in its covering the head is then carefully 
ithdrawn, and with it the antenne and parts 
the mouth, and afterwards the anterior seg- 
nts and single pairs of legs. The first and 
arently the most difficult part of the shed- 
g of the skin is its detachment from the 
terior segments of the body and from the 
; ior of the colon. To effect this the ani- 
tal, which has been previously lying coiled up 
im a circular form, first straightens its whole 
body; it then forcibly contracts and shortens 
: tself, especially at the posterior part, and by 
3 means becomes greatly enlarged in bulk 
its middle portion, but smaller at its extre- 
ties. During these efforts, which are some 
the most powerful it is able to make, the 
__ Skin becomes loosened from its posterior parts, 
__ and while still contracting its segments, the 
extremity, and with it the entire lining of the 
_ Golon, become completely detached, and from 
5 
} 


_ these it gently withdraws itself within the old 

4 in whicn the body is encased as from the 
er ofa glove. This is precisely what takes 
in the shifting of the skin in insects. 
ng effected this part of its labour all the 
erlor segments are again shortened; the 
mal once more disposes itself in a circular 
and after repeated exertions succeeds in 
ursting the tegument of the head in the part 
ust described. As in the case of true insects 
the young Julus entirely empties the alimentary 
al by voiding its fceces and ceasing to eat 
one or two days preparatory to undergoing 
h transformation. When examined imme- 
diately before the change there are no other 
Symptoms of new legs than slight elevations of 
the skin, and this perhaps accounts for the 
length of time occupied in the change, the new 

| Jegs requiring time for further developement 

before the old skin is thrown off. 

Having cast its skin and thus attained the 


MYRIAPODA. 


559 
the young Ju- 
on each side 


fifth period of developement, 
lus (fig. 325) has three delli 


Fig. 325. 


Fig. 326. 


of the head, seven i 
joints to the antenna, 
thirty-four legs, and 
twenty-one segments 
to its body. On the 
forty-eighth day this 
has been accomplished, 
and the young Ju- 
lus exhibits a marked 
alteration in its ap- 
pearance. The an- 
tennz are considerably 
longer than the head, 
with seven distinct 
joints, and, as in the adult, the apical one 
is short and inserted into the sixth. The single 
eye has disappeared, and in its stead three 
distinct ocelli, arranged in a triangle, have 
been developed. The new segments of the 
body produced at the former change of the 
animal, from the eighth to the twelfth in- 
clusive, (8—12,) are now of the same size as 
the original ones, and each has developed 
from it two additional pairs of legs, so that 
the whole number of legs is now thirty-four. 
The thirteenth, or, if we may so name it, 
germinal segment of the last period, is less de- 
veloped than the preceding ones, and is distin- 
guished from them by the circumstances that it 
is smaller, possesses no legs, and has no lateral 


560 


spot which exists on each of the preceding seg- 
ments to the seventh, marking the existence of 
the foramina repugnatoria. The germinal 
space (13-19) which existed in the preceding 
period and was then seen to be forming seg- 
ments, is now developed into six new apodal 
segments, from the 14th to the 19th inclusive, 
very much smaller and shorter than the rest, 
and a germinal s (A) is again forming be- 
tween the last of these and the penultimate 
segment of the body, which, as above stated, 
undergoes no marked change. The whole 
body is thus composed of twenty-one segments, 
including the head. The first twelve of these 
are now perfectly developed, as well as the last 
two, the intermediate ones being only in their 
preparatory states. The animals at this period 
ate voraciously some decayed leaves, rotten 
elm-bark, and raw potato. 

On the sixty-third day the Julus again 
changed its skin, and entered its sixth period 
of developement (fig. 326). It then had ac- 
quired twenty-seven segments to its body, 
which had greatly increased in size and was of 
a brown colour. It had now six distinct ocelli 
on each side of the head, and all the segments 
to the eighteenth inclusive were furnished with 
legs, of which it had now fifty-eight. Six addi- 
tional new segments had also been developed 
to its body. as in the preceding changes anterior 
to the penultimate segment (1 g h1i2345 6), 
and the germinal membrane behind them (2) 
was still in further course of developement, the 
penultimate segment (26) remaining always 
unchanged. The six i pats (28) from which 
legs had been developed had also the foramina 
repugnatoria marked with small spots, while 
the spots on the preceding six had become 
larger and darker in colour, and the animal 
might now be regarded as having acquired all 
the essential parts of its body, its subsequent 
growth doubtless being effected by a repetition 
of the same interesting phenomena. 

The observations of Monsieur Gervais rela- 
tive to the developement of the Scolopendroid 
Myriapoda, are the only ones on record with 
which we are acquainted ; and although these 
are extremely desultory and incomplete when 
compared with the masterly baw oe of Mr. 
Newport concerning the Julide, detailed above, 
they seem to shew that the changes under- 
gone by the Scolopendride, before they arrive 
at maturity, are scarcely less important than 
those we have been considering. M. Gervais 
studied more particularly the growth of Litho- 
bius, (fig. 309,) Scolopendre, which possess, 
when mature, fifteen pairs of feet, and also some 
individuals belonging to the genus Geophilus. 
A young Lithobius captured in the month of 
May was found as yet to possess only seven 
pairs of feet, ten segments in its body, two 
eyes on each side of its head, and but eight 
joints in its antenne Moreover, that only one 
segment, the anal, was deprived of feet, a cir- 
cumstance which at once forms a remarkable 
difference between the young Lithobii and the 
young Juli, which latter have several apodal 
segments at the posterior extremity of the 
body. By the eighth of June the same Litho- 
bius had fourteen joints in the antenns, and 


MYRIAPODA. 


-changed, another proof of the numero 


eight pairs of legs, tozether with eleven seg- 
ments to its body, including an apodal one for 
the anal segment. 

Another Lithobius of nearly the same age 
had already three eyes on each side, and a th 
only ten pairs of feet, of which the two post 
rior were still rudimentary and scarcely fe 
In another example, even when all if 
legs were present, the creature had not as | 
got its full complement of eyes, there being o1 
eight stemmata on each side, whilst in | 
adult animal the optic facets are numerous. 

It appears manifest, therefore, that the 
thobii, like the Juli, have the number of th 
segments increased as well as of their legs, a 
of the joints of their antenne; and, moreo 
that the number of their eyes increases ¥ 
their age, a remarkable fact, which M. Gers 
seems to have been the first to signalize. _ 

With respect to the manner in which — 
number of pairs of feet and of segments is | 
creased as the young Lithobius grows ok 
M. Gervais gives us the blow n 

ents 


i 
4 


a 


mation: “ Examined upon the ven 
of the body, the pedigerous 
adult Lithobius are found to arly 
size equal, but examined from above w 
they are, as it were, imbricated, some app 
larger and others smaller. The largest of 
pedigerous ents are the 1st, 3¢ 
7th, 8th, 10th, 12th, 13th, and 14th, the & 
last corresponding inferiorly to four hal 
ments, and consequently to four pairs of 
The 2d, 4th, 6th, 9th, and 11th, are | 
and feet already exist upon these sms 
ments even before the dorsal portion is d 
loped, so that what is permanently obsery 
in one of the posterior segments, which 
superiorly only one shield, obtains also : 
riod for two of the posterior 3, wi 
ave as yet but one dorsal plate, the sma 
the two dorsal plates not having as 
its appearance. This fact is remarkab 
we suppose the same phenomenon to be | 
stant with all the rings, it is easy to 
how at all ages there are fewer dorsal seg 
than there are pairs of feet.” : 
As relates to the Geophili, M. Gerva 
sures us the process is, in them, alto; 


1 


® ‘ 
c< 


rences met with in the physiology of the) 
genera of the class under consideratio 
not having completed his researches upo 
subject, the author of the memoir from 
we have quoted has not as yet inforr 

the result of his observations concernit 
Geophilide. 


Ss aoe a = : 
and physiology of these animals ry | 
The padeetiony refer to the followi: gw 
Newport, Philosophical Transactions 
Savi, Observazione per servire alla ia 
specie di Julus communissima. Bol , 1817. 
letin des Sciences Naturelles, Dec. - d 

scientificke di Paolo Savi, Pisa, 1828. De 
Abhandlungen zur — der In: >! 

» Revne zoologique, 

ivteniing 1839. T Ri pet G 
of the animal kingdom. 


ss 


a 


Ot 


NECK. Gr. teayndros; Lat. collum, cer- 
viv; Fr. le cou; lial. id collo; Ger. der Hals. 
This word denotes that contracted, ribless por- 
tion of the trunk or column of support, which, 
in vertebrate animals, immediately sustains the 
head. Disease and accidental lesions so fre- 
quently submit it to surgical examinations and 
operative treatment, that familiar acquaintance 
with its intricate anatomy is of indispensable 
necessity to the practitioner. 
The order which I shall adopt in the ensuing 
article is, first, to describe fully and in order 
_ the muscles and fasciz of the neck, and sub- 
Sequently the various regions into which it may 
_ be divided with the parts contained in them; 
the earlier portion giving, as it were, a mere 
skeleton view or diagram of the anatomy; the 
latter presenting the organs in their more natural, 
_or regional arrangement, and treating of them 
im their living relations to disease, casualty, 
‘and surgical operation. I should recommend 
the student of this important part to pursue a 
similar plan; first, namely, thoroughly to im- 
press on his mind those relatively firm and fixed 
textures which admit of practical use as land- 
marks, and not, till this task is completed and 
_ these anatomical boundary lines are vividly and 
individually before him, to fill up his sketch 
with important organs, or perplex his mind 
_ with their surgical relations. 


Cc I. Tae muscxes. 
_ he muscles of the posterior region of the 
' neck and those of the shoulder having been 


=. described in a previous article (see Back), the 


__ femainder may be considered in three classes— 
1. those which most nearly cleave to the 
 Vertebre, are attached to their processes, and 
hee incipally affect their motions; 2. those, 
on Bs z : 
' chiefly in or near the median plane, which 
2 belong to the cervical portions of the respiratory 
_ and digestive apparatus, to the pharynx, larynx, 
tongue, and os hyoides; 3. the superficial 
_ muscles of the side of the neck, the sterno- 
cleido-mastoideus, and the platysma myoides. 
The first class includes—1. antiriorly, the 
i a colli and rectus capitis anticus major; 
2. laterally, the scalenus anticus, scalenus pos- 
ticus, and inter-transversales, with which may 
‘be reckoned the rectus capitis lateralis and 
_ Tectus capitis anticus minor. 
1. Anterior vertebral muscles—M. longus 
i ( Pre-dorso-atloidien: Chauss.) is a thin 
ongated muscle, which occupies an extent in 
the pre-vertebral region, corresponding to the 
three upper dorsal and to all the cervical ver- 
bre. In form it is triangular, having its 
gase at the bodies of these vertebrz, and its 
truncated apex at the middle transverse pro- 
cesses of the cervical region, and consists of 
three distinct, though united, parts, which would 
be ed by the three sides of such a 
triangle. One portion, the largest, is nearly ver- 
tical, next to the median line, and a direct 
flexor of the spine : it originates from the bodies 
of the three upper dorsal and four lower cer- 
vical vertebra, as also from the intervening 
fibro-cartilages, and, ascending, is inserted by 


two slips into the anterior surface of the bodies 
VOL. UI. 


4 


NECK. 


561 


of the second and third vertebre. The second 
part is directed trom the transverse processes of 
the third, fourth, and fifthycervical vertebra, at 
which it arisesby tendinous slips,—upward and 
inward to be inserted into the anterior tubercle 
of the atlas, and it so continues to that bone the 
previous insertion of the muscle. The remain- 
ing part detaches itself from the main body of 
the muscle at the bottom of the neck, and 
ascends obliquely outward, to infix itself by 
small tendons at the anterior tubercles of the 
transverse processes of the third and fourth 
cervical vertebre. The muscle may, in short, 
be described as passing from the bodies of the 
three upper dorsal and four lower to those of 
the three remaining cervical vertebra, receiving 
above an oblique reinforcement from the middle 
transverse processes of the neck, to which it 
has likewise below detached slips of insertion. 

M. rectus capitis anticus major ( Grand- 
trachelo-basilaire: Dumas) lies closely on the 
vertebre in the upper part of the neck, to the 
outside of the preceding muscle. It is an 
elongated, but thickish, muscle, arising by ten- 
dinous slips from the anterior tubercles of the 
transverse processes of the third, fourth, and 
fifth cervical vertebre. These become fleshy, 
unite as they ascend, and are inserted into the 
under surface of the basilar process of the 
occipital bone, beside the median line, and just 
behind the spine, which attaches the raphe 
of the pharynx. Its inner edge overlaps the 
longus colli. These muscles correspond ante- 
riorly to the great vessels of the neck, to the 
nerves which accompany them, and to the 
cervical portions of the respiratory and diges- 
tive tubes, but are separated by their own dense 
fascia from immediate relation to these parts. 
Their deep surface is in intimate connection 
with all the vertebre and intervertebral discs, to 
which they correspond. ‘Their action is incon- 
siderable; the rectus will slightly rotate and 
bend the head to its own side, or in conjunction 
with its fellow directly flex it. The longus colli, 
cooperating with its fellow, bends the cervical 
spine; or, acting singly, can slightly rotate by 
its higher fibres toward, by its lower fibres 
away from, the side on which the contraction 
occurs. 

2. Lateral vertebral muscles.—The inter- 
transversales colli are almost described by their 
name. They form, on each side, a double 
series of small square muscles, occupying the 
spaces between the adjoining transverse pro- 
cesses, which afford them attachment by both 
borders of their surface. Arising from the lips, 
which the channelled upper surfaceof each trans- 
verse process presents, they ascend in each space 
to the borders of the process immediately above, 
and are there inserted. Between the inter- 
transversales antici aud postici the spinal nerves 
of the region emerge, and the vertebral artery 
ascends. 

Strictly analogous to these are the two small 
muscles which pass to the occiput from the 
transverse process of the atlas, the rectus ca- 
pitis lateralis and rectus capitis anticus minor. 
The former would represent a posterior, the 
latter an anterior inter-transversalis. The former 

20 


562 


passes from the upper edge of the trans- 
verse process of the atlas to the transverse or 
jugular process of the occiput: the latter, on 
a plane anterior to this, from the anterior root 
of the transverse process and side of the an- 
terior arch, inclines upward and alittle inward, 
to be inserted into the basilar process of the 
occipital bone behind the rectus capitis anticus 
major, between its outer edge and the foramen 
um. The rectus capitis lateralis separates 
the vertebral artery from the jugular vein. _ 

These muscles in approximating their points 
of attachment can give lateral flexion to the 
neck and to the head. 

The sealeni ( Costo-trachelien : Chauss.) are 
situated at the lower lateral part of the neck, 
extending from the transverse processes to the 
first two ribs, and are of triangular form. 
They have been variously described by different 
anatomists, soine considering their fleshy mass 
as a single muscle, others distinguishing in it 
two, three, and even five parts. I shall adopt 
the more usual modern division, which recog- 
nises two muscles, sculenus anticus and scalenus 
posticus. 

Scalenus anticus arises from the third, fourth, 
and fifth cervical vertebrz, at the anterior tuber- 
cles and notched extremities of their transverse 

rocesses, by slips of tendon, to which muscular 
fibres directly succeed, and descends with an 
inclination outward and forward to be inserted 
by a flat strong tendon into a roughness about 
the middle of the anterior third of the first rib. 
This insertion is important as affording a guide 
to the position of the subclavian artery, which, 
in arching over the rib, lies behind this tendon 
and separates it from the insertion of the 
scalenus posticus. It is triangular in shape 
and fleshy in nearly its whole extent: externally 
it presents a free border, from behind which 
emerge the elements of the brachial plexus 
and the subclavian artery ; internally its origin 
adjoins that of the rectus apes anticus major, 
from which it is demarked by the arteria cervi- 
calis ascendens, and toward its insertion is 
separated from the longus colli by a space in 
which the vertebral artery ascends; its anterior 
surface is crossed from above by the phrenic 
nerve, and transversely by branches of the 
thyroid axis; its deep surface is separated from 
the scalenus posticus by the emerging trunks 
of the nerves, and the space between them, 
broadening towards the first rib, includes there 
the brachial plexus and subclavian artery—the 
latter being below and in front of the former, 
and in immediate contact with the rib. 

Scalenus posticus, larger than the preceding, 
behind which it is situated, arises by six ten- 
dons, to which muscular fibres directly succeed, 
from the posterior tubercles of the transverse 

rocesses of the six last cervical vertebre. The 

rst slip (often p iad derived from the atlas) 
is ae} as it descends, by the others in suc- 
cession, and a large triangular muscle results, 
which has its base at the transverse processes 
and its apex at the second rib. It is inserted, 
first, by an anterior broad slip into the outer 
edge of the first rib, from the tubercle behind 
as far forward as the arterial impression in 


NECK. 


longed from the posterior su 
is to the upper edge of the second rib 
near its tuberosity. This muscle correspon¢ 
anteriorly to the scalenus anticus, from wi 
it is separated by the brachial plexus and 
clavian artery; posteriorly to the levator angu 
scapule; by its inner edge to its points ¢ 
origin; by its outer edge to the serratus m: 
and transversalis colli artery, to branches of # 
cervical and brachial plexus of nerves, and t 
the sterno-mastoid muscle ; each 
ferior-internal edge to the longus colli, fro 
which it is divided by the anterior branch 
the first dorsal nerve, and by the (general: 
common trunk of the deep cervical and fil 
intercostal arteries. 5 

The action of the scaleni, as of the r 
previously described, consists rather in nm it 
taining steadiness and resisting lateralisation | 


front ; secondly, by a smaller 9 hich 


Ets 


the neck, than in effecting any considerak 
movement. They may, however, in a sli 
degree, bend the neck laterally. The verteb 
being fixed, their muscles by acting togethe 
may elevate the first two ribs and so assist 
inspiration. The scalenus anticus ean, fro 
its advanced insertion, act more e! li 
thus. This action is illustrated in all 
inspirations; for these differ from 
breathing therein, that the chest is expand 
by the elevation of the ribs and sternum, in 
antero-posterior and transverse diameters, — 
addition to the ordinary increase of capa 
which it gains by the descent of the | 
phragm ; and, in order to the effective ac 
of the intercostals, the first rib must be 
dered immoveable. The scaleni, in raisin 
anterior extremity of the first ribs, fa ai 
advance of the sternum, and then rigidly” 
these bones enable the intercostal muse 
give to the ribs beneath that slight axial 
tion by which the transverse diameter 0 
chest is increased.* sg 
The intrinsic muscles of the larynx 
already been described (see Larynx 
those of the pharynx being for future de 
tion (see Paarynx), our second class wi 
prise only the muscles of the os hyoide 
tongue, viz. depressors of the os hoide 
sterno-hyoid,omo-hyoid, and sterno-thyroi 
its continuation the thyro-hyoid; its ele 
the digastric, stylo-hyoid, mylo-hyoid, 
hyoid ; muscles of the tongue, 
genio- hyo-glossus, and lingualis. 
The sterno-hyvid and sterno-thyroid : 
riband-like muscles, having respect 
attachments denoted by their names,— 
beside the median line, so as to b 


ee 


‘- 


* Within the last year I have observes 
subjects an importantly anomalous i i 
scalenus anticus. Its main bulk of 
on both sides to an insertion behind 
very small slip only taking the usual 
Strong flat tendon, which is usually so trust 
a guide to the artery, would in these cases h 
volved an operator in the misfortane of 
the nerves with his ligature ; and the 
illustrates the necessity of trying the 


porary pressure on a — 2 
canclaelvely tightening the ligature 


; 


L 


from their fellows on the opposite side only by 
the mesial raphe of the cervical fascia,—cover- 
ing the trachea, thyroid body, with a portion of 
the larynx, and overlapping the sheath of the 
carotid vessels. They are isolated from each 
other, and from the other muscles of their neigh- 
bourhood, by processes of the cervical aponeu- 
rosis. The sterno-hyoid arises just within the 
thorax from the deep surface of the manubrium 
Sterni, from the cartilage of the first rib, and 
from the ligament of the sterno-clavicular joint, 
and is separated from that of the opposite side 
by nearly the whole breadth of the sternum. 
As it ascends, it more nearly approaches its 
_ fellow, and the two are inserted side by side into 
the under surface of the body of the os hyoides, 
in close connexion, by their outer edges, with 
the omo-hyoid muscles, which are inserted be- 
sidethem. The sterno-hyoid lies in its whole 
length on the sterno-thyroid muscle and its 
prolongation the thyro-hyoid, and these sepa- 
fate it from immediate contact with the impor- 
tant organs to which it is related. 
The sterno-thyroid is broader and rises lower 
‘within the chest,—from the cartilage of the 
‘second rib, and from the adjoining surface of 
_ the sternum, on which it extends almost to the 
median line: its fibres ascend nearly vertically, 
‘and terminate at an oblique fibrous arch on the 
_ ala of the thyroid cartilage, and at the tubercles, 
to which this arch is attached ; hence a muscle 
_ of similar volume is prolonged, (which may be 
lescribed as rising from the oblique cord and 
from its points of attachment, but which, in 
_ direction, size, and form, accurately continues 
_ the sterno-thyroid,) and, after a course of an 
inch and a half, is inserted into the body and 
a of the cornu of the os hyoides, beneath 
the omo-hyoid and sterno-hyoid, and superfi- 
_ @ially to the thyro-hyoid membrane. To this is 
"given the name of thyro-hyoid. 
__ The sterno-thyroid and thyro-hyoid are co- 
 vered throughout by the sterno-hyoid and in 
part by the sterno-mastoid and omo-hyoid 
‘muscles. The sterno-thyroid corresponds by 
its inner edge to the inferior thyroid vein,—by 
‘its outer edge receives the terminal branch of 
the descendens noni, by its deep surface covers 
the thyroid body and many of its vessels, the 
trachea and part of the larynx, and the sheath 
of the carotid vessels: by its origin it enters 
into the mediastinum, covers the great arterial 
trunks springing from the arch of the aorta and 
‘the brachio-cephalic veins. From these parts 
it is separated by the remains of the thymus 
gland. The thyro-hyoid muscle covers the su- 
ng laryngeal nerve and artery as they pierce 
wall of the larynx. These muscles are 
fleshy in their whole extent, with exception of 
the short tendinous fibres, by which they 
have their origin and insertion: the sterno- 
thyroid has frequently a transverse tendinous 
intersection in some part of its course. 

The omo-hyoid is a slender but long bi-ventral 
muscle, obliquely extending from the superior 
costa of the scapula to the os hyoides. It 
arises by short tendinous fibres at the root of 
the coracoid process, from the ligament which 

_ Grosses the coracoid notch, and from the ad- 


NECK. 


563 


joining part of the costa, directs itself with a 
slight ascent towards the median line, and, in 
emerging from behind the clavicle, frequently 
derives a few fibres from i\; posterior edge. It 
contracts to a flattened tendon as it passes be- 
neath the sterno-mastoid, and abruptly changes 
its direction from a nearly horizontal to a ver- 
tical course, by undergoing a trochlear re- 
flexion in a loop of the cervical fascia,—and, 
again becoming fleshy, ascends beside and 
parallel to the outer edge of the sterno-hyoid, 
to which it is closely united,—to be inserted 
into the lower border of the hyoid bone at the 
junction of its body and cornu. The very im- 
portant relations of this muscle will be more 
fully given in the detailed surgical anatomy of 
the region. It may for the present suffice to 
say, that, in crossing the direction of the sterno- 
mastoid muscle, it furnishes the subdividing 
line of the great triangles of the neck; that its 
posterior belly lies parallel to and just above 
the subclavian artery and brachial plexus, is 
covered by the platysma and partly by the 
trapezius, clavicle and subclavius, and crosses 
the scaleni and phrenic nerve: that its looped 
tendon is covered by the sterno-mastoid, and 
lies on the sheath of the carotid vessels, across 
which its anterior belly continues obliquely to 
run. 

The two omo-hyoid muscles acting in con- 
cert are capable of depressing the os hyoides ; 
but their chief action is of a different nature. 
Being contained in their whole bent course 
within a sheath of cervical fascia, they affect 
this membrane by their contraction, tensely 
Spanning it across the median line in a space 
which extends from the hyoid bone to its 
clavicular attachment. This appears to be one 
of the consensual movements in the act of de- 
glutition, designed to give, during that act, 
additional efficacy to the protection against at- 
mospheric pressure, which Burns has shown to 
be an important function of the fascia of the 
neck.* 

The digastric muscle is likewise, as its name 
imports, double-bellied; it passes from the 
mastoid process of the temporal bone to the 
symphysis of the jaw, but is looped down in 
its course to the side of the os hyoides. Its 
temporal attachment is to the groove, which is 
named from it, on the inner surface of the 
mastoid process: a large fleshy belly proceeds 
from this origin downward and forward, con- 
tracts to a round tendon, which usually pierces 
the stylo-hyoid muscle, traverses an aponeu- 
rotic ring lined by synovial membrane, which 
strongly binds it to the hyoid bone, near its lesser 
cornu, and is then reflected upward, expanding 
again to a strong muscular belly, which fixes 
itself by short aponeurotic fibres into the lower 
border of the jaw, at an oval depression be- 
side the symphysis. Its tendon, just after pass- 
ing through the fibrous pulley that maintains 
its curve, gives off a fascial process toward 
the median line: this attaches itself strongly 
along the upper edge of the hyoid bone, and 


* Surg. Anat. of Head and Neck, p. 36. Glas- 
gow, 1 
202 


564 


internally joins a similar process from the op- 
posite side to form with it a tendinous expan- 
sion, (often assisted by a few fleshy fibres from 
the anterior belly of the digastric,) which reaches 
from the os hyoides as far as the jaw, and con- 
tributes to support the floor of the mouth. 

The relations of this muscle are complicated 
and important: the convexity of its curve is 
the upper limit of the anterior triangle of the 
neck ; its concavity bounds a space, the area 
of which extends within the jaw to the myloid 
ridge, containing various parts, and named 
from the muscle the digastric space; its pos- 
terior belly crosses the external and internal 
carotid, the facial, lingual, and occipital branches 
of the former, the internal jugular vein, the 
three divisions of the eighth, the ninth, and the 
sympathetic nerve, the side of the pharynx, the 
trachelo-mastoid and styloid muscles, and the 
hyo-glossus. The sternu-mastoid and splenius 
cover its origin; the portio dura emerges at its 
anterior edge, along which the posterior aural 
artery runs, and round which the posterior part 
of the parotid gland is folded. Its anterior 
belly and tendon support the submaxillary 
gland, are covered by fascia and platysma, and 
correspond to the mylo-hyoid muscle, which 
is covered and strengthened by the aponeurotic 
expansion derived from the digastric. 

he action of this muscle varies according to 
the fixity of the jaw: when the mouth is firmly 
closed, the contraction of the two bellies will 
draw the hyoid bone vertically upward, and 
communicate to the pharynx the movement 
of elevation, which adapts it for receiving the 
masticated food. A firm closure of the jaw, a 
contraction of the digastric muscles, and conse- 
quent shortening of the pharynx, (indicated by 
rising of the pomum Adami,) are well known 
acts in the process of deglutition. When the 
hyoid bone is fixed by its depressors (and 
perhaps in some degree radiniea by the joint 
actions of the mec belly of the digastric 
and of the omo-hyoid), the anterior belly, both 

sively as a reflected cord, and actively, 
in virtue of its muscular fibres, depresses the 
lower jaw and opens the mouth. Simulta- 
neously, too, with its act of raising the pharynx, 
this muscle must tighten, by its posterior belly, 
the mesial aponeurotic expansion, which joins 
it to its fellow; and, by so doing, must assist 
the mylo-hyoid in raising the floor and reducing 
the capacity of the mouth. It fulfils, there- 
fore, important uses in the mechanism of de- 
glutition. 

The stylo-hyvid muscle is an accessory to the 
posterior belly of the digastric, and arises from 
the outer surface of the styloid process, about 
midway from its base, by a small round tendon, 
which soon swells into an elongated body. 
This lies along the posterior belly of the digas- 
tric, parallel to its anterior edge, and, when it 
reaches the os hyoides, is inserted into the outer 
surface of that bone, at the union of its body 
and cornu, by short aponeurotic fibres. It 
usually divides, just previously to its insertion, 
to give passage to the tendon of the digastric. 
The portio dura of the seventh pair emerges 
between its origin and that of the digastric: in 


NECK. 


‘rated from the mylo-hyoid muscle by 


other respects its relations so entirely agree with 
those of the descending belly of that muscle, as 
do likewise its uses, that no particular descrip- 
tion of these is necessary. ek 
The mylo-hyoid muscles are so mutually de 
pendent that they might almost be de: 
as a single muscle. They arise on either sid 
from the oblique or myloid ridge on the buc 
surface of the lower jaw in its whole exten 
i. e. from opposite the last molar tooth to the 
neighbourhood of the symphysis. The flesh 
fibres, that succeed = rt ve SIS | 
origin, proceed lelly toward medi 
line, ee. are eae a raphe, which reache 
from the symphysis of the jaw to the body 
the hyoid bone, and likewise into the upper 
border of the body of that bone. The an' 
fibres are short ; those which succeed progre 
sively increase in length, and the posteriol 
which are fixed to the hyoid bone, are of all th 
longest. Each muscle is, therefore, triangular 
having an outer edge by which it rises fi 
the jaw, an inner edge of union with its fe 
and a posterior edge, which is seen to ext 
in the digastric space, from the posterior € 
mity of the myloid ridge to the upper edg 
the body of the hyoid bone, close to its cor 
The under surface of the muscle corr ¢ 
the submaxillary gland and to the insertio 
the digastric; its upper surface sustains 
tongue and floor of the mouth,—from t 
cous membrane of which it is separated 
Wharton’s duct, the sub-lingual gland, and 
tatory nerve; it also corresponds to the 
glossus, genio-hyoideus, and genio-hyo-gle 
and to the termination of the ingeay aur 
and nerve. The duct of the sub-max 
gland winds round its posterior edge, in pi 
ceeding to open beside the frenum lin 
The habitual state of this muscle is om 
which it is rendered, with its fellow, 
downward by pressure of the superine 
parts; and so its surfaces cannot 
said to face upward and downward, 
a modification of these directions r 
inward and outward. Thus the twom 
furnish a concave floor to the mouth, ane 
only in their contraction, which acco 
diminishes the cavity, that this becomes! 
horizontal. Their action, especially w 
sisted by other muscles, is to propel t 
ticated food by lessening the capacity 
mouth. an 
The hyo-glossus is a thin quadril: 
of parallel muscular fibres, a 1e 
ments which its name indicates. It ms 
the entire length of the great cornu ‘ 
joining part of the body of the os hyoi 
their upper surface, and ascends to be: 
into the side of the tongue. From bet 
anterior thicker edge the lingual artery 
its posterior thin border receives the 
of the stylo-glossus; its deep s 
fer to the genio-hyo-glossus 
rom the former of which it is par 


4 
baal 


by the lingual artery ; its e 


gual and gustatory nerves and duet of # 
maxillary gland. my 


NECK, 


‘The siylo-glossus arises, as a round fleshy 
bundle, from the tip of the styloid process, 
and from the adjoining part of the stylo-maxil- 
lary ligament, becomes flattened into divergent 
parts, as it approaches the side of the tongue 
at the posterior border of the hyo-glossus, after 
a short course downward, forward, and inward, 
and is there inserted. A part is continued for 
Some distance along the hyo-glossus, crossing 
the direction of its fibres, and interwoven with 
them; other fibres seem to bend into the sub- 
Stance of the tongue, near its base and at right 
angles to its axis. Its surface corresponds to 
the parotid gland, external carotid aitery, in- 


ternal pterygoid muscle, and mucous mem- 


brane of the mouth ; deeply, it lies on the in- 
ternal carotid artery, the superior constrictor 
of the pharynx, the tonsil and hyo-glossus. 
The genio-hyo-glossus is a large, fan-shaped 
muscle, radiating from within the symphysis 
of the jaw to the entire length of the tongue, 
and constituting, with its fellow, the chief mus- 
cular bulk of that fleshy organ. It rises by a 
Strong square mass of short tendinous fibres 
from the upper genial tubercle, and the fleshy 
fibres, which succeed, immediately and widely 
diverge; the highest bend upward and some- 
what forward to the tip of the tongue; those, 


_ which next follow, occupy its entire remaining 


length, spreading with more or less obliquity 
into the substance of the organ, through which 
on a section they may be followed even to the 
dorsum: some of these may be traced beyond 


the posterior edge of the hyo-glossus, expand- 


ing on the side of the pharynx just above the 
hyoid attachment of the middle constrictor, 


and constituting the so-called lingual origin of 


the superior constrictor, (see Puarynx); the 
remaining fibres complete the semicircular 
spread of the muscle, by passing downward 
and backward, to be inserted into the upper 
border of the body of the os hyoides. This 


muscle is opposed by its entire mesial surface 


to its fellow: their tubercles of origin are 
almost blended on the symphysis, and their 


_ fleshy fibres are only to be distinguished by 


a thin intermediate layer of adipose tissue : 
their upper edges raise the mucous mem- 


_ brane of the mouth on either side of the 
 frenum; their lower edges extend to the 
__ hyoid bone in perfect parallelism to each other, 


and to the genio-hyoidei, which cover them ; 
their outer surfaces, partly covered by the hyo- 
glossi, form with these on each side the inner 
wall cf a triangular space (roofed by the mu- 


‘cous membrane and floored by the mylo-hyoid 
_ muscle) in which lie the terminal branches of 


the lingual and gustatory nerves, the lingual 
artery, the sublingual gland, and the excretory 
duct of the submaxillary. 

Close at the implantation of this muscle in 
the tongue, between its fibres and those of the 
hyo-glossus, and crossing the direction of both, 
is asmall bundle of fleshy fibres, which runs 
longitudinally from base to apex, and, since 
it has no fixed attachment, may most fitly 
be considered among the intrinsic muscles of 
the organ; it has been named Jingualis. (See 
Toncue.) 


565 


The genio-hyoideus is a strong cylindrical 
muscle intimately associated with the genio- 
hyo-glossus, and ordinarily co-operating with 
its posterior fibres. It rizes by a square tendon 
from the inferior genial tubercle, beside its 
fellow of the opposite side and just below the 
genio-hyo-glossus. From this origin it directs 
itself backward and downward, and is inserted 
into the upper surface of the body of the os 
hyoides. Its insertion is somewhat broader 
than its origin: its inner surface corresponds 
to that of the opposite side; its upper surface 
is parallel to the genio-hyo-glossus, which it 
supports; its under surface rests on the mylo- 
hyoid, beside its raphe; its outer surface has 
similar relations to that of the genio-hyo- 
glossus, contributing with it to form the inner 
wall of the sub-lingual space just described. 

The action of the extrinsic muscles of the 
tongue is modified and more nicely adapted to 
the delicate offices of speech by the co-opera- 
tion of other and intrinsic muscles. These 
will be described in a future article (see 
Toncue). Those already considered operate 
on the tongue en masse;—elevate, advance, 
depress or retract it, shift its volume to either 
side, and direct its extremity, by a kind of 
circumduction, over a wide range of surface. 
Thus, the stylo-glossus can elevate and retract, 
the hyo-glossus depress and lateralise; the 
anterior fibres of the genio-hyo-glossi, with the 
linguales, regulate the motions of the tip, while 
the genio-hyoid and adjunct fibres of the genio- 
hyo-glossi can cooperate in these movements by 
shifting the base of support in any direction. 
As the genio-hyo-glossus is of largest bulk, 
so is it of most various office in the tongue; 
by its posterior fibres it gives an elevation to 
the os hyoides by which the tongue is protruded 
from the mouth; or, half antagonizing this 
action by its middle fibres, it may so forcibly 
hollow the dorsum of the tongue as to direct 
its apex within the incisor teeth, and, with aid 
of the stylo-glossi, enable it to sweep the con- 
cavity of the palate; or, by this co-operating 
with either hyo-glossus and with the opposite 
lingualis and stylo-glossus, the tongue may be 
made, as it were, to probe with its eminently 
tactile extremity the entire length of the alve- 
olar arches, or by a yet more definite contraction 
to exert suction on any spot with which its 
dorsum can have contact. 

The third class includes the sterno-cleido- 
mastoideus and the platysma myoides. 

The sterno-cleido-mastoideus is a long and 
powerful muscle, obliquely crossing the side 
of the neck, from the neighbourhood of the 
sterno-clavicular joint to the mastoid process 
of the temporal bone. It is fleshy in almost 
its whole extent; flattened at the extremities, 
but rather prismatic in the intermediate portion ; 
and the anterior edge, which is more particu- 
larly continuous with the sternal origin of the 
muscle, and which, in certain positions of the 
neck, raises the integuments in a well-known 
diagonal relief, considerably exceeds the thick- 
ness of the posterior border. The name of 
the muscle is a summary of its attachments. 
It arises by two heads, which are usually 


566 


separated by a distinct cellular interspace, cor- 
responding to the sterno-clavicular articulation : 
1. from the anterior surface of the first bone 
of the sternum close to its clavicular joint, by 
a very strong flat tendon which is directed up- 
ward and backward for the space of more than 
an inch, before terminating in fleshy fibres ; 
2. from the upper edge of the inner third of 
the clavicle by a thin origin composed of pa- 
rallel aponeurotic fibres, which directly be- 
come fleshy, and take a nearly vertical course. 
As these two bundles ascend, the sternal, more 
oblique in its course, seems to overlap the 
other, and, both by difference of direction and 
by a line of cellular separation, can often be 
distinguished from it in the lower two-thirds of 
the neck ; but in approaching the mastoid pro- 
cess they are indistinguishably fused together. 
The insertion is, 1. by a strong and rounded 
tendon into the mastoid process, of which it 
seems to embrace the tip and anterior border ; 
2. by a thin aponeurosis along the posterior 
edge of the process, and about a third of the 
superior semicircular line, which is continued 
into it. 

This muscle, to which I shall have abun- 
dant occasion to refer in speaking of the sur- 
gical anatomy of the neck, has very important 
relations: the space between its heads corres- 
ponds to the bifurcation of the arteria inno- 
minata; and the broad band-like muscle, as 
it ascends, crosses in succession the subclavian 
and carotid arteries, the jugular and subclavian 
veins, the hypo-glossal, ppeumogastric, phrenic, 
sympathetic, spinal accessory nerves, and a 

rtion of the cervical plexus; the sterno- 
fyoid, sterno-thyroid, omo-hyoid, scaleni, le- 
vator anguli scapule, splenius, and digastric 
muscles, besides many lymphatic glands and 
branches from several of the nervous and vas- 
cular trunks which have been enumerated. Its 
superficial aspect corresponds to the integu- 
ments and platysma, to the external jugular 
vein and superficial branches of the cervical 
plexus; its thick anterior edge bounds the 
anterior triangle of the neck, receives branches 
from the external carotid artery or from its 
thyroid branch, and corresponds above to the 
parotid gland and posterior aural artery ; its 
thin posterior edge limits the other great trian- 
gle of the neck, is pierced by the pit acces- 
sory nerve, corresponds to a chain of lymphatic 
glands, and is wound round by the nerves and 
vein which lie on the surface of the muscle. 

The two sterno-mastoid muscles acting toge- 
ther directly bend the head on the chest, and 
their joint action is well illustrated in an en- 
deavour to raise the head from the supine 

ition. But when the head is thrown far 

k, a predominance is given to the posterior 
fibres of the muscle, which being attached 
behind the line of the jt, sre arti- 
culation, become then capable of increasing 
this direction of the head. The sterno-mastoid 
of one side, acting singly, rotates the head and 
flexes it with a lateral inclination to its own 
side, so as to bring the side of the head nearer 
to the shoulder, and to turn the face in the op- 
posite direction. 


NECK. 


The platysma myoides (latissimus colli of 
Albinus) is a broad, thin, membraniform mus- 
cle, which covers the side of the neck and 
lower part of the face, and is in its whole 
course subcutaneous. It arises scattered — 
fibres in the superficial fascia below the clavicle, 
and covers by its origin the upper of 

toralis major and deltoid, as also the spa 
atween those muscles, which corresponds to— 
the coracoid process, This origin does not 
extend within an inch or two of the median 
line, but reaches as far outwardly as the acro- 
mial process. The fibres become more closely 
aggregated as they ascend, and the muscle 
accordingly narrows. Its direction is obliquely 
upward and to the median line; it ver 
the base of the lower jaw, and its fibres again 
spread to their insertion: those which are pos- 
terior lose themselves in the skin covering the 
parotid gland and masseter muscle; others 
from this neighbourhood bend forward toward 
the angle of the mouth, and in some subject 
constitute a very distinct horizontal acto 
anguli oris, which is generally known as th 
risorius Santorini: some fibres from the midd 
of the muscle obtain a more fixed insertion 
about the base of the jaw and into the 
covering it; while the anterior portion ¢ 
muscle, which is most constant in its i 
is inserted into the lower lip by blending 
fibres with those of the depressor labii i 
rioris, and by decussating toward the boi 
of the lip and ia the substance of the « 
with the mesial fibres of its fellow. 

This muscle is subcutaneous in its w 
extent, and by its extremities intimately 
tached to the deep surface of the skin w 
covers it. In approximating its extreme atte 
ments, it wrinkles the skin in a directio 
verse to that of its fleshy fibres. It is. 
and partial relique in the human — ubjec ' 
that general muscular investment, which fu 
various functions in different orders of Mi 
malia, as an appendage of the tegumen 
system: rolling the hedge-hog in a ball » € 
ing the quills of the porcupine, and the br 
of the ten, or dislodging insects from 
hide of grazing cattle. Its relations to 
deeper parts in the neck will be detailed hi 
after: between it and the cervical apor 
rosis lie chiefly, cutaneous nerves and ye 
branches from the cervical division of | 
portio dura are distributed to its upper po 
reaching the deep surface just below the ar 
of the jaw, and branches from the cer 
plexus crossing the sterno-mastoid p: 
ply the platysma, partly pierce it in their co 
to the skin; the gi aaa > pectoral b 
lie beneath it till they reach the clavicle 
external jugular vein lies immediately bet 
this muscle, and runs nearly parallel to 
fibres, crossing transversely those of the st 
mastoideus. oe! 


: 
bn 


we 
- 


IIl.—Fasci# OF THE NECK. 


Pa >- 


1. The superficial fuscia, or subcutanec 
| 


areolar tissue, presents characters in com 
with the same structure in other parts of | 
body, and is universally continuous with tha 


NECK. 


general investment; being prolonged without 
interruption, below, into the superficial fascia 
of the chest,—above, into that of the head and 
face. It consists here, as elsewhere, of two 
layers, which have the local peculiarity of 
being separated by the platysma myoides in the 
greater part of their extent. Its deeper layer 
occurs in the form of delicate, scarce, lax, fat- 
less areolar tissue, interposed between the 


Fig. 


567 


proper aponeurosis of the region and the pla- 
tysma myoides, furnishing means for the loose 
gliding of this muscle, and continued, without 
adhesion or sensible change, into the adjoining 
regions. Its subcutaneous layer is of coarser 
materials and of less uniform thickness, is in 
close union with the skin, and follows its move- 
ments : it contains the variable amount of fat, 
which the region presents; and so, though it 


327. 


Transverse horizontal section of the neck, seen from above. 


A, fourth cervical vertebra. 
» cricoid cartilage. 
» pharynx. 
» Medulla spinalis. 

@, prevertebral aponeurosis. 

6, posterior pharyngeal aponeurosis. 

€, middle constrictor. 

d, thyroid body. 

€, sterno-mastoid muscle, in the space behind which 
1s seen a section of the great vessels, and of their 
sheath. 

J, sterno-hyoideus. 

9» Omo-hyoideus. 

h, Sterno-thyroideus, 

#, crico-thyroideus. 


i 


j» trapezius. 

k, splenius. 

l, complexus. 

m, semi-spinalis and multifidus. 
n, levator anguli scapule. 

o, scalenus posticus. 

p, scalenus anticus. 

q, longus colli. 

r, rectus Capitis anticus major. 
s, superior thyroid vessels. 

t, ascending cervical vessels. | 
u, deep cervical vessels. 

v, external jugular vein. 

w, anterior jugular vein. 
#, platysma and superficial fascia. 


568 


constitutes, in lean subjects, a manifest and 
resisting lamina, yet, in those of an opposite 
character, it is rendered indistinet by the pre- 
dominant adipose tissue which oceupies its 
areole. Along the side of the neck, from the 
clavicle to the jaw, these layers are kept asun- 
der by the platysma myoides, which adds, as 
it were, a third lamina to the subcutaneous ex- 
pansion; but beth in front and behind, where 
the muscle ceases, they are in close relation, 
and constitute a single covering to those regions 
of the neck. The deep layer of this fascia is 
traversed by the cutaneous nerves and vessels, 
including the external jugular vein. 

2. The cervical fuscia is a proper aponeu- 
rotic investment of this region, and corresponds 
in its general characters to the fibrous sheath- 
ings of the limbs, Like these, it not only 
forms a general, compressive, and modelling 
cincture for the part, but, by various secondary 
sputng®, furnishes dissepiments which isolate 
the different organs, and allot to each its proper 
sheath or fascial chamber. It may be briefly, 
but insufficiently, described as originating from 
a kind of linea alba, or mesial commissure in 
front, and in its backward course to the spinous 
processes furnishing a separate investment to 
every organ which it encounters, and attaching 
itself, both below and above, to the chief bony 
eminences which present themselves. (A sec- 
tion of it, as it thus cellu/ates tlie neck, is re- 
presented, with Bourgery’s almost invariable 
accuracy, in a lithograph, (vol. vi. pl. 10,) from 
which the accompanying woodcut is copied.) 
It requires, in at least many regions of the 
neck, a more particular description than this 
summary contains; and I shall accordingly 
proceed to consider such portions of it with 
some detail. The sterno-cleido-mustoideus is 
ensheathed through its whole extent; the fascia, 


on reaching its anterior edge, is bi-laminated, - 


encloses the muscle, and becomes again single 
at its posterior border. When this sheath is 
laid open by removing its anterior wall, and the 
muscle carefully everted from its prismatic cell, 
it will be seen that the posterior lamina is of 
greater strength than the removed anterior one ; 
and this surface is the one from which the dis- 
sector may most conveniently trace the further 
spread of the membrane. Le will find that 
the cervical fascia (of which the portion cover- 
ing the sterno-cleido-mastoideus is but a se- 
condary slip) extends itself from behind that 
muscle in all directions; inwardly to the me- 
sial line,—outwardly to the trapezius,—up- 
wardly to the jaw,—downwardly to the cla- 
vicle. a. Traced inwardly, its arrangement 
differs in the upper and lower parts of the 
neck: 1. in that below the os hyoides a su- 

rficial lamina covers the subhyoid muscles, 
oins its fellow in the median line, and is fixed 

low to the interclavicular notch of the ster- 
num; a second, thin process divides the sterno- 
thyroid from the sterno-hyoid muscle; a third, 
stronger one, passing between the sterno-thy- 
roid and air-tube, covers this latter organ and 
the thyroid body, is attached below to the inner 
surface of the manubrium sterni, internally joins 
the layer from the opposite side, and helps with 


NECK. 


it to forma raphe, reaching from the os hyoides 
to the actin notch. Previously to the divi- 
sions here mentioned, the fascia encloses the 
flat tendon and anterior belly of the omo-hyoid — 
muscle ; and in a line, which will presently be 
more particularly indicated, covers the carotid — 
artery, jugular vein, and nervus vagus. Just 
external to these parts, along the outer edg 
the jugular vein, it detaches a delicate process 
which behind the vessels, separating 
them from the sympathetic nerve, and is con- 
tinued inwardly to join its fellow from the 
opposite side, as a cellular clothing to th 
esophagus. 2. Above the os hyoides, th 
arrangement of the fascia is simpler; coverin 
the mylo-hyoid and submaxillary gland, r 
inclosing the anterior belly of the dig rie, i 
is fixed to the lower er of the symphysis 
and hence to a mesial raphe as far as the ¢ 
hyoides. It has some deep connexions, to wl 

1 shall return directly; and, to the sheath of 
great cervical vessels it P the sai e 
lations as below, its process lo 
itself on the pharynx. 6. Traced upwardly, 
fascia is seen to split on the inferior edge of 
digastric muscle; the su ial lamina is 
tached, behind, to the mastoid process, 
front, joining the part last described, t 
lower edge of the jaw, > intermediz 


ascends upon the id gland, which it 
vests ; shia deel 0 is fixed to the sty 
process of the temporal bone, and gives or 
to a remarkable septal slip, (sometimes cal 
the stylo-maxillary ligament,) which, just - 
front of the posterior belly of the digastric, pass 
outwardly, is inserted into the deep surface 
the superficial lamina and into the angle of | 
jaw, so serving to separate the space, circu 
scribed by the digastric muscle, into two pal 
and isolating the parotid gland, which ocew 
the posterior of these, from the submaxillai 
which is situated m the anterior one. Furthe 
this deep layer (joined by a slip from the fase 
which covers the submaxillary gland and is: 
tached to the jaw) prolongs itself around WI 
ton’s duct, between the mylo-hyoid and hy 
glossal muscles, and likewise furnishes oris 
to the investing cellular tissue of the phary 
c. Below, the cervical fascia attaches it 
around the insertions of the muscles, whi 
incloses, viz. towards the median line to” 
notch of the sternum, and—with the sub-hj 
muscles—to the deep surface of the manul 
and to the cartilage of the first rib, and the 
the clavicle in its entire length, both ar 
and between the sterno-cleido-mastoid and 
pezius. In descending to the clavicle, 1 
sheathes the posterior belly of the omo-hy 
and a firm process of it, folded aroun 
muscle and directed backward to the 
anguli scapule, is infixed along the su 
costa of that bone, and circumseribes th 
called omo-hyoid space. d. Traced oulwa 
and buckwardly the fascia covers in the i 
val between the trapezius and sterno-maste 
(posterior triangle) from the clavicle to the 
ciput, and, on arriving at the anterior edgi 
the trapezius, splits to enclose it. The fur 


mi 


distribution of it, in this direction, is im 


_———-. 2 + ~e, 


i 


\ 


| hi 
\ 
} 


Mh 


Shews from below the cervico-thoracic septum constituting the roof of the thorax, ‘ 
It represents a transverse and horizontal section through the 


passage to the great vessels. 


569 


a 
iN ! 
AVA 
a ia 


and giving 


second intervertebral disc, and parts at the same level. 


A, second dorsal vertebra. 

B, tranverse division of the manubrium sterni. 

C, first ribs. 

D, vertebral extremity of second ribs. 

a, a, fascia, extending between the great vessels 
and first two ribs. 

6, b, its insertion at the first ribs. 

¢, c, its insertion at the second vertebre. 

d,d, lamina between the great vessels, attached 
centrally to them,—in front to the sternum, where 
it forms a cul-de-sac,—and behind to the second 
dorsal vertebra. 

cordance with the general law of its arrange- 

ment for the separation of muscles; is desti- 

tute of any particular surgical interest, and 
forms no exception to the general observations 
given in a preceding article. (See Back.) 

A portion (but a very distinct portion) of this 
great aponeurosis is the pre-vertebral fascia. 

It extends from the occiput—to which it is 


e, the aponeurosis, extending within the sternum. 

Jf, the trachea. 

g, the esophagus. 

A, the arteria innominata. 

i, the right vena innominata. : 

k, the left vena innominata, tranverse band uni- 
ting the two sides of the aponeurosis. 

I, the left carotid artery. 

m, the left subclavian artery. 

m, section of the muse. long. colli. 


fixed in front of the recti capitis anticito the 
inlet of the chest, where it adheres, beside the 
longus colli, to the neck of the first rib; it 
binds down the pre-vertebral muscles, is at- 
tached deeply to the tips of the transverse pro- 
cesses, and receives by its surface a septal slip 
from the cervical fascia just externally to the 
sheath of the vessels. An important process 1s 


570 


the prolongation which it sends downward on 
the scaleni; and which partly fixes itself to the rib 
around the attachments of those muscles, partly 
extends itself, as a strong infundibulum on the 
brachial plexus and subclavian vessels. From 
this—their fascial sheath—an horizontal slip 
detaches itself and passes forward to the pos- 
terior surface of the clavicle, where it fixes 
itself by two lamine ; the upper of these is 
inserted just above the attachment of the sub- 
clavius muscle, while the lower is continued 
into the sheath which that muscle derives from 
the coraco-costal fascia. The horizontal pro- 
cess separates the cavity of the axilla from the 
lower triangle of the neck, and the vaginal 
prolongation, contracting as it descends, be- 
comes lost in the sheath of the axillary vessels. 
Finally, as these various layers of fascia at- 
tach themselves about the inlet of the thorax, 
(the sub-hyoid part of the cervical aponeurosis 
in front, and the pre-vertebral behind,) they 
are connected to one another and to the large 
vascular and mucous canals, which traverse 
that passage, by certain horizontal processes of 
fibrous membrane, which constitute together a 
kind of diaphragm, or cervico-thoracic septum. 
Viewed from below this would seem a vaulted 
membrane, overarching the tops of the pleu- 
re, and giving infundibular passage to the 
great arterial and venous trunks and to the 
trachea; viewed from above it would present 
the various deep implantations of the cervical 
fascia, and a surface without aperture or breach 
of continuity, prolonging itself in several di- 
rections round the canals, which it thus indi- 
rectly transmits. The obvious use of these ar- 
rangements is to supply adequate resistance to 
the atmospheric pressure, which, were it not 
borne off by the tension of these fascia, would 
at each inspiratory effort tend to flatten the 
trachea, or to rush through the upper strait of 
the thorax. Allan Burns, who in this country 
first drew attention to the importance of the 
cervical fascia, carefully illustrates its func- 
tions in health, and the inconveniences which 
accompany its destruction. (Op. cit.) 


III.—RectonaL DISTRIBUTION AND SUR- 
GICAL ANATOMY OF THE NECK. 

The posterior parts of the neck having been 
described in a previous article (see Back), the 
present will be restricted to an account of its 
anterior aspect. 

The cervical vertebre (by their bodies, inter- 
vening fibro-cartilaginous discs, and transverse 
processes), together with the anterior and la- 
teral vertebral muscles, already described, com- 
pose the skeleton and supporting fabric of this 
region; the anterior fibres of the trapezii, as 
they descend on either side to the inner edge of 
the acromio-clavicular arch, form its lateral 
boundaries ; the larynx and trachea (covered 
by their own extrinsic riband-like muscles, and 
partly covering the pharynx and cesophagus) 
separate the nearly symmetrical halves of the 
neck by constituting alonz its median line a 
marked columnar relief, in the recesses beside 
which lie the great cervical vessels; the base 
of the skull and the oblique line of the jaw are 


NECK. 


the upper limits of the region; the clav 
(just behind which the great vascular and ner- 
vous trunks of the upper extremity course 
bounds it below; the skin, the platysm 
myoides (in its cellular covering), and the ¢ 
vical a rosis are stretched across it as ge 
neral investments; while the last-named fast 
ensheathes the various parts by special pre 
cesses from its deeper surface. 

Thus, in general terms, the structure of fl 
neck may be described ; but, for the more pi 
cise and particular account, which the imp 
tance of its anatomy renders 
division of it into spaces of small ex 
convenient. The arrangement, which I prop 
following, differs but little from that usua 
adopted, and, perhaps, somewhat exceeds it 
precision. y 

The upper limits of the neck having t 
stated as the oblique line of the jaw 
base of the skull (which parts, as we si 
sently see, are brought into relation 
eitachanpats of the constrictor pharyng 
rior), our highest region has in that diret 
these parts for its boundary, and extends b 
as far as the curve of the muscle, from wh 
is named the digastric space. - ¥ 

A small space that can hardly be referr 
the digastric,—from which it is separated by 
vaginal process of the temporal bone, am 
attachments of fascia,—and which, from thei 
portance of its contents, deserves careful eo 
deration, is the posterior pharyn, 3 it 
closely beneath the base of the skull, (from 
vaginal process to the median line) be 
pharynx and spine, and includes the 
jugular, and condylic canals, and the 
traversing them. 

If now an oblique line be carried 
neck, from the sterno-clavicular artieu 
the tip of the mastoid process, it divides, 
diagonal, the remaining quadrilateral sui 
the neck into two triangles; an anterior 
having its apex at the sterno-clavicular 
and its base along the posterior bell 
the digastric muscle; a posterior one, ha 
its base at the inner two-thirds of the 
vicle,—its apex at the mastoid process, 
posterior side formed by the trapezius,— 
terior border defined by the imaginar 
which demarks it from the anterior tra 
The omo-hyoid muscle, in its reflected « 
crosses both these triangles, subdividing | 
and since the angle of its bend falls just 
line of their separation, and since it pr 
from behind the outer third of the clay 
the body of the hyoid bone, it acts as a 

j 


nece: 


er 


arx? 


diagonal in the neck, dividing each 

upper and a lower triangular space. 
four triangles will be described in deta 
since the sterno-mastoid (which is too 
stantial to be treated as a mere bow 
enters into all of them, and has to p 

relations of the extremest practical imp 
some separate, chiefly recapitulatory 
deration will be given to its relative anate 
Finally, to ensure for the organs of the me 
line the consideration — require (the use 
ness of which mainly depends on their be 


viewed connectedly), it may be weli to take 
them in that relation. 
Thus, (1) a region of the median line, (2) an 
antero-inferior, (3) an antero-superior, (4) a 
tero-superior, and (5) a postero-inferior tri- 
angle, (6) a digastric, and (7) a posterior pha- 
ryngeal space, ave to be severally considered ; 
and a few preliminary remarks may be given 
_ to the tegumentary parts, which are more or 
less common to all. 
__ The skin is fine, thin, and extensible, espe- 
cially below and in front; becoming coarser 
and more adherent toward the upper part of 
the posterior triangle; it frequently presents 
me transverse wrinkling above the hyoid 
bone, which seems to depend on the platysma 
nyoides ; here, too, the follicles are larger and 
e abundant than in the other parts of 
the neck, and, in the male subject, the surface 
‘is overgrown by the beard. The subcutaneous 
cellular tissue has already been described ; in 
the upper part of the posterior triangle it be- 
comes almost inseparably confounded with the 
ical aponeurosis ; the platysma myoides lies 
yeen its layers and keeps them apart 
the greater surface of the neck; the 
; es of this muscle are absent in the lower 
1 of the anterior, and upper part of the 
ferior triangle, and at these spots the two 
Tayers of the superficial fascia fall together and 
are nearly confounded. In the deeper lamina 
this texture, subjacent to the platysma in the 
_ parts where it lies, run the superficial veins and 
| nerves. The external jugular vein commences 
: in the parotid gland, usually by radicles, which 
' = pond to the terminal branches of the ex- 
: ternal carotid artery, temporal, internal maxil- 
_ lary, and transverse facial; pierces the fascia 
Rear the angle of the jaw, and directs itself al- 
Most vertically toward the middle of the cla- 
vicle, in the deep layer of superficial fascia : 
aut at the edge of the clavicular insertion of 
_ the sterno-mastoid muscle it bends inward, 
i the aponeurosis, and discharges itself 
{ into the subclavian vein. It thus very ob- 
_ liquely crosses the sterno-cleido-mastoideus 
_ from its anterior to its posterior edge, sepa- 
tated from that muscle by its fascial sheath ; 
the auricular nerve runs upward parallel 
to its posterior border; the platysma covers 
it in its whole course with fibres which cross 
its direction ; its place of discharge into the 
subclavian vein is usually just opposite the 
Scalenus anticus, covered by fascia and by the 
Sterno-mastoid muscle. It receives superficial 
_ Occipital, superior and posterior scapular veins ; 
branches from the posterior triangle of the 
neck, and from the trapezius; it has uncertain 
irregular communication with the anterior 
jugular vein, and receives a certain, though not 
regular, branch from the internal jugular; this 
is usually given to it at the lower part of the 
parotid, or on its emergence from that gland, 
and occasionally seems to constitute its com- 
mencement. Obvious surgical inferences from 
the anatomy of this vein are: the relief that its 
communication with the internal jugular en- 
ables it to give, when opened in cases of cere- 
bral congestion; the eligibility of its line of 


NECK. 


571 


passage over the thick belly of the sterno- 
mastoid for that mode of venesection; the ne- 
cessity for dividing some fibres ¥ the platysma 
transversely to theirlength (by an \acision nearly 
in the direction of the sterno-mastoid) in order 
to obtain a clear opening and free jet of blood ; 
the need for care in this operation, but still 
more in proportion as the vein is wounded 
lower in the neck, to hinder the possibility of 
air being inspired through its cavity. 

The anterior jugular vein is an irregular sub- 
cutaneous supplement to the external: it com- 
mences in the submental region, near the hyoid 
bone; descends vertically beside the median 
line, receiving branches from the larynx, and 
sometimes from the thyroid body; on arriving 
at the sternum, or near that bone, it bends 
horizontally outward, piercing the fascia, and 
runs behind the origin of the sterno-mastoid, to 
throw itself into the subclavian vein, somewhat 
within the termination of the external jugular. 
It generally has free communications with its 
fellow and with the internal and external ju- 
gular. Its size is in inverse proportion to that 
of the external; and, in absence of this, it is 
generally a very considerable branch; it is 
sometimes single and mesial; but more usually 
two exist, which are commonly of unequal 
calibre. 

The superficial nerves are of two classes, 
being partly derived from the cervical plexus, 
partly from the portio dura. 

The cervical plexus sends its superficial 
branchings in three directions : the mastoid and 
auricular pass upward ; the anterior cervical 
runs forward ; the supra-clavicular and super- 
acromial, as their names denote, descend more 
or less obliquely. 

The muastoid, originating from the second 
cervical nerve, winds upwardly across the sple- 
nius, and almost parallel with the posterior edge 
of the sterno-mastoid, which it crosses in its 
ascent. It pierces the fascia soon after its 
origin, and becomes subcutaneous. Its distri- 
bution is entirely to the skin of the mastoid and 
occipital regions. The auricular, rising from 
the second and third cervical nerves by a trunk, 
common to it with the anterior cervical, di- 
rectly pierces the fascia, loops round the pos- 
terior edge of the sterno-mastoid, and ascends 
across its surface (the fascial sheath intervening) 
toward the angle of the jaw; where, after sup- 
plying twigs to the integuments over the pa- 
rotid gland, it divides into terminal branches, 
which are distributed to the external and in- 
ternal surfaces of the auricle and to the adjoin- 
ing integument, in a manner which need not 
be particularised in the present article. In 
crossing the sterno-mastoid it is parallel to the 
external jugular vein, and behind it. The 
anterior cervical rises in common with the last, 
and pierces the fascia in its company ; bends 
at right angles across the sterno-mastoid muscle, 
and is itself crossed by the external jugular vein. 
On arriving at the edge of the muscle, it di- 
vides into many twigs, which, traversing the 
platysma at several spots, distribute themselves 
to the skin of the anterior triangle of the neck, 
and to that of the adjacent part of the digastric 


572 


space. This nerve, where crossed by the external 
jugular vein, gives one or two minute twigs, 
which follow its direction toward the angle of 
the jaw. 

e supra-clavicular and super-acromial are 
the two superficial branches in which the 
plexus terminates: as they descend, they di- 
vide into a lash of twigs, which diverge in the 
oars triangle of the neck, and at various 

eights pierce its fascia, become subjacent to 
the platysma, and contribute to supply it. Their 
ultimate branching takes a very wide range: the 
inner filaments obliquely cross the clavicular 
origin of the sterno-mastoid ; the outer, the 
anterior fibres of the trapezius; the middle 
ones, the clavicle itself; and are dis- 
tributed, in their respective regions, to the in- 
teguments of the scapula, shoulder, chest, and 
sternum. 

The branch from the portio dura, which enters 
the neck, is the lower division of its cervico- 
facial part. From near the angle of the jaw, 
where it traverses the fascia, it passes toward 
the hyoid bone, and supplies the platysma 
from its deeper side. Some of these twigs, 
approaching the cutaneous surface of the 
muscle in the anterior triangle of the neck, 
communicate with filaments of the anterior cer- 
vical nerve. 

1. Mesial region of the neck.—This presents 
different relations, as considered above or below 
the level of the os hyoides. 

Above the os hyoides, and extending from 
the body of that bone to the symphysis of the 
lower jaw, is the narrow space which separates 
the anterior bellies of the digastric muscles. It 
is an elongated triangle, broadest below—where 
the tendons of the digastrics are kept apart by 
the body of the hyoid bone—having its apex 
above, where these, having expanded into the 
fleshy anterior bellies, are infixed side by side 
at the median line of the jaw. The platysmata 
in their cellular sheath cover this space, and 
sometimes decussate across it with each other. 
The cervical aponeurosis likewise extends over 
it, adhering to its bony limits, and strength- 
ened by the tendinous slip, which is derived 
from the digastric. Deeper than the digastrics 
are seen the fibres of the mylo-hyoid muscles, 
meeting in the median raphe, which runs along 
the space. The natural direction of this raphe 
is almost antero-posterior, and that of the fibres 
which meet in it almost horizontally transverse : 
but when (as in any operation on this part of 
the neck) the head is thrown back and the chin 
elevated, the raphe presents a considerable 
downward slope, and the fibres of the mylo- 
hyoid have a corresponding obliquity. The 
same observation applies to the deeper fibres 
which course from the tubercles within the sym- 
physis to the body of the hyoid bone—those, 
namely, of the genio-hyoid and genio-hyo-glos- 
sal muscles. This little region can hardly be 
said to have any special surgical relations; it 
contains neither vessels nor nerves of size ;its 
injuries only assume importance when taey 
extend beyond it into the adjoining digastric 
space; its diseases derive a0 peculiarities from 
their situation, and for the most part belong to 


NECK. 


the integuments, which are vascular, 
folliculated, and in the male densely beardes 
sycosis often extends to them, and they are 
frequent seat of sebaceous tumours. es 
Below the os hyoides, the anatomy, ¥ 
involves the surgical relations of the laryn: 
trachea, becomes of extreme importance. — 
tween the two layers of the fascia superfi 
the platysma no longer intervenes; they 
cordingly lie together and are blended. ' 
vaginal processes of cervical fascia, which | 
isolated the sub-hyoid muscles, become wi 
into a strong and single raphe along the mi 
line, from above to within a short distane 
the sternal notch; but here the layers rem 
distinct, a superficial one fixing itself 
notch and to the interclavicular ligame at, W 
the deeper one descends with the muscles ii 
the mediastinum. The interval contains” 
cellular tissue, and sometimes (as Burns 
ticed) an absorbent gland. Accordingly, in 
very median line, an operator may expose t 
larynx, trachea, or thyroid body without 
ding or displacing any portion of muscle ; 
a lateral deviation from this imaginary 
would imply an exposure of the 
muscles on one side or on the other. 
the muscles so nearly approach to the lit 
question, and constitute in their lamin: 
rangement so useful a guide to the subje 
parts, that the bare possibility of avoiding 
is wisely neglected, and the surgeon | 
from them his nearness to the organs 4 
they cover. = 
In tracing, from the hyoid bone dowm 
the irregular profile of the air-tube, the 
may distinguish through the integume 
following changes of outline. 1. A horiz 
semicircular notch, limited below by the 
minent angle of the thyroid cartilage, am 
responding, in the interval of the mu: 
the thyro-hyoid membrane ; the lateral p 
this give passage, as we shall presently. 
the laryngeal artery and nerve, but its 1 
art, with which alone we are now oct 
1as only a small twig from the thyro 
rainifying over it: the membrane is thie 
composed of strong vertical fibres in the 
line ; it becomes weaker and of laxer 1 
pene backward. Its deep aspei 
utes to the skeleton of the pharynx, 
responds to the epiglottis, from the 
portion of which it is separated onl 
lular tissue and the epiglottidean glan 
above, the mucous membrane, in bein 
forward to the epiglottis, intervenes bi 
and the membrane. This notch is fre 
invaded by the knife of the suicide; an 
is perhaps no part of the neck on whi 
may be inflicted with less serious ijt 
large vessels are far removed, and tl 
lies below the blade, which may, if mi 
hyoid bone, enter the pharynx 
glottidean fold of mucous mem 
the epigicttis unhurt, or, if more m 
proached to the thyroid border 
may partly or entirely sever that 
its inferior attachments. No sp 
operation belongs to the space; if inc 


oi 
" 
m 


a 
A ey 
tir Nn 
a 


except a proposal made by M. Malgaigne* 
for reaching the larynx through it, which 
has not yet received the sanction of practice. 
2. Theangle,in which the ale of the thyroid car- 
tilage meet, having—under the quaint name of 
um Adami—its extreme prominence above. 
Within it are the essential organs of voice, 
which, buckler-like, it protects: the inward 
aspect of its angle attaches the vocal ligaments ; 
its outward jutting marks their length, and mea- 
sures the development of the larynx. Hence 
the pomum Adami, as indicating by its promi- 
mence that matured growth of the organs of 
_ voice, which belongs to male puberty, is a phy- 
_ siognomical character of sex. Desault’s mode 
of laryngotomy consists in a vertical division 
_ of this angle from below upward, and has the 
_ recommendations of easy performance and of 
efficiency for the extraction of a foreign body. 
That it invades parts of high functional endow- 
_ ment and extreme irritability, —that ossification 
of the cartilage may unexpectedly prevent its 
‘completion—that perfect reunion of the di- 
‘yided structure is uncertain—are alleged as 
objections to it, and perhaps over-estimated 
‘as such; for to the first may be answered, that 
‘the operation is of relief, and hence little 
ae to aggravate an irritation, the cause of 
a ich it removes; to the second may be con- 
ceeded, that the mode of operation is not eligible 
for cases likely to present the bony deposit 
referred to; and against the third may be ad- 
duced the evidence of the French surgeons, 
_ by whom chiefly the operation has been per- 
formed, that the parts are as quickly repaired, 
__ and their functions as completely recovered, as 
after any other mode of operative procedure. 
__ As regards its anatomy, nothing can be easier 
than to lay bare the pomum Adami; a division 
of the skin, of the superficial and proper fascie, 
with some lateral displacement of the sub-hyoid 
muscles, will suffice for its exposure: and, for 

its division,—the closest following of the me- 
dial line, in order that the knife may pass be- 
tween the vocal ligaments, leaving both unin- 
geet, is the chief precaution to be observed. 
The upper edge of the glottis is on a level just 
below that of the superior thyroid notch. The 
prominence of the thyroid cartilage and the 
unyielding support which the borders of its 

arched surface receive from the bony column 
behind it, render it liable to be crushed by any 
considerable, direct, antero-posterior violence. 
Such has, more than once, been the cause of 
immediate death where a straightforward blow 
hhas reached the larynx in prize-fighting ; and 
Such, too, isa not infrequent effect in death by 
hanging, especially where, as in the English 
Mode of judicial execution, the rope is made 
to tighten itself jerkingly. The thyroid carti- 
lage is sometimes partially divided in attempts 
at self-destruction, which it commonly frus- 
trates by defending more important parts. 
3. A depression which answers to the crico-thy- 
roid ligament: it is here that the usual opera- 
tion for urgent glottic dyspnea is performed. 
The common integuments and the fascial raphe 


—————————————— 


* Médecine Opératoire, 1840, p. 517. 


NECK. 


573 


cover the little interspace in question, which is 
safely reached—hetween the crico-thyroidei— 
by displacing in a slight extent \he sub-hyoid 
muscles. It has about half an inch of trans- 
verse breadth, and about a third of an inch of 
height,—is bounded by the inferior thyroid 
notch and by the anterior part of the circum- 
ference of the cricoid cartilage; which borders 
give attachment to the strong yellow elastic 
membrane that closes the space. This depres- 
sion is so readily felt through the integuments 
—its boundaries are so definite and its relations 
so simple, as to render it a peculiarly eligible 
spot for bronchotomy, when suddenly and ur- 
gently required. A small artery sometimes 
forms, with its fellow of the opposite side, a 
transverse communication across this mem- 
brane, and its presence has been much insisted 
on as a circumstance of practical importance : 
it is of extreme minuteness, and by no means 
constantly present : it is the erico-thyroid, and 
arises from the thyroid branch of the external 
carotid, near the upper angle of the thyroid 
body, and runs across the membrane toward 
the median line. The necessity for haste is 
commonly of too urgent a character to admit of 
any deliberate, layer-by-layer, dissective opera- 
tion : a single steady puncture with a canulated 
trocar, or with a bistoury—directly followed by a 
tube—is the usual mode of conducting it. In 
such instances the minute artery can hardly be 
avoided with certainty, but neither can its 
division be injurious, since the closely fitting 
canula will secure the cavity of the air-tube 
against its trifling hemorrhage. In the rarer 
cases, where time is allowed for a slower divi- 
sion of the tissues, it would be desirable not to 
puncture the membrane till the artery, if pre- 
sent, had been disposed of. It usually lies 
near to the border of the cricoid cartilage, and 
might easily be drawn downward away from 
injury; or its division might be rendered harm- 
less by torsion, or by a fine ligature. In the 
more extemporaneous mode of laryngotomy the 
bistoury should be guided flatly, close beneath 
the thyroid cartilage; in so making a transverse 
division of the membrane, it is parallel to the 
line of the artery, but above its usual position. 
4. The slight prominence of the cricoid car- 
tilage, and the series of tracheal rings—be- 
coming progressively deeper toward the ster- 
num,—are next felt. In some subjects their 
chain is seemingly interrupted by a transverse 
fleshy eminence (which, however, is in health 
generally imperceptible through the skin), 
the isthmus of the thyroid gland. To the la- 
teral portions of this body I shall presently 
return: the isthmus is its only part having re- 
lations in the median line, which it crosses to 
a very variable extent. Most frequently it 
measures about half an inch in breadth, and 
corresponds by its middle to the second ring 
of the trachea: but from this, its normal ex- 
tent may vary on the one hand to the ex- 
treme of entire absence—on the other to that 
of being an uncontracted, flattened union 
of the lateral lobes, which it may so equal in its 
vertical dimension. Downward from its lower 
edge, in front of the remaining rings of the 


574 


trachea, the inferior thyroid venous 
plexus, on a level with which would be found, 
in rare cases, the middle thyroid artery (of 
Neubauer) ascending from the aortic arch : 
these vessels are covered by a layer of fascia 
dividing them from the sterno-thyroid muscles, 
These are variously involved in the two 
remaining modes of bronchotomy; one of 
which—the tracheal—consists in dividing three 
or four rings of the tube, below the isthmus of 
the thyroid gland; the other—the crico-tracheal 
—in dividing its upper rings and with them the 
cricoid cartilage of he larynx. The first—tra- 
cheotomy—{after a vertical division of the 
tegumentary parts and a separation of the 
muscles from the lower part of the larynx to 
the sternum) exposes the tube in that portion 
of its extent in which it is deepest and most 
nearly related to vessels. The operator is 
required to bear in mind the possible presence 
of a middle-inferior thyroid artery, lest he 
wound it inadvertently; he must avoid, or, 
before opening the air-tube, must secure the 
inferior thyroid veins ; in recollecting the great 
lateral mobility of the trachea and its close 
parallelism to the carotid arteries in the lower 
part of the neck, he must guard against any 
oblique glancing of his knife, by which these 
great vessels might be injured ; in proceeding to 
divide the cartilaginous rings, he must com- 
mence below and on a completely exposed 
part of the tube, and with the blunt border 
of his knife toward the middle line of the 
sternum, and with its point directed slightly 
upward, lest (as might happen in neglect of 
these precautions) the great vena innominata, 
transversely crossing the tube just below the 
level of the sternum, or the large arterial trunks, 
which are there diverging from the median line, 
should sustain injury: nor must he rudely 
transfix the tube and encounter the risk of 
pee ate arts, normally or abnormally be- 

ind it.* The second operation, crico-tracheo- 
tomy, first proposed by Boyer,+ pretends to 
preference over that just mentioned, on the 
ground of obtaining an equally free opening 
with less invasion of important parts. Indeed, 
although M. Boyer, in proposing it, seems to 
have considered the section of the thyroid 
isthmus inevitable, and accordingly included 
its division in his estimate of risks,—perhaps 
even that objection might be withdrawn from 
the operation, if performed in exact agreement 
with his description ; since the finger may de- 
press the thyroid body to an extent which 


* In suggesting the possibility of injuring organs 
abnormally situated behind the trachea, the text 
particularly refers to the occasional passage of a 
right subclavian artery, from the left part of the 
arch, either between the cesophagus and trachea, 
or behind both those tubes. The anomaly is not a 
very rare one ; and a case is reported, in which the 
artery, so running, was pierced by a bone, arrested 
in and perforating the esophagus. ( in Hos- 
pital , vol. ii.) The irregularities of the 
aorta itself, quoted by Tiedemann from Hommel 
and Malacarne, are of almost uniqne occurrence, 
hardly furnishing an additional argument for that 
uniform caution, which the above less infrequent 
abnormality makes imperative. 

+t Maladies Chirurgicales, vol. vii. p. 131. 


NECK. 


. | 


admits a safe division of the first two rings 
the trachea. But it seems to have pi 
notice, while theorising on the operation, t 
a section of the cricoid cartilage must be use. 
less, unless abused ; that a rigid ring, dividi 
at one point of its circumference, remains 1 
loosened ; that a single section of the erie 
cartilage could not made available a 
means for increased access to the air-tube, ov 
and above that afforded by division of th 
chea, except by employing onita disruptivefo 
that should effect a counter-fracture at s 
other part of its circumference. Such viol 
on such an organ M. Boyer was far too ju 
cious a surgeon to have sanctioned ; and { 
the single instance, appended (p.142 bi 
speculations on the subject, it appears probak 
that the upward extension of his opening in 
air-tube was useless; that an incision throu 
the upper rings of the trachea sufficed for | 
escape of the foreign body; and that, in- 
essential particulars, the crico-tracheal ope 
tion is but tracheotomy at a higher than 
nary level, complicated with an unadvantage 
and therefore objectionable intrusion on — 
larynx. 
2. The antero-inferior triangle djoins | 
wardly the space last described, is boun 
outwardly by the decussation of the omo-hy 
muscle (which separates it from the supt 
compartment of the great anterior trial 
with the imaginary diagonal, which demar 
from the postero-inferior or supra-clavic 
space. Its various parts and contents rec 
some separate description. As regards thei 
guments, it will be remembered that the 
tysma only pee? covers this space, and 
the anterior jugular vein, when it exists, is 
tained here in the lower part of its course. - 
sterno-cleido-mastoideus follows the outer 
of the triangle, but extend over it by its 
border, so as to cover a large portion ¢ 
area. Beneath this muscle, the stronge 
layer of the cervical fascia is extende 
splits internally to enclose the sterno- 
deus, which likewise encroaches on the 
by its inner side. Under this fascia the eo: 
carotid artery (beside which are the ji 
vein and the pneumogastric nerve) asee 
tically, and is slightly overlapped from 
by the thyroid body. The anatomy of th 
is well developed, in considering the b 
of reaching the carotid artery: a vertici 
sion falling on the sterno-clavicular j¢ 
poses the superficial fascia and part of t 
tysma; these being divided, the she 
sterno-mastoid is seen, and on its being © 
the sternal fibres of the muscle present 
selves, obliquely ascending outward: 
vision and displacement exposes the p 
layer of their fascial investment, which 
seen to ensheath the sterno-thyroid muse 
descending branch of the lingual nerve 
scendens noni) seems almost embedded 1 
deep layer of the aponeurosis, and reach 
outer edge of this muscle in the upper pi 
the space:—beneath the stratum of par 
constituted, the carotid lies with the associ 
organs: the jugular vein is on its outer” 


NECK. 


___ the nervus vagus lies deeply between the two 
| vessels and behind them; the cellular mem- 

brane, which invests and binds them together, 
4 appears to form an indistinct septum to isolate 
the artery; crossing the front of the sheath,— 

from the median line toward the jugular trunk, 
eon which they pierce—are many veins, 
of which some are occasionally considerable in 
size: they are branches from the larynx, trachea, 
thyroid body, and sub-hyoid muscles, and 
among them, when it exists, must be counted 
the anterior jugular: they are capable of caus- 
ing much inconvenience to the operator, and 

uire to be carefully managed: on the left 
side, the internal jugular vein itself, inclining 
__ toward the median line below, slightly overlaps 
_ the artery: the posterior layer of the sheath of 
these vessels is a thin process of the fascia in- 
terposed between them and the sympathetic 
nerve, which descends vertically behind: se- 
parated in like manner from the great vessels, 
_ we find the inferior thyroid artery, which as- 
ends in an obliquely serpentine course to the 
lower angle of the thyroid body, and the recur- 
rent laryngeal nerve, mounting (on a plane 
_ deeper than that artery, internal to which it is 
Situated) toward the posterior part of the cri- 
_ coid cartilage; the nerve is therefore very nearly 
approached to the hindermost part of the tra- 
ot cartilages, and, on the left side, ascends 
_ between them and the cesophagus, closely ap- 
 Plied to the latter.* 


__* The cardiac branches of the sympathetic,—although 
they require notice in connexion with the anatomy 
‘of the large vessels,—have little particular interest 
‘in regard of the surgical operations, which are prac- 

4 a on these, and some account of them is there- 
_ fore better appended in a note than blended with 
_ the text. They are seldom or never distinctly seen 
_ im operations; and the rule for their management 
is bat a part of the general principle (which ought 
_ to be supreme in every surgical exposure of an ar- 
_ tery, and the neglect of which has been, I doubt 
“not, at the root of most unsuccessful issues) that 
the disturbance of surrounding parts, and the de- 
nudation of the artery, should both be in the very 
least degree, which will permit the ligature of the 
vessel to be accomplished. The cervical cord of 
the sympathetic lies, as already mentioned, behind 
the sheath of the cervical vessels, and presents 
e ganglia, from which, and from the cord, va- 
rious branches originate. Of these ganglia,—the 
uppermost has often above an inch in length, is of 
_tapering rounded form, and is situated in the pos- 
terior pharyngeal region, on the second and third 
vertebrz : the second, of smaller size and incon- 
stant occurrence, usually lies upon the inferior thy- 
roid artery: the third, frequently confused with 
the first dorsal ganglion, is deeply imbedded behind 
the origin of the vertebral artery. From these 
sources, assisted and reinforced by the pneumo- 
gastric and other nerves, the cardiac branches ori- 
gimate in a manner and succession which will be 
described in a future article. (See SYMPATHETIC 
NERVE.) In descending, they lie posterior to the 


sheath, and the superior one internally to it, close 
to the trachea, and, on the left side, to the cso- 
phagus. When they approach the inlet of the 
thorax, they comport themselves variously in regard 
of the subclavian artery; sometimes passing behind 
it, on each side, and furnishing twigs, which cross 
its anterior surface ; sometimes, on the contrary, 
crossing its front by their main branches; and some- 
times so dividing as to envelop the artery in an 
abundant nervous plexus. They are very irregular ; 


575 


The thyroid body belongs to this space by its 
lateral parts, and, when of moderate develop- 
ment, overlaps the carotid sheathy It consists 
of symmetrical Jobular halves, united by the 
isthmus already alluded to: its lobes are pear- 
shaped, on a section, the small end being up- 
ward ; they are plump outwardly where the 
fascia gives them a smooth envelope, but hol- 
lowed inwardly where they adapt themselves 
to the air-tube: the isthmus commonly con- 
nects the lobes by their lower part only, by over- 
bridging the trachea at about its second and 
third rings; the apex of each lobe reaches to 
the ala of the thyroid cartilage, covering the 
fibres of the constrictor pharyngis, which arise 
there, and receiving the superior thyroid artery 
from the external carotid : the circumference of 
the organ presents, then, upward a crescentic 
sinus in which the angle of the thyroid 
cartilage, the crico-thyroid membrane and 
muscles, the cricoid cartilage, the first one, 
two or three rings of the trachea are 
seen: its thick outer margin,—running from 
the apex to the third, fourth, or fifth 
ring of the trachea—corresponds in that extent 
to the carotid artery, which it more or less 
overhangs, and below to the recurrent nerve of 
the larynx; by the extremity of this border the 
inferior artery reaches it from the thyroid axis ; 
the inferior margin gives exit to veins, which 
have already been mentioned, and not infre- 
quently receives by its middle a fifth artery 
from the arch of the aorta or from the arteria 
innominata. 

From the remarkable vascularity of this 
body, so disproportionate to its volume and 
apparent unimportance in the ceconomy, it 
readily falls into the heterogeneous group which 
the German anatomists have named “ Blood- 
ganglia” ( blut-knoten ). Fiom thesame circum- 
stance, and from the probably vicarious func- 
tion which it seems to discharge, it is extremely 
lfable to hypertrophy, the different forms of 
which, attended by whatever structural change, 
are confounded under the name of goétre or 
bronchocele. From the account given of its 
anatomy, the symptoms of its enlargement may 
be surmised; for it is obvious that a tumour, 
so related to the windpipe and so checked in 
its outward growth by tense aponeuroses, must 
gravely affect respiration. Overlapping the 
common carotid arteries, the tumour derives 
from them a strong and often visible impulse ; 
and, over and above the jerk, which they com- 
municate to it, a general thrill of distensive 
pulsation, arising from its own almost erectile 
vascularity, may be felt by the surgeon. Su- 
perficial observation might fail to distinguish 
such a tumour from carotid aneurism, but 
anatomy establishes the diagnosis; for, in each 
movement of deglutition, the diseased mass 
accompanies the larynx, and is seen to rise and 
fall in the neck. Attempts at extirpating 


but, in all cases, largely communicate with the re- 
current nerves, behind the subclavian arteries, and 
furnish numerous continuations, which descending 
around the three great vascular trunks to the areh 
of the aorta, hence prolong themselves to the base 
of the heart. 


576 


goitres by the knife have been almost super- 
seded hy the discovery, that iodine exerts a 
marked controul over many enlargements of 
the thyroid body; and it would evince other 
boldness than that of knowledge, lightly to 
undertake the excision of a tumour so impor- 
tantly connected. The jugular vein, the caro- 
tid , the pneumogastric nerve, which on 
each side the diseased body would overt 
—the trachea and esophagus, which it would 
almost encircle, might indeed be avoided in an 
attempt at its removal; but the enormous ve- 
nous as well as arterial hemorrhage that must 
occur, and the extreme likelihood of dividing 
the recurrent nerves, would involve a not small 

ssibility of accelerating the fatal result, and 
sae every prudent surgeon from attempting 
an operation of such extraordinary risk, except 
under circumstances that might justify the most 
favourable remote prognosis. e ligature of 
its nutrient arteries has been advocated as a 
cure for bronchocele ; but, although this mode 
of procedure presents fewer anatomical difficul- 
ties than that last mentioned, yet, from surgical 
considerations of its extreme uncertainty and 
unsafe protraction, it seems little entitled to 
preference. 

On the left side, the esophagus, inclining 
from the median line, presents itself in the 
antero-inferior triangle. It only half emerges 
from behind the trachea (which still covers its 
right portion), and closely lies on the vertebra : 
it continues the canal of the pharynx, from a 
line of abrupt distinction opposite the lower 
edge of the cricoid cartilage, downward. It is 
at its commencement that this tube most fre- 
quently interests the surgeon, by becoming the 
seat of stricture, or by arresting and fixing 
foreign bodies. To this space the operation of 
cesophagotomy belongs; and the left side is, 
for obvious reasons of convenience, chosen for 
its performance. In Mr. Arnott’s instructive 
paper on the subject the following directions 
occur, which may serve to illustrate the ana- 
tomy of the region in regard of the operation in 
question: “ The situation of the external in- 
cision will, in some measure, depend upon 
that of the body to be removed, but as the 
pharynx, tapering gradually in its descent, ter- 
minates in the esophagus immediately under 
the larynx, it is here that a bulky substance is 
most apt to be detained. In reaching the 
cesophagus at this place, taking as a centre a 
spot corresponding to the level of the lower 
margin of the cricoid cartilage and the first 
ring of the trachea, the only a of conse- 
quence, whose injury is to be dreaded, are the 
inferior thyroideal artery and recurrent nerve, 
(the superior thyroideal artery being too high 
to run any risk ;) but these will not be wound- 
ed, if the same plan is adopted as that in the 
case related, of separating the deeper-seated 

by the handle of the scalpel and the 
finger instead of by the knife. Here they were 
not seen during the operation, in fact they 
were not within the sphere of the wound, for, 
on examining the parts after death, the artery 
and nerve were found below and on the inner 
side of it. Still I am satisfied by trials on the 


NECK. 


py. 
dead body, that the artery is likely to be: 
vided if the operation is completed by | 
knife, and hence the expediency of procee 
ing deliberately, cutting but little at a tim 
sponging carefully, so as to see and avoid 
artery, if possible, or to tie it immediat 
when cut. The recurrent nerve runs 
as it reaches the side of the trachea, to 
it is attached in its ascent, lower down. IT 
not allude to the carotid artery as being 
pened to any peril. 1 think, with Mr. A 
urns, that he must be wanton indeed in 
use of his knife, who hurts this vessel. 
making the incision into the cesophag 
to be remembered that the recurrent nerve 
in the angle between this tube and the trac 
and therefore the incision is to be ma 
little behind this angle.” * . 
3. Antero- superior triangle.— This pr 
nearly corresponds to the depression whi 
lean subjects is seen at the side of the 
beneath the jaw and in front of the ste 
cleido-mastoid muscle. It is bounded be 
by the diagonal line to which we have so ¢ 
referred ; the posterior belly of the dig; 
and the superior belly of the omo-hyoid 
stitute, respectively, its upper and le 
ders, and their convergence to the h 
anteriorly forms its apex. The fascia 
ficialis, enclosing the platysma myoides 
tends uninterruptedly over its borders; al 
cervical aponeurosis splitting at each, 3 
singly over the area which they enclose 
transverse processes of the vertebra, ¢ 
by muscular attachment and by the pre-t 
bral aponeurosis, form its floor. The cor 
carotid artery enters it below, and, at ab 
level of the lower border of the third ver 
divides into the internal carotid, which 
tinues to the cranium the direction of thet 
and the external, which runs and rami 
more superficial parts; the sympathetic, 
other regions of the neck, lies betwe 
posterior layer of the sheath of the ves: 
the pre-vertebral fascia ; the superior lar 
nerve lies in the same interval, oblique 
ing from above to the posterior part 
thyro-hyoid membrane behind the 
is on the confines of this triangle and 
gastric space that the posterior belly 
muscle, accompanied by the stylo-hyoi 
cle above and the lingual nerve belos 
across the external and internal carotid: 
about this level the stylo-glossus and st 
ryngeus with the glosso- nt 
tervene between those large arteries. It 
below this crossing that the vessels fal 
our present consideration, and their stu 
be facilitated by extending an arbitrary 
division from the os hyoides ( t the ape 
space) transversely backward. 
would have below it the trunk, bifurea 
continuing branches of the common 
and the origin from the external of th 
rior thyroid artery alone; while, above th 
referred to, the continued ; 
would be seen, and many of 


tt 5 
——s 


seconc 7 
, =o 

t 

a 


* Medico-Chirurgical Transactions, 


NECK. 


which spring from the external one, viz. the 
occipital passing obliquely toward the mastoid 

_ process, under cover of the posterior belly of 
_ the digastric, and hooked round by the hypo- 
_ glossal nerve; the muscular, which is not in- 
variably present, inclining outward to the 
P sterno-mastoideus; the lingual and facial (di- 
vided by an imaginary prolongation of the 
cornu of the os hyoides from the superior thy- 
roid) entering the digastric space, the former 
transversely by running along the cornu of 
_ the os hyoides between the hyo-glossus and 
middle constrictor, the latter more obliquely 
ascending; and the pharyngeal artery deeply 
‘unning upward beside the pharynx. To 
all these riches a more particular descrip- 
tion has been given in a previous article, 
‘than would be suitable to the present one; 
ind to that the reader is referred for the 
ails of their distribution. (See Carorip.) 
é jugular vein descends externally to the in- 
al, as to the common carotid, the vagus 
ing, as in the lower region of the neck, be- 
een the two vessels and rather behind them. 
® vein receives several branches, in travers- 
g this triangle, from the larynx and tongue, 
d usually the facial vein: all these, since 
come from within, must cross in front of 
‘artery, and sometimes form an intricate 
*xus, which much embarrasses an operator. 
front of the sheath descends, with a slight 
rd obliquity, the branch of the lingual 
®, which at the lower part of the space, 
md while lying over the vein, forms a reversed 
rch of communication with the cervical plexus, 
Whence branches are distributed to the sub- 
hyoid muscles. The integuments and pla- 
: Bi ens require no particular notice ; their veins 
_ and nerves have already been described ; 
_ among the former must be reckoned the an- 


i. jugular; the space contains a great num- 


of lymphatic glands, a long chain of which 
le concatenate) lies along the outer 
e of the sheath of the vessels, while some 
_ also lie about the thyroid and lingual arteries 
_ on the inner side of the sheath. The surgical 
a of this space are chiefly confined to 
ie arteries: ligature of the common carotid 
or of either of its branches may easily be per- 
formed here, since the vessels lie under a much 
less thickness and variety of parts than below. 
A vertical incision falling on the point of inter- 
section of the omo-hyoid and sterno-mastoid 
muscles, and successively dividing the super- 
ficial fascia (in which the platysma and cuta- 
neous nerves are contained) and the cervical 
aponeurosis (a single layer, as it stretches 
across the space, but, of course, double where 
it encloses the sterno-mastoid,) exposes the 
sheath of the vessels, the veins which trans- 
versely cross its arterial portion, and the de- 
scendens noni which runs on the part of its 
wall corresponding to the jugular vein: and 
here, as he might open the sheath lower or 
higher, the surgeon would expose the common 
carotid or its branches; and, in remembering 
that the internal (so named from its distri- 
bution only) lies at first external to and behind 
the other, he would be able to isolate and 
VOL. IIT. 


el 


577 


secure either of these at his option. In any 
attempt to tie the branches of (re external 
carotid, a clear notion of their respective re- 
lations to the hyoid bone is of indispensable 
necessity; and, in ascending toward the di- 
gastricus, it must be remembered that the 
lingual nerve crosses the carotid sheath but 
just below the border of that muscle, and that 
it and the facial vein are consequently exposed 
to injury. Attempts at suicide by cutting the 
throat seldom succeed; the incision is usually 
made closely either above or below the hyoid 
bone; in the former case entering the digastric 
regions, and dividing, with the muscles of the 
tongue, the lingual and perhaps the facial 
artery; in the latter case, traversing the thyro- 
hyoid membrane, penetrating the pharynx, per- 
haps implicating the epiglottis, dividing the 
thyroid artery, and very rarely reaching the 
external carotid. The mode of searching for 
these vessels must vary according to circum- 
stances, but, in all essential particulars, may 
readily be deduced from their anatomy. 

4. The postero-superior triangle is a large 
space of singularly little interest, having its 
inferior boundary fixed by the omo-hyoid mus- 
cle, its anterior by the diagonal which inter- 
sects this, its posterior by the edge of the trape- 
zius, and its apex by the mastoid process. It 
contains, below, a part of the brachial plexus 
(the anterior branches, namely, of the fifth and 
sixth cervical nerves, which directly pass be- 
neath the omo-hyoid muscle into the adjoining 
inferior triangle,) the whole of the cervical 
plexus and many of its branches, the spinal 
accessory nerve, obliquely crossing from the 
sterno-mastoid to the trapezius, which it enters 
near its clavicular insertion, and some rami- 
fications from the arteria transversalis colli, 
which, under the name of superficial cervical, 
ascend in the space, supply its cellular mem- 
brane and lymphatic glands, and ultimately 
inosculate with descending twigs from the 
occipital. The pre-vertebral fascia covers its 
deep parts; the common cervical extends be- 
tween its borders; the platysma myoides exists 
as a covering for it only in its lower part. 

5. The postero-inferior triangle, (that of the 
subclavian artery,) is one of manifold impor- 
tance. The well-known lines of the omo-hyoid 
and clavicle limit its area above and below, 
the former dividing it from the space last con- 
sidered, the latter from the pectoral region ; 
intersecting the omo-hyoid, our imaginary di- 
agonal, as it stretches from the centre of the 
sterno-clavicular joint upward and outward, 
bounds it internally, and constitutes an arbitrary 
but most useful separation between the space, 
exclusively appropriated to the subclavian artery 
with its branches and that internally adjoining 
it, (the antero-inferior,) which is the proper ter- 
ritory of the carotid. The parts forming its 
deep or posterior wall are, the transverse pro- 
cesses of the lower cervical vertebra and head 
of the first rib, the outer edge of the longus 
colli and the broad lower part of the scalenus 
posticus: its inferior wall presents the upper 
surface of the first rib, and within the curve 
of this bone a part of the upper inlet of the 

2 P 


578 


thorax, at which during life the pleura bul- 
gingly rises, deriving considerable support 
from the horizontal infixion of the cervico- 
thoracic fascial septum. Externally to the curve 
of the rib, (with the coracoid process bounding 
it outwardly, the clavicle in front, and the su- 
perior costa of the scapula behind,) is the space 
through which vessels and nerves connect the 
cervical and axillary regions; to the borders of 
which, deep layers of aponeuroses are so fixed 
that-the regions only communicate in the line 
of the vessels, within the infundibulum of pre- 
vertebral fascia. Its anterior or covering wall 
presents, in addition to the platysma and sub- 
cutaneous areolar tissue, which in all direc- 
tions extend beyond its margins, the cervical 
fascia, as a single layer (except where it splits 
at the trapezius and sterno-mastoid) fixed to the 
clavicle below, and enclosing the omo-hyoid 
above. From the higher part of its posterior 
wall, originating at the anterior tubercles of 
the transverse processes, descends the scalenus 
anticus to fix itself in the floor of the space, 
on the upper surface of the rib, anteriorly. It 
intercepts, like a flying buttress, a space be- 
tween itself and the posterior wall, occupied 
by the brachial plexus and subclavian artery, 
round a!] which, as also round the subclavian 
vein, which lies in front of the scalenus, the 
prevertebral aponeurosis is folded and prolongs 
itself as a funnel; it is from this, that the slip 
of fascia is derived, which passes to the cla- 
vicle, in the manner described above, as a ho- 
rizontal process, dividing the axilla from the 
neck. 

As the distributive anatomy of the vessels 
and nerves will be detailed in a future article, 
(vide Spinat Nerves, SuscLavian ARTERY), 
their arrangement will now be only sketched, 
in its regard to surgical relations. The many 
important points of distinction between the 
right and left sides of the body in this region 
will presently be considered, the description 
meanwhile applying to both indifferently. The 
subclavian artery, from the sterno-clavicular 
joint outward, over-arches the floor of this 
region, presenting upwards a convexity in the 
interspace of the scaleni, downwards a con- 
cavity, which adapts itself to the pleura and to 
the rib. It gives off, as from an axis, branches 
from the four cardinal points of its cireum- 
ference: 1. downwards the internal mammary, 
which, crossed at its origin by the phrenic 
nerve, descends within the cartilages of the 
ribs; 2. upwards the vertebral, which, after a 
course of an inch between the scalenus anticus 
and longus colli, enters the canal of the trans- 
verse processes, usually at the sixth; 3. for- 
wards the thyroid axis, a short trunk giving 
origin to the inferior thyroid branch (already 
seen obliquely ascending behind the carotid 
sheath), the ascending cervical, which mounts 
beside the phrenic nerve, along the scalenus 
anticus, two transverse branches, which 
direct themselves outwardly, crossing that mus- 
cle,—the transversalis humeri along the clavicle, 
the transversalis colli higher, amid the branches 
of the brachial plexus and winding round the 
sealenus posticus to gain the inner edge of the 


NECK. 


scapula; lastly, 4. backwards an artery, which, — 
directing itself to the neck of the rib, sub 
divides there into two branches, one of which 
descends across the rib to the thorax, the supe- 
rior intercostal, while the other continues, = 
tween the neck of the rib and the seventh cer= 
vical transverse process, the backward dif 
tion of the common trunk, and then ascends 
among the deep muscles of the dorsal region— 
the arteria cervicalis profunda. The course of 
the subclavian artery is conveniently di 
into three stages ; a last or distal one, in whiel 
after having behind the scalenus anticus, 
it has, behind it, the scalenus posticus, below 
it the groove of the rib, above it (exter 

likewise a little behind) the brachial plexus — 

nerves, in front of it the coverings of the space 
we are considering, a familiar knowledge of 
which is here especially needed, since it is in 
this portion of its course that the artery is 
usually tied for axillary aneurism: a second 
stage, in which it lies between the scaleni, itt 
convexity toward their origin from which th 
brachial plexus divides it, its concavity re 
posing ou the pleura; and a first or trachea 
portion of its course, differently related on th 
two sides of the body, but thus far alike? 
both, that from it the branches originate, t 

its concavity is to the pleura and its convexit 
almost at right angles to the direction of t 
carotid, looks upward; that it is ed, b 
hind, to the sympathetic and to the last cervic 
transverse process,—in front, to the vagus ¢ 
phrenic nerves and to the jugular and si 
clavian veins,—inwardly to the carotid ar 

The circumstances of difference are ' 
to the fact, that, while on the right side a ea 
mon brachio-cephalic trunk exists—the art 
innominata,—which lies at no great dept 
the sternum, so that its branches di 
their respective destinations from a compa 
tively superficial and single point, behind @ 
sterno-clavicular joint ; on left side, « 

trarily, the carotid and subclavian arise 

rately from the arch, the latter, ata ' 
from the surface, actually beside the 
with the exception of having a thoracic ¢ 
mencement (nearly corresponding to the 
cheal Aalf of the arteria innominata), th 
carotid can scarcely be said to differ i 
tantly from the right, at least in virtue 
own course; it is somewhat deeper, hi 
front of the esophagus from the inel 
of that tube, has the thoracic duct 
at its outer side, and is, as will be 
directly, overlapped by the jugular 
lower part of the neck. The subclaviat 
on the right side passes from its ori 

transversely to the scalene space, COV 
the muscles which have been enw 
crossed at right angles by the 
pneumo-gastric nerves and by the jugular 
the left subclavian, on the other hand, 1 
the groove on the rib after a v ep a 
very oblique course ; it can | 
have any transverse direction, but gra 
by an inclination outwards and forward 
proaches the rib during its ascent, sO” 
traced toward its origin from the trach 


maint’ 


aE 


4 
“Ft 


NECK. 


of the scaleni, it would appear, instead of 
having, as its fellow has, a certain length of 
transverse course, to bend abruptly toward the 
arch of the aorta, becoming deeper and deeper; 
or, in other words, while the right subclavian 
has a considerable extent at its highest level, 
from the sterno-clavicular joint to the scalene 
space, the left has comparatively but a cul- 
minating point, to which it suddenly rises and 
from which it quickly sinks. Thus the nerves, 
which cross the course of the right, are nearly 
parallel to that of the lefi: and the relation of 
the jugular vein is similarly changed, while the 
_ Subelavian vein, having a longer course than 
‘on the right side, obliquely crosses the thoracic 
_ portion of its artery. 
_ The anatomy of the veins requires some sepa- 
_ rate notice: in crossing the scalenus anticus at 
‘itsinsertion, the subclavian vein is, on both sides, 
_ anterior to the artery, from which the tendon di- 
_ Vides it,and somewhat inferior to it; the jugudar 
_ vein in the upper part of the neck descends as 
already mentioned, beside the internal and com- 
“mon carotid arteries, to which it is external, 
“similarly on both sides. The union of these 
veins, however, to form the vene innominate 
differs in the following manner. On the right 
‘side, the jugular vein, inclining from its artery 
Ow, joins the subclavian on the insertion 
the scalenus anticus: the arrangement of 
@ important parts is such that they form 
together an elongated triangle, of which the 
| + id artery is the inner side, the jugular vein 
__ the outer, and the first stage of the subclavian 
_ the base, here crossed ata right angle by the 
: ‘pneumogastric nerve, (which reflects its recur- 
3 


wnt branch upward and inward behind the 
tery,) and more outwardly by the phrenic : 
this point of junction the innominata vein 
rans toward the pericardium on the pulmonic 
‘side of its artery, that is, externally to it and 
0n an inferior plane. On the opposite side the 
\ egelas vein, anticipating its ultimate destina- 
_ tion, obliquely bends toward the right side, 
_ Overlapping the carotid artery, in front of 
_ which it receives the subclavian vein by its 
side: the resulting vena innominata 
Sst runs almost transversely across the arch 
join its fellow at the right extremity of this. 
The vertebral vein opens into the innominata, 
i internally to the confluence which forms 
lat trunk. On the left side it crosses the sub- 
clavian artery: on the right side it is usually, 
though not always, behind it. 
_ The thoracic duct, mounting from the medi- 
astinum, passes behind the arch, emerges be- 
tween the carotid and subclavian arteries in 
the root of the neck, and, curving abruptly 
downwards, outwards, and forwards, crosses the 
latter artery and discharges its contents by a 
valvular opening into the subclavian vein close 
to the angle of its confluence with the jugular. 
_ The surgical relations of this region regard 
the subclavian artery and the operations which 
are practised on it. Of these the most usual 
is its nee on the outside of the scalene 
Fp ere lying upon the upper surface of 
the rib. An onion; eeok ert to the 
middle of the clavicle, through the skin, super- 


OO 


———EE 
———— 


579 
ficial fascia, and platysma, and through the 
strong single layer of cervical Serene 
which is fixed to the bone,—extending, if neces- 
sary, to the origin of the sterno-mastoid and to 
its sheath, with careful avoidance of the ex- 
ternal jugular vein, here bending round the 
outer edge of the muscle,-—opens a space, where- 
in loose cellular tissue alone veils the conti- 
nuation of the pre-vertebral fascia, which is 
prolonging itself from the scaleni around the 
subclavian vessels: a division of this lamina, 
as near as possible to the costal attachment of 
the scalenus anticus, completes the exposure 
of the artery, which is recognised by the finger, 
as it emerges from behind the tendon of that 
muscle, in immediate contact with the mb. 
The steps of the operation thus considered 
seem of no great difficulty, and are, in fact, 
so long as the parts retain their normal bear- 
ings, of extremely easy performance: the artery 
is at an inconsiderable depth; its relations are 
singularly definite and unembarrassed. But 
such is not their practical facility, under cir- 
cumstances which necessitate the operation. 
To tie the subclavian artery for axillary aneu- 
rism may be one of the most difficult opera- 
tions in surgery, involving extreme patience 
and much manual skill in him who undertakes 
it; for the disease, as it extends, not only fills 
the axilla, but encroaches on the neck, thrust- 
ing up the clavicle, and obliterating the in- 
terval between that bone and the omo-hyoid 
muscle. The operation might almost be com- 
pared to one of tying the axillary artery in its 
normal relations from above the clavicle. It 
lies at the bottom of a deep and narrow cavity, 
in which the operator must be guided entirely 
by the sense of touch, and can only apply this 
under the disadvantage of distance. The cir- 
cumstances of such a case are well given by 
the late Mr. Todd of Dublin,* who states 
that, “so much was the relation of parts al- 
tered by the magnitude of the tumour and 
consequent elevation of the clavicle, that the 
omo-hyoid was situated an inch below this 
bone, and it was found necessary to draw it 
up from its concealment, and to cut it across, 
that the subjacent parts might become acces- 
sible.” It must be under the influence of 
such changes that the aneurismal sac, by en- 
croaching on the very seat of the operation, 
becomes liable to injury, and may, as I have 
witnessed, be actually transfixed by the needle. 
The relation of the brachial plexus is com- 
monly such that it lies on a plane posterior to 
the artery, and for the greater part above it; 
occasionally, however, its last root passes in 
front of the vessel, and in the disguised con- 
dition of parts is not readily to be distin- 
guished from it; since the touch fails in its 
ordinary discrimination, where exercised with 
so much difficulty, and it is hardly practicable 
to apply the test of compression to the sup- 
posed arterial trunk, in the view of ascertain- 
ing its relation to the tumour, without un- 
intentionally extending the same pressure to 
the subjacent artery and mis-informing one’s- 


* Dublin Hospital Reports, vol. iii. 
2P2 


580 


self accordingly. It must have been through 
these means of fallacy that I have seen a 
most cautious and experienced operator de- 
ceived: he compressed the supposed ar- 
tery, raised on the aneurism-needle, with 
his finger; the pulsation ceased, the ligature 
was tightened, and the severe ~ occa- 
sioned by this step at once declared the error 
(which was in the course of a few moments 
remedied, and the operation ultimately and 
entirely successful); the convexity of themee- 
dle was doubtlessly resting on the artery, and 
compressed it upon the surface of the rib. 
€ application of a ligature to the sub- 
clavian artery on the tracheal side of the sca- 
Jeni presents, perhaps, fewer merely mecha- 
nical difficulties than that just described, but 
involves a disturbance of more important or- 
gans, and requires perfect acquaintance with 
their anatomy. A separation of the sterno- 
cleido-mastoideus from its inferior attachment, 
and a division of the sterno-hyoid and sterno- 
thyroid muscles and of their sheaths (includ- 
ing that deep layer which lies beneath the 
sterno-thyroideus and immediately covers 
the vessel) will expose the artery.* The ju- 
gular vein is seen crossing it, close to the 
scalenus, at the outer part of the wound, be- 
hind which lies the phrenic nerve; at the inner 
art of the wound the bifurcation of the arteria 
innominata is brought into view, and the sub- 
clavian is seen diverging from the carotid, 
Between this point and the border of the ju- 
gular vein, from half an inch to an inch of 
artery intervenes, about midway on which the 
nervus vagus crosses at a right angle. If 
the nerve require to be drawn aside, this ma- 
neuvre must be executed with the extremest 
delicacy and gentleness;+ and the operator 

* The description in the text is confined to the 
mode of tying the right subclavian artery, on which 
alone, as yet, the operation has been performed. As 
regards the left, the course of the vagus and phrenic 
nerves (which run parallel to the vessel), and of 
the thoracic duct (which almost surrounds it) 
would enormously multiply the risks of the opera- 
tion ; and the increasing depth and oblique descent 
of the artery, as traced from the scalenus inwardly, 
would, it is believed, defeat every endeavour to 
effect its adequate exposure. Should it be desi- 
rable to secure the vessel internally to its passage 
over the rib, the most available method would pro- 
bably be that of tying itin the scalene space. 
This operation was performed in a single instance 
by Dupaytren in 1819 with success. The section of 
the scalenus anticus, if it were carefully executed, 
would be less perilous than on the right side, and 
might, under favourable circumstances, afford a 
sufficient space, between the branches of the arter 
and the aneurismal sac, to admit the safe appli- 
cation of a ligature. A complete division of the 
clavicular origin of the sterno-cleido-mastoideus 
would be required; and it would be necessary to 
obtain a distinct view of the phrenic nerve, before 
cutting the scalenus: the internal mammary artery 
might, as M. Malgaigne remarks, be injured even 
more readily than the nerve, if this incision were 
carelessly extended toward the median line. 

+ It is difficult, in reading the record, or in wit- 
nessing the progress of unsuccessful cases of ope- 
ration at this part of the neck, to avoid believing 
that a neglect of cautious tenderness in managing 
the pneumogastric nerve, has tended to compromise 
the safety of the patient. No surgeon, who con- 
siders its vital importance to the functions and 


NECK. 


should not fail to remember his dangerous 
imity to the pleura. The view of these 
is obscured by considerable venous 
rhage, which is here especially incon 
from the imperative necessity which exists for 
clearly seeing the artery and ascertaining the — 
position of its branches before maki n 
attempt to pass the needle. It is considered 
desirable to apply the ligature on the inner 
side of the vertebral branch, and as near toi e 
as possible: yet, even under the most favou 
able circumstances, the adhesive actions at the © 
seat of ligature must be seriously ¢ d, 
both by the near direct stream of the carotid, 
and by the recurrent tides of the vertebral, 
mammary, and thyroid arteries. The single in- 
tance, in which I have seen this rare operatic 
performed, was by my friend, Mr. Partridge, 
who brought to bear on its execution a Ff = 
fect familiarity with every actual relation, ane 
with every possible contingency; nor could i 
have been confidently undertaken, or \ 
conducted, by one of inferior resources. 
case was in so far favourable, that the tumou 
was small, the position of parts unal the 
arteries regular and free from disease, 
venous hemorrhage not so troublesome as it 
many cases it certainly would be; the part 
were clearly seen, and the artery secured wi 
out the least unnecessary disturbance of 
tiguous parts. Yet, I confess the impressior 
which I derived from this single instance 
Operation, and from frequent consideration ¢ 
the parts in a great variety of subjects, to ha 
been, that ligature of the arteria innomir a 
would in all cases be as easy, and, in mai 
far easier to perform, would (by inve 
organs of less delicacy and oe th 
those interested in the tracheal ligature of | 
subclavian) render hemorrhage a less emb 
rassing obstacle, and would afford a be 
poet of —— adhesion in Aes a 
le steps, neces ‘or exposing one, 
quire ai little modification, +6 Sa 
adapted for the other, that the surgeon m 
even be determined in his choice of 
by considerations developing themselves du 
the operation, by greater or smaller branel 
extent of the subclavian artery, by the ¥ 
bral vein obscuring a large portion of th 
by other circumstances of the kind. 
Although the arteria innominata cann 
anatomical strictness be considered as b 
ing to the neck, yet, in regard both of d 
and of surgical operation, its affinity to 
region is so close as to warrant its 2 
this place. It rises from the convexity 
arch of the aorta, just as that main 
having terminated its ascent, inclines le! 
This point is in young subjects the 
level to which the aorta attains ; but, as € 
hier notices, in old age the extreme part ¢ 
arch, which corresponds to the origin 
left subclavian artery, is higher. In earl, 
too, from incomplete development of the: 
num, the convexity of the arch more D 


‘f 
ny 
y. 


< 


aa 


nutrition of the lung, can avoid viewing an 
naeeerney disturbance or rude traction of © 
eminently perilous. 


NECK. 


approaches the root of the neck than in adult 
growth, and, as also the branches arising from 
it, may more easily be endangered in trache- 
otomy and other operations in the neighbour- 
hood. Its length is somewhat above an inch : 
its direction obliquely upward and outward, 
toward the sterno-clavicular joint, opposite to 
which it divides. In this course it corres- 
ponds, behind, to the trachea,—in front to the 
sternum, from which the remains of the thy- 
mus gland, the origin of the sterno-hyoid and 
sterno-thyroid muscles, and (close to its origin) 
the transverse crossing of the left vena inno- 
minata separate it,—externally, to its accom- 
yanying vein, and, mediately, to the pleura,— 
internally, to the left carotid from which it is 
separated by a triangular interval in which the 
thymus, or its remnant, lies upon the trachea. 
The frequency of its undue extension be- 


_ yond the precise limit assigned to it, and con- 
_ Sequent appearance in the sub-hyoid region of 


the neck, together with the fact of its often 
furnishing a middle inferior thyroid artery, are 


contingencies never to be disregarded in ope- 


rations thereabout. , 

This artery has now been tied for cure of 
anevrism at least six times; unsuccessfully— 
it is true—but with such nearness to success 


_ a8 not to forbid cautious repetition.. The mode 


of procedure adopted by Dr. Mott consisted 


iM a transverse division of the skin, muscles, 


and fascie along the edge of the clavicle and 


_ Sternum,—in raising these, and taking the sub- 


clavian and carotid arteries (which he seems to 
have denuded to some extent) as guides to the 
innominata, in drawing the jugular vein, the 
Vagus, phrenic and recurrent nerves outwards, 
mm pressing the pleura carefully downwards 

the convexity of the needle, while he 
carried its point from below upwards around 
the vessel. —- 

6. The digastric space is bounded below by 
the curve of the digastric muscle, and extends 
above within the angle and horizontal ramus of 
the jaw, so that, if considered as a triangle, it 
may be described as having its base represented 
by the internal oblique (or myloid) ridge of 
the lower jaw, and an imaginary prolongation of 
this to the root of the mastoid process,—its an- 
terior border formed by the ascending belly of 
the digastric muscle,—its posterior by the de- 
scending fibres of the same; and its apex will 
obviously be at the point of their reflexion by 
the hyoid bone. The skin, the superficial fascia 
with the platysma, and the cervical aponeurosis, 
wall it in, and that part of the inferior maxilla 
which lies beneath the oblique line, to the ba- 
sial edge of which the fascia adheres, overhangs 
it; its deep surface is constituted by the mylo- 
hyoid muscle and by the side of the tongue and 
pharynx in front, by the vaginal and styloid 
processes of the temporal bone behind. A 
fibrous slip, reflected outwardly from the sty- 
loid process to the angle of the jaw, and to the 
deep surface of the aponeurosis, distinctly di- 
vides the digastric space into two parts. Of 
these, the posterior is the smaller; its vertical 
extent is to the temporo-maxillary articulation : 
backwards it is bounded by the auditory canal 


581 


and mastoid process; inwardly, by the vaginal 
plate, the styloid process and its quscles. In 
the anterior direction the border of the jaw, to- 
gether with the septum just described, are its 
limits: whence it seems, within the neck of the 
jaw, to prolong itself as an interspace between 
the attachments of the pterygoid muscles. 

Between the unyielding walls of this nar- 
row space, the parotid gland contracts itself 
into a wedge-like form, reaches in the one 
direction to the styloid process and is folded 
round it, in the other is prolonged with the max- 
illary vessels between the insertions of the 
pterygoidei. In its substance the external ca- 
rotid ascends to its terminal subdivision—the 
portio dura curves from the stylo-mastoid fora- 
men, and breaks into the lash of communicating 
branches, known as pes anserinus,—the roots of 
the external jugular vein unite to assume that 
name,—and junctions of the portio dura with the 
superficial temporal nerve, and with the auri- 
cular branch of the cervical plexus, are met 
with. Its remarkable impaction behind the 
jaw is probably designed for affecting its func- 
tion by the mechanical stimulus of the masti- 
catory movements. Its enlargement may in- 
conveniently hinder these motions, and, where 
accompanied by much induration, actually lock 
the jaw. The merely anatomical difficulties of 
extirpating the parotid gland have probably 
been somewhat over-rated ; but cases requiring 
the operation must be of exceeding rareness. 
Absorbent glands lie on many points of its sur- 
face, and in its substance ; their enlargement is 
frequent, and has been mistaken, in several 
instances, for an affection of the parotid itself. 

The arteries met with in this space are all 
branches of the external carotid: the occipital 
and auricular follow its posterior border, the 
latter usually traversing a part of the gland ; 
the temporal artery emerges at the upper, the 
transverse facial at the anterior edge of the pa- 
rotid, while from its deep portion the internal 
maxillary passes forward, within the neck of 
the jaw, toward the zygomatic fossa. 

The anterior division of the digastric space 
considerably exceeds the posterior in size: its 
vertical extent behind is from the curve of the 
digastric up to the outward surface of the buccal 
mucous membrane, where reflected from the 
molar alveoli to the side of the tongue ; but an- 
teriorly it seems to be limited by the lower sur- 
face of the mylo-hyoid muscle, and so to be 
shallower ; though, in reality, this is not the 
case, for the muscle referred to merely forms a 
partial septum, dividing the shallow and super- 
ficial part, just mentioned, from a deeper, sub- 
lingual portion of great importance. The ante- 
rior division of the digastric space may accord- 
ingly be considered as bounded above by the 
mucous membrane of the mouth in its reflexion 
from the oblique line of the jaw to the border 
of the tongue, in an extent reaching from the 
base of the coronoid process to the symphysis ; 
and, internally, by the side of the tongue, 
(presenting the muscular substance of the genio- 
hyoideus, genio-hyoglossus, hyoglossus, and 
stylo-glossus,) and by that of the pharynx. It 
is only in front that the mylo-hyoid muscle, as 


582 


a partial septum, divides a superficial space 
from the general submucous tract; and it is 
necessary to understand this arrangement, in 
order to apprehend the mode in which the sub- 
maxillary g'and approaches the mucous mem- 
brane of the mouth: the gland lies in the su- 
perficial division of the space, and it is round 
the posterior edge of the mylo-hyoid muscle 
that its duct is reflected in proceeding to dis- 
charge itself, which by so entering the sublin- 
gual space it is enabled to do. The anterior 
division of the digastric space contains, super- 
Sicially the gland just mentioned, the facial 
artery and vein with some of their branches, 
the mylo-hyoid twig from the third division of 
the fifth, and many lymphatic ganglia. The 
gland receives a thin capsular investment from 
the deep surface of the fascia, closing the space, 
and this prolongation contracts and condenses 
itself round the posterior extremity and duct, 
accompanying these in their turn round the 
mylo-hyoid, and furnishing the duct with a 
dense fibrous tunic. The artery enters the 
space from below, by passing beneath the pos- 
terior belly of the digastric muscle, very tor- 
tuously winds through the submaxillary gland, 
and bends over the basial edge of the jawa 
little in front of the masseter. It furnishes a 
deep ascending branch (the tonsillary) near the 
angle of the jaw and many glandular twigs; 
but its only considerable branch in this region 
is the sub-mental, which runs toward the me- 
dian line just beneath the jaw, and, supplying 
the mylo-hyoid muscle on which it is applied, 
and the anterior belly of the digastric, termi- 
nates by freely communicating with its fellow. 
The sub-mental branch derives additional im- 
portance from the frequency of an anomalous 
distribution, by which, a the mylo-hyoid 
muscle and entering the sublingual space, it 
partly discharges the functions of the lingual 
artery in supplying the sublingual gland. The 
facial vein lies behind the artery, and quits the 
space below in passing over the digastric and 
stylo-hyoid muscles, which divide it from the 
artery. Its usual or chief termination is in the 
internal jugular; but it frequently contributes 
more or less to form the external or the ante- 
rior jugular vein. The mylo-hyoid nerve runs 
parallel to the origin of the muscle, which gives 
it its name, and supplies it and the anterior 
belly of the digastric. The lymphatic glands 
are numerous and important: they receive the 
absorbent vessels from the face and likewise 
from the mouth and pharynx, are the frequent 
seat of strumous inflammation, readily sympa- 
thize in disordered conditions of the fauces and 
alveoli, and take an active part in propagating 
the malignant influence of cancerous ulcerations 
on the face. These parts are all covered in by 
the aponeurosis,—which fixes itself to the base 
of the jaw,—and by the platysma and superficial 
fascia,—which continue themselves on the face. 
They are readily accessible to the surgeon, but 
seldom subjected to any operation of impor- 
tance. The deep or sublingual portion of the 
digastric space has its roof formed by the mu- 
cous membrane, which, between the tongue and 
alveolar arch, constitutes the floor of the mouth; 


NECK. 


the side of the tongue and the continuous sur- 
face of the pharynx, as already described, com- 
pose its inner wall; and it follows from the — 
previous description that, in part at least, the — 
mylo-hyoid is its floor. The gustatory nerve — 
runs through it beneath the mucous membrane, 
which it supplies: the hypo-glossal, describing” 
a parallel but inferior curve, is distributed in — 
succession to the muscles of the inner wall of 
the space ; the glosso-pharyngeal between these 
two in height, but confined to the root of the 
tongue, bends inwardly beneath the ylo- 
glossus; the lingual artery, emerging from 
under cover of the hyo-glossus, which has 
hidden its tortuous ascent, divides anteriorly 
into two branches; a ranine, which follows the - 
curved border of the tongue to its tip, where 
archingly unites with its fellow; a sublingual ey 
which directing itself a little outward, supplies — 
the third salivary gland: this little body lies on 
the divergent fibres of the genio-glossus, near 
their origin, and close beneath the membrane 0 
the mouth : finally, the duct of the submaxillary” 
gland, traversing the space obliquely, era 
contents, and communicates with the cavity o 
the mouth just beside the frenum. This space 
is the seat of ranula (a tumour formed by ob 
struction of the submaxillary duct), and ¢ 
some salivary concretions ; in both which com 
plaints the distended canal is brought soimme- 
diately beneath the mucous membrane, whic! 
it raises, that other parts are little liable to | 
jury: here, too, it is that the surgeon, wher 
obliged to divide the frenum lingue, mi 
cautiously cut the too tight fold near to th 
symphysis, and vertically, lest, in extendit 
his incision backward, he should wound # 
ranine artery. Sharp instruments penetrat 
downward beside the tongue may wound - 
sublingual artery, and the consequent heme 
rhage, distending the submucous space, ra 
the reflected membrane on each side into swe 
ings of such size, as to suggest imminent pe 
of suffocation.* .. 
7. The small region to oa under» 
name of posterior pharyngeal, zi" 
brief notok; has tbr its roof the benllar rt 
of the occiput and petrous part of the temy 
bone, and presents in this direction the or 
of the jugular, carotid, and anterior cond 
canals: it extends downwards between the 
rynx and vertebre into the anterior tri 
the neck, and is separated from the post 
division of the digastric space, within wh 
lies, by the styloid and vaginal processe 
by the attachment to these of a strong 
fascia, which passes beneath the digastric 
cle. The internal carotid artery, surround 
branches from the superior cervical gan 


* Such an accident I have seen arise frot i 
inadvertent thrust of a tobacco-pipe ; the sw 
was very considerable on both sides, and 
duced alarming distress. Cold (aided, no dot 
by the pressure of the effused blood) succeed 
staying the hemorrhage ; had this not been 
case, it would have been neeessary to xpos 
lingual artery on the cornu of the os h es 
to secure it; or, had its ligature not sufficed, 
wise to tie the adjoining trunk of the facial, 


* 


which the sublingual branch is occasionally deri 


Pe a >t 


NECK. 


ascends here ; and since, from the angle of the 
jaw to the base of the skull, it lies beside the 
pharynx, covered by the lateral parts of that 
cylinder, it is liable to be involved in a punc- 
tured wound from the mouth; and this unfor- 
tunate accident has not unfrequently occurred 
in operations on the tonsil, which organ in its 
swollen state is so closely applied to the in- 
ternal carotid artery, that if it were transfixed 
by a bistoury in an outward direction, the 
vessel could hardly escape. Hence the im- 
portance of care, in relieving tonsillary ab- 
Scesses, to direct the point of the instrument, 
as much as possible, towards the median line, 
and to select for incision that part of the cyst 
which most nearly adjoins the palate. The 
jugular vein emerges behind the artery and 
runs downwardly along its outer side: of the 
three divisions of the eighth nerve, which leave 
the cranium in front of the vein, the glosso- 
pharyngeal is applied to the outer, the vagus 
and spinal accessary to the inner part of its 
circumference. The muscular branch of the 
latter winds from within behind the vein, and 
obliquely descends to the sterno-mastoid : the 


Vagus continues to descend vertically along its 


inner side, but both the glosso-pharyngeal and 
hypo-glossal nerves obliquely cross between it 
and the artery, and subsequently arch over the 
latter in their passage to the tongue. From its 
Telations to the vertebre in this space, the pha- 
Iynx may participate in their diseased condi- 
tions, and give vent to abscesses, dependent on 
caries of the cervical spine. The surgeon may 
sometimes assist his diagnosis of complaints so 
Situated, by introducing his finger into the 
nx.* 

8. Lastly, I proceed to recapitulate, briefly 
and in connexion, the practical relations of the 
sterno-cleido-mastvideus in regard of the spaces 
which have been described. Its clavicular 


_ Origin is in the inferior division of the posterior 


triangle, covers the subclavian artery in the first 


and second portions of its course, and in many 


instances extends this origin so far outwardly 
as to hide the vessel during a considerable part 
of its third stage ; it likewise, of course, covers 
Many parts lying between it and the artery,— 
the jugular and subclavian veins, the vagus and 
phrenic nerves, the scalenus anticus and omo- 

yoid muscles, and the origin and divergence 
of many arterial branches: these fibres obviously 
Tequire division, varying according to circum- 
‘stances, when the subclavian artery is to be 
exposed. The interval between its origins cor- 
Tesponds to the sterno-clavicular joint, and, on 


the right side, to the bifurcation of the arteria 


imnominata : along the cellular line, prolonged 
from this interval, (which answers to the dia- 


eel dividing the two great triangles,) M. Se- 
lot proposes to penetrate, without section of 


* A case has lately occurred to the writer illus- 
trating this fact. It was one of neuralgia; the pain 
was of extreme severity and obstinacy ; it affected 
peorapical region, and was referred to the great 
occipital nerve. An examination through the 
pharynx succeeded in detecting, as its probable 
cause, a firm (apparently bony) tumour, connected 
with the transverse processes, between which that 
nerve emerges. 


583 
muscular fibre, in order to reach the common 
carotid artery. The sternal head of tue muscle, 


directing itself backward, obliquely crosses, in 
the inferior segment of the great anterior trian- 
gle, the sheath of the vessels, from which tbe 
sub-hyoid muscles partly divide it. In order 
to reach the common carotid artery these fibres 
are accordingly cut asunder, except where the 
operator prefers the anatomical finesse of M. Se- 
dillot’s plan. Tracing the muscle in the middle 
of the neck, we find it a most serviceable guide 
in operations on the common carotid, and on 
its primary or secondary branches. A vertical 
incision directed to the point of its intersection 
with the omo-hyoid muscle (nearly opposite the 
cricoid cartilage) enables the surgeon conve- 
niently to draw these muscles aside, and to 
expose, according as the wound is higher or 
lower, the external and internal carotids, or the 
trunk from which they originate, and, in close 
connexion with the anterior layer of theirsheath, 
the descending branch of the hypo-glossal. 
Finally, about and above the level of the hyoid 
bone, the anterior edge of the sterno-mastoid, 
with the posterior belly of the digastric, and 
the cornu of the os hyoides, furnish definite 
marks for discovering the superior thyroid, the 
lingual, the facial or the continued exterral 
carotid artery; since, in the space so bounded, 
the last named vessel vertically ascends, the 
first almost horizontally advances, and the other 
two pass to their destinations with intermediate 
obliquity. 


IV.—ADDITIONAL PRACTICAL OBSERVATIONS. 


It yet remains, in conclusion, briefly to 
review some circumstances in the anatomy of 
the neck, which particularly bear on its dis- 
eases and on the operations undertaken for 
their cure. 1. In endeavouring to form a 
diagnosis of tumours in this region, the surgeon 
will, in the first place, remember their extreme 
liability to deceptive pulsation, and will neg- 
lect no precaution for ascertaining their rela- 
tion to the large arterial trunks. The glands, 
which lie about the common and external ca- 
rotid arteries, in the anterior triangle of the 
neck, and those which are situated in the 
supra-clavicular space, are particularly subject, 
when enlarged, to derive pulsation from the 
vessels to which they are respectively conti- 
guous. The history of the case,—the signs 
afforded by auscultation,—the manner in which 
a non-aneurismal tumour may frequently be 
moved away from the artery that communi- 
cates an impulse to it,—the marked difference 
even to the unpractised hand, between the 
mere jerk of elevation in the one case, and the 
thrilling diastole in the other, are materials for 
distinction, to which it is here enough to allude. 
Nor must it be forgotten, that, from the near- 
ness of the aortic arch to the root of the neck, 
its aneurisms, as they grow upwards and clear 
the strait of the thorax, may simulate the cha- 
racters of a like disease in the carotid or sub- 
clavian artery. Cases constantly occur, (and 
may be found abundantly quoted in systematic 
surgical works,) in which tuinours of this kind, 


584 


rising in the vicinity of the sterno-clavicular 
articulation, have been mistaken for aneurisms 
of the innominata, on the one side, or of the 
carotid or subclavian on the other, according as 
they have, in their growth, deviated right or 
left from the median line. Burns records a 
case, in which an aneurism so originating from 
the aorta, was even falsely attributed to the 
right subclavian : it bulged first on the acromial 
side of the sterno-mastoid muscle, “a point, 
where no one would expecta tumour to present, 
which had worked its way from within the 
chest.”* This is an extreme and rare instance ; 
but not so are the misapprehensions, previously 
alluded to: it is certain, and matter of frequent 
experience, that aneurisms of the arch, where 
they escape from the resisting stricture of the 
sternum and clavicles, project so abruptly, as 
to have the appearance of belonging to the 
artery, over which their fundus is situated. 
They frequently have (as in the case which 
Burns quotes from Sir Astley Cooper) a Flo- 
rence-tlask-like form, the neck of which may 
be narrow, and the fundus high in the neck. 
In several such cases the deception has been 
so complete, as to suggest to the surgeon the 
propriety of tying the common carotid below 
its supposed aneurism:f but no instance is on 
record, as I believe, of the adoption of so 
calamitous a proceeding. It is, indeed, true 
and almost self-evident that an aneurismal 
swelling, formed at the root of the carotid, 
will commonly first be perceived in the small 
interval between the heads of the sterno-mas- 
toid, and, in its further growth, may displace 
these, or cause their absorption:—that one 
connected with the arteria innominata is likely 
to project nearer to the trachea, and on the 
inner side of the sterno-mastoid :—that one 
originating from the subclavian will usually 
rise on the outer side of the same muscle; 
and that the force of the pulse is generally 
diminished in the branches of a trunk affected 
with aneurism :{ yet, while such facts may have 
their weight, as excluding certain tumours from 
the respective categories of subclavian, carotid, 
or innominata aneurism, and as so assisting the 
negative diagnosis of these diseases,—it admits 
of no doubt that they are insufficient to establish 
grounds for positive recognition. The aortic 
aneurism may imitate every circumstance of 
position in the neck, which has been men- 
tioned; and can hardly fail by its abnormal 
pressure to affect the circulation through the 
contiguous artery, and to weaken the pulse of 
its branches. To other criteria, than the mere 
symptom of external prominence, the cautious 
surgeon will look for a safe diagnosis of swell- 
ings in the root of the neck. The minutest 
inquiry into the history of the patient during 
the period, which preceded any outward pro- 
jection of the tumour, and into the actual state 
of his thoracic organs and of their functions 
(with notice of every pain, palpitation, or dys- 
pneea),—an observation of any existing impe- 
diment to the return of blood, as evidenced 
* Op. cit. p. 62 et seq. 
+ Hodgson, Diseases of Arteries, p. 90. 
¢ Vide Cyclopedia of Surgery, vol. i. p. 237. 


NECK. 


by venous congestion,*— and complete and — 
careful stethoscopy, are all requisite to that 
study of the particular case, which alone can — 
justify an opinion. ee 
2. An important subject for mention, in re-— 
gard to the surgical anatomy of the neck, is_ 
the provision for collateral circulation, when 
the main trunks are obliterated. Mr. Burns, — 
in discussing the question of tying the arte 
innominata, speaks of these natural resow 
in the spirit of confidence, which has been 
familiar to English surgery, since the time 
its profound lawgiver, John Hunter: “ y 
entertained no dread of the circulation bei 
supported in the right arm; nay we reducec 
it to a demonstration. On the dead subject, IT 
tied the arteria innominata with two ligatures, 
and cut across the vessel in the space between 
them, without hurting any of the surrounding 
vessels. Afterwards, even coarse injection 
impelled into the aorta, passed a oe the 
anastomosing vessels into the arteries 
right arm, filling them and all the vessels « 
the head completely.” The fluid passed (as 
the blood would, under similar circumstance 
pass in the living subject) from the carotid 6 
the left side to that of the right, through 
mesial inosculations of the thyroid, ling 
facial, temporal, occipital, and (not least 
rebral arteries: from the left subclavian, in lik 
manner, chiefly through the thyroid and vel 
tebral branches; and thus a regurgitant stred 
would flow into the main vessels, up to th 
very site of ligature. Partly through the e 
tinued trunk of the tied vessel, so reinfore 
by its fellow, and partly by secondary comm 
nications (as of the occipital with the ce 
rofunda, of the facial with the internal 
illary, of the pharyngeal and palatine arterie 
the blood is distributed in its legitimate dt 
nation. If the subclavian alone be obliter 
at its commencement, the inferior thyroid 
vertebral (communicating with their felle 
but still more largely with the carotid of 
same side) helped by the muscular bran 
of the occipital, will convey the derived curt 
If the ligature have been applied beyond 
scaleni, the transverse branches of the thyt 
axis, by their free inosculations with the arti¢ 
branches of the axillary, and with its s 


a 


. 
“"y 
pa e 

’ 


ae 


ste 


a 


* An interesting case is given by F 
Pattison, in his Appendix to the edition of — 
(on the Surgical Anatomy of the Head ‘N 
from. which L have already quoted. A perso 
had suffered during six months with ob 
about the lower region of the neck, wi 
attributed to rheumatism, died comatose. — 
found on dissection that there arose from abo 
arteria innominata a large tumour, which pr 
forwards, adhering to the sternum, which its 
sure had rendered carious; and that ** the 1 
verse vein, formed by the union of the | 
vian and jugular veins, presented a very unco! 
appearance. It had more the character of « 
mentous cord than of a distended ves: 
when opened, it was found filled with coagu 
lymph, which completely obliterated its cavity 
being traced downwards towards the right aa 
the vein was seen to terminate at the sternal a 
of the aneurismal tumour, that portion of it w 
crossed the tumour having from pressure 
obliterated.” " 


\ 


: 


NERVOUS SYSTEM. 


_ pular branch, abundantly restore the circula- 
tion. Should the carotid have been tied, its 
mesial communications, already mentioned, es- 
pecially those within the skull, and about the 
thyroid gland,—assisted at those places and 
elsewhere by anastomoses with the subclavian, 
—adequately fulfil their vicarious duty. So 
abundant are these various communications, 
that the ligature of a main trunk, in the dead 
subject, in no degree interferes with the dis- 
tension of its branches by fine injection: if we 
inject water, or any equally fluid material, 
through one carotid artery, it freely returns by 
the other. Under these circumstances, it ex- 
cites our surprise that the cure of aneurism by 
Tigature should be so certain; for the amount 
circulation through the affected vessel can at 
first be little affected, and the arrest and ulti- 
mate cure of the disease must be referred rather 
to the withdrawal of a distensive impulse than 
to any considerable derivation of current. It 
Seems to have been considered, in operating 
for aneurism, that, so long as no large branch 
arose from the vessel closely on the cardiac 
side of the ligature, it mattered not what 
branches might arise on its distal side,—how 
large, or how near. In many instances secon- 
dary hemorrhage, inducing death, has mani- 
festly depended on defective adhesion at the 


_ distal side of the ligature, and for an ob- 


vious reason. ‘The condition of that part of the 
artery has been neglected : it has been thought 
_ unimportant though a large vessel should arise 
just beyond the ligature ; or, if a great length 
of artery have been injudiciously denuded, the 
cardiac portion has had an exclusive preference 
of security given to it, by the ligature being 
drawn as high as possible in that direction. 
If an equal attention were bestowed on both 
sides of the proposed seat of ligature,—if like 
Care were taken, in both directions, to avoid 
the likelihood of disturbance to the adhesive 
eee by side currents,—if, where the artery 
has been much denuded, (instead of a single 
thread being applied at the cardiac extremity 
of that isolated portion, by which plan the 
Succeeding part of the tube,—though sepa- 
rated from its connexions, and likely to ulce- 
Tate or slough,—is yet left open to the stream 
of recurrent blood,) a second ligature were 
placed at the distal limit of the endangered 
part, there would seem no greater reason to 
anticipate the occurrence of secondary hemor- 
rhage than when arteries are tied after an am- 
putation. 
_ 3. Anomalous arrangement of the cervical 
vessels is a contingency which the surgeon 
must bear in mind. Most of these are com- 
prehended in the abnormalities of the arch 
already described. (See Aorta.) The ex- 
istence of a median inferior thyroid artery, de- 
rived from the arch, or from the arteria inno- 
minata;—the irregular passage of the right 
subclavian artery from the left side, behind the 
esophagus, or between that tube and the tra- 
chea ;—an early division of the carotid, even 
to nearly the level of the sternum, or so late a 
one, that the common trunk furnishes many, 
or most, of the branches normally originating 


585 


from the external ;—the absence of .an arteria 
innominata, its branches arising S.parately 
from the arch, or in irregular combination with 
those of the left side; the occasional origin of 
the vertebral from the common carotid,* are 
the deviations which it most behoves the prac- 
titioner to remember. 

4. Certain veins in the neck have an anato- 
mical disposition, rendering them liable, when 
opened in surgical operations, to become chan- 
nels for inspiration of air to the cavities of the 
heart, the fatal tendency of which is well 
known. The internal jugular, innominate, and 
subclavian veins are, as M. Bérard notices, 
“at the root of the neck, so firmly united by 
fascial lamin and cords to the adjacent bones 
and muscles, that they do not collapse on divi- 
sion, but gape:” and it is obvious that this cir- 
cumstance (but for which they would be flat- 
tened, and rendered impervious, by the atmo- 
spheric pressure on their outward surface) must 
expose them remarkably (perhaps alone) toa 
dangerous participation in the inhaustive move- 
ments of breathing. M. Velpeau (who has 
written a paper of excellent critical research on 
the subjectt) recommends the following pre- 
cautions in approaching veins of the nature 
described (veines canalisées): studiously to 
avoid wounding them,—to detach no deeply 
fixed tumour from its adhesions, without 
having previously commanded the vessels at 
its base,—and to maintain no unnecessary ten- 
sion on the fascie, by forced positions of the 
shoulder. 


For the BIBLIOGRAPHY see that of ANATOMY 
(INrRODUCTION), and the references under the 
various articles referred to. One work may be 
Porarein at as belonging to the region, and as 

aving, more than any book of the age, given an 
impetus to the study of anatomy in that most prac- 
tical form, which interests the surgeon by unfolding 
the relations of disease and of operative measures, 
Through the happy combination referred to, the 
mere barren description of regions has become 
surgical anatomy ; and to Dr. Colles of Dublin, and 
Allan Burns of Glasgow, belongs the merit of 
having, first in this country, illustrated that natural 
connexion, which gives to anatomy the interest of 
application, and to practice the security of know- 


ledge. 
(John Simon.) 


NERVOUS SYSTEM.—In proportion as 
our knowledge of the intimate texture of ani- 
mal and vegetable organisms advances, the 
doctrine gains ground that many of the phe- 
nomena, called vital, are to be attributed to 
the special endowments of distinct forms of 
animal or vegetable matter ; distinct as regards 
their anatomical characters as well as their 
chemical composition ; distinct, therefore, as 


* A single instance has occurred to me in the 
dissecting-room, of an arrangement, which I believe 
to be very rare. An innominata (for so its origin 
and course entitled it to be named) divided at the 
sterno-clavicular joint into common carotid and 
vertebral: the right subclavian arose from the de- 
scending part of the arch, and directed itself to the 
scalene space by passing behind the cesophagus. 

+ Médecine Opératoire; and Lettre sur V’Intro- 
duction de l’Air dans les Veines. Paris, 1838, 


586 


regards their physical properties; and, as ap- 
pears not unreasonable to conclude, capable 
of manifesting a distinct series of vital forces. 

If great strength and power of resistance be 
requisite, a particular form of animal matter 
(gelatine) is united with an earthy material to 
constitute bone; for the developement of 
strength, combined with elasticity or flexibility, 
this same kind of animal matter, or a modifi- 
cation of it, is again employed, containing 
none or a very slight proportion of earthy:ma- 
terial, and forming the various kinds of cartilage 
and ligament; but for the play of the active 
powers of life—for the developement of living 
movements— whether in the performance of 
the nutritive functions, in growth and repro- 
duction, or in the display of muscular force 
and activity, two substances, the most complex 
in chemical constitution of any in the body, 
and possessing the greatest atomic weight, are 
made use of to form the structures, on which 
these remarkable phenomena depend, namely, 
muscle and nerve. These structures are com- 
posed respectively of fibrine and albumen ; 
they are organized in analogous forms, and by 
their mutual reactions they exhibit the mar- 
vellous effects which animal power is capable 
of producing. 


GENERAL OBSERVATIONS ON THE DISPOSITION 
AND COMPOSITION OF THE NERVOUS MAT- 
TER, THE NATURE OF NERVOUS ACTIONS, 
AND THE SUBDIVISIONS OF THE NERVOUS 
SYSTEM. 


The nervous matter presents the singular 
peculiarity that it alone, of all the varied forms 
of animal texture, is directly influenced by the 
mental acts of animals. It is that part of the 
organism through the immediate agency of 
which mind operates upon body and body 
upon mind. rough this connexion with the 
psychical principle of the animal, sensation is 
produced, and volition is enabled to exercise 
its influence on muscular organs. And in the 
whole range of the mysterious phenomena, which 
the student of nature meets with, there is no- 
thing so inscrutable as the fact that the work- 
ings of the mind can disturb and impair the 
organization of the nervous matter; or, on the 
other hand, that the disorganization of the ner- 
vous matter is capable of deranging mental 
manifestations. 

The existence of this remarkable and pe- 
culiar kind of organic matter is limited to the 
animal kingdom, and is therefore one of the 
characteristic features of animals as distin- 
guished from plants. It is obviously the pre- 
sence of a psychical agent controlling and di- 
recting certain bodily acts of animals, which 
has called into existence the particular appa- 
ratus which the nervous matter is employed to 
form. 

In the largest proportion of the animal king- 
dom, the nervous matter is so disposed or 
arran as to form a system complete in 
itself, and distinct from, although connected 
with, the other textures and organs. This is 
called the NERVOUS SYSTEM—the deve- 
lopement of which has always a direct relation 


NERVOUS SYSTEM. 


(Nervous Marrer.) 


to the bodily organization and psychical endow- 
ments of the animal. - 
The nervous matter is accumulated 
masses, forming what are denominated cE 
TREs of nervous actions; and it is also ¢ ve. 
loped in the form of fibres, filaments, or mi. 
nute threads, which, when bound tos 1 
constitute the nerves. The latter an 
ternuncial in their office; they establi 
communication between the nervous ce 
tres and the various parts of the body, anc 
vice vers; they conduct the impulses of the 
centres to the periphery, and carry the img 
sions made upon the peripheral nervous & 
fications to the centres. Nor are the ner 
mere passive instruments in the performance ¢ 
their functions ; but produce their proper 
through their susceptibility to undergo moleeu- 
lar change under the influence of appropriat 
stimuli. ; 
The centres are the great sources of 
vous power; they are the laboratories in 
the nervous force is generated. 
appears to be more immediately cc 
with one of them, which, pre-eminent on thi 
account, exerts a certain control or influenc 
over its fellows. ‘ 
In the centres there are two kinds of ne 
vous matter, distinguished by certain anat 
mica! characters and by certain physiologic 
properties and uses. The one is globular 
vesicular in structure, grey in colour—dyna: 
as regards office. The other is fibrous, its fib 
being tubes containing nervous matter; it 
white in colour, and is devoted to act as 
conductor of impulses to and from the 
matter. The white matter is that of which 
nerves are composed, and the two s 
matter do not occur together any where but 
the nervous centres ; in fact, their ‘co-existe 
in any part of the nervous system is sw 
to constitute that part a centre of nervous act 
In the lowest creatures the existence of 
vous matter is as yet problematical. 
supposed by some physiologists that it is 
fused in a molecular form throughout the 
of the animal, and the muscular tissue 
likewise disposed in a similar way, t 
may act upon the other at ony Pa 
this supposition true, it might be furth 
Tecan that, under such circumstances, 
one kind of nervous matter, the dynamic, ¥ 
exist; for as the office of the white ne 
matter is chiefly to propagate or condi 
distant parts the changes which origin: 
the grey matter, the former would not 1 
queed in animals, in which the elem 0 
the grey matter are in contact with thos 
other textures at every part of the body. 
The form in which nervous matter fir 
velopes itself as a distinct tissue is in 
threads or cords, into the composition 
areolar tissue and bloodvessels gene 
The class of animals in which this arranger 
revails has been designated by Mr. 
ematoneura ; and, in many of these at | 
the existence and the disposition of grey mi 
have yet to be ascertained. » a 
The nervous matter of both kinds is a) 


se 


< 


NERVOUS SYSTEM. (Nervous Marrer.) 


stance of extreme softness and delicacy, liable 
to break up under the least pressure; the 
nervous tissue owes much of its physical tena- 
city to the other tissues which are associated 
with it, and to the numerous bloodvessels 
which play among its elements. 

The chemical composition of this matter has 
been an object of investigation with several 
observers, but it is remarkable that few com- 
parative analyses of the two kinds of ner- 
vous matter have been made with a view to 
determine on what the differences hetween 
them depend ; and, indeed, such an analytical 
investigation is as yet a great desideratum. 
The part which has chiefly been selected for 
analysis is the brain, in which doubtless both 
kinds of nervous matter were indiscriminately 
examined. 

Among the earliest investigations of this kind 
were those of Leming; some time afterwards 
Thouret examined the brain; and still later 
Fourcroy. The last writer notices the large 
admixture of water with the cerebral substance, 
and points it out as one of those animal sub- 
Stances in which water exists in the largest pro- 

ttion; from constituting, as it does, three- 

urths or four-fifths, and in many instances 
seven-eighths of its weight. Vauquelin’s ana- 


lysis, made in 1812, gave a considerable insight 


into the true composition of the brain. This 
chemist showed that the cerebral substance is 
an emulsive mixture of albumen, fatty matter, 
and of water, the last holding in solution certain 
Saline and other ingredients common to the 
brain with other parts of the body. By solu- 
tion in boiling alcohol, Vauquelin was enabled 
to obtain the two constituents of the fatty 
substance, namely, the elaine and stearine 
(margarine). Vauquelin also recognised the 
ime of phosphorus in the brain. His ana- 
ysis yielded the following result: — 
PTT aviaiss d' evs dese! siceese. 7.00 
. ¢ stearine ..4 53) 
Cerebral fat.... Velaine,...0.70§ °°°° 9°23 
SPL S FUcle ss oss veces 1:50 
mMazome .......... SO ae eoee 1.12 
Acids, salts, sulphur ..........2.0006 515 
PeMeP oss... 


100.00 


John, who specially analysed the grey ner- 
vous matter, states that it is deficient in fatty 
Matter, and that its albumen is less tenacious 
than that of the white. | And Lassaigne states 
that the grey substance is deficient in white 
fatty matter, but contains a greater proportion 
of red, 3.7 per cent. being the amount con- 
tained in the grey, and 0.9 per cent. in the 
white.* 

Vauquelin remarks that the medulla oblon- 
gata and the medulla spinalis have the same 
composition as the brain, but contain a much 
greater quantity of cerebral fat, with less albu- 
men, Osmazome, and water. 

M. Couerbe’s elaborate analysis does not ap- 
pear to be entitled to much confidence, since the 


* Valentin Repert. 1837, p. 186. 


587 


compounds into which he resolved ‘ cerebral 
matter did not, on analysis, always present 
the same composition. ‘This variation of ele- 
mentary constitution he attributed to physiolo- 
gical differences in individuals. 

The latest and apparently the most complete 
analysis of the brain is that by Fremy, pub- 
lished in the Annales de Chimie for 1841. 
In the main his results agree with those of 
Vauquelin. 

He states that the cerebral mass is formed, 
as had been already shown by Vauquelin, of 
an albuminous matter containing a great quan- 
tity of water, and which is found mixed with 
a peculiar fatty matter; and that these different 
substances exist in the following proportions, 
seven parts of albumen, five parts of fatty 
matter, and eighty parts of water. 

The chemical examination of the albuminous 
matter yields nothing of importance. This sub- 
stance is insoluble in water, in alcohol, and in 
ether. M. Fremy’s principal care has been to 
determine the composition of the fatty matter, 
and this he has endeavoured to do by an ana- 
lysis of the brain in different animals, but prin- 
cipally in man. 

His method of proceeding is, to cut the brain 
into small pieces, and to treat it with successive 
portions of boiling alcohol,leaving them forsome 
days in contact with the spirit. The object of 
this is to remove from it its large quantity of 
water, which interferes with the action of ether 
upon it. The coagulated mass thus obtained 
is submitted to pressure, is divided rapidly in 
a mortar, and is then treated by ether, first cold 
and subsequently hot; the resulting fluids when 
submitted to distillation yield a viscid residue, 
which is called the ethereal product. 

The principles which he extracts from the 
brain by this method, are—1. a white sub- 
stance called cerebric acid; 2. cholesterine ; 
3. a peculiar fatty acid called oleophosphoric ; 
4. traces of elaine, margarine, and fatty acids. 
These principles are not always found in an 
isolated state; for the cerebric acid is often 
combined with soda or phosphate of lime; and 
the oleophosphoric acid is commonly found in 
the state of a salt of soda. 

Cerebric acid, when purified, is white, and is 
in the form of crystalline grains. It dissolves 
without residue in boiling alcohol, is almost 
insoluble in cold ether, more soluble in boiling 
ether, It has the remarkable property of swel- 
ling up, like starch, in boiling water, but ap- 
pears to be insoluble in that liquid. It enters 
into fusion at a high temperature, approaching 
closely that at which it is decomposed, and is 
combustible. It contains no sulphur, but some 
aoe gta The result of its analysis by 

remy is 66.7 per cent. ofcarbon, 10.6 of 
hydrogen, 2.3 of nitrogen, 0.9 of phosphorus, 
19.5 of oxygen. 

Oleophosphoric acid is separated from cere- 
bric acid by its solubility in ether. It is still 
accompanied by elaine and cholesterine, which 
are withdrawn from it by alcohol and ether. 
This acid is of a viscid consistence, insoluble 
in cold alcohol, but dissolving readily in boil- 
ing alcohol; it is insoiuble in ether. Placed 


588 


in contact with soda, potass, and ammonia, it 
immediately gives soapy compounds. It forms 
compounds insoluble in water with other 
bases. M. Fremy has observed a remarkable 
transformation of oleo-phosphoric acid. When 
boiled fora long time in water or alcohol, it 
gradually loses its viscidity and becomes a fluid 
oil, which is pure elaine, while the liquor con- 
tains phosphoric acid. This decomposition be- 
comes very rapid, when the wel is rendered 
slightly acid. Although M. Fremy’s attempts 
to form this acid directly, by uniting elaine and 
phosphoric acid, were unsuccessful, he still 
deems it probable that this acid may consist of 
the elements in question and be analogous to 
the compound of sulphuric acid and elaine, or 
sulph-oleic acid. It contains from 1.9 to 2 per 
cent. of phosphorus in the condition of phos- 


NERVOUS SYSTEM. (Nervous Martrer.) 


ously done, that cholesterine may be ne 
from the brain in considerable quantity. ' 
obtains it by boiling the ethereal pid a 
alcohol rendered strongly alkaline by potass. 
A cerebrate, an oleate, and a es of pot- 
ass are thus obtained, with glycerme and cho- 
lesterine. On cooling, the alcohol deposits the 
cerebrate and phosphate of ste the cho- 
lesterine; and in treating the deposit by cold 
ether, we remove all the are cl 
may be purified by subsequent crystallizations. 
n yrepanstions of the brain, preserved - 

spirits, a substance of crystalline charaet 
which resembles cholesterine, is apt to 
round the piece. 

The quantity of phosphorus varies consi: 
rably in different periods of life, and is great! 
diminished in idiotcy. The following tab 


phorie acid. from some analyses of L’Heritié will ill 
M. Fremy also finds, as Couerbe had previ- this statement. 
Infants. Youth. Adults. ~ Old Men. Idiots. 
OS eee 7.00 10.20 9.40 8.65 8.40 
Cerebral fat .....ccoos 3.45 5.30 6.10 4.32 5.00 
PRODUCE. anda naskes 0.80 1.65 1.80 1.00 0.85 
Osmazome and salts .... 5.96 8.59 10.19 12.18 14.82 
snicnnine aes 82.79 74.26 72.51 73.85 70.93 
100.00 10000 100.00 100.00 100.00 


From these comparative analyses it appears 
that the minimum of phosphorus exists in in- 
fancy, in idiotcy, and in old age; and that the 
maximum of water is found in the infant. This 
latter fact is of practical interest, and affords 
some explanation of the greater tendency to 
liquid effusions in early childhood than in more 
advanced life. 

Nervous actions.—In order to offer a clear 
explanation of the working of the nervous sys- 
tem, it will not be amiss to quote a few ex- 
amples of actions effected through its instru- 
mentality. 

Let me, however, first remark, that as the 
mind is connected more especially with the 
nervous system, so that system becomes the 
channel of its mandates, as well as of impres- 
sions conveyed to it. But there can be no 
doubt that the nervous system can act inde- 
pendently of the mind, and that certain actions 
which need the intervention of nerves and ner- 
vous centres, are accomplished without the 
consciousness of the individual, and some- 
times in spite of his Will. 

It seems, therefore, a correct, as it is cer- 
tainly a convenient arrangement of nervous 
acts, to divide them into those in which the 
mind is concerned, either as an agent or asa 
recipient, ( mental nervous acts, ) and into those 
which result from mere modifications in the 
nervous matter, quite independent of mental 
interference (physical nervous acts ). 

Let me illustrate this division by examples. 
Any ordinary act of the will, the voluntary 
movement of the arm for instance, is effected 
by a mechanism to which the first impulse is 
given by a change in the mind; I will to move 
my arm ; this mental change affects the nerves 
of the arm, which excite certain muscles to act. 


That the nerves are the channels for conveyit 
this influence of the will is proved, beyond : 
doubt, by experiment and disease. If 
continuity with the brain be injured, the 
is necessarily lost, although the will itse 
tinue unimpaired. 4 
We feel through the instrumentality of © 
nerves. In writing, [ am conscious, throug 
the sensibility of my fingers, that I hold a pe 
in my hand. Were that sensibility destroy 
although the power of holding - 
mained, I should lose the consciousness 
presence between my fingers, and they 
cease to grasp it. This sensibility is due t 
communication of the nerves with the bi 
for any solution of continuity destroys it; 
can any part be said to be sensible or to po 
sensibility which does not communicate 
the brain through the nerves. And 
parts differ as regards the degree of ser 
which they enjoy, according to the 
nerves distributed to them, and pe 
according to the manner in which the née 
are connected with them. A touch on 
skin covering the olecranon is scarcely 
whilst the finest point impinging with 
slightest force on the skin of the tip of 
finger is instantly perceived. - 
Sensations difier in kind as well as in ¢ 
The power by which we are made sens 
contact, or by which, under the i 
undue stimulation, we become ous 
pain, is called common sensibility. Dout 
nearly all textures possess this to a cer 
degree. Tendon and cartilage enjoy a 
much less amount of it than skin m 
But we can also appreciate the influence 
light, of sound, of odor, of flavour, and ' 
are enabled to do this by means of particu 


>] 


NERVOUS SYSTEM. 


nerves. This power is that of special sensibility. 
The nerves, which convey these impressions of 
special sensation to the mind, are incapable of 
responding in any other way, even to a me- 
chanical stimulus. When the retina is stimu- 
lated with the point of a needle, the sensation 
of a flash of light is produced: when the audi- 
tory nerve is excited by a mechanical impulse 
upon the tympanum, sound is heard. 

The mechanism (so to speak) of sensations 
of whatever kind is exactly in the reverse di- 
rection to that of voluntary motions. In the 
latter the change begins in the mind and ends 
in the body; in the former the impression is 
made first on the body and is conveyed to the 
mind. In both cases mental change, whether 
active or passive, is necessarily associated with 
the nervous act. 

There are other actions in which the mind is 
concerned, although the wil/ does not take any 
Share inthem. These are, such as may be 
produced under the influence of those sudden, 
momentary, and involuntary mental changes, 
which are called emotions, and which may be 
excited, either by an impression conveyed to 
_ the mind from some external cause, through 

the senses, or by some change in the mind itself, 

arising in the train of its thoughts. Who has 
not feit the thrill which pervades every part of 
the frame, in listening to some harrowing tale 
of woe? or, when the imagination, in its mu- 
Sings, conjures up before the mental vision 
some fearful scene of lamentation and wretched- 
ness? How keenly do the emotions of joy 
and sorrow, anger and pity, cause themselves 
_ to be felt at every point of the system. The 
blush of shame, the pale curling lip of anger, 
_ “theeye in a fine frenzy rolling,” are al! examples 
of the emotions of the mind influencing bodily 
actions. The changes which the countenance 
undergoes in accordance with varying states of 
_ the mind result from the same cause. The will 
May acquire the power of controlling to a great 
extent this influence of emotion upon the ex- 
wession of the features; but to attain this 
aculty in great perfection requires great strength 
of will and frequency of exercise. Few men 
ever acquired such controul over the play of 
the features, and such power of resisting the 
influence of emotion as well as of imitating that 
influence, as Garrick and Talleyrand. 

The power of the emotions over the nervous 
system is shewn not merely in those actions 
which the will may controul, but also in others, 
which, as being in no degree voluntary, and 
therefore in a great measure disconnected from 
the animal functions, have been called organic. 
em none of these does emotion exert more 
influence than upon the circulation. In blush- 
ing, in the deadly paleness of the blood-de- 
serted cheek, in the cold sweat of fear, in the 
depression of the heart from syncope, we find 
unequivocal instances of actions of an involun- 
tary kind, produced by this influence. Many 
of the sensations which are felt in grief, fear, 
anxiety, or in the paroxysm of hysteria, are in 
a great measure due to local changes in the 
capillary circulation caused by the power of 
emotion over it. It would seem that there is 


589 


no part of the nervous system which mental 
emotion may not reach; and no fact\: of more 
general application than this, to the explana- 
tion of the multifarious forms of morbid sen- 
sation. 

Of the physical nervous actions.—When the 
eyelid is raised so as to admit light suddenly to 
the bottom of the eye, the pupil instantly con- 
tracts, nor is the individual conscious of the 
change which is taking place in it, and he is 
equally unable to controul or prevent it. The 
degree of contraction appears to be propor- 
tionate to the intensity of the stimulus. 

When a morsel of food is applied to the 
isthmus faucium, an action of deglutition is 
instantly induced. The palato-pharyngei mus- 
cles and the constrictors of the pharynx are 
immediately brought into play. This action is 
entirely involuntary, and cannot be controlled 
by the power of the will; it may be brought 
on even in the state of coma, when the indi- 
vidual is insensible to any external impression, 
and the fact is one of practical application, 
as shewing how persons in that state may be 
made to swallow by bringing the morsel 
into contact with the mucous membrane 
of the pharynx. Moreover it is an action 
which the will cannot imitate unless there be 
something to be swallowed. If the fauces be 
completely clear of any solid or fluid, this 
action cannot be performed; to call it into play, 
we instinctively bring mucus or saliva to the 
region of the fauces, and that stimulus brings 
about the required action. We have here, 
then, an instance of an action, which may take 
place despite of the will, which the will cannot 
imitate, which may be produced when. con- 
sciousness and will are in abeyance: it is, there- 
fore, an action independent of the mind’s in- 
fluence, and which may fairly be ascribed to a 
cause purely physical. 

The sudden application of cold to the surface 
of the body or to any part of it, more especially 
to the face, causes an immediate and involun- 
tary excitement of the muscles of respiration, 
and may be quoted as an instance of an action 
of similar kind to those mentioned in pre- 
ceding paragraphs. The will may control this 
action to a limited extent, but never entirely. 

A large number of movements in the living 
body, and especially of those which are com- 
monly called organic, might be referred to as 
examples of physical nervous actions, in which 
the stimulus acts independently of the mind. 
These actions may be produced by a physical 
change taking place in the nervous centre and 
propagated directly to the muscular texture of 
the part (the moving power), as in the case of 
convulsive movements produced by irritant dis- 
eases of a nervous centre; but the ordinary 
manner in which they are effected is by the 
application of a stimulus toa surface. Through 
afferent nerves this stimulus affects the nervous 
centre, and produces a change there, which 
excites certain other nerves proceeding from 
that centre to the organ in which the move- 
ment occurs. To take, as an example, the 
act of deglutition above referred to. The 
morsel of food stimulates certain nerves, the 


(Nervous Actions.) 


haryngeal, which are freely distributed 

pon the mucous surface of the pharynx. This 
stimulus causes a change in the medulla ob- 
longata, in which those nerves are implanted, 
and that change is propagated thence by the 
pharyngeal branches of the vagus to the mus- 
cles which contract the pharynx in the act of 
deglutition. 

n such an action the change in the nerves 
by which the muscular contraction is excited 
must take place in a two-fold direction,—first, 
from the circumference to the centre, from the 
point of application of the stimulus to that at 
which the nerves become implanted in the 
centre; and, secondly, from centre to circum- 
ference, from the point at which the stimulus 
falls upon the centre to that where the nervous 
fibres mingle themselves with the muscles of 
the part to be moved. The stimulus, which is 
incident upon the nervous centre, is said to be 
reflected 3 it to the muscular textures, the 
immediate agents of the required movement. 
Hence Dr. Marshall Hall has proposed to dis- 
tinguish a special system of incident and reflex 
nerves, or of excito-motory nerves, the former 
being exrcitor, the latter motor. ‘This distine- 
tion, considered anatomically, is as yet quite 
hypothetical, for we have no unequivocal proof 
that the nerves of sensation and volition, which 
in their ordinary mode of action are ufferent 
and efferent as regards the brain, may not be 
competent by the relation which they must 
necessarily bear to the spinal cord, to perform 
the actions which are thus assigned to a dis- 
tinct system. The determination of this point 
depends more upon the solution of certain pro- 
blems respecting the anatomical constitution 
of the nervous centres, than upon any purely 
physiological experiments. It will be made 
the subject of careful examination at a subse- 
quent part of this article. 

The great peculiarity of this class of nervous 
actions is their independence of the mind. An 
act of the mind forms no necessary part of their 
mechanism. At the same time there are certain 
of them which do not take place without the 
mind being conscious of the change. The act 
of deglutition above referred to, although quite 
independent of the mind, does not generally 
take place without being felt. But the change 
in the pupil, consequent upon the stimulus of 
light acting through reflex nerves upon the iris, 
is not at all perceived by the individual, and is 
therefore in every respect independent of mental 
change. Let it be remembered, then, that 
there are some physical nervous actions which 
the mind is not conscious of, and others of 
which the mind will always, or at least generally, 
take eognizance. 

We may conclude this brief reference to 
nervous actions by the following classification 
of them :— 

Psychical or mental nervous actions :— 

Actions of perception. 

Actions of emotion. 

Actions of volition. 

Physical nervous actions :— 

Actions from a physical change originating in 

the nervous centre; as in disease. 


590 
& 
u 


NERVOUS SYSTEM. (Nervous Actions.) 


Reflex actions— 

a, with consciousness. 

b, without consciousness. 
Anatomical subdivision of the nervous sys- 


tem.—The nervous centres, as they are four 1 
in the Vertebrate series, are distinguished as t 
brain, or encephalon, the spinal cord (medulla 


spinalis ), the ganglions. In the Invertebrata, 
the centres all bear the anatomical characters of 
ganglions, although, doubtless, they present 
some analogy in office to those specially distin- 
guished among Vertebrata. Their arrangemen 
varies considerably according to the differe 
of form of the various invertebrate classes. 

The brain and spinal cord, and the s 
of nerves connected with them, constitute the 
cerebro-spinal portion of the nervous system 
which Bichat distinguished as the nervous 
tem of animal life, a distinction which, as i 
was dependent on his untenable hypothesis of 
the two lives, ought now to be discarded. The 
only subdivision of the nervous system c 
can be conveniently adopted must rest upoi 
the basis of anatomy. There is not a sufficient 
distinctness of function in different portions 
the nervous system to justify the separation 0 
them on physiological grounds. Di 

There are very numerous ganglions connecte 
with the cerebro-spinal system. These are tl 
ganglions on the posterior roots of spinal n 
the ganglion of the fifth pair, 
glosso-pharyngeal, and of the vagus. They 
conveniently distinguished as cerebro 
ganglions. 

A large portion of the nervous system 
made up entirely of ganglions, with their e 
necting cords and nerves, which ramify in 
plexiform manner among various internal vis 
and upon the coats of bloodvessels. In 1 
vertebrated animals, where it is highlyd yp 
it is disposed as a chain of ganglia on each | 
of the spine, and at the base of the skull, r 
the foramina, through which the spinal 
encephalic nerves pass out; and at all 
situations it forms a very intimate conn 
with the nerves of the brain and spinal coi 

This portion of the nervous system exh 
many peculiarities referable to its compe 
its mode of arrangement, and its conneé 
with the organs among which its nerves ran 
which, at least, entitle it to be considered ¢ 
from the cerebro-spinal system; and 
so far as to affirm its entire independen 
that system, and to assign to it a peculiar a 
different from that of the nerves connectec 
the brain and spinal cord. Bichat calls 
nervous system of organic life. Previ 
time it was known as the great 
(nervus intercostalis), the great sympe 
nerve (nervus sympathicus magnus ), and 
it is very commonly described under the 
name. The term visceral nerve has also 
proposed for it. It has also been distingui 
as the ganglionic system. It is diffieult to fit 
an unexceptionable name for it which does 
involve the adoption of some theory resf 
its function. On the whole, the terms sympat! 
nerve and ganglionic system are those ¥ 
appear liable to fewest objections, although 


oc 


1 


- 


‘and tissues and the nervous centres. 


NERVOUS SYSTEM. 


no means free from them, and they will be 
employed in the course of this article. 

uch are the only subdivisions of the nervous 
system which anatomy appears to warrant. 
Others have been proposed; but as they are 
founded upon physiological opinions which are 
as yet hypothetical, it is unnecessary to discuss 
them at present. 

Having thus given a brief and general account 
of the nervous system and of nervous matter, 
we proceed to consider the anatomy and phy- 
siology of this system under the following 
divisions:—I. THE GENERAL ANATOMY OF 
NERVES. IJ. THE COMPARATIVE ANATOMY 
OF THE NERVOUS SYSTEM OR ITS DISPOSI- 
TION THROUGHOUT THE ANIMAL KINGDOM. 
Hil. Tue anaroMy OF THE NERVOUS CEN- 
TRES, THE GANGLIA, BRAIN, AND SPINAL 
corp. IV. aND LaSTLY, THE OFFICE OF 


‘THE NERVOUS SYSTEM AND THE FUNCTIONS 


OF ITS VARIOUS PARTS. 


NERVE.—(vevgor, nervus; Germ. nerve ; 


Fr. nerf.) The nerves perform the internuncial 


office in the nervous system by maintaining 
communications between the various organs 
They are 
bundles of threads of various size, surrounded 
by sheaths of membrane, with more or less of 
areolar tissue interposed. 

The nerves of the cerebro-spinal system and 


of the great sympathetic exhibit such different 


characters as regards their anatomy, that they 


may be examined separately. 


bro-spinal nerves—In examining a cere- 
bro-spinal nerve, we find it invested by a sheath 
of membrane, which has adherent to its inner 
surface thin layers of areolar tissue which pass, 
like so many partitions, between the threads or 
fibres of which the nerve is composed. This 
sheath is commonly called the neurilemma ; it 


_ is analogous to the sheath which surrounds mus- 


cles. Its office is chiefly mechanical, namely, 


that of binding the constituent fibrillz and fas- 


cicles of the nerve together, so as to protect 
them and to support the delicate plexus of 
capillary bloodvessels from which they derive 
their nutriment. 

The neurilemma is composed of fibres of the 
white fibrous kind. It exhibits to the naked 
eye the appearance of a fibrous membrane, 
white and almost silvery; and its microscopic 
characters are those of the white fibrous ele- 
ment, although not presenting much appearance 
of wavy fibres. The fibres are, for the most 
part, parallel to the axis of the nerve; but 

re are some which cross the nerve at right 
angles, or appear to pass spirally round it. The 
septa between the secondary bundles of the 
nerves seem to consist of a less perfect fibrous 
tissue, containing the remains of numerous 
cytoblasts. A yellow fibrous tissue of the 
finest kind exists here in very small quantity. 

The bloodvessels are distributed upon the 
external investing sheath and upon the septa. 
In some of the large nerves, the sciatic for 
example, these may be often seen minutely 
injected with blood. They are disposed some- 
what similarly to those of muscles, running 


(NervE.) 591 


peeiel to the fibres and fascicles of the nerve. 
he capillaries are among the small st in the 
body: they form oblong meshes of considerable 
length, completed at long intervals by vessels 
which cross the fibres of the nerve more or less 
in the transverse direction. Henle assigns to 
them, when empty, a diameter not exceeding 
sdoth of an inch. These bloodvessels are 
generally derived from neighbouring arterial 
branches; sometimes a special vessel accom- 
panies a nervous trunk, and even perforates it, 
passing along its central axis, as is well known 
to descriptive anatomists in the sciatic and the 
optic nerves. 

After the external part of the neurilemma 
has been dissected off, the nerve may be torn by 
needles and divided into secondary bundles and 
fibres. The ultimate fibre can then be readily 
distinguished by the aid of the microscope, from 
its being incapable of further subdivision by 
mechanical means ; and an accurate knowledge 
of its structure is of the utmost importance to 
the formation of correct opinions respecting the 
actions of the nervous system. 

The ultimate (or, as it is also called, the pri- 
mitive) nervous fibre, is a tube composed of a 
fine transparent homogeneous membrane, in a 
great degree resembling the sarcolemma of 
muscle. It is elastic, like that membrane, per- 
fectly homogeneous, and, according to Schwann, 
in young nerves has the nuclei of cells connected 
with it. Itmay be called the tubular membrane 
of nerve (a, fig. 329). The contents of this tube 
consist in a soft, semifluid, whitish, pulpy sub- 
stance, which is readily pressed out of its cut 
extremity. In the nerve that is quite fresh, 
having been taken from an animal just dead, 
this pulpy matter is quite transparent and appa- 
rently homogeneous. The tube membrane pre- 
sents the appearance of a delicate line, resem- 


Fig. 329. 


Nerve tubes altered by re-agents. 


a, tube altered by water. The light external line 
is the tubular membrane; the dark inner double- 
edged one, broken here and there, is the white 
substance of Schwann, 6, shows the change pro- 
duced by the action of ether on the nerve-tube of 
the common eel ; several oil globules have coalesced 
in the interior, and others have accumulated around 
the exterior of the tube.’ 


592 


bling, when perfectly fresh and unaltered by 
re-agents, the margin of an oil globule. When 
the nerve-tube has been treated with water, or 
has been allowed to remain a little time ona 
piece of glass, we observe within the tubular 
membrane a double-edged layer of a whitish 
material of different refracting power from either 
that which occupies the centre of the nerve- 
tube or the tubular membrane itself. The later 
after death the nerve is examined, the more dis- 
tinct does this inner layer become. The addi- 
tion of water, alcohol, and other re-agents always 
renders it more evident, and seems to destroy 
the apparent homogeneousness of the pulpy 
contents of the nerve tube. This layer within 
the tubular membrane is that which, according 
to Schwann, gives to the nerve-tubes their white 
colour; it is therefore called by him the white 
substance. Within this and occupying the 
centre of the tube is a transparent, somewhat 
flattened, band, which is extremely delicate, and 
in which it seems impossible to recognize any 
more definite structure. 

Thus Remak and others describe three dis- 
tinct parts in the nerve fibre :—1, the outer in- 
vesting membrane, tubular membrane; 2, an 
inner layer of membrane (the white substance 
of Schwann) lying immediately within the first; 
3, a central substance of nervous matter, called 
flattened band by Remak, and supposed by 
him to consist of several filaments, or the aris- 
cylinder of Rosenthal and Purkinje. 

It is evident that the contained matter of the 
nerve-tube is extremely soft: it yields under very 
slight pressure, and may be readily made to pass 
from one part of the tube to another. When 
pressed out of the nerve tube, it is apt to assume 
the appearance and form of globules varying in 
shape and size, which are easily distinguished 
from the true nervous globules by the absence 
of nucleus. Firm pressure will also completely 
empty the tubular membrane, and thus afford 
us a good opportunity of examining its struc- 
ture, which has always appeared to present the 
same homogeneousness as the sarcolemma of 
muscles to which we have compared it. Some 
observers, however, admit a complexity of struc- 
ture in this tubular membrane; an ap nce 
of longitudinal fibres has been noti by Va- 
lentin and Rosenthal, and the former describes 
a fibrous arrangement, as of oblique fibres wind- 
ing in opposite directions, surrounding the tube.* 

The addition of water causes the contents 
of the tubular membrane to separate from the 
inner surface of the tube, owing to a shrivelling 
or coagulation which it excites in the nervous 
pulp. Alcohol produces a similar effect, but 
occasions a more perfect coagulation of the soft 
nervous matter; and it is particularly worthy of 
observation, that the complication of structure 
remarked by various observers and above de- 
scribed, in the tubular membrane as well as in 
its contents, is never seen in the perfectly fresh 
nerve, but is always rendered visible by keepi 
or by the influence of various re-agents. And 


* The spiral arrangement of fibres described by 
Barry is attributed by him to the membranous layer 
which forms within the tubular membrane, the white 


substance of Schwaun, 


NERVOUS SYSTEM. (Nenve.) 


this fact may well excite a doubt as to the re. 
ality of the complex structure of the nervy 
tube, as described in the preceding paragraph 

In a word, the real structure of the primit 
nerve fibre appears to be a tube composed 
homogeneous membrane, containing a delice 
soft, pulpy, semi-fluid and nedu 
or nervous substance, which is readily disturb 
by manipulation, and altered by the addition | 
the simplest substances—even water. The tu 
when quite fresh are perfectly cylindrical ; br 
pressure or separation alters them in shape lik 
wise, probably by disturbing the position 
the nervous oregon pushing more than is ni 
into one part, and consequently dimini 
the bulk of the contents of anode part 
the latter will consequently collapse, and 
former become enlarged, distended, and eve 
varicose. ( Fig. 330.) The margins of nerve 
tubes that have been separated, for this reaso 
constantly appear wavy, and at other tim 
distinct swellings or enlargements form in th 
course of the fibre, separated by constricte 
portions. These swellings sometimes occu 
one side of the tube only: in shape they: 
globular or ovoidal, and more frequently involv 
the whole tube ; they exist at irregular intery: 


Fig. 330. 


= 


A, Nerve tubes becoming varicose at thi 
trance into the spinal cord. Ata, b, ¢ the 
diminution of the thickness of the wall is 
B, a single nerve tube, cylindrical at one 
varicose in the rest, (From Valentin.) 


NERVOUS SYSTEM. (Nenve.) 


from each other, and are extremely variable in 
shape and size. Two conditions appear to 
_ favour the production of this varicose state of 
__ the nerve-tube,—namely, a feeble power of re- 
sistance in the tubular membrane, and, se- 
condly, perhaps, a semi-fluid state of the con- 
tained nervous pulp; and hence we find that 
some nerve-tubes are much more prone to 
become varicose than others. In the nerves 
_ of pure sense the tubes are very delicate in 
_ Structure and very apt to exhibit this change of 
form, and in the brain and spinal cord they 
exhibit the same tendency. Ehrenberg sup- 
posed formerly that these varicosities were 
natural and existed during life, and that they 
afforded a valuable morphological character of 
the nerves of pure sense and the cerebro-spinal 
centres. But many circumstances favour the 
Opinion that the varicosities are accidental; 
thus, the very irregularities above noticed in 
their shape, size, form, and number on a single 
tube are not likely to occur in the natural 
State. Moreover, in a piece of the brain or 
Spinal cord not much pressed nor torn, the 
ones may be distinctly seen: even in 
the manipulated specimens the varicose tubes 
form only a small portion of the whole. And 
in those nerves whose fibres are not prone 
to become varicose, such as muscular nerves, 
may be made so by firm pressure and 
fiolence in manipulation. In the nerve-tubes 
‘of young animals, in whom the tissues are more 
tender and contain more abundant water, these 
' ges are also very apt to take place. 
_ A cerebro-spinal nerve, then, consists of a 
_ Congeries of fascicles or bundles of the nerve- 
‘fibres or nerve-tubes (and we shall use these 
‘terms synonymously) above described, enve- 
| and bound together by fibrous mem- 
brane, the nerve-sheath. The nerve-tubes lie 
Side by side, parallel, and sometimes have 
@ wavy course within the general sheath (fig. 
331). The relation of the nerve-tubes to each 


‘ 


| 


Fig. 331. 


Diagram to illustrate the wavy course of the nerve 
tubes within the neurilemma. 


other is simply that of juxta-position. All 
observers, from Fontana down to those of 
the present day, agree in denying the ex- 
istence of any inosculation or anastomosis 
between the fibres in vertebrate animals; 
and it seems almost certain that this complete 
isolation of the nerve-tubes is not limited 
to those of the nerves, properly so called, but 
may be observed in the nervous centres also. 
When a piece of nerve is examined on a dark 
ground, as an opaque object, with an object 
glass of a quarter of an inch focus, the disposi- 
tion and relation of its component tubules are 
more beautifully seen than by any other mode 
of examination. The primitive fibres present 
the appearance of a series of transparent tubes, 
containing an exquisitely delicate, soft, pearly- 
white material. 
VOL. III. 


593 
In point of size the nerve tubey present 
considerable variety even in the same trunk, 


while they maintain an identity of structure. 
The smallest tubes have very delicate walls, 
and are more easily rendered varicose than the 
larger ones. The following table gives a state- 
ment of the results of the admeasurement of 
the cerebro-spinal tubules in Man and other 
Vertebrata. 

Man, and other Mammalia, from yJ35 to g455 

of an inch. 

Birds, sfyp tO sqyp Of an inch. 

Reptiles, Frog, 355 tO sig5 Of an inch. 

Fish, Eel, y4j3 of an inch. 

Codfish, optic nerve, g$, of an inch. 

It has already been remarked that no such 
thing as subdivision or branching of the pri- 
mitive tubules takes place in the cerebro-spinal 
nerves of the vertebrate series. Whatever be 
the connection which each primitive tubule 
forms with the nervous centre, or with the 
textures to which it is distributed at its pe- 
riphery, it passes from one point to the other 
without any change, save perhaps in size, and 
without any communication with neighbour- 
ing tubules, beyond simple juxta-position, or 
investment by a common sheath. This fact 
was recognized by Fontana, whose description 
of the structure of nerve, although drawn up 
from observations made at a great disadvan- 
tage through the imperfection of his instru- 
ments, corresponds in all essential particulars 
with modern observations.* And as there is 
the same absence of subdivision in the con- 
tinuations of these nerve-tubes in the nervous 
centres, we may fairly infer that each point on 
the periphery which is in contact with a nerve- 
tube, is, as it were, represented by that same 
nerve-tube in the centre. 

The structure of the cerebro-spinal nerve 
admits of an obvious comparison with that 
of the striped muscle. Both are composed 
of bundles of fibres, united by a sheath, 
which also passes between the bundles, 
and is a nidus for the support of the nu- 
trient vessels. Both admit of being subdi- 
vided into primitive fibres, which are very 
analogous in structure. The primitive fibre of 
muscle (primitive fasciculus of some authors) 
consists of the true muscular tissue, or sarcous 
elements contained in a transparent sheath of 
homogeneous elastic membrane called sarco- 
lemma by Mr. Bowman. The peculiar mor- 
phological characters of the primitive fibre 
depend upon the arrangement of the sarcous 
particles within this transparent tube; and to 
this arrangement is due any further subdivision 
of which the primitive muscular fibre may be 
susceptible. So is it with the primitive nerve- 
fibre: its tubular membrane is strictly analo- 
gous in structure and other characters with the 
sarcolemma. It contains the elements of the 
true nervous tissue or neurine, and this ad- 
mits of a certain subdivision which may be ren- 
dered more apparent under the influence of re- 
agents, and which is variously interpreted by 
different observers, and has been compared to 


* Fontana sur le venin de la vipere. 
2a 


594 


the separation which takes place in the fat cells 
between the solid and the fluid elements of fat. 
As the combination of the primitive muscular 
fibres, ina common sheath, forms the muscle, 
so the union of the primitive nervous fibres, in 
a similar way, forms the nerve. And as the 
primitive fibre of muscle passes undivided from 
one point of the muscle to another, so the nerve 
tube exhibits no subdivision in its course. 

Branching of nerves.—The main trunk of a 
nerve breaks up into its component bundles, as 
it passes from centre to periphery, yielding up 
branches to the various parts it is destined to 
connect with the nervous centre. These branches 
generally come off at acute angles, and soon 
plunge into the muscles and other parts to which 
they tend, dividing and subdividing as they pro- 
ceed. Such is the most common mode of sub- 
division, but there are many exceptions: some- 
times a branch separates from the parent trunk at 
an acute angle, and then turns to run in an op- 
posite direction, forming an arch, from the con- 
vexity of which several branches are given off. 
Such a nerve is said to be recurrent; the in- 
ferior laryngeal nerve takes this course. The 
anastomotic arches between the emerging spinal 
nerves, round the vertebral laminz, are also 
exceptions to the separation at acute angles. 

Before a branch separates, it often happens 
that the parent trunk presents an enlargement 
for some distance above the point of visible 
separation. This is due to the fact that the fibres 
which compose the future branch begin to 
loosen their connection with the trunk for some 
way before they actually leave it; and the con- 
necting areolar membrane becomes conse- 

uently looser.and more abundant. Hence 
the trunk of the nerve appears enlarged, with- 
out any increase in the number of its nervous 
elements. This may be well seen in the auri- 
cular nerve of the neck, as it winds upwards 
over the sterno-mastoid muscle. 

Anastomosis of nerves—In their branchings 
nerves subdivide, not only to pass immediately 
to their muscles or other distant parts, but 
also to connect themselves by certain of their 
filaments with other nerves, and to follow 
the course of the latter, whether onward or re- 
trograde, peripherad or centrad, instead of ad- 
hering completely to that of the primary trunk. 
By these means, nervous filaments connected 
with very different parts of the brain and spinal 
cord become bound together in the same fasci- 
culus, and a nerve is formed compounded of 
tubes possessing very opposite functions. The 
anastomosis of nerves thus formed differs very 
obviously from the more correctly named anas- 
tomosis of bloodvessels, for in the latter case the 
canals of the anastomosing vessels are made to 
communicate and their contents are mingled; 
but in the former the nerve filaments are simply 
placed in oe apni There is no fusion 
of the one into the other, no admixture of the 
pulpy contents of the nerve-tubes, which con- 
tinue their course as perfectly insulated as if 
we were placed singly and had no connexion 
with others. 

The simplest kind of anastomosis is that 
which occurs in the formation of almost every 


NERVOUS SYSTEM. (Nerve.) 


down the limb: those filaments which 


spinal nerve. The anterior and the posterior — 
roots of these nerves, emerging from different 
of the spinal cord, and possessing, as 

is now proved, very different functions, are — 
united after passing through the dura mater 
and bound together as one nerve; the com 
ponent tubules being so completely intermixec 
that the future ramifications of the nerve ma 
enjoy the double function derived from the 
diverse endowment of the originally compo- 
nent tubules. al 
And even in a nervous trunk thus forme 
there occurs a remarkable interchange of place 
between the component filaments, which are 
thereby made to decussate each other within the 
trunk of the nerve (fig. 332). Bichat s: 
amused myself one day in attentively following 
all the filaments of the sciatic nerve some distance 


Diagram to show the decussation of the primitive j , 
within the trunk of a nerve. (After Valentin, ) 
the exterior of the trunk above, I fou 
greatest part, forming its centre 
Kronenberg states that in some nerves the 
communications are so frequent that one cann 
follow a single fascicle for any distance; wh 
in other nerves, as the external cutaneous ner 
of the arm, he found — bundles wh 
passed through a distance of upwards ¢ 
inches without uniting with eighboast z OF 
This is an anatomical fact of no mean imp 
tance, as applicable to the explanation of mat 
apparently anomalous symptoms in neu 
and other nervous affections. 4 
A second form of anastomosis may be 
explained by referring to that with which 
who have made the superficial dissection © 
neck must be familiar,—namely, the ang 
mosis of the descending branch of th 
with the cervical plexus. Certain fibres, ¥ 
pass from the medulla oblongata as part 
ninth nerve, leave that nerve as it cros 
carotid artery, pass down in front of the‘ 
and apply themselves to a descending brat 
the cervical plexus, forming in front of thi 
tid artery and jugular vein an arch with the 
cavity directed upwards, several nerves p 
from the convexity to neighbouring mu 
A little careful dissection shows that se 
the nervous filaments which are given 0 
the convexity are derived from the ninth 
and others from the descending branch of 
cervical plexus ; whilst others seem to fo1 
complete arch and to be equally connected w 
both nerves. If we trace them from the) 
nerve, we find them passing upwards at 
wards into the descending branch of t 


* Anat. Générale, t. i. p. 128, ed. Il a 1. 


x 


mi 
¥ 


NERVOUS SYSTEM. (Nerve.) 


lexus, and so returning to the spinal cord. 

he nervous arch which is thus formed must 
evidently establish a communication between 
the cervical region of the spinal cord and that 
portion of the medulla oblongata whence the 
ninth nerve appears to arise. 

We find in connexion with the optic nerve a 
remarkable example of this kind of anastomosis, 
which, as in the instance just mentioned, serves 
more to connect different portions of the ner- 
vous centre than to associate particular nerves. 

In the optic tracts of man three series of fibres 
may be distinguished, one which passes to the 
retina of the same side, another series which 
goes to the retina of the opposite side, decus- 
Sating with the corresponding fibres from that 
side, and a third which passes from right to left, 
being apparently identified with or fused into 
one another at what is called the commissure, 
_and forming a series of nervous arches, which 
Serve to connect the opposite sides of the brain. 
These arches are convex towards the eyes and 
concave towards the brain. In the mole, in 
which I have failed to discover an optic nerve, 
this commissural band exists alone, the other 
two series of fibres being absent. Mr. Mayo 
has given a representation of these three sets of 
fibres belonging to the human chiasma in his 
| admirable plates of the brain. 
___ Volkmann gives an account of several anas- 
__ tomoses of this kind which he distinguishes by. 
___ the expression “verschmelzungen,” to which that 
_ of “ fusion” appears sufficiently to correspond. 
The fibres of one nerve appear as if they had been 
fased into those of an adjacent one, and thus 
_ feturn to some part of the cerebro-spinal centre 
different from that at which it had emerged. 
_ The instances cited by Volkmann are as follows : 
4. In the calf he has found an anastomosis 
nm the fourth pair of nerves and the first 
branch of the fifth pair, forming an arch from 
_the convexity of which several branches passed 
off in a peripheral direction. By far the greater 
_ part of these appeared, on microscopic exami- 
Nation, to receive their fibres from the fourth ; 
- while those fibres of the fifth which contributed 
to the formation of the nervous arch, passed 
centripetally to the brain, bound up in the 
Sheath of the fourth nerve. 2. A similar ner- 
vous arch is found very generally among 
Mmammifera between the second or third cer- 
vical nerve and the accessory. Certain fibres, 
when traced from the former nerve, appeared 
to to the centre in the sheath of the latter. 
_ Thisanastomosis Volkmann found in the human 
Subject, and in horses, dogs, calves, and cats.* 
Another example of this kind of anastomosis 
has been described by Gerber, but I am not 
aware whether his statements have been con- 
firmed by other observers. This consists of 
one or more simple loops contained in one 
and the same neurilemma. Certain primitive 
fibres emerge from and return to the nervous 
centre, forming a loop, with convexity directed 
s the periphery, without connecting 
| themselves with any peripheral texture or going 
‘ond the nerve-sheath. Gerber has desig- 


* Miiller’s Archiv. 


595 


nated these loops nervi nervorum, frt_n a sup- 
posed rather fanciful analogy to the vasa vasorum. 

Plexuses.—The plexuses are nervous anasto- 
moses of the most complicated and extensive 
kind. Those which are connected with the 
spinal nerves are found in the neck, the 
axilla, the loins, and the sacral region, and are 
well described by anatomists. There are also 
plexuses connected with the fifth nerve, the 
portio dura of the seventh, the glosso-pharyn- 
geal, and the par vagum. Each plexus is 
formed by the breaking up of a certain number 
of nervous trunks, the subdivisions of which 
unite together to form secondary nerves, and these 
again, by further interchange of fibres, give rise 
to nerves which emerge from the plexus, and 
consequently in their construction may derive 
their fibres from several of the trunks that 
enter the plexus. 

The object of the various kinds of anasto- 
mosis of nerves above enumerated appears to 
be to associate together nervous fibres con- 
nected with different parts of the brain or 
spinal cord. Thus nerve-tubes of different pro- 
perties or endowments become united together 
in one sheath, forming compound nerves; and 
certain sets of muscles, instead of receiving 
their nerves from a very limited portion of the 
cerebro-spinal centre, are supplied from a con- 
siderable extent of that centre, and each muscle 
may probably receive nerves which arise in dif- 
ferent and distant parts of the spinal cord or 
brain, an arrangement whereby remote parts of 
those centres may be brought into connection 
with neighbouring muscles or other parts, or 
even with a single muscle. 

Origin of nerves—The connexion of a nerve 
with the nervous centre is called by descriptive 
anatomists its origin. The determination of 
the exact nature of this connexion is of the 
last importance to the adoption of a correct 
theory of nervous action. Yet but little is 
known upon this subject. The fibres of the 
nerves are continuous with some of those 
fibres of the centre, in passing into which they 
experience considerable diminution of size 
and perhaps some change of texture, (see 
Jig. 330, A,) as evinced by their much greater 
tendency to become varicose under mecha- 
nical means than we generally find in the 
nerves themselves. Thus far we may con- 
fidently assert, that every nerve at its central 
extremity forms a connexion with grey matter. 
This fact, proved by anatomy to be constant 
and universal, may be considered as a law of 
the morphology of nerve which has the most 
important bearing upon its physiological action. 
What is the precise nature of the connexion 
between the two kinds of nervous matter in 
the centres has not yet been determined. We 
can see the white nerve-tubes passing between 
the elements of the grey matter and the vascular 
plexus, in the meshes of which they are depo- 
sited; but whether they form any continuity of 
substance with those elements, or simply come 
into contact with them,has yet to be demonstrated. 
We shall recur to this interesting and important 
question in the article Nervous Centres. 

Termination of nerves.—Under this term 

292 


596 


we describe the peripheral connexion of nerves 
with the various tissues and organs, and it is 
much to be regretted that our knowledge in 
reference to that connexion is scarcely more 
complete or accurate than that of their origin. 
The only instance in which we can speak 
pretty confidently respecting the tk eons 
connection of nerves, is with regard to mus- 
cles. In the striped muscle, nerves appear to 
form loops, the convexities of which are di- 
rected across the fibres of the muscles. Each 
nerve-fibre passes at first parallel to the direc- 
tion of the muscular fibres, and then crosses 
them in an arched form to pass back into the 
bundle from which it had emerged, or to be 
mingled with the fibres of some neighbouring 
bundle, passing back in it to the centre, pro- 
bably to some part of it different from the 
place of origin of the nerve. As far as present 
means of observation enable us to judge, there 
does not appear to be any other connexion be- 
tween the nerve-tubes and the muscular fibres 
beyond the simple contact of the tubular mem- 
brane of the former with the sarcolemma of the 
latter. We have no evidence of any mingling 
of the true nerve-substance with the sarcous 
elements, and, therefore, we are forced to con- 
clude that whatever be the nature of the in- 
fluence which nerve exerts upon muscle to pro- 
voke it to contraction, that influence is exer- 
cised through the two layers of homogeneous 
membrane which form the investments of the 
nervous and sarcous elements respectively. 

The best mode of observing the disposition 
of nerve in muscle is to examine under the 
microscope very thin and transparent muscles 
of some small animals. The abdominal mus- 
cles of the frog first afforded to Hales, and long 
after him to Prevost and Dumas, this opportu- 
nity; the muscles of the eyeball in small birds 
were used by Valentin; Burdach examined the 
muscles of the frog’s tongue; I have found the 
intercostal muscles of the mouse very suitable 
for the purpose. 

Peripheral expansion of nerves on sentient 
surfaces—With regard to the disposition of 
nerves on sentient surfaces (the skin, for ex- 
ample) the most probable view appears to be 
that they are disposed in a plexiform manner, 
The nervous trunks pass toward the surface 
dividing and subdividing, the ramifications pass- 
ing backwards to the centre in conjunction with 
neighbouring bundles; so that, whilst a very 
intricate plexus is formed, the looped arrange- 
ment, similar to that described in muscle, pre- 
vails, the convexities of the loops being di- 
rected towards the deep surface of the integu- 
ments. Gerber states, that in those parts of 
the skin which are provided with papille, the 
nerve-loops pass into the bases of the papille 
and form an element of their composition; and 
he adds, that in some instances the nerve-tube 
which forms the loop exhibits tortuosities or 
convolutions similar to those which are seen 
upon bloodvessels. According to the same 
author, in parts of the skin where the tactile 
sensibility is acute, the meshes of the nervous 

lexus are extremely small, whilst they are of 
bite size where the skin is not highly sensitive. 


NERVOUS SYSTEM. (Nerve.) 


The arrangement of the primitive fibres in — 
loops has been seen by Henle on some parts 
of mucous membrane, in the membrana nie 
tans of the frog for example, and in the 
cous membrane of the throat in the same ani- 
ition has been described 


mal. A similar dis 1 
and delineated by Valentin on the pulps of the — 
teeth. ( Fig. 333.) ™~ 


Fig. 333. 


sharin | on at se of the a a 
of t jaw in t. » showing ‘an 
apo (From Valoctin ) L 
Retina and optic nerve-—The examinat 
of the peripheral connexions of the net 
of pure sense has not thrown light om # 
general question. The peripheral expat 
of the optic nerve or the retina prese 
the elements of a nervous centre; th 
matter is present in it in considerable 
tity, and certain fibres continuous with the 
mitive nerve-tubes are likewise expanded 
But the connexion of these fibres with 
matter has not been detected here any more 
in the centres themselves, nor has any arr 
ment of looping or of plexuses been di 
strated. Mr. Bowman has been led, by: 
examinations, to the opinion that these 
are the central parts of the nerve-fibre (the 
of Remak) which have been deprived ¢ 
tubular membrane and of the white sut 
of Schwann. It is worthy of notice that 
called optic nerve itself presents certain p 
characters, which entitle it more to be r 
as a prolongation of the nervous 
than as a distinct nerve. The nerve-tubes’ 
are met with in it are for the most part 
minute size; they admit of separation 
great difficulty, owing to their not being 
posed in fascicles like those of other ¢ 
spinal nerves: they appear to be surrou 
by and deposited in an abundant gi 
blastema, in which there seems to be } 
scattered elements of grey matter. . 


NERVOUS SYSTEM. (Nerve.) 


characters, with the peculiar construction of 
the peripheral expansion, would induce me to 
regard what is generally described as the optic 
nerve as a process of the brain itself, around 
the peripheral portion of which a dioptric appa- 
ratus has been disposed in order to produce 
those refractions in the rays of light which are 
necessary to the formation of an image upon the 
retina. And my friend, Mr. Bowman, has been 
led to adopt a similar conclusion from examin- 
ing the structure of the retina and optic nerve. 
Olfactory nerves.—The true olfactory nerves 
are very numerous and pass from the bulb of the 
olfactory process or olfactory nerve of descrip- 
tive anatomists. The peculiar characters of this 
process, as distinguishing it from a nerve properly 
so called, have long attracted attention. In truth, 
this process has the characters of a portion of 
the brain in a much more obvious way than the 
optic nerve, for it contains a larger portion of 
grey matter which adheres as a distinct layer to 
e white matter, as in the formation of the 
convolutions; and, moreover, its anterior ex- 
tremity or bulb contains a ventricle which may 
easily be demonstrated in a recent brain. It is 
from this bulb that the minute threads, which 


_ may be properly called olfactory nerves, take 
their rise and pass down through the foramina 


of the cribriform plate. Nothing satisfactory 
is known as to the disposition of the ultimate 


‘ramification of these nerves upon the Schnei- 
_ derian mucous membrane. 


The statement of 


_ Valentin that they form loops similar to those 


of cutaneous nerves is probably correct. It is 
not improbable that the papilla described by 
reviranus were particles of columnar epithe- 
ium to which cilia are attached. 
_ Auditory nerve.—The auditory nerve exhibits 
characters sufficiently distinct from the portio 
dura of the seventh, beside which it lies, to have 


Ted the anatomists of former days to separate it 


under the name of portio mollis. In fact, it pos- 
Sesses all the appearance of cerebral substance, 
and it wants the fasciculated disposition which 
Mere nerves exhibit. Its fibres are delicate 
and very prone to become varicose, and, as in 
the case of the olfactory process, it passes out 
of the cranium, not as a trunk, but by means 
of several minute filaments of various size 
which pee the foramina of the cribriform 
floor of the internal auditory foramen. Most 
observers express themselves in favour of the 
Opinion that the terminal filaments are disposed 
in a looped form upon the membranous laby- 
rinth and the cochlea. Valentin describes and 
delineates a plexiform arrangement, with loop- 
ings ofsome of the primitive fibres ; others ofthem, 
however, he says, do not affect this disposition, 
but appear to have free extremities. And this de- 
Scription corresponds with that which Henle has 
given. This author states that from researches 
which he has made upon the lamina spiralis of 
mammifera and the ampulle of the frog, he has 
no doubt of the existence of fibres which pass 
from one fascicle to another in a looped form ; 
but he finds it difficult to determine whether all 
the tubes contained in each fascicle form 
similar loops. Wagner delineates the looped 
arrangement, and Pappenheim adopts the 
same view. Mr. Wharton Jones states that 


597 


the tubular structure of the ner{us fila- 
ments ceases among grains of nervous matter, 
arranged into a sort of expansion, (see OrGan 
or Hearne), and he denies the existence of 
an arrangement in loops. My own observation 
leads me to concur in this description; and I 
would add that there seem to be here, as in the 
retina, some elements of the grey nervous 
matter scattered among the primitive filaments. 
This fact did not escape Valentin, for he 
remarks the existence of ‘“ very large globules” 
among the primitive fibres, similar to what he 
and Purkinje had noticed in the grey matter of 
the olfactory bulbs.* If this view of the peri- 
pheral expansion of the auditory nerve be cor- 
rect, its analogy with the optic is very obvious; 
and it may be conjectured of the ear, as in 
reference to the eye, that around a process from 
the brain an apparatus has been organized fitted 
to transmit and modify sonorous undulations, 

In the present state of observation we should 
not be justified in making any positive state- 
ment with reference to either the central or 
peripheral connexions of the nerves, beyond the 
following: that at the centres the grey and white 
elements are always associated, and that nerves 
may be truly said to arise out of grey matter; and 
that at the periphery, the nervous fibres, which 
in their progress from centre to circumference 
were bound together, become separated, and 
connect themselves, probably by intimate ad- 
hesion, with the elementary parts of the tissues 
and organs to which they are distributed. 

Of the ganglionic nerves.—Without more 
exact information respecting the minute ana- 
tomy of these nerves, our knowledge of the 
peculiar function of the ganglionic system must 
be very incomplete. The following questions 
suggest themselves in reference to this system. 
1. Are its anatomical characters sufficiently 
distinct from those of the cerebro-spinal system 
to warrant us in separating it from that system, 
if only for purposes of description? 2, Is it 
an independent system, as some have conjec- 
tured, giving fibres to the cerebro-spinal nerves 
as well as receiving some from them. 3. If it 
be an independent system, wherein consist the 
peculiar features by which its fibres are to be dis- 
tinguished from those of cerebro-spinal nerves ? 

There are many features belonging to this 
system which justify its separation from that of 
the brain and spinal cord. The great number 
of ganglions connected with it, suggests the 
propriety of designating it ganglionic system, 
nor does the existence of ganglions on the pos- 
terior roots of spinal nerves render this appella- 
tion less proper; for in this system every nerve, 
nay every fibre, is connected with or passes 
through one or more ganglions. The external 
aspect of these nerves is very characteristic. 
Their neurilemma is very dense, and has more 
of the silvery appearance of white fibrous tissue 
than the sheaths of cerebro-spinal nerves; they 
want the fasciculated character of the latter 
nerves, and their colour has a diffused greyish 
or greyish red hue. The smaller ramifications 
are exceedingly delicate and appear to be soft, 


* Valentin, tiber den Verlauf und die letzen 
Enden der Nerven, p. 


598 


and therefore have been classed among the 
nervi molles by auatomists. In its peripheral 
distribution this nerve is prone to attach itself 
to the coats of bloodvessels, so much so, in 
fact, as to give it the character of an arterial 
or venous nerve; for, with a very few exceptions, 
it is always conveyed to o along the 
bloodvessels which are distributed to them. 
In its distribution it is entirely or almost con- 
fined to the trunk, and probably has no con- 
nexion with the extremities; or, if it have,that 
connexion must be by very few fibres, and 
those attached exclusively to the larger trunks 
of bluodvessels. The peripheral ramifications 
of this nerve are always plexiform, and being 
distributed on some non-symmetrical parts, 
the plexuses which are derived from opposite 
sides of the body meet and anastomose along 
the mesial plane. The solar plexus, for example, 
derives filaments from the right and left trunks 
of the sympathetic, and the plexuses which 
accompany the superior and inferior mesenteric 
arteries, are also supplied from each side. Of 
the precise nature of these plexuses nothing is 
known: it is obvious, however, that their me- 
dian anastomoses constitute a very peculiar 
feature, which strikingly distinguishes the sym- 
pathetic from the cerebro-spinal nerves, which 
do not anastomose along the mesial line. If in 
these anastomoses the looped arrangement exist, 
it might be conjectured to form a commissural 
connection between opposite and symmetrical 
portions of the sympathetic or of the brain or 
spinal cord. 

To determine the independence of this por- 
tion of the nervous system on the brain and 
spinal cord, it would be necessary to shew 
either that it possessed peculiar fibres distinct in 
characters from the cerebro-spinal fibres, which 
originated in the ganglia, and were occasion- 
ally bound up with cerebro-spinal nerves, or 
that fibres belonging to the ganglionic nerves, 
although exhibiting no essential difference from 
the cerebro-spinal, had their origin from the gan- 
glia and not from the brain or spinal cord. The 
present state of the investigations into this sub- 
ject does not enable us to determine these 
points; but there can be no doubt that at least 
a large proportion of the fibres which compose 
the sympathetic exhibit no essential difference 
from those of the cerebro-spinal nerves. 

When a portion of a sympathetic nerve is 
examined under the microscope, it is found to 
contain an unusually large quantity of white 
fibrous tissue, the fibres of which are arranged 
longitudinally. Crossing these are some fine 
circular fibres (of yellow elastic tissue) which 
are placed at some distance apart from each 
other. When the nerve is torn up by needles, 
numerous small oval cells may be seen among 
the fibres, their long axes being parallel to the 
fibres; these cells become much more visible 
when the fibrous tissue has been acted upon by 
acetic acid. They are scattered among the other 
elements of the nerve, and are probably persis- 
tent nuclei of the same kind as those which 
exist in muscle and other tissues. Numerous 
nerve-tubes are also seen entering into the for- 
mation of these nerves. These tubes appear 
to correspond in structure exactly with those 


NERVOUS SYSTEM. (Nenve.) 


of the cerebro-spinal system; they present th 
same clear outline, and contain a semifluid — 
pulpy matter, which is acted upon ina similar — 
way by reagents as that in the nerve-tubes i 
the cerebro-spinal system. They resemble, 
however, the nerve-tubes of the brain or spinal 
cord more than those of nerves, for they re 
much smaller and more delicate than the latter, 
and more prone to form varicosities. lie 
side by side of each other as in other ne 
and do not inosculate. The number of these 
nerve-tubes seems to vary in different parts of 
the sympathetic, apparently without regard to 
the size of the nerve, so that a small nerve m 
contain several nerve-tubes, while a large ont 
contains but a few. In the abdominal ramifi- 
cations the nerve-tubes are very numerous, 
also in the cardiac nerves, while the pa- 
thetic trunk in the neck contains but a few, which — 
are situated quite in the centre of the nerve. 
So far all observers appear to agree in the 
statements respecting the elementary compost 
tion of this nerve, and so far its intimate 
structure justifies the opinion that in its fum 
tions it must be intimately connected with 
cerebro-spinal nerves. A coarser anatomy 
already taught us that this nerve has extensi 
communications with the cerebro-spinal 
with all the encephalic nerves, excepting t 
of pure sense, and with all the spinal nerve 
by their anterior and posterior roots. It i 
now evident from microscopic observation th 
the object of these communications must be’ 
enable cerebro-spinal nerve-tubes to pass il 
the sympathetic system; and, in 
these communications may be 5 
many origins of the sympathetic from the bra 
and spinal cord. , 
It remains to inquire whether there is ar 
good foundation for the doctrine that the sy 
pathetic nerve contains distinct and peculi 
fibres, (grey fibres of some authors, 
independent of the brain and spinal cord, ; 
which by anastomosing with cerebral or sp 
nerves may confer upon them, to a certain ext 
the peculiar endowment which is supposed 
characterise the nerves of the former kind. — 
Retzius and Miiller appear to have bee! 
first to put forward distinctly the opinion 
certain cerebro-spinal nerves received 
cular fibres from the sympathetic, as the! 
received filaments from the former. 
Miiller* suggested that both the ganglionit 
the cerebro-spinal nerves should be k 
upon as compound in structure; “ 
ganglionic nerves contain motor, sensitive 
organic fibres, of which the latter kind % 
have the power of regulating the veg 
processes, and have a special relation 
ganglia; that the cerebro-spinal ne’ 
likewise com of motor, sensitive 
organic fibres, of which those of each 
have their specific destination, and run- 
course together without uniting with the 
that the ganglionic nerve consequently’ 
only in having numerous ganglia, and im 
taining a large number of grey fibres, - 
give it a proportionally greyer colour; W 


* 


* Miiller’s Physiology, by Baly, p. 710, 


NERVOUS SYSTEM. (Nerve.) 


in the cerebro-spinal system, the grey fibres are 
less numerous, and are seen as grey fasciculi 
lying in the larger mass of white fibres.” 
Neither Retzius nor Muller has given a 
clear description of these organic fibres as seen 
by them. Muller quotes and adopts Remak’s 
account of the microscopic examination of these 
fibres. ‘ They are,” according to the latter 
anatomist, “‘ much more minute than the cere- 
bro-spinal fibres; they are perfectly homo- 
geneous, that is to say, not composed, as far 


__as can be distinguished with the microscope, of 
_ atube and contained portion; and are so pale 


and transparent that in a strong light they are 


not visible; lastly, a completely characteristic 


pearance is produced by the small roundish 
ral bodies Thich here and there beset their 
surface.” They are almost gelatinous in their 
“nature ; they have on their surface the appear- 
ance of fine longitudinal lines, and are easily 
resolved into very fine fibres.* 
Schwann seems to confirm this description, 
and to regard the organic fibre’ as a less per- 
_ fectly developed state of the nerve-tube of the 
-eerebro-spinal system. 
Henle in his description of the grey or soft 
nerves gives the following account of these fibres 


 (fig.334).They are flat fibres,very clear, of homo- 


Fig. 334. 


Gelatinous nervous fibres from a soft nerve in the 
_ Calf ( from Henle. 
_ A, fibre resolving itself into fibrilfa. 


B, A fibre doubled on itself, shewing the flattened 
character. 


C, Two fibres lying in juxtaposition. 
a, a, oa al 
- , c, a nuclear re . 
oe, d, a fibrilla. dnaieaneihte 

_ geneous appearance, in diameter from 0.002 to 
0.003 of a line (g,5th to 44th of an inch), with 
numerous nuclei of cells, round and oval, most 
vA of them laid flat, and arranged at nearly equal 
distances, many presenting regular nucleoli, 
and pointed at their opposite poles. Their 
longest diameter is generally parallel to the 
tudinal axis of the nerve. Sometimes one 
of these fibres resolves itself into more delicate 
fibrille, resembling the primitive fibre of cellu- 
tissue. Acetic acid dissolves them, and 
leaves the nuclei untouched. Henle admits 
that the greyish colour of the nerves depends 
on the quantity of these fibres ; the greater the 


* Miiller’s Physiology, translated by Baly, p. 
‘20, and Remak Obs. anat, et microscop. de sys- 
tem. nervos, structura, 


599 


number of nerve-tubes, the more th bundle 
resembles an ordinary cerebro-spinal nérve. In 
the roots of the sympathetic the number of the 
grey fibres is in large proportion, there being 
four to six of them for one nerve-tube, so 
that each nerve-tube appears surrounded by the 
nucleated fibres.* 

Valentin, who admits the existence of fibres 
of a similar kind to those described by Henle, 
maintains that they are continuations of the 
sheaths of the globules which exist in the gan- 
glia, and which are prolonged from them into 
the nervous trunks, and they serve as an enve- 
lope or protecting sheath to the cerebro-spinal 
nerve-tubes. Henle, who had formerly regarded 
these fibres as nerves distributed to the con- 
tractile cellular tissue and to vessels, (“ the 
slight developement of the nerves of these 
tissues seeming to correspond to the imperfec- 
tion of their contractile power,”) now expresses 
great doubts as to their nature and office, and 
proposes to call them gelatinous nervous fibres ; 
“a name,” he says, “ which has no other end 
but to designate their presence in certain nerves, 
in the same way as we continue to call the 
fibres of cellular tissue, which are met with in 
tendons, tendinous fibres.” 

Miller conjectures that they may serve the 
purpose of establishing a communication be- 
tween the ganglia; in short, that they are so 
many commissures between these centres. 

Purkinje and Rosenthal describe the organic 
nerve-fibre as the same as the central axis of 
the cerebro-spinal nerve-tube deprived of its 
investing membrane, and from comparing the 
sympathetic fibres with the cerebro-spinal fibre 
in the young embryo, they state their opinion 
that the latter, in an early stage of develope- 
ment, is identical with the former, but they do 
not appear to recognise, as Remak did, any 
continuity between these organic fibres and the 
ganglionic globules. 

Volkmann and Bidder have lately put for- 
ward an examination of this question; and 
these observers maintain the existence of a 
series of fibres peculiar to the sympathetic and 
distinct from those of the brain and spinal cord. 
Their work, however, contains many statements 
so much at variance with those of preceding 
writers, and with what I have myself seen, that 
I am led to entertain a strong suspicion that 
there must have been some fallacy affecting 
their observations throughout. 

The sympathetic fibre, according to these 
writers, differs from the cerebro-spinal fibre in 
the following particulars; it exhibits at its mar- 
gin a single contour, instead of the double one 
which is so constant a feature of the cerebro- 
spinal fibre, especially when examined some 
time after death; the distinction between a 
containing tube and the pulpy contents is not 
manifest; the fibre has sometimes a greyish 
aspect, which the authors regard as independent 
of any admixture with material foreign to that 
of the nerve-fibre itself; it is much smaller 
than the cerebro-spinal fibre, nearly one-half; 
in the cerebro-spinal as well as the sympathetic 


* Henle, Algemeine Anat. 
+ Archiv. 1839, p.ccv. 5 
$+ De Formatione granulosa, Vratislav. 1839. 


600 


nerves both kinds of fibres may be found, but 
in the latter these peculiar fibres are enormously 
predominant, so that ,%,ths of their elements, or 
even a larger proportion, are composed of them ; 
in passing into neighbouring trunks they run as 
often centrad as to the periphery. When the 
Sympathetic fibres occur in cerebro-spinal 
nerves, they are collected into separate bun- 
dles. The nervous branches which go to the 
involuntary muscles contain almost exclusively 
the smaller or sympathetic fibres. Mucous 
membranes are almost exclusively supplied by 
these fibres. The viscera of the chest and ab- 
domen receive nerves which are made up 
almost exclusively of sympathetic fibres. 

These statements are quite at variance with 
the results of my observations, as well as of 
those of Henle and Pieqeee 

The authors remark a considerable difference 
as regards the relation which these peculiar 
fibres bear to the cerebro-spinal centres in 
Frogs, Mammalia, Birds, and Fishes. In 
frogs the fine fibres originate in greatest part 
from the ganglions on the posterior roots of 
Spinal nerves and from those of the sympa- 
thetic. In Mammalia the brain and spinal 
cord are not the only sources of the aeen etic 
fibres. The ganglia also probably give off some. 
In birds the ganglion of the vagus is a pro- 
bable source of sympathetic fibres; and in 
fishes the great thickness of the branches of the 
vagus, which are very rich in the fine fibres com- 
pared with the small size of its roots which are 
deficient in them, indicates that the 
ganglion of that nerve is a source of 
very numerous sympathetic fibres. 

e anatomical statements of these 
writers would, if founded in fact, go 
far to confirm the opinions of those 
physiologists who uphold the inde- 
pendence of the sympathetic system, 
and to prove the ganglia to be distinct 
centres of nervous influence. It is 
impossible to enter further upon the 
discussion of this question at present, 
without introducing physiological ar- 
guments. Ina subsequent part of the 
article we shall return to the subject.* 

Nerves of Invertebrata—In those Inverte- 
brata in which a definite arrangement of the 
nervous system has been made out, the same 
elements of the nervous matter are to be found 
as in the Vertebrata. The grey matter consists 
of globules with nuclei and nucleoli precisely 
like those of the human brain. From the gan- 
glia the nerves radiate ; the nerve-tubes, which 
are very delicate and transparent in the recent 
state, contain a soft pulpy matter easily altered 
by re-agents. They are themselves collected 
into bundles which are surrounded by a clear 
transparent membrane, of the same kind as 
the sarcolemma of muscle, which accompa- 
nies and surrounds the branches of the nerves. 
As the nerve-tubes separate from the primary 
trunk into smaller fascicles, these sheaths bi- 
furcate, so as to adapt themselves to the new 
branches. From the clear outline of the 


* Die Selbstandigkeit des sympatheschen Ner- 
vensystems, &c. von. Bidder und Volkmann. 


NERVOUS SYSTEM. (Nerve.) 


sheath, and the faintness and indistinctness of 
the margins of the nerve-tubes contained within 
it, this arrangement in the smaller nerves has 
very much the appearance of a bifurcation of the 
nerve-tubes themselves. There seems, however, — 
no reason to believe that the nerve-tubes of I 
vertebrata follow a different law from thatwhich 
regulates their disposition in the Vertebrate — 
series. It is likewise highly probable that the 
relations of these nerve-tubes to both periph ; 
and centre are essentially the same as in Ver. 
tebrata. Plexuses occur much more 
according to Valentin, in the nerves of 
tebrata. 

Of the developement of nerve-—We can add — 
nothing to the account given by Schwann of © 
the developement of nerve. The 
quoted from Wagner’s Physiology. 

“ The nerves appear to be formed 
the same manner as the muscles, viz. by the 
fusion of a number of primary cells a 1 
in rows into a secondary cell. The fp 
mary nervous cell, however, has not yet been 
seen with perfect precision, by reason of the 
difficulty of distinguishing nervous cells whilst 
yet in their primary state, from the indiffe 
cells out of which entire organs are evol 
When first a nerve can be distinguished as su 
it presents itself as a pale cord with a longi 
dinal fibrillation, and in this cord a multit) 
of nuclei are apparent. ( Fig. 335,a.) It is 
easy to detach individual filaments from a cor 


Fig. 335. 


4 


oad 


J 


of this kind, as the figure just refer 

shows, in the interior of which many n 
are included, similar to those of the primi 
muscular fasciculus, but at a greater distar 
from one another. The filaments are p. 
granulated, and (as appears by their fart 
developement) hollow. At this period, a 
muscle, a secondary deposit takes place u 
the inner aspect of the cell-membrane of 
secondary nervous cell. This secondary 

it is a fatty white-coloured substar 

it is through this that the nerve acquires 
opacity (fig. 335, 6). Superiorly the fibr 
still pale; inferiorly, the deposition of 
white substance has occurred, and its effeet 
remieing ry fibril dark is obvious. aoa 
advance of the secondary deposit, the fibr 
become so thick, that the double outline 
their parietes comes into view and they 
quire a tubular appearance (c). On the ¢ 
currence of this secondary deposit fhe nue 
of the cells are generally absorbed; yet a fe’ 
may still be found to remain in 


sy 


9 


for some- ti 


NERVOUS SYSTEM. (Comparative Anatomy.) 


Jon when they are observed lying out- 
sori between ie deposited substance and 
the cell-membrane, as in the muscles (c). The 
remaining cavity appears to be filled by a pretty 
consistent substance, the band of Remak, and 
discovered by him. In the adult a nerve, 
consequently, consists, 1st, of an outer pale 
thin cell-membrane—the membrane of the ori- 
ginal constituent cells, which becomes visible, 
when the white substance is destroyed by de- 
grees (d); 2d, of a white fatty substance de- 

ited on the inner aspect of the cell-mem- 

e, and of greater or less thickness; 3d, of 

a substance, which is frequently firm or con- 
sistent, included within the cells, the bund of 
Remak.” re , 
From the ‘description given in the foregoing 
we have seen that the prevailing anato- 
mical element of nerves is a tube composed of 
homogeneous membrane containing a soft pulpy 
matter, the true nervous substance, divisible 
jnto the white substance of Schwann and the 
‘band of Remak, and that through the medium 
of these nerve-tubes or fibres the grey matter 
‘of the central masses is brought into connection 
with the peripheral textures and organs. 
Whether he fibres which Henle has desig- 
nated gelatinous fibres, which resemble very 
‘much the central band of the nerve-tubes de- 
prived of tubular membrane and white sub- 
i , perform a sithilar office, or whether they 
" serve to establish a connection between the grey 
matter of the several nervous centres, are ques- 
tions which we must leave for future considera- 
_ The sagacity of Galen long ago pointed out 
that every part, which is capable of motion, 
and at the same time possesses sensibility, 
‘must receive two classes of nerves, motor and 
; sensitive. And it was reserved for the genius 
of Bell in our own times to demonstrate that 
__ the office of a nerve depends upon the powers 
or endowments of its component fibres or 
_ tubules, and that a nervous trunk may be 
_ made up of fibres of different endowments 
Tying in juxta-position with each other. 
" It is at the roots of the nerves that tubules 
of distinct endowments are isolated from each 
other. Thus Bell’s experiments, which have 
been confirmed by subsequent observations, 
shewed that the anterior roots of spinal nerves 
were motor, and the posterior sensitive; and 
the determination of this important fact is the 
foundation of all our knowledge of the phy- 
siology of nerves. 

The difference in the powers or endowments 
of the nerve-tubes does not appear to depend 
upon any variety in their structure, or other 
physical characters, (size perhaps excepted,) for 
repeated examination has failed to detect any 
such, but rather upon their peripheral and cen- 
tral connexions. A sensitive nerve, while it is 
organized at its periphery in such a manner as to 
adapt it to the reception of impressions, must 
be connected with that part of the brain whose 
office it is to perceive the changes which such 
impressions can produce. And a motor nerve 
must be on the one hand connected with mus- 
cular fibres, and on the other associated with 


. 


601 


such a part of the brain or other nervow centre 
as is capable of exciting in it that change which 
when communicated to a muscle will stimulate 
it to contract. 

The precise mechanism of those nervous acts, 
which I would distinguish as purely physical, 
by reason of their independence of the mind, 
is as yet unknown. It is still undetermined 
whether a distinct series of fibres (excitomotory) 
is necessary for them, or whether they may 
not be performed by the same fibres which are 
the channels of the mandates of the will, and 
of the impressions of those stimuli which are 
capable of producing sensation. 

(R. B. Todd.) 


NERVOUS SYSTEM, Comparative Ana- 
tomy of.*—In the following article it is in- 
tended to describe the anatomy of the nervous 
system in the different classes of animals as 
they rise upwards in the scale. 

Acrita.—tThe class acrita consists of ani- 
mals whose very characteristic is, that in them 
the nervous system is molecular, consisting 
of globules diffused through the cellular 
tissue of their bodies. Amongst them we 
distinguish, first, the Polygastrica, which are 
minute microscopic animals, furnished with 
numerous digestive cavities, in whom no ner- 
vous filaments have as yet been traced; still 
they, many of them, possess eye-specks, they 
show some indications of the sense of taste, 
and perform their various motions in the diffe- 
rent fluids as if under the well-directed gui- 
dance of nervous power. These animals appear 
as a punctiform homogeneous mass, in which 
a nervous system does not as yet exist in a 
distinct form: the nervous matter may be, 
perhaps, every where diffused through the cel- 
lular tissue of their body. These latter re- 
marks will equally apply to the next class— 
the Porifera; of which the spongia officinalis 
may be cited as an example. Its texture is 
soft and gelatinous, and is probably made up 
of nervous and muscular globules. 

Potypirera.—No nervous filaments have 
been discovered, or described, in any of the 
various forms and sizes of polypiferous ani- 
mals, excepting in the genus actinia, respecting 
which a doubt, almost amounting to a denial 
of the statement, exists. The actinia may be 
considered as an isolated polypus; it has no 
calcareous skeleton, and fixes itself to the rocks 
by its fleshy base. Spix, a German anatomist 
of high repute, gave plates of its nervous sys- 
tem thirty years ago, and described it as con- 
sisting of filaments with minute ganglia, sur- 
rounding the fleshy base just mentioned, from 
which were given off nerves to the different 
parts. [ Professor Rymer Jones believes he has 
detected a delicate nervous thread, passing 
round the roots of the tentacles, embedded in a 
strong circular band of muscle, which sur- 
rounds the orifice of the stomach.] Mr. Bell, 
in dissecting several of these actinia, has not 
been able to detect any nervous filaments ; 


* The Editor is responsible for the passages in- 
cluded between brackets. 


602 


Cuvier has also been unable to make out any 
traces of a nervous system, and doubted the 
accuracy of the statement made by Spix. These 
animals are, however, extremely sensible to the 
touch, when expanded, and to the light when 
exposed to its influence. This would indicate 
some degree of nervous sensibility, but which 
we can conceive to be afforded by the nervous 
elements being distributed in their homoge- 
neous structure in a manner similar to the 
preceding classes. In the next class,” the 
Acalepha, which consists of gelatinous marine 
animals, Trembley,* Gede,+ Carus,} and other 
anatomists have failed to detect any distinct 
nervous filaments. Dr. Grant,§ however, de- 
scribes what he considers a nervous system in 
the Beroé pileus, and describes it as “ consist- 
ing of a double circular nervous filament, 
situated around the oral extremity of the body, 
which sends off minute filaments in each of 
the spaces between the eight longitudinal bands 
of cilie; these eight points, from which the 
longitudinal filaments come off, present minute 
ganglionic enlargements.” This statement has 
been recently called in question, and it is pro- 
bable that the nervous system in these animals 
is diffused throughout the gelatinous mass of 
which their bodies are composed. Dr. Milne 
Edwards describes and figures part of the 
nervous system in a larger species of Beroé 
( Lesueura vitrea ), as radiating from a single 
small ganglion which is closely connected with 
a coloured eye-speck, situated at the middle of 
the superior extremity of the body.|| 
Raprata.—In the next group of animals, 
the Radiata, nervous filaments are for the 
first time discoverable; and this being the 
case, it is important that we should notice 
what form and direction they assume: it is 
that of a ray and a central point, or a nerve 
and a ganglion; of these several are de- 
veloped; and as it is the very essence of a 
nervous system that it should consist of gan- 
glions united and not separated, threads of 
communication are developed, called commis- 
sures, and a ganglionic system is formed, the 
inferiority of which is expressed in the Echi- 
nodermata by the perfect equality of all the 
ganglions: these ganglions are also situated at 
an equal distance from each other, and are 
determined in their number and origin by the 
general organization of the animals: thus we 
shall find that in the Asterias, or star-fish, with 
five rays, there are five ganglions (with radia- 
ting nerves) sending off commissures, which, 
inasmuch as they are situated on a spherical 
surface, unite them in the form of a ring. 
(See Eco1nopERMATA, i's. 23, p. 44, vol. ii.) 
This ring we may call the primary nervous 
ring; it is that form which we shall hereafter 
recognize as the essential base of even the 


* Mémoires pour servir 4 l’histoire d’un genre 
de porypes d'eau douce, 1774. ees 

t oa zur Anatomie un siologie der 
Medusen, 1816. serenyd 


Anatomie Comparée, vol, i. 

Lectures on Comparative Anatomy. 

Ann. des Sc. Nat. n.s, t. xvi., and Owen’s 
Lectures, by White, p. 106. 


NERVOUS SYSTEM. (Comparative Anatomy.) 


+] 


j 


most varied forms of a nervous system. Tt is — 
only in the genus Asterias that a nervous ystem 
has been distinctly seen; and we are indebted — 
to Tiedemann for the first description of it, in” 
his Monograph of the Echinodermata.* In a 
small species of this genus, it consisted of 
a circular cord around the mouth, from 
which proceeded a filament along each ray, 
having, at its origin, a minute ionic en- 
largement ; the nervous ring u 
extreme edge of the central aperture in the 

careous frame-work of the body, and the fil 
ments rested on the inferior surface of the 
concealed by and at the base of the tubula 
feet and suckers. Two other filaments, muce 
shorter than those just described, according to 
Tiedemann,t are given off from each of the 
ganglionic enlargements, to be distributed te 
the stomach and other viscera. And Ehrenber 
affirms that the red points situated at th 
tremity of each ray are eyes, and receive nert 
connected with special ganglia. The stateme 
however, has not received confirmation fr 
any subsequent observer; but Mr. E. Fe 

describes a kind of protective apparatus 
taining to these points, consisting of a pe 
arrangement of the spines around them. [T 
existence of ganglia is questioned by man 
observers. Microscopic examination we 

decide the point. ] 

In the inus no nervous filaments fh 
hitherto been discovered; but in the gen 
Holothuria, Cuvier observes, “ that there a 
pears to be a very attenuated nervous 
around the cesophagus.”{ This Delle Chi: 
denies entirely.6 Dr. Grant, however, d 
scribes their nervous system to exist in 
form of a collar around the anterior part | 
the body, giving off longitudinal filaments. 

[{t is remarkable that, although the nervy 
system be very obscurely developed in thes 
animals, the action of the muscular integum 
is extremely powerful. The slightest irri 
of the surface is sufficient to occasion fo 
contraction of the integument to such a de 
that the thin membranes of the cloaca bec 
lacerated, and large portions of the inté 
and other viscera are forced from the 
aperture. “So common is this occurre 
says Professor Rymer Jones, “ that the 
anatomists were led to suppose that, | 
natural instinct, the ani . Ww S 
vomited their own bowels. It is, in 
extremely difficult to obtain speci 
of the Holothuride from the constant o 
rence of this accident.” 

We may next ask what are the chi ! 
of an increase in developement of the pri 
nervous ring just mentioned, as the ~ 
mental form of every nervous system. — 
are precisely these: either that it is it 
more highly developed, or that it is multi 
and repeated several times. This we shi 
illustrated in nature; the former in # 


* Anatomie der Rohrenholothurie, &c. 1 
t Loc. cit. “y 
¢ Régne Animal, vol. iv. 

§ Memoir sull’ asteria, &c, 1823. 

{| Lectures on Comparative Anatomy. 


a] 


% 


NERVOUS SYSTEM. (Comparative Anatomy.) 


lusca, the latter in the Articulata. In the 
Mollusca, what is it that constitutes an increase 
in developement of the primary nervous ring, 
the characteristic form of the nervous system 
of that class? 

1. The greater volume of a central medul- 
lary mass, and its situation on the dorsal aspect 
of the animal. 

2. A small number of ganglions in the pri- 
mary nervous ring, proportioned to the deve- 
lopement of the muscular system, one predo- 
minating in size over the rest, especially if that 
‘one be situated on the dorsal aspect of the 
animal. These ganglia are disposed unsym- 
metrically throughout the body, whence Pro- 
fessor Owen has designated these animals, in 
ete, to their nervous system, Heterogan- 

al. 
- Mottusca.—1. Tunicata—Many of the 
Tunicata, the lowest of them, approach in cha- 
racter the Zoophytes ; for no particular medul- 
_ lary mass constituting a nervous system is dis- 
coverable in the soft texture of their bodies, 


_ except in but few of the genera, principally in 


the forms of Ascidie. In the Ascidia mam- 
“millata (fig.336), Cuvier describes and figures 
the nervous system* as consisting of a single 
oblong ganglion, situated near the anus of the 
animal, and between that and the branchial 


Fig. 336. 


Wa 


Ascidia Mammillata, (after Cuvier, ) shewing the 
single gangliun between the branchial and anal 
ort . 


* Anatomie des Mollusques. 


603 


orifice; from this ganglion branches ae given 
off, some of which, passing to the esophagus, 
encompass it in the form of a ring. 

[ Mr. Garner, in his valuable paper on the 
nervous system of molluscous animals, de- 
scribes the nervous system of Phallusia intes- 
tinalis. The single yellowish ganglion lies 
upon the muscular coat between the two ori- 
fices. One set of filaments coming from it 
surrounds the branchial orifice, and gives nerves 
to its tentacula, appearing to meet on the oppo- 
site side, forming a nerve which seems to run 
along the edge of the elongated branchial fold. 
The other set supply the muscular tunic and 
go towards the mouth. In Cynthia and those 
tunicata that have thick muscular tunics, the 
ganglion is not visible external to the muscular 
sac, it being situated in its interior. 

As the actions of these animals are ex- 
tremely simple, so is their nervous system: by 
the branchial orifice water is drawn in to supply 
the branchie and to convey nutrient matters 
to the mouth. It is propelled by the action of 
numerous cilia which cover the surfaces with 
which it comes in contact. Through the anal 
orifice are expelled both the current which sup- 
plied the respiratory surface and that which 
passes through the digestive canal. Each ori- 
fice is provided with a sphincter muscle, which 
may oppose the entrance of various matters at 
one orifice, or resist their exit at the other. These 
muscles receive filaments from the ganglion. 
The animal is surrounded by a muscular sac, 
which by its contraction can compress and 
empty its general cavity. This, too, receives 
some nervous filaments. The solitary ganglion 
of this ascidian seems to regulate the actions 
of its orifices of ingestion and egestion, and of 
its enveloping sac on which depends the slight 
locomotive power of the free species. We are 
not prepared to deny to even this simple being 
that prevailing attribute of animals, a will, and 
therefore it may be assumed that its actions are 
partly volitional and partly reflex (mental and 
physical)—while some are, no doubt, due 
simply to the inherent irritability of its muscu- 
lar tunic. 

2. Conchifera—In this order the nervous 
system is precisely adapted to the functions these 
animals have to perform. These are ingestion 
of the food, respiration, and locomotion. Their 
nervous centres or ganglia are, consequently, 
placed in immediate relation to the organs 
destined to those functions; but as one pair 
communicate with the others, it may be pre- 
sumed to exercise an influence over them, and 
to be the principal centre, the analogue of the 
brain in the higher animals, the focus of sen- 
sation and volition. 

The esophageal or labial ganglia are for this 
reason the most important. They are two in 
number; they are situated more or less near 
the mouth, and are united bya transverse branch 
which arches over it. From these ganglia 
nerves are given off to the mouth, and to the 
tentacles, and to the anterior parts of the vis- 
cera. Each ganglion has a branch of commu- 
nication to the pedal ganglion and also to the 
branchial ganglion. 


604 


Second in importance is the branchial gan- 
glion. In those Conchifers in which the two 
branchie are conjoined, the ganglion continues 
single ; where they are separate, it becomes sub- 
divi From this ganglion or these gan- 
glia nerves are derived to the branchie and 
to the respiratory siphons, when present, to 
the posterior parts of the viscera, and to the 
posterior adductor muscle, also to the mantle, 


Fig. 337. 


Nervous system of the Oyster, ( Ostrea ). 
@,a@, anterior ganglions. 6, posterior ganglion. 
e,c, branches to branchia. d, d, connecting 
trunks. ¢, transverse branch uniting anterior 


ganglia. 

In the oyster (fig. 337), the cockle (Car- 
dium), and many others, the branchie are 
united, and there is consequently but one bran- 
chial ganglion. 

In the mussel (Mytilus), in the scallop 
( Pecten ) (fig.338), &c. the branchie are sepa- 
rated and the ganglion is divided into two; 
their connection, however, is maintained by a 
commissural band. The branchial ganglia or 
ganglion are also united to the anterior or 
esophageal ones. 

Fig. 338. 


Sy 


ee 


Ss 
ANN 
X (| NS 


Nervous system of Pecten ( Scallop ). 
a, anterior ganglia. 6, branchial ganglion, c, 
pedal ganglion. d, esophagus. 
A third ganglion, the pedal, is not deve- 
loped in all the genera ; and this circumstance, 


NERVOUS SYSTEM. (Comparative Anatomy.) 


as well as its position and the distribution of 
its nerves, throws much light upon its function 
It is immediately connected with the wsopha- 
geal ganglia by two nerves; it is always deve- 
ey in the substance of the foot, generally: 
its base, and its size 1s always proportioned t& 
the power and dimensions of thatorgan, _ 
In the genus Ostracea it is entirely absent 
for the foot is wanting, and whatever locomo 
tive power is enjoyed by these animals is per 
formed by the rapid closure of their 
through the action of the adductor musc 
The arrangement of the nervous 
Conchifera is of the highest physiological it 
terest. It affords a beautiful example of 
complete analysis of the more comp icater 


nervous system of the vertebrata. e ha 
here an anterior pair of ganglia, from whic 
filaments proceed to all parts of the boc 
associated too with the ingestive faculty; the 
are connected with whatever degree of psych 
cal endowment the animal possesses and fort 
its sensorium commune; they are the soure 
of its voluntary actions. The respiratory ¢ 
gans likewise have their special centre 
branchial ganglion or ganglions, the develo 
ment of which is always proportioned to th 
of the branchie. And there is a special cent 
provided for the locomotive organ, too, wh 
development is strictly in relation with its si 
and activity, and which is absent when 
organ does not exist. And it must be observ 
that these special ganglia (respiratory and ped 
although unconnected with each ) 
municate with the cesophageal ganglia, 
Have we not here distinctly marked out 1 
Cone (the centre of volition and sensatiot 
the medulla oblongata (the respiratory centre 
and the corsbollonl (looogeaneee centre), 
they occur in the higher vertebrata? And 
the aggregate of the chords by 
cesophageal ganglia communicate with © 
pedal and branchial ones, do we not see 
analogue of at least a portion of the sp 
cord, that portion which consists of affe 
and efferent nerves to and from the bra 
The nervous system is distinctly ad 
wants of the animals and their limited ps) 
cal endowment, and the same law prev: 
throughout the scale of animals. It is no’ 
nervous system which developes the pow 
and instincts of the animal; on the cont 
these latter determine the development of 
nervous system. This is well illustrated 
comparison of the oyster and the m 
These moliusks differ only in a greate 
motive power belonging to the mussel, te 
which it possesses an organ called the 
the oyster is devoid of such an organ. 
mussel has an additional ganglion (the 
which the oyster has not, and this gang! 
not an isolated centre, but, like the bran 
ganglion, is connected by distinct fila 
with the anterior or cerebral ganglia. 
A large series of careful dissections of 
nervous system of these and other Inverte 
well displayed is a t desideratum in 
public museums. We are happy to pe 
that this want is likely to be supplied by 
2 


2 


NERVOUS SYSTEM. (Comparative Anatomy.) 


Council of the College of Surgeons under the 
judicious direction of Professor Owen. The 
beautiful preparations of the nervous system of 
the mussel and other animals by our friend 
Mr. Goadby, cannot fail to excite the delight 
and admiration of every friend to the advance- 
ment of Physiology. One is not less asto- 
nished at his remarkable power of manipu- 
lation, as displayed in the dissection of the 
soft and fragile nerves of these delicate animals, 
than at the great ingenuity with which he has 
displayed and perpetuated these witnesses to 
his anatomical skill. We hope, for the sake of 
science, that, under the liberal patronage of 
the College Council, Mr. Goadby will be able 
to form a large collection of dissections of the 
Invertebrate Nervous System; and sure we 
are, that in nothing can the Council contribute 
more to promote the designs of John Hunter 
than in making his Museum the depository of 
such a series by such an artist. 

3. Gasteropoda.—{In this order of Mollusks 
the locomotive function is freely enjoyed, and 
is effected in many of the genera.by a powerful 
muscular organ, which generally acts as a 
Sucker and enables the animal to adhere forci- 
bly to the surface and draw itself on in a 
crawling manner—the well known mode of 
progression of the common snail and slug. In 

_ other genera the foot is modified according to 
the objects to which the animals adhere, or loco- 
_ Motion is performed by portions of the mantle 
_ adapted to act as oars or fins in swimming. 

- The respiratory function, whether adapted to 
an aquatic or a terrestrial mode of existence, 
‘is much more highly developed in these animals 
than in the Sieeceding order. Their digestive 
System, too, is more perfect, the accessory 
organs being more fully developed. We per- 
ceive, too, the unequivocal existence of a 
visual organ. There are also special organs 
(tentacles) for the exercise of the sense of 
touch, and it has been supposed that the power 
of smell and that of hearing existed, although 
the respective seats of these senses cannot be 
determined. 

It is well known that if the surface of a 
Snail or slug be touche ever so slightly, a con- 
traction of the part so stimulated will imme- 
diately take place. This is probably due to 
the inherent irritability of the subdermic mus- 
cular layers, or it may result from the 
reflexion of the impression upon the motor 
organs from some nervous centre with which 
the nerves of the skin are in connexion. It 
Seems very unlikely that we can refer it to a 
Sensibility of the surface, for the observations 
of Ferussac clearly imply that the terrestrial 
Gasteropods present no signs of pain when 
injured or wounded. We cannot, therefore, 
agree with Professor R. Jones in assigning 
tactile sensibility to the general cutaneous sur- 
face of these animals, nor do we think it neces- 
Sary to regard the phenomenon in question (as 
Dr. Carpenter suggests) as an example of 
motion excited by a reflected impression, which 
1s not accompanied with sensation; but rather 
as an instance of muscular contraction, pro- 
duced by the immediate influence of the stimu- 
lus on the irritable fibre. 


605 


Now this more active exercise of certain 
functions necessarily implies a greater develop- 
ment of the nervous system; but the same 
general plan as that described in the Conchifers 
prevails. The principal part of the nervous 
apparatus is connected with the csophagus, 
and has communications with the other ganglia. 
There is also a centre of locomotion, and a 
respiratory centre.* 

The cesophageal nervous centre is developed 
either as two small ganglia, situate on either 
side of the «esophagus, or as a single large 
ganglion placed on the median line and above 
the esophagus ; or, lastly, a single ganglion is 
formed beneath the esophagus. In each of 
these varieties the common type of a nervous 
ring or collar around the esophagus is pre- 
served, however the situation of the cephalic 
centre or the number of its ganglia may differ. 

The centre of locomotion consists of two 
ganglia, from which nerves proceed to the foot 
and to the mouth; which latter, however, is 
sometimes supplied from distinct ganglia. These 
ganglia are connected to each other by com- 
missural nerves and also to the cephalic centre, 

The respiratory apparatus and the viscera 
receive nerves from a proper centre, which 
sometimes is formed by one ganglion, some- 
times by two separate ones, which, however, 
have a connexion with the cephalic ganglia. 
The branchial and the pedal ganglia are some- 
times conjoined, and in some genera there is a 
still further concentration, so as to form a com- 
mon centre from which nerves are distributed 
to all the organs. 

The following examples will serve to illus- 
trate the principal points in the nervous system 
of these animals :— 

In Patella (limpet) there are two ganglia 
situate on either side of the esophagus (A, fig. 
339). From these ganglia the tentacles and 


A, cerebral ganglia. B, 
pedal ganglion. C, bran- 
chial ganglion. a, fila- 
ment of communication 
from cerebral to bran- 
chial ganglion. 4, fila- 
ment of communication 
from cerebral to pedal 
ganglion. E, labial gan- 
glia. D, connecting band 
liq between labial ganglia. 


Nervous system of Pate 
vulgaris ( Limpet). 


eyes are supplied with nerves, and they are 
connected to each other by a simple nervous 
band which passes above the esophagus. From 
the posterior part of each ganglion two nerves 
pass back : the outer one terminates in the bran- 
chial ganglion, and theinneronein the pedal. The 
apparatus for mastication in this animal being 
complicated, it is supplied from a transverse 
band or two ganglia, situated beneath the 
cesophagus, and connected with the anterior or 
cerebral ganglia. This band is connected with 
two ganglia that supply the lips, called labial 


* See article GASTEROPODA, p. 394, vol. ii., 
and Dr. Carpenter’s Lectures on the Nervous Sys- 
tem, Lond. Med. Gazette for 1841. 


606 


lia. appear to be liar to Patella, 
ut are found more dintiantly developed in the 

Cephalopoda. 
Fig. 340 is a repre- 


Fig. 340. sentation of the nervous 

i system of Chiton Mar- 

moratus from the dissec- 

tion of Mr. Garner, in 

which the annular form 

of the nervous system is 

very perfect. The animal 

D presents many points of 

resemblance to Patella, 

and there is essentially 

the same arrangement of 

Jj its nervous system. The 

absence of ganglia on the 

/ upper of the ring (i) 

is attributed by Mr. Gar- 

ner to the want of eyes 
and of Ewen 

: Chit In Aplysia there is 

= aly an pin * cerebral 

. al lion. ganglion resulting from 

©, bedachial S agiienk the function of two 


D ? pharyngeal lion.above the cso s 
Toad Ving (cotebral gan. (°? 6° 241)> frome which 
glion.) small nerves pass to 


form the pharyngeal gan- 
glion (p) beneath the pharynx: from this two 
nerves pass backwards to form the pedal gan- 
glion, which also gives nerves to supply the 
mantle (P), and in the posterior part of the 
body there is an additional ganglion, the 
branchial (B, fig. 341). 


Fig. 341. 


Nervous system of Aplysia. 


In Scyllea, according to Mr. Garner, the 
brain is entirely supra-cesophageal ; it appears 
to be com of four united ganglia, pro- 
bably the cerebral and branchial. The foot has 
become too insignificant to require appropriate 

glia. Mr.Garner has noticed two minute 
black spots, one on each side of the brain, 
composed probably of black pigment, which 
he considers to be rudimentary of eyes. 


NERVOUS SYSTEM. (Comparative Anatomy.) 
Fig. 342. 


Nervous system of Scyll@a Pelagica. 3 
A, cerebral ganglion, D, pharyngeal gangli 
ce, d, i, visceral branches, ae 


In Limar ater oeons: slug) the ners 
system is apparently much more si Bu 
FA a little ecauiastinn it will be Pos i e 
sist of the same essential A large s 
cesophageal ganglion, bilobed, constitr es 
brain (a, fig. 343), from each side of which a 
of nerves passes downwards to join a large s 
esophageal ganglion, - 343. 


which supplies nerves si 
to the respiratory sac «a J 


and to the foot or loco- Ra 4 
wm 


motive a’ tus. And 
the sharenaial ganglia 
are, as in Patella, con- 
nected with theanterior 
ganglion. In the sub- 
esophageal ganglion 
we see, conjoined, the 
pedal and branchial 
ganglia. 

In Buccinum unda- 
tum the principal ner- 
vous mass is sub-ceso- 
phageal, and from it 
nerves pass to the bran- 
chie and viscera, and 
also to the foot and 
integument. The for- 
mer nerves form a gan- 
glion, which may be 


7 


regarded as the bran- Nowe a i 
chial ganglion. ]* ater) aq 
For the nervous sys- 4, supra - esc : 


tems of Pteropoda and ganglion d 
Capeaiahom, == phageal lion 
articles under those terior ony 
titles. ganglions, = 
Arricutata.—In taking a general : 
of the structure of the articulated animals 
observe that their body is divided into a ce 
definite number of segments, each one of ¥ 


’ ae 


* See Garner’s paper, loc. cit. As oa 


NERVOUS SYSTEM. (Comparative Anatomy.) 


may be considered as a repetition of the other; 
of these, the most anterior acquires the greatest 
developement, and is called the head. So in 
examining their nervous system, we shall find 
that a primary nervous ring (formed of a gan- 
glion and two semi-circular radiating nerves) is 
contained in each segment. This ring, no 
longer closed, as in the preceding classes, but 
open, varies in degree of developement, accord- 
ing as the segment which encloses it is in a 
high or low degree of developement: thus, in 
the cephalic segment, or head, we shall always 
find developed a cerebral or supra-csophageal 
_ ganglion; and, inasmuch as when a true ner- 
yous system was first formed—was first sepa- 
rated from the punctiform homogeneous mass 
of the gelatinous acrita—commissures were 
found uniting the primary masses of medullary 
_ Substance (as we saw in the Asterias), so ought 


| 
, 


we to find, in the Articulata, commissures 
uniting the primary nervous rings ; which latter 
are now become longitudinal, and the com- 
missures of the nervous ring itself are now 
become radiating nerves. We ought also to 
find that these commissures depend, in degree 

_ of developement and in situation, on the same 

_ characters of the primary nervous ring, and 
consequently on the ganglia thereon developed. 
We may next ask, what will mark the high 

or low degree of organization of a nervous 

_ System composed of several primary nervous 
_ rings? The researches of philosophical anatomy 
"inform us, that, first, a low degree will be 
characterized by an undetermined number of 
__ those rings—by a nearly equal developement of 
_ the whole, and by the central mass of nervous 
Matter accumulated on them being situated on 
the ventral surface of the animal. Secondly, a 
higher degree of organization exists when the 
primary nervous rings are repeated in a deter- 
Minate manner—when some of them predomi- 
nate in developement over the others, and their 
central medullary masses, or ganglions, are 
Situated on the dorsal aspect of the animal. 
Again, as regards the uniting commissures, 
these will, of course, depend, in degree of 
developement, on the organization of the gan- 
glions united by them; and the more perfect 
and the more intimate is the connexion esta- 
blished by these commissures, the more highly 
ees is the nervous system. 
n the Articulata about to be described, we 


shall always find the most anterior nervous 
ring developing a ganglion on its superior sur- 
true cerebral ganglion. We shall find 
this nervous ring repeated in the other segments 
of the body, but in a much more imperfect 
manner, for ganglions are developed only on 
the ventral surface of the animal; and from 
this latter circumstance, they, as well as their 
commissures, cannot be highly developed. 

1. Entozoa.—In the lower forms of Entozoa, 
as in the tenia and cysticercus, no nervous 
System is discoverable. These animals consist 
of a gelatinous, more or less homogeneous 
mass, in which no distinct nervous system 
exists. In the Distoma hepaticum, the nervous 
System consists, according to Bojanus,* of a 


* Isis, 1821, vol. i. p. 168. 


607 


nervous collar or ring, with two latex 1 gan- 
glions entwining the ceesophagus, and twO nerves 
which are distributed on the posterior part of 
the body. In the Ascaris lumbricoides, the 
nervous system consists of a thin double fila- 
ment, without ganglia, situated in the median 
line of the abdomen, which separates to enclose 
the opening of the vulva, and to encompass 
the esophagus at the lower part of the mouth. 
In the Strongylus gigas, according to Otto,* 
the median nervous filament consists of very 
closely approximated ganglia, thus advancing 
a step higher in organization, and approaching 
to the character of the true articulated classes. 

2. Rotifera.—The Rotifera are minute mi- 
croscopic animals: in them Ehrenberg has 
discovered and described a rather complex ner- 
vous organization, sufficiently so to justify their 
being ranked thus high in the scale of animated 
beings.t In the Hydatina senta, according to 
this anatomist, the nervous system consists of 
two closely approximated filaments running 
along the abdomen, and giving off lateral 
branches in their course forwards: arrived at 
the anterior part of the body, these nerves form 
a large ganglion, and then ascend to embrace 
the esophagus in the form of a ring, on which 
minute ganglia are developed, giving off nu- 
merous filaments to the surrounding parts. 
There are four of these lateral ganglia, besides 
the large supra-cesophageal ganglion. 

3. Cirrhopoda.—In the Cirrhopoda, the 
abdominal nervous cords have regular ganglia 
developed on them, and there is a nervous 
collar round the esophagus, as in the preceding 
classes. Cuvier observes, { that in a species of 
Lepas he found two nervous cords situated on 
the ventral surface of the body, with five double 
ganglia developed on them, from which were 
given off lateral filaments to supply the curled 
feet. Anteriorly, and at the lower part of the 
mouth, these cords separated more widely, to 
encircle the esophagus, above which they de- 
veloped a quadrilobate ganglion, from which 
were given off four nerves to the viscera and 
muscles. 

4. Annelida—The nervous system of the 
Annelida consists of a varied number of ganglia, 
united by double longitudinal commissures, 
running along the ventral surface of the body, 
from which lateral filaments are given off. 
There is also a supra-cesophageal ganglion, 
which, being connected by lateral nervous cords 
with the first pair of infra-cesophageal ganglia, 
form a ring or collar, surrounding the cesopha- 
gus: this we at once recognize as the most 
anterior of the column of primary nervous 
rings, with the ganglion developed on its supe- 
rior surface. I have examined the nervous 
system in the genera Lumbricus, Aphrodita, 
and Hirudo; the general plan was the same in 
all. In the Lumbricus terrestris, or common 
earth-worm, a nervous cord passed along the 
whole ventral surface of the animal, and pre- 
sented, in a small species, the appearance 


* Berliner Magazin, 1814, p. 178. 

+ Organisation Systematik der Infusions-Thier- 
chen, Berlin, 1830. 

} Anat. des Mollusques. 


608 


of an irregular white line, the structure of 
which, when viewed under a lens, appeared 
to consist of a number of closely approxi- 
mated nervous threads. In a larger species the 
nervous cord had a more jointed, knotted ap- 
pearance, and its structure was more homoge- 
neous; the ganglia were, however, but very im- 
oy, developed, for at each segment of the 

y of the worm, the nervous cord only offered 
an enlargement or swelling of rather an elongated 
form (fig. 344, d): the first or most anterior 


Fig. 344. 


Hoy 


Upper fourth of the nervous cord of Lumbricus 
terrestris (earthworm ). 


a, supra-csophageal or 
e, infra-cesophageal ganglion. 0, b, lateral ner- 
vous cords, forming the oral primary nervous 
ring. d,d,d,d, enlargements of the ventral cord, 
or imperfect ganglia, developed on the ventral 
surfaces of the series of primary nervous rings. 


cerebral ganglion. 


of these (the infra-cesophageal ganglion) was 
the largest (c). These caingeanents were more 
closely Ad aig weary towards the anterior part 
of the body; from each of them were given off 
two pair of nerves, one passing to the right, 
the other to the ieft, to supply the integuments. 
From the more attenuated intervening portions 
of the cord, a single pair of filaments was given 
off; these filaments we at once recognize as the 
commissures of the nervous ring of the Radiata 
and Mollusca; they pass round the body and 
approach each other on the dorsal surface, but 
do not unite: in this way is an open nervous 
ring formed. The infra-cesophageal ganglion 
before mentioned diverged at its anterior part, 
sent tee two lateral nervous cords (6), 
which developed a large bilobate cerebral or 
supra-cesophageal ganglion (a) of a transversely 
elongated oval form, thus forming a distinct 
nervous ring, embracing the esophagus. From 
the angles formed by the divergence of the 
infra-cesophageal ganglia, a nerve of rather firm 
texture was given off; another filament had its 
origin from the lateral and ascending portions 
of the nervous collar; and from ae eral 
ganglion two pairs of nerves passed forwards to 
supply the saits about the head. In the 
Aphrodita, a marine Annelide, the nervous 


NERVOUS SYSTEM. (Comparative Anatomy.) ¥ 


cord had a more flattened appearance: it was — 
about equal in width throughout its whole 
length, and presented similar enlargements in — 
its course, from which nerves were given of 
as in the Lumbricus; no nerve, however, arose 
from the intervening spaces. In the 
the abdominal nervous cord was surroundet 
by several delicate vessels, and at the anterior 
os of the commissures was distinctly seen to” 
composed of two separated columns: the 
ganglia were very distinct, of a round form, 
and twenty-four in number,—the last four o1 
five were more closely approximated; from 
each were given off two diverging pair of ate 
filaments, which passed to supply the muscles 
and viscera. The cerebral ganglion is bilobed, 
and sends off ten distinct optic nerves besides 
many smaller filaments to the integument and 
other of the head; each optic nerve T 
minates by expanding upon the base of a black 
eye-speck or ocellus.* 
According to Brandt, a simple nervous fi 
ment is continued from the cesophageal ganglia 
along the dorsal aspect of the alimentary 
“ This,” says Professor Owen, “is an inte- 
resting structure, since it offers the first trace 
of a distinct system of nerves, usually calle 
the stomato-gastric in Entomology, and to 
which our great sympathetic and nervus vagus 
seem answerable. 
These four classes comprise the whole ¢ 
the helminthoid Articulata; and on reviewins 
the statements just made with regard to their 
nervous system, we observe that the lowest 
them bear a great analogy to the Acrita 
some of the Tunicata, in having no distinct 
nervous system discoverable; that where such 
does exist in the higher orders of them, it bears 
more or less the character before noticed as the 
type of the Articulata, which was, it will be 
recollected, a series of primary nervous rings 
connected by hegre nN in the Ascari 
the ganglia are so imperfectly patie #~. nd 
consequently their conantaahiiae that hol 
has the appearance of only a single nervous 
filament. As we proceed through the Rotifer 
and Cirrhopoda, we observe the rathe 
more perfectly developed, but undetermined 
number. In the highest of the Annelides, 
the Leech, we find distinct ganglia develope 
and arranged in a determinate numerical ser 
Again, the cerebral ganglion, from bh 
first little more than a simple enlargement: 
the superior surface of the anterior prim 
nervous ring, has acquired, in the 
form of a distinct ganglion. 
We next pass to the examination of the | 
tomoid Articulata, in which we shall find 
cerebral ganglion becoming more and 1 
developed, and the ventral ganglia more : 
termined as to number, and more concentr 
as to situation; their longitudinal commissui 
have been supposed to two disti 
nervous tracts, composed of motor and s 
sitive columns, giving origin to nerves hav 
sentient and motiferous properties. . 
1. Crustacea.—In the lowest of the 


Crustacea, the nervous system preser 


* Owen’s Lectures, p. 141, 


ey | 


| NERVOUS SYSTEM. (Comparative Anatomy ) 


merous forms and degrees of organization. 

! In the common Talitrus, an inferior genus, 
it consists of a regular series of ganglia, 
developed at an equal distance from each 
other, united by two distinctly separated 
longitudinal cords, from which are given 
off transverse nerves. 1 have found the same 
arrangement in the genus Oniscus, in which 
also a close analogy to the nervous system 
_of the Annelides was apparent. In the 
_ Cymothoa, an animal a little higher in the 
seale, these longitudinal columns have become 
closely approximated, and the ganglia have 
coalesced transversely. Rising higher in the 
Seale, we find a still greater degree of concen- 
_ tration and coalescence in the Decapoda, this 
_ being directed to two ponies points—the 
thorax in the long-tailed Decapods, and the 
_ thorax and abdomen in the short-tailed ones. 
_ With regard to the former, I have examined 
the nervous system in the genera Crangon, 
Processa, and Pagurus, in all of which it pre- 
sented a similarity in developement. In the 
lengthened abdomen the longitudinal cords 
were very closely approximated, and the gan- 
‘glia developed were nearly of an equal size, 
‘and équidistant from each other; from them 
‘were given off transverse nerves. In the thorax, 
the ganglia were very closely approximated 
eed, longitudinally, so as nearly to have 
@ appearance of one nervous mass, from 


a hich were given off large transverse nerves to 


part of which there passed off two long nervous 
_ ¢ords, which encircled the esophagus, and de- 
os a ganglion on its superior part. In 
the short-tailed Decapods, as in the common 
_ edible crab, the abdominal ganglia have co- 
al into one large nervous mass, from 
which radiate nerves to the legs, &c ; from its 
anterior part there pass two long filaments, 
— it with the coalesced ganglia in the 
There is a supra-esophageal gan- 
_ glion, as in the precedihg, but it is compara- 
_ tively small. 
2. Myriapoda.— Amongst the Myriapoda, 
he next class, we find the nervous system 
pinning by a low state of organization, 
milar to the lower Crustacea, this being prin- 


ee ee 


cipally characterized by a considerable number’ 


ganglions. In the Scolopendra morsitans, 
the nervous system consists of a series of 
twenty-one double ganglia, situated on the 
ventral surface of the body, connected by in- 
tervening distinctly double longitudinal cords. 
fom each ganglion are given off lateral nerves 
to supply the neighbouring muscles, viscera, 
and feet. Those ganglia are nearly all equal 
mM Size excepting the first, which is the largest, 
and ftom which are given off additional nerves 
to supply the maxilla, &c. Beyond this first 
Sub-esophageal ganglion, and from its anterior 
part, proceed the longitudinal connecting cords, 
which diverge to encircle the esophagus, above 
_ which they meet and develope a bilobate supra- 
esophageal ganglion. (See Myrrapopa, (. Fig. 
313.) [Mr. Newport’s recent researches on 
the nervous system of Myriapoda favour the 
— that a distinct series of excitomotory 
OL. III. 


‘the neighbouring parts, and from the anterior . 


609 


fibres connected with the ganglia of te seg- 
ments (and not with the cerebral ganglion) exist 
in these animals. See the forthcoming volume 
of the Philosophical Transactions, 1843.] 

3. Arachnida—lIn the Arachnida the ner- 
vous system is more concentrated, and the gan- 
glia are fewer; they may be considered, indeed, 
as intermediate in the developement of this sys- 
tem between the Insecta and Crustacea. In the 
Scorpions, according to Dr. Grant,* ** the gan- 
glia of the trunk have formed one large nervous 


mass, from which all the nerves of the legs and 


the surrounding parts take their rise as from 
a single ganglion.” The cerebral ganglion is 
comparatively small, and, according to Cuvier 
and Carus,+ the two nervous cords, proceeding 
thence, unite at intervals to form seven gan- 
glions, the last of which belongs to the tail. 
Grant observes,} that the motor column is very 
loosely connected with the two inferior or sen- 
sitive columns, particularly in the region of the 
abdomen, and that this conformation is more 
obvious here than in any other of the Articu- 
lata. In Spiders, the nervous system consists, 
according to Professor Owen’s description, of a 
brain, a bilobed ganglion which supplies the 
optic nerves, and also two large nerves to the 
mandibles. From it a short and thick collar, 
embracing the gullet, extends to a second very 
considerable stellate or radiated ganglion, si- 
tuate below the stomach upon the plastron. 
From this ganglion five! principal nerves are 
sent off on each side, “the first to the pedi- 
form maxillary palpi, the second to the more 
pediform labial palpi, which are usually longer 
than the rest of the legs, and used by many 
spiders rather as instruments of exploration 
than of locomotion; the three posterior nerves 
supply the remaining legs, which answer to the 
thoracic legs of Hexapod Insects. The ner- 
vous axis is prolonged beyond this great gan- 
glion, as two distinct chords, into the beginning 
of the abdomen, where, in the Epira diadema, 
it divides into a kind of cauda equina; but in 
the Mygale a third ganglion of very small size 
is formed from which the nerves diverge to 
supply the teguments of the abdomen and its 
contents.” * * * “ The stomatogastric nerves 
are sent off from the posterior and lateral parts 
of the brain and form on each side a reticulate 
ganglion, which distributes filaments to the 
stomach.” § 

4. Insecta—We have now to examine the 
last and highest class of articulated animals— 
the Insecta, in which we shall find the nervous 
system very highly organized, leading us by 
strict analogies to the Vertebrata. It consists, 
in almost every order, of a ganglionic nervous 
cord, running along the abdominal surface, as 
in the preceding classes, and of a similar supra- 
cesophageal nervous mass, called by Cuvier the 
brain, from which are given off eight pairs of 
nerves and two single ones. This nervous cord 
consists of a varied number of ganglia, giving 
off lateral nervous filaments, and connected to 


* Lectures on Comparative Anatomy. 

+ Op. cit. 

t Op. cit. ; 

§ Owen’s Lectures, by White, p. 255. 
2k 


610 


each other by sensitive columns. A tract has 
also been recently described by Mr. Newport,* 
pare along the dorsal surface of these co- 
mns, and giving off lateral nervous branches ; 
this has been regarded as a molar tract. Mi- 
nute anatomy has also unfolded to us what 
may be considered as the analogue of the re- 
Spiratory system of nerves, and a par vagum. 
ints we will now notice in detail, 
commencing with the Hemipterous Insecta, in 
which the nervous system is least precy or- 
po. In the perfect state of the Ranatra 
inearis the nervous system consists (besides 
the su phageal nervous socnmenieners 
of a small round ganglion (fig. 345, a), situa’ 
below the wsophagus at its very commence- 


Fig. 345. 


Ye 


Ventral nervous cord of Ranatra linearis (perfect 
state ), magnified to about twice the natural size. 
a, small round sub-csophageal ganglion. 6, 
large quadrilobate thoracic ganglion. ec, ¢, fila- 
ments passing down the lengthened abdomen. 


ment; from this two longitudinal commissures 
pass to join with a large quadrilobate ganglion 
()s situated at the further extremity of the 

orax. From each side of this ganglion there 
are given off three nervous threads, passing 
superiorly, transversely, and inferiorly; and 
from the lower of the ganglion, which is 
slightly fusiform in shape, there are given off two 
bundlesof most minute and delicate nervous fila- 
ments (cc), each containing five branches, which 
pass downwards into the lengthened abdomen to 
supply the parts situated in that region; there is 
also a supra-cesophageal nervous accumulation. 
In the Orthoptera the nervous system presents 
a certain d of concentration worthy of no- 


tice. In the perfect state of a species of 
* Philosophical Transactions for 1832 and 1834, 


NERVOUS SYSTEM. (Comparative Anatomy.) q 


_ the larva of the Oryctes nasicornis, 


Acrydium there are two comparatively large 
thoracic ganglia, very near each other, and 
connected, as usual, by commissures; in 
abdomen there are five ganglia of much smaller 
size, connected in a similar manner, and givin 
off lateral filaments: the first and secon 1 o 
these abdominal ganglia are some distance from 
each other; the three last are much mor 
closely approximated, and are rather larg 
and more distinct ; the cerebral ganglion is 
small size. we 
Proceeding with the Coleoptera, we find th 

many of the Lamellicornes, in their perfe 
state, have a singular and rather unusual m 
of developement of their nervous system; | 
ganglia are but few in number, closely approx 
mated, and the two posterior ones give off nume. 
rous radiating filaments: this is the case wi 


?- e 


to a dissection by Swammerdam.* In th 
Geotrupes stercorarius (fig. 346), 


Fig. 346. 


pe weieisy feta: He corar 
fect state), magnified to three tin 
natural size. ae 


a, bilobate thoracic ganglia. 6b, abdomi1 
glia. c, c, filaments to the intestine. d, 


state, another of the Lamellicorn 

found in the pss distinctly 
ganglia (a), connec ongituc 
aed and one ier nglion at t 
tion of the thorax with the abdom 
ately contiguous with which are + 
and three smaller ganglia, closely 
mated to each other B: the last. 
longest, of rather a fusiform shape, a 
off radiating nervous filaments, particule 
long branches to the abdominal visce 
adjacent parts (c,c). The more usua 
however, of the nervous system, is § 
will be described in the subsequent 


hT 
(i 


* Biblia Nature. 


the nervous system consists of a distinctly vous system is met with. 


j 
} 
: 
} 
J 
» 


NERVOUS SYSTEM. (Comparative Anatomy.) 


In the larva of Dyticus marginalis (fig. 347), 
bilobate supra-esophageal ganglion (a), from 
Fig. 347. 


Ventral nervous cord of Dyticus marginalis (larva 


_ state), magnified to about twice the natural size. 


_ 4a, bilobate supra-cesophageal or cerebral gan- 


6, nerves passing to the antenne. c¢, c, 
to the eyes. d, infra-cesophageal 
a the nerves passing to the maxilla, 
, ae andlabium. e¢,¢,e,e, thoracic and ab- 

inal ganglia. /f, f, nervous filaments passing 


to the caudal extremity of the larva. 


7 


which are given off nerves to the antenne, and 
and the eyes (b,c), and of twelve abdominal 
lia, connected by longitudinal cords (c). 
difference in distance of these ganglia is 
ae remarkable, and worthy of mention. The 

it, Or true infra-cesophageal ganglion (d) is 
situated as usual ; atiosens this and the second 
a long space intervenes, and the connecting 
cords are firm and distinct; the spaces between 
the second, third, fourth, and fifth are about 
equal, and not more than one-third the distance 
between the first described ; the remaining seven 
are so closely approximated as to touch each 
other: from the terminal ganglion are given 
off long and minute nervous filaments, which 
may be traced down to the caudal extremity 
of the larva. 

In the Hymenoptera a very great concen- 


= 


611 
tration and increased developement of the ner- 
In the he the 


cerebral ganglion is of a large proportional size; 
from its anterior part are given off two nerves, 
which pass forward to the base of the antenna, 
and have their origin marked by a very distinct 
conical-shaped ganglionic enlargement. In the 
thorax all the ganglia coalesce into one central 
large ganglion, and a smaller one closely at- 
tached to it, giving off lateral nervous filaments ; 
in the abdomen there are five smaller ganglia ; 
they are connected by commissures, as in the 
preceding classes, the double nature of which 
is distinctly seen by a lens: the first abdominal 
ganglion is situated at some distance from the 
thoracic ganglion; the second and third are 
much nearer together, but the fourth and fifth 
are quite closely approximated: from them are 
given off radiating nerves. 

The most highly developed nervous system 
in the Articulata occurs in the Lepidoptera, 
the characters of which we shall next describe. 
In the larva of the Saturnia pavonia minor 
(fig. 348), the nervous system consists of a 
bilobate supra-cesophageal or cerebral ganglion, 
and of twelve sub-cesophageal or abdominal 
ganglia (a), united by longitudinal fissures. 

The cerebral ganglion consists of two closely 
approximated oblong ovate medullary masses, 
giving off nerves supplying the eyes and the 
antenne, and a pair of nerves from its anterior 
and lower parts, which takes a direction for- 
wards, and which meeting inwards and joining, 
forms a ganglion: from the posterior surface 
of this ganglion arises a nerve (the recurrent of 
Lyonnet) which passes backward beneath the 
cerebral ganglion along the csophagus, and 
gives off filaments to itand the stomach.* The 
existence of this nerve, and particularly its si- 
tuation, is of very high importance, according 
to the laws of philosophical anatomy: the 
branching filaments it sends off form nervous 
rings, which are important in being open be- 
low and not above, and in developing a gan- 
glion on the dorsal aspect of the animal; this, 
we shall find presently, leads by strong ana- 
logies to the Vertebrata. The cerebral gan- 
glion is supported or produced by two lateral 
nervous filaments, which, having their origin 
at its posterior part, pass downwards by the 
sides of the esophagus, at the inferior part of 
which they converge, and are connected with 
the first sub-cesophageal ganglion; in this way 
a nervous collar or ring is formed, which en- 
circles the esophagus. This first inferior gan- 
glion (6) is of rather a quadrilateral form ; it 
gives off a pair of nerves to the maxille and 
to the labium (c,d), which have their origin 
within, the termination of the lateral commis- 
sures just described. The second ganglion is 
longitudinally continuous with the first; from 
them are given off lateralnerves. The (supposed ) 
motor and sensitive connecting nervous columns 
are widely separate between the second and third 
ganglia, and between the third and fourth ; 
between all the others they are very closely 


* This nerve is considered by Mr. Newport as 


the analogue of the par vagum. 
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NERVOUS SYSTEM. (Comparative Anatomy.) 


~ 


Seren though by a lens the fissure or 
mark of separation may in some be perceived. 
The abdominal ganglia are of a lengt 
ovoid form; and when viewed couta a 
have a dense opaque white ae 
in particular ba pei eer as it were i 
neurilemma, have a distinctly bilobate ap 
pearance; in others there appears 
nucleus of opaque nervous matter(8&9); from 
each of them are given off three lateral pairs o 
nerves, some of which pass to su 
viscera, while others pass rourd the 
the larva to near the dorsal vessel, thus formir 
a nervous ring, open superiorly, which bein 
repeated in each segment, and the whole ec 
nected by commissures, forms a cont 
Series at once recognised as a column of ori- 
mary nervous rings, the type of the nervous 
system of the articulata; the eleventh 
twelfth ganglia are closely joined to each o 
and from the latter are given off two radi 
pairs of nerves, ing to the caudal e: 
of the larva. ere is also a. minute ner 
(fig. 348, f), which I have traced in this | 
passing ie at the angle of separation between 
the divided longitudinal connecting t th 
second and third, and per Pi and 
abdominal ganglia, and whi midway 
tween these ganglia, divided into a ri 
left transverse filament (g, g), each 
had connexion with the steel nerves 
from the ganglia themselves. Some have ec 
sidered these nerves as sympathetic, ¢ 
as motor, but from their principal b 
going to supply the trachee, I cesider a 
Mr. Newport, that they must be respira 
nerves. ’ 
I have examined the nervous cord in 
larva of Pontia brassica, naan r 
two species of Arctia, and have ¢ 
position of the ganglia, &c. to be the 
as the insect, however, advances towards t 
turity, considerable and important char sat 
place in the nervous system. it 
described and figured them in the Por 
sica,* and Mr. Newport has investiga’ 
with the minutest accuracy in the § 
gustri.+ It appears that during the p upa 
a contraction of the nervous colum st 


lace, the lia (more B} become 
ay third fourth, and fifth) become 
mated ; the distance between the ¢ 
glion and the first sub-ceso 
becomes much less, and the cesophage 
becomes much smaller; this is preparat 
the subsequent | concentration nd ji 
which we find in the perfect insect. — 
this latter phenomenon takes place, th 
just mentioned become consolidated to; 
and the oral nervous ring is scarcely 
tible: this is the case in the perfe 
Mormo maura (fig. 349), where also t 
dominal ganglia are snail (cc), and ¢ : 
the disappearance of two of the thoracie 
are situated at some distance fone 
which are of large size (6 6), and t 


* Entwickelungsgeschichte des § etterli 
+ Phil. Trans. for 1832 and 1834, 4 


NERVOUS SYSTEM. (Comparative Anatomy.) 


matter of which they are composed appears 
more dense and opaque in its texture.* 


Fig. 349. 


be 


aN 
IK 


f Ventral nervous cord of Mormo maura ( perfect state ), 
: 


magnified to about twice the natural size. 

a, infra-cesophageal ganglion. 6, large thoracic 
> ganglia. c¢, c, c, small abdominal ganglia. 
In Insects we observe a remarkable corre- 
 paled between the disposition of the ner- 
Yous system and the form of the animal, and 

_ this is conspicuous not only in the adult but 
“also in the larva state. Indeed the changes 
which take place in the arrangement of the 
_ hervous system as the creature passes from its 

‘immature to its mature condition, are sufficient 

to indicate that the same law which influences 

that alteration of form, promotes the adaptation 
of the nervous system to it; and yet, notwith- 

‘Standing its apparent complication, the nervous 

System of insects has the same physiological 

Signification as that of Mollusks. A cephalic 

Ganglion, with which are united the nerves of 

the organs of sense, is so connected with the 

Temaining ganglions, that its influence can ex- 

tend throughout the whole system. Each seg- 

ment is provided with a ganglion, which has 
no power beyond the limits of the segment, 
- which cannot act consentaneously with its 
fellows, except under the direction of the ce- 
ae ganglion. The pedal ganglion of Mol- 
usca is in insects represented by the aggregate 
of these ganglia of the segments, which are 
also doubtless the centres of the respiratory 
actions. And those nerves which, arising from 
the cephalic ganglion, are distributed to the 
ive organs, the stomato-gastric nerves, 
are analogous to the sympathetic or to the 


agus. 

baat has been supposed by some anatomists 
that a distinct isolation of motor and sensitive 
function occurs in the ganglionic and non-gan- 
glionic cords of the abdominal nervous chain of 


/ 


4 * This is, however, but a rough sketch of the 
interesting changes that take place in the nervous 
System during the progre s of the insect from its 
larva to its peifect s ate. Those who are interested 
in the matter, 1 beg leave to refer to Mr. Newport’s 
highly valuable paper, where, as I have before ob- 
served, the chanzes of the Sphinx ligustri are de- 
tailed with minute accuracy. See also INSECTA. 


613 
insects, as well as of other Articulatg (See 
Jig. 411, art. Insecta, vol. ii. p. 05a But 


there are many objections to this hypothesis, 
which, indeed, must be regarded as quite un- 
tenable. It has been founded upon the anato- 
mical fact, which is true as regards the verte- 
brata, that sensitive nerves have ganglions while 
the motor ones are devoid of them. But it is 
going too far to compare nerves and centres, 
and to argue from the nerves of vertebrata re- 
specting the centres of Invertebrata. More- 
over, as Prof. Owen remarks, the presence of 
ganglia on the sensitive roots of spinal nerves 
is not their constant character. This hypo- 
thesis also received some support from a doc- 
trine which was countenanced by Bell, namely, 
that the columns of the spinal cord of verte- 
brata corresponded in function with that of the 
roots of the nerves, the anterior columns being 
motor as the anterior roots were, and the poste- 
rior columns and roots being sensitive. But this 
doctrine is utterly without foundation, as will 
be shewn in a subsequent part of this article. 
Prof. Owen adduces an important fact respecting 
two nearly allied Crustacea, which further inva- 
lidates the supposed difference of function of the 
ganglionic and non-ganglionic columns. “ In 
the lobster ( Astacus) and in the hermit-crab 
(Pagurus) we have two opposite conditions 
of a large and important part of the trunk. In 
the lobster the abdomen or tail is encased in a 
series of calcareous rings forming a hard and 
insensible chain armour, but as it is almost the 
exclusive organ by which the animal swims, it 
enjoys considerable motor power, a large por- 
tion of the muscular system being devoted to it. 
In the hermit-crab, on the other hand, the mus- 
cular system is almost abrogated in the long 
abdomen, for this in fact takes no share in the 
locomotive functions of the body: it is occu- 
pied by part of the alimentary canal and by 
glandular organs: the sensibility of the external 
integument is not impaired or destroyed by the 
deposition of calcareous particles in its tissue, 
but it retains the necessary faculty of testing 
the smooth and unirritating condition of the 
inner surface of the deserted shell which the 
animal chooses for its abode: minute acetabula 
are developed in groups upon this sensitive 
integument, to which also delicate ciliated pro- 
cesses are attached. The muscular system is 
reduced to a few minute fasciculi of fibres regu- 
lating the action of the small terminal claspers. 
Now,” adds Professor Owen, “ if, as has been 
conjectured, the ganglionic enlargements of the 
abdominal cords monopolize the sensorial func- 
tions, and the non-ganglionic tracts the motor 
powers, we ought to find the nerves, which 
supply the muscles of tail constructed almost 
exclusively for locomotion, to be derived from 
non-ganglionic columns; whilst in the tail, 
which is almost as exclusively sensitive, the 
ganglions ought to have been large and nume- 
rous for the supply of nerves to the integument. 
The contrary, however, is the fact; six well- 
developed ganglions distribute nerves to the 
muscular fibres of the lobster’s tail; non-gan- 
glionic columns supply the sensitive tail of the 


614 


hermit crab. One ganglion, indeed, is present 
in the Pagurus, but both its situation and office 
alike militate against the hypothesis of its spe- 
cial subserviency to sensation: it is developed 
upon the end of the smooth abdominal chords, 
and seems to have been called into existence 
solely to regulate the actions of the muscles of 
the claspers by which the hermit keeps firm 
hold of the columella of its borrowed dwel- 
ling.” *} 

in reviewing these statements of the»ner- 
vous system of the entomoid Articulata, we 
observe that the superior ganglion of the pri- 
Mary nervous ring, or the cerebral ganglion, 
ey through several degrees of complication 
rom the Crustacea, where it presents only 
slight traces of a division laterally up to the 
Insecta, as in the bee for instance, where it 
preponderates greatly in size over the gan- 
glions, and where the sensorial nerves arising 
from it present distinct ganglionic enlarge- 
ments. e anterior or cephalic primary ner- 
vous ring itself we see to be gradually de- 
creasing in size from the Crustacea, where it is 
large and lengthened, to the highest Insecta, 
the Lepidoptera, where it is much smaller, 
and almost coalescing the superior and inferior 
ganglions developed on it into one ganglion. 
We observe that the number of primary ner- 
vous rings, with their ganglia, gradually be- 
comes more constricted from the Crustacea 
through the Myriapoda (where they are de- 
veloped in an undetermined length) and the 
Arachnida, where they are much fewer, to the 
Insecta, where, in their larva state, they ap- 
proach the Annelides, but in their perfect state 
we find them developed in a regular series, 
and more concentrated in the regions of the 
head, thorax, and abdomen. These anato- 
tical details, together with the complicated 
nature of the longitudinal commissures, a dis- 
tinct system of nerves supposed to be for re- 
Spiration, and a par vagum, demonstrate a 
close analogy between the ganglionic cord of 
the Insecta and the spinal cord of the Verte- 
brata, and may be considered as reasonable 
grounds for ranking this interesting tribe of 
animals the highest of the Articulata. 

Further details respecting the anatomy of the 
nervous system of Insects will be found in the 
article Insecta. 

Vertesrata.—We now to the last 
and highest group, the Vertebrata, where the 
powery nervous rings of the preceding classes 

ave become ganglions, and their commissures 
have become primary nervous rings. In each 
segment of their bodies there is but one gan- 
glion developed, but that one large, and situ- 
ated on the dorsal aspect, and each one in the 
different segments is united to the other by 
commissures, thus forming a large median ner- 
vous mass, the primary characteristic of a true 
cerebral system. This will be, of course, sub- 
ject to infinite modifications aud degrees of 
organization. In the lower Vertebrata the gan- 
glia and their commissures will be nearly 


* Owen’s Lectures, p. 171-72. 


NERVOUS SYSTEM. (Comparative Anatomy.) 


ually developed; in the higher ones the 
pone 1s Soe eetion will predominate; and — 
as these animals are vyte we pA 
dominance of ganglion, its great develo a 
takes place ior that -: of their body. which 
is itself the most highly developed, the head, — 
and the ganglionary mass itself is called the — 
brain. On the ye the developement of — 
the commissures, or of the longitudinal fibres, 
takes place in the opposing point to the he Z 
viz. the trunk, and from that results what is 
called familiarly the spinal marrow. Again, 
as it is the very characteristic of the nervous 
matter to accumulate and develop itself on t 
dorsal aspect in preference, it can easily be 
conceived that as the ganglionic nervous matter, — 
or brain, increases in developement, so will it 
influence the direction of the spinal marrow, 
and, indeed, also of the whole body. For 
instance, in the lower nervous formations the” 
brain and spinal marrow are perfectly hort 
zontal. ‘As the former proceeds in develope- 
ment, an angle, at first very acute, is formed, 
which gradually decreases until, in the human 
brain, the most perfect of all, it becomes acom 
plete right angle. Another important poit 
is, the number of ganglia and commissures tha 
may be developed. We have already observe 
that each segment of the body of the Ve 
brata contains a ganglion and a primary né 
vous ring: the number, therefore, of the 
latter is unfixed and variable, and depends e 
tirely on the number of the segments of 
body, or, in other words, the length of # 
spinal cord depends on the length of the an 
mal. But, with regard to the masses of gal 
glionic nervous matter situated in that segm 
of the body which is the most highly dev 
loped—the head—they ought to be develop 
in a manner fixed and determined ; and st 
indeed, is the case: a division into three 
observable in the brains of all the Vertebrat 
an anterior portion or cerebrum, @ poste 
portion or cerebellum, a median portion, 
tubercula quadrigemina. Thus the numbe 
ganglia forming the brain, the most hig 
organized part of the nervous mass, is def 
and invariable, while the number of yan 
forming the spinal cord, the least highl} 
ganized part of the nervous mass, is inde’ 
and variable. The three portions of the¢ 
bral mass, the anterior, median, and post 
will be designated by the names of first, se 
and third cerebral masses ; and we shal 
deavour to point out the analogies whieh 
of these portions bears in the brains of t 
ferent animals, as we ascend the scale, resp 
which anatomists have various opinions. — 

These observations being premised, we 
to the consideration of the vertebrated | 
individually, in the manner proposed, ~ 
mencing with the lowest, the fishes. = 

1. Pisces.—In these animals the ner 
system presents an immense variety of f 
and degrees of development. Even in- 
Cyclostomata, a division into brain and 8 
marrow (in the general acceptation of the ter” 
is evident: in the former, a division into ti 


‘ 


) 
| 


| 


NERVOUS SYSTEM. (Comparative Anatomy.) 


is at once seen; in the latter, the ganglia are 
numerous and undetermined. We will notice 
these parts separately. 

The spinal cord* (fig. 351, g,) is remarkable 
for its great relative size in this class of animals: 
it is continued (with but very few exceptions) 
the whole length of the vertebral column, even 
into the caudal vertebra, and it has on its an- 
terior and posterior aspects a longitudinal fis- 
sure (fig. 351, h), the latter being the deepest ; 
internally it is hollowed out by a canal (i) 
which traverses it in its whole extent, and 
which, at the upper part, immediately posterior 
to or underneath the cerebellum, forms a con- 
siderable dilatation or enlargement—the fourth 

 yentricle (fig. 352, e). The posterior fissure 
extends to this canal. In a river lamprey 
( Petromyzon fluvialis ), weighing 570 grains, 
brain weighs only four-tenths of a grain, 
while the spinal cord weighs three grains, the 
proportions being as 100: 750. We thus ob- 
serve how much the latter preponderates in 


| size, being seven and a half times heavier than 


the brain. 


It is inclosed in a semicartilaginous 


_ case, and I satisfactorily traced it into the ex- 


treme point of the caudal extremity of the 
animal : it presents a thin flattened appearance, 
_ so much so that no trace of a central canal is 
perceptible ; but immediately posterior to the 
Eo. the rudimentary corpora restiformia of the 
two lateral longitudinal columns diverge to 


_ form a large excavation, which is covered over 


a net-work of delicate vessels, a sort of 
us choroides ; this is the fourth ventricle. 
_ Amongst the true osseous fishes I have found 
acanal traversing the spinal marrow with this 
dilatation or ventricle at its superior portion, 
in the eel (Anguilla), perch ( Perca fluvialis), 
gurard ( Trigla gurnardus ), cod ( Gadus mo- 
vhua), mackarel (Scomber vulgaris), pike 
( Esox lucius ), roach ( Leuciscus rutilus ), dace 
Leuciscus vulgaris ), chub ( Leuciscus ?), 
carp( Cyprinus carpio ), and skate ( Raia ?) 
Tn the gurnard there are six pair of ganglia 
developed on the superior surface, immediately 
posterior to the cerebellum, at the origins of 
the nerves distributed to the large pectoral fins ; 
this remarkable conformation only exists in this 
genus. In all the other species the spinal cord 
is of nearly equal diameter throughout, except- 
ing towards its termination ; and in the dace I 
traced it running to the extremity of the tail, 
and ending in a point: in the moon fish ( Te- 
trodon mola) it is remarkably short, and termi- 
Nates in a true cauda equina. 
_ [Asimilar exception to the usual length of 
the spinal cord in fishes, is found in the Lophius 
_ piscatorius, in which that organ ceases as high 
as the eighth vertebra, and in one instance 
by Leuret as high as the second. 
rest of the canal is occupied by cauda 
equina. } 
The superior portion of the spinal cord, which 
takes the name of medulla oblongata, is large and 


* In the description of the spinal cord the terms 
anterior and posterior are used in the same signi- 
fication as in the human subject ; anterior to signify 
the surface next the bodies of the vertebrz, posterior 
that next the spinous processes. 


615 


broad in most fishes: on it are perceptible the 
corpora pyramidalia and restiformia; the t.ivaria 
are not yet develo The former, situated on 
either side of the anterior longitudinal groove, 
are flattened and broad, and are distinctly seen 
continuous with the crura cerebri, the pons 
Varolii being wanting. The corpora restiformia, 
or cerebellic fasciculi, are situated posteriorly ; 
they separate (as before observed) at their upper 
part to form the fourth ventricle, and pass after- 
wards into the cerebellum. According to 
Leuret there is no decussation of the fibres of 
the spinal cord in fishes. 

[A singular little fish which haslately attracted 
the attention of naturalists, and for the reception 
of which Mr. Yarrell has instituted the genus 
Amphioxus, exhibits the apparent anomaly of 
an absence of all outward distinction between 
the brain and spinal cord. It is the Amphioxus 
Lanceolatus, of which a very perfect specimen 
has lately been presented to the Museum of 
King’s College, London, by Professor Edward 
Forbes. 

An elaborate examination of the anatomy 
of this little creature has been published by 
Mr. John Goodsir in the Transactions of the 
Royal Society of Edinburgh, from which we 
extract the following account of its neuro- 
skeleton and of its nervous system. 

“ Neuro-skeleton.—The osseous system, pro- 
perly so called, consists of a “ chorda dorsalis” 
tapering at both ends, without the vestige of a 
cranium, and of a dorsal and ventral series of 
cells, the germs of superior and inferior inter- 
spinous bones and fin rays. The “ chorda 
dorsalis” consists of sixty to seventy vertebrae, 
the divisions between which are indicated by 
slight bulgings, and lines passing obliquely from 
above downwards on the sides of the column. 
In this way a separation into individual ver- 
tebre is rather indicated than proved to exist; 
for although the column has certainly a ten- 
dency to divide at the points above-mentioned, 
yet that division is rather artificial than natural. 
There’ is no difficulty in ascertaining above 
sixty divisions, those at each end above the 
number stated run so much into one another 
that no correct result can be obtained. 

_ The chorda dorsalis is formed externally 
of a fibrous sheath, and internally of an im- 
mense number of lamin, each of the size and 
shape of a section of the column at the place 
where it is situated. When any portion of the 
column is removed, these plates may be pushed 
out from the tubular sheath, like a pile of coins. 
They have no great adhesion to one another, 
are of the consistence of parchment, and appear 
like flattened bladders, as if formed of two 
tough fibrous membranes pressed together. 

“ As the fibres of the sheath are principally 
circular, provision is made for longitudinal 
strains on the column by the addition of a su- 
perior and inferior vertebral ligament, as strong 
cords stretching along its dorsal and ventral 
aspects. The superior ligament lies imme- 
diately under the spinal cord, and may be re- 
cognized as a very tough filament, when the 
column is torn asunder, or some of the ver- 
tebree removed. The inferior ligament may be 


616 


raised from the inferior 
surface of the column in 


%y = the form of a tough rib- 
Z ~— bon. From the sides of 
= the column aponeurotic 
lamine pass off to form 


septa of attachment be- 
tween the muscular bun- 
dies; and along the me- 
sial plane above the co- 
lumn, a similar lamina 
separates the superior bun- 
dies of each side, and by 
splitting below and run- 
ning into the sides of the 
column, forms a fibrous 
canal for the spinal cord. 
Foramina exist all along 
the sides of this canal for 
the passage of the nerves. 
A similar septum is situ- 
ated along the inferior part 
of the column, from the 

where the inferior 
muscular bundles unite at 
the anus, to the extremity 
of the tail. Along the 
superior edge of the apo- 
neurotic septum, between 
the dorsal muscular bun- 
dles, and stretching from 
the anterior point of the 
vertebral column toa point 
beyond the anus, and half 
embedded between the su- 
perior extremities of the 
muscles, is a series of 
closed cells of a flattened 
cylindrical form, adhering 
firmly to one another by 
their bases, so as to pre- 
sent the appearance of a 
tube flattened on the sides 
with septa at regular dis- 
tances. Each of these 
cells is full of a trans- 
parent fluid, in the centre 
of which is an irregular 
mass of semi-opaque glo- 
bules, apparently cells. 
This series of cylindrical 
sacs consists of the ru- 
diments of inter-spinous 
i bones, and probably of fin 

Fig. 350. rays, and if attached be- 
The nervous system of low to the fibrous inter- 
Amphiosxus lanceolatus. muscular 1 pe half co- 

a,a, the spinal cord; vered on each side by the 
b, the first pair of Jateral muscles, and en- 
Beret ical etal losed above by the tegu 

. : mentary fold which con- 
“a tales stitutes | the dorsal fin. 

“ A similar series of cells, with the same 
relations, is situated on the ventral surface of 
the body, and stretches from the spot where 
the abdominal folds terminate, to a point 
nearly opposite the termination of the dorsal 
series. 

“ Nervous system. —The spinal cord is 


WI 


a 


= — 


MT 


TI 


NERVOUS SYSTEM. (Comparative Anatomy.) 


situated on the upper surface of the chorda 
dorsalis, enclosed in the canal formed in the 
manner above on Ply whole | 
length of this canal is displa emoving: 
aaa and then carefully opened, he 
spinal cord is seen lying in the interior, » 
nerves passing out from it on each side. I 
stretches along the whole length of the spi 
is acuminated at both ends, and exhibits 
the slightest trace of cerebral development. 
its middle third, where it is most develope 
has the form of a ribbon, the thickness o h 
is about one-fourth or one-fifth of its breadth; 
and along this portion, also, it poe 
ae surface © hnlal but low groove. 
e other two-thirds of the cord are not so flat 
and are not grooved above, are smaller than 
the middle third, and taper gradually; the one 
towards the anterior, the other towards the 
posterior extremity of the vertebral column. 
A streak of black pigment runs along thi 
middle of the upper surface of the cord. 1] 
is situated in the groove already described 
and is in greater abundance anteriorly and p 
teriorly, where the nerves off at short 
intervals, than at the middle or broadest par 
of the organ. From fifty-five to sixty ner 
pass off from each side of the cord; but, : 
the anterior and posterior vertebra are yer 
minute, and run into one another, and as tl 
spinal cord itself almost disappears at the 
extremities, it is impossible to ascertain 
exact number, either of vertebre or of s 
nerves. These nerves are not connected to 
spinal marrow by double roots, but are in 
at once into its edges in the form of 
cords. q 
“ The nerves pass out of the inte nt 
foramina of the membranous spinal can: 
divide into two sets of branches, one of wl 
run up between the dorsal muscular bund! 
(dorsal branches); the other (ventral branch 
run obliquely downwards and back 
the surface of the fibrous sheath of the 
column ; attach themselves to the antero-j 
terior aspect of each of the inferior museu 
bundles, and may be distinctly traced b 
the extremity of each bundle. When an ¢ 
animal is examined by transmitted light, a 
sufficient magnifying power, the anterior € 
mity of the spinal cord is observed, as be 
mentioned, to terminate in a minute fila 
above the anterior extremity of the vert 
column. The first pair of nerves is 
minute, and passes into the membranous: 
at the anterior superior angle of the mé 
The second pair is considerably larger, 
like the first pair, passes out of the eane 
front of the anterior muscular bundle. ~ 
second pair immediately sends a con: 
branch (corresponding to the dorsal bran 
of the other nerves) upwards and backwi 
along the anterior edge of the first dorsal m 
cular bundle. This branch joins the dor 
branch of the third pair, and, passing on, jo 
a considerable number of these in success 
and at last becomes too minute to be ff 
farther. After sending off this dorsal brant 
the second pair passes downwards anc 


’ 


Ad 


ae. = 


gy 


NERVOUS SYSTEM. (Comparative Anatomy.) 


wards on each side above the hyoid apparatus, 
and joins all the ventral branches of the other 
spinal nerves in succession, as its dorsal branch 

id along the back. This ventral branch of 
the second pair is very conspicuous, and may 
be easily traced along the line formed by the 
inferior extremities of the ventral divisions of 
the muscular bundles, the ventral branches of 
the other nerves joining it at acute angles 
between each bundle. It may be traced be- 


_ yond the anus, but is lost sight of near the 


extremity of the tail. Twigs undoubtedly pass 
from the spinal and lateral nerves towards the 
abdominal surface of the body, but, on account 
of their minuteness, and the difficulty of de- 
tecting them in detached portions of the 
abdominal membrane, they could not be satis- 
factorily seen. 

“ When a portion of the spinal cord is 
examined under a sufficient magnifying power, 
itis seen to be composed entirely of nucleated 


_ cells, very loosely attached to one another, but 


i 


enclosed in an excessively delicate covering of 


mater. The cells are not arranged in any 

Refinite direction, except in the middle third 
of the cord, where they assume a longitudinal 
linear direction, but without altering their 
Primitive spherical form. The black pigment, 
eiserty mentioned as existing more particu- 
larly on the upper surface and groove, is 
observed to be more abundant opposite the 
origin of the nerves; and, as it is regularly 
arranged in this manner in dark masses along 
the anterior and posterior thirds of the cord, 
the organ in these places, on superficial inspec- 
tion, resembles much the abdominal ganglionic 
cord of an annulose animal. Along the middle 
third the pigment is not so regular, but appears 
in spots at short intervals. When any portion 
of the cord, however, is slightly compressed, 
and microscopically examined, it becomes evi- 
dent that there is, along the groove and mesial 
line of its upper surface, a band, consisting of 
cells of a larger size than those composing the 
rest of the organ. Some of these cells only 
are filled with black pigment, but all of them 
contain a fluid of a brown tint, which renders 
the tract of large cells distinctly visible. When 
the compression is increased the cells burst ; 
and the fluid which flows from the central 
tract is seen to contain jet-black granules, 
be age may be detected as they escape from the 
cells. 

“ The nerves consist of primitive fibres, of 
a cylindrical shape, with faint longitudinal 
strie. The primitive fibres of a trunk pass off 
into a branch, in the usual way, without 
dividing ; and, where the trunks join the spinal 
cord, the primitive fibres are seen to approach 
close to it, but without passing into it. The 
greater part of the slightly protuberant origin 
consisting of the nucleated cells of the cord, 
with a few pigment cells interspersed, the 
exact mode of termination of the central ex- 
tremities of the primitive nervous fibres could 
not be detected.’ 

We hope we may be excused for quoting the 
following additional remarks. 
“ One of the most remarkable peculiarities 


617 


in the Lancelet is the absence of thé brain. 
Retzius, indeed, describes the spinal marrow 
as terminating considerably behind the anterior 
extremity of the chorda dorsalis, in a brain 
which exhibits scarcely any dilatation; but 
careful examination of the dissection of my 
own specimen, which I have also submitted to 
the inspection of Dr. John Reid, and of other 
competent judges, has convinced me that the 
spinal cord, which may be traced with’ the 
greatest ease to within 1-16th of an inch of 
the extremity of the chorda dorsalis, does not 
dilate into a brain at all. It may be urged that 
we ought to consider the anterior half of the 
middle third of the spinal marrow, where it is 
most developed, to be the brain, and all that 
portion of the chorda dorsalis which is in con- 
nection with the branchial cavity, as the cra- 
nium. That this does not express the true 
relation of the parts, is evident from the fact, 
that this portion of the cord, to its very extre- 
mity, gives off nerves, which are too numerous 
to be considered as cerebral, but more espe- 
cially from the mode of distribution of the 
first and second ‘pairs, which, in my opinion, 
proves the anterior pointed extremity to be the 
representative of the brain of the more highly 
developed vertebrata. A brain of such sim- 
plicity necessarily precludes, on anatomical 
grounds alone, the existence of organs of vision 
and of hearing. These special organs, deve- 
loped in the vertebrata at least, in a direct 
relation with the cephalic integuments and the 
brain, could not exist, even in the form of 
appreciable germs, in the Lancelet. The black 
spot which Retzius took for the rudiment of an* 
eye may probably have been, what also deceived 
me at first, a portion of the black mud which 
floats about in the branchial cavity, and which 
adheres cbstinately to the parts in the neigh- 
bourhood of the oral filaments. The first pair 
of nerves, although very minute, in accordance 
with the slight development of the parts about 
the snout, and the want of special organs of 
sense, might, from their position and relations, 
be considered as corresponding to the trifacial 
in the higher vertebrata. The second pair 
appears to be the vagus, not only from its 
distribution as a longitudinal filament on each 
side of the body, as in other fishes, but also 
from its relations to the hyoid apparatus and 
branchial cavity, to which division of organs 
the eighth pair of fishes is specially devoted. 
The distribution of a branch of this nerve, 
however, along the base of the dorsal fin, and 
the course: of the posterior part of the main 
branch, would appear to shew that this nerve, 
which [ have provisionally denominated the 
vagus, is, in fact, the trifacial, which, in the 
higher fishes, is not only distributed to all the 
fins, but holds exactly the same relations to the 
dorsal and anal fins, and to the spinal nerves, 
as the nerve now under consideration in the 
Lancelet. 

“The peculiarities in the structure of the 
spinal cord are not less remarkable than those 
of its configuration. It is difficult to under- 
stand, according to the received opinions on 
the subject, how a spinal cord destitute of 


618 


primitive fibres or tubes, and com alto- 
gether of isolated cells, arranged in a linear 
direction only towards the middle of the cord, 
can transmit influences in any given direction ; 
and more especially how the tract of black or 
grey matter, if it exercises any liar fune- 


tion (excito-motory) communicates with the 
origin of the nerves. The nerves, also, are 
remarkable, originating in single roots, and 
containing in their composition one kind only 
of primitive fibres (cylindrical).”’] 


Fig. 351. 


a, first cerebral mass 
or olfactory tubercle. 6, 
olfactory tubercle sliced, 
showing its solid struc- 
ture. c, second cerebral 
mass or optic lobe, of large 
relative size. d, optic 
lobe, cut open to shew 
the internal cavity. e, 
tubercles in the cavity. 
J, third cerebral mass or 
cerebellum, tongue-sha- 
ped. g, spinal cord. h, 
posterior longitudinal fis- 
sure of spinal cord. 4, 
central canal of spinal 
cord. _ k, olfactory nerves. 
l, optic nerves. m, fifth 
pair of nerves, m, acons- 
tic nerve. 0, glossopha- 
ryngeal nerve of Cuvier. 
p» eighth pair—par va- 
gum. gq, bristle passed 
under the cerebellum and 
along the fourth ventricle, 
‘shewing the communica- 
tion of this latter with the 
cavity of the optic lobes 
or third ventricle. 


Brain and portion of spinal marrow of Gadus morhua 
( Cod-fish ), about natural size. 


The brain, especially in the lowest of the 
fishes, presents quite the appearance of a series 
of ganglia developed on the superior surface of 
the cords of the spinal marrow (fig. 351, a, b, 
c). In many species it is extremely small, and 
by no means fills the cranial cavity; in the 
mackarel, the volume of the brain and of the 
cavity destined to receive it are nearly equal. 
Its very small size is at once evident by com- 
paring its weight with that of the whole body 
of the animal: thus in a chub, weighing 842 
scruples, the brain weighed only one scruple, 
the proportions being as 100 : 84200; ina 
carp, weighing 11280 grains, the brain weighed 
only fourteen grains, the proportions being as 
100:80600 ; in a roach, weighing 5030 grains, 
the brain weighed only nine grains and a half, 
the proportions being as 100: 52,900; and, as 
before observed, in a lamprey weighing 570 
grains, the brain weighed only four-tenths of a 

in, the proportions being as 100 : 142,500. 

In Leuret’s table a discrepancy still more 
striking oe be observed. is author gives 
as a mean the proportion 1: 5668.7] We thus 
observe how small is the proportion which the 
size of the brain bears to that of the rest of the 
body, and consequently how imperfect is as yet 
the developement of the encephalic mass. 


* Systéme nerveux, t.i. p. 153, 


NERVOUS SYSTEM. (Comparative Awatomy.) a 


On taking a general review of the con- 
formation of the cerebral masses forming the 
brain of fishes, we find it to consist of a suite 
of ganglia arranged behind each other—tw 
pairs and a single one: ist, there are two gan 
glia or lobes, situated the most anteriorly, the 
olfactory lobes; immediately behind h ar 
two others, generally of larger size, the 
lobes; and behind these, in, is a sing 
ganglion or lobe, situated in the median line 
the cerebellum. On the inferior surface, im 
mediately underneath the optic lobes, are tw 
more ganglia. The names thas haste el iv 
to these parts are extremely various; and r 
specting the relations and ies which 
bear to the brain of the higher animals, 
wane of opinion exists. ‘on _ 

ist. The olfactory tubercles, or cerebr 
mass (figs. 351 and 352, a, a), which, wil 
Arasky,* Serres,+ Desmouli Carus,§ an 
Tiedemann, ||and contrary to Collins,{{ Monro, 
Camper,t+ Ebel,{} Treviranus,§§ and Cuvier, 
I consider as analogous to the cerebral het 
spheres of man, are generally of small size, a 
contain no cavity (fig. 351, 6). In the 
they consist of three pairs of ganglia, wh 
increase in comparative size from before 
behind ; in the carp and mackarel, of only ¢ 


Fig. 352. 


er 


Brain and portion of spinal marrow of L 

( Chub ), about natural poly. 
a, first cerebral mass or olfactory tube | 

second cerebral mass or optic lobe. e, thi 

bral mass or cerebellum. d, spinal marrow 

its posterior longitudinal fissure. e, fourt ' 

cle. hk, olfactory nerve. 1, tuberculous | 

ment of the olfactory nerve. 


* De piscium cerebro. a. i 
+ Anatomie Comparée du Cervean. r i 
¢ Comparative Description of the Braiz 
Four Classes of Vertebrated Animals. 
§ Anatomie Comparée. 
|| Anatomy of the Foetal Brain. s 
considers them as more particularly * 
to the corpora striata, on the external b 
which the membranous hemispheres a e 
elévated.” ay 
4] System of Anatomy. edit 
** Anat. of Fishes. : 
tt Memoir on the Ear of Fishes, 1 
tt Observationes Nevrologice ex Ani 
parata, 1788. 5 
§§ Memoir on the Brain, 1817. 
\\} Lecons d’Anatomie Comparée. 


pSTY 


2 
zg 
¢ 


" 


NERVOUS SYSTEM. (Comparative Anatomy.) 


ganglion, situated in the median line; in the 
perch, gurnard, cod, pike, roach, chub, carp, 
and dace, of a pair of ganglia, and this is the 
most usual arrangement. In the skate, one of 
the Plagiostome fishes, where the brain is alto- 
gether more highly developed, there is one large 
ganglion or cerebral mass; it is solid, but in 
some of the sharks it contains a cavity. From 
these eminences, whatever be their number, the 


_ olfactory nerves (processes or lobes) arise (figs. 


350 and 351, k, k), which, running together in 
an osseous canal for some little distance, 
diverge, and form large tubercles on the cribri- 
form plate of the ethmoid bone (fig. 352, 1); 
from these tubercles nerves arise, which are 


distributed to the pituitary membrane of the 
1 nose. 


2dly. The optic lobes, or second cerebral 


mass (figs. 351 and 352, c,b), which Collins,* 
- Monro,* Camper,* Ebel,* Treviranus,* and 


Cuvier,* considered as analogous to the cere- 
ral hemispheres of the mammalia, but which, 

with Serres,+ Desmoulins,t Arsaky,+ Carus,+ 
and Tiedemann,+ I consider as analogous to 
the tubercula quadrigemina, are generally of 
large size in fishes, and contain internal tuber- 
cles and cavities, which communicate with the 
rth ventricle. These masses may be said to 


arrive in this class at their maximum of deve- 


ment, and we may recollect to have traced 
out their first radiments in the cerebral ganglion 
of the Gasteropodous Mollusca, and to have 
noticed their successive complication of deve- 
ent in the varied classes of articulated 
animals. In the lamprey these optic lobes are 
er and more developed than any other parts 
of the brain; and this is what we should be 
led to expect from the low organization and 
vermiform nature of these Cyclostomous fishes : 
they contained in their interior a cavity. In 
the eel, perch, cod (fig. 351, c), gurnard, 
mackarel, pike, roach, chub (fig. 352, 6), carp, 
and dace, true osseous fishes, the optic lobes 
are well developed, and, excepting in the eel, 
much larger than the olfactory tubercles before 
them ; they are hollow, and contained tubercles, 
which vary in number, size, and position. Inthe 
eel there are two of these tubercles in each hollow 
lobe, equal in size, and situated posteriorly ; in the 
cod there are also two, the outermost being the 
largest, and smooth, the inner one being smaller, 
and constricted in the middle (fig. 351, e); in 
the mackarel there are two, the anterior one 
being exceedingly small, the posterior much 
larger, slightly convoluted, somewhat resemb- 
ing the Greek letter =; in the pike there are 
two, and the floor of the cavity had a striated 
appearance; in the roach there is only one 
large tubercle; and in the carp there are two, 
the anterior being rather long, and passing 
backwards in a curved manner. From these 
lobes the optic nerves (fig. 351, /) arise, and 
cross each other, without, however, any other 
connexion than mere cellular tissue. The third, 
fourth, and sixth pairs have also their origins 
from these ganglia. 
[The optic lobes have a direct relation in 


* Op. cit. + Op. cit. 


619 


point of volume with that of the eyes, and in 
the pleuronecta, in which the eyes are 6 une- 
qual size, Gottsche states that the optic lobes 
are unequal. | 

The tubercles situated on the inferior surface 
of the brain, and immediately beneath the 
optic lobes just described, are generally of 
small size, and seldom contain a cavity; be- 
tween them are the infundibulum and pituit 
gland, generally of very large proportional size, 
Respecting their analogies and names, very 
much difference of opinion exists. Haller 
termed them the inferior protuberances of the 
olfactory nerves ;* Cuvier considered them as 
the true optic lobes ;+ Dr. Grant calls them 
the cerebral hemispheres, and supposes they 
are the representatives of those parts in the 
higher animals ;{ Serres considers them appen- 
dages to the optic nerves, and analogous to the 
tuber cinereum ;§ Vicq d’Azyr,|| Arsaky,§] and 
Carus, consider them analogous to the corpora 
mamumnillaria of higher animals :** Tiedemannt+ 
does not decide upon this point, but judges 
(from the situation and form of the tubercles) 
that the latter hypothesis is the more probable 
one. 

3dly. The cerebellum, or third cerebral mass 
(fig. 351, f; fig. 352, c), is but imperfectly 
developed in fishes ; it is generally of a round 
form, and covers in the cavity formed by the 
divergence of the two cords of the spinal mar- 
row and an enlargement of its canal, the fourth 
ventricle. In the lamprey there are scarcely 
any traces of a cerebellum, a thin transverse 
band of medullary matter being all that stands 
for it; the fourth ventricle is here, therefore, 
quite open and exposed. In the eel it is large, 
and of a rounded form ; in the perch its sum- 
mit is directed backwards; in the mackarel, 
forwards; in the cod (fig. 351, f) and pike it 
consists of a tongue-shaped lobe ; in the gur- 
nard, roach, chub (fig. 352, c), and dace, it is 
round, and of moderate size; in the carp it is 
also of a rounded form, but immediately be- 
hind and below it is situated another ganglion 
of smaller size, on each of which is a larger 
ganglion, principally destined for the origin of 
the branchial nerves, thus rendering the struc- 
ture of the cerebellum very complicated, and 
its size very voluminous. In the Plagiostome 
fishes the cerebellum is much more highly de- 
veloped. In the skate it is of large relative 
size, furnished with two lateral appendages, 
the commencement of lateral hemispheres, on 
the external surface of which transverse and 
longitudinal strie were developed. 

On reviewing these statements of the nervous 
system of the fishes, we observe two things 
that more particularly mark its low organization 
—the equality and the horizontal position of the 
brain and spinal marrow. In fact, as regards 


* Opera minora, vol. ii. 

+ Anatomie (omparée. 

¢ Lectures on Comparative Anatomy. 
Anatomie Comparée du Cerveau. 

i Opera minora. 

{ De piscium cerebro. 

**® Anatomie Comparée. 

tt Anatomy of the Feetal Brain. 


620 


the mass of nervous matter, it is greatly in 
favour of the spinal marrow, though, as regards 
complexity of structure, the brain preponde- 
rates. Again, the extreme smallness of this 
latter compared to the rest of the body, the 
simple formation of the different masses com- 
posing it, and the predominance of the median 
one, (which in the lower animals is the only 
one developed,) are points that also mark its 
low degree of developement. Still the ground- 
work of the most important structures has been 
laid, and we shal! trace these identical parts in 
the succeeding classes of animals through vari- 
ous modifications of form and phases of deve- 
fopement. 

2and 3. Amputpra anp Reptiria.—We 
now proceed to the Amphibia, the Batrachia of 
Cuvier, which, in a system of arrangement, 
must be considered as a class distinct from the 
true Reptilia; but their nervous system pre- 
senting so great a similarity in structure and 
conformation to that class, and, indeed, differ- 
ing only in an inferiority of developement, we 
will, to save time and space, notice the two 
classes of Amphibia and true Reptilia con- 
jointly. The nervous system in these animals 
bears a great similarity in structure and deve- 
lopement to the fishes. 

The spinal cord presents much the same cha- 
racter as in the class just described, with regard 
to its relative size, its extent, (excepting in the 
frog,) and its physical conformation. Ina 
species of Triton weighing 39 grains, the spinal 
marrow weighed } grain, and the brain only 4 
grain, the proportion being as 100 to 180. We 
thus observe that the weight of the spinal mar- 
row preponderates over that of the brain, al- 
though not to so great an extent as in the fishes, 
in consequence of the increased developement 
of the latter. In most of the Amphibia, and 
in all the Reptilia, the spinal cord passes down 
the whole length of the caudal vertebree, as in 
the fishes, but to this the frog forms an exce 
tion. In that animal it descends no lower in 
its adult state than barely midway between the 
anterior and posterior extremities, and termi- 
nates by a few nervous filaments, which pass 
downwards towards the sacrum; in the young 
and tadpole state, however, it is prolonged 
into the coccygeal vertebre, and terminates in 
a point. The form and structure of the spinal 
cord, and of the medulla oblongata, differ but 
little from what has been described in the 
fishes. In the triton and frog there is a lon- 
gitudinal fissure on its anterior and posterior 
aspects and a central canal communicating with 
the cavity of the fourth ventricle which is very 
large, covered over by a vascular plexus, is 
formed in the same manner, and bears great 
resemblance to the fourth ventricle described 
in the lamprey: in the lumbar region the 
spinal cord is thickened where the nerves of 

e extremities are given off; in the tadpole state, 
however, no such enlargement is visible. 
Amongst the true Reptilia, in the ringed snake 
( Coluber natrix ), lizard ( Lacerta viridis), and 
turtle ( Testudo mydas, fig. 353), the spinal cord 
has an anterior and posterior longitudinal fis- 
sure, and a central canal (g) communicating 


NERVOUS SYSTEM. (Comparative Anatomy.) 


with the fourth ventricle (/), which in the 
ringed snake and lizard is small, but deep ; in 
the turtle, large, but shallow, and partly €o- — 
vered in by the cerebellum. According to~ 
Bojanus,* the spinal cord in the Chelonia be- 
comes enlarged where the nerves for the ante- 
rior and posterior extremities are given off, and 
very thin between those enlargements. Carusf 
has observed the same enlargements, but ii 
less degree, in a young crocodile. 

The brain is composed of a suite of gangliz 
approaching very much in form and charac 
to the fishes, especially the Rays and Sharks. 
In the triton (Triton cristata), frog (Ran 
temporaria), 


sae 


viper (Coluber verus), rin, 


snake (Coluber natrix), lizard (Lacerta viridis, 
fig. 354), and turtle (Testudo mydas, fig. 353) 
ig. 353. a, first cerebral mass 


| 
| 


or cerebral hemisph 
__ b*, first cerebral mass ex 
open, shewing its inte 
nal cavity and tub 
b, seconu 
or opticlobe, c*, 
cerebral mass cut op 

shewing the small inte 
nal cavity. c¢, third ce: 
bral mass or cerebellui 


ing cavit 
l, bristle shewing t 
communication betw 
the cavity of the olfacto 
nerve and the cer 
hemisphere. m, 

shewing the commu 
tion between the ¢ 
of the optic lobe and 
fourth ventricle. m,t 


raise it upware 
the fourth vent: 
distinctly, 
Brain and portion of spinal marrow o; 
gr pet fos: natural  & el 
it fills the cranial cavity destined to rece? 
though that cavity is very small when con 
with the whole head ; thus the size of thé 
is no criterion for the size of the brain 
weight, too, when compared with the bor 
another proof of its small size. In a 
weighing npwenia of 50 pounds, the 
(with the olfactory nerves, and a very 
portion of the spinal marrow), weighe 
77 grains, the proportions beingas 100:4¢ 
and, as before observed, in a triton weighi 
grains, the brain weighed only } grain, the 
portions being as 100 : 27,300. a 
On taking a general review of its struct 
we find, as before, three principal parts to 


* Anatome testudinis Europea. 
+ Op. cit. vol. i, p. 78. 


: 
| 
| 


. 


NERVOUS SYSTEM. (Comparative Anatomy.) 


cupy our attention,—the olfactory tubercles, 
situated most anteriorly, the optic lobes, situated 
posteriorly to these, and the cerebellum. 

ist. The olfactory tubercles, or first cere- 
bral mass (figs. 352, 353, a, a, a), now be- 
come obviously the cerebral hemispheres, are 
of an increased proportional size, are com- 
Mencing to cover the tubercula quadrige- 
mina, and contain a cavity which was first 
developed in the Plagiostome fishes ; they are 
Very various as to form. Amongst the Am- 
phibia, in the triton they are elongated and 
oblong; in the frog, more oval they are united 
at their anterior parts by a commissure, but 
posteriorly they are separated. Amongst the 
true Reptilia, in the viper and ringed snake 
poy are of a rounded form, and extended late- 

lly; in the lizard and turtle they are oval 
(figs. 353, 354, a,a); in the crocodile they 
are more extended laterally. On cutting into 
them, in the turtle there is found an oblong 
tubercle analogous to the corpus striatum (fig. 
353, b*), on the inner side of which is a plexus 
choroides. From the anterior part of these 
hemispheres in the different animals mentioned, 
the olfactory nerves arise, and run forwards to 
the cribriform plate of the ethmoid bone, on 
the upper surface of which, in the viper and 
lizard, they form a bulbous enlargement (fig. 
354, g): in the turtle this is wanting, but at 
their origin they form a large round hollow 
Swelling, situated immediately anterior to the 


_ cerebral hemispheres, and communicating with 


the cavities in their interior (fig. 353, i, k, /). 


Fig. 354. 


Brain and portion of spinal cord of La- 
certa viridis (lizard ), slightly magnified. 


a, first cerebral mass or cerebral 
hemispheres. 6, second cerebral mass 
or optic lobes. c, third cerebral mass 
or cerebellum. d, spinal cord, with 
its posterior longitudinal fissure. e, 
fourth ventricle. f, Pineal gland. g, 
olfactory nerves, with their bulbous 
enlargements, 


2d. The optic lobes, or second cerebral mass 
(figs. 353, 354, 6, b, 6), are of small size, 
and are more solid than the same parts in the 
fishes, the internal cavity being smaller: we 
thus see them gradually approaching to the 
form and character of the tubercula quadrige- 
mina of the Mammalia, and of wd Cf In the 
triton, frog viper, ringed snake, lizard (fig.354), 
and er Cig. 353); they are of a rounded 
form, and situated on a plane immediately pos- 
terior to the cerebral hemispheres. In all these 
species there is found also, immediately anterior 


to them, and partly covered by the cerebral © 


hemispheres, a pair of small ganglia, analogous 


’ to the optic thalami of the human brain, on the 


superior surface of which was situated the pineal 
gland (fig. 354). These different eminences 
give origin to the fibres of the optic nerves. 

3d. The third cerebral mass, or cerebellum 
(figs. 353, 354, c), presents some inte- 
resting grades of developement in these two 


621 


classes of animals. In all of them it is small, 
in most of them extremely small, an@:overs 
in the fourth ventricle in a similar manner to 
what has been described in the fishes. In 
the triton and frog it consists of a thin 
transverse band of medullary matter, pre- 
cisely analogous to the cerebellum of the lam- 
prey, and, as in that animal, leaving the fourth 
ventricle quite open and exposed : in the viper 
and lizard (fig. 353) it presents a similar ap- 
pearance, but the band of medullary matter is 
rather thicker; in the turtle (fig. 352) it con- 
sists of a tongue-shaped lobe, very similar to 
the cerebellum of the cod: there are very dis- 
tinct lateral appendages, the rudiments of 
which we first observed in the Plagiostome 
fishes, and which we shall trace in the suc- 
ceeding classes to increased degrees of deve- 
lopement: these lateral appendages are found 
also in the crocodile; they lead us, by strict 
analogies, to the cerebellum of the birds. 

On reviewing these statements of the ner- 
vous system of the Reptilia, we observe that 
the equality and horizontality of the brain and 
spinal marrow again claim our attention as 
marks of low organization. Still, however, 
the preponderance of the spinal marrow over 
the brain is less, while the weight of this latter, 
compared with the body, is greater. The first 
cerebral mass has increased in size; cavities 
are developed in its interior, and it is united 
into two portions, which are divided by a com- 
missure. The second cerebral mass, or tuber- 
cula quadrigemina, has decreased in size, and 
the cavities are much smaller. The third cere- 
bral mass, or cerebellum, is in the lower Rep- 
tilia imperfectly developed, but in the higher 
ones it is of some size, and marked by ex- 
ternal strie. 

4. Aves.—In the class Aves, or birds, the 
nervous centre has acquired a high degree of 
developement in all its parts, but particularly 
as regards the cerebellum, and the different 
portions composing the cerebral mass are ar- 
ranged more above and less behind each other. 
The spinal cord (fig. 355, d) is of less re- 
lative size, and of less extent, than in the fishes 
and reptiles, but it still is traversed by an 
anterior and posterior longitudinal fissure, and 
still contains a central canal. In a pigeon 
weighing (according to Carns) eight ounces, 
(360 grains) the brain weighed 37 grains, and 
the spinal marrow only 11 grains, the propor- 
tion bene as 100:30. We thus observe that 
the brain now preponderates in size over the 
spinal cord for the first time; this at once 
marks its increased developement. Where the 
nerves supplying the anterior and posterior ex- 
tremities are given off, the spinal cord presents 
distinct enlargements, the inferior of which is 
the largest, and is placed in the sacrum : this 
may be considered as the termination of the 
spinal cord, for Carus considers that portion 
passing through the coccygeal vertebra to be 
only a large terminal filament. <A canal passes 
through the whole extent of the spinal cord, 
which, at the inferior enlargement, forms a 
large and remarkable excavation, called the 


622 


thomboidal sinus: this may be seen in the 
goose. The medulla oblongata, with the py- 
ramidal and cerebellic fasciculi, present similar 
characters to the same parts in the fishes; the 
corpora olivaria, and pons Varolii, are not yet 
developed. 

The brain of birds is composed of a similar 
number of as in the reptiles, but they are 
more highly developed, and they are no longer 
arran in a longitudinal series as formerly, 
but more on the top of each other. In the 
sea-gull (Larus cyanorhynchus, fig. 355), 
— (Scolopax gallinula), red start ( Mota- 
ci ?), goldfinch ( Fringilla carduelis ), 
fowl (Phasianus gallus, fig. 356), pigeon 
( Columba ——?), and hawk (Falco nisus ), 
the brain fills entirely the cranial cavity, this 
cavity now corresponding exactly with the size 
and form of the head. It is of increased re- 
lative size compared with the body: in a pi- 
geon, weighing according to Carus 3360 grains, 
the brain weighed 37 grains; the proportions 
being as 100 : 9,100. 

On taking a review of its structure, we find 
three principal portions, as heretofore, to oc- 
cupy our attention, the conformation of each 
being very uniform in the whole class: 1st, the 
cerebral hemispheres ; 2d, the optic lobes; 3d, 
the cerebellum. 

ist. The cerebral hemispheres, or first cere- 
bral mass, are large (figs. 355, 356, a, a), of 
greater relative size than any other parts of the 
brain, and vary but little in form ; in the embryo 


Fig. 355. 


Brain and portion of spinal marrow of Larus cyano- 
th |, about natural size. 

@, @, first cerebral mass or cerebral hemispheres. 
5, b, second cerebral mass or optic lobes. c, third 
cerebral mass or cerebellum, with its transverse 
grooves. d, spinal cord, with its posterior longi- 
tudinal fissure. 


chick on the sixteenth day, however, I found 
them very little larger than the optic lobes 
(fig. 357, a). In the sea-gull and snipe they 
are of an oblong form, and larger posteriorly ; 
in the hawk more round and short; in the 
red-start, goldfinch, pigeon, and embryo chick, 
on the twentieth day, more lengthened in form 
and covering quite the optic lobes (fig. 357, a). 
In the ostrich they are also lengthened and 
pig very much the form and characters 
of the same _— in the lower Mammalia, 
These hemispheres are united to each other by 
a commissure (the anterior commissure); above 


NERVOUS SYSTEM. (Comparative Anatomy.) 


Fig. 356. Fig. 357. 


cord of Pha 


Brain and ion of spinal I 
(fowl), state, age 16 days, slight 
ae ‘st 


stanus 


a, a, first cerebral mass or cerebral hemi: 
of a triangular form. 5, b, second cerebi a 
or optic lobes, touching at their inner borders. , 
third cerebral mass or cerebellum, small. d, sp 
cord, with its posterior longitudinal fissure. 
olfactory nerves. 4 


Fig. 357. The same, age 20 days, slightly 


a, a, first cerebral mass or cerebral hemis; 
oval in form. b, b, second cerebral mass or op 
lobes, widely separated from each other. ¢, thi 
cerebral mass or cerebellum, greatly increased 
developement and pushing asunder the optic lob 
d, spinal cord, with its posterior longitudinal fissu 
g, olfactory nerves. 


this there is another one, which Meckel eo 
siders as the first rudiment of the corpus ¢a 
losum ;* they contain cavities which are tr 
lateral ventricles, and in a a tubercle o 
enlargement corresponding to the corpus st 
eas of the Manmalik From the ante 
part of this primary cerebral mass the olfactor 
nerves arise (figs. 356, 357, g, 8), and pa 
forwards to the cribriform plate of the ethmo 
bone; their origin is marked by two distin 
enlargements, which are hollow and commit 
cate with the lateral ventricle. ’ 
2d. The optic lobes, or second cerebral m 
4 Sig. 355, 6), are of small size, and are more 
widely separated from each other than in 
preceding classes, though they still are 
nected by a medullary membrane corresp 
ing to the roof of the aqueduct of Sy 
In the embryo of the chick on the sixteenth 
however, these parts, as before observed 
nearly as large as the cerebral hemispl 
their inner borders touching each other, 
the reptiles and fishes (fig. 357, 6): at the: 
tieth We they are widely separated (, fig. 3 
In the sea-gull (fig. 355), snipe, hawk, 
start, goldfinch, fowl, and pi they 
a rounded form, and situated immediate 
neath the cerebral hemispheres. On ¢ 
into them in the sea-gull and pigeon, 
found to contain a cavity, which, in the 
is very small, in the latter larger, an 
taining a solitary dark-coloured tu 
their cavities _communicate with the — 
ventricle. Between these optic lob 
immediately inferior to - cerebral 
spheres, in the pigeon, there is situat 
pair of ganglia, ph i flattened form (the 
istence of which has been before noticed it 
a 


* Archiv. fiir Physiologie. : 


NERVOUS SYSTEM. (Comparative Anatomy.) 


receding classes) analogous to the optic tha- 
ini of the brain of man: between them is the 
canal leading to the infundibulum. . 
3d. The cerebellum, or third cerebral mass, 
(fig. 355, ¢), is particularly well developed, 
exhibiting an amazingly increased degree of 
organization when compared with the preced- 
ing classes, and bearing great analogy to the 
cerebellum of the higher animals. In the be- 
fore-mentioned species it consists of a more or 
less rounded median lobe, with very small 
lateral appendages; its external surface is 
marked by transverse sulci, varying in number, 
that extend a short distance into the interior of 
its substance. On cutting into it in the sea- 
gull, fowl, and pigeon, the appearance of the 
“arbor vite is slightly perceptible. In the em- 
o of the chick on the sixteenth day, however, 
the cerebellum is very small, not yet suffici- 
ently developed to separate the optic lobes; 
very slight traces only of grooves were a 
_ parent on its surface (fig. 356, c). On the 
‘twentieth day it presents all the characters of the 
full-grown bird, both as regards relative size, 
‘position, and external strie (fig. 357, c). 


! 


Fig. 358. 


Brain and portion of spinal cord of Lepus cuniculus 
( ook petal size, left hemisphere sliced. 
a, first cerebral mass or cerebral hemispheres, 
ightly grooved on the external surface. 6, corpus 
, short. c, cavity of lateral ventricle. d, 
ogy of corpus striatum, e, tenia semicircu- 
aris. f, hippocampus major, the superior surface 
ES + g» masses or ganglia of the olfactory nerves, 
with their cavities. h, bristle passed, shewing the 
communication between the cavity of the olfactory 
nerve and the lateral ventricle. k, second cere- 
bral mass or tubercula quadrigemina,—the anterior 
gg largest. 1,1, third cerebral mass or cere- 
llum, very much grooved. d*, spinal cord, with 
its posterior longitudinal fissure. 


On reviewing these statements of the ner- 
vous system in the birds, we observe that the 
brain and spinal marrow are no longer situated 
on the same horizontal plane, and that the 
preponderance is now in favour of the brain: 


623 


its weight, too, when compared with the body, 
is greater; and the ganglia composing\t are 
more above, and less behind each other. The 
axiigdd cerebral mass has now acquired so 
igh a degree of developement as to surpass 
the others in size; no convolutions are, how- 
ever, yet apparent on its surface; no large 
commissure yet exists to unite them. The 
optic lobes, or median cerebral mass, are small, 
separated from each other, and their cavities 
have decreased. The cerebellum, or third 
cerebral mass, is large; traces of lateral lobes 
are evident, and external striz are perceptible. 

Mammatia.—lIn the last and highest class, 
the Mammalia, will be found some most in- 
teresting grades of developement and structural 
forms of the cerebral mass to arrest our atten- 
tion, and we shall observe how rapidly the 
different parts are added, and those already 
formed are more highly developed, to consti- 
tute the complex brain of the human species. 
The spinal cord (figs. 358, 321, 322, 323, d*) 
is of still less relative size than in the pre- 
ceding classes; it has an anterior and pos- 
terior longitudinal fissure. In a full-grown 
mouse, weighing 227 grains, the spinal 
marrow weighed one grain and a half, the 
brain six grains and a half—the proportions 
being as 100:22. We thus observe that the 
former is of much less relative size than the 
latter. 

The following is a table shewing the relative 
proportions of the brain and spinal marrow in 
the four classes of Vertebrata :— , 

Spinal 

Brain. Marrow. 
Lamprey.... as 100 : 750 
Triton...... as 100 : 180 
Pigeon..... as 100 : 30 
Mouse. ..6. a8 100 : 22 


The spinal cord passes lower down the ver- 
tebral column than in man, but terminates by 
a true cauda equina, as in the bat and mouse, 
in which latter animal it is continued into the 
sacrum, but not into the caudal vertebra, as 
in the preceding classes. In the bat the 
spinal cord descends no lower than the eleventh 
dorsal vertebra, a conformation rather un- 
usual :* the fissure on its posterior surface was 
deep in those animals, but it becomes less evi- 
dent as we approach the human species. It 
presents three distinct enlargements in its 
course : a superior one, the medulla oblongata; 
a median, and a posterior one, where the nerves 
for the extremities are given off: this is the 
case in the mouse and bat, though in the for- 
mer animal the superior and median enlarge- 
ments are so closely approximated as to render 
the spinal cord of great thickness in the tho- 
racic region of the body.+ 

The following is a table shewing the relative 
proportions of the body and brain in the four 
classes of Vertebrata ;— 


Pisces .... 
Reptivia.. 
AVES .is\s.5' 
MamMAtia 


* Meckel (Archiv. fiir Physiologie) also states, 
that in the hedgehog the spinal cord terminated in 
the thoracic vertebra. 

+ Carus remarks the same thing in many of the 
Mammalia with a short neck; the Rodentia, for 
instance. 


624 
Brain. Body. 
Carp...... as 100: 80,600 
; Chub. .... as 100: 84,200 
Pt) we. a8 100: 52,900 
Lompeey .. as 100 : 142,500 
4 Triton..... as 100: 27,300 
REPritta.. > Turtle. |... as 100 : 454,500 
AVES,.... . Pigeon.... as 100: 9,100 
Sheep..... as 100: 22,600 
Mammatiay Pig. ...... as 100 : 32,300 
Mouse..... as 100: 3,500 


Tn the brain of the Mammalia we shall find 
the same parts as heretofore to occupy our 
attention, though at an extraordinarily in- 
creased degree of developement: this, however, 
varying greatly in the different orders. Its 
direction, with regard to the spinal marrow, 
is no longer horizontal, as we found in the 
fishes and reptiles, but approaching more or 
less to a right angle; the first traces of which 
inflection were perceptible in the birds. In 
the bat ( Vespertilio murinus ); mouse (Mus 
musculus); rat (Mus rattus); rabbit ( Lepus 
cuniculus, fig. 358); pig (Sus scrofa domes- 
tica); horse ( Equus caballus); ass ( Equus 
asinus ); sheep ( Ovis ammon) ; deer ( Cervus 
dama ) ; mole ( Talpa Europea); stoat ( Mus- 
tela euninea ) ; cat ( Felis catus ); and monkey 
( Callithrix ? fig. 359); the brain exactly 
fills the cranial cavity, that cavity correspond- 
ing with the shape and size of the head. The 
size and bulk of the brain are greater than in 
any of the preceding classes, as shown by its 
relative weight compared with the body. In 
a sheep weighing, as near as could be calcu- 
lated, 7466 drachms, the brain weighed 33 
drachms; the proportion of the brain to the 
body being as 100:22600. In a pig weighing 
about 7116 drachms, the brain weighed 22 
drachms ; the proportion being as 100:32350. 
The brain of a horse weighed 156 drachms. 
In a mouse weighing 327 grains, the brain 
weighed 6} grains, the proportions being as 
100:3,500. 

On taking a review of the structure of the 
brain in Mammalia, we find that it presents a 
great variety of form and developement in its 
different parts. 1. The cerebral hemispheres, 
or first cerebral mass, which vary greatly in 
their size and extent, and are united in the 
median line by a commissure, the corpus cal- 
losum. 2. The optic lobes, or second cerebral 
mass, which are here small and divided into 
two pairs, presenting more particularly the 
characters of the tubercula quadrigemina in 
the human brain, under which name they will 
in future be noticed. 3. The cerebellum, or 
third cerebral mass, which is greatly increased 
in developement, and presents a division into 
median and lateral portions. 

1st. The cerebral hemispheres, or first ce- 
rebral mass (figs. 357, 353, a) are of large 
size, but this varies according to the order 
in which they are examined. In the lower 
ones they resemble very much the same parts 
in birds, with regard to their small size 
and their want of convolutions, In the dol- 
phin they are very short and broad; in the 
ornithorynchus they are oval, and narrowed 


NERVOUS SYSTEM. (Comparative Anatomy.) 


’ 


anteriorly. In both these animals their sur- 
faces are smooth and unconvoluted. The same — 


occurs in the opossum and m cooper ‘ 
dactyla, manger Woe Marsu inte. n the bat — 
they are no longer than wide (2% lines each 
way), leaving the ap gas quadrig em na 
quite exposed ; they are of a triangu orm, 
and perfectly smooth on their surface. In the 
rabbit (fig. 358, a), rat, and mouse, rodent 
animals, they are oblong ovate, but much nar 
rowed anteriorly, The tubercula quadrigemina 
are quite exposed, but scarcely so much so as in 
the bat ; their surfaces are smooth and uncon- 
voluted, though in the rabbit there are a 
slight furrows; on their inferior surface there 
is a faint groove, dividing them into lobes, the 
rudiments of the fissura Sylvii. In the pig, 
horse, ass, sheep, and deer, the hemispheres 
are more oval in form, more convex, and ; 
narrowed anteriorly ; they extend ba 

as quite to cover the tubercula quadrigeming 
and their surfaces are marked with numerou 
convolutions ; the fissures of Sylvius are me 
strongly marked, and the division into lobe: 
more apparent. In the stoat and cat they are 
similarly shaped and convoluted on their surface, 
and they extend backwards, covering the tuber- 
cula quadrigemina and a portion of the cerebel- 
lum. In the monkey (fig.359, a) they are more 


+ 


vad 


ara: 


HHL 
| 


RAncaniell > | 
Brain of Callithrix ? (Me Dy 
size, right lateral ventricle exposed. — 
a, First cerebral mass or cerebral i 
elevated and broad, and extending back 
covering the cerebellum. a*, posterior lobe 
rebrum, free from convolutions. 6, corpus 
sum. c¢, cavity of lateral ventricle. d, | 0 
of corpus striatum, e, tenia semicireularis 
third cerebral mass or cerebellum. d*, § 
cord, eal 
rounded, very much elevated, broader mn 
middle, and extend backwards, covering: 
cerebellum. The convolutions are more 


a 
4 


NERVOUS SYSTEM. (Comparative Anatomy.) 625 


rous than in the preceding classes ; the fissure 
of Sylvius is a deep groove, marking the divi- 
sion into anterior and median lobes, and here, 
for the first time, are observed the posterior 
lobes (a* ), as yet but of small size, narrowed 
posteriorly, and free from convolutions. In 
the orang-outang they are altogether larger, and 
more approaching the form and character of 
the human brain, covering the cerebellum en- 
tirely, and convoluted on their posterior lobes.* 
_ These cerebral hemispheres are united by an 
important commissure, which makes its first 
appearance in mammiferious animals, the cor- 


; _ callosum ; in the lower orders, as in the 
t, 


rabbit (fig. 358, 6), rat, and mouse, it 
is very short,—shorter even than the tubercula 
quadrigemina ; in the pig, ass, and sheep, it is 
longer and broader; in the stoat, cat, and 
monkey (fig. 359, 6) it is increased in length 
and width, approaching the characters of the 


_ corpus callosum in the human adult brain. 


D cutting into the cerebral hemispheres, 
cavities are found in their interior, the lateral 
ventricles. In the bat and rodent animals, as 
in the rabbit (fig. 358, c), they are of small 
size, but large in proportion to the hemi- 
Spheres; in the pig, sheep, stoat, and cat they 
are larger and broader, but smaller in propor- 
tion to the hemispheres. In all these animals 
the anterior and descending cornua are obser- 
vable; the posterior are found only in the mon- 
key (fig. 359, c), where the lateral ventricles 
quite pepech the characters of the same parts 
in the human adult brain. In the interior of 
these ventricles are to be observed the corpora 
Striata, tenia (for the first time observable), 
Optic thalami, and fornix. In the bat genus 
and Rodentia, the corpora striata are very 
large, forming, indeed, the greater parts of the 
hemispheres of the brain, and the tenia very 
natrow (fig. 358, d, e); in the pig, sheep, and 
cat they are oblong and smooth; in the mon- 
key they were also oblong (fig. 359 d, e), and 
though in reality large, appear smaller, when 
compared with the hemispheres, than in the 
preceding classes, which apparent defects 
of relation Tiedemann considers evidently to 
depend on the greater augmentation of the 
hemispheres. The fornix, with its appendages, 
is for the first time observable in this class of 
animals, and exists in the brains of all the 
animals before mentioned ; in the lower orders, 
its relative size, particularly of the hippocampus 
major, is somewhat considerable. 

rom the anterior part of these cerebral 
hemispheres the olfactory nerves arise, which 
still possess many points of extreme interest. 
In the dolphin and other Cetacea, they are 
entirely wanting. In all the mammiferous 
animals before enumerated,-except the Quadru- 
mana, they consist of oblong or rounded me- 
dullary masses, situated on the cribriform plate 
of the ethmoid bone, from which filaments are 
given off to be distributed on the pituitary 
membrane. In the lower orders, as in the bat, 


* For the length, by measurement, of the cere- 
bral hemispheres in these different animals, see 
the table. 


VOL. ITI, 


rabbit, rat, and mouse, these masses o& zanglia 
of the olfactory nerves are situated ona plane 
directly anterior to the cerebral hemispheres, 
and may be seen on looking upon the superior 
face of the brain, these latter not being yet 
sufficiently developed anteriorly to cover them; 
in the pig they are nearly covered by the 
hemispheres; in the horse, ass, sheep, and 
deer, they are quite covered by them, and are 
only to be seen on the inferior surface of the 
brain; in the cat they are similarly situated, 
but the anterior edge of the hemispheres pro- 
jects still further beyond them. In all these 
animals a medullary band or tract (A) con- 
nects them with the median lobes of the hemi- 
spheres, and in all they contain cavities (i), 
which communicate with the lateral ventricles. 
In the monkey the olfactory nerves (processes) 
consist of free, flattened, medullary bands situ- 
ated on the inferior surface of the anterior 
lobes of the brain, precisely the same as in the 
human adult brain. 

2dly. The optic lobes, or second cerebral 
mass, or, as they are now to be called, the 
tubercula quadrigemina, consist of an anterior 
and posterior pair of ganglia, in which cavi- 
ties are no longer perceptible. They differ 
in size, relatively to each other as well as 
to the cerebral hemispheres, and in position. 
In the bat, rabbit (fig. 358, k), rat, and 
mouse, the anterior pair are the larger, 
and, compared with the cerebral hemispheres, 
are very voluminous; in the pig, horse, ass, 
sheep, and deer, the anterior pair are also the 
larger, but they are of less proportional size 
with the brain; in the cat and stoat the pos- 
terior pair are the larger; in the monkey they 
are nearly of equal size and present less relative 
volume, thus approaching very much the cha- 
racters of the tubercula quadrigemina in the 
human adult brain. With regard to their po- 
sition, as before observed, in the lower orders 
they are situated behind the cerebral hemi- 
spheres and are quite exposed, while in the 
higher orders they are situated underneath the 
hemispheres, and quite covered by them, as in 
the human adult brain. 

3dly. The cerebellum, or third cerebral 
mass (figs. 358, 359, 1), is remarkable for 
its great developement; nevertheless, it passes 
through many grades in the different orders. 
In the animals before enumerated it is marked 
externally by transverse striz and small con- 
volutions, and presents a division into me- 
dian and lateral lobes. The relative size of 
the mass itself, and of its different parts, and 
the number of external strie, differ accord- 
ing as the animal examined is high or low 
in the class. In the bat it is within half a 
line as long as the cerebral hemispheres, the 
popes being as 100: 125; the lateral 
obes are just observable, smooth on their sur- 
face, but on the large median portion there are 
two transverse strie. Inthe rabbit (fig. 358, 1) 
its proportional length in the median portion to 
that of the cerebral hemispheres is as 100: 207; 
in the rat, as 100: 166. The lateral lobes in 
both are more distinctly developed, and the 
strie are better marked. In the horse its pro- 

25s 


626 NERVOUS SYSTEM. 


portional is as 100: 256. In the sheep, 
as 100: 232. In the deer, as 100:233. The 
lateral lobes are very evident in all, and con- 
volutions are observable on the external sur- 
face, ly in the horse. In the cat its 
proportional length is as 100: 200; in the 
Stoat as 100 ; 228. The external convolutions 
in both are numerous: in the monkey (fig. 
359, 1), the proportional length is as 100 : 305 ; 
lamine are numerous and small, thus ap- 
proaching very much the characters of the same 
in man. 
The following is a table, shewing the actual 
and relative lengths of the cerebral hemispheres 
and the cerebellum in the Mammalia :— 


Length of 
Animal. | Cerebral of Proportions, 

Hemisphere |Cerebellum 
Bat....} 2} lines. | 2 lines.| As 100: 125 
Rabbit 144 — | 7 — 100 : 207 
Rat....| 7} — | 4} 100 : 166 
Mouse .| 4 — | 23 — 100 : 160 
Horse. ./64 — |25 — 100 : 256 
Sheep../36 — |15} — 100 : 232 
Deer.../42 — [18 — 100 : 233 
Stoat...}8 — | 3} — 100 : 228 
Cat..../18 — | 9 — 100 : 200 
Monkey/30} — [10 — 100 : 305 


On cutting into its substance in many of 
these animals, the appearance of the arbor vite 
is more or less distinct, similar to the human 
cerebellum. On its inferior surface is situated 
its great commissure, the pons Varolii, which 
first makes its appearance in this class of ani- 
mals, and, with the exception of the transverse 
fibres forming it being thinner and fewer in 
number, particularly in those lower orders of 
Mammalia where the cerebral hemispheres 
were small, it presents but little differences from 
the same part in the human adult brain. This 
latter remark will equally apply to the fourth 
ventricle, which has been an object of consi- 
derable interest, and which, from being at first 
an open exposed cavity, is now shut in and 
concealed. 

[On the peculiarities of the brains of the 
implacental class of Mammalia, see the ar- 
ticles Marsupratia and Monorremata.] 

On reviewing these statements of the nervous 
system in the Mammalia, we observe that the 
brain now preponderates greatly in bulk over 
the spinal marrow ; this latter is also shorter, 
and terminates by a true cauda equina. The 
Jirst cerebral mass has now acquired its maxi- 
mum of developement as regards size ; the two 
portions of which it is composed are united by 
a large commissure; their exterior surface is 
convoluted. The second cerebral mass is divi- 
ded into two pairs of ia, in which the 
cavities are obliterated. onthe third cerebral 
mass has lateral hemispheres developed, strie 
and convolutions on their exterior surface, and 
an important commissure, the pons Varolii, on 
its inferior surface. 

Having thus completed the investigations 
proposed at the commencement of this. paper, 


(Comparative Anatomy.) 


it may not in conclusion be without i 
and utility to take a very rapid review te : 
developement of the nervous system in the five” 
large groups of animals in the system i 
rapgement, as follows :— é 

a. The nervous s (perhaps) first e 
an molecaler fre > that is, me made u 
globules dispersed throughout the homoger : 
texture of the animal, oo. in, the Acta 
won Entozoa, &c. 

b. This nervous matter arranged in a 
gitudinal direction forms filaments. The d d 
rection which they assume is that of a raj 
nerve, and a central point, or 3 he 
latter communicate with each comm 
sures, which unite them in the e form of a 
This ring is situated around the ae orifice ¢ 
the animal; it takes the name of 
nervous ring; and from it issue filaments 
a radiated manner, as in the E . 

¢. This oral nervous ring becom 
more complicated in itself; sraglons are . 
developed on its lateral and inferior pc 
from which nerves off in a longitud 
direction, as in ees lower Mollusca, a 
secondly on its superior surface, as bak 
higher animals of this class: a sup 

ganglion is at first proporti 

in fo the Gasteropoda, but afterwards large, 
sometimes very large, as in the Cephalope 
It is the analogue of the tubercula quadrigemil 
of the higher animals. 

d. This nervous ring, in its me 
highly pam yen y Fs now becomes repeat 
several times in the body of the animal 5 J 
in an undetermined number, as in the E 
thoid Articulata; secondly. in a detern 
number, as in the Entomoid Articulata. _ 
nervous rings are united by poet 
missures, and the most anterior one always. 
a highly developed ganglion on its supe 
surface. The uniting commissures posse 
two distinct nervous tracts ; 
sympathetic nerves exist, as in the In 

e. These primary nervous rings es 
become ganglia (brain); the uniting ¢ 
sures are become primary nervous rings 
marrow). First, the ganglia and theis e 
sures are neatly equally sero, 
horizontal, as in the lower Vertebrata ; r 7 ) 
the ganglionic formation predomina te 
direction, with regard to the comm 
comes more that of a right anges _ 
higher Vertebrata; thirdly, the pi r 
of the ganglionic formation is ¥ 
creased, and its relative direction is 1 
complete right angle, as in the human 5) 


es. 


(John Andet 


NERVOUS CENTRES. 
tomy).—A nervous centre ma po os bad s 
mass composed of grey mm 
matter with which nerves are intim ratel 
nected. Ina physiological ig balls. i 
a centre of nervous action, as nerve 
to conduct to it as well as from it. 

The nervous centres in the human § 
are the GANGLIONS, the SPINAL CORD, 2 
BRAIN. 


hinodermata. 


ESP Ory 


ecta. 


NERVOUS CENTRES. (Human Anatomy. Tue Menryces.) 


The ganglions are small masses occupying 
certain situations in the body. They are ex- 
tremely numerous in the human body, and very 
variable in shape and size. Que great sub- 
division of them, in man and the mammalia, 

_ 48 connected with the posterior roots of the 
7 inal, and with certain encephalic nerves. 
. class belongs to the sympathetic sys- 
tem. In the Invertebrata the nervous system 
is made "p of a series of them variously dis- 
_ posed, with their afferent, efferent, and con- 
necting nerves. 
_ The spinal cord and the brain are peculiar 
to the great class of vertebrated animals. They 
may be regarded as compound ganglions, being 
_ physiologically resolvable intoa series of smaller 
centres, which are, to a certain extent, inde- 
——— of each other. Viewed anatomically, 
; are not so obviously divisible: in the 
> m cord, in which the independent influence 
‘Of separate segments may be most easil 
_ demonstrated, no Siiomixal subdivision x 
obvious, for the segments are fused together 
“Into a cylindroid body, which has a certain 
_ elation to the length and muscular activity of 
the animal. Indications, however, of this 
ite form of the spinal cord are afforded, 
marked difference of dimensions which 
ain parts of it present when compared with 
hers being always a manifest corres- 
‘a 2 between the size of any segment of 
the cord and the motor or sensitive endowment 
__ Of that segment of the body which receives its 
erves from it. And the case of the common 
nard ( Trigla Lyra) may be here quoted as 
markable instance of the developement of 
act gangliform bodies on a portion of the 
cord, in accordance with a particular exaltation 
_Of tactile sensibility. 
The brain is much more evidently made up 


Of a series of separate centres or smaller masses, 
exhibiting sufficiently distinct boundaries on 
uurfaces, but so intimately connected by 
what are called commissural or uniting fibres, 
as to manifest the same kind of fusion (although 
to a less degree) as that noticed in the spinal 
d. These gangliform bodies are so readily 
nguishable from one another, that from the 
i iods of anatomical investigation each 
been designated by a distinct name, 
is generally derived from some prominent 
of the body itself, or from the name of 
ye familiar object which it has been sup- 
_ posed (often fancifully) to resemble. The 
_ aggregate of these bodies is known in popular 
Tangy by the name of Brain, (a word of 
_ Saxon origin, sometimes used in the plural); 
¢ this word, however, anatomically speaking, is 
licable only to the great hemispheric lobes 
lich form the largest portion of the whole 
Mass; and the term Encephalon may be more 
correctly used to denote the whole of the intra- 
en contents. 
_ At is proposed in the present article to con- 
sider the general and uncriptive anatomy of 
these hervous centres severally, beginning with 
examination of their coverings. 
Covertnes oF THE NERVOUS CENTRES. 
ERINGS OF THE GANGLIONS. — Every 


627 


ganglion is covered by a more or led dense 
layer of white fibrous tissue, similar to that 
which forms the neurilemma of nerves. It per- 
forms precisely the same office for the elements 
of the ganglions that the neurilemma does for 
those of nerves; that is, it gives them a me- 
chanical support, and is the medium through 
which bloodvessels are conveyed to their ner- 
vous matter. It is continuous with the neu- 
rilemma of the nerves which are connected 
with the ganglions. It is found in all forms and 
classes of ganglions, presenting the same essen- 
tial characters. These bodies are generally 
surrounded by and imbedded in a considerable 
quantity of fat, which also involves more or less 
the nerves that proceed from them. 

CovERINGS OF THE SPINALCORD AND BRAIN. 
—These are also called the membranes of these 
centres, or the meninges (jmvsyé, membrana). 
They are three in number. Those of the brain 
are continuous with those of the spinal cord, 
but, as there are certain distinctive characters 
proper to each, it will be convenient to describe 
the cerebral and spinal meninges separately. 
They are, enumerating them from without in- 
wards, the dura mater, the arachnoid mem- 
brane, and the pia mater. 

The term, mater, pnTne, originated with the 
Arabian anatomists, who regarded these mem- 
branes as the parents of all others in the body. 
Galen adopted the word pny, and distin- 
guished the first and last of the membranes 
above enumerated by the adjectives rayutegn 
and Aswrn. The Germans use the word haut, 
and designate these membranes as hautige 
Hullen des Gehirns und des Ruckenmarkes ; 
die harte Hirnhaut, die harte Ruckenmark- 
haut, the dura mater of the brain and spinal 
cord; die Spinnwebenhaut, the arachnoid ; and 
die weiche Haut, the pia mater. 

Dura mater —The dura mater is a dense 
membrane com almost exclusively of 
white fibrous tissue. It has all the characters, 
physical and vital, of that texture, possessing 
great strength and flexibility with but little 
elasticity. It is freely supplied by blood- 
vessels, and at certain situations, which will 
be more particularly described by-and-bye, 
it separates into two lamine, which inclose 
prolongations of the lining membrane of the 
venous system, forming peculiar sanguiferous 
channels, which are commonly known by the 
name of sinuses. It has an apparent lamellar 
disposition, from the fact of its fibres being 
arranged in different planes. In the child a 
subdivision into two layers may sometimes be 
easily effected. Some nerves have been de- 
monstrated in the dura mater; a branch of the 
fifth nerve has been particularly described and 
delineated by Arnold, as passing in a recur- 
rent course between the laminz of the tento- 
rium, and Pappenheim has found nervous 
fibres in the cerebral dura mater derived from 
the superior maxillary division of the fifth, 
from the fourth nerve, from the vidian, and 
probably also from the frontal branch of the 
ophthalmic.* 


* Valentin Repertorium, vol. v. p. 87. 
232 


~ 


628 


The spinal dura mater is in shape adapted 
to the vertebral canal. It is a hollow cylinder, 
tapering somewhat at its lower extremity to cor- 
respond with the sacral portion of the canal. 
Itadheres very firmly all round the foramen mag- 
num of the occipital bone. From thence it 1s 
continued down to the sacrum without forming 
any adhesion to bone. On the posterior and 
lateral surfaces it is covered by a layer of soft, 
oily, reddish fat, which intervenes between it 
and the inner surfaces of the vertebral lamin 
and processes, and in these situations, as well 
as to a less degree in front, we find a very in- 
tricate plexus of veins, some of which are of 
considerable size. The fatty deposit is most 
abundant in the sacral region. In front the dura 
mater adheres by a close areolar tissue to the 
posterior common ligament, and here of course 
the adipose tissue is deficient. At the foramen 
magnum the continuity of the spinal dura 
mater with that of the cranium is distinct, and 
here, indeed, the former appears as a funnel- 
shaped prolongation of the latter; both are, 
in trath, portions of the same membrane 
adapted to the difference of shape of the ner- 
vous centres with which they are respectively 
connected. 

On the sides the spinal dura mater is per- 
forated by orifices which give exit to the roots 
of the nerves which arise from the spinal cord. 
When examined from within, these foramina 
are found to be arranged in pairs, each pair 
corresponding to the point of exit of a spinal 
nerve. The foramen which transmits the an- 
terior root is separated from that which gives 
passage to the posterior one, by a narrow slip 
of fibrous membrane. These foramina are 
slit-like in form, taking the vertical direction. 
On the outer surface of the dura mater the 
distinction between them is not evident with- 
out dissection, for there the fibrous membrane 
being prolonged from the margins of the open- 
ings around the nerves, the sheaths thus formed 
coalesce and surround both roots. The number 
of these orifices is of course the same as that 
of the roots of the nerves which pass through 
the dura mater. 

The internal surface of the spinal dura mater 
is perfectly smooth and moist in the healthy 
state, Owing to its being lined by the parietal 
layer of the arachnoid membrane. In the 
intervals between the orifices for the transmis- 
sion of each pair of spinal nerves, it receives the 
pointed attachments of the ligamentum denti- 
em to be described more fully by-and- 

e. 
rhe is evident from the preceding description 
that the spinal dura mater cannot perform the 
office of a periosteum to the osseous walls of the 
spinal canal, for at every point it is separated 
from them by texture of a different kind, and, 
moreover, the vertebra are provided with a 
distinct periosteum. The prolongations of dura 
mater over the nerves at each of the interverte- 
bral foramina serve to fix that membrane at 
the sides throughout the whole extent of the 
vertebral canal, so as to prevent its lateral dis- 
placement. At the lower extremity of the 
sacral canal the dura mater ends in a blunt 


NERVOUS SYSTEM. (Nervous Centres. Tur Meninces.) 


oj 
4 


int, and from this certain may be 
285 towards the coecyx. Bf these the de J 
tral one is continuous with the filiform pro 5 
longation from the pia mater, which is inserted 
into the inferior extremity of the dura er, 
and is implanted oy He e last per i 
coceyx. e thread-like processes which ¢ 4 
ain 0 each side are the sheaths of the last 
sacral nerves and of the coccygeal nerve, which — 
pass some distance in the canal before pe! 
reach the foramina for their transmission 
wards. 5 
It is easy to convince oneself that the spinal — 
dura mater is far larger than would be neces- 
sary for the reception of the cord. When the 
fluid immediately surrounding this organ 
been suffered to escape, the dura mater appears” 
quite loose, flaccid, and wrinkled. By blowing — 
air or injecting water into its canal, it may be» 
rendered tense again. This looseness e 
dura mater is most conspicuous at its st 
, in the lumbar and sacral regions, where 
it forms, as Cruveilhier says, “ autour de la 
queue de cheval une vaste ampoule, qui parail 
n‘avoir d’autre utilité que de servir de 
au liquide cephalo-rachidienne.” a 
The dura mater adapts itself, in point of : 
to the varying dimensions of the s cana 
in its different regions, which Bey appear to 
be influenced by variations in dimensior 
of the spinal cord. Thus, it swells in th 
cervical and in the lumbar region, at bo 
which places there are corresponding enlarg 
ments of the cord. Its most contracted port 
is that which occupies the dorsal region. __ 
Cranial dura mater.—The dura mater of 
cranium differs in one leading cireumstal 
from that of the spine,—namely, that it fo 
a periosteum to the inner surface of the era 
bones. We find it, therefore, very clos 
adherent to the whole interior of the craniun 
and the free communication between the ves 
of the dura mater and those of the bones se 
materially to enhance the connexion bet 
this membrane and the osseous surface. 
some situations the adhesion is so very i 
that we experience great difficulty in atten 
to separate the fibrous membrane from the 
jacent bone. On the roofs of the ork 
wings of the sphenoid bone, the petr 
tions of the temporal bones, the margin 
occipital foramen, and opposite the 
the adhesion is very intimate. wll 
This adhesion of the dura mater to the 
is found also to vary in degree at differ 
tiods of life. It is very intimate in 0 
so much so that, in removing the 
layers of bone often chip off, remaining” 
nexion with the fibrous membrane. — 
adult, such a degree of adhesion as woul 
rise to this effect, ought to be regarded as 
bid. In the young subject, while i 
and growth are going on, the adhesion 
intimate, so that in them great diffic 
experienced in removing the calvaria. D 
less this intimate adhesion at this 
of life is due to the active share © 
dura mater takes in conveying the mater 
nutrition and growth to the cranial pariete 


NERVOUS CENTRES. (Human Anatomy. Tue MEnrnces.) 


The cranial dura mater is not a simple bag. 
From its internal surface partition-like processes 
pass inwards, which serve to separate certain 
subdivisions of the encephalon. These are, 
the falx cerebri, the tentorium cerebelli, and the 

Jalz cerebelli. 

The falx cerebri is a process of fibrous mem- 
brane corresponding to the mesial plane and 
lying in the great median fissure of the brain, 
where it separates the lateral hemispheres from 
each other. Its shape is falciform ; its superior 
convex border corresponds to the frontal and 
Sagittal sutures, and encloses the great longitu- 
dinal sinus; its inferior border is concave and 
much shorter than the superior, and corres- 
ponds to the superior surface of the corpus 
callosum, which connects the hemispheres of 
the brain. In front the falx is very narrow and 
almost pointed ; it embraces the crista galli of 
the ethmoid bone, which appears to be enclosed 
between its layers. As the falx proceeds back- 
wards it increases considerably in depth; its 
Superior edge may be traced back to the internal 
Occipital protuberance ; its inferior edge termi- 
nates at a point corresponding to the middle 


line of the posterior margin of the corpus 


callosum. The falx cerebri contains within it, 
along its posterior border, a large vein, which 
is called the inferior longitudinal sinus. 

The falx cerebri is continuous at its posterior 
border on each side with the tentorium cere- 
belli. This process is nearly horizontal in its 
direction ; it forms a vaulted roof to a cavity 
the floor of which corresponds to the occipital 

) in which the cerebellum is lodged. Its 
upper surface is convex on each side of the 
attachment of the posterior extremity of the 
falx cerebri: it supports the posterior lobes of 
the brain. The inferior surface is adapted to 
the upper convex surfaces of the cerebellar 
hemispheres. Its posterior and outer edge 
adheres to the occipital bone and to the pos- 
terior border of the petrous portion of the 
temporal bone, reaching as far inwards as the 

osterior clinoid processes of the sella Turcica. 

@ occipital portion of this edge contains a 
considerable part of the lateral sinus (fig 362, e) 
and that portion which adheres to the petrous 
bone contains the superior petrosal sinus. The 
anterior or inner margin of the tentorium is 
concave and free in the greater part of its 
extent; it forms the posterior and lateral boun- 
dary of a large opening (which the sella Tur- 
cica completes in front), through which the 
crura cerebri and other parts connected with them 
pass. This margin is attached by its anterior 
extremities to the anterior clinoid processes, to 
reach which it crosses the posterior border. 
The crossing of these two edges at a point 
external to the sella Turcica gives rise to the 
formation of a little triangular space, the base 
of which corresponds to the sella Turcica; its 
outer angle is perforated for the transmission of 
the third pair of nerves, and its anterior one for 
that of the fourth pair. 

From the inferior surface of the tentorium 
cerebelli at its posterior edge, a short and thick 
fold of very slight depth descends to the pos- 
terior edge of the foramen magnum. This is 


629 


the falx cerebelli ; it corresponds to thé ned ian 
notch between the hemispheres of the cerebellum. 
Its anterior border is slightly concave. Two 
veins called occipital sinuses are contained in it. 

The internal surface of the cranial dura mater 
presents the same smooth appearance as we 
have noticed in the spinal membrane of the 
same name. We observe, however, an excep- 
tion to this on each side of the line along the 
great longitudinal sinus. Here it is very com- 
mon to find the membrane presenting a peculiar 
cribriform appearance, which occupies a space 
of from half an inch to two inches in length and 
not more than a quarter of an inch in breadth, 
but exhibiting great difference in various sub- 
jects as to the number and depth of the foramina 
or depressions upon which the sieve-like struc- 
ture depends. These depressions are caused 
by the presence of little bodies which grow 
from the layer of arachnoid that covers the 
brain, glandule Pacchioni, which will be 
described by-and-bye. The anatomist may 
expect to find in a large proportion of adult 
brains a greater or less degree of adhesion 
between these parts of the dura mater and the 
edges of the hemispheres of the brain. 

The dura mater is perforated by numerous 
orifices fur the transmission of the encephalic 
nerves. It adheres firmly to the border of each 
of the foramina in the cranial bones, and is 
partly continued in the shape of neurilemma 
over the nerve that escapes through it. In the 
case of the optic nerve a strong fibrous sheath 
is prolonged from the dura mater, and at the 
same time that membrane appears to become 
continuous with the periosteum of the orbit, as 
if it had, opposite the optic foramen, split into 
two layers, one of which formed the sheath of 
the optic nerve, and the other applied itself to 
the interior of the orbit, forming a periosteum 
to the walls of that cavity. 

Of the arteries and veins of the dura mater. 
—tThe disposition of the bloodvessels of the 
dura mater, both of the spine and of the cra- 
nium, deserves a special description. The 
former membrane derives its arteries from the 
numerous vessels which take their rise close to 
the spinal column in its various regions. These 
are ramifications of the abdominal and thoracic 
aorta or of their large primary branches. In the 
neck the deep cervical, the occipital, and the 
vertebral arteries send in numerous branches, in 
the back the intercostal arteries, and in the loins 
the lumbar arteries. These vessels pass in at 
the vertebral foramina, and send branches to 
the spinal membranes as well as to the bones 
themselves. 

The blood which is returned from the spinal 
cord and its membranes, as well as from the 
vertebra, is poured into a very intricate plexus 
of veins which surrounds the dura mater on 
its lateral and posterior surfaces, ramifying 
among the iohites of soft fat by which the 
exterior of that membrane is invested. This 
plexus is less ‘intricate in the dorsal than in 
the cervical or lumbar regions; it communi- 
cates very freely with the plexus of veins which 
lies on the exterior of the vertebral laminz and 
processes (the dorsi-spinal veins of Dupuytren). 


630 


In front of the dura mater and situate between 
the outer edge of the posterior common liga- 
ment of the vertebre and the pedicles, we find 
two remarkable venous sinuses which extend the 
whole length of the vertebral column, from the 
occipital foramen to the sacral region (fig. 360). 


_ Fig. 360. 


~ 


Spinal sinuses viewed from before. 
(After Breschet.) 

The anterior part of the basis cranii and the face 
have been removed, as also the bodies of the 
vertebra. 

i, lateral sinus descending to form its junction 
with the jagular vein; c, cavernous sinus; 0, ver- 
tebral artery, the longitudinal sinuses with their 
transverse connecting veins, lying immediately be- 
hind the bodies of the vertebre. The interior 
petrosal and the cavernous sinuses appear like con- 
tinuations of them within the cranium, and the 
transverse and circular sinuses are analogous to the 
transverse spinal branches. 


These veins are loosely covered by a thin pro- 
cess, which is prolonged from each margin of 
the posterior common ligament, and which is 
sufficiently transparent to allow them to be seen 
through it without removing it. They have 
been known since the time of Fallopius, and 
were described by Willis as the longitudinal 
spinal sinuses. In calibre they present many 
inequalities, being dilated at one part and con- 
stricted at another, according to the number 
and size of the vessels which communicate 
with them. The sinuses of opposite sides run 

rallel to each other and communicate by cross 

ranches, which pass between the posterior sur- 
face of the body of each vertebra and the pos- 


NERVOUS SYSTEM. (Nervous Centres. Tut Mentners.) 


terior common ligament. These cross branches 
present the same characters as the sinuses them- 
selves, being of variable calibre, and presenting 
the greatest degree of dilatation at their middle. 
At this point these branches receive veins which | 
emerge from the spongy texture of the bodies of 
the vertebre (basi-vertebral veins of Breschet) 
(fig. 361,d). The vertebral sinuses diminishin 
fe - 


Fig. 361. a4 


Ages 
; Ay 


Basi-vertebral veins, convergi the spongy stru 
ture of the sedge?’ he coveain e 
size at the highest part of the vertebral canal, a 
passing through the anterior condyloid foramina 
communicate with the internal jugular vei 
In the sacral region they diminish considerab 
likewise, and are lost in becoming conti 
with the lateral sacral veins and other 
veins in that region; and they communic 
with the deep and superficial vertebral veins 
the neck, with the intercostal veins in the bar 
and with the lumbar ones in the loins. Th 
evidently differ from the sinuses of the crat 
dura mater in not being enclosed betweet 
layers of fibrous membrane as those ve 
Bloodvessels of the cranial dura mat 
The bloodvessels of the cranial dura 
are much more numerous than those 
spinal, in consequence, no doubt, of that mi 
brane performing the office of a periosteu 
the cranial bones. The arteries are de 
from numerous sources; in front from 
ophthalmic and ethmoidal arteries, — 
middle from the internal maxi 
the middle meningeal, which enters d 
at the foramen spinosum, and by small t 
from the internal carotid which 
called inferior meningeal arteries. Post 
the vertebral, the occipital, and the asce 
pharyngeal supply branches which go’ 
name of posterior meningeal arteries. 
y The veins of the dura mater are form 
rly to those in other parts, being deri 
radicles which take their rise in the mem 
itself as well as from the osseous walls ¢ 
cranium, from the diploic veins of those! 
(See Bont, figs. 187, 188, vol.i.) All oft 
with the occasional exception of one or 
which accompany the middle meningeal ¢ 
and pass out at the foramen spinosum, 
their blood into the great venous canals 
closed between the lainine of the duran 
which are called Sinuses. 7" 


— 


_ from parts exterior to the cranium. 


NERVOUS CENTRES.: (Homan Anatomy. Tar MentnGes.) 


The sinuses of the duru mater.—At certain 
situations, processes of the inner membrane of 
the venous system are included in canals formed 
by the separation of the lamine of the dura 
mater. ‘The channels that are thus formed for 
the passage of the venous blood do not admit 
of being dilated beyond a certain size, and in 
this consists an important peculiarity in the 
venous system within the cranium. These 
channels empty themselves into the internal ju- 
gular vein, which thus forms almost the sole 
channel by which the venous blood is returned 
from the brain and its membranes as well as in 
a great measure from the bones of the skull. 
And thus is explained the rapid influence which 


_ is produced upon the brain by any impediment 
_ to the passage of the blood through the superior 
_ vena cava. 


It is important to notice that the sinuses 


- communicate with and receive blood from cer- 


tain external veins which carry blood derived 
Among 
these may be enumerated the ophthalmic vein, 


and several small veins in the neighbourhood of 


the mastoid and condyloid processes, and in 


the parietal bones. 


e following sinuses may be described. 
| The superior longitudinal sinus. — This 


sinus corresponds to the superior margin of the 
_ falx cerebri. It commences very narrow by one 
_ Or two small veins from the dura mater in the 


vicinity of the crista galli and cribriform plate 


_ of the ethmoid bone. Thence it proceeds back- 


wards, gradually increasing in calibre, and it 


terminates a little above the internal occipital 
‘protuberance by communicating with a small 


cavity or reservoir, situated between the layers 
of the dura mater there, which is called Tor- 
cular Herophili. 1f a vertical section of this 
sinus be made in the transverse direction, it will 
be seen to be triangular in shape, the apex cor- 
Tesponding to the falx, the base slightly curvi- 
linear and lodged in the groove which passes 
along the median line of the cranial vault. 
When the sinus is laid open in its length by 
slitting up its superior wall, we find that its 
Sides are perforated by a great number of mi- 
nute orifices, which are the openings of veins 
passing into it from the dura mater and from 
brain itself. These veins pass into the 
sinus chiefly at right angles to it, or in the 
direction from behind forwards; a few, situate 
in front, enter the sinus from before backwards. 
In the interior of the sinus we observe little 
bands (trabecule of Haller, chorde Willisii ), 
stretching across from right to left, connected 
only with the lateral walls and leaving a free 
Space above and below them. These bands 
are numerous, and various as regards breadth. 
Haller has.seen them so numerous that they 
appeared like a septum dividing the sinus into 
two portions, of which the superior was the 
er. 

walls of the sinus, towards its inferior 
angle, have frequently a cribriform appearance, 
which puts on somewhat the aspect of erectile 
tissue. There is no appearance of valves in 
the interior of the sinus; frequently, however, 
the oblique entrance of a small vein into the 


631 


sinus produces a fold near the venous ag-rture, 
which, under the retrograde pressure of the co- 
lumn of blood, might close the orifice, and 
probably, when the veins open into the sinus 
from behind forwards, they may be protected 
fiom the regurgitation of the blood by this 
mechanism. 

Several of the small bodies, previously al- 
luded to bythe name of Pacchionian glands, 
project into the cavity of the sinus through 
apertures in its wall. They appear as if they 
had worn their way by pressure and friction 
through the walls of the sinus, and it is here 
that the cg of an erectile structure is 
most manifest. We cannot suppose that these 
bodies are bathed in the blood of the sinus, but 
rather that they push the lining membrane of 
the sinus before them. It has been supposed 
that these bodies are natural structures destined 
to perform a mechanical office somewhat on 
the principle of the ball-valve, but they are 
frequently absent altogether, and when present 
they have no constant relation to the venous 
orifices. 

The inferior longitudinal sinus (sinus infe- 
rior falcis ) is a small vein lodged in the inferior 
part of the falx cerebri, running parallel to and 
a little above its inferior margin for about the 
two posterior thirds of its length. It gradually 
increases in calibre from before backwards, 
being formed by tributary veins from the falx ; 
it bie into the strait sinus. 

he strait sinus corresponds to the middle 
line, at the place where the falx cerebri unites 
with the tentorium cerebelli. It seems to be 
enclosed between the layers of the former. Like 
the cther large sinuses, it presents in its section 
the form of a triangle, whose base is inferior. 
Its direction is from before backwards and a 
little downwards, with a slight degree of curva- 
ture corresponding to that of the tentorium. It 
corresponds at its commencement to the space 
between the posterior reflected portion of the 
corpus callosum and the quadrigeminal bodies, 
and here it receives two large veins (vene magne 
Galeni), which carry the blood from the inte- 
rior of the ventricles, and a third vein, the in- 
ferior longitudinal sinus. It opens into the 
conflux of the sinuses or torcular by a round 
Opening or sometimes by two openings, sepa- 
rated by a slip of fibrous membrane. This 
sinus likewise receives veins from the inferior 
surface of the posterior and middle lobes of 
the brain, and from the superior surface of the 
cerebellum. 

At the posterior extremity of the straight sinus 
we find a reservoir somewhat polygonal in 
shape, which corresponds to the occipital pro- 
tuberance; this is called the Torcular Hero- 
phili,* (the press of Herophilus,) the conflux 
of the principal sinuses of the dura mater; it 
has six openings, one for the superior longitu- 


* This absurd name might with great advantage 
be discarded, for it seems quite uncertain what 
precise part Herophilus intended to apply it to. 
The term proposed by Cruveilhier is much better, 
the occipital conflux of the sinuses. Various other 
names were applied to it formerly, such as Lacuna, 


platea, pelvis, laguncula, 


632 


dinal sinus above; one for the straight sinus in 
front; two for the lateral sinuses on each side ; 
and two for the occipital sinuses inferiorly 


(fig. 362, t). 


Posterior part of the cranium removed, to shew the 
dura mater and the superior itudinal, and the 
lateral sinuses, with the torcular Herophili. 

é, lateral sinus ; ¢, torcular Herophili; s, superior 
longitudinal sinus. 


Lateral sinuses —From each side of the con- 
flux of the sinuses, there proceeds in a some- 
what serpentine course outwards, downwards, 
and forwards, a wide canal, the largest of the 
sinuses, which conveys the blood from the 
torcular to the internal jugular vein. A groove 
exists on each side of the internal occipital pro- 
tuberance, for the reception of this sinus, which 
marks the occipital bone, the mastoid portion 
of the temporal, and a small portion of the 
occipital bone again. In a great portion of 
their course, the lateral sinuses correspond to 
the posterior margin of the tentorium cerebelli, 
as far forwards as the mastoid portion of the tem- 
poral bone. Here each sinus winds downwards 
to reach the jugular foramen in the posterior 
lacerated opening. These sinuses are never 
equal; that of the right side being, with few 
exceptions, the larger, a circumstance which 
Vicq d’Azyr, Soemmering, and Rudolphi attri- 
buted to the fact that most persons sleep on the 
right side, on which account the blood is apt 
to accumulate to that side. They are more 
capacious at their termination in the jugular 
veins than at their commencement from the 
torcular. The inner surface of this sinus is like 
that of all the others; it is not, however, tra- 
versed by any of the bands which are found so 
numerous in the longitudinal sinus. Cruveil- 
hier states that he once saw in the horizontal 

rtion of this sinus, a few of the Pacchionian 

ies. 

In its course each lateral sinus receives veins 


NERVOUS SYSTEM. (Nervous Centres. Tut Meninces.) 


4 


from the inferior surface of the brain and supe- — 4 
rior of the cerebellum; it also receives the supe- 
rior petrosal sinus near the base of the us 


portion of the temporal bone. A large id 
vein communicates with this sinus and pene- — 
trates to the exterior, where it forms one of the 
principal sources of the occipital vein, thus 
establishing a free and direct communication — 
between the circulation within and that with- 
out the cranium.* Near the josular a 
the lateral sinus receives the inferior petrosal. 
None of the sinuses has been more fre- 
quently the seat of inflammatory disease tha 
the lateral. Being the principal channel for 
the return of the venous blood from the in- ~ 
terior of the skull, a slight morbid action within 
them can scarcely fail to induce a material de- 
rangement of the cerebral circulation, and the 
nearness of their position to the cerebellum and — 
to the posterior lobes of the brain renders it 
very unlikely that those parts would escape 
participating in any acute disease which might 
arise within it. - 
Occipital sinuses. — These are small 
lodged between the layers of the falx cerebe 
They collect the blood from the dura mater and 
from the cranial bones in the immediate vici- 
nity of the posterior margin of the fe 
magnum, and from thence they pass upward 
and inwards to open into the lower part of th 
torcular. Cruveilhier suggests that the direc. 
tion and position of the occipital sinuses ar 
best indicated by describing them as being th 
cords of the arcs which the lateral sinuse 
form. 
Petrosal sinuses. — These sinuses are s¢ 
named from their connection with the pet 
portion of the temporal bone. The 
petrosal sinus corresponds, on each side, to th 
posterior superior edge of the Dor 
along the three outer fourths of which a groow 
exists for its reception. This groove is inter 
rupted in front by a depression in which th 
tifth nerve is lodged, so that at this place th 
nerve lies between the sinus and the bone. T 
superior petrosal sinus is about large eno 
contain an ordinary sized surgeon’s pre 
communicates with the lateral sinus post 
and with the cavernous sinus in front, an¢ 
its course it receives several small veins ff 
the dura mater in the middle fossa of the 
nium. It receives a vein from the anterior p 
tion of the corresponding hemisphere of 
cerebellum, and also, sometimes, one from 
inferior surface of the brain. Small veins 
the pons Varolii empty themselves into its 
terior extremity. re! 
The inferior petrosal sinuses also forr 
additional channel of communication bety 
the lateral and cavernous sinuses. h 
larger but shorter than the superior. Inst 
ation they correspond to the interval betwee 
the petrous bone and the occipital. They ops 
into the inferior portion of the lateral sint 
before it unites with the jugular vein. i 
Transverse sinus.—This sinus establis 
a communication between the 


Se 


per 


* Cruveilhier, An, Desc. t. iii. p. 268. 4 


NERVOUS CENTRES. (Human Anatomy. Tue Mentnces.) 


cavernous sinuses of opposite sides across the 
basilar process of the occipital bone. Some- 
times there are two running parallel to each 
other. Cruveilhier states that the capacity of 
this sinus is much greater in old than in young 
subjects. 

Cavernous sinuses.—In point of shape these 
sinuses differ considerably from all the other 
sinuses of the dura mater. They are venous 
reservoirs, situated on each side of the sella 
Turcica, from which they are separated by the 
internal carotid arteries. Their name is derived 
from the spongy appearance which they present 
in their interior, owing to the existence of some 
filaments within them, which, by their inter- 
lacement with each other, form a reticular 
texture there. It was formerly supposed that 
the carotid arteries lay in the cavity of these 
sinuses and were bathed by their blood ; but it 
is easy to demonstrate by a little careful dis- 
_ section that the inner membrane of the sinus 
adheres loosely to the outer wall of the artery, 
and that the sixth nerve passes between them. 
In the outer wall of each cavernous sinus there 
are channels for the reception of those nerves, 
which pass from the cranium into the orbit. 
These are the third nerve which is placed 
highest up, the fourth nerve which holds the 
next place, and the ophthalmic portion of the 
fifth. The cavernous sinus receives at its ante- 
rior extremity the ophthalmic vein, which col- 
lects the blood from the eye-ball and other 

Structures within the orbit, and which commu- 
" Ricates also with the angular vein and with the 
frontal vein. (Hence the injected state of the 
vessels of the eye-ball when the brain is con- 
gested, as in fever.) Veins from the inferior 
Surface of the anterior lobes of the brain also 
Open into it, also some from the middle lobe 
and from the dura mater. Posteriorly it com- 
municates with both the petrosal sinuses, and 
veins from the cranial bones open into its 

superior wall. 
__ Circular sinus—A communication is esta- 
blished between the cavernous sinuses by means 
of the circulur or coronary sinus which em- 
braces the pituitary body, one portion lying in 
front of it and the other behind it, both open- 
ing by a common free orifice into the right and 
left cavernous sinuses. The posterior portion 
of the circular sinus is much larger than its 
anterior portion. Its size is much greater, 
according to Cruveilhier, in old subjects than 
in young ones. It receives small veins from 
the pituitary body, and also from the sphenoid 
bone and from the dura mater. 

It is impossible to examine this complicated 
atrangement of venous channels in connexion 
with the dura mater of the brain without ad- 
miring the beautiful provision which it affords 
against the undue accumulation of blood in 
the venous system within the cranium. In 
the first place, we observe that these veins do 
not admit of dilatation beyond a prescribed 
extent, by reason of their being enclosed be- 
tween layers of an inelastic and inextensible 
membrane. Next, we remark the safety pro- 
vision which is afforded by the frequent com- 
munication between them, so that if one chan- 


633 


nel were altogether closed or material con- 
tracted, there are many others by whitn the 
blood could return. Nor is a local congestion 
likely to take place to any extent, for such 
is the freedom of communication between the 
sinuses and the veins of the exterior of the 
cranium, that (all being devoid of valves) an 
overflow would readily be received by the 
latter without the least impediment. Lastly, 
we learn the great importance and value of 
local depletion as an agent for relieving vascu- 
lar fullness within the head, owing to the free 
communication between the extra- and the 
intra-cranial circulation, and especially of the 
veins; and we may infer from anatomy that 
local depletion would most probably be more 
serviceable than general, for although the latter 
would diminish the amount of the mass of 
circulating fluid, it would not affect the relation 
between the venous and arterial systems, whilst 
it is evident that the former must affect the 
venous system more directly than the arterial. 
Moreover, the free communication between the 
circulation within and that without the cranium 
may explain somewhat the advantage that is 
often derived from the application of an intense 
cold to the external surface of the head. 

Of the pia mater. ( Tunica intima vel vascu- 
losa..)—The pia mater is the most internal mem- 
brane of those which have been enumerated 
as belonging to the spinal cord and brain. 

Pia mater of the spinal cord.—This mem- 
brane stands in precisely the same relation 
to the spinal cord as the neurilemma does to 
the nerves; and as long as the spinal cord 
could be, as it formerly was, regarded merely 
as a bundle of nervous fibres, the analogy of 
this membrane to the nervous sheath would 
be perfect. It is composed almost entirely 
of white fibrous tissue; it closely invests the 
cord and supports the minute bloodvessels 
which carry the nutrient fluid to it. Not 
only does it thus form a complete sheath to the 
cord, but it likewise sends in processes which 
dip into the anterior and posterior median 
fissures of that organ. That which passes into 
the anterior median fissure is a true fold or 
duplicature of the pia mater; but the posterior 
fissure, which is much narrower than the ante- 
rior, is occupied only by a single and extremely 
delicate layer, which at some parts almost 
entirely disappears, and seems to consist merely 
of a few minute capillary vessels. The pia mater 
becomes continuous with the neurilemma of 
the roots of the nerves on each side of the cord, 
and at its inferior extremity it tapers in accor- 
dance with the shape of the spinal cord, and is 
prolonged as a delicate thread which is inserted 
into the extremity of the dura mater. This 
prolongation is quite gradual, so that at the 
upper part it encloses a portion of the medullary 
substance of the cord ; in the greater part of its 
extent, however, it is merely a membranous 
thread, and, therefore, goes by the name /fili- 


Jorm prolongation of the pia mater (filum 


terminale). The late Dr. Macartney used 
to regard it as highly elastic, but my friend 
Mr. Bowman has called my attention to the 
fact that it consists almost entirely of white 


634 


fibrous tissue, which cannot confer elasticity. 
And if a portion removed from the cord be 
stretched, it will be found to possess very little 
elasticity ; but if the cord be held up by the 
filiform prolongation, and a slight jerking move- 
ment be communicated to it, it may be made 
to dance about as if by the elastic reaction of the 
filliform process. The movement which may 
be thus produced is very well calculated to 
deceive, and Dr. Macartney must have founded 
his opinion upon that experiment alone, omitting 
to try the effect of stretching a detached portion 
of the process. The fact is that when the cord is 
suspended in this way, the pia mater becomes 
stretched, and its anterior and rior por- 
tions are approximated and the cord flattened ; 
when it is raised with a jerk, this tension of 
the pia mater is diminished, and the cord re- 
turns to its previous form until it falls again, 
stretches the pia mater, and becomes once 
more flattened, producing a degree of reaction 
which favours its elevation, but which alone 
would be insufficient for that purpose. Thus 
it appears that the elastic reaction, which Dr. 
Macartney attributed to the filiform process, is 
in reality due to the compression and conse- 
quent flattening of the cord by the tension of 
the pia mater. It should be stated, further, 
that this process is not formed of pia mater 
alone, but also of a continuation of the liga- 
mentum denticulatum on each side to be 
described by-and-bye. 

The pia mater is abundantly supplied by 
bloodvessels, many of which are extremely 
tortuous. These vessels are derived from the 
anterior avd posterior spinal arteries. Along 
the anterior surface of the spinal cord in front 
of the anterior median fissure there is a narrow 
band of fibrous tissue which is stretched across 
this fissure like a bridge, and occupies its 
whole length. No such arrangement exists on 
the posterior surface. 

e pia mater of the spinal cord esses 
considerable strength and density. e ner- 
vous matter may by pressure be squeezed out 
of it, leaving a hollow cylindrical membrane, 
or it may be dissolved out by the action of 
liquor potasse. In the quite recent state, 
while the cord is as yet firm, the pia mater 
may be readily dissected off, its adhesion to 
the cord being through the medium of nu- 
merous exceedingly minute capillary vessels. 
On its exterior the pia mater adheres to the 
visceral layer of the arachnoid membrane by 
means of a loose fibrous tissue. 

Pia mater of the brain.—In tracing the pia 
mater of the spinal cord upwards, it will be 
found gradually to become much thinner and 
more delicate as it passes from the medulla ob- 
longata to the hemispheres of the cerebellum 
and cerebrum. In connexion with these latter 

it becomes of extreme tenuity, and owes 
its physical tenacity chiefly to the intimate con- 
nexion of the visceral layer of the arachnoid 
membrane with it. The cerebral pia mater is al- 
most exclusively composed of numerous ramifi- 
cations of minute vessels which are accompanied 
by white fibrous tissue in small quantity. These 
vessels divide and subdivide to the last degree 


NERVOUS SYSTEM. (Nervous Centres. Tue Mentnoes.) 


of minuteness, and are admirable objects for 
examining the structure of capillary vessels. 
The pia mater adheres closely to the whole 
surface of the brain, cerebellum, and connect- 
ing parts, and numberless vessels pass from it 
into the nervous substance in contact with it. 
On the surface of the brain it dips down into th 

sulci or furrows between the convolutions, an 
adheres to the superficial grey matter. Whe 
ever there is a depression or fissure of t 
brain, the pia mater is found dipping into } 
It likewise sinks into the fissures 
lamine of the cerebellum. 

We shall obtain, however, a very inadequat 
notion of the extent of the pia mater, 
confine our examination of it to the exterior 
the brain and cerebellum. At certain situation 
this membrane is continued into the caviti¢ 
or ventricles of these organs, where it doubt 
fulfils some office connected with the supp 
and nutrition of certain parts of them. Th 
situations are four in number, as follow: ¢ 
each side, the fissure between the crus cerel 
and the middle lobe of the brain, behind, 
transverse fissure between the cerebellum < 
cerebrum, and, lastly, the inferior extremity 
the fourth ventricle. 

Choroid plexuses of the lateral ventricles 
These are apparently folded processes © 

ia mater which enter the inferior part of 

teral ventricles on each side, and are conti 
upwards and forwards to their middle portic 
where they become continuous with each 01 
in the foramen commune anterius, 
a middle process, the velum. Each cho 
plexus forms a somewhat cylindrical pre 
which, when traced from below upwards” 
from behind forwards, will be found to foll 
the direction of the lateral ventricle as far 
wards as the apex of the horizontal portic 
the fornix, gradually diminishing in thie! 
and assuming the character of a simple 
branous expansion. It projects freely in 
cavity of the ventricle, having no comm 
with the walls of that cavity excepting | f 
the margins of the fissure, at which itt 
where the membrane of the ventricle a 
to it, being probably reflected upom it, 


a, villus; 6, epithelium; ¢, nucleus 6 
lium. re 


. 
/ 
we 
Very numerous and tortuous blood 
contained in these processes, forming’ 
which has given name to the folds themsel 


NERVOUS CENTRES. (Human Anatomy. Tue Menrnces.) 


The surface of each choroid plexus presents 
many slight projections or folds resembling 
villi, in which are contained loops and plexi- 
form anastomoses of minute vessels, very si- 
milar to the arrangement of the vessels of the 
villous processes of the chorion of the ovum, 
or those of the tufts of the placenta. These 
vessels are surrounded by an epithelium which 
has much the appearance of that of serous 
‘membranes. From the great number of these 
vessels and from the delicate nature of the 

ithelial covering which surrounds them, it is 

lain that the choroid plexuses are well suited 
either for the purpose of pouring out fluid or 
of absorbing it. 


t 


De 


oO 


UME s a8 su 
y, Kee U Q b & 
Y 


ws je 
Oe 


Side view of villi of the choroid plexus of the lateral 

- ventricle in the brain of a Goose, to show the 

_ disposition of the bloodvessels. Not to obscure the 

view of the bloodvessels, the edge of the epithelium 
shown. 


h only has been 
ia 4, epithelium; 5, bloodvessels. 
. (After Valentin. ) 


vy ~ 
_ The epithelium may be best seen by examin- 
ing the edge of afold. It becomes very distinct 
when acted upon by acetic acid. As its particles 
“are very delicate and consist only of a single 
layer, they are easily detached. The cells of 
epithelium are most of them six-sided, and 
contain a clear nucleus, or several minute gra- 
nules. Valentin states that cilia may be seen 
playing upon this surface, especially in the 

yo. Ihave observed the peculiar punc- 
tiform or spiniform formations to which he 
alludes, which look like the remains of former 
vibratile cilia. 

Velum interpositum. (Toile Choroidienne, 
Vieg d’Azyr.)—The choroid plexuses are con- 
nected to each other by the velum interpositum, 
which is a triangular fold of pia mater that 
passes in at the transverse fissure between the 
upper surface of the tubercula quadrigemina 
and the posterior reflected portion of the corpus 
callosum. This process is continuous with the 

ia mater of the inferior surface of the posterior 
lobes of the brain, and with that of the superior 
surface of the cerebellum, and it therefore con- 
sists of two lamine; as it passes forwards, it 
sends downwards a little process which em- 
braces the pineal body ; it forms the roof of the 
third ventricle, being interposed between that 
cavity and the fornix, (hence its name,) and 
at its sides as well as its apex its continuity 


635 


with the choroid plexuses may be readily de- 
monstrated. At its anterior extremity it(_orre- 
sponds to the foramen commune anterius. The 
velum interpositum is best exposed in the dis- 
section from above downwards by removing 
carefully in succession the corpus callosum and 
the fornix. In raising the velum itself, in order 
to disclose the cavity of the third ventricle, it 
is necessary to be very careful, as from the in- 
timate connexion which the pineal body has 
with it towards its base, that body may be 
readily disturbed from its position. 

Choroid plexuses of the fourth ventricle.— 
The choroid plexuses of the fourth ventricle 
are two small processes of pia mater united 
along the median line, presenting the same 
villous character as those of the lateral ventri- 
cles. These folds seem as if they had been 
tia up into the fourth ventricle by the 
ower lamine of the inferior vermiform process. 
Their position may be best seen by opening the 
fourth ventricle from above, where they will be 
found lying on each side of that portion of the 
median lobe of the cerebellum which stops up 
the inferior extremity of the fourth ventricle. 
These plexuses are in every respect similar, as 
far as regards structure, to the larger ones 
which are found in the lateral ventricles, and, 
like them, exhibit a delicate epithelium upon 
their surface. Upon the centre of each epithe- 
lium cell Valentin states that a pigment cor- 
puscule is deposited. ( Fig. 365.) 


Fig. 365. 


A highly magnified villus of the choroid plexus of 
human cerebellum. ( After Valentin. ) 
a, the villus; 6, the epithelium cells; c, the 
nuclei. 


These internal processes of the pia mater 
contain minute crystalline formations, a kind 
of very fine sand, which, however, is not con- 
stantly present in all brains. 

The grains are deposited in the meshes of the 
vascular plexuses. Sometimes they accumulate 
in masses so as to be visible to the naked eye 
or easily recognized by the touch. In general, 
however, they are microscopic, in form glo- 
bular, and connect themselves with the minute 
vascular ramifications like little bunches of 
grapes. They are found principally in the 
choroid plexuses of the lateral ventricles, and 
in that portion of the velum  interpositum 
which embraces the pineal body. In the for- 
mer they are most numerous at that part which 
was called by the Wenzels glomus, where the 
choroid plexus turns up from the inferior cornu 
into the horizontal portion of the lateral ven- 
tricle.* As regards chemical composition this 


* See Van Ghert de plexubus choroideis, 
Utrecht, 1837 ; Valentin, in Soemmering Anat., and 


636 


sabulous matter consists chiefly of phos- 
phate of lime with a small proportion of phos- 
phate of magnesia, a trace of carbonate of lime, 
and a small quantity of animal matter. 

The pia mater adheres a closely to the 
surface of the brain, coming for the most part 
into contact with grey matter. When a portion 
of it is raised carefully in a fresh brain, num- 
berless extremely minute bloodvessels are seen 
Passing from it into the cerebral substance. 

ese are the principal nutrient vessels of the 
brain. On its outside the pia mater adheres 
partially to the arachnoid membrane. At those 
points which correspond to the convex portions 
of the convolutions the adhesion of arachnoid 
to pia mater is close; but at other places the 
latter membrane separates completely from the 
former. 

The pia mater of the brain differs from that 
of the spinal cord in its great delicacy and 
tenuity ; it wants the strength and density of the 
latter membrane. This 1s owing to its being 
com almost entirely of extremely minute 
and delicate bloodvessels, whilst the spinal 
membrane consists chiefly of white fibrous 
tissue. The bloodvessels of the former are in- 
finitely more numerous than those of the latter, 
and the reason of this probably is that the 
cerebral membrane is chiefly in contact with 
grey matter, which requires a great quantity of 
blood, but the spinal membrane immediately 
embraces white matter, which is much less 
vascular. 

It is important, in a pathological point of 
view, to notice that this membrane is the me- 
dium of nutrition, not merely to the nervous 
matter of the brain and cord, but also to the 
arachnoid membrane which is immediately 
adherent to it, and to which it bears the same 
relative position as the sub-serous areolar tissues 
elsewhere to their respective serous membranes, 
Hence the difficulty, if not the impossibility, 
of adopting distinctions which systematic wri- 
ters endeavour to make out between arachnitis 
and superficial inflammation of the brain. It 
is physically impossible that there shall be 
arachnitis without serious disturbance of an 
inflammatory kind in the circulation of the 
pia mater, nor can this exist without affecting 
the superficial layers of the grey matter of the 
convolutions. It may, therefore, be confidently 
affirmed that arachnitis, when affecting that 
portion of the arachnoid membrane which co- 
vers the hemispheres of the brain, is synony- 
mous with inflammation of the superficial 
layers of the grey matter of the convolutions. 
Whatever be the point of departure, it seems 
impossible that inflammation of the one can 
exist without a similar and equal affection of 
the other. And thus we may explain the ap- 

ntly anomalous statement of authors that 
inflammation of the arachnoid should give rise 
to a more violent train of ew than deep- 
seated inflammation of the brain. The real 
difference is, not between membranous and 


Bergmann, iiber die innern Organisation des 
Gehirns. The last author states that he has seen 
the sandy deposit excessive in connexion with 
mental derangement. 


NERVOUS SYSTEM. (Nervous Centres. Tat Mentnces.) 


cerebral inflammation, but between an inflan 
matory affection of the superficial grey matte 
of the convolutions, the great source and seat 
of the physiological activity of the brain, am 
a similar morbid action of the more centra 
white substance, the function of which is ina 
certain sense subservient to that of the super- 
ficial grey matter. — 
Of the arachnoid membrane.—This met 
brane is intermediate to those already describ 
We have preferred giving the description of 
last, because to understand it demands | 
acquaintance with the details of both the 
membranes. 7 
The arachnoid is a great serous mem 
pervading the entire cranio-spinal cavity. | 
— layer adheres intimately and insepar 
ly to the inner surface of the dura mater bo 
cranial and spinal, and its visceral q 
attached to the outer surface of the pia matet 
In point of structure and general dispositi 
the arachnoid membrane resembles other 
rous membranes, so much as to render it ine 
pedient to enter into any minute comparis 
of them. It will only be necessary to refer 
such peculiarities of arrangement as may 4 
from the anatomical characters of the nery 
centres with which it is connected. 
Spinal arachnoid —The serous che 
the spinal arachnoid is best seen by e: 
a transverse section of the spinal cord ar 
membranes. If the section be made ac 
the interval between two sets of spinal ner 
the visceral and parietal layers of the m 
brane may be seen in contact with each oth 
the parietal layer closely attached to the ¢ 
mater, the visceral layer adherent to the 
mater of the spinal cord so loosely as to hi 
a considerable space between it and the o 
surface of that membrane. 2% 


Fig. 366. 


Transverse section of spinal cord and its 
between the fifth and sixth cervical 
( After Arnold, ) 
v, visceral layer of arachnoid membrane; 
arachnoid space; c, arachnoid cavity. _ 
We may here notice an im dis 
which the student of this ion of ar 
will do well to note particularly, e 
the space between the two layers of are 
membrane is the arachnoid bag or & 
which it is very rare for any fluid to ac 
late; and that that between the visceral 
the arachnoid and the pia mater is t 
arachnoid cavi'y, in which, as will be 
by-and-bye, a considerable quantity of 
exists in the natural state. a 
When the section is made on a level wit 
nerves as they emerge through the dura 
we may notice the manner in w 
noid membrane is prolonged upon 
in the form of a loose sheath, 


’ f 
ormir 


itt ii 


NERVOUS CENTRES. (Human Anatomy. Tat Menrnces.) 


uls-de-sac at the orifices through which the 
erves escape. ) 


Fig. 367. 


Transverse section of the same on a level with the fifth 
4 cervical nerves. (After Arnold. ) 
"The same parts are displayed as in the last figure, 
ind the reflection of the arachnoid at the exit of 
he nerves is seen. : 
af, anterior fissure ; m, ”, spinal nerves. 
In the interval between each pair of nerves, 
ve find a triangular process of fibrous mem- 
wane which is inserted by its apex into the 
mater. This process lies in the sub- 
arachnoid cavity and adheres by its base to the 
ia mater. It seems to pierce both layers of 
1e arachnoid, or to pin them down, as it were, 
) the dura mater. 
At the foramen magnum the spinal arach- 
noid may be seen to be continuous with that 
of the brain, and here its visceral layer invests 
the medulla oblongata loosely. Inferiorly we 
trace the membrane down quite to the lowest 
extremity of the dura mater, and in this region 
the visceral layer is particularly loose and free, 
as it lies over the cauda equina. 
When the dura mater is carefully slit up 
either the anterior or the posterior surface, 
‘the arachnoid sac is laid open. It does not 
always happen that the parietal layer separates 
very Seay from the visceral: frequently the 
two layers adhere firmly at several minute 
points, yet this adhesion is effected without any 
connecting membrane, and appears to arise from 
the two layers becoming dried at several corres- 
ponding points, and thus being, as it were, glued 
together. We may frequently observe this in 
specimens that have been some time kept in 
spirits. This point is deserving of notice, as 
these adhesions might be (and indeed they have 
been) noted as of a morbid nature. 

The visceral layer of the spinal arachnoid is 
connected to the pia mater by means of a num- 
ber of long filaments of fibrous tissue which in- 
terlace slightly, and in the areole thus formed 
the fluid is contained. This tissue is most dis- 
tinct and abundant in the cervical region, and 
exists in very small quantity in the dorsal. It 
ceases nearly altogether over the cauda equina. 
Numerous minute bloodvessels are also to be 
found in it passing from the pia mater to the 
arachnoid. Majendie gives to this tissue the 
name “ tissu cellulo-vasculuire sub-arachnoide.” 

In general the adhesion of the visceral layer 
of the arachnoid to the subjacent pia mater is 
closer along the posterior than along the ante- 
rior surface of the cord. 

Along the posterior surface of the cord on 
the median line, the sub-arachnoid space is 
divided by means of a septum, which is most 

rfect in the dorsal region, but which in the 

umbar and cervical regions is cribriform or 


> 


637 


pectiniform, as may be shown by pouring 
quicksilver on either side of it, which will be 
retained in the dorsal region, but will readily 
ass from right to left in the other situations. 
t is highly probable that this septum is a mo- 
dified portion of the sub-arachnoid tissue. 

The existence of this septum (erroneously 
described as complete) dividing the posterior 
part of the sub-arachnoid space into a right 
and a left portion, appears to have led to the 
opinion that this space is lined by another 
serous membrane, which has been called the 
internal arachnoid, by which the fluid is sup- 
posed to be secreted, and that the septum is 
formed by the reflection of its visceral into its 
parietal layer along the median plane. But there 
are many objections to this hypothesis. In the 
first place, if the septum were formed by the 
reflection of a serous membrane, it would be 
complete, and not a very imperfect one such as 
it is; it ought to resemble the mediastinum in 
the chest, or one of the processes of the perito- 
neum in the abdomen. Secondly, it is quite 
contrary to all experience to find the cavity of a 
serous membrane in the normal state traversed 
by a quantity of filamentous tissue, as the sub- 
arachnoid space is throughout a great part of its 
extent. Thirdly, were there a serous membrane 
in this space, the microscope ought to detect an 
epithelium on its inner surface, but sucha struc- 
ture does not exist here. Lastly, such a serous 
membrane must necessarily be continued into the 
encephalic sub-arachnoid space. But the close 
adhesion of the visceral layer of the arachnoid 
to the pia mater, opposite to the prominent 
parts of the cerebral convolutions, seems quite 
incompatible with such an arrangement. 

Cerebral arachnoid.—The cerebral portion 
of the arachnoid exhibits essentially the same 
general arrangement as the spinal portion. Its 
parietal layer adheres very intimately to the pia 
mater at certain points, leaving in the intervals 
a considerable space for the accumulation of 
liquid. If we trace it over the surface of the 
hemispheres, it will be found to give them that 
smooth and uniform character which is always 
distinct on the recent healthy brain. The 
arachnoid passes from convolution to convolu- 
tion, adhering closely to the pia mater over the 
most convex portions of those convolutions, 
but allowing that membrane to separate from 
it in the intervals between them, and to dip 
down to the bottom of the sulci. Hence liquid 
accumulated in the cerebral sub-arachnoid space 
will be found to take the direction of the inter- 
gyral sulci, and to cause the membrane to 
bulge opposite to them; and if air be blown 
underneath the arachnoid, it will be found to 
take the tortuous course of these sulci. 

The arachnoid sinks into the great longitu- 
dinal fissure of the brain, lining the surfaces 
which bound it on each side, and passing 
across from right to left beneath the inferior 
margin of the falx, and above the corpus cal- 
losum. 

On the base of the brain, the arachnoid has 
the same arrangement on those parts where 
there are convolutions, as on the superior and 
lateral surfaces of the hemispheres. It. passes 


638 


over the fissure of Sylvius from the anterior to 
the middle lobe, and here its distinctness from 
the pia mater may be clearly demonstrated ; 
here too it appears much stronger and more 
opaque than elsewhere, which is probably 
due to the existence of an increased quantity 
of fibrous tissue beneath it. 

In that space on the base of the brain which 
is bounded on each side by the middle lobes, 
and which is limited in front by the optic 
nerves and behind by the pons Varolii, the 
arachnoid membrane stretches across from one 
middle lobe to the other, leaving a considerable 
space between the tuber cinereum and the pons, 
in which it is connected to the pia mater by 
several long filaments similar to those which 
are met with on the surface of the spinal cord. 
This s is favourable for the accumulation 
of fluid, and it communicates in front with the 
fissures of Sylvius and other deep fissures into 
which fluid might make its way. Cruveilhier 
calls it the anterior sub-arachnoid space, and 
regards it as the principal reservoir of the cra- 
nial serosity. Immediately in front of it we 
observe that the arachnoid membrane is conti- 
nued around the infundibulum to the pituitary 
body. 
re tracing the arachnoid backwards from the 
great longitudinal fissure of the brain, we ob- 
serve that it stretches down from the posterior 
edge of the corpus callosum to the superior 
surface of the cerebellum, crossing over the 
tubercula quadrigemina. At this situation the 
arachnoid is reflected upon the vene magne 
Galeni as they pass to the straight sinus. It 
was at this place that Bichat described the 
canal which goes by his name, through which, 
as he thought, a process of the arachnoid mem- 
brane was carrried in to line the interior of the 
ventricles. 

The arachnoid covers the superior surface of 
the cerebellum and also its inferior surface, 
stretching across the longitudinal fissure from 
one hemisphere to the other, and it is also ex- 
tended downwards, and a little forwards from 
the superior surface of the cerebellum to the 

terior surface of the medulla oblongata, 

low the inferior extremity of the fourth ven- 
tricle. A considerable space is thus left, situate 
posteriorly between the cerebellar SA NRC 
and bounded in front and inferiorly by the 
medulla oblongata, which also forms a conside- 
rable reservoir for cerebral fluid, and communi- 
cates freely with the sub-arachnoid space of the 
spinal canal; but as the arachnoid is tied down 
somewhat more closely over the posterior sur- 
face of the spinal cord, there is an appearance 
of constriction where the cerebral passes into 
the spinal arachnoid. This space is called by 
Cruveilhier the posterior sub-arachnoid space 
(posterior conflux of Majendie). It commu- 
nicates with the anterior sub-arachnoid space 
through the furrows around the crura cerebelli. 

Of the cerebro-spinal fiuid—In examining 
such a dissection of the membranes of the 
spinal cord as that above described, we shall 
find that at various points the visceral layer 
of the arachnoid membrane appears raised up 
by fluid or by a bubble or two of air from 


NERVOUS SYSTEM. (Nervous Centres. Tar Mentnoes.) 


If a small po ion of 


the subjacent viscus, 
this layer be taken up in a id 
blow-pipe be introduced into it, air may be 


blown underneath it, raising it up all a 
the spinal cord to a considerable distance fron 
that organ. The inflation is more easily e 
fected in the cervical and in the lumbar region: 
than in the dorsal, and the air will pass dow 
quite to the lowest part of the canal of the dur; 
mater, where the connexion of the rn 
membrane to the cauda equina is particulal 
loose. In the same way col Auid, 
some material which may assume the solid forr 
as size, tallow, &c, may be injected to demo 
strate this anatomical arrangement. If now v 
examine a transverse section, it will be observe: 
that a considerable interval exists between th 
visceral layer of the arachnoid and the pi 
mater of the cord, and that this interval 1 
much greater in the neck and in the loins 
in the back. We observe too that the spit 
cord is by no means of sufficient size to fill 
spinal canal, and that as a considerable intery 
exists between its surface and the visceral lays 
of the arachnoid, so also a still greater one 
found between it and the inner surface of 
dura mater. Now as it is of the very natu 
of a serous membrane that its free smo¢ 
surfaces should always be in contact (for it 
in that way that it favours the movements 
the viscus with which it is connected), it 
plain that the sub-arachnoid space in the sp 
must, during life, be kept in a state of distens 
otherwise the object of a serous mem 
would not be attained. 
Moreover, in tracing the arachnoid mi 
brane upwards over the medulla oblongata : 
the other parts of the encephalon, we obs 
an evident continuity between the spinal ; 
the cranial sub-arachnoid cavity, which is m 
evident at the base of the brain, where 
latter possesses the greatest dimensions, so tl 
air or fluid may be readily made to pass | 
one to the other. This is most conspicu 
old subjects, in which the brain being : 
and more or less shrunken, leaves a cons 
able interval between its surface and the 
ceral layer of the arachnoid. ‘ 
On opening the spinal canal in a bod 
cently dead, the visceral layer of the arac 
will almost always be found raised by 
When a portion of the posterior wall 
spinal canal is removed in a living an 
in one just killed, the dura mater is fe 
be quite tense from the fluid which is ae 
lated within it. In a horse, whose spina 
I opened in the dorsal region imme Jiatels 
he had been knocked down in the k 
yard, I found the dura mater perfectly 
and semi-transparent from bei etc 
firmly over fluid. Upon making a @ 
puncture in it, a fine stream of clear fluid 
ejected with much force to a considerable 
tance, and immediately the dura mater be 
quite flaccid. By a little careful diss 
through the dura mater and parietal | 
arachnoid, it may be shewn that this 1 
not contained in the arachnoid sac, bat 
sub-arachnoid cavity. we 


4 


NERVOUS CENTRES. (Human Anatomy. 


Fig. 368. 


atloido-vecipital articulation. 
_ (After Majendie. ) 


¢, the spinal cord. 

d, the dura mater and arachnoid membrane. 

, the sub-arachnoid space, divided into an 
rior and posterior portion by 

J, the ligamentum denticulatum. 


ection in the dorsal region. 

‘he same letters indicate similar parts as in A. 
n, the posterior median septum. 

% the roots of the nerves. 


_ We can thus demonstrate the existence of a 
fluid, which during life and in a state of health 
upies the sub-arachnoid cavity and main- 
ins the two layers of the arachnoid membrane 

‘contact with each other. This fluid is 
i by Majendie the . cerebro-spinal 


_ The first distinct recognition of this fluid in 
/ proper locality is due to Cotunnius, who 
the results of his observations in his 
emoir “ de Ischiade Nervosa,” preserved in 
Sandifort’s collection of dissertations. Cotun- 
hius was led to the discovery by remarking the 
on between the dimensions of 
the spinal canal and the bulk of its contents, 
so that a considerable interval exists between 
the internal surface of the former and the spinal 
cord, which must be filled by something ; and 
r attributes its having been so completely 
verlooked by previous anatomists to the fa- 


A, Transverse section of the spine at the situation of 


Tue Mentnces.) 
Fig. 369. 


639 


aitatrs 


Manes 
Mi 

Bag SOX VE 

AGE 


vy 


Sections of the spine in the lumbar region. 


A, shews the section of the cord as well as of 
many roots of nerves descending to form the cauda 
equina, . 

B, shews the section of the cauda equina. 

In both these regions the sub-arachnoid space is 
large and uninterrupted by bands or septa. The 
fluid permeates between and surrounds the roots of 
the nerves. 


shion of opening the head before the spine, 
which favoured the escape of the fluid. This 
anatomist was also aware that the fluid was 
formed and contained in the sub-arachnoid 
cavity. 

It is, however, to M. Majendie that we are 
chiefly indebted for our present knowledge of 
the physiological history of this fluid. Majen- 
die’s first researches were given to the public 
in his Journal de Physiologie for the year 1827, 
and he has lately collected the results of his 
inquiries in a volume entitled “ Recherches 
Physiologiques et Cliniques sur le Liquide 
Cephalo-rachidien,” and published in 1842. 

The cerebro-spinal fluid is found wherever 


640 


pia mater exists in connexion with brain or 
spinal cord, whether on the surface of these 
organs, or in the ventricles of the former. It 
serves to fill up various inequalities in the cra- 
nial or spinal walls, and it accumulates in 
greatest quantity in those situations where the 
sub-arachnoid space affords the greatest ca- 
pacity. 

Majendie describes four situations at which 
this fluid accumulates in greater quantity than 
at other places on the surface of the brain.. The 
most considerable of these, which he desig- 
nates the posterior conflux, is situated below 
and behind the cerebellum; it corresponds to 
the posterior surface of the medulla oblongata, 
and is covered behind by the layer of arachnoid 
which extends between the medulla and the cere- 
bellum. (Vid.supr. p.638.) It is here that, ac- 
cording to Majendie, a communication takes 

lace between the fluid on the exterior and that 
in the ventricles, at a point corresponding to 
the inferior extremity of the fourth ventricle. A 
second, or inferior conflur is found immedi- 
ately in front of the pons Varolii; it is situated 
between the crura cerebri, and contains the 
basilar artery. It is, in fact, only the posterior 
part of what Majendie designates the anterior 
conflux, which extends forwards to the com- 
missure of the optic nerves, pees i Aa the 
central depression between the middle lobes 
of opposite sides, and bathing in its fluid the 
commissure, the tuber cinereum, the infundi- 
bulum, and the trunks of the anterior cerebral 
arteries. It communicates with the posterior 
fissure beneath the crura cerebelli. € posi- 
tion and the extent of this conflux is indicated 
by the separation of the visceral layer of the 
arachnoid membrane over the central part of 
the base of the brain. Doubtless the accumu- 
lation of fluid around so many parts of impor- 
tant function and delicate structure, is a va- 
luable safeguard to them against the communi- 
cation of shocks from the walls of the cra- 
nium. A fourth conflux is called superior ; it 
is situated behind and a little below the level of 
the corpus callosum, behind the pineal gland, 
and above the tubercula quadrigemina. It 
communicates around the crura cerebri with the 
anterior conflux, and with the posterior conflux 
by the fissures which separate the superior ver- 
miform process from the hemispheres of the 
cerebellum. The fluid contained in it bathes 
the pineal gland, the tubercula quadrigemina, 
the superior vermiform process, and the vene 
Galeni as they empty themselves into the strait 
sinus. 

As the fluid is in contact with pia mater, 
it is plain that it must surround and support 
the roots of all the nerves which proceed from 
both the brain and spinal cord, and that all 
the bloodvessels which penetrate or emerge 
from those organs, or which ramify in the 
pia mater, must also be bathed by it. The 
fluid surrounds the nerves as they emerge from 
the cranium or spine, and maintains contact 
between the layers of arachnoid membrane 
which compose the sheaths that accompany 
them in their outwards. Majendie 
states that this aid ‘covvenpatiies the roots of 


NERVOUS CENTRES. (Human Anatomy. Tut Mewrnces.) 


the fifth pair of nerves as far as the Gasserian 
ganglion, and that it bathes and mingles with 
the fibres of the ganglion itself, as well as of 
the three nerves which originate from it. : 
however, I think extremely doubtful. . 

That fluid exists in the ventricles of # 
brain has long been known to anatomists; an 
it seems highly probable that this fluid is s 
creted by the of pia mater which 
found in all i caviticn te ibly by dl 
membrane which lines their vihing 
internal fluid communicate with that in 
sub-arachnoid space? Majendie affirms that 
communication takes place by means of an opt 
ing which is situated at the inferior extremity 
the fourth ventricle. I have not been q 
satisfy myself of the existence of such an a 
ing; the following is Majendie’s description 
it: “ The true orifice, constant and normal, | 
which the cerebro-spinal fluid contin 

either to enter the ventricles or 
issue from them, may be seen at the infer 
termination of the fourth ventricle, at the p 
named ‘ le bec de la plume’ by the old ana 
mists. 

“ To demonstrate the existence of this o 
fice it is necessary to raise up, and to sep 
slightly from one another, the lobules of t 
inferior vermiform process of the cerebellu 
and without breaking any of the vascular | 
lesions which unite this part of the cerebell 
with the spinal pia mater, we ive 
angular excavation which terminates the fe 
ventricle. Its surface is smooth, even (px 
and is prolonged as far as the ventricle of 
cerebellum. Such is the anterior part of 
orifice : the lateral and superior parts are for 
by the choroid plexuses of the n and 
horny medullary lamella (valve of Tarin), 
extent of which is variable, and which adh 
to the prominent border of the fourth 
The form and dimensions of the opening 
with the individual, and with the quan 
cerebro-spinal fluid, so that when the 
exists in considerable quantity the open 
admit the extremity of a finger. Most 
quently, when the quantity of the ligt 
normal, the orifice does not exceed | 
three lines in diameter in every direction 
it is frequently subdivided by vessels 4 
= from the medulla oblongata to the ce 
um. Sometimes the orifice is icl 
one or by both of the posterior cerebell: 
ries which pass across it.” 

Such is the description of the or 
which Majendie has given the high 
title “* Orufice des cavités encephaliques 
states that when fluid is injected into the 
sub-arachnoid cavity, it makes its in 
ventricles of the brain through this or 
Statement sufficiently difficult to pre 
veilhier, who seems to Jean towards ] 
opinion, admits nevertheless several 
objections to it. The most important 
appears to me to be that the m 
oritice which is brought into view b 
thod directed by Majendie, are i 
have the appearance of neml 
And it is recorded by M. Martin St. Ange 


Pn. 


NERVOUS CENTRES. (Humax Anaromy. Tue Cerepro-spinan Fruip.) 641 


the authority of Cruveilhier, that in fifteen sub- 


_ jects in which the latter anatomist found this 
orifice, its margins had the torn appearance in 
every one; “that around the opening, here 
and there, there existed the debris of mem- 

_ branes.”’* 

___ My own opinion is that this orifice does not 
exist naturally, but that it is produced by the 

_ violence to which the brain is subject in its 

emoval, or in the manipulations necessary for 

demonstrating it. It appears to me that the 
fourth ventricle is closed in the same way as 

‘the inferior horn of the lateral ventricles, namely, 

by the reflection of its proper membrane from 

its floor on to the adjacent pia mater. This 
embrane is so extremely delicate that the 
ightest traction upon it is sufficient to dis- 
rb its connexions. Its existence may be 
2st proved by the resistance which a probe 
pushed into the fourth ventricle from above 
experiences at its inferior extremity, a resist- 
ance, however, which a little force can over- 
come. Or, if the fourth ventricle be opened 
from the side, by a vertical section of the 
median lobe of the cerebellum some dis- 
nce to one side of the median plane, and 
if this be done on a brain previous to its re- 
moval from the body, or on one which has been 
removed with great caution, so as to occasion 
the least possible disturbance to the parts, it 

ll be found that the ventricle is closed below 

y the reflection of its proper membrane upon 

@ pia mater. There can be no doubt that 

uid driven against this membrane with force 

Would easily rupture it, whether from with- 

hn the ventricle or from the sub-arachnoid 


‘Space.t 
_Itis plain that if there be a direct commu- 
tion between the fluid in the ventricles and 
in the sub-arachnoid cavity at the inferior 
emity of the fourth ventricle, it must take 
ce through an opening in that portion of the 
mater which ascends into the fourth ven- 
icle to form the choroid plexus. But it is 
bt necessary to have recourse to such a sup- 
sition to account for the transmissibility of 
from one cavity to the other, for the 
Mater is evidently hygrometric, and will 
lily admit of the passage of fluid through 
by endosmose, and it is highly probable 
, if any interchange of fluid takes place 
the intra-ventricular cavity and the 
‘sub-arachnoid space, it is accomplished through 
‘the influence of endosmose and exosmose, 
etiected not merely by the pia mater at the 
in extremity of the fourth ventricle, but 
likewise by that at the inferior cornua of the 
jateral ventricles, and perhaps also by that of 
| the third ventricle, at the velum interpositum. 
id it is worthy of remark, as tending to con- 
firm this opinion, (which, so far as I am aware, 
has not previously been suggested.) that at 
each of these situations there is a conflux (to 
eiedie’s phrase) of the sub-arachnoid 

uid. 


_* Martin St. Ange. Sur les membranes du 
cerveau et de la moelle epiniere. 
| Be the description of the fourth ventricle fur- 
on, . 


VOL. IIIf. 


Cruveilhier lays some stress upon the fact that 
in apoplexy the blood escapes from the-ventricle 
into the sub-arachnoid space. For my own part, 
I would say that:this occurrence takes place as 
often, if not more frequently, at the inferior cor- 
nua of the lateral ventricles, as at the fourth ven- 
tricle. And therefore, if such a fact be used as 
an argument in favour of the direct communica- 
tion of the latter with the sub-arachnoid space, it 
ought equally to lead to the supposition of the 
existence of similar orifices at the former situa- 
tions, the absence of which may be easily proved. 
Moreover it may be stated that blood sometimes 
extravasates into the arachnoid sac, breaking 
through the arachnoid membrane; it is, there- 
fore, less difficult to conceive its bursting the 
pia mater, which is evidently more porous, and 
is the seat of those vessels from which the he- 
morrhage comes, a morbid condition of which 
is the frequent precursor of the apoplectic 
attack. 

The best way of obtaining the sub-arachnoid 
fluid with a view to form an estimate of its 
quantity, is to open the dura mater and arach- 
noid in the lumbar region of the spine, having 
previously, by means of a trephine, made a 
small perforation in the skull, so as to allow the 
pressure of the atmosphere to bear upon the 
cranial contents. “ If,” says Cotunnius, “ you 
open the vertebre of the loins before the head 
is touched, and cut the enclosed tube of the 
dura mater, a great quantity of water will burst 
out, and after all this spontaneous flux of water 
is spent, if you lift up the head, and shake it 
toward the aperture, a more plentiful stream 
will burst out, as if a new fountain was un- 
locked. In these experiments, which I made 
on the bodies of near twenty adults, and which 
I repeated at different times, I could draw off 
freely from the hollow of the spine four and 
sometimes even five ounces of water: I com- 
monly found it very clear in such subjects, 
although it sometimes inclined a little to a 
yellow colour; but in foetuses strangled in 
difficult labour, little as it was, I observed 
it to be always red and opaque.’””* 

The estimate of the quantity of sub-arach- 
noid fluid here assigned by Cotunnius exceeds 
that which Majendie deduces from his expe- _ 
riments, who states that in general in a subject 
of adult age and mean size, and in moderate 
condition, two ounces may be regarded as the 
minimum quantity. Much depends upon the 
age and size of the subject and the state of nu- 
trition of the nervous centres. In children the 
quantity is very small; in old age, when the 
brain and spinal cord have shrunk considerably, 
the quantity is large. In examining the bodies 
of the aged poor, as Majendie remarks, eight, 
ten, or twelve ounces of fluid may be obtained 
from the cranio-spinal cavity, according as 
there is a greater or less degree of atrophy of 
the brain. 

In judging of the quantity of fluid around 
as well as within the cerebro-spinal centres, 


* From an English translation of Cotunnius’s 
essay, entitled, A Treatise on the Nervous Sciatica, 
or Nervons Hip Gout, translated by Henry Crantz,» 
London, 1775. | 

2T 


642 


the time which has elapsed since death must 
be taken into account. As advancing decom- 
position favours the transudation of fluids 
through the tissues, it is plain that the longer 
this period is, the less liquid will be found ; and 
the earlier after death the investigation takes 
place, the nearer will be the resemblance of the 

rts to their condition during life. On the other 

d, a very advanced stage of decomposition 
will favour the developement of liquid, wher- 
ever mee may be found for its accumulation. 
It is, therefore, in vain for the pathologist to 
attempt to form an opinion respecting the quan- 
tity of the fluid found in the cranio-spinal 
cavity, unless the inspection have been made 
at an early period after death. 

Practical men are too much in the habit of 
attributing morbid phenomena of the nervous 
system to the influence of the pressure of a 
liquid effusion upon the brain or spinal cord. 
Many facts tend to shew that in a large pro- 
portion of cases, especially in the adult, the 
occurrence of an increased quantity of fluid, 
either around those centres or within the ven- 
tricles, is a result, and that it is probably a 
result of a conservative kind, consequent upon 
a morbid change which depresses the general 
nutrition of those organs themselves. We have 
seen how the universal decay of the tissues, 
which characterizes old age, favours the increase 
of the cranio-spinal liquid, when it affects the 
brain and spinal cord. In examining the 
bodies of habitual drunkards, patients who die 
of delirium tremens, or of cirrhose of the 
liver, the quantity of fluid is always found 
to be considerable and the brain shrunk. In 
bed-ridden persons who have ceased to exer- 
cise their faculties for some time, whether for 
mental or bodily exertion, the same pheno- 
mena are witnessed. When there has been 
much anemia, as in cases where death has 
terminated a protracted illness, in phthisis 
for example, or in persons who have died of 
hemorrhage, or after excessive venesection, 
the nervous centres will be found to be small 
and the liquid in large quantity. In extreme 
cases of lead cachexy, in which the nutri- 
tion of the nervous and muscular tissues is 
materially diminished, I have observed similar 
appearances. And, when an ial atroph 
of either brain or spinal pe igs sentinel 
there will invariably 2 found, at a point cor- 
mwpending to it on the exterior of the organ, 
a local accumulation of fluid occupying a 
depression on its surface which has been 
caused by the giving way of the nervous sub- 
stance within. 

On the other hand an increase in the quan- 
tity of the nervous substance, or an enlarge- 
ment of the brain or spinal cord, consequent 
on an undue injection of their bloodvessels, 
is invariably accompanied with a diminution 
in the quantity of this fluid or with the total ab- 
sence of it. In hypertrophy of the brain no 
fluid is found in oe subarachnoid space, and 
very little or none in the ventricles. In cases of 
tumour of the brain encroaching upon the cra- 
nial cavity, we find no fluid; and the same is 
observed where chronic inflammation of the 


NERVOUS SYSTEM. (Nervous Centres. Tae Menrnces.) 


brain has given rise to a new deposit which 
increases the bulk and the density of the cra- — 
nial contents. In all cases where a considera- 
ble quantity of fluid has accumulated 
the ventricles, that upon the surface is eithe 
greatly diminished or entirely disappears. In 
the ordinary hydrocephalus internus of chil 
- fluid is never found on the exterior of th 
rain. 
When an arrest in the developement of any 
portion of the cerebro-spinal axis has taken 
plete; the space which ought to be occupier 
y the organ of imperfect growth is filled by 
liquid. oe examining the heads of idiots we 
always find a considerable quantity of sub- 
arachnoid fluid, either general, or partial 
a portion only of the brain be deficient. Or 
if any portion of the wall of the cranio-sping 
cavity be defective, the contained viscus is 
protected by the accumulation of an increases 
quantity of liquid in the situation of the de 
ficiency. Hence the explanation of thos 
watery tumours which occur over various 1 
gions of the spine, in cases of spina bifida, } 
which the accumulation of water is 
by the absence of the resisting osseous wall - 
the spine for a greater or less extent. Ami 
similar tumours are found projecting from 1 
cranium, being occasioned by a protrusion - 
the cranial meninges through a congenital ap 
ture, containing fluid and sometimes a por 
of the encephalon itself. - 
Enough has been said to show, that th 
ternatural increase of this fluid should 
general be regarded as to and | 
sequent upon‘the diminished size of the cere 
spinal centre itself, and that it has most p 
bably little or nothing to do with the man 
tation of peculiar symptoms during life in 
great majority of instances. Whatever 
immediate cause of the shrinking of the cers 
spinal centre or of any portion of it, the ine 
of the fluid goes on pari passu, and 
quantity duly proportionate to the decreas 
bulk, so that it is in the highest degree i 
bable that, in such cases as I have enum 
the nervous centre experiences any if 
degree of pressure beyond that which it 
the normal state. If, however, the fluid, 
within or without the brain, were to in 
while that organ itself either preservs 
same bulk or became enlarged, it is p 
it must experience an increased degree ¢ 
pression, which doubtless would pro 
rious symptoms. This very 
according to my experience, as rega 
subarachnoid fluid on the exterior of t 
we more is ag meet with an in 
the fluid within the ventricles, and, 
cases, we shall find evidence of the 
sion in a manifestly greater firmne 
density of its structure, and in this f 
the lateral ventricles, when laid open 
rizontal section, do not collapse, a8 
ordinary state of the brain, but re 
patulous, owing to the firmness 
of their walls. And this patulous state 
ventricles may be ed as a gooG 1D 
that the fluid, collected in them, 


NERVOUS CENTRES. (Human Anatomy. Tue Ceresro-sprnat Fruip.) 643 


some time occasioned a preternatural amount 
of pressure.* 
ajendie infers, and as it appears to me 
with justice, that the cerebro-spinal fluid is 
secreted from the vessels of the pia mater. 
He states that, when a portion of the pia mater 
is exposed in a living animal, “an attentive 
eye may observe the transpiration of a liquid 
whith evaporates, it is true, almost as soon as 
_ itappears, but which is sufficient to prevent 
_ the drying of the membrane.” “To render 
_ this phenomenon of vital physics still more 
' manifest,” he adds, “it is necessary to inject 
@ certain quantity of water, at 30° R., into the 
_ veins of the animal which is subjected to the 
_ €xperiment; immediately the liquid exhalation 
of the pia mater takes place in a more rapid 
manner, and consequently becomes more ap- 
el We ought to be content with M. 
_ Majendie’s statement respecting this experi- 
“ment: the point in question is by no means of 
‘Sufficient consequence to warrant the repetition 
‘of so cruel an experiment. 
__ Majendie’s experiments have demonstrated 
further that this fluid can be as quickly rege- 
berated as the aqueous humour of the eye. 
_ He found that on puncturing the theca of the 
ose cord, and perforating both layers of 
_ arachnoid membrane, the fluid quickly escapes 
_ at first as a fine continuous jet, and afterwards 
per saltum in correspondence with the efforts 
of expiration. If the orifice be closed up and 
| the animal left to go at large for twenty-four 
hours, the fluid is reproduced in as conside- 
/ table quantity as before the first experiment. 


_ What has been described as the movement 
Of this liquid consists in an alternate elevation 
‘and collapse synchronous with expiration and 

aspiration, seen only when a portion of the 
cranio-spinal wall has been removed, and 
caused by the repletion of the venous system 
of the spine which occurs in the former state 
of the respiratory movements, and its collapse 
_ which takes place in the latter. The distended 
_ Spinal veins compress the cerebro-spinal fluid, 

and cause it to rise towards the head in expi- 
_ fation; their collapse in inspiration favours 
the movement of the fluid in the contrary 
direction. We have no evidence from exper- 
ment or direct observation that there is any 
Movement in the fluid of the ventricles; but 
the discovery of cilia upon the inner surface of 
these cavities seems to indicate that this fluid 
is not quite stationary within them. 

“The following account of the physical and 
chemical properties of the cerebro-spinal fluid 
is derived from Majendie’s researches. When 
removed from the body a few moments after 
death, this fluid is remarkably limpid, and 
may be compared in this respect to the aqueous 
humour of the eye; sometimes it has a slightly 
yellowish tinge. In temperature it ranks 
among the hottest parts of the body. It has a 
sickly odour and a saltish taste ; it is alkaline, 
restoring the blue colour of reddened litmus. 


4 


__™ See an important paper by the late Dr. Sims 
hd effusion in the brain, Med. Chir. Trans. 
ol. xix, 


Lassaigne’s analysis of the human fly*4 yielded 
the following result. 


Water ...... er ewersive vee 98.564 
Albumen........ee..e00- 0.088 
Osmazome ...600...0000. 0.474 
Hydrochlorate of soda and ) 

Of potass ....ccse..00 § agg 


Animal matter and phos- 2 


phate of soda.........§ a 
Carbonate of soda and phos- 2 0.017 

phate of lime....... eh Nae 
99.980 


According to M. Couerbe, some of the secon- 
dary organic products which he has obtained 
from the brain are to be found in this fluid. 
The following constituents are enumerated by 
this chemist: 1. an animal matter insoluble 
in alcohol and ether, but soluble in alkalis; 
2. albumen; 3. cholesterine; 4. cerebrote ; 
5. chloride of sodium; 6. phosphate of lime; 
7. salts of potass ; 8. salts of magnesia. 

What is the use of the cerebro-spinal fluid ? 
An obvious mechanical use of this fluid is to 
protect the nervous centres with which it lies 
m immediate contact. By the interposition of 
a liquid medium between the nervous mass 
and the wall of the cavity in which it is placed, 
provision is made against a too ready con- 
duction of vibrations from the one to the 
other. Were these centres surrounded by ma- 
terial of one kind only, the slightest vibrations 
or shocks would be continually felt, but when 
different materials on different planes are used, 
the surest means are provided to favour the 
dispersion of such vibrations. 

The nervous mass floats in the midst of this 
fluid, being maintained in equilibrio in it by 
its uniform pressure on all sides, and the spinal 
cord, as we shall find by-and-bye, is supported 
by an additional mechanism which prevents 
its lateral displacement. 

By its accumulation at the base of the brain, 
this fluid must protect the larger vessels and 
the nerves situate there from the unequal pres- 
sure of neighbouring parts. 

It is not improbable also that this fluid may 
contribute to the nutrition of the brain and 
spinal cord, by holding in solution their proper 
nutrient elements preparatory to their absorption 
or addition to the nervous masses themselves ; 
and this view would receive great support if 
Couerbe’s analysis, which detects some of these 
elementary matters in the fluid, should be con- 
firmed by the observations of other chemists. 
Nor must we omit to notice here, the fact as- 
certained by Majendie, that when certain sub- 
stances which find their way readily into the 
blood have been injected into the veins, they 
may be soon after detected in this fluid, such 
as iodide of potassium. 

Majendie observed serious symptoms to 
ensue upon the removal of this fluid from 
living dogs, but it is impossible to ascribe such 
symptoms solely to this cause, for the intro- 
duction of air into the subarachnoid cavity, the 
disturbance and consequent irritation to which 
the nervous centres must necessarily be ex- 

27 2 


644 


posed in the performance of the experiment, 
oar fairly to be considered to have a share, 
and that not an inconsiderable one, in any im- 
irment of the nervous function that might 
ome apparent. The sudden removal of the 
fluid brings on fainting or even death, effects 
due to shock, and analogous to those which 
result from the sudden removal of dropsical 
fluid in particular cavities, when the organs and 
the circulation in them have become adapted 
to its pressure, as 1 cases of ascites, hydtotho- 
rax, &c. 

The interior of the arachnoid sac is moistened 
by an exhalation of a similar kind to that which 
is found in the other serous membranes. Ac- 
cumulations of fluid in the arachnoid sac, how- 
ever, are of very rare occurrence. 

Of the glandule Pacchioni—To these bo- 
dies we have already had occasion to refer in 
the description of the sinuses. We proceed 
now with a more special notice of them. 

These bodies were first formally described by 
Pacchioni, and were regarded by him as con- 
globate glands of the dura mater, from which 
lymphatics proceeded to the pia mater.* They 
have been recognized by all subsequent anato- 
mists under the name here assigned to them, 
although the idea of their physiological office 
suggested by Pacchioni has not met with ge- 
neral acceptation. Bichat suggested a more 
appropriate and scientific appellation in that of 
cerebral granulations. No anatomists have in- 
vestigated the history of these bodies so exten- 
sively as the brothers Wenzel.t+ 

The Pacchionian bodies are found principally 
along the edge of the great hemispheres of the 
brain on either side of the great longitudinal 
fissure. Here, in general, they cause the obli- 
teration of the sac of the arachnoid for a greater 
or less distance by producing adhesion between 
the visceral layer of that membrane and that 
portion of its parietal layer which adheres to 
the angle along the superior border of the falx 

cerebri. In cases where these bodies are 
numerous and well sp apt 84 it is found very 
difficult to separate the dura mater from the 
subjacent arachnoid by reason of the firmness 
of the adhesion effected by them; and when 
this adhesion exists, the corresponding surface 
of the dura mater has generally a very com- 
plicated cribriform appearance. The extent 
of surface which they occupy is very variable, 
Sometimes, but very rarely, they extend along 
the entire edge of each cerebral hemisphere; 
but generally they occupy its central for 
an extent of from one to three inches. Very 
frequently they extend outwards over the sur- 
face of the cerebral hemispheres, rarely beyond 
half an inch or an inch. The arachnoid mem-’ 
brane in their immediate vicinity is always 
opaque. 
Bodies, somewhat similar, are also found oc- 


* Ant. Pacchioni diss. epistolaris ad Luc. 
Schroeckhium de glandulis conylobatis dura: me- 
ningis humane, &c. &c. Rom, 1705, et Opuscu- 
lum Anatomicum de dura meninge, in Opera Omnia. 
Rom. 1741. a 

t+ Wenzel, de penitiori cerebri structura, Tu- 
binge, 1812. 


NERVOUS SYSTEM. (Nervous Centres. Tue Mentxces.) 


casionally on the choroid plexuses of the latera 
ventricles. Very frequently we meet with 
nulations of a like kind in the fringe-like pro= 
cess of pia mater which descends from the 
velum interpositum to surround the pines 
gland, and also upon the little processes of 
that membrane which go under the name_ 
choroid plexuses of the fourth ventricle. = 
Wherever these bodies are found, they show 
a remarkable tendency to congregate in clust 
around venous trunks. In examining the 
along the edges of the hemispheres, we ni 
that they are most numerous around the veir 
which pass from the pia mater in that situatio 
into the superior longitudinal sinus. This 
dency, probably, explains the occurrence ¢ 
these bodies in some of the sinuses. They ai 
most commonly met with in the superior long 
tudinal sinus, as already stated ; are al 
found in the lateral sinuses, and sometimes bi 
rarely in the straight sinus. In all these si 
ations these bodies appear to stand in a sir 
relation to the sinuses; they have penetrated t 
fibrous tunic of their walls, and pushed befo 
them the inner or venous tunic. i 
In point of size and shape the Pacchic 
bodies resemble minute granulations; their 
lour is white, like that of coagulable lym 
and not unlike that which is occasionally s 
upon serous surfaces after chronic infl 
tion. A granular lymph, taking son 
similar form, is occasionally seen on 
ripen membrane of the rectum after dy. 
t some the granulations 
as ssclatel Siemmrice of the a 
arachnoid membrane. At others they are 
lected in clusters round a common stem; 
when the membrane is removed and float 
water, this bothryoidal disposition may be 
displayed. A large proportion of them ¢ 
by their pressure, an adhesion between 
opposed surfaces of arachnoid membrane; 
those which are attached to a stem are 
most likely to project into the interior 
sinuses. ‘ 


When examined by a ner 
these bodies appears to consist of a mi 
minute granules enclosed in a membr 
sac; when the body is pediculated, its 
exhibits a series of strise which take the di 
of its length, and probably result from 
tudinal folds of the membrane which fot 
Dilute acetic acid causes them to sw 
gelatinifies the bodies, and sometimes ¢ 
epithelial scales upon the surface of thi 
brane which covers them. is 

The following explanation of this” 
may be offered. he primary 
granular lymph takes place among fl 
of the pia mater. e small boe 
formed push the arachnoid membrani 
oo as asac or covert in a 
the granular mass is only partially covere 
then it causes merely a slight projection 
surface of the visceral layer of arachno 
in others the mass is completely covered 
stalk is gradually formed ; and when 
granular masses have been deposited 
ately contiguous to each other, thes 


ks 


4 


NERVOUS CENTRES. (Human Anatomy. Tat Mentnces.) 


be attached in a cluster to the same stem. The 
fact that epithelial particles may be seen upon 
the surface of the membranous sac of some of 
the bodies is sufficient proof that it is derived 
from arachnoid membrane. If this be ad- 
mitted, then it seems impossible to come to 
any other conclusion than that the pia mater is 
the seat of the primary deposit, and this opi- 
nion is confirmed by the fact that we meet with 
_ the Pacchionian bodies on the internal pro- 
_ cesses of the pia mater, when we have no evi- 
_ dence of the existence of arachnoid membrane. 
Orit might be conjectured that these bodies 
indicate a degenerate condition of the elemen- 

tary particles of the superficial layer of the grey 
- matter of certain convolutions, produced by 
equent irritation. 

_ Arethe Pacchionian bodiesnatural structures? 
The great frequency with which these bodies 
‘are met with in the various situations above- 
‘meutioned, has induced many, even in the 

resent day, to regard them as normal struc- 

ures, the physiological office of which is as 
yet unknown. But there are many facts which 
Strongly militate against such a conclusion. In 
‘the first place it may be observed that Pacchi- 
onian bodies never occur in the earliest periods 
of life. In the course of a long experience in 
anatomical investigations I have never seen 
them at a period antecedent to six years. The 
others Wenzel, who made a series of special 
examinations with a view to determine this 
stion, make the following statement. In 
dren, from birth to the third year, these 
ies, if they ever occur, must be very few. 
From the seventh to the twentieth year they 
ometimes are numerous. From the latter pe- 
iod to the fortieth year their number is consi- 
ble, and the nearer we approach the fortieth 
year the greater does.it become. Lastly, from 
he fortieth to the one hundredth year these 
bodies are found in great numbers. 

_ It must be further remarked that even at 
those periods of life when the Pacchionian 
ies are found in greatest numbers, cases fre- 
‘quently occur in which no trace of them can 
be found. There is likewise the greatest variety 
as to their number and size, in different indivi- 
als of the same age. 
has always occurred to me to find them 
numerous in cases where I had reason to 
ww that the brain had been subject to fre- 
uent excitement during life. In persons ad- 
dicted to the excessive use of spirituous liquors, 
se of irritable temperament and who were 
quently a prey to violent and exciting passions, 

are almost uniformly highly developed. 

@ Pacchionian bodies are peculiar to the 
man subject. Nothing similar to them has 
n found in any of the inferior classes of 


teference, then, to the question, what is 
the nature of these bodies, I have no difficulty 
in stating my opinion that the evidence greatly 
preponderates in favour of their morbid origin ; 
that they are the product of a chronic very 
gradual irritation due to more or less frequent 
functional excitement of the brain itself. It is 
not unlikely that the friction to which the 
Opposed surfaces of the arachnoid are conti- 


645 


nually subjected in the movements of the 
brain, especially when they are of a more rapid 
and violent kind, as under states of cerebral 
excitement, may contribute to the develope- 
ment of many of the appearances connected 
with these bodies. The opaque spots which 
are of such frequent occurrence upon the sur- 
face of the heart may be quoted as an example 
of a morbid change, very commonly met with, 
and resulting probably from the friction against 
each other of opposed serous surfaces. Were 
the Pacchionian bodies normal structures, they 
would not be so frequently absent from brains 
which afforded every other indication of being 
in a healthy state; nor should we find opacity 
of the arachnoid (a decidedly unhealthy con- 
dition) so commonly coexistent with the full 
developement of them. Again, were they 
a necessary part of the healthy orgamism, we 
might expect to find them more constant as 
regards size, number, and the extent of surface 
over which they were placed. 

Of the ligamentum dentatum (serrated 
membrane of Gordon).—This structure forms 
a part of the mechanical arrangements con- 
nected with the spinal cord and the roots of its 
nerves. It is found in the subarachnoid 
space, adhering on the one hand to the pia 
mater, and, on the other, attached at certain 
intervals to the dura mater. 

The ligamentum dentatum consists of a nar- 
row longitudinal band, adhering by its inner 
straight border to the pia mater on each lateral 
surface of the spinal cord, midway between 
the anterior and posterior roots of the spinal 
nerves, reaching from the highest point in the 
cervical region down to the filiform prolongation 
with which it becomes incorporated. Its outer 
border exhibits a series of tooth-like trian- 
gular processes which are inserted by their 
apices into the dura mater. The first pointed 
process, which is longer than the rest and less 
triangular in shape, is inserted into the dura 
mater on the margin of the occipital bone, 
where it stands in relation with some parts of 
interest. The posterior root of the sub-occi- 
pital nerve, and the filaments of origin and the 
resultant trunk of the spinal accessory, are on a 
plane posterior to it. The vertebral artery and 
the ninth pair of nerves are anterior to it. The 
number of teeth varies from eighteen to twenty- 
two. The last is attached to the dura mater 
about the level of the first or second lumbar 
vertebra. The points of attachment are be- 
tween the points of exit of the spinal nerves, 
being almost always nearer the lower than the 
upper nerve. The intervals between each pair 
of dentated processes vary in different regions of 
the spine as the distances between. the roots 
of the nerves vary. At its insertion into the 
dura mater each process pins down the visceral 
and parietal layers of the arachnoid membrane, 
probably piercing them to reach the fibrous 
membrane. At its lowest part, a little above 
the extremity of the cord, tie denticulated 
margin ceases, and the longitudinal portion 
may be traced downwards, gradually dimi- 
nishing in size, along each side of the filiform 
prolongation of the pia mater. 

The dentated ligament has to the naked eye 


646 
Fig. 370. 
pp 


i 
bat 


Dura mater of part of the spinal cord laid to 
git as teosasstoas delice. iii 


dddd, dentated processes. On the right the 
roots of the nerves and the ganglia of the pusterior 
roots are retained, 


all the characters of white fibrous tissue, of 
which it is chiefly composed. In its dentated 
processes, however, a considerable quantity of 
yellow fibrous tissue may be found. The simi- 
larity of its constitution with that of the pia 
mater evidently justifies its being regarded as a 


NERVOUS SYSTEM. (Nervous Centres. Grey Nervous Marrer.) 


, fibres of the nerves, and serve to connt 


process of that membrane, and not, as some 
anatomists thought, of the dura mater, } 
which it has a much less intimate and extensive 
connexion. Its anterior and posterior surfaces 
are uncovered by any membrane; are 
smooth, and have the glistening silvery appear- 
ance of white fibrous membrane. Itis evident 
that during life these surfaces must be bathed — 
by the subarachnoid fluid. wall 
The office of this peer 8 structure see 
evidently to be mechanical; to preserve t 
spinal sel in a state of equilibrium; and to 
prevent lateral movement of it, whilst at the 
same time it forms a partition between th 
roots of the nerves. a 
General remarks on the structure of the 
nervous centres.—It has already been shewn 
a former part of this article that the nerves 
properly so called are composed 
of one kind of nervous substance,—namely 
the fibrous nervous matter, which is disposed in 
bundles of peculiar fibres. It is only in the 
nervous centres or in continuations of t 
that we find an union of the white and the grey 
nervous matter; and, indeed, it may be ( 
in general, that the peculiar and distinctiv 
anatomical character of a nervous centre con 
sists in this combination of the two kinds « 
nervous matter. 
In the nervous centres the white matter 
bits, for the most part, the same essential ch 
racters of structure as in the nerves; that is 
say, it is disposed in tubes containing a cer 
pulpy matterin them, Ithas been found, 
ever, that these tubes are much more pron 
become varicose under the influence of press 
or of any other disturbing cause. They : 
not, as in the nerves, bound together by areo 
tissue, but are disposed in bundles and 
different planes, with their nutrient bloodvess 
ramifying among them, and in some situat 
the elements of the grey matter are interpos 
between them. Certain parts of the ner 
centres are composed exclusively of ¥ 
matter, as a portion of the hemis ol 
brain, and of the cerebellum, and upel 
parts of the spinal cord. r. 
The white fibres which are found in the 
vous centres may be distinguished acco 
to their physiological office into four di 
kinds. Two of these are continuations ¢ 


re 


aa 


PXCIU 


To 


a. 


nervous centres with other organs or te} 
either by conveying the influence of the: 
to them, or by propagating impression 
them to the centres. The er are 
efferent, the latter afferent fibres. In 
to these, we find a third and large series 0 
which serve to establish a connection b 
different centres, or between different port 
the same centre. These are called comm 
fibres ; they form a large portion of the n 
the brain and spinal cord. And Henle sug) 
that the brain contains a fourth series of 
associated with the operations of though 
We remark in the nervous centres, €s 
in the brain and spinal cord, a greater di 
as regards size between the different nerve 
than may be observed elsewhere, and it: 
to be a constant character that they dit 


4 


in size as they approach and enter the grey 
matter. 

Of the grey nervous matter.—The grey ner- 
vous matter differs very materially in its ana- 
tomical characters from the white. Its ele- 
ments are vesicles or cells, with nuclei and 
nucleoli. Although this vesicular or cell form 
is universally prevalent, the cells present much 
_ diversity of shape, size, and colour in different 
_ Centres or even in the same centre, which ap- 
parently have reference to some peculiarity 
of function. The most prevalent form is that 
of a globular vesicle, composed of a very deli- 
_ Cate transparent membrane. Within this mem- 
brane is contained a soft minutely granular sub- 
Stance, which forms the principal mass of the 
body, parenchymmasse (Valentin). The grey 
colour of the vesicle, which becomes very ma- 
nifest when a number of them is congregated 
together, is dependent on this granular matter. 
Gee fig.371, a,b,c.) When the vesicle bursts 
‘and its substance is broken up, the granular 
‘matter is diffused, and confuses and darkens 
the specimen under examination. Sometimes 
the outer vesicle is removed, the contained 
F: lar matter retaining the globular form. 
fithin the external vesicle (a, fig. 371) there 


Nerve vesicles from the Gasserian ganglion of the 
a human subject. ™ 

- @, a globular vesicle with defined border; 6, its 
nuc 3 ¢, its nucleolus; d, caudate vesicle; 
@, elongated vesicle with two groups of pigment 
ticles ; f, vesicle surrounded by its sheath or 
stile nucleated particles; g, the same, the 
ith only being in focus. 


is another much smaller and adherent to a 
art of its wall, so as to be quite out of the 
centre of the containing vesicle. This is the 
nucleus (6, fig. 371). Its structure is ap- 
parently of the same nature as that of the ex- 
é vesicle. The nucleus contains in its 
tre another minute and remarkably clear 
and brilliant body, also vesicular in structure. 
This is the nucleolus (c, fig. 371). Sometimes 
it is replaced by two or three much smaller 
but similar bodies. The softness of the vesicle 
admits of its yielding, whether from the dis- 
turbance occasioned in the necessary manipu- 


* Iam indebted to the accurate pencil of my 
Mr, Bowman for this illustration. 


NERVOUS CENTRES. (Human Anatomy. Grey Nervous Marrer). 


647 
lation or from the pressure of the neighbouring 
elementary parts as it lies in its proper situation. 
Hence it is that these vesicles exhibit a consi- 
derable diversity of form. 

Very frequently we observe that, besides the 
granular substance above described, there are 
certain pigment particles of large size and dark 
colour, which are collected into one or two 
roundish or oval groups, situate at or towards 
one or both sides of the vesicle (fig. 371, e). 
These masses of colouring matter sometimes 
occupy considerable space, and enable the ob- 
server readily to detect the position of such 
vesicles as contain them. hen the mass of 
pigment is placed at one side, we may com- 
pare the containing vesicle, as Volckmann has 
done, to a fruit which is coloured only on that 
side which is exposed to the sun. The aggre- 
gation of many such vesicles at any one spot 
gives the nervous matter there a peculiarly dark 
colour. A remarkable example of this is found 
in that portion of the crus cerebri which is 
known by the name of locus niger. 

A very interesting form of nerve-vesicle is 
that which exhibits the greatest departure from 
the globular shape by the prolongation of the 
wall of the outer cell into one or more tail-like 
processes. These bodies may, from this pecu- 
liar character, be designated caudate nerve- 
vesicles. They possess the nucleus and nucleo- 
lus, as in the more simple form, and contain 
one or more of the masses of colouring matter; 
indeed, in them the quantity of pigment is 
generally much more considerable than in any 
other form. I have noted an observation which 
shewed two nuclei in one vesicle. They vary 
much in size and shape, and so also do the 
processes. The largest nerve-vesicles are found 
among those of this description. The variety 
in shape may depend in some degree upon the 
situations from which the caudate processes 
take their rise. In some (fig. 371, d) they 
proceed from opposite poles of the vesicles; 
in others they arise near each other from the 
same region of the vesicle, and when numerous, 
give to it somewhat the form of a cuttle-fish 
with extended tentacles. In examining the 
structure of one of these processes, we find it 
evidently exactly similar to that of the matter 
contained in the outer vesicle, exhibiting the 
saine minutely granular appearance. The pro- 
cesses are implanted in the surrounding sub- 
stance, and firmly connected with it, so as to be 
with great difficulty separated from it. They 
exhibit much strength of cohesion, but are fre- 
quently broken off quite close to their points 
of origin, and the broken ends present a dis- 
tinctly lacerated edge (d, fig. 371). More 
rarely we are able to trace these processes to 
a considerable distance, and then we observe 
them to bifureate or even to subdivide further, 
and to terminate in exceedingly fine transpa- 
rent fibres, the connexion of which with the 
other elements of the nervous matter has not 
yet been ascertained.* 


* See a beautiful illustration of one of the largest 
of these vesicles in the second part of Mr. Bowman’s 
and my work on Physiological Anatomy and 
Physiology. 


648 


It is in vain, in the present state of our 
knowledge, to speculate upon the use of these 
caudate processes. Do they constitute a bond 
of union between the nerve-vesicles and certain 
nerve-tubes? or are they commissural fibres 
serving to connect the grey substance of different 
portions of the nervous centres? Until a more 
extended research has made us better acquainted 
with the peculiarities of these vesicles in various 
localities, it would be premature to offer any 
conjecture concerning their precise relation to 
the other elements of the nervous centres. They 
exist, with different degrees of developement, 
in the locus niger of the crus cerebri, in the 
lamine of the cerebellum, in the grey matter 
of the spinal cord and medulla oblongata, and 
in the ganglions, and in the grey substance of 
the cerebral convolutions, in which latter situa- 
tion they are generally of small size. 

When a portion of grey matter from a con- 
volution of the brain is examined with a high 
power in the microscope, we observe it to con- 
sist chiefly of a mass of granular matter, in 
which nerve-vesicles are imbedded with consi- 
derable intervals between them. Henle states, 
with much truth, that the superficial part of the 
grey matter of the convolutions seems almost 
entirely composed of finely granular substance, 
in which lie, scattered here and there, several 
clear vesicles which, as he remarks, look almost 
like openings (fig. 372). In the middle por- 
tion the vesicles appear larger, and the gra- 
nular matter becomes less abundant, and on 
the most deep-seated plane the nerve-vesicles 
are much increased in size and lie in closer 
juxtaposition, being, however, covered by a 
thin layer of granular matter, which forms a 
sheath to each vesicle. Nerve-tubes are found 
throughout the whole depth of the grey matter. 
Those in the most superficial layer are ex- 
tremely fine and varicose, and seem to corre- 
spond in number and situation to the vesicles. 
For wherever there is a nerve-vesicle, we find an 
extremely fine varicose nerve-tube apparently 
adherent to it. 


Fig. 372. 


Grey substance from the surface of the cerebral hemi- 
sphere of a full-grown rabbit treated with dilute 
acetic acid. (After Henle. ) 

a, nerve-vesicle ; b, a similar one with two nu- 
clei; c, another viewed along its edge ; d, vesicles 
indistinctly apparent ; e, granular matter. 


In the grey matter of the ganglions we find 
that the vesicles are also deposited in granular 
matter, which surrounds each of them as a 
sheath (fig. 371, f, g), completely investing it 


NERVOUS SYSTEM. (Neavous Cextres Grey Nervous Mattern) 


on every side, and separating it from the neigh- 
Satine nse. Here, however, the sheath is 
formed not only of a finely granular matter, but 
also of numerous bodies which resemble nucle 
or cytoblasts, and this sheath invests both th 
globular variety of nerve-vesicles and the cau- 
date ones. Nerve-tubes lie in immediate con. 
nexion with these vesicles, and sometimes en- 
twine themselves around them, and seem te 
indent their sheaths (fig. 375.) . 
Other vesicles, much more simple in form, are 
found in the grey matter in certain situations, 
The outer layer of the optic thalamus, accord= 
ing to Henle, contains only small homoge 
neous globules, analogous to the nuclei of the 
ganglionic globules, in immediate appositior 
with each other, and towards which the tuk 
seem to ascend in the vertical direction. Pure 
kinje states, that a similar layer is met with in 
the cortical substance of the brain quite close 
to the medullary substance.* I find a lays 
of similar particles in the grey matter of 
cerebellic lamine. And, according to 
report of Valentin,+ Purkinje has found 
inteior of the ventricles in the normal s 
covered by an oily matter, which consis 
of distinct, large, transparent globules, ff 
and lying near each other. A similar lay 
has been found by him in the interior of t 
fifth ventricle. The cavity of the rhomboi 
sinus in Birds likewise contains a gelatino 
mass, which consists of large globules lyi 
close to each other. { ; " 
Developement of grey matter —In the 
fect nerve-vesicle, the cell form of primi 
developement is persistent. We have the 
cleolus and nucleus (cytoblast) and the ce 
and, according to Schwann, the only cha 
which the full-grown cell exhibits consists i 
increase of size and in the developement of) 
igmentary granules within. The following” 
alentin’s description of the developemen 
nerve-vesicle. In the very young embryo 
Mammalia, as the sheep or calf, the cen 
mass in the course of formation contains, if 
midst of a liquid and transparent blas 
transparent cells, with a reddish yellow nue 
The wall of the cells is very thin and sit 
their contents are colourless, transparent 
mogeneous, and manifestly liquid; the nut 
with well-defined contour, is general! 
sometimes central, at other times exe 
solid, and nearly of the same colour 
corpuscles of the blood. Around these 
tive cells of the central nervous system, 
we find likewise formed after the same 
the spinal cord, a finely granular mass bee 
deposited, which probably is not at fi 
rounded by an enveloping cell-membra 
this early period of formation the prin 
still preserves its first delicacy to such a 
that the action of water causes it to bu 
mediately. This rupture of its membrane 
effusion of its contents often take place st 
denly and quickly that they can per 
* Henle, loc. cit. t Uber den Verlauf, 
¢ See further remarks on the grey ma 
account of the minute structure of the br 
spinal cord in a subsequent part of the artic 


da 


, 


) 
| 


| 


NERVOUS CENTRES. (Human Anatomy. Tut GanGtions.) 


only by the movement of the nucleus, which is 
the consequence of it. * * * In proportion as 
the granular mass contracts itself within certain 
limits, (sich immer mehr abgrenzt,) a cell-mem- 
brane probably becomes developed around it, 
so that the vesicle gradually acquires its precise 
form and size, and its contents their proper 
characters, which belong to a fully formed cen- 


_ tral nervous corpuscule.* Valentin compares 
_ the developement of these vesicles to that of 


the ovum. The nucleolus of the nerve-vesicle 
is always first formed, then around it the primi- 
tive cell, and around this the outer cell. This 
process resembles exactly that which takes 
place dunng the formation of the ovum, for the 
_ germ corresponds to the nucleolus, the germina! 
_ vesicle to the nucleus, the yolk to the contents 
_ of the outer enveloping cell, and the vitelline 
membrane to the delicate wall of this cell, sup- 
_ posing that this latter membrane always exists. + 
_ The great simplicity in the form of the ele- 
“ments of the grey nervous matter is one of its 
Most remarkable characteristics. That a tissue, 
which, as will be shown by-and-bye, plays so 
“prominent a part in the nervous actions, whether 
they are prompted by mental change, or are 


purely corporeal, should exhibit scarcely any 


‘More complexity of structure than that which 


textures, or in structures that have not passed 


fen, in the simplest animal or vegetable 


_ their earliest phase of developement, is an ana- 


_ tomical fact pregnant with great physiological 
interest. Have this simplicity of form and de- 


. 2 


% 
{ 


__ licacy of structure reference to the celerity of 


the 


> 
‘a 


hervous actions? or to that proneness to 
ge which must be induced by the constant 
“and unceasing round of impressions which the 
"grey matter must receive from the ordinary nu- 
trient actions that are going on in the body, as 
‘well as from the continual action of thought? 
Tf, according to common acceptation, we ad- 
‘mit that the mind is in immediate connexion 
with the cerebral convolutions, it may well be 
imagined that no part of the frame can be the 
‘seat of such active change, from its being on the 
‘one hand the recipient of impressions from the 
body, and, on the other, from an association with 
the nl principle so intimate that probably, 
u ordinary circumstances, an affection of 
the one cannot occur without being communi- 
cated to and producing a change in the other. 
_ Another curious fact, in connexion with the 
imtimate structure of the grey nervous matter, 
is the large quantity of pigment or colouring 
matter which exists in it, and which appears 
to form one of its essential constituents, more 
abundant in some situations than in others, 
but present in all. We are utterly ignorant 
of the design of this peculiarity of structure. 
If this pigment bear any resemblance of che- 
nical composition to the colouring matter of the 
» hematosine,—and it is not improbable 
that it does,—an increased interest attaches to 
the el importance of minute attention, 
on the part of practitioners, to avail themselves 


oo in Soemmering vom Baue, &c. t. iv. 


+ Loe. cit. § 25. 


649 . 


of all the means which are capable of impro- 
ving that important element of the nutrient 
fluid both in quantity and quality, for it is 
most reasonable to presume that the pigment 
of the nervous matter would derive its nou- 
rishment from that of the blood. 

It may be further remarked that pigment oc- 
curs in connexion with the nervous system in 
another form besides that of incorporation with 
its elementary particles, that is, upon the exte- 
rior of parts of the nervous centres or of parti- 
cular nerves. Examples of this may be re- 
ferred to in the case of the olfactory nerve of 
the sheep and of other Mammalia, the bulb 
of which is surrounded by black pigment con-* 
nected with the pia mater. It is also found 
sometimes on the pia mater of the spinal cord 
of the human subject. Valentin, who deli- 
neates a magnified view of this pigment, states 
that it occurs chiefly in the cervical region. In 
frogs, the whole spinal cord and encephalon 
are covered with a silvery pigment interspersed 
with black. The same occurs in fishes. The 
black pigment in connexion with the retina has 
an obvious use. On the choroid gland of fishes, 
which lies immediately contiguous to the re- 
tina and surrounds the optic nerve, there is a 
silvery membrane which contains a quantity of 
the same kind of pigment as that alluded to 
upon their nervous centres. On some of the 
ganglia of the invertebrata particles of pig- 
ment are likewise found. 

Of the structure of ganglions——The descrip- 
tion of the minute anatomy of ganglions as 
well as of all other nervous centres may be 
regarded as the solution of the following pro- 
blem: to determine the relation which the 
white substance of these centres bears to the 
grey matter on the one hand, and to the nervous 
trunks connected with them on the other hand. 

The white substance of the ganglions con- 
sists of a series of minute nerve-tubes, as well 
as of some gelatinous fibres, which are conti- 
nuous with those which exist in the nerves 
themselves. If we trace a nerve into a gan- 
glion, it is found to break up into its com- 
ponent nerve-tubes, and it does so by a se- 
paration of the tubules within into smaller 
bundles, or single tubes. Sometimes adjoining 
bundles interlace, each yielding to its neigh- 
bour one or more tubes. The nerves which 
emerge from the ganglia derive their component 
nerve-tubes from different bundles, so that the 
same kind of interchange of tubules, which we 
have noticed as taking place in plexuses, occurs 
also in ganglia. The emerging nerves result 
from a further subdivision and greater inter- 
mixture of the bundles of nerve-tubes which 
enter the ganglions. The arrangement is well 
shown in fig. 373, where the nerve (a), which 
enters the ganglion, may be seen breaking up 
into a plexus, from which three branches (), 6, 
b) emerge, and it may be observed that these 
emerging nerves derive nerve-tubes from very 
different and opposite parts of the ganglionic 
plexus. In the meshes, which are left be- 
tween the interlacing nerve-tubes, the gangli- 
onic globules or nerve-vesicles are situate (figs. 
373, 374). Certain fibres, according to Valen- 


650 
Fig. 373. 


Pn 


ASW gy — \ 


i/ 


Fa 
-_ 


Second abdominal ganglion of a greenfinch, slightly 
compressed under the compressor. The course of the 
nerve-tubes only is represented. 

a, fibres passing in ; 6, emerging fibres; c, sur- 
rounding fibres. ‘The meshes for the reception of 
ganglion globules are shown. 


Fig. 374. 


A small piece of the otic ganglion of the sheep, slightly 
compressed, ow the interlacement of the Score 
nal fibres and the grey matter. 

(After Valentin. ) 


tin, travel round the margin of the ganglion, 
and to these he gives the name of umspinnende 
Fasern, surrounding fibres, and some fibres 

from them to the more central ones, or 
fom the latter to the former. Nerve-vesicles 
exist at the circumference of the ganglion as 
well as in its interior, and to them is due the 
peculiar grey colour of that body. 

The best mode of examining these points is 
to select the smallest ganglia of very small 
animals, birds, mice, &c.; these, when sub- 
jected to compression, become very transpa- 
rent, and display much of their intrinsic ar- 
rangement. Or thin slices of large ganglia may 
be placed under the microscope, and when torn 
up by needles the disposition of the nerve- 
vesicles and the caudate processes, when pre- 
sent, are rendered visible. And none is more 
suitable for this ees than the Casserian 
ganglion of the fifth nerve, which by the ab- 
sence of a dense sheath and its greater loose- 
ness of texture is more easily examined. 

It is a highly important problem, in minute 


NERVOUS SYSTEM. (Nervous Centres. Tue Sprvat Corp.) 


anatomy, to determine whether there are any 
nerve-tubes which terminate in the grey matter: 
the ganglion, or originate in it,—which in 
are not continued through the ganglion. 
present we are unable to state further than the 
the tubes appear to have an intimate connect 
with the nerve-vesicles wherever the latter 
be found, and that they often appear to be col 
tinuous with the sheaths of the nerve-vesic! 


Nerve vesicles from the Gasserian ganglion covered 
their sheaths of nucleated particles, to shew the u 
mate relation of the nerve-tubes to them. 

t, t, nerve-tubes; v, v, vesicles. 


There does not ap to be any mate 
difference of structure between the ganglion: 
the sympathetic and those of the cereb 
system, excepting, as Henle states, the ex 
ence of a greater number of gelatinous 
in the former. a 

Of the cerebro-spinal centre.—The nerve 
mass which occupies the cavities of the 
nium and spine doubtless constitutes ¢ 
centre, as there is a perfect continuity thro 
out all its . But the differences of ext 
form and characters in some regions of it, 
the obvious diversity of endowment of the née 
connected with certain portions, denote — 
justify an anatomical as well as a physiolo 
subdivision of it into segments, each of ¥ 
is a centre of nervous action independent ¢ 
rest, yet so connected with them that the 
tions of all are made to harmonize in the 
perfect manner. 

The subdivision which the external an 
indicates, although not perfectly coineid 
that which the differences o i 
suggest, has been so long sanctioned by 
and is so convenient for description, — 
advantage would be gained by ade tin 
other, Our description of the ¢ 
centre, or axis as it has also been caller 
be given under the following ds: 
spinal cord; 2. the encephalon, includin 
medulla oblongata; 6, the mesoceph 
cerebellum; d, the cerebrum. 

1. Or THE sPiNaL cornp.—Syn. Spin 
row, Medulla spinalis; Fr. La moé ee 
Germ. Das Riickenmark. The follo 
the anatomical limits which may be a 
the spinal cord. It occupies a large 
the spinal canal, terminating inferiorl 
point which, in different subjects, rang 
tween the last dorsal and the second 
vertebra. Below this point the sheath fo 
by the dura mater contains leas 
nerves which is called the cauda equim 


a 


ae 


oe ae 


——— 


ge Be gray ma 


a 


NERVOUS CENTRES. (Human Anatomy. 


the centre of which lies the filiform * nape 
gation or process of the pia mater. The su- 
perior limit of the spinal cord is marked by 
the plane which lies between the occipital 
foramen and the first vertebra of the neck. A 
section made in the direction of this plane 
Separates the spinal cord from the medulla 
oblongata. Immediately above this plane the 


decussation of fibres of the anterior pyramids. 


takes place, and may be regarded as the na- 
tural inferior limit to the medulla oblongata. 
Such is the position of the spinal cord in the 
adult. In the foetus at the third month of 
intra-uterine life, it occupies the whole spinal 
canal, and extends quite to the point of the 
sacrum. At this early period the os coccygis 
consists of seven vertebre. Coincident with 
its reduction to its normal number of segments, 


__ is the retraction of the spinal cord within the 
Spinal canal. If the ascent of the cord be ar- 
rested, the foetus is born with a tail, for the 
_ changes of the coccyx become arrested also. It 
is remarkable that among the inferior animals 
there is a direct proportion between the length 


of the spinal cord and that of the tail. The 


‘Shorter the former, or the higher in the spinal 
“Canal it may be, the less will be the latter. 


In 
animals with long tails there is no cauda equina, 
as is the case in the ox, the horse, the squirrel, 
&e. and the opposite is likewise true, namely, 
that in animals with a short tail the spinal 
cord is much shorter and is placed higher up 
in the spinal canal. In the embryo of the bat, 


_ Which has a tail, the spinal cord extends down- 


wards, but when it loses its tail the cord ap- 


_ pears to occupy a much smaller portion of the 


Spinal canal. In the tadpole of the frog, like- 
Wise, the spinal cord extends into the tail, but 
when the tail has disappeared the cord occupies 
“7 * portion of the spinal canal.* 

_In point of shape, the spinal cord is cylin- 
droid, slightly flattened on its anterior and pos- 
terior surfaces, more so on the former than on 


the latter. At its inferior extremity it gradually 


to a point. Sometimes, however, we 


observe a small tubercle immediately above 


this pointed extremity, situated on the posterior 
surface. The perfect cylindrical form of the 


cord is destroyed, not only by this pointed ter- 


mination and the flattening before and behind, 
but likewise by a marked change of dimen- 
sions in certain regions. In the cervical re- 
gion we observe a distinct swelling or enlarge- 
ment, which begins a short distance beneath the 
medulla oblongata, and gradually passes into 
the dorsal portion, which is the smallest, as 
well as the most cylindrical part of the cord. 
This cervical enlargement (intumescentia cervi- 
calis ) begins opposite the third cervical vertebra, 
and ends about the third dorsal. The cord con- 
tinues of a cylindrical form as low as about 
the ninth or tenth dorsal vertebra, and then 
— into the lumbar swelling (intumescentia 
umbalis vel cruralis ), which occupies a space 
corresponding to about two vertebre. is 
swelling is both shorter and of less diameter 


* Cuvier’s Report upon Serres’ work, Sur I’ Anat. 
p- duCerveau, Par. 1824, 


Tue Sprnat Corp.) 651 
than that in the region of the neck. The inferior 
extremity of the spinal cord tapers rather sud- 
denly, and at its point is enclosed in the com- 
mencement of the filiform prolongation of the 
pia mater. 

The bulk of the spinal cord is in the direct 
ratio to that of the body throughout the verte- 
brate series. And not only is this true with 


regard to the whole cord, but with respect to 


its segments. For when any segment supplies 
nerves to a greater sentient surface, or to more 
numerous or more powerful muscles than an- 
other, it exhibits a proportionally greater size. 
It is thus that we may satisfactorily explain the 
occurrence of the cervical and lumbar enlarge- 
ments. Both supply nerves to the extremities, 
whilst the dorsal portion furnishes them only 
to the trunk. The upper extremities enjoy, in 
part, a high degree of tactile sensibility, and 
they possess great power and extent of mus- 
cular movement. That portion of the cord 
therefore from which the nerves to the upper 
extremities proceed is larger in every way than 
that which supplies the lower extremities, 
which, although provided with large and pow- 
erful muscles, do not enjoy such a range or 
variety of motion as the upper extremities, nor 
are they endowed with so exquisite a sensi- 
bility. 

There are many interesting facts among the 
lower animals which illustrate and confirm this 
law. Thus, in animals which have no limbs, 
as serpents, the cord is of equal size through- 
out, excepting at its pointed extremity. It is 
said that in the foetus, before the developement 
of the limbs, no distinction of size can be dis- 
covered in the cord, and in persons in whom 
an arrest in the developement of the upper 
extremities has taken place, there is no cervical 
enlargement. Cruveilhier refers to the case of 
the tortoise as strongly confirmatory of this law. 
That portion of the spinal cord which corre- 
sponds to the carapace, which is equally devoid 
of sensation and motion, is reduced to a mere 
thread, whilst those segments between which 
it lies, and from which the nerves of the ex- 
tremities emanate, are of size duly propor- 
tionate to their muscular activity and their sen- 
sibility. In Fishes, the enlargements corre- 
spond to the fins which are possessed of great- 
est muscular power. In the gurnard there 
exist certain very remarkable ganglionic swel- 
lings, situate on the oa se of the cer- 
vical segment of the cord. ith these swel- 
lings nerves are connected, which are distri- 
buted to organs placed immediately behind the 
head on the lower part of the body. These 
organs are endowed with much tactile sensibi- 
lity, and seem to serve the office of feelers, as 
the animal gropes along the bottom of the 


sea. 

The length of the spinal cord in the adult is 
from sixteen to eighteen inches, according to 
the statement of Cruveilhier. Its circumfe- 
rence measures twelve lines at the smallest and 
eighteen lines at the most voluminous part. 
Chaussier states that its weight is from the 
nineteenth to the twenty-fifth part of that of 
the brain in the adult, and about the fortieth 


652 


part in the new-born infant. The actual weight 
of the spinal cord in an adult male may be 
stated to be a little more than one ounce. 

We may here again notice the interesting 
fact that there is a great disproportion between 
the size of the spinal cord and that of the ver- 
tebral canal, and that consequently a consider- 
able space is found between the cord and its 
membranes which is occupied by the cerebro- 
spinal fluid. 

The consistence of the medullary substance 
of the spinal cord, in the fresh state, is of much 
greater firmness than that of the brain. This 
lasts, however, but for a very short time, for 
decomposition sets in quickly, and then the 
cord acquires a pultaceous consistence, and 
the nervous matter may be easily squeezed out 
of the sheath of pia mater in which it is en- 
closed. 

The pia mater adheres very closely to the 
surface of the cord, as intimately as the neu- 
rilemma to a nerve. In order to examine the 
surface of the cord, the best mode of proceeding 
is to dissect off the pia mater carefully, the 
cord having been fixed under water. The dis- 
sector will then perceive that numerous minute 
vessels, accompanied by delicate processes of 
the membrane, penetrate the cord at all points 
from the deep surface of the pia mater, and to 
this is due the adhesion of this membrane 
above-mentioned. This arrangement may also 
be shewn by dissolving out the nervous matter 
through the action of liquor potasse. The pro- 
longations from the deep surface of the sheath 
may be shewn by floating the preparation in 
water. 

The spinal cord is penetrated both on its 
anterior and posterior aspect by fissures, each 
of which corresponds to the median plane. 
They are separated from each other by a trans- 
verse bilaminate partition of white and grey 
matter, of which the grey layer is posterior. 
This serves to connect the equal and symme- 
trical portions into which the cord is divided 
by these fissures. 

The anterior fissure is very distinct and 
easily demonstrated. A folded portion of the 
pia mater may be traced into it down to the 
commissure. The edges of this fold, as it 
enters the fissure, are connected by a band of 
white fibrous tissue, which may be traced 
through the whole length of the cord on the 
exterior of the pia mater, and indicates pre- 
cisely the position of the anterior fissure, and 
which covers the anterior spinal artery. When 
this fold is carefully removed, the floor of the 
fissure becomes apparent, formed of a lamina 
of white nervous matter. This layer is per- 
forated by a great number of minute orifices, 
which give to it quite the cribriform character, 
and are for the reception and transmission of 
bloodvessels. In many parts the layer appears 
to be composed of oblique and decussating 
fibres, as if the same kind of decussation 
which occurs at the lower part of the medulla 
oblongata extended through the whole length 
of the cord. There is not, however, any real 
decussation : the Cesare of it results from 
the foramina not being always on the same 


NERVOUS SYSTEM. (Nervous Centres. Tue Spinat Corp.) 


level. For, in those places where they lie qui 
on a level with each other, no one could su 
se that such an arrangement of fibres ¢ 
isted. Here, as elsewhere, the fibres 
the transverse direction. The depth of © 
anterior fissure is not the same all down | 
cord ; it gradually diminishes towards its lov 
point ; its deepest part, however, corresponds 
the cervical enlargement, and here it 1s 
one-third of the thickness of the cord me 
from before backwards. 
The whole cribriform layer which f 
the floor of the anterior fissure constitute 
commissure between the lateral halves of 
cord in their whole length. It is callec 
anterior or white commissure of the cord. 
The posterior fissure is vee much finer ; 
more difficult to demonstrate than the ante 
It is not penetrated by a_ fold of the pian 
a single and very delicate layer of that m 
brane is continued from its deep surface d 
to the floor of the fissure. It is at thiss 
tion that the spinal pia mater assumes 
appearance and character of that of the t 
Here and there, within the fissure, the pia m 
appears interrupted and the vessels extre 
few, and in such situations the fissure bee 
very indistinct and difficult to recogr 
process of pia mater becomes extremely 
cate towards the lowest extremity of the 
The posterior fissure is deeper than 
terior. Through a great ie of its 
equal to fully one-half of the thickne 
cord ; in the lumbar region, however, 
is very much less. Its floor is formed 
layer of grey matter, which connects the 
ritious matter of each lateral half of t 
and which is called the grey commi: 
the lumbar region, however, it does 1 
to reach the grey commissure. i 
Arnold denies the continuity of the pos 
fissure through the greater part of the ce 
and dorsal regions. According to his ft 
ceases on a level with the second cerviea 
and reappears about the second dorsal vel 
This does not at all accord with my ok 
nor is it confirmed by any anatomist 
know of. It appears to me that the ¢o 
of the fissure might be more proper 
tioned at the lowest third of the ¢ 
it is often so feebly developed as te 
tection. In three out of four 
before me, the fissure is sufficiently t 
marked down to quite the lowest ex 
the cord, and the posterior columns : 
readily from each other along it. In the 
which is quite recent, the fissure at the 
rt of the cord is only to be distin 
ere and there by a solitary red vess 
ing to the grey commissure, 
distinct in the cervical ion. The 
cimens which shew it well have been 
ened in a preserving liquid, which, t 
stringing the substance of the posterior ¢ 
renders the fissure much more distinct. 
seems little doubt that the posterior co 
have no connexion with each other as far 
as the lumbar region. Below that, hower 
is not improbable that they may be united 


c 


. 


. 
spec 


NERVOUS CENTRES. (Human Anatomy. Tae Sprxat Corp.) 


the middle line, and that to this cause the in- 
distinctness of the posterior fissure may be due. 
And this anatomical fact may be quoted as, in 
some degree, adverse to the theory which re- 
gards these columns as sensitive: for were they 
columns of sensation, it is probable that the 
reservation of their distinctness would have 
n more fully provided for. 
The anterior and posterior fissures, as Cru- 
veilhier remarks, leaving on each side a per- 
fectly symmetrical organ, serve to demonstrate 
the existence of two spinal cords, one for each 
side of the body, and both presenting a perfect 
resemblance of form and structure. 

_ There are no other fissures in the cord 
_ besides those just described. Several anato- 
mists regard the lines of origin of the anterior 
_and posterior roots of the nerves as constituting 
distinct fissures. But a little careful examina- 
tion will readily convince any one that there is 
no real separation of the nervous substance of 
the cord corresponding to these lines, and that 
1 is no anatomical indication of a sub- 
division into columns or segments in connexion 
with them. When the roots of the nerves have 
been removed on each side, nothing is seen but 
‘a series of foramina or depressions correspond- 
ing to the points of emergence of the nerve- 
fibres, of which the roots are composed. 

_ The most natural subdivision of the spinal 
cord is that which is obviously indicated by its 
internal structure. In examining a transverse 


Section (fig. 376), we observe that the interior 
Fig. 376. 


of each lateral portion is occupied by grey 
_ matter, disposed somewhat in a crescentic form. 
“The concavity of the crescent is directed out- 
wards: its anterior extremity is thick, and is 
‘Separated from the surface of the cord by a con- 
‘siderable layer of white nervous substance. The 
grey matter is prolonged backwards and out- 
wards in the form of a narrow horn, which 
reaches quite to the surface of the cord, and near 
‘the surface experiences a slight enlargement. 
‘This posterior horn constitutes, on each side, a 
natural boundary between the two columns of 
which each lateral half of the cord consists. All 
that is situate in front of the posterior horns is 
called the antero-lateral column, and this com- 
prehends the white matter forming the sides and 
tront of the semi-cord, limited anteriorly by the 
anterior fissure and posteriorly by the posterior 
roots ofthe nerves. The posterior column is 
situate behind the posterior horn of grey matter, 
and is separated from its fellow of the opposite 
side by the posterior fissure. 
_ According to this view, then, the spinal cord 
will be found to consist of four columns, 
between which an obvious line of demarca- 
tion exists throughout the whole length of the 
organ. ese are two antero-lateral columns 


653 


and two posterior columns. The former con- 
stitute by far the largest proportion of the white 
substance of the cord, and they envelope the 
anterior obtuse portion or horn of the grey 
matter. The white commissure at the bottom 
of the anterior fissure unites them. The anterior 
roots of the nerves are connected with them, 
and the posterior roots adhere to them when 
the cord is split up along the plane of the pos- 
terior horn. The posterior columns are small, 
in section triangular, placed in apposition with 
each other by their inner surfaces. Their apices 
are directed forwards, and their bases, which 
are slightly curvilinear, hackwards. No distinct 
commissure of white fibres can be detected 
uniting these columns, save, perhaps, in the 
lumbar region. The connexion of the posterior 
roots of the nerves with them must necessarily 
be very slight, as they invariably separate from 
them in the longitudinal splitting of the cord. 
The arrangement of the grey matter in the 
cord, as already partly explained, is as follows: 
In each lateral half there is a portion of grey 
matter, which is crescentic in form, having its 
concavity directed outwards and its convexity 
inwards towards its fellow of the opposite side. 
The anterior extremity or horn of the crescent 
is thick and roundish, and its margin has a 
jagged or serrated appearance, which is more 
conspicuous in some situations than in others. 
The posterior horn is directed backwards and a 
little outwards: it reaches the surface of the 
cord, and near its posterior extremity it presents 
a swollen or enlarged portion, which differs in 
colour and consistence from the rest of the 
crescent, being somewhat paler and _ softer. 
This portion of grey matter has been called by 
Rolando substantia cinerea gelatinosa. It is 
that part of the grey matter which appears to 
be more immediately connected with the pos- 
terior roots of the nerves. . 
There is an exact symmetry between the 
grey crescents of opposite sides, and they are 
united by means of the grey commissure, a 
layer which extends between the two crescentic 
portions, being attached very nearly to the 
central point of each. This commissure, then, 
when examined in its length, forms a vertical 
plane of grey matter, extending throughout the 
whole of the cord. The lateral portions are 
solid masses of grey matter, with which the 
nerve-tubes of the white substance freely inter- 
mingle, and in which, as in the grey matter 
elsewhere, very numerous bloodvessels ramify. 
There seem to be no good grounds for the opi- 
nion advanced by Mayo that these crescentic 
| ney are hollow capsules. It was supposed 
y this anatomist that each crescent resembled 
the dentated body in the cerebellum or that 
in the corpus olivare; but careful examination 
must convince any one who takes the trouble 
of it that such is not the fact. It is true that 
the grey matter contains white fibres, but they 
mingle with its elements and are not enclosed 
within a layer of it, as described and delineated 
by Mayo. 
When sections of the spinal cord in different 
regions are examined, they are found to exhibit 
differences of dimensions affecting both the white 


654 


and the matter, and remarkable varieties 
as regards shape of the lateral portions of 
the latter. The relative proportion of the grey 
matter to the white appears to be much greater 
in the lumbar than in the cervical or dorsal 
regions. In the upper part of the cord the 
crescentic portions are narrow, and the white 
matter is abundant. The posterior horn a 
pears as a thin lamella extending back to the 
surface, while the anterior is a small, roundish, 
slightly stellate mass, remote from the sutface 
of the anterior columns. In the dorsal region 
the grey matter is at its minimum of develope- 
ment: here it appears much contracted and 
diminished in size, although presenting the 
same general form as that in the region of the 
neck. In the lumbar region both horns acquire 
a manifest increase of thickness, the terior 
still extending back quite to the surface, and 
the anterior, more stellate than in the higher 
parts of the cord, separated from the corre- 
sponding surface of the cord by a much 
smaller quantity of white substance. At a 
still lower part of the cord, where the lumbar 
swelling begins to diminish in size, the pos- 
terior horn is short and thick, and some- 
times seems not to reach quite back to the 
surface of the cord,—an appearance, however, 
which might be produced by some accidental 
obliquity of the section; and its posterior 
extremity has somewhat of the form of a 
hook, its hindermost portion being directed 
a little forwards and inwards, forming a very 
sharp angle with the rest of the grey sub- 
stance which constitutes the horn. At the 
lowest part of the cord the crescentic form of 
the lateral portions of grey matter ceases, and 
the transverse section of it presents the form of 
a solid cylinder slightly notched on each side, 
and surrounded completely by the white sub- 
stance. ( Fig. 377.) 

There are also differences deserving of notice 
as regards the white substance in the different 
regions of the cord. The largest quantity of 
white substance is found in the cervical en- 
largement, as may be shown on a transverse 
section. Both the antero-lateral and the pos- 
terior columns are large, but by far the greatest 
 sapamtte of the mass of white substance must 

assigned to the antero-lateral columns. It 
is also important to remark that the quantity of 
white substance which is placed between the 
posterior horns in a great part of the cervical 
region is augmented by the existence of two 
small columns of white matter, which will be 
more particularly described when we come 
to speak of the medulla oblongata. These 
columns extend from the inferior extremity of 
the fourth ventricle, very nearly as far down 
as the termination of the cervical enlarge- 
ment, where they gradually taper to a fine 
point and disappear, allowing the posterior 
columns of the cord to come into apposition 
along the posterior fissure. These small co- 
lumns, the posterior pyramids of some authors, 
do not appear to be completely isolated from 
the proper posterior columns of the cord. There 
is generally a very clear line of demarcation 
between them, visible on the posterior surface, 


NERVOUS SYSTEM. (Nervous Centres. Tue Sprxat Corp.) 


Fig. 377. 
A 


ts 
= 


-s-@ 9OO@ 80-2 


- 


~ 


ce 
ie 


c 


' 


> 
Lis 


> Ot 


545 


' 


Transverse sections of are small; the 


inal cord. 
Arnold. ) 


the 
( After 


1, cervical region at 
the upper part of 


the swelling. 


2, the same at the tionally to the oth 


largest part of the 
swelling. 
3, dorsal region. 
4, lumbar region. 
5, pointed extremity. 
A, anterior surface, 
P, posterior surface. 


the posterior columns than u 


antero-lateral ones. 


‘the cord the white matter has gradually 


peared, and in the 


minal filiform process 

sent, according to Remak and Valentin. 
These facts lead to some interesting p 

logical conclusions bearing upon the 


of the cord as well 


in the upper extremities that volu ntary 
and sensibility are in their most highly 
loped state, and accordingly the size « 
portion of the cord from which the ne 
these parts emanate is greater than au 


portion of the cord. 


pendent on the grey matter or upon the 
terior columns, as has been conjectur 


by a distinct depression or 
fissure which n th 
length of the cord; bi 
this fissure does not exten 
much deeper than the su 
face, nor does any distin 
process er: mater sin 
into it. Nevertheless, i 
the spinal cord, which hi 
been hardened in aleohe 
or by any other chemic 
reagent, these columns w 
readily by te 
in the longitudinal dire 
tion, both from each oth 
and from the posteric 
columns between whi 
they are placed. Th 
occupy rather less 
one-half of the interval 
tween the posterior roots: 


the nerves, ppting 
their lowest part, 
from their ing 
they obviously take 
much less space. 
ao the dorsal regi 
th white and n 
ter are small pa it 
the posterior columns, hot 
ever, do not appear to € 
perience a diminution — 
size at all commensur 
with the general shrini 
of the organ in this regi 
nor with the reduced : 
of the antero-latera 
lumns. 
In the lumbar 
the antero-lateral colui 


of 


a 


is large in quantity, am 
the posterior columns 
pear to retain their s 
they are, indeed, 


of the cord, larger in 
than in the cervical 
and the — 
appears to depend © 
more upon the large 
of the grey matter: 

the k 
At the lowest 


- 


commencement of t 
grey matter only; 


as of its colanil 


Were the 


might most legitimately be expected that a 

proportionate developement of these parts 

would exist in the cervical region. Yet a 
_ comparison of the cervical with the lumbar 
swelling demonstrates that the developement 
' of both the grey matter and the posterior co- 
lumns, (if not absolutely, certainly relatively to 
the bulk of the segment,) is inferior in the 
former to that in the latter, whence nerves are 
| supplied to the inferior extremities in which 
Sensibility is much less acute, and in which 
there is a much less perfect adjustment of 
the voluntary power to the muscular move- 
_ ments. 
_ __ The difference of the respective sizes of the 
antero-lateral columns in those parts of the cord 
which supply the upper and lower extremities 
__ is perfectly consistent with the difference in the 
_ sensibility and voluntary power of those parts.* 
And as in the trunk these endowments are 
at their lowest point of developement, so the 
region of the cord is that which exhibits 
the antero-lateral columns of the smallest 


_ In the lower parts of the body, which re- 
ceive their supply of nerves from the lumbar 
Swelling of the cord, there are certain peculi- 
arities worthy of the attention of the physiolo- 
i, Thus the sphincter muscles of both the 
er and rectum are to a great degree inde- 
pendent of voluntary influence, and act inde- 
dently of consciousness. The principal 
ion of the lower extremities is that of 
locomotion; they are the pillars of support to 
the trunk, and the chief agents in the main- 
ance of its attitudes. And, although in 
hese actions the will exercises a not inconsi- 
derable control, still the principle of purely 
physical nervous action renders them in a 
great degree independent of the mind.+ 
the reflex or excito-motory actions are much 
more evident in the lower than in the 
er extremities; the former are much 
ore independent of cerebral lesion than the 
ter. And let it be remarked that these 
phenomena are associated with high deve- 
pement of grey matter, and with posterior 
columns of large size, while the antero-late- 
Tal columns are comparatively small. May 
“not the high developement of the grey matter 
hhave reference to the exalted state of the phy- 
sical nervous actions of the lower part of the 
, and that of the posterior columns to the 
ive actions? To these points we shall 
in to refer when we discuss the func- 
ew the spinal cord. 
Ts there a central canal in the'spinal cord? 
Many anatomists have affirmed that the spinal 
was traversed in its entire length by a 
anal, which was continuous with the fourth 
} ventricle. If such a canal exist, it must be 
| extremely difficult to demonstrate, as I have 
Never, after numberless examinations, been 


* Weber’s experiments sufficiently indicate that 
the general as well as the tactile sensibility of the 
lower extremities is considerably inferior to those 
of the upper extremities. 

t See the observations at the commencement of 
1c article, p. 589, 


NERVOUS CENTRES, (Human Anatomy. Tue Spinat Corp.) 


655 


able to see it. In transverse sections of the 
spinal cord, which have been dried upon glass, 
there is sometimes an appearance which may 
be attributed to the presence o1 4 minute canal ; 
but I should be more disposed to ascribe it to 
the patulous mouth of a bloodvessel which had 
been divided in making the section, for it is 
by no means constant even in different regions 
of the same spinal cord. The situation which 
some have assigned to this supposed canal is 
between the grey and white commissures ; but 
Stilling and Wallack* place it in the grey 
matter. It is obvious that an artificial sepa- 
ration of these layers, which is easily effected, 
and more especially while the preparation is 
being dried, would give rise to the appearance 
of a canal upon a transverse section. It may 
be stated, further, that the deepest part of the 
longitudinal fissure is wider than any other 
portion of it, and, if cut across, might appear 
like a canal. 

The observations of Tiedemann appear to me 
to put this question in its true light. I shall, 
therefore, make the following quotation from 
his learned work on the anatomy of the fetal 
brain, without, however, subscribing to the ac- 
curacy of all the statements it contains. 

“ The spinal marrow,” says Tiedemann, 
“¢ represents a hollow cylinder, the thin walls 
of which are bent backwards, the posterior part 
representing a longitudinal opening; for it is 
hollowed by a groove, termed the canal of the 
spinal marrow. This canal exists through the 
whole cylinder, and communicates with the - 
calamus scriptorius, with the fourth ventricle, 
which, strictly speaking, is but a dilatation of 
it. During the first periods we can, without 
difficulty, separate the thin and flexed walls of 
the spinal marrow, and thus expose the canal 
which they contain. This canal is somewhat 
broader in those points where the spinal marrow 
sensibly enlarges exteriorly, as at the origin of 
the nerves for the pectoral and abdominal ex- 
tremities. The mechanism of its formation is 
very simple: the pia mater, acquiring more 
extent, is folded longitudinally backwards and 
dips into the substance of the spinal marrow, 
which, as we have seen, had been previously 
in a fluid state. It is very evident that, in the 
commencement of the second, third, and even 
fourth months, this canal has, in proportion to 
the thickness of the walls of the spinal marrow, 
a much greater capacity than it subsequently 
acquires. The contraction which it undergoes 
in the progress of the developement of the 
embryo, arises from the pia mater depositing 
a new substance, the materials of which it 
derives from the blood sent by the heart, and 
which, augmenting the volume of the walls of 
the cylinder, ought necessarily to diminish the 
calibre of the central canal. This substance is 
soft, reddish, and traversed by numerous small 
vessels during the period of the last two 
months. We cannot doubt, then, that the 
grey substance of the spinal marrow has an 
origin subsequent to that of the medullary 


* Untersuchungen iiber die Textur des Riicken- 
marks. Leipz. 1842, 


656 


fibrous substance, and that it is applied from 
Within outwards on the surface of this latter. 
Consequently, the opinion of M. Gall, that it 
is formed prior to the medullary, and is, as 
it_ were, the matrix, is absolutely false with 
regard to the spinal marrow, for we already 
perceive the roots of the spinal nerves, in 
the second and third months, although at this 
period there is no cortical yet deposited in its 
canal.” 

* It is very remarkable that the canal ofthe 
Spinal marrow exists constantly and during the 
entire life of the animal, in fishes, reptiles, and 
birds. I have met it in a great number of 
fishes, both of salt and fresh water, such as 
the ray (Raia), shark (Squalus), bream 
( Cyprinus brama ), bandfish ( Cepola), pike 
( Esox ), salmon, carp, &c.; and I have always 
found its internal surface covered with a layer 
of grey substance. The observations of M. 
Arsaky agree perfectly with mine in this re- 
spect.””* 

“ I have observed the same canal, in ques- 
tion, in the hawk’s-bill tortoise, common tor- 
toise, a young crocodile of the Nile, wall li- 
zard, ringed snake, land salamander, green 
frog, and the common toad. In front it is 
continuous with the fourth ventricle, or rather 
it dilates to give origin to this cavity, and its 
interior was covered with a thin layer of cortical 
substance.” 

“ Birds possess this canal both in their 
embryo state and in adult age. In these it 
forms, at its inferior part, a remarkable exca- 
vation, which Steno, Perault, Jacobceus, and 
some other authors have described under the 
name of the rhomboidal sinus. In birds, also, 
the grey substance occupies the interior, and is 
no where in greater abundance than on the 
walls of this sinus.” 

“ The canal equally exists in the spinal mar- 
row of the fetus of mammiferous animals, as 
also in the young animals of this class (?) F. 
Meckel has found it in the embryo of the rab- 
bit;+ and G. Sewell in young animals of the 
genus dog, sheep, ox, and horse.{ This latter 
writer observes that it was filled with a colour- 
less fluid, nearly opaque, and of the same na- 
ture as that which existed in the ventricles. 
F. Meckel has even meta small canal full of 
fluid in the spinal marrow of some of the adult 
mammiferous class, such as the dog, cat, rabbit, 
sheep, and ox. Blaes has met it also in many 
adult mammiferous animals. 

“ Although we cannot find this canal in the 
spinal marrow of the human adult in its nor- 
mal state of developement, still it has undoubt- 
edly been met with; we should, then, consider 
it as the result of a retardation in its develope- 
ment. Charles Stephen§ was the first who 
gave a description of it; and Columbo,|| Pic- 


* Diss. de piscium cerebro et medulla spinali. 
Halle, 1813, p. 9. 

+ Beitriige zur Vergleichend: Anatomie, cap. ii. 
No. i. p. 32. 

+ Phil. Trans. for 1809. 

§ De dissectione partium corporis humani, lib. iii. 
Par. 1545. 

De re anatomica, Ven, 1559. 


NERVOUS SYSTEM. (Nervous Centres. Tue Sprvat Corp.) 


colhomini,* Bauhin,+ Malpighi,t Lyser 
Golles,|| Morgagni,4 Haller,** and M. Portal, 
have since observed it. Many of these write 
have even considered it as a constant and ne 
mal disposition; an hypothesis which Varol 
Monro, Sabatier, and some other anatom 
have justly opposed. Nymman procees 
even still further, for he spoke of two ca 
prolonged into the spinal marrow. Gall) 
tends to have found in the spinal marrow 
new-born infants, in infants of a certain 
and even in certain adults, two canals | 
from all communication with the fourth 
tricle, but which extended through the } 
Varolii,the tubereula quadrigemina and the n 
dulla oblongata into the interior of the a ptic 
lami, where they formed a cavity sufficient 
lodge an almond! These two supposed cana 
with their termination in the optic thalami, 
not exist; we must suppose that they are ] 
duced by a forced insufflation: I have ne 
met them either in the adult or in the foe 
nor do we find them in animals in which 
canal of the spinal marrow always comm 
cates with the fourth ventricle, by means 
the calamus scriptorius.”’ tf 4 
We shall notice further on the recent si 
ment of Stilling and Wallack on this subje 
Bloodvessels of the spinal cord.—The art 
of the spinal cord are derived from the vi 
bral arteries as well as from the small ve 
which ramify upon the spinal column i 
cervical, dorsal, and lumbar regions. = 
Of these the largest and most importat 
the two spinal arteries which spring fron 
vertebral on each side, distinguished as 
anterior and posterior spinal arteries. 
The anterior spinal artery is the larger 0 
two. It arises from the vertebral artery ne 
the basilar: sometimes it comes from the 
silar itself, or from: the inferior cerebellar; % 
sometimes the arteries of opposite sides 
different origins, one arising the vel 
and the other from the basilar. It passes 
vertically downwards, inclining inwards, it 
of the medulla oblongata, and having 
for a short distance in front of the e 
unites at an acute angle with its fellow 
opposite side, forming a single vesse 
passes down in front of the anteric 
fissure, under cover of the band of white 
tissue which is found along the middl 
anterior surface of the cord. The arte 
formed is called the anterior median ari 
the spinal cord. 
“« The anterior or median spinal arter 
Cruveilhier, “ therefore, results from th 


at 


* Anatom. Przlectiones, Rom. 1586._ 
+ Theatrum Anatomicum. Francf. 160 
t De cerebro, in his Opera Minora, t. ti 
§ Culter Anatomicns. Copsanas: HSS. 
KT de l’ceconomie du grand et petit 
4 Adversar, Anatom. Animady. xiv. — 
** Elem. Physiologie, t. iv. a 
tt Observ. sur un spina bifida et sur le! 
ies epiniere ; dans Mém, de l’Acad, 


tt Dr. Bennett’s translation of Tiedemam 
tomy of the Fetal Brain, pp. 124 et sqq. 


NERVOUS CENTRES. (Human Anatomy. Tae Sprnat Corp.) 


tomoses of the two anterior spinal branches of 
_ the vertebral. In one case there was no artery 
_ on the left side, but the right was twice as large 
_ as usual. The vessel is of considerable size 
until it has passed below the cervical enlarge- 
: ment of the cord, from which point down 
nearly to the lumbar enlargement it becomes 
_ exceedingly delicate; a little above the last- 
named enlargement it suddenly increases in 
_ size, again gradually diminishes as it ap- 
. sae the lower end of the spinal cord, and 
ming capillary is prolonged down to the 
sacrum, together with the fibrous string in 
_ which the spinal cord terminates.” 
“ During its course this artery receives la- 
_teral branches from the ascending cervical and 
_ the vertebral in the neck, and from the spinal 
“Dranches of the intercostal and lumbar arteries 
in the back and loins. Those branches pene- 
trate the fibrous canal formed by the dura 
‘mater around each of the spinal nerves; be- 
come applied to the nervous ganglia to which 
they supply branches, yet intermixed with and 
follow the course of the corresponding nerves ; 
send small twigs backwards to the posterior 
‘spinal arteries, and terminate in the anterior 
Eical trunk at variable angles, similar to those 
at which the nerves are attached to the cord.”’* 
_ The posterior spinal arteries arise from the 
vertebral or from the inferior cerebellar artery: 
they incline backwards to the posterior surface 
of the spinal marrow, along which they descend 
in a tortuous manner, anatomosing freely with 
each other and with the small arteries which 
accompany the nerves in the intercostal fora- 
mina. A network of vessels surrounds each 
posterior root of a spinal nerve, derived from 
ramifications of those arteries. We can trace 
n agi spinal arteries as low down as the 


region, distinct throughout their entire 


_ Veins—The blood is returned from the 
_ Spinal cord by a venous plexus which emerges 
the pia mater and is spread over its 
| whole surface: opposite the roots of each nerve 
a small vein is formed, which passes outwards 
with the nerve in the same sheath, and empties 
itself into the large vein which is situate in the 
intervertebral foramen. Veins accompany the 
‘anterior and posterior spinal arteries in the 
“upper part of their course. Branches from 
this plexus frequently pass to the dura mater 
volved in a fold of arachnoid, and thus com- 
unicate with the general plexus which sur- 
Tounds the sheath. 

We observe that the arteries of the spinal 
rd are reduced to a very minute size before 
etrate the substance of that organ. 
e t vessels are therefore found on its 
or in its fissures. And it may be 
further remarked that when vessels of a size to 
| be readily detected by the naked eye penetrate 
| the substance, numerous foramina, produced by 
the Separation of the nervous fibres, become 
distinetly visible. This is very obvious in the 
white commissure. 
The purpose of such a minute subdivision of 


’ * Cruveilhier, Anat, Descr. 
VOL. IIT, 


657 


bloodvessels, prior to their entrance into the 
substance of the cord, must evidently be to 
guard the nervous substance agaipst the impulse 
of several columns of blood of large size. A 
similar provision, made in a more conspicuous 
manner, is manifest in the brain, and will be 
noticed by-and-bye. 

Of the spinal nerves.—There is a pair of 
Spinal nerves for each intercostal foramen, and 
for that between the atlas and occiput. We 
can thus enumerate in all thirty-one pair of 
nerves having their origin from the spinal cord, 
and this number is exclusive of the spinal ac- 
cessory nerve which is connected with the 
upper part of the cervical region. 

he spinal nerves have the following very 
constant characters. Each has its origin by 
two roots, of which the anterior is distinct- 
ly inferior in size to the posterior. The 
ligamentum denticulatum is placed between 
these roots. Each root passes out through a 
distinct opening in the dura mater. Imme- 
diately after its emergence a ganglion is 
formed on each posterior root, and the ante- 
rior root lies embedded in the anterior surface 
of the ganglion and involved in the same 
sheath (fig 378), but without mingling its 
fibres with those of the ganglion. Beyond it, 


Origin of a spinal nerve. 


( After Beil. ) 


A, A, anterior root. 

P, posterior ditto. 

G, ganglion on the posterior root. 

C, compound nerve resulting from the commin- 
gling of the fibres of both roots. 


the nervous fibres of both roots intermingle, 

and a compound spinal nerve results. The 

trunk thus formed passes immediately through 

the intervertebra! tube and divides into an an- 

terior ‘and posterior branch, which are distri- 

buted to the muscles and integument of the 
20 


658 


trunk and the extremities. Of these branches 
the anterior one is generally much the larger. 

An exception, however, to this arrangement 
occurs in the case of the first nog nerve (the 
tenth pair of Willis), to which Winslow gave the 
appropriate name sub-occipital nerve, to indicate 
its peculiarity of character. This nerve some- 
times has only one root, and that corresponds to 
the anterior. More generally it has two roots, 
of which, unlike the other spinal nerves, the 
anterior is the larger, containing, according 
to Asch, from three to five or seven bun- 
dies of filaments, whilst the posterior contains 
two or three, or at most four much smaller 
bundles. Very frequently the posterior fila- 
ments of either the right or left side unite with 
the spinal accessory, a slight enlargement or 
knot being formed at the point of junction ; 
from this place a bundle of filaments emerges 
equal in size to the posterior root, and takes 
the ordinary course of that root, a small gan- 
glion being formed upon it at the usual situa- 
tion. Frequently, however, this ganglion is 
wanting. The compound nerve formed from 
the junction of these two roots, besides giving 
off communicating filaments to the sympathetic, 
divides as the other spinal nerves do into an 
anterior and posterior root, of which, however, 
contrary to the usual arrangement, the posterior 
is the larger. , 

The spinal nerves are arranged naturally into 
classes according to the regions of the spine in 
which they take their rise. We number eight 
in the cervical region, the sub-occipital in- 
cluded ; twelve in the dorsal region ; five in 
the Inmbar, and six in the sacral regions. All 
the nerves, after the second, pass obliquely 
outwards and downwards from their emer- 
gence from the spinal cord to their exit from 
the vertebral canal, and this obliquity gradu- 
ally increases from the higher to the lowest 
nerves. The roots of the nerves possess cer- 
tain characters, of which some are common to 
all, and others are peculiar to the nerves of 
particular regions. ‘ 

All the spinal nerves arise from the cord by 
separate fasciculi of filaments, which, as they 
approach the dura mater, converge to each 
other and are united together to constitute the 
anterior or the posterior roots. The posterior 
roots of opposite sides lie at a pretty uniform 
interval, from the upper to the lower part of 
the cord, indicating but a very trifling change 
in the thickness of the posterior columns 
throughout their entire course. The ganglia 
on the posterior roots are all proportionate to 
the size of their respective roots. 

The characters proper to the nerves of parti- 
cular regions may be stated as follows :*— 

The cervical nerves exhibit much less obli- 
quity of their roots than the other vertebral 
nerves. The second cervical nerve is trans- 
verse (the first passing a little upwards as well 
as outwards); the succeeding nerves slope 
downwards and outwards, the lowest being 


* In the succeeding statements I have followed 
Cruveilhier’s description, which I have verified, 
excepting in a few points which are specified. 


NERVOUS SYSTEM. (Nervous Cextres. Tur Sprnat Corp.) 


the most oblique; the obliquity, he 
never exceeds the depth of a single verte 

The roots of the nerves in the cervical re 
gion are of considerable size. The pe 
roots bear a larger proportion to the ¢ 
than in any other part of the spine. Accor 
ing to Cruveilhier, the ratio is as 3 to 1, am 
this estimate is probably correct. It applie 
not only to the entire root, but to the fascieu 
of filaments which enter into their formation. 

The nerves in this region increase rapid! 
from the first to the fifth, and then maintai 
nearly the same size to the eighth. — 

The dorsal nerves, with the exception of 
first, which closely resembles a cervical nerv 
have very peculiar characters, . 

There is a manifest increase in the obliquit 
of the roots, so that the length of each rot 
within the spinal canal equals the height of ; 
least two vertebra. And it may be remark 
that the apparent obliquity is less than the rea 
for each root remains in contact with the co 
for a short distance after its actual emerge 
from the substance of it, so that the po 
separation is some way below the point ¢ 
emergence. 

The interval between the roots is greater 
the dorsal region than any other segment: 
the cord. The bundles, which compose t 
roots, are smaller than elsewhere. “4 

We observe a very slight disproportion 
tween the anterior and posterior roots in 
dorsal region. The latter, however, still 
tain predominance of size. 

Lumbar region—From the dorsal regic 
its terminal extremity the surface of the sp 
cord is covered both on its err ind | 
rior aspects by the fasciculi of origin 
Peiaber geil sacral nerves. They emerg 
close to each other upon those surfaces, 
the intervals between the sets of fase 
proper to each root are extremely short 
that they form an uninterrupted series of 
dles on each surface. a. 

The proportion of the posterior to the 
rior roots in the lumbar region is as 2 to” 
cording to Cruveilhier, or as 14 to 1, W 
seems to me to be nearer the trath 
there does not —_ to be any materia 
ference in point of size between the pos 
and anterior fascicles.* 

A very interesting feature in the origin 
lumbar and sacral nerves may be seen | 
serving the relation to each other of tl 
rior and posterior roots of opposite si 
the vanpelaive surfaces of the ‘could T 
terior roots of opposite sides may be Ss 
approximate the median line gradually a 
descend, until at the lowest points they 
touch. On the contrary, the posteri 
continue nearly in the same sequence 
way down. It may, therefore, be sup 
that in the tapering of the cord the ar 


eos, 
“2 


. 


? 


* M. Blaudin assigns the following proj 
of the posterior to the anterior roots in the 
regions ; in the cervical region as 2 = 15 
dorsal region as 1 : 1; and in the lumbar ant 
regions as 1}: 1. ‘ 


NERVOUS CENTRES. (Human Anatomy. Tue Sprnat Corp.) 


fibres of the antero-lateral columns separate 

most quickly from it. 

The direction of these roots is almost vertical, 
and their length within the canal of the dura 
Mater is very considerable. The aggregate of 
them forms the cauda equina. 

I have not observed that the situation in 
which the ganglia of the sacral nerves are 
formed is different from others. They are 
contained, as elsewhere, in sheaths of dura 
mater, and lie in the sacral foramina, sur- 
‘rounded by fat, and from the looseness of their 
“connection with the walls of those foramina 

5 may be very easily detached. 

___ I cannot confirm Cruveilhier’s statement that 

the anterior and posterior roots in the sacral 
region together form the ganglia. 

_ The roots of the sacral nerves gradually di- 

Minish in size, so that the lowest are smaller 

than any others which emerge from the spinal 

In connecting the peculiar anatomical cha- 
facters of the spinal nerves in the various re- 
= with their physiological action, some 
‘interesting points are presented to our notice. 

_ The great size of the cervical nerves is quite 

‘in conformity with the exalted vital actions of 
the upper extremities. And the predominance 
of the posterior over the anterior roots, both 
positive, and as compared with other regions, 
corresponds with the great developement of 
Sensation in the upper limbs. 

The posterior root of the second cervical 
nerve, as has been noticed by Longet, is con- 
siderably larger than the anterior, as 3:1; and 
it is from this source that the occipital and 
mastoid nerves, the sensitive nerves of the 

“integument in the occipital region, derive their 
ents. 

In the dorsal region the almost equality of 
‘the anterior and posterior roots and the small 
“size of both is consistent with the absence of 

any great degree of developement either of the 
" Sensitive or motor power. Or if, as there is 
“some reason for believing, many of the move- 
ts in that segment of the body which is 
‘supplied from this region of the cord be of 
the excito-motory kind, then we might suppose 
each posterior root contains an excitor fila- 
‘Ment for each motor one in the anterior root; 
and if the sensitive fibres are superadded to the 
former (allowance being made for the smaller 
‘size of sensitive fibres,) the slight predominance 
of the posterior root may be accounted for. 
Lastly, the increased muscular activity of 
the lower extremities and their greater sensibi- 
lity as compared with the dorsal segment, ren- 
ders necessary the increase of size which the 
Toots of the lumbar and sacral nerves experi- 
ence. And it may be conjectured that the 
predominance of the posterior roots has refer- 
ence to the exalted sensibility of some parts 
of the lower limbs. 

One of the most important problems in the 
anatomy of the spinal cord is to determine the 
ia relation which the roots of the nerves 
bear to the columns of the cord and to the grey 
Matter. As far as coarse dissection enables me 
to determine, I would venture to make the fol 


659 
lowing statement, founded upon my own ob- 
servations. 

The anterior roots derive their(>bres wholly 
from the antero-lateral columns. Of these fibres 
it is probable that some are continuous with the 
longitudinal fibres of the cord, and that others 
pass into the grey matter. This, however, is 
very difficult, if it be possible, of demonstra- 
tion by the ordinary modes of dissection. The 
posterior roots adhere to the posterior part of 
the antero-lateral columns, and derive their 
fibres chiefly from that source. I have never, 
in numerous dissections, seen any thing to in- 
duce me to believe that the posterior columns 
contribute to the formation of the posterior 
roots. If they do, it must be by few and ex- 
tremely delicate fibres. It seems highly pro- 
bable (although the demonstration of the fact is 
attended with great difficulty) that the fibres of 
the posterior roots have a similar disposition to 
that described for the anterior, and that some 
pass into the posterior horn of the grey matter, 
and others are continuous with the longitudinal 
fibres. 

Various conflicting statements have been 
made by the anatomists who have written 
upon the spinal cord, with regard to the actual 
connection of the roots of the nerves with the 
pepe substance of the organ. Nor is this to 

e wondered at, when we consider the great 
delicacy of the investigation. It is very easy 
to trace any set of filaments to the pia mater; 
but after they have passed beyond that covering, 
the nervous fibres lose their main support and 
their bond of union, and they separate from 
each other. Their exquisite delicacy and mi- 
croscopic size render any further dissection of 
them extremely difficult. Mr. Grainger, in 
his excellent treatise on the spinal cord,* re- 
commends certain precautions which I have 
adopted with advantage. The cord should be 
examined immediately after death, as the delay 
even of a few hours increases the softness of 
the medullary substance. Great advantage is 
derived from placing the cord, immediately 
after its removal, in a very weak mixture of 
alcohol and water, as by these means firmness 
is given to the parts without rendering them 
crisp and brittle, as happens if strong alcohol 


be used. The parts should be dissected with 


very fine instruments under water. “I have 
met with most success,” says Mr. Grainger, 
“ by dividing the pia mater at the median fis- 
sure, and very cautiously raising it as far as the 
lateral furrow, leaving its connection with the 
fibres of the nerves intact; it is then necessary 
to open either the anterior or posterior lateral 
fissure aceording to the root examined, at a 
little distance above the exact place where the 
nerve which is to be dissected is attached to 
the cord, when by cautiously proceeding to 
open the fissure, the threads which dip into the 
grey matter are perceived.” Mr. Grainger re- 
commends the adoption of a similar mode of 
dissection for the cranial nerves, care being 
taken in every case not to disturb the connec- 


* Observations on the Structure and Functions 
of the Spinal Cord, p. 37. Lond. 1837. 
2Urs 


660 


tion of the pia mater with the nervous fibres 
themselves. He also very properly cautions 
the dissector against a deceptive appearance 
connected with the passage of those blood- 
vessels which enter the lateral fissure, in 
order to reach the internal grey substance. 
“ Without due precaution,” he adds, * these 
vascular branches may themselves be readily 
mistaken for nervous fibrils; but they are es- 
pecially liable to be productive of error, be- 
cause, when they are made tense, they cause 
those portions of the longitudinal fibres of the 
cord, which are left between them to assume 
exactly the appearance of flat transverse fibres ; 
this circumstance probably misled Gall, and 
induced him to suppose that all the fibres of 
the spinal nerves were connected with the grey 
substance.” 

The following is Mr. Grainger’s account of 
the result of his examinations conducted with 
the precautions above specified. 

“ After repeated examinations, I satisfied 
myself that each root was connected both with 
the external fibrous part of the cord and the 
interna! grey substance. The following is what 
appears to be the structure: after the two 
roots have perforated the theca vertebralis, -and 
so reached the surface of the cord, it is well 
known that their fibres begin to separate from 
each other; of these fibres, some are lost in 
the white substance, whilst others, entering 
more deeply into the lateral furrows, are found 
to continue their course, nearly at a right angle 
with the spinal cord itself, as far as the grey 
substance in which they are lost. But this ar- 
rangement has no resemblance to the distinct 
division into fasciculi, depicted by Mr. Mayo; 
on the contrary, it is with great care only that 
small, delicate, individual threads or strie, as 
it were, are traced, dipping into the lateral 
fissure, and at length joining the grey matter. 
This difficulty is owing to the fact that whilst 
the fibres on the outer surface of the pia mater 
adhere very intimately with that strong mem- 
brane, on its inner surface, the membrane be- 
comes so extremely delicate, that the fibres 
lose much of their firmness, and break on the 
application of the least force; an accident 
which always happens if the pia mater be raised 
from the surface of the spinal cord, beyond the 
point where the nerves are attached. When 
the filaments have penetrated into the fissure, 
they lose their rounded figure and become flat- 

tened, and are then seen passing to the grey 
substance at a right angle to the longitudinal 
fibres. It is extremely difficult, owing to the 
delicacy of the parts, to determine the exact 
relations which exist between the above fila- 
ments and the grey matter; but in a few dis- 
sections 1 have been able to perceive these 
fibrils running like delicate striz in the grey 
substance. In one instance the fibres, being 
more distinct than usual, an appearance was 
presented having a remarkable resemblance to 
that which is seen on making a section of the 
corpus striatum in a recent brain, after the 
method of Spurzheim. My friend and col- 
league, Mr. Cooper, in this case counted dis- 
tinctly five separate fibrils passing from the 


NERVOUS SYSTEM. (Nervous Cextres. Tue Spina Corp.) 


anterior root of one nerve, and there were | ‘on 
other fibres derived from the same root, whir 
were not so plainly seen.” ‘& 
“ From numerous examinations,” contini 
Mr. Grainger, * I am induced to believe t 
whenever the white fibres of the nervous syst 
become connected with the grey substan 
whether in the different masses of the brain, 
the spinal cord, or in the ganglions, the 
rangement is similar to what is seen in t 
section of the corpus striatum to which re 
ence has just been made. The fibres become 
it were encrusted with the grey matter, a dis 
sition which may even be seen by a careful 
spection in the convolutions of the cerebre 
in which the radiating fibres of the crus 
rebri are observed like delicate striae.” = 
I have repeated the dissections of the ro 
of the nerves in the manner described 
Mr. Grainger, and am enabled to confirm 
general results. It appeared to me, howey 
that considerably the greater number of | 
fibres passed in at right angles, whilst th 
which might be sup to take an upw 
course were few and indistinct, and sé 
rather to pass obliquely inwards and lig 4 
upwards than to approach the vertical direct 
In short, when the fibres had penetrated 
medullary substance, they seemed to diy 
from one another,—those which occupie 
central position preserving much more of pa 
lelism than either the upper or the lower: 
It is extremely difficult to demonstrate 
direct continuity between the fibres o 
nervous roots and those of the cord. Va 
has, indeed, depicted the transition of 1 
fibres into the spinal cord (see fig. 330, p. 
as seen by the microscope; but these maj 
passing to the grey matter of the cord. 
continuity of the fibres of the nerves wit! 
longitudinal fibres of the cord would pro 
take place at the surface of the latter in gr 
numbers than at more deeply-seated p 
In the dissections above described, such 
would be very apt to be destroyed or 
overlooked. Mr. Grainger, in the work 
referred to, speaks evidently with mu ch § 
confidence of the connexion of the roots: 
nerves with the grey matter than of the’ 
tinuity with the longitudinal fibres. & 
presses his conviction, however, th ts 
continuity does exist, although the exact 
of connexion and the situation at whi 
occurs cannot be demonstrated, 
This question, respecting the preci: 
of the roots of the nerves to the cord, is 
those in which physiology in a certai 
takes the lead of anatomy. 
made it certain that while the spinal cor 
as a propagator of nervous power toa 
the brain, as in the ordimary se 
voluntary movements of the trunk 
ties, it is likewise capable of 
independent nervous centre, and that 
ments of a very definite character may 
duced in parts connected with it, even % 
communication between it and the bra 
been cut off. And it has been st 
one of the most zealous labourers in t 


peria 


NERVOUS CENTRES, (Human Anatomy, Tue Encepnatoy.) 


ment of physiology, that a distinct series of 
nervous fibres is directed to each class of 
actions, those, namely, of sensation and volition, 
and those which are independent of the brain. 
Mr. Grainger was the first who offered a distinct 
solution to the anatomical problem which arose 
out of this hypothesis. Probable as his expla- 
nation appears to be, a candid review of the 
observations which have been hitherto made 
obliges me to state my opinion that the question 
is still sub judice, and that further research is 
“necessary to prove unequivocally that of the 
fibres composing the roots of the nerves, some 
“pass upwards and enter the brain, and others 
do not pass beyond the grey matter of the 
inal cord. And this inquiry demands more 
an ordinary care, for the mind of an observer 
“would be easily biased by so attractive an hy- 
pothesis as that above referred to. 
__ It is not from physiological experiment nor 
from coarse dissections that we can expect a 


a 
: 
: 


i a 
q q 
i) 
e 
* 
Ts) 
» 
ony 
Bay ES 
te \ 


ac Gk ot eee 


9 a eh ean 


is figure displays well the subdivision of 
the encephalon adopted in this article, 
(After Mayo. ) 
1.—Medulla oblongata. 
Pp, anterior pyramids, 
0, Olivary bodies. 
F r, restiform bodies. 
3 
re proceeding, 


fo however, to the description of 
these portions, 


ie } it will be necessary to take a 
ief review of some general points connected 
vith the entire encephalic mass. 


The size of the encephalon by no means 


661 


solution of this difficult but most important 
problem. We must look to the mrroscopical 
analysis of the anatomical elements of the 
spinal cord, as well as of the encephalon, for 
the most exact results upon all questions con- 
nected with the working of these centres. In 
a subsequent part of the article I shall give an 
account of the present state of our knowledge 
of this most interesting subject, having first 
examined the coarser anatomy of the several 
parts of the encephalon. 

2. Or THe Encepuaton. Gr. eyxePadov or 
syneDaros (ev tn xePaan); Fr. l’ Encephale, le 
cerveau; Germ. das Gehirn ; The Brain.—This 
term is used here in its strictly etymological 
sense to denote that part of the cerebro-spinal 
centre which is contained within the cavity of 
the cranium. Although it forms a great mass, 
continuous throughout, it offers certain very 
obvious subdivisions, which may be more con- 
veniently described separately (fig. 379). Be- 


379. 


2.—Mesocephale— 
¥Y» pons Varolii. 


¢, corpora quadrigemina. 
3.—Cerebellum. 
4,—Cerebrum— 
a, anterior lobe. 
m, middle lobe. 
J, fissura Sylvii. 
5, posterior lobe. 


keeps pace with that of the body. In com- 
paring that of the four classes _ of vertebrate 
animals, we observe a manifest increase of its 
size as compared with the body in the follow- 
ing order, fishes (minimum), reptiles, birds, 


662 


mammalia.* This statement, although appli- 
cable to the encephalic mass when viewed as a 
whole, does not apply to certain of its parts, 
which are often more developed in the less 
perfect than in the more highly organized ani- 
mals. The cerebrum and cerebellum, however, 
exhibit this gradual increase of developement, 
and their enlargement is in accordance with a 
gradually increasing manifestation of mental fa- 
culties. And itis upon the great size of these 

that the superiority of the human brain 
over that of all other animals depends. 

In comparing the brains of some of the 
larger mammalia with that of man, we observe 
an evident want of correspondence between 
the bulk of the encephalic nerves and that of 
the encephalon itself. This does not accord 
with what we have had occasion to notice 
respecting the spinal cord, in which large 
nerves were always concomitant with high 
developement of the organ itself. The maximum 
weight, as Miiller remarks, of a horse’s brain is, 
according to Soemmering, 1 lb. 70z.; the mini- 
mum of an adult human brain 2 Ib. 54 oz.; and, 
nevertheless, the nerves at the base of the brain 
are ten times thicker in the horse than in the 
human subject. 

This want of correspondence between the 
developement of the mass of the body and that 
of the brain, as well as between the size of that 
organ and of the encephalic nerves, must surely 
be admitted to indicate an incorrectness in the 
assertion of the distinguished physiologist who 
has just been quoted, namely, that ‘ all the 

rimitive fibres of the nerves terminate in the 
rain; those of the cerebral nerves immediately, 
those of the spinal nerves through the medium 
of the spinal cord.”+ The human brain must 
evidently contain numerous other fibres besides 
those which are continuous with the roots of 


Taste I. 
Average weight of the encephalon, &c. between 25 and 55 years of age, in the two 
and the average difference between them—Males, 53 brains weighed—Females, 34 


weighed :— 


NERVOUS SYSTEM. (Nervous Cenrazs. Tae Enceruaton.) 


the nerves, and it is likely that the horse’s brain 
contains similar ones, although less numerous 
it seems, therefore, impossible that the small 
brain of the horse can be the point of con- 
vergence of the large spinal and cerebral nerves 
of that animal; and if this be true as regan 
the horse, it is so likewise in man. It isn uc 
more probable that a large proportion of them 
do not extend beyond the spinal cord, and tha 
the greater number of the fibres of the ene¢ 
phalic nerves do not go beyond the part i 
which they are immediately implanted. 

It must be admitted, however, that althou 
this disproportion is very manifest as regal 
the hele encephalon, it is hot so evident 
we compare the nerves with those segmen 
the organ from which they immediately ari 
Thus, the medulla oblongata is always, 4 
regards mere bulk, in the direct ratio of 1 
nerves ; the optic lobes are large when | 
optic nerves are so; the olfactory lobes t 
close relation to the number of the olfae 
nerves, and it may be added, to the complicati 
of the olfactory organ. It is to the cerebi 
hemispheres, to the cerebellum and the syster 
of fibres immediately connected with them 
we must attribute the oe rtion in questio 
those parts being smal we the nerves ; 
large, as in the horse, and large when the ner 
are of small size, as in man. 

The human encephalon weighs about 4 
for the male, and 44 oz. for the female.* 
estimate, which was formed by Krause, ¢ 
not differ very materially from that der 
from Professor phi Reid’s careful obse 
tions made at the Infirmary at 
burgh. The scllowine tables are extra 
from a paper by this excellent anatomist i 
London and Edinburgh Monthly Journ 
Medical Science for April, 1843. > 


% 


Male. Female. 

Ib. ox. dr. Ib. os. adr. 
Average weight of encephalon ...+++.... ; 3 . * ) Py bi Ps * 
Cerebrum eee Ce eee eeee ee eee eee eeeee 43 15% 38 12 
Cerebellum eee eee ee eee eee eee eT eee er eeee 5 4 4 12} 
Cerebellum, with pons & medulla oblongata 6 3% 5 12 

Taste II. a 

Relative weight of encephalon to cerebellum, and to cerebellum with medulla oblonga 


pons Varolii, between 25 and 55 years of age, in the two sexes (53 male and 34_ 


brains weighed). Male. 
Relative weight of encephalon to cerebellum........ coccse coe 281 to 
Ditto to ditto, with pons and medulla oblongata........... Te wo 

From this table it would appear that, inthe in the first table quoted. For this 
female, the average cerebellum is, relative tothe 253 brains were weighed. 


encephalon, a little heavier than in the male. 
In a third table, which has been reduced 
from that published by Professor Reid, the 
average weight of the encephalon, cerebellum, 
with pons Varolii and medulla oblongata, is 
given over a much wider range of age than that 


* See the table at p. 623 of this volume. 
t Physiol. trans], by Baly, 2nd ed. p. 796. 


* According to Mr. Hamilton’s investi 
the adult male brain in the Scot’s head weig 
an average, 3 Ibs. 8 oz. troy; about one’ 
seven is found about 4Ibs. troy; the e 
weighs 3 lbs. 4 0z.; and one of a hund 
brains weighs 4 Ibs. : 

t Reference may also be made to an_ 
series of observations on the weight of the 
by Dr, Sims, Med. Chir. Trans. vol, > | “ 


=" 
. 

. 

< 


NERVOUS CENTRES. (Human Anatomy. Ture Encepuaton.) 


Taste III. 
MALES, 

ay Pies! Cerebellum 
Sahl Fe Encephalon, | Cerebellum. eer 
As oz. dr. | oz. dr. | oz. dr. 

1to 4; 5] 39.. 42 | 3..13: | 4.. 6 
5— 7 3 | 43..10 DS ry f 5526 
7—10} 6] 46.. 24 | 4..102 | 5..10§ 
10—13)| 3) 48.. 74 | 4..14 5.212 
43—16| 5 | 47...82 —— 6.. 1} 
16— 20| 6] 52..10 5.. 44 | 6.. 64 
20 — 20} 25 | 50... 93 | 5.. 34 | 6.. 2 
30 — 40} 23 | 51..15 5.. 3h | 6.. 44 
40 — 50| 34 | 48..133 | 5.. 34 | 6.. 48 
50 — 60} 29 | 50.. 2 5.. 58 | 6.. 2% 
60— 70; 8/| 50.. 68 | 5.. 0 Gsiewr2 
70 &upw. 7 | 48.. 42 | 4..14 5..144 

Total male brains weighed 154. 
FEMALES. 

2to 4 Ore... 9 3.. 9$ | 4.. 5 
ae fl 3} 39.. 91 | 3..11 4.. 83 
ma. 8 3 | 42.. 7§ | 4.. 7 | 5.. 5B 
16 .. 20 8 | 44..113 | 4..144 | 5..11 
20 .. 30| 18 | 45.. 23 | 4..11} | 5.. Of 
30 .. 40| 23 | 44.. 14 4. 134 | 5..11 
(640... 50} 18 | 44..104 | 4..14 5.144 
50 .. 60 3 | 45.. 4¢ | 4.. 73 | 5.. 8 
60... 70/ 11 | 42..14§ | 4..104,| 5.. 9 
70 &upw. 2] 38.. 84 | 4.. 54 | 5.2. 2 


From this table we are led to conclude that 
the brain reaches: its greatest absolute weight at 
an early age. The maximum is found in the 
table at between 16 and 20; but, as Dr. Reid 
States, it is plain that the apparent excess of 
weight at this period over that for the next forty 
years must have arisen from sources of fallacy 
incidental to insufficient data. And in the 


663 


group between 40 and 50, Dr. Reid states that 
some brains much below the average weight 
were found, so as to leave no doubt that the 
diminution in the average weight in that group 
was attributable to that circumstance. 

A decided diminution in the average weight 
of the brain was noticed in females above 60 
years of age; but, among the males, this was 
not apparent until a later period. Upon this 
point Professor Reid makes the following judi- 
cious observation, which I am anxious to 
quote as according with the views I have ex- 
pressed at page 642 respecting liquid effusions. 
“ We certainly did expect,” he says, “ also to 
find a similar diminution in the average weight 
of the male brain above 60 years of age, for 
we are perfectly satistied, as the tables contain- 
ing the individual facts will shew, that we more 
frequently meet with a greater quantity of 
serum under the arachnoid and in the lateral 
ventricles in old people than in those in the 
prime of life. We are also satisfied from an 
examination of the notes we have taken at the 
time the brains were examined, that a certain 
degree of atrophy of the convolutions of the 
brain over the anterior lobes, marked by the 
greater width of the sulci, was more common 
in old than in young persons. We have, how- 
ever, frequently remarked these appearances in 
the brains of people in the prime of life who 
had been for some time addicted to excessive 
indulgence in ardent spirits.” 

The ratio between the weight of the body 
and that of the brain is greater in early age than 
at the subsequent periods. The following pro- 
portions were obtained by Tiedemann, in infants 
just born. In two boys the proportion of the 
brain to the body was as 1: 5.15 and 1 : 6.63, 
and in two girls as 1: 6.29 and 1:6.83. The 
following table gives Professor Reid’s results 
from the examination of 92 bodies. 


Taste IV. 
Relative weight of entire body to encephalon, cerebrum, cerebellum, cerebellum with pons 
Varolii and medulla oblongata, in 92 bodies. 


pd 5S &-d | Cerebellum sy 

ee 2s Es with pons 26 

Ages. Encephalon.| 3 2 Cerebrum a Cerebellum. | & 2 Varolii and | 3.3 

Ze ZB 7 2\| medulla | Ze 

[| 1 to 5 years. 1to 88 | 4] 1to 98] 4] 1to 88} 4|1to 763 | 4 
at 5 years. 1 O88] 2)1 10h] 2/1 97% | 211 81%] 2 

|| at 7 years. 1 109 | 2]1 11 2/1 1074 | 2|/1 gag] 2 
& 13to15 years. | 1 1542] 3] 1 218] 3] 1 14228] 111 1469 | 3 
a4) 20 30 ,, 1 3542/11] 1 403%] 11] 1 3522] 10/1 2934] 11 
=|| 30 40 ,, 1 378] 6)1 412] 51/1 342] 5]1 3063] 6 
40 50 ,, 1 38 |14]14 4219/12]1 3484] 12/1 2954) 12 

50 60 ,, 1 367 | 11] 1 42) | 10/14 370! | 8| 1 318% | 10 

|| 60 70*,, 1 39) | 4|1 441 | 4] 1 427) | 4/1 3481] 4 
’ : : ‘ 1 8 | 4/1 OF) 4/1 8441 4]1 71] 4 
” ee e-. ee ee ee ee ee 

- 7 10 , 1 °138Q)° 3°12 25441 9 [4 125 3|1 105)2] 3 
5 1S 15 ae A : + “a 4 a ate 
J} 16 20 ,, 1 SOF aha Sie] 387) 4 Beak} 3).1, 1814) 3 
=) 20 30 ,, 1 334] 4/1 373 | 4/1 3274] 4]1 275, |] 4 
m1!) 30 40 ,, 1 348 | 8]1 393 | 6|1 3162 | 5|1 2853} 6 
40 50 ,, 1 35 5|]1 412 | 4/1 3245 | 4/1 277, | 4 

50 60 ,, 1 384) 2|1 41) 2 }4° 9703} 211 307%] 2 

‘| 60and upwards. | 1 38) | 6/1 43! | 6|1 346 | 6] 1 2885] 6 


* One of these was above 70 years of age. 


664 


The geveral conclusions deducible from the 
preceding statements are, that the human brain 
reaches and maintains its highest degree of de- 
velopement between the ages of 20 and 60; 
that the female brain is materially smaller than 
that of the male; that the proportion of the 
weight of the brain to that of the body de- 
creases with age, and the most marked 
diminution in this respect takes place between 
the ages of 20 and 30 years, although it has 
already begun at 5 years, and occurs veryide- 
cidedly at from 13 to 15 years; and lastly, that 
the great preponderance of the human brain 
over that of most of the lower animals depends 
upon the great developement of the cerebrum 
and cerebellum. 

It was formerly admitted, pretty generally, 
that the human brain was larger, both abso- 
lutely and relatively to the size of the body, 
than that of any other animal. This assertion, 
however, must now be received with some mo- 
dification. Exceptions to its superiority in ab- 
solute weight are found in the elephant and 
the whale. The brain of an African elephant, 
seventeen years old, which was dissected by 
Perrault, weighed 9 lbs.* The brain of an 
Asiatic elephant weighed, according to Allen 
Moulins, 10lbs.t Sir Astley Cooper dissected 
an elephant’s brain, which weighed 8 lbs. 1 oz. 
2 grs. (avoirdupois.){ Rudolphi found that 
the brain of a whale, 75 feet long, ( Balena 
mysticetus,) weighed 5 lbs. 104 0z., and that 
that of a narwhal ( Monodon monoceros, ) 17 to 
18 feet long, had a weight of 2lbs.30z, And 
there are likewise exceptions to the statement 
that the human brain is larger than that of other 
animals, relatively to the size of his body. 
Pozzi§ has shewn (as quoted by Tiedemann) 
that many small birds (for instance, the spar- 
row) have, in comparison to the size of their 
body, a larger brain than man; and Dauben- 
ton, Haller, Blumenbach, and Cuvier, found 
the brain of some of the smaller apes of the 
Rodentia, and singing birds, relatively to the 
size of the body, larger than in man.|| 

“ We must seek for the cause of man’s su- 
periority,” says Tiedemann, “ not merely in the 
greater bulk of his brain in comparison to that 
of his body, but regard must also be had to the 
size of his brain with respect to the bulk and 
thickness of his cerebral nerves, and likewise 
to the degree of perfection in its structure. 
Soemmering was the first to show that the 
human brain, in comparison to the size and 
thickness of the nerves, is larger than that of 
any other animal, even the elephant and whale, 
both of which have an absolutely larger brain 
than man. Blumenbach’s, Obels’, Cuvier's, 
Treviranus’, and my own researches have suffi- 


* Descr. Anatom. d’un Elephant, Mém. de 
l’Acad. des Sciences de Paris, t, iii. 

+ An anatomical account of an Klephant. Lond. 
1682. 

Quoted in Tiedemann’s paper on the Brain of 

a Negro. Phil. Trans. 1836. 

§ Observat. Anatom. de Cerebro, an sit in homine 
proportione majus, quam in aliis animalibus ? 

|| Tiedemann’s paper on the Brain of the Negro, 
before quoted. See also Leuret’s Table, Anat. Comp. 
du Systeme Nerveux, t. i. p. 420. 


NERVOUS SYSTEM. (Nervous Centres. Tart ExcePuaton.) 


ciently corroborated this. It is also satisfac 
torily shewn that the organization of the huma 
brain is far superior to that of any other anima 
not even excepting those apes which bear th 
closest resemblance to man.’ Pe 

The following conclusions, which Tiedema 
deduces from his observations, are so imp 
tant that I cannot refrain from inserting th 
here.* “a 

“ 1. The weight of the brain of an adult m 
European varies between 3 Ibs. 2 oz. and 4 
60z. The brain of men.who have distinguish 
themselves by their great talents is often 
large. The brain of the celebrated Cuy 
weighed 3 Ibs. 11 oz. 4 dr. 40 grs. avoirdup 
or 4 lbs. 11 oz. 4 dr. 30 grs. troy wei 
The brain of the celebrated surgeon Du puytr 
weighed 4 lbs. 10 oz. troy weight. (Both 
these eminent individuals, it ought to be- 
marked, died with the brain in a state of 
ease.) The brain of men, with feeble in 
lectual powers, is, on the contrary, often ¥ 
small, particularly in congenital idiotismus. 
brain of an idiot, fifty years old, weighed ~ 
1 Ib. 8 oz. 4dr., and that of another, forty ye 
of age, weighed but 11b. 110z. 4 dr. . 

“2. The female brain is lighter than tha 
the male. It varies between 2 Ibs. 8 oz. 
3 lbs. 11 0z. troy. I never found a fer 
brain that weighed 4 Ibs. The brain of a. 
an idiot, sixteen years old, weighed only 
60z. 1dr. The female brain weighs, on 
average, from four to eight ounces less 
that of the male ; and this difference is aln 
perceptible in a new-born child. 

“ 3. The brain arrives, on an average, @ 
full size towards the seventh or eighth | 
Soemmering says, erroneously, that the 
does not increase afier the third year. 
and Spurzheim, on the other hand, are o 
nion that the brain continues to grow till 
fourteenth year. The brothers Wenzel 
shewn that the brain arrives at its full gi 
about the seventh year. This is confirme 
Hamilton’s researches.” 

(The reader will perceive that these : 
ments do not exactly accord with the resi 
Dr.John Reid’s observations. It seems pro 
that the data upon which Tiedemann’ 
sions were founded have been too limi 
number. In calculating the weight of the 
in adolescence and adult age, some alle 
should be made for the greater propo 
water at the former period; the qua 
that fluid being at those ages 72 and 7 
in 100 respectively, according to L’Héri 

“4. Desmoulins 1s of opinion thatth 
decreases in old people. From this” 
stance he explains the diminution ~ 
functions of the nervous system and 1 
tual powers. The truth of this assert 
not as yet been determined. The br 
Wenzel, and Hamilton deny it. J 

. It is mpeene ey brain of 
eighty-two years old, was v ma 
selighed buts Ibs. 2 oz. 3 dr., aa the bi 
a woman, about eighty years old, wei 


* Loc. cit. p, 502. 


i 


_ or diminution of the body. 


NERVOUS CENTRES. (Human Anatomy. Tue Encepuaton.) 


(2lbs. 90z. 1dr. I have generally found the 
cavity of the skull smaller in old men than in 
_ middle-aged persons. It appears to me, there- 
fore, probable that the brain really decreases in 
old age, only more remarkably in some persons 


i than in others. 


“5. There is undoubtedly a very close con- 
nection between the absolute size of the brain 
and the intellectual powers and functions of the 
mind. This is evident from the remarkable 
smallness of the brain in cases of congenital 
idiotismus, few much exceeding in weight the 
brain of a new-born child. Gall, Spurzheim, 
Haslam, Esquirol, and others have already ob- 
served this, which is also confirmed by my own 
researches. The brain of very talented men, 


on the other hand, is remarkable for its size. 


« Anatomists differ very much as to the weight 


__ of the brain compared with the bulk and weight 

_ of the body; for the weight of the body varies 
_ so much, that it is impossible to determine 

_ accurately the proportion between it and the 

brain. 

~ to 800 lbs., and changes both in health and 

: when under the influence of disease, depending 


The weight of an adult varies from 100 


‘m great measure on nutrition. The weight of 


_ the brain, although different in adults, remains 


generally the same, unaltered by the increase 
; Thin persons 
have, therefore, relative to the size of the 


_ body, a larger brain than stout people. 


“From my researches I have drawn the fol- 


lowing conclusions. 


_ 1, The brain of a new-born child is, rela- 
_ tively to the size of the body, the largest ; the 
proportion is 1: 6. 

_* 2. The human brain is smaller, in compa- 


__ tison to the body, the nearer inan approaches to 


his full growth. In the second year the pro- 
" portion of the brain to the body is as 1:14; in 
the third, 1: 18; in the fifteenth, 1:24. In 
_a full-grown man, between the age of twenty 
and seventy years, as1:35to45. In lean 
“persons the proportion is often as 1: 22 to 27; 
in stout persons, as 1 : 50 to 100 and more.” 

_ (This estimate, as far as regards the early 
ages, differs from that of Dr. John Reid, pro- 
bably owing to the difference in the number 
weighed.) 

__ * 3. Although Aristotle hasremarked that the 
female brain is absolutely smaller than the male, 
‘it is nevertheless not relatively smaller com- 
pee with the body; for the female body is, 
in general, lighter than that of the male. 
The female brain is for the most part even 
Targer than the male, compared with the size 
of the body. 

_ “The different degree of susceptibility and 
Sensibility of the nervous system seems to de- 
pend on the relative size of the brain as com- 


} pared with the body. (qu.?) Children and 


young people are more susceptible, irritable, 
and sensitive than adults, and have a relatively 
larger brain. Thin persons are more suscep- 
ible than stout. In diseases which affect the 
nourishment of the body, the susceptibility 
icreases as the patients grow thinner. The 
Susceptibility and sensibility decreases, on the 


| other hand, with persons recovering from a 


665 


long illness, gradually as they regain their 
strength. The degree of eo SN 
is also in proportion to the size of the brain. 
Mammalia and birds have a larger brain and 
are more susceptible than amphibious animals 
and fishes.”’* 

Enough has been said to show, that in con- © 
trasting the brain of man and that of the lower 
animals, with reference to the much agitated 
question of the connexion of mental faculties 
and intellectual endowments with that organ, 
no one standard of comparison must be se- 
lected. We must look to absolute and relative 
size—we must compare the bulk of the several 
portions of the encephalon with each other— - 
we must notice the size of the encephalic 
nerves in relation to the whole organ—and, 
above all, we must compare the intimate or- 
ganization of brain one with the other. Unless 
all the features of the brains that are subjected 
to comparison be carefully taken into the ac- 
count, erroneous conclusions will be obtained. 
For instance, the brain of the elephant is ab- 
solutely larger than that of mau: the convo- 
lutions of the hemispheres are very highly de- 
veloped, and exhibit a degree of complexity 
almost equal to that of the human brain. At 
first sight we might be led to infer a very close 
approximation to the human, and place the 
elephant very high up in the scale of cerebral 
developement. In comparing, however, the 
brain of this animal with that of the monkey, 
the following result is obtained. The encepha- 
lon of the elephant is above that of the monkey 
by the superior developement of the cerebral 
convolutions; it is equal to it, as regards the 
quadrageminal bodies, but from the general 
form of the brain, the length of its transverse 
diameter, the presence of olfactory eminences, 
the position of the cerebellum (uncovered by 
the posterior lobes), it must be placed on a level 
with that of the inferior Mammalia.t 

Of the brain in different races of mankind. 
—When so much diversity is observable in the 
form of the cranium in different races of man- 
kind, it seems reasonable to expect a corres- 
ponding variety in the shape and other charac- 
ters of the encephalon. The external form of 
this latter organ will correspond with that of the 
cranium, and its size with the capacity of that 
cavity. But it is plain that as the capacity of 
the skull is no wise necessarily affected by its 
shape, so the absolute bulk of the brain need 
not vary, although its containing case may ex- 
hibit much variety of form. The great ques- 
tion for the physiologist to determine is, whe- 
ther, in the various races of mankind, the brain 
exhibits any striking peculiarities, characteristic 
of one or more of them, or whether it presents 
no more variety of shape, size, weight, and 
structure than may be observed in different in- 
dividuals of any one of those races. 

It should be premised that actual observa- 
tions of the brain of different races are few. 
In Europe, where hitherto anatomy has chiefly 


* Tiedemann on the Brain of the Negro com- 
pared with that of the European and the Orang 
Otang. Phil. Trans. 1836. 

+ Leuret, op. cit. p. 448. 


4 


666 


been studied, the means of instituting such 
inquiries on a large scale have been altogether 
wanting. But it may be confidently expected 
that the many well-educated men who now 
visit distant climes, accompanying our fleets 
and armies, will not let slip the opportunities 
which they possess, without contributing some- 
what to the solution of so interesting a 
question. 

Many years ago it was thought that the brain 
of the coloured races possessed a greater qtian- 
tity of colouring matter than that of the white, 
and this opinion appears to have originated with 
J. F. Meckel, who asserted that the grey sub- 
stance was of a darker hue than in the Euro- 
pean brain, and also that the medullary sub- 
stance was not so white, but yellowish grey or 
light-brown.* Walter, Camper, Bonn, Soem- 
mering, have, however, amply refuted this state- 
ment. 

Walter denied more particularly that part of 
the assertion which attributed a darker colour 
to the white substance. He states that it is 
just as white as in the European, but that the 
cortical substance is darker, that is, of a greyish 
brown colour, which he attributed to the darker 
colour of the blood in the Negro.+ 

Soemmering, with a view to decide the ques- 
tion, dissected three perfectly fresh Negro brains 
in the presence of other anatomists, Professors 
Weichmann, Schumlanski of Petersburgh, and 
Billman of Cassel, taking the very proper pre- 
caution to compare on the spot the fresh brain 
of an European. The result was that he could 
not discover either the cineritious or medullary 
substance to be in the least darker than in 
Europeans; he even thought that the colour 
was rather paler in the African than in the 
European brain.} 

It is true that Caldani and Rudolphi appear 
to have considered the grey substance darker 
in the Negro than in the European, the former 
having examined the brains of two Negroes, 
and the latter that of a Mulatto. But little 
dependence is to be ‘placed on statements 
founded upon such a limited number of ob- 
servations, and moreover it is well known that 
the aspect of the grey substance varies in dif- 
ferent individuals according to the quantity of 
blood which it may contain. 

Tiedemann affirms that the brain of the 
Negro does not present any material difference 
from that of other nations. Judging by Cam- 
per’s rule, founded upon the measurement of 
the facial angle, which is smaller in the Negro 
than the European, it had been supposed that 
the latter was smaller. The results of a few 
cases in which the Negro brain was weighed do 
not confirm this statement. The brain of a 
Negro boy according to Soemmering weighed 
2 lbs. 10 oz, 3dr. avoirdupois, or 3 Ibs. 6 oz. 


* De la diversité de couleur dans la substance 
medallaire de Negres, Hist. de l’Acad. de Berlin, 
1753. Du Cervean des Negres, ibid. 1757, quoted 
in Tiedemann’s paper. 

t Epistola Anatomica ad W. Hunterum de venis 
oculi. Berolin. 1 

t Vom Korperlichen Unterschied des Negers, 


p- 18. 


NERVOUS SYSTEM. (Nervous Centres. Tae Encernaton.) 


6dr. troy. The brain of a tall handsome Negn 
about twenty years of age, weighed 2 lbs. 13 0; 
4 dr. avoidupois, or 3 lbs. 9 oz. 4 dr. tm 
weight. A Negro’s brain, examined b 
Astley spd weighed 3 lbs. 1 oz. or 

and that of a young Negro, aged twenty-fi 
short and thin, examined by Tiedemann hi 
self, weighed 2 lbs. 30z. 2dr., having been 
short time kept in alcohol. ; 

Tiedemann has also contrasted the c pa 
of the Negro skull with those of men of 
Caucasian, Mongolian, American, and 
races. This was done by first weig 
skull with or without the lower j: 
Then the skull was weighed, having been fi 
with dry millet seed through the foramen m 
num. Lastly, by deducting the weight of : 
empty skull from that of the filled one, 
capacity of the cranial cavity was obtained 

In the Ethiopian race, the range of cap 
was found to be, in male skulls from 5: 
2 dr. 33 gr. to 31 0z. 5 dr. 16 gr. troy, in 
eight observations, and in female skul 
310z. 4dr. to 2402. 7 dr. 39 gr. in 
servations. 

Tn the Caucasian race, the capaci 
skulls of European uations was found to Ta 
between 57 oz. 3 dr. 56 gr. to 32 oz. 6 dr 
seventy-seven observations, and that of 
skulls of Asiatic nations from 41 oz. 5 dr. ¢ 
to 27 oz. 6 dr. 30 gr. (a Hindoo B 
head), in twenty-four observations. 

The male skulls of the Mongolian rae 
hibited a capacity from 49 oz. 1 dr. 22 gt 
25 oz. 0 dr. 18 gr. (a native of Nootka So 
in eighteen observations. ‘ 

In the American race the capacity of t 
male skulls ranged between 59 oz. and § 

1 dr. 44 gr. (a Toway Indian), in 
observations. 

And in the Malayan race it ranged 
49 oz. 1dr. 45 gr. to 30 oz. 5 dr. in 
eight observations, and in five female 
from 37 oz. 5 dr. to 19 oz. 2dr. 49 gr. (al 
woman). q 

These researches certainly give no ¢o 
nance to the doctrine which assigns the 
in the chain of human vari ies, 

egro as regards cerebral developemen 
far is this from being the case, that the 
pian race differs to a very trifling degre 
the European ; and, indeed, the exai 
skulls of the smallest capacity are found 
Asiatic natives (Hindoos) and American 

The following conclusions are dé 
Tiedemann from his comparison of t 
brain with that of other races. 

“1. The brain of a Negro is uponth 
quite as large as that of the Europe 
other human races. 

“ 2. The nerves of the Negro, relatively 
size of the brain, are not thicker than the 
Europeans, as Soemmering and his foll 
have said. , 

“3. The outward form ofthe spinal cord, 
dulla oblongata, the cerebellum and o 
of the Negro show no important difference 
that of the European. 

* 4, The Negro brain does not resemble t 


} 


the orang otang more than the European brain 
_ does, except in the more symmetrical distribu- 
tion of the gyri and sulci. It is not even cer- 
_ tain that this is always the case. We cannot 
_ therefore coincide with the opinion of many 
_ naturalists, who say that the Negro has more 
_ resemblance to apes than Europeans in refe- 
_ rence to the brain and nervous system. It is 
| true that many ugly and degenerate Negro tribes 
on the coast show some similarity in their out- 
_ ward form and inward structure to the ape; for 
_ instance, in the greater size of the bones of the 
_ face, the projecting alveoli and teeth, the pro- 
minent cheek-bones, the recession of the chin, 
_ the flat form of the nose-bones, the projecting 
and strong lower jaw, the position of the fora- 
| men occipitale magnum, the relative greater 
_ length of the ossa humeri and the bones of 
_ the foramen, the flat foot, and in the length, 
breadth, shape, and position of the os calcis. * 
_ * * These points certainly distinguish many 
Negro tribes from the Europeans, but they are 
hot common to all the Negroes of the interior 
of Africa, the greater number of which are well 
| made, and have handsome features.”’* 

_ A series of researches so extensive and con- 


: oh Tes 


SS 


Section in the vertical direction, to show the relation 
_ and mode of connection of the various segments of the 
_ encephalon. ( After Mayo. } 

9, fibres passing to the posterior lobe of the brain; g, 
_ corpus geniculatum externum; x, anterior of the 
corpora quadragemina (nates); b, posterior of cor- 
_ pora quadragemina (testes) ; f, olivary fascicles ; 

@, olivary bodies ; v, ponsVarolii ; p, anterior py- 
* > 7, restiform bodies (forming part of the 
| crus cerebri) ; ¢, processus e cerebello ad testes 

| (cerebro-cerebellar commissure of Solly); c, 

14 um ; 8, spinal cord. 


_ The inferior limit of the encephalon is the 
- The remaining observations of Tiedemann on 
the intellectual condition of the Negro merit atten- 
tive perusal, See also Prichard on the Physical 


NERVOUS CENTRES. (Humay Anatomy. Tue Encepnaton.) 


667 


ducted with so much care, (although the actual 
comparison of the brains themsely-= is yet 
wanting,) cannot allow a doubt to arise as to the 
conclusion which ought properly to flow from 
them. It would appear from them that no 
very marked differences exist between the 
brains of any of the classes of mankind—that 
the same relative inferiority of women to men 
is universally met with—and that a very dimi- 
nutive state of brain may be, when not an ac- 
companiment of idiotcy, either a part of a frame 
originally very small in stature, or a degenerate 
condition consequent upon a life of the lowest 
barbarism, under every possible physical impe- 
diment to the developement of bodily vigour, 
wholly deprived of moral or intellectual cul- 
ture, a state which becomes more and more 
degenerate in each succeeding generation, or, 
lastly, the effect of the mechanical compression 
to which many tribes subject the crania of their 
offspring in early infancy, 

In proceeding to the examination of the hu- 
man encephalon, it seems expedient to pre- 
mise a few observations on the method which 
it is most advisable to adopt for this purpose. 


Fig. 380. 
Ns 


SQ \) \ 
> WSs \\ \ My} 


plane of the occipital foramen. In examining 


History of Mankind, vol. i. p. 197, and vol. ii. 
p- 346. . 


668 


that great nervous mass which is situate above 
this plane, it will be obvious, even to the most 
Superficial observer, that it admits of a con- 
venient subdivision into certain great segments, 
each of which, although extensively connected 
with the neighbouring ones, may yet be capable 
of acting as an independent centre, and, in short, 
possesses the anatomical as wel! as physiolo- 
gical properties of a ganglion. And on a more 
minute investigation the number of gangliform 
segments will be found to be greater than the 
observation of the mere surface of the ence- 
phalon would lead us to conclude. The sub- 
division, huwever, which it is most conve- 
nient for the purpose of description to adopt, 
is that already stated at page 650, into, 
1, the medulla oblongata, which is immedi- 
ately continuous inferiorly with the spinal cord. 
This segment has certain characters of struc- 
ture which decidedly indicate its ganglionic 
nature; several nerves of considerable size and 
of great physiological importance are implanted 
in it, and its external anatomy very clearly in- 
dicates its distinctness from the spinal cord 
inferiorly and from the other encephalic seg- 
ments above, of which that next in order pro- 
ceeding from below upwards, is, 2, the meso- 
cephale. To this mass, so called because of its 
intermediate position between the other seg- 
ments, the term isthmus has been also very 
appropriately applied, as it is the connecting 
liuk between all the encephalic segments. In- 
ferior and posterior to it is placed, 3, the cere- 
bellum, which has very intimate relations to the 
medulla oblongata as well as to the segment 
last described, but much less extensive ones to 
that which forms by far the largest proportion 
of the encephalon, namely, 4, the cerebrum, 
which therefore occupies the principal portion 
of the cranial cavity. 

The distinction between these different seg- 
ments is very obvious on an examination of the 
surfaces of the brain, which indeed ought to 
be the first step to be taken by the anatomist. 
To discover how they are connected to each 
other and to the spinal cord, how the corres- 
ponding portions on opposite sides of the 
mesial plane are associated tozether, what fibres 
are common to all the segments, and what 
peculiar to some, and, lastly, how the grey 
matter is related to the white,—these are the 
chief objects to be attained in the dissection 
of the brain. No one method of dissection 
will suffice for this purpose. The anatomist 
should first make himself familiar with the 
simple topographical anatomy of the brain, 
that is, with all those parts in it which possess 
such characters of form or structure as may 
entitle them to be regarded as distinct and de- 
serving of separate description, and have ob- 
tained for them a special appellation. The 
form, size, general structure, and relations of 
these parts should be carefully noted. And 
this method of examination is equally applica- 
ble to the dissection of each segment of the 
encephalon. But the most convenient way in 
which it can be conducted for ordinary prac- 
tical purposes, is to commence with the cere- 
bral hemispheres, and having studied their 


NERVOUS SYSTEM. (Nervous Centres. Tae Excepnaton.) 


general structure as displayed on a horiz 
section, to examine the extent and connectio 
of the fibres which connect the right and 
hemispheres with each other (the corpus ¢ 
losum); then to open the ventricles, exan 
their shape and extent, and note the var 
particulars connected with the numerous ] 
which are brought into view by exposing | 
cavities. The dissector may next ot 
certain of the parts concealed by t 
ventricles are connected with the mesoe 
(the optic thalami for instance), and, 
been already acquainted with the vario 
minences which are seen upon the sur 
the latter, he may by vertical, or tran 
horizontal sections, investigate the m: 
which the white matter of this segme 
nects itself with that of the neighbourin 
In examining the cerebellum, the 
sures afford sufficient indication for 
venient subdivision of the organ, and by 
zontal or vertical sections at various pai 
the connexion of the grey and white 
may be displayed, and of the latter to 
socephale and medulla oblongata. T 
dulla oblongata has upon its surface” 
lines or fissures which denote the prop 
of its constituent columns, and which 
sufficient guide to the dissector in tr 
extent and connexions of each. 
and longitudinal sections also afford us 
formation respecting the structure of th 
ment of the encephalon and the relation 
parts. 

Such is the mode of dissection ’ 
downwards, against which it has been 
the fashion of late years to declaim wi 
vehemence. But, however the advo 
a particular theory may object, 
no dovbt that this method is b 
useful for all practical purposes. It ena 
anatomist, without difficulty, to study 
minent parts or landmarks (so to speak 
brain, without a knowledge of whicl 
vain to attempt any other mode of dis 
And for pathological investigations | 
only method which can be conveniently) | 
It is plain, therefore, that all who are | 


© 


of becoming acquainted with the an 
this organ should begin by making @ 
in this way. An additional advantage i 
in this mode of investigation, from its 
eae to the dissection of the br 
ower animals, of the Mammalia 
especially, for the purpose of compar 
with the brain of the human subject. 
The method of our celebrated ¢ 
Willis was very much the same as 1 
described. He removed the mem 
the posterior lobes of the hemisph 
thus separated the latter from the- 
parts, and by raising them as far 
as possible he was enabled to obser 
nections of the cerebral hemisphe 
mesocephale, and the attachments of 
behind. He also must have studi 
stance of the hemisphere by horizon 
By then dividing the or pi 
hemispheres horizontally along the p) 


NERVOUS CENTRES. (Human Anatomy. Tut Encepuaton.) 


corpora striata, he raised a large flap consisting 
of the upper part of the hemispheres, with the 
intervening corpus callosum and the adherent 
fornix ; and thus were exposed the inferior sur- 
face of the latter, and the cavities of the three 
Yentricles, the fourth being shewn by a vertical 

ection of the cerebellum on the median plane, 
by the separation of the segments thus 
ade. This is an admirable section to display 
the connection of the hemispheres with what 
Willis described as the medulla oblongata, 
namely, in the words of his translator, * all that 
substance which reaches from the inmost cavity 
bf the callous body and conjuncture in the 
isis of the head to the hole of the hinder part 
_ of the head, where the same substance being 
"yet further continued ends in the spinal mar- 
Tow.” The fourth, seventh, and eighth plates 
in Willis's work display this mode of dis- 


the modern researches of Reil, Gall and 
sim, and others, directed attention more 
rticularly to the physiological anatomy of the 
fain. Their principal object was to discover 
e mode of connexion of the several segments 
of the cord with each other, and of the whole 
encephalon with the spinal cord. And their 
‘method of dissection consisted in tracing the 
urse of the fibres chiefly from below upwards. 
Reil found it necessary to harden the brain in 
cohol, in order to give it such firmness as 
ould enable him to tear portions of it in the 
ection of its fibres, and thus to make these 
er conspicuous. There can be no doubt 
yers of the brain will separate most rea- 


* Thomz Willis, Cerebri anatome, nervorumque 
‘descriptio et usus, in Opera Omnia, Amsterdam, 
$2, cap. xiii. Also an English edition by S. 
Pordage, London, 1684. The following extract 
gives the description of Willis’s dissection in his 
own words. ‘* Ut cerebri ita proprie dicti anatome 
rite celebretur, haud vulgari sectionis modo proce- 
ndum esse existimo. Verum ubi totius eyxepadov 
aalyaria exempti compages coram sistitur, im- 
imis posterior cerebri limbus, ubi cerebello ac 
medallz oblongatw connectitur, membranis undique 
iscissis aut avulsis, a cohesione cum partibus sub- 
tis (quantum fieri potest) liberetur ; tunc facile 
abit quod cerebri substantia corporibus istis 
quam unitur, verum per se, nisi quod 
branarum nexu superficie tenus conjungitur ab 
ino libera ac independens fuerit: quinetiam 
f ri puppis a vicinis partibus eo ritu divisa, 
Si anterius reclinetur, medulle oblongate crura, 
Prorsus nuda, ac a cerebro et cerebello (nisi in 
appurebunt. illi appenduntur) omnino distincta 
; bunt, * * * * * FX 


eee Ee 
s cerebri recessus adhuc clarius patebunt, 
ms ejus a medullw oblongate cohesione, 
mtum fieri potest, ex omni parte separatus et 
vatus, ad latera ejusdem medulle, quibus juxta 
ra striata unitur, paulo ulterius per substan- 
lam secetnr, simulque fornix juxta radices 
ssus una cum cerebro reflectatur, tunc enim 
" compages penitus elevari, antrorsum re- 
lecti, ac in planum explicari potest, ita ut corporis 
callosi in aream latam expansi interior superficies 
en ganeb et tractari possit. Ubi, preter medul- 
et nitidissimam illius substantiam, observare 
est plures lineas albas paralelas que cerebri disse- 
| pimentum rectis angulis secant ; quasi essent trac- 
_ | tus quidam, sui vestigia, in quibus spiritus animales 
ab uno cerebri hamispherio in alterum migrant 
Tesiliuntque.” Op. cit. cap. i. p. 5, 6, 


| si 


669 


dily when torn in the direction of their fibres ; 
and thus this mode of preparation becomes of 
great importance to the anatomist, as he can 
thereby determine easily the direction of those 
fibres which form the principal portion of the 
part under examination. It will not, however, 
suffice to display the direction of all the fibres, 
nor indeed is any mode of preparation adequate 
for that purpose, which can only be accom- 
plished by extensive and patient microscopic 
investigation.* 

The great advantage of pursuing the dissec- 
tion in the direction from below upwards con- 
sists in this, that we proceed from the more 
simple to the more complex. The problem 
which the anatomist has to solve is, Given cer- 
tain columns or bundles of fibres in the me- 
dulla oblongata, to determine how they connect 
themselves with the other segments of the brain. 
But it is obvious that without some knowledge 
of the topesraphy of the other more compli- 
cated parts of the encephalon, the dissector 
would have considerable difficulty in pursuing 
his researches. Nor must he content himself 
with the solution of this fundamental question ; 
he is to explore for other fibres in these seg- 
ments besides those which connect them with 
the medulla oblongata, and he has to ascertain 
how they comport themselves, whether as form- 
ing an integrant portion of the segment in which 
they are found, or serving to connect it with 
one or more of the others. 

Although we are mainly indebted to modern 
anatomists for following out more completely 
this method of dissection, it cannot be denied 
that such men as Willis, Vieussens, and Mal- 
pighi were quite alive to the importance of ex- 
amining the fibres of the brain, with a view to 
the physiological action of its different parts. No 
one can peruse Willis’s admirable account of 
the brain without perceiving how completely 
he unites structure and function, and with what 


* Reil’s methods of preparing the brain are best 
described in his own words: ‘‘ Of the methods 
which I have employed in preparing brains, those 
contained in the following directions answered best. 
1. Let the brain be hardened in alcohol, and then 
placed in a solntion either of carbonated or pure 
alkali, in the latter two days, in the former for a 
longer period, and then again hardened in alcohol 
if thus rendered too soft, The advantage of this 
method is, that the fasciculi of nervous matter are 
more readily separable, and the brown matter more 
distinguishable from the white than after simple 
maceration in alcohol; the grey matter is rendered 
by the alkali of a blacker grey, and assumes the 
consistence of jelly. 2. Let the brain be macerated 
in alcohol, in which pure or carbonated potass or 
ammonia has been previously dissolved ; the con- 
traction of the brain is lessened by this process. 
3. Let the brain be macerated in alcohol from six 
to eight days, and then its superficial dissection 
commenced, and the separation of the deeper parts 
continued, as the fluid, in which the brain is kept 
immersed, penetrates its substance. This method 
appears to me better than the preceding, and would 
very likely be improved if the alcohol were ren- 
dered alkaline. The fibres in a brain, thus pre- 
pared, are more tenacious than otherwise, and the 
deeper parts are sooner exposed to the influence of 
the alcohol.”—Mayo’s translation of Reil’s Eighth 
Essay, in the former’s Anat. and Phys. Commen- 
taries, p, ii. p. 50, 


670 


ingenuity he ascribes the passage of the nervous 
force(under the name of animal spirits) from one 
part to another, to the anatomical relations of 
those , and the direction of the consti- 
tuent fibres, And, indeed, we may find in the 
writings of this great man the germs of many 
a theory which, in our own times, has been 
brought forward with a more plausible aspect, 
disencumbered of the quaint phraseology and 
superabundant metaphor so common in his 
day. I shall quote one remarkable instance 
as very much in point. Speaking of the fourth 
pair of nerves as connected with the corpora 
quadragemina, he says: “ Concerning these 
little nerves it is observed, that when (although) 
many others proceed from the sides or the basis 
of the oblong marrow, these arise from the 
aforesaid Prominences in the bunching forth at 
the top (nates and testes). The reason of which, 
if I be not mistaken, is this,—we have affirmed 
that these prominences do receive and commu- 
nicate to the brain the natural instinct delivered 
from the heart and bowels to the cerebel; and 
on the other side, or back again, do transfer 
towards the Precordia, by the mediation of the 
cerebel, the forces of the passions or affections 
received from the brain; but in either action 
the motion of the eyes is affected with a certain 
manifest sympathy. For if pain, want, or any 
other signal trouble afflicts the viscera or the 

recordia, a dejected and cast-down aspect of 
the eyes will declare the sense of its trouble: 
when on the contrary, in joy, or any pleasant 
affection of the precordia or viscera, the eyes 
are made lively and sparkle again. In hike 
manner the eyes do so clearly show the affec- 
tions of the mind, as sadness, anger, hatred, 
love, and other perturbations, that those who 
are affected, though they should dissemble, 
cannot hide the feeling and intimate concep- 
tions of the mind. Without doubt these so 
happen because the animal spirits tending this 
way and that way in this deviating place be- 
tween the brain and the precordia, do at once 
strike those nerves as the strings of a harp. 
Wherefore, from this kind of conjecture, which 
we have made concerning the use of these 
nerves, we have called them Pathetical, al- 
though indeed other nerves may deserve the 
same name.”* 

Malpighi and Vieussens were well acquainted 
with the fibrous structure of the brain, and 
appear to have had very correct notions as to 
the general direction which they assume, and 
the parts which they serve to connect to each 
other. The former describes the fibres of the 
brain and cerebellum as taking their origin 
from the trough of the spinal marrow contained 
within the cranium (medulla oblongata); “ for 
they ramify from four reflected crura of this 
medulla in all directions, until they end by their 
branched extremities in the cortex.” Vieus- 

sens states that the medullary substance is com- 
posed of innumerable fibrils connected together 
and arranged into various fasciculi, which be- 
come very obvious when it is boiled in oil.t 


* English edition of Willis’s Works, p. 90, fol. 
684 


Lond. 1684. F 
t Malpighi, Exercitatio Epistolica de Cerebro, 


NERVOUS SYSTEM. (Nervous Centres. Tut Encepnaton.) 


The great merit of Reil, Gall and Spurzhei 
and their followers in later years, consists 
their having followed out with great diligs 
the coarser anatomy of those fibres, and de 
mined many important and undeniable ti 
But in the statements of all anatomists, 
avail themselves of no other aid than 
which the naked eye affords, there is much 
must necessarily be uncertain or doubtful 
is there any other mode of removing the: 
certainties but by the successful applic 
microscopical analysis to the whole e 
structure. a 
Of the surface of the encephalon—W 
proceed to examine the various p 
of notice in the superficial anatomy 
encephalon. 2 
The shape of the brain is determine 
of the cerebral hemispheres. A lil 
around the surface of the latter, so as to 4 
them, would describe an oval, the sn 
tremity of which is directed fo ds. 
The superior and lateral surfaces 
encephalon are convex, and have 
ap nce from the visceral layer of 1 
noid being extended over them, adher 
subjacent pia mater. When the m 
have been removed, the convoluted 
of these surfaces, previously seen thror 
becomes very manifest, as will be m 
cularly described by-and-bye. The lor 
and transverse diameters of these sui 
respond to those of the cranial cavit 
he superior surface is divide 
median plone into two equal and 
degree symmetrical portions by a 
passes vertically between them and re 
great falciform process of the du 
front and behind, this fissure complet 
the central lobes. In the latter sit 
grea cerebelli is seen at the b 
it when the hemispheres are sep 
encephalon be in situ; if it have been | 
however, the superior surface of the ee 
forms the floor of the fissure. In @ 
the fissure is interrupted by a horizont 
of white fibres, which is called the e 
losum, the great commissure of the 
hemispheres. 4 
The inferior surface of the encep) 
called commonly the base of the & 
sents many points worthy the 
anatomist. . 
It is not all upon one level: in 


it corresponds with the disposition of 
of the skull. We find, indeed, three: 
each on a different plane, and corresp' 
each of the three fosse of the craniu 
is best observed by examining a vert 
of the head, the brain being reta 
situation, or by removing the wall | 
nium on one side quite down to i 
surface. nd 
The anterior segment, and hat 


4 


1664. Vieussens, Neurographia Univer 
cap. x. See the whole passages quot 
Gordon’s Observations on the Structure 0 
Edin, 1817, p. 21. = 


NERVOUS CENTRES. 


(Human Anatomy. Tor Encernatoy.) 671 


Fig. 381. 


= 


The superior and part of the lateral surfaces of the encephalon, exposed by the removal of the calvaria. The 


falx cerebr 


hich i is seen ee longitudinal fissure. 
which present some degree of symmetrical character. 
the hemispheres of the abs ‘a 


the highest level, corresponds to the anterior 
fossa of the cranium. It rests, therefore, upon 
the roofs of the orbits, and its surface is on 
each side slightly concave to adapt it to the 
form of its resting-place. The continuation of 
the anterior median fissure separates its right 
and left portion, and the attachment of the falx 
to the crista galli of the ethmoid makes the 
distinction more complete. Ina distinct sulcus, 

rallel to and immediately on each side of the 
ongitudinal fissure, we find the olfactory pro- 
cess ornerve. This segment forms the inferior 
surface of what anatomists commonly designate 
as the anterior lobes of the brain. It presents 
the convoluted appearance which is conspicuous 
on the proper cerebral surface every where. A 
curved fissure of considerable depth, called the 


The figures on the convolutions indicate those of opposite sides 
They will be referred to further on in the description of 


fissure of Sylvius, is the posterior limit of each 


anterior lobe. 

The fissure of Sylvius corresponds on each 
side to the posterior concave edge of the lesser 
ala of the sphenoid bone, which is received into 
it. It may be traced from within, commencing 
at a triangular flat surface (locus perforatus 
anticus ), which corresponds to the posterior 
extremity of each olfactory process. From this 
situation it proceeds outwards and curves back- 
wards and a little upwards; its convexity is 
therefore directed forwards. Towards the lateral 
surface of the brain it becomes continuous with 
the fissures of neighbouring convolutions. 

The fissure of Sylvius is of considerable 
depth, especially at its internal extremity, and, 
like all the fissures of the brain, large or small, 


672 


is lined by the pia mater. We notice here a 
large interval between the arachnoid and pia 
mater, in which a considerable accumulation 
of the cerebro-spinal fluid takes place, com- 
municating with the anterior conflux of that 
fluid. In this space runs the middle artery of 
the brain, giving off its branches to the sides 
and floor of the fissure. When the convolu- 
tions which bound the fissure are separated, 
a variable number of small convolutions is 
found, projected from its floor as an insulated 
lobe, which is enclosed by a bifurcation of the 
fissure. This lobe constitutes the island (insed ) 
of Reil. 

The middle segment which lies immediately 
behind the Sylvian fissure, is on a plane much 
lower than the anterior, and corresponds on 
either side to the deep and hollow median 


A, anterior lobe; B, middle lobe ; C, posterior lobe; D, cerebellum ; a, olfactory nerves; b, 
nerves; €, third pair of nerves; d, fourth pair of ditto; e, fifth pair—portio major; é, fifth 
ninor g, seventh pair; A, filaments of origin of the glosso-pharynge 
vagus ; #, spinal accessory nerve, k, ninth nerve; I, pituitary body and process proceedi 

tuber cineream; m, mamillary bodies; n, pons Varolii; 0, medulla oblongata, 


portio minor ; fi sixth pair ; 


NERVOUS SYSTEM. (Nervous Centres. Tur Encepiaton.) 


Base of encephalon viewed from below. 


fossa of the cranium. It consists of two la- 
teral very convex lobes, commonly known 
as the middle lobes of the brain, which an 
separated from each other by a deep depres- — 
sion. These lobes, which are very accu 
limited in front by the fissure, have no e 
boundary behind, but pass off very gradually 
into the posterior lobes of the hemispheres, 
as may be seen by raising up the cerebellum. 
The transition from the middle to the pos- 
terior lobe of the hemisphere is only indicate 
by the different character of the inferior sui 
of the hemisphere, the former being convex, 
the latter concave. The subdivision, indee¢ 
of the cerebral hemisphere into middle and 
posterior lobes is purely conventional, and I 
agree with Cruveilhier that it ought to be dis- 
carded, for it has no foundation in the anatomy 


= QYy) 


= 
i 


_ the middle line. 


_ 382). 


NERVOUS CENTRES. (Human Anaromy. Tur Encepnaton.) 


of the parts. The whole of that portion of 
the cerebral hemisphere which is situate behind 
the Sylvian fissure should be called the pos- 
terior lobe. 

The hollow space between the middle lobes 
of the brain corresponds to the principal ante- 
rior reservoir of subarachnoid fluid. It is 
situate immediately above the Sella Turcica, 
and, indeed, the brain is, as it were, tied to the 
pituitary body, which is firmly lodged in this 
excavation of the sphenoid bone, by a funnel- 
shaped hollow process of nervous matter, called 
pituitary process or tube, (m, l, fig. 382), which, 
enveloped in a sheath of arachnoid membrane, 
is inserted into it by its small extremity. This 
Space communicates with the anterior fissure 
in the middle, and with the Sylvian fissure on 
either side. 

Commencing at the anterior fissure and pas- 
sing backwards, we notice the following parts, 


_ to see which clearly it is necessary that the 
_ adherent pia mater and the arachnoid should 


have been previously carefully dissected away. 


_ The anterior fissure is limited by the anterior 


fold or reflection of the corpus callosum : 
behind this we find a thin layer of a lightish 
grey matter, which, like a triangular plate, 
Seems to stop up the third ventricle at its in- 
ior surface. is, indeed, which is called 
tuber cinereum, constitutes a principal part of 


‘the floor of that ventricle. The pituitary pro- 


fess is continuous with and is probably an 


extension of it. A probe introduced into the cut 


extremity of this process will be found to pass 
readily into the third ventricle. 

Immediately in front of the pituitary process, 
the union of two white bands, which form la- 
teral boundaries to a large portion of the tuber 
Cinereum, the optic tracts, takes place along 
This forms the commissure 
of the optic nerves, from which these nerves 
diverge. Behind the pituitary process the tuber 


_ cinereum extends back to two small pisiform 
__ bodies of an extremely white colour on their sur- 


face, corpora mamillaria or albicantia (m, fig. 
ese, we shall see by-and-bye, are con- 
nected with one of the most important of the 
cerebral commissures, namely, the fornix. 
Behind the mamillary bodies we find a deep 
depression into which the pia mater sinks, car- 
tying with it very numerous bloodvessels., This 
depression lies between two thick processes of 
fibrous matter, which, traced from below, pass 
be. rc and outwards, expanding as they 
vauce, and upon which each hemisphere is 
placed (to use Reil’s simile) like a mushroom 
on its stalk. These are the crura cerebri, the 
peers of the cerebral hemispheres. The 
epression above described, which separates 
them, is the intercrural or interpeduncular 
space. When the pia mater has been removed 
from it, its surface appears cribriform from the 
perforations of the numerous minute vessels 
which penetrate it; it has been named by Vicq 
d’Azyrsubstantia perforata media. The nervous 
matter which forms the floor of this space has a 
greyish hue, and connects the crura to each other, 
like a bridge, whence the designation pons 
Tarini. At the interpeduncular space we see 
VOL. III, 


673 


the third pair of nerves emerging from their 
connexion with the crura cerebri. 

The inner margin of each middle lobe of the 
brain is separated from the corresponding crus 
cerebri by a fissure which passes from behind 
forwards, and terminates in the fissure of Syl- 
vius. If this fissure be followed backwards, it 
will be found to become continuous with a 
transverse fissure which separates the cerebrum 
from the cerebellum, and corresponds to the 
posterior edge of the corpus callosum. A con- 
tinuity is thus established between the lateral 
and the transverse fissures, whence results one 
great fissure of semicircular form, the concavity 
of which is directed forwards. This is the 
great cerebral fissure of Bichat, or the great 
transverse or horizontal fissure (Cruveilhier.) 
It may be described as commencing at the fissure 
of Sylvius on one side, turning round the oppo- 
site cerebral peduncle, and ending at the oppo- 
site Sylvian fissure. The anterior and lateral 
portions of this fissure have already been no- 
ticed as the situations at which the pia mater 
enters the brain to form the choroid plexuses of 
the lateral ventricles. And it may be remarked 
here, how freely the subarachnoid fluid may pass 
along this fissure from before backwards. Pa- 
rallel to this fissure we find the fourth pair of 
nerves as it passes to its point of exit from 
the cranium. 

Not the least interesting and important of the 
objects presented at this central portion of the 
base of the brain is that remarkable arterial 
anastomosis, called the circle of Willis. This 
will be more particularly described by-and-bye ; 
but it may be stated here, that the anterior 
bifurcation of the basilar artery is immediately 
behind the interpeduncular space, on each 
side of which the posterior cerebral artery 
passes for a short distance. The posterior 
communicating artery is parallel to the inner 
edge of the middle lobe; the subdivision of 
the carotid corresponds to the commencement 
of the Sylvian fissure; and the anterior com- 
municating artery is at right angles with the 
longitudinal fissure immediately behind the 
anterior reflection of the corpus callosum. 
This anastomosis of arteries is bathed in the 
liquid which occupies the subarachnoid space 
in this situation. 

The tentorium cerebelli is situate on a plane 
a little beneath that of the middle segment of the 
base of the encephalon just described. It forms 
a septum between the posterior lobes of the ce- 
rebral hemispheres, which are continuous with 
the middle segment, and the posterior segment 
of the encephalon, which we now proceed to 
describe. 

The posterior segment, as occupying the pos- 
terior fossa of the cranium, is ona level con- 
siderably below that of the middle segment. 
The parts which are deserving of more par- 
ticular notice here, are, proceeding from before, 
the pons Varolii (n, fig. 382), the inferior and 
anterior surface of the mesocephale, which is 
situate immediately behind the interpeduncular 
space, the crura cerebri appearing to emerge just 
above its anterior border. From its posterior 
edge the medulla oblongata (0) extends down- 

2x 


674 


wards, and a little backwards. As the brain 
rests on the upper surface of its hemispheres 
with its base upwards, the medulla oblongata 
is seen to occupy a notch or depression be- 
tween the hemispheres of the cerebellum. The 
fibres of the pons Varolii are seen passing out- 
wards and backwards into each hemisphere of 
the cerebellum, forming the inferior layer of 
each crus cerebelli. On each side of the me- 
dulla oblongata is the inferior convex surface 
of each hemisphere of the cerebellum marked 
by its fissures and lamine. The basilar artery 

in a groove along the middle of the pons 

m before backwards. The fifth nerve emerges 
’ from the crus cerebelli, the sixth immediately 
below the posterior margin of the pons, and 
the seventh, eighth, and ninth nerves are seen 
springing from each side of the medulla by a 
series of fascicles similar to those which form 
the roots of the spinal nerves. 

Of the dissection of the brain from above 
downwards.—It will facilitate our subsequent 
descriptions, if, previous to examining the se- 
veral segments of the encephalon in detail, 
I give a rapid sketch of the dissection of the 
brain according to the topographical method, 
proceeding from above downwards. 

This dissection is commenced by making a 
horizontal section of one hemisphere, a little 
above the level of the corpus callosum. The 
surface, which is thus ex , has in shape 
the charaeter of a demi-oval. Itis chiefly com- 
posed of white substance, which occupies the 
centre of the space, bounded by a wavy border 
of grey matter. Anatomists designate it cen- 
trum ovale minus. We find this is a convenient 
section on which to study the anatomy of the 
convolutions, and to give some idea of the 
composition of that portion of the hemispheres 
of the brain which is situate above the ventricles. 
On making a similar section of the other hemi- 
sphere at the same level, a similar surface 
is exposed, and the conjunction of both con- 
stitutes what Vieussens denominated the cen- 
trum ovale majus. 

By separating the hemispheres slightly, after 
this section, the horizontal portion of the cor- 
pus callosum is well displayed. The con- 
tinuity of its transverse fibres with the white 
substance of the hemispheres may be traced ; 
and by following its anterior and posterior 
reflections they will be found to connect the 
hemispheres at their inferior as well as their 
superior parts. The corpus callosum, wher 
examined in its full extent, exhibits somewhat 
of a vaulted shape, and is found to enter 
largely into the formation of the roof of the 
lateral ventricles. 

We notice some remarkable longitudinal 
fibres, passing along the middle of the corpus 
callosum, varying greatly in developement in 
different brains. These consist of two bundles 

laced in juxta-position, but easily separable. 
We may trace them throughout the whole length 
of the corpus callosum. They cut the trans- 
verse fibres at right angles, and may be readily 
dissected up from them. They seem to tie the 
pene l rk together, and are probably com- 
missural. They form what has been improperly 


” 


NERVOUS SYSTEM. (Nervous Centres. Tue Excernatoy.) ; 


called the raphé of the callosum, m 
correctly the longitudinal tracts (Vieq d’Az 
By scraping away the white substar x 
each side of the corpus callosum, the latera 
ventricles may be opened. If this be dor 
with great care, a considerable portion of the 
membrane that lines the interior of each ve 
tricle may be exposed, but such is its gi 
delicacy that a very slight force ruptures 
When there is fluid in the ventricles, 
membrane may be more easily demonstr 
from its floating upon the fluid. The place 
which the ventricles may be most cer 
opened without the risk of injuring any of 
carts contained within them, is about the i 
of an inch external to the blending of the fi 
of the corpus callosum with the white subst 
of the centrum ovale. With the handle ofa k 
the fibrous matter which forms the roof of 
ventricle may be torn through in the ante O-p 
terior direction, and the cavity 2X pos 
Each lateral ventricle consists of a horizo 
and a descending portion. The former 
sembles in shape an inverted italic S. Its 
terior extremity, or cornu, is directed outwa 
the posterior turns inwards towards that of 
opposite side. The descending cornu pas 
downwards, forwards, and inwards in a curt 
course with the concavity forwards and inw 
and terminates at the fissure of Sylvius. 
first has been appropriately designated 
JSrontal ventricle, the second the occipital, | 
the third the sphenoidal, from their relatior 
the bones after which they have been r 
tively named. The posterior cornu is also ni 
the digital, or ancyroid cavity. a 
The anterior cornua of the lateral 
are separated from each other by a vertical : 
tum situated on the median ry 
and transparent, the septum lucidum. 
may be easily demonstrated on a a 
tion of the heatti made a little to one. 
of the mesial plane, or if both lateral 
tricles have been o , by supportin 
corpus callosum on each side with the ha 
of a knife, by which means the eptul 
stretched, and its extent and connections 
be more readily determined. The sept 
of a triangular form with curvilinear base, } 
is directed forwards, and fits into the at 
reflection of the corpus callosum. Post 
it tits in between the corpus callosum 
the anterior extremity of the horizont 
of the fornix. “ 
The septum lucidum, although so ext 
delicate and transparent, is very obvious! 
posed of two layers, which enclose a sj 
cavity called the fifth ventricle. This 
shewn by dividing the septum horizont | 
J 


rd 


? 


behind forwards. Each of these lamin 
sists, as may be easily observed by ex 
the margin of the section, of four laye 
outer one is derived from the rr r 
of the ventricles ; i within 

layer of a pale ish matter continuous 
a similar 5 ae hiss covers the of ic t ; 
and the internal surface of the third ve 

consisting of clear nucleus-like particles: 
geneous in texture; a third layer is com 


= 


NERVOUS CENTRES. (Human Anatomy. Tur Encepuaton.) 


pf white or fibrous matter; and a fourth con- 
sists of an extremely delicate membrane, pro- 
bably covered by ciliated epithelium, which 
lines the internal surface of the fifth ventricle. 
The fifth ventricle is closed at every point, 
and has, therefore, no communication with the 
___ lateral or other ventricles. It has been regarded 
by some as resulting merely from the artificial 
_ ‘separation of the lamine of the septum luci- 
_ dum. And it seems unlikely that in life, 
during health, the surface of these lamine 
should be otherwise than in contact, lubricated, 
however, by a slight moisture exhaled by the 
membrane. Ina fewrare cases fluid has been 
known to accumulate in this cavity. 
In the fifth month of uterine life, according 
_ to Tiedemann, this ventricle communicates with 
the third through a small space, situate be- 
_ tween the anterior pillars of the fornix and 
_ above the anterior commissure, and indeed it 
may be looked upon as a portion of the latter 
ventricle closed off by the formation of the fornix 
__ and septum lucidum. 
___ ‘The following parts are to be noticed in each 
Tateral ventricle :—1. In the anterior horn, the 
“corpus siriatum, a pear-shaped eminence, the 
_ obtuse extremity of which is directed forwards 
_ and inwards. Posteriorly this body is apparently 
_ prolonged backwards into the inferior cornu of 
‘the lateral ventricle by a long tapering process 
which terminates there. 2. Internal and pos- 
terior to the corpus striatum is the optic tha- 
Zamus, a gangliform body of a greyish colour, 
_ but considerably paler than that last named. 
3. These two bodies are separated from each 
_ other by a superficial groove, in which lies a 
delicate band of fibrous matter, the tenia semi- 
circularis, which is covered by a lamina of 
_ horny-looking matter, /amina cornea, the forma- 
ion of which is attributed by some to a thick- 
ening of the lining membrane of the ventricle 
along this groove. 
The choroid plexus in a great degree covers 
‘and conceals from view the optic thalamus. It 
i up from the descending cornu, and just 
behind the septum lucidum and anterior pillars 
of the fornix turns inwards to unite with its 
sllow of the opposite side. On its inner side 
it is slightly overlapped by the thin margin of 
the horizontal portion of the fornix. 
the posterior horn we observe, on its in- 
_ ternal wall, a projection inwards of one of the 
_ conyolutions to which the name hippocampus 
» or ergot, has been given. It isan in- 
mal convolution, covered by a layer of fibrous 
atter derived from the fornix. It is traversed 
by a deep suleus, which may be exposed by 
_ cutting it across. 
The descending horn contains a remarkable 
prominence, the hippocampus major, (also called 
. cornu Ammonis,) which projects into it from its 
_ inferior wall, and follows the curve of the horn. 
It likewise may be regarded as an internal con- 
volution, and is covered by a layer of fibrous 
matter derived from the fornix, which overlaps 
concavity of the hippocampus by a thin 
margin, called corpus fimbriatum. Beneath this 
is a peculiar disposition of grey matter con- 
nected with the hippocampus, to which the name 


, 


‘ 
F 


| 
‘ 
i" 


675 


fascia dentata has been given. The commence- 
ment of the choroid plexus is found in this horn, 

The anterior extremity of the descending horn 
of the lateral ventricle corresponds with the 
porenier extremity of the fissure of Sylvius. 

t is closed, not by nervous matter, but simply 
by the reflection of the membrane of the ven- 
tricle on the choroid plexus. This is the only 
provision against the escape of fluid from the 
ventricle. It seems highly probable, as we 
have already intimated, that there may be a 
communication at this situation, as well as 
at the fourth ventricle, between the fluid of 
the ventricles and that of the sub-arachnoid 
cavity by endosmose and exosmose. And 
the delicacy of the barrier which is opposed to 
the escape of fluid from the ventricle explains 
the occurrence of sanguineous effusions at the 
base of the brain from the rupture of vessels 
within the ventricle. 

Postponing the more minute description of 
the parts found in the lateral ventricle, as above 
enumerated, we proceed with the examination 
of those which are brought into view beneath 
the corpus callosum. 

The corpus callosum, which we have seen to 
consist of bundles of transverse fibres, passes 
directly from one hemisphere to the other. At 
its anterior and posterior extremity it is folded 
downwards, so as to connect those parts of the 
hemispheres which lie on a plane inferior to 
the lateral ventricles. Its anterior reflected 
portion, therefore, contributes to form the floor 
of the anterior horn, and the posterior one 
mingles with the fibres of the inner wall of the 
posterior horn. This disposition of the corpus 
callosum is best seen on a vertical section of 
the brain, which shows the vaulted form of this 
body. The greater abruptness of reflection of 
its posterior than of its anterior extremity, how- 
ever, impairs in a great degree this character. 

Of the fornix. —We have seen that the an- 
terior reflection of the corpus callosum is oc- 
cupied along the median plane by the vertical 
septum lucidum. This septum rests posteriorly 
upon the apex of a horizontal stratum of fibrous 
matter which forms part of a series of fibres 
called the Fornix or Vault. It is inconvenient 
to change names which have long been in use, 
more especially when there is no very certain 
scientific foundation for the adoption of a new 
one; otherwise the term anteru-posterior com- 
missure, which is suggested by the direction and 
the extensive connection of its fibres, might be 
appropriately assigned to it. 

The principal portion or body of the fornix lies 
immediately beneath the three posterior fourths 
of the corpus callosum. By cutting this body 
across just at the posterior extremity of the 
septum lucidum, and dissecting the anterior 
segment forwards, and the posterior one back- 
wards, its horizontal portion is exposed. In 
this dissection it is found that the latter portion 
of the corpus callosum is intimately adherent 
to the fornix. So close indeed is this adhesion 
that the separation is always attended with 
injury to the fornix. The deep-seated fibres of 
the corpus callosum seem to unite the lateral 
halves of the fornix. 

2x 2 


. 


676 


The horizontal portion of the fornix, as ex- 
posed by this dissection, has the form of a 
triangle, the apex of which is directed forwards, 
and nds to the posterior angle of the 
septum lucidum. Its base is situate behind, 
and is enclosed by the posterior folded portion 
of the corpus callosum. The apex is prolonged 
into two rounded cords of fibrous matter, which 
pass downwards and outwards, in a somewhat 
curved course, with their convexity directed for- 
wards. These are the anterior pillars of the 
fornix. As they descend, they diverge from 
each other. We can follow them down to the 
base of the brain, where they form two small 
tubercles, the corpora mamillaria, from which 
fibres are continued upwards and outwards 
into the substance of the optic thalamus. 

The posterior pillars of the fornix are ex- 
pansions of fibrous matter which are continuous 
with the angles of the base of its horizontal 
esata These bands are continued into the 
ateral ventricle, and expand partly over the 
posterior horn, and partly over the hippocampus 
major in the inferior horn. The portion of the 
fornix which is thus continued into the inferior 
horn presents a fine concave edge directed in- 
wards, which is the corpus fimbriatum. 

It would thus appear that the fornix consists 
of a horizontal triangular portion (corpus for- 
nicis ) resting on four pillars, which take some- 
what of a curved course, and form numerous 
connections with deep-seated and important 
portions of the brain. The anterior pillars are 
closely connected with the optic thalamus, 
with the tuber cinereum, with the white matter 
which forms the floor of the ventricle. The 
posterior pillars are in intimate union with the 
posterior and middle lobes of the brain. 

The fibres of the fornix are distinctly longi- 
tudinal. So that, supposing it to be commis- 
sural in its office, it may be stated to connect 
the anterior lobe of the brain and the optic tha- 
Jamus with the posterior and middle lobes. 

The fornix is divisible into two equal and 
symmetrical portions, one belonging to each 
cerebral hemisphere. These portions are united, 
as has been a my stated, by the deep-seated 
transverse fibres of the corpus callosum, and 
by the terminal fibres of its posterior reflexion, 
which form, on the inferior surface of the fornix, 
a peculiar appearance called the lyra. The 
transverse white fibres stand out in relief, cross- 
ing at right angles the proper fibres of the 
fornix. In many subjects, however, this ap- 
pearance is but faintly indicated. 

The horizontal portion of the fornix rests 
upon a triangular process of pia mater, which 
is introduced into the interior of the brain, at 
the fissure beneath the posterior reflexion of 
the corpus callosum. This process is the velum 
interpositum already described at page 635. 

The anterior pillars of the fornix bound in 
front a space in which the velum interpositum 
and choroid plexuses unite, and through which 
the lateral ventricles communicate with each 
other. This is the foramen commune anterius, 
described by the first Monro.* If a probe be 

* But previously recognised and described by 
Vieussens. 


NERVOUS SYSTEM. (Nervous Cenrnes. Tar Enceruaton.) 


a 


laid transversely in this orifice, it will have’ 
above it the anterior extremity of the for 
in front the anterior pillars, and behind it th 
point of junction of the three processes of pi 
mater. fi 
Of the third ventricle —If the fornix be di- 
vided transversely at about its middle, and the 
segments reflected, and if the velum inter 
positum be removed, a fissure, the third vei 
tricle, is exposed, situate between the opti 
thalami. This fissure extends forwards betwet 
the anterior pillars of the fornix, where it | 
limited by a band of white matter visible wit 
out dissection in that interval. That band 
the anterior commissure, which lies just in fro 
of, and as a tangent to the convex border ¢ 
the anterior pillars of the fornix. a 
At its posterior extremity the third ventric 
becomes very much contracted in all its dimer 
sions, and is continuous with a canal whiel 

leads to the fourth ventricle (iter eta 
it). The 


quartum ventriculum, Aqueductus Sylv 
orifice of this canal is apparent at the 
extremity of the third ventricle, and is bound 
superiorly by a transverse cord of white matt 
the posterior commissure, which extends for 
short distance into the cerebral matter on eithe 
side. The base of the pineal gland rests upoi 


this commissure. 
In this stage of the dissection, a joes rie’ 
of the third ventricle is gained. This cavit 
evidently results from the apposition of th 
lateral halves of the brain proper, the pai 
which more immediately correspond being t 
inner surfaces of the optic thalami. The dept! 
of the ventricle corresponds, in a great degre 
to that of these bodies; but it manifestly i 
creases towards the anterior extremity. Its floc 
is formed by a layer of grey matter continue 
from one side to the other, of the same natu 
as that which has been already described a 
covering the thalami. The de part of the 
ventricle is an infundibuliform depression, fron 
which the tubular process, seen at the base of tl 
brain (fig. 382, h is continued down to tl 
pituitary body. Just beyond this part is 
anterior extremity of the ventricle, situate 
tween the anterior pillars of the fornix a 
behind the anterior commissure; the de 
which is much less than that of the in 
bulum. 1 
The floor of the third ventricle correspo 
to several parts of interest which have b 
enumerated along the middle of the bas 
the brain. Corresponding to the posteri 
tremity of the ventricle is the interval bety 
the crura cerebri, the pons Tarini, or 1 
peduncular space. Next in order, in the dire 
from behind forwards, are the m 
laria, which are succeeded by the cine? 
and commissure of the optic nerves. The 
terior extremity of the ventricle correspot 
that portion of the tuber cinereum which 
tends between the optic commissure anc 
anterior reflection of the corpus callosum. — 
The roof of the third ventricle is formed 
the velum interpositum, already describe 
giving support to the horizontal portion of 
rnlx. 7 


‘ke 


ad 


= 


4 
ub 
i’ 
j 


___ The direction of the long axis of the third 
ventricle is obliquely downwards and back- 
wards. Its anterior extremity being on a 
higher plane than its posterior, is therefore 
_ likewise superior. 
Pineal gland—We may here conveniently 
_ hotice the position and connections of the 
' pineal gland. This body, rendered famous by 
_ the vague theory of Des Cartes, which viewed 
it as the chief source of nervous power, is 
_ Placed just behind the third ventricle, resting 
‘in a superficial groove which passes along the 
_ Median line between the corpora quadrige- 
if mina. It is heart-shaped, and of a grey co- 
Tour. Its apex is directed backwards and 
downwards, and its base forwards and up- 
wards. A process from the deep layer of the 
‘lum interpositum envelopes it and serves to 
in it in its place. From each angle of its 


These processes serve to con-: 
“nect the pineal body to the optic thalami. 
they are called the peduncles of the pineal 
land, also hubene. In general they are two 
im number, one for each optic thalamus. They 
may be traced forwards as far as the anterior 
lars of the fornix. Posteriorly these pro- 
ses are connected along the median line by 
ome white fibres which adhere to the base 
the pineal gland, as well as to the posterior 
amissure beneath, and which seem to 
m part of the system of fibres belonging to 
that commissure. A pair of small bands 
‘Sometimes pass off from these fibres, along 
Optic thalami, parallel to the peduncles 
ve described. 
___Itappears, then, that the pineal gland has no 
er connexion with the brain than that which 
e habene or peduncles secure for it ; other- 
this body might more appropriately be 
egarded as an appendage to the pia mater, in 
ich it is involved, and from which it derives 
trition. 


ted with the internal processes of the pia 
ter, are found in the pineal body ina large 
“proportion of instances in the adult. They 
han. be accumulated as it were in a cavity 


is situate towards its base. Hence So- 
“emmering gave to this collection of sabulous 
ae we name acervulus. When, however, 
the sand is abundant, it may be found upon 
the: as well as in the centre. 
_ the anterior commissure. —In examining 
the third ventricle, a rounded cord of very pure 
white. matter is seen through the interval which 
is isi.by the divergence of the anterior pillars 
| of the fornix in their descent to the base of the 
| brain. This band is transverse, and a pears 
| to form a tangent to the convex border of 
those pillars. It may be traced outwards on 
. either side through the anterior extremities of the 
} Co striata into the white substance of the 
middle lobes of the brain. A very little dis- 
Section is required to expose this cord in its 
entire extent. It seems placed in a canal hol- 
lowed in the cerebral matter. When exposed, 


i 


NERVOUS CENTRES. (Human Anatomy. Tne Encepaton.) 
7 


677 


its surface is perfectly smooth, indicating that 
fibres do not pass from it to the wall of the 
canal in which it lies. Examined in its whole 
extent, it presents the form of a curve with an- 
terior convexity, and becomes gradually flat- 
tened and expanded towards each extremity, 
its component fibres becoming divergent and 
mingling with the white substance of that por- 
tion of the brain. 

This system of fibres possesses the characters 
of a commissure or bond of connection between 
symmetrical portions of the brain on either side 
of the median plane as distinctly as the corpus 
callosum itself. 

The soft commissure.—The cavity of the 
third ventricle is partly occupied by a lamina 
of a light grey matter, which extends between 
the optic thalami of opposite sides. It forms a 
transverse horizontal plane dividing the ven- 
tricle into two portions, one above, the other 
below it. Sometimes it is divided and disposed 
as two planes. There is but little power of cohe- 
sion between its particles, so that in the recent 
state the separation of the thalami in the neces- 
sary manipulations will frequently cause its 
rupture. Hence the adjunct “ soft”? is appro- 
priately applied to it, and by its connecting the 
thalami of opposite sides, this structure may be 
ranked with the other commissures. It does 
not extend throughout the entire length of the 
ventricle: both its anterior and posterior mar- 
gins are concave and leave an open space be- 
tween each extremity of the ventricle. 

Thus far our examination includes the topo- 
graphical anatomy of the cerebrum proper. 
The pineal body, indeed, scarcely lies within 
the confines of that segment of the encephalon, 
but from its internal relation to the third ven- 
tricle and the optic thalami, it must be included 
in the description of those parts. This body 
rests on the upper surface of that segment of 
the brain which lies intermediate to the ce- 
rebroum, cerebellum, and medulla oblongata, 
namely, the mesocephale. And we shall now 
proceed to a brief notice of this part and its 
connection to the other segments. 

The mesocephale—F our eminences are seen 
immediately behind the third ventricle. A 
transverse furrow separates them into an 
anterior and a posterior pair, and a longitudinal 
furrow along the median line divides the 
right and left pair from each other. The pineal 
body rests in the anterior extremity of the lon- 
gitudinal depression. The anterior pair have 
been long named the na/es, the posterior the 
testes. In the human subject the former are 
the larger. In the inferior mammalia these 
bodies are much more highly developed than 
in man, and exhibit a more marked difference 
of size. : 

The posterior of the corpora quadrigemina 
are apparently connected to the cerebellum by 
two columns of white matter, one of, which 
passes into the central white substance of each 
cerebellar hemisphere. These are the processus 
cerebelli ad testes. They enter into the for- 
mation of the crura cerebelli. Each of them 
forms the superior layer of the crus cerebelli of 
its own side. 


678 


The interval between the processus cerebelli 
ad testes is occupied by a horizontal stratum of 
nervous matter composed of a thin layer of grey 
and of white matter. This is called the valve of 
Vieussens, although there is evidently nothing 
valvular in its nature or office. Its surface is 
marked by slight transverse depressions and 
eminences. The median lobe of the cerebel- 
Jum overlaps and conceals it from view. 

The valve of Vieussens* must be regarded 
as a portion of the median lobe of the cerebel- 
lum, which is extended forwards between the 
processus cerebelli ad testes. Its constitu- 
tion is precisely the same as the lamine of that 
body, and the transverse markings upon its 
superior surface are indications of imperfectly 
developed fissures between the lamin. 

The corpora quadrigemina form the anterior 
superior part of the mesocephale. They lie above 
the crura cerebri, upon those columns of nervous 
matter by which the latter bodies are connected 
with the medulla oblongata. These columns 
are continuous above with the optic thalami, 
and below with the central portion of the me- 
dulla oblongata, the olivary tracts, or fasciculi 
innominati of Cruveilhier. They are distin- 
guished by their reddish grey colour and their 
close resemblance in point of structure to the 
optic thalami. In transverse section they appear 
as two columns, circular in outline, quite dis- 
tinct from the surrounding greyish matter in 
which they seem imbedded (fig. 388, i). 

The lower half of the thickness of the me- 
socephale is formed by transverse curved fibres 
with anterior convexity, which extend between 
the lateral lobes of the cerebellum, and of 
longitudinal fibres which interlace with the 
superior layers of those transverse fibresand cross 
them at right angles. The former constitute 
the om Varolii, a great commissure between 
the hemispheres of the cerebellum ; the latter 
are, in greater part at least, the fibres of the 
anterior pyramids of the medulla oblongata, 
which ascend through the pons, and enter into 
the formation of the inferior layer of each crus 
cerebri. 

In examining the inferior surface of the me- 
socephale, the pons Varolii, we observe that a 
longitudinal ve extends along its middle 
from above downwards. In this lies the ba- 
silar artery. Above the anterior edge of the 
pons, the crura cerebri are seen emerging, and 
diverging from each other as they pass, to enter, 
stalk-like, into the inferior surface of the cere- 
bral hemispheres. Beneath its posterior edge, 
the medulla oblongata is seen, its anterior and 


* Valvula cerebri major is the name which Vi- 
eussens applied to this process. He describes it as 
** membrana quam transversus medullaris tractus 
circa anteriora subit, processui vermiformi anteriori, 

rocessibus a cerebello ad testes et postice pontis 

arolii parti adhwret et unitur.” He further adds, 
** illam valvule vices gerere asserimus. Ex quo fit, 
ut habita officii et magnitudinis illins ratione, 
ipsam valvulam cerebri majorem nominemus, ut 
eam a membranaceis ligamentis distinguamus, que 
intra longitudinalis et lateralium sinuum cavitates 
valvularum minorum vices supplent et munia pre- 
stant.”—Neurographia Uni 


niversalis, p. 76, Ed. Lugd. 


NERVOUS SYSTEM. (Nervous Centres. Tue Encermaton.) 


middle columns ing through the mesoce-— 
phale to the crate caleli. “Om aa side the 
fibres of the pons off into each he 
sphere of the cerebellum and form the infer 
lamina of each crus of that organ. 

The cerebellum—Some account of the 
neral disposition of the cerebellum will 
to conclude this brief review of the topog 
of the brain. The superior surface of this 
organ is a little above the level of the qua- 
drigeminal bodies. It is smooth and slightly 
convex. The lamelle of the cerebellum are 
visible upon it, but cannot be se with- 
out removing the arachnoid pia mate 
A notch is seen, dividing the posterior ¢ 
into two equal portions, and a larger note 
exists in front, at which the cerebellum forms 
its connection with the mesocephale. These 
notches denote a subdivision of the organ into 
two lateral portions, or hemispheres, and @ me- 
dian portion. The superior surface of the 
median portion is called the superior 
miform process; its anterior terminal lamina 
form the valve of Vieussens. On the inferior 
surface the hemispheres of the cerebellum ar 
much more convex than on the superior. Th 
median portion too is somewhat different 
arranged on its inferior surface; it consists of ; 
series of lamine, following a transverse direc- 
tion ; those in its centre are of greater tran 
verse extent than those bs either extremity 
whence the a rance of a crucial figure re 
sults. This ie the inferior vermiform process 

The posterior margin of the cerebellum 1 
convex, and corresponds to the concave surfac 
of the occipital bone, the falx cerebelli oceup 
ing the notch in its middle. Along the line « 
this margin, the pia mater sinks into a de 
fissure, which takes a horizontal direction fr 
behind forwards, and divides the cerebellu 
into a superior and inferior portion. 

As the brain, removed from the craniu 
lies with its base upwards, the medulla of 
longata is seen between the lateral hemispher 
of the cerebellum occupying a portion of 
depression between them, in which is t 
ferior vermiform process (fig. 382). 

The fourth ventricle is a lozenge 
cavity situated in the upper and poste 
of the medulla oblongata, and formed by 
separation of its postero-lateral columns (¢ 
pora restiformia). The cerebellum contrib 
to inclose it above by means of the 
lamine of the superior vermiform process” 
the valve of Vieussens, and below and be 
by the inferior vermiform process (fig. 

We now proceed to the examination 0 
various segments of the encephalon, w 
more special reference to the structure 
physiological bearing of each, It may 
remarked that, while all the segments ai 
timately connected with each other 
therefore mutually dependent, there 
in their structure to justify the assumption 
each is capable of exercising an indep 
function, which is, however, liable to b 4 
dified by the influence which any one, or 2 
the other segments may have upon it. 

Or THE MEDULLA OBLONGATA. (Fr. mt 


vw 


“ow 


bats 
: ve 


oe 
th 


F B 
4 


- 


J! 


S 


_— ee 


( 
H NERVOUS CENTRES. (Human Anatomy. Tae Encepnaton.) 


A 
_allongée, bulbe rachidien. Germ. das Verlan- 
= gerte Mark. Ital. midollo allungato.)—We 
; Récin with the description of this segment be- 
cause of its immediate connection with the 
Spinal cord, for it is plain, since this is the 
connecting link between that centre and the 
intra-cranial mass, that whatever influence the 
latter may exercise upon the former, must be 
conveyed or propagated by the medulla ob- 
longata. 
It is proper to notice that the term medulla 
_ oblongata has not been employed in a uniform 
_ sense by all anatomists. Willis and Vieussens 
_ comprehended under this title all the parts 
_ from the corpora striata and optic thalami 
(both Ghdinded): doven to the commencement 
_ 0f the spinal cord.* The same signification 
was adopted by the writers who immediately 
followed these great anatomists. Winslow con- 
siders the medulla oblongata as “ one middle 
“medullary basis common to both cerebrum and 
cerebellum, by the reciprocal continuity of 
‘their medullary substances.”+ The crura, or 
pedunculi cerebri, constitute its anterior part : 
se seem to be lost in the corpora striata, as 
_ Winslow states, and therefore they are looked 
upon as the peduncles of the cerebrum. Its 
posterior portion is called the extremity or 
_ cauda of the medulla oblongata (queue de la 
As 2 allongée ). It is to this latter portion that 
_ Haller restricted the term medulla oblongata, 
and most modern anatomists follow his example. 
_ Rolando, however, still applies the term in its 
_ more extended sense. 
Inthe nang article, we adopt the phrase- 
blogy of Haller as far as regards the term me- 
- dulla oblongata. It seems to form an upper 
‘ portion of the medulla spinalis, to 
_ which it stands in somewhat the same relation as 
__ thecapital to the shaft of a column. Its superior 
___ limit is indicated by the posterior edge of the 
___ pons Varolii; its inferior is denoted by a horizon- 
. &. ah ge extended between the occipital foramen 


i 


' , the first vertebra. A more natural line of 
demarcation, however, between this part and 
3 


e< 


decussating fibres which are seen crossing the 
anterior median fissure of the former at its infe- 
rior extremity. No such limit as this, however, 

is found on the posterior surface (fig. 383). 
The medulla oblongata has somewhat of a 
_ @onical shape, its base being situate above at 
the posterior margin of the pons. It is slightly 
flattened on both anterior and posterior sur- 
faces, more so on the latter than on the former. 
__ _Themedulla oblongata admits of the same pri- 
__ marysubdivisionas the medulla spinalis, namely, 
into two equal and symmetrical portions sepa- 
rated from each other by an anterior and a poste- 
Tior median fissure. e former is wide but not 
| of greatdepth. Itis occupied bya fold of pia 
| mater. Its floor is formed by a layer of fibrous 
| Matter which has the same cribriform appear- 
} ance as that of the anterior spinal fissure. 
These fibres are commissural, connecting the 


_ the medulla spinalis may be found in certain 


* See the quotation from the English editi f 
Willis, at p. 669. i he 
+ Winslow’s Anatomy, 


translated by Douglas, 
— vol. ii. p.316. Edin. 1763. om 


679 
Fig. 383. 


Anterior view of the medulla oblongata and pons 
Varolit. (After Arnold.) 

a, anterior extremity of the pons. 

p» anterior pyramids. ; 

d, decussating fibres of anterior pyramids. 

0, olivary bodies. 

A, arciform fibres. 


D, portio dura lager pair 


I, portio intermedia of Wrisberg of Sareal: 


M, portio mollis 
G, glosso-pharyngeal nerve ee pair 


V, par vagum of nerves. 


S, spinal accessory 
two portions of the medulla oblongata. The 
posterior fissure is very deep and narrow. It is 
not limited in front by a grey commissure as the 
posterior spinal fissure is, but by the posterior 
surface of the white commissure just described. 
A single layer of the pia mater passes. into it. 
The continuity of the anterior fissure of the me- 
dulla oblongata and of that of the spinal cord is 
interrupted by the decussating fibres of the py- 
ramids, (fig. 383, d,) but the posterior fissures 
are distinctly continuous with each other. 

On either side of the median plane there are 
indications on the surface of the medulla ob- 
longata, which suggest a subdivision of each 
half of the organ into four columns of nervous 
matter, through the medium of which it forms 
its connection with certain parts of the cere- 
brum and cerebellum on the one hand, and of 
the spinal cord on the other. These columns 
are the anterior pyramidal, the olivary, the 
restiform, and the posterior pyramidal. 

The anterior pyramidal columns, or anterior 
pyramids, (figs. 383, 384, 385, p,) are two 
prismatic bundles of fibrous matter which 
extend between the antero-lateral columns of 
the spinal cord and the lateral hemispheres 
of the brain. In the medulla oblongata 
each of these columns forms a compact body, 
which, when cut transversely, exhibits a tri- 
angular outline in its central portion, but that 
of a cylinder at either extremity. Each pyramid 
is limited on the outside by a superficial groove, 
which separates it from the olivary column, 
and on the inside by the anterior median fis- 


680 


Anterior view of the medulla oblongata, shewing the 
decussation 0 he pyramids, and of the upper part 
of the spinal cord. (After Mayo. ) 

Pp» anterior pyramids. 

0, olivary bodies. 

7, restiform bodies. 

d, decussating fibres. 

al, antero-lateral column of the spinal cord. 

¢c, anterior fissure of the cord, the floor of which 
forms the anterior commissure. 


sure. Superiorly the pyramids pass into the 
mesocephale above the inferior fibres of the 
pons Varolii, and interlace with other fibres of 
the same system which occupy a more elevated 
plane. In its passage into the mesocephale, 
each pyramid experiences a marked constric- 
tion, which alters its form from a prism to a 
cylinder. The fibres, however, soon diverge 
and expand. As they ascend through the me- 
socephale they are crossed by the transverse 
fibres of the pons, and some grey matter occu- 
pies the interstices between them, with which it is 
probable that other fibres are connected, and are 
added to those of the pyramids, as they emerge 
from the mesocephale at its anterior extremity. 
The pyramids gradually diminish in size 
towards the inferior extremity of the medulla 
oblongata. And here three sets of fibres may 
be distinctly noticed. The first, or decussating 
Sibres, are the most numerous; they pass 
downwards and backwards into the antero- 
lateral column of the spinal cord on the oppo- 
site side, so that the right pyramid sends fibres 
into the left half of the cord, and the left pyra- 
mid into the right half of the cord. These decus- 
sating fibres consist of from three to five bundles 
from each pyramid, which in their descent cross 
and interlace with each other /figs.384, 385, d). 
They differ in distinctness as well as in number 
in various subjects. The point at which the 
decussation takes place is about ten lines below 
the margin of the pons Varolii, and the inter- 
ruption to the fissure, occasioned by the cross- 
ing of the fibres, occupies a space of from two 
to four lines. To expose these fibres clearly it 
is necessary to remove the pia mater carefully 
from the anterior surface of the medulla ob- 


NERVOUS SYSTEM. (Nervous Centres. Tue ENcEruaton.) 
Fig. 384. 


longata to some distance below the decussation, — 
and it is, in general, of advantage to the pre-. 
paration to place it in alcohol immediately after 
the removal of the pia mater. wk 
A second set of fibres, very few in numbe 
are continued from the pyramids directly d 
to the anterior surface of the cord on the 
side, and appear to be continuous with 
of the superficial fibres of the antere 
column. These fibres may be regard 
the direct channel of communication of 
half of the medulla oblongata with the co 
sponding half of the spinal cord (fig. 385, ” 
The third series of fibres vary consic 
in point of developement in different indiy 
dane They pass een the pyramids at 
the postero-lateral columns of the medulla o 
longata, the restiform columns. They fe 
series of curves with their concavities direete 
upwards (fig.383,A),crossing beneath the: 
rior extremity of the olivary body, and 
times extending over a considerable portion | 
its surface. I have on several occasions — 
these fibres so largely developed as to ¢ 
nearly the whole surface of each olivary 
These fibres are appropriately distinguist 
the name arciform from their arched 
(processus arciformes, Santorini). 
When these fibres are so numerous as | 
cover the surface of the olivary body, we mi 
observe that those which are nearest the mang 


Anterior surface of the medulla oblongata, with a, 
pomp ps pach fie pi» Varolii, a 
obliquely from the right side, (After M 0.) 
P, pons Varolii—its left half. ; 
0, 0, olivary bodies. : 
p» part of the right anterior pyramid, eu 

near the inferior edge of the pons, and torn do 

showing the of some of its fibres ove 

the left side and backwards. ia 
d, decussating fasciculus of fibres of right 

ramid. heme rh 
d’, decussating fasciculas o pyramid. a 
n, non-decussating fibres of the right pyramil 


NERVOUS CENTRES. (Human Anatomy. Tue Encepsaton.) 


of the pons Varolii are the least curved, and 

in some rare instances the uppermost ones ex- 
hibit no more curvature than the posterior fibres 
of the pons. 
Both Santorini and Rolando have figured 
_ these fibres in their most highly developed 
state. The delineation given by the latter au- 
thor, whilst it serves admirably as a diagram to 
show the general relation of the fibres, repre- 
sents them as more numerous and distinct than 
_ Thave ever had an opportunity of seeing them, 
, and likewise exhibits them as passing upwards 

through the pons. This is certainly not the 
case. These fibres appear to incorporate them- 
selves with the restiform bodies which connect 
the medulla oblongata with the cerebellum. 

It seems to me that the arciform fibres may 
be properly regarded as a part of the same 
stem as those which form the pons Varolii. 
They are largely developed in some quadru- 
os although they assumeadifferent form. The 

bres which constitute what Treviranus called 
| the trapezium, appear to answer the same 
pu as the arciform fibres; but, by reason 
_ of the non-developement of the olivary bodies 

on the exterior of the medulla oblongata, they 
do not take the curved course, which cha- 
 yacterizes them in the human subject. These 
fibres cross the anterior surface of the medulla 
oblongata parallel to but distinct from the pons 
_ Varolii. They connect the pyramids and res- 
_ tiform bodies on each side. 
_ By their continuation upwards the pyramidal 
___ bodies form a connection with the mesocephale, 
e and also with the hemispheres of the brain 
y through the medium principally of the corpora 
_ striata, and perhaps also of the optic thalami. 
_ Through the decussation of fibres which takes 
place just before the pyramids sink intothe spinal 
cord, each cerebral hemisphere is connected 
with that half of the spinal cord which belongs 
to the opposite side of the body. By this ar- 
rangement is explained the influence which 
cerebral disease exercises upon the side of the 
body opposite to that on which it occurs. If 
the right hemisphere be irritated, convulsions 
are produced on the left side; if the right he- 
misphere be compressed, the left arm and leg 
and side of the face will be paralysed. So 
constant is this “ crossed” influence of cerebral 
lesion that it can be attributed only to some 
uniform physical condition of the nervous cen- 
tres. And that the anatomical disposition on 
which it depends is situate at the lower part 
of the medulla oblongata is proved, not only 
by the existence of these decussating fibres at 
this situation, but likewise by facts revealed 
by the phenomena of disease, and the results 
of experiment. Morbid lesions, for example, 
which have their seat above the decussation are, 
with rare execptions, accompanied by affection 
of the opposite half of the body—those which 
involve the nervous centre below the decussation 
affect the body on the same side. Mechanical 
injury to the brain or spinal cord produces like 
effects. And so constantly is this the case that 
when we meet a case of paralysis or of con- 
vulsion affecting only one side, we confidently 
ges that the lesion on which it depends will 

e found on the opposite side of the brain. 


681 


This law of cerebral action has been known 
from the earliest periods of medical science, 
but the anatomical explanation of it, the sugges- 
tion of which dates as far back as the time of 
Areteus,* has been generally admitted only 
within a comparatively recent period. This 
explanation was founded on the hypothesis of 
a decussation of fibres in the medulla oblon- 
gata to a greater or less extent. Santorini, in- 
deed, laid it down that decussation took place 
not only in the lower part of the medulla ob- 
longata, but likewise at the anterior and pos- 
terior margins of the pons Varolii.+ But it is 
quite impossible, by our ordinary means of ob- 
servation, to detect any such connection be- 
tween the anterior pyramids elsewhere than at 
their inferior extremity. In many instances I 
have thought that the fibres of the commissure 
which forms the floor of the anterior fissure 
presented an appearance as if decussation took 
place along the entire length of the pyramids. 
But the numerous foramina by which the com- 
missure is penetrated to give passage to vessels 
for the central substance of the medulla, are 
very apt to give rise to a fallacious appearance 
of this kind. 

It has been stated that there are exceptions 
to this law of cerebral action. Such certainly 
must be extremely rare, for in the course of a 
considerable experience for many years I have 
not met with an unequivocal instance in which 
paralysis occurred on the same side with cere- 
bral lesion. The analysis which Burdach has 
given of 268 cases of paralysis in which there 
was lesion of a single hemisphere, shows very 
strikingly how rare must such an exception be. 
Of these cases he states that 10 were accom- 
panied with paralysis of both sides, and that 
258 had hemiplegia. And of the hemiplegic 
cases, the paralysis occurred on the same side as 
the cerebral lesion in only 15. 

The full explanation of these exceptions has 


* Tlep: asrimy nar onetiov ypovsav maw, BBA. Ay 
xep. ¢, p. 87, Ed. Kuhn. 

+ Santorini must have been well acquainted with 
the decussating fibres of the pyramids, which he 
clearly describes. The whole passage is worth 
being quoted here. ‘ Id autem triplici potissimum 
in loco animadvertere potuimus ; in utraque scilicet 
priore, posterioreque annularis protuberantiz cre- 
pidine atque maxime in imo medullaris caudicis 
qua in spinalem abit. In priore itaque annularis 
protuberantie parte, qua superius reflexa pro com- 
prehendendis oblongate medulle cruribus in an- 
guli formam interiis producta tenuatur, sic ex 
concurrentibus fibris, strictiorique agmine coeun- 
tibus altera alteram scandit ut preter mirum im- 
plexum decussatio luculentissimé appareat. Idip- 
sum fermé in postica ipsius crepidine occurrit. Eo 
iterum in loco, qui quarto ventriculo subjicitur, 
preter varios fibraram ordines et colores, in adver- 
sum latus productas et decussatas fibras commodé 
spectavimus. Si ea tamen evidenter uspiam con- 
spicitur, profectd quam evidentissimé duas vix 
lineas infra pyramidalia atque adeo olivaria cor- 
pora conspici potest. Qua enim in longitudinem 
producta linea seu rimula pyramidalia corpora dis- 
cernuntur, si leniter deducantur, probé prius eo 
potissimum loco arctissimé herente tenui meninge 
nudata, non tenues decussari fibrillas, sed validos 
earundem fasciculos in adversa contendere, quam 
apertissimé demonstrabunt.” Oberv, Anat. cap. iii. 
§ xii. p. 61. Ed. Lugd. Bat. 1739. 


682 


yet to be discovered. The anatomical con- 
nection of each anterior prams with the 
= ey cord, however, affords some clue to it. 
is takes place, it will be remembered, not 
by the decussating fibres only, but by straight 
and perpendicular ones also; so that each py- 
ritpia, is connected with both halves of the 
spinal cord, first and principally with the op- 
Sot half; and, secondly, and by much fewer 
bres, with that of the same side. When those 
ba of the brain are affected, with which the 
ecussating fibres are connected, the paralysis 
will be crossed ; when, on the other hand, the 
direct fibres are engaged, the pelyve affection 
will occur on the same side of the body as that 
on which the lesion has occurred. But even 
on this explanation it is difficult to understand 
how these latter cases should be of such rare 
occurrence, and still more, how hemiplegia is 
so frequently accompanied with a perfect. state 
of sensation and motion on the other side. In 
the present state of our knowledge, however, 
this is the only contribution which anatomy 
can Offer towards the determination of this 
difficult question. 
Of the restiform bodies.—The lateral, and, in 
gteat part, the posterior portion of the medulla 


Fig. 386. 


Posterior view of the medulla oblongata, with mesocephale 
and part of cerebellum of an infant. ( After Foviile, ) 


S, pineal gland. 
D, nates. 
D’, testes. 


+ +, point of emergence of fourth pair of nerves. 


Y, posterior pyramids. 
X, restiform columns. 


A, F, floor of the fourth ventricle, formed by the olivary The fibres which form the lateral and 
columns, the fissure between which is the calamus scrip- sora ing of the restiform bodies pa 


torius. 
Y’, posterior surface of mesocephale. 
B, valve of Vieussens. 
N, anterior surface of crus cerebri. 
R, corpus dentatum or rhomboideum. 


NERVOUS SYSTEM. (Nervous Centres. Tut Encepnaton.) 


oblongata is formed on each side by a thick — 
and rounded rope-like column, called the corpus — 
restiforme. It is composed chiefly of fibr 
matter, and its constituent fibres take a 
gitudinal direction. There is no line of demar- 
cation between them and the fibres of the sp 
cord, with the antero-lateral and posterior 
lumns of which they seem to be continu 
Traced upwards, the restiform bodies p 
little outwards, and by their divergence e 
tribute to the increased size of the med 
oblongata at its base. 

To see the connexions of these bodies ¢ 
pletely, the posterior surface of the medu 
oblongata should be examined, The resti 
bodies form the greater part of this 
They increase in thickness as they n¢ 
Their outer margin forms a gentle curve, whi 
is concave. Their inner border is connected it 
its lower portion to two small bands of fibrot 
matter, between which the posterior media 
fissure is situate ; these are the posterior p 
ramids (Y, fig. 386). In its apes portion, 
inner border of each restiform body is free, a 
forms the outer boundary of a lozenge-s! 
depression, the fourth ventricle, hilst t 
connection of the cerebellum with the po 
terior surface of the medulla oblongata is u 
disturbed, the exact relation of these bodies 
the ventricle cannot be seen. It is necess: 
to raise up the inferior portion of the 
lobe of the cerebellum, to expose the cay 
of the ventricle; or this may be effectec 
writing the median lobe along the midi 
ine, a 
Each restiform body ascends to the her 
sphere of the cerebellum of the cc ( 
ing side. The whole of its fibres 
to penetrate that organ, and contribut 
the formation of its crus, the middle la 
or peduncle of which it forms. This i 
well shown in the analytical figur 
667, (fig. 380,) where r is the restifi 
body passing upwards and out in 
the hemisphere of the cerebellum. __ 

The distinction between the a 
olivary bodies on the surface is indic 
by the line of origin of the eighth 
nerves, which may be said to emerge ; 
the anterior margin of the former. A 
row band of fibres, very distinct in § 
brains, occupies the depression betweet 
posterior edge of the prominent oli 
and the line of emergence of thes 
This band has been well delineat 
Rolando, Reid, and others; it pr 
forms a part of the cerebral fibres | 
medulla oblongata, and ascends # 


the ns. , ie vi 
The direction of the fibres of the res 
bodies is longitudinal. Those wh 


situate most posteriorly pass directly « 
wards, and are dstoaig cai uous 
the posterior columns of the spinal 


™ 


. 
estifo 


2 and Seemeeiesoee antero-latera 
lumns. A superficial groove, varying 
much in pcre in different 
which passes upwards from the 


P Bint 


wee. > 


NERVOUS CENTRES. (Human Anatomy. 


emergence of the posterior roots of the spinal 
nerves, indicates the distinction of these two 
sets of fibres. If the posterior column be sepa- 
rated from the antero-lateral in the spinal cord, 


' the separation may be easily carried upwards 


along this line, in a specimen which has been 
sufficiently hardened. 

From the description now given, the res- 
tiform bodies may be regarded as the con- 
necting fibres between the cerebellum and the 
spinal cord. They may be designated the ce- 
rebellar fibres of the medulla oblongata in con- 
tradistinction to the others, which are entirely 
connected with the mesocephale and with the 
cerebrum. 

Rolando describes the restiform body as con- 
taining grey matter—the grey tubercle of Ro- 
Jando. This grey matter, however, may be more 


_ correctly regarded as a portion of the central 
nucleus of the medulla, from which very pro- 
‘gill some fibres of the restiform body emerge. 


he posterior pyramidal columns.—On each 


_ side of the posterior fissure we find a narrow 
column, sufficiently distinct from the restiform 
columns. These may be traced downwards 
through the cervical region of the cord, and 
even into the dorsal or lumbar, according to 
 Foyille. They taper gradually to a fine point, 
the situation of which varies in different sub- 


jects. Superiorly they form the inferior and 
part of the lateral boundary of the fourth ven- 


 tricle. Their innermost fibres end abruptly in 
‘a blunt extremity, whilst the external ones are 


continued upwards on each side of the ven- 
tricle (fig. 386, Y). 

iwary columns.—The oval bodies, which 
form a relief upon the surface of the medulla 
oblongata, have been long known by the names 


corpora olivaria, olive. They occupy the in- 
‘terval between the anterior pyramids and the 
‘restiform bodies, separated, however, from the 


latter by the narrow band of fibrous matter 
above described. 

The surface of each olivary body is crossed 
to a greater or less extent by the arciform fibres, 
‘as already described. Sometimes it is neces- 
sary to remove these fibres, in order to expose 
the proper texture of the olives. 

e superficial layer of each olivary body is 
evidently fibrous, and the constituent fibres seem 
to take a longitudinal course. If a section be 
made so as to remove the prominent convexity 
of this body, it will be seen that the white 
Matter of which it principally consists en- 
closes a layer of vesicular or grey matter dis- 
posed in a peculiar manner. This grey layer 
presents the appearance of a waving line en- 
closing white matter. If the section of the 
olivary body be made transversely, the grey 
waving line is still present, but it presents a 
convex border outwards, and is open within, 
being evidently continuous with the central 
and less definitely disposed grey matter of the 
medulla. And when the section is vertical, 
and so as to divide the olivary body in its entire 
length, the convex border of the grey line is 
still external, but it is open towards the interior 
of the medulla. 


This grey layer, contained within the olivary 


Tue Encepuaton.) €83 


Fig. 387. 


Transverse sections of the medulla oblongata. 
A, anterior. P, posterior. 
o, olivary bodies, in which are seen the undula- 


ting line of grey matter which forms the corpus 
dentatum. 


body, is called the corpus dentatum (corps 
Jestonné, Fr.) It is evidently a capsule of ve- 
sicular matter continuous below with that of 
the cord, internally with that of the central 
substance of the medulla oblongata, and supe- 
riorly with that of the mesocephale (0, fig. 
387). Its disposition, in a convoluted form, 
has doubtless reference to the packing of a 
certain quantity of this matter into a given 
space, and to the important object of bringing 
the vesicular and fibrous matter into connec- 
tion as extensively as possible. 

It has been very commonly supposed that 
the olivary bodies are mere gangliform masses 
laid upon certain ascending fibres of the me- 
dulla, and that they may be readily removed 
without injury to the deeper-seated parts. 
Either of the two following modes of dissec- 
tion will, however, serve to point out the 
erroneousness of this view. If the anterior 
pore be removed, a concave surface is left 

tween the two olivary bodies, in which their 
continuity with the central substance of the 
medulla is distinctly seen. This central sub- 
stance, which forms a substratum on which 
the anterior pyramids rest, and from which it 
is not improbable that some of the fibres of the 
pyramids emerge, is of considerable density. 
Each olivary body appears gradually to merge 
into it; or, adopting another mode of descrip- 
tion, it seems to protrude, forming a relief on 
the exterior, in the interval between the pyra- 
midal and restiform bodies on each side. Ora 
transverse section, as in fig. 387, will exhibit a 
similar continuity between the olivary bodies 
and the central substance of the medulla. 

According to this view, then, the existence 
of the olivary bodies in the human brain and 


_that of the Quadrumana indicates a high de- 


velopement of the central substance of the 
medulla oblongata as compared with its other 
nervous columns. In all the vertebrate ani- 
mals below man, the medulla oblongata in- 
creases with the bulk of the body, and like 
the spinal cord evidently bears a direct relation 
to it. This high developement appears, how- 
ever, to affect more especially the restiform and 
pyramidal bodies, and their connecting fibres, 
the trapezium. The former do not leave any 


684 


space between them, and the central columns 
do not extend to the surface; and from the 
absence of any great developement of grey 
matter, we find no such arrangement as that 
which gives rise to the corpus dentatum in man. 

The olivary or central columns of the me- 
dulla oblongata pass into the mesocephale, 
occupying a plane superior to that of the py- 
smal fibres and of the transverse fibres. 
They may be traced upwards to the crus cerebri, 
where they seem to merge into the optic tha- 
lami, and to form a connection with the corpora 

uadrigemina posteriorly. 

, Ron's iaene are a distinctly in their 
ascent to the brain in the fourth ventricle, as 
two cylindrical columns (A, F, fig. 386). They 
form the floor of that cavity and are separated 
from each other by the longitudinal fissure 
which is continued upwards from the posterior 
fissure of the medulla oblongata. 

In the fourth ventricle the olivary columns 
are crossed by the fibres of origin of the 
portio mollis of the seventh pair of nerves, 
the white colour of which in the recent speci- 
men contrasts strikingly with the greyish hue 
of the columns themselves. We here see dis- 
tinctly that these columns are the source of 
origin of these nerves, and no doubt they are 
equally so of all the nerves which are con- 
nected with the medulla oblongata, namely, 
the fifth pair, the eighth, the ninth, and pro- 
bably also of the sixth. : 

The relation of the olivary columns in 
their upward course, to the other constituents 
of the mesocephale and crura cerebri, may 
be conveniently demonstrated in examining 
tranverse sections of those parts. We shall, 
therefore, return to this subject in descri- 
bing the anatomy of those portions of the 
brain. 

The following interpretation of the various 
columns of the medulla oblongata, referred to 
in the preceding description, has much foun- 
dation in their anatomical relations. 

The olivary or central columns constitute the 
fundamental of the medulla oblongata ; 
that, on which its action as a distinct and in- 
dependent centre depends, and in which the 
proper nerves of this segment of the ence- 
phalon are implanted. The continuity of those 
columns with the optic thalami and corpora 

uadrigemina materially enhances their phy- 
siological influence, and denotes their intimate 
association with some of the most important 
functions of the brain. And it may be added, 
that this connection of the medulla oblongata 
with which are ordinarily described as 
pertaining to the brain itself, shews that the 
original application of the term by Willis and 
Vieussens to a much greater extent of the en- 
cephalon is certainly more consistent with the 
physiological anatomy than that which is now 
employed for the convenience of description. 
There can be no doubt that the extent of this 
central and fundamental portion of the nervous 
system is limited above by the optic thalami 
and below by the spinal cord. 

The anterior pyramids connect the cerebral 
hemispheres with the spinal cord, the prin- 


NERVOUS SYSTEM. (Nervous Centres. Tue Encepmaton.) 4 


F 
cipal bundles of fibres decussating each other 
on the middle line, so that the right pyre 
is the medium of connection by the g 
number of its fibres between the right hemi 
sphere of the brain and the left half of the cord, 
but by a much smaller number between that 
same hemisphere and the right half of th 
cord. And so also of the left, mutatis mu= 
tandis. [tis highly probable too that the anteric 
pyramids derive fibres from the locus niger ¢ 
the crus cerebri and the vesicular matter of t 
mesocephale. These fibres, therefore, connec 
those segments with the spinal cord, but whe 
ther they contribute to the formation of th 
decussating or non-decussating bundles, or | 
that of both, it is impossible to determine, 
The restiform es ane evidently the con. 
necting fibres between the hemispheres of the 
cerebellum and the posterior and antero-lateral 
columns of the spinal cord. And the pos- 
terior pyramids connect the beg a? part of 
the medulla oblongata with the cervical and 
dorsal regions of the cord. 
Nerves—Numerous nerves are connectet 
with the medulla oblongata—a fact whie 
serves greatly to enhance its importance as_ 
centre of nervous action. These nerves are thi 
sixth pair, which are connected with the ante- 
rior pyramids just behind the posterior bordel 
of the pons; the ninth pair, or hypogloss 
nerves, which emerge along the anterior borde 
of the olivary body ; the seventh pair (portio 
mollis and portio dura), which emerge just b 
hind the upper extremity of the olivary body 
and the eighth ir, which arise alog te DOS: 
terior margin of the olivary body. ; 
OF THE MESOCEPHALE. — 
and olivary columns may be readily traced, a 
already explained, from the medulla oblongati 
up to the cerebral hemispheres; the form 
becoming united chiefly with the corpora strial 
the latter with the optic thalami. ; 
In that part of their course which is interm 
diate to the medulla oblongata these columns 
become mingled with certain transverse fibre 
and with more or less of vesicular matter, an 
with them contribute to form a mass which i 
the connecting link between all the segments: 
the cerebellum, and may be com to a ra 
road station, at which several lines meet ¢ 
cross each other. This is the mesocephale 
mesencephale. The name was suggested 
Chaussier, inasmuch as it forms “ to a cert: 
extent the middle and central part of the ent 
pate organ, the bond which unites the seve 
undles of fibres which contribute to its f 
mation.” -. 
The mesocephale may be isolated from 
other segments by dividing the crura cere 
just beyond the anterior margin of the pons, a 
the crura cerebelli as they penetrate the 
mispheres, and the medulla oblongata ona: 
with the posterior edge of the pons. ec 
cerebri emerge from it in front: the medu 
oblongata is connected with its poste 
face : on either side it is prolonged into 
cerebelli. Its inferior surface, which 
convex and looks forwards, is composed ¢ 
thick layer of arched fibres which fort 


i 


—) 


e@ pyram dal 


NERVOUS CENTRES. (Human Anatomy. Tur Encrpnaton.) 


pons Varolii ; and on its superior surface, which 
looks backwards, are the corpora quadrigemina, 
the processus cerebelli ad testes, and part of 
the floor of the fourth ventricle (fig. 386). 

According to Chaussier, its weight is equal 
to about the sixtieth or sixty-fifth part of the 
entire brain. 
~ We shall describe separately the inferior and 

the superior surfaces of this segment of the en- 
cephalon, and its intimate structure as unfolded 
by sections. } 
it The inferior surface, (pons Varolii, annular 
_ protuberance, ) convex from side to side, is inter- 
rupted along the median plane from behind for- 
wards by a shallow groove in which the basilar 
artery usually lies, giving off in its course nu- 
merous minute capillaries to the nervous struc- 

ture of the mesocephale. 

___ When the pia mater has been stripped off 
_ this surface, it is seen to be very evidently 
composed of a series of transverse fibres which 
take an arched course. The fibres are collected 
into large fascicles separated from each other 
by very distinct intervals, so that there is no 
_ part where the fibrous structure is more appa- 
rent than here. They form ares of circles, not 
" concentric, lying one behind the other in a se- 
fies nearly parallel. Owing to this want of 
_ complete parallelism the width of this surface 
_ measured from before backwards is much less 
at each extremity than in the centre. The an- 
terior margin is convex, and forms a thick edge 
_ crossing the crura cerebri like a bridge; hence 
the term pons was applied by Varolius to the 
"whole series of fibres. The posterior border is 
concave, less curved than the anterior, and 
crosses the anterior pyramids and olivary co- 
lumns, as the latter does the crura cerebri. The 
‘intervening fascicles of fibres become gradually 
less curved as they approach the posterior 
margin. 

These transverse fibres form a stratum of 
considerable thickness at the inferior surface of 
the mesocephale. Some grey matter is depo- 
sited between the less superficial layers which 
constitute it. The more deep-seated layers are 
penetrated and crossed at right angles by the 
ascending fibres of the anterior pyramids. A 
remarkable interlacement takes place at this 
Situation between the vertical and transverse 
fibres—the latter passing alternately in front of 
and behind adjacent bundles of the former. 
Some of the vertical fibres seem to sink into 
and connect themselves with the grey matter. 

A transverse vertical section of the meso- 
cephale gives a more complete view of the 
exact extent of the transverse fibres. They are 
found to occupy rather more than one-third of 
the depth of the exposed surface. Their dispo- 
sition in lamine is very apparent. Those which 
are nearest the centre of the mesocephale have 
between them considerable intervals, which 
are filled up by grey matter, through which 
pass Rariically the fibres of the pyramids. The 
imtervals between the laminz gradually dimi- 
nish towards the inferior surface of the pons, 
and the quantity of intervening grey matter 

mes proportionally less, and disappears 
altogether from between those lamine the in- 


685 


tervals of which are not traversed by the fibres 
of the pyramids. 

The transverse fibres pass on either side into 
each hemisphere of the cerebellum, contributing 
with the processus cerebelli ad testes and the 
restiform bodies to form the crura cerebelli. 
They are the inferior peduncles of these crura. 

The anatomy of these transverse fibres evi- 
dently denotes that they serve to connect the 
right and left cerebellar hemispheres, as com- 
missures, and in a manner strikingly analogous 
to that in which the fibres of the corpus callosum 
connect the cerebral hemispheres. This view 
of the office of these fibres is strongly confirmed 
by the fact that their number is always in the 
direct ratio of the size of the lateral hemispheres, 
and that when the hemispheres are absent, these 
fibres no longer exist. When, therefore, the 
cerebellum consists only of a median lobe, there 
is no pons Varolii. 

Some of the transverse fibres nearer the in- 
ferior surface appear to dip in along the me- 
dian line, and to pass upwards and backwards, 
forming a vertical plane of fibres which divides 
the mesocephale into two symmetrical portions, 
and Chaussier imagined that a decussation 
took place at this situation. The groove in: 
which the basilar artery lies is formed partly 
by the greater condensation which is produced 
along the median plane by this arrangement, 
and partly by the slight bulging on either side 
of it, caused by the ascent of the anterior py- 
ramids. These fibres are continuous with a 
series of similar ones in the medulla oblongata 
(antero-posterior fibres of Cruveilhier). 

The extent of the superior surface of the me- 
socephale may be limited in front by a line 
which passes from side to side just before the 
anterior of the corpora quadrigemina, and pos- 
teriorly by the base of the valve of Vieussens. 
This occupies a much greater space than the 
inferior surface. It is an inclined plane, and 
passes downwards and backwards, being con- 
cealed by the anterior lamine of the superior 
vermiform process of the cerebellum and the 
posterior border of the corpus callosum. 

The corpora or tubercula quadrigemina are 
four rounded eminences—gangliform bodies— ~ 
disposed in pairs (fig. 386, D, D’). The ante- 
rior pair are larger than the posterior. The for- 
mer have been distinguished. as the nates, the 
latter the ¢estes.* These bodies are situate further 
forwards than the pons, and are chiefly connected 
with the superior surface of each crus cerebri. 

The nates are of a deeper grey colour than 
the testes. In this respect they resemble the 
optic thalami. Both pairs are similar in struc- 
ture to those bodies. When cut into, they ap- 
pear to consist of fibrous matter intermingled 
with vesicular. Thin sections examined with 
the microscope exhibit intricate interlacements 
of tubular fibres with vesicular matter inter- 
posed—a true ganglionic structure. 

An important fact deserves special notice as 
indicating that vesicular matter is found in 

* In reference to these absurd appellations Willis 
has the following remark : ‘ Prominentia orbicularis 
—quarum usus longé nobilior videtur, quam ut 
viliora ista natium et testium nomina mereantur.” 


686 


these bodies in considerable quantity. The 
pia mater which adheres to their surface 
abounds in minute bloodvessels, and in sepa- 
rating it these are seen to penetrate the tuber- 
cles in vast numbers. This layer of pia mater 
contributes to form the velum interpositum. 

The quadrigeminal bodies are the analogues 
of the optic lobes in birds, reptiles, and fishes. 
In these classes there is only a single pair of 
tubercles. They are of considerable size in 
birds, and form a conspicuous portion of their 
encephalon. The division into four takes place 
only in Mammalia. The anterior are the larger 
in herbivorous animals, the posterior in the 
Carnivora. In most quadrupeds these bodies 
are concealed from view by the posterior lobes 
of the brain; but in Rodentia they are exposed 
in consequence of the imperfect developement 
of the brain in the backward direction, 

The quadrigeminal bodies rest upon two 

rocesses of fibrous matter, which extend 

ckwards to the median lobe of the cere- 
bellum, and forwards to the optic thalami. 
These processes form a connection between 
the thalami and the quadrigeminal bodies and 
the cerebellum. They have been variously 
designated processus cerebelli ad testes, proces- 
sus cerebelli ad corpora quadrigemina, processus 
cerebelli ad cerebrum. 

The valve of Vieussens intervenes between 
these processes, and closes the fourth ventricle 
at its upper part. 

A longitudinal groove separates the right and 
left pair of quadrigeminal bodies. The ante- 
rior extremity of this groove forms an expanded 
and somewhat flattened surface on which rests 
the pineal gland (fig. 386, S). From the pos- 
terior extremity a small band extends to the 
valve of Vieussens, called frenum. An inci- 
sion made vertically downwards along the 
course of this groove exposes the canal through 
which the fourth ventricle and the third com- 
municate (iter a tertio ad quartum ventricu- 
lum). This canal communicates with the pos- 
terior part of the third ventricle by an opening 
which is situate beneath the posterior commis- 
sure, and with the superior extremity of the 
fourth ventricle beneath the valve of Vieussens. 

The fourth pair of nerves are seen upon this 
surface, attaching themselves to the processus 
cerebelli ad testes, or to the Vieussenian valve, 
or to the posterior pair of quadrigeminal bodies. 

Besides the anterior pyramids, the olivary 
columns are continued through the mesoce- 

hale to form with the former the crura cerebri. 
ese columns are exposed along the floor of 
the fourth ventricle; higher up, however, they are 
surrounded by a lightish grey matter, form the 
superior stratum of each crus cerebri, separated 
from the quadrigeminal tubercles by the pro- 
cessus cerebelli, and finally merge into the 
optic thalami. Their course is well displayed 
in fig. 380, where f represents the olivary 
columns, ¢ the processus cerebelli ad testes, 
and v the pons penetrated by p, the pyramids. 

The olivary columns retain their greyish hue 
in their upward course. Their cylindrical form 
is very apparent on the floor of the fourth ven- 
tricle; but it is still more obvious on viewing 


NERVOUS SYSTEM. (Nervous Centres. Tar Encernaron.) 


—- — - 


a transverse section, when each olivary column 
appears as a cylinder, to be distinguished — 
from the rest by its roundness and its peculiar 
colour. a 
No other mode of dissection conveys 80 
much knowledge of the anatomy of this part 
as a transverse section, carried from above 
downwards through either pair of quadrige- 
minal bodies, and mune alee rds 
so as to throu e 8. parts 
which Bye nO papi: a ectio 
enumerated from above downwards,—are, 1, 
either pair of quadrigeminal tubercles; ‘ 
between and beneath them, the iter cut across 
3, on either side of this, fibrous matter; 4, 
below this on each side, the section of eac 
olivary column; 5, planes of transverse fibre 
interlacing with longitudinal ones, and gre 
matter between the planes; 6, transverse fibres 
forming the pons Varolii. 


Fig. 388, 


Plan of a transverse vertical section of 


cephale anterior to. the pons, passing through t 
crus cerebri. . 


p, iter a tertioad quartum ventriculum. This is si 
mounted by a pair of the quadrigeminal tubere! 
é i, olivary columns. a 
n, locus niger. . 
a, the inferior plane of fibres diverging up 
which are continuous with the anterior pyrami 


a 


From the preceding description of the t 
socephale it may be concluded that two clas 
of elements enter into its formation. Th 
are intrinsic and extrinsic. The former ¢ 
sists in the masses of vesicular matter, 
which the fibrous matter, whatever be its cot 
is intimately connected. Such are the 
matter of the quadrigeminal bodies; th 
grey matter which surrounds the olivary 
lumns in their upward course; the da 
matter which intervenes between the trans 
fibrous lamelle ; and more in front, that ¥ 
forms the locus niger of the crus a 

The extrinsic elements are those which 
through this segment, being continue 
some portion of a neighbouring segme 
serving to connect the grey matter of th 
socephale with the hemispheres of the 
brum or cerebellum, or with the medu 
longata. The fibres which form the it 
layer of the pons are perhaps the only 
that does not connect itself in some 
the grey matter of the mesocephale, : 
seem simply to across from one crus ce 
belli to the other. The deeper transverse fil 
the pyramids, the olivary columns, the 


ne ie 


_" 


<a 


NERVOUS CENTRES. (Human Anatomy. Tut Encepuatoy.) 


eessus cerebelli ad testes, all connect neigh- 
bouring parts with the intrinsic matter of the 
mesocephale. 

It is plain, then, that anatomy affords abun- 
dant grounds for the conclusion, that the me- 
socephale must be regarded as a distinct centre, 
connected by numerous bonds of union with 
the other segments of the brain. 

If further proof of this were wanting, it 
would be found in the connexion of two im- 
portant nerves with this segment. These are 
the fifth and the fourth pair. The former pene- 
trate between the superficial fibres of the pons 
which spread out upon the crus cerebelli; the 
latter are connected with the superior surface 
of the mesocephale. 

Or THE CEREBELLUM.— (rageyxeParss, 
omscbsos eynearss; Fr. cervelet ; Germ. Kleine 
Gehirn.) This remarkable portion of the ence- 
phalon, so called from its general resemblance 
to the cerebrum, of which it is, as it were, the 
diminutive, is situate behind the mesocephale 
and medulla oblongata. It is lodged in a com- 

rtment of the cranium, the floor of which is 
ormed by the fossz of the occipital bone, and 
which is separated from the cavity occupied by 
the cerebrum, by the horizontal process of the 
dura mater, previously described as the tento- 
rium cerebelli. This process forms a partition 
between the inferior surface of the posterior lobes 


_and the superior surface of the cerebellum. 


The cerebellum, like the cerebrum, is at its 


highest point of developement in the human 
subject. 
__ the encephalon in all the classes of vertebrate 
_ animals, and exlibits a marked gradation of 
increase from Fishes, through Reptiles and 
_ Birds, up to Mammals. 


It exists as a very distinct portion of 


In Fishes and Reptiles it consists of a sin- 

gle lobe, overhanging the posterior surface of 
é medulla oblongata, and closing the fourth 

ventricle partially like a valve. It is, in ge- 
neral in these classes, smooth on its surface, 
and exhibits no complication of structure, no 
Subdivision into lamine. But in the sharks 
@ manifest increase in size and an incipient 
lamellar arrangement are distinctly observable, 
which shew that in them this organ is more 
highly developed than in any other fishes. 

In birds a similar complication of structure 
takes place to a much greater extent, and a 
lateral lobe or appendage is added on each side 
to the single central organ which constitutes 
the cerebellum of fishes and reptiles. And in 
the mammiferous series, the lateral lobes along 
with the central portion experience a progres- 
Sive augmentation of size (proportionally to the 

dy), and a corresponding complexity of 
Structure up to the quadrumana and man. 

The best and most obvious subdivision of 
the human cerebellum is into the median lobe 
and the lateral lobes or hemispheres. The 
former is the fundamental and primitive portion 
of the organ; the latter, although each exceeds 
the median lobe in size, and therefore they con- 
Jointly form far the largest portion of the 
cerebellum, are appendages, which in man 
assume great physiological importance. The 
median lobe has likewise been called vermi- 


687 


form process, the upper and lower lamine 
being distinguished as the superior and inferior 
vermiform processes. 

From the tables already given it would ap- 
pear that the cerebrum is to the cerebellum in 
the proportion of 8 or 9 to 1 in the adult, and 
in the infant, according to Chaussier, as 16 or 
18 to 1. The average weight of the cere- 
bellum is, according to Professor Reid’s re- 
searches, 50z. 4dr. in the male, and 4 oz. 
12 dr. in the female. 

The cerebellum seems to keep pace, in its 
developement, with that of the cerebrum. It 
attains its greatest size, both in male and fe- 
male, at the same age as the cerebrum. 
At the most advanced ages, however, it seems 
to diminish with greater rapidity than that 
organ. 

Some variety appears to occur as regards the 
relative developement of cerebellum to cere- 
brum in the adult. Chaussier remarks that he 
had in some instances found the cerebellum 
equal to a seventh or a sixth part of the weight 
of the cerebrum, but rarely the eleventh or 
twelfth. 

There do not appear to be any good grounds 
for the assertion that the cerebellum is more 
developed in proportion to the brain in the 
female than in the male. Professor Reid’s 
extensive series of researches show, beyond all 
question, that it maintains the same propor- 
tionate bulk in both sexes. 

It has also been asserted that castration, or 
disease of the genital organs, such as would 
destroy the generative instinct, causes wasting 
of the cerebellum. If both testicles be re- 
moved, the whole cerebellum, it is said, dege- 
nerates; if only one, the hemisphere of the 
opposite side is affected. 

The most complete refutation of this assertion 
is afforded by M. Leuret’s series of observations 
of the brains of geldings and entire horses. 
These researches, indeed, shew that in stallions 
the cerebellum is proportionally smaller than in 
mares or geldings, and that in geldings it is 
larger than in mares. It is very evident from 
them that mutilation of the sexual organs does 
not cause degeneration of the cerebellum. 

The shape of the cerebellum is that of “ an 
ellipsoid flattened from above downwards.”* 
Its principal diameter, which is transverse, is 
from three-and-a-half to four inches in length ; 
the antero-posterior diameter is from two in- 
ches to two inches and a half; the anterior part 
is about two inches in thickness; whilst near 
its posterior edge it does not measure above 
half an inch. 

Atitsanterior edge the cerebellum is notched, 
and receives fibres by which it is connected to 
the cerebrum and mesocephale. This notch is 
of considerable transverse extent, and is semi- 
lunar in shape. The greater portion of the 
posterior part of the mesocephale corresponds 
to it. By Reil this is called the semilunar fis- 
sure. In it we find several parts which the 
anatomist should study; namely, on the highest 
plane, the processus cerebelli ad testes, sepa- 


* Cruveilhier. 


688 


‘| 


Jig 
Varia 

Ow Gait he ae 

. MB ce 


SAN 


TAN 


Front view of the cerebellum, with medulla oblongata and mesocephale. ( After Foville. ) 


m,m, medulla oblongata. 


5 n, the flock on the right side, or 3503 of pee ih 360 ° vail +3 
, fifth nerve. On the left side a layer appears to be extended from this nerve whi to 
a 


form the crus cerebelli. 


rated by the valve of Vieussens, and, beneath 
these, the fibres of the restiform columns, and 
the right and left extremities of the pons 
Varolii, all of which combine to form the crus 
cerebelli or central stem of each lateral lobe. 

The posterior margin is interrupted in its 
middle i a vertical notch, which divides it 
into a right and left portion. This notch is 
wider in front than behind, whence Reil called 
it the purse-like fissure. The term posterior 
notch is preferable. It receives the falx cere- 
belli, and at its bottom we observe a continuity 
between the superior and inferior lamine of 
the median lobe of the cerebellum. 

The superior surface of the cerebellum is 
slightly convex, inclined backwards and down- 
wards, It terminates in front by a concave 
margin, which overlaps the parts contained in 
the semilunar fissure. This surface is more 
convex along the middle than on either side. 
In the latter situations it is inclined and nearly 
plane; but in the former it resembles more the 
surface of a cylinder. This middle portion 
corresponds of what is commonly agnée et 
superior vermiform process: it is in fact the 
upper surface of the median lobe of the cere- 
bellum. 

On its inferior surface the subdivision of the 


NERVOUS SYSTEM. (Nervous Cenrres, Tur Encernaton.) 
Fig. 389. 


wy 


rec 


h, h, semilunar fissure. . 


cerebellum into two symmetrical portions i 
very apparent, by reason of the existence of 
deep fissure which proceeds from before ba 
wards along the median line, and is continuow 
behind with the posterior notch. This fisst 
is called the valley (vallecula, Haller; grana 
scissure mediane du cervelet ). It separates t 
hemispheres of the cerebellum, each of whit 
presents a very convex surface, co 
to each occipital fossa. The arachnoid me: 
brane is extended from one to the other, towan 
the posterior part of the fissure, leaving a 
siderable space between it and the pia matt 
which is traversed by some fine bundles 
fibrous tissue and occupied by subs 
fluid. This space has a efer 
to as the posterior conflur of Majendie. 
The anterior part of this fissure receives 
upper and gi portion of the me 
oblongata. e remainder of it is oceup 
by the inferior surface of the median lobe 
the cerebellum, presenting a remarkable 


PSDONG. 


ciform arrangement, which will be p 
described. 
Another very remarkable fissure 


special notice. It is horizontal, and pas: 


into the substance of the cerebellum, divid 


4 


it into an upper and an inferior portion. By 


NERVOUS CENTRES. (Human Anatomy. Tuer Encrpnaton.) 


inserting the handle of a knife along the pos- 
terior margin of the cerebellum, this fissure 
may be shewn to pass forwards to a consider- 
able depth, and to communicate on each side 
with the semilunar fissure, whilst it is inter- 
rupted in the middle posteriorly, by the notch. 
Its inner surface is lined by a process of pia 
mater, which sinks into it. 

The right and left cerebellar hemispheres 
exhibit a general symmetry, which is, however, 
not always perfect, as a manifest ditference is 
sometimes observable in their sizes. And a 
corresponding want of symmetry may be fre- 
_ quently seen in the right and left fosse of the 
occipital bone. 

_ Both the hemispheres and the median lobe 
_ are composed of an assemblage of laminz 
_ closely applied to each other. Each lamina 
_ consists of a thin layer of white or fibrous 
matter, between two of grey or vesicular sub- 
_ Stance, which are continuous along the outer 

Besargin of the former. Thus the exterior of the 
_ cerebellum consists of a stratum of vesicular 
Matter, which forms a cortex to the enclosed 
white or fibrous substance. The lamin are 
_ separated from each other by fissures, and they 
__ are covered by pia mater, which adheres closely 

_ to them, and penetrates to the floors of the fis- 
sures. 

The laminz are collected into sets on the 
_ Superior as well as on the inferior surface. Each 
set forms a lobe. Each lobe is surrounded by 
_adeep fissure, which separates it from the next 
_ adjacent lobes. 

It is necessary to distinguish the fissures 
_ which separate the lamin from those by which 
_ the lobes are bounded. The former are very 
Shallow: the latter are deep, and penetrate 
quite to the central stem of the hemisphere. 
By removing the pia mater carefully from 
the surface of the hemispheres, and from the 
deep fissures, the shape and boundaries of the 

lobes may be clearly demonstrated. Or if a 

_ vertical section of a hemisphere be made, the 
deep fissures may be readily distinguished from 
the superficial ones which separate the laminz ; 
and in this way also the lobes may be demon- 

‘strated 


i 


& 


_ The floor of each deep fissure is formed by 
white matter. And as the deep fissures inter- 
vene hetween the lobes, lamine of the lobes 
constitute their walls, and the superficial fis- 
sures which separate these lamine open into 
m. 
On the superior surface of the cerebellum 
two principal lobes may be distinguished. 
ese are the square lobe and the posterior 
ior lobe, according to the nomenclature 
of Reil, whose descriptions cannot be sur- 


eS) in minuteness or accuracy. ( Fig. 390, 
> . 


The anterior margin of the square lobe over- 
hangs the semilunar fissure ; its posterior mar- 
gin isa little behind the level of the floor of the 
cd notch. By careful separation of its 

mine or by a vertical section, it may be 
Shewn to consist of eight lobules, each having 
a stem of fibrous matter derived from the cen- 
tral one of the hemisphere. 

VOL, III. 


689 


The posterior superior lobe (P, fig. 390,) 
forms the posterior part of the superior surface 
of the cerebellum ; its posterior margin is that 
of the hemisphere ; the horizontal fissure sepa- 
rates it from the posterior inferior lobe. It is 
separated from its fellow of the opposite side by 
the posterior notch. 

On the inferior surface of each hemisphere 
the following lobes are readily distinguishable. 
( Fig. 391.) We enumerate them, passing 
from before backwards. 

1. The amugdala, so called from its resem- 
blance to an enlarged tonsil. This and its 
fellow of the opposite side form the lateral 
boundaries of the anterior extremity of the 
valley, and are in great part covered by the 
medulla oblongata. 

2. Behind the amygdala is the biventral 
lobe, wedge-shaped, narrow towards the valley, 
wide towards the semilunar fissure. Its lamine 
are curved with their concavity forwards and 
inwards, and it is united with its fellow of the 
opposite side by lamine which cross the val- 
ley forming part of the inferior vermiform 

rocess. 

3. The slender lobe, which consists of a few 
lamine curved parallel to the posterior ones of 
the biventral lobe. 

4. The inferior and posterior lobe, which 
extends to the posterior edge of the hemi- 
sphere. The inner margin of each of these 
lobes constitutes the lateral boundaries of the 
posterior notch. 

Such is the constant disposition of the supe- 
rior and inferior surfaces of the cerebellum. 
A defect of symmetry is sometimes apparent 
in the inequality of corresponding lobes; but 
those above enumerated are always present. 
So definite an arrangement must obviously have 
some physiological import. What that may 
be it is impossible even to conjecture, and 
we must be, for the present, content with a 
concise statement of the facts of the anatomy. 
Some analogy exists between this arrangement 
and that of the convolutions on the surface of 
the brain, many of which exhibit a constancy 
of position and form quite as remarkable. 

The median portion of the cerebellum is also 
composed of lamine, which are continuous with 
those of the hemispheres, but their arrangement 
on the superior and inferior surfaces is so diffe- 
rent as to demand a separate description. On 
the superior surface the lamine are separated 
from each other by fissures, in the same way as 
those which constitute the hemispheres, and 
they are collected into sets forming lobes which 
correspond to and connect those of the lateral 
hemispheres. These lamine are curved, their 
anterior margin being very slightly convex 
(fig. 390). The edges of these laminz, as they 
le in close apposition, resemble the segments or 
rings of a worm; whence the term vermiform 
las been applied to this as well as the inferior 
surface of the median lobe. The lamine take 
for the most part a vertical direction, with the 
exception of the anterior and posterior ones, 
which pass gradually to the horizontal, the free 
margins of the former being directed forwards 
and those of the latter backwards. The pos- 

2Y 


690 NERVOUS SYSTEM. (Nervous Centres. Tar Encepnaton.) 
Fig. 390. 


Superior surface of the cerebellum, 
A, the square lobe; P, the posterior superior lobe ; S, superior layer of the crus cerebri ; 
q, tubercula quadrigemina ; /, Jocus niger; é, inferior layer of the crus cerebri. 
terior lamine form the floor of the posterior which the hemispheres are subdivided on the 
notch: the anterior form, by their adhesion inferior surface. 
to each other, the layer known by the name These segments may be very readily 
of valve of Vieussens, which fills up the interval guished from each other, and the names 
between the processus cerebelli ad testes. the accurate Reil has given them are 
The lamine which form the superior surface ciently appropriate. By separating each se 
of the median lobe, (or the superior vermiform ment from the adjacent ones and tracing i 
process,) are considerably fewer than those of lateral relations, the anatomist may form 
the hemispheres. This explains the less depth _ better idea than by any other means of they 
of the median lobe, when measured from before in which this portion of the cerebellum is 
backwards, than of the hemispheres. Two or nected with the hemispheres. . 
more of the lamine of the latter are united to The anterior extremity of the inferior’ 
a single lamina of the former, and thus the form process projects into the cavity of the foi 
superior vermiform process serves as a trans- ventricle, and serves to close it at its inferic 
verse commissure to the superior lamine of the tremity. Itisa pointed process, 
hemispheres. versely, continuous by its base with the res 
The inferior surface of the median lobe, or the vermiform process. Reil has named it 
inferior vermiform process, is likewise com- Nodule. From either side of it a valve 
posed of lamine, which take a transverse di- membrane of exquisite delicacy extends for 
rection and present a free convex border, with and outwards towards a lobule which is 
some resemblance to the rings of a worm in tached to each crus cerebelli near to the or 
action. ( Fig.391.) These laminearenotall of of the auditory nerve. These membranes 
equal transverse extent. The middle and pos- semble very much in shape the semi 
terior are the broadest; the anterior gra- valves of the aorta. By their attached mar 
dvally diminish in size. Hence the body which _ they adhere to the crus cerebelli, and their 
results from the conjunction of all the lamina margin projects into the cavity of the 
has a triangular form, its apex being anterior ventricle. eir inner extremities adhere to 
and its base posterior, corresponding to the nodule, and are connected to each other 
notch between the hemispheres. The lamine thin membrane of precisely similar te) 
which occupy its middle have a greater depth which is a commissure to them. Reil give 
than the rest, and consequently the body is the two membranes and their intermediate ¢ 
more prominent at this situation. necting one the name of posterior medul 
Certain deep fissures divide the inferior ver- velum.* The lateral membranes were first 
miform process into segments which evidently —* The valve of Vieussens is the anterior me 
correspond with and connect the lobes into  Jary velum. or 


NERVOUS CENTRES. (Human Anatomy. Tur ENCEPHALON.) 


seribed by Tarin and Malacarne. When the 
fourth ventricle has been carefully opened in a 
recent cerebellum, it is very easy to demon- 
Strate them by passing the handle of a knife 
under them. 

The structure of these lateral wings of the 
inferior medullary velum is readily ascertained. 
Their delicacy is such that they admit of being 
examined by the microscope without pressure 
or other manipulation. They consist of tubular 
fibres of various sizes, taking a transverse di- 
rection, that, namely, of the long diameter of 
each wing, covered by a layer of nucleus-like 
particles as an epithelium. They seem to con- 
nect the nodule to the small lobules of the 

neumo-gastric nerve above mentioned (the 
Jtocks of Reil), or to connect those lobules them- 
selves as a commissure.* 

The nodule pushes before it, into the fourth 
ventricle, a fold of the pia mater, connected 
_ with which on either side are several small 
granulations, or Pacchionian bodies. It is called 
_ the choroid plexus of the fourth ventricle. We 
_ ¢an easily trace it to be continuous with the pia 
mater which covers the lobules of the seventh 
_ pair of nerves. 

Next to the nodule, below and behind it, is a 
_ small lobe, called by Reil the spigot ( Zapfen ), 
with a pointed extremity directed downwards 
_ and forwards. It consists of several small la- 
mine separated by their fissures. Behind it is 


_ a larger lobule, which forms the most prominent 


Fig. 


691 


portion of the inferior vermiform process, called 
by Reil, from its form, the pyramid. Its apex 
is directed downwards and backwards, and it 
likewise consists of numerous small laminz. 

These lobules of the inferior portion of the 
median lobe serve to connect others of the 
lateral hemispheres. The spigot connects the 
almond-like lobes; the pyramid the biventral 
and the slender lobes. 

Posterior to the pyramid are a series of la- 
mine which extend to the posterior notch and 
form its floor. These pass directly from one 
side to the other, their free margin being con- 
vex and directed backwards. They connect 
the posterior inferior lobes. And some of the 
most anterior of them, which do not project to 
the surface, connect the slender lobes as well 
as some of the anterior lamin of the posterior 
inferior lobes. These latter lamine of the in- 
ferior vermiform process, Reil distinguishes 
by the name of long and hidden commissure 
(langen verdeckten Commissur ), and the former 
constitute his short and exposed commissure 
( Kurzen und sichtbaren Commissur ). 

Above the last-named commissure is a single 
lamina which forms a line of demarcation be- 
tween the inferior and the superior vermiform 
processes, serving to connect the upper and 
posterior lobes of the hemispheres. This is the 
single commissure (einfache quer Commissur ). 

It will serve to elucidate the foregoing neces- 
sarily intricate description, if I sum up with 


391. 


Inferior surface of the cerebellum. 


V, inferior vermiform process ; p, posterior pyramids ; r, restiform bodies. 


the following enumeration of the lobes of the 
hemispheres, specifying at the same time the 
commissures by which they are connected, i. e. 

* Although it does not appear that Reil used the 


microscope, his statement respecting the structure 
of these wings is perfectly correct. 


the lobes of the superior and inferior vermiform 
processes which serve that purpose. _ 
1. On thesuperiorsurface of the hemispheres. 
‘a. The square lobes, consisting of eight 
lobules, which are connected by as many, or 
nearly so, of the superior vermiform process. 
2x2 


692 


b. The upper and posterior lobes, connected 
by the single commissure, to be sought for on 
the floor of the posterior notch. 

2. On the inferior surface of the hemi- 


a. The dale, united by the spigot. 

b. The bisentral lobes. ' ; 

c. The slender lobes. 

The biventral lobes and the anterior lamine 
of the slender lobes are united by the pyramid. 

d. The posterior inferior lobes, connected 
by the short and exposed and the long and 
hidden commissures. 

The flocks or lobules of the pneumogastric 
nerve, (lobule of the auditory nerve, Foville,) 
which are situate altogether anterior to the 
hemispheres and attached to each crus, are 
united by the posterior medullary velum, and 
through it appear to have some connection with 
the most anterior portion of the inferior vermi- 
form process. 

A vertical section of either hemisphere of 
the cerebellum or of its median lobe displays 
its structure, and serves further to demonstrate 
the subdivision into lobes above described. 
When either hemisphere is cut in the vertical 
direction, the surface of the section displays a 
beautiful ramification of fibrous matter, the 
smaller branches of which are enveloped by 
lamine of grey matter. This ap nce has 
such a resemblance to the trunk of a tree with 
its boughs and branches, that it early received 
and has continued to retain the name of arbor 
vite. The trunk of the tree is represented by 
a central nucleus of white matter, from the 
upper and lower surfaces of which branch off, 
some at a right, others at an acute angle, 
several lamin, each of which forms the parent 
stem of a number of other branches. Each of 
the primary branches is the foundation or cen- 
tral stem of a lobule. Laminz of fibrous mat- 
ter are seen branching from both sides of it 
immediately after its separation from the nu- 
cleus. Sometimes the primary branch bifur- 
cates, and each division of it forms the stem 
of what may be called a sub-lobule. The ul- 
timate branchings are covered by a layer of 
grey matter. If we suppose that one of the 
primary branches is composed of a certain 
number of lamine of fibrous matter, the se- 
condary ramifications from it will in a great 
degree correspond. In most instances these 
secondary branches subdivide into two or 
more tertiary ones, which, as well as the branch 
from which they spring, are enclosed in grey 
matter. ( Figs. 380, 386.) 

A vertical section of the median lobe gives 
quite a similar appearance to that of the 
hemispheres. The central nucleus breaks up 
into primary branches, which become the centre 
of = lobules of which it consists. ( Figs. 386, 
393. 

The ramifications of the central nucleus, 
whether of the median lobe or of the hemi- 
spheres, separate from it only in the vertical 
eens or from before backwards; in the latter 

irection, however, to a very slight extent. 
Hence these branches are directed only u 
wards, or downwards, or backwards. The 


NERVOUS SYSTEM. (Nervous Centres. Tus Encepnaton.) 


fibrous matter of the median lobe is continuous, 
without any line of demarcation, with that of 
the hemispheric lobules. By reason of this 
disposition of the fibrous matter, the surface 
which is exposed by a horizontal section — 
through the entire cerebellum, presents a very — 
different appearance from that which results 
from a vertical section. It consists of a y 
of fibrous matter bounded on the sides and 
behind by a narrow cortex of grey matter. 
The white matter consists exclusively ¢ 
fibres, chiefly of the tubular kind and of all 
degrees of size. These, in the more distant 
ramifications, penetrate the vesicular matter of 
their grey cortex, and form some unknown cot x 
nection with its elements. The grey matter 
consists of three layers, readily distinguishab' 
by the naked eye from their difference of ec 


a, 
lour. The external layer is the darkest, a 
consists chiefly of granular and vesicular mat- 
ter. The next or intermediate layer is of a 
light colour, and is composed of a stratum of fine” 
nucleus-like particles. The third layer has the 
greatest thickness, and is immediately in con- 
tact with the fibrous matter; it is intermediate 
in point of colour to the other two, and con- 
sists of numerous vesicles of the caudate kind, 
coreeny with branching and nerve- 
tubes of all sizes. The dark colour of the 
external layer is doubtless owing in a grea 
measure to the great numbers of capillary ves 
sels which enter it; the greater paleness of th 
inner stratum is to be attributed to the inter 
mixture of the white fibres, whilst the ligh 
colour of the middle stratum is intrinsic. Fron 
the usual dependent position of the cerebellum 
in the dead body, it always appears to contail 
more blood than the a 
Corpus dentatum.—If, in making a vert: 
oodincnt either hemisphere of the cerebellan 
the incision be made so as to leave two-thit 
of the hemisphere on its outside, a pecu 
will be observed on the surface of the sect 
which deserves a separate consideration. ‘Tl 
central white nucleus is interrupted by a ver 
remarkable undulating line of vesicular matte 
which is convex towards the posterior mat 
of the hemisphere, but open in front 
the crus cerebelli. 
This constitutes the corpus denta 
rhomboideum of the cerebellum. It p 
remarkable resemblance to the structure of 
same name which is met with in the oli 
body of the medulla oblongata. It is evid 
a capsule of vesicular matter which is ene 
in the inner third of the substance of the ¢ 
white nucleus of the cerebellar hemi 
being nearer its superior than its inferio 
face. The peculiar undulating arrangem 
it doubtless has reference to the accom 
tion of a certain extent of surface in a li 
space. The fibrous matter enclosed by it 
derived from the processus cerebelli and 
the restiform body. 7... 
The central stem of fibrous matter to 
the several lobules, both of the hemisphe 
and the median lobe of the cerebellum, adl 
( crus cerebelli, ) is formed by three bund 
fibres, each situate on a different plane- 1 


NERVOUS CENTRES. (Human Anatomy. Tur Encepnaton.) 


are the peduncles of the crus cerebelli. Through 
them the cerebellum forms a connection with 
other parts of the encephalon. The superior 
layer or peduncle is a bundle of fibres which 
extends to the corpora quadrigemina, and may 
be traced beneath them to the optic thalami. 
These are the processus cerebelli ad testes, but 
from their being obviously a medium of con- 
nection between the cerebellum and the cere- 
brum, they may be better named cerebro-cere- 
bellar commissures. It is worthy of remark, 
that these are the only fibres which appear to 
connect these two segments of the brain. The 
middle layer is continuous with the restiform 
ies, processus cerebelli ad medullam oblon- 
gatam. And the inferior layer is evidently de- 
rived from the transverse fibres of the pons 
Varolii, which thus pass from one hemisphere 
to the other, and constitute a great commissure 
to the cerebellar hemispheres. These fibres, 
_ moreover, connect each hemisphere to the me- 
_ socephale (fig. 380, ¢, r, v). 
_ From this triple constitution of the crus 
 ¢erebelli, it is plain that the cerebellum may 
exert an influence upon, or be affected by the 
optic thalami or quadrigeminal bodies, the 
_ restiform columns, or the mesocephale. 
e Of the fourth ventricle —This is a rhomboi- 
_ dal cavity, situated at the upper and posterior 
_ part of the medulla oblongata, and extending 
_ over i of the superior surface of the meso- 
f cephale. 


Itis limited superiorly by the poste- 

"rior margin of the testes, and inferiorly by the 
Superior blunt extremity of the posterior pyra- 
mids. Its two lateral angles correspond to the 
entrance of the restiform bodies into the crura 

_ cerebelli. In fact, it is formed by the diver- 
_ gence of the restiform columns in their ascent 
to the hemispheres of the cerebellum. The 

_ Median lobe of the cerebellum lies over the 
fourth ventricle, and conceals it from view. 

the anterior lobule of the inferior vermiform 
Process, the nodule, projects into it, and 
closes it below. On either side of this lobule 
@ process of pia mater, with small granulations 
upon it, is found. These processes are the 


_ choroid plexuses of the fourth ventricle. A- 
round these and thence on to the nodule, the 


and 


cavity of the fourth ventricle. 


Vertical section of the median lobe of cerebellum, mesocephale, 
lulla oblongata, to shew the fourth ventricle. 

0, corpus dentatum ; f, posterior surface of medulla oblon- 
gata; p, pons Varolii; a, processus cerebelli ad testes; v, 


693 


proper membrane of the ventricle is reflected, 
and thus its cavity is shut out from any com- 
munication with the subarachnoid cavity. A. 
vertical section in the median plane, or a little 
to one side of it, displays this arrangement 
well. ( Fig. 392.) 

Along the floor of the fourth ventricle we 
find the central or olivary columns of the me- 
dulla oblongata extending upwards to the optic 
thalami. A fissure, continuous with the pos- 
terior median fissure, separates these columns, 
and terminates above in a canal which pene- 
trates the mesocephale, to reach the third ven- 
tricle: iter a tertio ad quartum ventriculum or 
aqueduct of Sylvius. On either side of the 
fissure certain bundles of white fibres, conti- 
nuous with the auditory nerves, join it at right 
angles, crossing over the olivary columns. This 
fissure, with its white fibres on each side, has 
been compared to a pen with its barbs, and 
hence called calamus scriptorius. 

The fourth ventricle, although sometimes 
called the ventricle of the cerebellum, properly 
belongs to the medulla oblongata. Itis present 
in all the vertebrate classes, and in size bears 
a direct proportion to that of the medulla 
itself. 

OF THE HEMISPHERES OF THE BRAIN.— 
A mass of fibrous matter, covered on its ex- 
terior by a convoluted layer of vesicular matter, 
inflected towards the mesial plane above and 
below a pair of gangliform bodies, (optic tha- 
lami and corpora striata, ) which it thus encloses 
in a cavity or ventricle—this, with certain fibres 
connecting its anterior to its posterior parts, 
forms a cerebral hemisphere. The hemispheres 
of opposite sides are applied to one another 
along the mesial plane, leaving the fissure-like 
interval called the third ventricle; and they are 
united by a plane of transverse fibres, the 
greater part of which is placed above that ven- 
tricle, but which bends down anteriorly as well 
as posteriorly, closing the fissure at those 
situations. 

Of the convolutions.—That which first at- 
tracts attention in connection with the cerebral 
hemispheres, as affording the highest phy- - 
siological as well as anatomical interest, is 
their convoluted surface. This can 
only be well displayed by strip- 
ping off the pia mater. The ap- 
pearance which is then presented 
has been variously described by 
different writers. It has always 
seemed to metoresemblethe folded 
surface formed by the mucous mem- 
brane of the stomach when the mus- 
cular coat is very much contracted. 
The ruge of that membrane be- 
come enormously developed by the 
excessive contraction of the mus- 
cular coat: the mucous membrane 
not possessing any contractile power 
is thrown into thin folds to adapt 
it to the diminished capacity of the 
stomach. Its folded state indicates 
a great disproportion between the 
extent of the mucous surface and 
that of the muscular tunic. If both 


694 


surfaces were equal, neither of them would be 
thrown into folds. In examining thesurfacecalled 
centrum ovale, which is exposed by a horizontal 
section through the hemisphere above the level 
of the corpus callosum, we obtain an explanation 
of the formation of the convoluted surface of the 
brain. That plane of fibrous matter is surrounded 
by an undulating margin of vesicular matter, 
the foldings of which give rise to the convoluted 
appearance of the cerebral surface. The fibrous 
matter is adapted to this irregular surface, not 
by any similar folding, but by the prolongation 
of its fibres into the concavities of the folds. 
It is only by means of these Prvlongenons that 
an equality obtains between the surface of grey 
matter and that of fibrous matter which it 
covers. In brains devoid of convolutions, 
the vesicular and fibrous surfaces are applied 
to each other as two layers disposed in con- 
centric circles. There are no irregularities in 
either one or the other. But any increase in 
the extent of the grey surface involves a cor- 
responding complication in that of the fibrous 
matter, which is effected by the prolongation 
of the fibres at certain situations. Were we to 
suppose two brains in which the quantity of 
fibrous matter in the hemispheres was equal, 
the quantity of grey matter in one might be 
increased considerably, and therefore become 
convoluted without involving any other altera- 
tion in the fibrous matter than the elongation 


ig. 393. 


Vertical section of the adult human brain, (After Arnold.) 


NERVOUS SYSTEM. (Nervous Cextazs. Tur Encepnaton.) 


of certain bundles of fibres at particular — 
situations. . ae 
The existence of convolutions on the surface 
of the hemispheres, as contrasted with the ab- 
sence of them, indicates an increase in the de- 
velopement of the dynamic matter. A convo 
luted brain, even although ge malle 
than one with a smooth surface, would yet in- 
dicate a higher degree of mental power, im 
much as it possesses a larger qastag 
vesicular matter relatively to its fibrous matter, 
Cerebral convolutions are wanting in all th 
classes below Mammalia. They are likewis 
absent from the brains of many animals of | 
families Rodentia, Cheiroptera, Insective 
some of the Marsupialia, and Monotrem: 
The brains of these Mammalia resemble ve 
closely, as regards the characters of the cereb 
hemispheres, the brain of Birds. There is n 
a trace of a convolution Op them, and 
only fissure is the imperfectly developed one 
Sylvius. The squirrel, the bat, the mole a: fo 
examples of brains deficient in convolution 
In some genera of the families Insectivora 
Marsupialia, however, we find an approach 
the convoluted cerebral surface in a 
pressions marked on the exterior of each | 
misphere. The fissure of Sylvius is more ¢ 
veloped, and certain depressions, taking for t 
most part a longitudinal course, are seer 
the surface of each hemisphere. The br 


Ven 


Certain | 


The position of the internal convolution with reference to the corpus callosum is well display d 


median lobe of the cerebellum has been cut through, and the fourth ventricle exposed. a, a 
convolution, (d’ourlet, Foville); c, corpus callosum; 0, fornix; n, septum lucidum; f, 


i, anterior commissure, h, hypophysis, or pituitary body; ¢, pons Varolii; II, second pait ms 


nerves; IV, fourth ventricle. 


5 


, 


ee 


: 


ay) 5 oa 


x 


NERVOUS CENTRES. (Human Anatomy. 
Fig. 394. 


Tue Encepuaton.) 


Z 


of the rabbit, the beaver, the guinea-pig, the 
agouti shew these fissures. They are generally 


‘regular in different individuals of the same 
_ genus, and they are symmetrical, i.e., of the 
same length and direction, and occupy the 
‘same place on each hemisphere. 


Leuret remarks, in reference to the dogma 
of Gall and Spurzheim, that the presence and 
number of the convolutions are in direct rela- 


_ tion to the volume of the brain, that such is far 


from being universally the case; and I am 
glad to refer to so excellent an authority in 
confirmation of the view which I have advo- 
cated respecting the true signification of the 
cerebral convolutions. According to this ana- 
tomist, the ferret, which has several well-marked 
convolutions on each hemisphere, has a brain 
no larger than that of the squirrel, which is 


_ entirely devoid of them, and which has not 


even the few fissures which faintly indicate 
their first developement in the brains of the 
rabbit, the beaver, the agouti, &c. And these 
animals last named have the brain actually 


larger than that of the cat, the pole-cat, the 


roussette, ( Pteropus vulgaris, ) the unau, ( Bra- 


. dypus didactylus, ) the sloth, ( Bradypus tridac- 
tylus, 


) and the pangolin, all of which possess 
convolutions. 

All mammiferous animals, excepting those 
mentioned in the preceding paragraphs, have 
convolutions which exhibit more or less of 
complication. This complication has evidently 
no connection with the general organization of 
the animal, inasmuch as we find animals, in 
the same family with those which possess 
numerous convolutions, exhibiting a very slight 
developement of them. The monkeys, the 
dolphin, the elephant, exhibit the most nume- 
rous convolutions of any of the Mammalia 
inferior to man, in whose brain the convoluted 
surface reaches its highest point. 

Each fold on the surface of the brain is 
ordinarily called a convolution, whatever be 
it$ position, size, or direction. It consists of 
a fold of grev matter, enclosing a process of 


Superior surface of the right hemisphere of the adult human brain. 


j 
‘The undulating form of many of the convolutions is very well seen, and the general characters of the 
‘ convoluted surface are displayed. 


white or fibrous matter. On each side of it is 
a sulcus or groove, in which we find the same 
elements, a fold of grey or vesicular matter— 
concave externally, convex internally — the 
fibrous matter adhering to its convex surface. 
As the convolution exhibits no essential diffe- 
rence of structure from the sulcus, it is plain 
that the former portion of the brain’s surface 
cannot differ in physiological office from the 
latter. We describe particular convolutions, 
not because they are to be regarded as 
endowed with special functions distinct from 
the less prominent portions of the cerebral 
surface, the sulci, which are continuous and 
identical in structure with them, but because 
they afford good indications of a particular 
arrangement of the surface of the hemispheres 
by which one brain may be coveniently com- 
pared with another, whether they belong to the 
same or to different groups of animals. 

The folded arrangement of the surface of 
the hemispheres, dependent as it is upon the 
grey matter, is evidently destined to bring the 
central and deep-seated parts of the hemispheres 
into union with a large extent of vesicular 
surface. 

That the disposition of the convolutions, 
like that of all other parts of animal bodies, 
follows a particular law, is well illustrated by 
comparing the brains of different groups of 
animals, in their gradation from the more simple 
to the more compiex. 

M. Leuret very justly makes a distinction 
between those convolutions which are constant, 
and to be found throughout the whole series of 
convoluted brains, occupying the same position, 
and differing only in size and extent of connec- 
tions, and those which are not constant, even 
in the brains of the same group of animals, 
but are dependent on the extent of the primary 
ones, and the connections which they form 
with others near them. According to this idea 
we may classify the convolutions as primary 
and secondary. 

The primary convolutions are all formed after 


696 


one type. Of this, as M. Leuret suggests, the 
brain of the fox may be taken as the basis, 
The fissure of Sylvius is well marked in this 
brain ; it is owned by a prominent convolu- 
tion, which encloses it above, below, and 
behind—tbus forming a curve, the concavity of 
which is directed forwards and downwards. 
Above and behind this we find a second con- 
volution forming a similar curve and parallel to 
the first. It exhibits a slight undulation, and 
is marked by a short fissure—signs of ad- 
st complication. Still further back and 
upwards there is a third convolution, parallel 
and curved similarly to the second ; this bifur- 
cates at one point. Above all, near the 
summit of the hemisphere, a fourth is found 
disposed in the same curved manner, but ex- 
hibiting some sinuosities or undulations at its 
anterior portion. A fifth convolution exists on 
the inferior surface of the anterior lobe and 
rests upon the roof of the orbit. Leuret de- 
signates it the supra-orbitar convolution. The 
sixth convolution is of great extent; the prin- 
7 portion of it is found on the inner surface 
of each hemisphere above the corpus callosum ; 
in front it bends downwards and backwards to 
the fissure of Sylvius, and behind it extends to 
the middle lobe and forms the hippocampus 
major. This convolution exists in a high state 
of developement in the human brain, and has 
attracted very generally the attention of ana- 
tomists. Foville describes it by the name 
convolution d’ourlet. 

Such is the most simple arrangement of the 
convolutions. The complication of this takes 
place by undulations being formed in the con- 
volutions themselves, by a subdivision of them 
at certain situations, by the junction of neigh- 
bouring ones through smaller folds crossing the 
sulci between them, and in the highest classes 
by the addition of totally new convolutions. 

Animals, whose brains have nearly the same 
degree of developement as that of the fox, 
have exactly the same convolutions, differing, 
however, somewhat in point of size. This in- 
crease of size is denoted by undulations formed 
in the course of convolutions throughout more 
or less of their extent. The dog may be taken 
as anexample. M. Leuret states that, in com- 
paring the brains of several dogs together, he 
found with all of them the same convolutions, 
differing only in the extent of undulations and 
the number of depressions, both of which were 
greatest in the largest brains. The brain of a 
large mastiff (chien dogue ), a good watch-dog, 
of such great ferocity that he attacked the person 
who fed him, had all the convolutions very 
Jarge and much undulated, with numerous 
depressions in them. 

A froup of animals, consisting of the cats 
and the hyena, exhibits another stage of in- 
crease in the developement of convolutions. 
The same type prevails as in the fox and dog; 
four external convolutions, one internal, and a 
supra-orbitar, These convolutions, however, 
are united to each other at numerous points by 
means of small folds crossing the sulci. These 
uniting folds form the secondary or supple- 
mentary convolutions. Nearly all the primary 


NERVOUS SYSTEM. (Nervous Centres, Tue Encepwaton.) - 


convolutions have supplementary ones con- 
nected with them. “4 
A group, which includes the sheep and other — 
ruminant animals, exhibits much more com- — 
plication in the cerebral convolutions, but still — 
preserves the same type. The undulations — 
and the supplementary convolutions are more 
numerous. The primary appear less nu- 
merous because less distinct. The anteric 
part of the internal convolution is much in- — 
creased in developement, and the supra-orbitar 
is much more complex. In the fissure ¢ 
Sylvius some small convolutions are found — 
which are the first developement of those which 
9 the human subject constitute the insula of — 
il. 4 
In the brain of the elephant new convolu- 
tions are added. — consist Oe 
ing in a dicular direction ; primitive — 
po eae ca taking a longitudinal — 
course. These latter are divided by the former — 
into an anterior and a posterior set. Others — 
are found above and in front of the fissure of 
Sylvius; three superior convolutions are found, — 
the continuations of which 
situate above the internal convolution. 4 
the convolutions of the elephant are remark=— 
ably undulating and exhibit numerous depres-— 
sions. The brain of the whale is imilar 
to it in this respect, and both resemble that of - 
man. 
Monkeys have not the tortuous or com- 
plicated convolutions which are found in the 
whale and elephant. Yet the developeme 
of the hemispheres at their ior part, the 
general form of the brain, the extent and in= 
clination of the fissure of Sylvius approximate 
the brain of monkeys to of man much 
more nearly than the whale’s or elephant’s, 
which, notwithstanding their complicated con- 
volutions, are generally inferior in organization 
and resemble the brains of other Mammalia. 
The internal convolution in monkeys is simple; 
below and behind it forms the hippocampus, 
from which convolutions are prol — back- 
wards, forming the posterior lobe. upe- 
rior convolutions are met with above the fissure 
of Sylvius, between which is placed a trans. 
verse fissure very constant, called the fissure 
Rolando. The orbitar convolutions are largely) 
developed. a 
In comparing the human brain with that | 
the inferior animals, we notice great exactnes 
of symmetry between the conrolat a 
posite hemispheres in the latter, and the wa 
of it in the former. It cannot, however, b @ 8: 
that the convolutions of opposite hemisph res: 
the human subject are a un 
cal. A careful examination wi he 
same convolutions exist on each side, but app 
pe of differentsizes, and soe correspt 
ing as regards situation. My meaning will 
more readily understood by referring to jf 
381, p. 671, where the same numbers ha 
been affixed to corresponding convolutions 
No. 1 on the right has a certain al re- 
semblance with No. 1 on the left, which we 
be much more perfect but for the fissui 
which marks the convolution of the right he- 


> 
‘ 


iF 
nt ¢ 


sg) = eS nea 


wee ee 


= 


NERVOUS CENTRES. (Human Anatomy. Tur Encepnaton.) 


misphere. Again, Nos. 2, on opposite sides, 
resemble each other so closely that their sym- 
metrical relation cannot be doubted. The like- 
ness, however, is impaired by slight fissures in 
the convolution on the left which do not exist in 
that on the right side. Nos. 3 and 3 evidently 
correspond, but that of the right side is the larger 
and more undulating. And it may here be 
remarked that this great developement of the 
convolution marked 3 on the right side affects 
materially the position, relations, and shape of 
those in its neighbourhood, by throwing them 
backwards or outwards and altering their 
form. Thus the position and shape of con- 
volution 4 seems evidently modified by the 
large posterior undulations of convolution 3. 
In the brain from which the figure was taken, 
the convolutions on the right side are evidently 
larger and more highly developed than those 
of the left. It does not appear that there is 
any constancy with respect to the relative size 
of the convolutions of the right and left side, 
sometimes one side predominating, sometimes 
the other; nor have we any clue to discover 
the cause of the difference between the two 
hemispheres, or the reason of the variation as 
regards predominance of size. 

In the imperfectly developed brains of the 
infant or young child, the convolutions are 
quite symmetrical. They are so likewise in 
idiots, or persons of very inferior intellect, 
and, as has been already stated, in some Negro 
brains. 

The following convolutions of the human 
brain are constant in their position, although 
they differ much in different brains in size 
and developement. 


Fig. 


697 


1. The internal convolution, or that of the 
corpus callosum, called by Foville convolution 
dourlet (processo cristato, Rolando). The 
principal portion of this convolution is above 
and parallel to the corpus callosum : in front it 
curves down parallel to the anterior reflection 
of the corpus callosum, as far as the locus per- 
foratus, connecting itself with some of the ante- 
rior conyvolutions. Behind it passes in a similar 
manner round the posterior reflexion, connecting 
itself with some of the posterior convolutions, 
and in the middle lobe forming the hippocam- 
pus major, the anterior extremity of which is 
situate immediately behind the fissure of Sylvius 
and locus perforatus. Its horizontal portion 
appears to be connected with some nearly ver- 
tical ones, which seem indeed to branch off 
from it. (Fig. 395, O.) 

This is the most constant and regular con- 
volution of the brain. It exhibits with its fel- 
low of the opposite side very exact symmetry. 
Its inferior or concave border is smooth and 
uninterrupted, and forms the superior boun- 
dary of a sulcus, which intervenes between it 
and the surface of the corpus callosum. It 
forms, to use Foville’s expression, a hem or 
selvage to the cortical layer of the cerebral 
hemisphere. The fibrous matter which is in- 
closed by the cortical layer of this convolu- 
tion consists of longitudinal fibres following 
the same general direction, a large number of 
them no doubt bending inwards into the cor- © 
tical layer. These fibres are evidently com- 
missural in their office, and will be referred to 
by-and-bye as constituting the superior longi- 
tudinal commissure. 

The free margin of this convolution varies in 


395. 


Internal surface of the left hemisphere of the brain, shewing the connections of the internal convolution and the 
band of longitudinal fibres by which it is formed (d’ourlet), 


C, C, co 
, fornix 3 c, su 


by the locus niger. 


rpus callosum; O, O, O, internal convolution ; 6, septum lucidum; a, anterior commissure ; 
perior layer of the crus cerebri; d, inferior layer of the same separated from the former 


The fibres of the internal convolution are seen in the middle lobe extending tothe hippocampus major. 


698 


its characters in different brains, according to 
the of tortuosity it exhibits, and the 
number of small fissures which are met with in 
it. The small folds which connect it with other 
conyolutions on the inner surface of the hemi- 
sphere vary in number, and are generally found 
most numerous at its posterior me of 
these folds are not distinctly visible unless the 
sulcus above it has been freely opened, as they 
are situated quite on its floor. 

2. The convolution of the Sylvian fissure — 
This convolution forms the immediate boun- 
dary of this great fissure. We have seen its 
early developement in the simple brain of the 
fox, and we may observe it gradually rising in 
complexity through all the intermediate stages 
up to the most highly developed brains. In 
the elephant it is remarkably tortuous, and is 
connected anteriorly as well as posteriorly with 
convolutions which pass to the anterior and su- 

rior and to the posterior part of the brain.* 

nh man it is also very tortuous, and the nume- 
rous folds which pass from it forwards or back- 
wards, forming primary or secondary convolu- 
tions, render it Fificult to isolate it sufficiently 
for the anatomist to follow it throughout its entire 
course. Its inner border is likewise interrupted 
by the connections which it forms with the con- 
volutions of the floor of the Sylvian fissure. 

3. Within the fissure of Sylvius we find that 
remarkable group of convolutions called by Reil 
insula, the island. It consists of a series of 
small folds radiating from a common centre and 
connected with the convolution last described 
by still smaller folds, which cannot be seen 
unless when the fissure has been very freely laid 
open. The centre from which the convolutions 
radiate is the apex of a cone, the base of which 
adheres to the floor of the fissure. 

4. On the inferior surface of the anterior 
lobe there is a pair of longitudinal convolutions 
which enclose between them the fissure of the 
olfactory process. The external of these con- 
volutions is continuous with the convolution of 
the Sylvian fissure. 

The numerous secondary convolutions which 
are found over the surfaces of the brain render 
it difficult to distinguish the primary ones. 
These latter are indicated hy the antero-poste- 
rior course which they take—the former being 
more or less vertical. The largest and most 
tortuous convolutions are found on that part of 
the external surface which corresponds to the 
parietal bone. Next to them, in point of size, 
‘ are the convolutions of the anterior lobe, but 
the smallest of all are those of the posterior 
lobes. 

The hippocampi, major and minor, are 
constant convolutions, which project into the 
lateral ventricles, the latter into its posterior, 
the former into its descending horn. 

In general the constituent fibres of the white 
matter of the convolutions converge from the 
inner surface of the cortical layer to the cen- 
trum ovale, or if followed from the centrum 
ovale, they radiate to the grey surface, whether 


* See Leuret, pl. xiv. representing the external 
surface of the elephant’s brain. 


NERVOUS SYSTEM. (Nervous Cenrres. Tur Encepnaron.) : 


of a convolution or of a suleus. A remarkabl 
exception is in the case of the internal cony 
glade fibrous prac Rea g constitutes, 
as has been already explai a itudin 
commissure. The thickness ‘of a cortica 
layer is pretty uniform, at least relatively te 
the size of the folds themselves. Throughou 
its entire thickness it is mixed with fibres, whie 
are most numerous at its adherent sur 
but extremely few and scattered at its fix 


surface. _p 

In hydrocephalus the convolutions disap 
pear. The fibrous matter becomes e 
panded by the fluid accumulated in the vei 
tricles, and when its expansion has gone so 

as to equal the grey surface, the folded cha= 
racter of the latter disappears. This take 
place precisely in the same way that the rug 
of the contracted stomach (as before referred te 
become obliterated when muscular coat rm 
laxes and allows the full distension of the org a 

Mayo supposes that other fibres are found 
the convolutions besides those which are ce 
nued into the centrum ovale. These are con 
missural ones, which pass from convolution | 
convolution—either between adjacent or dis 
tant ones—forming arches the convexities 
which are directed to the centrum ovale. — 
have never succeeded in satisfying myself ¢ 
the existence of such fibres either in the fin 
brain or in that preserved in spirit. If the 
exist, it is evident that they must be commi: 
sural between particular convolutions. T 
same anatomist supposes that similar com 
sural fibres connect the lamine of the 
bellum. 

The principal bulk of the hemispheres 
formed by fibrous substance. This is shor 
by the horizontal section which displays 
centrum ovale. These fibres radiate from th 
surfaces of the optic thalami and corpora striz 
which are in contact with the substance of t 
hemisphere. Most of the fibres which emer 
from these gangliform bodies to the gi 
matter of the convolutions, me, howeve 
turn inwards towards the mesial 
form the corpus callosum by their union ¥ 
those of the opposite side. , 

It cannot be supposed that all the rema 
fibres, after subtracting those which forr 
corpus callosum, through halami ; 
corpora striata. The dispenoaian of num 
between the fibres of the medulla oblong 
and these is too striking to allow such an 
pothesis, They mingle with the vesicular 
ter of both; some do not pase beyonaa 
others are continued into the ulla © 
gata, either to its olivary or its pyramid 
ne 

orpora striata and optic thalami.— 
corpora striata and optic thalashi beara s 
resemblance in general character and stru 
to ganglia. They are ovoid masses place 
tween the fibrous substance of the hemisp 
on the one hand, and the medulla oblongati 
the other. These bodies, which are best 
played by laying open the lateral ventr 
(p- 675), are very closely united to each 
The corpus striatum is placed a little in fi 


ie 


i 


Saye 


| 


+ 


NERVOUS CENTRES. (Human Anatomy. Tue Encepuaton.) 


ard to the outside of the thalamus. It is pear- 
shaped : its thick end is directed forwards and 
inwards, and it gradually tapers backwards 
into a caudate process of considerable length, 
which winds downwards, forwards, and inwards 
into the descending cornu of the lateral ventricle, 
at the anterior extremity of which it terminates. 
Placed on the outside of the thalamus, it seems 
to embrace it there, and to adhere very inti- 
mately to it. The tenia semicircularis lies in 
@ groove between the two bodies, and as it 
were constricts their connecting fibres. 

he corpus striatum is of a dark grey colour. 
A considerable portion of it projects free into 
the cavity of the ventricle, forming an extensive 
convex surface there. The rest is firmly im- 
bedded in the fibrous substance of the hemi- 
sphere, and in position corresponds to the base 
of the insula, which for that reason has been 
called the lobule of the corpus striatum. The 
free surface as contributing to form the ventri- 
cular wall is covered by the lining membrane 
of the ventricle and a layer of nucleus-like 
particles; it is traversed by several veins. This 
surface is limited on the outside by the plane 
of fibres, which, after emerging from it, incline 
inwards and contribute to form the corpus cal- 


 losum. On the inside it is limited by the tenia 


semicircularis, which separates it from the optic 
thalamus. That portion of the free surface 
which is seen in the inferior horn of the ven- 
tricle has, as already stated, the appearance of 
a caudiform prolongation of the upper portion ; 
this probably arises from the diminution of the 
body in thickness at its inferior part, the portion 
which belongs to the inferior cornu forming the 
apex of a cone, of which the upper convex 
portion forms the curvilinear base. 

When sections are made through the corpus 


_ Striatum, it is found to be traversed by very 


humerous bundles of fibres. It is necessary 
that these sections should be directed obliquely 


_ from below upwards in a direction parallel to 


the inferior layer of the crus cerebri. The 
bundles are thicker and more closely approxi- 
mated to each other inferiorly; but as they 


ascend, they diverge, and radiate, some for-’ 


wards, others outwards, and others backwards ; 
some pass nearly vertically upwards. A section 
made ee in the horizontal direction cuts all 
these fibres more or less transversely, so that 
the cut surface presents a grey colour inter- 
Spersed with white spots of variable size, ac- 
cording as the bundles have been cut trans- 
versely or obliquely; but when the section is 
made in the oblique direction, as above di- 
tected, then the surface presents a striated ap- 
pearance like numerous and regular white 
veins in a dark marble, the bundles of fibres 
being cut lengthways. 

In tracing the bundles of fibres through the 
corpus striatum, we find that they divide and 
subdivide and occasionally anastomose. Each 
subdivision becomes clothed as it were with 
grey matter, which fills up the space between 
it and the adjacent ones. The grey matter en- 
sheathes these bundles of fibres, as the areolar 

_ tissue does the fascicles of coarse muscles, and 


699 


it may be dissected away from them, as we 
remove the areolar tissue from the muscular 
bundles. 

It is an important problem to determine the 
exact source of these fibres and their precise 
destination. There can be no doubt that many 
of them are continuous with the inferior plane 
of the crus cerebri. Of those, the major part 
are usually supposed to pass through to the 
white substance of the hemisphere, and some 
no doubt proceed no farther than the corpus 
striatum. The other fibres which are found in 
this body may be viewed as taking their point 
of departure from its vesicular matter, and 
radiating, some outwards into the centrum 
ovale, others backwards to the optic thalamus, 
forming a bond of connection with that body. 
It must be borne in mind that, as the corpus 
striatum is a body of considerable thickness, 
these fibres which emerge from it must pro- 
ceed in very different planes and with varying 
degrees of obliquity. Other fibres are found 
in the corpora striata, which however do not 
contribute to its striation. These are the fibres 
of the anterior commissure. 

From a comparison of the small amount of 
fibrous matter in the inferior plane of the crus 
cerebri with the immense mass which forms 
the white substance of the hemispheres, (even 
if we exclude those fibres which form com- 
missures,) it is impossible to suppose that the 
latter is derived from the former only; nor, 
indeed, can it be admitted that even the greater 
part of the fibrous matter of the hemispheres 
is continuous with that of the crura, whether 
on their superior or inferior plane. A con- 
siderable portion of them doubtless, when traced 
from the hemispheres downwards, will be 
found not to pass below the corpora striata 
or optic thalamus. 

We may regard the corpus striatum as a 
mass of grey matter with fibres implanted 
in it which connect it with the other parts 
of the encephalon. These parts are, ist, the 
hemispheres; 2d, the optic thalami; 3d, the 
crura cerebri, mesocephale, and medulla ob- 
longata. Of these last fibres it is probable, 
(but I am disposed to think far from certain,) 
that some of those which form the inferior 
layer of the crus pass through the corpora 
striata, and diverge among the other fibres of 
the centrum ovale. 

Thus the corpora striata are connected to the 
optic thalami by fibres which pass from their 
concave or inner border to those bodies; to the 
convolutions of the brain by fibres continuous 
with some of those which form the white sub- 
stance of the hemisphere, and we have seen 
that the convolutions of the insula have a very 
close relation to them; to the mesocephale and 
medulla oblongata by the fibres which form the 
inferior layer of the crus; and to each other by 
those which, emerging from them, contribute 
to form the corpus callosum, and also by the 
anterior commissure. 

The vesicular matter of the corpora striata 
does not differ from that of the convolutions, 
It is traversed by a multitude of fibres. These, 


700 


however, do not form any intricate interlace- 
ment as in ganglia, but are collected into bun- 
dies of very variable size; the largest being 
placed at the inferior part of the body, the 
smallest towards the hemispheres. The free 
or ventricular portion of the corpus striatum 
contains comparatively few fibres. When a 
portion of the striated part of the body is 
examined under the microscope, the nerve- 
fibres, of which the bundles are composed, ap- 
pear to be reduced to their smallest size, and 
to be very compactly applied to each other, 
so that they transmit very little light, and 
therefore put on the appearance of dark cylin- 
ders. It is only by very high powers that we 
can discover their fibrous structure. In many 
of the bundles the fibres appear to terminate 
at one extremity as if by forming an adhesion 
around a large vesicle, faint indications of the 
nucleus and nucleolus of which may be some- 
times seen through the surrounding fibres. The 
appearance which the fibrous cylinders which 
exhibit this structure present calls to mind 
very strongly the representation of the nucleus 
of a comet with its tail. And this peculiarity 
of structure may be adduced as an argument 
that many if not the greater number of the 
fibres of the striated body form intimate connec- 
tions with the elements of its vesicular matter. 
Optic thalami.—In the internal concave sur- 
face of each corpus striatum, the optic thala- 
mus is placed. The latter body is therefore 
sewed and internal to the former. The 
ighter colour of the optic thalamus distin- 
guishes it at once from the corpus striatum. 
The optic thalami come into close relation to 
each other by their inner surfaces, which form 
the lateral boundaries of the third ventricle. 
Each optic thalamus, like the corpus stria- 
tum, presents a free and an attached portion. 
The Poeiton projects into the ventricle—the 
intra-ventricular portion ; the latter adheres to 
the inner side of the corpus striatum and to 
the mass of the hemisphere, and posteriorly, to 
the olivary columns, the quadrigeminal tuber- 
cles, and the processus cerebelli. The supe- 
rior surface is free and forms part of the floor 
of the lateral ventricle; the internal surface is 
likewise free-and forms the lateral wall of the 
third ventricle, being, however, interrupted in 
a very small space by the adhesicn of the soft 
commissure. A portion of its external and 
posterior surface is also free, and projects back- 
wards and outwards into the inferior horn of 
the lateral ventricle, presenting a pointed ex- 
tremity in that situation. These free surfaces 
are smooth and moist, being covered by the 
membrane of the ventricles. The velum in- 


terpositum, which again is overlapped by the 
fornix, rests upon i superior surface of the 
optic thalamus. 


The optic thalami are placed obliquely, so 
that they are nearer each other at their anterior 
than at their posterior extremities. Each mea- 
sures about an inch and a half in length, nine 
to ten lines in height, and about eight lines in 
breadth. In colour they are very much lighter 
than the striated bodies, and they appear to be 


NERVOUS SYSTEM. (Nervous Centres. Tae Encepnaton.) 


covered with a delicate layer of fibrous matter. — 
A band of fibrous matter passes along the inner 
surface of each from behind 
posteriorly is connected to the pineal gla 
and forms, with its fellow, the peduncles of 
that body. = 

Beneath the posterior free extremity of the 
thalamus, situated in the angle between that 
body and the superior surface of the crus, wi 
find a small rounded eminence of a dark; 
grey colour Paes n= by very numerous fora- 
mina for the transmission of bloodvesse 
This is the corpus geniculatum internum, 
Lower down and more external and anterior, 
there is another similar body, somewhat smalle 
and less dark, the corpus geni ernum. 
Both of these bodies are connected with the 
quadrigeminal tubercles. A band of fibrous 
matter passes from the testes to the external 
geniculate body, and from the nates to the in- 
ternal one. si 

In point of structure the thalamus resemble: 
a ganglion much more closely than does the 
corpus striatum. A light reddish is the 
colour of the surface when cut into ; it be 
not inappropriately compared to that of coffe 
mixed with . good deal of milk (café au lait) 
When thin sections are examined, are founc 
to consist of very numerous fibres interlacin 
freely, with nerve vesicles occupying their in- 
tervals. The fibres are not coll into bun 
dles as in the corpus striatum, nor do they take 
a radiating course in the thalamus, The reti 
wiped oath form is very like that i 

e ganglia on the posterior spinal roots. 

The fibres of the optic thalami, i I 
they are very numerous, have extensive. con 
nections. Along its ventricular surface the 
are evidently continuous with those of the he 
misphere, which appears to radiate from it 
the grey matter of the convolutions. Posterior 
the fibres of the processus cerebelli ad te 
and those of the olivary columns pass into 
The anterior pillars of the fornix are connecte 
with it in front, and derive from it some nervoi 
fibres ; and below and within, a cylinder | 
fibres emerge from it to the mamillary bodie 
Thus the optic thalami are connected with 
hemispheres on one hand, with the olivary ¢ 
lumns and with the cerebellum on the ¢ 
hand. The quadrigeminal tubercles pla 
upon the processus cerebelli may have so 
connection with them through the bun 
of fibres. Although these bodies have b 
viewed as having a special connection with 
optic nerves, it does not appear that | 
nerves have any relation to them but thi 
the geniculate bodies or the quadrigem 
tubercles. It is important to bear in m 
respecting the optic thalami that they are 
rectly continuous with the superior portio 
the crus cerebri, so that in viewing a ver 
section of the encephalon we see no Ii 
demarcation between. The thalamus gi 
as it were, from the superior extremity of th 
crus; it is recognised from the latter by 7 
swelling into an ovoidal mass. It is ¢ 
tically, as Willis long ago expressed it, 


‘ 


+ 


—— re ,—“‘ ee 


the substance of the thalamus. 
glionic structure of the mamillary bodies is 
_ unfavourable to this view, and renders it more 
_ probable that they are independent structures, 
_ exercising proper functions as nervous centres ; 


NERVOUS CENTRES. (Human Anatomy. Tuer EncepHaton.) 


epiphysis upon the crus cerebri; and in this 
sense it may be classed with the striated bodies 
and the quadrigeminal tubercles, which, with 
the thalami, form a series of gangliform masses, 
pen in pairs, one beyond the other. 

e geniculate bodies, although intimately 
connected with the optic thalami, appear to be 
distinct from them, But very similar in struc- 
ture. A section made into the thalamus through 
either of them shows a distinct line of demar- 
cation between them. ‘The optic tracts adhere 
to the lower surface of each thalamus by their 
inner margins, and when followed backwards 
are found to form a very evident connection 
with both the geniculate bodies. 

Corpora mamillaria.—These bodies may be 
conveniently noticed here, as forming part of 
the series of gangliform masses in connection 
with the brain. They are of a spherical shape, 
covered on the exterior by very pure white 
matter, which is apparently derived from the 
anterior pillars of the fornix. When cut into, 
they are found to consist of a mixture of vesi- 
cular and fibrous matter, surrounded by a thin 
cortex of the latter. Microscopic examination 
proves this structure of the interior substance 
to be of the same nature as that of ganglia, 
and to resemble the optic thalamus. 

The fibrous matter is connected, at the upper 
part of each body with the anterior pillar of 
the fornix, and on the outside with a fascicu- 
lus of fibres from the optic thalamus. It has 
been supposed that these two bundles are con- 
tinuous, and that the mamillary body results 
from a twisting of the anterior pillar of the 
fornix as it changes its direction to pass into 
But the gan- 


and the constancy of these bodies in, at least, 


_ the mammiferous series, increases this proba- 


bility. 

Of the commissures of the brain.—A large 
number of fibres connected with the hemi- 
spheres or the two gangliform bodies just de- 
scribed, seem to serve the purpose of connect- 
ing different parts, either on the same side of 
the mesial plane, or on opposite sides of it. 
Those on the same side constitute the longitu- 
dinal commissures ; those on opposite sides the 
transverse. 

Of the longitudinal commissures.—These are 
four in number. They all evidently belong to 
the same system of fibres, separated from each 
other lg developement of intermediate 
parts. at which is on the highest plane is 
the superior longitudinal commissure, which is 
the fibrous matter of the internal convolution. 
Internal and a little inferior to this is a se- 
cond, very small, band of fibres, longitudinal 
tract, (Vicq. d’Azyr,) which passes from be- 
fore backwards along the middle of the corpus 
callosum, parallel to the superior longitudinal 
commissure, from which it is separated only 
by the grey matter of the convolution. Both 
these commissures are separated by the corpus 


701 


callosum from a third, which takes a parallel 
course to them, namely, the fornix, which 
occupies a plane considerably inferior to both. 
External to this and separated from it by the 
ventricular projection of the optic thalamus, 
we find a fourth band, which passes parallel to 
the fornix: this is the tenia semicircularis. 

As these parts have been already described, 
it will be unnecessary to do much more at pre- 
sent than indicate the connections which they 
serve to maintain. 

1. The superior longitudinal commissure con- 
nects the convolutions of the inferior surface 
of the anterior lobe with the hippocampus 
major; and as its fibres pass above the corpus 
callosum they form connections with some of 
the other convolutions on the internal surface 
of the hemisphere (fig. 395). 

2. The longitudinal tracts of the corpus cal- 
losum may be traced from about the same region 
of the inferior surface of the anterior lobe as 
the preceding commissure, near the perforated 
space, and they pass backwards, winding over 
the posterior reflection of the corpus callosum 
to its inferior surface. 

3. The fornix* is, next to the corpus callo- 
sum, the most extensive of the cerebral commis- 
sures. That it consists of longitudinal fibres 
cannot be doubted. Although commonly de- 
scribed as a single structure united at the body 
of the fornix, and spreading backwards and 
forwards by its crura, it nevertheless isdistinetly 
divisible along the middle line into two per- 
fectly symmetrical portions. The adhesion of 
the transverse fibres of the corpus callosum on 
its upper surface, and of the terminal fibres of 
its posterior reflection on its inferior surface 
which form the lyra, is the principal bond of 
union of these two lateral halves of the fornix. 

The separation of its anterior pillars in 
front affords strong indication of its double 
form. These pillars pass downwards in a 
curved course, through the grey matter of 
the tuber cinereum, to the mamillary bodies, 
which are connected to the optic thalami by a 
bundle of fibres which may be easily traced 
into them. ‘This bundle is described by Reil 
as the root of the anterior pillar of the fornix. 
From the gangliform structure of the corpus 
mamillare, I prefer to regard this band asa 
medium of connection with the optic thalamus, 
and to trace the anterior pillars to the ma- 
millary body. 

The parts with which the fornix is connected 
in front are the optic thalami, the mamillary bo- 
dies, and the septum lucidum, which consists of 
fibres having the same physiological import as 
those of the corpus callosum, altered however in 
direction by the backward position of the anterior 
pillars, which adhere to the body of the fornix. 
The tuber cinereum and the grey matter which 
adheres to the lower half of the inner surface of 
each optic thalamus, are connected~with it ; 


* This commissure is called votite a trois piliers by 
the French, Trigone cérébrale, Chaussier: arise, 
cope Varsoerdes of the Greeks. Mr. Solly has given 
an excellent delineation of the fornix in his work 
on the brain, pl. ix. 


702 


and as its anterior pillars pass upwards in this 
situation, they receive fibres from the neigh- 
bouring convolutions. These pillars remain 
separate from the mamillary bodies to the fo- 
ramen of Monro, where they adhere to each 
other and form the apex of the body of the 
fornix. Traced backwards, the fibres of the 
fornix pass into the posterior and inferior horns 
of the lateral ventricle. In the former they 
connect themselves with the hippocampus 
minor by expanding over it, and in the latter 
they spread over the hippocampus major, 
forming the posterior pillar of the fornix, or 
tenia hippocampi. 

The relation of the anterior pillars of the 
fornix to the foramen commune anterius has 
been already sufficiently described. Superiorly 
the fornix adheres to the corpus callosum or to 
the septum lucidum, and the anterior commis- 
sure crosses in front of its anterior pillars, and 
almost touches them. 

4. The fourth longitudinal commissure is the 
tenia semicircularis. It may be traced from 
the corpus mamillare outwards and back- 
wards in the groove between the optic thala- 
mus and corpus striatum into the inferior 
horn of the lateral ventricle, when its fibres 
mingle with those of the middle lobe. It is 
evidently part of the same system of fibres with 
the fornix. 

Take away the corpus callosum, the grey 
matter of the internal convolution, the-veutri- 
cular prominence of the optic thalamus, and all 
these commissures fall together and become 
united as one and the same series of longitu- 
dinal fibres. 

It is very remarkable how few fibres pass 
between the great mass of the cerebrum and 
the cerebellum. The processus cerebelli ad 
testes are the only fibres which can be regarded 
as forming commissures between these two seg- 
ments of the encephalon, and they are of the 
nature of longitudinal commissures. 

The transverse commissures are the corpus 
callosum, the anterior commissure, the posterior 
commissure, the soft commissure. 

1. The corpus callosum, so called according 
to some from the density of its tissue, is the 

reat commissure of the lateral halves of the 

rain proper—commissura cerebri maxima of 
Soemmering. The fasciculated character of 
this structure is as obvious as that of any nerve 
in the body, and the direction of the fibres is 
clearly from one hemisphere to the other, 

From the description already given of the 
corpus callosum, it is evident that its fibres 
sink into the white substance of each hemisphere 
above the level of the corpora striata, as well 
as into that of the anterior and of the posterior 
lobes. By its principal or horizontal portion 
it connects the white matter of the lesser cen- 
trum ovale ofeach side, and by the fibres which 
form the anterior and erior reflexions it 
connects the anterior and posterior lobes. It 
needs only a very superficial dissection to ascer- 
tain thus much. 

To determine the precise fibres with which 
those of the corpus callosum are continuous, 


NERVOUS SYSTEM. (Nervous Centres. Tue Excepuatoy.) 


and the relation which bear to the lateral 
ventricles, demands a much more minute dis- 
section. This must be done, according to the — 
directions of Foville, who has’ given a most 
elaborate description of this commissure, by 
carefully separating it in the transverse direc. 
tion from the internal convolution, on a har 
dened brain. Pursuing the dissection in this 
direction, it may be detached from the sub- 
stance of the hemispheres as far outwards a 
the external border of the co callosum an 
optic thalamus. Along this edge the fibre 
curve downwards and inwards, and appear} 
become continuous with some of those whic 
radiate from those bodies. The anterior 
posterior fibres enclose the anterior and pos- 
terior horns of the lateral ventricles in rat 
ating forwards and backwards from the corpor 
striata and optic thalami to those parts of thes 
cavities, phe 
This view of the connections of the corpu 
callosum would indicate it to be a commissu 
between the thalami and Striata, 
between the crura cerebri, as Tiedemann su: 
osed, rather than between the hemispher 
othing is more difficult than the dissecti 
of the fibres of the corpus callosum bey: 
the internal convolution: and it cannot | 
regarded as in any d certain that the cot 
nections of its fibres are limited to those’ 
described. 
The developement of the corpus calle 
in the fetus, se to that of the hemisp 
or convolutious, is favourable to the 
its connections maintained by Tiedemann 
Foville. Comparative anatomy is, howe 
more in accordance with the opinions 
Gall and Reil, that it is a commissure 
tween the convolutions of opposite sides. 
exists only in those animals in which con 
lutions are amply developed. In Fish, Rept 
and Birds it is absent, and the Mammalia 
least perfect brains, as the Rodents and I 
supialia. ‘% 
1e corpus callosum is a stratum of 
siderable thickness. Its fibres are situ 
different planes, which interlace 
other so much as to render it impossibl 
separate any layer for any distance, an 
difficulty is much increased as the fibr 
nearer the white mass of the hemisphere 
2. The anterior commissure may be re 
as truly a bond of connection betwe 
hemispheres, as well as between the ¢ 
striata. It is a cylindrical cord of 1 
matter, very definite in its course am 
nections, and easily traced throughout its 
extent. Its situation in front of the an 
~~ of the fornix has been already de 
f followed on either side from this « 
portion, it may be traced through th 
matter of the anterior and inferior por 
each corpus striatum into the fibrous 
of each middle lobe of the brain. Its 
is curved witli convexity directed fore 
As it passes outwards on each side it beet 
flattened, and after it has traversed each e¢ 
Striatum, it expands considerably and its 


fu 
: 


el 


NERVOUS CENTRES. (Human Anatomy. Tus Encepnatoy.) 


radiate extensively. It may be stated to con- 
nect the convolutions of the middle lobes and 
the corpora striata. 

3. The posterior commissure is a band of 
fibres, extended between the posterior extre- 
mities of the optic thalami, upon which rests 
the base of the pineal body. Those fibres, 
which immediately support that body, have 
been distinguished as the pineal commissure ; 
but as they are evidently part of the same 
system as those which constitute the posterior 
commissure, there seems no good reason for 
separating them. 

4. The soft commissure is also extended be- 
tween the thalami. It is composed of vesi- 
cular matter with fibres, which pass from 
one side to the other. The intermixture 
of its fibres with vesicular matter distin- 
guishes it from the other transverse commis- 
sures already described. A layer of a simi- 
lar nature connects the locus niger of each 
crus cerebri, and fills up the space between 
the crura—interpeduncular space. This has 


_ been already described as the pons Turini, 
posterior perforated space. 


It consists of 
fibrous matter intermixed with vesicular, ex- 
tended between the crura cerebri. It seems 
analogous to the soft commissure, and there- 
fore entitled to be regarded as a commissure. 
Of the manner in which the commissures 
connect the various parts between which they 


are placed, it is difficult to form an exact 


opinion. It is most probable that they form 
an intimate union with the grey matter of the 
Segments which they serve to connect. It 
might also be conjectured that they are conti- 
‘nuous with some of the fibres of the segments 
which they unite, or that they interlace with 
them in some intricate way, so as to come into 
intimate or frequent contact with them. 

Tuber cinereum.—At the base of the brain 
we have already described a layer of pale grey 
matter which fills up the interval between the 
mamillary bodies and the optic commissure. 
It extends above the optic commissure for- 


_ wards to the anterior reflexion of the corpus 


callosum, and forms intimate connections with 
the anterior pillars of the fornix, the optic 
tracts, the septum lucidum, and at the floor 
of the third ventricle with the optic thalami. 
It consists of vesicular matter with fibres, and 
resembles very much the soft commissure, to 
which it is very probably analogous in office. 

The process called infundibulum or pituitary 
process extends from the inferior surface of the 
tuber cinereum down to the pituitary body. 
It is hollow, wide above, where it commu- 
nicates with the third ventricle, and narrow 
below at the pituitary body. When cut across, 
fluid will escape from the third ventricle 
through it, and a probe passes readily from 
that cavity into it. It is composed of a layer 
of granules, derived, no doubt, from the epi- 
thelial lining of the third ventricle, and some 
vesicular matter with bloodvessels and fibrous 
tissue, which latter is derived from the pia 
mater, and the special sheath of arachnoid 
reflected upon it. 


{ 


703 


Pituitary body—The process just described 
is the connecting link between the brain and 
that glandiform body, the pituitary gland or 
hypophysis. This body, situate in the sella 
Turcica, is of a rounded form, longer in the 
transverse than the antero-posterior direction, 
concave on its superior surface, into which the 
_onpevans process is inserted. It is surrounded 

y dura mater, which projects over it, leaving . 
an opening for the passage of the infundi- 
bulum. 

The pituitary body is about six lines in its 
transverse diameter and three lines from before 
backwards: its weight, including the infundi- 
bulum, is about eight grains. It consists of 
two lobes, one anterior, the other posterior. 
The former is kidney-shaped and lodges the 
latter in the notch of its posterior edge. In 
point of size the anterior lobe is nearly double 
the posterior. 

The colour of the posterior lobe is lighter 
than that of the anterior, and resembles that of 
the grey matter of the brain. 

This body is proportionally larger in early 
life than at the later periods, and it is certainly 
more developed in the lower mammalia than 
in man. It is very large in fishes, and pro- 
bably reaches its maximum of size in that class 
of animals. 

The structure of the pituitary body resem- 
bles very much the grey cerebral matter. It is 
composed of large nucleated vesicles, sur- 
rounded by a granular matrix, with bundles of 
white fibrous tissue. This fibrous tissue either 
forms an essential element in its constitution, 
or accompanies the bloodvessels which are 
found in it in great numbers. Its substance is 
soft, but not so soft as the cerebral matter, 
and when pressed between the fingers is re- 
duced to a greyish pulp, like the substance of 
an absorbent gland in an early stage of suppu- 
ration. 

Earthy concretions have been occasionally 
but very rarely found in the pituitary body. 
This circumstance, its colour, its glandiform 
character, and its extra-cerebral situation in 
connexion with the third ventricle, give it a 
certain degree of analogy to the pineal body. 
But in this latter nervous fibres have been 
found, of which I have failed to discover any 
trace in the pituitary, nor is the pituitary body 
connected to the brain by fasciculi of fibres as 
the pineal body is. The use of both is equally 
involved in obscurity; but from their con- 
stancy it may be argued that their function is 
not unimportant. It has been supposed that 
the pituitary body is a large ganglion belong- 
ing to the sympathetic system: this opinion, 
however, wants the all-important foundation of 
anatomy to rest upon, inasmuch as we find 
that the body in question is devoid of the ana- 
tomical characters of a ganglion. It-may w th 
more propriety be classed with the glards 
without efferent ducts; and from its numerous 
vessels, and its close relation to part of the 
venous system within the cranium, it may be 
connected with the process of absorption or re- 
moval of the effete particles of the brain. 


704 


Of the ventricles of the brain.—The third 
ventricle results from the apposition of the 
lateral halves of the brain along the median 
plane, and the lateral ones from the folding 
inwards, above and below, of the convoluted 
surface of each hemisphere. They must not 
therefore be ed as cavities hollowed in 
the substance of the brain: on the contrary, 
their walls must be viewed as part of the 
cerebral surface, and the eminences which 
project from them as convolutions. The cor- 
pora striata and optic thalami are from their 
structure entitled to be considered in this light, 
and still more the hippocampi, which, how- 
ever, are somewhat complicated by the addi- 
tion of the layers of white matter derived from 
the fornix. 

The distinction between the lateral and the 
middle or third ventricle results from the de- 
velopement of the corpus callosum and of the 
formx, which form horizontal strata by which 
the ventricles are closed in ahove; and the 
extension of the anterior pillars of the fornix 
downwards, and the close application of the 
free margin of the body of the fornix to the 
optic thalami, assign more complete limits to 
the third ventricle. 

The fourth ventricle is also evidently formed 
by the lateral adaptation of the symmetrical 
halves of the medulla oblongata. The iter is 
obviously a continuation of it closed behind 
by the quadrigeminal bodies and their con- 


necting fibres. This ventricle remains open in . 


the embryo, uncovered by any portion of the 
encephalon until the full developement of the 
cerebellum causes it to extend over it. 

The fifth ventricle must be viewed as ori- 
ginally part of the third, which has been 
closed off by the full developement of the 
septum lucidum and fornix, and the union of 
their lateral halves along the median plane. 

All these cavities are lined by a delicate 
membrane nearly allied to, if not identical 
with, serous membranes. It is covered by an 
epithelium, ciliated according to Purkinje and 

alentin, beneath which are delicate fibres of 
_areolar tissue exactly of the same kind as those 
found in connection with serous membranes. 
I have never seen any basement membrane. 
This membrane is reflected around the pro- 
cesses of pia mater which are found in the 
ventricles, and in this respect presents an ad- 
ditional point of analogy to the serous mem- 
branes, the portion which lines the walls of 
the ventricles corresponding to the parietal 
layer, and that which adheres to the pia mater 
resembling the visceral layer of those mem- 
branes. it is the reflection of this membrane 
from the walls to the enclosed pia mater which 
serves to shut off the ventricular cavity from the 
sub-arachnoid space, at the anterior part of the 
horizontal fissure, and at the inferior extremity 
of the fourth ventricle. If any communication 
take place between the intra-ventricular and 
sub-arachnoid fluid, it must be, as already 
remarked, by transudation through this mem- 
brane. 

Of the circulation in the brain.—Haller cal- 


NERVOUS SYSTEM. (Nervous Centres. Tae Encepmaton.) 


culates that the human brain receives i 
more than one-fifth of the whole blood of the — 
body. Whether this calculation be correct or 
no, it is certain that an organ of such great size, 
of such high vital endowments, so active, ; 
which exerts so considerable an influence up 
all other parts of the body, must necessari 
require a large supply of the vital fluid. Fe 
large arteries carry blood to the brain, name 
the two internal carotids and the two vertebra 
Each carotid penetrates the cranium at 1 
foramen on the side of the sella Turcica, at 
almost immediately divides into three branche 
pate aapieed and the middle cerebral arteri 
and the posterior communicating artery. = 
The anterior cerebral pert the 
sides of the anterior lobes of the : th 
ascend through the great longitudinal fissui 
and pass along the upper surface of the corpa 
callosum, giving off enthes to the inner con- 
volutions of both hemispheres of the brain 
These arteries anastomose with each other jus 
beneath the anterior margin of the corpus cal 
losum by a transverse branch, called ri 
communicating artery. The middle cereb 
arteries, the largest branches of the carotid, pas 
outwards in the fissures of Sylvius, and supp 
the outer convolutions of the anterior I< 
and the principal portion of the middle le 
At the inner extremity of each fissure of Sylvii 
numerous small branches of these arteries pent 
trate, to be distributed to the corpus 1 
The choroid arteries which supply the chor 
plexus sometimes arise from these 3, be 
— occasionally come from the carotid itse 
e posterior communicating artery is an at 
stomotic vessel, which m4 backwards alor 
the inner margin of the middle lobe on the ba 
of the brain, and communicates with the post 
rior cerebral artery, a branch of the basilar. — 
The vertebral arteries, having passed throu 
the canals in the transverse processes of # 
cervical vertebre, enter the cranium throu 
the occipital foramen towards its anterior 7 
In their ascent they incline towards each oth 
in front of the medulla oblo and at 
posterior margin of the pons coalesce 
form a single vessel, the basilar, which extent 
the whole length of the pons. 
The vertebral arteries furnish the anter 
and posterior spinal arteries, and the infer 
cerebellar arteries. These last ve: a 
from the vertebrals very near their coalescem 
they pass round the medulla oblongata to re 
the inferior surface of the cerebellum, to w 
they are principally distributed. " 
rom the basilar artery numerous small 
sels penetrate the pons. At its anterior e 
ri it meg into four arteries, two on | 
side. ese are, the two ior cereb 
and the two posterior cerebral eet " 
The superior cerebellar arteries pass b 
wards round the crus cerebri, el to 
fourth nerve, and divide into numerous brant 
on the upper surface of the cerebellum, sor 
of which Tees epnnse with peer: of the inf 
rior cerebellar a over posterior mar 
of the constalbane Some branches of t 


ete 


. 
‘triat 


4 


+f 


T= 


ee 
ee ae 


te ee ~ 


NERVOUS CENTRES. (Human Anatomy. Tut Encepsaton.) 


arteries are distributed to the velum interpo- 
situm. 

The posterior cerebral arteries are the largest 
branches of the basilar. They diverge and pass 
upwards and backwards round the crus cerebri, 
and reach the inferior surface of the posterior 
lobe, anastomosing in the median fissure with 
ramifications of the anterior cerebral, and on 
the outside with branches of the middle cere- 
bral arteries, Numerous small vessels pass from 
these arteries at their origin, and penetrate the 
interpeduncular space, and one or two are dis- 
tributed to the velum. Shortly after its origin 
each of these arteries receives the posterior com- 
municating branch from the carotid. 

A remarkable freedom of anastomosis exists 
between the arteries of the brain. This takes 
place not only between the smaller ramifica- 
tions, but likewise between the primary trunks. 
The former is evident all over the surface of 
thecerebrum and cerebellum. The latter con- 


_ stitutes the well-known circle of Willis. This 


anastomosis encloses a space, somewhat of an 


oval figure, within which are found the optic 


nerves, the tuber cinereum, the infundibulum, 
the corpora mamillaria, and the interpedun- 


_ cular space. The anterior communicating ar- 
tery, between the anterior cerebral arteries, com- 
_ pletes the circle in front. The lateral portion 
_ of the circle is formed by the posterior com- 
_ amunicating artery, and it is completed behind 
by the bifurcation of the basilar into the two 
_ posterior cerebral arteries. Thus, a stoppage 


either carotid, or in either vertebral, would 


_ speedily be remedied. The coalescence of the 
_vertebrals to form the basilar affords conside- 


Table security to the brain against an impedi- 


Ment in one vertebral ; and, shou!d the basilar 


be the seat of obstacle, the anastomoses of the 
inferior cerebellar arteries with the superior 
ones would ensure a sufficient supply of blood 
to that organ. If either or both carotids be 
Stopped up, the posterior communicating arte- 
ries will supply a considerable quantity of 
blood to the intracranial portions of them ; or, 
if one carotid be interrupted, the anterior com- 
municating branch will be called into requisi- 
tion to supply blood from the opposite side. 

Interruption to the circulation in both caro- 
tids and both vertebrals is productive of a com- 
plete cessation of cerebral action, and death 


immediately ensues, unless the circulation can 


bb 


be quickly restored. This was proved clearly 

Sir A. Cooper's experiments on rabbits. 
4@ circulation may, however, be interrupted 
in both carotids, or in both vertebrals, without 
permanent bad effect ; or in one carotid or one 


_ vertebral, provided the condition of the remain- 
_ Ing vessels be such as not to impede the circu- 


lation in them. In cases where the neighbour- 


ing anastomotic branches are not sufficient to 
restore the circulation to a part from which it 
has been cut off by the obliteration of its proper 
vessel, the cerebral substance of that region is 
apt to experience a peculiar form of softening* 


* In the last volume of the Med. Chir. Trans. I 
have related a remarkable case in which white 
softening of one hemisphere followed the plugging of 
the common carotid on the same side by coagulum. 

VOL, III. 


‘ the brain. 


705 


or wasting, which is distinguished by the ab- 
sence of any discoloration by the effusion of 
blood, or of any new matter. 

The four great channels of sanguineous sup- 
ply to the brain are continued up straight from 
the aorta itself, or from an early stage of the 
subclavian. The columns of blood contained in 
them are propelled very directly towards the 
base of the brain, through wide canals. Were 
such columns to strike directly wpon the base 
of the brain, there can be no doubt it would 
suffer materially. Considerable protection, how- 
ever, is afforded to the brain ; first, by the blood 
ascending against gravity, during at least a 
great portion of life ; secondly, by a tortuous 
arrangement of both carotids and vertebrals 
before they enter the cranial cavity; the carotid 
being curved like the letter S in and above the 
carotid canal, and the vertebral being slightly 
bent between the atlas and axis, then taking 
a horizontal sweep above the atlas, and after it 
has pierced the occipito-atlantal ligament, in- 
clining obliquely upwards and inwards ; thirdly, 
by the breaking up of the carotids into three 
branches ; by the inclined position of the ver- 
tebrals, and by their junction into a single 
vessel, which takes a course obliquely upwards, 
and afterwards subdivides into smaller branches. 
Such arrangements most effectually break the 
force of the two columns, and, as it were, scat- 
ter it in different directions. 

A further conservative provision is found in 
the manner in which the bloodvessels penetrate 
The larger arterial branches run in 
sulci between convolutions, or at the base of 
the brain; smaller branches come off from 
them, and ramify on the pia mater, breaking 
up into extremely fine terminal arteries, which 
penetrate the brain; or these latter vessels 
spring directly from the larger branches, and 
enter the cerebral substance. As a general 
rule, no vessel penetrates the cortical layer of 
the brain, which, in point of size, is more than 
two removes from the capillaries; and, when- 
ever any vessel of greater size does pierce the 
cerebral substance, it is at a place where the 
fibrous matter is external, and that part is per- 
forated by foramina for the transmission of the 
vessels. Such places are the locus perforatus, 
the interpeduncular space, &c. The capillaries 
of the’ cerebral substance are easily seen to 
possess an independent diaphanous wall, with 
cell-nuclei disposed at intervals. The smaller 
arteries and veins can also be admirably studied 
in the pia mater of the brain. 

The venous blood is collected into small 
veins, which are formed in the pia mater at 
various parts of the surface, and in the interior 
of the brain. The superficial veins open by 
short trunks into veins of the dura mater, or 
into the neighbouring sinuses; the superior 
longitudinal, the lateral, and the straight sinuses 
receiving the greatest number. Those from the 
interior form two trunks, vene magne Galeni, 
which pass out from the ventricles between the 
layers of the velum interpositum. The cere- 
bral veins are devoid of valves. 

We remark here, that the venous blood of 
the brain is returned to the centre of the circu- 

22 


706 


lation through the same channel as that of the 
dura mater, of the cranial bones, and of the 

eball: the internal jugular veins are the 
channel towards which the venous blood of the 
cranium tends. An obstacle, therefore, in both 
or either of these vessels must affect the entire 
venous system of the brain, or at least that of 
the corresponding hemisphere. A ligature tied 
tightly round the neck impedes the circulation, 
and may cause congestion of the brain. The 
bodies of criminals who have died by hanging 
exhibit great venous congestion, both of the 
walls and the contents of the cranium, in con- 
sequence of the strong compression to which 
the veins have been submitted. 

We have seen that, when the blood of one 
carotid artery is cut off, the parts usually sup- 
plied by it are mes to become exsangueous and 
softened ; and this is more especially the case 
if the vertebral be stopped up, or the circula- 
tion in it impeded. And it has been remarked, 
that these effects will follow the application of 
a ligature to either common carotid artery. 

Notwithstanding these facts, a doctrine has 
received very general assent, and the support 
of men of high reputation, which affirms that 
the absolute quantity of blood in the brain 
cannot vary, because that organ is incom- 
pressible, and is enclosed in a spheroidal case 
of bone, by which it is completely exempted 
from the pressure of the atmosphere. 

The cranium, however, although spheroidal, 
is not a perfectly solid case, but is perforated 
by very numerous foramina, both external and 
internal, by which large venous canals in the 
diploe of the bones communicate with the cir- 
culation of the integuments of the head as well 
as with that of the brain; so that the one can- 
not be materially affected without the other 
suffering likewise. And as the circulation in 
the integuments is not removed from atmo- 
pene pressure, neither can that which is so 
closely connected and continuous with it, be 
said to be free from the same influence. Still 
it must be admitted, that the deep position of 
the central vessels, and the complicated series 
of channels through which they communicate 
with the superficial ones, protect them in some 
‘degree from the pressure of the air, and render 
them less amenable to its influence than the 
vascular system of the surface. 

If it were essential to the integrity of the 
brain that the fluid in its bloodvessels should 
be protected from atmospheric pressure (as the 
advocates of this doctrine would have us to 
believe), a breach in the cranial wall would 
necessarily lead to the most injurious conse- 
quences ; yet, how frequently has the surgeon 
removed a large piece of the cranium by the 
trephine without any uatoward result ! me 
years ago I watched for several weeks a case in 
which nearly the whole of the upper part of 
the cranium had been removed by a process of 
necrosis, exposing a very large surface to the 
immediate pressure of the atmosphere ; yet in 
this case no disturbance of the cerebral circula- 
tion existed. In the large and open fonta- 
nelles of infants we have a state analogous to 
that which art or disease produces in the adult : 


NERVOUS SYSTEM. (Nervous Centres. Tus Encepnaton.) 


yet the vast majority of infants are free from 
cerebral disease for the whole period duri: 

which their crania remain incomplete ; and in 
infinitely the greatest number of cases in which 
children suffer from cerebral disease, the pri 
mary source of irritation is in some distan 
organ, and not in the brain itself. - 

It cannot be said that the brain is incom 
pressible. That only is incompressible, th 
particles of which will not admit of being moi 
closely packed together under the influence o 
pressure. That the brain is not a substance 
this kind is proved by the fact that, while it 
always undergoing a certain degree of pressui 
as essential to the integrity of its functions, 
slight increase of that pressure is sufficie 
produce such an amount of physical change ii 
it as at once to interfere with its healthy actior 
Too much blood distributed among its element 
and too much serum effused upon its surfa 
are equally capable of producing such an effeet 

Majendie’s experiments, described in a fo 
mer part of this article, show that the braii 
and spinal cord are surrounded by fluid, # 
pressure of which must an ise that 
is exerted through the bloodvessels. The 1 
a of this fluid i —_ ns ¢ 

ese centres, a ntly by allowing ass 
to become too fall. The preane exerted | 
the former may be called the fluid pressure fro 
without the brain; that by the blood, the pi 
sure from within. As long as these two a 
balanced, the brain enjoys a healthy state 
function, supposing its texture to be norn 
If either prevail, more or less of disturk 
will ensue. Their relative quantities, if not 
just proportion, will bear an inverse ratio’ 
each other. If there be much blood, the 
rounding fluid will be totally, or in a gr 
measure, deficient ; if the brain be aneen 
quantity of surrounding fluid will be large. 

The existence of these two antagonizing for 
may be taken as a proof that either of th 
may prevail ; and, therefore, from the pres 
of the cerebro-spinal fluid, we ae fe rs 
the actual quantity of circulating blood in” 
brain is liable to variation. 

The cerebro-spinal fluid is a valuable t 
lator of vascular fullness within the cranii 
and a protector of the brain against too m 
pressure from within. So long as it exis! 
normal quantity it resists the entrance of © 
than a certain proportion of blood in 
vessels. Under the influence of an un 
force of the heart an undue quantity of b 
may be forced into the brain, the effe 
which will be, first, the displacement of. 
or of the whole surrounding fluid; and, 
the compression of the brain. ~-_ 

When the brain receives too little blood 
requisite degree of pressure will be mainta 
and the healthy cerebral action preserved, | 
surrounding fluid do not increase too raf 
But if the brain be deprived of its due pi 
tion of blood by some sudden depression Of 
heart’s power, there is neither time nor Sot 
for the pouring out of a new fluid, anda 
of syncope or of delirium will ensue. * 
seems to be the explanation of those cas 

. ] ‘ 


ha 


a 


NERVOUS CENTRES. (Tuer Microscopicat Anatomy.) 


delirium which succeed to hemorrhages, large 
bleedings, or the sudden lighting up of inflam- 
-Mation in the pericardium or within the heart. 
In nearly all these cases, however, it is important 
to notice that the blood is more or less damaged 
in quality, deficient in some of its staminal 
principles, or charged with some morbid matter ; 
and this vitiated state of the vital fluid has no 
doubt a considerable share in the production of 
the morbid phenomena.* 
Of the encephalic nerves.—There are no com- 
mon characters possessed by these nerves, such 
as have been enumerated at a preceding page 
for the spinal nerves. They are, however, dis- 
pared in pairs, and are quite symmetrical. 
ith the exception of the olfactory, optic, and 
third pair, they are all connected with the 
mesocephale or medulla oblongata. 
The arrangement of these nerves originally 
proposed by Willis has been so long adopted 
in this country and on the continent that no 
advantage would arise from abandoning it, un- 
_ less some other of an unexceptionable nature 
could be substituted for it. It has, therefore, 
been followed in this work, and the anatomy 
and physiology of the encephalic nerves have 
been described in articles prefixed by their 
__ numerical titles, in all cases except the olfactory 
and optic, and the eighth pair of nerves. + 

Twelve pairs of nerves are found in con- 
nection with the base of the encephalon. Five 
pairs have been so classed by Willis as to form 
two in his arrangement, three pairs being al- 
lotted to his eighth pair of nerves, and two to 
his seventh. Willis’s arrangement, therefore, 
comprises nine pairs of nerves, which he 
enumerates, beginning at the anterior and pas- 
_ sing to the posterior part of the base of the 
brain. These are the first pair or olfactory 
nerves; the second pair or optic; the third 
_ pair, motores oculorum; the fourth pair,’ pa- 
 thetici ; the fifth pair; the sixth pair, abdu- 
_ centes oculi; the seventh pair, including the 
_ portio mollis or auditory nerve, and the portio 
_ dura or facial nerve; the eighth pair, including 
_ the glosso-pharyngeal, the pneumo-gastric, and 
the spinal accessory ; the ninth. pair or hypo- 
_ glossal. The first cervical nerve or the sub-occi- 
_ pital was considered by Willis as an encephalic 
nerve and counted as the tenth pair. 

As the cranium may be shewn to be com- 
ed of the elements of three vertebra, it 
been attempted to prove that among these 

nerves some may be classed with the vertebral 
_orspinal nerves. The fifth is obviously of this 
kind from its anatomical characters, namely, 
two roots; one, small, gauglionless ; the other 
large, ganglionic; but with the former, which 
is analogous to the anterior root of a spinal 
nerve, the third, fourth, and sixth nerves may 
be conjoined from their similarity in structure 
and distribution. Thus one cranio-vertebral 


————— 


* The subject of the circulation in the cranium 
has been very ably discussed by Dr. G. Burrows in 
the Lumleian Lectures for 1843, Lond. Med. Ga- 
zette, vol. xxxii. 

+ The olfactory nerve is described in the atricle 
NosE, the optic in OpTic Nerves, and the eighth 
pair under the titles of its three portions. 


707 


nerve is formed, the anterior root of which 
consists of the small portion of the fifth, the 
third, fourth, and sixth nerves; and the pos- 
terior or sensitive root, of the large portion of 
the fifth. A second cranio-vertebral nerve 
consists of the eighth pair, to which might be 
added the facial contributing to its motor por- 
tion; and a third is formed by the hypoglossal. 
The analogy, especially in the latter case, is far 
from being very obvious. 

Sketch of the microscopical anatomy of the 
spinal cord and brain.—We conclude our ac- 
count of the anatomy of the spinal cord and 
brain with a rapid glance at the present state 
of our knowledge of their minute anatomy as 
revealed by microscopical observation. 

The elements of the two kinds of nervous 
matter, fibrous and vesieular, have been al- 
ready sufficiently described. We shall only 
remark here that the great object of the ana- 
tomist’s research should be to find out the 
precise manner in which the nerve-fibres are 
united with the nerve-vesicles. Of their in- 
timate connection there can be no doubt,— 
much less of the influence which they are 
capable of exerting mutually upon each other.* 

Among the peculiarities of the fibrous mat- 
ter in the centres it may be here stated that 
the fibres pass through a much greater range of 
size than in the nerves, that here we meet with 
nerve-tubes of the largest size, and, on the other 
hand, with minute fibres which seem to be con- 
tinuous with the branching processes of the 
caudate nerve-vesicles. These fibres are per- 
fectly transparent and differ from the nerve-tubes 
in the absence of any ef the white substance of 
Schwann, and of the tubular membrane. 

Some idea of the relation of the vesicular 
and fibrous matter in different parts of the cere- 
bro-spinal centre may be formed by examining 
thin sections of the several portions of them 
made in various directions. It is impossible 
to make these sections sufficiently thin to enable 
us to explore a large surface with a high power, 
for which great transparency is necessary. Such 
sections, however, may be examined with low 
powers, as Stilling and Wallach have done. It 
1s important, however, to notice that the ap- 
pearances observed in this way afford no certain 
indication of the course and direction of the 
nerve-fibres, nor of the situation of the finer 
elements of the vesicular matter. The nerve- 
tubes are too minute to admit of being followed 
with an object-glass which magnifies less than 
from two hundred to three hundred diameters; 
yet Stilling’s researches have been made with a 
power of no more than ten or twelve diameters. 

The fibrous matter of the spinal cord consists 
of some fibres which pass either in a vertical 
direction, or obliquely, taking a long course, 
and deviating but slightly from the parallel to the 
axis of the cord. The fibres of the posterior 
columns are the most obviously longitudinal, 
and those which lie quite on the surface of the 
antero-lateral columns follow very much the 
same direction. Among the elements of the 
grey matter, fibres are found in great numbers, 


* See the article NERVE, and pp. 646, 7, et seqq. 


708 NERVOUS SYSTEM. (Microscoprcat Anatomy or tas Nervous Cenrnes.) 


the direction of which is probably oblique or 
transverse, as considerable portions of them 
may be seen taking such a direction when a 
piece of grey matter, cut transversely, is exa- 
mined under the microscope. 

The grey matter of the cord contains caudate 
and spherical vesicles imbedded in their usual 
granular matrix. They are found in the horns 
as well as in the commissure. The caudate 
_ vesicles are most numerous, and distend in the 
anterior horn and at the root of the posterior 
one. The remainder of the posterior horn and 
the gelatinous substance which is found at its 
posterior border, resemble very closely in struc- 
ture the grey matter of the cerebral convolu- 
tions. 

By examining thin transverse sections of the 
cord, carefully hardened by immersion in 
spirits, a good view of the relative disposition 
of the grey and fibrous substances may. be ob- 
tained. Stilling has carried investigations of 
this kind to a great extent, and has published 
some beautiful plates, which are quite true to 
nature. Fig. 396 is copied from one of them. 


Fig. 396. 


Transverse section of human spinal cord, close to the 
third and fourth cervical nerves. Magnified ten dia- 
meters. ( From Stilling. ) 

Lb —— columns; #7, gelatinous substance of 
the posterior horn ; k, posterior root ; /, supposed 
anterior roots; a, anterior fissure; c, posterior 
fissure ; b, grey commissure, in which a canal is 
contained, which, according to these writers, ex- 
tends through the length of the cord ; g, anterior 
horn of grey matter containing vesicles ; e, an- 
tero-lateral column, from k to a. 


It is impossible, however, to obtain any 
information from such examinations, except 
of the most general kind. On referring to the 
figure, the reader will perceive several lines, of 
the same colour and appearance as the central 
mass, to radiate from each horn of the grey 
matter to the surface of the cord, and not only 
to its external surface, but to that of its fissures. 
At whatever part of the cord the section be 
made, whether on a level with the roots of the 
nerves or between their points of emergence, 
the same appearance of radiating lines is seen, 
and the radiation will be found to extend be- 
tween the central grey matter and whatever 


part of the surface of the cord the pia mater — 
comes into contact with. . 
Stilling and Wallach suppose that these line 
are continuous with the roots of the nerves; 
that they are, in fact, nerve-tubes proceeding 
from the grey matter to form these roots. But 
this supposition seems quite untenable, for th 
following reasons: 1st, because these lines an 
met with in situations intermediate to the poit 
of emergence of the nerves ; 2dly, because th 
pass to situations, such as the surface of t 
fissures, from which no nerve-roots emanalt 
3dly, because, if they were nerve-tubes, the 
could not be so distinctly seen with so low 
power. It is much more probable that th 
may be processes of grey matter prolonge 
wards the surface, to which bloodvessels n 
pass from the pia mater, or simply bloodves: 
passing from the pia mater to the grey matter. — 
some well-injected specimens, which Mr. Smee 
had the goodness to shew me lately, the bloo 
vessels were seen to take the sar 
direction and course as these lines. = 
Besides the pect erp ound 
considerable numbers in the grey matter, 
branching processes of the caudate vesicles ; 
met with in it also, which may be distinguish 
from the nerve-tubes by the absence of 
white substance of Schwann, by their greyi: 
colour, by their branching, and by their minut 
granular texture. Capillary bloodvessels ¢ 
met with in great numbers, ramifying in 1 
grey matter, where they are much more nt 
rous than in the fibrous matter. ’ 
Stilling and Wallach describe a canal passi 
through the centre of the grey commissure, ¢ 
extending the whole length of the cord. T 
is certainly visible in most regions, but no 
all. It seems to me to have much more 
appearance of a bloodvessel than of a car 
According to these authors, it is the persist 
condition of the much-talked of canal 
spinal cord referred to at a. previous page. 
Situation in the grey matter seems ral 
posed to this view. The point, howeve' 
one upon which I am not prepared to ex 
a decided opinion at present, and which 
serves more extended careful examination. 


From a review of the preceding statem: 
it is plain that a large number of fibres 
into the grey matter of the cord, and prol 
form some intimate connection with its 1 
elements; and this fact is favourable te 
supposition that the spinal nerves derive 
origin, at least partly, from the grey matter 
must be admitted, either that these fibres” 
with the vesicles of the grey matter in” 
way, or that they pass up to the brain thr 
the grey matter; the former seems thet 
reasonable supposition, and more cons 
with the apparent oblique or transverse” 
tion which the fibres take in the g 2 hee: 

The minute structure of the medulla 0 
gata resembles in many particulars that ¢ 
spinal cord. There is not, however, so ¢ 
plete an isolation of the fibrous matter in 1 
in the latter. Excepting in the anterior | 
mids, and quite on the posterior and lat 
surfaces, the two kinds of nervous substi 


“NERVOUS CENTRES. (Tuerr Microscoprcat Anatomy.) 


freely intermingle. The anterior and posterior 
yramids and the restiform bodies consist, at 
Sst in great part, of longitudinal fibres, but the 
remainder of the fibrous matter appears to be 
made up of transverse or oblique fibres. Most 
of these are doubtless connected with the roots 
of the many nerves which arise from the me- 

. dulla oblongata. Stilling refers to special ac- 
cumulations of vesicular matter connected with 


709 


the roots of each nerve, and which probably 
form its proper origin. These contain large 
vesicles. It is impossible to give an exact in- 
terpretation to all the parts which are seen by 
his method of examination, imperfectly defined 
as they are from the use of such low mag- 
nifying powers. It would be waste of time 
and space to do more than refer to the repre- 
sentation given by Stilling ( fig. 397) of the 


Fig. 397. 


4 
WP 
a, Rathi: , 


" Pransverse section of the medulla oblongata through the lower third of the olivary bodies. (From Stilling. ) 
ii Magnified ten diameters. 


Ra; anterior fissure; b, fissure of the calamus scriptorius; c¢,raphé; d, anterior columns; e, lateral 
_ columns; f, posterior columns; g, nucleus of the hypoglossal nerve, containing large vesicles; h, 
sb nucleus of the vagus nerve ; i, i, gelatinous substance ; k, k, roots of the vagus nerve ; I, roots of the 
_ hypoglossal, or ninth nerve ; m, a thick bundle of white longitudinal fibres connected with the root of 
the vagus; n, soft column ( Zartstrang, Stilling); 0, wedge-like column ( Keelstrang, Stilling) ; p, trans- 
_ yerse and arciform fibres ; \g, nucleus of the olivary bodies; r, the large nucleus of the pyramid ; 
_ 8,8,8, the small nuclei of the pyramid; wu, a mass of grey substance near the nucleus of the olives 


Nebenkern ) ; 


structure, as viewed by a magnifying power of 
‘ten diameters. Nothing can be more true to 
re, so far as it goes, but its correct explana- 
ion must be sought for by diligent investigation 
with high powers. Numerous bloodvessels pe- 
netrate the central matter of the medulla, and 
‘no doubt many of the lines, which Stilling 
“tas te to represent fibres, «are in reality ves- 
se petal to the grey matter. 

é mesocephale has very much the same kind 
of structure as the medulla oblongata; trans- 
verse fibres (those of the pons) at its anterior 
part, longitudinal ones just behind these (pyra- 
mids), with vesicular matter freely intermixed. 
Its posterior part is the same in structure as 
the optic thalamus, and consists of numerous 
fibres with an abundant quantity of grey matter. 
The inferior layer of the crus cerebri is purely 
fibrous; its superior portion is identical in 


| u,q,7, are traversed by numerous fibres passing in a transverse semicircular 
direction ; v, w, arciform fibres; x, grey matter near the root of the vagus. 


structure with the optic thalamus, and the locus 
niger contains large caudate nerve-vesicles, 
with a considerable quantity of pigment con- 
tained in them. 

Microscopic investigation has as yet thrown 
no light on the direction and connections of the 
fibres of the cerebrum or cerebellum. What is 
known upon these points is derived from coarse 
dissection. The tubular fibres of which the 
white matter is composed, appear to be dis- 
food on different planes, and perhaps inter- 
ace with each other, so as to render it difficult 
to isolate any plane to any great extent. This 
arrangement is more obvious in the cerebellum 
than in the cerebrum. The grey matter of 
both these segments contains the ordinary ele- 
ments, caudate and spherical vesicles; but in 
the cerebellum those of the latter variety are 
much larger and more distinct than those which 


7ro 
are met with in the brain. The peculiar struc- 
ture of particular parts, as the opie thalami, 


corpora striata, tuber cinereum, &c. has been 
already described. , 


The grey matter of the convolutions of the 


brain presents the same characters throughout, 
excepting in certain convolutions of the poste- 
rior lobe near the posterior and inferior horns 
of the lateral ventricles. Here, we may ob- 


serve, in a horizontal section, the grey matter 
of the convolutions separated into two portions 
by a delicate white line, well represented in 

Jig. 398. This layer of light matter was first 


Fig. 398. 


White line in the grey matter of convolutions of the 
posterior lobe. 


described by Vicq d’Azyr, but has attracted 
very little attention from subsequent anatomists. 
I have never looked for it without finding it. 
It consists of nucleated particles, similar to 
those in the grey matter of the cerebellum. 
The layer of grey matter external to it contains 
few nerve-fibres ; that internal to it contains them 
in great numbers, passing into it at right 
angles. 


It is not intended in this part of the article 
to discuss the physiology of the brain. But in 
order to develope more clearly than can be 
done in a mere description the connection of 
its several parts and the views of its struc- 
ture which i believe to have the best founda- 
tion, I shall state briefly what appears to be the 
probable modus operandi of the organ, whether 
as the source of voluntary action or as the re- 
cipient of sensitive impressions. 

It will be necessary first to state the follow- 
ing earn as postulates. 

1. The vesicular matter is the source of ner- 
vous power. In mental actions it is the part 
immediately associated with changes of the 
mind : whether in the working of the intellect, 
or in the exercise of the will, or in the per- 
ception of sensitive impressions. 

2, The convolutions are the parts immedi- 
ately concerned in the intellectual operation. 

3. The simple exercise of the will, for a 
voluntary movement, is probably connected 
with the corpora striata. 

4. The mere reception of sensitive impres- 
sions is connected with the optic thalami and 
the superior layer of the crus cerebri. 


NERVOUS SYSTEM. (Nervous Centres. Tus Encepnaton.) 


- cord; from their small size it is highly imy 


5. Mental emotions affect the posterior and 
superior part of the m ‘ baal 
6. The cerebellum is the regulator of the 
locomotive actions. ae 
These propositions, which, it is admitter 
although not improbable, are far from be’ 
proved, will serve as the basis of an hypot 
of the action of the brain. a 
In apf operations of thought, as in th 
exercise of the reasoning powers, or of thos se 
the imagination, the convolutions of the br 
are immediately engaged. We do not say’ 
material changes give rise to the mental action 
but rather that the changes of the immate 
mind and those of the vesicular matter o! 
conyolutions are simultaneous. 
If an intellectual act gives rise to the 
cise of the will, the change in the super 
vesicular matter is propagated by the fibr 
the hemisphere to the corpus striatum, where 
the will is excited, and the change in the ve 
cular matter of that body is od alon 
the inferior layer ee the crus i, and 
passing through the mesocephale, along the: 
terior pyramids to the spinal cord, each an 
rior pyramid acting u that antero-late 
column of the cord which is on the opr 
side of the body to itself. 7 
The pyramids connect the vesicular mai 
of the corpora striata with that of the 


oe 


Wr 


4 
. 


bable that they can be viewed as continuat 
of spinal nerves up into the brain. 
Simple solution of continuity of the» 
of the hemispheres, which does not ca 
pressure, nor affect in any way the cor 
striata, would therefore merely cut off 
communication between the seat of intelle 
action and the centre of voluntary action. 
will, although unaffected, is unable to 
up with the train of thought, and mental | 
fusion is the result. The loss of speec! 
sometimes precedes a paralytic attack, 
which may remain even after the paralysis 
been wi ti may be accounted for in 
way. e intellect is competent to 
the thought, but unable to excite the 
upon which the exercise of the organs of s 
is so obviously dependent. % 
Changes, originating or excited in 
hemisphere, may be propagated to the 
sponding parts of the other hemisphere 
transverse commissures, the 
anterior commissure, &c. How far 
mispheres are in simultaneous action 
the rapid changes of the mind in thoug 
scarcely be determined; it seems pr 
however, that, in certain acts of volition 
only is the seat of the change which prot 
the movement. If I will to move m 
arm, the change by which that moyem 
prompted belongs to the left hemisphe 
corpus striatum. rua 
ertain cases of disease confined to: 
misphere, in which a considerable de 
least, of intellectual power persists, : 
that the sound one may suffice for the m 


tation of the changes connected with th 
and it may be reasonably su thi 


Pin: 


NERVOUS CENTRES. (Iluman Anatomy. Tus Encrpnaton.) 


sound hemisphere may excite to action the 

centre of volition (corpus striatum) on the dis- 

eased side. ; 

The existence of hemiplegic paralysis, then, 
implies an affection, direct or indirect, of the 
‘centre of volition (corpus striatum) on the op- 
posite side. Pressure, or a morbid change in 
the physical state of its tissue originating in it 
or propagated to it, is all that is necessary for 
this purpose; and this change, like the change 
in the normal actions, may be of such a kind 
as to elude our means of observation. 

When a sensation is excited, the stimulus 
acts from periphery to centre. The change is 
propagated by the sentient nerve to the optic 
thalamus, which, by its numberless radiations 
and its many commissures, is well calculated 
to excite all parts of either hemisphere, and 

| even of both hemispheres. When the nerve 
ened is one of pure sense, the change is 
_ wrought more directly in the brain; if the fifth, 
_ orany of the nerves of the medulla oblongata, 
the stimulus acts directly on the part; but if a 
nerve of either limb be stimulated, the change 
_ must be propagated through the spinal cord. 

It will be asked, if this be the modus ope- 
randi in sensations, how does it happen that 
disease of one optic thalamus does not impair 
Sensation in one-half of the body? And how 
is it that such disease is much more frequently 
_ associated with hemiplegic paralysis, of a kind 
“not to be distinguished from that which de- 
pends on diseased corpus striatum. The answer 
to the first question is as follows. The optic 
thalamus, or, more properly, the centre of sen- 
_ Sations, is never wholly diseased, for this centre 

is not confined to the optic thalamus of descrip- 
_ tive anatomists, but extends to the mesocephale 

and olivary columns. Extensive disease of 
_ this centre would probably be fatal to sensa- 
tion. But the most ample provision exists for 
‘Opening up new channels of sensation if those 
on one side or a part of them be impeded. 
The centres of opposite sides are intimately 
5 , especially in the medulla oblongata 
‘and mesocephale, by commissural or by decus- 
‘ating fibres; the optic thalami of opposite 
sides are connected to each other by the poste- 
Tior commissure and the soft commissure, and 
the immense multitude of fibres which radiate 
from each thalamus insure its connection with 
a considerable extent of the brain, so that a 
change in any part of it cannot fail to be com- 
‘Municated to some portion of the hemisphere. 
It is sufficient for mere sensation that the centre 
of sensibility should be affected. Intellectual 
change resulting from that affection depends 
upon fibres which radiate between it and the 
optic thalami. 

_ Itofien happens that at the onset of a cerebral 
} lesion sensation as well as motion is paralysed 
| in the opposite side of the body. Ina few days, 
| however, the sensibility returns whilst the pa- 
| ralysis of motion remains,—a fact which is 
| sufficient to show that the motor and sensitive 
power must have different channels in: the 
| centres as well as in the nerves. The primary 
paralysis of sensation may be due to a lesion 
on one side affecting the centre of sensibility, 


711 


or to the shock which that centre may have 
received from the sudden occurrence of lesion 
in some other neighbouring part. In the latter 
instance the recovery of sensibility takes place 
evidently on the subsidence of the effects of 
shock : in the former it may depend on the 
existence of other channels of sensitive impres- 
sions, independently of those involved in the 
lesion. Hence there may be lesion of one 
optic thalamus without loss of sensibility. 

The answer to the second question is ob- 
tained from considering the intimate connection 
of the corpus striatum and optic thalamus. 
No two parts of the brain are so closely united 
by fibres in vast numbers passing from one to 
the other. Disease of the thalamus therefore 
may excite a morbid state of the corpus 
striatum, without producing any change in its 
structure, which may be recognised by the or- 
dinary means of observation. And thus he- 
miplegia will take place, and remain as long 
as the morbid state of the corpus striatum re- 
mains. A lesion of the corpus striatum may 
in a similar manner affect the optic thalamus 
of the same side; but as that is not the only 
channel of sensitive impressions, a loss of sen- 
sibility does not necessarily occur. 

Emotions are for the most part excited 
through the senses. A tale of woe, a dis- 
gusting or painful spectacle, a feat of won- 
derful power or skill, the sudden appearance 
of a person not expected, are calculated to 
produce corresponding emotions of pity, dis- 
gust or pain, wonder or surprise. But emo- 
tions may likewise be produced by intellectual 
change. The workings of the conscience 
may remind one of some duty neglected or 
some fault committed, and the emotion of 
pain, or pity, or remorse may ensue. Now 
emotion may give rise to movements indepen- 
dently of the will. The extraordinary influ- 
ence of emotion on the countenance is well 
known, and this may affect one -side of the 
face, which is paralysed to the influence of the 
will, or it may excite movements of the limbs, 
even when the will can exert no controul over 
them. From these facts it is plain that that 
part of the brain which is influenced by emo- 
tion must be so connected that the convolu- 
tions may affect it or be affected by it; that it 
may be readily acted on by the nerves of pure 
sense; that it may influence the spinal cord 
and the motor nerves of the face when the 
ordinary channels of voluntary action have been 
stopped. No part possesses these conditions 
so completely as the superior and posterior part 
of the mesocephale, which we have already 
noticed as concerned in acts of sensation. Is 
an emotion excited by an impression made 
upon one of the senses? this part becomes 
directly affected, and through the optic thala- 
mus the emotional feeling causes intellectual 
change. The working of the intellect on the 
other hand may act on the seat of emotion 
through the same channel. And an excite- 
ment of this part may produce movement of a 
limb, or of all the limbs, through its influence 
on the spinal cord through the olivary columns. 

The cerebellum influences the antero-lateral 


712 


columns of the cord, partly through the deep 
fibres of its great commissure, the pons Varolii, 
which interlace freely with the fibres of the 
anterior pyramids, vesicular matter being in. 
_ terposed, and partly through those portions of 
the restiform bodies which penetrate the antero- 
lateral columns of the spinal cord. It asso- 
ciates and harmonizes the movements of the 
trunk, and especially those of the lower ex- 
tremities, for locomotion, through those por- 
tions of the restiform bodies which are con- 
tinued with the posterior columns of the cord. 

The crossed influence of deep lesion of either 
hemisphere of the cerebellum is diffieult to 
explain in the absence of any peers decus- 
sation of the restiform bodies. The connection 
of the deep fibres of the pons, however, with 
the anterior pyramids in the mesocephale does 
afford some explanation. If, for instance, the 
left cerebellar hemisphere be the seat of lesion, 
these fibres will be affected, and they may in- 
fluence the fibres of the left pyramid, which 
again will affect the right half of the cord and 
the right side of the body. Those fibres of 
the restiform bodies which incorporate them- 
selves with the antero-lateral columns, are 
doubtless too few to produce much influence. 

ABNORMAL ANATOMY OF NERVES AND NER- 
vous CENTRES.—The great space already occu- 
pied by this article obliges me to compress into 
as small a compass as possible the observations 
which I propose to make under this head. 

An interesting preliminary question is to de- 
termine to what extent nervous matter is capa- 
ble of being regenerated, when any solution of 
its continuity may have occurred. In nerve it 
has long been proved that such regeneration is 
capable of taking place. If the nerve be 
simply divided, without loss of substance, 
union may take place immediately ; but if a 
piece of it have been cut away, a considerable 
period must elapse before its complete restora- 
tion. This was satisfactorily proved by Dr. 
Haighton’s* experiments, in which he found 
that the function of the inferior laryngeal nerve 
in dogs was restored six months after division 
of the vagus, but with altered tones. Tiede- 
mann divided in a dog the nerves of the fore- 
foot and leg, and at the expiration of eight 
months observed that sensation and motion re- 
turned ; after twenty-one months the sensi- 
tive power had increased considerably, and 
at length the dog regained the complete use of 
his foot. Schwann divided both sciatic nerves 
of a frog, in the middle of both thighs: imme- 
diately after the operation the frog’s movements 
were very imperfect; after a month it had 
gained some power; but in three months it 
leaped as well as if no division had taken place. 
The sensibility of the foot, which was destroyed 
by the section, became nearly entirely restored ; 
and irritation of the nerve with a needle above 
the cicatrix produced strong contractions in the 
muscles supplied from the nerve below the 
wound. On examination with the microscope, 
Schwann found that the cicatrix consisted of 
true nerve fibres disposed in their usual way.t 


* Phil. Trans, 1795. 
t Quoted in Miiller’s Physiology. 


NERVOUS SYSTEM. (Nervous Centres. Asnormat Anatomy.) 


Miiller mentions the interesting fact of the 
return of some degree of sensation in the flaps — 
of skin used for the Taliacotian operation for 
new nose, as an argument in favour of the re- 
production of nerves. Dieffenbach, however, 
who has had so much expetience in these ope. 
rations, states that the return of sensibility 
only very imperfect, which is to be expe te 
since the divided extremities of the same fib 
cannot re-join, except in very small number 
The evidence of restoration of ; 
divided nerves in the human subject is in 'p 
fect, although not op to what has be 
above stated. Gruithuisen’s observations 
the consequences of an accidental division 
the dorsal nerve of the thumb in his own p 
son are sufficiently conclusive. Eight mon 
after the division, although the sensation | 
returned, it was so imperfect that the mil 
could form no conception of the precise px 
stimulated, as if the isolation of the fibres 
necessary to exact sensation had been 
stroyed in the cicatrix, or as if the fibres of 
peripheral portion of the nerve had not unit 
with the corresponding ones in its central po 
tion. Mr. Earle relates a case in which a p 
of the ulnar nerve was cut out; at the end 
four years the little finger was useless, and 
sensations very imperfect. é 
Indeed there is much difficulty in dra 
conclusions from the restoration or non-rest 
tion of function after division of nerves, for 
artificial disposition of the cut extremities ¥ 
insure the corresponding fibres meeting. As 
sitive fibre may be joined to a motor, and t 
the office of both would be neutralised ; or 
ferent sensitive fibres might unite, from w 
doubtless some confusion as to the natu 
position of the impression would ensue. 
The microscopic examinations of Seinrt 
Hermann, Nasse, and Klencke have rend: 
certain that true nerve-fibres are 
the cicatrix of a divided nerve. Nasse states 
they are smaller than the natural size; | 
he has likewise pointed out an interes 
fact, in the decrease of size of the fibres 
peripheral segment of the nerve as comp 
with those of the central segment, showi 
a certain degree of atrophy takes place im 
portion of the nerve, even after it has bes 
parated for a short period from its conn 
with the nervous centre, This author | 
Saw sensation and motion return, althor 
kept the animals for three quarters of a 
Perhaps this was owing to his having ret 
large portions of the nerves he operated 1 
With respect to the reproduction of sol 
of continuity in the nervous centres, wh 
is known must be viewed as unfavourable 
supposition that perfect restoration of 
oa takes place. If the brain or spin 
wounded, union will take place; & 
not appear from Arnemann’s observati¢ 
from Flourens’s that the uniting subs 
true nervous matter, Further researche 
much needed upon this interesting subject. 
Abnormal anatomy of the spinal cord a 
membranes.—The membranes of the sf 


'o i 


are liable to those morbid changes which | 


_: 
tine 


monly affect the tissues of the same kind oc- 
curring in other parts of the body. 

Inflammatory affections of the dura mater are 

_ exceedingly rare, and occur chiefly in connexion 
with wounds or injuries of the spine, or in 
extension of disease from the bones. Occa- 
_ sionally but very rarely we find osseous or 
cartilaginous deposits upon it, which are most 
obvious on its arachnoid surface. Blood is 
sometimes, but not frequently, effused externally 
to it, and effusions of serous fluid are still more 
rare. Such effusions, from the usually depen- 
dent position of the spinal canal, and from the 
large venous plexus which exists around the 
dura mater, are very likely to be pseudo-morbid, 
resulting from the gravitation of the fluids after 
_ death. Cancerous or fungoid tumours may 
_ originate from the dura mater, or may arise 
externally and grow to it afterwards. Tuber- 
eles may form between the dura mater and its 
; arachnoid lining. 
When a deficiency of more or less of the 
_ posterior osseous wall of the spinal canal occurs, 
we find a corresponding dilatation of the dura 
_ mater and arachnoid sac, which, being filled 
~ with water, causes an external tumour, consti- 
tuting what has been called Hydrorachis, the 
_ consequence of spina bifida. These tumours 
"are altogether dependent on the congenital 
Biliaperfection of the bones of the spine, and 
_ whatever peculiar disposition of the spinal cord 
_ or its nerves may be found within them is due 
"to an arrest of or a disturbance in the process of 
_ developement of those parts. The details of the 
| anatomy of these tumours will be found in the 
article Spine. 
Whe arachnoid —The spinal arachnoid exhi- 
bits marksof the inflammatory process more fre- 
i ee Saitedura mater. Butin neithermem- 
_ brane does this state of disease occur often, ex- 
_ €ept as a complication of injury or of a morbid 
_ State of other parts,either of the vertebral column 
. Or of the spinal cord itself. The signs of an 
inflamed state of this membrane are lymph 
_ @ffused on its free surface, recent, or indurated 
_ €ausing more or lessthickening. Adhesions be- 
_ tween corresponding parts of the two arach- 
‘noid layers are also a good indication of a 
previously existing inflammation. But care 
Must be taken not to mistake the adhesion, 
which is often found between points of these 
membranes, for inflammatory adhesion. The 
former occurs in minute points, and is probably 
a result of drying of the membranes at the 
points of contact; the latter is always ac- 
companied by the formation of new matter 
which forms the medium of union between the 
layers. 

Cartilaginous spots are by no means unfre- 
quently found on the arachnoid membrane, 
chiefly in connection with its viscerallayer. They 
are generally small detached lamine thoroughly 
incorporated with themembrane,rarely exceeding 
in size the flat surface of a split pea, more fre- 
quently much smaller. They generally occur on 
the posterior surface of the arachnoid. I have 
seen such deposits in cases where there were no 
previous symptoms to denote any affection of 
the central nervous system, and I am disposed 

VOL. III. 


i 
é 
f 


NERVOUS SYSTEM. (Nervous Cenrres. AsNormMat Anatom ¥.) 


713 


to believe that such deposits, separated as they 
must be from the surface of the cord, are not 
likely to occasion much if any irritation to that 
organ. They are found mostly in the dorsal and 
lumbar regions. Sometimes spots of bone, of 
similar size and shape, are found scattered over 
the membrane. 

The pia mater.—The spinal pia mater being | 
the seat of the vascular ramifications which con- 
tribute to the nutrition of the cord, is also sub- 
ject to congestions often depending on causes 
quite extraneous to the spinal canal or cord. 
Thus the congestions which are produced in 
animals drowned, or asphyxiated in any other 
way, exist in the vessels of this membrane. The 
most frequent cause of congestion in these 
vessels, however, is the position of the corpse 
after death. After deaths, preceded by violent 
convulsions, there is always congestion of the 
vessels of the pia mater. But this congestion 
must be regarded as a consequence, not asa 
cause of the convulsions. The holding of the 
breath, which accompanies continued convul- 
sions, gives rise to a very general congestion of 
the venous system. 

When the congestion is very considerable, it 
may occasion rupture of bloodvessels and 
effusion of blood into the sub-arachnoid cavity. 
This constitutes a form of spinal apoplexy, which 
is apt to follow concussion of the cord, caused 
by a fall or by a blow inflicted upon the back. 
It may follow any of those diseases which are 
accompanied by convulsions—tetanus, hydro- 
phobia, epilepsy, cerebral apoplexy. 

Inflammatory affections of the niembranes, 
deposits of tubercle or other foreign matter 
which may cause induration of the cord, have 
their primary seat among the vessels of the pia 
mater. Inflammation of the membranes is 
more apt to occur among children than in 
adults. 

Abnormal anatomy of the spinal cord.—The 
absence of this organ (amyelia ) occurs chiefly 
in anencephalous foetuses. In such cases the 
posterior wall of the spinal canal is often defi- 
cient, and the canal is occupied by a reddish, 
vascular pulpy substance. It is a question 
whether the absence of the cord, in such cases, 
is to be attributed to a real defect of its deve- 
lopement or to its destruction ‘while yet in a 
very delicate semi-fluid state, by the formation 
of a dropsical effusion, either around it or in 
the canal or ventricle which exists in it at an 
early period of its developement. This latter 
explanation is rendered probable by the fact 
that all the recorded cases are of foetuses which 
had reached an advanced period of intra-uterine 
developement; and in some of them move- 
ments had been distinctly felt by the mothers, 
which could not have taken place with a com- 
bined or definite character without the existence 
of the cord. And in some of the records it is 
affirmed that the children lived some hours and 
exhibited movements and even signs of sensa- 
tion, or at least of excitability to stimuli. 
Such phenomena, if true, leave us no alterna- 
tive but to suppose that the whole cord could 
not have been absent—some portion must have 
existed as the centre of these movements, 

22 


714 


but, being of small size, it eseaped the notice 
of the observer. 

This explanation is likewise contirmed by the 
occurrence of cases (rare, it is true) in which 
the brain existed, but the spinal cord was 
wanting. A very able narrative of a case of this 
kind has lately been published by Dr. Lonsdale 
of Edinburgh. “ The anterior and middle 
lobes of the brain appeared to be properly 
developed, and occupied their usual positions 
in the cranial cavity ; whilst the posterior lobes 
were much smaller, and were partially squeezed 
through a large abnormal opening or deficiency 
in the occipital bone. e cerebellum and 
that part of the occipital bone in which it is 
normally lodged, were wanting. There was not 
the slightest vestige of medulla oblongata or 
spinal cord, and the posterior arches of the 
vertebre did not exist.’* The fcetus had 
reached its full term, and its body and limbs 
‘were well formed. 

An interesting feature which had been well 
observed in this case, although probably not 
peculiar to it, but hitherto overloo ed, was the 
relation of the nerves in the cranial and spinal 
cavities. All the nerves of the medulla oblon- 
gata, and the first, second, and third cervical 
nerves, hung as loose threads in the cranial 
cavity or in the upper part of the spinal canal, 
and presented a looped arrangement, seeming to 
denote that such is their normal disposition in 
the nervous centre. 

Partial deficiencies of the spinal cord, al- 
though also rare, are more frequent than the 
total absence of the organ. ese occur in 
connection with other defects of developement. 
Thus, in spina bifida much of the cord is defi- 
cient, either throughout its entire extent or in 
those parts where the vertebral wall is defective. 
In such cases it is probable that the deficiency 
is attributable to the destructive influence of the 
dropsical effusion rather than to an original de- 
fect of the organ. In cases in which the upper 
or the lower extremities have not been deve- 
loped, the usual cervical or lumbar swelling is 
imperfectly developed, owing to the absence or 
atrophy of the fibres which would have formed 
the nerves to those limbs. 

Excessive congenital developement of the 
spinal cord occurs only in those monstrosities 
which arise from the junction or fusion of the 
spinal columns of two embryos. 

The diseased states of the spinal cord may be 
enumerated as follows :—hypertrophy, atrophy, 
induration, sofiening, suppuration, deposits of 
tubercle or of other morbid products. 

In abi the cord is enlarged and 
looks full and plump, without any alteration of 
its consistence or of its intimate structure. It 
is not improbable that the elementary fibres as 
well as the vesicles of grey matter may be en- 
larged in such cases, and that the increased 
dimensions of the whole organ must be attri- 
buted to this cause, and not to the deposition 
of any new material in it. I have not, however, 
had any opportunity of ascertaining this point 
by microscopic examination. 


* Edin. Med. and Surg. Journal. 


NERVOUS SYSTEM. (Nervous Centres. AsNnonmat Anatomy.) 


Atrophy occurs in the cord lly as the 
result of some local re a tumour 
developed in connection with some one of the — 
membranes or external to them. In a case of © 
this kind which I lately examined, the tumour — 
consisted of a mass of scrofulous matter situate — 
between the vertebra and the dura mater in the — 
upper part of the dorsal region. That part of - 
the cord which was pressed upon by the tumour 
was wasted to one-half its natural size, whilst 
below it the cord exhibited its natural size. 

Atrophy of the cord occurs as part of that 
general rene of the nervous centres which 
accompanies advanced life, or a state of general — 
cachexy. In persons long bedridden the cord 
is found in a wasted state; and in cases of @x- 
tensive hysterical paralysis, in which exercise of 
the enfeebled limbs has been neglected, the 


cord will participate in the wasting of the nerve 
which supply the affected \. ‘8 
Induration of the cord is not of unfrequent 


occurrence, and appears to be the result of 
some abnormal nutrition analogous to if not 
identical with chronic inflammation— inflam- 
mation modified, perhaps, in the nature of 
event by some peculiar state of the blood. e 
hardness occurs generally in patches, involvin 
more or less of the thickness of the cord, an 
affecting the peripheral of the body, in pro 
rtion as it involves the immediate points 
implantation of the roots of the nerves, or those 
roots themselves. It is generally accompanier 
by some discolouration of a light brownish hue 
as if the first changes which gave rise to it wer 
attended with extravasation of the colouri 
matter of the blood. : 
Sometimes, however, induration seems to re 
sult from the changes which accompany 
phy of the cord, as if from an imperfect 
ply of the fluids necessary for perfect nutritio 
Softening of the cord is found in two stat 
which are probably essentially different in the 
intrinsic nature and origin. One is that of F 
softening ; the other is that of white or colourle 
softening. In the former the tissue of 
spinal cord is much softer than it ought to 
and is readily disintegrated by a m 
water directed upon it; its colour is due to 
full injection of the bloodvessels whie 
verse it, or to some extravasated blood. 
latter the nervous matter is reduced to a 
semifluid mass, like thick cream, withot 
least appearance of injected vessels. 
former the nerve fibres are more or less bri 
down and softened; in the latter there is lit 
no breaking down of the fibres, but theya 
tenuated and have lost the distinctive ¢ 
of the white substance and central axis to a gt 
or less degree. Red softening ob 
rca in its origin, but white softenin, 
dicates a deficient supply of blood, and _ 
resembles the gangrene which occurs in ex! 
soft parts. A 
The anatomist should be to di 
guish the white softening, which is the pro 
of a morbid process during life, from © 
which occurs death as the result of deee 
position, or which may be produced by vi 
compression of a part of the cord in ope 


& 


NERVOUS SYSTEM. (Nervous Cenrres. Apnnormat Anatomy.) 


the spinal canal. The softening which results 
from decomposition, in general, occupies the 
greatest part of the cord or the whole of it, and 
~ does not exhibit so pure a white colour as the 
morbid softening. It sometimes has a greenish 
or a dusky hue, and is more or less fetid. 
The softening from injury is very circumscribed, 
and is surrounded by nervous matter perfectly 
healthy in colour and consistence. There is, 
moreover, generally evidence of injury to and 
rupture of the pia mater, the softened matter of 
the cord protruding through the rent in this 
membrane. Where the softening is morbid, 
it wants the abruptness which occurs in the 
latter case, and the diseased part gradually 
passes into healthy structure. 

The inflammatory softening is sometimes 
infiltrated with purulent matter, which, if not 
recognizable by the naked eye, may be easily 
detected by the microscope and by reagents. 
In rare cases the pus is collected into a circum- 

_ Seribed abscess, occupying more or less of the 
__ thickness of the cord. 
___ The cord may be the seat of an effusion of 
blood, and may thus present the condition of 
_ apoplexy, like that which is of so frequent 
_ occurrence in the brain. In such cases there 
may be more than one small clot occupying 
the central part of the cord. They are of 
are occurrence, and are generally found in 
_ the upper part of the cord. 
Tubercle may occur in the cord, and, as in 
_ the brain, connected with the pia mater, either 
deposited in a group or forming a mass which 
_ gradually encroaches upon the substance. The 
| cervical region is that in which it most fre- 
| quently is found, and it forms tumours of va- 
ious sizes, each of which is generally enclosed 
in membranous cyst. 
_ Cancer of the cord is a lesion of extremely 
_ ¥are occurrence. Olivier relates several cases 
of it, but Rokitansky remarks that he has seen 
_ but one example of a cancerous tumour in the 
Spinal cord. It is in cases where the cancerous 
liathesis prevails, and where cancerous matter 
‘is deposited throughout various parts of the 
_ body, that we may look for it in the cord. 
_ Abnormal anatomy of the brain and its mem- 
—The remarks already made with re- 
to the membranes of the cord apply 
kan to those of the brain. The latter mem- 
d » however, are more frequently found in 
abnormal state than the former. 
_ The dura mater—There may be a general 
or partial deficiency of the dura mater and of 
t membranes according as there is a 
general or partial defect in the brain itself. 
_ The partial defect is mostly observed in the 
falx cerebri or in the tentorium cerebelli. The 
| cribriform appearance of the former process is 
of frequent occurrence and is unaccompanied 
by any obvious defect in the brain, and some- 
times even a considerable portion of it is want- 
| ing, while the brain is quite normal. 

Acute disease of the dura mater is rare, and 
only occurs as an effect of wounds or injuries 
_ | of the cranium, or in connection with syphilitic 
. er strumous disease of the bones; or, inde- 

\pendently of diseased bone, as an effect of the 


715 


syphilitic poison, like that which occurs on ex- 
ternal fibrous membranes, A syphilitic in- 
flammatory state of the dura mater is frequently 
the cause of serious affection of the brain. A 
condition analogous to that of node will cause 
pressure on the brain and paralysis; and, 
whilst it resists the ordinary antiphlogistic 
treatment, will speedily yield to antisyphilitic re- 
medies, such as mercury and iodide of potassium. 

We meet with great variety as regards the 
firmness of adhesion of the dura mater with 
the cranium. There is a tendency in some 
perverted states of nutrition for this membrane 
to become incorporated with the inner table of 
the skull. This seldom takes place conti- 
nuously, but in patches, so that in removing the 
calvaria a portion of the inner table of the skull 
remains in connection with the fibrous mem- 
brane, or a hole is left in the latter when the 
conversion of the fibrous membrane into 
bone may be complete. It is in the 
more advanced periods of life that this mor- 
bid condition is chiefly found; indeed we 
seldom open the skull of a person who has 
passed the age of threescore without finding 
more or less of it. At that period of life it 
may be regarded rather as one of the series of 
changes which accompany advancing years 
than as a diseased state. When, however, it 
occurs at the earlier ages, it must be viewed as 
resulting from a morbid process. 

Patches of bone are frequently found in the 
processes of the cranial dura mater, as in the 
falx, tentorium. They occur more frequently 
in the former than in the latter. In size they 
vary much: they are placed between the layers 
of the dura mater, and are completely enclosed 
by them; sometimes, however, they encroach 
upon these layers, which then seem as if they 
had been completely converted into bone. 

Fibrous tumours are sometimes formed at 
various parts of the dura mater. These vary 
considerably in size and number. They pro- 
ject inwards upon the brain, and indent that 
organ more or less according to their size, and 
sometimes they project outwards, and by 
causing absorption of the bone by pressure 
form depressions for themselves, and even wear 
holes in the bone by their outward growth. 

Tubercles of a strumous character are some- 
times deposited in connection with the dura 
mater. The most remarkable example I have 
seen of these morbid tumours is a preparation 
in the museum of King’s College, London, 
taken from a patient who suffered severely from 
epilepsy. é internal surface of the dura 
mater and of the falx is covered with numerous 
tumours of this kind, some of which are nearly 
as large as a walnut, others not larger than a 
small filbert. This specimen belonged to the 
collection of the late Dr. Hooper, who has 
given an excellent delineation of it in his plates 
of the morbid anatomy of the brain. : 

The dura mater participates in the diseased 
states of the cranial bones. Cancer or fungoid 
disease affecting the calvaria or any part of the 
cranial wall which is covered by dura mater, 
will extend to the dura mater and subjacent 


* parts. 


716 


When there has been a solution of continuity 
and a loss or removal of any portion of the 
cranium, the exposed surface of the dura mater 
1s apt to throw out a growth of granulations 
which constitute the fungus of the dura mater, 
analogous to that which sprouts from the sur- 
face of a similar fibrous membrane—the tunica 
albuginea of the testicle. In point of structure 
this fungoid growth is the same as the granula- 
tions on the surface of external ulcers. 

Effusion of blood, constituting a form of 
meningeal apoplexy, may occur on the external 
surface of the den mater separating it from the 
bone; or on its internal surface, dissecting 
away thearachnoid membrane from its adhesion 
to the dura mater. The former kind is mostly 
if not always traumatic, that is, resulting from 

' the application of violence to the exterior of the 
cranium. The latter kind is of extremely rare 
occurrence, and must be carefully distinguished 
from that variety of effusion into the arachnoid 
sac in which the effused blood appears to be 
covered by a serous membrane. This mem- 
brane, however, results from the condensation 
of the superficies of the clot by its friction 
against the parietal arachnoid, and it may be 
distinguished | from a true serous membrane by 
the absence of epithelium from its free surface. 
Effusions of either kind generally occur on 
some part of the surface of the cerebral hemi- 
spheres above the level of the petrous bone. 

The arachnoid membrane. — The arach- 
noid membrane is sometimes the seat of 
acute inflammation, and presents the same 
signs of that process as are met with in other 
serous membranes. The chief and, indeed, 
the only unequivocal sign of his condition 
as of recent occurrence is the exudation of 

lastie lymph upon the free surface of either or 
th layers of the membrane, with or without 
pus. This is attended with a highly injected 
state of the subjacent tissue (pia mater or dura 
mater, generally the former). The arachnoid 
itself, it will be remembered, contains no blood- 
vessels, but derives its nourishment from the 
vessels of the subserous tissue. Its apparent 
vascularity is due to its great tenuity and trans- 
parency, which allow the bloodvessels lying 
underneath to be seen through it as if they be- 
longed to the membrane itself. 

An opaque condition of the arachnoid, vary- 
ing both in degree and extent, is a very common 
appearance of this membrane, especially at the 
middle and advanced periods of life. This 
occurs sometimes in patches; at other times it 
is generally diffused over the whole membrane. 
It is most conspicuous on the convex surface 
of the brain, especially towards the great longi- 
tudinal fissure, and it is frequently associated 
with large and numerous Pacchionian bodies. 
It occurs, however, very commonly at the base, 
and frequently opposite the confluxes of the 
subarachnoid fluid. 

The opacity of the arachnoid is commonly 
attributed to a former acute inflammation of 
the membrane, or to a chronic inflammation 
going on up to the time of death. But this 
state of the membrane is of such frequent oc- 


currence, and is so often found in persons who ° 


NERVOUS SYSTEM. (Nervous Cexrres. Asyormat Anatomy.) } 


evinced no sign of important organic change 
during life, that it seems scarcely correct to — 
attribute it to such a cause. It is not meant 
to deny that previous inflammation or chroni¢ 
inflammation is capable of causing these 
opaque spots, but undoubtedly other causes 
may produce them as well. friction 0} 
two opposed surfaces may do it, and depo: 
upon the free surface of the membrane, an ab 
tered condition of the epithelium, may 
the same effect. Some recent mi 
examinations convince me that morbid deposit 
similar to those which are formed on the coa 
of arteries, may be found here, and occur ii 
those morbid states of the blood, and cons 
quently of the whole system, which are f 
able to the deposition of a morbid mate 
throughout the arterial system, or in the 
stance of viscera.* 
In confirmation of this view it may be st 
that opacities of the arachnoid are most com 
mon after the middle period of life, and th 
they are then almost uniformly associated wil 
a morbid state of the arteries of the brain ai 
of other portions of the arterial system. : 
Adhesion between the opposed surface 
the visceral and parietal layers of the arachno 
is (and the fact is curious) not of frequent ¢ 
currence, excepting at the convex border of 
falx cerebri, where the Pacchionian bodies a 
found. And the intrusion of these bodies in 
the longitudinal sinus frequently increases t 
closeness of that adhesion. cellular ¢ 
hesion so common in other serous membrat 
is rarely found in the arachnoid. f 
Small plates of cartilage or of bone are sor 
times found in connection with the arachnoi 
Their formation is generally the result of a 
vious morbid deposit which has subseque 
become converted into cartilage or bone. 
Effusion.—Effusions take place either | 
the subarachnoid or the arachnoid cavity. — 
existence of serum, in undue quentians 
former situation, must be looked on as am 1 
crease. in the fluid which naturally occup 
that space, and as we have already remé 
in a former part of this article, it takes pl 
consequence of the failure of the normal 
sure upon the vascular surface, and may 
be regarded as tending to preserve the fune 
of the brain than as producing an inju 
pressure upon it. Indeed I have always 1 
that in cases where an abnormal quart 
fluid existed in the subarachnoid cavi 
brain afforded no indication of its having 
rienced undue pressure previous to ¢ 
such cases the brain seems to contal 
blood than natural, and its anemia 1s 
obvious in the grey matter. n 
is hyperemia of the veins in the white 
of the hemispheres, as if the heart's foree, 
necessary to the venous circulation witl 
cranium than even to that of other part 
body, had been prevented from exertin 
influence through the capillaries upon 
blood in the veins. “7 
* It is probably to deposits of this kind thi 
kitansky sso wader “the title of “ Gallent 
Concretionen,” : 


- 
USUCUL 


OMe 


NERVOUS SYSTEM. (Nervous Centres. Asnormat Anatomy.) 


The existence of serous fluid in the arach- 
noid cavity is of very rare occurrence. In some 
instances old adhesions of the two layers of 
arachnoid to each other circumscribe a space in 
which fluid accumulates. 

Blood is sometimes effused into the subarach- 
noid cavity. This is frequently the case in 
injuries of the head, the blood escaping from 
broken vessels of the pia’ mater. Sometimes 
the blood effused into either lateral ventricle 
will escape into the subarachnoid cavity, break- 
ing down the membrane of the ventricle. If an 
apoplexy occur near the surface of the brain, 
the laceration of the cerebral substance may 
extend quite to the surface, and the blood may 
pass through the pia mater into the subarach- 
noid space. 

In some instances we find blood in the 
cavity of the arachnoid (the arachnoid sac). 
The blood is either loose in the sac, or it is 
more or less closely connected with the inner 
surface of the membrane lining the dura mater. 
__. In arecent communication from Mr. Pres- 
_ cott Hewitt, published in the last volume of 
the Medico-Chirurgical Transactions, the prin- 
cipal facts relating to this subject have been 
_ collected and arranged in an interesting form. 
_ Mr. Hewitt describes these effusions of blood 
as existing in four forms’:— 

“1. The extravasated blood may be either 
liquid or coagulated ; if in the latter state, it 
may be in clots, or spread out in the shape of a 
thin membranous layer, covering a greater or 
less extent of the surface of the brain. 

“2. Sometimes the extravasation presents 
itself under the shape of a false membrane, 
possessing more or less of the original colour of 
_ the blood. 

_ 3. The blood may be fixed to the free 
_ surface of the arachnoid and there maintained 

G by a membrane, which to the naked eye pre- 

? pa all the characters of the serous membrane 
itself. 

* “4, The blood is frequently found enclosed 
ina complete cyst of various degrees of thick- 
ness, which may be removed unbroken from 
_ the cavity of the serous membrane. 

__ “The four divisions above referred to,” adds 
Mr. Hewitt, “‘ may be and often are combined 
" with each other, but in whatever state the extra- 
-vasated blood has been found, it has, in the 
‘Majority of cases, corresponded to the upper 
‘surface of the brain, and has been rarely met 
with in the cerebellar fossz.” 

It is impossible that these effusions of blood 
can have any other source but the minute 
bloodvessels of the pia mater or the dura mater, 
which becoming ruptured allow the blood to 
burst through the serous membrane by which 
they are covered. They occur mostly in per- 
‘sons of a scorbutic or hemorrhagic habit, or 
in whom the arteries have become brittle from 
abnormal deposits in them; and it is not im- 
probable that whilst the imperfect nutrition of 
the arteries is going on, the serous membrane 
itself suffers, becomes wasted, and therefore 
easily yields to the force of the blood as it 
escapes from the bloodvessels. - ‘ 

Pus is found in the subarachnoid cavity 


717 


where there has been inflammation of the pia 
mater and arachnoid, and more rarely in the 
arachnoid sac. 

Of the pia mater—This membrane being 
the vascular membrane of the brain, and con- 
taining the nutrient vessels as well of the sur- 
face of the brain as of the visceral layer of the 
arachnoid, is the seat of all those changes in 
the condition of the bloodvessels or of their 
contents, which give rise to, or are caused by, 
morbid states either of the nervous matter or 
of the serous membrane. 

All those changes which indicate hyperemia 
or anemia of the convolutions of the brain 
occur in the pia mater ; and the colour of this 
membrane will vary according to the quantity 
of blood contained in its bloodvessels. 

There are no definite signs which enable the 
anatomist to pronounce whether an hyperemia 
be of the active and inflammatory kind, or 
passive, and dependent on some cause remote 
from the brain itself, or even upon a post- 
mortem cause, unless it be accompanied with 
those undoubted products of the inflammatory 
process, pus or lymph. 

A highly injected state of the vessels of the 
pia mater will frequently be caused by the 
manner of the patient’s death. Where the 
respiratory actions have been laboured and dif- 
ficult prior to death, this is sure to occur: we 
find it also when death has been caused by 
asphyxia, however produced. 

In convulsive diseases the pia mater and the 
whole brain become highly injected more as a 
consequence of the impeded circulation caused 
by the struggles of the patient interfering with 
the due exercise of the respiratory movements, 
than as the cause of the convulsions. Indeed, 
there seem good grounds for believing that con- 
vulsions are more frequently caused by a de- 
ficient supply of blood to the brain than by a 
superabundant flow of it to that organ. 

he pia mater is the seat of the principal 
morbid deposits which affect the brain. Of 
these tubercle is among the most common ; 
it most frequently occurs on the surface of the 
convolutions; but it may be found wherever 
the pia mater exists, either in the interior or on 
the outside of the brain. It occurs less fre- 
quently on the pia mater of the cerebellum 
than in any other situation. 

The tubercular deposit in the pia mater com- 
mences by the developement of minute granu- 
lations of a grey, clear, or semi-transparent 
material. These are deposited close to each 
other over a greater or less surface, forming a 
group, and several such groups may be formed 
near each other. After a time this grey ma- 
terial is changed into a yellow granular matter, 
which is sometimes enclosed in a cyst. _ 

Tubercular matter originally deposited on 
the surface of the pia mater in the sulcus of a 
convolution may have the appearance as if it 
had been formed in the substance of the brain. 
The sulcus is obliterated, and the tubercle, 
enlarging towards the brain, becomes, in a 
short time, surrounded by cerebral matter. 

Sometimes tubercle deposited in some part 
of the pia mater excites inflammation in the pia 


718 


mater and arachnoid immediately near it,— 
tubercular meningitis ; and this may affect more 
or less of the substance of the brain in its 
vicinity, causing red softening. 

Cerebral tubercle is seldom or never alone. 
Other organs of the body are almost invariably 
affected at the same time, the lymphatic or the 
mesenteric glands, or the lungs. It is most 
commonly found in children, and it is not im- 
probable that it may lie dormant for years until 
roused to action by some newly-developed 
morbid excitant. 

Connected with diseased states of the mem- 
branes of the brain, it should be remarked, that 
in many instances acute affections of the mem- 
branes of the brain find their point of departure 
in inflammation of the sinuses. The sinus 
which is most frequently inflamed is the lateral ; 
the inflammatory state of this spreads to the 
neighbouring arachnoid and pia mater, and 
induces all the consequences of a primary me- 
ningitis. 

Mf the abnormal states of the brain.—The 
abnormal conditions of the brain may be con- 
sidered under the heads of —1, congenital ; 
2, acquired or morbid. 

1. Congenital abnormal conditions.—A total 
defect of the brain is found in that state in which 
the head is wanting (Acephalia); and also 
where there is deficiency of the parietal bones 
of the cranium, the occipital, temporal, sphe- 
noid, and frontal being present in an imperfect 
state, and there being also, in general, spina 
bifida of the upper cervical vertebre, there is a 
deficiency of a considerable portion of the en- 
cephalon, the medulla oblongata or a portion 
of it being alone present ( Anencephalia 15 

The acephalic state is very frequent. It is 
always associated with complete or nearly com- 
plete absence of the cranial bones, and frequently 
more or less of those of the spine. In some 
the trunk and extremities are perfect, but in 
very many there are deficiencies to a greater or 
less degree in the formation of these parts. 

In anencephalia there is a defective state of 
encephalon, but not an absence of it; and it 
seems highly probable that this condition is 
due, not so much to an original arrest of deve- 
lopement as to the occurrence of an hydroce- 
— state at an early period of intra-uterine 

ife, the accumulated fluid breaking down the 
newly formed nervous matter, which wants the 
support of the cranial bones. 

e extremest degree of this defect is when 
a large portion of the cranial bones is wanting, 
and also when there is a large fissure in the 
spine. In other cases the spinal fissure does 
not exist. The cranium is largely open on its 
eo and superior aspect, the head thrown 

k, the neck very short and thick, the eye- 
balls very large and prominent, and the mouth 

ially open, giving to the features a very 

ideous expression. 

The hollow of the base of the cranium is, in 
these cases, filled up by a red, soft, highly vas- 
cular substance, continuous with the pia mater 
of the spinal cord. This, in general, appears 
to be nothing more than the cranial pia mater, 
which has collapsed into this state by the de- 


NERVOUS SYSTEM. (Nervous Centres. Annormat Anatomy.) 


struction of the nervous matter, and in which — 
sometimes small masses of nervous matter may 
be discovered here and there. It is eovered by — 
a smooth membrane, which may be an imper- 
fect arachnoid. In some instances, however 
the tumour is of considerable size, more volu- 
minous, according to Geoffroy St. Hilaire, than 
even the normal brain. It is disposed in lobes, 
which resemble somewhat those of the brain, 
and which sometimes contain a considerab 
quantity of serum. 

In less degrees of this condition the crani 
bones are more developed, the skull is les 
open, and the brain and its monbreeene ch: 

a greater degree of perfection. In all 

water is ore the cerebral 
The following case quoted from Penchienati bi 
Breschet in his article Anencephalie, in th 
Dictionnaire de Médecine, illustrates the ap 
pearances in a by no means advanced se © 
the deformity. The subject was a girl which 
had lived three days. striata, 
optic thalami, were present with the hem 
spheres. The lateral and third ventricles wer 
greatly enlarged. The tubercula quadrigemin 
retaining their vesicular condition were likewi 
present, and also the pineal . € 
parts presented at the superior part of the er 
nium a red eminence which was u 
the skin. 

In some cases where the degree of ope 
of = cranium is reduced ye a fissure, in fro 
or behind, a tumour is found protruding thro 
either fissure, consisting of the brain, ir 
fectly developed, inclosed in its membrai 
This condition is frequently combined 
greater or less extent of spina bifida. ’ 

The partial deficiencies of the brain its 
are infinitely various. Those parts which ¢ 
most frequently either altogether absent or 
perfectly developed, are those which are 1 
essential to the production of the organie ¥ 
phenomena. e commissures are very 1 

uently wanting, the smaller ones oftener th 
the larger, such as the corpus callosum and t 
af itaagene The hemispheres of the b 
are uently very imperfectly devel 
The medulla oblongata and mesecepall 
exhibit any material imperfection. ; 

In all cases of idiotcy there is a mat 
imperfection in the developement of the bi 
This is sufficiently plain to the most si 
ficial observer from the small size of the 
which is so frequent a character of this” 
and which is more especially remarkak 
adult life, where the developement of the 
nium by no means keeps pace with that 0 
rest of the body. a 

As an example of the class of changes | 
take place in the brains of most idiots, I sha 
scribe the appearances observed in the br 
an adult idiot which I examined in Oc 
1844. a 
On the upper surface of the brain the con 
lutions were not developed ; the surfac 2 of 
hemispheres was perfectly smooth. ‘The fi 
of Syivius was very deep and well m 
extending upwards and backwards; at its 
terior extremity there was a slight puck 


tac 


i 
* 


NERVOUS SYSTEM. (Nervous Centres. Asnormat ANATOMY.) 


indicating a feeble developement of the insula 

of Reil. 

A few fissures and imperfectly developed 
convolutions were found upon the inferior sur- 
face of the middle lobe, as well as upon the 
lateral and inferior surfaces of the anterior lobe. 

The olfactory fissures were perfect but very 
small; the olfactory nerves appeared natural. 

The optic nerves were natural but small. 

The tuber cinereum was large and well 
developed. 

The corpora mamillaria appeared to be fused 
together along the median line. 

The pons Varolii very narrow from before 
backwards; the groove which passes along its 
middle was imperfect. 

The corpus striatum was exceedingly small, 
and the groove between it and the optic thala- 
mus was greatly increased in size. The tenia 
semicircularis was large. 

The convolution of the corpus callosum was 

_ very imperfectly developed. The hippocampus 
_ Major was very smal), and there could scarcely 
_ be said to be any trace of the hippocampus minor. 
_ _ The fornix was well developed, as was also 
the corpus callosum. The longitudinal tracts 
_ on the surface of the corpus callosum were also 
well developed. 

The pineal gland was large and situate very 
far forwards, corresponding very nearly to the 
_ middle of the optic thalamus. The quadri- 
_ geminal tubercles seemed imperfectly deve- 
loped, and the distinction between them was 
badly marked. 

_ The optic tract was small, but natural in its 
connections. The cerebellum was well deve- 
_ loped: its laminz seemed natural. The lateral 
| ventricles were large and rather dilated. The 
entire brain, after having lain in spirits for some 
days, weighed 1 Ib. 4} oz. avoirdupois. 

4 In some instances the hemispheres of the 
brain are fused together, there being little or 

‘no trace of a longitudinal fissure to separate 
them. This condition occurs generally in the 
Cyclopic monsters, or in monsters in which 
‘there is a total absence of the organs of vision. 

here there is this singleness of brain there is 
also sometimes a fusion of the corpora striata 
and optic thalami of opposite sides together. 

_ A total absence of all the transverse com- 
missures of the brain constitutes, as Rokitansky 

‘observes, the opposite condition to that just 
detailed. 

Idiotey results from any change which im- 
— to a material extent the structure of the 
hemispheres of the brain and of the fibres by 
) which they are connected to each other, as well 


} recorded instances of dissections of the brains 
. of idiots shew that the evil consists in such an 

pecan of the hemispheres and their con- 
) voluted surface as must have materially pre- 

vented their proper action. This may have 
begun in intra-uterine life or in infancy. The 
brain of infants at birth is far from being fully 
formed, and that part of it which is imperfectly 
developed is that upon which depends the mani- 
festation of mental actions, namely, the hemi- 
spheres of the brain and of the cerebellum ; the 


} as to the other parts of the encephalon. All the’ 


719 
other parts, which are mostly concerned in phy- 
sical nervous actions, are sufficiently perfect, 
being, however, generally small from the in- 
fluence of the deficiency of the hemispheres. 

Hypertrophy of the brain would occasion 
idiotcy, just as well as atrophy or imperfect 
developement of that organ (agenesie). Well- 
marked cases of idiotcy resulting from the 
former cause are, however, as far as I know, yet 
wanting in medical records. 

When there is a deficiency in any part of the 
cranial wall, a protrusion of a greater or less 
portion of the brain takes place—this consti- 
tutes hernia cerebri or encephalocele. It is in 
point of size proportionate to the size of the 
opening in the cranium. The tumour is co- 
vered externally. by the common integuments, 
and the displaced portion of the brain pushes 
before it the dura mater and the other mem- 
branes of the brain. 

The most frequent situation for hernia cerebri 
is in the occipital region of the head near the 
middle line, and next in point of frequency 
somewhere on the median line, where the bones 
of opposite sides remain for so long a time 
disunited: near the great fontanelle is a fre- 
quent site of a protrusion; sometimes it takes 
place on the side of the skull in the temporal 
region, or at the root of the nose. Such cases, 
however, are rare. 

2. Morbid conditions of the brain —Hy- 
pertrophy.— The examples of hypertrophy 
of the brain which are on record are not 
numerous, and it is difficult to attribute the 
appearances, which are said to indicate this | 
condition, to a mere increase in the nutrition 
of the organ. Adopting the term, however, in 
deference to the high authorities who have ap- 
plied it, it may be stated that the anatomical 
characters of a hypertrophic brain are as fol- 
lows :— 

The brain appears too large for the skull; 
on the removal of the calvaria the dura mater 
seems perfectly tense and filled by the brain ; 
it appears thinner and more transparent than is 
quite normal, and there is no trace of fluid in 
the subarachnoid space. 

The hemispheres are large, and their convo- 
lutions lie closely packed beside each other, 
and flattened. The ventricles of the brain are 
small, exhibiting the same condition as the 
fissures between the convolutions. The surface 
of the arachnoid as well as of the intra-ventri- 
cular eminences is dry or nearly so. 

The substance of the brain is universally 
firm, and cuts somewhat like cartilage ; it is 
exsangueous, the principal accumulation of 
blood being in the pia mater. The colour of 
the grey matter becomes so changed as to be 
scarcely different from the white. 

It is as yet uncertain what is the precise 
change which the brain undergoes in this con- 
dition. We know that there is an increase of 
substance, but whether that be an increase in 
the normal size of the fibres and vesicles of the 
two varieties of nervous matter which are found 
in the brain, or in their number, or whether it 
be a deposition of new material, with or with- 
out increase in the size or number of the ele- 


720 


mentary parts of the organ, has yet to be deter- 
mined by microscopical examination. 

It is most probable that the disease consists 
not merely in an increased, but also in a per- 
verted nutrition, and that new material is depo- 
sited between or in the proper anatomical ele- 
ments of the brain. 

In some instances there is, along with the 
signs of increased nutrition in the brain,evidence 
of a similar condition of the cranial walls. 
The bones of the skull are, in such cases, much 
thicker than usual. In others, however, the 
bones seem to yield under the pressure, from 
within, and they become thin, and more or less 
transparent in parts. 

There appear to be two classes of cases in 
which an hypertrophic state of brain occurs. In 
‘one class the functions are carried on well, and 
the only sign of the morbid change is derived 
from the undue enlargement of the head, which 
becomes almost too large for the body, and too 
heavy for the muscles of the neck to support 
conveniently ; in the other there may or may 
not be enlargement of the head, but there are 
marks of cerebral disturbance in more or less 
dullness of intellect, and in the frequent re- 
currence of epileptic fits. 

Dr. Watson has placed upon record two in- 
stances of this enlargement of the brain’s sub- 
stance which are highly interesting and will 
serve to illustrate the varieties above alluded to. 

One case was that of a young woman et, 19. 
Her countenance was sallow, lips pale. She 
complained of pain in her chest and limbs, of 
great and increasing debility and wasting, and 
of nightly perspirations, and she was subject to 
attacks of epilepsy. She died in a prolonged epi- 
leptic paroxysm. The following appearances 
were observed at the post-mortem examination. 

“ When the surface of the brain was exposed 
by the removal of the skull-cap and dura mater, 
it was observed that the convolutions were re- 
markably flattened, so that the little furrows be- 
tween them were nearly effaced, and the sur- 
face of the arachnoid membrane was perfectly 
dry. These are not very unusual, although 
they are unnatural appearances. I had often 
seen such before; and I ventured to say we 
should find some cause of strong pressure in 
the central part of the brain, effusion of serum 
into the ventricles, or a large extravasation of 
blood. But to my great surprise, and much to 
the discredit of my prophecy, we found nothing 
of the kind. The ventricles were even smaller 
than natural, and contained scarcely any 
moisture. The skull-cap was afterwards exa- 
mined, and the bone was found to be uncom- 
monly thick, dense, and heavy; and its inner 
surface without being rough was very irregular.” 
The state of the bloodvessels of the brain was 
not noticed. It is to be regretted likewise that 
the weight of the brain has not been stated, for 
it is obvious that a gradual and pretty uniform 
diminution of the cranial cavity by the thick- 
ening of the bone might have produced the flat- 
tening and condensation of the brain described. 

A second case recorded by Dr. Watson oc- 
curred in the practice of the late Dr. Sweatman. 
The patient was a little boy two years old; his 


NERVOUS SYSTEM. (Nervous Centres. AnnormaL ANATOMY.) 


head bad been gradually increasing from the 
age of six months until it had become so large 
as to prevent the child from continuing long in 
the upright posture. The boy was active ane 
lively although thin. He never had any cor 
vulsion, but occasionally seemed uneasy, @ 
then would relieve himself by laying his heat 
upon a chair. He had never squinted, no 
was he subject to drowsiness or startings durin 
sleep, and his pupils contracted naturally. H 
appetite was good, and all the animal function 
were properly performed. The head measur 
from ear to ear twelve inches, from the supel 
ciliary ridges to the occipital thirteen inche 
and in circumference twenty-one inches, T 
brain was sound. The convolutions were di 
tinct and retained their shape. The surfaces 
the medullary matter, exposed by differ 
sections, presented very unusual vascularity.* 
In this case the yielding of the cranial wal 
prevented compression of the brain, whilst 
admitted of the growth of the organ withi 
Hence, no doubt, the absence of any sympton 
of compressed or irritated brain. ‘ 
Ilypertrophy of the brain sometimes coe: 
with hydrocephalus, and is congenital, ai 
prevents by the great size of the organ the: 
velopement of the cranial bones. (Otto, I 
kitansky.) Af 
Hypertrophy may affect only particular p 
of the ebony as ths atid thalami, the pons, 
the medulla oblongata, instances of which 
been placed on record. 
Atrophy of the brain—At the advan 
alge: of life we generally meet with mor 
ess of wasting of the brain; resulting fron 
change in the nutrition of that organ whit 
experiences in common with all other org 
and which is only the natural result of the 
gress of age. It is remarkable, however, | 
much more of this senile atrophy is observ 
some individuals than in others. . 
In cases of epilepsy of long standing I 
invariably noticed wasting of the brain, aff 
ing chiefly the convolutions, or sometimes 
corpora striata, optic thalami, &e. The © 
wastes likewise in cases of long-cont 
intemperance, the patient generally dyi 
delirium tremens. In such instances all 
of the brain waste, but the convolutions 
rience the most marked change. 7m 
The following are the: marks of an atre 
state of brain. There is a considerable qt 
of fluid in the subarachnoid cavity, indicat 
increase in the interval between the sui 
the brain and the interior of the skt 
brain has a shrunk appearance. Its 
feels firm, and in cutting the knife grates: 
it as in cutting cartilage. In point o 
the grey matter is frequently extrem: 
and scarcely to be distinguished from th 
cent white substance ; in some instance 
ever, it is of a dark brownish hue. — 
cases the layer of grey matter which Cov 
convolution is much less deep than is nati 
The convolutions are evidently shrunk 
the sulci between them have greatly ine 


Ar 


* Lectures on the Practice of Physic, 


“ 


NERVOUS SYSTEM. (Nervous Centres. Apnormat Anatomy.) 


in width. The white substance of the brain 

has increased in density, and in the transverse 

section several vessels are cut across, the sec- 
tion of which occasions numerous bloody 

— upon the surface of the centrum ovale. 

he corpora striata, optic thalami, pons, and 
medulla oblongataare all obviously shrunk and 
firm in consistence. 

In several instances of persons long bed- 
ridden, 1 have noticed a shrunk state of the 
cerebellum, with or without atrophy of the 
cerebrum. The layers of white matter in the 
cerebellar laminz look particularly small; and 
in the section the white layer seems to shrink in 
within the fold of grey matter in which it is 
involved. 

As a constant accompaniment of the wasted 
brain, we find a more or less opaque condition 
of the arachnoid membrane, with considerably 
enlarged Pacchionian bodies. The ventricles 
of the brain, too, are generally wide and con- 

_ tain a good deal of fluid. There is also very 
frequently a diseased state of arteries, atheroma- 
_ tous or ossific deposits being scattered freely 
amongst those, which form the circle of Willis, 
"and their principal branches. 
___ Atrophy of particular parts of the brain is of 
_ not unfrequent occurrence, either in cases where 
_ particular nerves are atrophied, as the optic 
_ nerve, inducing atrophy of the opposite optic 
tract or of that of the same side, and of the 
_ quadrigeminal bodies on the side of the wasted 
_ tract ; or where from previous disease of a por- 
_ tion of the brain the remainder of that part has 
| wasted—as wasting of thecorpus striatum from 
| the previous existence of a small clot in it, or of 
a red softening. 
| _ Softening. — One of the most common 
changes of structure in the brain is softening. 
| This is of two kinds, namely, white softening, 
or that without discoloration, and red softening, 
| or that with discoloration. 
_ _ White softening. —The anatomical characters 
of the true white softening may be thus de- 
scribed. The diseased portion has diminished 
considerably in its consistence ; if it be gently 
Tubbed with the edge of a knife it becomes 
Obviously disturbed by an amount of friction 
which would produce no change upon the sur- 
face of a healthy brain; a stream of water di- 
Tected upon it, even with slight force, is suffi- 
tient to break it up and separate as well as 
‘Tupture its constituent fibres, while a similar 

Stream directed against a neighbouring healthy 
_— produces little or no effect upon it. 
‘When examined by the microscope, its consti- 
‘tuent fibres appear to have undergone no change 
but that of consistence; they exhibit vari- 
Cosities, more numerous than usual, nor can 
‘any products of inflammation, or any other ab- 
Normal material, be detected among them. The 
oodvessels are empty and pale. The colour 
is very commonly that of cream, sometimes a 
little more yellow. 

This form of softening occurs chiefly in old 
persons, in whom the arteries of the brain have 
een more or less ossified, or in whom the 
ssels leading to the seat of softening have 
been so diseased as materially to interrupt or 
VOL, III. 


720a 


diminish the quantity of blood flowing to the 
part. It has occurred after ligature of the 
common carotid artery, as must be inferred 
from the numerous cases of hemiplegic para- 
lysis after this operation, on the side opposite to 
that of the tied artery; and I have myself re- 


_corded a remarkable example in which it was 


produced throughout nearly the whole hemi- 
sphere of the brain by the plugging of the com- 
mon carotid artery by a dissecting aneurism.* 

Any condition of the arteries of the brain, or 
of the general system, which may impair the 
nutrition of the brain, is favourable to the pro- 
duction of this form of softening. I have seen 
instances of it after inveterate contamination 
of the system by lead, in house-painters, who 
have had epileptic seizures before death, chemi- 
cal examination shewing that the nervous mat- 
ter of the brain contained lead in considerable 
quantity. It also occurs in persons dead with 
cerebral symptoms, epilepsy, coma, &c., in 
Bright’s disease of the kidneys. 

This softening frequently surrounds apoplec- 
tic clots, and in such cases is most probably 
the precursor of the apoplectic effusion. Fre- 
quently small apoplexies are found throughout 
a patch of softening of this kind, and sometimes 
the effused blood is infiltrated throughout the 
softened part to a great extent, and puts on an 
appearance which has been likened by Rostan 
and many others to one of the ecchymosed spots 
which are seen in scurvy. 

A colourless softening is found in hydroce- 
phaloid brains. This is probably due to an 
arrest in the nutrition of the organ, in conse- 
quence of which that condition of it which be- 
longs to infancy (when a much larger quantity 
of water enters into its composition than in the 
later periods of life, and when the brain-sub- 
stance is naturally very soft) becomes unduly 
developed, and water accumulates in the sub- 
stance as well as in the cavities of the brain. 
The softening under these circumstances is 
generally seen most distinctly in the thin lamellar 
portions of the brain, such as the corpus cal- 
losum, the fornix, the Vieussenian valve, the 
anterior and middle commissures, the septum 
lucidum. These parts are so soft that unless 
the greatest care and gentleness are used in the 
removal of the brain they give way. The 
softening is not limited to these parts, although 
greatest in them; it is general throughout the 
brain. When, however, the hydrocephalic 
state has been very chronic, the substance of 
the hemispheres becomes condensed by the 
pressure from within the ventricles, and the 
water having thus been pressed out of it, it 
appears of a natural consistence, or even more 
dense than natural. ; 

In all the cases of general paralysis of the 
insane which I have examined, the consistence 
of the brain generally bas been considerably 
less than natural. There have also been marks 
of chronic disease of the arachnoid in various 
patches of opacity, which I am disposed to 
view rather as a deposit from an abnormal 
blood than as the result of what is called 


* Med. Chir. Trans, vol. xxvii- 
Q 7 ** 


720B 


chronic inflammation. The softened condition 
of the brain is doubtless due to a similar cause, 
the blood yielding vitiated materials for the 
nutrition of the organ. In brains of this de- 
scription the dilated and congested state of the 
veins, and the enlarged and lax condition of the 
arteries, abundantly demonstrate how sluggish 
had been the force by which the circulation is 
maintained in the capillaries, that force of at- 
traction between the blood and the nervous 
matter, by which more than by any other means 
active nutrition is maintained. 

The parts in which softening when partial is 
apt to occur in the brain may be thus enume- 
rated according to the order of their frequency 
—the fornix and septum lucidum, the corpus 
striatum and optic 1 a the mesocephale, 
the corpus callosum and other transverse com- 
missures, the hemispheres of the brain, the 
cerebellum, the medulla oblongata. 

Of the inflammatory or red softening. — 
Another form of softening of less frequent oc- 
currence than that just described possesses very 
distinctive characters. It is generally pretty 
circumscribed in extent, of a diffused redness, 
most commonly of a bright hue; the consistence 
of the part is much diminished, and it readily 
breaks up under the stream of water. Nerve 
tubes are found in it, more or less varicose and 
friable, also red particles of the blood, and many 
of those large nucleated cells commonly known 
as exudation corpuscles, within which an active 
molecular motion may be often seen. 

The red colour of this form of softening is 
due partly to the injection of the bloodvessels, 
and partly to the extravasation of the red parti- 
cles of the blood throughout the softened part. 
Sometimes the red colour is absent, although 
the lesién is essentially the same. In such cases 
the colour may be yellowish and due to the 
presence of a less injection of the bloodvessels 
and a slighter extravasation of the colouring 
matter of the blood. Dr. Bennet states that he 
has found exudation corpuscles in a softening of 
a brilliant white colour, a fact which seems to 
indicate that the products of inflammation may 
be present without discoloration, and that all 
instances of white softening ought not to be 
considered non-inflammatory. 

The researches of Dr. J. H. Bennett, of Edin- 
burgh, are among the most important contribu- 
tions to the morbid anatomy of the brain of late 
years. I think he has clearly established that 
the great characteristic of inflammatory soften- 
ing is the presence of exudation corpuscles 
about the minute vessels, and among the ele- 
ments of the softened cerebral tissue. This is in 
in the vast majority of instances accompanied 
with discoloration, which sometimes is due 
solely to the dark colour of the exudation cor- 
puscles themselves. When these corpuscles 
are not present, and especially when the soft- 
ened portion of brain is free from colour, then 
we must regard the lesion as non-inflammatory, 
the result of imperfect nutrition, or as produced 
by physical causes coming into operation shortly 
before or after death. As the same process of 
softening which involves the cerebral structure 
often extends to the minute vessels, small extra- 


NERVOUS SYSTEM. (Nervous Centres. Apnormat Anatomy.) 


vasations, constituting the capillary apoplexy of 
Cruveilhier, frequently occur where no indica- 
tions of inflammation exist ; in such instances the 
softening, although non-inflammatory, may be 
of a yellow colour from the effused colourin 
matter of the blood. _, 
1 cannot agree with Dr. Bennett in regardi 
white softenings as generally post mortem, ax 
the result of maceration in serum. The softer 
ing of very thin parts, such as the fornix an 
septum lucidum, no doubt, is frequently of # 
character. But I have seen many instances 
white softening of other parts of the bra 
which were not exposed to the physical ec 
tions calculated to produce such a change 
consistence. “g 
Inflammatory softening occurs most f 
quently in parts which are near the great vast 
lar surface of the pia mater; the convol 
and the white matter of the centrum o 
corpus striatum, and the optic thalamus are t 
most common situations of this lesion. — 
thirty-three cases collected by Durand-Fare 
the softening was situated in the convolution: 
thirty-one, and in nine of them the convolutic 
were the sole seat of softening. The fe 
table will illustrate the statement above mai 
it represents the results of fifty-three cases: 
lected from different sources, ! 
Convolutions and white substance ...... 
Convolutions alone .........eeeeseeene 
White substance alone .......+sseeeee 
Corpus striatum and optic thalamus. ..... 
Corpus striatum alone ........eeeeeees 
Optic thalamusalone .... 
Pons Varolii .. 
Crus cerebri .. 0... 00.sco00 6eWNine 
oye apes eer. ee eeeee 
Walls of the ventricles, septum ...+.+-.. 
Fornix teeter reese ee ee ee 
Cerebellum o0-0 ceecctocces esses enn 
Suppuration—From what has been sta 
the previous paragraphs it is plain that the 
important sign of inflammation of the br 
is red softening. Infiltration of pus is 
Dr. Bennett states that in no single instai 
humerous examinations made by hii 
softening be traced to the presence or in 
of pus. This is a direct refutation of 
mand’s assertion that this form of softening 
its colour to the infiltration of pus. Pus, 
ever, is sometimes collected into a cavity ii 
brain, forming an abscess. An exca) at 
greater or less size is formed in the substa 
the brain, and this is lined by a yellowish’ 
braniform layer, which resembles either lyt 
an expanded form, or the purulent ma’ 
in a less liquid form, compressed into th 
of a membrane by the accumulated liquit 
Pus in the brain is of slow formatio 
has often become collected in consi 
quantity before it betokens its presence 
symptoms. Sometimes we have the: 
nity of examining it before it has acquin 
yellow colour and oily consistence of lau 
pus. In this stage it may be mistaken f r 
malignant formation ; it is whitish, semi-st 
and sometimes mixed with streaks of DI 
Its true nature may be recognized by m 
t 


& 


ser eee weet ete 


NERVOUS SYSTEM. (Nervous Cenrres. ABNoRMAL ‘ANATOMY.) 


scopical examination, which discloses the cha- 
racteristic pus globules with little or no liquor 
puris, and by mixing some of it with liquor 
potasse, when it becomes converted into a 
viscid material resembling white of egg. 

Pus in the brain is frequently of a green 
colour, and very commonly exhales an ex- 

_ tremely fetid odour. 

The cerebral matter around the purulent col- 
lection is either somewhat indurated or it is in 
an edematous state, or in one of inflammatory 
softening. When in this latter state the ab- 
Scess is not so defined; the softened cerebral 
Matter around it is broken up and mingled 
with pus; this, however, is rare. 

An abscess of the brain may open upon the 
exterior and so evacuate its contents. This 

_ May occur either into the nose through the 
_ cribriform plate, or into the tympanic cavity or 
the external auditory meatus. It is sometimes 
_ difficult to determine whether inflammatory dis- 
_ ease had arisen in the ear, extending to the brain 
_ and exciting the formation of abscess, or whether 
the abscess already formed in the brain had not 
burst into the ear. A cerebral abscess may 
_ empty itself into either of the ventricles. 
} Abscesses are most commonly found in one 
of the cerebral hemispheres, or in the cerebel- 
lum; they are very rarely met with in other 
‘parts of the brain. Sometimes collections of 
_ pus form upon the surface of the brain between 
_ the pia mater and the grey matter of the cere- 
bral convolutions. And pus or puriform mat- 
ter is frequently found between the arachnoid 
and pia mater, where there has been inflamma- 
Li ion of either or of both those membranes. This 
is most common in children. 
 Hyperemia and Anemia.—An organ so 
largely supplied with blood as the brain, is 
liable to variations in the amount of that sup- 
ly under various circumstances. It is unne- 
@essary to recapitulate here the arguments 
‘already adduced to show that the opinions of 
those who maintain that the quantity of blood 
in the brain cannot vary, is erroneous. Indeed 
it is much to be wondered at how persons 
eee to inspect the brain post mortem 
‘ould have adopted such a doctrine. 
ba the greatest degree of hyperemia of the 


in, all the vessels of the organ are full; 
the veins which lie between the convolu- 
tions are full; the vessels of the pia mater are 
fally injected. Often there are diffused extra- 
vasations through the areole of this membrane, 
Causing a red blotch over more or less of the 
surface of the brain. The grey matter of the 
convolutions is extremely dark in colour, and 
if a small portion of it be examined under the 
microscope the minute vessels which abound in 
it are found distended with blood. On the sur- 
}face of a section of the white matter numerous 
jbloody points are found, being the orifices of 
jvessels cut across. These points are sometimes 
jvery large; sometimes they are surrounded by 
jsmall extravasations of blood, proceeding from 
he rupture of some small vessel. In this state 
of the brain the vessels of the choroid plexus 
and of the velum interpositum are very full, 
jand also those of the dura mater. 


720c 


Cerebral hyperemia is generally caused by 
some obstruction to the free return of the blood 
to the right side of the heart. Hence we see it 
always after death by asphyxia, and very com- 
monly in cases of disease of the heart. When 
the breathing has been seriously impeded just 
before death, there will always be considerable 
hyperemia of the brain. Hence in judging of 
the nature of a cerebral hyperemia, the anato- 
mist may be materially assisted in coming to a 
correct conclusion if he can ascertain the cause 
of death and the symptoms immediately pre- 
ceding it; a fact which clearly denotes how 
little is the value of mere dissection of morbid 
parts, unassociated with some knowledge of the 
symptoms manifested during life. 

In the bodies of persons dead of epilepsy, 
during or immediately after the epileptic fit, 
there is always cerebral hyperemia. In these 
cases the hyperemia is due to the retardation 
and obstruction of the venous circulation, occa- 
sioned by the convulsive struggles of the pa- 
tient and the resulting impediment to respira- 
tion. It may be caused, likewise, by an in- 
creased attraction of blood to the organ taking 
place at the moment of the occurrence of the 
fit. For the same reason, whenever death is 
ushered in by convulsions, the brain will be 
found in a state of congestion, the amount of 
which will vary with the quantity of blood in 
the body. Whatever may be the condition of 
the brain prior to the epileptic paroxysm, it is 
always in a more or less congested state during 
and immediately after it. The too prevalent 
notion that cerebral congestion is the cause of 
the epileptic paroxysm has but little foundation, 
while there is abundant evidence to prove that 
the epileptic paroxysm may give rise to cerebral 
congestion. It is well known that animals 
bled to death die in convulsions; and many 
cases of puerperal convulsions are clearly 
caused by excessive loss of blood resulting 
from parturition. 

Hyperemia of the brain is frequently found 
after death from depressing and exhausting 
maladies, typhus fever, &c., all diseases of the 
low typhoid type, and in cases of general 
paralysis. The powers by which the circulation 
is carried on in the vessels are greatly depressed, 
and the blood accumulates in them, especially 
in the veins. ' 

I know of no means of distinguishing active 
from passive hyperemia, excepting probably 
that the capillaries may be more injected in the 
former, and the veins more filled in the latter. 
To enable the anatomist to make a correct dis- 
tinction, the detail of symptoms during life must 
be called to his assistance. , 

Aneémia.—This condition, the opposite to 
that last considered, is very common. It is 
frequently met with in children, and in such 
cases is accompanied with more or less of 
serous fluid, either in the subarachnoid space 
or within the ventricles. The brain of the ill- 
nourished strumous child is generally an anemic 
brain. 

Anemia of the brain occurs when death has 
been caused, whether quickly or gradually, by 
the loss of blood, It is also present when the 


720D 


heart, oppressed by some disease affecting its 
own structure, fails to propel the blood with its 
proper force to the brain. The delirium which 
comes on in rheumatic fever, when pericarditis 
or endocarditis commences, is indicative of an 
anemic state of the brain; and in some in- 
stances in which I have had the opportunity of 
examining the brain, when the patient died in 
this delirium, I have found marked and obvious 
anemia of this organ. 

Anemia of the brain, according to my ob- 
servation, is of two kinds, general and partial. 
In the former, pallor prevails throughout the 
brain. This is met with, as before mentioned, 
in ill-nourished children ; and it is also present 
to a remarkable degree in persons, house- 
painters and others, who have largely imbibed 
the poison of lead, as if the presence of that 
= interfered greatly with the process of 

wematosis. Partial anemia is where the defi- 
ciency of blood is observed chiefly in the grey 
matter. I have frequently seen the grey matter 
of the convolutions perfectly bloodless, and the 
white matter of the hemisphere covered with 
bloody points of congested veins. This is the 
condition generally met with after death from 
rheumatic or gouty delirium. 

When the brain is very anemic a consider- 
able quantity of fluid is generally found beneath 
the arachnoid membrane, with or without a 
small quantity in the ventricles ; or more rarely, 
a good deal of fluid in the ventricles, with 
little or no subarachnoid fluid. 

Of cerebral hemorrhage. — Effused blood 
from one or more ruptured bloodvessels is 
found upon the surface, in the substance, or in 
the ventricles of the brain. Effusion of blood 
in any or all of these situations constitutes the 
most common form of cerebral apoplexy. 

The blood is sometimes effused simply upon 
the surface of the brain; it is diffused beneath 
the arachnoid membrane, and even under the 
pia mater, raising up that membrane and sepa- 
rating it from its connection with the cerebral 
substance. Not unfrequently such a diffusion 
of blood beneath the pia mater is connected 
with an internal extravasation which has made 
its way to the surface either through broken down 
cerebral substance or from the ventricles. 

A recent apoplexy in the substance of the 
brain is no more than a dark clot of blood, like 
a mass of black currant jelly, filling a cavity 
which it has formed for itself in the cerebral 
substance. Such is the appearance when the 
examination has been made a few hours or even 
a few days after the qa fit. If the 
patient survive this period, we find evidence of 
changes in the clot and in the surrounding 
cerebral substance. These changes vary ac- 
cording to the condition of the brain prior to 
the apoplectic effusion. 

If the brain has been quite healthy up to the 
occurrence of the rupture, a condition which is 
extremely rare, then the changes towards cica- 
trization take place quickly; the serum of the 
clot becomes absorbed ; the torn brain-substance 
around the clot contracts; the solid matter of 
the clot assumes a reddish instead of a black 
hue; it gradually diminishes in quantity, and 


‘ 


NERVOUS SYSTEM. (Nervous Centres. AsnonmaL Anatomy.) 


the brain-substance, not contracting to the same 
extent as the clot has done, a cavity remains, 
which contains serum, and more or of the 
remnant of the clot. The cerebral substance — 
forming the wall of this cavity has a yellowish — 
colour, somewhat of the same hue as that which — 
is seen after extravasated blood in the subcuta~— 
neous tissue, and it is denser than is natural. 
After the lapse of more time the cavity con- 
tracts, and nothing remains but a spot of dis- 
coloured and somewhat indurated cerebral 
substance. When the apoplectic clot has been 
of large size, and has occasioned an extensiv 
solution of continuity, the contraction of the 
surrounding substance is not sufficient to ¢ 
terate the cavity, which in such instances 
occupied by a soft, loose, areolar tissue, infil- 
trated with fluid. In other cases the cavity is 
lined by a distinct membrane and is filled with 
fluid, forming a true cyst. Cruveilhier affirm 
that the most frequent sequel to the apoplecti 
clot is the indurated and discoloured 
cerebral substance; next in frequency is t 
cavity with the loose areolar tissue ; and last, the 
cavity lined by a membrane or the serous cyst. 
The morbid condition which surrounds the 
apoplectic effusion is generally that of cole 
less softening. This state doubtless precede 
the rupture which gave rise to the hemo 
Sometimes, however, red softening exten 
around it more or less; this generally follor 
the effusion. The existence of either of the 
morbid states is very unfavourable to the 
traction and cicatrisation of the pte ans cy 
It frequently happens that in the cereb 
substance around an apoplectic clot we 
very numerous small points of effused blo 
sometimes accompanied by minute streaks 
lowing the direction of the cerebral f 
This constitutes what is called capillary 
plery. Sometimes this is the only mark 
appearance present, and no large clot has b 
formed. This occurs not uncommonly in 
plexy affecting the medulla oblongata and + 
mesocephale. When many such minute ef 
sions take place very near to each other, il 
easy to understand how by their coalition t 
may form a large apoplectic clot; and — 
most probable that large effusions gen 
arise in this way, not from the ru of 
or even of a few vessels, but 
numerous minute ones. 
The size of the pata clot varies e¢ 
derably (excluding the cases of capillary 
lexy in which no coalition has taken 7 
rom the size of a millet seed to that of 
fist, the clot sometimes breaking up the 
nervous matter of the hemisphere with 1 
rounding grey layer, and completely ocet 
its interior. There is no part of the 
so favourable for the occurrence of a” 
apoplectic clot as the hemisphere, beea 
sofiness and magnitude afford the least resis 
to the flux of blood. : 
Apoplectic effusions occur most frequt 
in the hemispheres of the brain, affecting 
the corpora striata or optic thalami, and sf 
ing from them into the white substance ¢ 
hemisphere, or sometimes breaking up 


rh4 


NERVOUS SYSTEM. (Nervous Cenrres. Apynormat Anatomy.) 


substance and passing into the lateral ventricle 
of one side, and thence through the foramen of 
Monro into the lateral ventricle of the other 
side. The convolutions are the next most 
frequent seat of apoplexy, and after them 
either hemisphere of the cerebellum, and either 
crus cerebri. The pons, crus cerebri, crus 
cerebelli, are much less frequently affected by 
hemorrhage. These parts are denser in struc- 
ture and less freely supplied with blood, and, 
therefore, less prone to apoplectic effusion than 
those before mentioned. 

Cancer of the brain.—Cancer is occasion- 
ally, although very rarely, found affecting some 
part of the encephalon; most frequently it ex- 
tends into some portion of it from the meninges. 

Andral has given a good history of this 
diseased condition, founded upon the analysis 
of forty-three cases.* Of these, the hemispheres 
were the seat of the cancer in thirty-one, in five 
the cerebellum was affected, once the meso- 
cephale, three times the pituitary body, and 
_ three times the spinal cord. 

The number and size of the cancerous tu- 
_ mors are very various. The cancer may begin 
in the meninges, and attack the bone on the 
_ one hand and the brain on the other ; or it may 
be first developed in the substance of the 
_ hemisphere. When the disease is superficial 
_ the cranial walls may become extensively im- 
plicated. I have seen the greater part of the 
parietal bone implicated in a cancerous tumor. 
_Andral mentions a case in which the frontal 
_ and temporal bones were completely destroyed, 
and another in which the cancer, developed at 
the inferior surface of the brain, passed out 
through the foramina of the base of the cranium. 
Cerebral cancer is most frequently of the 
soft or fungoid kind, but sometimes it occurs 
in the form of small hard tumours, deposited 
in various parts of the brain, and separated 
| from the surrounding cerebral substance by a 
distinct membrane or capsule. Frequently it 
appears to be primary, or at least there seems 
no evident connection between it and any other 
“eancerous deposit situate elsewhere. Of An- 
dral’s forty cases only ten were associated with 
neer in other situations. 
Tubercle of the brain. —The anatomical 
‘characters of tubercle of the brain are very 
“definite. The colour is yellow, the more con- 
picuous by reason of the white or grey of the 
Surrounding cerebral texture; the consistence 
¢ . Its section affords a smooth and clean 
rface, but if broken up by the point of the 
nife, its texture appears to be minutely granu- 
ar. Sometimes this tubercular matter may be 
icked out of a very distinct capsule. The 
tubercles vary very much in size, sometimes as 
Small as a millet seed, frequently the size of a 
- i pea, or even as large as a filbert or a wal- 
nut, rarely much larger. 
The parts of the brain most frequently af- 
fected by tubercle are the cerebral hemispheres 
jand those of the cerebellum. The mesocephale 
be the medulla oblongata are rarely the seat 
of it. It is generally situated near the surface 


_ 


* Clin. Med., t. v., p. 633. 


72058 


or near some process of pia mater; conse- 
quently it is most commonly met with in the 
grey matter of the brain. 

Cerebral tubercle excites inflammation in the 
surrounding brain substance, which is then 
found in the state of red softening ; and some- 
times suppuration may be established, the 
tubercular matter being more or less broken 
down and diffused in the pus. It is thus that 
tubercles of the brain prove so destructive to 
life. They may remain quiescent and unde- 
tected and even unsuspected until someirritation, 
often propagated from the periphery, excites 
surrounding inflammation, which by reason of 
the presence of the foreign matter of the tuber- 
cle, is kept up, and refuses to yield to any 
measure of treatment. Cerebral tubercle exhi- 
bits no spontaneous tendency to soften, nor 
does it frequently degenerate into earthy con- 
cretions. 

Enitozoa—The entozoa found in the brain 
are the cysticercus cellulose, and the acephalo- 
cyst, with its denizen the echinococcus. Like 
tubercles, these are always placed near the vas- 
cular surface, and they may be said more 
properly to infest the pia mater than the sub- 
stance of the brain; by their growth, however, 
they encroach more or less upon it. The ani- 
mals sometimes die, and their containing cysts 
shrink up and become converted into earthy 
matter, forming calcareous tumors of variable 
size in the substance or on the surface of the 
brain. 

Morbid states of the ventricles of the brain. 
—The diseased conditions of the ventricles of 
the brain are referable, first, to the cavities 
themselves ; secondly, to their contents ; thirdly, 
to their lining membrane and to the choroid 
plexus. 

The most frequent morbid condition of the 
ventricles is a state of dilatation, which is always 
passive, being produced by the accumulation 
of water in it. This retention of fluid within 
these cavities appears to be a true dropsy, and 
is in most cases connected with an external 
meningeal inflammation in a strumous constitu- 
tion. It is in children that we most frequently 
meet with this dilatation of the ventricles, and 
in them it constitutes the disease called hydro- 
cephalus internus. In adults it occurs some- 
times, but extremely rarely. In the former, 
when the disease is of a very chronic nature, 
the fluid will accumulate to a very great extent, 
and enlarge not only the ventricles but the 
cranium itself to an enormous size. 

In persons in advanced age, in lunatics of 
long standing, and in old epileptics, we fre- 
quently see a dilated state of the ventricles 
from distension by water. This is always asso- 
ciated with a wasted state of the brain; this 
fluid, as well as the external fluid, serving to 
fill up the space from which the cerebral matter 
had receded. 

In all these cases the ventricles which expe- 
rience dilatation are the lateral ventricles, the 
third and the fourth. Ina very few instances the 
fifth ventricle has been found similarly dilated. 

The fluid contained in the ventricles is gene- 
rally a clear straw-coloured serum, varying in 


720F 


uantity from half an ounce to several ounces. 
metimes it is milky, and has shreds of lymph 
floating in it; at other times it may be sero- 
purulent, but this is extremely rare, and only 
occurs when the lining membrane has been the 
seat of acute inflammation and of inflammatory 


i 

e lining membrane of the ventricles, which 
in health is of extreme tenuity, becomes fre- 
quently thickened and partially opaque in chro- 
nic disease of the brain, where the ventricles 
are more or less dilated. In acute disease 
lymph is sometimes deposited upon it in large 
and loose flakes, easily removeable from it. 
And sometimes there is a deposit all over its 
surface of a fine granular semitransparent 
lymph, which gives to the internal surface of 
the membrane the appearance of an extremely 
fine and delicate reticulation. 

As the choroid plexus are covered by a pro- 
longation of the membrane of the ventricles, 
their investment is apt to participate in any 
morbid process which may take place in the 
former. In acute affections it will be covered 
with lymph, as the membrane lining the ven- 
tricles is elsewhere. When much water has 
been accumulated in the ventricles, the choroid 
plexus are pushed against their floor, flattened, 
and rendered pale by maceration. On the other 
hand, whatever causes much vascular congestion 
in the vessels of the brain will produce the same 
effect in a marked manner upon those of the 
choroid plexus. 

Earthy concretions are sometimes found in 
the choroid plexus, which may probably be an 
augmentation of the crystalline matter found in 
them in their healthy state. These appear to 
agg chiefly of phosphate and carbonate of 
ime. 

A very common appearance found in the 
choroid plexus consists in certain vesicles, very 
variable both in size and number. These are 
simple cysts, containing a straw-coloured fluid. 
Formerly they used to be regarded as hydatids, 
but they are now known to be essentially dis- 
tinct from them. They occur frequently in 
brains which exhibit no other departure from 
the normal condition. Of their precise nature, 
and of their cause and mode of formation, 
nothing is known; and as they are seldom of 
a large size they are not likely so to disturb 
the functions of the brain as to give rise to 
symptoms by which their presence could be 
detected. 

On the pseudo-morbid appearances of the 
nervous centres and their coverings——The ac- 
tual indications afforded by any departure from 
- the normal physical condition of the nervous 
centres after death are so important to the attain- 
ment of right conclusions respecting the patho- 
logy of the nervous system, that it behoves the 
anatomist to take fully into account all those 
circumstances which may give rise to appear- 
ances in the cerebro-spinal centres or their 
membranes simulating disease. Such appear- 
ances, not inappropriately termed pseudo-mor- 
bid, occur in the greater or less vascular fulness 
of the membranes and of the centres themselves, 
in the variations in the quantity of fluid around 


NERVOUS SYSTEM. (Nervous Cenrres. Asnormat Anatomy.) 


or within the brain, or around the spinal cord, — 
and in the consistence of the nervous matter, 
The circumstances which affect the amount 
of blood in the vessels are the mode of death 
and the position in which the head has beer 
laid after death. Death by asphyxia, wheth 
rapid or gradual, favours the accumulation ¢ 
blood in the vessels of the brain. Convulsion 
preceding death likewise cause turgescence o 
these vessels. Any impediment to the cireu 
tion through the heart has the same effect, bi 
to the greatest degree when the impediment 
much felt on the right side of the heart. 
The position of the head after death affe 
the vascular fulness by favouring the accumu 
tion of blood in the most dependent pa 
From this circumstance and from the custo 
of placing bodies on the back, we always fi 
the posterior lobes of the cerebral hemisphere 
and the cerebellum most filled with blood, at 
it is on this account that the straight and oth 
posterior sinuses of the dura mater are 
filled with blood. a 
The quantity of fluid around the brain at 
spinal cord is least in the young and greatest 
the old: it is influenced by the bulk of 
brain or spinal cord, sometimes disappearin 
entirely when the brain is so large as to fill @ 
cranial cavity ; it is inversely as the quantity 
blood, and therefore is considerable in ¢ 
of anemic brain, unless the bulk of the org 
have increased from some other cause. Sk 
deaths from chronic disease favour the act 
mulation of this fluid by diminishing the sup 
of blood to the brain. In phthisis and c 
lingering maladies there is almost always a 
siderable amount of subarachnoid fluid. 7 
practitioner should bear in mind that the 
sence of subarachnoid fluid is always abnorr 
and is in general due to an enlargement of 
brain from hyperemia or from some other eat 
Softening of the nervous matter n 
pseudo-morbid. The spinal cord soften 
soon after death; but if examined 
twenty-four hours it exhibits more densi 
the brain. With the advance of decompos 
the cord becomes extremely soft and alt 
diffuent. In the brain the pseudo-m 
softening is colourless, and may be re 
mistaken for disease. That the brain is 
prone to imbibe fluids is shown by Dr. Pi 
son’s experiments. The brains of sheep 
allowed to remain for a certain nun 
hours in a given quantity of water, which 
rapidly absorbed. The weight of the b 
was increased proportionally to the quan 
water which had been imbibed, and the 
most exposed to the fluid were found in i 
ened state. In one instance the brain w 
rived of its membranes on one side, an 
ours after death it was immersed in a mi 
composed of equal parts of ox-bile and ¥ 
It weighed three ounces, seven drams, and 
grains when prepared for experiment. A 
remaining in the mixture thirty-six hour 
weighed eight ounces and one dram.* Th 


* On the pseudo-morbid appearances of 
meee Ed. Med. and Surg. Journ. for 
vol, . ad 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


experiments show that the brain readily imbibes 
fluid, and that parts in the vicinity of and 
bathed in fluid may present a pseudo-morbid 
softening from such imbibition. The fact, 
thus ascertained, serves to account for the 
more frequent occurrence of softening in the 
fornix and septum lucidum than in other 
parts of the brain. It is obvious that pseudo- 

morbid softening of this kind would occur 
only in parts within the ventricle or in the 
cerebral substance forming their walls, or 
on the surface of the brain itself, and that it 
is less likely to be limited to one side than the 
morbid softening. Now and then, however, in 
cases of general anasarca, where the blood is 
in a very watery condition and much fluid is 
effused, the brain exhibits a softened state from 
the imbibition of this fluid. 

ABNORMAL ANATOMY OF NERVES.—Certain 
nerves are sometimes absent, from a defect in 
the developement of the organ to which they 
eraesoted 5 as the optic nerve, or the olfac- 
tory, when their respective organs are wanting. 

_ The non-developement of the eye will also 
cause a non-developement of the fourth pair 
_and the other orbital nerves which influence the 
movements of the eyeball. 


Inflammation of a nerve rarely occurs idiopa- 
_thically or primarily. Occurring from what- 
_ ever cause, it would be distinguished by hyper- 
xmnia, enlargement, and by deposit of more or 
less of lymph or pus. In the acute inflam- 
‘mation the nerve would be softened ; but in the 
| chronic it would become indurated. Abscess 
_ of a nerve is of very rare occurrence. 
Inflammatory affections of nerves occur chiefly 
im connexion with rheumatic or gouty states of 
the system. Sciatica is, no doubt, an in- 
lammatory affection of the sciatic nerve of the 
“gouty kind. In lumbago probably the mus- 

cular nerves of the lumbar muscles are similarly 
fected. 
| Atrophy is a condition into which nerves 
may fall from disuse or from pressure. In it 
the nerve-fibres shrink, their central axis wastes, 
and in extreme cases disappears entirely, the 
tubular membrane becoming plicated and as- 
Suming the characters of fibrous tissue. The 
herve experiences a great diminution in size, 
‘and the wasting is obvious to the naked eye. 
Hypertrophy.— Whether a nerve becomes 
enlarged when more work is thrown upon it, as 
a muscle does, is as yet quite uncertain. I 
am disposed to think that the nerve-fibres may 
acquire some increase of size; but it seems 
to me impossible that they should become more 
humerous. ‘The number of nerve-fibres in in- 
dual nerves, as that of muscular fibres in 
Muscles, is probably determined at their pri- 
mary developement,* and they undergo no 
change but that of length and thickness subse- 
quently. It would not be difficult, by destroy- 
ing the office of the vagus nerve on one side, 
jto ascertain whether, after the lapse of some 


* A similar law probably prevails with other tis- 
ues, namely, that the number of their proximate 
Plements is determined at primary developement, 
And that in subsequent growth these elements may 

herease in bulk but not in number. 


The morbid states of nerves are few and rare. . 


720G 


time, the other, upon which its function would 
devolve, acquired any increase in the size of its 
nerve-fibres. 

Certain gangliform tumours are formed upon 
nerves, to which the term neuroma has been 
applied. They consist of areolar tissue and of 
nerve-fibres, and seem to be formed by an 
increased developement of the areolar tissue 
between the nerve-fibres. These tumours vary 
considerably in size and number; sometimes 
they are not larger than a filbert or a gooseberry 
sometimes as large as a walnut. In genera 
they are few and limited to one nerve, and their 
size is proportionate to that of the nerve with 
which they are connected. In a few rare cases 
tumours of this kind have been found in im- 
mense numbers scattered over the whole cere- 


bro-spinal system. 
(R. B. Todd. ) 


NERVOUS SYSTEM, Puystotocy or 
THE.—In inquiring into the physiology of the 
nervous system, the first step is to determine 
the vital endowments of nerves and of nervous 
centres. 

When a nerve is laid bare in a living animal, 
and a mechanical or electrical stimulus is ap- 
plied to it, we do not find as in muscle that a 
visible change in the nerve takes place; on the 
contrary, the nerve seems to be uninfluenced 
by the applied stimulus, and the evidence we 
have to the contrary is derived from the con- 
traction of certain muscles, if the nerve be 
muscular, or from indications of pain, if it be 
a nerve of common sensation. 

We infer, then, from the contraction of the 
muscle in the one case, or from the affection of 
the mind in the other, that the application of 
the stimulus has wrought a change in the 
nerve, which, however, is of such a nature as 
not to be discerned by any means of observation 
within our reach. We get, however, excellent 
proof of the excitation of the change in the 
nerve, from the fact that when a ligature is ap- 
plied to a nerve sufficiently tight to produce a 
solution of continuity in the nerve fibres, the 
propagation of the influence of the stimulus 
beyond the ligature is checked. No kind nor 
degree of stimulation of a muscular nerve above 
a ligature so applied is capable of exciting 
muscular contraction. 

The most remarkable feature which we notice 
in the experiment of stimulating a muscular 
nerve, is the instantaneousness with which the 
muscular contraction takes place. Although 
the muscles may be at a considerable distance 
from the point of the nerve to which the stimu-. 
lus is applied, there seems no appreciable 
interval of time between the application of the 
stimulus and the contraction of the muscle. 
And the cessation of the muscular contraction, 
instantly upon the removal of the stimulus, is 
equally conspicuous. 

It would appear, then, that the change in 
the nerve is produced and is propagated along 
the nerve to distant parts, as it were at one and 
the same moment. This rapidity of the pro- 
duction, and the instantaneousness of propaga- 
tion of the change in the nerve, denote that the 
nerve fibres must be the seat of a molecular 


720 


change rapidly propagated along the nerve, 
from molecule to molecule, from the point of 
ao of the stimulus. The change is 
obviously analogous to that which takes place 
in the particles of a piece of soft iron, in virtue 
of which the iron acquires the properties of a 
magnet, so long as it is maintained in a certain 
relation to a galvanic current; the magnetic 
power being instantly communicated when the 
Circuit is completed, and as rapidly removed 
when it is interrupted. 

The action of the stimulus, then, excites a 
state of polarity of the particles of the nerve 
stimulated ; and this polar state may be in- 
duced in other icles, whether muscular or 
nervous, with which the nerve stimulated may 
be in organic connexion. Just as the polar 
state of the electrical apparatus is capable of 
being communicated to the piece of soft iron, 
which thereby acquires the well-known mag- 
netic properties during the continuance of the 
excited polarity. 

Thus, then, we learn that such is the nature 
of the nerve fibre, that under the application 
of a stimulus, mechanical, chemical, or galvanic, 
it is capable of generating a polar force analo- 
gous in many particulars to that of muscle; 
this force we call the nervous force, vis nervosa, 
or nervous polarity.* 

And if we examine the ordinary mode of the 
development of the nervous force, in the usual 
actions of the frame, we find that under the 
influence of a mental stimulus, the will, it is 
propagated from the nervous centre along the 
netves to muscles, or under the influence of a 
physical stimulus it is propagated along the 
nerves to the centres, where it is capable of 
exciting either a sensation or muscular motion 
in a secondary manner, or both. 

But the application of a physical stimulus 
to a nervous centre may cause the development 
of nervous force, which may be conducted 
away from it by nerves which are implanted in 
it. And thus we learn that the same polar 
condition which may be produced in nerves is 
equally capable of being excited in nervous 
centres. The polar condition of the nerve fibre 
may be propagated to the nervous centre, or that 
of the nervous centre to the nerve fibre. 

In some of the nervous centres, however, no 
visible change of any kind takes place upon the 
_ irritation of the nervous matter, nor does the ani- 
mal seem to suffer pain. Such is the case when 
the hemispheres of the brain are the subject of 
experiment. We are not to infer from this that 
the nervous force is not developed in these 
centres, but that they have no direct connexion 
with the muscular system, nor have they that 
peculiar organization which would enable them 
when irritated to excite painful sensations. 

There are certain nerves which when stimu- 
lated excite neither muscular motion nor com- 


* I have been in the habit of taking this view of 
the nervous force in my lectures for the last four or 
five years, and of using the term, nervous polarity, 
as expressive of the nature of the nervous force. 
This term has likewise been adopted by Mr. Bow- 
man and myself in our work on the Physiological 
Anatomy and Physiology of Man, vol. i. p. 56, and 
in the chtiptiies on the Nervous System, passim. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


mon sensation or pain, but a sensation peculiar 
to themselves. Thus if the optic nerve be sti- — 
mulated by a mechanical or galvanic stimulus, — 
a sensation of light is produced ; if the auditory 
nerve be stimulated in like manner, a sensa 
of sound is produced. 

These facts prove not only that a peculia 
force is generated by the nervous matter, but 
they also show that the nerve fibres in the cen 
tres, as well as in the nerves, specia 
endowments depending, in all probability, upoi 
their central as well as upon their peripher 
connexions. Thus nerve-fibres conne wit! 
muscles are capable of exciting muscular con 
traction, and are therefore called motor or mus. 
cular nerves. Nerve-fibres, which are di: 
buted to a sentient surface, as the skin or mi 
cous membrane, and have a certain relatio 
with that part of the nervous centre which ¢ 
stitutes the centre of sensation, (vide p. 711 
are when stimulated capable of exciting a fet 
ing which may be agreeable or painful, ace 
ing to the degree of stimulation. These ¢ 
called sensitive nerves, or nerves of comm 
sensation. To the class of sensitive ner 
belong those which, owing no doubt to a pe¢ 
liarity in their connexion with the centre, 
well as to their relation to a special apparat 
at their periphery, develope peculiar sensation 
as the nerves of sight, hearing, taste, &c., a 
they have been distinguished as nerves of spec 
sensation. & 

Very many sentient nerves are implanted 
the nervous centre near to certain motor ner 
so that a stimulus applied to the former 
capable of reacting upon the latter, and of 
citing motion through their connexion with t 
muscles. Dr. M. Hall, however, ingeniou 
supposes that this power resides only in a] 
ticular class of nerve-fibres (and not it 
ordinary sentient nerves through their close 
of relation with the ordinary motor nerves), 
nerve of this kind would constitute an 
consisting of an incident and a reflex portic 
which are united at the nervous centre. — 
stimulus is conveyed to the centre by the’ 
dent portion, and is then reflected into 
reflex or motor portion. Such nerves, Dr. 
designates ercito-motor. We shall exa 
further on the grounds of this hypothesis. 

It is an important fact, which Sir C. 
was the first clearly to prove, that 
of different endowments may be bound t 
in one sheath, forming, in anatomical lang 
one nerve. Thus a nerve may contain set 
and motor fibres, as the median nerve” 
arm, or if we admitted Dr. Hall’s 
it might contain sentient, motor, and € 
motor fibres. And most nerves in the 
rent regions of the body are of this desert 
i. €. compound nerves, made up of sentiet 
motor fibres bound together in the sa 
in very different proportions. In ma 
nerves, as in the spinal nerves, and 
pair, the separation of the fibres of mot 
those of sensation exists at the implan' 
the centre, and there the fibres of each 
ment are collected into a separate | 
which possesses the endowment proper t 
constituent fibres, These are the roots of 


vo 
i? 
10; 


Te 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


nerves, of which one has been satisfactorily 
proved to be sentient, the other motor, the 
former being generally the larger, and having 
the peculiar feature of a ganglion being formed 
upon it. 

There is scarcely a nerve in the body, which, 
in strictness, ought not to be regarded as a com- 
pound one; the physiological character of each 
nerve must depend on the endowment of the ma- 
jority of its fibres, and the nerve will be called 
sensitive or motor, according to the predomi- 
nance of motor or sensitive fibres in it. For 
example, the facial nerve, or portio dura of the 
seventh pair, is called motor, because it is almost 
wholly composed of motor fibres; but it 
contains, besides, in very much _ smaller 
number, some sensitive filaments which it 
derives from anastomoses with neighbouring 
nerves. The third, fourth, and sixth nerves 
are of similar constitution to the facial. In the 
ramifications of the fifth nerve, on the other 
hand, the filaments of sensation are predomi- 
nant; those of motion being much fewer, and 
confined to the ramifications of its inferior 
maxillary division. 

There is no difference between a motor, and 
a sensitive nerve as regardsstructure. Ehrenberg, 
indeed, endeavoured to establish that the vari- 
cose character of the fibre belonged to nerves 
of special sense; but subsequent observation 
showed this to be incorrect. We can attribute 
the difference of endowment of the fibres to 
no other cause, but to the nature of their peri- 
pheral and central connections. The same 
nervous force is propagated by the fibres of 
each kind, but whether that force is to excite 
motion or sensation must depend on the connec- 
tion of the fibres with muscles in the one case, 
and with the centre of sensation in the other. 

The terms afferent and efferent have been 
used in expressing the function of different 
fibres, and they are convenient terms to a cer- 
tain extent. But the use of them tends to con- 
yey erroneous ideas respecting the change which 
takes place in a nerve when stimulated, as if 
that change took place only in one direction. 
It is true that, in a motor nerve, the stimulus 
ordinarily acts from the centre, and the nervous 
force is propagated peripherad; and on the 
other hand, in the sentient nerve, the stimulus 
is usually applied at the periphery, and the 
nervous force proceeds centrad. It is the place 
at which the stimulus is applied which usually 
determines the direction in which the nervous 
force travels. But there are no good grounds 
for supposing that the molecular change con- 
sequent upon the stimulation of a nerve is 
limited to that part of the nerve-fibre which 
is included between the point stimulated, and 
the centre or the muscles, where the effect 
of the stimulation appears; on the contrary, 
t is not improbable that, at whatever point 
the stimulus be applied, the whole length 
of the nerve-fibre participates in the change. 
his is not unlikely in the case of motor 
nerves. For a continued or violent irritation of 
motor nerve, in some part of its course, caus- 
ng spasm or convulsive movement of the 
nuscles it supplies, may be propagated along 
VOL. III. 


7201 


its whole length to the centre, and may there 
give rise to irritation of neighbouring fibres, 
whether motor or sensitive, exciting more con- 
vulsion and pain. The phenomena of many 
cases of epilepsy, in which the fit begins with 
irritation of a few muscles, may be referred to 
in illustration of this position.* And it is also 
very probable as regards sensitive nerves. If 
the ulnar nerve be irritated when it passes be- 
hind the internal condyle, a sensation of tingling 
is excited, which is referred to the sentient 
surface of the ring and little fingers; and if 
the irritation is kept up, the skin of those fingers 
becomes tender to the touch, its sensibility 
being very much exalted. This fact cannot be 
explained unless upon the supposition that 
the molecular change in the nerve-fibres, pro- 
duced by the irritation, extended to the peri- 
phery as well as to the centre, exalting the 
excitability of their distal extremities. 

It is a highly interesting physiological fact, 
which has an important practical bearing, that 
at whatever part of their course sentient nerve- 
fibres be irritated, the same sensation will he 
produced, whether the seat of the irritation be 
the centre, the periphery, or the middle of their 
course, provided only the same fibres are irri- 
tated in the same degree. Thus it frequently 
happens that sensations are referred to the ex- 
tremities of a nerve when the existing irritation 
is situated at its point of implantation in the 
centre. The sensation of tingling or formica- 
tion, in the hand or foot, arm or leg, is fre- 
quently an indication of cerebral or spinal 
disease ; but the practitioner should not forget 
that precisely the same sensation may be caused 
by an irritation taking place in the course of the 
nerve. I have frequent occasion to estimate 
the importance of this fact in the treatment of 
cases of Sciatica. This disease generally con- 
sists in an irritated state of the nerve in some 
part of its course by a gouty matter, and it may 
be treated with the best effects by blisters ap- 
plied over the nerve. As, however, the morbid 
impregnation may have taken place at any part 
of the course of the nerve, it is a very useful 
practice, when a single application fails, to apply 
the blisters over different parts in succession, 
instead of confining the vesication to one region. 

This law of action of sensitive nerves gives 
the clue to the explanation of the extraordinary 
but well-attested fact, that persons who have 
suffered amputation will continue to feel a con- 
sciousness of the presence of the amputated 
limb, immediately after, and often for a long 
time, or even always, after its removal. I have 
met with two cases, in one of which the arm, 
in the other the leg, was amputated so long 
before as forty years; yet each person declared 
that he-had the sensation of his fingers or toes 
as distinctly as before the operation. And not 
only does the consciousness above referred to 
exist, but likewise, when the principal nerve 
of the limb is irritated, the patient complains of 
pains or tingling, which he refers to the fingers 


* Tam aware that these phenomena admit of 
another explanation, but there is no reason why 
they might not likewise originate, in many cases, in 
irritation of a few motor fibres. 

Q2z *** 


- 720K 


or toes.* Insuch cases the central segments 
of the amputated nerve-fibres remain; if they 
retain their healthy condition, they continue 
to represent in the sensorium the various 
points on the surface of the amputated limb, 
and likewise the muscles which they were 
destined to supply. If, however, the inte- 
gtity of the nerve-fibres has been impaired in 
consequence of any morbid action which may 
have followed the operation, then the sensation 
exists imperfectly or not at all. 

It may be stated in connection with this 
subject, and in confirmation of the view above 
taken, that in many cases of complete paralysis 
of a limb from cerebral disease, the patient, 
although perfectly clear in his general mental 
perceptions, is not conscious of the presence of 
the paralysed member, and really feels as if it 
did not exist. I have known instances in 
which this unconsciousness has been so great 
that the patient has actually mistaken the para- 
lysed part for the limb of some other person 
coming in contact with him, or for some en- 
tirely foreign substance. One man fancied that 
his paralysed arm was bis wife’s, and called to 
her to take itaway. In such cases the morbid 
state of the brain prohibits the developement 
of that affection of the centre of sensation upon 
which the feeling of the connection of the limbs 
depends.t 

The same law of action applies to nerves of 
a as to those of common sensation. 

hus, whilst ordinarily they propagate to the 
centre impressions made at the periphery, we 
find nevertheless that irritation of the nervous 
trunk at any part of its course may give rise 
to its peculiar sensation; and if the brain be 
stimulated at the part in which the nerve is 
implanted, similar sensations may be produced. 
The phenomena of vision and hearing which 
are excited in these ways are called “subjective ;” 
they are familiarly known to medical men as 
not unfrequent precursors of more serious 
symptoms of cerebral disease. Musce voli- 
tantes, ocular spectra, and tinnitus aurium, are 
the most common instances of these pheno- 
mena. Pressure on the eyeball, a galvanic 
current passed through it or very near it, rota- 
tion of ike beady, are capable of giving rise to 
similar phenomena, by exciting the retina or 
the central connections of the optic nerve, or by 
disturbing the circulation of the blood in them. 
A sense of giddiness, similar to that produced 


* Miiller records several instances in his Physio- 
logy, vol. i. p. 746. ( Eng. edition. 

There is a man now in King s College Hospital 
who suffered amputation at the upper third of the 
arm, and whose entire scapula, with the shoulder 
joint and great part of the clavicle, was removed by 
Mr. Fergusson within the last two months, i 
man still feels his fingers, 

t Valentin states that persons who are the sub- 
jects of congenital imperfections, or absence of the 
extremities, have nevertheless the internal sensa- 
tions of such limbs in their ect state. Accord- 
ing to the view above taken this could not be, 
unless the primitive nervous fibres are present 
in their fall number in the trunks of the nerves des- 
tined for the limb. Repertorium far Anat. und Phys. 
1836, p. 330, and note to Baly’s translation of 
Miiller’s Physiol. vol. i. p. 747. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


by the means last-named, is also a very com- 
mon symptom of cerebral affection arising from 
a disturbed circulation, or from the blood being 
deficient in one or more of its staminal princi- 
ples, or vitiated by some morbid elemeut. 

The stimuli of nerves—Nervous action is 
ordinarily provoked by stimuli of two kinds, 
mental and physical. Menta) stimuli are those 
resulting from the exercise of the will, or from 
thought. Physical are due to some external 
excitant; light, heat, sound, mechanical stimu-— 
lation, chemical substances, as acids or alkalis, — 
or electricity. 4 

In all voluntary movements an act of the 
mind is the excitant of the nerve. ions 
are caused generally by the influence of physi- 
cal agents upon the peripheral extremities 
nerves, which communicate with the sensorii 
commune. The change thus produced in thi 
nerve gives rise, through the medium of this 
communication, to a corresponding affection 
the mind. A mental stimulus, however, 
affect a nerve of sensation. Such stimulu 
would originate in that part of the brain cl 
is the seat of the changes connected with thi 
intellectual actions, and affecting the centre o 
sensation, would excite in certain 
nerves a change similar to that which a physic 
stimulus applied to their oe eral extremiti 
is capable of producing. In this way the mit 
is capable of exciting pain in any part. W 
the attention has been long directed to a 
particular situation, whether it has been 
viously the seat of ize or not, painful sen 
tions may be excited there. this we 
many instances in practice. In the treatm 
of cases of hysteria it is of great impe 
on this account, to direct the attention of 
pence: as much as possible away from 
ocal affection. 

Motor nerves are never immediately exci 
by a physical stimulus in the ordinary acti 
of the body. A physical stimulus acts w 
motor nerve always through a sensitive ner 
the actions thus produced are, commonly, cal 
reflex actions from the apparent reflexion 6 
change excited by the afferent or sensitive 
in the nervous centre into the motor or ef 
nerve. This class of actions was first po 
out and described by Prochaska, who v 
them as consisting “ in reflexione impress 
sensoriarum in motorias.” The contact 
foreign substance, pressure, titillation, are 
ordinary physical means by which such at 
may be excited. As a good example of 
may be quoted the act of deglutition a 
isthmus faucium. 

Physical stimuli of other kinds, 
may excite motor nerves. The pre 
morbid growth of any kind may irritate 
nerves and create spasm of the musel 
supply. Any virulent fluid applied to: 
nerve will irritate in a similar way—hot 
—liquor potasse—a mineral acid—a sol 
of strychnine, &e. And for the same f 


7a 


: 


certain morbid matters in the blood may 
nerves whether sensitive or motor, causit 
so-called neuralgic pain in the one case, 
cramp or spasm in the other. 


a. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


Effects of the galvanic stimulus—The most 
perfect and powerful! physical stimulus of motor 
nerves, and that which most nearly imitates the 
natural mental stimulus, is the galvanic current. 
That the nerve should be duly excited by the 
galvanic current it is necessary that the current 
should pass along its fibres for however short a 
distance. If it pass across the fibre, and at right 
angles to it, it will produce no effect upon the 
muscles; but if it travel along it, even for the 
twentieth or a smaller portion of an inch, it will 
effectually excite the nerve and its muscles, 
just as when the will stimulates it to action. 

The influence of the galvanic current upon 
nerves is so remarkable that it deserves the 
careful study of physiologists and of practition- 
ers in medicine who often have recourse to the 
galvanic stimulus with the hope of rousing the 
dormant energies of nerves. Ht is to the Italian 
school of Physiciens that we owe the highly 
interesting series of facts which have been col- 
lected upon the influence of the galvanic cur- 
rent upon nerves, to Galvani, Valli, Volta, 
Marianini, Nobili, and, although last not 
least, to my distinguished friend, Professor 
Matteucci, of Pisa, by whose well-devised ex- 

riments and researches a flood of light has 

n thrown upon this hitherto obscure and 
difficult subject. 

Ishall content myself here with briefly no- 
ticing the points most deserving of attention as 
bearing upon the laws of action of the nerves. 

1. When agalvanic current is passed for how- 
ever short a distance along a nerve which 
contains motor fibres, muscular contractions 
will be excited at the moment of completing 
as well at that of breaking the circuit, but not 
while the current is passing. These phenomena 
take place whatever be the direction in which 
the current be passed, whether from the nervous 
centre towards the periphery, (when the current 
is distinguished as the direct current, ) or from 
the periphery towards the centre (when the 
current is styled the inverse current ). 

These effects may be produced in warm as 
well as in cold-blooded animals. In the former, 
however, the physical conditions necessary for 
the display of the vital forces continue for so 


720L 


brief a period that cold-blooded animals should 
be selected for the experiments. On this ac- 
count, as well as because of their peculiar sus- 
ceptibility to the galvanic current, frogs are ge- 
nerally employed for this purpose. The most 
striking way of exhibiting the influence of the 
current, direct and inverse, upon the nerves is 
illustrated by the annexed woodcut. It repre- 
sents a frog prepared in the manner adopted by 
Galvani. The integuments have been removed 
from the lower extremities, which have been 
separated from the trunk by the division of the 
lumbar region of the spine. The lumbar nerves 
are carefully raised from the muscles on which 
they lie, but are suffered to retain their con- 
nection with the spinal cord and with the 
thighs. The pelvic bones, however, are re- 
moved so as to admit of the more free separa- 
tion of the extremities, as well as to isolate the 
nerves more completely. Each leg is immersed 
in a glass or cup of water, and the current is 
made to pass through the limbs by immersing 
each wire of the battery in the water of the 
cups. It is obvious that in one limb the current 
is direct, whilst in the other it is inverse. 

The advantage of this arrangement is that it 
affords great facility in making and breaking the 
current without bringing the conducting wire 
of the battery into actual contact with either 
limb. One wire may be left constantly in the 
water, while the other can be alternately intro- 
duced or removed from it as we wish to ob- 
serve the effects of completing or of breaking 
the current. 

2. If the current be allowed to pass for a 
short time through the nerves of a frog, pre- 
pared as before-mentioned, contractions will no 
longer take place in both limbs at the same 
time, but only in one upon completing the 
circuit, in the other on breaking. And we 
shall always find that the contractions occur on 
making in the limb in which the current is direct, 
on breaking in the limb in which the current is 
inverse. I find it useful to adopt the following 
formula to impress this fact upon the memory ; 
MD, BI, making direct, breaking inverse. 

3. If the current continue to pass for some 
time longer, these phenomena cease completely 


Fig. 398a. 


Lower extremities of the prepared Frog. 
P, positive wire of the battery; N, negative ditto. In the limb A the current will be sade in . it will be direct. 
Z 


720M 


and no contractions are produced. They may, 
however, be reproduced by inverting the 
direction of the current by transposing the 
conducting wires of the battery. The cur- 
rent will now be inverse in B, and direct in 
A, fig. 398a. Or the fact may be illustra- 
ted by another disposition of the legs of the 
frog. Let both feet be immersed in one vessel 
and the pelvis in the other. The direct current 
may now be passed along the nerves in both 
limbs at the same time, until the phenomena 
of contraction on making or breaking cease. 
Inverse the current, and the contraction will 
again become manifest. This fact was first 
discovered by Volta, and this mode of exhibiting 
it has been described under the title Alternatives 
Voltianes. If the inverted current continue 
some time, exhaustion will be produced ; but on 
inverting it again or restoring it to its former 
course, the actions will recommence. 

4. These effects cannot be produced unless 
the nerves be in a state of integrity. If a liga- 
ture be tightly applied to the nerve of either 
limb close to the muscles, the contractions in 
that limb will no longer take place. Or to give 
a more striking illustration of this important 
fact, if adrop or two of pure sulphuric ether be 
applied to a point of either nerve, the contrac- 
tions in the limb of that side will be suspended 
until the effects of the ether pass off. These ex- 
periments unequivocally shew that the nerves 
are not merely conductors of the electrical cur- 
rent, but that the passage of the current through 
them developes in them a change which influ- 
ences the contractile force of the muscles. 

5. The influence of the galvanic current af- 
fords the most striking results when motor 
nerves are made the subject of the experiments, 
but Matteucci has shown that sensitive nerves 
are affected in an analogous way by the inverse 
and direct current. Ina living rabbit the sciatic 
nerves were exposed, and one nerve was devoted 
to the direct current, the other to the inverse. 
Opening and closing both currents were accom- 

nied with marked signs of pain, which, 

owever, were greatest at the closure of the 
inverse current. After a short time, the signs of 
pain are manifested only on opening the direct 
current and closing the inverse. 

The reader will scarcely fail to observe that 
both as regards the sensitive and motor nerves, 
the effect of the electric current, whether in 
causing pain or in producing contractions, is 
greatest when the current passes through the 
nerve in the course in which the nervous force 
would naturally proceed in the ordinary nervous 
actions. It is further worthy of notice that the 
continuance of the direct current exhausts the 
power of the nerve, while the reversal of the 
direction of the current, if not too long delayed, 
restores it. The continuous passage of the 
current, however, is not marked either by con- 
tractions or by pain. The interruption of 
the current by any means at once developes 
these phenomena; or even the diversion of a 
portion of it produces the same effect, as Mari- 
anini showed long ago. If, for instance, the two 
vessels in which the frog’s paws are immersed 
be connected by a conductor, as an arc of copper 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


or silver wire, contractions will take place on 
making or breaking the connection ; or if the 
wires of the battery be connected by a third wire 
of the same material before they dip into the _ 
cups, the same effects will be produced. 
Me continued transmission of an inverse 
current through a nerve increases to a remark- 
able extent its excitability. This is shewn by 
the following experiments: let the limbs of a 
frog be placed in two vessels of water and the 
current be passed through them in the manner 
above described, and let this be continued for 
a few minutes. After the lapse of this period, 
if the circuit be broken by taking one of the 
wires out of the water, the limb in which the 
current was inverse will be thrown into a state 
of tonic or tetanoid spasm for a few seconds, 
the tetanus ceasing with a clonic convulsion on — 
the renewed completion of the circuit:* 
That these phenomena are due to a change 
developed in the nerve (not to any affection of 
the muscles) by the passage of the galvanic — 
current, is clearly demonstrated by applying the | 
galvanic current to a muscle directly, having 
first removed as much nerve out of it as pos-— 
sible. The -muscle will contract equally on 
making and breaking the circuit, whatever 
be the direction of the current; nor is it 
sible to produce tetanic spasm, however long: 
the current may have been continued through 
it. The following experiment, suggested by 
Matteucci, also strongly confirms this view. 
Let the current be passed through the limbs 
of a frog in the ordinary way. After the curren 
has passed for 25 or 30 minutes, cut the nervé 
traversed by the inverse current, at the poin 
where it plunges into the thigh, and there wil 
instantly ensue a violent contraction of thal 
limb, which ceases very quickly. If, howeve 
instead of this the nerve be cut where it issue 
from the spinal cord, so as to leave a certai 
length of A nerve attached to the thigh, the 
will be a violent contraction of the mu 
which will be followed by others, and the lim 
will remain in a tetanic state for 10 or 1 
seconds or longer.t i 
The tetanoid contractions of the muselk 
may be produced by a rapid series of curren 
passed through the nerve alternately in the it 
verse and direct course, as by the electro-ma 
netic or the magneto-electric instrument. Th 
are always greatest and last longest if a port 
of the nervous centre remain connected 
the limbs. E. H. Weber has lately made 
very interesting series of researches by mes 
of the magneto-electric rotation instrumgé 
developing the peculiar mode of action of p 
ticular muscles.{ 7 
We cannot explain these remarkable phe 
mena on any other principle than on that 
supposes the developement of the nervous fo 
to be associated with the assumption of a pt 
condition by the molecules of the nerves un 
the influence of certain stimuli. The in 
current excites a polar state of greater int 


we 
DOS=— 


* Mattencci, Phil. Trans. 1846. 
+ Comptes Rendus, March 15, 1847. 
¢ Wagner, Worterbuch. Art. Maskell 


— 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


and of longer duration than the direct current : 
hence the tetanic contractions which remain 
after the interruption of the current. 

It is sufficiently obvious why a contraction 
should occur at the moment of completing 
the circuit in a nerve. But why the same 
phenomenon should occur on breaking the cir- 
cuit is not easily explained. Marianini sup- 
posed that during the passage of a direct cur- 
rent through a nerve a part of the electricity 
accumulated in it, and on qhe interception of 
the current discharged itself, traversing the 
nerve in an opposite direction, and thus giving 
rise to contractions. It is not, however, likely 
that such an accumulation would take place, 
when the conducting power of muscle is so 
much better than that of nerve. And further, 
it is evident that this will not explain the ab- 
sence of contractions in the direct limb after a 
time on breaking the circuit. 

The truth is, that when a continuous current 
has been passed through the limb of a frog 
for some time a different state of excitability 
is established in the nerve of each limb ac- 
cording to the direction which the current 
had taken. That in which the direct current 
passes becomes exhausted in its powers, while 
that in which the inverse current passes has its 
excitability augmented. In the quiescent state 
a nerve maintains a certain state of tension: the 
application of a stimulus modifies this tension 
and causes the nerve to assume a new polar 
state, which displays itself in the contraction of 
muscles or the excitation of a sensation or of 
pain. The electric current is a powerful sti- 
mulus of the nervous force, and the greatest 
disturbance of the quiescent state of tension 
is produced by making the direct current. 
Upon this current beginning to pass, a new 
State of tension is established, which is disturbed 
by breaking the circuit: but if the current have 
continued to pass too long, the maintenance of 
the state of unnatural tension exhausts the ner- 
vous power, and the nerve ceases to respond 
to any stimulus. Whilst, however, the nerve 
of the direct limb has assumed one condition, 
that of the inverse limb has taken on a different 
one, in which the molecules of the nerve may 
be conceived to have a disposition the opposite 
to that which the direct current would produce. 
Hence only two electric stimuli would restore 
the particles of the inverse nerve, and so disturb 
the state of tension into which it had been 
thrown, namely, making a direct current through 
the nerve, or simply breaking the inverse. 

The tetanoid state which results from the 
continued passage of the inverse current through 
@ nerve is a phenomenon resulting from the ex- 
treme augmentation of its polarity. This state 
‘4s never produced by the direct current; and 
the instantaneousness with which it is removed 
by resuming the current, thereby restoring the 
State of tension which had been disturbed by 
breaking the circuit, is highly favourable to this 
Supposition. Anything which weakens the 
force of the current, or diverts a portion of it 
from the nerve, as the contact of muscles with 
the nerve, or of much moisture, or the occa- 
Sional reversal of the current making it direct 


720N 


where it had been inverse, will materially re- 
tard and diminish, or altogether prevent the 
developement of this phenomenon. 

The rapidity with which the changes in the 
nerves, however they may have been excited, 
are propagated, and the precision with which 
they are perceived by the mind in the case of 
sentient nerves, or produced by it in the case of 
motor nerves, are well calculated to excite our 
admiration. If the communication between 
the nerve and the centre be cut off, the will can 
exert no influence upon the muscles supplied 
by the nerve below the section; nor will the 
mind perceive any stimulus applied to parts 
which derive their nerves from below the sepa- 
ration. And this for an obvious reason; be- 
cause the solution of continuity of the nerve 
interrupts the propagation of the change which 
the mental or physical stimulus excites in it. 
In the case of the voluntary nerves, the effects of 
the mental stimulus are propagated no further 
peripherad than the point of section; and in 
that of the sensitive nerve, the change travels no 
further centrad than the same point. That this 
interruption is caused solely by the solution of 
continuity, and not by any alteration in the pro- 
perties of the nerve, is proved by the fact that 
the lower segment of the motor nerve will still 
continue to respond to a physical stimulus. 
Mechanical or chemical irritation, or the pas- 
sage of an electric current along it, will cause 
its muscles to contract. Such a degree of in- 
jury to a nerve as will break the continuity of 
the nervous matter within the tubular fibres is 
likewise sufficient to destroy its power as a 
propagator of nervous change. This effect may 
be produced by tying a ligature very tightly 
round a nerve, or by pressing it with great force 
between the blades of a forceps. The paralysis, 
which results from the compression of a nerve 
by a tumour or in any other way, is, no doubt, 
due to a similar solution of continuity in the 
nervous matter. 

These facts strongly denote the important 
principle in nervous physiology, that, in pro- 
pagating the influence of a stimulus, either 
from periphery to centre, or vice versa, the 
whole extent of the nerve-tibre between the point 
stimulated and its peripheral or central con- 
nection is the seat of change; and that the power 
of developing the nervous force is inherent in 
the nerve-fibre itself is shown by the fact that 
the stimulation of a muscular nerve, which has 
been separated from the centre, below the point 
of section is capable of exciting muscular action. 
The conducting power of a neive, then, results 
from its proneuess to undergo certain changes, 
physical or chemical, under the influence of 
stimuli. 

We may perceive, then, how important it 
must be to the healthy action of nerves to pre- 
serve them in a sound physical condition. A 
morbid fluid impregnating a nerve at any point 
may irritate it, or may suspend or destroy its 
inherent property by modifying its nutrition or 
impairing its physical condition. Thus we 
may paralyse nerves by soaking them in a so- 
lution of opium, or of belladonna, aconite, or to- 
bacco, in sulphuric ether, or other sedative or 


7200 


narcotic substances ; or, on the other hand, we 
may unduly excite them by applying a strong 
solution of strychnia. The contact of a solid 
body with a nerve may irritate and keep up a 
continual state of excitement, if it do not destroy 
its properties. A spiculum of bone, in contact 
with nervous fibres, is often the cause of the 
severest forms of neuralgia; inflammation may 
produce like effects. Various physical agents 
may produce similar consequences. The benumb- 
ing influence of cold is explained inthis way. Ex- 

sure to a continuous draught of cold air is a 
requent cause of facial paralysis. The giving 
way of a carious tooth will immediately occa- 
sion toothache by exposing the nerves of its 
pulp to the irritating influence of the air, or of 
the fluids of the mouth. And undue heat is 
likewise injurious to the physical constitution, 
and, therefore, to the action of nerves. These 
facts are of great interest in reference to the 
pathology of nervous diseases, and suggest that 
the attraction of a morbid material in the blood 
to a nerve or set of nerves, or to that part of the 
nervous centre in which such nerves may be 
implanted, may afford satisfactory explanation 
of many obscure phenomena of nerves of sen- 
sation. 

The organic change, whatever be its intrinsic 
nature, which stimuli, whether mental or phy- 
sical, produce in a nerve, developes that won- 
derful power long known to physiologists by 
the name vis nervosa, the nervous force. This 
force is more or less engaged in all the func- 
tions of the body, whether organic or animal. 
In the former its office is to regulate, control, 
and harmonize; in the latter it is the main- 
spring of action without which none of the 
phenomena can take place. Itis the natural ex- 
citant of muscular motion, and the display of that 
wondrous power depends uponits energy ; with- 
out vigour in the developement and application 
of the nervous force, a well-formed muscular 
system would be of little use, for it would 
quickly suffer in its nutrition if deprived of that 
exercise which is essential to it. 

In the various combinations of thought 
which take place in the exercise of the intellect, 
there can be no doubt that the nervous force is 
called into play in the hemispheres of the 
brain. Here the stimulus is mental ; the inde- 
pendent operations of the mind excite the ac- 
tion of the appropriate fibres of the brain, and 
the developement of the nervous force in the 
brain immediately succeeds the intellectual 
workings. It is thus that we explain the 
bodily exhaustion which mental labour in- 
duces; and thus, too, we can understand the 
giving way of the brain—the inducement of 
cerebral disease—under the incessant wear and 
tear to which men of great intellectual powers 
expose it. On the other hand, physical changes 
in the brain, of a kind different from those 
which are normal to it, the circulation of too 
much, or too little, or of a morbid blood, may 
excite mental phenomena in an irregular way 
and give rise to delirium or mania. 

Of the conditionsnecessary for the maintenance 
of the power of developing the nervous force.— 
From what has been already stated, it is mani- 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


fest that a healthy physical state of the nervous 
matter, whether in the nerves or in the nervous 
centres, constitutes the main condition neces- 
sary for preserving in them the power of deve- 
loping the nervous force. And as nerves will 
not maintain their healthy nutrition unless they 
be in union with the nervous centres, this union 
becomes an important condition for the main- 
tenance of this power in nerves. In the ner- 
vous centres the nerves form a connexion with 
the vesicular matter. We therefore infer that 
this connexion of the fibrous and vesicular matter 
is necessary for the exercise of the pa power — 
of nerves, because we know of no instance, 
either in the human economy or in that of the — 
inferior creatures, in which the nervous power is — 
developed without this union. ; 
It is true that if a motor nerve be separated — 
from the nervous centre, its peripheral segment — 
will evince a susceptibility to stimuli, or, in 
other words, it will retain the power of gene- 
rating the nervous force for some time after the 
separation. This is, however, only for a short — 
period, as the experiments of Longet disti 
show. Longet cut out a portion of the sciatie 
nerve in dogs, and irritated the lower segment 
of the nerve on each succeeding day by me 
of galvanism from a pile of twenty couples, 
by mechanical irritation. The nerve ceased to” 
be excitable on and after the fourth day, (* des” 
le quatrieme jour.”)* These results, although: 
they appear to differ from those obtained by 
Miller and Sticker, and Steinruch, are not really 
inconsistent withthem. Theseobservers, inste 
of examining and irritating the lower segn 
of the nerve each succeeding day after the 
tion, allowed it to remain for an arbitrary pe 
untouched, and then reopened the wound to ty 
the effect of stimulating the nerve. Thus Malle 
and Sticker waited eleven weeks in one it 
five weeks in a second, and two months and ; 
half in a dog, and in all the cases found 
nerve inexcitable ; and Steinruch waited 
weeks, at which time he found that the powel 
of the nerve had disappeared. It is obvio 
that there was nothing in any of these expe 
ments to cast a doubt on the possibility ¢ 
nerve having lost its excitability at a m 
earlier period after the section, and that 1 
selection of five or eight or eleven weeks, 
period when to inquire whether the ne 
tained its excitability or not, was entirely ar 
trary on the part of the experimenters. 
The pidag with which a nerve lo 
power after it has been separated from 
nervous centres clearly denotes that connec 
with the centre is a necessary condition for 
nutritive activity of nerves, and is, therefor 
necessary condition for their functional acti¥ 
or, in other words, for the full developem 
of the nervous force under its appropriate! 
muli. There are, however, ay facts wh 
inasmuch as they enhance the importan 
the vesicular i in the mani station 
nervous phenomena, give great wei 
proposition under consideration. 


os 
ng 


* Longet, Recherches Experimentales sur!’Irr 
bilité Musculaire: PExaminateur Med, Dec. | 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


1. That there is invariably an accumulation 
of vesicular matter around the points of im- 
plantation of nerves in the centres, as already 
referred to. This is true of all nerves in 
the vertebrata and the higher invertebrata, 
and we know of no reason to doubt it in the 
lower invertebrata. 2. The quantity of the vesi- 
cular matter around the point of implantation 
of a nerve is in the direct ratio of its size and 
of the activity of its function. Under par- 
ticular cireumstances the quantity of vesicular 
matter becomes so large as to cause a special 
ganglionic enlargement of the portion of the 
centre in which the nerve or nerves may he 
implanted. The cervical and lumbar enlarge- 
ments of the spinal cord are due to this 
cause: the gangliform swellings on the upper 
a of the spinal cord in the gurnard (érigla 
lyra) are connected with the exalted func- 
tions of the nerves of touch distributed to the 
feelers, and contain a large quantity of vesi- 
cular matter. A remarkable instance of the 
developement of vesicular nervous matter under 
similar circumstances is to be found in the 
electric lobes of the Torpedo, in which are im- 
planted the nerves distributed to the electrical 
organ. These lobes are of very considerable 
size, much exceeding that of any other part of 
the brain, and they contain vesicular matter in 
large quantity. The nerves implanted in them 
are of great size.* 

Such facts as those cited in the preceding 
paragraph denote clearly that the developement 
of the nervous force is to a certain extent con- 
nected with the vesicular nervous matter, and to 
such a degree as to justify the opinion that this 
element of the nervous centres may be viewed 
as the dynamic matter, the originator of the 
force. At the same time it must be borne in 
mind that this form of nervous matter never 
occurs alone, and that probably the union of 
the two is necessary for the developement of 
nervous power. Just as the union of two 
metals in the galvanic battery is necessary for 
the developement of the current, while one of 
them, that, namely, which possesses the greatest 
affinity for the fluid interposed between them, 
seems to originate the current, and is on that 
account called the generating plate, whilst the 
other is called the conducting plate. 

Of the nature of the nervous force.—All 
that we have said respecting the mode of deve- 
lopement and the laws of the nervous force 
denotes its polar character. 

We can no more detect by our senses any 
physical change in the piece of soft iron which 
is rendered magnetic by the galvanic current, 
than we can discover a change in the particles 
of a nerve stimulated to action by the same 
current. That both the iron and the nervous 
matter are thrown into an analogous state by 
the same agent seems highly probable. In the 
case of the iron the indication of the assump- 
tion and of the maintenance of the polar state 
is afforded by its power of attracting particles 
of iron; while in a muscular nerve the assump- 
tion and maintenance of the polar state are 


* Savi, Etudes Anat. sur le Systéme Nerveux et 
sur ’Organe Electrique de la Torpille. 


720P 


shown by the active contraction of certain mus- 
cles, or a more tonic state of passive contrac- 
tion. While the current is passing through a 
motor nerve there is no active contraction of 
the muscles; but that these organs are in a 
more excited state than the ordinary one of 
passive contraction seems evident enough, from 
the readiness with which they assume a tetanic 
condition upon the cessation of the passage 
of an inverse current which had been allowed 
to pass through their nerves for some time. 
And the fact demonstrated by Marianini and 
Matteucci, that the passage of a continuous 
current through a nerve will after a time exhaust 
its excitability, although not so quickly as a 
current frequently interrupted, denotes that the 
nerve is in an excited state during the actual 
passage of the galvanic current. 

Is the nervous force electricity ?—There is 
so much resemblance, as regards their mode 
of developement and propagation, between 
the nervous force and electricity, that many 
physiologists have been led to regard these 
forces as identical. The nervous force, how- 
ever, presents striking points of difference 
from electricity, which render it highly impro- 
bable that it is identical with that force, and 
which show that if it be so it must be an 
electricity of extremely low tension. 

1. The ordinary tests for electricity fail to 
detect the existence of a galvanic current in the 
nerves, whether during their quiescent or their 
active state. The most delicate galvanometers 
have been employed for this purpose, in vain, 
by Prevost and Dumas, who were themselves 
advocates of the electrical theory of nervous 
action, by Person, by Miiller, by Matteucci, 
and by myself. Person connected the wires of 
a galvanometer with the surfaces of the spinal 
cord in kittens and rabbits, in which spasmodic 
action of the muscles had been excited by the 
influence of nux vomica, and was unable to 
discover any evidence of electrical action. It 
had been affirmed that needles introduced into 
the nerves or muscles of living animals became 
magnetic during nervous and muscular action, 
so as to attract iron filings, but neither Miiller 
nor Matteucci has succeeded in obtaining such 
a result from their experiments. Matteucci 
took the precaution of employing astatic needles 
for the purpose, but could detect no signs of 
magnetization. He also introduced the pre- 
pared limbs of a frog into the interior of a 
spiral covered on its inside with varnish; the ~ 
extremities of this spiral were united to those 
of another smaller spiral, into which he intro- 
duced a wire of soft iron. The nerves of the 
frog were irritated to excite muscular action, 
and at the same time Matteucci sought to 
ascertain if an induced current would traverse 
the spirals and magnetize the wire, but to no 
purpose. 

2. Were it to be admitted that the nervous 
force and electricity were identical, it cannot 
be doubted that the provision made for propa- 
gating the latter force in the nerves is very 
Inadequate. The nerves are very imperfect 
conductors of electricity; Matteucci assigns to 
them a conducting power four times less than 
that of muscle; Weber states that they are very 


720q 


inferior to the metals as conductors. And 
from experiments made on this subject in 1845 
by Dr. Miller, Mr. Bowman, and myself, we 
were led to conclude that nerve was infinitely a 
worse conductor than copper. ‘The provision 
for insulation, however perfect for the nervous 
force, seems most insufficient for electricity, 
unless, perhaps, for a current of very feeble 
intensity. Yet we know that the nerve fibres 
convey the mandates of the will with the nicest 
precision to the muscles, and propagate the 
effects of physical stimuli applied to the peri- 
hery with the greatest exactness to the centre. 
his could scarcely be if the force so propagated 
were an imperfectly insulated electric current, 
for jt is evident that in such a bundle of fibres 
as a nervous trunk disturbances would conti- 
nually be taking place, from the secondary 
currents induced in neighbouring fibres by the 
electricity passing through those in action. 

3. The nrm application of a ligature to a 
nerve stops the propagation of the nervous 
power along that nerve below the point of 
application; the passage of electricity, how- 
ever, is not interrupted by these means. The 
nervous trunk, indeed, is as good a conductor 
of electricity after the application of the ligature 
as before it, provided it do not become dry at 
the point of ligature. 

4. If a small piece be cut out of the trunk 
of a nerve, and its place supplied by an electric 
conductor, electricity will still pass along the 
nerve and along the conductor ; but the nervous 
force, excited by a stimulus applied above the 
section, will not be propagated through the 
conductor to the parts below. 

5. The existence of an organ in certain ani- 
mals capable of generating electricity is un- 
favourable to the electric nature of the nervous 
force. The best examples of this organ are 
found in the Torpedo and the Gymnotus; and 
experiment has placed it beyond doubt that the 
organ generates electricity, which is capable of 
giving a shock similar to that from a Leyden 
jar; which developes a spark during the dis- 
charge, and can effect electrolysis; by which, 
likewise, the galvanometer may be disturbed, 
and needles rendered magnetic. 

The electrical organs have no resemblance, 
in point of structure, to nerves; they, however, 
present a remarkable analogy in that respect, as 
well as in their physiological action, to the 
striped variety of muscles. They are composed 
of a number of prisms, each of which consists 
of a membrane closed at both extremities, and 
containing a soft albuminous substance, but 
subdivided by transverse very delicate septa 
into a multitude of small compartments. The 
bloodvessels and nerves are distributed upon 
the enclosing membrane and upon the septa, 
but do not penetrate the albuminous material. 
On these septa, according to Savi, the nerves 
form a network, in which the disposition of 
their terminal fibres differs from that in muscle 
in there being a true anastomosis or fusion of 
the primitive tubules. The analogy of the struc- 
ture of the electrical prisms with that of mus- 
cular fibres is sufficiently obvious, the latter 


* See ELECTRICITY, ANIMAL. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


being prismatic columns of fibrine, enclosed by 
a membrane, the sarcolemma, and separable 
into dises, the nerves and vessels being distri- 
buted upon the sarcolemma, and not penetrating — 
the contained sarcous elements. In both these 
textures the anatomical disposition has evident 
resemblance to the artificial arrangements for 
generating electricity, and accordingly in one 
(the electric organ) true electricity is generated ; 
in the other, as we shall see further on, either 
electricity, or a force in close relation to elec- 
tricity, is developed. In both cases the genera- 
uon of the force is independent of the nervous 
system ; its exercise and application, however, 
are under the influence of that system. "4 
The arrangement of the nerves and nerve 
centres is essentially different from that of 
muscle or of the electric organ, and so far 
would suggest a decided difference in the 
racter of the force which they can develope from 
that produced by the latter textures. ; 
6. A comparison of the muscular with the 
nervous force throws somelight on the nature of 
the latter, and upon its true relation to elec 
tricity. me 
Matteucci has established beyond a sh 
of doubt that electricity of teeble tension is gene= 
rated in the ordinary nutrition of the muse 
of all animals, and by a particular arrange 
this may be made to assume the current 
passing from the interior to the exterior of 
muscle. The source of this electricity is” 
doubt to be found in the chemical action 
accompanies the nutrition of the museu 
tissue, “ gp gots that which takes place. 
the contact of the arterial blood with’ 
muscular fibre.”* The intensity of this ew 
rent increases in proportion to the activity 
muscular nutrition, and in proportion to 
rank the animals occupy in the scale of beings 
It requires a particular artificial arrangement t 
accumulate the electricity in such a manner as 
that it shall affect the galvanometer; “ durin 
life the two electric states evolved in the mu 
cle neutralize each other at the same poimts 
from which they are evolved;” but in 
arrangement of a muscular pile as devised b 
Matteucci, “a portion of this electricity is p 
in circulation just as it would be ina pilee 
posed of acid and alkali, separated from 
other by a simply conducting body.” 
During the active contraction of a muse 
however, a force is developed which has | 
semblance to electricity, and in his early 
ments was regarded in that light by M 
This power is capable of affecting the t 
the frog in the same manner as electricity. 
following experiment displays this :— 
lower extremity ofa frog and skin it; di 
the sciatic nerve from among.the muscles” 
the posterior part of the thigh, and then se 
rate the thigh by cutting it across just ab 
the knee-joint, leaving the nerve connect 
with the knee and leg; this a4 ion is | 
galvanoscopic frog, so called by Matteucci fo 
the readiness with which it indicates an ele 
tric current; next prepare the lower 
mities of a frog according to Galvani’s m 


‘ 


* Phil. Trans. 1845, p. 294. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


the nerve of the leg is to be laid upon the mus- 
cles of either thigh, and if these muscles be 
excited to contraction by mechanically stimula- 
ting the lumbar nerves, or the spinal cord, or by 
passing a galvanic current through the nerves 
or the cord, the muscles of the galvanoscopic 
leg will be simultaneously contracted. If a 
second and a third galvanoscopic leg be pre- 
pared, and the nerve of the second be laid on 
the muscles of the first, and that of the third be 
laid upon the muscles of the second, contrac- 
tions will take place in all three whenever the 
muscles of the prepared thighs are thrown into 
contraction. Matteucci, to whom we owe the 
discovery of this important fact (which he 
terms induced contraction* ) has failed to cause 
a fourth leg to be thus affected. 

If the galvanoscopic nerve be laid on the 
muscles of a frog’s thigh in which tetanoid con- 
vulsions have been produced by the cessation 
of a long continued inverse current, the in- 
duced contractions will be likewise tetanic.t 

The annexed woodcuts (figs. 398b & 398c) 
will serve to show the manner in which these 
experiments may be performed. 

It is plain, then, that during the contraction 
of muscles, whatever be the means used to sti- 
mulate them, a force is evolved capable of ex- 
citing a nerve laid upon the exterior of the con- 
tracting muscle to such a degree as to cause 
contraction of the muscles it supplies. What 
is this force? The readiness with which it 
excites the nerve of the galvanoscopic leg re- 
sembles the action of electricity, and this view 
of its nature is favoured by the known fact that 
during muscular contraction heat is evolved, and 
in some of the marine animals, light also, ac- 
cording to the observations of Quatrefages. If 
heat and light be produced during muscular 


The limbs of a frog prepared after Galvani’s fashion. 
prepared, but the sciatic nerve is left in connection with the lumbar plexus and the spinal cord. 


Fig. 


720R 


contraction, it is not unreasonable to expect 
that electricity should be evolved likewise. 
Matteucci’s experiments, however, throw some 
difficulty in the way of viewing it as such. He 
finds that this force will freely permeate very 
imperfect conductors of electricity, whilst it will 
not traverse substances which are known to con- 
duct electricity. If gold leaf be placed upon 


the muscle between it and the nerve, the con- 
Fig. 3986. 


The limbs of a frog prepared according to Gal- 
vani’s method, the nerve of the galvanoscopic leg 
being laid across the muscles of one thigh. When 
these muscles are thrown into contraction by any 
means, mechanical or galvanic, those of the leg con- 
tract at the same moment. ° 


398c. 


In another frog the galvanoscopic leg is 
If this 


nerve be laid across the thighs of the frog and the limbs be made to contract, contractions will be 


simultaneously excited in the galvanoscopic leg and also in the other one. 


It is plain that while the 


contractions in the galvanoscopic leg are excited by the direct stimulation of the sciatic nerve, those in 
the other leg are excited through the excitation of the spinal cord by the sensitive fibres of the same 


Sviatic nerve. 
* Phil, Trans, 1845, p. 303. 


+ Id. 1846, p. 487. 


720s 


tractions of the galvanoscopic leg will not take 
place. If, however, a slight tear be made in 
the gold leaf, then the nerve may be excited. 
It is possible that this may arise from the 
electricity being carried off by the gold leaf, so 
that it does not affect the nerve at all. Matteucci 
never succeeded in obtaining the induced con- 
tractions when a solid body was interposed 
between the nerve and muscle, however thin 
it might have been and whatever might be its 
nature ; for this purpose he used flakes of mica 
extremely thin, flakes of sulphate of lime, gold 
leaf, paper smeared with glue, and ieaves of 
vegetables.* 

On the other hand, in interposing some sub- 
stances which are known to be bad conductors 
of electricity, the contractions were obtained. 
The thackat contractions may be excited if the 
nerve be laid upon the skin over the muscles of 
the inducing frog. ‘The experiment,” says 
Matteucci, “ never fails of success, whether the 
inducing contraction be excited by the electric 
current or by any stimulus applied to the lum- 
bar plexuses of the inducing frog.”” The use 
of a very bad conducting body, Venice turpen- 
tine, did not prevent the induced contractions. 
The nearly solid Venice turpentine was ren- 
dered more or less liquid by adding to it a little 
of the volatile oil ofturpentine,and with this the 
muscles were smeared over, and the nerve of 
the galvanoscopic frog was wetted. To prove 
the bad conducting powers of the mixture em- 
ployed, one pole of the exciting pile was ap- 
plied to the muscle and the other to the galva- 
noscopic frog without exciting the least con- 
traction. Yet the contractions were induced 
in the galvanoscopic frog by stimulating the 
muscles of the thigh. This experiment clearly 
proved, as Matteucci remarks, that the induced 
contraction may be excited through a stratum 
of an insulating substance that prevents the 
propagation not only of the muscular and proper 
currents, but also of that current which excites 
the inducing contraction. 

We are forced then by the results of the re- 
markable experiments above detailed to adopt 
the conclusion at which Matteucci has himself 
arrived—that there is no current of electricity 
in the act of muscular contraction. What then 
is the evolved force? It is either an electric 
discharget or a force very analogous to electri- 
city, affecting nerves in a similar way, travelling 
apparently with great rapidity, traversing bodies 
which the galvanic current cannot traverse, and 
yet restrained by substances which freely con- 
duct it. 

I confess myself at a loss to understand how 
Matteucci comes to regard this asa phenomenon 
of the nervous force. In truth, it is a pheno- 
menon which accompanies muscular contrac- 


* Phil. Trans. 1845, On induced contractions. 

t From a letter addressed to M. Dumas by Pro- 
fessor Matteucci, and pnblished in the Comptes 
Rendus for March 15, 1447, it appears that he now 
is rather disposed to regard it as an electric dis- 
charge, as he says, “‘ C’est aprés avoir prouvé que 
des décharges electriques de la bouteille tellement 
faibles qu’elles ne pouvent étre montrées par aucun 
instrument, excepté par la grenouille, que j’ai 
pensé que la contraction induite pouvait étre duc a 
une décharge electrique de ce genre.” 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


tion, and has no relation to the nervous force, 
excepting so far as that is the excitant of the 
muscular action. The essential point of the 
phenomenon is, that during the contraction of 
a muscle a nerve which is laid on it is stimu 
just as it would be by electricity, and causes 
the muscles to which it is distributed to contraet. 
The electric discharge from a muscle which is 
excited to contract through the exercise of 
vous power is in close analogy with the electric 
discharge from the electrical organ 8 
Gymnotus or Torpedo, which is excited through 
the same agency. 7 

Now the proved existence of a muscular 
force, the developement of which is accompa. 
nied with heat, and most probably electricity 
and in some instances, if the statements o 
Quatrefages be correct, with light, justifies us in 
adopting the opinion, as regards the nervous 
force, that this is of an analogous kind, yet exhi- 
biting still less resemblance to electricity than 
the muscular force; and it strikingly illustrates 
the remark of Faraday, that if there be 
for supposing that magnetism is a higher 
tion of force than electricity, so it may well be 
imagined that the nervous power may be of 
still more exalted character and yet within th 
reach of experiment. 

We are a led to these conclusions resp 
ing the muscular and nervous forces. 

1. That both are polar forces and in elo: 
analogy with light, heat, electricity —magnetist 

2. That either may be excited by or trans 
formed into the other—the nervous may & 
the muscular, or the muscular the nervous. 
seems not improbable that it is by this 
of the muscular upon the nervous force 
muscular sense is developed, and as Matteue 
has ingeniously suggested, many moven 
independent on the will, yet following: oth 
which may be voluntary or otherwise, may rest 
from the same cause. 

3. That the same analogy which exists b 
tween electricity and magnetism is found b 
tween these organic polar forces ; the museulg 
being more nearly allied to the former, the 
vous to the latter. : 

4. Both these forces are dependent on 
healthy nutrition of their respective tiss 
muscle and nerve, and the slightest distu 
in that process in either tissue will 
affect the intensity of the force. 

5. Nevertheless there is a certain mutual: 
pean between these two tissues and t 
orces; for the exercise of each is, within cer 
limits, impossible without the other; am 
this exercise is necessary to maintain he 
nutrition, so these forces are to a certain ¢ 
dependent on each other for their normal ¢ 
lopement. The practitioner in medicine 
duly appreciate the great importance 
conclusion. 

The mutual reactions of the nervous 
muscular forces constitute a new and hi 
important field of inquiry, which, if duly 
vated, may clear up many obscurities im 
physiology and pathology of the nervous sy: 

Having thus far considered certain g 
ties in the physiology of the nervous §) 
we may now proceed to inquire into the 


7 


io 


a 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


which each part of this great system takes in 
the production of nervous phenomena. This 
inquiry naturally divides itself into two branches, 
namely, first, the functions of nerves ; secondly, 
those of nervous centres. 

Of the functions of nerves——Nerves are in- 
ternuncial; they possess in themselves (sepa- 
rate from the nervous centre) only a very limited 
power of developing the nervous force, and that 
only in response to a physical stimulus, for 
connection with a centre is necessary for the 
exercise of a mental stimulus. 

In inquiring into the function of any parti- 
cular nerve, the problem is to determine whether 
it propagates the nervous force centrad or periphe- 
rad, and whether it be connected with the centre 
of sensation or with the centre of volition; whe- 
ther, in short, it be sensitive or motor, It must 
be always borne in mind that most nerves con- 
tain nerve-fibres of different endowments, and 
that the office of any given nerve will be deter- 
mined by the endowment of the greatest por- 
tion of its fibres. When we say, therefore, that 
a nerve is motor or sensitive, it is not to be un- 
derstood that all its fibres are exclusively of that 
function, and that it contains no others of a dif- 
ferent endowment. 

In enquiring into the function of a nerve, 
the first point to determine is its anatomy, where- 
by we learn whether it be distributed to mus- 
cular parts or to sentient surfaces; and then to 
ascertain whether its distribution in man corre- 
sponds with that in the inferior animals. Ana- 
tomy, human and comparative, affords by far 
the most certain grounds to enable us to decide 
upon the endowment of a nerve: if the nerve 
be distributed to muscular parts, it is evident 
that it cannot be a merely sentient nerve, 
although it may contain some sentient fibres. 

Experiment upon animals recently dead also 
affords considerable aid in reference to questions 
of this kind. . Mechanical or chemical or galvanic 
irritation of a nerve will cause muscular contrac- 
tions if it be a motor nerve, and will produce 
no perceptible change in either nerve or muscles 
if it be not muscular. Under certain circum- 
stances, however, simple irritation of a nerve, 
while it evinces no change in the nerve itself or 
in the parts with which it is connected, will affect 
the portion of the nervous centre in which it is 
implanted, and will through that excite certain 
motor nerves to stimulate their muscles. To 
affect motor nerves through sensitive ones, it is 
generally necessary to stimulate their peripheral 
fibres, the entire trank remaining uninterrupted 
in its course; and it would appear as if a cer- 
in peripheral organisation, as for instance a 
evelopement of papille on the tegumentary 
urface, were necessary for this purpose. Very 

ely irritation of the trunk of a sentient nerve 
roduces this effect; the least equivocal in- 
tance indeed in which, so far as I know, 
uscular action can be produced in this way, 
. €., by irritation of the central segment of the 
unk of a’nerve, is in the case of the glosso- 
oharyngeal nerve. Dr. John Reid has suc- 
peeded, after section of this nerve, in producing 
traction of the pharyngeal muscles by stimu- 
ing its central segment. 

MM. Longet and Matteucci affirm that a 


720T 


motor nerve may be distinguished from a com- 
pound one by the different effect produced on 
each by opening or closing a galvanic current, 
according to the direction in which it passes in 
the nerve. We have referred above to the 
results of experiments on compound nerves, the 
sciatic for instance, by means of the electric 
current. Compound nerves, as has been shown 
by these means, may at first be affected equally 
On opening as on closing the circuit, whether 
the current be direct or inverse; but after a 
time they are excitable, as shown by the con- 
traction of the muscles below the point stimu- 
lated, only on closing the direct current or 
opening the inverse. With a purely motor 
nerve, however, such as the anterior root of a 
spinal nerve, a different result is obtained after 
the first period has passed; inasmuch as the 
contractions of the muscles can only be excited 
on opening the direct current or closing the in- 
verse.* 

Experiment upon living animals likewise 
affords us some assistance in determining the 
functions of nerves. This mode of inquiry, how- 
ever, must be used with great circumspection, and 
great caution must be observed in the inter- 
pretation of the results which it elicits. Section 
of a nerve paralyses its function, and occasions 
loss of motor or of sensitive power, according 
to the nature of the parts to which the nerve is 
distributed. Experiment of this kind, however, 
frequently leads to very unsatisfactory results, 
because it is often a matter of extreme difficulty 
to reach the nerve in question; the operation 
for that purpose may involve other parts and 
nerves as well, and sometimes it may be impos- 
sible to divide one nerve without injuring ano- 
ther immediately adjacent toit. Moreover, the 
shock of a severe operation frequently produces 
so much disturbance in the entire system of the 
animal as to render it extremely difficult to 
form any accurate opinion as to the effects of 
the section of the nerve under examination. 

Clinical medicine gives very important aid 
to physiological enquiries of this nature. 
Disease or injury of certain nerves impairs or 
destroys or modifies certain functions. The 
various forms of partial paralysis, especially 
those affecting the face, may be referred to in 
illustration of this assertion. Thus a very dis- 
tinct series of signs accompany disease of the 
facial nerve or the portio dura of the seventh 
pair; and these signs mark it very distinctly as 


* Matteucci et Longet, sur la relation qui existe 
entre le sens du courant electrique, et les contrac- 
tion musculaires dues a ce courant. Paris, 1844. 

It is an extraordinary circumstance that the 
excitability of motor nerve-fibres should be mo- 
dified by their simple juxtaposition with sensitive 
fibres. 

I learn from a recent communication from Prof. 
Matteucci, (May, 1847,) that he finds that etheriza- 
tion in dogs modifies the excitability of the nerves, 
so that the mixed nerves, while connected with the 
nervous centre, react with the direct or inverse 
current as the motor nerves do, and excite contrac- 
tions on opening the direct current or closing the 
inverse ; but the moment their connection with the 
cord is destroyed they exhibit the phenomena 
of mixed nerves, causing contraction with the 
direct current on closing, and with the inverse on 
opening, 


720u 


the motor nerve to the muscles of the features, 
and to the orbicular muscles of the eyelids. 
Clinical research, indeed, taken in conjunction 
with anatomy, forms the basis of our present 
accurate knowledge of the office of this nerve. 
In like manner we learn that loss of sensibility 
of the face is dependent on disease affecting the 
fifth nerve, and from the parts of the face 
which are affected by anesthesia we can tell 
what portions of that great nerve are diseased. 
Here again anatomy and clinical medicine have 
mainly contributed to the advance of our know- 
ledge. The partial palsies which affect the 
muscles of the eye-ball likewise give very dis- 
tinct interpretation to the functions of these 
nerves, such as the third and sixth, the action 
of whose muscles is well understood. Many 
other instances might be quoted which clearly 
show that, while clinical medicine and anatomy 
are of infinite service in building up and con- 
firming our knowledge of the function of nerves, 
this knowledge, in its turn, does great service 
in increasing the facility with which we can 
distinguish disease. 

Of the functions of the roots of spinal nerves. 
—The greatest part of the bedy is supplied 
with nerves which are implanted in the spinal 
cord, or which, in anatomical language, have 
their origin in that nervous centre. As these 
nerves present very definite and constant cha- 
racters as regards the manner in which they are 
connected with the centre, characters which are 
not limited to the human subject, but which be- 
long to all classes of vertebrate animals, it was 
a point of primary importance to discover the 
object of an arrangement so peculiar as regards 
its anatomical characters, and so universal. To 
our countryman, Sir C. Bell, belongs the great 
merit of having seen the importance of deter- 
mining this point as a preliminary step in the 
investigations into the nervous system; and to 
him must be awarded the credit of having 
achieved the discovery of the difference in the 
endowment of the anterior and of the posterior 
roots of these nerves. He experimented on 
young rabbits, by removing the posterior wall 
of the spinal column. “On laying bare the 
roots of the spinal nerves,” says Sir C. Bell, “I 
found that r could cut across the posterior 
fasciculus of nerves, which took its origin from 
the posterior portion of the spinal marrow, 
without convulsing the muscles of the back ; 
but that, on touching the anterior fasciculus 
with the point of the knife, the muscles of the 
back were immediately convulsed.”’ + 

Numerous experimenters, subsequent to Bell, 
obtained precisely similar results. Muller, 


* Sir C. Bell’s first essay on this subject was 
rinted in 1811. In 1822 Majendie published his 
rst essay in the Journal de Physiologie Exp. t. iii; 
in 1831 Miiller’s experiments were published in the 
Annales des Sciences Nat. and in Froriep’s Notizen. 
Mr. Alexander Shaw has published a temperate 
and judicious vindication of Sir C. Bell’s claims in 
a volume entitled, ‘‘ Narrative of the Discoveries 
of Sir C. Bell in the Nervous System.” Lond. 1839. 
Valentin is so satisfied of Sir C. Bell’s claim to 
the discovery of the distinct endowments of the 
roots of the spinal nerves, that he designates the 
law thereby determined by a title not very eupho- 
nous to English ears, Lex Belliana. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


however, obtained the most decisive evidence of — 
the proper functions of the roots of the nerves, 
by experimenting on frogs instead of on mam- 
malia; in the former the spinal canal is of 
great width, especially at its lower part, and 
the roots of the nerves can be exposed with 
great facility, whilst in the latter the operation 
is tedious, painful, and bloody, the spinal 
canal narrow, and the roots of the nerves small 
and difficult to get at. Moreover, the exci 
bility of the nerves lasts very much longer ii 
frogs than in mammalia, and on this account 
the former animals are well adapted for dis- 
playing the effects of section of the roots ant 
the influence of mechanical and other stimu 
upon them. 

In these experiments, (which I have frequent 
repeated with similar results,) irritation, mech 
nical orgalvanic, of the anterior root of the spina 
nerve always provokes muscular contractio 
No such effect follows irritation of the posterio) 
root. Section of the anterior root causes para 
lysis of motion; section of the posterior roo 
paralysis of sensation. This latter effect 1 
shown by the entire insensibility to pain evince 
on pinching a toe, whilst in the limb of whi 
the posterior roots of the nerves remained en 
tire such irritation is evidently felt acutely. | 
the anterior roots of the nerves which are di 
tributed to the lower extremities be cut on ¢ 
side, and the posterior roots on the ot 
voluntary power without sensation will 
in the latter, and sensation without vole 
power in the former. ‘ 

Valentin, Seubert, Panizza, and Longet 
performed similar experiments on mammifero 
animals with precisely similar effects. 

I have never seen motion produced by i 
tation of one of the posterior roots of the spin 
nerves still in connexion with the cord, exce 
ing when the galvanic stimulus has been a 
plied, and too strong a current has been € 
ployed. Valentin states that he has obse 
motions so produced in rabbits, but not in frog 
and tortoises. Dr. Hall has seen them in 
turtle and skate. Van Deen speaks of 
as constantly occurring. But Miuiller denies 
power of the posterior roots to excite mo 
except by “ traction on the cord itself.” 
such effect ever follows any kind of stimula 
of the posterior root when it has been separ 
from the cord. = 

The conclusion which inevitably follows fi 
these experiments is that the anterior rot 
each spinal nerve is motor, and the po 
sensitive. 

Comparative anatomy confirms this ¢0 
sion, by showing that a similar arrangemel 
the roots of spinal nerves prevails amo 
classes of vertebrate animals, and that if in 
particular class either the motor or 
power predominate, there is in correspond 
with it a marked developement of the 
or posterior roots. The frequent occurrer 
likewise, of paralysis of sensation and 
as a consequence of disease within the 
canal, also tends to the same in 

Kronenberg finds a small nerve of ec 
nication between the posterior and the antet 
root, which is looked upon by some as be 


- 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


the means of giving to the anterior root the 
slight degree of sensitive power which Majendie 
attributes to it. 

From the determination of the office of each 
root of the spinal nerves we obtain the further 
important result, that the nerve, which is formed 
by the junction of these two roots, is sensitive and 
motor, and that nervous fibres of different en- 
dowments may be bound together in the same 
sheath constituting one nerve, which is com- 
pound in its functions. And the anatomical 
distribution of spinal nerves, both in man and 
the inferior animals, to the muscles and sen- 
sitive surfaces of the trunk and extremities, is 
entirely confirmatory of the results thus derived 
from experiment. 

By the use of the various means for deter- 
mining the functions of nerves, above detailed, 
and aided by the determination of the law dis- 
covered and developed by Bell and others, 
as to the motor nature of the anterior and the sen- 
sitive endowment of the posterior roots, and the 
subsequent binding together of these fibres in one 
sheath to form a compound nerve, physiologists 
have made great advances in determining the 
functions of the various encephalic nerves, and 
our knowledge on this subject may be said to 
have approached more to perfection than that 
of any other physiological questions. The main 
facts connected with the anatomy and _ physio- 
logy of each of these nerves will be found under 
the articles headed by their names. 

Of the functions of the nervous centres.— 
In examining into the functions of the va- 
rious parts of the cerebro-spinal axis I shall 
adhere to the definitions already adopted in the 
previous part of this article, and use the term 
spinal cord as denoting the nervous cylinder 
within the spinal canal, and the encepha/on as 
the intra-cranial mass, consisting of medulla 
oblongata, mesocephale, cerebellum, and cere- 
brum. ; 

Of the functions of the spinal cord.—It was 
long held that the spinal cord was no more 
than a bundle of nerves proceeding from or to 
the brain, and emerging at various points of 
the vertebral canal to be distributed to their 
destined regions.* 

The anatomy of the organ, however, suffi- 
ciently exposed the error of this opinion. The 

| existence of a large quantity of vesicular matter 
in it varying in quantity according to the bulk 
of its segments showed that it was more than a 
mere fasciculus of nerves. Although the true 
office of the spinal cord was known to physio- 
logists long before, to Prochaska for example, 
Gall appears to have been the first who ad- 
duced the best proofs from anatomy to show 
that the spinal cord was not a mere appendage 
to the brain, but a special centre in itself. His 
principal arguments were derived from the 
want of any constant proportion in bulk be- 
tween it and the brain, the spinal cord being 
small with a large brain, as in man, and large 
with a small brain, as in the inferior mammalia 
and in other vertebrata, from the fact that it 
does not taper gradually in proportion as it 


* That this was Willis’s view a perusal of chap- 


4 Xviii. and xix. of his Cerebri Anatome will 
ew. 


—— 


720x 


gives off nerves, but on the contrary is alter- 
nately large orsmall according to the numberand 
volume of the nerves which are given off from 
its various segments; and, lastly, from the ana- 
logy which he indicated between the spinal 
cord of vertebrata and the ganglionic chain of 
articulata, the former consisting of a series of 
ganglia fused together, the latter remaining 
separate by reason of the peculiar disposi- 
tion of the bodies of these animals in distinct 
segments. 

The determination of the functions of the 
nerves which are intimately connected with or 
implanted in the spinal cord affords some clue 
to the solution of the problem as to its own 
office. There can be no doubt that as the 
nerves of sensation as well as those of motion 
of the trunk and extremities are all, to say the 
least, intimately connected with the cord, this 
organ must be the medium of the reception 
and propagation of the sentient impressions 
made upon the one, and of the mental or phy- 
sical impulses which excite the others. 

If, moreover, we look to the results of expe- 
riments on the lower animals, or to the effects 
of injury or disease in the human body, we 
obtain the following important facts :—1st, that 
the perfect connexion of this organ, in all its 
integrity, with the encephalon is the essential 
condition for the full and complete exercise of the 
nervous force, whether for sensation or voluntary 
motion, as far as regards the trunk and extremi- 
ties; 2nd, that division of the cord, so as com- 
pletely to separate the lower from the upper 
segment, causes paralysis both of sensation 
and voluntary motion in the parts supplied with 
nerves from the lower segment; 3rd, if the 
section be made high up in the neck so as to 
separate the cord from the medulla oblongata, 
all the parts supplied by spinal nerves will be 
paralysed in the same way; by such an expe- 
riment the spinal cord remains entire, but its 
continuity with the encephalon is interrupted. 

In cases of injury to the vertebral column 
it may be laid down as the rule that the higher 
the seat of injury the more extensive will be 
the paralysis. A man whe has received exten- 
sive injury of the spinal cord high up in the 
neck is like a living head and a dead trunk, 
dead to its own sensations, and to all voluntary 
control over its movements. The same rule 
prevails with regard to the effects resulting from 
disease of the vertebre or from any intra-spinal 
growth, or from a morbid state of the cord itself, 
there being only this difference, that where the 
morbid change is chronic, the paralytic effects 
are less marked than in injury or acute disease. 
In all cases the extent of the paralysis affords 
a correct indication of the seat of the solution 
of continuity. ; 

If the spinal cord be divided partially in 
the transverse direction, there will be paralysis 
of parts on the same side with the injury. 
Dr. Yellowly has put on record an experi- 
ment of Sir Astley Cooper’s, in which he 
divided the right half of the spinal cord in 
a dog just above the first vertebra. The effect 
was paralysis of the motions of the ribs on the 
right side, and of the right posterior and pos- 
terior extremities, with irritation of those of 


720y 


the left side.* A longitudinal section of the 
cord along the median line in frogs does not 
cause paralysis; it gives rise, however, to a 
temporary disturbance of the functions of the 
cord which soon subsides.+ 

Continuity of the spinal cord and encepha- 
Jon is then the condition necessary to establish 
the control of the former organ over the volun- 
tary movements and sensations of the trunk. 
The disunion of the cord or any portion of it 
from the encephalon dissociates the cord or 
the separated segment of it from all participa- 
tion in mental nervous actions. So long as the 
cord is united with the brain, it takes a certain 
share in mental! nervous actions, in acts of sen- 
sation and volition; this, however, it loses 
when disease or accident separates the one from 
the other. 

It is plain, then, that the spinal cord, although 
apart from the encephalon it takes no share 
in sensations and voluntary actions, (for then, 
indeed, these phenomena cannot take place as 
far as regards the trunk and extremities,) while 
united with the encephalon participates fully 
in sensori-volitional actions, and its integrity 
is quite necessary to the perfection of those 
actions. 

I repeat that we are not justified in supposing 
that the mind localises itself exclusively in some 
orall of the gangliform bodies, the assemblage 
of which constitutes the encephalon; but this we 
may assert, with perfect justice, that when the 
cord has been separated from the encephalon, 
the mind appears as it were to cling to the 
latter organ, and to lose all its connection with 
the former. 

Does then the cord, under these circum- 
stances, lose all its power? Does it, when sepa- 
rate from the encephalon, shew no indication 
of acting as a nervous centre? Undoubtedly 
it does show abundant indications. A series 
of actions, which had attracted the notice of 
several physiologists, are still capable of being 
developed through the instrumentality of the 
whole cord or of any portion of it, the nerves 
of which may remain uninjured both as to their 
central and peripheral connections. 

Phenomena of this nature may be produced 
in all vertebrate animals. They are, however, 
especially marked in the cold-blooded classes, 
in consequence of the more enduring character 
of the nervous force in those creatures than in 
the warm-blooded. Hence frogs, salamanders, 
snakes, turtles, fishes, have been generally 
selected by physiologists for exhibiting these 
phenomena. In the young of warm-blooded 
animals they are more manifest than in adults 
of the same class. 

If a frog be pithed by dividing the line of 
junction of the medulla oblongata with the 
spinal cord, the following effects may be ob- 
served. After the first disturbance, general 
convulsions, &c., consequent upon the division 
of the cord, the animal, if placed on a table, 
will assume his ordinary position of rest. In 
some cases, however, frequent combined move- 
ments, much resembling acts of volition, will 


* Med. Chir. Trans, vol. i. p. 200. 
+ See Flourens’ Experiments, Syst. Nerveux. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


take place for a longer or shorter time after 
the operation. When all such disturbance 
has ceased the animal remains perfectly still” 
and as if in repose, nor does it exhibit the 
slightest appearance or give the least expre 
sion of pain or suffering. It is quite unable 
to produce any spontaneous or voluntary move- 
ment of parts supplied with nerves from be~ 
low the section, that is, of the trunk or extre- 
mities. However one may try to frighten it, 
it remains in the same place and posture 
The only appearance of voluntary motion is the 
winking of the eyelids, which, however, proba- 
bly is not excited by the will. If, now, a toeb 
pinched, instantly the limb is drawn up, or the 
animal seems to push away the irritating agent 
and then draws up the leg again into its ob 
position. Sometimes a stimulus of this kin 
excites both legs, and causes them to be thrown 
violently backwards. A similar movement 
most constantly follows stimulation of the 
If the skin be pinched at any Parts ome 
neighbouring muscle or muscles will be thro 
into action. Irritation of the anterior extre 
mities will occasion movements of them; bt 
it is worthy of note that these movements an 
seldom so energetic as those of the poster 
extremities. ; 
We may remark here, that phenomena + 
this kind are not confined to the trunk am 
extremities, which are supplied only by sping 
nerves. The head and face, with which 
encephalon remains in connection, exhib 
similar actions. The slightest touch to t 
margin of either eyelid or to the surface” 
the conjunctiva causes instantaneous winkin 
the attempt to depress the lower jaw for 
purpose of opening the mouth is resisted ; 
the act of deglutition is provoked by apply 
a mechanical stimulus to the back of 
throat.* 
Actions similar to those which take place 
the decapitated frog, occur in the human subj 
when the spinal cord has been separated fin 
its encephalic connections by disease or ace 
dent. In such cases it is found thatal ht 
will cannot move the paralysed parts, the loy 
extremities for instance, movements do ¢ 


* Sir Gilbert Blane, in his admirable Croo 
Lecture on muscular motion, having drawn the | 
tinction between instinctive and voluntary 
makes the following remarks. ‘‘ There 
which show that instinctive actions, even in 
mals endowed with brain and nerves, do not 
pend on sensation. I took a live kitten, a few: 
old, and divided the spinal marrow by cutti 
across at the neck. The hind paws being th 
tated by pricking them, and by touching 
a hot wire, the muscles belonging to the pi 
extremities were thrown into contraction, 80. 
produce the motion of shrinking from the i 
The same effects were observed in another k 
after the head was entirely separated fi 
body.” And again, ‘‘ In an acephaloas 
the like phenomena were observable. It 
its knees, when the soles of its feet were tic 
it performed the act of suction; passed rin 
feces ; and swallowed food.” * * * The! 
takes place with regard to insects; for, after | 
head of a bee is separated from the 
hinder part will sting, upon the application 
a stimulus as would excite the same action 
animal in a perfect state.” : 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


in them of which the individual is wholly un- 
conscious, and which he is utterly unable to pre- 
vent. Sometimes these take place seemingly 
quite spontaneously; at other times they are 
excited by the application of a stimulus to some 
surface supplied by spinal nerves. The move- 
ments of this kind, which seem to occur 
spontaneously, exhibit so close a resemblance to 
voluntary actions as to render it impossible to 
distinguish them, did not the consciousness of 
the patient in some cases assure him of the in- 
active state of his will in reference to them. 

The comparison of the phenomena which 
occur in pithed or decapitated animals with the 
actions developed in man under these morbid 
states, affords most conclusive evidence as to the 
important question of the connection of these 
phenomena with the mind. In a pithed or de- 
capitated animal we can only judge of the 
exercise of volition or the perception of sensitive 
impressions by external signs. And so far as 
these go we are justified in maintaining that, 
while the mental principle is unextinguished, it 
nevertheless has lost its influence over or connec- 
tion with that portion of the cerebro-spinal axis 
which is separated from the encephalon. But 
in the human subject we have the evidence of 
the individual himself, who, from his own con- 
sciousness, avows the integrity of his will and 
perception, but admits their dissociation from 
those parts of the body whose nerves are im- 
Biante) in the severed portion of the cord. 

Let us refer to such a case as has been 
already quoted. A man has fallen from a 
height and fractured or displaced one or more 
of his cervical vertebre; we find the patient 
presenting the following phenomena. His 
trunk and extremities appear as if dead, ex- 
cepting the movements of the diaphragm, 
while the head lives. In full possessien of his 
mental faculties and powers, he is, nevertheless, 
unconscious, save from the exercise of his sight, 
of any changes which may affect the parts 
below his head, nor is the utmost effort of his 
will sufficient to produce a movement of any, 
even the smallest, of these parts. If the stun- 
ning effect of the accident have passed off, 
tickling the soles of the feet will be found to 
cause movements, of which, as well as of the 
application of the stimulus, the patient is un- 
conscious ; the introduction of a catheter into 
the urethra, which the patient does not feel, 
excites the penis to erection. The limbs may 
be irritated in various ways, but without ex- 
citing any effect which the patient can per- 
ceive, excepting movements, and these he is 
aware of only from his happening to see them. 
It is important to notice that, in cases of this 
kind, movements are difficult of excitation in 
the upper extremities, while they are aroused 
with great facility in the lower. 

In these cases movements may be excited in 
both lower extremities by passing a catheter 
into the bladder. Sometimes internal changes, 
the precise nature of which we cannot always 
appreciate, but which are often the result of 
the irritation of flatus or other matters in 
the intestinal canal, excite movements in the 
lower or even in the upper extremities, and the 
patient is disturbed by cramps and spasmodic 


+ 


7202 


movements, more or less violent, at night. It 
is very remarkable, that while a patient is almost 
wholly insensible to external stimuli, he feels 
and even suffers pain from cramps of this 
kind. 

In the hemiplegic paralysis which results 
from an apoplectic clot, or some other lesion 
affecting one side of the brain, when the para- 
lysis is complete, the influence of the will over 
the paralysed side is altogether cut off, sensi- 
bility, however, generally remaining. In such 
cases it is wonderful how easily movements 
may be excited in the palsied leg—very rarely 
in the arm—by the application of stimuli to 
the sole of the foot, or elsewhere with less 
facility. The patient, who acknowledges lis 
utter inability to move even one of his toes, is 
astonished at the rapidity and extent to which 
the whole lower extremity may be moved by 
touching the sole of the foot, even with a feather. 
It is proper to add that there is much variety as 
regards the extent to which these actions take 
place in hemiplegic cases, owing to causes not 
yet fully understood; still they do occur in a 
large proportion of instances, and in the most 
marked way. Their developement is frequently 
in the inverse proportion of the withdrawal of the 
power of the will. When the paralysis to voli- 
tion is only imperfect, the effect of stimuli in 
exciting motions is less obvious, because of the 
restraining power of the will. 

The cases of anencephalic foetuses may be 
properly referred to as affording instances of 
similar movements. In these beings we have 
no movements which can be supposed to 
originate in any effort of the will, nor is there 
any proof of the existence of sensibility. Move- 
ments, however, of definite kind do occur under 
the influence of a stimulus applied to the 
surface. 

Actions of the same kind, i. e., provoked 
by stimuli applied to some surface to which 
nerves are distributed, will continue to be 
manifested in animals after decapitation, not 
only in the trunk and extremities, but also in 
those segments of the former with which a portion 
of the spinal cord remains connected. If the 
body of a snake or an eel be divided into 
several segments, each one will exhibit move- 
ments for some time upon the application of a 
stimulus. The same thing may be observed in 
frogs, salamanders, turtles, and other cold- 
blooded creatures. It may be shown in a re- 
markable manner in the male frog in the early 
spring, during the copulating season. At this 
period an excessive developement of the papil- 
lary texture of the integuments covering the 
thumbs takes place; and this seems to be con- 
nected with the tendency which the male frog 
exhibits during this period of sexual excite- 
ment to lay hold on any thing that is brought 
within the embrace of his anterior extremities 
and in contact with the enlarged thumbs. If 
the animal be made to lay hold firmly of any 
object, two fingers of the observer, for instance, 
the head and the posterior half of the trunk 
may be removed, and yet the anterior extre- 
mities will maintain their grasp with as much 
firmness as if the animal were unmutilated. 
And when the frog is in full vigour, they will 


720y 


the left side.* A longitudinal section of the 
cord along the median line in frogs does not 
cause paralysis; it gives rise, however, to a 
es sae disturbance of the functions of the 
cord which soon subsides.+ 

Continuity of the spinal cord and encepha- 
lon is then the condition necessary to establish 
the control of the former organ over the volun- 
tary movements and sensations of the trunk. 
The disunion of the cord or any portion of it 
from the encephalon dissociates the cord or 
the separated segment of it from all participa- 
tion in mental nervous actions. So long as the 
cord is united with the brain, it takes a certain 
share in mental! nervous actions, in acts of sen- 
sation and volition; this, however, it loses 
when disease or accident separates the one from 
the other. 

It is plain, then, that the spinal cord, although 
apart from the encephalon it takes no share 
in sensations and voluntary actions, (for then, 
indeed, these phenomena cannot take place as 
far as regards the trunk and extremities,) while 
united with the encephalon participates fully 
in sensori-volitional actions, and its integrity 
is quite necessary to the perfection of those 
actions. 

1 repeat that we are not justified in supposing 
that the mind localises itself exclusively in some 
or all of the gangliform bodies, the assemblage 
of which constitutes the encephalon; but this we 
may assert, with perfect justice, that when the 
cord has been separated from the encephalon, 
the mind appears as it were to cling to the 
latter organ, and to lose all its connection with 
the former. 

Does then the cord, under these circum- 
stances, lose all its power? Does it, when sepa- 
rate from the encephalon, shew no indication 
of acting as a nervous centre? Undoubtedly 
it does show abundant indications. A series 
of actions, which had attracted the notice of 
several physiologists, are still capable of being 
developed through the instrumentality of the 
whole cord or of any portion of it, the nerves 
of which may remain uninjured both as to their 
central and peripheral connections. 

Phenomena of this nature may be produced 
in all vertebrate animals. They are, however, 
especially marked in the cold-blooded classes, 
in consequence of the more enduring character 
of the nervous force in those creatures than in 
the warm-blooded. Hence frogs, salamanders, 
snakes, turtles, fishes, have been generally 
selected by physiologists for exhibiting these 
phenomena. In the young of warm-blooded 
animals they are more manifest than in adults 
of the same class. 

If a frog be pithed by dividing the line of 
junction of the medulla oblongata with the 
spinal cord, the following effects may be ob- 
served. After the first disturbance, general 
convulsions, &c., consequent upon the division 
of the cord, the animal, if placed on a table, 
will assume his ordinary position of rest. In 
some cases, however, frequent combined move- 
ments, much resembling acts of volition, will 


* Med. Chir. Trans, vol. i. p. 200. 
+ See Flourens’ Experiments, Syst. Nerveux. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


take place for a longer or shorter time after 
the operation. When all such disturbance 
has ceased the animal remains perfectly still — 
and as if in repose, nor does it exhibit the 
slightest appearance or give the least expres- 
sion of pain or suffering. It is quite unable i 
to produce any spontaneous or voluntary move- — 
ment of parts supplied with nerves from be- 
low the section, that is, of the trunk or extre- 
mities. However one may try to frighten it, 
it remains in the same place and posture, — 
The only appearance of voluntary motion is the 
winking of the eyelids, which, however, proba- 
bly is not excited by the will. If, now, a toe be 
pinched, instantly the limb is drawn up, or the 
animal seems to push away the irritating L 
and then draws up the leg again into its old 
position. Sometimes a stimulus of this kind 
excites both legs, and causes them to be thrown 
violently backwards. A similar movement al-~ 
most constantly follows stimulation of the anus. 
If the skin be pinched at any cm some 
neighbouring muscle or muscles will be thrown — 
into action. Irritation of the anterior extre- 
mities will occasion movements of them; but 
it is worthy of note that these movements are 
seldom so energetic as those of the posterior 
extremities. « 
We may remark here, that phenomena ¢ 
this kind are not confined to the trunk M3 
extremities, which are supplied only by spinal 
nerves. The head and face, with which the 
encephalon remains in connection, exhibit 
similar actions. The slightest touch to the 
margin of either eyelid or to the surface of 
the conjunctiva causes instantaneous winking 
the attempt to depress the lower jaw for the 
purpose of opening the mouth is resisted ; a 
the act of deglutition is provoked by applyit 
a mechanical stimulus to the back of the 
throat.* ‘- 
Actions similar to those which take place 
the decapitated frog, occur in the human suk 
when the spinal cord has been separated fi 
its encephalic connections by disease or 
dent. In such cases it is found thatal 
will cannot move the paralysed parts, the lows 
extremities for instance, movements do oce 


~*~ 


em 
¥ 

Dug 
: x 


* Sir Gilbert Blane, in his admirable C 
Lecture on muscular motion, having drawn the 
tinction between instinctive and voluntary action 
makes the following remarks. ‘‘ There are fat 
which show that instinctive actions, even in a 
mals endowed with brain and nerves, do i 
pend on sensation. I took a live kitten, a few di 
old, and divided the spinal marrow by cutti 
across at the neck. The hind paws being then | 
tated by pricking them, and by touching m } 
a hot wire, the muscles belonging to poste 
extremities were thrown into contraction, 80 a 

roduce the motion of shrinking from the inju 
The same effects were observed in another kit 
after the head was entirely separated from 
body.” And again, ‘In an i 
the like phenomena were observable. It 
its knees, when the soles of its feet were tickle 
it performed the act of suction; passed rine @ 
feces ; and swallowed food.” * * * «Thel 
takes place with regard to insects; for, after 
head of a bee is separated from the body, 
hinder part will sting, upon the application of 
a stimulus as would excite the same action in 
animal in a perfect state.” ' 


4 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


in them of which the individual is wholly un- 
conscious, and which he is utterly unable to pre- 
vent. Sometimes these take place seemingly 
quite spontaneously; at other times they are 
excited by the application of a stimulus to some 
surface supplied by spinal nerves. The move- 
ments of this kind, which seem to occur 
spontaneously, exhibit so close a resemblance to 
voluntary actions as to render it impossible to 
distinguish them, did not the consciousness of 
the patient in some cases assure him of the in- 
active state of his will in reference to them. 

The comparison of the phenomena which 
occur in pithed or decapitated animals with the 
actions developed in man under these morbid 
states, affords most conclusive evidence as to the 
important question of the connection of these 
phenomena with the mind. In a pithed or de- 
capitated animal we can only judge of the 
exercise of volition or the perception of sensitive 
impressions by external signs. And so far as 
these go we are justified in maintaining that, 
while the mental principle is unextinguished, it 
nevertheless has lost its influence over or connec- 
tion with that portion of the cerebro-spinal axis 
which is separated from the encephalon. But 
in the human subject we have the evidence of 
the individual himself, who, from his own con- 
sciousness, avows the integrity of his will and 
perception, but admits their dissociation from 
those parts of the body whose nerves are im- 
planted in the severed portion of the cord. 

Let us refer to such a case as has been 
already quoted. A man has fallen from a 
height and fractured or displaced one or more 
of his cervical vertebre; we find the patient 
presenting the following phenomena. His 
trunk and extremities appear as if dead, ex- 
cepting the movements of the diaphragm, 
while the head lives. In full possession of his 
mental faculties and powers, he is, nevertheless, 
unconscious, save from the exercise of his sight, 
of any changes which may affect the parts 
below his head, nor is the utmost effort of his 
will sufficient to produce a movement of any, 
even the smallest, of these parts. If the stun- 
ning effect of the accident have passed off, 
tickling the soles of the feet will be found to 
cause movements, of which, as well as of the 
application of the stimulus, the patient is un- 
conscious ; the introduction of a catheter into 
the urethra, which the patient does not feel, 
excites the penis to erection. The limbs may 
be irritated in various ways, but without ex- 
citing any effect which the patient can per- 
ceive, excepting movements, and these he is 
aware of only from his happening to see them. 
It is important to notice that, in cases of this 
kind, movements are difficult of excitation in 
the upper extremities, while they are aroused 
with great facility in the lower. 

In these cases movements may be excited in 
both lower extremities by passing a catheter 
into the bladder. Sometimes internal changes, 
the precise nature of which we cannot always 
appreciate, but which are often the result of 
the irritation of flatus or other matters in 
the intestinal canal, excite movements in the 
lower or even in the upper extremities, and the 
patient is disturbed by cramps and spasmodic 


7202 


movements, more or less violent, at night. It 
is very remarkable, that while a patient is almost 
wholly insensible to external stimuli, he feels 
and even suffers pain from cramps of this 
kind. 

In the hemiplegic paralysis which results 
from an apoplectic clot, or some other lesion 
affecting one side of the brain, when the para- 
lysis is complete, the influence of the will over 
the paralysed side is altogether cut off, sensi- 
bility, however, generally remaining. In such 
cases it is wonderful how easily movements 
may be excited in the palsied leg—very rarely 
in the arm—by the application of stimuli to 
the sole of the foot, or elsewhere with less 
facility. The patient, who acknowledges lis 
utter inability to move even one of his toes, is 
astonished at the rapidity and extent to which 
the whole lower extremity may be moved by 
touching the sole of the foot, even with a feather. 
It is proper to add that there is much variety as 
regards the extent to which these actions take 
place in hemiplegic cases, owing to causes not 
yet fully understood; still they do occur in a 
large proportion of instances, and in the most 
marked way. Their developement is frequently 
in the inverse proportion of the withdrawal of the 
power of the will. When the paralysis to voli- 
tion is only imperfect, the effect of stimuli in 
exciting motions is less obvious, because of the 
restraining power of the will. 

The cases of anencephalic foetuses may be 
properly referred to as affording instances of 
similar movements. In these beings we have 
no movements which can be supposed to 
originate in any effort of the will, nor is there 
any proof of the existence of sensibility. Move- 
ments, however, of definite kind do occur under 
the influence of a stimulus applied to the 
surface. 

Actions of the same kind, i.e., provoked 
by stimuli applied to some surface to which 
nerves are distributed, will continue to be 
manifested in animals after decapitation, not 
only in the trunk and extremities, but also in 
those segments of the former with which a portion 
of the spinal cord remains connected. If the 
body of a snake or an eel be divided into 
several segments, each one will exhibit move- 


. ments for some time upon the application of a 


stimulus. The same thing may be observed in 
frogs, salamanders, turtles, and other cold- 
blooded creatures. It may be shown in a re- 
markable manner in the male frog in the early 
spring, during the copulating season. At this 
period an excessive developement of the papil- 
lary texture of the integuments covering the 
thumbs takes place; and this seems to be con- 
nected with the tendency which the male frog 
exhibits during this period of sexual excite- 
ment to lay hold on any thing that is brought 
within the embrace of his anterior extremities 
and in contact with the enlarged thumbs. If 
the animal be made to lay hold firmly of any 
object, two fingers of the observer, for instance, 
the head and the posterior half of the trunk 
may be removed, and yet the anterior extre- 
mities will maintain their grasp with as much 
firmness as if the animal were unmutilated. 
And when the frog is in full vigour, they will 


721A 


continue their hold for as long as a quarter of 
an hour or twenty minutes after the removal of 
the head and the posterior segment of the 
body. But let the portion of the cord which 
is connected with the anterior extremities be 
destroyed, and all such power of movement 
becomes completely annihilated. 

In birds and mammalia phenomena of this 
kind are less conspicuous than in the cold- 
blooded animals, because in them the nervous 
power becomes extinct so speedily after any 
mutilation of the body. The power itself is 
no doubt more energetic, as the muscular 
power is, but it is less lasting. 

In the articulate classes movements of pre- 
cisely the same nature may be observed. The 
common earthworm may be divided into seve- 
ral pieces, and each piece will continue to 
writhe so long as the irritation produced by the 
subdivision remains, and after that has ceased, 
movements may be excited in any seginent by 
stimulating its surface: the same phenomena 
are observable in leeches and various insects. 
These actions are exactly analogous to those in 
the segments of the divided body of a verte- 
brate animal. 
creature has in its proper ganglion the analogue 
of the piece of the spinal cord remaining with 
the segment of the vertebrate animal. These 
phenomena of function, conjoined with certain 
anatomical resemblances, make it quite certain 
that the abdominal ganglionic chain of the 
articulata is analogous, not, as formerly sup- 
posed, to the sympathetic system, but to the 
cerebro-spinal centres of Vertebrata. In both 
the Vertebrata and the Invertebrate Articulata 
each segment of the body is provided with its 
proper ganglionic centre, which is to a certain 
extent independent of the rest. In the latter, 
the centres of the segments remain distinct, 
although connected by fibres which pass from 
one to the other; but in the former they are as 
it were fused together at their extremities, and 
from that fusion results the single cylindrical 
nervous centre which we call the spinal cord. 

An experiment, to which attention has been 
directed by Flourens, illustrates very well the 
difference in the character of the actions of two 

ortions of the spinal cord, according as the 

rain is connected with or dissociated from it. 
The spinal cord of an animal is divided about 
its middle; when the anterior segment (that 
which still retains its connection with the brain) 
is irritated, not only are movements of the 
anterior extremities produced, but the animal 
evinces unequivocal signs of pain; when, how- 
ever, the posterior extremity is irritated, the 
animal seems not only insensibie to pain, but 
unconscious even of the movements that have 
been excited in the posterior extremities. If a 
frog be divided in the back into two segments, 
the anterior portion crawls about, exhibiting all 
the indications of sensation and volition; the 
png segment remains quite motionless un- 
ess some stimulus be applied to it, when 
movements more or less active may be ex- 
cited. 

Nothing can be more conclusive than such 
an experiment, in illustration of the fact that 
connection with the encephalon is necessary to 


Each portion of the articulate. 


.Jiritation of its substance, or by the infly 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


sensation; and that movements, not only with- 
out volition, but also without consciousness, 
may be excited by stimulating the segments 
separated from it. But there is nothing in this 
experiment to justify the conclusion that during 
the entire and unmutilated state of the cerebro- 
spinal axis the mind has no connection with 
the spinal cord. The experiment only shows 
that when a portion of that great centre has 
been removed, the mind retains its connection 
with the higher or encephalic portion, deserting 
that which is merely spinal. . 

Direct irritation of the spinal cord is capable 
of exciting these movements as much as when 
the stimulus is applied to the skin. 

All these motions cease when the spinal cord 
is removed ; no movement of any kind, volun- 
tary or involuntary, can then be excited, except 
by directly stimulating the muscles, or the nerves 
which supply them, and such movements want 
the combined and harmonious character which 
belongs to those which are excited through the 
nervous centre. 

Division of all the roots of the nerves at 
their emergence from the spinal cord annihi- 
lates these movements as completely as the 
removal of the cord itself. Under sueh circum- 
stances no motion can be excited by stimulation 
of the surface of the body, nor by irritating the 
cord itself; and this fact may be regarded as 
an unequivocal proof that the nerves, in ordi- 
nary actions, are propagators of the change 
produced by impressions to or from the centres ; 
and that in the physical nervous actions -the 
stimulus acts, not from one nerve to another 
directly, but through the afferent nerve upon — 
the centre, which in its turn excites the motor — 
nerve. i 

All these facts in the physiological history 
of the spinal cord lead unequivocally to the 
following conclusions respecting its office :— 
1. that the spinal cord (that term being used in 
its simple anatomical sense, the intra-spinal 
mass ) in union with the brain is the instrument 
of sensation and voluntary motion to the trunk 
and extremities; 2. that the spinal cord may — 
be the medium for the excitation of moveme 
independently of volition or sensation in p 
supplied by spinal nerves, either by di 


1 


™ 


of a stimulus conveyed to it from some surface 
of the trunk or extremities by its nerves distri- 
buted upon that surface. 

Of the physical nervous actions of the co 
We must pause here to make a more exte 
reference to those actions of the De gp 
which are capable of being excited by per 
pheral stimulation, and which are independent 
of mental change. There is no point in the 
physiology of the nervous system of more inte 
rest or importance than this, inasmuch as these 
actions are not limited to the cord, but 
place in other portions of the cerebra 
centre, in which nerves are implanted, and 
even in ganglions from which nerves take their 
rise. 

The existence of a class of actions like th 
has long been known to physicians and physio- 
logists. By the name of sympathetic act 
they excited great interest as to the mode 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


their production. And anatomists explored 
the frequent and often intricate anastomoses 
of nerves in their peripheral distribution with 
the hope of finding in them some clue to the 
explanation of these phenomena. 

To these actions I prefer to apply the name 
physical nervous actions to mark their peculiar 
characteristic, namely, independence of the 
mind, and to denote that they are the result of 
a physical change produced by a physical im- 
pression, and therefore, in their causation, wholly 
independent of mental influence. The term ex- 
cito-motory has been applied to them by Dr. 
Hall. To this term, however, there appear to 
me to be several serious objections. First, this 
term implies that the excitation of motion takes 
place in no other way than by a mechanism 
similar to that by which these movements are 
produced. Secondly, it denotes the existence of 
a peculiar excito-motory power different from 
the ordinary vis nervosa, the agent in all ner- 
vous phenomena. As if this force were not 
capable of being roused into action at one time 
by a mental stimulus, at another by a physical 
stimulus, or at a third by a mental and phy- 
Sical stimulus united. Persons get into the 
habit of using the terms “excito-motory power,” 
* excito-motory phenomena,” as if this power, 
or these phenomena were something quite pe- 
culiar, quite sw: generis, and limited to a spe- 
cial part of the nervous system, losing sight of 
the real truth that they differ from voluntary 
actions only in their mode of excitation, that 
is, by a physical and not by a mental stimulus. 
Thirdly, it limits the reflecting power of the 
nervous centres (i.e. the propagation of the 
change induced by the application of a physical 
stimulus at the periphery) to reflection from 
Sensitive to motor nerves. Now there are many 
facts which shew that reflection may take place 
from a sensitive to another sensitive nerve, and 
many of the phenomena of sympathy admit of 
no other explanation excepting on this prin- 
ciple. And I am by no means prepared to 
affirm that reflection may not take place from 
motor to sensitive nerves, or even from motor 
to other motor nerves, under circumstances of 
an exalted polarity of the nerves and the centres. 
Fourthly, some of these so-called excito-motory 
phenomena have nothing to do with muscular 
action. Take, for example, erection of the penis: 
it has not been shown that muscular fibres take 
any part in the production of this phenomenon, 
or that the stimulus which gives rise to it does 
more than create a change in the vessels of the 
penis, which seems due to muscular relaxation 
rather than to muscular contraction. The exci- 
tation of a gland to secrete by stimulating some 
surface connected with it, as the mammary 
gland by stimulating the nipple, is no doubt 
a phenomenon of the same kind, but not one 
in which muscular fibres are excited to contract. 

The term “ reflex actions,” in accordance 
with Prochaska’s view of the reflecting power 
of the nervous centre, is objectionable inas- 
much as it fails to denote fully the physical 
character of the phenomena ; and, moreover, it 
1s applicable only to a class of the actions in 
question, those, namely, in which the excitation 

VOL, IIT. 


721s 


of a motor or sensitive nerve takes place through 
the primary excitation of another motor or sensi- 
tive nerve. Either this term, however, or that 
which I have proposed, may be used without in- 
convenience to science because they involve no 
particular theory, and yet sufficiently express 
some leading feature of the phenomena, 7eflec- 
tion at the centre, in the one case—a physical 
exciting cause of a phenomenon purely physical 
in the other. It may be objected to the term 
“physical nervous action” that the actions 
produced by the mental stimulus are equally 
physical in their intrinsic nature. When, how- 
ever, the term is habitually used in contrast with 
“ mental nervous action,” all practical difficulty 
or objection vanishes—both are physical pheno- 
mena,—but one is physical in its essence and 
also in its exciting cause; the other is physical 
in its essence, but mental in its cause. The 
term physical nervous actions may be regarded 
as a generic expression for all those nervous 
phenomena in which the mind takes no neces- 
sary share; reflex actions being a specific term 
denoting those physical nervous actions of which 
reflexion at the centre is a prominent character. 
In this sense I shall use these terms respectively. 

By none were these phenomena more care- 
fully studied than by Whytt and Prochaska. 
In 1764 Whytt published his “ Observations 
on Nervous Diseases,” a work full of the most 
valuable clinical and practical information. In 
the first chapter of this book, “ on the structure, 
use, and sympathy of the nerves,” he enumerates 
Various instances of sympathetic actions, and 
discusses the mode of their production. To 
show that he regarded in this light the actions 
which we are now considering, I shall quote 
one which he adduces as an example. He 
says: “ When the hinder toes of a frog are 
wounded, immediately after cutting off its 
head, there is either no motion at all excited 
in the muscles of the legs, or a very inconsider- 
able one. But if the toes of this animal be 
pinched, or wounded with a penknife, ten or 
fifteen minutes after decollation, the muscles 
not only of the legs and thighs but also of the 
trunk of the body are, for the most part, 
strongly convulsed, and the frog sometimes 
moves from one place to another.’’* 

Whytt’s most important work, in which this 
subject has been most fully discussed, is the 
essay on the vital and other involuntary motions 
of animals, published ten years earlier, in 1754. 
This physiologist was deeply imbued with a 
righteous dread of materialism, which led him to 
such extraordinary lengths in spiritualism, that 
he ascribed every action and movement of the 
body to “ the immediate energy of the mind 
or sentient principle;” while he completely 
repudiated all notion of any mechanical dispo- 
sition in the intimate nature of these pheno- 
mena. Asan example of his mode of reason- 
ing upon this subject, and as further evidence 
that he was well acquainted with the class of 
actions which we now call reflex or physical, 
the following passage from the eleventh sec- 
tion of this essay may be cited :— 


* Whytt’s Works, 4to. edit. p. 501. 
if 22 FRR 


721¢ 


“ The objection against the mind’s produ- 
cing the vital motions, drawn from their being 
involuntary, must appear extremely weak ; 
since there are a variety of motions equally 
independent upon our will, which yet are cer- 
tainly owing to the mind. Thus, as had been 
already observed, the contraction of the pupil 
from light, and the motions of the body from 
tickling, or the apprehension of it, undoubt- 
edly flow from the mind, notwithstanding their 
being involuntary. The shutting of the eye- 
lids, when a blow is aimed at the eye, is an- 
other instance of a motion performed by the 
mind in spite of the will; for, as the threat- 
ened blow does not, by any corporeal contact, 


affect the orbicular muscle of the palpebre, its - 


contraction must necessarily be deduced from 
the mind, moved to perform this action from 
the apprehension of something ready to hurt 
the eye: and if there are some who, by an 
effort of the will, can restrain this motion of 
their eyelids, yet this does not proceed so 
much from the mind’s making no attempt, in 
consequence of the apprehended danger, to 
close the palpebra, as from the superior eye- 
lid’s being kept up by a strong voluntary con- 
traction of its levator muscle. We cannot, by 
an effort of the will, either command or re- 
strain the erection of the penis; yet it is evi- 
dently owing to the mind: for sudden fear, or 
anything which fixes our attention strongly 
and all at once, makes this member quickly 
subside, though it were ever so fully erected. 
The titillation, therefore, of the vesicule semi- 
nales by the semen, lascivious thoughts, and 
other causes, only produce the erection of the 
penis, as they necessarily excite the mind to 
determine the blood in greater quantity into its 
cells.” 

Whytt’s view is best explained in the follow- 
ing passage of the same work :—‘* Upon the 
whole, there seems to be in man one sentient 
and intelligent pRrrnciPLEe, which is equally 
the source of life, sense, and motion, as of 
reason; and which, from the law of its union 
with the body, exerts more or less of its power 
and influence as the different circumstances of 
the several organs actuated by it may require. 
That this principle operates upon the body, by 
the intervention of something in the brain or 
nerves, is, I think, likewise probable; though, 
as to its particular nature, I presume not to 
allow myself in any uncertain conjectures ; 
but, perhaps, by means of this connecting me- 
dium, the various impressions, made on the 
several parts of the body, either by internal or 
external causes, are transmitted to and perceived 
by the mind ; in consequence of which it may 
determine the nervous influence variously into 
different organs, and so become the cause of 
all the vital and involuntary motions as well as 
of the animal and voluntary. It seems to act 
necessarily and as a sentient principle only, 
when its power is excited in causing the 
former; but in producing the latter it acts 
freely, and both as a sentient and rational 
agent.””* 


* Op. cit., 8vo ed., p. 290. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


The third fasciculus of the Annotationes 
Academice of Geo. Prochaska was pub- 
lished in 1784. It contains the Essay on 
the Functions of the Nervous System. It is 
impossible to — too highly of this profound 
and accurate dissertation. Although short, it 
comprehends all the leading facts connected 
with the working of the nervous system, and 
affords abundant indications that its author had 
thought deeply on the subject. I know of no 
essay, of more modern date, which exhibits the 
same profound knowledge of nervous pheno- 
mena, and which is equally comprehensive. 
How it came to be so long neglected can only 
be explained by the too general incom 
of physiologists to appreciate his views. Yet 
his language is remarkably clear and precise, 
No one can have done more ample justice to 
his predecessors and contemporaries. His lite- 
rary research was extensive and accurate, and 
his historical summary is most interesting and 
instructive. The attentive perusal of this essay 
more frequently than once has impressed me . 
strongly with the conviction that Prochaska wasa 
man of the highest menta! oie rp and of great 
power of generalization, I shall rejoice to — 
see his work made easily accessible toall medical 
readers. a 

A brief summary of this important work will 
not be out of place here. Ley 

In the first chapter, the first seven sec= 
tions are occupied with an historical account 
of the views of preceding philosophers, begin- 
ning with Aristotle and Galen. {In the eighth i 
section, he remarks, “* At length we abandon 
the Cartesian method of philosophizing in this 
part of animal physics, he cntesetile v- 
tonian, being persuaded that the slow, nay, the 
most uncertain road to truth is that by hypo- 
thesis and conjecture, but that by far the more 
certain, more excellent, and the shorter 
that, que a posteriori ad causam ducit. Newta 
distinguished the inscrutable cause of the phy- 
sical attractions by the name ‘ force of attrac 
tion ;’ he observed its effects, arranged them, 
and detected the laws of motion, and thus 
blished a useful doctrine, honourable to huma 
genius. In this way we ought to proceed int 
study of the nervous system; the cause late 
in the nervous pulp, which produces 
effects, and which hitherto has not been det 
mined, we shall call vis nervosa ; its ¢ V 
effects, which are the functions of the ney 
system, we shall arrange, and ex : 
and in this manner we shall be able to cons 
a true and useful doctrine, que arti me 
novam lucem et faciem elegantiorem datun 
pro certo.” Haller, he admits, had pre 
used the term “ vis nervosa” to expr 
power by which nerves cause muscles to ¢ 
tract, but to Unzer he assigns the eredit 
having thrown the greatest light upon this 
ject, although he states that to not 
himself to the times in which he wrote and 
make himself more generally und d, 
still used the term “ animal spirits,” ; 
his doctrine was quite independent of such 
hypothesis. i 


o ae 


In the second chapter Prochaska gi 


. 
PIT. 


accomTE 


a 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


admirable summary of the leading anatomical 


characters of the nervous system. His succinct 
description of the nervous centres is excellent, 
and shows that he had anticipated views which 
long afterwards were put forward as original. 
Speaking of the crura cerebri, he describes them 
thus, “ duo magnacrura cerebri, inquibus omnis 
medulla ab utroque cerebri hemispherio collecta 
videtur.” The compound origin of the fifth and 
spinal nerves and the existence of the ganglion 
on one of their roots he was well acquainted 
with. He concludes thus, ‘‘ However complex 
be the mechanism of the nervous system, I 
think it can be divided into three parts, just as 
the functions themselves are conveniently divi- 
sible into three classes : namely, first, the animal 
organs, or those associated with the faculty of 
thinking, these are the brain and cerebellum ; 
secondly, the sensorium commune, which con- 
sists of the medulla spinalis and oblongata, not 
excepting also such part of the medulla of the 
brain as gives immediate origin to nerves; and, 
thirdly, the nerves properly so called, which are 
prolonged from the sensorium commune to the 
whole body.” 

An examination of the comparative anatomy 
of the nervous system next follows, affording 
a clear and concise exposition of the existing 
state of knowledge on that subject. 

The question discussed in the succeeding 
section is, “ quid per vim nervosam intelligitur, 
et que sint generales ejus proprietates ?”’ and he 
affirms the principle of the inherence of the vis 
nervosa in the nervous structure itself, and the 
developement of that force by changes taking 
place in it. Leaving it to those who devote 
themselves to the study of experimental physics 
to inquire into the nature of the nervous force, 
he endeavours to determine its general proper- 
ties or laws before inquiring into the special 
functions of the nervous system. 

1. The first law which he lays down is that 
the vis nervosa requires, for its action, a stimu- 

Here, likewise, he repeats the assertion, 
that the vis nervosa is an innate property of the 
nervous medulla—“ innata pulpe medullaris 
proprietas. Sicut scintilla latet in chalybe ac 
Silice, nee prius elicitur, nisi attritus mutuus 
chalybis, silicisque accesserit: ita vis nervosa 
latet, nee actiones systematis nervosi prius pro- 
ducit donee stimulo applicito excitatur, quo 
durante durat, ablato cessat agere, et redeunte 
iterum reddit.” 

2. The stimulus necessary for the develope- 
ment of the nervous force is twofold, stimulus 
corporis and stimulus anime. The former is 
any body fluid or solid applied externally or 
internally to the nervous system. ‘The latter is 
that of the mind, which, through its connection 
with a part of the nervous system, is capable 
of influencing, to a certain extent, the rest of 
that system and through it the body. 

3. The vigour of the nervous actions bears a 
direct relation to that of the nervous force and 
to the power of the exciting stimulus. The 
actions of the nervous systein will be greater 
and more vigorous in proportion as the vis ner- 
vosa may be more active (mobilior) and the 
stimulus more efficacious; on the other hand, 


721b 


the nervous force will be more sluggish and 
the stimulus less effective, where the nervous 
actions are more languid. A less stimulus is 
sufficient for a more active vis nervosa, as the 
application of a stronger stimulus may com- 
pensate for a more sluggish vis nervosa, yet an 
equal effect may be produced in the nervous 
actions. The nervous force, however, is not 
equally susceptible to every kind of stimulus ; 
sometimes it obeys one more than another, 
although both may appear equally powerful : 
nay, sometimes it experiences a more powerful 
effect from the stimulus which may seem the 
mildest. According to Haller, the heart and 
intestines are more powerfully stimulated to 
contract by air blown into them than by water 
or by any poison ; on the contrary, a drop of 
water let fall into the trachea excites violent 
cough, whereas air passes through it in breath- 
ing as if unfelt by it. 

4. The nervous force is augmented by va- 
rious circumstances. Among these he enume- 
rates age—at an early age the vis nervosa being 
greater than at a more advanced period of life— 
climate, and disease. 

5. On the other hand, the vis nervosa may 
be depressed or diminished by all causes which 
depress the powers of life, by the direct appli- 
cation of opium and other sedatives to the 
nervous matter. 

6. ‘ Vis nervosa est divisibilis et absque cere- 
bro in nervis subsistit.” In illustration of this 
law he adduces the instances of nerves remain- 
ing excitable after they have been separated 
from the cord or from the brain ; also the exci- 
tability of paralytic limbs by the electrical 
stimulus. And, he states, the vis nervosa not 
only remains fora long time in the spinal cord 
and nerves which have been separated from the 
brain, but even in nerves which never had any 
connection with the brain, as is shown by the 
acephalous fcetus, which, without a brain, and 
by the sole force of the nerves and medulla 
spinalis, if this be not deficient, lives the full 
time in the uterus of the mother, is nourished, 
grows, and, when it comes into the light, shows 
often no obscure signs of life. To this law he 
attributes the persistence of the rhythmical ac- 
tion of the heart after the decapitation of ani- 
mals. 

7. Idiosyncrasy is a peculiar affection of the 
nervous force. Among the examples of idio- 
syncrasy he enumerates, fainting at the sight of 
blood, the uneasiness and even terror produced 
in some persons by the exhalations from a cat, 
which may be in the same room, although un- 
seen ; fainting from the perception of particular 
odours. 

In his third chapter Prochaska proceeds to 
examine the functions of nerves. He describes 
the mode of action of nerves, their power of 
receiving impressions with great facility, and of 
propagating them with the greatest velocity 
either to the centre or to the periphery. This 
power he calls the vis nervosa of nerves, which 
also may be called the sensibility or mobility 
of nerves, and to which Unzer had given the 
name corporeal sense without concomitant per- 
ception. And he shows that this power is-in- 

222 HOEK 


721E 


herent in the medullary pulp of the nerves, and 
is not simply derived from the brain, but that 
a certain cohesion of the medullary pulp of 
the nerves is necessary for the developement 
of the vis nervosa, because if by compressing 
a nerve strongly we injure its medulla, so as 
to disturb the connection of its particles, the 
nervous force ceases in that part of the com- 
ressed nerve, nor are impressions propagated 
urther by it, nor if that part of the nerve be 
stimulated can sensation or motion be pro- 
duced. 

Although, he says, a nerve is necessary for 
sense and motion, it is not it alone which feels 
or moves ; it feels by the brain, which, when an 
impression made upon a nerve is conveyed to 
il, represents that impression to the mind; and 
a nerve causes motion by the muscle when an 
impression, communicated to the nerve, de- 
scends to the muscle and excites it to motion. 
He concludes thus: “ Par itaque nervi, in sensu 
et motu ciendo, est officium, nimirum im- 

ressionem stimuli recipere, et per totam suam 
ongitudinem celerrimé propagare, que dum 
ad cerebrum pervenit, sensus perceptionem 
causat, dum vero ad musculum, ejus contrac- 
tionem ciet.” 

Prochaska recognises the influence of the 
nerves upon the bloodvessels, and ascribes va- 
rious familiar phenomena to this influence, 
either excited by direct contact of the nerves 
of the part, or, if the nerves be indirectly 
affected through the brain (si isti nervi non 
immediate, sed mediante cerebro afficiantur). 
Thus he refers to redness of the skin of the 
face occasioned by exposure to a cold wind, 
redness of the conjunctiva caused by some irri- 
tant, erection of the nipple of the breast by 
titillation, erection of the penis by similar 
means or through mental emotion, blushing, 
&c. He puts forward the notion that the aug- 
mentation of the nervous force in any part 
causes an attraction of fluids to that part, as 
sealing-wax, when rubbed with cloth, becomes 
electrical and attracts various small particles. 
To a similar attraction of fluids he ascribes 
muscular action and many other phenomena, 
such as the menstrual Mux, the action of the 
iris, &c. He also discusses the question whe- 
ther the nerves have any power over the secre- 
tions, whether they contribute in any way to 
the production of animal heat, and how far 
they are necessary to nutrition. 

The fourth chapter describes the sensorium 
commune, its functions, and its seat. Lfere it 
is that Prochaska has put forward his views 
respecting reflex actions. External impres- 
sions, which are made upon sensitive nerves, 
are propagated with great velocity throughout 
their entire length to their origin, where, (to 
use his own phrase,) when they have arrived, 
ter are reflected according to a certain law, 
and pass into certain and responding (certos ac 
respondentes) motor nerves, by which again 
being very quickly propagated to muscles they 
excite certain and determinate movements. This 
place, he says, in which, as in a centre, nerves 
of sense and of motion meet and commu- 
nicate, and in which “the impressions of 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


sensitive nerves are reflected into motor nerves,” 
is called, by a term already received by most 
hysiologists, “ the sensorium commune.” 
laving referred to the various views of different 
physiologists as to the seat of the sensorium 
commune, he expresses his own opinion, that 
the sensorium commune, properly so. called, 
extends throughout the medulla oblongata, the 
crura cerebri and cerebelli, a part of the optic 
thalami, and the entire spinal cord,—in.a word, 
as far as the origins of the nerves extend. That 
the sensorium commune extends to the spinal 
cord is shown by those movements which con- 
tinue in animals after decapitation, which can- 
not be effected without the cooperation of — 
nerves which arise from the spinal cord; forif 
a decapitated frog be pricked, not only does it 
retract the stimulated part, but also it creeps, 
and leaps, which could not be done without the 
consentaneous action (absque consensu) of sen- 
sitive and motor nerves, the seat of which con- 
sentaneous action must be in the medulla spi- 
nalis, superstite sensorii communis parte, 

That Prochaska viewed these acts as purely 
physical in their nature, is apparent from his 
statement, that they take place under peculiar 
laws, written, as it were, by nature on the me- 
dullury pulp of the sensorium. The general 
law, however, whereby the sensorium com- 
mune reflects sensorial into motor impressions 
(impressiones sensorias in motorias reflectit) is 
our preservation; so that certain motor impres- 
sions should succeed to such external impres- 
sions as might be injurious to our bodies. In 
illustration he refers to certain acts of this 
such as, irritation of the mucous membrane o} 
the nose creating a violent act of expiration 
(sneezing) to expel the offending material from 
the nostril; the spasmodic closure of the glottis 
when “a particle of food or a drop of fi 
touches it, or the act of winking excited by 
the finger being brought close to the eye. 

Prochaska points out that these reflex a 
may take place with or without consciousr 
(vel anima inscia, vel vero anima conscif). — 

roof of this occurrence without conscious 

refers to certain acts which are observe 
apoplectic patients, to the convulsions of 
lepsy, and to certain actions in profound 
all those actions which occur in decapitat 
animals he refers to this class, and regards th 
as being regulated by the remaining porti 
the sensorium commune which is seated i 
spinal cord. “ Omnes iste actiones ex orge 
et physicis legibus, sensorio communi p 
fluunt, suntque, propterea, spontanez 
tomatice.” Actions, however, which the 
directs and moderates by its control, althou 
the sensorium commune may take its share 
producing them, may be called animal, % 
not automatic. lies / 

The second paragraph of this chapter: 
tains an excellent discussion of the qué 
how far the anastomoses of nerves contri 
their mutual action upon each other, or) 
that takes place only through the sen: 
commune. On this subject Prochaska adoy 
opinions of Whytt, who regarded the nervol 
centre as essential to these actions, and in” 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


next paragraph he enquires whether nerves can 
establish any communication or consent with 
each other in their ganglia, and also discusses 
the use of ganglia, giving his assent, in some 
degree, to the doctrine which he assigns to 
Unzer and Winterl,* that external impressions 
are capable of being reflected by ganglia as they 
are reflected in the sensorium commune, and 
that ganglia are particular centres of sensonal 
impressions (sensoria particularia). He sup- 
poses that the action of the heart may be ex- 
plained in this way through the impressions 
made by the blood upon its sensitive nerves 
which are reflected at the ganglia ;+ and he con- 
cludes by admitting it to be probable that besides 
the sensorium commune which resides in the 
medulla oblongata, the medulla spinalis, &c., 
there are sensoria particularia in ganglia and 
anastomoses of nerves (concatenationibus ner- 
vorum) if which external impressions are re- 
flected, without their reaching the sensorium 
commune. f 

In the fifth and last chapter Prochaska dis- 
cusses the animal functions of the nervous 
system. He shows that the soul, ens incor- 
poree prosapie, uses the nervous system as an 
instrument, and that, in all animal functions, it 
is the principium agens et determinans. He 
describes the principal parts into which the 
animal functions can be conveniently resolved, 
as perception, judgment, will, to which may be 
added imagination and memory. For the ex- 
ercise of these he lays down that the joint and 
harmonious action of the mind and brain is 
necessary, and he assigns to each of them a 


-_* Unzer, Gundriss eines Lehrgebaudes von der 
Sinnlichkeit der thierischen Korper, 1768 ; also, 
Ertse Grunde einer Physiologie der eigentlichen 
thierischen Natur thierischer Korper. 1771. Win- 
terl, Inflammationis nova theoria, Viennz, 1767. 
Ihave not had an opportunity of perusing any of 
the works of Unzer. They are, indeed, little known 
in this conntry, having first appeared at a time 
when German literature was scarcely at all culti- 
vated here. The only English medical writer with 
whom I am acquainted, who has made distinct re- 
ference to Unzer from having apparently studied 
his works, is Sir Alexander Crichton, who seems to 
have formed a high estimate of Unzer’s Erste 
Grunde einer Physiol, as I gather from his work on 
Mental Derangement, published in 1798. Dr. Baly, 
the learned translator of Muller’s Physiology, also 
refers to Unzer ; and I must express my obligations 
to an interesting article in Dr. Forbes’s journal (the 
British and Foreign Medical Review) for July, 
1847, which contains a good abstract of Unzer’s 
views, with an account of his writings. From this 
it is plain that Unzer had very enlarged views with 
reference to the phenomena of the nervous system, 
and perfectly appreciated the distinction to be made 
between those actions with which the mind is con- 
cerned either as excitor or recipient, and those 
which in their causation and developement are 
wholly independent of the mind, although not un- 
perceived by it. The publication of Unzer’s prin- 
cipal works and also of Prochaska’s in an English 
dress would be a great boon to the student of the 
physiology of the nervous system, and would most 
fegitianarsty come within the scope of the Sydenham 
Society. 
t This is the doctrine in most favour at the pre- 
sent day. 
¢ Itis plain from the context that Prochaska had 
no idea of these sensoria having any connection with 
the mind, or with the mental power of perception. ° 


721F 


different locality in the brain. In the last see- 
tion he again defines the animal actions, and 
distinguishes them from those which are de- 
pendent on a physical exciting cause; and 
argues against the Stahlian doctrine, which 
placed each movement and function of the body 
under the contro! of the soul. 

These doctrines are repeated and somewhat 
enlarged upon in a much later work by Pro- 
chaska, published at Vienna in 1810, entitled, 
“ Lehrsatze aus der Physiologie des Men- 
schen,” a third and much enlarged edition of 
a text book for his lectures. The whole section 
on the nervous system will repay an attentive 
perusal, and especially the chapter headed 
“ Verrichtung des allgemeinen Sensoriums,” 
which contains a review of the doctrine of re- 
flex actions. A later edition of the same work, 
somewhat compressed in some parts, published 
in 1820, contains a repetition and a distinct 
enunciation of the same doctrines (p. 92).* 

It is not a little remarkable, and at the same 
time highly discreditable to physiologists, that 
views so comprehensive and so striking should 
have been suffered to fall into neglect and to be- 
come almost wholly forgotten, and that the pe- 
culiar power of nervous centres to develope 
motions in response to sensorial impressions, or, 
in Prochaska’s language, “ to reflect sensorial 
into motor impressions,” should have been lost 
sight of. Le Gallois, indeed, had recognized this 
power, and Blane had evidently much insight 
into it; Mayo, likewise, had formed a very 
correct appreciation of it, as shown by his 
observations on the actions of the iris. But 
none of these physiologists were fully impressed 
with its immense importance. It is to Dr. 
Marshall Hall in this country and to Professor 
Miler in Germany that science is most in- 
debted for awakening the attention of physi- 


* Geo. Prochaska was born in 1749, and studied 
medicine at Vienna, where he was clinical assistant 
to the celebrated De Haen. He published an in- 
augural dissertation de wrinis, but the works which 
first attracted notice were his Questiones Physiolo- 
gice, Vienna, 1778; and his treatises De Carne 
Musculari, and De Structura Nervorum. In 1778 
he was made professor of anatomy and of ophthal- 
mic surgery at the University oi Prague, where he 
formed a valuable cabinet of preparations of mor- 
bid parts. In 1791] he was translated to a similar 
chair in the University of Vienna, with the title of 
Lehrer der hohern Anatomie, Physiologie, und 
Augenarzneykunde. M. Dezeimeris, from whose 
Dictionnaire Historique de la Médecine (art. Pro- 
chaska) this acconnt is abridged, remarks of him 
that ‘‘ he was one of those who strove to reduce 
the laws of life to the general laws of nature, and 
to make physiology a branch of experimental phy- 
sics.” Prochaska died on the 17th of July, 1820. 
The works in which he propounded his views re- 
specting the nervous system are, 1. Annotation. 
Academic. fasc. iii., Prague, 1784. 2. Lehrsiatze 
aus der Physiol. des Menschen, Ist ed., 1797, in 
2 vol.; 2nd ed. 1802; 3rd ed. 1810. 3. Opera 
minora Physiologici et Pathologici Argumenti, 
p-i.etii. 4, Physiologie oder Lehre von der Na- 
tur des Menschen, 1820. To these, perhaps, may 
be added a Latin edition of his Physiology, Insti- 
tutiones Physiologie Humane, 1805-6; and Disq. 
Anatom. Phys. Organismi Corporis Humani, ejusq. 
Processus Vitalis, 1812; but neither of these works 
have I seen. 


72ic 


ologists to the existence of a power in the 
nervous centres which no doubt exercises a wide 
influence on the phenomena of living creatures ; 
and yet it seems extraordinary that neither of 
these physiologists in their earlier writings 
should have made the slightest allusion to 
Prochaska, who had offered a more precise 
and more comprehensive, and, as I hope to 
show, a truer explanation of the phenomena 
than either of them. 

I shall here cite various facts, in addition 
to those already adduced, which unequivocally 
demonstrate that a power exists in the cord of 
exciting movements in parts which receive 
nerves from it, by changes occurring in its 
substance, which may arise there from some 
modification of its nutrition developed in the 
cord itself, or be excited by a stimulus brought 
to act upon it by afferent or sensitive nerves. 

But more than this: the cord has the power 
of reflecting the change wrought in it by im- 
pressions conducted to it into adjaceut sensi- 
tivé nerves, thus creating a large class of reflex 
phenomena under the name of reflex or radia- 
ting sensations. 

When a stimulus is applied to the spinal 
cord, either directly or through the medium 
of afferent nerves, the actions excited by it are 
generally limited to. those parts which derive 
their nerves from that segment of the cord which 
has received the stimulus. In some instances, 
however, parts supplied from other and even 
distant segments are thrown into action. Thus 
irritation of one leg may cause movements of 
one or both of the upper extremities ; the intro- 
duction of a catheter into the urethra will some- 
times give rise to forcible contractions of the 
muscles of the lower extremities or even of all 
the limbs. These effects are due, no doubt, to 
the extension of the stimulation in the cord be- 
yond the point first acted ee ; and they may 
be regarded as proofs that that peculiar state of 
physical change which nervous stimulation can 
excite in a centre may be propagated in the 
spinal cord upwards, downwards, or sideways, 
from the seat of the primary stimulation. 

This fact was pointed out first, so far as I 
know, by Dr. M. Hall, who regards it asa 
eke of the cord in its normal state. This, 

am inclined to think, is an error; I believe 
it to be a property of the cord, only when its 
polarity is exalted. It is, however, an important 
property, and we shall, by-and-bye, make use of 
it in considering the mechanism of the various 
actions of nervous centres. Meantime we may 
obtain, from examining into the morbid states 
which are apt to arise in the spinal cord and 
in other parts of the cerebro-spinal centres, in- 
teresting confirmation of it. 

A wound in the sole of the foot or ball of the 
thumb, or in some other situation favourable to 
the maintenance of prolonged irritation, is ca- 
pable of exciting a particular region of the 
cord, from which the state of excitement spreads 
so as to involve not only the whole cord, but 
part of the medulla oblongata also ; and in this 
state a large proportion of the motor nerves 
participate, so as to induce tonic contraction of 
the muscles they supply. This is the rationale 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


of the developement of that fearful malady 
called ¢e¢tanus. It consists not in an inflamma- 
tory condition of the cord or of its membranes, 
nor in congestion of them, but simply in a 
state of prolonged ee excitement, the 
natural polar force of the centre being greatly 
exalted and kept so by the constant irritation 
propagated to it by the nerves of the wounded 
part. Intestinal irritation is capable of, pro- 
ducing a similar condition, which, if the irrita- 
tion have not been allowed to remain too long; 
may be speedily removed by getting rid’ of the 
irritating cause. The following case illustrates 
this: an unhealthy looking girl, about, fifteen 
years of age, was brought into King’s College 
Hospital suffering from severe tovie spasms of 
the muscles of the spine and lower extremities. 
The spasms were so powerful as to produce 
successive paroxysms of opisthotonos, during 
which the trunk became bent like a bow, so that 
the patient rested on her occiput and on her 
heels. This state was speedily removed bythe 
use of a large purgative clyster containing tur- 
pentine, which brought away a large number of 
ascarides from the rectum. re aly 
In cases of paraplegia from disease of the 
spinal cord, the paralysed parts, are frequently 
troubled with cramps and_ startings occurring 
chiefly at night, and preventing sleep and ocea- 
sioning great distress to the . patient., 
are very often traceable to intestinal disturb- 
ance, the presence of irritating matters, which, 
stimulating the mucous membrane, through its 
nerves excite the spinal cord, and thus produce 
these involuntary movements. seer pl 
The rigid and contracted state of the muscles 
of paralysed limbs, which fiiequently accompa- 
nies red softening of the brain, arises. from. 
propagation of the excited state of the diseased 
part of the brain to that portion of the Fern , 
cord which is connected with it, and from whie 
the nerves of the paralysed parts arise, thet se 
nerves likewise participate in. the irritation of — 
the cord, and thus keep the muscles. ina state — 
of continued active contraction. There is no~ 
organic lesion of the cord in these cases; its 
state of excitement is dependent on the cerebral 
irritation, and disappears if the latter yields to 
the influence of remedial measures. if 
To a similar extension of cerebral irritation, 
although of a much briefer duration, the con- 
vulsions of epilepsy may be attributed. Th 
brain becomes the seat of irritation, and 
spreads to the whole or a part of the spi 
cord and to the nerves which arise from it. In 
many instances of epilepsy the convulsions aré 
limited to one half of the body, and this is espe- 
cially the case where a chronie lesion exists im 
the brain and forms a focus of irritation, whieh 
is propagated only to one half (the opposi 
the cord. 
Some substances exert a peculiar influence 
upon the spinal cord and throw it into a st 
of considerable polar excitement... Strychr 
is the most energetic substance of this class. 
a certain quantity of this drug be injected into 
the blood or taken into the stomach of an ami 
mal, a state of general tetanus will qui 
ensue, sensibility being either unaltered or som 


PHYSIOLOGY OF THE NERVOUS SYSTEM.’ 


what exalted. The slightest touch upon the 
surface of the body, even a breath of wind 
blown upon it, will cause a general or partial 
convulsive movement. The whole extent of 
the spinal cord is in a state of excitement, and 
even the medulla oblongata may be involved 
in it, whence the closed jaws, the spasmodic 
state of the facial muscles, the difficult degluti- 
tion. When this polar excitement is raised to 
its highest degree, the slightest mechanical sti- 
mulus applied to any one point of the cord 
affects the whole organ and throws all the mus- 
cles which it supplies into spasmodic contrac- 
tion, just as the least stimulus to peripheral 
parts has the same effect. 

It is a very interesting fact, which I have fre- 
quently satisfied myself of by careful examina- 
tion, that, however great the polar excitement 
may have been into which the cord has been 
thrown by strychnine, it exhibits no change of 
structure which can be detected by our means 
of observation. The nerve tubes and other 
elements entering into the formation of the 
cord have preserved their natural appearance 
in all the cases which I have examined. 

Opium has the effect of creating a similar 
State of polarity in the cord. This is most.con- 
spicuous in cold-blooded animals ; it produces 
a similar effect in the warm-blooded classes, 
but in a much less degree. Hence there is 
an objection to the use of opium in large doses 
in cases of tetanus; and experience has shewn 
the inefficacy and the injurious influence of tbis 
drug when administered in large quantities. 
When the cord is in this state of excitement, a 
stimulus applied to one part may excite a re- 
mote part of it with great facility. 

The curious tendency already referred to, 
which the male frog has to grasp objects. pre- 
sented to them by his anterior extremities, is to 
be attributed in part toa spontaneous exaltation 
of the polar foree of the cord which takes place 
at the copulating season, in the spring of the 
year, and which is associated with an extraor- 
dinary developement of the papillary texture of 
the integument of the thumb. 

This exaltation of the polar force of the cord, 
in connection with the generative function, is a 
point highly worthy of the attention of the 
physiologist as offering some explanation of the 
sympathy which exists between different organs, 
between those even which are remote from 
each other, during the rutting season, or during 
utero-gestation. 

It is worthy of notice here that cold has a 
considerable influence in controlling this polar 
State of the spinal cord, and of other nervous 
centres likewise. Ice applied along the spine, 
or the cold douche, may be frequently em- 
ployed with great benefit in cases of muscular 
disturbance dependent on this polar state of the 
cord. It seems to me more than doubtful that 
many of those drugs which have the character 
of possessing a sedative influence upon the 
nervous system can be employed for this pur- 
pose either with safety or advantage. This 
applies certainly to hydrocyanic acid and to 
opium in large doses; animals poisoned by 
these substances become convulsed before 


721i 


death, and this denotes their tendency to exalt 
the polarity of the cord. Conium and bella- 
donna, according to my experience, exercise the 
most beneficial influence of any of the sedative 
drugs, and I have found them very useful in 
restraining the cramps and startings in para- 
plegic cases. 

I have ascertained by several experiments 
that the inhalation of ether has considerable 
effect in controlling the natural polar state 
of the cord, as well as that which may be 
produced by strychnine. A pigeon deprived of 
its cerebral hemispheres lives in a state of sleep 
for a considerable time; it flies when thrown 
in the air, spreading and flapping its wings ; 
stands when placed on its feet. A bird thus 
mutilated was made to inhale ether; it could 
not stand, and when thrown into the air it fell 
to the ground like a heavy log, its wings 
remaining applied to the sides of its body, or 
if the wings were drawn out as it was thrown 
into the air, they quickly collapsed. As soon 
as the effects of the ether had passed off, it 
stood and flew as before. I gave strychnine to 
a rabbit, a guinea-pig, and a dog, so as to 
excite the tetanoid state. Immediately the 
spasms showed themselves, I brought it un- 
der the influence of ether; the spasms ceased 
immediately, and the animal became perfectly 
relaxed ; but as soon as the effects of the ether 
passed off, the spasms came on again, but were 
soon subdued by a fresh inhalation of ether. 
And thus I found that the life of an animal 
poisoned by strychnine could be greatly pro- 
longed through successive inhalations of ether ; 
for animals of the same kind, poisoned by 
equal doses of strychnine, but not subjected 
to the influence of ether, perished very rapidly. 

The examples which show that the spinal 
cord possesses the power of reflecting sensitive 
impressions are chiefly derived from disease. 
Every practitioner is familiar with the pain in 
the knee which accompanies the early stages of 
disease of the hip joint. The patient some- 
times refers his sufferings so exclusively to the 
former joint, that the disease of the latter may 
be entirely overlooked by his medical atten- 
dant. Yet the really painful part is healthy, 
while the hip joint is the seat of a morbid 
process. The pains which are felt in the thighs 
from the presence of a stone in the bladder, 
and the itching which is referred to the extre- 
mity of the prepuce from the same cause, are 
phenomena of the same nature. Pain in the 
right shoulder from irritation of the liver is a 
well-known sympathetic sensation : sometimes 
this pain extends over a very large surface. 

Numerous other instances of similar sympa- 
thetic phenomena might be adduced, but the 
above are sufficient for our present purpose. 
Taking into account the well-proved fact that 
nerves form no real junction of their fibres 
in their anastomoses, and that there is no more 
than a simple juxta-position of the nerve-tubes 
in these anastomoses, it is plain that we must 
trace these fibres up to the nervous centres to 
discover any connection between the fibre first 
irritated and that to which pain is referred. In 
the case of hip-joint disease, the nerves of the 


721L 


muscular coat of the bladder are the usual 
means by which the action of this viscus is 
promoted, It is possible that, as with the rec- 
tum, under peculiar circumstances the physical 
stimulus acting reflexly on the muscular fibres 
themselves may come in aid of that of volition ; 
but such a mode of action is not the ordinary 
one. A line of argument similar to that which 
disproves the reflex nature of the action of 
the sphineter ani tells equally against that of the 
sphincter vesice. Were the action of this mus- 
cle reflex, it ought to remain perfect when- 
ever a sufficiently large segment of the cord 
remains in connexion with the bladder. “Now 
when the spinal cord is severed in any region 
so as to occasion paralysis of the lower extre- 
mities, there is almost always incontinence of 
urine from the removal of voluntary influence 
from the sphincter vesice : such ought not to 
be the case, if Dr. Hall’s views were correct. 

Respecting the cardia and the valvula coli, I 
shall only remark that the evidence of reflex 
action is extremely defective. The cardia, in- 
deed, has no sphincter; it is closed by the 
lower circular fibres of the esophagus, which 
keep that canal in a contracted state by their 
tone or passive contraction, The pylorus is 
provided with a sphincter muscle of great 
power, which closes that orifice by its passive 
contraction, and which in animals recently 
killed will continue to close the orifice as long 
as the muscle retains its tone. If an animal 
be killed during stomach digestion, the stomach 
may be removed, and yet the pylorus will retain 
the food in it even against gravity ; the cardia, 
if a sufficient portion of the c@sophagus be 
retained, will resist the escape of the food; 
but, from the absence of a true sphincter, to a 
much less degree than the pylorus. It is im- 
possible that, under these circumstances, there 
could be any reflex action, as the stomach is 
removed from its connection with the nervous 
centre. The valvula coli appears to act simply 
on mechanical principles. 

There is, I apprehend, no more evidence of 
the exclusively reflex nature of the acts of 
expulsion than of that of the acts of retention. 
The expulsion of the feces and that of the urine 
are voluntary acts, aided essentially by the con- 
tractile power of the muscular fibres of each vis- 
cus, and perhaps, under Pesala circumstances, 
by a physical excitant. Were this power reflex, 
the expulsion would be no doubt much more 
frequent and much less under control, and, 
therefore, productive of frequent serious incon- 
venience. The expulsion of perspiration is 
probably effécted by the simplest mechanical 
means, the newly secreted fluid pushing before 
it that which was previously formed. The 
expulsion of the semen does, indeed, exhibit 
the characters of a true reflex act; but here 
how marked is the physical stimulus, and how 
necessary that it should reach a certain point of 
excitement before the action of expulsion re- 
sponds to it!- As to the expulsion of the fatus 
in parturition, while I am willing to admit 
that the physical power of the cord excited by 
the sensitive nerves at the neck of the uterus 
may exercise some influence on the contrac- 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


tions of the uterus, it seems to me quite evi- 
dent that the actions of this organ are reflex 
only to a very slight degree. In the first place, 
anatomy teaches us that the muscular parts of 
the uterus have a very trifling connexion with 
the spinal cord; the nerves distributed, to it 
being few, and these only partially derived 
from the spinal cord. Secondly, | parturition 
may take place even when the spinal cord has 
been diseased or divided so as to cut off its in- 
fluence upon the inferior half of the. body, 
Thirdly, it has lately been ascertained that in 
women under the influence of ether, the act.of 
parturition may take place with vigour, 
the nervous power have been very i 
depressed by the influence of that agent... 

Ihe immediate agent of expulsion in, defe+ 
cation, micturition, and parturition is the inhe- 
rent contractility of the muscular coat of the 
proper organ. Being hollow muscles, the sti+ 
mulus of distension is well, adapted to excite 
them to contract. The will exercises consider- 
able power in defecation and micturition, 
both upon the muscular fibres of the viscera 
themselves, and on the abdominal. muscles, 
In parturition the voluntary contraction of these 
latter muscles may give some assistance, but 
the main force of expulsion is due to the con-— 
traction of the uterine muscular fibres... In all 
the three actions, however, the influence of the 
muscular fibres of the viscera Fespenreas as 
gaged may be materially promoted by the.con- 
tractions of the abdominal muscles, which: 

ly voluntary and partly reflex, being excited 


y the pressure of the mass to be expelled 
the sensitive nerves in the ceighboureell 


which, acting on the spinal cord, stimulate the 
muscular nerves, and through them cause the 
muscles they supply to contract, in harmony 
with the muscular tunic of the expelling viscu 
rectum, bladder, or uterus, as the case may be. 
I may here remark, that whilst it is suf 
ciently evident that expulsion of the semends 4 
physical or reflex act, it cannot be admitted 
that erection of the penis is essentially so in its 
ordinary mode of production. This act is on 
of emotion—a simple emotion.of the mind is 
sufficient to develope it: it may, however, bi 
developed by the application. of a stimulus t 
the penis or scrotum, when it clearly partak 
of the character of a reflex act, although eve 
under these circumstances it would be ineo 
rect to say that emotion had no influence in 
production. It is well known, however, 
in cases where the spinal cord has been sever 
injured, severed indeed, by fracture and 
placement of some of the vertebra, erection 
the penis may be produced, although the ¢ 
is insensible, and the influence of the mind « 
the lower half of the body is suspended 
that even a slight stimulus, as the friction 
the bedclothes, or the introduction of a cath 
is sufficient for this purpose. . This is clea 
purely reflex act, wholly independent o 
tion or emotion; but it may be likewise p 
duced or kept up by the irritated state of 
cord itself. The painful erection of the per 
called chordee, which occurs in cases of infi 
matory gonorrhea, is partly a reflex pheno 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


non, but is chiefly due to a change in the 
circulation of the penis, to an increased attrac- 
tion of blood to the organ in virtue of the 
inflammatory state. 

Enough has been said to shew that, to lay it 
down that every act of ingestion, of retention, 
of expulsion, and of exclusion, is a reflex act, 
is opposed to all that we know of the intimate 
nature of these actions, The power resident, 
not in the spinal cord only, but in every ner- 
vous centre in which nerves are implanted, 
whereby, to use Prochaska’s words, sensory 
impressions may be converted into motor im- 
pulses, is no doubt of immense importance to 
the animal economy; but Dr. M. Hall has 
been evidently led, by an imperfect analysis of 
the functions we have been considering, to 
assign to this power too large an influence in 
them; and on the other hand, he has over- 
looked its obvious and important influence in 
other phenomena. 

Dr. Marshall Hall also attributes to the spinal 
cord a direct action or influence which mani- 
fests itself, first, in the tone, and secondly, in 
the irritability of the muscular system. 

I regret to be compelled to differ again from 
Dr, Hall with respect to this point, and to 
express my opinion that this dogma is incon- 
sistent with established doctrines of physiology. 

By the tone of the muscular system, I un- 
derstand that state of passive contraction which 
every healthy muscle exhibits when not in active 
contraction. It is this state which gives the firm, 
resisting, resilient feel, which the physician 
knows to be characteristic of a healthy state of 
the muscle. By virtue of it a muscle can 
adapt itself to changes which may take place 
in the distance between its two points of attach- 
ment; and it is in virtue of this property that 
a muscle shortens itself when the stretching 
force of its antagonist has been removed. 
When the muscles of one side of the face have 
been paralysed for some short time, the features 
lose their balance, because the muscles of the 
sound side have contracted to within a smaller 
space, having lost the resistance of those of the 
Opposite side. It is equality of tone which 
preserves the equilibrium between symmetrical 
muscles; it is tone or passive contraction 
which keeps hollow muscles quite closed, if 
they are empty, or firmly contracted on their 
contents, if not so, as the heart and intestine ; 
the tone of the predominant flexor muscles 
keeps limbs, whilst at perfect rest, in a semi- 
flexed position ; it is tone which keeps sphinc- 
ter muscles in a closed state. 

The question is, do the muscles derive their 
state of tone from the spinal cord, and is this 
property dependent on that organ ? 

This question is answered in the negative, if 
we can shew that there are good and sufficient 
grounds for affirming that muscles possess 
within themselves all the conditions necessary 
for the generation of their proper force. That 
muscles do enjoy these conditions is manifest 
from the following considerations: 1. their 
peculiar chemical composition, their main con- 
Stituent being fibrine, a substance which, we 
know from the phenomena of the coagulation 


721M 


of the blood, exhibits a remarkable tendency 
to contract; 2. their anatomical constitution ; 
the arrangement in fibres, the intimate texture 
of those fibres, which in the muscles of the 
greatest power, the voluntary muscles, is highly 
complicated; 3. from the large quantity of 
blood sent to muscles, which are probably more 
freely supplied with that fluid than any other 
texture in the body, and which receive it in the 
greater quantity when that contractile power is 
more active; 4. from the fact pointed out by 
Mr. Bowman, that a single muscular fibre, en- 
tirely deprived of all nerves, may be made to 
contract by a slight stimulus applied to any 
part of it; 5. from the knowledge which we 
now possess that the mechanism of these ac- 
tions may be seen by the microscope even in 
detached portions of muscular fibres ; 6. from 
the fact that muscles dissociated from the ner- 
vous centres by the section of all the nerves 
distributed to them, retain their power of con- 
traction for a very considerable period, long 
after the nerves which sink into them have lost 
their excitability. 

All these points afford the highest degree of 
probability that there is no direct dependence 
of muscle upon the nervous centres for the 
developement of its proper force ; and that this 
force is the result of the nutrient actions of 
muscle. The only way in which the nervous 
system can be said to have an influence upon 
the muscular force is by promoting the actions 
of the muscles, and thereby their nutrition. If 
a muscle have its nerves divided, and be left to 
itself, its nutrition fails after a certain period, 
and its contractility with it; but if it be exer- 
cised daily by galvanic stimulation, its nutri- 
tion remains unimpaired, and its contractility 
likewise. 

The tone of a muscle is nothing but the 
effect of the continuous developement of the 
muscular force resulting from the natural 
changes in the muscle; it is this state of ten- 
sion which denotes that these changes are 
actively proceeding, and that a uniform degree 
of attraction is being exerted between all the 
parts of the muscular fibre, in a degree propor- 
tionate to their masses, and that by this the 
muscles are maintained in a uniform state of 


‘tension so long as they are undisturbed by sti- 


muli conveyed to them through the nervous 
system, or from some other source. 

It seems, therefore, as reasonable as any pro- 
position in physiology, to affirm that the passive 
contraction or tone of muscles is due to a pro- 
perty inherent in the muscular tissue itself, and 
dependent solely on its proper nutrition, and 
that it is not derived from any other tissue. 
And if this be true, it is clear that the spinal 
cord cannot be the source of the tone of the 
muscular system. 

This statement is confirmed by the result of 
the experiment of removing the whole spinal 
cord in frogs or other animals. When this has 
been done, the limbs of the animal fall quite 
flaccid, the ‘muscles being no longer capable 
of preserving that degree of active contraction 
which is necessary to maintain attitude. A 
decapitated frog will continue in the sitting 


721N 


posture through the influence of the spinal 
cord, but, immediately this organ has been 
removed, the limbs fall apart from the loss of 
the controlling and co-ordinating influence of 
the nervous centres. And careful examination 
of the muscles in such a case as this will show 
that the molecular phenomena which charac- 
terise passive contraction continue in the mus- 
cular fibres. The state of rigor mortis, which 
is analogous to that of tone, comes on just as 
readily in animals which have been deprived 
of the brain and spinal cord, as in those 
in which these centres have been undisturbed 
before death. In short, healthy nutrition sup- 
plies all the conditions necessary for the main- 
tenance of tone or passive contraction ; nor is 
the spinal cord (although itself healthy) able to 
preserve the tense condition of the muscles, if 
they are not well nourished. 

These remarks apply equally to Dr. Hall’s 
doctrine, that the spinal cord is a direct source 
of irritability to the muscular system. The 
same arguments whith prove that tone is not 
derived from it are of equal weight with refe- 
rence to irritability. : 

It cannot be admitted as an argument in 
favour of the view which derives muscular irri- 
tability from the spinal cord, that muscles lose 
their firmness and waste, when they have been 
for some time separated from their proper ner- 
vous connections. They suffer, in this way, 
merely for want of a proper amount of exercise, 
which they cannot obtain in consequence of 
the influence of the will being cut off from the 
limb. If, however, the paralysed limb be ex- 
ercised artificially, as by the galvanic current, 
their nutrition and their plumpness may be 
preserved. For this important observation we 
are indebted to Dr. John Reid, who likewise 
called attention to the confirmatory fact, that, 
in those palsies with which there is combined 
more or less of irritation of the nervous centre, 
the muscles do not suffer so much in their 
nutrition, in consequence of the exercise they 
undergo in the startings so frequently excited in 
them by the central irritation. This is not 
unfrequently seen in cases of paraplegia from 
irritant disease of the spinal cord. 

The supposition that the spinal cord might 
be the source of irritability to the muscles led 
Dr. Hall to the very extraordinary inference, 
that in hemiplegic paralysis, in which the in- 
fluence of the brain is cut off from certain 
muscles, while that of the cord remained, the 
irritability of those muscles becomes augmented. 
He arrives at this conclusion by the following 
line of argument: assuming the cord to be the 
source of the irritability of the muscles, the 
brain may then evidently be looked upon as 
the exhauster of that irritability in the volun- 
tary actions; if, then, the influence of the 
brain be cut off, it naturally follows that, as the 
great agent of exhaustion has lost its power, 
the irritability, which is ever, as it were, flow- 
ing from the cord, will accumulate in the 
muscles. From numerous experiments I am 
enabled to state that in nearly all the cases of 
hemiplegic paralysis from cerebral lesion there 
is no evidence of any augmentation of the 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


irritability of the muscles of the palsied limbs. 
If the readiness with which they will respond 
to the galvanic stimulus be taken as a test, 
it may on the other hand be stated very 
confidently that there is evidence of the di- 
minution of the irritability of the paralysed 
muscles, for in nearly all these cases the same 
current being passed through both sound and 
palsied limbs at the same time, the latter have 
contracted either not at all or with very little 
power as compared with the healthy limbs. 

But there are exceptions to this: in some 
cases (and only in those in which there is 
more or less rigidity of the paralysed muscles) 
these muscles respond to the galvanic stimulus 
with more force and readiness than the sound 
ones. In these cases the palsied muscles are 
kept in a state of excitement by some irritant 
disease within the cranium, and this constant 
condition of more or less active contraction 
augments the nutrition, and therefore the irri- 
tability of the muscles. 

It seems, however, most probable that in all 
the cases of paralysis, the excitability of the 
muscles to the galvanic stimulus is d 
not so much upon any change in the condition 
of the muscles themselves as upon the state of 
the nerves. If the nervous force in the nerves 
on the palsied side be depressed, the galvanic 
stimulus will produce little or no effect upon 
the muscles of that side, whilst those of the 
other side will be distinctly excited: butshould 
the nerves participate in any excitement 
gated to them from disease within the craniu 
as in red softening, or an irritating tumor, or 
contracting cyst, they will then respond to the 
galvanic current more readily than those of the 
opposite side.* . 


ca 


I have thus endeavoured to show that the 
spinal cord is a centre of nervous actions, 
tal and physical, to all parts which derive nerve 

Jrom it, the mental actions, however, requiring 
its association with the brain. Whatever phy- 
sical nervous actions occur in parts whose 
nerves are spinal, must be referred to the cord 
alone; and whatever mental nervous actio’ 
occur through the agency of spinal nerves must 
be referred to the cord in conjunction with t 
brain. 


Of the office of the columns of the cord.— 
shall now inquire whether the parts into whi 
the anatomist can divide the spinal cord 
special functions. These parts are, on € 
side of the median plane, an antero-lateral S 
lumn and a posterior column. It has been 
very prevalent opinion that the antero-t: 
column corresponds in function with the ant 
rior roots of the spinal nerves, and that the pos 
terior column corresponds with the posteri 
roots. This doctrine might have had a goo 
foundation if it could be proved that the poster 
or sensitive roots were implanted solely in tt 


* I have discussed this subject more at large if 
a paper presented to the Royal Medico-Chirargic 
Society in June last, and which will appear in th 
ree volume of its Transactions. Aug 


“PLYSIOLOGY OF TIE NERVOUS SYSTEM. 


posterior, and the anterior roots solely in the an- 
terior columns. Nothing, however, is more cer- 
tain than that both roots are implanted in the 
antero-lateral columns, and it is extremely doubt- 
ful that the posterior roots have any connection 
at all with the posterior columns. Hence, as far 
as anatomy enables us to judge, this distinction 
of function between the two columns cannot be 
admitted. On the contrary, anatomy indicates 
that the antero-lateral columns are compound 
in function. Their connection with the 
corpora striata and optic thalami, and with 
the mesocephale through the anterior pyramids 
and fasciculi innominati, their reception of 
both the anterior and posterior roots, and their 
size in each region of the cord bearing a direct 
proportion to that of these roots, denote that 
these columns with the associated vesicular 
matter are the seat of the principal nervous 
actions, both mental and physical, with which 
the cord is concerned. 

This view of the office of the antero-lateral 
columns is confirmed by comparative anatomy, 
which shows that the bulk of the organ or the 
variety in the size of its various parts depends 
mainly on these columns. 

Pathological ohservations are also in favour 
of this doctrine. They distinctly denote that 
lesion of the antero-lateral columns impairs the 
sensitive as well as the motor power to an extent 
proportionate to theamountoflesion. Itis worthy 
of note, however, that while a slight lesion of 
the cord appears sufficient to impair or destroy 
the motor power, it requires a considerable ex- 
tent of injury or disease to impair in any very 
marked degree the sensitive power. Some 
lesions of these columns destroy the physical 
nervous actions of the diseased or injured part 
of the cord—augmenting those of the portion 
below the seat of lesion, doubtless by increasing 
its polarity ; this is seen especially in cases of 
injury tothe cord by fractures or dislocations 
of the spine. 

Direct experiments afford no aid in deter- 
mining the functions of the columns of the 
cord. Attempts to expose this organ either in 
living or recently dead animals are surrounded 
with difficulties, which embarrass the experi- 
menter and weaken the force of his inferences, 
if, indeed, they afford any premises from which 
a conclusion may be drawn. The depth at 
which the cord is situate in most vertebrate 
animals, its extreme excitability, the intimate 
connection of its columns with one another, so 
that one can scarcely be irritated without the 
others being affected, the proximity of the 
roots of its nerves to each other, and the diffi- 
culty, nay the impossibility, of stimulating any 
portion of the cord itself without affecting 
either the anterior or the posterior roots, are 
great impediments to accurate experiments, and 
sufficiently explain the discrepancies which are 
apparent in the recorded results of experi- 
ments undertaken by various observers. More- 
over, the resultant phenomena, after experi- 


ments of this kind, are extremely difficult of 


interpretation, especially with reference to sen- 
sation. “ The gradations of sensibility,” re- 
marks Dr. Nasse, “ are almost imperceptible ; 


7210 


the shades are so delicately and so intimately 
blended, that every attempt to détermine the 
line of transition proves inadequate. There is 
a great deal of truth in an expression of Calmeil, 
that it is much easier to appreciate a hemi-pa- 
ralysis of motion than a hemi-paralysis of sen- 
sation. If the anterior fasciculi of the cord 
possess sensibility but only ina slight degree, 
the mere opening of the spinal canal and laying 
bare the cord must cause such a degree of pain 
as would weaken or destroy the manifestations 
of sensibility in the anterior fasciculi. This 
has not been sufficiently attended to by expe- 
simenters. Again, the practice of first irritating 
the posterior fasciculi, and afterwards the ante- 
rior, must have had considerable effect in pro- 
ducing the same alteration. It is plain, that in 
this way the relation which the anterior fasci- 
culi bear to sensation must be greatly obscured ; 
yet, with the exception of some few experiments, 
this has been the order of proceeding generally 
adopted.”* 

All the experimenters agree in attributing to 
the antero-lateral columns more or less power 
of motion, but we gain no satisfactory infor- 
mation from this source respecting their sensi- 
tive power, and probably for the reasons so 
well expressed by Nasse in the passage above 
quoted. But, indeed, we do not need the 
appeal to experiment in reference to this ques- 
tion, although, if a distinct and unequivocal 
response could be elicited by means of it, the 
additional evidence would be of great value. 

There is great difficulty in determining pre- 
cisely the functions of the posterior columns of 
the cord. 

Both anatomy and comparative anatomy are 
opposed to the view which assigns them sensi- 
tive power. In the first place, as already 
stated, there is no evidence to show that the 
posterior roots of the spinal nerves are con- 
nected with them ; even Sir C. Bell, who once 
held that these columns were sensitive because 
the sensitive roots were connected with them, 
gave up that view, having satisfied himself 
that no such connection existed.t Secondly, if 
they were sensitive, it is not unreasonable to 
~expect that they would exhibit an obvious en- 
largement at the situations which correspond to 
the origins of the largest sensitive nerves; so 
little, however, is this the case, that the pos- 
terior columns exhibit little or no variation of 
size throughout their entire course. Thirdly, 
the researches of the morbid anatomist afford 
evidence unfavourable to the assignment of the 
sensitive function to these columns. Cases are 
on record which show that disease of the pos- 
terior columns does not necessarily destroy 
sensibility ; that perfect and even acute sensi- 
bility is compatible with total destruction of 
the posterior columns in some particular region, 
the posterior roots remaining intact: and others 


* Nasse, Untersuchungen zur Physiologie und 
Pathologie, Bonn, 1835-36. The passage is quoted 
from an abstract of the work published in the Brit. 
and For. Med. Review, vol. iv. 

+ See his paper on the relations between the 
nerves of motion and of sensation and the brain, 
The Nervous System, p. 234. 8voed., 1844, 


721p 


have occurred in which sensibility has been 
impaired or destroyed, while the posterior co- 
lumns remained ectly healthy. In a re- 
markable case related by Dr. Webster, there 
was complete paralysis of motion in the lower 
extremities, but sensibility remained; yet there 
was total destruction of the posterior columns 
in the lower part of the cervical region. Dr. 
Webster did me the favour to allow me to 
examine the spinal cord in this case, and I was 
struck with the complete solution of continuity 
of the posterior columns in the region of the 
neck: it was impossible in this case that the 


nervous force could have travelled along the. 


course of these columns, whether from above 
downwards, or from below upwards. Sucha 
.case as this shows distinctly that sensation may 
be enjoyed in the inferior extremities indepen- 
dently of the posterior columns, and if it does 
not prove that these columns are not the ordi- 
nary channels through which sensitive impres- 
sions are conveyed to the brain from parts sup- 
plied by spinal nerves, it at least shows that 
there must be some other channel besides them 
for the transmission of sensitive impressions. 
Other cases to the same purport are on re- 
cord. Mr. Stanley pablekor an account of a 
case of this kind in the twenty-third volume of 
the Medico-Chirurgical Transactions. He 
States, ‘there was no discoverable impairment 
of sensation in any part of either limb: on 
scratching, pricking, and pinching the skin, 
nowhere was any defect of feeling acknow- 
ledged by the patient. In the upper limbs 
there existed no defect, either of motion or 
sensation.” There was inability to expel the 
urine or retain the feces. The report of the 
post-mortem appearances in this case is not 
quite so exact as might be desired. The pos- 
terior half of the cord and the posterior co- 
lumns are spoken of as if synonymous; now 
it is evident that the posterior half of the cord 
consists of a great deal more than the posterior 
columns; it includes the posterior part of the 
antero-lateral columns. The record of the case 
States as follows: “ The substance of the cord 
throughout its posterior half or column, and 
in its entire length, from the pons to its lower 
end, had undergone the following changes of 
colour and consistence; it was of a dark brown 
colour, extremely soft and tenacious. The 
substance of the cord through its anterior half 
and entire length exhibited its natural whiteness 
and firm consistence ; and on making a longi- 
tudinal section of the cord through its centre, 
and in the antero-posterior direction, the boun- 
dary line between the healthy and diseased 
nervous matter was seen to be most exact: it 
was a straight and uninterrupted line from the 
pons to the lower end of the cord. The roots 
of the spinal nerves were unaltered.” 
Supposing that the posterior columns are the 
media of sensation to parts supplied by spinal 
nerves, we can by no means infer that the 
lesion in this case recorded by Mr. Stanley was 
sufficient to destroy sensation ; it cannot, how- 
ever, be conceded that, if this view were 
correct, such a lesion could exist without im- 
pairing sensation in some way or other, inas- 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


much as the whole of the posterior columns 
were involved in a notably diseased condition. 
The following case is related by Cruveilhier. 
A young amaurotic girl, paraplegic of move- 
ment only, died from some unknown cause. 
The spinal cord presented on its posterior sur- 
face in its entire length a large reddish-grey 
(gris-rosé) column, formed by. the »posterior 
columns. All the rest of the cord was per~ 
fectly healthy. sual t 
In a case recorded by Dr. Wm. Budd it is 
stated that the lower extremities were quite: 
deprived of motion, * but with sensation un= 
affected.” The disease was the result of a 
severe blow on the back from the boom of a 
ship, which led to a curvature of the: spine, 
formed by prominence of the dorsal vertebra: 
from the fourth to the ninth inclusive. After: 
death a portion of the cord, about: two inches 
in length, corresponding to the curvature, was 
found softened in the posterior columns... The: 
tissue was not diffluent, but became flaky and 
partially dissolved when a small and gentle 
current of water was poured on it. In this: 
case, no more than in that of Mr. Stanley, the 
lesion was not enongh to destroy sensation, but 
surely it was sufficient to impair it, ifsthe 
posterior columns are to be regarded as the 
channels of sensation.* ' 
Serres records the case of a woman who had 
been paraplegic for two months: sensibility 
was preserved in the lower extremities; the 


lesion consisted in disease of the posterior 
columns of the cord below the middle of the 
dorsal region.+ val 
In two cases which occurred in King’s Col- 
lege Hospital under my own care, the promi- 
nent symptom was impairment of the motor 
power, without injury to the sensitive; yet the 
seat of organic lesion in both was in the pos-— 
terior columns of the cord. | ie 
Nasse, in the paper before referred to, allades’ 
to several cases of the same nature, in which 
disease affected the posterior columns, but did 
not impair sensation. eee 
Longet, who is a warm advocate for t 
identity of function between the posterior 
and posterior columns, cites some instances in 
which total loss of sensibility coexisted. with 
degeneration of the posterior columns as. 
only lesion: in these cases, however, the pos: 
terior roots of the nerves were involved in the 
disease, and their function became impaired or 
destroyed in consequence. A case of 
kind, to be conclusive upon the point in 
tion, ought to exhibit complete destructi 
the posterior columns, or of a considerabl 
portion of them, with perfect integrity 0 
sterior roots and of the antero-lateral e¢ 
umns. If in such a case there were to 
of sensibility in the parts in nervous commun 
cation with the diseased portion of the spit 
cord, then, indeed, we would be justifie 
affirming that the antero-lateral columns too 
no part in propagating sensitive impressions 
and that the loss of sensibility was due to th 
morbid state of the posterior columns. P 
* Med.-Chirurg. Trans., vol. xxii. ; 
t Anat. Comp. du Cerveau, vol, ii., p. 221 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


When to these results, obtained from patho- 
logical researches, we add those of experiment, 
nothing is gained which can be favourable to 
the attribute of sensitive power to the posterior 
columns of the cord. Dr. Baly’s experiments 
on tortoises showed that movements might be 
excited whether the anterior or the posterior 
columns were irritated, much stronger mo- 
tions being excited by the posterior than by 
the anterior columns. Longet found that mo- 
tions might be excited by irritation of the 

terior columns of the cord if the experiment 

d been made immediately after the transverse 
division of the cord, and he refers such mo- 
tions, probably with justice, to an excited state 
of the cord. After a little time this subsides, 
and then M. Longet was able to pass the 
galvanic current through each or both of the 
posterior columns, without exciting any mo- 
tions when the lower segment of the cord was 
acted upon, but causing pain, as evinced by 
loud cries and writhing of the body, when the 
nt segment was tried. From experiments 
of this kind no satisfactory deductions can be 
made: to irritate the posterior columns of the 
spinal cord in a living dog without affecting in 
some degree the posterior roots of the nerves, 
appears to me to be quite impossible, even in 
the hands of the most practised vivisector. 

Neither anatomy, pathological observation, 
nor experiment, lend sufficient countenance to 
the doctrine of the identity of the function of 
the posterior roots and posterior columns to jus- 
tify us in concluding that these columns are the 
ordinary channels for the transmission of the 
sensitive impressions made upon the trunk and 
extremities. 

I have long been strongly impressed with the 
ota that the office of the posterior columns 
of the spinal cord is very different from any 
yet assigned to them. They may be in part 
commissural between the several segments of 
the cord, serving to unite them and harmonize 
them in their various actions, and in part sub- 
servient to the function of the cerebellum in 
regulating and co-ordinating the movements 
necessary for perfect locomotion. 

This view is suggested by a comparison of 
the spinal cord with the brain, and by the ana- 
tomical connections of the posterior columns. 

The brain is an organ composed of various 
segments, which are connected with each other 
by longitudinal commissures. The cord is 
obviously divisible into a number of ganglia, 
each forming a centre of innervation to its 
proper segment of the body. These portions 
must be connected by similar longitudinal 
commissures to those which confessedly exist 
in the brain. If we admit such fibres to be 
necessary to ensure harmony of action between 
the several segments of the encephalon, there 
are as good grounds for supposing their exist- 
ence in the cord as special connecting fibres 
between its various ganglia to secure consen- 
taneousness of action between them. 

The attribute of locomotive power rests upon 
the connection of the posterior columns with 
the cerebellum, and the probable influence of 
that organ over the function of locomotion and 


721Q 


the maintenance of the various attitudes and 
postures. Ifthe cerebellum be the regulator of 
these locomotive actions, it seems reasonable to 
suppose that these columns, which are so largely 
connected with it, each forming a large propor- 
tion of the fibrous matter of each crus cerebelli, 
should enjoya similar function, and that, as they 
are the principal medium through which the 
cerebellum is brought into connection with the 
cord, it must be through their constituent fibres 
that the cerebellum exerts its influence on the 
centre of innervation to the lower extremities 
and other parts concerned in the locomotive 
function, and on the nerves distributed to 
these parts. 

The nearly uniform size of the posterior co- 
lumns in the different regions of the cord, 
whilst it may be noted as unfavourable to their 
being viewed as channels of sensation, may be 
adduced as a good argument in favour of their 
being concerned in locomotion and acting as 
commissural fibres. It is a fact worthy of 
notice that these columns experience no marked 
diminution in size until the large sacral nerves, 
which furnish the principal nerves of the lower 
extremities, begin to come off. The reason of 
this is probably because the fibres of these co- 
lumns connect themselves in great part with 
the lumbar swelling of the cord, and some of 
them perhaps pass into the sacral nerves. 

The following remarks will serve to explain 
the manner in which the posterior columns may 
contribute to the exercise of the locomotive 
function. In examining a transverse section of 
the cord in the lumbar region, we observe a 
great predominance of its central grey matter ; 
the posterior columns appear large, and the 
antero-lateral columns seem inadequate in pro- 
portion to the large roots of nerves which 
emerge from it. Now, an analysis of the loco- 
motive actions shows, with great probability, 
that they are partly of a voluntary character, 
and partly dependent on the influence of phy- 
sical impressions upon that segment of the 
cord from which the nerves of the lower extre- 
mities are derived. There are two objects to 
be attained in progression, namely, to support 
the centre of gravity of the body, and to propel 
it onward. The former object is attained by 
physical nervous actions, the latter by mental. 
The support of the centre of gravity of the body 
requires that the muscles of the lower extremi- 
ties, the pillars of support to the trunk, should 
be well contracted in a degree proportioned to 
the weight they have to sustain. The contrac- 
tion of these muscles seems well provided for 
in an arrangement for the developement of 
nervous power by a stimulus propagated to the 
centre, and then reflected upon the motor 
nerves of these muscles. The stimulus is 
afforded by the application of the soles of the 
feet to the ground ; it is therefore proportionate 
to the weight which presses them down- 
wards. It is well known that reflex actions 
are more developed in the lower than in the 
upper extremities, and the surface of the sole 
of the foot is well adapted for the reception of 
sensitive impressions. No object can be as- 
signed for this peculiarity, unless it have re- 


721k 


ference to the locomotive actions, and the great 
developement of the vesicular nervous matter 
in these regions betokens the frequent and 
energetic evolution of the nervous force. All 
the structural arrangements necessary for this 
ape are found in the antero-lateral columns. 

he posterior columns come into exercise in 
balancing the trunk and in harmonizing its 
movements with those of the lower extre- 
mities. 

Some support is obtained for this view of the 
function of the posterior columns from the phe- 
nomena ef disease. In many cases, in which 
the principal symptom has been a gradually in- 
creasing difficulty of walking, the posterior 
co!umns have been the seat of disease. Two 
kinds of paralysis of motion may be noticed 
in the lower extremities, the one consisting 
simply in the impairment or loss of the 
voluntary motion, the other distinguished by 
a diminution or total loss of the power of co- 
ordinating movements. In the latter form, 
while considerable voluntary power remains, 
the patient finds great difficulty in walking, and 
his gait is so tottering and uncertain that his 
centre of gravity is easily displaced. These 
cases are generally of the most chronic kind, 
and many of them go on from day to day with- 
out any increase of the disease or improvement 
of their condition. In two examples of this 
variety of paralysis I ventured to predict dis- 
ease of the posterior columns, the diagnosis 
being founded upon the views of their func- 
tions which I now advocate; and this was 
found to exist on a post-mortem inspection ; 
and in looking through the accounts of re- 
corded cases in which the posterior columns 
were the seat of lesion, all seem to have com- 
menced by evincing more or less disturbance 
of the locomotive powers, sensation being af- 
fected only when the morbid change of struc- 
ture extended to and more or less involved the 
posterior roots of the spinal nerves. 

Bellingeri put forward the opinion that the 
anterior columns of the spinal cord influenced 
movements of flexion, and the posterior co- 
lumns those of extension; to the grey matter 
he assigned the office of propagating sensitive 
impressions to the brain; and the lateral co- 
lumns, according to him, exercised an influ- 
ence upon the organic functions of nutrition 
and circulation. 

The views already referred to respecting the 
grey matter show that it cannot be regarded as 
devoted exclusively to one function of the ner- 
vous system; nor can it be viewed as capable 
of taking its part in nervous actions without 
the white or fibrous matter. 

Valentin adduces some experiments not un- 
favourable to the supposition that the nerves of 
extensor muscles pass towards the posterior part 
of the cord, and those of the flexor muscles to 
the anterior part. He found that if, in frogs, 
the posterior surface of the cord on one side of 
the posterior median fissure in the region of the 
second or third vertebra were irritated by the 
point of a needle, the anterior upper extremity 
of the same side was extended and drawn 
backwards. When the anterior surface was 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


irritated, the limb was drawn forwards to the 
head. Irritation of the posterior column in 
the region of the sixth vertebra and below it 
caused extension of the posterior extremities, 
but they were thrown into flexion by irritation 
of the anterior columns. 

These are remarkable results; they need, 
however, the confirmation of other observers. 
If they be correct, the fact of the connection 
of the nerves of extensor muscles with the 
posterior columns has an interesting relation 
with the supposed locomotive’ function, for 
there can be no doubt that movements of ex- 
tension contribute largely to the ordinary 
attitudes and to the various modes of pro- 
gression. 

Valentin refers to cases in which the anterior 
columns having been the seat of tumor or of 
softening, more or less permanent flexion of the 
lower limbs had ensued. These cases do not 
favour his view unless he can show that the 
lesion in all the cases was of the irritant kind, 
inducing a spasmodic contraction of the flexor 
muscles; for if the lesion be of a paralysing 
kind, the effect would be to paralyse the flexor 
muscles and allow the exteusors full sway. The 
explanation of the flexed state of limbs in~ 
cases of this kind is probably to be derived 
from a chronic state of contraction induced 
in the muscles themselves by the lesion of the 
nervous centre, and the state of flexion is as- 
sumed rather than extension in consequence of 
the predominance of flexor muscles over ex- 
tension. a 

Sir Charles Bell's doctrine, which assigned 
to that portion of the cord which is interme- 
diate between the roots of the nerves, (his 
middle column, ) a special power over the move 
ments of respiration, has long ceased to gain 
attention from physiologists. It wanted th 
support of anatomy. The so-called midé 
column had no defined limits, nor could it 
proved that any respiratory nerves were cc 
nected with this region of the cord, excep’ 
a few fibres of the spinal accessory nerve. 
distinct anatomy of a respiratory system 
nerves existed only in the imagination v 
inventor of the doctrine. It could not b 
shown by experiment that the so-called ne 
of respiration had any special respiratory fun 
tion beyond that which they exercised as 
motor nerves of certain muscles. And ame 
the nerves which Sir C. Bell had classed t 
ther as nerves of respiration, were some 
certainly had no necessary connection with t 
function. Of these the portio dura and the gh 
pharyngeal are examples. 

Influence of the s inal cord upon the orga 
Junctions—The influence of the spinal ea 
upon certain organic functions has engage 
large share of the attention of experimen 
physiologists. It has been said to have a ve 
direct control over the functions of cireulati 
calorification, secretion, especially that ¢ 
kidneys. 

If it can be shown that the organs concerneé 
in these functions receive several nerves 
the spinal cord, then we do not stand in ne 
of vivisections to indicate to us that 1 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


functions with which they have to do are, to a 
certain extent at least, influenced by this organ. 
Now it is almost certain that the heart and 
kidneys receive filaments from the cord which 
pass to them chiefly in the sympathetic nerve ; 
but as it is equally certain that they receive 
nerves from other sources likewise, as from the 
vagus nerve, and the proper filaments of the 
sympathetic, it would be erroneous, so far as 
anatomy teaches us, to affirm that these organs 
were wholly dependent on the cord. 

As regards the heart, observation and expe- 
riment on man and animals tend to confirm the 
conclusion which anatomy indicates, namely, 
that while the heart possesses a certain inherent 
power, and while it has an immediate connec- 
tion with the medulla oblongata and with the 
sympathetic, it is also not independent of the 
spinal cord. A slight injury to the cord ora 
chronic lesion of it affect the heart but little or 
not at all, because of its other sources of in- 
nervation; but a sudden and extensive injury 
to the cord, or a rapidly-developed destructive 
disease of it, materially depresses and weakens 
the action of the heart, and thereby the general 
circulation. The experiments of Clift, Wedeme- 
yer, and Nasse may be cited as leading dis- 
tinctly to this conclusion. Nasse’s experiments 
were on dogs, in which he maintained artifi- 
cial respiration; he found that as soon as the 
spinal cord was destroyed, the heart failed so 
completely that the jet of blood from the femo- 
ral artery, which before had gone to a distance 
of some feet, could not reach as many inches, 
or the blood did not escape per saltum from 
the wounded artery. In performing a similar 
experiment, Longet compared the action of the 
heart in two dogs, destroying the cord in one, 
but allowing it to remain intact in the other, 
and he found that in the animal whose spinal 
cord was destroyed the cardiac movements be- 
came enfeebled in a very striking manner, 
when compared with those of the animal 
whose cord was left uninjured. 

If, then, we can prove that the spinal cord 
exercises an influence upon the central organ 
of the circulation, there can be no doubt that 
its power extends to the peripheral parts of the 
circulating system, to the capillary vessels, 
and, therefore, that injury or disease of it, espe- 
cially if sudden or extensive, must to a certain 
extent affect the functions which are performed 
through the agency of these vessels, namely, 
nutrition, calorification, and secretion. 

It seems most probable that it is only in this 
secondary manner that the influence of the 
spinal cord becomes extended to these func- 
tions, and that they suffer, when, through lesion 
of the cord, this influence has been greatly 
diminished or removed. The indications of 
its connection with nutrition and calorification 
are derived from the wasting and the coldness 
which are manifest in the paralysed parts when 
there is lesion of the spinal cord of a depress- 
ing kind. Sometimes, too, the nutrition of 
these parts is so feeble that gangrenous sloughs 
are formed on parts exposed even to slight 
pressure. This is more apt to be the case where 
the disease of the cord has been of a destruc- 

VOL. III. 


721s 


tive kind, and has involved a considerable 
portion of the organ and of the roots of its 
nerves. 

The influence of the spinal cord upon secre- 
tion has been inferred chiefly from the frequent 
occurrence of an alkaline state of urine in con- 
nection with injuries of that organ, and less 
frequently in diseased states of it. The urine, 
when passed, is found to be highly alkaline 
from the existence in it of a large quantity of 
carbonate of ammonia. The urine, in cases 
of this kind, is very apt to contain more or 
less of what has been very commonly, although 
erroneously, called ropy mucus, which is in 
truth pus formed from the mucous membrane 
of the bladder. This membrane is irritated 
and inflamed by the sojourn in it of the urine 
which the paralysed bladder is unable to expel. 
The secretion of a large quantity of phos. 
phate of lime and of mucus, and afterwards of 
pus, is provoked by inflammation of the vesical 
mucous membrane. And the addition of these 
matters to it, especially the former, neutralises 
all free acid and gives rise to decomposition of 
the urea, and the production thereby of car- 
bonate of ammonia. The alkalescence of the 
urine favours the precipitation of the triple 
phosphate. Hence urine obtained from pa- 
tients suffering under spinal disease resembles 
very closely that of patients with diseased blad- 
der without spinal disease. We may see in it 
mucus or pus globules, triple phosphates, blood 
particles, and amorphous masses of phosphate 
of lime mingled with the mucus. But in 
some instances the period of the sojourn of 
the urine in the bladder appears too short for 
these changes to take place; and hence it has 
been supposed that the urine may be secreted 
alkaline by the kidneys. Mr. Smith, of St. 
Mary’s Cray, in Kent, made experiments on 
this subject by washing out the bladder care- 
fully with warm water several times, withdraw- 
ing the water each time and testing for am- 
monia until all indication of its presence 
ceased. He then injected a small quantity of 
clear water, and allowed it to remain fifteen or 
twenty minutes; it was then drawn off, and the 
odour of ammonia could be distinctly per- 
ceived. It is to be regretted that a more accu- 
rate test of the presence of ammonia had not 
been used. Admitting, however, that am- 
monia did exist in this fluid, the experiment 
by no means disproves the formation of am- 
monia in the bladder. So small a quantity 
of urine as might trickle into the bladder in 
twenty minutes might readily be neutralised 
and decomposed by any alkali or mucus pre- 
sent in the bladder which might have eluded 
the previous washing out of that organ. If the 
secretion of urine in the alkaline state were 
common, it might reasonably be expected that 
such urine would be more frequently met with 
than it is in spinal complaints. Dr. Golding 
Bird, indeed, states that in the case of a woman 
in Guy’s Hospital, labouring under complete 
paraplegia, and passing, with the aid of a ca- 
theter, fetid, alkaline, and phosphatic urine, he 
washed out the bladder with warm water, and 


after the lapse of half an hour obtained some 
Q 7 RRR 


721T 


urine from the bladder by the catheter; this he 
found to be acid, a sufficient proof that the 
urine was not alkaline when secreted, but un- 
derwent the change during its stay in the 
bladder. 

In those affections of the spine which are 
not attended by a paralysed state of the blad- 
der, the urine is not alkaline; let, however, the 
power of the bladder be impaired, even to a 
slight degree, and the quality of the urine will 
soon suffer. And it is well known that in cases 
where impediment to the flow of urine from 
the bladder occurs independently of any para- 
lysis of the organ, as from stricture of the 
urethra, a similar derangement in the quality 
of the urine is apt to take place. 

It must not, however, be forgotten that 
chronic disease of the brain or spinal cord is 
frequently accompanied by phosphatic urine, 
even when the power of the bladder is unim- 

ired, and that in such urine the addition ofa 

ittle liquor ammoniz or potasse will cause a 
more or less copious precipitate of triple phos- 
phate. There can, therefore, be no doubt that 
the cerebral or spinal lesion affects in some way 
or other the renal secretion so as to favour the 
developement of alkaline phosphates in it, and 
thus to create a tendency to its becoming 
alkaline. This, however, may arise not from 
any special influence upon the kidney, but 
from an undue waste of nervous matter, which 
would furnish the material for the formation of 
the phosphatic salt. 

A very striking connection between the 
spinal cord and the kidneys, whereby a dis- 
eased state of the latter organs induces a func- 
tional derangement of the former, is shown by 
the history of those cases to which the attention 
of medical men was first called by Mr. Stanley. 
The patients are more or less completely para- 
plegic, and all the symptoms of disease of 
the spinal cord exist: but at the same time 
there exists irritation or actual organic lesion of 
the kidneys, which, however, may be over- 
looked or attributed to the spinal disease. 
When the renal disease has been completely 
removed and the kidneys restored to their normal 
condition, the paralysis gets well; but more 
frequently both the renal disease and the pa- 
raplegia resist all remedial means, and the 
patients die. On examination, both the brain 
and spinal cord are found perfectly free from 
any organic lesion; but distinct evidence of in- 
flammatory or other irritant disease of the 
kidneys exists.* 

In a case of this kind which came under my 
own observation, there was, along with com- 
eee paralysis of sensation and motion in the 

ower half of the body, excessive hematuria, 
which had all the characters indicative of renal 
hemorrhage. From theman’s habits and history 
I suspected that the affection of the kidney had 
something to do with suppressed gout, and 
accordingly I used every means to attract gout 
to the feet. These means were successful, for, 
no sooner was my patient attacked with an 
active paroxysm of gout in one great toe than 


.* Med. Chir. Trans. vel. xviii, 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


the renal disease began to subside, and the pa- 
ralytic affection disappeared simultaneously. 

ayer, in his valuable work on diseases of 
the kidneys, relates several cases, which, in 
addition to those put on record by Mr. Stanley, 
leave no room to doubt that renal irritation may 
be propagated to the cord, and may occasion 
each an amount of disturbance of the functions 
of that organ as to give rise to paralysis of the 
lower extremities. 

There seems no other mode of explaining 
these cases than by ascribing them to irritation 
of the cord excited by irritation of the kidneys, 
the nerves of the latter organ being the medium 
through which the renal affection excites the 
spinal. Yet there is no special connection be- 
tween the nervous system of the kidney and 
the spinal cord, excepting probably th such 
tubular fibres as may be found in the renal 
plexus. These probably run a short course, 
and their origin in the cord is in close proximi 
to their distribution in the kidney; and on 
account they may be more obnoxious to the 
influence of irritant disease of the latter 
organ. 
The power which irritation of the cord has 
to develope erection of the penis may be here 
noticed as a remarkable instance of the influ- 
ence of that organ over a local circulation. 
For it is only by assigning it to a temporary 
turgescence of the complex vascular system of 
the penis that we can explain this erect state 
Even in ordinary erection, excited by a stimu- 
lus applied to the glans, as already poin 
out, the influence of the cord is called int 
action, and the phenomenon is produced by 
reflex, or what Dr. M. Hall would call 
excito-motor act. Yet, (and here we may 
tice how ill-chosen has this term “ excite 
motor” been,) there is in reality no excitatio 
of muscular action, but the influence of — 
stimulus propagated to the spinal cord 
extended by a reflex act to the nerves 
are distributed to the vessels of the penis, a 
they, instead of being excited to any contra 
tion, become rather relaxed, and are thus p 
ei to receive a larger supply of blood; 

y the extension of this excited influence 
the cord, the attractive force (vis a fronte 
the capillaries is increased, and thus a la 
quantity of blood is attracted to the organ 
erection takes place. The influence ¢ 
nervous system on this act is shown by 
most convincing evidence—by the highly 
sitive state of the organ, especially of the gh 
by the large size of its nerves; by the effec 
injury or disease affecting the cord it 
diately, or by extension from some part | 
encephalon; and lastly, by the expe 
Giinther, who divided the nerves on the 
sum of the penis in a stallion, and th 
destroyed the power of erection, althe 
vessels were uninjured. 1 

On the mechanism of the ior 9 
cord.—Haying shown that the spinal con 
concerned in voluntary motions and in set 
tion, (mental nervous actions,) and in cet 
reflex actions, as well as in certain Of 
functions, (physical nervous aetions,) it 1s 


* 
Pa 
* 


eS. —-~S 


2 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


portant to ascertain what is the mechanism by 
which these various actions take place. 

The most convenient way to discuss this 
point will be to examine into the value of cer- 
tain hypotheses which have been framed to 
explain it. We shall find it necessary in this 
discussion to keep before us two propositions 
in favour of which sufficient evidence has al- 
ready been adduced. These are, 1. That the 
brain or some part of it is essential to the 
production of mental nervous actions ; in other 
words, that acts of volition and sensation cannot 
take place without the brain: and, 2. That the 
vesicular is the truly dynamic nervous matter, 
that which is essential to and the source of the 
developement of all nervous power. 

The first hypothesis which we shall notice is 
one of so much ingenuity that one is tempted 
thereby to adopt it, and would gladly do so if 
it were found sufficient to explain the pheno- 
mena, and if it were consistent with that sim- 
plicity which characterises the mechanism of 
the body. It originated with Dr. Marshall 
Hall, and has been advocated by him with great 
zeal and ability; it may be distinguished as 
the hypothesis of an excito-motury system of 
nerves, and of a true spinal cord, the centre of 
all quvsical nervous actions. 

Is hypothesis may be stated as follows.* 

The various muscles and sentient surfaces of 
the body are connected with the brain by nerve 
fibres which pass from the one to the other. 
Those fibres destined for. or proceeding from 
the trunk to the brain pass along the spinal 
cord, so that that organ is in great part no 
more than a bundle of nerve fibres going to 
and from the brain.- These fibres are specially 
for sensation and volition—sensori-volitional. 


* I am very desirous that this hypothesis should 
be stated correctly, as I consider that both physio- 
logy and practical medicine are greatly indebted to 
Dr. Marshall Hall for the attention his labours 
have awakened to the inherent powers of the ner- 
vous system. Nevertheless I have shown in the 
text that great advances in our knowledge of these 
powers had been made by certain physiologists of 
the last century, whose views and researches had 
been completely or almost forgotten. 

I have collected the statement of Dr. Hall’s 
hypothesis in the text chiefly from his later wri- 
timgs. The history of Dr. Hall’s labours on this 
part of physiology, as I gather it from his writings, 
ae eT to be as follows : — 

n 1832 a paper was presented by him to the 
Zoological Society, of which, so far as I can ascer- 
tain, no other record has been kept than that which 
is to be found in the printed summary of the Proceed- 
ings of that Society. 1 have not had any opportunity 
of consulting these proceedings, but find an extract 
from them printed in Dr. Hall’s work entitled Me- 
moirs of the Nervous System, published in 1837, 
This paper was entitled, “<A brief Account of a par- 
ticular Function of the Nervous System,” and its 
object was to point out the existence of a source of 
muscular action distinct from all those hitherto no- 
ticed by physiologists. The peculiarity of this mo- 
hon is stated to consist in its being excited by irrita- 
tion of the extreme portion of the sentient nerves, 
whence the impression is conveyed through the 
corresponding portion of the brain and spinal marrow 
as a centre, to the extremities of the motor nerves. 
Experiments upon salamanders, frogs, and turtles 
were detailed, from which Dr. Hall drew the follow- 


721u 


But, in addition to these, there is, according 
to Dr. Hall, another class of fibres proper to 


ing conclusions: 1. that the nerves of sensibility 
are impressible in portions of an animal separated 
from the rest; in the head, in the upper part of 
the trunk, in the lower part of the trunk; 2. that 
motions similar to voluntary motions follow these 
impressions made upon the sentient nerves; and, 
3. that the presence of the spinal marrow is essen- 
tial as the central and cementing link between 
the sentient and motor nerves. 

Other experiments were detailed in this paper 
upon frogs rendered tetanic by a solution of opium ; 
these showed that in this state the cutaneous nerves 
became ‘‘ extremely susceptive, and the motor 
nerves extremely excitative.” Decapitation of a 
tetanized frog did not destroy the tetanic condition 
of the trunk and extremities. ‘‘'The exalted con- 
dition of the function of the sentient and motor 
nerves continued in each part.” ‘“ All was changed 
in removing the brain and the respective portions 
of the spinal marrow.” 

«« These experiments,” Dr. Hall continued, ‘‘ ap- 
pear to me to establish a property or function of 
the nervous system, of the sentient and motor 
nerves, distinct from sensation and voluntary or in- 
stinctive motion,’ 

Dr. Hall’s next publication appears to have 
been a paper read before the Royal Society on 
the 20th of June, 1833. This paper is entitled 
“© On the reflex function of the medulla oblongata 
and medulla spinalis.”” Having noticed the con- 
clusion arrived at by Le Gallois, and confirmed by 
the reporters of the Institute, that section of the 
spinal marrow in the neck arrests only the respira- 
tory movements, leaving sensation and voluntary 
motion to remain in the whole body, he points out 
that the causes of muscular motion may be centric 
or eccentric in the nervous system. When the 
cause is eccentric, that is, distant from the nervous 
centres, Dr. Hall states that the phenomena are 
due to a peculiar function, which he considers 
had not previously been understood. Its charac- 
teristic is that it is ‘* excited in its action and reflex 
in its course ; in every instance in which it is ex- 
cited, an impression made upon the extremities of 
certain nerves is conveyed to the medulla oblon- 
gata or medulla spinalis, and is reflected along 
other nerves to parts adjacent to, or remote from, 
that which has received the impression.” 

“« It is by this reflex character,” he adds, ‘ that 
the function, to which I have alluded, is to be 
distinguished from every other.” Yet, curious to 
say, he assigns to it powers which certainly cannot 
be excited in the reflex manner. He says, ‘ the 
reflex function exists as a continuous muscular 
action, as a power presiding over organs not ac- 
tually in a state of motion, preserving in some, as 
the glottis, an open, in others, as the sphincters, a 
closed form, and in the limbs a due degree of equi- 
librium or balanced muscular action, a function 
not, I think, recognised by physiologists.” 

Dr. Hall points out the distinctness of this func- 
tion from sensation and voluntary motion, and re- 
lates experiments on decapitated animals, (snakes, 
turtles, vipers, toads, frogs, and efts,) to show 
that the motions which occur in them are not spon- 
taneous but only excited, and that these ‘* excited 
motions in decapitated animals are dependent upon 
a principle different from sensation and volition.” 
He then shows the difference between the reflex 
movements and those arising from irritability, by 
comparing the motion of the heart, when touched, 
with that of the glottis of an animal when similarly 
stimulated. Both movements take place equally 
after the removal of the brain; but if the medulla 
oblongata be removed, the contractions of the 
larynx cease, while those of the heart continue. 
«« The difference consists, then, in the presence of 


the medulla oblongata, which is essential to the 
Q 7 Qeese* 


721x 


the spinal cord and to its intracranial continu- 
ation, which form a connection with the grey 


contractions of the larynx, but of which those of 
the heart are entirely independent. The influence 
of the stimulus upon the heart is immediate. That 
of a stimulus applied to the larynx must pass to 
the medulla oblongata, and be reflected upon the 
part moved.” 

The details of further experiments next follow. 
The author refers to the reflex function the power 
which the hedgehog has of assuming the form and 
firmness of a ball.(?) Cases of infants born without 
orain or cerebellum are referred to in proof of the 
existence of reflex actions in the young of the hu- 
man subject. The experiment of dividing the spinal 
marrow between the nerves of the superior and 
inferior extremities is described, to show ‘‘ two 
modes of animal life; the first being the assem- 
blage of the voluntary and respiratory powers with 
those of the reflex function and irritability; the 
second, the two latter powers only; ” “if the spinal 
marrow be now destroyed, the irritability alone 
remains, all the other phenomena having ceased.” 

Dr. Hall next shows that the reflex function ad- 
mits of exaltation and diminution. Frogs are made 
tetanic by opium and strychnine, and the tetanus 
disappears on removing the spinal marrow. On 
the other hand, a few drops of hydrocyanic acid 
placed upon the tongue of a frog depress the reflex 
function ; ‘‘ the contractions which depend on the 
reflex function are observed to become less and less 
energetic and excitable, and at length cease alto- 
gether.” 

Some highly interesting references are made to 
the light thrown upon the nature of certain diseases 
by our knowledge of this reflex function. The mor- 
bid states produced by dentition, epilepsy, asth- 
ma, tenesmus and strangury, tetanus and hydro- 
phobia, are the principal diseases mentioned. 

The rest of the paper consists of inferences from 
the preceding parts and a recapitulation. 

Dr. Hall had formed, at this time, no distinct 
hypothesis respecting any special mechanism for the 
reflex function. He makes the following remarks, 
which seem to foreshadow his subsequent hypo- 
thesis referred to in the text. ‘* It appears pro- 
bable,”’ he says, ‘‘ that the facts of this paper may 
lead to some important additions to our knowledge 
of anatomy, by inducing an accurate inquiry into 
the origin, course, connection, and distribution of 
the subcutaneous, or submucous, and muscular 
nerves, which constitute the arcs of the reflex 
function.” 

In reviewing this interesting and important paper, 
it is impossible not to feel the greatest regret that its 
author should have done so much injustice to him- 
self as well as to those who had preceded him, by 
neglecting to give an exact account of the state of 
science in reference to this question at the time he 
wrote. No one who peruses with candour the essay 
of Prochaska can deny that it contains, with re- 
gard to the reflex fun. tion, everything that Dr. Hall’s 
paper contains, everything which will bear the test 
of careful analysis, omitting those views which are, 
indeed, peculiar to Dr. Hall, and which do not 
appear in this paper, assigning to the cord pow- 
ers over ingestion, egestion, muscular tone, and 
irritability, &c. Throughout the whole paper no 
allusion whatever has been made to Prochaska’s 
essay. The Report of certain members of the In- 
stitute upon the work of Le Gallois, (both of which 
Dr. Hall quotes, ) makes distinct reference to Pro- 
‘chaska’s views of the reflection of sensorial impres- 
sions. It must not, however, be forgotten that 
Prochaska’s views had fallen into oblivion and 
neglect, and that Dr. Hall revived them, illus- 
trated them by experiments, and showed their ap- 
plication to the pathology of the nervous sys-~ 
tem, I may add, that nothing would be more 
excusable than that a physician, working at these 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


matter of the cord. Of these fibres some 
are afferent or incident, others efferent or re- 


subjects in 1832, should be ignorant of Prochaska’s 
essay published in 1784, more especially as it was 
overlooked even by his own countrymen—by such 
men as Treviranus, Rudolphi, and Miiller. 

Dr. Hall’s next publications, as he himself stat 
(Preface to Memoirs on the Nervous System, 1837, 
were a course of lectures, delivered from a prin’ 
syllabus in the summer, and repeated in the winter 
of 1835, of which one was inserted in the Medical 
Gazette for January, 1836, and the whole in his 
Lectures on the Nervous System and its Diseases, 
published in April, 1836. 

It is in this latter work that, so far as I have been 
able to ascertain, Dr. Hall first put forward the hy- 
pothesis detailed in the text. It is stated, however, 
not as a hypothesis, but as a discovered fact. Having 
described two divisions of the nervous system, the 
first consisting of the cerebrum and cerebellum 
with sentient nerves, which pursue their course fo 
them, and of motor nerves, which 
them either along the base of the brain or 
the spinal marrow, and then along every ex 
e second com- 


pointing out in all its fullness. pt ae cere- 


division of the nervous system, and the ganglionic 
or the second subdivision of this system remo 

this remains. It consists of the true spinal m 
distinguished from the sentient and motor ne 
which run along its course as an axis of 
and motor nerves. It is the seat of a pecu 
series of physiological phenomena, and of a 
culiar class of pathological affections.” In he 
former are included all (sic) the functions whic 
relate to the immediate acts of ingestion and egestic 
in the latter, all spasmodic diseases.” (Loc. cit 


Further on, in the same work, Dr. Hall gives a 
analysis of his true spinal or excito-motory sy 
tem, which consists, according to his description 
of, 1. the Membranes; 2. the True Medulla; 
the True Spinal Nerves. The principal divis 
of the true medulla, he specifies as follows = 

1, The Tubercula Quadrigemina, 
2. The Medulla Oblongata, f 
3. The Medulla Spinalis, and especially 
1. Cervical, : 
2. Dorsal, 
3. Lumbar, and 
4. Sacral portions.* 
The reader who has perused with attention 
analysis of Prochaska’s work given in the tex 
perceive a striking resemblance between t 
Medulla and the Sensorium commune of I 
p- 721E. ‘ 

In this work there is no allusion to the 
tant essay of Prochaska, although Sir 
Bell is corrected for attributing the discover 
ganglia on the posterior roots of the spin 
and on the portio major of the fifth to 
stead of to Prochaska (p. 17), and two quote 
are made from the latter author without spec 
the work from which the passages are quoted 

In 1837 Dr. Hall published a quarto vi 
with the title, ‘‘ Memoirs on the Nervous 5 
This consists of a reprint of the pa 
in the Philosophical Transactions, * the 
Function of the Medulla Oblongata and 


Spinalis;” and also of a paper which was 


* An anatomical oversight, as the 
nalis has no sacral portion. 


ees 


a> O- eee 


ee 


. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


flex, and these two kinds have an immediate 


but unknown relation to each other, so that- 


before the Royal Society on February the 16th and 
23d, and March the 2d, 1837, but was uot pub- 
lished in the Transactions. This paper is entitled, 
“© On the trne Spinal Marrow and the Exciio- 
motory System of Nerves.” 

The object of this paper the author states to be 
the developement of a great principle in physio- 
logy—that of the special function of the true spinal 
marrow and of a system of excito-motory nerves. 

*« It is this principle,” he continues, ‘‘ which 
Operates in all those actions which have been de- 
signated sympathetic, which regulates the func- 
tions of ingestion and expulsion in the animal 
economy, and which guards the orifices and sphinc- 
ters of the animal frame.” 

«< The principle to which I allude,” he proceeds, 
*« has been confounded with sensation, and vo- 
luntary, and what has been designated instinctive, 
motion, by all (sic) physiologists, with one single 
pescption (Sir Gilbert Blane). It has been sup- 

to be a function of the rational (Stahl) or 
irrational (Whytt) sonl. It has been considered 
by some (Haller, &c,) as attached to the brain; 
by others (Whytt, Soemmering, Alison, Muller, ) 
as attached to the brain and spinal marrow; by 
others (Le Gallois, Flourens, Mayo,) as peculiarly 
attached to segments of the spinal marrow ; it has 
been viewed by others as the function of the sym- 
pathetic (Tiedemann, Lobstein,) or of the pneu- 
mogastric nerve (Bell, Shaw); and, lastly, by 
others as operating through identity of origin or 
anastomoses of nerves (Mayo).” 

How very strange it is that amidst all the re- 
search displayed in this paragraph, no mention 
should have been made of Unzer and Prochaska, 
the only authors who really had clearly stated the 
correct doctrine respecting nervous phenomena in- 
dependent of the mind !! 

n this paper Dr. Hali falls into the curious error 
of affirming that the power which is developed in 
the nervous system in connection with sensation 
and volition, is different from that through which 
the reflex actions are produced. To the latter he 
limits the term vis nervosa, and, having quoted 
Haller’s very correct description of the course 
which it takes in motor nerves, he affirms that his 
Tesearches have disclosed a series of phenomena 
** directly at variance with the conclusions of 
Haller.” 

I confess myself quite unable to discover in what 
respect Dr. Hall’s results are at variance with the 
laws of the vis nervosa as laid down by Haller. All 
that the latter physiologist affirmed was that the 
nervous force travelled from trunk to branches in 
motor nerves, and that irritation of the spinal cord 
caused convulsions of the limbs which derived their 
nerves from below the point of stimulation. Now 
these facts are strictly true—by whatever stimulus 
the nervous force is excited in motor nerves it travels 
from trunk to branches; and the statement made 
by Haller respecting the spinal cord is equally true, 
namely, that the motor force travels downwards, 
and that irritation of the cord affects only the 
limbs below the irritated point. All that Dr. Hall 
has made out which is at variance with this pro- 
position is, that sometimes the anterior extremities 
may be thrown into action by stimulating that seg- 
ment of the cord from which the posterior extre- 
Mities derive their nerves, from whence he con- 
cludes that “‘ the motor power in the spinal mar- 
row will act in a retrograde direction.” 

This conclusion, however, does not follow from 
the experiments adduced in support of it. If the 
spinal cord of a turtle be irritated in the segment 
from which the nerves to the hinder extremities 
Spring, and all four extremities are thrown into 
action by that stimulus, we are not authorized to 
conclude that the motor power will act in the spinal 


721x 


each afferent nerve has its proper efferent one, 
the former being excitor, the latter motor. 


marrow in a retrograde direction; all that we°are 
justified in affirming is that the same change which 
would excite the nerves of the irritated part of it 
may be propagated from its lower to its upper part. 
How this takes place is uncertain, whether by sen- 
sitive fibres or by commissural fibres, or by vesicular 
matter, most probably by the last. 

It may, however, be stated that such phenomena 
as those described take place chiefly in an excited 
state of the cord, as when the animal is under 
the influence of. strychnine—or in tetanus—and 
their occurrence is far from being in accordance 
with a normal state of action of the spinal cord. 
I have frequently irritated the cord in healthy 
animals without producing any movements save 
in parts below the point stimulated. (Vide supra, 
p. 721G.) 

Dr. Hall in this paper draws the same conclusions 
as in his work last referred to as to the existence of 
a “ true spinal marrow physiologically distinct from 
the chord of intra-spinal nerves ; of a system of 
excito-motory nerves, physiologically distinct from 
that of the sentient and voluntary nerves ; and of a 
nervous influence—the excito-motory power—ope- 
rating in directions incident, upwards, downwaids, 
and reflex, with regard to the true spinal marrow, 
the centre of this excito-motory system.” When 
Dr. Hall uses the term physiologically distinct, of 
course he means, likewise, anatomically distinct. 
One part cannot be physiologically distinct from 
another without being anatomically so also. 

In the second section of this paper Dr. Hall gives 
**a slight sketch of the opinions of physiologists 
upon the subject of this memoir.”” He alludes to 
the views of Haller, Monro, Whytt, Blane, Le Gal- 
lois, and the Reporters of the Institute upon Le 
Gallois’ Essay, Mayo, Flourens, Alison, and Mul- 
ler, but makes no allusion to either Unzer or Pro- 
chaska. 

I pass over the third, fourth, fifth, and sixth sec- 
tions, and proceed to the seventh. Here the laws 
of the excito-motory system are stated, and those 
extravagant powers are attributed to it, which I 
have in the text endeavoured to show it cannot 
exercise. But, in addition, this system is made to 
be’the nervous agent of the appetites and passions ! 
What strange confusion! that a system, devised as 
the special centre of nervous actions independent 
of the mind, should be the seat of phenomena 
preeminently mental, and intimately connected 
with sensation. 

The remainder of this essay consists of further 
remarks on the anatomy, physiology, pathology, 
and therapeutics of the excito-motor system, and 
concludes with some observations on the ganglionic 
system of nerves. 

In 1841 Dr. Hall published his work on the Dis- 
eases and Derangements of the Nervous System. 
In this work I am not aware that any new or addi- 
tional fact has been stated not mentioned in those 
already quoted, It includes a reprint of several 
memoirs read to the Medico-Chirurgical Society. 

In 1843 a ‘* New Memoir on the Nervous System” 
appeared, dedicated to Professor Flourens as to 
one ‘* who has in his responsible office displayed 
the most candid, impartial, and generous judgment 
of the works of others.” 

I find it necessary to notice an assertion con- 
tained in a note to the advertisement of this work 
Dr. Hall observes :— 

«« My first memoir was entitled, ‘ On the Reflex 
Function of the Medulla Oblongata and Medulla 
Spinalis.’? This important function as the nervous 
agent in all the acts of ingestion and of egestion in 
the animal economy was previously unknown. It 
is not mentioned by Whytt, or Prochaska, or any 
other author; who, however they may cite the 
term reflex, or detail experiments, or treat of sym- 


721z 


The aggregate of these fibres, together with 
the grey matter, constitutes the true spinal cord 


pathetic actions, have not, I affirm, associated one 
physiological act with any such reflex function of the 
spinal marrow. This is, therefore, my poweary A 

Upon this passage I must remark, Ist, that if Dr. 
Hall merely claims the discovery of the reflex func- 
tion, it cannot be conceded to him, for Prochaska 
had already distinctly announced the existence of 
this function in the medulla oblongata and spinalis, 
using even the term functio, as in the following pas- 
sage: —‘* Cum itaque precipua functio sensorii 
communis consistat in reflexione impressionum sen- 
soriarum in motorias, notandum est, quod ista re- 
flexio vel animé nescia, vel vero anima conscié fiat.” 
Loc. cit. pp. 118-19. 

If, however, Dr. Hall claims the discovery of this 
function *‘ as the nervous agent in all the acts of inges- 
tion and egestion in the animal economy,” then I have 
only to remark that I know of no physiologist in 
the present or in former times who would care to 
dispute such a discovery with him. I have already 
shown that the idea that these acts of ingestion and 
oycetion are dependent on this function is a fiction 
of the fancy—an idolon 4s—which rests upon 
an imperfect and erroneous analysis of these acts, 
and on very narrow views of the nature and mode 
of developement of the nervous force. If, finally, 
Dr. Hall limits his claims, as he says he might do, 
to the discovery (?) of the anatomy and physiology 
of the true spinal system, as a combined system of 
“« 1, incident nerves; 2, their spinal centre; and, 3, 
reflex nerves, constituting the anatomy of the whole 
series of the acts of ingestion and egestion,” I am 
quite sure that no anatomist or physiologist of the 
present day would seek to deprive him of such a 
discovery, or dispute the opinion of Professor 
Flourens that it belongs to Dr. M. Hall. That this 
so-called true spinal system is no more than an hy- 
pothesis, and one which has but an infirm basis to 
rest upon, I have endeavoured to show in the text. 
That a centre of reflex actions exists—but not dis- 
tinct from the centres of sensori-volitional acts— 
every physiologist will admit, and the limits of that 
centre were most correctly defined more than fifty 
years ago by Prochaska under the name sensorium 
commune, which extends, according to him, ‘* quam 
late patet nervorum origo,” and which, as I have 
already remarked, completely foreshadowed Dr. 
Hall’s “ true spinal marrow.” 

In sections 5—1] of this work Dr. Hall states 
the real objects of his researches as follows. 

“«« First, to separate the refiex actions from any 
movements resulting from sensation and volition. 

Secondly, to trace these actions to an acknow- 
ledged source or principle of action in the animal 
economy—the vis nervosa of Haller—acting ac- 
cording to newly discovered laws. 

Thirdly, to limit these actions to the true spinal 
marrow, with its appropriate incident and reflex 
nerves, exclusively of the cerebral and ganglionic 
systems, 

Fourthly, to apply the principle of action in- 
volved in those facts to physiology, viz. to the 
physiology of all the acts of exclusion, of inges- 
tion, of retention, and of expulsion in the animal 
frame. 

Fifthly, to trace this principle of action in its 
relation to pathology, viz. to the pathology of the 
entire class of spasmodic diseases ; and, 

Sixthly, to shew its relation to therapeutics, 
especially to the action of certain remedial and cer- 
tain deleterious physical agents. 

Finally, it is to these objects, taken together as 
a whole or as a system, that I prefer my claims; 
and I do not pretend that an occasional remark 
may not have been incidentally made by some 
previous writer, bearing upon some one or other 
of them,” hae 

It is in this work that Dr, Hall has, for the first 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


of Dr. Hall, which is not limited to the spinal 
canal, but passes up into the cranium as far as 


time, ventured to notice the remarkable views of 
Prochaska. I wish, for the sake of English phy- 
siology, and also for the sake of Dr. Hall’s own 
character as one who professes great admiration 
for those who ‘‘ display a candid, impartial, 
generous judgment of the works of others,” that the 
extracts which he has made from Prochaska’s work, — 
few and imperfect as they are, had been accompa- — 
nied by some more dignified and more ingenuous re~ 
marks than those contained in the following para- 
graph. = 
** It is impossible to adduce specimens of 
complete confusion than these, in which vol 
acts, and the actions of the heart, stomach, 
intestines—functions of the cerebral and of the 
glionic systems ens are arranged 
certain reflex experimental facts, and very 
sympathetic actions, which really belong to the 
true spinal system.” 
I have carefully examined the gprs a quot 
from Prochaska by Dr. Hall, and myself 
unable to discover any of that ‘‘ complete con- 
fusion to which he alludes.” Prochaska states, — 
that numerous examples (plurima exempla) prov 
the general law of the reflecting power of the 
sensorium commune, of which, however, he s ys, 
a 
& 


it will suffice to adduce only afew. He mentior 
sneezing produced by irritation of the mucous 
membrane of the nostrils,” the violent cough pm 
duced by irritation of the glottis—per micam ¢ 
vel guttulam potus illapsam,—and the wi é 
cited by bringing the finger close to the e 
these are not fair examples of reflex acti 
know not what are. 

Prochaska then proceeds to show that the: 
reflex actions may take place with or without t 
cognizance of the mind; and here I must refert 
a very disingenuous proceeding on the par 
Dr. Hall in his quotations. He disp 


2. 9y 
rey 
= 


laces 
sages from their right order and therefore from tl 
context, and thereby introduces an appe ce | 
confusion which does not exist in the origin 
The passage commencing ‘‘ Si amicus digito,” & 
occurs before and in a different paragraph fre 
that commencing ‘‘Cum itaque precipuo,” & 
Dr. Hall quoting them as if the latter stood fir 
He has similarly transposed the passages ¢ 
mencing ‘ Sed fieri tamen,” &c. and “ 
cordis, ventriculi.” “a 
In the pemcing portion of this work Dr. 
has systematized his views more completely t 
in his previous writings—repeating, however, m 
the same experiments, re-asserting the same ex 
nations of certain actions as before, and adi 
some new remarks in vindication of his views” 
ready expressed. Yet in this volume there” 
indications as if Dr. Hall had no great confid 
in his own hypothesis, notwithstandin; 
thought it worthy of being designated a dise 
At § 149, referring to Dr. Carpenter’s and | 
Newport’s opinions in favour of the existent 
excito-motory fibres distinct from sensori-volit 
fibres, he remarks, “‘ I doubt not that the im 
gations of these gentlemen are correct; they h 
therefore, confirmed what I had : ’ 
done.” But in ye having mention 
ger’s assertion that in the roots of the spin: 
one set of fibres passes up to the brain, 
other pursues its course to the grey matter, he’ 
«Tt is probable, therefore, that the former 4 
reality nerves of sense and voluntary motion, W 
the latter are the nervous channels of the 


eS 


* Prochaska supposes that the olfactory nery 
propagate the irritation which excites sneezim 

the centre ;— the office of the fifth nerve was} 
made out in his day. a 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


the crura cerebri. (Its extent, indeed, is much 
the same as that which has been assigned by 


motor power and action. I say it is probable this 
is the case.” And in § 151 he says, ‘‘It has al- 
ways appeared to me that, observing the difference 
between the cerebrum and the spinal marrow, the 
olfactory and the trifacial nerves, in regard to the 
psychical and the excito-motor properties, it is very 
improbable that in any part of the nervous system 
the two functions should co-exist in any one indivi- 
dual fibre.” I am, therefore, not premature in 
refusing to accept as a discovery that which Dr. 
Hall himself regards only as probable —and not 
proved, Lastly, at § 370, he quotes an experiment 
by Van Deen and Stilling, in which one-half of the 
aie! marrow is divided above the origin of the bra- 
chial nerves, and the other half below the same point, 
with the effect of leaving sensation and voluntary 
motion undestroyed. On this he remarks, ‘‘ There 
is, therefore, no continuous rectilinear course of 
nervous fibre from the brain to the extremities.”! ! 

{ shall here contrast the points made out by 
Prochaska with the statement of Dr. Hall’s “ real 
objects” as quoted a few paragraphs back. 

1. Prochaska forms a large estimate of the im- 
— of the vis nervosa; he attributes to it a 

igh place among the forces which concur in the 
production of vital phenomena—not limiting the 
term, as Haller did, to the force by which nerves 
excite muscles to contract, but viewing it as THE 
agent in the production of all the phenomena of 
the nervous system. ; 

2. He investigates the laws of this force as it is 
developed in the pulp of the nerves, Jeaving the 
enquiry into its nature to those who are engaged 
with physical experiments. 

3. He shows that this nervous force, although 
in truth an innate property of the medullary pulp, 
nevertheless needs a stimulus for its developement. 

4. This stimulus, he further shows, may be either 
physical or mental. 

- He investigates the causes and effects of the 
increase and of the diminution of the vis nervosa, 
and how it is influenced by age, sex, and tem- 
perament, 

6. He shows that the nervous force remains in 
nerves separated from the centres (within certain 
limits) even in ‘ singulis dissectorum nervorum 
frustis.”” 

7. Prochaska lays down that nerves act in pro- 
ducing motion and sensation in virtue of their 
power of propagating impressions made on them, 
whether at their origin or at their periphery. 

8. He shows that external impressions made 
upon sensitive nerves are quickly propagated to 
their origin and there are reflected, according to a 
certain law, into corresponding motor nerves, 
whereby certain definite motions are effected. 

9. This takes place whenever motor and sensitive 


heryes are implanted in the neighbourhood of each | 


other, and all that part of the cerebro-spinal axis in 
which nerves are so implanted is called by Prochaska 
sensorium commune. 

10. This reflexion of sensitive impressions into 
motor ones is a physical ph independent of 
the mind. 

ll. The mind, however, may or may not be con- 

scious of its occurrence. 
_ 12. Examples of refiex acts of this kind are found 
in sneezing, in the winking of the eye when the 
finger is suddenly directed A to it, in the violent 
cough produced by a particle of food or a drop of 
water passing into the trachea. In all these in- 
stances the effects of the stimulus applied to the 
sentient nerves of the part irritated are propagated 
to the centre, and there reflected into the nerves of 
those muscles by which the respective movements 
are ipretaces 

13. The motions which may be produced in de- 
capitated animals by excitation of the surface are 
of this kind, the reflexion taking place in the resi- 


T22a 


Prochaska to his sensorium commune.) These 
fibres are quite independent of those of sensa- 
tion and volition and of the sensorium com- 
mune, using that term as indicating the centre 
of intellectual actions. Although bound up 
with sensitive and motor fibres, they are not 
affected by them, and they maintain their sepa- 
rate course in the nerves, as well as in the 
centres.* 


dual portion of the sensorium commune, which is in 
the spinal marrow ; and those produced in patients 
labouring under apoplexy are of the same kind. 

14. A similar reflexion takes place in ganglia to 
that which occurs in the sensorium commune. 

15. Prochaska has, therefore, shown that the 
nervous centres may affect nerves implanted in them 
in three ways: 1, through mental change, as in vo- 
luntary actions ; 2, through a physical change ori- 
ginating in the centres themselves ; 3, through the 
reflexion of the change wrought in a sensitive nerve 
by peripheral stimulation, into a motor nerve: and 
that nerves may affect centres, 1, so as to excite a 
feeling in the mind (sensation) ; and, 2, so as to 
cause the reflexion of a peripheral change in the 
afferent sensitive nerve into an adjacent motor 
nerve, independently of the mind. 

16. Prochaska concludes his observations by 
drawing a careful distinction between those motions 
which are animal, being directed by the mind, and 
those which are mechanical or automatic (physical ), 
of which the mind may or may not take cognizance, 
but in the production of which it takes no part. In 
these latter are included the reflex actions. 

Such are the conclusions to which Prochaska’s 
observations lead him respecting the nervous system, 
and in them I confess there appears to me to be a 
large and an exact view of the phenomena of the 
nervous system, more comprehensive than the 
views of Dr. M. Hall respecting an excito-motor 
power and a special system of excito-motor nerves, 
and their centre, the true spinal nerves, 

In his latest publication, a volume of essays, 
(1845) Dr. Hall asserts his conviction of the truth 
of his views, and re-affirms his claims to discovery. 

I fee] that I owe the reader some apology for this 
long note. The views of Dr. Hall have been so 
zealously pressed upon the attention of physiologists 
and of medical men, that it seemed to me thata 
work like this onght to contain as full a statement 
of them as its limits would permit, more especially 
as I have felt it my duty to express my dissent from 
them to a very great extent, and to criticize them 
with much freedom. 

Throughout all my remarks it has been my an- 
xious wish to express my opinions regarding Dr. 
Hall’s views as of a pure question of science, omit- 
ting all personal considerations. It would have 
been infinitely more grateful to my feelings to have 
been able to express my concurrence in these doc- 
trines, (as, indeed, I was at one time much dis- 
posed to do,) than to have found myself compelled 
by regard to truth to refuse assent to his claims to 
original discovery as well as to his hypothesis, and 
even to the accuracy of some of his experiments. 
The cause of science demands that views which are 
essentially unsound, but which from the urgency 
with which they continue to be put forward on va- 
rious occasions and in various shapes, are in danger 
of being adopted by those who have no time nor 
opportunity to investigate them closely, should be 
exhibited in their real shape and purport by means 
of a careful and searching analysis. Having 
weighed them in this balance, I must confess that 
they have been found wanting. 


* It would be unjust to a most able physiologist 
and pleasing writer, Mr. Grainger, not to state that 
he has contributed much to the distinct enunciation 
and apt illustration of this hypothesis. See his 
excellent work on the Spinal Cord. Lond. 1837, 


722B 


2. A second hypothesis is that which accords 
with the views of Miiller and many other phy- 
siologists of the present day, and likewise pro- 
bably with those of Whytt. It assumes that 
the fibres of sensation and volition proceed to 
and from some part or parts of the intracranial 
nervous mass, —that every nerve-fibre in the body 
is continued into the brain. Those which are 
distributed to the trunk and extremities pass 
along the spina! cord, separating from it with the 
various roots of the nerves, and in their course 
within the spine mingling more or less with the 
vesicular matter of the cord. There are, accord- 
ing to this hypothesis, no other fibres but these, 
(save the commissural,) and they are sufficient 
to manifest the physical as well as the mental 
acts. Nerves of sensation are capable of ex- 
citing nerves of motion which are in their vici- 
nity; and they may produce this effect even 
when the spinal cord has been severed from the 
brain, for their relation to the grey matter of 
the cord is such that their state of excitement 
is readily conveyed to it. 

3. According to a third hypothesis, it is as- 
sumed that all the spinal and encephalic nerves, 
of whatever function, are implanted in the 
grey matter of the segments of the cerebro- 
spinal centre with which they are severally con- 
nected, and do not pass beyond them. The 
several segments of the cerebro-spinal axis are 
connected with each other through the conti- 
nuity of the grey matter from one to another, 
and through the medium of commissural! fibres 
which pass between them. Through these 
means, motor or sensitive impulses may be 
propagated from segment to segment; and a 
stimulus conveyed to any segment from the 
poe may either simultaneously affect the 

rain and cause a sensation, or it may be re- 
flected upon the motor nerves of that segment 
and stimulate their muscles to contract. Or 
both these effects may take place at the same 
moment, asa result of one and the same sti- 
mulus. According to this hypothesis, each 
segment of the cord, so long as it retains its 
proper commissural connection with the brain 
(by commissural fibres and continuous grey 
matter), is part and parcel of the centre of voli- 
tion as well as of that of sensation, and the 
mind is as directly associated with each seg- 
ment of the cord as it is with any portion of 
the encephalon. Let that commissural con- 
nection be dissolved, and the mind will imme- 
diately lose its hold upon the cord; but the 
various segments of that organ may nevertheless 
still be acted upon by physical impulses, and 
may still continue to evolve the nervous force in 
connection with the natural changes which may 
take place within. 

I am not aware that this view of the me- 
chanism of the various actions of the nervous 
system had been ever distinctly enunciated 
before it had been stated by Mr. Bowman and 
myself in our work on the Physiological Ana- 
tomy and Physiology of Man, in 1845.* There 
is nothing, however, in this hypothesis at 
variance or inconsistent with the views of 


* The Physiological Anatomy and Physiology of 
Man, by R. B. Todd and Wm. Bowman, vol. i. 
p. 323. 


PHYSIOLOGY OF TIE NERVOUS SYSTEM. 


Prochaska ; for this’ physiologist seems to 
have held the opinion that the nerves are im- 
planted in the segment of the cerebro-spinal 
axis into which they sink, and do not pass 
beyond it. 

I shall now examine into the merits of each 
of these hypotheses, and, first, of the excito- 
motory hypothesis. 

It is unnecessary to repeat the objections — 
already stated (p. 7218) to the use of the — 
term excito-motory. I shall only remark that 
some of these objections are equally opposed 
to the hypothesis as to its name. 

Nevertheless this hypothesis has much to 
commend it: and not the least argument in its — 
favour is that drawn from the compound nature: 
of spinal nerves, as proved by Bell, in which 
nerve-fibres of different endowments are bound — 
together in the same sheath. If it be proved 
(as it has been) that fibres of sensation and of — 
motion may be thus placed in juxtaposition 
in the same nervous trunk, it seems not an 
unreasonable conjecture that fibres of other 
function (excitors and their corresponding mo- 
tors) might be enclosed in the came shell 
with them. . 

Both anatomy and experiment, however, unite 
to prove the existence of sensitive fibres distinct 
from motor fibres; they are found separate in t 
roots of the nerves, and combined in the 
cords: but neither anatomy nor experiment fa-— 
vours the existence of a distinct series of excite 
and of corresponding motor nerves. Anatomical 
research affords not the slightest indication of 
such a series of nerves. And experiments ¢ 
the roots of the nerves, where it might reason- 
ably be expected that the excitors would b 
separated from the motors (following the ana 
logy of the motor and sensitive fibres), are by 
no means favourable to the existence of sue 
fibres in the roots. The failure of experi- 
menters to excite motion by irritation of th 
posterior roots of the spinal nerves has been 
already referred to. A new and extensiv 
series of experiments is much needed to 
this question. I would remark that galvani 
should not be used in them, as the results 
stimulation by that agent are extremely 
lacious, from its liability to extend beyond 
parts included between the electrodes. 

Other very serious anatomical objects 
may be urged to this hypothesis. It suppo 
the existence of two sets of fibres in the spit 
cord. Evidence in favour of these is war 
just as much as in favour of those in the rot 
of the nerves. Many facts favour the conel 
sion that the fibres which constitute the root 
the nerves of any segment of the cerebro-sp 
centre are implanted in the grey matter of 
segment, and that none of them are contint 
beyond that segment up into the brain. — 
penetrate the spinal cord more or less obliqa 
and form their connection with the grey m 
a little higher up than the point of penetratio 
but there is no evidence to show that the) 
assume a completely vertical direction to pas 
up to the brain. a 

The form and varying dimensions of 
spinal cord in its several regions are oppost 
to this view. If the sensori-volitional fibr 


wow 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


all continued up into the brain, and the (so- 
called) excito-motor fibres are implanted in the 
cord, that segment of the cord should be the 
largest in which the greatest number of these 
fibres is to be found. Now the great extent of 
excitor surface in the lower extremities, the 
magnitude of their muscles, the importance of 
their movements, and, at the same time, the 
great developement of reflex actions in them, 
would lead most reasonably to the expectation 
that the lumbar segment of the cord to which 
these nerves belong should exceed considerably 
in size the cervical segment which gives nerves 
to the upper extremities, where the excitor sur- 
face is of less extent, where the muscles are less 
powerful,and the reflex actions considerably less 
conspicuous. Moreover,the lumbar region of the 
cord would be, if Dr. Hall’s views were correct, 
the centre of those excito-motor acts connected 
with defzcation, micturition, parturition, &c., of 
which he speaks so much, and on this account 
might fairly claim a greater amount of substance. 
But the fact is, that the lumbar swelling of the 
cord is smaller than the cervical ; and that while 
it contains, and owes its bulk mainly to, a large 
quantity of vesicular matter, but a small pro- 
portion of fibrous matter is found in it. More- 
over, it is impossible to understand the great 
superiority of size of the lumbar portion over 
the dorsal segment of the cord, if we are to 
-admit that this latter segment contains in addi- 
tion to its own fibres (sensori-volitional and 
excito-motory) the sensori-volitional fibres of 
the lumbar, swelling also, which ought to be 
very numerous. 

It is very generally admitted that the only 
channel by which the will can influence the 
spinal cord is through the fibres of the anterior 
pyramids of the medulla oblongata, the greater 
number of which decussate each other along 
the median line. But it is in the highest de- 
gtee improbable that these fibres, occupying so 
small a space as they do, should form the ag- 
gregate of the volitional fibres (still less of the 
sensori-volitional fibres) of the trunk and extre- 
mities. The whole of these fibres (of both 
sides) collected together would scarcely equal 
in bulk the anterior portion of one of the antero- 
lateral columns of the spinal cord. 

It has been affirmed that much support is 
given to the excito-motory hypothesis by Dr. 
Carpenter’s and Mr. Newport’s supposed de- 
monstration of the two sets of fibres in the Arti- 
culata. But these observations are far from 
deserving the name of demonstration. The 
inferences from them are derived from the 
apparent direction of certain fibres, and not 
from any actual tracing of them by dissection 
or by microscopic inspection. The observa- 
tions, too, have been made with low powers, 
which are very insufficient for determining the 
precise disposition of the fibres and their rela- 
tion to the vesicular matter of the ganglia. 

These writers affirm that the longitudinal 
fibres of the ganglionic chain of Articulata 
pass up to the brain and constitute the sensori- 
volitional fibres, whilst other fibres pass in a 
transverse direction and are implanted in the 
ganglia. Were this the case, it might reason- 


722 


ably be expected that the brain would be the 
largest of the ganglia as containing the sum of 
the sensori-volitional fibres of the whole body. 
But let any one compare the size of the cere- 
bral ganglia of the scorpion (as figured by 
Mr. Newport*) with the size of the animal 
and that of its cord, and it will be evident to 
him how disproportionately small such a centre 
is to the number of sensori-volitional fibres 
which must be distributed over so large a sur- 
face and to so many muscles. Anatomy, how- 
ever, offers no objection to the hypothesis that 
the roots of the nerves are implanted in the 
ganglia, and that the longitudinal fibres act 
as commissures between different segments 
(adjacent and remote) of the cord. 

Neither do Mr. Newport's experiments on the 
myriapods and other Articulata throw any new 
light on the question of the existence of two 
orders of fibres; nor do they add anything to 
our knowledge beyond the important fact that 
actions take place in certain Invertebrata after 
decapitation, which are of the same nature with 
those which occur in Vertebrata after a similar 
mutilation. The mechanism of these actions 
has not been at all elucidated by these expe- 
riments. : 

The excito-motory hypothesis is sufficient for 
the explanation of the movements of decapi- 
tated animals, of parts in connection with small 
segments of the spinal cord, of limbs paralysed 
to sensation and voluntary motion from dis- 
eased brain or spinal cord. But there are two 
phenomena familiar to those who observe dis- 
ease with care, which cannot be explained by 
it; these are the movements which may be ex- 
cited by mental emotion in limbs paralysed to 
the influence of the will, and the total paralysis 
of the sphincter ani, which frequently accom- 
panies diseased brain, whilst at the same time 
the limbs are only affected to a partial extent or 
not at all. aes 

Cases occur sometimes in which hemiplegia. 
arises from an apoplectic clot, or other destruc- 
tive lesion in one hemisphere of the brain. The 
arm and leg, or either of them, are completely 
removed from the influence of the will; yet 
occasionally, as the effect of some sudden emo- 
tion, fear, joy, surprise, the paralysed limb is 
raised involuntarily. Even so slight a cause as 
yawning (an act of emotional kind) will excite 
the palsied limb. Every time the patient yawns 
the arm will be raised involuntarily. 

Such phenomena as these receive no ade- 
quate explanation from the excito-motory hypo- 
thesis. Mental emotions probably affect some 
part of the brain; if the only communica- 
tion between the brain and the limbs be by 
fibres of sensation and volition, it is impossible 
to understand how the emotional influence 
could be conveyed to them through a channel 
which has long been interrupted. If we are to 
adopt the excito-motory hypothesis, it will be 
necessary to suppose with Dr. Carpenter the 
existence of certain emotional fibres to explain 
the phenomena of this particular case. But it 
is difficult to admit the existence of three orders 


* Phil, Trans. 1844. 


722d 


of fibres in each muscle, which, to be effective, 
must have the same relation to the component 
elements of the muscle. It is impossible to 
imagine how each order of fibre should comport 
itself with reference to the other two, so that 
their actions may not interfere. Nor can any 
one fail to perceive that the emotional fibres 
must be infinitely less frequently employed 
than the others, and in some individuals so 
seldom called into action as to be greatly ex- 
posed to the risk of atrophy for want of use. 

Another phenomenon, which this hypothesis 
fails to explain, is the paralysis of the sphincter 
ani muscle which accompanies certain lesions 
of the brain, generally of grave import. Such le- 
sions are almost always accompanied by para- 
lysis, chiefly of the hemiplegic kind, but not ne- 
cessarily complete. On the contrary, in several 
such cases distinct reflex actions exist, indicating 
that, although the brain’s influence is withheld 
from the limbs, that of the cord is not. If, 
then, the cord be sufficiently free from morbid 
depression to allow of reflex movements taking 
place in the inferior limbs, why is the sphincter 
ani (the actions of which according to Dr. 
Tiall are eminently reflex) so completely para- 
lysed that it offers not the slightest resistance 
to the introduction of the finger into the anus ? 
So long as the cord is free from lesion and so 
capable of performing its functions that the 
lower limbs exhibit reflex movements, the 
sphincter ani muscle ought not to be paralysed, 
if the excito-motor hypothesis be true. For, 
admitting that this muscle has sensori-volitional 
fibres which are paralysed by the cerebral le- 
sion, it should have excito-motor fibres likewise 
which ought to enable the muscle to resist the 
entrance of the finger into the rectum. Such 
resistance, however, it certainly does not make, 
for the muscle is completely paralysed in 
the cases referred to. And it is plain that, ac- 
cording to the excito-motory hypothesis, a cere- 
bral lesion ought not to affect the sphincter ani 
further than to destroy the control of the will 
over it, unless the depressing influence of the 
lesion extend to the whole cord, and in sucha 
case there ought to be complete paralysis of the 
limbs likewise. 

In fine, it cannot be denied that the excito- 
motor hypothesis takes a narrow and confined 
view of that power of the nervous centres which 
it professes to elucidate. As I have before 
remarked, it limits this power to the excitation 
of motion, and it confines the exciting agency 
to nerves which naturally propagate centrad, 
and which only propagate such impressions as 
may excite movements. 

Now it admits of unquestionable proof that 
impressions on sensitive nerves may, by a pro- 
cess of reflexion, excite other sensitive nerves. 
Are we to suppose the existence of a special 
series of fibres for such phenomena? Such 
a supposition would involve the most palpable 
contradictions, and is wholly inadmissible. 

The second hypothesis, which accords with 
the views of Miiler, is just as competent to 
explain the phenomena of decapitated animals, 
and of limbs lysed to cerebral influence, 
as that of Dr. Hall. It receives considerable 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


support from the universal concurrence of sen- 
sation or mental perception with those normal 
actions which Dr, Hall would attribute to excito- 
motory fibres. If it be supposed that these 
fibres have a certain relation to the vesicular 
matter of the cord, there are as good grounds 
for the further supposition that they may con- 
tinue to be affected by it Sygate has 
been separated from the cord. This od gpm 
reach is as inadequate as that of excito- 
motory fibres to explain the influence of emotion 
on lysed limbs; and it likewise fails to 
explain the paralysis of the sphincter, which, 
under this hypothesis, ought to occur in every 
case of cerebral disease. The chief objection, 
however, to this hypothesis is anatomical; for — 
it is far from being proved that the fibres of the 
spinal nerves are continued upwards through 
the cord into the brain. For instance, what 
evidence have we that the fibres of the lumbar — 
region of the cord pass into the brain? The — 
fibres of the anterior pyramids, no doubt, are 
true cerebro-spinal fibres, because they com- 
municate equally with brain and cord, and 
distinctly pass from the one to the other; but it 
cannot be shown that they have any continuity 
with the fibres of any of the spinal nerves, 
Much less can it be shown that they contain 
the fibres which are continued up from, to say 
the least, the anterior roots of aut the spinal - 
nerves, which ought to be the case if this 
hypothesis be correct. The bulk of the pyra- 
mids is very much opposed to this view. 
most —— that the pyramids are f 
spinal commissures. The apparent longitudinal 
course of the fibres in the spinal cord affords no 
indication that they pass into the brain, for 
it is well known that many of the fibres forming 
the roots of spinal nerves take a very oblique 
course from their point of separation from the 
cord to their emergence from the spinal canal 
and it is probable that this obliquity is ¢ 
tinued in the cord itself, so that their 
origin would be much higher up than their apps 
rentone. This great length of oblique cour 
gives to the fibre the appearance of being strie 
longitudinal, whereas it may be implanted i 
the vesicular matter of the cord. “J 
The third hypothesis is more consonant 
either of the others with what appears to be t 
true anatomy of the spinal —namely, 
each segment has its proper nerves implani 
in it, that it is connected with adjacent se 
ments by commissural fibres, and that 
whole cord is connected with the cei 
and cerebellum by commissural fibres; by 
anterior pyramids and olivary columns 
the former, and by the restiform bodies wi 
the latter. - 
This hypothesis, the reader will bear in 
assumes that mental and physical actions 
performed through the same fibres—affecte 
a mental stimulus in the one case, anda physi 
stimulus in the other—the change proc Da 
the physical stimulus being, in the case 6 
reflex actions, reflected at the centre. 
same afferent and efferent fibres are exci 
the one case as in the other, the former 
as sensitive or excitor, or both; the 


 - 
re 
5 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


channels for voluntary, emotional, or strictly 
physical impulses to motion. 

The mechanism of a voluntary action in 
parts supplied by spinal nerves would be, 
according to this hypothesis, as follows:— 
The impulse of volition, excited primarily in 
the brain, acts at the same time upon the grey 
matter of the cord (its anterior horn), and 
through it upon the anterior roots of the nerves 
implanted in it. This grey matter, in virtue of 
its association with the brain by means of the 
anterior pyramids, becomes part and parcel of 
the organ of the will, and therefore as distinctly 
amenable to acts of the mind as that portion 
which is contained within the cranium. If we 
destroy the commissural connection with the 
brain through the pyramidal fibres, the spinal 
cord ceases to take part in mental nervous ac- 
tions; or, if that connection be only partially de- 
stroyed, that portion of thecord which the injured 
fibres had associated with the brain is no longer 
influenced by the mind. Again, if the seat of 
volition in the brain be diseased, the cord or part 
of it participates in the effects of the diseaseas far 
as regards voluntary actions. That it is not too 
much to ascribe such power to the pyramidal 
fibres appears reasonable, if we consider how 
the fibres of the corpus callosum, and perhaps 
other transverse commissures, so connect the 
hemispheres and other parts of the brain that 
the separate divisions of a double organ act 
harmoniously so as to excite but a single train 
of thought, or, conversely, that two impressions 
from one and the same source on a double 
sentient organ are perceived as single by the 
mind. 

An objection to this explanation will readily 
be raised—namely, that the excitation of the 
anterior horn of the grey matter, in the way 
Stated, does not explain the remarkable power 
which the will has of limiting its action to one 
or two, or a particular class of muscles. To 
this, however, it may be replied that there can 
be no reason for denying to the mind the 
faculty of concentrating its action upon a par- 
ticular series of the elementary parts of the 
vesicular matter, or even upon one or more 
vesicles, if we admit that it can direct its 
influence to one or more individual fibres, as 
the advocates of the first and second hypotheses 
do. If, indeed, we admit the one, we must 
admit the other; for whether the primary exci- 
tation of a fibre take place in the encephalon 
or in the spinal cord, the part first affected 
must probably be one or more vesicles of grey 
matter. 

The series of changes which would develope 
a sensation admits of the following explana- 
tion according to this hypothesis :—A stimulus 
applied to some part of the trunk or extremities 
18 propagated by the sensitive nerves to the 
posterior horn of the grey matter of the spinal 
cord, and from the junction of this part with 
the brain, either through the direct continuity 
of the vesicular matter of the cord with that of 
the centre of sensation, by the olivary column, 
or through longitudinal commissural fibres, 
analogous to or even forming a part of the an- 
terior pyramids, this is simultaneously affected. 


722E 


To this, likewise, it will be objected that the 
limitation of sensation is not sufficiently ex- 
plained. But the reply is obvious ; the intensity 
and kind of sensation depend upon the nature 
of the primary stimulus at the surface, the 
extent upon the number of fibres there stimu- 
lated. Wherever these fibres form their proper 
organic connection with the vesicular matter, 
that matter will participate in their change to 
an extent proportionate to the number of fibres 
stimulated, and with an intensity commensurate 
with the force of the primary stimulus. It is 
not necessary to the developement of sensation 
that the fibre stimulated should be implanted 
directly in the brain; if it be conrfected with 
this centre through the medium of vesicular 
matter or through commissural fibres, all 
the conditions necessary for the developement 
and propagation of nervous force would appear 
to be fulfilled. It must not be supposed, 
however, that in making this statement we 
mean to assign the spinal cord to be the seat of 
sensation ; all we assert is, that the posterior 
horn of the grey matter, as being the part in 
which the sensitive roots are implanted, is the 
seat of physical change excited by the stimulus 
applied to the sensitive fibres, which change 
must be perceived by the mind before true 
sensation can be produced. In fine, by the 
union of the posterior horns of the spinal grey 
matter with the vesicular matter of the brain, 
they become a part of the centre of sensation 
so long as that union is unimpaired.* 

This hypothesis offers an explanation of the 
hitherto unexplained phenomenon of impaired 
sensation on that side of the body which is 
opposite to the seat of cerebral lesion. If we 
regard the anterior pyramids as commissures 
between the sensitive as well as between the 
motor portions of the cerebro-spinal centre, it 
will be obvious that the posterior horns of the 
spinal grey matter on the right side will be 
associated with the left centre of sensation, and 
vice versa. ° 

And we gain, moreover, an explanation of 
the almost universal association of sensation 
with reflex or physical nervous actions. The 
excitor nerves of these actions being the same 


as the sensitive nerves, the impression con- 


veyed by them is calculated at once to excite 
motion and sensation. The controlling influ- 
ence of the will prevents many of the sensitive 
impressions made through the spinal cord from 
developing corresponding movements. And 
this controlling influence is best explained by 
this hypothesis, for as it admits no other motor 
nerves connected with the cord but those over 
which the will can exert an influence, it follows 
that such mental influence, if more powerful 
than the physical stimulus which the sentient 
nerves convey, may prevail over it and neu- 
tralize its force. On the other hand, under 
certain conditions of great physical excitation, 
(exalted polarity,) physical changes overcome 


* Tn all discussions relative to sensation it should 
be kept in view that true sensation involves a men- 
tal act, namely, the perception of a physical impres- 
sion, and of the concomitant physical change in 
the nervous matter. 


722K 


mental stimuli, and the mind loses all control ; 
this is the case in poisoning by strychnine, in 
tetanus, in convulsions. 

The difference of structure of the anterior 
and posterior horns of the vesicular matter of 
the spinal cord may be appropriately referred 
to as indicating a difference in functions be- 
tween these horns. The anterior horns contain 
large caudate vesicles of a remarkable and 
peculiar kind, containing a considerable quan- 
tity of pigmentary matter; the posterior horns 
resemble very much in structure the vesicular 
matter of the cerebral convolutions and of 
other parts of the cerebrum, and do not contain 
caudate vesicles, except near the base. Here, 
then, we find associated with the well-attested 
difference in the functions of the anterior and 
posterior roots, a striking difference in the 
structure of the anterior and posterior horns of 
the spinal grey matter in which they are re- 
spectively implanted. 

We gain from this hypothesis that which 
neither of the others could supply, namely, an 
explanation of the influence of emotion on 
limbs paralysed to volition. Mental emotion 
excites a change in the brain, probably in that 
part which forms the upper and posterior por- 
tion of the mesocephale: this change is readil 
propagated to the spinal grey matter thrown 
the olivary columns, independently of the py- 
ramidal fibres. The spinal grey matter being 
excited, the nerves implanted in it are stimu- 
lated, and motions are produced closely resem- 
bling those which the will can develope. 

We have noticed that the will can control 
reflex or other physical nervous actions. When 
the influence of the will is- suspended, reflex 
actions may be more easily excited. These 
facts admit of the most obvious explanation by 
the hypothesis under examination. 

Some reflex actions are imperfectly control- 
lable by the will; such as the contraction of 
the pupil, and the movement of deglutition at 
the isthmus faucium. This, however, cannot 
be cited as at all opposed to the view we are 
advocating ; for there is nothing in this hypo- 
thesis repugnant to the idea that certain nerves 
may be connected in the nervous centres with 
masses of vesicular matter over which the will 
usually exercises little or no control, and which, 
perhaps, may have but a slight connection 
with the centre of volition through commissural 
fibres. Still, respecting the two actions above- 
mentioned, it must be remarked that in de- 
glutition the mental influence is not sufficient 
by itself: we cannot perfectly contract the fau- 
ces, if food or some other physical stimulus be 
not present; the double stimulus—physical, as 
of the food, and mental, the will—appears 
necessary for the perfect performance of this act. 
In theaction of the pupil, the mental stimulus 
can only be brought to bear on the pupil, by di- 
recting it to another muscle at the same time, 
namely, the internal rectus muscle of the eyeball. 
When the eyeball is directed toward the nose, 
the pupil is usually simultaneously contracted. 

A double stimulus, mental and physical, 
appears to be necessary to the perfect develope- 
ment of many actions. This by potuesis offers 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


a ready explanation of the way in which the — 
two stimuli may combine to promote the same 
action. The:mental stimulus acts directly on 
the vesicular matter, the physical is propagated 
to it by sensitive nerves; and thus both acting 
on the same region of vesicular matter excite 
the same motor nerves. We have already no- 
ticed how this takes place in deglutition at the 
isthmus faucium. In locomotion there can be — 
no doubt that the double stimulus is in opera- 
tion: the degree of contraction of the muscles 
of the lower extremities necessary to maintain 
the superincumbent weight is obtained by the 
physical stimulus of pressure against the soles 
of the feet, where the skin is peostiets fitted 
for the reception of such a stimulus; but the 
movements of the limbs, and the harmonizi 
association of the muscular actions, are eflechall 
by mental influence. The pressure against the 
soles is felt, however, and the skin of the soles 
is known to be highly sensitive ; and the same — 
nerve-fibres which excite the sensation stimulate 
the vesicular matter in which the motor nervesare 
implanted. In many actions of familiar oe 
currence the voluntary effort is greatly en h 
by the simultaneous application of a physical 
stimulus to a part of the surface which is sup- 
plied with nerves from the same region of the 
cord. The horseman feels more secure when 
his legs are in close contact with the horse's 
flank. We gain a much firmer hold of an 
object which adapts itself well to the palmar 
surface of the hand, than of one which, al- 
though of no greater bulk, is yet so irregular 
in surface as not to allow of such intimate con- 
tact with the palm. Closure of the eyelids ig 
winking is an action of similar kind, resulting 
from a physical stimulus, which in the pe 
state of the cerebro-spinal centre produces se 
sation, and excites motion which is at once th 
result of the physical impression, and of th 
exercise of volition provoked by the sensation 
Every one must be conscious that he exere 
considerable control over the movements of h 
eyelids, and that it requires a great effort i 
revent winking for a certain period. | 
ength, however, the physical impression, @ 
ing from the contact of air with the conjuneti 
and the diminution of temperature from @ 
poration on the surface of that memb 
which at first caused but a slight sensat 
produces pain; the physical stimulus ¢ 
comes the mental resistance, and causes & 
traction of the orbicular muscle. And it 
be remarked further, that the closure ¢ 7 
lids by voluntary effort is much more powel 
if a stimulus be applied at the same tif 
the conjunctival surface, than if left so 
the exercise of the will. 
In the action just referred to, as well 
all other instances of reflex actions 
will can prevent, no satisfactory éxplan 
this controlling power of the mind can be gi 
by Dr. Hall’s hypothesis. Do the volit 
fibres exceed in number the excito-motory! 
this were admitted, then we could understat 
that an excito-motory act might be p 
by substituting a voluntary act for it; but 
the cases in question, the mind prevents ac 


Z Me 


. 


| 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


altogether, notwithstanding the exciting influ- 
ence of the impression. The true explanation 
seems to be, that the mind can exert upon the 
vesicular matter a power which can prevent 
the exercise of that change, or neutralise the 
change, without which the motor fibres will 
not be affected by a physical stimulus. 

Reflex actions are more manifest in some 
situations than others: thus, in cases of hemi- 
plegia from diseased brain, they are generally 
very obvious in the lower extremity, but to- 
tally absent in the upper. This, the advocates 
of the excito-motory theory ascribe to a paucity 
of excito-motory fibres in the latter limb, and 
to a larger amount of them in the former. Or, 
it has been attributed to the greater and 
more enduring influence of shock upon that 
segment of the cord from which the nerves of 
the upper extremities arise, as nearer the seat 
of lesion, than upon the lumbar segment. But 
another explanation of this important fact may 
be offered, which is equally satisfactory, and 
more accordant with other phenomena. A 
certain disposition of the nerves upon the tegu- 
mentary surface is as necessary for the develope- 
ment of reflex actions as of sensations ; and 
these movements will be more or less easily 
manifested, according as this organization of 
the nerves on the surface is more or less perfect. 

That disposition of the cutaneous nerves 
which renders the surface easily excitable by 
titillation seems most favourable to the deve- 
lopement of these actions. Hence, there is no 

lace where they are more readily excited than 
in the lower extremities by stimulating the soles 
of the feet or the intervals between the toes, 


.both of which situations are highly susceptible 


of titillation. At the isthmus faucium the 
slightest touch on the surface excites a move- 
ment of deglutition; and this touch, at the same 
time, produces a very peculiar sensation of 
tickling, quite distinct from that which may 
be excited at other parts of the pharynx, or 
mouth. When this part of the mucous mem- 
brane is in a state of irritation as an effect of 
coryza, this tickling sensation is present, and 
repeated acts of swallowing are provoked. 

Two facts may be stated here, which illus- 
trate the position above laid down respecting 
the necessity of a certain disposition of the 
nerves on the tegumental surface, for the de- 
velopement of reflex actions. The first is one 
which has been noticed by Volkmann, and 
which I have repeatedly observed, namely, that 
in frogs, and other animals, reflex actions are 
readily excited by stimulating the feet; but 
irritating the posterior roots of the spinal nerves, 
which supply those parts, is not sufficient for 
this purpose. I have already remarked that in 
humerous experiments upon the posterior roots 
of the nerves movements have not been ex- 
cited whilst they have been subjected to irrita- 
tion, except when galvanism was employed, 
which, being diffused, affected the cord itself: 
the recorded statements of most modern ex- 
perimenters agree in the main with this state- 
ment. The second fact is this: in the male 
frog the developement of a papillary structure 
on the skin of the thumb seems to have refe- 


. 


722G 


rence to the excitation of the physical power of 
the cord, to enable the animal to grasp the 
female without the necessity of a prolonged 
exercise of volition. Stimulating the fingers 
will scarcely produce reflex actions, but the 
slightest touch to the enlarged thumb will 
cause the animal to assume the attitude of 
grasping. If the papillae be shaved off the 
thumb, its power of exciting these actions 
is instantly lost. 

When the polarity of the cord is greatly ex- 
cited by strychnine or other substances, or 
when tetanus exists, all parts of the surface 
are equally capable of exciting reflex actions. 
The least touch will cause them, not only in 
the limb touched, but in all that side of the 
trunk, or even throughout the whole body. 
So general is the excitation, that the least im- 
pression made on the peripheral extremity of 
a sensitive nerve in any part of the body is 
instantly converted into muscular spasm, more 
or less general. A slight current of air, in 
tetanus, is sufficient to excite general spasm. 
Miller remarks that, in such states of the 
cord, the reflex actions excited by stimulating 
the nerves themselves are much less than those 
produced by excitation of the surface. 

The readiness with which a physical change, 
induced in one part of the centre, is propagated 
to others, whether above or below it, is due no 
doubt to the vesicular matter. An experiment 
made by Van Deen illustrates this statement. 
If, in an animal poisoned by strychnine, the 
cord be divided in its entire length along the 
median line, leaving only a slight bridge of 
grey matter, stimuli applied to any part of the 
surface will exhibit as extensive reactions as if 
the cord were entire. It is evident that the only 
medium of communication between the oppo- 
site halves must be the small portion of vesi- 
cular matter left undivided. 

Impressions conveyed to the cord by the pos- 
terior roots of any of its nerves, may be reflected 
to the corresponding motor nerves, and cause 
movement, or may extend irregularly along the 
posterior horns of grey matter and stimulate 
the nerves implanted in them, and thus give 
rise to new sensations, which may be referred 
to other and even distant parts of the body or 
to new motions. 

The hypothesis under consideration affords 
us an explanation, more satisfactory than any 
other, of the paralytic state of the sphincter 
ani in brain disease, already referred to, as well 
as in that of the spinal cord. This muscle is 
certainly chiefly under the influence of the will. 
In ordinary cases of diseased brain, where the 
lesion is confined to one side, the centre of 
volition is not sufficiently impaired to affect its 
influence upon the sphincter. In graver lesions, 
however, although the will may still continue 
to exert its control upon one side of the body, 
it loses its power over the sphincter, which is 
not excitable by any stimulus. In disease of 
the spinal cord, there is paralysis of the sphinc- 
ters if the lesion involve asufficient portion of the 
cord’s substance, in whatever region of the cord it. 
may exist. Even when the lesion is situate high 
up in the neck, or in the dorsal region, leaving 


722H 


the lumbar portion perfectly whole, the sphincter 
will nevertheless be paralysed. In the former 
instances, the centre of volition in the cranium 
is diseased ; in the latter, the defect consists in 
the destruction of the communication of the 
brain with that portion of the cord in which 
the nerves of the sphincter inuscle are im- 
planted. 

An examination of the action of the sphinc- 
ter will show, as has been already noticed, that 
the anus is kept closed ordinarily by the passive 
contraction of the muscle itself; but that its 
active contractions are mainly excited by vo- 
luntary influence, allowance being made for 
some slight action which may be produced by 
the stimulus of sudden distension, as in other 
circular muscles. Now, as a stimulus to sen- 
tient nerves constitutes no necessary part of 
any of these actions, it is probable that the 
motor nerves of the sphincter have little or no 
connection with the sentient ones; and, conse- 
quently, that muscle is not usvally excitable to 
contraction by a stimulus appled to a sentient 
surface. Hence, whenever the influence of the 
will upon the lumbar portion of the cord is 
suspended, this muscle ceases to act, whether a 
mental or a physical stimulus be exerted. 

We have remarked before that all that is 
shown by Dr. Hall’s experiments on the horse 
and on the turtle is that the spinal cord influ- 
enced the sphincter only whilst it was in a state of 
irritation consequent upon its division. There 
probably was no real reflex action at all, and the 
closure of the anus on the application ofa stimu- 
lus was probably only apparently due to that 
cause, frequent contractions taking place in the 
muscle in effect ofthe irritated state ofthe cord. 

On the same principle, animals will exhibit 
movements of voluntary character for some 
time after decapitation, the continued irritation 
of the cord acting asa stimulus. A bird thus 
treated will fly for some distance, and with 
considerable energy, and will flap its wings if 
the cut surface of the cord be irritated. A fly 
decapitated pursues its course for some way 
immediately after the removal of the head; and 
Walckenaer observed a singular fact respecting 
the Cerceris ornata, a wasp which attacks a bee 
that inhabits holes: “ at the moment that the in- 
sect was forcing its way into the hole of the bee, 
Walckenaer decapitated it; notwithstanding 
which, it continued its motions, and, when 
turned round, endeavoured to resume its posi- 
tion and enter the hole.”* The change in the 
vesicular matter of the ganglia necessary for 
the movements of the wasp in pursuit of its 
_prey, had already been excited by a powerful 
stimulus of volition, which continued even 
after the removal of the centre from which it 
had emanated. Actions at first voluntary, 
which by frequent repetition become habitual 
and involuntary, are, no doubt, to be accounted 
for by the persistence of that condition of the 
vesicular matter which the will at first induced, 
and to which the frequency of repetition gives 
a character of permanence. Thus Habit is due, 

* Quoted in Miiller’s Physiol by Baly, vol. i. 
p- Ter 2nd ed. si a a 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


as it were, to the fixation of a certain state of 
vesicular matter—it is the conversion of a men- 
tal into a physical nervous action by frequent 
repetition. - 
So similar is the change which a physical — 
stimulus can excite in the grey matter to that 
produced by the influence of the will, 
as has been often remarked, the actions exci 
in decapitated animals present a striking re- 
semblance to the ordinary voluntary move- 
ments. When a certain portion of the skin is — 
irritated, the animal pushes against the offend-— 
ing substance, as if trying to remove or dis- 
place it. If the anus be irritated, both 
are excited to action. It may also be o 
that the same motions follow the same irrita- — 
tions of the skin. If, in a frog, the seat of 
irritation be on the right side, the correspond-— 
ing hind-foot will be raised, as if to remove 
the irritating cause. The exact resemblance 
of these to voluntary movements seems to 
admit of being explained only on the suppo: 
sition that the same fibres are employed in he 
execution of both. . 
It must be kept in view, that, while thi 
hypothesis rejects the class of sensori-volition 
fibres which are supposed to pass with the 
spinal nerves along the cord into the brain, it 
admits the existence of only three orders of 
fibres implanted in the various segments of the 
cord, viz. those at once sensitive and excitor, 
those at once for voluntary and involuntal 
motion ; and commissural fibres ; of which he 
former only contribute toform the nerves. J 
must not be supposed, however, that it is inte 
ed by this hypothesis to assume that the inter 
vention of sensation (i.e. the perception of at 
impression by the mind) is necessary for th 
production of those muscular actions 
are excited by stimulation of the surface. . 
more is affirmed than that the same stimuh 
to the sensitive nerve which can and do 
excite a sensation, may simultaneously, bi 
independently, cause a change in the vesie 
matter which shall stimulate the motor nerves, 
and that this change is of the same kind 
that which the will may excite, and affee 
same motor nerves. 
Lastly, this hypothesis involves the € 
ciation of a highly important proposition \ 
reference to nervous centres. It is this: 
all the centres which are connected to the b 
by commissural fibres, are thereby submit 
to, and brought into connection with, the mii 
to an extent proportionate to the numbet 
connecting fibres, so that veluninas imp 
act upon them as part and parcel of the cel 
of volition; and sensitive impressions, 
fecting them, affect the mind simulte 
In voluntary actions, then, it may be st 
that, while the brain is the part primarii 
fected, the mental impulse is also di 
that portion of the cord upon which the 
action depends. oe 
In the developement of sensation the stim 
lus affects the posterior horns of the grey mi 
of the cord, which, from its commiss' : 
nection with the brain, is in reality a part 
the sensorium. When the power of meg 


a 
t 


=. 


5 


ad 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


interference is removed, or kept under con- 
trol, physical actions develope themselves ; 
being effected through the same nerves as those 
which volition influences or which sensitive 
impressions affect. The latter are, in such 
instances, the excitors of the former, no doubt 
through the vesicular matter in which they are 
implanted. These actions become most mani- 
fest when the connection of the brain with the 
spinal cord has been severed; and they occur 
in the most marked way in those situations 
where the cutaneous nerves are so organized 
as readily to respond to the application of a 
stimulus applied to the surface, or they be- 
come universal when the cord is in a state of 
general excitement. 

The movements in locomotion and the main- 
tenance of the various attitudes are effected 
through the ordinary channels of the physical 
and volitional actions; and the posterior co- 
lumns of the cord, by their influence on the 
vesicular matter of the segments in which the 
nerves are implanted, co-ordinate and _har- 
monize the complicated muscular actions of 
the limbs and the trunk under the controul of 
that portion of the encephalon which probably 
is devoted to that purpose. This power of co- 
ordination is probably mental, and - intimately 
connected with the muscular sense. 

Functions or THE ENncEPpHaton. — It 
will be convenient first to examine the func- 
tions of those parts of the encephalon which in 
structure most nearly resemble the spinal cord. 

Functions of the medulla oblongata, mesoce- 
phale, corpora striata, and optic thalumi.— 
The medulla oblongata most nearly resembles 
the cord in form and structure, at the same 
time that it exhibits most marked and impor- 
tant differences from it. Its subdivisions form 
connections superiorly with other parts of the 
brain, namely, the mesocephale, corpora striata, 
and optic thalami. These connections are so 
intimate, that, however convenient it may be to 
the descriptive anatomist to describe these 
parts each by itself, it is impossible, in exa- 
mining into their functions, to separate them 
completely. The functions of one part are so 
readily affected by a change in any or all of 
the others, that the effects of experiments are 
not limited only to the part operated upon, but 
affect or are affected by the rest. Thus, the 
olivary columns, which form the central and 
most essential part of the medulla oblongata, 
extend upwards through the mesocephale to 
the optic thalami; and the anterior pyramids 
form an intimate connection not only with the 
vesicular matter of the mesocephale, but, to a 
great extent, with that of the corpora striata. 
All these parts taken together, with the quadri- 
geminal tubercles, will be found to be the 
centre of the principal mental nervous actions, 
and of certain physical actions. which are very 
essential to the integrity of the economy. 

The office of the nerves which arise from this 
segment of the encephalon throws light upon 
its function. These nerves are partly destined 
for respiration, partly for deglutition, and partly 
also for acts of-volition and sensation. 


722t 


Destruction of the medulla oblongata is fol- 
lowed by the immediate cessation of the pheno- 
mena of respiration ; and this takes place whe- 
ther it be simply divided, or completely re- 
moved. When an animal is pithed, he falls 
down apparently senseless, and exhibiting only 
such convulsive movements as may be due to 
the irritation of the medulla by the section, or 
such reflex actions as may be excited by the ap- 
plication of a stimulus to some part of the trunk. 

If, in an animal which breathes without a 
diaphragm, as in a bird or reptile, the spinal 
cord be gradually removed in successive por- 
tions, proceeding from below, up to within a 
short distance of the medulla oblongata, loss of 
motor and sensitive power takes place succes- 
sively in the segments of the body with which 
the removed portions of the cord were connected. 
But the animal still retains its power of per- 
ceiving impressions made on those parts of the 
body which preserve their nervous connection 
with the medulla oblongata, and continues to 
exercise voluntary control over the movements 
of those parts. The movements of respiration 
go on, and deglutition is performed. The 
higher senses are unimpaired.* 

These phenomena are sometimes observed in 
man—in such cases as that alluded to in a 
former page; where, from injury to the spinal 
cord in the neck, below the origin of the phrenic 
nerve, the patient appears as a living head with 
a dead trunk. The sensibility and motor 
power of the head are perfect; respiration goes 
on partially, and deglutition can be readily 
performed. The senses and the intellectual 
faculties remain for a time unimpaired. 

Irritation of any part of the medulla oblon- 
gata excites convulsive movements in muscular 
parts which receive nerves from it, and, through 
the spinal cord, in the muscles of the trunk. 
Spasm of the glottis, difficulty of deglutition, 
irregular acts of breathing, result from irritation 
of the medulla oblongata; and, if the excite- 
ment be propagated to the cord, convulsions 
will become more or less general. 

If a lesion affect one half of the medulla ob- 
longata, does it produce convulsions or paralysis 
on the opposite side of the body? This ques- 
tion may be certainly answered in the affirma- 
tive, when the seat of the lesion is in the conti- 
nuations of the columns of the medulla oblon- 
gata above the posterior margin of the pons. 
It is not so easily solved, however, when the 
disease is situate below the pons. The results 
of experiment on this subject are contradictory, 
owing probably to the extreme difficulty of 
limiting the injury inflicted to a portion of the 
medulla on one side; and those of Flourens 
are of no value for the decision of this question, 
as it appears that he injured chiefly the resti- 
form bodies. Anatomy suggests that a lesion 
limited to either anterior pyramid would affect 
the opposite side of the trunk, for it is known 
that such an effect follows disease of the conti- 


_ nuation of it in the mesocephale or crus cerebri ; 


and that lesion limited to the posterior half of 


* Flourens, p. 179. 


722k 


the medulla on either side would affect the 
same side of the body, no decussation existing 
between the fibres of opposite restiform or pos- 
terior pyramidal bodies. The irritating or de- 
es influence of the lesion would probably 

extended to the spinal grey matter of the 
same side. 

That the medulla oblongata is the channel 
through which the operations of the brain are 
associated in voluntary actions with the spinal 
cord, is shewn by the fact that paralysis of all 
the muscles of the trunk follows the separation 
of the latter organ from the former. It seems 
not improbable that the centre of volition is 
connected with one of the gangliform bodies 
in which the columns of the medulla oblon- 
gata terminate above (the corpora striata), so 
that the column connected with each corpus 
striatum (the anterior pyramid) is well placed 
for conveying voluntary impulses downwards. 
When the cerebral hemispheres have been 
removed, as in Flourens’ and in Magendie’s 
experiments, the bird is thrown into a deep 
sleep, a state of stupefaction, and insensibility 
to surrounding objects. But as he can main- 
tain his attitude, stand, walk when first pro- 

lled, fly if thrown into the air, it may be 
inferred that some degree at least of mental 
or volitional effort remains. Some of the ani- 
mal’s movements have the appearance of the 
exercise of will, although, doubtless, many of 
them are’in a great degree excited by physical 
stimuli. I may instance, in particular, what I 
have noticed in my own repetition of Flourens’ 
experiments, a peculiar movement of the head, 
as if the bird were trying to shake off some 
object which irritated the head, and a frequent 
opening and shutting the bill, with movements 
of deglutition. Hence there seems reason to 
believe that the will may be exercised inde- 
pendently of the cerebral convolutions and 
their fibres, and that, under all circumstances, 
it exerts a primary influence upon either or 
both of these gangliform bodies, more vigorous 
when aided and guided by the power of the 
cerebral hemispheres. The frequent paralysis 
of motion apart from sensation, when the up- 
ward continuations of the pyramidal fibres in 
the corpora striata are diseased, renders it ex- 
tremely probable that these fibres are the media 
of connection between the brain and cord in 
voluntary actions. 

The medulla oblongata is also the medium for 
the transmission of sensitive impressions from 
all the regions of the head, trunk, and extremi- 
ties; and from its olivary columns at their upper 
and posterior part in the mesocephale being, as 
it were, the concourse of all the nerves of pure 
sense, it seems fair to assign these parts as the 
prime seat of those central impressions which 
are necessary for sensation. e reception of 
these impressions by the cerebral hemispheres 
is the stage immediately associated with mental 
perception. Perfect sensation, therefore, cannot 
take place without cerebral hemispheres. Ina 
sensation excited in parts suppled by spinal 
nerves, the first central change is probably in 
the posterior horn of the vesicular matter of the 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


cord; and the olivary column of the medulla — 
oblongata is simultaneously affected, from its 
connection with the cord. The change in this 
latter part is then propagated to the cerebral 
hemispheres. 
Thus much is suggested by anatomy, as re=— 
gards the share which the medulla oblongata — 
takes in the mechanism of sensitive impressions, 
Experiment affords us no aid in this intricate — 
and difficult subject; neither does peholeaay 
anatomy : for the parts are so closely associated 
with each other, that any morbid state of one 
readily involves the others, so that it is almost 
impossible to find a morbid state of the p 
devoted to sensation, apart from an affection: 
those more immediately concerned in motion, 
The function of the restiform bodies is pro- 
bably associated with that of the hemisp 
of the cerebellum, and of the posterior columns — 
of the spinal cord. ae 
The experiments of Le Gallois and Flourens — 
make it certain that the medulla obl is 
the centre of respiratory movements. : 
ter physiologist assigns as the “ primum 
vens”’ of these acts all that portion of the me- 
dulla which extends from the filaments of ori 
of the vagus nerve to the tubercula quadrig 
mina, the former only inclusive. Dest 
of this portion, in whole or in part, invariabl 
impairs or destroys the respiratory actions, ant 
a morbid state of it gives rise to irregular © 
excited movements of respiration. Sighing 
yawning, coughing, are probably connected 
excitation of this centre, either direct, or f 
gated to it from some sentient surface 
seems not improbable that a portion of 
spinal cord as low down as the spinal 
sory nerve goes, is associated with this ce 
in the respiratory movements. th 
This portion of the encephalon is 
centre of action in the movements of de 
tion, through fibres of the glosso-pharyngs 
and vagi nerves. A morbid state of it occasio 
difficulty, or even bayer of deglutitio 
Animals deprived of the cerebral hemisp 
and cerebellum will preserve the pe 
swallowing food introduced within tl 
of the fauces, so long as the medulla oblon 
continues uninjured. In foetuses born 
cerebral hemispheres, those actions are p 
which depend on the spinal cord and me 
oblongata; all the movements of respirat 
and deglutition are performed as well as in 
perfect fetus. Mr. Grainger’s experim 
shew that puppies deprived of the hemisph 
of the brain can perform the movemen 
suction with considerable vigour, » 
finger is introduced into the mouth ;* ane 
remarkable fact of the adhesion of the fa 
the kangaroo to the nipple within the pot 
no less than its respiratory movements, mus 
this author remarks, be regarded as a most 
teresting display of the physical power oi 
medulla oblongata, while the rest of the bra 
as yet undeveloped. a 
The actions of respiration and phary 


we, 


ie 
. 


* Loc, cit. pp. 80-1, 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


deglutition are, to a great extent, of the physi- 
cal kind, being excited by impressions propa- 
gated from the periphery. In those of respira- 
tion, the ordinary exciting cause is probably, 
as Dr. Hall suggested, due to the chemical 
changes in the respired air which are effected 
in the lungs. These movements may be, toa 
certain extent, contrelled by the will; but every 
one is conscious, from his own sensations, that 
after a time the physical stimulus is capable of 
conquering the restraining influence of the 
mind ; a striking example of a mental stimu- 
lus giving way to a physical one, and illustra- 
tive of the doctrine that the same fibres 
are affected by both stimuli. The excitation 
of the medulla oblongata in respiration does 
not, however, depend solely upon the pul- 
monary nerves. Those of the skin are ca- 
pable of exciting it, either directly as the fifth 
ir, or through the spinal cord, as is proved 
y the inspirations which are instantly excited 
by suddenly dashing cold water on the face or 
trunk. 

In deglutition, the exciting cause is the sti- 
mulus of contact applied to the mucous mem- 
brane of the fauces. So highly sensitive is the 
mucous membrane in this situation, that the 
slightest touch of it with a feather is sufficient 
to produce contraction of the muscles of deglu- 
tition, which the will is scarcely able to con- 
trol. Without this stimulus, it is doubtful 
whether these muscles would obey the will 
alone, and it seems probable that this part of 
the act.of deglutition must be regarded as one 
of those actions referred to at a former page, 
which require a double stimulus, both mental 
and physical, for their full performance. 

The medulla oblongata and its continuations 
in the mesocephale appear to be the centre of 
those actions which are influenced by emotion. 
The common excitement of movements of de- 
glutition or respiration, or of sensations referred 
to the throat, under the influence of emotion, 
evidently points to this part of the cerebro- 
spinal centre as being very prone to obey such 
impulses; and as the nerves of pure sense, 
especially the optic and auditory, are very 
commonly the channels of sensitive impressions 
well calculated to arouse the feelings, it seems 
highly probable that the centre of such actions 
should be contiguous to the origin of these 
nerves. This office may be assigned to that 
Tegion of the mesocephale which is in the 
Vicinity of the quadrigeminal tubercles. It is 
not a little remarkable that the nerves which 
arise from this and the neighbouring parts are 
very readily influenced by emotions. Thus, 
the third and fourth pairs of nerves regulate 
the principal movements of the eyeballs, those 
especially which most quickly betray emotional 
excitement; and the portio dura of the se- 
venth pair, the motor nerve of the face, is the 
medium through which changes of the counte- 


hance are effected. It may be added, that the 


centre of emotional actions ought to be so situ- 
| \ated that it might readily communicate with 
_ \the centres of all the voluntary actions of the 
_|body, and with the immediate seat of the 
_\intellectual operations, as well as with the 
B\ (VOL. 111. 


722. 


nerves of pure sense; and no part possesses 
these relations so completely as that now under 
examination. 

In those diseases which mental emotion is 
apt to give rise to, many of the symptoms are 
referable to affection of the medulla oblongata. 
In hysteria, the globus, or peculiar sense of 
suffocation or constriction about the fauces; in 
chorea, the difficulty of deglutition, the pecu- 
liar movement of the tongue, the excited state 
of the countenance, the difficulty of articula- 
tion, may be attributed to the exalted polarity 
of the centre of emotional actions. In hydro- 
phobia this part is probably always affected, 
and frequently so in tetanus. 

Certain gangliform bodies are connected with 
the upward continuations of the medulla ob- 
longata, both in the brain and in the mesoce- 

hale, which doubtless have proper functions. 
hese are the corpora striata, optic thalami, 
and quadrigeminal bodies. 

Corpora striata.—The anatomy of the cor- 
pora striata and optic thalami, while it denotes 
a very intimate union between them, also shows 
so manifest a difference in their structural cha- 
racters, that it cannot be doubted that they 
perform essentially different functions. In the 
corpora striata the fibrous matter is arranged 
in distinct fascicles of various sizes, many, 
if not all of which, form a special connection 
with its vesicular matter. In the optic thala- 
mi, on the other hand, the fibrous matter forms 
a very intricate interlacement, which is equally 
complicated at every part. Innumerable fibres 
pass from one to the other, and both are con- 
nected to the hemispheres by extensive radia- 
tions of fibrous matter. The corpora striata, 
however, are connected chiefly, if not solely, 
with the inferior fibrous layer of each crus 
cerebri; whilst the optic thalami are continuous 
with the superior part of each crus, which is 
situate above the locus niger. 

It will be observed, then, that while these 
bodies possess, as a principal character in com- 
mon, an extensive connection with the convo- 
luted surface of the brain, they are, in the most 
marked way, connected inferiorly with separate 
and distinct portions of the medulla oblongata; 
the corpora striata with the inferior fibrous 
planes of the crura cerebri and their continua- 
tions, the anterior pyramids; and the optic 
thalami with the olivary columns, the central 
and probably fundamental portions of the me- 
dulla oblongata. This anatomical fact must 
be taken as an additional indication that these 
gangliform bodies perform separate functions. 

Now, it may be inferred, from their con- 
nections with nerves chiefly of a sensitive kind, 
that the olivary columns, and the optic thalami, 
which are continuous with them, are chiefly 
concerned in the reception of sensitive impres- 
sions, which may principally have reference 
merely to informing the mind (so to speak), or 
partly to the excitation of motion, as in deglu- 
tition, respiration, &c. The posterior horns of 
the grey matter of the cord, either by their 
direct continuity with the olivary columns, or 
their union with these columns through com- 


missural fibres, become part and parcel of a 
22 KEREER 


722m 


great centre of sensation, whether for mental or 
physical actions. 

he pyramidal bodies evidently connect the 

grey matter of the cord (its anterior horns ?) 
with the corpora striata; and not only these, 
but also the intervening masses of vesicular 
matter, such as the locus niger, and the vesi- 
cular matter of the pons, and of the olivary 
columns; and, supposing the corpora striata 
to be centres of volition in intimate connection 
with the convoluted surface of the brain by 
their numerous radiations, all these several 
parts are linked together for the common pur- 
poses of volition, and constitute a great centre 
of voluntary actions, amenable to the influence 
of the will at every point. 

It has been pretty generally admitted by 
anatomists, that both the corpora striata a 
the anterior pyramids are concerned in volun- 
tary movements. The motor tracts of Bell 
were rded by that physiologist as passin 
pirate I from the sated ie columns of the cord 
to the corpora striata, and, after traversing 
those bodies, as diverging into the fibrous mat- 
ter of the hemispheres; and the fact of the 
origin of certain motor nerves, in connection 
with those fibres, was considered to be very 
favourable to this view. The decussation of 
the pyramids, likewise, so illustrative of the 
cross influence of the brain in lesions sufficient 
to produce paralysis, has been looked upon as 
an additional indication of the motor influence 
of these parts. 

The invariable occurrence of paralysis as the 
result of lesion, even of slight amount, in the 
corpora striata, must be regarded as a fact of 
strong import in reference to the motor func- 
tions of these bodies. 

Nor is this fact at all incompatible with the 
statements made by all experimenters, that 
simple section of the corpus striatum does not 
occasion either marked paralysis or convulsion ; 
and that in cutting away the different segments 
of the brain, beginning with the hemispheres, 
convulsions are not excited until the region of 
the mesocephale is involved. The influence of 
the corpora striata is not upon the nerves di- 
rectly, but upon the segments of the medulla 
oblongata or of the spinal cord, and, through 
them, upon the nerves which arise from them. 
Were the nerve-fibres continued up into the 
corpora striata, according to an opinion which 
has been long prevalent, there would be no 

ood reason for supposing that they should 

‘ose in the brain that excitability to physical 
stimuli which they are known to possess in the 
spinal cord, and at their peripheral distribution. 

The latest experiments of this kind, which are 
those of Longet and Lafargue, agree in the fol- 
lowing result, which is not at variance with that 
obtained by Flourens. The animals remain 
immoveable after the removal of the corpora 
striata, whether those bodies have been removed 
alone or in conjunction with the hemispheres ; 
nor do they show any disposition to move, un- 
less strongly excited by some external stimu- 
lus. None of these observers had noticed the 
irresistible tendency to rapid propulsion, which 
was described by Magendie. Removal of the 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


corpus striatum of one side caused weakness 
of the opposite side. 

ln order to form a due estimate of these ex- 
periments, it must be borne in mind, that the 
effects of simple excision of either corpus 
striatum would be very different from those of 
disease of it. The depressing effects of the 
latter would be absent, at least, until some 
alteration in the process of nutrition had been 
set up in the mutilated Simple excision 
of the centre of volition, and inflammatory dis- 
ease of its substance, or an tot sonar 
must produce essentially different effects ;- 
the one simply cuts off the influence of the 
will, the other affects the vital action, and, com= 
sequently, the vital of the centre, and 
of the commissural fibres connected with it. 

Judging from structure only, it might be 
conjectured that the locus niger, that remark- 
able mass of vesicular matter bree $s 
the anterior and posterior planes us 
cerebri, estore & davtob atapeiin Tt resemb ‘ 
in structure the anterior horns of the @ rey 
matter of the cord, and contains numérous 
large caudate vesicles with very abundant pig- 
ment, and is the immediate centre of implanta 
tion of a very im t motor nerve, the thi 
pair, which regulates the movements of 
all the muscles of the eyeball. 

Optic thalami—The same line of arg 
which leads us to view the striate 
the more essential of the nervous 
ratus which controul direct voluntary mo 
ments, suggests that the optie thalami may | 
viewed as the principal foci of. sen 
without which the mind could not pere 
physical change resulting from a se 
pression. ae 

The principal anatomical facet which fa 
this conclusion is the connection of a 
nerves of pure sense, more or less di 
with the optic thalami or with the olivary 
lumns. e olfactory processes, which a 
rently have no connection with them, fe 
doubt, t h the fornix, such an union Wi 
them, as readily to bring them within the 
fluence of the olfactory nerves. “ 

According to this sense of its office we 
regard the optic thalami as the upper and 
fd of an sane 

wer part is formed olivary ec 
which oa have ie referred to as ti 
part in the mechanism of sensation. The 
tinuity of the olivary columns with the” 
thalami justifies this view: nor is it it 
by the fact, that some of the nerves 4 
arise from the medulla oblongata are mo 
function; for Stilling’s researches re 
probable that these fibres have their ori 
special accumulations of vesicular matter, ¥ 
contain caudate vesicles of the same 4 
those found in the anterior horns of the 
matter of the cord. ( 

The results which experiments have yie 
add little that is positive to our knowled 
the functions of these bodies. Flourens 
that neither pricking nor cutting away the oj 
thalami by successive slices occasioned 
muscular agitation, nor did it even mduce’ 


is 


a 


a 
. 


? 


> 


Ee 


“only 


PHYSIOLOGY OF THE NERVOUS SYSTEM, 


traction of the pupils. Longet found that re- 
moval of one optic thalamus in the rabbit was 
followed by paralysis on the opposite side of 
the body. It appears, however, that this was 
done after the removal of the hemisphere and 
corpus striatum, whereby the experiment was 
so complicated as to invalidate any conclusion 
that might be drawn from it respecting the 
function of the thalamus. Indeed, vivisections 
upon so complex an organ as the brain are ill- 
calculated to lead to useful or satisfactory 
results; but one does not hesitate to refer to 
such as have been made, because they afford a 
certain amount of negative information, imper- 
fect though it be. 

Nothing definitive respecting the proper 
office of the thalami can be obtained from pa- 
thological anatomy. Extensive disease of 
these bodies is attended with the same phe- 
nomena during life, as lesion of similar kind 
in the corpora striata. Hemiplegic paralysis 
accompanies both; nor does it appear that sen- 
‘sation is more impaired when the thalamus is 
diseased, than when the corpus striatum is 
affected. 

There is nothing in the phenomena attendant 
on morbid states of the thalami which can be 
fairly regarded as opposed to the conclusion 
which their anatomical relations indicate, name- 
ly, that they form a principal part of the centre 
of sensation. The intimate connection between 
the striated bodies and the thalami sufficiently 
explains the paralysis of motion which follows 
disease of the latter; whilst, as the thalami do 
Not constitute the whole centre of sensation, but 
a part thereof, it cannot be expected that 
lesion of this part would destroy sensation, so 
Jong'as the remainder of the centre on the same 
side, as well as that of the opposite side, retain 
their integrity. Complete paralysis of sensation 
‘on one side is very rare in diseased brain: a 


- slight impairment of it frequently exists in the 


early periods of cerebral lesion, apparently as 
an effect of shock; for it quickly subsides, 
although the motor power may never return, 

According to the views above expressed, the 
‘corpora striata and optic thalami bear to each 
other a relation analogous to that of the ante- 
rior to the posterior horn of the spinal grey 
ter. The corpora striata and anterior horns 


} are centres of motion; the optic thalami and 


posterior horns, centres of sensation. The 
‘anterior pyramids connect the former; the 


| olivary columns, and perhaps some fibres of 


the anterior pyramids, the latter. The olivary 
columns, however, are in great part continu- 


| ations of the thalami on the one hand, and of 


the grey matter of the cord on the other; and 
‘contain abundance of vesicular matter, in which 
herves are implanted. 

And it must be admitted that the intimate 
connection of sensation and motion, whereby 
Sensation becomes a frequent excitor of mo- 
tion,—and vol motion is always, in a 
state of health, attended with sensation,— 
would @ priori lead us to look for the respec- 
tive centres of these two great faculties, not 
only in juxta-position, but in union at least as 
intimate as that which exists between the corpus 


722N 


striatum and optic thalamus, or between the 
anterior and the posterior horns of the spinal 
grey matter. 

Saucerotte, Foville, Pinel Grandchamps, and 
others, advanced the opinion that the corpora 
striata and the fibrous substance of the anterior 
lobes of the brain had a special influence upon 
the motions of the lower extremities, and that 
the optic thalami and the fibrous substance of 
the middle and posterior part of the brain pre- 
sided oyer the movements of the upper ex- 
tremities. We find, however, but little to 
favour this theory either in the results of ex- 
periments, in pathological observation, or the 
anatomy of the parts. Longet states, that, in 
his experiments upon the optic thalami, the 
paralysis affected equally the anterior and the 
posterior extremities. | Andral analysed se 
venty-five cases of cerebral lesion limited to 
the corpus striatum or optic thalamus. In 
twenty-three of these cases, the paralysis was 
confined to the upper extremity: of these, 
eleven were affected with lesion of the corpus 
Striatum or of the anterior lobe; ¢en with lesion 
of the posterior lobe, or of the optic thalamus; 
and two with lesion of the middle lobe.* 
Hence it is plain that a diseased state of the 
corpus striatum is as apt to induce paralysis 
of the upper extremity as lesion of the tha- 
lamus ; and we are forced to conclude, that 
pathological anatomy is not competent to de- 
cide the question. Lastly, the anatomy of these 
two bodies renders it highly improbable that 
they perform a function -so similar, as that of 
directing the movements of particular limbs, 
The great size of the optic thalamus, its mul- 
titude of fibrous radiations, its extensive con- 
nections both in the medulla oblongata and in 
the hemispheres by means of commissural 
fibres, the marked difference of its structure 
from that of the corpus striatum, its con- 
nection more with the posterior horns of the 
spinal grey matter than with the anterior ones, 
and its intimate relation to nerves of sensation, 
are sufficient anatomical facts to warrant the 
opinion that the thalami must perform a func- 
tion which, although it may be subservient to, 
or associated with, that of the striated bodies, 
is yet entirely dissimilar in kind. 

It has been supposed that the corpora striata 
are special centres or ganglia to the olfactory 
nerves, and to the sense of smell. But such 
a supposition is altogether superfluous, imas- 
much as a very distinct and obvious centre to 
these nerves exists in the olfactory process or 
lobe, miscalled nerve by descriptive anatomists. 
The small olfactory nerves are implanted in 
the anterior extremity or bulb of this process, 
which is provided with all the structural cha- 
racters of a nervous centre, and contains a 
ventricle. This lobe, moreover, is always de- 
veloped in the direct ratio of the size and 
number of the olfactory nerves, and of the 
developement of the sense of smell; and in 
the Cetacea, a class in which the olfactory 
nerves and process either do not exist at all, 
or ate so imperfectly developed as to have 


* Clin. Med. t. v. 
2 7 2 RRERER 


7220 


escaped the notice of some of the ablest ana- 
tomists, the corpora striata are of good size 
proportionally to that of the entire brain. 

orpora quadrigemina——The marked con- 
nection of these gangliform bodies with the 
optic nerves plainly indicates that they bear 
some special relation to those nerves, and to 
the sense of vision; and this indication be- 
comes more certain when we learn, from com- 
perative anatomy, that in all vertebrate tribes 
mm which the encephalon is developed, special 
lobes exist, bearing a similar relation to the 
optic nerves. When the optic nerves are large, 
these lobes are large; and in the Pleuronecta, 
in which the eyes are of unequal size, Gottsche 
states that the optic lobes are unequal, and are 
related in size to each other, as the eyeballs are. 
Still,as Serres has remarked, the quadrigeminal 
tubercles probably perform some other office 
besides that which refers to vision; inasmuch 
as the absence, or extremely diminutive size, 
of the optic nerves in some animals (the mole 
for instance) does not materially affect that of 
these bodies.* 

Flourens found that destruction of either of 
these tubercles on one side was followed by 
loss of sight of the opposite side, and con- 
sequently that the removal of both deprived 
the animal altogether of the power of vision, 
but didenot affect its locomotive or intellectual 
powers, nor its sensibility, except to light. In 
these experiments the action of the iris was 
not impaired if the tubercles were only par- 
tially removed; as long as any portion of the 
roots of the optic nerves remained uninjured, 
the iris continued to respond to the stimulus 
of light, but the total removal of the tubercles 
paralysed the irides. If the lobes of the brain 
and cerebellum were removed, leaving the 
tubercles untouched, the irides would continue 
to contract. These experiments leave no room 
to doubt that the optic tubercles are the ence- 
phalic recipients of the impressions necessary 
to vision, which doubtless are simultaneously 
felt by means of the optic thalami; and that 
they are the centres of those movements of the 
iris which contribute largely not only to pro- 
tect the retina, but likewise to increase the 
perfection of vision. The optic nerve is at 
once the nerve of vision, and the excitor of 
motor impulses which are conveyed to the iris 
by the third nerve, which takes its origin very 
near to the optic tubercles. It is interesting 
to add, that irritation of an optic tubercle on 
one side causes contraction of both irides :— 
this is quite in accordance with the well- 
established fact, that, if light be admitted to 
one eye so as to cause contraction of its pupil, 
the other pupil will contract at the same time. 
So simultaneous is the action of the two cen- 
tres; so rapid must be the transmission of the 
stimulus from one side to the other. 

When the injuries inflicted on these tuber- 
cles were deep, more or less general convulsive 
movements were produced; if one tubercle 
were injured, the opposite side only was so 
affected. These convulsions were due to the 


* Vid. Optic NERVEs. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


lesion of the central parts of the medulla ob- 
longata, with which the optic tubercles are in- 
timately connected. A remarkable vertiginous 
movement was likewise caused, the animal 
turning to the side from which the tubercle had 
been removed. It does not appear that this 
rotation could be attributed to any special in- 
fluence of the medulla oblongata, but rather to 
a state of vertigo induced by the partial destrue- 
tion of vision; for Flourens found that the 
same effects could be produced in pigeons 
blindfolding one race The movements, rie 
ever, were not so rapid, nor did they continue 
solong. And Longet saw the same movements 
in pigeons in which he had evacuated the hu- 
mours of one eye.* . 
It may be remarked, that deep injuries to 
the quadrigeminal tubercles are very likely to 
ma the only commissural connection between 
e cerebrum and cerebellum (processus cere- 
belli ad testes), the integrity © which must. 
doubtless be essentially necessary to ire 
harmony of action between these two great 
nervous centres, ond 
There are many instances on record in 
blindness was coincident with pathologic: 
alteration of structure in one or both quadrigs 
minal tubercles. In some of the cases w 
the lesion extended to parts seated beneat 
tubercles, disturbed movements were obser 
as in the experiments above related. a 
We are ignorant of the object of the ex 
sive connections of the optic tracts with | 
tuber cinereum, the crura cerebri, and 
wet agarip-ad. but these points are hig 
worthy of future inquiry, especiall th 
ference to the office of these inst all DO 
which is at present involved in much obseuri 
Many of the fibres of the optic tracts an 
doubtedly commissural between the coi 
ponding points of opposite sides, and 
when those which form the optic nervy 
deficient. y 
We see, then, in the quadrigeminal tubere 
centres, which, whatever other functions th 
may perform, have a sufficiently obvic 
tion to the optic nerves, the eye, and the 
of vision. This is clearly indi by 
tomical facts, especially by those of ¢ 
tive anatomy, by the results of experiment 
by the phenomena of disease. b 
may, therefore, be justly reckoned as 5} 
ganglia of vision; and we are led to se 
similar centres in connection with the | 
senses. The olfactory processes : 
probably to perform a similar office in r 
to the sense of smell. Their struct re, 
relation to the olfactory nerves, and thei 
proportion of bulk to that of these nervy 
to the developement of the o apr 
place this question beyond all doubt. It 
so easy to determine the special ganglia 0 
ing; but the olivary bodies, or the sr 
bules connected with the crura cerebelli ¢ 
by Reil the flocks, may be referred to as b 
a sufficient close anatomical relation | 


. 


A 


e, 
col 


~ 


* Flourens’ experiments have been amply 
firmed by those of Hertwig and Longet. 


Ls 


p's 
- 


= 2 


— 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 
auditory nerve to justify our regarding either. 


of them as well calculated to perform this func- 
tion, And, with respect to touch, the ganglia 
on the posterior roots of the spinal and the 
fifth nerves may perhaps be considered in the 
same light; for this sense being diffused so 
universally, in various degrees, over the whole 
surface of the body, and being seated in a great 
number of different nerves, would need ganglia 
in connection with all those nerves which are 
adapted to the reception of tactile impressions. 
The analogous sense of taste has its ganglia in 
those of the glosso-pharyngeal and the fifth.* 
The upper and posterior part of the mesoce- 
phale has already been referred to, as being 
most probably that part of the brain which is 
most directly influenced by emotional excite- 
ment. Dr. Carpenter appears to localize the 
seat of emotional influence more specially in 
the corpora quadrigemina, and refers to certain 
fibres, which he considers terminate in those 
bodies, as channels of emotional impulses. 
Although I am compelled to differ from this 
able writer in this limitation of the centre of 
emotion (so to speak), and am far from admit- 
ting the existence of a distinct series of fibres 
for emotional acts, I nevertheless think that the 


arguments he advances are most applicable to 


that view which refers the influence of emotion to 
the grey matter of this entire region, which is 
brought into connection with the spinal cord 
by the fibres of the anterior pyramids, as well 
as probably through the continuity of the olivary 
columns and the posterior horns of the spinal 


‘grey matter. 


Every one has experienced in his own person 
how the emotions of the mind, whether excited 
by a passing thought, or through the external 
senses, may occasion not only involuntary 
movements, but subjective sensations. The 


_ thrill which is felt throughout the entire frame 


when a feeling of horror or of joy is excited, or 
the involuntary shudder which the idea of im- 
minent danger or of some serious hazard gives 
rise to, are phenomena of sensation and motion 
excited by emotion. The nerves which take 
their origin from the medulla oblongata, meso- 
cephale, or crura cerebri, are especially apt to 
be affected by emotions. The choking sensa- 
tion which accompanies grief is entirely refer- 
able to the pharyngeal branches of the glosso- 
pharyngeal and vagi nerves, which come from 
the olivary columns. The flow of tears which 
the sudden occurrence of joy or sorrow is apt 
to induce may be attributed to the influence of 
the fifth nerve, which is also implanted in the 
olivary columns, upon the lachrymal gland ; or 
of the fourth nerve, which anastomoses with 
the lachrymal branch of the fifth. The more 


_ ™ It may be urged against this conjecture respect- 
ing the functions of the ganglia of the spinal nerves 
and the fifth, that the analogy between these bodies 
and the quadrigeminal tubercles is incomplete, in- 
asmuch as the optic nerves are probably implanted 
in the latter, but the nerves of touch merely pass 
through the former, But, in truth, we know so 
little of the positive relation of the nerves in ques- 
ion to the ganglia, that no argument, either for or 
against the above view, can rest upon such imper- 
fect information. 


722P 


violent expressions of grief, sobbing, crying, 
denote an excited state of the whole centre of 
emotion, involving all the nerves which have 
connection with it, the portio dura, the fifth, 
the vagus, and glosso-pharyngeal; and even 
the respiratory nerves, which take their origin 
from the spinal cord, as the phrenic, spinal 
accessory, &c. And laughter, “ holding both 
his sides,” causes an analogous excitation of 
the same parts of the central organ and of the 
same nerves. The very different effect pro- 
duced by the excitement of the same parts 
must be attributed to the different nature of 
the mental stimulus. 

As the passing thought—the change wrought 
during the exercise of the intellect—may excite 
the centre of emotion, so this latter may exert 
its influence upon the general tenor of the mind, 
and give to all our thoughts the tinge of mirth 
or sadness, of hope or despondency, as one or 
the other may prevail. We say of one man, 
that he is constitutionally morose ; ofa second, 
that he is naturally gay and mirthful; and of a 
third, that he is a nervous man, and that he is 
never likely to be otherwise. One man allows 
his feelings to hurry him on to actions which 
his intellect condemns ;_ whilst another has no 
difficulty in keeping all his feelings in entire 
subjection to his judgment. “ Of two indivi- 
duals with differently constituted minds,” re- 
marks Dr. Carpenter, “ one shall judge of 
everything through the medium of a gloomy 
morose temper, which, like a darkened glass, 
represents to his judgment the whole world in 
league to injure him; and all his determina- 
tions, being based upon this erroneous view, 
exhibit the indications of it in his actions, 
which are themselves, nevertheless, of an en- 
tirely voluntary character. On the other hand, 
a person of a cheerful, benevolent disposition, 
looks at the world around as through a Claude- 
Lorraine glass, seeing everything in its brightest 
and sunniest aspect, and, with intellectual fa- 
culties precisely similar to those of the former 
individual, he will come to opposite conclu- 
sions: because the materials which form the 
basis of his judgment are submitted to it in a 
very different form.”* Such examples abun- 
dantly illustrate the important share which the 
emotions take in the formation and develope- 
ment of character, and how all things presented 
to the mind through the senses may take their 
hue from the prevailing state of the feelings. 
Ifacertain part of the brain be associated with 
emotion, it is plain that that part must be in 
intimate connection with the seat of change in 
the operations of the intellect, in order that 
each may affect the other; that the former may 
prompt the latter, or the latter excite or hold in 
check the former. And this association of the 
emotions with a certain portion of the brain 
explains the influence of natural temperament, 
and of varying states of the physical health, 
upon the moral and intellectual condition of 
individuals. We may’ gather from it how 
necessary it is to a well-regulated mind that 
we should attend not to mental culture only, 


* Carpenter’s Physiology. 


722qQ 


bat to the vigour and health of the body also ; 
that to ensure the fall developement of the 
mens sana we must secure the possession of the 
corpus sanum. 
ertain diseases are evidently associated 

with disturbed or excited states of emotion. 
In such cases, the nerves most affected are 
those connected with the mesocephale and 
medulla oblongata, denoting an excited state of 
these portions of the encephalon. Of these 
diseases the most remarkable are Aysteria and 
chorea; both of which may be induced either 
by a cause acting primarily upon the mind} or 
by functional disturbance of the body, as de- 
ranged assimilation, in persons of a certain 
character of constitution. In hysteria, the 
globus, the tendency to cry or laugh, the dis- 
turbed breathing, the variously deranged state 
of the respiratory acts, all denote affection of 
most, if not all, the nerves coming from these 
segments. In chorea the frequent movements 
of the face and eyes, the peculiar and very 
characteristic mode of protruding the tongue, 
the impaired power of articulation, are depen- 
dent on an aliered state of that part in which 
the portio dura of the seventh pair, the third, 
fourth, and sixth, and the ninth nerves are 
implanted. In both diseases the principal 
central disturbance is in the mesocephale; and 
this may be caused either by the direct in- 
fluence of the mind upon it, or by the propa- 
gation of a state of irritation to it from some 
part of the periphery.: Chorea, even of the 
most violent and general kind, is very commonly 
produced by sudden fright; and it is well 
known how frequently mental anxiety or ex- 
citement developes the paroxysm of hysteria. 

There is no part of the cerebro-spinal centre 
which appears to exercise such extensive sway 
over the movements and sensations of the body 
as this portion, the mesocephale, which may be 
regarded as the centre of emotional actions. 
Its influence extends upwards to the cerebral 
convolutions—bhack s to the cerebellum— 
downwards to all the nerves of sensation and 
motion. Through its connection with the 
terior horns of the spinal grey matter, it can 
excite the sensitive as well as the motor nerves 
of the trank. Hence it is not to be wondered 
at that a highly disturbed state of this centre is 
capable of deranging all the sensitive as well as 
motor phenomena of the body and even the 
intellect. Hence we may explain the extra- 
ordinary movements in hydrophobia and ge- 
neral chorea, in both of which diseases this 

art of the nervous centre is doubtless affected. 

t has often been remarked how much more 
powerful are the voluntary actions when 
prompted by some strong emotion, than when 
excited only b hr effort * a will. Rage, 
or despair, is able to magnify the power of the 
fined to an incalculable aren” This may 
be due to the increased stimulus derived from 
the influence of the centre of emotion being 
conjoined with that of the centre of volition. 

The intimate connection of the olivary co- 
lumns with the grey matter of the cord, and 
through that with all the roots of the spinal 
nerves, illustrates the power of emotional 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


changes upon the organic . How 

often does the state of the feelings influence 

the quantity and quality of the secretions, no 

doubt through the power of the nerves over — 

the capillary circulation! Blushing is pro- — 

duced through an affection of the mind, <a ; 
? 


primarily on the centre of emotion. 
through it on the nerves, which are distributed 
to the capillary vessels of the skin of the face. | 
The sexual passion must be ranked 
the mental emotions. Like them, it may be 
excited and ministered to by a certain line of 
thought, or by particular physical states of the — 
sexual organs. It therefore, more 
-_ 4 refer this emotion to the common cei 
of all, than to a special oi —aecording: J 
Gall’s theory; and Te euty bb VOR that: 
great developement of this part of the brain is” 
just as likely to produce great width of cs 
in the occipital region as a large cerebellum. 
Of the functions of the cerebellum.—Allana- 
tomists are in admitting, in the whole. 
vertebrate series, (the amphioxus, pee X- 
cepted,*) the existence of a portion of n- 
cephalon which is analogous to the cerebellum. 
This extensive existence of such an organ indi- 
cates its great physiological importance, as’ 
special clament ‘of #6 @ on. The 
rebellum exhibits much di both as 1 
gards size and complexity of strueture in 
different classes; and although, upon t 
whole, it increases in its devel ‘in th 
same ratio as the hemispheric lobes, it exbibi 
no constant relation of size to those parts. 


commissural connection with that segment 
the encephalou is not extensive,—have exci 
the interest and curiosity of speculative phi 
logists; and, accordingly, we no | 
respecting which a greater variety D 
have been suggested, most of them being 
tirely devoid of foundation. The experim 
of Flourens have, however, thrown more 
on this subject than any previous obse 
and his hypothesis appears nearer the truth 
any which has been proposed. ol 
The facility with which the cerebell 
be removed or injured, especially in | 
without involving the other of 
brain, renders it a much more favoura 
ject for direct experiment than them, A 
ful operator may remove the greater part ¢ 
whole of the cerebellum without inflict 
injury on the hemispheres or other f 
Flourens removed the cerebellum ff 
geons by successive slices. During the 
of the superficial layers there appeared” 
slight feebleness and want of harmony it 
movements, without any ion 0 
On reaching the middle layers an 
versal agitation was manifested, 
sign of couvulsion: the animal performed 
and ill-regulated movements; it could I 
* The observations of Quatrefages rer 
doubtful that even the amphioxus can be re 
as forming an exception. Ann. des Se. 


aa 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


see. After the removal of the deepest layers, 
the animal lost completely the power of stand- 
ing, walking, leaping, or flying. The power 
had been injured by the previous mutilations, 
but now it was completely gone. When placed 
upon his back, he was unable to rise. He did 
not, however, remain quiet and motionless, as 
pigeons deprived of the cerebral hemispheres 
do; but evinced an incessant restlessness, and 
an inability to accomplish any regular or defi- 
nite movement. He could see the instrument 
raised to threaten him with a blow, and would 
make a thousand contortions to avoid it, but 
did not escape. Volition and sensation re- 
mained; the power .of executing movements 
remained; but that of coordinating those move- 
ments into regular and combined actions was lost. 

Animals deprived of the cerebellum are in a 
condition very similar to that of a drunken man, 
so far as relates to their power of locomotion. 
They are unable to produce that combination 
of action in different sets of muscles which is 
necessary to enable them to assume or main- 
tain any attitudes. They cannot stand still for 
a moment; and, in attempting to walk, their 
gait is unsteady, they totter from side to side, 
and their progress is interrupted by frequent 
falls. The fruitless attempts which they make 
to stand or walk are sufficient proof that a cer- 
tain degree of intelligence remains, and that 
voluntary power continues to be enjoyed. 

Rolando had, previously to Flourens, ob- 
served effects of a similar nature consequent 
~ mutilation of the cerebellum. In none 

his experiments was sensibility affected. 
The animal could see, but was unable to exe- 
cute any of the movements necessary for loco- 
motion. ; 

Flourens’ experiments have been confirmed 
by those of Hertwig in every particular, and 
they have been lately repeated with similar re- 
sults by Budge and by Longet. The removal of 
i of the cerebellum appears capable of pro- 
ducing the same vertiginous affection which 
has been already noticed in the case of deep 
injuries to the mesocephale. After the well- 
known experiments of Magendie, of dividing 
either crus cerebelli, the animal was seen to 
roll over on its long axis towards the side on 
which the injury was inflicted. 

The effects of injuries to the cerebellum, ac- 
cording to the reports of the experimenters 
above referred to, contrast in a very striking 
manner with those of the much more severe 
operation of removing the cerebral hemispheres. 
“ Take two pigeons,” says M. Longet; “ from 
one remove completely the cerebral lobes, and 
from the other only half the cerebellum ; the 
next day, the first will be firm upon his feet, 
the second will exhibit the unsteady and un- 
certain gait of drunkenness.” 

Experiment, then, appears strikingly to fa- 
vour the conclusion which Flourens has drawn, 
namely, that the cerebellum possesses the power 
of coordinating the voluntary movements which 
originate in other parts of the cerebro-spinal 
centre, whether these movements have reference 
to locomotion or to other objects. 

That this power is mental, i. e. dependent 
on a mental operation for its excitation and ex- 


722n 


ercise, is rendered probable from the experience 
of our own sensations, and from the fact that 
the perfection of it requires practice. The vo- 
luntary movements of a new-born infant, al- 
though perfectly controllable by the will, are 
far from being coordinate: they are, on the 
contrary, remarkable for their vagueness and 
want of definition. Yet all the parts of the 
cerebro-spinal centre are well developed, except 
the cerebellum and the convolutions of the ce- 
rebrum. Now, the power of coordination im- 
proves earlier and more rapidly than the intel- 
lectual faculties; and we find, in accordance 
with Flourens’ theory, that the cerebellum 
reaches its perfect developement of form and 
structure at a much earlier period than the 
hemispheres of the cerebrum. 

It may be stated as favourable to this view of 
the mental nature of the power by which vo- 
luntary movements are coordinated, that, in 
the first moments of life, provision is made for 
the perfect performance of all those acts which 
are of the physical kind. Thus, respiration 
and deglutition are as perfect in the new-born 
infant as in the full-grown man; and the exci- 
tability of the nervous centres to physical im- 
pressions is much greater at the early age, 
partly perhaps in consequence of the little 
mterference which is received at that period 
from the will. 

That the cerebellum is an organ favourably 
disposed for regulating and coordinating all 
the voluntary movements of the frame is very 
apparent from anatomical facts. No other 
part of the encephalon has such extensive 
connections with the cerebro-spinal axis. It is 
connected slightly indeed with the hemispheres 
of the brain, by the processus cerebelli ad 
testes, but most extensively with the mesoce- 
phale, the medulla oblongata, and the spinal 
cord. Now it is not unworthy of notice that 
its connection with the brain proper is more 
immediately with that part, which may be re- 
garded as the centre of sensation; namely, with 
the optic thalami. This connection of the 
cerebellum with the centre of sensation may 
probably have for its object to bring the mus- 
cular sense to bear upon the coordination of 
movements, in which the individual experience 
of every one shows that that sense must mate- 
rially assist. 

The cerebellum is brought into union with 
each segment of the great nervous centre upon 
which all the movements and sensations of the 
body depend; through the restiform bodies it 
is connected with the medulla oblongata and 
the spinal cord; by the fibres of the pons 
with the mesocephale, and thus with the ante- 
rior pyramids and corpora striata; and through 
the processus e cerebello ad testes with the 
optic thalami. What can be the object of 
these extensive connections? It would be 
difficult to conceive any function for which so 
elaborate a provision would be more necessary, 
than that of regulating and coordinating the 
infinitely complex movements which the mus- 
cular system is capable of effecting; more 
especially when it seems highly probable that 
the antero-lateral columns of the cord, and the 
anterior pyramids and olivary columns supply 


722s 


all the anatomical conditions necessary for 
the developement of acts of sensation and 
volition. 
~ It thus appears that Flourens’ views re- 
specting the office of the cerebellum derive 
considerable support both from experiment and 
from anatomy. When we come to collect the 
evidence on this subject which has been fur- 
nished by the effects of disease, we obtain very 
little information of a satisfactory kind. A 
superficial lesion of either cerebellar hemi- 
sphere or of the median lobe does not cause 
paralysis, but may produce delirium or ¢on- 
vulsions, as a superficial lesion of either ce- 
rebral hemisphere may; but a deep-seated 
Jesion of the cerebellum involving the central 
white substance which is continued from the 
crus cerebelli causes hemiplegia on the oppo- 
site side. This similarity between the effects 
of cerebellar and of cerebral disease is a re- 
markable and highly interesting fact, but one 
which pete ii increases the difficulty of 
obtaining from pathological phenomena any 
contribution to the solution of Bg ketal 
questions. It may be explained thus:—the 
transverse fibres of the pons passing through the 
mesocephale would propagate to this segment 
the morbid influence of any deep-seated lesion 
of the cerebellum, and thus affect the adjacent 
ar which again would affect the opposite 
alf of the body just as if the morbid influence 
originated in the cerebral hemisphere. It is, 
then, this secondary affection of either pyra- 
midal body which obscures the proper signs 
referable to cerebellar lesion. 

A few cases, however, have been put on re- 
cord, in which a tottering gait, like that of a 
drunken man, and a defective power of co- 
ordination existed in connection with a diseased 
state of cerebellum. A striking instance of 
this occurred under my own observation: a 
young surgeon, who had recently received an 
appointment in the medical service of the 
army, was in attendance in the military hos- 
pitals at Chatham, preparatory to his nomina- 
tion to a regiment. It was observed that as 
he walked he staggered to so great a degree 
that he was suspected of drinking to excess, 
and was put under arrest on this account. 
It was soon, however, found that he was suffer- 
ing under symptoms of diseased brain, and 
he was sent up to town and placed under my 
care. I found that his ‘ei symptom was 
extreme difficulty in the coordination of his 
movements, accompanied by a sense of gid- 
diness in the head. He could neither stand 
nor walk, yet there was no distinct paralysis, 
for while he was in the recumbent posture he 
could move about his limbs freely. After a 
time he became amaurotic and comatose. The 
post-mortem examination revealed softening of 
the left crus cerebri and a patch of yellow soft- 
ening on the corresponding restiform body: 
there was in addition a recent deposit of lymph 
at the base of the brain around the optic com- 
missure. 

I must now notice two other hypotheses as 
to the office of the cerebellum ; the first is that 
of Foville; the second that of Gall. Foville 


PLYSIOLOGY OF THE NERVOUS SYSTEM. 


supposed that the cerebellum is the centre of 
sensation, “the focus of sensibility.” The 
objections which appear fatal to this hypothesis 
are derived from anatomy and from patholo- 
gical observation. The cerebellum wants that 
general connection with sentient nerves, (direct 
as well as indirect,) which might be oe 

if it performed the office in question. Not one 

of the nerves of pure sense has any connection 
with it. Moreover the diseased states of cere- 
bellum do not give rise to any privation of 
sensibility such as might be expected where 
the centre of sensation was the part involved. 

The most celebrated view of the office of the 
cerebellum is that put forward by the distin- 
guished Gall. He supposed. that the instinet 
of propagation has its seat in this organ, and 
therefore referred to it as the source of all 
sexual and generative impulses. R 

Gall’s view rests on two assumptions ; first, 
that the instinct of generation or of uc- 
tion is “ the most indispensable and most pow- 
erful of all the instincts ;” and, secondly, that 
great width of the occipital region of the skull — 
and thickness of the back of the neck indicate 
great developement of the cerebellum. Be 

It is by reason of the assumed 
importance of the generative instinct that 
large a portion of the encephalic’ mass (an 
eighth or ninth part of the whole) has been 
assigned by Gall to exercise an exclusive in- 
fluence over it. ~ 

This first position taken by Gall seems to me 
untenable. Can we separate the sexual instinet 
from the emotions, from those especially 
are clearly instinctive in their nature? La 
prehend not. The same part of the bra 
would probably exercise its influence upon 
the emotional actions. But even if the sexu: 
instinct were separable from the other instir 
it seems very questionable whether it is of th 
paramount importance as to need a separ 
organ of great magnitude, of complex structt 
and of extensive connections with the rest « 
the cerebro-spinal centre. If we 
with the instinct of self-preservation, as 
fested in providing either for the wants of 
body or for defence against assault, it certai 
cannot be admitted to have a superior infl 
to this the most pressing of all. Yet, eve 
this instinct, a separate seat has not be 
assigned in the brain.* ‘" 

The second position which Gall 


iC 
owl 


* This argument was used, nearl 
bis, in Mr. Bowman’s and my Ph 
discussing this subject. It and other objec 
to Gall’s doctrine, which we made, have 
criticised by Mr. Noble, of Manchester, 
zealous phrenologist, who, like many of 
school, is impatient of the slowness of b 
of those who do not completely embrace the opit 
which he advocates. Mr. Noble seems to 1 
that the existence of a surmise of Spurzhi 
of a single recorded observation of Dr. A. Co 
which led him to suggest that a certain large et 
lation, seen by him in the brain of a lady wht 
great fear of death, who evin “* perpt 
anxiety about her own death,” should be asst 
as the seat of a faculty to be called “ love of | 
and some observations of Dr, Vimont, which Mr 
ble does not value so much as the single obse 


o- 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


and which is certainly necessary to the validity 
of some of the premises upon which his doc- 
trine rests, is, I think, likewise open to strong 
objection. I cannot understand that great 
width of the occipital region and thickness of 
the back of the neck should necessarily indi- 
cate a great developement of the cerebellum. 
I do not mean to assert that a large cerebellum 
would not give rise to a large occipital region, 
but I do assert that great developement of the 
mesocephale may give rise to the very same 
external indications. This latter segment of the 
encephalon is of considerable size, and, as I have 
shown in a former part of this article, of com- 
plex anatomical structure, and contains all the 
elements of a distinct centre, while it possesses 
extensive connections with the cerebral hemi- 
spheres, the cerebellum, and the medulla ob- 
longata. The largest portion of it, however, is 
independent of the cerebellum, and it is this 
portion which contains the greatest abundance 
of vesicular matter, and which has most dis- 
tinctly the characters of a separate centre of 
nervous influence. Now the position of the 
mesochephale, in front of and between the 
hemispheres of the cerebellum, is such that a 
great developement of it would push the hemi- 
spheres to each side, and thus, notwithstanding 
a small size of the hemispheres themselves, the 
occipital region would become expanded. 

The great and pre-eminent size of the cere- 
bellum in the human subject would warrant 
the belief that the sexual instinct in man far 
exceeded that of other animals, if Gall’s doc- 
trine» were correct. Yet this seems by no 
means to be the case; for, although in man this 
instinct is more frequently in operation, it 
cannot be said to influence the whole system 
to the same extent as in many of the inferior 
animals. Surely this instinct is not more pow- 
erful in man than in the feline class, both male 
and female ;—the common cat, for instance, 
in which the lateral lobes of the cerebellum 
are very imperfectly developed! There are 
other animals, likewise, peculiarly distinguished 
by the strength of this instinct and the re- 
markable extent to which it influences their 
entire functions. I have already referred to 
the extraordinary state of polar tension to which 
the spinal cord of the male frog, or a portion 
of it, is liable during the state of sexual ex- 
citement. Yet in this animal the cerebellum 
is very small; nor does it at this period acquire 


of Dr. Combe, justify him in charging us with ig- 
norance in making this assertion. Mr. Noble like- 
‘wise dignifies our argument with the title of “« non- 
sense.” Iam content to repeat the argument and 
to leave it to persons of calmer judgment to decide 
whether it is of sufficient weight. Mr. Noble has 
been so courteous and so complimentary in his re- 
marks generally, that I cannot allow myself to be- 
lieve that he intended offence by the use of this term. 
IT hope, however, that he will excuse me for ob- 
Serving that it is much to be regretted that the ad- 
‘vocates of particular views should allow their zeal 
80 far to outrun their judgment as to lead them, in 
the sober seriousness of print, to make use of 
terms which they would hardly venture upon in the 
less premeditated colloquial argument,—See Noble 
on the Brain, p. 142. 


722T 


any increase of size; and, moreover, there is 
no appreciable difference between the cerebel- 
lum of the male frog and that of the female, 
which exhibits no indication of increased ex- 
citement at this period. In fishes the instinct 
is in all probability strong; and the generative 
impulse, unaided as it is by sexual commerce, 
would seem to be dependent, more than in 
cases where copulation occurs, on the change 
which may take place in the nervous centre in 
accordance with the manifestation of that in- 
stinct; yet the cerebellum is by no means large 
in these animals. Dr. Carpenter refers to the 
kangaroo as affording a good instance of dis-= 
proportionate developement of the cerebellum 
to the generative instinct. He says, “ a friend 
who kept some kangaroos in his garden, in- 
formed the author that they were the most 
salacious animals he ever saw, yet their cere- 
bellum is one of the smallest to be found in the 
class (Mammalia). Every one knows, again, 
the salacity of monkeys; there are many which 
are excited to violent demonstrations, by the 
sight even of a human female; and there are 
few which do not practise masturbation when 
kept in solitary confinement; yet in them the 
cerebellum is much smaller than in man, in 
whom the sexual impulse is much less violent.” 

According to Gall and most of his followers 
mutilation of the genital organs or their decay 
in the advance of age is attended by marked 
effects on the cerebellum. If one testicle be 
destroyed, a distinct diminution, according to 
Gall, takes place subsequently in the cere- 
bellar hemisphere of the opposite side. The 
kind of evidence upon which phrenologists 
rest their views of this matter will appear from 
the following specimens: 1. Dr. Gall relates 
that at Vienna he was consulted by two officers 
who had become impotent in consequence of 
blows from fire-arms, which had grazed the 
napes of theirnecks. 2. “ Baron Larrey,” says 
Gall, “sent to me a soldier who, in undergoing 
an operation for hernia, had lost the right tes- 
ticle. Several years afterwards his right eye 
became weak. He began to squint with the 
diseased ‘eye, and could scarcely any longer 
distinguish objects with this eye. I examin- 
ed the nape of his neck, in presence of the 
two physicians who had brought him, and 
I found the occipital swelling of the left side 
much less prominent than that of the right side. 
The difference was so perceptible that the two 
physicians were struck with it at first sight.” 
3. Baron Larrey’s cases:—a. An artilleryman 
received a wound from a musket-ball, which 
traversed from side to side the insertions of 
the extensor muscles of the head, grazing and 
dividing the two inferior occipital swellings 
which correspond to the hemispheres of the 
cerebellum. This individual experienced a 
diminution in the size of his testicles, which fell 
into a state of atrophy. 6. A light horseman, 
of very amorous disposition, received a sword- 
cut, which divided the skin and all the convex 
portion of the occipital bone through to the 
dura mater. The right lobe of the cerebellum 
was seen through the opening of the dura 
mater, and the slightest pressure upon this organ 


722u 


caused giddiness, fainting, and convulsive 
movements. The patient loses sight and hear- 
ing of the right side, experiences acute pain 
in the course of the dorsal spine, and tingling 
in the testes, which in fifteen days were reduced 
to the size of a bean. The patient dies of 
tetanus, with loss of the functions of sight, 
hearing, and generation.* On dissection there 
was great loss of substance at the occiput, the 
medulla ata and upper part of the spinal 
cord were of dull white, of firmer consistence, 
and reduced in size one-fourth. The nerves 
arising from these parts were likewise wasted. 
c. A chasseur received a sabre cut, which di- 
vided the skin and external protuberance of the 
occipital bone, and the extensor muscles of the 
head as low down as the sixth vertebra. This 
man gets well, but Larrey states that he de- 
clares “ that he has been deprived of his gene- 
rative powers ever since that wound.” 4. Gall 
caused rabbits to be castrated, some on the 
right side and others on the left. Having had 
them killed six or eight months afterwards, he 
finds diminution of the cerebellar lobe eo 
site the removed testicle, and flattening of the 
corresponding occipital swelling. Vimont, 
however, found no diminution of the o ite 
fobe of the cerebellum im four rabbits on which 
castration had been effected on one side, and 
which had been kept eight months; but in 
four other rabbits, similarly treated, but kept 
eighteen months, a very grape diminution 
in the opposite lobe of the cerebellum was 
found.+ 

The results of mutilation of the generative 
organs, as obtained by the researches of M. 
Leuret, are far from being favourable to Gall’s 
theory. M. Leuret took the weight of the 
cerebellum both absolutely, and, as compared 
with that of the cerebrum, in ten stallions, 
twelve mares, and twenty-one geldings. The 
following table shows the results of the abso- 
lute weights, 


Average. Highest. Lowest. 
Stallions., 61 .. 65 .. 56 
Maresics 9 61" 45, | 06 ge 58 
Geldingi.g 70" <a Woes. ! Bh 


Thus the remarkable result is obtained, that 
castration tends to augment the weight of the 
cerebellum, and not to reduce it, as Gall and 
his followers atfirm. 

What is further very remarkable in these re- 
searches is that the cerebrum in geldings is on 
the average less in weight than that in stallions; 
and the fact gives great confirmation to the 
results of weighing the cerebella, rendering it 
in the highest degree improbable that the excess 
of weight in the cerebellum was accidental. 

The general expression of the facts obtained 
by Leuret is this, that in horses, mutilated as 
regards the principal generative organs, the 
cerebellum is heavier than in horses and mares 
not mutilated in the generative organ; and he 
compared twenty-one of the former with twenty- 
two of the latter. 


* I apprehend the loss of the generative function 
is not uncommon in tetanus! 
¢t Quoted from Mr. Noble on the brain. 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


these observations with those above 
Mr. Noble, a most ardent 
think most u judiced 
of ob- 


Com 


observations were conducted, and in their free+ 

dom from sources of , the researches of 

M. Leuret have greatly advantage over 

those upon which Gall rests his conclusion. — 
Yet Mr. Noble, while he itati 


those of sane men and women, a very slight 
advantage existed in favour of the former; and, — 
thirdly, because the author of the observations is 
an opponent of phrenology. ia 
I must say, however, upon this point, that, 
while 1 do not reckon myself among the op- 
ponents to phrenology, but rather among those — 
who are anxiously looking for and ane ea 
romoting a truly scientific phrenology,* I can- 
oo but regard the facts brought forward b 
M. cmerigsts of the po sdebrcaaal - 
portance, not to ected by an 
arguments as those of Mr. Noble; nor ne 
to be met at all, save by similar weighi in 
the same, or still better, in double the nw ; 
of animals. r 
The last point to be noticed with reg 
Gall’s theory of the office of the cerebe' 


i= 


um 
that it certainly derives no support from f 
logical observations. The Je cases quote 
by Gall, in which the injury in the neig 
hood of the cerebellum seemed to affect se 
instinct are far from being conclusive, for the 
might apply equally, if it were assumed th 
the seat of the instinct were in the posters 
lobes of the cerebrum, in the medulla 
longata, or in the spinal cord. Indeed Baro 
Larrey’s second case is much more favou 
to the localization of the generative im pulse 
the centre of emotions, than in the eerebellu 
For the latter organ was free from disea 
whilst the medulla oblongata was indural 
And, further, the assumed connection bety 


* The following passage from Dr, Holland’s ¥ 
able ‘* Medical Notes and Reflections ” ex; 
so well the true position of phrenology, that I 
glad to quote it as an excellent ona f 
own creed relative to this point. ‘* In the 
state of our knowledge of the brain,” ones 
land, ee ene x 
an impartial view re’ requires, 
the doctrine should e onal altogether, 
that great abatement should be made of it 
sions asasystem. To say the least, it is el 
with what Lord Bacon has called ‘an ¢ 
and peremptory reduction into acts and 
and with the adoption of various cone 
warranted by any sufficient evidence. 
subject thus obscure in all its parts, and 
actual knowledge is still limited yer 

esumptions, there is enough to justify a 

ing kept before us, as one of the ines 
which future observations may apply; not 
as they now are, by the trammels of a p 
arrangement.” P. 517. 


n~ 


er 


te: 


Koss 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


the generative instinct and the cerebellum, from 
the occasional existence of an abnormal erection 
of the penis, is not justified by the facts. This 
symptom is far from being constant in cerebellar 
disease—indeed it occurs in but a very small 
number of cases—and, as a symptom pomting 
to lesion of a particular portion of the cerebro- 
spinal axis, it is much more indicative of 
disease of the medulla oblongata or of the 
cervical portion of the spinal cord. 

Office of the cerebral convolutions—The 
great sheet of vesicular matter which forms the 
cortex of the human brain, is of such vast 
extent that it is forced to assume the convo- 
luted form in order to its being packed within 
the ordinary compass of the cranium. A little 
consideration will shew that the convoluted 
Jorm can be regarded no otherwise than as a 
convenient mode of packing, and that the 
number and depth of the convolutions are the 
best indications of the superficial extent of this 
expanse of vesicular matter. In certain cases 
a slow and gradual accumulation. of water 
within the ventricles of the brain, causing a 
corresponding enlargement ‘of the cranium, 
expands the matter of the cerebral hemispheres, 
by which the ventricles are enclosed, and the 
convolutions become unfolded. We thus ob- 
tain a distinct demonstration of the true arrange- 
ment of this part of the hemisphere, which 
must be regarded as a nervous centre, con 
sisting of a vast mass of the potential vesi- 
cular matter freely supplied with bloodvessels 
from a vascular surface on its exterior (the pia 
mater), and giving rise to an infinite multitude 
of nerve-fibres, which pass from its internal 
Surface to the corpora striata and optic thalami, 
the centres of volition and sensation. The 
name which Mr. Solly has given to this ex- 
panse of nervous matter, hemispherical gan- 
glion, is very expressive, not only of its true 

cter as a centre of nervous power, but 
likewise of the wnity of the organ on each side, 
‘consisting as it does of an uninterrupted layer 
of vesicular matter with its emerging or im- 
merging fibres, and not of a great number of 
a" organs, as the term convolutions would 
imply. 

This vesicular surface with the fibrous matter 
which connects it with the optic thalami and 
corpora striata forms by far the largest portion 
of the encephalon in the higher classes of 
animals. This fact alone ought to stamp it 
with great physiological importance. Bot, 
further, it is a well-proved fact, that the com- 
plexity of the convolutions in the animal scale 
% in the direct ratio with the advance of in- 
telligence. At the same time it must be re- 
membered that the complexity of the convo- 
lutions is in part determined by the size of the 
head and the capacity of the cranium. If, for 
example, the habits and mode of life of the 
animal require a small head and at the same 
time a certain degree of intelligence, the brain 
would exhibit a greater number and complica- 
tion of convolutions than would be found in 
an animal of corresponding intelligence, but 
which required and possessed a larger head. 
Hence neither the size nor the weight of the 


722x 


brain, whether absolute or in relation to the 
body, affords any certain criterion of the extent 
of the convoluted surface. Highly complicated 
convolutions may exist along with a brain 
both absolutely and relatively small. Thus, the 
ferret, as shown by Leuret, whose habits require 
a small head, has several well-marked convo- 
lutions on each hemisphere, and a brain no 
larger than that of the squirrel, which has no 
convolutions at all, and which wants even the 
few fissures which mark their first develope- 
ment in the rabbit, the beaver, the agouti, &c. 
And the last-named animals have the brain 
both absolutely and relatively larger than that 
of the cat, the pole-cat, the roussette, the 
unau, the sloth, and the pangolin, all of which 
possess convolutions. 

At the early periods of human life, in in- 
fancy and childhood, the convyolutions of the 
brain are very imperfectly developed, but their 
increase of size goes on simultaneously with 
the advance of mental power. If the former 
be arrested, or if some congenital fault pre- 
vent the further growth of the convolutions, 
the mental powers are of the lowest and fee- 
blest kind, but little or not at all above those 
of the brute with imperfect convolutions. In 
all idiots the brain is not only small, but its 
convoluted surface is extremely limited. 

Anatomy points to the conclusion that the 
office of the convolutions is connected with the 
functions of the mind. Perception, memory, 
the power of abstraction, judgment, imagina- 
tion, all possess, as instruments of corporeal 
action, these folds of vesicular matter. And 
it seems not improbable that the phrenological 
view which assigns to certain convolutions a 
special office connected with some particular 
faculty or faculties is true. This is strongly 
supported by the fact of a regular disposition 
of certain primary convolutions im the various 
classes of animals, so that each form of brain 
has its proper convolutions, and that in tracing 
the convolutions from the most simple to the 
most complex, indications are found of the 
persistence of the primary and fundamental 
convolutions in the midst of many secondary 
and superadded ones. 

It may be here mentioned that Gall was by 
no means the first to assign this function to the 
convolutions. Our countryman, Willis, in the 
seventeenth century, distinctly advanced this 
opinion, and conjectured that the various gy- 
rations were intended for retaining the animal 
spirits “for the various acts of imagination 
and memory” within certain limits. 

It is important to ascertain the endowments 
of the fibres which connect the vesicular sur- 
face of the convolutions to the corpora striata 
and optic thalami. They might be supposed to 
possess similar endowments to those of sensi- 
tive and motor nerves, if we adopted the views 
of those who hold that all the nerves are con- 
tinued up into the brain. This point, however, 
has been settled in the most decisive manner by 
experiments, dating as far back as the time of 
Lorry.* Mechanical injury to them excites 


* Mém. de l’Acad. des Sciences, 1760, 


722¥ 


neither pain nor disturbance of motion. Even 
the electric current ed through them pro- 
duces no sensible idivet: (Matteucci). We are 
led, therefore, to the conclusion that these fibres 
have endowments quite distinct from those of 
sensitive and motor nerves, (a fact, by the 
way, quite irreconcileable with the doctrine 
which makes the brain the concourse of these 
fibres,) and that they are internuncial between 
parts which are beyond the immediate influence 
of the ordinary physical agents, and which 
have no direct connection with muscular organs. 
The proper stimulant of these fibres is the 
mind on the one hand, or the nutrient changes 
in the brain on the other. But, under the 
influence of a continued morbid irritation, they 
may excite either pain or convulsion, or both, 
as is frequently the case in disease of the 
cerebral meninges ; this, however, is effected 
through a change produced in the corpora 
striata and optic thalami, and propagated thence 
to the origins of motor and sensitive nerves, or 
through irritation of the nerves of the meninges, 
which affect the centres of motion and sensa- 
tion, just as the nerves of other parts do. 

The experiments of Flourens and of Hertwig 
show that removal of the cerebral hemispheres 
produces a state of stupor, and, to use Flourens’ 
expression, as it were condemns the animal to 
perpetual sleep, but deprives it even of the fa- 
culty of dreaming. There is, however, no para- 
lytic state produced by these mutilations. It is 
evident, then, that the effect of these experi- 
ments is psychical, and it may be adduced as 
confirmatory of the view which associates the 
functions of the cerebral convolutions with the 
operations of the mind. 

Pathological anatomy affords interesting con- 
firmation to this view. Inflammation of the 
membranes of the brain, more especially of 
the pia mater, is invariably attended by dis- 
turbance of the mental faculties, as manifested 
by more or less delirium. It appears that 
any material alteration of the circulation in 
the grey matter of the convolutions is capa- 
ble of giving rise to delirium; in the in- 
stance above quoted, the circulation in this 
part is affected in consequence of the inflam- 
mation of the pia mater, the bloodvessels of 
the one being distinctly continuous with those 
of the other; but in other instances of violent 
delirium, such, for example, as delirium tremens, 
the vesicular matter of the convolutions is found 
after death to be bloodless, as if its wonted 
supply of blood had been cut off or abstracted 
from it. We find this state in the delirium 
after great operations, after puerperal floodings, 
in the delirium of rheumatic fever, and in that 
of gout, and likewise in that which occurs in 
the more advanced stages of fever. 

We learn from the most trustworthy reports 
of the dissections of the brains of lunatics that 
there is invariably found more or less disease of 
the vesicular surface and of the pia mater and 
arachnoid in connection with it, denoted by 
opacity and thickening of the latter with altered 
colour or consistence of the former. 

From these premises it may be laid down as 
a just conclusion that the convolutions of the 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


1 
| 


brain, in other words, that vast sheet of vesicular 
matter which crowns the convoluted surface of | 
the hemispheres, constitute the centre of intel- 
lectual action, as distinguished from the centre 
of volition and the centre of sensation (corpora 
striata and — thalami). It is essential to the — 
perfection of cerebral action that these centres 
should be connected, and that the centre of in- 
tellectual action should be capable of exciting 
or of being excited by the centres of volition — 
and sensation. This connection and mutual — 
influence is effected through the innumerable — 
fibres which pass from the one to the other. 
To determine the precise connection which 
exists between the mind and the brain is beyond — 
the reach of our means of observation and = 
periment. All we are justified in affirming is 
that the mental acts are associated with this por- — 
tion of the brain, which I would call the centre 
of intellectual actions ; and that the integrity 
of this is 0 to the perfect exer-— 
cise of the mind ; that, in the language of Cu- 
vier, this centre is the sole receptacle in which 
the various sensations may be as it were con- 
summated, and where all sensations take a 
distinct form and leave lasting traces of their 
impression, serving as a seat to memory, @ 
adele by mnesind a which the animal is fur- 
nished with materials for his judgment. = 
The actions of the convoluted surface of thi 
brain, and of the fibres connected with it, be’ 
altogether to the class of mental nervous acti 
that is, they either excite or are excited b 
mental change. The physical changes in the 
parts give rise to a corresponding manifestatic 
of ideas, and every thought is accompanied ‘ 
a change in this centre. Modifications in 
nutrition, or interruptions to it, uce ¢ 
responding effects on the mind. increas 
activity of nutrient change causes a rapid d 
velopement of ideas, which, being generally 
controllable by the will, and therefore 
rected, assumes the form of raving or deliri 
The shock of concussion so far check 
organic changes of the vesicular surface, ¢ 
perhaps also of the fibrous matter, as to i 
rupt for a time those conjoint actions 
mind and the brain which are necessary 
perfect consciousness. The condensation 
the substance of the hemispheres, whic 
produced by an apoplectic clot, or by 
effusion of some other foreign matter, prey 
a similar consent of action, and thus gives 
to the phenomena of coma, a state in whic 
mental nervous actions are destroyed or 
pended, and which, if continued long ent 
will annihilate the physical nervous ac 
likewise. i 
It will be observed that, in this descrip 
the workings of the mind are not view 
mere functions of the brain. The term: 
expresses the mode of action of the Sou 
entity which both reason and revelation é 
us is essentially different from the Body,* I 
incorruptible and indestructible, in t 
in which we suppose that both corruption a 
destruction may affect material things. — 


* Ens incorporee prosapia, Prochaska. . 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


will, to feel, to perceive, to think, are so many 
states of Soul or acts of Mind. 

Mind is, then, the mode of action of the Soul, 
as Life is the mode of action of the Body. The 
latter we distinguish as material, and the phe- 
nomena of life as specially belonging to orga- 
nized matter; the former we denominate imma- 
terial, to mark its essential difference from the 
body, admitting, however, that it exists in a 
mysterious union with the nervous system of 
the body in a manner so intimate that in a 
state of health the smallest change in either 
readily affects the other. 

Such is the doctrine which seems most con- 


sonant with reason and experience, and, above 


all, with revelation. But there are those who 


‘maintain that not only are certain states of 


mind preceded by certain states of body, but 
that all our ideas, our sensations, our volitions, 
are the result of, and as it were generated by, 
certain organic changes. 

This view, which is that of materialism, 
while it necessarily tends to destroy our hopes 
of a future life, by denying even the very ex- 
istence of aSoul, and not its immortality only, 
is opposed by the consciousness which we 


“possess of a power inherent in the mind to 


direct and control the actions of the brain, and 
by the knowledge that the mind will rise supe- 
rior to the fatigue and exhaustion of the body, 


_and will survive, unimpaired, even its wreck. 


There are, moreover, some excellent persons, 


‘who, while they admit the existence of an 


immortal soul distinct from the mind, never- 
theless regard the phenomena of the mind 
as functions of the brain, resulting from the 
changes which are continually taking place in 
that organ. The mind, they say, is “ the ag- 
gregate of the functions of the brain,” and is 


entirely dependent on its integrity. But the 
_ adoption of these views involves the advocate 


of them in as great a difficulty as that from 
which he flatters himself he has escaped. If 
there be a soul, what is its relation to the 
mind? What is its office? Is it simply asso- 
ciated with the body without being affected by 
it or affecting it in turn? Surely it must have 
some office, and if it be admitted to be capable 
of exercising any influence, either on the mind 
or on the body, then the whole matter in dis- 
pute vanishes. If the soul can affect the mind, 
it must do so according to these views through 
the body; and, if this be admitted, why make a 
difficulty about admitting that the will, as a 
faculty of the soul, can influence some portion 
of the brain? : 

On the other hand, if it be denied that the 
soul can affect either mind or body, then must 
we come to the conclusion that the soul is 
inert, or else an entity totally distinct from the 

y, a looker-on as it were, which watches 
the corporeal functions and the mental pheno- 
mena, but takes no part in them, and has no 
true sympathy with them.* 


_ ™ I beg the reader to peruse with attention the 
following passage from Bishop Butler:—™ Human 
creatures,” says this profound thinker, ‘* exist at 
present in two states of life and perception, greatly 


7222 


An acute and ingenious writer, Dr. Wigan, 
who has advocated with great zeal and ability 
the docrine of the duality of the mind, seems 
to think that the progress of mental philosophy 
and of cerebral physiology is much hindered 
by the views of those who advocate the spiritual 


different from each other; each of which has its 
own peculiar laws, and its own peculiar enjoyments 
and sufferings. When any of our senses are affected 
or appetites gratified with the objects of them, we 
may be said to exist or live in a state of sensation. 
When none of our senses are affected or appetites 
gratified, and yet we perceive and reason and act, 
we may be said to exist or live in a state of reflexion. 
Now, it is by no means certain that any thing 
which is dissolved by death is any way necessary 
to the living being in this its state of reflection, after 
ideas are gained. For though, from our present 
constitution and condition of being, our external 
organs of sense are necessary for conveying in ideas 
to our reflecting powers, as carriages, and levers, and 
scaffolds are in architecture, yet when these ideas 
are brought in, we are capable of reflecting in the 
most intense degree, and of enjoying the greatest 
pleasure and feeling the greatest pain by means of 
that reflection without any assistance from our 
senses; and without any at all, which we know of, 
from that body which shall be dissolved by death. 
It does not appear then, that the relation of this 
gross body to the reflecting being is, in any degree, 
necessary to thinking—to our intellectual enjoy- 
ments or sufferings; nor, consequently, that the 
dissolution or alienation of the former by death 
will be the destruction of those present powers 
which render us capable of this state of reflection. 
Further, there are instances of mortal diseases 
which do not at all affect our present intellectual 
powers; and this affords a presumption that those 
diseases will not destroy these present powers. 
Indeed, from the observations made above, it ap- 
pears that there is no presumption that the dissolu- 
tion of the body is the destruction of the living 
agent from their mutually affecting each other. 
And, by the same reasoning, it must appear too 
that there is no presumption that the dissolution of 
the body is the destruction of our present reflecting 
powers from their mutually affecting each other; 
but instances of their not affecting each other afford 
a presumption of the contrary. Instances of mortal 
diseases not impairing our present reflecting powers 
evidently turn our thoughts even from imagining 
such diseases to be the destruction of them. Seve- 
ral things, indeed, greatly affect all our living 
powers, and at length suspend the exercise of them 5 
as for instance drowsiness increasing till it ends 
in sound sleep; and from hence we might have 
imagined it would destroy them, till we found by 
experience the weakness of this way of judging. 
But, in the diseases now mentioned, there is not so 
much as this shadow of probability to lead us to any 
such conclusion as to the reflecting powers which 
we have at present. For, in those diseases, per- 
sons, the moment before death, appear to be in the 
highest vigour of life. hey discover apprehension, 
memory, reason, all entire ; with the utmost force 
of affection ; sense of character, of shame and ho- 
nour; and the highest mental enjoyments and suf- 
ferings, even to the last gasp; and these surel 
prove even greater vigour of life than bodily senate 
does. Now what pretence is there for thinking that 
a progressive disease when arrived to such a degree, 
I mean that degree which is mortal, will destroy 
those powers which were not impaired, which were 
not affected by it during its whole progress quite up 
to that degree? And if death by diseases of this 
kind is not the destructioh of our present reflecting 
powers, ’t will scarce be thought that death by any 
other means is.” See the admirable chapter, «* Of 
a future Life,” in Butler’s Analogy of Religion, 
natural and revealed. 


723a 


nature of the mind.* But no doubt his fears 
are unfounded ; for if we hold that a connec- 
tion subsists between soul and brain so intimate 
that every change in either affects the other 
more or less, surely the strongest inducement 
is held out for the minutest investigation of 
the organ which can exercise so wonderful an 
influence on the immortal part of our nature. 

I would, then, lay it down that the 
fanction of the brain is to generate the nervous 
foree, and that that force affects the soul and 
excites its action for the developement of mental 
phenomena. On the other hand, the action of 
the soul affects the brain, exciting it to the de- 
velopement of nervous force, and directing that 
force for the production or regulation of other 
cor phenomena. 

‘aking this view of the nature of the mind, 

and of the relation of mind and body, we may, 
with advantage, arrange the principal mental 
states into two classes, according as they are 
preceded by certain states of body, or as they 
precede and are capable of exciting certain 
States of body. 
' In the first class I would place sensation, 
and such mental states as are immediately asso- 
ciated with or produced by sensation, as the 
emotions and the i = this class I 
would likewise refer that iar power which 
is, with the highest probability, exercised by 
the cerebellum, and to which we must give the 
name of balancing or coordinating power. It is 
a power which, like the emotions and passions, 
is exercised without any previous train of 
thought or intellectual process, and seems sim- 
ply to be evolved as an immediate consequence 
of certain sensations, which are developed un- 
der the influence of impressions made upon 
the organs which are to be submntted to its 
regulation. Thus, in locomotion, the exercise 
of the muscles produces the sensation upon 
which the evolution of this mental power de- 
pends, which reacts upon the same muscles 
with an intensity proportionate to the exciting 
impulse. In the exercise of this power there is 
much analogy with the ordinary reflex acts ; but 
while the latter are purely physical in their 
nature, the former may be clearly shown to be 
mental. The proofs of this are derived, 1, from 
its being never accomplished without conscious- 
ness; 2, from its being always associated with 
volition ; 3, from the curious differences in the 
mode of its exercise in different individuals, 
according to differences of mental and physical 
constitution, one man being and precise 
in all his movements, another awkward and 
clumsy; 4, from the marked improvement 
which may be effected in it by instruction and 
dul ted tice. 

in ened oe I would place volition 
and attention. In these the mind has clear- 
ly the initiative, and is capable of inducing 
certain states of body, either to move certain 
organs (voluntary motion), or to concentrate 
one or more of the inlets of sensation upon 
some external objects (attention). The power 


* Wizan on the Duality of the Mind. Lond., 
44, 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


of abstraction, imagination, and all purely in- 
tellectual processes, are obviously associated 
with these. 

The symmetrical disposition of the parts of 
the encephalon on side of the median 

> has been recognised by all anatomists. 

his symmetry is so complete on we 
with correctness, s two brai 
Nani cad left brain, Esch are caine 
each other by transverse commissures. The 
right brain corresponds exactly with the left, 
just as much as the right eye corresponds with 
the left. This doubleness of the brain, no 
doubt, accords curiously with the double 
ness of all the organs of sense, and very pro- 
bably is rendered necessary by the existence of — 
the double set of inlets to sensation. It is” 
remarkable, however, that a symr : 
of the convolutions is not found in the hig 5 
races of mankind, and in individuals of high 
intellectual powers; and that the greater the 
mental power, the less symmetrical are the 
convolutions. In the inferior races, on ~ 
other hand, as Tiedemann has well shown, 
symmetry of the convolutions is exact. 

Upon the proved existence of two brains, as 
thus explained, Dr. Wigan, adopting the mat 
rialist view of mental phenomena, re: 
theory that the mind is dual; that we hk 
two minds; that each brain performs its 
mental functions, which are in perfect harmony. 
if the two brains harmonise in quality, structun 
and action. 

it cannot be doubted that two brains, 
symmetrical in structure, must have a t 
mount symmetry of function, if I 
allowed the expression ; and that, the: 
order to insure harmony of action b 
them, and to prevent the actions of one fi 
interfering with or neutralising those of | 
other, some such organic connection b 
them is n as that which exists betw 
the two retina, and which converts the st 
rate and im some degree dissimilar physi¢ 
impressions made on each of them into oI 
sensation. 

And as any interference with the 
conditions necessary to secure si 
with two eyes produces double vision, so 
not unreasonable to expect that an anak 
imperfection in the organie union betwee 
two brains may occasion doubleness of 
impression and action. Such acon 
Dr. Wigan has ingeniously ted, 
the clue to the explanation of enol 
as states of double consciousness, delus 
irregular volitions, and some forms of insa 
and, if fairly worked out by physiological 
chologists, may solve other obscurities 
nected with the phenomena of the 
While, therefore, I admit that = Fac 
interest and value attach to Dr. Wigan’s 
respecting the action of two brains, Tal 
prepared to infer the existence of two ™ 
from that of two brains; no more thal 
can assume a duality of our visual sem 
from the existence of two eyes. The 
cases, indeed, are strictly analogous. 1 
organic change in each retina develope: 


= 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


corresponding sensorial impression; and from 
the connections which subsist between the reti- 
ne, and still more from that between the cen- 
tres of sensation, these impressions become 
fused into one. In like manner the organie 
changes in the two brains developing nervous 
force in similar modes and proportions, each 
being capable of affecting the mind similarly, 
although perhaps not identically, are yet so 
united in their action that the double organic 
affection acts on the mind as one. But if, 
through default of the connecting media of the 
two brains, or through lesion of one, the organic 
changes in each do not harmonise with those 
in its fellow, then it is plain that two separate 
and distinct mental affections will result, and 
more or less of confusion must ensue. I can 
see no ground for inferring the existence of two 
minds from such a supposition. The confu- 
sion results from the want of simultaneous 
affection of the same mind by two distinct and 
Separate brains. If, in vision, each centre of 
Sensation affected only its own mind, or, in 
other words, de d only its own mental 
_ phenomena, as Dr. Wigan’s theory would 
_ Compel us to assume, then each mind would 
pereeive a different pective projection 
of the object presented to the eyes, and an 
elaborate and eomplex mental process would 
be required to combine the two sensorial im- 
pressions. How much simpler is the view of 
ony cess which assigns the combination of 
the brain of each physical change in the retina ; 
8o that, in truth, but one impression, different 

each of its excitant ones, reaches the 
mind. So also, in the normal intellectual ac- 
tion, the organic changes of the two brains are 
united by the various transverse commissures, 
so that but one physical stimulus affects the 
mind and excites but one train of thought. 
Not so, however, when from any defect in the 
brains themselves, or in the commissures, the 
Le bana conditions necessary for the organic 

es of the two brains cannot be fulfilled. 

Dr. Wigan’s theory is inconsistent with the 
acknowledged fact of the existence of an im- 
ae symmetry of the convolutions in per- 

§ possessing the highest order of mind. If 
the two brains always act in harmony, there 
ought to be perfect symmetry. But if we ad- 
‘mit that the mind may have the initiative, then 
it is easy to understand how one brain may be 
used more than another. 

' That a power exists of using one brain more 
than another, seems probable from the more 
uent and more perfect use of one hand ; 
and the existence of such a power implies also 
te ae of keeping one brain in suspense 
ile the other is acting, under particular cir- 
| €umstances, just as we can suspend the use of 
‘one arm or one finger or one eye, although the 
exercise of its fellow prompts greatly to its 
simultaneous action. 
| Sleep is an affection of the centre of intel- 
Tectual action, a condition rendered necessary 
by the incessant working of the mind. It is 
indicated by the cessation of all mental nervous 
actions. In deep sleep the body is given up 


ble impression to a physical union in- 


723B 


to the physical nervous actions only, without 
which the functions of breathing, circulation, 
&c., could not be carried on. Dreaming occurs 
only in imperfect sleep,—often, if not always, 
just before waking,—and serves to show how 
the organic changes of the centre of intellectual 
action, when uncontrolled, may produce the 
most rapid trains of thought, recalling events 
or impressions that have passed away, and 
which we may have thought had been forgotten. 

Coma is none of the profoundest kind, a 
paralysis, indeed, of the centre of intellectual 
action, as well as of sensation and volition. 
It occurs under states of disease, which induce 
compression of the brain, or under states of 
shock, which suspend or greatly diminish its 
natural changes, as in concussion. Or it may 
be induced by the influence of certain poisons 
of the sedative or narcotic kind, as opium and — 
belladonna, which, if given in too large a dose, 
paralyse first the centres of mental nervous ac- 
tions, and ultimately those of physical nervous 
actions. 

Somnambulism must be regarded as a state of 
intense dreaming, in which the person is 
es pags to the performance of certain acts. 

alking in one’s sleep, the curious changes of 
position which are made under the influence of 
nightmare, and even the most complex actions, 
as walking, or taking things from one place to 
another, or holding a long conversation, are all 
induced by the same state, a morbid condition 
of the centre of intellectual action, generally 
produced by deranged assimilation or great pre- 
vious disturbance of mind. The somnambulist, 
in short, is one who dreams and acts in his 
dream as if he were awake, and as if all the 
phenomena of which he takes cognizance were 
real. 

Delirium is a condition very analogous to 
dreaming. The organic changes in the centre 
of intellectual action are too rapid to be con- 
trolled by the will, or the influence of the 
centre of volition is impaired. The ravings of 
a delirious patient generally take place uncon- 
sciously, as if the centre of sensation were im- 
paired likewise. In most instances, however, 
the patient may be roused; a strong stimulus, 
as in addressmg him with a loud voice, will 
affect his centre of sensation, and he either 
controls his thoughts for a brief space, and 
directs his attention to what is going on, or the 
effect of the stimulus is to direct his ravings 
into some new channel. The incoherent and 
unconnected manner in which thought follows 
thought in the delirious state is sufficient proof 
that the centre of intellectual action requires 
the controlling power of a will for perfect 
trains of thought, as much as any particular 
set of muscles requires the same influence for 
the accomplishment of definite action. 

Delirium, indeed, may be viewed as a sub- 
jective phenomenon of the centre of intellectual 
action, just as ¢innitus awrium or ocular spectra 
are subjective phenomena of the centre of sen- 
sation. 

In analysing the fibres of the centrum ovale 
we find that a large number of them is com- 
missural, but that the greates proportion of 


723c 


them serves to establish a communication be- 
tween the centre of intellectual action, and the 
centres of volition and sensation. It is through 
this connection that the intellect and the will 
are capable of mutually affecting each other, 
the intellect prompting or exciting the will; 
and the will, on the other hand, controlling or 
applying the powers of the intellect. The 
faculty of attention, and, therefore, in a certain 
degree, that of memory, are dependent on the 
influence of the centre of volition upon the 
centre of intellectual action. Every one is sen- 
sible of a power which he possesses of fixing 
his attention on any given subject, as distinct 
as that by which he can contract any particular 
muscle. The association of the intellectual 
centre with that of sensation is necessary to en- 
sure the full perception of sensitive impressions. 
The experience of each individual can supply 
him with numberless instances in which, while 
the mind was employed upon some other ob- 
ject of interest, an impression was made upon 
some one of the organs of sense, and indistinctly 
Jelt, but not fully perceived. When the mind 
has become disengaged, the fact that an impres- 
sion had been made is recalled, without any 
ability to recollect its precise nature, And in 
many lunatics the centre of intellectual action 
is so impaired as to destroy or greatly reduce 
the power of perception, whilst there is abun- 
dant evidence to shew that the affections of the 
organs of sense make a sufficient impression on 
the centre of sensation, although in such cases 
this centre may likewise participate in the general 
hebetude. 

Perfect power of speech, that is, of expressing 
our shonchas in suitable language, depends 
upon the due relation between the centre of 
volition and that of intellectual action. The 
latter centre may have full power to frame the 
thought; but, unless it can prompt the will to 
a certain mode of sustained action, the organs 
of speech cannot be brought into play. A loss 
of the power of speech is frequently a precursor 
of more extensive derangement of sensation and 
motion. In some cases the intellect seems 
clear, but the patient is utterly unable to ex- 
press his thoughts ; and in others there is more 
or less of mental confusion. The want of con- 
sent between the centre of intellectual action 
and of volition is equally sppernt in cases of 
this description, from the inability of the patients 
to commit their thoughts to writing. 

The hemispheres of the brain, as has been 
already stated, are insensible to pain from me- 
chanical division or irritation; in wounds of 
the cranium in the human subject, pieces of the 
brain which had protruded have been removed 
without the knowledge of the patient. Never- 
theless, pain is felt in certain lesions of the 
brain, even when seated in the substance of the 
hemispheres, or in the optic thalami or corpora 
striata. This results from the morbid irritation 
extending to other parts with which nerves are 
connected, as the medulla oblongata; or in 
which nerves are distributed, as the membranes. 
The nearer a cerebral lesion is to the membranes 
or to the medulla oblongata, the more likely is 
it to excite pain. Headaches, of whatever na- 


round, and then erect when standing st 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


ture, must be referred to pe hig sites at 
their centres or at their iphery, of those — 
nerves which are y anrceen 4 "be dura mater 
or in the scalp. The branches of the fifth pair, 
of the occipital nerve, and the auricular brane 
of the cervical plexus, are those most frequently 
affected. hal 
Certain sensations are referred to the he 
ig may occur from a moray state, or maj 
roduced by changes 0 ition in 
we Such are vertigo, a say ness, Or 
of a weight in the head, a feeling of a tig 
cord round the head. These are, no dou 
truly subjective, arising from altered states 
the distribution or in the quality of the 
sent to the brain. A sensation of a»rusl 
blood to the head is often consequent ups 
excessive hemorrhage, or accompanies. d 
of extreme debility from any cause. — ; 
doubtless, owing in great part to the feeble tom 
of the arteries, resisting im ctly the flow 
blood to the head, and allowing it to i 
the nervous matter too much. It is well ku 
that, by turning round quickly on one’ 
axis, the sense of vertigo may be produced 
confused feeling in the head, and an inabi 
to maintain the balance of the body, accom 
nied by an appearance as if external 
were revolving. Ifthe eyes be kept shut, 
uneasy feeling of the head will take, plac 
no true vertigo. To obtain this feeling 
fectly, the eyes must be open, and. objects ] 
sented to them. And Purkinje has shewn 
the direction in which external objects 
to revolve is influenced by the position 
body and of the head while turning round, 
by the position of it afterwards, when the. 
rimenter has ceased to move round... I 
experimenter have kept his head in the ve 
position while moving round, and : 
when standing still, the objects appear to 
volve in the horizontal direction. “at the | 
be held with the occiput upwards while tu 


oa 


— 


objects seem to rotate in a vertical plan 
a wheel placed vertically revolving roun 
axis.* It is highly probable that these : 
tions, as well as those which arise spontane 
are due to some irregular distribution of | 
to various parts of the brain, . A sense ¢ 
diness frequently precedes fainting, and — 
tributable to the temporary deficiency im 
supply of blood to the head. _ If the hon 
age be immediately adopted, or the 
laid with the head inclined downware 
faint may be prevented. The sense of 
ness which is experienced upon rising fro 
horizontal position after illness, is doubt 
the same kind. Anemic patients expe 
this feeling of giddiness even in the hor 
position; and both it and the headach 
delirium, which accompany this state of 
lessness, may be relieved by placing the 
on an inclined plane with the head down 
The mind possesses a remarkable p 
exciting and of exalting painful sensatit 
various parts of the body. If the attentic 


* Miiller’s Physiology, by Baly, vol. i. p. 8 


PHYSIOLOGY OF THE NERVOUS SYSTEM. * 723D 


directed very strongly, and for some time, to 
any part, it may become the seat of pain, for 
which the most effective remedy is to engage 
the thoughts as much as possible on some other 
object. In many instances, where pain has 
been excited by a physical cause, there can be 
no doubt it has been continued long after the 
cessation of its exciting cause, by the attention 
of the patient having been directed to it. It is 
probable, that in such cases the perceiving parts 
of the brain (so to speak) become habituated to 
_ acertain condition of the centre of sensation, 
_ produced by the original exciting cause of the 
_ pain. And, on the other hand, pain, at first 
excited by the mind, may be rendered perma- 
nent by habit; a certain physical alteration in 
some part of the centre of sensation being in- 
“duced by the frequent repetition of the mental 
_ act in reference to a particular part of the body. 
_ Those parts of the brain which are capable 
only of mental nervous actions, that is, of ac- 
tions by which the mind is immediately affect- 
1, or which the mind can develope, have no 
rves implanted in them. Such are the con- 
‘lutions, the corpora striata, the optic thala- 
“mi, and the cerebellum. The only apparent 
exceptions to this statement are the olfactory 
and optic nerves: these nerves, however, have 
in truth no immediate connection with any of 
the parts above mentioned. The former are 
mplanted in the olfactory lobe; the latter in 
le chiasma, which is formed by the junction 
of the optic tracts, and these ought no more to 
garded as portions of the optic nerves, than 
2 olfactory lobes should be considered as 


unctions of the commissures.—The anatomy 
ae parts which we call commissures indi- 
that the name by which they have long 
known is not misapplied, inasmuch as 
seem to unite particular portions of the 
ous centres with each other. The most 
ous object of such an union would be to 
ure the harmonious cooperation of the parts 


thus united. And this view of their function 
is strengthened by the fact that the principal 
commissures bear a direct ratio in point of 
velopement to that of the parts they unite, 
i that, when these parts are absent or defec- 

_ the commissures are deficient or wholly 
iting. Thus the corpus callosum and the 
0 *P s are developed together; the fornix 
i the hippocampi, the pons Varolii and the 
erebellar hemispheres. 

Tn Stilling’s experiments on the spinal cord 
was found that when division of that organ 
was made along the median plane, a stimulus 
applied to one leg caused only reflex actions of 
hat leg, and not at all of the other side of the 
;. The power of transmitting organic 

2 from one side of the cord to the other 
was destroyed by the section of the commissure. 
_ The anatomy of the corpus callosum is fa- 
\vourable to the hypothesis that it is the bond 
of union to the convoluted surface of the hemi- 
Spheres, and that it is in all probability the 
medium by which the double organic change 
is made to correspond with the working of a 

VOL, III. 


oe 


single mind.* There is nothing in the recorded 
observations of morbid change or congenital 
defect of this part to militate against this idea; 
but as all these cases are accompanied with 
lesion or defect of some other parts, and of the 
convolutions themselves, it is impossible to 
gather from them what is the precise conse- 
quence of the defect of the corpus callosum. 
This commissure is defective in the marsupiate 
class, as was shown by Professor Owen, and 
likewise in birds; but we have yet to learn 
whether there is any psychological character in 
either of these groups of animals, which would 
give us material assistance in our search into the 
nature of its function. \ 

Direct experiments upon the corpus callo- ~ 
sum yield only negative results. Longet and 
others found that mecnanical irritation of it did 
not cause convulsions ; and Longet states that 
injury to the corpus callosum in young rabbits 
and dogs did not appear to disturb voluntary 
movements; and that when he incised this 
body in its whole length in rabbits standing, 
they continued to maintain that position, or, 
when urged on, ran; and that no convulsive 
movement whatever, nor any sign of pain, 
was manifested. Such effects are not unfa- 
vourable to the view above taken, as the con- 
nection of the centres of intellectual action is 
probably in no degree necessary to locomotion, 
which function would no doubt be as well per- 
formed without a corpus callosum as with one. 

The fibres of the fornix manifest the same 
insensibility to mechanical irritants, and their 
obvious anatomical connection with particular 
convolutions warrants but one conclusion, that 
they associate the actions of those parts. The 
connection of this commissure with the optic 
thalami and the corpora mamillaria indicates 
that it also associates these gangliform bodies 
with :the convolutions at the posterior part of 
the brain, and with the hippocampi. A marked 
relation exists between these latter convolutions 
and the fornix; they bear, indeed, especially 


* Mr. Solly and Mr. Grainger think that they 
can trace the fibres of the corpus callosum distinct] 
to the convoluted surface of the hemispheres. Wit 
the greatest respect for these able anatomists, 
I must express my doubts that all the fibres which 
they have represented can be regarded as fibres of 
the corpus callosum. See fig. 99 in Mr. Solly’s 
work on the Brain, p. 251, ed. 1847. Although 
the anatomical views of these writers correspond 
with and confirm the physiology of the organ advo- 
cated in the text, I feel that great caution should 
be used in drawing conclusions from tracing the © 
fibres of brains hardened in alcohol. By these 
means any speculative.anatomist may make prepa- 
vations to illustrate his views, as is, indeed, abun- 
dantly shown by what I must call the fanciful ana- 
tomy of the brain put forward by Foville. 

+ An excellent account is given by Mr. Paget of © 
a case in which the corpus callosum and fornix 
were imperfect, in the xxixth vol. of the Med. 
Chir. Trans., accompanied by some very judicious 
remarks upon the office of those commissures, and an 
analysis of other similar cases. Mr. Paget refers 
to some oblique fibres as existing in the corpns cal- 
losum, and serving to connect the anterior convo- 
lutions of one hemisphere with the posterior ones 


of the other. 
Q z eRERERE 


723 * 


as the posterior pillars of the fornix, a 
direct ratio to each other. 

Lallemand relates a case in which the symp- 
toms were altogether limited to mental distur- 
bance, without any affection of the sensitive or 
motor powers, and the fornix and corpus callo- 
sum were found in a state of complete softening 
without discolouration. : 

The fibres of the pons Varolii bring the 
cerebellar hemispheres into connection with 
each other, and with the vesicular matter of 
the mesocephale. Direct experiments on these 
fibres can yield no satisfactory result, because 
they are so intimately associated with the dee 
er seated of the mesocephale, and with 
the nerves of the fifth pair and others, that it is 
impossible to irritate them in the living animal 
without affecting these parts likewise. The 
anatomy of the fibres, however, sufficiently in- 
dicates that they belong properly to a double 
cerebellum : for when the cerebellum becomes 
single, as in birds, reptiles, and fishes, no such 
fibres are found in the encephalon. Morbid 
lesion of the pons is productive of very serious 
results from the number and importance of the 
parts in its neighbourhood, the pyramids, the 
medulla oblongata, the quadrigeminal tuber- 
cles ; so that the symptoms it produces cannot 
be referred solely to the injury to the commis- 
sural fibres. It is very probable, however, that 
the crossed effect of deep-seated disease of 
either hemisphere of the cerebellum may be 
accounted for by the influence of these com- 
missural fibres upon the adjacent anterior py- 
ramids, which again would influence the oppo- 
site side of the spinal cord. 


Having thus brought to a termination our 
review of the physiology of the encephalon, I 
may now sum up the principal conclusions 
which our examination of this difficult and im- 
portant subject leads to; and these are embraced 
in the following propositions. 

1. That the encephalon consists of a series 
of centres, each of which has its proper influ- 
ence in the exercise of the mental and bodily 
functions. These are the centre of intellectual 
actions, the centre of volition, the centre of 
sensation, the centre of the coordination of 
muscular movements, the centre of emotion, 
and the centre of respiration and of deglutition. 

2. That the cerebral convolutions, with the 
fibres which connect them to the corpora striata 
and ore thalami, constitute the centre of intel- 
lectual action. 

3. That the centre of volition consists prima- 
rily of the corpora striata ; the inferior layers of 
the crura cerebri, which are continuous with the 
anterior pyramids, connect these gangliform bo- 
dies with the vesicular matter of the crura (locus 
niger), with the vesicular matter of the mesoce- 
phale, medulla oblongata, and with that of the 
spinal cord (the anterior horns), all of which with 

e corpora striata probably form the dynamic 
nervous matter in the impulses of volition for 
nerves implanted in them respectively. 

4. The optic thalami, which by the extension 
of the olivary columns through the mesocephale 


PHYSIOLOGY OF THE NERVOUS SYSTEM. ‘ 


and medulla oblongata to the posterior horns — 
of the vesicular matter of the spinal cord, — 
become: continuous with those constitute — 
the centre of sensation, having implanted in it 
or connected with it less directly all the sentient 


nerves of the body. a 
The nerves of the higher senses probab 
have each special ganglia or centres, which, 


however, are connected with the general centre; 
as the olfactory lobes for smell; the retina 
corpora geniculata, or corpora adrigemina 
Sa vision ; the vesicular ee which the 
auditory nerves are implanted or the floc 
of Reil for hearing; the ganglia of the fiftl 
Gome-pharyngeel, and posterior roots of spin 
nerves for taste and touch. a 
5. The cerebellum constitutes the centre 
the coordination of muscular movements, bot 
in locomotion and in all the complicated move 
ments of the weayest m -— a 
6. The upper a i me. 
socephale, including Bre greatest pot 
tion of the corpora quadrigemina, constitu 
a special centre of actions referable to the em 
tions, among which may be reckoned sexu 
impulses. This centre connects itself with t 
medulla oblongata by the oli columns, @ 
through the same channel with the -postet 
horns of the spinal vesicular matter. = 
7. The medulla oblongata constitutes — 
centre of respiration and deglutition, but 
cannot be considered as wholly devoted 
these functions, inasmuch as it consists li 
wise of continuations of the centres of voliti 
of sensation, and of emotion.* ‘¥ 


Of the functions of the ganglions.— 
ganglions are small nervous centres we 
bound to believe, from the existence in 
a considerable quantity of vesicular matter 1 
gled with fibrous matter. And the views) 

we have already expressed respecting the 
namic character of the vesicular matter wai 
the assumption that wherever a special ace 
lation of fe form of nervous matter is f 
there must be a special source of | 
power. _<— 


* 


* I have great pleasure in referring the 1 
a very able seeny oe the physiology of the 
(which I did not see until this article was al 
in which very similar views to those expr 
the text are advocated, based on compai 
tomy. ‘The author, who in justice to himse 
not to withhold his name, is evident 
by his adhesion to the excito-motory doct 
allude to the Review of Noble on the 
Dr. Forbes’s Journal for October, 1846. 
already put forward similar opinions respe 
saben of the ery the uses of 
in the section headed ‘ An hypothesis of | 
of hea ra Niky the pate worth Ce 7 
ished in , and su uen his 
volume entitled ‘‘ The physiological m 
tive Anatomy of the Brain, &c.”’ chap, x 
same views were expressed in Mr. Bowm 
my ‘“* Physiological Anatomy and 

an,” part ii. 1845, p. 291 and p. ¢ 
that the review to which I refer co 5 
complete and masterly exposition of the wi 
of the present system of phrenology, 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


There are certain facts connected with the 
larger nervous centres-which Serer, indicate 
the correctness of this assumption. Thus, the 
existence of special accumulations of vesicular 
matter connected with them, where any parti- 
cular developement of the nervous force is 
needed, is much in favour of this view. As 
instances, we may cite the special electrical 
lobes in the electrical fishes, the ganglionic en- 
largements on the medulla oblongata of the 
gurnard, the median lobe, occupying a similar 
position to the electrical lobe above referred 
to, which is found in the remora or sucking- 
fish, and from which nerves are supplied to 
the suctorial disc on the head of that animal. 
Allied to these is the remarkable fact pointed 
out by Professor Sharpey, that the arms of the 
cuttle-fish contain ganglia which furnish nerves 
to the suckers which exist upon them in great 
number. Furthermore, the anatomy of the 
. _mervous system in some of the Mollusca, the 
_ Conchifera for example, in which a separate 
_ ganglion appears to exist for each function, for 
respiration, for locomotion, for deglutition, &c., 
is beautifully illustrative of the office of ganglia. 
_ When, however, we come to inquire into the 
Office of the particular ganglia which exist in 
Man and the Vertebrata, it is, in some instances, 
difficult to determine what object can be gained 
by a special evolution of nervous force by some 
of them. It may be inquired what is the func- 
tion performed by the ganglia on the posterior 
roots of spinal nerves, on the large root of the 
fifth, on the glosso-pharyngeal, on the vagus 
nerves? Can it have reference, as already 
_ suggested in a former part of the article, to 
. the part which these nerves perform in connec- 
_ tion with tactile sensibility or with the sense of 
_ taste, as in the fifth and glosso-pharyngeal, in 
analogy with the ganglia attached to the olfac- 
West and optic nerves, and probably with the 
auditory? Or have these ganglia anything to 
do with the nutrition of the parts among which 
‘their nerves are distributed, as Dr. M. Hall 
Suggests, in which case they would present an 
obvious analogy, and might be classed with the 
sympathetic ganglia? 
& e data which would assist in coming to 
a right conclusion upon this subject are so few, 
that, with our present knowledge, it is impos- 
Sible to form anything like a distinct hypothesis 
ing it. LI would remark with reference 
to the last-mentioned conjecture that it would 
Teceive great support if gelatinous nerve-fibres 
ere found to take their rise from the ganglia 
d to follow the course of bloodvessels. 
_ With regard to the use of the ganglia of the 
Sympathetic, the proved existence of gelatinous 

bres, peculiar to these ganglia and taking 
their rise from them, distinctly indicates that 
they are the seat of a special developement of 
hervous power, whether spontaneously arising 
in the nutrient changes of ganglia, or by the 
Teflexion of a change propagated to them by 
afferent nerves implanted in them. The va- 
rious facts which show that the sympathetic sys- 
jtem enjoys an existence and power independent 
jof the cerebro-spinal axis also confirm this view. 
But we must enquire further what is gained 


+ 


. 


723F 


by the passage of certain nerve-fibres through 
these ganglia, as is the case with most if not all 
the tubular fibres connected with them? It 
may be that in their passage through the gan- 
glia the tubular fibres acquire an arrangement 
in new sets or fascicles in a manner analogous 
to that which occurs in the plexuses. But 
this can scarcely be the only object of this 
connection. Do these fibres associate the cere- 
bro-spinal centres with the ganglionic system ? 
or do they themselves in passing again through 
vesicular matter experience some modification 
in their vital endowments? These questions 
cannot be satisfactorily solved in the present 
state of our knowledge. 


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I. Of the Nervous System in general. 

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Il. Of parts of the Nervous System. 

THE BRAIN. Malpighi, De cerebro; et de cere- 
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agni, Adversar Anatom. 1741. Albinus, De cortice 
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circa corpus callosum, &c. in vivis animalibus in- 
stituta, Gotting. 1749, and in Haller’s Dissert. Anat. 
t. vii. Ludwig, Scriptores Neurologici minores, 
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ray, Soemmering, &c. Malacarne, Encefalotomia 
nuova universale, 1780, et Nervo-encephalotomia, 
1791. Sdemmering, De basi encephali et orig. nerv. 
cranio egredientium, in Ludwig, Script. Neurol. min. 
t. ii. 1792 ; De lapillis intra gland. pineal. sitis, 
sive de acervulo cerebri, in Ludwig, t. iii.; Vom 
Hirn und Ruckenmark, 1788 ; Uber das Organ der 
Seele, 1796; Tabula baseos encephali, 1799; Qua- 
tuor hominis adulti encephalum describentes ta- 
bulas comment. illust. E. d’Alton, Berlin, 1830. 
Vicg d’Azyr, Various papers in Mém. de l’Acad, 
des Sc. 1781-1783; ‘Traité d’Anat. et de Phys. 


7236 


avec des planches; prem. partie, organes contenu 
dans la boite asseuse du crane, 1786-90; C2uvres 
completes, edit. Moreau, t. vi. Rudolphi, Com- 
ment. de ventriculis cerebri, 1796, et in Anat. Phys. 
Abhandlang: 1802. Chaussier, Exposition sommaire 
du Cerveau, 1807. Wenzel, Ch. et Jos. Prodro- 
mus einer Werkes iiber das Hirn der Menschen 
und Thieren, 1806; » De penitiori struc- 
turi cerebri hominis et brutorum, 1812. Cuvier, 
Rapport a l’Institut. sur un Mém. de Gall et 
Spurzheim, 1808. Gall et a ranierey: Sur les 
fonctions du cerveau et sur celles de chacnne de 
ses purties, 1822-25, zheim, The Anatom 

of the Brain, &c. by R. Willis, 1826. Gall, Vi- 
mont, Broussais, On the functions of the cerebellum, 
by Geo. Combe, with answers to the objections 
against phrenology urged by Roget, Rudolphi, Pri- 
chard, and Tiedemann, 1838, il’s Memoirs on 
the brain, in Reil’s Archiv. fur die Physiologie, 
and translated in Mayo’s Anat. and Phys. Comm. 
1822-23. Ribes, Exposition sommaire des re- 
cherches faites sur quelques parties du cerveau, 
Gaz. Méd. 1839. Carus, Versuch einer Darstellung 
des Nervensystems, 1814. Burdach, Vom Baue 
und Leben des Gehirns, 1819-26. Rosenthal, 
ein Beitrag sur Encephalotomie, 1815. Gordon, 
System of Human Anatomy, vol. i. 1815, and 
Observations on the structare of the Brain, com- 
prising an estimate of the claims of Drs. Gall 
and Spurzheim to discovery in the agrong, * of 
that organ, 1817. Doellinger, Beitrage zur Ent- 
wickelungsgeschichte des Menschlichen Gehirns, 
1814. Tiedemann, Anat. und Bildungsgeschichte 
des Gehirns in fuwtus des Menschen, 1816; and in 
English, by Bennett, Anat. of the Fotal Brain, 
1826, Ejusdem, Icones cerebri simiarum et quo- 
rumdam mammalium rariorum, 182]. Ejusdem, 
On the brain of the Negro compared with that of 
the European. Phil. Trans. 1836. Lauth, Ke- 
cherches sur Ja structure du cerveau et de ses an- 
nexes, in Journ. Compl. du Dict. des Sc. Méd., 
1819. Rolando, Saggio sopra la vera struttura del 
cervello e sopra le funzioni del Sistema Nervoso, 
1828. Serres, Anat. Comp. du Cerveau, 1824. 
Laurencet, Anat. Comp. du Cervean, 1826. Hert- 
wig, Experimenta quedam de effectibus lesionum 
in partibus encephali, 1826, Mayo, a series of 
engravings intended to illustrate the Structure of 
the Brain, 1827 (the best plates of the brain ex- 
tant). Langenbeck, Icones Anat. Neurologice, 1830. 
Arnold, Tabulz Anat. Fascic. 1, Icones Cerebri et 
Medullz Spinalis, 1838. Bourgery, Traité Compl. 
de l’Anat. de l’Homme (now in course of publica- 
tion). Leuret, Anat. du Systeme Nerveux consi- 
deré dans ses Rapports avec |’Intelligence, 1839, 
Wilbrand, Anat. und Phys. der Centralgebilde des 
Nervensystems, 1840. Stilling, Disquisitiones de 
structura et funct. Cerebri, 1846. Ejusd., Uber die 
textur, und fanct. der Medulla Oblong., 1843. Par- 
ta , Gaz. Méd., 1842. Foville, Traité Complet 
de l’Anat. Phys, et Pathol. du Syst. Nerveux Cere- 
bro-spinal, 1844, P. 1. H. Jones, On the struc- 
ture of the Cerebellum. Lond. Med. Gaz., 1844. 
Baillarger, Recherches sur la Structure de la 
Couche Corticale du Cerveau, Mém. de l’Acad, 
de Méd., 1840. Reid, J., M.D., On some points 
in the Anatomy of the Medulla Oblongata, Ed. 
Med. and Surg. Journ., Jan. 1844. Swan, The 
rincipal offices of the Brain and other Centres, 
1844. Todd, The dacscriptive and Physiological 
Anat. of the Brain, Spinal Cord, and Ganglions, 
1845. Solly, The Human Brain, its Structure, 
Physiology, and Diseases, 2nd ed., 1847. ‘The 
various systems of anatomy, especially Hildebrandt 
by Weber; Cruveilhier ; ing, by Valentin ; 
Mechel; Bell; Quain and Sharpey. 

THE SPINAL CORD AND ITS NERVES: Huber, De 
Medulla Spinali, 1741. Frotscher, Descript. Me- 
dul. Spinalis, ejusq. Nervorum, 1788, and in Lud- 
wig, Script. Neurol. Min., t. iv. Keuffel, Dissert. 
de Medul, Spinal., 1810, and in Reil’s Archiv, 
t. x. Nicolai, Dissert. de Medulla Svinali avium, 


PHYSIOLOGY OF THE NERVOUS SYSTEM. 


1811. Rachetti, Della Strattura, delle Funzioni, — 
et delle Malattie della Medall. Spinal., 1816. J/a- 
gendie, Examen de l’Action de quelques Vegetaux 
sur la Moélle Epiniere, 1809. Ejusd., Sur le Siege - 
& evens = a Sentiment dans la Moélle, 
ournal de Physiol. Experim., t. iii. Bellingeri, D 
Medulla Spinali et Nervis ex en prodeunt. 1a 
Rolando, Ricerche Anatom. sulla Struttura l. 
Midoll. Spinale, 1824, and in Journ. Comp. de 
Dict. des Sc. Méd. Fodera, Rich. Experiment. 
sur le Syst. Nerv., Journ. de Phys. Exp., t. 
1823, Imeil, Rech. sur la Structure, les Fonet., 
et le Rammollissement de la Moelle Epiniere, 
Journ. des Progr., 1828. Backer, C » a 
Quest. Physiol. a Facult. Medic. Acad. B 
Trajectane, anno 1828, proposit. 1830. Seuber 
Commentat. de Functionib. Radic. Anterior et Pos 
Nerv. Spinal., 1833. Ollivier, Traité de la 
Epiniere et de ses Maladies, 1837. i 
servations on the Structure and Functions 
Spinal Cord, 1837. Uber Reflexbe: 
ungen, Miiller’s Archiv, 1838. Longet, Recher 
m2 et Pathol. sur les Fonctions des Faiscez 
de la Moélle Epiniere, Arch, Gén. de Méd., 184 
—- ing and Wallach, Untersuch. uber die Texts 
des Ruckenmarks, 1842. Van Deen, ite 
Decouvertes sur la Physiologie de la Moelle I 
niere, 1841. The Treatises on Anatomy and 
Physiology already referred to. 


u 


THE INTIMATE STRUCTURE OF NERVES, G/ 
GLIA, AND OTHER NERVOUS CENTRES, d 
hoeck, Opera Omnia, t. i. and liy., 1722. 
Torre, Nuovi Osservazioni Microscopici, 
Prochaska, De Structura Nervorum, 1779. M 
Microscopical Enquiries into the Nerves and Bi 
1780. Fontana, Traité du Venin de la Vipere, 
1781. Scarpa, Annot. Acad. de Nervor. gan 
plexib., 1792. Pfeffinger, De Structura Nervor 
in Ludwig Script. Neurol. Minores,t.i. Hi 
Trans., 1821, 1824, 1825. Mascagni, Prodre 0 
Grande Anatomia, 1819. Treviranus, Beitrage 
Aufklarung des Organ. Lebens. 1836. Ehren 
Beobachtung einer bisher unibekannten | 
lenden Struktur des Sielenorgans bei Mens 
und Thieren, Mém. de l’Acad, de Berlin, 
translated in the Ed. Med. and Surg. Journal. 
mak, Miiller’s Archiv., 1836. Ejusdem, Ob: 
Anat. et Microscop. de Systematis Nervosi § 
tura, 1838, Schwann, Miiller’s Archiv., 
Mikroskop untersuch. Burdach, Beitrage 2 
croscop. Anat. der Nerven, 1837. Emi 
ungsweise der Nerven in den Muskeln, 1836. 
lentin, Uber dén Verlauf und die letzten | 
der Nerven, 1836. Purhinje, Bericht tiber di 
samml, d. Aerzte und Naturf. in Prag., 1 
senthal, De formatione granulosa in Ne 
partibus organismi animalis, 1839. Ha 
cherches microsc. sur le Systeme Ne 
Johnston, On the use of Ganglions of 
1771. Haase, De Gangliis Nervorum, 1772 
Ludwig, Script. Neurol. Min.; Volkmann wi 
der, Die Selbst standigkeit des Sympath. 
system, 1842. Kolliker, Die Sel 
Abhangigkeit des Sympathischen Ne 
1844. Henle, Algem. Anat., 1841. Bru 
Anat., 184]. Gerber, Handbuch der All 
Anat. des Menschen und der Hanssau; 
1840, and in English by Gulliver, 1842. 
Muller’s Archiv., 1844, Wagner, Neue un 
ung. uber den Ban und die Endigung 
ven, und die Struktur der Ganglien, 1% 47 
work contains a confirmation and e: 
Savi’s statement respecting the 
the phnbive tee of the —— v. 
trical organ of the torpedo. agner sh 
the meow takes place by the break 
one primitive fibre into numeroas filamen 
each of which a network is formed amon, 
ments of the electrical organ, He describes’ 
what similar arrangement of the nerves int 


(R. B. To 


ees 


by * 


NINTH PAIR OF NERVES. 


NINTIT PAIR OF NERVES (Nervi 
hypoglossi, vel gustatorii, Winslow; Lingualis, 
Vie d’Azyr; Ninth nerve of Willis; Twelfth of 
Semmering.) The ninth pair of nerves take 
their origin from the side of the medulla ob- 
longata, commencing by a variable number of 
small radicles in the fissure which separates 

_ the corpus olivare from the pyramidale. 
__ The superior of these radicles are attached 


about the centre of this fissure, and the infe- , 


rior a little below its termination; they are 
laced on a line one below the other, which 
ine describes a slight curve looking upwards 
_ and backwards, following the curved form of 
_ the olivary body. 
___The origin of this nerve is superior to that 
_ of the first cervical, to which also it lies ona 
_ plane a little anterior ; it is separated from the 
_ origins of the par vagum by the olivary body, 
_ and has lying immediately in front the corpus 
_ pyramidale and the vertebral artery. 
_ The radicles which form the origin of this 
“nerve vary in number from five to ten or 
twelve ; and if any of these radicles be ex- 
amined closely, they will be found to consist of 
fee, or more minor filaments, so that it is very 
‘difficult to say exactly by how many roots or 
Origins the ninth nerve is attached to the me- 
_dulla spinalis.* 
__ These filaments in general unite into two 
fasciculi, which pass in a direction downwards, 
forwards, and outwards to the anterior condy- 
~ loid foramen, through which the nerve escapes 
rom the cavity of the cranium. 
It rarely happens that these fasciculi unite 
in the cavity of the cranium; in general, they 
‘pass on separately until they reach the foramen, 
' where in passing through the dura mater they 
yecome united into one trunk, which is here 
invested with a strong neurilemma, derived 
from the dura mater. 
__ The ninth pair of nerves, on emerging from 
the anterior condyloid foramen, is in close re- 
-Tation to the eighth pair of nerves, the internal 
rotid artery, internal jugular vein, and with 
@ superior cervical ganglion of the sympa- 
etic. » 
Here the nerve lies external to the vagus. 
onnected to it by a dense cellular tissue, for a 
about the eighth of an inch, it passes 
hind the internal carotid artery immediately 
fore that vessel enters the carotid canal, and 
ties in front of the jugular vein; here also the 
‘herve is connected to the anterior and superior 
‘Part of the superior cervical ganglion, in a 
‘Manner to be presently described. 
__ In this situation the ninth nerve lies deep in 
neck, being covered by the origins of the 
Styloid muscles, the posterior belly of the di- 
gastric, the sterno-mastoid, the skin, platysma, 
and fascia 


"The trunk of the nerve then passes down- 
wards, outwards, and slightly forwards, escapes 
from beneath the posterior belly of the digas- 


* Quarum incertus numerus causa est, cura a 
Variis varie descripte et delineate exstent. Alii 
enim quatuor, alii octo componi fasciculis dixe- 
rar = ppteete Basi encephali et originibus 
nervorum, page 168, 

VOL. IIL. 


72t 


tric and anterior edge of the sterno-mastoid, 
becomes more superficial, is crossed in -this 
part of its course by the occipital artery, and 
at a point in the neck corresponding to the 
level of the third cervical vertebra,* and 
opposite the angle of the jaw,t the nerve 
turns forwards and upwards, forming an 
arch, the convexity of which looks downwards 
and backwards; here the nerve is covered only 
by the skin, platysma, and fascia, crosses and 
lies in front of the origin of the occipital 
artery, the internal jugular vein, external ca- 
rotid artery, and vagus nerve ; passing still in- 
wards and upwards towards the posterior edge 
of the hyoglossus muscle, the nerve is crossed 
by the tendon of the digastric, lying here su- 
perior to the lingual artery. 

Itthen passes between the mylo-hyoid and the 
hyo-glossus, and having reached the anterior edge 
of the last-named muscle, it enters and passes 
through the fibres of the genio-hyoglossus, in 
the substance of which muscle it divides into 
its terminating branches, the connections and 
distribution of which shall be examined after 
we have considered the connections of this 
nerve and the branches which it gives off and 
receives in its course through the neck. 

The ninth nerve, on escaping from the an- 
terior condyloid foramen, is connected to the 
par vagum, as was before noticed, by dense cel- 
lular tissue, but also by a nervous filament; 
further on, as the ninth nerve approaches the 
transverse process of the atlas, it receives a 
twig from the first cervical nerve, or from the 
nervous loop formed round the transverse 
process of the atlas by the communicating 
branches of the first and second cervical 
nerves.{ 

In this situation, also, the ninth is connected 
by a small nerve with the superior cervical gan- 
glion. 

Ramus cervicalis descendens, seu descendens 
noni.—The next regular branch given off by 
this nerve is immediately before it turns in front 
of the jugular vein and carotid artery, when it 
gives off a large and regular branch called cer- 
vicalis descendens,. or descendens noni. 

The point at which the ninth nerve gives off 
this branch is immediately below the angle of 
the jaw, and where it escapes from under the 
edge of the sterno-mastoid muscle. The de- 
scendens noni from this passes downwards and 
forwards to the inferior part of the neck; at 
its origin this nerve frequently receives a twig 
from the par vagum ; it passes down the neck 
in front of the jugular vein and carotid artery, 
crossing these vessels obliquely, being in this 
course superficial to the cellular investment de- 
rived from the cervical fascia which constitutes 
the sheath of these vessels. 

Omo-hyoid branch.—About the centre of the 
neck, the cervicalis descendens gives off a con- 
siderable branch, which, passing in a direction 
upwards and inwards, enters the interior belly 


* See Meckel, Manuel d’Anatomie, vol. iii. 
page 53. - 
+ See Boyer, Traité d’Anatomie, vol. ili. p. 359. 
t See Traité d’Anatomie, Boyer, vol. iii. p. 359, 
3A 


722 


of the omo-hyoid muscle, in the substance of 
which it ramities. 

Plexus.—\mmediately below the tendon of 
the omo-hyoid, the descendens noni, uniting 
with branches given off by the second and 
third cervical nerves, forms a nervous arch, the 
convexity of which looks downwards and for- 
wards. This plexus lies under cover of the 
sterno-mastoid, and in front of the jugular 
vein. 

Sterno-hyoid and thyroid branches—From 
the convexity of the arch formed by this plexus 
two or sometimes more nerves proceed down- 
wards and inwards, and ramifying on the super- 
ficial surface of the sterno-hyoid and thyroid 
muscles, are distributed tothem. 

Cardiac branch.—Meckel states, that on the 
left side particularly he has been able to trace 
a branch from this plexus into the thorax along 
the pericardium as far as the heart. The cervi- 
calis descendens is observed sometimes to vary 
from the above description, in its course down 
the neck, and in its relation to the great vessels ; 
for, instead of lying anterior and external to 
the sheath, it is occasionally found to pass down 
within the sheath, and sometimes even behind 
it. Ihave also seen it pass for a short dis- 
tance within the sheath in the upper part of its 
course, becoming superficial about the centre 
of the neck, and then running down in ‘front 
of the sheath in the usual manner. 

These varieties in the course and relations of 
this nerve are not, however, very commonly 
met with. ' 

Thyro-hyoid branch.—The next branch given 
off by the ninth pair is where the nerve is 

sing under the tendon of the digastric, a 

ittle above the cornu of the os hyoides. Here 

it gives off a considerable branch named thyro- 
hyoid, from its distribution. This nerve passes 
from its origin downwards and inwards, cross- 
ing the lingual artery, to which it lies super- 
ficial, and is distributed to the thyro-hyoid 
muscle. 

From the origin of the thyro-hyoid branch 
the ninth nerve passes inwards between the 
hyoglossus and mylo-hyoid muscles, and at the 
anterior edge of the hyoglossus it plunges into 
the genio-hyoylossus, in the substance of which 

its terminating branches ramify. In this course 
the ninth nerve supplies filaments to the mylo- 
hyoid, the hyoglossus, the genio-hyoid, genio- 
hyoglossus, and lingualis. 

In the substance of the genio-hyoglossus the 
branches of the ninth nerve form distinct anas- 
tomoses with branches of the fifth (the gusta- 
tory); with this nerve the branches of the 
ninth form nervous loops or arches, the con- 
vexities of which look forwards, and from which 
branches pass off which may be traced to the 
mucous membrane of the tongue. There can 
be little doubt that these nerves are to be con- 
sidered as compound, containing filaments de- 
rived both from the ninth and fifth pair. Most 
anatomists state, that the ultimate branches of 
the ninth can be traced no further than the 
structure of the muscles which enter into the 
formation of the tongue, and this appears to be 
true with respect to the branches which do not 


NINTH PAIR OF NERVES. A 


anastomose with the fifth pair; but it is more 
than probable, although difficult to demon- 
strate, that from the anastomosis 
above, a nerve, com of filaments boll 
of the ninth and fifth, proceeds, and | 
distributed to the mucous membrane of th 
tongue. ; 
Comparative anatomy.—It has been t 
by Professor Mayer, that in the ox and som 
other Mammalia he has discovered a sma 
posterior root to the ninth nerve, having on 
a ganglion; to the investigation of this ha 
paid particular attention. I have repeatec 
and with care sought for this posterior root @ 
ganglion in the ox, and have never been 
to satisfy myself as to the existence of a 
posterior root to this nerve. = 
The anatomy, however, of this part in t 
is extremely interesting, and when exar 
may, perhaps, explain Mayer’s opinion, —__ 
In the dissections which I have made of 
ninth pair in the ox, the nerve was fou 
arise in the depression between the co 
olivare and pyramidale by several deli 
roots, in a manner very similar to what is 
served in the human subject; these roots 
formly formed two bundles, which perfo 
the dura mater separately, before doing w 
however, the most inferior of these two bu 
received a twig, which at first sight ap 
to be given off by the spinal accessor; 


/ 
os 


upon further and careful dissection, thi 
was found not to come from the spinal a 
sory, but to arise by a number of distinet 
from the side of the medulla spinalis, an 
to the roots of the spinal accessory, in ft 
and distinct from which it passed up int 
cranium, and joined the inferior of the 
bundles, which formed the origins of the 
and uniting with this passed out th 
anterior condyloid foramen. 

When this nerve was cleansed, the pi 
and coagulated blood removed, which ; 
loads these parts in the slaughtered ox, B 
largement or any thing resembling ag 
could be discovered on its course. This 
cannot be considered a posterior rool 
ninth pair, for its origin from the me 
anterior to that of the spinal accessory ; 
am inclined to think that this nerve in 
holds the same relation to the ninth 
spinal accessory does to the eighth. — 
be what Mayer supposes to be a poste 
to the ninth ? - 

Winslow speaks of a communica’ 
tween the spinal accessory and nin 
within the cranium, the existence of + 
the human subject is described by Se 
Meckel ;* I have never been able to 
such communication in man. 

On tracing the ninth nerve in the 
the anterior condyloid canal, it ¥ 
united into one trunk, and envelope 
strong neurilemma; nor could any 
be detected on the nerve in this part 
course. . 

In Birds, the ninth nerve is foun nt 


* See Manuel d’Anatomie, Meckel, v Li 


| NOSE. 


nicate with the par vagum, to divide into two 
branches, one of which is distributed to the 
tongue and the other to the esophagus. Miiller 
_ States, that in the rattlesnake he has found this 
__ herve escaping from the cranium by a special 

Opening behind that for the eighth pair, with 
which it communicates, as also with the first 
cervical.* 

In Fishes, the last cerebral nerve is described 
by Weber as arising by three roots, the poste- 
rior having a ganglion, and passing out of the 
cranium by a special foramen in the occipital 
bone, and being distributed to the pectoral fin. 
__ From these circumstances Miller conceived 
that an analogy exists between the hypoglossal, 
_ Or ninth nerve, and the spinal nerves, and says, 
_ “ If we now take into consideration that the 
first spinal nerve in the human subject has 
_ Sometimes only an anterior root, and that the 
hypoglossal in man has only an anterior root, 
but that in some mammalia (according to the 
_ hypothesis of Mayer) it has a posterior root 
“also, it will be evident that the hypoglossal 
erve belongs to the class of spinal nerves, and 
is as it were the first spinal nerve, which, how- 
€ver, generally passes out through a foramen in 
the cranium; this consideration renders the 
ialogy between the last cerebral nerve in 
_ fishes and the hypoglossal nerve still greater.”’+ 
_ Physiology. —That the ninth pair is the 
“herve which influences the motions of the 
tongue is generally admitted, and that it de- 

Serves the name given to it of motor lingue 
_has been proved by the experiments of Mayo, 

4 ae and Muller. 

_ When in the living animal this nerve is ex- 
posed and excited by pinching or galvanism, 
lent spasms of the entire tongue are pro- 

ed, and its division is followed by paralysis 
| that organ. 
if On this subject Mayo performed the follow- 
ing experiment. “ I divided the ninth nerve 
_ On one side of the tongue in a dog; the ani- 
5 did not seem much incommoded, but 
_ flapped up milk readily. I then divided the 
@ on the opposite side; the animal ap- 

sared distressed, and did not again lap up the 
“milk offered to it, though it smelt to it; and 
finally, when mustard was smeared on its nos- 
 trils, it made no use of its tongue to remove 

7 though evidently suffering from it.” Further, 
Ae ae found that when the nerve was divided 

on both sides in a rabbit, and the tongue drawn 
out of the mouth, the animal had not the 
| power of again retracting it. 

i “hed interesting case is related by Montault 

nd quoted by Miiller, where a tumour pressing 
0n the ninth nerve of the left side at its exit 
from the cranium produced an atrophy of this 
| Nerve; the symptoms were paralysis of the left 
de of the tongue with gradual wasting of the 
n on that side ; but the sense of taste was 
} Mot in the least affected, being as perfect on 

the paralysed side as on the other. 
Weare warranted from these facts in consi- 


_™ Elements of Physiology. 
+ See Elements ot Physiology. 
4 See Mayo, Commentaries, part ii. p. 11. 


723 


dering the ninth nerve as that which influences 
the motions of the tongue in articulation and 
deglutition ; but, besides directing the motions 
of the tongue, the ninth nerve influences the mo- 
tions produced upon the os hyoides by the sterno- 
hyoid, sterno-thyroid, and thyro-hyoid muscles, 
which muscles receive branches, as before de- 
scribed, from the ninth and cervical plexus. 
The importance of this connection in action of 
these muscles with the tongue, in the perform- 
ance of the functions of articulation and deglu- 
tition, is obvious; and in the turkey Miller 
has found a long branch going from this nee 
to supply the muscles which in that bird_ 
shorten the trachea. ; 

It is asserted that the ninth nerve, in addition 
to its motor influence, is also endowed with a 
certain degree of sensibility, and that, if the 
nerve be stretched or pinched in a living ani- 
mal, there is evidence of the animal suf- 
fering pain; this has been tried on dogs and 
cats. Now if in these animals this nerve has 
a double origin, this would be easy to under- 
stand; but Mayer himself could not detach a 
posterior root in the cat; so that if this nerve, 
either in man or other animals, has any of the 
properties of a nerve of sensation, it is owing 
to the filaments which it receives from the cer- 
vical plexus. But the degree of sensibility 
communicated to the tongue through the in- 
fluence of this nerve in this way must be very 
trifling; and it is now as well proved that the 
tactile sensibility of the tongue is owing princi- 
pally to the influence of the gustatory branch 
of the fifth, as that the motions of that organ 
are directed by the influence of the ninth pair. 

(G. Stokes.) 


NOSE. (Human Anatomy.)—(Gr. giv; Lat. 
Nasus; German, Nase; French, Nez; Italian, 
Naso; Dutch, Neus.) The nose is the organ 
of the sense of smell, and a part of the appara- 
tus of respiration and voice, and in accordance 
with the variety of its oftices is complex both in 
form and in structure, many different tissues en- 
tering into its composition. The most simple 
method of describing its anatomy in man is 
the synthetical; I shall thetefore give an ac- 
count, first, of its skeleton, composed of bones 
and cartilages ; and then, in succession, of each 
of the parts placed on the skeleton, and subser- 
vient to its several functions. 

The bones of the nose are chiefly concerned in 
the formation of the internal deeply-seated part 
of the organ, that part which is called the nasal 
fossee, (cave nares, or nares interné, ) or the ca- 
vities of the nose. These cavities are open 
widely anteriorly to the atmosphere, and poste- 
riorly to the pharynx. The anterior aperture 
is, in the osseous skeleton, heartshaped, broader 
below than above, bounded below and on each 
side by the palatine and ascending processes of 
the superior maxillary bones, and above by the 
nasal bones. Its borders are, in the lower half, 
smoothly rounded; in the upper half, sh 
and uneven. Below and in the middle line 
the anterior nasa} spine projects forwards and 
upwards; and above it is the osseous septum, 
which divides the fosse into two equal er 

3 A 2 


724 ; 


nearly equal portions, but of which the lower 
part alone reaches to the anterior aperture. 

The posterior aperture of the nasal cavities 
is quadrilateral. It is bounded below by the 
palatine plates of the palate bones, with the 
posterior nasal spine formed at their junction ; 
on each side by the internal pterygoid plate of 
the sphenoid Sow and above by the ale of 
the vomer and the body of the sphenoid bone. 
The posterior edge of the vomer divides it into 
two equal lateral parts. 

The space of which these are the apertures 
is altogether irregular in its form, but each of 
the halves into which it is divided by the sep- 
tum may be described as having four walls or 
boundaries, a superior, inferior, and two late- 
ral. The superior wall or vault of each cavity 
of the nose is formed io front by the posterior 
surface of the nasal bone; above and in the 
middle by the inferior surfaces of the nasal 
spine of the frontal, and of the cribriform plate 
of the ethmoid bone; behind by the anterior 
and inferior surfaces of the body of the sphe- 
noid bone, and its turbinated bone, and by the 
ala of the vomer. The anterior part of this 
wall looks downwards and backwards, and 
shea shallow branched grooves in which 

ranches of the internal nasal nerve lie, and 
one or more apertures through which one of 
those branches and an artery or two pass. The 
middle part of the wall is nearly horizontal, 
and is perforated by many apertures for the 
branches of the olfactory nerve, and for the in- 
ternal nasal nerve; the posterior part looks 
downwards and forwards, and presents an 
aperture leading into the sphenoidal sinuses. 

The lower wall or floor of the nasal cavity 
is nearly horizontal ; it is concave transversely, 
a little raised at each end, and narrower before 


Fig. 399. 


View of the outer wall of the nasal cavity on the right 
side. 


1, nasal bone; 2, frontal bone ; 3, frontal sinus; 
4, sphenvidal sinus ; 5, palatine surface of the hard 
palate; 6, edge of the palate bone ; 7, anterior edge 
of the superior maxillary bone. 


NOSE. 


than behind. It is formed by the u ia 
faces of the palatine plates of the sopertor ia 
illary and palate bones, and its inner border is — 
a little prolonged both behind and before upon 
their nasal spines. Near its anterior border it 
is perforated by the superior orifice of the 
anterior palatine canal. J 
The outer wall is the most complicated. 
( Fig.399.) Ifa vertical line be drawn down- 
wards from the base of the nasal spine of the 
frontal bone (a), it will have in front of it the 
plain part of this wall, a slighty concave tr 
angular surface, formed by the ascending pro 
cess of the superior maxillary bone (6), an 
resenting nothing but some shallow groovi 
or bloodvessels and nerves. And, if a similar 
line be drawn downwards from the front of th 
body of the sphenoid bone (c), it will ha 
behind it another plane surface formed by tl 
internal pterygoid plate (d). Between t 
vertical lines there is a large quadrilateral su 
face divided into three parts by the three tur 
binated bones, whose edges project in neat 
parallel and horizontal lines, at about eq 
distances one above the other. At the upp 
part of this surface and anteriorly is a th 
quadrilateral plate (e) belonging to the cell 
ap of the ethmoid bone, made very re 
y grooves and apertures which lodge bran 
of the olfactory nerve. The anterior 5 
this plate forms the inner wall of iy 
ethmoidal cells; the terior ay 
little curved outienidiat and sated as 
between its surface and the body of the sj 
noid bone into which the sphenoidal 
opens. The lower border of this plate is 
tinuous anteriorly with the inner surface 0 
middle turbinated bone, and posteriorly 
free margin which is slightly curled outs 
From the form of this margin the plate is ¢ 
the superior turbinated bone, (cornet 
rieur ; oberste Muschel;) and the space 
it here covers, and which is a kind of hor 
tal channel between its outer surface an 
wall of the adjacent ethmoidal ce’ 
superior meatus of the nose. Into thi 
the posterior ethmoidal cells open, usi 
two or more orifices concealed by the tur! 
bone; behind and a little below it” 
spheno-palatine foramen (A), at which th 
branches from the spheno-palatine ge 
and the spheno-palatine vessels enter th 
and yet further backward, and nearly 
the end of the superior turbinated bom 
opening into the sphenoidal sinuses. 
Below this upper plate, and continu 
it anteriorly, is the inner surface of the 
turbinated bone (g), another portion of 
moid bone, (cornet moyen; mitt Mr 
It is larger than thé superior, more con 
its inner surface, and presents a f 
through the whole extent of its lowe 
which is thick, and abruptly curled 0 
and sometimes has cavities within it” 
of Santorini), communicating with the 
moidal cells. The inner s he bi 
deeply grooved and perforated by blood 
and branches of the olfact n 
tine nerves. Of the grooves, whi 


> 


the olfactory nerves run from above downwards, 
and those in which the naso-palatine nerves lie 
are directed forwards ; at its lower margin also 
is a particular groove in which a large blood- 
vessel runs. The outer surface is concave and 
smoother than the inner, and forms the inner 
boundary of the middle meatus of the nose. 
On the outer wall of this meatus, which is a 
_ much larger channel than the superior one, ex- 
tending through nearly the whole length of the 
outer wall of the nasal fossz, there are pre- 
sented from before backwards, after removing 
_ the turbinated bone,—1. a part of the ascend- 
ing process of the upper jaw-bone; 2. part of 
_the inner surface of the lachrymal bone; 3. the 
walls of some of the anterior ethmoidal cells; 
4, the infundibulum, along, narrow, and slightly 
_eurved passage, leading obliquely upwards and 
forwards into the anterior ethmoidal cells, and 
rough them into the frontal sinuses; 5. the 
trance into the antrum, a large aperture of 
ertain size and form; and, lastly, a flat 
_ surface of the vertical plate of the palate bone. 

Below the middle meatus is the inferior 
~ turbinated bone, the largest of the three, and 
lly described as a separate bone, because 
it is not so soon united to the adjacent bones. 
it is very uncertain in form and size; its depth 
specially varies; so that its lower border some- 
s nearly touches the floor of the nasal ca- 
and sometimes is half an inch above it; 
Ometimes, also, it is so much curled outwards 
at it nearly forms a canal between its outer 
order and the outer wall. On the whole, 
wever, this turbinated bone presents the 
me general characters as the others. Its 
per margin is fixed to a prominent ridge 
ong nearly the whole length of the outer wall 
the nasal fossee ; its lower margin is free, 
ts outer surface forms the inner boundary 
ie inferior meatus of the nose, of which 
outer boundary is formed by the ascending 
s of the superior maxillary (k) and palate 
s. At the anterior part of this meatus is 
inferior orifice of the nasal canal, a passage 
med at its sides, larger at its extremities 
‘in the middle, and passing, with a slight 
r curve, upwards, forwards, and a little 
tds to the inner angle of the orbit. It 
the nasal duct. At the level of this 
s also, behind the edge of the internal 
oid plate, and about midway between 
or of the nose and the end of the inferior 
ated bone, is the opening of the Eusta- 
tube; but nothing of this is seen in the 
The inner wall of each cavity of the nose 
s formed by the septum, a median partition 
composed of the perpendicular plate of the 

moid bone, and the vomer, whose edges cor- 
pond to ridges formed at the median sutures 
of th eerenpenor maxillary, and palate bones, 
| and on the inferior surfaces of the frontal and 
| sphenoid bones. The septum is not commonly 
quite vertical: it may lean to either side, or 
iloy be curved slightly in both directions, or 
\May be convex on both sides and have a cavity 
fins interior. 


RL 


ee cl ae 


? 


— 


Of 


Each of its sides exhibits at 


: upper and back part the grooves of some of 


Op acd ae 


NOSE, 


725 


the olfactory nerves, becoming more shallow as 
they descend ; and in various parts it is slightly 
marked by the passage of bloodvessels and 
other nerves. 

Thus, the bones which form the proper 
cavities of the nose are fourteen; viz.—the two 
nasal, two superior maxillary, two palatine, the 
two inferior, and two sphenoidal turbinated, 
bones, the frontal, ethmoid, sphenoid, and vomer. 
And, with the space which these enclose, many 
adjacent cavities communicate; viz—1. The 
frontal sinuses, which open through the ante- 
rior ethmoid cells and infundibulum into th 
middle meatus. 2. The anterior ethmoid cells, » 
which open by the same canal or by separate 
apertures, into the same meatus. 3. The pos- 
terior ethmoidal cells, which open into the 
superior meatus. 4. The sphenoidal sinuses, 
which open through the posterior part of the 
roof of the nose behind the same meatus: and 
5. The antrum, which opens into the middle 
meatus. 

The osseous parts hitherto described form the 
skeleton of the interior of the nose, but con- 
tribute little to the formation of its external 
prominent part. Of this part the osseous ske- 
leton is composed of the two nasal bones, and 


. the nasal or ascending processes of the superior 


maxillary bones, which together form the bridge 
of the nose and a small portion of its lateral 
walls. Each nasal bone is elongated, quadri- 
lateral, and narrower above than below. Its 
anterior surface is convex from side to side, and 
either presents a double curve from above down- 
wards, or is slightly concave in its whole length. 
The two together form a prominent arch above 
and in front of the anterior aperture of the nose: 
their surface is continued outwards and down- 
wards over the ascending processes of the supe- 
rior maxillary bones, is smooth, and is marked 
only by small apertures giving passage to blood- 
vessels and nerves. 

The internal edges of the nasal bones are 
united in the median line by a straight suture, 
the continuation of the sagittal.suture. In front 
their union is smooth; but behind and above, 
where the bones are much thicker than they are 
below, a deep ridge or crest is formed which is 
received into that part of the septum of the 
nose which is formed by the nasal spine of the 
frontal bone, and the vertical plate of the 
ethmoid. Sometimes, however, these margins, 
instead of forming a ridge, are separate, and en- 
close a groove in which the edge of the septum 
is received. The superior thick borders of the 
nasal bones articulate by a serrated suture with 
the notch and the nasal spine of the frontal 
bone; and this suture, which forms part of the 
great transverse suture, is continued into that 
uniting the nasal processes of the superior 
maxillary bones with the internal angular pro- 
cesses of the frontal. The outer and largest 
margin of the nasal bone articulates with the 
nasal process of the superior maxillary, and is 
slightly overlapped by its sharp edge. The lower 
free margin is sharp and uneven. 

The median suture of the nasal bones, and 
the short portion of the sagittal suture imme- 
diately above it, are the parts of the median 


726 


suture of the skull which remain longest un- 
ossified : in ordinary cases, indeed, they do not 
close even in the latest periods of life, This, in 
some measure, distinguishes man from the other 
quadrumana: in the Chimpansé, the nasal 
bone is single; in the Orang, also, it usually 
is so; and in the adult Siamang (whose skull 
approaches nearest in form to that of man) and 
other Gibbons, the nasal bones are always 
united.* But a more distinctive character is 
the treadth and shortness of these bones in 
man, and the elevation of their inner borders, 
on which the projection of the upper part of the 
bridge of the nose depends; a projection in 
which the nose of the lowest negro surpasses 
that of either the Chimpansé or the Siamang. 

The structure of the bones of the nose pre- 
sents little that is peculiar. The thin lamelle of 
the ethmoidal pals, tbe turbinated bones, and 
others of similar structure, receive their mate- 
rials of nutrition entirely from the bloodvessels 
of the Schneiderian membrane. They contain 
no vascular canals within their own substance. 
Their corpuscles and minute canals which pro- 
ceed from them are larger than those of average 
size: the former are very numerous and closely 
set, and the latter ramify in 4ll directions ; 
arrangements which seem to be adapted to the 
combination of the least possible weight with 
the necessary firmness of support. 

Cartilages of the nose.—Of these, one com- 
pletes the septum, and the rest form the skele- 
ton of the lower and lateral portion of the exter- 
nal nose. 

The cartilage of the septum (septum mobile 
nasi) (fig. 400) is the only one immediately 
connected with the bones. It occupies, in ge- 
neral, nearly the middle vertical rae of the 
nose; but, like the osseous septum, it often 
deviates to one or the other side, and has sur- 
faces more or less curved. Its outline varies 
with the general shape of the nose, but is 
usually bounded by three unequally curved 
lines, of which the inferior is the longest, and 
the anterior and superior are of about equal 


length. Its superior border (a, fig. 400) is 
fixed in the whole length of the groove which 
usually exists in the lower margin of the per- 
pendicular plate of the ethmoid bone: it is 
directed very obliquely backwards and down- 
wards, and at its posterior extremity is conti- 


Fig. 400. 


Cartilage of the septum nasi. 


1, lateral ; 2, anterior view. 


* G. Vrolik, Recherches d’Anatomie Comparée 
sur le Chimpansé, p. 4, 


NOSE. 


- are closely attached by fibro-cellular 


The cartilages of the ala of the nose in site. 
nued with a curve into the lower border (b/ 
which a part fits in the same manner it 
anterior margin of the vomer, while the ren 
der projects straightforwards in front o 
anterior nasal spine, and forms the base 
middle part of the columna (sous-cloison 
partition between the apertures of the no: 
Anteriorly, this lower border of the 
ginous septum is continued with a curve ¥ 
lies at the apex of the nose, into the an 
border (¢). This last lies immediately 
neath the skin, and, becoming gradually | 
er, is continued upwards to the junction 
nasal bones, where the cartilage (at « 
thicker than at any other part. yy 

Of the lateral cartilages, two on eac 
are regularly found. The upper pair, (¢ 
401,) which are named superior, lateral 
triangular cartilages, have each in ge 
form of a triangle with its angles roun 
In front they are continuous, or very 
connected with the upper half of the 
edge of the cartilage of the septum;* | 
of them projects a little beyond it, s 
lies in a kind of groove between then 
sometimes, each is prolonged downw: 


free sharp process by its side. Behl 


ae 


the rough part of the free margins of 
and superior maxillary bones. Be 
margins are connected with the cart 
neath them (6, fig. 401) by a toug 
and pliant fibrous membrane, in wh 
small oval portions of cartilage are 
arranged in a row. ; 

The inferior cartilages (fig. 402, @ 
401) are also called pinnal cartilage 
lages of the ala, because they fo 
the more freely moveable lateral 


* Hence Winslow, Bichat, and sor 
have described these as forming one nasa 
with the septum, and have divided th 
cartilages into anterior and posterior porth 


_ 


~ 
~ $ 
hen 4 


~ LE: 


1 4 


the side of the lower margin of the cartilaginous 
+ 


_ Septum, to which, as well as to its fellow on the 


* 
ri 


NOSE. 


Lateral view of the pinnal cartilages. 


nose, and the cartilages of the nostrils, be- 
cause they surround and in great measure de- 
termine the form of those apertures. The chief 
portion of each of them is nearly elliptical, 
and occupies the anterior part of the ala of the 
nose. Posteriorly, this portion either becomes 
suddenly narrower, and is continued in a long, 
undulating, and curved process through the 
middle part of the ala to the posterior and 
outer boundary of the nostril; or else it ab- 
ruptly ceases, and, in place of the process, 
there is a row of three or more small oval 
ttions of cartilage, (sesamoid cartilages, ) 
imbedded in the fibrous membrane which 
forms the rest of the basis of the ala, and 
connects all the moveable cartilages to one 
another. Anteriorly, this chief elliptical por- 
tion is also continued into a narrow process, 
which, after ap erat for a very short dis- 
tance forwards, turns round abruptly, and is 
directed backwards and a little downwards by 


“Oppusite side, it is pretty closely connected by 
fibro-cellular tissue. In this course, the carti- 


ii 


~ A] 


lage reaches a little beyond the anterior edge of 
_ the septum, so that, at the tip of most noses, 
_ there isin the middle line a small fossa bounded 
_ 0n each side by the lateral cartilages, and at the 
bottom of which is the anterior edge of the 
Septum. The inner portion of this cartilage 
extends along about two-thirds of the inner 
“boundary of the nostril, and terminates in an 
évenly rounded border; its lower Margin is 
always rather lower than that of the cartilagi- 
“hous septum, and assists in giving width and 
Support to the columna. Sometimes, but more 
rarely, this inner process of the inferior cartilage 
is, like the posterior and outer process, separate 
from the chief elliptical portion. 
_ The structure of the cartilages of the nose 
is essentially similar to that of the articular 
and other true cartilages, (cartilagines figu- 
rate, Meckauer.) Their cells are numerous, 
very close set and large; and next to each of 
their surfaces there are two or three layers of 
thin flattened cells, which give the borders of a 
Section through the thickness of the cartilage a 
somewhat fibrous aspect. But the basis-sub- 
Stance is, in reality, entirely destitute of fibres. 
The greater rigidity and firmness of the sep- 
tum-cartilage is due to its greater thickness ; 
its minute structure is similar to that of the 
cartilages of the ale. The latter are easily 
flexible, but the pliancy of the sides of the nose 
does not depend on them alone, but in as great 
a degree on the tough fibro-cellular membrane 
in which they are imbedded. The combination 
of the two tissues is indeed admirably adapted 
to the purposes which are to be served. The. 


27 


cartilages are sufficiently rigid to give the ale a 

definite form during rest; and they are so 

elastic that, when the nostrils have been either 

compressed or expanded, they are restored to 

their natural position by the recoil of the carti- 

lages, without any muscular effort. If the 

whole side of the nose had been formed of 
cartilage, much stronger muscles would have 

been needed for the several movements of the 

nostrils; but, by the intervention of small por- 

tions of fibro-cellular membrane, these move- 

ments, whether rapid or long-sustained, are ef- 

fected by some of the weakest muscles of\the 

‘body, and with a scarcely perceptible effort of 
the will. The arrangement is somewhat ana- 

logous to that in which strength and flexibility 

are combined by strong scales or plates being 

set on the pliant substance of the skin of va- 

rious animals. 

The muscles of the nose, like those of the rest 
of the face, are but ill-defined, and anatomists 
have differed much in both the description and 
the enumeration of them. The following ac- 
count is drawn from the results of several dis- 
sections purposely made, and compared with 
the descriptions of Santorini,* Arnold,t+ 
Theile,t and others, who have examined the 
matter for themselves. 


Fig. 403. 


Muscles of the nose. 
a, nasal bone; 6, nasal process of superior 


maxillary bone; c, pyramidalis nasi; 4, d, leva- 
tor labii superioris alzque nasi; e, e, triangularis ; 
J; depressor ale nasi; g, compressor narium minor; 
A, dilatator narium anterior; i, orbicularis oris; k,° 
depressor septi narium. 


* Observationes Anatomice, cap.i- __ ' 

¢t Icones Anatomice, Fasc. II. tab. viii. 

¢{ Soeramering, Vom Baue des Menschlichen 
Korpers, Bd. iii. 


728 


1. Pyramidalis, (Casserius ; procerus, San- 
torini; sronto-nasal, Chaussier.) This (c, fig. 
403) cannot be strictly called a separate muscle 
of the nose, and it is described with the, front- 
alis by Haller, Theile, and many others. It 
consists of those fibres of the median portion 
of the frontalis muscle which descend in a 
fasciculus over the upper part of the nose. 
They terminate in the cellular tissue covering 
the superior cartilage, and, through its medium, 
they are attached to the cartilage itself, and to 
the adjacent border of the nasal bone; many of 
them also are continued onwards and mingled 
with the upper fibres of the triangularis nasi 
(e), with el aponeurosis, moreover, theirs 
is always continuous. At their inner margin 
these fasciculi are in contact above, but they 
diverge below as they pass over the surface of 
the nasal bones, and they thus assume that 
appearance of two distinct slender triangular 
slips of muscle which led Santorini to give 
them a distinct name, though they have not 
that distinct origin which he assigns to them. 

The pyramidales do not appear to have the 
power of acting alone. When the rest of the 
frontalis contracts, and, by drawing down the 
scalp, wrinkles the skin of the forehead, they 
also act, raising and tightening the skin over 
the upper part of the bridge of the nose. They 
produce the same effect when the brows are 
drawn up, as in surprise. 

2. Levator labii superioris aleque nasi, (Al- 
binus, Weber, &c.; pyramidalis, Santorini ; 
oblique, ou lateral, Winslow; elevateur com- 
mun, Bichat, Bourgery, &c.) This, (d, d, fig. 
403,) which is the largest and strongest of the 
muscles of the nose, arises, internally, by a 
narrow slip of fibres from the upper and outer 
part of the ascending process of the superior 
maxillary bone, and, externally, by a broader 
origin from below the inner part of the lower 
border of the orbit. Its origins are covered by 
the orbicularis palpebrarum, and from them its 
fibres proceed downwards and diverge. About 
two-thirds of them pass to the outer part of 
the upper lip, mingling with the fibres of the 
orbicularis oris (i) and levator labii proprius, 
and inserted for the most part in the skin; the 
remainder go downwards and a little forwards 
over the posterior third of the ala of the nose. 
Of these last, some are attached more or less 
intimately to the posterior parts of the inferior 
cartilage and the membrane in which it is im- 
bedded ; many more terminate in the skin over 
the lower part of the ala, and are there mingled 
with fibres which run in various directions, but 
usually form a complete layer of muscular fas- 
ciculi beneath the skin of the outer border of 
the nostril. 

In contracting, the nasal portion of this 
muscle draws up the ala of the nose, espe- 
cially its posterior and lower half; and as the 
cartilage and other dense tissues of this part 
do not admit of wrinkling, the muscle, in its 
full action, turns the nostril outwards, and 
expands its aperture at the same time that it 
wrinkles the skin above it. 

3. Triangularis, (Cloquet, Bourgery, &c.; 
transversus, Santorini, Winslow, Theile; com- 


NOSE. 


pressor nasi, Albinus, Haller; ¢, e, fig. 403) is 
a thin pale muscle whose origin is covered by the 
ing. It arises by a narrow aponeurosis 
from the upper and outer part of the canine 
fossa, behind and external to the base of the ala 
of the nose. Its fibres thence diverge, the lower 
ones passing almost horizontally, the upper 
ones forwards and inwards, and they form a 
thin triangular muscle which covers the upper — 
part of the ala of the nose and reaches to the 
dorsum. Sometimes many of its fibres pass — 
over the dorsum of the nose and mingle with 
those of the muscle of the opposite side; but 
more often there intervenes between the two 
muscles a pliant fibro-cellular expansion, into 
the borders of which many of their fibres are 
inserted, and which thus forms a kind of me-- 
dian aponeurosis extending over the front of the — 
nose and enabling both the muscles to act — 
at once and equally upon it and the ala. In — 
general, also, the upper or outer fibres of this — 
muscle aré continuous with those of the pyra- — 
midalis or are fixed in its aponeurosis; and th i 
s 


lower fibres are mingled with fibres of the 
pressor ale nasi, and pass into the i 
assemblage of fibres beneath the skin he 
lower border of the ala. Many of the fibre 
are connected through their whole course more 
or less intimately with the other tissues of the 
ala and the skin; and probably it was from 
this last circumstance that Santorini was in- 
duced to describe this muscle as having the 
whole of its origin among the fibres of the 
levator labii superioris aleque nasi, or rather 
as a muscle peculiar for having its middle p r- 
tion fixed (on the dorsum of the nose) and its 
two extremities moveable in the substance 
each side of the upper lip. 

These muscles have been described by som 
as compressors, by others as dilators of t 
nose, and in different circumstances they pre 
bably do act very differently. When the c at 
or maxillary insertion of each is fixed, th 
assist in compressing the nostrils, and in cot 
bination with the true depressors (presently 
be described) their lower fibres draw the a 
backwards. When, on the other hand, 
take their fixed point in the median apone 
on the dorsum of the nose, and contract te 
it. those of their fibres which are conne 
with the skin will wrinkle it, as in the act 
‘sneering, and those which are attached to 
deeper tissues of the ala will draw it upw: 
and in some degree expand the nostril. W 
they compress the nostrils they commonly 
draw backwards the apex of the nose iT 
manner usually seen in the act of 
carefully. 

4. Depressor ale nasi, (Haller, 


A 


Theile; Myrtiformis, seu pinne dilatator, 
torini; Petit dilatateur de Vaile du nez, : 
gery ; incisif mitoyen, Winslow; dilatatorna 
Arnold ; f. fig. 403) arises by short aponeu 
fibres from the alveolar margin above th 
cond incisor and canine teeth of the upper j 
below and on the inner side of the origin 
the triangularis. Its fibres proceed upwi 

forwards, and inwards, some going to the 
terior part of the skin under the sides of 


septum, and many more to that of the ale; 
many of them, also, first rising and then de- 
scending, form arches which are continued over 
_ the outer and posterior margin of the nostril, 
and are mingled with the fibres of the two 
preceding muscles, where they meet in the skin 
covering that part. 

These muscles draw back and flatten the 
nostrils. Some of their fibres are mingled with 
those of the depressor labii superioris, or su- 
perior incisive muscle, and, whenever they act, 
the upper lip is fixed and somewhat elongated. 

5. jon sai septi narium, or nasalis labii 
superioris, (Haller, Albinus; naso-labial, Bour- 
gery; k, fig.403;) may be regarded as a part of 
the upper portion of the circumference of the 
orbicularis oris, from which several fibres pro- 
_ ceed forwards and inwards, converging from 

_ each side towards the septum of the nose. They 
are attached to the fibro-cellular tissue at the pos- 
erior borders of the nostrils, and the middle 
fibres pass forwards under the septum between 
it and the skin of the columna, many of them 
_ extending nearly to the tip of the nose. 
When the rest of the orbicularis is fixed, this 
portion will draw the columna and the apex of 
he nose backwards and downwards; and when 
rest of the orbicularis is relaxed, it will 
ww the middle of the upper lip upwards. 
_ 6.1 have mentioned a layer of pale mus- 
sular fibres arranged in various directions under 
“the skin of the lower part of the ala nasi, 
‘among which fibres of the compressor, de- 
ssor, and levator ale nasi appear to mingle. 
is by these fibres that the dilatation of the 
til is commonly effected; for, as any one 
ay feel and see in his own person, this act is 
bt usually performed by any of the muscles 
et described, but by fibres which are situated 
blow the triangularis and entirely within the 
‘Moveable part of the ala. In most instances, 
_ ho definite arrangement of these fibres can be 
"a ived; yet they certainly sometimes form 
"y Bee: fasciculi, which may be described as 
Separate muscles. Arnold makes from them 
wo muscles: 1. Compressor narium minor, 
_ &fig. 403), a small triangular muscle pass- 
g from the skin of the tip of the nose back- 
wards and a little upwards, with its fibres 
diverging, to the anterior part of the inferior 
_ ¢artilage. Theile has never seen this muscle; 
in One very muscular subject I found a dis- 
t trace of it; and it nearly corresponds to 
hat which Santorini has drawn, (tab. i. e, e) 
d which he says he once saw in action du- 
ring dyspnea in a woman. He regarded it 
asa dilator of the anterior part of the pinna; 
ld considers it a compressor; the former 
{ on is the more probable. 2. Arnold 
bas figured a larger quadrilateral muscle, /e- 
_ vator ale nasi proprius (h, fig. 403), which is 
“nearly the same as Theile’s dilalator narium 
| «anterior, Theile describes it as arising from 
| the upper edge and outer surface of the inferior 
Cartilage, its origin extending from within two 
lines of the dorsum of the nose to the sesa- 
‘moid cartilages. Hence its fibres proceed 
‘downwards and are lost in the skin on the 
| anterior part of the edge of the nostril. Its 


‘ NOSE. 


_if not with the naked eye. 


729 


action is to draw the anterior part of the ala 
outwards, and thus to dilate the nostril. Theile 
also describes a dilatator narium posterior, 
which may be found by removing all the 
fibres of the common levator, the depressor 
ale nasi and the triangularis. A mass of cel- 
lular tissue is thus exposed on the inferior and 
posterior part of the ala, in which muscular 
fibres may always be seen with the microscope, 

They arise ge 
nous from the edge of the ascending process of 
the superior maxillary bone and from the Ssesa- 
moid cartilages, and thence descending are lost_ 
in the skin of the posterior half of the edge of 
the nostril. Their action is to draw the poste- 
rior part of the ala outwards, and thus to dilate 
the nostril. 

7. One more muscle may be mentioned, 
though it is only. indirectly connected with the 
nose. It is that named rhomboideus by San- 
torini (tab. i. f), and anomalus by Albinus, 
from its being fixed at both its ends to immovable 
points. Its origin is confounded with that of 
the triangularis at the upper and outer part of 
the canine fossa; whence its fibres proceed in 
a broad fasciculus upwards and inwards in the 
fossa by the side of the nose to be attached to 
the surface of the superior maxillary bone close 
to the outer origin of the levator communis. 
The strength of the fibres of this singular mus- 
cle indicates that they must act frequently; but 
the only effect which their contraction can be 
supposed to have is that of tightening and 
drawing in the tissues over them with which 
they are pretty closely connected. . 

The purposes served by the muscles of the 
nose are but few. Their action contributes 
little to the various expressions’ of the con- 
dition of the mind. The sneer of contempt 
is perhaps the only expression in which they 
take achief part. In extreme fear they appear 
also to be all contracted; but in this they are 
affected in common with the other muscles of 
the face, which all seem to be seized by a tem- 
porary spasm. Their other acts have reference 
to respiration, and are observed in their ex- 
treme degrees, in the dilatation of the nostrils 
to permit the freer ingress of the air in dys- 
pnea, and in their contraction in the endea- 
vour to perceive a slight odour, by drawing the 
air quickly upwards towards the seat of the 
most numerous filaments of the olfactory nerve. 

Integuments of the nose-—I\n their general 
characters these resemble the skin and mucous 
membrane of other parts: their peculiarities 
alone therefore need be here described. 

The skin of the nose is smooth and fine, its 
papillz being small and its cuticle very thin. 
It is soft, also, and pliant, and usually abun- 
dantly furnished with the sebaceous secretion. 
The hairs growing in it are numerous and ex- 
ceedingly fine, so that many have denied their 
existence; the largest and most closely set are 
at the lower part of the ale. The follicles 
enclosing them are deep and narrow; the co- 
nical pulps long and slender. The sebaceous 
glands are narrow and elongated ; they lie near 
the sides of the follicles, have very short ducts, 
and are placed at but a little distance below 


730 


the surface of the skin. Their secretion is 
copious, so that after death a mass of seba- 
ceous matter may be squeezed from. the orifice 
of each hair-follicle; and their ducts as well 
as the follicles themselves are said to be espe- 
cially liable to be infested by the acarus fol- 
liculorum \ately discovered by Dr. Simon.* I 
find none of the simple utricular follicles de- 
scribed by Cloquet and others in the skin of 
the nose; probably they were empty hair fol- 
licles. 

On the upper three-fourths of the nose, the 
skin moves freely on the subjacent bones and 
cartilages, a thin layer of pliant cellular and 
adipose tissue being placed between them. In 
the lower fourth, and especially about the base 
of the nose, the skin is thicker and more com- 

ct than it is above; there is very little fat 

neath it, and what there is is arranged in 
‘small and discrete granules; and the cutis, 
muscle, and fibrous membrane are so closely 
connected that they are moved together as one 
mass. 

At the nostrils the skin of the nose turns in- 
wards and is continuous with the mucous 
membrane, which, after lining the nasal fosse 
and the cavities opening into them, is con- 
tinued into the pharynx through the posterior 
nares, and into the nasal duct and Eustachian 
tube. The boundary between the skin and 
mucous membrane cannot be strictly drawn. 
It may be fixed, however, at the part just below 
which those hairs are implanted which con- 
verge from the inner circumference towards the 
centre of the nostril, so as to entangle any light 
body floating in the inspired air. These hairs 
are of the kind named wibrisse. Like the eye- 
lashes they are short, stiff, slightly curved, and 
pointed at their free extremities; and they are 
peculiarly well adapted for examining the mi- 
nute structure of hair. In them also, as well 
as in the eye-lashes, one may best see the mode 
in which hairs are shed. In all which fall off 
spontaneously, or which, being about to fall, 
may be pulled away without pain, the conical 

’ cavity at the lower end, into which the vascular 
pulp fitted, is closed, having gradually con- 
tracted and shifted itself off the pulp as the 
hair ceased to be nourished and died. 

The follicles of these hairs are similar to 
those of the hairs of the externa! integument, 
and each of them is associated with sebaceous 
glands, which, like those accompanying the 
hairs about the orifice of the vagina, are more 
numerous than in parts less exposed to the con- 
tact of fluids. A whorl of four or more small 
glands is often associated with a single hair- 
follicle; and when the hairs fall off, and their 
follicles partially close, the glands open, as if 
directly, by a common duct upon the surface. 

The mucous membrane (Schneiderian or pitu- 

itary membrane) of the nose is far from uni- 

form in its different parts. It is everywhere, 
and in some parts inseparably, connected with 
the periosteum or perichondrium which imme- 
diately covers the bones and cartilages, and 
which is often spoken of as the internal or deep 


* Miiller’s Archiv. 1842, p. 218. 


NOSE. 


layer of the fibro-mucous membrane ; but, whe 
the latter is in all parts nearly similar, differing — 
only in thickness and degree of ity, 
the mucous membrane itself presents con- 
siderable diversities. a 
In the antrum and other supplemental cavi- 
ties of the nose the mucous membrane is th in, 
but little vascular, and of the simplest kind, 
having neither papille nor glands embedded 
in it. On the turbinated bones, the septum, 
and the floor of the nostrils, it is thick, spongy, 
red, and turgid with blood collected in the 
lexus of large vessels in its areolar tissue. 
ese vessels seem to form in some partsa 
distinct layer between the perios and the 
proper mucous membrane, but they are ex 
actly analogous to those of the areolar or sub 
mucous tissue of other compound 
membranes, in all of which there is a plane o 
large vessels from which those of smaller si 
ascend to the a tus disposed u tb 
surface. In die hneiderian pratt oe he 
veins of this plexus far exceed the arteries it 
size, and their close connection with the vein 
within the skull may be a provision for re 
lieving the latter when subjected to an undt 
pressure of blood. The epistaxis of pletho 
rsons and of those who read hard 
as its origin in this connection; for the pr 
sure of the blood in the congested cereb 
vessels being communicated to the walls” 
these of the mucous membrane, these w 
burst more readily than those which are 
every side supported by scarcely yielding 
ra The size of these veins, too, nd 
cility with which they permit distens 
(almost resembling in this the veins of 
erectile tissue,) account for the rapidity 
which the membrane sometimes swells up, 
as ina minute or two to obstruct the pass 
of the nose. ' 
The free surface of that portion of the 
cous membrane which lines the proper cat 
of the nose is smooth. It presents the oril 
of many simple follicles or crypts. 
most numerous about the lower and 
parts of the walls of the fosse, are of 
sizes, and in many places lie in or 
The follicles hemnpclvad are hemisphe i 
deep and more or less elongated. 
and anterior part of the septum, there is 
a single long duct running horizontal 
leading to a collection of gland-cells wh 
appear to open into it; and, generally 
others of the larger orifices are connect 
composite glands. “—- 
The epithelium of the nose is, in part 
laminated, in part of the ciliary, kind. — 
says that if an imaginary plane section 
nose be made from the anterior free be 
the nasal bones to the anterior na: 
the superior maxillary bones, all the 
membrane below and in front of this 
covered by laminated epithelium, and a 
and behind it by ciliary epithelium. The 
covers not only all the walls of the nasal 
but is continued from them to the sui 


MmuUuc 


Rt 


* Allgemeine Anatomie, p. 246, 


“ 


NOSE. 


: the mucous membrane lining all the supple- 
mental cavities, the nasal duct and lacrymal 
sac, and the upper part of the pharynx. 

The course (as it is called) of the mucous 
membrane next merits consideration. Ascend- 
ing from the floor of the nasal fossa up the 
outer side of the inferior meatus, it becomes 
gradually thicker and more spongy. From this 
meatus it is continued anteriorly into the nasal 
duct, around whose lower orifice it forms an 
annular fold or reduplication. The orifice in 
the bones is elliptical and rather obliquely 
placed, its anterior edge being somewhat lower 
than the posterior. The fold of mucous mem- 
brane around it is especially deep on the inner 
side and posteriorly, and not only contracts 
the size of the orifice, but acts as a valve to 
_ guard it, and, when pressed upwards and for- 
_ wards, to close it. Hence, though some per- 
sons can inflate their lachrymal sacs, in most 
men, when the nostrils are closed, and air is 
_ pressed forcibly into the nose from behind, 
__ hone ever escapes from its cavities. 

___ As the lining membrane descends again upon 
_ the outer surface of the inferior turbinated bone, 
it becomes thicker, more spongy, and more vas- 
_ cular. At the lower edge of the bone it forms 
a deep fold, which, in its congested state, 
touches the floor of the cavity. The fold is 
peculiarly thick at the two ends of the bone, and 
in disease in scrofulous children it sometimes 
_ forms a loose and very vascular spongy mass, 

which has been mistaken, it is said, for a poly- 
F 4G Immediately behind the deep posterior 
fold the membrane becomes again thin and ad- 


heres closely to the pterygoid plate of the 
‘Sphenoid bone, behind which, and on a level 
with the extremity of the inferior turbinated 
 boné, it is continued into the orifice of the 
_ Eustachian tube. 
As it passes from the inferior turbinated bone 
_ to the outer wall of the middle meatus, the 
_ Schneiderian membrane becomes again thinner 
and more compact. About the middle of this 
‘meatus it enters the deep channel of the infun- 
_ dibulum, whose form it scarcely alters, and 
_ along which it passes to the anterior ethmoidal 
 ¢ells, and through them to the frontal sinuses.- 
_ Above the commencement of the infundibulum 
_ it enters into the antrum by a narrow orifice 
directed obliquely from before backwards. Of 
"the great opening into the antrum when the 
Superior maxillary bone is separated, a large 
Portion is covered by the palatine and turbi- 
nated bones ; and of what remains, all but a 
Narrow circular orifice at the upper and anterior 
‘part is closed by a thick annular fold of the 
mucous membrane; and even permanent closure 
is no rare consequence of the swelling to which 
the membrane is subject. Cloquet* says that 
this fold contains in man a gland with numer- 
ous orifices analogous to one of large size which 
Surrounds the orifice of the antrum in many 
animals. I have not been able to find such a 
structure, and even E. H. Weber+ has not been 
more successful, 


* Osphresiologie, p. 247. 
+ Hildebrandt’s Anatomie, Bd. iv. 


731 


The membrane covering the middle turbi- 
nated bone and the anterior portion of the cel- 
lular part of the ethmoid is thick and spongy, 
but less so than that on the inferior turbinated 
bone. In the superior meatus it is thin; and 
it becomes still thinner as it passes into the 
one or more orifices of the posterior ethmoidal 
cells, on the borders of which it is tightly ap- 
plied, and whose size, as it forms no loose pro- 
jecting fold, it diminishes but little. It closes, 
at this part, the spheno-palatine foramen} and 
in the vault of the nasal fosse all the foramina 
of the cribriform plate, through which nerves 
and vessels are admitted to the outer surface of 
the mucous membrane, and the inner surface 


‘of the periosteum. At the lower borders of the 


superior and middle turbinated bones it forms 
thick folds, which make the meatus appear far 
smaller than they do in the dry bones. These 
folds are not so deep as that on the inferior tur- 
binated bone; but, as they probably receive 
many filaments of the olfactory nerve, both they, 
and perhaps the inferior fold also, may be 
regarded as means for the multiplication of the 
sensitive surface, and as analogous, in some 
measure, to the folds of mucous membrane by 
which alone in Fish and the Proteus anguinus 
the same object is attained 

In all the rest of its extent over the septum, 
the nasal bones, and the lateral cartilages, the 
Schneiderian membrane has a uniform surface 
and is of about middle thickness: its layers 
are intimately united, and it adheres with mode- 
rate firmness to the bone and cartilage. 

Nerves of the nose.-—The olfactory nerve, 
or, as it may be more properly called, the 
olfactory lobe of the brain, arises from the 
posterior, inner, and inferior part of the an- 
terior lobe of the cerebrum. It lies in the 
groove between the two most internal of the 
convolutions of this part of the brain, and may 
be divided into three parts ;—the posterior, 
or pyramid, the anterior, or bulb, and the 
middle, or proper ¢runk of the nerve or lobe. 
At its origin it may be traced backwards into 
three roots. Of these, the outer or long root 
appears first in the fissura Sylvii at the junction 
of the anterior and middle lobes of the cerebrum, 
just above the trunk of the middle cerebral 
artery. Hence, its chief portion proceeds in- 
wards, forwards, and a little downwards on the 
under surface of the anterior lobe and in front 
of the substantia perforata antica; and on 
coming near the other roots it turns more 
directly forwards and unites with them at the 
beginning of the groove between the two convo- 
lutions. In this course it receives on its outer 
border.one or more separate fasciculi, which 
come from the deeper part of the lobe and are 
sometimes completely concealed by grey mat- 
ter covering them. 

The inner or short root is first visible at the 
inner and posterior part of the anterior lobe of 
the cerebrum, in front of the beginning of the 
fissura Sylvii, and just outside the great me- 
dian division of the cerebrum. It consists of 
one or more fasciculi, and passes outwards and 
forwards to the commencement of the groove, 
where, curving round like the preceding, but 


732 


in the opposite direction, it joins the other roots 
to form part of the pyramid. 

The middle root* arises between the two 
preceding roots, and first appears in two or 
three bands of fibres just in front of the sub- 
Stantia perforata antica, whence they proceed 
forwards to join the other roots. 

Each of these roots is connected with grey 
matter prolonged from the surface of the ante- 
rior lobe and the fissura Sylvii, and especially 
from two slight elevations, one of which lies in 
the concavity of the internal, the other in that 
of the external, root, as they severally turn for- 
wards where they join the middle root. The 
grey matter connected with the external root 
covers part of its origin, is continued along 
both its sides, and conceals more or less the 
filaments which join its outer border. Then 
connecting itself with the grey matter around 
the fibres of the middle root, they pass forwards 
together, and are lost near the apex of the pyra- 
mid ; part of them entering its substance, but 
a greater portion forming a thin layer (propago 
cinerea externa) which covers its surfaces, 
especially the upper one. The grey matter 
connected with the inner root conceals many of 
the fasciculi of its origin, and two streaks pro- 
ceed from it, of which one passes into the inte- 
rior of the pyramid, separating the internal and 
middle roots, and the other, of much larger 
size, is continued over its surface. This latter 
is the middle or grey root of Cloquet, &c. (the 
propago cinerea interna.) It has a somewhat 
pyramidal form, and covers a part of both sur- 
faces of the pyramid, but chiefly the upper 
surface. Its deepest edge penetrates to the 
middle root, and its outer edge sometimes 
joins the superficial layer covermg the other 
roots. As it proceeds forwards it becomes 
more and more slender; and it is prolonged 
further on the upper than on the lower surface 
of the pyramid, near the apex of which it ceases. 

Thus, the pyramid of the olfactory nerve is 
formed by three fasciculi of white filaments, 
separated by streaks of grey matter, by which also 
it is covered on both its borders and on a great 
part of its upper surface. It is between two and 
a half and three lines long ; its base lies in the 
angle where the two internal convolutions of the 
anterior_lobe diverge; and at its anterior extre- 
mity, becoming gradually smaller and flatter, it 
is continued into that which may be called the 
trunk of the nerve, the éractus olfactorius. This 
is nearly flat: it is grooved along the middle of 
its under surface, which rests on the upper part of 
the body of the sphenoid bone, and has a ridge, 


* Confusion has arisen in the use of this name. 
The root here meant is that called middle root by 
Soemmering, Sir C. Bell, Mr, Swan, and Valentin. 
Weber and Hildebrandt, and Cloquet call that mid- 
dle or grey root which lies above the others, and 
forms a thin grey band on the upper surface of the 
nerve: and under the internal root they include, as 
Haller and others did, who described only two roots, 
both the intefnal and middle ones. The names 
. here adopted are preferable, because the white 
fasciculi alone could properly be regarded as roots 
of a nerve, they alone being continued to the 
branches, and becanse their arrangement is more 
constant than that of the grey matter. 


‘ 


NOSE. 


or is altogether convex upon its u surface, 
which lies in the cropee' betereee thay enone 4 
tions. It is striated in its whole length, and — 
nearly white; though some matter is col- 
lected within the meshes of the plexuses, which _ 
its fibres form as they proceed forwards and a — 
little inwards towards the bulb in which they 
expand. After long immersion in spirit, the 
groove on the under surface of the trunk, 
which, in the recent state, varies much in 


in different persons, always becomes deeper 


and more distinct. Valentin* suggests 
indicates the course of the canal which in the 
human embryo from the lateral ventricle 
to the end of the olfactory bulb. The analogue — 
of this canal is persistent in the olfactory nerves 
of lower Mammalia; but there is no sufficient - 
evidence of its having been ever seen in the 
human adult; at least in this part of the 
nerve.t a 
The bulb of the olfactory nerve is a nearly — 
elliptical flat body, about half an inch long, 
slightly furrowed above, convex on its lower 
surface, and evenly rounded in front. It rests” 
be the dnra mater covering the cribriform 
plate; its inner margin is in contact with that 
covering the crista galli, and with the anterior 
part ts falx cerebri; by which alone it is 
separated from the bulb of the onperes ide 
It is of a greyish-red colour from the quantity 
of grey nervous matter which is placed upoi 
its surface and among the plexuses formed b 
the nervous filaments within it. In its in 
a small cavity or ventricle may be ge 
detected by a vertical antero-posterior section 
it is the remains of the embryonic conditio1 
just alluded to. a 
From the lower surface of the bulb procees 
the numerous branches of the olfactory nerve 
They vary much in number and size both | 
different persons, and on the two sides of th 
same individual; a want of symmetry whic 
may often be seen in the perforations of 
cribriform plate. The ordinary number o 
branches is from fifteen to twenty on each sidi 
Each of them, invested by a very delicate ne 
rilema, passes through an aperture in the erik 
form plate, through which also a tubular 5 
longation of the dura mater passes and becot 
continuous with the periosteum of the ni 
fosse. The nerves, which become rather fin 
when they have passed through the cribri 
plate, ramify between the periosteum and 
mucous membrane, and are divisible into ~ 
chief sets, some being placed apon the sept 
others upon the outer wall of the nose. 
The internal or septual branches are a 
twelve in number. After passing through 
cribriform plate, they diverge a little as 
descend; the anterior going somewhat forw 
the posterior backwards. The trunks soon 
often while within the foramina of the | 
form plate, break up into tufts of filar 
which unite into plexuses with long and na 
quadrilateral meshes; and from these, sn 


* Soemmering, Vom Baue des Menschl. | 
pers. Bd. iv. p. 2 a 
+ See on this question Cloquet’s Osphres 

and Metzger’s Historia, 


oar 


po il 
TL 


Branches of the olfactory and naso-palatine nerves on 
the septum of the nose, 


branches proceed which again form finer plex- 
uses. They may be traced nearly to the lower 
fourth of the septum. 
. The external or labyrinthic branches are 
_ rather more numerous and smaller. They 
_ diverge and ramify like the preceding, lying in 
the channels and grooves upon the upper two 
 turbinated bones. They have been traced to 
the lower border of the middle turbinated bone, 
but not to its outer concave surface, nor to any 
part below it; yet the similarity of the structure 
and arrangement of the inferior turbinated bone 
and the mucous membrane over it makes it 
. very robable that they ramify on it also. The 
mi dle branches are the longest; the posterior 
_ ones form curves directed backwards towards 
e sphenoidal sinuses, but not entering them. 
the posterior angle of the middle turbinated 
1e some of them are described by Mr. Swan* 
_by Soemmering as anastomosing with a 
nch from the spheno-palatine ganglion ; but 
falentin + could not find any such communica- 
ay tion. A few branches in addition to these are 
_ said to be distributed in the membrane covering 
_the cribriform plate itself (Cloquet). 
How the primitive filaments of the olfactory 
ere terminate has not yet been ascertained ; 
their softness and the density of the tissue in 
which they lie have hitherto prevented an accu- 
rate observation of them in this part of their 
____ Compared with the other nerves the olfactory 
_ present many peculiarities of structure and 
arrangement, especially in the part which is 
within the skull. 1. They are the softest of the 
_ herves within the skull, possessing only the 
_ most delicate neurilema; and a rather less de- 
i‘) ee this softness is characteristic of their 
4 ranches, so that their dissection is more diffi- 
cult than that of any others of equal size. 2. 
They have grey nervous matter both upon and 
. Ween their fasciculi, and their bulbs are not 


1 ga Bee oenirations of the Nerves, folio, p. 14, pl. 
x1. . . . 
+ Loc. c. p. 303. 


NOSE. 


733 


like the ganglions of other nerves, but like 
portions of the brain, 3. They are not, as 
other nerves, cylindrical, but triangular in one 
and flat in another part of their course. 4. 
Their trunks converge, while those of all 
others diverge from their origins. 5. They 
liein deep furrows on the surface of the brain, 
and they leave the skull by several distinct 
orifices. In many of these characters they are 
more like portions of brain than nerve ad, 
as Valentin observes, there is no other ner 
in the adult human body which shows its 
origin as an immediate prolongation of the 
central nervous mass so plainly as these do. 
It was on account of these characters that the 
olfactory nerves were regarded by the an- 
cient anatomists as processes of the brain 
(mamillary or papillary processes), through 
the central canals in which they supposed 
that the pituitary humour was carried from 
the lateral ventricles to the nose, and air was 
drawn into them by the nostrils. And al- 
though this notion was derived from dissect- 
ing the nerves of animals in which the trunks 
remain hollow, yet their true nature was 
doubted on the same grounds by many, even 
after Willis had demonstrated their structure in 
man.* 

In accordance with its numerous offices, the 
nose receives, in addition to these,—the nerves 
of its peculiar sense,—others for common sen- 
sation, for the movements of its muscles, and 
for the government, in some degree at least, of 
the organic processes which are carried on in 
it. Its sensitive and organic nerves are de- 
rived from the internal nasal or ethmoidal 
branch of the first or ophthalmic division of the 
fifth, from the naso-palatine and numerous other 
branches, from the spheno-palatine ganglion, the 
nasal branches of the Vidian, palatine, anterior 
dental, and infra-orbital nerves; all of which 
are described under the title Frrru parr or 
NERVES. Its motor nerves are supplied by 
the facial or seventh pair [SEVENTH PAIR OF 
NERVES]. 

Vessels of the nose.—Its arteries are derived 
from the ophthalmic, the internal maxillary, 
and the facial. The ophthalmic artery gives it 
the anterior ethmoidal, which enters with the 
ethmoidal nerve, the posterior ethmoidal, and 
the nasal, which anastomoses near the angle of 
the eye with the angular branch of the facial 
artery. From the internal maxillary trunk the nose 
and the adjacent cavities are supplied through 
many branches, namely, the alveolar, which 
sends branches into the antrum, the infra-or- 
bitar, of which the terminal branches partly 
supply the skin, the Vidian, anterior palatine, 
pterygo-palatine, and spheno-palatine, each of 
which, as it passes towards or through the canal 
after which it is named, sends branches to the 
mucous membrane of the adjacent part of the 
nose or of the cavities opening into it. From 
the facial artery branches are derived both 
through the superior labial and from the trunk 
itself. Indeed, the dorsal arteries of the nose 
may generally be regarded as the termination 


* See Cloquet, and Metzger, I. c., and Sprengel, 
Histoire de la Médecine, iv. p. 69. 


734 


of the facial artery, for they are usually larger 
than the angular artery, which is given off as a 
branch from one of them. They chiefly supply 
the skin and muscles; they form a complete 
network over the nose, and those of one side 
anastomose freely in the middle line with those 
of the other. Many of their branches also 
pass between the cartilages or turn in at the 
nostrils and supply the anterior part of the 
mucous membrane. 
_ _ The veins of the nose, so far as they are 
known, are associated with its arteries. Their 
communication with the veins within the skull 
has been already mentioned. The anastomosis 
is chiefly effected by means of the branches of 
the ethmoidal and aphenc- palatine veins, which 
communicate with branches opening into the 
longitudinal and coronary sinuses. 

The lymphatic vessels of the nose have not 
been particularly examined. Cloquet says 
their principal trunks accompany the blood- 
vessels and go to the jugular ganglia. 

Developement of the nose—The develope- 
ment of the nasal cavities lays, as it were, the 
foundation for the construction of the face.* 
They are first formed as a kind of canal, whose 
lateral walls are chiefly composed by the ante- 
rior and lateral frontal processes of Reichert— 
those processes which grow out from the sides 
of the covering of the first cerebral vesicle 
(Stirnkappe ), in front of the first visceral arch. 
This canal has on its outer side and behind it 
the rudimental substance for the upper jaws, 
(the superior maxillary processes of Reichert,) 
and above it the base of the skull and the 
origins of the first pair of visceral arches thence 
arising. As the upper jaws grow with a rapi- 
dity far exceeding that of the growth of the 
frontal processes, they come at last to form 
alone the lateral walls of this canal, while the 
frontal processes form its inner walls; and, 
together with those changes, the canal becomes 
deeper, and its external apertures, which at 
first lay at the sides of the head between the 
two frontal processes of each side, approach 
the median line, and assume a lower position. 
After this, as the upper jaw of each side, con- 
tinuing to grow inwards, approaches that of 
the opposite side, they at length unite to form 
the palate, and thus separate the common ca- 
vity, which at first existed, into an oral and a 
nasal cavity. 

Of the parts just mentioned, the anterior 
frontal process is regarded by Reichert as the 
basis in which the nasal bone is developed ; 
and the lateral frontal, or naso-frontal process 
as the basis for the lachrymal bone. The supe- 
rior maxillary bone appears to be developed in 
the part named after it; the intermaxillary bone 
in a portion of the anterior frontal process, or 
its junction with the superior maxillary pro- 
cess; the palate bone and the pterygoid pro- 
cesses in the upper part of the first visceral 
arch. 

The formation of the parts within the nasal 
cavities is, he says, thus effected: within the 

* Reichert, Ueber die Visceral-bogen, Miiller’s 


Archiv. 1837, pp. 144 and 159. This account is 
drawn from the developement of the Pig. 


. 


NOSE. 


formative substance enclosed between the walls 
of the one rudimental cavity two cartilages 
form; one of these is the prolonged cartila- — 
ginous body of the first cephalic vertebra which _ 
forms the septum of the nasal cavities, and m 4 
be traced without any breach of continuity to 
their outer orifice, where it ends membranous 
in the adjacent formative mass. The other — 
cartilage is double, and appears somewhat — 
later than the preceding, on each side of which 
it lies close to the lower of the first ce- — 
phalic vertebra, with an arched surface directed — 
outwards to the eye. Each of these second, or 
lateral cartilages becomes the cellular portion — 
of the ethmoid bone, the lamina wee 
and may be easily separated from the vertebra 
and its visceral arch, from which its formation 
is entirely distinct. Even for some time after 
they are ossified this separation may be effected — 
without injury to the surrounding parts; but at 
a later period they completely coalesce. J 
ossification of the septum takes place later than” 
that of the other bones of the face. In all 
Mammalia it makes progress from the base of 
the skull downwards and forwards, and in all a 
part of the septum in front and below is left 
unossified ; so that divisions are produce 
which had originally no existence. The vome 
Reichert thinks, is formed separately when thi 
SESE portions of the superior maxillary 
nes meet together. a 
The olfactory nerve is originally, like th 
optic and auditory nerves, a kind of vesicu! 
or tubular prolongation from the medulla 
tube which constitutes the cerebro-spinal as 
of the embryo. According to Valentin,* — 
proceeds from the most anterior A > of t 
tube, that is, from the foremost of the thi 
embryonic cerebral vesicles; but, according — 
Reichert, from the lower and front part of t 
side of the second of them. Von Baer+ fo 
the olfactory nerves presenting this vesicul 
form in the chick during the third day of 
cubation; they projected from the lower surf 
of each hemisphere into the formative ti: 
of the skull, and exhibited a small round | 
lucid surface bordered by a dark circle. Rat 
observed similar appearances in the sheep” 
adder. The interior of the vesicle is li 
according to Valentin, by a delicate ci 
epithelium. Anteriorly it appears to termi 
at the end of the olfactory bulb; posterior 
is continuous with the anterior part of 
lateral ventricles of the cerebrum. 4 
The early developement of the haman 
has not been particularly studied, but is 
bably very similar to that just described 
observations in the lower animals. 


i, 


Ina 
formed embryo an inch in length, I have 
the nasal cavities of etsaeiooe large 
On their lateral walls they present distinet 
of the rudiments of the two lower tarb 
bones in prominent horizontal folds of the 
membrane. The palate is at this time! 
only anteriorly and at its sides ; its midd 
tion is widely open, exposing to the 

* Soemmering, I. c. p. 404. 

+ Quoted in Bischoff, Entwickelung: 
(Soemmering, Vom Baue, &c. B. viii.) 


vend 
ve 
>. = 
ap 
~ il 


NOSE. 


below the free inferior border of the septum. 
The upper edge of the septum is firmly fixed to 
the base of the skull, and its posterior edge 
gradually slopes back to the upper and back 
rt of the wide cavity of the pharynx. There 
1S no appearance of a vomer; and the nose 
_ does not project upon the face. Its position is 
_ marked externally by the nostrils, which are 
elongated vertically, oval and narrow, situated 
about three-fourths of a line from the margin of 
the upper lip and at the like distance from each 
_ other. They are not at this time closed, but 
lead straight backwards into the common nasal 
and oral cavity. 

In the following periods the chief changes 
are effected by the gradual closure of the palate, 
the fixing of the lower margin of the septum, 
the developement of the vomer, and the growth 
of the anterior part of the septum and of the 
tudiments of the nasal and superior maxillary 
bones. With these changes the nose gradually 
becomes more prominent, and the nostrils, 
which at first look straightforwards, are gradually 
_ turned obliquely downwards, and at last are 
" directed as in the adult nearly straight down- 
_ wards. During the third and fourth months, 
according to Burdach, the nostrils are closed bya 
fine membrane, which in the fifth month is again 
removed. Together with the change in their 
_ direction already spoken of, the septum becomes 
"narrower and the distance between them is 
_ diminished. Changes perfecting these are con- 
_ tinued’ even long after birth in the gradual 
_ elevation and elongation of the bridge of the 
nose, and in the narrowing of its base ; and it is 
- in these changes subsequent to birth that noses, 
- which present little variety in infants, acquire the 
_ almost infinite diversities of form by which they 
characterize the faces of adults. 

_ Physiology of the nose—Most of the pur- 
_ poses to which the nose is subservient in the 
economy are described in otherarticles. [Smext, 
‘Laryyx, Mucus, Facz.] Here, however, it 
May be considered as the first portion of the 
Tespiratory passage, and as a feature character- 
fete of Be foumnan race and of its several 
varieties. 
___ Thenose is the proper channel through which 
the air is drawn into and expelled from the 
lungs. It alone is habitually used in respi- 
Tation by most animals, and though in man the 
_ Mouth is as often used in breathing as the nose, 
_ (and, indeed, oftener in our own climate, in 
~ which, from various causes, few persons have at 
all times both the nasal passages free,) yet it is 
not adapted to this office so well as to be used 
__ long without inconvenience. Most persons 

Must have suffered the discomfort of breathing 
j through the mouth during a few hours’ sleep : 
__all its lining membrane, as well as that of the 
_ fauces and of the upper part of the larynx, be- 
_ Comes dry, and an excretion of saliva must be 
artificially produced before the annoyance and 
the danger of choking can be removed. No 
such inconvenience attends the breathing 
through the nose for any length of time. Its 
More extended mucous membrane supplies a 
fluid sufficient to keep its own epithelium moist, 
and to saturate with vapour the air which passes 


735 


over it, so that this air does not abstract so much 
moisture from the surface of the epiglottis and 
the glottis as the drier air which has passed 
through the mouth alone. 

Again, the nose is far better adapted than the 
mouth is for the arrest of the particles of foreign 
solid bodies which float in the air. If such 
particles have passed through the hairs which 
lie at the orifices of the nostrils, and which are 
sufficiently close-set to stop even very minute 
bodies, they are in their further course liable to 
be caught in the irregular surfaces of the walls 
of the nasal fosse and entangled in the moisture 
of their lining membrane. Hence, most per- 
sons can breathe through the nose for some time 
without inconvenience even in a cloud of dust: 
and the nasal cavities of the horse and other 
Mammalia are, in this respect, still better 
adapted for the protection of the lungs. Some 
experiments were performed in France to de- 
termine whether great injury of the respiratory 
passages of horses were produced by their ex- 
posure to the dust of roads. Horses were made 
to trot for a considerable distance in the clouds 
of dust thrown up by the wheels of carriages 
driven before them ; they were killed directly 
afterwards, and not a particle of dust appeared, 
on the closest scrutiny, to have passed beyond 
their nasal fosse. 

The nose is further adapted to be the first 
portion of the respiratory passage by the acute 
and peculiar sensibility of its mucous mem- 
brane, and by the connection of its nerves in 
the nervous centres with the nerves of all the 
set of respiratory muscles. Through the ol- 
factory nerve the nose detects the impurity of 
the air from those gases whose deleterious pro- 
perties are indicated by odour; and its acute 
common sensibility affords a warning of the 
presence of any mechanical or other common 
irritant. The act of sneezing, which in this 
last case is excited through the already-men- 


. tioned connection of these nerves, is an ex- 


ample of that class of half-involuntary acts* 
which are consequent on acute sensations; and, 
in this respect, it is widely distinguished from 
the other reflex acts with which it is commonly 
classed, but which are never, or*at least not 
necessarily, connected with sensation. Every 
one must have felt that a certain acute sensation 
is necessary in order that a sneeze should occur; 
and if the sensation does not arise to that cer- 
tain degree of acuteness, the disposition to the 
sudden forcible expiration gradually passes off, 
though the act had been desired and had 
seemed on the point of being accomplished. 
In this respect sneezing is exactly analogous to 
coughing,—an act which is never thoroughly 
effected except in consequence of a certain 
acuteness of sensation at the glottis. And the 
analogy is maintained in this also,—that the 
cause of irritation which produces sneezing 
may be seated either in the nose itself, where 
it is always felt, or in another part. In cough- 


* They may be thus called, because, though the 
sudden and simultaneous exertion cf all the mus- 
cles concerned is involuntary, and almost inimitable, 
yet the putting them in a position for that exertion 
is always voluntary. 


736 NOSE. 


ing, the sensation which immediately precedes 
the act may be the consequence of direct irri- 
tation of the glottis, or of irritation of another 
such as the distant bronchial tubes, from 
which the impression is conveyed to the brain, 
and there, as it is supposed, is radiated to the 
central extremities of the nerves of the glottis, 
and is felt as if it were applied to their peri- 
pheral extremities. In either case the peculiar 
sensation at the glottis is the necessary pre- 
cedent of the act of coughing; and it is the 
same in sneezing. A sudden vivid impression 
of light upon the retina, or, sometimes, the 
irritation of a tender point on the skin of the 
face, produces a sensation of pain or irritation 
in the mucous membrane of the nose, and 
sneezing follows. The sequence of events may 
be supposed to be,—an impression on the peri- 
pheral filaments of the retina,—its conveyance 
to their central extremities in the brain,—its 
radiation to the central extremities of the sen- 
sitive nerves of the nose, producing the same 
sensation as if their peripheral extremities had 
been irritated,—and, through that sensation, 
whether it be objective or subjective, the half 
involuntary act. 

The great prominence of the external nose, 
and the comparative smallness of its internal 
cavities, form one of the most distinguishing 
characters of the human face. Cuvier has 

inted out how the relative proportion in size 
bctwieen the cranium and the cavities of the 
nose and mouth affords an indication of the 
approach towards perfection of the internal and 
intellectual faculties in comparison with the 
external or sentient. For the senses of smell 
and taste “ are those which act on animals 
with the most force, which most powerfully 
master them, through the energy which two of 
the most pressing desires, hunger and lust, 
communicate to their impressions.”* But in 
man the sense of smell is, in both these re- 
gards, subordinate to that of sight; and the 
developement of his internal olfactory appa- 
ratus is, in comparison with that of lower ani- 
mals, extremely small. In the varieties of the 
human race the gece of the sense and the 
developement of its organ are the less the 
more civilized their several habits of life are. 
Among ourselves, the blind alone maintain the 
sense in the energy of which it is capable, and 
in which it is said to be habitually exerted in 
some less civilized tribes. In the latter a 
greater developement of the organ of smell, 
and even of its osseous part, corresponds with 
its greater acuteness and the degree in which it 
is exerted. The greater distance between the 
orbits, which is especially remarkable in the 
Kalmucks and other Mongolian tribes, may be 
an indication of this greater developement ; 
but a more important one is the size and com. 

lexity of the turbinated bones. The nasal 
a of the skulls of Negroes are larger in all 
their dimensions than those of Europeans; and 
Soemmering,t in numerous examinations, found 
the sinuses within the middle turbinated bones 


* Lecons d’ Anatomie Comparée, ii. 160. 
+ Ueber die Verschicdenheit des Negers. 


constant in the Negro, though rare in others. 4 
Blumenbach* confirms both these observations, 
and mentions particularly the skull of a North- 
American Indian in his collection, in which — 
these sinuses were of extraordinary size. How- 
ever, these differences of size are probably not — 
a full measure of the differences of acuteness 
of the sense: it is most likely that in the nose 
as in the other organs of sense, acuteness ¢ f 
perception is connected with fineness of di- — 
vision, rather than with extent of distrib ation, 
of the recipient nerve. poe 
The prominence of the nose is even more 
characteristic of man than the smallness ¢ . 
cavities. In other Mammalia it stands out, 
indeed, much further from the skull, but is 
in company with the upper jaw, beans which 
it does not, as in man, project. For the same 
reason, the nostrils, which in man are hori- 
zontal and directed downwards, in adaptatiot 
to his erect posture, and to his hand ever ready 
to carry objects to them, are, in the lower ai 
mals, vertical. The nasal processes of the 
superior maxillary bones, also, lying flat ane 
being very broad, and the small-size of thei 
nasal bones, prevent the peculiarly hun 
elevation of the bridge of the nose. 
The forms of the external nose are amon 
the characteristics of the varieties of our sp 
cies. In all its almost infinite varieties of forn 
the Caucasian nose is on the whole narr 
elongated downwards, and elevated at # 
bridge; the Mongolian is flat eee 
at its base; the American less flat than 1 
Mongolian, but less prominent thau the Ca 
casian; the Ethiopian flat, broad, and ~ 
thick at its base; the Malay full and bro 
and, in general, thicker at its apex than | 
other varieties are. As for the varieties 
form in the individuals of the same rac 
nation, they have little, if any, physiolog 
interest: they are not known to have any ¢ 
nection with differences of function, and 
importance they have acquired is founded 
the unsupported notion that they are chai 
teristic of corresponding varieties of te 
and of intellect. 


MORBID ANATOMY OF THE NOSE. 
Congenital defects.—The extreme of th 
found when the normal state of the very 
feetus continues and the nose is nearly a 
Such a case is described by Soemmering. 
child was born at the full term: the brait 
malformed, and there were no olfactory t 
In place of nasal bones there was but one 
lens-shaped bone, and the ethmoid bo 
little developed: the eyes were close t 
but the orbits had not coalesced. A‘ 
example is mentioned by Roederer, in 
child with malformed ears had in place 
a scarcely perceptible elevation, no Ml 
and for nasal fosse a blind pouch form 
mucous membrane. Vrolik,t by whom 
cases are quoted, describes another | in a 
* Institutiones Physiologicx. £ 
+ Handhoek der Ziektekundige -Ontlee 
D. ii. p. 70. 


NOSE. 


which is in Sandifort’s museum, and in which 
the olfactory nerves and the nasal, lachrymal, 
and ethmoid bones are all absent.. 

Next to these are cases in which the nose 
exists, but has not its naturally complex form. 
Otto* describes two such in mature female 
anencephalous children. The nose was in both 
flat and broad; it had but one nostril, and the 
septum was absent. The inferior turbinated 
__ bones were approximated posteriorly, so as in 
_ one case to close the nasal cavity, and in the 
_ other to reduce it to a very narrow aperture 
_ pening into the pharynx. In one of these 

children, also, the olfactory nerves were absent. 
Sometimes a state like this exists on one side 
only. Vrolik+ mentions a child still living in 
which the right half of the nose was fully deve- 
 loped, but on the left side there was a kind of 
_ snout hanging from the root of the half nose, 
orated and giving passage to mucus and air. 
rofessor Broers cut off this appendage and the 

ure closed. 

The floor of the nasal fosse remaining in the 
_ state which it naturally presents up to the third 
_ month, constitutes cleft palate, a slight degree 
_ of which, since it produces no inconvenience, 
_ is more common than is generally supposed. 
_ When the membrane described as closing the 
nostrils after about the ninth week is not 
_ removed, the atresia narium results. Several 
_ cases fairly referable to this arrest of develope- 
_ ment have been recorded. 

_ Defects of developement at a later period 
_ are seen in the cases of absence of one or more 
sinuses, of which also several cases have been 
recorded. And with these, as errors of deve- 
lopement produced perhaps by some accidental 
presstre, may be enumerated the examples of 
extreme obliquity or curvature of the septum, 
in which the apex of the nose is turned com- 
pletely to one side or even backwards towards 
the cheek. Such are the cases for the remedy 
of which Dieffenbach has lately applied with 
success the subcutaneous division of the carti- 
_ tages and the adjacent contracted tissues.§ 
Another slight defect is that in which part of 
_ the septum is deficient, or in which the bone is 
ie ot but is closed by membrane. Haller] 
_ describes a case in which the vomer was com- 
_ pletely and widely perforated; but much more 
_ commonly the defect is in the vertical plate of 
the ethmoid bone. Very rarely there is an 
aperture in the cartilaginous part of the septum. 
‘The excellent anatomist Hildebrandt had a 
defect of this kind.{ 
| Aclass of cases, which, though congenital, 
cannot be certainly referred to-arrest of deve- 
_fopement, are those of fissure of the nose. 
Sometimes the nose alone is said to be divided 
deeply in the median plane,** and this may 


ee 


8 * Monstrorum sex centoram descr.anat.N.vii.viii. 
 t Lic. p. 260. 
__ t See Vrolik, 1. c. and Meckel, Handb. der pa- 
‘thologischen Anatomie, Bd. i. p. 107. 

asper’s Wochenschrift, Sept. 18, 1841. 
|| Elementa Physiologie, v. 137. 

Hildebrandt’s Anatomie, by E. H. Weber, iv. 


_™ Isidore St. Hilaire, Traité des Anomalies, t. i. 
p. 603. 
VOL. ILI, 


737 


represent the foetal state in which the frontal 
processes have not united, or in which the 
septum is not yet formed. But the cases are 
more numerous in which the fissure exists on 
one or both sides of the face. In some it 
extends from the angle of the mouth, through 
one or both ale of the nose, to the internal or 
external angle of the eye, laying into one the 
cavities of the mouth, nose, and one or both 
orbits. Four such cases, differing but little 
from each other, are recorded by Vrolik. He 
possesses also an example in which, in a much 
less degree of the same defect, there is only a 
fissure of the skin from the mouth to the eye 
by the side of the right ala nasi; and another, 
in which a deeper fissure extends in the same 
direction on both sides. These cases, how- 
ever, like those of hare-lip, cannot be regarded 
as mere arrests of developement: there is no 
period in which the foetus is known to present 
these as normal conditions. 

A very remarkable congenital defect in which 
the nose is concerned, is that of which the 
subjects have been called Cyclopian or Cyclo- 
cephalian monsters. It has been admirably illus- 
trated in a special memoir by Dr. Vrolik,* who 
points out five varieties of it, In the first, the 
eyes are absent or not externally visible, and 
the nose is either absent altogether or replaced 
by a kind of proboscis or snout-shaped member, 
consisting of little more than skin, and attached 
above the orbit. In the second there is a single 
orbit in the middle of the forehead which con- 
tains a single eye-ball, and above which there 
is sometimes a proboscis representing the nose. 
In the third, the eye appears externally to be 
single, but is internally double; and with this 
again the nose may exist in the form of a pro- 
boscis. In the fourth, the two eye-balls are 
separated, but they lie in one orbit in contact, 
or with only a narrow partition between them, 
and above them there is a proboscis which, as 
in the other cases, may be curved either 
upwards or downwards. In the fifth, the pro- 
boscis, approaching more nearly to the form of 
a natural nose, has an osseous nucleus, and is 
directed downwards; and the eye, above which 
it is placed, is either double or single. In this 
series, therefore, there is a regular gradation 
from the natural to the most unnatural condi- 
tion, in regard to both the nose and the eyes. 
For the eyes, there is in some no eye at all; in 
some a single eye-ball placed in the middle 
liné; in some again ar eye-ball, which appears 
single, contains parts of two; and in some two 
eye-balls lie close together in a single median 
orbit. For the nose, it is in some altogether 
absent; in some it exists in the form of a snout , 
which is little more than a prolongation of skin; 
in others it has a more or less well-formed 
osseous nucleus; in some it is curled upwards 
and backwards, in others directed obliquely 
downwards: and among all these there are 
numerous gradations of deformity. Now, any 
of these conditions of the nose may co-exist 
with any of those of the eye: there is no regular 


* Over den aard en oorsprong der Cyclopie, in 
the Transactions of the Netherlands Institute, Am. 
sterdam, 1836, and in his Handboek, D. ii. p, 14, 

3B 


738 NOSE. | 
correspondence between their respective degrees acne, in which all the d textures rto 
of Getlopenieck, This is soodewed by the be confused in one hard brawny su . 


cases of the monsters in which the eyes are 
completely absent, but the orbits are naturally 
placed and the nose is well formed; and by 
those others already mentioned, in which the 
nose is absent, but the eyes and orbits are 
natural and almost naturally placed. From all 
these, and from the constancy of the deformity 
of the nose when the orbits are united, it may 
be deduced that the eye and the nose are deve- 
loped independently, except in regard to their 
position, and that the displacement of the nose, 
which constitutes one of the chief features of 
the Cyclopian monsters, is generally the con- 
sequence of the orbits having taken up the 
place of the nasal cavities. 1t cannot be said 
that the displacement of the orbits is the only 
cause of that of the nose, because there are a 
few cases in which the nose occupied the 
Cyclops position, though the orbits had their 
natural place; and one case in which the orbits 
and eyes were absent, and yet the nose was 
elongated like a proboscis and set high upon 
the forehead. But these do not invalidate the 
truth of the general deduction already drawn. 

The displacement of the nose is thus ex- 
plained with much probability by the precedent 
displacement of the orbits, and the latter is 
probably due to an arrest in the develope- 
ment of the eyes. But the cause of the 
— deformity of the nose is very obscure. 

ere is generally some degree of relation be- 
tween the approach to completeness of the nose 
and that of the brain and its nerves, and es 
cially of the anterior lobes and the olfactory 
nerves : yet these nerves are sometimes present 
when the nose is most deformed, and when it 
has neither ethmoid bone nor cavity, nor even 
any osseous nucleus ; and in other cases they 
are absent when there is a distinct though mis- 
shapen external nose. Tiedemann’s suppo- 
sition, therefore, that these, like other malforma- 
tions of organs, depend on a precedent defect 
in the corresponding nerves or parts of the ner- 
vous centres, cannot be maintained. 

Diseases of the nose—These are so far gene- 
Her similar to those of the similar tissues in 
other parts that some of their peculiarities on! 
need be mentioned here. " $ 

The skin of the nose is perhaps more than 
any other part of the face subject to the erup- 
tions of acne, &c. And these acquire a some- 
what peculiar character from the small vessels 
of the nose being so liable to distension. In 
the common red nose, all the small veins are 
usually dilated and in a measure varicose; and 
even in healthy persons the circulation through 
the skin of the nose is carried on with com- 

ratively little force, if we may judge by the 
fequene with which it is partially arrested by 
cold. is dilatation of the vessels and con- 
sequent slowness of circulation not only render 
the diseases of the nose peculiarly obstinate, 
but permit them to produce changes of structure 
which are very rarely found among their defects 
in other parts. Such is the tuberculated indu- 
ration and thickening with deep red or livid 
congestion of the skin after long-continued 


When this state continues very long and the 
congestion somewhat abates, the thickened — 
tissues remain, and sometimes grow into a kind 
of pendulous tumour from the end of the nose. — 
Such tumours, (which, however, may form with 
little precedent acne,) are usually three-lobed, 
one portion seeming to correspond to the end, 
and one to the fore of each of the ale, of 
the nose. One which I dissected was com- 
posed throughout of a compact, white, fibro- 
cellular tissue, like that of which the pendulous 
tumours consist which grow from other parts o 
the skin, and especially from the female k 
It seemed very little vascular,* and the h 
follicles and sebaceous glands were enormously 
enlarged. Some of the latter measured not les} 
than a line ip width, and their ducts, 
opened at the bottoms of deep fosse, admitt 
full-sized bristles. The same enlargement 
these organs takes place in certain large growt 
of the skin of the scrotum, a 
The position of the cavities of the 
been an effectual hindrance to the examinatio! 
of the changes of structure produced by the 
ordinary diseases. Nothing is known of | 
State brought on by repeated colds. While the 
continue, the mucous membrane is gorged wil 
blood, swollen, and red, so as to close, with t 
assistance of the increased secretion of mueu 
the passage to the pharynx. Probably 
mucous membrane is in time cond l a 
thickened ; and from this it may result that 
looking over a number of sections of heads, | 
Schneiderian membrane is found by no me 
uniform in its thickness, consistence, or vas 
larity even on corresponding _ 
M. Mareschal+ has lately stated that, in 
examination of eight persons who had had 
taxis shortly before their deaths, he found i 
a circumscribed portion of the membrane wh 
was very congested, and dark red or livid. 
two of them this congested part was situa 
anteriorly, near the junction of the septum a 
the floor of the nostrils; in the others p 
riorly on the fold of mucous membrane ai 
lower border of the inferior turbinated bo 
Simple abscesses sometimes occur benea 
mucous membrane of the nose, especially 
injuries ; and after passing through an ore 
course leave their usual effects in thické 
induration, and unnatural adhesion of th 
trized tissues. ol 
A thickening of the mucous 1 a 
ting polypus has been already mention 
curs especially in scrofulous children and 3 
persons, and presents the same characters 
its duration and progress, which are obser 
the other chronic inflammations to wh 
are subject, and with one or more of wh 
commonly associated. This spongy thi¢ 


“> 
« 


‘te 


~ 


* Sir W. Blizard lost a patient h 
rhage after the removal of a tumour of th 
from the nose ; but it is possible that this 
have been owing to something wrong in the, 
state of the patient, for ennai li blood is” 
in such operations. ot all 

+ Annales de Chirurgie, Janvier, 1843. 


NOSE. 


usually affects at once the whole or a large por- 
tion of the membrane, though, of course, it is 
most obvious at the folds on the borders of the 
turbinated bones. It is sometimes attended 
by superficial ulceration or excoriation of the 
membrane ; but even without either of these 
the discharge has usually a purulent character. 
If it continue long, this chronic inflammation 
produces not a mere swelling, but a more solid 
thickening and induration of the membrane 
sufficient nearly to close the passage through 
the nose ; or if there have been ulceration of the 
membrane, a part of the passage may be closed 
by adhesion of the opposite surfaces of the 

‘thickened and approximated membranes. Such 
_ obstructionsare usually situated near the entrance 
of the nasal ducts, and when the swelling of the 
membrane which preceded their formation has 
decreased, they are drawn out, and look like trans- 
verse thin membranes passing across the cavity, 
just within the nostrils. Such obstructions are 
particularly apt to occur when, by obliquity of 
the septum, one of the nasal cavities is unna- 
turally narrow. 

Sometimes, from chronic inflammation of the 
mucous membrane of the nose, substances are 
produced altogether unlike the discharges com- 
monly seen. Mr. Cesar Hawkins, who has 
paid much attention to these diseases, speaks of 
“ several portions of substance like chalk in 
‘consistence, exceedingly fotid, and in shape 
exactly like the spongy bones: they were pro- 
bably composed of phosphate, or perhaps car- 
bonate, of lime, with fetid mucus secreted 
from the upper spongy bones.” A similar case, 

bably, in which a hard concretion was found 
™m a nose, is recorded by Dr. Grandoni.* In 
another case, Mr. Hawkins saw small bodies, 
like half-formed cartilage, which had the shape 
of the superior spongy bone, and which had 
been occasionally separated during many years ; 
and in another, a very tough and tenacious 
mucus which was constantly secreted from a 
_ soft and relaxed membrane covering a diseased 
_ vomer. The exact condition of the membrane 
in these cases has not been determined ; in one 
it seemed connected with diseased bone. The 
_ Secretion of earthy matter from it is perhaps 
_ analogous to that which produces the phosphatic 
_ inerustations of the diseased mucous membrane 

_ of the urinary bladder. 

___ The ulceration of the mucous membrane of 
the nose which attends this state of chronic 
inflammation is usually superficial. Deep and 
destructive ulcerations (such as give rise to the 
_ symptoms of Ozena) occur, however, under 
“Many circumstances; for example, from ne- 
_ glected injuries, scrofula, syphilis, &c. Their 
effects are often not confined to the membrane, 
_ but are propagated either to the skin, through 
all the intermediate tissues, or to the subjacent 
cartilage or bone, which then are ‘ulcerated or 
suffer necrosis secondarily, as, more rarely, they 
do primarily. The appearances of the ulcers 
from various causes do not materially differ. 
They may commence in any part of the nasal 
cavities; but they are said to be most frequent 


_ * Annali Universali di Medicina, Ottobre, 1840. 


739 


near the exterior in common or scrofulous ul- 
ceration, and in the more interior parts of the 
membrane in syphilis. Their first appearance 
is in the form of a small pustule or collection 
of matter beneath the membrane; and the 
ulceration by which this opens externally makes 
progress more or less rapidly, spreading in 
both extent and depth without any signs. of 
resistance to its course in the adjacent textures, 
When such ulcers have exposed the cartilages, 
these are gradually perforated by the ulcerative 
process; they do not suffer necrosis, but in 
this, and probably in all their morbid changes, 
they follow the course of the articular cartilages, 
which they resemble in their structure and in 
their exemption from being ossified. The sep- 
tum is the part in which the effects of such 
ulcers are most commonly seen. Sometimes 
it is perforated through its centre, and, in these 
cases, though the aperture be large, the shape 
of the nose may be unaltered, for the remain- 
ing borders are sufficient for its support. But 
when a part of these borders is destroyed, de- 
formity is the certain result; the point of the 
nose is drawn backwards and downwards when 
the lower part of the septum is destroyed ; or 
the middle of the bridge falls in, and the, point 
projects and is turned upwards when the upper 
part is lost; or, when the destruction is more 
general, the nose falls nearly flat below the 
nasal bones. When the ulceration reaches the 
bones it may continue to spread through them, 
destroying them gradually without necrosis; 
or, if its progress be rapid, or matter collect 
beneath the periosteum, so as to expose a large 
surface of bone, this being deprived of its 
supply of blood, perishes and gradually ex- 
foliates. Thus, the nasal bones, or large por- 
tions of the septum, or the turbinated bones, 
and parts of the palate may be destroyed, and 
the most hideous deformities be produced. 
Sometimes, no doubt, the syphilitic affections 
of the nose may commence in the bones or 
cartilages themselves; but, most commonly, 
they are affected secondarily after being ex- 
posed by the destruction of the mucous mem- 
brane. In the worst cases, the ulceration 
spreads with a ragged sloughing to the mem- 
branes of the palate, pharynx, and other ad- 
jacent parts, and through them to the bones 
and other tissues which they cover. The dis- 
ease has its centre of severity in the nose, but 
the pain around the nasal cavities indicates a 
simultaneous slighter affection of the adjacent 
sinuses; sometimes, also, it extends to the 
membranes and substance of the brain; and 
sometimes it passes up the nasal duct and pro- 
duces all the signs of fistula lacrhymalis. 

Polypi.—The mucous membrane of the nose 
is more subject than any other part to the 
growth of polypi, which may occur in either 
one or both of the nasal fosse, or in the cavi- 
ties adjacent to the nose. Those which grow 
in the fosse, and which alone will be con- 
sidered here, are of several kinds, and, though 
the lines of distinction cannot be clearly drawn 
between them, are commonly arranged as 
vesicular, gelatinous, fibrous, and malignant 
polypi. 

3B 2 


740 


The vesicular polypi, or, as they have been 
called, hydatid polypi, are composed of masses 
of large, pellucid vesicles, filled by a trans- 
parent and slightly viscid fluid, or consist of a 
substance somewhat like the vitreous humour. 
They can be broken by a very slight force, and 
after they have discharged their fluid nothing 
remains but shreds of fine membrane, like 
films of washed fibrine. They commonly grow 
from the upper and side walls of the nasal 
fosse, and their growth is very rapid. They 
frequently also burst spontaneously, discharge 
their contents, and are reproduced ; and their 
reproduction is almost always very rapid when 
they are artificially destroyed, and the patient 
is not in other respects effectually treated. The 
thin membrane investing them is easily per- 
meable, and their size varies according to the 
rapidity with which evaporation can take place 
from them, so that they may serve as a sort of 
hygrometer, indicating by their size the relative 
quantity of moisture in the atmosphere. Their 
nature is as yet unknown; they are probably 
entirely new productions, and not, as some 
think, distended mucous follicles. 

Gelatinous polypi are more common than 
those of any other kind, and are those which 
are commonly called mucous polypi, though, 
under this term, Boyer and some others in- 
clude both these and the preceding variety. 
They are much firmer than the vesicular polypi, 
and grow in one or more distinct and circum. 
scribed masses. They are of a dull white or 
yellowish colour, soft and easily torn, com- 

osed of a fine tissue with fluid infiltrated in 
it, like anasarcous cellular membrane. Gene- 
rally they appear to have a few opaque white 
filaments running through their substance, and 
their surface and interior are traversed by long 
meandering bloodvessels. When small, they 
are nearly round and elongated; but as they 
increase they adapt themselves, as the other 
kinds also do, to the form of the nasal cavities, 
spreading towards their apertures, but rarely 
having sufficient force of growth to expand the 
firmer parts of the nose. They almost always 
grow nearer the anterior than the posterior 
nares, from about the middle of the outer wall 
of the nose, ,or from the middle turbinated 
bone, to which they are fixed by a narrow base 
more or less deeply rooted in the tissue of the 
Schneiderian membrane, and sometimes tightly 
adherent to the bone. It is only very rarely 
that this or either of the other innocent forms 
of polypus grows from the septum; but Mr. 
Hawkins has seen one example. Sometimes 
one only grows at a time, but more often there 
are several crammed together. They are co- 
vered by a fine membrane, like a thin con- 
tinuation of the mucous membrane of the nose, 
like which, also, it is said to be va Ne by 
ciliary epithelium and appears to produce 
penne im polypus of this Kind, which I re- 
cently uietinet: was composed throughout of 
a tough interlacement of fine, crooked, pale 
filaments like those composing a fibrinous coat 
of blood, in which there were thickly em- 
bedded a vast number of flat, circular, granu- 
lated cells, or cells with granulated nuclei. 


NOSE. 


Each cell was about 3th of an inch in di- 
ameter, and in each, three or four of the gra- 
nules appeared much darker than the rest. T 
whole presented on dissection a tough fibrous _ 
grain, and appeared to the naked eye much 
more highly organized than the microscope 
proved it to be. From its minute structure, 
which resembled in its general characters — 
that of many other kinds of tumours, it is — 
evident that these polypi, as well as the last, — 
are not mere changes or out-growths of 
mucous membrane, but are altogether new pro- 
ductions and belong to the class of tumours 
rather than to that of degenerated tissues. 
Fibrous, sarcomatous, or lypi are 
masses of firm, well organized, and vas 
tissue, growing like the others from a com= 
paratively small base. Their substance is of a 
pale reddish or brownish colour, and they are 
invested by a thin smooth membrane. In 
ferent examples their degrees of firmness differ, 
so that, on the one hand, it is not easy to drat 
a line between this and the i iety 
this | 


and, on the other, some specimens” 
found nearly as hard as the denser fibrous 
tissues. The base, or pedicle, of these growth 
is usually firmer and more fibrous than the res 
of their substance, and parts of them are com 
posed sometimes of tissues like cartilage « 
bone. Like the preceding they grow from th 
outer wal] of the fosse, but from the poste 
more often than from the Sc Som 
times one only is produced, so aver 
and their force and rapidity of growth are s 
ficient to stretch, if unchecked, all the 
around them, to expand and the | 
and protrude through the skin of the 
where ulcerating they may present nearly 
the characters of enaligaiiat diseases. — 
this resemblance to malignant growths becoi 
the greater from the polypus itself sof 
and growing more vascular on its surfac 
even throughout its substance. -_ 
The apparent transition from the precedi 
to this variety of eee a makes it probah 
that these also are new formations; and th 
they are sometimes firm and apparently fib 
even when they are very small, yet pe 
they are often produced by the further 
lopement of the gelatinous variety. _Mr. 
kins says that, in general, when the pr 
grows from the surface only of the 
membrane it is soft and gelatinous; but 
whole thickness of the membrane, ine 
also the periosteum, be its seat, or if it 
from a part where there is much fibrous 
as for example, near the posterior nare 
fibrous ; mn this, no doubt, is generall 
yet the frequency with which portior 
turbinated bones are pulled away in ¢ 
gelatinous polypi proves that these 
often deep attachments. ta 
What are called malignant polypi ' 
nose do not truly deserve the generi¢ 
They are cancerous diseases of the i 
membrane or of the parts situated on il 
terior, from which they gradually mak 
way into the nasal cavities. In ge era 
racters they do not differ from the simi 


EK 2 
_ 


se 


NUTRITION. 


eases of other parts. One form in which they 
appear is, that of common cancer of the mu- 
cous membrane analogous to the hard or warty 
cancer of the skin, and pursuing the same 
course of apparently unresisted ulceration as 
that disease does. It occurs in old persons, 
and usually makes its progress very slowly, 
destroying all the adjacent parts till the patient 
is exhausted, or till it affects by its contiguity 
the brain, as in a case mentioned by Mr. Haw- 
kins. The other chief form in which the nose 
___ is affected by malignant disease is that of the 
soft or medullary cancer; but it is not certain 
whether this has yet been seen as a primary 
disease of the mucous membrane, or whether 
it be not always seated at first in some deeper 
tissue, from which as it makes its way it ac- 
quires a covering from the mucous membrane, 
and appears to be truly a disease of the nose. 
Whichever it be, there is nothing peculiar in its 
: characters or course to need a special descrip- 
_ tion of it here. 
im 
__ BrB_iogRapHy.—l. Of the nose in general.— 
_ Galen, De instrumento odoratus. Tinctorius, Diss. 
| de fabrica et usu nasi humani, Regiom. 1640. 
_ ©. V. Schneider, De osse cribriformi et sensu ac 
_ Organo odoratus, et morbis. Witteb. 1655. C. V. 
Schneider, De catarrhis libri quatuor. Viteberg, 
_ 1660-64. J, A. Sebiz, Diss. de instrumento olfactus. 
_ Argentor. 1662. Casp. Bartholin, De olfactus 
organo, disq. anat. Havn. 1679. G. Frank, Diss. 
_ de naso, Heidelberg, 1679. J. M. Hoffmann, Diss. 
_ de faciei promontorio, odoratus organo, Altorf. 1682. 
GLU. , Obs. Anat. sur l’organe de la vue 
et de Vodorat. Mém, de l’Acad. de. Paris. t. i. 
©. F. Paullini, De naso mobili. Misc. Ac Nat. cur. 
«16 D. Santorini, De naso, Venet. 1724, 
 H. van de Poll, De partibus que in homine olfactui 
wserviunt. Lugd. Bat. 1735. Fr. Boerner, Comm. 
.--mirabili narium structura. Brunsy. 1747. 
J. A. J. Scrinius, Diss. de organo, sensu, atque 
obj olfactus, Prage, 1749. S. ZT. Quelmalz, Pr. 
narium earumque septi incurvatione, Lips. 1750. 
‘F. J. du Toy, De tunica pituitaria, Prage, 1753. 
- £. Aurivillius, Diss. de naribus internis. Upsal. 
1760. J. G. Tenner, De organi olfactus differentia, 
Lips. 1777. J. C. Loder, Anat. obs. tumoris..... 
vis disq. de vero olfactus organo, Jenz, 1789. 
, Anat. Disq. de auditu et olfactu. 
cini et Mediol. 1789-92, and, Annot. anat. lib. ii. 
. olfactus deque nervis nasalibus., Ticin. 
mn Ue P. H. T. Simon, Diss. de conchis narium 
infer. Erlang. 1802. S. J. Soemmering, Icones 
organorum ham. olfactus, Francof. ad Men. 1810. 
_ J. F. Schroter, Die menschliche Nase. Leipz. 1812. 
_ Lawrence and Watt, Anatomico-chirurgical views 
_ of the nose, mouth, &c. Lond. 1809. Riefsteck, 
Diss. de structura org. olfactus mammalium non- 
ull, Tubing. 1823.  Hippolyte Cloquet, Osphre- 
_ siologie, ou Traité des Odeurs, &c. Paris, 1821. 
_ #, Picht, De gustus et olfactus nexu. Berol. 1829. 
2. Of the olfactory nerves and other parts of the 
nose.—J, H. Stevoyt, Diss. qua processus cerebri 
“mammillares ex nervorum olfactoriorum numero 
“exemptos disq. submittit. Jenz,1715. D. W. Andree, 
e ssibus mammillaribus,.Lugd. Bat. 1715, 
J. HE. Neubauer, De processuum cerebri mammil- 
Tarium cum naribus connexione. Nov. act. acad. 
‘Tat, cur, vi. 293. J. Weitbrecht, De vera signifi- 
eatione processuum mammillarium : Comm. Petrop. 
xiv. 1741. G. J. Duverney, Comp. des nerfs olfactifs 
| dans l’homme et dans les animaux. Mem. de Paris, 
t.i, A. Matthieu, Tent. phys.-anat. de nervis in 
Bencre, &c, Lugd. Bat. 1758. J. D. Metzger, 
| Primi paris nervorum historia, Argent. 1766, and 
jin Sandifort’s Thesaurus, t. iii., and Ludwig, 
| Script. Neur., t. iv. J. Hunter, A description of 


, 


741 


the nerves which supply the organ of smelling. 
Works by Palmer, vol. iv., p. 187. J. G. Haase, 
Pr. de nervis narium internis, in Ludwig, Script. 
Neurolog., t. iv., Lips. 1791. #F. Magendie, Le 
nerf olfactif est-il ’organe de l’odorat? Journ. de 
physiologie, 1825., iv. 169. 

Morbid anatomy of the nose.—S. Peyerus, De mor- 
bis narium, Basil, 1756. J. G. Haase,De morbis 
narium expositis, Lips. 1794. J. F. L. Deschamps, 
Traité des maladies des fosses nasales et de leur 
sinus, Paris, 1804. J. EH. Vort, De ozena, diss. 
inaug. Lugd. Bat. 1725. F. A. Meyer, Comm. de 
ozena, in Frank. Del. Opusc. Med. Germ. v. x., 
p- 249, Chr. le Cerf, De polypo narium, Jenz, 1715. 
G. A. Langguth, and S. G. Kichler, De polypo 
infantis, in Haller, Disp. ad Morb. v. vi., p, 301. 
And. Levret, Observ. sur la cure radicale de plusieurs 
polypes, Paris, 1749. J. C. Hesse, De polypo 
narium, Argent, 1777. J. J. Waser, Diss. inaug. 
recessum ossium nasi exhibens, Argent. 1767. 
G. F. Gruner, De polypis in cavis narium obviis, 
Lips. 1825. C. H. Dzondi, Ergo polypi narium 
nequaqnam extrahendi, Hale, 1830. Caesar Haw- 
kins, Clinical observations on some diseases of the 
nose. London Medical Gazette, August 23, 1834, 
and Clinical Lecture on Polypus of the Nose, July 


24, 31, 140. 
( James Paget.) 


NUTRITION.—The function thus designated 
may be regarded as including, in the most ex- 
tended acceptation of the term, the whole series 
of operations, by which the alimentary mate- 
rials are converted into living organised tissue : 
but as many of these changes are separately 
treated of in other parts of this work, we shall 
here confine ourselves to a more limited range ; 
and shall consider the nutritive process as com- 
mencing with the absorption of the materials, 
which have been prepared by the digestive pro- 
cess; and as including all the changes, which are 
involved in the conversion of the fluids so intro- 
duced within the system, into solid organised 
tissue, forming an integral part of the fabric. 

The object of the process of nutrition is the 
continual production of new tissue, either for 
the augmentation of the-original structure, or 
for the reparation of that part of it, which is 
continually undergoing decay or disintegration. 
And by this continual renewal of the tissues, 
we gain, as will hereafter appear, a constant re- 
invigoration of those vital powers or forces, the 
exercise of which has been one of the chief 
causes of the previous waste. It is a principle 
now generally acknowledged by physiologists, 
that the processes of disintegration and decay, 
in any organ or tissue, are more rapid, in pro- 
portion to the functional activity which it has 
been called on to manifest ;* and we find that 
the tendency to decomposition in the different 
tissues after death, which doubtless bears a 
general relation to their respective needs of re- 
newal during life, is the greatest in those, whose 
vital powers are most remarkable—the ner- 
vous and muscular tissues for instance ; whilst 
it is the least in those, whose properties are 
most purely physical—such as bone, cartilage, 
yellow elastic tissue, &c, Hence it is in the 
former that the greatest activity of nutri- 


* This doctrine, strongly put forth in regard to 
the muscular system by Liebig, and restricted to it 
by him, had been taught long before the publication 
of his treatise. 


742 


tion is required, for the maintenance of 
their normal texture and properties; but its 
amount will vary, according to the demand 
created by previous activity, and the conse- 
quent decay. ‘ 

The materials required for the nutrition of 
the tissues of the animal body seem to be sup- 
plied, for the most part at least, in forms pos- 
sessing a similar chemical composition, by the 
vegetablekingdom. It will be presently shown 
that albumen may be regarded as the pabulum, 
at the expease of which all the organised tex- 
tures (properly so called) of the animal fabric 
may be constructed. The really-organised part 
of this fabric, indeed, appears open to de- 

widely from the protein type of composi- 
Rou, Thus in fat, the areata by 
contained within cells, whose kl: ee com- 
posed of a protein principle ; and in the ner- 
vous tissue, re is Gectanblar that the walls of the 
cells and tubes are composed of an albuminous 
compound, though their interior is occupied by 
a substance of a character much more nearly 
approaching that of fat. Even with respect to 
the gelatinous tissues, as they are termed, 
there is much doubt to what extent they con- 
tain gelatin in their normal state; for where 
this can only be extracted from them by long 
boiling, it is not improbable that an actual con- 
version takes place ; since we know that pure 
fibrin may be converted, by long boiling, 
(which occasions the liberation of ammonia,) 
into a compound resembling gelatin in many 
respects. And in those which are most purely 
gelatinous, it is doubtful how far the gelatin is 
itself organized. The writer has lately ex- 
amined the sound of a cod with great care, both 
before and after the action of hot water upon 
it, and is satisfied that the gelatinous portion 
of it exhibits nothing that can be properly 
called organization—the only distinct appear- 
ances of fibres, cells, &c., being presented by 
portions which were left undissolved by the hot 
water, and which were, therefore, to be regarded 
as more allied to albumen than to gelatin in 
their composition. Similar remarks may be 
made in regard to the horny substance de 
sited in certain tissues; and it may roti 
be stated as a general theorem, that whilst in 
the plant, the materials which it derives from 
the elements around are combined and elabo- 
rated into non-azotized compounds for the pro- 
duction of organized tissue, and into azotized 
roducts for deposition in its cavities, these 
ast alone form the materials of the animal or- 
ganism, any non-azotized substances contained 
in it being inorganic in their condition. 

In considering the various stages of the nu- 
tritive process in animals, we shall do well to 
bear constantly in mind the leading facts in re- 
gard to the same process in the simplest cellu- 

plant: for we shall find that the elementary 

parts of the most complex animal organism go 
through a series of changes essentially the same ; 
so that the type of the function is everywhere 

. uniform, notwithstanding the vast apparent dif- 
ferences in the mode in which it is performed. 
The cell of the red snow or yeast plant, for 
instance, is developed from an almost imper- 


NUTRITION. 


ceptible germ, by its own power of attracting 
to itself certain nutritive materials in its neigh-° _ 
bourhood, which it combines into the new 
forms required both for its own growth and in- 
crease, for the elaboration of certain peculiar 
matters contained in its cavity, and for the 
duction of the germs of new cells; and these, 
being liberated in time by the death of their — 
parent, go through, in their turn, the same series — 
of changes. We shall now trace these changes — 
in the highest and most ee form in 2 5 
they are presented to us ;—that is, as they oc-— 
cur in man, or any vertebrated animal. ss 
Elaboration of organizable materials —The 
alimentary substances taken in by the absorbent 


vessels uire to unde important — 
changes within the body, before they can b 
oer to the nutrition of its structure. Th 
chief constituents of the chyle, as at first al 
sorbed, are albumen and fat; the former is” 
destined to be converted into the material of 
the solid tissues ; the latter is chiefly designed 
for the maintenance of the animal temperature, 
by the combination it is made to undergo with 
the oxygen introduced through the lungs. 
is questionable, as already explained, wheth 
fatty matter, or any other non-azotized com 
pound, can ever be applied to the ' 
the animal body. Even if it should 
proved to be subservient to the 
of the azotized tissues, there can be no dou 
that it must have been first converted into a 
albuminous compound—that is, into some m 
dification of protein; and as the evidence h 
such a transformation ever takes place is | 
from being satisfactory, we have as yet node 
for examining the mode in which it is effect 
We shall, therefore, consider albumen as 
starting-point of the animal tissues, and sh 
endeavour to trace, so far as the present stati 
our knowledge admits, the processes by 
this is converted into the organized fabric. — 
In this assumption we seem justified by | 
very obvious considerations. First, in the | 
of a bird, (or any other oviparous animal,) 
find that, putting aside the fatty, matter o 
yolk, albumen is the sole organic compout 
the expense of which all its tissues are | 
formed ; so that, by the wonderful proe 
chemical and vital transformation, whic 
poe during the period of incubation, 
umen which it contained at first is 
morphosed into bone, cartilage, nerve, mi 
tendon, ligament, membrane, areolar t 
gelatinous matter, horny substance, fe: 
&e.,&c. Secondly, a similar metamo 
appears to be continually taking place” 
body of the adult animal; for every” 
compound employed as food appears to 
duced to the form of albumen in the di 
process ; so that this becomes the essentia 
stituent of whatever fluid is absorbed ~ 
nutrition of the tissues, It is true that 
taken in as food, may be absorbed and ¢2 
into the current of the circulation ; but) 
no doubt that it is altogether incapable of | 
applied to the re-construction of any b 
gelatinous tissues; and, as already st 
seems questionable whether, even in th 


be ev 


p-construc 


we! 


NUTRITION. 


exists in a condition that can rightly be termed 

organised. Moreover, as it is clear that the 

gelatinous tissues may be formed at the ex- 

pense of albumen, we are justified in regard- 
ing this substance as the common pabulum 
forall. 

In order to form a definite conception of the 
nature of the transformations, which this prin- 
ciple is destined subsequently to undergo, it is 

important to bear in mind, in limine, that al- 
____ bumen cannot be regarded as possessed of any 
_ properties that characterize it as a vital com- 
_ pound—or, in other words, that essentially 
distinguish it from compounds of an ordinary 
chemical nature. In its coagulability by heat 
or by acids—in its combination with alkalies 
as an acid, or with acids as a base—and in the 
absence of any power of spontaneously passing 
_ into forms more decidedly organic than the 
granules which are seen when it is made to 
coagulate slowly—it is closely analogous to 
many substances which belong to the domain 
of inorganic chemistry. It appears, then, to be 
_ totally unpossessed of the property of plasticity ; 
_ by which we mean the power of being at once 
converted into organised tissue: so that any 
_ deposit, whether fluid or solid, which mainly 
hi consists of albuminous matter, must be regard- 
ed as aplastic. This is a principle of great 
importance, as we shall see further on. 
re albumen is ready to be appropriated 
_ by the tissues as the material for their nutri- 
tion, it must undergo a very important change— 
not so much, however, in its chemical compo- 
Sition, as in the re-arrangement of its particles 
in a new mode, by which its properties are es- 
Sentially changed. There seems reason to 
believe that, in the proportions of its ultimate 
elements, it is identical with the substance 
_ termed fibrin, into which it is changed during 
| its passage through the chyliferous and sangui- 
_ ferous vessels. [See Arpumen and Fisrin.] 
But there are such decided and well-marked 
ifferences between these two compounds, as 
' indicate that they fulfil entirely different pur- 
_ poses in the animal economy ; and that whilst, 
_ chemically speaking, they are isomeric, the 
_ fibrin is endowed with properties of a distinctly 
vital character—that is, altogether different 
_ from any with which mere chemistry brings 
_ US acquainted, One of the most obvious mani- 
2 of this difference is the property 
_ which is universally regarded as distinctive of 
fibrin—its tendency to coagulate spontaneously 
when withdrawn from the living vessels, and to 
_ pass into the form of a tisswe more or less 
' definitely organised. As will presently be 
_ shown, the completeness of this transformation 
my ds upon two circumstances in particu- 
i er perfect elaboration: of the fibrin it- 
self, and the vitality of the surface upon 
gwhich the concretion takes place. When the 
fibrin is highly elaborated, it will coagulate in 
the form of a definite network of minute fibrille, 
even upon a dead surface, as a slip of glass; 
| this is the case, for instance, with the fibrin of 
| the buffy coat of the blood, or with that of the 
| liquor sanguinis (coagulated lymph,) poured 
| out for the reparation of an injured part. But 


743 


in the ordinary fibrin of the blood, the fibrilla- 
tion is less distinct, when the concretion takes 
place upon a dead surface. When it occurs in 
contact with a living surface, however, the co- 
agulation takes place more gradually ; and it 
seems as if the particles, having more time to 
arrange themselves, become aggregated into 
more definite forms, so that a more regular 
tissue is produced—just as crystals are most 
perfectly formed, when the crystalline action 
takes place slowly. It was formerly imagined, 
that the muscular tissue is the only one pro- 
duced at the expense of the fibrin of the blood ; 
the other tissues being formed from its albumen. 
This, however, is unquestionably erroneous. 
There is no proof whatever, that albumen, as 
long as it remains in that condition, ever be- 
comes organised; whilst, on the other hand, 
there is abundant evidence that the plasticity 
of any fluid deposit—that is, its capability of 
being metamorphosed into organised tissue—is 
in direct relation with the quantity of fibrin 
which it contains. Thus the liquor sanguinis 
or coagulated lymph, thrown out for the repa- ~ 
ration of injuries, contains a large amount of 
fibrin ; and this substance is converted, not at 
first into muscular fibre, but (whatever may be 
the tissue to be ultimately produced in its 
place) into a fibrous network, which fills up the 
breach, and holds together the surrounding 
structure. This may be regarded as a simple 
form of areolar tissue, which gradually be- 
comes more perfectly organised by the exten- 
sion of vessels and nerves into its substance, 


and in which other forms of tissue may subse- 


quently make their appearance. This process 
will be more particularly described hereafter ; 
it is at present noticed here, as an illustration 
of the general fact, that fibrin is to be regarded 
as the plastic element of the nutritive fluids. 
The change from albumen to fibrin is, there- 
fore, the first important step in the process of 
assimilation. It commences in the absorbent 
system ; for the chyle is usually found to con- 
tain fibrin, even before it enters the mesenteric 
glands (as is indicated by its tendency, however 
feeble, to spontaneous coagulation) ; and after 
it has passed through them, the quantity of 
fibrin is considerably increased, so that chyle 
drawn from the thoracic duct usually coagulates 
with tolerable firmness. This process of elabora- 
tion continues in the blood: for the quantity 
of fibrin it contains is always kept up, in health,’ 
to a certain standard, although there must be a 
continual withdrawal of it for the nutritive pro- 
cesses, without a corresponding regular supply 
from the chyle ; and we find it, moreover, un- 
dergoing a sudden and remarkable increase, 
under the influence of local agencies. The 
question naturally suggests itself, therefore— 
what is the cause of this change? It has been 
usually attributed to some influence effected 
upon the albuminous fluid, by the living sur- 
faces over which it is passing; and the increase 
in the amount of fibrin in the chyle, which is 
specially noticed after its passage through the 
mesenteric glands, has been thought due to 
some peculiar action of the blood that may 
come into relation with it, through the thin walls 


744 


of that capillary plexus, which forms, with the 
convoluted lacteal tubuli, nearly the whole bulk 
of those bodies. The writer is inclined to at- 
tribute it, however, to another agency—the 
Vitalizing influence of certain floating cells, 
which the chyle and the blood contain; and 
the chief points of the evidence of this doctrine 
will now be set forth. 

A comprehensive survey of the vital pro- 
cesses, performed both by plants and animals, 
enables us to bring together a number of ex- 
amples in which ce//s are developed in a tem- 
porary manner, growing, arriving at maturity, 
and then disappearing; apparently without 
having performed any particular function. In 
the albumen of the , for instance, this often 
takes place to a remarkable extent. In the 
yolk of the egg there is a similar transitory 
developement of cells, of which several genera- 
tions succeed each other, without any perma- 
nent structure being the result. In the germi- 
nal vesicle, again (according to Dr. Barry*), 
several annuli of cells are seen to occupy its 
cavity, when it is prepared for fecundation ; 
and the oldest and largest of these contain 
another generation : yet all these disappear by 
liquefaction, as soon as the two permanent cells 
begin to be way ie in the centre. Further, 
in the subsequent developement of all the cells 
which are descended from these, and form the 
' “mulberry mass,” the same process is re- 
peated ; a great number of temporary cells being 
produced, only to liquefy again as soon as 
the two permanent central cells make their 
appearance. It can scarcely be imagined by 
the well-judging physiologist, that all this ced/- 
life comes into existence without some decided 

urpose ; and if we can assign to it an object, 
the fulfilment of which is consistent with the 
facts supplied by analogy elsewhere, this may 
be reasonably considered as having a fair claim 
to be received as a physiological induction. 

In all these instances, and in many more 
which might be quoted, the crude alimentary 
materials are being prepared to undergo conver- 
sion into permanent and regularly organised 
structures. The very first union of the inorganic 
elements into the simplest coer aria 
is effected by the cell-life of plants. The change 
of these principles into the peculiar compounds 
which frm the characteristic secretions of 
plants, is another result of their cell-life. And 
there seems equal ground for the belief, that 
the change of the proximate principles, sugar 
and gum (of which the latter appears to hold 
the same place in the vegetable economy that 
albumen does in the animal), into the peculiar 
glutinous sap, which is found wherever a forma- 
ion of new tissue is taking place, is equally 
dependent 2 > the agency of cells. The 

is probably commenced in the leaves ; 
Bt as the ordinary descending sap, which is 
the product of their elaboration, is not so re- 
markable for its plasticity as the fluid drawn 
from certain rapidly growing parts, it seems 
probable that a local agency takes place in 
these, analogous to that which we shall be able 


* Embryological Researches, third series, 


NUTRITION. 


af 
a 
{ 


to trace in certain conditions of the animal 
economy. Thus, the starchy fluid which is 
contained in the ovule, previously to its fecun= 
dation, is probably not in the state in which it — 
can be immediately rendered subservient to the 
nutrition of the embryo; and the devel 
of successive generations of cells, which exert 
upon it their vitalizing influence, may be rea- 
sonably regarded as the means by which the 
requisite change is effected. Exactly the same 
may be said of the albuminous matter con- 
tained in the yolk of the egg, which is certainly 
not in a condition in which it can be imr 
diately applied to the purposes of nutrition 
and it coteittinn eee regarded as cc 
mencing with the developement of transite 
cells within its own wriyreape. as being 
completed by means of the cells forming the 
ielean layer of the germinal membrane, b: 
which it is subsequently taken up and intro- 
duced into the current of blood flowing through 
the vascular area. A similar pu is pro 
bly answered by the transitory cells develo 
within the germinal vesicle; and by thos 
which appear at a similar period in the evolu. 
tion of the descendents of the “ twin cells 
produced in it. _ 
Many other examples of a similar proce 
might be adduced, but they would all lead t 
the same general conclusion, which harmoniz 
well with the important principle of gene’ 
physiology,—that the higher the grade of str 
ture ultimately to be attained by any part, an 
the more permanent its character is destined t 
be, the longer and more elaborate are the p 
minary stages of its evolution. As an inst 
of this law, which bears a remarkable a 
with the facts just recorded, we may ac 
the production of a temporary respirate 
paratus in the higher plants and anim: 
responding with that which is permane 
the lower parts of the scale. There are pr 
bly cases, however, in which cells are ve 
rapidly called into existence, without that pn 
paratory elaboration of their nutrient mater 
which we regard as due to the vital operat 
of a preceding generation. Thus the B 
giganteum, a large fungus of the 
tribe, has been known to increase, in 
night, from a mere point to the size of a | 
gourd, estimated to contain 47,000,000 
cellules. In such a case it is difficult to” 
pose that any but the most rapid m 
generating cells can have been in opere 
and the idea tbat these could not ha 
developed by any such elaborate proce 
that just alluded to, is borne out by the! 
their extremely transitory character, the 
of such a structure being almost as rapic 
production. The same may be 
those fungous growths in the 
which sprout forth most rapidly, 
apparent exception assists in ing 
We have thas a class of fants 
that the conversion of the chemical com 
into the organizable principle—the aplasti 
the plustic material—is effected in the 
cular situations where it is most wanted | 
vital agency of transitory cell-life ; th 


i 
ge 
* 


roe 
oi 
| 


* 


NUTRITION. 


| the production of cells which are not them- 
_ selves destined to form an integral part of any 
__ permanent structure, but which, after attaining 
_ certain maturity, reproduce themselves and 
| disappear, successive generations thus following 
one another until the object is accomplished, 
after which they altogether vanish. We shall 
now consider another class of facts which seem 
to indicate that a change of this kind is being 
_ continually effected in the nutritious fluids of 
_ animals during their circulation through the 
: body, by cells which are either carried about 
_ with them, or which are developed for the pur- 
_ pose in particular situations, as in plants. The 
_ former is the more common occurrence ; since 
the conditions of animal life, usually involving 
a general movement of the body, require also a 
_ constant general reparation of its parts, and an 
adaptation of the circulating fluid therefore to 
the wants of the whole fabric. 
In the chyle drawn from the lacteals near 
the intestinal tube, there is but little fibrin; and 
_ very few of the peculiar chyle-corpuscles are 
seen in the fluid. In the chyle of the mesen- 
_ teric glands, on the other kand, the corpuscles 
are extremely numerous; and they are always 
_ readily seen in the chyle of the central lac- 
 teals, receptaculum chyli, and thoracic duct,— 
“though their number is considerably less than 
in chyle drawn by pricking the lacteals of the 
“Mesenteric glands. The average size of these 
corpuscles is about ,4,th of an inch ; but they 
vary from about 44,th to ,31th. The smallest 
are usually found in the peripheral lacteals; 
largest in the thoracic duct. They are 
evidently ced/s in process of developement ; and 
from the appearances presented by those which 
” are seen in the chyle of the thoracic duct, there 
tan be little doubt that they have the power of 
ucing themselves in the ordinary mode. 
first appearance of these cells in large 
_ Dumber is exactly coincident with the first 
| appearance of fibrin in the chyle,—at least to 
an amount sufficient to produce spontaneous 
_ Coagulation; and the delay of the chyle in the 
mesenteric glands appears to aid in their deve- 
lopement, and to assist their operation. In the 
lower Vertebrata the absorbent system has none 
these (so called) glands; and hence we see 
‘that they are not essential to the performance of 
its functions. But in such animals the vessels 
‘are immensely extended in length; whilst in 
the warm-blooded Vertebrata, in whose con- 
formation the principle of concentration ope- 
‘Tates to the greatest possible extent, we see no 
such prolongation ; the end being answered by 
_ the excessive convolution of the absorbents in 
_ the mesenteric glands, where it seems probable 
“ the chyle is delayed during the develope- 
- ment of its characteristic cells. . Similar state- 
‘ments apply to the /ymph, and to the lymphatic 
vessels and glands. This fluid is probably to 
be regarded, not as a product of the decompo- 
Sition of the tissues, which is destined to be 
thrown out of the system, but as the product 
/ 4 that secondary digestion, by which a portion 
of the materials that have formed a component 
) 7 of the tissues, and have been set free by 
eit disintegration, is again rendered subser- 


iY 


745 


vient to nutrition, and reconveyed into the 
current of the circulation. Into the arguments 
in favour of this view (which differs from the 
ordinary doctrine regarding the function of 
the lymphatic system) we cannot here enter ; 
but it may be remarked that the animal matter 
of the lymph is mainly of an albuminous cha- 
racter, and that it gradually undergoes a trans- 
formation into fibrin during its passage through 
the absorbent vessels and glands. 

The continuation of this process in the blood 
is believed by the writer to be effected by 
means of the white, or colourless, corpuscles, 
to which increased attention has lately been 
directed. That these are identical with, or are 
the immediate offspring of, the corpuscles of 
the chyle and lymph, there seems much reason 
to believe from their similarity in size and ap- 
pearance. Whilst the red corpuscles vary in 
dimension from less than y)5;th of an inch 
(Musk Deer) to 3},th (Proteus), the colourless 
corpuscles have not been observed to depart 
widely from the diameter of s,{,th of an inch in 
any vertebrated animal; consequently, while 
they are but little larger than the average of red 
corpuscles in man, and are scarcely distinguish- 
able from them, except by the practised micro- 
scopist, they are far more minute than the oval 
blood-dises of reptiles and fishes, and are at 
once recognised, even by a cursory observer, 
Now it is a fact of great physiological interest 
and importance, that whilst the colourless cor- 
puscles are to be met with in the nutritious 
fluids of all animals, which possess a distinct 
circulation, the red corpuscles are restricted to 
the blood of Vertebrata. This observation, 
which was first put forth by Wagner,* has been 
confirmed by the writer of this article, who 
had been previously struck with the very close 
analogy between the floating cells carried along 
in the current of the circulation in some of the 
very transparent aquatic larvee, (especially thosé 
of the Culicide,) and the lymph-corpuscles of 
the Frog. Now it is evident from this fact, 
that, as the blood of Vertebrata is distinguished 
from their chyle solely by the presence of red 
corpuscles in the former, and by their absence 
in the latter, the nutritious fluid of invertebrated 
animals is rather analogous (as Wagner has 
remarked) to the chyle and lymph, than to the 
blood of Vertebrata. Or, to put the same idea 
in another form, the presence of the colourless 
corpuscles in the nutritious fluids appears to 
be the most general fact in regard to its cha- 
racter throughout the whole animal scale; 
whilst the presence of red corpuscles in that 
fluid is limited to the vertebrated classes. 
Hence it would not be wrong to infer that the 

Junction of the colourless corpuscles must be 
of a general character, and intimately connected 
with the nutritious properties of the circulating 
fluid ; whilst the function of the red corpuscles 
must be of a limited character, being only re- 
quired in one division of the animal kingdom. 
Further, it has been noticed by Mr. Gulliver 
that in the very young embryo of the Mam- 
malia, the white globules are nearly as nume- 


* Physiology, by Willis, Part II. 


746 


rous as the red particles: this, Mr. Gulliver 
has frequently noticed in fatal deer of about 
an inch and a half long. In a still smaller foetus 
the blood was pale from the preponderance of 
the white corpuscles. It is, therefore, a fact of 
much interest that, even in the mammiferous 
embryo, at the period when growth is most 
rapid, the circulating fluid has a strong analogy 
to that of the Invertebrata. It then, too, bears 
in other respects the most striking analogy to 
chyle; since it consists of the fluid elaborated 
from the organizable matter supplied by the 
parent, and direct/y introduced into the current 
of the circulation. The function of the placental 
vessels may be regarded as double ; for the 
are at the same time the channel, through which 
the alimentary materials supplied by the pa- 
rent are introduced into the circulating system 
of the fetus, aud the medium of aerating the 
fluid which has traversed the fetal system. 
Hence the placenta may be regarded as at 
once the digestive and the respiratory appa- 
ratus of the fetus, and the fluid circulating 
through the cord as at once chyle and blood. 
It is not until the pulmonary and lacteal vessels 
of the embryo have commenced their indepen- 
dent operation, that the distinction between the 
blood and the chyle of the fatus becomes evi- 
dent; and we should expect, therefore, to find 
that the circulating fluid, up to the time of 
birth, contains a large proportion of white cor- 
puscles, which is actually the case. There is a 
gradual decrease, however, in their proportional 
number, from the earlier to the later stages of 
embryonic life, in accordance with the dimi- 
nishing energy of the formative processes. It 
has been also observed by Wagner* that the 
number of colourless corpuscles is always re- 
markably great in the blood of well-fed frogs 
just caught in the summer season ; and that it 
is very small in those, which had been kept long 
without food, and in those examined during the 
winter. 

The most remarkable evidence, however, of 
the connection between the generation of white 
corpuscles in the blood, and the production of 
fibrin, is derived from the phenomena of in- 
flammation. A decided increase in the normal 
proportion of fibrin in the blood (from 24 to 
3$ parts in 1000) may probably be looked 
upon as the essential indication of the existence 
of the inflammatory condition. For it appears 
from the observations of Andral and Gavarret 
(which have been confirmed by many other 
pathologists) that such an increase uniformly 
manifests itself, when a local inflammation com- 
mences,—even when the proportion of fibrin 
~ has previously been abnormally low, as in 
febrile diseases ; that it bears a constant rela- 
tion with the extent and intensity of the diseased 
action ; and that it diminishes with the abate- 
ment of the morbid condition of the part affected. 
In some instances, the proportion of fibrin was 
seen to rise as high as 9 or even 10 parts in 
1000; but an increase to the amount of 6, 7, 
8 parts, was more common. That this pro- 
duction of fibrin is due to a local change can 


* Op. cit. p. 245. 


NUTRITION. 


scarcely be doubted; since it is frequently — 
chaired to commence before 7 ee i 
tutional symptoms manifest themselves; and it — 
may be regarded, in fact, as one cause of these — 
symptoms. Now the recent mi ic ob- 
servations of Mr. Addison* and Dr. Willi a 
which were made independently of each other, — 
have established the im t fact, that a 
great accumulation of white corpuscles takes 
place in the vessels of an inflamed part; and 
this seems to be caused at first by a deter- 
mination of those already existing in the cireu- 
lating fluid, towards the affected spot; but 
partly by an actual increase or generation ¢ 
these bodies, which appear to have the powe 
of very rapidly multiplying themselves. The 
accumulation of white corpuscles may be easily 
seen, by applying irritants to the web ofa fro s 
foot. Mr. Addison has noticed it, in the 
human subject, in blood drawn b Fee Dr 
of a needle, from an intlamed pimple, the base 
of a boil, the skin in scarlatina, Ke. Am 
the writer, without any knowledge of thesi 
observations, had remarked a very obviou 
difference between the proportions of whiti 
corpuscles, in blood drawn from a wound — 
the skin of a frog immediately upon the ineisi 
being made, and in that drawn a few minu 
after; and had been led, like the observ 
just quoted, to refer this difference to a dete 
mination of white corpuscles to a part irritates 
The absolute increase, sometimes to a very cor 
siderable amount, in the quantity of whi 
corpuscles in the blood of an inflamed subj 
has been verified 5 Gulliver and sever 
other observers. ese facts, therefore, affo 
strong ground for the belief, that the producti 
of fibrin in the blood is closely connected 
the development of the white corpuscles; a 
when we consider them in connection with | 
facts previously urged, there scarcely appear 
be a reasonable doubt, that the elaboratior 
fibrin is a consequence of this form of cell- 
and is, in fact, its express object. . 
A recent observation of Mr. Addison’, t 
over, would seem to indicate, that no ineonsi 
able proportion of the fibrin of the cireuls 
blood is contained within the white corpus 
“ Provide six or eight slips of glass, su cha 
usually employed for mounting micros¢o) 
objects ; and as many smaller pieces. 
drawn blood from a person with 
fever, or any other inflammatory dise 
a drop of the colourless liquor sanguinis, b 
it fibrillates, on each of the large slips of | 
cover one immediately with one of the 
slips, and the others one after anuther af 
vals of thirty or forty seconds: th 
examining them by the microscope, 
will exhibit colourless blood corpt 
various conditions, and numerous 
cules distributed through a more or less ¢ 
fibrous network ; and the last will be 
coherent, and very elastic membrane, 
cannot be broken to pieces nor resolv 
en Gazette, Dec, 1840; Jan. and 
+ Medical Gazette, July, 1841; and Pr 
of Medicine, pp. 209, 210. ae 


NUTRITION. 


smaller fragments, however roughly or strongly 
the two pieces of glass be made to rub against 
each other. This is a ‘glaring instance’ of a 
compact, tough, elastic, colourless, and fibrous 
tissue, forming from the colourless elements of 
the blood ; and the several stages of its formation 
_ may be actually seen and determined. Nu- 
merous corpuscles may be observed, in all these 
ae to have resolved themselves, or to 
ve fallen down into a number of minute 
molecules, which are spread out over a some- 
what larger area than that occupied by the 
entire corpuscles; and although still retaining 
a more or less perfectly circular outline, yet 
refracting the light at their edges, in a manner 
very different from that in which the corpuscles 
themselves are seen to do. It is from these 
and various other larger and more irregular 
masses of molecules on disintegrated corpuscles, 
that the fibrinous filaments shoot out on all 
_ sides, as from so many centres ; or frequently 
_ the filaments are more copious in two opposite 
directions.” * 
A different view of the cause of the produc- 
tion of fibrin, however, has been entertained by 
“some eminent physiologists; and it does not 
seem right to allow the opinions of Wagner, 
‘Henle, and Wharton Jones to pass without 
_ notice, even though they appear to the writer 
to be easily set aside. By these observers, the 
elaboration of fibrin has been attributed to the 
red corpuscles, and has been regarded as one, 
‘at least, of their special functions. Nearly all 


— 


4 . 


assign this duty to the white corpuscles, tell 
equally against the doctrine now under con- 
Sideration. The presence of fibrin in the circu- 
_ lating fluid may be regarded as a universal fact ; 
_ but the red corpuscles are restricted to verte- 
_ brated animals : how, then, is the plastic element 
elaborated in the invertebrata? The number of 

_ red corpuscles in the blood of different classes 
bears an obvious relation to their amount of 
respiratory power, and to the functional activity 
of the several organs, which is closely connected 
_ with the amount of oxygen introduced into the 
_ system; but it does not bear the same relation 
with the activity of the formative processes, 
_ which may be taking place energetically (as in 
_ the developement of the embryo, or in the re- 
paration of parts in the adult) in a state of 
functional quiescence. That the proportion of 
d corpuscles in the blood had a special rela- 
ion to the nervous and muscular energy of an 
_ animal, and to the amount of oxygen consumed 
by it, has long ranked as a physiological truth ; 
‘and the opinion has been gradually gaining 
ground, that although the liquor sanguinis is 
‘undoubtedly affected in a considerable degree 
by exposure to oxygen in the respiratory capil- 
-laries, the red corpuscles are the special agents 
'y which oxygen is conveyed into the systemic 
pillaries, that it may furnish the conditions 
required for muscular contraction and other 

| functional operations, which depend upon a 
| due supply of arterial blood. In the inverte- 


_ * Transactions of the Provincial Medical Asso- 
ciation, 1843, 


the arguments, however, which have led us to- 


747 


brated animals in general, the amount of respi- 
ration is so low, that this special provision is 
not required. There is an apparent exception, 
however, in the case of Insects, which have no 
red corpuscles, and which yet can display a 
greater amount of animal energy, and which 
consume (when in a state of activity) a larger 
quantity of oxygen in proportion to their size, 
than beings of any other class whatever. But 
here the exception proves the rule ; for the con- 
veyance of oxygen through the tissues is not 
accomplished in Insects by the circulating fluid, 
which has a comparatively sluggish movement, 
but is effected more directly by the ramifying 
trachee, which introduce air into the minutest 
portions of the structure. 

The pathological evidence that the red cor- 
puscles are not the elaborators of the fibrin, 
i to the writer to be quite conclusive. 

hilst the quantity of fibrin is so remarkably 
increased in inflammation, the number of red 
corpuscles undergoes no decided change. 
Again, the augmentation of the fibrin is not in- 
compatible with a chlorotic state of the blood ; 
the peculiar characteristic of which is a great 
diminution in the proportion of red corpuscles. 
By such alterations, the normal proportion be- 
tween the fibrin and the red corpuscles, which 
may be stated as a : B, may be so much altered, 
as to become, in inflammation, 3a : B, in chlo- 
rosis 4:48. Again, in fever, the characteristic 
alteration in the condition of the blood appears 
to be an increase in the amount of red cor- 
puscles, with a diminution in the quantity of 
fibrin; yet if a local inflammation should 
establish itself during the course of a fever, the 
proportion of fibrin will rise ; and this without 
any change in the amount of corpuscles. 
Lastly, the effect of loss of blood has been 
shown by Andral’s investigations to be a marked 
diminution in the number of red corpuscles, 
with no decided reduction in the quantity of 
fibrin, even when this is much above its normal 
standard ; and in this condition of the blood it 
has been observed by Remak that the coleurless 
id Saab are very numerous. 

ormation of tisswe—With the elaboration 
of the alimentary materials into fibrid, the pre- 
paratory processes of nutrition may be regarded 
as terminating ; since the next step is the trans- 
formation of this substance into organised tissue. 
Upon the mode in which this is effected, much 
light has been thrown by recent enquiries ; but 
several points still remain obscure. We shal! 
endeavour, in the following account, to dis- 
tinguish what has been satisfactorily ascertained 
from what is merely hypothetical. 

That the particles of perfectly-elaborated 
fibrin are capable, in solidifying, of spontaneously 
assuming a definite arrangement, cannot now 
be questioned. In the ordinary crassamentum 
of healthy blood, this arrangement can be seen, 
by examining thin slices under the microscope ; 
especially after the clot has been hardened by 
boiling. A-number of fibres, more or less dis- 
tinct, may be seen to cross one another; form- 
ing by their interlacement a tolerably regular 
network, in the meshes of which the red cor- 
puscles are entangled. This fact was known to 


748 


Haller ; but it has been generally overlooked 
by subsequent physiologists, until attention was 
drawn to it by the enquiries of Messrs. Addison, 
Gulliver, and others. It is in the buffy coat, 
however, that the fibrous arrangement is best 
seen; On account, as it would appear, of the 
stronger attraction which the particles of fibrin 
have for one another, when its vitality has been 
raised by the increased elaboration to which it 
has been subjected. That there are varieties of 
plasticity in the substance, which, on account 
of its power of spontaneously coagulating, we 
must still call fibrin, appears from this fact 
among others,—that, in tuberculous subjects, 
the guantity of fibrin in the blood is higher 
than usual (Andral and Gavarret), although its 
plasticity is certainly below par. It is easy to 
understand, that its plasticity may be increased 
as that it may be diminished ; and this either in 
the general mass of the blood, or in a local de- 
posit In fact, the adhesions which are formed 
y the consolidation of coagulable lymph,—or 
in other words, of liquor sanguinis, whose plas- 
ticity has been heightened by the vital actions 
of the white corpuscles in the capillaries of the 
part on which it has been effused,—often 
acquire very considerable firmness, before any 
vessels have penetrated them ; and this firmness 
must depend upon that mutual attraction of the 
particles for one another, which in aplastic de- 
posits is altogether wanting, and which in 
caco-plastic deposits is deficient. A very inte- 
resting example of a structure entirely composed 
of matted fibres, and evidently originating in 
the simple consolidation of fibrin, has lately 
been discovered by the writer. This is found 
in the membrane adherent to the interior of the 
egg-shell (membrana putaminis); and also in 
that which forms the basis of the egg-shell itself. 
Between the two, there is no essential difference; 
as may be seen by examining “ an egg without 
shell,” as it is commonly termed, (or rather one 
in which the shell-membrane has been uncon- 
solidated by the deposition of calcareous matter) ; 
or by treating the egg-shell with dilute acid, so 
as to remove the particles of carbonate of lime, 
which are deposited in the interstices of the net- 
work. The place of the shell is then found to 
be occupied by a membrane of considerable 
firmness, closely resembling that which sur- 
rounds the albumen of the egg, but thicker and 
more spongy. After maceration for a few days, 
either of these membranes may be separated 
into a number of lamine, each of which (if suf- 
ficiently thin) will show the beautiful arrange- 
ment of reticulated fibres, which is delineated 
in the accompanying figure (fig. 405). It is 
impossible to refuse to such a structure the desig- 
nation of an organised tissue, although it contains 
no vessels, and must be formed by the simple 
consolidation of fibrin, poured out from the lining 
membrane of the oviduct of the bird. It is 
probably in the same manner, that the chorion 
of the mammiferous animal originates; since 
this is a new envelope, formed around the ovum, 
during its passage along the Fallopian tube. In 
the latter, for an ulterior purpose, vessels are 
afterwards developed, by extension from the 
contained ovum; and by the nutrition they 


NUTRITION. 


“os 


gy 


supply, its size is increased, and changes 
place in its texture. But in the mem brat 
of the bird, there is no need of 3 because 
no subsequent change in its texture is required, 
and its duration is sufficient for the purpose it 
has to answer. ae 
In all these instances, the fibrillated structure 
contains a certain amount of corpuscles, which 
lie in the meshes of its network. These ha 
been termed “ exudation-globules” by some 
authors,-—by others “ organie germs,”"—and_ b 
others (especially Mr. Addison) are regarded as 
identical with the white corpuscles of th 
blood. They may present considerable varie 
ties in size and appearance; having in som 
instances the characters of fully-formed cells 
whilst in others they rather resemble nuclei ' 
aggregations of granules. It seems difficult t 
believe, that they can be identical with the wh 
corpuscles of the blood ; since if the exudati 
has been poured forth by open orifices, suf 
ciently large to admit these to pass, there wou 
be no obstacle to the escape of the red corpus 
cles,—at least where the latter are of bly. 
size, asin mammalia. They are — 
be regarded as originating in the fibrinous ¢ 
posit, from germs which it contained, whe 
effused from the vessels; of which germs 
white corpuscles may have not improbab 
been the parents. The degree of their dev 
lopement into pie pea ap - re lepe 
upon the degree of plasticity o depo 
Not unfrequently hey seem arrested in 
progress ; especially in cases where the ex! 
tion verges towards a pena charac 
In the egg-membrane, very of these | 
puscles are seen; and as it is thus alt 
entirely composed of consolidated fibrin 
possesses considerable toughness. The § 
1s the case with highly plastic exudations 
inflamed serous surfaces. But in de 
which are less plastic, we see a larger numb 
these corpuscles, and a diminution and 
creased tenacity of the fibres; the meml 
then becomes quite friable, and approach 
character of a purulent exudation. The 
plastic deposits will be presently notice 
der the head of Abnormal States of Nut 
At present we shall proceed to consider 
application of these facts to the ordinary 
ditions of that process. : 
The question naturally suggests itse 
limine, whether any of the tissues of the at 
body are formed by the simple effusion of 


* 


f f 
J 


- 


a 


: 

| 
| . 
_ from the bloodvessels, and its subsequent con- 
_ solidation in the manner already described. 
__ No such idea seems to have occurred to the 
_ continental physiologists, who, following in the 
th which had been marked out by Schwann, 
ave sought to trace, for ad the tissues, an imme- 
diate origin in cells. Butthe writer does not find 
that any of them are sufficiently aware of the 
facts already detailed, in regard to the definite 
: structure which fibrin will assume, when it has 
__undergonea high degree of elaboration, and has 
_ coagulated under the most favourable circum- 
Stances ; and with the greatest respect to their 
authority, he ventures to attach sufficient weight 
to the observations of Messrs. Gulliver and 
Addison, confirmed as they are by his own, to 
_ induce him to adopt a different explanation, 
_ which he offers with diffidence, to be confirmed 

_ Or set aside by future enquiries. 
__ The fibrous tissue existing in false mem- 
_ branes, and still more that which has been dis- 
_ covered by the writer in the egg-shell, may be 
_ regarded in his opinion as a type of those sim- 
ple fibrous tissues, which form a large porpor- 
‘tion of the bulk of the body in the higher 
animals, and of which the function is purely 
“mechanical. When we contrast the fabric of 
‘an animal with that of a plant, we are struck 
with this important difference in their conform- 
ation,—that whilst the latter is made up solely 
of elements which are to perform their several 
parts in the performance of the nutritive and 
productive operations, (the only exception 
ing in the case of those more solid portions 
C e fabric which are destined to give 
mechanical support to the remainder),—the 
former is composed of a much greater variety 
of parts, which are adapted to move upon each 
other. Now this purpose requires, not only 
the addition of certain new tissues, to which 
nothing analogous is to be found in plants, for 
ing and exercising the motor power, but 
9 an adaptation of the whole structure to this 
y condition. The tissues of plants entirely 
nsist of cel/s, or simple modifications of them. 
me of these cells being strengthened by in- 
deposits, form the solid woody frame- 
“work of the stem and branches, which gives 
“Support to their wide-spreading foliage and 
“humberless blossoms. Others coalesce, by the 
- dise ce of their intervening partitions, 
‘Into tubes, which serve for the conveyance of 
fluid between the most distant parts. But the 
reat bulk of the fabric still consists of cells, 
ly adherent to each other, and actively par- 
ating in the various operations of organic 
fife. In like manner in the animal body, a 
certai oth the cells have contributed to form 
the solid osseous and cartilaginous framework, 
Which not only gives support and protection to 
body, but contributes to its power of move- 
ment, by affording fixed points for the attach- 
ment of its muscles. Others again have coal- 
esced into vessels, as in plants,’ for the rapid 
conveyance of fluids. Others, too, after a simi- 
ar coalescence, have developed new and re- 
markable products in the interior of the tubes 


hervous and muscular tissues, to which nothing 
| 


NUTRITION. 


thus formed, and become transformed into those 


749 


analogous is found in plants, and whichare the 
peculiar instruments of animal life. Yet still 
there remains a large number of unchanged 
cells scattered through the body, which perform, 
as in plants, the essential part in the functions 
of nutrition, reproduction, &c. These, how- 
ever, could not be held together in their con- 
stantly-varying relative positions without some 
intervening substance altogether different from 
true cellular tissue. It must be capable of 
resisting tension with considerable firmness and 
elasticity ; it must admit free movement of 
the several parts upon one another ; and it must 
still hold them sufficiently close together to 
resist any injurious strain upon the delicate 
vessels, nerves, &c., which pass from one to 
another, as well as to prevent any permanent dis- 
placement. Now all these offices are performed 
in a remarkably complete degree, by the areolar 
tissue,* the reason of whose restriction to the 
animal kingdom is thus evident. It is chiefly 
composed of interlacing fibres and shreds of 
membrane, which do not seem possessed of any 
other than simply physical properties; the small 
degree of vital contractility which it possesses 
in some spots (as in the dartos,) being attribut- 
able to the intermixture of fibres analogous to 
those of the unstriated muscular tissue. One 
of its most remarkable peculiarities is the ra- 
pidity ofits regeneration ; and this is obviously 
due, in part, to the large amount of bloodvessels 
by which it is traversed. The accounts given 
of its developement by Schwann and Henle do 
not by any means correspond ; and it appears 
to the writer, that the evidence of the partici- 
pation of cells in the process, in any other way 
than as elaborating the fibrin, is very insufti- 
cient. The observation already quoted from 
Mr. Addison ( p. 746) seems to explain some 
appearances occasionally met with, which in- 
duced those observers to assign a more direct 
cell-origin to this tissue; for he notices that the re- 
mains of the white corpuscles, and little aggrega- 
tions of the granules they had emitted, seemed 
to be the centres, as it were, of the fibrillation.+ 

If we once admit this doctrine in regaid to 
areolar tissue, it is not difficult to extend it to 
those fibrous structures in general, which re- 
semble it in the physical nature of their func- 
tions; and we shall then leave to the tissues of 
cell-origin, in animals as in plants, the perform- 
ance of those operations which must be re- 
garded as vital in their character. As an ad- 
ditional argument in support of this view, the 
appearances presented by the semi-fibrous car- 
tilages may be adduced. In the cartilages of 


* This was formerly termed CELLULAR tissue, 
under which designation it is described in the pre- 
sent work ; but the appellation here given is the 
one under which it .is now generally spoken of, for 
the sake of distinguishing it from tissues really 
composed of cells. 

+ Since writing the above, the author has become 
aware that a view of the developement of areolar 
tissue, essentially corresponding with that advanced 
above, has been recently put forth by Mandl, 
(Manuel d’Anatomie Générale, p. 552,) although 
he too seems quite unaware of the degree in which 
the fibrinous part of the blood fibrillates in cva- 
gulating. 


\ 


750 


the ribs, for instance, a more or less distinct 
fibrous appearance may be frequently seen in 
the intercellular substance ; this is sometimes so 
faint, that it might be considered as an illusion, 
occasioned by the manipulation to which the 
section has been subjected ; but it is often so 
well-defined, as almost to present the appear- 
ance of the true fibrous structure. No indica- 
tion of the direct operation of cells in the 
developement of these fibres has ever been wit- 
nessed ; and we can scarcely do otherwise than 
regard them as produced by the regular ar- 
rangement and consolidation of the particles of 
the blastema or plastic element, in virtuevof its 
own inherent powers, 

The production of the simple structureless 
membranes which exist in various parts of the 
body must be attributed, we think, to the con- 
solidation of a thin layer of blastema, rather 
than to any metamorphosis of cells. The 
basement or primary membrane which lies 
beneath the epithelium of the mucous and 
serous membranes, and of the glandular pro- 
longations of the former, as well.as the mem- 
brane lining the bloodvessels, and bearing 
epithelium upon its inner surface, must pro- 
bably be regarded in this light. It may be 
questioned, however, whether this is not to be 
regarded, in most cases at least, as a transitional 
form, rather than as a permanent structure. 
We have reason to believe that in many situa- 
tions (as the lining of the alimentary canal and 
of its glandular prolongations,) the nuclei con- 
tained in this membrane must be continually 
developing themselves into epithelium-cells ; 
and in some other instances it would seem, that 
a fibrous structure developes itself from it by a 
metamorphosis of a different kind. It is not 
difficult to imagine, that these variations may 
have their origin in the degree of plasticity of 
the element, of which the membrane was origin- 
ally composed, and in the number of cell-germs 
which it includes. Considerable differences in 
the appearance of this primary membrane may 
be seen, in examining the residua left after dis- 
solving away the calcareous matter of shells by 
_ dilute acid. Putting aside the cellular tissue 
which certain shells exhibit,* the most general 
animal basis of each layer is a very delicate 
membrane, which sometimes appears com- 
pletely homogeneous, even when viewed with 
the highest powers of the microscope; but 
which in other instances presents a distinctly 
granular ‘aspect, as if it consisted of a layer of 
molecules consolidated together by a structure- 
less cement. These membranous films are in- 
cluded between strata of calcareous matter, 
poured out from the surface of the mantle, and 
thus undergo no change subsequent to their 
first production. 

e have next to consider the mode in which 
the tissues, whose form is distinctly celfular, or 
which can be clearly proved to originate in 
cells, derive their nutriment from the blood. 
In the early stage of embryonic developement, 


* See a paper by the author on the Microscopic 
Stracture of Shell, in Annals of Natural History, 
December, 1843. 


NUTRITION. 


as already stated, the whole fabric is com 
of cells which present no recognizable 
ences amongst themselves, and which yet, by a 
process of histological transformation, 
the elements of the different organs,—some of 
them still retaining the form of cells, ilst 
others undergo changes which remove them 
altogether from that category. To the former 
class belong adipose tissue, pigment-cells, the 
— kinds of epithelium and epi 
cartilage-cells, &c. Of the latter, the capillary 
bloodvessels, and the muscular i eee 
tissues, are characteristic examples. Now there — 
would seem much reason to believe, that in the — 
regular process of nutrition, each of these 
tissues draws from the blood the materials 
necessary for its reparation and growth, as it 


does in the earlier stages for its cee 
ment; and that the iartien of the blood is 
confined to the supply of these materials,—the 
germs of the new tissue being supplied by that 
previously existing. At any rate it may be 
safely affirmed that no evidence has been ad- 
duced which renders any other view probable 
The self-nutrient power of the tissues is evinces 
by this fact among others,—that in no instan 
are their ultimate elements 
capillary bloodvessels. Thus although adi 
tissue is traversed by a minute capillary 
work, the fat-cells lie in the meshes of this 
work, and are as independent of it, excep 
regards the supply of nutrient materials whic 
they derive from it, as if they adhered closel 
to each other. The muscular fibres and ne 
tubes, again, are not penetrated by capille 
vessels, but are only surrounded by 2 
connection of the cartilage-cells with the 1 
sels is still more remote; for the true cellu 
cartilages are not penetrated by bloodvessels- 
all (in the healthy state at least), but 
nourished by the imbibition of fluids fron 
plexus of dilated vessels that comes into m 
tion with their external surface. We may ini 
therefore, that the bloodvessels are sub 
to the act of nutrition only by conveyin 
nutrient fluid into the neighbourhood wh 
is required,—justas, in the irrigation of an 
dow, the water is carried in channels over 
general surface, but has to find its wa 
percolation into thespaces between these 
that it is by the materials which they 
from it that the several tissues are enable 
maintain their integrity, by reproducing 
structure as fast as it is disintegrated. A 
may not be unreasonable to infer that, i 
very act of the death and disintegration 
parent structure, the germs of the new 
tures destined to replace it are set free, ¢ 
ie in the reproduction® of the simple 
ar plants. -* 
t may be doubted, however, whe 


; 
: 


0 


same holds good in regard to newly- 
parts, or with res to the epitheliun 
which are formed on the free surfa 


basement membrane, and which 
without reproducing themselves. 
seem to originate in germs contained 
subjacent membrane, and a continual su 
such germs must therefore be required. — 


NUTRITION. 


scarcely be doubted, therefore, that these are 
supplied directly from the blood. Dr. Barry 
and Mr. Addison have spoken with much con- 
fidence of the metamorphosis of the white cor- 
puscles of the blood into epithelium-cells ; but 
that this idea is totally inadmissible is proved 
by the existence of a continuous stratum of 
basement-membrane, between the capillary net- 
work and the epidermic or epithelial layer. It 
is not impossible, however, and perhaps may 
be considered probable, that the cell-germs 
contained in this basement-membrane, from 
which the cells on its external surface appear to 
take their origin, may be the offspring of the 
white corpuscles of the blood, which thus sup- 
plies both the plastic materials and the germs 
of the constantly-forming new crops of epithe- 
lial cells. There is no other tissue in the body, 
after all its organs had attained their full deve- 
lopement, which can be regarded as taking its 
_ origin from the blood in the same degree ; but 
__ it may be questioned whether in the formation 
of new parts, either during the developement of 
the embryo, or in the reparation of injuries, 

the office of the blood is not of a similar du- 
_ plex character. Thus when plastic lymph is 
thrown out, between the two surfaces of a 
wound, the first process, as already mentioned, 
is its fibrillation; but at the same time a deve- 
 lopement of cells takes place in it, which cells 
may possibly undergo a subsequent metamor- 

osis into the various forms of tissue which 
newly-formed part afterwards contains, 
precisely as in the first developement of the em- 
ryonic structure. Such a view, at least, would 
seem probable in regard to the capillary vessels, 
which seem to be formed at least as much by 
the inherent powers of the coagulum, as by the 
extension of the vessels from the subjacent 


urface. 
‘These views are thrown out as hints, rather 
than as settled ideas. It would be premature, 
in the present state of our knowledge, to at- 
_ tempt to decide questions of ssuch importance 
ithout much further examination; and we 
an only attain a balance of probabilities by 
nterpreting the insufficient results of observa- 
‘tion by the aid of the best analogies we can 
 d nd. The whole subject has made immense 
| progress during the few years which have 
elapsed since the commencement of the pre- 
sent work ; but here, as elsewhere, retardations 
have occurred through hasty generalization and 
dogmatic assumptions ; and much patient, well- 
directed, sagacious observation will he needed 
‘to unravel the many intricate questions that yet 
Temain to be solved. 
Varying activity of the nutritive processes. 
—Without any change in the character of the 
Nutritive processes which we have been de- 
seribing, there may be considerable variations 
in their degree of activity ; and this, either as 
regards the entire organism or individual parts, 
though most commonly the latter. These va- 
Tiations may be so considerable as to constitute 
; though there are some which take 
jplace as part of the regular series of physiolo- 
gical phenomena. Thus the nutritive processes 
hould have a degree of activity more than suffi- 


751 


cient to supply the waste of the body during 
the whole period of infancy, childhood, and 
adolescence, until, in fact, its full dimensions 
are attained ; whilst, on the other hand, they 
are usually less rapid than the disintegrating 
processes in old age, so that the bulk of the 
body diminishes. Now as the waste of the 
body, so far from being more rapid in old age 
than in childhood, is much less so, it follows 
that the difference in the activity of the nutri- 
tive processes in these two states must be very 
considerable; and this is manifested, not only 
in the greater demand for food which exists in 
the child (relatively to the bulk of its body), 
but also in the greater quickness and facility 
with which injuries are repaired. Local va- 
tiations may also occur as part of the regular 
train of vital actions in the adult; thus we 
perceive an enormous increase in the amount 
of tissue contained in the uterus and mammary 
glands during pregnancy, and a decrease in 
the bulk of the thymus gland after the first 
year of infancy.’ Now in these cases we see 
that increased nutrition is invariably connected 
with increased functional activity, and dimi- 
nished nutrition with diminished functional 
activity : and this we shall tind to be the con- 
stant rule in regard also to those variations 
which must be considered as abnormal. 
Increased nutrition, or hypertrophy, is 
never known to affect the whole body to a de- 
gree sufficient to constitute disease. It cannot 
be produced as a consequence of the ingestion 
of an undue supply of food, for this does not 
increase the formative activity of the tissues, 
but merely renders the blood richer in nutritive 
materials, a part of which the excreting organs 
are called on to be continually removing, with- 
out its being rendered subservient to the wants 
of the body; whilst another part may be em- 
ployed in the nutrition of one particular tissue, 
the adipose, which has a tendency to increase 
with the superfluity of non-azotized food, pro- 
vided that the requisite amount of cellular tissue 
be generated to hold the fatty matter. But 
examples of hypertrophy of particular tissues 
or organs are very common. Thus any parti- 
cular set of muscles which is subjected to fre- 
quent and energetic use acquires a great in- 
crease in bulk, as we see in the arms of a black- 
smith or waterman, the legs of an opera-dancer, .. 
&e. The hypertrophy of these muscles is a 
consequence of their increased functional acti- 
vity, which being produced by an exertion of 
the will, and unaccompanied with any inju- 
rious effects on the system, can scarcely be re- 
garded as morbid. But there are many in- 
stances in which the involuntary muscles ac- 
quire a greatly-increased strength, in conse- 
quence of an obstruction to their action which 
results from disease. Thus we see the right 
ventricle of the heart become hypertrophied 
(and dilated at the same time) where chronic 
pulmonary disease produces a difficulty in the 
propulsion of the blood through the vessels of 
the lungs ; the muscular fibres of the bladder 
become enormously hypertrophied, when stric- 
ture, diseased prostate, or other causes pro- 
duce a demand for increased expulsive force 


752 


on the pepot the bladder; and those of the 
stomach also become so in cases of stricture of 
the pylorus. As an instance of hypertrophy of 
a secreting organ in consequence of an undue 
excitement of its function, we may notice the 
enlargement which usually takes place in the 
kidney, when its fellow is incapacitated by 
disease, And the nervous system presents us 
with a very remarkable case of hypertrophy of 
a part resulting from over-excitement of its 
function ; for if young persons who naturally 
show precocity of intellect are encouraged 
rather than checked in the use of their brain, 
the increased nutrition of the organ (which 
grows faster than its bony case) occasions 
pressure upon its vessels, it becomes indurated 
and inactive, and fatuity and coma are the 
result. Local hypertrophy may be induced 
also by local congestions ; but in such cases it 
will usually be found that the form of tissue 
produced is of the lowest kind, unless the 
functional activity of the part be increased by 
the. congestion. Thus when disease of the 
heart produces long-continued congestion of 
the lungs, liver, spleen, &c., the bulk of these 
organs increases; but chiefly by the produc- 
tion of an additional amount of interstitial 
areolar tissue, which may result (as we have 
seen) from the simple consolidation of fibrin ; 
and partly also (in the case of the spleen espe- 
cially) by the gorging of their distensible veins 
with blood.—One of the least explicable cases 
of hypertrophy is that which takes place in the 
thyroid gland, causing bronchocele. So little 
is known of the normal office of this organ, 
that it cannot be determined whether its in- 
creased size be due to an increased activity of 
its functional operations, or to an unusual 
formative activity in its tissue, depending on 
some hidden cause. The connection of this 
disorder with causes which affect the whole 
constitution, rather than individual parts, would 
seem to indicate the former. 

When the waste of the tissues is more rapid 
than their replacement by nutrition, atrophy is 
said to take place; and this may affect either 
the whole body, or individual General 
atrophy, marasmus, or emaciation, may result 
from an insufficient supply of plastic matter, 
from want of formative power in the tissues 
themselves, or from their too rapid disintegra- 
tion. The insufficiency of the supply of nutri- 
tive matter may depend either on deficiency in 
the azotized substances ingested as food, or on 
imperfect performance of those processes by 
which they are converted into the plastic 
element,—fibrin. Hence, even when there is 
an ample supply of food, atrophy- may take 
place to a very severe extent, in consequence of 
disordered digestion, or of want of vital power 
in the fibrin-elaborating cells. Again, we have 
reason to believe that the formative power in 
the tissues themselves may be diminished, so 
as to check the process of nutrition, even when 
the plastic material is supplied ; thus there 
seems to be a complete stop of this action 
in fever, and a diminution of it in that irritable 
state of the system, which results from excessive 
and prolonged bodily exertion or anxiety of 


NUTRITION. 


mind, especially when accompanied by want of 
sleep. It is difficult to separate this cause, 
however, from mal-assimilation on the one 
hand, or too rapid decay of the tissues on 
the other: for we know that, in such states, 
there is a tendency to imperfect elaboration of 
the fibrinous element, and at the same time 
an unusually rapid disintegration, as mani- 
fested by the increased amount of urea in the 
urine. The influence of excessive waste in 
causing atrophy of the body is well shown in — 
the cases of diabetes mellitus and colliquative — 
diarrheea ; for in both these, the increase and — 
depravation of the secretions are a 
to be regarded as the effects, and not the causes, — 
of the textural changes with which they are as- 
sociated. Colliquative diarrhea is a constant — 
occurrence on the last day or two of life in 
animals reduced by starvation, and is accom- 
panied by that feetid odour of the body, which 
indicates that decomposition is already going on 
throughout the system. The same thing occurs: 
as the ordinary termination to many diseases of 
exhaustion ; in which inanition is unquesti y 
the immediate cause of death. Partial 
may occur in consequence of disuse of the organ 
affected, occasioning inactivity in its formative 
processes ; or as a result of a deficiency of nt 
triment, occasioned by an obstruction to— 
circulation. Of the operation of the formel 
cause we have many examples in the ordinar 
processes of the economy. Thus the uterus 
atrophied, relatively to its previous condition 
as soon as parturition has taken place; and: 
mammary glands, when lactation has been dit 
continued. It is probably in part to this cau: 
and in part to the diversion of the blood in 
other channels, that we are to attribute | 
atrophy of many parts, as the developement 
the system advances, which at an earlier y 
were of large comparative size,—such as 
corpora Wolffiana, the suprarenal cap 
the thymus gland. Many instances mig 
adverted to, of the influence of suspension 
functional activity, as a result of disease 
injury, in producing local atrophy. One of 
most common cases is the atrophy of mus 
which is consequent upon their disuse. — 
disuse will produce the same effect, whet 
be occasioned by paralysis, which preven 
nervous centres from exciting the m 
contraction ; or by anchylosis, which 
poses a mechanical impediment to 
or by fractures or other accidents, 
paration of which requires the limb tot 
at rest. Or even if, without having s 
from any injury, a limb be fixed during 
time in one posture, its muscles wil 
come atrophied, as is seen in the case” 
Indian fakirs. It has been shown by 
Reid, that the atrophy of the muscles, am 
consequent loss of contractility, is not te 
puted to the withdrawal of nervous in 
in any other way than as producing ce: 
their activity ; for he found that, when th 
cles of one leg ofa frog, both whose crural | 
had been divided, were daily exercised b 
vanism, they retained much more of theit 
size and firmness than those of the leg whic 


rs 
itropny 


‘aa 


NUTRITION. 


left at rest. A case has fallen under the writer’s 
observation, in which both limbs were affected 
with almost complete (hysteric) paraplegia ; 
but one was also frequently seized with violent 
cramps, from which the other was free; the 
difference in the muscularity of the two limbs 
was very striking, and was evinced by the 
greater circumference of the one affected with 
cramps (which was an inch and a half larger 
round than the other), as well as by its greater 
firmness of flesh. Similar facts may be ad- 
duced, in regard to atrophy of nerves, from 
interruption of their normal function. Thus 
when the cornea has been rendered so opaque 
by accident or disease, that no light can pene- 
trate to the interior of the eye, the retina and 
the optic nerve lose, after a time, their charac- 
teristic structure ; so that scarcely a trace of the 
peculiar globules of the former, or of the nerve- 
tubes of the latter, can be found in them. 
These and similar facts are readily understood, 
when connected by the general principle for- 
merly laid down,—that every proper vital 
' Operation involves an act of nutrition ; in such 
a manner that, whilst the vital properties ofany 
part are dependent upon its. due nutrition, the 
amount of its nutrition will in return depend 
_ upon the degree in which these properties are 
exercised. 
_ Partial atrophy may depend, however, upon 
causes of a purely mechanical nature; such, 
for example, as produce an interruption of the 
current of blood through the part. This may 
result from changes in the arteries supplying it, 
such as ossification, or other forms of obstruc- 
tion. Or it may be consequent upon disease 
in the part itself; as when the deposits produced 
_ by inflammation tend to contract, and thus to 
press upon the vascular structure, which fre- 
quently happens in the lungs, liver, and 
kidneys; or when the inflammation occurs in 
the vessels themselves, causing adhesion of 
their walls, and obliteration of their tubes; or 
_ when a new growth absorbs into itself all the 
_ hutritive materials which the blood supplies. 
_ _ Abnormal forms of the nutritive process.— 
Under the preceding head we have considered 
the chief variations in the degree of activity 
| that are witnessed in the ordinary or normal 
conditions of the nutritive process,—that is, 
| those conditions in which the products are 
adapted by their similarity of character to re- 
‘place those which have been removed by dis- 
| integration. But we have now to consider 
“those forms of this process, in which the pro- 
ucts are abnormal,—being different from the 
tissues they ought to replace. We shall con- 
_ fine ourselves to a brief examination of the two 
_ most important of these states ;—that which is 
‘termed inflammation, and that which gives 
Tise to tubercalar deposit. The former results 
from an eacess of the plastic element in the 
blood : the latter from a depraved condition of 
it, og its plasticity is impaired or de- 


B Nowithstinding all the attention which has 

: given to the state of the vessels in inflam- 

mation, a careful consideration of its phenomena, 

with the light which recent investigations have 
VOL. III. 


753 
thrown upon these, leads us to attach com- 
paratively little importance to this, and to seek 
for the essential character of ‘the process else- 
where. The researches of Addison, Williams, 
Barry, Gulliver, Andral, and others, all seem 
to point to the following conclusions.—1. That 
there is a peculiar afflux or determination of the 
white corpuscles of the blood towards the in- 
flamed part. 2. That the total amount of these 
corpuscles in the circulating blood undergoes 
a great increase. 3. That the quantity of fibrin 
in the blood augments in proportion to the ex- 
tent and intensity of the inflammation; and 
this even when it was previously, from the 
influence of some other morbid condition, 
below the usual standard. With its quantity, 
its plasticity or tendency to organization also 
increases in a, healthy subjéct. Now when 
these facts are compared together, and are con- 
nected with those formerly adduced, in regard 
to the probable function of the white corpuscles 
of the blood, they lead almost irresistibly to the 
conclusion, that the process of inflammation 
essentially consists in an undue stagnation of 
the white corpuscles of the blood in the vessels 
of the part, an excessive multiplication of these 
by the ordinary process of generation, and a con- 
sequent over-production of fibrin. By these 
changes, and by the results which follow them, 
inflammation may be distinguished from the 
various forms of hyperemia and congestion. 
To the results, then, we shall next direct our 
attention. 

It may be inferred, we think, from various 
phenomena, that whilst the formative power of 
the blood is increased in inflammation, that of 
the ¢issues is diminished. Certainly this is the 
case in regard to the system at large, when 
febrile irritation has been established ; for, not- 
withstanding the increased plasticity of the blood, 
we see the body wasting, instead of increasing in 
vigour. And it may be inferred, also, in regard 
to the tissues of the part affected, from the ten- 
dency to atrophy and disintegration which they 
exhibit ; and whichis greater (leading even to the 
death of whole parts) in proportion as the ifi- 
flammation is more intense, and as the tendency 
to the deposit of new products is the more 
decided. That a stagnation of blood takes 
place in the vessels of the inflamed part is 
another general fact, which throws some light 
upon the nature of the process ; for this stag- 
nation is obviously favourable to the transu- 
dation of the fluid plasma of the blood, through 
the walls of the vessels, into the surrounding 
tissue, or upon a neighbouring surface. This 
deposition of the fibrinous element, possessing a 
high degree of plasticity, and capable of spon- 
taneously passing into simple forms of tissue 
(which may be gradually replaced by higher 
forms, when penetrated by vessels from the 
surrounding parts), may be regarded as the 
first characteristic result of inflammation. That 
this deposition of the fibrin, which has accu- 
mulated to an unusual extent in the blood, 
should take place only in the inflamed part, 
cannot perhaps be very readily accounted for; 
but we see that, when the inflammatory 
diathesis is once established,—or, in other 
3c 


754 


words, when the quantity of fibrin in the cir- 
culating part is much increased,—local inflam- 
mat.ons will be excited by very trifling causes 
(at other times quite inoperative), which are 
followed by the same results as the original one. 

But it frequently happens that the fibrinous 
element of the blood, though increased in 
quantity, does not possess its normal plasticity ; 
and the deposits which are the consequence of 
its effusion are far from being as organizable 
as in the preceding case, and are either im- 
perfectly organizable, or caco-plastic, or alto- 
gether unorganizable or aplastic. The tendency 
to such deposits may arise from various causes. 
Thus, when the inflammation is from the first of 
a low or asthenic character, or when the blood 
is previously in an unhealthy condition (as, for 
instance, when there is a deficiency in the 
number of red particles, the presence of the 
normal amount of which seems important to the 
complete elaboration of the fibrin), no other 
kind of deposit takes place from the first; and 
even when organizable plasma has been co- 
piously thrown out in the first instance, it is 
not unfrequently succeeded by caco-plastic, or 
ae products,—either from a change in the 
character of the inflammatory process itself,—or 
because the late products are thrown out in 
such a position as to be cut off from that influ- 
ence of living surfaces around, which is neces- 
sary to their complete organization. Between 
the organizable or euplastic, and the caco-plastic, 
and aplastic deposits, the gradations are almost 
insensible. The cells and fibres which are 
characteristic of the first diminish in number 
and are less perfectly formed; and they are 
replaced by a granular amorphous matter, which 
possesses but little cohesion, and which, being 
totally incapable of entering into any form of 
tissue, acts as a foreign body, and becomes a 
source of irritation. The limited space allotted 
to this subject prevents any more particular 
description of these products from being here 
given; but there is one which must not be 
overlooked, since its occurrence is very fre- 


quent, its effects upon the system most im- 


portant, and its character very peculiar. The 
1 alluded to is pus. This is characterized 
y the presence of a number of cells of a pe- 
culiar aspect, having a very tuberculated or 
- Mnulberry surface, which are seen floating in a 
fluid, termed liguor puris, which is of an albu- 
minous or low fibrinous character, being 
entirely destitute of organizability. Now the 
production of pus in an infamed part, or in 
other words, the act of suppuration, may be 
due to one of three causes, viz.,—the intensit 
of the inflammation ; the presence of air, whic 
mes a source of irritation ; and a previously 
vitiated state of the blood. Various attempts 
have been made to show that the pus-globule is 
a degenerated red or white corpuscle of the 
blood ; but it seems more probable, however, 
that it does not escape from the vessels asa 
complete cell, but as a cell-germ, which may 
have had its origin in a white corpuscle of the 
blood; and which, under favourable circum- 
stances, might have produced an exudation- 
corpuscle. Atany rate, it must be regarded as 


NUTRITION. 


a degenerated form of cell ; and the liquor puris 
must be considered as analogous to the plasma 
of the blood in a degenerated state.* 

In what manner the inflammatory 
determines the formation of the pus and 
the consequent degradation of the product, we 
are at present unable to state; but that the 
degree of irritation in the part has an influence 
upon it is evident from the effects of the contact 
of air upon inflamed surfaces, causing those 
elements to take the form of pus, which would 
otherwise have been thrown out as a plastic 
deposit. This circumstance would seem to 
indicate, beyond all doubt, that the exudation 
and pus-corpuscles, the plastic lymph, and the 
aplastic liquor puris have the same origin, but — 
that their character is determined by local cir- — 
cumstances. There is great reason to believe, 
that when pus is introduced into the blood, it 
me peinrs such a change in the ier 
the fluid, as speedily to impair its vital proper- — 
ties ; so jr rieag tags ea: will 
propagate themselves in the blood, the 
plasticity of the liquor sanguinis will be dimi- 
nished. In this manner the whole will 
be seriously affected, and there will be a tend- 
ency to deposits of pus in various 
especially those which, like the lungs liver, 
serve as emunctories to the system—without 
any previous inflammatory changes in these 

rts 


P'The last form of disordered nutrition which 
we shall consider is that which takes place ir 

the tuberculous diathesis, and which is marked 
by the deposition of tubercular matter, in place 
of the normal elements of tissue, both in the 
ordinary process of nutrition, and still more 
when inflammation is set up. From an exam 
nation of the blood of tuberculous subjects 

appears that the fibrinous element is not de 
cientin amount, but that itis notduly elabora’ 
so that the coagulum is loose, and the red ¢ 
puscles are found to bear an abnormally lov 
proportion to it. We can understand, the 
that such a constant deficiency in plasticity 
must affect the ordinary nutritive process; an 
that there will be a liability to the deposit o 
caco-plastic products, without inflammatio 

instead of the normal elements of tissue. § 
appears to be the history of the formation | 
tubercles in the lungs and other organs, 
it occurs asa kind of metamorphosis of tl 
ordinary nutritive process; and in this mann 
it may proceed insidiously for a long period, 
that a large _ of the tissue of the lungs sh 
be replaced by an amorphous deposit, withi 
any other ostensible sign than an increas 


* It would not seem improbable that the lig 
puris is the product of the action of the pus 
puscle, in the same manner as we have endeay 


to show that the li inis is the result o 
elaborating <ctine Ot tas onlonrieus : 
blood. This idea seems confirmed by the 
vation of Mr. Gulliver, that the mb 
which lines the cavity of an a , and 
which the fiuid appears to be secreted, is ch 
composed of cells that bear a strong resemblance, 
the one hand to the pus-corpuscles, and on | 
other to the colourless aca of the blo 
these cells are held together by fibrinous fibri 63 


A 


NUTRITION. 


difficulty of respiration. It is in the different 
forms of tubercular deposit that we see the 
gradation most strikingly displayed between the 
euplastic and the aplastic formations. In the 
semi-transparent, miliary, grey, and tough yel- 
low forms of tubercle, we find traces of organi- 
zation in the form of cells and fibres, more or 
less obvious ; these being sometimes almost as 
paeetly formed as those of plastic lymph, at 
* least on the superficial part of the deposit, 
which is in immediate relation with the living 
Structures around, and sometimes so degen- 
erated as scarcely to be distinguishable. In no 
instances do such deposits ever undergo further 
organization, and therefore they must be re- 
_ garded as caco-plastic. But in the opaque, 
_ ¢rude, or yellow tubercle, we do not find even 
these traces of definite structure; for the matter 
of which it consists is altogether granular, more 
resembling that which we find in an albuminous 
coagulum. The larger the proportion of this 
kind of matter in a tubercular deposit, the more 
is it prone to soften, whilst the semi-organized 
tubercle has more tendency to contraction. 


Microscopic appearances of tubercular matter in the 

lungs, after Gulliver. 

_ To the left, magnified 190 diameters, is shown a 

‘central portion of tubercle, from the lungs of a man 
ged 22, who died of pulmonary consumption; the 


tubercle is contained in the air-cells, and surrounded 
by the fibres of their walls. To the right is depicted 
; ne of the same tubercle, separated and magnified 
about 820 diameters. 
4 Now although tubercular matter may be 
slowly and insidiously deposited, by a kind of 
degradation of the ordinary nutritive process, 
“yet it cannot be doubted that inflammation has 
great tendency to favour it; so that a larger 
uantity may be produced in the lungs, after a 
monia has existed for a day or two, than it 
uld have required years to generate in the 
ious mode. But the character of the de- 
it still remains the same ; and its relation to 
1 plastic element of the blood is shown by the 
interesting fact, of no unfrequent occurrence,— 
hat, in a pneumonia affecting a tuberculous 
subject, plastic lymph is thrown out in one part, 
hilst tubercular matter is deposited in another. 
Now inflammation, producing a rapid deposi- 


tion of tubercular matter, is peculiarly liable to 
arise in organs which have been previously 


* From Wagner’s Physiology, p. 360. 


755 


affected with chronic tubercular deposits, by an 
impairment of the process of textural nutrition ; 
for these deposits, acting like foreign bodies, 
may of themselves become sources of irritation ; 
sd, the perversion of seammnetice and func- 
tions of the part renders it peculiarly suscep- 
tible of the influence of external morbific 
causes. These views, at which several recent 
os hook ay and pathologists have arrived on 
independent grounds, seem to reconcile or 
supersede all the discordant opinions which 
have been upheld at different times regarding 
the nature of tubercle, and lead to the soundest 
views with respect to the treatment of the 
diathesis. 

Parasitic growths——Besides the products 
of disordered nutrition, which have been just 
considered, there is another class of morbid 
structures, differing from the preceding in well- 
marked and important characters. Their exist- 
ence and mode of growth cannot generally be 
traced to simple variations in the local circula- 
tion and in the formative powers of the parts 
affected ; and they enjoy an independent vitality, 
which causes their maintenance and increase to 
be influenced but little by the state of the 
textures around, except so far as this may 
affect the supply of blood which they receive. 
They bear a certain resemblance to other tis- 
sues, in an early stage of the developement of 
the latter; being for the most part composed of 
cells and fibres, combined in different modes’: 
and they also correspond with them in chemical 
constitution. It is by this last character, in- 
deed, that they are to be distinguished from the 
vegetable organisms, which are unquestionably 
developed occasionally in the living animal 
body, and which often closely resemble them 
in aspect. The best practical division of 
parasitic growths is into the non-malignant and: 
the malignant ;—the former being of local 
origin, not tending to reappear in distant parts 
of the body, and having no injurious effect 
upon the surrounding tissues, except by the 
pressure they may exercise upon them, or the 
nourishment they may withdraw ;—whilst the 
latter, having once made their appearance in 
the body, tend to reappear at distant parts (even 
after the original growth has been removed), 
induce a complete change of structure and of 
actions in the organs in which they are de- 
veloped, and exert a very depressing influence 
upon the bodily system at large. 

The non-malignant growths may present 
various characters, intermediate between those 
of the tissues they replace, and those of malig- 
nant structures. In regard to their pathological 
cause, “we cannot at present go beyond the 
supposition, that they arise from altered vital 
properties in some of the molecules of the 
textures in which they are developed ; so that, 
instead of being assimilated to these textures, 
and conforming to the laws of their growth 
and decay, these molecules grow of themselves 
in modes more or less peculiar, and more or 
less independently of the influences of the 
adjoining living parts. Where these modes 
are less peculiar,and more dependent upon the 
nutrition of the adjacent structures, the growths 

3c 2 


756 © 


are less abnormal, vary less from these struc- 
tures, and more resemble either hypertrophy or 
euplastic deposits ; and they do mischief rather 
from their size and situation than from their 
intrinsic nature. Where the mode of growth 
is more peculiar, and more independent of that 
of the textures in which they arise, the resulting 
tumours are more abnormal in their nature and 
mode of developement; they approach in 
character to malignant diseases, acting inju- 
riously, not only by their bulk and position, 
but also by abstracting the nourishment of the 
body, and tending to supersede the natural 
structures.”’* 
Among the malignant growths, too, there 
are various shades or degrees of malignancy ; 
one or more of the characters just now assigned 
to them being either absent or imperfectly de- 
veloped. Thus there are certain growths which 
have a tendency to spread through the system, 
and even to propagate themselves from one 
individual to another, and which agree with 
true malignant growths in being composed, 
like them, of cells having a tendency to rapid 
multiplication, but which yet exert no serious 
influence upon the general constitutional state, 
and which cannot, therefore, be properly termed 
malignant: such are molluscum and porrigo 
Javosa. And in other instances we meet with 
large tumours, producing a very injurious effect 
upon the surrounding textures, and exerting a 
very serious influence upon the system at large ; 
the malignancy of which, however, is doubtful, 
because they show no tendency to reappear in 
other parts of the body. The origin of all these 
growths is involved in great obscurity; but 
there does not appear to the writer to be any- 
thing so specific in their character as to require 
the supposition that their germs are introduced 
into the body from without. It is true that 
when they have once established themselves 
they may be propagated by inoculation, which 
transplants some of the cells or cell-germs into 
a new locality; and the appearance of the dis- 
ease in parts of the same body distant from 
those which were first affected, is probably due 
to the diffusion of the germs by the current of 
the circulation. But this power of reproduc- 
tion is by no means limited to malignant 
growths, since it belongs to all cells at a cer- 
tain stage of their developement. And, as Dr. 
W. Budd + has remarked, the causes which 
have been supposed to induce cancer are not 
such as can, in any intelligible way, favour the 
introduction of germs from without the body. 
Thus in chimney-sweeps and others the conti- 
bued application of soot has been observed to 
be followed by the occurrence of cancer in the 
scrotum in such a number of cases, as to justify 
the inference that it has been the exciting cause ; 
and the often-repeated contact of a tobacco-pipe 
with the lip has also been considered a cause 
of cancer of that part. But neither of these 
causes can in any conceivable way promote the 
developement of cancer from extmnsic germs. 
We are quite in the’dark, however, as to the 


be Williams’s Principles of Medicine, § 574. 
+ Lancet, May 28, 1842, 


NUTRITION. 


mode in which any perversion of the ordinary 
nutritive processes arising from external irrita- 
tion of whatever kind, can give rise to struc- 
tures so peculiar in their nature and history as 
are the various forms of cancerous growths. 
For a detailed account of their characters as 
unveiled by recent microscopic the 
reader must seek elsewhere ; since all thatwe 
can here attempt is to give a general idea of their 
liar nature. (See a Morbid.) — 
e greater part of every true malignant 
is Sale up of cells, which, instead of under- — 
going transformation into other kinds of tissue, — 
continue in their original state, and enjoy the — 
ase of rapid multiplication. In the harder 
rms of cancer the masses of cells are traversed — 
by bands of solid fibrous texture, and such are 
of slow growth, and may remain with but little © 
change for many years, apparently because the 
pressure to which they are subj prevents 
their rapid increase. But the softer forms ar f 


‘composed almost entirely of cells, and th 
of the most rapidly multiplying character ; so 
that, in the rapidity with which they shoot up, 
they remind us of the vegetable fungi. Now 
the influence of either of these forms of morbid 
growth upon the constitution is very decided, 
and distinguishes them from non-malignam 
structures ; but this is more evident, the mor 
time is afforded for the manifestation of thei 
effects. It is evident even from the appearance: 
of the subject of them that the blood must b 
in a very depraved state, for there is a peculi 
dirty sallowness about the complexion whi¢ 
is seen in no other disease; the emaciatic 
reaches a point unequalled under any oth 
circumstances ; and accidental injuries w 
may occur during the progress of the mala 
are but very imperfectly repaired. In their ¢ 
leterious effects upon the c of the circ 
lating fluid, therefore, we may not impropel 
compare cancer-cells with pus-globules. 
General summary.—From what has b 
Stated it appears evident, that the process 
nutrition essentially consists in the growth 
the individual cells composing the fabric; ; 
that these derive their support from the orgs 
compounds with which they are supplie 
the blood, just as the cells composing the: 
plest plants derive theirs from the inor 
elements which surround them. And as 
rent species of the latter select and cor 
these in such modes and proportions as_ 
rise to organisms of very diversified form 
properties, so is it easily intelligible # 
different parts of the fabric of the highe 
mals, whether normal or 
exercise a similar selective power, in re 
the materials with which the blood st 
them. The structure composing every $ 
portion of the body has what may be 
a special or elective affinity for some pal 
constituents of the blood; causing it to; 
from that fluid and to convert into it 
substance certain of its elements: and 
exercised not only in regard to the norm: 
stituents of the blood, but also towards 1 
matters which may be circulating wit 
the causes which enable the cells of : 


< 


AULIOTI: a % 
4 


? 


NUTRITION. 


vegetable structure to exercise these varied 
attractions, our knowledge is at present very 
limited. It will probably long remain an ulti- 
mate fact in physiology that cells have the 
power of growing from germs, of undergoing 
certain transformations, and of producing germs 
_ that will develope other cells similar to them- 
selves, just as it is an ultimate fact in physics 
that masses of matter attract each other ; or in 
chemistry, that the molecules of different sub- 
_ Stances have a tendency to unite, so as to form 
_ a compound different from either of the ele- 
ments. It is of such ultimate facts that the 
_ Science of vitality essentially consists. The 
_ conditions under which the assimilating power 
_ Operates are, however, like the laws of chemical 
affinity, freely open to our investigation ; and 
it is a great step in the progress of the inquiry 
_ to become aware that these are so closely con- 
formable throughout the organized world, as 
_ we have endeavoured to show them to be. 
_ It may be stated as a general fact, that in 
assimilating or converting into its own sub- 
_ stance matter which was previously unable to 
_ exhibit any of the manifestations of life, every 
- cell thereby participates in the process of orga- 
nization and vitalization ; for by the new cir- 
cumstances in which the matter is placed its 
sensible properties are altered,—some which 
were previously dormant being now caused to 
manifest themselves, whilst others, which were 
‘previously evident, become latent. No mat- 
a that is not in a state of organization can 
exhibit these properties, which, from their being 
peculiar to living bodies, and altogether diffe- 
rent from those of which physics and chemistry 
take cognizance, are termed vital ; and it may 
also be asserted that no matter which exhibits 
perfect organization is destitute of the peculiar 
vital properties belonging to its kind of struc- 
ture. (See Lire.) Hence every act of nutri- 
tion is, in fact, the creation of a new amount of 
_ vital force ; and when that vital force has been 
_ expended, no more can be developed except by 
the nutritive process. 
_ From the foregoing details it further results 
that we must regard each part of the organism 
as having an individual life of its own, whilst 
contributing to uphold the general life of the 
entire being. This life, or state of vital action, 
ends upon the due performance of the func- 
tions of all the subordinate parts which are 
osely connected together. The lowest classes 
of organized beings, and even the highest at 
| an early stage of their embryonic developement, 
are made up of repetitions of the same ele- 
| ments; and each part, therefore, can perform 
if ts functions in great degree independently of 
‘the rest. But in ascending the scale or in 
tracing the advancing developement of the em- 
‘bryo, we find that the individual lives of the 
¢ells become gradually merged (so to speak) in 
the general life of the structure; for they be- 
come more and more different from each other 
in function, and therefore more and more de- 
| pendent on each other for their means of sup- 
ons 3 So that the activity of all is necessary for 
the maintenance of any one. Hence the inter- 
Tuption of the function of any important organ 


, 
i 


757 


is followed by the death of the entire structure; 
because it interferes with the elaboration, circu- 
lation, and continual purification of that nutri- 
tious fluid which supplies she pabulum for the 
growth and reproduction of the-individual cells. 
But their lives may be prolonged for a greater 
or less duration after the suspension of the 
regular series of their combined actions ; hence 
it is that molecular death is not always an im- 
mediate consequence of somatic death. (See 
Deatu.) Butif the function of the part have 
no immediate relation to the indispensable 
actions just referred to, it may cease without 
affecting them; so that molecular death may 
take place to a considerable extent without 
somatic death necessarily resulting. 

The foregoing considerations have a very 
important bearing on the question of the de- 
gree to which the process of nutrition is under 
the influence of the nervous system, a question 
on which, as it appears to the writer, very erro- 
neous ideas have been commonly entertained. 
For it has been customary to speak of this pro- 
cess (as well as of secretion) as dependent upon 
nervous agency; or, in other words, to assert 
that the nervous system is not only the instru- 
ment of the functions of animal life, but is also 
the primum mobile of the organic operations. 
Now the independent properties of the cells in 
which all organized tissues originate, might be 
of itself a satisfactory proof that in animals, as 
in plants, the actions of nutrition are the results 
of the powers with which they are individually 
endowed; and that whatever influence the 
nervous system may have upon them, they are 
not in any way essentially dependent upon it. 
Moreover there is an evident improbability in 
the idea “that any one of the solid textures. of 
the living body should have for its office to 
give to any other the power of taking on any 
vital actions;” and the improbability becomes _ 
an impossibility, when the fact is known, that 
no formation of nervous matter takes place in 
the embryonic structure, until the processes of 
organic life have been for some time in active 
operation. The influence which the nervous 
system is known to have on the function of 
nutrition may operate in several ways. Thus, 
if the nerves proceeding to any set of muscles 
be divided, those muscles will be atrophied in 
consequence of the cessation of their activity, 
as already explained. In other instances we 
may not improbably regard the influence of the 
nervous system to be exercised through the 
medium of its controlling power over the dia- 
meter of the bloodvessels, by which it may 
govern the afflux of blood. And there can be 
little doubt that, in some manner yet unex- 
plained, the nervous system exerts an influence 
over those preliminary processes, by which the 
plastic element of the blood is elaborated; so 
that long-continued anxiety or depression of 
mind may produce general atrophy, or a ten- 
dency to tuberculous deposit. It appears to 
be invariably through emotional states of the 
mind that the nutritive process is affected ; the 
will not possessing any direct power of influ- 
encing them. But there can be no doubt that 
the continual voluntary direction of the atten- 


758 


tion to the sensations of any part, giving rise to 
emotions on which the mind frequently dwells, 
may so far modify the nutrition of the as 
to become a cause of diseased action in it. All 
these facts, however, point rather to the influence 
which the nervous system s over the 
organic functions, than to the dependence of 
these upon its agency; and it may be safely 
asserted that no such proof of its more direct 
influence, as is required to counterbalance the- 
manifest improbability which has been shown 
to attend it, has yet been given. Some addi- 
tional considerations upon this important sub- 
ject will be offered under the head of Se- 


CRETION. 
(W. B. Carpenter.) 


CESOPHAGUS. (Ofw, I carry, and dayw, 
I eat.)\—Gr. oicoPayos; Fr. esophage; Ital. 
gola; Germ. Speiserdhre. The cesophagus is 
that portion of the alimentary canal which 
intervenes between the inferior extremity of the 
pharynx and the cardiac orifice of the stomach. 

t occupies the lower part of the cervical region, 
traverses the thorax, and enters the abdomen. 

Direction.—The direction of the esophagus 
is nearly vertical; in the cervical region it 
deviates slightly to the left; in the upper part 
of the thorax it inclines somewhat to the right, 
and in the lower part of the same region it is 
again directed to the left, so as to occupy the 
median line during its passage through the 
diaphragm. 

imensions.—The cesophagus is not of uni- 
form diameter throughout its entire length. 
In the neck it is narrower than in any other 
region; it consequently happens that a morsel 
of food too large to pass readily along the 
esophagus, is usually arrested immediately 
after it has been transmitted from the pharynx. 
In its upper part the esophagus is somewhat 
flattened and compressed in the antero-pos- 
terior direction, but its inferior portion is more 
or less cylindrical, and presents the appearance 
of a rounded cord. 

Relations.—The cesophagus has many im- 
portant relations, which may be considered 
successively in the cervical, thoracic, and ab- 
dominal regions. In the cervical region it 
corresponds anteriorly to the membranous part 
of the trachea, with which it is connected by 
some intervening cellular tissue: in the lower 

of the neck where it deviates to the left 
it comes in contact anteriorly with the left 
sterno-thyroid muscle, the thyroid gland, the 
inferior thyroid artery, aud the left recurrent 
nerve. Posteriorly it has the cervical vertebra 
and the longus colli muscle, with which it is 
connected by means of loose cellular tissue, so 
that free movement of the csophagus upon 
the spine is allowed during the process of 
deglutition. Laterally it is in relation with the 
thyroid body, with the common carotid arteries, 
and more externally with the vagi nerves and 
the internal jugular veins; In consequence of 
the @sophagus deviating slightly to the left in 
the lower of the neck, its relations are 
somewhat different on the two sides. Thus the 
left common carotid is in closer relation with 


(ZSOPHAGUS. 


, es - 


the esophagus than the right. The left recur- 
rent nerve is anterior to the cesophagus, while — 
the right is somewhat posterior. “ 
The thoracic portion of the cesophagus is — 
placed in the posterior mediastinum. It cor 
responds anteriorly to the trachea, aad imme- 
diately below the bifurcation of the trachea to- 
the left bronchus, which crosses it obliquel, 
to the arch of the aorta, to the left subclavian 
and carotid arteries, and to the base of the heart, 
from which it is separated by the pericardium. 
Posteriorly it has the spine, with which in the 
upper part of the chest it is in close contact; 
but as it descends it becomes separated from 
the spine by cellular membrane, by the right 
intercostal arteries, by the vena azygos, and bi 
the thoracic duct, which in the lower part 
the chest is on the right of the esophagus, ba 
ascending it passes behind and above is plac 
= its left side. At the inferior _ 
thorax, immediately before passi rough the 
diaphragm, the cceophoget has aa it the 
thoracic aorta. Laterally it has on its left 
aorta, and on the right side the pleura forn 
the right layer of the posterior mediastinam 
It is accompanied by the two vagi nerves, © 
on each side, which send numerous filamen 
from one to the other, and thas form — 
lexus gule ; at the lower part of the chest # 
eft vagus nerve becomes somewhat anter 
and the right posterior. This portion of 1 
cesophagus is surrounded by a considera 
quantity of loose cellular tissue and by seve 
vee glands. 
The abdominal portion of the esophagus 
very short, and has no relations of impo’ 


€ 
‘4 


After ing through the diaphragm it is ¢ 
vered both anteriorly and posteriorly -by 
peritoneum. It also comes into contact al 


riorly with the left lobe of the liver. With 
depressing the stomach and elevating th 2 
aa this portion of the a 

e seen, and, in fact, can scarcely 
exist. 

Structure —The cesophagus is composet 
a muscular and a mucous coat, with some 
necting cellular tissue. The muscular 
the esophagus, which is considerably th 
than that of any other portion of the alli 
tary canal, consists of two distinct layers. 
external layer is composed of fibres arra 
in a longitudinal direction, and is twice 
thickness of the internal layer, the 
which surround the canal in a cireula 
ner. The longitudinal fibres are re 
disposed around the esophagus; sup 
they arise in the median line from th 
terior surface of the cricoid cartilage 
laterally on each side from the le 
of the inferior constrictor muscle of 
rynx; at the inferior extremity of the @ 
gus they spread out and are continuo! 
the longitudinal fibres of the stomac 
circular fibres are a continuation of th 
terior part of the inferior constrictor m 
but they are much more delicate than the 
of this muscle. These fibres pass for th 
part transversely ; the spiral arrangement 
some anatomists have described de 


2 
4 
es 


| 


. 


(SOPHAGUS. 


nerally exist in the human subject. ‘The co- 
lour of the muscular fibres is pale red, less 
pale than those of the succeeding portions of 


the alimentary canal, and less deeply co-— 


loured than those of the pharynx. A micro- 
scopic examination shews them to be com- 
posed of both striped and unstriped fibres, 
mingled to an uncertain extent. “ In some 
specimens from the human subject we have 
failed in detecting any striped fibres in the 
lower half of the csophagus, either in the 
circular or longitudinal layer; but in other 
examples we have found them to within an 
inch of the stomach.” * , 

Mucous membrane.—The mucous membrane 
of the esophagus is of a pale colour; it pre- 
sents a number of longitudinal furrows, which 
are produced by a slight folding of the mem- 
brane during the partial contraction or ordi- 
nary tonicity of the circular muscular fibres: 
the apparent laxity of the mucous membrane 
is no more than sufficient to allow of the dila- 
tation of the canal which occurs during the 
“nase of deglutition. In addition to the 

ngitudinal furrows there are some finer lines 
or wrinklings passing in various and indefinite 
directions, which are analogous to the fine 
grooved lines observed in the skin of various 

of the body. The mucous membrane is 
remarkable for its thickness; the epithelium is 
so abundant as to be distinctly visible to the 
naked eye ; it forms a thick layer similar toa 
cuticle, and terminates at the cardiac orifice 
- of the stomach in a well-defined irregular 
| fringed border. It is composed of the lamel- 
liform or scaly variety of epithelium.t The 
mucous membrane is connected with the sub- 
_ jacent muscular layer by the intervention of an 
_ abundant lax areolar tissue, which allows of 
_amovement of these membranes upon each 
_ other during the repeated variations to which 
_ the diameter of the cesophagus is subject in the 
| process of deglutition. 
_ Csophageal.glands.—In the submucous areo- 
lar tissue of the esophagus are found a number 
of small glands. They may be felt through the 
(nracons membrane, which they elevate here 
ty there, as little’ circular or oval flattened 
_ granular bodies ; they are most numerous at 
_ the lower extremity of the tube. Their struc- 
ture is the same as that of the buccal and duo- 
denal glands. From the duct, which opens 
on the free surface of the mucous membrane, 
a few ramifications proceed and become em- 
\ ed in the submucous areolar tissue. The, 
branches are short and sacculated, having the 
“appearance of small vesicles collected on a 
‘common stalk. The epithelium lining these 
glands is of the spheroidal variety.{ 
_ Vessels and nerves.—The arteries distributed 
to the @sophagus are derived from several 
‘sources. In the neck they come from the in- 
-ferior thyroid artery ; in the chest some come 
directly from the aorta, others from the inter- 
) costals, and occasionally some from the internal 


; 


* Physiological Anatomy and Physiology of 
‘Man, by Todd and Bowman. 

| + See the article Mucous MEMBRANE. 

|. ¢.lbid, 


759 


Mammary arteries; in the abdomen, branches 
are derived from the coronaria ventriculi and 
from the phrenic arteries. The veins corre- 
sponding to these arteriés_empty themselves 
into the inferior thyroid, the superior cava, the 
azygos, internal mammary, coronaria ventriculi, 
and phrenic veins. The lymphatics open into 
the glands which surround the csophagus in 
considerable numbers. The nerves are derived 
chiefly from the pneumo-gastric. The recur- 
rent branch of the pneumo-gastric in its course 
upwards sends numerous filaments to the cso- 
phagus. In the chest, as the trunks of the 
pneumo-gastric nerves lie on the cesophagus, 
each one sends off filaments which pass 
backwards, ‘encircling the tube, and meeting 
with branches from the opposite nerve. The 
plexus thus formed is called the plexus gule ; 
it is joined by some filaments from the thoracic 
ganglia of the sympathetic. 

Function—The office of the esophagus is 
to receive the aliment from the pharynx and to 
convey it into the stomach. This, the third and 
last stage of the process of deglutition, is un- 
attended by sensation and uninfluenced by vo- 
lition. The following is the mode in which 
the food is transmitted along the cesophagus. 
After being duly masticated and moistened in 
the mouth, it is received into the pharynx, and 
is thence propelled into the upper orifice of 
the ceesophagus. The muscular fibres, both cir- 
cular and longitudinal, of that part.of the tube 
into which the food is propelled are at once 
stimulated to contract; the mass is conse- 
quently pushed onwards into the relaxed por- 
tion of the tube immediately succeeding; the 
stimulus of contact with this part produces the 
same effect upon it as has already been pro- 
duced upon that part of the tube which the 
food has just quitted, and the contraction of 
the first portion continuing at the time when 
that of the second portion is taking place, the 
substance is necessarily propelled onwards: it 
thus comes into contact with successive portions 
of the tube, and in each successive portion the 
same effect is produced, the contact of the sub- 
stance exciting contraction, and the remaining 
contraction of the part which it has just quitted 
preventing regurgitation. These phenomena 
occur in a much less space of time than is 
occupied in their description, and the food is 
rapidly transmitted along the entire length of 
the canal. A notion may be formed of the 
rapidity with which these contractions are trans- 
mitted along the esophagus by observing the 
rapid vibrating movements in the neck of a 
horse while drinking. The secretion constantly 
poured out by the esophageal glands has the 
effect of moistening and lubricating the interior 
of the tube, and thereby of facilitating the 
transmission of solid portions of food. The 
contractions of the cesophagus, which ordinarily 
commence at its pharyngeal and terminate at — 
its cardiac extremity, sometimes take place in 
a reverse order, the direction of the movement 
depending on the part to which the stimulus is 
first applied. Dyspeptic persons are not un- 
commonly troubled with eructations of a liquid 
from the stomach, giving rise to what is fami- 


760 


liarly called heartburn; and in is, or water- 
brash, the amount of liquid which suddenly 
enters the mouth is often very considerable. 
This inverted action of the esophagus admits 
of a ready explanation. By the contraction 
of the muscular fibres of the stomach a portion 
of liquid is expelled into the lower extremity 
of the esophagus; here it immediately excites 
contraction of the muscular fibres which sur- 
round it, and being prevented from again en- 
tering the stomach by the momentary continu- 
ance of the same effort which has expelled it 
into the esophagus, it must necessarily pass 
into the relaxed portion of the tube immedi- 
ately above; and thus, by the contraction of 
successive portions of the tube, the liquid soon 
reaches the te In ruminants, the greater 
portion of the food is returned from the sto- 
mach to the mouth by this inverted action of 
the esophagus.’ During the action of vomiting 
’ there is an inverted action of the esophagus in 
addition to the propulsive effort arising from 
the contraction of the stomach and abdominal 
muscles. 

We have now to point out the precise mode 
in which these contractions are induced, to 
explain the intermediate links between the ap- 

lication of a stimulus to the mucous mem- 

rane and the occurrence of the muscular con- 
traction. In the first place, unless we swallow 
a very large or-a very hot morsel of food, no 
sensation attends its passage along the cso- 
phagus. After the food has passed that portion 
of the pharynx upon which the glosso-pha- 
ryngeal nerve is distributed, we cease to be con- 
scious of its presence; and again, when a bitter 
liquid is eructated from the stomach, it pro- 
duces no sensation of taste until it reaches the 
same point. As the passage of food along the 
cesophagus is unattended by sensation, so is it 
uninfluenced by volition. We cannot by any 
effort of the will perform the action of deglu- 
tition unless we bring a portion of food, or a 
liquid (as the saliva), into contact with the pha- 
rynx, by means of which the action of the parts 
may be excited. Again, no effort of the will 
can arrest the process of deglutition after the 
food has entered the esophagus, and if a liquid 
be made to pass into the pharynx of a person 
in whom the exercise of volition is suspended by 
a fit of apoplexy, deglutition is performed in a 
manner almost as perfect as bya person in health. 
An apparent exception to the general rule that 
‘the movements of the cesophagus are beyond 
the control of the will is afforded by the very 
rare examples of persons possessing the power 
of rumination. A voluntary power over the: 
cesophagus, however, appears by no means neces- 
sary to account for this. It probably depends 
on the possession of an unusual degree of vo- 
luntary power over the movements of the sto- 
mach, and especially of its cardiac orifice, by 
means of which the contents of the stomach 
can be expelled at will into the inferior extre- 
mity of the esophagus, and thus are brought 
within the influence of its involuntary move- 
ments. Any one may satisfy himself that he 
possesses some degree of voluntary power 
over the cardiac orifice of the stomach, if after 


(ESOPHAGUS. 


swallowing a bottle of soda water he will — 
direct attention to the power which he pos- — 
sesses of preventing the sudden escape of gas 
from the stomach, and, on the contrary, of — 
increasing the propulsive effort probably by 
contracting the abdominal muscles. It is pro- 
bable that many persons might by practice 
acquire the power of rumination. Since the — 
contractions of the esophagus cannot be ex~ 
cited by volition, are they dependent on the 
direct stimulus of the muscular fibres by cor 
tact of the food, independently of the ner 
and of the nervous centres? ‘Phat this is 
the case is proved by an experiment performe 
by Dr. J. Reid.* He divided ina rabbit 
vagus nerve on each side above the cesophageal 
lexus, but below the ngeal ches. 
e animal received the food which was offered 
to it, and by a propulsive effort of the tong 
and pharynx transmitted it to the cesoph 
which, having lost all power of contraction, 
remained passive, and became at | com: 
pletely distended and choked up b 1 
rials thrust into it from above. It is evide 
then that the cesophagus loses its power © 
contraction if we cut off its communicatior 
with the nervous centres. As we have b 
seen that the will is not the agent which deter 
mines the contractions of the esophagus, ther 
remains but oneexplanation of these movement: 
which is, that they belong to the class of refle 
actions. An impression made upon the mucot 
membrane of the cesophagus is communicate 
by the afferent nerves to the medulla oble 
gata, and thence an influence, the precise 
ture of which we are ignorant of, is reflec 
along the efferent nerves to the muscular fi 
of the part to which the stimulus was applic 
The only parts of this circle of actions wh 
we recognise by our senses are the applicat 
of the stimulus and the occurrence of the m 
cular contraction; but these are doubtless ¢ 
nected in the manner above mentioned. 
cesophagus receives both its excitor 
motor nerves from the pneumo-gastric; it” 
derives its nervous influence from that po 
of the nervous centre, namely, the m 
oblongata, which is the centre of the respi 
movements. Hence it will be seen that: 
in any case of disease of the nervous e¢ 
deglutition becomes seriously impaired, th 
much reason to fear that the moreimportant 
tion of respiration will soon become inv 
Abnormal anatomy.—The esophagus m 
viate from the normal state in form or in 
ture. In some cases malformation 
without obvious change of structure, b 
more common to find them combined. 
formation of the esophagus may be eithe 
genital or acquired. “9 
Congenital malformation.— It som 
happens that the esophagus is cor 
deficient, terminating above in a ¢ 
the inferior extremity of the pharynx 
minating in the same manner. This is 
associated with an imperfect developem 
the oral cavity and of the lower jaw, ti 


+4 


~? hale 


¥ 


7. 


* See the Edin. Med. and Surg. Jou 


7: 


(ESOPHAGUS. 


being in great part or altogether deficient. In 
some cases the pharynx does not terminate in 
a cul-de-sac, but opens by a small orifice at 
the side of the neck. Another congenital mal- 
formation more rare than the last consists in 
the division of a portion of the esophagus into 
two canals placed side by side. 

Acquired malformation —One of the most 
common kinds of acquired malformation is 
dilatation either general or partial. In the 
Museum of King’s College there is a remark- 

_ able specimen of a dilated esophagus. At each 
extremity it is healthy and of the natural size ; 
the intermediate part is enlarged to an extra- 
ordinary degree of dilatation ; the lining mem- 
brane is thickened and opaque, ae a the 
a e of having partially yielded from 
aaiatico. The eo fibres were of the 
natural colour and thickness. The dysphagia 
_ in this case was as great as in a case of stric- 
 ture.* Dilatation is a common consequence 
of stricture. In such cases the dilatation 
‘usually occupies the whole circumference of 
‘the canal. Insome rare cases dilatation occurs 
in the form of a pouch projecting on one side 
of the canal. Occasionally the mucous mem- 
brane alone becomes pouched, protruding as a 
hernia between the muscular fibres, but more 
‘commonly the muscular coat also dilates and 
expands over the pouch. Bleuland mentions 
‘a case in which a large pouch containing ali- 
Mentary matters compressed the canal below 
so as completely to close it, and to prevent the 
assage of food into the stomach. These 
pouches are most common at the upper ex- 
tremity of the esophagus, probably in con- 
sequence of the sudden constriction which the 
anal undergoes at this point, and partly too in 
eonsequence of the muscular coat being thinner 
here than in any other part. 
_ Structural changes.—Among the most com- 
/mon are those which result from inflam- 
“ation, which however is seldom idiopathic, 
but generally the consequence of swallowing 
itating substances, hot liquids, the strong 
s or alkalies. The effects in such cases 
jary in degree from slight redness and sofien- 
ig of the mucous membrane, to ulceration 
id sloughing of the “Whole circumference of 
he tube. The Museum at King’s College con- 
ins a aaa of an esophagus and of a 
Slough discharged from it, which was taken from 
young woman who had swallowed oil of vitriol. 
week afterwards she brought up a slough 
aving a tubular form, and consisting of the 
ole lining membrane of the gullet. Some 
the muscular fibres were plainly visible on | 
e outside of the slough, in its recent state.{ 
r. Baillie gives a drawing of a false mem- 
rane lining the pharynx and cesophagus, taken 
om a patient who had thrush. 
E The esophagus is very frequently the seat of 
ricture, the causes of which are various. Not 
anfrequently it depends on the contraction of 
a cicatrix after sloughing produced by the con- 


oo = 


= 


ee 


n> Gr jel et Oe ee a 


| * This case has been fully described by Mr. Mayo 
jm the third volume of the Medical Gazette. 

+ Meckel, Manuel d’ Anatomie. 

| } Dr, Watson’s lectures, vol. ii. p. 332. 


761 


tact of some irritating agent. The constriction 
in these cases appears to go on continually in- 
creasing. Sir ¢: Bell mentions-a case in which 
starvation was the consequence of stricture of 
the esophagus, twenty years after swallowing 
a quantity of soap lees. Another common 
cause of stticture is cancerous disease. This 
is generally confined to the lower extremity, 
but occasionally it pervades every part of the 
cesophagus.* A more rare case of stricture is 
described by Sir E. Home.t In this case a 
membranous partition extended across the canal ; 
in the centre of the partition was a narrow 
passage ; the coats of the esophagus surround- 
ing the stricture were but slightly changed. 
In cases of simple imflammatory stricture all 
the coats of the esophagus are thickened and 
indurated at the seat of stricture, lymph is 
effused between them, and the bloodvessels 
are enlarged and distended. In consequence 
of stricture the esophagus above becomes 
much dilated; sometimes ulceration and abscess 
occur. Dr. Monro mentions a case in which 
death occurred suddenly in’ consequence of 
purulent matter escaping into the trachea. 

Morbid growths are occasionally found in 
the esophagus. Dr. Monroj describes the 
dissection of a man aged 68, in whom the 
cesophagus was dilated by a large fleshy excre- 
scence or polypus. It was attached three 
inches below the epiglottis and reached down 
to the upper orifice of the stomach. Haller§ 
gives an account of the dissection of a man, 
in whom was found a polypus about seven 
fingers’ breadth long, and of the thickness of 
a worm, which in its general appearance it 
very much resembled; it had a carneo-fibrous 
appearance, a soft consistence, and a deep red 
colour. Fatty and steatomatous tumours have 
occasionally been found in the gullet. In 
other cases a portion of the canal has been 
found converted into bone, or cartilaginous 
tumours have grown from.it. 

An aneurism springing from the posterior 
part of the arch of the aorta may compress 
the csophagus against the spine. The imme- 
diate consequence is difficulty of swallowing 
and other symptoms of stricture, and at length 
in many cases ulceration and sloughing of the 
cesophagus with escape of blood from the aneu- 
rism either into the mouth or the stomach. 


BIBLIOGRAPHY.—WMeckel, Manuel d’Anatomie. 
Cruveilhier, Anatomie Descriptive. Bleuland, De 
sana et morbosa cesophagi structura. Todd and 
Bowman, Physiological Anatomy and Physiology 
of Man. Miiller, Physiology, by Dr. Baly. Monro, 
Morbid Anatomy of the haman gullet, stomach, 
and intestines. Sir E. Home, Practical observa- 
tions on strictures. Haller, Disputationes ad 


morbos. 
( Geo. Johnson. ) 


OLFACTORY NERVES. See Noss and 
SMELL. 


* Monro’s Morbid Anatomy of the Haman Gul- 
let, Stomach, and Intestines. 

+ Practical Observations on Strictures, vol. ii. 
p- 407, 3d ed. 

FOpsicies) 

§ Disputationes ad Morb. tom. iii. p. 596. 


762 


OPTIC NERVES. Under this heading it 
is proposed to describe the special nerves of 
vision in man, for although other names are 
also employed by anatomists to denote the 
nerves in question, the above is preferred as 
being expressive of their functions. It should 
be borne in mind that the optic nerves are like- 
wise fiequently called “the second pair;” a 
term derived from their numerical position on 
the base of the brain, as they are the second 
from before backwards on the under surface of 
the encephalon. , 

The anatomy and physiology of the optic 
nerves in man constitute the more immediate 
subjects of the present article, but as these 
would be imperfectly treated without the aid 
of comparative anatomy, the reader will find 
in the following pages frequent references to 
the condition of the nerves of vision in other 
animals also. 

DescripTIVE ANATOMY. 

Apparent origin.—The optic nerves com- 
mence by two broad medullary tracts (the 
tractus optici), each of which becomes first 
apparent at the under surface of the corres- 
ponding optic thalamus. 

Tractus opticus.—This appears to derive its 
principal origin from the corpus geniculatum 
-externum: from that tubercle a narrow band 
arises which is soon reinforced by another (not 
in general equally large or distinct,) from the 
corpus geniculatum internum, and by the 
junction of the two the tractus opticus is 
formed: thus constituted, the tractus opticus 
takes a course forward and inward around the 
outer and inferior surface of the crus cerebri: 
it is at first deeply concealed from view in the 
great cerebral fissure, being overlapped from 
without by the middle lobe of the cerebrum, so 
as to be invisible until a portion of the brain, 
together with the arachnoid membrane and pia 
mater, have been displaced. Emerging from 
under cover of the middle lobe, the tractus next 
gains the front of the crus, runs along the 
margin of the tuber cinereum, and at length 
unites with the other tractus opticus to form 
the chiasma. 

At the crus cerebri the tractus opticus in- 
creases in breadth, and of its two edges the 
“anterior or external is here the thicker, while in 
the vicinity of the chiasma the tractus loses its 
flattened appearance, and becomes nearly cylin- 
drical. 

The tractus opticus is soft in texture through- 
out, being devoid of the tough neurilemma from 
‘which the proper optic nerve derives its uncom- 
mon firmness. 

_ The tractus opticus receives a very extensive 
investment from the pia mater, which covers 
and adheres to all its surface: anteriorly, 
where the tractus is approaching the chiasma, 
nearly two-thirds of its .circumference are 
clothed by pia mater; and further back, that 
membrane even insinuates itself a short distance 
between the posterior or inner margin of the 
‘tractus, and the adjacent surface of the crus 
cerebri. The arachnoid has a far less extensive 
relation to the tractus opticus: in the early 

of its course the tractus has no serous covering, 


OPTIC NERVES. 


but in the interval between the middle lobe of 
the brain and the chiasma, the eymersi . 
beneath the tractus opticus, and so ita 
partial investment. " 
The anterior or external margin of the tractus 
opticus is so closely connected to the crus — 
cerebri that in attempts to separate them the 
medullary substance is torn, and consequently 
some anatomists are of opinion that the crus 
furnishes filaments of origin to the tractus; but 
the posterior or inner edge of the tractus is no’ 
identified with the crus, for there the two 
structures can be separated without any vic 
to either. ‘ 
The third and fourth nerves, before react 
the cavernous sinus, cross ee ractus 
opticus, but not immediately, for Dt 
ad vascular membranes of the brain, and in 
general the edge of the middle cerebral le 
are interposed; the posterior communic 
artery also across the tractus inferiorly 
and the artery of the choroid plexus, in it 
course to the great cerebral fissure, runs 
neath it, the pia mater alone intervening be 
these bloodvessels and the tractus opticus. 
The chiasma is somewhat ilat 
and receives by each posterior angle the 
responding tractus opticus, while its anteri 
angles are prolonged respectively into eith 
optic nerve; when “ in situ,” it is supported 
a transverse groove of the sphenoid bone 
front of the sella Turcica. P iorly, 
identified with the tuber cinereum, 
upper surface the peculiar greyish memt 
which closes up the third se is adher 
The chiasma has complex relations to h 
vessels ; behind and below this body the 
rior portion of the coronary sinus is situ 
external to the chiasma the termination of 
internal carotid artery is placed, and in fre 
it are the anterior communicating, and a» 
of the anterior arteries of the cerebrum. 
Optic nerve proper.—This proceeds 
the chiasma, and after passing throug! 
foramen opticum into the orbit, and arrivit 
the eye-ball, it perforates the sclerotic 
choroid coats, and terminates in the retina 
First stage.—In the short interval b 
the chiasma and the optic foramen, the 
nerve is directed forward and outward ; its 
is perceptibly greater than that of the t 
opticus : it is not perfectly aaa ns 
being slightly flattened above and below; 
covered immediately by a dense tough 
lemma, and provided besides with a 
sheath of arachnoid membrane, whie 
accompanying the nerve fairly into 
the sphenoid bone, becomes reflected | 
— of dura mater lining that a 
hortly after its commencement the opti 
is separated from the olfactory by the a 
artery of the cerebrum. The ophthalmi 
leaves the cranium by the foramen optiet 
and lies beneath the optic nerve’ and to? 
side, being there enveloped in a spec 
of foore preg ‘oie 
cond stage.—Having entered 
the optic Bt inclines more directly fort 
in consequence of this change of direc 


. A ’ J 


=: 
‘or 


OPTIC NERVES. 


appears slightly bent at the optic foramen, the’ 

convexity of the curvature being turned outwards, 

and it traverses the fibrous and vascular coats 
__ of the eye at a point not exactly corresponding 
to the axis of the organ, but a little inferior 
and internal to that imaginary line. 

Whilst in the orbit the optic nerve is com- 

letely cylindrical, but a circular constriction 
indents it just before piercing the sclerotic. 

In this, its second stage, the optic nerve has 
still its neurilemmatous investment, and in ad- 
dition, a perfect sheath of fibrous membrane, 
_ derived from and clearly traceable to the dura 

mater; this latter covering of the nerve pos- 
sesses great strength and density; it is white 
and tough, and admits of ready separation from 
the proper neurilemma ; moreover, it becomes 
continuous with the sclerotic, as the nerve is 
perforating that tunic. 

In its course through the orbit the optic nerve 
‘is related to many of the important parts in that 
_ Cavity; on leaving the foramen opticum it is 
surrounded by the posterior attachments of the 
tmouscles of the eye, and afterwards proceeds 
forwards to its destination through the centre of 
the space which has the recti for its limits. The 
_ nerve is here imbedded in a quantity of soft 
fat, from which it derives protection, and 
wherein other nerves and bloodvessels are 
_ immersed. 

_ The nasal branch of the ophthalmic division 
_ Of the fifth nerve (immediately after entering the 
orbit), the lenticular ganglion with its roots, and 
some of the ciliary nerves at their origin, the 
xth nerve, and the ophthalmic vessels in their 
irst stage, intervene between the outer surface 
of the optic nerve and the external rectus 
muscle. 
Between the upper surface of the optic nerve 
‘and the superior rectus muscle, the superior 
division of the third nerve, the nasal branch of 
the ophthalmic division of the fifth nerve, and 
| the ophthalmic artery and vein (in the second 
Stage,) take their course; the vein being gene- 
¥ placed farther forwards than the artery. 

th the optic nerve, the inferior division 
of the third nerve is placed, and those twigs 
the latter which are destined for the inferior 
and internal recti muscles separate the optic 
from the inferior rectus. 

_ To the inside of the optic nerve and upon a 
higher plane, the ophthalmic vessels in their 


le ee 


d external aspects, but nevertheless one or 
wo of the ciliary branches of the nasal nerve, 
as well as one or more from the lenticular gan- 
glon, before piercing the sclerotic coat, gain, in 
‘general, the inner side of the optic nerve. 

‘The long and short ciliary arteries in their 
course to the globe of the eye are intimately 
tated tothe optic nerve, some. of the latter 


763 


vessels appearing actually to twine around it in 
a spiral manner: and many of the muscular 
branches of the ophthalmic artery lie immersed 
in the surrounding adipose tissue, at no very 
great distance from the nerve in question. 

Communication with other  nerves—The 
optic nerves have no direct communication with 
the other cerebral nerves,tbut certain anatomists 
have traced filaments from the ganglionic 
system to them. Arnold (Icones nervorum 
Capitis, Tabula Sexta) has described and 
delineated two slender threads which run from 
the spheno-palatine or Meckel’s ganglion to 
the optic nerve, and Hirzel observed in several 
instances the same arrangement. Tiedemann 
has seen an excessively delicate filament from 
the lenticular ganglion accompanying the arteria 
centralis retinze through the optic nerve: he 
has also discovered branches of the ciliary nerves 
taking the same course, and has even suc- 
ceeded in following them as far as the retina; 
and M. Ribes (Mémoires de la Société Médi- 
cale d’Emulation) has asserted, that a minute 
subdivision of the cavernous plexus extends 
along the arteria centralis retin, being derived 
from that division of the plexus which accom- 
panies the ophthalmic artery. 

Organization.—The organization of the optic 
nerve is in many respects peculiar. Firstly. 
From the chiasma to its distal extremity it is 
enveloped by a strong coating of neurilemma, 
and from the inner surface of this tunic a 
number of processes are detached which divide 
the interior of the envelope into longitudinal 
canals wherein the medullary substance is 
lodged ; the optic nerve is not therefore a mere 
bundle of nervous cords (the structure prevalent 
in other nerves), but it is “a cylinder of collected 
tubes.” Secondly. From the optic foramen to 
the sclerotic a sheath of dura mater is super- 
added to the optic nerve, and since none of the 
other cerebral nerves possess a similar covering, 
it must be pate her a special provision for 
the security of the second pair Thirdly. The 
arteria centralis retine runs through the centre 
of the optic nerve (an anatomical arrangement 
of exceedingly rare occurrence): and the pri- 
mitive fibres of the optic nerve evince a marked 
tendency to appear “ varicose,” a condition 
discovered by Ehrenberg, and considered by 
him and others peculiar to certain parts of the 
nervous system. 

Real origin.—Anatomists have entertained 
very conflicting views upon this interesting 
question, so that from time to time different parts 
of the human encephalon have been considered 
the true origin of the optic nerves. 

The older writers very generally believed 
that these nerves originate in the optic thalami, 
as the names “thalami nervorum opticorum ” 
still applied to the bodies in question suffi- 
ciently attest, and. Eustachius, Varolius, 
Lieutaud, Haller, &c. supported this opinion. 

Others conceived that the nates (or anterior 
pair of the tubercula quadrigemina) are the 
principal source of the optic nerves; this 
was maintained by Ridley, Winslow, Zinn, 
Morgagni, Sanctorini, Girardi, Hildebrandt, 
Boyer, Bichat, and Scemmerring ; and the same 


764 


views were still more powerfully advocated by 
Gall and Spurzheim, although they admitted 
that the nerves derive a reinforcement from the 
corpora geniculata externa and the tuber 
cinereum. 

Tiedemann (although fully aware that some 
filaments of the optic nerves are traceable to 
the surface of the optic thalamus both in the 
foetus and adult) yet believed the nates and 

geniculata externa to be the true origins 
of the nerves under consideration, and in this 
opinion he was strengthened by the Report on 
the Memoir of Gall and Spurzheim, made to 
the Institute by Cuvier, Portal, Sabatier, and 
Pinel. 

_ According to Serres the tubercula quadri- 
gemina are the proper sources of the optic 
nerves, and by Leuret the second pair are traced 
to a triple cerebral attachment, viz. the nates, 
testes, and optic thalamus. 

It is proposed to examine in this place some 
of the grounds on which the foregoing opinions 
have been founded, and to this inquiry the aid 
of comparative anatomy is indispensably re- 
quisite. 

Fisu.—In these animals the optic nerves 
are distinctly traceable to two of the ganglia 
which compose the diminutive brain. The 
gunglia in pens are called “ optic lobes,” 
from being the principal sources of the nerves 
of vision ; they are hollow, and their position 
in the brain is between the cerebral hemispheres 
and the cerebellum (fig.407.) The optic lobes 


Fig. 407. 


Brain of a Hake. ( From nature. ) Side view seen from 
below. 


aa, optic nerves; 6b, oblique crossing of ditto ; 
ce, ovtic lobe of left side, being the chief source of 
the right optic nerve; dd, two inferior lobes from 
which the nerves of vision in fishes generally 
derive roots, 


in fish very generally bear proportion to the size 
of the optic nerves (a proof of their physiological 
relations); and this ahaa becomes par- 
ticularly apparent in fish which possess either 
unusually small organs of vision, as the Eel ; or 
eyes of different dimensions, as the Pleuronectes. 


Fig. 408. 


Brain an Eel. (A 
Solly. ae from ibs sa 


a, optic nerve ; bb, o 
tic lobes, which are small, 
being proportional to the 
size of the optic nerves. 


In many kinds of fish the optic nerves de- 
rive some of their-filainents fiom a pair of 


OPTIC NERVES. 


Brain of a Halibut. ( From nature. ) 


A, seen from above. _B, seen from below. — 
__¢, large optic nerve in both ; d, small optic 
in both ; e, large optic lobe in both; f, small 
lobe in both ; gg, inferior lobes ing the 
proportion to each other in size that the oy 
obes exhibit. 

N. B. The optic nerves derive their rot 
from the large lobes, and the small optic nerves 
their origin in the small lobes. = 


tubercles placed on the under surface of 1 
encephalon beneath the optic lobes (fig. 411 
Fig. 410. ) 


The writer does not: 
sume to decide wh 
these tubercles are re 
identical with the m 
millary eminences of 
human brain as m 
tained by Desm 
and others; or 1 
the tuber cineream 
Carus, Spurzheim, 
have’ contended : 
that they have a § 
in the origin of the: 
nerves is certain, 
in those fish whic 
two optic nerves ¢ 
equal size, the tub 
to which allusion is 
Brain of a Ray. (From present espo 
nature. ) Seen from rE differences 7 
aa, optic nerves; by gj Jf 
pre te ec, inferior > tha (fi. Aa 

lobes from which the op- whtbton 
class the optic 


tic nerves derive some of 
their roots ; dd,opticlobes are derived fro 
the principal sources of lobes v 
the optic nerves. those in ; 1 
two in number and interposed bets 
cerebral hemispheres and the cerebellu 
size is proportional to the developeme 
optic nerves, and they are best seen att 
or dorsal surface of the brain (fig. 41 
Birps.—In birds the optic nerves 6 
chiefly in two lobes situated at the 
lateral aspect of the brain, and ca 
class also “ optic lobes.” The 
lobes is in proportion to that of the optie 


and organs of vision, and they are 


ae 


* Brain of a Turtle. ( From nature.) Lateral view. 


aa, optic nerves ; b, chiasma ; ¢, optic lobes; d, tractus opticus, 
; coanecting the right optic lobe to the chiasma. 


immense in birds of prey, and much smaller in 


NERVES. 


765 


what parts of the mammal’s brain 
are analogous to the optic lobes of 
the lower classes. 

The tubercu drigemina in 
man and the mammalia are iden- 
tical with the optic lobes of the 
lower vertebrata; they occur as 
four small tubercles arranged in 
pairs, of which the anterior are 
called the nates, and the posterior 
the testes. In some of the class, 
as for example, Ruminantia, Soli- 
peda, and Rodentia, the nates are of 
larger dimensions than the testes; in 
others, as for instance, Carnivora, the testes 


other birds not equally remarkable for perfec- predominate in size over the nates, and in 


» 


tion of sight (fig. 412). ° 
; Fig. 412. 


in of an Eagle. ( From nature. ) Seen from below. 
_ @, a, optic nerves ; c, chiasma, of immense size ; 
6, b, optic lobes of large dimensions, placed at the 
inferior and lateral aspect of the encephalon, 


_ The situation of these bodies in the brain of 
the bird, so different from their position in 
eptiles and fish, created at one period some 
doubts as to their true analogies ; but Serres 
as shown that during the early stages of deve- 
ement the optic lobes occupy precisely the 
@ position in the encephalon of the chick 
h they hold permanently in the brain of 
@ reptile and fish, and he has thereby divested 
is subject of much of its obscurity. Thus 
efore the tenth day of incubation the optic 
Tobes of the chick are placed between the cere- 
bellum and the cerebral hemispheres, and are 
| then best seen at the dorsal aspect of the brain : 
ut after this epoch the hemispheres and cere- 
ellum approach each other at the expense of 
(the optic lobes—the hemispheres extending 
backwards, and the cerebellum inclining for- 
| wards. By this double movement the optic 
lobes are soon overlapped behind, separated 
from each other, and at length pushed down- 
‘wards and outwards to their permanent si- 
‘tuation (fig. 413). _ 

~ In Man the optic nerves derive some roots 

— _ from the tubercula quadrigemina. 

In birds, reptiles, and fish, the optic lobes 
lonstitute the principal sources of the optic 
erves, and therefore in any attempt to ascer- 
ain the true origin of the second pair in man, 
a necessary preliminary will be to determine 


Man and Quadrumana the two pairs are nearly 
equal. ‘ 


Brain of achick. (After Serres.) At three different 
stages of incubation. 

A, at sixth day; B, at tenth day; C, at four- 
teenth day. 

A, a, a, optic lobes ; 6, rudimental cerebellum 3; 
¢, ¢, cerebral hemispheres. 

» @, a, optic lobes separated from each other in 
front, and here slightly depressed; 5, cerebellum 
inclining upwards and forwards between optic lobes ; 
c, c, cerebral hemispheres growing backwards so as 
to overlap the optic lobes. 

C, a, a, optic lobes still farther separated from 
each other and depressed towards base of brain; 
b, cerebellum growing upwards between the optic 
lobes ; ¢, c, cerebral hemispheres carried backwards 
so as to come nearly into contact with the cere- 
bellum. Reference to fig. 412 will shew the brain 
of the bird in its full-grown condition. 


The tubercles in question have but little 
apparent similarity to the optic lobes of the 
lower Vertebrata : they occur as four eminences, 
while the optic lobes of birds, reptiles, and 
fish, are but ¢wo in number: they are of dimi- 
nutive size; the optic lobes of birds, reptiles, 
and fish are of large dimensions in proportion 
to the brain: they are solid; the optic lobes of 
birds, reptiles, and fish are Aollow: and in 
Man and most Mammalia they are covered 
upon the upper surface by the cerebral hemi- 
spheres, while the optic lobes in reptiles and 
fish are not so covered. Such obvious dissimi- 
larity tended materially to obscure the real 
nature of the tubercula quadrigemina, but a 
careful study of the developement of these 
bodies in the fcetal brain led anatomists at 
length to discover their true analogies; and 
the researches of Tiedemann and Serres have 
chiefly contributed to establish the following 
particulars. 

“‘ In the earlier stages of uterine life the tuber- 
cula quadrigemina of Man and Mammalia 


766 


occur in the form of two masses; they persist 
as such during two-thirds of foetal existence; 
they are hollow at first and not covered by 
the cerebral hemispheres, and their size is im- 
mense in proportion to the bulk of the ence- 
phalon. As developement advances, a trans- 
verse groove appears on the surface of the 
future tubercula quadrigemina; this divides 
them into four eminences, which are now for 
the first time really entitled to be called “ qua- 
drigemina :” nervous matter is gradually depo- 
sited from within on their walls, in conse- 
om of which they henceforth become solid ; 
their growth in size is arrested, and the» cere- 
bral hemispheres having grown backwards, 
overlap and conceal them from view. This 
overlapping occurs in all except a few of the 
lowest families of the mammalia, in which the 
tubercula quadrigemina remain permanently 
uncovered. 

From the foregoing exposition it appears 
that during their ae Rca the tubercula 
quadrigemina in man and mammalia assume 
tora time all the characters which the optic 
lobes of birds, reptiles, and fish exhibit in the 

anent condition ; and hence it can scarcely 
questioned that the nates and testes of the 
former class are identical with the optic lobes 
of the latter animals; but since the optic 
nerves in the oviparous Vertebrata are trace- 
able to the optic lobes and manifestly derive 
from them the greater proportion of their roots, 
there is so far prima facie evidence that the 
optic nerves in man have their origin in part 
from the tubercula quadrigemina. In further 
confirmation of the same view it may be re- 
marked that some of the roots of the optic 
nerves in certain orders of the mammalia are 
seen to spring from these bodies ; for example, 
in the horse a large proportion of the nerves 
can be traced distinctly to the nates. In Ro- 
dentia and Carnivora numbers of the fibres of 
the nerves emanate obviously from the same 
ir of tubercles, and in the Ruminants a simi- 
anatomical arrangement prevails. 

As an additional proof Tiedemann asserts 
that although much difficulty is encountered in 
attempts to follow the optic nerves to the tuber- 
cula quadrigemina in the adult human subject, 
he has succeeded in tracing them to the nates 
in foetuses of the third month, and at the fourth 
and fifth months he has frequently repeated 
the same observation. 

Human pathol would seem to furnish 
“some corroborative facts: thus in every case of 
long-continued atrophy of the optic nerve, 
where the wasting had involved the tractus 
opticus, Gall and Spurzheim found the nates 
of the side corresponding to the diseased tract 
diminished in size; and the experiments insti- 
tuted upon living animals with a view to deter- 
mine the functions of the several constituents 
of the brain by the successive removal of the 
different of the organ and careful obser- 
vation of the disturbance thereby produced, 
lead also to the belief that the optic nerves have 
an origin in the tubercula quadragemina. Of 
course great allowance must be made for inac- 
curacy in the result of such mutilations, but 


OPTIC: NERVES. 


Flourens, Magendie, Desmoulins, and Hertwig, 
all agree that destruction or mutilation of the 
nates and testis of one side invariably produces 
blindness of the opposite eye. 

The writer fully with Cruveilhier in — 
the belief that the optic nerves in the human 
subject can be rarely traced to the tuber- 
cula quadrigemina satisfactorily ; but never- — 
theless with the above facts before them, — 
anatomists can scarcely refuse to allow that 
the optic nerves in man derive a share of — 
a roots from these eminences. a 

he tubercula igemina probably fulfil 

other purposes leeides that of affording origin 
to the optic nerves. : : 

This may be inferred from the fact that the 
optic nerves are not invariably d in 
direct proportion: to the tubercles ; in 
certain mammals which are either devoid of 
optic nerves altogether, or in which they 
are so excessively diminutive as to be with 
difficulty discovered, the tubercula quadri- 
gemina are as large and perfect as in othe 
allied species possessed of well-marked org 


of vision. 


The nates and testes, ¢ 
bercula quadrigemina, 
of immense size ; 
bral hemispheres are sm 

The common mole, for example, has ¢ 
diminutive and imperfect in structure, and | 
subterranean habits bespeak so little neces 
for organs of vision, that many excellent ar 
mists believe it to have no optic nerves; ne 
theless the tubercula quadrigemina in | 
animal are of immense size. ( Fig. 414.) Ser 
never could satisfy himself that the mole 
sesses optic nerves, although he examined th 
or forty specimens for the express purpe 
if they do exist (as has been maintaine 
Carus and Treviranus) their minuteness 
be almost microscopic. (See Lysecrn 
vol. ii. fig. 453.) 

Other examples confirmatory of the | 
views are afforded by the mammalia; 
stated on the authority of Serres that it 
rat-mole of the Cape, and the Zanni, or 
rat-mole, there is no appearance whate 
proper optic nerves, (the rudimental é es 
supplied by the fifth pair,) and yet in 
animals the tubercula quadrigemina ex 
great perfection. ; Pe 
The human optic nerve probably de: 

JSrom the optic thalamus, 

The writer is of opinion that modern 
mists have fallen into error in supposil 
none of the roots of the second pair are dt 
from the optic thalamus, although the 
ments by which that supposition has 
pacar lly are sufficiently imposing, viz. + 


a 


OPTIC NERVES, 


“The size of the optic thalami is not in 
general in direct proportion either to.that of the 
optic nerves or the acuteness of vision in 
animals. 

__ “In most fishes the optic nerves are of great 
_ size, and the perfection of vision is extreme, yet 
in this class the optic thalami are absent. _ 

“In birds, some of which enjoy exquisite 

» powers of sight, the optic thalami are small. 
__ “ In mammalia the optic nerves bear no fixed 
proportion to the optic thalami; for instance, 
the horse, the ox, and the stag have larger optic 
nerves than the human subject, and yet the 
optic thalami in these animals are infinitely 
smaller than in man.” 

The foregoing arguments are not conclusive, 
for if the want of direct proportion between the 
Optic thalami and optic nerves were a proof that 
the optic nerves draw none of their roots from 
_ the optic thalami, the very same principle would 
deprive the tubercula quadrigemina likewise of 
claim to be considered a source of the 


ed 


question and the tubercula quadrigemina ac- 
ually Occur in inverse proportion to each other. 
In considering this question it should be 
ecollected that in the mammalia large optic 
lalami are always found associated with small 
la quadrigemina, and vice versi; and 
he same remark applies to the optic thalami 


irds, the optic thalami are small, but the optic 
bes are of large dimensions: in reptiles the 
me ee prostione are apparent: in fish the 
ptic thalami disappear, but the optic lobes are 
amense, and two inferior lobes (an additional 
urce of the optic nerves) are superadded. 
hese facts favour the presumption that the 
tie nerves derive roots from the optic thalami; 
if (as is most probable) the optic thalami 
and the tubercula quadrigemina both afford 
Origin to the optic nerves, they may be mutually 
supplemental to each other; and in that case 
l€ reciprocal proportions of these eminences 
ill be a matter of no consequence, provided 
nly that their sum be proportional to the 


farther support of the opinion here adyo- 
Fig. 415. 


fetal brain. (From nature.) Lateral view, 
About fourth month. 


a, a, optic nerves; b, chiasma; ¢, right tractus 
“cus; e, right optic thalamus; f, mass of the 
ercula quadrigemina; g, g, cerebellum; d, 
terior extremity of right cerebral hemisphere, 
placed to exhibit the origin of the optic nerve. 


second pair; since in the Mole and some other \s 
Mammalia, already specified, the nerves in WS 


767 


cated, it should be borne in mind, that the 
tractus opticus is clearly traceable to the surface 
of the optic thalamus inthe human adult sub- 
ject, and the writer’s experienee~ has convinced 
him that the same anatomical disposition is 
very apparent in early foetal life (fig. 415). It 
may be well to add that in all the orders of the 
mammalia which he has had an opportunity of 
examining, the tractus opticus derives filaments 
from the optic thalamus: in the horse, although 
a large proportion of the tractus can be traced 
to the nates, its anterior fibres spring most 
distinctly from the optic thalamus (fig. 416); 


Tubercula quadrigemina, together with portions of the 
optic thalami and tractus optici of a horse. (From 
nature. ) 

a,a, nates; b,b, testes; c,c, optic thalami; 
d, d, tractus optici, springing partly from the nates, 
but deriving a great portion of their roots from the 
optic thalami, c¢, c. ' 


in the sheep precisely the same arrangement 
exists: in the hare many filaments of the 
tractus opticus originate in the optic thalamus: 
and in carnivora and quadrumana a similar 
disposition prevails. 

ecent microscopic discoveries in ovology 
(if it be fair to argue from the developement of 
the chigk to the evolution of the human feetus) 
tend to confirm the views here put forward. 
Baer states that on the fourth day of incubation ‘ 
the encephalon of the chick consists of several 
cells, one of which corresponds to the third 
ventricle, and another to the optic lobes, and 
that these two cells are distinct from each other. 
The first rudiment of the eye observable in the 
chick occurs in the form of a vesicle which 
shoots out from the parietes of the cell of the. 
third ventricle, and which becomes gradually 
elongated and drawn out into a canal. On the 
fourth day the eye represents a spherical cavity 
communicating with the third ventricle by a 
canal ; this canal is the rudimental optic nerve, 
which becomes gradually solid, its cavity disap- 
pearing after the sixth day. During the earlier 
periods of growth there is no connection what- 
ever between the optic nerves and the cell of 
the optic lobes, but the nerves just specified 
are from the very commencement in free com- 
munication with the cell of the third ventricle, 
and in the walls of that cell the optic thalami 
are developed. 


768 


The evidence which pathology has afforded 
upon this question must be considered unsa- 
tisfactory in the extreme; for, on the one 
hand, well authenticated cases are recorded in 
which vision remained perfect although the optic 
thalamus was extensively diseased, and Gall 
and Spurzheim have observed atrophy of the 
optic nerves to reach the nates without affecting 
the optic thalamus: while, on the other, Cru- 
veilhier has seen the corpus geniculatum ex- 
ternum involved in the wasting of the optic 
nerve, and Magendie and Desmoulins, from 
their own researches and experiments as well 
as from those of Nethig and Scemmerring, 
infer that after long-continued blindness the 
atrophy of the-optic nerve in man sometimes 
affects the optic thalamus. 

The following is a summary of facts favour- 
able to the supposition that the optic nerves in 
man derive roots from the optic thalami. 

1. The human tractus opticus admits of 
being distinctly traced to the optic thalamus, 
both in the foetal condition and subsequently 
to birth. 

2. In many, if not all, of the mammalia, the 
optic nerves in the clearest manner derive roots 
from the optic thalami. 

3. The optic nerve of the chick first appears 
as an offset from the third ventricle, and the 
optic thalami are developed in the walls of that 
ventricle. 

4. The inverse proportion known to subsist 
between the tubercula quadrigemina and the 
optic thalami in mammalia, and also between 
the optic lobes and the optic thalami in birds, 
reptiles, and fish, may probably be considered 
corroborative facts. 

Corpora geniculata: their relation 
to the optic nerves. 

That there is an intimate physiological rela- 
tion between the optic nerves and the corpora 
geniculata can scarcely admit of doubt, for the 
principal band of the human tractus opticus 
is, in every instance, traceable to the corpus 
geniculatum externum, and may be seen actually 
‘ incorporated with that tubercle ; and a similar 
connection between the lesser band of the 
tractus and the corpus geniculatum internum 
is also, for the most part, discoverable : more- 
over, in various orders of the mammalia a 
portion of the tractus opticus emanates most 
distinctly from the corpus geniculatum in- 
ternum ; and in quadrumana, carnivora, rodentia, 
&c., this has been frequently verified by the 
writer. 

From the statements of Tiedemann, it appears 
that the corpus geniculatum externum is much 
more tardy of developement in the foetus than 
the optic nerve itself, for the eminence in ques- 
tion secon only for the first time apparent 
about the sixth month of feetal life: again Serres 
affirms that both corpora geniculata appear so 
late as the sixth month of uterine existence ; 
and according to the joint testimony of these 
two authorities, the corpora geniculata are de- 
veloped in the course of the tractus opticus, and 
superadded to the rudimental optic nerve. 

late appearance of the corpora geniculata 
in the embryo, and the manner of their develope- 


‘between the optic nerve and tuber ciner 


OPTIC NERVES. 


ment, would seem to assimilate these tubercles 
to the ganglions found in the course of certain 
nerves of special sense in many animals, and 
which are perhaps destined to exalt the sensi- 
bility of the nerves in which they occur. The 


optic ganglions of the loligo (fig. 424, ¢), and 
ce 


the olfactory ganglions of many 


good examples of the nervous masses to whi 
allusion is here made. ny 
Tuber cinereum : its relation to the 
optic nerves. og 
The same difficulties uniformly encountered 


ae 


in all attempts to determine the particule 
functions of individual parts of the brain pr 
vail in the case of the tuber cinereum : s¢ 
physiologists maintained that the optic nerve 
derive a great number of filaments from tha 
body, and that the nerves are considerably ir 
creased in dimensions by this addition: Gal 
for instance, was. of this opinion, and gave 
rather exaggerated representation of the enla 
ment supposed to arise out of this reinforcer 
to the nerves. eG 
The optic nerves in man may doubtle 
draw some of their roots from the tuber cit 
reum, but there is an absolute certainty that 
body in question has other and probably 
important functions than any connected 
the origin of the nerves of vision. P 
and ven preeriare observations upon the sub 
are still a desideratum, but in the absences 
more direct evidence the anatomy of the mi 
brain is calculated to throw some light u 
the enquiry. In the mole the optic ne 
either wholly absent, or if t, it is m 
rudimental; nevertheless, the tuber cinere 
of enormous dimensions; it extends forw 
the olfactory lobes, and so far backwe 
nearly to reach the pons. In this animal, 
fore, there is an inverse proportion app 


cad 


4 


a fact little favourable to the hypothesis 
cated by Gall. ; 
Of the chiasma of the optic 
word chiasma (from the Greek ysacpeos, t 
satio,) means in strictness a decussatic 
crossing at acute angles, like the legs” 
letter X;* and, for convenience-sake, th 
expression (with a like latitude of app 
will be here employed to designate th 
responding structure in the lower animal: 
The organization of the human chias 
abundantly exercised the ingenuity ¢ 
mists, who seem to have encountere 
difficulty in their attempts to trace th 
filaments through it; and consequer 
withstanding all the attention w 
the subject, opinions the most conflie 
prevailed upon the true nature of the: 
in question. In no other instance is; 
junction between two corresponding 
opposite sides known to fe) 
anomaly affords strong presumptive e¥ 
the existence of some unusual properti 


... 


* In Human Anatomy the term is used | 
perhaps sufficient regard to its e log 
press the nervous mass in which t 
nerves are conjoined, ’ 


—— 


OPTIC NERVES. 


nerves thus united; and for these reasons the 

physiology of the chiasma is inyested with 

uncommon interest. 

The existence of a chiasma is not general 
throughout the animal series, and even when 
present it exhibits much diversity of appearance 
and structure in different classes. <A brief ex- 
position of some of its more striking varieties, 
in animals, will probably constitute the best 
introduction to the study of the chiasma in man, 

Invertebrata.—In the invertebrate classes 
nothing like a chiasma has been demonstrated, 
nor has any mutual crossing of the special optic 
nerves been proved to exist. The nerves which 
are furnished to the compound eyes of insects 
and crustaceans pass in a direct course to their 
destination ; the same remark applies to the 

merves from which the lens-eyes of insecta, 
yj arachnida, crustacea, and mollusca, derive their 
p sensibility; and it may be presumed that the 

nerves which supply the simple eye-dots of 
__annelida and other inferior animals are similarly 
__circumstanced. 

Osseous fish—In osseous fish the optic 
nerves generally cross each other at an acute 
‘angle, in such manner that the nerve which 
comes from the right side of the brain goes 
‘distinctly to the /eft eye, and vice versa: at the 
“point of decussation the nerves lie one over the 
other ; they are usually flattened at this spot, and 
closely joined together, but this junction is 
‘effected by means of cellular or fibrous ad- 
hesions only, as no intermingling of the nervous 
laments takes place, and the nerves themselves 
ean be isolated without injury to their proper 
Structure (fig. 407). 

Cartilaginous fish—In cartilaginous fish a 
well-marked chiasma occurs. In this class the 
unction of the two optic nerves is no longer 
effected by means of mere cellular adhesions, 
as in the osseous fish, buta perfect union of the 
proper substance of the nerves constitutes a 
“tue chiasma. The optic nerves arise each 
_ from the corresponding optic lobe chiefly; they 
“quickly converge, and soon become confounded 
‘with each other in the chiasma; and so inti- 

aate is their connection, that anatomists possess 
fittle information as to the exact arrangement 
of the nervous filaments in this structure 
ig. 410). 

Birds.—In birds the chiasma is large, being 
Proportional to the size of the optic nerves; by 
@ little management its organization can be 
accurately demonstrated. Maceration for a 
few days in spirits hardens this structure suffici- 
ently to enable the operator to strip off the 
meurilemma, and then, even without the aid ofa 
ens, the chiasma may be seen to consist chiefly 
of lamine. Forcible extension of the optic 
merves, in such a manner as to tear through the 
nperficial stratum of the chiasma on its lateral 
spect, greatly facilitates the examination. 
The laminz originate in the tractus opticus, 
and appear to spring from the inner part alone 
of that mass ; they gain the chiasma, and here 
those derived from opposite sides of the brain 
yorm areciprocal interlacement. A perfect and 
egular decussation of the inner filaments of the 
Wo tractus optici thus takes place in the 
VOL. 11. 


=P 


763 


chiasma, in such manner that a large proportion 
of the tractus of one side is evidently traceable 


. 


to the opposite optic_nerve, and vice versa: 
but the outer part of waa toto opticus con- 


tinues on to form the outer part of the optic 
nerve of its own side, and has no concern in the 
formation of the decussating lamine. 

The number of lamine in the chiasma of 
different birds is subject to some variety, but 
in the entire class, without exception, the lami- 
nated structure prevails (fig. 417). 


Fig. 417. 


My: 
Chiasma of the common fowl. (After Miiller.) 

a, a, optic nerves; 6, chiasma, dissected so as 
to shew its decussating lamine; c, ¢, tractus 
optici. 

Amphibia and reptiles—In amphibia and 
reptiles a laminated chiasma, somewhat similar 
to that just described in birds, occurs; but 
the decussating lamine are very variable in 
number, and in general much fewer than in 
birds. 

Thus, in Amphisbeena, according to Miiller, 
there are only five laminz in all, two trom one 
side, and three from the other; and in lacerta 
ocellata, according to the same authority, as 
many as eight have been counted, four on either 
side (fig. 418), In some reptiles the posterior 
part of the chiasma is strictly commissural, the 
inner part of each tractus opticus being appro- 
priated to the formation of a band-like com- 
missure: in Amphisbeena a triangular space 
separates this band from the remainder of the 
chiasma (fig. 418). 

. Fig. 418. 
A. B. 


a 
pe 
© | 
Chiasma in Amphisbena. (After Miiller.) 

A, section of chiasma to exhibit the decussating 
laminz, of which there are three from one side and 
two from the other. ‘ 

B, chiasma seen from below. 

a, a, optic nerves; 5, b, tractus optici; ¢, com- 
missural band; d, triangular space; f, true chi- 
asma, 

Mammalia and man.—In mammalia and man 
the chiasma is no longer laminated, and great 
difficulty occurs in attempts to display its real 
structure. 

The older anatomists were evidently unable 
to trace the filaments of the human optic nerves 
satisfactorily through the chiasma, and in con- 
sequence they relied either on pathological 
facts, or the results of experiments, or the data 
furnished by comparative anatomy, to determine 
the mutual relations of the second pair in this 

3D 


770 


part of their course. The conclusions arrived 
at by such modes of investigation were un- 
satisfactory, and remarkable for much dis- 
crepancy. 

1. Some maintained that the nerves are 
merely placed in exceedingly close juxta- 
position in the chiasma, without any inter- 
crossing of their respective filaments, and that 
each tractus opticus in reality passes on to form 
the optic nerve of its own side. 

These views were supported by Vesalius,* 
who detailed thé particulars of a case in which 
after death the two optic nerves were. found 
perfectly distinct from each other throughout 
their whole course, and consequently no chiasma 
existed, although, during life, vision had been 
unimpaired ; and the same hypothesis was 
Strengthened by Santorini and others, who, in 
certain instances where one eye had been 
destroyed many years before death, observed on 
the post mortem examination the correspond- 
ing optic nerve atrophied as far back as the 
chiasma, and the tractus opticus of the same 
side wasted, while the nerve and tractus of the 
opposite side were perfectly healthy. 

2. Others were persuaded that a perfect de- 
cussation exists in the chiasma, and that all the 


filaments of the tractus opticus of one side pass - 


fairly across to form the optic nerve of the other, 
and vice versa. In favour of this opinion it 
was urged that in the majority of cases of long- 
continued blindness of a single eye the opposite 
tractus opticus, and not the tractus on the sume 
side with the affected eye, becomes atrophied. 
Scemmerring observed several such cases in the 
human subject, and traced the same appearances 
in the horse, dog, squirrel, rabbit, hog, cat, and 
chamois: and Cuvier preserved in spirits the 
brain of a horse in which the wasting of one 
optic nerve continued backwards into the oppo- 
site tractus. The evident manner in which the 
optic nerves in osseous fish cross each other (see 
fe. 407) was also considered favourable to this 
view, and the results of experiments on living 
animals were confidently appealed to in farther 
confirmation of the same. 
of Rolando, Pourfour Petit, Saucerotte, Hertwig, 
Flourens, and others led to the conclusion, that 


if in the Mammalia one hemisphere of the ce- - 


rebrum be injured deeply or removed, vision 
becomes impaired or destroyed in the opposite 
eye; if the ¢wo cerebral hemispheres be suc- 
cessively subjected to the same treatment, vi- 
sion becomes successively impaired or destroyed 
in both eyes; if one of the nates be removed, the 
‘animal sees no longer on the opposite side; and 
if both be removed, blindness affects both eyes 
in succession and occurs constantly in the eye 
opposite to the injured tubercle; if in birds one 
of the cerebral hemispheres be removed, vision 
becomes extinguished in the opposite eye ; if the 
two hemispheres be removed in succession, a 
cross paralysis affects the éwo retine : if one of 
the optic tubercles be removed, the sight of the 
opposite eye fails, and if both be removed, per- 
fect blindness ensues. 

3. Another class of physiologists believed 


* Vesalius de Corp, Hum. Fab., |. iv. c. iv. 


hus the experiments - 


OPTIC NERVES. 


that a partial decussation occurs in the human 
chiasma, and that some of the filaments of each 
tractus opticus continue on into the nerve of their 
own side, while others cross obliquely into the 
optic nerve of the opposite side. facts in 
pathology seemed difficult of explanation on — 
any other supposition ; thus cases of long-con- ~ 
tinued blindness of a single eye, the result of 
accident, have been met with, in which after 
death the corresponding optic nerve was four 
atrophied se fir back ap the chiaiiall (the optic 
nerve belonging to the healthy eye being of 
fully its ordinary dimensions, or 
than natural) while both tractus optici 
wasted. : an 
That a partial decussation does 
human chiasma can now no longer 


section, and it can be rendered a to 
naked eye by the precaution of teardening the 
nervous substance before the dissection is com: 
menced. According to the writer’s experience 
immersion in mie hardens the prereaaam 
the most satisfactory manner. performing 
the dissection the neurilemma must be first care- 
fully removed from the chiasma, and also \ 
the adjoining portions of the optic nerves and 
tractus optici ; after this pein optic 
nerve should be divided transversely a little in 
front of the chiasma ; a transverse incision car- 
ried horizontally into the cut surface of thi 
cerebral extremity of each nerve will ther 
enable the operator to split it in a directiot 
backwards towards the chiasma, and by pro. 
ceeding cautiously a horizontal division of th 
chiasma, and of a part of the optic nerves am 
. ¢ Fig. 419. 


E 


: 


the tractus optici, will be effec 
The annexed 
Fig. 419. gure represents — 
reparation made 


the manner de 
bed, and it is esse 
tially similar to 
diagram of the h 
man chiasma pt 
lished some ye 
Sy pines 
Human Chiasma. ( Froma dis- geet: ar 
section made by the writer. ) of ‘course fate 
aa, opticnerves ; 6b, trac- but the directic 
tus optici. the larger fast 
admits of not the slightest question; the 
fasciculi of each tractus opticus cont 
onwards without interruption to form the 
of the optic nerve of the same side 
middle fasciculi cross the chiasma oblis 
and after decussating the corresponding fé 
of the other tractus, contribute to the for 
of the optic nerve of the opposite side; 2 
internal fasciculi cross the posterior part 
chiasma transversely and uniting direct 
the corresponding fasciculi of the other’ 
seem to be strictly commissural; acro 
front of the chiasma some fasciculi ta 
arched course, and being prolonged ~ 
along the inner edges of the optic nen 
are likewise apparently commissural. — 


7-2 


a 


OPTIC NERVES. 


Some difficulty no doubt arises when the 
physiologist attempts to reconcile with this 
anatomical arrangement certain facts already 
detailed : it may be remarked, however, that 
arguments derived from the pathology of the 
optic nerve can be but of little value, since 
they have been relied on in turn by the framers 
of each hypothesis as affording proof of their 
_ Own peculiar views ; and in the Museum of the 
Richmond Surgical Hospital, Dublin, the writer 
has seen specimens of atrophied optic nerves in 
man which furnish the most contradictory evi- 
dence upon the subject under discussion. The 
preparations alluded to were cases in which one 
eye had been destroyed either by local disease 
or accident, many years previous to death, and 

_ where in consequence the corresponding optic 
nerve became wasted from disuse, while the 
_ other optic nerve continued healthy. In the 
_ majority of these specimens the wasting has 
been propagated backwards to the opposite 
tractus opticus and has implicated that structure, 
while the corresponding tractus has been spared 
_ (See fig.420, A); in some examples both tractus 
optici have suffered a diminution of size and 
in general to an unequal amount ; and in one 


Fig. 420. 
A 


ltrophy of one optic nerve, the consequence of long- 
_ continued disuse. (From preparations in the Museum 
_ of the Richmond Hospital, Dublin.) 

_A. a, right optic nerve in a state of atrophy; }, 
eit optic nerve healthy ; c, chiasma; d, right trac- 
is opticus healthy ; e, left tractus opticus wasted. 
B. a, right optic nerve atrophied ; 6, left optic 
erve healthy; c, chiasma; d,right tractus opticus 
asted; e, left tractus opticus healthy. 


771 


very remarkable instance the tractus opticus of 
the same side with the shrunken nerve has 
dwindled into a peiete Mc while the other 
retains fully its normal dimensions (fig. 420, B). . 

It may be fair to add, that the case quoted 
from Vesalius is considered by many, and 
amongst others by Gall and Spurzheim, as of 
doubtful authenticity, and the results of expe- 
riments on living animals should be received 
with caution, for to argue from experiments on 
birds to the human subject is plainly fallacious, 
since the structure of the chiasma is not iden- 
tical in the two cases, and the great obstacles 
encountered in the performance of such expe- 
riments on the mammalia renders them of trifling 
value. 

Use of the chiasma.—In the direct junction 
between two corresponding nerves of opposite 
sides displayed in the chiasma, the second pair 
form an exception to a general law; for in no 
other known instance does a similar union 
occur ; it therefore becomes a subject of great 
interest to determine how far this anomaly 
admits of explanation by any unusual properties 
in the nerves so circumstanced. — 

The optic nerves possess the remarkable 
power of conveying to the individual the sen- 
sation of a single impression only, while a 
separate impression affects each nerve simul- 
taneously, so that although a perfect picture of 
the object be depicted on each retina severally, 
nevertheless to the spectator it appears to be 
single (as is really the case); or to speak still 
more intelligibly, a spectator sees an object 
single, although he looks at it with two eyes. 

This property would seem to belong in an 
especial manner to the optic nerves, and: inas- 
much as the second pair differ from all the 
others in possessing a chiasma, there is so far a 
presumption, that the unity of sensation mani- 
fested by the optic nerves depends on the 
chiasma. 

The idea that single vision may be explained 


-by a partial decussation in the chiasma originated 


(upon theoretical grounds) with Newton ; it has 
since been adopted by Wollaston, Solly, and 
others, and many facts have been from time 
to time brought forward in its favour. The 
hypothesis may be thus enunciated. “ Each 
tractus opticus sends some filaments across 
the chiasma ‘to form the inner part of the 
opposite optic nerve, while its outer filaments . 
continue on to form the outer part of the optic 
nerve of its own side; the same arrangement 
of the filaments prevails to the retina, so that 
the right side of each retina comes from the 
right tractus opticus, and the left side of each 
retina from the left tractus opticus; if then 
in vision the pictures of an object be depicted 
simultaneously either on the right sides of 
the two retine, or on the left sides of the two 
retin, the impressions in either case will be 
communicated to one and the same tractus opti- 
cus; such impressions will of course be referred 
to one and the same side of the brain, and 
they will therefore produce the sensation of a 
single impression on/y, although in reality two 
several impressions affect the retine; the unity 
of sensation depending on the fact that the two — 
3 D2 


772 


impressions are referred to the same side of the 
brain, and not to opposite sides of the brain as 
occurs in other cases.” 

Wollaston adopted this hypothesis in conse- 
quence of the ready explanation it affords of 
certain cases of visus dimidiatus: he on several 
occasions in his own person experienced a tem- 
porary defect of vision, in consequence of which 
one and the same lateral half of every object 
became invisible, whilst he still continued to 
see the other half distinctly; and the same 
amount of blindness subsisted whether he em- 
ployed one or both eyes in looking at the 
object. 

Examples of the same form of amaurosis are 
of no very unfrequent occurrence, dnd according 
to the theoretical notions just propounded this 
partial loss of vision originates in some func- 
tional affection of one tractus opticus whilst the 
other remains healthy ; those parts of the two 
retine which derive their origin from the faulty 
tractus being supposed to labour under a tem- 
porary amaurosis, while all other parts retain 
their ordinary sensibility. 

In further support of this hypothesis, Mul- 
ler’s researches have convinced him that in 
man single vision by the two eyes occurs only 
when certain parts of the two retinz are affected 
simultaneously, and that under other circum- 
stances double vision ensues. This conclusion 
has been arrived at, chiefly from the results of 
experiments upon the eye-ball. Thus, when 
the eye-lids are closed in a dark room, if 
pressure be applied deeply to the eye so as to 
affect the retina, luminous spectra are produced. 
When certain parts of the two eye-balls are 
subjected to pressure at the same time, a single 
Spectrum occurs, and when other parts of the 
two eye-balls are pressed upon simultaneously 
two spectra appear. Those parts of the two 
retina which in the above experiment furnish a 
single spectrum are styled “ identical,” in con- 
sequence of their identity of sensation; and 
those parts which produce two spectra are de- 
nominated “ non-identical,” for obvious reasons. 
Some of the conditions under which single and 
double vision respectively take place, seem to 
be confirmatory of this doctrine of “ identical ” 
and “ non-identical” parts in the two retine ; 
thus double vision is a common consequence 
of any cause having a tendency to disturb the 
relative directions of the optic axes: for exam- 
ple, diplopia frequently occurs in cases of 
strabismus, and double vision may (according 
to Muller) be produced in perfectly healthy 
eyes by a simple experiment: ifa spectator fix 
his eyes upon an object and then press on one 
of them in such manner as to alter the direction 
of its axis, the object which at first seemed 
single will assume a double appearance. These 
phenomena admit of explanation on the suppo- 
sition that in consequence of the distortion of 
the axes of the eyes, the visual impressions take 
effect on “ non-identical” parts of the two 
retine, which therefore propagate two impres- 
_ sions instead of one to the sensorium. 

These views apparently strengthen Newton's 
hypothesis, for it may be presumed that the 
“ identical” parts of the two retine are those 


OPTIC NERVES. 


which derive their origin from the same tractus 
opticus, and the “ non-identical” on the con- 
trary those which come from different tractus 
optici. 
the comparative anatomy of the nerves in 
uestion furnishes some facts favourable to 
ewton’s hypothesis; thus many animals in 
which the eyes are directed /aterally, in such 
manner that each embraces a totally different 
field of vision, have no chiasma, and their optic — 
nerves cross each other, so that the right retina 
is in connection solely a the left side of the — 
brain, and vice versa. is arrangement. pre- — 
vails in the majority of osseous fish, and, for so 
far, affords negative a of the h esis 
under consideration. following retical 
explanation may be offered. “ In theseanimals, 
owing to the position of their eyes, the same 
object can never be depicted on the two re- 
tine simultaneously ; consequently, in them no 
provision to ensure single vision of the same 
object by both eyes is required, and 
no parts of the two retine have a common con- 
nection with one and the same side of the br 
the two optic nerves being derived respecti 
from opposite sides of the organ.” ; 
Again, Mr. Solly has shown that in r 
fish, such as the skate, (in which the eyes ang 
so set that the respective fields of vision ma 
comprise in a great measure the same ob 
a chiasma exists: and the anatomy of th 
chiasma in birds is likewise on the whole 
vourable to the hypothesis; for in these anit 
the optic axes are in general very diverg 
and consequently the respective fields of visic 
can have but little identity ; a fact which ag 
theoretically with the pam Or ; 
observable in their laminated chiasma. 
Although this explanation of single vi 
has been sanctioned by the authority of N 
and Wollaston, and supported by | 
tomical facts and analogies, it will scar 
stand the test of critical examination ; s 
lidity has therefore been much questioned 
apparently with justice, for the following reasoi 
1. “ Identity of sensation” is not exclus 
a special attribute of the second pair; alt 
it exists in them in great perfection, other ni 
must also be admitted to the same 
perty ; thus notwithstanding that both ear 
commonly employed simultaneously for the 
nary purposes of hearing, thesensation of a 
impression of sound is in general propaga 
the sensorium; and although both nai 
used in the appreciation of odours, the sen 
of single impressions of scents is most 1 
produced: now since neither the § 
nor the auditory nerves are provided ¥ 
chiasma, and nevertheless these nerves 
niably evince a unity of sensation, there 
reason for scepticism when the be sal 


perty in the optic nerves is attribu’ 
sence of a chiasma. . 
2. Many facts in pathology are obvi 
variance with Newton’s theory; if it1 
true explanation of single vision, mort 
tions of one side of the brain (wh 
ductive of amaurosis) ought to imptical 
or less of one half of each retina, wheres 


OPTIC NERVES. 


rience proves that in the majority of such cases 
one or other retina is wholly paralysed, and not 
unfrequently vision continues perfect in one 
eye although extinguished in the other. More- 
over, although the theory in question affords an 
ingenious explanation of the defect in vision 
noticed by Wollaston, such explanation can 
_ scarcely be the true one, for Mayo has known 
_ “ this visus dimidiatus to alternate in the same 
individual with temporary insensibility of the 
centre and circumference of the retina,” and, 
as he observes, “the three phenomena. being 
_ alternative no doubt proceed from the same 
_ organic source, but as the hypothesis will not 
_ explain ¢wo of them, it is probably not the 
right explanation of the third.” 
3. The structure of the human chiasma does 
“Rot afford satisfactory explanation of the so 
_ called “ identical” and “ non-identical ” parts 
of the two retine as laid down by Miiller, and 
this has been so clearly shown by himself that 
his own words are quoted :— 

* With reference to their identity of sensa- 
tion, the two retinze must be considered as in- 
cluded one within the other, so that all points 
_ of the two retin which lie within the same 
degrees of latitude and longitude (the eyes being 
regarded as globes) are identical in their sensa- 


opposed to each other or different, just as any 
two yee in the retina of the same eye. 
_ . “If the image fall on identical points in 
- both eyes it will be seen single, and if the 
image does not fall on such identical points it 
will appear double. 
| The two globes of the eyes are most mi- 
nutely divided into degrees, minutes, and 
_ seconds of latitude and longitude; at all cor- 
| responding points they are identical, at all dif- 
ferent points non-identical. The outer lateral 
_ portion of one eye is identical with the inner 
portion of the other eye ; the upper part of one 
' retina is identical with the upper part of the 
other, and the lower parts of the two eyes are 
identical with each other. 
/_ “The left half of the retina A, from 1 to 5, 
however, (fig. 421,) is not, as a whole, identical 
_ with the left half of the retina B, from 1 to 5, 
_ but certain points only of the left halves of both 
retine are identical, viz. those which in the two 


Fig. 421. 


Diagram to represent the supposed identical parts 0 
the fas Satins, CAfter Muller.) f 
1, 2, 3, &c., the identical parts of the two retinz ; 
} ¢, ¢, the optic axes. 
| retin occupy the same degrees of latitude and 
longitude: 1 is identical with 1, 2 with 2, 
| and so on ; but 1 in the one eye is not identical 
with 5 in the other eye. 


tions; all other points in the two retine are 


773 

“To explain the single vision, therefore, it 
is necessary that not ‘merely each root of the 
optic nerve, but each primitive fibre of each 
root should in the chiasma divide into two 
branches for the two optic nerves, so that the 
identical fibres of the two nerves might com- 
municate with the brain at one point only, viz. 
by one radical fibre, as in the annexed wood- 
cut (fig. 422). But such a division of the fibres 
in the chiasma does not exist: Treviranus and 
Volkmann were unable to detect any division 
of fibres in the chiasma,and I also was unsuc- 
cessful in my search for such dividing fibres. 
( Fig. 422.) 


Fig. 422. 


Li 
Diagram to represent an ideal division of the fibres in 
the chiasma suitable to this theory. ( After Miller.) 
a, a, optic nerves ; b, b, tractus optici; c, c, sup- 
posed division of each radical fibre in the chiasma 
into two branches, one for each optic nerve. 


. 4. If single vision in man be explained on 
the assumption that certain parts of the two 
retine are reciprocally identical, and that such 
identity depends upon a partial decussation in 
the chiasma, single vision in animals should of 
course admit of explanation upon the same 
principles; and if this be granted, the relative 
directions of the optic axes in the vertebrate 
classes ought to afford a good criterion of the 
extent to which the retine are reciprocally 
identical ; for when the optic axes have a 
strictly lateral direction (as in many osseous 
fish), the same object can never be depicted on 
both retine simultaneously, and consequently 
it may be inferred that, in such cases, no parts 
of the two retine are reciprocally identical. 
Again, when the optic axes are very divergent, 
as in many quadrupeds, the respective fields of 
vision must comprise in great measure different 
objects, and under such circumstances it may 
be presumed that the two retine have but little 
identity. And when the eyes are so set that the 
optic axes are parallel, or capable of becoming 
parallel, or convergent (as in man), the same 
objects, or nearly the same, will almost con- 
stantly occupy the two fields of vision; and in 
such case the greatest amount of reciprocal 
identity may be assumed to occur in the two 
retine. 

Now, if the relative directions of the optie 
axes in animals bear relation to the amount of 
reciprocal identity in their retine, and if this 
reciprocal identity depend upon the decussa- 
tion in the chiasma, as has been assumed, the 
structure of the chiasma in animals generally 
should vary as the relative directions of their 
optic axes. 

Such variation in the structure of the chiasma 
has not, however, been proved to occur gene- 


774 


rally throughout the animal series ; on the con- 
trary, the chiasma usually conforms to the type 

evalent in the class to which the animal 

longs, without evincing in its conformation 
much regard to the relative directions of the 
optic axes ; and examples are not unfrequent in 
which the anatomy of the optic nerves is at 
variance with what the relative directions of the 
optic axes would require theoretically. 

Thus in the pleuronectes fish, (fig. 409,) the 
optic axes are so directed that the two retinee may 
be inferred to have a certain amount of identity, 
and nevertheless, in such of them as have been 
examined by the writer, the optic nerves are 
severally derived from opposite sides of the 
brain, and cross each other without forming a 
chiasma; or in other words, retine evincing 
mutual identity are supplied by optic nerves 
which have no identity of origin; the type pre- 
valent in osseous fish being preserved, without 
respect to the directions of the optic axes. In 
many of the cetacea, the direction of the 
optic axes is such that the retin can have no 
identity, and nevertheless a perfect chiasma, 
such as occurs in other mammalia, exists in 
these animals. And in the owl the eyes look 
more directly forwards than those of most other 
birds, from which it may be presumed that the 
amount of mutual identity in the two retine is 
much greater in them than in those birds whose 
eyes have a lateral aspect; but nevertheless 
the structure of the chiasma in the owl appears 
in nothing different from that which prevails in 
birds whose optic axes have a strictly lateral 
direction. 

But further, when the optic axes are very 
divergent, as in some quadrupeds, any object 
which can be depicted upon both retine simul- 
taneously, will throw its images on the outer 
parts of the two retin, and in order to explain 


Fig. 423. 
@ 


am to shew how in eyes with di 


axes, 
the images of every object placed so as to be seen by 
both eyes si fh on the outer parts of the 


two retine. (After Miller. ) 

x, 2’, y,y, axes of the eyes diverging, a,b,c, 
objects seen by both eyes; a’, a”, parts ot the two 
retine on which the object a is depicted; J’, b”, 
parts of the two retine on which the object 5 is 
depicted ; c’, c’, parts of the two retin on which 
the object c is depicted. 


OPTIC NERVES. 


single vision under such circumstances, the 
outer of the two retine should therefore 
be reciprocally identical; but these are 
formed by the outer filaments of i 
nerves, which come respectively from the cor- 
responding sides of the brain, so that here, 
reciprocally identical parts of the two retine, 
instead of having a common origin at one and 
the same side of the brain (as’ they in 
order to suit theoretical views), are derived seve- 
rally from opposite sides of the organ, and con- 
sequently bave no identity of origin (, 
These considerations are sufficient to 
explanation of single vision put forward ; 
and the writer is of opinion that hitherto the 
exact use of the chiasma has not been disco- — 
vered. (See Visron.) i 
Some remarkable varieties of optic nerves. — 
Optic nerves in certain c —The — 
loligo or calamary exhibits in its optic nerves 
a singularly beautiful arrangement, which the — 
physiologist cannot but contemplate with the 
greatest interest, as it presents the most perfect — 
decussation of nervous filaments hitherto dis-— 
covered. The loligo, in common with some of 
the allied families of the cephalopoda, posse 
an extremely perfect organ of vision; so elabo- 
rate is the mechanism of the. eye that it h 
attracted a considerable share of attention from 
comparative anatomists ; and the developement 
of the optic nerve bears proportion to the per- 
fection of the other parts of the visual apparatu 
The nervous system of the loligo conform: 
to the cyclogangliate type, and from each late. 
ral surface of the supracesophageal ganglion 
(fig. 424,) one of the optic nerves comes 0 
After pursuing a short course outwards th 
nerve swells into a large ganglion (the optic) 
this body is oval in shape, and of enormou 
dimensions ; it exceeds considerably the volu 
of the supracesophageal ganglion’ One su 
of the optic ganglion is directed towards 
eye, and emits an immense number of filamen 
which spring chiefly from its edges, and 


Organ of vision, together with the optic nere 
supra-@. lion in the loligo, 
, nified, Frees Sinncton iy the writer.) 


a, supra-cesophageal ganglion; 6, optic | 

c, optic ganglion; d, d, one series of fi 

springing from the edge of the ; 

second orcs ¢ Slemente foe ( | 

posite edge of the ganglion, and in view 

Sear thelr tersaisation only ; f, f, points at’ 
ies decussate 5 — 


the filaments of the two series 
of the eye. 


OPTIC NERVES: 


after making their way to the eye-ball, and 

aap the sclerotic, terminate in the retina. 

hese filaments are arranged at their origin in 

a double linear series, each series streaming 

forth from one of the opposite margins of the 

ganglion. After becoming free of the ganglion 
the filaments of each series approach those of 
the other series, and a most perfect and regular 
interlacement of the two sets ensues ; so com- 
pletely do they decussate that either half of the 
_ Yetina is formed by filaments which spring 
_ from the opposite edge of the ganglion ; those 
filaments which shoot out from the anterior 
margin of that body terminating in, and actu- 
ally forming, the posterior moiety of the retina, 
and vice versa. 
The reciprocal interlacement of these nervous 
filaments reminds one of the manner in which 
__ the two series of threads in a weaver’s loom 
_ (technically called the woof and the warp), cross 
each other; this illustration is exact, for the 
_interlacement of the threads in the one case is 
not more perfect or regular than that of the 
nervous filaments in the other. 

The writer is indebted to his colleague, Dr. 
Power, for a knowledge of this curious arrange- 
ment, which was discovered by that gentleman 
_ while inspecting a preparation of the nervous 
system in the loligo made by the writer, and 
which still exists in the Museum of the Rich- 
mond Hospital School, Dublin. 

__ Subsequent dissections have proved satisfac- 
torily that the decussation in question occurs 
‘variably in the loligo, and that in the octopus, 
which exhibits close affinity to the loligo, the 
same arrangement prevails, In the sepia 
officinalis the optic ganglion is reniform, and 
_ its filaments come off in a double series, as in 
- the loligo ; the majority of the filaments decus- 
" Sate after the same manner as that above de- 
| scribed in the other two species, but some of the 
| extreme filaments of each series pass in a direct 
| course to the retina, without exhibiting any de- 
_cussation. 

__ The peculiar disposition of the optic filaments 
in these cephalopods was unnoticed until the 
| publication of Dr. Power’s paper on the sub- 
| ject in the “ Dublin Journal of Medical Science,” 
—an omission the more surprising, as accurate 
descriptions of the eye in this class of animals 
jn appeared from some of the ablest ana- 


_ Swammerdam long ago described and de- 
ineated the optic ganglion of the sepia offici- 
| nalis, but without making any mention of the 
| mtercrossing of the filaments which emanate 

from that body. Cuvier, in his memoir on the 
Mollusca, describes the eye of the poulpe 
Aectopus) with great accuracy, but makes no 
allusion to the decussation in question ; and in 
the most recent descriptions of the cephalopods 
the same omission occurs. , 

_ The above discovery seemed at first likely 
to afford an explanation of the problem so 
\difficult of solution, namely, the, well-known 

, that objects appear erect to a spectator 
jalthough their images on the retina are inverted ; 
and for some highly ingenious observations 
tending to elucidate this obscure question, the 


ck i 
reader is referred to the paper by Dr. Power, 
already quoted; it may be stated, however, that 
many difficulties remainto_be removed before 
such an explanation can be received, for 

1. The filaments of the optic nerve of the 
loligo have not as yet been traced back to the 
central masses of the nervous system, and there 
can therefore be. no certainty that they preserve 
in the first part of their course the same relative 
positions which they are known to maintain in 
the interval between the optic ganglion and 
point of decussation. 

2. In vision the object is known to be wholly 
reversed in the image on the retina; for ex- 
ample, that which is above in the object is 
below in the image, and vice versa; and that 
which is to the right in the object is to the left 
in the image, and vice vers’; now, although 
the decussation in question might possibly 
explain the correct appreciation of an object 
whose image is reversed in one particular 
direction (say from above downwards), it never 
can fully explain the correct impression made 
by an object of which the image is reversed in 
all directions simultaneously. 

3. In order that this explanation may apply 
to human vision, the same interlacement of 
filaments must first be demonstrated in the optic 
nerve of man, a task which has not as yet been 
accomplished. 


Optic nerves of the compound eyes of Insects. 


These nerves are excessively large and appear 
proportional to the size of the organs of vision 
in the Insect. 

Each nerve on arriving at the eye swells out 
into a bulb, which is convex and varies con- 
siderably in dimensions in different species ; 
this bulb in general represents a segment of a 
sphere, and from its surface nervous filaments 
in immense numbers arise and diverge like the 
radii of a circle. Several thousand of these 
filaments have been counted in a single nerve ; 
each of them is connected by its distal extremity 
to the apex of a small conical transparent body 
interposed between the filament and the cor- 
responding facet of the cornea, but the most 
striking péculiarity of the nerve is found in the 
perfect isolation of each of these filaments by 
the interposition of pigment. 

The pigment is variable in colour, being 
sometimes light, at others dark; it may be 
nearly black, dark violet, dark blue, purple, 
brown, brownish yellow, light yellow, or green, 
and sometimes several layers of different colours 
lie one over the other; the pigment extends 
from the bulb of the nerve to the cornea ; it sur- 
rounds each filament and separates it com- 
pletely from adjacent filaments. 

The effect of this disposition is to isolate the 
rays of light incident on each filament, and 
to prevent the transmission of all rays except 
such as fall in the direction of the axis of the 
filaments ; since all oblique rays must of neces- 
sity impinge upon the colouring matter and be 
in consequence absorbed. 

The reader is referred to the article Insecta 
for further details concerning the optic nerve in 
these animals. 


4 


776 


Plaited optic nerve. 

The optic nerve in some animals exhibits a 
peculiar plaited appearance; this condition 
occurs in perfection in certain fishes, 
and in many birds a somewhat similar organi- 
zation may be detected, though not at all so 
perfectly as in the fish tribes. 

When the plaiting prevails in perfection, the 
nerve consists essentially of a thin membrane 
folded on itself exactly like a closed fan or a 
plaited frill ; but the arrangement referred to is 
not at first sight apparent, particularly if the 
nerve be inspected in that part of its course only 
which is external to the cranial cavity, for there 
the neurilema is so thick, dense, and tough, 
that a correct estimate of the disposition of the 
bervous structure cannot be formed until this 
investment has been removed. 

Deprived of its neurilema, the nerve seems to 
consist of a number of parallel lamine placed 
in juxta-position ; on closer examination these 
lamine turn out to be continuous with each 
other at their edges, and by a little care the 
nerve can be unfolded into a membrane of 
which the breadth is proportional to the num- 
ber and depth of the original lamine. 

When the plaited condition is perfect, it pre- 
vails along the entire length of the optic nerve, 
becoming manifest at its cerebral attachment, 
and continuing to the eye-ball; even the retina 
seems to participate in the same disposition, 
as folds or plaits are observable on the surface 
of that nervous expansion ; and in certain fish 
the optic lobes themselves present a similar 
organization, for the walls of the cavities which 
these tubercles contain are in some instances 
covered with lamine. 

The plaiting must be considered an essential 
attribute of the nervous substance and totally 
independent of the neurilematous investment, 
for this disposition of the nervous material 
occurs occasionally in the optic lobes and re- 
tina, structures which are devoid of neurilema. 
( Fig. 425.) 

Fig. 425. 


Plaited optic nerve of a 
Mullet. (From nature. ) 
a, optic nerve deprived 
of neurilema, exhibiting 
the plaited disposition ; 
b, sclerotic coat of the 
eye through which the 
nerve is passing; ¢, 
retina, in which the 
nerve terminates. 


Laminated optig nerve. 

In certain birds the optic nerve is laminated 
and bears a close resemblance to the plaited 
condition just described. 

In these birds a careful examination of the 
nerve is required for the discovery of its true 
texture, for the neurilema (endowed with un- 
common strength) adheres so firmly to the 
' nervous structure that without a careful dis- 
section its lamine elude observation. 

When viewed on one side the nerve seems 
perfectly smooth, but on the opposite side 
numerous lamine may be distinctly observed ; 
these are parallel to each other, and runplong 


OPTIC NERVES. 


the nerve in the longitudinal direction: they 
are of considerable depth and variable thick- 
ness; they are applied closely to each other, 
being separated by thin processes of neuri- 
lema only, and altogether (their straight course 
excepted) this arrangement bears a 1g 
similarity to the disposition of the lamine on 
the human cerebellum. A short section of the 
mate gare of its neurilema is not unlike a 3 
c k, the laminz representing the leaves, 
and the opposite smooth pales | the nerve ~ 
bearing a resemblance to the back and cover — 
of the book. The laminated optic nerve of the 
bird does not admit of being unfolded into a 
flat membrane, a proceeding which can be 
accomplished with care in the plaited optic 
nerve of the fish: and in birds \ 
structure occurs in that part of the nerve only 
which is in front of the chiasma; in its cerebr 
perm no such organization prevails. ( Fig. 
426. = 
4 


. 
aminatec 


ee. 


Fig. 426. 

, Eagle. ( From per 
a, chiasma; b, ‘ 
divested of neuri a 
exhibiting laming on o1 
surface ; ¢, : 


Desmoulins, who has paid the greatest ¢ 
tention to these varieties, 1 as the re 

of his extensive researches, that the plait 
arrangement of the optic nerve in fish, at 
its laminated condition in birds bears 
portion to the perfection of vision in the at 
mals under consideration; for those bi 
which are endowed with the most po 
piercing sight possess the laminated struet 
at a maximum of developement. For exat 
birds of prey, such as the eagle, the fal 
and the kite, evince an acuteness of this fac 
truly surprising; from heights in the ata 
phere, at which they are themselves alm 
invisible, they discover their prey on the gro 
and pounce on it with the most unerring 
tainty, whilst at the trifling distance of a 
yards other animals recognise such objects: 
difficulty: now birds of this class affore 
most perfect specimens of the laminated 
nerve. It is further stated on the same at 
rity that birds which at short distances po 
remarkably quick and accurate pe 


vision (more especially when in suc 1 
this faculty is exercised in media of di 
laminated optic nerves, and that me t 
A 
j 


degrees of density) are also provi 
which the plaited optic nerves occur are 
dacious habits, and consequently require 
erful organs of vision just as the birds: 
propensities. a 
e writer has examined the optie ne 
the stork, kingfisher, eagle, &e., and i 
as well as in all the fishes which have 
within his reach, his dissections have 
verified the anatomical descriptions givé 
Desmoulins. oo 
It is difficult to explain the superior 
bility supposed to be thus conferred” 


OPTIC NERVES. 


optic nerve; but the more obvious effect of 
this organization is to increase the surface of 
the nervous material. A similar contrivance is 
at times resorted to in the nervous centres, as is 
exemplified in the cerebral hemispheres ; these 
masses in the higher and more intelligent 
animals being covered with large convolutions 
and deep sulci, while in the lower classes they 
are smooth and consequently possess a super- 
ficies of limited extent. 


Optic nerve in that form of monstrosity known 

by the varied appellations of “ Cyclops,” 

“ Fetus a trompe,” “ Monops,” “ Rinence- 

phale,” Sc. §c. 

The abnormal anatomy of the optic nerve is 
not in strictness comprised within the scope 
of the present article, but nevertheless a brief 

_ description of the above malformation will pro- 
bably not be considered out of place. 

A single eye placed in the middle line of the 
forehead, and in general a trunk or proboscis 
growing immediately above this solitary organ 
of vision, constitute the most striking apparent 
anomalies in monsters of this class. The 
writer is indebted to Dr. Johnson, Master 
of the Dublin Lying-in Hospital, for permis- 
sion to dissect a specimen of this species of 

monstrosity in the human subject, and he 
has obtained through the kindness of Dr. 
William Wilson Campbell, (formerly assistant 
‘in the same establishment,) the particulars of 
another similar case exa- Fig. 427. 


_ mined by that gentleman in 
| the year1834. ‘The annexed 
' wood-cut (fig. 427) gives a 
faithful representation of the 
| optic nerve in the prepara- 
_ tions dissected by the writer 
-and Dr. Campbell; and it 

ees exactly with the ap- 
arances found by Geoffroy 
aint-Hilaire, in the cases 
which fell under his obser- 
vation. The tractus optici 
present a very natural ap- 


in front, and from it, only writer.) : i 
a single optic nerve pro- 4% 4 tractus opti~ 
ceeds ; Bi ppance ditectly nated na al > 
f s to the back of the gie optic nerves d, 
ball, where it penetrates sclerotic coat of "the 
e sclerotic and terminates eye perforated bythe 
in the retina. optic nerve. 

_ Fig. 428 represents the encephalon, optic 
hherve, and organ of vision in a kitten at the full 
iod of gestation, (the subject of the same 
of monstrosity,) which lately came into 
he writer's possession : the preparation is pre- 
served in the Museum of the Richmond Hos- 
ime School, Dublin. In all essential particu- 
this specimen bears the closest resemblance 
jto the human monsters of which the dissection 
has just been described. 

The fundamental defect in these monstrous 


777 
\ Fig. 428. 


a d 

Brain and organ of vision of 
b @ Cyclops katten, at the full 
i period of gestation. Seen from 
Wi Mil— qd below. ( Natural size.) 


wail 


a, organ of vision, single, 
and of great dimensions; b, b, 
cerebral hemispheres seen from 
below ; d, d, tubereula quadri- 
gemina ; c, optic nerve, single, 
and of great size. 
fetuses consists in the total absence of the 
organ of smell, in consequence of which de- 
ficiency the symmetrical organs at either side 
become united in the middle line and actually 
engrafted upon each other: the ¢wo eyes are 
conjoined so as to form but a single organ of 
vision, and the very same metamorphosis occurs 


-in the two orbits, the two optic foramina, the 


two optic nerves, &c. 

That this is the rationale can scarcely admit 
of doubt, since in some parts of the organs 
the fusion remains incomplete ; thus two crys- 
talline lenses still exist in the interior of the 
solitary eye-ball: a double set of muscles with 
their corresponding nerves are provided for the 
globe of the eye; and four eye-lids protect the 
organ in front, causing the aperture of the lids 
to assume a quadrangular form. 


General developement of the optic nerves in the 
higher classes of animals. 

Fish.—In fish as a general rule these nerves © 
are highly developed, and exhibit a marked 
preponderance in size when contrasted. with 
the corresponding nerves in many animals 
holding a more exalted position upon the scale. 
This may be explained by the nature of the 
medium which the fish inhabits; for some of 
the light incident on the surface of the water is 
reflected, and another part, after penetrating the 
water, becomes absorbed, in consequence of the 
continual disturbance to which the transparency 
of this fluid is subject; so that fishes necessa- 
rily require a greater developement of visual 
apparatus than would suffice /and animals for 
an equal amount of vision. 

Birds.—In birds the sense of sight exists in 
great perfectio, and the optic nerves exhibit 
corresponding developement. 

Mammalia.—In Mammalia the faculty of 
vision ceases to preponderate, and accordingly 
the proportions of the optic nerves in this class 
are no longer excessive. 

Many facts in comparative anatomy war- 
rant the conclusion that the senses of smell 
and vision are at times supplemental to each 
other; for example, the mole either possesses 
no optic nerve, or if any such exist it is so 
diminutive as to be most difficult of recogni- 
tion, but the olfactory lobes of the brain and 
the whole olfactory apparatus of the animal 
exist in great perfection, and its subterranean 
habits enable it to turn this latter function to 
‘account, whilst a highly finished organ of 
vision would have been an useless appendage. 
In certain fish which frequent the mud or slimy 
waters (as for instance the eels), the visual 
apparatus is poorly developed, and the optic 


778 


nerves are particularly small ; but the olfactory 
nerves preponderate, and there can be little 
doubt that the superiority of the sense of smell 
in them serves in great measure to supersede 
the necessity for highly-wrought organs of vision, 
and in probably the majority of the Mammalia 
the olfactory nerves preponderate in size over 
the optic, but the corresponding faculty by its 
acutetiess makes amends for any inferiority in 
vision. Thus the keen scent of many Carni- 
vora renders the eye of secondary importance 
in the pursuit of their prey, and the vegetable 
feeders are much indebted to the perfection of 
their sense of smell for the discrimination’ they 
evince in their choice of nutriment. 


FUNCTIONS OF THE OPTIC NERVE. 

The optic nerves when present are essential 

to vision. 

In all animals which possess optic nerves 
they must be considered essential to vision, 
for diseases which destroy the organization of 
the “second pair” invariably deprive the organs 
of sight of their sensibility to.luminous impres- 
sions ; and were other proof wanting, the ex- 
eee instituted of late years by Magendie, 

ayo, and others, would afford sufficient 
evidence of the special function of the nerves 
in question. Magendie found that division of 
either optic nerve in front of the chiasma was 
instantaneously followed by complete loss of 

"vision in the correspondingeye of the animal sub- 
mitted to the experiment; and when both optic 
nerves were thus divided évtal blindness en- 
sued, and no means which could subsequently 
be devised for concentrating light upon the 
eye appeared to excite in the retina the slightest 
sensibility to its accustomed stimulus. 

Although the foregoing facts would warrant 
the conclusion that the only nerves capable of 
endowing the eyes with their special sensibility 
are the optic, nevertheless many considerations 
favour the presumption that the fifth pair exert 
direct influence on the sense of sight, so much 
so that some have considered these nerves 
essential to vision, whilst others have even sup- 
posed that the faculty in question may be main- 
tained through the agency of the fifth nerves 
alone. 

In those animals which possess special optic 
nerves, the fifth pair are totally inadequate 
to support vision. 

There are no facts on record to prove the 
possibility of such animals continuing to see 
after destruction of the second pair. The experi- 
ments already cited may be looked on as con- 
clusive, and those performed by Magendie to 
show that divison of the fifth nerves within the 
cranium in living animals produces blindness, 
can never justify physiologists in the belief that 
the “trifacial” may endow the eyes with their 
special sensibility. 

Certain facts furnished -by the comparative 
anatomy of the second and fifth pairs have been 
A, ape fe time adduced to shew that the 

in the human subject possesses this power. 

Thus it is stated on good authority, that pHs 

mon Mole, the Proteus anguinus, the Mus Ca- 

pensis, the Chrysochlore, the Mus typhlus, and 


J 


OPTIC NERVES. ~ 


the Sorex araneus, in which organs of vision occur, _ 
are not provided with special optic nerves, and — 
that in them the fifth pair furnishes the only 
nerve which the rudimental eye receives. It is” 
argued from these data (and Serres would seem — 
to be one of the ablest advocates for this view) — 
that a branch of the fifth nerve assumes in 
such cases the functions of the optic, becomin: 
endowed with special sensibility to light, and 
that therefore lien analogy the ophthalmi 
division of the fifth in man may be presumed to 
possess similar properties. 33 
Conclusions pit ae at by such reasoning 
should be received with caution in the absence 
of more direct proofs; the weight to 
they are entitled has been already fully ¢ 
cussed under the article Firra Parr 01 
Nerves, and reference is made to that artic 
for further particulars touching this interesti 
topic. The writer fully concurs in the vie 
therein advocated, and feels disposed to attri 
bute little value to arguments founded, as th 
appear to be, on imperfect analogies. Th 
cases of the human subject and the anim 
specified are essentially dissimilar; the pi 
sence of a special optic in the one case, and 
absence in the others, destroys their parallel: 
and may create important differences in 
functions of accessory nerves; and, morec 
the little knowledge we possess of the natut 
and amount of vision enjoyed by animals 
which special optic nerves are wanting, shot 
e hesital argue from them to 


* 


make us hesitate to 

human subject. 
That the fifth pair exercise some influet 

over vision can scarcely be denied, bu' 
nature and amount of this influence are no 
easily determined, and have probably bi 
much exaggerated. 

In the present state of their knowledge phy 
logists have not sufficient proof that in— 
higher animals the influence of the fifth 
is absolutely essential to sight. ial 
Magendie discovered that the section of 

fifth nerve on both sides within the cranium 

a living animal greatly impairs, af it de 

actually annihilate vision, and such a m 

seems, no doubt, to argue that the facul 

sight has a necessary dependence on 
integrity of the “trifacial nerves,” but tl 
periment when critically examined wi 
pear not to warrant such an inferem 
demonstrates that so rude an injury inflie 
the nervous centres deprives an animal ¢ 
of ‘its faculties, and this might 
anticipated on general principles; but: 

not prove that the loss of the di 

on the injury to the fifth nerves alone. 

a destructive proceeding there can be 

surance that the fifth pair have been t 

pores of importance mutilated ; the con 

y much the more probable presumptie 
therefore, the conclusion “ that the fil 

are essentially necessary to vision ” is 1 

deducible from the experiment. But 1 

the facts (detailed even as they 

Magendie) suffice to show, that the eye 

continue sensible to luminous impressio 

complete division of the fifth pair, for ac 


OPTIC NERVES. 


to his own account, “the eye of the rabbit on 
sudden exposure to the sun’s rays, after the fifth 
pair had been divided, was ‘still sensible to 
strong solar light; and the effect was more 
marked when a lens was used to test its 
sensibility.” 
Mayo’s experiments on pigeons afford still 
more convincing proof of the ability of the 
optic nerve, unaided by the fifth, to maintain 
_ the special sensibility of the eye; this physio- 
_ logist succeeded in dividing the fifth nerve 
within the cranium of a living pigeon (leaving 
the optic uninjured,) without rendering the 
retina insensible to light. 
The results of pathological observations on 
man furnish also abundant evidence that vision 
continue after disease has destroyed the 
_ fifth nerve. Opportunities do not ofteri occur 
_of bringing this to the test of dissection, for in 
most of these cases changes of structure involve 
other parts of the nervous centres simultane- 
ously with the fifth nerve, and so deprive them 
of their greatest value; and the destructive in- 
flammation of the eye-ball, which so constantly 
“accompanies morbid alterations of the fifth pair, 
is another fruitful source of embarrassment in 
attempts to investigate their history, but even 
a few well-attested observations are amply 
ufficient to establish a negative proof. Miiller 
cites a case of disease involving the whole trunk 
of the fifth nerve of the left side, in which 
insensibility of the entire left side of the head 
d the corresponding side of the tongue and 
eye, occurred, while vision remained perfect ; 
| and in the article Frrra Parr or Nerves, other 
imilar examples are related. 
The conjecture that the fifth pair is essential 
| to vision receives probably its strongest support 
‘from the occasional results of injuries to cer- 
tain branches of that nerve, for numerous 
cases are on record in which wounds or con- 
usions of its frontal twigs have been fol- 
‘lowed by blindness, and the same unfortu- 
‘Mate event has resulted (though rarely) from 
itations affecting some of its other branches. 
Thus, Mr. Travers has known amaurosis to 
ginate from irritation of the dental nerves. 
He says, “I have seen.an incipient amaurosis 
arrested by the extraction of a diseased tooth, 
when the delay of a similar operation had 
teasioned gutta serena on the opposite side 
t os before.” And Professor Galenzowski 
of Wilna “ observed severe neuralgia and 
blindness produced by a splinter of wood. be- 
coming entangled in a diseased tooth, and 
these symptoms were cured by the-extraction of 
he tooth together with the offending material.” 
The value of such facts as these in assisting 
ysiologists to determine the influence exerted 
the fifth nerve over vision, appears to have 
been much overrated ; for in a large proportion 
‘these cases it may be inferred with great pro- 
ability that the same injury which affected the 
jupra-orbital nerves exerted also pernicious in- 
juence on the deeperseated contents of the orbit, 
d that the optic nerve, or retina, or even the 
in itself participated in the effects of the vio- 
ence, although from the more superficial posi- 
and greater exposure to danger of the frontal 


oe 


) 


779 


branches of the fifth,\they alone were believed 
to have suffered. This explanation will undoubt- 
edly not apply to cases in which blindness has 
been produced by very trivial injuries, such as 
simple incised wounds or punctures of the 
nerves in question ; but nevertheless the weight 
of evidence which these latter cases would seem 
to afford is much diminished by the consideration 
that loss of sight has likewise ensued from inju- 
ries and affections of other nerves, to which, 
while healthy, no participation in the support of 
vision can be conceded. For example, Dr. Jacob 
recites the case of an officer in whom amaurosis 
occurred in consequence of injury inflicted by 
a ball on some branches of the portio dura ;* 
and irritations in the digestive organs (dyspeptic 
disturbance of the stomach more especially) 
are well known to produce at times amaurotic 
symptoms. Now, although these facts un- 
questionably establish the existence of curious 
pathological affinities between the nerves of the 
part thus irritated and those which are subser- 
vient to vision, no physiologist would be hardy 
enough to infer from such premises that the facial 
nerve, the par vagum, or those which supply the 
intestinal tract, exercise in the normal state 
any control over the faculty of sight. 

If, in addition to these considerations, it be 
recollected that blindness occurs only as an 
occasional consequence of injuries to the frontal 
nerves, and that loss of vision is found to ensue 
very rarely from the irritations to which other 
branches :of the fifth are so peculiarly liable, - 
the importance of such cases in determining 
the question must be still further lessened. 
The observations of Dr. Jacob on this sub- 
ject appear to the writer so apposite that 
he is induced to insert them. ‘This gentle- 
man writes, “* Blindness does not seem to have 
followed any of the operations formerly so 
much practised of dividing the branches of this 
nerve, and in some of the worst cases of that 
form of neuralgia called tic douloureux, vision is 
not impaired. Moreover, thousands of children 
suffer from dentition and thousands of adults 
from tooth-ache, yet none of these become 
blind in consequence.” + 

The coincidence of loss of sight with injuries - 
or irritations affe¢ting branches of the fifth’ 
nerve, admits of explanation on other principles 
without assuming the fifth to be essential to 
vision ; the hypothesis that in such cases reflex 
irritation becomes propagated from the parts pri- 
marily affected through the nervous centres to 
the optic nerve, seems in the present state of 
physiological science sufficiently plausible; 
for while it applies to cases of amaurosis 
resulting from abnormal conditions of other 
peripheral branches of the nerve as well as its 
ophthalmic division, it also affords a solution 
of the still more obscure dependence of the 
same disease on irritations in remote organs. 

The experiments of Magendie, confirmed 
as they have been by pathological observations, 


* Cyclopedia of Practical Medicine, art. AMAU- 
ROSIS. 

t+ On Paralytic Neuralgia and other Nervous 
Diseases of the Eye, by Arthur Jacob, M.D. 


780 . 


justify the inference that the fifth nerve endows 
the eye with its general sensibility, and also 
exerts some influence over the nutrition of that 
organ. 

is distinguished physiologist divided the 
fifth nerve within the granium of an animal 
and found the tactile sensibility of the surface 
of the eye completely abolished by the expe- 
riment; opacity, ulceration, and sloughing of 
the cornea, followed by expulsion of the hu- 
mours, and total destruction of the eye subse- 
quently ensued; and nearly the same results 
have been observed to oceur in the human 
subject from disease affecting the fifth nerve 
within the cranium. It must be perfectly ob- 
vious, however, that these facts have no bearing 
upon the question more immediately under 
discussion. 

An impartial review of this highly interesting 
question leads to the conviction that notwith- 
standing the great plausibility of the arguments 
by which the contrary view has been sustained, 
there is as yet no evidence that in man any 
other nerve than the optic enjoys special sensi- 
bility to light. 

Ordinary tactile sensibility—Although the 
optic nerves are endowed with such acute 
sensibility to the influence of light, they would 
seem to possess little ordinary tactile sensibi- 
lity,—a circumstance the more surprising, as 
it is difficult to imagine any impressions more 
delicate than those of light; and where nerves 
evince such exquisite susceptibility of excite- 
ment from the stimulus of that imponderable 
agent, an equal obedience to those rougher 
stimulants which produce such marked effects 
on the common sentient nerves might at least 
be expected. 

Magendie infers from his experiments on 
living rabbits that the retina in them is not 
susceptible of pain from mechanical irritation ; 
so much so, that puncturing or tearing that 
hervous expansion appeared to him to cause 
these animals no sort of suffering.* Precisely 
the same results followed from injuries inflicted 
by him on the retina in fish and reptiles, 
although in birds, cats, and dogs similar expe- 
riments seemed to create some uneasiness. 
This physiologist asserts that the human retina 
also is devoid of ordinary tactile sensibility, for 
in operating for .cataract he has proved that 
the membrane in question exhibits little if any 
susceptibility of pain. 

His experiments were likewise extended to 
the optic nerves; and in the course of his in- 


vestigations frequent opportunities were afforded . 


for testing the comparative sensibility of the 
second and fifth pairs. 
whether the injury was inflicted in front of or 
behind the chiasma, the second pair seemed 
quite insensible to mechanical irritation; and 
whenever the slightest disturbance affected the 
fifth nerve, the animal, by its cries and struggles, 
immediately manifested the most acute suffer- 
ings. 
The phenomena noticed in extirpation of the 
human eye are favourable to the same views, 


* Journal de Physiologie, t. iv. 


In all the mammalia, 


OPTIC NERVES. 


for division of the optic nerve in this operation 
is not attended with the agonizing torture which 
an equal amount of injury to a nerve of the — 
same dimensions endowed with common sensi- — 
bility would unavoidably produce. This fact — 
should have some weight with physiologists in 
their attempts to form a just estimate of the 
properties of the nerve under consideration, 
although the results of such observations are 
inconclusive; for in many cases of extirpation 
of the organ the optic nerve is itself diseased, 
and under such circumstances it would be 
unfair to argue from the known effects of 
injuries on a diseased structure, to the probable 
effects of injuries on the same structure when 
healthy. ») 
The optic nerve is not singular in its insensi- 
bility to pain from mechanical irritation, for 
experiments on other nerves of special sense 
countenance the belief that some of them labour 
under the same disability. Magendie laid bare 
the olfactory of a dog, and the animal did 
not manifest the slightest pain when the nerve 
was compressed, pinched, or even torn; an 
when the auditory of a rabbit was subjected to 
similar rough treatment at his hands, the animal 
afforded no indication of suffering.” ; 
The specific stimulants of the organs of sense 
act however at times so intensely as to produc 
painfully disagreeable impressions on their 
spective organs, and it therefore becomes diffi- 
cult to reconcile, with the foregoing statemen 
facts such-as the following, which apparent! 
favour the opinion that the optic as well as 
other nerves of special sense commor 
sensibility. “ An intense light dazzles the ey 
so as to become actually insupportable. A harsl 
or discordant sound produces a most distress 
ing impression on the organ of hearing; 
certain odours are disgusting and intolerable 
the pituitary membrane.” ~ = 
In estimating the weight to which these latte 
facts are entitled, it should be recollected 
the above sensations still preserve their speci 
characters, no matter how intensely disagreeah 
they become : thus light, although sufficien 
brilliant to dazzle the retina, still continue 
be a luminous impression, and in like mai 
sonorous vibrations and odours, though actual 
offensive to their respective organs, are § 
nothing more than sounds and scents. So 
on the whole, however questionable may be t 
propriety of such experimental zeal as wot 
induce a French physiologist to test the 
bility of the human retina in operations fore 
ract, the general proposition that the optic 
in man and the higher animals enjoys litt! 
any, tactile sensibility, seems pretty 
tablished. "i 
Effects of stimulants—Although the o 
nerve betrays little indication of pain in | 
sequence of injuries, nevertheless mec 
and other stimulants produce upon it pect 
effects: mechanical injuries and irritants are 
its special sensibility instead of exciting pai 
sensations—their ordinary effects on ce 
sentient nerves. 4 


. 


* Journal de Physiologie, t. iv. 


, 


OPTIC NERVES. 


For example: firm pressure applied to the 
globe of the eye when the lids are closed and 
light excluded, gives rise to the sensation of 
luminous spectra which present different colours. 
Concussion of the eye-ball is often followed by 
the same results: division of the optic nerve in 
extirpation of the organ of vision generally 
causes the patient to perceive a great light ; 
and an electric current transmitted through the 
optic nerve, or its immediate vicinity, seems to 

roduce a flash of light. The second pair, in 
Sccer their special sensibility excited by such 
varied stimulants, merely conform to the laws 
by which other nerves of special sense are go- 
verned ; for electricity applied to these nerves 
severally may be made in each case to elicit 
the peculiar sensibility of the nerve which hap- 
pens to be the subject of the experiment: in the 
optic nerve it produces the sensation of a flash 
fi of light ; in the auditory it excites a loud sound ; 
in the gustatory it gives rise to a peculiar taste; 
_ in the olfactory it developes a particular smell ; 
and in the common sentient nerves it causes 
“painful sensations. In like manner a blow 
may occasion the optic nerve to flash fire, the 
_ auditory nerve to hear sounds, the common 
sensitive nerves to feel pain; and more examples 
| might be added to this catalogue. 
+ The nerves of special sense seem in general 
to be endowed with but one determinate sort 
of sensibility; and though this is commonly 
excited by a specific stimulus only, it may be 
elicited occasionally by other means. 
_ Excito-motory properties—The optic nerve 
is one of those paths through which incident 
impressions are propagated so as to excite 
| reflex motions. The impression of light on 
' the retina is instantaneously followed by con- 
traction of the pupil, a phenomenon indicative 
of reflex motion developed in the iris; and 
_ the sudden closure of the eye-lids under the 
| influence of a strong light or a threatened blow 
| is also a familiar example of reflex motion 
| produced by impressions upon the terminal 
_ expansion of the optic nerve. 
is Te tet, Fontana, and Caldani, have de- 
monstrated that the optic nerve is the channel 
gh which the incident impression travels 
im order to excite reflex motion in the iris. 
n their experiments, rays of light transmitted 
through a hole in a sheet of paper, and by this 
contrivance conveyed through the pupil di- 
rectly to the retina, produced immediate mo- 
tion of the iris; but when the light was al- 
9a to impinge upon the iris a/one without 
‘Teaching the retina, no contraction of the pupil 


_ Mayo’s experiments on pigeons taken in 
‘connection with the foregoing facts appear par- 
ticularly instructive, proving as they do that in 
the bird, irritation propagated along the optic 
nerve in a centripetal direction may excite reflex 
otion in the iris. When the optic nerves were 
divided within the cranial cavity of a living 
pigeon by Mayo, the pupils became fully dilated 

and were no longer obedient to luminous im- 
| pressions even when dazzling light was admitted 
mto the eyes. When a pigeon was decapitated 
the same experimentalist, and its optic nerves 


781 


subsequently divided within the cranial cavity, 
irritation of that portion of the divided nerves 
which continued in connection with the eye pro- 
duced no effect on the iris; but contraction of 
the pupil immediately ensued when the other 
extremity of the nerves, viz. that which re- 
tained its connection with the brain, was irri- 
tated. 

In general the reflex motion is developed in 
the iris of the same eye on which the impres- 
sion is incident, or in other words light falling 
on the right retina produces in general con- 
traction of the right pupil and not of the left, 
and vice versa; but it sometimes happens 
that an impression propagated along one optic 
nerve (for instance the right) may cause the 
reflex phenomena to appear in the iris of the 
other eye (viz. the left). 

Certain forms of amaurosis in which the dis- 
ease affects but one eye while the other con- 
tinues healthy will serve for illustration. 

In such cases it occasionally happens that 
little or no difference in the size of the two 
pupils can be detected so long as both eyes 
remain exposed to the light, the iris of the dis- 
eased organ contracting and dilating simulta- 
neously with that of its healthy neighbour; 
but as soon as the lids of the sound eye are 
closed, the pupil of the amaurotic eye becomes 
dilated, and the most intense light admitted into 
this diseased organ takes no effect on the iris, 
now become perfectly motionless. 

The explanation of these phenomena is found 
in the preceding proposition; so long as the 
healthy eye continues exposed to light, the 
impression falling on a sound retina excites 
reflex motion in the pupils of both eyes, as 
well the amaurotic as the sound; but when the 
light is excluded from the healthy retina, the 
influence of that agent upon the diseased retina 
of the other eye has no longer the power to 
excite reflex motions. 

. The exercise of these excito-motory proper- 
ties of the optic nerve is generally accompanied 
with excitement of its special sensibility; thus 
a.person is in general conscious of the lumi- 
nous impression, or, in other words, he sees 
the light which causes contraction of his pupil ; 
but the reflex phenomena may be manifested 
by the iris, althoagh the incident impression 
pass unnoticed by the individual. 

In certain cases of general insensibility (as, 
for example, concussion occasionally) the pupil 
contracts upon the admission of light while 
the patient remains perfectly unconscious, and 
something similar seems to occur at times even 
in health; for the iris varies its dimensions 
‘with each successive change in the volume and 


- intensity of the light, although from inatten- 


tion we do not perceive these trifling changes. 
Some degree of attention appears requisite in 
order that weak or transitory impressions should 
arouse the special sensibility of the optic nerves, 
whereas attention is not a condition essential 
to the production of reflex phenomena. 

Mayo’s experiments here again admit of 
application; he found that in decapitated pi- 
geons in which the optic nerves were subse- 
quently divided, irritation of the cerebral ex- 


782 


tremity of the cut nerve produced contraction 
of the pupil, although under the circumstances 
the animal could not have been conscious of 
such irritation. 

Radiated or sympathetic sensations. 

The optic nerve participates in a class of ob- 
scure sensations to which a brief allusion may 
be here permitted ; these are called radiated or 
Sympathetic sensations; they occur occasion- 
ally in health, though they are more frequently 

ptomatic of disease or irritation elsewhere 
situated, and as they are likewise manifested 
by other nerves it would be erroneous to con- 
sider them peculiar to the optic. The pheno- 
mena to which allusion is made are for the 
most part transitory affections of sensitive 
nerves which do not seem to depend on any 
direct impression made upon the nerve af- 
fected, but rather to be | sive te by causes 
which act on other (generally distant) parts of 
the system. 

The following will serve as examples of the 
affections under consideration. 

A discordant sound, such as that produced 
by setting a saw or scratching glass, gives rise 
to shuddering, or a sensation as if water were 
dropping over the surface. Tickling the soles 
of the feet occasions general sensations of the 
most disagreeable nature; and the impression 
of a strong light on the eye is often followed 
by a sense of irritation in the nose, with violent 
sneezing. 

Similar affections of the optic nerve will 
readily occur to the reader’s recollection ; thus 
various forms and degrees of temporary insen- 
sibility or excitement of the retina, which are 
known to depend on gastric disturbance, belong 
to this category, and many other such instances 
might be adduced. 

acts, such as the foregoing, have long been 
familiar to physiologists; but to account for 
them seems still to be a matter of difficulty. 
The supposition that the connections of the 
r domes etic with the nerves affected explain 

e problem is far from satisfactory; the 
most plausible theory is that which supposes 
the primary irritation to be propagated in 

' a centripetal direction along the nerves of the 
part to the cerebro-spinal centres, and thence 
reflected upon the roots of those nerves in 
which the sensations are developed, in some- 
what the same way that excito-motory impres- 
sions on nerves come to produce reflex motions; 
the difference in the two cases amounting to 
this, that in the one the primary impression 
reacts upon motor nerves, giving rise to reflex 
motions, in the other on sensitive nerves causing 
thereby reflex sensations. 

Though this may be the true explanation, it 
is nevertheless not perfectly satisfactory, for it 
does not shew why the reflex irritation should 
be prone to fall on one sensitive nerve in pre- 
ference to another, yet the optic is known in 
such cases to suffer more frequently than the 
auditory or olfactory. 

BIBLIOGRAPHY.—The following books may be 
referred to in addition to the several sytematic 
treatises on Physiology and Descriptive Anatomy. 
Sir J. Newton, his optics, query 15, London, 1718, 


ORBIT. 


John og peeg Fe of nature, translated by 
Thomas Flloyd, 1758. Sam. Thom. ing, De 


basi encephali et originibus neryorum, B.. 
A Monro, The structure and physiology of 
fishes, Edinb, 1785. F. J. Gall et é. Spurzheim, 
Anatomie et physiologie du systéme nerveux, F 
1810. Cuvier, Mémoires servir hi 
et a V’anatomie des mollusques, Paris, 1é 
ilaire, Philosophie anatomiqu 
monstruosités humaines, Paris, 1822. F 
Recherches expérimentales sur les p evés et les 
fonctions du systéme nerveux, Paris, 1 Herber 
Mayo, Anatomical pg amc comme 
taries, second part, July 1823. Wm. HydeWoll 
On semidecussation of the optic nerves, Ph 
phical Transactions, 1824. H, R, A. Serres, J 
tomie comparée du cervean, Paris, 1824. gen 
Journal de physiologie experimentale et pathe 
logique, Paris, 4. Desmoulins et Magendi 
Anatomie des systémes nerveux des animaux ¢ 
vertebrés, Paris, 1825, rederick Tiedemann, ' 
anatomy of the fcetal brain, translated from th 
French by Wm. Bennett, 1826. Miiller, Physiolog 
des Gesichts-sinnes, Leipz. 1826. Joseph Swa: 
demonstration of the nerves of the human body 
London, 1830. Frederici Arnoldi, Icones ne 
capitis, 1834. Catalogue of the physislogseat 
of comparative anatomy in the Museum of 
Royal College of Surgeons, London, 1833 to 
Samuel Solly, The human brain, its configuratio 
structure, &c. London, 1836, Catalogue of tl 
Museum of the Royal Col of Surgeons i 
Ireland, by John Houston, M.D. Dublin, 
Marshall Hali, Lectures on the nervous system ar 
its diseases, London, 1836: also ‘‘ Memoirs on t 
nervous system,” by same. Fr. Leuret, Anaton 
comparée du systéme nerveux, Paris, 1839. H 
Mayo, On the chiasma of the 
London Medical Gazette, November 1841. A: 
Jacob, On paralytic, ne ic, and other 
diseases of Ak eye, Dublin, 1841. John H, Pou 
Observations on the arrangement of the optic ne 
of the loligo, &c. Dublin Journal of | 
Science, 1843. % 
(Robert Mayne. 


ORBIT. ( Orbis, any thing round; Fr. 7 
bite ; Germ. Augenhihle. )—Inthe presentar 
it is intended to describe, first, the bony frat 
work of the orbit; secondly, the contents* ¢ 
orbit in the order in which are exposed 
a dissection from the roof to the floor of the cat 
and, lastly, to give some account of the ai 
of the muscles contained in the orbit and 
serted into the upper lid and globe of the ¢ 

The orbits are two in number, situated a 
anterior and — part of the face. ‘ 
have the form of quadrangular pyramids, 
bases of which are directed forwards an 
wards, the apices backwards and it 
Each orbit-presents for examination’ four ¥ 
four angles, formed by the meeting of the 
a base, and an apex. " 

The superior wall or roof is concave 4 
rected downwards and slightly forward 
chiefly formed by the orbital plate of the 
bone ; at the posterior part to a slight é: 
the lesser wing of the sphenoid. It 
the suture between the orbital 
frontal and the lesser wing of the sphenoii 
anteriorly on the outer side, the lach 
fossa, which receives a gland of the same i 


* The relative anatomy only of these part 
be given in this article, a special description 
Eye and LACHRYMAL ORGANS having 
been given. 4 “* 


* 


piat 


ORBIT. 


on the inner side a depression for the insertion 
of a pulley, through which rans the tendon of 
the superior oblique muscle. 

The inferior wall or floor is less extensive 
than the roof, and is directed upwards, out- 
wards, and forwards. It is formed chietly by 
the orbital plate of the superior maxillary bone, 
in front of this by the orbital process of the 
malar, and at the posterior part to a slight ex- 
tent by the orbital process of the palate bone. 
It presents a suture marking the union of the 
malar with the maxillary, and of the maxillary 
with the palate bone; about the middle of the 
floor is the infra-orbital groove, which passes 
forwards and becomes the infra-orbital canal. 

The external wall is directed inwards, for- 
wards, and slightly upwards; it is formed in 
_ front by the orbital process of the malar, and 
_ posteriorly by the orbital surface of the greater 
_ wing of the sphenoid. It presents a vertical 
_ suture at the junction of the malar with the 
sphenoid bone, and the orifices of some small 
eanals which open externally in the temporal 
fossa, and on the facial surface of the malar 
bone; some of these canals transmit filaments 
_of nerves from the lachryma!l branch of the 
ophthalmic, and from the superior maxillary 
herve. ' 
The internal wall is directed outwards, and 
‘slightly forwards and upwards: it is formed 
chiefly by the os planum of the ethmoid, in 
front of this by the lachrymal, and behind by 
‘the side of the body of the sphenoid. It pre- 
sents a vertical suture between the lachrymal 
‘bone and the ethmoid, and another between the 
latter bone and the sphenoid ; and anteriorly a 
vertical groove which lodges the lachrymal sac. 
_ Anetrs.—The superior and external angle 
formed by the junction of the superior with 
the external wall presents posteriorly the sphe- 
noidal fissure, sometimes called foramen lace- 
Tum anterius; in front of this a horizontal 
suture at the junction of the orbital plate of 
| the sphenoid with the orbital plate of the frontal 
| bone, and anterior to this the junction of the 


The superior and internal angle formed by 
e meeting of the superior and internal walls 
ents a suture between the os planum of 
the ethmoid and the orbital plate of the frontal ; 
in this suture are two small holes, the anterior 
i and posterior internal orbital holes ; the ante- 
b ior transmits the nasal branch of the ophthal- 
mic nerve, and the anterior ethmoidal artery ; 
the posterior gives passage to the posterior 
hmoidal artery; in front of the last-mentioned 
Suture is another between the lachrymal and 
frontal bones. 
The inferior and external angle, formed by 
the meeting of the inferior and external walls, 
esents posteriorly the spheno-maxillary fis- 
Sure, which is bounded externally by the orbital 
late of the sphenoid, internally by the orbital 
plates of the superior maxillary and palate 
bones, and in front usually by the orbital pro- 
cess of the malar bone, but occasionally by the 
Junction of the orbital plates of the superior 
maxillary and sphenoid bones at this point. 
The inferior and internal angle formed by 


4 


783 


the meeting of the inferior and internal walls 
presents a continuous horizontal suture, which 
in front connects the maxillary bone with the 
lachrymal, behind this the maxillary with the 
ethmoid, and still more posteriorly the palate 
bone with the ethmoid. 

The base or circumference is of an irregular 
quadrilateral form with curved sides and 
rounded angles; it inclines obliquely from 
within outwards. It is formed above by the 
supra-orbital arch of the frontal bone, on the 
outer side by the external angular process of 
the frontal and by part of the orbital border of 
the malar; below by the continuation of the 
orbital border of the malar, and by the corres- 
ponding orbital border of the superior maxillary 
bone; on the inner side it is completed by the 
nasal process of the superior maxillary, and the 
internal angular process of the frontal bone. At 
the junction of the middle with the inner third 
of the supra-orbital arch is the supra-orbital 
notch or foramen, which transmits the frontal 
nerve and vessels. There are three sutures in 
the margin of the orbit, one between the fron- 
tal and malar, a second between the frontal 
and superior maxillary, and a third between 
the malar and superior maxillary bones. At 
the junction of the lower with the inner border 
of the orbit is a small tubercle, the lachrymal 
tubercle, which is sometimes pointed out as a 
guide in the operation for fistula lachrymalis, 
but it is seldom very prominent even in the 
bare bone, and it could scarcely be detected 
through the tumefaction consequent on ob- 
struction of the lachrymal duct. The lachry- 
mal groove is immediately behind the internal 
margin of the orbit. 

In the apex of the orbit is the optic foramen 
situated between the two roots of the lesser 
wing of the sphenoid bone; the direction of 
the optic hole is backwards and inwards to- 
wards the centre of the sella Turcica. The in- 
ferior root of the lesser wing of the sphenoid, 
which separates the optic hole from the sphe- 


_noidal fissure, presents anteriorly a small tuber- 


cle which gives origin to the common tendon 
of the inteynal, external, and inferior recti 
muscles. 4 : 

Dissection of the orbit—Having removed 
the skull-cap and brain, the roof of the orbit 
may be taken away by two vertical cuts with 
a saw, the inner cut extending from a point 
just external to the internal angular process, 
backwards along the roof to the optic foramen, 
the outer cut extending from a point just in- 
ternal to the external angular process, also back- 
wards to the optic foramen. In making these 
cuts care must be taken to avoid injuring in 
front on the inner side the pulley and tendon 
of the superior oblique muscle, on the outer 
side the lachrymal gland with its vessels and 
nerves, and posteriorly the optic nerve and 
ophthalmic artery passing through the optic 
hole. Having removed the bony part of the 
roof the periosteum is exposed, and must be 
examined before proceeding farther. 

The periosteum of the orbit appears to be a 
continuation of the dura mater; it passes in 
through the optic hole, and through the sphe- 


784 


noidal fissure. Entering the optic hole it 
divides into two portions, one forming a tu- 
bular sheath for the optic nerve, and becoming 
continuous with the sclerotica, the other form- 
ing the proper periosteum. Where it enters 
the sphenoidal fissure it also forms a sheath for 
the vessels and nerves which pass through that 
opening. At the anterior margin of the orbit 
this fibrous membrane divides into two por- 
_ tions, one becoming continuous with the pal- 
pebral ligament or fascia, the other with the 
periosteum of the forehead. 

The periosteum may now be removed, and 
the following parts are seen immediately be- 
neath it: in the middle line the frontal branch 
_ of the ophthalmic division of the fifth nerve, 
on the outer side the lachrymal branch of the 
same nerve, and on the inner side is the fourth 
nerve. Immediately under the fourth nerve is 
the superior oblique muscle; beneath the fron- 
tal nerve are the levator palpebre and superior 
rectus, and below the lachrymal nerve is the 
external rectus muscle; beneath the external 
angular process is the lachrymal gland. Some 
branches of the ophthalmic artery are seen in 
this part of the orbit. A considerable quantity 
of soft fat exists in the orbit, filling up the 
intervals between the muscles and other parts ; 
some of this must be removed before a clear 
view can be obtained of the parts which we 
have enumerated as being visible in this stage 
of the dissection. 

The lachrymal gland is contained in a de- 
pression on the roof of the orbit, beneath the 
external angular process of the frontal bone. It 
is generally about as large as a filbert, of an 
irregular ovoid form, with its long diameter 
placed transversely. Its upper surface is con- 
vex, and connected by means of fibrous pro- 
cesses to the periosteum; its under surface is 
concave, and is in relation with the external 
rectus muscle and the eye-ball. The excretory 
ducts of this gland, from ten to twelve in num- 
ber, run parallel to each other, and open by as 
many orifices beneath the upper lid, about a 
line from the tarsal cartilage. 

The fourth nerve enters the orbit by passing 
through the inner part of the sphenoidal fissure. 
At this point it is above the other nerves, which 
pass through the same opening. It then passes 
forwards and inwards immediately under the 
periosteum, crossing over the origin of the leva- 
tor palpebre and superior rectus muscles, and 
it is distributed to the orbital surface of the 
superior oblique muscle. 

e frontal nerve,a branch of the ophthalmic 
division of the fifth, enters the orbit with the 
fourth nerve, but a little below it and on its 
outer side. It passes forwards between the 
periosteum and the levator palpebre, and soon 
divides into two branches, internal and external 
frontal, or supra-trochlear, and supra-orbital. 
The supra-orbital is the larger branch ; it passes 
out through the supra-orbital notch or foramen, 
and divides into ascending frontal branches, 
usually two in number, which are distributed to 
the skin of the forehead, and descending palpe- 
bral filaments, which are very numerous and are 
distributed in the substance of the upper eyelid. 


ORBIT. 


The supra-trochlear nerve passes out of the 

orbit between the supra-orbital notch and the © 
pulley of the superior oblique; it gives off — 
ascending frontal filaments to the skin of the ; 
forehead, and descending palpebral and nasal 

filaments to the upper eyelids and dorsum of the — 
nose, “a 

The lachrymal nerve is the smallest of the 
three divisions of the ophthalmic; it enters the 
orbit through the sphenoidal fissure external 
and inferior to the frontal nerve ; in its pa: 
through the sphenoidal fissure it is invested in 
a sheath of dura mater. It runs along the si 
perior border of the external rectus muscle, 
immediately under the periosteum; it passes 
through the lachrymal gland, sending numerous: 
filaments to it, and terminates by sending 7 
pebral filaments to the upper isd, ene of 
passes on and is distributed to the skin of the 
anterior temporal region. In its course it gives 
off a malar branch, which passes through a 
canal in the malar bone and is distributed to 
the skin on the cheek ; it also sends down c 
or two filaments which anastomose with # 
superior maxillary branch of the fifth nerve.* — 

e may now examine the three muse! 
which are placed most superficially in the uppe 
part of the orbit, and which are visible in th 
stage of the dissection, viz. the levator palpebr: 
a espe rectus, and the superior oblique. 

e levator palpebre supertoris arises té 
dinous from the inferior surface of the less 
wing of the sphenoid bone above the op 
foramen, also from the fibrous sheath of t 
optic nerve; it passes forwards, and upwar 
becoming broader and thinner towards the a 
terior part of the orbit, where it suddenly curt 
downwards and ends in a broad thin a 
neurosis, which is inserted into the upper 
der of the tarsal cartilage, behind the palpe 
ligament. This muscle is of a triangular fo 
the apex being posterior; it is crossed by 
fourth and frontal nerves, the latter passing | 
ward above and parallel to it, and separatin 
from the periosteum; it covers the 
rectus and eyeball. 

In order to expose the superior rectt 
through and turn aside the levator palpet 
doing so a small branch of the third ne 
seen to enter its inferior surface. 

The rectus superior arises from the v 
part of the fibrous sheath of the optic nerve 
from the outer and upper part of the m 
the optic foramen ; the fleshy fibres frot 
point of origin pass forwards and outwal 
the direction of the axis of the orbit; the: 
becomes broader and thinner anterior 
ends in a broad aponeurotic expansion, 
is inserted into the upper aspect of the s 
a little behind the margin of the corné 
small synovial bursa is said to exist betw 
sclerotic and the tendon at its insertion 
muscle is covered above by the leva 
pebre, and by the nerves which cross the 
palpebre ; below it is in relation with the 


* For a more minute account of the dis 
of these branches of the fifth nerve, see 
Fiera NERVE, . a 


ORBIT. 


the third, and the optic nerves, with the 
ophthalmic artery and the eye-ball. 

The vbliquus superior is a long and slender 
muscle, which is sometimes called the trochlearis 
muscle from the fact of it being reflected through 
a trochlea or pulley. It arises from the fibrous 
sheath of the optic nerve, and from the inner 
part of the optic foramen between the superior 
and internal recti muscles ; it passes forwards 
along the internal superior angle of the orbit, in 
the form of a rounded fleshy belly, to which 
succeeds a rounded tendon, which after passing 
through the pulley beneath the internal angular 
process is directed backwards, outwards, and 
downwards, passing beneath the superior rectus 


' muscle to be inserted by a thin aponeurosis into’ 


the sclerotic coat between the superior and exter- 

nal rectus, rather behind the anterior half of the 
_ globe. This pulley or trochlea, through which 
»passes the tendon of the superior oblique, is a 
_ small cartiliginous ring, inserted by means of 
fibrous tissue into a depression beneath the 
internal angular process ; it is lined by a syno- 
vial membrane. The orbital surface of the 
superior oblique is in contact with the perios- 
| teum; the fourth nerve passes into this surface 
_ about its centre; the relations of its ocular 
_ surface are the same as those of the superior 

rectus. 
_ The superior rectus and superior oblique 
| Mouscles may now be cut through and turned 
_ aside, and after removing carefully some fat 
_and cellular tissue the following parts are 
brought into view :—the internal and external 
_ recti muscles, the optic, the third, and the nasal 
_ branch of the ophthalmic nerves, the lenticular 
ganglion between the optic nerve and external 
rectus muscle, and the ophthalmic artery and 
vein. 
| The third nerve before entering the orbit 
divides into two portions; a superior smaller, 
and an inferior larger ; it enters the orbit through 
_ the sphenoidal fissure between the two heads of 
the external rectus muscle ; the inferior division 
t er om beneath the globe of the eye and 
‘must be examined in a subsequent stage of the 
‘dissection. The superior division is now visible; 
it passes to the under surface of the superior 
Tectus muscle, to which it sends numerous fila- 
‘Ments; some filaments also pass on the inner 
ide of the superior rectus and enter the deep 
‘surface of the levator palpebre superioris ; these 
are the only muscles supplied by this division 
(of the third nerve. 
i The nasal nerve is in size the second branch 
of the first division of the fifth. It enters the 
orbit through the sphenoidal fissure, passing 
between the two heads of the external rectus 
nuscle, in company with the third and sixth 
lerves, being external to the former, and be- 
yeen its two divisions, and internal and some- 
what superior to the latter. Having entered the 
Orbit, it passes forwards and inwards towards the 
hternal wall, crossing over the optic nerve 
between it and the superior rectus muscle; it 
las also above it the levator palpebr and supe- 
jior oblique muscles, and the superior division 
bf the third nerve; it passes out of the orbit 
jhrough the anterior internal orbital hole in 
} VoL. 111. 


785 


company with the anterior ethmoidal artery. 
Within the orbit it sends off lenticular, ciliary, 
and infra-trochlear branches. The lenticular 
branch is given off on the outer side of the optic 
nerve ; it anastomoses with the superior division 
of the third nerve, and joins the posterior supe- 
rior angle of the lenticular ganglion. The 
ciliary branches are two or three in number ; 
given off above the optic nerve, they pass for- 
wards and pierce the posters part of the 
sclerotic. The infra-trochlear branch is given 
off near the inner wall of the orbit ; it passes out 
beneath the pulley of the superior oblique 
muscle, and sends branches to the superior eye- 
lid, the lachrymal sac, and integuments of the 
nose; within the orbit there is an anastomosis be- 
tween thisand thesupra-trochlearor frontal nerve. 

The denticuldr or ciliary ganglion is situated 
in the posterior and outer part of the orbit 
between the optic nerve and the external rectus 
muscle; it is very small, and of a somewhat 
square form. Its superior posterior angle is 
joined by.the lenticular branch of the nasal nerve, 
which constitutes the long root of the ganglion ; 
its inferior posterior angle receives a branch 
from the inferior division of the third nerve ; this 
forms the short root of the ganglion. To its 
posterior part is also connected one filament 
from the cavernous plexus, and occasionally 
one from, the spheno-palatine ganglion. From 
the anterior part of the ganglion a number of 
delicate ciliary nerves pass off; they are divided 
into two sets, one set coming from the superior 
anterior, and the other from the inferior anterior 
angle of the ganglion ; the former are the more 
numerous; in all they are from twelve to sixteen 
in number; they pass forwards and pierce the 
sclerotic near the optic nerve. 

The optic nerve passes forwards from the 
optic hole to the inner and back part of the 
eyeball, which it enters to terniinate in the re- 
tina. It is invested by a sheath of fibrous 
membrane, which is continuous behind with the 
dura mater, and in front with the sclerotic ; the 
outer surface of this sheath posteriorly gives 
attachment to the recti muscles, which surround 
the optic nerve ast emerges from the optic 
hole. The optic nerve is crossed above by the’ 
nasal nerve and the ophthalmic artery, below by 
the branch of the inferior division of the third 
nerve, which supplies the internal rectus muscle ; 
it is surrounded by numerous delicate ciliary 
nerves aud arteries. 

The ophthalmic artery passes through the 
optic hole in company with the optic nerve, 
and inclosed in a sheath derived from the dura 
mater. It is very tortuous and twines round 
the optic ‘nerve, being at first inferior to the 
nerve, then passing to its outer side, and soon 
crossing over it to reach its inner side; it then 
passes across to the inner wall of the orbit, 
where it breaks up into its terminal branches. 
The branches of the ophthalmic artery are very 
numerous ; they may be arranged in three sets ; 
the first set arises from the artery as it lies ex- 
ternal to the optic nerve; it consists of the 
lachrymal and the centralis retine ; the second 
set comes off from the artery, when it 1s above 
the optic nerve; this consists of the supra- 

3 E 


786 


orbital, ciliary and muscular; the third is given 
off when the artery has passed over to the nasal 
side of the orbit, and consists of the ethmoidal, 
palpebral, nasal, and frontal arteries. 

e lachrymal artery is one of the largest 
branches of the ophthalmic ; it arises from the 
ophthalmic either within the optic hole or imme- 
diately after that artery has entered the orbit. 
It sometimes arises from the middle meningeal 
artery, and enters the orbit through the sphe- 
noidal foramen. It passes forwards along the 
outer wall of the orbit between the periosteum 
and the external rectus muscle; it enters the 
lachrymal gland, sending numerous branches to 
it; it then emerges from the gland and supplies 
the conjunctiva and the upper eyelid. It gives 
a malar branch which passes through the malar 
bone and anastomoses in the substance of the 
temporal muscle with the anterior deep tem- 
poral artery. The lachrymal artery generally 
anastomoses with the middle meningeal by a 
branch sent in through the sphenoidal fissure. 

The central artery of the retina is a small 
branch which enters obliquely the optic nerve ; 
it passes forwards in the centre of the nerve, 
enters the globe of the eye, and expands out 
into a vascular membrane on the inner surface 
of the retina. One small branch passes through 
the vitreous humour and reaches the posterior 
surface of the capsule of the lens. 

The supra-orbital artery arises from the oph- 
thalmic while it is above the optic nerve ; it is 
one of the largest branches of the artery: it 
passes forwards close under the periosteum of 
the roof, and above the levator palpebre, in 
company with the frontal nerve. It escapes 
from the orbit at the supra-orbital notch, and 
sends branches on the forehead, some between 
the skin and muscles, and others between the 
occipito-frontalis and the periosteum. In the 
orbit it supplies the levator palpebra and supe- 
rior rectus muscles, and sends some branches 
to the upper lid. 

The ciliary arteries are very numerous, and 
are divided into three sets—anterior, middle, 
and posterior. The anterior ciliary arteries are 
irregular in number and origin; they usually 
come off from the muscular branches at the 
anterior part of the orbit; they perforate the 
sclerotic about one or two lines behind the 
cornea: some branches go to the iris and anas- 
tomose with the long ciliary arteries; others go 
to the choroid and anastomose with the short 
ciliary. The middle or long ciliary arteries are 
two in number; they accompany the nerves of 
the same name. They pierce the sclerotic at 
some distance from the optic nerve, and pass 
horizontally one on each side between the scle- 
rotic and the choroid. They pass through-the 
ciliary ligament and supply the iris. The pos- 
terior or short ciliary arteries are remarkably 
delicate and tortuous ; they are accompanied by 
the ciliary nerves from the lenticular ganglion. 
Their origin is somewhat irregular; most of 
them arise from the ophthalmic artery, but oc- 
casionally some from the supra-orbital or from 
some muscular branches. There are as many as 
fifteen or twenty of these arteries, which sur- 
round the optic nerve in a spiral and tortuous 


ORBIT. 


manner; they pierce the sclerotic about two 
lines anterior to the oe of optic nerve, 
and supply the choroid and ciliary processes. 
(For ibe inode of arrangement of these ciliary 
per in the choroid and iris see the article 
LYE.) uy 
The muscular branches are uncertain in num- — 
ber and origin; they usually consist of two — 
sets, a superior and an inferior. The superior — 
set often come from the frontal artery, and 
supply the levator palpebre, the superior 
oblique and the superior rectus muscles. The 
inferior muscular artery is a regular branch 
from the ophthalmic ; it descends on the inner 
side of the optic nerve ; it first sends a t 
to the external rectus and then suppli 
inferior and internal recti, and n 
oblique; some branches pass on to the 
eyelid and the lachrymal sac. These arterie 
are usually distributed to the ocular surface o 
the muscles. 7. 
The ethmoidal arteries, two in number, 
given off from the ophthalmic near the inne’ 
— of the orbit. The posterior is usually 
arger; it passes through the ae 
foramen dick nests the skull, where it sends 0 
some anterior meningeal branches, then passe 
down through the cribriform plate of the ¢ 
moid bone, and is distributed on the muce 
membrane of the nose. The anterior ethmoid: 
passes through the anterior internal orbital f 
men with the nasal nerve; it has the sai 
distribution as the posterior braiich. . 
The palpebral arteries, two in number, 
near the inner angle of the orbit. The superi 
arises above the tendon of the orbicularis palp 
brarum ; it passes outwards and supplies 
upper lid, one branch running near tt 
margin of the lid, while the others are di 
buted to the muscles and integuments of | 
middle and upper part of the lid, where 
anastomose with the sap ae a 
inferior palpebral artery own beh 
the reckon nf the obicaarial then runs 0 
wards along the lower lid, forming an 4@ 
near the free margin of the lid, and is grada@ 
lost near the external canthus. It anastom 
with the angular branch of the facial, wit 
infra-orbital branch of the internal maxil 
with the transverse facial and temporal art 
Beneath the internal angular process the 
thalmic artery terminates by dividing inte 
nasal and the frontal branches. . 
The nasal artery emerges from . 
above the tendon of the orbicularis; it at 
moses freely with the angular artery, 
branches to the lachrymal sac, and tert 
in a branch which passes down the de 
the nose, and communicates at the € 
of the nose with the corresponding ai 
the opposite side. mi 
The frontal artery passes out of th 
with the nasal, then turns upwards, and 
tributed to the muscles and integument 
forehead, anastomosing with the supra: 
and with the arteries of the opposite side 
The ophthalmic vein commences at the 
angle of the orbit, where it communic 
with the angular and frontal veins; it 


Dab > 


-e 2 


Oro 


— 


ORBIT. 


backwards in the same direction as the artery, 
but it is much less tortuous. It receives 
branches corresponding to those which the 
artery gives off, and passing between the two 
heads of the external rectus muscle below the 
nerves, it terminates in the anterior extremity 
of the cavernous sinus. 

The ophthalmic artery and vein may now be 
removed; cut through the optic and ciliary 
nerves and remove some fat and cellular tissue 
which obscures the remaining muscles and 
nerves ; we now obtaina more clear view of the 
internal and external recti muscles, and at the 
same time we expose the sixth nerve and the 
inferior division of the third, as well as the 
inferior rectus and the inferior oblique muscles. 
_ The siath nerve passes between the two 
heads of the external rectus muscle below the 

_ third nerve, and above the ophthalmic vein, 
_ from which it is separated by a process of dura 
mater. Having entered the orbit it passes along 
the inner surface of the external rectus muscle, 
_ to which it is distributed by numerous delicate 
- filaments. 
_ The inferior division of the third nerve 
enters the orbit, as we have seen, between the 
_ two heads of the rectus muscle, where it lies a 
little above the sixth nerve ; having entered the 
‘orbit it passes down towards the floor between 
the optic and the sixth nerves, and below the 
level of the latter. It almost immediately di- 
vides into three branches: an internal, which 
passes inwards beneath the optic nerve towards 
the internal rectus muscle, to the ocular surface 
‘of which it is distributed ; a middle branch, 
which is distributed in the same manner to the 
ocular surface of the inferior rectus; and an 
vternal, which passes forwards along the ex- 
ternal border of the inferior rectus, and enters 
the posterior border of the inferior oblique, 
almost at right angles. The short filament 
hich joins the posterior inferior angle of the 
enticular ganglion, forming the short root of 
‘the ganglion, is usually given off from the 
branch which goes to the inferior oblique 
_ muscle. ; 
The external rectus muscle has two origins, 
2 from a tendon, the tendon or ligament of 
inn, which is common to this muscle with 
he inferior and internal recti, and which is 
‘attached to a little tubercle behind the optic 
‘foramen; the other origin of the external rectus 
ts above, from the inner margin of the sphe- 
noidal fissure ; this origin is united with the 
origin of the superior rectus. Between these 
‘two origins pass the third, the sixth, and the 
asal branch of the fifth nerves, with the oph- 
‘thalmic vem. From its origin the external 
us passes forwards along the external wall 
the orbit; it turns over the globe of the eye, 
d is inserted by a thin tendinous expan- 
ion just behind the margin of the cornea. A 
small bursa intervenes between the tendon and 
the sclerotic, as is the case with the tendons of 
| the recti muscles. 
_ The internal rectus arises from the common 
lendon or ligament of Zinn, and from the 
ibrous sheath of the optic nerve; it passes 
iorwards along the internal wall of the orbit, 


787 


turns over the globe\of the eye, and is inserted 
immediately oppositethe external rectus, in 
the same manner as the other recti muscles. 

* The inferior rectus muscle arises from the 
common tendon, between the internal and ex- 
ternal recti; it passes forwards under the globe 
of the eye and is inserted into the sclerotic in 
the same manner as the preceding muscles, 
and immediately opposite the superior rectus. 
The recti muscles have all the same form, viz. 
that of a long isosceles triangle, having the base 
directed forwards, and the apex backwards. 
They differ in length and thickness; the in- 
ternal rectus being the shortest and thickest, 
the external rectus the longest, and the superior 
rectus the smallest.* 

The inferior oblique muscle is the only one 
which does not arise from the apex of the orbit. 
It arises from the orbital plate of the superior 
maxillary bone, just within the margin of the 
orbit, and near the groove for the lachrymal sac. 
From its origin it passes obliquely outwards, 
upwards, and backwards beneath the globe of 
the eye and the inferior rectus, thén between 
the former and the external rectus; it ends in 
an aponeurotic expansion which is inserted 
into the sclerotic between the superior and ex- 
ternal recti, opposite the insertion of the su- 
perior oblique, and rather nearer the optic 
nerve than the insertion of that muscle. The 
superior surface of this muscle is in contact 
with the inferior rectus and the globe of the 
eye; the inferior touches the floor of the orbit 
and the external rectus muscle; its borders are 
anterior and posterior ; a branch of the third 
nerve enters the posterior border. ' 

The orbital portion of the superior maxillary 
nerve may now be exposed by cutting through 
the external rectus muscle, and drawing the 
eye with its muscles towards the inner part of 
the orbit. The nerve having crossed the spheno- 
maxillary fossa enters the orbit through the 
spheno-maxillary fissure; in company with a 
branch of the internal maxillary artery it passes 
along the jnfra-orbital groove, covered by a 
layer of periosteums it then passes through the 
canal and emerges from the infra-orbital fora~ 
men. The trunk of the nerve is but little vi- 
sible on the floor of the orbit. While the supe- 
rior maxillary nerve is in the foramen rotun- 
dum, or during its passage across the fossa, it 
sends off a temporo-malar branch which passes 
through the spheno-maxillary fissure superior 
and external to the trunk of the nerve; it passes 
along the floor of the orbit, beneath the inferior 
rectus muscle, and about the middle divides 
into two branches, a temporal and a malar. 

The temporal branch goes towards the outer 
wall of the orbit, passes up between the bone 
and the external rectus muscle, and joins with 
a temporal branch from the lachrymal ; it then 
pierces the orbital process of the malar bone 
and enters the temporal fossa, where it com- 
municates with the anterior deep temporal 
nerve, sends branches to the temporal muscle, 
and piercing the fascia is distributed to the 
skin over the temporal region. 

* Cruveilhier. Descriptive Anatomy, 
3 E2 


‘ 


788 


The malar branch passes on to the inferior 
external angle of the orbit, where it sometimes 
communicates with the lachrymal nerve; it 
enters one or more canals in the malar bone, 
and appears on the facial surface, supplying 
the orbicularis and the integuments, and com- 
municating with the portio dura. 

In addition to the structures ordinarily 
described as existing within the orbit, Mr. 
O’Ferrall has described * a fibrous structure, to 
which he gives the name of “ tunica vaginalis,” - 
and which invests the globe of the eye, one 
rating it from the muscles and fat of the orbit. 
In order to expose the outer surface of this 
Structure, a vertical incision must be made 
through the integument of the upper lid; after 
removing carefully the orbicularis and a fascia, 
between the two layers of which the tendon of 
the levator palpebre is inserted, the part 
next in order is the tarsal cartilage. Tracing 
this upwards and backwards its thin’margin is 
found to be continuous with a fibrous lamina, 
which passes back into the orbit and separates 
the globe of the eye from the superior rectus 
muscle, but presenting a well-defined opening, 
through which the tendon of the muscle passes 
as overa pulley, to be inserted into the scle- 
rotic coat. In order to examine the ocular sur- 
face of this membrane, Mr. O’Ferrall advises 
a vertical division of both palpebra, then an 
incision through the conjunctiva at the angle 
of reflection from the eyelid to the ball of the 
eye. ' 

The incision being made and the edges of 
the divided membrane separated, we expose 
the ocular surface of “a distinct tunic of a 
yellowish white colour and fibrous consistence, 
continuous in front with the posterior margin 
ofthe tarsal cartilage, and extending back- 
wards to the bottom or a ta of the orbit, where 
its consistence becomes less strongly marked.” 
This ocular surface is smooth where the eye 
glides over it in its movements, and is con- 
nected to the surface of the globe by fine cel- 
lular tissue. The muscular substance of the 
recti muscles is on the outside of this tunic 
and invisible through it; but about half an 
inch posterior to its anterior margin are six 
well-defined openings through which the ten- 
dons of the muscles emerge in passing to their 
insertion in the sclerotic coat. Mr. O’Fer- 
rall was induced to look for this structure in 
consequence of meeting with cases in which 
the globe of the eye and the conjunctiva were 
protruded in a manner not satisfactorily ex- 
plained by reference to any previously described 
structure. He believes these to have been cases 
of inflammation of this tunic, with effusion 

. between its deep surface and the globe of the 
eye. 

Mr. O’Ferrall believes that “the uses of 
this tunic are to present a smooth surface, faci- 
litating the movements of the eye; and by its 
density and tension, to protect it from the pres- 
sure incidental to the swelling of its muscles 
during their action. That the openings in this 


* Dublin Journal of Medical Science, July, 


ORBIT. 


tunic perform the office of pulleys, giving a 
proper direction to the fores exerted by the 
muscles,—securing the motions of rotation, and 
opposing those of retraction, which would other- 
wise predominate.” 
Action of the muscles.—The action of the 
levator palpebre muscle is to raise the 1 
lid, and thus to ex the anterior part of the 
eye-ball. In this action it is an associate of the 
frontal portion of the occipito-frontalis, and an— 
antagonist of the orbicularis palpebrarum. 
C. Bell* affirmed that the action of the levator 
palpebee is not simply that of raising the upper 
id, but that the swelling and tension of th * 
muscle during its pene the be 
ushing forwards the eye- us ing the 
Ga lid to slide off the convex oan + 
eye, and to be depressed whilst the upper lid 
is elevated. There is no proof of any such 
action of the levator palpebre, and it seems 
improbable that it should exert any such in- 
fluence, separated as it is from the 
the superior rectus, by a considerable quantity 
of fat and by the “ tunica vaginalis.” The re- 
sult of paralysis of this muscle is a dropping of 
the upper lid, to which the term ptosis is applied. 
It is evident from an examination of the 
origin, course, and insertion of the recti museles 
that each of them acting singly is capable of 
making the eye-ball revolve in its own direc 
tion; the superior rectus directs the cor 
upwards; the inferior rectus antagonises t 
superior and directs the cornea down 
the external rectus directs it outwards and i 
antagonised by the internal, which draws th 
cornea inwards towards the nose. It is 
evident that the action of any two contigu 
recti muscles will give the cornea a di 
intermediate between that which it would a 
sume from the action of each of them singly 
the superior and internal recti acting toget 
will direct ‘the cornea upwards and inwar 
while the inferior and external will direct 
downwards and outwards ; so that the con 
may be made to assume any intermediate 
tion by the action of the recti muscles alone. 
The successive action of all the recti mi 
cles would produce a movement of the ¢ 
ball analogous to circumduction of a li 
and as the circumduction of a limb is a m 
ment altogether distinct from rotation, st 
this circeumduction of the eye-ball entirely 
tinct from any rotation upon its antero-post 
axis. In cireumduction the centre of 
cornea describes a circle, whereas in ro 
this point remains fixed, forming the a 
extremity of an imaginary axis, round 1 
the circumference of the cornea revolve! 
is of much importance to have a di 
notion of each of these movements, as wi 
thus avoid one source of confusion in 
sidering the action of the straight and ¢ 
muscles of the eye. Having thus ¢ 
rotation, no argument is necessary to pro 
the recti muscles are incapable of pros 


such a movement; a glance at their dire 


2 


recih 


4 
* The Nervous System of the Human Bos 
Sir C, Bell. a 


ORBIT. 


and their position with regard to the eye-ball 
will at once deterinine this point. If then any 
such movement occurs, other muscles must be 
provided in order to effect it. 
We now proceed to consider the action of 
the oblique muscles. 
It may be well to remind the reader that, in 
all the vertebrate animals, these muscles have 
essentially the same direction and relations ; 
the only difference being that in fishes, rep- 
tiles, and birds, the superior oblique arises 
from the anterior part of the orbit, whence it 
passes backwards and outwards to its insertion ; 
whereas, in Mammalia, it comes from the pos- 
terior part of the orbit and passes through a 
tendinous pulley before taking its course back- 
_ wards and outwards ; the action of the muscle 
will obviously be the same in both cases. One 
function which has been assigned to the oblique 
muscles, is that of antagonising the recti so as 
to prevent the retraction of the eye-ball within 
_ the orbit during the action of the latter mus- 
cles. To this conclusion Sir C. Bell asserts 
there are many objections: two of these ob- 
jections we subjoin in his own words. “4. 
In creatures where the eye is socketed in a 
cup of cartilage and cannot retract, the oblique 
muscles are nevertheless present. 2. Where a 
‘powerful retractor muscle is bestowed in ad- 
dition to the recti muscles to pull the eye-ball 
back, the oblique muscles have no additional 
Magnitude given to them to pull the eye-ball 
forwards.” Now we must not suppose that the 
gonism exerted by the oblique muscles is 
“such as to oppose the conjoint forcible action, 
| or active contraction, of all the recti muscles, 
d of a retractor when such a muscle exists. 
| If such were the case, we should certainly find 
‘the developement of the oblique muscles in 
Some degree proportioned to that of the mus- 
‘tles they were intended to antagonise, and a 
cup of cartilage at the back of the eye-ball 
Would apparently supersede the necessity for 
‘ny antagonism on the part of the oblique 


' 
" 
; 


e oblique muscles probably exert upon the 
fecti is equally necessary whether the eye-ball 
be encased in cartilage or supplied with a re- 
tractor muscle. It is simply the same kind 
antagonism which the muscles on the op- 
Osite sides of the face exert upon each other. 
paralysis of the pertio dura on one side is 
uttended with a traction of the features to the 
Opposite side; this results from the ordinary 
lonicity or passive contraction of the muscles 
m the one side, unopposed by the correspond- 
§ force on the other; the distortion is gene- 
‘ally conspicuous enough when the muscles are 

test, but when they are thrown into active 
Ontraction it becomes still more marked, 
md the movements of the sound side are un- 
teady and oscillating. During the healthy 
ate then the symmetry of the features is 
naintained by this antagonism of the muscles 
nh opposite sides of the face. In like manner 
hen the muscles are at rest, the eye-ball is 
ept delicately balanced between its six mus- 
es; the superior rectus opposes the inferior, 
d the external opposes the internal, while 


muscles; but the kind of antagonism which 


789 


the obliqui are opposed to each other, and 
the recti conjointly are_antagonised in their 
retracting tendency by the opposite force of the 
obliqui. This is the condition during a state 
of rest, when the contraction of all the mus- 
cles is merely that of their ordinary tonicity or 
passive contraction. Now, suppose one straight 
muscle to be thrown into a state of voluntary 
"active contraction; immediately the cornea is 
directed towards that muscle, the antagonism 
of the other five muscles serving the important 
purpose of preventing any irregular oscillatory , 
movement of the eye-ball; when the contrac- 
tion of that muscle ceases, the eye is at once 
restored to its original position. One of the 
uses of the oblique muscles then is by their 
antagonism of the recti to assist in preventing 
any unsteady motion of the eye-ball. This, 
however, is by no means the only or the chief 
use of the oblique muscles, and the question 
arises, what movements of the eye-hall are 
effected by the contraction of these muscles? 
Upon this subject the most contradictory state- 
ments have been made; on the one hand 
Scemmering, Cloquet, and Harrison assert, that 
the superior oblique directs the pupil down- 
wards and inwards, the inferior oblique moves 
it upwards and outwards; on the other hand, 
according to Miiller, Monro, and Sir C. Bell, 
the superior oblique directs the pupil down- 
wards and outwards, the inferior oblique up- 
wards and inwards. All these anatomists 
agree in supposing that the oblique muscles 
effect what we have called circumduction of 
the eye-ball, but their disagreement as to the 
direction in which circumduction occurs under 
the influence of these muscles, is of itself an 
argument against the probability of any such 
movement being produced by them. We have 
before stated that the recti muscles are of them- _ 
selves capable of circumducting the eye in all 
directions; this was admitted and proved ex- 
perimentally by Sir C. Bell. He “ cut across 
the tendon of the superior oblique muscle of 
the right eye!of a monkey. He was very little 
disturbed by this experiment, and turned 
round his eyes with his characteristic inquiring - 
looks, as if nothing had happened to affect the 
eye.” In another experiment he “ divided the 
lower oblique muscle of the eye of a monkey. 
The eye was not, in any sensible manner, af- 
fected; the voluntary motions were perfect 
after the operation.” The result of these ex- 
periments appeared to Sir C. Bell to confirm 
the opinion which he entertained that the 
oblique muscles perform certain involuntary 
movements, such as the forcible elevation of 
the cornea under the upper lid when the eye 
is irritated, and the rolling of the cornea under 
the lid when tne eye is closed. He appears 
anxious to prove that the fourth nerve presides 
over the upward movement of the eye-ball 
which he says occurs during sneezing and 
certain other respiratory movements ; but as he 
has previously stated that the superior oblique 
to which the fourth nerve is distributed turns 
the eye downwards and outwards, in order to 
reconcile the two views he says, “ if we sup- 
pose that the influence of the fourth nerve is, 


790 


on certain occasions, to cause a relaxation of the 
muscle to which it goes, the eye-bal! must be 
then rolled upwards.” * 

Sir C. Bell adduces no proof that the involun- 
. tary movements which he mentions are performed 
by the oblique muscles; on the contrary they 
may all be effected by the straight muscles. The 
fact that these movements are involuntary is 
no argument against their being produced by 
muscles, which under ordinary circumstances 
are strictly voluntary. Thus, Sir C. Bell says, 
when the eye is exposed and irritated, the 
cornea is directed upwards to a greater extent 
than can be done by a voluntary effort. This 
probably is the case, but we need not have 
recourse to the oblique muscles in order to 
explain it. Under the influence of the irri- 
tation applied to the eye the superior rectus 
contracts violently in order to elevate the cornea 
beneath the upper lid, and thus to remove it 
from danger; precisely in the same manner 
under the irritating influence of strumous 
ophthalmia the orbicularis muscle contracts 
with a spasmodic force much exceeding that 
of any voluntary contraction of that muscle. 
Both oblique muscles have the striated struc- 
ture of voluntary muscles, and the inferior 
oblique receives a branch from the third nerve, 
all the other muscles supplied by which are 
known to be voluntary in their action. We 
may, therefore, dismiss the idea that the ob- 
lique muscles are specially concerned in pro- 
ducing the involuntary movements of the eye. 

Further, it is our firm conviction that the 
oblique muscles are in no way concerned in 
circumduction of the eye-ball; that they nei- 
ther abduct nor adduct, neither raise nor depress 
the cornea, nor do they produce any of the in- 
termediate movements. The following are the 
circumstances which appear to us to favour 
this conviction. 1st. Both oblique, muscles 
pass outwards almost at right angles with the 
recti muscles, and are inserted close upon a 
line intermediate hetween the anterior and pos- 
terior half of the eye-ball: this direction and 
insertion are evidently most unfavourable for 
the production of any of the above-mentioned 
movements. 2d. Those who assert that the 
oblique muscles have the power of circum- 
ducting the eye make the most contradictory 
statements as to the direction which the eye 
assumes under their influence. These opposite 
statements are sufficiently accounted for when 
we consider that they are founded on the re- 
sults of traction on the oblique muscles after 
death, when the fat and other parts in the orbit 
have become firm and unyielding, and. the 
steadying influence arising from the antagonism 
of the other muscles has ceased. 3d. The 
recti muscles are of themselves capable of cir- 
cumducting the cornea in all directions; this 
is evident from their direction and insertion, 
and was proved by Sir C. Bell’s experiments 


* See Sir C. Bell on the Nervous System, p. 177. 
This dia t yen apron to us as unphilosophical 
as the old theory of Phlogiston, which, in order to 
explain the fact of a body becoming heavier when 
deprived of this imaginary agent, attributed to 
phlogiston a property of lightness. f 


ORBIT. 


above-mentioned. 4th. There is an important — 
movement of the eye-ball which can be effected 
by no other than the oblique muscles, and for 
the production of which in all probability these 
muscles are provided: the movement to which 
we refer is rotation of the eye upon its antero- 
posterior axis. “ra ! 
The true use of these muscles we believe — 
to have been pointed out by John Hunter 
in a paper on the use of the — ~muscles, 
in his “ Observations on certain Parts of the — 
Animal Economy.” He first explains that fo 
perfect vision it is essential that when we are 
examining an object, any motion of the object” 
or of our own bodies should be so counter- 
acted by the movements of the eye-ba ‘that 
the image of the object may be kept on the 
same point of the retina, and not be od 
to move over its surface. We have a fami 
illustration of this when we keep our eyes 
motionless and fixed on the ground, while 
moving rapidly in a carriage; the surface of 
the road appears confused and the stones ar- 
ranged in lines, as their images pass rapidly 
over the retina: it is only when we allow the 
eye to follow these objects that we have a dis 
tinct perception of any of them. Hunter then 
goes on to explain the use of the obliqu 
muscles. “ To prevent any progressive motio 
of the object over the retina of the eye, eithe 
from the motion of the object itself, or of th 
head in some motions of that part, the straigh 
muscles are provided, as has been explai 
but the effects which would arise from 
other motion of the head, as from shoulder 
shoulder,* cannot be corrected by the acti 
of the straight muscles, therefore the oblic 
muscles ate provided. Thus, when we k 
at an object and at the same time move: 
head to either shoulder, it is moving in 
arch of acircle whose centre is the neck, 
of course, the eyes would have the same q 
tity of motion on this axis if the oblique 1 
cles did not fix them upon the object. W 
the head is moved towards the right shoul 
the superior oblique muscle of the right 
acts, and keeps the right eye fixed on 
object, and a similar effect is produced 
the left eye by the action of its inferior a 
muscle. When the head moves in a com 
direction, the other oblique muscles fp 
the same effect.” a 
If we again consider the direction and i 
tion of the oblique muscles, it is evider 
they are intended for the office which E 
has assigned them. Passing ou s 
above, the other below, in a direction aln 
right angles with the antero-posterior 
the eye-ball to their insertion near its 
their action must obviously be to ro 
eye upon that axis. The reason of th 
quity probably is that their direction bat 
as well as outwards, by enabling ther 
gonise the straight muscles, more cer 


* 


ca 


no 


* The motion here meant is that whic 
fected by flexion of the neck laterally, so @ 
proximate the ear to the shoulder, not 
ment which takes place between the 
cond cervical vertebra. 


cures the delicate suspension of the eye-ball 
when the muscles are at rest, and a steady 
movement of it when any of them are thrown 
into action. We have the following experi- 
mental evidence to offer in support of the state- 
ment which Hunter has made. A dog was 
_ killed by the injection of air into a vein, and 
_ immediately the inferior oblique muscle was 
_ exposed by dissecting off the conjunctiva, with- 
Out in any way interfering with the surrounding 
parts; by means of two fine wires a slight 
electric current was then directed through the 
muscle. The effect was a rapid rotation of the 
eye upon its antero-posterior axis, so that a 
piece of paper placed at the outer margin of 
the cornea passed downwards and then inwards 
towards the nose. The superior oblique was 
then exposed at the back of the orbit, and was 
treated in the same manner. The rotatory 
movement produced was precisely the reverse 
of the former; the paper at the outer margin 
of the cornea passed upwards, and then in- 
wards towards the nose. In the case of the 
superior oblique the movement was less exten- 
_Sive, the irritability of the muscle being less, 
perhaps from the delay in exposing it, and from 
some slight injury inflicted on it in so doing. 
There could be no doubt as to the direction of 
the movement in both cases; there was not the 
slightest appearance of elevation, depression, 
abduction, or adduction of the cornea. This 
| experiment was witnessed by Dr. Todd and 
Mr. Bowman. The experiment was subse- 
_ quently repeated on another dog with precisely 
the same result. The superior oblique in the 
_ Second experiment did not contract so vigo- 
rously as the inferior, but the movement it pro- 
duced was the same as in the first experiment ; 
and when gentle traction was made in the pos- 
terior part of the muscle, the rotation of the eye 
_ was very decided, and in a direction the reverse 
of that in which it rotated under the influence 
_ of the inferior oblique; again there was not the 
_ slightest movement of circumduction. There 
can be no doubt that the function of these 
_ muscles is the same in all animals in which 
they exist; and any experiments to determine 
‘their use must be more satisfactory when per- 
formed on animals immediately after death 
‘than in the human subject at a considerable 
period after death, when the fat and muscles 
have become equally firm and _ unyielding. 
Under such circumstances it is evident that the 
results of traction upon the muscles cannot be 
relied upon as accurate. It is remarkable that 
this rotation of the eye should have excited so 
little attention; since, if we only recognise the 
_€xistence of such a movement, the use and 
“hecessity of the oblique muscles must be ac- 
d nowledged, it being evident, as we have pre- 
iously stated, that the straight muscles are 
‘Incapable of effecting it. 
__ Consensual movements of the two eyes.— 
‘Upon this subject we subjoin the following 
extract from Miiller: *#—‘ There is an innate 
tendency and irresistible impulse in the cor- 
‘tesponding branches of the third nerve to asso- 
A 


: 
J 
t 


* Physiology, by Dr. Baly, p. 99. } 


ORBIT. 


791 


ciate action; while\in the sixth nerve, not only 
is this tendency absent, but the strong action 
of one of these nerves is incompatible with 
the action of the other. These innate ten- 
dencies in the third and sixth nerves are ex- 
tremely important for the function of vision, °- 
for if, in place of the sixth nerves, the external 
recti muscles had received each a branch of the 
third nerve, it would have been impossible to 
make one of these muscles act without the 
other; one eye, for example, could not have 
been directed inwards while the other was di- 
rected outwards, so as to preserve the paral- 
lelism or convergence of their axes, but they 
would necessarily have diverged when one 
rectus externus had been made to act volunta- 
rily. To render possible the motion of one 
eye inwards while the other is directed out- 
wards, the external straight muscles have re- 
ceived nerves which have no tendency to con~ 
sensual action. In consequence, however, of 
the tendency in the two internal straight mus- 
cles to associate action, it is necessary, where 
one eye is directed inwards and the other out- 
wards, that the contraction of the rectus ex- 
ternus of the latter should be so strong as to 
overcome the associate action of the rectus inter- 
nus of the same eye; and in the effort to direct 
one eye completely outwards we actually feel 
this stronger contraction of the external rectus.” 

It is certainly contrary to our general notions 
of the skill and economy of nature to sup- 
pose that she would so clumsily construct and 
endow the muscles and nerves of the eye, that 
in order to direct one eye outwards the external 
rectus muscle must struggle with and overcome 
the internal rectus of the same eye in conse- 
quence of this “ irresistible impulse in the cor- 
responding branches of the third nerve to 
associate action.” Doubtless the generality of 
those who have no theory to support will acknow- 
ledge that in directing the eye outwards they are 
unconscious of any such struggle between 
opposing muscles as is here supposed, and that 
abduction'of the eye is attended with as little 


effort as either its elevation or depression. 


There is then no such irresistible tendency to 
associate action between the branches of the 
third nerve supplied to the internal recti muscles. 
Both internal recti muscles may be made to act 
at the same time, and thus to produce a con- 
vergence of the optic axes; and this being an 
unnatural position of the eyes is attended with 
a considerable and a painful effort, each inter- 
nal rectus having to overcome the external 
rectus of the same eye, which has a tendency to 
consentaneous action with the external rectus of 
the other eye. That the external rectus must 
have the advantage in any struggle between it 
and the internal rectus is evident from the 
greater thickness and consequent strength of the 
former muscle. The only muscles supplied by 
the third nerve in which this tendency to con- 
sentanecus action is irresistible, are the superior 
and inferior recti of both eyes; we cannot pos- 
sibly raise one eye without at the same time 
raising the other, nor can we depress one eye 
without a corresponding movement of the other. 


- Then, as we have seen, there is no tendency to 


792 ORGANIC 


consentaneous action between the branches of 
the third nerve supplied to the internal recti 
muscles, and it is only by a considerable effort 
that they can be made to act together; whilst 
the branches of the same nerve supplied to the 
levatores palpebrarum, which for the most part 
act consentaneously, may by a very slight effort 
of the will be made to act separately; but few 
persons experience any difficulty in opening 
one eye while the other is closed. Again, the 
tendency to consentaneous action between the 
internal rectus supplied by the third nerve and 
the external rectus supplied by the sixth nerve, 
as well as between the inferior oblique supplied 
by the third nerve and the superior oblique by the 
fourth, is as irresistible as that between the supe- 
rior and inferior recti of the two eyes. We see 
then that all the muscles supplied by corres- 
ponding branches of the third nerve have not 
this tendency to consensual action, and two 
muscles supplied by the third nerve act con- 
sentaneously with two other muscles supplied 
by the fourth and the sixth nerves respectively. 

For the maintenance of the parallelism 
between the axes of the two eyes, it is evidently 
necessary there should be a consentaneous 
action of the superior recti as well as of the in- 
ferior recti; it is also necessary that the internal 
tectus and the inferior oblique of one eye should 
act with the external rectus and the superior 
oblique of the other; but it is by no means 
evident why it is necessary, in order to effect 
this, that the external rectus and the superior 
oblique should each have a nerve specially 
provided for them. We must not suppose we 
are explaining the necessity for this arrange- 
ment by asserting that “ if in place of the sixth 
nerves, the external recti muscles had received 
each a branch of the third nerve, it would have 
been impossible to make one of these muscles 
act without the other,” because, as we have 
seen, there is no such irresistible innate ten- 
dency in all the corresponding branches of the 
third nerve to consentaneous action. Assuming 
that the use of the oblique muscles is such as 
we have mentioned, it is certainly curious to 
observe that when corresponding muscles of the 
two eyes are intended to act together, as the 
superior rectus of one eye with the superior 
rectus of the other, and the same with the infe- 
rior recti, both muscles are supplied by the 
third nerve, but the external rectus which acts 
consentaneously with the internal rectus of the 


opposite eye has a separate nerve, the sixth, and 


the superior oblique, which acts with the infe- 
rior of the opposite eye, has the fourth nerve 
entirely devoted to it. 

There is one other phenomenon to which we 
may briefly allude, namely, the adaptation of the 
eye to distances. This will be found fully dis- 
cussed under the article Visron ; but it deserves 
a ing notice in this place, since one hypo- 
thesis by which an aticinos has been ete Ae 
explain it is that a change is effected in the form 
of the eye by the action of its external muscles, 
some writers attributing the influence in ques- 
tion to the recti muscles, and others to the 
obliqui. It seems by no means improbable 
that the action of both sets of muscles at the 


ANALYSIS. 


same time might have the effect of increasi 
the antero-posterior diameter of the eye ; 
and thereby of adapting it for vision at small 
distances. The following experiment seems to. 
favour the notion that there 1s some muscular 
action in the adaptation of the eye to vision at 
es : small distances. at? 
lace a printed page closer to the eyes than 
the natural focal distance, and merely look 
upon the letters without making any effort to — 
read them; they appear confused and indis- — 
tinct; then by a considerable voluntary effort 
which cannot be long sustained, and which is — 
attended with some pain, we may so adjust the — 
eyes that the letters appear perfectly distinet 
and legible. This subject is attended with 
great difficulties, indeed it is scarcely possible — 
to determine the precise mode in whee eda 
tation is effected; the hypothesis we have now — 
mentioned appears at least as provaliets ny 
other ; it is, however, open to objections. 
state of adaptation of the eye is often entire 
changed in a very short time by the local action 
of narcotics, which at the same time dilate the 
pupil, and this change is effected without any 
apparent influence over the voluntary contrac- 
tions of the muscles. Most observers state that 
the eye is rendered long-sighted (presbyopic), 
while others have experienced an opposite 
result, Miiller has recorded the results of the 
application of belladonna to his own eye; the 
general effect was to render the eye presbyopie, 
but the capability of adaptation was not de 
stroyed by it. When the solution of b 
was applied to one eye both eyes were affeete 
but in different degrees, so that both eyes ¢ 
not be adapted to distinct vision of the - 
object at the same moment. These effects we 
attended with great dilatation of the pupil, 
inasmuch as they were probably in some w 
dependent on this, they are opposed to the hyp 
thesis that adaptation is effected by any acti 
of the external muscles. at 
(G. Johnson.) 


ORGANIC ANALYSIS.—Under thet 
organic analysis are included the various 
thods of discovering the constituent parts 
substances, formed either directly by 
actions of organized beings, or indirectly 
subjecting the products of such actions to 
further operation of re-agents. To treat 
subject in its full extent would, howe 
foreign to the purpose of the present art 
in which I shall confine myself to the an 
of the products of animal life, and part 
of those combinations liable to be met 
the human frame. 4 

In this analysis two distinct objects pp 
themselves : the first consists in the det 
ation of the proximate principles which 
into the constitution off the substance 
analyzed, and the second in the discov 
the elementary composition of the dif 
proximate principles. ' = 

I shall therefore in the first place deser 
the various means by which we recognize 
occurrence of the more important proxi 
animal principles, and determine as 


adc 


mn ORGANIC ANALYSIS. 


\ 
are able the quantities in which they may be 
present: this portion of the subject I shall con- 
clude with a brief sketch of the general method 
of analysing the principal secretions in the 
healthy and more ordinary morbid conditions,— 
for more ample details I must refer to the articles 

specially devoted to the history of each secretion. 

_ I shall then, in the second place, proceed with 
_ an outline of the processes best adapted to the 
_ ultimate analysis of organic bodies in general. 
if To the pathologist the first of these objects 
is the most important, and it is he alone who 
ft es the extensive facilities requisite for 
__investigating the different varieties exhibited by 

the secretions in disease, whether these varieties 

_ present themselves in the undue prevalence of 

_ one or more of the proximate principles, the 

undue deficiency of any of them, or the unu- 

_ sual occurrence of any of them among the 

secretions, or in the tissue of particular organs. 

The value of such information to the enlightened 

_ practitioner is sufficiently evident, for an accu- 

rate and ready mode of appreciating these 

_ changes not only affords him some of the most 

| unerring indications of the nature and progress 

_ of disease, but enables him likewise to appre- 

ay ciate the effects and influence of the remedial 

_ Measures that he may think it needful to adopt. 

‘To the chemist, on the other hand, belongs more 

‘appropriately the task of determining what 

Ought to be considered as really proximate prin- 

‘ciples, of insulating them in a pure state, and 
finally of ascertaining their elementary com- 
position by ultimate analysis. 

__ In every case, before proceeding to analysis, 

it is desirable, nay, in the present state of 
science almost necessary, to subject the mate- 
lal to a careful microscopic examination ; for 
although this does not of itself suffice to deter- 
mine the chemical nature of the substances 
with which we have to deal, it yet furnishes us 
vith the most important preliminary information 
ve can acquire, and is frequently, owing to 
their close chemical relationship, the only means 
ertaining what is the form of the azotised 
stituents of the body with which we have to 
do. In truth, unless a chemist be likewise in 
some degree acquainted with the resources 
pl iced at his disposal by the microscope, he is 
but half fitted for the task of organic analysis. 

For the necessary information respecting the 

inute structure of the different products of 
uimal organization, I must again refer to the 
farious articles on the subject in different parts 
is work. (See Broop, Cuyze, Mirk, 

Mucus, Pus, Satrva, Urine, &c.) 

& I,—ProximaTE aNaLysis. 

As the limits of this article preclude the pos- 
bility of my entering into detail upon the 
dinary operations of analysis, a task happily 
endered unnecessary by the excellent manuals 
€ possess on the subject, I shall limit myself 

a few remarks on processes connected more 
amediately with organic analysis. 

It is needless here to insist upon the impor- 
nce of scrupulous attention to the purity of 
e re-agents employed, as it is a precaution 
ficiently obvious. These re-agents are few 
number: sulphuric, nitric, hydrochloric (or 


793 


muriatic), and acetic\acids, solutions of potash, 
ammonia, and carbona’ ammonia, alcohol, 
and ether, constitute the most important; if to 
these we add solutions of 

Chloride barium, Acetate lead, 

Nitrate silver, Subacetate lead, 

Oxalate ammonia, | Sulphate copper, 


Phosphate soda, Sesquichloride iron, 

Ferrocyanide potas- { Bichloride platinum, 
sium, Tincture galls, 

Alum, Hydrosulphuret am-~- 


Lime water, monia, 
with a blowpipe, platinum foil, spirit-lamp, 
forceps, test-tubes and a stand for them, a few . 
watch-glasses, evaporating dishes and Florence 
flasks, a retort stand, funnels of different sizes, 
filtering paper and some lipped glasses, with 
pieces of glass rod and strips of window glass, 
we shall be tolerably well prepared for the 
operations of proximate analysis. Of course 
distilled water must always be employed in 
analytical enquiries. 

For proximate analysis scales weighing 2000 
grains and turning with th of a grain, when 
fully loaded, will be sufficient; but for ulti- 
mate analysis they should be sensible to 4},th 
of a grain when each pan carries 1000 grains. 

When the weight of a dry residue is to be 
ascertained, the object is attained with most 
accuracy by first counterpoising the vessel when 
empty, and then determining the increase of 
weight after the desiccation is completed. 

The desiccation of all organic substances is 
best performed, where practicable, in the ex- 
hausted receiver of an air-pump, over sulphuric 
acid, by Leslie’s process: a flat dish of oil of 
vitriol is placed on the plate of the pump, and 
the substance to be dried supported above it 
in a basin by a triangular framework of wire; 
the air is exhausted, and care taken to maintain 
a good vacuum ; the residue thus procured is 
always much purer and whiter than that fur- 
nished by any other means, but it is a tedious 
and circuitops process, and requires ten days or 
a fortnight for its completion. Upon this ac- 
count, and for other reasons, this method can- 
not generally be adopted. The plan which, ° 
next to it, presents the fewest objections, con- 
sists in evaporating by a steam or water heat, 
so that the temperature can never exceed 212° 
Fahr. Various methods may be resorted to 
for effecting this object; by placing one basin 
within another containing water, an extempo- 
raneous bath is procured ; but the end is more 
conveniently attained by the employment of a 
shallow box of copper, zinc, or tin plate, in the 
top of which are half-a-dozen circular apertures 
of different sizes with projecting vertical rims, 
upon which lids may be fitted when not in use; 
any vessel to be heated is placed over one of 
these apertures, and the temperature maintained 
by oil, gas, or sand heat. 

Perfect desiccation is essential to accuracy, 
and from the destructible nature of some or- 
ganic compounds, especially under the com- 
bined influences of atmospheric oxygen and an 
elevated temperature, it is dangerous to effect it 
by heat and difficult by any other means. In 
some delicate experiments the following plan, 


794 ORGANIC 


which combines the application of moderate 
heat with Leslie's Seethind: already described, 
may be advantageously employed, though the 
manipulation is rather complicated and trouble- 
some. In a counterpoised retort which will 
sustain exhaustion, a given weight of the sub- 
stance to be dried is placed and connected with 
a tubulated receiver containing oil of vitriol, by 
a sound cork secured on the exterior with several 
folds of bladder, well soaked before applying it. 
Through the tubulure of the receiver passes a 
small glass tube. This junction likewise is ren- 
dered air-tight, with a cork and bladder. The 
tube, about an inch from the tubulure, is, previous 
to its insertion, drawn out and narrowed toa 
capillary bore, so that at pleasure it may be easily 
drawn off and sealed by a jet of flame from the 
blowpipe. Matters being thus arranged, the 
tube from the receiver is united by a connecter 
of caoutchouc with another tube, and this again 
with the air-pump, and exhaustion is performed. 
When a sufficient vacuum has been produced, 
the whole is allowed to stand for an hour. If, 
at the end of that time, the mercury in the 
gauge retain its level, the apparatus is air-tight 
and may be detached from the pump by seal- 
ing the tube proceeding from the receiver in 
its capillary portion. We may now apply a 
gentle heat to the bulb of the retort by means 
of a water bath, or otherwise, and can cool the 
receiver. Great caution is of course requisite 
in handling the exhausted vessels, as the 
slightest abrasion of the surface might cause 
fracture. 

In some cases, as in drying blood, a tempe- 
rature of 230° may be safely used by employing 
a boiling solution of Rochelle salt as the exte- 
rior bath; and in the analysis of the bile a heat 
of even 260° is recommended by Berzelius. 
Where sugar or urea is present, even a heat of 
200° is injurious, and must therefore be avoided, 
The operation we are now considering appears 
one of the simplest that the chemist can have 
to perform, but I have been induced to dwell 
the longer upon it as it is one from which, 
without great care, more mistakes arise than 


from any other, owing to the pertinacity with, 


which water adheres to most organic substances. 
The temperature attainable in an open basin 
over the water bath is much lower than we 
should, @ priori, have been led to imagine. 
I found, for example, that the temperature of 
some wheat flour thus drying in an open basin 
was only 144° F., whilst the water in the bath 
continued steadily at 196° F. When the basin 
was covered with a piece of paper, a tempe- 
rature of 161° F. was the highest attained, 
while a thermometer placed in the water of 
the bath stood at 194° F. With liquids eva- 
porating it rises somewhat higher ; when plain 
water was evaporated it stood at 164°, the water 
in the bath being 208°; and in the case of a 
viscid fluid like yeast, it varied between 176° 
and 180°, while the bath raised a thermometer 
inserted in it to 210°. 

It is therefore desirable to have an appa- 
ratus in which we can ensure any given tempe- 
rature from 212° upwards. For this purpose 
Liebig has contrived a kind of hot-water oven, 


i, 


- 
ANALYSIS. ¥} 


consisting of a double box of copper; in the 
interval between the outer and inner walls, 
water, saline solutions, or oil, may be poured 
and heated in the usual way. In one side of 
this box is a door which may be closed whe 
necessary. The interior chamber and its con. 
tents can thus be maintained with certainty 
the same temperature as that of the fluid around 
them. The best plan of proceeding consists 
evaporating liquids to apparent dryness up 
the open water bath ; and parnaatld subjectin 
the solid residue, when a temperature of 
is not injurious, to complete desiccation — 
Liebig’s oven. So long as the material un¢ 
examination loses weight, the application 
heat must be continued. 
Capsules of Wedgewood ware or B 
porcelain are indispensable, and one or | 
small platinum dishes will be found most val 
able, especially in the evaporation of al 
minous fluids, as the dry residue adheres 
strongly to the glaze of earthen vessels that 
portion of the basin is invariably remov 
along with the animal matter, which 
quires an undue increase of weight, and 
surface of the vessel becomes rough and ut 
for use from the difficulty of cleaning it. — 
Berlin porcelain crucibles are excellent ve 
for evaporation, as, being fitted with covers, 
dry residue may be preserved from absorl 
moisture during the operation of weighing 
exposure to air. It may be worthy o 
tice that adhering organic substances ma 
removed from the surface of vessels in wh 
they have been kept, by digestion in cot 
trated nitric or sulphuric acid, or else by si 
solution of potash. ' 
Incineration of the dry residue is ac 
plished by taking a counterpoised porcela 
platinum capsule with a determinate quanti 
say 10 or 12 grains, of the material to be bu 
and heating it over a circular wicked spirit 
until the ash completely loses its black ¢ 
The capsule should at first be covered t 
vent loss by dispersion on the first appli 
of heat; when visible fumes cease to ar 
cover may be removed to allow freer a 
air; as, however, the temperature 
when the vessel is covered, it will o 
found advantageous to leave it loosely ¢ 
and maintain a steady heat; sufficient a 
access to consume the carbonaceous — 
Sometimes the ash may be stirred ¢: 
a platinum wire in order to expose it moi 
to the air. When the ash contains | 
phosphates, the last traces of carbon are 
off with difficulty, as the phosphates fu 
protect the unburned particles from th 
action of the air. This inconvenience 
overcome by moistening the residue ( 
capsule has been allowed to cool) wil 
drops of nitric acid, and again ignitin: 
ing this maneeuvre as often as mayb 
sary. A new difficulty, however, aris 
chlorides are present, as is almostalw 
case; for ata high temperature th 
decomposed by nitric acid, and t 
therefore appears to contain less chlort 
is really combined withit. ~~ ~ 


~ 


im 
' a 


re 


As the alkaline chlorides are, moreover, not 
completely fixed at a red heat, some loss is not 
unfrequently sustained by a long continued 
_ ignition. We may dispense with the employ- 
_ ment of nitric acid and avoid loss from volati- 
lization by shortening the period during which 

a high temperature is kept up, and simply char- 
__ Ting the mass at a low red heat so as to destroy 


all organic matter; the black residuum is then 


digested in water, by which the alkaline salts 
dissolve, and after well washing, a little weak 
nitric acid is employed to remove the earthy 
compounds: charcoal alone remains undis- 
solved. By evaporation of the solutions the 
amount of saline matter is ascertained. 
Filtration may be performed on good white 
unsized blotting paper cut of a size to drop 
completely within the funnel; before pouring 
in the fluid to be cleared, the filter should be 
_ moistened, if the solution be aqueous, with 
water; if alcoholic or ethereal, with a few drops 
of alcohol or ether, as the case may be. In 
order to ascertain the quantity of dry residue, 
’ the preferable plan is to employ two filters pre- 
_ viously counterpoised one against the other, 
and to insert one into the other; the excess of 
weight the inner filter shews when the filtra- 
_ tion is complete, after both have been carefully 
dried on the water-bath, will furnish the quan- 
_ tity of solid matter. To render the filtration 
more rapid, the apex of the outer filter may be 
cut off so as to leave only one thickness of 
_ paper at the point. “Occasionally we may 
_ weigh the filter itself and mark its weight in 
pencil upon it; the objection to this plan con- 
| Sists in the difficulty of obtaining the paper 
always at the same point of dryness. It should 
| be first dried at :212°F., placed in a light covered 
_ capsule over sulphuric acid, and allowed to 
_ cool, then weighed whilst covered from the air. 
| The same care must be observed on again 
weighing it with the precipitate. Of course 
' in washing an organic precipitate, the same 
_ precautions will be required as when pro- 
ceeding with the analysis of a-mineral. The 
‘stream of washing liquid should be speci- 
| ally directed to the edges of the filter, which 
_ may be known to be sufficiently washed, when 
by the evaporation of a drop of the liquid 
‘which passes through on a slip of glass, no 
perceptible stain is produced. 
_ Whenever decantation, or pouring off from 
the sediment, can be. substituted (as it very 
frequently may in alcoholic and ethereal di- 
gestions) for filtration, it is to be preferred, as 
‘some loss is unavoidably occasioned by every 
filtration; whereas by decantation the preci- 
ee may be dried in the vessel, and if this 
have been previously counterpoised we can 
ascertain the weight of adhering matter with 
‘great exactness. By this method the precipitate 
may be as perfectly washed as when filtration 
is adopted ; the fluid may be poured off very 
close to the solid matter, which may again be 
\diffused through a fresh portion of washing 
jfluid, again allowed to subside, and the wash- 
jing repeated as often as may be necessary. In 
pouring a fluid from one vessel to another, loss 
jis avoided by moistening a glass rod in the 


ORGANIC ANALYSIS. 


795 


liquid, bringing it into contact with the lip of the 
glass or basin, and pouring the liquid down this 
rod, which is not removed until the side of the 
vessel is nearly restored to the vertical pusition ; 
by observing this precaution we escape the risk 
of losing any portion from its running down 
the outside of the vessel. The drops adhering 
to the rod are washed into the rest of the 
solution. 

The animal substances that we have to ex- 
amine naturally arrange themselves into fluids 
and solids, and as this division is convenient 
in a practical point of view, I shall here adopt 
it, beginning with those presented to us ina 
fluid state. 

In order to fix some definite limit to our 
enquiries, those principles only will here be 
noticed, which, from the frequency of their 
occurrence or their importance as constituents 
or products of the living frame, are most likely 
to be the special objects of attention to the 
physician and pathologist. In this number 
among the fluid products I shall enumerate 
fibrin, albumen, casein, fatty matters, urea, 
sugar, the uric, urobenzoic, lactic, and oxalic 
acids, mentioning a few other compounds, as 
ptyalin, sulphocyanic acid, &c. &c., when 
describing the general plan of analysing the 
secretions in which they most commonly 
occur. 

A. ANALYSIS OF ANIMAL FLUIDS. 

» When an animal fluid is presented for ana- 
lysis, it is necessary in the first place to acquire 
a knowledge of the ingredients which enter 
into its composition in order to be able to 
decide upon the best method of ascertaining 
their proportions. The means of determining 
the nature and quantity of the organic con- 
stituents will be first described, leaving the. 
saline matters for a subsequent section. 

1. For the organic constituents. 

It is possible that all the principles just 
enumerated may occur together; this, however, 
will very rarely happen unless we have to 
examine the contents of the stomach, when a 
still more ‘heterogeneous mass may be pre- 
sented to us. 

Having, where practicable, taken the specific 
gravity of the liquid in order to acquire an 
idea of its degree of concentration, we place 
a portion under the microscope, and are thus 
enabled at once to decide upon the presence 
of blood globules, pus globules, fatty or oily 
matters in suspension, the debris of tissues, 
crystals of various substances, as uric acid, 
cholesterin, &c., and may then pass to tests 
purely chemical for its 

Qualitative analysis. 

a. By allowing the liquid to stand at rest for 
a few hours, we at once determine the presence 
of fibrin, which coagulates and separates spon- 
taneously, at the same time enveloping the 
red globules and suspended particles in its 
meshes. 

6. The clear liquid is heated to boiling; if 
albumen be present it coagulates, unless the 
solution bealkaline, when the addition of a few 
drops of nitric acid causes an immediate curd- 
ling. A drop or two of acetic acid added to 


796 


the original liquid, if it produce coagulation, 
shews the presence of casein. We need not 
seek for casein if the fluid shews an acid re- 
action, asit is coagulated by free acids in general. 
If mucus be present, some ambiguity may arise 


from the action of acetic acid, as this re-agent _ 


causes the coagulation of the mucus furnished 
7 the alimentary canal and its appendages, 
When present, however, in appreciable quan- 
tity, mucus always communicates to the fluid 
a certain degree of ropiness which leads us to 
suspect its presence. A confirmatory test for 
casein under such circumstances consists in 
adding a few grains of milk sugar and a little 
washed rennet; if the mixture be heated for an 
hour or two to about 120°, the casein coagu- 
lates completely. 

c. Fatty matters and cholesterin are revealed 
by the microscope, and may be separated by 
evaporating the fluid to dryness, digesting the 
residue with ether and filtering; by sponta- 
neous: evaporation of the ethereal solution, 
they are left behind with their usual physical 
characters. 

d. The presence of sugar is best discovered 
by mixing the suspected fluid with yeast and 
placing it in an inverted tube over mercury for 
twenty-four hours, at a temperature of from 
70° to 80° F., making at the same time a 
comparative experiment with an equal bulk of 
the same yeast diluted to the same extent with 
pure water. We cannot by yeast determine 
with certainty the presence of sugar in a pro- 
portion less than ;1;th of the liquid employed. 
A much more delicate test, and one which fur- 
nishes more immediate results, has lately been 
proposed by Trommer, founded upon the fact 
that organic bodies, to which free alkali has 
been added in excess, and especially solutions 
of grape and milk sugar, dissolve freshly pre- 


cipitated oxide of copper; when the saccharine | 


solutions are boiled they are decomposed, and 
sub-oxide of copper is deposited of a charac- 
teristic reddish brown colour. To apply this 
test, add to the suspected liquid a few drops 
of solution of caustic potass, so as to render 
it distinctly alkaline, then a small quantity of 
a dilute solution of sulphate of copper, agita- 
ting to dissolve the precipitate ; a liquid of a 
blue colour varying in intensity with the quan- 
tity of copper held in solution is obtained. 
Apply heat, and if sugar is present an ochre 
yellow or red precipitate of sub-oxide takes 
place, as soon as ebullition begins. I-have 
already mentioned that the presence of milk 
sugar has the same effect as grape or dia- 
betic sugar; other animal matters produce 
a similar change. It is, however, very deli- 
cate in its indications; a negative result 
therefore may be considered as decisive of the 
absence of sugar. If a precipitate occur, the 
presumption that we are examining a saccha- 
rine liquid ought always to be confirmed by 
recourse to the unequivocal expedient of fer- 
mentation. It is easy to concentrate the fluid 
if the sugar is very small in quantity; the only 
case in which any ambiguity can arise. Sugar 
of milk has never been found but in the secre- 
tion from which it derives its name. 


ORGANIC ANALYSIS. 


Jowed to crystallize from a moderately dilute — 


e. Urea can only be discovered satisfactorily 
by evaporating the suspected fluid to dryness 
and treating the residue with alcohol, again 
evaporating this alcoholic solution to dryness, 
redissolving in water,and adding nitric or oxalie 
acid with the precautions to be menti 
hereafter when treating specially of the deter- 
mination of urea. When common salt is al- — 


solution of urea, the form of the crystals is 
modified, and instead of obtaining cubes or 
octohedra the crystals developed assume a — 
more or less penniform appearance, often shew- 
ing the figure of a Maltese cross with serrated 
edges. These modifications have been proposed” 
as a test of the presence of urea: they are 
not, however, certain indications, though useful — 
as affording a presumption of its presence, 
When a fluid which contains urea is concen- 
trated by evaporation, and nitric acid is then 
added, by spontaneous evaporation on a glass” 
plate we obtain lamellar crystals of nitrate of 
urea in irregular rhomboidal plates with the 
acute angles often truncated. ; 
J. To detect the existence of uric 
and the urates, if albuminous principles ar 
present, the liquid is evaporated to dryne 
and the residue digested for some hours with 
solution of caustic potash, till every thin 
soluble has been taken up. It is dilutec 
filtered, and supersaturated with h ry dre 
chloric acid; a flocculent precipitate forms 
which is redissolved by excess of acid; am 
the uric acid separates; this is collec 
on a filter. We are enabled by this pre 
cess, where considerable quantities of 
acid are present, as in the excrements 
birds of prey, to obtain results of consider 
ble accuracy ; but where the proportion of t 
acid is very minute, it cannot be relied upo 
for quantitative experiments; the residue 
these cases must be subjected to microscop 
examination. If no azotised matters are 
sent, the mere addition of free hydrochlorit 
acid after a lapse of some hours usually cau 
a separation of rhombic crystals of \ 
or by evaporating to dryness and treating 
residue with water acidulated with hy 
chloric acid, the uric acid remains undissoly 
the residue is proved to contain this compo 
either by the appearance of its crystals ut 
the microscope, or by evaporating a small 
tion to dryness with nitric acid ona 
glass, when a red stain is left; a drop o 
monia added produces a fine crimson; if 
be evaporated to dryness, a drop of sc 
of caustic potash converts it into a beat 
purple, which is destroyed by the applic 
of heat. 4 
The methods for testing the other acid 
be described when treating of their quanti 
determination. 
Having now obtained an idea of t 
of the fluid we have to examine, we are 
to proceed with its “ 
Quantitative analysis. 
A thin porcelain or platinam 


ORGANIC 


This is evaporated to dryness in a water-bath. 
It is carefully weighed and the total solid con- 
tents determined; the loss indicates volatile 
matters consisting almost entirely of water. 
The residue is carefully incinerated with the 
usual precautions until all traces of carbon 
are removed: on weighing again we obtain 
the fixed saline constituents. 

By this means we have determined 

Water and volatile matters. 
Organic matters and ammoniacal salts. 
Fixed saline matters. 

The quantity of each organic substance has 
now to be estimated. We have at present no 
absolutely exact method of determining all the 
ingredients from one portion only of a fluid ; 
the following offers the nearest approximation. 

a. Fibrin separates by spontaneous coagula- 
tion; it is washed and determined in the manner 
to be described hereafter. 

__ 6. If casein and albumen be both present, a 
given portion of the clear liquid is acidulated 
with a few drops of acetic acid, and evaporated 
_ to dryness in vacuo over sulphuric acid. The 
_ residue is digested with successive portions of 
_ water at 120°, as long as any thing. dissolves ; 
_ this residue is then dried upon a water-bath, 
| pulverised, and treated with ether, by which 
_ all fatty matters are removed; casein alone 
remains behind. It is completely dried, weigh- 
_ ed, incinerated, and the ashes deducted. This 
method of separating the casein is imperfect, as 
_ a portion of this substance generally redissolves 
_ on the addition of water. If uric acid be pre- 
sent, it will be found with the casein, which 
_ must be dissolved in solution of potash, diluted, 
filtered, supersaturated with acetic acid, by 
which the azotised matter at first precipitated 
| is redissolved. Uric acid alone remains; it is 
‘A collected on a weighed filter, and the quantity 
| determined. It should always be tested by the 
microscope or by nitric acid. 

_ c. The aqueous solution filtered from the 
‘casein, or the liquid for examination, if this 
principle be absent, is evaporated to dryness 
by a water-bath. If much fat is present, the 
residue is washed with ether to remove the 


‘greater part of the oily matter, then dried tho- 
roughly, and powdered; an operation which, 
“after the preliminary treatment with ether, may 
be effected without much difficulty. The pul- 
verized mass is digested with ether, and the 
ethereal solutions, including that in which the 
casein was digested, are mingled and evapo- 
rated to dryness. Cholesterin, fatty matters, 
lactates, and a trace of urea are obtained; 
by digesting with water the cholesterin and 
fats alone remain and may be collected on a 
filter and weighed. 

_ d, The residue, after digestion with ether, is 
eased with boiling water; the solution thus 
Obtained may contain urea, sugar, sugar of 
milk, extractive and saline matters,—in short, 
every thing except the albumen, which is com- 
pletely dried and then weighed. When no 
jcasein is present, the uric acid, if any, will 
jaccompany the albumen, and may be separated 
from it in the manner directed for its separation 


ANALYSIS. 797 


e. The filtered liquid is evaporated to dry- 
ness and treated with a mixture of one part of 
anhydrous ether with-two of absolute alcohol, 
by which urea, muriate of ammonia, lactates, 
the alcoholic extractive matters so called, and 
a small part of the sugar, are dissolved. The 
remainder of the sugar, sugar of milk, aqueous 
extractive matters, urates, sulphates, chlorides, 
and phosphates remain behind, forming re- 
sidue (1). 

J. The alcoholic solution is evaporated to 
dryness and weighed: the solid matter divided 
into two portions; one is dissolved in water 
acidulated with nitric acid, and treated with. 
nitrate of silver, by which the chlorine is sepa- 
rated as chloride of silver, and hence the mu- 
riate of ammonia is determined ; from the’ other 
portion we determine the quantity of urea by 
oxalic acid with the usual precautions. Having 
thus determined the weight of the muriate of 
ammonia and of the urea, we infer the defici- 
ency to consist of a little sugar, lactates, and 
alcoholic extract. 

g. The residue (1), which contains sugar, su- 
gar of milk, watery extract, and salts, is boiled 
with proof-spirit as long, as any thing is dis- 
solved ; the solution is evaporated to dryness, 
and if grape sugar be present, half, the residue 
must be dissolved in water and fermented with 
yeast to determine the proportion of this sub- 
stance, and its weight is deducted from the 
weight of the residue left on evaporating the 
spirituous solution; the other half residue is 
incinerated, and the quantity of saline matter 
ascertained; by deducting the weight of the 
sugar and salts we then obtain that of the sugar 
of milk, together with the alcoholic extract, 
from which we possess no exact means of se- 
parating it. It, however, very rarely happens 
that in the same fluid we meet with grape 
sugar and sugar of milk ; the absence of sugar 
will obviously much simplify the method of 
proceeding. 

h. The portion undissolved by proof-spirit 
is dried and weighed; it is incinerated and 
again weighed; the difference between. the two 
weighings gives the quantity of watery extract, 

This will be the general plan of operations 
if it be required to determine the quantity of 
each individual ingredient. From the number 
of operations required, and the destructible na- 
ture of the ingredients, the result, as already 
mentioned, is not rigidly accurate. Frequently, 
however, it is merely necessary to ascertain the 
proportion in which one substance only is 
found; the presence or absence of others being 
all that it is desired to know concerning them. 


We proceed now to the special consideration 
of the different animal principles. 

Fibrin.—Although the identity, in chemical 
composition, of fibrin, albumen, and casein has 
lately been strongly insisted on by Liebig and 
his pupils ; yet, as in their physical properties 
at least, and in the offices they perform in the 
body, they differ considerably, it is frequently 
of great importance to determine the relative 
proportion of each in the fluids and secretions. 
These three principles occur both in the coagu- 


798 


lated and uncoagulated state. When coagulated, 
the separation of fibrin and albumen cannot be 
effected by any means with which we are ac- 
quainted, and, indeed, the first authorities 
differ when they attempt to decide which of 
the two they have to deal with, if they occur 
in the coagulated state. When uncoagulated, 
their separation and quantitative determination 
may be effected with considerable accuracy. 
Pure fibrin, when moist, is white and some- 
what elastic, is insoluble in water, alcohol, or 
ether. It is readily taken up by strong acetic 
acid, and from this solution it is precipitated 
by ferrocyanide of potassium (prussiate of ‘pot- 
ash); fibrin also dissolves in solution of pot- 
ash; if, when thus dissolved, it be heated gently 
and the liquid neutralized by an acid, a white 
flocculent precipitate occurs, which redissolves 
in excess of acid, and the solution emits an 
odour of sulphuretted hydrogen. Strong nitric 
acid turns fibrin yellow, forming a yellow so- 
lution with gradual evolution of gas; in con- 
centrated hydrochloric acid it slowly dissolves 
with a rich violet colour. These are properties 
it possesses in common with albumen and ca- 
sein; but it is distinguished from them and 
from all other animal matters by its sponta- 
neous coagulation when removed from the living 
body. This furnishes us with a certain test 
of its presence when in the liquid form, and 
enables us to separate it in good degree from 
other bodies ; within its pores, however, is ob- 
_ Stinately retained a quantity of the fluid from 
which it has just separated itself, together with 
most of the globules and particles suspended 
in the secretion. It becomes necessary, there- 
fore, to wash out these ingredients, an opera- 
tion rendered possible by the insolubility of the 
fibrin in cold water. e coagulum from a 
known quantity of fluid is cut into very thin 
shreds by a sharp knife, tied in a piece of linen, 
and a gentle stream. of water allowed to fall 
upon it; from time to time the clot is gently 
kneaded and the washing continued; in the 
case of blood, till all traces of colouring matter 
are removed, or, where no colour is present, so 
long as may be deemed necessary ; the residue 
is then removed from the linen, dried, digested 
in ether to remove adhering fatty matters, again 
dried and weighed. A portion is then incinerated, 
the weight of the fixed matters determined and 
deducted from the gross weight of the dried 
fibrin, by which we obtain that of the organic 
matter.* 

Fatty matters.—Several peculiar oily sub- 
stances occur in the fluids and solids of the 
animal body. Among the saponifiable fats 
chemists have distinctly ascertained the pre- 
sence of margarin, elain, and butyrin; besides 
these we have cholesterin and serolin, which 
are not saponifiable by boiling in alkaline solu- 
tions, and there are others containing phos- 
phorus and sulphur, but their composition and 
properties are yet involved in uncertainty. Our 


* It has been objected that the insoluble nuclei 
of the red particles are retained in this process. It 
is, however, superior, both in the accuracy of its 
results and the facility of its performance, to any 
other method hitherto pro as its substitute. 


ORGANIC ANALYSIS. 


analytical processes for separating these bodies — 
are very imperfect ; the fats are all soluble in — 
boiling alcohol, and still more freely in ether. 
Cholesterin and serolin may be isolated from 
the other fats by boiling the residue, after eva- 
poration of the ether, with solution of caustic 
potash, as they remain undissolved by this’ 
menstruum, whilst the margarin, elain, and 
butyrin form soaps which are dissolved by the 
water. : a 
Serolin is an azotised fat, which has hitherto 
only been found in the blood ; it is readily dis- 
tinguished from cholesterin by its fusing 
being much lower, 97° F., whereas chole 
does not melt below 278°, and is found in 
blood only in minute quantity.. By pressing 
them between folds of filtering paper we mig 
therefore, if careful to maintain a temperatur 
near that of boiling water, effect a tole: 
complete separation of these bodies. ‘s 
from th 


POL 


Butyrin rapidly absorbs oxygen 
air, setting free a volatile acid, the butyric 
it possesses the peculiar odour of rayeid butte 
by which its presence is always easily reeog 
nized. : 

In analytical inquiries it is best to separ 
fatty matters by ether as the first step after t 
liquid has been evaporated to dryness; we m 
then safely proceed to determine the 

Albumen.—In chemical properties it d 
little from fibrin, excepting in the fact of 
requiring heat or some chemical agent to pi 
duce coagulation; towards nts it cc 
ports itself in the same way. When liq 
Its separation from fibrin and fats is effee 
as just described. The residue, after 
fats have been removed by ether, i 
gested in boiling water, and the residue 
washed ; the albumen remains upon the’ 
and must be dried and weighed. A g 
quantity is incinerated to determine the p 
portion of saline matters, which must be 
ducted from the weight previously fou 
uric acid existed in the solution, it woul 
mixed with the albumen. In case the colot 
ing matter of the blood were contained i 
fluid, a small part would remain mixed 
the albumen, and might be removed b 
gestion in alcohol acidulated with sul 
acid, by which the hematosin is dissolvet 
greater part, however, subsides by a 
the liquid to stand undisturbed in a tall 
for forty-eight hours. If the solution + 
free alkali, a part of the albumen is red 
on the addition of water; when, 
filtered liquid presents an alkaline rea 
should be very carefully and exactly 1 
by acetic acid, evaporated to dryness, at 
treated with hot water; the weight of this 
portion of albumen must be added tot 
obtained. Casein hardly ever occurs 
same solution with albumen; if pr 
would be separated by the aceti¢ aci 
manner me described. a 

Casein is distinguished from albumen 
non-coagulability by heat; when its s0 
are evaporated at a high tempe ,% 
luble skin or film forms upon 
which is almost characteristic, the ¢ 


: 
: 


ORGANIC ANALYSIS. 


with which it can be confounded being an alka- 
line solution of albumen, which resembles it 
in this and in some other particulars. Acetic 
acid in small excess causes its immediate 
coagulation ; a great excess of the acid redis- 
solves the coagulum. ‘The fibrin, fats, and 
albumen having been separated in the manner 
already described, we may proceed to deter- 
Mine the casein by adding a few drops of 
acetic acid and evaporating to dryness. Boiling 
water removes from the residue every thing ex- 
cept saline matters and casein ; this residue is 
dried, weighed, incinerated, and the salts de- 
ducted ; a portion of casein is apt to redissolve 
in the water, so that this process is not perfectly 
accurate.* 
Urea.—It is best, when practicable, to make 
a separate analysis for this principle ; if this be 
impossible, we may proceed with the fluid from 
which albumen, casein, and fats have been se- 
parated, as already mentioned. In either case 
the liquid is evaporated to dryness, and the re- 
siduum digested with alcohol; we thus obtain 
a solution of urea freed. from every thing ex- 
_ cept chlorides, sugar, some “extractive” mat- 
_ters, besides fats and lactates, unless previously 
“removed by ether. The alcohol having been 
‘driven off, the residue is dissolved in sufficient 
‘water to produce a liquid of syrupy consistence. 
Colourless nitric acid is diluted till of a specific 
gravity of 1°25, which is a convenient strength 
for precipitating the nitrate of urea. The eva- 
‘porating basin with the impure solution of urea 
His next placed in a vessel containing a frigorific 
‘Mixture composed of 1 oz. of nitre, 1 of sal 
t ammoniac, each finely powdered, and 4 oz. of 
‘water; when the basin and its contents have 
deen thus cooled, colourless nitric acid, sp. gr. 
1°25, rather more than equal in bulk to the 
Solution of urea, is added drop by drop, stir- 
ie : ; 
Ting carefully ; if added too quickly, the tempe- 
ature rises, a little effervescence ensues, and 
part of the urea is decomposed. A flaky precipi- 
tate shows nitrate of urea; the whole is al- 
lowed to remain in the freezing mixture for 
hree or four hours, or even longer; the nitrate 
Of urea is then collected on linen, the linen is 
folded up, placed between several layers of 
iiterimg paper, and then subjected to strong 
wressure. ‘The mother-liquor and excess of 
cid are thus almost entirely expelled; a slightly 
iscoloured firm dry mass of nitrate of urea is 
procured, which may be exposed for some time 
© a temperature of 212°, and then weighed ; 
00 parts contain 48°78 of urea. The amount 
# impurity which this nitrate contains is usu- 
ly very small, as is easily proved by ultimate 
ni lysis. 
| The nitrate of urea crystallizes in flat rhom- 
bidal tables, is sparingly soluble in water, 
etty freely in alcohol even when cold, very 
nightly in pure ether. It is wholly vola- 
ized by heat; when digested with carbon- 
e of baryta suspended in water, effervescence 
Sues; on evaporating to dryness, exhausting 


* Proof-spirit may be substituted for water as a 
vent, but it leaves more animal extractive mat- 
, though it dissolves less of the casein. ~ 


799 


with hot alcohol ard evaporating slowly, long 
prisms of urea are obtained. 

Other methods have been proposed for esti- 
mating the urea, and when the proportion is 
small the substitution of oxalic for nitric acid 
furnishes results of greater accuracy ; but the 
urea must then be separated by absolute alco- 
hol instead of rectified spirit from its other ac- 
companiments; the oxalic acid is rubbed to a 
thin cream with water, and a portion of this, 
equal in bulk to the syrupy solution of urea, is 
added to the liquid, which is gently warmed ; 
it is then allowed to cool, and the whole im- 
mersed in the frigorific mixture. The crystals 
are drained on calico and subjected as before 
to strong pressure; the firm dry cake of oxalate 
of urea and oxalic acid is allowed to digest at 
a temperature of 100° F. for about eight hours, 
with rather more than its own weight of chalk 
and six or eight times its weight of water. 
Effervescence ensues, an insoluble oxalate of | 
lime forms, and urea is dissolved ; the solution 
is filtered and evaporated’ to dryness ; long 
crystals of nearly pure urea form, from the 
weight of which the quantity. is ascertained : 
they ought to dissolve completely in absolute 
alcohol; anything undissolved is oxalate of 
ammonia. 

If the amount of urea be very small, as is 
sometimes the case with diabetic urine or the 
serum of the blood, Dr. Rees recommends the 
employment of ether instead of alcohol to the 
dry residue. Urea is very sparingly soluble in 
this menstruum and will be obtained with the 
fats; the ethereal liquid evaporated and the 
residue treated with water, filtered and again 
evaporated, furnishes long delicate prisms of 
urea; this process, however, must be re- 
garded more as a test of the presence of urea 
rather than as a means of estimating its quan- 
tity. Sometimes urobenzoic (hippuric) acid 
occurs in diabetic urine, and it would then be 
extracted by ether along with the urea and 
crystallize with it; but it is easily separated 
and distinguished by the sparing solubility of 
its crystals in cold water. 

Sugar.—It is best to take a separate portion . 
of the fluid to determine the quantity of sugar. 
A jar, with its aperture ground smooth, gradu- 
ated to tenths of a cubic inch, and capable of 
containing from 12 to 20 cubic inches, is turned 
with its mouth upwards and filled to within an 
inch or two of the top with mercury ; from 100 
to 200 grs. of the liquid for analysis is accu- 
rately weighed and transferred to the jar with 
the usual precautions; 8 or 10 grs. of yeast are 
introduced, and the jar accurately filled with 
water; the mouth is closed by a glass valve, 
which is retained in its place by a piece of 
linen or any other convenient means ; the jar is 
inverted in a basin of mercury and the valve 
removed. The apparatus is set aside for two 
or three days in a temperature of about 70°, till 
the fermentation is complete. The quantity of 
gas is now accurately read off; the temperature 
of the room and height of the barometer care- 
fully noted, as well as the difference between » 
the level of the mercury within and without 
the jar. As the liquid will be saturated with 


£00 


its own bulk of carbonic acid at the observed 
temperature and pressure, we must in our cal- 
culations add the bulk of the liquid to that of 
the gas actually observed. Having reduced 
the bulk of gas to the standard ‘pressure of 30 
inches and the temperature of 60° F., accord- 
ing to the rules given in all works on physics, 
we deduce the quantity of sugar, since 100 
cubie inches of carbonic acid are furnished 
by the decomposition of 106°6 grs. of grape 
sugar. 

If mercury be not at hand, we may, by 
adapting a tube containing chloride of cal- 
cium, and a bulb apparatus charged with 
strong solution of potash,* the weight of which 
is accurately known, to a tubulated retort, ob- 
tain a result of considerable accuracy. Ina 
half-pint retort, so adjusted, 500 grs. of urine 
are placed, and 30 or 40 grs. of yeast added ; 
through the tubulure of the retort a straight 
tube passes, and dips below the surface of the 
fluid ; the upper extremity is closed by a cork, 
It is set aside to ferment at a temperature of 
70°; the chloride of calcium retains the mois- 
ture, and the potash ley absorbs the carbonic 
acid; by the increase of weight we know the 
quantity of carbonic acid formed. As at the 
close of the experiment the apparatus will be 
full of carbonic acid, it must be displaced by re- 
moving the cork from the straight tube passing 
through the tubulure of the retort, and then 
gently drawing air through the apparatus for 
some minutes by careful suction at the extre- 
mity of the potash apparatus, in the manner 
to be described presently when treating of the 
process of ultimate analysis. 100 grs. of car- 
bonic acid indicate 225 grs. of diabetic sugar. 

Another method of ascertaining the quantity 
of sugar consists in adding to a given quantity 
of the fluid a known weight of yeast—having 
by experiment determined the quantity of fixed 
matter contained both in the yeast and in the 
fluid operated on. After fermentation is com- 
plete the solution is evaporated to dryness, and 
the loss of solid matter sustained indicates the 
quantity of sugar which has passed off as alcohol 
and carbonic acid; the urea likewise is de- 
stroyed in the process, and its quantity must be 
deducted from the total loss. It is very desi- 
rable when sugar is present in considerable 
quantity that the evaporation to dryness should 

rformed in vacuo over sulphuric acid, as 
it is the only method that ensures our ob- 
taining the sugar always in the same state of 
hydration. This process, however, is tedious, 
always requiring many days for its completion : 
some comparative experiments, showing the 
een of this precaution, will be detailed here- 

r. 
Our methods of exactly determining the 
erie of sugar of milk are imperfect; I 
shall describe the plan which answers best 
when treating of the analysis of milk. 

Uric acid.—This is one of the most inte- 
resting and important animal products from the 


* These pieces of apparatus will be described in 
detail in the directions for the performance of ulti- 
mate analysis, 


ORGANIC ANALYSIS. 


part it frequently performs in some of the most 
serious and distressing diseases to which weare- 
hable. The method of detecting its presence 
by evaporation on glass with nitric acid has” 
already been described. When no albuminous 
principles are present, the solution is evapore 
to dryness and the residue treated with ; 
acidulated with hydrochloric acid; the inso- 
luble portion is dried and weighed, then 
burned ; the weight of the remaining ash 
(silica), if any, is deducted ; the loss indicates 
the quantity of uric acid. er 
robenzoic, or, as itis often called, hippur 
acid, has hitherto been found only in the urine, 
in which it generally exists in minute quantity 
according to Liebig. Its quantity may be a 
certained by adding hydrochloric oat to th 
liquid concentrated by evaporation. It is ey 
porated to dryness by a water heat, and th 
residue digested with pure anhydrous ether as 
long as any thing is dissolved. By spont: 
neous evaporation it is left behind nearly pun 
and may be weighed ; traces of urea c! ) 
with it, and a little of the odorous priney 
which obstinately adheres to it. If the eth 
have dissolved any fatty matter, the addition 
boiling water will dissolve the acid and lea 
the fats. Urobenzoic acid may be detected 
heating a crystal in a test tube; benzoic a 
and benzoate of ammonia, and a few red di 
of an oily matter, sublime, accompanied b 
smell of bitter almonds and of the Tonka 
Alcohol dissolves it freely, and the solutio 
evaporation leaves stellated groups of nee 
shaped crystals. With perchloride of — 
solutions of the urobenzoates furnish a ¢ 
mon brown precipitate. ‘ 
Lactic acid cannot be quantitatively ¢ 
mined without difficulty. The best me 
is as follows:—The solution if acid is” 
tralized with ammonia, evaporated to dry 
and the residue exhausted with alcohol 
the filtered liquid sulphuric acid is added | 
by drop as long as a precipitate ensues 
bases are thus removed as sulphates. The 
tion is filtered and the precipitate washed 
alcohol; the clear liquid is digested with 
Far agitation, at a moderate heat, for t 
our hours, with carbonate of lead: hydroe 
sulphuric, and phosphoric acids are thus 
rated as insoluble salts, while lactate of le 
solves. The solution is a second time fil 
sulphuretted hydrogen gas transmitted th 
the clear liquid, and the sulphuret of lead 
rated by another filtration; the filtered | 
evaporated to dryness to expel thealce 
cess of gas, the residue redissolved in 
digested with carbonate of zine ; by eva} 
of the filtered liquid crystals of lactate 
are obtained. If the solution is now 
with carbonate of potash in excess, eval 
to dryness, exhausted with boiling wal 
the residue dried and ignited, pure « 
zine is obtained: 100 grs. of this oxide 
202.5 grs. of lactic acid. , 
If oxalic acid be mies go" in any I 
must be super-saturated with lime wate 
treating the precipitate with acetie ac 
phosphates dissolve, and oxalate of Ii 


ORGANIC 


mains, as the phosphate of irou is insoluble in 
acetic acid. The absence of iron must be 
determined by dissolving the precipitate in 
nitric acid, nearly neutralizing with ammonia 
and adding hydrosulphuret of ammonia; the 
iron, if present, would fall as a black sulphuret, 
mixed with oxalate of lime. Oxalate of lime 
dissolves in dilute nitric acid, and, on super- 
saturating with ammonia, is thrown down un- 
changed. By converting the oxalate of lime 
into the carbonate or sulphate, as directed when 
speaking of the estimation of lime, the quan- 
tity of oxalic acid may be inferred—100 grs. 
of the carbonate indicate of anhydrous oxalic 
acid 72 grs., and 100 of the sulphate 51.94 of 
the acid. 
2. For the inorganic constituents. 
To ascertain the nature and proportion of 
the saline matters incineration is resorted to in 
the manner already described. This process, 
however, only tells us what the fixed ingre- 
dients are, and their quantity, in the form of 
oxides, chlorides, sulphates, phosphates, or 
carbonates. All the ammoniacal salts are ne- 
cessarily dissipated, frequently carrying off 
portions of sulphuric acid and chlorine. The 
organic acids that may have been combined 
_ with the bases are entirely decomposed and 
their place supplied by carbonic acid, which 
renders it difficult to decide whether any car- 
bonate actually existed as such in the com- 
pound ; and moreover the metals, as iron, cal- 
cium, and magnesium, with other bodies, as 
sulphur and phosphorus, are for the most part 
estimated, not (as is sometimes probable, and 
at others certain, that they existed) in the me- 
tallic or unoxidized form, but as oxides or 
acids. The information we derive from inci- 
neration is therefore incomplete, and the mere 
deduction of the weight of ashes from the 
entire weight of the body burned by no means 
furnishes us with a correct estimate of the pro- 
portion of volatile ingredients ; generally speak- 
ing, however, it is the nearest approximation 
we can obtain. ’ 
_ I shall here describe very briefly the means 
t adapted to the qualitative and quantitative 
rmination of the saline matters, referring 
those requiring more ample instruction on this 
Subject to Rose’s Manual of Analytical Che- 
Mistry, and the various systematic treatises on 
the science. 
_ Although during incineration portions of 
aline matter, and especially of chlorine, are 
arried off, and the sulphates are sometimes 
reduced to sulphurets, we find it the only 
method by which any thing like an accurate 
estimate of the inorganic constituents can be 
obtained, inasmuch as many of these bodies 
cur in the form of chemical compounds 
‘ith organic matter, and are thus prevented 
rom forming precipitates with the ordinary re- 
gents: iron is particularly liable to be thus 
fiected. When practicable, we should usually 
ake an analysis of the solution for the inor- 
fanic acids before evaporation, and afterwards 
second examination of the fixed residue after 
ynition. 

The inorganic materials for which we shall 
VOL, III. 


ANALYSIS. 


have in general to search are comparatively 
few in number; among the acids, hydro- 
chloric, sulphuric, phosphoric, and carbonic, 
with traces of silica, will be those of most fre- 
quent occurrence. Occasionally we may have 
to seek for iodine, fluorine, and unoxidized 
sulphur. Potash, soda, ammonia, lime, mag- 
nesia, and oxide of iron, are the bases that will 
be most frequently the objects of experiment, 
and now and then we may have to look for 
copper, lead, and some other metals. 
Qualitative examination. 

a. The saline residuum, after ignition, is 
boiled with a little water (solution A) and fil- 
tered from the insoluble residue (B). 

A. b. The solution, except in special cases, 
will only contain sulphates of potash, soda, lime, 
and magnesia, as well as chlorides of the same 
bases, and phosphates and carbonates of potash 
and soda. When the alkaline carbonates are 
present, lime and magnesia need not be looked 
for; nor need we search for either of these 
bases if the solution contain phosphates, unless 
the liquid reddens litmus paper. The liquid 
is, therefore, in the first place tested with blue 
and with reddened litmus paper, by which 
acidity, alkalinity, or neutrality is rendered 
evident; we then proceed to determine what 
acids are present. The absence of a precipitate 
should not be too hastily decided on. As a 
general rule the tests should be allowed to 
stand twelve hours before a negative result is 
recorded. 

c. A portion of the liquid is acidulated with 
nitric acid, and to a smal! quantity of it a drop 
or two of solution of chloride of barium added ; 
a white cloud indicates sulphuric acid. 

d. Into another portion of the acidulated 
fluid nitrate of silver is dropped in slight excess ; 
a bluish white flocculent precipitate shews the 
presence of chlorides. 

e. The solution (d) is filtered from the chlo- 
ride of silver, is boiled for a few minutes, then 
saturated exactly withammonia. If phosphoric 
acid be present, a yellow precipitate of phos- 
phate of silver, very soluble in excess of ammo- 
nia, is produced. 


801 


J. A little of the aqueous solution is evapo- - 


rated to dryness, and a drop of nitric acid added 
to the residue : effervescence indicates carbonic 
acid, due in all probability to the decomposition 
of some organic acid by ignition. 

We have next to test for the bases in solution. 

g- The liquid is rendered slightly alkaline 
by ammonia free from carbonate.* A white 
precipitate shews phosphate of lime or magnesia, 
or both. 

h. The filtered liquid is tested by oxalate of 
ammonia; if lime be still in solution, a white 
cloud falls. 

i. The oxalate of lime is separated by filtra- 
tion and phosphate of soda or ammonia added ; 
brisk stirring with a glass rod causes a white 


* The absence of carbonic acid is easily ascer- 
tained by adding some lime-water to the solution 
of ammonia; it ought to remain perfectly transpa- 
rent; opalescence indicates the existence of carbo- 

_ hic acid, 
3 F 


802 ORGANIC 


crystalline precipitate if any magnesia were 
still contained in the liquid. 

k. A portion of the original liquid (6) is 
acidulated with a drop or two of hydrochloric 
acid ; if sulphuric or phosphoric acid have been 
detected (by ¢ and e), chloride of barium in slight 
excess is added, the solution filtered, heated, 
and precipitated by a mixture of caustic and car- 
bonate of ammonia ; it is again filtered, the 
liquid evaporated to dryness and ignited, the 
residue dissolved in alcohol, and sufficient alco- 
holic solution of bichloride of platinum added 
to eceene a yellow liquid: a yellow precipitate 
indicates potash. If no sulphuric or phosphoric 
acid be present, the use of the chloride of ba- 
rium and ammonia will become unnecessary. 

l.. Decant the yellow solution just obtained 
(k) from the precipitate, if there be any, and 
allow it to evaporate spontaneously or at a very 
gentle heat. If soda be present, !ong prismatic 
yellow needles of the double chloride of pla- 
tinum and sodium form. This is the best test 
of the presence of soda. The yellow tint which 
its salts communicate to the exterior flame of 
the blowpipe, when heated on a platinum wire, 
has been proposed, but this is by no means an 
unequivocal appearance. Almost all the animal 
fluids contain soda in the form of common salt. 

B m. The insoluble fixed residue (B) may 
contain phosphates and carbonates of lime and 
magnesia, as well as phosphate and oxide of 
iron, and traces of silica. The residue is treated 
with nitric acid, by which every thing but the 
silica is dissolved. Carbonic acid, if present, 
is manifested by effervescence. 

n. The solution is diluted and filtered; to 
one portion ammonia free from carbonic aeid 
is added ; if phosphoric acid be present, a preci- 
pitate occurs whilst the liquid still remains 
acid; under these circumstances ammonia is 
added as long as the precipitate at first formed 
re-dissolves in the solution, still acid. Ifa solu- 
tion of acetate of lead, carefully dropped in, 
cause a white precipitate, soluble in nitric acid, 
and which if collected and dried fuses before 
the blowpipe into a semi-transparent bead, 
which assumes a crystalline structure on cool- 
ing, phosphoric acid is indicated by the phos- 
phate of lead thus obtained. 

o. Another portion of the acid liquid is neu- 
tralized by ammonia, and the precipitate, if any 
occur, re-dissolved by acetic acid. Ovxalate of 
ammonia shews lime by the formation of a 
white precipitate. 

p- To the liquid filtered from the oxalate of 
lime carbonate of ammonia is added in slight 
excess; if the previous examination’ have 
shewn phosphoric acid to exist, a crystalline 
precipitate indicates the double phosphate of 
ammonia and magnesia. If no precipitate be 
thus obtained, boil the liquid, and the magnesia 
in solution falls as carbonate. 

g. Oxide of iron is detected instantly by 
adding a drop of solution of ferrocyanide of po- 
tassium to the acid solution: an immediate Prus- 
sian blue precipitate shews iron, if present. The 
precipitates obtained in the previous experi 
ments for lime and magnesia will, instead of 
being white have a more or less decided rusty 


ANALYSIS. 


brown tint, especially when dry, if iron form 
any considerable part of the matter examined. 

For the detection of iodine, lead, and the 
other bodies enumerated in the list of inorganic — 
substances for which we may occasionally have 
to look, the reader is referred to the followin 
directions for the quantitative estimation of the 
different compounds. ” 

Quantitative estimation. 

For the convenience of analysis our sa 
matter may be divided into two portions, one 
of which is employed for determining the acids, 
the other for the bases. The first portion 
enable us to ascertain the quantity of carboni 
and phosphoric acids, of chlorine, and of s1 
phuric acid. From the second portion w 
obtain the potash, soda, lime, magnesia, iro! 
and alumina, if, as rarely occurs, the latter b 
present. 

Other ingredients will usually be matter ¢ 
special examination ; the details of the meth 
to be pursued are subjoined. 

We begin by treating the salts to be 
mined with water (solution A). Nothing 
carbonates and phosphates of the earths 
thus remain undissolved (residue B). "4 

(A.) Carbonic acid.—The aqueous solution 
treated with lime-water, or with a mixture 
ammonia and nitrate of lime, as long 
precipitate is produced. If no phosphates 
present, this consists of carbonate of lin 
the solution is boiled—filtered, the p 
ignited, and after adding a few drops of str 
solution of carbonate of ammonia heated be 
redness and weighed, 100 grs. of carbonate 
lime indicate 44 of carbonic acid When ph 
phates are present, we proceed as follows + 

Phosphoric acid—The precipitate ob 
by lime-water, as thus directed, contains 
phosphoric acid that may be present. 
fore phosphates existed in our solution, the: 
cipitate, after its weight” has been ¢ 
ascertained, must be dissolved in nitrie 
and caustic ammonia (free from carboni¢ 
added in slight excess. The phosphe 
separates as a gelatinous precipitate of j 
phate of lime. It must be ignited am 
weight deducted from that of the mi: 
cipitate previously obtained ; the differen 
dicates the quantity of carbonate of lime: 
precipitated phosphate of lime contains 
per 100 of phosphoric acid. Phosphate oi 
dissolves in nitric, hydrochloric, or aceti 
without effervescence, and is thrown dow 
ammonia in a gelatinous form. The | 
phates and carbonates being thus 
the filtered solution is treated for, 

Hydrochloric acid— The quantity 0 
acid or of the chlorine it contains maj 
be determined by precipitating the 80 
pretty strongly acidulated with nitri 
means of nitrate of silver. The eh 
silver thus obtained is completely se 
ammonia, but resists the action of str 
acid even when boiling. The precipita 
be ignited; it should undergo fusi 
horny mass at a heat a little below 
Tt is now weighed; 100 parts indic 
chlorine. "1 


. 
PCIT 


— 


\ 


ORGANIC 


___ Sulphuric acid may be precipitated from the 
filtered liquid or from any fluid suspected to 
contain it by acidulating (if not already acid), 
not too strongly, with nitric acid, and preci- 
pitating with nitrate of baryta. The preci- 
pitate should be well washed with boiling 
water as long as any thing is dissolved, then 
ignited and weighed. Boiling nitric acid is 
without effect upon it; 100 grs. contain 34.19 
of sulphuric acid. 

(B.) The insoluble portion consists of carbo- 
nates and phosphates of the earths, and per- 
haps of iron. We bring them into solution 
by means of nitric acid, and supersaturate 
with caustic ammonia to separate the phos- 
phates; filter if necessary, and add oxalate of 
ammonia; collect and ignite the precipitate, 
moisten with solution of carbonate of am- 
monia; it is once more heated to incipient 
redness, and it then consists of carbonate of 
lime: the carbonic acid is estimated in the 
manner already directed. The filtered liquid 
is boiled with solution of carbonate of am- 
monia; the magnesia, if any, precipitates and 
must be strongly ignited; 100 parts indicate 
110 of carbonic acid, which must be added to 
that combined with the lime. 

Phosphoric acid—The quantitative estima- 
tion of this body is attended with some dif- 
ficulty, as it cannot be effected by direct oe 
cipitation, but is inferred from the loss. e 
precipitate by caustic ammonia just obtained 
consists entirely of earthy phosphates and phos- 
phate of iron. It is ignited and the weight 
ascertained. It is then brought into solution 
by means of concentrated hydrochloric acid, and 
ammonia’added until the precipitate from the 
Still acid solution is no longer perfectly re- 
dissolved. Acetic acid is now added and then 
More ammonia, taking care that the liquid is 
still strongly acid. Phosphate of iron alone 
precipitates; this is separated by filtration, and 
after strong ignition consists of 57.44 phos- 
phoric acid and 42.56 sesquioxide of iron. 
From the filtered liquid the lime and mag- 
hesia are separated by oxalate of ammonia and 
austic ammonia, as will presently be de- 
ribed ; then deducting the united weight of 
he oxide of iron, lime, and magnesia from that 
of the ignited mixed phosphates, the remainder 
$ phosphoric acid. 

+ order to bring the tests for analogous 

odies together, I shall here interrupt the course 

f the analysis to describe the methods of pro- 

eeding with those substances for which occa- 
ionally, though more rarely, we have to look. 
Todine, in organic fluids, always occurs in 

née form of an iodide, and is not met with in 
ne human body in its normal condition. We 
ust evaporate to dryness and treat the residue 
ith alcohol. The iodide will be dissolved ; 
® again evaporate to dryness and re-dissolve 
water: (if the quantity be not very minute, 
is preliminary process may be dispensed 
ith, merely concentrating the liquid and 

Owing it to cool;) iodine may now be 
tected by adding a little cold solution of 

, and pouring into the mixture a few 

ps of solution either of chlorine or of chlo- 


ANALYSIS. 803 


ride of lime (bleaching liquor), when a blue 
colour, more or less intense, is produced. The 
quantitative estimation of iodine in these ana- 
lyses is seldom required ; when it is, a neutral 
solution of chloride of palladium is added to 
the solution, accurately neutralized, and the 
whole set aside in a warm place for twenty- 
four hours, a black precipitate of iodide of pal- 
ladium forms: it should be collected on a 
weighed filter and dried at a very gentle heat, 
otherwise part of the iodine escapes. 100 grs. 
of iodide of palladium contain 70 of iodine. 
By suspending this iodide in water and adding 
starch and a little chlorine water, the blue 
colour is produced as usual. 

Fluorine, when present, and it appears to be 
a universal constituent of bones, is always in 
exceedingly minute quantity. To discover it 
we incinerate the dried matter, pulverize and 
make it into a thin cream with oil of vitriol in 
a shallow platinum crucible; instead of its 
usual cover the mouth is closed by a piece of 
flat glass, the under surface of which has been 
covered with a film of melted bees’ wax or 
some resinous varnish ; when firm or dry, a few 
characters are traced with a sharp point to 
expose the glass underneath; the glass: is 
pressed upon the crucible so as completely to 
close it, and the whole heated over a spirit- 
lamp for a quarter of anhour. The glass 
is kept cool by a piece of moistened paper. 
If any fluorine be present, the traces upon the 
glass from which the wax has been removed 
will be more or less corroded ; the superfluous 
wax may be removed by oil of turpentine, and 
the corrosion may be rendered distinct by 
rubbing a little powdered charcoal over the 
surface. If any marks are produced, it is an 
unequivocal proof of the presence of fluorine. 
This method, however, is not very delicate. 

Free sulphur is detected by boiling the sub- 
stance with solution of potash; if this element 
be present in the unoxidized state, a black pre- 
cipitate of sulphuret of lead is formed on add- 
ing a few drops of acetate of lead. 

If we desire to know the quantity of free 
sulphur, we first satisfy ourselves of the ab- 
sence of sulphuric acid, or determine its quan- 
tity accurately by the method already de- 
scribed ; then deflagrate the substance or dry 
residue with eight parts of pure nitre and two 
of pure carbonate of potash, throwing the mixture 
in successive small portions into a platinum 
crucible heated to redness; the sulphur is thus 
converted into sulphuric acid at the expense of 
the oxygen of the nitre, and its quantity may 
be determined by dissolving the saline residue 
in water, supersaturating with nitric acid, and 
precipitating by a salt of baryta as usual: the 
process is one requiring more than ordinary 
care to ensure accuracy. 

To resume the usual process of analysis, we 
now proceed to determine the bases. Most 
of the acids may be determined with consi- 
-derable exactness before the organic matter has 
been destroyed by ignition; it is not so with 
the bases. Incineration should always precede 
an attempt to estimate them. The second por- 
tion of saline matter is dissolved in water as 

3 F2 


804 


before, separating it thus into a solution (A), 
and an insoluble residue (B). 

(A.) Potash —The solution rarely contains any 
but the alkaline salts. If, however, any of the 
earths are present, they must first be separated 
in the form of carbonates, by adding a mix- 
ture of carbonate and caustic ammonia; the 
filtered liquid is evaporated to dryness, the 
residue ignited to expel ammoniacal com- 
pounds and re-dissolved in water, which then 
contains only salts of potash and soda. If 
sulphuric or phosphoric acids be present, it is 
necessary for a quantitative determination of 
each alkali to convert the mixed sulphates or 
phosphates into chlorides. The method for 
accomplishing this object is rather circuitous : 


chloride of barium in slight excess is added to — 


the solution, which is filtered from the sulphate 
or phosphate of baryta that then precipitates ; 
the filtered liquid is heated with a mixture of 
caustic and carbonate of ammonia, again fil- 
tered, evaporated to dryness, and ignited ; the 
bases are thus obtained in their desired con- 
dition of chlorides; they are then carefully 
weighed, re-dissolved in a small quantity of 
water; bichloride of platinum in solution is 
added, and the whole evaporated to dryness on 
a water-bath. The dry residue is digested with 
rectified spirit, and the washing continued as 
long as the liquid passes coloured through the 
filter; the precipitate, consisting of anhydrous 
double chloride of platinum and potassium, is 
dried and weighed ; 100 grs. indicate 19.43 of 
tash. 

Soda.—After the potash has been determined, 
the corresponding quantity of chloride of pot- 
assium is deducted from the weight of the mixed 
chlorides, and the deficiency inferred to be chlo- 
ride of sodium; 100 grs. of chloride of sodium 
correspond to 53.33 of the anhydrous alkali. 
The platino-chloride of sodium, which the 
alcoholic solution contains, crystallizes in bold, 
well defined, flattened prisms readily soluble 
in water. 

Ammonia, when present in organic fluids, 
cannot be quantitatively determined with ac- 
curacy. Its presence is easily recognized by 
the characteristic pungent fumes which are 
given off when the residue of evaporation is 
mixed with caustic potash and gently warmed. 

(B.) Iron.—The precipitate by carbonate and 
caustic ammonia from A and the insoluble re- 
sidue B are dissolved in hydrochloric acid. 
When no phosphates are present, the acid 
solution is nearly neutralized by caustic am- 
monia; then an excess of hydro-sulphuret of 
ammonia added; the iron falls as a black sul- 
phuret. This is collected on a filter, washed, 
re-dissolved in! hot hydrochloric acid, and the 
iron thrown down as sesquioxide by ammonia 
in excess. It is thus completely separated from 
lime and magnesia.* 


* In the rare instances in which alumina presents 
itself in the animal fluids, this earth would pre- 
cipitate along with the sulphuret of iron, and would 
again be thrown down with the sesquioxide. It is 
however easily separated by digesting the oxide 
while still moist in a solution of caustic potash ; 
the oxide of iron alone remains behind. ‘To sepa- 
rate alumina from the alkaline liquid, it is feebly 


ORGANIC ANALYSIS. 


If the earthy phosphates are present in mix- 
ture with iron, the process already described, 
when speaking of phosphoric acid, must be 
employed. 

ime—The acetic solution of the phos- 
phates filtered from the iron, or if no iron be — 
present, the acid solution supersaturated with 
ammonia and the precipitate re-dissolved in 
acetic acid, (a precaution indispensable, as 
‘oxalate of lime is soluble in nitric or hydro- — 
chloric acids,) is treated with solution of ox- 
alate of ammonia in excess. A white precipitate — 
of oxalate of lime falls; it is allowed to 
some hours in a warm place (the ieee would 
otherwise pass turbid through the filter), sepa- 
rated by filtration, ignited, and then moistened 
with a saturated solution of carbonate of am= 
monia, after which it is thoroughly dried ata 
temperature short of redness. Carbonate of 
lime is thus obtained; 100 grs. contain 56 of 
pure lime. ‘ 

Magnesia.—The filtered liquid is super 
saturated with ammonia, well agitated, and : 
lowed to stand for some hours; if any mag: 
nesia be present, it separates as a crystallin 
precipitate, which must be washed with 
weak solution of phosphate of ammonia; it” 
dried and ignited ; the residue contains 35.7 
of magnesia in every 100 grs. , 

Our ordinary analysis terminates here. 

Lead is sometimes found as a morbid ca 
stituent of certain parts, more particularly ¢ 
the soft solids; the fluid or part to be examin 
is dried and incinerated, (if bulky, in a ele 
earthen crucible,) and the c 2c 
as far as may be; the residue is digested 
nitric acid diluted with thrice its bulk of wi 
filtered, nearly neutralized by ammonia, ai 
current of sulphuretted hydrogen transmit 
through the liquid. The gas is easily g 
rated for this purpose by adapting to a e¢ 
mon phiat a glass tube bent twice at f 
angles, one limb being considerably le 
than the other; the short limb aint 
through the cork of the phial, and the ‘ 

lunges nearly to the bottom of the liqui 
he examined. In the phial 100 or 200 
of coarsely bruised proto-sulphuret of 
are placed, and an ounce or two of | 
sulphuric acid (1 of acid and 5 or 6 of w 
abundant effervescence arises from 
engagement of the sulphuretted 
If lead be present in the tested liquid, a 
or black precipitate of sulphuret of 
and the liquid becomes milky from the 
decomposition of the gas; when it” 
strongly of the sulphuretted hydrogt 
liquid is filtered, the precipitate is tre 
nitric acid, to which a few drops of su 
acid have been added, and the whole 
a white residue of sulphate of lead is ol 
which contains 68.42 per cent. of 
lead. Sulphate of lead is insoluble i 
acid, but is completely dissolved by 
solution of acetate of ammonia. __ 


supersaturated with hydrochloric , a 
rendered slightly alkaline by ammonia ; thea 
precipitates, is collected on a filter, th 
washed, ignited, and weighed. 


ORGANIC 


The presence of copper is determined in the 
same way by incineration, treatment with nitric 
acid and sulphuretted hydrogen ; the resulting 
sulphuret is dissolved in nitric acid, and the 
oxide thrown down from the boiling solution 
by excess of caustic potash: it is ignited and 
weighed; 100 parts contain 80 of metallic 
copper. If the nitrate of copper be treated 
with ammonia instead of potash in excess, a 
beautiful transparent blue solution is obtained, 
which, when procured as just mentioned, is 
characteristic of the presence of copper. 

Mercury, arsenic, antimony, and a variety 
of other substances may occasionally be met 
with after poisoning with these bodies; but 
abundant directions for their discovery are 
given in the works on Toxicology, and to these, 
and in particular to the excellent treatise of 
Dr. Christison, the reader is referred. 

_B. ANaLysIs OF ANIMAL SOLIDS. 

Solid matters, as tumours, concretions, and 
sediments, are best subjected to a preliminary 
test by the action of heat; the sediments are 
separated by filtration from the liquids in 
which they are deposited ; by ignition on plati- 
num foil of a few small fragments we observe 
either, 

1. It is wholly or almost wholly dissipated, 
in which case it consists of, 

Cholesterin, which fuses and burns with 
flame ; 

Uric acid, or which are gradually dissi- 

Urate ammonia, § pated, producing transient 
blackening of the foil around ; 

Cystic oxide, which is consumed with a pe- 
culiar odour; 

_ Albumen, fibrin, or hairs, which swell up 

and burn with flame: 

__ 2. Or it blackens, leaving a less bulky re- 

idue ; 

_ In which case it may be 

_Urate of soda, potash, . they leave an alka- 
_ Lime, or magnesia, ‘§ line ash, which in 

the two first fuses at a red heat, or it may arise 

Tom a mixture of some of the preceding list 

with some of those that follow. 

_ 3. Or, lastly, it undergoes little or no change 

n bulk, when it is composed of 

Phosphates of the earths ; 

Carbonate of lime, or magnesia ; 

Oxalate of lime, which generally decrepi- 


_ Having by these simple trials acquired some 
mowledge of the nature of the substance we 
ave to deal with, we proceed to a more spe- 
jal examination. 
a. Cholesterin is the principal constituent of 
lliary calculi in the human subject, mixed 
ith variable proportions of colouring matter. 
ese calculi, when numerous, generally pre- 
facettes more or less flattened and po- 
hed ; when solitary, they often attain consi- 
able bulk, and are usually crystalline and 
mitransparent on the surface. Before the 
owpipe they fuse and burn with a bright 
noky flame, leaving but little ash. Boiling 
hol dissolves the cholesterin, and on cool- 
3 deposits the greater part in pearly glisten- 


ANALYSIS. 805 


ing scales. Caustic potash dissolves. the co- 
louring matter and leaves the cholesterin. This 
last reaction distinguishes it from other fats, 
and particularly from lithofellic acid, recently 
discovered as an occasional constituent of be- 
zoars and of gall-stones in the inferior animals ; 
the lithofellic acid fuses at a higher tempera- 
ture than cholesterin, and separates from its 
alkaline solution as an insoluble fat on neu- 
tralizing by a stronger acid. 

b. Uric acid generally assumes the form of a 
reddish-brown crystalline sand, or of lighter- 
coloured rounded masses. Before the blow- 
pipe it blackens and burns away, leaving only 
a minute trace of ash, usually alkaline, owing 
to the presence of a very small quantity of lime 
or soda. The manner of applying nitric acid, 
so as to produce the characteristic colour from 
the decomposition of uric acid, has been al- 
ready mentioned. When powdered it dissolves . 
completely in solution of potash by the aid of 
heat, and if the solution be supersaturated 
with hydrochloric acid, uric acid again preci- 
pitates in minute white crystals. 

The urates are much more soluble in hot 
water than uncombined uric acid: they form 
amorphous deposits usually of a light brown 
colour. 

Urate of ammonia before the blowpipe pre- 
sents phenomena resembling uric acid; when 
rubbed with solution of caustic potash, ammo- 
niacal fumes are emitted. In its other reac- 
tions, except that it is more soluble in boiling 
water, it closely resembles uric acid. 

Urate of soda is distinguished by the large 
proportion of fusible alkaline ash left on igni- 
tion after the application of a red heat; the 
residue dissolves with effervescence in hydro- 
chloric acid and gives no precipitate when this 
solution is treated with an alcoholic solution of 
chloride of platinum. If potash were present, 
it would be indicated by the formation of crys- 
tals on adding this test. 

Urate of lime occasionally accompanies uric 
acid ; the residue by incineration then yields the 
usual reactions of lime, such as a precipitate 
with oxalate of ammonia when added to a 
solution of the ash in acetic acid. 

c. Cystic oxide is wholly dissipated by heat, 
emitting a peculiar odour. - It is soluble readily 
both in acids and alkalies, and is deposited in 
hexagonal plates by spontaneous evaporation 
of its ammoniacal solution. The peculiar form 
of its crystal is at once recognized by the em- 
ployment of the microscope. 

d. Albumen and fibrin are discovered by 
their solubility in diluted alkalies and in acetic 
acid. Neutralization causes a flocculent preci- 
pitate soluble in excess of acetic acid or of the 
alkalies ; the acetic solution gives a precipitate 
on adding ferrocyanide of potassium. Before 
the blowpipe they swell up, leaving a bulky 
coal which burns with difficulty to a small 
white or yellowish ash; they always contain 
saline matter. Albumen and fibrin, in com- 
mon with all the compounds of protein, are 
further characterized by dissulving slowly in 
the concentrated acids; with sulphuric acid a 


806 


crimson liquid is obtained, with nitric a yellow 
solution attended with effervescence during the 
action, and with hydrochloric acid a character- 
istic violet-coloured liquid is procured. 

e. The gelatinous tissues may be shewn to be 
such by continued boiling in water for twenty- 
four or forty-eight hours; the liquid, if not too 
dilute, has then the property of gelatinizing on 
cooling; with infusion of galls it should pro- 
duce an abundant flocculent buff-coloured pre- 
cipitate. 

J. Sometimes we meet with concretions formed 
principally of Aairs; their texture and appear- 
ance generally betray their composition. Be- 
fore the blowpipe they are dissipated with the 
well-known smell of burnt feathers. Solution 
of potash dissolves them slowly, and the liquid 
then gives the reactions furnished by alkaline 
solutions of albumen. 

g. Earthy phosphates—Phosphate of lime 
rarely occurs alone, either as a sediment or cal- 
culus; though in combination with others it is 
one of the most usual constituents of morbid 
concretions. Before the blowpipe, unless mixed 
with animal matters, it undergoes little change ; 
usually a transient blackening appears from the 
charring of a little organic matter always pre- 
sent; by continuing the heat it becomes white. 
Nitric acid dissolves it readily, and phosphoric 
acid may be shewn by adding acetate of lead 
as directed when speaking of the detection of 
phosphoric acid. Ammonia in excess added 
to the acid solution causes a bulky gelatinous 
precipitate of bone earth; on redissolving in 
acetic acid, and adding oxalate of ammonia, 
we obtain abundance of oxalate of lime. 

Phosphate of ammonia and magnesia, or, as 
it is frequently termed, triple phosphate, is a 
common constituent of calculi and of white 
sand; when in the form of a sediment it ge- 
nerally occurs in hemihedral six-sided prisms ; 
heated before the blowpipe it emits ammonia, 
agglutinates, but is almost infusible; the addi- 
tion of a fourth or a sixth of its bulk of phos- 
phate of lime, as a shaving of bone or ivory, 
causes its immediate fusion to a white enamel- 
like bead. It is soluble in acids, and ammo- 
nia causes a crystalline precipitate of unchanged 
phosphate ; a horic acid may be discovered 
by acetate of lead as before; oxalate of ammo- 
nia causes no precipitate in the acetic solution 
unless lime be present. 

Not unfrequently these two kinds are mixed, 
constituting what has been termed the fusible 
calculus, from its property of forming the ena- 
mel-like bead before the blowpipe just men- 
tioned. Heated with potash it evolves ammo- 
nia. Phosphoric acid and lime may be shown 
as before. After the separation of lime b 
oxalate of ammonia, supersaturation wit! 
ammonia throws down the crystalline phos- 

hate of ammonia and magnesia. 

h. Carbonate of lime.—These calculi be- 
fore the blowpipe are converted into caustic 
lime, and then give a brown stain to turmeric 
paper. In dilute nitric or hydrochloric acid 
they dissolve with effervescence. Lime may 
be shown in the solution by appropriate tests. 


ORGANIC ANALYSIS. 


i. Oxalate of lime is now and then met 
with, forming a gravel crystallized in pale 
amber-coloured prisms, but usually in the — 
form of larger concretions, from their tuber- 
culated exterior termed mulberry calculi; for 
the most they have a dark brown or ma- 
hogany colour. Heated moderately before the 
blowpipe they yield a white ash, ing 
principally of carbonate of lime, and dissolving 
with effervescence in acids. If the heat be 
greater, quicklime alone remains. It stain: 
turmeric paper brown when moistened. Lim 
may be detected in the ash by the usual 
agents. Oxalate of lime, when powdered, di 
solves in nitric acid readily, more sparing 
hydrochloric acid. Ammonia throws it doy 
unchanged from these solutions, and the pre: 
pitate is insoluble in acetic acid. 

The whole of the preceding experiments ma 
be made upon portions of matter not exceedin 
two grains, and most upon a quantity mue 
smaller, especially if our examinations 
aided by the microscope. Examinations | 
these matters are rarely quantitative; the sm 
quantity of material procurable, and an unw 
ingness to sacrifice morbid products of t 
description for the purposes of analysis, prev 
us from possessing information so full a 
detailed upon the constituents of concretit 
in general as the numerous collections in e 
tence would have led us to expect. 

Calculi, especially urinary calculi, ar 
from presenting a uniform and homoger 
structure throughout, being in many if n 
most cases composed of lamine differing m 
rially in composition. It would be of I 
value to the pathologist to know the cor 
nents of all the different layers mingled 
criminately ; the information he would deri 
to the process by which the stone was for 
and of the means by which tendencies to. 
formations might be counteracted, would | 
the most confused and indefinite deseri 
tending rather to mislead than to aid h 
forming correct conclusions. Just so it i 
chemical analysis is applied to organize 
tures in general without due regard to the 
ture and disposition of the proximate 
within them; and hence the confused n 
of substances obtained by subjecting the 
whole to the action of chemical agents. 
texture, however, once known, and the 
of our reagents upon it being watched 
the field of the microscope, we can at pl 
separate the different ingredients, and 
with comparatively little difficulty, ~ 
which are fixed and producible at will; 
which strictly belong to the domain of & 
to whose enlargement and successful cult 
they then really contribute. ‘s 

When soft tumours or malignant grov 
submitted to our examination, one portiol 
as usual be carefully desiccated, to di 
the proportion of moisture ; and anothe 
being shred finely, macerated for some 
with water at a temperature not exceedr 
F.; in this way the soluble albumen 
separated from the fibrous and other 


. 
ODSISLUD ‘ 


tne 


it > 


ee cee oe ee ee eS eS eee 


ORGANIC 


matters. The analysis must afterwards be pro- 

ceeded with upon the principles already laid 

down, being first directed to the soluble ingre- 
dients and then to the insoluble matters. 

C. ProximaTr ANALYSIS OF INDIVIDUAL 

SECRETIONS. 
1. Of the urine. 

The following is a detailed example of the 
method of analysing healthy urine:— 

As there was abundance of the fluid for exa- 
mination, fresh portions were taken whenever 
it seemed desirable to do so for determining 
any particular ingredient. 

* The secretion had a sp. gr. of 1020.4. It 

distinctly reddened litmus paper, and exhi- 

bited a slight cloud of floating mucus. 

(@) 3200 grs. were filtered through a weighed 
filter, and the mucus collected. It amounted 
to 0.53 grs. 

3200 : 1000 : : 0.53 : 2 (= 0.165) mucus. 

(b) 200 grs. evaporated in a counterpoised 

capsule left 8.64 grs. 

200 : 1000 : : 8.64 : # (= 43.2) solid mat- 

ters. 

1000 — 43.2 = 956.8 water. 

_ (©) The residue, 8.64 after evaporation, ig- 

nited in the capsule left 2.36 grs. of saline 

matter. 

200 : 1000 : : 2.36 : w (= 11.8) fized salts. 

(d) 1000 grs. of urine (freed from mucus by 

filtration) was evaporated to dryness in a pla- 
tinum capsule. It was treated with water, 
acidulated with hydrochloric acid, and left 
0.37 grs. of uric acid; after incineration of the 
uric acid a trace of silica remained. 

(e) During the last three years I have made 
Many careful analyses of the urine with express 
attempts to obtain from it the lactic acid it 
is said to contain; but though I employed 
various methods, and in some instances large 
eras of urine, I have never succeeded in 
eliminating it from fresh urine, and I therefore 
(as the methods used were capable of detecting 
small quantities of the lactates when purposely. 
mingled with the urine) concluded that lactic 
acid is not a normal constituent of human 
urine. Liebig has lately stated the same fact 
founded on his own recent examinations of the 
ecretion. 

(7) 1000 grs. of urine were evaporated to 
dryness and exhausted with alcohol. This 
Icoholic solution was evaporated, the dry mass 
reated with water, and nitric acid added, 
ith the precautions already mentioned, fur- 
aished 29.17 grs. of nitrate of urea. 

100 : 29.17 : : 48.78: « (= 14.23) urea. 
_(g) The residue after exhaustion with alco- 
aol weighed 6.6 grs. It was ignited, and left 
Saline mass, amounting to 4.46 grs. 
6.6—4.46 = 2.14 organic matter. 

‘rom this we deduct the uric acid 0.37 (d), and 
acus 0.165 (a), the residue 1.605, is “ watery 
wtract. 

(h) The portion soluble in alcohol amounts 
».43.2—6.6, or 36.6 grs., which we find com- 
osed as follows: 

The total saline matter of the urine (in- 
uding the sulphuric acid volatilized by igni- 
on (r)) 


ANALYSIS. 807 
amounts to, .13.388 grs. (= 11.8 + 1.588) 


deduct .... 4.46 salts insoluble in 
alcohol (g) 
remain .... 8.928 salts dissolved by 
alcohol. 
fixed salts .... 8.928 
UFEA seoeeeee 14.230 by (f) 
mur.ammonia 0.915 by (v) 
24.073 


36.6 —24.073= 12.527 alcoholic extract. 


The composition of the urinary salts has now 
to be determined. 

(2) 1000 grs. of urine were acidulated with 
nitric acid, and mixed with a solution of ni- 
trate of silver, an abundant precipitate of 
chloride of silverensued. 

The filter with the precipitate weighed 39.13 

The filter alone.....scccesscecevs 15.23 


Total wt. of the chloride before fusion 23.90 


23.12 of chloride fused in a counterpoised 
porcelain capsule gave 19.12 grs., weight of 
chloride after fusion. 

23.12 : 23.90 :: 19.12: # (= 19.77) fused 

chloride silver. 

100 : 19.77 : : 25: a (= 4.942) chlorine. 

(k) The filtered liquid was treated with 
nitrate of baryta, the precipitate collected, well 
washed with boiling water, ignited, weighed 
4.97 grs. 

100 : 4.97 : : 34.19 : x (= 1.702) sulphuric 

acid, 

(2) 1000 grs. of urine were supersaturated 
with ammonia; a bulky precipitate of the 
earthy phosphates fell, which after ignition 
weighed 0.65 grs. 

(m) The filtered liquid supersaturated with 
lime-water gave a precipitate, which weighed 
after ignition 3.57 grs. : 

100 : 3.57 : : 49.1 : w (= 1.753) phosphoric 
acid, which is in combination with al- 
kaline bases. 

To determine the bases a considerable por- 
tion of urine was evaporated, and the residue 
burned to whiteness. 

(n) 41.5 grs. of the saline residuum left 
2.45 grs. insoluble in water. 

41.5 —2.45 = 39.05 alkaline salts. 

41.5 : 11.8 (c):: 2.45 : 0.6956 insoluble 

salts in 1000 urine; by (1) we found the 
earthy phosphates 0.65. 

11.8 — 0.7 = 11.1 alkaline salts per 1000 
urine. 

(0) The insoluble portion dissolved in a little 
nitric acid, supersaturated with ammonia and 
redissolved in acetic acid, gave by oxalate of 
ammonia a precipitate which yielded on igni- 
tion 1.32 grs. carbonate of lime. 

2.45 : 0.6956 :: 1.32 : x (= 0.3753) carb. 

lime. 

100 : 0.3753 : : 56 : x (= 0.2101) lime. 

(p) The solution filtered from the oxalate of 
lime and supersaturated by ammonia gave, on 
agitation followed by repose for some hours, 
a crystalline precipitate, weighing 1.18 grs, 
after ignition. 


“ 


808 


2.45 : 0.6956: : 1.18: # (= 0.3345) 
100 : 0.3345: : 35.71 : # (=0.1198) mag- 


nesia. 

(q) 0.6956 — (0.2101 + 0.1198) = 0.3659 

phosphoric acid with the earths. 

0.3659 + 1.753 (m) = 2.1189 total phos- 

phoric acid in 1000. 

(r) 15 grs. of thealkaline salts (m) were dis- 
solved in water and converted into chlorides 
by admixture with chloride of barium in ex- 
cess; a precipitate of 6.4 grs. of sulphate and 
phosphate of baryta formed ; on treating this 

recipitate with nitric acid, 0.45 sulphate of 

remained. 

15 : 11.1 (nm) : 045 : 0.333. 

100 : 0.333 : : 34.19 : 0.114 sulphuric acid 
in the ash, from 1000 parts of urine. 

But 1000 grs. of urine we found (by &) to 
contain 1.702 grs. sulphuric acid, therefore 
1.702 — 0.114 = 1.588 grs. of sulphuric acid 
have been expelled by ignition. 

(s) The filtered solution was heated with 
caustic and carbonated ammonia to precipitate 
the excess of baryta as carbonate. The whole 
filtered, evaporated to dryness, and ignited to 
expel the ammoniacal salts. ‘The fixed chlo- 
rides weighed 14 grs. They were dissolved in 
water, treated with bichloride of platinum, eva- 
porated nearly to dryness by a water-bath, 
then treated with alcohol, the platino-chloride 
of potassium amounted to 13.40 grs. 

15. : 11.1.:.:.18.40 : 9.916. 

100 : 9.916 : 19.43 : : (= 1.926) potash. 

© But 247, (1 eqt. platino-chlor. potassium) 

: 13.40 : : 76, (1 eqt. chlor. potassium) 
sa (=A: 123) chloride potassium, and 
14— 4.123 = 9.877 chloride sodium. 

15:11.1:: 9.877: 2 (= 7.3089) chloride 
sodium, 

and 60, (1 eqt.chlor. sodium) : 7.3089 :: 24 
(1 eqt. sodium) : x (= 2.9235) sodium. 

(u) 10 grs. of the alkaline salts were dis- 
solved in water, the solution acidulated with 
nitric acid, and nitrate of silver added in slight 
excess: the precipitate of chloride of silver 
amounted to 15.61 grs. 

10 : 11.1 :: 15.61: 2 (= 17.3271) 

100 : 17.3271 :: 25: # (= 4.3317) chlo- 
rine in the ashes of 1000 parts of urine. 

We find the equivalent quantity of sodium 
as follows :— 

36 : 4.3317 :: 

_ equivalent to the chlorine. 

The chloride of sodium therefore amounts to 
7.2195 grs.; deducting the sodium com- 
bined with chlorine from the entire quan- 
tity in the urine (¢), we obtain 

2.92356 — 2.8878 = 0.03576, or 0.0536 
soda. 


24: « (= 2.8878) sodium, 


(v) Now before ignition the chlorine (by i) 
amounted to 4.942 grs. 
deduct.... 4.3317 combined with so- 
dium in the ash. 
0.6103 chlorine volatilized, 
probably in the form of muriate of am- 
monia, the amount of which appears by 
the ape calculation : 
0.6103 : 
ammonia. 


36: 


ORGANIC ANALYSIS. 


x (= 0.9154) muriate. 


The results of the analysis are here sub- 


joined. 
sameie hes kira pore 0 
TER wevecs 2900 
*Organic Uric acid... 0.3700 
matters & / Alcoholicext. 12.527 
ammoni- (77°24 Watery ext.. 1.605€ 
acal salts \ Vesical mucus 
Mur. ammonia 
Chlor. sodium 
Phosphe. acid 
Fixed sa- ? Sulphuric acid 
line mat- -13.1494 Lime, eneeee 
ters... 9 Magnesia ... 


Potash. ..... 
Soda 


In analysing diabetic urine the method m 
be modified, as will be seen by the fe Ow 
example. . 

It was feebly acid, and had a a g 
of 1038. 

Evaporated in vacuo over sul 
it furnished a pale amber-colou 
which weighed, 

On the third day.... 55.9 grs. 
sixth ,...6-. 54-1 
BIND 4). 4.0% 53.4 
fourteenth... 53.1 
thirtieth..... 52.2 

The temperature varied between 60° and 
and the vacuum shewed from 1 inch te 
inches on the pressure gauge. 

The presence of even a very small por 
of air materially retards the progress ¢ 
evaporation. 

rom the weight on the thirtieth day 
500 : 1000: : 52.2: 2(= 104.4) 
contents, and 
1000—104.4 = 895.6 water. 

As a contrast to this evaporation in va 
the remainder from 500 grs. was ey - ' 
by water-bath, the temperature never 
above 180° F. 

In 24 hours the residue weighed 


“a4 


48 @ereseeereerer eres ee etee 
72 ecccecce 0066s 00s 
96  @e eres er ene eeeeee ee ae ) 


By this time it had assumed a dee 
colour, and from being soft and s 
with the exception of a small pone 
centre, become hard and brittle; by @: 
to the air it speedily deliquesced ; 30.6 
the dry mass dissolved in water ; 
with 16.7 grs. of yeast, which from th 
poration of another portion was four id te 
tain 3.5 grs. of solid matter. The 
was set aside for four days at a tempera’ 
70° to ferment; gas was slowly di 
when fresh bubbles ceased to form, tl 
tion was evaporated to dryness, anda 
to 25.8 grs.; deducting 3.5 solid ma 
the yeast, we have an unfermentable n 


* The sulpharic acid has been deduce r 
amount of organic matter detexmiiied’ 
and added to that of the saline matters. 


ORGANIC ANALYSIS. 


22.3 grs. out of 30.6, shewing the quantity of 
sugar to have amounted to. only 8.3 grs., instead 
of about 24.5 grs. The foregoing experiment 
shews the impossibility of obtaining an accurate 
result if the solution be evaporated in air even at 
temperatures considerably below 200°. Diabetic 
sugar, in fact, loses by this treatment 5 equiva- 
lents of water, and becomes converted into a spe- 
cies of caramel, insusceptible of fermentation. 
To proceed, however, with the analysis: 
The salts were found by incineration to 
amount to 3.09 per 1000 parts of urine. 
To determine the quantity of sugar, 250 grs. 
of the secretion were mixed with yeast and 
placed in a tall graduated jar capable of con- 
taining 25 cubic inches; filled with mercury, 
_ and inverted in a basin holding that metal, 
The barometer stood at 30.33 
The thermometer ............ fork, 
Air in the jar, which accidentally entered 
during the act of inversion 1.00 cub. in. 
Quantity of fluid........... 1.45 cub. in. 
Exterior level of the mercury 12.33 inches 
below the interior level. 
Tn three days fermentation was complete. 
The barometer then stood at.... 30.34 
The thermometer..... Aviat kalels 80° 
Exterior level of the mercury 1.14 below 
that of the interior. 
The quantity of gas amounted to 19.3 cub.in. 
» adding the bulk of the fluid... 1.45 


We obtain total gas.......... 


Correcting for pressure we obtain 

30 : 30.34 — 1.14 : : 20.75: x (= 20.1828) 
Correcting this again for the temperature, 

528 : 508 : : 20.1828 : x (= 19.41) 

Subjecting the air which was in the jar at 
he commencement of the experiment to. the 
same corrections, in order to deduct, we ob- 


_ For the temperature 

D205. 508.2: 1 : « (=0.9769) 
_ For the pressure , 
30 : 30.33—12.33 :: 0.9769 : x (= 0.586) 
-19.41—0.58 = 18.83 corrected volume 

of carbonic acid. 

Now 100 : 18.83 :: 106.6: x (= 20.072) 
i total number of grs. of sugar in 
F 250 grs. of urine, and 
» 250 : 1000 : : 20.072 : x (= 80.29) sugar. 
The urea was found by a separate analysis ; 
00 grs. were evaporated in vacuo, the residue 
feated with hot absolute alcohol (f.3f3). It 
as allowed to cool in order to deposit part of 
@ sugar, then decanted; this was repeated 
ree or four times. ~The alcoholic solutions 
are evaporated to dryness, re-dissolved in 
ater, and treated with oxalic acid and sub- 
uently with chalk, observing the precautions 
ady enumerated: 1.06 grs. of prismatic 
edles of nearly pure urea were obtained. 
» 500 : 1000 : : 1.06 : « (= 2.12) urea. 
As a comparative experiment 500 grs. were 
aporated by the water-bath and nitric acid 
bstituted for the oxalic; only traces of crystals 
nitrate of urea were thus obtained; a con- 


809 


clusive proof of the superior delicacy of the 
first method. 

The syrupy residue after exhaustion with ab- 
solute alcohol was ith rectified spirit 
as long as any thing dissolved: 2.15 grs. of 
saline matters, uric acid, mucus, and matters 
soluble in water only were left. Hydrochloric 
acid left only 0.04 of uric acid and mucus. 

500 : 1000 : : 0.04 : # (= 0.08) uric acid, 

c 


The acid solution evaporated to dryness and 
incinerated, gave 0.69 grs. 
500 : 1000: : 0°69 : x (= 1.38) salts inso- 
luble in alcohol. 
2.15 — (0.04 + 0.69) = 1.42. 
500 : 1000: : 1.42 : x (= 2.84) watery ex- 
tract. 
By calculation, as in the previous analysis, 
the alcoholic extract is 15.98 grs. 
The composition of the urine is thus deter- 
mined to be 


Water. cree QL: 895.60 
Fined salts: 0. ccce5.c 3 OR 3.09 
: Sugar ....%. 80.29 
Organic r Urea Vay oe fe 2.12 
Pastore 101.31 , Alcoholic extr. 15.98 
Eloshtte ( Watery extract 2.84 
i Uricacid& muc. 0.08 

1000.00 


Where albumen occurs in the urine, we por- 
ceed as in the following instance. 

The fluid was rather turbid, feebly alkaline, 
and of sp. gr. 1013.1. It was found to 
contain 30.2 per 1000 of solid matter, of 
which 9.17 were salts and 21.03 organic vo- 
latile matters. 

500 grs. evaporated to dryness, and the 
residue finely powdered, taking care that none 
of the particles were lost (by placing the 
mortar on a large sheet of paper, and co- 
vering the mouth of it likewise with paper). 
It was treated with boiling water and washed 
as long as any thing dissolved. The insoluble 
portion collectéd on a filter, dried and weighed, 
amounted to 3.1 grs. 

500 : 1000 : : 3.1 : # (= 6.2) albumen, with 

traces of uric acid. 

The filtered liquid was evaporated to dry- 
ness, and treated with alcohol and nitric acid 
for urea in the usual manner: the urea per 
1000 = 4.72 grs. 

The other ingredients were determined as 
usual and furnished the following results. 


Water vad ouete ls. catia is cd's 969.80 

Saline matters .......... wetter 9.17 
Albumen and ’ 

O : { uric acid .. § 6.20 

rganic r] 1 U P 

matters § 21.03 TOR: 6.55 clolee 4.72 

Alcoholic extract 8.43 

Watery extract. . 1.68 

1000.00 


2. Analysis of the blood. 
Unless. present when the blood is drawn, we 
are obliged to proceed as in the following 


810 


example, furnished from a patient sufferin 
from : chronic cerebral affection. : 
(a) The entire blood employed amounted to 
6735 grs.; it had been drawn 24 hours, and 
had formed a tolerably firm but flat coagulum, 
which weighed 3560 grs. The serum that had 
weighed 3175 grs., and had a sp. gr. 
of 1029.3, es a 
The proportions of clot and serum were 
therefore as follows, in 1000 parts. 
6735 : 1000 : : 3560: « (=528.6)coagulum. 
6735 : 1000 : : 3175 : «(= 471.4) serum. 
The analysis divides itself into two portions, 
that of the serum, and that of the clot. 


Analysis of the serum. 


(6) 200 grs. of serum were dried at a tem- 
perature of 212°. The residue amounted to 


18.69grs. 
200 : 1000 :: 18.69 : « (= 93.45) solids 
in serum. 
Therefore 1000 — 93.45 = 906.55, water 
in the serum. 


(c) The residue was incinerated over the cir- 
cular wicked spirit lamp, and amounted to 
1.46 grs. 

200 : 1000 :: 

matters. 

(d) 500 grains of serum were dried in a pla- 
tinum capsule, the dry mass carefully detached, 
pulverized, and digested in boiling ether, which 
was decanted and renewed three or four times. 
The ethereal solutions evaporated left 0.35 grs. 
of fatty matter; of this cold alcohol dissolved 
0.12 oily fat, leaving 0.23 of crystalline fats. 

1000 parts of serum therefore contain 0.24 
oily fat, and 0.46 crystalline fats. 

(e) The undissolved residue was heated to 
expel adhering ether and treated with boiling 
water. It was thrown on a filter and washed 
repeatedly, until nitrate of silver produced an 
insignificant cloud when applied to a few 
drops of the washings. The filter and its con- 
tents were dried; when weighed the albumen 
amounted to 41.73 grs. 

10 grs. when incinerated yielded 0.19 grs. of 

ash ; 10 : 41.73::0.19 : e(= 0.79287.) 

41.73 — 0.793 = 40.937; 40.937 x 2 = 

81.974 albumen. 

(f) The filtered liquid evaporated weighed 
4.66 grs. It was digested with alcohol, which 
was renewed as long as any thing was dis- 
solved. The alcoholic solution evaporated 
amounted to 3.32grs. (If urea, sugar, or bile 
be present, they will be contained in this extract 
and must be sought for in the usual manner.) 

4.66 — 3.32 = 1.34 grs. watery extract, 

1.34 x 2 = 2.68, 1gr. of watery 
extract incinerated left 0.82 grs. of 
salts, and 1. : 2.68: 0.82 : t = 2.197, 
and 2.68 — 2.197 = 0.483 watery 
extract 1000. 

) 1.4 grs. of alcoholic extract, incinerated, 
left 1.00 grs. of saline matter. 

Now 1.4:1 :: 6.64 : x (= 4.74) saline 

matters, 

And 6.64 — 4.74 = 1.90 alcoholic extract 

per 1000, 


1.46 : « (= 7.3) saline 


ORGANIC ANALYSIS. 


The serum therefore consists of } 
Water, 25.00. chan ones 906.550 . 
Fixed saltssicee cath. d3% 7.300 
Albumen ...........4.- 81.974 
Alcoholic extract .....8.. 1.900 
Watery extract .......2.. 0.483 
Fats, oily Core erersces “* 0.240 

»» crystalline ,......... 0.460 
998.907 
Analysis of the clot. 4 

(hk) 1000 grs. shred finely with a sharp knife 

were tied in a piece of calico and washed till 


colourless under a gentle stream of water. 
The fibrin that remained carefully dried at 212° 
weighed 5.67 grs. - 
Ether dissolved from this 0.07 grs. of oily fat. — 
The pure fibrin therefore amounted to 5.60 grs. 
1000 : 528.6 : : 5.6 : x (= 2.962) fibrin. 
1000 : 528.6 by (a) : : 0.07: (= 0.04) © 
Sat from firm. q 
(i) 500 grs. of the coagulum completely dried 
at 212° left a residue of 143.6 grs. 
500 : 528.6 : : 143.6 : t (= 151.81) solids 
in the clot. 
k) 528.6 — 151.8 = 376.8 water in the clot. 
upposing the water entirely due to the 
serum with which the clot is penetrated, 
should find it contain— 
Since by (6) 906.55 : 376.8:: 93.45 : & 
(= 38.86) solids of the serum retained 
by the clot, and a 
376.8 + 38.86 = 415.66 weight of tl 
serum retained. y 
But 415.66 + 471.4 by (a) = 887.06 tot 
serum in 1000 parts of blood. 
(2) 20 grs. of the dried matter of the coagu- 
lum ignited lefta red ash, weighing 0.52 grs. 
20 : 151.81 :: 0.52: 2 (= 3.947) salts it 
the clot. 
But 1000:471.4 2: 7.3 by (c) : 2 (= 3.4 
salts in the exuded serum. 
3.947 + 3.441 = 7.388 salts in 1000 


of blood. ». 
(m) Since the coagulum contains 2.962 fibrin, 
And the serum retained ...... 38.860 solic 


The sum of the two = 41,822 


And by deducting this sum from the 
solids contained in the clot we find 
151.81 — 41.822 = 109.988 red p 
in 1000 of blood. 

(n) In order therefore to deduce the comp 
sition of 1000 parts of blood, we have only 
calculate the following proportions from + 
knowledge of the corepostion ae the serum. 
1000 : 887.06 :: 906.55: 2 (= &@ 


holic extract. 
1000 : 887.06 :: 0.483 
watery extract. 
1000 : 887.06 : : 0.24 : x (= 0.213) of 
To this we must add 0.04 from the fi 
making the total oily fat = 0.253. 


: a (= 0. 


ORGANIC ANALYSIS. 


~ 1000 : 887.06 : : 0.46 : (= 0.408) crys- 


talline fat. 

1000 parts of this blood therefore consist of 
Water Ce ee 2 804.164 
teed SONS oss en's ceecesesios 7.388 

(Red particles .. 109.988 

Albumen ...... 72.716 

: Fibrin ..... ses, 2-908 
agen 1 ne Alcoholic extract 1.685 
Fane Watery extract... 0.428 

Oily fat....-... 0.253 

| Crystalline fat .. 0.408 

999.992 


3. Analysis of milk. 

Occasionally we may have to aka an 
analysis of milk: we may proceed as in the 
following instance. 

The milk was rather thin, watery in appear- 
ance, and had a sp. gr. of 1031. It was ob- 
tained from a woman aged 25, three weeks 
after the birth of her fourth child. 

(a) 100 grs. evaporated to dryness left 
11.49 grs. of solid matter. 

100 : 1000 : 11.49 : «(= 114.9) solids 

per 1000. 

1000 — 114.9 = 885.1 water per 1000. 

(6) On incinerating the residue, an alkaline 
ash was left amounting to 0.24 grs. = salts 
2.4 per 1000. 

(c) 158 grs. of the milk were mixed with a 
few drops of acetic acid and evaporated to dry- 
ness, and digested repeatedly in ether (the 
_ ether was first allowed to macerate upon the 
residue unpowdered. It was decanted and 
the greater part of the fat thus removed; the 
residue was completely dried, powdered, and 
again subjected to three or four digestions with 
ether. All the ethereal solutions were then 
| evaporated.) The fatty matter amounted to 
| 4.61 grs. 

158 : 1000 :: 4.61 : x (= 29.13) butter 

er 1000. : 
__ (@) The portion insoluble in ether was di- 
_ gested in dilute alcohol (sp. gr. 920) as long 
as any thing dissolved. The solution on eva- 
_ poration yielded a yellowish granular mass, 
_ consisting of milk sugar, and a little extractive 


_ perfectly free from casein. 
158 : 1000 :: 9.7: «(= 61.39) sugar of 
milk per 1000. 

€) The insoluble residue consisted almost 
entirely of casein, with a small quantity of sa- 
line matter. Calculating by the deficiency, 
(as, owing to an accident, it was not weighed,) it 
amounted to 3.85 grs. 

158 : 1000 :: 3.85 : «(= 24.37) casein 
per 1000. 
~ The results of the analysis may be summed 
up as follows :— 


IS a6 evere «0 PLR RIO Cie devs 885.1 

Bison? Fatty matter 29.13 
nae ety Sige and alco- 

Sali a5. holic extract. . t 61.39 

ine residue, . 
2.4 Casein and bak 24.38 
‘iti tery extract .. 5 
1000.00 


_ matter : it amounted to 9.7 grs. and appeared « 


811 


The proportion of “ extractive matter” in 
milk varies, but I am not aware of any ready 
method of determining its quantity, apart from 
that of the sugar casein. If we attempt 
to digest casein in water, it swells up and partly 
dissolves, becomes gelatinous, and does not 
allow the fluid to pass through the pores of the 
filter. Ifa cold saturated solution of sugar of 
milk in proof spirit, (sp. gr. 920,) be allowed 
to digest for a few days in a closed flask upon 
the spirituous extract (d), the liquid assumes a 
yellow colour from dissolved extract, and the 
sugar is left in white crystalline grains, but this 
can hardly be used as a process for analysis. 

4. Analysis of bile. 
Our methods for analysing this complicated 
and important secretion are very inadequate. 
Still, such as they are, I have endeavoured to 
illustrate them by the following example :— 
The bile analysed was obtained from a man 
wt. 75, who died of gangrena senilis, The 
gall-bladder was removed entire, and the bile 
examined 48 hours after death. 
It was a brownish, turbid, scarcely ropy 
fluid, of sp. gr. 1024, and amounted to about 
240 grs. 
(a) 65.16 grs. evaporated to dryness left 
4.83 grs. This residue on incineration left 
0.75 grs. of saline matter. 
65,16 : 1000: : 0.75 : a (= 11.51) salts per 
1000. 

4.83 — 0.75 = 4.08 and 

65.16 : 1000: : 4.08 : 7 (= 62.61) organic 
matter per 1000. 

Therefore 1000 —(11.51 + 62.61) = 925.88 
water per 1000. 

(6) 171.2 grs. mingled with thrice its bulk 
of alcohol, and filtered, left a yellowish ropy 
residue of mucus, which, when well washed 
with alcohol and dried, amounted to 5.1 grs. _ 

171.2 : 1000 :: 5.1: 4 (= 29.78) mucus 

per 1000.* 
(c) The filtered liquid was evaporated nearly 
to dryness and mingled with ether. A bright 
yellow solution was obtained ; it was decanted, 
and the residue repeatedly digested with ether. 
The mixed ethereal solutions, on evaporation, 
left 2.8 grs., of which 0.6 grs. was soluble in 
water (being biliary matter). 
2.8 — 0.6 = 2.2 ethereal extract. 
(d) The ethereal extract was treated with a 
weak solution of ammonia; a brown liquid was 
obtained, and a white crystalline residue of 
cholesterin was left, amounting to 0.31 grs. 
171.2 : 1000 :: 0.31 : # (= 1.81) choles- 
terin per 1000 

2.2— 0.31 = 1.89. ~ 

171.2 : 1000: : 1.89 : 2. (= 11.04) uncom- 
bined fatty and resinous acids per 1000. 

(e) The residue insoluble in ether was treated 
repeatedly with hot alcohol. It left undis- 
solved a remainder, which when dry amounted 
to 2.92 grs. 

171.2: 1000 :: 2.92 : (= 17.05) watery 

extract. 


* The proportion of matter insoluble in alcohol 
in this instance was very great, probably it con- 
tained something besides ordinary mucus; but 
circumstances prevented my examining it more 
minutely. 


812 

(f) An attempt was made to separate the 
colouring matter from the alcoholic extract by 
baryta water, and to obtain it free from baryta 
by solution in carbonate of ammonia, but it 
did not succeed; indeed I have never been 
able by this or any other process to separate the 
colouring matter ta the other ingredients of 
the bile with sufficient accuracy to warrant its 
adoption for analytical purposes. 

(g) The quantity of alcoholic extract was in 
this case from the experiment with the baryta 
necessarily inferred from the deficiency. 

Since 1000 grs. contain 74.12 of solid mat- 
ters, 171.2 grs. will contain 12.69; we must, 
therefore, deduct the ethereal and watery ex- 
tract, and mucus :— 

(2.2 + 2.92 + 5.1) = 10.22 grs. 

12.69 — 10.22 = 2.47. Biliary and co- 
louring matter :— 

171.2 : 1000: : 2.47: « (= 14.37) biliary 

matter per 1000. 

The specimen of bile thus examined, there- 

fore, furnishes the following results :— 


Water 
MECCOB Gi iccceas 29.78 
: Biliary and co- 2 
Oren footie, louring matter § 14.37 
asescey Resinous and 
er a fatty acids ..§ nt OF 
thes Cholesterin ...... 1.81 


Watery extract.... 


999.93 


M. Pettenkofer has recently proposed the 
change of colour produced by the action of 
sulphuric acid and sugar upon bile as a test of 
its presence. Having freed the liquid sus- 
pected to contain it from albumen by eva 
rating to dryness and exhausting the residue 
by boiling water, the solution is concentrated 
by evaporation, and when cold mingled with 
about one-third of its bulk of oil of vitriol, 
so as to raise the temperature of the mixture 
from 150° to 160° of Fahrenheit, but not higher. 
A few grains of sugar are now added to the 
liquid, and the whole suffered to stand fora 
few minutes. If bile be present a beautiful 
crimson colour is developed, increasing in in- 
tensity for some minutes. The tint is un- 
equivocal provided the solution contain not less 
than 4, of its weight of dry bile, or J, of the 
recent secretion. This reaction is independent 
of the mucus and colouring matter. 


5. Of the saliva. 

The saliva is not often the object of analysis; 
when it is, it may be proceeded with as in the 
following instance, in which healthy saliva was 
examined. It was obtained several hours after 
taking food. It hada sp. gr. of 1001.5, was 
slightly alkaline, restoring the colour of reddened 
litmus paper ; and was ropy and opalescent. 

(a) 111 grs. evaporated to dryness in a pla- 
tinum capsule and incinerated, left 0.22 grs. 
of ash. 

111 : 1000 : : 0.22 : (= 1.98) saline mat- 

ter per 1000. 

(6) 500 grs. evaporated by a water-bath left 

2.51 grs. 


ORGANIC ANALYSIS. 


500 : 1000: : 2.51 : (= 5.02) total solids, 

5.02 — 1.98 = 3.04 organic matter. 

1000 — 5.02 = 994.98 total quantity of 

) The dry residue wus digested in lial 

c) The residue was in ether; 
ae ethereal solution decanted and evaporated 
left 0.03 grs. of an oily matter with a strong 
peculiar odour. It contained a trace of sulpho 
cyanide of potassium, as was shewn by the re 
colour struck by a very dilute solution of 
quichloride of iron. 

500 : 1000 :: 0.03 : x (= 0.00) , 
odorous matter with traces of sulpho- 
cyanide potassium. 

The residue undissolved by ether 
treated with boiling alcohol; the solution de- 
canted and evaporated left 0.61 of a crystalline 
yellowish deliquescent salt, in which the pn 
sence of sul Sisepanide of ium wa 
proved ; ist, by its striking a blood-red liquit 
with a very dilute solution of sesquichloride ¢ 
iron; and 2ndly, this solution, according 4 
Dr. Percy’s suggestion, was acidulated wi 
hydrochloric acid, and a fragment of zin 
dropped in. Immediate effervescence ensue 
with a strong odour of sulphuretted hydroge 
due to the decomposition of the sulphocyanie 
Its acidulated aqueous solution gave no prec 
pitate with nitrate of baryta; but after a sm 
portion of the alcoholic extract had been ine 
nerated and the residue dissolved in wa 
feebly acidulated with nitrie acid, abunda 
precipitation was manifest on adding a solutic 
of chloride of barium; during incineration t 
sulphocyanide had been decomposed and — 
sulphur, by absorbing oxygen, converted ii 
sulphuric acid. : 

500 : 1000: : 0.61: (= 1.22) alcoh 
extract. 

(e) The residue left undissolved by aleo 
was treated with water and thrown upon 
weighed filter; the insoluble portion amouni 
to 0.68: it consisted of mucus, debris of e 
thelium, &c. _ 

500 : 1000 :: 0.68 : r (= 1.36) mucus, — 

(f) The filtered solution contained trace 
albuminous matter (mucus) held in solution 
the soda. This was precipitated by exact i 
tralization withaceticacid,evaporated to dry 
redissolved, and again filtered. This aqu 
liquid contained the ptyalin, or peculiar; 
vary matter, and a certain proportion of wi 

extract so called. Ptyalin has never yet b 
obtained in a state of purity. It always cc 
chlorides and phosphates mixed with it. Tl 
lution was mixed with twice its bulk of ale 
by which the ptyalin in company with § 
watery extract was precipitated. Its solt 
when redissolved in water, gave precip 
with acetate and triacetate of lead, infusio 
galls, and nitrate of silver, but none wit 
rosive sublimate, sesquichloride of iro 
ferrocyanide of potassium, either alone or 
the addition of acetic acid. Each time i 
evaporated to dryness a small portion rem 
behind in an iooplehal form. Dedueting t 
ethereal and alcoholic extract, and mucus, — 

5.02 — (1.22 + 0.06 +1.36 (e))= 3 
presents the ptyalin and watery ext? 
per 1000. 7 


ORGANIC 


This specimen of healthy saliva therefore 

contained, 

Le ae 

{ Fatty and odorous 
matter .....6 

Alcoholic extract 
and salts ..... 

Mucus and epithe- 
lium 1.36 


Ptyalin, watery ex- 
: 2.38 


994.98 


0.06 
_ Organic matter, 1.22 
{ 3.04. 


_ Fixed salts, 1.98. 


tract, salts and 
traces of mucus 


. 


1000.00 


If mercury were sought for, the best plan 


liva, evaporate to dryness, mingle the dry mass 
with well-dried carbonate of soda, to place the 
_ mixture ina fine glass tube sealed at one end, 
_ and apply the heat of a spirit lamp. If the 
_ metal were there, it would sublime and condense 
__ asa dew of metallic globules on the cool part 
_ of the tube. 
; IJ.—Uttimare Anatysis. 

__ Organic bodies consist principally of carbon, 
hydrogen, oxygen, and nitrogen, with occa- 
_ sionally small quantities of sulphur, phos- 
phorus, and various metallic, earthy, and saline 
_ Matters in minute proportions. In cases where 
_ the four first elements only are present, the 
aualysis is comparatively easy; and if, as some- 
times occurs, the substance to be analysed is 
_ capable of assuming a crystalline form, its 
oe is a matter of little difficulty, 
_ When, however, saline compounds enter es- 
" sentially into its constitution, as in most animal 
aa crystallization is never found to take 
place. 


_ This general absence of crystalline form in 
| animal principles, and the consequent difficulty 
of ascertaining that they are free from all mois- 
ture, which does not chemically enter into their 
constitution, have, by rendering us uncertain 
of the purity of the substances analysed, mainly 
_ contributed to the slow and uncertain progiess 
of this department of chemistry, and have 
given rise to the numerous 
Contradictory statements 
with which it abounds. By 
“Multiplied researches and 
ee we are, how- 
. ever, at length arriving at 
“results on the accuracy of 
which tolerable confidence 
ogy laced. 
_ The determination of the 
four elements, carbon, hy- 
n, Oxygen, and nitro- 
as they constitute the 
d of most organic sub- 
‘Stances, is that part of the 
process which now claims 
ur attention. It is to Gay 
} Lussac and Thenard that we 
| are indebted for the funda- 
| mental principle that re- 
gulates our operations. The 
Process proposed by them 


would be to mix a little nitric acid with the sa-_ 


ANALYSIS. 813 


has subsequently been modified and improved 
by many chemists, especially by Berzelius, 
Prout, and Liebig,.and in the hands of the lat- 
ter eminent philosopher it has acquired a de- 
gree of facility and accuracy hitherto unap- 
proached in any other department of analytical 
research. 

Our object being to determine the relative 
proportion in which each of the ultimate ele- 
ments exists, it becomes necessary to the success 
of any analytical process that we should pro- 
cure them in the form of definite compounds 
that can easily be collected; and it has been 
found most convenient, by supplying the sub- 
stance to be analysed with a sufficient quantity 
of oxygen, to convert the carbon into carbonic 
acid, which may be absorbed by potassa and 
weighed, and the hydrogen into water, which 
may likewise, by passing over a substance that 
has a powerful attraction for it, such as chloride 
of calcium or sulphuric acid, be collected 
and weighed, whilst the nitrogen escapes 
as gas, which is collected over mercury and 
measured. 

In cases where nitrogen is present, it has re- 
cently been proposed to heat the substance to be 
analysed along with hydrate of soda or potash; 
all the nitrogen is thus converted into ammonia, 
in. which form, like carbonic acid and water, it 
admits of being weighed. By calculation it is 
easy to find the weight of the carbon, hydrogen, 
and nitrogen respectively contained in the car- 
bonic acid, water, and ammonia collected. Car- 
bonic acid contains three-elevenths of its weight 
of carbon; water, one-ninth of hydrogen, and 
ammonia fourteen-seventeenths of nitrogen. 
When by incineration of a portion of the mass 
the proportion of saline matter has been deter- 
mined, the quantity of oxygen the substance 
contains may be known by deducting the united 
weight of the carbon, hydrogen, nitrogen, and 
salts from the total weight of the body ana- 
lysed; the deficiency (supposing sulphur and 
phosphorus not to have been present) is oxygen. 

Scrupulous attention to the purity of the 
matter submitted to analysis is of course of 
primary importance, a very slight admixture 


Fig. 429. 


zl 
enn | 


Apparatus for desiccation of organic substances. 

A, tube containing chloride of calcium resting on the support B; 
c, bent tube containing the matter to be dried and plunged in the bath 
D; d,d, caoutchouc connectors; E, vessel containing water, which flows 
out gradually by the stop-cock f to maintain a current of air through the 
apparatus, 


814 


with other com 3 being sufficient to vitiate 
the conclusions deducible from our experi- 
ments. Having ascertained the purity of our 
substance, the next care is to ensure its com- 
lete desiccation. For this purpose the fol- 
owing plan, recommended by Liebig, will be 
found the most efficient (fig. 429). A small 
quantity of the material to be dried is placed 
in an inverted syphon-tube (c), the bend of 
which is plunged into a vessel (D), contain- 
ing water gradually heated to the boiling 
point. When plain water is used, the tem- 
re of course will not rise above 212°; 
ut by substituting for it different saline solu- 
tions we may at pleasure obtain any degree of 
heat between 212° and 300°, according to the 
nature of the compound to be analysed. A 
current of dry air is made to pass over the 
substance by connecting one limb of the sy- 
hon with a tube containing chloride of calcium 
EA), and the other with a vessel (E) closed at 
top, excepting the aperture by which it is con- 
nected with the syphon-tube, and filled with 
sa which is allowed ae run out at the 
ttom with a s regulated by a stop-cock 
(f), the place oP the liquid being supplied by 
air, which has passed over the chloride of cal- 
cium and then through the sypbon-tube. Vo- 
latile liquids that are unchanged by distillation 
shoal te allowed to stand two or three days 
upon fragments of fused chloride of calcium; 
the liquid should then be decanted and dis- 
tilled in a small retort; in other cases, as in 
the examination of fats or fixed oils, it may be 
more convenient to dry the material in a watch- 
glass placed in an ordinary water-bath or the hot- 
water oven previously described. The further 
progress of the analysis will vary according to 
the form and composition of the substance to 
be examined. 
We shall describe the methods of analysing— 
1. A solid, which does not contain nitrogen. 
2. A fluid, which does not contain nitrogen. 
3. A substance, which does contain nitrogen. 


1. Analysis of a solid not containing nitrogen. 


The combustible which answers best in these 
experiments is charcoal ; it is the least expen- 
sive, and very manageable, but dusty. Spirits 
of wine or pyroxylic spirit, no doubt, are 
cleaner, but their expense is a great objec- 
tion. Gas has been tried by myself and others 


ORGANIC ANALYSIS. 


in a variety of ways, but though some modi- 
fications of burner answer tolerably well, it is- 
not on the whole to be recommended. és 
The best furnace to be used with the char- 
coal is represented at A, fig. 430, and is made 
of stout sheet-iron bent into the form of a 
trough, open at one end; the plate which 
closes the other is perforated with an aperture 
three-quarters of an inch in diameter, to allow 
the passage of the combustion tube; the fur- 
nace is about twenty inches long, five inch 
at top, two inches and three-quarters at bottom 
and three inches high. Transverse slits are 
made along the floor at intervals of two inches 
for draught, and between each are rivetted ve 
tical stiff pieces of sheet-iron one inch high 
terminating in a concave edge above, for the 
support of the combustion tube. The appi 
ratus may rest on bricks during the operatio 
as represented in the wood-cut. ra 
The tube in which the mixture is burne 
the combustion or retort tube, (fig.430, a, b, ¢,) 
should be of difficultly fusible glass free fre 
lead, about fifteen insta long and half an ine 
in diameter: the hard Bohemian glass an: 
the purpose perfectly. The tube may on cer 
tain occasions be drawn out into a fine 
strong tail bent upwards at an obtuse an 
and the mouth should be smoothed by makir 
it red hot in the flame of the blowpipe, | 
that a cork need not be torn in adjusting it. 
The apparatus for containing the chloride ¢ 
calcium which collects the water, or dryin 
tube, is conveniently made of the shape 
picted (fig. 430, B): it consists of a t 
about half an inch in diameter and four ine 
long. Upon one end is blown a bulb, to cc 
a larger portion of the chloride, and fre 
bulb a strong tube of small diameter exten 
for an inch anda half. The chloride of ¢ 
cium with which it is filled must not be fuss 
but should be prepared merely by evapor. 
the solution of the chloride in 
strong sand heat. A porous mass is thus 
tained, which does not crystallize by absorb 
moisture, as the fused variety does, to the 
struction of the tube that contains it. In 
to charge the apparatus a few fibres of co 
wool are put into the bulb, and by sucki 
through the small end adjusted over the a 
ture of the fine tube to prevent any m 
particles from falling out: into the app 


ie Fated 


© Fig. 430. 
* > d. I 
: b as eee 4 
Vari re ot O~ 
VV ~ tas 


— Pe ee ee 


: Sor the combustion of organic bodies. 
A, sheet iron trough or furnace containing the retort tube a, b, c, and resting on 


Liebig’s 
the bricks E E. 


B, the drying tube charged with chloride of calcium, or pumice stone moistened — S by 


with sulphuric acid. 


e, the potash bulbs; d, caoutchouc connector. ak a 
D, the suction tube, shewing the mode of its adjustment when used for draw- 
ing air through the apparatus at the termination of the experiment. ray 


eae 


~ 


: ; ORGANIC ANALYSIS. 


within three-quarters of an inch of the large 
end, the chloride broken into fragments about 
the size of peas, is put, and a loose piece of 
cotton-wool, occupying another quarter of an 
inch, thrust in; the opening is then closed by 
a cork, through which passes a bit of straight 
tube, rather larger in the bore than that at- 
tached to the bulb, and projecting about an 
inch outside the whole; the cork is trimmed 
close to the large tube and covered neatly with 
f melted sealing-wax; and, lastly, air is drawn 
through the apparatus by the mouth to ascer- 
tain that no obstruction exists. It is now ready 
for use: after two or three experiments the 
chloride should be renewed, or there will be a 
danger of the gases being imperfectly dried. 
The tube when not in use must always be 
placed in a rack with the bulb end uppermost 
to prevent the loss of any small pieces of chlo- 
ride. Concentrated sulphuric acid may be 
advantageously substituted for chloride of cal- 
_ cium in the drying tube. In this case the 
_ tube is filled with fragments of pumice-stone; 
_ these are moistened with the oil of vitriol, and 
_ the apparatus is fitted up as usual, excepting 
that the employment of the cotton-wool is dis- 
pensed with. 
__ The combustion tube is then prepared by 
_ selecting a sound elastic cork, which is made 
- accurately to close the mouth of the tube; it is 
_ pierced with a round file, and fitted firmly 
ri pee the fine tube proceeding from the bulb 
_of the drying tube; the cork is then well 
dried on the sand-bath, and forms the medium 
bu ee naetion between the retort and drying 
tube. 
The potash apparatus is one invented by 
 Liebig, represented in fig. 430, e. It consists 
of a fine but stout tube, upon which is a series 
of bulbs, three in the middle horizontal part 
_ of the instrument, and one on each of the 
ascending limbs; one of the latter bulbs is 
made considerably larger than the other; the 
| apparatus is filled by adjusting a suction tube 
_to one of the openings, and exhausting by the 
heeks until a certain measured quantity of 
lution of potash has entered; when the 
iquid fills each of the three lower bulbs rather 
_ More than three-quarters of their capacity, suf- 
cient has been introduced. 
_ The solution of potash employed has a 
p- gr. of from 1.25 to 1.27, and must be 
‘renewed for every experiment; the portions 
‘that have been used may be put aside, and 
afterwards, when sufficient has been collected, 
May again be rendered caustic in the usual 
way by quicklime. 
_ The compound commonly used for supply- 
ing oxygen to the substance burned is oxide 
of copper, which readily imparts oxygen to 
} combustible matter in contact with it, but 
bears a very high temperature per se without 
decomposition. It is best procured by dis- 
| solving copper in pure nitric acid, evaporating 
| to dryness and decomposing the nitrate by 
| heating it strongly in an earthen crucible. Ig- 
ition is kept up till red fumes cease to appear ; 
if the heat be too great the oxide becomes 
agglutinated, and requires strong pounding in 


815 


an iron mortar to pulverize it; it however, in 
this dense state, is much less hygroscopic, and 
therefore better adapted for the purposes of 
analysis. The powdered oxide is sifted through 
a fine copper sieve, and secured in stoppered 
glass bottles. 

Immediately before each analytical ope- 
ration a sufficient quantity of the oxide is 
ignited, and while still hot transferred to a dry 
tube, by plunging the mouth of the tube into 
the oxide in the crucible and then shaking it 
in piecemeal. The tube with the oxide is 
immediately closed with a dry cork, and al- 
lowed to cool. Meantime the interior of the 
retort is completely dried by heating each por- 
tion of it in succession in the flame of a spirit- 
lamp, beginning at the closed end, and draw- 
ing air through the heated tube, by means of 
a narrower tube passed down just beyond the 
heated part and exhausting by the mouth; 
when every part has thus been dried, the 
retort is corked and allowed to cool. Five 
or six grains of the powdered and dried sub- 
stance are put into a perfectly dry test tube, 
and the whole is very accurately weighed ; its 
contents are then added to the oxide of copper 
in the mortar and the empty tube again 
weighed ; the difference gives the weight of the 
substance employed. 

The best kind of mortar is one of Wedge- 
wood ware or Berlin porcelain, capable of con- 
taining about half a pint, with a pestle com- ° 
posed of a single piece of the same material ; 
it should be thoroughly dried and well warmed. 
Much caution is requisite in charging the re- 
tort. The warm dry mortar is placed on a sheet 
of glazed paper and first cleared out with a 
little of the dried oxide of copper, which is 
put aside. Oxide to the depth of an inch is 
poured into the combustion tube; a small 
quantity of oxide is put into the mortar, then 
the substance to be analysed, then more oxide ; 
the mixture must be made quickly and care- 
fully, adding so much oxide as shall be suf- 
ficient to fill a little more than half the retort ; 
the mortar is then taken in the palm of the left 
hand and the mixture introduced, carefully 
picking it up piecemeal by the retort tube it- 
self; fresh portions of oxide are rubbed in the 
mortar to clear out the last traces, and the 
retort is then filled up with pure oxide of cop- 
per to within two inches of the extremity. 

The proportions of the mixture are repre- 
sented in fig. 430: the portion from the tail of 
the tube to the letter a consists of pure oxide 
of copper, from a to b of the mixture, from 
b to ¢ of the rinsings of the mortar, and from 
c to within an inch of the cork is again pure 
oxide. 

If the process of mixing has occupied much 
time, it may be advisable to subject the tube 
and its contents to a further operation to re- 
move any traces of moisture that may have 
been absorbed. The tube is struck smartly in 
a horizontal position on the table, to clear the 
tail-like prolongation, and to make an air-way 
above the oxide from end to end; an exhaust- 
ing syringe made fast to the table by a screw- 
vice or other convenient means, is attached toa 


816 ORGANIC 


long tube filled with chloride of calcium; and 
this drying apparatus is fitted by a sound cork 
to the retort he. This latter is laid in a shal- 
low trough open at one end, which is slightly 
elevated ; the trough is then filled with sand 
heated to about 212° F., and cautious exhaus- 
tion is performed by the syringe, taking care 
that none of the charge is carried out of the 
tube by the current of air; on gradually open- 
ing the stop-cock air is slowly re-admitted, 
being dried in its passage over the chloride of 
calcium ; it is allowed to remain in the appa- 
ratus a few seconds, and the exhaustion re- 
peated ; these operations are performed in suc- 
cession ten or twelve times. - is, acho 
rarely necessary to resort to this process o 
desicetion, and it is objectionable from the 
ease with which many compounds rich in hy- 
drogen decompose the oxide of copper at com- 
tively low temperatures. 
PaThe rying isha dave been accurately 
weighed is next fitted to the dried perforated 
cork, and connected by it air-tight to the retort 
tube; this is now placed in the furnace, which 
has been disposed’ in a convenient place rest- 
ing on bricks; to the drying tube the potash 
apparatus, also previously weighed, is attached 
by a connecting piece of caoutchouc, taking 
care that the largest bulb is on the arm con- 
nected with the drying tube; the ager ap- 
paratus should be slightly inclined by placing 
a cork under the end of the horizontal portion 
nearest the open extremity. Matters being 
thus arranged, we proceed to ascertain if the 
whole be tight, and for this purpose expand 
the air in the large bulb by heat, so as to ex- 
pel a few bubbles; if, on cooling, the liquid 
rise in the limb and maintain its elevation 
steadily for a few minutes, the combustion may 
safely be begun. Charcoal broken into pieces 
about the size of a walnut is ignited in a cru- 
cible furnace or by any other convenient 
means, and when red-hot applied to the por- 
tion of the tube nearest the cork where the 
te oxide of copper lies; the action of the 
feet is limited by a double sheet-iron screen 
which fits into the furnace, and has a central 
slit which allows it to bestride the tube; this 
screen can by degrees be moved further and 
further down the furnace until the whole tube 
is heated. An additional screen of single iron 
plate is hung over the closed end of the fur- 
nace to protect the cork, which usually should 
reach to within an inch of the fire, care being 
taken that the heat never rises so high as to 
scorch it, or falls so low as to allow of the 
condensation of moisture in the portion of the 
retort which projects from the furnace. 
' When the first part of the retort is red-hot 
and the escape of air from expansion has 
ceased, about an inch more of it may be 
heated, and so the fire gradually carried 
down; about three bubbles of air may pass in 
two seconds, it is better not to attempt a more 
rapid disengagement. At first but a small 
portion of erg gas is absorbed, but when the 
substance is fairly undergoing decomposition, 
and the atmospheric air in the apparatus has 
been expelled, it is almost entirely taken up by 


ANALYSIS. 4 | 
the potash-ley. When the whole tube is ig- — 
nited the heat must be continued till bubbles 


are no longer disengaged ; the potash-ley will — 
now gradually recede into the pe 
ad 


when this is observed to commence, the ¢ 
coal must be removed from the tail of the tubes 
and as soon as the potash has risen to fill half 
the large bulb, the tip of the tail must be 


i a off, and over the opened extremity; 
tube about eighteen inches long, and one quarter 
in diameter, should be supported; gen’ c 
tion is then effected by spi 7 tube (fig. 43 
D) fitted to the free extremity of the potas 
apparatus, drawing air through the combustio} 
tube to displace the carbonic acid and aqu 
vapour it contains. The use of the 
over the end of the retort is to supply pure ai 
and to prevent that from the furnace ch 
with carbonic acid from passing freely 
the apparatus: the actual process of com 
tion performed in the manner above deseril 
yanally poompias from an hour to an hour a 
a half. : 
The plan of drawing air through the tube 
that practised by Liebig, and it admits of cor 
siderable accuracy. Dumas, however, co 
nects the extremity of the retort with a dryit 
tube, and this again with a receiver containiz 
oxygen, which gas is carefully driven over 
contents of the tube. This renders the o 
ration somewhat more complicated, but if 
unquestionably more exact, pe pe in ¢ 
poende where the proportion of carbon is grez 
he tube for supplying oxygen is easily 
justed to the retort by drawing out the t 
horizontally instead of obliquely, fitti 
on by a caoutchouc connector, care being tal 
to screen the junction from the influence 
heat. i ' 
The apparatus is now dismounted, 
whole pia to cool; in about an h 
drying tube may be weighed, and the inere 
of weight carefully noted; one-ninth of 
gain indicates the quantity of hydrog 
substance contained ; the potash apparatus 
also weighed, and three-elevenths of wha 
has gained shews the quantity of carbon, — 
deficiency is oxygen. 
The oxide of copper used in the 
riments may again be rendered servic 
moistening it with nitric acid, and ignitii 
before. _ 
2. Analysis of a liquid not containing 
trogen. _Z 
f the fluid be volatile, we take a pie 
tube rather less than a quarter of an 
meter, heat it in the blowpipe flame, an 
on it a capillary portion about four i 
long; about a quarter of an inch below 
the tube is sealed ; the little piece of tub 
left connected with the capillary part h 
and blown into a small bulb tas b 
good-sized pea; this is cut off, i 
pillary neck of about two inches long. ; 
made a sufficient number of these Ob 
we take two of them, which we haye 
tained will freely enter the combusti 
and weigh them accurately ; a little of t 
to be analysed is put into a small tube, an 


/ 


a 


_—- 
_as 


ORGANIC ANALYSIS. 


capillary neck of the bulbs inverted into the 
liquid; the bulbs are then warmed by the flame 
of a spirit-lamp, so that on cooling they shall 
be about three-fourths filled with the liquid. 
The necks are now sealed by the blowpipe- 
flame, and the bulbs again weighed ; the in- 
-_ erease of weight gives the quantity of the 
_ liquid which has entered, and which is to be 
_ analysed. The oxide of copper having been 
heated, and allowed to cool with the usual pre- 
cautions, about an inch and a half of the retort 
is filled with pure oxide; we then take one of 
the bulbs, draw a file across the capillary neck, 
put the bulb into the tube, break off the neck 
by pressure against the glass, and drop the 
broken portion in with the bulb; we then pour 
in a couple of inches of oxide of copper, 
introduce the second bulb in the same manner 
as the first, and fill up the tube with oxide, 
cork it and strike it smartly on the table as 
before to secure free air-way. The combustion- 
tube is now connected with the exhausting 
__ syringe, but no heat applied; on gently working 
_ the syringe, the air and vapour in the bulbs 
_ will expand and drive out the liquid, which 
_ will be quickly absorbed by the oxide of 
| copper around ; we adjust the apparatus in the 
_ furnace as before, and gradually heat the upper 
half of the tube; when this is red, we vola- 
_ tilize the fluid by cautiously approximating a 
piece of ignited charcoal, taking especial care 
not to heat the tube too much ; by degrees all 
the liquid in the first bulb is expelled, and we 

in like manner with the other; the 
_ whole tube is finally heated carefully, and the 
_ after part of the process conducted in the 
manner already described. 

If the liquid be not volatile, an oily acid 
for example, a small vessel is made by taking a 
_ piece of glass tube about a quarter of an inch in 
diameter, sealing one end, and while hot press- 
_ ing it on a flat surface, so as to make a firm 
_ basis on which it may stand upright; it should 
be cut off the tube so that the little vessel be 
about an inch high. It is weighed at first 

mpty, and a second time with the liquid for 
analysis; an inch or two of oxide of copper is 
put into the combustion-tube, then the vessel 
with the liquid. On inclining the tube suffi- 
ciently, the liquid runs out and is made to 
diffuse itself over the inner surface of the lower 
half of the tube, which is to be filled with oxide 
of copper, and the analysis to be cautiously 
] ed with in the usual way. 

_ Substances which contain a great excess of 
carbon sometimes escape complete combustion 
by this process; when this is feared, all danger 
may be averted either by adopting the plan of 

umas, already mentioned, or by pulverizing 

me chlorate of potash finely, which is care- 
fully dried, mixed with about four times its 
< of oxide of copper, and the first portion 
of the retort is filled with it for about an inch ; 
| the tail-like prolongation may in this case be 
| dispensed with at the close of the operation ; 
| instead of sucking air through the apparatus, 

we very cautiously apply heat to the chlorate, 
| oxygen is evolved, which burns the last traces of 
_ | carbonand displaces the gas and aqueous vapour 
VOL. III. 


817 


which the tubes contain. When the chlorate 
has been used, the last inch of oxide of copper 
must be kept separate from the rest, as it will 
be mingled with chloride of potassium, and 
must not be employed again until it has been 
washed from the salt, for as chloride of copper 
is slightly volatile it would be deposited in the 
drying tube and unduly increase its weight. 
If the heat is too suddenly applied, a portion 
of the chlorate is apt to be carried forward me- 
chanically, and this constitutes the chief ob- 
jection to its use. 

Sometimes chromate of lead is advantage- 
ously substituted for oxide of copper with sub- 
stances difficult of combustion, as by a bright 
red heat alone it gives off a portion of its oxy- 
gen. It is easily prepared by precipitating the 
chromate or bichromate of potash with solution 
of acetate of lead. It should be well washed 
and heated to incipient fusion before it is used 
for analysis. It has the advantage of being 
much less hygroscopic than the oxide of cop- 
per. To ensure accuracy, when much gas (as 
in this case, and in instances where nitrogen is 
present,) passes through the potash apparatus 
during the whole experiment, it is best to con- 
nect the open extremity with an additional 
drying tube, charged with solid hydrate of 
potash instead of chloride of calcium, the 
weight of which has been carefully noted, as 
a portion, very small but still susceptible, of 
aqueous vapour is carried off from the solution 
of potash by the gas, and would otherwise be 
lost, making the quantity of carbon appear 
somewhat too little. 

3. Analysis of a body containing nitrogen, 

Two separate analyses are in this case re- 
quired ; the first, to discover the proportion of 
carbon and hydrogen; and the second expressly 
for the nitrogen. When bodies containing 
nitrogen are burned with oxide of copper, a 
variable proportion of the lower oxides of 
nitrogen is formed, which being retained by 
the chloride of calcium or potash would render 
the analyses incorrect. A precaution is there- 
fore employed which renders it necessary to 
make use of a retort-tube somewhat longer 
than common; it is charged as usual to within 
four inches of the opening, and then filled up 
with clean copper turnings; the apparatus is 
arranged as before directed, the copper turnings 
are brought to full redness, and the analysis 
proceeded with cautiously in the ordinary man- 
ner. As the oxides of nitrogen pass slowly over 
the ignited copper they are decomposed, the 
oxygen combining with the copper while pure 
nitrogen escapes; the quantity of carbon and 
hydrogen is determined exactly as heretofore. 

To ascertain the proportion of nitrogen, the 
most accurate method is that recently devised 
by Varrentrapp and Will, and suggested about 
the same time by Berzelius; the fundamental 
fact consists in the observation of Gay Lussac, 
that when azotised matters are heated with a 
large excess of hydrate of potash (soda answers 
equally well), the whole of the nitrogen is ex- 
pelled in the form of ammonia. In order to 
render it available for the purposes of analysis 
the subjoined precautions are requisite. 

3G 


318 


A mixture of two parts of quicklime and 
one of hydrate of soda is an ge by slaking 
some well-burned lime with the necessary 
quantity of a solution of soda; the whole is 
evaporated to dryness, ignited, the dry mass 
pulverized as quickly as possible, and then 
transferred to well-stopped bottles, in order to 
exclude carbonic acid and moisture. When an 
analysis is to be made we proceed as usual, 
making the mixture in a warm mortar, only 
substituting the alkalized lime for oxide of 
copper; the accidental presence of a little 
moisture, after the weight of material for ana- 
lysis is accurately known, is of no consequence 
in this case. Ae 

Having introduced the mixture, it is better 
loosely to plug the aperture of the retort with a 
few fibres of asbestus (which has been ignited 
just before) to prevent any mechanical trans- 
port of the mixture into the apparatus through 
which the gases are passed ; on applying heat 
to the combustion-tube in the ordinary way, 
and with the usual precautions, the substance 
is decomposed, and the whole of the nitrogen 
escapes as ammoniae The drying tube and 
potash apparatus are dispensed with, and the 


Fig. 431. 
ce 


d d 


A.—a, mouth of the combustion-tube ; 5, three- 
legged brass tube furnished with the stop-cock 
(c); d, d, caoutchoue connectors; e, glass tube, 
upwards of 30 inches long, recurved at the lower 
extremity for delivering gas in the mercurial 
trough. 

B.—Bulb-tube for containing hydrochloric acid 
in the determination of nitrogen by the method of 
Varrentrapp and Will, 

.—a, mouth of the combustion-tube; 8}, 
caoutchouc connector ; c, gas delivering tube. 


ammonia is collected by attaching a bulb-tube of 
the form represented (fig. 431, B), air-tight with 
a good cork, to the retort-tube, the apparatus 
having been previously charged with hydro- 
chloric acid sp. gr. 1.1, as high as the lines in 


ORGANIC ANALYSIS. 


the figures indicate. Pure hydrochloric acid. 
is easily procured for this purpose by diluting: 
the ordinary acid of the shops till it has a 
sp. gr. of 1.1, and distilling in glass ves- 
sels—the first eighth may be rejected. Dis- 
ullation may be proceeded with until three- 
quarters of the acid employed have passed 
over. It is better for the operator always to 
rectify his own acid, in order to be quite 
sure of the absence of any trace of aim- 
monia. The tube connecting the bulbs should 
be somewhat larger in diameter than that of the 
ordinary Lage apparatus, in order to allow — 
the liquid to be poured out readily. When — 
the operation is complete, absorption will take — 
place and the fluid rise in the bulb nearest the 
fire; at this moment we nip off the top of the 
combustion-tube and draw air carefull — 
the apparatus in the usual way. When 
a is terminated, ie of the 
ulb-tube are emptied into a evaporating — 
dish, and the hopieaak washed out first with a 
little alcohol and ether, and afterwards several 
times with water; some solution of bichloride 
of platinum is added, and the whole do 
to dryness by a water-bath or chloride of cal- 
cium bath; when dry, it is digested with a 
mixture of two parts of alcohol, sp. gr. & 
and one of ether, which dissolves the excess 
bichloride of platinum, and leaves the doubl 
chloride of platinum and ammonium in a crys= 
talline form. 7 
This must now be brought upon a weighed 
filter, (or better, upon two rd of hich 
has been counterpoised against the other,) am 
washed repeatedly with the mixture v0 
parts of alcohol and one of ether until noth 
further is taken up; the precipitate and filte 
must be dried by a water heat and the weigh’ 
accurately observed. According to Va 
and Will, 220.52 grs. of the ammonia-chlori 
are equivalent to 14 grs. of nitrogen; the est 
mate of these writers is too high, and 225 grs. ar 
more nearly equal to one equivalent or 14 
of nitrogen. Practically, however, their ¢: 
lation is very near the truth, as during 
operation a minute quantity of hydrochlorat 
of ammonia escapes uncondensed, and the tw 
errors compensate each other. 4 
This method of determining nitrogen ai 
swers for all cases excepting those in whi 
occurs in the form of nitric acid, when it m 
be determined by volume and its weight the 
deduced. For this purpose the proces 
Dumas is the most trustworthy. A retort 
of about twenty inches long is em > 
drawn out into a tail, but sealed with a roun 
extremity; about two inches of the tube 
filled with carbonate of oe or of lead, 
then the mixture with oxide of copper a 
and covered as usual with a layer of | 
oxide; beyond this the last two or three im 
of the tube are filled with clean coppert 
ings, as already directed, to decompose ai 
the oxides of nitrogen which may orn 
The retort tube is then connected with a th 
legged apparatus of brass or copper (fig. 4: 
b), one limb of which is furnished i 5 
cock (c). The connection with the ret 


Sie 


Ez 
¥ 
? 


ORGANIC ANALYSIS. 


best made by passing a piece of glass tube 
throngh a cork fitting accurately into the mouth 
of the combustion tube and connecting the 
brass apparatus to this small glass tube by a 
caoutchouc connector; the limb (b) is fastened 
by a similar joint to a glass tube (e) bent at 
right angles near one end, with a straight por- 
tion upwards of thirty inches long, the other 
extremity of which is turned up at an acute an- 
gle for the convenience of safely delivering the 
gas; the tube is placed in a vertical direction 
with its lower upturned extremity dipping into a 
small mercurial trough ; the stop-cock tube (c) 
is connected with an exhausting syringe and 
a vacuum produced ; the apparatus is left for 
half an hour to ascertain that all the joints are 
tight: if the mercury after this lapse of time 
still stands at the same level, the experiment is 
proceeded with ; a moderate heat is applied by 
a spirit lamp to the end of the retort contain- 
ing the carbonate ; by this means carbonic acid 
is set free and displaces the last portions of air; 
the exhaustion and disengagement of gas are 
repeated alternately three or four times, taking 
care to leave sufticient carbonate undecom- 
posed to renew this expulsive process at the 
termination of the experiment. The stop-cock 
{c) is now closed, the air-pump is removed, 
and a graduated jar containing some solution 
of potash is inverted in the mercury over the 
recurved -extremity of the long glass tube. 
The copper turnings are then brought to red- 
_ hess in the usual way by charcoal, and the 
_ €xperiment conducted with the customary pre- 
cautions, the decomposition being caused to 
_ take place less rapidly than usual; when the 
_ part of the retort containing the matter for 
_ analysis is red-hot through its entire extent, 
heat is gradually applied to the carbonate at 
the end, and the last portions of gas from the 
_ combustion in the apparatus are driven into 
_ the receiver by the disengaged carbonic acid. 
As the products of combustion are only 
_ water, carbonic acid, and nitrogen, the two 
_ former are retained by the solution of potash, 
_ whilst the latter alone presents itself for mea- 
_ surement. I need hardly say that the height 
of the barometer and thermometer must be 
_ carefully noticed, when the apparatus by stand- 
ing for an hour or two has reached the tem- 
_ perature of the atmosphere ; as the gas will be 
Saturated with moisture, its volume must be 
_ corrected by the known methods for the three 
_ points of temperature, pressure, and moisture ; 
then, since 100 cubic inches of nitrogen at 
Standard temperature and pressure weigh 
30.15 grs., the weight of the nitrogen that a 
given quantity of the matter analysed contains 
is easily determined. In this process, as in 
every case where the proportion of nitrogen 
alone forms the object of our experiment, after 
the weight of the material for analysis has been 
once accurately determined, it is evident there is 
nothing to fear from the absorption of moisture. 
Occasionally the quantity of nitrogen, where 
large, is advantageously determined by making 
the combustion just as though we were going 
to ascertain the proportion of carbon and hy- 
drogen; but, instead of condensing the car- 


819 


bonic acid and weighing it, the whole of the 
gases produced are collected over mercury. 
A bent gas-delivering tube is substituted for 


the usual are ee ( Fig. 431.) In 


this case it is best to begin at the closed ex- 
tremity of the tube, and having expelled the 
atmospheric air by a portion of gas generated 
from the substance, to collect the rest of the 
gaseous products in a graduated jar; by agi- 
tating the gas with solution of potash the pro- 
portion of nitrogen to carbon is at once deter- 
mined, as equal volumes of carbonic acid and 
nitrogen represent single equivalents of carbon 
and nitrogen. It is not necessary in this case 
to determine accurately the quantity of mate- 
rial acted upon. 

Experience has shewn that in the preceding 
process for organic analysis the quantity of 
hydrogen deducéd from it ‘is always slightly in 
excess, usually about 0.2 parts in 100, whilst, 
unless chromate of lead or chlorate of potash 
is employed, the carbon is sometimes as much 
deficient. A deficiency of carbon also occurs 
if the ash contain carbonates in any form. Oc- 
casionally sulphur and chlorine are among the 
constituents of organic bodies ; the methods of 
analysis must then be modified. For details 
upon these subjects the reader is referred to the 
treatise of Berzelius. ’ 

We will suppose the labour of analysis thus 
brought to a successful issue. It is, however, 
evident that the information derived from this 
source alone is but scanty, as we can thereby 
form no idea either of the number of equiva- 
lents of each element entering into the com- 
position of an organic body, or of its relations 
to the substances concerned in its production 
or obtainable from it by its decomposition. 
Whenever it is possible,the equivalent or com- 
bining proportion of the compound must be 
determined. This is effected by preparing a 
compound of the body with some substance, 
whose equivalent is well known, and proceed- 
ing to analyse the new product. If our or- 
ganic substance be soluble in water, and 
capable of entering into combination with 
oxide of silver, this oxide is for many reasons 
preferred. Oxide of silver combines with very 
many organic bodies, and forms with them 
compounds insoluble or sparingly soluble in 
water. They may generally be formed by 
double decomposition, and washed from all 
adhering impurities ; fifteen or twenty grains of 
the silver compound is accurately weighed in 
a counterpoised porcelain crucible. It is then 
carefully incinerated till pure silver alone re- 
mains. On again weighing, the loss will give 
that of the body combined with the silver, and 
in addition that of one equivalent of oxygen 
expelled from the oxide of that metal at a red 
heat. The residual silver should dissolve 
without remainder in nitric acid. Now, 
since the equivalent number of silver on the 
hydrogen scale is 108, it is evident that by 
simple calculation we may determine the equi- 
valent, number of the organic body that had 
combined with it. 

An example will perhaps elucidate my mean- 
ing more distinctly. 

36 2 


“820 


48.73 grs. of acetate of silver left 

31.49 grs. of metallic silver. 

17.24 grs. will therefore express the loss, 
due to the united weight of acetic acid and 
oxygen combined with the silver. 


Equ.of sil. 

31.49 : ; 108 ot: 

lequ. oxy. 

59—} 8 = 51, the equivalent num- 

ber of acetic acid. 

Another example will shew the method of 
calculating the number of equivalents of each 
element in the compound. 

By analysis with oxide of copper we find 
10 grs. of acetate of silver yield 

5.277 grs. of carbonic acid and 
1.620 grs. of water 
and calculating from the 
previous experiment, . 6.462 silver, 
this is equivalent to .... 1.439 carbon 
0.180 hydrogen 


17.24 : + (=59) 


The deficiency is .......- 1.919 oxygen. 
10.000 

Then by proportion— 

Silv. oe te § Carb. C. 

6.462 : 108 :: 01.439: 2 (= 24), or 4 
Hydrog. H. 

6.462 : 108 ; 0480 :a(= 3),0r3 
Oxygen oO. 

6.462 : 108 ; 1.919 : x (= 32), or 4 


Total.. = 59 
deduct 1 equivalent of oxygen 8 


C4 
t stor 3 


Sometimes no compound with silver can be 
obtained, and a salt of lead is then, if prac- 
ticable, substituted for it. The residue, how- 
ever, in this case does not consist entirely of 
metallic lead, neither is it all oxide of lead. 
It is carefully weighed, treated with acetic acid 
in the crucible itself; the oxide of lead is thus 
dissolved and washed away. When the con- 
tents of the crucible have been carefully dried, 
a second weighing gives the quantity of me- 
tallic lead, whilst the loss furnishes that of the 
oxide. From the metal we calculate the quan- 
tity of oxide to which it is equivalent; this 
added to the portion dissolved by acetic acid 
furnishes the whole quantity of oxide con- 
tained in the compound :—a calculation similar 
to that employed for the silver salt, then sup- 
plies us with the means of determining the 
equivalent number of the body analysed. This 
method is not quite so accurate as the preceding; 
it involves more manipulation, and the com- 
pounds of lead are — to undergo slight loss 
by volatilization at a high temperature. 

It would here be out of place to enter into 
detail into the methods of checking the cor- 
rectness of an analysis in its various parts. 
Upon this point the reader is referred for in- 
formation to Liebig’s Introduction to Organic 
Analysis. The subject is an important one, 


and we obtain the equivalent 
of anhydrous acetic acid... 


ORGANIC ANALYSIS. 


face of the ground, or raise 


and by no means sufficiently attended to by the 
majority of those who devote themselves to — 
analytical researches of this description. 

The number of authors who have written — 
upon the methods of analysis is great; 
a3 their instructions are hae sate eden 
tached papers, scattered through the various” 
scientific periodicals than in systematic treatises, 

The works which may be consulted with espe- 
cial advantage on proximate analysis are Berze- 
lius’s Lehrbuch ber Chemie, third German — 
edition, translated by Wohler, 10 vols. 8vo.; the 
fourth edition of Prout’s Treatise on Diseases 
of the Stomach and Urinary Organs, and hi 
papers in the Medico-Chirurgical and Philoso- 
phical Transactions; G.O. Rees on the Analysi 
of Blood and Urine; Lecanu, Ann. de Chimie 
xlviii., and various papers on the blood ; Simon, 
Handbuch der augewandten Medizinischen 
Chemie, 2 vols. 8vo. 1840-42; one of the 
most recent and best treatises on animal che- 
mistry, full of laborious and careful analyses 
with copious and accurate directions for thei 

rformance. This work is now being trans. 
ated into English. < 

For directions for analysing the inorgat 
constituents of organized compounds the reade 
is referred in particular to Rose’s Analytic 
Chemistry, either the fourth German edition, « 
the Engiish translation of the first edition b 
Griffin. : 

Ample instructions for the ultimate an: 
of organic substances are furnished in Liebi 
Organic Analysis, translated by Gregory, a 
forming one of the series of works publish 
in Griftin’s Scientific Miscellany, and in t 
fifth volume of Dumas’ Traité de Che 
Appliquée aux Arts, as well as in the volun 
of Berzelius already referred to. 

A valuable treatise has recently been pi 
lished in German by Vogel, jun. on the | 
plication of the microscope to the field” 
animal organic chemistry—*“ Anleitung 2 
Gebrauche des Mikroskops zur Zoochemise 
Analyse und zur Mikroscopisch-chemischi 
untersuchung uberhaupt.” f. 

( W. A. Miller. 


OSSEOUS SYSTEM. (Compara 
Anatomy.)—One of the most striking — 
distinctive characters peculiar to the hig 
grades of animal existences, the VerTEBR 
is that they have their bodies support 
and as it were moulded upon, an int 
frame-work, which is generally made u 
numerous pieces, very various in their { 
and uses, which are called the bones ; at 
assemblage of them, whatever their mot 
tion, constitutes the skeleton. y 

Seeing the great diversity of forms and h 
in the innumerable races of animals const 
this great group of living beings, se 
specially appointed to a the wate 
our globe, others to inhabit the marsh ang 
swamp, whilst others again tread the firm § 

. 


_s 


the regions of the thin air; and that 
the diversified shapes of Fishes, Reptil »B 
and Mammifers, we are prepared, @ priori 


a 
4 


OSSEOUS SYSTEM. (Comp. Anat.) 


expect, in the construction of this skeleton, va- 
rieties correspondingly great both in the mate- 
rials employed and their mechanical arrange- 
ment, inasmuch as the machinery employed 
for effecting progression under circumstances 
so dissimilar must be changed in every race, 
and adapted to the peculiarities of habit con- 
ferred upon any given creature. 

The substance of which the internal ske- 
leton of a vertebrate animal is composed differs 
moreover very remarkably from that employed 
to build up the organs of support in any of the 
other divisions of the animal kingdom. In all 
the great group of Radiata (Cuv.), wherever 
a hard material is employed, it is built up by 
the slow external accretion of earthy particles 
deposited in successive layers from the living 
substance of the body, arranged not unfre- 
quently with admirable precision; but, when 
once formed, such a skeleton is entirely devoid 
of vascularity, and almost placed beyond the 
reach of vital influences. Throughout all the 
Articulata the skeleton is an external crust 
exuded from the surface of the skin, which is 
so entirely destitute of all capability of growth 
or expansion, that it must be cast off frequently 
during the life of the animal, to be renewed 
again and again as the bulk of its body is 
enlarged. In all the Mollusca, too, with the 
exception of the Cephalopods, in which a true 
bony structure begins for the first time to be 
_ developed, all the hard parts of the body are 
_ Cuticular and composed of shell. In the Ver- 
tebrata alone is found a real osseous skeleton 
nourished by bloodvessels, consisting essen- 
tially of a living tissue that is capable of con- 
_ Stant growth and renovation, having its texture 
hardened in proportion to the necessities of the 
case by an interstitial deposit of various earths, 
especially of phosphate of lime, which is con- 
tinually removed and renovated as age ad- 
vances, and, in short, is subject, during the 
whole existence of the creature, to vital in- 
fluences, its hardness and composition being 
Subject to great variations. In making use of 
the terms bone and osseous tissue, we must 
therefore be understood by no means to employ 
these words as indicating portions of the animal 
fabric endowed with any particular degree of 
density or firmness, that being entirely an ad- 
ventitious circumstance depending upon the 
‘greater or less abundance of the earthy matters 
deposited in the living tissues, and even in the 
Same animal, in this respect, offering at dif- 
ferent periods of its life the most opposite con- 
ditions. 

_ In the lowest and most feeble Fishes, which, 
im consequence of their sluggish movements 
through an element that buoys them up on all 
sides, no firmness is required in any part of their 
construction, and few of the locomotive levers 
met with in more highly-gifted forms are pre- 
Sent, the whole osseous system consists per- 
Maunently of the softest cartilage undivided as 
yet into distinct pieces; and it is only as we 
ascend from this point through successive 
groups of Cartilaginous Fishes as they are 
called, the Sharks, Rays, Sturgeons, &c., that, 
Owing to an increased deposit of the hardening 
earths within the cartilaginous web, firm- 


821 


ness and solidity are slowly given. Even in 
the most perfect Fishes the bones remain soft 
in comparison with theircondition in terres- 
trial Vertebrata, whilst it is only in Carnivorous 
Mammalia, and more especially in Birds, that 
the maximum of hardness is conferred upon 
the osseous system, a density and a strength 
commensurate with the powerful muscular 
exertions required by the conditions under 
which those races live. Equally remarkable 
are the differences observable in the texture 
of the osseous skeleton at different ages in 
the same creature The Tadpole of the Ba- 
trachian Reptile, for example, at the time 
when it commences its earliest struggles in 
the element wherein it passes the first por- 
tion of its existence, is, as relates to the condi- 
tion of this part of its economy, inferior even to 
the My.xine and the Lamprey amongst Fishes, 
consisting of the most delicate cellulosity 
or of the softest gristle. As growth proceeds, 
osseous particles accumulate, and the condition 
approximates that of the more perfect Fishes. 
Lastly, as the anterior and posterior extremities 
sprout, the bones acquire progressively the den- 
sity essential to the construction of a terrestrial 
animal, and the whole internal framework 
becomes consolidated to an extent proportioned 
to the vigorous movements of the perfect Frog. 
In the higher Mammalia the succession of the 
phases of developement is still further pro- 
longed. At its first appearance, the osseous 
system is represented by a mere web of cellular 
tissue, which slowly attains to a cartilaginous 
texture; this cartilage, during foetal growth, is 
converted into bone by the deposition of earth 
in its substance; but it is not till long after 
birth, when adult age has need to exert all the 
energies of life, that the bones are fully formed, 
hardened, and lightened to the utmost required 
extent by consolidating their substance to the 
ma.cimum, and excavating the caverns and can- 
celli that characterize the most perfectly ma- 
tured conditions of the osseous framework. 
But passing from these general views, for a 
more complete consideration of which the reader 
is referred to another article, (Osszous Tis- 
SUE,) we proceed to examine more closely the 
composition and developement of the skeleton, 
and here we find difficulties to be encountered of 
nocommonkind. Did the skeleton invariably 
consist of the same number of bones, only modi- 
fied in their shape or position according to'the 
necessities of the different races of Vertebrata, 
the task of the comparative anatomist would be 
easy when he came to investigate their analo- 
gies and relations with each other ; but this is 
far from being the case: the skeleton of the 
adult animal does not present the same 
number of pieces as that of the same creature 
in a less advanced condition, numerous parts, 
originally distinct, having become fused and 
consolidated into one; and, on the other hand, 
the juvenile being differs from the embryo from 
circumstances precisely the reverse, seeing that 
the full complement of bones or centres of 
ossification has not as yet been developed. 
Now, as in ascending the scale of living beings 
belonging to the Vertebrate division of the ani- 
mal creation, we find that nature can arrest the 


822 


further advance of ossification at any assignable 
point of developement, leaving some parts per- 
manently — ied, while others are allowed 
to attain their full growth, we find great varieties 
in the composition of the osseous framework. The 
Tadpole, were its growth arrested before its limbs 
begin to sprout, would bea Fish. The Frog, if it 
ceased to grow when its limbs were but par- 
tially formed, would be a Siren or a Proteus, 
having little or nothing in common with the 
adult creature as regards the configuration or 
even the number of the bones in its skeleton. 
Which of the three conditions must the com- 
parative anatomist refer to in order to estimate 
the condition of the bones composing the frame- 
work of this Batrachian? The importance of 
this inquiry will be at once obvious, as, either 
in the first instance there must have been a 
much greater number of bones developed than 
are met with in what is usually considered a 
complete skeleton, or in the adult animal the 
bones have become too much confused with 
each other to allow us at all to estimate their 
real condition. It is sufficient indeed for any 

rson who is only acquainted with the osteo- 
ogy of man, to cast his eyes over the bones 
entering into the composition of the skeleton 
of a fish to perceive at once that the nomen- 
clature employed by the human anatomist is 
by no means sufficiently ample to afford names 
to one-half of them, which indeed have no re- 
presentatives in the human body; or even the 
bare comparison of the adult human cranium 
with that of the infant of tender age would 
convince us that in the former there are many 
more distinct bones than in the latter. The 
only mode of solving these difficulties is ob- 
viously to study the composition of every part 
of the skeleton in the most complicated form 
under which it is met with, and having ascer- 
certained the number and disposition of the 
pieces of which it then consists, and settled 
the names and analogies of each, it becomes 
comparatively easy to point out what parts are 
deficient in less complex forms of the ske- 
leton. 

The number of pieces which can normally 
enter into the construction of any portion of 
the osseous apparatus having been thus deter- 
mined, these are regarded as the primary ele- 
ments of the skeleton, by the developement, 
suppression, enlargement, or modified form of 
which every required variety of the bony 
framework may be explained, and the con- 
struction of this portion of the animal economy 
proved to be in accordance with certain immu- 
table laws that may be traced throughout the 
immense series both of the existing and of 
extinct races of Vertebrata. 

It will readily be perceived after the above 
remarks that a perfect skeleton, that is, a skele- 
ton presenting all the parts of which it might 
normally be composed in a complete state of 
developement, does not exist in nature. 

A spinal column may exist alone without 
either cranium, face, or limbs, as is the case in 
that strange and rare fish the Amphioxus.* Or 


* Vide a Memoir on the structure of this extra- 
ordinary production of nature, by John Goodsir, Esq. 


OSSEOUS SYSTEM. (Compr. Anat.) 


the spine, cranium, face, and extremities may — 
coexist without ribs or thorax, as in the Frog. 
The spine and cranium form almost the entire 
skeleton of many apodal Fishes, while in Ser-— 
pents the ribs become the chief instraments 
employed in locomotion, not even vestiges of 
legs or arms being visible. = 
Imagining, however, that a fully formed ske- 
leton, having every apparatus belonging to it, 
could be potnted eat leu us now orocbal briefl; 
to glance at the parts of which it would consist, 
eth these we should find to be the following. — 


‘ig. 432. 


oy 


LARAA ADS 
a i (eee 


* 


Skeleton of the Crocodile. 


- OSSEOUS SYSTEM. (Comp. Anat.) 


1. The spinal column, the centre of the whole 
fabrie enclosing in a canal formed by arches 
surmounting its dorsal aspect the medulla spi- 
nalis or the axis of the spinal portion of the 
nervous system. 

_ 2. The cranium, essentially composed of 
vertebre ; but here, in consequence of the 
enlarged size of that of the cerebro-spinal 
axis of the nervous apparatus placed within 
them, exaggerated in size and modified in form. 

3. Of a frame of bones appended to the 
anterior part of thecranium for the lodgement of 
the organs of those senses that are immediately 
in connection with the encephalon, forming 


_ what, taken collectively, is called the face. 


4. Of a hyo-branchial apparatus forming the 
framework of the throat, and supporting the 
organs connected with aquatic respiration. 
These last of course are only present in animals 


breathing by gills, and can only be expected to 


exist in a state of complete developement in 
the class of Fishes. 

5. Of the thoracic apparatus, composed of 
two sets of ribs—a dorsal and a sternal series— 
and of the sternum, which itself, when fully 
developed, is made up of numerous bones. 

_ 6. Ofa pair of anterior extremities, divisible 
into shoulder, arm, forearm, carpus, meta- 


carpus, and digits. 


7. Of a pair of posterior extremities, con- 


_ structed after the same model as the last, and 
_ presenting corresponding parts, to which the 


names pelvis, thigh, leg, tarsus, metatarsus, 


; _ and toes are respectively appropriated. 


The most complete skeleton with which we 


_ are acquainted among existing Vertebrata is that 
_ of the Crocodiles, the study of which cannot be 


too strongly recommended *to the comparative 
osteologist, as in these creatures all its parts 


_fTemain permanently in a medium condition, 


so that the arbitrary divisions of the skeleton 
adopted by the human anatomist are at once 
recognisable, although we find others which in 
Man have noexistence. Thespineis divisible into 
acervical region (fig. 432, a, b) interposed be- 
tween the cranium and the thorax, although ribs 
© are appended even to the cervical vertebre. 

e dorsal region (b, c) supporting the thoracic 
ribs, the lumbar (c,d), the sacrum (e), and the 
caudal (f') are distinguishable for the same rea- 


_ sons as in the human subject, notwithstanding 
__ that the caudal portion resembles anything rather 
_ than the human os coccygis; for here, so far 
_ from its being formed merely of the rudiments 
_ of the bodies of almost obliterated vertebre, 
__ the processes form very powerful levers, and of 


there are some developed inferiorly (g) 


_ of which no vestiges exist in the human skeleton. 
_ The bones of the cranium and face are far more 
_ Mumerous than in the skull of our own species, 
_ as we shall explain more minutely hereafter: 
_ see fig. 441, where they are delineated on an 


enlarged scale. The thorax consists of dorsal 
ribs (/) and of sternal ribs (m), which are equally 
important elements of the skeleton and of the 
sternum, here situated much as in the human 
subject. Behind the sternum, moreover, and 
extending from it quite to the pubic bones, 


_ there is in the Crocodile a set of ventral ribs () 
| towhich in Man there is nothing analogous, 


823 


except, perhaps, the tendinous intersections still 
lingering in the recti muscles of the abdomen. 
The shoulder (p, g) consists, like the pelvis 
(A, z), of three distinct and important bones, 
while all the pieces entering into the formation 
of the extremities very nearly resemble what is 
met with in the human subject. 

Having premised thus much, we may now, 
without further preface, plunge more deeply 
into our subject, and, taking in detail all the 
elements that are recognised by modern anato- 
mists as belonging to the osseous system, exa- 
mine them separately in the various aspects 
under which they present themselves in the 
different classes composing the Vertebrate por- 
tion of animated nature. 

Spinal column.—Commencing our analysis of 
the skeleton by an examination of the spine as 
being the most essential portion of the osseous 
system, the primary or central part to which all 
others that are met with in the different classes 
of Vertebrata may or may not be superadded in 
accordance with the conditions under which 
they are aspomies to exist, we shall soon per- 
ceive that both in texture and composition it 
offers very important varieties. In the Myxine 
and Lampreys it is a simple stem of extremely 
soft cartilage, almost gelatinous in its con- 
sistence, which traverses the axis of the body, 
presenting, when superficially examined, no 
appearance of division into separate vertebre ; 
and it is not uninteresting to observe how, 
advancing from this simplest form of spine 
through various tribes of Fishes, its separation 
into distinct pieces is gradually effected. But 
even in the Lamprey, on strict examination, 
there are perceptible in the arches that embrace 
the spinal canal and on the surface of the soft 
cord that represents the bodies of the vertebra, 
slight indications of an incipent division into ver- 
tebral pieces, which are represented by slender 
rings of ossific matter that encircle at intervals 
the soft cartilage upon which they sensibly 
encroach. In a more advanced form of the 
spine, these ossified rings are considerably 
increased in their relative proportions, and en- 
croach further and further upon the cartilaginous 
stem until they penetrate even to its centre, and 
are then no longer dubiously the representatives 
of the bodies of so many vertebre. In the 
generality of Fishes, indeed, the central part 
remains unossified, so that a cartilaginous axis 
traverses the vertebral column from end to end. 
At last even this is obliterated, and the vertebral 
centres are completely formed. 

But even before the bodies of the vertebra 
are thus perfected, the lamine destined to 
enclose and protect the spinal cord are fully 
formed by the deposition of osseous matter, as 
may be readily seen in the Sharks and Rays 
and many other cartilaginous Fishes, in which, 
although the complete consolidation of the 
body has not yet been achieved, the spinous 
and other processes destined to form the fulcra 
upon which muscular action is to be exerted 
are so ossified as to afford the needful solidity 
and strength. In these races of Fishes, indeed, 
the condition of the spinal column is not a 
little remarkable, inasmuch as in the Skates the 
anterior vertebre are so consolidated by an 


824 


Elements of a vertebra (after Owen ). 


encrustment of bone as to resemble a single 
mass; and in both the Rays and Sharks there 
are many more lamine enclosing the x sem 
canal than there are bodies of vertebra, bony 
plates being developed over the junctions of 
vertebral centres with each other as well as in 
the usual situation,—a circumstance which might 
at first sight seem to militate against the views 
adopted by modern physiologists concerning 
the elemental constitution of this part of the 
body, but from which, in reality, no legitimate 
inference is deducible, seeing the extremely 
confused and incomplete progress of ossification 
in all the cartilaginous Fishes. 

Advancing to the osseous Fishes, such con- 
fusion no longer exists, and every vertebra 
assumes a precise form corresponding with the 
particular uses assigned to it in the region 
which it occupies. Before, however, proceed- 
ing further, it behoves us to resolve an isolated 
vertebra into the primary elements of which it 
may itself be made up, and then we shall 
understand how all the varieties of shape pre- 
sented by these bones are easily obtainable by 
the simple exaggeration, diminution, or suppres- 
sion of some of the elements composing it. 

Geoffroy St. Hilaire was the first anatomist 
who pointed out the importance of thus analysing 
the different portions of the osseous system, 
and the views which were promulgated by that 
learned writer were generally adopted until 
Professor Owen, in the course of his researches 
concerning the composition of the skeletons of 
extinct British Reptiles, was led, as we think 
very justly, to modify considerably the views 
which had been previously entertained upon this 


OSSEOUS SYSTEM. (Comp. Avat.) 
Fig. 433. 


subject; we cannot therefore do better than lay 
before the reader the conclusions deduced by 
Professor Owen from a very elaborate and exten- 
sive survey of the various forms of the skeleton. 

“ A vertebra,” says Professor Owen,“ may 
be traced through its various degrees of com- 
plication, either during the fs veapect stages 
of its developement, or by taking permanently- 
formed vertebre of different es of com- 
pany in different animals; or in many instances — 

y comparing the vertebrae in different parts of 
the spine in the same animal.” 

The terminal vertebre of the tail in most — 
species exhibit the simplest condition of these 
bones. The most complicated vertebre are 
those of the lower part of the neck of certain — 
birds, as the Pelican, or at the beginning of 
the tail of a Python or other large Serpent. ‘ 

The parts or processes of such a vertebra 
may be divided into autogenous, or those which 
are independently developed in separate carti- 
lages, and exogenous, or those which shoot out 
as continuations from these independent con-— 
stituents. The autogenousor true elementsare— 

1. The centrum or body of the vertebra’ 
(fig. 433, d,) which in Mammalia, as Cuvie 
has observed, is complicated by two epiphyses. 

2. Two superior lamine (6, 6) developed 
protect the great nervous cord which rests on 
the upper surface of the centrum, and which 
Professor Owen therefore proposes to cal 
Neurapophyses. 

3. Two inferior lamine (e, e€) develop 
generally to protect the great bloodvessels on 
the under surface of the centrum, and which 
may be called Hemapophyses. a 

4. The superior spinous process (a) which i; 
connected and gerferally anchylosed with the 
distal extremities of the neurapophyses, 
forms, in conjunction with those processes, th 
superior arch of the vertebra. 

5th. An inferior spinous process which i: 
connected and commonly anchylosed with th 
distal extremities of the Hemapophyses, for 
ing in conjunction with these a chevron ot 
V-shaped bone. . 

To the category of autogenous vertebr 
pieces likewise belong the ribs (ce), 
are generally anchylosed to the other vy I 
elements in the cervical, sacral, and cai 
vertebra of the warm-blooded oe class 

The propriety of regarding the ribs as ver 
bral elements is well illustrated in the y 
Saurus, in the cervical, sacral, and caut 
vertebre of which they have been general 
described as transverse processes, although th 
are separate bones. f 

True transverse processes are always exog 
nous, or mere projections from the centrum 
the neurapophyses, and are of secondary imp 
tance. They are of two kinds, superior a 
inferior ; both are present in the cervical ¥ 
tebree in most classes of the vertebrated anima 
the inferior transverse processes alone are dey 
loped in Fishes. aa 

The oblique or articulating processes are als 
exogenous, and may be developed either fro 
the neurapophyses or the base of the supe 
spines of the vertebra. ¥ 

As in other complicated bones resulting fro 


OSSEOYS SYSTEM. (Comp. Anat.) 
Fig. 434. 


Skull of the Perch ( Perca fluviatilis ), after Cuvier. 


an association of several osseous pieces, certain 
elements of a vertebra may be modified in 
Position and proportions so as to perform the 
ordinary functions of others which may be 
atrophied or absent : thus in Fishes the inferior 
transverse processes are gradually bent down- 
wards until in the dorsal region their extremities 
meet and perform the functions of the hema- 
pophyses. 

From the vertebral elements named above 
every possible variety is presented by these bones 
throughout all the races of animals possessing 
them. The body alone (fig. 433, d) may be de- 
veloped without the addition of any of the other 
parts, as in the terminal bones of a Mammal’s 


Fig. 


Ran nee ae 
ase of skull and opercular bones of Perch. 


825 


tail or of the human os coccygis, or the neura- 
pophyses may exist without an ossified body, as 
in some cartilaginous Fishes. The vertebre of 
the human skeleton present body, neurapophy- 
ses, neural spine, and transverse processes, as do 
the rib-bearing vertebre of the Fish. The 
caudal vertebre of the Fish, in order to give the 
great vertical expansion required in this region 
of their skeleton, have the centre, the neura- 
pophyses, and neural spine as well as the 
hemapophyses and hemal spine to the ex-. 
clusion of the transverse, while in the earlier 
caudal vertebre of the tail of the Crocodile 
(fig. 433, g ) all the elements enumerated exist 
in a medium state of developement. 

From these data, therefore, the osteologist 
is enabled to explain the composition of any 
vertebra that may be offered to his inspection ; 
nevertheless there are. numerous apparent ex- 
ceptions which are well calculated to puzzle the 
student, met with, especially in the vertebra of 
Serpents or of the neck of some Birds, where the 
processes are so complicated by the bifurcation of 
their extremities, or by foramina passing through 
their roots, or the great size of the articulating 
processes, or lastly, by the exuberant deposition 
of osseous matter in particular parts of the 
bone, that the greatest possible distortion may 
easily be h gem without at all violating the 
prescribed laws in accordance with which the 
osseous system is organized. Not unfrequently 
indeed stunted ribs, or even derivations from 
the exoskeleton, may become consolidated with 
the proper vertebral elements in such a manner 
as not to be readily distinguishable from them, 
producing additional complications which are 
sometimes very embarrassing. 

Skull—The osseous framework of the head 
appended to the anterior termination of the 
spinal column is by far the most complex part 
of the skeleton, being composed of very nume- 
rous bones connected together by suture or 
otherwise, but differing marvellously in their 


435. 


826 


character and entering into the formation of very 
numerous and diversified sets of organs, which 
have in: reality no alliance with each other 
except that of mere juxta-position. 

One compartment in Man, exceeding in size 
all the rest put together, but in the lower Ver- 
tebrata forming but a very small part of the 
whole, is obviously merely a continuation of 
the vertebral canal lodging the most anterior 
ganglia of the cerebro-spinal axis, which it 
arches over and defends, at the same time 
affording passage to the nerves that emanate 
therefrom, being essentially itself composed of 
vertebrae, although, in consequence of the 
preponderating size of the brain over the spinal 
ganglia behind, considerable distortion is re- 
quired, a distortion which in human beings is 
necessarily carried to such an extent that the 
normal construction of this part of the skeleton 
is in man almost wholly indistinguishable. As 
the vertebral column forms the centre and sup- 
port of the trunk and limbs, so does the cranial 
portion of the skull sustain various additional 
apparatus, which may be enumerated as follows. 

1. The auditory apparatus most frequently en- 
closed in aspecial bone, the petrous, and interca- 
lated among the proper bones of the cranium. 

2. The temporal apparatus, which in man 
is confused into a single irregular mass that 
forms part of what the human osteologist calls 
the temporal bone, but which in the lower Ver- 
tebrata, such as the Reptilia, consists of several 
important pieces, which being withdrawn from 
the composition of the cranial box are employed 
for the articulation of the lower jaw, and more- 
over in the osseous Fishes sustain the bones of 
the gill-covers. ( Nos. 12, 13, 23, 26, 27.*) 


* The following table, showing the numbers by 
which the corresponding bones appertaining to the 
cephalic portion of the skeleton are indicated in all 
the figures, is given to facilitate comparison be- 
tween them. 


Fig 436. 


Skull of the Cod ( Gadus Morhua ). 


OSSEOUS SYSTEM. (Comp. Anat.) 


3. The pterygo-palatine apparatus repre- 
sented in the human skeleton by the internal 
pterygoid processes of the (so-called) sphenoid 
and the ossa palati. These form the framework 
of the fauces. ( Nos. 25, 22.) 

4. The olfactory apparatus, into the compo- _ 
sition of which enter the ethmoid, over which — 
the nerve of smell is more particularly dis- — 
tributed, together with the nasal, the superior — 
maxillary, the vomer, the inferior turbinated — 
bones, and others more remotely connected with 
the formation of the cavity of the nose. ( Nos. 3, 
20, 16, 18, d.) . 

5. The orbito-lachrymal apparatus, or the 
bones which assist in forming the orbital cavity 
and lachrymal passages. 

6. The superior maxilla formed of the max 
illary and intermazillary bones. ( Nos. 18,17.) 

7. The inferior set Se which in the lower 
animals consists of several pieces, to be more 
fully noticed hereafter. : 

Before proceeding to describe the individual - 
bones that enter into the composition of the 
cranial portion of the skull, in order to lay before” 
the reader the comparative structure of that 
important portion of the skeleton, it will be 


1 Frontal. 

2 Anterior frontal. 

3 Nasal (ethmoid,Cuv. ) 
4 Posterior frontal. 

5 Inferior occipital. 


18 Maxillary. 
20 Presta + 
22 Palatine. 
= Masto-temporal. 


Transverse. 


6 Sphenoid. 25 Internal pte 
7 Parietal. 26 Zygomatic. 
8 Supra-occipital. 27 Squamo-tempor: 


9 External occipital. 
10 Lateral occipital. 
11 Alar. 

12 Mastoid. 


28 Opercular. 
29 Styloid. 


30 Pre ular, 
31 Symplectiae -— 


13 Petro-temporal. 32 Subopercular. — 

14 Ingrassial. 33 Interopercular. — 

15 Cthmoid (anterior 4 Dental, re ual 
henoid, Cuv. 5 Supra-an, 4 

16 Vonate. 4 36 A i lar. = 

17 Intermaxillary. g Suborbital p 


OSSEOUS SYSTEM. (Comp. Anat.) 
Fig. 437. \ 


827 


Wt iy 
Wi Mit? 42 


Hyoid apparatus and branchiostegous rays of Perch ( after Cuvier ). 


‘proper to examine how far it is entitled to be 
ooked upon as we have already stated it to be, 
as forming a continuation of the spinal column, 
and if so, to define the vertebree of which it 
consists. In the human cranium indeed this 
would be no easy task, partly in consequence 
of the extreme exaggeration of every element 
composing it, and partly from the manner in 
which some bones, distinct in the lower animals, 
are here consolidated into single masses ; more- 
over in consequence of the prodigious develope- 
ment of the cerebral hemispheres every partis dis- 
torted and pushed aside as it were out of its pro- 
per situation relative to the neighbouring bones. 

In the cranium of the Reptile, however, and 
even of the less intelligent Mammalia, these 
difficulties are to a great extent done away with, 
and the vertebral form is preserved, while, in 
addition, the elements composing them fre- 
quently remain permanently disunited. 

The first cranial vertebra (commencing from 
behind) is the occipital, and this can present 
no difficulty. In Fishes, indeed, and in many 
Reptiles, the occipital bone, of which this ver- 
tebra is entirely made up, has not only the 
exact shape of one of the spinal bones, but the 
elements composing it remaining often perma- 
nently disunited, they are most easily and 
Satisfactorily identified. Inferiorly there is the 
body (or basilar bone, 5) connected with the 
body of the first spinal vertebra in the same 
Manner as the corresponding portion of the 
other vertebra are connected with each other. 
On each side the neurapophyses (or extra-occi- 
pital bones, 10.) arching over the commence- 
ment of the spinal cord, and lastly, the neuro- 
Spine (or supra-occipital bone, 8) oceupying its 
normal situation, and in many of the lower 


Vertebrata forming a real spinous process, 
although in the human subject, owing to the 
prodigious size of the hinder part of the ence- 
phalon, it is enormously spread out in propor- 
tion to the dimensions of the parts it protects. 

The second or parietal vertebra of the cra- 
nium is slightly more distorted, and its real 
nature masked, particularly in the higher Ver- 
tebrata, by the interposition of the petro-tem- 
poral bone, which does not normally belong 
to the cranium, between it and the preceding. 
Its body is the sphenoid bone, represented in 
the human subject by the posterior part of the 
sella Turcica, but which in Reptiles is a dis- 
tinct element of the skull; its arches are 
formed by the ale majores of the sphenoid, 
(likewise separate pieces of the cranium in the 
lower animals, although in man they are con- 
solidated with the former,) while the spine is 
converted into the expanded parietal bone or 
bones spread out over the central regions of 
the brain. 

The anterior cranial vertebra is called the 
Jrontal, receding still more from the normal 
appearance of a vertebra than the parietal, the 
preponderance of magnitude in the different 
elements that form it being completely in- 
verted; the body being quite rudimentary, 
while the enormously developed spinous ele- 
ments are now converted into frontal bones. 
In man its body and its arches are represented 
by the ale minores of the sphenoid or ingrassial 
bones, and the os frontis constitutes its dispro- 
portionately expanded spine. These three 
vertebrae, therefore, are the essential consti- 
tuents of the skull; and, although in the hu- 
man cranium the most aberrant of any met 
with in creation, their nature is not at once 


828 


obvious; it is only necessary for the student 
to recur to less distorted forms of the head at 
once to recognise the reality of the resem- 
blance. 

Should other proof indeed be wanting, the 
manner in which all the cerebral nerves make 
their exit from the cranium would in itself 
offer a convincing argument. In every other 
part of the cerebro-spinal axis the nerves in- 
variably are given off through passages situated 
between contiguous vertebre, which are called, 
from this circumstance, par excellence, inter- 
vertebral foramina ; nay, so sure is this guide, 
that in those instances where the vertebral 
pieces are confused, so as to be otherwise un- 
distinguishable from each other, the position 
and number of these foramina is sufficient to 
indicate the number of vertebre of which the 
part of the skeleton in question originally con- 
sisted, before the pieces composing it became 
permanently anchylosed. Precisely in the 
same manner the nerves derived from the 
encephalon pass out through the interspaces 
between the occipital and parietal vertebrae, 
or between the latter and the frontal; and, 
although from the great bulk of the encephalic 
masses and the number of nerves derived 
therefrom, the passages through which they 
principally escape have been named foramina 
lacera, indicating their size and irregularity ; 


Fig. 438. 


ye N 
He \I 
Z 
ZY 
YH, F 
Izy S\\ ¥ 
KS 
4 SS A 
> V) 
o S 
Gg -S 
Zz Y): 
Z S| 
YZ 
J CA x} 
* a we TY. 
aa ~~ * 
s oH r 
in| ae 
s(a , SH, Ye 
\.| Al ii 
a ly Zt Sit 
Ke BW OL 
Ve C~ ie, 
bt > faa 
Skull of Boa Constrictor. 


they are not on that account less the repre- 
sentatives of the intervertebral foramina pro- 
perly so called. The mere circumstance of the 
channels of some of these nerves being, in the 
human subject and in other Mammifera, cir- 
cumscribed by rings of bone and thus con- 
verted into distinct foramina, to which special 
names have been given by the human osteo- 


OSSEOUS SYSTEM. (Comp. Anat.) 


Fig. 439. 


_ Section of skull of Boa. 


logist, militates in no degree against the grand 
fact that it is between the cranial vertebra th 
all make their exit. _ 

Having given the above general view of t 
composition of the osseous skeleton, a ™ 
difficult task now remains to be accomplished 
viz. to identify and compare with othe 
the individual bones entering into the com: 
position of the osseous system throughout tl 
different vertebral classes, and thus to analyse 
the entire fabric. Various and conflicting im- 
deed are the opinions of different writers oF 
this important subject, of whose names ani 
works an ample list will be given in the Biblio. 
graphy affixed to the end of this article; bu 
to enter into the argumentation of disputed 
points would of course be impossible in ow 
prescribed limits. Suffice it to say, th 
views of the acute and sound-judging Cuvi 
have been principally adhered to, and whe 
occasion has been found to dissent from h 
opinion we have expressed our reasons for 
doing.* 

Bones of the cranium.— Frontals(1). The 
bones in fishes form the roof of the orbit at 
the anterior portion of the cranial box, havi 
in front and behind them other pairs of b 
forming the anterior and posterior boundafi 
of the orbit which correspond with the an 
rior and posterior frontals in Reptiles. In 
Frog the whole of the anterior portion of t 
cranium is made up of a single bone, whi 
entirely surrounds it like a ring or girdle, a 
represents the two frontal bones of Serpet 


* We must here especially nowledge 0 
obligation to Professor Owen, who has most kindl 
placed at our disposal the result of his rch 
concerning the homology of the cranial bones: 
Fishes : his opinions have been introduced in tht 


proper places. D 


OSSEOUS SYSTEM. (Comp. Anat.) 


(fig. 438, 1) united together. In the Siren 
and Proteus, however, the principal frontals are 
divided as in other Reptiles. In all Birds and 
Mammalia these bones become at an early 
period confused with the anterior and posterior 
frontals and ultimately with each other, so as 
to form but one piece, the os frontis of man; 
nevertheless, even in the human fetus, they are 
separated by a suture which, in the lower 
Mammalia and also in the human subject, is 
not unfrequently persistent to alate period oflife. 

The anterior /rontals (2) in the osseous 
Fishes bound the orbit anteriorly. Between 
these bones pass out the olfactory nerves, but 
they are not always distinctly recognisable, 
being occasionally permanently cartilaginous. 
In Reptiles these bones are generally distinct, 
but in Birds and Mammalia they coalesce with 
the preceding. 

he posterior frontals (4) form the posterior 
margin of the orbit, and are present in Fishes 
and the Reptilia, but in Birds and Mammifers 
they are no longer recognisable as distinct 
bones. 

The parietal bones (7) are placed behind the 
frontals; but these bones do not always touch 
each other, being separated, especially in Fishes, 
by the interposition of an azygos bone from 
which projects the occipital spine, which is 
frequently, more especially in Fishes, of very 
good size: this impair bone, the interparietal 
of some authors, is in reality the representative 
of the superior occipitals of Cuvier (supra- 
occipitals, Owen ;) (8) and in some Fishes, es- 
pecially in the Si/uri, where the parietals are 
totally wanting, their place is supplied by the 
enormous developement of this element of the 
skeleton. 

The external occipitals (9) contribute to form 


Fig 440. 


Section of the skull of Turtle ( Testudo Myas). 


829 


the lateral portions of the occipital region of 
the skull, in conjunction with two other pieces 
called ~ 

The /ateral occipitals (10), which partially 
bound the foramen magnum. 

The inferior occipital or basilar bone (5) is 
that which invariably is articulated to the body 
of the first cervical vertebra, but occasionally 
in Fishes there are two additional articulations 
connecting the cranium to the spinal column 
formed by the lower portions of the lateral 
occipitals. All these elements of the so-called 
occipital bone of the human cranium remain 
permanently distinct in Fishes and Reptiles, and 
even in the feetal condition of Birds and Mam- 
mals are more or less recognisable; but they 
soon coalesce into one large piece that enters 
largely into the formation of the cranial box, 
and constitute the first or occipital cranial 
vertebra, as has been already seen. 

The sphenoid (6) invariably occupies the cen- 
tral portion of the base of the cranium, and in 
Fishes and Birds is prolonged anteriorly into a 
lengthy process which passes beneath the inter- 
orbital septum, which,in these classes of Verte- 
brata, remains most frequently membranous. 

The alar bones (11; ali-sphenoid, Owen,) 
represented in the human subject by the greater 
ale of the sphenoid, are in reality distinct 
elements of the cranium, and are recognizable 
by several important characters, especially by 
their position being joined by suture to the 
oo frontral, and, conjointly with the latter 

ne, to the temporal. Moreover, through 
these bones the two posterior divisions of the 
fifth pair of nerves always pass out from the 
skull. In Fishes and Reptiles they are im- 
portant pieces and quite detached from the 
sphenoid. 

The squamo-temporal bones, Owen (mastoid 
bones, Cuv.: 12) in Fishes are manifestly the 
representatives of the bones so named in Rep- 
tiles. They contribute in conjunction with the 
posterior frontal, and occasionally with the alar, 
to furnish the articular surface that sustains the 
first bone of the palatine and tympanic appa- 
ratus, or, in other words, of the masto-tem- 
poral (23). 

The petro-temporal bones, Owen, (13) are in 
Fishes placed between the mastoid, the lateral, 
occipital, and the alar bones. They are gene- 
rally of small size, but occasionally, as in the 
Gadide, very largely developed, descending to 
reach the inferior occipital and the sphenoid. 
On the other hand, they are frequently entirely 
wanting, as, for instance, in the Pike, the Carp, 
and the Eel. 

In all the Reptilia the petro-temporal bones 
are recognizable as distinct pieces forming part 
of the cranial box, and become interesting, 
inasmuch as it is in them that the auditory 
apparatus is lodged. 

In Birds and Mammalia, however, the 
petrous bones become at an early period 
inseparably soldered to the other pieces, form- 
ing the so-called “ temporal bone.” 

' The ingrassial bones (14), as they have been 
named by Geoffroy, are, in the human subject, 
regarded as portions of the sphenoid, although 


830 


in reality they are distinct elements of the 
skull. In the higher Vertebrata they are con- 
solidated with the sphenoid, and have received 
the names of ale minores or apophyses ingrassii. 
Above these pass out the olfactory and beneath 
them the optic nerves, a circumstance which 
in itself sufficiently indicates their real nature. 
Sometimes, as in the Carp, they are united 
together inferiorly, so as to form a roof over 
the optic nerves. 

The ethmoid, Owen (anterior sphenoid, Cuv.: 
15,) so highly developed in the carnivorous 
Mammalia, is in the lower Vertebrata reduced 
to an extremely simple condition. In Fishes 
(fig. 437) it is generally distinct enough, form- 
ing the posterior boundary of the interorbital 
septum, but sometimes it is quite wanting or 
represented by membrane. When present, it is 
generally placed upon the sphenoid, sending 
off processes to join sometimes the ingrassial 
bones, sometimes the alar bones, or occasionally 
to remain suspended in the interorbital mem- 
brane that unites all these parts. The ethmoid 
appears to be deficient throughout all tribes of 
Reptiles. In Birds it is recognizable as a bone 
of considerable size, os tiga the posterior 
parts of the orbits, which it assists in forming 
the two lateral facets that enter into the com- 
position of those cavities corresponding with 
the ossa plana, as they are called, of the human 
subject; but these are obviously only portions 
of the ethmoid itself. In the Mammalia, 
owing to the prodigious developement of the 
olfactory apparatus, the e@thmoid becomes ex- 
tremely increased in size and importance, 
closing the anterior extremity of the cranial box, 
where it is perforated so as to present a central 
crest and cribriform plate, while inferiorly it 
has superadded to its body the superior tur- 
binated osseous lamelle that enter so largely into 
the construction of the olfactory organ. 

The vomer (16) is in Fishes a large and im- 
portant bone, joined posteriorly to the sphenoid 
and above to the @thmoid, forming a vertical 
portion, on each side of which are situated the 
organs of smell. Inferiorly it forms part of the 
roof of the mouth, and is often armed with teeth. 
Throughout all the Vertebrata this portion of the 
skeleton holds an analogous position and is re- 
cognized with facility. In Frogs and Lizards the 
bone is double, but in Tortoises and the higher 
animals generally there is but a single vomer, 
which enters more or less into the composition 
of the nasal septum. 

The nasal bones, Owen; (@thmoid, Cuv.: 
3) in Fishes are represented by a single bone 
impacted between the mid-frontals and the pre- 
frontals, and inferiorly joined to the vomer, 
forming a kind of septufh between the nasal 
organs, and thus in position resemble some- 
what the vertical lamella of the ethmoid of 
Mammalia. Sometimes, as in the Eel and the 
Conger, the bones in question are inseparably 
united into one piece. In the higher animals 
the nasal bones are two in number, covering 
the nasal cavity like an arch. They are present 
in all Reptiles except the Chelonians, and in 
Birds and Mammals are easily recognizable 
from their position. 


_Tumerous rows of teeth attached to its und 


OSSEOUS SYSTEM. (Comp. Anat.) 


The inferior turbinated bones, although in 
consequence of the construction of their nose 
quite wanting in Fishes, must not be omitted 
in enumerating the elements composing the 
skull in higher animals. In the humbler Rep- 
tiles, indeed, no traces of it are distinguishable ; 
but when the olfactory apparatus becomes fully 
developed, as in the Mammalia, they form an 
important part of the nasal character, and are 
found of large size, connected inseparably with 
the bones that surround the nose, 

The bones of the face have been already 
considered as constituting a very com { 
framework, destined to lodge the organs of the . 
principal senses or to constitute the instruments 
appropriated for the prehension or mastication 
of food. Seeing, however, that the same bone 
not unfrequently enters into the composition of 
several distinct cavities, we are unable to classify 
them further, and must therefore content our- 
selves with enumerating them seriatim as they — 
occur to our notice. , Y 

The maxillary (18) perform only a secon 
office in forming the upper jaw of a Fish, being 
in the finny tribes genera!ly destitute of teeth, — 
which in them are principally implanted upon 
the intermaxillary (17) that form the greater 

rtidn of the upper jaw. The maxillary in 

ishes is moveably articulated with the inter- 
maxillary, the vomer (16), and the palatine (22). 
Sometimes, as in the Herring and Lepisosteu: 
this bone is divided into several pieces. In 
Skates and Rays the whole upper jaw is made 
up of a single ossified mass, which bears the 


: 


surface. af 
But in all Reptiles, in Birds, and in Mam- 
malia the maxillary bones form the principé 
portion of the upper jaw, more particularly in 
the Mammalia, where the intermaxillary bone; 
are comparatively of small size. In this portio 
of the upper jaw are fixed the grinding teeth 
where such are present, a circumstance which 
in itself demands great strength in this part o 
the face; and, consequently, wherever powe 
of jaw is required to be conferred, it is prin 
apeny obtained by the increased developeme 
of this element of the skeleton, which thus 
comes the largest and, as it were, the cent 
bone of the whole fabric. 
The intermazillary bones (17) form the pri 
cipal part of the upper jaw in Fishes, and up 
their shape depends that of the snout. Se 
times these bones are flattened horizontally, 
compressed laterally, or prolonged into a be 
their form being modified by circumstan 
inalmost every genus. In the Chondroptery 
nevertheless, they are mere rudiments imbed 
in the substance of the upper lip. They 
persistent throughout all orders of Rept 
Birds, and Mammals, until we arrive 
Quadrumana, where they become anchyle 
with the maxillary, and in Man they are qi 
obliterated at an early period. ’ 
The bones of the face in osseous Fishes : 
exceedingly numerous and irregular, neith 
it easy to identify many of them as being at 
analogous to those which normally make 
the face, even of those Reptiles which pre 


- 


OSSEOUS SYSTEM. (Comp. Anat.) 


Fig. 441. 


Skull of the Crocodile of the Nile. 


the most complicated condition of this portion 
of the skeleton. The higher cartilaginous 
Fishes, however, ( Chondropterygii,) form a 
very remarkable exception; for in the Rays 
and Sharks the face is reduced to a very simple 
condition, in consequence of the want of sepa- 
_ Yation between the different pieces of the skele- 
_ ton, consequent on the permanently cartilaginous 
State of the osseous system in these tribes. 
The suborbital bones in Fishes (fig. 437, 
 & 8 8; g) form a kind of chain composed of a 
_ very variable number of pieces which surround 
_ the inferior and external margin of the orbit, 
 eovering the muscles of the face instead of 
giving attachment to them, a circumstance 
which induced Cuvier to believe that they did 
not normally belong to the series of facial bones. 
They are doubtless referable to the exo-skeleton 
or cuticular bones so largely developed in some 
fishes, and in this light they will be considered 
in another place. 
_ The prenasal bones, Owen; (nasal bones, 
Cuy.) of a Fish (fig. 436, 20) are found 
in a situatior very analogous to that which 
they occupy in the higher Vertebrata. They 
form the internal boundaries of the nasal cham- 
ber, and articulate superiorly with the frontal 
(1). These bones are regarded by Professor 
Owen as being the representatives of the 


831 


moveable cartilages of the nose of other Ver- 
tebrata ossified and entering into the composi- 
tion of the facial skeleton. 

Besides the suborbital chain of bones (g,g,¢,¢) 
above mentioned as partially surrounding the 
orbit, and which in the Gurnards and other 
hard-cheeked Fishes cover the cheeks as with a 
bony case, entitling them to the name applied 
to them by Cuvier of “ joues cuirassés,” another 
chain of bones called the supra-temporal is not 
unfrequently met with, placed on each side, 
over the interval that separates the external from 
the middle prominent ridge, developed from 
the exterior of the cranium so as, together with 
these projections, to cover the articulation of 
the supra-scapular bone (46). These bones are 
evidently peculiar to Fishes, and, like the sub- 
orbital, must be referred to the exoskeleton 
and not deemed to belong properly to the 
osseous system. In this light they will be con- 
sidered in another place. 


Fig. 442. 


Section of Crocodile’s skull. 


The palatine arch or osseous roof of the 
mouth is composed of analogous bones in all 
the different races of Vertebrata; but in the 
lower Vertebrata there are found in connection 
with this region of the skeleton several pieces 
that have no representatives in the higher 
classes. 


832 


The palatine bones (22) are easily recog- 
nisable in Fishes, occupying the same place as 
in Serpents (fig. 439), and, moreover, further 
distinguished by being frequently armed with 
teeth which project into the roof of the mouth. 
In Reptiles, also, teeth are often attached to 
them where they assist in forming the cavity of 
the mouth. These bones are found in all the 
vertebrate classes. 

The transverse bones (24) occupy nearly the 
same situation in Fishes as in Reptiles, but in 
the latter they are most distinctly seen. In the 
Crocodile each is a bone of considerable size, 
composed of three branches and extending 
between the pterygoid bone and the junction of 
the jugal, the maxillary, and the posterior 
frontal. This bone is not met with, either in 
Birds or Mammalia, not even in the fetal 
period of their existence. 

The internal pterygoid ‘bones (25) are like- 
wise distinct in fishes, stretching between the 


Fig. 443. 


Shull of a young Ostrich ( Struthio Camelus ). 


eae bone and that which supports the 
ower jaw (26). In Reptiles they are large and 
im t detached bones, occupying the 
sition of the pterysoid of the sphe- 
noid ; but in Birds and Mammals they become 
completely anchylosed with the sphenoid, so 
that, by the human osteologist, they are erro- 
neously regarded as apophyses of that bone. 


OSSEOUS SYSTEM. (Comp. Anat.) 
Fig. 444. 


LE ‘ | 


a, 


Section of skull of young Ostrich. 


The zygomatic, Owen, (jugal, Cuvier,) are 
in Fishes broad pieces, generally of a ars r 
shape, placed behind the transverse, which by 
their inferior angle support the articulation 
of the lower jaw. In Reptiles, too, it may al- 
ways be distinguished by the latter cireum- 
stance, and in Serpents it is particularly re- 
markable (figs. 438, 439, 26), = 
from the squamo-temporal (mastoid, py) 
like a branch, and thus giving that extra 
dinary mobility to the articulation of the in 
ferior maxilla which enables those Reptiles” 
swallow prey so disproportioned to the size’ 
their mouths. In other Reptiles this mobili 
is in a great degree lost. But in Birds th 
zygomatic bones again assume very importa 
functions. They are here known by the nat 
ossa quadrata, and standing out to a ¢ 
siderable distance from the skull allow of gr 
mobility to the zygomato-maxillary articu 
and also to the bones supporting the supel 
maxilla. In Mammalia this zygomatie be 
is so firmly and undistinguishably unite 
the temporal that the human osteologist 
calls it the zygomatic process of that bone. 

The masto-temporal, Owen, ( Ci 
23), are in Fishes and Reptiles distinct elemet 
of the skull, which in the human cranium a 
consolidated with the other elements co 
posing the “ os temporis.” - 


OSSEOUS SYSTEM. (Comp. Anat.) 


The styloid bones(29), mererudiments ' 
in the human skeleton, anchylosed with 
the rest of the temporal bone, of which 
they are called the “ styloid process,” 
in the water-breathing Vertebrata are 
distinct pieces interposed between the os 
hyoides and the base of the skull, serving 
to unite the former to the latter. 

The symplectic bones (31) seem to be 
peculiar to Fishes ; they accompany the 
transverse, and assist in connecting the 
articulation of the lower jaw with the 

te latine apparatus. 

F The lawer jaw, Ephotsh in the adult 
human subject formed of a single piece, | 
in the /etus consists of two lateral halves 
united by a symphysis, as it is perma- 
nently in many of the lower Quadru- 
peds. In Reptiles and Fishes, how- 
ever, each half consists of numerous 
jieces, to which distinct names have 
m given by the comparative anato- 
mist. In the Crocodile and most reptiles 
there are six in number, viz. the dental 
portion (34), in which are situated all 
the alveoli of the teeth, uniting with its 
fellow to form the symphysis of the jaw- 

The opercular, covering almost all the inner 
aspect of the jaw except in front. 

The angular (36) and the supra-angular (35), 

placed one above the other, reaching quite to 
the posterior extremity of the jaw. In the 
Crocodile they leave between them a conside- 
rable space occupied anteriorly by the end of 
the dental portion, and then by a large oval 
aperture. 
The urticular (e), bearing the articular pro- 
cess, whereby the jaw is connected with the 
skull. Likewise another small and unimpor- 
tant plate of bone sometimes seen on the inver 
aspect of the inferior maxilla. 

In the Chondropterygious Fishes the lower 
jaw is made up of only one bone, the arti- 
ar, upon which the teeth are affixed: rudi- 


Fig. 446. 


Human Shull. 


833 
Fig. 445. 


Padi Un 


Human Shull. 


ments of the others are, however, met with 
imbedded in the flesh beneath the skin. 

The hyo-branchial apparatus—The osseous 
framework to which in the human subject the 
name of os hyotdes has been appropriated, from 
the trivial circumstance that in the simple con- 
dition under which it presents itself in man 
it resembles the Greek letter v, is found in the 
lower Vertebrata to be permanently composed 
of very numerous pieces, which are made sub- 
servient to respiration, and from their size and 
number render the whole apparatus, which 
they assist in forming, really worthy of the 
name of an anterior thorax. The hyoid system 
of bones may indeed be regarded as being in 
some respects vicarious in function with the 
true thorax, the former belonging especially to 
the aquatic, the other to the aerial mode of 
respiration ; whilst, therefore, as 
in Fishes, the gills form the only 
meansof breathing, andthe branchial 
arches exist in their full state of 
developement, the hyo-branchialap- 
paratus is complete and preponde- 
rates in importance over the thorax ; 
but, in proportion as pulmonary 
respiration is established, as we 
ascend the scale of animal existence, 
the thoracic system of bones as- 
sumes the principal duties con- 
‘ nected with the inspiration and 
expiration of air, and the os hyoides - 
dwindles into a very rudimentary 
condition. The above circum- 
stances however, interesting as they 
are when a mere comparison is 
instituted between the hyoid bones 
of various animals as to their com- 
position when in the adult state, 
assume additional importance when 
we reflect that all the higher Ver- 
tebrata possess in the earlier stages 

3H 


834 


of their life a true branchial apparatus, which 
subsequently becomes absorbed to give place 
to thoracic or pulmonary respiration, and 
consequently they are furnished in the first 
portion of their existence with the hyoid 
system of a fish, which, passing through dif- 
ferent phases of gradually diminishing com- 

lexity, is slowly converted into the simple 
orm it presents in their mature or adult 
condition. So diversified, in fact, is this por- 
tion of the osseous skeleton in the different 
classes of Vertebrata, that the anatomist only 
acquainted with human osteology would never 
~be able to recognise the analogy between what 
he sees in man and the condition in which it 
exists in its more complicated states, or at all 
understand the metamorphosis which it un- 
dergoes in the embryo of Mammalia, without 
tracing it through all its forms, as we shall 
now proceed to do with as much brevity as is 
compatible with our subject. 

In the Fish the os hyoides is situated as in 
_all the other Vertebrata, and is composed of 
twelve bones. It consists of two branches, 
each made up of five distinct elements, namely, 
the styloid bone (29), which suspends it to the 
temporal; two broad lateral pieces (fig. 436, 
37 and 38) placed one behind the other, and 
two small bones (39 and 40) placed one above 
the other at the anterior extremity of each 
branch, and forming with their fellows of the 
opposite side a kind of symphysis uniting the 
two halves of the bone. In front of this sym- 
physis is a single bone, the lingual (41) situ- 
ated as in Birds and Reptiles, and behind in 
the angle formed by the union of the two 
branches another azygos piece representing the 
tail of the os hyoides so distinct in Lizards and 
in Birds. This latter piece becoming joined to 
the symphysis of the Scant bones forms the 
isthmus that inferiorly separates the two bran- 
chial apertures of the fish. 

Appended to the inferior and external mar- 
gin of each branch of the os hyoides of a fish, 
are the branchiostegous rays (fig. 437, 43), 
destined to support the branchiostegous mem- 
brane that completes the gill-covers. These 
are very various both in number and form in 
different fishes; they are fixed to the os hy- 
oides by distinct articulations, sometimes by 
simple ligaments. Autenrieth and Geoffroy 
suppose these branchiostegous rays to be the 
representatives of sternal ribs, but doubtless 
they belong rather to the exo-skeleton. 

0 facilitate, however, a comparison between 
the above complicated series of bones and the 
corresponding pieces met with in other classes, 
it will be advisable to lay before the reader the 
result of the elaborate analysis of this part of 

‘the skeleton made by Geoffroy St. Hilaire, 
whose names applied to the various elements 
composing it are not only classically elegant, 
but from their simplicity will save much useless 
circumlocution. When complete, the distin- 
guished anatomist alluded to considers the 
os hyoides to consist of the following parts: 
The body or basihyal piece, forming the central 
portion of the fabric; the urohyal or tail of 
the os hyoides (fig. 437, 42); the entohyal, 


OSSEOUS SYSTEM. (Comp. Anat.) 


a piece sometimes int between the two 
former; two glossohyals or posterior cornua 5 
two apuhyals (39) forming the first pieces of the 
anterior or styloid cornua; two ceratohyals(40) 
forming the second pieces of these 3 
and lastly, two stylohyals (29), which are re~ 
presented in the human subject by the styloid 
rocesses of the temporal Lie a oa 
Appended to this hyoid apparatus are a 
ledias' of lateral arches a alatien in their im- 
portance the ribs in the water-breathing Ver- — 
tebrata, and indeed somewhat resembling them — 
in structure and arrangement, along which run 
the branchial vessels to the gills, and subse- 
quently from the gills to form the aorta. These 
arches have in Sct, by soe continental an ato 
mists, been actually loo upon as repre-— 
senting the thorax of Vertebrata that respire 
the air, but with little reason, as must be evi- 
dent on considering how, as the real thorax is 
called into play, these are gradually absorbed 
and disappear. ee. 
The branchial arches of a fish, from which 
are suspended the branchial fringes, consist om 
each side of four chains of bones adherent by 
their inferior extremities to an intermedi te 
series of ossicles, which is connected ante- 
riorly with the symphysis of the os hyoide 
between the four anterior elements of that bo 
and above its ¢ail. Superiorly the_bravichiz 
arches are fixed by a ligamentous attachmen 
beneath the cranium. 
The series of intermediate bones with whiel 
the pairs of branchial arches are connected | 
feriorly, are placed behind the lingual and ar 
three in number, forming a kind of little ste 
num to the hyoid apparatus. 
branchial arches consists of a superior and i 
ferior portion that are moveable upon eai 
other. The inferior portion (, Sig. 437, 58) 
that connected with the intermediate chat 
bones, and in the anterior three pairs of are 
this is formed of two pees t 
ir has this part composed of only one pi 
The upper Seine of the branchial ar 
are made up of a single bone. The tht 
posterior (fig. 437, 61) support the phar 
geal bones (fig. 437, 62), while the anteric 
attached to the skull by the intervention 
little style (59), which might be regardet 
the pharyngeal bone belonging to this pair. 
Internally all the branchial arches are 
vided with osseous plates or ridges whic 
generally covered with teeth. per 
in some degree the function of the epi 
of Mammalia, inasmuch as they p even 
thing taken into the mouth from getting 
the gills along with the water as it passes 
respiratory organs. ma 
e pharyngeal bones are iar to 
and .. ainated in the dueat: whe 
powerfully assist in masticating the food 
are usually two inferior and six superior, 
inferior (fig. 437, 56) are attached behi 
branchie in the angle formed by the i 
of branchial arches; they are generally 
triangular shape, and form a kind of fi 
the pharynx. The upper pieces (figs 
62) are three in number on each side, 


OSSEOUS SYSTEM. (Comp. Anat.) 


attached to the extremity of 
the upper portion of one of 
the three last branchial 
arches. 

Condition of theos hyoides 
én Reptiles.—The condition 
of the os hyoides ina per- 
fect Reptile is very simple 
when compared with that 
of the Fish, or even, as is 
most strikingly apparent in 
the Raa bs ails, 
with that which it exhibits 
previous to the accomplish- 
ment of the metamorphosis 
which changes the mode of 
respiration from that ofa fish 
into that of the Frog. In the 
adult Reptile, indeed, the 

_ composition of this bone 
gives no indication of its pre- 
vious complexity of struc- 
ture, consisting only of the 
remains of the anterior cor- 
nua (26, a) and a broad hatchet-shaped disc 
forming the body of the bone. In Lizards its 
Structure remains more complicated, resembling 
that of Birds. The body is generally simple, 
with two and sometimes three sets of cornua- 
like appendages connected with it. From the 
_ fore part of the body projects along and slender 
_ process, more or less cartilaginous, which pe- 

_ netrates the substance of the tongue. The ante- 
_ fior pair of cornua are variously folded, and the 
_ posterior placed differently in different genera; 
while the third pair, which is but seldom met 
with, seem rather to be prolongations of 
the body of the bone than separate elements 
_ appended to it. In the Chelonian Reptiles the 
_hyoid apparatus varies remarkably in form in 
different species. It generally consists of a 
central part, which is frequently itself divisible 
into several pieces, and of two or sometimes 
three pairs of cornua. Moreover, beneath the 
| anterior part of the body, there is suspended 
a bone or cartilage, which is sometimes double 
and represents the special bone of the tongue, 
which in Birds is articulated to the fore part 
_ of the body of the os hyoides. 

The os hyoides of the Crocodiles is the sim- 
 plest met with in the class of Reptiles, its 

central portion being a mere broad cartilagi- 
nous plate, convex below, concave above ; its 
" anterior part having a semicircular form, while 
_ its posterior margin is hollowed out into a con- 
| €ave edge; there are no remnants of cornua 
visible, and the os hyoides here seems to per- 
form the duties of epiglottis, hyoid, and thy- 
roid cartilage. 

_ Metamorphosis of the os hyoides.— Pro- 
_ fessor Bell having already described the most 
remarkable changes which the branchial appa- 
Tatus of the Frog undergoes during its meta~ 
‘morphosis, it would have been needless to 
Tecur to the subject again in this place, were it 
not for the purpose of collating the facts there 
‘ecorded with the series of changes we are now 
discussing, and indicating the nature of the 
‘Tespective bones delineated in a preceding 


Fig. 447. 


volume (vide Article AMpuisra, vol. i. figs. 21, 
22, 23, 24, 25, 26). Weshall, however, embrace 
the opportunity afforded of adding a few circum- 
stances to those there recorded, extracted from 
the observations of M. Martin St. Ange, con- 
nected with this most remarkable and interest- 
ing process. 

Some days before the birth of the Tadpole 
the os hyoides consists of a single median 
piece, of a pair of broad cartilaginous plates 
situated on each side of the former, anteriorly, 
and of two other similar plates occupying a 
like position behind, to each of which last are 
appended four separate styliform pieces repre- 
senting the branchial arches, making thirteen 
pieces in all. 

Examified-a little after birth, the whole car- 
tilaginous frame-work is found to have increased 
considerably in breadth, more espscially the 
eight last-mentioned cartilaginous styles upon 
which the branchial vessels run, sufficiently 
indicating their nature—moreover, they become 
united together by their distal extremities so as 
to form a series of arches, as represented in fig. 
21, vol.i. p. 98, ate. At this point of its deve- 
lopement the hyoid system of the Frog is at its 
maximum of complexity, and we will therefore 
pause to examine the elements that enter into 
its composition. The median ite (fig. 21, b, 
vol. i. p. 98) represents, according to Geoffioy, 
the glossohyat, basihyal, and urohyal elements of 
the Fish. The elements marked a will be the 
stylhyal bone, suspending the whole from the 
tympanic bone of the skull (¢ ), while the broad 
eae c, c, regarded by the same author as 

eing dismemberments of the larynx, imme- 
diately sustain the branchial arches. 

At that period, when in consequence of the 
changes that take place in the circulation of the 
Tadpole the branchial vessels are to be oblite- 
rated, the condition of the os hyoides too 
becomes rapidly changed. The cartilaginous 
arches become diminished, especially in length, 
and at last become completely absorbed except- 
ing two remnants, which are found appended to 

3H 2 


836 


the posterior margin of the os hyoides even in 
the adult Frog, although they remain for a very 
long while in a cartilaginous condition. The 
two pieces a, a, then speedily become dimi- 
nished in breadth, and the whole shape of the 
os hyoides approximates that of the adult Frog, 
the condition of the pieces marked a, a, forming 
the chief difference between them. This at 


length becomes gradually more slender and 


elongated, assuming at last the shape delineated 
in fig. 26, vol. i. (a), where the permanent and 
complete condition of the os hyoides of this 
Reptile is fully established. 

he different pieces composing the os hyoides 
of a Bird having been already described and 
figured (vide Article Aves, jig. 151), it only 
remains for us in this place to complete our 
review of the hyoid apparatus by examining its 
condition in the Mammiferous races, in which 
it is found gradually to become stripped of 
many parts that before entered so conspicuously 
into the construction of this portion of the 
osseous frame-work of the throat, and assume a 
simplicity of structure that progressively assi- 
milates to the shape it presents in the human 
subject, in which alone indeed the name of 
hyoides is at all applicable. In Man, observes 
Geoffroy, the os hyoides is generally said to 
consist of a body and four symmetric pairs of 
branches or cornua. The anterior cornua (su- 
perior when man stands in the erect posture) 
are reduced to mere rudiments, but in those 
Mammalia that have the head elongated these 
anterior cornua are very largely developed, 
appended from the sides of a special pair of 
bones, the styloids, which, although in mankind 
they are reduced to simple and almost useless 
apophyses, consolidated with the temporal 
bones in the generality of Mammifers, are very 
large and important pieces, so connected with 
the anterior cornua that they are frequently 
regarded as being additional parts of the os 
hyoides. But although in the human body 
these apophyses are comparatively small, and 
are respectively removed, as it were, to their 
proper places, the styloids to the cranial bones, 
and the anterior cornua to the os hyoides, they 
perform the same office of connecting the hyoid 
apparatus to the cranium in Man by the inter- 
position of a cartilage, and in quadrupeds still 
more effectually by an uninterrupted chain of 
bores connected with each other. 

The posterior cornua, each consisting of a 
single piece, resemble each other in office at 
least, in all the Mammalia, forming with the 
body of the os hyoides a horse-shoe figure, to 
which the larynx is appended. The body itself, 
or central portion of the bone, although in the 
human subject only represented by a slight 
tuberosity, will be found in the Rodentia, 
Ruminants, and more especially Solipeds, to 
become very conspicuous, and in the last case 
obviously distinct elements of the skeleton. In 
these Mammalia indeed, the os hyoides is 
found to consist of no fewer than nine pieces, 
without enumerating the styloid bones ; a con- 
dition of complexity almost approaching that 
met with in the Birds and inferior Vertebrata. 

Leaving the consideration of the bones of the 


OSSEOUS SYSTEM. (Comp. Anat.) 


face, and those which enter into the compo- a 
sition of the hyo-branchial apparatus, which 
may be all regarded as forming a succession of 
arches depending from the sides of the cranial 
vertebra, of the transverse processes, of which 
they are indeed regarded by some writers to be 
ee costal prolongations; the anatomist finds 
a more or less extensive series of bones derived 
from the sides of the spinal vertebre, and fre- 
quently arching downwards to enclose and pro- 
tect the viscera either of the thorax or of the 
abdomen, or of both. These lateral appa z 
dages to the spinal column are invariably in 
connection with the transverse processes, of 
which in their simple forms they might seem to — 
be derivations, but when largely developed, as 
for example in the thorax of Mammiferous 
animals, they attain to a prodigious size, form-— 
ing, almost by themselves, the frame-work of 
the thorax, and constituting the paneer agents” 
employed in the performance of the mechanical 
actions connected with the inspiration and ex- 
piration of the air used for the purpose of 
respiration. The pee of the ribs thus 
employed for the formation of a thorax is ex- 
tremely variable in different races. In Man 
and all other Mammalia, in obedience to a law 
at present unexplained, they commence inva- 
riably at the eighth spinal vertebra, counting 
from the skull; but in Birds the whole thorax 
is removed much further backwards in order’ 
allow of the greater elongation of the neck. __ 
Besides the dorsal ribs thus derived from the 
spine, and which exist alone in the human 
subject and in Mammalia generally, anothe; 
series of additional elements is met with in 
Reptiles and in Birds, which must be called 
sternal ribs, and these, conjoined with the la 
enter into the composition of the thoracic cavit 
In Fishes only dorsal ribs are met with, and thes 
are connected bya simple articulating facet to th 
sides of the bodies of the vertebrae placed imme 
diately above the abdominal cavity. Frequenth 
however, the ribs of Fishes have supplements 
bones appended to them, which in the livin 
fish are embedded amongst the lateral musel 
of the body. Sometimes, indeed, these adi 
tional rib-like processes arise immediately fro 
the bodies of the vertebre themselves, giv 
an appearance of complexity to this portion 
the skeleton that is calculated to puzzle | 
young osteologist. In the Cyprinide and 
Herring tribe a small osseous piece is interpo 
between the vertebra and the rib that is 
pended to it; this is obviously a detached t 
verse process. In the Batrachia de 
only are found, and these, even when | 
largely developed, are mere rudiments appen 
to the ends of the transverse processes 0 
vertebree. ) 
In Serpents likewise the enormously 
longed thorax is entirely made up of 
elements, but these, existing as they do a 
along the whole length of the body, and 
moved by an elaborate muscular appat 
perform to a certain extent the office of | 
motive organs, =: 
In the Chelonian and Saurian Reptile 
construction of the thorax becomes much 1 


OSSEOUS SYSTEM. (Comp. Anat.) 


complicated hy the developement of additional 

elements hereafter to be described, and in these 

tribes the examination of the dorsal ribs ex- 

hibits to the osteologist several points of very 

great interest relative to this portion of the 

skeleton. In the Crocodile, for example, the 

elements derived from the vertebre present 

every gradation of form between the simplest 

and most complex condition of the costal 

pieces. The hinder ones are loose and floating, 

being mere appendages to the transverse pro- 

cesses, to the ends of which they are fixed as in 

the Batrachia, by a simple undivided articu- 

lation; but as we advance forwards from this 

point along the true thorax, their connection 

with the vertebrae becomes progressively changed 

through a series of most beautiful gradations 

of form; the head of the rib becomes slowly 
_ divided into two distinct articulating surfaces, 
both of which are at first attached to ‘the trans- 
verse process of the corresponding vertebra, 
but more anteriorly the bifurcation of the head 
of the rib being completed, one division be- 
comes attached to the body of the vertebra, 
while the other, the tubercle, is fixed to the 
transverse process, and every gradation inter- 
mediate between the two extremes of structure 
presented in this portion of the skeleton is 
thus exhibited in the same animal. But dorsal 
ribs are developed in the Crocodile anterior to 
the thorax and with a very different office. costal 
"appendages (fig. 432, 0.) being attached to all 
the transverse processes of the cervical vertebra. 
These, instead of being prolonged downwards, 
spread out anteriorly and posteriorly, assuming 
the shape of the letter T, and forming a con- 
tinuous chain of bones, that trammels the lateral 
movements of the neck, but at the same time 
affords ample surface for the attachment of the 
unusually strong muscles of this Reptile’s neck. 
The dorsal ribs of the Chelonian Reptiles are 
equally interesting on account of the strange 
modification in the manner of their connection 
with the spine, whereby they are absolutely 
brought quite to the exterior of the body, and 
in the Tortoises so completely united by suture 
to the spinous processes of the vertebrae, and 
likewise to each other, as to form the greater 
portion of the dorsal shield or carapax peculiar 
to these races. In order to effect this total 
change in the position of the costal elements of 
_ the skeleton, the anatomist finds to his asto- 
nishment that very simple arrangements are 
necessary. The neuro-spinal apophyses of the 
vertebre are prodigiously developed and spread 
out into broad flat osseous plates firmly con- 
_ nected with each other and with the tubercles 
of the ribs by means of their broad serrated 
_ tiargins; this being accomplished, the usual 
_ attachments between the head of the rib and 
oth spine become unnecessary ; the bodies of 


= 


a 


Ne a ee 


_ the vertebrae remain quite rudimentary, the 
_ transverse processes are obliterated, and the 
-f head of the rib itself reduced to a ligamentous 
condition, the carapax being left sufficiently 
‘Strong without any necessity for the usual 
. _ abutments of the ribs on the vertebral column. 
___ In Birds, on the contrary, a precisely oppo- 
site arrangement is required in order to com- 


Py 
Tse i 


837 


bine strength and lightness in the construction 
of the framework\of their thorax, which must 
bear the strain ofthe strong muscles used in 
flight. The bifurcation of the commencement 
of the rib is here exaggerated to the utmost ; 
its strongly developed head is firmly articulated 
to the vertebral bodies, and by means of its 
tubercle it is additionally secured to the trans- 
verse processes of the dorsal vertebra, and 
moreover, besides the strong buttresses thus 
made to sustain the thorax, additional long 
splints of bone project backwards from the 
dorsal ribs much in the same manner as in 
Fishes, only here the superadded processes are 
prolonged until they overlap the rilb succeeding 
next behind, binding the whole together; and 
materially assisting to strengthen the thoracic , 
framework. 

But even in Birds, as in the Crocodile, the 
dorsal ribs are found developed from the ver- 
tebre anterior to as well as behind the proper 
thorax. 

In Mammals, the great portion of the chest 
consists of dorsal ribs, which are eked out in 
front by costal cartilages connecting them on 
each side to the sternum. Yet still the floating 
ribs behind the proper thorax are persistent, 
and in one rare instance, namely, the Sloth, 
they exist in front as well, appended to what 
else the anatomist would cal] cervical vertebra. 
We therefore see at once that the division of 
the spine into the different regions pointed out 
in the human skeleton is quite arbitrary, as the 
existence of ribs and the possession of a thorax 
are by no means necessarily linked together. 

A very singular illustration of the co-exist-" 
ence of thoracic and non-thoracic ribs is met 
with in Reptiles belonging to the remarkable 
genus Draco, in which, although the anterior 
ribs are completely developed so as to form a 
true chest, the six hinder pairs are converted to 
a totally different use, being prolonged laterally 
to a great extent, and covered with a duplica- 
ture of the integument so as to form an ample 
parachute, by the assistance of which these 
agile little lizards are in some degree supported 
in the air as they leap from branch to branch. 

The thoracic portion of the skeleton is only 
met with ina complete state in Birds and the 
higher Reptilia, the Saurians and Chelonians, 
in which races it constitutes a very elaborate 
framework composed of numerous elements, of 
which no traces are perceptible in the human 
subject or in the generality of Mammalia. In the 
Crocodile it is seen to be made up of the fol- 
lowing parts—1st, of a complete apparatus of 
dorsal ribs (fig. 482, 1), connected to the 
transverse processes and bodies of the dorsal 
vertebra ; 2ndly, of an equal number of sternal 
ribs (m_), interposed between the ends of the 
former and the sides of the sternum; and, 
3dly, of the sternum (n), forming the pectoral 
boundary of the chest. 

The sternum itself, although usually consi- 
dered by the human osteologist as being ex- 
tremely simple in its composition, is, when 
fully developed, made up of several distinct 
elements equalizing in importance any that 
assist in building up the skeleton. It is, how- 


* 


838 


ever, only in the Chelonian Reptiles that the 
sternal bones present themselves in full complete- 
ness, forming the broad shield or plastron that 
defends the ventral aspect of the body in those 
animals, which, being solidly connected on each 
side with the dorsal plate or carapax, forms a 
kind of box to shelter the whole body. 

The sternum, thus necessarily amplified to 
the utmost, consists of no fewer than nine dis- 
tinct elements, to all of which names have 
been applied expressive of their position rela- 
tive to each other. First, there is an azygos 
element occupying the mesial or central 
portion of the anterior part of the plastron, 
which from its situation has been named 
the entosternal element. This central piece is 
bounded anteriorly by the episternal bones, 
and posteriorly by another pair named the hyo- 
sternal, being as it were set in the centre of 
these lateral pieces as ina frame. The poste- 
rior half of the sternum consists of two pairs 
of elements, the larger and most anterior being 
designated as the hyposternal, whilst the pos- 
terior occupying the position of the xiphoid 
cartilage in the human skeleton are fitly deno- 
minated the «iphosternal pieces, which are 
united to each other and to the last-mentioned 
pair by strong serrated sutures, as indeed are 
all the elements above enumerated. 

In the aquatic Chelonians, the Turtles, the 
same elements are met with entering into the 
formation of the enormous sternnm, and their 
positions with respect to each other are pre- 
cisely similar; but here, in order to lighten 
the skeleton, large excavations are hollowed 
out in the centre of the bone, so that the 
three posterior pairs of sternal elements do 
not meet in the mesian line; but in all other 
respects their identity is at once evident. The 
sternal apparatus, however, although most fre- 
quently it enters largely into the formation of 
the thorax, is stili more nearly related to the 
anterior extremity, with the movements of which 
it is invariably intimately connected, and fre- 
quently gives origin to the most important 
muscles of locomotion. The sternum can 
scarcely be said to exist in Fishes, with the ex- 
ception of a very few (Clupea), and in these 
it is represented by a few azygos bones, on 
which the ribs abut inferiorly. 

In the Anourous Batrachia, as the Frog and 
Toad, the sternum is remarkable as existing in 
a very complete state of developement quite 
independently of any other elements of the 
thorax, seeing that in these animals there are 
no ribs to be attached to it. It consists here 
of a chain of bones, in which most of the 
elements above enumerated are easily recog- 
nizable, placed along the mesian line of the 
breast, and supporting on either side the cora- 
coidand clavicular bones that enter into the com- 
pen of the shoulder; the whole apparatus 

as been already figured in the article Ampur- 
Bia, (fig. 17,) where the episternal bones 
forming the most anterior part of the series, 
the hyosternal bones (e), the entosternal bone 
(g), to the sides of which are attached both the 
clavicle (c) and the coracofd (d), the hypo- 
sternal bones (f'), and the xiphisternal elements 


OSSEOUS SYSTEM. (Comp. Awar.) 


oe the chain posteriorly, are all indi- 
cated. 


The sternum of Birds is peculiar on account 
of the prodigious developement of the azygos 
or entosternal element of which it is principally 
composed, a circumstance obviously intended: 
to strengthen this part of the skeleton, and 
prevent the tearing asunder of the lateral 
tions of the bone by the enormous strain of the 
strong and massive muscles of flight, an acci- 
dent of which there would have been : 
danger had the mesial sutures that exist in the 
sternum of the Tortoise been here ited. 
The pieces composing it are pointed out in fig. 
129, vol. i. p. 282, where the following elements: 
are delineated, viz. the entosternal (a), the hyo- — 
sternals (b), the hyposternals (c), and the xiphi= 
sternals (g). iy 

The sternum of Mammalia becomes once — 
more reduced to its simplest form, consisting” 
of a chain of osseous pieces situated along the — 
mesian line on the anterior aspect of the thorax, - 
which they partially assist in forming. In some — 
races, however, as, for example, in the Mono- 
tremata, so closely allied to Birds in all the 
details of their economy, and also in Quadru: 
peds possessing great power of using the an- 
terior extremities either for flight” or digging, 
as, for example, the Bat and the Mole, 
importance of this part of the osseous frame= 
work becomes considerably increased, and it is 
developed accordingly. 3 

Frequently connected with the sternum, t 
by no means to be ed as derivation 
from that bone, are the other importantelem 
of this part of the skeleton already noticed 
which, though entirely deficient in hum: 
subject and in the Mammalia generally, ar 
found in Birds and many Reptiles to be 
sential to the structure of the thorax. nes 
are the sternal or abdominal ribs (fig. 432, m 
a series of distinct bones in betwee 
the spinal ribs and the sides of the sternum, § 
as to form a complete osseous framework to th 
chest. In Fishes, as well as in the Ba chi 
and Ophidian Reptiles, these bones are abs 
lutely wanting, though in the Frogs and Toa 
the sternum is so large. But in the Sauria 
as, for instance, in the Crocodile, they | 
essential parts of the thoracic rece nd 
materially the movements requisite ) 
tion. In the Crocodile these ventral rit 
tend indeed much further backwards than 
dorsal ones that form the posterior bound 
of the thorax, being continued along the 
domen almost as far back as the pelvis 
bedded in the abdominal muscles, the at 
of which they doubtless materially strer 

In the higher Vertebrata, i.e. the Mama 
the sternal ribs are entirely represented b 
costal cartilages, and the abdominal w 
seem to be completely wanting; still 
seems but little doubt that, even in Ma 
lingering rudiments of ventral ribs are 
able in the tendinous intersections of the 
muscles of the abdomen. ~ 

In Birds the sternal ribs assume still 
importance as regards their effect in stre 
ening the thorax, and converting the ss 


fa 


i +f 


Ee - 


OSSEOUS SYSTEM. (Comp. Anwar.) 


portion of the skeleton into an osseous frame- 
work able to sustain the stress of. those power- 
ful muscles that wield the instruments of 
flight. At one end each of these pieces 
is moveably articulated with the distal ex- 
tremity of the corresponding dorsal rib, whilst 
at the opposite it is firmly attached to the sides 
of the expanded sternum by joints that admit 
of a certain extent of motion. 

It is in the Chelonian Reptiles that these 
accessory portions of the thorax attain their 
greatest growth, spreading into broad plates 
that are connected by strong sutures to the ex- 
tremities of all the spinal ribs and likewise to 
each other in the Tortoises, completing thus 
the cara or dorsal shield; and, moreover, 

__ being solidly united at the sides with the enor- 
_ mous apparatus of sternal bones, the whole 
__ body of the Tortoise becomes encased in bony 
_ armour, derived entirely from the thoracic 
_ elements of the skeleton. 

: The anTerror timss of Vertebrate animals, 
_ although essentially composed of similar ele- 
ments throughout all the classes belonging to 
this great division of animated nature, are 
made subservient to very various and opposite 
uses; the pectoral fin of the Flying Fish, the 
enormous hand of the Skate, the paddle of 
the Turtle, the flipper of the Whale, the wings 
of the Bird and of the Bat, the broad shovels 
of the Mole, and that masterpiece of organiza- 
_ tion, the human hand, being respectively but 
_ simple modifications of the same structure. 

In the osseous Fishes, indeed, it is not 
always easy to recognise the elements that are 
correlative with those of the higher Vertebrata ; 
but a little attention is sufficient to prove the 
construction of the pectoral fins among the 
_ finny tribes to be true representatives of the 
_ anterior extremities of other races, as will be 
_ evident from the following masterly analysis of 
the parts composing the pectoral fin of the 
_ Perch, given in Cuvier’s great work on Fishes. 
_ Immediately behind the gill-openings there is 
placed on each side a framework of bones 
that bound the branchial apertures. This frame 
| is attached superiorly to the back of the head, 

butinferiorly the two halves are united together, 
‘forming a bony zone that surrounds the body 
this part; and being connected inferiorly 
vith the body of the os hyoides, forms here a 
kind of isthmus that separates the gill-open- 
“ings from each other. The bony zone above 
“described is made up on each side of three 
| pieces, which represent the bones of the 
Shoulder and of the arm, to which is affixed 
steriorly a group of two or three other bones 
“that represent the forearm, wherewith is con- 
“nected the fin itself, the representative of the 
hand. The names applicable to these pieces 
Of the skeleton when their analogies are strictly 
Investigated are as follow :—The suprascapular,* 
the scapular,t the humerus,} the radius and ulna, 


‘ 


po 
ad 


2. Synonyms — Omoplate, Omolite, Pedicule de 


5 t Syn,— Omoplate (Geoffroy), Acromion ( Bakker). 
_ + Syn.—Clavicle (Meckel, Geotl.), Camosteon 
(Bakker). 


eae 


839 


to which succeed the carpal bones and the 
phalanges of the fin, In addition to these must 
be noticed the two pieces regarded by Cuvier 
as representing the coracoid bone of Reptiles. 

When fully developed, the anterior extremity 
is made up of a greater number of elements 
than exist in the human skeleton. The shoulder 
is a strong framework, composed of three dis- ~ 
tinct pieces, named respectively the scapula, 
the clavicle, and the coracoid bone. The other 
bones of the limb resemble each other in their 
general arrangement throughout all the Verte- 
brata, and in the Crocodile, where all parts of 
the limb present a mediym state of develope- 
ment, the analogies between the bones com- 
posing it and those of the human arm are at 
once recognised. The humerus, a single bone, 
supports the first division of the limb. Two 
bones, the radius and the ulna, are met with 
in the forearm, while the bones of the carpus, 
the metacarpus, and the phalanges of the fingers 
present an arrangement similar to what is found 
in the human body. In order, however, to 
appreciate the important modifications required 
in the disposition and conformation of these 
elements in the different races possessing them, 
it will be needful to examine them successively 
in the order in which they have been enu- 
merated. 

The scapula is the most important piece 
entering into the composition of the shoulder, 
and not unfrequently, among the Mammiferous 
races, is the only bone developed for the sup- 
port of the anterior limb. In Reptiles and in 
Birds, where so great freedomt of motion as is 
required in terrestrial Quadrupeds would be 
inadmissible, the movements of this part of 
the skeleton are considerably restricted, and a 
kind of anterior pelvis formed which gives 
great strength and firmness to this part of the 
skeleton. The scapule are generally laid like 
splints along the exterior of the chest, in which 
position they are, as it were, suspended by 
strong muscles; but frequently this arrange- 
ment is necessarily departed from for obvious 
reasons. In the Batrachia, for example, such 
as the Frog and the oad, the ribs are 
altogether wanting, and the strength of the 
shoulder must consequently be provided for in 
a peculiar manner. The scapule are enormously 
developed so as to perform, to a certain extent, 
the office of ribs; and, moreover, each being 
divided, as in Fishes, into two portions, united 
by cartilage to each other, the strength and 
resiliency of a chest is in some measure obtained. 
It is, however, in the Chelonian Reptiles that 
the most extraordinary deviation from the usual 
arrangement is witnessed, where the scapule 
are absolutely placed in the interior of the 
thorax, where they are connected by one extre- 
tremity to the sides of the bodies of the dorsal 
vertebra. 

No spine or acromial process exists in the 
scapule of the oviparous Vertebrata, and even 
in the quadrupedal Mammals these parts of the 
bone are very imperfectly developed when com- 
pared with their condition in Man, in whom 
alone they assume their full importance. 

The clavicle forms the second element em- 


840 


ployed in constructing the shoulder-joint, but 
is by no means constantly present. In Fishes its 
existence as a distinct bone is not recognisable ; 
but in all the Reptilia it constitutes a highly 
pe eo piece of the skeleton. 

n Birds the clavicles, in consequence of the 
elasticity and strength indispensable in the 
composition of the bony framework of the 
shoulder in animals constructed for flight, pre- 
senta very peculiar arrangement, being generally 
solidly anchylosed to each other in the mesial 
line, where they meet, forming a single bone, 
to which the name of furculum is generally 
given. In Birds, however, that are not organized 
for flight, such as the Ostrich, this peculiarity 
is dispensed with, and two distinct clavicles 
are found articulated with the sternum, as in 
the generality of Vertebrata. 

In the Mammalia again the clavicles are 
much reduced in importance and frequently are 
entirely wanting, as in all the pachydermatous 
races. It is only when extensive movements 
are required in the anterior limbs, either for the 
ocr of flight, climbing, digging, or pre- 

ension, that clavicles are interposed between 
the shoulder of a quadruped and the anterior 
portion of the sternum, so as to form a kind of 
pivot on which the whole shoulder moves, and 
in the human subject the freedom of motion 
obtained for the arms and hands by this arrange- 
ment contrasts strongly with the fixed condition 
of the shoulder, both of Birds and Reptiles. 

The coracoid bone, forming the third element 
employed in constructing the shoulder-joint of 
Vertebrate animals, is only fully developed in 
the Reptilia and in Birds. In Fishes it is but 
doubtfully represented by two beny pieces 
already referred to; but in all the Batrachian 
and Saurian Reptiles it constitutes the strongest 
support of the shoulder, abutting on the sternum 
on the one hand, and on the other firmly con- 
nected with the shoulder-joint. In the Chelo- 
nian Reptiles, too, the coracoids are very large, 
and remarkable on account of the extraordinary 
inversion of the skeleton of these animals, the 
scapulz being here actually placed inside the 
thorax within the ribs, and fixed by ligaments 
to the sides of the bodies of the vertebre ; 
while the coracoid bones, equally placed within 
the thoracic box, are similarly circumstanced as 
regards the p/lastron or enlarged sternum that 
covers them inferiorly. 

In Birds the coracoid bones are of peculiar 
strength and solidity, serving as buttresses to 
support the shoulder against the vigorous trac- 
tion of the enormous pectoral muscles. It 
stretches trom the anterior margin of the 
sternum, with which it is firmly articulated, to 
the junction of the scapula and clavicle, where 
it assists in forming the glenoid cavity. 

Throughout all the Mammalia, with the 
exception of the Monotremata, the coracoid 
bones are wanting or only represented by a 
small apophysis, consolidated with the neck of 
the scapula, as is the case in the human skeleton, 
to which the term coracoid process has been 
generally applied. 

The humerus, the first bone of the anterior 
extremity, is invariably a single bone interposed 


OSSEOUS SYSTEM. (Come. Anat.) 


between the glenoid cavity and the forearm. It 
is invariably present throughout all the Reptilia, 
excepting of course the apodal Ophidian races, 
and is at once recognisable by the anatomist. 
In Birds, likewise, the humerus offers nothing 
remarkable except the mechanical arrangement 
of its articular extremities. a 
Neither in the Mammalia is there any aberra- — 
tion from the common type of structure, the © 
only variations being in the length, form, or 
proportions of this piece of the skeleton, adapt- 
ing it to the necessities of the different races of 
Mammifera. 
The forearm, or second division of the upp 
extremity, is normally made up of two bon 
called respectively the udna and the radi 
These are incomparably most complete in t 
human subject, where their admirable conn 
tions with the humerus, with each other, 
with the hand, are amongst the most strikin 
instances of perfect mechanism met with in tht 
animal creation. ; 
In Fishes and in the Batrachian F 
they are most imperfectly develo nc 
invariably anchylosed together. In the Ch 
nian and Saurian Reptiles they become ¢ 
distinct from each other, but the movements 
pronation and supination are extremely limi 
The ulna of Birds 1s the principal bone of 
forearm, while the radius is a 
co? distinguishable by the relations it b 
to the other parts of the wing ; here likewise, 
consequence of the uses of the anterior extt 
mity as instruments of flight, these bones ¢ 
almost immoveably fixed in a state of pronati 
In the unguiculate Quadrupeds general 
the ulna and radius are separate bones, 1 
a few exceptions, such as the iropte 
where one bone only constitutes the fe 
but amongst the Ungulata they are frec 
more or less consolidated and fused toge 
towards their distal extremities, as, for exam 
in the Ruminants and in the Solidungula, 
The carpus, forming the third division of 
upper extremity, generally consists of sever 
short and thick bones firmly bound toget 
ligaments, but allowing of sufficient motion 
tween each other to afford a slightly mow 
basis to support the parts composing the 
either to prevent concussion in walking 
permit increased mobility to the fingers. 
most completely developed, as they are 
in the human subject, they are eight in nu 
to which names indicative of their 
been applied, such as scaphoides, unas 
Jorme, pisiforme, trapezium, trape: 
num, and unciforme ; but these names ¢ 
be supposed to be applicable to the carpal 
of other Vertebrata, in which they pres 
many varieties both in their shape and’ 
as frequently to be quite unrecogn 
analogues of each other, their nt 
varying most considerably, either on 
of the coalescence of elements origina 
tinct, or from their total suppression. 
The bones of the carpus in Fishes are 
rally represented by four or five small 
interposed between the bones of the fo 
and the pectoral fin. With these bom 


OSSEOUS SYSTEM. (Comp. Anat.) 


fin rays, however numerous, are connected ; 
with the exception of the first, which articulates 
immediately with the radius. In some Fishes, 
as in the Lophius, these bones are extraordi- 
narily Jengthened, while the radius and ulna 
are diminished in proportionate size; so that 
some writers have mistaken the bones of the 
ca a for those of the forearm. 

n the Batrachia, and in all four-footed Rep- 
tiles, they are small ossicles interposed between 
the bones of the forearm and metacarpal bones, 
resembling very much those of the human sub- 
ject; butin Birds, in consequence of the peculiar 
condition of the hand, here converted into a 
wing, they are reduced to two, so disposed as to 
form with the bones of the forearm a mere 
hinge-joint moving laterally, so as to allow the 
wing to be folded up. 

In the Cetacea the carpal bones exist, it is 
true, but so separated from each other by an in- 
terposed cartilaginous mass that they assist in 

_ forming a broad paddle, strengthened by super- 
ficial ligaments, and only useful for progression 
in the water. 

__Imall other Mammalia the carpal bones are 
met with, their form and number varying with 
_ the uses for which the limb of which they form 
a part is adapted. 

The metacarpal bones form the immediate 
basis on which the individual fingers are sup- 
ported, and, accordingly, are as variable in their 
number and arrangement as are the digital 
portions of the anterior extremity. 

In Fishes, owing to the numerous fingers or 
rays as they are here called, the metacarpal 
bones are met with in far greater numbers than 
in animals where the extremities assume a more 
concentrated form,—a fact most remarkably 
exemplified in the Chondropterygious Fishes, 
where the number of digital phalanges is enor- 
mous. But in Reptiles, where the hands are 
not only reduced to what may be called the 
normal type of structure, but developed in a 
medium condition, little remarkable is met 
_with in this part of the hand. It is only as we 
come to animals appointed to extraordinary 
conditions of life that aberrations from the 
usual form become conspicuous, as, for exam- 
_ ple, in the feathered races. The metacarpus of 
Birds, although in some cases it might at first 
appear composed of a single bone, in others of 
_ two bones anchylosed together at both ends, 
contains, in reality, the elements of three meta- 
_ carpal bones consolidated ; two of these, which 

are much elongated, supporting the fingers, 
while the third, an exceedingly small element 
confused with the base of the central one, sus- 
_ tains the rudimentary thumb. 
__In the metacarpal bones of the unguiculate 
- Quadrupeds there is nothing worthy of notice 
_ in this general survey of the osseous system ; but 
in the Ungulata a coalescence almost as re- 
_markable as in Birds is observable, whereby 
the peculiar structure of the feet of such animals 
is provided for. In the Ruminantia and So- 

idungula the whole metacarpal apparatus 
_ Would at first sight appear to consist of a single 
bone, to which the name of canon-bone is gene- 
ee 


841 


tally appropriated ; but this apparently single 
bone is easily seen to_be in reality made up of 
two, anchylosed together-throughout their whole 
length, so that the line of demarcation between 
them is only indicated by a deep longitudinal 
groove, visible on the anterior and posterior 
aspects of the bone; in most cases, however, 
there are two more lateral pieces, unattached to 
the principal or canon-bone except by the soft 
parts, but evidently real metacarpal elements in 
an imperfect and rudimentary condition. 

The digital phalanges being the most remote 
from the central portion of the skeleton are 
likewise the most variable in number and ap- 
pearance, being moulded into shapes as various 
as are the uses to which the anterior limbs are 
convertible, becoming in turn the framework of 
oars, of paddles, of pillars, of rakes, of wings, 
or of hands, in accordance with the different 
natures of the animals possessing them. Neither 
is it at all an easy task to say how many of 
these elements might exist in the construction 
of this part of the skeleton, seeing that the 
number of fingers that may enter into the com- 
position of a hand seems not at all determinate, 
nor even the number of phalanges in a given 
finger. The pectoral fins of osseous Fishes, the 
representatives of the hands of higherVertebrata, 
differ exceedingly in this respect, sometimes 
consisting of a single ray, at others being dilated 
and extended, as in the Flying Fishes, until both 
rays and phalanges become extremely numerous. 
The hand or pectoral fin of the Skates is per- 
haps one of the most remarkable structures 
that can he offered to the contemplation of the 
osteologist, whether we regard its apparently 
disproportionate size or the immense number 
of digital elements that enter into its composi- 
tion ; it forms, in fact, the great bulk of their 
bodies, and is made up of upwards of a hundred 
distinct fingers, each composed of numerous 
phalanges ofenormous length. Throughout the 
Serpent tribes all traces of, anterior extremities 
are lost, but in the Anourous Batrachia fingers 
again appear under a new and more elevated 
form, although feeble when compared to the 
digital phalanges of the hinder extremities in 
the same Reptiles. 

Throughout the Saurian and Chelonian races 
as they now exist, nothing remarkable appears 
in the construction of this portion of the skele- 
ton, the chief modifications observable being in 
the number, length, and position of the fingers, | 
although in extinct forms of nearly allied genera, 
such as the Ichthyosaurus and Plesiosaurus, 
the number both of toes and phalanges are so 
prodigiously increased that we are once more 
reminded of the fins of Fishes, 

The digital phalanges in the wing of a bird 
are reduced to an exceedingly rudimentary 
condition, the thumb being represented by a 
single bone. The central or radial finger is the 
longest and most complete, consisting, when 
fully developed, of three distinct joints, though 
sometimes there are only two. The ulnar or 
third finger is, like the thumb, represented by a 
single phalanx appended to the distal extremity 
of the ulnar metacarpal bone. 


842 


. In all the mammiferous Quadrupeds pos- 
sessed of unguiculate feet, the digital phalanges 
of the anterior extremity present nothing worthy 
of special notice in this place, minor differences 
being noticed under the proper heads; but in 
the ungulate Pachydermata, such as the Rumi- 
nants and Solipeds, remarkable exceptions to 
the usual arrangement are met with. In the 
Ruminants only the two central fingers are well 
developed, each consisting of three large pha- 
-langes, the distal one of which is enclosed in a 
strong hoof, so as to give the cloven appearance 
to the whole foot which is so characteristic of 
the order; but besides these, two rudimentary 
toes exist, one on the outer, the other on the 
inner side of the foot, but so small as not to 
reach the ground or to be serviceable in the or- 
dinary progression of these creatures. 

In the Solipeds even the division between 
the central large toes that exists in the Rumi- 
nant becomes obliterated, and the whole foot 
appears to be made up of a single toe consisting 
of three strong phalanges, the distal one being 
encased in a large semicircular hoof. Even in 
these animals, however, rudiments of two other 
toes are distinguishable, but very imperfectly 
developed. 

Ilium.—This is the principal bone entering 
into the composition of the pelvic arch, and fre- 
ews is the only one met with in this part of 

e skeleton. In the osseous Fishes it is not yet 
connected with the spine, so that the posterior 
part of the body is left perfectly free and un- 
trammelled, in order to allow of the extensive 
movements of the tail required for the propul- 
sion of these aquatic animals through the water. 
There is consequently here no sacrum, and we 
are not surprised to see the posterior limbs ex- 
tremely variable in their arrangement, being 
placed far back or advanced towards the ante- 
rior part of the body as circumstances require. 
Even in the cartilaginous Fishes the pelvis has 
no connection with the spine, the whole con- 
sisting of a broad transverse osseous band 
placed beneath the terminal portion of the 
abdomen. 

In the Batrachia, too, the iliac bones retain 
to some extent the form of ribs, and in the 
Frog are two bones of considerable length 
attached to the prolonged transverse processes 
of the last vertebra, which of course, in this 
case, represents the sacrum, 

In the Toad another step is made towards 
strengthening the posterior part of the spine, 
preparing it to support locomotive organs of 
greater energy by fixing the iliac bones to two 
of the vertebral transverse processes, forming a 
sacrum composed of two bones, which is in 
fact the usual condition of this part of the ske- 
leton in the higher Reptiles. ; 

In the Chelonians, however, the iliac bones 
are again attached to asingle vertebra and pelvis, 
like the bones of the shoulder placed internal 
to the ribs which form the carapax or dorsal 
shield, 

The ilium, in all the class of Birds, is enor- 
mously developed in proportion to the unfa- 
vourable circumstances under which they sup- 


OSSEOUS SYSTEM. (Comp. Anat.) 


rt themselves wu their posterior extre- 
ary It extends aan the sides of the ver- 
tebral column, to which it is solidly anchy- 
losed, converting into one immense sacrum — 
from eight to nineteen of the posterior vertebra, — 
which are so completely fused to each other 
and to the iliac bones that their number is only 
distinguishable from the positions of the inter- _ 
vertebral foramina through which the nerves 
escape from the spinal canal in this region, 
In Mammals the iliac bones are likewis 
greatly developed, except in the Cetacea, w 
in consequence of the necessity for fish-lil 
flexibility in the hinder part of the body, m 
hinder extremities exist. The sacrum is cor 
pave of a considerable number of ve 
ere anchylosed together and consid Y 
dified in their form, to which the 
ilii are firmly secured by ligaments and ar 
interposed cartilage, giving a firmness to this 
part of the skeleton second only to what is 
observable in the feathered races. a 
The ossa ischit, the second elements entering 
into the composition of the pelvic frame ’ 
are not so invariably present as the iliac bor 
In Fishes they are not to be found: but in 
the Reptilia, where the elements of the skeleton 
remain permanently disunited to a much greate) 
extent se in warm-blooded animals, they are 
constantly present, except, of course, where t 
hinder extremities are deficient, and are sepa. 
rated by a very distinct line of demarcat 
from the other bones of the pelvis. 
As in the shoulder, the articular cavity for 
the attachment of the anterior limbs when al 
the elements of that part are fully developed, 
formed by the union of three bones, so li 
in the pelvis, which is only a repetition of 
same apparatus modified in form, do all th 
three bones of which it consists enter into th 
formation of the cotyloid cavity, a cireumst: 
which, in Reptiles, is particularly conspi 
In the class Aves, notwitl 


a 


hstanding the 
rant condition of the pelvis, the ischia are € 
distinguishable from their position, boundi 
as they do the obturator foramen on the o1 
side, and the sacro-ischiatic notch on the othe 
In the Cetacean Mammals this element 
the skeleton is again obliterated, but in allt 
other orders it is present, and in the ear 
stages of life is readily demonstrable as a ¢ 
tinct bone of the pelvis. a 
The ossa pubis are the third pair of eleme 
entering into the composition of the pelvic 
vity, and to these the same remarks are 
cable as we have already made concerning 
ischia. In Fishes they are not present, 
throughout the Reptile orders that posse: 
pelvis they are very distinct and important 
of the skeleton, meeting each other anter 
in the mesial line, where they are unit 
strong symphysis. , 
The pubic bones in Birds occupy 2 
responding position; they are here, how 
remarkable from the circumstance that t 
distal extremities never (except in the 
trich) meet to form a pubic symphysis, but 1 
always widely separated from each othe 


OSSEOUS SYSTEM. (Comp. Anat.) 


arrangement which is here convenient to permit 
of the extrusion of the egg through the pelvic 
cavity, and may be permitted in this race of 
animals in consequence of the prodigious con- 
solidation of the dorsal parts of the pelvis. 

In the Cetacea only the pubic elements of 
the pelvis are developed, both ilia and ischia 
being deficient, so that they are quite detached 
from the rest of the skeleton. In all other 
Mammalia they correspond both in position 
and general arrangement with what is found in 
the human subject. 

The marsupial hones are peculiar to the mar- 
supial division of Mammals. They are two 
triangular pieces articulated to the anterior sur- 
face of the pubic bones, and imbedded in the 
parietes of the abdomen behind the marsupial 
eee which they assist in supporting. It has 

4 asserted that rudiments of these bones 
may be traced even in the human subject in 
_the shape of minute cornicles sometimes at- 
tached to the pubis. 
__ The femur represents, in the posterior extre- 
-mity, the humerus of the anterior, articulating 
immediately with the pelvic arch, but modified 
in form according to the difference of its func- 
tion. In Fishes this element of the skeleton 
does not exist at all, the digital rays and tarsal 
bones of the ventral fin, the representative of 
‘the posterior extremities of other Vertebrata, 
_heing affixed immediately to the pelvic bone, 
which sustains it. In the Perennibranchiate 
Amphibia it is but very feebly developed when 
he hinder extremities are present, which is not 
always the case. In the Anourous Amphibia, 
owever, as, for example, in the Frog, it sud- 
denly assumes a very great importance in ac- 
ordance with the saltatory habits of those 
Batrachia. It exists also in all other quadru- 
pedal forms of the Reptilia, only modified in 
hape according to their different modes of 


_ In Birds the femur is short and strong, but 
‘presents no peculiarity requiring special notice. 
__ In the Mammalia, likewise, except in the 
Cetacea, it is invariably present, its size and 
Shape altering in the different tribes as their 
habits vary. 

_ The tibia, the principal bone of the leg in all 
/quadrupedal Vertebrata, does not exist in Fishes, 
where all the elements of the skeleton, usually 
interposed between the foot and the pelvis, are 
found to be deficient. 

_ In the Batrachian, Saurian, and Chelonian 
J eptiles it is invariably a bone of very consi- 
derable importance, whether it be united with 
the other bone of the leg, the fibula, or remain 
rate and distinct. 

n the feathered races this bone is of great 
strength, having to support the weight of the 
body in a very unfavourable position, and in 
il the Mammalia that are possessed of poste- 
i0r extremities it is necessarily present. 

_ The fibula, which in the hinder extremity re- 
presents the ulna of the anterior limb, like that 
one, isnot unfrequently very imperfectly deve- 
yped, especially where great strength is re- 
wired in this part of the limb, and mobility 
ecomes a secondary object. In Fishes it is 


843 


not yet developed. In the Batrachian Reptiles 
it exists, but is generally so completely anchy- 
losed to the tibia throughout its whole extent 


_as only to be distinguished from that bone by 


very accurate examination. In the Saurian 
Reptiles it is a distinct and very important bone, 
as is likewise the case in the Chelonians, al- 
though here the two bones of the leg are so 
firmly connected by ligaments that but little 
motion is permitted. 

The fibula of Birds is a mere rudiment, a 
slender splint appended to the external aspect 
of the tibia, distinct above, but inferiorly com- 
pletely lost, being gradually solidly united to 
the latter bone, with which it becomes com- 
pletely confused. 

In the Monotremata, notwithstanding the 
near relations that exist between these singular 
quadrupeds and the feathered races, the fibulz 
are very largely developed, as likewise in most 
of the unguiculate Quadrupeds; but in the un- 
gulate Mammalia the fibula is reduced to a 
mere rudiment attached to the outer side of the 
tibia. 

The tarsal bones are, in the posterior extres 
mity, the representatives of the carpus of the 
anterior, but from various circumstances are 
very considerably altered in form, and not un- 
frequently differ in number from the latter, even 
in the same animal, in consequence of the very 
different offices not unfrequently assigned to 
the two pairs of limbs. In Fishes they are 
very imperfectly developed, or confused with 
the other elements entering into the composition 
of the ventral fin. In Frogs and Toads, how- 
ever, they are very distinctly formed, being in 
these amphibious reptiles six in number ; but 
of these the two proximal ones, corresponding 
to the astragalus and os calcis, are remarkably 
elongated, and by the uninformed might easily 
be mistaken for the tibia and fibula. In Sau- 
rian and Chelonian Reptiles they present what 
may be called their normal or medium state of 
developement, the os calcis being here left pro- 
minent for the insertion of the extensor muscles 
of the foot. 

No tarsal bones are distinguishable in the 
adult bird, the few elements which in the 
young animal are developed by distinct points 
of ossification being rapidly confused with the 
metatarsal portion of the limb, so that both 
these divisions of the hinder extremity are here 
represented by a single piece,to which the 
appropriate name of tarso-metatarsal bone has 
consequently been applied. 

In all unguiculate Mammalia the tarsal 
bones are well developed and more or less 
resemble the human; but in the Ungulata, 
owing to the extreme length of the metatarsus 
or canon bone, they seem to occupy a position 
corresponding with that of the knee in other 
animals; and the remarkably prominent os 
calcis, to which the tendo Achillis is fixed, is 
well calculated to remind the anatomist of the 
olecranon of the ulna. 

The metatarsal bones are but a repetition 
of the metacarpal bones of the atlantal ex- 
tremity, and immediately support the digital 
phalanges of the foot, varying in number as the 


844 


toes are more or less numerous. In_ their 
most normal state of developement these bones 
are five in number as in the human skeleton, 
but from this variations occur in almost every 
order of Vertebrata. 

The metatarsus of Reptiles is, however, well 
developed, consisting of a series of moderately 
elongated bones extended between the carpus 
and the proximal phalanx of the corresponding 
toe, but offering nothing worthy of special 
comment. 

The tarso-metatarsal bone of Birds, repre- 
senting both the tarsal and metatarsal portions 
of the skeleton, seems to consist of three and 
sometimes four metatarsal bones consolidated 
into one piece. These are distinguishable in- 
feriorly by the four trochlear surfaces that sup- 
port the moveable toes ; while the presence of 
an ossified spur in some gallinaceous birds, 
regarded by many anatomists as the rudiment 
of a fifth toe, might indicate the existence of a 
fifth metatarsal element lost in the general 
consolidation of these pieces. 

In all the unguiculate Mammals the meta- 
tarsal bones hold the same relations with the 
other bones of the foot as in the skeleton of 
Man, and need no special notice; but in the 
Ungulate families their appearance and arrange- 
ment are necessarily much changed. In the 
Solipeds and Ruminants the metatarsal division 
of the extremity is so much elongated as to 
constitute a very considerable portion of the 
limb. It is principally made up of a single 
piece generally called the “canon bone,” 
which in reality consists of two enormous meta- 
tarsal bones consolidated into one, being fused 
together in the central line along their whole 
length, although the real composition of the 
canon bone is always distinguishable both on 
account of a deep furrow which indicates the 
union of the two pieces, and from the con- 
dition of the two widely separated trochlear 
surfaces at its distal extremity. Besides the 
two largely developed pieces forming the canon 
bone, two other metatarsal pieces assist in form- 
ing the foot of a Ruminating Quadruped ; these 
sustain the supplementary toes developed in a 
rudimental condition on the outer and inner 
aspects of the member. — 

The digital phulanges of the posterior ex- 
tremity are among the most variable elements 
of the skeleton, being, like those of the anterior, 
made subservient to a great variety of uses both 
in terrestrial and aquatic forms of Vertebrata. 

In the osseous Fishes they are represented 
by the fine rays of the ventral fin, and are of 
course employed in natation ; but in the carti- 
laginous Fishes, as the Sharks and Rays, 
although the resemblance between this part of 
the skeleton and the feet of higher animals is 
more striking than in the gsseous races, they 
are appropriated to a different office, serving 
the purpose of claspers, whereby the intercourse 
between the sexes is facilitated. 

Throughout all the Reptilia that possess 
hind feet, the phalanges of the toes offer 
nothing remarkable; neither in Birds is there 
anything peculiar in their structure, the only 
circumstances of interest connected with this 


OSSEOUS SYSTEM. (Comp. Anat.) 


part of the skeleton in the feathered races _ 
relating to the number and disposition of the — 
toes, and the presence of more or less numerous 
joints entering into their composition. =. 
In the Mammalia this part of the foot cor- 
responds in its composition with that of the 
hand, and therefore need not be further noticed. 
In enumerating the elements of the endo- 
skeleton it would be — to omit certain 
supplementary pieces, which, though not strie 
belonging to the osseous system, are of important 
mechanical assistance to the muscles inserte 
into different portions of the skeleton. 
are alone: in the substance of 
tendons where much friction is encountered, : 
where it is of importance to remove the line ¢ 
traction to some distance from the centi 
motion in order to gain additional 
When developed in the tendons of the finger 
or toes, these detached pieces of osseous sul 
stance are called ‘ sesamoid bones,” but i 
such situations their existence is by no meat 
constant. Connected with the great joi 
corresponding with the knee and elbow of t 
human subject, bones of this kind are ¥ 
generally developed, and their size and ij 
portance renders them worthy of special remai 
In the anterior extremity the superadded bo 
are named “ olecranon,” and very generally | 
found solidly cemented to the proximal end 
the ulna, forming a prominent process, thatgi 
great mechanical advantage to the exte 
muscles of the forearm. The correspon¢ 
bone appended to the knee-joint has, from 
condition in the human subject, received 
name of “ patella.” a 
Such being the elements employed 
nature in constructing the locomotive e% 
mities of Vertebrate animals, our only 4 
der is that by simply modifying the 
of the bones, by suppressing some — 
exaggerating others, or else by fusing sev 
of them together, such infinite diversity 
apparatus is provided in the various 
ertebrata. Seldom, indeed, does a 
present all the pieces we have enumerated 
complete state of developement, and freqt 
the majority of them, or even the whole 
is entirely dispensed with. In many F 
as in the Lamprey and Myxine, all fot 
tremities are absolutely wanting, a circum 
which again becomes remarkable in the ¢ 
Ophidian Reptiles. Occasionally 
only are called into existence, and that 
very rudimentary state, as for example, it 
Serpents, Anguis, Boa, &c. More fre 
the anterior limbs are found without t 
terior ; such is the case in the apodal Fy 
the Siren and Bimanes among a 
still more conspicuously in the Cetacea 
ExoskeLeTon.—Having thus exam 
the elements that belong properly to the 
system or endo-skeleton, we must 
our attention to another important sy 
organs equally concerned in building 
framework of the body, and. that to an 
which the human osteologist would | 
imagine possible. We allude to the 
or cuticular skeleton, which, although fF 


OSSEOUS SYSTEM. (Comp. Anat.) 


in Man to a most rudimentary condition, 
being represented merely by the common 
cuticular covering of the body and its appen- 
dages, the hair and the nails, we shall find 
among the lower Vertebrata performing a much 
more important part in the animal economy, 
and occasionally entering largely into the 
construction of the organs of locomotion, re- 
placing and not unfrequently actually assuming 
the appearance and oftice of the endo-skeleton 
or proper osseous system. Examined in their 
remotest aspects, few textures indeed appear 
less allied, the osseous tissue and that of hairs, 
horns, feathers, and other cutaneous appen- 
dages ; nevertheless we doubt not that, on taking 
an enlarged view of the subject, it will not be 
difficult to prove that the two are absolutely 
interconvertible, both in use and even com- 
position, the cuticular skeleton being not unfre- 
quently had recourse to by nature to eke out 
and complete organs for the construction of 
which the elements of the endo-skeleton would 
_have been insufficient. 
_ Let any one who is only conversant with the 
“composition of the skeleton of Man, or of the 
phigher Vertebrata, examine that of a fish, more 
especially of one of the osseous Fishes, and he 
will soon perceive how impossible it is to point 
out anything analogous to a very considerable 
Eeeiaber of the parts composing it, in the bony 
framework even of those Reptiles that are most 


nearly approximated to Fishes in their general 
economy, or from the elements above enu- 
merated, various as they are, to build up those 
“additional structures that render the osseous 
‘Support of a fish’s body so complicated and so 
berrant in its composition from what is seen in 
‘any other class of Vertebrate animals. In the 
irst place there are numerous bones forming 
a chain of osseous plates surrounding the 
ferior margin of the orbital cavity, which have 
been named by Cuvier “ suborbital bones,” and 
by Geoffroy “ jugal bones,” although, having 
ready seen that the jugal are represented 
elsewhere by an important element easily iden- 
fied, it is surely anomalous, to say the least of 1%, 
to find the same element thus multiplied and 
‘divided, more especially when in many of the 
hard-cheeked fishes, such as the Gurnard, these 
Supplementary pieces become the largest bones 
of the face. 
| The opercular bones, which form the gill 
flaps of the fish, are a set of bones which from 
eir very office are evidently peculiar to the 
skeleton of a fish, and could scarcely have been 
Spected to have any analogue in animals 
tally destitute of gill openings, as are all other 
Vertebrata in their adult condition. These 
‘bones are four in number, and have received 
from writers onichthyology the following names: 
St, the preoperculum,* (fig. 436,30) which 
forms the basis supporting the other three ; 
2nd, the operculum+ proper, (fig. 436, 28) 
articulated to the former, on which it moves 
hike a door on its hinge. Beneath the last- 
ed bone is a third, named the sub- 
* 
4 


Tympanal bone (Geotfroy). Malleus (Spix). 
Stapeal (Geoffroy). Incus (Spix). 


6 ¥. « 
A Oe 


845 


operculum,* (fig. 436) 32) and still lower down 
placed immediately behind the articulation of 
the lower jaw, a fourth, to which the name of 
interoperculum+ (fig. 436, 33) has been ap- 
lied. 

i In the Chondropterygii this apparatus is 
entirely wanting. ‘To explain the analogies of 
these pieces the most desperate theories have 
been broached by transcendental osteologists, 
the boldest and most celebrated of which is 
that of Geoffroy St. Hilaire, that these opercular 
bones are the ossicula audités reproduced in an 
altered form after they were no longer required 
to form part of the auditory organ; an opinion 
which has found supporters even in this 
country notwithstanding the withering criticism 
of Cuvier, who, remarking upon this theory, 
very justly observes, that he has seen but little 
of such sudden reappearances of parts after 
they had been progressively made to disappear 
in the scale of animal life. Cuvier was com- 
pelled to regard the opercular bones as being 
superadded elements of the skeleton peculiar to 
Fishes, and having no representatives in other 
Vertebrata. De Blainville suggested that the 
pieces in question might be derived from a 
dismemberment of the lower jaw, by the 
detachment of the opercular elements from the 
ramus; but this hypothesis is refuted by the 
fact that in some Fishes, as the Lepidusterus, all 
the elements of the inferior maxilla are co- 
existent with the opercular apparatus. Pro- 
fessor Owen first suggested that they were 
mere derivations from the dermal skeleton, an 
opinion that seems every day to receive con- 
firmation. 

The supra-temporal bones of Fishes, a chain 
nearly resembling the sub-orbital, which in 
many species arches over the temporal fossa, 
belong to the same category, and cannot be 
said to resemble any bones found in other 
creatures. 

But the most anomalous of all the bones 
found in a fish’s skeleton are those large and 
important ones that support the azygos fins 
placed along the mesian line of the body, con- 
stituting the dorsal, caudal, and anal fins. 
These bones consist of several distinct pieces, 
and frequently assume a very complex struc- 
ture: first, there is the fin ray itself, either 
simple, as in the dorsal fins of the Acantho- 
preryeiis or many-jointed, as in the fin rays of 

alacopterygious fishes. These moreover are 
individually articulated with other pieces of a 
more decidedly osseous character, called the 
interspinous bones, which are imbedded in the 
flesh of the back, and might be, as indeed 
they have been, mistaken for appendages to the 
neuro-spines of the vertebra. 

The hypothesis promulgated by Professor 
Grant upon this subject is as follows: “ The 
spinous processes in Fishes give rise to other 
pieces. The spinous processes extending from 
the vertebra of the fish when they have become 
largely developed ‘themselves, give origin to 
new bones and afford us an illustration of a 


* Malleal ( Geoffroy). 


t Inceal (Geoffroy). Stapes (Spix). 


846 ; 


fact which is remarkable for its uniformity in 
other parts of the skeleton and in other animals. 
A separate centre of ossification is developed, a 
new source of nutrition is conveyed directly to 
the extremity of the _— new bone is formed 
from the end of the spinous process.” But 
even this dilatable explanation is by no means 
sufficient for the required purpose, for having 
= in this way the interspinous bones 
from the spinal elements of the vertebra, the 
fin rays themselves are referred to the same 
source, and thus materials are afforded for com- 
plicating the endoskeleton ad libitum, upon the 
simple supposition that when any element be- 
comes inordinately developed, it can develope 
other elements to eke it out. 

Geoffroy adopted another mode of explaining 
the origin of the supernumerary bones that 
support the dorsal and anal fins of fishes. Sup- 
posing the upper and lower vertebral spines 
(i. e. the neuro-spines and hemo spines) to be 
each composed of two elements conjoined in 
the mesial line, he asserts that, instead of re- 
maining side by side, one half of the spine is 
removed and placed above the other to form 
the interspinous bone. Yet even this would 
by no means get over half the difficulty, for 
the fin rays themselves remain to be accounted 
for, and where are elements to be procured for 
the construction of these? Moreover, as Cu- 
vier remarks, it by no means unfrequently 
happens that several interspinous bones belong 
to a single vertebral spine, a circumstance 
which is quite incompatible with the supposi- 
tion that any dismemberment of the spine can 
account for their presence. 

Failing, therefore, to find any materials for 
the construction of the bones we have enume- 
rated among any known elements of the endo- 
skeleton, we are compelled to look elsewhere, 
and shall soon find, by tracing the exoskeleton 
of Fishes through the different aspects under 
which it offers itself, abundant means of supply- 
ing all deficiencies. 

The scales that usually invest the bodies of 
ordinary Fishes would certainly appear at first 
sight to have no relationship whatever with the 
osseous system, as neither in texture nor mode 
of growth do they at all resemble bone, being 
simply com of layers of epidermis se- 
creted one after the other until they attain the 
required thickness. But these bs em scales, 
if but very slightly exaggerated, become sus- 
ceptible of such varieties of form and structure 
that they often entirely-lose their nature, and 
becoming solidified until they emulate true 
bone in hardness and compactness of structure, 
are often converted into weapons of defence 
or attack of very diversified descriptions; the 
dense and bone-like armour of the Ostracious, 
the formidable spines of the Diodon, and even 
the crystalline tooth-like points that stud the 
skins of Sharks and Rays, forming what is called 
shagreen, being mere modifications of the same 
cuticular appendages. Having advanced thus 
far in tracing the changeable character of the 
scale of a fish, adapting it to various functions, 
we are quite prepared to admit other important 
facts of still greater interest. It is only neces- 


OSSEOUS SYSTEM. (Comp. Anat) 


sary to examine the spines met with upon the — 
back of a common Skate or Thornbock to pees 
ceive that they are of very different character in 
different parts of the surface of the body. The 
minute scale-like points are at times converted 
into large hooks fixed upon the surface of the 
skin, which really become formidable defences 
On approaching the mouth they become aga 
so much reduced in size as to represent an eX- 
ceedingly fine tessellated pavement, ch 
covers the lips and passes even into the interior 
ofthe mouth. On reaching the margins of the 
upper and lower jaw their appearance agai 
1 changed ; they are saeeselal in siz 
and hardness, bemg in fact converted int 
teeth which pave the whole surface of the jaw, 
covering it with osseous plates, or pow 
hooks, or cutting teeth, such as the Shark f 
sesses; but these teeth are still quite unec 
nected with the jaw and may be easily strippe 
off with the cuticle, of which, indeed, they forn 
a part. Even the tongue itself is covered with 
similar plates of hard substance, smaller in siz 
indeed, but in every thing comparable to 
teeth both in character and mode of growtl 
Finding that the teeth in their simplest for 
are merely epidermic structures, nothing wo 
be more easy than to point out a long series | 
almost insensible gradations through whi 
they become more and more decidedly ec 
nected with the bones of the endoskelete 
until at length they absolutely become implant 
into it, and fixed to the jaw-bones as intimate 
as if they were really themselves portions of t 
true osseous skeleton. The ligamentous bon 
of union between the teeth and jaw-bones 
Lophius, the soldering together of the 
and the numerous bones which, in Fishes. 
made to support dental appendages, and 
gradual appearance of alveolar depressioi 
the jaws of the higher Reptilia, are all so ma 
Steps of progressive approximation, the int 
diate phases of which the scientific reader y 
easily supply. These facts therefore satisfactoi 
rove that, as far as the teeth are concernec 
east, the exoskeleton and endoskeleton ar 
nearly approximated in texture that they 
tually become appendages one of the-other 
the teeth are infixed into the jaw-bones — 
support them. 4 
Having thus convinced ourselves that in 
case of the teeth the cuticular and os 
systems become articulated together, or SO 
solidated as only to be distinguishable — 
the microscopic texture that they resp 
present, we are prepared with greater con! 
to expect similar phenomena in other pi 
the body, and to find the exoskeleton ane 
skeleton to a certain extent vicarious in fut 
and interchangeable with each other. 
No one will deny that the spines 
common Sticklebacks ( Gasterosteus ), 
bony-looking weapons affixed to the root 
tail of the Sting-ray, are cuticular in thi 
ture and mere derivations from the exoskelt 
yet we have only to advance one step fu 
and we find spines in every way simi 
their nature absolutely articulated by ¢ 
and most beautiful moveable joints to di 


P: 


OSSEOUS TISSUE. 


parts of the osseous system, of which we need 
only adduce as instances the fishing filaments 
upon the back of the head of Lophius, and the 
powerful weapons of Silurus and Balistes else- 
where described (vide Art. Pisces), where 
muscles are implanted into the spear-like arms 
here formed entirely from the cuticle, although 
brought into close union with the bones of the 
real skeleton. 

Having arrived thus far and found in the 
cases alluded to that epidermic spines, when 
thus far exaggerated in their dimensions, are 
really converted into fin-rays and moved by 
appropriate muscles, it is impossible to deny 
that such organs may have a similar origin in 
other parts of the skeleton, and that the rays of 
the azygos, dorsal, caudal, and anal fins, as well 
as the interspinous bones, which cannot be re- 
ferred toany known element of the endoskeleton, 
are in reality derivations from the exoskeleton, 
although implanted in the flesh and wielded 
by an appropriate system of cutaneous muscles. 
Even in their internal texture these pieces be- 
come assimilated to real bones, and that to such 

- anextent that it even yet remains for the minute 
_ anatomist and the microscopical observer to 
_ point out satisfactory differences between the 
_ two skeletons when they thus become blended 
_ together, notwithstanding the wide interval 
_ which separates the scale, the hair, or the fea- 
ther, all modifications of the epidermic system, 
from the tooth in its fully developed state, or 
from perfectly organized bone permeated by 
_ vessels and nourished by interstitial deposition. 


_ BrBLIoGRAPHY.—In addition to the authorities 
| quoted in the text the comparative osteologist is re- 
BD firred to the following sources of information. 
| Cuvier, Lecons d’anatomie comparée, 5 tom. 8vo. 
ann. VIII—XIV. - Cuvier, Recherches sur les 
ossemens fossiles, 5 tom. 4to. 1821-24. Cuvier 
et Valenciennes, Hist. nat. des poissons, tom. 1, 
| 1828. Jo. Bapt. Spix, Cephalogenesis sive capitis 
| ossei structura, formatio et significatio per omnes 
_ animalium classes, familias, genera, ac etates, fol. 
onach, 1815. Carl Gustav Carus, Von den Ur- 
theilen des Knochen und Schalengeriistes, fol. 


Leipzig, 1828. 
(T. Rymer Jones.) 


_ OSSEOUS TISSUE. Bone. Bone 
SuBstance.—The tissue of bone has, within 
| the last few years, undergone close examination 
_ by various anatomists of note. These exami- 
a ations have been followed with much success, 
and have led to much increase of knowledge of 
| the nature of bone, both as regards its deve- 
lopement and its minute structure. 

_ The general character, the varieties of exter- 
hal conformation, and the anatomical relation 
‘of bone to the contiguous textures, have been 
ably related in a previous article. Under the 
present head it is proposed to treat only of the 
Minute structure and of the developement of 


_ For the sake of precision in the description, 
the elements which conjointly form bone, or 
which are commonly found connected with 

us formation, will be considered under 
te heads. 


¥ 


847 


But before proceeding to this consideration 
of the separate parts it will be well to give a 
general description of them collectively in their 
natural relations. 

The canals which are found every where 
traversing variously the. substance of bone, 
and giving passage to the bloodvessels for 
the nourishment of the tissue, are known by 
the name of Haversian canals, Clopton Havers 
having been the first to give a full description 
of them. The parietes of these canals have a 
laminate arrangement. The lamine themselves 
are numerous and placed concentrically, the in- 
ternal lamina, that which is in immediate con- 
tact with the vessel or vessels, being the most 
distinctly marked, and each succeeding one, as 
you proceed from the canal, having a less dis- 
tinct outline. 

Besides the concentric laminz there are others 
which surround the exterior of the bone, and 
may be known as the superficial lamine. In 
connection with the latter as well as the former 
system of lamine area third set, which can- 
not be traced to belong to either of the foregoing 
orders, but which are placed between them, and 
form the bond of union between each system. 

Late writers on this subject have said much 
of the corpuscles of bone; these are small 
cells of oval form placed between the lamine, 
and having numerous distinct tubes running 
from them in almost every direction. They 
have not inaptly been compared to a spider 
with many legs. 

The corpuscles, or, as others have called 
them, the culcigerous cells, have a definite rela- 
tion to the Haversian canals and to each other. 
These points, however, will be considered in 
detail in a subsequent page. 

The foregoing are the leading points that are 
spoken of in treating of the structure of bone, 
namely, the Haversian canals, the osseous la- 
ming, and the corpuscles. But, upon a closer 
view, it will be seen that the lamine only are 
bone ; the canals and corpuscles are spaces ex- 
isting in bone, and are not really necessary to 
the existence of osseous tissue, though they are 
necessary to its existence where the amount of 
substance is appreciable to the unaided senses. 

Having given a general sketch of the struc- 
ture as it appears when placed under a low 
magnifying power, it will be well to describe 
particularly each of the points which have been 
noticed. 

The most important and that which will be 
placed first in the division is the bone sub- 
stance of which the laminz are composed. 

Of the substance of bone, or hyalitic sub- 
stance.—Writers have, with one or two excep- 
tions, considered the substance of bone as ho- 
mogeneous and without appreciable structure. 
If, however, it be examined under advantageous 
circumstances, with high magnifying powers, 
there will be no difficulty in detecting a very 
definite though delicate structure. For the 
purpose of examination it is best to take a very 
small portion of a thin plate of bone ; such may 
be found in the ethmoid bone of small ani- 
mals, as of the rat. If the piece be well se- 


848 


a, Haversian canal; b, concentric lamine ; c, lamine of connection ; 
d, corpuscles, with their system of tubes. : 
The parts marked a, b, and d constitute an Haversian system. 
figure includes three systems with lamine of connection uniting them, 


lected, it will be found to contain no Haversian 
canals or corpuscles, but to be extremely thin 
and transparent. Such a portion, when viewed 
with the one-eighth of an inch object-glass of 
Mr. Powell’s microscope, will present a deli- 
cate granular aspect with the surface nodulated. 
This granular appearance arises from the sub- 
stance of the bone being composed of minute 
irregularly spherical granules. It is not diffi- 
cult to trace this structure in any specimen of 
bone, though in some it is much more distinct 
than in others. Specimens put up in Canada 
balsam do not show the minute structure very 
well. It. is best to pies the object between 
two slips of glass with a little plain water. 

A delicate spicula from the point where os- 
sification is going on is usually very good for 
illustrating the granular tissue. 

But the granules may be obtained separated 
from each other, so that each individual may be 
eXamined apart from its fellows. When so 
eee to view, they exhibit a tolerably re- 
gular character, being mostly spherical, some 
few having an oval form. In some specimens 
the oval predominates over the spherical con- 
formations. Often a few will be found which 
are egg-shaped, with the smaller end elongated, 
(see fig. 449,) though to no great extent. The 
osseous granules may be gained by subjecting 
bone to high-pressure steam, or to a red heat, 
till all the animal matter is removed. In either 
instance the granules may be obtained by taking 


OSSEOUS TISSUE. 
Fig. 448. 


Transverse section from the dense portion of the femur. 


The 


Ultimate osseous granules obtained by depriv 
bone of its animal matter. 
a small portion of the so treated bone, & 
ting it with water, and then gently redu 
to a powder between the slips of glass 
manipulation the granules individually ¥ 
rendered evident when the specimen 
mined under ahigh power. But, by t 
ing down of the mass, man ules are 
sarily broken ; to remedy this imperfect ai 


OSSEOUS TISSUE. 


fused state of the specimen, a little dilute 
muriatic acid should be placed upon the glass 
in contact with the specimen. Solution of the 
powdered mass will instantly commence, but 
the broken granules will have disappeared be- 
fore the entire ones are appreciably affected. If 
at this point of the experiment the acid be re- 
moved and replaced by pure water, a perfect 
specimen will be gained. In examining the 
tissue under consideration it is most satisfactory 
to watch the action of the acid upon the cal- 
cined or steamed bone, and especially its action 
upon the small masses, for in these, when un- 
dergoing the action of dilute acid, the granules 
composing them become particularly distinct, 
so that their individual character may be stu- 
’ died ; and if the solvent be not removed, their 
Separate disappearance may be watched as the 
superficial ones are exposed and acted upon by 
the solvent fluid. Ifthe acid be left with the 
so treated bone for a sufficient length of time, 
all the earthy matter will be dissolved and there 
will remain a transparent indistinctly cellular 
mass, which may be supposed to be an inter- 
granular substance, the purpose of which was 
_ to unite the granules into a compact whole. 
Bone which has been treated with dilute 
acid without the previous removal of the ani- 
mal matter, soon loses the earthy component, 
leaving only the animal. This, however, does 
not tend to develope the granularity; indeed 
_ it seems, in most cases, to render it less dis- 
_ tinct than in either the unaltered or the calcined 
bone. The granules themselves are subject to 
some variety in size, commonly varying from 
the one-sixth to one-third the size of a human 
blood globule. 

Of the lamine—The form taken by the 
bone substance is that of lamine, and these 
_ Jaminz have a definite arrangement, so much 
_ so that three distinct systems may be recognised, 
' namely, lamine of the Haversian canals; 
_ secondly, the lamine which connect the 
' Haversian systems; and thirdly, the lamine 
_ which form the surface of the bone and enclose 
_ the two previous orders, 

The lamine of the Haversian canals have a 
concentric arrangement, and present, when 
_ divided transversely, a series of more or less 
aim and perfect rings : see figs. 448 and 450. 

ey are subject to considerable variety in 
_ number, but the more common amount is ten or 
' twelve. Of these, the internal lamina, that which 
forms the parietes of the Haversian canal,is most 
distinctly marked, while each succeeding one as 
‘ou proceed outwards becomes less distinct. The 
ncentric lamine with bone cells and central 
nal have received the name of Haversian 
stem from Dr. Todd and Mr. Bowman in 
eir work on Physiology. 

Connecting these Haversian systems is a 
nd series of lamine, without which the 
former would exist but as a bundle of loose 
tubes. (See fig. 448, c). 
In this substance we find the laminated 
‘arrangement less distinct, far less regular, and 
the lamine individually subject to great 
larity of thickness. “It is often also more 
‘fansparent than either the Haversian or exter- 
VOL. III. 


849 


nal system. Bone cells contained in it are 
also more irregular in shape than those found 
in other situations. The last division consists 
of those lamin which surround the exterior of 
thes bone. These have greater individual 
extent, but are the least numerous. They are 
continuous with the lamine of the Haversian 
system whenever the latter arrive at the surface 
of the bone; the external lamine in this case 
being continuous with the inner laminz of the 
Haversian system. 

Some authors have doubted the existence of 
a laminated arrangement in bone. If, however, 
young bone be examined, all doubt upon the 
subject will be dispelled, and especially if it 
be first macerated in weak muriatic acid, when 
the appearance represented in fig. 450 will be 
seen. In bone so treated the lamin may with 


Fig. 450. 


The lamine as they appear after the removal of the 
animal matter by the action of acid. 


the assistance of two needles be separated. In 
the bones of old animals the lamine are much 
less distinct ; in these, however, they may be de- 
monstrated if acid be used. Though the external 
lamina is very distinct, and therefore the boun- 
dary of each Haversian system, yet in bone of 
advanced age the distinctness is lost in com- 
mon with the definite outlines of the three 
orders of lamine. The cancelli of the can- 
cellous portion of bones are but enlarged 
Haversian canals, which in addition to vessels 
contain fat; the lamine therefore which form 
the walls are those of the Haversian system. 

In connection with this division of the sub- 
ject, the effect of madder. given to an animal 
with its food upon the osseous system may be 
noticed, since the colour is imparted to the 
lamine. By the taking of madder into the 
stomach the effect of giving a deep red tinge is 
very soon observable. Ina pigeon the bones 
were rendered brilliantly red in twenty-four 
hours. In a young pig a similar effect was 
produced in three weeks. 

On making sections of bone so affected the 
colour is found to be present in the external 
laminz of the bone, and in the inner lamine of 
the Haversian system, thereby proving that the 
action of colouring takes place upon those sur- 
faces which lie in contact with vessels. This 
fact, with many others in this article, was men- 
tioned in a paper by the author read before 
the Royal Society in June of 1838. 

Of the Haversian sassateain canals 

I 


; 


850 


have to be considered in relation to their num- 
ber, their size, and the parts which they contain. 
The number of canals in a given s is 
— a little variable, but this variation will 

regulated in some degree by the situation of 
the bone, but more especially by the age of the 
bone. Thus the transverse section of the femur 
of a human feetus of seven months will present 
many more canals than a section of equal mea- 
surement from the femur of an adult. 

In certain fish of which the Scarus is a spe- 
cimen, the Haversian canals are extremely nu- 
merous, so that bone cells become unnecessary, 
for here we find very few indeed, and in ‘some 
sections none. ( fig. 451.) 


Fig. 451. 


Section if bone from the Scarus; showing that where 
the Haversian canals are very numerous the bone 
cells are absent. 


The size of the Haversian canals takes a con- 
siderable range, varying from the yj,rd to the 
sisth of an inch, as stated by Mr. Smee. In the 


young subject they seem larger than in the old. & 
But by far the most marked difference in size of § 


these canals is to be observed in the antlers of 


the stag at different periods of their growth. f 


At an early period of the existence of the antler, 
the vascular canals are large and numerous, 
while at the time of their completion in size 
the canals are less numerous in an equal 
space, and very small: indeed many seem all 
but iabnended The density of bone is pro- 
duced more by the small size of the canals than 
by their comparative infrequency, though un- 
doubtedly they are less frequent in the compact 
bone, as that composing the shafts of long bones. 

In tracing individual canals, it will be found 
that the majority maintain the same size as far 
as we can follow them. This is not, however, 
observable in all. If a large canal be taken 
where it first enters the substance of the bone, 
it may be found giving off branches from time 
to time in various directions, and then again 
sending off smaller branches, which anastomose 
freely with each other, often joining at right 
angles. 

Although it is very easy to trace a large 
canal pervading a bone, and then dividing from 
time to time into smaller ones, I have never 
been able to satisfy myself that these small 
canals again unite to form a second large canal, 
and thus to leave the bone. I am therefore 
led to the opinion that such does not occur, 
but that the small even-sized canals open and 


OSSEOUS TISSUE. 


give exit to their vessels upon the surface of the 
bone generally, while the large canals give 
entrance to arteries. 

The Haversian canals undoubtedly give pas- 
sage to bloodvessels, which is their principal, 
if not their only purpose. Whether they con- 
tain one or more vessels seems to admit 
of a little doubt. Dr, Carpenter, in his work 
on Physiology, states that they contain an 
artery and vein. From my own observation I 
= not able 2 confirm his view. Indeed I am 

i d to the opinion that they give passage 
to nee vessel ain that du ieone canals 
which are found entering the bone an 
artery ; that it divides from time to time after the 
manner of the canals described ; and that the 
vessels emerge again from the surface of the 
bone as capillaries. This branch of the ~—— 
requires some further investigation. The 
going observations apply only to di bone. 

hare bone ip. Goneaiielen for the reception of 
fat, the vessels occupy but a small space in the 

cancelli. 
uscles or cells of bone; also 


Of the corp 
called /acune by Dr. Todd and Mr. Bowmar 


The so-called corpuscles are nothing more 
than small cells existing in the substance of th 
tissue, and might with ory be called bone 
cells. Some anatomists have designated them 


Fig. 452. 


Section of a flat bone, showing the bone cells in 
granular tissue, 

calcigerous cells, from the supposition t 
they contain in their interior an amorphi 
salt of lime. That this view is incorrect } 
be subsequently shown. The cells cannot 
described as having any definite ur ur 
shape or size. The general form is a | 
pressed oval, though not unfrequently the 
circular, but flattened from side to side. A 
they are sometimes almost triangular 
outline, while in other instances they appre 
linear shape. These are the most comm 
rieties ofoutline to which the bone cells are 
ject ; as they occur in the bones of man an 
higher animals. But connected with 
are numerous delicate branching tubes, 
slightly dilated as they enter the cells. 
number arising from each cell does not 


2 


OSSEOUS TISSUE. 


Fig. 454. 


_ Various forms of bone cells found in the bone of the 
| .. Boa Constréctor. 


Fig. 455. 


a a Se 


‘orm of bone cell in the common frog; b, bone 
tells from the crania of the common goldfinch ; 
€,form of bone cell in the sheep’s-head fish ; 
d, form of bone cells in the green-boned fish. 

y very definite enumeration, since no two 
will be found possessed of a like number of 
inching tubes. The general arrangement of the 
is radiate as regards the cells, which forms 
ircommon centre. This statement requires 
ne qualification, for not uncommonly a much 
feater number of tubes arise from one side of 
}cell than from the other, and these tubes all 


B51 


take one direction. \A tube after passing some 
little distance from the cell will in many in- 
stances divide, and each division pass on 
distinct from its fellow, equalling in size the 
pevent tube. Frequent anastomoses are effected 
tween different tubes arising from the same 
cells, but far more frequently between those 
which arise from neighbouring cells. So fire- 
quent are the connections that a free com- 
munication is established between the various 
cells and branching tubes throughout the 
substance of the bone. 

So numerous are the connections between 
the tubes, and immediately between the cells 
through the tubes, thata fluid introduced into one 
cell in a bone may find its way into every other 
cell of the bone. Indeed this does take place, 
though not from a single cell, yet from the 
surface of the bone. If, for instance, you place 
a bone that is dry, and opaque as a conse- 
quence of being dry, in spirits of turpentine, in 
a very little time this bone, before opaque, will 
become comparatively transparent, and this 
through the fluid having passed through the 
tubes into the cells. For, as will be shown, it 
is the tubes only that open upon the surface of 
the bone, either the external surface or the sur- 
face of the canals for vessels. Indeed, if a 
thin section of bone be taken and all moisture 
removed, and spirit of turpentine be added to 
it, when under the microscope, the passage of 
the fluid through the tubes may be seen, an ex- 
periment suggested by my friend Mr. Bowman. 

Besides this relation between the tubes them- 
selves and their cells, they have a very definite 
relation to the Haversian canals as well as to the 
free surface of the bone and also to the lamine. 

The position occupied by the cells is between 
the lamine, or on the surface of the lamine ; 
and where concentric lamine occur, as in the 
Haversian system, the cells are arranged in cir- 
cular lines between the laminz, each line of cells 
having as an exit common to it and the con- 
necting lamine the Haversian canal. The 
flattened sides of the cells are parallel with the 
circumference of the Haversian canal, while 
their greater diameter is in the direction of the 
circular line of the lamina, or with the length 
of the canal to which they belong. Bone 
cells so placed send out numerous tubes, which 
pierce the lamine at right angles and proceed in 
great numbers to the vascular canal, into which 
they enter, there terminating in an open mouth 
upon the surface ; thereby establishing a. con- 
nection of tube channels between the bone cells 
of the Haversian system and the canal of the 
system. (See fig.448.) Although these cellssend 
out many tubes in the above direction, yet others, 
though comparatively few, take an opposite 
course, and then establish by anastomosis a con- 
nection with the tubes of the surrounding bone 
cells. This is more particularly seen when we 
look upon a transverse section of an Haversian 
system; but if a section taken in the length of 
an Haversian system be examined, the tubes 
will for the most part be seen dividing the cells 
equally in point of number from every part of 
the circumference of the cell, and of course pro- 
ceeding in the length of the lamine between 

312 


852 


which the cell is placed. As in the transverse 
section of the Haversian system these tubes 
that take the longitudinal direction are not 
seen, so in this section the tubes proceeding 
directly towards the Haversian canal are but 
badly shown. So many of the delicate tubes 
take the direction of the Haversian canals and 
enter it, that the parietes of each canal at first 
sight have a radiate ap nce, which has led 
some writers to describe a system of radiate 
tubes ing through some of the lamine, but 
the bate failed to trace their connection 
with the bone cells not far distant. When the 
cell with its radiating system of tubes is situated 
near the surface of the bone, the direction of 
the latter will be mostly towards that surface, 
unless indeed there is a vascular canal near at 
hand, in which case many will proceed towards it. 

Those cells which are placed in the connect- 
ing lamine send out their tubes tolerably 
equally in each division, anastomosing freely 
with the tubes coming from the cells belonging 
to the Haversian or superficial system of lamine, 
and so establish a communication between the 
cells of the three systems of lamine. The 
number of tubes and the size of the bone cells 
bear to each other no definite proportion ; thus 
a small cell may have many tubes while a much 
larger one has comparatively few. The number 
of the cells in a given space is subject to con- 
siderable variety, as well as the number of the 
radiating tubes, though generally the number of 
tubes will exist in inverse proportion to the num- 
ber of the cells. Thus in the crania of small 
birds the cells are of very frequent occurrence, 
while the tubes connected with each cell are but 


Section of a bone of an osseous fish. 


a, transverse section of Haversian canal; 6, longitudinal 


section of an Haversian canal with system of tubes opening 
into it, 


OSSEOUS TISSUE. 


I was disposed to hold a like opinion, but fi 


few. Again, in dense bones of quadrupeds and 
of man, the cells are less frequent, but the tubes 
of each cell far more numerous. 

Where the canals for vessels are very nu- 
merous the bone cells become more rare, and 
in some cases they are nearly absent,as shown in 
fig. 451. 

From the foregoing description it may be 
seen that the infinitely numerous tubes every- 
where connected amongst the cells, converging” 
at certain points and entering into cells, in fact 
form these cells ; that the cells are nothing more 
than many tubes coming toa point and le 
their individual parietes. ‘ 

In other cases where the tubes to each cell 
are not numerous, the cell itself may be cc 
pared to a dilatation of those tubes. This vies 
of the subject is borne out by the fact that ever 
in the human subject we find here and then 
tubes occupying the place of the cells and 
their radiating tubes, while in certain fish the 
cells are almost entirely absent and the simple 
tubes general. , 

In such instances the tubes hold the sa 
relation to the Haversian canals as do the bon 
cells where they exist. (See fig. 456.) 

The cells when seen by transmitted light, esp 
cially in a transverse section of bone, appé 
perfectly opaque; this has given rise to th 
opinion that they contain some am al 
and the fact that these same cells become tra 
parent when the bone has been subjected to 
action of acid, confirmed observers in t 
opinion, and that this salt was a salt of lim 

hen first these observations were commen 


therinvestigation has convinced me that asa Mm 
the cells are empty. I have seen, and that 
very frequently, cells which were 
viously without contents, and | 
observation may be repeated in ; 
bone where the cells are toler 
large by making a section in 
length of bone, and so L 
the direction of most of the Haver 
canals. By making such a sec 
you expose the cells in their la 
diameter, when they may be seen 
whereas if cut through in theirm 
diameter they are so deep tha 
produce complete interference of] 
- and so seem black, as though 
with some opaque substance. 

Again, if turpentine or thin Cs 
balsam be added to a section | 
dry beforehand, the dark cells 
become filled with turpentine © 
sam, and so become transparent 

The function performed by th 
cells is no doubt that of eiret 
Atmospheric pressure would 
them from remaining empty, 
their openings are always U 
surface where there are blood! 
the fluid portion of the blood 
bably carried into them. Sap 
them once filled with rp sang 
the varying density of ood 
would produce a slow kind of 


OSSEOUS TISSUE. 


lation, even though the contents of the cells 
remain unaltered, which is not probable. 

Cells of smaller form and having branching 
tubes are to be found in the vegetable world. 
The shells of various fruits, as the cocoa-nut, 
peach, common nut, &c. present cells so like 
those of bone that a section of shell has often 
been mistaken for one of bone. In this instance 
they also answer the purposes of circulation. . 

Lhe growth of bones.—Many experiments 

have been made to ascertain the mode of 
growth in bones, but they have given as their 
results the direction of increase rather than the 
process of interstitial growth. The experiments 
alluded to are commonly spoken of as the 
madder experiments, and were instituted by 
Du Hamel, Detlif, Hunter, Stanley, Paget, 
and others. 

It was discovered that phosphate of lime 
acts upon the colouring matter of madder as a 
mordant. Thus, if phosphate of lime be pre- 
cipitated from a state of chemical combination 
in a solution of madder, the colouring matter 
of the madder is carried down with the phos- 
phate in a state of chemical combination, im- 
parting to the phosphate a red colour, which is 
not diminished by repeated washing, but gra- 
dually fades by exposure to light. But, before 
this discovery was made, it was found that the 
bones of some pigs that had been accidentally 
fed upon madder were rendered red. Atten- 
tion having been drawn to this curious fact that 
madder given in the food reddens the bones 
of the animal, the madder experiments were 
undertaken, and !ed to the following results. 

If madder be given to a growing animal, 
and the bones be examined by making a sec- 
tion of a cylindrical bone, a ring of reddened 
bone will be seen to form the circumference of 
‘the bone, and a similar reddened ring to form 
the parietes of the medullary cavity. If in this 
‘experiment the animal had been old, these 
rings of red would not have been seen, or, if 
‘Seen, only very faintly. From these two ex- 
periments it has been deduced that the bone, 
or rather the phosphate of lime, which has 
been deposited during the exhibition of the 
-madder, has alone been reddened. 

_ ff, however, after giving madder to a grow- 
ing animal for a time, its use be discontinued 
for awhile and then be again given, several 
Tings of reddened bone will be observed on 
Making a section of a cylindrical bone, that is, 
reddened bone will be deposited during the use 
of the madder, and white bone at the interval 
f its discontinuance. So that, by the alter- 
mate use and disuse of madder, rings of red 
and of white bone will be formed to a consi- 
erable number. From these experiments it 
has been deduced that bones increase in their 
jameter by the development of the bone on 
surface somewhat in the same manner that 
crystal increases in size by additions to its 


ce. 
_Mr. Gibson, however, for a while threw some 
bts on the value of the madder experiments 
the deductions from them, by stating that 
serum of the blood had an affinity for the 


853 


colouring matter of madder superior to that of 
the phosphate of lime, and that the bone became 
stained only after the serum had been tho- 
roughly saturated with madder, and more, that 
the serum, from the discontinuance of madder 
in the food, or losing the colouring matter, 
absorbed that existing in the bones. 

Mr. Paget has, however, proved that the 
affinity is far stronger between phosphate of 
lime and the colouring matter of madder than 
between serum and the latter. These experi- 
ments seem at first sight far more valuable than 
a closer investigation will prove them to be, as 
will be seen on considering the following fact, 
namely, that not only is the surface of the bone 
with the walls of the medullary cavity tinged red 
by the exhibition of madder, but also the cir- 
cumference of every Haversian canal through- 
out the bone, in fact every surface that lies in 
contact with a vessel or vessels. The fact that 
every Haversian canal has its coloured ring had 
escaped observation, as these experimenters 
had been limited to the use of the naked eye, 
whereas the Haversian canals, with their co- 
loured rings, are only seen by the use of the 
microscope. 

It therefore remains for observation to be 
made upon the effects of consecutive feeding 
with and without madder, upon the Haversian 
canals, before any very accurate deductions 
can be made. 

Other experiments have been tried in inves- 
tigating the growth of bones. 

Rings of metal have been lightly fixed round 
a long bone, which after a while has been found 
to contain the rings in its medullary cavity, 
from which it has been inferred that the bone 
has grown by additions to its circumference, 
while the medullary cavity has been enlarged by 
the absorption of the bone forming its parietes. 
These experiments, which were made by Du 
Hamel, have been confirmed by Hunter and 
Stanley. 

Experiments of a similar nature have been 
made to determine the manner of growth in 
the length of bones. Thus holes have been 
bored in the tibia of a dog at definite intervals, 


which intervals, after the lapse of some days, 


have been found altered in the relative lengths. 
The intervals near the ends of the bone have in- 
creased considerably, while those situated near 
the centre of the bone have scarcely changed. 
Mr. Stanley has shown that in some animals 
the growth is greatest at the distal end, while in 
other animals it is greater toward the proximal 
end of a long bone. ; ; 

In the two experiments which I have related 
in a previous part of this article the walls of the 
medullary cavity were as distinctly reddened as 
the circumference of the bone, and the cir- 
cumference of each Haversian canal as either. 
These would therefore prove too much for the 
theory which supposes that a long bone in- 
creases its diameter by the depositions upon its 
surface and under its medullary cavity by the 
absorption of the walls. Supposing the idea 
that phosphate of lime, which is deposited 
during the exhibition of madder, is alone red- 


854 


dened to be correct, the parietes of medullary 
cavity should not show colour, as here absorp- 
tion 1s sup to be going on. 

From what is already known, I think that 
the bones are coloured by the madder just in 

portion to their powers of imbibition, which 
will be in inverse proportion to the amount of 
phosphate of lime which they contain. 

As the growth of bone, the laws 
common to the growth of every other tissue 
and to the whole body will, I think, be found 
to hold good. And the growth of these organs 
will be found to be interstitial, pervading the 
whole substance, though the action will be 
more energetic at some points than at others, 
as the neighbouring organs may require greater 
length or breadth in one direction than in an- 
other. 

The younger the bone the more rapid will be 
its growth, but this law is common to all the 
tissues. The increase of length of a long bone 
at the epiphysis must not be confounded with 
growth of the bone, for here, so long as car- 
tilage connects the shaft with the epiphysis, 
osseous tissue is being developed; whereas, in 
speaking of the growth of bones, the increase 
of the tissue already developed is alone meant. 

Of the developement of osseous tissue.—As 
the developement takes place in cartilage, and 
as the cartilage undergoes some change pre- 
vious to its giving place to bone, it will be 
well to give a slight sketch of the structure of 
temporary cartilage before going into the for- 
mation of the more permanent tissue. The 
rudimentary condition of cartilage may be best 
examined in the feetal chicken, a few days 
after the commencement of incubation. The 
exact time for making the observation will be 
found by taking an egg for examination every 
six hours, commencing after the eggs have been 
exposed to the due temperature for thirty-six 
hours. On the first appearance of the verte- 
bral column, which will present a semitrans- 

nt line in the length of the developing 
cetus, the whole must be removed with great 
care to the field of the microscope. This part of 
the operation requires some care, but with a little 
management may be successfully performed. 
I found but little difficulty in removing the 
delicate object after adopting the following 
plan. Having, in the first place, placed the 
egg in adish of water of sufficient depth to 
cover it, letthe shell be carefully removed ; then, 
by moving the water with the assistance of a 
camel’s-hair brush, take away the albumen so 
as to leave the yelk free. The point where deve- 
lopement is going on will then be sufficiently 
conspicuous. Ata considerable distance around 
this the membrane of the yelk should, with 
a pair of sharp scissors, be cut through, and 
carefully separated with the aid of a camel’s- 
hair brush and a pair of forceps. This having 
been effected, the subject for examination will 
be left on the surface of the yelk, and may, 
with delicate manipulation with the pencil, be 
removed to a slip of glass held near it under 
the surface of the water. Having completed 
your purpose so far, the glass must be raised 


OSSEOUS TISSUE. 


very slowly from the water, so that the spe- 
cimen may not float off, and this being covered _ 
with a little thin tale or glass supported at the — 
sides, so that it shall not upon the em- — 
bryo to be removed to the field of the micro- 
scope. If the specimen be favourable, the — 
semitransparent line of the vertebral column 
will under a low power a’ made up of a 
vast number of clear colourless oval 
closely pray Bc a. no appreciable 
8 between the indivi composing the 
saan: Under a higher power, however, each 
cell will present a definite outline with a central 
nucleus or rmee and even in oy nucleoli 
The cells give appearance of density 
clearness \Pecbinances and with their d 
and smooth outline present a 
the highly granular cells of developement tha 
surround them. In each vertebra there it 
some show of a radiate arrangement, for mar 
cells are egg-shaped, and have their small 
placed towards the centre of the Care ‘ 
At this period of the formative Cs cell: 
are so close to each other that is no spac 
for intercellular tissue. i 
With the growth of the embryo the cartilag 
advances, and its developement as a perfe 
tissue is completed by the of | 
cells from each other by the interposition 
an intercellular tissue. This latter is tra 
parent and dense, but without traces of di 
nite structure, unless it be a minutely rant 
tissue. Temporary cartilage is thus shown 
be composed of cells having parietes and ¢ 
tents, and intercellular, (see fig. 457) or, as Se 
have called it, hyal 


substance, 
which the cells or 
puscles areeq uli i j 
tributed. In carti 
preter 
evelo of 
eam ne 
commencement of 
developement of 

great changes oe¢ 

the arrangement ¢ 


cartilage COPD > ] 
the immediate 
a, temporary carti- dents of ossifi¢ 
lage, with the corpus- They are no 
cles and _ intercellular equally distri 
tissue; 5, tempo te 
cartilage, with eae through the * 
puscles forming for ossi- Substance, but 
fication. found arranged 


rallel columns of 
ble lengths, in the line of the length of the 
The corpuscles forming into columas 
sarily leave intervening columns of i 
lular tissue. A notion has pretty ge 
prevailed that the corpuscles already 
marshal themselves into this order. . 
however, that on further investigation 
found that each corpuscle has developed 
and that they have been developed 
direction only, and that towards the 
where osseous formation has commence 
we find that the first perceptible chal 


we 


Temporary cartilage, 
with corpuscle arran- 


oy of the corpus- 


_ parietes of the cor- 


OSSEOUS TISSUE. 


temporary cartilage on the approach of ossifi- 
cation is that the corpuscles, instead of being 
solitary, are arranged in groups of variable 
numbers according as they are near or far off the 
site of immediate ossification ; that they have 
a linear arrangement, and where there are two 
or three only this is somewhat semilunar, with 
the straight edges near each other ; and that the 
greatest diameter is lateral. (See fig. 457, 0.) 
Moreover, the columns are not continued unin- 
terruptedly through the cartilage, but are broken 


off, and near their terminations new ones com- 


mence, not, however, in a line with the former, 
but opposite their intercolumnar spaces. (See 


fig. 458.) 


Supposing this view of 
the subject to be correct, as 
I believe it to be, the growth 
of a bone in its length ad- 
mits of easy solution, name- 
ly, by the developement of 
cartilage at the epiphyses. 

The formation of co- 
lumns having commenced, 
developement in the lines 
proceeds with rapidity, and 
the corpuscles composing 
them hold a different rela- 
tion to each other at each 

rt of the same column. 

us atthe end farthest from 
the point of ossification the 
corpuscles are flattened and 
closely arranged, present- 
ing an appearance not un- 
ie. like a pile of pence. Butas 
we trace the line down. to- 


Fig. 458. 


ged in columns. — 


a, intercolumnar 
or cellular tissue ; 5, 


puscle; c, central 


_ wards the bone, each corpuscle becomes more 


distinct, is separated from those on either side, 


_ becomes itself enlarged, and of nearly equal 
' dimension in each direction. (See figs. 458 and 


460.) The intercellular tissue becomes distinctly 


- visible between each corpuscle. The space also 
between the columns, though always consider- 


able, is increased when the corpuscles have 


“undergone the above change. (See fig. 459.) 
a4 
bs Fig. 459. 


of the intercellular or hyaline substance, the 
‘corpuscle having been removed. * 


ot only are the described changes in form 


855 


and relative position observable, but a further 
remarkable developement-takes place in each 
corpuscle. The parietes of the cell, which at 
first formed but a small part of the whole, at 
this latter situation has so far increased in di- 
mension that it forms by far the greater part of 
the mass, while the central portion, which at 
first appears to constitute the whole corpuscle, 
notwithstanding its increase of size, is now to be 
regarded only as a nucleus, presenting the ap- 
pearance of a cavity or granular cell, of a form 
approaching that of a sphere. (See fig. 460.) 

Cartilage, when it has 
been subject to the 
above changes, in the 
nexttransition becomes 
bone. In order to un- 
derstand this process 
it will be necessary to 
bear in mind the fol- 
lowing points: first, 
that the enlarged carti- 
lage corpuscles are ar- 
ranged in vertical co- 
lumns; that each co- 
lumn is surrounded by 
the intercellular tissue, 


Section of temporary car- 


tilage, which has under- 


gone the last stage towards 
ossification. 


a, intercolumnar tis- 
sue ; 6, the enlarged pa- 
rietes of corpuscle; ¢, 
central nucleus of the 
corpuscle. 


and that each corpuscle 
is separated from those 
above and below by a 
layer of intercellular 
tissue; and, lastly, that 
each corpuscle has dis- 
tinct parietes with cen- 
tral nucleus, or cavity, 
containing granules or 


having granular parie- 
tes. Osseous tissue is in all instances developed 
in the form of minute granules, so the earliest 
appearance of bone in cartilage is marked by 
the presence of these spherical granules in the 
intercolumnar and intercellular tissue, which is 
thereby increased in density and opacity. This 
constitutes the first stage in the process of the 
developement of bone, and may be observed 
by making a thin section of a bone at the point 
of junction of the bone and cartilage, where the 
shaft is connected with the epiphysis. (See 


Jig. 461.) The granular appearance will be 
Fig. 461. 


Transverse section of temporary cartilage in the first 
stage of ossification. 

a, a, intercellular tissue ossified; b, the trans- 
parent parietes of the enlarged corpuscle; c, the 
central nucleus, which in the specimen from which 
this figure was taken was granular. 


856 


increased if a little acid be added to the sec- 
tion; caustic alkali will produce a similar 
effect. The intercellular tissue having become 
granular, the parietes of the corpuscles next 


undergo a similar change, and the central’ 


nucleus or cavity can no longer be identified. 
The accession of granules to the parietes of the 
corpuscles constitutes the second stage of the 
process of ossification. 

The third stage is an action of a different 
nature, and is fulfilled in the absorption of the 
osseous matter interposed between ‘the cells, 
and also of that portion of the ossified cells 
which lay in contact with the intercellular 
tissue of the columns. 

By this change, the column, once composed 
of closed cells, is converted into a tube marked 
by numerous indentations corresponding in 
number to the cells which entered into its 
formation, there being a contraction at the 
points of junction between the cells. The 
tube so formed, supposing this condition to be 
sarge would eb closed ends, and the 
ength would be determined by the ends of 
the columns of cells from which it was formed. 
(See fig. 462.) 

These elongated tubes, I believe with the 
authors of “The Physiological Anatomy,” to 
be the Haversian canals in their rudimentary 
state. They do not, however, retain this form 
of tubes with closed ends, but like individual 
cells become perforated and communicate 
with other tubes similarly formed ; but as these 
do not follow each other in straight lines, the 
openings are formed at the sides of the tubes 
instead of their ends, so that these commu- 
nications are at angles with the tubes. These 
and other openings which are formed between 
the cells or tubes lying parallel to each other are 
those Haversian canals in their rudimentary 
state which traverse bone at right angles to its 
length, and form anastomoses with the longi- 
tudinal Haversian canals, which in hone are by 
far the most numerous. 

In the tubes no trace is left of the central 
nucleus or cavity of the original cartilage cor- 
puscle; they contain, however, small spheri- 
cal bodies composed of very minute granules. 
These are transparent and resemble in appear- 
ance those peculiar globules found in the blood 
and commonly designated lymph globules. 
(See fig. 462). 

They are very numerous, and, indeed, al- 
most fill the cavity. They have a red tinge, and 
constitute almost entirely the mass of red 
matter found in the interior of all recently 
formed and forming bone. These bodies were 
described by Dr. Todd and Mr. Bowman, and 
they suppose them to be concerned in the 
developement of vessels, since up to this period 
of ossification no bloodvessels exist in the 
forming tissue, but make their appearance so 
soon as the tubes become pervious. 

If a transverse section be made of bone 
in this stage of its formation, there will be 
no difficulty im recognising, first, the ossified 
intercellular tissue, then the ossified parietes 
of the once cartilage corpuscle, which, being 


OSSEOUS TISSUE. 


_ Haversian canal in its ra- (0)) generates: 


now the lining of the tube, will eventually — 
be the external lamina of an Haversian system 5 
and, lastly, the granular globules contained in 
the tubes. vy 
The last point for consideration in the de-_ 
velopement of bone is — 
the formation of the 
hone-cells. Several re- 
cent authors consider 
the cells to be formed 
from the nucleus of th 
cartilage corpuscle; I 
have not been able to 
confirm their state. 
ments, but have bee 
led to entertain a diffe 
rent opimon of the 


origin. The ormati 0 

in of the bok fi of tubes having beer 
dian ts Bb a 
by the eis completed, the inne 


layer formed from the 
parietes of the corpus 
cle is at first thin, ¢ 


a, intercellular tissue 
ossified ; b, ossified pari- 
etes of the corpuscles ; ¢, ( 
granular globules con- could it be withdraws 
tained in the tubes, entire, would look li k 
a tube formed by the junction of a number 
hollow beads. Partial separation mae howeve 
be produced, as seen in fig. 463. This stat 
alternate dilatation and contraction seen int 
tube at its first formation is soon lost, and 
tube becomes of nearly equal diameter throug! 
out from the filling up of the dilatations by t 
deposition of osseous matter in the ust 
nular form. But in this filling up of the di 
tations small cells are left, and these are 
bone-cells in the rudimentary condition, ai 
form the outer layer of cells in the Havers 
system. (See fig. 463.) At first it is diff 
to distinguish the tu 
of the bone-cells , dD 
if a section be ta 
near the perfectedbe 
they will be seen in 
rious stages of di 
lopement. At this 

riod of the forma 

one-cells appear 
the ossified interet 
lar tissue, which | 
the first formed a 
nection between 
systems of tubes, 
which in fully fo 
Section showing the develope- bone unites the 
ment of the bone cells and sian systems. Wit 
the separation that maywe have bone | 
be produced between the perfect state. 
ossified intercolumnar tis- From what ha 

sue and the tissue of the . 

united cells. stated it will be 

a, ossified intercolumnar that the cartilage 
tissue ; 5, ossified parietes corpuscle is the 
of the united cells; c¢, the part formed ;_ tha 


dimentary state; d, bone Be: 
cells in their first stage of that Be , pg 
developement. lining ©} the p 

tube; that the 
becomes the external lamina of an Hav 
system: so that the parietes of the « 


5 


OSSEOUS TISSUE. 


the embryo may be considered the element of 
the lamine. 

Again, the intercellular tissue found in the 
embryo forms the medium of connection be- 
tween the cartilage cells or corpuscles, as 
theyare called, between the primary tubes, where 
bone is developing, and lastly, becomes the bond 
‘of union between the Haversian systems. 

The foregoing description applies to the 
growth of the shaft of a long bone in the carti- 
‘lage connecting it with the epiphysis. 

The laws regulating the growth of the epiphysis 

in the cartilage which unites it to the shaft of 
‘the bone are but a slight modification of those 
which regulate the growth of the shaft. The 
cartilage corpuscles, however, here form sinall 
rounded groups, and ossification proceeds in 
the intercellular tissue around them, and the 
groups themselves eventually form a cavity, by 
which means the spongy head of the bone is 
formed. The flat bones are developed much 
as the long ones, the thin edges of these being 
sapped with cartilage, which developes its cells, 
and intercellular tissue. 
_ A bone at the time of its development is of 
equal density through the whole diameter at 
the point where ossification is just perfected. 
The arrangement of compact and spongy, as 
seen in the various bones, is an after process 
which takes place gradually, and in relation to 
the individual bones of which the framework of 
the body is composed. 

On considering the process of developement 
of bone, it will be apparent that the arrange- 
ment of cells, intercellular tissue, &c. answers 
the purpose of giving a definite form and 
arrangement for the future nourishment of the 
bone, but that osseous tissue is independent of 
any particular form. Thus intercellular be- 
<omes osseous tissue, as does the tissue of the 
cells. I wish to lay stress upon this point, as 
it bears particularly upon the character of 
certain formations of bone in unnatural 
Situations, or adventitious bone. 

Ossification of permanent cartilage-—The 
cartilages of the larynx at an advanced age are 
‘liable to become ossified, and in such cases, as 
the formation of osseous tissue goes on but 
slowly, the process may be observed with ease. 
In this case the corpuscles do not develope 
others as in temporary cartilage where increase 
of size is required, but retain their usual 
appearance. While the osseous granules are 
developed in the intercorpuscular tissue, at first 
but few of them are seen, and these spherical 
and isolated; they soon, however, become 
numerous, and unite, thereby forming an osseous 
mass. The intercellular or intercorpuscular 
tissue having advanced in ossification, the cor- 
puscles, or rather their parietes, pass through 
the same process, and by degrees the whole 
cartilage becomes converted into bone. 

The formation of the individual granules is 
more readily observed in these cartilages than 
in any other situation. This form of ossifi- 
cation establishes an interesting and explanatory 
link of connection between bone and the various 
osseous plates we find in abnormal situations. 
For in the latter the spherical granules appear, 


857 


and these, at first few and isolated, and lying 
amongst the fibres of the tissue, rapidly in- 
crease in number;.unite, and form an osseous 
mass. reeet 

Osseous plates occur in various soft tissues 
as the result of deranged action, where in the 
healthy condition of the part they are not found. 
Thus we have osseous plates formed in the coats 
of arteries, in. the pleura, in the diaphragm ; 
also osseous masses in the uterus; and some- 
times in the muscular tissue and in the pla- 
centa. These plates are all formed in the same 
manner, namely, by the developement of 
minute spherical osseous granules, which form 
into a mass, the shape of which is modified by 
the form of the tissue in which the develope- 
ment occurs. 

I have examined many of thése formations 
and find them to be composed of true osseous 
tissue, but not true bone ; for they have not the 
definite Haversian systems, which, formed of 
osseous tissue, constitute bone. But they have 
cavities scattered through them ; these, however, 
have no definite shape, but assume all kinds of 
irregular forms, and though they are no doubt 
necessary to the vitality of the mass, yet their 
action cannot be very perfect. Spicule of 
osseous matter are sometimes met with in 
cancerous tumours, but here it is very rare to 
find an Haversian system. The osseous plates 
found in the dura mater are, however, true 
bone, and are developed like the flat bones. 
I am decidedly of opinion that these masses 
are endowed with vitality, and are not mere 
concretions as some have regarded them, 
though this vitality is of a low degree. 

Formation of osseous tissue in union of frac- 
tured bones.—Supposing the subject in which 
the fractures occur to be young, cartilage 
similar in every respect to temporary cartilage 
is produced between the fractured extremities 
of the injured bone. In the centre of this 
ossification commences, the process being 
somewhat similar to ossification of permanent 
cartilage, or holding an intermediate place 
between that process and the ossification of 
epiphyses. 

The corpuscles here increase in size but not 
in number. The ossification commences in 
the intercellular tissue, and proceeds: to the 
parietes of the cells, thus forming areole of 
bone. 

The action may also commence in the carti- 
lage in contact with the fractured surface. 
This I believe to be the process by which repa- 
ration is effected in all cases where union of 
fractured bones takes place, but my experi- 
ments have been confined to young animals. 

I have examined various cases where union 
has not been effected in consequence of the 
patient’s advanced age, and the fracture being at 
the neck of the femur or of the shaft of the same 
bone. In these I found no cartilage, and but 
a scanty amount of condensed cellular tissue. 
In this latter, however, traces of an attempt 
at repair may generally be found in the pre- 
sence of osseous matter in granules or granular 
masses. In these there is no arrangement of 
tubes or bone-cells of definite character; indeed 


858 


these osseous masses are generally small, and 

sometimes without material density, the indi- 

vidual granules not having firmly united. In 

8 they resemble in every point adventitious 
ne. 

If in a young animal the fracture be not 
kept tolerably quiet, the motion between the 
fractured bone will prevent the formation of 
cartilage, which seems necessary to the deve- 
lopement of bone, and here, therefore, osseous 
masses will alone present themselves. This 
fact is very interesting in a surgical point of 
view, and might be treated more at length ; but 
having given a detailed account of the deve- 
lopement of bone and of the distinction to be 
made between true bone and adventitious 
osseous tissue, I shall conclude the article. 

(J. Tomes.) 


OVARY.—See Supprement. 
OVUM.—See Suprremenrt. 


PACHYDERMATA.—An extensive group 
of herbivorous quadrupeds, constituting a dis- 
tinct order of the class Mammalia, generally 
remarkable for their ponderous bulk and un- 
wieldy appearance, and seemingly forming the 
transition between the gigantic Cetacea, which 
from their size are only adapted to an aquatic 
existence, and the vegetable-eating Mammals 
of strictly terrestrial habits. Even the localities 
where they are met with would seem to indi- 
cate that they constitute such a connecting 
link, seeing that their most typical forms are 
peculiarly adapted to be occupants of the river 
and the marsh, from the Hippopotamus, that 


5a aQVe 


of ee > > 


PACHYDERMATA. 


Sheleton of Elephant ( Elephas Indicus ). 


might almost be considered an aquatie ani 
to the Tapirs and the Hog, which still ore 
wallow in mud although they approximate in 
their habits to the ruminatin undreaae At 
the present day the order Pachydermata con- 
tains but few genera, and these for the most 
x embrace a very limited number of species. 
ut in former periods of the history of our 
globe they must have existed under much — 
greater variety of form, seeing that the tertiary 
deposits yield to the geologist, in abundance, 
the remains of iM humerous genera now 
totally extinct, to the list of which modern 
researches are adding day by day; it is indeed 
more than probable that many of the existing 
races will ily perish, for the hand of man 
is against them, and the bullet and the pear 
are doing their work of extermination rapidly, 
so that the Tapir and the Elephant, like the 
Palcotherium and the Mastodon, may soon be 
classified with extinct existences. 
The order of Mammalia under consideration 
is usually divided into Prososcrprans, in- 
cluding such Pachydermata as are provided 
with a proboscis and tusks, of which the Ele 
hant is the only existing example, and into 
RDINARY PacHyDERMATA, which are unpro- 
vided with a proboscis, and characterized by 
possessing four, three, or two large digits or 
their feet, which are cased in horny hoof 
last group being distinguishable from the Run 
nantia by the simple construction of thei 
stomachs, although closely approaching them 
in many points of their economy. The abor 
division, however useful to the zoologist, i 
nevertheless by no means based on n 
proboscis of the Elephant being onlya maximur 


‘ 


) 
~ 


PACHYDERMATA. 


degree of developement of the snout of the Pig 
and the semi-proboscidean nose of the Tapir. 

The following genera of Pachydermatous 
Quadrupeds have been distinguished by natu- 
ralists, many of which are still in existence, 
but the majority are met with only in a fossil 
State, the names of the latter being printed in 
italics. 


Elephas, (fig. 464. ) Hippopotamus 
Mastodon Toxodon 
Dinotherium Coryphodon 
Tapirus Acerotherium 
Paleotherium Elasmotherium 
Lophiodon Macrauchenia 
Hyrax Hexaprotodon 
Rhinoceros Anthracotherium 
Anoplotherium Cheropotamus 
Dicotyles Hyracotherium 
eT Dichobune. 

us 


Osseous system.—The skeleton of the Pachy- 
dermata is generally remarkable for the massive 
character which is conspicuous in every region, 
indicative, at a glance, of the ponderous strength 
and generally inactive habits of the animals 
belonging to this order; but inasmuch as they 
are destined to obtain their food under very 
various circumstances, which demand a cor- 
responding diversity of structure in different 

of their bony framework, some detail will 
necessary in adverting to this part of their 
economy. 

Cranium.—The cranium of the Elephant, the 
only living genus of Proboscidian Pachyderms, 
is quite unique in its external configuration, 
and from its vertical elevation confers a re- 
markable aspect of sagacity to the animal ; its 
intelligence, however, although really surpri- 
sing when contrasted with the stupidity of 
other genera belonging to this class of quadru- 
peds, has doubtless been much exaggerated in 
consequence of its imposing appearance. This 
peculiar contour of the skull depends upon 
several circumstances having nothing whatever 
to do with cerebral developement, but being 
entirely dependent upon mechanical arrange- 
ments required to support the enormous tusks 
that project from the upper jaw, and to give 
origin to the muscles of the proboscis, a nasal 
apparatus here only met with in a state of 
complete developement. The extreme short- 
ness of the bones of the nose, the nearly vertical 
position of the upper maxilla and ossa incisiva, 
and the swollen vault of the forehead produced 
by an excessive enlargement of the frontal 
sinuses, (fig. 466, ) which gives extent of sur- 
face to the exterior of the skull, all concur to 
mask the real condition of the cranial cavity, 
which, as is easily seen in the next figure, 
(fig. 465,) occupies but a very small portion of 
the posterior and central portion of this gigantic 
cranium. 

The general character of the individual bones 
of the cranium and their modifications in the 
principal Pachydermatous races will be under- 
stood from the appended figures better than 
from any lengthened description. 

The occipital bone is very extensive, forming 
by itself the entire posterior wall of the cranial 


859 


Skull of young Indian Elephant. 

a, intermaxillary bone; 6, nasal bone; c, superior 
maxillary; d, jugal; f, frontal; g, parietal; 
h, temporal ; 2, inferior maxilla. 


cavity, and even in the Elephant advancing 
considerably upon its upper surface, where at an 
early period it becomes so firmly consolidated 
with the parietals, and these again with the fron- 
tals and temporals, that the whole roof ofthe skull 
appears to be formed of one bone. In the hog 
tribe, the Hippopotamus and the Tapir, it termi- 
nates superiorly in an abrupt and broadly ex- 
panded crest, into which the muscles of the neck 
are inserted ; and not unfrequently the deep fossz 
and prominent ridges visible upon its posterior 
aspect testify to the massive strength required 
in this part of the muscular system, either to 


Vertical section of Elephant’s skull, shewing the relative 
ortions between the cranial cavity and the sinuses 
of the skull. 


860 


support the unwieldy head or to tear up the 
ground in search of food, as the hog tribe do 
with their powerful snouts. In the young 
animal this bone always consists of four sepa- 
rate pieces—a basal, two lateral, and a superior 
occipital (fig-A71, c 1, ¢ 2, c 3 :) but these soon 
become inseparably united into one mass. 


Skull of Hippopotamus. 
Letters as in Fig. 465. 


The parietal bones ( figs.465,467, 468,471, f) 
are moderately extensive, covering the superior 
and lateral portions of the skull. In the young 
animal they are always separated by a mesial 
suture, (_ Fg. 469, b,b,) but in the adult are united 

obl 


by the iteration of this suture into one 
piece, so as to appear but a single bone; a pro- 
vision, no doubt, for admitting the enormous 
force of the temporal muscles to be exerted 
without danger of divaricating the two lateral 
halves, which might otherwise be torn asunder 
at the line of junction. In the Tapir there is a 
lofty interparietal crest, giving great additional 
surface for the origin of the temporal muscles. 


PACHYDERMATA. 


Fig. 469. 


Shull of a young Boar, Sus Scrofa, shewing the osteology of the cranium and faces, ~ 


The frontal bones are of very great extent, 
and besides enclosing the anterior part of the 
cranial box, form a large proportion of the 
orbital cavity. In the young animal (fig. 469, 
a, a) they are invariably two in number, 
separated by a suture along the mesial line, 
and in the American Tapir this separation is 
permanent; but generally they become con- 
solidated at an early age, leaving no trace of — 
their original separation. 

The ethmoid is, in the Pachydermata, of very 
considerable size, ass ie to the acuteness 
of the sense of smell with which these animals 
are gifted. The cribriform plate holds a posi- 
tion exactly similar to that which it presents 
in the human subject, implanted between the 
frontal and sphenoid bones, and testifies, by 
its great extent of surface and the numerous 
foramina which pierce it, that the olfactory 
organs are highly developed. Towards the 
nasal surface, likewise, the cethmoidal cells and 


Skull of Rhinoceros. 
~~ Letters as in Fig. 465, 


PACHYDERMATA. 861 
Fig. 470. | 


- Ally. ge 


Vertical section of the skull of a young Boar. 


minores almost along their whole length and 
mask the pterygoid processes, so as to give a 
very peculiar appearance to the base of the 
cranium. 

The bones of the face are remarkable for 
their massive developement, but as their posi- 
tion is sufficiently indicated in the next wood- 
cuts, it would be useless to particularize them 
further, 

Ribs and sternum.—The thoracic cavity 
throughout all the Pachydermatous genera is 
enormous in proportion to the great bulk and 
excessive weight of the viscera. The ribs, in 
fact, are continued backwards almost to the 
pelvis, and from their extraordinary size and 


Occipital bone of a young Boar, shewing its division 
into four pieces. 


Tn the above three figures the parts indicated are 
as follows :—a, a, frontals; 6, b, parietals; c,c, 
12, ¢ 2, ¢3, occipital; d, temporal; e, lateral 
processes of occipital bone; f, sphenoid; g, 
supra-orbital plate of os frontis; h, os lacrymale ; 
i, jugal bone; &, superior maxillary; J, inter- 
maxillary; m, nasal; n, inferior maxilla; 0, Fig. 473. 
ossified nasal cartilage ; p, palatine. 


_turbinated lamine are very large, so that the 
Belicacy of the sense with which they are con- 
“nected is evidently only inferior to that of the 
carnivorous quadrupeds. 

The sphenoid occupies the same position as 
the skull of Man, and in the hog tribe is 
similar in its shape and the general ar- 
f rae of its processes to the human. In 
the Elephant the anterior and posterior clinoid 
esses are but slightly developed, so that the 
base of the cranium internally has a very flat 
appearance, whilst externally, such is the enor- — 

mous developement of the sphenoidal cells, Skull of Sus Larvatus. 
that they stretch on each side beneath the ale Letters as in figure 465. 


in 


t 


862 


ites 


ee ae 


Kg pp Bs 
> ” YY / 


2. é 


breadth constitute a kind of osseous case, en- 
closing a considerable portion of the abdominal 
cavity, and calculated to give origin to muscles 
of power proportioned to its ponderous con- 
tents. 

In the Hyrax, dissected by Pallas, there 
were twenty-two ribs on the left side and only 
twenty-one on the right: of these seven were 
true ribs, six false attached to the sternum by 
the intervention of costal cartilages, and the 
rest merely imbedded in the muscles of the 
flanks. e sternum consisted of six pieces, 
of which the last or ensiform was further pro- 
longed by a spathulate cartilage. 

In the Tapir the ribs are twenty in number 
on each side, whilst there are but four lumbar 
vertebre. The Elephant, likewise, has twenty 
ses of ribs and only three lumbar vertebre. 

e Rhinoceros has nineteen pairs of ribs, and 
the Hog only fourteen. 

The sternum is of considerable length and 
compressed laterally. In many genera, more- 
over, it is prolonged in front to a considerable 
distance, in order to allow more ample space 
for the attachment of muscles. 

Anterior extremities.— The limbs of the 
Pachydermata are necessarily constructed more 
with a view to ensure strength adequate to sus- 
tain their ponderous bulk than to permit of 
agile and active movements. The smaller 

enera, indeed, such as the Snide, have their 
nes so arranged as to permit of considerable 
fleetness in running, but in the more colossal 
genera the condition of the extremities secures 
support at the expense of speed, and flexibility 
is sacrificed to solidity and firmness. 

Scapula.—The shoulder-blade of the Ele- 
phant, independently of its size, might be 
distinguished from that of any other living 
animal by the following circumstances. When 
in situ, its posterior side, which is deeply con- 
cave, is by far the shortest of the three, while 
the anterior and spinal coste are of nearly 
equal length. In consequence of the preceding 
circumstance this scapula is broader in propor- 
tion to its length than that of any other 
large quadruped, and, moreover, the spine of 
this bone, besides its acromial process, has 
towards its middle a broad sickle-shaped pro- 
jection, looking backwards and spreading over 


PACHYDERMATA. 


the infra-spinatus muscle. In all other Pachy- 
dermata the shape of the scapula is that of a 
elongated triangle, with the angles of the base 
much rounded off and the spine very short in 
proportion to the extent of the dorsum; never= 
theless, in the Rhinoceros there is a falciform 
aged projecting from the spine somethin 
ike that of the Elephant, and both in th 
Hippopotamus and the Tapir rudiments of 
coracoid process. The scapula of the Tapir (fig 
475) is also remarkable for a deep and almo: 
circular notch between the rudimentary 
mion and its anterior costa. 

Clavicle.—None of the Pachydermata I 
the slightest rudiment of a clavicle, an ; 
ment which permits the anterior shoulders — 
be closely approximated beneath the thora 
and thus temas nearer to the centre of gravit 

Humerus.—The humerus is in all cases she 
massive, and remarkable for the size and stren 
of the ridges and prominences for the orig 
and insertion of the muscles connected with 
The head of the bone which articulates 
the scapula is very flat, and although lar 
forms but a very small proportion of its seapu 
extremity, the rest being made up of enormous’ 
protuberances, to which are affixed the mus 
of the shoulder. ( Figs. 474 and 475.) 

The lower articulating surface is a sim} 
pulley, articulating with the conjoined hi 
of the radius and ulna, so as to admit of flex 
and extension only, no movements of pronal 
or supination being here admissible. a 

The humerus of the ar ee (fig. 464 
distinguishable from that of all other quadrup 
by the prodigious extent of the external cond 
which extends upwards nearly one-third of 
length of the bone, where it terminates abru 
ae to give a square form to this part 

ne. 

Radius and ulna.—As the position 
fore-arm in the Pachydermata is perma 
that of pronation, no arrangement has 
made in any instance to articulate the f 
with the ulna by means of a moveable joi 
certain degree of elasticity (the result of 
mentous connection) being all the m 
allowed even where the separation between 
two bones is most complete. Sometimes, 
deed, as in the case of the Hippopotamus 


PACHYDERMATA. 


some of the hog tribe, the two bones of the 
fore-arm are completely consolidated into one 
mass, the only vestiges of their having been 
originally distinct being the indication of a 


Fig. 475. 


863 


suture near the distal extremity of the fore-arm 
and adeep groove running along the middle third 
of the bone for the lodgement of the inter-osseous 
artery. In the Rhinoceros and Tapir, (figs. 475 


Skeleton of American Tapir. 


and 476,) however, these bones remain perma- 
_nently distinct, the elbow-joint being formed by 
the radius in front, which articulates with both 
condyles of the humerus and the ulna pos- 
teriorly, which completes the articulation, At 
their distal extremity the radius lies in front and 
to the inner side of the ulna, with which it is 
either anchylosed or immoveably connected by 
ligaments, both assisting to form the radio- 
carpal articulation. In the Elephant, the 
arrangement of these bones is very curious and 

erhaps unique: the upper head of the radius 
is firmly fixed between two projections in front 
of the head of the ulna, and assists in forming 
the elbow-joint articulating with the outer con- 
dyle of the humerus only. It then passes 
obliquely downwards across the anterior face of 
the ulna to its distal extremity, where it expands 
into a broad articulating surface, and assists 
almost coequally with the ulna in forming the 
ap joint. 

_ Carpus.—The bones of the carpus are chiefly 
emarkable for their large dimensions; they 
are, however, always distinct and generally 
the same in number as in Man, although from 
their altered shape they little conform to the 
names bestowed upon them in the human sub- 
ject. The first row, consisting of the analogues 
of the scaphoid, the lunar, the cuneiform, and 
he pisiform bones, is firmly connected by liga- 
ments with the distal extremities of the ulna 
and radius to form the wrist-joint, which, how- 
aver, is here only capable of the movements of 
lexion and extension. The second row consists 
of the representatives of the trapezium; the 
apezoid, the os magnum, and the unciform 
ones support the metacarpus and are generally 
ite distinct, although occasionally two or 
nore of them are consolidated into one mass. 
In the Rhinoceros, which has but three toes, 
ne trapezoid, the os magnum, and the unciform 


bones each support a single metacarpal bone. 
The trapezium is totally wanting, but there are 
two supernumerary pieces in connection with 
the scaphoid and unciforme. 

Metacarpus.—The metacarpal bones are ge- 
nerally short and excessively robust, their num- 
ber of course corresponding with that of the 
toes. Thus in the Elephant there are five, and 
in the Hippopotamus, Hog, and Tapir only 
four, which are small and extremely massive 
in proportion to the weight they have to sus- 
tain. In the genus Sus, where the whole bur- 
den_of progression is thrown upon the two 
middle toes, and a considerable degree of ac- 
tivity is permitted, the corresponding metacarpal 
bones are much elongated, and far surpass in 
size and strength those which support the ex- 
ternal and internal fingers, which have rather 
the appearance of appendages to the outer and 
inner sides of the metacarpus, than bones ar- 
ticulated with the carpal series. 

The metacarpus in the Rhinoceros consists 
of only three bones conformable to the number 
of fingers. 

Phalanges——The Elephant alone of all the 
Pachydermata has five complete fingers; but, 
although the bones are thus perfectly developed, 
they are so concealed in the living animal by 
the hoof and overhanging skin of the fore-foot, 
that such a condition of this part of their 
skeleton would hardly be suspected. 

In the ungulate tribes, which have only four 
fully formed fingers, there is still a little bone 
representing the rudiment of a thumb, although 
in the generality of artificial skeletons this 
ossicle is wanting. In the Suide the two 
lateral fingers are much shorter than the two 
middle ones, so that in walking the former do 
not touch the ground at all; they are, however, 
quite complete as relates to the number of their 
phalanges ; and the last phalanges of all the 


864 


toes are moreover moulded to the shape of the 
horny roof which covers them, a circumstanee 
in which they differ remarkably from the larger 
genera. 

Pelvis.—The pelves of the larger genera are 
of enormous size, accommodating themselves 
in this respect partly to the prodigious masses 
of muscle to which they give origin, and partly 
to the monstrous capacity of the abdominal 
cavity. In the Elephant and Rhinoceros the 
ossa ilii are ve broad, rounded anteriorly and 
concave towards the abdomen. In the Tapir, 
the ilium has somewhat the form of the letter 
T, one branch being articulated with the ster- 
num, while the neck of the bone forms the 
handle. The pelvis of the Hog very nearly 
approximates in shape that of carnivorous 
quadrupeds. 

Femur.—The femur of the Elephant ( fig.464) 
is remarkable for the simplicity of its shape, 
which has some resemblance to that of the human 
skeleton, owing to its general smoothness and 
the absence of those strong crests and ridges 
which characterise it in most other gigantic 
pc s. In all other tribes of the Pachy- 

erms these bones are short, straight, and flat- 
tened in the middle, presenting upon the outer 
border a wide and prominent ridge terminating 
inferiorly in a hook-like process, which, as 
well as the trochanter major, is in the case of 
the Rhinoceros excessively prolonged. 

Tarsus.—The bones of the tarsus are simi- 
lar both in number and arrangement to those of 
the human skeleton. The astragalus is of 
great size, and all its articulating surfaces very 
extensive so as to afford a wide basis of sup- 
port. The calcaneum is likewise remarkably 
prominent and massive. 

Metatarsus.—The metatarsus is in the Ele- 
a made up of five distinct bones, of which, 

owever, the external one is but imperfectly 
developed. In all the other Pachydermatous 
genera there are only four metatarsal bones 
corresponding with the number of the toes. 
Of these the two central ones are far the largest, 


4a ar ai 
ts Vee ell ~ 
ss 


PACHYDERMATA. 


Skeleton of Rhinoceros. 


and sustain alone the entire weight of the hin» 
der part of the body, seeing that the most ex~ 
ternal and most internal toe of each foot scareely 
reaches the ground ; and at length in the Suide 
the metatarsal bones of these toes become re- 
duced to mere rudiments appended to the sid 
of the foot, and serve less as organs of support 
than as appendages given to prevent the crea- 
tures so organized from sinking into the marshy 
soils or soft mud, which they mostly frequent 
as though to testify the intermediate position 
which they occupy between the aquatic 
terrestrial Mammalia. 

Phalanges.—The namber of toes upon the 
hind foot of the Elephant is five, each of them, 
with the exception of the outer one, consisting ¢ 
three short and massive phalanges ; but the ex. 
ternal toe is represented by a single massive 
and irregular-shaped piece. In the living ar 
mal all these bones are so encased in the thick 
skin covering the sole, that the division of the 
foot is only indicated by the prominent extre: 
mities of the toes. rf 

The skeleton of the Elephant is, indee¢ 
quite peculiar in form, so that there is not ; 
single bone or extremity of a bone which ma 
not easily be distinguished from that of an 
other animal ; and it may likewise be remark 
that many of the bones of the Elephant mo 
nearly resemble those of the human ' 
than the analogous ones of any other quadr 
ped, especially of the larger inhabitants of t 
part of the world, such as oxen or horses. , 
examples of this, may be pointed out the atl 
all the cervical vertebra, and the bodies of | 
dorsal vertebre ; the scapula and pelvis o 
count of their great breadth, the femur from 
length and the simplicity of its shape, 1 
astragalus, the os cahels; and all the bone 
the metacarpus and metatarsus. It is, the 
fore, scarcely to be wondered at that even ] 
fessed anatomists, who had never examined 
skeleton of the Elephant, have sometimes m 
ken the bones of this animal for the fossil 
of human beings, and consequently of 


ENT 
“4 


(6 aaa 
—_ 
S 


PACHYDERMATA. 


In the Hippopotamus, the Rhinoceros, and 
the Tapir, the separation of the toes is more 
apparent externally, but still the phalanges, 
which are three in number to each of the four 
toes, are excessively strong and bulky when 
compared with their length. A kind of grada- 
tion is likewise to be traced through these 
genera, whereby the foot of the Elephant be- 
comes gradually transformed into the cloven 
hoof of the hog tribe, owing to the progressive 
diminution in size of the inner and outer toes, 
and the gradual conversion of the terminal 
pares of the central toes into that prismatic 
form which adapts them to fit the horny enve- 
lopes that encase them like shoes. 

Throughout all the hog genera the weight of 
the hody is entirely supported on the two cen- 
tral digits, the bones whereof are propor- 
tionally strong and well developed, while the 
phalanges of the inner and of the outer toe, 
which do not touch the ground, remain per- 
manently of very rudimentary size. 

Teeth—In no order of Mammiferous ani- 
mals do the teeth present so much diversity of 
Structure and irregularity of disposition as 
among the Pachydermatous races ; it will be 
therefore necessary, in adverting to this part of 
their economy, to describe the principal modifi- 
cations which the dental organs assume in 
different genera, before we proceed to investi- 

gate the manner of their formation ; and this we 
do more willingly, because from the character 
and arrangement of the teeth we can alone sa- 
tisfactorily determine what have been the habits 
of extinct genera, the list of which is already 
considerably more extensive than that of living 
forms. Professor Owen, to whose labours in 
this department science is already so deeply in- 
debted, has in his recent work on the Com- 
parative Anatomy of the Teeth* examined this 
part of our subject with all the minuteness re- 
quired for ‘geological researches, and from his 
tindness we are enabled to lay the following 
abstract before our readers. 

In the genus Sus, the wild progenitor of our 
domestic breeds of Hogs, Sus scrofa, the com- 
ete set consists of forty-four teeth, viz— 


Incisor. Canine. Premolar. Molar. 
é i i: | 4.4 333 
43:4 4.4 31:3 


In the wild Boar both the upper and lower 

nines curve forwards, outwards, and up- 
wards ; their sockets inclining in the same di- 
ection, and being strengthened above by a 
idge of bone which is sometimes extraordina- 
ily developed, these teeth become converted 
nto most formidable weapons. These teeth, 
hich have the character of true tusks, are 
ree-sided ; the broadest convex side being 
irected obliquely inwards and forwards, while 
ne outer and posterior sides are nearly flat; and 
ne hinder surface being destitute of any cover- 
ig of enamel; whilst the two other sides are 
cased with that material, the tusk wears ob- 
quely from behind upwards and forwards to 
point, while its posterior margins present 


* Odontography, Bailliere, 8vo. 1845. 
VOL. III. 


865 


enamel edges that\ are always sharp and tren- 
chant. Each of these tusks in the lower jaw 


* Fig. 477. 


of the German wild Boar will measure eight 
inches in length along its curve, and in the 
wild Boars of Assam they have been noticed 
measuring one foot, so that when wielded by 
such strong and brawny muscles as those of a 
Hog’s neck, it is easy to conceive that terrific 
wounds may be inflicted by such instruments. 

In the Baberoussa or “ Horned Hog” the 
developement of the canines is still more ex- 
traordinary. Those of the upper jaw seem as 
if their sockets had been pulled out or pro- 
duced from the alveolar border of the upper 
maxillary bone, and then abruptly bent up- 
wards, giving the tooth a direction upwards. 
and backwards. The tooth pierces the integu- 
ments of the upper lip like a horn, and its 
growth being unchecked by any opposing tooth, 
sometimes forces the lip again through the in- 
tegument and into the substance of the skull. 
The lower tusks have the ordinary direction, 
but rise rather more vertically and much higher 
than in the wild Boar. These strangely situated 
teeth are well adapted by their position to de- 
fend the eyes and assist in the act of forcing 
the head through the dense entangled under- 
wood of a tropical forest, as suggested in 
Home’s Comparative Anatomy, vol. i, p. 221, 
but their use has not been determined by actual 
observation. 

In the next group of Pachydermata ( Chero- 
potamide ) the dental formula of the existing 
type of the family Dicotyles, the Peccari, is 
as follows. 


Incis. Canine. Premolar. Molar. 
2:32 4:.1 $a:3 323 
BS SR S'ct a | 323 


The upper canines are moderately long, narrow, 
and compressed, with an entire covering of 
enamel ; while the lower are long, slightly 
curved, and have no enamel posteriorly. To 
this type of dentition belonged the Hyracothe- 
rium and the Cheropotamus, both extinct genera, 
the former having been about half the size of 
the existing Peccari, while the latter was about 
one-third larger. The Hippophyus, likewise 
an extinct genus, found in the Himmalayan 
3K 


866 


tertiary deposits, and of about the size of the 
Cheropotamus, ap ined to the same family. 

A third kind of dentition characterizes the 
Hippopotumide, in which the tendency to ex- 
cessive and, as it may be termed, monstrous 
developement of the canine teeth, for which 
the typical Suide are remarkable, affects both 
the canines and the incisors. Of this group 
the only existing representative is the Hippo- 

tamus of the great rivers of Africa. In the 

ippopotamide the implanted base of each of 
the incisive and canine teeth is simple and 
excavated for a large persistent matrix, which 
causes their perennial growth by constantly 
adding materials at the base of each to replace 
what is worn from their abraded extremities. 
The direction of the abraded surfaces is in part 
provided for by the partial disposition of the 
enamel; in the upper median incisor this is 
laid upon the fore and outer part of the tooth, 
while in the lateral incisor there is a narrow 
strip of enamel along the convex side of the 
tooth. The enamel is soon worn away from 
the crowns of the lower incisors, but it is per- 
sistent in the canines, where it extends to the 
end of the implanted base; in the upper canine 
being laid upon the posterior and outer, but not 
on the fore part, whilst its position is reversed 
upon the inferior canine. 

The extinct genera of Hippopotamoid Pachy- 
derms at present discovered are the Herapro- 
tadon, the Merycopotamus, and the Anthraco- 
therium. 

Perhaps one of the most singular forms of 

“the dental apparatus hitherto met with among 
Pachydermal Quadrupeds is that of the Toxodon, 
a large extinct genus, represented by two spe- 
cies both equalling the Hippopotamus in size, 
whose remains have been discovered by Mr. 
Darwin and M. de Angelis in the recent tertiary 
deposits of South America. The teeth of the 
Toxodon consisted of molars and_ incisors, 
separated by a long diastema or toothless 
space. In the upper jaw the molars were 
fourteen in number, seven on each side, and 
the incisors four, which latter differ in their 
proportions in the two species. In the lower 
Jaw there were six incisors and twelve molars. 

All the molar teeth are long and curved and 
without fangs, as in the Wombat and most of 
the herbivorous species of the Rodent order: in 
existing races, however, with curved grinders, as 
the Aperea or Guinea-pig, the concavity of the 
upper grinders is directed outwards, the fangs of 
the teeth of the opposite sides diverging as they 
ascend in the sockets; but in the Toxodon the 
convexity of the upper grinders is outwards, as in 
the Horse, but with so much greater curvature 
that the fangs converge and almost meet at the 
middle line of the palate, forming a series of 
arches capable of resisting great pressure. It was 
this structure which suggested to Professor 
Owen the generic term conferred by him upon 
this most remarkable extinct Mammal.* 

Of the upper incisors there are two small 
ones situated in the middle of the front of the 
intermaxillaries, and exterior to these two large 


* Tofo, arcus; dvds, dens, 


PACHYDERMATA. 


ones, in close contiguity with the small incisors, 
which they greatly exceed in size. 

The sockets of the two large incisors extend 
backwards in an arched form, ing an 
uniform diameter, as far as the commencement 
of the alveoli of the ri teeth ; o curve 
which they describe is the segment of a circle, 
the peaiend form, and extent of the sockets 
being such as are only found in those of the 
corresponding teeth of the Rodentia among 
existing Mammalia; and it may likewise be 
inferred that the pulp which formed them was 
persistent, and that the growth of those incisors, 
like those of the Rodentia, continued through- 
out life. The six lower incisors were all of — 
nearly equal size, hollow at their bases, and 
partially coated with enamel, like the “dentes 
scalprarii” of the Rodentia; they differed, how- — 
ever, from these in havi or figure, 
like the incisor teeth of the Sumatran Rhino- 
ceros, or the tusks of the Boar. That they 


were op to teeth of a corresponding struc= — 
ture in the upper jaw is proved by their oblique 
chisel-like cutting edge. to 


The name of Elasmotherium has been given — 
to an extinct Pachyderm with fangless me 
surpassing the Toxodon in size, and of which 
only the lower jaw and its dentition is yet 
known; but the characters of the teeth an 
sufficiently remarkable, owing to the beautiful 
undulating folds into which the enamel is 
thrown, a circumstance from which the name 
of the genus is derived.* The original jaw, 
preserved in the Museum of Moscow, is uniqui 
and was discovered in the frozen drift or di 
vium of Siberia. “| 

In the Rhinocerotide, including the pical 
Rhinoceros, the extinct Acerotherium, which 
had no horn, and the equally hornless sm 
existing genus Hyrar, the molar teeth are 
implanted by distinct roots. There are m 
canines ; and as to the incisors the species vary 
not only in regard to their form and proportions 
but also their existence, and in the varieties 0 
these teeth we may discern the same in 
relation to the developement of the horns whiel 
is manifested by the canines of the Ruminat 
Thus the two-horned Rhinoceroses of Af 
which are remarkable for the great lens h 
one or both of the nasal weapons, have 
incisors in their adult dentition, neither h 
that great extinct two-horned species ( RA. tic 
rinus ), the prodigious developement of wh 
horns is indicated by the singular modificatic 
of the vomerine, nasal, and intermaxi 'y bo 
in relation to the firm support of those weapo 
The Sumatran bicorn inoceros Ce 
with comparatively small horns moderate 
developed incisors in both jaws, and the sa 
teeth are present in the nearly allied two-hon 
Rhinoceros called after its discoverer Sehle 
macher. ar 

The incisors are well developed in both 
existing unicorn Rhinoceroses, indi 
and Rh. Sondaicus, but they attain the sensi 
dimensions in the singular extinct hornl 
species, the Rh. incisivus of Cuvier. — 


cae 


* *Enacua, a plate; Onpicy, a beast. 
a 


PACHYDERMATA. 


adult Rhinoceros no traces of canine teeth are 
visible, but Professor Owen succeeded in de- 
tecting their existence in a rudimentary condi- 
tion in the mature fetus of the Rhinoceros 
Indicus, although both the teeth and their 
sockets disappear at a very early age. 

The vast hiatus which in the series of existing 
Mammals divides the Rhinoceros from the 
Tapir, and this from the Elephant, was once 
filled up by interesting transitional species, 
which have long become extinct, such as the 
Paleotherium and the Macrauchenia, the 
Lophicdon, Coryphodon, and others requiring 
no particular notice in this place. But that 
most extraordinary of extinct Pachyderms, the 
Dinotherium, must not be so lightly passed 
over, inasmuch as its dentition appears to have 
been quite unique in character, as may be seen 
on reference to fig. 478, which represents the 
lower jaw of this gigantic quadruped. From 
this it will be seen that the molar and premolar 
teeth resemble in some respects those of the 
‘Mastodon; but the great peculiarity of the 
Dinotherium exists in its tusks projecting from 
the lower jaw. These tusks are two in number, 
implanted in the prolonged and deflected sym- 
physis of the lower jaw, in close contiguity 
with each other, and having their exserted 
_erown directed downwards and bent backwards, 


867 


while their dee ly implanted base is excavated 
by a wide and™deep conical pulp cavity, like 
the tusks of the Mastodon an Elephant, No 
such tusks nor germs of such have yet been 
discovered in the upper jaw, so that it is highly 
probable that this gigantic Pachyderm was of 
aquatic habits, like the Hippopotamus, and 
that its tusks served to detach and tear up by 
the roots the aquatic plants upon which it fed, 
as well as for weapons of defence or combat. 
No family of Mammalian Quadrupeds has 
suffered more from the destructive operations 
of time than that of the Proboscidian Pachy- 
dermata. Two species only, the Indian and 
the African Elephants, continue to represent 
this type in the Mammalian series of the 
present day; whilst those that manifested the 
modifications of the dental system which gra- 
dually reduce the complexity of the Elephantine 
dentition to the comparative simplicity of that 
of the Dinothere and Tapir, have long since 


-been blotted out of the series of living beings. 


Of these the gigantic Mastodons are the most 
conspicuous — animals nearly allied to the — 
existing Elephants, but differing from them in 
the construction of the grinding surfaces of 
their molar teeth, which had their crowns 
studded with conical eminences more or less 
resembling the teats of a cow—whence the 


Fig. 478. 


generic name is derived.* In addition to these 
_ gtinding teeth the Mastodons were provided 
| with two enormous tusks, resembling those of 
the Elephant, implanted into the intermaxillary 
§ of the upper jaw; and moreover those 
_ Mastodons with the more simple and typical 


‘ 


* Mactis, a nipple; dois. a tooth. 


j 


, 


Lower jaw of Dinothertum. 


molar teeth likewise manifest the Dinotherian 
character in having tusks in the lower jaw of 
the adult male and in the young of both sexes. 

The dentition of the Elephant, the sole 
surviving genus of the great Proboscidian family, 
consists. of two long tusks, one situated in 
each of the intermaxillary bones, and of large 
and complex molars in both jaw. Of the 

3K 


868 


latter there is never more than one wholly, or 
two partially in place and use on each side at 
any given time; for like the molars of the 
Mastodons, the series is continually in progress 
of formation and destruction, of shedding and 
replacement, and in the Elephants all the 
grinders succeed one another horizontally, from 
behind forwards, none being displaced and 
replaced by vertical successors or premolars. 

The total number of teeth developed in the 
Elephant Professor Owen believes to be 

2.2 6.6 
Incis. ——- Molars —— 
0.0 6.6 
the two large permanent tusks being preceded 
by two small deciduous ones, and the number 
of molar teeth which follow each other being 
at least six; but Mons. Corse was of opinion 
that this replacement of teeth is repeated at 
least eight times in the Indian Elephant, which 
would consequently have thirty-two teeth suc- 
cessively taking their respective places in the 
jaws. 

The deciduous tusk makes its appearance 
beyond the gum between the fifth and seventh 
month; it rarely exceeds two inches in length, 
and is about a third of an inch in diame- 
ter at its thickest part, where it protrudes 
from the socket; the fang is solidified, and 
contracts to its termination, which is commonly 
a little bent and is considerably absorbed by 
the time the tooth is shed, which takes place 
between the first and second year. 

The socket of the permanent tusk in a new- 
born Elephant is a round cell about three lines 
in diameter, situated on the inner and posterior 
side of the aperture of the temporary socket. 
The permanent tusks cut the gum when about 
an inch in length, a month or two usually after 
the milk teeth are shed. The widely-open 
base of the tusk is fixed upon a conical pulp, 
which, with the capsule surrounding the base, 
progressively increases in size, stimulates a 
concomitant increase in the capacity and depth 
of the socket, which. cavity soon obliterates 
that of the deciduous tusk. 

These incisive teeth of the Elephant not 
only a other teeth in size, as belonging 
to a quadruped so enormous, but they are the 
largest of all teeth in proportion to the size of 
the body, representing in a natural state those 
monstrous incisors of Rodents which are the 
result of accidental suppression of the wearing 
force of the opposite teeth. 

The molar teeth of the Elephant are remark- 
able for their great size, even in relation to the 
bulk of the animal, and for the extreme com, 
plexity of their structure. The crown, of which 
a great proportion is buried in the socket, and 
very little more than the grinding surface ap- 
pears above the gum, is deeply divided into a 
number of transverse perpendicular plates, 
consisting each of a y of dentine, coated 
by a layer of enamel, and this by a less dense 
bone-like substance which fills the interspaces 
of the enamelled plates, and here more espe- 
cially merits the name of cement, since it binds 
together the several divisions of the tooth 
before they are fully formed and united by the 


28, 


.PACHYDERMATA. 


confluence of their bases into a common body 
of dentine. 
The manner in which these complex teeth 
are formed is a subject of great interest, and 
has been ably investigated by many celebrated 
anatomists, particularly by the two Ca 
father and son, M. Corse, Robert Blake, 
John Hunter, whose splendid preparations illus- 
trative of the process are contained in the 
Museum of the Royal College of Surgeons in 
London. It is to Cuvier, however, we are 
indebted for the most complete and lumi- 
nous exposition of this important piece of 
physiology, as may be gathered from the fol- 
owing account extracted from his great work, 
“ Recherches sur les Ossemens Fossiles. 
“ The molar tooth of the Elephant, like every 
other mammiferous tooth, is formed in the in- 
terior of a membranous sac, now general 
called the capsule of the tooth. This 
has in the Elephant a rhomboidal form, and is 
closed on all sides, excepting the small open- — 
ings for the passage of nerves and vessels. It 
is lodged in a bony cavity of the same be ‘ 
as itself, excavated in the maxillary bone, 
afterwards forms the socket of the tooth.” 
“ It is, however, only the external lamina of 
the capsule which is thus simple in its mpm 
ment, the inner lamina being, as in all « | 
herbivorous animals, thrown into numerous 
folds, as will be understood when we have 
described the pulp upon which the tooth is 
formed.” ; : 
“ This pulp has in every animal its liar 
arranger To represent that of the I Ele- 
phant, we must imagine that from the bottom 
of the capsule as from a base, there arise nu- 
merous parallel and transverse walls whi 
mount upwards towards that part of the 
sule which is placed next to the gums. These 
little walls are only adherent to the floor of thi 
capsule, their opposite extremity or summ 
being free from all adherence.” 
“ The free summit is much thinner than th 
base, so that it might be called the edge, ar 
is moreover deeply cleft in many parts, so ast 
form numerous sharp points and indentatio 
The substance of these little walls is soft, trai 
parent, and very vascular, containing ap 
rently much gelatine: it becomes hard, 
and opaque in spirits of wine.” 2 
“It will be now easy to understand 
manner in which the inner membrane of 
capsule is folded, if we imagine it to form ] 
longations which penetrate into all the inte! 
between the little walls above described. T 
prolongations adhere to the u 
capsule, that is, to the side of Pip Pnich is T 
the gums, and also to its lateral pari 
are not adherent to its base, from 
little gelatinous walls above described 
Consequently it is easy to understand t 
may be a continuous cavity amazin 
upon itself, extending between all t 
nous walls (which are descending in the u 
teeth, ascending in the lower teeth) and tl 
membranous partitions (ascending in the uj 
teeth, descending in the lower teeth.” 
“It is in this conceivable cavity that the 


| 


PACHYDERMATA. 


terials will be deposited to form the teeth, viz. 
the bone or ivory (dentine) which will be 
formed by the gelatinous processes coming 
from the bottom of the capsule, and the enamel, 
which will be deposited by the membranous 
septa, and by the general internal surface of 
the capsule and its prolongations, the base only 
excepted.” 
ere is, however, according to Cuvier, a 
very delicate membrane interposed between the 
ivory and the enamel, which, previous to the 
deposit of the ivory, immediately infolds the 
ivory pulp wall, and invests it very closely ; but 
as the ivory pulp transudes the ivory, it is 
ushed inwards, and separated from this mem- 
rane, which then forms a covering common 
both to the ivory and to the pulp that secretes it. 

On the other side the enamel is deposited 
upon the exterior of this membrane by the sur- 
face of the prolongations of the internal lamina 
of the capsule, and by its pressure upon the 
ivory obliterates the intervening membrane, so 
that the latter soon becomes imperceptible in 
the newly formed tooth, or its place is only 
indicated when a section is made, by a fine 
greyish line which separates the enamel from 
the ivory. It is, however, evident that this 
thin membrane is the only bond of union be- 
tween the two substances as they become in- 
durated at the bottom of the capsule, for with- 
out it they would indubitably separate from 
each other. : 

The ivory and the enamel are therefore 
tonjoined by a kind of juxta-position. ‘The 
former is deposited by layers advancing from 
without to within, the internal layer being that 
last formed and also of greatest extent, exactly 
as in the growth of shells; and as its deposition 
commences at the most prominent points of the 
gelatinous, ivory-forming pulp of the tooth, it 
is at these points that the ivory-forming sub- 
Stance is thickest, and goes on becoming thin- 
her as it recedes from them. 

If, therefore, we bring our thoughts to bear 
upon the epoch when the deposition of ivory 
commences, it is easy to conceive how there is 
first formed a little crust of ivory upon each of 
the prominent points of the indented margins 
of the ivory pulp, and as new layers are conti- 
_ Dually within each other, the little crusts are 
changed into conical caps; when the newly 
deposited internal layers have descended as far 
as the bottoms of these indentations, all the 
caps become united into a single transverse 
ers and lastly, when the deposition of ivory 

proceeded as far as the bases of the ivory 

pulps, all the transverse plates will become 
united into a single crown of a tooth, which 

_ would present the same eminences and the 

_ Same depressions as were conspicuous in the 
_ pulp which formed it, if in the mean time other 
substances had not been in progress of deposi- 

_ tion, and partially filled up the intervals be- 
tween them. 

‘The enamel is deposited upon the external 
Surface of the ivory by the internal membrane 
of the capsule, under the form of little fibres, 
or rather of miuute crystals, all disposed per- 
pendicularly to that surface, so as to form, 


869 


during the earlier.periods of its deposition, a 
kind of velvet with a very fine pile. When a 
capsule of a young tooth is opened, the little 
molecules of the future enamel are in fact 
easily perceived adhering to the inner surface 
of the capsule, from which they are easily de- 
tached. Some are even seen floating in the 
fluid that intervenes between the capsule and 
the germ of the tooth. The opinion of Hunter 
that the enamel is only a sediment deposited 
from the fluid interposed between the capsule 
and the tooth is inexact, inasmuch as he does 
not attach sufficient importance to the functions 
of the capsular membrane, from which in rea- 
lity the molecules of enamel proceed ; never- 
theless, it is yery true that these molecules are 
originally situated between this membrane and 
the tooth before they become attached to the 
latter. But to proceed. 

A thick layer of enamel being thus deposited 
around the ivory forming the crown of the 
tooth, partially fills up the intervals by which 
the transverse plates and their indentations 
were formerly separated. The remainder of 
these interspaces now remains to be filled up, 
which is effected by the formation of a third 
substance, called the cementum or crusta pe- 
trosa. This superadded material, which is very 
different in its characters from either of the 
others, is formed by the same membrane and 
the same surface as formerly produced the ena- 
mel. The proof of this is, that the membrane 
in question always remains external to the 
cementum, in precisely the same relation to it 
which it previously had to the enamel, and that 
it continues soft and free as long as the depo- 
sition of the cementum leaves room for it. 
The only change perceptible is in its texture. 
Whilst it continued to secrete enamel, it was 
thin and transparent; but when it begins to 
secrete cementum, it becomes thick, spongy, 
opaque, and of a reddish colour. 

The membranous prolongations of the cap- 
sule of the tooth are retracted towards the top 
and towards the sides of the cavity, in propor- 
tion as the cementum which they deposit fills 
up the spaces between the different lamina of 
the tooth. The summits even of the lamine 
are covered with cementum before the tooth 
begins to be worn. Sometimes, indeed, the 
same prolongation of the capsule is secreting 
cementum ‘near around the top of a lamina, 
whilst it is forming enamel lower down. From 
the same cause, the upper portion of the inter- 
spaces is already filled up with cementum, 
while the lower parts remain separate, under 
which circumstances the lower portion of the 
capsular prolongation becomes separated from 
the upper, and only receives its nourishment 
through its lateral adhesions to the capsule. 

The deposit of enamel commences almost at 
the same time as the formation of the ivory, 
and the secretion of the cementum speedily 
follows; so that the summit of each lamina has 
all the three substances belonging to it com- 
pletely formed long before its base and conti- 
guous lamine are soldered together by their 
upper portions, even before their bases are 
completed. We may likewise add that all 


870 


these different operations are by no means 
equally in progress in all points of the tooth at 
the same time, but they occur much earlier in 
front than behind; so that the anterior lamine 
= be already consolidated by their summits 
and even by their bases while the bases of the 
middle ones remain separate, and when the 
posterior lamine are not even formed, or only 
represented by the patches of ivory that are 
first deposited upon the apices of the pulps. 

There was formerly much discussion as to 
the number of grinding teeth proper to the 
Elephant, and as early as 1715 the Royal 
Society of London observed that there is 
sometimes only one and sometimes two on 
each side in either jaw, and moreover that the 
first tooth is longer or shorter in proportion to 
the second in different individuals. Pallas first 
explained the real mode of the succession of 
these teeth, accounting for all these irregu- 
larities, and showing that the Elephant has at 
first only a single tooth on each side, until a 
second, developing itself, replaces the first, so 
that during a certain period there are two, until 
the shedding of the first again leaves only one, 
Cuvier first announced that this succession and 
consequent alternate change in the number of 
the teeth was repeated more than once, because 
he found the detached germs of a third grinder 
in the jaw of an Elephant, with two teeth in 
situ. 

It thus becomes easy to understand how the 
grinding teeth of the Elephant, notwithstanding 
the enormous wear to which they are perpetually 
subject, are kept constantly ready for use, and 
renovated in front as fast as they are worn away 
behind. No sooner has the body of the first- 
formed tooth pierced the gums than it begins to 
undergo important changes. As the Elephant 
is herbivorous, its teeth are necessarily worn 
away by mastication like the teeth of all other 
herbivorous animals, a circumstance which is 
indeed necessary in order that the grinding 
surface may be constantly kept in a condition 
‘to bruise vegetable substances. The little in- 
dentations on the tops of the lamine are first 
worn off, until the wearing down has reached 
the interior of the tooth, when each denticle of 
course presents an oval disc of ivory, surrounded 
by a ring of enamel and enclosed in the ce- 
mentum, three substances, which, being of very 
different degrees of hardness, are ground away 
unequally, so as always to present a rough 
grinding surface like that of a mill-stone. 

The tooth, moreover, by its rhomboidal figure 
and very oblique position in the jaw, presents 
its anterior portion above the gums long before 
the posterior, so that the surface produced by 
mastication forms an obtuse angle with the 
plane of the upper surface of the tooth: hence 
it happens that when the front of the tooth is 
deeply worn away, the middle lamine are 
scarcely used at all, and the hinder ones remain 
quite intact, tera the summits of the 
indentations of their crowns under the form of 
little round eminences. In the same way the 
anterior denticles are altogether destroyed before 
the posterior are very far worn down, a circum- 
stance which explains another phenomenon 


PACHYDERMATA. 


which is peculiar to the Elephant, viz. that its 
teeth diminish in length at the same time that 
pm Bo worn away in depth. ” 
hilst the exposed part of the tooth is thus 
worn away, that part of the root which corre- 
sponds with the portion ground down is re- 
moved by a very different process. When — 
examined under these pte am the er! 
of the anterior denticles have the He 
being eaten away as by a kind of caries, so 
that all the front of the tooth is thus re 
when the grinding surface has ceased to be 4a 
efficient, and the tooth, when about to be shed, — 
is reduced to a very small size, however large 6 


it might have been originally. 

The tooth which is in use is therefore per- — 

tually moving forward in consequence of this 
paree and making room for that which is in — 
progress of formation in the hinder part of the — 
jaw to succeed it. This latter, in turn, by its” 
development assists in pushing the first for- 
wards, so that it is strictly true that in the 
Elephant the second set of teeth grows behind 
the milk set, instead of above or below them, 
as in other animals (fig. 479). 


The tusks of the Elephant are very differe 
in their structure from the molar teeth, cot 
sisting of two substances only, the ivory @ 
the enamel. These tusks grow during tf 
whole life of the animal, and sometimes att 
enormous dimensions, measuring eight or ni 
feet in length, and weighing upwards of t 
hundred pounds. In the females of the Asiat 
Elephant the tusks are very small, but in 
African Elephant both sexes have these 
largely developed. These remé et 
which are evidently the representatives of 
enormous tusks bestowed on some of the { 
cea, such for example as the Narwal ( Mi 
don ), are implanted in enormous sockets 
iy the intermaxillary bones of the t Le! 

he central portion of each tusk, the # 
which forms by far the greatest pe ) 
tooth, is secreted by an enormous pulp 10 
in a deep cavity which is excavated Im 
from the surface of which it is deposited” 
by layer in successive strata. ne pul 
nucleus from which the mass of the too 
thus formed has not the slightest organi 
nection with the ivory which has bee 
product of its secretion; not a fibre or’ 
or even the slightest cellulosity p 
one to the other. The tusk is therefore 
kept in its socket by the tight embrace of 
parts around it, and its direction may be re 
changed by gentle and continued pressut 


» 


the same way as dentists succeed in chan 


wr 


PACHYDERMATA. 


he direction of the single-fanged teeth of their 
patients by the application of wires. 

_ Digestive System —The digestive apparatus 
is enormously developed in all the animals be- 
longing to this order, being in this respect not 
only adapted to the quantity of materials con- 
sumed for the support of their unwieldy bodies, 
but likewise in accordance with the strictly 
vegetable nature of the aliment upon which 
they feed, which, compared with animal sub- 
stances, is necessarily bulky and innutritious. 
We select a few examples. 

_ The stomach of the Elephant is simple, but 
in shape it is much more elongated than in the 
human subject. Its cardiac extremity is pro- 
longed into a pouch of considerable size, the 


lining membrane of which is gathered into 


thirteen or fourteen large valvular folds, which, 
from their great size, seem to form so many 
broad valves. The muscular tunic of this 
pouch and around the cardia is remarkably 
thick, and its contents such as to indicate some 
ni A between this portion of the stomach 
and the abomasus or fourth stomach of rumina- 
ting quadrupeds. 

e small intestines are very voluminous, 
and the colon and cecum of enormous dimen- 
Sions, presenting longitudinal tendinous bands 
and wide pouches as in the human subject. 
The following table will serve to shew the pro- 
digious extent of the intestinal canal of an 


Elephant seventeen years of age, and only 
seven feet and a half in height. 
ft. in. 
Length of the small intestines from 
the pylorus to the cecum ..... 38 0 
Circumference of ditto ......... 230 
Length of cecum ............ it -6 
Circumference of cecum........ 5 0 
Circumference of colon......... 6 0 
Length of colon and rectum to- 
See Pe utiees 655) osc 20 0 


Total length of intestinal canal, ex- 
clusive of the cecum ........ 58 6 
The diver requires no special notice, but the 
arrangement of the biliary ducts of the Ele- 
phant is very remarkable ; and various opinions 
are recorded by the older anatomists as to 
whether the Elephant did or did not possess a 


_ gall-bladder, most of them denying its existence, 


while others mistook enlargements of the biliary 
canals for a true vesiculum fellis. 

_ The gall-bladder of the Elephant (fig. 480) 
is, in fact, situated between the coats of the 
duodenum itself, (b, c, e, p,) quite at the ter- 
mination of the biliary duct which comes im- 
mediately from the liver. It consists of a great 
oval pouch divided by transverse valves or septa 
into four compartments (n, 0). The fundus 
and walls of this pouch are studded with glan- 
dular granules; the bile enters it at one ex- 
tremity from the hepatic duct, (f, g,) and at 
the opposite end passes into the interior of the 
Intestine (a, d, €,c) through a mamillary 
Projection, situated upwards of two feet from 
the pylorus, through the orifice of which the 
point of a probe (q, 7) is represented as pro- 
trading. The arrangement of the pancreatic 
conduits is likewise remarkable. The pancreas 


871 


consists of a loose arrangement of glandular 
masses not very closely connected with each 
other, from which separate ducts are given off, 
which terminate in a common canal. This 
latter, however, soon divides into two branches, 
one of which pours the secretion which it con- 
veys into the upper compartment of the biliary 
pouch, where it is mixed up with the bile therein 
contained preparatory to its introduction into 
the intestine, while the other branch of the pan- 
creatic duct opens into the duodenum itself, 
about two inches lower down, so that at the 
orifice bile mixed with the pancreatic secretion 
enters the duodenum, while from the lower 
aperture the fluid received is pure pancreatic 
uice. 

: The spleen of Pachydermatous animals differs 
in no noticeable respect from that of other 
quadrupeds. In the Elephant it measures 
four feet in length, yet even this is thought 
small when compared with the gigantic size of 
the animal. 

The stomach of the Hippopotamus, or, at all 
events, of a fetal Hippopotamus dissected by 
Daubenton, presents a very remarkable con- 
formation. Externally it appeared to be com- 
posed of three parts ; the principal portion, ex- 
tending from the cardiac extremity to the py- 
lorus, was much elongated, resembling more a 
portion of intestine than an ordinary stomachal 
receptacle. Besides this central part, extending 
from the wsophagus to the pyloric valve, were 
two long appendages like two cecums, one 
arising on the right side of the esophagus and 
running along the exterior of the stomach 
throughout almost its entire length, and then 
folding backwards, the other and shorter cul de 


. 872 


sac issuing from the posterior aspect of the ear- 
diac extremity of the stomach and_ projecting 
towards the right side. The construction of the 
interior of this stomach is still more extraordinary 
than its external appearance, for it is so divided 
bysepta, that food coming into this viscus through 
the esophagus may pass by different channels, 
either into the central portion, which seems pro- 
perly entitled to the name of stomach, or into 
either of the great diverticula appended to it. 
The inferior walls of the central stomach have 
nine or ten cavities in them, something like 
those of the Camel and Dromedary. The lining 
membrane both of the stomach and diverticula 
is granular and wrinkled except near the py- 
lorus, where the parietes become smooth and 
folded into numerous plicw somewhat resem- 
bling those of the third stomach of a ruminant, 
although there is no probability that rumination 
occurs in the animal under consideration. 

In the hog tribe the proportionate dimensions 
of the alimen canal are very great when 
compared with the size of the animal’s body, 
the large and small intestines of the Hog or 
wild Boar measuring together from sixty to 
sixty-five feet in length, the large intestines 
alone being in the wild Boar thirteen and in the 
domestic Hog fifteen feet long. The stomach 
is capacious, the entrance of the esophagus 
being situated nearly in the centre of its lesser 
curvature, so that the cardiac cul de sac is 
exceedingly large, and is moreover prolonged 
into a kind of cowl-shaped appendage, which 
gives it avery peculiar aspect. On opening 
the stomach the epithelium of the cesophagus 
is found to be prolonged for some distance into 
its interior, where it covers a square space of 
considerable extent, the borders of which are 
well defined. At the entrance to the pylorus 
there is a large nipple-shaped projection up- 
wards of an inch in length in the full-grown 
animal; and moreover, however much the 
stomach may be distended, there always re- 
mains a deep fold crossing it at its upper part, 
between the @sophagus and the pylorus, and 
another equally extensive bounding the com- 
mencement of the great cardiac cul de sac, 
these folds evidently indicating a relationship 
with the more complex stomachs met with in 
ruminating animals, especially as the lining 
membrane only assumes a villous aspect in the 
pyloric region of the viscus. 

The diver consists of four lobes, and there is 
a distinct gall-bladder, either lodged in a deep 
fissure, or imbedded in the substance of the 
middle lobe. The spleen is long, flat, and 
somewhat of a prisinatic shape, and the pan- 
creas consists of three portions, which unite 
near the pylorus. 

The Hyrax Capensis has a stomach which to 
a certain extent reminds the anatomist of the 
complex condition of that viscus met with in 
many animals nearly related to the Pachyder- 
mata. The cardiac extremity is large, and 
forms a capacious cavity, which is divided by a 
deep constriction from a second compartment 
of smaller dimensions, which opens into the 
pyloric portion of the organ. The whole viscus 
is moreover so bent upon itself owing to the 


PACHYDERMATA. Y 


smallness of the lesser curvature, that the py-— 
loric and cardiac extremities are almost in con- 
tact with each other. The cecum is likewise 
proportionably of enormous size, being 
than the stomach itself, and from this a spi 
folded intestine an’ no very oon ari runs to | 
a kind of second cecum o capacity, “ 
which has its commencement 
wards by means of two conical ap ike 
horns, whence it has been named by Pallas — 
intestinum bicorne, and this last, aher becom 
considerably diminished in size, terminates 
the rectum. 
Salivary 


lands.—The salivary organs are 
very large. In the Hog there are two sublingual 
glands; one, which is very long and narrow, — 
accompanies the duct of the maxillary gland, 
and is com of small lobes of a pale reddish 
colour ; the orifice of its excretory duct is near 
that of the maxillary. The second chine ; 
gland is placed in front of the former, and is 
of a square form; it discharges its secretion 
through eight or ten short ducts, which pierce 
the mucous membrane of the mouth. e- 
arotid is large, its duct opening opposite t 
bird er tooth; and int addition to these — 
there are the molar glands, which form 
elongated masses, situated along the alveoli of - 
the superior and inferior molar teeth, 
extending forward as far as the canines; these 
pour their secretion into the mouth through 
numerous little orifices. eal 
Os hyoides.—The os hyoides in the Elep ¥ 
has its body or central portion, which resemb 
a flattened lamina, slightly arched from b 
upwards, consolidated with the posterior corn 
which divide into two branches as they curve 
gently backwards and inwards. The anterior 
cornua articulate with the styloid process of the 
temporal. In other Pachyderms the general 
disposition of the hyoid pieces is very similar 
to the above, but in the Rhinoceros their ar 
rangement approximates what is met with — 
horned ruminants, the anterior cormua b 
articulated to the styloid by an interven 
osseous piece. ae 
The laryngeal apparatus exhibits not 
extraordinary in its arrangement. os 
Circulatory and respiratory systems.— 
organs of circulation and respiration hk 
in their general arrangement, differ from th 
of other Mammalia in no important particula 
We may, however, notice one or two deviatiot 
from the usual type in the origins of th 
venous and arterial trunks. ' 
In the Hyrax the arch of the aorta g 
the arteria innominata, which divides into 
right subclavian and the two common can 
and then a second single trunk, whi 
left subclavian. 4 
The Elephant in several points of its econot 
exhibits remarkable affinities with the Rod 
tia, in proof of which the ce dence 
the structure of its heart with that of some 
the Rodents is very striking. Thus the’ 
auricle receives three vene cave, a righta 
left superior and an inferior, which lat 
sents the usual arrangement. Moree 
Eustachian valve, which is placed 


ll 


F 
ype: 


yet 
a, 


PS VO 


be HL 


h - 


PACHYDERMATA. 


vhe orifices of the inferior and left superior 


. eave, present, in addition to the inferior portion 


= -- 


usually met with, the rudiment of a superior 
division of the valve, extending from the pos- 
terior aspect of the orifice of the superior cava. 
A similar arrangement is met with in the Por- 
cupine and other Rodents. . 

Urinary organs.—In the young animals the 
kidneys are separated into several lobes by very 
deep sulci, but in the adults this lobulated 
appearauce is in a great degree obliterated. In 
other respects the renal apparatus, ureters, and 
bladder have nothing peculiar in their structure 
or disposition. 

Generative organs (male).—In the structure 
of the external generative apparatus of the 
male Elephant, the principal feature worthy of 
remark is the existence of two special muscles 
destined to the retraction of the organ after its 
erection, an arrangement which is frequently 
rendered necessary in consequence of its enor- 
mous size in that animal, which is stated to be 
proportionately greater than in any other quad- 
ruped. These muscles arise from the anterior 
part of the os pubis on each side of the penis, 
and uniting at a little distance from their origin 
form a common tendon, which runs in a groove 
along the dorsum of the penis to be inserted 
into the glans. The action of these muscles 
will of course be to retract the member into its 
sheath after erection or after the discharge of 
urine, which requires a kind of semi-erection, 
precisely as is the case in the Horse. The 
other muscles connected with the generative 
apparatus agree exactly with those met with in 
the generality of quadrupeds, from which they 
only differ in size; these are the acceleratores 
urine and the transversales perinai. 

The corpora cavernosa, besides the mesial 
tendinous septum between them, are traversed 
by strong secondary septa derived from the 
external envelope, which is of great thickness 
in eae to the enormous size of the organ. 
€ verumontanum, the prostates, Cowper's 
gland, the vasa deferentia, and the vesicule 
seminales occupy their usual positions, and have 
nothing remarkable in their structure or ar- 
rangement. 

The testes of the Elephant are not contained 
in any scrotal pouch or even lodged in the 
groins, as has been asserted by some authors, 
who have been deceived by the existence of 
large glandular masses situated in the inguinal 
regions ; but are deeply situated in the abdomen 
in close contact with the kidneys, to which 
they are attached by membranous prolongations 
resembling little omenta; consequently the 
vasa deferentia, which are very large and tor- 
tuous, pass immediately to their destination in 
‘the commencement of the urethral canal, being 
closely accompanied by the ureters during the 
greater part of their course, and lying between 


_ those tubes and the rectum. 


As another example of the general structure 


_ of the male generative organs in Pachydermatous 
animals, we select those of the Boar. 


In this 
creature the glans penis is very long and nearly 
cylindrical except at the extremity, where it 


becomes of a prismatic shape ending in a point, 


873 


which is suddenly bent upon itself. The body 
of the penis consists of only a single cavernous 
body, and just above the testes at about four 
inches from the insertion of the prepuce pre- 
sents a very singular arrangement, being bent 
twice upon itself at intervals of about an inch, 
so as to form at this place a close sigmoid 
curve; it is flattened for the greater part of its 
length, but becomes rounded and thinner in 
the neighbourhood of the glans. The testicles 
are very large, and the epididymis of each 
upwards of an inch in length. The vesicule 
seminales are very extensive, occupying their 
usual position near the termination of the vasa 
deferentia. The prostates reach from the vesi- 
culz seminales as far as the ejaculator muscles, 
lying on each side of the urethra. Each pros- 
tate, moreover, is covered externally by a layer 
of muscular fibre, which is one or two lines in 
thickness. 

In the American Tapir, according to Pro- 


‘fessor Owen, the testes are elongated glands 


four inches in length, situated externally in a 
slightly indicated scrotum at the distance of six 
inches from the anus. The cremaster is remark- 
ably powerful, being composed of a strong 
fasciculus of fibres continued from the lower 
margin of the internal oblique muscle, of up- 
wards of one inch in breadth. The tunica 
vaginalis has, as usual, a free communication 
with the cavity of the abdomen. The penis, 
which is of great length, is not furnished with 
levator muscles, but is supported by a quantity 
of elastic cellular membrane, which extends 
from the abdominal muscles along the dorsum 
penis. 

Generative organs (female).—These present 
the arrangement usually met with in quadrupeds 
furnished with a cornuted uterus, the relative 
size of the uterine apparatus varying in propor- 
tion to the fecundity of each genus. 

The only description of the female generative 
organs of the Elephant with which we are ac- 
quainted is the following, given by M. Perrault 
of the parts of one dissected by him in the 
menagerie of Versailles, many points of which 
are sufficiently remarkable. That anatomist 
describes the vulva as being placed almost 
in the middle of the belly, at a distance of 
more than two feet from the place where it is 
usually situated in other animals. The clitoris 
extended all along this space beneath the 
vagina and was two inches in diameter, so 
that, although covered by the skin of the 
abdomen, it was so apparent as to have been 
always mistaken for a penis, and the animal 
was in fact considered to be a male until dis- 
section revealed the mistake. 

The vagina extended backward from the 
vulva to the pubis in a contrary direction to 
that which it takes in other animals, and at the 
pubis it formed an angle about the middle of 
its length, so that the second half ran forward 
in the usual manner: its lining membrane was 
very smooth. The edges of the orifice of the 
womb extended into the vagina for the length 
of two inches, the neck of the uterus being, as 
it were, closed by two sigmoid valves, so dis- 
posed, according to Mons. Perrault, to prevent 


874 


the urine from entering the womb, because the 
urethra opens into the vagina so near the os tince 
that the urine flows more readily towards the 
womb than towards the vulva, the angular bend 
in the vagina forming an obstacle to its passage 
in the latter direction. 

The body of the uterus was oval, and mea- 
sured a foot and a half in length by ten inches 
in breadth. The cornua uteri were each two 
feet eight inches in length, and four inches and 
a half in circumference: their openings into 
the womb were surrounded by a prolongation 
of their lining membrane, hanging into the 
uterus like a fringe or valve, so that any thing 
which had passed from the cornua into the 
uterus could not return again from the uterus 
into the cornua, which latter were united to 
each other for about a foot from the body of 
the uterus. The Fallopian tubes were only 
two inches in length, aud the ovaria of very 
small size. 

In the Sow the vulva occupies its usual 
situation between the pubic symphysis and the 
anus. The glans clitoridis is bent upon itself 
and terminates in a point resembling the penis 
of the Boar in miniature. The walls of the 
vagina are much plicated for an extent of two 
or three inches from the orifice of the womb, 
and in this part its canal is considerably wider 

near the entrance of the vulva. The 
os tince is only indicated by a slightly elevated 
margin. The cornua uteri are of great length, 
being convoluted much after the manner of the 
small intestines. The fimbriated extremities of 
the Fallopian tubes are only connected at one 
point with the ovaria, the rest being loose and 
floating. The ov ries in the common Sow are 
of very irregular contour, the Graafian vesicles 
(as big as peas) standing prominently out from 
their surface. 

In the Elephant the mamme are pectoral 
and only two in number, one situated on each 
side of the breast. 

The Rhinoceros, the Tapir, and the Hippo- 
potamus have likewise only two mammea, but 
they are placed beneath the belly. 

In the Hog there are generally ten nipples 
both in the male and female ; these are situated 
beneath the belly, five on each side, but some- 
times there are five on one side and six on the 
other, and occasionally six on both sides. 

Of the Nervous System. Brain.—The brain 
in the Pachydermata is largely developed, and 
the convolutions upon its surface comparatively 
small,though very numerous and separated from 
each other by deep sulci. In the Elephant the 
absolute size of the organ exceeds that of man, 
but is very small in proportion to the bulk of 
the animal, especially when we take into the ac- 
count the great size and intellectual aspect of the 
head. Inan Elephant dissected by the Parisian 
Academicians, which was seven feet and a half 
high from the ground to the top of the back, and 
eight feet and a half in length from the forehead 
to the tail, the brain and cerebellum together 
weighed nine pounds. The convolutions upon 
the surface of the cerebrum were well marked, 
and oe ne Ta size of the cerebellum is 
described to have been enormous; the brains of 


PACHYDERMATA. 


the Rhinoceros and Tapir are equally in 
proportion, but the relative size of the cerebrum, 
rc Whig of its anterior and superior regions, 
w — the rest a brain, is 
much less. ippocampus and corpus stria- 
tum are well devcenale sade lateral ventri- 
cles are continued forwards into the dilated 
olfactory bulbs. The cerebellum is very large 
and expanded transversely, its surface being stall 
further increased by numerous and complex 
anfractuosities. The pons Varolii rey 
in size with the developement of the 
lobes of the cerebellum, and the oli- 
varia are preps Aseereers In other re- 
spects the brain of the animals included in this 
order presents no peculiarities worthy of special 
notice. The nerves take their rise in the usual 
manner, and have the same distribution as in 
other Mammalia. In those races, however, — 
which have the nose largely developed, the — 
fifth pair is remarkable for its great size, and in 
the Proboscidian species these nerves are of 
enormous dimensions. ams - 
The dura mater is ick, proportioned 
rather to the size of the skull and of the entire — 
animal than to that of the brain itself; and 
its two fibrous layers are found in the ic 
species to be separated by a quantity of 
substance in which the vessels ramify. 
The spinal chord presents no peculiarity 
worthy of being distinctly alluded to. a4 
Of the Special Senses. Touch—TIn animals 
whose limbs seem to be converted into 3 
pillars of support, and whose hoof-cased feet ar 
totally destitute of all power oe it 
would hardly have been expected thatany nicety 
of appreciating tactile impressions should exist 
in the situations usually appropriated to this 
sense, more especially when we take into the 
account the thickness and density of the integu- 
ment with which they are clothed. “ 
The nasal apparatus, however, in all the 
Pachydermata, is richly endowed with nerve 
of sensation, and obviously forms a very per- 
fect organ of touch. It is moreover in some 
measure converted into ‘an instrument of pre 
hension, or is employed for digging the soil it 
search of food, as well as for the usual office 
assigned to it; in fact it is im this gre 
quadrupeds alone that the nasal cartilag 
the muscles of the nose assume their full de 


* 


' 


ad 


lopement, and accordingly will merit 
notice in this place. _ 
In the Hog the cartilages of the nose fort 

complete tube, which is a continuation of | 
bony nostrils, and near the end of the sne 
in the vicinity of the septum i 
extremity of the cartilages becomes ossi 
and in the dried skull seems to form an ad 
tional bone (fig. 481). Four pairs 
muscles, derived from the bones ne f 

confer upon the organ considerable power 
motion, and render it very efficient in teat 
up the earth. Of these muscles the first 
arises in front of the orbit from the lacrym: 
bone, and terminates in a strong hic 
spreads out upon the upper aspect of the nas 
cartilages. Two other pairs si 

the preceding are derived from the 


nwt eee 


PACHYDERMATA. 875 


maxillary bone in front of the zygomatic pro- 
cess: these muscles are partially united, but 
their tendons run separately to be inserted, one 
into the side, the other into the base of the 
snout. The fourth pair is comparatively of 
small size, arising from the nasal bone, and 
running obliquely beneath the tendons of the 
two last, terminates near their insertion. The 
snout and all the above longitudinal muscles 
are moreover enclosed by a layer of annular 
fibres, which are a continuation of the orbicularis 
oris, so that considerable mobility in any 
required direction is thus amply provided for. 

n the construction of the snout of the Tapir 
the arrangement of the nasal cartilages and 
muscles of the nose is still more elaborate, 
forming a rudimentary proboscis which is only 
surpassed in complexity by the trunk of the 
Elephant, the only existing type of the true 
Proboscidian Mammalia: in fact it is con- 
structed upon the same principles, the great 
difference consisting in the diminutive size of 
the organ in the Tapir when contrasted with 
the prodigious dimensions of the corresponding 
parts in the Elephant’s proboscis. The nose of 
the Tapir iscomposed of two membranous tubes, 
amply provided with mucous lacune, and en- 
closed in a fleshy mass surrounded by the skin, 
which consists of longitudinal muscles that take 
their origin beneath the lower margin of the orbit, 
and of fasciculi of transverse fibres passing be- 
tween the skin and the external surface of the 
membranous nasal tubes. There is a pair of 
muscles in every way similar to the elevators of 
the upper lip of the Horse, derived from the pre- 
cincts of the orbit, and uniting into a common 
tendon to be inserted into the upper aspect of 
the nose, a pair of depressors arising from the 
intermaxillary bones, and also a slip derived 
from the occipito-frontalis, which is implanted 
by the intervention of a tendon into the base of 
the proboscis. 

The proboscis of the Elephant, the only 
existing example of a completely developed 
nasal apparatus, forms an elongated cone of 
four or five feet in length, and gradually taper- 
ing from the root towards the point, which is 
terminated by a kind of thumb-like appendage 
which is endowed with exquisite sensibility, so 
as to be useful in picking up the smallest 
objects. Internally the Elephant’s trunk is 
perforated by a double tube, formed by a 
strong tendinous membrane, through which in- 
numerable mucous crypts pour fluid abundantly 
into the nose. The membranous tubes are 
continved upwards as far as the bony nostrils, 
but, a little before their junction with the latter, 
they form two curves, the nasal passages being 
closed at this point by a cartilaginous elastic 
valve, which may be opened at the will of the 
animal, but closes by its own elasticity when 
the muscles which open it cease to act. 

All the interval between the membranous 
tubes which follow the axis of the proboscis, 
and the skin by which it is invested externally, 
is filled up with a thick layer of muscular 
substance composed of two sets of fibres. Of 
these one set passes from the exterior of the 
membranous tubes to a strong tendinous mem- 


brane situated immediately beneath the skin in 
such a way that on making a transverse section 
of the trunk, these muscles represent the radii 
of acircle: their actiow will be, of course, to 
approximate the membranous tubes and the 
external integument of the trunk, and thus, by 
compressing the intervening space, their con- 
traction will have the effect of elongating the 
whole proboscis, without at the same time . 
diminishing the calibre of the membranous 
tubes, as would have been the case had annular 
fibres been employed instead of this remarkable 
arrangement. 

The other muscles of the proboscisare disposed 
longitudinally, and form a multitude of fasci- 


.culi, disposed in short curves in such a manner 


that the two extremities of each fasciculus are 
implanted into the membranous tubes, while 
the convexity of the arch is adherent to the 
external tendinous membrane. These fasciculi 
surround the whole trunk, and extend along 
its entire length; their effect being to shorten 
it from end to end or in any part the animal 
may please. It is evident that by these partial 
elongations or shortenings of one side or the 
other, the Elephant can bend its trunk in any 
direction. with the utmost ease, and make use 
of it as efficiently as a hand in the performance 
of many important offices. In addition to the 
above account of the anatomy of this remark- 
able apparatus given by the Parisian Acade- 
micians, Cuvier ascertained that all the longitu- 
dinal fasciculi which enter into the composition 
of the trunk are derivations from four great 
muscles, which, though almost blended together 
in the trunk itself, are distinct enough near 
their commencements. Of these the two ante- 
rior arise from the whole breadth of the frontal 
bone above the ossa nasi, while the two lateral 
muscles take their origins from the superior 
maxillary bones beneath and in front of the 
orbit. The posterior or inferior aspect of the 
Elephant’s proboscis is covered with fibres, 
which seem to be continuations of the orbicu- 
laris oris, and which run obliquely downwards 
and inwards so as to meet their fellows from 
the opposite side at an acute angle. With 
such a structure it is evident that the nasal 
prolongation of the Proboscidian Pachyderms 
is able to move in every needful direction, and 
perform all the duties of a lithe and flexible arm, 
strong enough to tear the branches from the 
trees, and sufficiently manageable to be avail- 
able for the most delicate manipulations. 

The instruments of the senses present few 
peculiarities. 

In connection with the organs of smell we 
may conveniently mention the sinuses which 
communicate with the nasal cavities, which in 
many Pachydermata are extremely developed. 
The frontal sinuses of the Elephant are of 
enormous extent, reaching throughout all the 
thickness of the frontal, of the parietal, of the 
temporal, and even extending into the condyles 
of the occiput. The whole of this extensive 
cavity is divided into cells by numerous imper- 
fect septa, irregularly disposed. In the Hog 
tribes they are equally extensive, but far more 
shallow; they reach as far back as the occiput, 


876 


PACINIAN BODIES. 


Fig. 481. | 


Sphenoidal and vomerine plates of a young Boar ( Sus Scrofa ). ; 


and are divided into communicating cells by 
longitudinal or slightly oblique lamell of bone. 
In the Babiroussa there are four rows of such 
cells, and in the common Hog seven or eight. 
In the Hippopotamus and Rhinoceros the fron- 
tal sinuses can scarcely be said to exist. 

The maxillary sinuses are very large in the 
Elephant, and are divided into numerous inter- 
communicating cells which open into the side 
of the nose by a wide orifice. In*the Hog 
tribe these sinuses do not exist, but in their 
stead their is a cavity in the malar bone, which 
in the Ethiopic Boar is very large. A similar 
cavity of smaller size exists in the Hippopo- 
tamus. 

The sphenoidal sinuses are very small except 
in the Elephant, in which, like the preceding, 
they are of unusual dimensions, extending even 
into the pterygoid processes ; but they are not 
divided into cells as are the other sinuses of 
this creature. 

Eye.—The optic apparatus requires but a 
few passing observations. 

The external boundary of the orbit is com- 
pleted by a strong ligamentous margin. 

The third eyelid is very largely developed in 
the Elephant, and can be drawn over the eye- 
ball to a considerable distance towards the outer 
angle of the eye. It is provided in this animal 
with two special muscles which do not exist in 
other quadrupeds. One of these, which seems 
to draw the nictitating membrane over the 
eye-ball, arises from the lower margin of the 
orbit, towards the outer canthus; while the 
other, which is the antagonist of the former, 
draws it back again towards the inner angle. 

The Harderian gland is of very great size, 
and opens by a capacious duct upon the inner 
surface and close to the base of the third eyelid ; 
in some species, however, as in the Elephant, 
numerous small accessory glands are met with, 
the excretory orifices of which terminate near 
the margin of the nictitating membrane. The 
nictitating membrane itself is very large, and 
sometimes contains a flat, thin, and slightly 
curved cartilage. Moreover, in the Elephant 
especially this membrane really deserves to be 
considered as a proper eyelid, being moved by 
a distinct muscle, the nictitator, the fibres of 
which pass in a regular curve over the base of 


the membrane, but afterwards deviate from 
curve and form an angle to include the ex- 
tremity of the nictitating cartilage, which con- 
sequently moves in the diagonal of the con- 
tracting forces so as to be drawn outwards over 
the front of the eyeball. : 

Ligamentum nuche. — The li 
nuche is of enormous strength, more especially 
in the larger Pachydermata, such as the Ele- 
paeg and Rhinoceros, where the ponderous 

ead necessarily requires unusual support. 

In the American Tapir this ligament consists 
of three strong portions,two of which pass in a pa- 
rallel direction from the elongated spinous pro- 
cess of the first dorsal vertebra, to be inserted 
together into the superior and posterior angle of 
the central ridge of the cranium supporting the — 
whole length of the elevated crest and mane; 
the third portion runs beneath the other two, to 
be inserted into the most elevated part of the 
elongated spinous process of the vertebra den= 
tata. ' 


BIBLIOGRAPHY. — Stukely, Essay towards the 
anatomy of an Elephant, 1722. i, Acta 
Petropolitana, 1727. Blair, Phil. Trans. abridged — 
by Baddam, vol. v. Perrault, Mémoires vit 
a Vhistoire naturelle des animaux. - Huff et Dar 
benton, Histoire naturelle, 4to. 1764. AMpeF » 
Description anatomique d’un Eléphant male, 
Pallas, Spicilegia zoologia, tom. i. 4to. 1784—eo 
tains an anatomical description of the Hyrax under 
the title of Cavia Capensis. Owen, Proceedings 
the Zoological Society of London, 1830-31, and 
Yarrell, in the fourth vol. of Zoological Journ: 
dissections of the Tapir. Owen, Odontogri 
or, a treatise on the comparative anatomy of the 
teeth, 8vo. 1845. Cuvier, Anatomie com , Bv 
Ossemens fossiles, 4to. 


eat 


Filippo Pacini, professor of anatomy at, Pi 
who discovered them in 1830, and su ntly 
published two memoirs upon them. They are 
peculiar minute organs appended to the ne 
vous system, and present an arrangement alt 
gether novel and full of interest, though as yet 
their use is entirely unknown, — 

The essential structure of these 
appears to be the following. A single tubular 
or white nervous fibre leaves the fasciculus © 


which it forms a part, and carrying with it @ 


PACINIAN BODIES. 877 


process of the fibrous neurilemma, advances 
right into the centre of a series of concentric 
-ovoidal capsules of fibrous membrane, through 
a channel which perforates them all, and which 
has its proper wall, to which every capsule is 
attached. All the capsules, except from five to 
_ twenty of the inner ones, have spaces between 
them containing a clear watery fluid. These 
spaces do not communicate with one another 
or with the channel in which the nerve runs, 
Each one is distended by its own fluid, and in 
the natural state is more or less tense, offering 


Pacinian corpuscle, from the mesentery of a cat ; in- 
tended to shew the general construction of these 
bodies. The stalk and body, the outer and the inner 
system of capsules, with the central cavity, are seen, 


a; Arterial twig, ending in capillaries, which 
form loops in some of the intercapsular spaces, 
and one penetrates to the central capsule. b. 
The fibrous tissue of the stalk, prolonged from 
the neurilemma. 2x. Nerve-tube advancing to the 
central capsule, there losing its white substance, 
and stretching along the axis to the opposite end, 
where it is fixed by a tubercular enlargement.— 
From -Todd and Bowman. 


resistance to external pressure. The innermost 
capsule of all is an elongated nearly cylindrical 
cavity, somewhat larger at the further end, and 
always contains a clear fluid, which distends it 
and prevents its sides from falling together. 
The nerve-tube has the ordinary double dark 
contour as well as every other character of 
those found in the ordinary cerebro-spinal 
fibres until its entry into the central capsule. 
At that point it becomes less bulky, somewhat 


flattened (so that.its section is oval instead of 
round), and in particular much paler. The 
dark border which has distinguishes it hitherto 
now disappears, and if it were not for the trans- 
parency of the contents of the capsules its fur- 
ther course would be untraceable. It is, how- 
ever, when fresh, and with a good light, dis- 
tinctly seen to proceed along the very axis of 
the central capsule from one end to the other, 
and finally to be implanted by more or less of 
a swelling (fig. 483) into the further extremity 


Fig. 483. 


Extremity of the pale nerve-fibre in the inner capsule 
of a Pacinian body from the mesentery of a cat, 
n, pale fibre advancing into the further end of 
the central capsule; a, conical swelling by which 
the nerve is fixed; 6, corpuscle of the inner cap- 


sule; c, capsules of the internal system. Magni- 
fied 300 diameters. From Henle and Kolliker. 


of this central compartment. The originally 
dark border of the nerve-tube does not cease 
with absolute abruptness, but the two lines of 
the border coalesce in a somewhat sloping 
manner, and the pale continuation has merely 
a single bounding line, and that so exceedingly 
thin as not to allow of being described as an 
investment distinct from the rest of the fibre. 
This line, as Henle and Kolliker have re- 
marked, is more evident when the edge of the 
flattened fibre is towards the observer than 
when the flat surface is upwards, in which 
latter position it is sometimes altogether absent. 

Such is the general plan of the structure of 
these bodies. Their usual length is from 1-20th 
to 1-10th of an inch, and their stalk is often 
1-10th of an inch long. Though usually oval, 
they are often more or less elongated and bent 
on themselves. Sometimes the internal cap- 
sules only are bent, while the outermost are 
simply oval. In the human subject they are 
found in large numbers, detached or in clus- 
ters, in the subcutaneous areolar and adipose 
tissues of the palm and sole, in connection 
with the cutaneous nerves, as well as more 
sparingly in the same connection at other parts 
of the extremities. A few are also met with in 
the sympathetic plexuses ; and in the catin par- 
ticular they are usually so abundant in the 
mesentery and omentum, as instantly to arrest 
the eye when these parts are spread before it. 
They are here indeed most favourably situated 
for examination. They are included merely 
between the duplicature of the transparent peri- 
toneum, can be obtained in great numbers per- 
fectly fresh, and admit of being inspected with- 
out the addition of any water or other medium. 


878 PACINIAN 


One of the nerves of the palm with the corpuscles 
— and of natural size. After Henle and 


To the naked eye they here present a beautiful 
semi-transparent pearly lustre, with a whitish 
opaline streak along the axis, resulting from the 
greater proximity and density of the series of 
internal capsules. In some animals of this 
species they have speared to me almost want- 
ing. It is remarkable that in no instance have 
they been detected in connection with nerves 
purely motor, nor, it is affirmed, on the fifth 
nerve or the glosso-pharyngeal. 

The stalk pt as has been said, of a 
production of the neurilemma enclosing a single 
nerve-tube. It sometimes happens that there 
are two nerve-tubes, but then there are two 
corpuscles on the single stem, either in close 
apposition, or actually enveloped by a few cap- 
sules common to both. The nerve-tube in the 
stalk is undulating, and being accompanied by 
white fibrous tissue is easily distinguished by 
its peculiar structure. The artery and vein 
supplying the corpuscle are also included in 
the stalk. 

_ The channel which the stalk occupies in its 
passage through the capsules, is conical and 
comes to a termination at the proximal end of 
the innermost capsule. ‘It is furnished with a 
membranous wall, with which the fibrous tissue 
of the stalk is united on the inside and the 
several capsules on the other, and by this means 
the intercapsular spaces are preserved closed, 
and their fluid retained. This wall usually 
presents irregularities of outline, and often a 
cellular ap ce, where the capsules, and 
especially the inner ones, join it. It is perfo- 
rated by the ae os We fo ea some 
of the intercapsular spaces (fig. 482). 

The ps ee are inelastic mem- 
branes, analogous probably to the white fibrous 
tissue, and trnisheld with clear transparent 
nuclei that project chiefly on the inner surface. 
This is true of all the capsules, but in the outer 
system or those thicker and stronger ones be- 
tween which fluid intervenes, there is evidence 
of a double wall; for in addition to the clear 


BODIES. 


double line which distinguishes all, these pre- 
sent also on their outside, when seen edgeways, 
a series of dots, which indicate a system of 
transverse or circular fibres, and in fact the 
corpuscle, when brought into focus, shows no 
other fibrillation than this transverse one. Al- 
most all appearance of a fibrous texture is re- 
moved by acetic acid, so that the yellow or 
elastic fibre does not 2 to form any portion 
of the capsular membranes. The outermost 
capsule, indeed, is invested with both the 
elastic and the inelastic fibres, but these are to 
be regarded as belonging rather to the areolar 
tissue in which the corpuscles are imbedded, 
than to these organs themselves. The ca 

are united together by the wall of the 

rd bsg They 3 also joined here and 
there by partial membranous septa passing 
directly Ps obliquely across the intercapsular 
Spaces, and which sega tote of the same na- 
ture as the capsules themselves. Pacini de- 
scribes further a union of the capsules at the 
distal end in the axis of the corpuscle, which is 
denied by Henle and Kolliker to exist. I 
have had, however, unequivocal evidence of its 
existence, especially between the inner on 
when they roe heen artificially distended. by f 
water, omens it often appears to cease to~ 
wards the surface. When the end of the cap- 
sules is bent on itself, the line of this intercap- 
uf union is less easy to trace. Pe ; 

e small artery supplyi corpuscle 
subdivides in the channel of the stalk into its 
three, four, or more capillaries, which pierce — 
the wall and enter the intercapsular spaces. 
After advancing in these for a variable distance 
they form loops, and return by a similar route © 
to the small corresponding vein. In the larger 
corpuscles I have seen a little bunch of vessels — 
formed near the further end by some of these 
capillaries. In most cases a single capillary 
accompanies the nerve-tube as far as the central - 
capsule, and then passes for some way upon its 
wall, sometimes in a spiral direction. If a 
perfectly fresh corpuscle from the mesentery of — 
a cat be examined before the blood has drained — 
off, the addition of a little water will oc 
sionally induce a rapid movement of the con- 
tents of these minute vessels under the eye o} 
the observer, by gaining entrance to th 
interior; and few objects are more beau 
than the miniature circulation thus artificiall 
brought about for a brief period. The capil- 
laries have their proper walls, furnished with 
nuclei. a 

The central cavity, in size, and partieula 
in aa is liable to much variety. It 
been already stated to be not unfrequently ber 
upon itself towards the further end ; sometimes 
it is bifurcated, or, more correctly, branched, 
the offset then passing in a recurrent course 
either from the commencement or the middle 
part of its length. In this case the brar ho 
surrounded by the same series of internal close 
capsules, and external ones separated by fluid, 
which encircle the principal cavity, only ace ts 
modated to the irregular conformation. How-— 
ever the central cavity is modified, it alway: 
retains its transparent character, and on its inner 


Ly 
: 


ies 


uae 


PACINIAN BODIES. 


Fig. 485. 


Portion of a Pacinian corpuscle, from the mesentery 
of a cat. 


aa, the internal capsules; 6 6, capsules of the 
external system, with intervening fluid. Corpuscles, 
as atc, are seen in all ‘the capsules. The outer 
‘capsules show a double layer, d; e, occasional form 
of corpuscle in the intercapsular spaces; nm, con- 
necting membrane between two capsules; 0, capil- 
vessel containing corpuscles or nuclei in its 
wall, and lying with p, a tubular nerve-fibre in g, 
the ape of the stalk, the fibrous tissue sur- 
rounding them not being represented. The vessel 
divides into two branches, one of which perforates 
the wall of the channel of the stalk and enters an 
intercapsular space, and the other advances as far 
as the central capsule. The nerve has the double 
contour as far as r, where it enters the central cap- 
sule; from that point it is pale and faint. This 
Specimen represents an offset of the central cavity, 
and of the pale nerve at s. The stem continues its 
course, ¢, towards the further end of the central 
cavity, while the offset follows the curved axis of 
the subordinate cavity as far as v, where it ends in 
a bulb by which it is fixed. Several of the cap- 
sules are united together at x. Magnified about 
diameters. 


surface exhibits very faintly marked elongated 
nuclei, which most probably belong to the wall 
of the inner capsule. 

There is little to add to the description of 
the nerve-tube already given. It is faintly 
granular in texture, and occasionally regains, at 


879 


one or more points-of its course within the 
central capsule, the dark contour which it had 
lost on entering it. This is particularly the 
case when it follows a bend of the cavity, and 
certainly seems to indicate the presence there of 
a material elsewhere deficient. It is rare, how- 
ever, to see this re-assumption of the dark 
border in any very well-marked degree. The 
mode of attachment of the end of the nerve- 
fibre varies, being generally by a single tubercle 
or conical swelling, sometimes by two, and 
sometimes even by three such. Whatever the 
number of branches, however, their aggregate 
thickness is about the same as that of the simple 
fibre from which they spring. Where the cen- 
tral cavity exhibits the offsets above-mentioned 
the pale nerve-fibre is also invariably branched, 
its subordinate branch always traversing the 
axis of the subordinate cavity, and being regu- 
larly fixed at its extremity. It is interesting to 
observe how accurately the nerve-fibre preserves 
its place in the axis of the central cavity, how- 
ever abruptly that may be bent or branched, a 
fact which might be supposed to indicate some 
degree of viscidity in the clear substance through 
which it runs. 

Respecting the function or use of the Paci- 
nian corpuscles no satisfactory account has yet 
been given, nor even a plausible explanation 
offered. Their presence in so great abundance 
on the nerves of the palm and sole, and their 
absence from motor nerves, suggests the ob- 
vious enquiry, whether they may not be con- 
nected in some way with the sense of touch, or 
at least with the function of sensation, to which 
the fact of their concentration in such numbers 
in the splanchnic nerves of some animals as 
obviously answers in the negative. Undoubt- 
edly, however, we may anticipate much from a 
more extended research into their connections 
with the several parts of the nervous system in 
man and animals, than the very recent date of 
their disvovery has yet allowed. The specu- 
lation that they may be concerned in the pheno- 
mena of what is called animal magnetism is 
not to be passed over with contempt, if only 
because it has been hazarded by their distin- 
guished discoverer, Pacini, who, in common 
with many other unprejudiced and not inca- 
pable observers, is inclined to believe in the 
reality of some of the less marvellous effects 
which popularly pass under that title, such, in 
particular, as the mesmeric somnolence and 
catalepsy. Yet so vague an hypothesis, per- 
haps, barely deserves to be placed in juxta- 
position with the descriptive anatomy of the 
corpuscles. 

t will be more to the purpose to institute a 
brief comparison between these bodies and the 
electrical organs of the torpedo, a description of 
which will be found under the head of ANIMAL 
Exectricity. Since that article was written, 
however, further researches, and especially 
those of Savi,* have added some points of im- 
portance which it will first be necessary to no- 


* Savi, Etudes Anatomiques sur le systéme ner- 
veux et sur l’organe électrique de la Torpille. Vide 
Matteucci, Traité des phénoménes electro-physiolo- 
giques, Paris, 1844, . 


880 


tice. The prisms of the electrical organ, as 
Hunter described, are divided by very nume- 
rous horizontal diaphragms into spaces con- 
taining a thin fluid, and on these diaphragms 
the nerves and vessels of the organ are ulti- 
mately distributed in great abundance. Each 
of these superposed diaphragms consists of a 
layer, pole te double, in and not upon which 
the nerves ramify. The nerves of the electrical 
organ have never any ganglia formed upon 
them. Their tubules always have the double 
contour which marks the presence of the white 
substance of Schwann. e ramifications pe- 
netrate between the prisms, and each diaphragm 
receives tubular fibres at several points of its 
circumference, though Savi is doubtful whether 
these are derived from two or more tubules of 
the branch supplying them. In the diaphragm, 
however, they are uniformly spread out in a 
network with five or six-sided meshes, the 
sides of which are everywhere formed by a 
single tubule with double contour of the same 
diameter and structure as the tubules of the 
trunk of the nerve. If this network is supplied 
from several different tubules, these tubules 
must be described as inosculating to form it; 
if from a single tubule, this must be regarded 
as again and again branching dichotomously, 
and the branches repeatedly anastomosing. 
Whichever be correct, the existence of a true 
network of ultimate nerve-tubes with double 
contour is certainly a fact of much importance, 
and hitherto unique; and it appears to be 
satisfactorily established by the repeated accu- 
rate observations of Savi. 

The series of superposed membranes in the 
prisms of the electrical organs may have an 
analogy with the concentric capsules of the 
Pacinian bodies. Their separation by inter- 
vening fluid is another point of resemblance. 
But in their relation to the nerves they are 
quite unlike. In the one, each membrane has 
a plane network of nervous tubules in its sub- 
stance; in the other a single nerve-fibre is 
placed in the axis of a series of concentric 
membranes. The condition of the nerves is 
also different. In the one the white substance 
of Schwann everywhere invests the nerve; in 
the other it is suddenly lost on entering the 
central capsule. The branching of the nerve- 
tubes in the electrical organ has a correspon- 
dence with the frequent tendency of the pale 
fibre of the Pacinian corpuscle to divide into 
two or more parts. On the whole, perhaps, 
the comparison may suffice to raise the ques- 
tion, whether the Pacinian corpuscles may not 
be organs designed to generate some kind of 
force, which the nervous communication with 
the centres may serve to connect either with 
volition or some emotional impulse or feeling.* 

There is another set of organs, however, in 
the electric torpedo, the discovery of which we 
owe to Savi, and which bear a closer resem- 
blance to the Pacinian corpuscles than the 
electric organs themselves. These are what he 
terms the follicular nervous apparatus, and 


* Henle and Kolliker endeavoured to elicit evi- 
dence of an electric discharge from the Pacinian 
bodies of the cat’s abdomen, but without success. 


_ terior part o 


PACINIAN BODIES. 


which I shall briefly describe nearly in his own 
words.* abe »- 

“ This tus is foun ering the an- 

pe pe mouth and nostrils, and ex- 
tends over the surface of the anterior part of the 
electrical organs, and over the front half of 
their outer edge, where it rests upon the carti- 
lage and aponeurotic coverings of the fin. 
Some parts of the apparatus are found on the 
back, but the greater portion on the ventral 
surface of the animal. It consists of extensive 
linear series of follicles, or closed membranous 
cells with double walls filled with a gelatinous — 
fluid, and enclosing a small aay cae granular 
mass, which nearly resembles amorphous — 
grey matter of the cerebral hemispheres. A 
nervous branch gives some fibres to this granu- 
lar mass, while other similar fibres united into — 
bundles pass out of the follicle, the 
grey mass of the adjoining follicle, and mingle 
with its nerve. 

“ The nerves distributed to this a er 4 
come exclusively from the fifth pair, more 
particularly from the branchesspringing from the - 
anterior portion of the root. Each follicle (fig. 
486) is of aspheroidal form, slightly compressed - 
on the side which adheres to the neighbouring fol. 
licle, and its diameter is about 4th of an inch. [ 
have found these dimensions the same in ani- 
mals of very different size. These follicles a 
never free or floating in the gelatinous fluid 
abundant in these fishes ; on the contrary, they 
are always firmly fixed, as if with a special view 
to their security, for they are planted on un- 
yielding aponeurotic expansions, like that o 
the muzzle, or else on fibrous bands extendin 
along the fin, and having no other use. Wher 
the gelatinous fluid which envelopes these folli- 
cles is examined under the microscope, it is 
seen to contain numerous fibres passing in | 
rious directions, and fixed to the surface ¢ 
follicles. 

“ Each follicle is formed of two membrai 
(f and g) which adhere together on the sit 
towards the fibrous band which supports th 
organ, whilst on the opposite side they : 
separated by about a third of the  vertic 
diameter of the follicle. These organs may 
easily examined by a very slight magnify 
power, it being only necessary in the first p 
to remove the investing gelatinous substai 
and then to subject them to moderate compr 
sion for the display of their interior. Ih 
follicle thus compressed, we observe first 
cut portion of the tendinous band ce, then 
outer membrane enclosing the other, in wh 
is the rounded granular mass e already m™ 
tioned. This latter seems to rest upo 
lower wall of the internal membrane. Thi 
ternal membrane adheres by its lower bord 
the fibrous band beneath it in such a way, © 
between this external wall of the follicle 
the internal is left a space, in which the 
ramification d advances and adheres 
rounded mass of granular substance. 

“ In the follicles of the longitudinal serie 
of the fin, of which we here speak, the nervo 


a 


* Op. cit. p. 332. 


PAR VAGUM. 


( Fig. 486.) 


One of the follicular nervous organs of the electrica 
_ torpedo. 

a, branch of fifth pair of nerves; 6, twigs going 
to the organ and passing through cc, the fibrous 
band; d, the nerve as it lies on e, the granular 
mass ; f and g, the inner and the outer capsules 
containing fluid ; &, anastomosing filament from the 
preceding follicle ; /, anastomosing filament to the 
succeeding follicle. Much magnified and slightly 
compressed. From Savi. 


twig is derived from the fifth pair and passes 
first through a slit in the tendinous band. After 
passing this aperture it bends underneath the 
granular mass, and again emerges at the base 
of the follicle, but at the opposite side from 
that at which it entered. It is remarkable that 
the nerve is much thinner at its exit, and re- 
duced to an exceedingly delicate filament (/), 
which proceeds along the tendinous band to 
the next follicle, penetrating its wall and join- 
ing its nerve at the point of its flexion under 
the granular mass (k). 

“* On examining under the microscope the 
rounded granular mass, made flat by the com- 
pressor, and after the removal of the membranes 
of the follicle, we see the nerve running length- 
wise over it from end to end, the anastomosing 
branch coming from the preceding follicle (k) 
and the very delicate filament which proceeds 
to that next in order (/). We further remark 
that the nerve of the follicle, in its course along 
the granular mass, gives off a great number of 
elementary fibres, which disseminate themselves 
through the mass and thus reduce the nerve to 
so small a size. Sometimes I have fancied that 
these fibres formed loops and returned; but I 
_ have never obtained a clear view of their termi- 
nation. I am no less doubtful regarding the 
course of the elementary fibres of the anasto- 
mosing branch coming from the preceding 
follicle. Sometimes I have seen these fibres 
return towards the slit in the tendinous band 
and rejoin the nerve in order to regain the 
centre. In other cases I have seen these fibres 
_ pursue their primitive direction, and ,pass on 
with the rest towards the opposite end of the 
granular mass. Hence I imagine that the fibres 
_ of the anastomosing bundle do not all follow 
_ the same course, and that while some advance 
_ into the granular mass, others turn back towards 
| Vou. 111. 


t 


~ 


881 


the centre through the slit in the fibrous band.” 
“ It occasionally happens that two nervous 
twigs pass from the main branch to the same 
follicle. When this happens, there are always 
two distinct granular masses.” M. Savi then 
describes accurately the arrangement of the 
several series of these follicles in the torpedos 
which he examined, an account of which is not 
necessary for our present purpose. In one 
example he found that the follicles amounted in 
all to two hundred and fourteen. 

We cannot adduce these remarkable and 
peculiar structures as at present throwing any 
light on the function of the Pacinian corpuscles, 
since we must confess with M. Savi that as yet 
we are entirely ignorant both of their real nature 
and use. Nevertheless the resemblance is such 
as, it is hoped, will warrant the introduction of 
the preceding account, which is new in this 
country, and very interesting in itself. It is 
unnecessary to recapitulate the several points of 
similarity and difference, which, after the de- 
tailed description of each now offered, may be 
readily apprehended by the reader himself. 

It only remains that we should direct atten- 
tion to the very admirable memoir of Henle 
and Kolliker on this subject. They corrobo- 
rated the principal results of Pacini, and added 
many most valuable observations which the use 
of higher powers of the microscope and perhaps 
greater experience in research had enabled them 
to make. These observations M. Pacini has 
recently informed me he has himself almost 
entirely confirmed. An excellent abstract of 
their labours appeared in the British and Foreign 
Medical Review for January, 1845, and in the 
following April Dr. Todd and myself gave an 
account of these structures, drawn up from origi- 
nal observations and containing some new results, 
though on the whole confirmatory of those 
previously published. See the PuysrotocicaL 
Anatomy aND Puysrotocy or May, vol. i. 
p. 395. 

It is right to add that MM. A. G. Andral, 
Camus, and Lacroix, met with these bodies in 
1833, and that they were noticed subsequently 
by Cruveilhier and Blandin in their respective 
works on descriptive anatomy, but without any 
real light being thrown on their nature or 
internal structure. 

( William Bowman. ) 


PAR VAGUM NERVE. (Human Ana- 
tomy.) —(Nervus Vagus; Pneumogastric ; 
part of the sixth pair of nerves of the older 
anatomists; one of the three divisions of the 
eighth pair in the classification of Willis; the 
ninth pair of Andersch; the tenth pair of 
Sommerring ; the moyen sympathique of Win- 
slow.) The par vagum, like the other cerebro- 
spinal nerves, consists of two nerves exactly 
similar at their origin, and placed on different 
sides of the mesial line of the body. It has a 
very long course,—passing down the neck, and 
through the thorax to the upper part of the 
abdomen,—is distributed upon numerous and 
dissimilar organs, and anastomoses very freely 
and extensively with the sympathetic and vari- 
ous cerebro-spinal nerves. It is the chief nerve 

3 L 


882 


of the lungs and stomach, and hence its appel- 
lation of pneumo-gastric. 

The nervus vagus arises by several filaments, 
generally from six to ten, from the restiform body 
of the medulla oblongata, parallel to and a little 
posterivr to the groove between the olivary and 
restiform bodies, and from a line to a line and a 
half distant from the posterior edge of the olivary 
body. Thearciform band of superficial filaments 
passing between the anterior eases and res- 
tiform bodies cross among the lower filaments 
of this nerve. The filaments of the vagus are 
attached to the restiform body in a vertical, 
straight, and thin band of from three to four 
lines in length, the upper end of which is eh on 
rated from the lower edge of the glosso-pha- 

eal nerve by a few small bloodvessels only. 
he upper half of these filaments of the vagus 
are at their origin closely approximated, so that 
the lower edge of the one above is in contact 
with the upper edge of the one below, while 
the lower filaments, pray the two last, are 
considerably more distant from each other. 
The lowest filament is placed only a little 
above and in the same line with the uppermost 
filament of the spinal accessory, and it is fre- 
quently difficult to determine where the fila- 
ments of the accessory begin, and where those 
of the vagus end. From this origin each vagus 
roceeds forwards and outwards between the 
ower surface of the lateral lobe of the cerebel- 
lum and that portion of the dura mater cover- 
ing the basilar process of the occipital bone, to 
reach the foramen lacerum posterius, through 
the anterior part of which opening it escapes 
from the interior of the cranium. In this part 
of its course it frequently anastomoses with 
the glosso-pharyngeal, and its filaments be- 
come more subdivided, but at the same time 
more closely aggregated, so that it is thicker 
and narrower. On reaching the foramen lace- 
rum posterius it enters a sheath or canal in the 
dura mater, anterior and a little internal to the 
commencement of the internal jugular vein, 
immediately anterior to the spinal accessory 
nerve, and posterior to the glosso-pharyngeal. 
As these three nerves enter the foramen lace- 
rum, they perforate the dura mater, the glosso- 
pharyngeal by a separate and distinct opening, 
the nervus vagus and spinal accessory by an 
opening common to both. Sometimes there is 
a small bridle of dura mater, at other times 
only a fold of the arachnoid separating the 
vagus and accessory at this part. At the lower 
part of the foramen lacerum the spinal acces- 
sory is closely applied to the posterior surface 
of the vagus. e dura mater is prolonged 
downwards into the foramen lacerum upon 
these three nerves in the form of two sheaths, 
one sheath surrounding the glosso-pharyngeal, 
and the other the vagus and accessory. From 
the proximity of these three nerves, as they 
pass through the foramen lacerum posterius, 
and from their intimate connection in some 
parts of their course and subsequent distribu- 
tion, they were long considered to form only a 
single nerve. 

As the’ vagus lies in the foramen lacerum 

it presents a greyish oblong swelling, resem- 


PAR VAGUM. 


bling the ganglion . the ior root of 
a spinal nerve ( ion prunum nervi vagi 
of Waser, pis one radicis n. v. of , 
anglion superius n. v., ganglion jugulare n. v. 
is ganglionic enlargement begins im 

ately after the nerve has entered the foramen 
lacerum, so that its upper edge may be some- 
times seen from within: the cranium ; it is of an é 
oval form, and it extends the course of 
the nerve from a line. and a half to two lines.* 
Mr. James Spencet has pointed out that a 
small filament bayer ae the lower Bon: of 
the vagus passes over the posterior surface of 
this ganglion without entering it, and joins” 
itself to the superior filaments of the spinal 
accessory.[ This fact, as we shall afterwards 
find, has a direct bearing upon the physi 

of the nerve. - A communicating filament 

between the ganglion superius of the vagus and 
the superior cervical ganglion of the sympathe- 
tic, another between it and the ganglion petro- 
sum of the glosso-pharyngeal, (vide article 
Grosso-PuaryNGEAL,) and one or St be- 
tween it and the spinal accessory. From the 


* Arnold (Der Kopftheil des vegetativen ere 


vensystems beim Menschen. S. 107) describes 
ganglion as varying little in size, and as 
a line and a half to aline and three quarters in 
breadth, a line to a line and a half in a a and 
three quarters to one line in thickness. He found 
a difference of about two lines between the mea- 
surement of the circumference of the . gneleeey 
the trunk of the nerve immediately w, the for- — 
mer generally measuring five and the latter three — 
lines. Bischoff (Nervi Accessorii Willisii, Anato- 
mia et Physiologia, 1832, p. 20) gives ne 
measurements as those of Arnold, from whom he has 
evidently copied them. Bendz (De Connexu inter 
Nervum Vagum et Accessorium Willisii, 1836, 
p- 17) describes it as a rounded saa ec 
flattened, measuring about two lines in the 
posterior diameter, and nearly two lines in the 
vertical direction. Valentin (Séemmerring’s Vom 
Baue des Menschlichen Korpers, Hirn und Ner- 
venlehre. Vierter Band. 1841. S. 482) deseril 
as an oblong rounded swelling, somewhat 
and about from a line and three quarters to two au 
a half lines in length, » bee Surgical el 
¢ Edinburgh Medical an i ourna 
No, 153, 1842. i 
¢ Remak (Froriep’s neue Notizen for 189; 
No. 54) states that some of the filaments of t 
vagus do not pass throagh this superior ¢ 
the vagus in the dog, cat, and rabbit; and Vol 
mann (Miiller’s Archives, Heft v. 1840) confir 
this observation of Remak on the dog; and furth 
mentions that the same enlargement exists i 
sheep, while in the calf all the Pp 
through the ganglion. The in of such | 
sections, especially those made on the human) 
cies, and the physiological inferences deduc ; 
them, have been called in question, (e.g. He 
Miiller’s Archives for 1844, p.336, and Bischo 
the same work for 1833, p. 156), om the gre 
that this anatomical ement is not- con 
and besides that it is difficult to distingnish betw 
the lower fibres of the root of the vagus ant 
upper fibres of the root of the nervus accessor 
i Bendz describes and delineates (De 
inter Neryum Vagum et Accessorium 
Hanniz, 1836) two small communicati 
passing between the spinal accessory the ga 
glion jugulare of the vagus. Valentin (Séemme 
ring Vom Baue des Menschlichen Korpers, H 
und Nervenlehre, Vierter Band, 1841) deseribe: 
similar anastomosis. Arnold (Icones v 


, 


‘y 


, 
t 


are 


a 


PAR VAGUM. 


lower and external part of this ganglion a 
small nerve arises, (ramus auricularis nervi 
vagi,) which is seen joined by another small 
branch from the lower part of the ganglion 
petrosum of the glosso-pharyngeal.* The ramus 
auricularis proceeds outwards and a little back- 
wards anterior to the jugular vein, and lies in a 
groove in that portion of the petrous portion of 

the temporal bone which assists in forming the 
fossa jugularis, perforates the osseous partition 
between the fossa jugularis and the aqueduct 

i ot Fallopius, and enters the internal side of the 
_ latter about one or two lines above its lower 
termination in the stylo-mastoid foramen. It 
now divides itself into two branches, a small 
ascending twig which joins the portio dura 
nerve, and a larger portion which enters a canal 
on the external side of the aqueduct of Fallo- 
pins, proceeding outwards and a little back- 
wards through that portion of the spongy por- 
tion of the temporal bone which forms the lower 
wall of the external meatus. The larger branch 
subdivides into two other branches as it lies in 
this canal. One of these emerges upon the 
external surface of the cranium through a small 
opening between the mastoid process and the 
posterior margin of the meatus auditorius, and 
divides into two or three twigs, which pass 
through openings in the cartilage of the pavillon 
of the external ear, and are ultimately distri- 
_ buted upon the tegumentary covering of the 
internal surface of the concha and meatus audi- 
torius externus. The other branch of the nerve 
passes through the mastoid process and joins 
itself to the auricular branch of the portio dura, 
and along with it is distributed upon the pos- 
terior surface of the pavillon of the external, 
ear.t The trunk of the spinal accessory is 
closely connected to the posterior surface of the 
superior ganglion of the vagus by cellular tissue, 
and immediately below the lower end of the 
ganglion it throws a considerable branch into 
the vagus. The exact place and manner in 
which these auxiliary fibres from the accessory 
join the vagus differ in different individuals, 
and sometimes in the two sides of the same 
individual, but most generally the spinal acces- 
sory divides itself at the lower part of the fora- 
men lacerum into two branches, the internal 
and external branches of the spinal accessory. 
The internal branch runs immediately into the 


ee) ee eee 


Capitis, plate iv.) represents an anastomosis be- 
tween the accessory and ganglion jngulare. Krause 

Hanbuch der Menschlichen Anatomie. S. 1066, 

843, and Hein ( Miiller’s Archives for 1844. Heft 
iy. p. 337) describe the superior filaments of the 
root of the accessory as connecting themselves to 
the lower filaments of the vagus, and that a few of 
the filaments of the accessory may enter the ganglion 
jugulare of the vagus. Bischoff (Nervi Accessorii 
Willisii Anatomia et Physiologia, 1832) neither 
_ delineates nor describes any communicating fila- 
_ ments passing between the spinal accessory and 
_ the ganglion jugulare of the vagus. 

_ _* In Valentin’s description (opus cit. p. 483) of 
this auricular branch, the strengthening twig is said 
_ to come from the hypoglossal nerve, (aus dem 
_ wangenfleischnerven,) but this must either be some 
_ error of the press or some la scribendi, 

+ Vide Arnold’s Icones Nervorum Capitis, tabul. 
iii. et v. 


883° 


anterior and outer part of the vagus, and while 
one portion of its fibres goes to form a part of 
the superior ‘yngeal branch of the vagus, 
the other portion joins itself to the trunk of the 
vagus, and accompanies it down the neck. 
Sometimes the fibres of the internal branch of 
the accessory are arranged in two bundles, and 
in such cases the one generally joins itself to 
the vagus a little below the other. The evrter- 
nal branch of the accessory proceeds downwards 
and outwards, perforates the upper part of the 
sterno-cleido-mastoid muscle, and ultimately 
terminates in the trapezius muscle. 

The superior ganglion of the vagus was known 
to Ehrenritter.* It appears also to have been 
well known to Wutzer, for it is both mentioned 
and figured by him in his monograph De Cor- 
poris Humani Gangliorum Fab. et Usu, 1818. 
Wutzer has in fig. vii. certainly represented it 
as being placed somewhat inferior to the gan- 
glion petrosum of the glosso-pharyngeal, instead 
of being rather above it: yet as he terms it 
ganglion primum n. v. and figures the ganglion 
secundum in its proper position, there can be 
no doubt that he was well aware of its exist- 
ence. It has been supposed by some that 
Lobsteint+ had also pointed out the existence of 
this ganglion, while others maintain that his 
description is not sufficiently explicit to enable 
us to decide whether it refers to the upper or 
lower ganglion of the vagus. It appears, how- 
ever, much more probable that it is the superior 
ganglion, for after mentioning that the vagus 
presents a reddish appearance, similar to a 
ganglion, (rubella parum quasi ganglion men- 
tiretur,) he describes the superior pharyngeal 
branch of this nerve as arising below it. Miiller{ 
has attempted to shew that Comparetti was the 
first anatomist who described this ganglion, 
and that he was even acquainted with the ramus 
auricularis of the vagus; but Arnold,§ on the 
other hand, maintains, and we think justly, that 
the description of Comparetti applies equally 
well, if not better, to the ganglion petrosum of 
the glosso-pharyngeal. Desmoulins and Ma- 
gendie|| observed the superior ganglion of the 
vagus in the carnivorous Mammalia and in the 
Ruminantia, and also a branch passing from it 
to join the portio dura, but denied that this 
ramus auricularis exists in man. Cuvier] had 
also previous to this pointed out the ramus 
auricularis in the calf. It was not, however, 
until Arnold’s description of this ganglion had 
been made public, that it became generally 
known to anatomists, and its true nature and its 
anatomical relations exactly ascertained.** Ar- 


* Salzburg, Med. Chir. Zeitung, 1790. B. 4. S. 
319, as quoted by Bendz. 

+ Dissertatio de Nervo Spinaliad Par Vagum Ac- 
cessario. Ludwig Scrip. Nerv. Min. Select, tom. 
ii, p. 235. 


; Archiv. fir Anat. Phys, &c. Heft ii. s. 275, 
1837. 


Bemerkungen tiber den Bau des Hirns und 
Riickenmarks, &c. S. 178. Zurich, 1838. 
| Anatomie des Systémes Nerveux des Animaux 
a Vertébres. Deuxiéeme partie, p. 435 & 463, 1825, 
{| Idem opus, p. 435, 
** Der Kopftheil der vegetativen Nerven Sys- 
temes. Heidelberg und Leipsic, 1831. 
3 L 2 


884 


nold was the first who described the ramus 
auricularis in the human species. 

Passage of the vagus ee the neck to the 
origin of the inferior or recurrent larungeal 
branch —After the vagus emerges from the in- 
ferior aperture of the foramen lacerum poste- 
rius, it lies between the internal carotid artery 
and the internal jugular vein, the artery being 
internal and anterior, and at first separated a 
small distance from it, the vein being immedi- 
ately posterior and external. The glosso-pha- 
ryngeal is still placed on its anterior side, but 
soon leaves it and crosses the anterior surface 
of the internal carotid artery on its way to the 
root of the tongue. The spinal accessory is 
still on its posterior side, but a little above the 
transverse process of the atlas the external 
branch begins to diverge backwards and out- 
wards, and passes beneath the upper part of 
the internal jugular vein to reach the inner sur- 
face of the upper A of the sterno-cleido- 
mastoid muscle. e sympathetic nerve lies 
immediately posterior to it. The hypoglossal 
approximates its outer edge immediately below 
the foramen lacerum, gradually gets upon its 
anterior surface, is seen emerging from the 
angle left between it and the external branch of 
the accessory, where these nerves begin to sepa- 
rate, and opposite the transverse process of the 
atlas, or sometimes a little below this, it has 
crossed over its anterior edge, and proceeds 
forwards and inwards to reach the tongue. The 
hypoglossal, in crossing over the anterior sur- 
face of the vagus, is very closely bound to it by 
cellular tissue, and some small communicating 
branches pass between them. Some small 
communicating branches also pass between this 
portion of the vagus and the external branch of 
the spinal accessory, the superior ganglion of 
the sympathetic, the glosso-pharyngeal, and the 
nervous loop formed by the anterior branches 
of the first and second cervical nerves in front 
of the transverse process of the atlas. The 
vagus also in this part of its course generally 
sends a branch to join the descendens noni, 
and more rarely the descendens noni is almost 
entirely or altogether formed by this branch of 
the vagus.* All these nerves and bloodvessels 
in the upper of the neck are surrounded 
and connected together by cellular devoid of 
adipose tissue. The vagus, after joining itself 
to the internal carotid artery, accompanies it to 
the point of bifurcation of the common carotid, 
and then continues its course down the neck, 
enclosed in the same sheath with the common 
carotid and internal jugular vein, the artery 
being internal, and the vein external and also 
anterior. The nerve maintains the same rela- 
tion to these two vessels on both sides as far as 
the lower part of the neck, where on the right 
side the artery and vein diverge from each 
other, the artery passing inwards and the vein 
outwards, to join itself to the vena innominata ; 
while on, the left side the vein and artery have 


* Krause (Handboch der Menschlichen Anato- 
mie, S. 1 & 1063. Hannover, 1842) states 
that probably these strengthening filaments of the 
vagus furnish the cardiac branch of the descendens 
noni. 


PAR VAGUM. 


scarcely separated from each other, when the 
junction between the former and left subclavian 
vein takes place. On the right side the nerve 
is seen lying in the interval between the inter- 
nal jugular and the internal carotid, and while | 
crossing the anterior surface of the right sub- 
clavian artery nearly at right angles, it sends off 
the right inferior laryngeal or recurrent nerve, 
On the left side it passes downwards into the 
thorax, still lying close to the outer side of the 
leftcommon carotid ; but as it proceeds onwards, 
it crosses obliquely the left subclavian artery 
near its origin, and passing over the transverse 
portion of the arch of the aorta, it there gives 
off the left inferior laryngeal nerve. On both 
sides it passes into the thorax beneath the vena 
innominata.. 

The vagus, on emerging from the foramen 
lacerum, is near to the outer edge of the 
rectus capitis anticus minor muscle and in 
front of the rectus capitis lateralis; in its pas- 
sage down the neck it first crosses the anterior 
surface of the lateral part of the atlas, then 
proceeds along the anterior surface of the rectus 
capitis anticus major muscle, and lastly it de- 
scends upon the longus colli. In theu 

of its course it lies deep, and crosses 

neath the styloid process of the tem bone 
and stylo-pharyngeus muscle. In the middle — 
of the neck the two vagi nerves have approached — 
nearer to each other, and are much more su- 
perficial. In the lower part of the neck they 
are again placed deeper, and are covered by 
the sterno-hyoid, sterno-thyroid, and sterno- 
cleido-mastoid muscles. 

As the vagus emerges from the lower part 
eof the foramen lacerum, its fibres are ; 
somewhat loosely together, and are not 
enclosed in any dense and com neuri- 
lema, so that it is larger here at the 
lower part of the neck ; and when the cellular 
tissue surrounding it is removed, the outline of 
the superficial fibres can be readily traced. 
About half an inch below = lower of 
the superior ganglion it enlarges sti rey 
paalitn.tete shicaa rounded swelling, from nine 
lines to an inch in length, and extending from 
about the transverse process of the atlas to 
midway between the transverse processes of the 
second and third cervical vertebre (plerus ge 

gliformis nervi vagi, ganglion 

of Wutzer, ganglion trunci n. v. of ; 
ganglion inferiusn.u.) In the human specie 
though this swelling has a greyish colour, } 
its appearance is that of a plexus more than | 
a true ganglion ; and Valentin states* that 
has not yet obtained satisfactory evidence thi 
it contains the ganglionic nucleated glot 
without the presence of which there can be 
true ganglion, and he believes that the g 


* In many of the Mammalia this 
more circumscribed and less elongated than in | 
human species, and forms a very distinct and t 
ganglion. Bischoff (oper. cit, tab. ii.) has giv 
representations of it in the cat, fox, sow, mol 
and weasel; and Mr. E. Cook, (Guy’s Hos} 
Reports, vol. iis ps 311,) in the guinea-pig, 
and sheep. In all these animals it rap th 
part of the trunk of the vagus from which 


rior laryngeal nerve arises. 


PAR VAGUM. 


appearance of this swelling depends upon fat 
globules placed in the intervals of the plexus. 
At the lower part of this gangliform enlarge- 
ment the nerve becomes smaller, rounder, 
firmer, and of a whiter colour.* This inferior 
or second ganglion of the vagus has been long 
known. Fallopius+ speaks of an oblong olivary 
swelling on the vagus soon after its exit from 
the cranium. Willis t has described it in the 
following words : “nervi truncus, ibidem major 
factus, in tumorem quemdam corpori calloso, 
seu ganglio similem, attolli atque excrescere 
videtur,” and in fig. ix. he has delineated it 
under the name of “ plexus gangliformis paris 
vagi.” Vieussens§ also describes and figures 
it, and terms it “ plexus gangliformis cervica- 
lis nervi octavi paris.” Winslow]|| describes it 
as “une espece de ganglion.” “It has also 
been described by Prochaska, {| Wutzer, Scarpa, 
Bellingeri, &c. Some have considered it to be a 
true ganglion, others only a plexus. Some re- 
strict the term of inferior ganglion to that por- 
tion of the enlargement of the nerve immediately 
below the origin of the superior laryngeal nerve, 
and have described it as being placed upon the 
internal fibres only, so that, according to this 
view, some of the external fibres of the vagus 
and the strengthening fibres of the spinal ac- 
cessory do not pass through it. 

The vagus in its passage down the neck gives 
off pharyngeal, laryngeal, esophageal, cardiac, 
and vascular branches. 

Superior pharyngeal branch (ramus pharyn- 
eus seu primus n. v.)—This is by much the 
argest and most important pharyngeal branch 

of the vagus, and is frequently designated, par 
excellence, the pharyngeal branch of the vagus. 
It arises from the anterior surface of the vagus 
shortly after its exit from the foramen lacerum, 
and opposite the upper part of the atlas, and 
is evidently formed by fibres, partly from the 
internal branch of the accessory, and partly 
from the vagus. Generally the greater part of its 
filaments, occasionally nearly the whole, appear 
to come from the accessory. It passes inwards 
and a little downwards across the anterior sur- 
face of the internal carotid artery, to which it 
is generally pretty closely connected by cellular 
tissue, and lies a little inferior to the glosso- 
pharyngea Inerve.** Immediately after crossing 
the internal carotid, it passes over the ascend- 
ing pharyngeal artery, and after a short course 


* Oper. cit. S. 484. 

+ Opera omnia, p. 407. Francof. 1600. 

¢ Cerebri Anatome, p. 226. 1666. 

§ Neurographia Universalis, P 118, and pl. xxiii. 
Edit. Novissima. Lugduni, 1716 

{| Exposition Anatomique de la Structure du 
Corps Humain, tom. iii. p.237. Paris, 1732. 

¥ De Structura Nervorum, 1779. 
_ ** Cruveilhier (Anatomie Descriptive, tom. iv. 

p- 958, 1836,) describes the pharyngeal branch as 
passing behind (derriére) and not in front of the 
internal carotid. Cloquet (Traité d’Anatomie De- 
scriptive, 2de partie, p. 620,) also described it as 
passing behind the internal carotid. No doubt this 
nerve may occasionally pass behind the artery, and 
similar varieties are to be found in the course of 
all nerves ; but it is equally certain that its usual 
course is in front of the artery, and this inaccuracy 
must have occurred through some inadvertency. 


885 


it reaches the surface of the middle constrictor 
muscle of the pharynx. As it is crossing the 
carotid it is-generally joined by one, two, or 
three small branches descending from the glosso- 
pharyngeal, and at the point of their junction 
a small plexus or ganglion is formed on the 
pharyngeal. (Vide article Giosso-Puaryn- 
GEAL Nerve.) At this point the pharyngeal 
generally divides into several branches.* ‘Two 
of these are considerably larger than the others, 
and one of them passes inwards and upwards, 
and the other inwards and downwards over the 
lateral surface of the pharynx; while the smaller 
branches, two or more in number, pass upon 
the surface of the internal carotid and neigh- 
bouring bloodvessels, especially the arteria 
pharyngea ascendens, to assist in forming the 
nervous plexuses surrounding them. The two 
larger branches which pass upon the surface of 
the pharynx are soon joined by branches from 
the superior ganglion of the sympathetic. The 
upper branch passes over the superior pharyn- 
geal constrictor to its upper edge, sending 
filaments to that muscle, to the elevator palati, » 
the palato-pharyngeus, the azygos uvule, and 
also to the stylo-pharyngeus, and anasto- 
moses freely with the pharyngeal and tonsillitic 
branches of the glosso-pharyngeal nerve and 
twigs of the sympathetic coming from its 
superior cervical ganglion. The lower runs 
downwards over the surface of the middle and 
inferior constrictors, distributes twigs to these 
muscles, and anastomoses with the inferior 
pharyngeal branch of the vagus, the pharyngeal 
branches of the superior laryngeal, and with 
some filaments of the sympathetic. 

Inferior pharyngeal branch (ramus pharyn- 
geus inferior ).—This branch arises a very little 
below the last, and runs parallel to it and across 
the anterior surface of the internal carotid. It 
is joined by a considerable branch from the 
superior ganglion of the sympathetic, which 
generally forms an arch with it around the 
ascending pharyngeal artery. It soon divides 
itself into different branches, which are distri- 
buted upon the lower part of the middle con- 
strictor muscle, and over the whole of the 
inferior constrictor, and anastomoses with the 
twigs of the other nerves found on the surface 
of these muscles. 

Valentin describes under the name of middle 
pharyngeal nerves (rami pharyngei medii seu 
tenwores n.v.) some small filaments arising 
from the anterior surface of the vagus imme- 
diately below the superior pharyngeal, and 
which pass forwards to join the pharyngeal 
branches of the glosso-pharyngeal. The free 
anastomosis of the nerves we have mentioned, 
viz. the glosso-pharyngeal and sympathetic, with 
the numerous subdivisions of the pharyngeal 
branches of the vagus, intermixed with a few 
twigs from the superior laryngeal, and also ° 
with some small filaments from the upper part 
of the cervical plexus of nerves, and an occa- 
sional twig from the hypo-glossal, form an 
elongated and intricate plexus (plexus pharyn- 


* Wrisberg (De Nervis Pharyngis, Ludwig’s 
Script. Min. Nerv. Sel. tom. iii. p. 58) describes five 
branches radiating from the ganglion pharyngeum. 


886 


geus) upon the lateral surface of the pharynx. 
(See article Gioss-Puarnynceat Nerve.) 

Superior laryngeal branch (ramus laryngeus 
superior) arises from the inner side of the 
vagus, about four or five lines below the 
superior pharyngeal branch, and from the upper 
and inner part of the second or inferior ganglion. 
It is considerably larger than the pharyngeal 
branch, and in the first. part of its course pro- 
ceeds almost directly inwards, then inwards 
and downwards, passing behind the internal 
carotid and in front of the longus colli muscle.* 
While it is behind the carotid it generally 
divides into its two branches, the internal and 
external, The internal is much the larger and 
more important, crosses the lateral part of the 
middle constrictor of the pharynx obliquely 
downwards, forwards, and inwards, joins itself 
to the Jaryngeal branch of the superior thyroid 
artery and runs along its upper edge, passes 
between the lower margin of the os hyoides 
and upper margin of the thyroid cartilage, and 
reaches the upper edge of the larynx by per- 
forating the thyro-hyoid ligament posterior to 
the external edge of the thyro-hyoid muscle, 
above the upper edge of the inferior constrictor 
and below the lower edge of the middle con- 
strictor of the pharynx, and a little in front of 
the round ligament connecting the superior 
cornu of the thyroid cartilage to the larger 
cornu of the hyoid bone. Sometimes one or 
two small twigs pass between the trunk of the 
vagus and the superior laryngeal soon after the 
origin of the latter, and the external branch 
of the superior laryngeal occasionally comes 
directly from the trunk of the vagus, a little 
below the origin of the internal branch. While 
the superior laryngeal nerve is passing behind 
the internal carotid, it sends off several small 
twigs, some of which communicate with the 
pharyngeal plexus, a few pass downwards and 
throw themselves into some of the cardiac 
nerves, and the greater part run upon the sur- 
face of the internal and external carotids, and 
assist in forming, with the more numerous 
branches from the sympathetic, the- arterial 
plexus of nerves winding round the carotid 
arteries and their branches. 

External branch of the superior laryngeal. 
It is strengthened by some twigs from the 
superior ganglion of the sympathetic, passes 
downwards and forwards over the inferior con- 
strictor muscle of the pharynx and_ lateral 
surface of the larynx, gets below the outer edge 
of the sterno-thyroid, and continues its course 
below it and the thyro-hyoid muscle. It gives 
some twigs to the inferior constrictor muscle, 
some: filaments also to the upper part of the 
sterno-hyoid and thyroid muscles, and to the 
thyroid body. The continuation of the nerve 
after sending a twig downwards to anastomose 
with another twig from the inferior laryngeal 
nerve behind the thyroid body, ultimately ter- 
minates in the crico-thyroid muscle.t 


* The superior laryngeal nerve rarely passes in 
front of the internal carotid. 

+ A small twig from the external branch of the 
superior laryngeal perforates the thyroid cartilage 
occasionally, and anastomoses with some of the 


PAR VAGUM. 


_thyro-arytenoid muscle, and between it and the 


Internal branch of the ior laryngeal. 
Anooon os:this beansh hapipacislenialaiiiaae * 
hyoid ligament and reached the outer surface 
of the mucous membrane immediately beneath 
it, it divides ne Liver branches which 
are flattened an iating, some ing w 
wards and forwards seniede the ios eae 
tongue and sides of the epiglottis, others for- 
wards, downwards, and inwards in the aryteno- 
epiglottidean folds to the surfaces of the epi- 
glottis, and others downwards upon the posterior 
surface of the larynx. The branches which 
proceed forwards and upwards are small and 
pass onwards to the glosso-epiglottidean folds; 
and while some of their filaments terminate in 
these folds and in the mucous membrane at the 
lateral and back part of the tongue, others turn — 
inwards and are distributed upon the sub- 
mucous glands and the mucous covering of — 
the anterior and upper part of the epiglottis. 
Several pretty strong branches forwards — 
and inwards in the aryteno-epiglottidean folds 
to the side of the epiglottis. Some of these 
proceed upon its anterior surface and are there 
distributed upon the mucous membrane and 
the submucous glands, sending also a few — 
filaments through small apertures in the epi- 
glottis to be ramified in the mucous membrane 
on its posterior or laryngeal surface; while 
other branches pass upon the posterior aspect — 
of the epiglottis—some of them ge 
notches on its outer edge,—and are distri 
upon the submucous glands and mucous mem= 
brane covering that surface. A few branches 
proceed downwards and forwards over the outer 
surface of the lining mucous membrane of the 
larynx, send some filaments to the larynge 
sac, and may be traced as far as the inferior or 
true vocal chords. A long slender brane 
passes downwards on the outer surface of th 


inner surface of the thyroid cartilage, and fr 
queutly anastomoses with an ascending b 
of the recurrent or inferior laryngeal. One or 
two slender filaments enter the thyro-aryteno 
muscle, and these, after a long and wind: 
course among the fibres of that muscle 
those of the crico-arytenoideus lateralis, ul 
mately run to the mucous mem of 1 
larynx. A pretty large branch runs backwai 
in the posterior part of the th id fi 
of mucous membrane, transmitting at the sa 
time a few filaments downwards ; and on rea 
ing the arytenoid cartilage it sends eve 
filaments upon the posterior surface of | 
proper arytenoid muscles, and continuing 
course downwards between the mucous ™ 
brane of the pharynx and the crico-arytenol 
posticus muscle, it anastomoses with one 
sterior ascending branches of the recur 
e greater part of the filaments which e 
among the fibres of the arytenoideus po 
and transversus muscles may be traced 
mucous membrane of the larynx, and | 
very few appear to terminate among the mus 
cular fibres; others anastomose with aryteno 


e 


a. 
descending branches of the internal branch of 
Same herve. - 


a 


pe 


PAR VAGUM. 387 


branches of the superior laryngeal of the 
opposite side, and with the arytenoid branch 
of the recurrent; and occasionally a filament 
perforates the arytenoid cartilage to reach the 


inner surface of the larynx. 


Vascular and cardiac branches.—The vagus 
in its passage along the neck sends off directly 
from its trunk several filaments, which throw 
themselves into the arterial nervous plexuses sur- 
rounding the carotid arteries and their branches ; 
and also others which pass downwards and 
join themselves, either directly or indirectly, to 
the cardiac plexus. These branches are very 
variable in their number, size, and origin, so 
that it is impossible to give any description of 
them which will be found generally applicable, 
and they commonly differ on the two sides in 
the same individual. 

Vascular branches (rami vasculares).— 
Several small branches arise from the trunk of 
the vagus between the origin of the superior 
laryngeal nerve, and about a line or so below 
the level of the bifurcation of the common 
carotid, and chiefly pass upon the carotid 
arteries and their branches. Valentin* has 
divided these into— 

1. Rami carotici, consisting of two or three 
larger and some smaller twigs, coming off 
from the vagus near the origin of the superior 
laryngeal and also from the commencement of 
the superior laryngeal. They run inwards and 
forwards upon the internal carotid. 

2. Ramus ad divisionem arterie carotidis is 
principally distributed upon the common carotid 
at its bifurcation. 

3. Rami vasculares posteriores et interni are 
generally three in number, come from that part 
of the trunk of the vagus on a level with the 
bifurcation of the common carotid, and run 
principally, as their name implies, to the 
nervous plexus on the posterior and inner part 
of the large neighbouring arteries. 

4. Rami vasculares anteriores et interni 
spring from the trunk of the vagus a very little 
below the origin of the last, run to the outer 
side of the common carotid, and assist with 


‘some of the other branches of the vagus and 


sympathetic in forming a nervous network on 
the outer and anterior side of this artery, while 
one or more twigs proceed downwards to join 
the superior cardiac nerve of the vagus. 
Cardiac nerves.—Two or three cardiac bran- 
ches come from the inner side of the vagus at 
some little distance from each other; the upper 
of these generally arises a little below the bifur- 
cation of the common carotid. These bran- 
ches proceed downwards and inwards, commu- 
nicate freely with each other, send some filaments 
upon the surface of the common carotid artery, 
anastomose freely with the cardiac branches of 
the superior and middle cervical ganglia of the 
sympathetic and with the recurrent, pass chiefly 
in front of the large arteries at the root of the 


_ neck, and terminate in the upper part of the 


cardiac plexus of nerves. Frequently, more 
especially when the upper cardiac branches 


are small, or when some of them are want- 


* Op. cit. 


ing, we \find a pretty large cardiac branch 
arising fromthe vagus about the upper part of 
the lower third of the neck, and passing down- 
wards, on the right side in front of the subcla- 
vian, on the left in front of the arch of the 
aorta, it throws itself into the upper part of the 
cardiac plexus. Two or more branches also 
leave the trunk of the vagus as it passes the 
subclavian on the right and the arch of the aorta 
on the left side, pass inwards and throw them- 
selves partly into the cardiac plexus and partly 
into the anterior bronchial plexus. 

Inferior laryngeal or recurrent branch.— 
( Ramus laryngeus inferior seu recurrens.) On 
the right side the recurrent arises from the vagus 
as it is passing over the anterior surface of the 
subclavian artery, while on the left side it is 
sent off from the vagus, generally from its inner 
side, as it is crossing the anterior surface of the 
transverse portion of the arch of the aorta. On 
the right side it hooks round the subclavian on 
the inner side of the scalenus anticus muscle, 
and passing upwards and inwards, first below 
the subclavian artery and then below the com- 
mon carotid, it reaches the right side of the 
trachea. On the left side it hooks round the 
arch of the aorta and obliterated ductus arte- 
riosus, and passing upwards and inwards below 
the aorta, the left subclavian at its origin, and 
the left common carotid, it reaches the left side 
of the trachea. The recurrent soon after its 
origin generally receives one or two additional 
twigs from the trunk of the vagus. Immedi- 
ately after it leaves the trunk of the vagus, it 
anastomoses freely with branches of the sympa- 
thetic, chiefly with the internal branches of the 
two inferior cervical and first dorsal ganglia of 
the sympathetic,—and while the right sends 
some twigs upon the outer surface of the sub- 
clavian artery, the left sends some upon the 
surface of the aorta. It also throws several 
twigs into the cardiac, tracheal, and bronchial 
plexuses. The left sends some twigs to the 
tracheal plexus, while the corresponding twigs 
of the right side come from the trunk of the 
vagus. The two recurrents then proceed up- 
wards along the sides of the trachea towards 
the larynx,—the left resting upon the anterior 
surface of the esophagus,—and are both co- 
vered by the sterno-hyoid and sterno-thyroid 
muscles. In this part of the course of the re- 
current it generally receives communicating 
twigs from the cardiac branches of the superior 
and middle cervical and sympathetic ganglia, 
and it also anastomoses with some of the upper 
cervical cardiac branches of the vagus. It also 
sends several twigs to the cesophagus and tra- 
chea, (esophageal and tracheal twigs of the 
recurrent, ) some of which perforate the fibrous 
membrane between the cartilaginous rings of 
the trachea, and reach its mucous surface, while 
others are distributed among the muscular 
fibres which complete the cartilaginous rings 
behind. As it approaches the larynx it sends a 
twig upwards and forwards, which anastomoses 
with a descending twig of the external branch 
of the superior laryngeal; and it gives 
some filaments to the thyroid body, to 
the mucous membrane of the lower part of 


888 


the pharynx, to the inferior constrictor of 
the pharynx, and also occasionally one or 
two slender filaments to the crico-thyroid 


muscle. It likewise sends a branch upwards 
over the posterior surface of the larynx, first 
passing between the esophagus and back part 


of the trachea, and then beneath the mucous 
membrane of the anterior part of the pharynx 
and crico-arytenoideus posticus muscle, sending 
some filaments to the esophagus and mucous 
membrane of the pharynx, and anastomosing 
with the posterior descending twig of the inter- 
nal branch of the superior laryngeal. The 
trunk of the recurrent now passes upwards in 
front of the lower edge of the inferior constrictor 
muscle, gets into the sulcus on the posterior 
surface of the articulation between the lower 
cornu of the thyroid cartilage and the external 
surface of the cricoid cartilage, and then passes 
along the outer edge of the crico-arytenoideus 
posticus upon the external surface of the crico- 
arytenoideus lateralis and thyro-arytenoid mus- 
cles, where it terminates. In its course along the 
side of the larynx it generally sends a twig up- 
wards to anastomose with one of the descending 
twigs of the internal branch of the superior 
laryngeal. As it is passing the crico-ary- 
tenoideus posticus it sends some twigs into the 
external edge of that muscle, all of which enter 
among its fibres except one. This last twig, 
which does not enter among the fibres of the 
muscle, runs beneath its outer edge, and pro- 
ceeding upwards and inwards between its an- 
terior surface and the posterior surface of the 
cricoid cartilage, it reaches the lower edge of 
the arytenoideus obliquus and transversus, and 
is lost among their fibres. As the continuation 
of the recurrent passes over the surface of the 
cricoid-arytenoideus lateralis, it sends some fila- 
ments inwards among the fibres of this muscle, 
and then proceeds upwards upon the thyro-aryte- 
noid, into the interior of which it dips. Its ter- 
minating filaments are distributed in the thyro- 
arytenoid muscle, and a few only can be traced to 
the lining membrane of the larynx. We have 
thus seen, that while nearly all the filaments of 
the internal branch of the superior laryngeal, 
distributed to the larynx, ultimately run to its 
mucous surface, the greater part of the filaments 
of the recurrent are distributed in the muscles 
which are attached to and move the arytenoid 
cartilages. 

The peculiarity in the course of the inferior 
laryngeal from which it derives its name of re- 
current, depends upon the changes in the rela- 
tive position of the branchial arteries to the 
larynx in the embryo, after they have assumed 
the form presented in the adult by the arch of the 
aorta and the large vessels which spring from it. 
In those cases where the right subclavian artery, 
instead of arising along with the right carotid 
by a common trunk (arteria innominata), comes 
off from the arch of the aorta beyond the origin 
of the left subclavian, or, in other words, is the 

~ last in order of the large arteries which supply 
the head and thoracic extremities, and then 
proceeds across the spine behind the cesophagus 
to reach its usual position behind the scalenus 
anticus muscle on the right side, the recurrent 


PAR VAGUM. 


does not arch round the right subclavian, but 
is given off from the trunk of the vagus as it 
is ing the larynx.* 

Cinires of the t vagus through the thorax.— 
After the right vagus has given off the recurrent, 
it passes behind the ascending portion of the 
arch of the aorta, and proceeding downwards, 
inwards, and backwards behind the right 
bronchus, right pulmonary artery and veins, 
reaches the cesophagus as it lies in the posterior 
mediastinum. The deft vagus, after passing 
from the anterior surface of the arch of the 
aorta, also proceeds downwards, inwards, and 
backwards Fehind the left bronchus, left pul- — 
monary artery and veins, and also reaches the — 
cesophagus in the posterior mediastinum at the 
same part where the right vagus joins it. Both 
nerves closely accompany the esophagus down 
the posterior mediastinum, and from the 
thorax into the upper part of abdomen 
through the same opening (esophageal open- 
ing) in the diaphragm. At the upper part of * 
the chest, the vagi become flat from before _ 
backwards, and are consequently broader and 
thinner than in the neck. “| 

Immediately after the vagus has given off the 
recurrent it sends numerous twigs inwards. 
Some of these pass upwards and inwards to 
assist in forming the cardiac plexus ; some pro- 
ceed transversely inwards upon the anterior 
surface of the lower part of the trachea, and 
anastomose with other branches from the vagus 
arising higher up, and also with branches from 
the recurrent and sympathetic to form the ante- 
rior and inferior tracheal plexus (plexus trache- 
alis anterior et inferior) ; while others pass upon 
the posterior surface of the lower part of th 
trachea, anastomose with other branches from 
the recurrent and sympathetic, and thus fe 
the posterior and inferior tracheal plexus. 
vagus at this part also sends a few twigs upon 
the upper part of the thoracic portion of the 
cesophagus, forming a free anastomosis on its 
surface with other twigs from the recurrent and — 
tlie posterior bronchial plexus (plexus a@sopha- 
gei thoracici superior). It likewise sends some 
branches inwards and downwards to throw 
themselves into the lateral portion of the low 
part of the cardiac plexus; while a few other 
pass still more downwards to reach the anterior 


* Two cases of this variety, in the origin 
course of the inferior laryngeal nerve and righ 
clavian artery, are recorded by Dr. Stedman ( 
Med. and Surg. Journal for 1823, p. 564) and 
Hart (in same Journal, 25th vol. 1826). I ha 
myself had an opportunity of examining two ¢ 
of this kind. In those cases of double mor 
where the head and larynx are double, and # 
two bodies are fused together immediately bel 
this, so that the lower part of the neck, the thor 
and thoracic extremities are single, and wh ce 
sequently we have four vagi nerves in the up 
part of the neck, and only two at the lower p 
the right recurrent of the right larynx hooks rour 
the subclavian artery, and the left recurrent of th 
left larynx hooks round the arch of the aor 
while the other two vagi, or the left recurrent ¢ 
the right larynx, and the right recurrent of th 
left, give off their superior | branches % 
they pass the larynges. I had an opportunity 0 
dissecting one case of this kind. 


aaa 


~~ 


PAR VAGUM. 


surface of the pulmonary veins and branches of 
the trunk of the pulmonary artery, and anasto- 
mose with branches from the inferior part of 
the cardiac plexus prolonged upon these ves- 
sels. Other branches proceed downwards and 
inwards upon the anterior surface of the bron- 
chii, and anastomose with the descending 
branches of the anterior and inferior tracheal 
plexus, with the nervous filaments accompany- 
ing the pulmonary bloodvessels, and with some 
branches direct from the sympathetic to form 


. the anterior pulmonary plexus (plexus pulmo- 


nalis anterior). A few twigs also proceed from 
this portion of the vagus into the anterior me- 
diastinum, and are chiefly distributed in the 
thymus gland. As the trunk of the vagus passes 
behind the bronchus it sends off several pretty 
Jarge branches upon the posterior surface of 
that tube, and also a few smaller ones upon the 
—, surface of the pulmonary bloodvessels. 

ese branches form a great part of the posterior 
_ pulmonary plexus (plexus pulmonalis poste- 
rior), and anastomose with twigs from the 
posterior and inferior bronchial, with some fila- 
ments from the superior thoracic esophageal 
and the anterior pulmonary plexuses. The 
branches of the pulmonary plexuses, after send- 
ing off some nervous filaments which run for 
some distance below the pleura, (vide Reissei- 
sen De Fabrica Pulmonum, 1822, tab. vi. 
plate 2,) accompany the bronchial tubes and 
bloodvessels into the interior of the lungs, and 
follow the divisions and subdivisions of the 
bronchial tubes. The two trunks of the vagi, 
after leaving the lower edge of the bronchi, 
soon reach the esophagus, where each nerve 
divides into three or four chords upon the sur- 
face of the esophagus; those formed by the 
subdivisions of the left vagus lying on its an- 
terior and left side, those by the right vagus 
on its posterior and right side. The chords of 
the same nerve anastomose freely by large 
branches, and also by smaller and less nume- 
rous branches on both sides of the esophagus, 
with those of the opposite nerve, and thus form 
an extensive and open network upon the sur- 
face of the esophagus, called the inferior ceso- 
phageal plexus (plexus cesophageus thoracis 
inferior).* From these chords nervous fila- 
ments pass into the walls of the esophagus, 
and they also exchange some communicating 
filaments with the sympathetic. Immediately 
before the vagi pass through the cesophageal 
opening of the diaphragm, the chords into 
which each nerve has divided again reunite ; 
those of the left nerve collecting into one trunk, 
while those of the right frequently form two 
branches which run close to each other.t As 


_ they pass through the cesophageal opening, the 


right nerve, or the larger, is placed on the 


_ * Some anatomists call that part of the plexus 


_ formed by the left vagus the left wsophageal plexus, 
_ and op formed by the right vagus the right @so- 


phag US. 
_ t Wrisberg (Ludwig’s Scrip. Nerv. Min. Select. 
_ tom. iv. p. 59) says, that he has seen the nervous 


_ chords of both vagi unite into a single trunk on the 


esophagus, which again divided itself into two 
_ branches (right and left vagi) before passing 
_ through the diaphragm. 


889 


posterior surface of the esophagus, and the 
left, or the smaller, on its anterior surface.* © 

Distribution of the vagus in the abdomen. 
Left vagus.—As it enters the abdomen it sends 
some small branches upon the anterior surface 
of the lower part of the cesophagus, some of 
which enter the walls of that tube, others anas- 
tomose with cesophageal twigs from the right 
vagus, and others are prolonged downwards 
upon the cardiac end of the stomach. As it 
proceeds downwards over the cardiac surface of 
the stomach it also passes towards the right 
side and forms a curve, the convexity of which 
looks to the left. From the convexity of this 
curve several small branches run across the 
anterior surface of the cardiac orifice and the 
upper part of the large cul de sac of the sto- 
mach, and some of these anastomose with 
filaments from the left portion of the solar 
plexus, and from the phrenic.nerve.+ From 
the concavity several small branches run up- 
wards and to the right between the layers of 
the smaller omentum to join the left hepatic 
plexus.{ The left vagus now divides itself into 
several branches, which pass towards the pylorie 
surface of the stomach, along the upper edge 
of the anterior surface of the stomach, very 
close to the smaller curvature of that organ, 
and along the lower edge of the coronary artery 
of the stomach, sending numerous filaments 
into the nervous plexuses of the sympathetic 
surrounding the coronary and superior pyloric 
arteries, and also branches downwards over the 
anterior surface of the stomach. These latter 
branches, after running a greater or less distance 
below the peritoneal covering of the stomach, 
penetrate the muscular coat where some of 
their filaments terminate, while others pass 
through it to reach the mucous coat. The few 
branches of the left vagus which reach the 
pyloric orifice are partly distributed upon the 
walls of that portion of the organ, and partly 
throw themselves into the ceeliac plexus. Some 
of the filaments of the latter portion may be 
traced into the numerous plexuses surrounding 
the gastro-duodenalis branch of the hepatic 
artery, into the right hepatic plexus, and may 
sometimes be followed as far as the artery of 
the gall-bladder. The branches which leave 
the left vagus as it lies on the anterior surface 
of the lower part of the esophagus, and cross 
the anterior surface of the cardiac orifice of the 
stomach, divide and subdivide below the peri- 
toneum in a forked manner, and also anas- 
tomose freely with each other, forming a kind 
of plexus which has been termed the anterior 
cardiac plexus of the stomach. As the branches 
of the left vagus pass along the smaller curva- 
ture of the stomach, they not only anastomose 
freely with the plexuses of the superior coronary 
and superior pyloric arteries, but with each 
other, forming a plexus along the upper edge 
of the anterior surface of the stomach, stretch- 
ing from the cardiac to the pyloric orifice, 


* Wrisberg (opus cit.) states, that the vagi send 
a few filaments to the diaphragm. 

+ Valentin, oper. cit. s. 500. : 

$ Vide Swan’s Demonstrations of the Nerves of 
the Human Body, plate viii. 1830 


890 
which Valentin® has termed plexus gastricus 


anterior et superior. 

Right vagus.—As the right vagus is entering 
the abdomen it sends numerous branches upon 
the ON ip of the termination of the 
«esophagus of the cardiac extremity of the 
stomach. Part of these disappear in the mus- 
cular fibres of the @sophagus and stomach ; 
others anastomose with the branches of the left 
vagus, while others proceed downwards and to 
the left side upon the posterior surface of the 
large cul-de-sac of the stomach, sending fila- 
ments into the muscular coat, and also anas- 
tomosing with the filaments of the splenic 
plexus accompanying the vasa brevia. The 
right vagus also sends some branches upon the 
arr ye surface of the stomach, to be distri- 

uted in that part of the organ, a few of which 
proceed as far as the large curvature, and 
course along it from left to right. It also 
sends two or three branches along the smaller 
curvature, which anastomose with the coronary 
plexus and branches of the left vagus. A 
considerable portion of the right vagus,—so 
large as generally to present the appearance 
of being the continuation of the trunk of the 
nerve,—proceeds from the posterior surface of 
the cardiac region of the stomach, backwards 
and downwards to the left side of the cceliac 
axis, sending branches to the splenic, the coro- 
nary, and to the superior mesenteric plexuses, to 
the plexus surrounding the pancreatic branches 
of the splenic artery; and it ultimately termi- 
nates in the left semilunar ganglion. The 
branches of the right vagus running upon the 
posterior surface of the lower part of the 
esophagus and cardiac orifice of the stomach 
have been termed the posterior cardiac plexus.+ 
Dr. Remak has discovered numerous small 
ganglia upon the filaments of the cardiac 
nerves, as they are ramified upon the surface 
of the heart;{ also upon some of the filaments 
of the pulmonary plexus, and upon some of 
the finer branches of the superior laryngeal 
nerve.§ These ganglia can scarcely be seen by 
the naked eye, and it is only when examined 
by the microscope that we can satisfactorily 
determine their nature. These ganglia appear 
to be placed upon the filaments of the sympa- 
thetic, conjoined with the branches of the vagi, 
and not upon those of the vagi. 

According to Volkmann and Bidder the 
vagus nerve contains, in all vertebrated animals, 
a greater number of sympathetic than cerebro- 
spinal filaments; and this preponderance of the 
sympathetic over the cerebro-spinal is more 
marked in the lower than in the higher verte- 
brata. This remark is in conformity with the 
observations of E. H. Weber upon the relative 
size of the vagus and sympathetic in the diffe- 
rent families of the vertebrata, from which it 
appears that in the lower vertebrata the vagus 

* Opus cit. 8. 503. 

+ Many anatomists describe the branches given 
off by both vagi near the cardiac orifice of the 
stomach as forming a single cardiac plexus, the 
larger portion of which is formed by the right vagus. 

¢ Casper’s Wochenschrift fiir die gesammte Heil- 
kunde den 9ten Marz, 1839, 

§ Medicinische Zeitung. Berlin, 8 Jan. 1840, 


PAR VAGUM. 


increases, the sympathetic diminishes, in size. 
The branches of the vagus distributed in the 
esophagus, —— lungs, — liver, and 
ills, are chiefly composed of sympathetic — 
Sia cass while the recurrent one of the motor — 
branches is chiefly composed of cerebro-spinal 
filaments.* ods « 


Connection of tesa le ee a 


We have seen that, as the vagus and 
emerge from the foramen lacerum 
the internal branch of the accessory joims — 
itself to the vagus, and that while part of its” 
filaments phe assist in forming pe ra 
pharyngeal branch of the vagus, rest pro-— 
pane peat with the pa of the foe 
and become incorporated with it. Bi 
statest that he has not been able to trace the 
filaments of the accessory into any of the — 
branches of the vagus except the phar 
while Bendz{ has been more s ss 
states that the portion * the a which — 
accompanies the vagus down the neck sends @ 
few pt ane to the upper part of the inferior 
ganglion of the vagus, and pa itself to 
some of the posterior and external fibres of the 
vagus which do not pass through the ganglion. 
Below the ganglion these fibres form part of 
the trunk of the nerve, being enclosed in the 
same neurilema with those which pass through — 
the ganglion. At the lower edge of the ga 
glion, or sometimes a little lower, the accessor 
portion sends off some filaments which often 
join the external branch of the superior 
geal, but more frequently give twigs to 
sterno-thyroid muscle. Other fibres of the 
accessory portion accompany the vagus into the 
thorax, and some of them assist in forming th 
recurrent nerve. Some small twigs from 
accessory join the pulmonary and cardiae p 
uses; the remainder accompany the 

the stomach, where they are lost. Mr. Spence 
states that those fibres of the vagus which di 
not through the superior ganglion ar 
jane the internal branch of the accessory 
and that these together form a small flat bane 
which may be traced among the other fibres 
the vagus to the lower part of the neck, wh 
it is joined by some of the other fibres of t 
vagus which have passed through the gangli 
and seems to go principally to the fo , 
the recurrent nerve. 

We have seen that the vagi are distribu 
over a large space and upon many of 
They send branches to the external a 

harynx, the larynx, the esophagus, the t 
the pada body, the nets the lungs, 
stomach; also to the liver, the spleen, 
pancreas, the small intestines, and p rc hs 
other viscera of the abdomen. In their cot 
they communicate very freely and extens 
with the sympathetic,§ and toa greater or 

* Dic Selbetatindigkert des Sympathisches 
vensystems, by Bidder and Volkmann. Als 
article Nervenphysiologie in W 
terbuch der Physiologie, p. 584. 

+ Oper. cit. p. 25. 

t Oper. cit. p. 20, 21, 23. - a 

§ In many of the mammalia the cervical por 
of the sympathetic joins the trunk of the ¥ 
immediately below the inferior ganglion of 


% 


da) 


agner’s Hands 
ae 


. PAR VAGUM. | 


extent with several of the other cerebro-spinal 
nerves, as the spinal accessory, the glosso- 
pharyngeal, the hypo-glossal, the portio dura, 
the two superior cervical, and sometimes with 
some of the lower cervicals. The vagi are 
very extensively ramified upon the internal 
tegumentary membrane, as the mucous mem- 
brane of the pharynx, larynx, «esophagus, sto- 
mach, trachea, and lungs, and send only one 
small branch, viz. the ramus auricularis, to 
the external tegumentary membrane. Many 
of its branches are distributed upon the mus- 
cular fibres surrounding the upper part of the 
digestive and respiratory tubes. 

Physiology of the nervus vagus.—From the 
distribution of this nerve in so many of the 
most important organs in the body which it is 
impossible to insulate, or prevent their mutual 
actions and reactions upon each other, and 
from its numerous and intimate connections 
with several other nerves, investigations into its 
physiology are beset with unusual difficulties, 
As, however, its lesions are attended by the 
most serious derangements of the respiratory 
and digestive organs, and as a knowledge of 
its functions bears in a prominent manner upon 
many interesting questions both in special and 
general physiology, it has naturally attracted 
the frequent attention of the physiologist, and 
has been made the subject of numerous experi- 
mental investigations. 

Do the roots of the vagus contain any motor 
filaments?—No one can for a moment doubt 
that the trunk of the vagus, in its course down 
the neck, does contain motor filaments, but 
there is every reason to believe that it derives 
at least the greater part of these from the spinal 
_ accessory. From the resemblance of the vagus 
and spinal accessory as they lie in the foramen 
lacerum posterius to the anterior and posterior 
roots of a spinal nerve,—the vagus with its supe-~ 
| rior ganglion corresponding to the posterior, 
| and the spinal accessory to the anterior root,— 
| many anatomists and physiologists have of late 

maintained that the roots of the vagus, like the 
| posterior roots of the “ng nerve, contain no 
_ motiferous filaments. It is scarcely necessary 
hi to add, that the junction of the internal branch 
_ of the accessory and the vagus immediately 
ty beyond the superior ganglion of the latter, in- 
| creases still further this resemblance between 
_ these and a spinal nerve. This opinion has 
_ been maintained on anatomical considerations 
t 
f 
| 


_alone, by Arnold, Scarpa, and Bendz,* and 
has been further strengthened by the experi- 
- ments of Bischoff,+ Valentin,t and Longet.§ 


* Tractatus de Connexu inter Nervum Vagum 
et Accessorium Willisii, Haunie, 1836. According 
to Miiller, this idea of the resemblance of the ana- 
tomical arrangement of the vagus and accessory to 
a spinal nerve had previously suggested itself to 
_ Gorres in his Exposition der Physiologie, 1809. 

+ Nervi Accessorij Willisii Anat. et Phys. 1832. 


_by experiment that the root of the vagus does con- 
tain motor filaments. } 

_ $ De Functionibus Nerv. Cereb. et Nerv. Sym- 

path. Caput xi. Berne, 1839. 

_ § Recherches Experimentales sur les Functions 

des Nerfs, des Muscles du Larynx, &c. p.31, Paris, 


pay 


+ aia 


Bischoff, however, has more lately satisfied himself - 


894 


It is on the.other hand maintained, that this 
opinion is too exclusive, and that, though there 
can be no doubt of the greater part of the fila- 
ments of the roots of the vagus being incident 
and sensiferous, yet they do contain some mo- 
tiferous filaments. We have seen that, proba- 
bly both in man and in some of the other 
mammalia, a few of the filaments of the vagus 
do not pass through its superior ganglion, and 
consequently the anatomical argument is not 
so conclusive as it at first appears to be. An 
examination of the experimental proof adduced 
in favour of these two opinions shews that the 
former is chiefly founded upon negative, and 
the latter upon positive evidence. Miiller* 
saw muscular movements of the pharynx follow 
excitation of the roots of the vagus within the 
cranium ; but from having neglected some pre- 
cautions in the performance of the experiment, 
he himself is not disposed to attach to it much 
weight. I have related some experiments in 
which I observed muscular movements in the 
pharynx, larynx, and esophagus, from irritation 
of the vagus within the cranium, on the dog 
immediately after death.t Volkmann has per- 
formed similar experiments upon calves, sheep, 
goats, and cats, and perceived muscular con- 
tractions in the levator palati, azygos uvule, 
the superior and inferior constrictor muscles of 
the pharynx, the palato-pharyngeus, and crico- 
thyroid.{ The experiments of Stilling,§ Wag- 
ner,|| Van Kempen,{j Hein,** and Bernard+t+ 
are also all in favour of the opinion that the 
root of the vagus contains motor filaments. 


1841, and Anatomie et Physiologie du Systéme 
Nerveux, &c. tom. ii. p. 262. Paris, 1842. 

* Elements of Physiology, translated by Baly, 
pp. 703-4. Second edition. 

+ Edinburgh Medical and Surgical Journal, 1838. 

$ Miiller’s Archives, p. 493, for 1840. Volk- 
mann expressly states that these muscular contrac- 
tions were also observed on irritating the vagus 
within the cranium in the calf, though in that ani- 
mal all the filaments of the vagus appeared to him 
to pass through its superior ganglion. 

§ Stilling states that he saw movements of the 
pharynx, the glottis, and the stomach in two cats, 
on exciting the roots of the vagus within the cra- 
nium. Vide Bischoff’s Bericht tiber die Fort- 
schritte der Physiologie in Jahre 1842, in Miiller’s 
Archives for 1843. Heft vi. p. 154. 

| Lehrbuch der Physiologie. Dritte Abtheilung, 
S. 329. Leipzig, 1842. 

{| Van Kempen observed contractions of the con- 
strictors of the pharynx, the palato-glossus, the 
esophagus, and the interior muscles of the larynx. 
Essai Experimental sur la Nature fonctionelle du 
Nerf-pneumogastrique, Louvain, 1842. Vide also 
Rischoff’s Bericht, &c. supra cit. pp. 154-5. Bischoff 
states (p. 155) that he himself observed movements 
of the soft palate, in which the contractions of the 
levator palati muscle were very decided, on the 
irritation of the roots both of the vagus and of the 
accessory. 

** Hein observed contractions in the elevator pa- 
lati, azygos uvule, and palato-pharyngeus, but in 
the. last muscle less frequently than in the two 
former, on irritating the root of the vagus, and the 
same muscles were thrown into contraction by irri- 
tation of the root of the accessory. He also per-~ 
ceived contractions in the stylo-pharyngeus from 
irritetion of the root of the glosso-pharyngeal nerve, 
as in the experiments of Mayo and Volkmann, 
Miiller’s Archives, Heft iii. 1844. S. 297. 

tt Archives Générales de Méd. 1844. 


892 


We believe that we are justified in concluding 
from the evidence here adduced, that the vagus, 
even at its origin, and before it has received 
any fibres from the accessory, does contain a 
few motor filaments.* 

We shall here make a few remarks upon the 
immediate effects of chemical and mechanical 
excitation of the trunk of the vagus as it lies in 
the neck, and then proceed to examine in detail 
the functions of its auricular, pharyngeal, laryn- 
geal, esophageal, cardiac, pulmonary, and gas- 
tric branches. When the trunk of the vagus 
has been exposed in the neck in a living animal, 
and is cut, bruised, or rendered suddenly tense 
by forcible stretching, the animal generally 
gives indications of severe suffering, while in 
some cases the animal remains quiescent, and, 
as far as we can judge, suffers little, if any. 

There can be no doubt, from the distinct 
testimony of numerous experimenters,+ that 
the trunk of the vagus does contain sensiferous 
filaments, but there are good grounds for be- 
lieving that the application of chemical agen- 
cies or the infliction of mechanical injuries 
upon this nerve below the origin of its superior 
laryngeal branch, are not attended with the 
same amount of pain as would attend similar 
lesions of one of the ordinary spinal nerves. 
Dr. Marshall Hall and Mr. Broughton re- 
marked, that when the compression of this 
nerve iscontinued “ for a few moments, an act 
of respiration and deglutition follows, with a 
tendency to struggle and cough.” { Romberg 
observed excitation of the vagus in the neck in 
a horse produce cough ;§ and it appears that 
Cruveilhier had made previously the same ob- 
servation.|| In some of the cases in which I 
made this experiment on dogs, I observed 
powerful respiratory muscular movements, but 
never succeeded in inducing cough. Longet 
has been equally unsuccessful in producing 
cough by this means.{ The respiratory mus- 
cular movements which follow excitation of the 
vagus in the neck are not dependent upon any 


* The opinion that the internal branch of the 
spinal accessory furnishes no motor filaments to the 
trunk of the vagus has been several times of late 
attributed tome. That this is a mistake, any one 
may satisfy himself by reading the account which I 
have given of these experiments, from which I 
drew the following conclusions. ‘‘ That the inter- 
nal branch of the spinal accessory assists in moving 
the muscles of the pharynx we are satisfied, not 
only from the experiments just stated, but also 
from those upon the pharyngeal branch of the par 

Of the probable destination and functions 
of the other filaments of the internal branch of the 
accessory, we cannot pretend to judge without more 
extended inquiries. We certainly do not consider 
that these experiments entitle us to assert that they 
are not motor filaments.’””? Edinburgh Medical and 
Surgical Journal, vol. 173, 1838. 

t We have elsewhere collected the statements 
of different authors on this point. (Edin. Med. & 
Surgical Journal for 1838-9.) 

¢ Transactions of the British Scientific Associa- 
tion, vol. iv. p. 677. 

Miiller’s Dohiwes for 1838. 

| Nouv. Biblioth. Med. t. ii. p. 172, 1828, as 
quoted by Longet. 

§ Anatomie et Physiologie du Systéme Nerveux, 
&c. t, ii. p. 309. : 


PAR VAGUM. 


direct action transmitted downwards to the 
lungs or muscles of respiration, but upon a 
reflex action, as Dr. Marshall Hall pointed out, 
arising from certain impressions being carried 
upwards to the medulla oblongata by the inci- — 
dent fibres of the vagus, followed by the trans- 
mission of a motor iufluence outwards from 
this portion of the central organ of the nervous 
system along the motiferous nerves distributed — 
in the muscles moved. The excitation and — 
mechanical injury of the vagus in the neck in- 
duces various other results, some of which -—— 
be included among their immediate effects, such — 
as those upon the movements of the intrinsic 
muscles of the larynx, the diminution of the 
frequency of the respirations, &e.; but these 
will be more methodically introduced amor 
the remarks which we have to make upon the 
functions of the individual branches of the 
nerve.* “a 

Auricular branch.—From the origin of this — 
branch from the superior ganglion of the vagus, 
and from being partly distributed to the inte- 
guments of the pavillon of the external ear, it 
is probable that it is composed of sensiferous 
filaments. If the portion of this branch 
throws itself into the portio dura be sensifere 
the portio dura may contain some sensifero 
filaments as it issues from the stylo-mastc 
foramen.t 

Pharyngeal branches.—As a great ome- 
times nearly the whole, of the superior pharyn- 
geal branch of the vagus comes directly from th 
internal branch of the spinal accessory, 
may, on anatomical grounds alone, conelv 
that it contains motor filaments. In irritati 
this branch in dogs, both alive and immediatel 
after death, we observed extensive movement 
of the muscles of the pharynx and soft palat 
without any distinct indications of pain. 
however, the animal must necessarily be 


* In some animals, as in the dog, the divisic 
compression of the vagus in the neck is 
ately followed by diminution of the pupil of 
of a side, the protrusion of the ilagix 
membrane at the inner canthus over the inner pi 
of the anterior surface of the eyeball, the retract 
of the eyeball deeper into the socket, and a shi 
approximation of the eyelids ; and subsequently 
inflammation of the conjunctiva, es Hi 
de l’Academie Royale des Sciences, 
was the first who observed these effects, and 
attributed them to injury of the sympathetic n 
It is only in those animals in be the sympa 
tic joints itself to the v in the u pee of 
neck, that the division srcouspeasalanil h 
of the vagus produces any change on the eye. — 
Edin. Med. and Surgical Journal, No. 140, fo 
periments on this subject by the author of this 
cle, and Valentin’s Treatise de Functionit 
Cereb. &c. p. 109. 

t Arnold believes that the sympathy oce 
observed between the external ear and the 
may be owing to this auricular branch of the ¥ 
He refers to some cases, where the preset 
hardened cerumen, of a bean, of a pea, and 
foreign bodies in the cartilaginous tube of 
ternal ear, has induced long-continued ce 
even vomiting. (Bemerkungen tiber den e 
Hirns und Ruckenmarks, &c. 8.168. Ziirich, 18 
In some individuals coughing can be 
duced by irritating the inner surface of the me 
auditorius externus. § 


at 


fee 


> oe 


-_— - 


Ee |S ee 


y& 


Det ee § 


PAR VAGUM. | 


jected to considerable suffering before the nerve 
can be exposed, this result cannot be taken as 
a conclusive test that it contains no fila- 
ments of common sensation. We also found 
that division of this branch on both sides ren- 
dered the second stage of deglutition difficult, 
by paralysing the muscles of the pharynx. The 
morsels of food were forced through the now 
passive bag of the pharynx to the commence- 
ment of the wsophagus by the repeated efforts 
of the muscles of the tongue and those attached 
to the larynx and hyoid bone. From these 
facts, we concluded that the pharyngeal branches 
of the vagus are chiefly, perhaps entirely, com- 
posed of motiferous filaments, and- that they 
convey outwards the motive influence by which 
the muscles of the pharynx and soft palate are 
excited to contraction in the reflex muscular 
movements of deglutition.* It is possible that 
they may also contain a few sensiferous and 
incident filaments. Valentin, on irritating these 
branches in different animals immediately after 
death, saw the pharynx contract in a marked 
manner through its whole length.+ 

Volkmann states, as we have already had 
occasion to mention, that various muscles of 
the soft palate and pharynx were thrown into 
contraction on excitation of the vagus within 
the cranium.{ He further observes, that he 
could not perceive any movements in the mus- 
cles of the pharynx or soft palate on irritating 
the spinal accessory within the cranium. This 
last result is certainly one which we would not 


expect, but the remarks we have to make upon 


it will be more appropriately introduced in the 
article Sprnat Accessory Nerve.§ Longet 
observed very marked contractions in the pha- 
rynx on galvanizing the pharyngeal branch of 
the vagus in the horse and the dog.|| Though 
the experiments we have referred to, in illus- 
tration of the functions of the pharyngeal 
branches of the vagus, differ in some respects, 
they all agree in this, that extensive and active 
muscular movements of the pharynx may be 
produced by their excitation, and that they 
therefore contain many motor filaments. We 
have adduced some facts which would seem to 
shew that they contain few, if any, motor fila- 
ments. 

Laryngeal branches—When the superior 


* Edin. Med. and Surg. Jour. 1838. 
+ De Functionibus Nerv. Cerebralium, &c, p. 17, 


¢ Volkmann concludes, as we have already men- 
tioned, from his experiments that the stylo-pharyn- 
geus and middle constrictor muscle of the pharynx 
do noi derive their motor filaments from the pha- 
ryngeal branch of the vagus, but from the glosso- 
pharyngeal. In the article GLosso-PHARYNGEAL, 


_ we have stated, that, when this nerve is insula- 


ted carefully from the neighbouring nerves, no 
direct muscular movements follow its excitation. 
Valentin (opus cit. p. 38) and Longet (opus cit. 


_ tom. ii. p.223) have from these experiments ar- 


rived at the same conclusions as we have on this 
point. 
§ We may merely state in the mean time that 


_ Longet (opus cit. tom, ii. p.27) has drawn from 
_ his experiments the conclusion that the spinal ac- 


cessory furnishes all the motor filaments of the 
muscles of the larynx. 
|| Opus cit. tom. ii. p. 271. 


893 


laryngeal nerve is laid bare in a living animal 
and pinched with-the forceps, the animal gives 
indications of severe suffering, while on re- 
peating the same experiment on the inferior la- 
ryngeal the animal seldom gives any indication 
of suffering pain. When an opening is made 
into the trachea, and a probe introduced through 
it into the interior of that tube and passed up- 
wards, it excites little or no uneasiness until it 
reaches the interior of the larynx, when violent 
paroxysms of coughing and signs of great un- 
easiness immediately tollow. The division of 
the inferior laryngeal nerves has no eflect in 
diminishing the severity of these paroxysms of 
coughing or in quieting the struggles of the 
animal, while they instantly cease on cutting 
across the internal branch of the superior la- 
ryngeal nerves. Before Magendie published 
his observations upon the functions of these 
nerves it appears to have been generally be- 
lieved that the different intrinsic muscles of the 
larynx received motor filaments both from the 
superior and inferior laryngeal nerves. Magen- 
die has, on the other hand, maintained that the 
superior laryngeal moves those muscles which 
shut the superior aperture of the larynx, and 
the inferior laryngeal those which open it, and 
he supposed that this view sufficiently ex- 
plained the closure of the superior aperture of 
the larynx on the division of both inferior la- 
ryngeal.* We found that on applying ditlerent 
excitants to the superior laryngeal nerve before 
it gave off its external branch in several animals 
immediately after death, that the crico-thyroid 
muscle was thrown into powerful contraction 
and the cricoid approximated to the thyroid 
cartilage, while all the muscles attached to the 
arytenoid cartilages remained quiescent. On 
irritating the inferior laryngeals all the muscles 
attached to the arytenoid cartilages were thrown 
into contraction, and as the force of those mus- 
cles which close the superior aperture of the 
larynx preponderates over that of those which 
open it, the arytenoid cartilages were drawn 
forwards and inwards, and the superior aperture 
of the larynx was closed. By applying the ex- 
citation to the nerves for a short time and in 
rapid succession,, the superior aperture of the 
larynx could be made to close and open alter- 
nately,—to close during the period of excitation 
and to open during the intervals,—and it was 
also remarked that the outward movement, or 
that of opening, was dependent upon the elas- 
ticity of the parts. The inferences from these 
results were strengthened by an examination of 
the anatomical distribution of the laryngeal 
nerves, and confirmed by experiments upon 
living animals.t From these and other facts 
related in the paper referred to, we arrived at 
the following conclusions. The superior la- 
ryngeal furnishes one only of the intrinsic 
muscles (the crico-thyroid) of the larynx with 
motor filaments, while it supplies nearly all the 
sensiferous and incident filaments of the larynx, 


* Compendium of Physiology, pp. 132 and 399. 
Milligan’s Translation, 4th ed. 1831. Legons sur 
les Phénomenes Physiques de la Vie, tom, ii, 
p- 228, 1837. 

+ Edin. Med. and Surg, Jour., pp. 138, 139, 1838. 


804 


and also some of those distributed upon the 
pharynx and back of the tongue, so that it 
1s chiefly composed of sensiferous and incident 
filaments. e inferior laryngeal furnishes 
incident and sensiferous filaments to the greater 
part of the trachea, to the cervical portion of 
the cesophagus, a few to the mucous surface of 
the pharynx, and still fewer to the larynx ; it 
supplies the motor filaments of the cervical 
portion of the esophagus and of all the muscles 
which are attached to and move the arytenoid 
cartilages, and is chiefly composed of motor 
filaments.* When any excitation is applied to 
the mucous membrane of the larynx in ‘the 
healthy state, this does not excite the contraction 
of the muscles which move the arytenoid carti- 
lages by acting directly upon these through the 
mucous membrane, but is the result, as Dr. M. 
Hall+ had maintained, of a reflex or excito- 
motory action, in the performance of which the 
superior laryngeal is the incident, and the infe- 
rior laryngeal the motor nerve. In each re- 
current nerve two sets of motor filaments are 
included, one set transmitting the nervous in- 
fluence which stimulates the opening muscles 
of the larynx to act synchronously with the other 
muscles of inspiration, the other set transmit- 
ting the nervous influence which calls the 
closing muscles into synchronous action with 
the muscles of expiration.{ 

Upon these views we can readily explain how, 
when the inferior laryngeal nerves are cut, all 
the movements of the muscles of the arytenoid 
cartilages are arrested, and the superior aper- 
ture of the larynx, as was first pointed out by 
Legallois, can no longer be dilated during in- 
Spiration. In fact, the sides of the larynx are 
not only no longer separated by an active in- 
fluence, but are rendered quite passive, and 
yield readily within the limits of their natural 
movements to any external force applied to 
them. When the recurrent nerves are cut in 
an adult animal, where the cavity of the larynx 
is large, a quantity of air may still find its way 
through the diminished aperture, adequate, in 
many Cases, to carry on the respiratory process 
in a sufficient manner, particularly if the mus- 
cles of inspiration are not acting violently. If, 
on the other hand, the capacity of the larynx be 
proportionally smaller as in young animals, the 
air rushes through the diminished superior aper- 
ture of the larynx in a narrower stream and with 
increased force, more especially when the in- 
Spiratory movements are powerful—or in other 
words, when the capacity of the thorax is sud- 
denly and greatly enlarged,—and an insufficient 
quantity of air reaches the lungs. This quan- 
tity is still further reduced a} the circumstance 
that the now passive sides of the superior aper- 
ture of the larynx are carried inwards by the 

* We also suggested that some of these filaments 
distributed in the trachea pe a be motor, though 
we had not succeeded in obtaining experimental 
evidence of it. 

t Lectures ‘on the Nervous System and its Dis- 
eases, Lecture 1, 1836. 

¢ Each of these two sets may again be subdivided 
into other two—one composed of the excito-motory 
filaments of Dr. M. Hall, the other of sensifero- 
volitional filaments. 


PAR VAGUM. ‘ 


current of air, and at each inspiration the ary- 
tenoid cartilages may be so closely Re a 
imated as to prevent the ingress of air and suf- 
focate the animal. It is the ina 3 
of the animal which is difficult, for the expira~ 
tion is easy. The occurrence or non-occurrence 
of dypsneea, or suffocation, after section of the 
inferior laryngeals, is to be explained by the — 
greater or less capacity of the larynx in the indi- — 
vidual animal, and the activity and extent of 
its respiratory movements at the time. Th 
crowing sound which frequently attends — 
condition of the larynx is a mere 
effect, and depends upon the current of air — 
rushing rapidly through the diminished aper- — 
ture of the larynx, and may be imitated in the — 
dead larynx. Severe dyspnea amounting to- 
suffocation may arise both from the opposite — 
conditions of irritation and compression of the 
inferior laryngeal nerves or the trunks of the 
penereapiette above the origin of this branch. 
e have stated above that on irritating one 
recurrent nerve we observed that the arytenoid 
cartilages were approximated so as in 
cases to shut completely the superior apertu 
of the larynx, and we have already explained 
how paralysis of this nerve by com i 
any other cause should produce this effect by 
arresting the movements of all the muse 
attached to the arytenoid cartilages.* We 
found that after the mae rabbits they “i0r 
laryngeal nerves in dogs an i 
load solids and fluids readily, and wi 
exciting cough or difficulty of breathing. 
Mr. Hilton has arrived at the conclusion, from 
the anatomical distribution of ev ce e 
that the superior laryngeal is chi ensitive 
and that honals motor filaments which it con 
tains are distributed in the crico-thyroid musel 
while the inferior laryngeal supplies all | 
muscles attached to the arytenoid -cartilags 
with motor filaments,—a view in exact a 
cordance with that which we have given abov 
Volkmann in his experiments found that 
movements of the glottis were not affected 
dividing the superior laryngealnerves.4 Longe 


* Professor Henderson (Cormack’s Journal 
Medical Science, p. 10, for 1841) adduces casi 
shew that in the human species the narrowin 
the superior aperture of the larynx, termed la 
gismus stridulus, may be induced both by irrit 
and paralysis of the recurrents. 4 

+ An account of the above experiments and 
ferences was read at the meeting of the Bi 
Scientific Association in 1837; a short epitom 
them was given in the Atheneum for Sept 
1837, and they were published in full in the I 
—— Medical and Surgical Journal for Jan 
¢ Guy’s Hospital Reports for October, 
forming part of the 2nd volume. — 

§ Opus cit. Volkmann states that on irr 
the external branch of the superior 
dogs and calves, not only the crico-thyroid 1 
was thrown into contraction, but also the con: 
penyecene superior and the thyro-hyoid. 

e confirmed, these two last muscles mu 
their motor nervous filaments from two 
the constrictor receives a supply from the pha 
geal branch of the vagus, and the th yoid f 
the hypoglossal. io 

\| Hocbetchat Expérimentales sur les Fa 
des Nerfs, des Muscles du Larynx, &c, Paris, 10 


y 
ee 


PAR VAGUM. 


has published various experiments upon these 
nerves very similar to those which we had per- 
formed, and obtained nearly the same results. 
Longet states that the respirations become in- 
creased in frequency after dividing the recur- 
rents. Other experimenters have lately satisfied 
themselves of the accuracy of these experiments. 

Effects of the laryngeal nerves on phonation. 
—The effect of the lesion of the recurrent 
herves in enfeebling the voice was well known 
to Galen and the older physiologists.* We 
found in making this experiment that the voice, 
as Monro Secundus+ and others have stated, 
is not altogether lost, for in some cases, at 
_ Teast, the animal could still emit a faint howl. 
_ Longett has observed that the voice is com- 

pletely lost in old animals, while young animals 

are still able to produce acute sounds different 

from the natural voice if the crico-thyroid 

muscle moved through the external branch of 
__ the superior laryngeal be not paralysed, and he 

attributes this difference to the relative size of 

the larynx at these ages. We can have no 
_ doubts in attributing the effects of lesion of the 
inferior laryngeals upon the voice to the para- 
lysis of the muscles attached to the arytenoid 
cartilages. § 

Magendie mentions that an animal after 
section of the superior laryngeal nerves “ loses 
almost all its acute sounds it acquires, besides 
a constant gravity which it had not previously.”|| 
This he attributed to the arrestment of the 
movements of the arytenoid muscles, but we 
have shown that the section of these nerves has 
no such effect. Bischoff could perceive no 
change upon the voice after he had divided 
_ these nerves in two dogs. -Longet states that 
the division of those nerves above the origin of 
_ the erternal branch, or of the external branch 
__ alone, is followed by a disagreeable hoarseness 
of the voice.** If the variations in the length 
| of a tube alter the graveness and acuteness of 
_ the sounds which it emits, we would expect that 

the lesion of the superior laryngeals should, by 
arresting the movements of the crico-thyroid 
muscle, produce some change in this respect. 
Longet believes that the crico-thyroid muscles 
are, during their contraction, tensors of the 
' vocal chords, and that the changes upon the 
_ voice induced by dividing the superior laryn- 
| geals depend upon the effect which paralysis 
| of these muscles has upon the tension of the 
ts vocal chords.++ 
| Csophageal branches——Muscular contrac- 
| tions have been observed in the ceesophagus on 


_ * Vide Haller’s Elementa Physiologie, tom. iii. 

 p. 408, Lausan. 1766, 

_ + Observations on the Nervous System, p. 65. 

_ $ Opus supra cit., p. 14 and 15. 

__§ 1 have seen some cases of partial aphonia in 
the human species arising from the compression of 

one recurrent in the upper part of the chest by an 

-aneurism of the aorta. 

_ || Compendium of Physiology, p. 138, 1831. 

Opus cit. p. 27. 

_** Dupuytren had previously maintained that 

econ of the superior laryngeals was followed by a 

‘disagreeable hoarseness, Biblioth. Medic. tom. 

Xviii., 1807, as quoted by Longet. 

tt Opus cit, p. 8 and 37, 


895 


irritating the trank of the vagus, by Arnemann,* 
Cruikshank,+ Mayo,t{ and others. When the 
trunk of the vagus is irritated above the origin 
of the recurrent, the muscular fibres of the 
cesophagus along its whole length are thrown 
into active contraction. In experiments upon 
rabbits we found that the esophagus became 
impacted with food eaten after section of the 
vagi in the neck, when very little of it had 
reached the stomach and when no efforts at 
vomiting had occurred, while its muscular 
fibres could still readily be thrown into active 
contraction by direct excitation. From this we 
inferred that before the presence of the ingesta 
in this tube can excite its muscular fibres to 
contract and propel its contents onwards, the 
same conditions of the nervous system are ne- 
cessary as for the production of the excito- 
motory movements, and that certain of the fila- 
ments of the vagi act as incident and others as 
motor nerves. That the food also collects in 
the esophagus in the horse and sheep after 
division of the vagi may be inferred from the 
experiments of Dupuy § and others. In subse- 
quent experiments upon dogs we found that 
substances seem to pass pretty freely along the 
esophagus in that animal after section of the 
vagi. It would appear, however, that even 
in the dog the food is occasionally retained in 
the cesophagus after dividing the vagi.|| Arnold 
(opus eit. p. 144) observed in his experiments 
upon hens and pigeons that the cesophagus and 
crop were so relaxed after section of the vagi 
that when the animals shook their head and 
neck, or kept the head in a depending position, 
a quantity of chyme flowed from the bill. 

From a review of all these facts we are in- 
clined to agree in the opinion lately expressed 
by Dr. M. Hall, that in some animals the 
muscular contractions of the cesophagus are 
excito-motory, while in others they are called 
into action by direct excitation. We cannot 
at present determine whether the propulsion of 
the food along the csophagus in the human 
Species partakes more of the former or of the 
latter class of movements. Magendie has as- 
certained that various muscular movements go 
on in the lower 7 of the csophagus, more 
especially when the stomach is full, by which 
this tube is contracted during inspiration and 
relaxed during expiration, and that they are 
suspended by dividing the vagi. These we 
may class among the reflex muscular move- 
ments. The esophagus is endowed with little 
sensibility, and in the natural and healthy con- 
dition of the organ the ingesta are propelled 
along it to the stomach without exciting any 
sensation. From a consideration of all the 


* As quoted by Soemmering Corporis Hum. Fa- 
brica, tom. iv., p. 272, 1794. 

t+ Medical Facts and Observations, vol. vii., p. 
153, or Phil, Transact., 1795 

¢ Anatomical and Physiological Commentaries, 
No. ii., p. 15. 

§ Journal de Médecine, Chirurgie, &c. Dec. 
1846, tom. 37, p. 351. 

|| Baglivi Opera Omnia, p. 676, Anvers, 1715, et 
Valsalve Opera cum Epistolis Anatomicis, &c. 
ae Morgani Epist, Anatom. xiii. 37, Venei. 


896 


above facts we believe that the cesophageal 
filaments are chiefly incident and motor, and a 
few of them only are sensiferous. 

Cardiac branches—We have in a former 
part of this work (article Hearr) had occasion 
to state that several celebrated physiologists 
have failed in exciting the muscular contractions 
of the heart by irritation of the trunk of the 
vagus before it gives off its cardiac branches, or 
of these cardiac branches themselves. We have 
very frequently repeated this experiment upon 
animals immediately after death, and we have not 
been able to satisfy ourselves that galvanic and 
mechanical excitation of these nerves has any 
effect in renewing or increasing the contractions of 
the heart. No doubt we have not unfrequently 
seen the contractions of the heart become more 
frequent and vigorous during the performance 
of this experiment ; but as similar changes in 
the strength and rapidity of its contractions are 
occasionally observed in an animal after death 
when no artificial excitant has been applied to 
these nerves, and from causes which cannot at 
present be explained, we did not think ourselves 
entitled to attribute these changes in the heart’s 
action to the excitation of the nerves. Valen- 
tin* has stated that he has produced muscular 
contractions in the heart in different animals -by 
irritation of the trunk of the vagus. He also 
statest that similar contractions of the heart 
were produced by excitation of the spinal ac- 
cessory and of the three superior (sometimes 
also of the fourth) cervical nerves, and he main- 
tains that the motor portion of the cardiac 
nerves comes from the spinal accessory and the 
superior cervical nerves. Longet{ mentions 
that he failed in influencing the rhythm of the 
heart by the application of galvariism to the 
vagi in dogs, rabbits, and sheep, but very fre- 
quently succeeded by scraping the cervical 
cardiac branches of the vagus. Allowing that 
it is possible to increase the contractions of the 
heart by galvanic or mechanical excitation of 
the vagus or its cardiac branches, it must be 
admitted by every one that there is a very 
marked difference hetween the heart and volun- 
tary muscles in this respect, for all those who 
have failed in their experiments on the nerves 
of the heart, have felt not the smallest difficulty 
in producing contractions of the voluntary 
muscles by excitation of their nerves. The in- 
creased frequency of the pulsations of the heart 
observed during and for some minutes after the 
division of the vagi may be fairly referred to 
the struggles and terror of the animal, and the 
feeble and rapid pulsation of the heart which 
precedes death from this experiment is not 
owing to any direct effect upon that organ. 
The sudden death occasionally remarked after 
the division of these nerves, and which some 
of the early experimenters attributed to arrest- 
ment of the contractility of the heart, was in 
fact dependent upon the suffocation of the 
animal by the suspension of the movements of 
the muscles which dilate the superior aperture 


* Opus cit. p. 48, 62 and 66, 


+ Opus cit. p. 62. 
t Opus cit, &c. tom. ii. p. 314. 


- airto the lungs is prevented ;{| and V: 


PAR VAGUM. 


of the larynx. We have related several expe- — 
riments which appear to prove that when in- 
juries of the brain and mental emotions affect 
the contractility of the heart, the nervous influ- 
ence is not transmitted by the — branches 
of the vagi alone, but may also pass along 
the filaments of the sympathetic or ganglionic 
system of nerves. 
Pulmonary branches——Do the pulmonar 
branches of the vagus contain motor y 
We have made various unsuccessful 
to produce contractions in the muscular fibres 
of the bronchial tubes by excitation of the vagi 
in the neck.* Dr. C. T. B. Williams} was 
also unsuccessful on attempting this experiment, 
though he succeeded in producing contractions — 
in the bronchial muscular fibres by their direct 
excitation, as by transmitting galvanism through 
the substance of the lungs, &c. Longet and 
Volkmann have not only succeeded in exciting 
contractions of the muscular fibres of the — 
bronchii by direct stimulation, but also by ex- 
citants applied to the branches of the none 
To what extent are the pulmonary branches 
the vagus sensiferous? Brachet relates some 
experiments which seem to prove that the sen- — 
sation arising from the want of fresh air in the’ 
lungs, or the besoin de respirer, is annihilated 
by the division of vagi.§ Mr. Grainger|| re- 
peated one of Brachet’s experiments, and seemed 
satisfied that his conclusions were correct. 


periments against which he has not taken 
necessary precautions. 
We have satisfied ourselves by nume 
experiments that the sense of anxiety ari 
from the want of fresh air in the lungs 


nues after dividing the vagi when the access of 


and Longett+ from their experiments have also 
arrived at the same conclusion. It is possible 
that certain impressions which may excite t 
besvin de respirer are conveyed upwards to t 
encephalon through the medium of the syr 
thetic, but it is more probable that in the ex 
ditions induced by the experiment it was me 
immediately dependent upon the circulation 
ill-arterialized blood through the tissues of # 
body, and more especially through the 
phalon. We do not mean to deny that im 
pressions conveyed along the vagi to the e1 
phalon may not exeite the besoin de respirer 5 
the other hand, we believe that it is very pre 
able that this sensation as first felt, when 
respiration is suspended for a short time it 
healthy condition of the body, is dependent 
impressions conveyed along this nerve. W 


* Opus cit. for 1839. 
+ Transactions of British Scientific 
for 1840, p. 411. 
¢ Longet, opus cit. tom. ii. p. 289, and 
mann in Wagner’s Handwo ch der Ph 
logie, article Nervenphysiologie, p. 586. 
Systéme Nerveux Ganglionaire, p. 
On the Spinal Chord. 
Opus cit. for 1838. $e 
4 - : alles gy for -_. os aot ‘or 
ritish and Foreign Review for Jan. pe 2 
tt Opus cit. tom. ii., 291-2, 1842. ; 


PAR VAGUM. \_ 


however, the respiration has been suspended 
for a longer time and venous blood begins to 
circulate along the arteries, the other excitants 
of the besoin de respirer come into operation. 
Brachet,* Krimer,t and Longet,f have from 
their experiments arrived at the conclusion that 
the sensations occasioned by irritation of the 
inner surface of the trachea and bronchial tubes, 
and which usually precede coughing, are anni- 
hilated by dividing the vagi. We have made 
repeated experiments on this point, and though 
we could not satisfy ourselves that these sensa- 
tions were affected to the extent maintained by 
these authors, we believe that they are at least 
blunted. 
To what extent do the filaments of the vagi 
act as incident nerves ?—It has been proved by 
_ the experiments of Legallois,§ Flourens,|| and 
| others, that all the respiratory and muscular 
movements cease on destroying the medulla 
oblongata, though the other parts of the ence- 
phalon situated above this may be injured in 
various ways without necessarily producing 
this effect. Itis further well known that if the 
Spinal chord be cut across, all the respiratory 
muscles are paralysed which receive their 
nerves from that portion of it below the point 
where it was divided, while those muscles 
which receive their nerves from that portion of 
the spinal chord still continuous with the me- 
dulla oblongata perform their usual functions. 
From these and other facts it may be consi- 
dered as ascertained that all impressions made 
at the lungs and elsewhere capable of causing 
respiratory movements, must be conveyed to 
the medulla oblongata before they can produce 
any reflex excitation of the muscles of respira- 
tion. That the vagi can convey these impres- 
sions from the lungs is not only rendered pro- 
bable from their attachment to the medulla 
oblongata, but may almost be considered as 
proved by the result of the experiments upon 
the spinal chord to which we have just referred. 
It, however, by no means follows that the vagi 
are the sole excitant nerves of respiration. It 
has been fully ascertained by numerous expe- 
rimenters, more especially by those who have 
investigated the functions of this nerve from the 
time of Legallois, that an animal will continue 
to breathe after the division of both vagi in the 
neck, if care be taken to secure the ingress and 
egress of air to and from the lungs. It is now 
' well known, as we have already had occasion 
to point out in examining the functions of the 
laryngeal branches, that if the vagi be injured 
_ above the origin of the recurrent laryngeals, 
none of the muscles attached to the arytenoid 
cartilages can any longer act in unison with the 
| muscles of respiration, all their movements 
_ cease, and the superior aperture of the larynx 
| can no longer be dilated during inspiration. 
If the larynx be large, and the animal refrain 
_ * Oper. cit. p. 157-8-9. 
3 ee agen iiber den Husten, as quoted by 
uller, 
m) t Oper. cit. tom. ii. p. 289. 
g ' Sur le Principe de la Vie. 
_ || Recherches Expérimentales sur les Proprietés 
t les Fonctions du Systéme Nerveux, &c. Paris, 


t VOL. III. 


897 


from any violent effort, an adequate quantity of 
air may still find its way to the lungs, and the 
respirations are at first performed with ease. 
If, on the other hand, the larynx be small, its 
superior aperture may be ‘mechanically closed 
and the animal may be immediately suffocated, 
or the air may still pass through the larynx but 
in diminished quantity, and the animal may 
labour under dypsneea from the moment the 
nerves are divided, up to its death. Even when 
means are taken to secure the free entrance of 
air into the lungs, an immediate and marked 
diminution in the frequency of the respiratory 
movements follows the division of both vagi 
in the neck. A.G.F. Emmert concluded, but 
apparently more upon theoretical grounds than 
from any direct observations made in the two 
experiments he had at that time performed on 
rabbits, that after lesion of the vagi the respira- 
tions become less frequent and prolonged.* 
Mayer reckoned the number of respirations, 
both before and at various periods after section 
of these nerves in five experiments upon the 
ass, dog, and rabbit, and found a very marked 
diminution in their frequency after dividing the 
nerves.t Mr. Broughton mentions, that in a 
horse in which the vagi were divided “ the 
respirations became slow, twelve in a minute ;” 
and in another horse “ the respirations fell to 
five in the minute.”{ At what period after 
the division of the nerves these last observations 
were made, and what was the number of the 
respirations previous to the commencement of 
the experiments, we are not informed. Sir 
Astley Cooper has given the result of two expe- 
riments upon rabbits which well illustrate the 
effect of the division of the vagi upon the respi- 
ratory movements.§ In our experiments we 
ascertained that the diminution in the frequency 
of the respiratory movements, generally to less 
than half of their former number, is an imme- 
diate effect of thedivision of both vagi. Therespi- 
ratory movements seem to be performed more 
slowly, and, generally, even from the first, in a 
somewhat heaving manner.|| Arnold in his expe- 
riments upon hens also observed a very consi- 
derable diminution in the frequency of the re- 
spiratory movements.f] Brachet has asserted** 
that an animal continues to breathe after sec- 
tion of the vagi, because it has acquired the 
habit of using the respiratory muscles. Dr. 
Marshall Hall has maintained that after the 
vagi are divided the respiratory movements are 
no longer a function of the excito-motory but 
of the cerebral portion of the nervous system ;++ 


* Archiv. fiir Physiologie von Reil und Auten- 
rieth, Neunter Band. 1809, s. 417. 

+ Tiedemann’s Zeitschrift fiir 
Zweiter Band, 1826, s. 77. 

¢ Quarterly Journal of Literature, Science, &c. 
vol. x., p. 305 and 307. 

fa Hospital Reports, No. 3, Sept. 1836, 

- 409. 


Physiologie, 


: || Transactions of British Scientific Association 
for 1838, and Edin. Med. and Surgical Journal for 
1839, vol 51. 

§ Bemerkungen tiber den Bau des Hirns und 
Riickenmarks, &c. s, 148. Zunch, 1838. 

** QOper. cit. p. 132. 

t+ Philosophical Magazine for Jan. 1835, Lee- 

3M 


898 


and he has adduced in support of this view the 
statement of Cruveilhier that after the function 
of volition has been suspended by destroying 
the cerebrum, the respiratory movements are 
instantly arrested on dividing the vagi near 
their origin.* In putting this opinion to the 
test of experiment we found that though the 
respirations were very much diminished in 
pee see by the removal of the cerebrum 
and cerebellum and then dividing the vagi, 
they nevertheless continued for a longer or 
shorter time.+ Similar results have also been 
subsequently obtained by Volkmann,} . by 
Flourens,§ and by Longet.{| From these facts 
we are entitled to conclude that the vagi are 
not the sole excitors of respiration, and that 
ee may be made upon the medulla 
oblongata capable of exciting the involuntary 
Tespiratory movements after the vagi have been 
divided in the neck, and when impressions 
made on their expanded extremities in the 
lungs can no longer be conveyed inwards to 
the central organs of the nervous system. The 
importance of the vagi as incident nerves of 
a is not only proved by the marked 
and immediate diminution in the number of 
the respirations which follows their division,{ 
but also in a more striking manner by the 
morbid changes which take place in the 
lungs. 

Morbid changes in the lungs after dividing 
the vagi—The injury or division of the vagi is 
almost always fatal after a few days, even when 
precautions are taken to secure the free ingress 
of air into the lungs. The period of death in 
such experiments varies in different animals. 
Rabbits generally die earlier than dogs. The 
greater number of dogs die before the third 
day, and comparatively few live beyond the 
fifth day. In seventeen experiments upon dogs 
we found that eleven died before the completion 
of the third day, and seven of these eleven before 
the completion of the second day. Longet 
says that he | avalgey this experiment on 
thirty dogs, and they all died on or before the 
fifth day, and none of the rabbits operated on, 
lived beyond thirty-six hours.** Dupuy in 
his experiments found that horses lived to the 
fifth, sixth, and seventh day, when care was 
taken to admit a sufficient quantity of air into 
the lungs.t+ De Blainville informs us that the 
pigeons on which he operated died on the sixth 
or seventh day ;{{ and in the experiments of 
Arnold§§ upon hens and pigeons, these animals 
died between the second and fifth day. In 


tures,on the Nervons System, p. 25. Memoirs on 
the Nervous System, p. 87, 1837, 

* Lancet, 17th Feb., 1838, p. 733. 

+ Opus cit. for 1839. 

Opus cit. for 1840. 

Opus cit. Seconde edition, p. 204, Paris, 1842, 
Opus cit. tom. ii., p. 307, 1842. 

A diminution of the number of respirations, 
but to a less extent generally, results from dividing 
one of the vagi, ’ 

** Opus cit. tom. ii., p. 306. 

tt Journal de Médecine, Chirurg., &c., tome 
xxxvii., p. 356, Dec. 181. 

tt Nouv. Bullet. de la Societ. Philom. tome i., 
ann, ii., p. 226. 

§§ Opus cit. s. 163. 


. internal caloric which 


PAR VAGUM. 


eral the lungs are the only organs found in 
sa 'abeoisial state after death from injury or 
division of the vagi. We found the lungs 
unfit for the healthy performance of their fune- 
tions in fifteen out of seventeen dogs experi- 
mented upon. These organs arealmost always 
more or less congested with blood, ially at 
the depending parts, and the bronchial tubes 
and air cells frequently contain much : 
serum. In some portions — ~ lungs the 
congestion of blood is occasi so great as 
to Peacien them dense and devoid of air. This j 
condensation is not unfrequently greater in 
some parts than what can be accounted for by 
the mere congestion of blood in the vessels, and — 
probably depends in a great measure upon the — 
escape of the solid of the blood into the © 
tissue of the lung. The frothy serum has fre- 
quently a greater or less deep tinge of red. 
Portions of the lung are likewise occasionally _ 
found condensed from pneumonic effusion. — 
In seventeen experiments on dogs distinct evi- 
dences of pneumonia were observed in five, and 
in two of these it had run on to gangrene. 
These morbid changes upon the lungs are suffi- 
cient to explain the imperfect arterialization of 
the blood, and“ the diminished evolution of 
es death. We 
have endeavoured to prove that these morbi 
changes in the lungs are the result of the dit 
nished frequency of the respiratory moveme 
which immediately follows the division of the 
vagi. The vagi are the chief excitors of t 
respiratory muscular movements, and 
they are tied or divided the respirations am 
instantly diminished to less than half thei 
former number. The flow of blood throug! 
the lungs is dependent upon the continuane: 
of the respiratory process, and the great di 
nution in the activity of the respiratory muse 
movements must be followed by a retardatic 
and congestion of the blood in the lungs. Sue 
a congestion of blood, as is well kno 
generally followed by an effusion of sert 
and also predisposes the organsso cireumstanee 
to various morbid changes, chiefly of an infla 
matory nature. In the lungs this congestiol 
not only followed by the escape of the set 
but also of the more solid material from 
vessels, rendering the tissue dense. The 
fused serum is mixed up with air moving < 
the bronchial tubes during inspiration and 
piration, and it thus becomes frothy. A li 
blood may also extide from the congested 1 
cous membrane of the bronchial tubes, gi 
the serum there effused a reddish tinge. 
these changes proceed, the respi 15 
becomes more and more imperfect, the 
flowing along the arteries approaches more 
more to the venous hue, all the vital pro 
of the tissue are enfeebled, the internal te! 
rature sinks, and the animal dies of proti 
asphyxia. The division and other mjur 
the pneumo-gastrics have no direct effect u 
the production of the animal heat; t 
occasion this indirectly by enfeebling 
tion of respiration. We have else 


“ Edinburgh Medical and Surgical 
1839, By 


o 


Bf if 
me 


PAR VAGUM. 


duced evidence to shew that these morbid 
changes do not necessarily follow the division 
of both vagi in all animals, and that the dog in 
a few rare cases may either die of inanition 
from the arrested secretion of the gastric juice 
and without any morbid alterations in the 
lungs, or may even survive the operation and 
recover from its effect. 

Magendie, Wilson Philip,* Mr. Swan,+ and 
Longet,j found that section of one vagus in- 
duced diseased action in the lung of the same 
side. The lesions observed by these experi- 
menters differed very considerably in their 
character. Dupuytren,§ on the other hand, 
could discover no alteration in the lung of the 
side on which the vagus had been divided in 
two dogs and a horse, though these animals 
were allowed to live more than a month. In 
an experiment made by Magendie before his 
pupils, the results were completely at variance 
with his former expressed opinions. The right 
lung of a dog was found perfectly healthy, 
though a portion of the vagus of that side was 
removed six months before.|| We have re- 
moved a portion of one vagus in seventeen 
animals, and allowed them to live a longer or 
shorter period,—from twenty-four hours to six 
months,—and in none of these could we detect 
any morbid changes in the lungs which we 
could attribute to the injury of the nerve. This 
immunity of the lung from the usual morbid 
changes, when one nerve only was divided, we 
attribute to the smaller diminution of the 
respiratory muscular movements, than when 
both nerves are divided. 

Functions of the gastric branches. _ Do 
the gastric branches of the vagus contain 
some, motiferous filaments ?—Mr. Mayo] and 
Miiller** failed in exciting muscular contrac- 
tions in the stomach by irritating the trunks of 
the vagi, while this experiment succeeded in the 
hands of Bichat,}+ Tiedemann and Gmelin, tt 
and Longet.§§ Breschet and Milne Edwards|||| 
inferred that muscular movementscan be excited 
in the stomach of a living animal by galvanizing 
the lower end of the divided vagi in the neck 
from its effects upon the digestive process. We 
have carefully and repeatedly performed the ex- 
periment of irritating the vagi, and are confident 
that though it occasionally fails, yet it often suc- 
ceeds.§] These muscular movements in thesto- 
mach differ considerably from those in the ceso- 
phagus. They are more slow and are vermicular. 


* Experimental Inquiry, &c. p. 145. 

+ Essay on the Connection of the Heart and the 
Functions of the Nervous System, &c. 

Opus cit. p. 351. 

t ; Biblioth. Méd., 1807, 
quoted by Longet. 

|| Legons sur les Phénoménes Physiques de la 
_ vie, tom. i., p. 203-4. 
__ 4 Anatomical and Physiological Commentaries, 
i No. 2, p. 15. 
__ +** Elements of Physiology. 
tt Anatom. Générale, tom. iii., p. 360. 


t. xvil., p. 21., as 


Paris, 
_ _ tt Recher. Experim. Physiol. et Chem. sur la 
Di estion, p. 374. 

' § Opus cit., p. 322. 

| Archiv. Gen, de Méd., tome vii. 

ra { Opus cit. 


899 


They generally commence at the cardiac orifice 
and proceed to a greater or less extent towards 
the pyloric orifice. Longet thinks that he can 
explain this discrepancy in the results of this 
experiment, as he found that it succeeded 
when the stomach was engaged in the process 
of chymification, and failed when it was empty. 
Though we are satisfied that the gastric branches 
of the vagus contain some motor filaments, yet 
we do not believe with Breschet and Milne 
Edwards, Brachet, Longet, and others, that the 
muscular movments of the stomach depend 
entirely upon the integrity of the vagi. Ma- 
gendie* observed these muscular movements 
continue after section of the vagi; and we ascer- 
tained from experiment that if a dog recovers 
from the first effects of the operation of cutting 
the vagi, the stomach can still propel the chyme 
onwards into the duodenum. Arnold,+ from 
his experiments upon hens and pigeons, con- 
cludes that the contractions of the stomach are 
less influenced than those of the esophagus and 
crop by division of the vagi. The grains taken 
into the stomach after this operation were found, 
however, to be considerably less bruised than 
in sound animals. 

Effects of lesion of the vagi upon the sensa- 
tions of hunger and satiety —Though the sensa- 
tion of hunger is referred to the stomach, yet it 
is evident from well established facts that this 
sensation is actually situated in the encephalic 
portion of the nervous system. ‘This sensation 
1s not dependent, as far as we know, upon any 


‘physical condition of the stomach itself, and in 


all probability arises from certain organic 
changes in the body, connected with the want 
of additional supplies of nutritious matters 
from without. Brachet relates two experiments 
to show that the sensations of hunger and 
satiety are arrested by section of the vagi,t but 
these are liable to certain sources of fallacy 
against which proper precautions were not 
taken. Four of seventeen dogs we experimented 
on, lived: beyond the fifth day after the division 
of the vagi, and exhibited no signs of having lost 
the sensation of hunger; on the other hand 
their actions indicated that they still retained 
this sensation. Longet has from his experi- 
ments arrived at conclusions on this point 
similar to ours.§ There can be no doubt that 
the sensation of hunger is almost always sus- 
pended for a longer or shorter time after the 
division of the vagi, probably occasioned in 
some measure by the pain and terror attending 
the operation, but if the animal live for a few 
days the sensation of hunger may return. 
Though the facts from which Brachet has 
arrived at the conclusion that the sensation of 
satiety is annihilated by the division of the vagi, 
do not, as we have elsewhere shown,|| warrant 
this inference, yet it is probable for reasons 
which will occur to every one in reflecting 


* Compendium of Physiology. 
Milligan, 4th edit., p. 261. 
+ Bemerkungen tiher den Bau des Hirns und 
Riickenmarks, &c., S. 145. 
+ Systéme Nerveux og ge Expt. 52-3. 
Opus cit., tom. ii., p. 329. 
i Opus cit. 


Translated by 


3M 2 


900 


upon the matter that this sensation is more de- 
pendent upon the physical condition of the 
stomach than that of hunger. At the same 
time we must confess that we have ourselves 
obtained no very satisfactory evidence from 
experiment, that this sensation is annihilated 
by division of the vayi. 

Effects of lesion of the vagi upon the 
function of digestion. — That section or liga- 
ture of the vagi is generally followed by 
-vomiting,—in those animals susceptible of it,— 
by loathing of food and arrestment of the di- 
sd process, has been incontrovertibly proved 

y numerous experimenters. That perfect di- 
gestion may occasionally take place after 
division of the vagi in the neck even when the 
cut ends are kept considerably apart, is now, 
we are fully convinced, sufficiently established. 
Leuret and Lassaigne have detailed an experi- 
ment where the process of digestion went on in 
a horse after division of the vagi with loss of 
substance.* In one of Arnemann’s experiments 
on dogs, the digestive process must have been 
re-established, as the animal was killed on the 
165th xf after the operation of dividing both 
vagi.t In an experiment made by Sédillot on 
a dog the digestion must at least have been par- 
tially restored, as the auimal lived two months 
and a half.{ Sédillot also mentions that Begin 
kept a dog alive for a month after the division of 
both vagi. M.Chaumet further states that no 
obvious change was observed in the digestion in 
this dog ;§ and he also mentions that in some 
similar experiments made by himself a dog 
lived fourteen days and digested. In four out 
of seventeen dogs experimented on, we obtained 
sufficient evidence of the restoration of the 
digestive process. In these animals we had 
not only removed a portion of the vagi, but 
also of the recurrent nerves. Many experi- 
menters, among whom we may enumerate 
Haller,|| Brunn,§’ De Blainville,** Dumas,t++ 
Dupuy,f{ Legallois,§§ Macdonald,|||| Wil- 
son Philip,{/] and Dr. Hastings,*** have never 
obtained evidence of the continuance of the 
digestion after lesion of the vagi, but such 
negative experiments cannot be considered 
as neutralizing the results of the positive 


* Recherches Physiologiques et Chemiques pour 
oan a l’Histoire de la Digestion, p. 133-4. Paris, 
t Versuche tiber die Regeneration der Nerven. 
hundert und zehnter versuch., S. 99. 1787. 
: eo Thése au Nerf Pneumogastric, &c. Paris, 
: aks Essa i sur la Physiologie de l’Estomac. Paris, 


Opera Minora, tom. i., p. 359-60. Expert. 
hsb : 


4 De Ligaturis Nervorum. Ludwig Scrip. Nerv. 
Min. Sel., tom. ii., p. 286-7. Expt. 2, 3, and 6. 

** Propositions extraites d’un Essai sur la Ke- 
spiration. Paris, 1 

tt Journal Général de Médecine, tom. xxxii, 

tt Journal de Médecine, Chirurgie, &c., tom. 
XXXVii. 

Sur le Principe de la Vie, p. 214. 

it Dissertatio Experimenta quedam de Ciborum 
Concoctione complectens. Edinburgh, 1818. 
4 Inquiry into the vital Functions. 
*** Quarterly Journal of Science, &c., vol. xi., 


p. 40. 


PAR VAGUM. 


pre ome we have mentioned above: they 
only show what every physiologist who has 
experimented much on this subject must be 
obliged to confess, that the digestive process is 
generally arrested after section of the vagi 
during the short time the animal usually lives 
after these nerves have been tied or divided, but 
they can never overthrow the results derived 
from positive experiments, provided that these 
have been accurately performed and are free 
from all sources of fallacy. a 
Effects of lesion of the i upon the 
secretion of gastric juice—We have already 
detailed facts sufficient to prove that the re- 
moval of a portion of both vagi does not always — 
arrest the digestion of food, and consequently 
does not necessarily prevent the secretion of 
the gastric juice. Mayer found the chyme acid 
in rabbits after section of the vagi. Dieckhof 
and Miiller state that in all their experimen 
performed upon geese the fluid secreted from 
the surface of the stomach after section of the 
vagi was always acid, but was less in quantity — 
than in the sound animal.* Breschet, Milne 
Edwards, and Vavasseur,t Dr. Holland,t and ~ 
Brachet,§ maintain that in their experiments the - 
gastric juice was secreted, since the food in the 
stomach was more or less altered. In two ex-_ 
periments we ascertained that the half digested - 
food vomited, though taken into the stomach 
some days after division of the vagi, perma- 
nently reddened litmus-paper; and we consider 
the presence of chyle in the lacteals and thoracie — 
duct as observed in the experiment of Leuret 
and Lassaigne, and in three of our own experi= 
ments, as furnishing decisive evidence of the 
secretion of gastric juice. In one of our expe- 
riments the animal was rapidly recovering flesh 
and strength when he was killed three weeks 
after division of the vagi and recurrents wi 
loss of substance. Arnold, in his experiments 
upon hens and pigeons, ascertained that the 
fluid secreted from the stomach was acid, thut 
it was not perceptibly diminished in ntity, 
and that it was capable of converting ( 
into chyme.||.  Longet, in his experiments 1 pe 
quadrupeds, found that the fluid secreted fro 
the stomach coagulated milk and reddent 
turnsol paper. He further states, that the quai 
tity of gastric juice secreted appeared to him t 
be greater than in the sound animal. 
great number of experiments, more especial 
if the animal survive the operation a short ti 
only, the secretion of gastric juice is tem 
rarily suspended, and this enables us to expla 
the frequent occurrence of negative results 
such researches. ; 
Effects of lesion of the vagi upon the 
cretion of mucus from the inner surface of 
stomach and intestines—Sir B. Brodie reli 
from experiments in which animals were ] 
soned by arsenic where the usual watery ¢ 
* Elements of Physiology, translated by Ba 
vol. i., p. 597, 2nd edit. e. 
t Opus cit. tom. ii. p. 483. : 
cae An Experimental Inquiry, &c, chap. x. Edit 


§ Opus cit. 
||. Opus cit. p. 142. 
Opus cit, tom. ii. p. 382. 


.) 


| Baly, vol. i. p. 263, 2nd edit. 


PAR VAGUM. 


mucous secretions were not poured out from the 
mucous surface of the stomach and intestines, 
though it presented the inflammation usual in 
such cases.* We have carefully repeated these 
experiments, and obtained different results. The 
quantity of watery and mucous secretions was 
nearly the same inanimals after the vagi had been 
divided, as in animals upon which this operation 
had not been performed.t These experiments 
upon the effects of lesion of the vagi upon the dif- 
ferent secretions poured out from the inner sur- 
face of the digestive canal, though they do not 
prove that the function of secretion is indepen- 
dent of the nervous system, seeing that nume- 
rous filaments of the sympathetic uerve are also 
distributed there, are yet sufficient to neutralize 
the evidence drawn from the effects of lesion of 
the vagi upon these secretions adduced by 
those who maintain that secretion is dependent 
upon the nervous system. 

Effects of lesion of the vagi upon the 
rapidity of absorption from the inner surface of 
the stomach.—lIt has been stated by Dupuyt 
and Brachet, that the most active poisons in- 
troduced into the stomach after division of the 
vagi in much larger quantities than usual, pro- 
duce their effects much more slowly. On the 
other hand Miiller mentions that in thirty ex- 
periments on Mammalia performed under his 
direction by M. Wernscheidt, “ not the least 
difference could be perceived in the action of 
narcotic poisons introduced into the stomach, 
whether the nervus vagus had been divided on 
both sides or not, provided the animals were of 
the same species and size.”§ We have made 
several comparative experiments on this point,|| 
and obtained results which agreed nearly with 
those mentioned by Miiller. 

The following short summary contains the 
principal conclusions founded upon the facts 
and observations above detailed, at which we 
have arrived regarding the functions of the 
nervus vagus. 

1. Though the trunk of the nervus vagus at 
its attachment to the encephalon principally 
consists of sensiferous and incident filaments, 
it yet contains a few motor filaments. The 
motor filaments contained in some of the 
branches of the vagus chiefly come from the 
spinal accessory. 

2. The filaments of the auricular branch of 
the vagus are sensiferous and incident. 

2. The pharyngeal branches of the vagus are 
principally if not entirely motor, and move the 
muscles of the pharynx and soft palate in 
obedience to certain impressions made upon 
the incident filaments of the glosso-pharyngeal 
and fifth pair of nerves distributed upon the 
mucous surface of these organs. 

4. The superior laryngeal branch is chiefly 
composed of sensiferous and incident filaments 


which are abundantly distributed upon the 


* Philos. Trans., 1812, p- 102. 
+ Opus cit. for 1839, vol. li. 
t Opus cit. p. 366. » 
| Opus cit. p. 186. 
Muller’s Elements of Physiology, translated by 


§ Opus cit. vol. li. 


901 


mucops surface of the larynx, and much more 
sparingly upon the inner surface of the lower 
part of the pharynx. The few motor filaments 
contained in the superior laryngeal are dis- 
tributed in, and move the crico-thyroid muscle. 
When the superior laryngeal branches are 
divided or tied, every excitation of the inner 
surface of the larynx fails to excite sensation, 
or any reflex and muscular movement, and the 
two crico-thyroid muscles are paralysed. 

5. The inferior laryngeal or recurrent 
branch is ramified in, and regulates the move- 
ments of all the muscles attached to the aryte- 
noid cartilages, viz. the crico-arytenvideus pos- 
ticus and lateralis, the thyro-arytenoideus, and 
the arytenoidei. The inferior laryngeal also 
furnish the sensiferous filaments to the upper~ 
part of the trachea, a few to the mucous surface 
of the larynx, and still fewer to the pharynx. 
The sensiferous filaments of the inferior laryn- 
geal are, however, few in number and do not 
impart much sensibility to the parts in which 
they are distributed, presenting a striking con- 
trast in this respect to the superior laryngeal. 
When the inferior laryngeal is cut or tied, the 
muscles attached to the arytenoid cartilages are 
no longer moved voluntarily as in speech, or 
involuntarily as in the muscular movements of 
respiration ; and the arytenoid cartilages may 
be mechanically carried inwards by the cur- 
rents of air rushing into the lungs, so as to shut 
up the superior aperture of the larynx and pro- 
duce suffocation. When any excitation is 
applied to the inner surface of the tarynx in the 
healthy state, this does not produce the con- 
traction of the muscles which approximate the 
arytenoid cartilages by acting directly upon 
them through the mucous membrane; but this 
muscular contraction is effected indirectly and 
by a reflex action, in the performance of which 
the superior laryngeal acts as the incident or 
afferent nerve, and the inferior laryngeal as the 
motor or efferent nerve. It is also probable 
that these filaments of the inferior laryngeal 
distributed in the muscular fibres of the trachea 
are motor. The inferior laryngeal branch is the 
principal nerve of phonation, and when para- 
lysed the voice becomes very faint. The 
effects of the paralysis of the superior laryngeal 
upon the voice are much less marked and are 
much more doubtful. 

5. The esophageal branches of the vagus are 
partly afferent and partly efferent nerves. In 
some animals, as in the rabbit, the section of 
the vagi in the neck is followed by the sus- 
pension of the movements of the esophagus 
during deglutition, and the food is no longer 
conveyed along it in the usual manner. This 
lesion of the vagi does not produce these effects 
by destroying the contractility of the muscular 
fibres of the cesophagus, but by breaking the 
continuity of the nervous circle necessary for 
the accomplishment of all reflex movements. 
In some other animals, as in the dog, the food 
is still propelled along the esophagus after 
section of the vagi, so that it is probable that in 
these animals the muscular fibres of the ceso- 
phagus are also called into contraction by direct 
excitation. 


902 


6. The cardiac branches of the vagus have no 
direct effect in maintaining the movements of the 
heart. Though the movements of the heart 
may be materially influenced by causes acting 
through the vagus, yet mental emotions and 
injuries of the central organs of the nervous 
system affect the heart's action through the 
sympathetic after the vagi and recurrents have 
been divided in the neck. 

7. The pulmonary branches of the vagus con- 
sist chiefly of incident filaments and convey 
impressions, capable of producing respiratory 

juscular movements, made on the inner sur- 

ice of the lungs to the medulla oblongata. 
When the vagi are cut or tied in the neck the 
respirations instantly fall in frequency, and are 
reduced to about one half their former number. 
The existence of motor filaments in these 
branches has not yet been satisfactorily esta- 
blished. 

8. Though excitation of the nervus vagus 
in the neck causes muscular contractions of the 
stomach, yet the muscular movements of the 
stomach are not entirely dependent upon the 
gastric branches of the vagus, and the stomach 
may still propel the chyme into the duodenum 
after the vagi and recurrents have been divided. 
Lesion of the gastric branches of the vagus does 
not necessarily arrest the secretion of the usual 
fluids poured out into the interior of the sto- 
mach, though these are generally changed toa 
considerable extent both in quantity and quality 
by causes acting through the nervous system. 
The rapidity of the absorption of poisonous 
substances from the inner surface of the sto- 
mach is not perceptibly diminished by the 
division of the vagi. 

9. Division or ligature of the vagi in the 
neck is almost always fatal. The cause of 
death, in by far the greater number of cases, is 
congestion of the lungs with blood induced by 
the diminished frequency of the respiratory 
muscular movements. In a few cases the ani- 
mal dies of inanition from derangement of the 
functions of the stomach.* 

(John Reid.) 


PAROTID REGION.—This region (in 
surgical anatomy) is of a somewhat pyramidal 
form, the base corresponding to the surface of 
the skin, and the apex to the pharynx. The 


* The author embraces this opportunity of cor 
recting some of the errors which have been over- 
looked in printing this article. 

P. 882, col. 1,1. 11, for ** cross,” read ‘‘ crosses.” 

= 2, foot note marked }, 1.7, for “ en- 
largement,” read ‘* arrangement.” 

P. 888, col. 2, foot note, 1.17, for ‘* while the 
other two vagi, or,’”’ &c. to the end of the 
sentence, read “‘ while the other two vagi 
give off the left recurrent of the right larynx 
and the right recurrent of the lett, as they 
pass the larynges.” 

P. 890, col. 1, last line, for “‘ that in the,” read 
«« that while in the.” 

P. 890, col. 2, 1. 5, for «* while the recurrent one 
of the motor branches is,” read ‘‘ while 
the recurrent, one of the motor branches, 
is. 

P, 893, col. 1, last line one, for ‘* motor 
filaments,” read ‘* sensiferous filaments.” 


PAROTID REGION. 


superficial boundaries of the region are, supe- 
ale the root of the zygoma and the articu- 
lation of the jaw; inferiorly, a line drawn from 
the angle of the jaw to the anterior borderof the 
sterno-mastoid muscle ; anteriorly, the posterior 
border of the masseter muscle ; and posteriorly, 
the meatus auditorius, the mastoid process 
with the anterior border of the sterno-mastoid 
muscle. 

In the present article it is intended to gis 
the relative anatomy of the parts contained in 
this irregular and ill-defined region. 

Commencing the dissection by removing the 
integument from the parotid region, we 2 
some delicate muscular fibres which constitute 
the upper part of the platysma or the risorius 
Santorini; these fibres, however, are not con- 
stantly present. After removing a fine reti- 
cular tissue, the superficial surface of the pa- 
rotid fuscia is seen. This is a strong fibrous 
fascia which is continuous below with the cer- — 
vical fascia; it passes over the superficial sur- 
faces of the parotid, being attached above to 
the zygoma, and behind to the cartilage of the 
ear, while in front it is thinner and is pro 
over the masseteric region. The fascia also 
dips down into the substance of the gland and 
divides it into lobes and lobules. 

The Parotid Gland, from which the name 
of this region is derived, is the largest of the 
three salivary glands. Its form is irregular, and 
is determined by the surrounding parts into the 
interstices of which it is packed and moulded. 

Relations of the parotid—A description ¢ 
the relations of the parotid gland will include 
the greater part of the relative anatomy of the 
parotid region. The external surface or base 
of the gland corresponds to the skin; it is of a 
somewhat irregular quadrilateral form, and its 
boundaries are identical with those of the pa- 
rotid region, except that a portion of the gland 
the socia parotidis, is prolonged forwards wit 
the duct over the masseter muscle. The anterio 
surface of the parotid is grooved to receive the 
posterior border of the ramus of the jaw; | 
also corresponds to the internal pteryge 
muscle, the stylo-maxillary ligament, and # 
masseter muscle, upon the external surface 
which it is prolonged, but from it | 
some loose cellular tissue, by branches of t 
portio dura nerve, and by the transverse fac 
artery. The posterior surface correspot 
to the cartilaginous portion of the exter 
meatus, upon the convexity of which it 
moulded, and to which it is connected 
dense cellular tissue; this surface is also rek 
to the mastoid process and to the sterno-n 
toid and digastric muscles. It is related § 
riorly to the zygoma and the tempero-maxi 
articulation ; inferiorly it fills up the space 
tween the angle of the jaw and the an 
border of the sterno-mastoid muscle. It 
comes into relation with the submaxillary g 
but is separated from it by the stylo-m: 
ligament. The internal or deep surface of t 
parotid is very uneven; it fills up the posteri 
part of the glenoid cavity and the space bi 
tween the ear and ramus of the re 
rounds the styloid process and I 


Se a 


Sehr EO 


o 


» of the jaw. 


PAROTID REGION. 


which arise from it, and passes down between 
the styloid process and the pterygoid muscles, 
so as to come in contact with the pharynx and 
the internal carotid artery, as well as the in- 
ternal jugular vein, and the eighth, ninth, and 
sympathetic nerves. A portion of the gland 
passes with the internal maxillary artery be- 
tween the ramus of the jaw and the internal 
lateral ligament; it here comes into contact 
with the inferior maxillary nerve, and some- 
times reaches the space between the external 
and internal pterygoid muscles. 

In addition to the relations here pointed out 
to the parts by which it is surrounded and 
limited, the parotid has important relations to 
vessels and nerves which pass through its sub- 
stance or are deeply imbedded within and 
beneath it. 

Arteries.—The external carotid artery passes 
into the lower border of the gland near its 
deep surface; as it ascends it becomes more 
superficial, and is continued upwards under 
the name of the superficial temporal, which 
passes up between the ear and the articulation 
of the jaw, crosses over the zygoma, and so 
emerges from beneath the parotid gland and its 

ia. 

The internal mazillary artery passes off 
from the carotid at right angles. At its origin 
it is imbedded in the substance of the parotid, 
and is nearly on a level with the lower extre- 
mity of the lobe of the ear; it bends down- 
wards and inwards, and escapes from the pa- 
rotid by passing between the ramus of the jaw 
and its internal lateral ligament. 

The transversalis faciei arises from the ca- 
rotid or from the superficial temporal artery at 
a variable distance between the angle and neck 
Its origin is imbedded in the 
substance of the parotid; it then goes upwards 
and forwards, and passes out beneath the ante- 
rior border of the gland, lying between it and 
the masseter muscle. 

The posterior auricular artery is a small 
branch of uncertain origin. When regular it 
arises from the external carotid, above the di- 
gastric and stylo-hyoid muscles, opposite the 
point of the styloid process; it is here partly 
concealed by the parotid gland, in the posterior 
part of which it is imbedded ; it then passes 
upwards and backwards between the ear and 
the mastoid process. While this artery is im- 
bedded in the parotid it sends off a small 
stylo-mastoid branch, which passes upwards 
to enter the stylo-mastoid foramen. In ad- 
dition to the above-mentioned arteries there 
are several branches variable in their number, 
size, and situation, which pass off from the 
carotid and its branches and are distributed to 
the substance of the parotid gland. 

Veins.—The veins corresponding to the ter- 
minal branches of the external carotid artery 
accompany the arteries and are consequently 
imbedded in the parotid gland. The temporal 


_ and internal maxillary veins unite and form a 


common trunk, which lies superficial to the 
external carotid artery. This common trunk 
receives the posterior auricular and the trans- 
verse facial veins, as well as some veins from 


[ 


903 


the substance of the parotid, and so the com- 
mencement of the external jugular vein is 
formed. There is also a communicating branch 
which passes through the parotid gland from 
the internal to-the external jugular vein ; this 
branch may be looked upon as one of the 
origins, and in some cases it is the chief origin 
of the external jugular vein. 

Nerves.—We have next to study the rela- 
tions of the nerves which are found in the 
parotid region. 

The nerve which lies most superficially in 
this region is the great auricular, some small 
branches of which lie superficial to the parotid 
fascia and are distributed to the skin of the 
parotid region, while other branches pierce the 
fascia, and pass through the parotid ina di- 
rection forwards and upwards to be distributed 
on the skin of the cheek. The nerve then 
sends off two branches, the superficial auri- 
cular and the deep auricular. 

The superficial auricular branch of the great 
auricular nerve passing vertically upwards in 
the dense fibrous tissue which connects the 
parotid with the skin, reaches the inferior part 
of the concha, and is distributed to the skin of 
the ear. 

The deep auricular branch passes through 
the substance of the parotid, to place itself in 
front of the mastoid process, crossing at an 
acute angle the auricular branch of the facial 
nerve, which is deeper than it, and with which 
it anastomoses by a branch of considerable size, 
The nerve then passes backwards and divides 
into branches which are distributed to the ex- 
ternal ear, and to the skin over the occipital 
region. 

The auriculo-temporal nerve arises from the 
trunk of the superior maxillary by two por- 
tions, between which passes occasionally the 
middle meningeal artery. It passes backwards 
beneath the external pterygoid muscle, and 
between the internal lateral ligament and neck 
of the jaw; it then divides into two branches, 
a superficial or temporal and a deep or auri- 
cular branch. The superficial temporal passes 
up between the ear and the articulation of the 
jaw, crossing the root of the zygoma, and be- 
coming superficial above the parotid gland ; it 
then supplies the skin of the temple and side 
of the head. In its course this nerve sends off 
one or two branches which communicate with 
the portio dura nerve; it also sends branches to 
the tempero-maxillary articulation and to the 
external auditory meatus. The auricular branch 
forms a plexus behind the neck of the jaw and 
around the internal maxillary artery; it then 
divides into several branches, some of which 
pass through the parotid to be distributed on 
the external ear, while others anastomose with 
branches of the cervical plexus, particularly 
with the great auricular nerve. One branch 
joins the dental nerve just before it enters the 


_ dental canal, and another passes into the tem- 


pero-maxillary articulation. 

The portio dura nerve passes out of the 
stylo-mastoid foramen and enters the substance 
of the parotid gland. At its exit from the 
foramen the nerve sends off three small branches, 


904 


the posterior auricular, the digastric, and the 
stylo-hyoid. 5 

The posterior auricular nerve passes off from 
the anterior part of the portio dura ; it passes 
upwards and forwards round the anterior sur- 
face of the mastoid process, and is joined by 
the great auricular nerve of the cervical plexus; 
it then becomes superficial, accompanies the 
artery of the same name, and is distributed to 
the ear and side of the head. ' 

The digastric nerve passes backwards and is 
distributed by several filaments to the posterior 
belly of the digastric muscle. It sends an anasto- 
motic filament to the glosso-pharyngeal nerve. 

The stylo-hyoid nerve arises often from a 
common trunk with the preceding ; it enters the 
stylo-hyoid muscle after passing along its supe- 
rior border. ; 

After the portio dura has given off the above- 
mentioned branches it passes forwards through 
the substance of the parotid gland below the 
meatus auditorius externus; it then crosses over 
the posterior auricular artery and the styloid 
process, the external jugular vein and the ex- 
ternal carotid artery, and before reaching the 
ramus of the jaw it divides into two branches, 
the tempero-facial and the cervico-facial, which 
diverge from each other. 

The tempero-facial division passes upwards 
and forwards in the substance of the parotid, 
forming with the trunk of the facial nerve an 
arch, the concavity of which is above; it then 
crosses the neck of the lower jaw and receives 
at this point one and sometimes two branches 
from the auriculo-temporal branch of the in- 
ferior maxillary nerve. The tempero-facial 
nerve then breaks up into a number of branches 
which anastomose and form arches, from the 
convexities of which proceed a number of di- 
verging filaments, some of which pass upwards 
and others forwards, emerging from beneath 
the parotid, to be distributed to the muscles of 
the bee, ean 

The cervico-facial division is smaller than 
the preceding ; it takes the same direction as 
the trunk of the nerve, passing downwards 
and forwards in the substance of the parotid ; 
at the angle of the jaw it divides into three or 
four branches ; these subdivide into secondary 
branches, some of which pass forwards to sup- 
ply the muscles of the lower part of the face, 
while others are distributed to the upper part 
of the cervical region. 

Lymphatic glands.—Several lymphatic glands 
are found imbedded in the superficial surface, 
and in the substance of the parotid. These 
may readily be distinguished from -the tissue 
of the parotid by their red colour. They 
are not uncommonly the seat of disease, and 
if their removal becomes necessary the opera- 
tion may be done without much difficulty and 
without great risk of wounding any important 
textures. But a slight consideration of the 
deep connexions of the parotid and of its close 
relations to the many important parts which 

s through it, and by which it is surrounded, 
will be sufficient to convince the surgeon that 
the removal of this gland cannot be effected 
without extreme difficulty and danger, and 


PARTURITION. 


that it must necessarily be attended by injury 

to some of the important in this region. 

The division of the facial nerve, and conse- 

quent palsy of the face, may be looked 

as one of the most serious and certain conse- 

quences of an attempt to excise the parotid. 
( George Johnson. ) 


PARTURITION, MECHANISM OF, 
Parturition is the act in which the matured frait 
of healthy conception and gestation is transmit- 
ted along the passages of the mother. “ Rien 
de plus curieux que le méchanisme par lequelle - 
foetus est expulsé ; tout s’y passe avec une pré- 
Cision admirable,” is the quotation which 
celebrated Naegelé has used for a heading to his — 
essay on this important process in the human 
subject, the first in which it has been completely 
and accurately described. Perhaps in no de- 
partment of physiology do we gain so much 
instruction from comparative anatomy as here; 
when we examine the ovipara, especially the 
higher orders of them, we are struck with the 
simplicity of the parturient process, and with 
the equally simple laws by which it is governed. 
The oval form of the egg shows that its long dia- 
meter must run parallel with the canal through - 
which it has to , and in these classes of 
animals this single law constitutes nearly the 
whole mechanism of parturition in them. 

In the vivipara the process becomes some- 
what more complicated ; the foetus enveloped 
in its soft and fluctuating bag of membrane 
and the more perfect pelvis bring many other 
relations into play which do not exist in the 
lower classes ; hence in the viviparous animals 
we see that the manner in which the feetus 
vances through the passages of the mother 
varies considerably, still however not so much 
as to render it incompatible with the law above 
mentioned. 4 

In considering the process of parturition ii 
the lower classes of animals it will be scarcel: 
necessary to go beyond the Vertebrata, for im 
the lowest classes, especially the zoophyte 
admits of but little comparison with them, 
analogy rather inclining in the contrary dire 
tion, viz. towards the vegetable kingdom. | 
some of the other classes, viz. Vermes, 
little certain is known as to this process beyo 
that the generative organs are of the sim 
tubular character; we must except, ho 
the Insecta, in many of which the ova and | 
mode of their expulsion strongly resemble 
much higher class, viz. the Aves. iy 

The Fishes, which are the lowest class of 
Vertebrata, have no bony canal or pelvis; 
whole apparatus for parturition is a tube 
lower part of which at least is fibrous; im 
larger fishes it is muscular and capable of ¢ 
siderable dilatation. In the Ray and § 
tribe we first see this canal divided int 
parts, viz. the ovary and oviduct; still the’ 
cess is of the simplest character, the ova t 
propelled precisely like the contents of am 
testinal tube. In the viviparous sharks, the Ble 
nius viviparus, and still more remarkably 
the Cetacea, where as belonging to the ¥ 
malia we first see the oviduct divided in 


PARTURITION. | 


tube and uterus, and where the fetus is gene- 
rally so large, the parturient process is equally 
simple, the uterus and vagina being converted 
by gradual dilatation into a simple continuous 
canal. In the higher classes of Reptilia we 
first perceive a regularly formed pelvis, viz. in 
the Sauria, and still more completely in the 
Chelonia, the pelvis in the latter being consi- 
derably advanced in point of developement, 
even as compared with the higher Mammalia ; 
indeed as regards pelvic developement these two 
classes of the Reptilia ought rather to be placed 
above the Aves, in whom, with one exception, 
the pelvis is much more imperfect. The rudi- 
mental trace of a pelvis which is seen in cer- 
tain of the fishes is evidently a modification of 
a scapula, and intended as part of the appa- 
ratus for propulsion, being connected with the 
ventral fin. In the Cetacea this is marked by 
the existence of two small thin flat bones im- 
bedded in muscle on each side the vent. In 
Birds this formation is still more marked, and 
here we first see distinctly the analogy pointed 
out by Meckel between the attachments to the 
trunk of the upper and lower extremities, the 
ilium corresponding to the scapula, the ischium 
to the coracoid process, and the pubic bone 
to the clavicle; the pelvis in them  pre- 
sents the transition from the scapulary bones 


_ of the lower extremities, if we may so call 


them, in some of the fish tribe, to the 
completely formed bony canal of the higher 
Mammalia. The pelvic bones in Birds are 
still subservient to little else than the purposes 
of locomotion, the ossa pubis not uniting in 
front, their points terminating at a considerable 
distance from each other, but connected bya 
ligamentous band which is elastic and capable 
of considerable dilatation ; the process of par- 
turition here is as simple as in the inferior 
classes, the egg passing along the cloaca through 
the half bony, half fibrous canal of the pelvis. 
One solitary instance of a perfect pelvis pre- 
sents itself among the Aves, viz. in the ostrich, 
and where the symphysis pubis does not seem 
capable of much dilatation, although from the 
size of the egg there can be but little room to 
Spare in the pelvis during its expulsion; an 
apparent approach to this formation is occa- 
sionally seen in birds which attain a consider- 
able age from the deposition of bony matter 
into the pubic ligament. An equally solitary 
example of an imperfect pelvis among the 
Mammalia is furnished by the lesser ant-eater, 
the pubic bones not being united. 

The lowest grade of parturition which (ex- 
cepting the Cetacea) is observed in the Mam- 
malia, is seen in certain Insectivora, viz. the 
mole, shrew, &c. in which this process is akin 
to that in those animals which either have no 
= at all, or have them of a very imperfect 

ind. In the mole, &c. the pelvie cavity is 
so small as to be utterly useless for the pur- 
poses of parturition, not even containing the 
rectum, which, together with the vagina, 
passes down in front of the pelvis. In this 
instance, therefore, we have once more a strong 
analogy to parturition in the lower ovipara, es- 


_ pecially as in the above-mentioned animals the 


| 


905 


uterus is still at a low grade of formation, being 
cylindrical and scarcely to be distinguished 
from its Fallopian tube. 

A still further advance towards the perfect 
pelvis is seen in the Guinea-pig, an animal in 


Fig. 487. 


Pelvis of the Guinea Pig at the time of parturition, 
Fig. 488. 


Pelvis of the Guinea Pig 72 hours after parturition. 


906 


which the fetus attains a size utterly incom- 
patible to pass through the small pelvis of the 
mother were it not for the extraordinary elas- 
ticity of the pubic ligament, being capable of 
allowing the ends of the pubic bones to diverge 
from each other to the distance of nearly an 
inch and a half. The capability of the pelvis 
being enlarged by this fos, a depends upon 
the shortness of its transverse, and the great 
length of its antero-posterior or sacro-pubal 
diameter, the ossa innominata running forwards 
from each side of the sacrum ina nearly parallel 
direction, or rather forming an isoskeles triangle, 
its apex at the pubes, its base at the sacrum. 
This greater length of the antero-posterior to 
that of the transverse diameter may be traced 
with few exceptions along the whole chain of 
pelviferous vertebrata until we reach the human 
subject, and even here, until the age of puberty, 
we find a similar relation between these dia- 
meters. This form of pelvis is eminently 
adapted for dilatation during parturition; the 
ossa innominata, moving, as it were, upon a 
hinge at their sacro-iliac synchondroses, are 
capable of a considerable separation at their 
pubic ends, by which means the pelvis is 
greatly enlarged and passage of the fetus much 
facilitated. 

In some animals, as cows, the swelling and 
softening of the ligamento-cartilaginous unions 
is distinctly seen on the approach of labour, 
the lumbar vertebra and sacrum sinking be- 
tween the ilia, and these bones “ slipping,” as 
it is called, over each other at their sacro-iliac 
i tes as the animal moves her hind legs. 

e axis of the pelvis in animals being with 
few exceptions parallel with the spine, and the 
outlet from the formation of the sacrum being 
so large, it will be seen that up to the Rumi- 
nantia the mechanism of parturition is extremely 
simple, the more so as until we reach this class 
the uterus in great measure preserves its tubu- 
lar formation, rendering it next to impossible 
that the foetus should come in any other direc- 
tion than with its long diameter corresponding 
to the axis of the canal through which it has to 


s. 

In the Marsupiata the foetus is expelled at so 
early a stage of developement, and is therefore 
so small, that little or no dilatation of the pelvis 
is required ; in these animals we see the pelvis 
well developed, and the difference between the 
length of the transverse and antero-posterior 
diameters inconsiderable : in them it is probable 
that litle or no separation of the pubic bones 
takes place during parturition. 

In the other and higher classes of the Mam- 
malia the hard and well developed head of the 
foetus and its inflexible limbs, especially in the 
Ruminantia,as also the horse, ass, &c., present 
very considerable obstructions to its passage 
through the pelvis, and require that it should 
take a certain position during labour in order 
that it may be born with such a degree of faci- 
lity and within such a period of time as shall 
not endanger its own life or that of its mother. 

Although the pelvis among the higher Mam- 
malia still presents many remarkable points 
of difference from that of the human race, least 


PARTURITION. 


pothens in the Quadrumana, still on the other 
and the mechanism of parturition in these 
animals resembles in many respects this process 
in man. The embryo has a somewhat similar 
position in the pa as ae ry the human 
subject. In the early periods of pregnancy in 
both cases, the limbs ond off rian the trunk, 
whereas in the latter months they are 

close to the body. The lower extremities or 
hind legs in animals are always turned upon ~ 
the abdomen ; in some instances the knees are 
bent, in others not. 

The arms of the child are crossed upon the 
breast; in animals the forelegs are usually 
placed along the side of the head and generally 
a little below it; it is rare that one or both are 
found above the head, although it has some- 
times occurred that the two forelegs have been 
found crossing each other over the head. The 
forelegs are seldom found bent down under the 
abdomen. 

The embryo usually lies upon its belly, or 
on one side; and from being scarcely ever 
found upon the back it may be presumed that 
this position is very rare.* The head is mostly 
turned towards the os uteri, although cases are 
by no means uncommon, even among the larger 
animals, of its being turned to the fundus uteri. 
In the larger animals (mare, cow, sheep, goat, 
&c.) the embryo at first lies tolerably uncon- 
strained, whereas at a later period it descends — 
into the smaller part of the uterus, and hence at — 
this time we usually find the nose bent down 
upon the breast. In the child this position 
with the chin upon the breast exists from a very 
early period. 1g 

In the smaller animals, viz. the dog, cat, rat, 
&c., the head at the end of pregnancy mostly 
lies flat on the lower jaw, and therefore presents — 
with the nose, whereas in the larger animals — 
the occiput presents, and this probably with- 
draws again as labour comes on. ears 
are always pressed close to the head, being 
turned either forwards or backwards; they are 
usually found bent forwards in the dog, cat, 
and horse, and backwards in the cow, sheep, 
goat, rabbit, hare, &c. 

Although the human foetus usually prese 
also with the head, the whole mechanism of it 
parturition is very different from that of the ani 
mals above-mentioned ; the angles of the pelvi 
axes with the spine and with each other, 
the relative size of the antero-posterior a 
transverse diameters, are so different that ¥ 
find the greater part of the process subservit 
to laws which do not exist in the lower animals 
nevertheless the grand primary law with whic 
we commenced holds equally good in the hu 
man subject as in the lowest ovipara, and uj 
this depends the great distinction betwe 
natural and unnatural presentations; for so lo 
as the long diameter of the child is par 
with the axis of the passage through whi 
comes, the child will present with its cephalk 
or its pelvic extremity, and can be born in that 
position ; whereas if its long diameter does mt 
correspond with that of the axis of the pel 


* Joerg. 


PARTURITION. 


the child lies across and presents with the arm 
or shoulder, a position in which it cannot be 
born. The two first are therefore called natural, 
the last unnatural presentations. In the human 
subject neither the antero-posterior nor the 


_ transverse are the longest, but the oblique dia- 


meters, both of the brim cavity and outlet of 
the pelvis, and it is only in the directions of 
these diameters that the pelvis is of a tolerably 
uniform size throughout. They are named the 
right and left oblique diameters according to 
that sacro-iliac synchondrosis from which they 
are drawn. 

The great peculiarity in the mechanism of 
human parturition is that in either of the natu- 
ral presentations the presenting part enters the 
pelvis obliquely, not only as to the transverse 
diameter, but as to the axis of its brim; it 
passes through the cavity and outlet nearly in 
the same position ; so that it not only takes that 
direction in which the pelvis is most roomy, 
viz. in the oblique diameters, but in which it 
will itself occupy the least possible space. 
Having stated this law, it will now be neces- 
sary to describe these presentations of the child 
in illustration of it. 

The cephalic end of the child may present 
in two ways, either with the head or the face; 
the former is by far the most common; it is also 
the most favourable for mother and child, and 
at one time was looked upon as the only natu- 
ral and favourable presentation. The head 
presents either with the right or left parietal 
protuberance, the sagittal suture running pa- 
rallel with the right or left oblique diameters, 
and in both cases, at the beginning of labour, 
crossing the os uteri. 

These three facts at once confirm the law 
above mentioned, viz. that the head enters the 
pelvis obliquely both as to its long and perpen- 
dicular diameters, or, as before expressed, ob- 
liquely as to the transverse diameter and axis 
of the brim; for if (as is well known to be the 
case) the os uteri at the beginning of labour is 
Situated at the upper part of the hollow of the 
sacrum, the vertex of the head will be turned 
towards this part of the pelvis, and the parietal 
protuberance being that part which is lowest 
and in the centre of the pelvis, it follows that 
the perpendicular diameter of the head will 
run obliquely upwards and forwards with the 
axis of the brim. 

The first position, viz. where the right pa- 
rietal protuberance -presents, and the sagittal 
suture corresponds to the right oblique diameter 
of the pelvis, is known by the posterior or 
small fontanelle being felt in the vicinity of the 
left foramen ovale, the anterior or large fonta- 
nelle in the opposite direction near the right 
sacro-iliac synchondrosis: this has been called 
the first position from occurring more frequently 
than the other, viz. in the proportion of five 
to two. As the head approaches the pelvic 
outlet, the occiput turns somewhat more for- 


wards, so that instead of the protuberance, the 


posterior and superior quarter of the right pa- 


_ rietal bone presents: this is the part of the 
__ head which the finger at this period of labour 
_ first touches upon during examination, which 


907 


first passes under the pubic arch, and first dis- 
tends the os externum ; the position of the 
head is nevertheless still oblique, for the right 
branch of the lambdoidal suture will be felt 
parallel with the left descending ramus of the 
pubic arch. In still further proof of what has 
now been stated, we may mention, that if the 
head be some time in its passage through the 
vagina, it becomes so tightly encircled by it as 
to produce a considerable obstruction to the 
circulation in the scalp ; hence we shall feel a 
tumefaction of the cranial integuments on that 
part of it which presents. On examining, 
therefore, the head of a new-born child which 
has presented in the first position, it has a cir- 
cular swelling of the scalp situated upon the 
posterior and superior quarter of the right pa- 
rietal bone. This is the caput succedaneum, 
the Vorkopf of the German authors, and, as 
was pointed out by the late Professor Chaussier 
of Paris, is a distinct evidence of the manner 
in which the child has presented during labour. 
The shoulders enter the pelvis in the contrary 
oblique diameter to what the head does, so that 
if the head in the first position has passed 
through with its long diameter corresponding 
to the right oblique diameter of the pelvis, the 
shoulders will be found in the left oblique dia- 
meter—from this circumstance, after the head 
is born, the face is turned backwards and to 
the right. 

The second position of the head is the reverse 
of the first. The left parietal protuberance 
presents. During the descent of the head 
through the brim into the cavity of the pelvis, 
the sagittal suture is in the right oblique dia- 
meter as in the first position, only now the 
posterior fontanelle is directed towards the right 
sacro-iliac symphysis, the anterior one to the 
left foramen ovale. The head descends in this 
position until it approaches the pelvic outlet, 
when it makes the quarter of a turn and passes 
from the right into the left oblique diameter, 
the anterior fontanelle now corresponding to 
the left sacro-iliac symphysis, the posterior one 
to the right foramen ovale. As the head enters 
the vagina and begins to pass under the pubic 
arch, it is the posterior and superior quarter of 
the left parietal bone which now presents, and 
upon which the puffy swelling of the scalp is 
situated ; as in the first position it was the right 
lambdoidal suture which corresponded to the 
left branch of the pubic arch, so here it is the 
reverse, the left lambdoidal suture at this moment 
will be found parallel with the right branch of 
the pubic arch ; in like manner, the face when 
born turns backwards and to the left. This 
change in the position of the head from one ob- 
lique diameter to the other is not peculiar to the 
second position, for we meet with it occa- 
sionally in the first, the anterior fontanelle being 
turned to the right foramen ovale, the posterior 
one towards the left sacro-iliac synchondrosis, 
the change in this case usually taking place at 
a much earlier period of labour than in the se- 
cond position, whether it is owing to the posi- 
tion of the rectum or not is difficult to say. 
The uniformity with which this change occurs 
in the position of the head from one oblique 


908 


diameter to the other was first pointed out by 
Professor Naegelé, of Heidelberg, and must 
be looked upon as a fact of great importance in 
the mechanism of parturition, second only to 
the discovery of the oblique position of the 
head by Solayres de Renhac and Matthias 
Saxtorph in 1771. Sometimes the head does 
not make the change above mentioned, but 
comes out with the forehead more or less for- 
wards, the swelling of the cranial integuments 
being situated on the right or left frontal bone. 

The face, like the head, may present in two 
ways, either with the right or the left side fore- 
most. As in the head presentations the sagittal 
suture crosses the os uteri, so in the present 
instance is this the case with the ridge of the 
nose. 

In that position which is of most frequent 
occurrence the chin is turned to the right side 
of the pelvis, the right eye and zygoma being 
lowest and in the middle of the pelvis ; this, 
therefore, shows that the face, like the head, 
comes obliquely not only as to the transverse 
diameter of the pelvis, but also as to the axis 
of its brim. The ridge of the nose is not only 
the part of the face which we first are able to 
distinguish when the os uteri is but slightly di- 
lated, but from its conducting the finger in one 
direction to the soft cushiony end of the nose, 
and in the other to the broad hard expanse of 
the forehead, it furnishes us with an excellent 
means of ascertaining not only that the face 
presents, but in what position. 

As the os uteri dilates and the face advances, 
the chin turns towards the right foramen ovale, 
so that by the time it has entered the vagina, it 
is no longer the right eye and zygoma which 
form the presenting part, but the right cheek, 
this being now the part which the finger first 
touches upon during examination, precisely as 
in the first position of the head, it is the su- 
aioe and posterior quarter of the right parietal 

ne; so, in like manner, it is this part of the 
face upon which the bruise-like swelling is 
situated, which it brings with it into the world. 
It would seem that there is a considerable ana- 
logy between the first position of the head and 
that of the face, and that the one can probably 
pass into the other ; in both the right side pre- 
sents, and if the head in this position swings 
round upon its transverse diameter, it becomes 
the first position of the face. 

The other or second position of the face is 
merely the reverse of the first. The left eye 
and zygoma present at the beginning of labour ; 
and as the chin, which is turned more or less 
to the left, moves somewhat forwards, it be- 
comes the left cheek which first passes through 
the os externum, and upon which the swelling 
of the face is situated. 

According to the best averages, we may state 
that face presentations occur about once in 290 
Jabours, and from the observations of Professor 
Naegelé, jun., the proportion of the second po- 
sition to the first is as 1.29 to 1. Beyond 
being now and then a little more tedious, la- 
bours where the face presents are not more un- 
favourable for the mother than where the head 
presents ; for the child, however, they are not 


PARTURITION. 


so favourable; the re upon the neck 
duces considerable baer crore which 
now and then proves fatal. : 

The lower part or pelvic extremity of the 
trunk may present with the nates, eg B= a 
the feet; but as the former are by far the most 
bulky, we may bring them under the general 
head of nates presentations. In this case the 
child may present with the back or abdomen 
forwards, in either of which the transverse dia- 
meter of its pelvis rans obliquely, that ischium, 
which is turned forwards, being lowest in the 
pelvis. The position with the back of the child 
more or less forwards is the most common, 
being in the proportion of 3 to 1 of the other — 
position. The presenting ischium advances — 
through the os externum; the abdomen “and — 
chest follow ; and the arms, which are crossed 
upon the breast, are usually born at the same 
moment. The shoulders follow in the same — 
direction, that shoulder being first expelled — 
which is turned more or less forwards. The — 
head, with the chin pressed upon the breast, — 
enters the pelvis in the opposite oblique dia- 
meter to what the shoulders did; and while 
the occiput rests against the symphysis pubis, 
the chin, followed by the rest of the face and — 
forehead, sweep over the perineum as the head 
turns upon its transverse diameter from below 
upwards. Sometimes, although rarely, the 
chin is not depressed upon the breast, but the 
head enters the pelvis in a contrary direction, 
viz. with the occiput pressed into the nape ¢ 
the neck, the face turned upwards, and is bor 
in this position. Where the abdomen of thi 
child is turned forwards, it almost invarial 
turns more or less backwards during the pro 
gress of the labour, either shortly after the 
nates are expelled, or as the thorax is advanei 
through the pelvic outlet. . 

In all these presentations, the process of I; 
bour appears to resemble, as far as possibl 
that in the lower classes of animals. ‘The fi 
stage is employed in attaining two importan 
objects ; firstly, in giving the child a natu 
position, viz. with its long axis parallel 1 
that of the passage through which it has to co 
and in so dilating the os uteri that the whole 
it shall disappear, the uterus and vagina formi 
one continuous canal, exactly resembling, as 
as the mechanism of the expulsion is concern 
the same process in the lower animals. 

As far as we know, it is only in the hun 
subject where it is possible for the foetus 
present across, or where its long axis does: 
correspond with that of the passage ; in this¢ 
it presents with the arm or shoulder, and ¢ 
not be born in this position. This unnat 
presentation chiefly arises from the contract 
of the uterus in the first stage being more or 
perverted or obstructed by certain causes; t 
if the uterus be much distended with lit 
amnii, the slight Parente contractions ai 
commencement of labour will have little ort 
effect in keeping the fetus with its long @ 
parallel with that of the uterus, for the sides” 
the uterus are now too far separated to act @ 
it, and as the uterus from its distention 
proaches to the globular form, the child will 


PENIS. 


just as well in one direction as in another. 
Moreover, when the uterus has been subject to 
irregular spasmodic contractions during the last 
week or two of pregnancy, by which its form 
is more or less altered, we frequently find that 
when labour comes on the child presents with 
the arm or shoulder. It is chiefly to this cause 
that we must attribute those remarkable cases 
which every now and then occur of the arm or 
shoulder presenting in four or five successive 
labours in the same individual, a fact which 
was first pointed out by Professor Naegelé, sen. 
The full-grown living foetus can, therefore, pre- 
sent in only three ways, viz. with the head or 
face, with the nates or inferior extremities, and 
with the arm or shoulder. When other parts 
of the child present, it arises either from its 
having been some time dead in utero or from 
being premature. 
(Edward Rigby.) 


PELVIS.—See SuprpLemeEnt. 


PENIS.—( Membrum virile ; Gree. cevpesoy 
edovov; Germ. das Glied, or die Ruthe; 
Fran. verge ; Ital. membro virile.) 

The term penis would appear from its deri- 
vation (a pendendo) to have been the popular 
designation of the male organ of man and of 
the higher animals among the Roman people. 
Like many other terms that we have received 
from our predecessors, the present has reference 
to a merely visual character of the organ in a 
small group of animals, irrespective of the 
important office which it is intended to fulfil in 
the general animal economy. At the present 
day, however, with a more enlarged scale of 
information with regard to the laws and attributes 
of living beings, while we retain the name, we 
assign to it a more comprehensive definition than 
its original application was intended to convey. 

The penis, throughout the animal kingdom, 
is the organ of transmission of the male fluid 
to the germinal product of the female sexual 
apparatus; and in the mammiferous class it 
performs the additional office of efferent duct 
to the urinary secretion. In consideration of 
its more obvious purpose, the penis has been 
termed the organ of intromission; but this 
appellation, though correct in general, is incor- 
rect in particular instances, for there are many 
among the inferior animals in which a rudi- 
mentary penis exists, but no intromission can 
possibly occur. 

As generation divides its claim with nutrition 
in the lowest animal organisms, we are natu- 
rally led to the expectation of finding the repre- 
sentative of this organ among the lowest divisions 
_ of the animal scale, and this expectation is 
realized by research. In proceeding to this 
_ investigation, however, it cannot too strongly 
_ be impressed upon the mind, that in the lowest 

even as in the highest, modifications do occur 
which are conformable to the wants or conve- 
nience of the animals in whom they are found, 
without reference to any supposed gradation of 
developement or improvement. Thus in Infu- 
_soria a sexual apparatus consisting of ovary, 
testis, and vesicule seminales, has been de- 


909 


scribed by Ehrenberg; and in Rotifera the 
same author has observed a contractile organ 
which serves to impel the seminal fluid into 
the oviduct. Here, then, almost on the boun- 
dary line of the animal world, is a self-impreg- 
nating animal, provided with a distinct trans- 
mittent organ by which impregnation is effected. 
But remarkable as this conformation may appear 
at first sight, examples equally wonderful 
become multiplied as we proceed onwards in 
our enquiry. 

Bory St. Vincent has pointed out the existence 
of an intromittent spiculum in the Vinegar Eel 
(anguillula aceti), one of the Vibrionide; and 
Ehrenberg has observed a similar structure in 
another species, the Anguillula fluviatilis. 
Among the Cestoid Entozoa, which are andro- 
gynous, a distinct intromittent organ is found 
in Ligula and Tenia solium. In Trematoda, 
which are likewise androgynous, but impregnate 
by mutual ‘concurrence, a penis is also met 
with, and is of considerable size. In Acantho- 
cephala, the large intromittent organ of Echi- 
norynchus gigas, the entozoon of the kidney, 
has been described by Cloquet; and in Nema- 
toidea the penis has attained a size and impor- 
tance which renders it a generic character. 
Thus the genus Filaria is distinguished from 
Trichoceplalus by a difference in form of the 
preputial covering, and a similar character 
distinguishes Ascaris from both the preceding. 
Most of the smaller species of Ascaris are 
remarkable, from possessing a double intro- 
maittent organ, and a similar conformation is 
met with in Linguatula, the entozoon of the 
frontal sinuses of the canine race; in Cucul- 
lanus, and in Syngamus trachealis, the tracheal 
parasite of gallinaceous birds. 

Proceeding a step higher in the ai-imal scale 
we find in the class Annelida that the organs 
of generation are hermaphrodite, and so dis- 
posed as to admit of mutual impregnation. 
In some genera the penis is well developed 
and distinct, as in Planaria and Hirudo; but 
in others the mutual apposition of the sexes is 
so perfect as to render an intromittent organ 
unnecessary. On this principle the penis is 
absent in the Earth-worm. In the Leech the 
penis is long and slender, placed on the twenty- 
fourth segment of the body, while the vulva 
occupies the twenty-ninth. 

In Cirrhopoda, the barnacles or-acorns of the 
sea, the intromittent organ is well developed, 
and from the mode of existence of these animals 
and their hermaphrodite organization, may be 
employed as a means of self or of reciprocal 
impregnation. 

The class Crustacea is composed of animals 
which are dicecious in their sexual organization, 
and whose males are provided with a distinct 
intromittent organ. In the lowest groups, 
namely, the Entomostracous Lernez, the penis 
is double; and in Decapoda and Brachiura it 
is temporary and formed by an eversion of the 
vas deferens, an adaptation of means to an end 
that we shall find repeated among the lower 
classes of Vertebrata. Throughout the whole 
of this class impregnation is effected by reci- 
procal union. 


910 


The class Insecta is dicecious, and an intro- 
mittent organ is a common character throughout 
the entire race. In some insects, as in Aphis, 
the penis is double, and in the greater number 
it is associated with special organs, termed 

which assist in the impregnating act. 
greater number of molluscous animals are 
inhabitants of the deep, and amongst them 
considerable diversity, as respects mode of 
generation, exists. athe are hermaphrodite 
in organisation, and self impregnating ; others 
are hermaphrodite and mutually impregnating ; 
a considerable proportion are diccious, the 
male and female apparatus being on different 
individuals, and the impregnating fluid being 
conveyed by the medium in which they live 
from the male to the female animal; while 
some few are diecious and impregnate by 
mutual concurrence. The air-breathers, or 
Pulmonary Mollusca, are all hermaphrodite 
and impregnate by reciprocal coitus. e two 
last alone of the preceding modes of impregna- 
tion are those in which a true intromittent organ 
is required; hence, although rudiments of a 
nis may be discovered in many Mollusca, it 
is only in the mutually impregnating herma- 
phrodites and in the concurring diccia that it 
attains a size sufficiently bulky to render it an 
important character. Thus in the class Tuni- 
cata, which for the most part comprises self- 
impregnating hermaphrodites, no intromittent 
organ has been described. In the inhabitants 
of bivalve shells, which are either self-impreg- 
nating hermaphrodites, as the Oyster, or medi- 
ately impregnating diccia, as the fresh-water 
Mussel, Anodonta, there is no penis. The 
marine Gasteropoda are diccious; some, as 
the Patella, impregnating their females through 
the medium of the sea water by which they 
are surrounded, and others, including the whole 
of the Pectinibranchiata, impregnating imme- 
diately, being provided with a large penis for 
that purpose. In the genus Trochus the vas 
deferens terminates at the root of the penis, 
and the latter is grooved ; and in Carniaria the 
intromittent organ is bifid as well as grooved. 
In the Pulmonary Gasteropoda, as the snails 
and slugs, the generative organization is her- 
maphrodite, impregnation being reciprocal, and 
the penis of very large size. Among En- 
cephalous Mollusca, as in Pteropoda, the orga- 
nisation is also hermaphrodite, and the penis 
of large size. In Cephalopoda, the highest 
class of molluscous animals, the generative 
structure is diccious, but the penis is not 
intromittent. The penis in Sepia and Octapus 
is short and rudimentary, and pierced by a 
canal for the transmission of the seminal se- 
cretion ; but in the hooked Calamary the organ 
is simply grooved along its under part. 

In passing from the higher invertebrata to 
the class of Fishes we meet with a degradation 
of organization as regards the generative system. 
The penis, which we have seen to be properly 
formed for intromission in several of the inver- 
tebrate classes, is reduced to a mere papilla 
on the surface of the cloaca in fishes. In the 
Viviparous Blenny, however, in which internal 
impregnation takes place, the penis is larger in 


PENIS. 


size, and is probably increased in length duri 
coitus by eversion of the mucous lining of the 
vas deferens. In some of the higher — 
nous Fishes it is interesting to remark that 
rudimentary state of the penis is compensated 
for by the developement of an apparatus which __ 
seems intended to secure the contact of the 
cloace for an appreciable time. This apparatus 
consists of a pair of clasping organs, a provi- 
sion to which we have already had occasion to 
advert when speaking of the generative organs 
of insects. 

In Amphibia, as in Fishes, impregnation is — 
efiected by means of a close approximation, 
and in most instances by contact of the cloaca. 
There is no penis, but as a substitute for this 
organ the male animal is of an orga- — 
nisation fitted to maintain an embrace for a 
considerable period. 

The penis of the Ophidian group of 
is a true intromittent organ, and rema' 
the peculiarity of its structure. It consists of — 
two cecal processes, developed from the cloaca 
at its posterior part, and extending back into a 
cavity prolonged for a short distance towards 
the tail. These cceca are lined by a horny pa- 
pillated epithelium; they are invested wal 
moderately thick layer of erectile tissue, and 
have oof muscles attached to their extre- 
mity. When the animal is excited by the vene- 
real orgasm the turgescence of the erectile tissue 
causes the eversion of the ceca and their pro- 
trusion through the aperture of the clo 
Restored to the state of repose, ey oo, e 
tracted by their muscles, and drawn into. 
their original position. In the Rattlesnake a 
singular modification of the intromittent orga 
occurs, in the bifid termination of each of 
ceca. We cannot view the peculiarity of strue- 
ture exhibited by Ophidia, without recalling t 
mind the similarly inverted disposition of the 
intromittent organ, which we have already seer 
among the Invertebrata, namely, in Arachnida 

The Lacertine Sauria are possessed of an in 
verted intromittent organ, similar to that o 
Ophidia. In the Crocodile, however, the penis 
is no longer an inverted cecal pouch; it | 
grooved along its under part, attached by tw 
crura to the pubic bones, and furnished with 
rudimentary glans at its extremity. But ev 
in the Crocodile there exists a peculiari 
structure which allies the family with the ] 
tine Sauria and Ophidia. The structure 
which I allude, is a canal which is pre 
from the peritoneal cavity for a short dista 
into the substance of the penis, and 
minates by a cecal extremity. ¥ 

In Chelonia, the same kind of intromit 
organ occurs as is found in Crocodiles,a groa 
penis contained within the vestibule of 
cloaca, attached to the pubic bones, ai 
lowed by one or more peritoneal canals. 


iles 
pak 


it 
a 


important difference, however, is met with 
we compare the two groups of Chelonia, 
marine and the land tortoises. In the form 
scarcely any obstruction to impregnation res 
from the covering of the animal; the penis 
consequently small. But in the land torto 
where the shell extends beyond the limit 


= 
i) 


PENIS. 


soft parts and acts as an obstacle to intromis- 
sion, the penis is remarkable for its size and 
length. 

Among Birds, the penis is rudimentary in a 
great proportion of the class. In aquatic birds, 
however, it is large and constructed on the 
same principle as the penis of serpents, so as to 
be capable of eversion. In the order Anseres, 
the intromittent organ is remarkable for its 
length, and is furnished with a groove which 
runs spirally around its axis. In terrestrial 
birds, the penis is large and grooved, and pro- 
vided with a ligament of elastic tissue, which 
effects its retraction. 

Throughout the whole class of Mammifera, 
the existence of an intromittent organ, furnished 
with an urethral canal, is a common character. 
In Monotremata, the penis is not conspicuous 
externally, but is contained in a sheath distinct 
from the cloaca, and protrudes through the 
latter under the influence of excitation. In 
this order, moreover, we meet with the inte- 
resting condition of an urethral canal, which is 
intended solely for the purpose of transmitting 
the seminal secretion, while the urine passes 
away by the cloaca. In Marsupiata, the penis, 
which is of large size, is also situated in the in- 
terior of the animal in a sheath contiguous to 
the cloaca, but it passes through the latter when 
in astate of erection. Among Rodentia, the most 
remarkable character of the intromittent organ 
is the presence of recurved spines upon the glans 
penis ; this apparatus reminds us of the clasp- 
ing organs seen in insects and in the higher 
cartilaginous fishes, and is obviously intended 
te fulfil a similar function. The order Edentata 
affords two opposite conditions of the intro- 
mittent organ in relation to. size; these condi- 
tions having reference, as in Chelonia, to the 
convenience of the animals. Thus in the Bra- 
dypus or Sloth, the penis is rudimentary, while 
in the Armadillo the organ is exceedingly large. 
In Cetacea, which from the nature of the me- 
dium in which they live, are subject to impedi- 
ment in the impregnating act, the penisis enor- 
mous. In Ruminantia and Pachydermata the 
organ is of large size, and presents but little 
variety of form. In some genera it is more or 
less curved, while in the state of repose; in 
others it is straight. The intromittent organ in 
Carnivora is rendered remarkable by the pre- 
sence of a bone, the os penis, which is more or 
less developed in different genera. Thus in 
Plantigrade Carnivora it is of large size, while 
in the feline race it is cartilaginous and rudi- 
mentary. 

In all the orders of Mammifera hitherto ex- 
amined, the penis is contained either within a 
sheath in the interior of the body, as occurs in 
Monotremata, Marsupiata, and Cetacea, or in 


_ a sheath of the integument upon the exterior. 


But in Quadrumana, the transition class to 
man, the sheath of integument no longer exists, 
and the organ hangs pendent from its attach- 
ment. The os penis still remains to identify 
the quadrumanous race with the inferior classes, 
but in the higher genera, the Chimpanzée and 
_ Orang, even this character of inferior organisa- 


911 


tion is lost. Mayer," it is true, has declared 
the existence of a small cartilage, of a prismoid 
form, and about a line or a line and a half in 
length, in man. This he regards as the homologue 
of the os penis in inferior animals. It is 
situated, he says, in the submucous tissue of 
the upper part of the urethra within the glans 
penis ; but he finds it only in strong and pow- 
erful men. Should this observation be con- 
firmed by succeeding research, we ought to be 
able to find such a structure, even more consi- 
derable in its development, in the Chimpanzée. 
For my own part, 1 am unable to corroborate 
Mayer’s discovery, having failed in numerous 
examinations of the human organ instituted for 
the purpose of finding it. 

Having thus briefly reviewed the animal 
kingdom in relation to the existence of an 
organ of transmission for the reproductive secre- 
tion of the male, and having determined the 
conditions under which that organ is developed 
and its modifications produced, we may in the 
next place proceed to consider the conformation 
and structure of the penis, taking as the proper 
standard of comparison the intromittent organ 
of man, 

The penis of man is situated at the lower 
part of the abdomen, below and in front of the 
symphysis pubis, and presents some difference 
in character, accordant with its state of excite- 
ment or repose. In the latter condition it is 
cylindrical in form and hangs loosely in front 
of the scrotum; in the former, its shape is 
prismoid, with rounded edges and slightly 
grooved along the sides, one facet of the prism 
broader than the other two forming the upper 
surface or dorsum of the organ, and a rounded 
angle the inferior border. Moreover, in the 
state of repose, the organ makes a sudden curve 
in front of the pubis, the concavity of the bend 
looking downwards; while in the state of erec- 
tion it is directed upwards, and forms a gentle 
curve towards the parietes of the abdomen. 

For convenience of description and refer- 
ence, we are wont to consider the penis as 
divisible into a middle portion or body; the 
upper surface of the body being called the 
dorsum, a free and rounded extremity the glans, 
and a root or attached extremity by which it is 
connected with the ramus of the ischium at 
each side. The length and bulk of the organ 
vary with the conditions of erection and repose, 
and also with the individual. 

The anatomical constituents of the penis 
are, the integument and subcutaneous areolar 
tissue, with the fascia penis ; two bodies proper 
to this organ, the corpus cavernosum and cor- 
pus spongiosum, mucous membrane, muscles, 
vessels, and nerves. 

The tntegument of the penis is remarkable 
for the thinness and fineness of its texture, its 
exceeding elasticity, and generally for a deeper 
tint of colour than that of the surrounding skin. 
The tenuity of the skin is equal to that of the 
eyelids, but is exceeded by the integument of 
the scrotum, and contrasts very strongly with 


sg Froriep’s Notizen, No. 883, 


912 


the thick and dense dermis of the neighbouring 
of the abdomen and thighs. Its colour 
1s brown, but varies in its d in different 
individuals, being darker in those of a dark 
complexion, and little differing from the skin 
of the rest of the body in persons of an oppo- 
site character. As in other parts of the body, 
it is well provided with sebaceous glands, but 
these are more numerous in that portion which 
invests the under part of the organ than in the 
dorsal region. Near to the free extremity of 
the penis the integument forms an ample fold, 
the fore-skin or prepuce (preputium ), which 
Serves to envelope the glans when the organ 
is in repose, and to increase the investing co- 
vering when it is distended and enlarged. The 
prepuce is connected to the glans on its under 
part by means of a narrow fold termed the 
Jrenum preputii, and is lined by mucous 
membrane. Along the edge of the prepuce 
the mucous membrane is continuous with the 
skin of the penis; at the base of the prepuce 
it is reflected over the glans, and at the summit 
of the latter is continuous with the mucous 
membrane of the urethra through the meatus 
urinarius. Upon the under part of the glans 
the mucous membrane enclosing some fibrous 
tissue constitutes the narrow fold above de- 
scribed, the frenum preputii. At the base 
of the body of the penis, the integument is 
continuous with that of adjoining parts, with 
the skin of the pubes superiorly, and of the 
scrotum laterally and beneath. In this situa- 
tion, moreover, it is altered in its characters ; 
it is thicker in its texture and furnished with 
numerous hairs. The latter differ from the 
hairs of the pubes in taking the direction of 
the axis of the penis, and in being, unlike the 
former, perfectly straight. Along the inferior 
border of the penis the integument presents a 
somewhat prominent line, which is continuous 
with the raphé of the scrotum behind and with 
the freenum of the prepuce in front. This is 
the raphé of the penis, and indicates the mode 
of formation of the urethra, by the conjunction 
of two lateral segments on the middle line. 
The subcutaneous areolar tissue connecting the 
integument to the body of the penis is extremely 
lax, and wholly devoid of adipose formation. 
The laxity of this tissue has the effect of per- 
mitting an enormous increase of size in the 
organ without inconvenience ; thus in the state 
of repose the prepuce usually covers the glans 
either partially or completely, and protects the 
mucous membrane from the attrition of dress ; 
but in the state of erection this duplication is 
wholly effaced, and the integument rendered 
tense over the entire organ. In large hernie 
and in very large tumours of the scrotum again, 
the integument, from its extreme looseness of 
attachment, is withdrawn from the penis, and 
contributes to the investment of the swelling. 
In this way the whole of the integument is 
sometimes distended with the tumour, and the 
penis lies buried in the enlargement ; its situa- 
tion being only distinguishable by means of a 
valvular opening, through which the urine 
trickles. Like all loose cellular tissue which 


PENIS. 


is indisposed to the production of fat, the cel- 
lular tissue of the penis, in a state of inflam- 
mation, is icularly liable to serous in- — 
filtration, which renders the organ swollen — 
and cedematous. | sar <n 
The fascia penis is a thin but deuse layer — 
of white fibrous tissue, which immediately in- 
vests the penis, forming for it a kind of sheath, 
and is continuous with the superficial perineal 
fascia. On the dorsum penis the fascia covers 
in the dorsal vessels and nerves, and is closely — 
connected with the aponeurosis of the erectores — 
penis muscles ; indeed it is rendered tense and 
stretched over the organ by the action of those 
muscles. ine 
The corpus cavernosum forms more than two- 
thirds of the bulk of the penis; it is usually 
described as two distinct bodies under the — 
name of corpora cavernosa, but it is more cor-_ 
rect to consider it as a single organ divided 
posteriorly into two parts, and separated in the 
interior by an imperfect partition. Apart from 
the other components of the penis the corpus 
cavernosum represents a lengthened cylind 
somewhat flattened from above downwards 
and grooved along the middle line both up 
its upper and under surface; the upper groove 
lodging the dorsal vein, arteries and nerves, 
and the under the corpus spongiosum. - 
riorly the corpus cavernosum terminates in an 
oblong and rounded extremity, which is re- 
ceived into a depression on the posterior surfac 
of the glans; and posteriorly it divides into 
two rounded and conical processes, about t 
inches in length, which se e from eac 
other and are firmly in into the ever 
edge of the ramus of the ischium and pubi 
under the name of crura penis. _. 
The corpus cavernosum is closely connectet 
to the glans penis and corpus spongiosum 
dense coulet aatee and ra a few vessels 
communication. Behind and inferiorly it 3 
attached to the rami of the ischia by its ts 
crura; and above it is connected to the syt 
physis pubis by means of a strong fibrous lis 
ment of a triangular form, the ligaments 
suspensorium penis. This ligament is insert 
by one border into the fibrous structure cov: 
ing the symphysis pubis, and by its base 
continuous with the aponeurosis of the erec 
penis muscles and with the fascia penis; 
remaining border being free and directed 
wards. In a few rare instances the ligament 
suspensorium penis has been found to cont 
some muscular fibres. ofl 
The corpus cavernosum is composed ‘ 
cellular structure enclosed in a thick fib 
tunic of great strength. The tunic is 
structed of longitudinal fibres closely im 
woven with each other so as to consti 
tissue which possesses perfect elasticity 
sii freely to distension up to a certain 
ut resists enlargement beyond that limit. 
the interior of this tunic are given off a nun 
of fibrous bands and cords ( trabecule ) whi 
in a radiated direction from the mid 
ine of its inferior wall to the rest of the. 
ternal circumference of the cylinder, to wh 


PENIS. 


they are firmly attached. The trabecule are 
most abundant in the middle line of the 
organ, where they are extended in a vertical 
direction from the middle line of the infe- 
rior to the middle line of the superior wall, 
forming a partial septum between the two 
lateral halves of the corpus cavernosum. The 
median partition is most complete posteriorly ; 
in front it is very deficient, and being com- 
posed of parallel tibrous cords, between which 
the cellular structure of the two sides of the 
organ communicate, has given rise to the idea 
from which it received its name of septum 
pectiniforme. The fibrous cords of the corpus 
cavernosum serve, by means of their attachment 
to every point of the interior of its fibrous 
tunic, to equalise the pressure of the circula- 
tion during erection, and prevent the undue 
distention of its walls. The fibrous tunic is 
variable in degree of thickness in different 
parts of its extent; thus it is thin upon the 
crura penis, and is thin also in the situation of 
the inferior groove and at its extremity; in the 
two latter situations it is pierced by several 
vessels which communicate with those of the 
corpus spongiosum and glans penis. 

fhe cellular structure of the corpus caver- 
nosum is composed of a plexus of dilated 
veins, which communicate with each other so 
freely as to represent, when divided by a sec- 
tion, a perfect network of cells separated from 
each other by membranous parietes. The aree 
of these venous cells are smallest near the cir- 
cumference of the corpus cavernosum, where 
they are separated by a greater thickness of 
parietes, and greatest in the centre of each la- 
teral half, where the intervening septa are thin 
and membranous. The veins are lined in their 
interior by a continuation of the common in- 
ternal coat of the veins, and the interspaces be- 
tween them are occupied by contractile fibrous 
tissue. The contractile fibrous tissue is dis- 
posed in parallel fibres separated to unequal 
distances by common areolar tissue ; it is most 
abundant in the thicker parietes of the veins of 
the circumference of the corpus cavernosum, 
and is diminished to two or three fibres in the 
thinner walls of the central veins. The fibres 
are straight in their direction, and arranged 
transversely with regard to the cylinder of the 
corpus cavernosum. Upon meeting the cy- 
linder of a vein in their course they diverge 
at an acute angle, and continue their straight 
direction until again obstructed by another 
vein, when they again separate without exhi- 
biting any tendency to converge and enclose 
the vein. At the point of divergence they are 
crossed by other fibres at the same angle, but 
coming in a different direction, so that the 
parietes between each vein are formed by nu- 
merous fibres of this tissue, crossing each other 
at the angles of interstice between three or four 
veins, but straight and parallel between every 
two contiguous veins. The contractile fibrous 
tissue is remarkably abundant in the horse, 
where, from the redness of its hue, it resembles 
muscular substance; in man it is not abun- 
dant but very distinct, and in some situations 
I was enabled to detect it encircling the cylin- 

VOL, III. 


913 


ders of the veins, and forming as it were an 
additional coat to those vessels. 

The contractile fibrous tissue of the corpus 
cavernosum has been made the subject of con- 
troversy between several of the physiologists 
of Germany, on account of its resemblance to 
muscular substance and the absence of other 
attributes of muscular fibre. It is described 
by Miller in the 48th number of the Medici- 
nische Zeitung des Vereins fiir Heilkunde in 
Preussen, as a peculiar, red, fibrous substance, 
and in the Archiv for 1835* he speaks of it as 
a “substance having a fleshy muscular appear- 
ance, of a pale red colour in the penis of the 
horse, and also in the dog and man. . It forms 
an irregular network of columns (Balken) dis- 
tantly resembling the network and trabecular 
structure of the muscular columns of the 
heart.” His next inquiry was to determine the 
nature of this substance. ‘To decide,” he 
says, “whether a reddish fibrous tissue be 
muscular or otherwise, there are three modes,— 
the microscope, chemical re-agents, and expe- 
riment on the living body. In vivisection of 
the horse, dog, and ram, I saw no contraction 
of this substance under the influence of the 
galvanic current. The results of microscopic 
investigation in the horse are unfavourable to 
the opinion that it is muscular, for the fasci- 
culi present no indication of the characteristic 
transverse strie of muscular fibre, for although 
the transverse strie be indistinct on the mus- 
cular fasciculi of organic life, they nevertheless 
exist. In stating the results of chemical in- 
vestigation, I must remark that I speak solely 
of this peculiar substance as examined in the 
horse, and not of that of any other animal or 
ofman. To render these experiments accurate 
and certain, it is necessary to remove from the 
tissue every particle of tendinous fibre which 
may pervade it, for this, as we shall perceive, 
has a very different chemical composition. In 
chemical characters, the substanice under con- 
sideration does not belong to those tissues which 
afford gelatine by boiling, as is the case with 
tendinous, cartilaginous, and cellular tissue; 
for, after seven hours’ boiling, I was unable to 
extract from the pure tissue, separated from all 
foreign substances, the slightest trace of gela- 
tine. By boiling we obtain a substance preci- 
pitable by infusion of galls, which does not 
gelatinize, but gives off.a powerful odour of 
osmazome. It agrees with muscular fibre and 
fibrine in being precipitated from a solution in 
acetic acid by ferro-cyanate of potash, and 
differs in this respect from the class to which 
cellular tissue, tendinous tissue, and elastic 
tissue belong, for these are not invariably pre- 
cipitable from a solution in acetic acid by ferro- 
cyanate of potash. It would, however, be 
incorrect to deduce the conclusion that this 
tissue must therefore be muscular, for there 
exists an entire class of substances whose solu- 
tion in acetic acid is precipitable by ferro- 
cyanate of potash, such as albumen, fibrine, 
muscular tissue, and corneous tissue.” 


* Page 28, in his report for the preceding year, 
in reply to a misapprehension on the part of 
Krause. 

3.N 


914 


Krause,* having recourse to the chemical in- 
vestigation of this substance in man, came to a 
very different conclusion from that of Miiller. 
“* After many hours boiling,” he says, “ the 
fibres of the corpus cavernosum of man are con- 
verted almost wholly into gelatine, whereas, in 
boiling muscular substance, the cellular sub- 
stance alone suffers this change, and the mus- 
cular fibre becomes still more evident. Again, 
if a portion of the boiled internal structure of 
the corpus cavernosum, not as yet reduced to 
jelly, and a portion of muscular fibre boiled for 
an equally long time, be examined with the 
microscope, the difference is more apparent 
than in the fresh condition. A solution of the 
fibrous structure of the corpus cavernosum 
(previously well washed with water) in concen- 
trated acetic acid is not precipitated by ferro- 
cyanate of potash, whereas a similarly treated 
solution of muscular fibre affords an abundant 
white or blueish-white precipitate.” In reply 
to Krause’s analysis, Muiller remarks: “ it will 
be seen that our investigation on the corpus 
cavernosum of the horse gives a precisely op- 
posite result to that of Krause on the same part 
in man; whence it follows, either that Krause 
has examined this peculiar substance mingled 
with other structures, as cellular tissue, &c., or 
that it does not exist in man. Had Krause 
investigated the tissue described by me in the 
penis of the horse, he would undoubtedly have 
met with the same results which I have so 
constantly obtained.” 

Besides the fibres of contractile fibrous tissue 
distributed through the parietes of the venous 
canals, the arteries and nerves of the corpus 
cavernosum also ramify in the intercellular sub- 
stance in their course through the structure of 
the penis. 

€ corpus spongiosum (corpus cavernosum 
urethre) is a lengthened cylindrical body situ- 
ated along the under surface of the corpus 
cavernosum in its inferior groove, and forming 
the inferior border of the penis. It commences 
posteriorly between and beneath the crura of 
the penis by a rounded enlargement, the bulb, 
and terminates at the extremity of the organ in 
the glans penis; the intermediate portion is 
cylindrical in form, and enlarges gradually from 
its middle towards the two extremities, the bulb 
posteriorly and the base of the glans in front. 

The glans penis resembles in form an oblique 
section of a cone, rounded at its apex; it is 
slightly compressed from above downwards, 
and is terminated posteriorly by a prominent 
border, the corona glandis. At the apex of the 
glans is a small vertical slit, the meatus urina- 
rius, which is bounded by two more or less 
protuberant labia, and extending backwards 
along the middle of its under surface is a 
grooved raphé, to which is attached the frenum 
preputii. The colour of the glans penis pre- 
sents a deeper tint of red than that of the 
neighbouring integument, and is invested by 
mucous membrane. At the meatus urinarius 
this membrane is continuous with the mucous 
lining of the urethra, and at the base of the 


* Hecker’s Annalen, February, 1834. 


PENIS. 


glans is reflected on the inner surface of the 
repuce, as far as the free margin of the latter. 

e corona glandis is studded by a number of 
small papillary projections, formed by sebaceous 
glands, the glandule Tysoni ( odorifere ), which 
pour out a whitish, unctuous, and strongly 
scented secretion to lubricate the surface of the 
glans and prepuce. Behind the glans is a 
deep furrow, bounded by the corona in front, 
and posteriorly by the fold of the prepuce. 

Examined with the microscope, the 
of the glans penis is found raised into small 
rounded papillae which cover every part of its 
surface. 

The corpus spongiosum is traversed in the 
direction of its length by the common urino- 
sexual canal, the urethra. At the commence- 
ment of the corpus spongiosum, the urethra 
occupies a groove upon the upper surface of 
the bulb ; further on it enters the substance of 
the body, but lies much nearer to the u 
than the lower surface, while at its termination 
it occupies the lower segment of ‘the glans. 

The corpus g ts gita resembles the co’ 
cavernosum in being composed of a plexiform 
vascular structure enclosed in a dense 
strong fibrous investment, but it differs from 
that body in the smaller size of its venous 
canals, the thinness of its fibrous tunic, and © 
especially in enclosing the canal of the urethra. — 
The vascular structure of the corpus spongio- — 
sum, like that of the corpus cavernosum, con= — 
sists of dilated veins of smaller size than those 
of the latter body, and separated in the same 
manner by membranous parietes. In the glans 
penis the veins are even smaller than in the 
body of the corpus spongiosum, particularly 
near the surface and around the em 
border of the corona glandis. The contractile 
fibrous tissue appears to me to be simila 
distributed between the veins, but is smaller in 
quantity than in the corpus cavernosum. Mayer 
also describes this tissue as existing in the 
parietes of the venous canals of the corpus” 
spongiosum, but Miiller denies its existence it 
that body, and observes, “ in the corpus spon 
giosum, where Mayer also admits this sub 
stance, it is not present, at least it is perfeet 
clear that it does not exist in that body in th 
horse.” The fibrous tunic of the corpus spon 
giosum is continuous at its bulb with the ant 
rior layer of the deep perineal fascia. 

The mucous membrane of the penis is t 
lining of the urethra and the investment of # 
glans and internal surface of the prepuce. — 
the canal of the urethra, near the extremity 
the organ, it is of a deep pink colour, and t 
comes gradually paler as it approaches 
bladder. By the contraction of the coats of 
urethra it is thrown into longitudinal fo 
and it is furnished with numerous small lacu 
which are especially numerous along the 
surface of the cylinder. The openings of th 
lacunz are directed forwards, and are caleu: 
lated to afford an impediment to the passage 
any small instrument into the bladder 
ing its point. One lacuna of larger size th 
the rest is situated in the upper wall of t 
urethra, at about an inch and a half from @ 


~ ae 


PENIS. 


meatus; it terminates by several ramified ducts 
in the submucous tissue of the canal. The 
mucous membrane of the urethra is separated 
from the tissue of the corpus spongiosum by a 
moderately thick fibrous layer, which is conti- 
nuous with the external tunic of the spongy 
body. 

Sir Everard Home conceived that the exter- 
nal tunic of the canal of the spongy portion of 
the urethra was muscular, and states with re- 
gard to it: “the muscular covering by which 
the membrane is surrounded or enclosed is 
made up of fasciculi of very short fibres, which 
appear interwoven together and to be connected 
by their origins and insertions with one another; 
they have all a longitudinal direction.” ‘“ The 
fasciculi are united together by an elastic sub- 
stance of the consistence of mucus.” Sir E. 
Home is mistaken with regard to the muscu- 
larity of the external tunic of the spongy urethra, 
but his description, as it relates to the disposi- 
tion of the fibrous tissue, is correct. Indeed it 
is evident that it is to this tissue that Sir E. 
Home alludes, from a subsequent passage in 
his essay, wherein he identifies his muscular 
coat with the fibrous lining of the canal of the 
corpus spongiosum. Thus he writes: “ Im- 
mediately beneath the muscular portion of the 
urethra is the cellular structure of the corpus 
spongiosum.” And this inference is still fur- 
ther corroborated by his belief that the external 
' fibrous tunic of the corpus cavernosum has also 
‘an admixture of muscular fibres.” 

The muscles of the penis are, the erectores 
penis, acceleratores urine, ischio-bulbosi, and 
compressores vene dorsalis. 

The erector penis (m. ischio-cavernosus) is 
the muscle of the corpus cavernosum. It arises 
by tendinous fibres from the anterior part of the 
tuber ischii, from the internal border of the 
ramus of the ischium, and from the root of the 
crus penis ; it then curves in an oblique direc- 
tion around the corpus cavernosum, and termi- 
nates partly by becoming inserted into the side 
of that body, and partly by a tendinous apo- 
neurosis, which is continuous with a similar 
aponeurosis derived from the opposite muscle. 
In the first part of its course the muscle is ten- 
dinous; where it is spread out on the crus 
penis and corpus cavernosum it forms a thin 
fleshy layer, which is prolonged for about one- 
third along the penis, while in the rest of its 
extent it is again tendinous, and constitutes the 
thin aponeurosis above described. The erector 
pe appears to effect its action as an erector 

y compressing the crura and vena dorsalis, 
and is aided in this office by the connection of 
its aponeurosis by means of the suspensory 
ligament with the symphysis pubis. When 
called into exercise both muscles act together, 
and by their united action embrace the root of 
the penis, and strongly compress it. The effect 
of pressure on the vena dorsalis must obviously 
be to impede the return of the venous blood 
from the penis, and the compression of the 
crura produces the same result on the veins of 
the corpus cavernosum. 

The acceleratores uring (m. bulbo-caverno- 
sus) are the muscles of the corpus spongiosum ; 


915 


they are situated on the posterior third of that 
body, and form a thin muscular plane which 
surrounds its cylinder, and is spread out upon 
the under surface of the bulb. Each muscle 
arises from the posterior border of the deep 
perineal fascia at the middle line, and from a 
median raphé which is closely adherent to the 
under surface of the bulb and corpus spongio- 
sum, and which connects it with its fellow of 
the opposite side. From this extensive origin 
the fibres of the muscle pass obliquely out- 
wards and forwards, the most posterior to be 
inserted into the ramus of the ischium and 
pubis, the middle and most numerous to en- 
circle the corpus spongiosum, and uniting by 
tendinous fibres with the muscle of the opposite 
side upon the upper surface of that body, to be 
inserted into the inferior groove of the corpus 
cavernosum ; and the anterior forming a narrow 
fasciculus to pass outwards upon the corpus 
cavernosum and be inserted into its fibrous 
tunic and into the fascia penis. The posterior 
fibres are almost transverse in their direction, 
and cross the triangular interval between the 
bulb and crus penis, being separated from the 
deep perineal fascia by the superficial perineal 
vessels and nerve, and by the ischio-bulbosus 
muscle when it exists. 

The acceleratores are well calculated to con- 
tract forcibly the canal of the urethra, and thus 
to communicate an expulsive impetus to the 
stream of urine or seminal secretion passing 
along the tube. The expulsive action of these 
muscles is made sensible to the hand when we 
withdraw a catheter; and the strength of its 
gripe, when the catheter has been lodged in 
the bladder. Indeed their complete contraction 
constitutes an impassable though temporary 
obstruction to the passage of the catheter along 
the urethra, and gives rise to that form of 
impediment which is known by the name of 
spasmodic stricture. The contraction of these 
muscles, moreover, acting suddenly on the 
urethra, serves to expel the last portions of 
urine and seminal secretion. Besides the in- 
fluence which they exert on the urethra, the 
acceleratores urine also enact the part of erec- 
tors of the penis, by producing so much pressure 
on the bulb and posterior part of the corpus 
spongiosum as may impede the return of blood 
through the ven corporis spongiosi, and at 
the same time press forwards the contents of 
the venous plexus of the bulb into the anterior 
part of the corpus spongiosum and glans penis ; 
and their action in this respect is increased by 
the tension made by their anterior fasciculi on 
the fascia penis, and through it on the vena 
dorsalis. 

The ischio-bulbosus (m. transversus perinei 
alter; m. transversus perinei profundus) is a 
small fan-shaped muscle situated in the trian- 
gular interspace between the bulb of the urethra 
and crus penis, and is not unfrequently want- 
ing. It arises by a pointed origin from the 
ramus of the ischium, and passing obliquely 
inwards across the triangular space above des- 
cribed, spreads out into a thin fan-shaped plane, 
and is inserted into the fibrous tunic of the 
bulb. On one occasion I found this muscle 

3.N 2 


916 


so large that it extended forwards to the middle 
of the penis, and usu the place of the 
accelerator urine, which was absent. The 
ischio-bulhbosus muscle is separated from the 
transversus perinei by the folded border of the 
deep and superficial perineal fascie, and from 
the compressor urethre by the anterior layer 
of the deep perineal fascia. It covers in the 
internal pudic vessels and nerve. 

The action of the ischio-bulbosi muscles is 
to compress the bulb, and by their pressure to 
aid the posterior fasciculi of the acceleratores 
urine in producing turgescence of the corpus 
spongiosum. In the variety to which I have 
alluded above, the ischio-bulbosi must have 
performed the whole of the duty of the accele- 
ratores. 

The compressor vene dorsalis penis is a small 
muscle, first described by Dr. Houston,* of 
Dublin. According to that gentleman it is 
found very commonly among mammiferous 
animals, and also in the human subject when 
the muscular system is well developed. To 
its existence in the dog and cat I can bear 
witness, having repeatedly prepared it for 
Dr. Jones Quain, who was wont to demon- 
strate it in his lectures; I have been less suc- 
cessful in the human subject, and have never 
obtained a satisfactory view of a distinct pair 
of muscles in the situation indicated by Dr. 
Houston. “In man,” writes this author, “the 
compressores vene dorsalis are less distinct 
than in most of the mammalia. They arise 
from the rami of the pubis above the origin of 
the erectores penis and crura, and ascending in 
a direction forwards are inserted above the 
vena dorsalis by joining with each other in the 
mesian line. They form a thin stratum of 
muscular and tendinous fibres about an inch 
long and three quarters of an inch broad, and 
may perhaps be looked upon as portions of the 
erectores penis, which, instead of being inserted 
into the sides and lower part of the corpora 
cavernosa, mount over those bodies to exert 
their compressing influence on the vena dor- 
salis. They enclose between these and the 
penis, the veins, arteries, and nerves of this 
region. Their anterior fibres are distinguished 
from those of the erectores by the fibrous at- 
tachment of the crura to the pubis; their 
posterior margins are kept distinct from the 
* front part of the levatores ani, known under 
the name of Wilson’s muscles, by the pudic 
artery, which divides them in its course towards 
the dorsum of the penis.” 

“The best procedure to display these mus- 
cles is the following. Detach the bladder and 
levator ani with the hand from one side of the 
pelvis; then divide with the saw the pubis and 
ischium about one inch from the symphysis, 
and break off the bones at the sacro-iliac arti- 
culation; next dissect away carefully the re- 
maining portion of the pubis from the symphy- 
sis, periosteum, and crura penis, and then the 
compressores vene, bearing still their natural 
relations to the crura and other muscles, may 
be exposed with very little difficulty. The 


* Dublin Hospital Reports, vol. v. page 459. 


PENIS. 


insertion of the muscles being in a great mea- 
sure outside the pelvis, they may also be 
demonstrated without the section of the bones, 
by cutting on them in front of the pubis and 
looking carefully for their tendon at the side of 
the vena dorsalis: from the tendon the knife 
may be carried downwards and backwards in 
the course of the fibres, and nearly the whole 
of the muscle can be thereby exposed. It 
must, however, be remembered that it will be 
needless to search for them in a thin emaciated 
individual, where the other muscles of the 
perineum are so pale and soft that even they 
can scarcely be distinguished. The subject 
should be robust, and the muscles red, in order 
to demonstrate them.” 

Respecting the action of these muscles Dr. 
Houston observes: “The use of the musculi 
compressores vene is self-evident and cannot 
be mistaken ; the effect of their contraction will 
be to close the vein and mechanically obstruct 
the current of blood. A simple experiment 
will prove to demonstration that such will be 
the necessary result of their contraction. Let 
the muscles be stretched in the natural direction 
of their fibres, and any fluid forced into the — 
vein will not find a passage through the vessel 
beyond the spot where it is compressed by 
their tendon: a very gentle pull of the muscles 
will be sufficient to produce this effect. In 
cases where the vein runs through the tendon — 
the pressure will be most efficacious, but 
in those in which the tendon is arched over the 
vein its descent from the contraction of the — 
muscles will sufficiently compress the delicate 
tunics of the vessel to produce the required 
effect.” A 

The arteries of the re are derived from 
the internal pudic, itself a branch of the inter-— 
nal iliac artery. They are three in number on 
each side; the artery of the bulb, the artery of 
the corpus cavernosum, and the arteria dors 
penis. 

The arteria corporis bulbosi is given off from 
the internal pudic at a point corresponding 
with the level of the urethra, and passes trans 
versely inwards to the bulb, which it ente 
close to the lower part of the urethra. In it 
course inwards it lies along the upper borde 
of the transverse portion of the compress¢ 
urethra muscle, and crosses that muscle 0 
liquely from within outwards. It is situatet 
between the two layers of the deep perine 
fascia, and is surrounded by a sheath derive 
from the anterior layer of the fascia as it ente 
the bulb. Having entered the corpus spe 
osum, the artery runs forwards in the midst 
the venous canals of that body to the gla 

nis, in which it distributes its ultims 

ranches. In its course the arteria bulbe 
gives off numerous ramuscules, which ram 
in the walls of the venous canals. 

Lhe arteria corporis cavernosi is given © 
from the internal pudic, somewhat nearer 
the symphysis pubis than the preceding, 
opposite the point of junction of the er 
penis; it pierces the fibrous tunic of the ef 
penis on its inner side, to enter the stractu 
of the corpus cavernosum. In the latte 


. 
+ 


PENIS. 


runs forwards by the side of the septum pec- 
tiniforme, distributing many branches in its 
course, which ramify in the parietes of the 
venous canals. 

The arteria dorsalis penis may be regarded 
as the continuation of the internal pudic, after 
the latter has given off the arteria corporis 
cavernosi. It commences opposite the junction 
of the crura penis, and piercing the anterior 
layer of the deep perineal fascia, ascends to 
the groove upon the dorsum penis. In this 
groove it runs forwards to the base of the glans, 
where it divides into several branches, which 
enter the substance of that body and are distri- 
buted to its structure. The arteria dorsalis is 
separated from its fellow by the dorsal vein, 
and gives off numerous branches in its course 
to the fibrous structure of the penis and inte- 
gument. 

The veins of the penis correspond with the 
arteries which they accompany in their efferent 
course. The vene corporis bulbosi and vene 
corporis cavernosi, issuing respectively from 
the bulb and crura penis, take the course of 
the internal pudic artery, and constitute the 
internal pudic veins. At the root of the penis 
these veins communicate with the dorsal vein. 

The dorsal vein commences by numerous 
largé branches, the chief of which issue from 
the base of the glans beneath the corona, and 
form by their communications a considerable 
plexus on the anterior part of the corpus cayver- 
nosum, the,others being the veins of the prepuce 
and integument. The union of these veins 
constitutes two trunks of equal size, which, 
afier running side by side for a short distance, 
unite and form the dorsal vein. The dorsal 
vein in its course towards the root of the penis 
passes beneath the aponeurosis of the erectores 
muscles, together with the attachment of the 
suspensory ligament, and after piercing the deep 
perineal fascia, divides into several branches 
which join the prostatic and vesical plexus. 
It receives in its course several large branches 
from the corpus spongiosum, which curve 
around the corpus cavernosum in order to reach 
it, and communicates at the root of the organ 
with the deep veins of the penis. The dorsal 
vein is situated in the middle line of the groove 
of the dorsum penis, having its corresponding 
artery at either side, and being covered in by 
the fascia penis and conjoined aponeurosis of 
the erectores penis muscles. It is this relation 
to the fascia penis and aponeurosis of the 
erectores that enables the latter to compress the 
vein forcibly against the dense fibrous coat of 
the corpus cavernosum, and thus intercept the 
current of venous blood. 

The question of the ultimate arrangement 
of the bloodvessels in the substance of the 
penis leads to enquiry into the nature of erec- 
tile tissue, a subject to which a separate article 
has been devoted in the earlier pages of this 
work, and to which I must now refer my 
reader. From my own investigations into the 
structure of this tissue in the corpus caverno- 
sum and corpus spongiosum, I have come to 
the conclusion that the arteries ramify and ter- 
minate in capillaries as in other parts of the 


917 


body, and that these latter very speedily be- 
come dilated veins. In the distribution of the © 
veins the only peculiarity of this tissue exists ; 
these by their tortuous windings form an in- 
extricable plexus, which fills the whole area of 
the fibrous tunics of the corpus cavernosum 
and spongiosum, and constitutes their com- 
ponent substance. In this plexiform aggre- 
gation of veins, the walls of the vessels so 
closely approach as to leave between them 
only so much connecting tissue as serves for 
the ramification of the arteries and nerves of 
the organ, and for the passage of the fibrous 
trabecule and fibres of the contractile tissue. 
It follows from this arrangement that the arez 
of the veins bear a much greater proportion to 
the bulk of the tissue than do the septa between 
them, and, consequently, that if a section of 
the corpus cavernosum be made, its parenchyma 
will have the appearance of a cellular net- 
work, an appearance that is rendered much 
more striking when the penis has been inflated 
and dried. It is obviously this appearance of 
the parenchyma of the corpus cavernosum 
that has gained for it the character of being 
composed of cells, and in truth, as far as the 
plane of the section is concerned, the portions 
of venous canals which open on the surface 
have all the attributes of divided cells. Ac- 
cording to the position of the veins at the point 
of section, the cell in one spot is shallow and 
small, in another it is lengthened, either in the 
longitudinal or in the transverse direction of 
the axis of the corpus cavernosum, and ina 
third, again, the apparent cell is irregular in 
form, from the conjunction at that point of two 
or more veins. If, in the next place, we turn 
our attention to the septa of the apparent cells, 
we shall meet with spots in which from the 
close assemblage of the veins the septum has 
the appearance of a star giving off a number 
of thin lines in a radiated direction to form 
partitions between three, four, or five veins 
which meet at that point. Now let us suppose 
that this observation is being made on the 
parenchyma of the corpus cavernosum, the 
arteries of which have been previously injected 
with fine injection. Where do we look for the 
injected arteries? Obviously in the septa, and 
especially at that thicker portion of the septum 
where several veins lie in contact. And what, 
we may ask, is the probable appearance of the 
arteries in that star-like point of septum which 
I have described above? I can answer this 
question, from repeated observation. It is 
that of a short trunk giving off two, three, or 
four small and short terminal branches, which 
diverge in an oblique direction from the ex- 
tremity of the small trunk, and terminate 
abruptly at the cut margin of the septum. I 
have seen the appearances here described many 
times, sometimes better, sometimes less dis- 
tinct, and more frequently as a bifid division 
than another, and these I apprehend are the 
arterie helicine of Miiller. Besides the pre- 
ceding, the special characters of the arterie 
helicine are their projection in the form of a 
tuft into a venous canal, and the curved, 
swollen, and conical form of the small branches 


918 


at their extremities. The first of these ap- 
sey nae is due to the accidental position of 

é section under the microscope, so that the 
short trunk with its terminal twigs appears to 
be placed within the area of a vein projecting 
into it like a blossom on its stalk; the second 
results from the contraction of the coats of the 
artery, the effects of the longitudinal contrac- 
tion giving rise to the curve and to the enlarge- 
ment near its extremity, and the transverse 
contraction, by producing the expulsion of 
some part of the injection, to the conical form 
of the extremity itself. “ These remarkable 
arteries,” writes Miiller,* “ have a great re- 
semblance to the tendrils of the vine, only that 
the arteries are much shorter in proportion to 
their thickness; from this resemblance I have 
named them arterie helicine or tendril-like 
arteries. We may also compare their ends to 
the top of a crook. By close examination 
with the microscope they may be seen pro- 
jecting into the venous cells, not, however, bare, 

ut covered with a fine membrane that under 
the object-glass looks horny.” 

If the description which I have here given 
of erectile tissue be the true one, it is clear 
that the arterie helicine have no existence, and 
that that appearance of the small vessels, to 
which Miiller has given this name, is a neces- 
sary consequence of the natural distribution of 
the ordinary vessels of the organ. I may be 
permitted to remind my junior reader that it 
was through the medium of the arteriz heli- 
cine that Miiller supposed the venous canals 
of erectile tissue to be filled during erection, 
while, for the purposes of nutrition and main- 
taining the ordinary circulation of the organ, 
the arteries pour their blood into capillaries, 
and these into veins. Excepting during the 
moment of discharging their blood, this phy- 
siologist conceived that the small curved ter- 
minal twigs were impermeable, and that it was 
only under the influence of the erectile nervous 
function attending erection that the impetus 
of the arterial blood was sufficient to open the 
concealed apertures at their extremities. 

The lymphatic vessels of the penis are found 
chiefly on its dorsum, taking the course of the 
dorsal vein. At the root of the organ they 
curve outwards to the groin, and communicate 
with the upper group of inguinal glands. I 
have frequently seen a small lymphatic gland 
on the dorsum penis near its root. 

The nerves of the penis are derived from the 
internal pudic and from the hypogastric plexus; 
those from the former source are the anterior 
superficial perineal nerve, the nerve of the bulb, 
and the dorsalis penis nerve. 

The anterior superficial perineal is a branch 
of the perineal division of the internal ae 
It enters the perineum at the posterior border 
of the deep perineal fascia, and passing on- 
wards in the groove between the erector penis 
and accelerator urine, gives branches to the 
scrotum, and is finally distributed to the inte- 
gument of the under part of the penis as far as 
the prepuce. 


- * Archiv, 1835, 


PENIS. 


The nerve of the bulb is also a branch of the 

ineal division of the internal pudic, and 
ikewise enters the perineum through the 

sterior border of the deep perineal fascia. 

tween the superficial and deep fascia, and 
behind the transversus perinei muscle, the 
nerve passes obliquely forwards to the bulb, 
where it gives off pl long and slender 
branches, which run forwards on the fibrous 
tunic of the corpus spongiosum, and then 
enters the bulb in company with the artery, 
to be distributed to the vascular parenchyma 
of that body and to the urethra as far as the 
glans penis. 

The perineal division of the internal pudie 
nerve also gives branches to the acceleratores, 
erectores, and ischio-bulbosi muscles. 

The dorsal nerve of the penis is the superior 
or deep division of the internal pudic. This 
nerve accompanies the internal pudic artery to 
the anterior part of the arch of the pubis, 
where it pierces the deep perineal fascia and 
 aeeaig onwards to the dorsum penis. In the 
atter situation it lies externally and somewhat 
superficially to the dorsal artery, and enters the — 
base of the glans penis by several branches, to 
be distributed to the papille of that body. — 
Near the root of the penis the dorsal nerve 
gives off a large branch, which passes obliquely 
along the side of the corpus cavernosum, 
divides into numerous long and slender branches, 
which are distributed to the integument of the — 
apeee and lateral aspect of the penis, to the 
fibrous covering and substance of the corpus 
cavernosum, and to the prepuce. The ne 
dorsales communicate with each other, on 
dorsum penis, by anastomosing filaments. 

The nerves derived from the hypogastric 
plexus are slender ramuscules, which accom- 
pany the arteries of the corpus cavernosum and 

ulb into the interior of the penis, and are dis- 
tributed to its internal structure. ; 

Developement.—The first indication of th 
developement of a penis is eived towards — 
the end of the fifth week after concep ion, & 
which time it exists in the form of a sligl 
prominence, situated immediately in front ¢ 
the common urino-sexual aperture. By th 
seventh or eighth week this prominence assumt 
the lengthened character of the future orga 
and is grooved along its under side, the groo 
being an extension of the common urino-sexu 
cleft. The glans penis makes its appearan 
during the ninth week, and the urinary groo 
is continued beneath it. During the tenth 
eleventh weeks the urinary groove becot 
separated from the anus by the 
transverse septum, and the borders of the gro 
begin to lengthen and coalesce on the me¢ 
line,dn order to form the urethra. This proe 
commences from behind, and proceeds” 
wards towards the glans, attaining its com 
tion at about the fifteenth or sixteenth ¥ 
When it remains imperfect from arrest of dé 
lopement, it constitutes that form of deficien 
which is termed Hypospadias. The prep’ 
is developed at the same time with the clos t 


of the urethra. & 
( Erasmus Wilse 


aed 


PERINEUM. 


PERICARDIUM.—See Heart. 


PERINEUM (in Surgical Anatomy).—The 
perineum (in the general acceptation of that 
term) is one of the names applied by anatomists 
to the extensive region which contains the lower 
part of the rectum intestine, together. with a 
portion of the genito-urinary organs and their 
appendages, and of which the circumference 
corresponds in a great measure to the periphery 
of the inferior aperture of the pelvis ; in the pre- 
Sent article, however, it is intended to describe 
the perineum in the male subject only, as the 
parts which it comprises in the female are no- 
ticed in detail under other headings in this 
work. 

The limits which we would assign to this 
region are sufficiently precise: superiorly, or 
towards the abdominal cavity, it extends as far 
as the reflections of the recto-vesical layer of the 
pelvic fascia and the great cul-de-sac of the peri- 
toneum, including within its precincts the pros- 
tate gland and the neck of the bladder, together 
with a part of the inferior surface of that viscus 
and the vesicule seminales and vasa deferentia; 
inferiorly, the perineum is quite superficial, 
being covered by the integuments only ; and it 
1s circumscribed partly by the fixed boundaries 
of the inferior aperture of the pelvis, and partly 
by the obturator fascia, an aponeurotic expan- 
sion which appears to line a portion of the 
inner surface of the os innominatum, but is in 
reality separated from the bone by the obturator 
infernus muscle and the internal pudic vessels 
and nerve. 

In describing this complicated region it will 
be advantageous to consider in the first place 
the osseous and ligamentous structures which 
cwcumscribe the inferior outlet of the pelvis, 
and to notice in a general manner the course of 
the rectum and urethra, together with so much 
of the urinary bladder as is connected with the 
perineum, for in the sequel it will appear that 
the rectum and the urethra are the principal 
elements of the region, and that almost all the 
other parts contained in it are appendages of 
either the one or the other, so that by the adop- 
tion of this method a key to the anatomy of all 
the subordinate structures will be obtained. 

The inferior aperture of the male pelvis exa- 
mined after the removal of the soft parts (the 
sacro-sciatic ligaments being preserved) is dia- 
mond-shaped; it is limited anteriorly by the 
arch of the pubis, posteriorly by the extremity 
of the coccyx, and laterally by the rami of the 
pubis and ischium, the tuberosity of the ischium, 
and the great sacro-sciatic ligament at each side 
respectively. It presents three diameters, viz. 
the antero-posterior, the transverse, and the 
oblique. The first extends from the coccyx 
posteriorly to the symphysis pubis in front; the. 
second passes transversely between the tube- 
rosities of the ischia; and the third stretches 
from the point midwayjbetween the tuber ischii 
and the arch of the pubis, to the centre of the 
great sacro-sciatic ligament of the opposite side. 
In a well-formed male pelvis these three diame- 
ters are almost equal, being each of them nearly 
three and a-half inches in extent; but in conse- 


919 


quence of the mobility of the coccyx that bone 
may be moved backwards considerably, and 
under such circumstances the antero-posterior 
diameter becomes increased to a corresponding 
amount. 

This large space admits of a very natural 
division into two triangles, one in front, the 
other posteriorly ; the base of each respectively 
corresponds to the line passing transversely be- 
tween the tuberosities of the ischia, and the 
apex of the one is formed by the arch of the 
pubis, whilst that of the other is constituted by 
the extremity of the coccyx. 

The anterior triangle is equilateral ; its sides 
are formed by the rami of the ischium and 
pubis, and are each from three inches to three 
and a-half inches in length; it contains the 
urethra and the root of the penis, with their 
appendages, and may be named the urethral 
division of the perineum, 

The posterior triangle is bounded laterally by 
the great sacro-sciatic ligaments, and in the re- 
cent state by the edge of the gluteus maximus 
muscle also. The coccyx usually protrudes 
forwards so much that the area of the posterior 


‘ triangle is less than that of the anterior, not- 


withstanding that the base of each of them is 
represented by the same line. This posterior 
triangle contains the anus with the inferior por- 
tion of the rectum, &c., and is usually called 
the anal division of the perineum. 

It should be borne in mind that the measure- 
ments of the inferior outlet of the pelvis may 
present considerable variations in different sub- 
jects, and that the operator may be obliged to 
modify the length and the direction of his inci- 
sions in lithotomy to suit such cases. M. Du- 
puytren, for example, in twenty-three subjects 
which he examined, found the distance inter- 
mediate between the tuberosities of the ischia to 
vary from two inches to three and a-half inches ; 
and M. Velpeau, who measured forty subjects, 
observed in one case these processes to be but 
an inch and three quarters asunder, whilst in 
another they were four inches apart. 

In order to perform successfully many of the 
operations in this region the surgeon requires 
an accurate knowledge of the axes of the pelvis, 
and to study the modifications which these 
imaginary lines exhibit in childhood and old 
age as compared with adult life. In the full- 
grown male the axis of the superior aperture of 
the true pelvis takes a direction from the vici- 
nity of the umbilicus downwards and back- 
wards to the coccyx, whilst the axis of the infe- 
rior aperture passes upwards and slightly back- 
wards through the mid space between the 
tuberosities of the ischia to the promontory of 
the sacrum; these two lines intersect each 
other in the pelvic cavity, forming an angle 
slightly obtuse and salient posteriorly: the axis 
of the true pelvis (or in other words a line pass- 
ing through the centres of the upper and lower 
apertures respectively) is therefore a curved 
line concentric with the curvature of the sacrum, 
and having its concavity directed forwards and 
downwards towards the symphysis pubis. 

During childhood the true pelvis is imper- 
fectly developed ; ithas but little depth, and its 


920 


capacity is so limited that the viscera which 
occupy the pelvis of the adult are mostly con- 
tained in the abdominal cavity of the infant. 
The straits of the pelvis have each of them 
likewise an aspect different from that of the 
adult; in the child the superior aperture looks 
much more directly forwards, and the inferior 
peeved much more backwards than they do 

puberty. These peculiarities are inherent 
in the infantile pelvis: they are independent 
of any inclination in the vertebral column, and 
they must therefore modify considerably the 
direction of the pelvic axes during the early 
years of growth. 

In the old subject again the superior aperture 
is once more directed forwards as in the infant, 
. whilst the inferior aperture inclines backwards ; 
at this period of life, however, the change in the 
pelvis arises not from any intrinsic alteration in 
ats bony parietes, but simply from the senile 
curvature of the spine above, added to the ha- 
bitual flexion of the hip and knee-joints below, 
so constantly observed in the aged individual. 

To understand the course of the rectum and 
the urethra, as well as the relations of the base 
of the bladder, the anatomist must study these 
parts within the pelvis, since it is impossible 
to display them satisfactorily in the ordinary 
dissection of the perineum; much assistance 
may be derived from preparations affording a 
side view of the pelvic viscera, and one of the 
most useful is an antero-posterior section carried 
through the middle line and dividing the ure- 
thra, prostate gland, bladder, and rectum, &c., 
after these organs have been moderately dis- 
tended and hardened by alcohol. 

Rectum.—tThe portion of intestine which 
belongs to this region commences at the great 
cul-de-sac of the peritoneum and terminates at 
the anus. It is perfectly devoid of any serous 
investment, and presents considerable varieties 
in size and direction in different subjects. The 
age and the habits of the individual are found 
to exert a remarkable influence upon its course 
and dimensions, and accidental variations in 
the line of reflection of the serous membrane, 
which create corresponding changes in the 
depth of the perineum, are occasionally ob- 
served even in the adult, and ought to be 
taken into account by the operator. 

The great cul-de-sac of the peritoneum is 
usually about three-and-a-half inches distant 
from the anus, so that, making allowance for 
the curved course of the intestine, we may 
estimate the length of the perineal portion of 
the rectum in the adult at somewhat less than 
four inches. In forming this estimate, the 
condition of the urinary bladder as regards its 
distension should not be overlooked, for when 
that reservoir is empty and contracted, the rec- 
tum receives an extensive serous investment, 
and at such times the cul-de-sac of the perito- 
neum approaches the anus perceptibly, whilst 
under the opposite condition (that of repletion) 
the bladder displaces the serous membrane par- 
tially, carrying its cul-de-sac upwards towards 
the abdomen. Individual varieties, irrespec- 
tive of these changes in the bladder, are, how- 
ever, of constant occurrence, and in many in- 


PERINEUM. 


stances the rectum in the adult is covered by 
serous membrane anteriorly to within two inches 
of the anus, the bladder being at the same 
time fully distended. In the youre subject 
the peritoneum stretches very far downwards 
along the surface of the bowel, and at birth 
it very generally covers the front of the rectum 
to within one inch of the anus; at the age of 
five years the cul-de-sac of the peritoneam — 
and the anus are still separated by a very — 
trifling interval; but from this period up to — 
puberty the intermediate distance tes in- 
creases, pari pussu, with the growth of the 
pelvis and the developement of the inferior 
fundus of the bladder. 4 
At its commencement the perineal portion of 
the rectum runs obliquely downwards and for- _ 
wards, this direction it maintains as far as the 
prostate gland, but it there alters its course and 
turns slightly backwards to terminate at the — 
anus. Superiorly it presents a slight curva- 
ture concentric with that of the sacrum, so 
that the anterior surface of the gut is there — 
slightly concave, and its posterior surface 
slightly convex from above downwards: infe- 
riorly, however, the curvature of the intestine 
is reversed ; it appears as it were to turn round 
the point of the coccyx to gain the anus, and 
therefore the convexity of the lower of the 
gut is directed forwards whilst its concavity 
looks backwards. This curved course of the 
rectum ought to be borne in mind by the sur 
geon in his attempts to introduce instruments 
into its interior. ‘y 
In the child the sacrum and coceyx present 
but a trifling curvature, and therefore the rec- 
tum reaches the anus by a less circuitous row 
than that just described, and which is the nor- 
mal condition in the adult; during childhoos 
the inclination backwards of the lower extre. 
mity of the gut scarcely exists, it Lara 
a single curve concave forwards, which, like tha 
of the sacrum and coccyx, is but faintly markec 
so that the intestine is much straighter in early” 
life than after puberty. In old age the rectut 
immediately ibocs the anus is sometimes ii 
flected from side to side so as to assume 
zigzag appearance: these lateral inclinations at 
the result of the enormous enlargement whi 
the bowel occasionally undergoes in the a@ 
vanced periods of life, its length being actua 
increased at the same time that its cavi 
dilated. 7 
In the adult subject the rectum is somet 
cylindrical in shape, but it increases in caps 
as it descends, and presents a marked dilatat 
just above the sphincters, whilst the anus 4 
so much of the gut as is embraced by thi 
muscles exhibit a decided contraction. In) 
child the dilatation just described is but li 
marked, whilst in advanced life it very 
quently becomes excessive, and is best ap; 
ciated when the intestine is fully distended ¥ 
feces or artificially inflated; under such 
cumstances the anterior wall of the 
hollowed into a deep depression or gutter, | 
which the prostate gland and base of the blade 
are imbedded, and the bowel swells outwa 
and forwards upon each side of the pre 


PERINEUM. 


losing altogether its cylindrical shape. It will 
be readily understood that when such a dispo- 
sition prevails in a calculous subject, the rectum 
must undergo serious danger during lithotomy 
performed according to the lateral or bilateral 
methods, and that therefore the precaution of 
emptying the bowel previous to these opera- 
tions is highly advisable. 

The relations of the perineal portion of the 
rectum deserve from the surgical anatomist his 
most attentive consideration. Anteriorly the 
inferior fundus of the bladder, together with 
the vesicule seminales and vasa deferentia, 
come into contact with the rectum immediately 
beneath the line of reflection of the peritoneum ; 
lower down the prostate gland rests upon the 
front of the rectum, to which it is very inti- 
mately connected, nothing but some cellular 
tissue intervening between them, whilst still 
lower down the membranous portion of the 
urethra and the bulb are related to the rectum, 
though not immediately, for neither of those 
parts of the urinary apparatus is found to touch 
the parietes of the gut. The bulb of the urethra 
in the adult is usually situated about half an 
inch in front of the rectum and about one 
inch above the anus; the membranous portion 
of the urethra lies about ten lines anterior to 
the rectum, and rather more than an inch and 
a half above the anus, whilst the prostate gland 
is placed within one line of the anterior wall of 
the gut, and about two inches above the anus. 
These anterior relations of the rectum explain 
how the finger introduced into its cavity may 
assist the catheter in its passage along the 
urethra in the living subject; how by the same 
manceuvre the surgeon obtains valuable infor- 
mation as to the state of the bladder and pros- 
tate gland in various morbid conditions of those 
organs; how, in sounding, he is able at times 
to raise up the calculus by his finger so as to 
bring it into contact with the instrument; how 
the bladder may be punctured from the rectum 
and the urine withdrawn by this route in certain 
cases of retention; how, acute inflammations 
and other diseases of the bladder and urethra 
or their appendages so frequently occasion mor- 
bid sympathies in the intestine, such as pro- 
lapsus, tenesmus, hemorrhoids, &c. ; and above 
all, how great must be the danger to the bowel, 
and how urgent the necessity for protecting it 
during the lateral operation of lithotomy. 

Posteriorly a quantity of loose cellular tissue 
connects the lower part of the rectum to the 
sacrum and coccyx; it is there related, parti- 
_ cularly when distended, to the pyriformis and 
_ ischio-coccygeus muscles, and towards its anal 
- extremity to some of the fibres of the levatores 
ani and the ano-coccygeal ligament. 

On either side the rectum gives insertion to 
a portion of the recto-vesical layer of the pelvic 
fascia, which, though weak and cellular in that 
locality, nevertheless admits of being fairly 
traced to the walls of the gut; but the levatores 
ani muscles constitute the principal lateral rela- 
tions of the intestine. In their descent they 
_ cover its surface extensively, and form in great 
measure the partition between the bowel and 
the ischio-rectal fossa. 


921 


The perineal portion of the rectum affords in 
some respects a striking contrast to the upper 
part of the same intestine; being totally devoid 
of serous investment, it is more fixed and 
(except at the anus) more dilatable than the 
superior division of the bowel, and its con- 
nexions with the recto-vesical layer of the pelvic 
fascia, the ano-coccygeal ligament, the genito- 
urinary passages, and the middle tendinous 
point of the perineum, contribute to fix it still 
more firmly in its position. 

The coats of the rectum present certain pecu- 
liarities interesting to the surgical anatomist. 
Its muscular tunic is of uncommon strength, 
and consists of two very distinct layers ana- 
logous in many particulars to those of the 
corresponding strata in the cesophagus; the 
superficial layer is formed of highly developed 
longitudinal fibres, florid in colour (as con- 
trasted with those of the remainder of the large 
intestine), and which spread out so as to invest 
the whole circumference of the gut: the fibres 
of the deeper layer are circular, and acquire 
increased developement towards the anal extre- 
mity of the intestine, where they are continuous 
with the internal sphincter. The mucous mem- 
brane is remarkable for its thickness and vascu- 
larity and for the great laxity of its connexion 
with the other tissues of the gut: it adheres so 
loosely to the subjacent coat in the vicinity of 
the anus that it sometimes protrudes through 
that opening, and in this manner one form of 
prolapsus ani is produced. 

Upon the free surface of the mucous mem- 
brane a number of longitudinal folds run down 
to the immediate neighbourhood of the anus ; 
they are called the columns of the rectum, and 
converge slightly as they descend ; their number 
is variable though it seldom exceeds eight or 
ten, and between them inferiorly some trans- 
verse semilunar folds may be observed, of which 
the free concave margins are directed upwards. 
In these folds of the mucous membrane the 
physiologist recognises a provision to facilitate 
the distension of the gut, and to their presence 
some surgeons attribute the occurrence of cer- 
tain morbid conditions of the intestine. In 
addition to these folds, which are constant, 
others have likewise been described within the 
rectum; these latter were named by the late 
Dr. Houston “ the valves of the rectum,” and 
appear at times remarkably distinct. When 
present they are each of a semilunar shape, 
and formed by a duplicature of mucous mem- 
brane containing cellular tissue and a few 
muscular fibres between its folds. Each valve 
is attached by its convex margin to the walls of 
the gut, whilst its free edge is directed more or 
less inwards towards the cavity of the intestine. 
One of these valves is situated (according to 
Houston’s statement) opposite to the base of 
the bladder, on the anterior wall of the gut and 
about three inches distant from the anus, whilst 
another is sometimes placed within one inch of 
the anal orifice. 

That projections from the parietes of the 
rectum, such as have been described by Houston, 
may be made apparent by a certain mode of 
preparation cannot be denied, but that they can 


922 


or do exert much influence in supporting the 
weight of the column of feces within the intes- 
tine, or in obstructing the progress of instru- 
ments through it, may be very fairly questioned ; 
for when the rectum has been removed from 
the dead subject and laid open, these valves 
are in general no longer visible, and the natural 
curvatures of the bowel explain sufficiently the 
difficulties encountered in the introduction of 
rectal tubes or bougies in the living. 

Bladder, vesicule seminales, and vasa defe- 
rentia.—It is here necessary to notice briefly so 
much of the under surface of the bladder as is 
uncovered by peritoneum, and to consider in 
a cursory manner the vesicule seminales and 
vasa deferentia. These structures are situated 
very deeply in the perineum, and therefore they 
are dissected with advantage from within the 

Ivis, 

On looking down into the pelvic cavity in a 
recent subject after the peritoneum has been 
displaced and the bladder drawn gently to 
either side, the anatomist obtains a satisfactory 
view of the course and connections of the 
recto-vesical layer of the pelvic fascia, which 
there constitutes the superior boundary of the 
aes The recto-vesical is the innermost 
ayer of the pelvic fascia; after investing the 
inner surface of the levator ani muscle it is 
reflected upon the prostate gland and side of 
the bladder, and more posteriorly upon the 
rectum ; a line drawn from the lower extremity 
of the symphysis pubis to the spinous process 
of the ischium is nearly the level at which this 
reflection takes place. This fascia is closely 
connected in front to the upper surface of the 
prostate gland, and in that situation it forms 
the anterior true ligaments of the bladder; it 
next adheres to the edges of the gland, and 
more posteriorly to the sides of the bladder, 
there constituting the lateral true ligaments of 
that viscus; whilst still further back it is iden- 
tified with the sides of the rectum as has been 
already described. Its attachments to the blad- 
der at either side respectively are situated a 
little above the vesicule seminales. 

This fascia forms the line of demarcation 
between the perineum and the upper portion of 
the pelvic and the abdominal cavity. It is of 
sufficient strength to resist powerfully the des- 
cent of any of the abdominal viscera through 
the space between the bladder and the parietes 
of the pelvis, and affords equal resistance to 
the progress upwards of matter or other effu- 
sions from below; it may be considered as a 
sort of shelving roof to the perineum, and a 
concave floor to the abdomen. Its density and 
strength are at their maximum in front, whilst 
both these properties diminish as it approaches 
the rectum. Above it, is found a quantity of 
loose adipose cellular membrane, continuous 
without line of demarcation with the subserous 
tissue of the abdomen, whilst below it are 
situated the cellular tissue of the perineum and 
the several parts comprised in the depths of 
that region. His knowledge of its connections 
teaches the anatomist that urine effused above 
the level of this fascia must soon reach the 
peritoneum and produce the most disastrous 


PERINEUM. 


consequences ; whilst the experienced surgeon 
endeavours in every operation upon the peri- 
neum to limit his incisions, so as to spare the 
fascia now under consideration. 

That portion of the inferior surface of the 
bladder which projects into the perineum is — 
bounded posteriorly by the peritoneal cul-de- 
sac, and extends forwards as far as the prostate 
gland, whilst the line along which the recto- 
vesical fascia takes attachment to the bladder 
forms its lateral limits. The dimensions of 
this part of the bladder are prance 2 vari- 
able, being modified by the degree of vacuity 
or repletion of the organ itself at the time of 
examination, as well as by the age of the 
individual; but its measurements are al | 
much greater transversely than from before 
backwards. In the adult it is in general of 
moderate extent, but it increases considerably — 
when the urinary reservoir is fully distended, — 
and it diminishes as that viscus becomes empty, 
whilst the variable depth of the cul-de-sac of 
the peritoneum (already dwelt upon in a former 
part of this article) is calculated still further to 
render its size uncertain. In the child this 
region of the bladder scarcely exists, an 
maly explained by the pyriform shape of the 
organ in early life, the narrow neck of 
bladder being then its most dependent portion, 
and the peritoneum being prolonged very 
downwards towards the anus. In old age th 
perineal portion of the bladder often exhil 
extraordinary developement, becoming 
the lowest part of the whole organ, and for 
ing a pouch which projects remarkably to 
the rectum. In many instances calculi becom 
lodged within this depressed part of the vi 
far beneath the level of the cervix vesicx, § 
as to elude detection by the sound ; and in 
manner is explained the valuable assist 
which the finger introduced into the 
so frequently affords the surgeon in orit 
the bladder for a stone. The perineal ic 
of the bladder rests in great measure upon the 
rectum; in the middle line it is in immed 
contact with the gut, but towards either side 

of the vesicula seminalis and vas defere 

1s inte : . 
This region of the bladder has 
special attention from anatomists in ¢ 
quence of its presenting a small trian 
space, in which the operation of recto- 
aracentesis is, or ought to be, perform 

e triangular space in question is ¥ 
small and very nearly equilateral; its b 
rected backwards and upwards, is formed 
the peritoneal cul-de-sac; the vasa defere 
and the vesicule seminales to the bee 
left respectively constitute its sides, whilst 
notch in the prostate gland represents its 
The surgeon ought to consider carefully | 
extent of surface which the area of this trian 
comprises, as well as the average distance fi 
the anus at which it is placed; for should th 
bladder be punctured behind this “pf 
election,” the peritoneum must be 
and should the trocar be introduced in 
it, the prostate gland and common ejacu 
ducts would be endangered, whilst the 


+ 


ag 


VUT 


PERINEUM. 


est deviation to either side brings the correspond - 
ing vas deferens and vesicula seminalis into 
peril. In the majority of full-grown subjects 
the space under consideration is about three 
inches distant from the anus, so as to permit 
the index finger of the operator to reach it 
without difficulty; but from statements already 
made the reader will perceive that many excep- 
tions to this rule may be encountered in prac- 
tice. Again, the sides and base of this triangle 
(so long as the neighbouring parts remain in 
situ) are in general each of them respectively 
less than one inch in length; yet when thee 
bladder is removed from the subject and artifi- 
cially distended, and when the connections of 
the peritoneum are disturbed by dissection, the 
space to which we refer becomes immensely 
enlarged, and the anatomist is then apt to form 
a most exaggerated and erroneous idea of its 
natural dimensions. 

Against the recto-vesical paracentesis many 
very serious objections may be raised. In 
early life it should not be attempted, because 
at that period the peritoneum descends so low, 
and the under surface of the bladder is so little 
developed, that injury to the serous membrane 
of the abdomen would almost necessarily en- 
sue. Even in the adult the great uncertainty 
of the depth of the peritoneal cul-de-sac, added 
to the utter impossibility of ascertaining its 
extent in the living subject, constitutes a weighty 
argument against the operation ; whilst the 
enlarged prostate (so very common in old men) 
must frequently forbid its performance in after 
life; and the danger of wounding the vas 
deferens or the vesicula seminalis, or of pro- 
ducing urinary infiltration or a permanent fis- 
tula, may be fairly urged against this mode of 
relieving the bladder, at whatever age under- 
taken. The other methods employed for the 
same purpose in extreme cases of retention of 
urine are also no doubt open to valid objec- 
tions, but any further consideration of this 
subject would be out of place in the present 
article. 

In order to perform lithotomy successfully, 
or to tap the bladder with safety, the surgeon 
should ever bear in mind the direction of the 
axis of that organ. In the adult male the axis 
of the bladder runs nearly parallel to the axis 
of the upper strait of the pelvis; but upon a 
_ lower plane, that is to say, nearer to the pubis, 
if produced, it would pass superiorly through 
the linea alba between the umbilicus and the 
pubis, and it would touch the inferior extre- 
mity of the coccyx below. In the child its 
direction is very variable, for the urinary reser- 
voir being then in the abdomen and in contact 
with the anterior wall of that cavity, must 
‘necessarily move in obedience to the abdominal 
muscles, and every change of position which 
‘the bladder undergoes exerts a marked influ- 
ence upon its axis. During childhood the axis 
of the bladder appears in the dead subject to run 
from before backwards nearly horizontally, be- 
€ause the distended bladder, no longer sup- 
ported by the abdominal muscles, turns for- 
wards over the pubis; but in the living child, 


923 


when the recti abdominis are forcibly con- 
tracted, the line in question becomes nearly 
vertical. 

Tue vuREeTHRA.— Anatomists describe the 
urethra as a canal presenting a double curva- 
ture, of which the anterior segment is highly 
moveable, and of which the posterior is in a 
great measure fixed. The anterior segment 
(comprising the spongy portion of the urethra 
from the meatus urinarius to the vicinity of the 
bulb) exhibits, in the flaccid condition of the 
penis, a marked curvature concave downwards, 
which disappears, however, during erection, and 
which exerts little influence upon catheterism, 
since the surgeon easily obliterates it by raising 
the penis until it forms an angle of about forty 
degrees with the anterior wall of the abdomen. 
The posterior segment (consisting of the whole 
of the prostatic and membranous portions of 
the urethra, and also of the posterior part of 
its spongy portion) presents on the contrary a 
permanent curvature concave upwards, and 
belonging essentially to the perineum, it re- 
quires in this place a special description. To 
dissect the perineal portion of the urethra with 
advantage, the anatomist ought to remove the 
greater part of the ossa pubis and the ascending 
rami of the ischia from a recent subject, with 
the penis, the bladder, and the rectum attached ; 
this can be easily accomplished by cutting the 
herizontal ramus of the pubis at each side 
perpendicularly with a saw as near the aceta- 
bulum as possible, after which the instrument 
may be made to traverse the foramen ovale, 
and divide the ramus of the ischium in the 
immediate vicinity of its tuberosity. If the 
bladder be then inflated from one of the ureters, 
and the rectum distended, the preparation will 
exhibit in a satisfactory manner the urethra and 
many other parts described in this article, of 
which but an imperfect view is obtained in 
the ordinary dissection of the perineum from 
below. 

The posterior segment of the urethra repre- 
sents a reversed arch, of which the centre lies 
about ten lines beneath the symphysis pubis, 
whilst the extremities incline upwards, the one 
in front and the other behind the symphysis. 
Ample provisions exist to render this arch per- 
manent; its centre, constituted by the mem- 
branous portion of the urethra, is transmitted 
through the triangular ligament, and adheres 
by its circumference to the edges of the opening 
through which it passes; its posterior extre- 
mity, formed by the prostatic urethra, is tied 
up to the back of the pubis by the anterior true 
ligaments of the bladder, whilst the true sus- 
pensory ligament of the penis in front, and the 
prolonged attachments of the crura penis, pin- 
ning that organ up to the anterior surface of the 
pubis, raise the spongy portion of the urethra 
at its commencement, and consequently elevate 
the anterior extremity of the arch. The per- 
manency of this arch depends of course mainly 
upon the strength and resistance of the afore- 
said ligaments ; yet, although the properties of 
these structures are well known to anatomists, 
a difference of opinion prevails as to the pos- 


924 


sibility of rendering the urethra straight by 
simple traction of the penis. 
he true suspensory ligament is calculated 
by its position and strength to prevent the 
surgeon from depressing the penis sufficiently 
to straighten the urethra, and in the dead sub- 
ject no force so applied, short of what suffices 
to tear the ligament in question and to rupture 
partially the attachment of the crura penis to 
the bones, can efface the curvature of the pos- 
terior segment of the canal, but if the suspen- 
sory ligament be divided by the knife, and if 
at the same time the crura penis be detached 
ever so little from the pubis, the slightest trac- 
tion exercised subsequently upon the penis 
renders the urethra perfectly straight. The 
writer by no means intends to deny that cathe- 
terism by straight instruments is a feasible 
operation: to straighten the urethra by drawing 
the penis in certain directions, and without any 
other aid, is one thing, and to introduce a 
Straight instrument into the bladder along the 
urethra is a totally different matter; to accom- 
plish the former, either in the living or the 
dead subject, so long as the true suspensory 
ligament is uninjured and the crura penis re- 
tain their attachments, will be found absolutely 
impossible, whilst the latter operation may 
very generally be performed by any surgeon 
who possesses ordinary dexterity. The princi- 
ple on which the introduction of straight in- 
struments is effected admits of ready explana- 
tion. By raising the penis as before described 
the operator renders the urethra, from the 
glans to the buib inclusive, perfectly straight, 
and therefore the staff traverses the passage 
so far without impediment, but any attempt 
to force it farther in the same direction would 
rupture the lower wall of the urethra, and pro- 
pel the point of the instrument towards the 
rectum. The hinder portion of the canal leads 
upwards and backwards to the bladder, and it 
therefore remains to be explained how a straight 
instrument, occupying the spongy part of the 
urethra, and with its point directed downwards 
and backwards towards the rectum, can have 
its course so changed as to pass upwards and 
backwards to the bladder. The solution of the 
problem is easy: the handle of the instrument 
is first drawn forwards so as to form a right 
angle with the pubis, and then depressed until 
it becomes nearly parallel with the patient’s 
thighs, whilst at the same time an onward 
movement is communicated to it, whereby the 
OF glides upwards and backwards into the 
ladder. In these movements the staff ob- 
viously represents a lever of the first order, the 
fulcrum formed by the lower wall of the ure- 
thra opposite to the true suspensory ligament of 
the penis, and the beak of the instrument 
being elevated as its handle is depressed. 

In addition to its curvature, that part of 
the urethra which belongs to the perineum pre- 
sents other features of interest to the surgical 
anatomist. In the dead subject its diameter is 
naturally far from uniform, whilst in the living 
its calibre is exceedingly liable to vary, accord- 
ing to the contraction or relaxation of the 


PERINEUM. 


_of which is directed forwards, whilst on eith 


muscular expansions which in certain situations 
invest it. Its parietes also exhibit in man 
places peculiarities of organisation calcu 
to embarrass the surgeon, and therefore some 
further notice of this part of the canal becomes 
here necessary. . ; 
The prostatic portion of the urethra is an 
inch and a quarter or at most an inch and a half 
in length. In the adult it takes an obli 
direction from above and behind down 
and forwards; but in the aged subject it rum: 
more horizontally, a change produced the 
developement of the “ bas fond” of the bladder; 
and in the child its course is nearly vertical in 
consequence of the position of the bladder at t 
period of life. The prostatic urethra is slight 
contracted at each extremity, whilst in the in- 
termediate space it is somewhat widened, the 
dilatation being most observable near its Ic 
wall. The verumontanum or caput gallina 
ginis, a prominent fold of mucous membrane 
extends in the middle line along the floor 6 
this part of the canal: it exhibits anteriorly 
depression named the sinus pocularis, the ori 


side the aperture of the common ejaculator 
duct usually opens. The verumontanum — 
placed between two deep depressions calle 
the prostatic sinuses ; these contain numero’ 
orifices of the prostatic ducts, a few only bei 
observable on the upper wall of the urethi 
At the posterior extremity of each sinus 
transverse fold of mucous membrane, of wi 
the free concave margin looks forwards, mi 
be occasionally observed; this has been ¢ 
the “ pyloric valve” by M. Amussat; t 
the majority of subjects no such structure ex 
and when present it is generally occasioned 
an incipient enlargement of the third lobe 
the prostate gland, which, projecting upws 
from below, elevates the mucous membra 
at either side, so as to produce the 
arrangement in question. 

From this brief exposition it follows 
many impediments to catheterism may be 
countered in the prostatic portion of the u 
The ducts which open upon its walls 
their orifices mostly directed forwards, 
sometimes morbidly enlarged, when they m 
easily arrest the point of a fine bougie; 
the prostatic sinuses forming depressions be 
the level of the floor of the urethra 
folds of mucous membrane just describe 
also calculated at times to entangle a si 
sized instrument. Most of these impedim 
are situated along the floor of the urethra, 
from their very nature they are likely to ob: 
none but the smallest instruments. To 
them, therefore, the surgeon should if pos 
select an instrument of large size and d 
the point along the upper wall of the pas 
The difficulties of catheterism are some’ 
vastly increased by disease of the prostate g 
but obstructions of that description are bey 
the scope of this article. emarka 
sympathy so constantly observed in pract 
between the testicle and the urethra is explail 
by the manner in which the lining men 


¢ 


1 


PERINEUM. 


of the vas deferens becomes continuous with 
that which carpets the urethra at the orifice of 
the common ejaculatory duct. 

The membranous portion of the urethra is 
intermediate between the prostatic and the 
spongy portions of that canal. In situ its 
length seldom exceeds three quarters of an 
inch, but when detached and extended it ap- 
pes about an inch long. Its direction is nearly 

orizontal, but its upper surface presents a very 
slight curve, concave towards the pubis. Its 
under surface is overlapped from before by the 
bulb, a disposition which diminishes somewhat 
the apparent length of its lower wall. Its 
anterior extremity is fixed by the triangular 
ligament of the urethra, a structure of uncom- 
mon strength, through which it passes; but 
erly it projects behind the triangular 
igament for a short distance, and being there 
girded by Wilson’s muscles, which support it 
like a sling, it possesses in that situation con- 
siderable mobility. The membranous portion 


of the urethra is naturally the narrowest part of » 


the canal, presenting in this respect a marked 
contrast to the prostatic and spongy portions. 
Its parietes are endowed with considerable 
agi of resistance, being strengthened in 
ront by the triangular hgament, which sends 
forwards upon them an expansion continuous 
with the fibrous covering of the bulb; whilst a 
still stronger expansion derived from the back 
of the triangular ligament surrounds the urethra 
beneath Wilson’s muscles, and affords it power- 
ful protection posteriorly. Between this latter 
investment and the mucous membrane a pecu- 
liar structure exists of which the exact nature 
is rather doubtful, some considering it a modi- 
fied erectile tissue, whilst others look upon it as 
muscular. 

The membranous portion of the urethra 
merits from the surgical anatomist an attentive 
consideration. It is here that the operator lays 
bare the groove of the staff in lithotomy per- 
formed after the lateral or bilateral methods; 
this is the situation in which spasm usually 
arrests the catheter, the obstruction being pro- 
duced by undue action of Wilson’s muscles. 
Foreign bodies, such as calculi, are very likely 
in consequence of its diminished calibre to be 
impacted in this part of the canal, and its 
anterior extremity is frequently the site of per- 
manent stricture. 

In using a curved catheter the surgeon should 
slacken the penis upon the instrument so soon 
‘as its point has fairly traversed the triangular 
ligament; for if, during the further depression 
‘of the handle, the penis be forcibly stretched 
upon the catheter, its point may push the upper 
‘wall of the urethra against the back of the 
pubis, and in that manner produce considerable 
mischief. It is also of advantage to communi- 
eate a slightly onward movement to the catheter 

this part of the passage, as the bladder is 
Situated much more posteriorly, and in the 
introduction of any instrument, whether curved 
or straight, it should be borne in mind that 
spasmodic obstructions yield in general to gentle 
ut continued pressure, and that attempts to 
ree such strictures are usually productive of 


925 


increased spasm, and, if persisted in, of lacera- 
tion of the urethral canal. 

In connexion with the perineum, so much of 
the spongy portion of the urethra only as is 
covered by the acceleratores urine muscles re- 
quires to be considered, and of this the bulb 
constitutes the largest and most important part. 
The bulb is an oval swelling, in which the 
corpus spongiosum urethre commences poste- 
riorly, it varies in size according to the sub- 
ject, being small during childhood, enlarging 
very much at puberty, and often presenting 
excessive dimensions in old men ; during erec- 
tion, too, it is turgid and swollen, though at 
other times it remains comparatively flaccid. The 
length of the bulb, when well developed, may be 
estimated at an inch and a half, and its thickness 
or depth from the cavity of the urethra at about 
eight lines. Its posterior extremity is thick and 
overlaps the membranous portion of the ure- 
thra, whilst anteriorly the bulb becomes gra- 
dually narrower, but there is no exact line of 
demarcation between that body and the re- 
mainder of the corpus spongiosum. The bulb 
is situated between the crura penis and in front 
of the triangular ligament of the urethra, to 
which it is connected by the expansion of 
fibrous membrane already described ; it is co- 
vered by the acceleratores urine, and derives 
from them a muscular sheath all but perfect. 
The bulk of this body is constituted by a 
spongy erectile tissue, remarkably soft, and 
possessing intrinsically little powers of resist- 
ance, but a thin fibrous membrane of invest- 
ment affords 1t some protection from without. 
The canal of the urethra in this situation pre- 
sents a slight dilatation (most observable infe- 
riorly) named the sinus of the bulb, and the 
delicate ducts of Cowper’s glands, two in num- 
ber, open into the lower and lateral parts of the 
passage still further forwards. It should be 
particularly noted that the bulb, measured at 
the exterior, is in point of size quite out of 
proportion to the width of the corresponding 
part of the urethral canal, the canal presenting 
but a slight dilatation, whilst the dimensions of 
the bulb are very considerable; and of equal 
importance in practice is the fact that the axis 
of the bulb differs widely from the axis of the 
corresponding portion of the canal, the axis of 
the bulb running in a very oblique direction 
downwards and backwards towards the lower 
extremity of the rectum, whilst the axis of the 
canal lies upon a higher. plane and runs much 
more nearly horizontally backwards. 

In a healthy urethra the principal difficulties 
of catheterism, whether performed by straight 
cr by curved instruments, are encountered at 
this part of the passage: the sudden change 
in direction which the urethra here undergoes, 
the abrupt narrowing of the membranous por- 
tion immediately behind the dilatation of the 
bulb, the mobility of the urethra in front of 
the triangular ligament, and its immobility 
where it passes through that structure, the ease 
with which a catheter perforates the delicate 
tissue of the bulb, and, above all, the striking 
difference in direction observable between the 
axis of the bulb and the axis of the correspond- 


~ 


926 


ing portion of the urethral canal, explain this 
sufficiently ; nor should it be forgotten that the 
muscular girth formed by the acceleratores 
urine is often the seat of spasm. 

The error in catheterism of most frequent 
occurrence here is the perforation of the floor 
of the urethra at the bulb, after which the ex- 
tremity of the instrument passes between the 
rectum and the urethra. The surgeon commits 
this mistake by neglecting to depress the handle 
of the catheter in time to raise the point out of 
the sinus of the bulb into the membranous 
portion, and so much the more readily as the 
slightest force exercised in this wrong direction 
is sufficient to perforate the spongy tissue. 

The premature depression of the handle of 
the catheter may likewise injure the urethra, 
but in a different manner, for if that ma- 
neeuvre be executed too soon and with undue 
force, the point of the instrument will lacerate 
the upper wall of the canal anterior to the tri- 
angular ligament. 

A difficulty may, however, be experienced 
in entering the membranous portion of the 
urethra, even though the handle of the catheter 
be depressed at the proper time; the surgeon 
in such cases fails to “hit off” the aperture in 
the triangular ligament which transmits the 
urethra, and the point of the instrument swerv- 
ing laterally, comes to press against the front of 
the triangular ligament at one side of the orifice, 
instead of traversing the orifice itself. To guard 
against such a casualty, care must be taken to 
keep the point of the catheter fairly in the 
middle line, and (should any obstruction arise) 
to exercise slight traction upon the penis for the 
purpose of rendering tense the fibrous covering 
of the bulb, and in that manner stretching the 
opening in the triangular ligament. 

From these principles it clearly follows that, 
except under peculiar circumstances, curved 
instruments are to be preferred, for their adapta- 
tion to the curvature of the canal enables them 
to reach the bladder without exercising undue 
pressure upon any part of the passage ; whilst 
the straight staff conducted ever so skilfully 
must to a certain extent strain or disturb the 
arn curved portion of the urethra. 

ut, besides this obvious advantage, the natural 
impediments to catheterism (placed chiefly 
along the floor of the e) are also most 
easily surmounted by the curved instrument, 
for its point can at any moment be readily 
raised by the operator, whilst he accomplishes 
the same object much more imperfectly in 
using the straight staff. It cannot be denied, 
however, that, for certain pr secs straight 
instruments possess a decided superiority, and 
therefore every surgeon should be prepared to 
employ them when the occasion suits. 

preceding outline describes with suffi- 
cient accuracy the course and relations of the 
principal organs belonging to the perineum, 
and therefore it now only remains to study the 
anatomy of this region from below, according to 
the usual method of dissection. The subject is 
of course supposed to be placed in the ordinary 
position, with a full-sized staff introduced into 
the bladder, the rectum artificially distended, 


PERINEUM. 


the scrotum raised and drawn forwards, the 
hands bound firmly to the ankles at each side 
respectively, the pelvis elevated on a block, and — 
the knees separated to a convenient distance 
from each other. if 

Prepared in this manner, the perineum pr 
sents auteriorly a well-marked median promi- 
nence corresponding to the urethra, and which 
for obvious reasons enlarges considerably in 
the living subject during erection. At either 
side of this urethral prominence a page 
pression exists, external to which sisting 
edges of the rami of the ischium and pubis may 
be always readily recognised by the finger. At 
the posterior part of the perineum the point 0 
the coccyx may be felt distinctly in the middle 
line ; the tuberosities of the ischia covered by; 
great depth of soft roject remarkably 2 
the Nae onetemiee tunetenal lateral limit 
of the region, whilst the mid space betweer 
these eminences exhibits a deep depressi 
containing the anus. In front of the ' 
central elevation of the skin termed the raph 
extends forwards along the perineum, and ma 
be traced distinctly to the scrotum and pent 
it serves as a guide to the surgeon in ma 
operations, pointing out the middle line ace 
rately so long as the integuments retain the 
normal relations. 

Integument.—The characters of the 
neous covering of the perineum are not uni 
throughout ; in some situations its thickness 
very considerable, whilst in others it appes 
remarkably delicate. In front the skin beee 
gradually finer as it approaches the sere 
and at the margins of the anus its delice 
extreme; but in the neighbourhood of t 
tuber ischii and along the edge of the glut 
maximus it possesses great cone and 
considerable resistance to the pel: at 
circumference of the region it in fact grade 
assumes the properties of the neighbouri 
gumentary membrane, resembling that ¢ 
scrotum anteriorly, merging insensibly into 
integument of the buttock and thigh later 
and even approaching to the characters of | 
cous membrane in the vicinity of the gut; 
generally of a dark brown colour in the h 
adult, and of a lighter hue in the child 
there are in this respect numerous indiy 
varieties ; the darker the teint the more h 
developed usually are the subjacent mu: 
Ciscoe follicles abound in the perit 
and occur in greatest numbers near the anus 
at the root of the scrotum, where 
tions are most required. The skin aroy 
anus is thrown into ruge disposed in a t% 
manner, and which produce a puckered aj 
ance so long as the orifice remains cont 
they pg a during its dilatation, and a 
signed to favour the extreme distension 
the anal extremity of the intestine is oce 
ally subjected during defecation. The 
question become at times the seat of 
ulceration, or excrescence, which may di 
surgical interference for their relief. 

In the lateral operation of lithotom y the 
incision should commence at the left side ¢ 
raphé, about an inch or an inch and a gt 


=a 


PERINEUM. 


in front of the anus, and extend in an oblique 
direction backwards and outwards to the point 
midway between the tuber ischii and the orifice 
of the gut. In the bilateral operation the first 
incision is semilunar, the cornua placed at 
either side between the tuber ischii and the 
anus, and equidistant from these points respec- 
tively, the centre situated about three quarters 
of an inch in front of the anal aperture, and the 
concavity of the curve directed backwards. 
For convenience the operator in general begins 
this incision on the right side of the perineum. 
On removing the integuments the anatomist 
brings into view anteriorly the superficial fascia 
of the perineum, surrounding the anus the cuta- 
neous sphincter, and at either side of the gut a 
large quantity of adipose cellular tissue, which 
fills up in great measure the interval between 
the intestine and the tuber ischii. If the dis- 
section have been carefully conducted, some ner- 
vous twigs are also visible near the rami of the 
ischium and pubis; they are mostly cutaneous 
and derived from the sciatic branch of the lesser 
Sciatic nerve (the “perineal cutaneous” of 
many authors, the “ long inferior pudendal ” of 
Semmering) in its course to the scrotum and 
root of the penis. This nerve or its branches 
are always superficial and liable to injury in 
many operations performed upon the perineum. 
The superficial fascia.—The superficial peri- 
neal fascia has been by some anatomists de- 
scribed as two membranes essentially separate 
and distinct from each other, that nearer to the 
surface being called the “ subcutaneous cellular 
membrane” of the region, and the deeper of the 
two being designated “ the superficial fascia of 
the perineum.” To the writer this description 
appears unnecessarily minute, for in fat subjects 
it is exceedingly difficult to effect such a sepa- 
ration, and under the most favourable circum- 
stances the dissection in question is too artificial ; 
with equal propriety might the superficial fascia 
of the abdomen be divided into layers, for like 
that in the perineum, its cutaneous surface is 
cellular and often loaded with fat, whilst its 
deeper surface assumes very much an aponeu- 
rotic appearance. : 
The superficial perineal fascia is a cellulo- 
aponeurotic expansion interposed between the 
integuments and the principal muscles, &c. of 
the region, (to this, however, the superficial 
sphincter muscle, which is absolutely subcuta- 
neous, forms an exception ;) in the anterior or 
 genito-urinary division of the perineum it is of 
“very considerable thickness, being mostly cellu- 
lar and fatty superficially, and becoming more 
“dense the deeper the dissection is carried; nu- 
merous fibrous bands are interwoven with this 
expansion, and appear more and more evident 
the farther from the integument it is examined, 
‘so that at length, just like the superficial fascia 
“of the abdomen, it assumes very much the cha- 
cters of fibrous membrane. The varieties in 
density which this fascia presents in different 
‘subjects are nearly endless; in corpulent per- 
Sons its grossness is sometimes excessive, and 
when condensed by inflammation its depth be- 
comes extreme: this explains the surprising 


927 


distance from the-surface to which the surgeon 
usually cuts in liberating the matter of a peri- 
neal abscess, and shews the lithotomist the ne- 
cessity of duly estimating the thickness of this 
structure before he commences his operation. 
Traced forwards the superficial fascia becomes 
gradually thinner until at length it degenerates 
into cellular membrane continuous almost with- 
out line of demarcation with the dartos, and as 
it approaches the scrotum it becomes loose in 
texture, whilst its cells communicate freely with 
each other and contain little adipose substance, 
if any. Followed laterally it seems at first 
sight to merge gradually into the subcutaneous 
cellular tissue of the thigh, but when examined 
from beneath by being raised in a flap from the 
middle line outwards, it is found to adhere by 
strong tendinous attachments to the edge of the 
pelvis, and so powerful is this adhesion that all 
attempts to pass the handle of a scalpel out- 
wards between the fascia and the rami of the 
pubis and ischium uniformly fail. 

In the posterior or anal division of the peri- 
neum the superficial fascia is little more than a 
cellular web, appearing, however, somewhat 
denser in the space between the tuber ischii 
and the anus; here its continuity with the 
subcutaneous cellular membrane of the gluteal 
region may be easily demonstrated, and it also 
dips in deeply into the ischio-rectal fossa, 
where its cells become inordinately loaded with 
fat. If the superficial fascia be carefully raised 
from before backwards, a deep process of this 
membrane may be seen to form a partition 
between the genito-urinary and the anal divi- 
sions of the perineum. The process referred to 
constitutes a septum, which, after dipping in 
deeply behind the wansversi perinei muscles, 
becomes identified with the base of the trian- 
gular ligament of the urethra; to demonstrate 
this connection, however, requires some nicety 
of manipulation and a suitable subject. In 
raising this fascia the anatomist cannot fail to 
observe that its adhesion to the subjacent parts 
is everywhere extremely loose, except in the 
situations already specified. 

The peculiar structure and the connections of 
the superficial perineal fascia afford a satisfac- 
tory explanation of the course which urinary 
effusions generally take in the living subject. 
When urine escapes into the perineum in con- 
sequence of rupture or ulceration of the ure- 
thra, provided the solution of continuity be 
seated superficial to the triangular ligament of 
the urethra, the liquid makes its way forwards 
to the scrotum, and after distending that part it 
proceeds upwards to the abdominal parietes, 
occasionally reaching the umbilicus, or even 
attaining to a higher level. The effusion rarely 
passes downwards along the thighs, or back- 
wards to the neighbourhood of the anus, and 
its progress to the surface in the perineum is 
invariably tedious. In such cases the close 
adhesion of the superficial fascia to the rami of 
the pubis and ischium prevents the urine from 
reaching the thigh; the connection of the 
superficial fascia to the base of the triangular 
ligament of the urethra opposes its progress 


928 


towards the anus; the density of the triangular 
ligament of the urethra impedes its passage 
into the pelvis; whilst the loose connection 
between the superficial fascia and the subjacent 
structures in front, the remarkable laxity of the 
dartos, and the continuity of this latter with 
the superficial fascia of the perineum on the 
one hand, and with that of the abdomen on 
the other, are so many circumstances inviting 
the stream to the scrotum, the penis, and the 
walls of the abdomen. The promptest treat- 
ment is demanded to remedy mischief such as 
has been described. A free division of the 
integuments and fascia in the perineum ‘over 
the seat of rupture, for the purpose of giving 
the urine vent and putting a stop to further 
effusion, becomes indispensable, and without 
this measure all others must be unavailing. 

The laxity of the superficial fascia as it 
approaches the scrotum should deter the sur- 
geon from commencing his cutaneous incisions 
in the lateral operation of lithotomy too far 
forwards, lest urinary infiltration should ensue ; 
and the density of the same structure in other 
situations indicates an early incision for the 
release of matter imprisoned beneath it. 

For a description of the posterior or anal 
division of the perineum, including the ischio- 
rectal fosse and the neighbouring fibrous mem- 
branes, the reader is now referred to the arti- 
cle Anus, where all the structures connected 
with the lower extremity of the rectum are 
described in detail. It should be borne in 
mind, however, that some branches of arteries 
(the inferior or external hemorrhoidal) pass 
across the ischio-rectal fosse, entangled in the 
fat which occupies those excavations. The 
inferior hemorrhoidal vessels are usually three 
in number at each side; they derive their origin 
from the internal pudic artery, as it lies be- 
neath the obturator fascia; their destination is 
the lower extremity of the gut and its appen- 
dages, and one of them (the most anterior) 
gains the front of the intestine to anastomose 
with a similar vessel from the opposite side, 
and with branches of the transversalis perinei 
also. The inferior hemorrhoidal vessels are 
remarkably tortuous and rather uncertain in 
their course ; the anterior of them is sometimes 
divided in the lateral or bilateral operations of 
lithotomy, a circumstance which has led to this 
cursory notice of their anatomy. 

When the superficial fascia has been dis- 
placed, many new parts become apparent in the 
genito-urinary division of the perineum; a 
quantity of loose adeps and also a very thin 
glistening fibrous expansion which adheres 
closely to the subjacent muscles and obscures 
’ the dissection, must, however, be carefully re- 
moved before the deeper structures are satis- 
factorily displayed. The central tendinous 

int of the perineum, the superficial perineal 

loodvessels and nerves, the transversalis peri- 
nei artery with its accompanying veins and 
nerves at each side respectively, the urethra 
itself, still however obscured by the accelera- 
tores urine muscles, the crura penis, each 
partly enveloped by the erector penis muscle, the 


PERINEUM. . 


transversi perinei muscles, and two small trian- 
gular spaces bounded by muscles and placed — 
one at either side of the urethral prominence, 
are the principal objects which come into view. 
The central tendinous point of the perineum — 
is situated in the middle line, equidistant from — 
the anus and the bulb of the urethra. It is a 
common point of insertion to many muscles; 
thus the superficial sphincter of the anus can 
be fairly traced to this spot, and so can many 
fibres of the acceleratores urine, the 5 
perinei, the levatores ani, and Wilson’s mus- 
cles. Here muscular fibres from opposite sides 
of the perineum become blended with eac 
other; here, too, those from before and those 
from behind are intermixed, and some even 
descend from within the pelvis to identifi 
themselves in this place with others which are 
subcutaneous. “* 
The superficial perineal artery (the perines 
artery of some anatomists), though not a large 
vessel, yet takes a lengthened and very regular 
course. Its origin is from the internal pudie 
artery at some little distance behind the trans- 
versus perinei muscle, whilst the parent trum 
is still under cover of the obturator fascia; 
immediately pierces that membrane, and like 
wise very generally passes through the base o 
the triangular ligament of the urethra. T 
artery next curves around the transversus f 
nei muscle lying on its superficial surface an 
running across its fibres. The vessel then in 
clines forwards and inwards through the tria 
gular interval between the accelerator uri 
and the erector penis muscles, until at lengt 
reaches the scrotum, and assuming the nam 
of “the arteria septi,” it terminates in a fre 
anastomosis with the other arteries supplyit 
the envelopes of the testicles. The superfic 
perineal artery lies deep posteriorly, but 
position becomes very superficial as it | 
roaches the scrotum; its branches are dis 
uted freely to the muscles and integuame 
and they likewise anastomose internally wi 
branches from the corresponding artery of th 
opposite side, and externally with superfic 
branches from the thigh. Two veins acc 
pany this artery; they are frequently di 
and tortuous in front, and in certain disi 
conditions of the testicle or its coverings 1 
sometimes form a complicated net-work it 
scrotum. al 
The inferior or superficial division of 
pudic nerve (“ the perineal nerve” of 
authors) follows pretty nearly the cot 
these vessels; like the artery, it is destine 
the scrotum, where it terminates by s 
long and very fine branches, after supply: 
its progress numerous twigs to the trans 
perinei, accelerator urine, levator 
erector penis muscles. One very 
branch of this nerve (the bulbo-ureth 
Cruveilhier) may be traced fairly into thi 
whilst another (the external perineal 
same anatomist) runs superficial 
lateral part of the region, reinforcing 
anastomosing with the perineal ecutan 
branch of the lesser sciatic nerve. 


a 
a 


PERINEUM. 


The transversalis perinei artery is of small 
Size; it springs from the internal pudic, a little 
anterior to the source of the superficial perineal 
artery, but these two vessels not unfrequently 
arise by a single common trunk. The trans- 
versalis perinei artery passes through the obtu- 
rator fascia, and often perforates the base of 
the triangular ligament of the urethra ; it quickly 
becomes superficial, applying itself to the cuta- 
neous surface, and running usually near the 
posterior edge of the transversus perinei mus- 
cle, it thus gains the central tendinous point 
of the perineum, where it anastomoses with 
the inferior hemorrhoidals from behind, the 
transversalis and superficialis perinei arteries 
from the opposite side, and with the neigh- 
bouring superficial perineal. This vessel is 
accompanied by two veins and by one or more 
branches of the superficial division of the 
pudic nerve. 

The accelerator urine muscle (the ejaculator 
seminis of some anatomists, the bulbo-caver- 
nosus of others) extends from the central ten- 
dinous point of the perineum forwards along 
the urethra, being identified with the correspon- 
ding muscle of the opposite side in a raphé 
which occupies the middle line; and so inti- 
mate is this connection that both might be 
conveniently described together as a single 
muscle. The fibres of the accelerator urine 
spring from the side of the raphé, and pass 
from thence outwards and upwards upon the 
urethra. The anterior fibres incline very ob- 
liquely forwards and outwards to arrive at 
the surface of the corpus cavernosum penis, 
where they terminate. In consequence of this 
disposition the acceleratores urine muscles 
are separated from each other in front by a 
Y-shaped interval in which the urethra appears. 
The succeeding fibres, after embracing the 
urethra laterally, are lost on a short horizontal 
tendon, which likewise receives the correspond- 
ing fibres of the opposite muscle. This tendon 
is placed above the urethra, beneath the junction 
of the crura penis, and anterior to the triangular 
ligament of the urethra. The posterior fibres 
incline outwards more than the others, and are 
inserted into the superficial surface of the 
triangular ligament of the urethra, many of 
them extending nearly to the crus penis. The 
accelerator urine muscle lies on the bulb and 
the neighbouring portion of the corpus spongi- 
osum. In conjunction with its fellow it con- 
stitutes a fleshy sheath, all but perfect, for the 
urethra. Its action is to compress the canal, 
and at the same time to draw forwards the 
bulb. It is employed in expelling the semen 
and the last drops of urine from the sinus of 
the bulb; and by contracting spasmodically it 
May even arrest the progress of a catheter, an 
occurrence explained by the manner in which 
“many of its fibres completely surround the 
passage. 

_ The erector penis muscle (called sometimes 
“the compressor penis,” or “ the ischio-caver- 
hosus,”) is placed obliquely along the lateral 
“Margin of the genito-urinary division of the 
perineum, where it partially envelopes and 
conceals from view the corresponding crus 
VOL. III. 


929 


penis. It is elongated, broader in the centre 
than at the extremities, and curved so as to 
embrace the crus on which it is moulded. 
The erector penis springs by a narrow tendi- 
nous attachment from the inner surface of the 
tuber ischii, and from the extremity of the great 
sciatic ligament beneath the transversus perinei 
muscle; the fleshy fibres soon succeed, and 
after continuing in an oblique direction up- 
wards, forwards, and inwards, they end in 
a fibrous expansion which inclines outwards 
and forwards to terminate by two processes on 
the surface of the corpus cavernosum penis. 
Anatomists are not agreed on the action of this 
muscle: it may serve to draw down and to 
compress the crus penis, and in that manner to 
influence the circulation therein, but it can 
have no direct concern in causing the erection 
of the organ. 

The transversus perinei muscle (“the ischio- 
perineal” of some anatomists) passes from the 
tuber ischii to the central tendinous point of 
the perineum ; in this course the muscle in- 
clines forwards and slightly downwards, so that 
its direction is not exactly transverse. It is 
attached externally to the inside of the tuber 
ischii, above the origin of the erector penis and 
the crus penis; and internally it is confounded 
with the several muscles already specified as 
reaching the central tendinous point. The 
transversus perinei is often of a triangular 
shape, the base at the ischium, and the apex 
at the central tendinous point of the perineum ; 
it is mostly fleshy, except at its insertion, which 
is aponeurotic. This muscle is exceedingly 
uncertain as regards its developement, being 
sometimes replaced by a few scattered fibres 
derived apparently from the levator ani, and 
occasionally reinforced by a second muscle, 
termed the transversus perinei alter. The 
transversus perinei alter, when present, lies 
anterior and superior to the other, and extends 
from the ramus of the ischium to the bulb, 
where it becomes confounded with the accele- 
rator urine. The transversus perinei is related 
by its superficial surface to the superficial peri- 
neal fascia, the superficial perineal and the 
transverse perineal vessels and nerves, the inser- 
tion of the superficial sphincter ani, and the 
origin of the erector penis and the crus penis. 
Its deep relations are the levator ani and Wil- 
son’s muscles, together with the triangular 
ligament of the urethra. The transversus peri- 
nei contributes to the strength of the perineum 
by raising and fixing the central tendinous 
point ; it also assists the levator ani in raising 
and supporting the rectum and the pelvic vis- 
cera. ‘The transversi perinei muscles have been 
by some described as a single digastric muscle, 
semilunar in shape, and with the concave mar- 
gin directed backwards and upwards towards 
the gut; the result of the simultaneous action 
of these two bellies would be to raise and 
compress the intestine in front, and thus to 
assist in completing the process of defecation. 

The triangular spaces are situated one at 
either side of the urethral prominence; each is 
bounded internally by the accelerator urine 
and the urethra, externally by the erector penis 

30 


930 


and the crus penis, posteriorly by the trans- 
versus perinzi, which constitutes the base of the 
triangle, whilst the apex is in front where the 
crus penis and the urethra unite. These spaces 
are small in the natural condition, but when 
carefully dissected they become very distinct ; 
the superficial perineal vessels and nerves 
traverse them from basé to apex ; by separating 
the accelerator uring from the erector penis 
the anatomist obtains a view of the triangular 
ligament of the urethra between these muscles, 
and he may also form some estimate of its 
thickness and strength by the touch. 

When the muscles and other structures be- 
longing to the same layer of parts have been 
removed, the crura penis along the sides of 
the region, the urethra in the centre, and the 
triangular ligament of the urethra stretching 
across the arch of the pubis, are brought fairly 
into view; still further back, in the middle 
line, the recto-urethral triangular space may 
be partially seen, and also some fibres of the 
levator ani muscle descending to their insertion 
from behind the triangular ligament. 

It is unnecessary in this article to describe 
the crura penis minutely. Each crus adheres to 
the rami of the ischium and pubis, becoming 
gradually thicker and larger as it approaches 
the symphysis, and at length the two crura unite 
to form the body of the penis; the lateral 
margins of the triangular ligament of the ure- 
thra, and the great pudic vessels and nerves in 
the last part of their course, are overlapped by 
the crura as they ascend. 

The anatomy of the urethra in respect to 
catheterism has received the fullest considera- 
tion already, but the position of the bulb may 
be now again studied with advantage. This 
body lies in front of the triangular ligament 
of the urethra, and projects backwards and 
downwards towards the rectum; it is situated 
about one inch from the anus, and scarcely 
more than half that distance from the anterior 
wall of the intestine ; yet the narrow interval 
between the bulb and the rectum constitutes a 
portion of the recto-urethral triangular space, 
through which the early incisions in the bila- 
teral operation of lithotomy are carried. The 
bulb is retained in its position by a thin expan- 
sion derived from the anterior layer of the tri- 
angular ligament, and continuous with the 
membrane which invests the corpus spongio- 
sum urethra. 

The triangular ligament of the urethra (“ the 
deep perineal fascia” of some anatomists, “the 
perineal ligament” of M. Carcassone, “the 
middle perineal aponeurosis” of M. Blandin) 
presents itself next for examination. To expose 
the superficial surface of this ligament it is only 
further necessary to detach the crura penis 
from the bones and to free the bulb from its 
connections, but to exhibit the deeper surface 
satisfactorily the dissection must be conducted 
from within the pelvis. The triangular liga- 
ment of the urethra extends from the rami of 
the ischium and pubis at one side to the cor- 
responding edges of bone on the other; its 
superficial surface, directed forwards and down- 
wards, is in contact (so long as the parts remain 


PERINEUM. 


in situ) with the crura penis, the bulb of the 
urethra, and the muscles already ified ; its 
posterior surface, directed upwards and back- 
wards, is related to the prostate gland, the 
membranous portion of the urethra, Wilson's 
muscles, and ie levatores ani; its base, directed 
downwards and backwards towards the rectum, 
gives attachment to the deep process of the — 
superficial perineal fascia, and presents a 
double curvature, being prolongedin the middle 
line into a peak, which adheres to the central 
tendinous point of the perineum; its ape 
corresponds to the lower extremity of the sym- 
physis pubis, and includes the sub-pubie liga- 
ment between its lamin, whilst its lateral mar- 
gins adhere firmly to the rami of the ischium and — 
pubis, and are distinctly continuous with the 
obturator fascia on either side. The ing 
which affords a e to the urethra is si- 
tuated about half an inch or rather less above — 
the base of this ligament, and nearly one inch 
beneath the symphysis pubis, whilst that which 
transmits the dorsal veins of the penis is placed — 
immediately below the sub-pubic ligament. 
The triangular ligament uncommon | 
strength; it serves to fix and to strengthen the 
urethra and to fill up the arch of the pubis, 
completing the walls of the pelvis where the 
bones are deficient, and thus supporting power 
fully the abdominal and pelvic viscera. It con- 
stitutes a perfect partition between the supe 
ficial and the deep structures in the periney 
dividing the genito-urinary portion of this 
gion into two distinct compartments; and 
consists of two lamine inseparably united te 
each other in some places, not so in others 
for Cowper’s glands, the sub-pubic ligament 
the arteries of the bulb, the interna 
vessels in a part of their course, and 
called muscles of Guthrie, are developed betwee 
its layers. 

Cowper’s glands may be displayed 
easefal wothoral of the cuperficial ye a 
triangular ligament ; they are two small greyis! 
bodies, each resembling a pea in shape and ¢ 
mensions, and placed one on either side | 
hind and above the bulb, beneath the me 
branous portion of the urethra, and between 1 
lamin of the triangular ligament. Their due 
which open into the urethra in front of the 
have been already described. 

Guthrie’s muscles, two in number, are si 
ated (according to their discoverer) between 
layers of the triangular ligament; each of thi 
as described by him, arises narrow and tei 
nous from the descending ramus of the p 
hear its junction with the ischium, and bec 
ing fleshy it passes tranversely inwards, — 
soon divides into two fascicull, of which 
spreads out on the upper surface and the o 
on the lower surface of the memb 
of the urethra. In this manner the mu 
from opposite sides meet in a tendinous 
on the middle line of the urethra both @ 
and below, the superior raphé being prolo 
from the prostate gland to the junction oj 
crura penis, and the inferior raphé exten 
from the prostate to the bulb. Viewed ¢ 
from above or from below, these muscle: 


Ls 


r 


anou: I 
P of 


PERINEUM. 


fan-shaped, appearing expanded at the urethra 
and contracted at their origin from the bone, 
and they are believed to have the power of 
compressing the urethra so as to close the canal. 
Notwithstanding the accurate descriptions of 
Mr. Guthrie, many excellent anatomists have 
failed to demonstrate the exact arrangement of 
fleshy fibres which he has remarked, but the 
majority incline to the opinion that the peculiar 
reddish material in question is of a muscular 
nature. 

The arteries of the bulb (one at either side) 
spring from the internal pudic after those ves- 
sels have arrived at the triangular ligament of 
the urethra, and whilst they are overlapped by 
the crura penis. Interposed between the la- 
mine, and situated about a quarter of an inch 
above the base of the triangular ligament, the 
artery of the bulb runs nearly transversely in- 
wards, and near the urethra divides into two 
branches, of which one is small and destined for 
Cowper’s gland, whilst the other is of large 
size and perforates the bulb to supply the 
corpus spongiosum urethre. The arteries of 
the bulb are of considerable magnitude, parti- 
cularly after puberty, so that they bleed pro- 
fusely when wounded ; they retract between the 
layers of the triangular ligament when divided, 
and this added to the narrowness of the peri- 
neum in front, and to the distance from the 
surface at which they are placed, renders it diffi- 
cult for the surgeon to secure their cut extremi- 
ties or otherwise to control their hemorrhage. 
The consequences of such an accident may 
prove speedily fatal; extreme care must there- 
fore be taken to protect these vessels from the 
knife during lithotomy. 

The artery of the bulb is endangered in the 
second period of the lateral operation whilst the 
surgeon cuts into the membranous portion of 
the urethra to lay bare the groove of the staff. 
The knife should be introduced into the urethra 
behind the bulb, and below and behind the 
course of the artery, and little or none of the 
triangular ligament except the posterior lamina 
where it invests the membranous portion of the 
urethra, should be divided in this incision, for 
the vessel requiring protection lies about one 
quarter of an inch above the base of the liga- 
ment, and therefore none but the very lowest 
fibres of that structure can be cut with impu- 
nity ; in short the incision must be made into 
_ the membranous portion of the urethra as it 
lies behind the triangular ligament, and the 
_ bulb must be studiously avoided. Irregularities 
_ in the direction of these arteries calculated to em- 
_ barrass the operating surgeon are occasionally 
encountered ; arising sometimes prematurely 
from the pudic, they ascend very obliquely to 
_ the bulb; and again, although given off from 
_ the pudic at the usual place, they now and then 
take a curved course to their destination, the 
‘convexity of the curvature looking downwards 
-and backwards; when either of these varieties 
occurs, the vessels in question run much closer 
‘to the base of the triangular ligament than 
“usual, and are therefore imminently endangered 
‘in lithotomy. 

_ The internal pudic arteries in their third 


931 


stage belong to the perineum. This stage com- 
mences where the vessel enters the pelvis at the 
lesser sciatic notch, and ends at the ramus of 
the pubis, where it divides into its terminating 
branches. Posteriorly the trunk of the internal 
pudic is (strictly speaking) placed outside the 
precincts of the perineum, being separated from 
the ischio-rectal fossa by the obturator fascia, 
but it runs so close to that part of the region, 
and sends so many of its branches through the 
intermediate partition to lose themselves in pe- 
rineo, that its description may be here legiti- 
mately given. At the commencement of its 
third stage, the internal pudic is interposed he- 
tween the obturator fascia and the obturator 
internus muscle, the muscle separating it from 
the bone, whilst the falciform process of the 
great sciatic ligament covers the artery infe- 
riorly : in this situation it les at a great depth 
from the surface, being upwards of an inch 
above the level of the tuber ischii, and at least 
two inches and a-half distant from the integu- 
ment; it here also describes a slight curve in- 
clining upwards, forwards, and inwards, towards 
the edge of the ramus of the ischium. In the 
latter part of its third stage the internal pudic 
artery insinuates itself between the lamine of 
the triangular ligament, and after continuing 
thus for some distance it at length perforates 
the superficial layer, places itself between the 
crus penis and the ramus of the pubis, and there 
finally divides into the artery of the crus and 
the dorsal artery of the penis. 

On entering the pelvis the pudic arteries of 
opposite sides are widely separated from each 
other, but in the neighbourhood of the pubis 
they gradually converge until their ultimate 
branches meet on the dorsum of the penis ; their 
position likewise becomes more and more su- 
perticial as they proceed. 

In the early part of its third stage the pudie 
artery is accompanied by the trunk of the inter- 
nal pudic nerve, and afterwards for a short dis- 
tance by both the branches of that nerve; but 
the deeper of the two (viz. the dorsalis penis) 
alone continues in relation with the artery in 
the latter part of its course. ‘Two veins accom- 
pany the artery throughout. 

The. position of the internal pudic vessels 
exposes them to injury in the lateral operation 
of lithotomy ; but if their relations be considered 
it will appear that the danger of hemorrhage 
from this source has been much exaggerated. 
The falciform process of the great sciatic liga- 
ment, the crus penis, the projecting edges of 
the bones, and the obturator fascia afford these 
vessels so much protection from below that the 
operator seldom wounds them in cutting into 
the bladder, nor is such an injury possible un- 
less the edge of the knife be lateralized to an 
extreme degree ; but if the knife be carelessly 
withdrawn from the bladder, they certainly 
incur considerable risk, for in that step of the 
operation a layer of fibrous membrane alone 
protects the vessels, and the convex edge of the 
instrument, if directed unduly outwards, might 
readily enough divide them. When such an 
accident has occurred, all attempts to tie the 
bleeding artery in the ordinary manner have 

302 


932 


usually failed, for so deeply do the pudic vessels 
ran, and so firmly bound < hoo are they by the 
triangular ligament and the obturator fascia, 
that the ligature, as commonly applied, has 
proved useless in the hands of even the most 
dexterous surgeons. The open mouth of the 
artery may, however, in such cases be often 
secured by the aid of a curved needle carried 
deeply into the wound, and some practitioners 
(amongst the number M. Roux) have succeeded 
by the same means in tying the pudic artery 
itself in the vicinity of the tuber ischii, a pro- 
ceeding attended with complete success. The 
judicious application of pressure to the bleeding 
point by an a so constructed as to plug 
the wound at the same time that it permits the 
urine to escape freely, has been also followed by 
satisfactory results. The same principles of 
treatment are applicable to hemorrhage from 
accidental wounds of the arteries of the bulb in 
lithotomy. 

On dividing the triangular ligament of the 
urethra the dissector arrives at the deep com- 
partment of the anterior division of the peri- 
neum, but to examine its contents with advan- 
tage he requires a section of the pelvis, such as 
that advised in a former part of this article. 
This compartment is limited superiorly or 
towards the abdomen by the recto-vesical 
layer of the pelvic fascia; inferiorly or towards 
the surface by the back of the triangular liga- 
ment of the urethra; and posteriorly by the 
rectum ; its shape is somewhat triangular, and 
it contains Wilson’s muscles, many fibres of the 
levatores ani, a part of the membranous por- 
tion of the urethra, the prostate gland, a plexus 
of veins excessively developed in some sub- 
jects, and at times also an irregular artery justly 
dreaded by the lithotomist. 

Wilson’s muscles (the compressores urethre) 
are two triangular fleshy fasciculi, which arise 
from the back of the symphysis para each by 
a narrow tendon ; their point of attachment is 
about one-eighth of an inch beneath the ante- 
rior true ligament of the bladder, and the same 
distance above the lower margin of the cartila- 
ginous arch of the pubis. The two muscles, 
expanding as they descend, separate from each 
other at the membranous portion of the urethra, 
and ing one, on each side of that part of the 
canal they again unite beneath it in a sort of 
tendinous raphé, which extends from the pros- 
tate gland to the bulb; many of their fibres may 
be likewise traced to the central tendinous point 
of the perineum. A cellular interstice inter- 
venes between the two muscles at their origin, 
and from the levatores ani they are separated at 
each side respectively by cellular tissue and 
some small veins. Wilson’s muscles may ele- 
vate and compress the urethra so as to close 
the canal; their influence in catheterism is 
decided and has been already discussed; one 
of them, the left, is divided in the lateral, and 
both are cut in the bilateral operation of litho- 
tomy. In some subjects Wilson’s muscles are 
absent, or rather they are inseparable from the 
levatores ani; but in such cases the anterior 
fibres of these latter muscles surround the ure- 
thra, perform all the offices assigned to the 


PERINEUM. 


compressores urethre, and are similarly cireum- 
stanced as regards operations on the perineum. 

The recto-urethral space, but partially seen 
so long as the triangular ligament of the urethra 
remains in situ, becomes fully exposed after 
the division of that fibrous septum. This 
Space results from the inclination back ‘ 
of the lower extremity of the rectum, whilst 
the urethra inclines forwards through the arch 
of the pubis; its form is triangular, the base 
at the integuments of the perineum, the a) 
at the prostate gland, the membranous and the — 
bulbous portions of the urethra constituting its 
anterior wall, and the rectum bounding it pos- 
teriorly. In cutting from the integuments to 
the urethra through the recto-urethral 
the anatomist encounters, first, the superficial 
perineal fascia; next, the extremities of the 
several muscles which meet and are confounded 
with each other at the central tendinous point 
of the perineum, and also the small arterial 
anastomosis situated in the same locality, still 
deeper the peaked prolongation of the trian- 
gular ligament; and, lastly, Wilson’s museles 
at their junction beneath the urethra. 

The membranous portion of the urethra is 
situated within ten lines of the rectum, and the 
bulb projects still further backwards, lying but 
half an inch apart from that intestine, so that, 
in the lateral and also in the bilateral operations, 
the lithotomist incurs some risk of wounding 
the bowel as he lays bare the groove in the 
staff. In the bilateral method the operator 
endeavours, by a semilunar incision carried 
across the recto-urethral triangular space, to 
reach the staff as it lies in the membranous 
portion of the urethra, and from the proximity 
of the bulb to the rectum both these parts are 
endangered as the knife traverses the interme- 
diate space. In the lateral method the rectw 
is not so likely to be injured in the correspond- 
ing step of the operation, because the bowel is 
further removed from the membranous portion 
of the urethra than from the bulb, and besides 
the urethra is incised somewhat upon its later 
aspect. In either case the surgeon best ensure 
the safety of the intestine by taking care to hay 
the faeces evacuated before the pe ce 
mences, by holding the staff well up into - 
arch of the pubis, and by directing 
the knife forwards as he cuts into the ureth 

The recto-urethral triangular space is the f 
sition usually occupied by that rare form 
rupture, a perineal hernia ; in this disease | 
hernia leaves the abdominal cavity at the bott 
of the great cul-de-sac of the peritoneum, - 
drawing down the serous membrane in its 
gress it gradually insinuates itself between 
prostate gland and the rectum, and at let 
sida between the rectum and the b 

n the perineum the sac is in general er 


. 
POINE ¢ 


 aingee The tumor occasionally dev 
rom the middle line, and projects outw 
and backwards behind the transversus per 
muscle into the ischio-rectal fossa; it ram 
undergoes strangulation, being in almost é1 
instance reducible. * 

The prostate gland demands the special 
tention of the surgical anatomist, for muel 


we - 


PERINEUM. 


the operator’s success in lithotomy turns upon 
his knowledge of the relations, the size, and 
the density of this organ as well as of the re- 
sistance of its capsule. The prostate is heart- 
shaped ; it has been also not unaptly compared 
‘to a chesnut. Its base, directed backwards 
and upwards, embraces the neck of the bladder, 
and usually presents a notch for the entrance 
of the ejaculatory ducts; its apex, truncated 
and directed forwards and downwards, is in 
contact with Wilson’s muscles and separated 
from the triangular ligament of the urethra by 
an interval of less than half an inch; its under 
surface, grooved longitudinally in the middle 
line, looks somewhat backwards and rests upon 
the rectum with the intervention of a quantity 
of rather dense cellular tissue, in which fat 
never accumulates ; its upper surface, inclining 
slightly forwards and less extensive than the 
lower, is connected to the pubis by the anterior 
true ligaments of the bladder; and its sides, 
which are rounded, are covered by the levatores 
ani muscles. The vesicule seminales are re- 
lated to the base of the prostate gland, and the 
dorsal veins of the penis lie upon its upper 
surface, which is scarcely three-quarters of an 
inch distant from the pubis. The rectum, when 
empty, is in contact with the under surface 
only of the prostate, but when distended, it 
also encroaches upon the sides of the gland; 
this occurs to an extreme degree whenever the 
bowel presents the dilatation so commonly 
observed in elderly persons; in such cases the 
prostate appears embedded in the walls of the 
gut, a disposition fraught with danger to the 
intestine in the ordinary operation for stone. 
The prostate gland varies so much in size at 
different periods of life, and even in different 
individuals of the same age, that it is impossi- 
ble to gps its exact dimensions. The organ 
is small in the child; it increases greatly at 
puberty; in middle.age its measurements are 
still larger, and in the decline of life they 
become not unfrequently excessive. In the 
healthy adult subject: the extreme length of the 
prostate gland from base to apex may be esti- 
mated at from an inch and a quarter to an inch 
and a half; its.depth at the base seldom ex- 
ceeds one inch, whilst from side to side it 
measures somewhat more than an inch and a 
quarter. ‘The urethra traverses the prostate from 
base to apex, and runs much nearer to the upper 
than to the lower surface of that body, so that the 
canal is very unequally surrounded by glandu- 
lar substance. At the base of the prostate the 
glandular substance above the urethra varies 
from two to four lines in depth; below the 
canal it is upwards of six lines deep ; laterally 
its thickness may be estimated at about eight 
lines, whilst in the direction of the ordinary 
“incision in lithotomy, viz. downwards and out- 
wards, from nine to twelve lines is the average 
measurement. Exceptional cases have been 
reported by Velpeau and others, in some of 
which no trace of glandular substance existed 
_ above the urethra, and in others little or none 
beneath it; the latter variety might lead to un- 
pleasant consequences in lithotomy. 
The prostate gland is enveloped by a dense 


933 


capsule continuous with the fibrous membrane 
derived from the posterior layer of the triangu- 
lar ligament of the urethra, and investing the 
membranous portion of that canal. This cap- 
sule is identified above with the anterior and 
lateral true ligaments of the bladder, and its 
strength is such as to impart great firmness to 
the prostate, and a power of resistance altoge- 
gether foreign to the glandular substance. The 
anatomist finds it extremely difficult to lacerate 
the prostate so long as the capsule retains its 
integrity, but a trifling force suffices to tear or 
to split the gland after it has been deprived of 
this covering. The strength of the capsule 
explains the difficulty experienced by lithoto- 
mists in dividing the prostate gland by the 
cutting gorget, and was doubtless in great 
measure the cause of those distressing accidents 
which so frequently resulted from the slipping 
of that instrument, and which have led to its 
disuse in latter years. The common ‘ejacula- 
tory ducts traverse the prostate gland from 
behind forwards and upwards ; they are closely 
approximated to each other, and for practical 
purposes may be considered to occupy the 
middle line. It would be impossible to 
effect with certainty a median section of the 
gland in the living subject without injury to 
one or both of these ducts: this constitutes a 
strong objection to the recto-vesical operation 
of lithotomy, but they are out of danger in the 
lateral and bilateral methods. 

The veins in the neighbourhood of the pros- 
tate gland and of the neck of the bladder are 
remarkable for their plexiform arrangement, 
and are called the vesico-prostatic plexus. This 
plexus, receiving anteriorly the dorsal veins of 
the penis after their entrance into the pelvis, 
and communicating posteriorly with the he- 
morrhoidal veins, delivers its blood into the 
internal iliacs; it lies chiefly upon the upper 
and lateral surfaces of the prostate, and on the 
lateral and inferior aspects of the neck and 
neighbouring portion of the base of the blad- 
der. The veins which constitute this plexus 
are covered: by a layer of the capsule of the 
prostate, and bound down to the bladder by a 
strong membrane derived from the recto-vesical 
lamina of the pelvic fascia. They communi- 
cate in the freest manner with each other, and 
are but moderately developed in young and 
healthy subjects, whilst in elderly persons and 
in cases of chronic disease of the bladder, as 
well as in calculous affections, they occasionally 
attain to an immense size and assume a vari- 
cose disposition, The hemorrhage from ves- 
sels so enlarged might be followed by a fatal 
result in lithotomy. The mouths of these veins 
remain permanently patent after they are di- 
vided; this results from the fibrous investment 
which binds them down, and has been supposed 
by the French surgeons to predispose them to 
phlebitis after operations, by exposing their 
delicate lining membrane to the irritating influ- 
ence of the urinary stream. 

An irregular artery is sometimes found along 
the side of the prostate gland, and has been 
the source of fatal hemorrhage when divided 
by the lithotomist. This vessel is destined to 


934 


replace one or more of the terminating branches 
of the internal pudic, and when present, always 
continues on to form the dorsal artery of the 
penis; it occasionally gives off the artery of 
the bulb and the artery of the crus penis, or 
this latter branch alone, during its progress. 
When the irregularity now described occurs, 
the pudie artery of the same side suffers a 
corresponding diminution in size, and stops 
short in the perineum after furnishing a variable 
number of branches. The irregular trunk here 
alluded to springs in general from the internal 
iliac, or from one of the branches of that 
artery; but from whatever source derived, it 
runs along the side of the prostate gland to the 
neighbourhood of the pubis, where it mounts 
above the urethra and passes beneath the sym- 
physis, in company with the dorsal veins of the 
penis. This irregular vessel runs nearly in the 
line of the incision in lithotomy, whether per- 
formed according to the lateral or the bilateral 
methods, and pursuing such an unfortunate 
course it can rarely escape the knife during 
these operations. Examples of this irregularity 
have been recorded by Blandin, Velpeau, 
Shaw, and others. 

The preceding description of the deep com- 
partment of the perineum would be imperfect 
without some application of the anatomy of that 
Space to practical purposes, particularly as the 
third incision in the lateral operation of litho- 
tomy is performed within its limits. In this 
step of the operation the surgeon, in order 
to make way for the calculus, cuts through 
the remainder of the membranous portion of 
the urethra, together with the left lobe of the 
prostate gland, and in doing so he must also 
divide Wilson’s muscle and some fibres of the 
levator ani. From the many important parts 
which surround the prostate, this incision is 
beset with difficulties. The rectum is much 
endangered ; this arises from its proximity to 
the under surface of the prostate gland, and 
from its occasional dilatation. To insure the 
safety of the gut it should be emptied by the 
administration of an enema previous to the 
operation; the handle of the staff should also 
be depressed before the third incision com- 
mences, and the edge of the knife should be 
duly lateralised ; without the latter precaution 
all other expedients to save the intestine are 
useless. The depression of the handle of the 
staff raises the beak of the instrument behind 
the pubis, and causes the knife to enter the 
bladder as much as possible in the axis of that 
viscus, a line of incision best calculated to 
protect the bowel; and by performing this 
manceuvre at the proper moment the operator 
raises the prostatic portion of the urethra from 
the rectum, thus contributing still further to 
the sa of the gut. 

Hemorrhage is the most formidable conse- 
quence of the third incision in lithotomy. The 
pudic artery incurs a certain amount of risk 
when the operator, in his anxiety to save the 
rectum, directs the edge of the knife too much 
outwards, but from a former part of this article 
the reader may perceive that such an accident 
is of rare occurrence. The irregular artery 


PERINEUM. 


which runs along the prostate is much more to 
be dreaded, for the surgeon can neither foresee 
nor avoid the danger, and from its position all 
attempts to tie the vessel when wounded must ne- 
cessarily prove fruitless, whilst the absence of a 
resisting surface beneath the bleeding orifice pre- 
vents the plug from commanding the hemorrhage. 
A profuse loss of blood from the vesico- 
prostatic plexus of veins may be also encoun- 
tered, and is most likely to happen in elderly 
persons. The largest of these vessels are situ- 
ated at the neck and along the base of the 
bladder, so that the surgeon guards against 
such a casualty most effectually by confining 
his incisions as much as possible within the 
limits of the prostate gland. “° 
The French writers consider phlebitis and 
diffuse cellular inflammations to be the most 
common causes of death after lithotomy, and 
they attribute both these fatal affections to an 
incision carried beyond the base of the —— 
They maintain that the cut surface of the gland 
is sufficiently tough and resisting to bear the 
urine with impunity, and that the lax cellular 
membrane around the neck of the bladder, 
and the veins in the same locality, speedily — 
inflame when irritated by that secretion. 
Paris the bilateral operation is therefore mostly 
practised, as it gives the largest incision prac- — 
ticable within the circumference of the prostate 
gland, at the same time that it protects the — 
common ejaculatory ducts, the rectum, and the 
pudic artery from injury. 
In these countries the lateral method is still — 
generally preferred, whether it be that British — 
surgeons usually find a section of one side of 
the prostate sufficient for the extraction of the 
calculus, or that a moderate division of the 
neck of the bladder in their hands seldom 
leads to the above described unfortunate results 
particularly if a ready outlet for the urine be 
ensured by a free section of the superficial 
Structures. 
In the bilateral operation a double risk o 
wounding the irregular dorsal arteries of t 
penis must be incurred ; and should the bl 
of the lithotome, in consequence of a misee 
ception of the width of the prostate gland o 
of the transverse measurement of the be 
boundary of the perineum, be too widely di 
varicated, a twofold liability to venous he: 
rhage and to injury of the rectum will be dl 
result, and the pudic vessels on both sides 1 
be endangered,—accidents which demand ¢ 
consideration from the practitioner in weigh 
the relative merits of these rival operations. 
In dividing the prostate gland the knife 
apt to slip from the groove of the staff 
reason of the great toughness of the cap: 
and to pass between the rectum and bla 
causing extreme mischief. When this pat 
the operation is performed with the si 
knife, the lithotomist guards against st 
unpleasant accident by incising the mem 
nous portion of the urethra freely before 
commences the third incision, and by depre 
ing the handle of the knife considerab 
pushes its blade onwards to the bladder; 
the former precaution he makes certain that 


PERITONEUM. 


point of the knife is properly lodged in the 
groove of the staff, and by the latter that it 
follows the groove fairly into the bladder. 
Some excellent instruments have been devised 
to prevent the occurrence of so serious an acci- 
dent, but to describe them here would be too 
wide a digression. 

The lithotomist is liable to commit other 
mistakes still in the same stage of the lateral 
operation. Tlis incisions may fall short of the 
bladder altogether, leaving the prostate insuffi- 
ciently divided; or he may, on the other hand, 
transfix the bladder by plunging his knife too 
deeply. The former error may lead to disap- 
pointment in extracting the stone, and to severe 
injury of the neighbouring parts in the attempt 
to do so; it admits, however, of correction if 
discovered in time, but the latter mistake must 
be irreparable. Occurrences such as_ these 
result from an imperfect knowledge of the 
depth of the perineum, and may be accounted 
for by the great variation in this respect which 
the region presents in different subjects. Du- 
puytren and Velpeau found the distance from 
the neck of the bladder to the integument of 
the perineum to vary in different cases to the 
extent of two inches and upwards, the disparity 
depending chiefly on the degree of obesity of 
the individual. 

The deep compartment of the anterior divi- 
sion of the perineum has claims upon the 

_attention of the practical surgeon independent 
of lithotomy. Matter sometimes forms within 
this space, and from the contiguity of the 
rectum on the one hand, and of the urinary 
organs on the other, such collections produce 
most distressing symptoms. The triangular 
ligament of the urethra prevents the abscess 
from gaining the surface directly, so that at 
length it either bursts into the rectum or makes 
its way gradually behind the base of the liga- 
ment. The finger introduced into the gut affords 
satisfactory information as to the nature of such 
cases, and free incisions through the perineum 
are followed by the most marked relief. 

Effusions of urine from accidental ruptures 
of the urethra occur less frequently behind the 
triangular ligament than in front of it, for in 
the former situation the canal is so thoroughly 
protected by its deep position that contusions 
inflicted upon the surface of the region but 
rarely affect it. False passages from the forci- 
ble introduction of instruments take place in 
general anterior to the triangular ligament; but 
when the urethra gives way behind a stricture 
in consequence of violent expulsive efforts of 
the bladder, the urine sometimes escapes into 
the deep compartment of the perineum, and 
destructive consequences are sure to ensue 
unless counteracted by timely treatment. 

Prostatic diseases are attended by a train of 
symptoms which depend upon the sympathies 
of neighbouring organs. When the gland sup- 
purates (not an uncommon consequence of 
acute inflammation), the matter usually dis- 
charges itself by the urethra, the tough capsule 
determining its route; but at times the abscess 
bursts into the rectum, or it may even point in 


935 


the perineum after passing behind the base of 
the triangular ligament. 


BIBLIOGRAPHY.—The following authorities may 
be consulted with advantage, in addition to the 
various systems of descriptive anatomy. Abraham 
Colles, A treatise on surgical anatomy, Dublin, 
1811. James Wilson, A description of two muscles 
surrounding the membranous portion of the ure- 
thra, Med.-Chir. Trans., vol. i, p. 175, London, 
1812. C. A. Key, A short treatise on the section 
of the prostate gland in lithotomy, London, 1824. 
Alf, A. L. M. Velpeau, Traité d’anatomie chirurgi- 
cale, ou anatomie des regions, Paris, 1826. Wil- 
liam Hargrave, A system of operative surgery, 
Dublin, 1831. Ph. Fred. Blandin, Traité d’anato- 
mie topographique ou anatomie des regions, Paris, 
1834, J. F. Malgaigne, Manuel de médecine ope- 
ratoire, Paris, 1834. G. J. Guthrie, On two new 
muscles of the membranous portion of the urethra, 
Lond. Med. and Surg. Journ., 1833. Robert Har- 
rison, The surgical anatomy of the arteries of the 
human body, Dublin. Thomas Morton, The surgi- 
cal anatomy of the perineum, London, 1838. Alf. 
A. L. M. Velpeau, Nouveaux elements de médecine 


opératoire, Paris, 1835. 
(Robert Mayne.) 


PERITONEUM.—The serous membrane 
of the abdomen, investing the inner surface of 
the abdominal walls and the outer surface of the 
abdominal viscera, and forming, by duplica- 
tion, sheets with both surfaces free, called 
omenta, mesenteries, suspensary ligaments, 
&e. 
The peritoneum of the male subject, in 
accordance with the rule of serous membranes, . 
is a shut sac: in the peritoneum of the female 
the single exception to this rule is met with: 
here the Fallopian tubes open into the perito- 
neal cavity, and their mucous surface is conti- 
nuous, through their fimbriated extremities, 
with the serous surface of the peritoneum. 
Another circumstance that renders the female 
peritoneum peculiar amongst serous mem-~- 
branes is, that it is necessarily ruptured in the 
occurrence of a normal process, namely, in 
the escape of an ovum. : 

The manner in which a single serous shut 
sac, by a kind of intus-susception, invests 
the external surface of viscera and the internal 
surface of the cavity in which they are con- 
tained, is admirably illustrated by the well- 
known comparison of a double night-cap. 
Where the cavity contains only a single viscus 
of a simple rounded form, as, for instance, 
the pericardium containing the heart, the com- 
parison is very apt. But when, as in the case 
of the abdomen, numerous viscera of irregular 
shape are contained in the cavity, the matter is 
much more complicated, and the resemblance, 
therefore, far less striking. Yet is the relation 
of the parietal part of the peritoneum to the 
visceral part, and of both to the abdominal vis- 
cera, essentially similar to that indicated in this 
well-known simile. The complexity of the 
peritoneal folds seems mainly to depend upon a 
strict adherence to such a simple relation, in 
the case of each of a great number of viscera, 
with their vessels, &c. contained in a single 
cavity. Each viscus, whatever its shape, whe- 
ther closely or loosely connected, must have its 


936 


arteries, its veins, its nerves, and its lymphatics 
passing to and from it, and the whole must be 
invested by a single shut sac without loss of 
continuity. The complexity thus arising de- 
mands for this membrane a lengthened descrip- 
tion. 

We propose, first, to trace its continuity 
throughout its entire extent; next, to describe 
the sheets with two free surfaces, which it 
forms by duplication; thirdly, to examine the 
manner in which it invests each of the viscera, 
and the abdominal parietes, that is to say, the 
extent to which it does so in the case of each, 
the point at which it arrives at and quits each, 
and so on; and, lastly, to describe its con- 
' nexions, or the adhesion of its external surface, 
varying in intimacy, with the parts which it 
invests. The most important points connected 
with the anatomy of the peritoneum will be 
incidentally involved in the consideration of 
the first of these propositions. 

ConTINUITY OF THE PERITONEUM.—To 
demonstrate the unbroken continuity of the 
peritoneum, we are compelled, in description, 
to trace it in various directions, starting 
from a certain point and following it up till, 
having performed a complete circuit, we 
return again to our starting point. In doing 
so we shall avoid restricting ourselves to the 
mesial or any other sectional line. We believe 
that such a restriction, closely adhered to, 
tends to convey an erroneous impression, 
namely, that of a line instead of a superficial 
expanse. In thus tracing the peritoneum, it 
is better to let the mind rest upon the idea of a 
free surface, rather than upon that of a mem- 
brane. By a membrane one is apt to under- 
stand a separable skin; but in some situations 
not only is it impossible, by any ordinary ma- 
nipulation, to separate the peritoneum from its 
connections, but two layers of it often form 
together a structure so thin that one can hardly 
help regarding it as a single membrane. In 
no instance is any part of a serous membrane 
free on both its surfaces. The external surface 
of the peritoneum, like that of all other serous 
sacs, is every where adherent, either to the sub- 
jacent structures, or, as in its duplications, to 
itself; whilst, on the other hand, its internal 
surface is, normally, every where free. It 
follows then, that wherever, in the peritoneal 
cavity, the finger can be placed on a free sur- 
face, there is a layer of peritoneum immedi- 
ately beneath it; that if a continuous free 
surface is demonstrated, the continuity of the 
serous membrane is proved; that in fact a free 
serous surface represents a layer of serous 
membrane, and may be described instead of it 
when continuity alone is sought to be proved. 
We shall therefore at present use the expres- 
sions free surface and layer of serous mem- 
brane as synonymous ; the free surface of a 
viscus instead of the serous membrane invest- 
ing a viscus. 

When the abdominal cavity is laid open in 
front by a crucial incision, the inner surface of 
the reflected flaps is seen to be free, glistening, 
and of a pale red colour. By a slight exami- 


PERITONEUM. 


nation of the cut edges this is found to be the 
free surface of a membrane, whereof the other 
surface is connected to the subjacent structures 
by areolar tissue: the free surface is the parietal 
serous surface of the abdomen: the membrane 
is the parietal portion of the peritoneum. If 
an incision has been carried from the navel to 
the xiphoid cartilage, a falciform, membrane- 
like process, strikingly resembling the freenum 
lingue, is seen connected with the anterior 
parietal peritoneum, a little to the right of the 
middle line, projecting backwards, and towards 
that aspect presenting a free concave border. 
It is the falciform ligament of the liver. The 
base or broadest extremity of the falx is sessile 
along an antero-posterior line upon the uppe 
surface and anterior edge of the liver; which 
line corresponds with and runs into the 
antero-posterior fissure on the under surface of 
the liver; and this fissure receives the round 
ligament, and consequently the free edge of 
the falx which encloses it. The apex of the 
falx is at a point on the inner surface of the 
anterior abdominal parietes, co ing to 
the navel. The surfaces of the falciform liga- 
ment are continuous with the serous surfaces of 
the parietes and liver; its free border, as inci- 
dentally mentioned above, encloses a structure 
called the round ligament of the liver, which 
gives a considerable thickness to this 

The round ligament of the liver is the umbi- 
lical vein of the foetus, degenerated to a fibrous 
cord in the adult, and it runs across, as that 
vein did, from the navel to the antero- or 
fissure of the liver, defining the free border of the 
falciform process in question. The composition, — 
then, of the falciform ligament of the liver is— 
a portion of peritoneum doubled or folded, so 
that its outer surface is brought in contact with 
itself, as happens when asheet of paper is folded 
so as to make two leaves. The two surfaces 
thus brought into contact, are united together 
by areolar tissue, as if the two leaves were 
stuck together with paste ; and the round liga 
ment lies along in the extreme edge of the fold, 
like a string that holds a sheet of two leaves in 
a book-cover. The vessels necessary for the 
nutrition of these structures ramify in the ic 
terposed areolar tissue. It seems as if 
umbilical vein, in making the shortest | out 
from the navel to the longitudinal hepatic fi 
sure, had carried back before it a fold of 
superjacent peritoneum. f aed 

e have spent more time in describing th 

the first peritoneal fold we have come to, t 
is due to its importance, because it affords | 
that which we want in this early stage of | 
description, an instance of the manner in whi 
the peritoneum invests the various orga 
having the advantage of extreme simplit 
A bowel is invested by the peritoneum and 
occupies a situation in a fold precisely am 
gous to that which the round ligament oceup 
in the falciform ligament; whilst the vess 
and nerves of the bowel to and f 
imbedded in the areolar tissue uniting the 
posed surfaces. ae. 

Placing a finger of each hand on each sid 


PERITONEUM 


of the falciform ligament of the liver, they may 
both be slipped along on the free surface of the 
anterior parietal portion of the peritoneum in a 
direction at first upwards, then slanting, then 
backwards, until they are each of them arrested 
in a corner, or cul-de-sac. They have passed 
along first on the peritoneal lining of the an- 
terior abdominal muscles, and afterwards on 
that of the diaphragm. They are now arrested 
from being slipped along any further in the 
same direction by the peritoneum leaping 
across, or extending across, from the lower sur- 
face of the diaphragm to the upper surface of 
the liver. In order to pass them along any 
further on the peritoneal surface they must be 
carried off laterally or slipped downwards over 
the upper surface of the liver. We will pursue 
the latter course. The corners, or cul-de-sacs, 
in which we suppose the fingers to rest, are 
those formed by the falciform ligament, the 
liver, the diaphragm, and the coronary liga- 
ment all meeting together: the latter is the 
name given to that portion of the peritoneum 
which extends across between the diaphragm 
and the liver. 

First, then, let the finger which is placed 
on the left side of the falciform ligament be 
slipped down over the upper surface of the 
left lobe of the liver, round its anterior edge, 
and backwards along its inferior surface ; it 
will be arrested by a membraniform sheet ex- 
tending across from the fissures of the liver to 
the lesser curve of the stomach, called the lesser 
or gastro-hepatic omentum. There for the 
present we leave it, and now let the other 
finger be in like manner passed down over the 
upper surface-of the right lobe of the liver, 
around its anterior surface, and backwards along 
its under surface, either over the gall-bladder 
or to the right of it: behind the neck of the 
gall-bladder, by giving it a direction inclining 
towards the left, it may be slipped behind the 
same sheet as arrested the other finger; that is 
to say, it may be brought to rest upon the pos- 
terior surface of the lesser omentum, upon 
whose anterior surface we left the other finger. 
This position it gains by being slipped- along 
on the narrow isthmus of liver called lobulus 
caudatus situated behind the portal fissure, 
in doing which it passes through a kind of fo- 
ramen, called the foramen of Winslow, whereof 
the lobulus caudatus is the superior boundary. 
The inferior boundary of this so-called foramen 
is formed hy the duodenum ; the posterior by 
the vena cava; and the anterior by the vena 
pres the gall-duct, and the hepatic artery. 

hese are the organs and vessels which sur- 
round the foramen of Winslow: they are, how- 
ever, all covered by peritoneum in such a 
manner that the finger passed round the fora- 
men, which is about one inch in diameter and 
of a somewhat semicircular form, glides around 
on a continuous circle of peritoneum. 

The free surface of the lower aspect of the 
right lobe of the liver has been seen to extend, 
through the foramen of Winslow, along the 
lobulus caudatus ; the continuity of surface of 
course extends to the lobulus Spigelii, from 
whence it may be traced towards the left and 


937 


forwards to the posterior aspect of the lesser 
omentum, and backwards to the posterior 
abdominal parietes. 

The finger being placed on that part of the 
peritoneum which covers the right kidney, it 
may be made to glide along the free surface 
up to the posterior boundary of the foramen 
of Winslow, and into the foramen itself, which 
demonstrates the peritoneal continuity in this 
direction. In much the same way the finger 
may be slid along on the duodenum until it is 
thereby conducted into the foramen. 

With regard to the continuity of the perito- 
neal surface of the anterior boundary of the 
foramen of Winslow, if the finger be placed 
on the anterior surface of the lesser omentum 
and slid along on it towards the right, it comes 
to a free edge thickened by the vessels and 
duct mentioned above; doubling around this 
edge it may be made to glide into the foramen ; 
thus demonstrating that the anterior and poste- 
rior surfaces of the lesser omentum are con- 
tinuous with one another around the vessels 
and duct that thicken its free border and form 
the anterior boundary of the foramen of Win- 
slow. 

Now since, as we remarked above, a free 
peritoneal surface always indicates a layer of 
peritoneum, the lesser omentum having two 
free surfaces consists of two layers ; and its two 
surfaces being continuous around the vessels 
mentioned, its two layers are continuous in like 
manner. It, therefore, is a portion of perito- 
neum doubled or folded upon itself, enclosing 
vessels and a duct in the extremity of the fold ; 
just as we saw was the case with the falciform 
ligament enclosing, in the extremity of its fold, 
the obliterated umbilical vein. 

When a double peritoneal sheet passes across 
from one bowel to another, or from the parietes 
to a bowel, it is described as attached along the 
lines where it first lights upon or comes in con- 
tact with such parts. Speaking in such a way, 
the lesser omentum is attached to the liver and 
stomach by the whole extent of its borders, 
except that small portion between the duode- 
num and porta which is free: and in fact this 
border is said to be free only because that which 
it encloses is small; if the gall-duct were an 
inch in diameter, the right border of the lesser 
omentum would be said to be attached to the 
gall-duct. Disregarding at present the last 
observation ; the line of attachment, then, of the 
lesser omentum is continuous all around except 
at its free border. Let us trace this line of 
attachment from the porta of the liver to the 
pyloric end of the stomach in the circuitous 
direction in which alone it can be done. From 
the porta, then, we trace this line along the 
posterior half of the antero-posterior fissure of 
the liver, inclining a little to the left of this fis- 
sure so as to reach the cardiac end of the sto- 
mach, and thence along the lesser curvature of 
the stomach to the pylorus. 

The gastric attachment of the) lesser omen- 
tum is placed transversely, whilst its he- 
patic attachment runs antero-posteriorly, with 
only a moderate inclination from side to side, 
so that this omentum has a kind of twist. 


938, 


It seems as though the gall-duct in gaining 
the shortest route from the liver to the duode- 
num had carried out the superjacent peritoneum 
from the cardia and lesser gastric curvature into 
a fold, as far out as the position of the straightest 
line from the porta to the pylorus; that this 
fold would have projected in the middle line, 
but that the enlargement of the right lobe of the 
liver displaced its posterior part with the cardia 
to the left, whilst the duodenum being brought 
into adhesion with the posterior abdominal 
walls displaced its anterior part to the right, 
and that both displacements have resulted in 
an almost transverse instead of an antero-poste- 
rior horizontal direction. In many vertebrate 
animals, especially those below the class Mam- 
malia, the duodenum is not adherent to the 
posterior abdomina! parietes, and the pylorus as 
well as the cardia is frequently in the middle 
line, whilst the two lobes of the liver are of 
pretty equal transverse extent; in such cases 
the lesser omentum extends antero-posteriorly 
in the middle line, (figs. 490, 491,) and this, 
we consider, is its typical position. This point 
will be more fully considered when we come to 
a particular description of the omenta; at pre- 
sent we are endeavouring to demonstrate the 
continuity, merely, of the peritoneum through- 
out: it is the existence of the omenta, or rather 
their distorted position in the human subject, 
that renders this demonstration so difficult. 

It is necessary at this stage of our description 
to study the peritoneal sheet, or bag, with two 
free surfaces, called the greater omentum. On 
making an incision, as above, through the abdo- 
minal parietes, the liver and stomach are at 
once brought into view; but the small intes- 
tines are concealed by the great omentum co- 
vering them in front. It is a membraniform 
apron, having plentiful reticulations of vessels, 
and often loaded with fat, especially near the 
vessels. Viewing it undisturbed it appears to 
be pendent from the greater curvature of the 
stomach, and to have a free inferior border 
touching, usually, the pelvic region; but on 
lifting it up and looking at its posterior aspect, 
it is seen to be attached also to the transverse 
portion of the colon, which at once informs one 
that it is double. The fact of its being double, 
however, may be much more strikingly demon- 
strated in the following manner. If a catheter 
be held in the foramen of Winslow, and air be 
blown through it, the great omentum (provided 
there be no abnormal breach of continuity or 
adhesion in it) will become inflated like a great 
bladder; the inflation extending, not only 
downwards below the greater curve of the sto- 
mach, but to the left beyond its fundus, and 
also to the lesser omentum. The cavity so in- 
flated is called the sac of the omentum, or the 
posterior cavity of the peritoneum, and the fo- 
ramen of Winslow is the orifice that leads to this 
sac—the neck that connects together the ante- 
rior and posterior cavities of the peritoneum, 
making them one. 

The foramen of Winslow is not generally big 
enough to admit more than one or two fingers 
to be passed through it; but an incision being 
made through the lesser omentum, the hand 


PERITONEUM. 


may be introduced into the omental sac and 
passed downwards behind the stomach and in 
front of the transverse colon, until it reaches the 
lowermost extent of the great omentum, or bot- 
tom of the great omental pouch ; it will thus be 
between the two layers of what we considered 
like a double apron, but which, rather, is a 
uch, The hand may now be carried in either 
teral direction until it is arrested by the sides 
of the pouch, which correspond, on the right 
with the point where the colon crosses'the duo- 
denum, and on the left with the point where 
the colon, from being transverse, becomes de- 
scending,—that is to say, the sides of the pouch 
hang down from these points. Above the latter 
a the hand may be carried towards the left, 
yond the fundus of the stomach and some- 
i behind the spleen, where it will ber 
y an attachment to the posterior pari 
line of which extends fron the carda to theleft 
ge of the colon. Sa 
here is, therefore, a great pouch of perito- 
neum, the inside and outside of which are both 
free; and consequently it has an internal or 
lining layer and an external layer; we will 
presently show how these are continuous with 
each other and with the peritoneal investments 
of surrounding parts. e left side of the 
mouth of this pouch is carried up into a long 
corner reaching the cardia ; its continuous line 
of attachment extends from the cardia along the 
greater curvature of the stomach to the pylorus; . 
then along a small extent of the duodenum till 
it reaches the transverse colon; next along the 
transverse colon to its left bend, and thence 
along on the posterior abdominal parietes of the 
left hypochondriac region, or rather over the 
left kidney, to the cardia whence we started. 
The spleen is sessile upon the external surface 
of this bag to the left of the fundus of the sto- 
mach. That portion of it which intervenes 
between the stomach and colon is called the 
great omentum, and that portion which is 
situated to the left of the fundus of the stomach — 
is called the splenic omentum. a 
We may now return to our demonstration of 
the continuity of the peritoneum by tracing it 
free surface as before. The two surfaces o1 
layers of the lesser omentum were seen to 
continuous around the vessels enclosed in its 
free right border, at the foramen of Winslow. 
These two layers, as yet adherent, separate 2 
the lesser gastric curvature, invest the stomacl 
—one behind and the other in the front—met 
again, and again adhere along the fundus al 
greater curvature, forming a sheet with two fit 
surfaces, which to the right extends to the sf 
and abdominal parietes, and downwards te 
transverse colon ; that part of it, however, wi 
intervenes between the stomach and co 
bagged out or excessively widened so as, 
ordinary circumstances, to hang down in 
pouch as low as the. pelvis. Having reael 
the front of the transverse colon, the layers 
separate to invest it—one above and the ol 
below—meet again on its posterior aspect, and 
again adhering together form the transverse 
socolon, which extends from the colo 
posterior abdominal parietes, where having: 


PERITONEUM. 


rived they finally separate, partially investing, as 
they do so, the transverse portion of the duode- 
num. Thus both layers reach the abdominal 
parietes along the continuous line of attachment 
of the splenic omentum and the transverse me- 
socolon ; the internal layer from this continuous 
line invests the pancreas and other parts behind 
the stomach, then the lobulus Spigelii, and thus 
is conducted to the posterior surface of the 
lesser omentum, from which we started. The 
external layer of the omental sac, having reached 
this line of parietal attachment as part of the 
splenic omentum to the left, passes off on the 
left kidney and the lateral abdominal parietes 
and diaphragm ; having reached it below as 
the transverse mesocolon, it may thence be 
traced downwards to the root of the mesentery. 

The small intestine is enclosed in the extre- 
mity of the fold of a duplicature of peritoneum. 
That part of the fold which extends across from 
the posterior parietes to the intestine is called 
the mesentery. The two component layers of 
_ the mesentery are adherent by their apposed 
surfaces, except where vessels, &c. intervene, so 
that it is a parieto-visceral sheet with two free 
surfaces. The parietal attachment of the me- 
sentery is called its root, and extends obliquely 
across the spine from the left side of the second 
lumbar vertebra, where the duodenum emerging 
from the root of the transverse mesocolon be- 
comes jejunum, to the right iliac fossa, where 
the ilium enters the cecum. Though the pa- 
rietal attachment or root of the mesentery is but 
a few inches in length, its visceral attachment 
by means, of numerous ample foldings, like a 
ruffle, corresponds in length with the twenty 
feet of small intestine. Tracing, then, the peri- 
toneum heretofore forming the external layer of 
the great omental sac from the point where it 
reaches the posterior parietes as part of the 
transverse mesocolon, downwards, we come to 
that side of the root of the mesentery which 
looks upwards and to the right; thence we 
trace this surface continuous along the mesen- 
tery, over the bowel, back again along the other 
side of the mesentery, so reaching that side of 
its root whose aspect is downwards and.to the 
left; in both which directions the peritoneum 
may be traced onwards. To the left it reaches 
the right side of the descending colon, invests 
the front of that bowel, and passes off on the 
other side of it to the lateral parietes: occa- 
sionally only does it dip beneath the descending 
colon so as to come in contact with itself and 
form a mesentery for it, A little lower down, 
however, namely, in the leftiliac fossa, it always 
forms a mesentery for the sigmoid flexure of 
the colon, and, stilk lower down, for the first 
part of the rectum. The distinction, however, 
between iliac mesocolon and mesorectum, as 
the mesenteries of the sigmoid flexure and rec- 
tum are called, is quite arbitrary and unnatural ; 
a continuous mesenteric duplicature, broad in 
the middle and tapering to each end, serves to 
give attachment to both the sigmoid flexure and 
the first part of the rectum. Proceeding from 
the root of the mesentery downwards in the 
middle line, the peritoneum covers the sacro- 
vertebral prominence, and, just below, it ar- 


939 


rives at the rectum and forms a mesentery for 
its first portion as above stated. The perito- 
neum invests the front only of the second por- 
tion of the rectum, and at a variable distance 
from the anus quits it and extends across to the 
back of the bladder in the male, or vagina and 
uterus in the female, so that the lowermost por- 
tion of the rectum is destitute altogether of pe- 
ritoneal investment. 

From the other side of the root of the me- 
sentery, namely, that which looks upwards and 
to the right, we may trace the continuity of 
peritoneal surface off to the right lumbar region, 
investing the ascending colon in a like, and 
similarly variable, manner to that in which it 
was described as investing the descending co- 
lon ; and to the right iliac fossa, where it invests 
the cecum, sometimes, but not most frequently, 
forming a narrow mesentery for it called the 
meso-cecum. A bit of mesentery is usually 
afforded to the vermiform process, but this, of 
course, we do not reach by proceeding off late- 
rally from the last-mentioned aspect of the root 
of the mesentery. 

As mentioned above, the peritoneum extends 
across from the front of the rectum to the back 
of the bladder, in the male subject; the level 
at which it does so varies with the state of full- 
ness or emptiness of the bladder, and also is 
said to vary, ceteris paribus, in different indi- 
viduals ; frequently it is so low that the peri- 
toneum, passing across, touches the prostate. 
This is in the middle, between the front of the 
rectum and back of the bladder, but laterally 
the peritoneum is elevated into two antero- 
posterior folds, which extend across from the 
sides of the rectum to the sides of the bladder; 
these are called the recto-vesical folds or pos- 
terior ligaments of the bladder: anterior and 
external to them there are two other small 
folds. External to the recto-vesical folds the 
peritoneum does not descend nearly so low as 
it does between them; and therefore there is a 
remarkable, deepish, cul-de-sac, of -the same 
breadth as the rectum, between that intestine 
and the bladder. 

The posterior and lateral aspects and fundus 
of the bladder are invested with peritoneum, 
but not its anterior aspect: the peritoneum 
passes from the fundus of the bladder, by an 
even slant, on to the anterior abdominal pari- 
etes, not making any dip in front of it except 
when it is much distended. In the female 
there is a deep cul-de-sac of peritoneum be- 
tween the rectum and uterus, descending low 
enough to be in contact with the vagina : 
between the uterus and bladder there is a 
second but much shallower cul-de-sac. 

We have now traced the peritoneum over 
the ascending and descending portions of the 
colon to the abdominal parietes in the right 
and left lumbar region; from the recto-vesical 
folds and sides of the bladder to the iliac 
fosse ; and from the fundus of the bladder to 
the anterior abdominal parietes of the hy 
gastric region; from all or any of these posi- 
tions, or from any point between them, we 
may trace the peritoneal free surface uninter- 
ruptedly up to our first starting point, the 


940 


navel and falciform ligament of the liver. 
From the last-named position we have before 
reached the anterior and posterior surfaces of 
the lesser omentum, the former by tracing the 
free surface over the left lobe, and the latter by 
tracing it over the right lobe, of the liver. 
From the sides of the falciform hepatic liga- 
ment, proceeding in each lateral direction, in 
a horizontal sectional line taken at the level of 
the foramen of Winslow, to the left we find 
the free peritoneal surface continuing, uninter- 
rupted by any folds, to the external surface of 
the gastro-splenic omentum in the left hypo- 


Diagram representing a transverse section of the human 
subject at the level of the first lumbar vertebra, i. e. 
through the foramen of Winslow. ¥ 
a, the st h, its descending portion; b, the 

spleen ; c, the gall-duct and hepatic vessels ; d, the 

round ligament of the liver; e, the lesser omentum ; 

Jf, the gastro-splenic omentum; g, the falciform 
ligament of the liver; h, the vena cava; i, the 
aorta ; k, k, the kidneys. The thick line represents 
the peritoneum. The space between the hepatic 
duct and vessels, c, and the vena cava, h, is the 
foramen of Winslow. 


Fig. 490. 


Diagram representing a transverse section of a Lizard, 
pies ig the st 3 spleen, lesser omentum, gastro- 
splenic omentum, and falciform hepatic ligament, in 
their mesial or typical position. 

a, the stomach; 5, the spleen; c, the gall-duct 
and hepatic vessels; d, the round ligament of the 
liver; e, the lesser omentum ; f, the gastro-splenic 
omentum; g, the falciform ligament of the liver ; 
h, the aorta, &c. The thick line represents the 
peritoneum. There is here no foramen of Winslow. 


It will be seen by comparing these diagrams, 
that much of what seems so intricate in the human 
peritoneum results from a lateral displacement of 
an extremely simple arrangement, a displacement 
which attains its maximum in man, and is due, 
partly to the lungs being confined to the thorax, and 
partly to the great lateral, and small antero-poste- 
rior, measurement of the human figure. 


PERITONEUM. 


chondriac region; to the right we find it conti- 
nuing uninterrupted through the foramen of 
Winslow, covering its posterior bo » to 
the internal surface of this same ic 
omentum: to witness its continuity, however, 
up to the latter point, it is of course necessary to 
cut through the lesser omentum—in the human 
subject, but not in those animals which have no 
foramen of Winslow. ( Figs. 489, 490.) 

We have now examined the continuity of 
the peritoneum in all the main directions, and 
the mode in which it is maintained over the 
principal viscera and along the connecting 
peer two free surfaces. There yet re- 
main for examination several folds. other 
remarkable arrangements of this membrane; 
the description of these is most conveniently 
deferred till we come to the consideration of 
our other propositions, when much that is at 
present wanting in order to render our proof of 
the continuity of the peritoneum throughout 
complete, will be supplied. 

The peritoneal cavity is one cavity, in the , 
same sense as the whole of the interiorof an 
hour-glass is one cavity; that is to say, it is 
two large cavities made one by being connected 
by an extremely narrow communicating neck. 
Supposing the whole of the peritoneal sae 
could be detached from the connections of its 
external surface and expanded, it would be a 
sac of exceedingly irregular figure, divided into 
two parts by an extremely narrow constriction. 

OMENTA, MESENTERIES, AND LIGAMENTS.— 
By these terms we understand the sheets with 
two free surfaces, formed by duplication of the 

ritoneum and adhesion of the surfaces there- 

y brought into apposition; to describe these 
is our second proposition, and to that we now 


ass. 
e A parieto-visceral sheet is usually called a 
mesentery or a ligament ; a sheet with two free 
surfaces passing from one viscus to another is 
called an omentum. 
The falciform ligament of the liver has — 
already been fully described. We agree with — 
Cruveilhier that its main use is to conduct the 
umbilical vein from the navel to the antero- 
posterior fissure of the liver. This, indeed, 
can hardly be called a use, especially in the 
adult; we would say rather that the existence 
of the falciform ligament necessarily results 
from the situation and course of the umbilical 
vein. It perhaps serves in some degree t 
retain the liver in situ, but it is not advanta- 
geously placed with regard to this office. 
The coronary ligament of the liver is t 
name given to those portions of the peritoneu 
which leap across, so to speak, from the un 
surface of the diaphragm to the upper an 
posterior aspect of the liver. The anterior ar 
posterior of these portions do not come il 
contact with one another in the middle, th 
liver being at that point in immediate conta 
with, and adherent to, the diaphragm; bu 
towards each side the two layers gradually 
approach each other, and at length come in 
contact and adhere, and are prolonged as fold: 
bearing another name. The coronary ligar 
fixes the liver to the diaphragm, or r 


PERITONEUM. 


deficiency of peritoneal investment to the dia- 
phragm and liver between its anterior and 
posterior portions allows the liver to adhere to 
the diaphragm, and small vessels and lym- 
phatics to pass from the one to the other. 

The triangular ligaments of the liver are the 
continuations of the layers of the coronary 
ligament, become adherent as above, leaping 
across from the rounded posterior corners of 
the liver to the nearest or postero-lateral portion 
of the upper concave abdominal parietes, that 
is to say, to the diaphragm. Their form is, as 
their name indicates, triangular; their anterior 
borders are free; their posterior and internal 
borders are attached, the former to the parietes, 
the latter to the liver. They help to keep the 
liver in situ. 

The lesser omentum has been partially de- 
scribed above. Between its layers are included 
the vena porte, the hepatic artery, the gall- 
duct, and the hepatic plexus, along its free 
border ; and the pyloric and coronaria ventriculi 
arteries, with accompanying veins and nerves, 
along its gastric attachment. Except in the 
course of these vessels, it is a thin transparent 
membranous sheet, with a very small amount 
of strength. The vessels destined for its own 
proper nutrition are extremely few and small. 
With regard to its use, Cruveilhier thinks that 
it is a true mesentery of the stomach, mesogas- 
trium, but on this point we would offer the 
following remarks. One characteristic of a 
mesentery is, that it retains its bowel in situ, 
and this office the lesser omentum doubtless 
partially performs towards the stomach; but 


another characteristic of a mesentery is, that it 


gives passage to the arteries and veins of the 
bowel to which it belongs, and this office the 
lesser omentum performs, not for the stomach, 
but for the liver. It is the splenic omentum, 
or that part of the great omentum whereupon 
the spleen is sessile, extending between the 
parietal line of attachment running from the 
cardia to the left bend of the colon, and the 
fundus of the stomach, that conducts the prin- 
cipal gastric vessels, as the coronaria ventriculi, 
vasa brevia, and gastro-epiploica sinistra, from 
the parietes to the stomach. The splenic omen- 
tum fulfils indeed both these offices towards 
the stomach, and occupies with regard to it the 
position of a parieto-visceral fold,a relation still 
more characteristic of a mesentery. We there- 
fore are inclined to consider the splenic omen- 
tum as the mesogastrium; and some facts in 
comparative anatomy, (figs. 490, 491,) as well 
as that mentioned above, of its affording transit 
to the hepatic vessels, seem to indicate that 
the lesser omentum is the mesentery of the 
gall-duct and liver.. } 

The splenic omentum is the name given to 
that long corner of the great omental pouch 
_ which extends up to the left of the fundus of 
the stomach as high as the cardia. It obtains 
its name from the circumstance of the spleen 
being situated on its outer aspect. The spleen, 
in a certain sense, is included between the 
layers; it is invested, however, by the outer 
layer alone,—the inner layer passes by it un- 
interruptedly. Soemmering mentions a liga- 


941 


mentum phrenico-gastricum, a peritoneal fold 
connecting the cardiac end of the stomach to 
the diaphragm ; itis the very uppermost corner 
of this part of the great omental sac, which 
gets somewhat behind the cardia, and is not 
unfrequently complicated by one or two small 
falciform folds, rendered very conspicuous by 
pulling up the stomach. The attachments of 
this part of the great omental pouch have 
already been described ; between its layers are 
contained, at its very tip or uppermost corner, 
the arteria coronaria ventriculi, with its accom- 
panying vein and nerves ;* and lower down the 
splenic vessels and nerves as far as from the 
parietes to the spleen, and the branches of the 
splenic vessels called vasa brevia and gastro- 
epiploica sinistra, as far as to the fundus of 
the stomach. There are a few lymphatic 
glands near the root of the spleen; such glands, 
together with fat in variable quantities, are very 
commonly included between the layers of the 
peritoneal duplicatures. The use of the sple- 
nic omentum is to retain the spleen and stomach 
in situ, and to give transit to the splenic and 
gastric vessels. 

The great omentum, called also the gastro- 
colic omentum. The apron-like appearance 
and the sac-like form of this singular structure, 
and also its attachments, have been described 
above; it is necessary to add the following 
remarks. It extends much further down in 
the adult than in the foetus. It reaches lower 
down on the left side than on the right. 
Owing to the proximity of its lower edge to 
the femoral and inguinal rings, it frequently 
constitutes a part or the whole of the contents 
of hernial sacs. It reaches lowest down when 
the stomach is empty, and is very considerably 
drawn up by distension of that organ. It is 
usually spread apron-like evenly over the small 
intestines, but is not unfrequently found lying 
folded up on one side or the other of the 
abdomen, occasionally even turned up over 
the liver and stomach. It is frequently loaded 
with immense quantities of fat, and indeed is 
seldom or never destitute of it along the sides 
of the vessels which form such a beautiful 
net-work between its layers. In the intervals 
or meshes of this network the omentum is so 
extremely thin that it is difficult to believe it 
composed of two layers, and not unfrequently 
the membrane is deficient in these situations, 
giving to the whole the ner of a piece 
of lace finely perforated. This is always the 
condition of the great omentum of the dog, in 


59 
which animal we have repeatedly assured our- 


* The arteria coronaria ventriculi is rarely ac- 
tually included between the layers of the splenic 
omentum in the human subject; the posterior as- 
pect of the cardiac end of the stomach coming into 
immediate adhesion with the diaphragm, frequently 
allows of this artery reaching it without being en- 
closed in any peritoneal duplicature; not unfre- 
quently, indeed, it is found to enter the corner of 
the gastro-hepatic omentum at once, and sometimes 
it occupies one of the little falciform folds just 
mentioned, but occasionally it is situated as the 
description indicates, and as this is its constant 
course in all or most of the inferior animals, we 
consider it and describe it as its normal one. 


942 


selves, by using great care in manipulation, 
that it is not the result of violence; it exists 
also in the mesenteries of same animals. 

The arteries that ramify in the great omen- 
tum are branches of the gastro-epiploica dextra 
and sinistra, and some anastomosing ones from 
the colica media which pass round the colon 
and enter the omentum on the side of the in- 
testine opposite to that on which the artery 
reaches it. Veins and doubtless nerves accom- 
pany these arteries, and there are some lym- 
phatic glands enclosed between the layers of the 
great omentum along the greater curvature of 
the stomach. 

The use of the great omentum has never 
been satisfactorily pointed out. It is peculiar 
to, and universal in, the class Mammalia, and 
therefore always co-exists with a diaphragm ; 
probably it has some reference to the incessant 
motion and constantly recurring compression to 
which the intestines are subject from the action 
of that muscle in respiration. It is frequently 
seen dipping very deeply between the convo- 
lutions of the intestines, and occupying their 
interspaces as a moveable packing material, 
as if thereby enabling them to retain their 
cylindrical form whilst subject to incessant 
disturbance. 

The great omentum, being continuous as one 
sheet with the splenic omentum, may be re- 
garded as a great pouch or widening of the 
mesentery of the stomach. In those animals, 
such as the Carnivora, which have a very short 
colon, the great omentum does not extend from 
the stomach to the colon, but from the stomach 
to the pancreas, or to a transverse line of attach- 
ment corresponding in position with that of the 
transverse part of the duodenum in the human 
subject. e large intestine in these animals 
crosses over the small intestine at a point very 
near the termination of the latter in the cecum, 
that is to say, over the lower part of the ileum, 
where it usually has a proper mesentery.* 

The annexed drawing represents the abdo- 
minal viscera of a lizard, There is a prepa- 
ration, showing the same parts of a lizard, 
in the Hunterian collection, (No. 444 D, Phy- 
siological Series.) The whole of the intestines 
of this animal, from the esophagus to the 
rectum, are copnected to the posterior abdo- 
minal parietes by one continuous mesentery 
attached along the mesial line. In the sheet 
situated anterior to the stomach, connecting 
that organ to the liver and enclosing the gall- 
duct in its free edge, we recognise the lesser 
omentum in what we heretofore considered its 
typical position. In that part of the mesentery 
which connects the upper part of the stomach 
to the posterior parietes we recognise the sple- 
netic omentum ; the spleen is seen enclosed 
between its layers—apparently a large mesen- 
teric gland. That art of the common mesen- 
tery which, immediately succeeding the last 
mentioned, connects the middle and lower part 
of the stomach to the parietes, we cannot help 
regarding as the great omentum (the pancreas 

* Insome Carnivora, as the cat, the large intes~ 


tine cannot be said fairly to pass over the small in- 
testine at all. 


is just below this). Now pouch out this p . 
towards the left, and a great omentum, nee 


PERITONEUM. 


LZ” 


Abdominal viscera of a Lizard, 

a, stomach ; 5, liver; c, lesseromentam; d, gall- — 

duct; e, duodenum; /, pancreas; g, great omen- 

tum; h, spleen; i, cecum; k, ovary and kidney; 
I, lung. :, 


is found in the Carnivora, is produced, with the 
same relation of other parts, except in the obli- 
quity of the parietal attachment in the last- 
named animals, which is but slight. We have 
but to enclose the transverse colon between th 
layers of this sac, to obliterate that portion o 
the mesentery which is connected to the pan- 
creas and duodenum, and to carry the trans 
verse portion of the latter across just in the line 
of parietal attachment, in order to uce the 
condition of the parts which exists in man. J 
will readily be perceived how, in the me: 
time, a foramen of Winslow will have bee 
formed by this imaginary manipulation.* W 
should deem this pouching or widening of t 
gastric mesentery to have reference to the gn 
distention to which the stomach is liable, b 
that the sac is far too ample to be obliterated b 
any possible distention of that organ. 
he transverse mesocolon, formed of t 
layers of peritoneum, derived as described abo 
is about six inches broad in the middle, a 
gradually narrows off on each side. It reta 
the transverse portion of the colon in situ, 
transmits the veins, arteries, and nerves to | 
part of the intestine. At its root its two Tay 
separate, leaving a prismoid space, which | 


* The whole duodenum of many mammal 
animals, the cat for instance, has a mesentery 
that case the lower boundary of the fe 
Winslow is determined by the hepatic 


s, so that no part of itis ra 


these animals this portion of the 
passes off downw 
verse. 


PERITONEUM. 


passage to the transverse portion of the duo- 
denum. 

The mesentery is the peritoneal fold that 
connects the small intestine to the posterior 
abdominal parietes, giving transit to the vessels 
and nerves of that part of the intestinal tube. 
Numerous lymphatic glands, called mesenteric 
glands, are also included between its layers. It 
is eight inches in breadth at its widest part, and 
narrows off towards each end, where the small 
intestine becomes adherent to the parietes. Its 
parietal attachment, as mentioned above, is 
only a few inches in extent, whilst its visceral 
border is usually twenty feet long. 

The ascending mesocolon, descending meso- 
colon, and mesocecum, when they exist, and the 
iliac or sigmoideal mesocolon and mesorectum, 
which always exist, perform all the offices of 
mesenteries to those parts, respectively, of the 
intestinal tube which are indicated in their 
names. 

The appendices epiploice are numerous smal! 
masses of fat, somewhat pyriform, and having a 
peritoneal investment, attached along the large 
intestine. Their use is not known; perhaps 
they serve as packing to the sacculated bowel 
on which they are placed. 

The recto-vesical folds give transit to some 
vesical vessels and the umbilical arteries of the 
foetus. The cellular tissue enclosed by them is 
very lax, so that they are easily unfolded by 
distention of the bladder. 

The broad ligaments of the uterus are two 
folds of peritoneum passing from the lateral 
borders of the uterus to the opposite abdominal 
parietes. The line of their summits is about 
level with that of the superior border of the 
unimpregnated uterus. This summit or supe- 
rior border of the broad ligament is defined by 
the Fallopian tube which it encloses; a little 
lower down on its posterior aspect the ovary is 
sessile upon it, invested in a secondary fold of 
its posterior layer: and the round ligament of 
the uterus passing between its layers from the 
side of the uterus to the inguinal canal carries 
out another little secondary fold in front of it. 
The broad ligament, then, and its secondary 
folds, enclose the ovary with its ligament, the 
Fallopian tube, the round ligament of the ute- 
rus, and the spermatic vessels and nerves. The 
layers of the broad ligament itself, but not those 
of its secondary folds, are connected together 
by loose areolar tissue, and are separated (the 
broad ligament itself becoming effaced) by the 
enlargement of the uterus in pregnancy. 

_ There are a pair of recto-uterine peritoneal 

folds in the female and a pair of vesico-uterine 
Jolds ; the former pass across from the sides of 
the rectum to the sides of the uterus, and repre- 
sent the recto-vesical folds of the male; the 
latter pass across from the sides of the uterus 
to the sides of the bladder. The layers of both 
pairs are very loosely connected together. 

There is a slight median fold and two slight 
lateral folds of the peritoneum lining the ante- 
rior abdominal parietes, converging from the 
fundus and sides of the bladder to the navel; 
they enclose the remains of the wrachus and of 
the two umbilical arteries of the fetus. 


943 


At the point corresponding with each inter- 
nal abdominal ring in the male subject, there 
is a little infundibuliform depression or dimple 
of.the peritoneal surface ; it indicates the point 
from which a portion of peritoneum, being car- 
ried down with the testicle in its descent, was 
separated to form the tunica vaginalis—in the 
female; from the same points a cylindrical 
sheath of peritoneum accompanies the round 
ligament a little way into the inguinal canal ; 
this sheath has been called the canal of Nuck. 

With regard to our third proposition,—THE 
SEROUS COAT AFFORDED BY THE PERITONEUM 
TO THE VARIOUS VISCERA invests some of them 
completely, except along little linear spaces, 
imaginary rather than real, where it reaches 
them as mesentery, &c.: others it invests on 
one side only, and others again still more par- 
tially. 

The liver has an investment of peritoneum 
complete, except at its posterior, thick, rounded 
border, over a space of inconstant form be- 
tween the anterior and posterior layers of the 
coronary ligament, where the liver is in imme- 
diate contact with the diaphragm, the space 
corresponding with the gall-bladder, and along 
the little linear spaces where the falciform and 
triangular ligaments and the lesser omentum 
are attached to it. 

The gall-bladder is invested with peritoneum 
on its lower aspect only; that side which is 
presented towards the liver is in immediate 
contact with it. 

The stomach is completely invested with pe- 
ritoneum, except at the two little linear’ spaces 
along its curvatures, where the lesser and greater 
omenta are attached to it. 

The spleen is invested by the peritoneum 
completely, except at its hilus, where its vessels 
enter from the omentum. 

The first or-ascending portion of the duode- 
mum has a complete peritoneal investment, 
except at a little linear space along its lower 
aspect, where the great omentum is attached to 
it, so that this portion is free to move. The 
second, or descending portion has peritoneal 
investment on its anterior aspect only. The 
third or transverse portion is invested with pe- 
ritoneum along a very narrow portion of the 
upper, and a somewhat less narrow portion of 
the lower part of its anterior aspect ; the whole 
of its posterior aspect and the middle part of 
its anterior are destitute of peritoneal covering, 
the former being adherent to the posterior abdo- 
minal parietes, &c., the latter corresponding 
with the root of the transverse mesocolon. Its 
upper aspect is adherent to the pancreas, which 
encroaches upon the upper one of the two 
spaces mentioned as invested with peritoneum. 
At the point where the duodenum is crossed by 
the colon, which is just where from descending 
it becomes transverse, the two bowels are in 
immediate contact, so that the duodenum is, at 
this point, destitute of peritoneal covering around 
its entire circumference. Where the superior 
mesenteric artery crosses the duodenum, the 
peritoneum is borne off from it by that vessel. 

The pancreas is invested with peritoneum on 
its anterior surface only. 


944 


The peritoneum passes over the anterior sur- 
face of theikidstige and suprarenal capsules, but 
is not usually in immediate contact with them ; 
a large quantity of loose areolar and adipose 
tissue being in . 

Lhe jejunum and ilium have a complete in- 
vestment of peritoneum, except along the little 
= space where the mesentery is attached to 

em. 

The cecum and the ascending and descending 
colon are always invested with a peritoneal coat 
in front, and this extends to a variable distance 
around their sides, sometimes completely cover- 
ing them except at the little posterior linear 
spaces where their respective mesenteries, in 
such cases existing, are attached to them. 

The transverse portion of the colon is com- 
nag covered by peritoneum except along two 

ittle linear spaces on the opposite sides of it, 
namely, on its anterior and posterior aspects, 
where the great omentum and transverse meso- 
colon respectively, as described above, are 
attached. 

The sigmoid flexure of the colon and the first 
portion of the rectum are invested completely 
with peritoneum, except along the line of at- 
tachment of their respective mesenteries. 

The second portion of the rectum has a peri- 
toneal investment on its front only: its lateral 
and posterior aspects are destitute of such co- 
vering. The peritoneum, as above stated, 
passes across from the rectum to the bladder 
without descending low enough to afford any 
investment whatever to the lowermost or third 
portion of the rectum. The conventional divi- 
sion of the rectum into three portions is, in 
fact, founded upon this circumstance of its 
being first completely, then partially, and lastly 
not at all invested with peritoneum, as you 
proceed from above downwards. Thesummits 
of the recto-vesical fclds landmark the point of 
junction of the upper and middle portions. 

The whole of the posterior aspect, the fundus 
and the three upper fourths of the anterior as- 
pect of the uterus are invested with a peritoneal 
coat. Theos uteri, which projects into the va- 
gina, the lower fourth of the anterior aspect, 
which is in immediate contact with the bladder, 
and the little lateral lmear spaces where the 
broad ligaments are attached, are destitute 
of it. 

The peritoneum reaches the vagina behind 
the uterus, and invests a small portion of it in 
that situation, but does not come into relation 
with it in front of the uterus. 

The ovary is very closely and completely 
surrounded with peritoneum, which reaches it 
at its attachment to the broad ligament; we 
must in this case as heretofore describe a little 
linear space, at the point of attachment, as des- 
titute of peritoneal vestiture. 

The b is covered by peritoneum over a 
different extent in the two sexes. In both male 
and female its anterior aspect is destitute of 
peritoneal covering; and its fundus, in both 
sexes, has a peritoneal investment equally com- 

lete: with regard to the posterior aspect, 
omen in the male, the peritoneum covers it 
often as far down as the prostate, whilst it leaves 


PERITONEUM. 


uncovered a large portion of the lower part of 
this aspect of the bladder in the female. . ’ 
The parietal portion of the peritoneum in- 
vests the anterior and lateral abdominal walls — 
completely, except at the lower part, where it 
is borne off from the anterior walls by the 
bladder and along the linear attachment of the 
falciform ligament of the liver; the under 
surface of the diaphragm, except between the 
layers of the coronary ligament of the liver, and 
along the linear attachments to it of the falei- 
form and triangular hepatic ligaments, the 
phrenico-gastric ligament, and the splenic 
omentum ; the posterior parietes, except where 
the viscera, ducts, and vessels enumerated 
above as invested with the peritoneum on their 
front only, intervene. It does not, however, 
reach the inferior abdominal parietes, that is to 
say the levator ani, at any point, a quantity of 
loose cellular tissue occupying the inters 
of the pelvic viscera between that muscle and 
the lowest point to which the peritoneum 
extends, a 
We now come to the last of our propositions. 
THE EXTERNAL OR ADHERENT SURFACE OF 
THE PERITONEUM is attached to the apposed 
tissues with different degrees of intimacy in — 
different situations—a circumstance of great 
importance with regard to certain i 
operations. This attachment is intimate or 
otherwise, according as the areolar tissue that 
constitutes the connecting medium is abundant — 
or scarce, loose or compact, in different situa~ 
tions. The connecting areolar tissue is con- 
tinuous through the openings in the abdominal 
eg me the pee cri) —_ of the 
y- e parietal portion o peritoneum: 
is Ailes. by S  hheoas layer, so that 
abscesses seldom burst through it; whilst the 
visceral portion, being destitute of this layer, 
is not unfrequently burst through by abscesses 
of an abdominal viscus, as the liver. The 
peritoneum lining the under surface of the 
diaphragm is the most firmly attached of all 
the parietal portion. That which lines the 
anterior abdominal parietes is intimatel 
adherent along the linea alba and sheath of th 
rectus, but very loosely just above the pu 
and about the internal abdominal ring. It 
extremely loosely attached to the poster 
abdominal parietes and immediately superjacet 
organs, and in the lumbar and pelvic regi 
and iliac fosse—a very fortunate cireumsta 
with regard to placing ligatures on the 
abdominal and pelvic vessels without k 
open the peritoneal cavity. ; 
The visceral portion, as it covers the | 
and spleen and the alimentary tube, is 4 
intimately adherent to them except at_ 
middle portion of the rectum. That wi 
partially covers the bladder adheres very lot 
to it; owing to which, together with the I 
ness of the peritoneal attachment above 
pubis in front, to the rectum behind, an 
itself in the recto-vesical folds, the bla 
when distended rises high above the pu 
between the abdominal parietes and pel 
neum, pushing the latter up so as to dim: 
the depth of the recto-vesical cul-de-sac _ 


PHARYNX. 


leave its inferior fundus uncovered by it; con- 
sequently the bladder when distended may be 
punctured above the pubis or through the 
rectum without injuring the peritoneum. 

In the mesenteries, omenta, and other peri- 
toneal duplicatures, where the external surface 
of the peritoneum adheres to itself, the adhesion 
is generally extremely intimate. They are most 
Separated where deposits of fat have taken 
place between them. The recto-vesical folds 
and the broad ligaments of the uterus alone, 
of all the peritoneal duplicatures, have their 
layers loosely adherent. 

The peritoneum is very frequently the seat of 
extensive inflammation, the lymph effused in 
which process, besides causing adhesions of 
the abdominal viscera to one another and to 
the parietes, frequently covers the free peri- 
toneal surface with a thick adherent layer or 
false membrane; and this, like some other 
tissues formed from lymph, shrinks or cicatrizes 
in every direction, and thereby produces some 
very curious secondary effects. In such cases, 
if the great omentum is free at its lower border, 
it becomes tucked up to the greater convexity 
_ of the stomach and apparently obliterated; or 
if adherent, as to a hernial sac, the shrinking 
of the new tissue that covers it drags down the 
stomach. The thin sharp edges of the liver 
become rounded by this agent, and the calibre 
of the intestinal tube diminished; sometimes 
the intestine is even strictured by the contrac- 
tion of an unusually large deposit at a par- 
ticular part. The tendency of this tissue to 
shrink, however, being controllable by suffi- 
cient mechanical resistance, is most manifest in 
those directions in which it experiences no 
such opposition ; for which reason it tells more 
on the length than on the circumference of an 
intestine, and Cruveilhier met with a case of 
chronic peritonitis in which the small intestine 
measured only seven feet in length. If the 
hand is placed on the belly of a person in 
whom this condition exists, the muscles are 
felt to glide loosely over the peritoneum ren- 
dered tense beneath them. 

For the minute anatomy of the peritoneum 
see Serous Membrane. 

(Simon Rood Pittard.) 


PHARYNX and Mourn. (Gr. Qaguré.)— 
The pharynx is a large, muscular, and membra- 
nous pouch, placed behind the nose, mouth, and 
larynx, and resting upon the cervical vertebre : 
it extends from the base of the skull above to a 
level with the fourth or fifth cervical vertebra 
and the lower border of the cricoid cartilage, 
and is at this point continued into the cesopha- 
gus: it occupies the middle line of the body 
and is a symmetrical organ : of a very irregu- 
larly funnel-shaped form, it is wide above and 
open in front to the cavities of the nose and 
mouth, and contracts as it descends behind the 
larynx : by the relation of this latter organ the 
interior of the pharynx is converted into a tube 
to be continued downwards to the stomach 
under the name of esophagus. A common 
channel to the digestive and respiratory pas- 

VOL. III. 


945 


sages, it is alike beautifully adapted by its con- 
struction, on the one hand to receive the food 
and convey it onward to the alimentary canal, 
and on the other to preserve a perfectly free 
communication between the atmospheric air and 
organs of respiration: to this latter function may 
be added the power of modulating vocal sounds. 
As the pharynx is so closely associated, both 
in function and anatomical relation, with the 
mouth and palate, I shall subjoin to its de- 
scription that of these latter organs. In the 
further examination of the pharynx the fol- 
lowing arrangement will be adopted. 1st. The 
description of its aponeurosis and muscles, 
2ndly. Its attachments considered generally. 
3rdly. To examine its cavity with the several 
Openings related to it. 4thly. The mucous 
membrane and glandular apparatus; and, 
lastly, the vessels and nerves distributed to it. 
1. The fibrous membrane.—This aponeurosis, 
named cephalo-pharyngeal, contributes to the 
formation of the pharyngeal parietes above, 
and is essentially the means by,which the pha- 
rynx is affixed to the base of the skull: it forms 
a sort of framework for the support of the mus- 
cular and mucous tunics above, and is imper- 
ceptibly lost as it descends between these 
Structures: it is thin but strong and well- 
marked superiorly, and connected, by uniting 
intimately with the periosteum, to the under 
surface of the basilar process of the occipital 
bone, and, by a particularly dense slip, to its 
spine centrally; this latter may be considered 
as the origin of that tendinous raphé which, 
descending in the median line along the back 
of the pharynx, acts as an uniting medium to 
the constrictor muscles of either side: the 
basilar attachment of the cephalo-pharyngeal 
aponeurosis occurs immediately anterior to the 
insertions of the recti capitis antici muscles, 
and is consequently some little distance in ad- 
vance of the occipital condyles and foramen : 
extending laterally, the aponeurosis next springs 
from the under surface of the petrous portion 
of the temporal bone as far outwardly as the 
external orifice of the carotid canal, just an- 
terior and internal to which it turns suddenly 
forwards and inwards, forming a sharp angle, 
then passes beneath the inner surface of the 
levator palati muscle, to attach itself to the car- 
tilaginous portion of the Eustachian tube, near 
the anterior extremity of which it terminates by 
being gradually lost upon the mucous mem- 
brane: descending from these several points, 
and bounding the upper part of the pharyngeal 
cavity posteriorly and laterally, it insinuates 
itself between the mucous membrane and su- 
perior constrictor muscle, and splitting up into 
filaments which pass between the numerous 
mucous glands that are found at this part of 
the pharynx is lost from an inch to two inches 
below the base of the skull: posteriorly, on 
either side the median line, and between the 
upper semicircular margins of the superior 
constrictor muscles and the base of the skull, a 
considerable part of this aponeurosis is unco- 
vered by muscular fibres, constituting what are 
called the sinuses of Morgagni: the fibrous 
3 P 


946 


membrane is of great width at its origin, the 
external carotid foramina marking off the la- 
teral limits, but it quickly narrows as it de- 
scends: the sharp angle which it forms is 
brought into relation with the internal carotid 
artery and superior cervical ganglia of the sym- 
pathetic nerve: in the interior of the pharynx 
a longitudinal sulcus, sometimes crossed by a 
transverse slip, will be found behind the open- 
ing of the Eustachan tube, leading to a cul-de- 
sac which occupies this angle. 

The pharynx is surrounded by muscular 
fibres which have been collected into three 
distinct muscles on either side, and named, 
from their action, constrictors; these may be 
considered as intrinsic: two other muscles on 
either side are inserted into its walls, and are 
extrinsic as not belonging so exclusively to it. 
The constrictor muscles are membraniform, 
Spreading as thin muscular lamine around the 
sides and back part of the pharynx, and have 
@ common insertion into a posterior median 
raphé: they partly overlap each other from 
below upwards, so that the inferior constrictors 
alone can be wholly examined without inter- 
fering with the rest, and are invested on their 
outer surface with a dense fascia: they arise by 
numerous and distinct points of attachment, 
which gave occasion to their being divided 
originally into several muscles, each with its 
appropriate name given according to its par- 
ticular origin: these are now reduced to three 
on each side, and arranged into superior, middle, 
and inferior. 

Constrictor pharyngis inferior.* — This 
muscle is the thickest and strongest of the set, 
has an irregular quadrilateral outline, and is 
situated at the lower part of the pharynx: it 
derives its origin from the cricoid and thyroid 
cartilages by two slips: the one, triangular and 
fleshy, arises from the side of the cricoid car- 
tilage between the origins of the crico-arytenoi- 
deus posticus and crico-thyroideus muscles : 
from the latter it occasionally receives a few 
fibres: the other, broader and more extensive, 
lies on the ala of the thyroid cartilage, and 
arises from the two tubercles, which the ala 
presents on its external surface, and from a 
tendinous structure that stretches obliquely 
from one tubercle to the other: it is here 
blended with the attachments of the sterno- 
thyroid and thyro-hyoid muscles: it also em- 
braces the inferior cornu of the thyroid carti- 
lage: from these f sears it spreads round the 
side and back of the pharynx to the posterior 
median raphé, into which it is inserted con- 
jointly with the muscle from the opposite side; 
the fibres pass in different directions: the su- 
perior are longer and pursue a more oblique 
course upwards, while the nearer they are ex- 
amined to the lower margin of the muscle, the 
shorter and less oblique they become, and at 
length assume nearly a transverse direction. 
The origins of the inferior constrictor muscle 
are concealed by the thyroid gland and sterno- 
thyroid muscle : it is in relation laterally to the 


* Thyro-pharyngeus, crico-pharyngeus. 


PHARYNX. 


sheath of the carotid vessels, and posteriorly to 
the cervical vertebra and deep muscles of the 
neck: its internal surface is applied partly 
upon the mucous membrane and the terminal 
fibres of the syle phacnges and palato-pha- 
ryngeus muscles, but to a greater extent upon 
the middle constrictor muscle: the obli 
upper margin extends as high as the middle of 
the pharynx and close by its thyroid attach- 
ment allows the superior laryngeal nerve to 
pass beneath it: the circular fibres of the ceso- 
Ee are connate. its nes i 

ut distinguishe their greater delicacy 
paler colour: ania Na the cricoid cartilage the 
inferior or recurrent laryngeal nerve slips be- 
neath its lower margin. Some of the lower 
fibres have occasionally been noticed to arise 
from the first ring of the trachea. 

Constrictor pharyngis medius* is of a trian- 
gular form, fixed by its apex to the hyoid bone 
and by an extensive base to the ian 
behind : its origin is received into the ang 
formed by the greater and smaller cornua of 
os hyoides, to which processes the muscular 
fibres are attached as well as to the lower part 
of the stylo-hyoid ligament: the origin extends 
along the greater cornu quite to its posterior 
extremity, and is concealed by the hyo-glossus 
muscle, the lingual artery intervening: from 
this contracted commencement the middle con- 
strictor spreads widely over the back of the 
pharynx, the superior fibres obliquely ascend- 
ing towards the basilar process of the occipital 
bone, to the spine of which they are connected 
through the medium of the raphé, the muscle 
itself rarely reaching so high; the middle fibres 
take a more or less transverse direction, while 
the inferior descend under cover of the inferior 
constrictor: the whole muscle is inserted, wi 
its fellow from the opposite side, into 
raphé. After emerging from beneath the hyo- 
glossus it is related to the external carotid ar 
tery and superior laryngeal nerve laterally, and 
to the aoe ait column behind: by its internal 
surface it overlaps the superior constrictor, at 
is applied upon the stylo- and palato-pharyng 
muscles and the mucous membrane. Near th 
great cornu of the hyoid bone the stylo-phi 
ryngeus muscle insinuates itself beneath 
upper border, separating it from the superi 
constrictor. 

Constrictor pharyngis superior,;> : 
teral in shape ood enelicaiad from its ¥ 
numerous attachments. The fibres of | 
muscle are paler and it is altogether thinner t 
the two former: it arises, firstly, by short ter 
nous fibres from the lower half of the pos 
edge of the internal pterygoid plate and its 
mular process ; secondly, from an aponeut 
described as the inter- or pterygo-maxillary | 
ment common to it and the buccinator mu 
and which stretches from the inner pteryg 

late to the posterior extremity of the aly 

rder of the inferior maxillary bone; thin 
from the back part of the mylo-hyoid 


; Brashear r 
+ Cephalo- pharyngeus, pterygo -f 
mylo-pharyngeus, glosso-pharyngeus, 


PHARYNX. 


and, lastly, is said to arise from the side of the 
tongue near its base: this lingual origin is con- 
sidered by some anatomists as a part of the 
genio-hyo-glossus muscle :* arising thus, the 
superior constrictor winds round the pharynx 
and is inserted into the cephalo-pharyngeal 
aponeurosis, upon which it is placed, and joins 
with its fellow from the opposite side at the 
median raphé. The superior fibres make a 
semicircular sweep upwards towards the spine 
of the basilar process, to which they are con- 
nected by the raphé: the rest pass more trans- 
versely to their insertion and are partially over- 
lapped by the middle constrictor: between the 
upper border of this muscle and the base of 
the skull the pharyngeal aponeurosis is left un- 
covered by muscular fibres. The superior 
constrictor corresponds posteriorly to the cer- 
vical vertebre, and is separated laterally from 
the internal pterygoid by a triangular space 
which is occupied by the internal carotid ar- 
tery, internal jugular vein, and the eighth and 
ninth pairs of nerves: the stylo-pharyngeus 
muscle is also related to its outer side before it 
descends beneath the middle constrictor: by its 
internal surface it is applied upon the levator 
palati and palato-pharyngeus muscles, the mu- 
cous membrane and tlie tonsil. 

The muscular layer thus formed round the 
pharynx is of varying thickness, the greatest 
strength prevailing behind the buccal cavity, 
where the inferior constrictor, in itself the 
strongest of these muscles, overlaps the middle: 
on the other hand, there is but little occa- 
sion for muscular action behind the nasal 
fosse, so we find, in accordance with this 
circumstance, a greater delicacy in the fibres 
of the superior constrictor and a defici- 
ency of muscle altogether higher up: pro- 
bably, also, the overlapping of these muscles 
from below upwards and the oblique direction 
of many of their fibres have reference to the 
downward passage of the food. The margins 
of the constrictors, as these muscles lie on each 
other, are not very distinct, particularly towards 
the back part of the pharynx. Additional mus- 
cular slips have occasionally been observed by 
different anatomists, which may be briefly no- 
ticed :—1. fibres from the petrous process of 
the temporal bone to pass downwards and back- 
walds; 2. from the basilar process directed 
inwards ; 3. from the internal pterygoid plate 
and hamular process directed senawirdl and 
inwards; 4. from the spinous process of the 
sphenoid and from the cartilaginous portion of 
the Eustachian tube. 

Use.—Besides constricting the cavity of the 
pharynx, the inferior and middle constrictors 
can raise the larynx and carry it backwards, 
the latter through the medium of the os hyoides. 

The extrinsic muscles of the pharynx are two 
on either side, the stylo- and palato-pharyngei. 


* Cruveilhier says ‘‘ that those fibres of the 
genio-hyo-glossus, which occupy the interval be- 
_ tween the os hyoides and the stylo-glossus, cover 
the corresponding portion of the pharynx, or rather 
the amygdaloid excavation.” Valsalva and San- 
_ torini regard these fibres as forming a distinct 

muscle, and name it the glosso-pharyngeus. 


947 


Stylo-pharyngeus——This is a long slender 
muscle, broader below than above, and arises 
from the inner side of the styloid process at 
its base, and from the neighbouring part of the 
vaginal process: it descends inwards and for- 
wards towards the greater cornu of the os 
hyoides, and expanding insinuates itself be- 
neath the upper edge of the middle constrictor 
muscle to be applied upon the mucous mem- 
brane of the pharynx: it is inserted with the 
palato-pharyngeus into the posterior border of 
the thyroid cartilage: soon after its origin it 
passes with the stylo-glossus muscle between 
the external and internal carotid arteries, lying 
upon the latter and the internal jugular vein: 
a particular feature in this muscle is its close 
relation to the glosso-pharyngeal nerve, which 
winds round its lower border from behind for- 
wards: as it descends, its next relation is the 
side of the superior constrictor, and passing 
between it and the constrictor medius it is 
applied upon the mucous membrane of the 
pharynx. 

Use.—The stylo-pharyngei raise and widen 
the pharynx, preparing it for the reception of 
the food: they are important muscles in deglu- 
tition: the larynx is also raised by them. 

Palato-pharyngeus—This muscle will be 
again referred to as belonging to the palate: its 
fibres are contained in the fold of mucous 
membrane known as the posterior pillar of the 
fauces : it expands upwards to the soft palate, 
and downwards to the pharynx under the supe- 
rior constrictor: it descends to spread its fibres 
on the mucous membrane, and is inserted with 
the stylo-pharyngeus into the posterior border 
of the thyroid cartilage. 

2. General review of the attachments of the 
pharynz.—By referring to the foregoing de- 
scriptive anatomy of its aponeurosis and mus- 
cles, the pharynx will be seen to form from 
one-half to two-thirds of a vertically elongated 
cylinder, open in front; and although before 
terminating, the interior of the pharynx is con- 
verted into a complete canal, it is so only by 
the relation of a totally distinct organ, viz. the 
larynx. Descending perpendicularly from the 
base of the skull to the lower border of the 
cricoid cartilage, the pharynx is applied evenly 
to the anterior aspect of the bodies of the cer- 
vical vertebrae and deep muscles of the neck, 
having a remarkably loose areolar tissue inter- 
vening, important as preserving to it a perfect 
freedom of motion, while, by its anterior edges, 
it is fixed to the internal pterygoid plates, to 
the pterygo-maxillary ligaments, by means of 
which it is continuous with the lateral walls of 
the mouth, to the inferior maxillary bone, the 
sides of the tongue and cornua of the os hyoides, 
thus forming behind the nasal and buccal cavi- 
ties a large pouch, whose parietes being con- 
stantly strained apart by these attachments, 
preserve a perfectly free cavity, a circumstance 
of considerable importance with reference to 
the continual passage of air to and from the 
respiratory apparatus : continuing downwards, 
the pharynx next embraces the sides of the 
thyroid and cricoid cartilages, but as there is 
no longer occasion for this tension of its walls, 

3 P 2 


948 


they become flaccid, and are loosely applied to 
the posterior surface of the larynx, and so con- 
tinued into the @sophagus: if examined from 
behind, the pharynx is seen to be of great 
breadth at the base of the skull, but narrows 
until opposed to the buccal cavity, where it 
again widens to contract somewhat abruptly at 
its termination : its lateral relations to the ca- 
rotid vessels and nerves of the neck have been 
considered in the descriptions of the constrictor 
muscles. 

3. The cavity and its openings.—The interior 
of the pharynx exhibits a cavity of considerable 
size, which is continuous with those of the 
nasal fossee and mouth anteriorly and the canal 
of the esophagus below. To study the varying 
dimensions of this cavity and the different 
openings which communicate with it, the pha- 
rynx must be slit up posteriorly and in the 
median line ; its greatest breadth is behind the 
mouth, the buccal portion, which may be mea- 
sured by the interval between the posterior ex- 
tremities of the alveolar border of the lower 
jaw, and is rather more than two inches ; thence 
narrowing upwards, the internal pterygoid plates 
will by their distance from each other, which 
is about one inch, give the diameter of the 
cavity at its nasal portion, while the distance 
between the posterior edges of the ale of the 
thyroid cartilage will denote its breadth at the 
inferior or laryngeal portion : the antero-poste- 
rior diameter can vary but little, in consequence 
of the relation which the vertebral column has 
to the pharynx behind: during the act of deglu- 
tition these measurements are of course altered, 
but there is much less change of form in the 
upper or nasal portion of the cavity than in the 
rest of its extent. Dropping into the cavity 
from before backwards and from above down- 
wards is the velum palati with the uvula de- 
pending from the centre of its posterior border : 
above this moveable curtain are seen the poste- 
rior openings of the nose with its median sep- 
tum, the vomer: these are situated between 
the internal pterygoid plates, extend upwards 
to the base of the skull, and are limited below 
by the velum; they are quadrilateral in their 
outline and continued into the upper part of 
the pharyngeal cavity; a little way within the 
nasal fosse and along their outer walls are seen 
the meatuses of the nose and the posterior 
edges of the inferior turbinated bones; pro- 
longing these latter backwards by an imaginary 
line, we are brought to the openings of the 
Eustachian tubes; they are two narrow ellipti- 
cal fissures, their long diameters, about three- 
eighths of an inch, directed from above down- 
wards, and situated one on either side of the 
pharynx above the soft palate, and impinging 
the posterior edges of the internal pterygoid 
plates; they look forwards and inwards towards 
the inferior and middle meatuses of the nose, 
and are marked by prominent and rounded 
margins internally; an accurate knowledge of 
their relation to the nasal fosse is of practical 
use in directing a probe or syringe into their 
canals ; behind the openings of the Eustachian 
tubes are the longitudinal sulci which lead up- 
wards and backwards toa cul-de-sac that occu- 


PHARYNX. 


sae the angle formed by the sudden bending 
orward of the aponeurosis of the pharynx 5 
below the velum is the posterior constricted 
aperture of the mouth, which will be again 
referred to in the description of the soft palate; 
it is limited above by the velum, below by the 
base of the tongue, and laterally by the poste- 
rior pillars of the fauces ; the uvula depending 
from the velum centrally gives it a double 
arched outline above, but it is capable of as- 
suming changes of form by the varied move-~ | 
ments of its boundaries, which are especially 
concerned in deglutition; below the isthmus 
faucium and behind the base of the tongue is 
the superior aperture of the larynx, surmounted 
in front by the epiglottis; it is a tri 
opening, the base directed forwards, and it has. 
also an oblique direction from above down- 
wards and from before backwards ; it is gene~ 
rally completely closed during deglutition by: 
the epiglottis being forced down upon it; on 
either side of the posterior surface of the larynx, 
between the thyroid and cricoid cartilages, are 
two gutters which lead sommes to the 
cesophageal opening of the pharynx; this " 
ing bas iis jong diameter se pre < to sid ein 
the flaccid state of its walls, but assumes a 
circular form when distended by the passage of 
food through it. : 
4. Mucous membrane and glands.—The inte- 
rior of the pharynx is lined by a mucous mem- 
brane continuous with that investing the several 
cavities which open into it; it is of a reddish: 
colour, and adherent to the muscular parietes 
by a thin submucous areolar tissue; from co- 
vering the back part and sides of the interior of 
the pharynx, it is to be traced along the under 
surface of the basilar process united to the 
periosteum through the medium of its sub-— 
mucous tunic, which at this part acquires co 
siderable thickness, and is occasionally the se 
of polypus; laterally and above it is ref 
over the guttural orifice of the Eustachian 
enters the canal, and is conducted by it to the 
cavity of the tympanum, forming an exceed 
ingly thin lining to both; continuous with th 
mucous membrane, investing the upper su 
of the velum, it passes through 
nasal openings into the nose; it may e 
traced through the isthmus faucium, coverin; 
the under surface of the velum and poste: 
pillars of the fauces, to be continuous with th 
membrane of the buccal cavity, while more 
teriorly, after assisting to form the aryten 
epiglottidean folds of the laryngeal mucot 
membrane, it is reflected over the poster 
surface of the larynx, to which it is connec! 
so loosely by an areolar tissue as to be throy 
into longitudinal folds, a provision for the di 


tation of this of the pharynx d ne p 
sage of the ane lastly, it is coniila into 
cesophagus. The mucous membrane above 
velum palati, upon its upper surface and wit 
the Eustachian tubes, is coated with epitl 
risms, corresponding in this res : 
rrhich lines the greater part of ihe neal cavitit 
while below the velum the epithelium assut 
the lamelliform or scaly character. Noy 
cous Memprane.) As it invests the up} 


PHARYNX. 


part of the pharynx its free surface presents 
numerous slight elevations occasioned by the 
glands which are situated beneath it; these in- 
deed are scattered over the whole pharynx, but 
are especially abundant at its upper part, where 
they form a compact lamina between its mus- 
culo-membranous tunic and the mucous mem- 
brane, opening upon the surface of the latter 
by slender ducts. 
5. Vessels and nerves. —The bloodvessels 
distributed to the pharynx are derived from 
several sources, but chiefly from an especial 
trunk, viz. the ascending or inferior pharyngeal 
artery ; this vessel arises from the posterior part 
of the external carotid, often its first branch, 
near the bifurcation of the common carotid ; it 
ascends to the base of the skull, lying close by 
the side of the pharynx and upon the rectus 
capitis anticus major muscle, sending off nu- 
merous small branches, which, intermingling 
with the pharyngeal plexus of nerves, are dis- 
tributed to the constrictors and stylo-pharyn- 
geus, to the velum, arches of the palate and 
tonsil, ending in minute ramifications on the 
mucous membrane ; the next most regular sup- 
ply is from the inferior palatine and tonsillitic 
ranches of the facial artery ; the internal max- 
illary, lingual and superior thyroid vessels con- 
tribute an irregular supply of small and unim- 
portant twigs. The veins form a considerable 
plexus, the pharyngeal venous plexus, which is 
produced chiefly by the frequent anastomoses 
of the pharyngeal vein with the small branches 
that accompany the inferior palatine and tonsil- 
litic arteries, and with some of the commencing 
twigs of the internal maxillary vein; the pha- 
ryngeal vein, which receives the blood from 
this plexus, opens, either singly or in conjunc- 
tion with the lingual, into the internal jugular 
vein ; of the lymphatics, but little is known; 
they probably enter the chain of glands which 
Jie along the outer side of the carotid sheath. 
An intricate plexus of nerves, the pharyngeal 
plexus, is situated upon the sides of the pha- 
rynx, the branches being particularly numerous 
upon the middle constrictor muscle near its 
origin; it is of some length, and subject to 
variety in the number of its filaments in diffe- 
rent subjects ; it interlaces with the ramifica- 
tions of the arterial twigs from the ascending 
pharyngeal, and derives its branches from the 
three portions of the eighth pair of nerves and 
from the superior cervical ganglion of the sym- 
pathetic; the glosso-pharyngeal nerve sends 
downwards two or more branches to the plexus; 
one of these I have seen to join the superior 
laryngeal nerve ; they are given off just before 
the nerve winds round the lower border of the 
stylo-pharyngeus muscle; subsequently one or 
two branches penetrate this muscle to be distri- 
buted to the pharyngeal mucous membrane ; 
the pneumo-gastric detaches one or two pharyn- 
geal branches; the larger one appears in a great 
measure formed by a branch from the spinal 
accessory nerve ; these join with the filaments 
from the glosso-pharyngeal ; the superior laryn- 
geal nerve by its external branch also contri- 


butes a few filaments ; lastly, from the superior: 


cervical ganglion of the sympathetic, twigs are 


949 


> 

derived, which, communicating with those 
already mentioned, complete this intricate 
plexus ; the branches from it are distributed to 
the pharyngeal walls, to the soft palate, and 
stylo-pharyngeus muscles. The digastric branch 
of the facial nerve and the lingual or its de- 
scending branch are described as sometimes 
communicating with this plexus: for the more 
minute anatomy of these nerves see Par 
Vacum, Gtosso-PHARYNGEAL NERVE, AND 
Sprnat Accessory. 

Mouth, (Gr. croua; Lat. os; Fr. bouche.)\— 
The mouth is an oval cavity, symmetrical, and 
situated at the lower part of the face, below 
the nasal fossee, between the jaws, and in front 
of the pharynx, with which it communicates by 
a posterior opening, called the isthmus fau- 
cium, and has also a dilatable aperture ante- 
riorly guarded by the lips: it is liable to con- 
siderable alterations of form and size, from 
complete closure to a state of extreme exten-. 
sion, when it represents a quadrangular py- 
ramid with the base in front: the greatest 
change occurs in its vertical diameter from the 
movements of the lower jaw; in it are per- 
formed the various functions of mastication, 
tasting, partly that of deglutition, and it is 
subservient also to the production of articulate 
sounds. The mouth or buccal cavity is bounded 
both laterally and anteriorly by the alveolar 
borders of the upper and lower maxillary bones 
and teeth, the lips completing the boundary 
in front and the cheeks laterally: above it is 
roofed in by the arched palate and more pos- 
teriorly by the velum palati; inferiorly the 
tongue forms its floor. In the examination of 
these boundaries the reader is referred to the 
articles Face and Trers for the description 
of the maxillary bones and teeth. 

The lips (labia) are two moveable curtains 
placed in front of the mouth, presenting be- 
tween them when applied to each other a 
transverse slit convertible by their separation 
into a more or less considerable opening, which 
constitutes the anterior aperture of the buccal 
cavity : the lips are united at the lateral limits 
of this fissure to form the commissures or 
angles; the anterior surface of the upper lip, 
which usually projects a little beyond the lower, 
is covered with hair in the adult male, and 
exhibits in the median line a vertical groove 
continued to its free border from the septum 
of the nose: two ridges bound this furrow on 
either side, and from thence the upper lip 
passes off laterally to the cheek, insensibly in 
the young and plump face, but otherwise a 
line of demarcation is produced by an oblique 
fold of the skin which descends from the side 
of the nose to near the commissure of the lips 
on either side of the face: the anterior surface 
of the lower lip descends more or less abruptly 
backwards to the chin, divided from it by a 
transverse groove: it is covered with hair usu- 
ally at the centre only, and slightly bulging 
near its free border shelves off gradually to the 
sides of the face: the free borders are the 
thickest parts of the lips, their large develope- 
ment forming a characteristic feature in the 
Negro; in their outline they differ, presenting 


950 


in the u lip a projection in the centre, from 
which . meted gently arching upwards, 
proceeds laterally, while, in the lower, the 
centre exhibits a depression, and the line from 
it proceeds in a contrary direction, so that 
when the mouth is closed these borders are 
pot pen evenly to each other: they are of a 

colour, turned outwardly, and marked 
from before backwards by slight wrinkles pro- 
duced by the contraction of the orbicular 
muscle; their chief interest to the anatomist 
is in showing the continuity of the skin with 

mucous membrane. Besides the tegu- 
Mentary coverings of skin and mucous mem- 
brane, these organs contain within their thick- 
ness the orbicularis muscle, with which are 
blended the insertions of the greater number 
of the muscles of the face (see Face), whose 
varied actions render these features so pecu- 
liarly expressive of the passions: numerous 
glands, vessels, and nerves, and an areolar 
tissue complete their structure. The labial 
glands constitute a thick lamina between the 
muscular and mucous layers, producing slight 
elevations upon the surface of the latter; they 
resemble the salivary glands in appearance, 
are of small but varying size, placed close to 
each other but perfectly distinct, each posses- 
sing a separate excretory duct, which opens 
upon the free surface of the mucous mem- 
brane. The lips are most abundantly supplied 
with vessels and nerves; the coronary arteries, 
from the facial, course along their free borders 
directly beneath the mucous membrane; they 
also receive numerous twigs from the buccal, 
infra-orbital, and mental branches of the in- 
ternal maxillary and submental branch of the 
facial ; the veins accompany the arterial branches; 
the lymphatics terminate in the glands at the 
base of the jaw, as evidenced by the frequent 
enlargement of the latter from the irritation of 
cancerous or other sores about the lips: the 
nerves are derived from the portio dura and 


fifth pair. 

Use_The lips are of great importance, more 
particularly the lower, in retaining the saliva 
within the cavity of the mouth, and are actively 
engaged in the acts of sucking and blowing ; 
the utterance of many articulate sounds de- 
pends chiefly upon their action, and when 
viewed as organs of expression they are parti- 
cularly adapted by their extreme mobility to 
indicate the passing thought. 

The cheeks (bucce) form the lateral exten- 
sible walls of the buccal cavity; examined 
from the interior of the mouth they will be 
found limited above and below by the reflexion 
of their investing mucous membrane upon the 
external surfaces of the superior and inferior 
maxillary bones: their superficial surface is 
bounded behind by the external ear and the 
posterior border of the lower jaw, below by 
the horizontal ramus of the same bone ; supe- 
riorly they may be arbitrarily separated from 
the temple by the zygoma, and from the orbit 
by the lower margin of its cavity, and are con- 
tinued anteriorly into the sides of the nose and 
lips; they therefore present somewhat of a 
quadrilateral outline, and in the young and 


PHARYNX. 


but in the emaciated 
mouth. The skin of the cheek is smooth, thin, 
and delicate in front and above, and remark- 
able for its extreme vascularity, as seen in the 
act of blushing; it is covered behind and 
below in the adult male with hair, and in the 
aged its surface is more or less furrowed with 
wrinkles: the subcutaneous cellular tissue is 
dense and loaded with a variable yer 4 
fat, a particularly abundant mass of which is 
lodged between the buccinator and masseter 
muscles. The muscular structure of the cheeks 
has been already described in the article Facer. 
Between the muscles and mucous membrane — 
are irregularly dispersed a considerable num- — 
ber of buccal glands; they are of small size, 
similar to those of the lips, and like them open 
upon the mucous surface by separate duets: 
these openings are not likely to be mistaken 
for that of the parotid duct, which is marked — 
by a very distinct prominence, is of larger size” 
and situated opposite the interval between the 
second and ‘hed stan teeth in the upper jaw: 
there is an aggregation of several of these 
buccal glands, imbedded in the fat between 
the buccinator and masseter muscles, form-— 
ing a larger glandular mass which opens into 
the mouth opposite the last molar tooth, and 
has been called the molar gland. The cheeks 
receive a rich supply of vessels from the facial, 
transverse facial, and internal maxillary arteries; 
the veins correspond to these branches am 
empty themselves into the internal and external 
jugular veins. The lymphatics probably ter- 
minate in the glands of the neck. As wit 
other parts of the face, the cheeks derive the 
nervous filaments from the portio dura am 
fifth pair. “ff 
Use.—While the tongue guides the fooc 
outwardly to the teeth, the cheeks act int 
taining it between them during mastication 
they are employed during the act of sucking 
and when distended by air or fluids they ate” 
actively engaged in forcibly expelling them, 
exemplified in playing upon wind instrume! 
or in squirting liquids from the mouth. 
The palatine arch and gums.—The palat 
arch or hard palate forms the greater part 
the superior boundary of the buceal cay 
it has a parabolic figure, bounded laterally ¢ 
in front by the teeth, and is continued pos 
riorly into the velum palati without exhibit 
any line of demarcation; it presents mesia 
a whitish ridge, more prominent before 
behind, which commences from a small € 
nence situated immediately behind the ine 
teeth and corresponding with the lower ori! 
of the anterior palatine canal; the ridge #l 
extends backwards and is traceable as fa 
the uvula; from it are passing laterally a ¥ 
able number of transverse rugee, apparent 0} 
at the anterior part of the palate, its buc 
surface being, in the greater part of its exte 
rfectly smooth. The palatine arch is frame 
y the palate processes of the superior maxih 
lary and palate bones,* and invested on ' 


" * 
*\) oa 


healthy form a rounded Fars eee 
in towards 


‘ 


aa 


en 


* See FACE. 


PHARYNX. 


under surface by a dense and thick mucous 
membrane: numerous glands with vessels and 
nerves also enter into its structure. The mu- 
cous membrane covering the bony palate with 
that forming the gums is of a paler colour than 
elsewhere in the interior of the mouth, and is 
united by a remarkably condensed and thick 
submucous areolar tissue to the periosteum, 
especially in the mesial line, where the two 
Structures appear blended: on either side the 
union occurs by fibrous prolongations, allowing 
a thick layer of glands and the vessels and 
nerves of the palate to intervene: the mem- 
brane has a thick investment of epithelial 
scales, and is capable of resisting considerable 
eee of greater thickness before than be- 
ind, indifferently sensible, and in structure 
bears some analogy to that of the skin: the 
glands in every way resemble those of the 
cheeks and lips, and open in like manner upon 
the mucous surface; two larger openings than 
the rest may often be seen on either side the 
median line towards the back part of the 
palate. 
_ The gums (Gr. ovaa, Lat. gingive ) resemble 
in colour and structure the palatine membrane, 
except that the glandular apparatus is here re- 
duced to mere follicular pores. They cover 
either surface of the alveolar processes of the 
jaws, intimately connected with the periosteum, 
and extend a little way beyond the alveoli to 
rest against the necks of the teeth by a festooned 
edge. The denticulated processes of this edge 
are continued across the alveoli between the 
teeth, by which means the gums on either sur- 
face communicate with each other; between 
these processes the concave margin of the gum 
is reflected upon itself to enter the alveoli, 
lining their inner surface, and closely applied 
to the fangs of the teeth. (See Teetu.) The 
palate and gums receive their arterial branches 
from the internal maxillary and facial arteries, 
and their nerves from the spheno-palatine or 
Meckel’s ganglion. (See Firta Parr or 
Nerves.) The palatine nerves gain the palate 
through the anterior and posterior palatine fora- 
mina, and course along immediately beneath 
the periosteum, lodged in grooves, together with 
the accompanying arteries, upon the inferior 
surface of the palatine processes of the superior 
maxillary and palate bone. The palatine arch 
constitutes the septum between the nasal and 
buccal cavities, and forms the fixed and resist- 
ing surface against which the tongue acts in 
deglutition and in the articulation of certain 
sounds; previous to the irruption of the teeth 
and after their decay, the gums are continued 
over the alveolar processes, and by their almost 
cartilaginous hardness supply their place ; they 
are rendered peculiarly soft and spongy by the 
influence of mercury and scurvy upon the 
system. 

The velum palati is a soft moveable curtain 
stretching backwards and downwards into the 
cavity of the pharynx from the posterior border 
of the hard palate, but so continuous with it as 
to exhibit no indication of their union. From 
its oblique direction the buccal or inferior sur- 
face is also anterior; it is concave, prolongs 


951 


backwards the roof of the mouth, and presents 
the median ridge already noticed on the under 
surface of the hard palate. The nasal or supe- 
rior surface looks upwards and backwards, is 
smooth, convex, and continuous with the floor 
of the nasal cavities; these surfaces terminate 
in a thin border posteriorly, which is prolonged 
downwards in the middle line to form the 
uvula. The uvula is of a conical shape, and 
varies in length and size in different indivi- 
duals; it is occasionally found to be bifid at 
its extremity; it gives rise on either side near 
its base to two folds of mucous membrane, 
called the pillars of the fauces, which descend 
diverging towards the sides of the tongue at its 
back part, leaving between them an interval which 
is in a great measure occupied by the tonsil ; 
the anterior pillar proceeds from the base of the 
uvula in front, and arching outwards and down- 
wards terminates at the side of the tongue a 
little in advance of the V-shaped ridge of pa- 
pille ; the two anterior pillars together form 
what is denominated the anterior arch of the 
fauces. The posterior pillars constitute in fact 
the free border of the velum; they are nearer 
to each other at their commencement than the 
anterior, and from this circumstance (although 
on a plane posterior) can be seen at the same 
time with the anterior pillars on looking into 
the mouth ; they spring from the sides of the 
uvula to take an arched course outwards and 
downwards and terminate in the sides of the 
pharynx. The posterior pillars laterally, with 
the velum and uvula above and the base of the 
tongue below, bound the constricted aperture 
between the cavities of the mouth and pharynx, 
which is‘called the isthmus faucium ; the uvula 
dropping in the centre gives the superior out- 
line of this opening a double arched form : it is 
extremely dilatable, and may be contracted 
nearly to complete closure by the muscular 
action of its walls; it is essentially concerned 
in the act of deglutition. The fossa which is 
left on either side between the anterior and pos- 
terior pillars is of a triangular shape, narrow 
above where the pillars approach each other, 
broader and deeper below as they diverge. 
The lower part of this will nearly correspond 
to the angle of the jaw. 

Muscles of the velum palati—These are on 
each side, the circumflexus or tensor palati and 
levator palati mollis, which descend from above 
to be attached to the velum near its upper sur- 
face; and the palato-glossus and palato-pha- 
ryngeus muscles, which descend from it to the 
tongue and palate; lastly there is the central 
azygos uvule muscle. 

The circumflexus palati, tensor palati, or the 
peristaphylinus externus (pterygo-staphylin. 
Chauss.) is a flat, thin muscle, lying to the 
inner side of the internal pterygoid, and with it 
occupying the pterygoid fossa; it arises by ten- 
dinous and fleshy fibres from the scaphoid de- 
pression situated at the upper part of the inner 
pterygoid plate, and extending more outwardly, 
from a part of the external surface of the carti- 
laginous portion of the Eustachian tube. The 
muscle descends, partly tendinous and partly 
fleshy, resting against the outer surface of 


952 

the internal 
breadth to extend beyond its gees edge, 
and terminates in a tendon which winds round 
the hamular process; it is here retained in its 
situation by a small ligament and is surrounded 
by a synovial capsule to facilitate its mdve- 
ments. The tendon now alters its direction, 
for suddenly expanding into a thin but strong 
aponeurosis it spreads horizontally forwards and 
a little upwards to be inserted into the whole of 
the posterior border of the palatine process of 
the palate bone and into its posterior nasal 
spine, uniting with the tendon from the oppo- 
site side in the median line. It is in relation, 
so far as regards the vertical portion of the 
muscle, by its outer surface with the internal 
pterygoid, and by the inner with the internal 
pterygoid plate and the superior constrictor 
muscle of the pharynx. The horizontal tendons 
of these muscles form a firm aponeurotic ex- 
' pansion in the substance of the velum, which, 
when tightened by the contraction of the ver- 
tical muscular fibres, affords a powerful resisting 
surface to the upward pressure of the food while 
being thrust by the tongue through the isthmus. 

The levator palati or peristaphylinus internus 
(petro-staphylin. Chauss.) is a flat and narrow 
muscle, and commences by a thin tendinous 
and fleshy origin which is attached to the 
under rough surface of the petrous portion of 
the temporal bone and neighbouring part of the 
cartilaginous portion of the Eustachian tube on 
its inner side ; from thence it descends, resting 
upon the cephalo-pharyngeal aponeurosis, then 
slips beneath the upper edge of the superior 
constrictor muscle, and passes upon its internal 
surface to reach the palate; the muscle now 
takes a more horizontal direction inwards, and 
expanding spreads its fibres in the substance of 
the velum to unite with its fellow from the 
Opposite side in the median line, and is also 
inserted into the posterior border of the ex- 
panded tendon of the circumflexus palati. The 
insertions of the levator and circumflexus palati 
muscles on either side form a thin stratum, 
tendinous in front and muscular behind, 
through the whole extent of the soft palate. 
The levator palati in its vertical course is re- 
lated by its outer surface to the Eustachian 
tube and circumflexus palati muscle, from 
which latter it is soon separated by the supe- 
rior constrictor of the pharynx; it is covered 
internally by the pharyngeal aponeurosis and 
mucous membrane: it is an elevator of the 
pendulous portion of the soft palate. 

The palato-pharyngeus or pharyngo-staphy- 
linus consists of a delicate bundle of fibres 
contained in the fold of mucous membrane, 
known as the posterior pillar of the fauces; it 
expands upwards into the substance of the 
velum and downwards into the pharyngeal 
walls. The muscular fibres which spread in 
the velum are very delicate and mingled with 
those of the palato-glossus: they are situated 
immediately beneath the levator palati muscle 
and reach across the palate to join with fibres 
from the muscle of the opposite side in the 
middle line: some of the fibres are attached 
also to the posterior edge of the circumflexus 


pterygoid plate, but of sufficient 


PHARYNX. 


| 


palati tendon: arching over the upper and 
posterior margin of the tonsil they contract to 
descend as a thin bundle in the posterior pillar 
of the fauces, and again expanding pass into 
the lateral wall of the pharynx between the 
mucous membrane and constrictor muscles; 
here they meet with the fibres of the stylo- 
pharyngeus muscle and have an attachment 
with them to the posterior border of the thyroid 
cartilage and to the pharyngeal mucous mem- 
brane. The principal action of these muscles 
is to contract the isthmus faucium, which they 
can do superiorly almost to obliteration; they 
can scarcely have much effect in raising the 
pharynx ; if this latter be the fixed point, they 
may draw down the velum and so act as anta- 
gonists to the levatores palati. 7 
The palato-glossus, or constrictor isthmus 
faucium (glosso-staphylinus), occupies the an- 
terior pillar of the fauces and Roe its fibres 
in the velum with the palato-pharyngeus, then 
descends to expand upon the side of the tongue 
near its base, mingling its fibres with the stylo- 
glossus muscle. They may either act upon 
the velum by depressing it or raise the sides of 
the tongue to it. joe 
Azygos uvule or palato-staphylinus is a slen- 
der fusiform muscle, or rather a pair of muscles 
lying side by side: a narrow slip of tendon — 
attached to the posterior nasal spine gives” 
origin to the muscular fibres, which d 
backwards and downwards in the middle line, 
resting upon the circumflexus and levator palati 
muscles, and are lost in the substance of the 
uvula, which organ they shorten, 7 
The thickness of the soft palate is mainly 
dependent on a dense mass of small glands, a 
continuation in short of the series already de- 
scribed as occupying the structure of the pal 
tine membrane. They form an extremely thick 
layer anteriorly, but as the velum thins to 
posterior free border, so these glands becom 
the more scattered as they are traced backwards; 
they lie between the muscles and the mucous — 
membrane investing the under surface of th 
velum; a few also are scattered beneath 
mucous membrane covering its upper s 
and a larger proportion of them in the sul 
stance of the uvula, its bulk being chiel 
formed by them. 4 
The tonsils or amygdale (apvydurca) @ 
lodged in the interval between the pillars” 
the fauces : they are almond-shaped, with th 
larger extremities directed upwards, but va 
in size in different individuals. They app 
to consist of an assemblage of mucous glan 
whose excretory ducts terminate in small 5 
that are imbedded in the substance of the ton: 
and which open by larger or smaller orifit 
upon the surface of the mucous membr 
hen the tonsils are inflamed these sacs ex) 
a whitish secretion, which has some resembla 
to an ulcer on their surface. The palato-glos 
descends in front of and the palato-pharyngt 
behind these organs; they are supported € 
ternally by the superior constrictor muscle, 
are covered upon their internal surface by @ 
mucous membrane of the mouth. In imi 


matory enlargements of the tonsil it is slosel 


PHARYNX. 


related to the internal carotid artery, which 
vessel will be applied to its outer side and be- 
hind it, so that when an opening is required in 
the tonsil, the point of the lancet should be 
directed inwards towards the cavity of the 
mouth. The tonsils and soft palate are well 
supplied with blood by the palatine and ton- 
sillitic branches from the facial, by the ascend- 
ing pharyngeal and internal maxillary arteries. 
A considerable plexus of veins is formed round 
the tonsil, which terminates in the pharyngeal 
venous plexus. Besides the nervous twigs de- 
rived from the palatine branches of Meckel’s 
ganglion, the soft palate also receives filaments 
from a plexus formed around the tonsils by the 
tonsillitic branches of the glosso-pharyngeal, 
which has been called the circulus tonsillaris. 
For the description of the tongue, the remaining 
boundary of the cavity of the mouth, see 
ToncuE. 

Course of the mucous membrane.—The mu- 
cous membrane of the mouth is continuous 
with that of the pharynx and larynx. Com- 
mencing with the gums anteriorly, it passes 
upon the exterior surfaces of the upper and 
lower maxillary bones, and from thence is re- 
flected on the cheeks laterally and upon the 
inner surface of the lips anteriorly, forming a 
small fold in the median line, called the frenum, 
to each ; it invests the free borders of the lips 
and becomes continuous with the skin at a well 
defined line of demarcation. When the jaws 
and teeth are closed, the cheeks and lips are 
naturally in apposition with them ; but if sepa- 
rated by distending the cheeks, the mucous 
membrane we have been tracing will be seen 
to line an anterior or second buccal cavity form- 
ing a kind of antechamber to the interior of the 
mouth. Proceeding from the gums posteriorly 
the membrane descends upon the interior of 
the lower jaw to be reflected upwards to the 
under surface of the tongue, and forms for it 
anteriorly and in the median line a prominent 
fold, the frenum lingue; this occasionally is 
prolonged forwards to the apex of the tongue, 
interfering with its movements in the act of 
sucking: a slight division of the frenum under 
these circumstances is all that is required. From 
the under surface of the tongue the mucous 
membrane invests that organ and is continued 
from its base to the epiglottis, and after forming 
three folds, called glosso-epiglottic, is reflected 
over its free edge to be continuous with the 
laryngeal membrane. From the gums of the 
upper jaw posteriorly it invests the hard and 
soft palate and passes round the posterior free 
border of the latter, after enclosing the uvula, 
to cover its nasal surface. From the cheeks 
laterally it is to be traced over the anterior 
’ pillars of the fauces, the internal surface of the 
tonsils dipping into its mucous crypts, and 
lastly forming the folds of the posterior pillars 
is continuous with the mucous membrane of 
the pharynx. Throughout the cavity of the 
mouth it is invested with epithelial scales, and 
its submucous areolar tissue is remarkably in- 
creased in thickness and density when forming 
the gums and palate. 


953 


Function.—The pharynx, mouth, and palate 
are most obviously associated in the process of 
deglutition, in-;which we may trace three suc- 
cessive stages: in the first, the food after being 
reduced to a softened pulp by mastication and 
admixture with the saliva is conveyed to the 
back part of the mouth by the movements of 
the tongue against the hard palate; this is a 
purely voluntary act and can be arrested at the 
will of the individual: the food carried past 
the anterior arch of the fauces, the second act 
of deglutition immediately succeeds ; this in- 
volves the consentient action of numerous mus- 
cles and isa most complicated process. If the 
movements of the velum palati and the poste- 
rior pillars of the fauces are examined during 
an effort to swallow, the former is perceived to 
become somewhat more arched towards the 
cavity ofthe mouth and to be rendered tense, 
but it appears to maintain nearly its naturally 
oblique direction. It has been supposed that 
the velum is raised during deglutition, in order 
to prevent the food from passing to the nose, 
but this opinion is now generally considered 
erroneous. Miiller says, “ Most writers incor- 
rectly state that during deglutition the food is 
prevented from entering the posterior nares by 
the soft palate being raised, a movement which, 
if performed, could not in any case completely 
cut off the pharynx from the posterior nares.” 
With the stretching of the velum the posterior 
pillars or palato-pharyngei muscles will be 
seen to approach each other, particularly above, 
so as to reduce the isthmus faucium toa narrow 
triangular slit, broadest below. If the food is 
now pressed backwards by the tongue, it will 
be urged through this dilatable chink in a 
direction downwards and backwards, occasioned 
partly by the oblique resisting surface of the 
velum, and partly by the wider aperture left 
between the posterior pillars inferiorly, perhaps 
also by their greater disposition to yield in 
that direction to the pressure of the food as it 
passes between them; meanwhile the pharynx 
(and the larynx with it) has been drawn up- 
wards, and at the same time widened by the 
action of the stylo-pharyngei muscles, to receive 
the morsel, which in passing into it presses the 
epiglottis down upon thesuperior apertureof the 
larynx, and gliding over it is then immediately 
carried on to the esophagus by the action of 
the constrictor muscles. The epiglottis in 
being shut down upon the opening of the 
larynx protects the respiratory tube, but it is 
not absolutely essential for that purpose; ex- 
periments have been performed on animals 
where the epiglottis has been removed, and it 
has been destroyed by disease in the human 
subject without any material difference evi- 
denced in deglutition, the action of the laryngeal 
muscles closing the aperture of the larynx. 
This second act of deglutition may be performed 
at will though only the saliva is swallowed, 
but the effort soon becomes fatiguing. When 
the food, however, has reached beyond a cer- 
tain limit in the mouth, no effort on our part 
can prevent deglutition from taking place. (For 
the influence of the nerves upon this function 


954 


and that of taste see Par Vacum, Sprnat 
Accessory, GLOsso-PHARYNGEAL.) The fur- 
ther of the food through the esophagus 
into the stomach (see (Esopuacus) constitutes 
the third stage of deglutition and occurs invo- 
luntarily. 

MORBID ANATOMY OF THE PHARYNX AND 


MOUTH. 

Congenital malformations.—The pharynx in 
a very few instances only, presents any mal- 
formation ; when such exists the pharynx ter- 
minates in a cul-de-sac. Sir A. Cooper has 
recorded a case of this kind, in which also the 
esophagus was altogether wanting and ‘the 
stomach without a cardiac orifice: the child 
lived eight days. In acephalous monsters a 
' total deficiency of the pharynx has been no- 
ticed, but this is of very rare occurrence. The 
hard and soft palates are occasionally liable to 
congenital fissure: owing to an arrest of de- 
velopement they fail to unite in the median 
line, and the result is what has been termed 
the cleft palate: this defect may be confined 
to the velum palati, or it may include the bony 

te, and will sometimes extend through the 
ront of the jaw: where the bony palate is 
involved the defect may vary from a mere fis- 
sure to an entire absence of the palatine arch, 
so that the nose and mouth are converted into 
acommon cavity. The upper lip is not un- 
frequently fissured either on one or both sides 
of the median line, constituting the single or 
double hare-lip. This deformity may exist 
with or without the fissured palate, but cannot 
be considered as dependent simply on an arrest 
of developement; for at no period of fetal 
life is the lip known to present this peculiar 
condition: the fissure may only partially divide 
the lip, or it may extend into the nose in an 
oblique or vertical direction. It is very rare 
to find the lower lip fissured. 

Foreign bodies in the pharynx may produce 
immediate suffocation, either by mechanically 
obstructing the opening of the larynx or by 
inducing spasm of the glottis; when any dif- 
ficulty occurs in the extraction of these bodies, 
it is more generally dependent on their form 
than size. Angular portions of bone, needles, 
&ec. are likely to become fixed by the con- 
traction of the pharyngeal walls upon their 
pointed edges. 

Structural changes—The mucous mem- 
brane of the pharynx and posterior part of the 
fauces is very frequently the seat of inflam- 
mation, either simple or of a specific cha- 
racter; thus, it rarely escapes in scarlatina and 
syphilis without exhibiting the effects of these 
poisons: the latter often producing, by ulce- 
ration and sloughing, total destruction of the 
soft or even of the hard palate and causing 
fearful mischief. The tonsils generally parti- 
cipate in these inflammatory affections, or they 
may become inflamed primarily. In quinsy, 
the swelling of the tonsil is excessively rapid, 
and the disease is prone to terminate in sup- 
puration. One effect of frequent inflammatory 
attacks is an indolent enlargement of the tonsil, 
a condition which is often with difficulty re- 


PHARYNX. | 


medied, and occasionally requires excision of . 
that organ. 

Abscess sometimes occurs in the reticular 
tissue between the pharynx and cervical ver- 
tebre, and protrudes the posterior wall of the 
former forwards, so as to interfere with de- 
— fins 

Iceration of the pharynx occasionally hap 
pens; it may be the result of a lea 
specific inflammation, and will aR 
ceed to the destruction of its walls: 
openings between it and the larynx or other 
neighbouring parts may be thus produced. 
Cancer of the pharynx is fortunately not com- 
mon, but cases have been noticed in which it 
has occurred. 

Polypi have sometimes been found to take — 
their growth from the mucous membrane of — 
the pharynx, and most commonly spring from 
that portion of it which covers the 
aspect of the larynx. Dr. Monro mentions a 
case of this kind in which the polypus was 
of considerable length, hanging down in the 
cesophagus; another seat of origin in the 
pharynx is from the membrane as it invests the 
under surface of the basilar of the 
occipital bone: they have been seen to grow 
also from the soft palate. . 

A pouch is occasionally formed either be- 
hind or on either side of the pharynx be fe 
extrusion through the muscular coat of its 
mucous membrane. A preparation in the Mu- — 
seum at St. Thomas’s Hospital exhibits such 
an arrangement: a blind pouch about three 
inches in length, and of course communicating: 
with the interior of the pharynx, descends by 
the side of it: the muscular parietes do not 
appear to have been at all prolonged upon i 
surface. 

The cheeks, gums, and lips in children are 
sometimes involved in a destructive ulceration, 
to which the term cancrum oris has been ap- 
plied; it may extend to almost any length, 
destroying the cheek, the lips, the — and | 
teeth: it is seldom seen in adults. gums 
besides the softened and spongy change im 
duced by scurvy and the well known effe 
caused by the introduction of mercury into th 
system, are also affected with the disease cal 
epulis. In this case the gum is enlarge 
reddened, and ulcerates, and demands @ 
cision of the entire diseased structure : 
generally considered of a malignant na 
The lower lip is sometimes the seat of ¢ 
cerous ulceration ; it has been questioned 
ther this disease is really true cancer. Sir 
Cooper, however, says, in his lectures, * T 
the disease is of a scirrhous nature, eve 
the beginning, any surgeon must be satisfi 
it is hard, has a bleeding surface, ev 
edges, and, as it proceeds in its destru 
course, communicates disease to the gla 
there is likewise felt in it, at particular pei 
the most dreadful pain. An operation for 
complete removal of the disease is the patiet 
only real hope of succour.” It is very rat 
the same disease to originate in the upper I 

( William Trew. 


PISCES. 


PISCES. (Eng. Fishes; Fr. Poissons; 
Germ. Fische. )—The lowest class of the ver- 
tebrate division of the animal kingdom, em- 
bracing numerous oviparous races of beings 
fitted by their organization to live only in 
water, and consequently they are the appro- 
priate inhabitants of the ocean and of inland 
streams and lakes. Being strictly aquatic in 
their habits, Fishes respire through the medium 
of the element in which they live by means of 
gills or branchie, that are connected with a 
framework of bony or cartilaginous arches situa- 
ted on the sides of the neck, to which the water 
obtains free access, generally passing in at the 
mouth and escaping through lateral openings 
situated behind the head. Their heart is bilocu- 
lar, and consists of an auricle and ventricle, 
which, receiving the venous blood from the sys- 
tem, propel it over the respiratory surface, 
whence it is collected into an arterial trunk, the 
aorta, by which it is distributed over the body 
without the intervention of a systemic heart. 
Their blood is of very low temperature, and their 
bodies are generally covered with scales of va- 
rious kinds, whereby they are preserved from 
maceration in the surrounding water, and fitted 
to glide smoothly through the fluid medium 
wherein they live. Their principal instrument 
of progression is their tail, which is generally 
expanded into a broad fin, that strikes the 
water by alternate lateral movements. Besides 
this caudal fin others are frequently met with 
situated along the median line of the body, to 
which the names of dorsal and anal fins have 
been appropriated accordingly as they are situa- 
ted upon the back or behind the anal outlet of 
the body. The position of these azygos fins is 
vertical, and their use to a fish is similar to that 
of the keel or of the helm toaship. The repre- 
sentatives of the anterior and posterior extremi- 
ties of other Vertebrata likewise take the form 
of fins, and are only fitted for progression in the 
water: these are generally four in number, 
namely, the two pectoral fins, which represent 
the anterior extremities; and the two ventral 
Jins, corresponding with the posterior limbs of 
Quadrupeds. Great variety is met with both in 
the number and position of these locomotive 
members; generally all four are present; fre- 
quently one pair is deficient, and sometimes 
they are altogether wanting. In situation they 
likewise vary, more especially the ventral pair, 
which in some races, instead of being behind, 
are situated in front of the abdomen, in con- 
nection with the scapular apparatus, and even 
anterior to the pectoral fins. 

In the construction of their cerebral system 
Fishes evidently stand lowest in the vertebrate 
scale, and every part of their economy indicates 
their inferiority to Reptiles, Birds, and Mam- 
mals. 

The general attributes of Fishes and their 
relative position in the animal scale are so well 
laid down by their great modern historian, 
Cuvier, that it would be presumptuous not to 
give his own words. 

“ Breathing by the medium of water, that 
is to say, only profiting by the small quan- 
tity of oxygen contained in the air mixed with 


955 


the water, their blood remains cold; their vita- 
lity, the energy of their senses and movements 
are less than in Mammalia and Birds. Thus 
their brain, although similar in composition, is 
proportionally much smaller, and their external 
organs of sense not calculated to impress upon 
it powerful sensations.””* 

“ Fishesare in fact, of all the Vertebrata, those 
which give the least apparent evidence of sensi- 
bility. Having no elastic air at their disposal, 
they are dumb, or nearly so, and all the senti- 
ments which voice awakens or entertains they 
are strangers to. Their eyes are as it were mo- 
tionless, their face bony and fixed, their limbs 
incapable of flexion and moving as one piece, 
leaving no play to their physiognomy, no ex- 
pression to their feelings. Their ear, enclosed 
entirely in the cranium, without external concha, 
or internal cochlea, composed only of some sacs 
and membranous canals, can hardly suffice to 
distinguish the most striking sounds, and, 
moreover, they have little use for the sense of 
hearing, condemned to live in the empire of 
silence, where every thing around is mute.” 

“ Even their sight in the depths which they 
frequent could have little exercise, if most of 
them had not, in the size of their eyes, a means 
of compensation for the feebleness of the light; 
but even in these the eye hardly changes its 
direction, still less by altering its dimensions 
can it accommodate itself to the distances of 
objects. The iris never dilates or contracts, and 
the pupil remains the same in all intensities of 
illumination. No tear ever waters the eye—no 
eyelid wipes or protects it—it is in the Fish but 
a feeble representative of this organ, so beau- 
tiful, so lively, and so animated in the higher 
classes of animals.” 

“ Being only able to support itself by pursuing 
a prey which itself swims more or less rapidly, 
having no means of seizing it but by swallow- 
ing, a delicate perception of savours would have 
been useless, if nature had bestowed it; but 
their tongue almost motionless, often entirely 
bony or coated with dental plates, and only 
furnished with slender nerves, and these few in 
number, shews us that this organ also is as 
obtuse as its little use would lead us to ima- 
gine it.” 

“ Their smell even cannot be exercised so 
continually as in animals which respire air and 
have their nostrils constantly traversed by 
odorous vapours.” 

“ Lastly, their touch, almost annihilated at the 
surface of their body by the scales which clothe 
them, and in their limbs by the want of flexibility 
in their rays, and the nature of the membranes 
investing them, is confined to the ends of their 
lips, and even these in some are osseous and 
insensible.” 

‘“< Thus the external senses of Fishes give them 
few lively and distinct impressions. Surround- 
ing nature cannot affect them but in a confused 
manner; their pleasures are little varied, and 
they have no painful impressions from without 
but such as are produced by wounds.” 

“ Their continual need, which, except in the 


* Cuvier and Valenciennes, Histoire des Poissons. 


956 


breeding season, alone occupies and guides 
them, is to assuage the internal feeling of 
hunger, to devour almost all that they can. To 
pursue a prey or to escape from a pursuer 
makes the occupation of their life; it is this 
which determines their choice of the different 
situations which they inhabit; it is the prin- 
cipal cause of the variety of their forms and of 
the special instincts or artifices which nature 
has granted to some of the species.” 

“ Vicissitudes of temperature affect them 
little, not only because these are less in the ele- 
ment which they inhabit than in our atmosphere, 
but because their bodies taking the surrounding 
temperature the contrast of external cold and 
internal heat scarcely exists in their case. Thus 
the seasons are not so exclusively the regulators 
of their migration and propagation as amongst 
Quadrupeds or more especially Birds. Many 
Fishes spawn in winter; it is towards autumn 
that herrings come out of the north to shed 
upon our coast their spawn and milt. It is in 
the north that the most astonishing fecundity is 
witnessed, if not in variety of species, at least 
in individuals; and in no other seas do we find 
anything approaching to the countless myriads 
of herrings and cod which attract whole fleets 
to the northern fisheries.” 

* The loves of Fishes are cold as themselves ; 
they only indicate individual need. Scarcely 
is it permitted to a few species that the two 
sexes should pair and enjoy pleasure together ; 
in the rest the males pursue the eggs rather 
than seek the females; they are reduced to 
impregnate eggs the mother of which is un- 
known, and whose produce they will never see. 
The pleasures of maternity are equally un- 
known to most species; a small number only 
carry their eggs with them for a short time; 
with few exceptions Fishes have no nest to build 
and no young to nourish: in a word, even to 
the last details, their economy contrasts diame- 
trically with that of Birds.” 

In no class of the animal kingdom do we 
find such diversity of form as in that of Fishes. 
Some amongst them are perfectly spherical, 
as the Diodons. Others are discoidal, or flat 
and circular, and this shape may be produced 
by two very different conditions, resulting either 
from an excessive narrowing or inordinate ex- 

nsion of the two sides of the body. In the 

rst case it is compressed and much elevated, 
as in Vomer and Orthagoriscus, while in the 
second case it is much depressed, flattened, and 
very broad, as in the Skates. Other species 
are oval, more or less elongated and slightly 
compressed laterally, such as Carp, Trout, &c., 
which is the most ordinary shape. Neverthe- 
less when these become extended longitudi- 
nally (as in the Pikes for example), we are 
insensibly conducted by all intermediate grada- 
tions of form to the cylindrical Eels, or to com- 
pressed and riband-shaped Fishes, such as 
Cepola. Perhaps the most remarkably shaped 
Fishes are those whose bodies are bounded by 
nearly flat surfaces, and which circumscribe 
angular figures, such as triangles, squares, pen- 
tagons, hexagons, &c.,( Ostracion, Syngnathus. ) 
There are even certain genera in which the two 


PISCES. 


sides are not symmetrical, one being flattened 
and the other vaulted, and in these races even 
the bones of the cranium are so disproportioned 
that both eyes are turned to the same side of 
the animal ( Pleuronectide ). 

The following arrangement, being a modifi- 
cation of the classification proposed by Cuvier, 
will facilitate our investigations relative to the 
anatomy of the numerous members of this 


extensive class. ou 


PISCES. . 
Division 1. —~ CHONDROPTERYGII. 


Skeleton cartilaginous, fins supported by 
cartilaginous rays. 


Orpver I.—Branchie fixed. 


1st Family. — PLaciostomata. 
Sygena, Squatina, Pristis, Raia. 


Onper II.—Branchie free. 
1st Family. — Srorionipz. Accipenser, 


Spatularia, Chimera. 


Division I1—OSTEOPTERYGII. 
Skeleton composed of true bone. wi, 


Orpen I—ACANTHOPTERYGII. _ 


The Fishes belonging to this division are at 
once recognised by the stiff spines which con= 
stitute the first fin-rays of the dorsal fin, orwhich 
support the anterior fin of the back in ¢ 
there are two dorsals. In some cases the an- 
terior dorsal fin is only represented by detached 
spines. The first rays of the anal fin are like- 
wise spinous as well as the first ray of the ven= 
tral fin. This order, which comprises by far 
the greater nuinber of osseous Fishes, is divi- 
sible into the following families. 

1st Family.— Percivz. Perca, Lab 
Lates, Centropomus, Grammistes, Aspro, Apo- 
gon, Cheilodipterus, Pomatomus, Ambassis 
Lucio-Perca, Serranus, Plectropoma, Diac pe, 
Mesoprion, Acerina, Rypticus, Polyp 
Centropristis, Gristes, Cirrhites, Chirone: 
Pomotis, Centrarchus, Priacanthus, Dule 
Therapon, Pelutes, Helotes, Trichodon, Sill 
Holocentrum, Myripristis, Berys, Trachichti 
Trachinus, Percis, Pinguipes, Percophis, Ura 
oscopus, Polynemus, Sphyrena, Para 

ullus. a 

2nd Family.—SciERocEntpz (hard cheek 
Trigla, Prionotes, Peristedion, Dactylopter 
Cephalacanthes, Cottus, Hemitripterus, He 
lepidotus, Platycephalus, Scorpena, Pt 
Blepsias, Apistes, Agriopes, Pelors, ce 
Monocentris, Gasterosteus, é * 

Sciena, Eq 


Squalus, 


3d Family. — Scianipz. 
Hemulon, Pristipoma, Diagramma, Lobo 
Cheilodactyles, Scolopsides, Micropterus, 2 
ee Premnas, Pomacentres, Dascyli 
Glyphisodon, Heliases. a 
4th Family.—Sparivz. argus, Chry 
phris, Pagrus, Pagellus, Dentez, ’ 
Boops, Oblada. a 
5th Family—Manyipz. Mena, Smar 
Casio, Gerrus. ss 
6th Family. — SguaMMIPENNES. 


PISCES. 


don, Psettus, Pimelepterus, 
Brama, Pempheris, Foxotes. 

7th Family. — Scomperipz. Scomber, 
Xiphias, Centronotus, Rhincobdella, Campi- 
lodon, Seriola, Nomeus, Temnodon, Caranz, 
Vomer, Zeus, Stromateus, Sesarinus, Kurtus, 
Coryphena. 

8th Family—Tezniorves. Lepidopus, Tri- 
chiurus, Gymnetrus, Stylephorus, Cepola, Lo- 
photes. 

9th Family —Tuevtipz. Siganus, Acan- 
thurus, Prionurus, Naseus, Axinurus, Priodon. 

10th Family. — WirH LaBYRINTHIFORM 
PHARYNGEAL BONES. Anabas, Polyacanthus, 
Macropodes, Helostomus, Asphromenus, Tri- 
chopodes, Spirobranchus, Ophicephalus. 

11th Family—Mocirivz. Mugil, Tetra- 
gonurus, Atherina. 

12th Family—Goxsivzx. Blennius, Anar- 
eg Gobius, Callionymus, Platypterus, La- 

ax. 
13th Family—WitH PECTORAL FINS FEET- 
LIKE. Lophius, Batrachus. 

14th Family—Lasrivzx. Labrus, Xirech- 
thys, Chromis, Scarus. 

15th Family. — Wits FLUTE-SHAPED 
Movrus. Fistularia, Centriscus. 

All the other osseous Fishes have the rays 
that support the fins soft and composed of 
numerous pieces articulated with each other, 
with the exception, in some cases, of the first 
ray of the dorsal or of the pectoral. These are 
divided in accordance with the situation of the 
’ ventral fins, which are sometimes placed be- 
neath the abdomen, sometimes appended to the 
framework of the shoulder, or, lastly, are alto- 
gether wanting. Three distinct orders are thus 
established, viz... MALACOPTERYGII ABDOMI- 
NALES, MaLACoPTrERYGII SUBRACHIALES, and 
MatacopreryGil APODES. 


Orver II—MALACOPTERYGII AB- 
DOMINALES. Having their ventral fins sus- 
pended beneath the abdomen and behind the 

torals, without any connection with the 

nes of the shoulder. This order compre- 
hends most fresh-water Fishes. 

16th Family.—Cyrrrinivz. Cyprinus, Co- 
bitis, Anableps, Pacilia, Lebias, Fundulus, Mo- 
linesia, Cyprinodon. 

17th Family—Esoctpz. Esox, Erocetus, 

ormyrus. 

18th Family —Sirvuripz. 
lapterurus, Aspredo, Loricaria. 

19th Family—Satmonipz. Salmo, Ster- 


Dipterodon, 


Silurus, Ma- 


noptyx. . 

20th Family—Cuurripz. Clupea, Odon- 
tognathus, Pristigaster, Notopterus, Engraulis, 
Megalops, LElops, Butirinus, Chirocentrus, 
Hyodon, Erythrinus, Amia, Sudis, Osteoglos- 
sum, Lepisosteus, Polypterus. 


Orver III—MALACOPTERYGII SU- 
BRACHIALES. This order is distinguished 
by the ventral fins being situated beneath the 
pectoral, the pelvis being suspended immedi- 
ately from the framework of the shoulder. 

21st Family—Gavinz. Gadus, Lepidole- 


957 


22nd Family—Pu.rvronectss. Platessa, 
Hippoglossus, Rhombus, Solea, Monochirus, 
Achirus. 

23rd Family.—Discoznort. Lepadogaster, 
Cyclopterus, Echeneis. 


Orver IV. — MALACOPTERYGII 
APODES. Ventral fins totally wanting. 

24th Family.—Anevuituirormes. Murena, 
Saccopharynz, Gymnotus, Gymnarchus, Lep- 
tocephalus, Ophidium, Ammodytes. 


Orver V.—LOPHOBRANCHII. In all 
the preceding orders the gills are pectinated, 
but in the Lophobranchii the respiratory organs 
consist of little round tufts, disposed in pairs 
along the branchial arches. 

25th Family—Synenatuipa. Syngnathus, 
Pegasus. 


Orver VI.—PLECTOGNATHI. This 
order of Fishes is distinguished by having the 
superior maxillary bones consolidated with or 
firmly united to the intermaxillaries, which latter 
form the margin of the jaw. The opercula and 
branchiostegous rays are, moreover, so con- 
cealed by the thick skin that nothing is visible 
externally but a small branchial fissure. 

26th Family.—Gymnopontes. Diodon, 
Tetraodon, Orthagoriscus, Triodon. 

27th Family.— Scieropermes. Balistes, 
Ostracion. 


Division III—DERMAPTERYGII. 
Skeleton cartilaginous or membranous; fins 
without either cartilaginous or bony rays, or 
possessing the merest rudiments of them. 


Orver I.—CYCLOSTOMATA. 
28th Family—Petromyzon, Myzine. 


Orver II.—BRANCHIOSTOMATA. 
29th Family.— Branchiostoma. 


As regards the texture of their bones, Fishes 
may be divided into osseous, fibro-cartilaginous, 
and true cartilaginous. 

The cartilaginous, otherwise called Chondrop- 
terygii, and which by their entire skeleton, by 
their branchie, the external border of which is 
fixed to the skin, and from which the water escapes 
through narrow and multiplied orifices, as well 
as by other details in their economy, are distin- 
guished from other Fishes, have never true bones ; 
their skeleton consists internally of a semi- 
transparent cartilage, which in Rays and Sharks 
is coated at its surface only with a layer of 
opaque and calcareous grains. 

The Sturgeon and Chimera have the bones of 
the spine as soft as those of the Chondropterygii, 
but the first of these genera has in many of the 
bones of the head and shoulder, at least a layer 
at the surface, completely ossified. 

Other Fishes differ widely from each other in 
the hardness of the parts of their skeleton, and 
the fibro-cartilaginous have from this cireum- 
stance been erroneously associated with the 
Chondropterygii. In these, however, the cal- 
careous matter, that is to say, the phosphate of 
lime, is deposited by fibres and layers in the 
cartilage, which serves as a basis to their bones, 
as is the case with the most perfectly osseous 


958 


Fishes. It is only less abundant, and conse- 
quently the texture of the bone does not be- 
come so hard or homogeneous. 

It is very gratuitously that the skeleton 
of ordinary Fishes has been supposed to be 
more flexible, of a softer nature, and more ex- 
tensible than in the superior classes of Verte- 
brata. Most Fishes have their bones as hard 
as or harder than other animals, and there are 
even some, in the texture of which neither 
pores nor fibres are distinguishable, and which 
appear homogeneous or even vitreous to the 


e. 
No Fish, either osseous or cartilaginous, has 


a medullary canal in its bones; but there are, 


some, as the Trouts, in which the bony tissue is 
more or less penetrated with an oily fluid. 

There are some Fishes in which, whilst the 
rest of the skeleton acquires great hardness, 
some parts remain always cartilaginous, as for 
example, the head of the Pike. 

SKELETON oF ossEous FisuEs.—In osseous 
Fishes, we shall regard the skeleton as being 
composed of the head, of the respiratory appa- 
ratus, of the trunk, comprising the body and 
tail, and of the limbs, viz, the pectoral and 
ventral fins. The vertical fins, viz, those of the 
back, anus, and tail, may be regarded as form- 
sof oy of the trunk. 

e head having more moveable appendages 
than that of Quadrupeds must be divided into a 
greater number of regions. We may distinguish 
in it the cranium, the jaws, the bones placed un- 
der the cranium behind the jaws, serving for their 
suspension and motions; the opercular bones, 
forming flappers, which open and shut the 
openings of the branchie ; the bones surround- 
ing the nostril, which are nearly external, as 
also are those around the eye or the temple, or 
which cover a part of the cheek. 

The respiratory apparatus comprises the os 
hyoides and its appendages, that is to say, the 
branchiostegous rays and the arches supporting 
the branchiz, as also the different pieces at- 
tached to these arches, and which altogether 

rform the functions of larynx and of trachea ; 
lastly, the bones placed at the entrance to the 
pharynx, forming in some measure a second 
pair of jaws. 

The trunk is composed of the vertebre of the 
back and tail (for we can hardly say there is a 
neck, neither is there any sacrum,) of the ribs, 
of the bones called interspinous, which support 
the dorsal and anal fins ; also the rays of these 
fins, as well as of the tail. These rays, whether 
they have branches or articulations, or are 
simply spinous, are always divisible into two 
lateral halves. There is rarely a sternum, pro- 

rly so called, in Fishes; and when it exists, 
it is formed of pieces which are almost external, 
and which unite the lower extremities of the 
ribs. 

The anterior extremity or b origeee fin com- 
prehends the shoulder, which is an osseous 
semicircle composed of many bones, suspended 
at the upper part to the cranium or spine, and 
uniting inferiorly with its fellow of the opposite 
side. We may here find bones analogous to 
the two pieces of the scapula of Reptiles, to 


PISCES. 


the humerus and to the bones of the forearm ; 
there is even generally a process rage ees of 
two pieces protruding backwards, in which we 
might seek to see the coracoid bones and even 
the clavicle. 

The two bones comparable to the radius and 
ulna carry at their edge a row of ossicula, 
which appear to represent those of the carpus, 
and which support the rays of the proees fin, 
with the exception of the first, which articu- 
lates at once with the radial bone. 

The posterior extremity is much more va- 
riable in position than among Mammalia; its 
external or moveable portion, called the ventral 
Jin, emerges sometimes before, sometimes behind, 
and sometimes immediately beneath the an- 
terior extremity. The pelvis is composed of four 
bones, the largest and most constant of which, — 
being always in front of the anus and genital 
orifices, may be considered as a sort of pubis, 


and these carry on a part of thei post ae 
out interme-— 


the rays of the ventral fin, wi 
diate bones which can nd either to 
femur, tibia, fibula, or tarsus. The rays of the 
pectoral and ventral fins, as of those of the 
single ones, are divisible longitudinally into 
two portions. 
ertebral column.—The vertebre of a Fish 

are at once recognisable by the deep conical 
cavities which form the articulating surfaces 
whereby they are connected together, so that a 
double hollow cone always occupies the 
terval between two vertebre, which in th 
living state is filled up by a soft membrane 
and gelatinous substance, which ror 
One intervertebral cavity into another through 
holes which generally perforate the centres 
the bodies of the vertebre. ; 

In Fishes, as in all other animals, each ver- 
tebra presents superiorly a ring for the passage 
of the spinal medulla bounded by the superio 
spinal lamine ( neurapophyses ), which is gene 
rally surmounted by a long spinous proces 
(fig. 493, 4,) at the base of which are situatet 
both upon the anterior and posterior aspect litt 
eminences that correspond to the articulat 
processes of other Vertebrata; but most gen 
rally these processes only touch or slight 
overlap those of the neighbouring vertebi 
without their being connected ‘4 
articulating facets. Sometimes, indeed, th 
exist on one side of the vertebra and 
on the other, so that they have no corr 
pondents wherewith to articulate. The | 
nular of the first vertebra is freque 
separated from the body during the whole 
time of the Fish, but in the other vertebra 
such separation is visible. > 

In some families, as in the Murenide, 
of the anterior vertebre have a little ere 
vertical apophysis developed from beneatl 
body. Geer fates ro a portion of 
bodies of their vertebre soldered to 
this there are examples among the 
Fistularide, and SHuridee. 

Those vertebra which are situated above 
abdominal cavity have transverse processes 
veloped to a greater or less extent. These, 
some instances, as, for example, in t 


ase 


PISCES. 


pte, remain for a long time only attached 
y suture to the bodies of the vertebra, from 
which they are easily distinguished. 

In certain Fishes, as, for example, in Merlus, 
the transverse processes are very large and give 
attachment to the swimming bladder. Some- 
times the ribs are suspended from the trans- 
verse processes, or sometimes they are derived 
immediately from the bodies of the vertebra. 
In this respect there are great varieties. 

In those vertebre that are situated behind 
the abdominal cavity there is an inferior fora- 
men for the lodgement of the great blood- 
vessels of the trunk bounded by inferior spinal 
lamin ( hemapophyses ), and, like the superior, 
generally supporting long spinous processes, 
(fig. 493, 5,) so that the vertebrae seem to consist 
of similar parts, both above and below the body. 

These inferior arches of the caudal vertebra 
are considered by Cuvier as being formed by 
the inordinate developement of the transverse 
processes, which he describes as here becom- 
ing directed downwards and united to each 
other, so as to form the inferior ring; and, 
certainly, in the generality of Fishes, by tra- 
cing the apparently gradual conversion of the 
abdominal into the. caudal vertebre, such is 
the conclusion at which the comparative anato- 
mist would naturally arrive. In many Fishes, 
however, as, for example, in the Murenide, 
these inferior arches with their appropriate 
— are in the caudal region co-existent with 

istinctly developed transverse processes, evi- 
dently shewing that they must be regarded as 
being totally different elements of the skeleton, 
namely, the hemapophyses. (See Osszous 
System.) 

The inferior or heemapophysial elements, like 
the superior arches, have in many instances 
oblique processes developed from tlem, which 
in some cases are very large and branched, so 
as to form a kind of interlacement around the 
vascular canal. This is especially observable 
in certain Tunnies. 

As the vertebre approach the tail, their pro- 
cesses are gradually shortened, and the verte- 
bral canal becomes narrowed or obliterated, 
(fig. 493, 8,) and at length the terminal vertebra 
have their apophyses consolidated with each 
other and with the interspinous bones, so as to 
form in some Fishes, as the Perch, a vertical 
triangular plate, to the posterior margin of which 
are articulated the rays of the caudal fin (9). 
In Fishes with long and pointed tails like the 
Eels this disposition is wanting; but in other 
races, such as the Pike, the real composition of 
this part of the skeleton is easily recognisable. 

Ribs and sternum.—The ribs of Fishes have 
nothing to do with respiration, merely serving 
to support the muscular parietes of the body ; 
they consist of the dorsal portion only, which 
is articulated by a single head, either to the 
transverse processes or to the bodies of the 
vertebre themselves. Frequently they give off 
long bony processes, which penetrate among 
the muscles; and sometimes also similar pro- 
cesses are attached above the ribs to the bodies 
of the vertebre themselves, so that the flesh of 
-some Fishes appears full of little bones as fine 


959 


as hairs. The ribs vary extremely in different — 
genera. Sometimes they are round and slen- 
der, sometimes compressed and _falciform ; 
occasionally they seem to surround the whole 
abdomen, and in many species are quite rudi- 
mentary or altogether wanting. The sternum 
is entirely deficient in most Fishes; sometimes, 
however, it does exist, as in Clupea, Vomer, 
&c.; in such cases it consists of a longitudinal 
series of impair bones, differently shaped in 
different genera, to the sides of which the ribs 
are attached inferiorly. 

Cranium.—The cranium of osseous Fishes, 
when all its parts are completely developed, is 
made up of no fewer than twenty-six bones, six 
of which are azygos, viz. the basilar, the principal 
sphenoid, the anterior sphenoid, the vomer, the 
ethmoid, and the interparietal or superior occi- 
pital; and twenty are in pairs, namely, the 

JSrontal, the anterior frontal, the posterior pre 
tal, the parietal, the mastoid, the external occi- 
pital, the lateral occipital, the petrous, the great 
alar and the lesser alar bones; but as these 
have all been described and figured in a pre- 
ceding article, and their homologies with the 
cranial bones of the other vertebrate classes 
fully discussed, (vide Ossrous System, Comp. 
Anat., vol. iii. p. 826,) it would be superfluous 
to dwell upon them more at length in this place. 

Bones of the fuce.—The bones of the facial 
apparatus have likewise been pointed out and 
figured in the article above referred to. They 
consist, when the series is complete, of the fol- 
lowing pieces, which, seeing the extremely vari- 
ous forms of the face in this class of animals, 
present innumerable varieties as regards their 
developement and relative importance, notwith- 
standing that their general arrangement is tole- 
rably persistent throughout the class. 

The mazillary (fig. 436, 18, vol. iii. p. 826) 
and the intermazillary (fig. 436, 17) form the 
anterior boundaries of the face and circumscribe 
the anterior and lateral limits of the mouth: the 
latter, however, is in Fishes the most important 
bone of the two, and is most commonly armed 
with teeth, while the former is very generally 
destitute of dental organs, and being imbedded 
in the fleshy substance of the upper lip, has been 
called by some authors the labial bone or os 
mystacis. It is indeed upon the relative shape 
and size of the intermaxillary bone that the 
form of the upper jaw of Fishes principally de- 
pends, and in some cases, as for example in 
the Sword-fish (Xiphias), Lepidosteus, &c. these 
bones are enormously pamonaee anteriorly, so 
as to form an elongated beak or powerful ros- 
trum which constitutes a formidable offensive 
weapon. 

e face of Fishes, properly so called, is 
made up of several bony pieces very variable 
both in their size and number, which have been 
named the prenasal (fig. 436, 20,) the subor- 
bital (fig. 436, g, g, g,) and the supra-temporal 
bones ; all of these, however, with the exception 
perhaps of the prenasal, belong to the exoske- 
leton (vide vol. iii. p. 845.) In the hard-cheeked 
Fishes (“ joues cuirassées” of Cuvier) these 
osseous plates are enormously developed, and 
indeed form a kind of bony mask enclosing all 


960 


the muscles and other soft parts of this region 
of the head. 

The Trigle or Gurnards offer the best ex- 
amples of the “ hard-cheeked Acanthopterygii,” 
which owe their name to the following arrange- 
ment of the above mentioned osseous pieces. 
The first suborbitals are of enormous size, en- 
tirely covering the face, articulating in front with 
the bones of the snout, and posteriorly with the 
preoperculum and twosmaller suborbitals placed 


Fig. 492. 


= 


\ 
ti 
~ 


y Fy, 
7p 


Skeleton of Trigla lyra, showing the bones of the face and the pectoral 1. body, This remarkable resale 


Jin rays. 


at the posterior angle of the orbit. Its articu- 
lation with the preoperculum is accomplished 
by means of an immoveable suture, so that the 
suborbital bones and the preoperculum must 
move together. The upper part of the face, 
moreover, is formed by the immoveable con- 
solidation of the anterior frontals with the an- 
terior extremity of the prenasal bones, which 
expand into a disc, and in some instances of 
the vomer likewise, which is slightly visible 
beneath the skin between the ossa nasi. All 
these bony pieces, as well as those composing 
the upper portion of the cranium, are hard, 
granular, and often armed with spines and 


Ye: - - 
3 . <P, b 


Qa See 


PISCES, ' 


cutting edges, so that few Fishes have their heads 
so well defended against the attacks of their foes. 
The Pleuronectide, or Flat-fishes as they are 
commonly called, offer a most remarkable ex- 
a 


ception to the usual arrangement of the bones 
of the face, which exhibits a want of symmetry 
unparalleled in any other vertebrate animals. 
In this jul oe includes the Turbot, the 
Plaice, the Sole, and others similarly organized, 
the whole trunk of the body is so pe com- 
pressed laterally that such fishes, 
instead of swimming in the usual 
position, lie upon their left sides 
—a circumstance which, z 
to the singular fact that the right 
side is equally coloured both up- — 
on the dorsal and ventral regions, — 
while the opposite is rege ‘ 
white, has given rise to the vul- — 
. gar supposition that the white — 
© surface is the ventral and the co- 
loured the dorsal region of the fish _ 
—an error of which the anatomist — 
is immediately made aware by a 
simple inspection of the skeleton 
(fig.493). But in the construction 
of the head, by a strange apparent 
distortion of the elements com- 
posing the face and cranium, both 
eyes are allowed to be situated 
upon the right or upper surface ¢ 


is entirely due to the suppres- 
sion of those processes and bones on the left 
side of the head which normally constitute the 
orbital cavity, whilst on the right side are: 
permitted to attain a very complete develope- 
ment. The principal frontal bone figs. 436 
437, 1, vol. iii. p. 826-7), which in all Fishes igs 
azygos, occupies its usual situation, but whils 
on the left side it is flat and bounded bya near 
straight margin, on the right side of the mes: 
line it presents as usual the processes which forn 
the roof and posterior boundary of the orbit. Th 
outer margin of the orbital cavity is formed by 
one large bony piece, the representative of t 
sub-orbital chain of bones, (fig. 436, gg 


PISCES. 


-which does not exist at all upon the opposite 
side of the head, while anteriorly the anterior 
frontals (2) and the nasal bone (20) complete 
this part of the face. An orbital cavity is thus 
constructed upon the right or upper side of the 
head of the Pleuronectide, which suffices for the 
Jodgment of the two eyes, which thus take the only 
position in which both could be made useful.* 

Another equally remarkable arrangement is 
‘observable in the construction of the jaws of 
the Pleuronectide, which are in many genera 
very unequally developed on the two sides of 
the median line, only in this case the prepon- 
derance of developement is just the reverse of 
what exists in the orbital portion of the face, 
for here the bones of the right or upper side are 
small, while those of the left or inferior half 
are of considerably greater size and strength. 
Moreover, the former are but sparingly fur- 
nished with teeth, while the latter support the 
chief part.of the dental apparatus; so that by 
this structure the mouth becomes twisted toward 
the ground, and the teeth so disposed as to 
work most effectually in that direction. 

In the Syngnathide, Ostracions, and other 
Fishes, where the exoskeleton is inordinately 
developed, so as to-form a suit of bony armour 
in which the exterior of the body is completely 
eovered, the endoskeleton is proportionately 
weak and imperfectly formed, many of the 


Fig. 494. 


bones remaining in a rudimentary condition. 
This is well seen in the osteology of the Fly- 
ing Hippocamp, (Pegasus draco, fig. 494,) 
where the bones both of the head and trunk 
Seem to perform quite a secondary part as 
contrasted with the dense tegumentary frame- 
work covering the body. The whole face seems. 


* The above description of the structure of the 
ce in the Pleuronectide is derived from a disarti- 
culated skull of the Halibut, contained in the Mu- 
um of the Royal College of Surgeons in London. 
VOL. III. 


961 


to be composed of a kind of snout (a), derived 
from the external armour of the head, in which 
the orbits (6) are excavated, the intermaxillary 
bones (d) and the lower jaw (e) alone being 
recognisable. The gill covers (h) belong to the 
exoskeleton, while the hyoid apparatus (f) and 
branchial arches (g) are but very imperfectly 
formed. The osseous zone that sustains the 
pectoral fins consists of a single bone, which is 
so consolidated with the tegumentary skeleton 
as completely to separate the abdominal cavity 
from the branchial chambers; and in the piece 
m, which forms the basis of the fin itself, the 
usnal divisions are quite undiscernible. The 
vertebrae, both of the back and tail, (0, g,) are 
reduced to mere bony rings, while the pelvic 
circle, (p,) that nd gree the abdominal fins, (/,) 
is, like the rest of the skeleton, firmly con- 
nected with the external bony armour. 

In the construction of the anterior extremities 
a few peculiarities may be specified. 

Certain genera, more especially the Salmo- 
nide and the Cyprinide, have attached to the ra- 
dius and ulna upon their inner side a third bone, 
which by its anterior extremity is connected to 
the anterior margin of the os humeri, thus 
forming a kind of buttress to support the fin. 
In the Siluride there likewise exist three bones 
in the fore-arm which at an early period be- 
come consolidated to each other, probably on 
account of the great strength requisite 
in that race of Fishes to support the great 
spinous ray of the pectoral fin. In the 

urenide, where there are but two 
bones, these are suspended to the arch of 
the shoulder at the point of junction be- 
tween the scapula and the humeral bone. 
In species that have no pectoral fins the 
radius and ulna do not exist. 

There still remains to be noticed a 
long styliform bone generally composed 
of two pieces (fig. 437, 49, 50, p. 827, 
and fig.493, 10), of which the upper piece 
(49), more or less flattened in shape, is 
suspended from the os humeri (48), to 
the posterior and superior part of the inner 
surface of which it is adherent. This 
styliform bone runs backwards along the 
side of the body behind the pectoral fin, 
and is plunged to a greater or less extent 
amongst the flesh.* Some anatomists 
have regarded this process as the homo- 
logue of the clavicle, but from the posi- 
tion which it occupies, running backwards, 
it seems rather to represent the coracoid 
bone, which is in this case lost among the 
muscles on account of the want of a 
sternum to which it might be articulated. 
It sometimes happens that this bone unites with 
that of the opposite side, and occasionally 
is of such length and strength as to reach 
backwards as far as the commencement of the 
anal fin. A not less curious disposition of this 
bone is observed in Batrachus, where the — 
rior division extends upwards beyond the hu- 
merus to be connected with the spinous process 
of the first vertebra. 


* Cuv. Hist. des Poissons. 
3. 


962 


In the Cyprinide this bone is of very rudi- 
mentary size, and is totally wanting in the 
Murenide, the Anarrhicus, and the Siluride. 

- The carpal bones, which support all the rays 

of the pectoral fin except the first, are gene- 
rally placed, as above Seciited, in a single 
row consisting of four or five pieces, but occa- 
sionally each of these bones presents a con- 
striction near its middle, so as to have the 
4 a of being divided into two. 

t is the bones of the carpus, and not 
those of the arm or fore-arm, which are elon- 

ted to give the pediculated structure to the 
eet of the frog-fishes, making them look like 
arms. In Lophius these are only two in num- 
ber; in Polypterus there are three, and in 
Batrachus five. In these Fishes the radius 
and ulna are reduced to a very small size. 

Posterior extremity—The os innominatum, 
the femur, the bones of the leg and of the tarsus, 
are all represented in the osseous Fishes by a 
single bone (fig. 493, 12) of a triangular shape, 
and presenting several processes and prominent 
Jamelle. The apex of this triangle is directed 
forwards, and in the subrachial Fishes is attached 
in the angle formed by the junction of the two 
ossa humeri (11), at the point where the latter 
bones are united to each other by symphysis 
beneath the throat. In the true abdominal 
Fishes the pelvic apparatus is unattached to 
any part of the skeleton, being simply imbedded 
in the muscles beneath the belly. 

The posterior extremity of the piece last men- 
tioned gives attachment to the rays of the ventral 
fin (13), at the inner margin of which it not 
unfrequently gives off a long process extending 
backwards. The two pelvic pieces of the op- 
posite sides are most frequently united to each 
other by a suture; but it sometimes happens 
that they remain partially separated either to- 
wards their anterior part, as in Lophius, or pos- 
teriorly, as in Batrachus. 

Many Fishes, as Murena, Gymnotus, Xi- 
phias, &c. have no ventral fins, and in such 
cases the pelvic apparatus is altogether wanting. 

Fin rays of the extremities—These rays, 
with the exception of the most external one 
belonging to the ventral fin, are all soft and 
nice ea of numerous articulations, but to- 

s their base they are more compact than 
elsewhere, the articulations being there scarcely 
visible. The base of each ray is enlarged so as 
to permit of its being firmly attached to the 
radial bone and to those of the carpus and 
pelvis. 

The first ray of the Sees fin is rarely 
branched, and its articulations are sometimes 
so completely consolidated as to simulate a 

inous ray. This is the case, for instance, in 

ilurus among many other Fishes; but in such 
cases they are not really spinous rays in spite of 
their near resemblance, but derivations from the 
dermal skeleton, so that such Fishes are in all 
respects strictly malacopterygious. 

ertical fins.—The vertical fins of the osseous 

- Fishes, namely, the dorsal, the caudal, and the 
anal fins, cannot be com to any portions of 
the skeletons met with in other Vertebrata. 
They belong, in fact, to the exoskeleton (see 


PISCES. 


Osszous System), but are so intimately re- 
lated to the real bones both in structure and 
office, that they must be described in this 
lace as being essentially connected with the 
ny framework of the body. 
Every one of the vertical rays entering into 
the composition of these fins consists of two 
rtions, an interspinous bone, which is im- 
edded in the flesh of the fish between the 
great lateral muscles, and serves as a basis to 
which the ray is attached, and the ray = 
which is visible externally and generally assi 
in supporting the membrane of the fin. = 
Interspinous bones. —The interspinous bone 
form a series reaching along the back to an ex= 
tent proportioned to the length of the dorsal 
fin, and in a similar manner are appended be- 
neath the post-abdominal region of the ventr 
surface coextensively with the anal fin, which 
they resemble. Each mayne 93, 
3, 3, 6, 6) resembles in its shape the blade of a 
dagger plunged into the flesh, while its head cor- 
meapobedinig with the handle of the daggerremains 
on a level with the skin to give attachment t 
the base of the ray. This portion of the inte 
spinous bone has an apophysis conjoined wi 
it by suture, which in many instances is pr 
longed into a point that is connected to th 
articulation of the next ray of the fin. — 
interspinous bones are generally so dispose 
that their points penetrate between the spinoi 
processes of the vertebra, each being attach 
to these processes by a ligamentous membr 
ry there are some Fishes, as a Pleuronectid 
(fig. 493), and (as regards the compositio 
the anal fin) the Siduri, in which there are t 
interspinous bones to each spinous process, ai 
in other cases the relations between the two’ 
come quite lost, as, for example, where three 
even four spinous processes are interposed 
tween some of the vertebral spines, a fact w 
in itself is sufficient to disprove the hypothes 
Geoffroy, extensively promulgated in this ea 
try by the writings of Professor Grant, nar 
that the interspinous bones of Fishes are’ 
memberments of the spinous processes, - 
half of the tented bebouping displaced and forn 


4 


the interspinous bone as well as the ray whi 


ocppet 
n this point Cuvier remarks that in” 
genera, such as Murena, Ophicephalus, 
Gymnotus, the inferior interspinous bones 
separated from the vertebra by the cavity 
the abdomen, which is prolonged to a @ 
derable distance beyond the commencem« 
the anal fin; whilst in other cases, as if 
Pleuronectide, there are interspinous | 
even upon the cranium (fig.493,1). Thes 
cumstances, joined to the fact that in those 
tions of the back or of the tail which have nm 
attached to them there are generally no int 
nous processesalthough thereare vertebral 
make it impossible to regard the bot 
question as being derivations from the vt 
column. ri 
Rays of the vertical fins.—Each fin-t 
493, 2,7) is connected with its corre: 
interspinous bone by a ginglymoid artic 
The rays are of two kinds: spinous r 


a 
ae 

Sd 
* 


' 


PISCES. 


\ \S3% 
hi! 
i 


963 


\ 


i 


¥ 
1 


"Skeleton of Lampris guttata, showing the interspinous bones, easily recognisable from their dark tint. 


are met with in acanthopterygious Fishes, and 
branched or soft rays, such as are found in the 
Malacopterygii. They are all divided by a 
longitudinal raphé, or suture, into two lateral 
halves, so that each appears to be formed of 
two rays conjoined,—a circumstance -which 
forms an additional argument against these 
parts of the skeleton being dismemberments of 
the vertebre. 

The rays of the caudal fin are always soft 
and articulated ; but in many Fishes some of 
those at its root, both above and below, are 
gradually diminished in size until nothing is 
left of them but the hard part forming the base. 

Skeletons of Chondropterygii.—In the true 
cartilaginous Fishes, such as the Sharks and 
Rays, the bones are always destitute of those 
osseous fibres which give hardness to the skele- 
ton in the preceding races possessing a true 
bony skeleton. Their interior remains perma- 
nently soft and cartilaginous, while their ex- 
ternal surface is strengthened by becoming en- 
crusted with a layer of granular-looking calca- 
reous matter. 

As there is in the Chondropterygii no depo- 
sition of bony particles radiating from ossific 
centres, there can be no division of the cranium 
into distinct bones, nor of course any sutures: 
the whole cranium consists of a single cartilagi- 
nous piece, in which, however, it is easy to dis- 


Fig. 


tinguish the same regions, the same fossz, the 
same eminences, and the same holes as in the 
skull of one of the osseous Fishes; but, although 
it is not difficult with a little attention to point 
out the situation of the different bones, to 
define their limits is impossible. 

The bones of the face are likewise consoli- 
dated with the great cranial mass, and conse- 
quently are quite undistinguishable except from 
their position in relation to organs into the 
composition of which they enter. 

The structure of the skull therefore appears 
exceedingly simple when compared ith that 
of an osseous fish. The whole pterygo-temporal 
apparatus is represented by two pieces, one of 
which corresponding with the temporal, tym- 
panic, symplectic, and jugal bones of Cuvier, 
or the tympanic pedicle, as Professor Owen 
calls the long stem, which in the osseous 
Fishes is composed of those elements, is here 
represented by a single piece (fig. 496, c) in- 
terposed between the side of the cranium and 
the point of junction between the upper and 
lower jaws—an arrangement precisely similar 
to that which is observable in the Batrachian 
Reptiles. 

The other piece belonging to the pterygo- 
temporal apparatus (fig. 496, e) forms, in con- 
junction with its fellow of the opposite side, 
almost the whole of the upper jaw, covering 


496. 


SSS 


—- 
== ———= 


: Anterior portion of the skeleton of a female Shark ( Acanthias niger ). 
a, a, cartilaginous skull; 5, nasal cavity; d, lower jaw; e, upper jaw; f, g, connecting pedicle ; 
1, 2, 3, 4, 5, branchial apparatus ; 6, 4, zone supporting (, /,) pectoral fins. 


3 Q 2 


964 


the greater part of the roof of the mouth, and 
likewise supporting all the formidab!e teeth with 
which this jaw is armed. Posteriorly it gives 
attachment to the inferior maxilla by two large 
articulating surfaces, and above it is only con- 
nected to the skull by the muscles implanted 
into it. From its upper margin it gives offa 
process, shown in the figure, which remains 
permanently cartilaginous, and in the living 
state is imbedded among the muscles that form 
the inner wall of the orbit; the whole is thus 
left completely moveable so as to give great 
latitude to the motions of the jaws. 

The superior maxillary bone (fig. 497, d) and 
the intermaxillary bone (c) are of very small 
size, being merely imbedded in the substance 
of the upper lip and connected superiorly b 
ligament to the face and the piece last described. 
Inferiorly these bones are attached to a third (fig. 
497, e, ) which is fixed by ligaments to the outer 


Fig. 497. 


i y m 
igs 


Inferior view of the skull, branchial arches, and pec- 
toral apparatus, of Squalus centrina. ( After Carus. ) 

a, nasal cavity; 6, wlfactory organ; ¢, superior 
labial or intermaxillary cartilage ; d, intermaxillary 
bones ; e, inferior portion extending between the 
preceding and the lower jaw; e, e, e, e, central 
sternum-like pieces ; /f. % FS, f, branchial arches ; 
i, i, iy branchial appendages; 4, scapular zone ; 
1, m, n, pectoral fins. 


PISCES. 


surface of the lower jaw at about one-fourth part 

of its length from the symphysis, so that the three 
together form an osseous and ligamentous hand 

that circumscribes the angle of the mouth and = 
materially diminishes the rictus of thejaws. The 
inferior piece (e) is most probably one of the 
elements belonging to the lower jaw d 

from its usual connections with that bone. - 

The inferior maxilla (fig. 497, 7) consists 
two lateral halves nie a Bi each 
half consists of a single piece of consid 
breadth, presenting a deep sulcus superiorly 
for the lodgement of the teeth. 

The branchial apparatus is placed further 
back than in the osseous Fishes, being situated 
beneath the commencement of the spine—a 
circumstance which causes the bones of the 
shoulder to recede backwards also. 

The whole of the opercular apparatus is 
wanting in the cnseibechana Fishes with the — 
exception of the Sturgeons ( Sturionide ), which 
seem in many respects to occupy an interme- 
diate place between them me the osseous 
division. { 

The os hyoides in Squatina and the Sharks — 
generally is com of three pieces, one 
situated in the mesial line, and two lateral — 
branches. The mesian piece or body of the 
os hyoides corresponds to the bones of osseous 
Fishes; while the large rami, i of 
mounting up to be connected with the sty- 
loid bones, terminate immediately ind | 
the articulation of the lower jaw, with which 
they are intimately conn by means of 
strong ligaments. From its posterior margin 
branchiostegous rays are given off precisely as 
in the former group, but these have nothing to 
do with the formation of an opercular flap, the 
branchial apertures being here of a very diffe 
rent character. a 

The branchial arches in their general arran ge 
ment resemble those of the osseous Fishes, b 
there are nevertheless important differences t 
beremarked. In Sguatina there exists inferiorly 
a kind of sternal apparatus which occupies th 
mesial line. This consists posteriorly of a cet 
tral piece (497, e, e, e,) that very nearly resemb 
a broad spear-head, forming a kind of sternut 
the handle of the spear closely representing t 
xiphoid cartilage of the human sternum ; @ 
in front of this are three pieces on each sit 
something like the costal cartilages. Of th 
the anterior pair are united to each other 
mesial line, while the second and third 
fixed to the sides of the central piece first-m 
tioned. The arches supporting the. b 
are five in number on each side, (fig. 497 
each consisting of an inferior and superior 
tion connected with each other by move: 
articulations. The inferior portion consists 
single piece, the superior of two, united tog 
by ligaments. The anterior arch is conm 
by ligaments to the body of the os hyoides 
also to the central pieces. The four posté 
are attached by ligament to the succeet 
lateral processes of the sternal apparatus, ‘ 
thus a framework is formed that almost entit 
surrounds the neck. The superior extrem 
of these arches are fixed beneath the ante 


4 


PISCES. 


vertebree of the spine by a loose ligamento- 
cellular substance. 

In other Sharks and in the Rays (fig. 496, 
1, 2, 3, 4, and fig. 500, 3, 4, 5) the ossification 
of these pieces is very imperfect ; the branchiz, 
in the latter more . 
especially, being al- Fig. 498. 
most entirely sustain- " 
ed by membranous 
structures. 

The pharyngeal 
bones in the true 
Chondropterygii are 
totally wanting. 

In some Sharks, 
as, for example, in 
Galeus, there are ves- 
tiges of a true sternum 
situated below the 
branchial apparatus, 
from the anterior edge 
of which it is sus- 
pended by ligamen- 
tous attachments, 
while posteriorly it is 
connected with the 
centre of the zone, to 
which the pectoral 
fins are attached. To 
the sides of this ster- 
num are appended 
five or six pairs of 
sternal ribs, but the 
ossification of these 
bones, as well as of 
the sternum itself, is 
very incomplete. 

The vertebral co- 
lumn of the cartilagi- 
nous Fishes presents 
two or three very 
remarkable peculiari- 
ties. In the Ray-tribe 
(fig. 500, 6) all the 
vertebre of the ante- 
rior portion of the 
spine for a considera- 
ble distance are im- 
moveably fixed toge- 
ther by an incrusta- 
tion of earthy matter 
that forms a kind of 
tube or sheath in 
which they are en- 
cased, the number of 
vertebre thus anchy- 
losed to each other be- 
ing only indicated b 
the foramina ditough 
which the spinal 
herves make their es- 
cape. 
Another peculiari- 
ty is that both in the 
Sharks and Rays 
there are twice as 


Many superior verte- gheleton of Sturgeon ( Acci- 
bral lamin as there penser Sturio ). 


SSS 


SS 


SS 


we 


SSS 


SM 


SS 


ST 


2 


_——wS 


2 Sy en 


965 


are vertebre. This is owing to the develope- 
ment of spinal laminz to cover the interverte- 
bral spaces, in addition to those which constitute 
the spinal canal in other vertebrata. 

To the transverse processes of the vertebre 
covering the abdomen rudiments of dorsal ribs 
are appended. In the Raide, however, these 
are very small; but in Sharks, (fig. 496, m,) 
and more especially in the Sturgeons (fig. 499, 
6, c,) they attain considerable dimensions. 

Along the whole length of the post-abdo- 
minal region of the vertebral column there 
are developed hemapophysial arches and infe- 
rior spinous processes, but the latter are always 
exceedingly short and imperfectly formed. This 
is well seen in the Sturgeon (fig. 498), in 
which fish, although the central portion of the 
vertebral column remains permanently cartila- 
ginous, the hemapophysial arches and spines 
are distinctly bony. 

There are no interspinous bones, the dorsal 
and anal fins being only connected to the 
spinous processes of the vertebre by broad 
ligamentous expansions. The structure of the 
caudal fin is likewise very different from what 
is met with in the osseous Fishes. In the Sharks 
and Sturgeons, (fig. 498,) which have the tail 
deeply furcate, the vertebral column is conti- 
nued into the upper portion along its entire 
length, the caudal fin being entirely supported 
by long rays connected both superiorly and 
inferiorly to the extremities of the spinous 
processes of the individual vertebre. 

The framework to which the anterior extre- 
mities or pectoral fins are attached is a strong 
osseous zone which encircles the body imme- 
diately behind the branchial apparatus. This 
zone consists superiorly of the scapular and 
supra-scapular pieces, and inferiorly of a broad 
osseous belt (fig. 497, k,) which encloses the 
fore part of the abdominal cavity, representing 
the curacoid and clavicular apparatus of the 
Reptilia. _ In the Raide the supra-scapular 
pieces are inseparably connected with the 
spinous processes of the dorsal vertebra, but 
in the different races of Sharks they are loose 
and unattached. At the junction between the 
dorsal and abdominal portions of the above 
zone are attached by strong articulations the 
pieces which support the rays of the pectoral 
fin. These pieces represent the whole brachial 
and carpal apparatus of the higher Vertebrata. 
In the Rays these are of enormous dimen- 
sions, (fig. 500, 8, 9, 10, 11) extending pos- 
teriorly so as almost entirely to surround the 
cavity of the abdomen, whilst anteriorly they 
are prolonged in a similar manner in front 
of the cranium. To the external aspect of this 
vast carpus are attached upwards of a hundred 
fingers supporting the enormous pectoral fins, 
which here form by far the greater portion of 
the body, giving it that square shape for which 
these Fishes are so reraarkable. Towards the 
circumference of the body each of the fin-rays 
bifurcates (12), so that the total number of 
phalanges entering into the composition of this 
prodigious hand is one of the most remarkable 
facts in comparative osteology. 


a, cartilaginous axis of spine ; 6, c, transverse apophyses and ribs; f, 
cranium ; i, A, ocular and nasal cranial cavities; m,n, pedicle by which the mow 
26, bone supporting the lower jaw; 18, 22, palatine cartilages; 0, p, s, cartilages representing 


cranium ; 
the superior maxilla, 


Fig. 500. 


Nei i il 
10 s Ut Me, My, 


\Nisp Y 
es y 


were only a moiety of the posterior division 
e 


is\ 
\ 
\p 
Cartilaginous skull and anterior portion of vertebral column of the Sturgeon ( Accipenser sturio ). 


299 g” , cartilaginous — 
AG AE Mire 


of the fin of the preceding genus. . 
The posterior extremities or ventral fins are 
attached to a zone similar to that which supports 
the pectorals (fig. 500,14). The pelvic zone is, 
however, very incomplete, the superior or iliac 
portion being quite deficient, so that it has n 
connection with the spine, but is simply im: 
bedded among the muscles at the posterior pari 
of the abdomen. ' 
Externally the pelvis supports the first 
of dicrvontat = (fig. 500, 15) 
which is very large, and li ¥ 
long stem (16) composed of r 
rous articulations, to the commen 
ment of which the succeeding 


rays are appended. Inferiorly | 


former is prolonged in the ma 


Rays into a very curious 


Skeleton of Ray. 


1, snout; 2,3, 4, 5, branchial arches; 6, conso- 
lidated anterior vertebre ; 7, humeral apparatus ; 
8, 9, 10, 11, carpus; 12, fin rays; 13, posterior 
detached vertebrz ; 14, pelvic apparatus ; 15, clasp- 
er; 16, tarsus; 17, fin rays of posterior extremities. 


The pectoral fins of the Sharks (fig.496, 497) 
and Sturgeons (fig. 498) are formed after the 
same plan as that of the Skate, only upon a 
considerably smaller scale, representing as it 


shaped a tus called the “clas 
ota ‘ic tai of which we shi 
have occasion to speak further on 
Skeleton of Dermapterygii. 
the cyclostomatous Fishes, such 
the Lamprey, the skeleton is of still more sim 
structure than in the plagiostomatous gent 
The cranium exhibits through life a soft ¢ 
laginous texture; nevertheless it is not dif 
to identify the different pieces of which it ¢ 
sists, and to point out their analogies with 1 
of the osseous Fishes. 
The spine consists of a soft cartilagi 
stem, which along the entire lengt 
the body. It is enclosed in a strong men 
nous investment, from which prolongation: 
given off that perform the office of spinal 
physes; but the only indications of dis 
vertebre exist in the presence of slight 
almost imperceptible rings of osseous subst 
distinguishable upon the surface of the ea 
ginous stem above mentioned. 
The Cyclostomata have neither pectot 
ventral fins, so that in this respect they 
most imperfect of all Fishes: even the ve 
fins situated above and beneath the tai 
only supported by a few soft and scarcely 
sible fibres representing the fin-rays. 
The most remarkable part of the skeleton 
the Lampreys (Petromyzon) is the cartil 


PISCES. | 


Skull of Sea Lamprey ( Petromyzon marinus). After J. Muller. 


@, cartilaginous spinal axis; b, c, rudimentary cartilaginous neural arches ; 
d, d, part of cartilaginous respiratory framework; g, auditory capsule; h, cra- 
nium; #, @’, 7, processes therefrom giving attachment to the muscles of the 
tongue; &, nasal capsule ; /, cartilage covering hinder part of mouth ; n, 0, p,q, 
anterior cartilages entering into composition of mouth ; 7, s, os hyoides. 


nous framework situated on the sides of the 
neck, enclosing the branchial apparatus, and 
allowing respiration to be accomplished by a 
peculiar mechanism which will be described in 
its proper place. This singular structure con- 
sists of seven pairs of cartilaginous arches de- 
rived from a kind of sternum situated in the 
mesial line beneath the throat. These arches, 
which have nothing in common with the bran- 
chial arches of Fishes, mount upwards inter- 
ruptedly towards the spine, giving off anterior 
and posterior processes to form a kind of frame 
to the branchial orifices. Anteriorly this re- 
markable apparatus is attached to the cranium, 
while posteriorly it terminates in a thin cartila- 
ginous capsule, which encloses the heart; it 
will, however, be better to describe it further on. 

In Ammocetes the skeleton is even more im- 
perfect than in the Lamprey, all its parts remain- 
ing permanently in a membranous condition, so 
that they would seem to resemble worms more 
than vertebrated animals, and in fact were ab- 
solutely classed as worms even by the great 
Linneus. 

Skeleton of Branchiostoma.—In this  re- 
markable Fish the entire spine is made up of 
a succession of very delicate membranous rings 
without any apophyses whatever; neither in 
young specimens is the slightest trace of a 
cranial dilatation of the vertebral column appa- 
rent, probably owing to its being at this period 
quite gelatinous in its texture, and conse- 
quently translucent; and even in adults such 
is its softness that it is impossible to distin- 
guish it satisfactorily ; but along the back from 
sixty to seventy vertebre are easily counted, 
the divisions between them being indicated by 
slight bulgings and lines passing obliquely 
from above downwards on the sides of the 
column. In this way a separation between 
the rachidian rings is rather indicated than 
proved to exists for, although there is, so to 
express it, a tendency to divide at the points 
indicated, the division is rather artificial than 
hatural. 

According to Mr. Goodsir, the chorda dor- 
Salis is formed externally of a fibrous sheath, 


967 


and internally of an 
immense number of la- 
mine, each of the size 
and shape of a section 
of the column at the 
place where it is situ- 
ated. When any por- 
tion of the column is 
removed, these plates 
may be pushed out of 
~ their sheath like a pile 
of coins. They have 
no great adhesion to 
one another, are of the 
consistence of parch- 
ment, and appear like 
flattened bladders, as if 
formed of two fibrous 
membranes pressed to- 
gether. 

Two ligaments may 
be detected, one run- 
ning along the upper, the other along the lower 
aspect of the spinal column; and from its 
sides aponeurotic lamine pass off to form 
septa of attachment between the layers of mus- 
cles. Along the mesial plane above the co- 
lumn a similar aponeurosis separates the supe- 
rior lateral muscular masses, and by splitting 
inferiorly, so as to join the sides of the rachi- 
dian chord, forms the canal for the spinal 
medulla. Foramina exist all along this canal 
for the passage of the nerves. A similar apo- 
neurotic septum is situated along the inferior 
part of the column from the anal opening to 
the extremity of the tail. Imbedded in these 
two aponeuroses are cartilaginous rudiments 
representing the superior and inferior vertebral 
spines, but these are of extreme softness and 
delicacy; and the traces which exist of the 
transverse processes and ribs are in the same 
soft condition, so that they are with difficulty 
distinguishable. In Branchiostoma, therefore, 
the locomotive skeleton may be said to consist 
of the vertebral column only, without either 
cranium or appended limbs. 

There is, however, an exceedingly elaborate 
framework of soft cartilaginous arches which 
surrounds the branchial chamber, and forms 
a kind of branchial thorax, the nature of which 
will be examined further on. 

Arthrodial system.—The articulations of the 
bones of Fishes present the same varieties as 
those of other animals; only the arthrodial 
and ginglymoid are more rarely met with 
because their limbs have not to execute such 
complicated movements. 

It is by means of a ginglymus that the 
lower jaw and operculum are attached to the 
pterygo-palatine apparatus, and the latter to the 
cranium. The same articulation occurs be- 
tween the rays of the dorsal and anal fins with 
the interspinous bones, and between the first 
ray of the pectoral fin with the bone analogous 
to the radius. 

There are, moreover, in Fishes two kinds of 
articulations having determinate movements 
which are not met with in the other classes: 
one is formed by two rings joined one to the » 


968 


other, as those of a chain, and another, which 
at the will of the fish becomes very moveable 
or very fixed. We find examples of both these 
in the family Silurus. 

The articulations with determinate move- 
ments offer ligaments, cartilaginous surfaces, 
and a synovial fluid, as in higher animals. 

The articulations between the bodies of the 
vertebre are effected by means of a fibro- 
cartilaginous substance which traverses the 
bodies, and which sometimes, as in the Stur- 
geon and the Lamprey, takes the form of a 
long cord. 

The articulations of the opercular bones be- 
tween themselves, the pieces composing the 
branchial apparatus, the bones of the shoulder, 
of the arm, of the carpus and pelvis, and of 
the last to the shoulder, are effected by means 
of interposed fibro-cartilaginous substance. 

Muscular system.—The general character of 
the myology of Fishes has been treated of in a 


Myology of the Perch. After Cuvier. 


trunk.—These are situated in the interspace 
between the lateral muscles, both along the 
middle of the back and also of the ventral 
aspect of the body. 

Proper muscles of the fins—In the caudal 
fin these are of three kinds, some being super- 
ficial, others deep-seated, and a third passing 
from one ray to another. 

In the dorsal and anal fins the arrangement 
of the proper muscles is very simple, because 
they are all disposed uniformly, each fin-ray 
having six, viz. four deep-seated and two su- 
perficial. 

The superficial muscles are inserted into the 
fin-ray at its base, one on the right and the 
other on the left side, and serve to move it in 
corresponding directions. The deep-seated set 
(figs 505, 3 and 4) arise from the interspinous 
bones, and are inserted into the anterior and 
posterior aspects of the base of the ray, serving 
to elevate or depress it vertically. 


PISCES. 


preceding article, (Muscutar System, Comp. 
Anat.) It will therefore only remain for us 
in this place to give such an account of 
their arrangement as the limits of this article 

rmit, dividing them into groups so as to faci- 
itate reference to the Watton. tome res, 
representing the dissected muscles of the Perch, 
as described by Cuvier. 

The great lateral muscles on each side of the 
trunk of the body form a mass that extends 
from the back of the head and posterior surface 
of the pectoral zone all the way to the sides of 
the base of the caudal fin. ese two great 
muscles are divided transversely by aponeurotic 


lamine into as many layers of fi as there 
are vertebra, giving the flaked ap to 
the flesh of Fishes, (fig. 502, /, g, h,) and 
are connected to all the vertebra and vertical 


processes of the spine as well as to the inter 
spinous bones. 


Superior and inferior slender muscles of the 


The movements of the shoulder are effected 
by the great lateral muscles inserted into the 
or by strips derived therefrom. ree 

The muscles of the pectoral fins (figs. 
503, 505, 14, 15, and 16) are inserted into the 
fin-rays, which they serve to elevate or depress 
at Seana 

he muscles of the ventral fins, (fig. 
17 and 18) arise from the pelvic bone, and 
to expand or advance the fin-rays of the abdo 
minal members. > 

The muscles of the jaws are represented 
large mass, (fig. 502, 20, 20,) derived 
palato-temporal arch and the anterior edge @ 
the preoperculum, which is inserted into t 
lower jaw, and serves to closesthe mouth 
arrangement very different from that of the 
temporal and masseter muscles of the higher 
vertebrata. a 

Muscles of the palato-tympanic arch ec 
of a depressor, (fig. 504, 32,) derived from 


‘Té 


PISCES. 
Fig. 503. 


969 


Myology of the Perch. After Cuvier. 


sphenoidal and alar bones; 
and an elevator, (fig. 502, 
24,) which comes from be- 
neath the orbit, and antago- 
nizes the preceding by dila- 
ting the cavity in which the 
branchie are lodged; these 
two are the principal muscles 
employed in respiration. 

uscles of the operculum. 
—The movements of the oper- 
culumare very similar to those 
of the palato-tympanic arch, 
and its muscles likewise con- 
sist simply of an elevator and 
a depressor (figs. 504 & 505, 
25, 26.) 

Muscles of the os hyoides. 
—The principal of these 
(figs. 503 & 505, 27) seems 
to correspond to the genio-hy- 
oideus, and has a similar of- 
fice ; its antagonist is a pro- 
longation of the great lateral 
muscle of the body (fig. 503, 
1, 1.) 

Muscles of the branchiostegous membrane.— 
These consist of a layer of fibres (figs. 503, 
504, 28) running transversely across the inner 
surface of the branchiostegous rays; this is 
in some Fishes assisted by accessory muscular 

_fibres derived from the os hyoides. 

Muscles of the branchial and pharyngeal 
apparatus.—These must be divided into several 
groups, some of which connect this apparatus 
with the skull, others to the spine, others to the 
humeral bone, and others to the os hyoides ; 
while some connect one part of the apparatus 
to another. Their general distribution is shewn 
in fig. 505, 32,35, 37, &c., but to describe them 
more minutely would carry us beyond our 
limits. 

In the Ostracions, or box-fishes, which have 
their entire body, with the exception of their 
jaws and fins, enclosed in a dense case of ar- 
mour, the arrangement of the lateral muscles of 
the trunk is considerably modified; they oc- 
cupy, indeed, the same situation, but are only 
attached at the head and tail. In this case 


Fig. 504. 


Myology of the Perch. After Cuvier, 


insertions into the vertebral column would have 
been useless, seeing that the tail is the only 
moveable part. The texture of these lateral 
muscles is also much simpler, their fibres 
being almost all longitudinal. The ribs are 
entirely wanting, these parts being replaced by 
a silvery aponeurosis, which forms the walls of 


, the abdomen and lines the interior of the shell. 


In the Plagiostome cartilaginous generathere 
are considerable differences in the arrangement 
of the muscular system which will demand a 
brief notice. The Raide, or Skates, for exam- 
ple, so remarkable for the construction of their 
skeleton, are not less so in respect to the dispo- 
sition of the muscles that move its different 
parts. In these fishes the muscles of the trunk 
resemble very strikingly those which are met 
with in the tails of quadrupeds. They are four 
in number, arranged upon two planes, so that 
there are two superior lateral and two inferior 
lateral muscles. 

The superior laterals arise from the middle 
portion of the vertebral column above the abdo- 


970 


Myology of the Perch. After Cuvier. 


anterior cartilages of the vertebral column. [t 
runs obliquely outwards, and 0. 

wards, so as to describe a curvature, the con- 
vexity of which is external. Its insertion is 


men by strong fleshy origins covered with dense 
aponeurosis. Above the pelvic arch they di- 
vide into numerous tendinous slips which run 
backwards in separate sheaths, each successively 
approximating the middle line of the body, 
where they are inserted on the dorsal aspect of 
each vertebra as far as the extremity of the tail. 

The inferior lateral muscles, like the prece- 
ding, take their origin in the lumbar region, 
and present nearly the same arrangement, only 
their tendons are much more slender than those 
of the superior set. At their termination each 
tendon bifurcates, allowing that appropriated to 
the succeeding vertebra to pass through it so as 
mutually to form sheaths to each other, so that 
they are all, except the last, both perforati and 
perforantes. 

Osseous Fishes have no special muscles ap- 
pointed for the movements of the head, but in 
the Rays there are three destined to this office, 
one serving to move the head upon the trunk, 
the other two raising and depressing the extre- 
mity of their elongated snout. 

e former is situated upon the upper as- 
pect of the body above the branchial cavity. It 
arises from the vertebral column and from the 
anterior portion of the pectoral zone. Its inser- 
tion is into the posterior region of the head, 
which it raises towards the back. 

Of the two muscles of the snout, the superior 
arises also from the scapular cincture by a short 
fleshy belly, from which a thin cylindrical ten- 
don is given off. This runs in a mucous sheath, 
above the branchie to the base of the snout 
where it is inserted, serving of course to raise it 
upwards. ' 

The other is situated beneath the body within 
the branchial cavity, where it arises from the 


y 


almost entirely fleshy into the base of the 
trum, which it bends or curves towards 
belly. 1% 
The muscles of the huge pectoral fins form 
two thick fleshy layers, covering these lit 
both above and below, and dividing into a 
many fasciculi as there are fin rays, into 
they are inserted. A similar arrangement exists 
likewise in the ventral fins, the represent ives 
of hinder extremities. all 
The muscles of the jaws in the cartilaginou 
Fishes are more numerous than in those po 
sessed of an osseous skeleton. The lower 
of the Skate is depressed by a large oblor 
muscular mass, composed of straight paral: 
fibres, which, taking its origin from the anteri 
margin of the transverse cartilaginous belt 
sustains the pectoral fins, runs forward to 
serted near the centre of the inferior maxil 
which it thus powerfully depresses, 
side, cor 


_ 
» 


Two small muscles, one on each 
tribute to the same effect. These are a 
in front near the commissure of the lips, at 
running inwards, almost cross each oth 
neath the preceding, which is azygos; thi 
they are attached partly to the skin, and partl 
to the transverse cartilage. . 

Those muscles which raise the lower j 
likewise upon the upper. One attached to 
lateral part mounts over the open jaw, as ove! 
a pulley, and runs to be imp ted above 
upper jaw, which is here moveable, into 
base of the cranium. iil 


A second is broad and short. Its fibres 


PISCES. 


straight, parallel, and fleshy, passing from the 
superior margin of the upper jaw to the infe- 
rior margin of the lower. 

The third presents a very singular arrange- 
ment, having its fibres interlaced in a very re- 
markable manner. These, however, may be 
divided into three principal masses, two of 
which are anterior aiid one posterior.* 

One of these masses is situated in front of 
and above the upper jaw near the commissure, 
It is attached to its superior margin, and runs 
obliquely to join the external edge of the second 
mass. This latter occupies nearly the same 

ition relative to the lower jaw; it passes be- 

ind the other and is conjoined with it exter- 
nally. The third or posterior mass is derived 
from the end of the upper jaw, and joins the 
hinder margin of the second. All these fibres 
so singularly interlaced co-operate in holding 
the mouth closely shut when the Skate has 
seized its prey. 

_ Lastly, there are two very long muscles de- 
rived from the spine, which pass between the 
palate and the cranium to be inserted into the 
upper jaw. These bring the mass of the mouth 
forward again after it has been retracted by the 
broad oblong azygos muscle above described, 
which passes between the pectoral zone and the 
inferior maxilla. 


971 


Head of Lamprey, after Carus, shewing muscles. 


a, b, c, cartilages of the mouth; d,e, f, external 
muscles inserted into ditto; g, h, muscles de- 
rived from the hyoid apparatus. 


In Sharks the lateral muscles of the body 
and fins resemble those of the osseous Fishes. 
Their jaws, however, constructed after the same 
principle as in the Skate, are equally moveable, 
and their muscles almost similar; only here, as 
their mouth is situated much nearer the anterior 
extremity of the skull, the two great muscles 
coming from the spine to the upper jaw are 
wanting. 


Fig. 506. 


- ' Myology of Shark ( Squalus glaucus). After Carus. 
' @, a, a, cranium; }, rostrum ; ¢, olfactory organ; d, eye-ball; e, muscles of eye; St upper-lip ; h, j, 
teeth ; #, lower surface of skull; J, m, muscular masses which close the mouth, resembling those of 
the Skate described above ; g, broad muscle passing from upper to lower jaw; p, depressors of lower 
jaw, asin the Skate; q, 9, g, entrances to the gill-chambers. 


In the Lampreys ( Petromyzonide ) the oral 
sucker is moved by slips derived from the ante- 
rior temination of the great lateral muscle (fig. 
507,f)) as well as by a set of very strong fasciculi 
derived from the hyoid apparatus, which, by 
retracting the interior of the disc, cause the 
adhesion of the sucker, and move the different 
parts of the dental apparatus described in a 
preceding page, (g, 4, m.) The action of 
these will, however, be better understood by 
inspecting the figures than by any detailed 
description. 

Tegumentary system.—The essential character 
of the skin, says Agassiz,t is that it completely 
envelopes an animal, and thus forms a kind of 
external skeleton which protects it over its whole 


* Cuvier, Legons d’Anatomie Comparée. 
+ Agassiz, Recherches sur les Poissons Fossiles, 
4to. 1834, 


surface, as the osseous skeleton protects and 
supports the internal viscera. In the invertebrate 
races of animals there are no other solid parts 
except those which are produced by or con- 
nected with the tegumentary system, but which 
nevertheless can by no means be compared 
with the osseous system of the Vertebrata, 
which is quite peculiar to the latter, and has 
no analogy whatever with the solid framework 
of the inferior classes. 

The skin, moreover, (observes the same 
illustrious author,) is not exclusively limited 
to the external surface of the body, but pene- 
trates into and invests the internal cavities, 
on the inner surfaces of which it likewise pro- 
duces solid structures of various kinds to 
which different offices are assigned, as, for 
example, the teeth and all the corneous pieces 
which in many classes are met with upon the 
lining membrane of the digestive tube. It 


972 


therefore becomes necessary to distinguish two 
modifications of the dermal skeleton, one con- 
Stituting the investments of the external sur- 
face of the body, the other developed from 
the internal surface. These two kinds of 
exo-skeleton exist simultaneously in all verte- 
brate animals in addition to the endo-skeleton 
or proper osseous system, which encloses the 
visceral cavities or affords a framework around 
which the soft parts are situated. In the ver- 
tebral division of the animal kingdom not only 
do these two modifications of the dermo- 
skeleton present numerous connexions with 
each other, but they are likewise intimately 
connected with the osseous system, and in 
many parts of the body insensible transitions 
may be perceived between one and the other, 
as in Fishes, more icularly between the 
opercular bones and the scales, or between the 
latter and the bones of the occiput and hu- 
merus, or between the pharyngeal bones and 
the teeth, (See Osszous System, Comp. Anat. 
vol. iii., page 846.) 

There exists, however, a constant antago- 
nism in the developement of the three kinds 
of skeleton above indicated, some of the dif- 
ferent parts of which attain to a more perfect 
growth in proportion as those of the other are less 
complete in the different regions of the body. 

Before proceeding further with this subject, 
it will be necessary to examine with a little 
attention the structure of the skin itself prepa- 
ratory to describing the various dermal appen- 
dages produced therefrom. 

The skin of Fishes is always much more 
tensely stretched over the surface of the body 
than in other animals, and, being closely united 
to the subjacent muscles by dense cellular 
tissue, is never endowed with that mobility 
which is observable among many of the higher 
Vertebrata. As in other classes, the skin is 
composed of an epidermis which forms the 
external envelope of the body, of a rete mu- 
cosum, consisting of the internal stratum of 
the corneous epidermis, which as yet remains 
soft and covers the surface of the corium by 
which it is secreted ; and lastly of the corium 
itself, or the internal living skin furnished with 
nerves and vessels by which the outer layers 
of the integument are secreted as well as the 
different colours that ornament the exterior of 
the tish. 

The varied colours of the fish result in fact 
from the deposition of corresponding pigments 
between the epidermis and the true skin, and 
in the class before us these colouring matters 
are particularly abundant. In the first place 
the inner surface of the scales is imbued with a 
pigment of metallic splendour, and generally 
of a silvery or golden hue and of brilliant lus- 
tre, besides which, more especially towards the 
back and over the re aspect of the body, are 
points or patches of black or diversely coloured 
pigments, which according to their abundance 
and character give the peculiar markings of the 
fish. 

The material which gives this metallic lustre 
to the scales of Fishes, known in commerce 
under the name of “ argentine,” was minutely 


PISCES. 


investigated by Reaumur,* who found that, 
when examined under high magnifying powers, 
it is — of crystalline lamine, divided 
transversely so as to form rectangular figures 
about four times longer than they are broad. 
These crystals he believed to be contained in 
vessels, or in delicate tubes of animal matter, 
mistaking for vessels the little bundles in which 
they are disposed.¢ These different pigments 
have been lately discovered to consistofextremely 
minute crystals of various earthy and metallic 
substances ; they are met with even in the interi- 
or of the body, as for example, upon the external 
surfaces of the peritoneum, of the brain and me- 
dulla oblongata, and in the interior of the e 
ball. Ehrenberg observed them in the Pike; 
they are met with in all Fishes, and present nu- 
merous varieties of form and composition in dif- 
ferent species. One very remarkable phenome- 
_ connected with the colour of a and 
which a ntly depends upon the abundance 
of these piconets sd the sapidity with which 
they are secreted and absorbed, is the ¢ 
of colour which many species undergo at diffe- 
rent periods of the year, as, for example, at 
spawning time; or during their growth, or even 
when excited to violent exertion, or lastly after 
their death, when they are exposed to different 
atmospherical influences. During the spawn- 
ing season, observes Agassiz, the tints of all 
species hitherto observed are more vivid and 
distinctly marked than at other periods; but — 
even whilst drawing living specimens, he has” 
observed that, when suddenly irritated or whilst — 
making violent movements to escape from the 
hand when seized, these colours suddenly be- 
come much deeper and more brilliant, after — 
which they become completely pale, and only 
return by slow degrees; a phenomenon which 
the writer above quoted supposes to depend 
upon a sudden exuberant secretion and subse- 
quent absorption of the coloured pigments. 
The surface of the body of living Fishes is 
moreover constantly lubricated by a great quan= — 
tity of mucus, which in some is possessed of 
little tenacity, and forms a very thin layer 
whilst in other species, especially in such 
have but slightly der Gpad scales, it is of me 
consistency and furnishes a covering of consi- 
derable thickness, as for instance in the ch 
and Eel. This fluid is secreted by a 
us canal, which extends along the whole 
ength of the body and ramifies extensively in 
the bones of the head. The fluid which it se~ 
cretes, which is very viscid and difficult to mn 
with water, exudes at the surface through a 
number of orifices which are visible upon th 
cranium, upon the bones of the face, along the 
jaws, upon the preoperculum, and hkewise 
through the series of tubes which perforate the 
scales along the lateral line. From thes 
sources it is distributed all over the surface of 


ao de l’Academie Francoise, 1716 
+ This substance, argentine, under the name 
** essence de l’orient,” was extensively employe 
in the time of Reaumur for the manufacture of art 
ficial pearls, and was on that account an 
ingly costly article, 


+ ; - 
do 
ye 


PISCES. 


the fish, as may easily be proved by drying it 
with a napkin, after which operation it soon be- 
comes again covered with mucus, which issues 
from the openings of these pores. 

In the Tunny ( Scomber thynnus ) there runs 
beneath the skin, following the entire length of 
the lateral line, an organ of a redder colour 
than the rest of the flesh, from which the little 
tubes forming the lateral line proceed, each 
tube receiving a nervous filament from the 

great lateral nerve. On raising the integument 

over this glandular organ a large vessel is seen, 
which, besides giving off arteries to the neigh- 
bouring muscles, furnishes an infinite number of 
branches to the glandular mass, beneath which, 
at nearly an inch from the surface, runs the lateral 
‘branch of the eighth pair of nerves, which in 
most other Fishes is situated immediately be- 
neath the skin. It is in the Raide or Skates, 
however, that this system of vessels is most 
largely developed. In these broad-bodied fishes 
there is found upon the ventral aspect of the 
body a large canal which surrounds the pro- 
minent muzzle, forming very regular angles and 
windings, distributes its secretion hy three or 
four branches on each side, and then winds 
upwards to terminate by different openings. 
There is, moreover, on each side at the external 
angle of the branchie a kind of sac which is 
round and of a whitish colour, which receives a 
large branch from the fifth pair of nerves, from 
which proceed a number of long simple vessels 
which run in radiating fasciculi in four or five 
different directions, and open at remote points 
on the surface of the body. 

In Sharks the entire substance of the snout 
is made up of a dense cellulosity filled with a 
mucilaginous fluid, in which are imbedded fas- 
ciculi of tubes that open upon the surface of the 
skin by wide orifices. Besides these there are 
large vessels of similar character, one of which 
runs along the whole length of the animal on 
each side. Innumerable muciparous follicles 
contribute likewise to lubricate the skin, more 
especially in the vicinity of the snout. 

By far the greater number of genera in the 
class before us are covered with imbricated 
seales, which overlap each other like the tiles 
of a house; the external and visible portion of 
these scales is covered with a thin layer of der- 
mis, which soon dries on exposure to the air; 
their internal or concealed part is lodged in a 
cavity which is a kind of sacculus hollowed out 
in the dermis itself, or formed by one of its 
replications—an arrangement which at first 
sight appears very different from what exists in 
Lizards and Serpents, in which what is called 
a scale is only a production of the cutis covered 
by the epidermis, that on the outer surface 
assumes a greater consistency and thickness ; 
but in the genus Scienus we have an inter- 
mediate arrangement between the imbricated 
scales of Fishes and what is met with in the 
scaly Reptilia. In the genus above mentioned 
the folds of the dermis are o¢cupied by a cal- 
careous plate, constituting a true scale easily 
separable from the cutis which envelopes it. 
We have only therefore to suppose the texture 
of this layer of cutis to be thinner and more 


973 


delicate, and we arrive at once at the scale of 
a fish, which seems in a fossa excavated in the 
cutis. In Fishes the scales thus implanted in 
the true skin were supposed by Cuvier to have 
no vascular connection with it, but to originate 
like a shell in the mantle of a mollusk by the 
gradual deposition of ‘consecutive layers depo- 
sited from the dermis; and all their varieties of 
surface, their different sculpture, the ridges or 
spines with which they are sometimes armed, 
and which frequently render them very beautiful 
objects for the microscope, were generally 
thought to have a similar origin. 

Dr. Mandl* appears to have been the first 
who, by a microscopic examination of the inti- 
mate structure of the tissues which enter into 
the composition of the scales of Fishes, arrived 
at just conclusions relative to the mode of their 
formation, and proved that, so far from being 
mere exudations of corneous matter, they are 
produced, like the teeth and osseous tissue, by 
a true internal growth and nutrition. 

The following is an abstract of the result of 
Dr.Mand1’s researches upon this interesting sub- 
ject, in which he satisfactorily proves that the 
scales of Fishes consist of two layers, of which 
the inferior exhibits a structure analogous to 
that of fibro-cartilage, whilst the superior re- 
sembles corpuscular cartilage, and is evidently 
formed by the developement of primitive cells. 

Taking a well-developed scale, as that of a 
Carp, for an example, it is easy to perceive that 
its surface is marked with longitudinal lines 
arising from a common centre, and running to- 
wards the periphery of the scale, the number 
of which it is generally very easy to determine. 
The place towards which these lines converge 
is ‘a space of variable dimensions, called by 
Dr. Mandl the focus. Between the longitudinal 
lines are seen, running parallel to the circum- 
ference of the scale, a very considerable number 
of concentric lines, which are crossed by the 
longitudinal ones at right angles; these are 
named “ cellular lines,” because they owe their 
origin to the developement of cells. Besides 
the parts above mentioned, many kinds of 
scales exhibit upon their surface, and upon 
one of their edges, spines of different forms, 
called by Dr. Mandl the deeth of the scale, a 
name which he founds upon the mode of de- 
velopement of these appendages. Around the 
longitudinal and transverse lines, more espe- 
cially near the point where the former converge 
towards the “ focus,’ are numerous yellowish 
corpuscles of an elliptical shape, named the cor- 
puscles of the scale. 

Lastly, if the upper layer of the scale be 
raised or torn, an inferior stratum is displayed, 
of a fibrous character. These different struc- 
tures he then proceeds to describe seriatim. 

1. The longitudinal lines, which, arising 
from the focus of the scale, run towards its 
periphery, play an important part in the ana- 
tomy of the tissue we are examining, and when 
highly magnified are found to be so many ca- 
nals exhibiting in the scales of different species 


* Recherches sur la Structure interne des Ecailles 
des Poissons. Par le Dr. L. Mandl. Ann, des 
Sc. Nat. tom. xi. 


974 


every degree of formation from a simple furrow 
to a perfectly enclosed tube. 

The broad scales or plates which form the 
armour of the Syngnathide are traversed b 
similar canals enclosed on all sides, which, al- 
though separate at the margins, anastomose 
freely towards the middle of the scale. 

The longitudinal lines in all their forms con- 
stitute a series of hollow tubes that must be 
regarded as true canals. These canals traverse 
the scale in a longitudinal direction converging 
towards a focus, which, as will be shown here- 
after, is a centre of nutrition, so that most pro- 
bably these tubes perform the functions of 
nutritive vessels. 

2. The cellular lines, supposed by preceding 
writers to be merely lines of growth analo- 
gous to those observable upon the exterior 
of a bivalve shell, attentive examination shews 
to owe their arrangement to a very different 
cause, Originating in the developement of pri- 
mitive cells, which are ienicnat in the super- 
ficial stratum of the scale and gradually assume 
an elongated form, become filled with corneous 
matter, and ultimately arrange themselves in 
concentric lines of greater or less breadth, 
which only indicate by their uneven edges 
their original nature. 

3. The corpuscles seen in scales are precise] 
similar in their appearance to those met'wi 
in bone and cartilage, and are obviously of the 
same nature, They are distributed in the basis 
membrane, which seems to be an amorphous 
tissue resembling that in which the corpuscles 
of bone are deposited, and which forms the 
superficial stratum of the scale. 

4. The fibrous layer—On scraping off with 
a penknife the external surface of the scale, the 
cellular lines and the corpuscles with their 
basal membrane are removed, and the deep- 
seated stratum of the scale becomes visible, 
which is then seen to consist of fibrous lamelle 
composed of fibres that cross each other at 
regular angles, giving to this tissue the appear- 
ance of fibro-cartilage. This layer is thickest 
near the focus of the scale, and become gradu- 
ally thinner towards the edges.. 

5. The focus is the space towards which the 
longitudinal lines converge, but is not always 
situated in the centre of the scale; it is occu- 
pied by very large pale a Hear and by 
interrupted circular lines; such at least is its 
appearance in the scales of Acanthopterygenous 

ishes, but in the Malacopterygii, and more 
especially in those species which have mem- 
branous scales, it presents nothing but a smooth 
circumscribed surface without corpuscles or in- 
terrupted lamine, and is then generally sur- 
rounded by the concentric cellular lines. 

6. The teeth of the scales—The growth of 
the spines and other appendages seen upon the 
outer surface and posterior margin of many 
forms of scales, more especially in those named 
ctenoid by Agassiz, is a subject of very consi- 
derable interest, and to the old physiologists, 
who believed all scales formed by mere exuda- 
tion, must have been quite unintelligible. The 
production of these spines is in fact, according 
to the researches of Dr. Mandl, in every respect 


PISCES. 


similar to the growth of teeth, each bei 
enclosed in a distinct capsule and pedro 
in the following manner, as exemplified by 
the growth of a scale of Corvina nigra, one of 
the Scienide. 

The posterior margin of one of these ss is 
occupied by conical appendages, represented in 
a highly magnified condition in fig. 508. Each 

: of the oblong processes 

ae tee. here depicted is seen to be 
encl in an env 

from which, however, it is 
entirely separate, as is 

be 4 ~ fact that w ae 

e capsule is ruptured 
auld spine can be re- 
moved from it with the ut- 
most facility. Examined in 
detail, every one of these 
spines exhibits an 
zation and mode of growth — 
precisely similar to that of 
a tooth, being formed in its 
capsule exactly in a similar 
manner. The germ begins 
gradually to develope itself; 
it acquires roots, and be- 
comes distinctly composed 
of different layers, = that 
these spines may_wi ) 
priety be called the teeth of . 
the scales, in allusion to 
the mode of their develop 


i bat ment. The marginal 
A small portion of the are most connate 
Ci 


After Mandl. ) formed, and the whole sur 
face of the tooth smooth and continuous. In the 
two next teeth below, the developement is 
less advanced ; the extremities are truncated, the 
external layer of the tooth does not entirely cover 
it, but the roots are visible. Still lower down 
the teeth of the scale become more and mo 
imperfect, until the lowest are scarcely at al 
developed, and are barely distinguishable amon 
the surrounding corpuscles. 

In other families with denticulated 
the growth of these appendages is prec 
sinoiler, as in the Gobinides, Percoides, F 
ronectide, &c. 

From the above observations it becomes evi- 
dent that the scales of Fishes can no longer b 

ed as mere productions of secretion fro 

the skin, but must be considered as pe 
an inherent power of nutrition and a tf 
growth. The denticles which exist upon ma 
of these scales offer by their successive dev 
lopement a striking proof of this importa 
fact; while the canals whereby they are t 
versed, and the corpuscles belonging to thet 
structure, plainly intimate that their mode of 
developement is similar to what exists in the 
teeth and in the osseous system. eg 

The chemical composition of the scales 
Fishes, moreover, very nearly approx 


of 


PISCES. 


that of their teeth and bones, as will be evident 
from the following analysis made by M. Che- 
vreul of the scales of a Lepidosteus, of a Cheto- 
don, and of the Perca labrax, after they had 
been thoroughly dried by exposure during six 
weeks to a dry atmosphere. In drying, the 
scales of Lepidosteus lost 11.75 per cent., of 
Chetodon 13 per cent., and those of the Perca 
labrax 16 per cent. 


Scales of 

Lepi- | Perca | Cheto- 

dosteus| labrax.| don. 

Fatty matter principally con- 

sisting of oleine . . ~.{ 0.40] 0.40) 1.00 
Azotized matter . . . «| 41.10) 55.0 | 51.42 
Chloride of sodium . . .| 00.10) Trace] Trace. 
Sulphate of soda. . «| 00.10} 00.90) * 1.00 
Subcarbonate of soda . .| 00.10} 00.00} ' 0.00 
Subcarbonate of lime . .{| 10.00} 3.06] 3.68 
Phosphate of lime (of bone) | 46.20] 37.80} 42.00 
Phosphate of magnesia. .| 2.20] 0.90} 0.90 
Peroxide of iron . - . . | Trace|Trace| Trace 

WOOBB Nits “eo “ens % % 0.00) 2.84 a 
100.00} 100.00} 100.00 


In a preceding article (see Osszous System, 
Comp. Anat.) we have endeavoured to shew 
that the scales which invest the exterior of the 
body constituting the exoskeleton of Fishes, 
by progressive modifications in their size, tex- 
ture, and arrangement, are converted into very 
various organs, namely, the apparently osseous 
plates that cover Lepidosteus and Ostracion, 
the formidable pieklce that stud the external 
surface of the Diodons, the opercular flaps of 
the Sturgeon, and even those of the osseous 
Fishes; the spines of Gasterosteus, and those 
which in Silurus, Ba- 
listes, and Lophius, 
were likewise proved 
to belong to the epi- 
dermic or tegumen- 
tary system; lastly, 
the fin-rays and in- 
terspinous bones of 
the vertical fins were 
found to be derivations 
from the exoskeleton, 
instead of being, as 
they have long been 
considered, parts ap- 
pertaining to the en- 
doskeleton or true 
Osseous system. . 

The dental organs 
-of vertebrate animals 
have very naturally 
been regarded by the 
old anatomists who 
confined their osteolo- 
gical researches to the 
investigation of the 
human skeleton, as 
forming a part of the 
bony framework of the 
body, notwithstand- 
ing that the teeth in 
every particular of their economy were con- 
fessedly very different from any other pieces 
of the skeleton. 


975 


Any one who with a little care examines the 
dental apparatus of Fishes will, however, 
speedily be convinced that the teeth in common 
with the epidermic structures above enumerated 
are all of cuticular origin, their connection with 
the real osseous skeleton, by their roots be- 
coming consolidated with certain bones of the 
mouth or implanted into the jaws, being by no 
means an essential or even constant circum- 
stance. 

Every one knows that the skin covering the 
body of the Skate or Thornback is thickly studded 
with calcareous spines, some of microscopic 
size, but others of considerable dimensions. 
On tracing these cuticular spines towards the 
mouth they are found, as they pass over the 
manducatory surfaces of the upper and lower 
jaws, to become suddenly very much increased 
in size, and are arranged with such regularity 
that they constitute a very formidable set of 
dental organs, consisting of ten or a dozen rows 
of sharp teeth, which answer every purpose con- 
nected with the seizing and swallowing of food. 
These teeth, however, or scales, for such they 
indubitably are, have no connection with the 
jaws that support them except through the in- 
termedium of the cutis or mucous membrane 
covering the mouth, from which they are deve- 
loped, and are continually in these Plagiostome 
genera in progress of formation behind as they 
are worn away in front, their developement 
being accomplished in the following manner.* 
A series of minute and closely aggregated pa- 
pilliform matrices or pulps rise in succession 
from the mucous membrane behind the teeth 
already formed, which gradually become ossi- 
fied by the deposition of calcareous salts in the 


Fig. 509. 


Skull and jaws of Port Jackson Shark ( Cestracion Philippii), shewing the forms 
and arrangement of the teeth. 


peripheral cells and radiating tubes of which 
the pulp consists. 
* Owen, Odontography, 4to. 1840. 


teeth are most y 
ner pteatare Ag 1 es connys pene 
tal i In this fish the 


pavement. 

In the Cestracion Philippii, or Port Jack- 
Shark, both the above descriptions of teeth 
found united in the same jaws, the anterior 


proof of a very convincing descri 
tion that the teeth of Fishes are developed 


animals, where the jaws and teeth are brought 
into closer relation with each other. 

The teeth of the Squaloid Fishes or true 
Sharks are renewed by a very similar mode of 
growth. In these redoubtable monsters of the 
deep the teeth consist of numerous rows of 
broad and trenchant lamine, the anterior row 
of which (fig. 510, a) stands up icu- 
larly from the jaws ready for use, while the 
succeeding layers are recumbent, being covered 
over by a fold of the mucous lining of the mouth. 
Seas penvimelygaial perme a 

ly new sharp rows bei 
constantly ready behind to replace the old and 
worn ones in front as soon as the latter fall out 
or become useless. 

The situation of these teeth and their mode 
of growth is represented in the annexed figure. 
Their only connection with the cartilaginous 
jaw is evidently through the medium of the 
interposed fibro-mucous layer (d), which, as 
it slowly advances , carries the teeth 
with it, and thus brings the successive rows 

gressively into use. In the Sharks there 
1s no distinct pulp, the dense exterior layer 
of the tooth being formed by the calcifi- 
cation of the “membrana propria” of the 

p» so that when divided they are found to 

permanently hollow, as represented in the 
figure (c). ; 

In the Cyclostomatous Fishes the teeth are 
still more evidently mere cuticular appendages, 
seeing that in their case there are no bony 
jaws to which they can be affixed. In the 
Myzine Glutinosa, the Hag-fish, one of the 
most humbly organized but at the same time 
the most formidable of the finny tribes, this is 
extremely evident. The Myxine is generally 
found buried in the substance of some large 


single sharp and recurved attached 
to the centre of the roof of their mouth and 
fixed to the cartilages of the cranium by strong 


which is quite distinct from the cartilaginou 
skeleton, and evidently purely com 
epidermic structures. Ine tesih of foe La 


prey posed of horny plates or tube 
cles of different forms, which are di pe 


mouth, much in the same manner as oth 
<r epidermic structures, and from tt 
isposition will evidently secure a deadly he 
of any victim seized upon. Besides these” 
bial teeth there is one fixed to the roof of 
mouth which is obviously analogous to” 


solitary ine fang of Myxine last deser 
This (fig. 511, 6) 1s composed of two Tor 
cones attached by fibrous ligaments to the p 


tine cartilages in the roof of the mouth. 
fongne (6), which, ike We Sam xu 
is here very moveable and capable of being ® 
tracted and ed by means of stron 
armed with 


«<5 


tears through the flesh of its prey. 


PISCES. 


Seeing, therefore, that the teeth of Fishes are 
derivations from pulps formed by the mucous 
lining of the mouth, it can be a matter of small 
astonishment to find that they can be developed 
‘mm any part of the oral cavity where the 
necessities of a given species may require 
their presence, without relation to the jaws, 
with which alone they are connected in the 
nates races of Vertebrata and in the human 
su 

Accordingly in the class under consideration 
teeth are found attached to any or all of the 
following parts of the mouth and of the pha- 
Fynx, viz. to the superior and inferior maxilla, 
to the intermaxillary bones, to the palate bones, 
to the vomer, to the tongue, to the branchial 
arches, and to the superior and inferior pharyn- 
geal bones. The ichthyologist is therefore com- 
pelled to designate the different parts of the 
dental system according to the bones or other 
Structures whereon they are situated, and distin- 
guishes intermaxillary teeth, maxillary teeth, 
mandibular teeth, vomerian teeth, palatine teeth, 
pterygoid teeth, lingual teeth, branchial teeth, 
superior pharyngeal teeth, and inferior pha- 
ryngeal teeth, all of which may sometimes be 
coexistent, rendering the teeth of Fishes prodi- 
giously numerous. As relates to their form 
the dental organs offer a far greater number of 
varieties than those of other vertebrate animals. 
Sometimes they are so minute as only to be 
perceptible by the rough or scabrous surface 
which the parts of the mouth to which they are 
attached present. If of larger size, they pre- 
sent the appearance of a file or rasp (dents en 
rape), or they may have the shape of small 
cones or hooks thickly scattered over the pa- 
rietes of the mouth. Sometimes they are so 
fine and slender as to resemble the pile of 
velvet (denis en velours ), or elongated, having 
the ce of fine bristles. In Citharina 
these bristle-shaped teeth are bifurcated to- 
wards their free extremities, or they may termi- 
nate in three diverging points, as in the anterior 
teeth of the genus Platax. Or the elongated 
cone may be compressed into a slender tren- 
chant plate, and this may be pointed, recurved, 
or even barbed like a fish-hook, as is the case 
an Trichiurus and some other Scomberoid 
Fishes; or it may be bent upon itself like a 

VOL. III. 


977 


tenter hook, as in Pemelepterus and Go- 
niodontes. Sometimes the dental cones 
present a thickened base, giving them the 
appearance of the laniary teeth of carni- 
vorous quadrupeds, as is the case with 
the large teeth of the Pike ; or they may 
be flattened into broad plates of hemi- 
spherical or other shapes, constituting a 
crushing apparatus adapted to bruise the 
food 


A thin lamella, slightly concave like a 
finger nail, is the singular form of the 
tooth of an extinct species of cartilaginous 
fish named by Professor Owen Petalo- 
dus.* Sometimes each tooth presents a 
flattened incisor crown deeply notched in 
the middle of the cutting edge, as in 
Sargus unmaculatus. Sometimes there is 
a double notch, rendering the margin of 
the tooth trilobate, as in Aplodactylus; or it 
may be divided into five lobes by a double 
notch on each side of the central and largest 
lobe, as in Boops. 

In the great Barracuda pike (Sphyrenc ) the 
crown of both the large and small lamelliform 
teeth is prolonged into a sharp point, closely 
resembling a lancet. A similarly shaped pier- 
cing and cutting tooth is in many of the Sharks 
furnished with one or more accessory cusps at 
its base, and the cutting margins of the tooth 
are frequently notched, serrated, or crenated. 
Prismatic teeth with three sides are fixed to the 
jaws of Myletes ; and in some instances, as in 
Scarus, they assume the shape of four-sided 
prisms. 

The teeth of Fishest present greater diversity 
in their mode as well as in their place of attach- 
ment than is observable in any other class of 
animals. In a few instances they are im- 
planted in sockets, to which they are attached 
only by the surrounding soft parts, as, e. g. 
the rostral teeth of the Saw-fish (Pristis). 
Some have their hollow base supported, like 
the claws of the feline tribes, upon bony pro- 
minences which rise from the base of the 
socket; the incisors of the File-fish ( Balistes ) 
afford this curious example of a double gom- 
phosis, the jaw and the tooth reciprocally 
receiving and being received by each other. 

The teeth of Sphyrena, Acanthurus, Dic- 
tyodus, &c. are examples of the ordinary im- 
plantation in sockets with the addition of a 
slight anchylosis between the base of the fully 
formed tooth and the parietes of the alveolar 
cavity. But by far the most common mode of 
attachment of fully formed teeth is by a con- 
tinuous ossification between the dental substance 
and the jaw, the transition being gradual from 
the dental to the osseous tissue. The tooth 
prior to its anchylosis is connected by ligamen- 
tous substance, either to a plain surface, an 
eminence, or a shallow depression in the bone. 

Sometimes not the end, but one side of the 
base of the tooth is attached by anchylosis to 
the alveolar border of the jaw; it might be 
supposed that in this case the crowns of the 


* Owen, Odontography, p. 2. 
¢ Owen, loc. cit. 


328 


978 


teeth in both jaws would project forwards in- 
stead of being opposed to one another, and 
such, in fact, must have been their position 
were it not that, as in Pimelepterus, the teeth 
are bent at nearly a right angle with their 
base. In the Scarus, and likewise in the mar- 
ginal teeth of the Diodon, where these organs 
are straight and attached horizontally to the 
margin of the jaws, their sides instead of their 
crowns are actually opposed to each other. 

In the Cod-fish, Wolf-fish, and some other 
species, in proportion as the ossification of the 
tooth advances towards its base and along 
the connecting ligamentous substance, » the 
subjacent portion of the jaw-bone receives 


Fig. 512. 


Portion o 


igamentous attachment of the teeth. 


a, a, a, anterior teeth; b, b, b, posterior teeth in their 
erect position ; c, one of these teeth laid flat towards 
the interior of the mouth, the dotted lines indicating 


its condition when erect. (After Owen.) 


a stimulus and developes a process cor- 
responding in size and form with the so- 
lidified basis of the tooth. In this case the 
inequalities of the opposed surfaces of the 
tooth and maxillary dental process fit into each 
other, and for some time they are firmly at- 
tached together by a thin layer of ligamentous 
substance; but, in general, anchylosis takes 
place to a greater or less extent before the tooth 
is shed. The small anterior maxillary teeth of 
the Angler ( Lophius) are thus attached to the 
jaw, but the large posterior ones remain always 
moveably connected by highly elastic glisten- 
ing ligaments, which pass from the inner side 
of the base of the tooth to the jaw-bone 
(fig. 512, d). These ligaments do not permit 
the tooth to be bent outwards beyond the ver- 
tical position, when the hollow base of the 
tooth rests upon a circular ridge growing from 
the alveolar margin of the jaw; but the liga- 
ments yield to pressure upon the tooth in the 
contrary direction, and its point may thus be 
directed towards the back of the mouth; the 
instant, however, that the pressure is remitted, 
the tooth flies back, as by the action of a 
spring, into its former position. The deglu- 
tition of the prey of this voracious fish is thus 
facilitated and its escape prevented. 

The teeth of the Wolf-fish, Anarrhicus, are 


B nal buttress and of thedome itself iscom 


the jaw of Lophius piscatorius, showing the 


PISCES. 


extremely remarkable. They do not adhere 
immediately to the jaw or to the palate bone, 
but are attached to conical or hemispherical 
osseous epiphyses, which are fixed to these bones 
by a kind of suture, and are easily detached at 
certain periods. The base of each of these 
epiphyses is surrounded with a row of small 
foramina, doubtless intended for the admission 
of vessels, and mark the line of separation. 
On the summit of these cones the true teeth, 
formed as usual of dentine and enamel, are at- 
tached, 

“ If,” says Professor Owen, in the valuable 
treatise from which we have extracted the pre- 
ceding paragraphs, “ the engineer would study 
the model of a dome of unusual strength and 
so supported as to relieve from its pressure 
the floor of a vaulted chamber beneath, let — 
him make a vertical section of one of the 

haryngeal teeth of the Wrasse (fig. 513). 

he base of this tooth is slightly contracted 
and is implanted in a shallow circular cavity, — 
the rounded margin of which is adapted to a 
circular groove in the contracted part of the 
base. The margin of the tooth which thus 
immediately transmits the pressure to the 
bone is strengthened by an inwardly project- 
ing convex ridge. The masonry of this inter- 


of hollow columns, every one of which is 
placed so as best to resist or to transmit in 
a due direction the superincumbent pres- 
sure.” The use of this beautiful piece of 
animal mechanics is to keep the delicate 
successional pulp which is lodged beneath 
the vault of the arched tooth, from being 
injured by pressure during the action of these 
powerful crushing teeth. 4 


Fig. 513. © 


Teeth of the Wrasse ( Crenilabrus). 

Portion of the pharyngeal bone of the Wrass 

a, structure of arched teeth; 6, successional te 
¢, bone. ; 


In Rhizodus, a large extinct spec 
Sauroid fish, the broad base of the too 
divided into a number of long and s! 
cylindrical processes, which are implant 
piles in the coarse osseous substance 
jaw. They diverge as they descend, 
extremities bend and subdivide like the 
of a tree and are ultimately lost in the 
tissue. This mode of attachment of a to 
perhaps the most complicated met with it 
animal kingdom. De. 

In order to complete our remarks concer 
the teeth of Fishes it only remains to notice 
few examples in which the dentition is peculi 
namely, in the Cyprinide, the Scari, the Di 
dons, and the Tetradons. 


ad 


PISCES. 


Teeth of the Tench. 

a, roof of the mouth ; b, the esophagus; c, dental 
projection from basilar bone ; d, d, pharyngeal teeth. 
(After Owen.) 


In the Cyprinide, or Carp-ge- 
nus, the bones composing the 
superior and inferior maxille are 
completely edentulous, but to 
make up for this deficiency the 
pharyngeal bones are armed with 
a remarkably powerful dental ap- 
a of very singular character. 

h of the inferior pharyngeal 
bones, which are exceedingly 
strong and form a kind of osseous 
framework at the commencement 
of the esophagus, supports four or 
five large teeth of great strength. 
These are opposed to a single 
dental piece of stony hardness and 
laminated structure, which is fixed 


979 


514), and thus forms a kind of anvil upon 
which the bruising pharyngeal teeth play, and 
thus crush and triturate whatever food passes 
into the esophagus. 

In the Scari, which have to feed upon the 
numerous corallines that clothe the rocks at 
the bottom of the ocean, the dental apparatus 
given to protect their jaws from injury while 
biting such hard substances is very remarkable. 
These Fishes have their jaws, which resemble 
the beak of a parrot (whence they receive their 
usual appellation “ Parrot-fishes,”) covered 
externally with a kind of pavement of teeth 
answering the same purpose as the horny 
investment of the mandibles of the bird. The 
teeth that form this pavement are perpetually 
in progress of developement towards the base 
of the jaw, whence they advance forwards, 
when completed, to replace those which become 


Fig. 516. 


Section of the jaw of the Parrot-fish, shewing the progress of dentition. 


c, teeth still enclosed in the jaw; 1, do. with their extremities 


upon a dilated projection from the protruded so as to form an external pavement. (After Owen.) 


basilar bone of the cranium (fig. 
Fig. 515. 


Beak of Parrot-fish ( Scarus muricatus ). 


@, upper mandible, the exterior of which is com- 
pletely encased in teeth; 5, lower mandible par- 
ially so, the inferior teeth not having as yet pro- 
truded ; ¢, lateral fangs. (After Owen.) 


worn away in front by the constant attrition to 
which they are subjected. 

In the annexed figure (fig. 515) the ex- 
ternal appearance of these singularly disposed 
teeth is well represented, while in the vertical 
section (fig. 516) the mode of their implan- 
tation into the anterior surface of the jaw is 
delineated. All these teeth were originally 
developed in a common alveolar cavity (516, c) 
situated in the substance of the jaw. The 
outer* wall of this cavity is much weaker 
than the dense and compact inner wall, and 
moreover it becomes thinner as it approaches 


D the margin of the jaws and disappears (fig. 


516, /,) at different distances in different spe- 
cies of Scari before it reaches that margin. 
Where it exists at the base of the jaws it is 
sometimes, as in Scarus muricatus represented 
in the figure, perforated by numerous small 
foramina, through which foramina in the recent 
fish processes of the external periosteum are 
continued to the analogous membrane lining 
the dentigerous cavity and forming the capsule 
of each denticle. These processes are analo- 
gous to the gubernacula of the second series of 
teeth in the Mammalia, and like them serve 
to conduct the new teeth to the exterior of the 
jaw. The growing denticles (516, /,) be- 


* Owen, Odontography, page 115. 
38:9 


980 


come elongated by the addition of successively 
calcified portions of their pulp to their basal 
or posterior extremities; the opposite end exerts 
a proportional pressure against the circum- 
ference of the foramen, and causing its ab- 
sorption begins to protrude. The tuberculate 
crown of the denticle is exposed about the 
time when its sides become anchylosed to those 
of the previously protruded row. Thus, from 
the close apposition of the protruding den- 
ticles, the whole of the outer parietes of their 
common alveolar cavity subjected to the sti- 
mulus of their pressure is finally removed, and 
is replaced by the pavement of mutually an- 
chylosed teeth (fig. 515, «). 

In the Diodons and Tetradons the structure 
of the teeth is equally peculiar, but of a very 
different character from what has been described 
above. In the former genus each jaw is fur- 
nished with a double compound tooth adapted 
to crush and bruise the food, the structure of 
which at once reminds the anatomist of the 
molar teeth of the elephant. Each tooth 
(fig. 517) consists of numerous laminz super- 
imposed upon each other, the upper ones 
being the oldest and most worn, while the 
lower ones are the largest and most recently 
formed. In consequence of this arrangement 


Fig. 517. 


Section of the lower jaw of the Globe-fish ( Diodon ), 
shewing the structure of its teeth. 


a, circumference of jaw; b, grinding surface of 
tooth within the mouth. (After Owen.) 


the exposed surface of the tooth that projects 
into the mouth (6) presents a grooved appearance, 
being formed of the edges of the contiguous 
lamella that are situated towards the upper 
part of the tooth. As these superior lamine 
are worn away, it is evident that they are con- 
tinually replaced by the advancement upwards 
of the inferior plates, so that the tooth is kept 
constantly efficient for service. The circum- 
ference of the jaw (a) is formed of super- 
imposed plates which grow from below in a 
precisely similar manner; but between these 
and the posterior laminated tooth a very diffe- 
rent structure is interposed, which is revealed 
by the microscope to consist of a series of 
narrow flattened denticles lying horizontally and 
at right angles to the anterior surface of the 
jaw. These denticles are developed in a cavity 

tween the outer and inner walls of the jaw, 
the floor of which is formed by a thin cribn- 
form osseous plate separating the cavity con- 
taining the teeth from the wide vascular canal 
which runs in the substance of the jaw. In 


PISCES. 


the Tetradons a somewhat similar structure of 
the dental organs is met with. 

The rostral teeth of the Saw-fishes, Pristis, 
are quite unique among the whole race of 
Fishes from the singular position which they 
occupy, as will be perceived by the a 
account of this strange apparatus ex 
from Professor Owen's elaborate treatise. 

_“ The maxillary teeth of the Saw-fish, which | 
is an active and predatory Shark, are, notwith- 
standing its habits, extremely small, simple, 
obtuse, and wholly inadequate to destroy and 
secure the prey requisite for its subsistence, 
But this seemingly imperfect armature of the” 
mouth is compensated for by the develope 
ment from the anterior ery of the head of 
very singular and formidable weapon provid 
with strong lateral teeth, and which from it 
resemblance to a saw has given rise to the ver 
nacular of ‘ Saw-fish,’ applied to the present 
species of Shark.” % 

In most of the Plagiostomes, but especiall 
in the group of Squaloids, a conical projection 
or cutwater is continued from the fore-part 
the head, and its framework is compesed © 
peculiar and superadded cartilages articulate 
to the anterior extremities of the frontal, 
and vomerine bones. These rostral cartilag 
in the Saw-fish (Pristis antiquorum) a 
blended into a horizontally flattened pla 
which is produced to a length equalling or 
third that of the entire fish: this process 
more completely ossified than any other p 


Fig. 518. 


= 


Rostrum of Saw-fish ( Pristis antiquorum ), she 
the marginal teeth. . 


« 


PISCES. 


of the skeleton, and a series of deep alveoli 
is excavated in each of its lateral margins (fig. 
518). 

The teeth which are lodged in these sockets 
are elongated, compressed in the same plane 
as that of the body of the saw, and their edges 
converge to a sharp point, which is situated a 
little behind the axis.of the tooth. Each ros- 
tral tooth is solid, its base being slightly con- 
cave and porous like the section of a cane, but 
the pores are finer and more numerous. The 
walls of the socket are formed by ossification 
of the rostral cartilages to an adequate extent ; 
but as unnecessary weight under any circum- 
stances, but especially at the fore-end of the 
fish, would be’a cumbrous impediment to its 
motions, the spaces intervening between the 
sockets are hollow and filled with a gelatinous 
medulla. A large vascular canal traversed by 
branches of the facial artery and of the second 
division of the fifth pair of nerves enclosed 
in a cellular gelatinous tissue, runs parallel 
with the axis of the saw along the back part of 
the alveoli, and supplies the materials for the 
increase of the teeth, which are not shed and’ 
renewed like the maxillary teeth, but grow 
with the growth of the body by constant 
addition of fresh pulp-material progressively 
ossified at their base. 

(Esophagus.—Owing to the extreme short- 
ness of the passage between the cavity of the 
mouth and the stomach, the length of this tube 
is extremely limited in the whole race of Fishes; 
nevertheless, occasionally its boundaries are 
well marked, and its structure sufficiently dis- 
tinct from that of the alimentary canal to entitle 
this part of the digestive apparatus to a brief 
notice. Its walls are generally strong and 
muscular for the purpose of passing the food 
into the stomachal cavity, but more especially 
so in those ‘voracious Fishes which swallow 
dense and indigestible shells of various kinds, 
or that are subject to have their stomachs 

loaded with the hard bones of digested fishes, 
all which materials are in such instances regur- 
gitated and thrown out of the mouth much after 
the manner of the “castings” of the Hawk or 
Owl among birds of prey. In a few races, how- 
ever, the esophagus exhibits peculiarities of 
structure that are remarkable. Thus in the 
Torpedo and others of the Ray genus, there is 
a very thick layer of a soft and semi-gelatinous 
substance interposed between the lining mem- 
brane and the muscular coat, the use of which 
it is by no means easy to conjecture. In the 
Sturgeon the mucous membrane of the gullet 
‘is prolonged into transverse valvular folds, 
_analogous in their nature to the conical pro- 
cesses found in that of the Turtle. But the 
most striking example of a valvular apparatus 
‘Situated in this part of the digestive tube is met 
with in the Sharks (fig. 519), in which race 
of Fishes the termination of the esophagus is 
indicated. by a great number of long fleshy 
‘stems, which divide and subdivide into very 
numerous branches, and thus form a dense and 
prominent fringe hanging loosely downwards 
towards the stomach, in such a way as to allow 
anything swallowed to pass freely im that direc- 


981 


tion, but by the interlacement of the fringes 
effectually preventing anything from returning 
towards the mouth. This structure is most 
conspicuously seen in the great Shark ( Squalus 
maximus ),in which species, owing to the com- 
parative smallness of the teeth which arm the 
Jaws, it is extremely probable that many Fishes 
are swallowed alive and might retain their vita- 
lity sufficiently long to struggle back again out 
of the stomach of their devourer, did not this 
strange gate effectually bar their progress. 

Stomach.—This viscus is, in the generality of 
species, a musculo-membranous bag of very 
simple structure and of variable shape in diffe- 
rent genera. Sometimes, however, its muscular 
walls are sufficiently strong to perform to a certain 
extent the functions of a gizzard: this seems to 
be the case, for example, in the Gillaroo Trout 
(Salmo fario), and to a far more remarkable 
extent in the Mullets (Mugil), in which the 
esophagus terminates inferiorly in a deep cul- 
de-sac that serves the purpose of a crop. The 
muscular stomach or gizzard opens from one 
side of this cesophageal bag, to which it is 
attached at right angles. Its shape is pyriform, 
the narrow end being directed towards the in- 
testine, and its muscular walls nearly half an 
inch thick. Internally it presents numerous 
longitudinal folds, all covered with a thick cu- 
ticular lining, and evidently the whole appara- 
tus is very analogous to the true gizzard of 
a granivorous bird. It was John Hunter’s 
opinion that neither of these can be justly 
regarded as gizzards, since they want the most 
essential characters, namely, a power and mo- 
tion fit for grinding, and a horny cuticular 
lining. According to Professor Owen, how- 
ever, the latter structure exists in the gizzard of 
the Mullet as a distinct layer of rough and 
easily separable cuticle. The stomach of the 
Gillaroo or Gizzard-trout is certainly, as de- 
scribed by Hunter, more globular in its shape 
than that of most Fisl, and endued with suffi- 
cient strength to break the shells of small shell- 
fish, which is probably accomplished by having 
more than one in the stomach at a time, and 
also by taking pretty Jarge and smooth stones 
into the stomach, which will answer the pur- 
pose of breaking, but not so well that of grind- 
ing; nor will they hurt the stomach, as they are 
smooth when swallowed ; but this stomach can 
scarcely possess any power of grinding, as the 
whole cavity is lined with a fine villous coat, 
the internal surface of which appears every- 
where to be digestive. The common stream- 
trout, which only differs from the “ Gillaroo”’ 
in having the walls of its stomach not so thick 
by two-thirds as the other variety, likewise 
swallows smooth round stones wherewith to 
crush the shell-fish which it occasionally de- 
vours. 

Intestinal canal.—The intestines of Fishes 
present as many variations as regards their rela- 
tive length when compared with that of the 
body, as do those of any ’of the higher Verte- 
brata, but their general arrangement’is of a 
much more simple character. In the Flying- 
fish ( Exocetus ), indeed, it presents the sim- 
plest possible form, being merely a straight 


982 


tube passing directly from the stomach to the 
anus. In the Mullets ( Mugil), on the con- 
trary, the intestine is of great length and is very 
curiously folded, being intervolved with the 
folds of the liver so as to form a mass of trian- 
gular form moulded to the shape of the abdo- 
minal cavity, and affording an example of the 
longest and, in its disposition, the most complex 
intestinal canal of any of the class. 

This arrangement, as Kathke very justly ob- 
serves, is an obvious approximation to the dis- 

sition of the viscera most generally met with 
in molluscous animals, in which the folds of 
the intestine are prolonged into and almost bu- 
tied among the folds of their very large liver. 

In the Electric Eel (Gymnotus electricus ) 
the disposition and termination of the intestinal: 
tube is curious. First descending to the lower 
end of the stomach, it passes to the left side 
and ascends again as far as the esophagus ; it 
then winds downwards and backwards so as to 
encircle the stomach, and, lastly, advancing for- 
wards along the ventral aspect of the abdomen, 
it terminates, as in the Cephalopoda, beneath 
the throat, in the immediate vicinity of the 
heart and root of the tongue. 

No fish has anything like a colon or cecum. 
The only distinction between small and large 
intestines is met with just at the termination of 
the alimentary tube, where it opens into a kind 
of cloacal cavity, usually called the rectum. At 
this point there is generally a prominent cir- 
cular fold of the lining membrane constituting 
a kind of valve. In the Salmon several of these 
valvular zones succeed each other, giving to this 
part of the gut an appearance similar to that of 
the intestine of the Plagiostome cartilaginous 
Fishes immediately to be described. 

In the Sharks and Rays, the Plagiostomes 


Fig. 519. — 


Alimentary canal of Shark. 


a, cesophugus ; b, b, cavity of stomach, at the 
commencement of which are placed the valvular 
fringes mentioned in the text; c, passage leading to 
pylorus; d, spleen; e, pyloric cavity; f, dilated 
chamber ; g, h, bile-ducts; i, orifice of pancreatic 
duct ; k, k, valvular intestine. 


PISCES. 


just referred to, and also in the Sturgeon, the 
intestine presents a very remarkable structure. 
Externally it resembles a wide bag nearly simi- 
lar in shape and size to the stomach itself, and 
so short and stunted that, without some special 
arrangement, obviously a sufficient surface 
would not be afforded for the re mt of the 


nutritious portions of the food. By the me-— 
chanism adopted, however, this is abundantly 
provided. of the © 


roughout the whole bm 
gut the mucous membrane is arranged in deep 
spiral folds (fig. 519), which wind from end to 
end, only leaving a small orifice in the centre of 
each valvular projection, whereby the different © 
compartments formed between the spiral lamina — 
can communicate with each other, so that the 
digested food by this unusual arrai t is 
spread over a very great superficial area, and all 
e benefits of a long and convoluted intestinal 
tube are secured. Each fold of this extensive 
spiral valve contains between the layers of mu=— 
cous membrane that compose it an elastic 
substance, whereby it is kept constantly spread 
,out and restored to its orginal position when 
displaced by the passage of food through the 
central channel that permeates the whole series. 
In the Sturgeons a similar valve exists, bul 
its spiral folds are not so closely arranged: the 
intestine, moreover, is remarkable on 
of the great thickness of its muscular and in- 
ternal tunics, the latter of which presents 
reticulated or honey-combed appearance, thi 
larger meshes including irregular spaces, whic 
are again subdivided into smaller cells. Sligh 
vestiges of the spiral intestinal valve are visibl 
even in the Lamprey. 4 
Salivary glands—From the circumstance 
under which Fishes swallow their food, th 
presence of any sali rd Be is evidentl 
uncalled for; no fish, therefore, 
salivary glands. Nevertheless, in the Cypr 
nide and some other races the whole palate 
covered with a soft spongy substance, fic 
which a kind of mucosity is discharged throug 
imperceptible pores, which has been regarde 
by Rathke and others as a salivary orgar 
Cuvier, however, denies the glandular charae 
of this substance, regarding it as a peculiar at 
highly sensible tissue destined to be the seat 
a sense more or less analogous to that of ta 
—a supposition that is rendered more proba 
from the great number of nerves that enter 
substance. 
Pancreas—In the osseous Fishes no- 
creas, such as that met with in the hi 
classes of vertebrate animals, exists; i 
however, represented by a variable numb 
cecal sd begirn doe which open into the du 
num in the vicinity of the pylorus. Thel 
membrane of these pyloric caeca is of a 
dular character, and secretes an abund: 
a thin glairy fluid analogous to the pane 
secretion. The existence of the appendagi 
uestion is, however, by no means cons 
thus in the Labride, the Siluride, the Cyp 
nide, and many members of the pike 
they are altogether wanting. When 
moreover, their number varies very remark 
in different Fishes ; thus, sometimes, as 1 


count 


PISCES. 


Salmonide, they are extremely numerous, while 
in other races, the Pleuronectide for example, 
there are only two ceca attached to the pylorus. 
That the pyloric appendages are strictly analo- 
gous to the pancreas, exhibiting that gland in 
its simplest condition, such as it presents in 
the embryonic state of the higher animals, is 
proved by the gradual transition that may be 
traced from the condition in which they exist 
as above described, and the undoubted pan- 
creatic gland met with in the more highly 
organized cartilaginous Fishes. Thus in the 
Cod-fish (Gadus morrhua) the pancreatic 
cwea unite together as they approach the duo- 
denum, so as to communicate with that intes- 
tine by comparatively few orifices situated in 
the vicinity of the pylorus; and in the Stur- 
geons this coalescence of the cecal tubes is 
still more conspicuous, for in that race of 
Fishes the pyloric appendages are very short, 
and so connected together by vessels and cel- 
lular membrane into a single mass, that they 
here present a precisely intermediate condition 
between the free coca of the osseous Fishes 
and the conglomerate pancreas possessed by 
the Sharks and Rays. 

In the plagiostome cartilaginous Fishes last 
named, the pancreas is in fact a true conglo- 
merate gland, resembling that of Quadrupeds, 
and in the same manner pouring its secretion 
into the intestine through a single excretory 
duct, which runs obliquely for a considerable 
distance between the coats of the duodenum, 
and terminates in the vicinity of the ductus 
choledochus. 

Liver.—The liver of Fishes is generally of 
very great relative size, and frequently contains 
in its tissue such an enormous quantity of oil, 
that this alone forms an important article of 
commerce. Its texture is exceedingly soft, and 
from the arrangement of the vessels in its inte- 
rior sometimes exhibits a fibrous appearance. 
The lobes of which it consists are generally 
very numerous, but there is always a gall-blad- 
der, from which the bile is poured into the 
intestines through a single duct, which termi- 
nates in the duodenum near the pylorus. 

Spleen—This viscus, which is peculiar to 
the Vertebrata, first makes its appearance as 
we trace the animal series upwards in the class 
under consideration. In Fishes it is of very 
variable size, but is always present. Its usual 
position is among the folds of the intestines, 
aud its relations with the stomach are so diffe- 
rent to what obtains in the mammiferous races, 
that its functions cannot be in any way influ- 
enced by pressure caused by the distension of 
that organ. In its supply of arterial blood, 
which is subsequently transmitted to the portal 
system, it differs in no essential particular from 
what occurs in the other vertebrate classes. 

All the above viscera are lodged in the cavity 
of the abdomen, in which they are suspended 
by numerous irregular folds of peritoneum; 
the generative and urinary organs, as well as 
the swimming bladder hereafter to be described, 
being situated beneath the spine external to the 
peritoneal sac, the peritoneum only covering 
their anterior surfaces. In many Fishes the 


983 


peritoneum does not form a closed bag, as is 
the case with the serous membranes in general, 
but on the contrary is penetrated by two large 
orifices situated in the vicinity of the anus, 
through which the peritoneal membrane be- 
comes continuous with the external integument, 
and in this respect assimilates a mucous sur- 
face. Such is the case in the Sturgeons, Lam- 
preys, Salmons, Sharks, and Rays: in the two 
last genera, indeed, the connection is still fur- 
ther extended by two orifices, through which 
the peritoneal bag communicates with the ca- 
vity of the pericardium. The mesentery is 
in Fishes very incomplete, consisting merely 
of irregular bands, which enclose the principal 
bloodvessels and unite the viscera to each other. 
Sometimes there are processes filled with oily 
fat representing the omentum. ' 

In the Branchiostoma the esophagus com- 
mences at the bottom of the buccal cavity be- 
hind the opening of the branchial sac, between 
the latter and the spinal axis, and after a short 
course terminates in a simple dilatation, which 
forms the stomach. About the middle of the 
branchial sac the alimentary tube becomes im- 
bedded in the liver, and terminates in a delicate 
intestine, which extends to the anal opening. 

Lymphatic system.—The principal lacteal 
vessels are situated near the large branches 
of the cceliac and mesenteric arteries and veins, 
and the large lymphatic trunks derived from 
the spleen, liver, and pancreas, accompany the 
chief bloodvessels of those parts.* 

The lacteals and lymphatics of the assistant 
chylopoietic viscera are much larger in propor- 
tion to the bloodvessels than in Quadrupeds, 
Birds, or even in Reptiles. Their branches 
communicate with each other freely and repeat- 
edly, and instead of uniting into one or two 
trunks, they form a right and left plexus, which 
are continued undiminished in size till they are 
about to join with the lymphatic system of the 
rest of the body. Neither the lacteal nor 
lymphatic vessels are quite cylindrical, but by 
being contracted a little in many places seem 
to be jointed, so that the anatomist would ex- 
pect to find numerous valves in their course, 
yet these are entirely wanting, except at the 
termination of the whole system. 

The lacteals terminate in a very remarkable 
structure, which is situated along the great 
curvature of the stomach. This consists of an 
elongated viscus, the interior of which is en- 
tirely cellular, so that, when prepared by infla- 
tion and drying, its internal texture resembles 
the cancellated structure of bones, being com- 
posed of a great many cells of very irregular 
shapes, and all communicating with each other, 
so that probably this cellular viscus may per- 
form the office of the absorbent glands of other 
animals, which in Fishes are totally wanting. 
Pursuing the right and left plexuses formed by 
the lacteals and lymphatics of the chylopoietic 
organs, we are led upwards along the sides 
and back part of the esophagus to the sides of 
the spine and of the inferior vene cave, and 


* Monro, Structure and Physiology of Fishes, 
fol, 1785. 


984 


near to large veins covered by strong cartilages, 
which resemble our clavicles, and which there- 
fore may be called subclavian veins. Towards 
these all the lymphatic vessels of the body are 
directed, the lymphatics of the kidneys and 
organs of generation with those of the tail and 
inferior parts ascending, those of the flesh and 
side fins of the trunk of the body running in- 
wards, and those of the superior parts and of 
the brain, organs of the senses, heart, and gills, 
descending. 

The branches ofthe lymphatic vessels form 
larger angles where they terminate in their 
trunks than are found in the veins, and the 
smaller branches are connected by transverse 
canals. The large lymphatics of the muscular 
organs, near their joining with the lacteals, are 
collected together in the most simple manner, 
without forming such intricate plexuses as are 
found in the course and near to the termination 
of the lactea! vessels: the lymph from the 
head and thorax in particular is conveyed 
chiefly by a single trunk, which receives large 
lateral branches from the adjacent parts. At last 
a single vessel on each side of the fish, and in 
which there is no dilatation or large receptacle, 
receives all the chyle and lymph, and terminates 
in the subclavian vein of the corresponding 
side very near its junction with the internal 
jugular vein, or nearly in the angle which these 
two vessels form by their joining. The blood is 
poe from getting into these two vessels 

y : pair of valves placed at the termination of 
each. 

In the osseous Fishes the course of the 
lymphatics has been traced both by Monro and 
Hewson,* principally in the Gadide and the 
Salmon: their general arrangement has been 
described above. 

Four lymphatic vessels which terminate in 
the subclavian receptacles chiefly merit attention. 
The first conveys the lymph from the ventral pa- 
rietes, from the ventral and pectoral fins,and from 
the heart. The second runs up the side of the 
fish parallel to the great mucous duct, and brings 
the lymph from the principal muscles of the 
tail and body. The third is deep-seated and 
conveys the lymph from the se spinal me- 
dulla, and upper part of the head, while the 
fourth lymphatic vessel, or rather plexus of ves- 
sels, brings the lymph from the brain and organs 
of the ’sensés, and from the mouth, jaws, and 
gills. 

The two receptacles into which all these ves- 
sels open communicate freely with each other 
by wide canals, which: pass chiefly behind the 
heart and cesophagus, and each ultimately 
empties itself into the upper end of its corre- 
sponding vena cava inferior, contiguous to the 
termination of the internal jugular vein, the 
communications between the lymphatic and 
venous systems being guarded by valves. 

It will be seen from the above description that 
the lymphatic system of Fishes offers several 
remarkable peculiarities when compared with 
what is met with among the ah ge ertebrata, 
amongst which may be noticed the total want 


* Phil. Trans. for 1769. 


PISCES. a" 


of lymphatic glands, and the absence of valves 
in the absorbent trunks. Owing to this latter 
circumstance, nothing is more easy than to in- 
ject them from trunk to branch, and thus dis- 
play their minute ramifications with the greatest 
ease. In this manner Mr. Hewson detected in 
the Cod a beautiful net-work of lymphatic — 
vessels situated between the muscular and vil- 
lous coats of the intestine, something analogous _ 
to what exists in the Turtle; but in Fish it is 
more evident that there can be no deception, — 
seeing that the injection is contained in cylin- 
drical vessels, not diffused in cells, as is the — 
case in the reptile. If mercury be injected — 
into this ne th it spreads ei in sien 
and if the intestine inverted and sli 
pressed, it can readily be seen to pass into the 
villi of the intestinal mucous membrane. In 
the stomach, however, the absorbents have a 
different arrangement. When minutely in- 
jected with mercury, they are seen to pass 
through the external coats, dividing into smaller — 
and smaller bratiches, without any appearance — 
of a net-work between the muscular and the 
villous coat, so that the absorbent vessels of the 
stomach manifestly exhibit a different arrange- 
ment from those of the intestine. 
By adopting a similar mode of injecting from — 
trunk to branch, Dr. Monro succeeded in de- 
monstrating numberless lymphatics in the brain, 
eye, ear, and nose, in all of which organs their 
existence had been previously doubted; and, 
also, in proving that their ramifications in 
the rest of the body were far more extensive 
than had been supposed. He, moreover, points 
out another circumstance of considerable im- 
portance in a physiological point of view, viz., 


+ 


that on examining the minute branches of the 
lymphatics, they are found to consist of an im. 
mense number of anastomosing canals, many 
of which enter the neighbouring lymphaties a 
right angles instead of being di owards 
the heart, by which means a net-work is pr 
duced so very intricate that, when a small por 
tion only is examined, it is difficult or next 
impossible to ascertain what has been t 
natural course of the lymph; it is therefo 
evident that, from the great number and un 
vourable direction of these canals, general pr 
sure cannot in this case be a chief cause of 
progressive motion of the lymph, but that ea 
vessel must contribute to its progress by a we 
regulated action. a 
Another remarkable circumstance is 
by Monro in connection with the lymp 
vessels, namely, that in the Skate they ¢ 
by patulous orifices situated upon the back | 
the Fish, of sufficient size to allow not only ; 
but water, milk, quicksilver, and even oil 
turpentine coloured with vermilion, to be 
charged upon the surface of the skin, ev 
when the force employed in injecting t 
fluids was very slight, and no extravasa 
produced into the cellular tissue either un 
the skin or in the muscular interstices. 
function attributed to these open vessé 
Monro is, however, even if they exist, 
hypothetical, namely, that they are for the 
purpose of absorbing from the ocean the fluic 


re 


, ee 


a - 
4 
) 


PISCES. 


which is interposed between the skull and the 
surlace of the brain. 

Organs of respiration—The respiration of 
Fishes is purely aquatic, the oxigenization of 
the blood being accomplished throughout the 
entire class by its exposure to the oxygen 
dissolved in the surrounding medium as it 
passes through the network of extremely mi- 
nute vessels that is spread out over the exten- 
sive surfaces furnished by the gills or branchiz. 

These organs consist of vascular fringes or 
lamine placed on each side of the neck, over 
which, in the great majority of species, the 
water taken in at the mouth is made to pass 
as it issues through the opercular cavities ; 
and in this way the branchial surfaces, being 
perpetually bathed with aerated water, perform 
the same office as the lungs of an air-breathing 
animal. 

But while respiration is thus accomplished 
throughout the whole class by means that are 
essentially similar, there are several modifica- 
tions in the mechanical arrangement of the re- 
Spiratery apparatus, each of which will demand 
our especial notice. 

Throughout all the extensive division of os- 
seous Fishes (with the exception of the Lopho- 
branchii) the construction of the breathing 
organs will be found to accord with the fol- 
lowing general description. To the external 
convex surface of each of the four branchial 
arches (fig. 522) is attached a double series of 
flat, elongated, cartilaginous lamine, tapering 
gradually towards their extremities, the whole 
forming a crescent-shaped pectiniform frame- 
work, over which is spread the highly vascular 
membrane that constitutes the respiratory sur- 
face. On making a transverse section of the 
gill it is found that towards their base, whereby 
they become attached to the branchial arch 
(fig. 520, b), the two series of branchial lamine 
are united to each other, and, moreover, the 
structure of each leaflet of the branchia becomes 
apparent. The branchial artery (c), whereby 
the blood is brought to the gills for the purpose 
of respiration, is seen running along the con- 
vexity of the supporting arch in the middle of 
the base of the branchial lamine opposite each 
pair, of which it gives off two branches, which 
pass outwards to the end of the substance 
which unites the two layers of gills at their 
bases, and then severally subdivide, one of the 
ramuli extending along the internal margin of 
each branchial lamina to its extremity, the other 
retrograding to its base. From these two ra- 
muli minute transverse vessels are given off, 
which distribute the blood over the general 
surface of the laminz, and ultimately form the 
branchial veins, from which the systemic artery 
is continued. Besides the respiratory lamine 
the branchial arches support a series of un- 
vascular processes, which project from their 
concave margins, and serve to prevent sub- 
stances taken into the mouth from escaping 
through the branchial fissures and thus getting 
among the gills; these processes in the Mullet 
(Mugil chelo) are extremely beautiful, forming 
long and delicate fringes along the concavity 


985 
of each branchial arch, adapted to bar the 
Fig. 520. 


passage of minute or finely 
comminuted food through 
the branchial interspaces. 
These internal unvascular 
appendages to the branchial 
arches act, therefore, the 
same part as the epiglottis of 
mammiferous animals. Fre- 
quently there are likewise 
tubercular projections from 
the contiguous margins of 
the concave surfaces of the 
branchial arches, for the pur- 
pose of preventing the gills 
from becoming too closely 
approximated to each other, 
and thus interfering with the 
free circulation of the blood 
over their surfaces. 

The mechanism of the 
respiratory process is, there- 
fore, in these osseous Fishes 
exceedingly simple. The 
water which is constantly 
taken into the mouth passes 
through the branchial fis- 
sures, and is forcibly driven 
by the simultaneous action 


Diagram of the cir- 
culation of the 
blood through the 


branchial leaf- of the branchial arches of the 
lets. os hyoides, of the palato- 
b, section of temporal flaps, and of the 


branchial arch; a, 
branchial artery ; 
c, branchial vein; 
d, d, e, e, the arte- 
rial and venous 
trunks derived 
from them. 


opercula, through the inter- 
spaces of the gills, and thus 
passes out through the wide 
fissure upon the side of the 
neck beneath the branchios- 
tegous membrane. 

In such genera as have this external opening 
very large and patulous, as it is, for example, 
in the Herrings and numerous other races, the 
death of the fish ensues almost immediately 
on its removal from its native element, not so 
much on account of a deficiency of oxygen 
wherewith to aerate the blood in the branchiz, 
seeing that that might be derived from the 
atmosphere, but because the gills, being no 
longer floated out, collapse, and thus, by pre- 
venting the passage of blood through the deli- 
cate vessels which ramify over the branchial 
lamin, put a stop to the circulation as com- 
pletely as strangulation could do; but in some 
genera a provision is made to permit of a more 
lengthened existence out of the water where 
the habits of the fish render such an arrange- 
ment necessary. In the whole tribe of Eels, 
for example, the external fissure is removed 
very far back and reduced to a very small yer- 
tical slit, converting the cavity wherein the 
branchize are lodged into an elongated cham- 
ber, wherein a considerable quantity of water 
can be retained : in such Fishes, therefore, the 
circulation of the blood is by no means put a 
stop to by taking the fish out of the fluid it 
usually inhabits, but, on the contrary, many 
species can exist for a considerable length of 
time in the air, and even make their way to 
a distance from their native ponds, the water 


986 


so retained in contact with the branchie con- 
tinually absorbing from the air a sufficiency of 
oxygen to carry on the respiratory process. 

An important group of Fishes (the “ Pha- 
ryngiens labyrinthiformes” of Cuv.) are cha- 
racterized by a very peculiar formation of the 
anterior superior pharyngeal bones, which 
enables them to live out of the water for a 
considerable length of time, so that many of 
them, as we are assured by authors, not un- 
frequently come on dry land, and even, as in 
the case of the Anabas scandens, or climbing 
Perch, mount into trees, a faculty for which 
they are indebted to the following remarkable 
conformation. 

Their inferior pharyngeals and the posterior 
of their superior pharyngeal bones present the 
usual arrangement and are studded with teeth, 
but the two anterior pharyngeals on each side 
are spread out into thin lamine folded upon 
themselves in divers ways, so as to form a light 
complicated mass, (which Cuvier* compares to 
a curly cabbage, or to certain forms of lami- 
nated eschars and millepores,) over which 
numerous vessels are distributed, but whether 
derived from the branchial artery or the aorta 
remains uncertain. In order to lodge these 
singular cellular organs the head is consider- 
ably dilated in breadth, and with the same 
intention the cranium is produced upwards by 
a vertical crest so as to increase the height of 
the lateral chambers in which the foliaceous 
masses are lodged. Externally, each of these 
chambers is partially covered by the bones of 
the cranium and by the opercular pieces ; and 
when the operculum is raised, a membrane is 
seen to be tightly expanded between it and the 
opercular bone so as to enclose the cavity, 
leaving only a small aperture of communica- 
tion with the exterior, which leads equally to 
the labyrinthiform apparatus and the branchial 
chamber. This bony labyrinth, therefore, so 
carefully enclosed on all sides, and which re- 
ceives water equally with the branchie when- 
ever the fish opens its mouth, will retain the 
water so taken in between its lamella where- 
with to moisten the branchiz for a considerable 
length of time, so that the fish may live for 
hours or perhaps even for days out of the 
water. 

The Lophobranchii form a remarkable group, 
distinguished from all other races of osseous 
Fishes by the peculiar structure of their bran- 
chial organs. In these, called from their pecu- 
liar shapes and external armour “ pipe-fishes,” 
(Syngnathus, Hippocampus, §c.) the vascular 
fringes appended to the branchial arches, in- 
stead of consisting of lamelle arranged in a 
pectinated form, are collected into tufts ar- 
ranged in a double series along the convexity 
of each branchial arch. The essential character 
of these tufts varies, however, in no respect 
from that of gills of the ordinary construction, 
and in like manner the water passes from the 
mouth through five apertures leading from the 
pharynx into the branchial chamber, whence, 


* Hist. des Poissons, tom. 8. 


PISCES. 


after bathing the tufted gills, it escapes through . 
a single small opercular fissure. : 

The Sturgeons ( Sturionide ), which in many 
points of their economy seem intermediate be- 
tween the osseous and cartilaginous Fishes, 
resemble the former in the disposition of their 
organs of respiration. The gills of the Stur- 
geon are constructed precisely in the same 
manner as in ordinary osseous Fishes, only 
differing in some respects as to form, the bran- 
chial arches being more bent and the vascular 
lamin united for a greater extent; the respired 
water, moreover, escapes in like manner through 
a single opercular slit. ’ 

In the Plagiostome cartilaginous Fishes 
(“ Chondropterygii & branchies fixés,” oa 
the mechanical arrangement of the i 
organs presents very important modifications, 
the water which passes from the mouth over 
the gills no longer escaping through an oper- 
cular opening, but being expelled through five 
distinct orifices situated on each side of the 
body. Inthe Sharks and Rays the condition of 
the breathing organs is essentially similar, so 
that the same description will apply to both. 
The four branchial arches in these Fishes are 
of a soft cartilaginous consistence, and instead 
of hanging free in the branchial chamber as 
they do in the osseous genera, stretch quite 
across that cavity to have their external a 
fixed to its outer walls, thus dividing it like so 
many bulk-heads into five distinct compart- 
ments, which have no communication with 
each other. A wide branchial fissure admits 
water from the pharynx into each of these com- 
partments, which after passing over the gills is 
expelled by as many orifices situated upon the 
exterior of the body, the external opie 
being situated upon the sides of the in 
the Squalide (fig. 506, 9,9,q), but in the Skates, 
in consequence of the lateral extension of the 
body, they are placed upon the ventral surface. 
The gills themselves are broad vascular mem- 
branes spread out over the opposite faces of each 
cartilaginous septum, so that every compartment — 
of the branchial chamber has its walls tapes- 
tried with a respiratory surface, and forms a 
kind of bag lined with innumerable blood- 
vessels, through which the water must int 
its course from the mouth to the ex Open-— 
ings upon the sides of the neck. 

The branchial membrane which thus covers 
the opposed walls that bound the respective” 
cavities into which the gi!l-chamber is divided, 
is entirely made up of numerous plicated, 
cular lamelle, each of which is gathered int 
close-set transverse folds sustaining the minute 
ramifications of the branchial vessels; and thesi 
again may be observed with a lens to be in like 
manner transversely plicated, thus presenting 
in the aggregate a surface of vast extent to thi 
influence ot the respiratory currents. In th 
anterior branchia the vascular layer is of cours 
affixed only to the posterior surface of the st 
porting membrane, the opposite side being st 
ported by cartilaginous rays.* : 


* Monro makes the following calculation rela- 


PISCES. 


In the Sharks the orifices of the pharynx 
leading into the branchial chambers are guarded 
by cartilaginous pyramidal processes ; but in 
the Skates, which have the cartilaginous arches 
much less perfectly formed, no such defences 
are visible. 

The Cyclostomatous cartilaginous Fishes, 
from the peculiarities of their habits, require 
another modification in the construction of 
the organs of respiration, seeing that, whilst 
they rest fixed by their suctorial mouths to 
the surfaces of stones or other foreign bodies, 
or while they are compelled to remain with 
their heads deeply plunged into the flesh of 
the prey upon which they live, the admission 
of water into the mouth and its subsequent ex- 
pulsion through pharyngeal fissures would, in 
their case, be impracticable. 

In the Myxine or Hag-fish the branchial 
apparatus presents externally seven round holes 
placed in a line along each side of the neck, 
and situated very far back in comparison with 
the usual situation of the gill-openings.. Each 
of the seven lateral openings leads internally 
into a flattened circular cavity, which likewise 
communicates by.a special canal with the inte- 
rior of the er. When opened, each gill- 
sac is found to have its lining vascular mem- 
brane gathered into closely set folds, which in 
turn exhibit, when accurately examined, smaller 
plice, and thus a great superficial extent of 
respiratory membrane is secured, much in the 
same manner as in the case of the Raide ; in- 
deed, the general disposition of the whole ap- 
paratus is essentially similar in the two groups, 
the great difference being that whereas in the 
plagiostome genera the water passes in at the 
mouth and out at the gills, in the Cyclosto- 
mata it alternately passes in and out through 
the same orifices by a mechanism which is best 
exhibited in the Lampreys ( Petromyzon ). 

In the last mentioned genus of Cyclosto- 
matous Fishes, the seven holes which lead to 
the breathing organs are seen, on removing the 
skin, to be supported by a curiously contorted 
framework of cartilaginous pieces, which we 
have already noticed as being the exaggerated 
representatives of the sternal ribs met with in 
the Sharks, and which we shall subsequently 
see in a much more highly developed condi- 


tive to the extent of the respiratory surface pre- 
sented by the gills of Fishes to the action of the 
surrounding medium. On each side of the body 
of a Skate, says he, there are four double gills, or 
gills with two sides each, and one single gill; or 
there are in all eighteen sides or surfaces on which 
the branchial artery is spread out. On each of 
these sides there are about fifty divisions or dou- 
blings of the membrane of the gills. Each division 
has on each side of it 160 subdivisions, doublings, or 
folds of its membrane, the length of each of which 
_in a very large skate is about one-eighth of an inch, 
and its breadth about one-sixteenth of an inch, 
so that in the whole gills there are 144,000 subdi- 
visions or folds, the two sides of each of which are 
equal to the 64th part of a square inch, or the sur- 
face of the whole gills in a large skate is equal to 
2.250 square inches, that is, to 15 square feet, an 
expanse equal to the whole external surface of the 
pare body.—Structure and Physiology of Fishes, 
p- 15. 


987 


tion in Branchiostoma. These form a kind of 
elastic thorax around the region of the body 
where the branchie are situated, which is made 
to perform alternate movements of contraction 
and dilatation, whereby the water is perpetually 
sucked in and again expelled through the exter- 
nal openings (fig.521, 2,7). The branchiz them- 
selves (h, h) present nearly the same structure as 
in the Myxine, consisting of as many distinct 


Respiratory apparatus of the Lamprey ( Petromyzon ). 
a, mouth with its teeth; b, phery 5 ¢, opening 
of tube from the back of the head; d, cavity com- 
municating with the respiratory sacculi of both 
sides ; e, commencement of esophagus; f, carti- 
laginous process connected with hyoid tooth, like- 
wise marked d; g, muscles of sucking disc; h, h, 
respiratory cavities and branchiz contained therein ; 
a, i, external openings of do. 3; m, cartilaginous sac 
investing the pericardium. 
sacculi as there are external openings, ranged 
along the sides of the neck, each sacculus having 
its vascular lining membrane finely plicated in 
order to increase the extent of surface to be 
exposed to the respired element. Every bran- 
chial sacculus, in addition to its communica- 
tion with the exterior through the lateral open- 
ings of the neck, has a passage that leads into 
the pharynx (d), so that by the intervention of 
the pharyngeal cavity the respiratory sacculi of 
the opposite sides of the body are made to 
communicate with each other, an arrangement 
which explains the circumstance, that when 
the breathing holes of one side of the Lamprey 
are kept above water, the respired fluid which 
enters the submerged orifices, after traversing 
the pharynx, fills the branchial chambers of the 
gpposite side, and is forcibly ejected therefrom 


988 


through the exposed apertures. There is, more- 
over, another remarkable arrangement in the 
Lampreys, whereby, notwithstanding the sucto- 
rial character of their mouths, the members of 
this genus have the character of their respiratory 
apparatus approximated to that of other races 
of Fishes. This consists in the presence of a 
small tubular orifice situated in the middle of 
the back of the head, just in front of the eyes, 
which leads downwards into the pharynx (6,) 
into which it opens by the orifice c, so that 
water can enter by this passage while the 
mouth is kept immoveably fixed to the surface 
whereunto the Lamprey has attached itself. 

The respiratory system of Branchiostuma is 
highly curious in its arrangement. It may be 
said to consist of two portions, a hyoid appa- 
ratas of a very remarkable kind, and a respi- 
ratory or branchial sac enclosed by a series of 
thoracic ribs, both of which will require a par- 
ticular description before we proceed further 
with this part of our subject. 

Hyoid apparatus. — The hyoid apparatus 
supports the mouth and guards its entrance, 
the oral aperture, which is in the form of a lon- 
gitudinal slit, being bounded on each side by a 
series of hyoid cartilages, each of which consists 
of several pieces articulated together so as to 
form a continuous chain, which gradually 
diminishes in thickness towards its anterior 
extremity. To every one of these pieces is 
attached a cartilaginous arch composed of two 
cartilaginous stems, which are armed with 
delicate denticulations, and covered with a fine 
membrane, which is extended along the base of 
the posterior ones like a thin interdigital web, 
which forms the margin of the mouth. 

Branchial cavity.—This is situated behind 
the hyoid apparatus, and consists of a kind of 
thorax composed of upwards of a hundred 
transparent, cartilaginous, and hair-like arches, 
the upper extremities of which are fixed in two 
streaks of a soft white substance, which runs 
along on each side of the inferior surface of the 
chorda dorsalis on the sides of the inferior lon- 
gitudinal ligament. The inferior extremities 
of the ribs terminate in a more complicated 
manner. Each alternate rib bifurcates. The 
inferior branch on each side meets its fellow of 
the opposite side at an angle in the median 
line, while the superior branch likewise curves 
up and meets the corresponding division of its 
Opposite, while the non-bifurcated ribs, which 
are shorter, terminate in a line with the bifur- 
cation of the neighbouring pairs. There are, 
moreover, slender cross pieces joining the 
neighbouring ribs together, disposed in an 
alternating series like the joinings of stones 

-in masonry. The heart is situated at the 
posterior extremity of the branchial sac be- 
tween its posterior extremity and the com- 
mencement of the liver; it consists, accord- 
ing to Costa, of two delicate cavities situated 
transversely above and a little to the right of the 
intestine. These cavities (“ orecchiette’”) com- 
municate, and the blood passes from one to the 
other, being driven forward by rapid pulsa- 
tions. From the second cavity of the heart 
the blood is driven into the trunk of the bran- 


PISCES. 


chial artery, which is situated between the in- | 
testine and the point of attachment between | 
the branchial ribs and the spinal column, The 
course of the blood is at first rapid and 
distinct, owing to the size of branehi 
artery being considerable; but as it runs for- 
wards, it expends itself in numerous spiral ves- 
sels, which, accompanying all the thoracic arches 
and their transverse attachments, thus present » 
a considerable surface and constitute the bran- 
chie of the fish. Finally, towards the anterior 
extremity of the respiratory cavity the branchial 
artery has become so much reduced in size as 

to be no longer distinguishable. J 

In addition to the extensive surface furnished 
by the respiratory sac there are three vascular 
lamellae situated on each side of the ) 
to which Costa applies the name of o lar 
branchie, believing them to be analogous to the 
branchie attached to the opercula of the Stur- 
geon and other Fishes; these receive their sup- 
ply of blood from an arterial teank that sur- 
rounds the back part of the roof of the mouth. 

Heart.—The heart of Fishes (fig.522, C, A) 
is situated beneath the throat immediately be- 
hind the inferior terminations of the branchial 
arches, where it is lodged in a com 

rtitioned off from the cavity of the abdomen 
i a strong tendinous septum, which forms a 
sort of immoveable diaphragm. In the Lam-. 
preys the heart nee encased A 2 cartila- 
ginous capsule (/ig.521, m) formed by the 
rior faetine of the cartilaginous Cameraman 
surrounds the branchial apparatus. 

In the course of the circulation the heart of 
Fishes is interposed between the systemic 
veins and the organs of respiration, its office 
being to propel the venous blood received 
through the vene cave into the gills, whence it 
is conveyed by the arterial system to be distri- 
buted to the body without the intervention of 
any contractile cavity devoted to its i 
through the arterial trunks. Fora diagram of 
the course of the circulation in Fishes the 
reader is referred to fig. 319, vol. i. 

The heart of a fish is therefore at once distin- 
guishable from that of any other vertebrate ani- 
mal by the circumstance of its consisting ofonly — 
two cavities, an auricleand a ventricle, the former 
of which receives the blood from the body, while 
the latter diffuses it over the branchial surfaces. 
The auricle (fig. 522, C) is very capacious, — 
having its walls made up of intercrossing mus- 
cular fibres, which from their frequent decussa- — 
tions present internally a reticulate appearance. 
It receives the venous blood from a sinus (D), 
formed by the conjoined cave through a — 
orifice, which is guarded by two large semilu- 
nar valves, arranged so as to prevent the reflux 
of blood into the veins. te” 

The ventricle is considerably smaller tha 
the auricular cavity, with which it communi- 
cates by a wide lateral orifice. Its shape it 
the osseous Fishes is most usually somewhat 


four-sided, and its muscular walls, considerably — 
thicker than those of the auricle, present inter 
nallya strong fasciculated appearance. Theau- — 
riculo-ventricular opening is generally guarded 
by two strong valves ordinarily of a semilunar 


PISCES. 


shape, but sometimes, as for example in the 
Sturgeon, resembling the tricuspid valve of the 
heart in Mammalia, having chorde tendinee 
passing from its margin to the muscular walls 
of the ventricle. 

In other cases again, as in the Sun-fish 
( Orthagoriscus Mola), the auricular aperture 
is guarded by four valves, two small semilunar 
valves being placed at right angles with and on 
the auricular side of the two large semilunar 
valves that usually exist in this situation. 

The branchial artery (fig. 522, B) which arises 
from the ventricle is very different in character 
from an artery of ordinary appearance, its walls 
being exceedingly thick and muscular, and fre- 
quently fasciculated internally ; its cavity is more- 
over dilated so as sometimes to equal in capacity 
that of the ventricle itself. This dilated portion 
of the branchial artery, to which the name of 


bulbus arteriosus has been given, is in fact 
almost equivalent to a second ventricular cham- 
ber, and doubtless by its contractile power 
forcibly assists in propelling the blood through 
the gills. 

The origin of the bulbus arteriosus is always 
guarded by strong valves, of which there are fre- 
quently only two of a semilunar form, but occa- 
sionally the valve is made up of four semilunar 
membranous folds. 

But it is not only at the commencement of 
the bulbus arteriosus that valves exist, these 
defences being frequently multiplied in this 
portion of the circulating system of Fishes in a 
very extraordinary manner. Thus, in the Stur- 
geon there are three series of semilunar valves, 
two at the commencement and one at the ter- 
mination of the bulb, the last being the strong- 
est and most perfectly formed. Those at the 
base are much thickened at their margins, 
which are attached to the parietes of the bulb 
by small chorde tendiner. The two lower 
valves are each made up of four semilunar 
folds, whilst in the upper one there are five. 
In the Skate ( Raia Batis) there are five dis- 
tinct sets of valves, increasing in size to the 
last row, which is at the termination of the 
bulb. 

The most probable reason of this unusual 


Heart and principal vessels of Perch. 


989 


fortification of the valvular apparatus of the 
branchial artery in Fishes is that, owing to the 
depth to which some of them descend or at 
which many races dwell habitually, as for ex- 
ample, the ground-frequenting Skates, the pres- 
sure upon the surface of the gills must render 
the passage of the blood over the branchie very 
difficult, so that unusual care has been taken in 
strengthening the bulbus arteriosus itself, and 
likewise the valvular structures in its interior. 

The bulbus arteriosus ultimately resolves itself 
into the branchial artery, which gives off the 
trunks that supply the venous blood to the 

ills. 

" Vascular system.—The general course of the 
blood during its circuit through the body of a 
fish has been already described in a preceding 
article (see CIRCULATION); we shall therefore 
limit ourselves in this place to describe the dis- 
position of the principal vas- 
cular trunks, and the manner 
in which the circulating fluid 
is distributed to different parts 
of the system. The vessels 
formed by the division of the 
branchial artery run in a deep 
groove along the convexity of 
each branchial arch external to 
the branchial vein, which runs 
in the same groove, taking an 
opposite course. The bran- 
chial vein, as we have already 
seen, is formed by collecting 
all the venules from the bran- 
chial lamine of the corre- 
sponding gill, and thus carries 
only the blood which has un- 
dergone the process of respira- 
tion. The branchial artery and 
the branchial vein are therefore 
placed under precisely inverse circumstances 
with respect to each other; the former dimi- 
nishing continually in size as it mounts upwards 
towards the dorsal aspect of the gills by giving 
off arterioles to the branchial laminz ; the latter 
increasing in bulk as it proceeds in the same 
direction, owing to the constant accession of 
little veins derived from the fringes of the gills. 
In the Skates there are two branchial veins to 
each gill, which, however, ultimately become 
united into one trunk. 

No sooner do the branchial veins issue from 
the dorsal extremities of the branchial arches 
than they assume the texture and the function 
of arteries, and ultimately all joining with 
each other and with those of the opposite 
side, they constitute by their union the aorta, 
by which the blood is distributed to the general 
system. Before their union into a single aortic 
trunk there are arterial vessels given off from 
the branchial veins themselves; thus the ante- 
rior give off, even before they leave the branchial 
arch, several vessels to supply the head and ad- 
jacent parts, while the heart itself and the neigh- 
bouring region beneath the throat likewise re- 
ceive their supply of arterial blood through a 
twig derived immediately from a branchial vein. 

The aorta, formed, as has been stated, by the 
union of all the branchial veins without the inter- 


990 


PISCES. 
Fig. 523. 


Lepidosiren. 


position of any contractile organs corresponding 
with the left side of the heart of Mammalia, 
immediately proceeds to give off branches to 
the trunk and abdominal viscera. Almost 
close to its commencement it sends into the 
abdomen the large visceral trunk, which sup- 
plies all the abdominal viscera with blood, 

ing distributed to the liver, to the stomach, 
to the intestines, to the spleen, to the generative 
organs, and to the swimming bladder. 

After giving off the above large visceral ar- 
tery, the aorta continues its course backwards 
beneath the bodies of the supra-abdominal ver- 
tebre ; but as soon as it reaches the post-abdo- 
minal vertebre, it enters the canal formed by 
their inferior arches (hemapophyses), through 
which it passes backwards to the tail. During 
its passage through the abdomen the aorta fur- 
nishes arteries right and left to the kidneys, 
between which it lies; but with this exception 
all its branches, which are given off opposite 
each vertebra like the intercostal arteries of 
the human subject, are distributed to the mus- 
cles of the trunk. 

Venous system.—All the arteries given off 
from the aorta are accompanied by correspond- 
ing venous branches, through which the blood 
is returned into two large veins, one above and 
the other beneath the vertebral column. The 
former running with the spinal cord in the su- 
perior vertebral canal, the other being in con- 
tact with the aorta through its whole length, 
these great veins frequently intercommunicate by 
means of inosculating branches, and the inferior 
one ultimately terminates in the great venous 
sinus that opens into the auricle of the heart. 
This sinus likewise receives through several 
different trunks the veins from the liver, from 
the generative organs, from the kidneys, from 
the pectoral and ventral fins, from the branchial 
organs and other parts of the throat, and like- 
wise from the head, the blood derived from the 
head having been previously collected in a 
large sinus. 

The highest form of the respiratory and cir- 
culatory apparatus met with in Fishes is found 
in the Lepidosiren, a remarkable genus found 
in the river Amazon and in the Gambia.* In 
this interesting creature the gills of the fish are 
combined with rudimentary air-sacs which per- 
form the office of lungs, and, in fact, the whole 
arrangement of its circulatory system approxi- 
mates so nearly that of the amphibious reptiles 
that, were it not for its otherwise completely 
icthyic characters, it might almost be regarded 


* Professor Owen, Description of Lepidosiren 
annectens. Trans. of Linnxan Society, vol. xviii. 


as belonging to that order of Reptilia with 
which it forms an interesting link of connec- 
tion. The branchie of the Lepidosiren consist 
of separate elongated filaments attached by one 
extremity to the branchial arches, which are 
four in number. These cartilaginous branchial 
arches are developed on each side in the sub- 
mucous tissue, and are not attached either to the 
os hyoides below or to the cranium above. The 
membrane covering the third, fourth, and fifth 
arches is minutely papillose, while the margins 
of the first and second are finely denticulated, 
and between these are five branchial apertures, 
or interspaces, through which bristles are repre- 
sented as passing in the accompanying figure, 
(ig 524, 1, 2, 3, 4, 5.) 

he gills do not form 
any external projection 
as in the gill-bearing 
Perennibranchian Am- 
phibia, but are con- 
tained in a moderately 
capacious __ branchial 
chamber, the ietes 
of which are formed by 
a mucous and muscu- 
lar stratum, the external 
outlet being a vertical 
slit situated immedi- 
ately anterior to the 
filamentary _ pectoral 
limb. 


Fig. 524. 


observes 
Professor Owen, “ al- 
though the organs of re- 
spiration through the 
medium of water cor- 
respond in all essential ° 
points with those of the 
true fishes, yet the gills 
approximate in their 
filamentary form to 
those of the Perenni- 
branchiate Reptiles. 
And again, although 
the gills are four in 
number on each side, 
as in the osseous fishes, 
yet the number of 4 
branchial —_ apertures 
and arches corresponds 
with that which cha- 
racterizes the higher 
cartilaginous fishes. So 
that, while we perceive, 
even in the organs for 
breathing water, a ten- 


larynx ; f, laryngeal or 

thyroid cartilage ; 1,2, 
3, 4, 5, interspaces be- 
tween branchial arches. 


PISCES. 


dency towards the amphibious type, we find 
at the same time that the branchial as well 
as the osseous system manifests a most interest- 
ing transitional structure between the plagios- 
tomous and osseous fishes. We have next to 
consider that part of the respiratory system 
which is organized for breathing immediately 
the atmospheric air, or the lungs; for I do not 
know how otherwise to designate, according 
either to their physiological or morphological 
relations, those organs which in the technical 
language of the ichthyologist would be termed 
the swimming orair-bladder. The trachea, or to 
use the same technical and partial nomenclature, 
the “ductus pneumaticus,” is a wide short 
membranous tube, as in the Perennibranchiate 
Reptiles. The glottis (fig. 524, e,) opens 
near the posterior part of a long rudimental 
thyroid cartilage (f): a few lines posterior to the 
_ isthmus faucium the opposite end of the trachea 
dilates into a membranous sac, which commu- 
nicates by two large lateral apertures with the 
lungs. These are widest at their anterior extre- 
mities, and gradually decrease in diameter to 
the cloaca, behind which they terminate each 


Fig. 525. 


Respiratory and circulatory apparatus of Lepidosiren 

annectens, after Owen. 

a, auricle; 6. ventricle laid open to show the ter- 
mination of the vena pulmonalis, in which a 
black bristle is placed; ¢, bulbus arteriosus laid 
open; d, pericardium; e, vena cava abdomi- 
nalis; f, vena pulmonalis; 1, 2, 3, 4, 5, 6, 
branchial arteries of left side; m, pulmonary 
artery; ”, pulmonary vein. 


in an obtuse point (fig. 525). They are 
lodged in the dorsal angle of the abdominal 
cavity behind the kidneys, and are attached by 
cellular tissue to all the surrounding parts, and 
especially to the ribs, of which they bear the 
impressions on their posterior surface. The an- 


991 


terior part of each lung is divided into four or 
five small lobes, behind which it takes on the 
form of a simple compressed bag, and so con- 
tinues to its posterior extremity. The parietes 
of the lung present a moderate thickness 
throughout, and the whole of the internal sur- 
face is cellular, the cells having the same pro- 
portional size and form as in the respiratory 
portion of the lung of a serpent. The cells 
are largest and most subdivided at the anterior 
part of the lung, the livid colour of which, in 
the specimen dissected” by Professor Owen, 
“attested the great vascularity of the part.” 

In tracing the arrangement of the circulatory 
system of the Lepidosiren the same interme- 
diate type of structure is most interestingly 
conspicuous. The heart consists of an auri- 
cle, (fig. 525, a,) ventricle, (b,) and a bul- 
bus arteriosus. The vena cava (e) termi- 
nates in the right side of the auricle; it is 
joined by the two superior cave and by the 
single large pulmonary vein; this vein (f)) 
does not, however, communicate with the sinus, 
but passes along entire and adherent to the 
inner surface of the vena cava as far as the 
auriculo-ventricular aperture, where it empties 
its contents into the ventricle by a distinct 
orifice protected by a cartilaginous valvular 
tubercle. It needed only that the pulmonary 
vein should have been dilated before its termi- 
nation, in order to have established a bi-auri- 
cular structure of the heart, as in the Amphi- 
bious Siren. The same functional advantage 
is, however, thus secured to the Lepidosiren 
with a maintenance of the simple dicelous 
type of the heart of the fish ; this continuation 
of the pulmonary vein preventing the admix- © 
ture of the respired with the venous blood, 
until both have arrived in the ventricle. 

The ventricle (fig. 525, b) is extremely 
small; its parietes are thick and reticularly 
muscular; a small round orifice leads to the 
bulbus arteriosus (c). This is formed by a 
short spiral turn of the dilated aorta, which is 
concealed under a simple continuous fibrous 
coat. The area of this part of the vessel is 
almost entirely occupied by two continuous 
valvular projections or their processes, which 
are attached by one edge to the internal sur- 
face of the aorta, and have the opposite margin 
projecting freely into the arterial cavity. 

The aorta in this remarkable species fulfils 
at once the office of a systemic, a branchial, 
and a pulmonary artery ; it distributes on each 
side six vessels, (fig. 525, 1, 2, 3, 4, 5, 6,) 
corresponding to the six branchial cartilaginous 
arches. The mucous membrane is produced 
into a branchial fringe on the convex side of 
the first, fourth, fifth, and sixth branchial arches, 
and the corresponding arteries are minutely sub- 
divided before they are continued to the dorsal 
side of the pharynx ; these four pairs of vessels 
are therefore true or functional branchial arte- 
ries. The mucous membrane merely invests 
with a simple fold the second and third bran- 
chial arches; and the corresponding arterial 
trunks undergo no subdivision as they wind 
round them, but are continued entire (as in the 
Amphiuma and Menopoma) to their termina- 


992 


tion at the opposite side of the vascular circle. 
The branches which afterwards unite to form 
the single pulmonary artery on each side are 
given off from near the termination of the 
second and third pairs of the primitive aortic 
trunk, which thus combine the functions of 
both systemic and pulmonary arteries. The 
rons artery, formed by the union of the 

ranches from the second and third branchial 
arteries, descends between the vena cava (fig. 
525, e) in front, and the left branch of the 
vena pulmonalis (f') behind to the interspace 
to the lungs; here it distributes branches to the 
anterior lobes, and then divides; each division 
extends along the mesial side of its correspond- 
ing lung to the extremity. The blood distri- 
buted by the capillaries of this artery over the 
cells of the lung is collected into a vein (7) 
which returns along the lateral or outer margin 
of the lung as far as the commencement of the 
lobulated part; here it crosses obliquely the 
anterior surface of the lung and unites with its 
fellow. The common pulmonary vein runs 
parallel with and behind the vena cava for a 
few lines, then obliquely pierces the pericar- 
dium, and enters the sinus formed by the ex- 
pansion of the vena cava, and continues attached 
to the parietes of that sinus till it reaches the 
auriculo-ventricular aperture, where it termi- 
nates close behind the cartilaginous knob 
before mentioned.* 

Portal system of veins—All the blood de- 
rived from the stomach, from the intestines, 
and from the spleen, is collected into one or 
sometimes into several trunks, which convey it 
into the liver for the elaboration of bile pre- 

' cisely as in other races of Vertebrata. In some 
genera, however, more especially the Cypri- 
nide, the lobes of the liver are so intervolved 
with the intestinal folds, that the venous blood 
from the intestines enters the liver through 
innumerable small branches, none of which 
are of sufficient size to be regarded as a main 
trunk of the portal vein. Rathke,ft indeed, 
observes, in relation to this subject, that 
the vena porte of Fishes exhibits a kind of tran- 
sition in its arrangement, a sort of tendency to 
perfection indicated by progressive concentra- 
tion of the venous trunks according to the fol- 
lowing ‘scale:—As an improvement upon the 
portal system of the Ciprinide, in Cottus scor- 
pio all the veins bringing the blood from the 
abdominal viscera form three aie trunks, 
which enter the liver separately. In Cobitis 
Jossilis most of these veins are found united 
into two trunks, which penetrate the liver sepa- 
rately; but besides these there are some strag- 
gling branches which keep themselves inde- 

ndent of the two great veins. In the Blenny 
and the Pike there are only two portal trunks. 
In the Lump-fish, the Shad, c., the two 
trunks are united into one; but there are still 
small veins which run isolatedly into the sub- 
stance of the liver; and lastly, in the Eel, the 
Perch, &c., there is only one vena porte, as in 
the most highly organized vertebrate animals, 


* See Professor Owen’s paper, ubi supra. 
+ Annales des Sciences Nat, tom. ix. p. 170. 


PISCES. 


There is a remarkable circumstance connected 
with the great venous trunk above alluded to 
which accompanies the spinal cord lodged in 
the superior vertebral canal, for this vein, al- 
though it receives a good proportion of the 
blood derived from the muscles of the upper 
part of the trunk, does not empty itself into the 
venous sinus of the heart, and, from the cireum- 
stance of its giving off numerous large branches 
to the substance of the kidney, has been re- 
garded as forming a renal portal system, similar 
to that described by Jacobson as existing in 
Birds. It must, however, be observed that this 
superior vein communicates very freely with the 
inferior vein, which indubitably represents the — 
vena cava inferior, and consequently the renal 
branches may be derived from, and not distri- 
buted to, the kidney. fed 

Lateral system of vessels—Dr. Marshall 
Hall discovered some years ago a peleing, 
cavity or heart situated near the caudal extre- — 
mity of the vertebral column of the Eel, the con- 
tractions of which were found to be quite inde- 
pendent of the pulsations of the branchial heart, 
this organ beating 160 times in a minute, while — 
the pulses of the branchial heart were only 60. 
This structure, the existence of which only was 
pointed out by Dr. Marshall Hall, has since 
been carefully investigated by M. Hyrtl,* 
and the following is the result of that gentle- 
man’s explorations. The organ in question is 
easily seen by stretching out the tail of an Eel 
upon a piece of glass, to which it readily ad- 
heres owing to the viscid secretion furnished by 
the skin. Its pulsations are very lively, and it 
seems surrounded by a transparent areola, which — 
eee to M. Hyrtl to consist of two 

e disorganization of, the spinal marrow by 
means of a wire had no effect upon the number 
of its pulsations, and even when the branchial 
heart was tied or the animal cut in two, the 
caudal heart continued to beat for five or six 
minutes. The genera in which the caudal 
heart and the apparatus connected with it 
were examined, were Accipenser, Salmo, P. 
Abramis Leuciscus, Gadus, Gobio, Silurus 
Esox, Cyprinus, Zeus, Lophius, and sever 
others, so that doubtless the system unde 
consideration is common to the whole class 
Fishes. ; 

Brain.—The encephalon of Fishes is remark 
able for its diminutive size in proportion to th 
dimensions of the animal, and also with rela 
tion to the nerves which are derived from it 
in fact it occupies but a very small portion ¢ 
the cavity of the cranium, the wide interval exi: 
ing between its surface and the dura mater th 
lines the cranial parietes being filled up w 
loose cellulosity filled with fluid, and sor 
times containing abundance of oil, or in certa 
instances, as for example in the Sturgeon ar 
Tunny, of a compact and fatty substance. — 

It has been remarked that this interval 
tween the cranium and the surface of the br 
is much less in young subjects than in adults. 


acs. 


* Archiv. fiir Anat. Phys. und Wissenscha 
eat herausgegeben von J, Muller. 


PISCES. 


circumstance which proves that their brain does 
not grow in the same proportion as the rest of 
the body; indeed Cuvier found the dimen- 
sions of the brain nearly similar in individua!s 
of the same species, though one might be 
double the size of the other. 


Fig. 526. 


Brain of Perch, upper surface. (After Cuvier. ) 


a, cerebellum; b, hollow (cerebral) lobes ; ¢, ol- 
factory lobes; other letters as in the two following 
figures. 


The encephalon consists of a series of lobes 
situated one behind the other (fig. 526), con- 
cerning the precise analogies of which no two 
authors seem to be agreed. In the following 
account of its general structure we shall there- 
fore closely adhere to Cuvier’s masterly analysis 
of the organization of the brain of the Perch, at 
the same time, however, noticing the opinions 
of anatomists, and the principal variations, ob- 
servable in other Fishes, from the form of brain 
selected for special description. 

The anterior pair of lobes (figs. 526, 527, c,c ) 
invariably give origin to the olfactory nerves, and 
consequently are very generally called the olfac- 
tory lobes of the brain. Their surface is most 
frequently smooth, but occasionally marked, as 
for example in the Cod, with slight sulci. 
Their relative size varies very much, but they 
are generally, but not always, smaller than the 
succeeding pair of lobes (6,6). They are con- 
nected with each other inferiorly by a commis- 
sure, which is sometimes double, and the in- 
ternal fibres of the medulla oblongata may be 
distinctly traced into their substance. 

In front of these olfactory lobes there are gene - 
rally one and sometimes two pairs of ganglia 
(figs. 526, 527, 528, i, 7) connected with the 
origins of the olfactory nerves, which, when very 
large, might be mistaken for additional lobes of 
the brain. They are, however, never connected 
by commissural fibres to their fellows of the 
opposite side, and the olfactory nerve can be 
traced along their under surface as far as the 

roper anterior lobes of the encephalon (c, c ). 

nternally they frequently present a ventricular 
cavity, which communicates beneath the ante- 
rior commissure with that of the cerebral masses 
next to be described. 

The second pair of cerebral lobes (figs. 526, 
527, 528, b, b) are of an oval form, and are re- 
markable from the circumstance that they enclose 
a wide cavity or ventricle, whence they have been 
designated by some anatomists the hollow lobes 
(fig. 527, b). They consist, like the cerebral 
lobes of the higher Vertebrata, of two layers, 
which are generally easily separable ; the outer 
layer consisting of grey or cineritious matter, the 
inner layer of the white or fibrous substance of 
the brain, the fibres of the latter running trans- 

VOL. III. 


- 


993 


versely so as to line the roof of the ventricular 
cavity, which is common to both sides of the 
brain; for although the hollow lobes are united 
to each other superiorly along the median line so 
as to form a kind of corpus collosum with a me- 
dian raphé, there is no septum between the two 
sides. The fibres lining the ventricular cavity 
seem to emerge from two semicircular bands of 
grey matter (fig. 527, h, kh.) situated upon the 
floor of the ventricle. 


Brain of Perch, with the ‘« hollow lobes” laid open, 
and the cerebellum turned to the right side. ( After 
Cuvier. ) 

Letters a, b, c, as in last figure ; g, supplementary 
cerebellic lobes; A, fibres lining the ventricular 
cavity. 


At the bottom of the ventricular cavity there 
are likewise, in osseous Fishes, two or four 
tubercles of grey substance placed in front of 
the base of the cerebellum, and arching over 
the canal which leads from the large cavity 
contained in the hollow lobes into the ventricle 
behind the cerebellum, which it is impossible 
to consider as anything else but the representa- 
tive of the fourth ventricle of the superior classes 
of animals, and the canal of communication as 
the “ iter a tertio ad quartum ventriculum” of 
the human anatomist, the tubercles themselves 
being evidently the homologues of the tubercula 
quadrigemina. 

The external fibres of the medulla oblongata 
are easily traceable into the lobes we are now 
considering, which, moreover, are connected 
with each other by a broad commissure exactly 
corresponding in situation with the anterior 
commissure of the human brain. There can, 
therefore, be no reasonable doubt that the 
“ hollow lobes” of the Fish’s brain represent 
the cerebral hemispheres of the encephalon of 
Reptiles, Birds, and Quadrupeds, and, with 
the data above given before us, it is not difficult 
to point out the analogies of the remaining parts 
not displayed in the figure. Thus, immedi- 
ately behind the commissure is a passage 
leading into the cavity, which corresponds to 
the third ventricle, and which leads as usual to 
the infundibulum and towards the pituitary 
body that occupies its usual situation at the 
base of the brain. 

The internal fibres of the medulla oblongata 
may be traced forwards into these hollow cere- 
bral lobes, in which they spread out as in the 
higher animals. 

At the inferior surface of the brain, beneath 
the “ hollow lobes” just described, are two oval 
protuberances ( fig. 528, e, e), which are desig- 
nated by Cuvier the inferior lobes, between the 
anterior extremities of which is situated the 

3s 


994 


pituitary body (f). These inferior lobes are 
generally of considerable size, of an oval or 
kidney shape, and sometimes, but rarely, con- 
tain ventricular cavities, which communicate 
with the third ventricle, and through it with 
the great ventricles contained in the “ hollow 
lobes ;” they furnish fibres of origin to the 
optic nerves, and it is from the fissure between 
them and the medulla oblongata that the nerves 
of the third pair take their origin. 


Fig. 528. 


Brain of Perch, lower surface. (After Cuvier.) 

Letters a, b,c, g, h, as in preceding figures; e, 
inferior lobes ; f, pituitary body ; i, swelling at com- 
mencement of olfactory nerve ; m, optic nerves; 0, 
olfactory ; p, g, r,s, t, encephalic nerves. 


The pituitary body (fig. 528, f) occupies its 
usual position on the base of the brain at the 
extremity of the infundibulum; it is generally 
of large size in Fishes, and is often connected 
with membranous and vascular appendages of 
various forms,—a circumstance which is, how- 
ever, most remarkable in the cartilaginous 
Fishes. Occasionally, as for example in the 
Lophius and the Haddock, the infundibulum 
is prolonged into a slender filament, and the 
punisey body is removed very far forward ; 

ut the uses of these parts are as problematical 
in Fishes as in the other classes of Vertebrata. 

The cerebellum (figs. 526, 527, a) in osseous 
Fishes is of considerable size, but consists of 
the median portion only, no lateral lobes being 
as yet developed, or at least they are only indi- 
cated by slight eminences. Its shape is gene- 
rally that of a blunted cone, the apex of which 
is bent backwards; but there are instances, as 
for example the Mackarel, in which it is di- 
rected forwards, and sometimes it extends so 
far forwards as to overlap all the rest of the en- 
cephalon. Owing to the deficiency of the la- 
teral lobes of the cerebellum there are of course 
no traces of a pons Varolii. 

Behind the cerebellum, on each side of the 
fourth ventricle, and sometimes even covering 
that cavity, are certain supplementary lobes 
’ (fig. 527, g ) which would seem to be peculiar 
to Fishes, and which are very variable in their 
proportions, forms, and connections. In most 
osseous Fishes they consist of two protuber- 
ances or swellings of the sides of the medulla 
behind the cerebellum, which touch each other 
along the mesial line or are united by a com- 
missure. 

In the Cyprinide their volume is so consi- 
derable that they cover the greater part of the 
medulla oblongata, and their sides are furrowed 
with transverse strie In the Grey Mullet they 
are also very large, and their surface is marked 
with tortuous sulci, giving the appearance of 
cerebral convolutions. It is, however, in the 
Trigle or Gurnards that these lobes are most 
largely developed, amounting in number to as 


PISCES. 


many as five on each side, and occupying a 
space equal in length to all the rest of the 
encephalon, and extending backwards as far 
as the second vertebra. It is from the last — 
of these lobes that the second pair of spinal — 
nerves is given off, which in this genus supplies — 
the free rays situated in front of the 

fins.* 

In the chondropteryginous Fishes the strue- 
ture of the encephalon offers many remarkable — 
peculiarities. Thus, in the Rays and Sharks the — 
proportionate size of the olfactory lobes is enor- 
mous, and instead of simply having a commis- 
sural communication with each other, are 
consolidated into one mass. The hemis 
enclose a capacious ventricle, but there are no 
distinct fibres visible upon its inner surface, 
neither are the representatives of the tubercula- 
quadrigemina of osseous Fishes apparent. The 
cerebellum is of great relative size, but of very 
variable form in different species; and not 
unfrequently it is divided into lamine by deep 
transverse sulci. The supplementary lobes 
behind the cerebellum are represented by folds 
or cords of nervous matter, which are ; 
from each side of the posterior edge of the 
base of the cerebellum and run backwards 
along the margin of the fourth ventricle. A 

The brain of the Tunny ( Thynnus vulg. 
Cuv). is remarkable for the extent of the cer 
bellum, and the complication of the internal 
tubercles. The olfactory nerves are small and 
oval. The hollow or cerebral lobes are of very 
great size, and nearly spherical, with a lateral 
fissure inferiorly. On opening them, instead of 
the tubercles generally met with in Fishes, 
there is found on each side a mass divided into 
three lobes, which are themselves grooved with 
a fissure, so that the whole resembles a cylinder 
or cord having six folds, twelve in all. 
cerebellum is larger than the rest of the ence- 
phalon, and, arising from the medulla oblon 
gata, curves forwards, overlaying both the 
hollow lobes and the olfactory lobes even as fa 
as the anterior extremity of the latter, its bread 
being little less than half its length. At 
posterior part of its base there is on each sid 
a rounded protuberance, different in characte 
from those enlargements which are frequentl 
met with in other Fishes at the commencemer 
of the medulla oblongata. : 

Nervous system.—The olfactory nerves (, 
529 ) arise from the olfactory lobes of the braii 


* The various names applied by different a 
to the different parts described above are calcula 
to create great embarrassment and confusion. Th 
Haller in his ‘ Physiology,” and likewise in_ 
“ Opera Minora,’ calls the lobes (¢, ¢ ) anterior ol} 
tory tubercles, the lobes (e, e) inferior olfactory 
bercles, the hollow lobes (0, 6) optic 7 
M. Arsaki, in his thesis ‘ De cerebro et med 
spinali pisciam,’ calls the hollow lobes (6, 6) tub 
cula quadrigemina, and regards the anterior | 
(c, c) as the representatives of the hemisphe 
M. Weber, in his ‘ Anatomia comparata nervi § 
pathetici,’ whilst he recognizes the hollow 1 
(6, b) as the cerebral hemispheres, regards # 
cerebellum (a) as the analogue of the tuberci 
quadrigemina, and the supplemen lobes 
at the commencement of the medulla oblong 
representing the cerebellum, : 


ba 


PISCES. 


and vary much in their size and composition in 
different Fishes. For the most part they are 
simple, but sometimes double or triple; and 
occasionally they are composed of numerous 
filaments united into fasciculi. Generally they 
present a ganglionic enlargement just after their 
origin from the brain, or immediately before 
their termination in the olfactory organ, to the 
plicated folds of the lined membrane of which 
they are ultimately distributed. 

2. Theoptic nerves (fig. 529, 2) arise from 
the second pair of the great cerebral masses, 
which from this circumstance have been called 
the optic lobes of the brain. Shortly after their 
origin the two nerves cross each other, but in 
the generality of osseous Fishes this is effected 
without any union of substance, the two nerves 
being simply united by cellular tissue (fg. 
528,”). In the Skates, however, a commissure 
exists similar to that which is met with in the 
higher Vertebrata. In some Fishes each optic 
herve consists of a broad flat nervous band 
folded upon itself like a fan, and enclosed in a 
tube of neurilemma derived from the dura 
mater; but in others their structure resembles 
that which exists generally in the higher ani- 
mals. 

3. The third pair or motor oculi (fig. 529, 3) 
arises from the medulla oblongata in the track 
of the pyramidal bodies, and is distributed, as 


995 


in other Vertebrata, to all the muscles of the >| 


eye, with the exception of the superior oblique 
and external rectus. It likewise furnishes cili- 
ary nerves, but no ophthalmic ganglion has yet 
been discovered in the class before us. 

4. The fourth pair (fig. 529, 4) arises just 
behind the posterior point of the optic lobe from 
the roof of the ventricle, and terminates in the 
superior oblique muscle cf the eye. 


5. The fifth pair of nerves (fig. 529, 5) G 


arises from the sides of the fourth ventricle 
near the base of the cerebellum. It issues from 
the cranium through a foramen in the great alar 
bone, and is distributed as follows:—1. It gives 
off an ophthalmic branch which runs along 
the roof of the orbit, and passing on towards 
the nose is distributed to the adjacent parts of 
the face as far as the snout and intermaxillary 
bone. 2. A superior maxillary branch, which 
passes under the eye to be distributed to the 
cheek and to the superior maxilla; it likewise 
sends a branch towards the nostrils and anas- 
tomoses with the pterygo-palatine nerve. 3. 
An inferior maxillary branch, which is fre- 
quently only a division of the preceding: this 
gives filaments to the posterior part of the 
palate, and passes on to the inferior maxilla 
and its dental canal. Frequently the palatine 
filaments proceed from a special branch. 4, A 
pterygo-palatine branch, which runs forwards, 
crossing the floor of the orbit beneath the 
muscles of the eyeball, follows the course of 
the vomer, and passes beneath this bone and 
the os palati to terminate at the end of the 
muzzle, where it is frequently joined by re- 
markable anastomoses with the superior maxil- 
lary branch. 5. An opercular branch, which 
passes through a canal in the os temporale 
and gives branches to the temporal muscle, 


Brain and cerebral nerves of Cod.fish ( Gadus mor- 
rhua), (After Swan. ) 

a, olfactory lobes; 6, hollow or cerebral lobes ; 
c, cerebellum; d, medulla oblongata ; e, olfactory 
apparatus ; f, eye-ball ; g, superior oblique muscle ; 
h, external rectus; the numbers lL, 2,3, 4, &c., in- 
dicate the corresponding cerebral nerves. 


to the cheek, to the muscles of the operculum, 
and to the operculum itself; it then penetrates 
internally to join with branches of the inferior 
maxillary divisions and to supply filaments to 
the branchiostegous membrane. 6. The fifth 
pair almost invariably gives off a branch which 
mounts to the upper part of the cranium, and 
joining a branch of the eighth issues 
38 


996 


through a foramen formed by the parietal and 
interparietal bones, and runs along the whole 
length of the back on each side of the dorsal 
fins, receiving in its course filaments from all 
the spinal nerves, and giving off branches 
to the muscles and rays of the fins of the 
back. This branch is superficial up to the 
point where it plunges beneath the little ex- 
ternal muscles of the fin-rays, and it sometimes 
gives off branches which are equally superficial, 
and that descend to the muscles of the trunk 
above the pectoral fins, and others which run 
backwards as far as the anal fin, where they 
form a longitudinal nerve resembling that of 
the back. Such is the general arrangement of 
this remarkable nerve, but it is by no means 
invariably so: thus, in the Carp it seems to 
proceed from the eighth pair, and not from the 
fifth. In the Silurus, on the contrary, it ema- 
nates from the fifth alone, while in the Perch, 
Cod, &c. it is derived, as has been described, 
equally from both these sources. 

6. The sixth pair of nerves, or abducens, (fig. 
529, 6) takes its origin, as in other Vertebrata, 
from the inferior surface of the medulla oblon- 
gata, and is entirely appropriated to the external 
rectus muscle of the eye. 

7. The seventh pair of nerves (fig. 529, 7) is 
appropriated, as in other Vertebrata, to the 
sense of hearing. It arises from the medulla 
oblongata between the fifth and eighth pairs, 
and is distributed over the sacculi which con- 
tain the otolithes and the ampulle connected 
with the semicircular canals of the ear. It has 
likewise connections with the last branch of 
the fifth pair, and one which is especially con- 
stant with the glosso-pharyngeal division of the 
eighth pair of nerves. 

8. The roots forming the eighth pair (fig. 529, 
8), or nervus vagus, are collectively almost as 
large as the fifth, behind which they take their 
origin generally by numerous filaments that 
issue in a single line, that runs longitudinally 
along the sides of the medulla oblongata be- 
neath the lobes situated behind the cerebellum, 
and which unite into a ganglion (fig. 530, ¢) 
before its divisions are given off. 

The distribution of the eighth pair of nerves 
in Fishes affords a striking example of the con- 
stancy with which a nerve presides over the 
same functions in every class of vertebrate 
animals, 

The glosso-pharyngeal issues from the cra- 
nium sometimes through an aperture in the 
lateral occipital, sometimes through a foramen 
in the petrous bone, and supplies the first 
branchia and the parts in its immediate vici- 
nity, whence it passes forward to the tongue, 
in which it is ultimately expended. 

The nervus vagus properly so called leaves 
the cranium through a special foramen in the 
lateral occipital bone, and soon dilates into a 
large ganglion, from which nerves proceed to 
supply the three last branchie and the inferior 
parts of the pharynx. The trunk of the nerve 
then passes on along the pharynx and ceso- 
phagus as far as the stomach, which it likewise 
supplies. This distribution, as will be seen, 
is similar to what is found to exist in all the 


PISCES. 


vertebrate classes as far as relates to the func- 
tions over which the nerve presides, although 
its arrangement is necessarily modified in con- 
sequence of the changed position of the respi- 
ratory organs. The eighth pair of nerves gives 
off one important branch, and sometimes two, 
the relations of which with what is met with 
in the superior classes are not so apparent. 
The first oF these is a branch which arises 
sometimes from the anterior roots of the S, 
and sometimes from the posterior margin of its 
ganglion, and runs ina straight line as far as 
the tail. In many Fishes, after having given — 
off a superficial filament which follows the 
commencement of the lateral line, the trunk 
of the nerve passes straight backwards im- 
bedded in the thickness of the lateral mus- 
cles, between the ribs and their appendices, — 
receiving special filaments from every one of — 
the spinal nerves quite distinct from the inter-— 
costals, and giving off branches to the skin, — 
which pass through all the intervals between — 
the muscular layers. In other cases, as in the 
Cod-fish represented in the figure, it is super 
ficial throughout its whole course, and a= 
rently has no communication with the spinal 
nerves, although perhaps such communications 
may exist in the shape of very delicate fibrille. 
The second remarkable branch is that already 
described as joining an offset from the fifth to” 
form the dorsal nerve. a 
The eighth pair likewise gives off filaments 
to the diaphragm or membranous septum 
which divides the branchial chamber from the 
abdominal cavity. i 
The last pair of cranial nerves arises behin« 
the eighth pair from the medulla oblongata 
and, after giving a branch to the swimmin 
bladder, is distributed to the muscles of th 
shoulder, and those which pass between th 
shoulder and the hyoid apparatus ; it also git 
branches which anastomose with those of th 
first spinal nerve, and from the plexus th 
priee the nerves proceed which supply t 
external and anterior muscles of the pects 
fins. t 
The second pair of spinal nerves supply 
internal and posterior muscles of the pee! 
fins. In the Trigle ( Gurnards ) these me 
are remarkable for their great size, and o1 
count of the large branches that they give © 
the free rays situated in front of the peet 
They arise from the sides of the last of the 
pairs of post-cerebellic lobes, which in this: 
of Fishes are so remarkable. we 
In Fishes which have their pelvis suspen 
to the bones of the shoulder, whether the ¥ 
tral fins a r in front of the pectorals or 
neath hear behind them, it is from the thi 
and fourth pairs of spinal nerves that the vi 
trals receive their supply; the third speen 
supplying the muscles of the pelvis, to wl 
likewise the fourth give some branches, but 
latter is more particularly distributed to 
rays. The muscles of this fin likewi 
some filaments from the fifth pair of 
nerves. 
In the jugular division of Malacopterygin 
Fishes, in which the ventral fins are attachet 


ppa- 


PISCES. 


—— 


Diagram of the encephalon of the Perch, showing the general distribution of the cerebral nerves. 
8, 8, vestibule of the ear ; other letters as in figs. 526, 527, and 528. (After Cuvier.) 


beneath the throat in front of the pectorals, they 
are supplied from the same pairs of nerves; 
bat in the abdominal division, where the 
ventrals are situated towards the hinder part of 
the body, they receive their supply from spinal 
nerves placed proportionally further back. 


997 


‘qf thi; 
be fer- 


Sympathetic system—The sympathetic sys- 
tem of nerves is in Fishes extremely small, so 
much so, indeed, that its existence has been 
denied by some anatomists; it is, however, in- 
variably present, although its filaments are of 
great tenuity. It runs along the sides of the 


Fig. 531. 


i \ } 
e 


\ 


Lateral and spinal nerves of the Cod ( Gadus morrhua). ( After Swan. ) 


1,1, 1, dorsal communicating branch, derived from the fifth pair and nervus vagus, which joins all the 
nerves of the dorsal fins 10; 2 and 3, two branches from the trank of the par vagum passing down along 
the side underneath the skin; 4, branch running beneath the skin, which communicates with the inferior 
branches of the spinal nerves ; 8, 9, exit of the nerves from the spinal canal. 


spine, as in the higher Vertebrata, receiving 
branches from each of the spinal nerves, and 
anteriorly it communicates with a branch of the 
fifth, and also with the nervus vagus. On the 


left side, after having sent a filament to join the 
trunk of the par vagum on the stomach,* it 


* Swan, Comp. Anat. of Nerv. Syst. p. 24. 


998 


sends a branch across to join its fellow on the 
right side in the splanchnic nerve. This forms 
a ganglionic enlargement on the mesenteric 
artery, and, after communicating with the right 
trunk of the par vagum, terminates on the intes- 
tines and other viscera. On each side of the 
aorta the prolongation of the sympathetic is 
continued down to the tail, giving filaments to 
the lateral branches proceeding from the aorta, 
and communicating with the spinal nerves. 
Near the anus filaments are sent off, which 
unite and accompany the spermatic artery to 
the ovaries. 

According to the united testimony of Costa, 
Rathke, and Goodsir, no vestige of a brain 
or encephalic enlargement of the medulla 
Spinalis 1s visible in Branchiostoma, a fact of 
extreme interest to the physiologist. In these 
extraordinary Fishes, the spinal cord, as de- 
scribed by the last mentioned gentleman, 
stretches along the whole length of the spine, 
is acuminated at both ends, and exhibits not 
the slightest trace of cerebral developement. 
It is most developed in its middle third, where 
it has the form of a riband, the thickness of 
which is about one-fourth or one-fifth of its 
breadth; and along this portion also it pre- 
sents On its upper surface a broad but shallow 
groove. The other two-thirds are not so flat, 
and are not grooved above. They taper off 
gradually, the one towards the anterior, the 
other towards the posterior end of the Fish. 

From fifty-five to sixty nerves pass off from 
each side of the cord; but as the anterior and 
posterior vertebra are very minute and run into 
one another, and as the spinal cord itself almost 
disappears at the two extremities, it is impos- 
sible to ascertain the exact number either of 
vertebre or spinal nerves. These nerves, Mr. 
Goodsir assures us, are not connected to the 
spinal marrow by double roots, but are inserted 
into its edges in the form of simple cords. 

The nerves pass out of the intervertebral for- 
amina of the membranous spinal canal, divide 
into two sets of branches, one set (dorsal 
branches) running up between the dorsal mus- 
cular bundles; the others (ventral branches) 
run obliquely downwards and backwards on 
the surface of the fibrous sheath of the vertebral 
column, and are distributed to the muscles of 
the ventral region. 

When an entire animal is examined by trans- 
mitted light and a sufficient magnifying power, 
the anterior extremity of the spinal cord is ob- 
served, as before mentioned, to terminate in a 
minute filament above the anterior extremity of 
the vertebral column. The first pair of nerves 
is excessively minute, and passes to the parts 
around the mouth. The second pair is consi- 
derably larger; it sends a considerable branch, 
corresponding to the dorsal branches of the 
other nerves, passes upwards and backwards 
along the anterior edge of the first dorsal mus- 
cular bundle. This branch joins the dorsal 
branches of the third and of a considerable 
number of the succeeding pairs of nerves, at 
last becoming too minute to be traced further. 

After sending off this dorsal branch the se- 
cond pair passes downwards and backwards on 


PISCES. 


each edge above the hyoid apparatus, and joins 
all the ventral branches of the other spinal 
nerves in succession, as its dorsal branch did 
along the back. This ventral branch of the 
second pair is very conspicuous and may be 
traced beyond the anus, but is lost sight of 
near the extremity of the tail ; it evidently cor- 
responds with the nerve represented in Sig. 531, 
1, as the dorsal communicating branch does 
with the nerve marked 4 in the same figure. 
Sense of smell.—In the structure of their 
olfactory apparatus Fishes present a remark- 
able difference from all other vertebrate ani- 
mals; their nostrils are in fact quite uncon- 
nected with the respiratory passages, consisti 
of mere sacculi, into which the surroundi 
water obtains free access, which are li 
with a pituitary membrane folded into regular 
plice, so as to offer an extensive surface for 
contact. Their usual situation is towards the 
fore part of the face, where they are supported 
by the vomer, the maxillary, and the intermax- 
illary bones, the first suborbital bounding their 
lower margin, while above they are arched — 
over by a bone distinguished by Cuvier as the 


nasal. 
The openings of the nostrils are of a round, — 
oval, or oblong shape; they are situated either 
at the end of the muzzle or upon its sides, or 
upon its upper surface, or sometimes even 
beneath, as in the Rays and Sharks, where 
they are found near the angles of the mouth. 
In the Lamprey they are placed quite at the ~ 
summit of the head, and open by a common 
orifice; but in the greater number of Fishes, 
perhaps in all the osseous races, each olfactory” 
sacculus presents two orifices, one in front, the: 
other behind, which are sometimes sufficiently 
remote from each other, but both orifices open 
into the same cavity. : 
The anterior orifice sometimes has its € zee 
tubular, as in the Eel, and sometimes this 
tubular edge is prolonged, as in the Lote and 
some of the Siluridz, into a tentacle of more 
or less considerable length: at other times these 
tubular prolongations are wanting, as in the 
Scombride, in which family, moreover, the 
posterior nostrils are but vertical slits. a 
The nostrils of the Lophius ~— me 
able peculiarity, each being suppo upon ; 
little gotta je! as to resemble a mushroom, th 
expansion of the mushroom containing th 
oltactary cavity, which, as usual, communicates 
with the exterior by two little orifices. " 
In some rare instances the posterior apertar 
of the olfactory sacculus is situated bene 
the lip, a circumstance which is more especial 
remarkable in some foreign Congers, and e: 
hibits a remarkable approximation to what 
met with in the amphibious Proteus and Sirei 
The disposition of the pituitary membra 
that lines the nasal sacculus is simp 
where the shape of the olfactory cavity is rot 
the folds of the membrane which lines it are’ 
posed like the radii of acircle (fig. 529); bu 
the nasal fosse are oblong or elon 
are arranged along the two sides of ana 
very regular folds, resembling in their arre 
ment the barbs of a feather. In the nun 


PISCES. 


and prominency of these folds there is great 
variety. Inthe Lump-fish ( Cyclopterus ) they 
are hardly perceptible; in the Perch there are 
only sixteen in each nasal sac, and in the 
Turbot twenty-four, whilst in the Conger or 
the Eel their number is prodigious, seeing that 
they extend along the entire length of the long 
tubular nostril. The rays themselves divide 
into secondary folds in the Sturgeon, and per- 
haps in other species ; in short, various modes 
of plication are adopted in different races, but 
the object obtained is the same in all cases, 
namely, an extension of the surface of the 
olfactory membrane. This surface exhibits nu- 
merous delicate vessels, and secretes an abun- 
dant mucosity which lubricates its interior. 

The olfactory nerve, at its commencement 
from the anterior tubercles of the brain, is 
sometimes single, sometimes double, and some- 
times divided into many filaments of variable 
number, length, and thickness in different ge- 
nera, which pass to the posterior or convex 
aspect of the olfactory sacculus. In its course 
and distribution differences are likewise observ- 
able. Thus, in some genera, as the Tetradons, 
it is exceedingly slender; in others, as in the 
Cod (fig. 529), it is likewise of great tenuity, but 
double or triple. The Rays and Sharks have 
it thick and single, and in these races it is 
_ sometimes so short as absolutely to appear 
merely an appendage of the brain. In the 
Tunny likewise it is simple throughout its 
whole length. In the Perch, about the middle 
of its course it divides into two, and its divi- 
sions become multiplied as it approaches the 
nose. In the Conger and Eel it is divided 
almost from its origin into two large trunks, 
each of which gives off successively a great 
number of branches, which subdivide into 
ramuscules to be distributed to all the lamella 
of their long nostril. 

In many genera of Fishes the olfactory nerve, 
at the point where it reaches the nasal cavity, 
dilates into a ganglion, as may be seen in the 
Cod-fish, the Carp,and the Cyprinide generally ; 
and, lastly, the terminal olfactory filaments 
penetrate into all the folds of the pituitary 
membrane, and terminate at their free margins. 

It does not appear, at least in the osseous 
Fishes, that the coverings of the nasal cavities 
or that their openings have any muscles calcu- 
lated to contract or to expand them. 

Eye.—The eye-ball of Fishes presents many 
peculiarities of structure which are rendered 
necessary by their habits for the purpose of re- 
taining the flattened figure of the cornea, and of 
meeting other circumstances of the condition 
under which aquatic vision has to be performed. 

The sclerotic coat which gives shape to the 
entire eye-ball is a dense and fibrous invest- 
ment enclosing the whole eye, except ante- 
riorly, where a space is left for the transparent 
cornea. Its thickness varies in different parts 
to a greater extent than in any other class of 
vertebrate animals, being generally greatest at 
the posterior part of the eye, so as to preserve 
the cup-shaped form of the eye. In the Stur- 
geon, for example, its thickness in this region is 
prodigious, and in the Cod-fish and Shark the 


999 


same circumstance is remarkable, although ina 
less degree. Still further to secure the requisite 
form of the eye strong plates of cartilage are 
very frequently developed in the substance of 
the sclerotic, generally at the back of the eye, 
but sometimes round the cornea likewise, 
which in the larger Fishes occasionally become 
ossified, of which a notable example is met 
with in the Sword-fish ( Xiphias ), where the 
ossified portion of the sclerotic forms a bony 
cup of a spherical form surrounding the entire 
globe of the eye, except opposite the cornea, 
and where the aperture is left for the entrance 
of the optic nerve. 

In the Rays and Sharks among the Chon- 
dropterygii, the sclerotic, which is of a cartila- 
ginous texture, presents another peculiarity in 
the presence of a prominent tubercle, which 
projects externally to be moveably articulated 
with a pedicle of cartilage derived from the 
back of the orbit, which thus forms a pivot or 
centre for the movements of the eyeball. The 
proper cornea is an exceedingly thin laminated 
membrane, filling up the anterior opening of 
the sclerotic; its thickness, however, is consi- 
derably increased by the external integument, 
which passes over it externally under the name 
of membrana conjunctiva: in some species 
indeed, as Cecilia and Gastrobranchus, such 
is the opacity of this tegumentary membrane 
that all vision is precluded. Immediately be- 
neath the sclerotic there is generally a large 
quantity of fatty cellular membrane; this is, 
however, sometimes wanting, but occasionally, 
as for example in the Moon-fish ( Orthagoriscus 
Mola ), its thickness is very considerable. 

On removing this cellular investment a deli- 
cate membrane presents itself, of a brilliant 
metallic lustre (membrana argentea), which 
indeed from its softness resembles rather a 
layer of pigment than a true tunic of the eye- 
ball. It is this layer which spreads anteriorly 
over the front of the iris, giving it the metallic 
brilliancy for which in Fishes it is so remark- 
able. 

The iris itself is formed as in other Verte- 
brata, but the pupil generally remains fixed 
and motionless; the most remarkable pecu- 
liarities noticeable in this part of the eye having 
reference to the shape of the pupil, which is 
very various in its form. Thus in the Grey 
Shark ( Galeus communis ) it is quadrangular ; 
in the Rays and Pleuronectide the pupillary 
aperture is closed by a kind of palmate mem- 
brane, which hangs down like a curtain from 
its upper border; while in one singular case, 
the Anableps, there is a double pupil as well 
as a double cornea, although in all other parti- 
culars the structure of the eye agrees with that 
of ordinary Fishes. 

The choroid of Fishes presents no peculiarity 
of structure worthy of notice; it is very vascu- 
lar and deeply stained with black or dark- 
coloured pigment. As in the higher animals, 
it is separable into two layers: the outer or 
true choroid, which is properly the vascular 
layer, is of considerable thickness, while the 
inner layer forms the tunica Ruyschiana. This 
latter tunic, as it approaches the margin of the 


1000 


iris, is gathered into numerous beautiful ra- 
diating folds (ciliary plice); these in very 
large eyes, as in the Moon-fish ( Orthugoriscus ) 
for example, are seen each of them to consist of 
two or three minute folds, which, as they run 
forwards, unite into one and terminate in a 
point at the circumference of the iris, but in no 
instance do they project freely inwards as dis- 
tinct processes, so as to resemble the ciliary 
processes of Mammiferous Vertebrata. The 
ciliary plice, as indeed most of the posterior 
surface of the iris,is in immediate contact with 
the membrane of the vitreous humour, to which 
it is intimately adherent; for in Fishes there is 
no posterior chamber of the aqueous humour, 
the anterior segment of the crystalline lens pro- 
jecting in many instances quite through the 
pupillary aperture. 

n a space enclosed between the proper 
choroid and the membrana argentea is a struc- 
ture quite peculiar to the osseous Fishes, for it 
is not met with even in the Chondropterygious 
races.* This consists of a spongy mass of 
irregular form, which partially surrounds the 
entrance of the optic nerve (fig. 532, h), and 
extends for some distance towards the front 


Coats of the eye of the Perch. ( After Cuvier. ) 

Fig. 1, muscles of eye-ball ; a, superior oblique ; 
b, inferior oblique ; 1, 2, 3, 4, recti muscles; i, optic 
nerve, Figs.2 and 3, f, f, f, fatty matter; g, cho- 
roid; A, ‘* choroid gland.” 


of the eyeball. This body, which has been 
absurdly called the choroid gland, is some- 
times divided into two portions; at others 
it assumes a somewhat crescentic form, but 
it is always deficient towards the lower part 


* Cuvier et Valenciennes, Hist. Nat. des Pois- 
sons, tom. i. p. 337, 


PISCES. 


of the eye. Its colour is always a deep red, 
and its tissue is principally made up of 
bloodvessels running transversely in close 
rallel lines. Other vessels issue from it which 
are frequently very tortuous and always much 
ramified; these run into the choroid, where 
they form so dense a network that it was de- 
scribed by Haller as a distinct membrane, and 
has been subsequently named membrana Hal-_ 
leri. The use of the foci 5 choroid = 
has not been fully ascertained ; most 

however, it is essentially composed  ecoctile 
tissue, which by its dilatation and contraction 
may have some influence in accommodating the 
form of the eye to the distance of objects, or 
the varying density of the medium through 
which they are seen. 

The optic nerve in many Fishes (at least — 
among the Acanthopterygii) is made up of a 
broad layer of nervous matter folded upon it- 
self like a fan (fig. 532) and enclosed in a 
fibrous envelope, which is continuous with the 
sclerotic coat of the eye. The nerve enters the 
eye at a point remote from the axis of vision, 
penetrating for the most part by an oblique 
course, so that after having piereed the sclerotic 
it has still a considerable distance to » 
through the substratum of cellular tissue and 
between the masses of the “choroid gland” 
before it pierces the choroid and Ruyschian 
tunics. Its diameter is much diminished at 
the point where it shews itself in the interior of 
the eye, where it appears sometimes as a mere 
point, at others under the form of a round or 
irregular spot, or sometimes represents a straight 
line. It then expands into the retina, which, 
when the nerve is folded, as above described, 
has likewise a plicated ap ce. The re- 
tina, as in other Vecesbane lines all the inte 
nal cavity of the eye as far as the ciliary plic 
thus enveloping the vitreous humour. r, 

Another peculiarity in the structure of the 
Fish’s eye is the existence of an apparatus 
apparently analogous to the marsupium of” 
Birds, which extends from the choroid to the 
back of the lens, passing quite through the 
vitreous humour, to which the name of faleé 
Sorm ligament has been given. This s re 
arises by a broad origin from the inner s 
of the choroid at the back part of the eye, 
extending forwards, following the coneavity 6 
the eyeball along its lower surface, arrives ai 
the ciliary zone and is connected with the bae 
of the capsule of the lens, Its shape is fal 
form, as the name indicates, the convexity ¢ 
the curve being attached along the floor of t 
interior of the eye. In the recent eye it is 
delicate and almost imperceptible membran 
but maceration in spirit by rendering it opac 
reveals it to consist of several layers of cell 
losity, most probably enclosing numerous vé 
sels. According to Cuvier and the young 
Soemmering,* the falciform ligament 
through the retina, which is fissured to let 
through; but an examination of the large ey 
of the Moon-fish after long immersion in sf ri 


* De oculorum hominis animaliumque section 
horizontali commentatio. Fol, Goettinge, 1818. 


PISCES. 


distinctly shews the plicated retina continued 
on to the surface of the ligament, which seems 
to be covered with the nervous expansion.* 

Humours of the eye—The quantity of the 
aqueous humour in a Fish’s eye is comparatively 
very small, owing to the flat shape of the cor- 
nea and the almost perfect immobility of the 
iris. The posterior chamber is, indeed, quite 
deficient, the uvea of the iris being adherent to 
the capsule of the vitreous humour ; and even 
the anterior chamber is frequently materially 
encroached upon by the protrusion of the 
crystalline lens through the aperture of the 
pupil. As a refracting medium it is evident 
that the aqueous humour, being nearly of the 
same density as the surrounding medium, could 
have little effect in concentrating luminous 
rays, this duty being principally assigned to the 
powerful lens imniediately behind it. 

The crystalline lens in Fishes is nearly of a 
spherical form, thus presenting the converse as 
regards its refractive power of what exists in 
the eye of Birds. The size of the lens in these 
aquatic animals is very great, so that it en- 
croaches largely upon the chamber of the 
vitreous humour, extending to more than half 
way between the pupil and the back of the 
cavity of the eyeball. Its consistence is very 
great, and its nucleus so hard as to remain 
transparent even after immersion in spirit of 
wine. It is enclosed in a soft capsule, between 
which and the surface of the crystalline lens is 
a small quantity of fluid, and is fixed in a deep 
depression in the fore part of the vitreous hu- 
mour by a circular membranous zone derived 
from the hyaloid tunic, which surrounds it like 
the artificial horizon of a geographical globe. Sir 
David Brewster, in an admirable paper on the 
anatomical and optical structure of the crys- 
talline lens,t gives the following interesting 
particulars relative to its minute organization in 
the class of Fishes. Its form is that of a prolate 
spheroid, the axis of revolution being a little 
longer than the equatorial diameter. This axis 
is the axis of the eye or of vision. The body or 
substance of the lens is enclosed in an exceed- 
ingly thin and transparent membrane, called 
its capsule ; and if this be punctured, a thickish 
fluid flows from the opening; but upon re- 
moving the capsule altogether, this fluid is 
found to constitute only the outer coat of the 
lens, the substance of the lens growing denser 
and harder as we approach the centre of it. 

The body of the lens is not connected with 
the capsule by any nerves or filaments what- 
ever ; on the contrary, it floats as it were within 
the capsule, and on holding the lens in his 
hand, Sir D. Brewster observed its axis of revo- 
lution take a horizontal position whenever it 
was placed in an inclined direction. This was 
repeated several times with the same lens, 
although the experiment was tried unsuccess- 
fully with others. When the lens is taken out 
of its capsule, and the softer parts removed by 
rubbing it between the finger and thumb, a 


* Vide Preparation 1650, in the physiological 
series of the Museum of the Royal College of Sur- 
geons, London. 


+ Phil. Transact. for 1833, p. 323. 


1001 


hard nucleus is ‘obtained, which consists of 
regular transparent lamine of uniform thick- 
ness, and capable of being separated like those 
of sulphate of lime or mica. 

When the surface of any lamina has been 
examined before it has been detached, it has 
the appearance of a grooved surface like mo- 
ther-of-pearl; and in large lenses it is often 
easy to trace these apparent grooves or lines to 
the two poles of the axis of revolution, the 
fibres bounded by them being consequently 
widest at the equator, and growing narrower 
and narrower as they approach the poles. The 
maximum breadth of these fibres is about the 
5500dth part of an inch, but of course they 
become gradually attenuated as they approach 
the poles of the lens in either direction. 

Having thus determined the form and size of 
the fibres which enter into the composition of 
the crystalline lens, it remained to ascertain the 
mode in which they were fastened together so 
as to resist separation and form a continuous 
spherical surface, and this was found to be 
effected by a very curious mechanism, the con- 
tiguous fibres being united by means of teeth 
exactly like those of rack-work, the projecting 
teeth of one fibre entering into the hollows be- 
tween the teeth of the adjacent one. It was 
further found that the fibres gradually diminish 
in size towards the centre of the lens, and the 
teeth in the same proportion, so that the num- 
ber of fibres in any spherical coat or lamina 
was the same from whatever part of the lens it 
it was detached. In conclusion, Sir David 
Brewster observes, “ In’ the lens of a Cod I 
found that there were 2000 fibres in an inch at 
the equator of a spherical coat or lamina, whose 
radius was £,ths of an inch; consequently there 
must have been 2500 in the spherical surface. 
If we now suppose that the breadth of each 
fibre is five times its thickness, and that each 
tooth is equal to the thickness of the fibre, or 
that five teeth are equal in breadth to a fibre, 
we shall obtain the following results for the 
lens of a Cod four-tenths of an inch in dia- 
meter :— 

Number of fibres in each la- 


mina or spherical coat 2,500 
Number of teeth in each fibre 12,000 
Number of teeth in each sphe- 

mical Coatitiey eee! APs 31,250,000 
Number of fibres in the lens . 5,000,000 
Number of teeth in the lens . 62,500,000,000 


or, to express the result in words, the lens of a 
small Cod contains five millions of fibres and 
sixty-two thousand five hundred millions of 
teeth. A transparent lens exhibiting such a 
mechanism may well excite our astonishment 
and admiration.” 

The vitreous humour in Fishes is proportion- 
ally less abundant than in other races of Verte- 
brata,—a circumstance which is partly owing 
to the shortness of the antero-posterior dia- 
meter of the chamber of the eye-ball, and partly 
to the extent to which it is encroached upon by 
the large spherical crystalline lens; in other 
respects it presents no peculiarities worthy of 
special description. 

Muscles of the eyeball. —The eyeball of 


1002 


Fishes is moved by six muscles analogous to 
those met with in other Vertebrata, and to 
which similar names are applicable. The recti 
muscles (fig. 532, 1, 2, 3,4) are four in 
number, arising from the back of the orbit 
near the margin of the optic groove, and run- 
ning forward to be attached in the usual manner 
to the sclerotic coat of the eye. The obliqui 
(fig. 532, a, 6) both take their origin from the 
anterior part of the walls of the orbit, and pass 
ina transverse direction towards the eyeball, into 
which they are inserted, one on its superior, the 
other on its inferior aspect. There is no troch- 
lear apparatus in connection with the superior 
oblique, as is the case in quadrupeds, but, like 
the inferior, it passes straight to its destination. 
The suspensory or choanoid muscle met with 
in Mammalia, in Fishes is totally wanting. 

In the Sharks the muscles moving the eye- 
ball are of very great strength, and, moreover, 
their efficiency is rendered more perfect by me- 
chanical contrivances that are not met with in 
the ordinary Fishes. In the latter the eye is 
simply supported in the orbit by a quantity of 
loose cellulosity filled with a gelatinous or fatty 
semifluid substance, admirably adapted to faci- 
litate the movements of the eye; but in the 
plagiostome cartilaginous Fishes the cartilagi- 
nous pedicle is provided, already mentioned, 
which, taking its origin from the back of the 
orbit between the origins of the recti muscles, 
runs forward to be moveably articulated, fre- 
quently by means of a very complete ball- 
and-socket joint enclosed in a capsular liga- 
ment, to the back of the selerotic, so as to 
form a pivot upon which the eye turns. In 
the attachment of the recti and oblique mus- 
cles to the eye-ball an additional piece of me- 
chanism is observable, each of these muscles 
being inserted into a prominent cartilaginous 
tubercle, which projects from the external sur- 
face of the sclerotic, and thus enables the 
muscle to act with greater advantage. 

In the generality of Fishes there are no eye- 
lids, the external tegument passing on to the 
front of the eye-ball without forming any fold 
or duplicature to which such a title is appli- 
cable; there are, however, exceptions to this 
arrangement which must not be passed over 
unnoticed. Thus, in the Mackarel (Scomber 
Scombrus ), the eye is partially defended by two 
vertical folds of the common integument, and 
in the Herring ( Clupea Harengus ) there is a 
similar provision for the defence of the eye-ball 
and orbit.* The vertical folds are unprovided 
with any muscular structure for their move- 
ment, and are consequently transparent so as 
not to interfere with vision when the front of 
the eye is brought beneath them. It is worthy 
of observation that, where these folds decussate 
one another at their inferior extremities, the an- 
terior one overlaps the posterior, so slight an 
impediment to progressive motion as the con- 
trary position would have occasioned having 
thus been foreseen and avoided. 

In the Sharks and Sturgeons the integument 


* Vide Catalogue, Mus, Coll. Surgeons, Lond. 
vol. iii. p. 171. 


PISCES. 


forms a deep circular fold around the front of 
the eye, which, although motionless, is evidently 
of a palpebral character. A secreting membrana 
conjunctiva is reflected deeply between this cir- 
cular fold and the globe of the eye, of which it 
covers the anterior half. In the Sharks* there 
is likewise a third eyelid, which is moveable; 
this is placed at the inferior and internal or 
nasal side of the orbit, and is moved over the 
front of the eye in a direction upwards and out- — 
wards by means of a strong round muscle (nic- 
titator ) which arises from the upper and poste- 
rior or temporal side of the orbit, and descends 
obliquely to be inserted into the lower and 
outer margin of the third eye-lid; passing in 
this course first through a muscular trochlea, 
and then through a_ligamento-cartilaginous 
loop. The trochlear muscle is not, however, — 
exclusively subservient to the action of the — 
nictitator, but has an insertion in the upper — 
part of the palpebral fold, which it depresses — 
simultaneously with the raising of the third — 
eyelid, a slight external groove above the upper — 
eyelid indicating the extent of motion all 

The lacrymal apparatus is totally wanting in 
the whole race of Fises, no trace of lacrymal 
glands or puncte lacrymalie being ever distin= 
guishable; neither could a lacrymal secretion” 
be needed in animals whose eyes are 
ally bathed by the water in which they live. 

Auditory apparatus.—The organ of hearing 
in Fishes undergoes a gradual improvement in 
its structure as we advance from the lower to t 
more highly organized genera, presenting alme 
every intermediate gradation the le 
complex form, in which it consists of the 
bule alone, without semicircular canals or other 
appendages, approximating in simplicity the 
ear of a Cuttle-fish (vide art. pgp ; 
to the most complete icthyic the 
auditory apparatus, a with in the Sharks 1 
Sturgeons. * 

It is in the Lampreys (Petromyzon) that 
the auditory organ exists in its humblest state ~ 
of developement.t In these Fishes the ear is 
enclosed in a simple cartilaginous capsule 0 
an elliptical figure, situated on each side of the 
skull external to the posterior cranial cartilages. 
The walls of these capsules are thin, and th 
cavity which they contain of an ovoid sha’ 
In that side of each cartilaginous capsule 
(vestibulum cartilagineum, Weber,) which is 
nearest the cranium, are two openings, th 
inferior, which is the larger, being of an a 
shape closed with a firm and elastic membrane, 
while the superior is extremely small, givin 
transit to the auditory nerve as it passes into 
the vestibule. With the exception of these 
apertures, which open into the cavity of the 
cranium, the cartilaginous capsule is closed on 
all sides. 

The whole of the elliptical cavity of 
cartilaginous capsule is filled by a pellucid 
membranous sac (vestibulum membranaceum ) 


€ 


“ 4 


x Catalogue, Mus. Coll. Surgeons, Lond. p a 

+ Vide Tract. de Aure animalium aquatilium, — 
= Ernesto Henrico Webero. Lipsia, 1820. — 
to. : 


PISCES. 


turgidly filled with a transparent fluid; the 
membranous vestibule, however, does not ad- 
here to the walls of the capsule except at the 
orifices leading into the cranium. The mem- 
branous vestibule has its cavity divided into 
several compartments by folds projecting into 
its interior, and receives the auditory nerve, 
which being changed into a pulpy mass spreads 
Out over its walls. 

In the Petromyzonidz therefore three 
important parts of the auditory appa- 
ratus, which are met with in the ear 
of all other Fishes, are wanting, viz. 
the sac of the otolithe, the otolithe 
itself, and the semicircular canals, ex- 
cept indeed rudiments of the latter may 
be represented by two curved folds of 
the membrane of the vestibule, which 
are joined: superiorly to a similar fold, 
an arrangement which is met with both 
in the river and sea-lamprey. The 
auditory nerve is derived immediately 
from the brain. 

From the above description it would 
appear that in the Lampreys there are two modes 
whereby sonorous vibrations may be commu- 
nicated to the vestibule, one through the car- 
tilaginous capsule of the ear, the other through 
the cranium, which communicating tremors 
impressed upon it from without to the fluid 
which is contained in its cavity, the vibration 
reaches the tense membrane that closes the 
large fenestra leading to the vestibule, and thus 
affects the membranous vestibular sac itself. 

Inasecond group Weber includes those forms 
of the ear which have no cartilaginous or osse- 
ous vestibule separate from the cranial cavity. 
This kind of ear exists in by far the greater 
number of Fishes, being met with in all the 
truly osseous and branchiostegous races as 
well as in some Chondropterygians; in none 
of which is the membranous labyrinth en- 
closed in a bony or cartilaginous envelope, the 
internal ear being contained in the cavity of 
the skull itself near the posterior part of the 
cerebrum, with which, in fact, it is for the most 
part in apposition; for in these Fishes the 
cranium being very large and having only a 
small part of its cavity occupied by the brain 
itself, performs the office of an osseous laby- 
rinth, not only by furnishing a receptacle to 
the internal ear in which every part necessary 
to the performance of its functions may be fitly 
suspended, but is filled with fluid with which 
the membranous labyrinth is every where sur- 
rounded, a provision not less necessary to the 
sense of hearing than is the fluid contained in 
the interior of the vestibule and semicircular 
canals. In all such Fishes, therefore, the 
auditory apparatus, consisting of a membra- 
nous vestibule and semicircular canals, is lodged 
on each side in cavities excavated in the base 
of the cranium and bounded by the temporal 
and lateral parts of the occipital bones. 

The internal ear itself (fig. 528) is composed 
of the following parts: ist. The membranous 
vestibule (fig. 525, i). 2d. The sac of the 
otolithe. 3d. The membranous semicircular 
canals. 


1003 


The membranous vestibule is an elongated 
smooth sacculus of very various form in diffe- 
rent Fishes. Its parietes consist of a pellucid 
membrane, and its outer surface is connected 
by loose cellular tissue to the sides of the 
cavity in which it is lodged. Its anterior 
extremity is somewhat dilated and contains 
a little otolithe; moreover into it open the 
ampulle of the anterior and external semi- 


Fig. 533. 


SSS 


Internal ear of Perch. (After Cuvier.) 


circular canals. The posterior extremity of the 
vestibule is narrower, and into this part opens 
the ampulla of the posterior semicircular canal 
and the hinder termination of the external one. 
Near the middle of the vestibular sac enters the 
wide duct formed by the conjunction of the 
terminations of the anterior and posterior semi- 
circular canals; but whether this wide duct 
ought rather to be looked upon as forming part 
of the vestibule or of the semicircular canals 
may be a matter of doubt, although the latter 
supposition is the most probable. 

Thus the six extremities of the three semi- 
circular canals communicate with the cavity of 
the membranous vestibule, not by six, but by 
five orifices. 

The membrane of which the vestibule con- 
sists is considerably thinner than that which 
forms the semicircular canals; indeed it is so 
delicate that if torn it at once collapses and is 
scarcely distinguishable from the surrounding 

arts. 

In the Pike ( Esox lucius) there is a re- 
markable appendage to the vestibule which is 
not met with in other Fishes. This consists of 
a pyriform membranous sacculus lodged in the 
commencement of the spinal canal, which opens 
into the vestibular cavity by a narrow orifice 
near the entrance of the posterior semicircular 
canal. The thickness of the walls of this 
sacculus is much greater than that of the pa- 
rietes of the vestibule, resembling rather in 
this respect the ampulle of the semicircular 
canals. Some of the upper spinal nerves are 
distributed to this organ, but they give off no 
branches, nor does it appear to receive any 
filament from the auditory nerve. 

The sac of the otolithe in most Fishes is 
immediately beneath and in close contact with 
the membranous vestibule, but in some it is 
hidden in the base of the occipital bone more 
remote from the vestibular cavity, with which it 
is joined by anarrower duct. The saccus is most 
generally divided into two portions by a median 
septum, in such a way, however, that the ante- 


1004 


rior is much the larger compartment, to which 
the posterior chamber seems a superadded ap- 
pendix. Both of these compartments are filled 
with a pellucid fluid, and each contains a stony 
mass or otolithe, of which that in the anterior is 
the largest, that in the posterior being compara- 
tively of small dimensions. In Orthagoriscus, 
however, according to Cuvier, the saccus is 
single, and instead of an otolithe only con- 
tains a few granules apparently rather of 
mucus than of cretaceous substance. 

Otolithes—Most Fishes are furnished with 
three stony masses, which are intimately con- 
nected with the function of hearing. Of these, 
the otolithes or lapilli, one, generally the small- 
est, is contained in the anterior extremity of the 
vestibule; the other two are situated in the two 
compartments of the succus. The otolithe con- 
tained in the anterior compartment of the saccus 
is generally of remarkable size, forming a con- 
siderable protuberance in the base of the occi- 
pital bone, in which it is lodged ; this is con- 
spicuously seen in the Gadide and some of the 

erch tribe. 

The substance of these otolithes consists of 
carbonate of lime, but they assume various de- 
grees of hardness and considerable diversity of 
colour in different Fishes. In most cases they 

resent a texture as hard and fragile as porce- 
fain. In a few instances, as for example in the 
Sturgeon ( Accipenser Sturio ), there is only one 
lapillus, which is soft and as easily crushed 
and reduced to powder as a piece of chalk ; as 
is likewise the case with the otolithes of the 
Raide and Squalide. 

In shape the otolithes vary exceedingly in 
different genera. For the most part they are 
smooth and present this character in common, 
that they are marked with asperities, fossee, and 
grooves for the attachment or reception of nerv- 
ous filaments. Those contained in the saccus 
are frequently surrounded by a serrated margin, 
which is rarely the case with the lapilli of the 
vestibule. But whilst there is so much diver- 
sity in the shape of the otolithes belonging to 
different genera of Fishes, the form of those met 
with in the species belonging to the same genus 
is wonderfully constant, so much so, indeed, 
that not only the general outline, but the most 
minute fossules and grooves were found by 
Weber accurately to correspond in different 
specimens, so that it was difficult to distinguish 
one from the other; from which circumstance 
those otolithes might be employed with advan- 
tage as affording excellent generic characters to 
the zoologist. The connection of the otolithes 
with the saccus or with the vestibule is so 
difficult to be perceived, that they might be 
thought to be loose in the contained fluid ; 
when, however, we find them smallin the 
younger Fishes, and increasing in size as age 
advances, it is evident that they must receive nu- 
tritious vessels; they are moreover attached b 
nervous filaments of extreme delicacy, which 
pass to them from the saccus. In many points 
they touch the membranous walls of the cavity 
in which they are lodged; when, therefore, the 
sac is but loosely connected with the bones of 
the cranium, sonorous vibrations cannot be 


PISCES. 


communicated immediately from the cranium 
to the lapilli, but must first be communicated to 
the surrounding fluid. 

Semicircular canals—Al\ Fishes, with the 
exception of the Petromyzonide, have three 
se canals entering into i formation 
of the internal organ of hearing, and the arrange- 
ment of which is as follows. The anterior 
arises by one extremity from the anterior part of — 
the vestibule, and, winding upwards and back- 
wards, meets the rior semicircular canal | 
derived from the hinder part of the vestibular 
cavity ; at the point of meeting the two join to” 
form one common duct, which enters the vesti- 
bule near its middle. Both these canals are 
placed perpendicularly. The third or external — 
semicircular canal issues from the anterior ; 
the vestibule, and winds horizontally outwards to 
join the vestibule again at its posterior part near 
the origin of the posterior canal. In this way 
the three semicircular canals open into the mem-_ 
branous vestibule by pipe ec Tn the — 
ring, however, ( Clu arengus ) not 
the anterior and paaaaied canals ie, 
external also joins the posterior, so that in thi: 
fish there are only four apertures communicating 
with the vestibule. 

Each of the semicircular canals near its com= 
mencement from the vestibule swells into an 
oval dilatation called the ampulla, so that three 
of these ampullz exist, two at the anterior part 
of the vestibule, and the third near its posterior 
extremity, “ 

The connection between the semicirculat 
canals and the cranium is effected by the assist- 
ance of osseous passages, in which one or ts 
(rarely all three) of the semicircular canals are 
lodged, and in some Fishes, as for example in 
Cobitis fossilis, these are entirely deficient 
The membranous canals are not at all adherent 
to the osseous passages, but are only connected 
with them by the intervention of a most delicate 
cellulosity, or are merely suspended in a flui 
with which all the osseous canals as well as the 
entire cranium is filled up; they are conse. 

uently extracted without the employment 0 
the slightest force. * 

Those canals which are not enclosed in bon 
channels are simply annexed to the bones of th 
cranium by a fine cellular web. 

From the above arrangement it may & 
clearly understood that these parts are pul 
posely left but loosely connected to the surfa 
of the bones, for otherwise the bony cana 
would not so greatly exceed the membrane 
ones in size, but on the contrary would 
filled and lined by them throughout; and t 
sonorous vibrations most readily arrive at 1 
labyrinth through the fluid with which th 
canals are surrounded. A 

In Murena anguilla the anterior and pos 
rior semicircular canals mount so high towar 
the vertex of the cranium that they are 1 
placed by the side of the brain, but absolutel 
rise above it and approximate their fellows of 
the opposite side. = 

The length and calibre of the semicireulai 
canals vary very much, not only in different sp 
cies, but also when compared with each othe 


‘ 


| 
| 


PISCES. 


The tissue of which they are composed is similar 
to that which forms the membranous vestibule 
and saccus ; it is, however, a tissue sui generis, 
being neither exactly comparable to cartilage, 
nor tendon, nor cellular membrane. It is pel- 
lucid, and when emptied of the enclosed fluid, 
inelastic, but flexible and easily torn. Its 
thickness is greater than that of the vestibule or 
of the sac of the otolithe; but the ampulle 
seem thicker than the rest, for when wounded 
and their contents allowed to escape they still 
retain their form and expansion. 

The membranous labyrinth is filled with a 
limpid fluid. 

Auditory nerves.—The labyrinth of the ear 
in Fishes receives its nerves from two sources,* 
1st, from the auditory nerve, properly so called, 
which is distributed to the membranous vesti- 
bule, and to the ampulle of the anterior and 
external semicircular canals; 2ndly, from the 
“‘accessory auditory nerve,” which, in most 
instances, seems to arise not from the brain but 
from the trigeminal or the vagus nerve, and 
supplies the ampulla of the posterior semicir- 
cular canal and the saccus. 

Ear of plagiostome cartilaginous Fishes.— 
In the Skate are two canals, regarded by Monro 
as representing the meatus auditorius externus. 
The orifices of these are situated at the upper 
and back part of the head at a short distance 
from the junction of the skull with the first cer- 
vical vertebra, the opening of each being large 
enough to admit the end of a probe. Each of 
these orifices leads to a winding canal about 
two lines in diameter, which, after describing 
more than three-fourths of a circle, may be 
traced into the membranous vestibule of the 
ear. This canal is generally found filled with 
a white viscid matter. The vestibule is a large 
sac containing a very viscid pellucid humour, 
in consistence like the white of an egg, in 
which is suspended a soft cretaceous substance. 
To the anterior part of the large sac there is 
a smaller compartment communicating with the 
former by a narrow passage, which is likewise 
filled with glairy fluid, and, posteriorly, there is 
a third very small sacculus, similarly distended, 
in both of which cretaceous matter is found. 

The remaining portion of the internal ear 
consists of three canals, analogous to the semi- 
circular canals of the higher Vertebrata, but 
which here rather deserve the name of circular, 
seeing that each forms a complete circle; of 
these the anterior and the middle are joined 
together at their commencement by the wide in- 
tercommunicating branch which opens through 
the intervention of a small membranous tube 
into the anterior small sac of the vestibule. 
The third or posterior canal communicates with 
the large sac of the vestibule by means of a 
wide canal, but has no direct communication 
with either of the others. 

Each circular canal has a dilated portion or 
ampulla near one of its extremities, and is filled 
with a pellucid viscid fluid. They are all con- 
tained in cartilaginous tubes excavated in the 
cartilaginous substance of the cranium, but 


* Weber, loco cit. 


1005 


much wider than the membranous canals them- 
selves, the latter being suspended in a fluid 
interposed between them and the perichondrial 
lining of the cartilaginous passages, to which 
they are fixed by a delicate cellulosity, in which 
slender vessels and very minute nerves are 
visible. 

The auditory nerve on entering the ear di- 
vides into several branches. Of these the prin- 
cipal spreads out upon the inferior aspect of 
the great sac of the vestibule, where it forms a 
rich plexus; a similar but smaller plexus is 
formed upon the smaller anterior sac commu- 
nicating with the vestibule, while the other 
branches are appropriated to the semicircular 
canals, on the ampulle of which they would 
seem to be exclusively distributed; at least 
after forming a very beautiful expansion upon 
the dilated portion of the canal, it is impossible, 
owing perhaps to their very minute size, to 
trace them any further over its cylindrical part. 

Generative system—One of the most re- 
markable circumstances connected with the 
history of the finny tribes is their extreme 
fertility, which, compared with that of the 
higher Vertebrata, is truly prodigious. A cod- 
fish has been calculated to produce 9,000,000 
of eggs in a single season, and innumerable 
races of the osteopteryginous Fishes exhibit 
per of reproduction equally extraordinary. 

© imagine that this exuberant fecundity is 
destined merely for the purpose of perpetuating 
the species would evidently be preposterous, 
and we are necessarily led to look for other rea- 
sons explanatory of such teeming births. There 
is this leading difference between the terrestrial 
and aquatic domains of animated nature—the 
earth is inhabited only at its surface, and the 
vegetable banquet which is there spread out in 
such rich abundance is sufficient to afford the 
means of subsistence to all earth’s progeny. 
But the sea, throughout all its depth, at every 
altitude which man has been able to explore, 
is peopled with innumerable races of voracious 
beings, all of which are necessarily dependent 
for their existence upon a supply of animal 
food, which must consequently be distributed 
as widely as the waves of ocean are diffused. 
It is to supply this great stock of living pro- 
vender that the Sponges and the Polyps and 
all the humbler marine forms of existence are 
continually pouring forth their multitudinous 
germs, and it is for the purpose of adding to 
this enormous store that the majority of the 
osseous Fishes are so inordinately prolific. 

From these considerations we perceive at 
once a reason for the extraordinary apathy and 
total absence of parental affection which forms 
so conspicuous a feature in the character of the 
whole race, and it is by no means a subject 
devoid of interest to observe how gradually 
the ties between parent and offspring are drawn 
closer and closer as we ascend from these 
humblest members of the Vertebrata and arrive 
at progressively increasing intelligence as we 
advance from class to class. 

The generative apparatus of Fishes, as we 
have pointed out in a preceding article, (Gr- 
NERATION, OrGaxs oF, Comp. Anat.,) pre- 


1006 


sents itself under three principal types, each of 
which will merit distinct considération. 

The first is that observed in the Dermapte- 
Pye ve or Cyclostomatous Fishes, such as 
the Myxine and Lamprey ; but it is not pe- 
culiar to this group, seeing that the Eels and 
perhaps other races have a similar organi- 
zation. 

On opening the abdomen of one of these 
Fishes, as, for example, the Lamprey, ( Pe- 
tromyzon marinus, fig. 534) an exceedingly 


S 


' Female generative organs of the Lamprey 
( Petromyzon marinus). 

a, parietes of abdomen; 5b, cavity of ditto; 
c, Ovary; e, external pesenge leading into abdo- 
minal cavity, through which the ova are discharged; 
g, kidney. 


extensive membranous expansion is found sus- 
ended in loose folds, which is attached by a 
ind of mesentery beneath the spinal column, 
and extending along the whole length of the 
abdominal cavity. Except in the breeding 


Fig. 535. 


One of the folds of the ovary of the Lamprey, 
( Petromyzon marinus, ) showing t losed ova. 


PISCES. 


season, this membrane, of which a portion only 
is represented in the figure, (fig. 534, c,) is 
thin and transparent, but at the same time 
exhibits considerable vascularity. When the 
breeding season approaches, innumerable gra- 
nules begin to 5 their appearance, between 
the two layers of which this expansion consists, 
which in the female soon proclaim themselves to 
be ova (fig. 535), and, as they increase in size, 
gradually distend the whole abdomen. On 
opening the fish in this condition the abdominal 
cavity appears to be completely filled with 
innumerable ova beautifully arranged in rich 
festoons, all of which are connected in front 
of the spinal column. When the ova are 
quite mature they are cast loose from the ovary 
and escape from the ovarian membrane in 
which they were formed, into the general ca- 
vity of the abdomen, wherein they may be 
found at this period floating quite loose prepa- 
ratory to their expulsion. This is ultimately 
effected through a simple but wide orifice (e) 
situated immediately behind the anal aperture, 
and causing a free communication to exist be- 
tween the peritoneal cavity and the exterior of 
the body, so that the ova easily pass out and 
are ejected into the surrounding water. ig 
In the males of those Fishes which offer this 
type of the generative system the appearance 
of the reproductive organ is, while in a state of 
inactivity, so exactly similar to that of the 
female as to preclude the possibility of distin- 
guishing the two from each other; but, as the 
breeding season advances, the difference be- 
comes apparent; the festooned membrane, 
which must in this case be called the testis, 
secretes a kind of milt or seminal fluid, rich in 
seminal animalcules, which in the same manner 
as the ova of the female escapes into the peri- 
toneal cavity and is expelled through a post-— 
anal orifice to be diffused through the sur- 
rounding water, by the agency of which it is 
applied to the previously deposited spawn of 
the female, whose ova thus ming vivified 
are left to the mercy of circumstances to be 
destroyed or hatched in due season. 
In the second form of the generative app 
ratus which is common to almost all the tru 
osseous Fishes, a very different arrangement 
met with. The folds of the ovarian membrar 
instead of being loosely suspended in the abe 
minal cavity, are now completely enclosed 
two capacious membranous capsules, situa 
one on each side of the spine, and which 
distended with ova occupy a very large share 
the abdomen. On opening one of these cap 
sules, the ova which it contains are seen, how- 
ever, to be developed between the two layers ¢ 
the proper ovary, exactly as in the case of 
Lamprey, and to be attached in broad festoons 
to the interior of its walls, the essential diffe. 
rence being that whereas in the preceding typé 
the eggs, when expelled from the ovary, ese 
into the peritoneal sac, they now are retained by 
the capsular envelope of the ovary, whence they 
are expelled through excretory canals provic 
for the purpose. These, as they exist in t 
Herring, are represented in the annexed figu 
(fig. 536); from the posterior extremity of ez 


PISCES. 


1007 


Fig. 536. 


Viscera of the Herring ( Clupea harengus ), 


a, esophagus ; b,c, stomach ; d, pyloric ceca; e, intestine ; f, anus; g, spleen; h, h, ovary; i, ovi- 
ducts ; k, air-bladder. 


ovarian capsule arises a short canal #, 7, and these 
two ducts uniting form a common tube, through 
which the ova pass out of the body through an 
aperture, f, situated immediately behind the 
anus. 

In the male the disposition of the genera- 
tive organs is precisely similar, the membrane 
contained in the two capsules secreting milt 
instead of spawn, which when expelled through 
the efferent duct and thus mixed with the water 
in the vicinity of the ova of the female, pre- 
viously deposited, impregnates them by asper- 
sion. Instances are recorded by Cavolini and 
others of a remarkable kind of hermaphrodism 
occasionally met with in Fishes presenting this 
type of structure, in which, while the generative 
capsule upon one side of the body contained a 
roe-secreting membrane, that of the other fur- 
nished milt, so that one half of the fish was 
male and the other female; such an arrange- 
ment, however, can only be looked upon as 
a lusus nature, although regarded by some of 
the older naturalists as a normal occurrence. 

Among the Salmonide a very interesting ar- 
rangement of the generative apparatus is met 
with, which would seem to offer an intermediate 
condition between that of the Lamprey and that 
of the ordinary osseous Fishes. In the Trout 
and Salmon for instance, the extensive folds of 
the ovarian membrane are only partially en- 
closed in an investing capsule, the interior of 
which communicates by means of a wide slit 
with the abdominal cavity. In the common 
Salmon (Salmo Salar, Linn.) the ovary is much 
reduced in its relative size when compared with 
that of the Lamprey or of the Eel, although the 
ova are still developed in the folds of an irregu- 
larly transversely plaited membrane. These 
folds and their contained ova are, however, en- 
veloped on their posterior and lateral aspects by 
a thin capsule, which is wanting on their ante- 
rior surface. Through this anterior opening in 
the capsule the ova are discharged into the 
cavity of the abdomen, whence they are finally 
expelled through the peritoneal apertures 
situated near the anus, as in the Lamprey. 

Notwithstanding that the great majority of 
the osseous Fishes shed their spawn to be im- 
pregnated out of the body, some rare instances 
are met with in which the females are vivipa- 
rous, producing their offspring not only already 
hatched, but even considerably advanced *in 
growth. Such, for example, is the Viviparous 


Blenny. In cases such as these it is evident 
that impregnation must occur internally, and 
accordingly a kind of copulation must be 
presumed to be effected. Yet, even in these 
Fishes no very obvious peculiarity is to be de- 
tected in the structure either of the male or 
female organs; neither is the male better pro- 
vided with an intromittent apparatus than the 
ordinary oviparous genera. 

The Syngnathide, or pipe-fishes, offer a very 
peculiar conformation, which is not inaptly 
comparable to what is met with among the mar- 
supial Mammalia, namely, a pouch wherein the 
ova are carried about until after they are hatched, 
and in which the young are defended during the 
earliest period of their growth. 

In the plagiostome cartilaginous Fishes the 
arrangement of the generative apparatus of both 
sexes is of a very different character, approxi- 
mating that type of structure which is common 
to the Reptilia and Birds. In the male Shark 
(Squalus acanthias), which may be taken as an 
example of the group, the anatomy of these 
parts is as follows. The testes, two in number, 
(for the minute structure of which the reader is 
referred to our preceding article GeNERATION, 
ORGANS oF, Comp. Anat.) are situated at the 
anterior part of the abdomen, on each side of the 
mesial line, (fig. 537, k,) where they are at- 
tached by their inner margins to a duplicature 
of the peritoneum, which connects them with 
the region of the spine. The vasa deferentia 
derived from each of these glands are long and 
tortuous tubes (/,/, ), increasing in size as they 
pass backwards towards the cloaca, into which 
they open by an orifice common to them and to 
the ureters upon a kind of papillary eminence 
(0), which is here in truth a rudimentary penis 
adapted to facilitate the impregnation of the 
female which takes place internally. 

The openings communicating between the 
cloaca and the cavity of the peritoneum (fig. 
537, p, p,) are situated a little lower down 
beneath a kind of valvular fold formed by the 
termination of the rectum. 

In the vicinity of the cloacal aperture are 
situated the claspers, or holders, (g, g,) so 
called because they are generally supposed to 
be used for clasping or holding the female 
during the sexual intercourse necessary for 
internal impregna‘ion, although some authors 
have imagined them rather to perform the office 
of an intromittent organ by being actually in- 


1008 : PISCES. 


Bilal i Ma 
Viscera of male Shark, (After Clift. ) 

a, heart; 6, liver; c, esophagus; d, stomach; e, 
pyloric portion of stomach ; g, pancreas ; h, i, in- 
testine ; k, testis ; 1, vas deferens ; m, urinary blad- 
der; 0, rudimental penis; p, p, peritoneal open- 
ings ; q, q, claspers. 


troduced into the cloaca of the other sex in the 
act of impregnation. The following is Cuvier’s 
description of these remarkable organs, which 
are met with in the males both of the Sharks 
and Rays and likewise of the Chimere, and 
from the composition and relations of the car- 
tilages and muscle which enter into their struc- 
ture are evidently only an extension orappendage 
of the ventral fins, They consist in the Rays 
and Skates of two cartilages articulated end to 
end, situated along the inner side, which forms 
the basis of the whole apparatus. The first of 
these cartilages, which is a sort of femur, ar- 
ticulates with the pelvis, and supports, in con- 
junction with the second (the tibia), the rays 
of the ventral fin. 

A third cartilage unites this fin with the 
genital portion like a kind of astragalus ; this 


. after to be described. 


articulates with the longest cartilage of the 
limb. 

On the side of the astragalus is an oval car- 
tilage having a sharp inferior margin, to which 
may be applied the name of os cu/cis. 

he os calcis articulates posteriorly with 
another principal piece of the limb which may 
be called the metatarsus. This extends all 
along the upper and inner border of the limb 
as far as its extremity, where it forms a sort of 
digit, to which is attached the tendon of the 
great abductor muscle. This large piece is 
formed by the consolidation of three smaller 
ones, two of which run parallel to each other, 
so as to constitute a semi-canal, into which 
opens a duct derived from a large gland here- 


To the metatarsus succeed seven other car- 
tilages, the shape of which is different in the 
various species of Chondropterygii, but which 
obviously represent the phalanges of the abdo- 
minal limb, which is moved by five strong 
muscles which may be named respectively the — 
depressor, the elevator, the abductor, the ad- 
ductor, and the expansor of the fin. It is, 
however, remarkable that there is no muscular 
apparatus calculated to approximate these 
members, and when separated they are brought 
together again entirely by their own elasticity, 
a circumstance which militates strongly against 
their being, as is generally su instru- 
ments of prehension. In the Sharks the clas- 
per contains morever a gland of considerable 
size situated beneath the fin, and extending to 
the exterior of the base of its genital append- 
age. Inferiorly, this gland is only covered by 
the skin, while above it is adherent by the in- 
tervention of cellular tissue to the rays of the 
fin. Its duct is a wide canal which opens into — 
the groove formed by the metatarsal cartilages 
above alluded to, and the fluid which it secretes 
of a highly viscid character. It is said that in 
the breeding season the contents of this gland, 
as well as the parietes of the spe in which — 
it is situated, are red with blood and appear to 
be in a remarkable state of turgescence. It is 
enclosed in a double tunic, one fibrous and the 
other muscular, by the assistance of the latt 
of which its contents are evacuated. 

At the lower extremity of this gland, near its” 
orifice, there is in each clasper a capsule with 
muscular and cavernous parietes, the on of 
which is traversed by slender tendinous fila~ 
ments. In thesesacs Dr. John Davy* has ob- 
served distinct pulsations, and finding that in 
the living fish they were filled with blood, con- 
siders them as accessory hearts destined 
assist the circulation of the blood in these 
appendages to the genital system. & 

he gland itself is of the shape of an olive; 
a longitudinal sulcus divides it into two por 
tions, in each of which a transverse series Of 
very delicate tubes is distinguishable. 

In the females of the Plagiostome Chon- 
dropterygii the arrangement of the sexual o 
gans conforms in an equally striking mann 
with the Reptilian type of structure, 


* Phil, Trans, 1839. 


PISCES. 


ovary is distinct from the oviduct, as in the 
three higher classes of Vertebrata. When the 
ovules are not developed,* the ovary of the 
Sharks forms a thick. oval lamina slightly 
notched or concave upon its inner border, sus- 
pended upon each side of the vertebral column 
at the very anterior extremity of the abdominal 
cavity, from which point it is prolonged back- 
wards for a greater or less extent. The inferior 
and internal surface of this lamina, that by 
which the ovaria would touch each other if 
approximated, presents no prominences, but is 
of a uniform milk-white colour. The posterior 
surface of the organ has the same appearance, 


Fig. 538. 


Viscera of female Shark, after Hunter. 

a, skin; 56, cut pectoral and pelvic arches; c, heart; h, 
cecal appendage to intestine; m, ovary; g, oviduct ; 7, ute- 
rine portion of oviduct ; s, s, termination of oviducts in clo- 
acal cavity ; ¢, papilla on which the ureters open. 


* Cuvier, Legons d’Anatomie Comparée, tom.viii. 1846. 


VOL, IIl. 


1009 


except that upon the anterior half or two-thirds 
of the ovary little rounded eminences of dif- 
ferent sizes are perceptible, the smallest of 
which are pearl-white, while the larger are of 
an opaque-yellow colour; these are the ovules 
in process of developement from the proligerous 
stratum of the ovary, which gradually increase 
in size as they advance towards maturity, and 

roject through the upper surface of the ovary. 

his latter expands itself in the form of a cap- 
sule over the ovules in such a manner that as 
their developement increases they become de- 
tached from each other, and separating them- 
selves more and more become atlength racemose. 

The remainder of the ovarian lamina 
retains its soft, milky, homogeneous ap- 
pearance, which is very characteristic, 
and resembles very closely one portion 
of the testis of the male. 

In many of the viviparous Sharks, 
that portion of the ovary only which does 
not form eggs is met with upon one 
(generally the left) side of the body, 
whilst upon the opposite the organ 
attains its full developement. 

The general disposition of the rest 
of the generative apparatus is well shewn 
in the accompanying figure (fig. 538) of 
the sexual organs of the female Dog-fish, 
(Spinax acanthias, Cuv.,) taken from 
one of the admirable drawings left by 
John Hunter, and engraved in the Cata- 
logue of the Hunterian Museum. 

The ovary (n) presents ovisacs in dif- 
ferent stages of developement attached 
by a duplicature of peritoneum to the 
side of the spine, immediately below the 
liver and esophagus. The anterior orifi- 
ces of the oviducts (g,q) are situated 
close together above the liver; their 
coats, which are at first thin and mem- 
branous, gradually increase in thickness, 
and about four inches from the orifice 
become suddenly thickened by the addi- 
tion of a laminated glandular structure ; 
this is, however, much less developed in 
the present viviparous species than in 
the oviparous cartilaginous Fishes, and 
the size of the oviduct continued from 
the glandular part more nearly corre- 
sponds with that of the preceding por- 
tion than in the oviparous races. Be- 
yond the glandular portion the oviduct 
gradually increases in diameter, having 
its lining membrane thrown into longi- 
tudinal plice, until suddenly it dilates 
into a wide uterine aa (r), in which, 
in the viviparous Sharks, the young are 
retained after the eggs are hatched, until 
they are fit for exclusion in a living 
state. 

In the dilated uterine portion the 
lining membrane is gathered in close 
longitudinal folds, and their free mar- 
gins, which are beautifully wavy, contain 
each a vessel, which follows the sinuosi- 
ties of the fold, and sends off branches 
to the parietes of the oviduct. To- 
wards the terminations of the oviducts 

3 T 


1010 


in the cloacal cavity (s, s), these folds gradually 
subside into a few simple plications. 

In some species ( Mustelus, Cuv.) of these 
viviparous Sharks a very close attachment is 
formed between the walls of the uterine portion 
of the oviduct and the contained ovum, so much 
so indeed as to remind the anatomist very for- 
cibly of the placental connection that exists in 
the Mammifera. In these, according to J. 
Miiller, the ovum, on its arrival in the oviduct, 
is only covered with a kind of membranous in- 
vestment or chorion, which is as thin and de- 
licate as the amnion of Mammalia, and without 
apparent organization. The sac which this 
membrane forms is seven or eight times as long 
as the vitellus, and its walls being regularly 
plicated, are embraced by corresponding folds 
of the lining membrane of the oviduct, so that 
there is a very intimate adhesion between the 
two. 

In the oviparous races of the plagiostome 
cartilaginous Fishes the structure of the 
oviduct is somewhat different, in order to pro- 
vide for the formation of the egg-shell or horny 
envelope wherein the egg is contained when 
extruded from the body, the organization of 
which is not a little curious. The glandular 
portion of the oviduct is extremely thick, or 
rather is enclosed in a dense glandular mass 
(rudimental gland ), the substance of which is 
entirely made up of close-set transverse secern- 
ing tubes, which pour their secretion into the 
oviduct through innumerable orifices, which are 
aggregated together in a part where the course 
of the lining membrane of the oviducal canal 
is interrupted, and free thus left for the 
escape of the rudimental secretion, which, be- 
coming thus deposited on the surface of the 
egg, hardens into a tough horny substance, 
which constitutes its external covering or egg- 
shell. The shape of these eggs is remarkable ; 
the egg-shell when completed resembles an ob- 
long horny pillow-case, the four corners of 
which are prolonged into tendril-like processes, 
the use of which appears to be that they serve 
as anchors by becoming interlaced with the 
branches of submarine plants or ramose corals, 
and thus preserve the egg and its delicate con- 
tents from being washed away by the agitation 
of the waves. From the tough coriaceous or 
horny texture of these egg-shells, another pro- 
vision becomes necessary, in order that the 
mature embryo shall be enabled to escape from 
confinement and enter upon an independent 
existence. In the eggs of Birds this is abun- 
dantly provided for by the brittle texture of the 
calcareous substance in which they are en- 
closed, allowing the chick to break its way out 
of its fragile covering, a mode of egress which, 
in the case before us, would evidently be im- 
saocrr es This difficulty is met by a very 

utiful contrivance. The horny walls of the 
eggs of the plagiostome Fishes are continuous 
all round, except at one extremity, where, to 
use a homely illustration, the end of the pillow- 
case remains unsewn, the edges of the slit thus 
left being merely kept in apposition by the 
elasticity of the ochy envelope. By this ele- 
gant arrangement all intrusion from without is 


PISCES. 


effectually prevented, and at the same time, 
seeing that the valves will separate on the ap- 
plication of a very slight pressure from within, 
they soon yield to the efforts of the young fish 
to escape from its cradle, and afterwards close 
again so accurately that it is difficult, without 
attentive examination, to detect the existence of 
the fissure. 

As amongst mammiferous animals certain 
races are provided with a marsupium or pouch, 
in which their immature young are carried 
about for a considerable period previous to 


their birth, so do we find certain Fishes provided 
Fig. 539. 


Viscera of Syngnathus acus (male). 

a, liver; 6, communication between the swim- 
ming bladder and the alimentary canal; ¢, sto- 
mach ; d, intestine ; f, allantoid bladder; g, ae ; 
testes ; m, kidney ; m, marsupial pouch 5 of 0, 


in interior of ditto. y 


PISCES. 


with a similar marsupial apparatus, in which 
the eggs are hatched and the young permitted 
to arrive at their full developement prior to 
their expulsion. These are the Syngnathida, 
or pipe-fishes. There is, however, this remark- 
able difference between the mammiferous mar- 
supials and these singularly organized genera, 
namely, that in the former it is the female that 
is furnished with the marsupial pouch, whereas 
in the Syngnathide the male only is so pro- 
vided. In fig. 539, representing the male of 
Syngnathus acus, the marsupial apparatus is 
well exhibited ; it consists of two large valves 
(m) situated beneath the tail, immediately pos- 
terior to the cloacal orifice. The internal sur- 
face of this pouch is indented with deep cells 
(0, 0), more especially towards its posterior 
surface, where the ova are principally lodged. 
Here the eggs are hatched, after which the 
young Syngnathi are retained in the pouch for a 
considerable period before they are finally ex- 
elled. 

° In the female Syngnathus there is no sub- 
caudal pouch developed, but in this sex the 
vulvais unusually prominent, apparently for the 
purpose of facilitating the conveyance of the 
ova into the marsupium of the male. 

In Syngnathus ophidion (Bloch) the ova, 
after extrusion from the female and impregna- 
tion, become attached to the cellular surface of 
the ventral parietes of the abdomen of the male, 
but are not protected by cutaneous processes or 
valves. 

Urinary apparatus.—The kidneys in Fishes, 
as in all other Vertebrata, are two in number, 
situated on each side of the spine. They 
are, however, in the class before us remarkable 
for their very great proportionate size, some- 
times extending from the anterior boundary 
of the abdomen quite to its posterior ex- 
tremity, and occasionally uniting together in 
the mesial plane, so as to have the appearance 
of being but a single gland. Internally they 
present no division into cortex and fasciculate 
ducts terminating in a pelvic cavity, but their 
parenchyma is homogeneous, being entirely 
composed of arborescent ducts, which are im- 
mediately continuous with the ureters, which, 
running along the anterior surface of the kidney, 
receive the uriniferous tubes as they pass along 
towards the cloaca, where they terminate. Most 
commonly there is a distinct urinary or allan- 
toid bladder situated behind or dorsad to the 


1011 


rectum (fig. 539, f), which, in some spe- 
cies, is bifid at the anterior extremity, as in the 
Frog and other amphibia. 

Occasionally the urinary canals unite and 
terminate by a common duct (ureter) upon a 
fleshy tubercle or penis-like projection of the 
walls of the cloaca, as in the female Shark 
(fig. 538, t.), where a bristle is represented in- 
troduced into the extremity of the urinary 
passage. 

Renal capsules —In the osseous Fishes these 
organs are supposed to be represented by two 
or sometimes three roundish bodies of a light 
grey colour, situated sometimes near the mid- 
dle, oftener at the hinder extremities of the 
kidneys, at or near the entry of the hemal 
canal; sometimes they lie free, sometimes they 
are imbedded in the renal tissue (Pike, Salmon, 
Eel); but they always possess a proper cap- 
sule and present a minutely granular texture 
without distinction of cortical and medullary 
parts.* In the yellowish suprarenal bodies of 
the Sturgeon, the granules are minute spherical 
cells filled by microscopic nucleated corpuscles. 
In the Plagiostomes they are represented by 
elongated narrow yellowish bodies situated be- 
hind the kidneys, and sometimes extending be- 
hind the dilated ureters. 


BIBLIOGRAPHY. — Cuvier, Legons d’anatomie 
comparée, 8vo. 1846. Cuvier et Valenciennes, His- 
toire naturelle des poissons, 4to. 1828. Haller, 
Opera minota, vol. iii. Monro, Structure and phy- 
siology of Fishes, fol. 1785. Observations on the 
organ of hearing in man and other animals, 4to. 
1797. Scarpa, De auditu et olfactu, fol. 1789. 
Comparetti de aure interna comparata, 4to. 1789. 
Hewson, Phil. Trans. vol. lix. Cavolini, Memoria 
sulla generazione dei pesci e dei granchi, 4to. 1787. 
Autenrieth, Anatomie de la plie. | Wiedemann’s 
Archiv, tom. i, 1800. Geoffroy St. Hilaire, An 
nales des Museum d’Hist. Nat. t. ix. & x. Rosen- 


. thal, Ichthyomische Tafeln, 4to. 1812-22. Spix. 


Cephalogenesis, fol. 1815. Carus, Lehrbuch der 
Zootomie, 8vo. et 4to. 1818. Erlanterungs-tafeln 
zur vergleichenden anatomie, fol. 1826. Weber, 
De aure et auditu. Van der Heaven, Dissertatio 
philosoph. de sceleto piscium, 8vo. 1822. Bakker, 
Osteographia piscium, 4to. 1822. Meckel, Traité 
d’anat comp. 8vo. 1828-9. Owen, Lectures on com- 
parative anatomy, Lond. 1847, 


* Owen’s Lectures, (Pisces, p. 285.) 


T. Rymer Jones.) 


PLACENTA. 


See Ovum (Supplement ) 
and Urerus. 


ANALYTICAL INDEX 


TO THE 


THIRD VOLUME. 


INSTINCT. 1 Trritability (continued). p 
Instincts designed for the preservation of the individual, 7 of the left side of the heart, but that venous bload is 


lefence and offence, 7 
relating to the eens of food, 7 
construction of habitations, 9 
_ connected with hybernation, 11 
instincts for the propagation and support of off- 
spring, 13 
migration, 13 
choice of place for the deposit of ova, I4 
nidification, 14 
incubation, 14 
procuring nourishment and protection for the 
_.. young, 15 
instincts relating to the welfare of the race or of the 
animal creation generally, 15 
common to man and brutes, 15 
motives of action contrasted with intellect, 16 
congregation, 16 
imperfect societies of insects, 16 
for society alone, 16 
of males in the pairing season, 16 
for emigration, 16 
for feeding together, 16 
for some common work advantageous to the commu- 
nity, 17 
of the higher animals for various purposes, 17 
perfect societies of insects, as ants and bees, 18 
reasons for considering the actions of ants and bees as 
_ the result of instinct, not of reasoning, 20 
instances of actions of the lower animals in which 
short bn ee of reasoning seem to have been con- 
cerned, 21 
acquired instincts, 93 
instinct viewed with respect to the part it takes in the 
unceasing changes going on at the earth’s surface, 23 
free will in man, 24 
instinct viewed with respect to final causes, 25 


Intestinal Canal, see Stomach and Intestinal Canal 
Irritability 


definition and use of the term, 29 
test of irritability, 29 
question whether irritability belongs to the muscular 
fibre alone, or to the muscular and nervous com- 
bined, 29 
— drawn from phenomena observed in the 
eart and other involuntary muscles, 29 
Legallois’s and Philip’s experiments of removing the 
spinal marrow, 29 
experiment shewing that the heart may be impressed 
through the ganglionic system after the removal of 
the brain and spinal marrow, 29 
effect of narcotics on the heart and bowels, 30 
vis insita in connection with vis nervosa, 30 
new laws of action of the vis nervosa, 30 
gy of irritability not the same in every organ of the 
_ body, 30 
different degrees of irritability in different animals, 31 
relation of the degree of irritability to respiration, 31 
I. Of the pneumatometer, 51 
Il. Of the measure of irritability, 33 
difference in the duration of the beat of the heart re- 
moved from the body in the fetal, early, and adult 
States of the ny aed animals, 34 
babe ine of the beat of the heart longest on the left’ 
side, 34 
experiment showing the effect of artificial respiration 
on the heart’s beat, 34 
deduction that arterial blood is the necessary stimulus 


a sufficient stimulus of the right, 35 
the power of enduring suspended animation a measure 
of irritability, 35 ; 
observations on the irritability of the heart in hyber- 
nating animals, 35 
properties of activity and tenacity of life, 35 
source of irritability, 36 
observations of Prochaska, 36 
of Nysten, 36 
of Legallois, 37 
experiments of Miiller, 37 
observations of M. Segalas on the effects of strych- 
nine, 31 
observations and experiments of the author, 38 
explanation of the discrepancies of former au- 
thors, 39 
deductions, 40 
application ‘of the principle deduced to patho- 
ogy, 40 
influence of emotion on paralytic limbs, 40 
influence of certain respiratory acts, 40 
effects of the tonic power, 40 : 
effect of strychnine on paralytic limbs, 40 
influence of the brain and spinal marrow respect- 
ively on the anterior and posterior limbs re- 
spectively, 40 A 
cases substantiating the foregoing observations, 41 
recapitulation, 42 
experiments of Dr. J. Reid, 42 fi 
experiments testing the relation of the ganglionic 
system to the irritability of the viscera, 43 ; 
Joint, see Articulation and the articles under the headings 
of the several joints 
Kidney, see Ren. 
Knee-joint (Normal Anatomy), 44 
bones, 44 
cartilages, 45 
semilunar cartilages, 45 
ligaments, 46 
synovial capsule, 46 
mechanical functions, 47 
adjacent burse, 48 
arteries and veins, 41 
comparative anatomy of the knee-joint, 48 
Knee-joint (Abnormal Conditions of), 48 
disease, 48 ae. 
simple acute inflammation of the knee-joint or ar- 
thritis genu, 49 
example of acute arthritis genu, 54 
simple chronic inflammation of the knee, 55 
description, 55 
cases, 56 | 
chronic rheumatic arthritis genu, 57 
cases, 58 
anatomical characters, 60 a 
white swelling, or chronic strumous arthritis genu, 60 
anatomical characters, 62 . 
acute arthritis genu combined with acute osteitis, 64 
with necrosis, 64 
abscess without necrosis, 65 ee 
displacements occurring in chronic necrosis in the 
vicinity of the knee, 65 
of the tibia backwards, 65 
rotation of the tibia outwards the patella on the 
outer condyle of the femur, 65 
with the tibia displaced backwards also, 66 
abnormal conditions resulting from accident, 67 


1014 
Knee-joint (continued). 


fractures, 67 
transverse fracture of the femur immediately 
above the condyles, 67 
oblique fracture of the lower end of the femur, 67 
nto the knee-joint, 68 
by detachment of the outer condyle, 68 
~) a of the inner condyle, 68 
fracture, 
fractures of the bie near the knee, 69 
transverse, 69 
oblique ‘ate the joint, 69 , 
fracture of the patella, 69 
cagagerraey~ 7 
of the femur from the tibia, 71 
of the femur backwards, 71 
of the femur forwards, 72 
lateral dislocations of the knee, 72 
- the femur inwards, 72 
of the femur outwards, 72 
dislocations of the patella, 73 
outwards, 73 
inwards, 73 
incomplete luxation of the patella, 73 
dislocation of the patella on its edge, 74 
internal carne of the knee, 75 
sprains, 76 
a small ent of the tibia (the insertion of the 
crucial es = up, 77 
rupture of the quad ne extensor tendon from its 
insertion into the be ja, 7 
rupture of the ligamentam aie: 78 
rymal Organs (all the accessory or hg parts of 
the eye except the orbit and muscles), 78 
1. The eyelids, 78 
general fr on ag td 
rima palpebraru 
ponent mS Saad re epelide, 79 
winking, 
Meibomian Fro Iitctes, 79 
adaptation of the eyelids, 79 
canthi, 79 
secondary fissure of inner canthus, 79 
lachrymal papilla and puncture, 80 
lacus lachrymalis, 80 
lachrymal nade ity 
plica map inet dal 
bi ager ge es, 
rot bobs ny eyelid, 80 


pa ht 7 she eyelids in concert with the iris, 80 
internal ry eee of the eyelids, 81 
ligaments, 81 
tarsal cartilages, 81 
fibrous condition of the lower tarsal carti- 
lage in ae pee of both in the lower 
mammalia, 8 
Meibomian follicles lie in the substance of 
Ri gh tarsal cartilage, 81 
pebral ligament, 81 
a Fern palpebral ligament, 81 
orbicu palpebrarum, 81 
levator palpebre superioris, 82 
palpebral conjunctiva, 82 
skin of the eyelids, 82 
cellular tissue of the orate 82 
roots of the eyelashes, 82 
sebaceous oor 82 
Meibomian glands, 82 
comparative roma of, 83 
secretion of, 83 
hordeolum, 83 
2. Conjunctiva in general, 8$ 
oculo-palpebral space "of the conjunctiva, 83 
superior and inferior palpebral sinuses of the con- 
unctiva, 84 
folds of the coaasere 84 
lachrymal caruncle, 84 
plica semilunaris, 84 
membrana nictitans, 85 
volcom conjunctiva, 85 
ocular, 
subconjumctival cellular tissue, morbid condition 
of, 85 
nature of the conjunctiva, 8 
continuity with other parts of the mucous mem- 
brane, 85 
lachrymal and conjunctival secretion, 85 
Lok ancee peecuss of palpebral conjunctiva, 85 
papillary body, 85 
epithelium, pd 
ae structure of sclerotic conjunctiva, 86 


re oti 
conjunctival cove cornea, 87 
3, Lachrymal properly so called, 88 
lachrymal gland, 
intimate @ round: 89 
sa ile ducts, 89 ° 
tears, 90 
chemical composition, or 
derivative lachrymal organs, 90 
lachrymal groove, 90 


ANALYTICAL INDEX. 


Organs (continued). 
argc osseous Canal for the lachrymal duct, 90 
—— papilla, points and consiiculiay gt 
ee dct, 02” = 


struct 
nol and vil villi, 92 


jon, 92 
echegueal muscle (tensor tarsi), 92 
origin, 92 
relations, 92 
action, 93 
nerves, 93 


fifth ne 
frontal di Siemon, 0 
inferior palpebral 


seventh igh g 93 
third pair, 93 
bloodvessels, 93 
arteries, 93 
distribution of vessels to the conjunctiva, 93 
Teens anatomy and developement, 94 
ds, 94 


in Man, 95 

in Birds, 95 

iy 

n Liza vg 

p= Cohen poda, 

n Ce te) > 
eyebrows and Neyelashes, 9 

Poa Mamenins 95 


in 
flocculent growth of the yong Be the La 


&e. 95 
Il, The ‘conjunctiy semalinnay et ieee 
nictitaus third ey rm 


runcle and slandate’ ‘t eden se 
oculo-palpebral space, 96 


in serpents, 96 
membrana nictitans, 96 
cartilage of the membrana nictitans, 97 
muscles, 97 
third eyelid id of Birds, 97 


in the Owl Parrot, 97 
in Chelonia and in the Frog, 97 
slandele of Deretss 98 


secretion, 98 
III. Gecreting san derivative lachrymal appa- 
t 
in Mammalia, 98 


lachrymal bone, 99 
infra-orbital glandular sacs of eerge 4 99 
development of the accessory parts of the eye, 99 


eyelids, 99 

tarsal cartilages, 99 
lachrymal gland, 99 
inner canthus, 99 
eonnrett caruncle, 99 


vemeeal description, 109 
cartila 


epiglottis, 103 
arvicalations aed if 


] thy o-ep ote ion 
os —— 


ligament, 105 
crico-arytenoid articulation, 105 
thyro-arytenoid ligaments or chord# vocales, 105. 
inferior, 105 
superior, 105 
muscles, 105 
extrinsic, 105 
intrinsic, 105 
maar? Mag 105 


at ts laterales, 107 
oidei, 107 


eibear 
aryten 


ANALYTICAL INDEX. 
Leg, Regions of the, Rca wae 


Larynx (continued) . 
7 obliquus, 107 
transversus, 107 
thyro-arytenoidei, 108 
action, 109 
crico-arytenoidei postici, 109 
thyro-epiglottidei, 110 
aryteno-epiglottidei, 110 
action, 110 9 B09 
recapitulation of the action of the instrinsic 
muscles of the larynx, 110 
bloodvessels, 110 
structures called glands, 110 
arytenoid gland, 110 
epiglottic gland, 111 
mucous membrane, 111 
glosso-epiglottic folds, 111 
aryteno-epiglottic folds, 111 
rima glottidis, 111 
mum Adami, 112 
ventricles of the larynx, 112 
nerves, 112 
superior laryngeal, 112 
inferior or recurrent laryngeal, 113 
functions of the laryngeal nerves, 113 
motions of the glottis during respiration, 113 
phenomena observed when the recurrent 
nerves are diseased, compressed, or cut, 113 
spasmodic closure of the rima glottidis, 113 
Lot dex get stridulus, 113 i 
description of the larynx deprived of its extrinsic 
muscles, 114 
anterior aspect, 114 
lateral, 114 


internal, 114 
Larynx (Morbid Anatomy and Pathology), 114 
general remarks on the recency of accurate know- 
ledge of the abnormal conditions of the larynx, 114 
general remarks on diseased conditions of the laryn- 
eal mucous membrane, 115 
of the submucous tissue, 115 
of the cartilages, 115 
of the muscles, 115 
of the ligaments, 115 
acute inflammation of the mucous membrane, 115 
of the child, or croup, 115 
adventitious membrane, 116 
post mortem appearance of the lungs and brain, 
116 


of the adult, 116 
cedema of the submucous tissue, 116 
varieties, 117 
idiopathic, 117 
traumatic, 117 
cedema without evidence of inflammation, 
17 


1 
causes of death, 117 
spasm of the glottis, 117 
diphtherite, 117 
scarlatina anginosa or angina maligna, 117 
- symptoms and appearance, 117 
sloughing, 118 
thickening by gradual deposit, 219 
nia A n stat 
_ §angrene of the softer tissues of the larynx, 120 
disehoed condition of the cartilages of the larynx, 120 
phthisis laryngea, 120 ~ 
alteration in size and shape of the epiglottis, 122 
morbid thickening, or shrinking, 122 
leaf-like expansion, 122 
derangements of the functions of the larynx unat- 
tended with organic change, 192 
exceptions to the use of the epiglottis, 122 
epiglottis inert, 123 
condition of the epiglottis in an animal asphyxi- 
ated by carbonic avid, 193 
pathological conditions of the muscles of the larynx, 
1 


diseased conditions of the laryngeal ligaments, 126 
Leg (Regions of the), 1296 
general survey, 197 
external form of the leg, 127 
calf, 127 
integument, 127 
varicose condition of the capillaries of the inte- 
gument, 128 
superficial fascia, 123 
superficial veins, 128 
major saphena, 198 
minor saphena, 198 
varicose ulcer, its treatment, 130 
superficial nerves, 130 . 
internal saphenus, 130, 
external saphenus or communicans tibialis, 130 
superficial lymphatics, 130 
aponeurosis, 130 
of the anterior region, 180 
of the posterior region, 130 
superficial layer, 130 


. layer, 130 
anterior region of the leg, 131 


1015 


muscles, 13 
anterior tibial artery, recurrent tibial, 191 
operations for ligaturing, varieties, 132 
relations, 139 
posterior region of the leg, 132 
muscles, 132 
superficial layer, 132 
trocnemius and soleus, 132 
ivision of the tendo Achillis, 132 
plantaris, 133 
deep layer, 133 
arteries, 133 
posterior tibial, 133 
course, 133 
relations, 133 
operation for ligaturing, 133 
peroneal, 134 
course, 134 
relations, 134 
operations for ligaturing, 134 
vene comites, 134 
nerve, 134 
deep lymphatics, 134 
difficulty of preserving the proper position of the 
fibula in fracture, 135 
precaution with respect to the projecting angle which 
the tibia, when amputated, presents anteriorly, 135 
arteries requiring ligatures in amputation, 135 
remarks on the application of artificial legs, 136 
the most eligible situations for exposing the tibia in 
order to trephine, &c., 136 
liability of the tibia to disease, 196 
curve of the tibia, 136 
fractures of the leg, 136 
of the fibula alone, 136 
Leg (Muscles of the), 137 
anterior group, 137 
tibialis anticus, 137 
extensor longus digitorum, 137 
relations, 137 
action, 137 
extensor proprius pollicis, 137 
action, 137 
relations, 137 
peroneus tertius, 137 
relations, 137 
action, 138 
external group, 138 
peroneus longus, 138 
action, 138 
relations, 138 
peroneus brevis, 138 
combined action, 138 
posterior group, 138 
superficial layer, 188 
* gastrocnemius, 138 
relations, 138 
soleus, 138 
relations, 139 
tendo Achillas, 139 
action, 139 
plantaris, 139 
action, 139 
deep layer, 139 
sean 139 
xor longus digitorum, 139 
accessory muscles, 139 
relations, 140 
fiexor longus pollicis, 140 
action, 140 
tibialis, 140 
Life, 141 F 
I. General views, 141 
definition, 141 
tendency of the changes exhibited by a living 
being, 141 
method of prosecuting the inquiry, 141 
difficulty in the attainment of general laws in 
some departments of science, 141 
difficulties which beset the investigation of the 
laws of vital action, 142 
conditions required for the production of vital 
actions, organized structure and stimulus, 142 
vital properties due to the act of organization, 142 
II. History of opinions, 143 
abstract terms used in the earlier ages of the 
world expressing a vague idea of a property 
inherent ina that exhibits it, 143 
the term life as applied by the older philosophers, 
143 


tendencies in the unenlightened mind from which 
the foregoing modes of explaining vital pheno- 
mena have resulted, 144 

modification which the forementioned doctrines 
have undergone, 144 

distinctness of life and mind, 144 

doctrine of the vital principle put forth byBarthez, 
vis medicatrix nature of Hoffman and Cullen, 
nisus formativus of Blumenbach, organic agent 
of Dr. Prout, and organic force of Miiller, 145 

Hunter’s doctrine of the vital principle, 145 

precise import attached to the term, 146 


1016 ANALYTICAL INDEX. 
Liver (continued). 


Lin tinued) . 
( Dr. Prout’s definition, 146 
111, Nature and causes of vital action, 146 
all changes the results of the properties of matter 
called into exercise by appropriate stimuli, 140 
functions groups of vital phenomena, 146 
sepennence of vital actions upon external sti- 
muli, 147 
every class of organs is excited to action by its 
particular stimuli, 147 
conditions of a more general nature requisite for 
the performance of vital actions, as heat, light, 
and electricity, 147 
analogy of vital phenomena to those of the 
universe at large, 147 
illustration—the earth, solar system, and uni- 
verse, 147 
illustration—the steam-engine, 148 
conclusion—vital actions the properties of organs 
called into action by appropriate stimuli, 148 
IV. br connection between vitality and organiza- 
tion, 148 
probability that the properties which give rise to 
vital action exist in all forms of matter or at 
least in all of those forms of if capable of be- 
coming organized, 148 
total change effected in the properties of certain 
forms of matter by their entrance into new 
combinations due to the act of combination, 
as analogous to vital properties being due to 
the act of organization, 149 
no poeay distinct from the matter which ex- 
hibits it, or capable of being superadded to it or 
abstracted from it, analogy of the magnetic 
roperties of iron to vitality considered, 149 
evidence of vitality being due to the properties of 
matter in the condition of organized tissues, to 
be found in the vital actions themselves, 149 
the assertion that the existence of organization 
implies a previous existence of life, considered, 
150 


many actions performed by living beings common 
to them and inorganic matter, 150 | 
reparation of materials for organization, 150 
V. Changes in composition, 151 
formation of proximate principles, 151 
grounds for the assumption of a distinct set of 
vital affinities, 151 
reasons for believing that the compounds with 
which organic chemistry supplies us have a si- 
milar constitution to that of inorganic com- 
pounds, 152 
the arguments in favour of vital affinity drawn 
from the spontaneous decomposition of organic 
matter, considered, 152 
organic matter, considered, 152 
presumed impossibility of artificially pro- 
ducing organic compounds or proximate 
principles, considered, 153 
artificial and natural conversion of gum, 
starch, and lignin énto sugar, 153 
catalytic action, 153 
evolution of electricity during the ordinary 
processes of growth of plants and animals, 
5 


154 
inability of chemists to produce organic com- 
pounds probably due to their want of ac- 
quaintance with the form or condition in 
which their components must be brought 
together in order to enter into the desired 
union, 154 
conclusions deduced from the foregoing para- 
_graphs of the chapter, 154 
VI. Vitality in a dormant or inactive condition, 154 
dormant vitality of seeds, eggs, &c. 155 
length of time during which the dormant 
vitality may be preserved, 155 
dormant vitality of seeds, 155 
dormant vitality of eggs, 156 
agents which destroy the vitality of seeds and 
eggs such as are calculated to produce im- 
portant changes in their structure and com- 
ition, 156 
dormant vitality of plants and animals that 
ome attained beyond the embryo condition, 
15) 
preservation of dormant vitality due to the main- 
tenance of normal constitution, 157 
suspension of vital action under other circum- 
stances, 157 
hybernation of plants, 157 
hybernation of animals, 157 
animals enclosed in rocks and trees, 158 
syncope, 158 
ae Ry of vital action in parts of the human 
ly, 159 
i tenor of Dr. Daubeny, 159 
Liver (Normal Anatomy), 160 
situation, 160 
ark 160 - 
tion, 1 
rondionh, 160 
ligaments, 160 


Liver (Pa ical Anatomy), 182 


fissures, 161 
lobes, 162 ; 
coverings, 162 
color, 162 
dimensions, 163 
chemical analysis of human liver, 163 
of bullock’s liver, 163 
varieties in form, 163 
varieties of position, 163 
gall bladder, 164 
relations, 164 
coats, 164 
excretory ducts of gall bladder and liver, 164 
coats, 164 
varieties in the gall bledder, 164_ 
structure of the liver, 164 
the terms lobule and acinus as used by Malpighi, 
Miller, and Kiernan, 165 
Glisson’s capsnle, 166 
vaginal portion, 167 
interlobular portion, 167 
lobular portion, 167 
tage die how hes and vaginal pl 
vaginal branc lexus, 167 
interlobular veins, 168 
lobular veins, 168 
abdominal and hepatic origins of the portal vein, 


168 
hepatic duct, 169 
vaginal ducts and be pe plexus, 169 
interlobular ducts, } 
lobular ducts and lobular plexus, 169 
termination of the biliary ducts, 170 
vascularity of the biliary ducts, 170 
mucous membrane and follicles of the biliary 
ducts, 171 
hepatic artery, 171 a % 
vaginal arteries, 171 
intralobular arteries, 171 
lobular arteries, 171 
distribution, 171 
hepatic veins, 172 
interlobular veins, 173 
sublobular veins, 173 
hepatic trunks, 173 
lymphatics, 173 
nerves, 174 
progressive development of the liver in the animal 
series, 174 ) 
liver in Invertebrata, 174 
in he ge a 175 £ the gall 
comparative anatomy of the bladder, 176 
bile secreted from arterial blood in Inverte’ 
formation of portal vein in the Vertebrate 
classes, anastomoses of portal and caval veins, 176 
hepatic veins of diving animals, 176 
development of the liver in the embryo, 177 
in the Fowl, 177 __ 
in the human subject, 177 
uses of the liver, 178 
secretion of bile, 178 
anomalous opening of the portal vein into the 
vena cava, 178 
quantity of the bile, 180 
expulsion of the bile, 180 
uses of the bile, 181 
red and yellow substances of Ferrein, 181 . 
researches of M. Dujardin, 182 


diseases of the serous membrane, 182 
acute inflammation, 182 
chronic inflammation, 183 
depositions iu the subserous tissue, 183 
diseases of the mucous membrane, 183 
disorders of the venous circulation, 183 
— congestion, 184 
epatic venous congestion, 184 
portal venous congestion, 184 _ - 
errors of Miller and Cruveilhier, with regard to 
the structure of the liver, 185-6 44 
disorders of the biliary excretion, 187 
biliary congestion, 187 
effects of obstruction of the gall ducts, 187 
diseases of the parenchyma, 187 
inflammation, 188 
hypertrophy, 188 
atrophy, 188 
cirrhosis, 188 
softening, 189 
induration, 190 
fatty degeneration, 190 
abscess, 1 
tubercle, 192 , 
scirrhus, 192 
medullary sarcoma, 193 
seat of origin of carcinoma, 194 
fungus hematodes, 194 
melanosis, 194 
disorders of pana 194 £ bile, 19 - 
suppression of secretion of bi 
alterations in the physical properties of the © 
ile, 195 P 


ANALYTICAL INDEX. 


Liver, Pathological Anatomy of the (continued). 
alterations in the chemical properties of the 
bile, 195 : 
biliary calculi, 195 
entozoa, 196 
Luminousness, animal, 197 
I. Enumeration of luminous animals, 197 
II. Characters and properties of animal light, 198 
colour, 198 
smell, 199 
III. Circumstances in which light is given out and by 
which its intensity is affected, 199 
natural circumstances, 199 
temperature, 199 
solar light, 199 
lunar light, 199 
abrupt collision with other bodies, 199 
loud noises, 200 
internal movements of the animals them- 
selves,—will, &c. 
artificial circumstances, 200 
accumulated electricity and electrical cur- 
rents, 200 


1017 


Lymphatic and Lacteal System (continued). 
superficial, 231 
lymphatics of the exterior of the upper part 
the trunk, 231 
vasa efferentia of the axillary glands, 231 
aoe lymphatics of the head and face, 
deep seated, 232 
Lymphatic System, Abnormal Anatomy, 232 
commeea variations from the normal distribution, 


diseased conditions of the lymphatic and lacteal ves- 
sels, 
inflammation, 233 
ulceration and adhesion of the valves, 233 
thickening of the coats, 233 
varicosities, 233 
diseased conditions of the absorbent glands, 233 
inflammation acute and chronic, atrophy, 233 
deposits, 233 i: 
tubercle, 233 
cancer, melanosis, and encephaloid matter, 234 
calcareous and carbonaceous deposits, 234 


immersion in various fluid and g 
media, 200 
pressure of their bodies, 201 
removal of the luminous organs, and removal 
of these and other organs, 201 ; 
exposure to various degrees of heat and mois- 
ture, 201 
immersion in vacuo, 201 
removal from all foreign sources of light, 201 
IV. Seat of luminousness in different animals, 201 
VY. Anatomy of light-giving organs, 202 . 
V1. Geographical distribution of luminous animals, 
203 
VII. Theories of animal luminousness, 203 
VIII. Uses of animal luminousness, 204 
1X. Luminousness of animals not innate, and other 
allied phenomena, 204 a0 5 
luminousness of the human body, and emission 
of light from the eyes of vertebrate animals, 204 
luminousness of dead fishes and other dead ani- 
mals, 205 
Lung.—See Pulmonary Organs. 
Lymphatic and Lacteal System, 205 
— description, 206 , 
istory of the discovery of the lymphatic vessels, 206 
distribution of lymphatic vessels in the human sub- 


ject, 206 
structure, 268 
inner tunic, 208 
fibrous tunic, 208 
lymph hearts, 209 
external tunic, 209 
valves, 209 
mode of origin of the lymphatics, 211 
yap or absorbent glands, 217 
loodvessels, 218 : 
nerves, 218 
structure, 218 
convoluted tube, 218 
lymph, 219 
analysis of, 220 
microscopic appearance, 221 
chyle globules, 221 
analysis of chyle, 222 
taken from the thoracic duct, 222 
J before reaching the thoracic duct, 223 
descriptive anatomy, 293 
position of lymphatic glands, 224 
in the lower and upper extremities, 224 
in the cervical region, 224 
on the head and face, 224 
in the great cavities, 224 
mesenteric glands, 224 
bronchial glands, 224 
thoracic duct, 224 
right lymphatic trunk, 225 
lymphatic vessels, 225 
of the lower extremities, 225 
superficial set, 226 
of the exterior of the lower part of the trunk 
and external genitals, 227. 
course of the lymphatics in the neighbour- 
hood of the iliac arteries and the aorta, 297 
lymphatics of the testicle, 227 
of the kidneys, 227 
of the suprarenal capsules, 227 
of the lower part of the intestines, 227 
lacteals, 298 
lymphatics of the stomach, 229 
of the pancreas, 229 
ofthe spleen, 229. 
of the liver, 229 
deep, 229 
superficial, 299 
of the thorax and thoracic viscera, 229 
of the thoracic parietes, &c. 229 
of the lungs, 230 
of the heart, 230 
“> seated lymphatics of the upper extremity, 
iv) 


VOL, Ill. 


changes in the lymph, 234 
Mammalia, 234 
characteristics derived from 
the circulatory system, 234 
the secretory system, 235 
the alimentary system, 235 
the generative system, 235 
the osseous system, 235 
the nervous system, 235 
the organs of sight, hearing, smell, and taste, 236 
prMhary classification of Mammals, according to 
Aristotle, 236 
Ray, 237 
Linneus, 238 
Pallas, 238 
Cuvier, 239 
subdivisions of the primary groups, according to 
Linneus, 241 
Cuvier, 241 
affinities and classification of Mammalia according to 
Macleay and the Quinary school, 242 
primary division into two sub-classes according to 
Owen, 244 
orders arranged with regard to their affinities, 244 
Mammary Glands, 245 
human mamma, 246 
position, form, 246 
nipple, 246 
cuticle, rete mucosum, cutis, 246 
areola, 247 
tubercles of the areola, 247 
internal structure of the breast, 248 
ligamenta suspensoria, 248 
secerning portion of the gland, cellules, glan- 
dules, milk tubes, reservoirs, 248 
arteries, 248 
veins, 249 
nerves, 249 : 
absorbents, 249 
mammary gland in the male, 250 
comparative anatomy, 241 
Kangaroo, 251 
Ornithorhynchus, 251 
Cetacea, 251 
number of efferent ducts in various animals, 252 
morbid anatomy, 252 
inflammation, 252 
hydatids, 252 
chronic mammary tumour, 253 
hypertrophy of the adipose tissue, 254 
irritable tumour, 254 
malignant diseases, 254 
cutaneous cancer, 254 
scirrhus, 255 
carcinoma reticulare, 255 
carcinoma alveolare, 255 
soft cancer, fungus hematodes, and medullary 
cancer, 255 
carcinoma fasciculatum, 256 
melanosis, 256 
Marsupialia, 257 
essential external character, essential internal charac- 
ter, 257 
general remarks on the geographical distribution, &c. 
of the Marsupialia, 257 
classification, 258 
tribe I. Sarcophaga, 258 
apa Thylacinus, 258 
asyurus, 259 
Phascogale, 259 
tribe 11. Entomophaga, 259 
group 4, Gressoria, 260 
genus Myrmecobius, 260 
group B, Saltatoria, 260 
genus Perameles, 260 
Cheeropus, 261 
Troup ¥» Scansoria, 261 
: obi Didelphis, 261 
tribe uk Carpophaga, 262 


3. 


1018 ANALYTICAL INDEX. 
Marsupialia (continued, 


Marsupialia (continued). 
genus Phalangista, 262 
Petaurus, 263 
Phascolarctus, 265 
tribe IV. ae sere aad 265 
+ panei Hypsiprymnus, 265 


tribe V. I. akintenane. 267 
genus Phascolomys, 267 
esteology of the Marsupialia, 268 
the skull * 
composition of the cranium, 209 
occipital bone, 269 
temporal, 269 


nasal, 272 
intermaxilla ' bg 
superior maxilla 
“ rforations of the bony palate, 273 
cavity of the peg 274 ; 
inferior maxilla, 97 
af ys Peasolethessom and Thylacotherium, 


setahens, column, 276 
cervical vertebra, 276 
dorsal, 277 
pot 9 
sacru 


sternum, 280 
pectoral extremities, 250 

scapula, 280 

clavicle, 281 

humerus, 281 

bones of the fore-arm, 23! 

carpus, 282 

metacarpus, 282 

L begnrsa. 20g 282 
pelvic extremities, 282 

os innominatum, 283 

marsupial bones, 283 

femur, 284 

patella, 284 

tibia, 284 

fibula, 235 

tarsus, 285 

metatarsus, 286 


mye; 287 
ominal muscles in a male Phatanger, 287 
external oblique, 287 
internal oblique, 288 
transversalis abdominis, 288 
pyramidalis, 288 
cremaster, 288 
muscles of the pectoral extremity in Perameles 
lagotis, 289 
trapezias, 289 
latissimus dorsi, 289 
omo-anconeus, 289 
serratus Magnus, 289 
su ra-spinatus, 239 
deltoides, 289 
subscapularis, 289 
teres major, 289 
triceps extensor, 289 
peereee major, 289 
iceps, 289 
peace teres, 290 
exor carpi ulnaris and radialis, flexor subli- 
mis digitorum, 290 
flexor profundus, 290 
pronator quadratus, 290 
supinator longus, 290 
muscles of the pelvic extremity, 290 
in the Kangaroo; sartorius, &c., 290 
ina Dasyure; sartorius and glutei, 290 
in Perameles lagotis; sartorius, rectus femo- 
ris, and biceps flexor cruris, 290 
in Dasyurus macrurus; plantaris, soleus, tibi- 
alis posticus, flexor longus pollicis, flexor 
communis digitorum, 
in Phalangista valpinea; muscles of the ante- 
rior part of the leg, 291 
in Perameles lagotis; gastrocnemius, soleus, 
and plantaris, 291 
nervous system, 291 
rain, 291 
spinal cord, 295 
organs of sense, 206 
digestive apetemes 297 
mouth, 297 
lips, 297 
masticatory muscles, 297 
teeth, 298 
cheek pouches, 299 
fauces, 299 
alimentary canal, 299 
sebaceous follicles of the rectum » 303 


Membrane, 331 
Meninges, 331 
Microscope, 331 


proper s bi incter of the anus, $03 4 
table of t : sg of the intestinal canal, ina 
few speci ne : 
salivary glands, 304 
tonsils, 304 
liver, 304 


respiratory organs, 309 
tracheal rings, 309 
thyroid glands, 310 
larynx, 310 
Herp 310 
thyroid cartilage, 310 
kidney, 310 
supra-renal glands, 310 
ureters and bladder, 310 
male — = generation, 310 


testes, 

vasa dchorvatia, Sis 

vesicula seminales, 311 

menos and prostatic portion of the arethra, 


Comper glands, 311 
penis, 911 
spermatozoa, 312 
erectores penis, 312 
retractor penis, 312 
levator penis, 319 
sphincter cloace, 313 
eens € organs, 313 
ovaries, $13 
(review of the female generative 
groups of vertebrate animals,) 316 
uteri and vagine in various spe bs 8 


t of th 1 
purposes: answered, bythe ai diferent forms of the 
marsupial a pr ’ 


enerative organs ©) 
gelatino-mucous secretion in the 
clitoris, $19 
developement of Marsupialia, $18 
Teview of the different opinions whick have 
- expressed on the subject, 318 4 
experiment performed with a view to ascertain 
eriod of ee estation, the structure of t! 
‘etal envelo e conditions of the new-be 
young, &c. in the Kangaroo, $21 
Ovarian ovum, 393 
examination and dissection of an embryo . 
at about the twentieth day of utero-gestation, 323 
condition of the foetus of the Kangaroo at a later stage 
of uterine developement, 325 
new-born feetus of the Kangaroo, 3 . 
new-born fetus of Didelphys virgiatinas and subse 
quent growth of the young, $25 : 
condition of the young o "Kangaroo whilst in the 
-marsupium, 325 - 
relative size of the brain of the Mer Too 
compared with that of the embryo of sheer, 26 
traces of the umbilical vessels, Prvcipp es Po 
mammary feetus of poping’ Bn Ge: 
dissection of asmall mammary feetus of Kangaroo, $I 3 
larynx of the mammary fetus of Kangaroo, 327 
maturation of the mammary feetus, 327 
mammary organs, $27 
marsupium, 327 
observations on the claims of the Marsupialia to 
be regarded as a natural group of coe as f 
table of classification of the Marsupialia, 330 


1. Optical poctier governing the coustveciaial f 
mit roscopes, 
influence ore conve and concave lenses on the 
of light passing through them, 331 
spherical ett tg =n $34 
correction, 334 
Herschel’s doublet, 335 
chromatic aberration, 335 
correction, 335 
simple microscope, 3 
(phenomena of onan vision), $37 
convex lens, 337 
’ Dr. Brewster’s lens of diamond, capphirey 
carbuncle, 337 ' 
Dr. Wollaston’s doublet, 338 
(ones le of a greirg $38 
dington lens, 339 
Stanhope lens, 339 
com — beers 339 


Ha Sento e-piece, 341 
Mr. Holland's doublet ‘microscope, $42 = 
eye-pieces intended to increase the eld, : J 
sthieeatic combinations, method of yar 


the magnifying power, 343 


ANALYTICAL INDEX. 


Microscope (continued). 
test objects, 344 
II. Of the mechanical arrangements of microscopes, 
344 


objects to be attained 
steadiness and firmness, 344 
capability of accurate adjustment, 345 
the power of placing the instrument in either 
a vertical or horizontal position, 345 
simplicity, 346 
best means of carrying on dissections under a 
magnifying power, 346 
dissecting instruments, 346 
compressorium, 347 
ordinary compound, or simple, microscope, 347 
superior compound microscope, 349 
illumination, 351 
mirror, 352 
direct light, 352 
condenser, 353 
achromatic condenser, $5$ 
illumination of opaque objects, 354 
condensing mirror, 354 
Lieberkuhn’s speculum, 354 
back ground, 354 
III. Magnifying power of microscopes, 354 


measurement of the magnifying power of mi- . 


croscopes, 355 
micrometers 
micrometer-screw, 355 
micrometer eye-piece, 355 
micrometry by means of the camera lucida, 356 
camera lucida, 356 
the degree of minuteness of objects which the 
magnifying power of the microscope renders 
visible, 356 
Milk, 358 
cow’s milk, 358 
common milk globules, cream globules, and yel- 
low granulated corpuscles, 358 
butter, 359 
casein, a 
aposepedine, $59 
Geese of milk, 360 
lactic acid, 360 
substances found in the ashes of cow’s milk, 360 
proportion of cream in cow’s milk, 360 
colostrum, 360 
human milk, 361 
milk from the male breast, 362 
milk of the ass, 362 
mare, 362 
goat, 362 
sheep, 362 
bitch, 362 
contamination of the milk byfvarious ingesta, 362 
analogy of milk to blood, 362 


; Mollusca, 363 


general characters, 363 
nervous system, 364 
senses, 364 
muscular system, 365 
digestive system, 365 
circulatory system, 365 
respiratory system, 365 
uropoietic system, 366 
generative system, 366 
classification, 366 
Monotremata, 366 
general characters, 366 
Echidna, 367 
Ornithorhynchus, $67 
Spectr: 368 
skull, Echidna, 368 
occipital bone, 369 
parietal bone, 369 
temporal bone, 370 
frontal bone, 370 
nasal bone, 370 
palate bone, $70 
superior maxillary bone, $70 
comparison with the skull of various Edentate 
and Marsupial animals, 371 
skull, Ornithorhynchus, 371 
occipital and temporal bones, 971 
rietal and frontal bones, 373 
oramina in the floor of the skull, $73 
ee canal traversing the squamous suture, 
7: 


facial bones, 373 
lachrymal foramen, $74 
ridges on the outside of the cranium, $74 
interior of the skull, 874 
lower jaw, 374 

vertebral column, $74 
true vertebra, 374 
ribs and costal cartilages or sternal ribs, $75 
sternum, 375 
sacrum, 375 
caudal vertebra, 375 

pectoral extremities, 376 

pelvic extremities, $78 

muscular system, Ornithorhynchus, 379 


1019 


Monotremata (continued). 
nervous system, 389 
brain, Ornithorhynchus, 382 
Echidna, 382 
spinal cord, Ornithorhynchus, 385 
Echidna, $85 
olfactory nerves, Ornithorhynchus, 385 
_Echidna, $85 
optic nerves, 385 
ever 385 
third and fourth pair of nerves, $*6 
fifth pair, ss6 
sixth and seventh pair, $86 
acoustic nerve, 386 
ear, 386 
eighth and ninth pair of nerves, 886 
brachial plexus, median nerve, $87 
lumbar plexus, ischiadic nerve, 387 
Digestive system, 387 
alimentary canal, Ornithorhynchus, 387 
Echidna, 387 
salivary glands, 388 
liver, 388 
pancreas, 388 
spleen, 389 
circulating system, 389 
blood, 389 
heart, Ornithorhynchus, $90 
Echidna, 390 
aorta and great arterial trunks, $91 
venz cave and renal veins, 391 
ortal vein, 391 
respiratory system, 391 
lungs, 391 
trachea, 391 
larynx, 391 
thymus and other glands, 39t 
renal system, 391 
supra-renal bodies, 391 
kidneys, ureters, 391 
organs of generation, $91 
male organs, 391 
testicle, 592 
penis, 392 
levator and retractor muscies, $92 
Cowper’s glands, 392 
female organs, 393 
ovaries, 394 
Fallopian tubes and uteri, 394 
uro-genital canal, $94 
common vestibule, 395 
clitoris, 395 
Cowper’s glands, $95 
products of generation, 395 
ovum, $95 
the young—Omnithorhynchus—external cha- 
racters, 399 
dissection, 399 
mammary organs, 402 
crural gland and spur, 405 
Monstrosity, vide Teratology. 
Motion, Animal; Animal Dy icss L 
gressive Motion of Animals, 407 
general remarks, 407 
Section I. 
fundamental axioms, 408 
composition and resolution of forces, 408 
parallelogram of forces, 408 
polygon of forces, 408 
parallelopipedon of forces, 408 
centre of gravity, 409 
the lever, 410 
the pulley, 410 
of uniform motion, 4}1 
motion uniformly varied, 411 , 
the legs move by the force of gravity as a pen- 
dulum, 411 . 
mechanical effects of fluids on animals immersed 
in them, 412 
resistance of fluids, 413 _ 
passive organs of locomotion, 413 
bones, 413 
joints, 415 
igaments, 415 
muscles, 416 2 
force of muscles at various stages of their 
contraction, 418 
Section II. Flying, 419 
flight of insects, 419 
Coleoptera, 4u1 
Dermaptera, 421 
Lepidoptera, 421 
nocturnal Lepido ptera, 422 
Neuroptera, 423 
Hymenoptera, 423 
Diptera, 493 ; 
table showing the arew of the wings and the 
weight of the body in various species of 
insects, 424 
flight of birds, 424 
use of the tail in flight, 499 
flight of fish and other animals, 429 
Dactylopterus and Exocetus, 429 


tion ; or Pro- 


* 1020 ANALYTICAL INDEX. 
Mucous Membrane 


431 

Section III. Swimming, 431 
ciliograde animals, 432 
Porifera and Polypifera, 432 
cirrigrade animals, 433 
pulmograde animals, 433 
syringograde animals, 439 
vermiform animals, 454 
aquatic insects, 434 
Deca 


pods, 436 
Cephal 8, 436 
436 


437 
shaped like the salmon, cod, and mackerel, 437 
flat fishes, 437 
analysis of the act of swimming in fishes, 438 
aquatic birds, 438 
quadrupeds, 439 
Section IV. Progression on solids, 440 
Radiata, 440 
Echinida, 440 
Annelida, 441 
Insecta, 44! 
apode larve of insects, 441 
pedate larva, 441 
perfect insects, 442 
Myriapoda, 443 
Arachnida, 444 
Decapoda, 444 
Gasteropoda, 445 
Cephalopoda, 445 
Ophidia, 445 
Amphibia, 448 
Sauria, 448 
Lacertz, 449 
Chelonia, 450 
birds, 450 
mammiferous quadrupeds, 451 
horse, 452 
walk, 452 
trot, 452 
gallop, 453 
Marsupialia, 453 . 
Rodentia, 454 
Ruminantia, 454 
Proboscidia, 454 
Carnivora, 455 
Cheiroptera, 455 
uadrumana, 455 
Section V. Man, 456 
the vertebral column, 456 
the legs, 457 
walking, 459 
tables of the measure of the inclination of the 
trunk in various modes of progression, 460 
estimate of forces employed in walking, 461 
running, 471 
the principles in which walking and running 
differ, 471 . 
forces employed in running, 471 
leaping or jumping, 474 
in insects, 475 
in quadrupeds, 477 
in man, 478 


increase of the respiration and circulation in pro- 


gression, 479 
the manner in which animal force is estimated, 480 
Mucus, 481 
mucus of the nose, 482 
urinary mucus, 482 
intestinal mucus, 482 
question of the existence of any substance to which 
the term mucus should be applied, 433 
analyses of ovarian effusions, effusion of ascites, and 
serum, 483 
synthetical formation of mucus, 483 
mucus globules, 483 
varieties of the mucus globule, 484 
distinction of pus and mucus, 484 
Membrane, 484 
ultimate structure of the mucous membrane, 486 
basement membrane, 486 
kidney, 486 
testis, 487 . 
salivary glands, 487 
liver, 487 
pulmotiary air-cells, 487 
alimentary canal, 487 
skin, 488 
cutaneous follicles, 489 
epithelium, 489 
lamellilorm or scaly variety, 489 
prismatic, 490 
spheroidal, 491 
non-ciliated and ciliated, 492 P 
elementary tissues appended to the mucous system, 492 
bloodvessels, 492 


+ oe 
lacteal a6 lymphatic vessels, 493 


rves, 
areolar tissue, 494 
of the glands, 494 
topographical view of the mucous system in man, 4: 
gastro-pulmonary tract, 495 
See Papen tract, 495 
peculiarities of the skin, mucous membranes, 
glands, 496 
skin, 496 
mucous membranes, 496 
glands, 497 
liver, 497 
kidney, 498 
testis, 498 
salivary glands, 498 
mammary glands, 499 ; 
general outline of the functions of the mucous sy: 
tem, 499 “g 
varieties in the qualities of the product 
secreted by different portions of the muco 
system, 503 4 
mucus, 503 
conclusions, 504 
review of researches, 504 : 


, 506 
general description of muscular tissue, 506 
characteristics of voluntary and involuntary m 


506 
a, striped clementary fibre, 506 
length, 507 
thickness, 507 
figure, 507 
colour, 507 
internal structure, 508 
microscopical appearance, 508 
transverse stripes, 508 
_ longitudinal lines, 508 
discs, 508 
fibrilla, 508 
primitive particles, or sarcous elem 
510 “* 


table of diameters, 510 
Dr. Barry’s opinion of spiral th 
corpuscles, 511 
sarcolemma, 512 
adhesion to elementary fibre, 512 
use, 513 ; 
attachment of the extremities of the fi 
other structures, 513 
developement, 513 
b. unstriped elementary fibres, 514 > 
¢. mode of aggregation of the elementary fibres, 51 
connecting areolar tissue, 516 
bloodvessels, 516 i 
venz comit panying arterial br ach 


77 


516 
proper capillaries, 516 
nerves, 517 “ann 
d, distribution of the striped and unstriped fibre, 5! 
striped, 517 "~ve 
unstriped, 518 a 
e. distribution of the striped and unstriped fibres 
the animal kingdom, 519 c 
J. chemical constitution, 519 
+ Motion— 
contractility, 519 ‘ 
a eer inherent in muscular fibre; doct: 
the ‘ vis insita’, 519 
source, 520 yi 
relation of contractility to the state of nut 
tion of the organ, 521 
Dr. John Reid’s experiments, 52! 
evidence furnished by cases of cer 
paralysis, 521 Ps 
corroborations afforded the fact tl 
throughout the animal kingdom ¢ 
vascular supply is accurate’ 1 
tioned to the muscular irri 
stimuli of muscular contraction, 521 
remote, 522 
immediate, 522 F 
visible changes occurring in muscle during ¢ 
tion, = er wn 
in the whole organ, 
in the elementary fibre, 522 
in the discs, 523 
in the fibrille, 523 
passive contraction, 524 
active contraction, 524 
muscular fatigue, 524 _ 
appearances presented by the elementary 
uring the contraction, 524 ‘= 
emission of sound, 
development of heat, 596 4 
appearances presented by ruptured muscle, 526 
opinions of various observers as to the nature: 


traction, 529 
System, tive Anatomy of). _ 
shown to be in conformity with the devel 
the nervous system, 530 ae 


. 


non-existent in the Acrita , 553 


' 


~~ 


¢ 


ANALYTICAL INDEX. 1021 


Musculur System (continued). Neck (continued). 


as apparent in the Nematoneura, 534 
in Celelmintha, 534 
in Bryozoa, 535 
in Rotifera, 535 
in Epizoa, 536 
in Echinodermata, 537 
Encrinus, Comatula, 537 
Asterias, Echinus, 537 
Holothuria, Siponculus, 537 
in the Homogangliata, 537 
in Annelida, 538 
in Myriapoda, 538 
in Insecta, 538 
in Arachnida, 539 
in Crustacea, 540 
in the Heterogangliata, 540 
in Gasteropoda, 540 
in Pteropoda, 541 
in Cephalopoda, 541 
in Vertebrata, 541 
vertebral system, 54} 
costal system, 542 
hyoid system, 542 
opercular system, 543 
muscles of the limbs, 543 
in skates and rays, 543 
in Lepido-siren, 543 
in Siren lacertina, 543 ° 
in Proteus, 543 
in Ophidia, 543 
in Sauria, 543 
muscles used in mastication, 543 
tegumentary system, 543 
vocal system, 544 
diaphragm, 544 
lingual system, 544 
ocular system, 544 
aural system, 544 
nasal system, 544 
generative system, 544 


general description of the class, 544 
classification, 545 
anatomy and physiology, 547 
alimentary canal, 549 
respiratory system, 549 
circulatory system, 549 
foramina repugnatoria, 550 
nervous system, 550 
in Scolopendra, 550 
senses, 550 
organs of generation, 551 
Ova, 553 
developement of the embryo, 553 
history of the process according to the observa- 
tions of Newport on the Julus, 553 
observations of Gervais on the growth of 
Lithobius, 560 


Neck. 


1. Muscles, 561 
a. anterior vertebral group, 561 
longus colli, 562 
rectus capitis anticus major, 561 
b, lateral vertebral group, 561 
intertransversales colli, 561 
rectus capitis lateralis, 561 
rectus Capitis anticus minor, 561 
scalenus anticus, 562 
posticus, 562 
c. depressors of os hyoides, 562 
sterno-hyoid, 563 
sterno-thyroid, 563 
thyro-hyoid, 563 
omo-hyoid, 563 
digastric, 563 
stylo-hyoid, 564 
mylo-hyoid, 564 
d. connected with the tongue, 564 
hyo-glossus, 564 
stylo-glossus, 565 
Sif A mc 565 
ingualis, 565 
genio-hyoideus, 565 
. superficial on the side of the neck, 565 
sterno-cleido-mastoideus, 565 
platysma myoides, 566 
risorius Santorini, 566 


Q. Fascie, 566 


superficial or subcutaneous areolar tissue, 566 
cervical, 568 

pre-vertebral, 569 

cervico-thoracic septum, 570 


3. Regional or surgical anatomy, 570 


superficial veins and nerves, 571 
mesial region of the neck, 572 
laryngotomy and the parts concerned, 573 
tracheotomy and the parts coneerned, 574 
crico-tracheotomy, 574 
anterior-inferior triangle, 574 
thyroid body, 575 
bronchocele, 575 


cesophagotomy, and the parts concerned, 576 


anterior-superior triangle, 576 
glandule concatenate, 577 
posterior-superior triangle, 577 
posterior-inferior triangle, 577 
subclavian artery, and operations connected 
therewith, 578 
subclavian vein, 579 
jugular vein, 579 
thoracic duct, 579 
arteria innominata, and operations connected 
therewith, 580 
digastric space, 581 
posterior pharyngeal region, 582 
relations of the sterno-cleido-mastoideus, 583 
practical observations relating to the anatomy and 
diseases of the neck, 583 
diagnosis of tumours, 583 
collateral circulation after obliteration of the main 
arterial trunks, 584 
anomalous arrangements of the cervical vessels, 
585 


remarks on the veins, 585 


Nervous System, 585 


general observations on the disposition and composi- 
tion of nervous matter, the nature of nervous actions, 
and the subdivisions of the nervous system, 586 
nervous matter, 586 
how disposed through the animal kingdom, 586 
chemical composition, 587 
Vauquelin’s analysis, £87 
Fremy’s method of analysis, 587 
cerebric acid, 587 
oleophosphoric acid, 587 
cholesterine, 588 
variation of the quantity of phosphorus in 
different periods of life, and its small amount 
in idiotcy, 588 
L’Heritié’s analyses of cerebral matter of in- 
fants, youth, adults, old men, and idiots, 
588 


nervous actions, 588 
mental nervous actions, 588 
actions of perception, 588 
common sensibility, 588 
special sensibility, 589 
actions of emotion, 589 
physical nervous actions, 589 
contraction of the iris occasioned by the sti- 
mulus of light, 589 
deglutition, 589 
excitement of the respiratory muscles by the 
sudden application of cold to the surface of 
the body, 589 
reflex action, 590 
anatomical subdivision of the nervous system ;—brain, 
spinal cord, and ganglions, 590 
nerve, 591 
structure of cerebro-spinal nerves, 591 
neurilemma, 591 
ultimate nervous fibre, 591 
tubular membrane, 591 
white substance of Schwann, 592 
flattened band of Remak, 592. 
changes produced by the action of water 
and other re-agents, 592 
varicose appearance of nerve-tubes, 593 
table of measurements of nerve-tubes in 
Man and the other Vertebrata, 593 
absence of anastomoses in nerve tubes, 598 
comparison of nervous witli muscular tissue, 593 
branching of nerves, 594 
anastomosis, 594 
decussation of the primitive fibres within the 
trunk of a nerve, 594 
anastomosis of descending branch of the ninth 
nerve with the cervical plexus, 594 e 
commissure of optic nerve, 595 
anastomosis by fusion; Volkmann’s observations, 
595 
nervi nervorum, 595 
plexuses, 595 
origin of nerves, 595 
termination of nerves, 595 
in muscle, 596 . 
peripheral expansion of nerves on sentient sur- 
faces, 596 
papille of the skin, 596 
retina and optic nerve, 596 
olfactory nerves, 597 
the auditory neive, 597 
structure of the ganglionic nerves, 597 
neurilemma, 597 
ramification, 597 
peripheral distribution, 598 
plexuses, 598 
nerve-tubes, 598 
cells, 598 
elatinous fibres, 599 
difference between the structure of the sympa- 
thetic and the cerebro-spinal fibre, according to 
Volkmann and Bidder, 599 
nerves of the Invertebrata, 600 


1022 ANALYTICAL INDEX. 


Nervous System (continued). 
developement of nerve, 600 
bie g nee cone, 601 

Nervous System, Comparative Anatomy of, 601 
in the Acrita, or 
in the Poly ota 601 

Actinia, 
in the Radiata, 602 
in the Mollusca, 603 
Tunicata, 603 
Asciolia mammillata, 603 
Phallusia intestinalis, 603 


Conchife: A 
Gasteropoda, 60s 
mpet (Patella), 605 


Chiton marmoratus, 606 


in the Articulata, 606 
Entozoa, 607 
Rotifera, 607 


eee 609 
Ranatra linearis, 610 
Geotrupes stercorarius, 610 
Dyticus marginalis, 611 
pootene poronts minor, 611 
Mormo Maura, 612 
motor and sensitive function of ganglionic 
and non-ganglionic cords, 613 
concluding general remarks, 614 
in the Vertebrata, 614 
Pisces, 614 
anatomy of the Amphioxus Lanceolatus, 615 
neuro-skeleton, 615 
nervous system, 616 
brain of fishes, 618 
weight of the brain compared with that of the 


body, 618 
olfactory tubercles, or first cerebral mass, 618 
optic lobes, or second cerebral mass, 619 
cerebellum, or third cerebral mass, 619 
Amphibia and Reptilia, 620 
rain, 620 
weight compared — that of the body, 620 
olfactory tubercles, 621 
brain and spinal cord of lizard, 621 
optic lobes, 621 
cerebellum, 621 
Aves, 621 
brain, 622 
weight compared with that of the body,622 
cerebral hemispheres, 622 
optic lobes, 622 
cerebellum, 623 
Mammalia, 623 
table of the relative proportions of the brain 
and spinal marrow in the four classes of 
Vertebrata, 623 
table of the relative proportions of the body 
44 brain in the four classes of Veriebrata, 


cerebral hemispheres, 624 
corpus callosum, 625 
ventricles of brain, 625 
olfactory nerves, 625 
optic lobes, 625 
cerebellum, 625 
table shewing the actual and relative lengths 
of the cerebral hemispheres and the cere- 
bellum in the Mammalia, 626 
general remarks in conclusion, 626 
“Nervous Centres. 
coverings of the nervous centres, 627 
coverings of the ganglions, 627 
coverings of the spinal cord and brain, 627 
dura mater, 627 
spinal, 628 
cranial, 628 
processes, 629 
falx cerebri, 629 
tentorium = 629 
falx cerebelli 
vessels of the spinal dura mater, 629 
of the cranial dura mater, 630 
a 631 
rior longitudinal, 631 
is erior longitudinal, 631 
strait, 631 
torcular Herophili, 631 
lateral sinuses, 632 
occipital, 632 
petrosal, superior and inferior, 632 
transverse, 
cavernous, 633 
a ge 633 
pia mater, 


of the eel cord, 633 


mater into 
cerebral ventricles, is 
— plexnees oft the lateral ventri 
cles, - 
velum interpositum, 635 a 
roa plexuses of the fourth ventr 
e, — 
Suryetalline. formations Men 
choroid plexuses, &c. 635 
ayn nas &c. of the pia — 
n reference to pathol ’ 
“ae 636 es ta € 


cerebral, 63 
cerebro-spinal uid, 637 
fluid in the cerebral ventricles, 0 * 
orifice of communication, as de 
Majendie, between the — v 


the sub-arachnoid 5; 
sar 5a of the qeanthey- ot teas the 


fluid, 
cerebro-spinal fluid in reference to 


Peace of its secretion, 643 
apt and chemical 
use, 
pee Bite Pacchioni, 644 

are they inp Fo structures? 645 
ligamentum dentatum, 645 
a on the structure of nervous c 


white nervous matter, 646 
grey nervous matter, 647 
a 648 
remarks on the great simplicity of form o 
elements of grey nervous matter, 649 
pigment, 649 
structure of ganglions, 649 
cerebro-spinal centre, 650 
spinal cord, 650 


bulk, 
length a circumference, 65! 
fissures, 652 
anterior, 652 
posterior, 652° 
commissure, 659 
internal structure as shewn by t: 
tions, 652 
eee ~ al in th 
st pokes ng canal in e spinal o 
bloodvessels, 
anterior "spinal artery, 656 
posterior spinal arteries, 657 
veins, 657 
spinal nerves, ae anterior and po 
roots, ganglion, 657 : 
sub-occipital nerve, 658 
characters proper to the nerves of pa 
lar regions, 658 
cervical nerves, 658 
dorsal nerves, 658 
lumbar nerves, cauda 
relations of the roots of the 
columns of the cord and ‘to 
matter, as determined ) 
as determined by physio! » 660 
encephalon, 661 
size compared with ye of the body in 
rent animals, 
ery with that of the 


» 662 
weight of t the human encephalon, on 
table showing the ave w 

of the human enceph int € 
females, 662 

relative weight of encep 

cerebellum, &c. in m : 

663 


relative weight of entire be 
cecrenenens cerebrum, cerebe! 


<a 
absolute weight of the brain of t 
phant and whale, 
weight of brain of some animals gr 
than that of man, 
weight of their bodies, 664 
conclusions of Tiedeman, d 
his observations, 


the brain in different races of mank: 
method of examining the brain, 667 
method < Willis, 663 a 
of Reil, Gall, and Sp 
surface of the ence €70 


ANALYTICAL INDEX. 7 1023 


Nervous Centres keene i 


ssure of Sylvius, locus perforatus 
anticus, island of Reil, 671 
middle segment, 672 
pituitary process, tuber cinereum, 
673 


7. 
optic tracts and optic commis- 
sure, 673 
corpora albicantia, 673 
crura cerebri, intercrural space, 
substantia perforata, pons Ta- 
rini, 673 
transverseor horizontal fissure,673 
circle of Willis, 673 
posterior segment, 673 
dissection of the brain from above 
downwards, 674 5 
centrum ovale minus and majus, 674 
corpus callosum, longitudinal tracts, 
674 


lateral ventricles, 674 

“ogo lucidum, 674 

fifth ventricle, 674 

parts seen in the lateral ventricles, 
675 


fornix, 675 
third ventricle, 676 
pineal gland, 677 
anterior commissure, 677 
soft commissure, 677 
mesocephale, 677 

corpora quadrigemina, 677 

processus cerebelli ad testes, 677 
valve of Vieussens, 678 

ns Varolii, 678 

cerebellum, 678 
fourth ventricle, 678. 


Medulla oblongata, 678 


anterior pyramids, 679 
course of fibres, 680 
restiform bodies, 682 
posterior pyramids, 683 
olivary columns, 683 
corpus dentatum, 683 
interpretation of the various columns, 68+ 
nerves connected.with the medulla ob- 
longata, 684, 


Mesocephale, 684 


pons Varolii, 635 

corpora quadrigemina, 685 
processus cerebelli ad testes, 686 
valve of Vieussens, 686 . 
conclusions, 686. 


Cerebellum, 637 


fissures, 688 

lamine, 689 

square lobe, 689 

amygdala, 689 

biventral lobe, 689 

slender lobe, 689 

inferior and posterior lobe, 689 
middle lobe, 689 

ae “Seno vermiform process, 689 
inferior vermiform process, 690 
nodule, 690 

posterior medullary velum, 690 
Spigot, 6y1 


ong and hidden commissure, and short 
and exposed commissure, 691 

single commissure, 691 

vertical section of cerebellar hemisphere, 
arbor vite, 692 

vertical section of median lobe, 692 

white and grey matter, 692 

corpus dentatum, 692 

crus cerebelli, 692 

fourth ventricle, 693. 


Hemispheres of the brain, 693 


convolutions, 693 

primary convolutions in the fox, 696 
in the dog, 696 
in cats and hyznas, 696 
in ruminants, 696 
in the elephant, 696 
in the monkey, 696 
in the human subject compared, 


696 
symmetry, 696 
constant convolutions in the hu- 
man brain, 697 
the internal convolution, 697 
convolution of the Sylvian fissure, 


698 
insula of Reil, 698 


pair of convolutions enclosing the - 


olfactory process, 698 
hippocampi, 698 
direction of the white fibres in the con- 
volutions, 698 
corpora striata, 698 
course of fibres, 699 
vesicular matter, 699 


Nervous Centres (continued). 
optic thalami, 700 
corpora geniculata, 700 
corpora mamillaria, 701 
commissures, 701 
longitudinal, 701 
superior longitudinal commissure, 701 
longitudinal tracts, 701 
fornix, 701 
tenia semicircularis, 702 
transverse, 702 
corpus callosum, 702 
anterior commissure, 702 
posterior commissure, 703 
soft commissure, 703 
tuber cinereum, 703 
pituitary body, 703 
ventricles of the brain, 704 
circulation in the brain, 704 
arterial, 704 
venous, 705 
question as to whether the amount of blood 
within the cranium is liable to variation, 706 
encephalic nerves, 707. 
Sketch of the microscopic anatomy of the spinul 
cord and brain, 707 
of spinal cord, 707 
medulla oblongata, 708 
mesocephale, 709 
cerebrum and cerebellum, 709. / 
Brief statement of the probable modus operandi of 
the brain, 710. 
Abnormal anatomy of nerves and nervous centres, 712 
regeneration of nervous matter, 712 
abnormal anatomy of the spinal cord and its 
membranes, 712 
membranes, 712 
affections of the dura mater, 713 
of the arachnoid, 713 
of the pia mater, 713 
cord, 713 
absence of the cord, 713 
partial deficiencies, 714 
excessive congenital development, 714 
hypertrophy, 714 
atrophy, 714 
induration, 714 
softening, 714. 
suppuration, 715 
effusion of blood, 715 
tubercle, 715 
cancer, 715. e 
Abnormal anatomy of the brain and its membranes, 
715. 
membranes, 715° 
dura mater, 715 
acute disease, 715 
adhesion to the cranium, 715 
patches of bone in the processes of 
the dura mater, 715 
fibrous tumours, 715 
cancer, 715 
fungus of the dura mater, 716 
effusion of blood, 716 
arachnoid, 716 
acute inflammation, 716 
opaque condition of, 716 
adhesion, 716 
deposits of bone or cartilage, 716 
effusions into the subarachnoid and 
arachnoid cavities, 716 
of serum, 716 
of blood, 717 
of pus, 717 
pia mater, 717 
injected state of the vessels, 717 
tubercle, 717 
brain, 718 
congenital abnormal conditions, 718 
absence of the brain, 718 
brain of idiot, 718 
fusion of the hemispheres together, 


‘ 


719 

absence of the transverse commis- 
sures, 719 

acquired or morbid conditions, 719 

hypertrophy, 719 

atrophy, 720 

softening, 720A 
white, 720A 
red, 720B 

suppuration, 720B 

hyperemia, 720C 

anemia, 720C 

cerebral hemorrhage, 720D 

cancer, 720E 

tubercle, 720E 

entozoa, 720E ¢ 

morbid states of the ventricles, 720E 

thickened and overs condition of 
the lining membrane, 720F 

— plexus, deposit of lymph on, 
720. 


1024 


Nervous Centres ( F 
earthy concretions in, 720F 
vesic! es ia reeny regarded as hy- 
is, 720 
pseudo-morbid mpeonrencts of the nervous centres 
and tk 2ir coverings, 720F 
abnormal! anatomy of nerves, 720G 
absence of, 720G 
inflammation, 720G 


atrophy, 73 
rtro) +» 720G 
tumours, 7206 


7 
Nervous System, Physiology of the,720G 
vital endowments pe yb Aon and of nervous centres, 


nervous polarity, 720H 
sensitive and motor, incident and reflex nerves, 


720H 
the stimuli of nerves, 720K 
mental stimuli, 720K 
physical stimuli, 720K 
effects of the galvanic stimulus, 720L 
of the conditions necessary for the maintenance of 
the power of developing nervous force, 7 
of the nature of the nervous force, 720P 
is the nervous force electricity? 720Q 
conclusions, 720S 
of the functions of nerves, 720T _ 
of the functions of the roots of spinal nerves, 720U 
of the functions of the nervous centres, 720X 
of the functions of the spinal cord, 720X 
Whytt’s views, 721B 
summary of Prochaska’s work, 721C 
facts which demonstrate a power in the cord 
of exciting movements it parts which re- 
ceive nerves from it by changes occurring in 
its substance, 721G 
stimulus applied to the cord, 721G 
substances exerting a peculiar influence upon 
the spinal cord, 721G 
strychnine, 721G 
opium, 721H 
cold, 721H 
ether, 721H 
sensitive apreeee may be reflected by the 
cord, 721 
enumeration of the functions of the body with 
which the spinal cord is immediately con- 
cerned, 7211 
Dr. Marshall Hall’s doctrine, 7211 
tone of the muscular system, 721M 
conclusions, 721N 
of the office of the columns of the cord, 721N 
antero-latera] columns, 7210 
posterior columns, 7210 
manner in which the posterior co- 
lumns may contribute to the exer- 
cise of the locomotive functions, 


721 
<a or respiratory column of Sir C. Bell, 
721 


influence of the spinal cord upon the organic 
functions, 721R 
on the kidneys, 7291S 
erection of the pent. 721T 
mechanism of the functions of the cord, 721T 
Dr. Marshall Hall’s hypothesis of an ex- 
cito-motory system of nerves and true 
spinal cord, 721U 
hypothesis of Mullerand others that every 
nerve-fibre in the body is continued into 
the brain, 722B 
Todd and Bowman’s hypothesis that all 
the nerves are implanted in the grey 
matter of the segments with which the: 
are connected, and do not pass beyond, 


722B 
functions of the encephalon, 7221 

_of the medulla oblongata, 7221 
corpora striata, 722L 
locas niger, 722M 
optic thalami, 722M 
corpora quadrigemina, 7220 
olivary bodies, and flocks of Reil, 7220 
mesocephale, 722P 

emotion, 722P 

diseases associated with disturbed state of 

emotion, 722Q 

of the cerebellum, 72290 

coordination of movements, 722R 


Gall’s views, connexion of the cerebellum . 


with the sexual functions, 7228 
of the cerebral convolutions, 722X 
Dr. Wigan’s doctrine of the duality of the 
* mind, 7 
sensation, 723A 
volition and attention, 723A 
dreaming, 723B 
coma, 723 
somnambulism, 723B 
delirium, 793B 
fibres of the centrum ovale, 723B 
of the commissures, 723D 


ANALYTICAL INDEX. 


ns Varolii, 723E 
summary of oe physiology of the encep 
723 


physiology of the ganglions, 723F 
functions of the ganglions, 723F 
Ninth pair of Nerves, 721 
origin and course, 721 
branches, 721 mY. 
of communication with the superior cervical g; 
glion, 721 , 


descendens noni, 721 
omo-hyoid branch, 721 
plexus, 722 
sterno-hyoid and thyroid branches, 722 
cardiac branch, 722 
thyro-hyoid branch, 722 
anastomoses with branches of the fifth, 722 
ultimate distribution, 722 
comparative anatomy, 722 
root of the ninth nerve in the ox, 792 
in birds, 723 
in fishes, 723 
physiology, 723 


structure of, 727 
muscles, 727 
posnieties 728 
evator labii superioris aleque nasi, 798 
triangularis, 728 
depressor ale nasi, 728 
depressor septi narium, 729 
muscular fasciculi which dilate and 
nostrils, 729 " . 
rhomboidens, 729 4 
integuments, 729 
skin, 729 
mucous membane, 730 
epithelium, 730 
course, 731 
nerves, 731 
olfactory, 731 
roots, 731 : . 
tractus olfactorius, trunk, 732 
bulb, 732 
branches, 732 
septual, 732 
labyrinthic, 733 
other nerves, 733 
vessels, 733 
development of the nose, 734 
physiology of the nose, 735 
Nose, Morbid Anatomy of the, 736 
congenital defects, 736 
diseases, 73 
of the skin, 738 
of the nasal cavities, 738 
simple abscess, 738 a. 
thickening of the mucous membrane, 738 
ulceration, 739 i 
polypi, 739 _ 
vesicular, 740 oe 
gelatine, 740 P 
brane. 740 
mal ant, 740 
Nutrition, 741 = 
the object of, 741 : 
materials required for nutrition, 742 
type of the process in cellular plants, 742 
elaboration of organizable materials, 742 = 
reduction of every proteine compound to 
men, 742 
change from albumen to fibrin, 743 
formation of tissue, 747 
homogeneous membrane and fibres fo 
fibrin independent of cells, 748 
a of tissues that originate in. 
7! de 
varying activity of the nutritive process, 751 " 
hypertrophy, 751 
ete 752 ‘ ua 
abnormal forms of the nutritive process, 753 
inflammation, 75S ' 
suppuration, 754 
tubercle, 754 
parasitic growths, 755 
non-malignant, 755 
malignant, 756 
general summary, 756 
G@sophagus, 758 
direction, 758 
dimensions, 758 
relations, 758 
structure, 758 


me » 759 
cesophageal glands, 759 
vessels and nerves, 759 
function, 759 


ANALYTICAL INDEX. 
Organic Analysis (continued). 


Gsophagus (continued). 


Olfactory 


abnormal anatomy, 760 
congenital malformation, 760 
acquired malformation, 760 

structural changes, 761 

stricture, 761 

morbid growths, 761 
Nerves, see Nose and Smell. 


Optic Nerves, 762 


descriptive anatomy, 762 
apparent origin, 762 
tractus opticus, 762 
chiasma, 762 
optic nerve proper, 762 
first stage, 762 
second stage, 762 
communication with other nerves, 763 
organization, 763 
real origin, 763 
evidence derived from comparative anatomy, 764 
Fish, 764 
Reptiles, 764 
Birds, 764 
in Mau the optic nerves derive some roots from the 
tubercula quadrigemina, 765 
the tubercula quadrigemina probably fulfil other 
purposes besides that of affording origin to the 
optic nerves, 766 
the human optic nerve probably derives roots 
from the optic thalamus, 766 
corpora geniculata: their relation to the optic 
nerves, 768 
tuber cinereum : its relation to the optic nerves, 768 
of the chiasma of the optic nerves, 768 
in Invertebrata, 769 
cortilagi Fish, ad 
cartilaginous Fish, 769 
Birds, 769 


irds, 
Amphibia and Reptiles, 769 
Mammalia and Man, 769 
use of the chiasma, 771 
some remarkable varieties of optic nerves, 774 
optic nerves in certain Cephalopods, 774 
optic nerves of the compound eyes of Insects, 775 
plaited optic nerves, 776 
optic nerves in cyclops monsters, 777 
general developement of the optic nerves in the higher 
classes of animals, 777 
functions of the optic nerves, 778 
the optic nerves when present are essential to 
vision, 778 
in those animals which possess special optic 
nerves the fifth pair are totally inadequate to 
support vision, 778 
absence of proof that the fifth pair is absolutely 
essential to sight, 778 
ordinary tactile sensibility, 780 
effects of stimulants, 780 
excito-motory properties, 781 
radiated or sympathetic sensations, 782 


Orbit, 782 


bones, 782 
dissection of the orbit, 783 
peewentes 783 
Fie hye gland, 784 
fo nerve, frontal and lachrymal nerves, 784 
levator palpebrz superioris, 784 
rectus superior, 784 
obliquus superior, 785 
third nerve, nasal nerve, 785 
lenticular ganglion, 785 
optic nerve, 785 
ophthalmic artery, 785 : 
lachrymal artery, central artery of the retina, 
supra-orbital, ciliary arteries, muscular 
branches, ethmoidal, palpebral, nasal arteries 
and frontal arteries, 786 
ophthalmic vein, 786 . 
sixth nerve, inferior division of the third nerve, 


787 

external, internal, and inferior recti muscles, 787 

inferior oblique, 787 

orbital portion of the superior maxillary nerve, 
temporal branch, malar branch, tunica vagina- 
lis of Mr. O?Ferrall, 788 

action of the muscles, 788 © 

levator palpebre, 788 

recti, 788 

obliqui, 789 

consensual movements of the two eyes, 791 

adaptation of the eye to distances, 792 


Organic Analysis, 792 


I, Proximate analysis, 793 
manipulation, 793 
reagents, &c. 793 
desiccation, 793 
incineration, 794 
filtration, 795 
decantation, 795 
A. Analysis of animal fluids, 795 
1, for the organic constituents, 795 
qualitative analysis, 795 
fibrin, 795 
VOL, IIT. 


1025 


albumen, 795 
fatty matters and cholesterin, 796 
sugar, 796 
urea, 796 
uric acid and the urates, 796 
quantitative analysis, 796 
process, 796 
special consideration of the different ani- 
mal principles, 797 
fibrin, 797 
fatty matters, serolin and butyrin, 798 
albumen, 798 
casein, 798 
urea, 799 
sugar, 799 
uric acid, 800 
urobenzoic or hippuric acid, 800 
lactic acid, 800 
oxalic acid, 800 
@. for the inorganic constituents, 801 
qualitative analysis, sot 
quantitative analysis, 802 , 
carbonic, phosphoric, and hydrochloric acid, 


sulphuric and phosphoric, 803 
iodine, fluorine, and sulphur, 803 
es, 203 
potash, soda, ammonia, 804 
Iron, lime, magnesia, lead, £04 
par al 805 
B. Analysis of animal solids, 805 
cholesterin, 805 
uric acid and urates, 805 
cystic oxyde, 805 
albumen and fibrin, 805 
—_ tissues, 806 
irs, 806 
earthy phosphates, 806 
carbonate of lime, 206 
oxalate of lime, 806 
C. Proximate analysis of individual secretions, 


807 
of the urine, 807 
healthy urine, 807 
diabetic urine, 808 
albuminous, 809 
of the blood, 809 
the serum, 810 ~ 
the clot, 810 
of milk, 811 
of bile, 811 
of saliva, 812 
II. Ultimate analysis, 813 
analysis of a solid not containing nitrogen, 814 
of a liquid not containing nitrogen, 816 
ofa body containing nitrogen, 817 
method of determining the equivalent number of an 
organic substance, 819 


Osseous System, 820 


general remarks, 822 
enumeration of the parts of a perfect vertebrate endo- 
skeleton, 823 
(skeleton of the Crocodile), 8293 
spinal column, 823 
elements of a vertebra, 824 
autogenous parts, 824 
exogenous parts, 824 
skull, 825 
occipital vertebra, 827 
arietal vertebra, 827 
rontal vertebra, 827 
bones of the cranium, 828 
frontals, 828 
anterior frontals, posterior frontals, $29 
parietals, 829 f , 
external occipitals, lateral occipitals, inferior 
occipital or basilar, 829 
sphenoid, alars, 829 : 
squamo-temporal, petro-temporal, 829 
pi tacos bones, 829 
cethmoid, vomer, nasal bones, 830 
inferior turbinated, 830 
maxillary, intermaxillary, 830 
suborbital, prenasal, supra-temporal, 831 
palatine bones, transverse bones, internal 
pterygoid, zygomatic, masto-temporal, 832 
styloid, symplectic, 833 
lower jaw, 833 
opercular, angular, articular, 833 
hyo-branchial apparatus, 833 
hyoid, 833 
branchiostegous rays, 834 
branchial arches, 834 
pharyngeal bones, 834 
condition of the os hyoides in Reptiles, 835 
metamorphosis of the os hyoides, 635 
thorax, 836 
vertebral ribs, 836 
sternum, 837 
sternal ribs, 838 
limbs, 839 
anterior, 839 


exoskeleton, 844 
suborbital bones, &c. 845 
ular bones, 845 
supra-tem 
rato —rh preety fins of Fish, 815 


sagged aah aeoetotion, 847 
hyalitic substance, 847 

Jamine, 849 
Haversian canals, 849 
corpuscles or cells, 850 

bone, 853 
madder experiments, 853 

developement of osseous tissue, 854 
ossification of permanent cartilage, 857 
abnormal osseous plates in the so’ tissues, 857 
formation of osseous tissue in the union of fractures, 


857 
Ovary, Supplement, 
stra peg Supplement. 


858 
enumeration of genera, 859 
osseous system, 859 
cranium, 859 
occipital bone, 359 
—- bones, 860 
mtal eo 860 
eethmoid, 860 
sphenoid, 861 
ribs and sternum, 861 
anterior extremities, 862 
scapula, 862 
clavicle, 862 
humerus, 862 
radius and ulna, 862 
carpus, 863 
metacarpus, 863 
phalanges, 863 
posterior extremities, 864 
lvis, 864 
emur, 864 
tarsus, 864 
metatarsus, 864 
peeenaess 864 
teeth, 
of Seiden, Ot 
Cheropotamide, 865 
Hippopotamide, 866 
Toxodon, re 866 
Rhinocerotide, 866 
Dinotherium, 867 
Proboscidia, 867 
Elephant, 867 
digestive system, 871 
stomach and intestines,’ liver, 871, 872 
spleen, 871 
salivary glands, 872 
os hyoides, 872 
circulatory and om taser system, 872 
urinary organs, 8 
generative organs, ‘o18 
male, 8 
female, 7S 
nervous system, 874 
brain, 874 
special senses, 874 
touch, 874 
snout, 87 
proboscis “of the elephant, 875 
smell, 875 
frontal, maseetys and sphenoidal si- 
nuses, 875-6 


i 


eye, 876 
Poclifamentum nuc ia 876 


onc ge ‘excxiption, 876 
Stalk, 3' 
pact g he the stalk, 878 


TY 
central cavity, 878 
nerve tube, 579 ~ 


ANALYTICAL INDEX. ie 


Pactaien Bodies (continaed). 


function, or eae 
errr with the electrical omens of the 
Par Pasay 881 . 
eee covata wees cranium, 882 
in su Us. 
- communicating filament with the g! 


ensietles tam branch, 


os - ~ —— ay the woth 884 


aes haryngeal, 885 
i erior Lawton #85 
middle pharyngeal of Valentin, 985 
superior laryngeal, a 
external branch, 886 
’ internal branch, 886 
vascular and cardiac hese iy = 887 
inferior or recurrent laryngeal, 887 
course of the vagus through the’ ston § 888 


eft vague of the vagus in the abdomen, & 


right ry dg 

connexion of the vagus and spinal accessory, © 
paydolog of the nervus vagus, 891 . 
e roots of the vagus contain any m 
filaments? 891 
sensitive filaments, 892 

functions of the various branches, 892 

auricular branch, 892 


act as incident nerves, 897 
mor id changes in the lungs after di 
the v. 


1» 898 
functions of the gastric bra’ 
do the : tet ee sens 
4 n some motiferous 


clams of lesion of the vagi t 
sensations of hunger and 
the function of digestion, 900 
upon the secretion of gastric j 
upon the secretion 
the inner surface of the 
and intestines, 900 : 
upon the rapidity of of absorpti 
the inner surface of the s 
ton of of conclusions respecting th 
tion of the nervus vagus, 901 
Parotid region, 902 
parotid gland, 902 
relations, 902 
arteries, 903 
_— Teo ar 
ne a 
apuunies glands, 904 ~< 
Parturition, Mechanism of, 904 ae 
in the lower animals, 904 
attitude and peeition of the fetus, 906 
in the human subject, 907 
presentation of the head, 907 
first position, 907 
second position, 907 
presentation of the face, 908 ; 
first position, 908 * 
second position, 908 
presentation of the lower extremities, 9 
cross presentation, 908 
Pelvis, see Su; t 
Penis, 909 
bias mi a 909 
Infusoria and Rotifera, 909 
, 


Fishes, 910 
Amphibia, 910 
Ophidia, 910 


Sauria, 910 
Chelonia, 910 
Aves, 911 
Mammalia, 911 
rumana, 9!1 
in nd an, gli ‘ 
ntegument, 911 
subcutaneous areolar tissue, 912 
fascia penis, 912 
corpus cavernosum, 912 
structure, 91 


a. . 
tum pectiniforme 919" 
vee ‘ul structure, 913 = 


ANALYTICAL INDEX, 1027 


‘ 
Penis (continued). 


contractile fibrous tissue, 913 
corpus spongiosum, and glans penis, 914 
structure, 914 
mucous membrane, 914 
supposed muscular fibres of the urethra, 
915 


muscles, 915 
erector penis, 915 
acceleratores urine, 915 
ischio-bulbosus, 915 * 
compressor vene dorsalis penis, 916 
arteries, 916 
arteria corporis bulbosi, 916 
artetia corporis cavernosi, 916 
arteria dorsalis penis, 917 
veins, 917 L 
vene corporis bulbosi, and venz corporis 
cavernosi, 917 
dorsal vein, 917 
ultimate arrangement of the bloodvessels, 917 
arteriz helicine, 917 
lymphatic vessels, 918 
nerves, 918 
development, 918 
onde see ye ) 
erineum (Surgical Anatomy), 919 
bony and ligamentous boundaries, 919 
axes of the pelvis at different ages, 919 
rectum, 920 
course, &c. 920 
relations, 921 
coats, 921 f 
bladder, vesiculz seminales, and vasa deferentia 
922 


urethra, 993 
prostatic portion, 924 
membranous portion, 925 
bulb and spongy portion, 925 
dissection, 926 
superficial compartment, 926 
integument, 926 
superficial fascia, 927 p 
central tendinous point of the perineum, 
928 
pepcrecial perineal artery and veins, 928 
inferior or superficial division of the pudic 
nerve, 928 
transversalis perinei artery, 929 
accelerator urine muscle, 929 
erector penis, 929 
transversus perinei, 929 
bulb of the urethra, 930 
triangular ligament, 930 
Cowper’s glands, 930 
Guthrie’s muscles, 930 
arteries of the bulb, 93) 
internal pudic arteries, 931 
deep compartment, 932 
illson’s muscles, 932 
membranous t pao of the urethra, 932 
prostate gland, 932 
vesico-prostatic plexus of veins, 933 
irregular artery sometimes found along 
the side of the prostate, 933 
application of the anatomy of this part 
to practical purposes, 934 


Peritoneum, 935 


continuity of the peritoneum traced, 936 
omenta, mesenteries, and ligaments, 940 
falciform ligament of the liver, 940 
coronary ligament of the liver, 940 
triangular ligaments of the liver, 941 
lesser omentum, 941 
splenic omentum, 941 
great omentum, 941 
use of, 942 
homology of, 942 
transverse mesocolon, 942 
mesentery, 943 
ascending and descending mesocolon, &c. 943 
appendices epiploice, 943 
recto-vesical folds, 943 
broad ligaments of the uterus, 943 
recto-uterine and vesico-uterine folds, 943 
other slight folds and depressions, 943 
the serous coating of the various abdominal 
viscera, 943 
external or adherent surface of the peritoneum, 


944 
abnormal adhesions and other results of perito- 
Nitis, 945 
and Mouth, 945 
fibrous membrane, 945 
muscles, 946 
constrictor pharyngis inferior, 946 
constrictor pharyngis medius, 946 
constrictor pharyngis superior, 946 
stylo-pharyngeus, 947 
palato-pharyngeus, 947 
general review of the attachmeuts of the pharynx, 947 
the cavity and its openings, 948 
mucous membrane and glands, 948 


Pharynz and Mouth (continued). 


vessels and nerves, 949 


Mouth, 949 


lips, 949 
cheeks, 950 
palatine arch and gums, 950 
gums, 951 
velum palati, 951 
muscles of, 951 
circumflexus palati, 951 
levator palati, 952 
palato-pharyngeus, 952 
palato-glossus, 952 
azygos uvule, 952 
glands, 952 
tonsils, 952 
course of the mucous membrane, 953 
functions, 953 
morbid anatomy of the pharynx and mouth, 954 
congenital malformations, 954 
forcing bodies, 954 
structural changes, 954 
abscesses, 954 
ulceration, 954 
polypi, 954 
pouching of the mucous membrane, 954 
cancrum oris, 954 


Pisces, 955 


general characters, 955 
classification, 956 
osseous system, 957 
skeleton of Osseous Fishes, 958 
vertebral column, 958 
ribs and sternum, 959 
cranium, 959 
face, 959 
anterior extremities, 961 
agains extremities, 962 
n rays of the extremities, 962 
vertical fins, 962 
interspinous bones, 962 
rays of the vertical fins, 962 
skeleton of Chondropterygii, 963 
skull, 963 
branchial apparatus, 964 
ribs and sternum, 965 
anterior extremities, 965 
posterior extremities, 966 
skeleton of Dermapterygii, 966 
skeleton of Branchiostoma, 967 
arthrodial system, 967 
muscular system, 968 
great lateral muscles, 968 
superior and inferior slender muscles, 968 
muscles of the pectoral fins, 968 
ofthe ventral fins, 968 
of the jaws, 968 
of the palato-tympanic arch, 968 
of the operculum, 969 
of the os hyoides, 969 
of the branchiostegous membrane, 969 
branchial and pharyngeal apparatus, 969 ’ 
peculiarities of the muscular system in particular 
Fishes, 969 
in Ostracions, 969 
in Raide, 969 : 
muscles of the jaws in Cartilaginous Fishes, 970 
in Sharks, 971 
in Petromyzonide, 971 
tegumentary system, 971 
the skin in general, 971 
pigment, 972 
mucus follicles, 972 
scales, 973 
teeth of scales, 974 
chemical composition, 974 
teeth, 975 
in Cyclostomatous Fishes, 976 ‘ 
position, form, mode of implantation, and deve- 
lopement, 977 
examples of peculiar dentition, 978 
Cyprinide, 979 
Scari, 979 
Diodons and Tetradons, 980 
Saw-fish, 980 
cesophagus, 981 
stomach, 981 
intestinal canal, 981 
salivary glands, 982 
ancreas, 982 
iver, 982 
spleen, 983 
lymphatic system, 983 
organs of respiration, 985 
in Osseous Fishes, 985 
in Lophobranchii, 986 
in Sturionide, 986 
in Plagiostome Cartilaginous Fishes, 986 
in Cyclostomata, 987 
in Branchiostoma, 988 
hyoid apparatus, 988 
branchial cavity, 988 
circulatory system, 988 m 


1028 ANALYTICAL INDEX. 


Pisces (continued). Pisces (continued). 
heart, 988 choroid, 999 
bulbus arteriosus and branchial artery, 989 choroid gland, 1000 
branchial and systemic arterial vessels, 989 ligament or marsupium, 1000 
systemic veins, 990 aqueous humour, 1001 Z 
(respiratory and circulatory apparatus in Lepi- ine lens, 1001 
dasiren,}. 990 vi humour, 1001 
robes system of veins, 992 muscles of the ey 1001 
teral system of 992 1002 
nervous system, 992 audi tus, 1002 
o in romyzon, 1002 
a 994 perce Ptvwin tae OF 
a 5 sac of the otolithe, 1003 
ird pair, 995 i 1004 ) 
— pair, os —— ayer Mase : 
sixt Tr, nerves, 
"Rent nro cy igiontome Crtaginons Ps 
r, 
bs ets Tr, 996 generative system, 1005 
second pair of spinal nerves, 996 in Cyclostomata, 1006 
sympathetic system, 997 in Osseous Fishes, 1006 
Nervous system of Branchiostoma, 998 in Plagiostome Cartilaginous Fishes, 
senses, 998 1007 
smell, 998 fem 1008 
eye, 999 in Syngnathide, 1010 
sclerotic coat, 999 urinary apparatus, 1011 
renal capsules, 1011 


membrana ntea, 999 
iris, 909 arge 


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1028 ANALYTICAL INDEX. ~~ hg 


990 
poe em of yeins, 992 
oad Getum o¢-vemeees 
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Seal, 008 a 
— 
> 
il 
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Johnson's Medico-Chirw 
«* The most remarkable encyclopedia hitherto possessed by the medical sciences.” _ 
Repertorium fiir Anatomie und Physiologie, von‘ 
«« The Cyclopedia of Anatomy and Physiology, a work peculiar in this respect, . 
joint Pa oF Enelish and French contributors. The able Editors have the merit 
an example of breaking down national distinctions, which are injurious to science, and of 
the time when men of enlarged minds shall be considered as belonging to no particular cou 
as members of a universal republic. The memoirs which have already appeared in this 1 
likely to obtain the approbation of scientific men in both countries.” be 
Dr. Prichard’s Address to the Provincial Med. Assoc 


Cemaais 


Jp) ai. 


Sherwood, Gilbert, & Piper, Paternoster Row. 3 


Now completed, the 


Cyclopadia of Practical Medicine, 


EpiTEeD By J. FORBES, M.D-F.R.S.; ALEX. TWEEDIE, M.D.; J. CONOLLY, M.D. 


This important work is now completed, in four large volumes, and consists of a Series of 
Original Essays upon all the subjects of Medicine, contributed by no less than sixty-seven of 
the most eminent practical Physicians of Great Britain and Ireland; forming a complete 
LIBRARY of MEDICINE. Each subject has been treated by a writer of acknowledged 
reputation, whose particular studies have eminently fitted him for the task, and all the articles 


W. P. Alison, M.D. F.R.S.E. 
James Apjohn, M.D. M.R.1.A. 

R. Arrowsmith, M.D. Coventry. 
Edward Ash, M.D. Norwich. 
James L. Bardsley, M.D. Man- 


chester. 
Edward Barlow, M.D. Bath. 
anes Edward Beattie, M.D. 


John J. Bigsby, M.D.F.L.S. Newark. 
. tock, M.D. V.P.R.S. F.L.S. 

_ F.G.S. &c. 

Joseph Brown, M.D. Sunderland. 

Thomas H. Burder, M.D. 


John Cheyne, M.D. F.R.S.E. 
M.R.I.A, 

Robert Christison, M.D. F.R.S.E. 

Sir James Clark, M.D. F.R.S. 

Henry Clutterbuck, M.D. 

J. Corrigan, M.D. Dublin. 


this way much sooner. 


e authenticated with the names of the authors; thus giving the work a character of originality 
and authority which does not belong to Cyclopedias upon the plan of anonymous publication, 
or to compilations by single writers, however learned and industrious. 


Contributors. 


John Crampton, M.D, M.R.1.A. 

Adair Crawford, M.D. 

Andrew Crawford, M.D. 

William Cumin, M.D. Glasgow. 

John Darwell, M.D. Birmingham. 

Frederick Duesbury, M.D. 

John Elliotson, M.D. F.R.S. 

J. Gillkrest, M.D. 

George Goldie, M.D. Shrewsbury. 

James Grant, M.D. Jedburgh. 

George Gregory, M.D. 

Marshall Hall, M.D. F.R.S.L. and 
E. &c. &e. 

Thomas Hancock, M.D. 

Bisset Hawkins, M.D. 

Charles Hastings, M.D. 

J. Hope, M.D. F.R.S. 

James Houghton, M.D. Dublin. 

Arthur 575s M.D. M.R.1.A. 

Charles Johnson, M.D. Dublin. 

William Bruce Joy, M.D. Dublin. 

J. P. Kay, M.D. Manchester. 

William Kerr, M.D. 


* Such a work as this has long been wanting in this country. British Medicine ought to have set itself forth in 
We have often wondered that the medical profession and the entirpeiting publishers of Great 
Britain did not, long ere this, enter upon such an undertaking as a Cyclopzedia of Practic: 


* The Cyclopzedia of Practical Medicine, a work which does honour to our country, and to which one is proud to 
see the names of so many provincial physicians attached.’’ 
Dr. Hasting’s Address to Provincial Medical and Surgical Association. 


‘* Of the medical publications of the past year, one may be more particularly noticed, as 


_ Robert B. Todd, M.B 


Robert Law, M.D. Dublin, 

Robert Lee, M.D. F.R.S. 

Charles Locock, M.D. 

David H. Mac Adam, M.D. Dublin. 
William F. Montgomery, M.D. 

J. A, Paris, M.D. F.R.S. 

J.C. Prichard, M.D. F.R.S. Bristol. 
Jones Quain, M.D. 

Archibald Robertson, M.D. 

P. M. Roget, M.D. Sec.R.S. 

John Scott, M.D. Edinburgh. 
William Stokes, M.D. Dublin. 
Robert J. N. Streeten, M.D. 

J. A. Symonds, M.D. Bristol. 

A. T. Thomson, M.D. F.L.S. 
Thomas Thomson, M.D. F.R.S.L. 
T. J. Todd, M.D. Brighton. 


Richard Townsend, M.D. M.R.I.A. 
Robert Venables, M.B. 

Thomas Watson, M.D. 

John Whiting, M.D. 

Charles J. B. Williams, M.D. 


Medicine.’ 
Medical Gazette. 


artaking, from its 


extent and the number of contributors, somewhat of the nature of a national undertaking, namely, the ‘ Cyclopedia 
of Practical Medicine.’ It accomplishes what has been noticed as most desirable, by presenting, on several important 
topics of medical inquiry, full, comprehensive, and well-digested expositions, shewing the present state of our 
knowledge on each. In this country, a work of this kind was much wanted, and that now supplied cannot but be 
deemed an important acquisition. e difficulties of the undertaking were not slight, and it required great energies 
o surmount them. These energies, however, were possessed by the able and distinguished editors, who, with 
diligence and labour such as few can know or appreciate, have succeeded in concentrating, in a work of moderate 
‘size, a body of practical knowledge of great extent and usefulness.’’ 

Dr. Barlow’s Address to the Medical and Surgical Association. 


«The Cyclopedia of Practical Medicine” is comprehended in four large vols., printed in 
‘oyal 8vo. double columns, containing as much matter as is usually found in twenty, or even 
thirty, ordinary-sized octavos, neatly done up in cloth, and lettered, price £6. 15s.; or hand- 
omely half-bound in morocco, gilt and lettered, with marbled edges, £7. 7s.; serving as a 


VALUABLE PRIZE-BOOK for MEDICAL STUDENTS. 


— 


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— 


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4 Medical Works, published by 


DR. WAGNER'S 


e a § 
System of Physiology; = — 
For the Use of Students and Practitioners in Medicine. 4 
Translated from the German 
By ROBERT WILLIS, M.D. 
With Notes and Additions by the Translator and others. 


The great object which the Author proposes to himself in this undertaking, and t i. 
which he will hold all others subordinate, is this—to give the most concise and clear | — 


of the Student and Practitioner of Medicine has been the chief aim of the Author, | 
he has not been unmindful of any one who would obtain a comprehensive view of | 
the recent progress and present state of Physiology. He has striven especially to 
make his book a guide in the path of observation and experiment to r 
remote from the appliances of great cities and amply-furnished institutions, are : 
anxious to investigate and to prove for themselves, with such means as they have at | 
theircommand. Even to the Physiologist of higher pretensions, however, vould | 
fain hope that he had brought a present not unacceptable on many accounts; for it | 
has still been his endeavour to see where possible with his own eyes, and to speak at | 
all times as feeling secure on his own footing. With all this, he cannot but hold | 
himself doubly secure in the support of the many distinguished Physiologists who | 
have afforded him original contributions upon those subjects to which they have more 
particularly devoted their attention. on 
The Translator has also to acknowledge important aid in the progress of his work, 
from distinguished Physiologists not only of our own country, But of the continent. } 
The work is distributed into Four Parts, each of which is in itself a distinct and | 
complete manval of the subject of which it treats.—Each part is illustrated by very | 
numerous engravings, mostly after the Author’s ‘ Icones Physiologice.’ The T. TRD : 
PART (price 10s.) now published, completes the SPECIAL PHYSIOLOGY, | 
which comprises all that is interesting or important to the student. It is therefore | 
issued with a Title and Preface, so that the Three Parts may be bound up together. 
The GENERAL PHYSIOLOGY will forma mere Supplement or yen 5 to 
these. aay 


CONTENTS OF PART I.—Price 10s. 6d. 


BOOK I, 
First Section.—ON GENERATION. : 
Cuap. 1. Analysis of the Germ- ing Organs and their Products.—2. On the Forms of the Organs 
of Gensention —8. Phenomena which accompany the Generative Act. ; 
Seconp Sxection.—OF DEVELOPEMENT. es 


Cuap. 1, The History of the Incubated Egg.—2. Developement of the Human 
ments from the History of that of the Mammiferous Animal.—History of 
of the various Tissues.—Histological Developement. 


AppEenpDIx.—Organization of Spermatozoa. 


CONTENTS OF PART II.—Price 9s. 


BOOK II. 
OF NUTRITION AND SECRETION. 


Cuar. 1. Of the Blood.—2. Of the Circulation of the Blood and the Vascular System.—3. Of Diges- 
tion.—4. Of Respiration.—5. Of Secretion.—6, Of Absorption and the more intimate — 
processes of Nutrition. . ee 


with 
’ 


J yal 
: ey ad 
A. eee ee 


So ee et ee es 


ZO) « 


Piatt , 4 


md 


Sherwood, Gilbert, and Piper, Paternoster Row. 5 


WORKS OF DR. MARSHALL HALL. 
1 


THE PRINCIPLES OF THE THEORY AND PRACTICE 


of MEDICINE; 
Including the Third Edition of the Author’s Work on DIAGNOSIS. Illustrated 
with numerous Cuts, and designed for the Use of Students. 
In 1 vol. 8vo. price 16s. cloth lettered. 

** As this work was written for the student and young medical practitioner, we are happy to have it 
in our power to recommend it to those for whom it was designed. Dr. Hall’s work, like most that he 
writes, is excellent ; so much so, that its brevity is the chief fault we have to find with it.’? 

Medico-Chirurgical Review. 


2. 


MEMOIRS I. AND Il. ON THE NERVOUS SYSTEM. 


4to. with 3 Plates, price 10s. 6d. cloth. 


“* It is questionable whether, since the time of Harvey, any discovery has been made in physiology 
so “gy ake as that developed in these Memoirs. 

* ongst a the author must take a high rank, and the name of Hall must henceforth be 
associated with that of Bell. To both, the physiological reputation of our country will be deeply 
indebted ; but Dr. Hall’s discovery is the more original of the two, because more unexpected.?’ 

Spectator. 


3 


OBSERVATIONS ON THE DUE ADMINISTRATION 
of BLOOD-LETTING ; 


Founded upon Researches principally relative to the MORBID and CURATIVE 
EFFECTS of LOSS of BLOOD. 9s. - 


“* We believe the credit of having first put forward, in a strong light, the practical utility of attending 
to these points (blood-letting) is emmently due to Marshall Hall. 

** We may take this opportunity of recommending Dr. Hall’s valuable work to our readers; they will 
find in it several rules and observations of great importance relative to blood-letting as a diagnostic of 
diseases.’’—Medical Gazette. 


4. 
CRITICAL AND EXPERIMENTAL ESSAYS . 
on the CIRCULATION of the BLOOD; 


Especially as observed in the Minute and Capillary Vessels of the Batrachia and 
. of Fishes. 8vo. with Plates, 9s. 


“5. 
COMMENTARIES ON THE: CONSTITUTIONAL 
DISEASES of FEMALES. 


In Two Parts. 
A New Edition, 8vo. with Plates, price 16s. 
Parr Frrst.—Of the Symptoms, Causes, and Prevention of Local Inflammation, 
Consumption, Spinal Affections, and other Disorders incidental to Young Females. 
Parr Seconp,—Comprehending the several Affections incidental to the middle 
and later Periods of Life, and of their Constitutional Origin. 


ee 


ee ee + eee ee 


ee ee ne 


—————EEeeEe 


-| volume in octavo (instead of two), and contains much new and valuable peers, 


6 Medical Works, published by 


MR. HOBLYN’S |. 
DICTIONARY OF TERMS USED IN MEDICINE = | 


and the COLLATERAL SCIENCES; a MANUAL for the USE of STUDENTS | — 
and the Scientific Reader: containing the Etymology and Meaning, Nomenclatures, | 
Classification of Nosology, Materia Medica, Poisons and their Antidotes, Analyses | 
of Mineral Waters, an Account of Climates, &c,; Tabular Sketches of Chemistry, Z 
Medical Botany, and Zoology. aes | 
Second Edition. In the Press. Ae 

« A work much wanted, and very ably executed.’’—London Medical Journal. 

** This compendious volume is well ted for the use of students. It contains a complete g 
of the terms used in medicine,—not y those in common use, but also the more recent and 
familiar names introduced by modern writers. ‘The introduction of tabular views of different : 
at Ly Rea _ pesireenrieg Parrasaie not, however, be that the volume is a 

h ; it is, on the contrary, an mely interesting manual, beautifully 

pete excellent matter in a little space, and is Ganktion of eed strong Bescrcren Poem. 

** Concise and ingenious.’’—Johnson’s Medico-Chirurgical Journal. 


“ Itis a very learned, pains-taking, complete, and useful work,—a Dictionary absolutely necessary in | 
a medical library.’’—Spectator. . ‘ : i 


DR. PARIS’S re | 
PHARMACOLOGIA; well 


Or, HISTORY of MEDICAL SUBSTANCES: © Ve 

With a view to establishing the Art of Prescribing and of Composing Extempora- | 
neous Formule upon Fixed and Scientific Principles. a 

A New Edition, being the Eighth, very considerably improved and closely printed, | 
in 1 vol. 8vo. price 20s. cloth. | 


*.* The Publishers have much pleasure in offering this new Edition of Dr. Paris’s- 
Puarmacotocia to the Public. It is now so printed as to form one handsome 


derived from the recent discoveries of Dr. Paris in Pharmacological and a 
Science ; and such additional observations respecting the apex of simple and com-— 
bined remedies as the extended experience of the Doctor has enabled him to offer. :| 
“ Dr. Paris’s happy illustration of the operation of medicines, as diversified by combination, appears 
to be peculiarly he own ; and he has so far succeeded in reducing his princi a to scientific 
and in rendering them applicable to practice, as justly to merit the praise of forming a new era in 
departments of pharmacy and prescriptions. ¢ PHARMACOLOGIA is a work entitled to the double 
commendation of being admirably suited to the wants of the profession, and the only one of the kind.’’ 
—Prefuce to the Second American Edition. 


DR. RYAN’S we4 
MANUAL OF MEDICAL JURISPRUDENCE AND STATE MEDICINE: | 


Being a Compendium of the Works of Beck, Panis, and Fonsranque, Orrr 
Curistison, and all standard modern writers. In four Parts. Part I. Medical 
Ethics.—Part IT. Laws relating to the Medical Profession.—Part III. All Medico- | 
Legal Questions which may arise in Courts of Justice —Part IV. Laws for the Pre- 
servation of Public Health. Intended for the Use of the Medical and Legal Profes- 
sions. hi a> 


Second Edition, considerably enlarged and improved, comprehending all that | ( 
essential in Percivay’s Mepicat Eruics, and in Becx’s celebrated work  __ 
on JURISPRUDENCE, 8vo. price 13s. cloth. a 


- 


‘ 


** We are acquainted with no work on Medical Jurisprudence that presents so valuable aad Be , 
tion in so condensed and yet so clear a form.”’—Americen Journal oF Medical Selewne a 


a8 


(LQ) 


2a = Sak 


Sherwood, Gilbert, § Piper, Paternoster Row. 7 


DR. CONOLLY’S 
| FOUR LECTURES ON THE STUDY AND PRACTICE OF MEDICINE; 


Delivered on different occasions in the University of London. 
Price 5s. neatly bound and lettered. 


“ Until we read these Lectures, we were not prepared to find so high a tone, so liberal and enlightened 
a spirit, and above all, such truly philosophical habits of mind, in a practising physician of the present 
day. Happy were the students of the University in such a guide: such a tutor was not only likely to 
lead to sound and safe notions in medicine, but to virtue and honour, peace and good name. These 
Lectures are as moral as they are medical. 

** Were we to extract all the passages in this little work that have.given us unfeigned pleasure, we 
should leave nothing behind. 

‘We trust that this volume will be put into the hands of every medical student in the country. If he 
do not feel interested in it, it is because he does not understand it: let therefore his master take the 
book up, peruse it in an evening before his pupils, and comment upon it, pointing out such illustrations 
and examples as every man’s experience will supply.’’—Spectator. 


MR. SOUTHS 
COMPLETE DESCRIPTION OF THE BONES; 


Together with their several Connections with each other, and with the Muscles. . 
Especially adapted for Students in Anatomy. 


Elegantly printed in fep. 8vo. Third Edition, enlarged, and illustrated with 250 accurate 
Woodcuts, by Branston, from Original Drawings, 12mo. price 7s. cloth lettered. 
*‘ This new edition is rendered far superior to its predecessors, by being richly illustrated with wood- 
engravings intermixed with the letter-press. We think it one of the best Manuals of Osteology for the 
Student.’’—Medical Gazette. 


SIR JAMES CLARK’S 


(Physician to the Queen, ) 
TREATISE ON PULMONARY CONSUMPTION ; 


Comprehending an Inquiry into the Nature, Causes, Prevention, and Treatment of 
TUBERCULOUS and SCROFULOUS DISEASES in general. 


8vo. price 12s. cloth lettered. 


‘Dr. Clark’s treatise on Consumption is the best that has yet been published in this country, or on 
the continent; it shows an intimate knowledge of the improved methods of diagnosis, and of the morbid 
anatomy so successfully investigated by the continental pathologists, and by Professor Carswell; while it 
displays an acquaintance with the resources of the system, and the power of therapeutic agents, only 
possessed in this country and in Germany.’’—Lancet. : 

‘© We recommend strongly the study of the author’s hygienic remarks to our professional brethren ;. 
indeed, we think that every parent ought to be acquainted with the excellent rules laid down on 
NursinG, Dress, BATHING, Air, ExeRcISEyand EpucatTion. We have seldom seen a medical work 
more deserving of general circulation, or one that-~we would more zealously recommend to the younger 
branches of the prafession.’’—Medical Quarterly Review. , 


DR. OSBORN 
ON THE NATURE AND TREATMENT OF DROPSICAL DISEASES ; 


In Four Parts. Parts I. and II. on Dropsies from Suppressed Perspiration and 
Diseased Kidney; with a coloured plate representing a kidney in an advanced stage 
of the disease.—Part III. On Dropsies from Impediments to the Circulation — 
Part IV. On Dropsies from Topical Affections. 

Second Edition, with considerable additions, price 7s. cloth. 


a9 


8 Medical Works, published by 


BOIVIN AND DUGES’ ) { 
PRACTICAL TREATISE ON THE DISEASES OF THE UTERUS | 


and its APPENDAGES, 


Translated from the French of Moe. Borvin, Sage-Femme Surveillante en Chef de | 
la Maison Royale de Santé, &c.; and A. Duces, Professeur Ala Faculté = | 

de Médecine, Montpellier, &c.; 
with copious Notes, 


By G.O.Hemine, Glasgow, F.L.S. Physician-Accoucheur to the St. Pancras Infirmary. : 


Elegantly printed in 1 large vol. 8vo. accompanied with 41 Plates to illustrate the 
Work, engraved from the original Drawings from Nature, by Mome. 
Boivin, price 26s. cloth ; or accurately coloured, 45s. 6d. cloth. 


«The work of Boivin and Dugés, on the Diseases of the Uterus, is indispensable to the library of 
every practitioner; nothing can exceed in fidelity the description here given of the natural structure of 
the uterus, and the various morbid aren, to which that organ is liable; and Dr. Heming has shown a R 
sound discrimination in rendering it into English.’’—Lancet. ; 

“The Preface, by Dr. Heming, contains a slight sketch of the recent improvements in ee q 
of medical science, in which the structure of the healthy uterus, and its appendages, is in 
the infantile, virgin, pre; t, and puerperal states.... Many excellent remarks are added, both from 
Dr. Heming’s own experience, and from the writings of the best authors of this country; and wherever 
he has stated his own opinions, they appear to be sensible, and to the purpose. The to the work | 
are of great assistance in understanding the author’s descriptions, and are Ke 
Medical Review. 


DR. HODGKIN'S 
LECTURES ON THE MORBID ANATOMY OF THE SEROUS 


and MUCOUS MEMBRANES. 


To which are appended, 


PARASITICAL ANIMALS, MALIGNANT ADVENTITIOUS STRUC- 
TURES, and the INDICATIONS AFFORDED by COLOUR. 


Vol. I. price 10s. 6d. cloth; Vol. II. Part 1., 12s. 


‘The importance of the subjects embraced by these Lectures, and the pts prea which Dr. Hodgkin 
has justly acquired, as a zealous cultivator of pathological anatomy, are sufficient to claim the earnest 
attention of every reader. It is scarcely doing justice to our judgment to say that the work is 

good: it is, in every respect, an excellent production, calcul to advance the a of 

science, and destined to take a permanent place among the higher order of the Classics of this 
and other countries.’’—British and Foreign Medical Review. 


DR. RYAN’S 
MANUAL OF MIDWIFERY AND DISEASES OF WOMEN 


AND CHILDREN; 
With a complete Atlas of Operations, intended as a Companion to all Obstetric Works. | 


Fourth Edition, rewritten and enlarged, price 10s. cloth. var, 
‘This manual contains three times more matter, according to its size, than any other we have seen’? 
Medical 


“It cannot fail to currency to principles and ractice such as every man of science must deste 0 It 
see universally adopted Dr. Co : t. ; : a 
** It evinces considerable research, discrimination, acuteness of observation, and talent.?? Z 
i Medico-Chirurgical Review. 
‘*T have no doubt it must prove useful to all the profession.’’—Professor Burns, G . 7 


‘*It is a work safe to follow, and one from which the experienced practitioner may find considerable 
information.’’—Dr. Dewees, Philadelphia. 


(ZO) Rey 


Sherwood, Gilbert, §& Piper, Paternoster -Row. 9 


WORKS OF DR. PRICHARD. 


“i. 
A TREATISE ON INSANITY, AND OTHER DISORDERS 


affecting the Mind. 
Accompanied with numerous Cases, exemplifying various descriptions of Madness. 
By JAMES COWELL PRICHARD, M.D. F.R.S. M.R.LA. &c. &e. 


Handsomely printed in 8vo. 14s. cloth. 

** The work, we may safely say, is the best, as well as the latest, on mental derangement, in the 
English language.’’—Medico-Chirurgical Journal. 

** Dr. Prichard’s work shows an extensive knowledge of his subject.’’—Lancet. 

“* Dr. Prichard’s rank among the most distinguished of medical authors is too well known to require 
any laboured introduction of him to the notice of our readers. The general character of his treatise 
may be said to be, that it contains the best information which is at present possessed on the various 
matters of which it treats. It is a fair, clear, and admirably condensed compendium of documents and 
statements from various authorities, collected in various establishments for the insane, in various 
countries ; so placed together, and with such discrimination commented upon, as to convince the reader 
that the first object of the author has been to elicit truths on which the practitioner, the moralist, the 
jurist, and the legislator might rely.’’—British and Foreign Medical Review. 


2. . 
RESEARCHES INTO THE PHYSICAL HISTORY OF MANKIND; 


Containing the Ethnography of the Nations of Europe. 
Vol. III. price 16s. 
Vol. IV., completing this portion of the Work, will very shortly be published. 


*.* A few copies of Vols. I. and II. of the same Work, price 30s. are still on sale. 


3 


THE EASTERN ORIGIN OF THE CELTIC NATIONS, 


Proved by a comparison of their Dialects with the Sanskrit, Greek, Latin, and 
~ Teutonic Languages. Forming a Supplement to “ Researches 
into the Physical History of Mankind.” 


8vo. price 7s. 


“* Dr. Prichard deserves much praise for establishing a point which has eluded the researches of his 
predecessors, and which may eventually prove a valuable contribution towards the history of the human 


race.’’—Quarterly Review. 
4 


AN ANALYSIS OF ECYPTIAN MYTHOLOGY. 


To which is added, a Translation of the Pretimrnary Essay, prefixed by Professor 
A. W. Von Scu ecet to the German Edition of the same Work, 


By James Yates, M.A. 
Royal 8vo. price 21s. cloth. 


5. 


A REVIEW OF THE DOCTRINE OF A VITAL PRINCIPLE, 


as maintained by some Writers on Physiology ; with Observations on the Causes of 
Physical and Animal Life. 


8vo. price 7s. 


Ke 


10 


Medical Works, published by a 


DR. COLLES’S 
PRACTICAL OBSERVATIONS ON THE USE OF MERCURY — 


In the CURE of VENEREAL and other Diseases. 
8vo. 9s. cloth. 


Ht.is one of those rere books whiqh proceed feces: msembere of our sauteanian, that we fel a 


n its like 
eories.’’—British Annals of 


should never look u 
useless speculative 
different effects produced by different modes 


varieties of inveterate syphilis, which assumed so destructive a character in the hands of practitioners of 
the old school, and so frequently baffle the efforts of disciples of the new doctrine.’’ 
Brit. and For. Med. Review. 


in; it is full 8 
“* We must rank, as a most important heap yan ir 


etails, and is quite 


knowledge, Dr. Colles’s demonstration of the — 
ing mercury, and its beneficial application to — 


DR. MONTGOMERY'S 
EXPOSITION OF SIGNS AND SYMPTOMS OF PREGNANCY, 


The Pertop of Human Gestation, and the Sicys of Detvery; 


Accompanied with a Series of Plates, accurately drawn and coloured from Nature 
(now for the first time made available for reference to the Profession), representing the — 
Changes observable in the Breasts and their ArEoLz, as Sions of PRecnancy, — 
from the Third Month to the period of Delivery ; also Seventeen Figures, coloured 
from Nature, illustrative of the Effects produced in the Ovaries by Impregnation: 
to which is added, an Essay on the Spontaneous Amputation of the 


Farvs, illustrated with Woodcuts. 


* It is distinguished b: t research and extensive original investigation. The are of great 
” we fe le ; they admirably illustrate the author’s * te ont aaa 


beauty and interest, very valuab 
observations.’’—Dudlin Journ. of Med. Science. 


‘* We here close a lengthened, and, we trust, impartial, review of Dr. Montgomery’s work, which — 
we strongly recommend to our readers as by far the completest and best that exists on the subject — 
of which it treats. We have already spoken of the plates, which are admirable.’’ 


‘* We notice this work with pleasure, for Dr. Montgomery has treated his subject in a complete 
and masterly manner. We have seldom seen more beautiful specimens of coloured drawings.’’—Lancet. 


q 


wre 
Lins of the | 


Brit. and For. Med. Rev. — 


DR. PARIS’S 


TREATISE 


With a view to establish, on practical grounds, a System of Rules for the Prevention | - 
and Cure of the Diseases incident to a disordered state of the Digestive Functions; | 


including 

Physiological History of Digestion 

iDtaendans of Old pi or 

Intermixture of Animal and Vegetable Food 

Luncheons objectionable 

Quality of the different Meals, and Periods 
best adapted for Breakfast, Dinner, Tea, 
and Supper 

Quantity of Food and Liquids that should 
be taken at Meals 

Necessity of Exercise 

Danger of Gas-light 


A New and Improved Edition, nearly re-written, price 12s. cloth lettered. 
eh. 
“ Dr. Paris’s work has become one of authority in the profession. This edition contains much new 
matter, and the reader will find many suggestions with regard to the nepulstion of Diet and ye bis 
departments of medicine which have been occupied by draughts and pills.’’—Brit. Annals of Medicine. | 
* Dr. Paris’s book should be in the library of every family 


investigation of all deran; 


ON DIET; , 


Importance of Ventilated Apartments , 

Sleeping after Dinner 

Of the Circumstances which influence the 
Sh pean of different species of Food | 
and of Drinks 


A Tabular Scheme for investigating the | — | 


| 


Causes, Nature, and Seat of Indigesti 

Of Headache arising from Indigestion, and 
its Cure 

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Acidity of Stomach, Flatulence, &c. 


- It forms an excellent manual for the — 


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ee 


‘ 


se ead 


eee - — SS 


(Ai) oe 


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MR. PORTER’S 
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A COMPLETE VIEW OF ALL THE DEPARTMENTS 


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EDITED BY W. B. COSTELLO, M.D. 


MEMBER OF SEVERAL LEARNED SOCIETIES, ENGLISH AND FOREIGN. 


The “ Cyclopedia of Practical Surgery” has been undertaken for the purpose of collecting 
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of Practice, which either rest on individual experience, or are inculcated in too isolated a 
manner for the general benefit. In order to stamp upon this important undertaking—hitherto 
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persons of acknowledged ability and experience in the several departments ; and thus the most 
distinguished writers in Great Britain and the Continent of Europe have been associated for 
the production of a work which, when complete, may fairly claim to be considered the most 
valuable publication of its kind extant in any language. 


Parts I. ro XII. are now published. 


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are made. Next, its subdivisions are discussed, its progress as a branch of science is historically traced, and the 
reader is then, in the body of the article, instructed by argument, exposition, and references, in the characters, the 
we: the consequences, and the treatment, or such other points as belong to the topic under explanation. The 

i ces of opinion entertained upon the facts amongst men of authority are stated and weighed with such 
judgment and absence of prejudice as the writers can command—a better plan to adopt in works of instruction, than 
making those interminable citations, which might more appropriately be termed contradictions. For the emergen- 
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rarity, misuse, or neglect. Engrayings and Woodcuts are freely employed to illustrate the text, and especially 


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The first Eight Parts, forming Vol. I. of the Work, may be had in Cloth, price £2:0:0. 


3 


— 


16 Medical Works, published by Sherwood, Gilbert, and Piper. — 
Pist of Contributors { 


CYCLOPADIA OF PRACTICAL SURGERY, 


John Adams, Esq. 

William Auchincloss, M.D. 
Sir G. Ballingall. 

Thomas Bell, Esq. 

Charles a M.D. M.R.LA. 
S. A. Bindley, : 

P. F, Blandin. oe 

Thomas Leigh Blundell, M.D. 
John Blackburn, M.A. 

Sir Benj. Collins Brodie, Bart. 
Andrew Buchanan, M.D. 
Thomas H. Burgess, M.D. 
John Burns, M.D. F.RS. 

R. Carmichael, Esq. M.R.I.A. 
Henry T. Chapman, Esq. 

Sir Astley P. Cooper, F.R.S. 
B. B. Cooper, Esq. F.R.S. 

W. Sands Cox, Fsq. F.R.S. 
Sir P. Crampton, M.D. F.R.S. 
J. Green Crosse, Esq. F.R.S. 
T. Blizard Curling, Esq. 

John Dal le, > 

John Birt Davies, a D. 

P. T. Dieffenbach. 

J.C. Donnellan, M.D. 
Robert Druitt, Esq. 

James Eager, M.D. 

John Elliotson, M.D. F.R.S. 


William Fergusson, F 
Valen. Flood, M.D. MELA. 


TO THE 


P. H. Green, M.D. 

George Gulliver, Esq. 

Geo. J. Guthrie, Esq. F.R.S. 

Marshall Hall, M.D.F.RS.L. 
and E, 

R. Harrison, M.D. M.R.A.I. 

M. W. Hilles, Esq. 

T. Hodgkin, M.D. 

A. Jacob, M.D. M.R.LA. 

G. Jewel, M.D. 

H_ J. Johnson, . 

T. Wharton Jones, Esq. F.R.S. 


_T. King, M.D. 


T. Wilkinson King, Esq. 
J. Kirby, LL D. 
George B. Knowles, Esq. 
R. Knox, Esq. M.D. F.RS.E. 
Robert Lee, M.D. F.R.S. 
W. J. Little, M.D. 
John Lizars, Esq. F.R.S.E. 
P. B. Lucas, Esq. 
ig Macfarlane, M.D. 

. F Malgaigne. 
J. Maya, Faq. 
H. Maunsell, M.D. 
Richard Middlemore, Esq. 
J. G. Millingen, M.D. 
Alexander Monro, M.D. 
John Morgan, le 
Thomas “+ tig a 


“ Dr. Costello (editor of the Cyclopeedia of Practical Surgery) earl 


branch of literature, by an article in his work, which req 
of its materials, and bears a high character among the essays with which it is 
here, as they have already obtained in ad 
ia are to be found, for the first time, the writings, in 
articles are distinguished by clearness and simplicity of 
hich it was the task of the writers to discuss. To stud 


? 
tors need not be repeated 
specially observe, that in this Cyclo 
and Velpeau. * * * 


style, and fairly perfect the subjects w 
i the work promises to become a first-rate text-book, levelling a host of obst 
view of surgery, which a dozen or so years since perplexed their attempts to inspect the ground.’’ 


active itioners, $ 


** The work itself has not disappointed the 
ions, with here and there one by an able 
monotonous mediocrity—an oasis in the waste. There is a uniformity, a substance, a power anda 
creditable not alone to the individual qwriters, but to the time and country in which we live. 

ical Surgery may not only challenge, but will advan 

of other countries ; and if we infer the extent and superiority 
high character of the work before us, considering it as a book “ 
ressly, we cannot but rejoice at the changes that have been brought about within the last quarter of ace 
The Practical to its conclusion in the spirit and style of the pres 
cannot fail of the object which it seems to aim at above all others, and which is, to form a work of 
state of surgery shall be fully and clearly expounded.’’—Medico-Chirurgical Review, Ji 


body, from the hi 


the present 


Upon the whole, the 


» conducted 


ly ced his to 
uired considerable ability in the ‘ 
vertisements ample 


ons of the profession. It is not made up of | 
nd, shedding its brilliancy and light over a 


usly sustain, comparison with any other 
of the education of the surgeons of this: 
of reference pi ‘ 


Sir J, Murray, M.D. 
James O’Beirne, M.D. — 
T. J. Pettigrew, F.S.A. | 


evin 


3” 


_MARCHANT, SINGER, AND SMITH, PRINTERS, INGRAM-COURT, PENCHURCH-S 


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CARDS OR SLIPS FROM THIS POCKET 


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