Anatomical and pathological observations

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BIOLOGY
UBRARv

JOHN GOODSIR, F.R.S.E..

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HA1UIY D. S. GOODSIR/ M.W.S.,

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EDINBURGH :

MY Li: S MACPII AIL.

LONDON : SIMPK1X, MAK8IIALL, A\!> ( < >.

*

THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

PRESENTED BY

PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID

ANATOMICAL

AND

PATHOLOGICAL OBSERVATIONS,

BY

JOHN GOODSIR, F.R.S.E.,

DEMONSTRATOR OF ANATOMY IX THE UNIVERSITY OP EDINBURGH,
AND

HARRY D. S. GOODSIR, M.W.S.,

CONSERVATOR OF THE MUSEUM OF THE ROYAL COLLEGE OF SURGEONS,
EDINBURGH.

EDINBURGH :

MYLES MACPHAIL.
LONDON: SIMPKIN, MARSHALL, AND COMPANY.

1845.

WILLIAM MACPHAIL,

PRINTER,
2 GREENSIDE PLACE, EDINBURGH.

6.

" Although it shew not the ag&nt, yet it sheweth a rule and analogy in
nature, to say, that the solid parts of animals are endued with attractive
powers, ivhereby from contiguous fluids, they draw like to like ; and that
glands have peculiar powers attractive of peculiar juices."

BERKELEY.

"Even herein consists the essential difference, the contra-distinction, of an
organ from a machine ; that not only the characteristic shape is evolved
from the invisible central power, but the material mass itself is acquired by
assimilation. The germinal power of the plant transmutes the fixed air and
the elementary base of water into grass or leaves ; and on these the organijic
principle in the ox or the elephant exercises an alchemy still more stupen-
dous. As the unseen agency weaves its magic eddies, the foliage becomes
indifferently the bone and ite marrow, the pulpy brain, or the solid ivory."

COLERIDGE.

PREFACE,

THE greater part of my share of these Anatomical and Patho-
logical Observations will be already, to a certain extent, familiar
to those who attended my lectures, in the theatre of the Eoyal
College of Surgeons, in Summer 1842, and Winter 1842-3.

The Memoir on the Secreting Structures is reprinted in a
modified form from the Transactions of the Royal Society of
Edinburgh for 1842, and that on the Intestinal Yilli from the
Edinburgh Philosophical Journal of the same year. Those on
the Placenta and Lymphatic Glands were read in the Royal
Society of Edinburgh in 1843, but were not submitted for
publication. Abstracts of some of the others have also appeared
from time to time in the reports of various Societies.

The observations on the healthy Structure and Economy of
Bone are, with the exception of those on the contents of the
corpuscules, an abstract of my lectures on this subject in the
College of Surgeons in Winter 1842-3. I have considered this
explanation necessary, in consequence of the resemblance be-
tween certain parts of my description, and those in the admirable
chapter on the same subject in Todd and Bowman's Physiological
Anatomy, drawn up from the observations of Mr. Tomes.

My brother has added some of his own zoological, anatomical,
and pathological observations, as confirmatory of the doctrines of
centres of Nutrition, and of Secretion.

11 PREFACE.

To sucli as may be inclined to object to the theoretical views
which run through and connect these anatomical details, I would
only say, that we shall be quite satisfied, if on finding the latter
correct, they will allow us to retain the former for future use :
feeling assured, that " there is a certain analogy, constancy, and
uniformity in the phenomena or appearances of nature, which
are a foundation for general rules" : and that " these are a
grammar for the understanding of nature, or that series of effects
in the visible world, whereby we are enabled to foresee what will
come to pass in the natural course of things."

JOHN GOODSIR.

EDINBURGH, 1845.

CONTENTS.

CHAPTER I.

CENTRES OF NUTRITION 1

CHAPTER H.

THE STRUCTURE AND FUNCTIONS OF THE INTESTINAL VILLI 4

CHAPTER III.

ABSORPTION, ULCERATION, AND THE STRUCTURES ENGAGED

IN THESE PROCESSES 13

CHAPTER IV.

THE PROCESS OF ULCERATION IN ARTICULAR CARTILAGES 17

CHAPTER V.

SECRETING STRUCTURES 20

CHAPTER VI.

THE TESTIS AND ITS STRUCTURE IN THE DECAPODOUS CRUS-
TACEA 35

CHAPTER VII.

SEROUS MEMBRANES 41

CHAPTER VIII.

STRUCTURE OF THE LYMPHATIC GLANDS 44

CHAPTER IX.

STRUCTURE OF THE HUMAN PLACENTA . . 50

IV CONTENTS.

CHAPTER X.

STRUCTURE AND ECONOMY OF BONE G4

CHAPTER XI.

THE MODE OF REPRODUCTION AFTER DEATH OF THE SHAFT

OF A LONG BONE 68

CHAPTER XII.

THE MODE OF REPRODUCTION OF LOST PARTS IN THE

CRUSTACEA 7 i

CHAPTER XIII.

ANATOMY AND DEVELOPEMENT OF THE CYSTIC ENTOZOA .. ..76

CENTRES OF NUTRITION.

BY centres of nutrition, I understand certain minute cellular
parts existing in the textures and organs. With many of these
centres anatomists have been for some time familiar,* but with a
few exceptions have looked upon them as embryonic structures.!
I am inclined to believe in the general existence of such centres,
for a certain period at least, in all textures and organs, and to
this I wish to direct attention at present.

The phenomena presented by these centres incline me to re^-
gard them as destined to draw from the capillary vessels, or from
other sources, the materials of nutrition, and to distribute them
by developement to each organ or texture after its kind. In this
way they are to be considered centres of germination ; and I
have elsewhere named them germinal spots — adopting the latter
term from the Embryologists.J

The centre of nutrition with which we are most familiar, is
that from which the whole organism derives its origin — the ger-
minal spot of the ovum. From this all the other centres are
derived, either mediately or immediately ; and in directions,
numbers, and arrangements, which induce the configuration and
structure of the being. As the entire organism is formed at first,

* The nuclei of the textures.

t Mr. Bowman in his Paper on Muscle, Philosophical Transactions, 1840, Part I, page
435. — Cyclopedia of Anatomy and Physiology, Art. " Hfusde" — Dr. Martin Barry in the
Philosophical Transactions, and most explicitly in his Paper " On the Corpuscles of the
Blood," 1841, Part I, page 269, paragraph 83.

I Trans. Roy. Soc. Ed. 1 842. " On the Serretwi 8tnu'tnw, find the Lairs of its Funct

A

-2 CENTRES OF NUTRITION.

not by simultaneous formation of its parts, but by the successive
developement of these from one centre, so the various parts arise
each from its own centre, this being the original source of all the
centres with which the part is ultimately supplied.

From this it follows, not only that the entire organism, as has
been stated by the authors of the cellular theory, consists of
simple, or developed cells, each having a peculiar independent
vitality, but that there is, in addition, a division of the whole into
departments, each containing a certain number of simple or de-
veloped cells, all of which hold certain relations to one central or
capital cell, around which they are grouped. It would appear
that from this central cell all the other cells of its department
derive their origin. It is the mother of all those within its own
territory. It has absorbed materials of nourishment for them
while in a state of developement, and has either passed them off
after they have been fully formed, or have arrived at a stage of
growth when they can be developed by their own powers.

Centres of nutrition are of two kinds : those which are peculiar
to the textures, and those which belong to the organs. The nu-
tritive centres of the textures are in general permanent. Those
of the organs are in most instances peculiar to their embryonic
stage, and either disappear ultimately, or break up into the various
centres of the textures of which the organs are composed.

A nutritive centre, anatomically considered, is merely a cell,
the nucleus of which is the permanent source of successive broods
of young cells, which from time to time fill the cavity of their
parent, and carrying with them the cell wall of the parent, pass
off in certain directions, and under various forms, according to
the texture or organ of which their parent forms a part.*

There is one form in which nutritive centres are arranged,
both in healthy and morbid parts, which is frequently alluded to
in the following chapters, and which may be named a germinal

* For the first consistent account of the developement of cells from a parent centre, and
more especially of the appearance of new centres within the original sphere, we are indebted
to the researches of Dr. Martin Barry. Whatever may be said in opposition to Dr. Barry's
views regarding the functions of the blood globules, and the structure of muscular fibre, ho
is yet entitled, above all physiologists of the present day, to the merit of having kept steadily
before him in his researches, the principle of the central origin of all organic form.

CENTRES OF NUTRITION. 3

membrane.* In a germinal membrane, the nutritive or germinal
centres are arranged at equal or variable distances, and in certain
directions, in the substance of a fine transparent membrane. A
germinal membrane is occasionally found to break up into por-
tions of equal size, each of which contains one of the germinal
centres. From this it is perceived, that a germinal membrane
consists of cells, with their cavities flattened, so that their walls
form the membrane, by cohering at their edges, and their nuclei
remain in its substance as the germinal centres.

Germinal membranes are only met with on the free surfaces of
parts or organs. One surface of the membrane is therefore
attached, and is applied upon a layer of areolar texture, inter-
mixed with a more or less rich network of capillary vessels.
The other surface is free, and it is on it only that the developed
or secondary cells of its germinal spots are attached. These
secondary cells are at first contained between the two layers of
the membrane, these layers being the opposite walls of each of its
component cells. When fully developed, the secondary cells
carry forward the anterior layer, which is always the thinnest,
leaving the nuclei or germinal centres in the substance of the
posterior layer, in close contact with the blood-vessels.

Of the forces which exist in connection with centres of nutri-
tion, nothing very definite can yet be stated. When this branch
of inquiry shall have been opened up, we shall expect to have a
science of organic forces, bearing direct relations to anatomy, the
science of organic forms. — J. G.

* The membranous tubes of glands on which the epithelium is situated, was described by
Henle, MiiUer's "Archiv," 1839. Mr. Bowman (Phil. Trans. 1842) " On the Structure and
Use of the Malpighian Bodies of the Kidney," &c., has applied to the membrane of these
tubes the very appropriate name of Basement Membrane. This membrane I consider to be
a primary or germinal membrane. The term, basement membrane, is good as involving no
hypothesis ; it is therefore a most appropriate descriptive term. I have always considered
the basement membrane, or elementary membrane of glands, as a form of the primary cells
of glands, and the source of the secondary or secreting cells, and have therefore been in the
habit of naming it primary, or germinal membrane. Mr. Bowman considers it to be simple,
or homogeneous. This is true as far as it contains no blood-vessels, and as regards its ex-
ternal or attached layer ; but as in its original condition it consists of cells, and when perfect
contains nuclei at equal or variable distances, I do not consider it as simply molecular.
These nuclei, or germinal spots, may be certain of the epithelial cells, which become mother
cells, between the two layers of the membrane ; or cells belonging to the order of the
nuclear fibres of Valentin and Henlo.

NO. II.

THE STRUCTURE AND FUNCTIONS OF THE
INTESTINAL VILLT.

Mr. Cruikshank, in treating of the orifices of the Lacteals and
Lymphatics,* states that he and Dr. William Hunter observed
the openings by which the lacteals communicated with the cavity
of the gut in portions of the intestine of a woman who died after
eating a hearty supper. The two preparations of the intestine on
which these anatomists made their observations, came into the pos-
session of the College of Surgeons in Edinburgh, as part of the
collection of the late Sir Charles Bell.

I removed one of the villi from Mr. Cruikshank's preparation,
and had no difficulty in recognising what had been described and
figured by the original owner of the preparation. With a low
power the extremity of the villus appeared bulbous and opaque.
With a higher power I observed that this opacity was due to the
existence, at the extremity of the villus, of a number of vesicles
of different sizes. The larger vesicles were pretty uniform in size,
and about twenty in number. The smaller were of different sizes,
and more numerous, and appeared gradually to pass into the gra-
nular texture of the attached extremity of the villus. No blood-
vessels could be detected, but along the neck of the villus distinct
traces of two or more opaque lacteals were visible. The vesicles

* William Cruikshank. The Anatomy of the Absorbing Vessels of the Human Body,
2d Ed., 1790, page 56.

THE STRUCTURE AND FUNCTIONS, &c. 5

and the lacteals, when viewed by transmitted light, were of a light
brown colour ; but when examiued as opaque objects, they stood
out of a dead white appearance, contrasting strongly with the semi-
transparency of the surrounding texture. Repeated examinations
of these preparations satisfied me that Dr. William Hunter and Mr.
Cruikshank were quite correct in describing and figuring radiat-
ing lacteals within the villi, but that they \vere led into error in
describing those vessels as opening on the free surface of the gut,
partly by imperfect instruments and methods of observation, partly
by the general prejudice of the period in favour of absorbent
orifices. I also satisfied myself of what appeared highly probable
from the commencement of the observations, that the villi, when
turgid with chyle, were destitute of their ordinary epithelial
covering. This circumstance I could not avoid connecting with
the fact of the stomach throwing off its epithelia during the pro-
cess of digestion. I determined, therefore, to investigate the pro-
cess of absorption of chyle in fresh subjects, as the facts exhibited
in Mr. Cruikshank's preparations indicated the probable existence
of complicated processes going on in villi during digestion. The
analogy of the vesicular bulbous extremity of the villus, to the
spongiole of the vegetable, forced itself upon me, and the existence
of milky chyle, within closed cells, led me to anticipate an expla-
nation of some of the phenomena of digestion.

A dog was fed. Three hours afterwards he was killed. The
lacteals were turgid, and the gut was found to be full of milky
chyme, with an admixture of thin brownish fluid of a bilious
appearance. The milky matter was situated principally towards
the mucous membrane ; the brown fluid occupied the cavity of
the gut.

The white matter consisted of a transparent fluid, with a few
oil globules, and numerous epithelia.

Some of the epithelia I recognised as those which cover the
villi. They were pointed at their attached extremities, flat at the
other. Many of them were single, others were united in bundles,
adhering principally by their flat or free extremities, as if a fine
membrane passed over and connected the edges of their extreme
surfaces. Occasionally these epithelia presented a distinct nu-
cleus ; but generally, and whether single or in bundles, they

6 THE STRUCTURE AND FUNCTIONS

exhibited in their interior a group or mass of oil-like globules,
which, when viewed as opaque objects, had a peculiar semi-
opaque or opalescent appearance.* Others of the epithelia, con-
tained in the chyme, were prismatic, single, or in columns. They
were the lining epithelia of the follicles of Lieberkiihn, and pre-
sented the usual nuclei.

The mucous membrane displayed the villi turgid, as if in a
state of erection, and, as I had anticipated, naked or destitute of
epithelia, except at their bases where a few still adhered. Each
villus was covered by a very fine smooth membrane, which from
its free bulbous extremity, passed on to its sides, and became
continuous with the germinal membrane of the follicles of
Lieberkiihn. These villi, when removed from the mucous mem-
brane, and examined with a low power, were semi-transparent,
except at their free or bulbous extremities, which appeared both
by direct or transmitted light white and opaque. Under higher
powers the summit of the villus, somewhat flattened, was observed
to be crowded, immediately under the membrane before men-
tioned j with a number of perfectly spherical vesicles. These
vesicles varied in size from 1000 to less than 2000 of an inch.
The matter in their interior had an opalescent milky appearance.
Towards the body of the villus, on the edges of the vesicular mass,
minute granular or oily particles were situated in great num-
bers, and gradually passed into the granular texture of the sub-
stance of the villus.

The trunks of two lacteals could be easily traced up the centre
of the villus, and as they approached the vesicular mass they sub-
divided and looped. In no instance could one of these lacteals
be traced to any of the spherical vesicles, nor could any direct
communication between the structures be detected.! The blood-
vessels and capillaries, with their columns of tawny blood disks,
could be seen passing in radiating lines and in loops across the
villus, immediately under the fine membrane already mentioned.
This membrane, perceptible on the body and neck of the villus
only by the smooth surface it presented, was most distinctly

* Is this appearance due to a partial absorption of chyle by these protective epithelia ?
t See Gulliver's translation of Gerber's General Anatomy, page 272 and 273.

OF THE INTESTINAL VILLI. 7

traced at the free extremity of the villus, as it passed from the
surface of one vesicle on to that of another.* The vesicles push-
ing the membrane forward, and grouped together in masses on
its attached surface, gave the extremity of the villus the appear-
ance of a mulberry7. When viewed on a dark ground as an
opaque object, the point directed to the light, a villus in this con-
dition is remarkably beautiful, the play of the light on the surface
of the highly refractive semi-opaque and opalescent vesicles,
giving them the appearance of a group of pearls.

In villi turgid with chyle, which have been kept for some time
in spirits, the contents of the vesicles are opaque, the albumen
having become coagulated.

To understand the part which the vesicles of the villus play in
digestion, it is necessary to be aware of certain of the functions
of the cell, with which physiologists are yet unacquainted. Not
only are these bodies the germs of all the tissues, as determined
by the labours of Schleiden and Schwann, but are also the imme-
diate agents of secretion. A primitive cell absorbs from the blood
in the capillaries, the matters necessary to enable it to form, in
one set of instances, nerve, muscle, bone, if nutrition be its func-
tion ; milk, bile, urine, in another set of instances, if secretion be
the duty assigned to it. The only difference between the two
functions being, that in the first, the cell dissolves and disappears
among the textures, after having performed its part ; in the other,
it dissolves, disappears, and throws out its contents on a free sur-
face. Now, it will be perceived, that before a cell can perform
its function as a nutritive cell, or as a secreting cell, it must have
acted as an absorbing cell. This absorption, too, must neces-
sarily be of a peculiar and specific nature. It is in virtue of it
that the nutritive cell selects and absorbs from the liquor san-
guinis those parts of the latter necessary for building up the
peculiar texture of which the cell is the germ. It is in virtue of
this peculiar force that the secreting cell not only selects and
absorbs, but also in some instances elaborates, from the same
common material, the particular secretion of which it is the
immediate organ. And it is by the same force that the cell

* Mr. Bowman in the Article " Mucous Membrane" Cyclopedia of Anatomy, does not admit
this portion of the membrane. It certainly cannot be detached as a separate membrane.

8 THE STRUCTURE AND FUNCTIONS

becomes the immediate agent of absorption in certain morbid
processes.

" Absorption,"* says Professor Miiller, " seems to depend on
an attraction, the nature of which is at present unknown, but
of which the very counterpart, as it were, takes place in secre-
tion; the fluids altered by the secreting action being impelled
towards the free surface only of the secreting membranes,
and then pressed onwards by the successive portions of fluid
secreted. In many organs, for instance in those invested
with mucous membranes — absorption by the lymphatics and
secretion by the secreting organs, are going on at the same
time on the same surface." It appears, however, from what is
stated in the present chapter, and in the Trans. Roy. Soc.
Edin.f that Prof. Muller, and indeed all the physiologists hitherto,
have been in error in supposing the forces of secretion and ab-
sorption as of different and opposite tendencies — the one attrac-
tive, the other repulsive. They are both attractive, absorption
being but the first stage in the process of secretion. Secretion,
in fact, differs from absorption, not physiologically, but morpho-
logically.

What has been stated in the present paper explains also how,
in the mucous membranes, " absorption by lymphatics and secre-
tion by secreting organs are going on at the same time on the
same surface." There is no physiological mystery in this. It
depends on a morphological circumstance. The absorbing chyle
cells are on the attached surface of the germinal membrane — the
secreting epithelia are on its free surface ; the former are inter-
stitial cells — the latter peripheral ; the former cast their contents
into the substance of the organism — the latter into the surround-
ing medium.

The primitive cell, then, is primarily an organ of specific ab-
sorption, and secondarily of nutrition, growth, and secretion.

As the chyme begins to pass along the small intestine, an in-
creased quantity of blood circulates in the capillaries of the gut.
In consequence of this increased flow of blood, or from some

* Miiller's Physiology, page 30. — Baly's Translation.

t Trans. Royal Society, Edin. 1842, '' On the Secreting Structure, and Laws of its
Function."

OF THE INTESTINAL VILLL 9

other cause with which I am not yet acquainted, the internal
surface of the gut throws off its epithelium, which is intermixed
with the chyme in the cavity of the gut. The cast-off epithelium
is of two kinds, — that which covers the villi, and which, from the
duty it performs, may be named protective epithelium, and that
which lines the follicles, and is endowed with secreting functions.
The same action, then, which, in removing the protective epi-
thelia from the villi, prepares the latter for then- peculiar function
of absorption, throws out the secreting epithelia from the follicles,
and thus conduces towards the performance of the function of
these follicles.

The villi, being now turgid with blood, erected, and naked, are
covered or coated by the whitish-grey matter already described.
This matter consists of chyme, of cast-off epithelia of the villi, and
of the secreting epithelia of the follicles. The function of the
villi now commences. The minute vesicles which are inter-
spersed among the terminal loops of the lacteals of the villus, in-
crease in size by drawing materials from the blood through
the coats of the capillary vessels, which ramify at this spot in
great abundance. While this increase in their capacity is in
progress, the growing vesicles are continually exerting their ab-
sorbing function, and draw into their cavities that portion of the
chyme in the gut necessary to supply materials for the chyle.
When the vesicles respectively attain in succession their specific
size, they burst or dissolve, their contents being cast into the
texture of the villus, as in the case of any other species of inter-
stitial cell.

The debris, and the contents of the dissolved chyle cells, as
well as the other matters which have already subserved the nu-
trition of the villus, pass into the looped network of lacteals,
which, like other lymphatics, are continually employed in this
peculiar function. As loiig as the cavity of the gut contains
chyme, the vesicles of the terminal extremity of the villi continue
to develope, to absorb chyle, and to burst, and their remains and
contents to be removed along the lacteals.

When the gut contains no more chyme, the flow of blood to
the mucous membrane diminishes, the developement of new

10 THE STRUCTURE AND FUNCTIONS

vesicles ceases, the lacteals empty themselves, and the villi be-
come flaccid.

The function of the villi now ceases till they are again roused
into action by another flow of chyme along the gut.

During the intervals of absorption, it becomes necessary to
protect the delicate villi from the matters contained in the bowel.
They had thrown off their protective epithelium when required
to perform their functions, just as the stomach had done to afford
gastric juice, and the intestinal follicles to supply their peculiar
secretions. In the intervals of digestion, the epithelium is
rapidly reproduced.

The germinal membrane, which, as I have stated, not only
forms the outer membrane of the follicles, under the epithelia,
but also the under-lying membrane of the villi, contains in its
substance germinal centres of an oval form, situated at pretty
regular distances. From these the epithelium appears to be
reproduced during the intervals of absorption, as stated in the
first chapter.

During this process of developement, the primary membrane
appears to split into two laminae, the epithelia passing out from
its nuclei between these. This would account for the epithelia,
particularly the prismatic and conical, adhering by their free
extremities.

Such are the processes which would appear to take place in
the villi of the intestinal tube during digestion and absorption.
When considered in relation to the functions of digestion and
absorption of chyle, these processes are highly interesting.

The labours of the chemist have now so far simplified the
theory of digestion, as to deprive the stomach of their vitalizing
or organizing powers so long ascribed to it.

Every step in this chemico-physiological inquiry leads to the
conclusion, that the changes which the food undergoes while in
the cavity of the gut are entirely of a chemical nature.

If we continue, then, to apply the term digestion to that series
of processes by which the aliment is assimilated to the matter of
which the body is composed, we must divide the series into two
groups. The first group will include all those changes which

OF THE INTESTINAL VILLI. 11

take place within the digestive tube, but exterior to the organism.
The second will include those which present themselves after the
alimentary matter is taken up into the animal body, and becomes
buried in its substance. The first group of processes are me-
chanical and chemical in their nature. They may be considered
in a great measure as peculiar to the animal, although even
vegetables throw out from their roots matter which, acting on
some of the materials of the surrounding soil, prepare these for
absorption.

The second group of processes is common to animals and vege-
tables. In these, for the first time, are alimentary substances
taken into the tissues of the organism. In animals, as in plants,
as I have already pointed out, these alimentary substances are
drawn by a peculiar force into the interior of the cells, after
escaping from which they pass on by the absorbent system.
The chemist has not yet informed us of the change which the
matter has undergone during its passage from the cavity of the
gut, or from the soil, into the afferent lacteals and the sap-
vessels ; but if in vegetables, as in animals, this matter passes
into the cavities of the cells of the spongiole before it passes on
to the sap-vessels, then it is highly probable that the organizing
and vitalizing part of the function of digestion commences in the
cells of the spongiole and of the extremity of the villus.

The extremity of the fibril of the root of a plant elongates by
the cells added to its tissue by the germinating spongiole. The
spongiole is, therefore, an active organ of growth as well as of
absorption. It is to the fibril of the root, what I have denomi-
nated in the animal tissues, the nutritive centre. I conceive it to
be probable, therefore, although as to this I have made no obser-
vations, that absorption by, and elongation of, the febril of the
root, vary inversely as one another. This supposition is founded
on the assumption, that the cells of the spongiole do not absorb
by transmission but by growth and solution.

In the villi of the intestines of animals, my own observations
lead me to believe that absorption by growth and solution is the
process which actually takes place.

The vesicular extremity, like the spongiole of the root fibril,
is the primitive nutritive centre of the villus. The villus

12 THE STRUCTURE AND FUNCTIONS, &c.

*>

originates in a cell. During the developement of the villus,
this spot or cell was employed only in procuring materials for the
growth of the organ. In the perfect animal the formative func-
tion of the spot ceases ; its action becomes periodical, active during
digestion, at rest during the intervals of that process. The same
function is performed, the same force is in action, and the same
organ, the cell, is provided for absorption of alimentary matters
in the embyro, and in the adult, in the plant, and in the animal.
The spongioles of the root, the vesicles of the villus, the last
layer of cells on the internal membrane of the included yelk, or
the cells which cover the vasa lutea of the dependent yelk, and
the cells which cover the tufts of the placenta, are the parts of
the organism in which the alimentary matters first form a part of
that organism, and undergo the first steps of the organizing
process.

J. G.

O- III.

ABSORPTION, ULCERATION, AND THE STRUCTURES
ENGAGED IN THESE PROCESSES.

Every organic cell, the most simple, as well as the most compli-
cated, when a separate organism, or when a part of a more
highly organized being, existing as a mere magazine of matter,
or performing some of the more striking of the vital functions,
invariably exhibits a phenomenon which is antecedent to all
others, absorption from without of materials for its own growth.

The various kinds of cells in any organism differ from one
another in this respect, that they have the power, each after its
kind, of selecting and procuring from the circulating medium, or
from other sources, the sort of matter necessary for their own
growth : or they have the power of elaborating, or of conducing
to the chemical change of the matter which is absorbed by them.
In this respect, the component cells of animals and vegetables re-
semble the various species of beings of which they form parts :
they have not only the power of selecting food, but the various
species out of the same kind of food are formed of matter and of
parts which are specifically different.

A most important circumstance in the history of cellular phe-
nomena is the duration of existence of a cell. Like the various
species of animals and vegetables, each species of cell has its own
average term of existence, each after its kind. This average term
is nevertheless contingent on the amount of action which each

14 ABSORPTION, ULCERATION, AND THE

species may, by peculiar circumstances in the organism to which
it belongs, be called on to perform. This variableness in the ave-
rage age of each species of cell, is dependent on those circum-
stances which have been named " nervous agency," " peculiarity
of constitution," " irritability of the parts," " morbid action,"
but may be studied independently of these agencies. The vari-
ableness in the term of existence of cells can no more be explained
at present, than the variety in the duration of the lives of species
of animals and vegetables : but the fact being known, its laws
ascertained will afford a clue to the explanation of many organic
phenomena and processes.

In the study of absorption, nutrition, and secretion, attention
has been directed to the vessels, as the active agents in the per-
formance of these processes. It is only a short time since we
have been willing to admit that the new matter which is con-
stantly replacing the old materials of the frame, is selected and
laid down, not by the ultimate vessels, but by the non-vascular
portions of the textures. It is only now that we are beginning to
know that secretion differs from nutrition in its anatomical rela-
tions, and not in its intimate nature. We still, however, retain
in full force the old belief in the active obsorbent powers of the
vessels, and in the agency of the capillary and lymphatic vessels
in removing parts and modelling the forms.

It is not my intention to question entirely the active agency of
the veins and lymphatics in absorption and ulceration, but merely
to direct attention to the subject ; and to point out, in some of
the following chapters, a few organic processes in which these
actions appear to be functions independent of the vessels, the
latter to be passive agents, mere ducts for conveying away the
products of action.

A rapidly extending ulcerated surface appears as if the tex-
tures were scooped out by a sharp instrument. The textures are
separated from the external medium by a thin film. This film is
cellular in its constitution, and so far it is analogous to the
epidermis or epithelium. It is a peculiarly endowed cellular
layer, which takes up progressively the place of the subjacent tex-
tures, these being prepared for dissolution, either by the state of
the system, the condition of the part, or by some influence in*

STIirCTl'KES ENGAGED IN THESE I'KOt'ESSES. 1 .">

duced by the contiguity of the new formation. Carrying out,
therefore, the principles at present regarded as regulating the
reciprocal functions of textures and vessels, the subjacent textures
disappear in consequence of a disturbance of their own forces,
consequent upon the appearance of new forces residing in the
cellular layer. The disturbance arid gradual annihilation of the
natural forces residing in the subjacent textures, is indicated by
the gradual disappearance of these. That new forces, not former-
ly existing in the part, are developed, appears from the formation
of the cells of the cellular layer. As these appear in rapid suc-
cession, and disappear as rapidly, the subjacent textures also dis-
appear, either by previous solution and subsequent absorption by
the properties and powers of the former ; or under the peculiar
circumstances of inflammatory action by the more vigorous
growth of the former, monopolizing the resources of the part, the
latter dissolving and disappearing by the usual channels of the
returning circulation, more rapidly, but according to ordinary
laws.

From this view of the process, it appears that so far from con-
sisting in a diminution of the formative powers of the part, such
a progressive ulceration is actually an increase of it. The ap-
parent diminution, is a consequence of the extremely limited
duration of existence of the cells of the absorbent layer, which
die as rapidly as they are formed, disappearing after dissolution,
partly as a discharge from the surface, but principally through the
natural channels by which the debris of parts, which have al-
ready performed their allotted functions, are taken up into the
organism.

When a portion of dead or dying bone is about to be separated
from the living, the process which occurs is essentially the same
as that which has now been described. The haversian canals
which immediately bound the dead or dying bone, are enlarged
cotemporaneously with the filling of their cavities with a cellular
growth. As this proceeds, contiguous canals are thrown into one
another. At last, the dead or dvincr bone is connected to the

«/ - O

living by the cellular mass alone. It is now loose, and has be-
came so in consequence of the cellular layer which surrounds it
presenting a free surface and throwing off pus.

1(5 ABSORPTION, ULCEKATION, &c.

In this process, the veins and absorbents act on the osseous
texture of the walls of the haversian canals in no otherwise than
in the natural state of the part. They are mediate, not imme-
diate instruments of absorption. It is the cells of the newly
formed cellular mass, contained in the haversian canals, which
are the immediate cause of the removal of the bone, either by
taking it up as nourishment, and substituting themselves in its
stead ; the bone being prepared for this absorption in a manner
analogous to that which occurs in the digestion of food previously
to absorption of it by the cells of the gut :* or by the active for-
mation of the cells of the new substance monopolizing the re-
sources of the part, and so inducing the disappearance of the
osseous texture by the natural channels of the returning cir-
culation.

The process by which a slough in the soft parts is separated
from the living textures, is similar to that which occurs in bone.

In this view of ulceration, there is substituted for the hypo-
thetical active, or aggressive power of absorption ascribed to the
veins and the lymphatics, a power which is known to exist in the
organic cell during the progress of its growth ; and the ultimate
removal of the matter from the scene of action is ascribed, partly
to the formation of discharge, partly to the yet unexplained, but
at the same time undoubted, and in all probability passive agency
of the returning circulation.

J. G.

* " Hence, the digestive process, instead of being confined to the stomach and duodenum,
is actually carried on without intermission, in all pails of a living animal body." — Prmifa
Bridyewater Treatise, page 534.

N°- IV.

THE PROCESS OF ULCERATION IN ARTICULAR
CARTILAGES,

The question as to the vascularity of cartilages cannot now
excite much interest, when we know that all the textures are in
themselves destitute of blood-vessels, which are accessary parts,
carriers of nourishment, not active agents in its deposition.
We do not consider cartilage as a texture into which no blood-
vessels pass, but only as less vascular than some of the others.
In a large mass of cartilage, as in those of the bulky mammals,
or in the thick cartilages of the foetal skeleton, canals containing
blood-vessels are found here and there ; but in the thin arti-
cular cartilages of the adult human subject few or no vessels
can be detected.

It is evident, therefore, that in the process of ulceration in car-
tilage, it cannot be the usual blood-vessels of the part which are
the active agents.* Still less likely is it, that lymphatics, the
existence of which has never been asserted in this texture, are the
absorbing instruments.

If a thin section, at right angles, be made through the articular
cartilage of a joint, at any part where it is covered by gelatinous
membrane in scrofulous disease, or by false membrane in simple
inflammatory condition of the joint, and if this section be exa-
mined, it will be found to present the following appearances.

* See Mr. Aston Key's Paper in the London Med. Chir. Trans., Vol. xviii., Part, I.,
" On the Ukeratire Process in Joints"

18 THE PROCESS OF ULCEBATION

On one edge of the section is the cartilage unaltered, with
its corpuscules natural in position and size. On the oppo-
site edge, is the gelatinous, or false membrane, both consisting
essentially of nucleated particles, intermixed, especially in the
latter, with fibres and blood-vessels ; and, in the former, with
tubercular granular matter. In the immediate vicinity, and on
both sides of the irregular edge of the section of cartilage, where
it is connected to the membrane, certain remarkable appearances
are seen. These consist, on the side of the cartilage, of a change
in the shape and size of the cartilage corpuscules. Instead of
being of their usual form, they are larger, rounded, or oviform ;
and instead of two or three nucleated cells in their interior, con-
tain a mass of them. At the very edge of the ulcerated cartilage,
the cellular contents of the enlarged cartilage corpuscules com-
municate with the diseased membrane by openings more or less
extended. Some of the ovoidal masses in the enlarged corpus-
cules may be seen half released from then' cavities by the removal
of the cartilage ; and others of them may be observed in the sub-
stance of the false membrane, close to the cartilage, where they
have been left by the entire removal of the cartilage which ori-
ginally surrounded them.

If a portion of the false membrane be gradually torn off the
cartilage, the latter will appear rough and honey-combed. Into
each depression on its surface a nipple-like projection of the false
membrane penetrates. The cavities of the enlarged corpuscules
of the cartilage, open on the ulcerated surface by orifices of a size
proportional to the extent of absorption of the walls of the cor-
puscule, and of the free surface of the cartilage.

The texture of the cartilage does not exhibit, during the pro-
gress of the ulceration, any trace of vascularity. The false mem-
brane is vascular, and loops of capillary vessels dip into the sub-
stance of the nipple-like projections which fill the depressions oil
the ulcerated surface of the cartilage ;* but, with the exception of
the enlargement of the corpuscules, and the peculiar development
of their contents, no change has occurred in it. A layer of

* The vascular loops described and figured by Mr. Listen, are not vessels in the car-
tila"-e, but the vessels described iu the text. — LTSTOX. Lorn!. Med. Cl.-ir. Trans.

IN ARTICULAR CARTILAGES. 19

nucleated particles always exists between the loops of capillaries
and the ulcerated surface.

The cartilage, where it is not covered by the false membrane,
is unchanged in structure. The membrane generally adheres
with some firmness to the ulcerating surface ; in other instances
it is loosely applied to it; but in all, the latter is accurately
moulded to the former.

In scrofulous disease of the cancellated texture of the heads of
bones, or in cases where the joint only is affected, but to the
extent of total destruction of the cartilage over part or the whole
of its extent, the latter is, during the progress of the ulceration,
attacked from its attached surface. Nipple-shaped processes of
vascular cellular texture pass from the bone into the attached sur-
face of the cartilage, the latter undergoing the change already
described. The processes from the two surfaces may thus meet
half way in the substance of the cartilage, or they may pass from
the attached, and project through a sound portion of the surface
of the cartilage, like little vascular nipples or granulations. The
cartilage may thus be riddled, or it may be broken up into scales
of varying size and thickness, or it may be undermined for a
greater or less extent, or be thrown into the fluid of the cavity
of the joint in small detached portions, or it may entirely
disappear.

On the principles already laid down, if absorbents exist, as we
have reason to believe they do in the false membrane, neither
they nor the veins are to be considered as the active or imme-
diate agents in the absorption of the cartilage. They certainly
are not so in the absorption of the walls of the corpuscules, and
this, as well as the analogy of similar processes, gives weight to
the opinion to which I have come, that they are not the imme-
diate instruments in the absorption of the free surface. The
cells of new formation appear to be the immediate agents in this
action. They absorb into their substance the hyaline matter of
the cartilage, the latter probably not being removed at once from
the spot, but merely converted into soft cellular texture ; the
jss being one of transformation rather than removal.

J. G.

O- V.

SECRETING STRUCTURES.

Malpighi was the first to announce that all secreting glands are
essentially composed of tubes, with blind extremities.* Miiller,
by his laborious researches, has brought this department of the
anatomy of glands to its present comparatively perfect condition.f
Purkinje announced his hypothesis of the secreting function of
the nucleated epithelium of the gland ducts, but made no state-
ment to show that he had verified it by observation 4 Schwann
suggested that the epithelium of the mucous membranes might
be the secreting organ of these surfaces. § Henle described mi-
nutely the epithelium cells which line the ducts of the principal
glands and follicles, but did not prove that these are the secreting
organs. The same anatomist has stated, that the terminal extre-
mities of certain gland ducts are closed vesicles, within wrhich the
secretion is formed, and which contain nucleated cells. Henle
has not, therefore, verified the hypothesis of Purkinje, although
he is correct in stating that the terminal vesicles of certain gland
ducts are closed.|| It will be shewn, that the secretion is not
formed, as Henle has asserted, in the closed vesicles, but in the
nucleated cells themselves.

* Exewitatwnes de Structura Vicerum, 1665.

t J. Miiller, De Gland. Struct. Penit. 1830.

J Isis, 1838.

§ Froriep. Notiz., 1838.

|| Muller's " Archw." 1838, 1839.

SECRETING STRUCTURES. 21

The discrepant observation of Boehm* and Krausef on the
glands of Peyer, were in some measure reconciled by Henle, who
referred them to the same class of structures as the closed vesi-
cular extremities of the ducts of compound glands. Dr. Allen
Thomson has observed, that the primitive condition of the
gastric and intestinal gland is a closed vesicle.J Wasmann
described the structure of the gastric glands in the pig ; and
his description will be fully explained by the following observa-
tions and views.. § Hallman has given a detailed account of the
testicle of the ray, which closely resembles that of the Squalus
comubicus, as described in another part of this chapter ,|| None of
the recent observations on the developement of the spermatozoa,
have proved, that the vesicles, in which they are formed, are the
epithelium cells of the ducts of the testicle. I am indebted to Dr.
Allen Thomson for directing my attention to a notice in Valen-
tin's Repertorium, 1841, of a Dissertation by Erdl,** in which
he describes, in the kidney of that mollusk, cells, the nuclei
of which pass out by the duct of the gland. It does not ap-
pear, however, that Erdl had discovered the uric acid within
the cell.tt

If the membrane, which lines the secreting portion of the
internal surface of the ink-bag of Loligo sagittata (Lamark) be
carefully freed from adhering secretion by washing, it will be
found to consist almost entirely of nucleated cells, of a dark
brown or black colour. These cells are spherical or ovoidal.
Their nuclei consist of cells, grouped together in a mass. Be-
tween these composite nuclei, and the walls of their contain-
ing cells, is a fluid of a dark brown colour. This fluid re-
sembles, in every respect, the secretion of the ink-bag itself.

* De Gland. Intestln. Struct. Penit., 1835.

t Miiller's " Archiv." 1837.

J Proceedings of British Association, 1840.

§ De Diyestione Nonnulla, Diss. manq. Berol, 1839.

|| Miiller's " Archiv." 1840.

** De Helicis Algirce vasts sanguiferis, 1840.

ft Mr. Bowman has shown that the fat in the fatty liver is contained in the secreting
cells. — " Observations on the Minute Structtire of the Fatty Degeneration of the Liverf
Jan. 1842.

22 SECRETING STRUCTURES.

It renders each cell prominent and turgid, and is the cause of its
dark colour.

The dilated terminal extremities of the ducts in the liver of He-
lix aspersa (Miiller) contain a mass of cells. If one of these cells
be isolated, and examined, it presents a nucleus, consisting of one
or more cells. Between the nucleus and the wall of the
containing cell, is a fluid of an amber tint, and floating in this
fluid are a few oil globules. This fluid differs in no respect from
the bile, as found in the ducts of the gland.

If a portion of the ramified glandular organ, which opens into
the fundus of the stomach of Uraster rubens (Agassiz) be exa-
mined, its internal surface is found to be lined with cells ; between
the nucleus of each of which, and the wall of the cell itself, a
dark brown fluid is situated. The organ secretes a fluid, sup-
posed to be of the nature of bile.

The dark brown ramified caeca of the same animal exhibit on
their internal surfaces an arrangement of nucleated cells, the
cavities of which contain a brown fluid. These caeca are also
supposed to perform, or to assist in the performance of the func-
tion of the liver.

The liver of Modiola vulgaris (Fleming) contains masses of
spherical cells. Between the nucleus and the wall of each of
these cells, a light brown fluid is situated, bearing a close re-
semblance to the bile in the gastro-hepatic pouches.

The nucleated cells, which are arranged around the gastro-
hepatic pouches of the Pecten opercularis, are irregular in shape,
and distended, with a fluid resembling the bile.

The hepatic organ, which is situated in the loop of intestine of
Pirena prunum (Fleming), consists of a mass of nucleated cells.
These cells are collected in groups, in the interior of larger cells
or vesicles. These nucleated cells are filled with a light brown
bilious fluid.

The hepatic organ, situated in the midst of the reproductive
apparatus, and in. the loop of the intestine of Phallusia vulgaris
(Forbes and Goodsir), consists of a number of vesicles, and each
vesicle contains a mass of nucleated cells. These cells contain
a dark brown bilious fluid.

The hepatic organ, in the neighbourhood of the stomach, in

SECRETING STRUCTURES. 2o

each of the individuals of the compound mollusk, the Alpiduun
Ficus (Linnaeus), consists of nucleated cells, which contain in
their cavities a reddish brown fluid.

The liver of Loligo sagittata (Lamark), contains a number of
nucleated cells, ovoidal and kidney shaped. These cells are dis-
tended with a brown bilious fluid.

The nucleated cells in the liver of Aplysia punctata (Cuvier),
are full of a dark brown fluid.

The ultimate vesicular caeca of the liver of Buccinum undatum,
contain ovoidal vesicles of various sizes. These vesicles contain
more or less numerous nucleated cells. The cells are full of a
dark brown fluid.

The hepatic caeca in the liver of Patella vulgata. Each of
these vesicles encloses a body, wrhich consists of a number of
nucleated cells, full of a dark fluid resembling the bile.

The simple biliary apparatus, which surrounds the gastric por-
tion of the intestinal tube of Nereis, contains nucleated cells,
full of a light brown fluid.

The hepatic caeca of Carcinus Mcenas contains cells full of a
fluid of an ochrey colour, along with numerous oil globules.

The hepatic caeca of Carabus catenulatus (Fabricius) contain
cells attached to their internal surfaces. Between the nuclei and
the cell walls, a brown liquid containing numerous granules is
situated.

The kidney of Helix aspersa (Miiller) is principally composed
of numerous transparent vesicles. In the centre of each vesicle
is situated a cell full of a dead white granular mass. This gland
secretes pure uric acid.

The ultimate elements of the human liver are nucleated cells.
Between the nucleus and the cell wall is a light brown fluid,
with one or two oil globules floating in it.

The vesicular caeca, in the testicle of Squalus twrnubicu*, con-
tain nucleated cells which ultimately exhibit hi their interior
bundles of spermatozoa.

The generative caeca of Edi'innis mlgaris (Lamark) contain
colls full of minute spermatozoa.

j»ni<-tata secretes from the edge and internal surface of

24 SECRETING STRUCTURES.

its mantle a quantity of purple fluid. The secreting surface of
the mantle consists of an arrangement of spherical nucleated
cells. These cells are distended with a dark purple matter.

The edge and internal surface of the mantle of Janthina fra-
gilis (Lamark), the animal which supplied the Tyrian dye, se-
cretes a deep bluish purple fluid. The secreting surface consists
of a layer of nucleated cells, distended with a dark purple
matter.

If an ultimate acinus of the mammary gland of the bitch be
examined during lactation, it is seen to contain a mass of nu-
cleated cells. These cells are generally ovoidal, and rather trans-
parent. Between the nucleus and the cell wall of each, a quantity
of fluid is contained, and in this fluid float one, two, three or
more oil-like globules, exactly resembling those of the milk.

In addition to the series of examples already given, I might
adduce many others to prove that secretion is a function of the
nucleated cell. Some secretions, indeed, are so transparent and
colourless, as to render ocular proof of their original formation
within cells impossible ; and we are not yet in possession of chemi-
cal tests sufficiently delicate for the detection of such minute quan-
tities. The examples I have selected, however, show that the most
important and most striking secretions are formed in this man-
ner. The proof of the universality of the fact, in reference to
the glandular structures which produce colourless secretions, can
only rest at present on the identity of the anatomical changes
which occur in their cellular elements. This part of the proof I
shall enter upon in another part of this chapter.

The secretion within a primitive cell is always situated between
the nucleus and the cell wall, and would appear to be a product
of the nucleus.*

* In the original Memoir the cell wall is stated to be the probable secreting structure.
" Now, as we kncfw that the nucleus is the reproductive organ of the cell, that it is from it,
as from a germinal spot, that new cells are formed, I am inclined to believe that it has
nothing to do with the formation of the secretion. I believe that the cell wall itself is the
structure, by the organic action of which each cell becomes distended with its peculiar
secretion, at the expense of the ordinary nutritive medium which surrounds it." — Trans.
Roy. Soc., Edin. 1842.

SECRETING STRUCTURES. 25

The ultimate secreting structure, then, is the primitive cell,
endowed with a peculiar organic agency, according to the secre-
tion it is destined to produce. I shall henceforward name it the
primary secreting cell. It consists, like other primitive cells, of
three parts — the nucleus, the cell wall, and the cavity. The
nucleus is its generative organ, and may or may not, according
to circumstances, become developed into young cells. The
cavity is the receptacle in which the secretion is retained till the
quantity has reached its proper limit, and till the period has
arrived for its discharge.

Each primary secreting cell is endowed with its own peculiar
property, according to the organ in which it is situated. In the
liver it secretes bile — in the mamma, milk, &c.

The primary secreting cells of some glands have merely to
separate from the nutritive medium a greater or less number of
matters already existing in it. Other primary secreting cells are
endowed with the more exalted property of elaborating from the
nutritive medium matters which do not exist in it.

The discovery of the secreting agency of the primitive cell does
not remove the principal mystery in which this function has
always been involved. One cell secretes bile, another milk ; yet
the one cell does not differ more in structure from the other than
the lining membrane of the duct of one gland from the lining
membrane of the duct of another. The general fact, however,
that the primitive cell is the ultimate secreting structure, is of
great value in physiological science, inasmuch as it connects
secretion with growth, as phenomena regulated by the same laws.
The force, of whatever kind it may be, which enables one pri-
mary formative cell to produce nerve and another muscle, by an
arrangement within itself of the common materials of nutrition,
is identical with that force which enables one primary secreting
cell to distend itself with bile, and another with milk.

Instead of growth being a species of imbibing force, and secre-
tion on the the contrary a repulsive, the one centripetal, the
other centrifugal, they are both centripetal. Even in their later
stages the two processes, growth and secretion, do not differ.
The primary formative cell, after becoming distended with its
peculiar nutritive matter, in some instances changes its form

2G SECKETIXG STRUCTURES.

according to certain laws, and then, after a longer or shorter
period, dissolves and disappears in the inter-cellnlar space in
which it is situated, its materials passing into the circulating
system, if it be an internal, and being merely thrown off if
it be an external cell. The primary secreting cell, again, after
distention with its secretion, does not change its form so much
as certain of the formative cells, but the subsequent stages are
identical with those of the latter. It bursts or dissolves, and
throws out its contents either into ducts or gland cavities, both
of which, as I shall afterwards show, are inter-cellular spaces,
or from the free surface of the body.

The general fact of every secretion being formed within cells,
explains a difficulty which has hitherto puzzled physiologists, viz.,
why a secretion should only be poured out on the free surface of
a gland-duct or secreting membrane.

" Why," says Professor Miiller, " does not the mucus collect
as readily between the coats of the intestine as exude from the
inner surface ? Why does not the bile permeate the walls of the
biliary ducts, and escape on the surface of the liver, as readily as
it forces its way outwards in the course of the ducts ? Why does
the semen collect on the inner surface only of the tubuli semeni-
feri, and not on their exterior, in their interstices ? The elimi-
nation of the secreted fluid on one side only of the secreting
membrane, viz., on the interior of the canals, is one of the
greatest enigmas in physiology." Miiller proceeds to explain this
enigma by certain hypotheses ; but the difficulty disappears, the
mystery is removed, when we know that the secretion only exists
in the interior of the ripe cells of the free surface of the ducts or
membrane, and is poured out or eliminated simply by the burst-
ing and solution of these superficial cells.

I have hitherto confined my observations to the structure
and function of the ultimate secreting element, the primary
secreting cell. I now proceed to state the laws which I have
observed to regulate the original formation, the developement,
and the disappearance of the primary organ. This subject
neccessarily involves the description of the various minute ar-
rangements of glands and other secreting structures.

If the testicle of Syurttux coniubicm (Gmelin) be examined

SECRETING STRUCTURES. 27

when the animal is in a state of sexual vigour, the following
arrangements of structure present themselves.

The gland consists of a number of lobes separated, and at the
same time connected by a web of filamentous texture, in which
ramify the principal blood-vessels.

The lobes, when freed from this tunic, present on their surface
a number of vesicles. "When the gland is dissected under water,
and one of the lobes is raised out of its capsule, an extremely
delicate duct is observed to pass from it into the substance of the
capsule, to join the ducts of the other lobes.

When a section is made through one of the lobes, it becomes
evident that the vesicles are situated principally on its exterior.

If a small portion be macerated in water for a few hours, and
dissected with a couple of needles, there are observed attached to
the delicate ducts which ramify through the lobe vesicles in all
stages of developement. These stages are the following: — 1st,
A single nucleated cell attached to the side of the duct, and pro-
truding, as it were, its outer membrane.

2d, A cell containing a few young cells grouped in a mass
within it ; the parent cell presenting itself more prominently on
the side of the duct.

3d, A cell attached by a pedicle to the duct, the pedicle being
tubular, and communicating with the duct ; the cell itself being
pyriform, but closed and full of nucleated cells.

4:th, Cells larger than the last, assuming more of a globular
form, still closed, full of nucleated cells, and situated more to-
wards the surface of the lobe.

5th, The full-sized vesicles already described as situated at the
surface of the lobe. These vesicles are spherical, perfectly closed ;
that part of the wall of each which is attached to the hollow
pedicle forms a diaphragm across the passage, so that the vesicle
has no communication with the ducts of the gland. The con-
tents of the vesicles are in various stages of developement Those
least advanced are full of simple nucleated cells ; in others, the
included cells contain young cells in their interior, so that they
appear granular under low powers ; in others, the included cells
have begun at a certain part of the vesicle to elongate into
cylinders, with slightly rounded extremities. In others the

28 SECRETING STRUCTURES. *

cylindrical elongation has taken place in all the included cells,
with the exception of a few, which still retain the rounded form,
at a spot opposite to that part of the vesicle in which the change
commenced, and at the same time it may be observed, that the
cylindrical cells have become arranged in a spiral direction
within the parent vesicle. Lastly, Vesicles exist in which all the
cells are cylindrical, and are arranged within its cavity in a spiral
direction.

The changes which occur in the included nucleated cells of
the vesicle are highly interesting. After the nucleus of each has
become developed into a mass of cells, the parent cell becomes, as
has been stated, cylindrical. The change in the shape of the
cell is contemporaneous with the appearance of a spiral arrange-
ment of the included mass of cells. This spiral arrangement is
also contemporaneous with an elongation of each cell in the
mass, in the direction of the axis of the parent cell. When the
elongation has reached its maximum, the original mass of in-
cluded cells has assumed the appearance of a bunch of spirals,
like cork-screws arranged one with another, spiral to spiral. In
particular lights the cylindrical cell presents alternate spots of
light and shade, but by management of the illumination, the in-
cluded spiral filaments become evident; the light and shade is
seen to arise from the alternate convexities and concavities of the
spiral filaments, combined in a spiral bundle.

In vesicles more advanced, the wall of the cylindrical cells
have become attenuated,

In other vesicles the diaphragms across their necks have dis-
solved or burst, the bundles of spiral filaments float along the
ducts of the gland, or separate into individual spiral filaments.
These filaments are completely developed spermatozoa, pointed
and filamentous at both extremities, thicker and spiral in the
middle.

In the centre of the lobe where the smaller ducts meet to form
the principal duct, there is a mass of grey gelatinous matter
through which the ducts pass. This gelatinous matter consists
of a number of cells lying between the converging ducts, and
from their peculiar appearance not presenting the usual nuclei.
I am inclined to believe that they are either vesicles which have

SECRETING STRUCTURES. -)\\

never become developed on account of the pressure of the sur-
rounding parts, or that they are old vesicles in a state of atrophy
after the expulsion of their contents.

Having now described the changes which are constantly taking
place in the testicle of this shark when the organ is in a state of
functional activity, I must defer till a future occasion an account
of similar changes which occur in the parenchyma of an order of
glands, of which the one already described may be considered as
a type. I may state, however, that I have ascertained the follow-
ing general facts in reference to glands of this order : —

1st, The glandular parenchyma is in a constant state of change,
passing through stages of developement, maturity, and atrophy.

2d, The state of change is contemporaneous with, and propor-
tional to, the formation of the secretion, being rapid when the
latter is profuse, and vice versa.

3d, There are not, as has hitherto been supposed, two vital
processes going on at the same time in the gland, growth and
secretion, but only one, viz., growth. The only difference be-
tween this kind of growth and that which occurs in other organs
being, that a portion of the product is from the anatomical con-
dition of the part thrown out of the system.

4:th, The vita] formative process which goes on in a gland, is re-
gulated by the anatomical laws of other primitive cellular parts.

5th, An acinus is at first a single nucleated cell. From the
nucleus of this cell others are produced. From these, again,
others arise in the same manner. The parent cell, however, does
not dissolve away, but remains as a covering to the whole mass,
and is appended to the extremity of the duct. Its cavity, there-
fore, as a consequence of its mode of developement, has no com-
munication with the duct.

The original parent cell now begins to dissolve away, or to
burst into the duct at a period when its contents have attained
their full maturity. This period varies in different glands, ac-
cording to a law or laws peculiar to each of them.

fa/i, In the gland there are a number of points from which
acini are developed, as from so many centres. These I name
the germinal spots of the gland.

30 SECRETING STRUCTURES,

1th, The secretion of a gland is not the product of the parent
cell of the acinus, but of its included mass of cells. The parent
cell or vesicle may be denominated the primary cell ; its included
nucleated cells, after they have become primary secreting cells,
may be named secondary cells of the acinus.

Sth, There are three orders of secretions, 1st, A true secretion,
that is, matter formed in the primary secreting cell cavities ;
or, 2d, A mixture of a fluid formed in these cell cavities with the
developed or undeveloped nuclei of the cells themselves ; and, 3c?,
It may be a number of secondary cells passing out entire.

In the liver of Carcinus Mcenas, and other Crustacea, it
may be observed, that each of the follicles of which it consists
presents the following structure. The blind extremity of the
follicle is slightly pointed, and contains in its interior a mass of
perfectly transparent nucleated cells. From the blind extremity
downwards, these cells appear in progressive states of develope-
ment. At first they are mere primitive nucleated cells ; further
on they contain young cells ; and beyond this they assume the
characters of primary secreting cells, being distended with yellow
bile, in which float oil globules, the oil in some instances occupy-
ing the whole cell. Near the attached extremity of the follicle
an irregular passage exists in the midst of the cells, and allows
the contents of the cells which bound it to pass on to the branches
of the hepatic duct.

This arrangement of the secreting apparatus may be taken as
the type of an order of glands, which consist of follicles more or
less elongated. Growth in glands of this kind is regulated by
the following laws : —

\stj Each follicle is virtually permanent, but actually in a con-
stant state of developement and growth.

2d, This growth is contemporaneous with the function of the
gland, that function being merely a part of the growth, and a
consequence of the circumstances under which it occurs.

3d, Each follicle possesses a germinal spot situated at its blind
extremity.

4£/i, The vital action of some follicles is continuous, the ger-
minal spot in each, never ceasing to develope nucleated cells,

SECRETING STKUCTt'RKS. 31

which take on the action of, and become primary secreting cells,
as they advance along the follicle. The action of other follicles
is periodical.

5th, The wall, or germinal menbrane of the follicle, is also in
a state of progressive growth, acquiring additions to its length
at its blind extremity, and becoming absorbed at its attached
extremity. My brother, in a paper on the Developement and
Metamorphoses of GaUgus, read in the Wernerian Society, April
1842, has stated that the wall of the elongated and convoluted
follicle, which constitutes the ovary in that genus, grows from its
blind to its free extremity, at the same rate as the eggs advance
in developement and position. A progressive growth of this kind
would account for the steady advance of its attached contents,
and would also place the wall of the follicle in the same cate-
gory with the primary vesicle, germinal membrane, or wall of the
acinus in the vesicular glands.

6^, The primary secreting cells of the follicle are not always
isolated. They are sometimes arranged in groups, and when
they are so, each group is enclosed within its parent cell, the
group of cells advancing in developement according to its
position in the follicle, but never exceeding a particular size in
each follicle.

In my original memoir, I stated my opinion, that there is an
order of glands, namely, those with very much elongated ducts,
which do not possess germinal spots in particular situations, but
in which these spots are diffused more uniformly over the whole
internal surface of the ducts. The human kidney is a gland
of this order.*

We require renewed observations on the original development
of glands in the embryo. From the information we possess, how-

* " I am the more inclined to believe this, from what I have observed in certain secreting
membranes. Thus the membranes which secrete the purple in Aplysia and Jantlmui are not
covered with a continuous layer of purple secreting cells, but over the whole surface, and at
regular distances, there are spots, consisting of transparent, colourless nucleated cells, around
which the neighbouring cells become coloured. Are these transparent cells the germinal
spots of these secreting membranes ? And may not the walls of the elongated tubes, and
the surfaces of the laminae within certain glands, have a similar arrangement of germinal
spots ?" — Trans. 7?o//. >Sw., AV/.v. 184:?,

32 SECRETING STRUCTURES.

ever, it appears that the process is identical in its nature with the
growth of a gland during its state of functional activity.

The blastema, which announces the approaching formation
of a gland in the embryo, in some instances precedes, and is in
other instances contemporaneous with, the conical blind pro-
trusion of the membrane upon the surface of which the future
gland is to pour its secretion.

In certain instances it has been observed that the smaller
branches of the duct are not formed by continued protrusion of
the original blind sac, but are hollowed out independently in the
substance of the blastema, and subsequently communicate with
the ducts.

It appears to be highly probable, therefore, that a gland is ori-
ginally a mass of nucleated cells, the progeny of one or more
parent cells ; that the membrane in connexion with the embryo
gland may or may not, according to the case, send a portion of
the membrane, in the form of a hollow cone, into the mass ; but
whether this happens or not, the extremities of the ducts are
formed as closed vesicles, and then nucleated cells are formed
within them, and are the parents of the epithelium cells of the
perfect organ.

Dr. Allen Thomson has ascertained that the follicles of the sto-
mach and large intestine are originally closed vesicles. This
would appear to shew that a nucleated cell is the original form of
a follicle, and the source of the germinal spot which plays so im-
portant a part in its future actions.

The ducts of glands are therefore inter-cellular passages. This
is an important consideration, inasmuch as it ranges them in the
same category with the inter-cellular passages and secreting re-
ceptacles of vegetables.*

Since the publication of my paper on the secreting structures,
in the Transactions of the Royal Society of Edinburgh in 1842,
l^have satisfied myself that 1 was in error, in attributing to the
cell wall the important function of separating and preparing the
secretion contained in the cell cavity. The nucleus is the part

* Honle, in his General Anatomy, has made a similar statement.

SECRETING STRUCTURES. 33

which effects this. The secretion contained in the cavity of the
cell appears to be the product of the solution of successive deve-
lopements of the nucleus, which hi some instances contains in its
component vesicles the peculiar secretion, as in the bile cells of
certain mollusca, and in others becomes developed into the secre-
tion itself, as in seminal cells-. In every instance, the nucleus is
directed towards the source of nutritive matter, the cell wall is
opposed to the cavity into which the secretion is cast. This ac-
cords with that most important observation of Dr. Martin Barry?
on the function of the nucleus in cellular developement.

I have also had an opportunity of verifying, and to an extent
which I did not at the time fully anticipate, the remarkable vital
properties of the third order of secretions, referred to in the me-
moir to which I have just alluded. The distinctive character of
secretions of the third order is, that when thrown into the cavity
of the gland, they consist of entire cells, instead of being the
result of the partial or entire dissolution of the secreting cells.
It is the most remarkable peculiarity of this order of secretions
that, after the secreting cells have been separated from the gland,
and cast into the duct or cavity, and therefore no longer a com-
ponent part of the organism, they retain so much individuality
of life, as to proceed in their developement to a greater or less
extent in their course along the canal or duct, before they arrive
at their full extent of elimination.

The most remarkable instance of this peculiarity of secretions of
this order, is that discovered by my brother, and recorded by him
in a succeeding chapter.* He has observed that the seminal se-
cretion of the decapodous crustaceans undergoes successive deve-
lopements in its progress down the duct of the testis, but that it
only becomes developed into spermatozoa after coitus, and in the
spermatheca of the female. He has also ascertained, that appa-
rently for the nourishment of the component cells of a secretion
of this kind, a quantity of albuminous matter floats among them,
by absorbing which they derive materials for developement after
separation from the walls of the gland.

This albuminous matter he compares to the substance which,

* See Page 39.

34 SECRETING STRUCTURES.

according to Dr. Martin Barry's researches, results from the
solution of certain cells of a brood, and affords nourishment to
their survivors. It is one of other instances in which cells do
not derive their nourishment from the blood, but from parts in
their neighbourhood which have undergone solution ; and it
involves a principle which serves to explain many processes in
health and disease, some of which have been referred to in other
parts of this work.

I conclude, therefore, from the observations which I have
made — 1st, That all the true secretions are formed or selected by
a vital action of the nucleated cell, and that they are first con-
tained in the cavity of that cell ; 2d, That growth and secretion
are identical — the same vital process, under different circum-
stances.*

J. G.

* In Mr. Bowman's elaborate Paper " On the /Structure and Use of the Malphigian Bodies
of the Kidney" read in the Royal Society of London, 17th Feb. 1842, and in his Article
" Mucous Membrane" in the Cyclopedia of Anatomy, written in Dec. 1841, certain parts
of the theory of secretion are well elucidated by a reference to human structure. In my own
Memoir, read in the Royal Society of Edinburgh, 30th March, 1842, I endeavoured, by an
appeal to facts hi comparative anatomy, to establish secretion as a function of the nucleated
cell, and to shew that glandular phenomena are only the changes which the cellular elements
of these organs undergo. Mr. Bowman's own observation on the secretion of fat by the
cells of the human liver in a state of disease, was an important and positive result ; and
Professor John Reid, with whom I had frequent conversations on the subject of secretion,
and to whom I had communicated my views on the subject, a year before the publication
of my Paper, was in the habit of supporting Purkinje and Schwann's hypothesis, by an
appeal to the structure of Mollmcum contagiosum, as described by Professor Henderson and
Dr. Paterson in the Edinburgh Medical and Surgical Journal, 1841.

O- YI.

THE TESTIS AND ITS SECRETION IN THE
DEOAPODOUS CRUSTACEANS.

The organs of generation in the male crustacean consist of
testes, vasa deferentia, and external or intromittent organs.

In no class of animals do these parts vary so much as in that
now under consideration. In every family, and almost in every
genus, they afford generic, and in some even specific characters.
This variableness of configuration and structure is not peculiar
to the organs of reproduction, but exists also in the other systems
— the vascular and respiratory, the nervous and locomotive.
Such a variableness is to be looked for in a class, the forms in
which pass from that of the annelids, through the articulata, to
the mollusk. Throughout all this range of form the organs
and functions vary in accordance with those in the group of
animals to which the crustaceans presenting them are analogous.

In all the higher, or brachyurous crustaceans, the internal
organs of generation are comparatively most highly developed.
These organs exhibit the greatest complexity of form and struc-
ture among the Triangulares, but in the next order, the Cyclo-
metopa, they are of great size. These crustaceans are accord-
ingly the most prolific, and in greatest demand as articles of diet.
The Catometopa, or rather the higher forms of that family, have
these organs also very large; this family containing the land-crabs
of tropical climates, which are used as food.

30 THE TESTIS AND ITS SECKETiON

As we descend towards the Anomoura the internal organs of
generation are found to give way gradually to others, which have
apparently a more important part to play in the economy, and
in the lowest forms of the Oxystoma they are in a minimum
state of developement.

In this division (Brachyura) they occupy both sides of the
shell, lying upon the liver, and sometimes entering the folds of
that organ, and separated with difficulty from it. In others, as
Cancer and Carcinus, when in an active state, they completely
cover and conceal the liver.

In Leptopodiwn and Hyas the testis is a body of considerable
size, lying upon the upper surface of the liver, and consisting of
irregular masses, formed by the twistings of its constituent duct.
It is covered by a delicate membrane, which is much stronger on
the body of the testis than elsewhere, and is analogous to the
tunica albuginea in the higher animals. The gland extending
forward, gradually enlarges, and when it has arrived in a line
with the stomach, curves slightly inwards to the mesial plane,
and terminates in a large tube on each side, which is its duct much
dilated. This large tube, making a number of convolutions,
proceeds inwards and downwards until it meets and forms a
junction with that of the opposite side. The anastomosis is in-
complete in this division of the class. After running in contact
for some distance the two ducts again separate, and each becom-
ing much smaller, terminates by opening at the base of the ex-
ternal organs.

In the Anomoura, instead of being situated in the thorax, as
in the Bracliyura^ the testes are contained in the abdominal seg-
ment of the body, lying on and above the liver. They are very
small in all the animals of this section, the tubuli semen if eri
being large, and after making a few convulutions, ending in the
vas deferens, which opens on the base of the 5th pair of legs,
without the intervention of an intromittent organ. The elon-
gated acini are confined to the lower part, and are contained
within the external tunic of the gland.

In the Macroura the testes commence on each side of the
stomach, and extend down to the middle parts of the abdomen.
In almost all the species of the section, these organs are narrow

IN THE DECAP0DOUS CRUSTACEA. 37

ribbon-shaped organs, connected with one another immediately
behind the stomach by a narrow commissure ; the vasa deferentia
come off behind this commissure, and are more distinct than in
any other of the sections. In Galcitliea these organs are more
complicated, the tube being more convoluted.

The ultimate structure of the testis consists of a germinal
membrane, covered externally by the common tunic of the organ,
or by processes from it. The germinal membrane in the upper
or first part of its course, developes from germinal spots in its
substance formative cells of a spherical shape and of small size,
which will be afterwards described. In the lower part of the
tube, the formative cells assume a peculiar linear or spindle-shape,
attached by one of their extremities to the germinal membrane,
and projecting either into the cavity of the gland duct, as in
Pagurus, or from its external surface as in Galathea, and therefore
in this case covered by the common enveloping tunic of the
gland, or by processes of it which correspond to the areolar vas-
cular matrix of the glands in the higher animals.

When the animal is getting into season, numerous small cells
are found, as just described, on the internal surface of the seminal
tube, and more particularly from that portion of the gland which
lies on the surface of the liver. As the animal becomes stronger,
these cells increase in size from the formation of young in their
interior. That these young or secondary cells are produced from
the germinal spots on the germinal membrane of the seminal
tube, from which the primary cells took its origin, appeared highly
probable among other circumstances, from this, that after the
latter had burst, its cell wall was smooth and regular, not broken
up or rough, as might have been expected, had the secondary
cells been formed from it. After these primary cells have burst,
the secondary cells contained in them pass down the seminal tube,
to undergo the changes to be afterwards described.

The spindle-shaped cells in the lower part of the seminal tube
are large primary cells, two or three generally arising from a
disk or spot in the germinal membrane. They correspond in
every respect, except in shape and size, to the spherical primary
cells further up the tube, and like them form in their interior
young or secondary cells. These secondary cells originate in a

38 THE TESTIS AND ITS SECKETION

germinal spot or nucleus, situated about a third from the attached
extremity of the cell. In such of the spindle-shaped cells as are
quite full of secondary cells, this nucleus cannot be seen, so that
it probably disappears after the primary cells have become fully
developed, that is, have become full of young. In such of these
elongated cells, again, as are not quite developed, with cavities
not entirely occupied by their progeny, the nucleus may be oc-
casionally seen in various stages of developement, with a brood
of young cells surrounding it, and enclosed in a membrane car-
ried off' by them from the nucleus. (Pagurus.)

These spindle-shaped primary cells of the lower part of the
seminal duct differ from the spherical primary cells of the upper
part of the same tube, principally in this, that whereas the latter
contain only a limited number of secondary cells, formed probably
by a single act of nuclear developement, the former are filled by
successive broods from the nucleus.

In Hyas, when these spindle-shaped cells project from the ex-
ternal surface of the seminal duct, instead of into its cavity,
the secondary cells pass off by a narrow valvular orifice in its
attached extremity, and replaced by others from the nucleus.
The cell in this case has become a secreting follicle, with an
active germinal spot.

The passage downwards of the secondary cells, both of the
superior spherical, and the lower spindle-shaped primary cells, is
retarded in the neighbourhood of the latter by long slips or
bands, which run up the cavity of the duct and terminate by free
edges ; the direction of these bands being opposed to the flow
of the seminal fluid downwards.

These peculiar spindle-shaped cells or acini, although present
in all the orders, are most apparent in the Anomoura and cuirassed
Macroura. In the Triangulares and succeeding families of Brachy-
ura, also in lower families of Macroura^ from the Cryptobranchiate
genera and downwards, they are by no means so elongated, re-
sembling rather widened and contracted portions of the seminal
duct. The arrangement is similar in the lower orders — as in
Stomapoda, Amphipoda, and Isopoda — the Lcemodipoda being
apparently exceptions to the rule. Neither is this structure
found in Branckiopoda, Entornostraca, Siphonostoma, and Xip-

IN Till-: DECAPOIMHS CIU'STACKA. ;j<)

, in which orders the structure of the testis would require
tor elucidation a separate inquiry.

The secondary cells, as has already been stated, continue to be
developed in their progress along the seminal tube. At the spot
where they are retarded by the folds at the necks of the spindle-
shaped cells, they increase much in size, from the increased
number and size of their contained cells. After this no great
change takes place, with the exception of a thinning of the walls.
In this state they pass along the narrow part of the duct, or vas
deferens, and are thrown during coitus into the spermatheca of
the female, there to undergo the essential change which is to fit
them for fertilization of the ova.

That this final change can only take place in the spermatheca
of the female does not appear to be the case, for precocious
secondary cells may occasionally be found bursting in the lower
part of the seminal tube, and even as high up as the spindle-
shaped cells. The greater number, indeed, with a few exceptions
the whole of them, are introduced into the female before bursting.

After lying in the spermatheca for some time, the wall of the
secondary cell becomes so thin that it bursts, and allows the
young cells to escape. These tertiary cells contain, and are the
formative cells of the spermatozoa. In the higher Crustacea,
BrachyurO) they each contain one or more spermatozoa, in the
Macroura one only. The spermatozoal cells are nucleated when
they first burst from the secondary cells, and shortly the head of
the spermatozoa is found to correspond to the nucleus.

The seminal fluid in all the species of Macroura is very pecu-
liar, the tertiary cells being in all cases armed with three long
slender seta?.* They are oblong, and dilated at the armed ex-
tremity. They are developed singly within their parent cells ;
sometimes, however, two may be observed in one cell. These
parent or secondary cells are oblong, and bulge slightly in the
middle. After they have remained for some time in the spindle-
shaped caeca (Galathea), the three seta? of the tertiary cell ex-
pand, and the cells begin their descent. In the progress down-
wards, the unarmed extremity acquires a small nucleated spot,

* Von Siobold in Miiller's " J/v/> />..'' 1836.

40 THE TESTIS AND ITS SECRETION, &o.

and in many instances small spherical cells are thrown off from
this, which are quaternary, and probably spermatozoa! cells.
In the cuirassed and digging Macroura these tertiary cells are all
armed with three seta?, many times longer than the body of the
cell. In the prawn these setaa are short and truncated.

Throughout the whole course of the lower part of the seminal
tube there may be observed during the active state of the gland,
and while the seminal cells are being produced, a large quantity
of albuminous matter in small irregular masses floating among
the cells in an aqueous fluid. I am induced to believe that the
cells derive their nourishment from this matter.

In the upper part of the tube, where the cells are small and
comparatively few in number, this matter is in small quantity ;
but in the lower part of the tube, where the cells are more nu-
merous, more developed, and in a more active condition, it exists
in the greatest abundance. Still lower down in the vas deferens,
where the cells are in a state of satiety, and are in fact absorbing
principally their own external wall, preparatory to bursting, it
again diminishes in quantity, and disappears.

This albuminous matter would appear to result from the debris
of dissolved cells. It is more abundant in the Brachyura than in
the other forms of Crustacea, in accordance with the greater
abundance of seminal cells.*

H. D. S. G.

* An abstract of more extended observations on the subject of this chapter was published
in the Ed. Phil. Journal, Oct. 1843.

NO- VII.

THE STRUCTURE OF THE SEROUS MEMBRANES.

A portion of the human pleura or peritoneum will be found to
consist, from its free surface inwards, of a layer of nucleated
scales, of a germinal membrane,* and of the sub-serous areolar
texture intermixed with occasional elastic fibres. The blood-
vessels of the serous membrane ramify in the areolar texture.

There is one stratum only of the nucleated scales in the super-
ficial layer of the serous membrane. This layer conceals the
germinal membrane, which can only be detected after the re-
moval of the scales.

The germinal membrane does not in general shew the lines of
junction of its component flattened cells. These appear to be
elongated in the form of ribbons, their nuclei, or the germinal
spots of the membrane being elongated, expanded at one ex-
tremity, pointed at the other, and somewhat bent upon them-
selves. The direction of these flattened cells and nuclei is the
same in any one part of the membrane, this direction being in
general parallel to the subjacent blood-vessels, in the neighbour-
hood of which they exist in greatest numbers. The germinal
spots are bright and crystalline, and may, or may not, according
to their condition, contain smaller cells in their interior. They

* 1 stated this fact in my Paper on the Intestinal Villi, in the Ed. Phil. Journal, July
1822. Dr. Todd and Mr. Bowman, in their " Physiology of Man," have described the
same membrane in the serous texture.

42 THE STRUCTURE OF THE SEROUS MEMBRANES.

tire not to be confounded with the fibres of the areolar texture, or
with elastic filaments, or with the nuclei of the capillary vessels of
the sub-serous texture, or with paler, ovoidal, somewhat indistinct
cells, scattered throughout that texture, and which appear to be
connected with the common areolar fibres.

These flattened ribbon-shaped scales, and bright crystalline
nuclei, which from the germinal or basement membrane of the
serous coat appear to be identical with the objects described by
Valentin,* Pappenheim,t and Henle,| and named by the latter
nucleated fibres.

In inflamed or aged serous membranes, I have found it im-
possible to detect this membrane, or even the super-imposed
scales. The germinal membrane in such instances appears to
break up into areolar texture, and to assimilate itself to the
bursse mucosse, or the ordinary enlarged areolse of the areolar
texture.

If these germinal centres be the sources of all the scales of the
superficial layer, each centre being the source of the scales of its
own compartment, then the matter necessary for the formation
of these during their developement must pass from the capillary
vessels to each of the centres, acted on by forces whose centres of
action are the germinal spots; each of the scales, after being
detached from its parent centre, deriving its nourishment by its
own inherent powers.

I have been in the habit of considering the highly vascular
fringes and processes of the synovia! membranes as more active
in the formation of epithelium, and therefore more closely allied
to the secreting organs than other portions of these membranes.
If this be the case, Clopton Havers § was not mistaken in his ideas
regarding the functions of these vascular fringes. They are
situated where they cannot interfere with the motions of the
joint. They hang into those parts of the cavity best fitted for
containing and acting as reservoirs of synovia ; and their high

* Valentin. " Repertorium" 1838.

f Pappenheim. " Zur Kentniss der Verdawung" 1839.

J Henle. " Anatomie Allgemeiw"

§ Clopton Havers. " Osteologia A'om," 1691.

THE STRl'C'ITRE OF THE SEROUS MEMBRANES. 43

vascularity, and the pulpy nature of their serous covering, tend
to strengthen this opinion.

The phenomena attending inflammatory action of the membranes
are highly interesting. The capillaries are all on one side of the
membrane, and yet the serum and lymph are on the other. The
capillary vessels in healthy action have no power in themselves of
throwing out any of their contents. They do not secrete in vir-
tue of any power inherent in themselves. Do they acquire this
power during inflammation ? Or will any of the hypotheses of
effusion account for the lymph and serum being on the free sur-
face of the serous membranes, and so little, if any, in the sub-
serous textures ?

I do not see how we can, in the present state of the science,
account for phenomena of this kind, by referring them to actions
of the extreme vessels. We must look . for an explanation, I am
inclined to believe, in a disturbance of the forces which naturally
exist in the extra-vascular portions of the inflamed part.*

J. G.

* " The primary change," in inflammation, " is in the vital affinities, common to the
solids and fluids, and acting chiefly in that part of the system where the solids and fluids
are most intimately mixed, and are continually interchanging particles." — Alison's Outlines
of Physiology and Pathology, page 437.

O- VIII.

STRUCTURE OF THE LYMPHATIC GLANDS.

It is now generally admitted, that the afferent communicate in
the interior of the lymphatic glands with the efferent vessels.
These glands, indeed, consist of a dense network of lymphatics,
in the meshes of which, the arteries, veins, and nerves, ramify.
Much difference of opinion still exists, however, as to the nature
of the communication between the afferent and efferent vessels,
and no definite idea is entertained regarding the parenchyma
of these organs.

We know that an efferent lymphatic, before it enters a
gland, consists of an external tunic of filamentous texture, a
middle tunic of fibrous texture, and an internal layer of epi-
thelium.

Immediately after the branches, into which the afferent vessel
divides, have penetrated the capsule of the gland, they lose their
external tunic. For a short distance, indeed, until they have
begun to anastomose with one another, a very thin external tunic,
accompanied by a little fat, is still observable. This fat is con-
tinuous with the layer of adipose texture, which generally exists
immediately under the capsule of the gland, and through which
the lymphatics must pass to and from the organ.

The branches of the extra-glandular lymphatics, then, which
pass to and from the glands, possess a very thin internal tunic ;
but the network of infra-glandular lymphatics which enter into

THE STRUCTURE OF THE LYMPHATIC GLANDS. 45

the structure of the. gland itself, present no external coat. The
external tunic of the extra-glandular lymphatics — the afferent
and efferent vessels — appears to leave them almost entirely at
their entrance and exit from the organ, and by passing on to the
surface of the gland form its capsule.

This capsule is moderately strong, somewhat smooth on its
free, more filamentous on its attached surface, sending inwards
from the latter the processes already described, which not only
support the larger branches of the vessels before they anastomose,
but also bind together and strengthen the substance of the organ.
The larger trunks of the arteries and veins, as they pass through
the capsule, and plunge into the substance of the gland, carry
along with them also a certain quantity of filamentous texture,
which is derived from the internal surface of the capsule, and
is continuous with the processes which surround the larger lym-
phatic branches.

The middle, or fibrous tunic of the extra-glandular lymphatics,
also begins to disappear after these vessels have penetrated the
capsule of the gland. It is still sufficiently apparent on the
lymphatics near the surface of the organ, but is met with spar-
ingly towards the centre. Different glands, however, differ in
this respect ; the human intra-glandular lymphatics appearing to
me to retain more of their fibrous tunic, than those in the more
granular and developed mesenteric glands of the dog and seal.

It is, however, to the changes which the internal tunic of the
intra-glandular lymphatics undergoes, that I shall now more par-
ticularly direct attention, as these have hitherto escaped obser-
vation, and as upon them depend those appearances and pe-
culiarities which are yet unexplained.

I shall first describe the internal tunic, and afterwards its
arrangement.

If this tunic be traced from the afferent lymphatics, in which
it presents the usual structure, into the branches immediately
after they have penetrated the capsule of the gland, it is found
to become thicker and more opaque. In the short dilated anas-
tomosing branches which form the intra-glandular network, this
tunic has become so thick and opaque, that the vessels will no
longer transmit the light, and appear as if they were stuffed full

40 THE STRITCTUBE OF THE LYMPHATIC GLANDS.

of a granular matter. When these thickened, and dilated vessels
are cut, torn, or broken, so as to display their structure, it may
be observed that two parts enter into their composition ; an ex-
tremely fine external membrane, and a thick granular substance,
which lines the membrane.

The external membrane is extremely thin and transparent.
In its substance there are arranged, at regular distances, ovoidal
bodies, so placed that their long diameters are all in the same
direction. The distance of these bodies from one another is
somewhat greater than their long diameters. They are embed-
ded in the substance, and form a part of the membrane. They
are hollow, and contain one or more rounded vesicles grouped
together in their interior. I have seen portions of this membrane
after it has been acted upon by acetic acid, present an appear-
ance of being broken up into flat semi-transparent scales, united
by their edges, each scale consisting of one of the nucleated
ovoidal bodies, and a portion of the surrounding membrane.

The thick granular substance which is attached to the internal
surface of the membrane just described, is composed entirely of
nucleated particles, closely packed together, and cohering to one
another. The thickness of this layer of granular substance is so
considerable as to render the vessel, of which it is a part, almost
opaque, encroaching on its cavity, and leaving a comparatively
narrow canal for the passage of the lymph and chyle. This canal
appears to be somewhat irregular, in consequence of the greater
exuberance of the granular substance in some spots, and its de-
ficiency in others. This circumstance also accounts for the greater
transparency of the vessels at certain parts of their extent. The
canal is not lined by a membrane, but appears to me to be irregu-
larly pierced through the granular substance, the projections and
hollows of which, as well as the superficial layer of its nucleated
particles, being freely bathed by the lymph and chyle.

The nucleated particles are on an average about the 5000 of an
inch in diameter. They are spherical, and contain a nucleus,
which consists of one or more particles. Their walls are very dis-
tinct, especially after being treated with acetic acid, which reduces
their size somewhat, without dissolving or breaking them up.

The layer of particles which has now been described is thickest

THE STRUCTURE OF THE LYMPHATIC GLANDS. 47

in the lymphatics towards the centre of the gland. If it be exa-
mined in either direction towards the afferent or efferent branches,
it will be found to become thinner, and, at last, to be continuous
with the layer of flat epithelium scales of the extra-glandular
lymphatics.

The anatomical relations of the membrane, and its layer of
nucleated particles, are identical with those which characterize
the primary cells or membrane, and the secondary or secreting
cells of certain glands. The oval vesicles in the substance of the
membrane are germinal spots or centres of nutrition, and the
membrane is a germinal membrane. I am inclined to believe
the spots on the membrane to be the sources from which the germs
of the nucleated particles of the thick layer are derived. These
spots are doubtless in a state of constant activity in all lymphatic
glands, but must be called into much more vigorous action periodi-
cally in the mesenteric glands, during the passage of the chyle.
If this be the case, these spots must exert a force by which matter
is abstracted from the blood which circulates in the neighbouring
capillaries, for the purpose of developing a steady succession of
nucleated particles.

The arrangement in the substance of the lymphatic glands of
this highly developed portion of the lymphatic system of vessels,
or, in other words, the mode in which the afferent communicate
with the efferent lymphatics, I have found to coincide with the
account usually given of it. The terminal branches of the afferent
form a more or less dense network with the radicals of the effe-
rent lymphatics. The question which has been so often agitated,
as to whether cavities exist, intermediate between the two sets of
lymphatics, is not one of much importance. Some lymphatic
glands, as has frequently been stated, exhibit, after injection with
mercury, nothing but a mass of lymphatic vessels ; others, again,
a mass of apparently intermediate cells, and Cruikshank correctly
remarks, that occasionally, when the mercury first passes through
a gland, cells only may appear, but after the injection has been
pushed a little further, vessels full of mercury may suddenly pre-
sent themselves.*

* Cruikshank. " The Anatomy of the Absorbing Vessels of the Human Body? page 82.

48 THE STRUCTURE OF THE LYMPHATIC GLANDS.

These various appearances may be explained by the following
facts. In some lymphatic glands the meshes are elongated, in
which case no force short of what is sufficient to burst the vessels
can obliterate tho vascular appearance. The mtra-glandular
lymphatics, like those in other parts, are liable to be over-distended
with injections, or by their own contents, so that short vessels or
rounded meshes, more especially after great distention, assume
the appearance of globular cavities.

There is another apparently cellular appearance, which is not
met with in the human lymphatic glands, but in some of the
lower mammals, which is produced by another cause, the partial
or entire obliteration of some of the meshes, so as to produce
cavities more or less extended, with bars or threads passing from
wall to wall, the lymphatics opening into them. This is the con-
version of a network of lymphatics into cavities and connecting
threads, by a process of absorption similar to that which I have
to describe as occurring in the placental decidua.*

The external surfaces of the intra-glandular lymphatics are
closely applied to one another. They are strengthened here and
there by fibrous bundles, the remains of the middle tunic. These
fibres are most distinct towards the surface of the glands, and at
the angles formed by the junction of one lymphatic with another ;
and when viewed in thin sections, seem to form arches inclosing
circular or oval spaces, like the fibrous matrix of the human
kidney.

The description usually given of the arrangement of the blood-
vessels in the lymphatic glands is sufficiently correct. The ulti-
mate capillaries, as I have observed, do not ramify in the sub-
stance of the germinal membrane of the intra-glandular lymphatics
but are merely in contact with its external surface. In this re-
spect they resemble the ultimate ducts of the true secreting glands.

The capillary network which surrounds the intra-glandular
lymphatics is as fine as that which supplies the ultimate secreting
ducts, and for the same purpose in both, to afford matter for the
continued formation of secreting epithelium on the internal sus-
face of the germinal membrane.

* See Page 61.

THE STRUCTURE OF THE LYMPHATIC GLANDS. 49

The structure I have described affords, in my opinion, satis-
factory evidence —

1. That the lymphatic glands are merely networks of lym-
phatic vessels, deprived of all their tunics but the internal, the
epithelium of which is highly developed for the performance of
particular functions.

2. That these peculiar lymphatics are supplied with a fine
capillary network, to supply matter for the continual renovation
of the epithelium.

J. G.

. IX.

THE STRUCTURE OF THE HUMAN PLACENTA,

I. — OF THE STRUCTUKE OF THE TUFTS AND VILLI OF THE

PLACENTA.

1. — Of the Configuration of the Tufts.

A placental tuft resembles a tree. It consists of a trunk, of
primary branches, and of secondary branches or terminal villi,
which are attached as solitary villi to the sides of the primary
branches, and to the extremities of the latter, in which case they
generally present a digitated arrangement. The villus, when
solitary, is cylindrical, or slightly flattened, or somewhat club-
shaped ; when digitated, each division may be much flattened,
or is then generally heart-shaped. The digitated villi are only
solitary villi grouped together at the extremity of a primary
branch.

2. — Of the External Membrane of the Tufts.

The trunk, the primary branches, and the terminal villi of
the tuft are covered by a very fine transparent membrane, appa-

THE STRUCTURE OF THE HUMAN PLACENTA. 51

rently devoid of any structure. This membrane may be described
as bounding the whole tuft, passing from the trunk to the branches,
and from these to the villi, the free extremities of which it closely
covers. Its free surface is smooth and glistening, — its attached
surface is somewhat rough.*

3. Of the External Cells of the Villi.

Immediately under the membrane just described is a layer of
cells.f They are flattened spheroids, slightly quadrilateral in out-
line, from the manner in which they are packed together. When
a tuft is viewed in profile, under compression, its edges exhibit
the appearance of a double line, wilich leads the observer to sup-
pose that its bounding membrane is double, with the cells just
described situated between the two laminse. In the space be-
tween the two lines, the nuclei of the cells may be seen in the
form of dark oval spots, and the septa formed by the walls of con-
tiguous cells are also visible.

At variable distances the space between the two lines widens
out into a triangular form, the base towards the external mem-
brane, the apex towards the centre of the villus. This wider space
is produced by a larger group of cells, which appear to be passing
off from a spot in the centre of the mass. The groups of cells I
am now describing are germinal spots. They are the centres
from which new cells are constantly passing off, to supply the
loss of those which have disappeared in the performance of their
important function.

As in the case of the intestinal epithelium, I am inclined to be-
lieve that a fine membrane lines the internal aspect of the layer
of cells. I have not been able to isolate it ; but the very sharp
outline in a profile view of a villus confirms me in my belief of the
existence of such a membrane.

* Professor Reid, " On the Anatomical Relations of the Blood- Vessels of the Mother 1o
those of the Foetus in the Hitman Species" Ed. Med. Surg. Journal, 1841, page 7.

t Mr. Dalrymple, " On the. Structure of (he Placenta.1" Med. Chir. Trans. London, Vol.
xxv., pages 23, 24.

52 THE STRUCTURE OF THE HUMAN PLACENTA.

4. Of the Internal Membrane of the Villus.

When a villus, under gentle compression, is viewed by trans-
mitted light, there is perceived under the structures already de-
scribed, and immediately bounding the blood-vessels, and other
parts to be afterwards examined, a membrane finer and more
transparent than the external membrane, but strong and firm in
its texture. This membrane is most distinctly seen when it passes
from one loop or coil of the blood-vessel of the villus on to an-
other. It separates very easily from the internal surface of the
layer of external cells. I am not disposed to believe that it is
attached to this layer, but am of opinion that the spaces which
frequently exist between them, even in villi which have under-
gone no violence, are due to the presence of a fluid matter, the
nature of which will be afterwards considered. Be this as it may,
pressure very easily separates this membrane from the external
cells, the latter invariably remaining attached to the external
membrane, the former continuing in every instance closely rolled
round the internal structures of the villus, and following them in
all their changes of position.

5. Of the Blood-vessels of the Tufts.

Within the internal membrane, and imbedded in structures to
be afterwrards described, are situated the blood-vessels of the tuft.
These vessels are branches of the umbilical arteries and veins.

In the trunk of the tuft, the artery gradually diminishes and
the vein increases in size. In some of the primary branches the
same rotation holds. In others of the primary branches, and in
all the villi, the vessel retains the same mean diameter through-
out. This species of blood-vessel, although it cannot be consi-
dered as either artery or vein, cannot nevertheless be denominated
in precise anatomical language, a capillary. It differs from artery
and vein in retaining throughout the same mean diameter ; and
from the capillary, properly so called, in its greater calibre, con-

THE STRUCTUKE OF THE HUMAN 1'LAC'KNTA. 53

taining four or six blood disks abreast. It is also peculiar in
exhibiting sudden constrictions and dilatations, like an intes-
tine.

These changes in form are most remarkable at the spots where
the vessel makes sudden turns, coils, or convolutions. Like a
capillary, however, this vessel may divide and again become
single, and may send off a division to a vessel of the same kind.
All such divisions and anastomosing vessels, however, preserve the
same mean diameter, and are in this respect distinguishable from
arterial and veinous branches.

As regards the general arrangement of the vessels, it may be
observed, that —

1. One vessel may enter a villus, and returning 011 itself, leave
it again.

2. Two vessels may enter a villus, may anastomose, and leave
it in one or two divisions.

3. One, or more may enter, may each separate into two or
more divisions, which may reunite and leave the villus as they
entered.

Many other modifications occur, but the general rule is, that
one vessel enters, and leaves the villus without dividing.

As regards the particular arrangements of the vessels within
the villus, we recognize those leading varieties : —

1. The simple loop, a vessel turning closely on itself.

2. The open loop, a vessel turning on itself, but leaving a space
within the loop.

3. The wavy loop, resembling the first, except that the vessel
is wavy instead of being direct.

4. The wavy open loops.

5. The contorted loop, the contortion being generally at the
extremity or sling of the loop; the limbs of the loop being
straight or wavy as the case may be.

6. The various modifications which arise from combinations of
the five foregoing forms, in single, double, triple, or quadruple or
anastomosing loops. The most common forms are the simple
and contorted loop. The simple loop, and the wavy loop, are
found in cylindrical villi. The open loop, and the wavy open
loop, occur in the flattened and heart-shaped villi. The contorted

54: THE STRUCTURE OF THE HUMAN PLACENTA.

and other varieties of loops exist in the club-shaped and tube-
rose villi.*

Lastly, It must be stated as a fact first recorded and re-
presented by Professor Weber, confirmed by the observations
of Mr. John Dalrymple, and to the accuracy of which I can
testify, that the same peculiar vessel, or umbilical capillary,
may enter and retire from two or more villi before it becomes
continuous with a vein.

6.— Of the internal Cells of the Villas.

Within the internal membrane, and on the external surface
of the umbilical capillaries, are cells which I have named
the internal cells of the tuft. When the vessels are engorged,
these cells are seen with difficulty. When the vessels are
moderately distended, and the internal membrane separated
from the external cells by moderate pressure, the cells now un-
der consideration come into view. They are best seen in the
spaces left between the internal membrane and the retiring
angles formed by the coils and loops of the vessels, and in the
vacant spaces formed by these loops. These cells are egg-shaped,
highly transparent, and are defined by the instrument with dif-
ficulty ; but their nuclei are easily perceived. They appear to
be filled with a transparent highly refractive matter. This
system of cells fills the whole space which intervenes between
the internal membrane of the villus and the vessels, and gives
to this part of the organ a mottled appearance.

* Mr. Dalrymple, in his Paper on the Placenta, in the Med. Chir. Trans., has described
with great accuracy the manner in which the foetal vessels ramify and coil in the tufts of
the placenta. I am indebted to Mr. Dalrymple for specimens of his injections of the pla-
centa; and to Dr. John Reid, for a portion of a placenta injected by Professor Weber of
Leipsic, and have satisfied myself of the accuracy of the descriptions given by these
anatomists. My own observations have been made on the unprepared placenta. The
drawings of the foetal vessels in Dr. Reid s Paper are plans, as the only point he was anxious
to establish was, that the villi terminated in blunt extremities unconnected by cellular or
other textures, the foetal vessels returning upon themselves. — REIO, in Edinburgh Medical
and Surgical Journal.

THE STRUCTURE OF THE HUMAN^PLACENTA. 55

II. — OF THE VILLI OF THE CHORION.

Without entering at present into the question as to the man-
ner in svhich the villi of the chorion take their origin, I may
state, that as soon as they are distinctly formed, they present a
structure which has to a certain extent been represented and
described by Raspail,* Seiler,f and others.

The substance of the tufts consists of nucleated cells. These
cells are of different sizes. The smaller are situated, some in the
interior, others in the spaces between the latter. The cavities of
the larger cells are full of a granular fluid. The surface of the
tufts is bounded by a fine, but very distinct membrane, which,
when minutely examined, is seen to consist of flattened cells
united by their edges.

The free extremity of each villus of the tuft is bulbous. The
cells which constitute this swelling are arranged round a central
spot. They are transparent and refractive, apparently from not
containing the same granular matter as the cells of the rest of
the villus and tuft. However short a villus may be, it invariably
presents a bulbous extremity, with the peculiar cellular arrange-
ment already described. Here and there, on the sides of the
stems of the tufts, swellings of a similar structure may be seen.
Each of these swellings is the commencement of a new villus or
stem, which, as it elongates, carries forward on its extremity the
swelling from which it arose.

These groups of cells in the bulbous extremities of the villi of
the chorion, and in the swellings on the sides of their steins, are
the germinal spots of the villi. They are the active agents in
the formation of these parts. The villus elongates by the ad-
dition of cells to its extremity, the cells passing off from the ger-
minal spot, and the spot receding on the extremity of the villus,
as the latter elongates by the additions which it receives from it.

The bulbous extremities of the villi of the chorion, are not
only the formative agents of these parts, but are also all along,

* Raspail. " Chemie Organique"
f Seiler.

56 THE STRUCTURE OF THE HUMAN PLACENTA.

but principally after the villi have become well developed, their
functional agents also. They are to the ovum what the spon-
geoles are to the plant — they supply it with nourishment from
the soil in which it is planted.

Up to a certain period of gestation, the chorion and its villi
contain no blood-vessels. Blood-vessels first appear in these
parts when the allantois reaches and applies itself to a certain
portion of the internal surface of the chorion. The umbilical
vessels then communicate with the substance of the viUi, and be-
come continuous with loops in their interior. Those villi in which
the blood-vessels do not undergo any further developement, as
the ovum increases in size, become more widely separated, and
lose their importance in the economy. The villi, again, in which
vessels form, in connection with the umbilical vessels, increase in
number, and undergo certain changes ki the arrangement of their
constituent elements, so as to become the internal structures of
the tufts of the placenta, as described in the first part of this
Memoir. The villi of the chorion always retain their cellular
structure. As the blood-vessels increase in size the cells diminish
in number ; but are always found surrounding the terminal loop
of vessels in the situation of the germinal spot. The fine mem-
brane, which was formerly described as bounding the villus of
the chorion, always remains at the free extremities of the villi of
the placenta ; but on the stems and branches of the latter it coa-
lesces with the contained cells.

The conversion into fibrous texture of the membrane and cells
of the stems and branches of the tuft of the chorion, forms the
tough white fibrous trunk and branches of the tufts of the foetal
portion of the placenta ; in each of which runs a branch of the
umbilical arteries and vein ; and the fine membrane of the villi
of the .chorion, with its contained cells and terminal blood-loops,
still persistant at the extremities of the villi, are the internal
membrane, the internal cells, and the blood-loops described in
the first part of this memoir,

III. — OF THE MATERNAL PORTION OF THE PLACENTA.

The mucous membrane of the uterus presents on its free sur-

THE STRUCTURE OF THE HUMAN PLACENTA. 57

face the orifices of numerous cylindrical follicles arranged parallel
to one another, and at right angles to the surface. In the spaces
between these follicles the blood-vessels form a dense capillary
network.

From the observations of Professors Weber and Sharpey,* it
has now been ascertained, that when impregnation has taken
place, the mucous membrane of the uterus swells, and becomes
lax, that its follicles increase in size, and secrete a granular mat-
ter, and that the capillaries increase in a proportional degree.
" In a uterus," says Dr. Sharpey, " supposed to have been re-
cently impregnated, and in which the vessels had been minutely
injected with vermilion, the lining membrane, or commencing
decidua, appeared everywhere pervaded by a network of blood-
vessels, in the midst of which the tubular glands were seen,, their
white epithelium strongly contrasting with the surrounding red-
ness." It must have been from a uterus in this condition that
Baer took the sketch of the structure of the commencing deci-
dua, which has been copied by Wagner in his Icones Physio-
logicce. Baer and Wagner, however, have mistaken the enlarged
follicles for papillae, and have represented the capillary loops in a
manner much too formal. I have examined a uterus which was
in a state described by Dr. Sharpey. There was a well formed
corpus luteum in one of the ovaries ; the decidua had appeared on
its internal surface, and presented in the most distinct and
beautiful manner the orifices of the follicles, and the vascularity
of the inter-follicular spaces. The follicles, bounded by their
germinal membrane, were turgid with their epithelial contents.
The inter-follicular spaces in which the capillaries formed a net-
work with polygonal or rounded meshes, was occupied by a tex-
ture which consisted entirely of nucleated particles. This is the
tissue represented by Baer and Wagner, described by them as
surrounding what they supposed to be uterine papillae, and con-
sidered by them as decidua. The free surface of the uterine
mucous membrane was covered by a membrane, which ap-
peared to me to be continuous with the germinal membrane of the
follicles.

* Miiller's Physiology, page 1574.

58 THE STRUCTURE OF THE HUMAN PLACENTA.

Dr. Sharpey has not described this inter-follicular substance,
as his attention appears to have been chiefly directed to the
follicles. As, however, it is to this iiiter-follicular substance, as
much as to the enlargement of the follicles themselves, that the
mucous membrane owes its increased thickness, it appears to me
worthy of being recorded.

A uterus in the condition which has just been described, is
said to be lined with the decidua, consisting, as has been stated, of
an inter-follicular cellular substance, and of an extended network
of capillary blood-vessels.

About the time at which the ovum reaches the uterus, the de-
veloped mucous membrane or decidua begins to secrete, the os
uteri becomes plugged up by this secretion, wrhere it assumes the
form of elongated epithelial cells ; the cavity of the uterus becomes
filled with a fluid secretion, the " hydroperione" of Breschet, and
in the immediate neighbourhood of the ovum, the secretion con-
sists of cells of a spherical form. The cells which are separated
in the neighbourhood of the ovum I consider as a secretion of the
third order. They have passed off from the uterine glands entire,
and possess a power peculiar to the third order of secretions, the
power of undergoing further developement after being detached
from the germinal spots or membrane of the secreting organ.

From what has now been stated, it appears, that the decidua
consists of twro distinct elements : the mucous membrane of the
uterus thickened by a peculiar developement, and of a non-vas-
cular cellular substance, the product of the uterine follicles. The
former constitutes at a later period the greater part of the de-
cidua vera, the latter, the decidua reflexa. This view of the
constitution of the decidua, clears up the doubts which were en-
tertained regarding the arrangement of these membranes at the
os uteri and entrances of the fallopian tubes. It is evident that
these orifices will be open or closed, just as the cellular secretion
is more or less plentiful, or in a state of more or less vigorous
developement. It also removes the difficulty of explaining how
the decidua covers the ovum, a difficulty which cannot be recon-
ciled with the views of Dr. Sharpey, who is obliged to suppose
the deposition of lymph, which is only the old view of the con-
stitution of the decidua.

THE STRUCTURE OF THE HUMAN PLACENTA. 59

When the ovum enters the cavity of the uterus, the cellular
decidua surrounds it, and becomes what has been named the
decidua reflexa, by a continuation of the same action by which
it had been increasing in quantity before the arrival of the
ovum. The cellular decidua grows around the ovum by the
formation of new cells, the product of those in whose vicinity the
ovum happens to be situated.

At this stage of its growth, the ovum with its external mem-
brane, the chorion, covered by tufts, the structure and functions
of which, have been described in the second pail of this Memoir,
is embedded in a substance which consists entirely of active
nucleated cells. The absorbing cells of the tufts are constantly
taking up either the matter resulting from the solution of the
cells of the cellular decidua, or the fluid contained in these cells.
The ovum is now deriving its nourishment, not from the supply
which it took along with it when it left the ovary, but from a
matter supplied by the uterus. I am, therefore, inclined to look
upon the cellular decidua, as representing in the gestation of the
mammal the albumen of the egg of the oviparous animal.
They are both supplied by a certain portion of the oviduct, and
they are both brought into play after the nourishment supplied
by the ovary is exhausted, or in the course of being exhausted.
The difference between them consists in this, that in the mam-
mal the albumen is applied to use as quickly as it is absorbed ;
whereas, in the oviparous animal, after being absorbed, it is kept
in reserve within the chorion till required. I have also been in
the habit of considering the uterine colyledons of the ruminant
and other mammalia as a permanent decidua vera, and the milky
secretion interposed between them and the foetal colyledons as
decidua reflexa in its primitive and simplest form.

I have been thus particular in the explanation of what I believe
to be the nutritive function performed respectively by the chorion
and decidua, as upon it I shall have to found my views regarding
the actions of nutrition in the fully developed placenta.

When the ovum has arrived at a certain stage of its growth,
the absorption and circulation of nutritive matter by the agency
of cells alone is no longer sufficient. At this period, the ovum
has approached the thickened mucous membrane, or that portion

GO THE STRUCTURE OF THE HUMAN PLACENTA.

usually described as decidua serotina. About the same time, the
allantois bearing the umbilical vessels applies itself to the in-
ternal surface of that portion of the chorion opposed to the de-
cidua serotina, and the villi of that portion become vascular, as
formerly described. The vessels of the decidua enlarge, and
assume the appearance of sinuses encroaching on the space for-
merly occupied by the cellular decidua, in the midst of which
the villi of the chorion are embedded. This increase in the
calibre of the decidual capillaries, goes on to such an extent,
that finally the villi are completely bound up or covered by the
membrane which constitutes the walls of the vessels, this mem-
brane following the contour of all the villi, and even passing to
a certain extent over the branches and stems of the tufts. Between
this membrane, or wall of the enlarged decidual vessels, and the
internal membrane of the villi, there still remains a layer of the
cells of the decidua.

From this period, up to the full time, all that portion of decidua
in connection with the group of enlarged capillaries, and vascular
tufts of the chorion, and which may now be called a placenta, is
divided into two portions. The first portion of the decidua, in
connection with the placenta, or forming a part of it, is situated
between that organ and the wall of the uterus. This is the only
portion of the placental decidua with which anatomists have been
hitherto acquainted, and I shall name it the parietal portion. It has
a gelatinous appearance, and consists of rounded or oval cells. Two
sets of vessels pass into it from the uterus. The first set includes
vessels of large size which pass through it for the purpose of sup-
plying the placenta with maternal blood for the use of the fostus.
These may be named the maternal functional vessels of the pla-
centa. The second set are capillary vessels, and pass into this
portion of the decidua for the purpose of nourishing it. These
are the nutritive vessels of the placenta.

The account given by Mr. Hunter of the manner in which the
functional vessels of the placenta pass through this portion of the
placental decidua is still doubted by many, notwithstanding the
more recent of Mr. Oweivs* dissections, and the observations of

* O\ven. Palmer's Edition of John Hunter's Works, Vol. iv.

THE STRUCTURE OF THE HUMAN PLACENTA. 61

Dr. Reid.* I have dissected the vessels of an unopened uterus at
the full time in the manner adopted by Mr. Owen, by opening one
of the large veins over the spot to which the placenta was attached.
Introducing a probe as a guide, I slit open the vein with a pair
of scissors, and repeated the same process with the probe and scis-
sors whenever a branch entered the vein already opened. I gra-
dually passed through the wall of the uterus. In my progress, I
occasionally found, that when the probe was pushed along an un-
opened vein, its point appeared at another opening ; and as I ap-
proached the internal surface of the wall of the uterus, these
anastomoses of the veins became more numerous, the spaces which
they inclosed presenting the appearance of narrow flat bands.
At last, in introducing the probe under the falciform edges of the
veinous orifices, it was found to have arrived at the placental
tufts, which could be seen by raising the edges of the falciform
edges. Having passed over the falciform edges, the veinous
membrane suddenly passed to each side to line the great cavity of
the placenta. The flat bands which I have just described as the
spaces inclosed by anastomosing veinous sinuses, became smaller,
and, on entering the cavity itself, the bands were seen to have
assumed the appearance of threads, which passed in great numbers
from the vascular edges of the veinous openings, and from the
walls of the cavity of the placenta on to the extremities and sides
of the villi and tufts of the placenta. The whole mass of spongy
substance, that is the whole mass of tufts, were in this manner
perceived to be attached by innumerable threads of veinous mem-
brane to that surface of the parietal decidua of the placenta which
was covered by the veinous membrane. On proceeding deeper
into the substance of the placenta, I perceived that, throughout
its whole extent, villus was connected to villus, and tuft to tuft,
by similar threads of veinous membrane. Sometimes the apex of
one villus was connected to the apex of another. In other in-
stances the threads connected the sides of the villi. On minute
examination these threads were found to be tubular, and the mem-
brane of which they were formed was seen to be continuous in one
direction with the lining membrane of the vascular system of the

* Reid. Edinburgh Medical and Surgical Journal, loc. tit.

62 THE STRUCTURE OF THE HUMAN PLACENTA,

mother, and in the other with the external membrane of the tufts
of the placenta, and passing from one tuft, or set of tufts, on to
another, so as to form the central containing membrane of the bag
of the placenta. These threads, as well as their cavities, are some-
what funnel-shaped at each extremity. The funnel-shaped por-
tions of the cavities of threads, and, in some instances, the whole
length of the tube, were found to be full of cells, which were con-
tinuous in the one direction with the parietal decidua of the pla-
centa, and in the other with the external cells of the placental villi.*

This observation led me at once to perceive the real signi-
fication of the external cells of the placental tufts. I saw that
this great system of cells was a portion of the decidua, all but cut
off from the principal mass by the enormous developement of the
decidual vascular network, but still connected with it by the minute
files of cells, which fill the cavities of the placental threads.

This system of cells, the external cells of the villus, with the
external membrane, are portions of the decidua, and, unlike the
other elements of the placental tufts, belong to the organism of
the mother. These cells, with their membrane, I name the
central division of the placental decidua, to distinguish it from
the other portion formerly described, and which I have already
called the parietal division of the placental decidua.

1. Mv observations have confirmed the statements of Professors
Weber and Sharpey as to the mode of formation of the decidua
vera ; but have led me to attach more importance to the inter-
follicular substance, and to the secreted or non-vascular portion
of the decidua.

2. The placenta, as has long been admitted, consists of a foetal
and of a maternal portion intermixed. But the maternal portion,
instead of consisting of a part of the vascular system of the mother
only, includes the whole of the external cells of the villi.

3. The external membrane of the placental villi is a portion of
the wall of the vascular system of the mother, continuous with
the rest of that wall, through the medium of the placental
threads and lining membrane of the placental cavity.

4. The system of the external cells of the placental villi be-

* These are the reflections of the veinous membrane of the mother, described by Dr. Reid.

THE STRUCTURE OF THE HUMAN PLACENTA. G3

longs to the decidua, and is continuous with tlie parietal division
through the medium of the cavities of the placental threads.
This portion of decidua has been named the central division of
the placental decidua, and the threads decidual bars.

5. The function of the external cells of the placental villi is to
separate from the blood of the mother the matter destined for the
blood of the foetus. They are, therefore, secreting cells, and are
the remains of the secreting mucous membrane of the uterus.

6. Immediately within the external cells of the placental villi
there is a membrane which I have named the internal membrane
of the villi. This membrane belongs to the system of the
foetus, and is the external or bounding membrane of the villi of
the chorion.

7. Inclosed within the internal membrane of the placental villi
is a system of cells, which belong to the system of the foetus, and
are the cells of the villi of the chorion. These are the internal
cells of the placental villus.

8. The function of the internal cells of the placental villi is to
absorb through the internal membrane the matter secreted by
the agency of the external cells of the villi.

9. The external cells of the placental villi perform, during intra-
uterine existence, a function for which is substituted in extra-
uterine life the digestive action of the gastro-intestinal mucous
membrane.

10. The internal cells of the placental villi perform during
mtra-uterine existence a function, for which is substituted in
extra-uterine life the action of the absorbing chyle cells of the in-
testinal villi.

11. The placenta, therefore, not only performs, as has been
always admitted, the function of a lung, but also the function of
an intestinal tube.

J. G.

THE STRUCTURE AND ECONOMY OF BONE

A texture may be considered either by itself, or in connection
with the parts which usually accompany it. These subsidiary
parts may be entirely removed without interfering with the ana-
tomical constitution of the texture. It is essentially non-vascular,
neither vessels nor nerves entering into its intimate structure.
It possesses in itself those powers by which it is nourished, pro-
duces its kind, and performs the actions for which it is destined,
the subsidiary or superadded parts supplying it with materials
which it appropriates by its own inherent powers, or connecting
it in sympathetic and harmonious action with other parts of the
organism to which it belongs.

In none of the textures are these characters more distinctly
seen than in the osseous. A well macerated bone is one of the
most easily made, and, at the same time, one of the most curious
anatomical preparations. It is a perfect example of a texture
completely isolated, the vessels, nerves, membranes and fat, are
all separated, and nothing is left but the non-vascular osseous
substance.

The osseous texture of a fresh bone, considered in this way,
consists of two parts, a hard and a soft. The hard part, com-
posed of earthy salts, deposited in a cartilaginous matrix, has
already been carefully examined by anatomists. The soft has
not yet attracted attention, in consequence of the manner in

THE STRUCTURE AND ECONOMY OF BONE. 65

which it is isolated, divided into small portions, and concealed in
the cavities of the osseous corpuscules.

The hard part of the osseous texture, considered in a long
bone, presents four surfaces, all communicating with one an-
other, a periosteal or external, a medullary or internal, a haver-
sian or intermediary, and a corpuscular or canalicular. The peri-
osteal surface communicates with the haversian in three ways : by
those haversian canals which open in it ; by the canal for the
medullary artery gradually subdividing and diminishing till it
breaks up into arterial haversian canals ; and by the more numer-
ous canals for the veins, principally met with at the extremities
of the bone. The medullary surface is to be considered as a
portion of the haversian, having been formed by the enlargement,
and subsequent blending of neighbouring haversian canals into
medullary cavities and cancelli. The canalicular or corpuscular
surface forms the walls of the innumerable corpuscules and cana-
liculi, and communicates by the latter with the haversian, me-
dullary, and less freely with the periosteal surface.

The compact osseous substance, in which the corpuscules and
then: canaliculi are situated, is not homogenious in texture* It
consists, of cells filled with bony substance, ossified or calcified
primordial cells.

The soft part of the true osseous texture is not continuous like
the hard, but is divided, as has been stated, into as many portions
as there are corpuscules in the bone. Each of these portions
consists of a little mass of nucleated cells of great transparency.
They do not appear to extend along the canaliculi, but to be con-
fined to the cavity of the corpuscule*

These two parts, the hard and the soft combined, constitute the
true osseous texture. They differ from one another only in this,
that the cells of the one are ossified, those of the other retain their
original delicacy and softness. The masses of soft cells in the cor-
puscules, I am inclined to consider as the nutritive centres, germi-
nal centres, or germinal spots of the texture. These centres are
the source of all the hardened cells, each of them being the centre
of all those comprehended within the range of its own canaliculi.
Each of these soft germinal masses is the centre of attraction
for the proper nutriment of bone, and is the active agent in with-

66 THE STRUCTURE AND ECONOMY OF BONE.

drawing this from the vessels, and appropriating it, partly for tho
nourishment of the hard cells, each of which has a centre of at-
traction within itself, but more probably for the formation of new
calcigerous cells, as the old cells dissolve and their debris falls
back into the returning circulation. The canaliculi are undoubt-
edly the principal channels for the passage of nutriment from the
capillaries to the calcigerous cells and germinal centres. They
are necessary in a hard texture, and like similar canals and fis-
sures in certain hard cells in vegetables, only appear at a late
stage in the developement of bone. Each osseous corpuscule has
its own system of canaliculi, these extending, for the purpose of
communicating with others, to the confines of its own territory ;
that is, to the boundaries of the space which was at one time
contained within the sphere of the primary cell of which it was
the nucleus.

The accessory parts of the osseous texture, are the vessels
nerves, membranes, and oil. For my present purpose it is only
necessary for me to allude to the membranes, as one of them, the
periosteum, has been held to play a most important part in the
formation and economy of bone.

The periosteum is not so important an element in the consti-
tution of a bone as has usually been supposed. In the adult
bone, it is nothing more than the fibrous sheath of the organ,
similar to the bounding or limiting membrane of other organs,
and in which the vessels ramify sufficiently to anastomose with
those of the comparatively few haversian canals which open on
the external surface. In the foetus it is much more vascular,
the external surface of the bone being at that period actively
engaged in growth.

There exists in every true bone, a membrane or layer of much
greater importance, and infinitely more extended than the peri-
osteum. Between the blood-vessels and the walls of the haver-
sian canals, there is a layer of cellular substance. This cellular
substance is the product, its cells being the descendants of the
corpuscules of the cartilage or matrix in which the bone was
originally formed. It forms a blastema, originally produced
round each cartilage corpuscule by developement into a linear
series perpendicular to the ossifying surface : each of the secon-

THE STRUCTURE AND ECONOMY OF BONE. 67

dary cartilage corpuscules remaining as centres, or the sources of
new centres of nutrition, of the future bone, their progeny form-
ing the cellular mass which becomes enclosed in the capsules of
compact primary bone. When these capsules have opened into
one another to form the haversian canals, a process similar to the
mode of developement of gland ducts, and capillaries, the cellu-
lar mass surrounds the vessels in their course, and separates them
from the walls of the canals.

That this cellular layer plays an important part in the economy
of bone, appears probable from the prominent position it holds in
its developement, and from the intimate connection of the haver-
sian canals with all the morbid changes of bone. Its existence,
great extent, and probable powers, cannot be overlooked in any
question regarding the economy of bone in health or disease.

The cellular mass, just described, fills the cancelli, or enlarged
haversian chambers, of foetal bones, and, in this situation, has not
been overlooked by former observers. In adult bones, it is in the
medullary cavity, cancelli, and, to a certain extent, in the larger
haversian canals, replaced by fat cells.

On the surface of young and vigorous bones I have observed
numerous cells, flattened, elongated, and more or less turgid,
belonging doubtless to the system of haversian cells.

J. G.

O- XL

THE MODE OF REPRODUCTION AFTER DEATH OF THE
SHAFT OF A LONG BONE.

The question at issue regarding the source of the new osseous
substance in regeneration of the shaft of a long bone, is thus
stated by Professor Syme.* " Whether the periosteum, or mem-
brane that covers the surface of the bones, possesses the power of
forming new osseous substance independently of any assistance
from the bone itself?" and the Professor has detailed some very
ingenious experiments, which satisfied him that this membrane
does possess the power of producing new osseous texture.

The first experiment consisted in exposing the radius of a
dog, and removing an inch and three quarters of it along with
the periosteum ; and in the other leg removing a corresponding
portion without the periosteum. In six weeks the cut extre-
mities of the radius, from which a portion had been taken, to-
gether with the periosteum, had only extended towards one an-
other in a conical form, with a great deficiency of bone between
thenij and in its place merely a small band of tough ligamentous
texture. In the other, where the periosteum had been allowed
to remain, there was a compact mass of bone, not only occupying
the space left by the portion removed, but rather exceeding it.

The objection to this experiment is, that it cannot be performed

* Trans. Roy. Soc. Edin., Vol. xiv., page 158. " On the Power of the Periosteum to
form New B<me"

THE MODE OF REPRODUCTION AFTER DEATH, &c. 69

accurately. I have satisfied myself, that it is impossible to se-
parate the periosteum from a dog's radius without removing
along with it minute longitudinal, filamentary, or ribbon-shaped
portions of the surface of the bone, more particularly, as may be
conceived, when performed in the manner which under the cir-
cumstances would be adopted, by slitting it up in front, and de-
taching it transversely before separating the portion of bone. It
remains to be proved that it is not from these minute shreds of
bone that the regenerated portion of the shaft has derived its
origin.*

In the other part of the experiment, in which the periosteum
as well as the bone was removed, it was not to be expected that
complete regeneration should have taken place, inasmuch as the
bounding or limiting membrane of the organ had been removed,
and the surrounding textures were allowed to collapse and unite.
Even under these unfavourable circumstances, the cut extre-
mities of the bone had lengthened themselves out in a conical
form.

The two subsequent experiments, by the insertion of tin plates,
though highly ingenious, differ in no essential particular from
the first, and are liable to the same objections. If a section had
been made through the denuded shafts, new bone would have
been found deposited in their interior, just as it had been at the
cut extremities in the first experiments.

The careful examination of numerous bones, the shafts of
which had died, and were in progress of replacement by a sub-
stitute in the form of a shell, has satisfied me that in no instance
do we ever see a new shaft, without at the same time observing
portions of the old shaft ulcerated to a greater or less extent —
the ulcerated portions invariably corresponding in the early
stages to the scales of new bone in the periosteum. Whenever
the old shaft is entire, its periostea! surface presenting the na-
tural appearance of a macerated bone, the part corresponding to
this in the new shaft is formed of bone which is seen to be shoot-
ing, in the manner peculiar to this mode of regeneration, from a
point corresponding to an ulcerated portion of the old shaft. So

* Baly. Note in his Translation of Miiller's Physiology, page 471.

70 THE MODE OF REPRODUCTION AFTER DEATH

striking is this peculiarity, that it will at once recur to those who
have had an opportunity of observing new shafts in an early
stage of formation ; as well as the remarkable contrast between
the smooth hard portions of the dead or dying bone and the
nodulated scales lying in the separated periosteum, alternating
with the former, and concealing from direct view the rough or
ulcerated portions of the dead shaft. In those instances in which
the shaft has died, with the exception of a ring or small portion
at each or one end, close to the epiphysis, the new bone shoots
in stalactitic masses in the longitudinal direction, their course,
direction and magnitude corresponding to the forms of the rings
or portions of ulcerated bone in the old shaft. This is an un-
favourable form of necrosis, in consequence of the difficulty en-
countered by the extremities of the new shell in meeting in the
centre, and the length of time required for the process of rege-
neration. This form has also given rise to a mistaken view of
the source of the new bone in necrosis, a belief that it is derived
from the epiphysis. I have never seen an instance in which the
epiphysis supplied the new shaft, and I have had occasion to
point out that the specimens on which such opinions were
founded are in fact exemplifications of the formation of the new,
from a ring or portion of the old shaft close to the epiphysis.
An epiphysis is a distinct part, arid has no greater tendency to
supply the losses of the principal mass of the bone to which it
belongs than the femur, fibula, or astragalus to supply the loss of
a tibia.

Another remarkable peculiarity, arising from the circumstance
of the new bone invariably shooting from spots corresponding to
ulcerated portions of the dead shaft, is met with in instances
where one side of a dead shaft is not ulcerated, and the other
side, or a portion of it, has undergone that process. In such in-
stances, the new bone proceeds from points corresponding to the
ulcerations, and shoots in the form of arches across the smooth
portion of the old bone, meeting from either side, and giving rise
to new processes wrhich ultimately enclose the whole. In instances
of this sort regeneration is effected with difficulty, and there is a
tendency in the old shaft to ulcerate out on the side on which it
has supplied no osseous centres of regeneration.

01- TIJE SHAFT OF A LONG BONK. 71

The death of the entire shaft of a long bone must be a very
rare occurrence. In a case of this kind, the shaft would be
found lying loose in a cavity formed by the epiphysis at each end,
and the separated periosteum on the sides. The bone itself, al-
though its surface might be opened up by inflammation, would
present no ulceration or actual deficiency of substance. In a
case of this kind, I believe no regeneration whatever woidd take
place. The epiphysis have no tendency to assist ; and the perios-
teum has separated without a single portion of the shaft from
which new bone might be produced.

In the majority of instances of what is incorrectly named death
of the entire shaft, ulcerated portions or deficiences of the surface
will be met with ; and in the periostea! sheath scales of new bone
corresponding to these will be perceived. I have observed the
process by which these ulcerations are produced, and have already
described it in the chapter on ulceration.

The first appreciable inflammatory changes in bone occur with-
in the haversian canals. These passages dilate or become opened
up, as may be seen on the surface of an inflamed bone, or better
in a section. The result of this enlargement of the canals is the
conversion of the contiguous canals into one cavity, and the con-
sequent removal or absorption of ail the osseous texture of the
part. This removal of the substance of the walls of the haver-
sian canals is not to be explained by pressure arising from effused
lymph, understood either in a mechanical sense, which is inappli-
cable to actions of this kind, or in the Hunterian sense in which
it is employed, as a mode of expression for an action, the details
of which have not been recognised.

By the enlargement of neighbouring haversian canals, and the
consecpient removal of all the osseous substance of a portion of
bone, an ulceration is produced, or a piece of dead or dying bone
is separated from the living organ. A stratum of what, in the
language of surgical pathologists, is named granulations, divides
the dead from the living, and ultimately casts the dead offj by
assuming a free surface towards it, throwing pus into the inter-
space.

When the entire shaft of a bone is attacked by violent inflam-
mation, there is generally time before death of the bone takes

72 THE MODE OF REPRODUCTION AFTER DEATH

place, for the separation, by the process just described, of more
or less numerous portions of its surface. When the entire peri-
osteum has separated from the shaft, it carries with it those mi-
nute portions of the surface of the bone. Each of these is covered
on its external surface by the periosteum, on its internal by a
layer of granulations, the result of the organised matter which
originally filled the inflamed haversian canals ; the gradual en-
largement and subsequent blending of which ultimately allowed
their contained vascular contents to combine with the layer of
granulations just described ; and to form the separating medium
between the dead shaft and its minute living remnants. These
minute separated portions, after having advanced somewhat in de-
velopement, appear, when carelessly examined, particularly in dried
specimens, to be situated in the substance of the periosteum, and
have been adduced by the advocates of the agency of that membrane
in forming new bone as evidences of the truth of their opinions.

In proportion to the equal manner in which these living
portions of the old shaft are arranged over the whole internal
surface of the periosteum, will be the facility and consequent rapi-
dity in the formation of the new shaft. The shape of the new
bone will also depend very much upon the same circumstances ;
for, if the centres of formation of the new shaft are separated
from one side only of the old bone, then an unshapely mass of
new bone is thrown out on the same side, for the purpose of
strengthening the part during the time necessary for shooting
across the bridges of bone which are to supply that side of the
new shaft, for the formation of which no osseous centres had
been separated. Every possible modification, resulting from
these principles, may be observed in looking over series of ne-
crosed long bones.

A remarkable fact in connection with cloacae is, that they are
almost invariably opposite a smooth or unaltered portion of the
surface of the dead shaft. They result from the pus thrown off
from the granulating internal surface of the new shaft making its
way to the exterior, by those parts not yet closed, in consequence
of having been opposite to portions of the old shaft, which had
not afforded separated osseous centres. After the new shell has
gained its full strength, the cloacae, like sinuses of the soft parts,

OF THE SHAFT OF A LONG BONE. 73

are prevented from closing by the continued flow of the pus.
The situation of cloacae is determined by circumstances in the
death of the old, and kept open by the continued flow of the
secretions of the new shaft.

As, therefore, it has been found impossible to separate the peri-
osteum in living animals, without detaching shreds of bone along
with it ; as in necrosis of the shafts of long bones, portions of the
old osseous texture may be detected in the periosteal sheath
opposite ulcerations of the dead shaft ; and as consistent with
what is at present held regarding the powers of capillary vessels,
and the origin of the textures, we are compelled to assent to the
doctrine that periosteum does not possess an independent power
of forming osseous substance.

The participation of the periosteum in the office of regenera-
tion— an important principle in surgery — is not denied in this
conclusion.

J. G.

NO. XII.

THF MODE OF REPRODUCTION OF LOST PARTS IN TEE
CRUSTACEA.

That all the species of Crustacea have the power of regene-
rating parts of their body which have been accidentally lost, is a
fact which has been long known. The particular manner in
which these new parts are developed, and also the organ from
which the germ of the new part is derived, has never yet been
sufficiently examined, or properly explained.

If one or more of the last phalanges of the leg of a common
crab be seriously injured, the animal instantly throws off the re-
maining parts of the limb close to the body. It has the power
of doing so, apparently for two purposes ; to save the excessive
flow of blood which always takes place at the first wound, and to
lay bare the organ which is to reproduce the future limb. As
soon as the injured limb has been thrown off the bleeding stops,
the reason of which will be explained hereafter ; but if the ani-
mal is unable, from weakness or other causes, to effect this, the
haemorrhage proceeds to a fatal termination.

It is apparently in the organs of locomotion only that the power
of reproduction resides. That it does not do so in all parts of
the body — in the higher Crustacea, at least — is proved by experi-
ment, and is also apparent from the circumstance of many species
being obtained with the body and other parts very much maimed,
and which have to all appearance been so for a considerable

THE MODE OF REPRODUCTION OF, &c. 75

period. Wounds of the body in general prove speedily fatal, if
they penetrate deeply, but if otherwise, a cicatrix only is formed,
which remains until the casting of the shell, when the new shell
takes on all the characters and appearance of the old one, before
it met with the injury. When the animal is weak and unhealthy,
and in that state meets with any severe injury of a limb, it is un-
able to throw it off at the usual place, and consequently very
soon dies from loss of blood ; but when strong and vigorous, it is
enabled to throw the injured limb off with little apparent pain or
exertion. It is a well known fact, that these animals can throw
off their limbs when seized by them, and also from several other
causes, to which it is unnecessary to allude at present.

When the crustacean does throw off a limb voluntarily, it will
be found on examination that this is always effected at one spot
only, near to the basal extremity of the first phalanx. This part
of the phalanx is very much contracted for the length of half an
inch, or a little more, in the common edible crab. The whole
of this portion is filled with a fibrous, gelatinous, glandular look-
ing mass ; the organ which supplies the germs for future limbs.
On looking closely into the surface of this body, we find that it is
divided into two unequal parts, by means of a transverse line.
The basal or proximal part of this body is the smallest. On
tracing this line towards the shell, we find that it runs into it, as
it were, and forms, instead of one line, two, by which means a
very thin ring is formed, and this ring is also found to run com-
pletely round the limb, being marked externally by means of a
thin band of small scattered hairs. By dissection this line can
be traced into the substance of the organ of reproduction,
and is found in this way to be the exact spot where the limb is
generally thrown off. Through the long axis of this, and near
to one edge, a small foramen exists for the transmission of the
blood-vessels and nerve. The microscopic structure of this gland
or organ is extremely beautiful. When a thin transverse section
is made, and placed under the microscope, it is found to present
the following appearances : — The foramen, for the transmission
of the vessels and nerves, which was distinctly seen with the
naked eye, is obscured on account of the pressure arising from
the glass plates, but its situation can be still distinctly made out

76 THE MODE OF REPRODUCTION OF

near to one edge of the section, and also within a thick fibrous
looking band, which, when traced, is found to surround a consi-
derable extent of surface. The space contained within this band
is also found upon examination to be much more transparent than
that beyond it, and to contain numerous small cells, all of which
have nuclei or nucleoli within them. These cells appear to be sus-
pended in a thickish transparent liquid. The thick fibrous band,
mentioned above, is composed of a great many fibres, all of which
run almost parallel to one another. Beyond this band, and occu-
pying the remaining space between it and the shell, lies a con-
fused mass of large primitive cells or blastema. The shell mem-
brane, covered by the shell, encircles this, — thus the whole struc-
ture of the leg at this part consists of, ls£, the foramen for the
transmission of the vessels and nerves ; the fibrous band, with
the semi-liquid mass containing small cells ; the blastema of larger
nucleated cells ; and, lastly, the shell membrane, covered by the
shell.

In reference to the fibrous band here mentioned, farther obser-
vations have proved it to belong to a very peculiar system of ves-
sels, which are very generally distributed throughout the body of
the animal. They ramify very freely over the membrane lining
the carapace, throughout the ovaries, liver, intestinal canal, and
on the blood-vessels of the organs of locomotion. In the latter,
they are arranged at regular intervals, and run parallel to one
another. They run in this manner, until that part of the leg is
reached about half an inch beyond the reproductive gland, when
they terminate by means of blind extremities. I have not yet made
out the exact relative anatomy of this very peculiar system of ves-
sels, or in what manner those running in the longitudinal direction
of the leg are connected with the circular one which surrounds the
foramen at the point of fracture, but immediately after the ani-
mal has thrown of the injured limb, the raw surface becomes co-
vered with these vessels. Before the separation, the vessels had
been partially empty ; but immediately on the separation taking
place, they became so distended as to become visible to the naked
eye. In all the observations made, it was generally found that
these vessels presented a radiated appearance on the newly made
surface, running from the circumference to the circular one sur-

LOST PARTS IN THE CRUSTACEA. 77

rounding the situation of the germ. The greater number also
appeared to terminate at the circumference by means of blind ex-
tremities. A dark circular disc was seen at the extremity of
many of these cul-de-sacs, which had all the appearance of a ger-
minal spot. When these vessels were first seen, they were
thought to be connected with the reproductive gland alone, but
after farther observations, this appeared to be incorrect ; and, as
already mentioned, their relations are so extensive and compli-
cated, as to require much more time for their elucidation than I
have had since they came under my observation. It is evident,
however, they perform some important function in the economy
of the animal, but whether it is connected with the reproduction
of lost parts or not, is a question to be decided by future obser-
vation.

Immediately on the limb being thrown off, a quantity of blood
escapes, which is soon stopped by the retraction of the vessels.
After this takes place, we see the small open foramen for the pas-
sage of the artery and nerve, which becomes closed almost im-
mediately by means of a slight film which spreads over the whole
of the exposed surface. When this surface is examined some
hours after the loss, we find that the small cavity of the foramen
is slightly filled up with a body resembling a nucleated cell.
This cell is the germ of the future leg, and very shortly encreases
in size, so as gradually to push out the film alluded to above,
which is now become a thick strong cicatrix. During the time
that this is going on, the whole of the exposed surface had be-
come tense and bulging, but this gradually decreases round the
circumference as the central nucleus encreases in size, which it
does at first longitudinally, and then transversely. As it en-
creases in size, the cicatrix, which still surrounds it as a sac, be-
comes thinner and thinner, until it bursts, when the limb, which
has hitherto been bent upon itself, becomes stretched out, and
has all the appearance of a perfect limb, except in size.

In the lower Crustacea, and even in the lower Macroura, we
find the power of regeneration more extended ; — a limb broken
off at any part of its phalanges will grow. The mode of repro-
duction in the lobster is peculiar, and differs from the higher
Crustacea. Instead of the young limb being folded upon itself,

78 THE MODE OF REPRODUCTION OF, &e.

as we found it in the Brachyura, it is quite extended, although
apparently enclosed in a sac.

As far as my observations have yet gone, it appears to me
that the germinal cell is derived from one of those which are
nearest the central opening on the raw surface. This cell,
following the ordinary course of developement, by the nucleus
breaking up into nucleoli, which in time become parent cells,
each of which again undergo the same process. This proceeds
for several stages, all the less important cells dissolving and
serving as nourishment to the central or more important ones,
until the number of centres are reduced to five, the number of
joints required, which, by a constant process of a similar nature,
assume the form of the future leg.

H. D. S. G.

XIII.

OF THE ANATOMY AND DEYELOPEMENT OF THE
CYSTIC ENTOZOA *

I. — OF THE ACEPHALOCYST.

The acephalocyst, or simple hydatid, consists of a vesicle com-
posed of several membranes, containing a quantity of fluid, in
which the young hydatids float, and from which they apparently
derive nourishment.

Although found in all parts of the body, these animals are
nevertheless more strictly confined to the liver, which appear to
be their natural habitat.

In examining an acephalocyst from without inwards, there is
met with, first, the natural tissues of the infested being, slightly
condensed, the condensation being greatest near the hydatid, and
becoming gradually less as the distance encreases. The next
part met with in the dissection inwards, is a strong fibrous mem-
brane, of considerable thickness, writh numerous blood-vessels.
This forms a sac for the hydatid. During the earlier stages of
growth, hardly a vestige of this can be seen ; for being formed of
the condensed tissues of the infested animal, it becomes percep-
tible only after the parasite has attained some size. It is highly

* Read before the York Meeting of the British Association, 1 844.

80 OF THE ANATOMY AND DEVELOPEMEST

vascular, and forms a cushion, to which the external surface of
the hydatid is applied. In this way, a steady supply of the blood,
or of debris of the textures of the infested animal is close at hand,
from which the hydatid may extract nourishment. This mem-
brane is best seen in aged hydatids, or in those in which the
process of obliteration has commenced, and in such can easily be
demonstrated by dissection. In such aged individuals also it is
found to be so intimately attached to the external membrane of
the hydatid, as to appear to form one membrane with it ; whereas
in younger individuals, a considerable space intervenes.

The external coat of the hydatid is gelatinous and slightly
fibrous in appearance, and presents no structure.

The middle membrane appears to be of the nature of a ger-
minal membrane, is much thinner, and more delicate than the
external membrane. In this membrane numerous cells, in
various stages of growth, take their rise, and project inwards
into the cavity of the hydatid, carrying the next membrane
along with them.

The internal membrane does not appear to be continuous over
the whole internal surface ; but observed only where it is re-
flected, as has been just stated, over the surface of the germinal
cells. It may, therefore, be considered as that portion of the
middle or germinal membrane which has been carried inwards
by the rise of the germinal cells in the substance of the former
membrane.

A small clear cell, or vesicle, jutting from the internal surface
of the second membrane, is the first vestige of the young hy-
datid. At first this vesicle is colourless, but as it encreases
slightly in size, it becomes opaque, and also carries the internal
membrane inwards before it, which in time, as the young hy-
datid becomes more pedunculated, before becoming free, almost
covers it entirely. Vestiges of this membrane may be seen
attached in shreds to the vesicle even after it has attained a
considerable size.

In all the hydatids which have already become independent
animals, with their external coat still gelatinous, and are still
enclosed within the cyst of the original acephalocyst, it may
be observed that one side presents shreds of membrane at-

OF THE CYSTIC ENTOZOA. 81

tached to it ; but that the other is quite free and almost trans-
parent. This transparent part was that originally attached to
the parent or germinal membrane ; and the shreds are conse-
quently the remains of the internal membrane of the parent.
Shortly before the young hydatid separates from the germinal
membrane of the parent, smaller cells are seen within it, which
increase in size along with it. These are another generation of
hydatids, and the fourth in the series I have been describing.

About this period in the process of developement, there may
be seen in some forms of hydatids of the tertiary growth, a dark
irregular flat nucleated spot, which always occupies the same
place, immediately opposite that of attachment. This spot is vi-
sible only before the separation. I am inclined to consider this
spot as the first appearance of the pedicle, or what is generally
termed a head in the class. This species I denominate Acephalo-
cystis armatus. This appearance is merely the nucleus or central
cell, from which all the others are produced ; thus illustrating that
the pedicles of Csenurus and Cysticercus are analogous to this
nucleus, both being reproductive organs ; — in the acephalocyst
being a reproductive organ only, in Csenurus and Cysticercus
being chiefly a reproductive organ with a slight adaption for the
purposes of prehension.

If the small cells which are seen in the tertiary hydatids are
the young, they must be the first of those which are afterwards
seen attached to the germinal membrane, for I have not met
with secondary hydatids enclosing separated young individuals.
It is only after the hydatid has obtained a nidus, or separate
habitat of its own, that it begins to throw off its young from the
germinal membrane, and those only which had been formed dur-
ing the tertiary and secondary periods. Thus, if the original
hydatid is buried deep in the textures of the infested being, or
from other causes is prevented giving exit to its young, (for it is
by the dilatation caused by the young within it that the parent
sac gives way,) it soon becomes unable to extract proper nourish-
ment from the infested being, the young within it become de-
composed, and the whole animal degenerates either into a firm
cicatrix, or, as is most general, into a fatty cretaceous matter.

F

82 THE ANATOMY AND DEVELOPMENT

I have in many instances found this matter forming upon the
external coats of young secondary hydatids, which were con-
fined, as above stated, in old and degenerating parent sacs. In
general this cretaceous matter originates in the internal and
germinal membrane of the parent sac ; these two membranes in
old hytadids being always thick, gelatinous, and homogeneous,
like pure gelatine. This thick gelatinous membrane presents no
trace of the two membranes of which it originally consisted ; it
is generally about the eighth of an inch in thickness ; and lies
in the most dependant part of the cavity, quite loose and de-
tached from the external coat. It presents no trace of young
vesicles or hydatids, but has upon its internal surface a number of
white, opaque, fatty looking spots of all sizes. Similar spots, but
of much smaller size, are also to be seen in the substance of the
membrane, and when examined by the microscope, present a
peculiar cellular network. As these spots become larger, they
from being quite smooth, become rough and nodulated, each of
the cells being apparently filled with the peculiar fatty substance.
As this mass encreases in size, it becomes more cretaceous, and
sends out branches in all directions, so as in time to fill the
whole cavity of the hydatid, which, as this process is going on,
shrinks up very much, so that it meets the fatty matter, and
enables the process of filling up to be more speedily completed.
Shortly before the cavity is completely filled up, the fatty matter
begins to lessen in quantity, being probably absorbed by the
cretaceous matter gaining the preponderance. In this way more
or less of the whole mass is absorbed, so that ultimately nothing
is left but a small quantity of cretaceous matter which becomes
very much condensed.

The middle membrane then appears to play the most import-
ant part in the economy of the hydatid ; the external membrane
acting only as an organ of defence.

Of this peculiar form of animal three species have been deter-
mined, the characters of which are derived from the structure
and appearance of the germinal membrane. In Acephalocystis
simplex, the lowest of these forms, the whole structure of the
animal is much more homogeneous, transparent, and gelatinous

OF THE CYSTIC ENTOZOA. 83

than that of the two higher forms ; the cyst is not divided into
separate parts, and the young are developed promiscuously
throughout its internal surface.

In Acephalocystis armatus, the young are developed from a true
germinal membrane, each of the young arising as a separate cell,
and afterwards throwing off internally successive broods of young
independently. It is also distinguished from the other species
by the teeth which it possesses during the period of its attachment
to the parent germinal membrane. These teeth are generally
exactly opposite the spot of attachment, are quite straight, barb-
less, and form an irregular circlet, somewhat similar to that of Cse-
nurus and Cysticercus. They are lost as soon as the animal leaves
the germinal membrane and becomes free, and not the slightest
vestige of them can be seen, even upon the shreds of membrane
alluded to above, which at one period formed the internal mem-
brane of the parent sac.

In the Medical Gazette for Nov. 22, 1844, p. 268, there is an
abstract of a Paper read before the Royal Medical and Chirnrgical
Society of London, by Erasmus Wilson, on the classification, &c.,
of Ecliinococcus hominis. There can be no doubt that the Echi-
nococcus here described by Mr. Wilson, and the Acephalocystis
armatus are both one and the same species. The bodies de-
scribed by Mr. Wilson as the echinococci, and which are at-
tached to the internal surface of the membrane, are merely the
young acephalocysts either of the secondary or tertiary stages of
developement. They will be, as already fully described in this
paper, of the secondary generation, if found growing from the
walls of the original containing sac, and tertiary if found grow-
ing from the w^alls of those sacs floating free in the fluid contained
within the original sac. This animal is an acephalocyst, and not
an echinococcus. Bremser, in the atlas of his work, On the
Intestinal Worms of Man, calls it an echinococcus, but upon
false grounds, for the proper definition of echinococcus, he
says, at p. 294 of his w^ork alluded to :* — a M. Rudolphi dis-
tingue les hydatides en vivantes et en non vivantes ; il regarde

* Trait^ Zoologique et Physiologique sur les Vers Intestinaux de 1'Homme, par M. Bret^r.
Traduit de I'Allemand par M. Grandler. Revu et augmente de Notes par M. de Blainville.

84 THE ANATOMY AND DEVELOPEMENT.

Pechinocoque provenant des intestins des bisulques (Ec/tinococcus
veterinorum) comine une hydatide vivante, par la raison que Ton
trouve dans le liquide qu'elle contient les echinocoques, propre-
ment dits, c'est-a-dire, des petits corps microscopiques, pourvus
de quatre sucoirs et d'une couronne de crochets." The animal
described by Mr. Wilson is also referred to in the same abstract
by Dr. Budd, " who examined seven hydatid tumors which had
been for many years in the Museum of King's College/' when he
found appearances exactly similar to those described by Mr.
Wilson. It is more than probable that the animals here alluded
to by Dr. Budd, are similar to that I have called Acephalocystis
armatus, which, if the case, from the want of suckers, cannot be
an Echinococcus, being merely a transitory stage of the ace-
phalocyst. For I have examined great numbers of these animals,
preserved in the Museum of the Koyal College of Surgeons in
Edinburgh — a Collection particularly rich in preparations of
these animals — and in no instance have I been able to make out
the slightest vestige of suckers. I had made out the existence
of teeth, and was anxious to determine whether or not the
animal was allied to the cephaloid hydatids.

The next form of Acephalocystis is one presenting a structure
peculiar to itself, and which at once distinguishes it from the
others. The external membrane is gelatinous and delicate ; the
germinal one is more fibrous, and is so slightly attached to the
external one, as to float in the contained fluid. When a small
portion of this germinal membrane is placed under the micro-
scope, its free or internal surface presents the following appear-
ances : — 1st, A fibrous texture forming the basis of the membrane ;
2d, A series of large irregular ovoid vesicles, arranged in irre-
gular rows. The fibrous texture surrounds the vesicles, and thus
presents a peculiar appearance of ramification of a very regular
form. Each of the vesicles contains one or more dark spots con-
taining nucleoli — these spots are the young hydatids.*

* This species I have named Aceplialocyslis Mom'oii, after Dr Monro, to whom I am in
clcbted for the opportunity of examining the species, and from whom also I have received
much^valuable information regarding hydatids generally. A very beautiful figure of A
Monroii is given in Dr. Monro's work on " The. Morbid Anatomy of the Stomach and Gullet,'"

OF THE CYSTIC ENTOZOA. 85

II. — OF ASTOMA.

Astoma acephalocystis is an animal very nearly allied to Ace-
phalocystis.* It was found attached to the peritoneum of an old
subject, generally by means of a broad basis, but very often by a
slender pedicle. The sac, composed of three membranes, of
more or less delicacy, was very strong, and the membranes were
easily separable from one another. They were all more or less
composed of fibrous texture, and as in the Acephalocystis the ex-
ternal appeared to serve as a means of defence, while the two
inner were devoted to nutrition and generation. The young
cells, after acting for a time as the organs of nutrition, become
free and independent animals after having thrown off young cells
internally, which in their turn act as organs of nutrition to their
parent, until they are fit to become independent animals them-
selves. The particulars relative to the peculiar mode of develope-
ment of this animal will be adverted to more at length, when we
come to treat of that function in Diskostoma, in the meantime a few
remarks on the external character of the animal may be useful.

It was of a greenish yellow colour when taken from its habitat,
and varied in size from a millet seed to that of a middle-sized
orange. The smaller specimens were all spherical, and very
much corrugated ; the larger were quite smooth and botryoidal —
the first of which appearances arose apparently from the distention
caused by the young ; the second, from the young within it en-
creasing irregularly in size. When a section was made of an
adult specimen, the interior was found to consist of an immense
number of young in various stages of advancement, and all of
them apparently having their origin from the enclosing sac,
either immediately or mediately. Along with these the inter-
stices contained a great quantity of gelatinous matter, which
appeared to be the assimilated food, analogous to the pabulum
of the seminal cells, already spoken of in another paper.

* Edinburgh Medical and Surgical Journal. No. clxi., p. 14.

86 OF THE ANATOMY AND DEVELOPEMENT

III. — OF DISKOSTOMA.*

Diskostoma aceplialocystis is anotlier animal belonging to the
Cystic Entozoa, and very similar in many respects to the pre-
ceding genera ; it is, however, more complicated in its structure
than either.

Diskostoma was met with in great numbers in the peritoneal
cavity of a middle-aged man. About six or eight gallons were
taken out of the abdomen after death, all of which had been ap-
parently generated in the course of a few months.t Like Astoma
they varied very much in size, but with very few exceptions
were all regularly globular, and of a bright straw colour, hang-
ing, when undisturbed, from the surface of the abdominal cavity,
like the ova in the active ovarium of the common fowl. The
sac consisted of two demonstrable membranes, the most external
of which was rather complicated.

The basis of the membrane itself was nbro-gelatinous, and
having a number of discs scattered at irregular intervals over its
surface ; these discs were connected with one another by means
of numerous tubuli, which also ramified freely through the mem-
brane. These were probably the organs of nutrition. The next
membrane was much more delicate, and was that from which the
gemmules arose. In some instances there was the appearance of
a third membrane, but it was most difficult of detection. The
greater mass of the body was composed of the gelatinous matter
already alluded to as occurring in Astoma.

The function of generation in all these lower Acephalocysts is
very interesting. In all of them the young cells, or gemmules,
arise from the middle membrane of the sac. In Aceplialocystis
and Astoma the young cells act at first as organs of nutrition,
and after a time become themselves independent animals. This
is probably the case in Diskostoma also, but it could not be de-
termined with certainty. The mode of devolopement of the
young in Astoma and Diskostoma is somewhat different from that

* Transactions of the Royal Society, Edinburgh, Vol. xv. p. 564.

t See Edinburgh Medical and Surgical Journal for October 1844, page 1.

OF THE CYSTIC ENTOZOA. 87

already described as takifig place in Aceplialocystis. There ap-
pears to be two modes of generation, namely, one for the enlarge-
ment of the original group, and another for the formation of new
groups in other parts of the peritoneum. The first of these
modes proceeds in the Astoma, from the animal becoming so dis-
tended, in consequence of the increased size and number of the
young within it, that it bursts when the young are exposed, and
the parent sac, which is now useless, absorbed, the progeny in
the meantime becoming attached to the peritoneum.* The ex-
ternal membranes in Diskostoma spread over the as yet uninfested
portions of the peritoneum, and give origin to a number of cells
from the attached surface, each of which, becoming parents, gra-
dually increase in size, from the addition of new matter within the
young cells. These young cells are the germs of the future animals.
The other mode of developernent or that intended for the forma-
tion of new groups is similar in both animals. The young or se-
condary cells, bursting from their formative cell, by some means
escape from the parent sac, and so gain a situation at some dis-
tance from the original group, where they become attached, in
time throw off young cells, and thus become the origin of a new
set.

Relative to the mode of reproduction in these animals, it is
found that in Astoma, and the higher cystic entozoa, the numbers
proceeding from one parent may be unlimited, whereas in ace-
phalocystis generation ceases with the quaternary series of young,
unless this series, or the gemmules of some of the preceding,
escape from the original sac, and are able to form a nidus in any
portion of the liver, or other organ yet uninfested. For it ap-
pears necessary to the existence of the common hydatid that it
be completely enveloped in the tissues of the infested being. To
ensure this normal habitat, then, the animal must escape during
the period of its gemmule existence from the parent; but, as
most generally happens, if the parent hydatid be so deeply buried
as not to allow free rupture of its coats within a certain period,
decomposition ensues as already described, and so existence is
terminated ; — if, on the contrary, the parent hydatid be so near

* See Preparation in Museum of Royal College of Surgeons, Edinburgh, No. 2244.

88 OF THE ANATOMY AND DEVELOPEMENT

a surface, or from other causes, as during its increase in size to
rupture, then the young escape, and so form new and altogether
independent animals. As the hydatid is by no means of unfre-
quent occurrence in the liver and other internal organs, this limi-
tation of the increase appears to be a beneficent law of nature,
for the purpose of preventing the fatal termination which the
rapid increase of these animals would infallibly produce. In Dis-
kostoma we have an instance of this rapidity of reproduction,
which happily appears to be of rare occurrence.

It may be well to state here also the opinions to be deduced
from the changes which take place in the germinal membrane of
Acephalocystis, and the other acephalic entozoa. It has been
already fully described in what manner the function of reproduc-
tion in these animals is stopped, namely, in consequence of the
thickening of the germinal membrane. After having made out
this fact, I was led to infer that many instances of the stoppage
of cellular formations at certain periods of life might be traced to
similar changes taking place in the germinal membrane of the
formative organ, and, with the view of determining this point,
examined the testes of several old men, after the fecundating
power had in all probability passed away, when the germinal
membrane in almost all cases had become thicker and quite dif-
ferent from what is generally seen in young males, a change
which (as we have attempted to describe) had taken place in the
germinal membrane of hydatids.*

IV. — OF SPHAIKIDION.f

Sphairidion aceplialocystis is an animal allied to Acephalocystis,
chiefly from its acephalic character, but also from its reproduc-
tive organ being enclosed within the centre of its sac. This re-
productive body or membrane is exactly similar to the pedicle of the

* The stoppage here alluded to, in the function of reproduction of these animals, may
be also greatly assisted, and the degenerating process made more active, in consequence of
the thickening of the external membrane preventing the absorbing cells extracting from it a
sufficient supply of nourishment.

f 2<p#/(»/^OJ/, a globule.

OF THE CYSTIC ENTOZOA. 89

Cysticercus, with the exception of its being entirely buried in the
body of the animal, consequently also it is neither furnished with
teeth nor suckers. There is no separate absorbent apparatus in
the sac of the animal, and this part of its body appears to be com-
posed of one membrane only, which is analogous to the external
membrane of the sac of Acephalocystis. The cyst of this animal
at first appears to be composed of three membranes, but a little
examination proves the outermost to consist of peritoneum only,
the two others being similar to the analogous membranes of the
cyst of Cysticercus rattus, namely, an external for defence, and
an internal for absorption of nourishment.

This animal was found attached to the intestines of the Balearic
Crested Crane (Balearicapavonia, Vigors) beneath the peritoneum.

V. — OF CJSXURUS.

The next animal we have to describe is Csenurus. It is in the
species belonging to this genus that the first vestiges of extremi-
ties are perceived, to which form of structure wre are led through
Diskostoma — the discs described in the latter being without doubt
analogous to the pedicles of the Caenurus.

Ccvnurus cerebralis, an animal frequently found in the brain of
the sheep and other ruminants, has been long known to natural-
ists. This animal is composed of a double sac, from the external
surface of which proceed a number of small bodies, termed pe-
dicles. These pedicles are contained between the two membranes
of the sac, project at right angles from its surface, and are armed
at the extremity with a double circle of teeth.

The sac of the Csenurus is composed of two membranes, the
outermost of which acts as an organ of defence, the internal,
containing a layer of absorbent cells, acts along with the larger
cells contained in the pedicles as organs of nutrition. The natu-
ral size of the pedicles is about the one-eighth of an inch in
length. It is divided into two parts, the basal and distal. The
former contains the absorbing cells already spoken of, which,

* Transactions of the Royal Society, Edinburgh, Vol. xv. p. 564.

90 OF THE ANATOMY AND DEVELOPEMENT

after a time become themselves independent pedicles. The cells
within the pedicle are arranged regularly in the form of concen-
tric circles, each cell as it becomes a parent forming a centre.
The latter, or distal portion of the pedicle, contains very few, if
any, of these cells, but bears on its extremity a double series of
bent barbed teeth, which enable the animal to attach itself firmly
to the infested body. Four suckers are also placed at regular in-
tervals round the sides of this portion of the pedicle.

When one of the smaller cells escape from the pedicles, and
obtains a situation between the layers of the parent sac, it shortly
commences to take on a new action, the nucleus enlarges and
presents a clear spot in the centre. As this spot encreases in
size, the nucleus becomes irregular on its edges, and shortly be-
comes nodulated, each of which nodules after a time are thrown
off as separate cells, a central cell occupying the place of the
clear central spot.*

This is the termination of the first stage of the developement
of the ovum, after which the nucleus of the central cell undergoes
a similar process, the cells proceeding from it pushing out nearer
to the circumference those of the previous generation. Thus we
have a great series of centres, round which all the other cells are
arranged in circles. This I have termed the discoidal period of
developement.

After numerous circles have been thus formed, the cells
nearest the circumference, and, of course, those first formed, be-
come parents, and consequently centres ; but a few of these gaining
the advantage, dissolve the more peripheral cells and absorb them,
thus becoming principal centres. As soon as this change in the
developement has taken place, the mode of growth, hitherto
discoidal, becomes vertical, or at right angles to the sac, and so
proceeds until the pedicle becomes perfect.

There is still another animal belonging to this series, and which
requires to be noticed in this place. It is nondescript, and its charac-
ters resemble so much both those of Acephalocystis and Csenurus
that I have not yet been able to decide with precision to which

* It will be noticed by all observers, the great similarity which exists between the develope-
ment of this animal and the mammiferotis ovum, as described by Dr. Martin Barry.

OF THE CYSTIC ENTOZOA. 91

genus it belongs. It has certainly more of the characters of the
Csenurus than Acephalocystis, although many also connect it
most intimately with the latter. In the meantime, however, I have
placed it along with Csenurus, and from its habitat called it C.
hepaticus. In all its more important characters, it is very-
similar to the C. cerebralis.

VI. — OF CYSTICERCUS.

Cysticercus is distinguished from Csenurus by its sac having
only one pedicle ; it is also always contained in a cyst, which,
in some cases, is formed from the compressed textures of the
infested animal, while in others it consists of two membranes,
viz., one similar to that mentioned, and another, sui generis, and
belonging entirely to the parasite. The pedicle of the Cysticer-
cus, is exactly similar in its structure to that of the Csenurus,
with the exception of the cells, which are not arranged so regu-
larly. The sac is also composed of two membranes, each having
structures exactly similar to that of the Caenurus.

I have divided the animals composing this genus of Entozoa
into two classes, in consequence of the difference of structures
met with in the cyst. Those species, in which the cyst is only
composed of one membrane, derived from the compressed tissues
of the infested being, have been placed near to the Acepha-
locysts ; and those in which the cyst consists of two membranes
already described, compose the other division.

The Cysticercus cellulosce is an example of the first of these divi-
sions. In this animal, the cyst is very vascular, i. e. more so than
the surrounding textures, so that in this respect it is quite similar
to the analogous structure in Acephalocystis. As an example of
the animals belonging to this division of the genus, there is an-
other species which appears to be nondescript. This Cysticercus
was found in the Museum of the Royal College of Surgeons, but
unfortunately the jar was not labelled, so that I am uncertain from
what animal it was got. It is enclosed in a cyst formed by the
omentum alone ; these cysts are pedunculated, and although quite

92 OF THE AMATOMY AND DEVELOPEMENT

continuous with the healthy portion of the membrane, it is so
puckered and constricted at the pedunculated portion, as to be
quite impermeable, so that the enclosed animal can obtain no
nourishment from without, except through the portion of omentum
forming the cyst. The cyst is very vascular, and generally con-
tains a quantity of thin granular looking matter, (probably the
matter intended for the food of the enclosed animal). The
double circlet of teeth in this species is remarkable for their great
length. In many specimens which came under my notice nu-
meroususmall globular bodies were observed, surrounded externally
with hooked spines, and attached to the internal surface of the
cyst, apparently by means of the spines. These bodies, although
the intermediate stages between them and the young gemmules
could not be seen, I considered the young Cysticerci in an ad-
vanced stage of growth, and I was led to do so, because they
were often observed on the free surface of the omentum, attract-
ing and puckering it together in folds, evidently the commence-
ment of the process for the formation of a cyst, and in many
instances they had completely enveloped themselves. It has not
yet been decidedly made out, in what manner the gemmules
escape from the body of the Cysticercus, but from the observa-
tions I have made, it appears that they must first escape from the
pedicle where they are formed into the sac, and then from the
sac to the cyst. I am led to this supposition in consequence of
having observed on several occasions the sac of the animal rup-
tured, and great numbers of the globular spined bodies attached
to the inner surface of the cyst. How they escape from the cyst
I have not been able to determine.

Those Cysticerci having the cyst composed of a double mem-
brane, do not differ in any other particular from those of the pre-
ceding division of the genus. The best example of this peculiarity
of structure, exists in a species found in the liver of the rat, and
which I have denominated Cysticercus Eattus. The specific
characters are given in the synopsis at the end of the Paper.

In all the details, then, we find a great similarity between
Csenurus and Cysticercus, with this exception, that the latter is
simple, whereas the former, like all the other Accphalocysts, is a

OF THE CYSTIC ENTOZOA. 93

compound animal. Why the pedicles of Csenurus should all
becdme attached to the same sac, is a fact, the cause of which it
will be impossible to determine with any degree of certainty ;
probably, however, it arises from the difference of strength in the
sacs of the two animals ; — the greater strength of that of Csenurus
preventing the escape of the young gemmule from between its
membranes. The mode of formation of the sac is also a point
interesting to the physiologist, and one deserving consideration.
In Acephalocystis and the other allied genera, the original gem-
mule, shortly after it has become an independent animal, begins
to swell out and be distended from the accumulation of new
matter within it. This new matter is drawn into it by means of
the young internal cells, which have just been formed, and which
have a power, inherent in themselves, of attracting and assimi-
lating nourishment from without. The cells referred to here, are
the young germs of future hydatids, and which afterwards, as
already explained, become independent animals ; but, at the same
time, there is in many cases also another series of cells, whose
only function is to act in this way, and throughout the term of
their existence : these have been termed absorbent cells. Now,
these cells drawing in the nourishment in this way, cause the
expansion of the original cell wall, so that the enlargement of
these bodies resembles a process of dilatation. This, then, ap-
pears to be the explanation of the peculiar forms assumed by the
Csenurus and Cysticercus, as well as the different species of ace-
phalocysts ; that it is so, can be proved from Sphairidion acepha-
locystis, an animal very nearly allied to Csenurus, and being a
connecting link between the acephalic and cephalic hydatids ; for
in this animal we find that portion of its body analogous to the
pedicle of Cysticercus, not exserted, as in the latter animal, but
situated in the centre of the body, where it forms the attracting
point for the nourishment absorbed, which accordingly dilates the
external and containing sac.

What I wish to be inferred from this is, that the sac of
Acephalocystis, Cffinurus, and Cysticercus, are analogous or-
gans ; and that the pedicles of these two latter animals are
analogous to the reproductive nucleus, which may be observed
during certain early stages of the developement of Acephalocystis,

94 THE ANATOMY AND DEVELOPEMENT

as well as the reproductive and absorbing nucleus of Sphairi-
dion. t

Species of Cysticercus have been found in almost every part
and cavity of the human body. In the brain, eye, lungs, liver,
in the walls of the intestines, and in the muscles. In the present
state of our knowledge, it is impossible to say how these animals
gain such habitats as the eye, &c. This is a question, however,
which has been the cause of much discussion.

VII. — OF THE HIGHER CYSTIC ENTOZOA.

Besides those already described, there are many other forms of
entozoa of the higher orders, which are inhabitants of cysts simi-
lar to these of Cysticercus ; we have examples of this occurring in
the Nematoidea, Cestoidea, and Aeanthacephala, &c. As exam-
ples of the worms alluded to, I may instance Trichina spiralix,
Gymnorliynchus horridus, and a small filaria inhabiting the livers
of some fish, but, as far as can be made out, not hitherto described
by any author. As another example, too, of these peculiar forms,
may be mentioned, a very interesting animal which will be after-
wards described, namely, Neuronaia Monroii.

The cysts of all these worms have similar structures to those
of Cysticercus, namely, an external membrane composed of com-
pressed cellular texture, and an internal membrane containing
absorbing cells, through which the contained animal obtains
nourishment.

In the descriptions of the acephalocysts already given, it will
be remembered how the animal died in consequence of the thick-
ening and hardening of the external membrane of the cyst, pre-
venting the absorption of nourishment from or through it ; so in
like manner do these higher Cystic Entozoa — Trichina — die
from a similar cause. In many cases where the subject is in-
fested with Trichina, it is found on examination, that with few
exceptions almost every specimen is converted into the hard cre-
taceous matter spoken of, many, at the same time, presenting all
the intermediate stages of decay. Gymnorhynchus presents us
with a very curious habit dependant upon this mode of structure,

OF THE CYSTIC ENTOZOA. 9;>

and which enables the animal to avoid the death from which all
its co-geners suffer. This species which I have fortunately had
an opportunity of examining in its natural habitat, but which
has been already described by my brother (Edinburgh Philoso-
phical Journal, Vol. 31) inhabits the liver of the sun-fish in great
numbers, and from its peculiar structure is enabled to move
slowly through the organ it infests. If the cyst of this worm is
carefully examined, it will be found that the inner membrane,
containing the absorbent cells, is covered anteriorly with a very
thin layer only of the external membrane, so that it is enabled
to absorb the nourishment from the external textures in great
abundance, which thus enables the animal to move forward, as
well as obtain a supply of food ; as we trace the cyst backwards,
the external membrane will be found to become thicker and
thicker, as also more impermeable, until we reach the tail of the
animal, after which it becomes a mere cord. This cord can be
traced for a great distance, becoming less and less perceptible,
until it is lost altogether, and the course only marked by a simple
line of a darker colour than the rest of the textures. It will be
observed that the external membrane of this animal presents
analogies similar to that of acephalocystis ; for instance, the ce-
phalic portion of the membrane is so thin as to be hardly distin-
guishable, being thus analogous to the young hydatid.

In regard to the cyst of these worms, it has been long a ques-
tion how far it is a part of the enclosed animal. Professor Owen*
holds, that it is merely condensed textures of the infested being,
and Dr. Knoxf again, that it belongs essentially to the parasite.
My brother, in the Paper already alluded to, says, regarding the
cyst — " May we not suppose them to be parts of the original
ovum, within which the animal was formed, and within which it
passes its term of existence." From observations made on the
developement of the acephalocystic entozoa, it may be safely
stated, I think, that the above statement is correct, for acephalo-
cystis must be considered as an enlarged ovum ; but Sphairidion
perhaps is the best example of this peculiar mode of formation,

* Owen. " Description of a Microscopic Entozoon infesting the Mtiscles of the Human
Body." Transactions of the Zoological Society, Vol. I., page 322.
t Knox, Edinburgh Medical and Surgical Journal.

96 THE ANATOMY AND DEVELOPEMENT

the " inserted pedicle" being analogous to the confined Trichina
or Gymnorhynchus — for we must look upon the inserted pedicle
as the active animal. In Csenurus, also, the pedicles are con-
tained within the external membrane of the sac.

I shall finish these observations on the Cystic Entozoa, with
the following account by my brother, of Neuronaia Monroii*

The observations of Pacinif on the peculiar bodies which are
appended to the digital nerves, induced me to direct my attention
to the " spheroidal bodies," described by the second Monro, as
existing on the surfaces of the brain and nerves of the gadida?.

O D

I accordingly examined the " spheroidal bodies" in the haddock,
and found that they were entozoa, referrible to the family Distom a,
and enclosed in cysts. I described these curious parasites at a
meeting of the Anatomical and Pathological Society, and a short
abstract was published in the monthly Journal of Medical Science.
Till lately, I had supposed that I was the first to observe the
true nature of these " spheroidal bodies," when Dr. Allen Thom-
son ascertained that Dr. Sharpey was in the habit of mentioning
them in his courses of lectures in the University College. I ac-
cordingly wrote Dr. Sharpey on the subject, and I am indebted to
that gentleman for the following interesting account of what has
been already recorded regarding this entozoon : —

" When I was in Berlin some years ago, the late Professor
Rudolphi remarked to me in conversation, that he thought it not
unlikely the little bodies discovered by Dr. Monro 2d, on jhe
nerves of the cod, haddock, and other allied fish, would turn out
on examination to be entozoa ; and he suggested that I should
take an opportunity of inquiring into the point on my return to
Scotland. Accordingly, in the autumn of 1836, 1 examined these
bodies in the haddock or whiting, I really forget which, but I
think it was the former, and found that each of them was a little
cyst, containing a Distoma, which could be easily turned out from

* Monro. " Observations on the Structure and Functions of the Nervous System,'" p. 59.

t Pacini. " Nuovo Giomale dei Letterate" March and April 1836, page 109. J. Henle

and Kolliker. " Ueber die Pacinischcn Korperchen an den Xcrven des Menschen nnd der

OF THE CYSTIC ENTOZOA. 97

its enclosure alive. The specimens I examined were from the
membranes of the brain.

" This observation was made in Edinburgh, and, on going to
London soon after, I mentioned the fact to Mr. Owen ; and I
have been accustomed to take notice of it in my lectures ever
since, suggesting at the same time that it would be well to search
for them, or for analogous parasites, in the nerves of other ani-
mals, as it was not likely that the gadus tribe of fishes should be
the only example. Indeed, unless my memory deceives me, some
one has met with something of the same kind in the nerves of
the frog ; and Valentin has seen the eggs of Distoma in the ver-
tebral canal of a foetal sheep. When I learned that the oval bodies,
which all must have seen in the cellular tissue of the palm of the
hand and fingers, were connected with the nerves, I at first ima-
gined they might be entozoa, (having been led to make just the
converse of your conjecture,) but Mr. Marshall, formerly of our
Museum, having examined these " Pacinian" bodies two or three
years ago, (quite independently of any suggestion from me,) I
found nothing to confirm this conjecture on his showing me their
structure. 1 have since seen Henle and Kolliker's memoir, which
includes the substance of Pacini's observations.

" Rudolphi, as far as I know, never examined the structure of
the spheroidal bodies of Monro ; and the only notice of them
which I have met with in his writings (to which he did not refer
me) is in his Historia Naturalis Entozoarum^ Vol. ii. Part 2, page
277, when, under the head of Dubious Entozoa, he enumerates
an object described and figured by J. Rathke, under the name
of " Hydatula Gadorum," which that observer found in the pia
mater of the Gadus Morrhua and G. Virens, often in great num-
bers, and which appeared to be a vesicle containing a worm. The
nature of the parasite was doubtful, but supposed in some degree
to resemble that of a cysticercus, and hence the name applied to
it by Rathke, but Rudolphi denies that it is a cysticercus, though
he does not know to what genus to refer it, he adds 6 an Cucul-
lanus.' "

This entozoon, as stated by Monro, is found in great numbers
in the gelatinous substance which surrounds the brain, spinal
cord, and semicircular canals, in the cod, haddock, and whiting.

98 THE STRUCTURE AND ECONOMY

They are also very numerous in the larger branches of the
nerves, and particularly on those of the pectoral and caudal fins.
In the former situation they are suspended in the gelatinous
fluid by fibres of areolar texture and by blood-vessels ; in the
latter they lie embedded in the substance of the nerve, the ulti-
mate fibres of which are spread in bundles over the surface of
the cysts.

The cysts are produced spheroids, somewhat flattened ; their
long axis measures about one-fourth of a line.

They consist of three tunics ; an external, which appears to be
derived from the areolar texture of the infested animal, and of a
middle and internal, belonging to the parasite.

Upon the surface, and in the substance of the external tunic,
the blood-vessels of the nerve can occasionally be seen, and re-
cognised by their contents. One or two vessels may thus be
observed coasting along the cyst, accompanied by single nerve
tubes, or by bundles of these, or by a mass which completely
encloses and conceals the cyst. The second tunic is a fine trans-
parent membrane, which lines the first, and has in its turn its
internal surface covered by an epithelial layer, which is the third
tunic of the cyst. The epithelia are flat, irregular in shape, and
somewhat opaque. The third, or internal layer, formed by them,
breaks up under the pressure of the glass plates, so as to present
rents or fissures passing in various directions over it.

The cyst, in addition to the worm, contains a small quantity
of fluid, in which oil-like globules of various sizes float.

The worm is a Distoma, oblong, dilated in front, tapering
slightly towards its posterior extremity. The mouth longitudi-
nally oval, and rather pointed posteriorly, is surrounded by the
usual suctorial disc. The acctabulum is situated at the junction
of the anterior and middle third of the animal, and can be pro-
truded from the surface of the body.

On the anterior edge of the acctabulum a minute pore is si-
tuated, and communicates with a sac, to be afterwards described.

At the posterior extremity of the animal another orifice is
placed, which forms the outlet of the large chyle sac, and ap-
parently also of another sac, to be afterwards alluded to.

The integument of the two anterior thirds of the body, is

OF THE CYSTIC ENTOZOA. 99

closely covered with short slightly curved spines, directed back-
wards. These spines are largest round the suctorial mouth, and
on the posterior part of the body are gradually replaced by mi-
nute tubercles or dots. Under this spiny or cuticular layer, the
integument is muscular, the fibres being principally transverse,
and so arranged that the animal appears to be made up of a series
of rings, as may be observed along its edges, when examined by
transmitted light.

From the anterior extremity to the acetabulum the integu-
ments are so opaque, from the dense covering of spines, that the
internal structure of the animal cannot be detected. It is pro-
bable, however, that the oesophagus terminates as in the family
Distoma generally, in two blind intestinal tubes. I have failed
in detecting an arrangement of this kind ; but I have observed
about the middle of the animal, and along the sides of its posterior
half, a sort of cellular structure, which may probably belong to
the digestive system, as in Distoma clavatum described by Pro-
fessor Owen.*

A large sac, evidently connected with the digestive system,
opens externally by the minute orifice, at the posterior part of
the animal. This sac, in every individual, is full of a matter,
which by reflected light is of a chalky whiteness, and described
by Monro, and conjectured by him to be of a cretaceous nature.
Examined by transmitted light, it is seen to consist of numerous
spherical globules of variable size, and resembling the matter
which fills the chyle cells of the intestinal villi. The larger sac
in which this matter is contained varies in shape, but it generally
passes up from its outlet for about a third of the length of the
body of the animal, then takes an acute bend to the other side,
and passing forwards in a curved direction, ends in a dilated
blind extremity between the acetabulum and the mouth. It is
the " sigmoidal" or " serpentine body" of Monro. This sac is
evidently the " cisterna chyli."

It does not communicate directly with the digestive system, as
in the apparently analogous receptacles in Distoma clavatum, nor,
as far as I could see, with the vascular system ; but I have seen it

* Owen. " On the Anatomy of Ditfoma Clavatum," Trans. Roy. Soc., Vol. 1.

100 THE STRUCTURE AND ECONOMY

discharge its contents by the posterior orifice, in the manner
described by Nordman in Diplostomum Volvens*

From the movements of the walls of this receptacle, or from
contractions of the animal itself, an active motion of the particles
of its contents is occasionally observed. The movements occa-
sionally resemble very much those produced by cilia. This sac
is apparently a secreting organ, and is probably the only arrange-
ment by which feculent matter is removed from the body of the
animal. The food of an animal, living as this does, in a cyst, is
already digested by the walls of its cyst. Its food, therefore,
yields no mechanical feculent matter, and its intestinal tube re-
quires no anus. The only outlet which such an animal requires,
Is for chemical feculent matter, which in all animals is the pro-
duct of secretion, and principally of the lung, gill, or kidney.
This sac may, therefore, be considered as a respiratory organ, or
kidney.

There is another sac, very uniform in shape and size, situated at
the posterior part of the body. This sac is elongated, extending
from near the outlet of the " cisterna chyli," forward about a
fourth of the length of the animal. Its posterior extremity is
funnel-shaped, and appeal's to me, although I have failed in
tracing it distinctly, to open externally along with the " cisterna
chyli." It appears to possess circular fibres, which constrict it
slightly at regular distances. The three anterior fourths of its
wall are so thick that the cavity appears linear. This thick part
of the wall exhibits an arrangement of fibres or particles perpen-
dicular to its surface. The thick portion terminates by forming
a curved projection into the thin posterior part of the organ, the
whole arrangement resembling the projection of the human os
uteri into the vagina. This organ in its relations and structure
appears to be the analogue of the cavity described by Professor
Owen, as opening into the posterior orifice of Distoma clavatum,
and supposed by him to be a respiratory organ.

A pyriform sac, communicating with the exterior, by the pore
in front of the acetabulum ; and two large, with occasionally two
smaller globular masses, would appear to be the analogues of the

* Nordman. " Micrographische Beitrage" page 38, hft. 1.

OF Till: CYSTIC ENTOZOA. 101

reproductive organs. The pyriform sac always contains highly
refractive oil-like globules, but larger than those in the chyle
receptacle. The two larger globular masses are very constant,
and as well as the two smaller contain a mass of particles appa-
rently nucleated. From the two larger, I have only been able
to see faint traces of what appeared to be ducts passing in the
direction of the smaller masses, and towards the neck of the pyri-
form sac. Whether these convoluted bodies be ovaries or con-
voluted oviducts, and the pyriform sac a uterus ; or whether the
former be the testes, and the latter the female organ, as in the
arrangement described in the other Distomas ; or whether they be
reproductive organs at all, I have failed in satisfying myself, in
consequence of the delicacy of their texture, and the compara-
tively dense integument of this part of the animal.

This Distoma possesses a vascular system forming a network
throughout the body. The two principal trunks, as in the other
genera, passing along the sides of the body and being most ap-
parent at its posterior third.

I. ACEPHALOCYSTIS.

Completely buried in the textures of the infested animal ; young
only consisting of three membranes ; adult of four, the external one
belonging originally to the infested being. Nourished by epithelial
cells, which are contained in one of the membranes composing the sac.
Generated by means of cells arising from a germinal membrane.
Internal cavity filled with a watery fluid.

1. — Acephalocystis Simplex (Mihi).

Parent sac quite transparent, with the membranes indivisible and the germinal cells very
minute.

2. — Acepltalocystis Monroii (Mild).

Parent sac transparent and gelatinous ; germinal membrane intersected by membranous
bands, which form flattened compartments, in which are large cells containing unequal
numbers of young cells. Each of the young are marked with one or more dark spots.

102 THE STRUCTURE AND ECONOMY

3. — Acephalocystis armatus (Mihi).

Parent sac opaque, membranes distinct, germinal membrane composed of a soft granular
matter, in which the germs are arranged irregularly ; they are globular and armed with an
irregular circlet of teeth at the part opposite that of attachment.

ii. — ASTOMA (MIHI).

Not buried, but attached by means of a pedicle, which becomes very
slender as the animal increases in size. Young, globular and corru-
gated ; adult, botryoidal and smooth ; epithelial cells ; with some appear-
ance of tubuli in external coat. Young remain and increase in size
within the membranes of the parent, till she bursts, when they become
attached to the peritoneum.

4. — Astoma acephalocystis (Mihi).

Botryoidal, that part of the interior not occupied with the young, filled with a yellowish
gelatinoiis matter.

III. DI3KOSTOMA (MIHl).

Peduncular. Whole group covered by a disk bearing tubular
membrane.

5. — DisJcostoma acephalocystis (Mihi).
Globular interior filled with gelatinous matter, of a transparent greenish yellow colour.

IV. SPHAIKIDION (MIHI.)

S. Animal enclosed within a cyst which is composed of two mem-
branes. Sac single, containing the pedicle or reproductive body in its
centre, and presenting a number of concentric coloured rings. Hab.
Peritoneum of Crested Balearic Crane.

OF THE CYSTIC KXTOZOA. 103

V. C^ENURUS RUDOLPHI.

Sac double, armed with numerous clusters of toothed pedicles.
Epithelial cells in the sac. Germinal cells in the pedicles. Buried.

6. — Ctmurus Hepaticus (Mihi).

Sac botiyoidal, opaque and thick ; pedicles internal, small, suckers obsolete ; teeth barbless,
small, irregularly bent, and forming one irregular series. Gregarious. Infests the liver of man.

7. — C. Cerebralis (Rudolphi).

Sac globular, transparent, thin, pedicles with four or five acetabula. Teeth thirteen,
about three times as long as the breadth of the disc from which they arise. Infests the
brain of sheep and other ruminants.

VI. CYSTICERC US.

Animal enclosed within a cyst provided with a single pedicle.

1. Cyst formed from the infested animal.

8. — C. Neglectus (Mihi).

Cyst formed from omentum of infested animal. Pedicle about three times the length
of sac, head rounded, teeth twenty-one in number, very long, slender, and bent at the extre-
mity, barbed on bent edge. Hab. unknown.

2. Cyst formed by parasite, as well as from textures of infested being.

9.— 6'. Eattm (Mihi).

Cyst small, globular, and transparent pedicle, not very long, teeth short, sickle-shaped,
being cunred throughout their whole length.

VII. ECHINOCOCH US.

H. D. S. G.

DESCRIPTION OF THE PLATES.

DESCRIPTION OF THE PLATES,

CENTRES OF NUTRITION-

PLATE I. Fig. 1. A portion of the middle and internal membranes
of a large encysted tumour situated under the
tongue, and removed by Professor Syme.
a The middle or second membrane, which is a
germinal membrane, consisting of flattened cells,
the lines of junction of which are faintly visible,
the nuclei remaining as the germinal spots of
the membrane.

b The internal membrane, a layer of small cells,
somewhat spherical, with slightly granular con-
tents.

The external membrane of the cyst, consisting
of areolar and elastic fibres, contained the blood-
vessels of the morbid growth.

The cyst contained a sx>ft mass resembling
thick honey in consistence. The outer layer of
this mass was white, and consisted of large, flat
transparent cells or scales, with few or no traces
of nuclei. The larger internal part of the mass
was reddish grey, and consisted of ovoidal cells,
resembling those of the external layer, except
that they were turgid with a transparent oily-
like fluid, and contained nuclei in various stages
of developement.

108 DESCRIPTION OF THE PLATES.

PLATE I. Fig. 2. a, PLATE I. Fig. 3. «, Cells of the ineliceritous
mass — those without nuclei being those of the
white external layer, the others belonging to the
reddish grey part of the mass, presenting nuclei
in various stages of developement.
b b Some of the latter cells, in which the nuclei
have become so much developed as to distend
their cells beyond the average size. In these
enlarged cells, it will be remarked, that the
nuclei, instead of remaining as single germinal
spots for each cell, have broken up into numerous
spots, or centres of nutrition.

In a tumour of this kind, the cyst and its
contents are two distinct parts, and perform two
distinct actions. The cyst is the active agent in
withdrawing materials of nutrition for itself and
its contents from the vessels which ramify in its
outer tunic. The organs which accomplish this
are the germinal spots in its middle tunic, which
in virtue of forces of attraction in each, select
and remove from the capillary vessels the mat-
ter necessary for the formation of the cells of
the internal layer. These after solution pass in
succession into the cavity of the cyst, to serve
as nutriment for the contained cellular mass.

This mass is evidently the principal element
of the morbid growth. The cyst is a subsidiary
or accessory part, arranged for the protection,
and due supply of nourishment for its principal.
The cells of which this mass consists have each
its own nucleus or germinal centre. These cells
would appear to be of two classes — those whose
nuclei produce young cells in their interior for
their own nutrition, but not for the reproduction
of new mother cells ; and those which act as
reproductive individuals for the whole morbid
growth. These latter cells are marked b b in
Figs. 2 and 3, and contain numerous nutritive
centres or .germinal spots in their interior. The
flat cells of the white external layer appear to

DESCRIPTION OF THE PLATES. 109

be those individuals of the first class, which arc
about to close their existence, their nuclei hav-
ing disappeared ; their food, therefore, no longer
supplied to them, and their position in the mass
removed to the exterior by the eccentric deve-
lopement of the younger and more active neigh-
bouring cells. In a morbid mass of this kind,
as in the textures and organs of an animal gene-
rally, certain parts are set aside as reproducers,
the remaining parts performing the functions of
the whole mass, texture, or organ ; just as in
certain communities of animals certain indivi-
duals are set aside to reproduce the swarm, the
others are devoted to the duties of the hive.

PLA.TE I. Fig. 4. Two portions of the primary or germinal membrane
from the tubes of the tubular portion of the hu-
man kidney. The germinal spots of the gland
are seen imbedded in the substance of the mem-
brane. The external layer of this membrane,
which may occasionally be seen with the nuclei
detached from it, is the basement or homege-
neous membrane of Mr. Bowman. In other in-
stances, as when the epithelia are but slightly
developed, it becomes difficult to decide whether
we have merely the germinal membrane, or both
the membrane and its epithelia before us.

INTESTINAL VILLI.

PLATE I. Fig. 5. Extremity of a villus immediately before absorption
of chyle has commenced. It has cast off its pro-
tective epithelium, and displays, when com-
pressed, a network of peripheral lacteals. The
granular germs of the absorbing vesicles, as yet
undeveloped, are seen under its primary mem-
brane.

110 DESCRIPTION OF THE PLATES.

PLATE I. Fig. G. Extremity of a villus, with its absorbent vesicles
distended with chyle, and the trunks of its lac-
teals seen through its coats.

Fig. 7. Protective epithelium cells from a villus in the dog.

Fig. 8. Protective epithelium cells cast off preparatory to
absorption of chyle ; instead of nuclei, they pre-
sent, in their interior, groups of globules.

Fig. 9. A group of the same cells adhering by their distal

extremities.
Fig. 10. Secreting cells thrown out of the follicles of Lei-

berkiihn during digestion.

Fig. 11. Diagram of mucous membrane of jejunum when
absorption is not going on. a Protective epithe-
lium of a villus. b Secreting epithelium of a
follicle, c c c Primary membrane, with its ger-
minal spots or nuclei, d d. e Germs of absor-
bent vesicles. / Vessels and lacteals of villus.
Fig. 12. Diagram of mucous membrane during digestion
and absorption of chyle, a A villus, turgid,
erect ; its protective epithelia cast off from its
free extremity ; its absorbent vesicles, its lacteals
and blood-vessels turgid, b A follicle discharg-
ing its secreting epithelia.

PROCESS OF ULCERATION IN ARTICULAR CARTILAGE.

PLATE I. Fig. 13. a A section of articular cartilage and absorbent
membrane. In the lower part of the section the
cartilage corpuscles retain their natural size
and appearance ; as they approach the rugged
ulcerated edge, they increase in size, and con-
tain numerous young cells, apparently the pro-
geny of their nuclei ; beyond this edge, rounded
masses of cells, originally contained within the
cartilage corpuscules, are seen embedded in the
cellular absorbent mass.

DESCRIPTION OF THE PLATES. Ill

b Absorbent cells of the false membrane, with two
globular masses derived from the cartilage cor-
puscules.

SECRETING STRUCTURES.

PLATE 1. Fig. 14. Four secreting cells from the ink bag of Loligo sa-

gittata.

Fig. 15. Five cells from the liver of Patella vulgata. In this
instance the bile is contained in the cavities of
the secondary cells, which constitute the nucleus
of the primary cell.

Fig. 16. Three cells from the kidney of Helix aspersa. The
contained secretion is dead white, and presents a
chalky appearance.

Fig. 17. Two cells from the vesicles of the testicle of Squa-
lus cornubicus. The contained bundles of sper-
matozoa are developed from the nucleus, — each
spermatozoon being a spiral cell.

PLATE II. Fig. 1. Five cells from the mamma of the bitch. In
addition to their nuclei these cells contain milk
globules.

Fig. 2. A portion of duct from the testicle of Squalus
cornubicus. A few nucleated cells, the primary
or germinal cells of the future acini are at-
tached to its walls.

Fig. 3. The primary cell of an acinus in a more advanced
stage. The nucleus has produced a mass of
young cells. The pedicle appears to have been
formed by the germinal cell carrying forward
the wall of the duct. A diaphragm accordingly
presents itself across the neck of the pedicle.

Fig. 4. A primary cell in a more advanced stage.

Fig. 5. A primary cell still more advanced.

Fig. 6. Some of the secondary cells, products of the

112 DESCRIPTION OF THE PLATES.

nucleus of the primary cell, are cylindrical, and
are arranged in a spiral.

Fig. 7. The cliange into cylinders, and the spiral arrange-
ment completed.

Fig. 8. a One of the secondary cells ; its nucleus a mass of
young cells, b A secondary cell elongated into
a cylinder, each cell of its composite nucleus
elongated into a spiral, c The spiral cells, or
spermatozoa, free.

Fig. 9. A bunch of acini, in various states of developement,
maturity, and atrophy. The four following
figures are diagrams, arranged so as to illus-
trate the intimate nature of the changes which
occur in vesicular glands when in a state of
functional activity.

Fig. 10. A portion of gland duct with two acini. One of
the acini is a simple primary cell : the other is
in a state of developement, its nucleus producing
young cells.

Fig. 11. Both acini are advancing; the second has almost
reached maturity.

Fig. 12. The second acinus is ready to pour out its contents,
the first to take its place.

Fig. 13. The second acinus is in a state of atrophy, the first
is ripe.

Fig. 14. Two follicles from the liver of Carcinus mcenas.
The colourless germinal spot is at the blind ex-
tremity of the follicle. The secreting cells
become distended with bile and oil, as they
recede from the germinal spot.

THE STRUCTURE OF THE LYMPHATIC GLANDS.

PLATE II. Fig. 15. A portion of the germinal membrane of the human
intra-glandular lymphatics, with its germinal
spots or nutritive centres diffused over it..

DESCRIPTION OF THE PLATES. 113

PLATE II. Fig. 1C. A portion of the same membrane, in which the
component flattened cells, with the centres, have
been rendered transparent, and are beginning to
separate, by the action of acetic acid. Five of
the glandular epithelia adhere to the membrane.
Fig. 17. A diagram of a lymphatic gland, showing the
intra-glandular network, and the transition from
the scale-like epithelia of the extra-glandular to
the nucleated cells of the intra-glandular lym-
phatics.

Fig. 18. A portion of an intra-glandular lymphatic, showing
along one edge the thickness of the germinal
membrane, and upon it the thick layer of glan-
dular epithelia.

THE STRUCTURE OF THE PLACENTA.

Fig. 19. The extremity of a placental villus.

a The external membrane of the villus, the lining
membrane of the vascular system of the mother.

b The external cells of the villus, cells of the

central portion of the placental decidua.
c c Germinal centres of the external cells.

d The space between the maternal and fetal
portions of the villus.

e The internal membrane of the villus, the ex-
ternal membrane of the chorion.

/ The internal cells of the villus, the cells of the
chorion.

g The loop of umbilical vessels.

Fig. 20. This drawing illustrates the same structures as the
last, and has been introduced to show the large
space which occasionally intervenes between the
internal membrane and the external cells. It
would appear that into this space, the matter
separated from the maternal blood, by the ex-

114 DESCRIPTION OF THE PLATES.

ternal cells of the villus, is cast, before being ab-
sorbed through the internal membrane, by the
internal cells. This space, therefore, is the
cavity of a secreting follicle, the external cells
being the secreting epithelia, and the maternal
blood-vessel system the capillaries of supply.
This maternal portion of the villus, and its
cavity, correspond to the glandular cotyledons
of the ruminants, and the matter thrown into the
cavity, to the milky secretion of these organs.

PLATE II. Fig. 21. A portion of the external membrane, with exter-
nal cells of the villus.
a Cells seen through the membrane.
b Cells seen from within the villus.
c Cells seen in profile along the edge of the villus.

Fig. 22. The extremity of a villus treated with acetic acid.
All the parts are distinctly visible, and the ger-
minal centres of the internal cells are seen sur-
rounding the umbilical vessel.

Fig. 23. A villus with a terminal decidual bar, along the
cavity of which the external cells are seen to be
continued, so as to pass forwards in the direction
of the parietal decidua.

PLATE in. Fig. 1. A portion of the external membrane of a villus,
with a lateral decidual bar. This portion of
membrane is seen from its foetal aspect, and in
this three or four germinal centres of the exter-
nal cells are perceptible.

Fig. 2. A drawing of the extremity of a villus treated with
acetic acid. In this villus all the parts described
are distinctly seen, and indicated by the same
letters, as in Fig. 19. Plate 2.

Fig. 3. The extremity of a villus, with a terminal decidual
bar, treated with acetic acid, to show the nuclei
of the decidual cells in the cavity of the bar,
and on the external membrane of the villus.

Fig. 4. Two tufts connected by a terminal decidual bar.

Fig. 5. A tuft with a lateral bar passing off from its stem.

Fig. 6. A diagram illustrating the arrangement of the
placental decidua.

DESCRIPTION OF THE PLATES. 115

a Parietal decidua.

b A veinous sinus passing obliquely through it by
a valvular opening.

c A curling artery passing in the same direction.

d The lining membrane of the maternal vascular
system, passing in from the artery and vein
lining the bag of the placenta, and covering e e
the fetal tufts, passing on to the latter by two
routes, first by their stems from the foetal side of
the cavity, and secondly by the terminal deci-
dual bars //from the uterine side, and from
one tuft to the other by the lateral bar g.
Throughout its whole course this membrane is
in contact with decidual cells, except along the
stems of the tufts, and the foetal side of the pla-
centa, where the decidual cells have degenerated
into fibrous or areolar fibres. All that portion
of the decidua which is in connection with the
bars, villi, and tufts, is the central or functional
portion of the decidua, and along with the lining
membrane of the maternal vascular system, or
external membrane of the tufts, constitutes the
true maternal portion of the placenta.
h h Two diagrams illustrating the fretal cellular
elements of the placental tufts. These are the
internal membrane, and the internal cells of the
tufts, and along with the loops of umbilical
blood-vessels constitute the true foetal portion of
the placenta.

THE TESTIS AND ITS SECRETION IN THE
DECAPADOUS CRUSTACEANS.

PLATE IV. Fig. 1. Figures of Entozoa from the tubuli semeniferi
of Orchestia littoralis, probably allied to filaria,
and supposed by M. Kblliker to be the sperma-

116 DESCRIPTION OF THE PLATES.

tozpa. This opinion, however, is incorrect, as
may be seen in the accompanying drawings,
where figures are given representing all the
details of the developement of the true sper-
matozoa. These are all produced from cells,
whereas the entozoa under consideration are
never seen within cells, but are in all cases
generally seen floating free in the seminal ves-
sels. These filaria have only been seen, so far
as I am aware, in Amphipoda and Isopoda. If
they are spermatozoa, they must be produced
from cells ; and from what has been stated in the
text, it will be seen that in all the Crustacea,
these cells, before producing the spermatozoa,
undergo several metamorphoses; and that the
final changes take place in the spermatheca of
the female, where the seminal animalcules are
produced. In Amphipoda, and Isopoda, where
these supposed filaria exist, we always find them
high up in the testicle, and not occasionally, but
in great numbers. In the tertiary seminal cells
also, which are floating about among them, not
the slightest vestige of the worm can be ob-
served. I am inclined to suppose, therefore, that
these thread-like worms, supposed by Kolliker
to be spermatozoa, are only parasites.

PLATE IV. Fig. 2. Representation of a primary germinal cell pro-
jecting from the wall of the seminal tube. It
has just burst, and the young secondary cells
are escaping and descending the tube ; during
the descent they increase in size, from their nu-
cleus throwing off nucleoli, the latter forming the
tertiary generation. In this figure it will be ob-
served that the cell walls of the parent are quite
smooth and unbroken, so that in all probability
the young arise from that portion of the cell at-
tached to the seminal tube.

Fig. 3. Is a small quantity of the fluid from the sperma-
theca of the female crab, showing the tertiary
or spermatozoa! cells after they have burst from

DESCRIPTION OF THE PLATES. 117

the secondary. As described in the text, the
spermatheca appears to be the organ in which
the seminal fluid undergoes the final and essential
change which fits it for impregnation.

PLATE IY. Fig. 4. This figure shows the adult seminal secondary cells
from the dilated part of the seminal tube. They
are full of tertiary cells. The fluid amongst which
they are floating is thick and albuminous, much
more so than it is higher up or lower down the
tube, and the large, clear, transparent looking
masses, are the pabulum for the nourishment of
the cells. It is much more abundant in this
part of the organ than any where else, and ac-
cordingly great numbers of the secondary cells
in all stages of developement, are constantly
found here. If a small quantity of the seminal
fluid from that portion of the testicle immedi-
ately preceding the dilated part, be placed
under the microscope, it will be seen that the
nuclei of the secondary cells are just throwing
off small nucleoli, and that the parent cell is not
very much larger than when it burst from the
primary. In the same part also, little or no
pabulum is observed. As we proceed down-
wards, however, we find them increasing rapidly
in size ; and, at the same time, an immense
quantity of pabulum floating about in large
masses. The lower part of the tube and the
vas deferens are almost destitute of pabulum,
the cells being satiated.

Fig. 5. Is the secondary cells of Hyas araneus from the vas
deferens. The walls of the parent cells, it will
be observed, are remarkably thin. The parent
secondary cells are of enormous size in this
species.

Fig. 6. Represents the testicles ofCarcinus Mcenas, of the na-
tural size, and shortly before they have reached
the maximum state of developement. The portion
included between a a is the tubular or hepatic,

118 DESCRIPTION OF THE PLATES.

that between b b is the dilated or gastric. The
vasa deferentia are not seen in this species so
well as in Hyas araneus, Fig. 8, c c. It is in the
gastric division that the pabulum lies in such
quantities.

PLATE IV. Fig. 7. Is the internal or sheathed portion of the external
organs of Cancer Pagurus ; proximal extre-
mity.

Fig. 8. Testes of Hyas araneus. a a Tubular portion, b b
Follicular portion, c c Vasa deferentia.

Fig. 9. External organs of Cancer Pagurus. a Is the in-
ternal or sheathed portion in situ. b Is the
sheath or external portion.

Fig. 10. External organs of Hyas araneus. A Sheath. B

Sheathed portion.

PLATE V. Fig. 1 . First stage of developement of secondary seminal
cell of Galathea strigosa.

Figs. 2, 3, 4, Second, third, and fourth stages of develope-
ment of the secondary cell.

Figs. 5, 6, 7, 8, 9, 10, 11, 12, 13, Various stages of deve-
lopement of the secondary cell of lobster.

Figs. 14, 15, 16, 17, The same treated with acetic acid.

Fig. 18. Tertiary or spermatozoal cells.

Fig. 19. Secondary cell of lobster seen from armed extre-
mity, to show the three setae.

Fig. 20. Primary cell, or coecum of testicle of Pagurus
Bernhardus full of secondary cells, c Attachment,
b Free extremity, a Nucleus.

Fig. 21. Primary seminal cell of Pagurus Bernhardus fill-
ing with secondary cells. As already described,
these cells grow in pairs from discs on the walls
of the seminal tubes, and hang free in the cavity
of the tube. It has also been described how the
secondary cells are produced from the parent
nucleus, namely, by means of successive growths,
each of which carries off a fold of the nucleus
before it.

a Disc from which the primary seminal cells grow.
b b The discs on each side of it.
c c The origins of the primary seminal cell?.

DESCRIPTION OF THE PLATES. 119

d One of the primary cells cut off.
e Nucleus of the primary cell in a state of activity ;
it has just thrown off a series of young marked
/In the diagram.
g g Are several old walls of former growths.

h Full extremity of primary cell.

PLATE V. Fig. 22. A small portion of the testicle of Pagurus Bew-
hardus magnified, showing the manner in which
the caeca hang from the walls of the seminal
tube.

Fig. 23. Small drop of seminal fluid of lobster, showing
the secondary cells before the armature had
expanded.

Fig. 24. Small drop of seminal fluid of lobster from vas de-
ferens. That part of the figure above a a, as seen
under the microscope, presents one dense mass
of secondary cells floating down towards £>, where
a few are seen separate.

Fig. 25. A coecum from the testicle of Carcinus Mcenas,
showing a germinal spot at its apex just being
filled with secondary cells.
Fig. 26. The germinal spot enlarged.

REPRODUCTION OF LOST PARTS IN THE CRUSTACEA.

.-

PLATE VI. Fig. 1. Represents the raw surface of the proximal or ad-
herent portion of the leg of Cancer Pagurus, after
the animal has thrown off the distal portion.
The figure represents the parts of the natural
size, and only a few hours after the separation
had taken place.

Fig. 2. Is a representation of the same part, after the young
leg had grown to some size. It will be observed,
that the cicatrix, which was formed upon 1lie
raw surface a few hours after separation, has

120 DESCRIPTION OF THE PLATES.

now become very strong, covers the young germ,
thus acting as a means of defence from external
injury.

PLATE VI. Fig. 3, 4, 5, Are the same parts in progressive states of
developement. Fig 5. presents a bifurcated cha-
racter, probably from some accidental cause it
thus appears smaller than it is in the normal
state.

Fig. 6. Represents the raw surface of the leg, already al-
luded to, in Car emus Mcenas, some time after
separation. A nucleated cell is seen in the
centre. This drawing was made from a very
small specimen, and was only procured in the
stage represented after great difficulty.
Fig. 7. Represents a longitudinal section of a very young
germ, for the purpose of showing its mode of
developement. The fibrous looking band which
surrounds it externally, is a circular canal
which belongs to a system of vessels described
in the text. The four striated bodies which
lie next to this canal are the rudiments of
the four joints of the future limb. The striated
appearance arises from the muscles already so
far developed, and the albuminous matter
within, and which they enclose, appears to
be pabulum for their farther nourishment. The
more defined globules, which may be observed
floating amongst the albumen, are oil glo-
bules. In the developement of this leg, it
will be observed that the external segments,
or those which are analogous to the thigh
and first tibial joints, are largest, and most fully
formed, — a fact we would be led to expect, from
the circumstance of their formative cells being
the first thrown off from the original parent
nucleus, and consequently the first that would
take on a central or more independant action.
From a similar mode of developement, we see
that the second tibial and tarsal joints are the
smallest, as they are the last formed of the

DESCRIPTION OF THE PLATES.

centres. The last or distal phalanx is the small-
est of the internal segments ; those nearest the
circular vessel are the largest, as was to be ex-
pected from the centres which formed them, being
the oldest and the first formed from the earlier
generations of cells ; and those again within them
are smaller, being formed from the later genera-
tions thrown off by the original parent.
PLATE VI. Fig. 8. Cells from the external series represented by c

in Fig. 9.

Fig. 9. Transverse section of raw surface of proximal or
attached extremity of the reproductive organ in
leg of Cancer Pagurus. This is the surface and
appearance which is seen immediately upon the
leg falling off; if it is seen half an hour, or a
little more, after the separation, it is covered
with a thickish film, which shortly becomes a
strong opaque cicatrix hiding every thing be-
neath it. The vessels seen in Fig. 15 are
also omitted, for the purpose of showing the
structure of the reproductive body more clearly.

a Is the circular vessel, of the system of vessels
mentioned in the text, and it surrounds

b A fluid or semi-fluid mass, containing small nuc-
leated cells, from which the germ is probably
derived.

c c Is a large mass of very large cells surrounding
the circular vessel, which appear to act as a
magazine of nutritive matter for the young germ
during its growth.

d Is the shell membrane, which is surrounded exter-
nally by the shell.

Fig. 10. A young limb of Carcmus Mcenas still enclosed
within its original cyst, which is formed probably
from the cicatrix mentioned above. Magnified
two diameters.

Fig. 11. Is a very young leg of the common lobster. The
reproduced leg of this species is not enclosed in
a cyst, and it is not folded upon itself, but pro-
jects straight forward. Nat. size.

122 DESCRIPTION OF THE PLATES.

PLATE VI. Fig. 12. Is a figure of the natural size of one of the large
claws of Pagurus Bernhardus, shortly after it
has burst from its containing cyst.
Fig. 13. Enlarged view of Fig. 11.

Fig. 14. One of the large claws of Carcinus Mcenas still
enclosed within the eyst. From observations
made, it appears that these young legs remain
within the cyst until their own covering or shell
is of sufficient strength to act as a means of
defence. They do not obtain a true shell for
some time after the cyst has burst.

Fig. 15. Raw surface of proximal extremity of leg in Can-
cer Pagurus, shortly after the animal has thrown
off the distal portion. This figure is made for
the purpose of shewing the distribution of the
peculiar vessels, and their mode of running from
the circumference towards the circular vessel in
the centre.
Fig. 16. Longitudinal section of young leg still within the

cyst.
a a Part of old leg containing the reproductive

organ.
b I External cells.

c Smaller nucleated cells.
d d Cyst of young leg.
e Femur of young leg.
/ First tibial joint of young leg.
g Second tibial joint.
h Tarsal joint.

Fig. 17. Natural size of young leg.

Fig. 18. Portion of blind extremity of one of the peculiar
vessels which are attached to the blood-vessel
running to the leg, Plate ix. Fig. 14. The con-
tents are oil globules, but in the figure have
somewhat the appearance of nucleated cells.
Fig. 19. An enlarged view, for the purpose of showing

the connection of these vessels.
Fig. 20. Two of the blind extremities from raw surface of

leg, where they present a clavate appearance.
Fig. 21. View of the extremity, shewing the dark spot
supposed to be a germinal spot.

DESCRIPTION OF THE PLATES. 123

PLATE IX. Fig. 9. Small longitudinal portion of shell from the large
claw of Cancer Pagurus, showing the thickness of
the annulus or ring in it at the point of separation.
Fig. 12. Longitudinal section of one of the legs of Can-
cer PaguruSj shewing the natural position and
relations of the reproductive organ.
a a Femur.

b b Reproductive organ.
c Natural appearance of line of separation.
d Coxa.

Fig. 13. Enlarged foramen as it is seen on raw surface
after the separation. This has been hardened
in boiling water, which gives it a much more
defined appearance, and also enlarges it more
than it naturally should be.

Fig. 14. Is a small portion of the femoral artery, about
half an inch in extent beyond the line of separa-
tion, which is covered as represented bv the
peculiar vessels.
a Distal extremity of blood-vessel.

ON THE ANATOMY AND DEVELOPEMENT OF THE
CYSTIC ENTOZOA.

PLATE VII. Fig. 1. Magnified view of one of the young of Acephalo-
cystis armatus still attached to the germinal mem-
brane of a secondary parent. It is taken from
the group shewn in Fig. 2, and is still in an
early stage of developement, the circlet of teeth
still being minute and not fully developed. The
absorbing series of cells may be seen internally.
Fig. 2. Small portion of the germinal membrane of a
secondary parent of Acephalocystis armatus highly
magnified.

Fig. 3. Small portion of germinal membrane of Acepha-
locystis armatus in a state of degeneration ; no-

124 DESCRIPTION OF THE PLATES.

thing is seen in the membrane, which is quite

homogeneous, except the small cells figured a a.

b Is the commencement of one of the cretaceous

fatty masses described in the text.
PLATE VII. Fig. 4. Several of the stages of developement of Cys-

ticercus.

a First stage represents spines ; hardly if at all seen.
b Their first decided appearance.
c Third stage.
d Fourth stage.
Fig. 5. Small portion of the germinal membrane of

Acephalocystis armatus.
Fig. 6. Small portion, highly magnified, of the granular

matter from the cyst of Cysticercus.
Fig. 7. Small portion of the inner surface of the external
membrane of Acephalocystis armatus while in a
state of degeneration.

Fig. 8. Ovum from the pedicle of Cysticercus.
Fig. 9. Small portion of the germinal membrane of Ace-
phalocystis Monroii, highly magnified.
a a Fibrous basis.
b b Germinal vesicles.

c c Secondary acephalocysts within the germinal
vesicles ; this portion was taken from the large
parent cyst which is the primary animal, buried
in the liver ; and each of the smaller vesicles
marked c c c belong therefore to the secondary
generation, their progeny again being the tertiary
generation.

Fig. 10. Is a specimen of Cysticercus neglectus ruptured at
the fundus of the sac, apparently for the escape
of the young germs into the cavity of the cyst,
where they become attached.

Fig. 11. Small portion of the cyst of Cysticercus neglectus
magnified, shewing its vascularity, and the mode
of attachment of the young Cysticerci to its in-
ternal surface.

Fig. 12. View from above the pedicle of Cysticercus,
shewing the disposition of the teeth. In all
works hitherto published on Helmiuthology,

DESCRIPTION OF THE PLATES. 125

there has been a great want of proper figures or
descriptions of the true generic and specific
characters of these animals, a point of the
utmost importance for the obtaining of a proper
knowledge of them : with this view the Author
has paid scrupulous attention to the leading
characters, and these he has placed in the
form of a synopsis at the end of the Chap-
ter. All the drawings have been made with
the view of illustrating these characters more
fully. The disposition of the teeth, and their
forms, are perhaps the most certain external
characters.

PLATE VIII. Fig. 4. Magnified view of a small portion of the external
or tubular membrane of Diskostoma acephalocystis.

a Larger disc.

b Smaller one on its surface.

c Tubuli.

d Extremities of tubes.
e e Gemmules, which at this stage of developement

may act as absorbents.

Fig. 5. Natural size of Diskostoma acephalocystis.
Fig. 6. Diskostoma acephalocystis in various stages of

developement.

a a a Small cells arising from the attached surface of
the tubular membrane. This is the manner in
which the original group increases in size.

b More advanced.

c First stage of second mode of developement, or
that for the extending of the parasite to as yet
uninfested parts of the body, for the purpose of
forming new groups.

d Second stage.

e Third stage.

/ Root where the original germ became fixed.

g External or tubular membrane.

Fig. 10. Section of Astoma acephalocystis, showing its in-
ternal structure.

PLATE IX. Fig. 1. Portion of sac of cysticercus, much magnified.
a a Absorbing cells of absorbing membrane.

126 DESCRIPTION OF THE PLATES.

b b Separate ova, after their escape from the pedicle.
Fig. 2. Cysticercus negkctas very much magnified.
Fig. 3. Small portion of omentum containing Cysticercus
neglectus, showing the bodies considered young
Cysticerci attached, the omentum has been folded
over, and the young are seen attached to the
fold.
Fig. 4. The natural size of the animal supposed to be a

new Caenurus. Ccenurus hepaticus.

Fig. 5. Magnified view of the head of Acephalocystis arma-
tus in a more advanced stage than the former
figure.

Fig. 6. The germinal membrane from which it was taken.
Fig. 7. The absorbing membrane of cyst of Cysticercus

Rattus highly magnified.

Fig. 8. Teeth of Cysticercus Rattus highly magnified.
Fig. 10. Ovum of Cysticercus Rattus highly magnified.
Fig. 11. Ova from pedicle of Cysticercus Rattus highly mag-
nified.
PLATE III. Fig. 8. Gymnorhynchus horridus within its cyst.

Fig. 9. exposed.

Fig. 10. First stage of Ccenurus cerebralis.
Figs. 11, 12, 13, 14, Second, third, fourth, and fifth stages
of the discoidal period of developement of Cce-
nurus cerebralis.

Fig. 15. One of the first stages in the vertical period of de-
velopement.

Fig. 16. Sphairidion acephalocystis highly magnified.
Fig. 7. Neuronaia Monroii. (J. Groodsir.)
a Suctorial mouth.
b Acetabulum.

c Orifice of organs, supposed to be reproductive.
d Posterior orifice, by which the sigmoidal " cistern a

chyli,"

e Opens, and apparently also,
/ The thick walled peculiar sac.
g Pyriform sac, a receptacle for the ova.
/ Male organs.

The figure also presents the arrangement of the
dermal spines, and the general form of the animal.

DESCRIPTION OF THE PLATES. 127

PLATE VIII. Fig. 2. The anterior extremity and suctorial mouth of

Neuronaia Monroii more highly magnified.
Fig. 7. The cyst of Neuronaia Monroii in a bundle of ner-
vous filaments. The fissured appearance of the
cyst, with its epithelia, are represented in this
drawing.

I am inclined to believe that the function of
the cyst in this and the other Cystic Entozoa is
to supply nourishment to the enclosed animal,
drawing it from the surrounding parts, and
throwing it into the cavity, the structure and
action being identical with that in the encysted
tumours, as already described.

The bulbous extremities of the cysts of Tri-
china spiralis contain masses of germinating cells,
to which I am inclined to attribute the same
function.

Fig. 8, 9, 11. The clavate extremities of the cysts of Tri-
china spiralis, with their germinating absorbent
cells.

The epithelium and absorbent cells of the
cysts of the entozoa may be considered as per-
manent yelk-cells, in the economy of these per-
sistent embryoes.

Figs. 1, and 3. Magnified drawings of Sarcena Ventriculi
described, but badly figured by me in the Edin-
burgh Medical and Surgical Journal, No. 151.
I am still of opinion, notwithstanding the argu-
ments of Mr. Busk, in the Microscopical Journal,
that this body is a vegetable parasite, its sudden
occurrence and sudden disappearance being
not more extraordinary than the rapid develope-
ment of many cellular structures ; the glandular
epithelium, for instance, during secretion. That
it is a Gonium, as has been suspected by
Professor Link, appears to me improbable, as
would be admitted, I believe, by that great
botanist, if he had had an opportunity of ob-
serving its peculiar vegetable aspect, so dif-
ferent from that of an infusorial animal.

ERRATA.

Page 11, line 30 — for febril, read fibril.
Page 14, line 21 — for obsorbent, read absorbent.
Page 17, line 3 — for accessary, read accessory.
Page 52, line 24 — for rotation, read relation.

PL. I

PL. n.

PL. in.

PL. W.

PL. T.

PL. VI

PL. YIt

PL.VIII.

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IN THE PRESS.

A SYSTEM OF DISSECTIONS,

B Y JOHN GOODS I ft. •

' ANATOMY IX TIIK VXTVKKSITY »L' I.DIM! •, ' IN .),'.

Tiiis Work will appear in Parts, each of which will be complete in
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