(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Elements of histology"

COLUMBIA LIBRARIES OFFSITE 

HEALTH SCIENCES STANDARD 



HX00025402 




LIBkmki 



OF THE 



ASSOCIATION 



fFlli ALUMNI I 




OF THE 



OF THE 




OLLEGE 



OF 



ICIANS AND 
SURGEONS 



!N THE 



CITY OF NEW YORK 



SCHOOL OF MEDICINE OF COLUMBIA UNIVERSITY 



C^^^o^x 



THE 

LIBRARY 



V'?*'^ 



OF THE 



ASSOCIATION 




OF THE 



ALUMNI 



OF THE 




COLLEGE 



OF 



PHYSICIANS AND 
SURGEONS 



IN THE 



CITY OF NEW YORK 



SCHOOL OF MEDICINE OF COLUMBIA UNIVERSITY 



Digitized by the Internet Archive 

in 2010 with funding from 
Columbia University Libraries 



http://www.archive.org/details/elementsofhistolOOklei 



MANUALS 



Students of Medicine 



HIS T'©*'®'&«. 



BY 

E. KLEIN, M.D., F.R.S. 

LECTURER ON GENERAL ANATOMY AND PHYSIOLOGY 
AND 

J. S. EDKINS, M.A., MB. 

JOINT LECTURER AND DEMONSTRATOR OF PHYSIOLOGY IN THE MEDICAL 
SCHOOL OF ST. BARTHOLOMEW'S HOSPITAL, LONDON 



WITH 296 ILLUSTRATIONS 



REVISED AND ENLARGED EDITION 




LEA BROTHERS & CO., 

PHILADELPHIA AND NEW YORK, 



Co tl&f fHfmorg 

OF 

SIR WILLIAM BOWMAN, LL.D., F.R.S., 

THIS BOOK IS DEDICATED, 

IN ACKNOWLEDGMENT OP HIS MANY AND GREAT DISCOVERIES 

IN ANATOMY AND PHYSIOLOGY. 



PREFACE TO THE 
REVISED AND ENLARGED EDITION. 



Since the last edition of this book in 1889, consider- 
able additions have been made to the knowledge of 
minute structural anatomy. The progress in the 
knowledge of the structure and life of the cell and 
nucleus, the remarkable discoveries in the structure 
of the central nervous system and sense organs 
— introduced bv the method of Golo-i, and followed 
up by the brilliant work of Ramon y Cajal, Kolliker, 
Lenhossek, Retzius, and others — have made it neces- 
sary to revise and to make considerable additions 
to the chapters dealing with these organs. While 
care has been taken to correct and amplify other 
jmrts of the book, the chapters on the central nervous 
system have been practically rewritten. 

The task of rewriting and re-editing the chapters 
on the brain and medulhx and on the alimentarv 
canal has devolved upon my colleague Dr. Edkins, 
who is now associated with me as joint-author. 

While a large number of the illustrations of the 
former edition have been retained, a considerable 
number has been added ; these are either original 
photograms prepared by Mr. Norman from Dr. 
Edkins's and my own speciiiiens, or they are copied 
from Kolliker's " Handbuch," from Ramon y Cajal, 
from Schiifer (Quain's " Anatomy "), from Halli- 
burton (Kirke's " Physiology "), and from Klein and 
Noble Smith's " Atlas of Histoloijv." To our colleague 
Dr. Tooth our special thanks are due for the loan of 
some of the lantern slides illustrating the medulla. 

E. KLEIN. 

St, B.uiTHOLOMEw's Hospital, 
LONDOX. — 1S98. 



COXTENTS. 



CHAPTER 

I.— Cells . , . . . 

II.— Blood 

III. — Epithelium .... 
IV. — Endothelium .... 
V, — Fibrous Connective Tissues 

VI. — Cartilage 

VII.- Bone 

VIII. — Xon-strii:)ed Muscular Tissue . 
IX. — fStriped Muscular Tissue . 
X.— The Heart and Blood-Vessels . 
XI. — The Lymjjhatic Vessels 
XII. — Follicles or Simple Lymph Glands 
XIII.— Compound Lymphatic Glands . 
XIV. — Nerve Fibres .... 
XV. — Peripheral Xerve-Endings 
XVI.— The Spinal Cord 

XVII.— The Medulla Oblongata or Spinal Bulb 
XVJII. — Continuation of the Medulla Oblongata throu^ 
Pons Varolii and the Region of the Crura 
XIX. — The Cerebrum and Cerebellum 
XX. — The Cerebro-Spinal Ganglia 
XXI. — The Sympathetic System 
XXII. — General Considerations as to the Anatomical Con 
stitution and Nature of the Nervous System 

XXIII. -The Teeth 

XXIV.— The Salivary Glands 

XXV.— The Moutli. Pharynx, and Tongue . 
XXVI. — The (Esophagus and Stomach .... 



h the 



PAGE 

1 

19 

30 

40 

46 

63 

68 

86 

90 

10.5 

117 

126 

134 

140 

155 

170 

202 

216 
235 
253 

2.58 

268 
275 
286 
298 
307 



xu 



Elements of Histology. 



. " CHAPTJER PAOE 

XKVIL— The Small and Large Intestine .... 317 

XXTIIL — The Glands of -Brunner andthe Pancreas . . 328 

XXIX.— The Liver 333 

XXX.— The Organs of Respiration 3.30 

XXXI.— The Spleen 3-51 

XXXII.— The Kidney. L'reter and Bladder . 356 

XXXIIL— The Male Genital Organs 372 

XXXIV.— The Female Genital Organs . . . .386 

XXXV.— The Mammary Gland 400 

XXXVI.— The Skin 404 

XXXVII.— The Coniuuctiva and its Glands . . .424 

XXXVIII. — Cornea, Sclerotic, Ligamentum Pectinatnrn 

and Ciliary Muscle 429 

XXXIX. — Iris, Ciliary Processes and Choroid . 436 

XL.-— The Lens and Vitreous Body ... 442 

XLI. -The Retina 44.5 

XLIL— The Outer and Middle Ear .... 4-58 

XLIIL— The Internal Ear . . \. . 460 

XLIV. — The Xasal Mucous Membrane .... 47-") 

XLV.— The Ductless Glands 484 



jprnpfrtn o( l\ft 

^sjuciaiimi uf i^e ^^lumni of t^e 

CoUtgc of I^DS. & iurgs.. gfto fork, 

Elements of Histology. 



CHAPTER I. 



CELLS. 



1. The ripe oviiiii (Fig. 1) of man and mammals 
is a minute spherical mass of a soft, gelatinous, trans- 
parent, granular-looking substance, containing nume- 
rous minute particles — yolk 
globules. It is invested by 
a radially striated delicate 
membrane called the zona 
pellucida. Inside this mass, 
and situated more or less 
excentrically, is a vesicle — 
the germinal vesicle — and 
inside this, one or more 
solid spots — the germinal 
spot or spots. The gela- 
tinous transparent substance 
of the ovum, containing a 

very large percentage of proteid material, is called 
protoplasm. Before and immediately after fertilisa- 
tion, the protoplasm of the ovum shoAv^s distinct 
movement, consisting in contraction and expansion. 
These movements are spontaneous — i.e. not caused 
by any directly visible external influence. 

The diameter of the ripe ovum in man and do- 
mestic animals varies between ^^^ and y^^ of an 
inch. But before it ripens the ovum is considerably 




V--^-c 



Fig. 1. — Ripe Ovum of Cat. 

a, Zona pellucida ; h, gerniinal 
vesicle; c, protoplasm. 



2 Elements of Histology. 

smaller — in fact, its size is in proportion to its 
state of develo])ment. 

2. Fertilisation causes marked changes in the 
contractions of the protoplasm of the ovum ; these 




Fig. 2.— From a Section through the Blastoderm of Chick, unincubated. 

a Cells foimiui,' ilie ectoderm ; b, cells forming the endoaerm ; c, larue 

formative cells ; /, segmentation cavity. {Handooolc.) 

lead to cleavage or division of its body into two jiarts, 
the germinal vesicle having previously split up into 
two bodies or nuclei ; so that we now find the ovum 

/ 




Fig. 3.— From a Section through the Rudiment of the Embryo Chick, 



e, rrimitive groove ; /, dorsal laminae of epihlast : d, raesoblast. The 
thin layer of spindle-shaped cells is the hypoblast. (.Handbook.) 

has originated two new elements, each of which 
consists of protoplasm, of the same substance as that 
of the original ovum, and each contains one nucleus 
or kernel. ; The investment of the ovum rakes no 



Cells, 



part ill this process of division. Not long afterwards, 
each of the two daughter elements undergoes cleavage 




Fig. 4.— Vertical Section tlirough the Ovum of Bufo Cinereiis, in the early 
stage of the Embryo Development. 

a, Tegmental layer of epiblast ; 6, dorsal groove ; c, rudiiuent of central nervous 
system ; d, notochord ; e, deep layer of epiblast ; /, mesoblast ; g, hypoblast ; 
ft, cavity of alimentary canal— Rusconi's cavity ; h, central yolk ; A:, remainder 
of von Baer's or segmentation cavity. ^Handbook.) 

or division into two new elements, the nucleus having 
previously divided into two, so that each new 
offspring possesses its own nucleus. This process 
of division is continued in the same manner for 



4 Elements of Histology. 

many generations (Figs. 2, 3, 4), so that after a 
few davs we find within the orioinal investment of 
the ovum a large number of minute elements, each 
consisting of protoplasm, and each containing a 
nucleus. 

3. From these elements, which become smaller as 
the process of cleavage progresses, all parts and organs 
of the embryo and its membranes are formed. It can 
be easily shown that the individual elements possess 
the power of contractility. Either spontaneously or 
under the influence of moderate heat, electricity, 
mechanical or chemical stimulation, they throw out 
processes and withdraw them again, their substance 
flowing slowly but perceptibly along. Hence they 
can change their position. In this respect they com- 
pletely resemble those lowest organisms which are 
known as amceb?e, each of these being likewise a 
nucleated mass of protoplasm. Wherefore this move- 
ment is termed amoeboid movement. It can be further 
shown that they, like amoeb?e, grow in size and divide 
■ — that is to say, the individuals of a generation grow 
in size l^efore each gives rise to two new daughter 
individuals. 

4. Although for some time during embryonic life 
the elements constituting the organs of the embryo are 
possessed of these characters, a time arrives when 
only a limited number of them retain the power of 
contractility in any marked degree. At birth only the 
white corpuscles of the blood and lymph, many of the 
elements of the lymphatic organs, and the muscular 
tissues, possess this power; while the others lose it, 
or at any rate do not show it except when dividing 
into two new elements. Some of these elements 
retain their protoplasmic basis ; as a rule, each con- 
tains one nucleus (but some two or more), and is 
capable of giving origin by division to a new genera- 
tion. Others, however, change their nature altogether, 



Cells. 5 

their protoplasm and nucleus disappear, and tliey 
give origin to material other than protopLism — e.g. 
collagenous, osseous, elastic, and other suljstances. 
As develojiment proceeds, and after birth of the 
fa3tus, different cells assume different functions, which 
for each kind are of a special character and constitute 
its specific character or its specific junction. 

5. Beginning with the ovum, and ending with the 
protoplasmic nucleated elements found constituting 
the organs and tissues of the embryo and adult, we 
have, then, one uninterrupted series of generations of 




Fig. 5. — Amoeboid iiioveinent of a Wliite Blood Corpuscle of Man ; various 
phases of nioveiiient. (Handbook.) 

elements, which with Schwann we call cells and with 
Briicke elementary organisms. Of these it can be said 
that not only is each of them derived from a cell 
(Virchow : omnis cellula a cellula), but each consists 
of the protoplasm of Max Schultze (sarcode of Dujar- 
din), is without any investing membrane, and includes 
generally one nucleus, but may contain two or more. 
We can further say that each of these cells shows the 
phenomenon of growth, which presupposes nutrition 
and reproduction. A.11 of them in an early stage of 
their life-history, and some of them throughout it, show 
the phenomenon of contractility, or amoeboid move- 
ment (Fig. 5). 

In a recent work, and following the procedure of 
V. Sachs on the life and activity of vegetable cells, v. 
KoUiker systematises and summarises those of animal 
cells thus : The protoplasm and nucleus constituting 



6 Elements of Histology. 

a vegetable cell is called by v. Sachs an energid; in 
the animal body it is represented by a nucleated 
protoplasmic cell without a cellulose membrane, and 
is called by v. Kolliker a protohlast (germinal matter 
of Beale). All protoblasts, as also all energids, are 
always derived from parent protoblasts ; they always 
propagate by division, and in this manner carry on 
the race from generation to generation ; they are the 
instruments of heredity. 

All growth of the protoblasts takes place by 
internal processes — that is, by intussusception. 

The active work of protoblasts consists in : («) 
formation of the typical organs ; (6) special move- 
ments of the protoplasDi — e.g. amoeboid movement ; 
(c) the formation of alloplasmatic organs (A. Meyer). 
These latter are derived from the livmg protoplasm, 
are organised, and are participating themselves in the 
living functions, but they are not capable of multipli- 
cation by division. Such alloplasmatic organs are : 
cilia, muscular fibres, nerve cells and nerve tibres, and 
the terminal cells in the sense organs, {d) The pro- 
duction of passive, partly non-organised, ergastic 
structures (A. Meyer), or formed matter (L. Beale) ; 
such are the cellulose membranes of vegetable cells, 
cuticular formations, fluids, and intercellular and 
other substances (collagenous, chondrinous, osseous, 
elastic, dental, etc.), cell-juices and granules of all 
kinds. 

Cells ditfer in shape according to kind, locality, 
and function, being spherical, irregular, polygonal, 
squamous, branched, spindle-shaped, cylindrical, pris- 
matic, or conical. These various shapes will be more 
fully described when dealing in detail with the various 
kinds of cells. Cells in man and mammals differ in 
size within considerable limits : from the size of a 
small white blood corpuscle of about tt/ou ^^ '"^"^ "^*^^^ 
to that of a laroe ganglion cell in the anterior horns of 



Cells. 



the spinal cord of about ^.^o of 'ii^ inch, or to that of 
multinucleated cells of the bone marrow — myeloplax — 
some of which suri)ass in size even the ganglion cells. 
The same holds good of the nucleus. Between the 
nucleus of a ganglion cell of about ^\-^ to yaVo ^^ ^^ 
inch in diameter and the nucleus of a white blood 
corpuscle of about -goVo ^^ tit wo ^^ ^^^ inch and less 
there are all intermediate sizes. 

6. Pi-otoplasiii or cytoplasm is a transparent 
homogeneous or granular-looking substance. On very 
careful examin- 
ation with good 
and high powers, 
and especially 
^vhen examined 
with c e r t a i n 
reagents, in 
many, but not 
in all, instances 
it shows a more 
or less definite 
structure (Fig. 
6), composed of 
fibrils, more or 
less regular, and 
in some instances grouped into a honeycomhed re- 
ticulum, sjyongioplasm, in the meshes of which is 
a homogeneous substance, /njaloplasm (Leydig). 
The closer the meshes of the reticulum, the less 
there is of this interstitial substance, and the 
more regularly granular does the reticulum appear. 
In the meshes of the reticulum, however, may be 
included larger or smaller granules of fat, pigment, 
or other material. Water makes protoplasm swell 
up and ultimately this becomes disintegrated ; so also 
act dilute acids and alkalies. All substances that 
coagulate proteids have the same effect on protoplasm. 




Fig. 6. — Anictboid pale leucocyte of the newt, 
showing the nuclei embedded in the cell proto- 
Ijlasni— this latter consisting of spongioplasm 
and hyaloplasm. (After Scho/er.) 



8 



Elements of Histology. 



In arrangement of its elements the spongioplasm 
ditfers in different cells ; while in some — e.g. spheroidal 
or cubical ej^ithelial cells — it is as a rule uniform ; in 
columnar cells it is elongated in the direction of the 
long axis of the cell, hence the reticulum appears as 
an eminently longitudinally fibrillated substance ; in 
ganglion cells it is concentrically arranged. In some 




Fig. 7. — Cell with radially disposed reticulum from the intestinal epithelium 
of a worm. (After Carnoy, from Quain's "Anatomy.") 

mc. Cell iiiembraiie ; j)c, cell protoplasm ; mn, nuclear membrane ; pn, nuclear 
achromatin surrounding the convoluted chromatin filaments bn. 

cells in the outer portion the spongioplasm possesses a 
different arrangement from that in the middle portion, 
and then a division is made between ectoplasm and 
endoplasni (Fig. 7). The hyaloplasm differs in amount 
in different cells, and in the same kind of cells it 
varies according to different states of cell activity. 
Thus in gland cells during activity the amount of 
hyaloplasm is increased, containing in these instances 
more or less of jjranular matter. 



Cells. 



In amceboid cells, such as the white corpuscles of 
the blood, the hyaloplasm is the substance in which 
the spontaneous or amoeboid changes and movement 
are principally lodged, as has been shown by instan- 
taneous electric illumination by Strieker. 

In the protoplasm of many cells are lodged 
granules of various kinds, microsomes ; they differ in 
size, shape, colour, and chemical nature, and are, as a 
rule, the result of cell activity. Such are the zymo- 
gen granules in secreting gland cells ; eosinophil e, 
basopliile, and neutrophile or amphophile granules 
in leucocytes ; glycogen granules in the liver cells, 
cartilage cells, and leucocytes ; pigment granules in 
various kinds of jDigmented cells ; fat granules and 
fat globules in wandering cells, in connective-tissue 
cells, in liver cells, in 
the epithelial cells of 
the milk gland, etc. It 
is not justifiable to as- 
sume with Altmann that 
these microsomes or bio- 
blasts are living entities 
in the sense that the 
whole cell is. 

In the cell proto- 
plasm of leucocytes, of 
epithelial and other cells, 
certain granules and 
fibrils have been de- 
scribed by Flemming, 
Boveri, Heidenhain, and 
others, which being of 
a constant and definite 

nature play an important part in the division of the 
cell and its nucleus. This is the centrosome, and with 
its radiating fibrillse forms the attractionsjyJiere (Fig. 8). 
The centrosome is a granule surrounded by a hyaline 




Fig. 8.— Leucocyte of Salamandra con- 
taining two nuclei, and showing the 
attractionsphere : the centrosome is 
already divided into two. (After Dr. 
Martin Heidenhain.) 



ro 



Elements of IIistologv. 



spherical space ; through this pass the fibrillse radi- 
ating from the former, aod connect it with the 
spongioplasm of the cell body. The whole — Le 




// ' ' -»— ^-^^-i '— — '^^ 



Fig. 9. — Blastomeres of Bi-segmented 0\-um of Ascaris megalocephala 
{Ajter Boveri,from Kdllik'jr, I.) 

A : a, Attractionsphere ; v, nucleus in resting- state ; B : nucleus in stage 
of convolution: c, attractionsphere nearly divided; D, attract ionsphere 
divided: E. attractionspheres arranged at the poles, chx-omosomes forming 
tiiC eauaiorial plate. 



centrosome and radiating tibrilhe — represents the 
attractionsphere. Preceding the division of the 
cell nucleus, the centrosome divides into two, 
each daughter centrosome, with its own hyaline 
areola and system of radiating fibrillar, forming 
by - and - by a separate attractionsphere, which 



Cells. i i 

migrating towards op})Ositc pules of the cell- 
Itody become separate jjoints of attraction for the 
divided nuclear mitoma. [See division of nucleus.) So 
that the division of the attractionsphere would be 
the tirst, the division of the nucleus the second, and 
the division of the cell protoplasm the third and final 
stage in the division of a cell (Fig. 9). 

7. The iiiicleiis, the size of which is generally in 
proportion to that of the cell, is usually spherical or 
oval. It is composed of a more or less distinct invest- 
ing cuticle and the nuclear contents ; the former is 
tlie membrane, the latter the nuclear substance, karyo- 
plasm, or nucleoplasm. This, again, is composed, in 
adult nuclei, of a stroma or network, mitoma, and the 
inter-Jibrillar suhsta^ice. The network consists of 
tibrils of various thickness, and trabecular or septa 
more or less irregular in thickness and length. In- 
timately connected with and lodged in the network 
are anijular or rounded masses called nucleoli. The 
number and size of these vary considerably ; in 
young nuclei they may be large and numerous, in 
adult or resting nuclei they are few, and in those 
about to divide they are altogether absent. Also the 
network is subject to great variation : while in adult 
or resting nuclei^ and particularly those about to 
divide, the network is of great uniformity and well 
developed ; it may be very imperfect in young nuclei, 
in which it is sometimes represented by a number of 
irregular masses joined by short bridges. The more 
perfect the nuclear network, the fewer are the nucleoli. 
Owing to the ready manner in which the fibrils of the 
nuclear network, i.e. the mitoma, take up certain dyes, 
their substance is called chromatin, and the fibrils 
are the chromosomes ; while the inter-tibrillar sub- 
stance not possessed of this character is called 
achromatin. Occasionally, also, the achromatin ap- 
pears composed of fibrils, and these are then called 



1 2 Elements of Histology. 

secondary fibrils, as distinct from tlie chromosomes or 
})rimary fibrils. Rabl and with him Heidenhain 
maintain, however, that the achromatin in typical 
adult nuclei is ahvays composed of tine fibrils, and 
that both the chromatin and achromatin fibrils possess 
a definite unipolar arrangement and convergence, 
while Carnoy and van Gehuchten assume a bipolar 
arrangement. But this distinction holds good only 
for adult nuclei ; in young nuclei the whole nuclear 
contents may possess this aflinity for the same dyes, 
and in this case the whole nucleus becomes uniformly 
stained. The nuclear membrane is a condensed outer 
stratum of the nuclear network. At the commence- 
ment of the division of the nucleus the membrane 
disappears. 

In some instances it can be shown that the 
nuclear filjrils are in continuity with the fibrils of the 
cell substance. In the moving white blood corpuscles 
Strieker and linger have seen the nucleus becoming 
one with the cell substance, and again afterwards 
diti'erentiated by the apjDearance of a membrane. 

8. During: division of the cell the nucleus 
generally divides before the cell i)rotoplasm. This 
division of the nucleus was formerly supj)osed to 
occur in the same manner as that of the cell proto- 
plasm — i.e. by simple cleavage. This mode is called 
the direct or amitotic division, or Remak's mode of 
division. In this division the nucleus is supposed to 
become constricted, kidney-shaped and hourglass- 
shaped and, if the division is into more than two, 
lobed. Nuclei of these shapes are not uncommon ; 
but they need not necessarily indicate direct division, 
because, being very soft structures, pressure exerted 
from outside, or the motion of the cell protoplasm, 
may produce these shapes ; and, further, the contrac- 
tility of the nucleus may, and occasionally has been 
observed to, cause these changes of shape. From the 



Cells. 



^3 



ol>s('r\ations of Schneider, Biitschli, Folil, Strass- 
burgor, Mayzel, van Beiieden, Schleicher, Fleniiiiing, 
liabl, and others, it is known that in the embryo and 
adult, in vertebrates and invertebrates, in all kinds of 
cells, both in the noi'nial as well as morbid condition, the 
division of the cell protoplasm is preceded by complex 
changes of the nuclear mitoma, leading to the division 
of the nucleus (Fig. 10). The sum-total of these 




Fig. 10. — Karyoinitosis. 
A, Ordinary nucleus of a columiiar opitlieli.al cell : b, c, the same nucleus in the 
stage of convolution ; D. the wreath, or rosette form; e, the aster, or single 
star; F, a nuclear spindle from the Desceiin't's endothelium of the frog's 
Cornea; G, H, I, diaster ; k, two daughter nuclei. 

changes is called indirect division, karyokinesis 
(Schleicher) or karyomitosis "^ (Flemming). Where 
this process occurs in its complete and typical form, 
the mitoma passes through the following phases 
(Flemming, Rabl) : — 

i. — Convolution or spireme or shein ; disappearance 
of the nucleoli, increase of the fibrils constituting the 

* Schleicher noticed that the fibrils duriuo; this process show 
movemeut ; hence the name Karyokinesis. Mitosis indicates the 
r- . grouping and changes of the fibrils (MtTos = fibril). 



14 Elements of Histology. 

chromatic substance, at the same time the fibrils 
become free, as it were, and bent and twisted at first 
into a dense, afterwards into a loose convolution. 
The fibrils of the loose convolution are thicker than 
before, less twisted, and more like masses of loops. 



/ 



"> c 



t 



^ ^If 



^?\r'.4\:^ 






'^^^ ■- .^^^'r>' 



^ 



(" 



Fig. 11. — Eiiithclium of iiiouth of einbiyo salamander, showing nuclei in 
various stages of karyomitosis (Flemming). 

These latter Ijy cross division along the periphery of 
the mass increase in number, and thereby are con- 
verted into simple loops, arranged more or less like a 
wreath or rosette. The whole nucleus is larger than 
before, its membrane has disappeared, and it is sur- 
rounded by a more or less clear halo of cell proto- 
plasm (Fig. 11). 

ii. — Longitudinal division of the loops, each loop 
giving origin to a pair of sister loops; the whole, 
viewed from the surface, looks like a star of numerous 
fine fibrils, joined centrally so as to form single loops. 



Cells. 



15 



iii. — The nuclear sjnndle^ a spindle shaped ar- 
rangement of tine threads of (possibly) achromatin 
extending between two opposite points of the cell 
protoplasm ; these points are the poles, and the 
transverse line midway between them — i.e. at the 













c 

Fig. 12. — Karyomitosis. {Ajter KolUker.) 

A, Spireme ; b, diasier; c, ilie nucleus lias divuled, cUe prucoi'lasiu of the cell 
In tbe act. of dividing. 

broadest part of the spindle — is called the equator. 
At each pole the threads of the spindle are connected 
with a granule of the cell protoplasm, tlie pole cor- 
puscle or centrosome, mentioned on a previous pa^-e ; 
from the centrosome radiate numerous fine fibrillar, 
connecting the centrosome or pole corpuscle with the 
cell protoplasm, thus forming " the suns " or attraction- 
spheres, one at each pole (van Beneden). 

The above-named sister loops so arrange themselves 
about the equator of the spindle as to form a star — 
the motJier-star, monaster, or aster. In this arrange- 
ment the vertex of the loops is directed inwards, the 
open limbs outwards. Seen in profile the aster would 
appear like a narrow granular - looking plate of 
chromosomes — the nuclear plate. 

iv. — Metakinesis : Of each pair of sister loops form- 
ing the aster one loop is attracted by — i.e. migrates 



1 6 Elements of Histology. 

towards one, tLe otlier towards the other pole of the 
spindle: that is, towards the attractionspheres, the 
vertex of the loops always leading. 

V. — Diaster : arrived at tlie pole, the loops form 
again an aster or daughter star for each pole (Fig. 12). 

\i. — Dispireme : the threads of each star become 
convoluted. 

ZS^ow follows usually the division of the cell proto- 
plasm in the line of the equator of the spindle. 

vii. — In the last phase all traces of the spindle are 
lost : a membrane appears around each of the two 
new nuclei, and the threads of the dispireme become 
branched and connected into a network. 

From the forecjoin^; it is clear that during division 
an intimate fusion Vjetween cell protoplasm and 
nucleus takes place : («) by the fusion of the nuclear 
interstitial suVjstance with the cell protoplasm after 
the disappearance of the nuclear membrane ; and (h) 
bv the connection of the nuclear spindle with the 
centrosomes and attractionspheres, the fibrils of the 
latter being part of the cell protoplasm. 

It ought to be mentioned, however, that some 
histolo^ists do not rec;ard the fibrils of the nuclear 
Spindle as part of and derived from the original 
nuclear substance (achromatin). Boveri regards the 
fibrils of the spindle as derived from the cell proto- 
plasm and as forming part of the attractionspheres 
— i.e. those fiVjrils which remain connecting the two 
attractionspheres, and which finally, after the nuclear 
division has Ijeen completed, by their transverse 
division, mark off and initiate the final stage — that is, 
the division of the cell body. 

While these various details and phases in the 
changes and division of the centrosome and attrac- 
tionsphere are well enough marked in the ovum, as is 
also their relation to the chromosomes of the dividing 
ovum nucleus, it is not sufficiently established that 



Cells. i 7 

the above are of general occurrence in the division of 
adult cells; the attractionsphere and its division have 
])een observed only in a few such instances — e.g. in 
the leucocytes of salamander and man. 

In some cases the process of karyomitosis has Vjeen 
found to be atypical, inasmuch as some of the above 
phases are left out, as it were ; while in other cases 
the nuclear division takes place already during the 
earlier phases — e.g. in the phase of the spireme. 
When the nucleus divides into two or three or more 
nuclei without the cell protoplasm also undergoing 
division, a cell with two, three, or more nuclei is the 
result. 

Multiplication of the nucleus by budding and 
direct fission has also been observed, but it is quite 
possible that this process is only as a sort of imper- 
fect and abnormal karyomitosis. 

This mode [)robably jDlays a more important part 
than the typical karyomitosis, whenever rapid multi- 
plication and rei^roduction are necessary. Thus, for 
instance, while in the epithelium cells covering the 
anterior surface of the normal cornea of the newt and 
frog here and there a nucleus can Ije seen which 
shows the process of typical karyomitosis, such forms 
cannot be found in cases of rapid regeneration of 
that epithelium. For example, after removing the 
whole thickness of the anterior epithelium from the 
middle part of the cornea, rapid multiplication of the 
epithelium cells takes place, starting from those 
immediately around the defect ; in consequence of 
this, in two or three days the defect becomes again 
quite covered with the new epithelium. Xow, ex- 
amining the epithelium cells at the margin of the 
defect, as well as those gradually pushed over and 
covering the defect, none of the nuclei are found in 
any of the phases of typical karyomitosis ; while a 
few days later, after the defect is covered by the new 
c 



1 8 Elements of Histology. 

epithelium, there is no difficulty in finding nuclei in 
one or another ])lia.se of the typical kar3"omito.sis. 

Paranuclei and cell enclosures, — It was 

mentioned above that cells may and do include in 
their j^rotoplasm formed substances like granules 
of various kinds, fat globules, pigment, etc. ; but in 
addition to these, and distinct from the attraction- 
spheres mentioned on a former page, occasionally the 
cell substance includes corpuscles of an altogether 
different nature. These corpuscles, in size and staining 
power, resemble the cell nucleus or parts thereof, and 
as a matter of fact are derived from the cell nucleus. 
Balbiani has called such bodies in the ovum cell 
'paranuclei^ and Griitzner has applied the same term 
to those that occur in the gland cells of the pancreas. 
Now it is a fact that preceding the segmentation 
of the ovum, and preceding the fusion of the sperm- 
and ovum-pronucleus, part of this latter is eliminated, 
and the same occasionally is observed to take place 
in other cells prior to the division of the nucleus, 
as also under various pathological conditions. The 
eliminated body or bodies, known as polar bodies, 
are part of the original nuclear substance, principally 
the chromatin. The paranucleus is as a rule smaller 
than the cell nucleus, lies close to this, and has 
similar affinit}'' to the dyes which stain the nucleus 
itself. 



19 



CHAPTER IT. 

BLOOD. 

9. Under the microscope blood appears as a 
transparent Huid, the liquor sanguinis or plasina, in 
which float vast numl^ers of formed bodies, the blood 
corpuscles. The great majority of these are coloured ; 
a few of them are colourless. The latter are called 
ivhite or colourless blood corpuscles, or leucocytes ; the 
former are called red or coloured blood coryuscles, or 
blood-discs. They appear red only when seen in a 
thick layer ; when in a single layer they appear of 
a yellow-greenish colour, more yellow if of arterial, 
more green if of venous, blood. The proportions of 
plasma and blood corpuscles are sixty-four of the 
former and thirty-six of the latter in one hundred 
volumes of blood. By measurement it has been found 
that there are a little over five millions of blood cor- 
puscles in each cubic millimetre {y-^^o^y of ^ cubic 
inch) of human blood. There appears to be in healthy 
human blood, on an average, one white corpuscle for 
600-1200 red ones. In man and mammals the re- 
lative number of blood corpuscles is greater than 
in birds, and in birds greater than in lower verte- 
brates. 

The number of red, and also of white, corpuscles 
is subject to variation, both in health and disease. 
After profuse haemorrhage, the number of red cor- 
puscles is temporarily greatly reduced, but in a short 
time, it may be even in twenty-four to forty-eight 
hours, they may approach again the normal number ; 



2o Elemexts of Histology. 

in constitutional chronic diseases the number of red 
corpuscles is, as a rale, decreased ; so also in anj^mia, 
spontaneous or following acute infectious diseases, 
fevers, etc. The number of white corpuscles is always 
greater after a copious meal than during fasting. 
Certain diseases are associated with a decrease, others 
wi.th an increase, of the white corpuscles of the cir- 
culating blood ; the decrease when pronounced is 
spoken of as leucopenia^ the increase as leucocy- 
th(emia^ leucctmia, or leucocytosis. 

10. The red blood corpuscles (Fig. 13) of man 
and mammals are homogeneous bi-concave discs (ex- 
cept in the camelida?, where they are elliptical), and 
do not possess any surroundmg membrane or nucleus. 
Being bi-concave in shape, they are thinner and 
more transparent in the centre than at the periphery. 
In other vertebrates they are oval, and more or 

less flattened from 
side to side, and each 
possesses a central 
oval nucleus. 

The diameter of 

Fig. 13. — ^arious kiuds of Red Blood i , i i i i 

Corpuscles. the human red blood 

A, Two human, one seen flat, the other COrpUScle is about 

edgeways ; b, a red corpuscle of the ■■ p " 1 ' 

camel; c, two red corpuscles of the solTo '^^^ mCll 111 

frog, one seen from the liroad, the \ ■\,\ ■ i , 

other from the narrow side. DreaCltn, I.e. aOOUt 

7 "8 ^. and its thick- 
ness about ^ ^QQQ of an inch. But there are always 
corpuscles present which are much smaller by about 
one-third to one-half than the others — microcytes. In 
normal blood these microcytes are scarce : but in 
certain abnormal conditions, especially in pernicious 
anfemia, they are conspicuous by their number. 

According to Gulliver, ^A'elcker, and others, tlie 
followinof are the averagfe diameters of the red blood 
corpuscles of various vertebrates : Man, -3-2V0 J ^^i 



08 



A 




"3 'sou ' ^"^j 4cFo^ y outc|7, 5 00^ } v.iv>^jii«.ij.v, :jTi 5" ^ 



1 • cat, ^ J^ ; sheep, ^^W i elephant, 



Blood. 



21 



horse, j:^ 
1 



\ . 

6 () O ' 

10 4 3 ; "ewt, 
1 

1 1 -t 2 • 
11 



musk deer, y^i^ 5 ; pigeon, ^g^y ; toad, 
proteus, yl^ ; pike, ^-qVo ; ^li^^i'k, 



1^ 

S 1 i 




In a microscopic specimen of fresh unaltered 
blood (Fig. 14) the red blood corpuscles form peculiar 
short or long rolls, like 
so many coins, from be- 
coming adherent to one 
another by their broad 
surfaces. Under various 
conditions — such as 
Avhen isolated, or when 
blood is diluted with a 
7*5-l p.c. saUne solution 
or solutions of other salts 
(sulphate of sodium or 
magnesium) — the cor- 
puscles lose their smooth ^• 
circular outline, shrink- 
ing and becoming crenate 
(Fig. 15, a). In a further 
lose their discoid form, and become 
spherical, but beset all over their sur- 
face with minute processes. This shape 
is called the liorse-chestnut shaj^e (Fig. 15, 
b, c). It is probably due to the cor- 
puscles losing carbonic acid, as the 
addition of the acid brings back their 
discoid shape and smooth circular out- 
line. On abstracting the carbonic acid 
they return to the horse-chestnut shaj)e. , 
Water, acid, alcohol, ether, the electric 
current, and many other reagents, 
produce decoloration of the red blood 



Fig. 14. — Human Blood, fresh. 

Piouleaux of red corpuscles ; b, iso- 
lated red fdrpuscle seen in pr<5flle ; c, 
isolated red corpuscle seen flat ; D, 
•ttliite corpuscles. 



stage 



of shrinking 
smaller 



they 
and 



a 

o o 



Fi 



h ^' 

15. — Human 
Red Blood 
Corpuscles. 

Crenate; b, c, 
horse-cbestnut- 
sliaped. 

corpuscles. 



the coloured matter — generally the combination of 
the blood-colouring matter with globulin, known 
as hcenioylohin — becoming dissolved in the plasma. 



2 2 Elements of Histology. 

What is left of the corpuscles is called the 
stroma. In ne^^i;'s and frog's blood a separation 
of the stroma from the nucleus and haemoglobin can 

be effected by means of 
^ ^ a'^ ^c^ boracic acid(Fig. 16, b); 

" Ai. ^i \^' ^8 ^F\ c ^^^^ former is called by 



O ^ {€^) Briicke the oekoid, the 



U^ B 



latter zooid. This stroma 
contains amongst other 

Fig. IG.— Red Blood Corpuscles of things mucll paraf'lobu- 
Man and Xewt. t mi j. c J.^ 

, ^ ^, . im. I he stroma or the 

A, Human red corpuscles after the action , i -i • 

of tannic acid; a, tbree red corpuscles, COrDUSCles Ot amplllljiaUS 
from which the hierauf^loliin is pass- . ■•■ •'• 

ing out: 5. Roberts's corpuscles. B, is scen, undcr Certain 

^ewt s red corpusdesafter theaction ' 

of boracic acid; a, corpuscle. show- reao^ents, to be of a re- 

mg Briicke s zooid and cekoid ;&,."' 

corpuscle showing the reticulated tlCUlated StrUCture, but 

stroma ; c, corpuscle showins the • ^ c i 

reticulum in the nucleus; d, thenu- ]n the fresh state appears 

cleus passing out. ^^ 

homogeneous and pale. 
Decoloration of the blood corpuscles can also be 
observed to take place in blood spontaneously without 
the addition of any reagents or with that of indifferent 
fluids, such as the aqueous humour of the eye, hydro- 
cele fluid, etc. The number of corpuscles undergoing 
decoloration under these conditions is, however, small, 

When blood is dried on a glass in a thin tilm, 
the corpuscles, forming a single layer onh", dr}^ on 
before they shrink, and thus retain their natural size 
and outline ; their strouia can then be easily stained 
with aniline dyes. 

12. The haeiiioglotoiii of the red blood cor- 
puscles forms crystals (Fig. 17), which differ in shape 
in various mammals. They are always of microscopic 
size, and of a bright red colour. In man and most 
mammals they are of the shape of prismatic needles 
or rhombic plates ; in the squirrel they are hexagonal 
plates, and in the guinea-pig they are tetrahedral or 
octahedral. 

The blood pigment itself is an amorphous dark- 



Blood. 



23 




brown or l)l;ick powder — the luematin ; but it can be 
obtained in a crystalline form, as liydrochlorate of 
hi\iinatin (Fig. 18). These crystals also are of micro- 
scopic size, of a 
nut-brown colour, 
of the shape of 
nari'ow rhombic 
plates, and are 
called lut^rnin cry- 
stals, or Teich- 
mann^s crystals. In 
extravasated hu- 
man blood, crystals 
of a bright yellow 
or orange colour 
are occasionally 
met with ; they are 
coverer, hctmatoidin. 
tical with bilirubin 
human bile. 

13. The white or colourless cor- 
puscles, or leucocytes, are in human 

blood of about 2-5 00 ^^ 2"5Vo *^^ ^^ ^^^^ 
in diameter — i e. about 10 fi — and are 
spherical in the circulating blood or in 
blood that has just been removed from the vessels. Their 
substance is transparent granular-looking protoplasm, 
some containing larger or smaller distinct granules. 
These granules are not all of the same nature, as 
will presently appear. In some kinds of blood, notably 
horse's, they are of a reddish colour, and these 
corpuscles were supposed by some observers (Semmer 
and Alexander Schmidt) to be intermediate between 
red and white corpuscles. The protoplasm of the 
colourless corpuscles contains occasionally glycogen 
(Ranvier, Schiifer). In the blood of the lower verte- 
brates the colourless corpuscles are much larger than 



Fig. 17. — Hitmoglobin crystals. 
A, Of guinea-pig ; b, of siiuirrel ; c, D, buiuan. 

called by Yirchow, their dis- 
They are supposed to be iden- 
obtainable from 




Fig. IS.— Ha-miii 
crystals. 



24 



Elements of Histology. 



in mammals. But in all cases tliey consist of proto- 
plasm (spongioplasm and hyaloplasm), include one, 
two, or more nuclei, and show amoeboid movement. 
This may he observed in corpuscles without any 
addition to a fresh microscopic specimen of blood, 
but it always becomes much more jironounced on 




Fig. 19. —Phagocyte (with three nuclei) from the iieritoneal fluid of a 
guinea-pig, iireviously injected intraperitoneally with cholera culture. 
The interior of the phagocyte contains numerous degenerated comma 
bacilli. (Photo, highly magnified.) 



applying artificial heat of about the degree of 
mammals' blood. It is then seen that either they 
throw out longer or shorter filamentous processes, 
which may gradually lengthen or be withdrawn, 
or the corpuscle changes its position either by a 
flowing movement, or it pushes out a filamentous pro- 
cess and shifts its body into it. During this move- 
ment the corpuscle may take up granules from the 



Blood. 25 

siuToiinding lluicl. Leucocytes, be they in the blood 
or in connective tissue or lymph glands {see below), 
that can, and in certain circumstances do, take up 
granules or similar matter are spoken of as phagocytes 
(eating cells) (Figs. 19, 20). Division by simple 



^ 




Fig. 20. — Hyaline Leucocytes (pus cells) from purulent matter ; the leuco- 
cytes contain in their hyaline protoplasm two, three, or more nuclei 
two of the cells contain in their protoplasm a number of cocci, these 
cells acting as phagocytes. {Photo, highly magnified.) 



cleavage of leucocytes of the blood of lower verte- 
brates has been directly observed by Klein and 
Ranvier. 

14. The white corpuscles or leucocytes in the 
same sample of blood differ in size and aspect. They 
may be classed into three groups : (a) The li/m2)hocyte, 



2 6 Elements of Histology. 

a small cell possessed of a relatively large single nucleus 
surrounded by a narrow zone of protoj^lasm. (6) The 
typical leucocyte or liyaline leucocyte is larger than the 
former, contains two, three, or even four relatively 
small nuclei ; its cell protoplasm appears hyaline, 
but includes a spongy network. This leucocyte is 




Fig. "21. — Frog's Blood, showing red blood discs and one oxypliile white 
cell. (Photo, highly magnified.) 

as regards numbers by far the predominating white 
corpuscle, and its amceboid movement is very striking, 
(c) The gramdar leucocyte forms a small minority, it 
contains a single large nucleus, occasionally two, and 
its cell })rotoplasm contains conspicuous granules. 

The lymphocytes are identical with similar cor- 
puscles of the adenoid tissue of lymph glands, from 



Blood. 27 

Nvliicli ill all probability they are derived. It is highly 
probable that they are young forms of the typical 
leucocytes. The grnnidar leucocytes — i.e. the white 
corpuscles that contain real gi'anules — behave dif- 
ferently when subjected to staining with aniline dyes. 
In some the granules stain readily with acid aniline 
dyes — e.g. eosin — so that they become bright red — 
eosinophile (Ehrlich) or o.vi/phile cells (Fig. 21); in 
others the granules stain only in basic aniline dyes 
— hasopJi He cells ; in still others they stain both with 
acid and alkaline aniline dyes — neutrophile or amjjho- 
phile. "What the exact relation of these different 
granule-cells amongst themselves and to the non- 
granular or hyaline cells is, is not definitely established. 
But it appears from the researches of Kanthack and 
Hardy that in the frog, at any rate, and probably also 
in the mammal, the oxyphile or eosinophile leucocyte 
does not act as a phagocyte, and that this function is mo- 
nopolised by the other or hyaline variety of leucocytes. 
15. In every microscopic specimen of the blood 
of man and mammals are found a variable number 
of large granules, more or less angular, 
singly or in groups. According to f^ 
Max Schultze they are derivatives of e^\ 

broken-up white corpuscles ; but ac- ^S ^^ 
cording to Bizzozero, they are present ^ 

al read}' in the living and fresh blood, © o^ 

as pale, circular, or sliijhtly oval „. ,., „ 

T-i- ->-» 7\ rr<i • • • FiLT. 22.— Human 

discs (Fig. 22, 0). Their size is only ^ Biooti. 
1 to i of that of the red blood cor- «. R^d bino.i cor- 
puscles. They are called bv him bhod platelets of biz- 

■•■ •' "^ zdzero. 

platelets^ and he supposes them to be of 
essential importance in the coagulation of the blood, 
originating the tibrin ferment. Hayem described them 
previously as being intermediate forms in the de- 
velopment of red blood corpuscles, and called them 
hjematoplasts, 



2 8 Elements of Histology. 

16. Development of blood eorpiii^cles. — 

At an early stage of embryonic Jife, when blood makes 
its appearance it is a colourless fluid, containing only 
white corpuscles (each with a nucleus), which are de- 
rived from certain cells of the mesoblast. These white 
corpuscles change into red ones ; the protoplasm 
becomes homogeneous and yellow ; then it assumes a 
flattened shape, and is in reality a coloured blood 
corpuscle containing a pale nucleus. All through 
embryonic life new white corpuscles are transformed 
into red ones. In the embryo of man and mammals 
these red corpuscles contain their nuclei for some 
time, but ultimately lose them. Xew red blood cor- 
puscles may, however, be formed also by division of 
nucleated red corpuscles. Such dis'ision has been 
observed even in adult blood of lower vertebrates 
(Peremeschko) as well as in the foetus of mammals. 

The cells of the mesoblast which cHve origin to 
vessels (cysts and strands) are capable of producing 
by budding and cleavage new white cells, which ulti- 
mately change into red corpuscles. (*See formation of 
blood-vessels.) 

An important source for the new formation of red 
corpuscles in the embryo and adult is the red marrow 
of bones (Neumann, Bizzozero, E-indfleisch), in whicli 
numerous nucleated protoplasmic cells (marrow cells) 
are converted into nucleated red blood corpuscles — 
erythrohlasts. The protoplasm of the corpuscle 
becomes homogeneous and tinged with yellow, the 
nucleus being ultimately lost. The spleen is also 
assumed to be a place for the formation of red blood 
corpuscles. Again, it is assumed that ordinary white 
blood corpuscles are transformed into red ones, but of 
this there is no conclusive evidence. In all these 
instances the protoplasm becomes homogeneous and 
filled with liEemoglobin, while the cell grows flattened, 
discoid, and the nucleus in the end disappears. 



Blood. 29 

Schiifer described intracellular (endogenous) for- 
mation of red blood corpuscles at first as small liH;mo- 
i;lobin particles, but soon growing into red blood cor- 
puscles in certain cells of the subcutaneous tissue of 
young animals. Malassez describes the red blood cor- 
puscles originating by a process of continued budding 
f I'om the marrow cells. 

The white corpuscles appear to be derived from 
the lymphatic organs, whence they are carried by the 
lymph into the circulating blood. 



CHAPTER III. 

EPITHELIUM. 

17. Epitlielial cells (Fig. 23)are nuchated proto- 

2)Io.srnic cells for ming co/dinuoas masses on the surface 
of the skin, of the lining membrane of the alimentary 
canal, the respiratory organs, the urinary and genital 
organs, the free sui'face of the conjunctiva, and the 
anterior surface of the cornea. The lining of the 
tubes and alveoli of secretin^ and excretinoj slands, 
such as the kidney, liver, mammary gland, testis and 
ovary, the salivary glands, mucous, peptic, and 
Lieberkiihn's glands, the sweat and sebaceous glands, 
the hair follicles, etc., consists of epithelial cells. 
Such is the case also with the sensory or terminal 
parts of the organs of the special senses. And, 
finally, epithelial cells occur in other organs, such as 
the thyroid, the pituitary body, etc. 

The bail's and nails, the cuticle of the skin, 
certain parts of the rods and cones of the retina, and 
the rods of Corti in the organ of hearing, are modified 
epithelial structures. 

Epithelial cells are grouped together by ex- 
ceedingly thin layers of an albuminous interstitial 
cement substance, which duiing life is of a semi- 
fluid nature, and belongs to the gi'oup of bodies 
known as globulins. 

18. As rec:ards shape, we distinguish two kinds 
of epithelial cells — columnar and squamous. The 
columnar cells are short or long, cylindrical or pris- 
matic, pyramidal, conical, club-shaped, pear-shaped, 



Epithelium. 



31 



or spindle-shaped ; their nucleus is always more or 
less oval, their protoplasm more or less longitudinally^ 
striated, l)eing a spongy reticulum with predominantly 



longitudinal arrange- 
ment. On the free 
surface of the cells 
— i.e. the part facing 
or 
-in 
a 
or 



r 



f^=f~ 



a cavity, canal, 
general surface - 
many instances 
Ijright thinner 
thicker cuticular 
structure is seen, 
with more or less 
distinct vertical stri- 
ation. The conical 
or spindle - shaped, 
club - shaped, and 
pear-shaped cells are 
drawn out into 
longer or shorter 
single or branched 
extremities. 

The squamous or 
polyhedral or scalj 









Fig. 23.— Various kinds of Epithelial Cells. 

A, Columnar cells of intestine; b. polyhedral 
cells of the conjunctiva; c, ciliated conical 
cells of the trachea ; d, ciliated cell of 
frog's mouth ; E. inverted conical cell of 
trachea; f, squainous cell of the cavity of 
inouth, seen from its broad surface ; G, 
squamous cell, seen edgeways. 



pavement cells are cubical. 
The nucleus of the former is 
almost spherical, that of the latter flattened in pro- 
portion to the thinness of the scales. In polyhedral 
cells it can be shown that the uniform granulation is 
due to the regular honeycombed nature of the cell 
protoplasm. 

19. As regards size, the epithelial cells dilfer 
considerably from one another in different parts, and 
even in the same part. Thus, the columnar cells, 
covering the surface of the ^^Ili of the small intestine, 
are consideraljly longer than tho.se lining the mucous 
membrane of the uterus : the columnar cells lining 
the larger ducts of the kidney are considerably longer 



z^ 



Elements of Histology. 






- Three Mucus-secreting 
Goblet Cells. 

A, From the jitomach of newt ; B, from 
a mucous glaml; c, from tbe sur- 
face of the mucous membrane of 
the intestine. 



regards ar- 



than tliose lining the small ducts ; the polyhedral 
cells covering the anterior surface of the cornea are 
considerably smaller than those on the surface of the 
lining membrane of the urinary bladder ; the scales 
lining the ultimate recesses of the bronchial tubes — 

the air cells — are con- 
siderably smaller than 
those on the surface of 
the membrane lining the 
human oral cavity and 
oesophagus (Fig, 24). 

20. As 
raiig:eiiieiit, the epithe- 
lial cells are arranged 
as a sinfjle layer or are 
stratified, forming several 
superposed layers ; in the 
former case we have a sin^le-lavered, in the latter a 
stratified epithelium. The simple epithelium may be 
composed of squamous cells, simjyle squamous or simple 
jjavement epitJiellum ; or it may be composed of columnar 
cells, siinple coliLinnar epithelium. The stratified epithe- 
lium may be stratified pavement or stratified columnar ; 
in the former case all or the majority of the layers 
consist of squamous or polyhedral cells; in the latter 
all cells belong to the columnar kind. Simple 
squamous epithelium is that whicli lines the air cells, 
certain urinary tubules of the kidney (the looped 
tubes of Henle, the cortical parts of the collecting 
tubes), the acini of the milk-gland, the inner surface 
of the iris and choroid membrane of the eyeball. 
Simple columnar epithelium is that on the inner 
surface of the stomach, small and large intestine, 
uterus, small bronchi, ducts and acini of mucous and 
salivary glands, of some kidney tubules, etc. Stratified 
pavement epnthelium is that on the epidermis, the 
epithelium lining the cavity of the mouth, pharynx, 



Epithelium. 33 

and oesophagus in man and mammals, the anterior 
surface of tlie cornea, etc. 

Functionally, epithelium can be classified as : (a) 
tegmental — p.y. tlie epidermis of the skin, the epithe- 
lium of mucous membrane ; (6) as secretory — e.g. the 
epithelium lining tlie alveoli and tubes of secreting 
glands, the liver, the kidney, etc.; (c) sensory — e.g. the 
epithelial-like cells forming the terminal organs of 
nerve fibres — e.g. in the retina, in the organ of hearing 
(cochlea, vestibule, and semicircular canals of the 
internal ear), in the taste buds, in the olfactory 
membrane, and in the skin; (':/) forming special horny 
organs — e.g. hairs, nails, the horny papillae on the tongue 
of feline animals ; [e) some specific, not well-understood 
function — e.g. the epithelium covering the glomeruli 
of the Malpighian corpuscles of the kidney, the 
epithelium (or endothelium) forming the wall of blood- 
capillaries and lymph vessels. 

•Jl. The epidermis (Fig. 25) consists of the 
following layers : — («) Stratum corneum : this is the 
superficial horny layer, and it consists of several 
layers of horny scales, without any nucleus. Its 
layers are separated from one another by narrow 
clefts containing air, and they are in process of des- 
quamation. This stratum is thickest on the palm 
of the hand and fingers and the sole of the foot. 
(6) The stratum lucidum, composed of several dense 
layers of horny scales, in which traces of an ex- 
ceedingly flattened nucleus may be perceived, 
(c) Then follow many layers of nucleated cells, 
forming the stratum or rete Malpighii or rete 
mucosum. The most superficial layer or layers of it 
are flattened scales, which are characterised by the 
presence around the nucleus of globular or elliptical 
granules of the nature intermediate between pro- 
toplasm and keratin. Their substance is called 
eleidin by Ranvier, keratohyalin by Waldeyer ; these 

D 



34 



Elements of Histology, 



cells 
bans. 



form the stratura granulosum of ^cv^.^ 



DeejDer down, the cells are 




Fi-. 25. 



a. The st 
c, the 



— From a Vertical Section tlirougli the 
Epidermis. {Atlas.) 

ratum Malpiirhii ; h. tlie Ptratuiu ,trranulo>iiiii ; 
stratum luciduiii ; d, the stratum corneum. 



Laiiger- 
less flattened 
and more 
polyhed r al , 
and the deepest 
form a layer of 
more or less 
columnar cells, 
placed verti- 
cally on the 
surface of the 
subjacent co- 
rium. 

The sub- 
stance of the 
hairs, nails, 
claws, hoofs, 
consists of 



horny scales. 




{See chapter on Skin.) 
22. The 
pavement 
liiiiii (Fig. 



Fig. 26. — From a Vertical Section 
tliroiigh the anterior layers of tlie 
Cornea. (Handbook.) 

a. The stratified pavement eiiithelium; 
b, the substantia propria, with the 
corneal corpuscles between its la- 
melht. 



Stratified 
epitlie- 

26) lining 
the cavity of the mouth, 
the surface of the tongue, 
the pharynx and oeso- 
phagus of man and mam- 
mals, and the anterior 
surface of the cornea, 
etc., is, as regards tlie 
style and arrangement 
of the cells, identical 
with the stratum Mal- 
pighii of the epidermis. 
The cell protoplasm is 
more transparent in the 
former, and the granular 
cells of the stratum 



Epithelium. 



35 



granulosum are not always present, but they generally 
are in the e})itheliiini of the tongue and of the rest 
of the oral ca^•ity. The most superficial scales show 
more or less horny transformation. 

23. Stratified roliiiiiiiai' €>|>itiic'iiiini is met 
with on the lining Hi('iiil)iane of the respiratory 
organs : in the larynx, trachea, and large bronchi. 
It consists of several layers of columnar cells ; a 
superficial layer of conical or prismatic cells, with a 
more or less pointed extremity directed towards the 
depth ; between these are inserted spindle-shaped 
cells, and finally inverted conical cells. 

The epithelium of the ureter and bladder is called 
transitional epitheUum. It is stratified, and the most 
superficial layer consists of j^olyhedral cells. Under- 
neath this is a layer of club-shaped cells, between 
which extend one or more layers of small spindle- 
shaped cells. 

Amongst the columnar epithelial cells occurring in 
man and mammals the ciliated cells and the gohlet 
cells, and amongst the squamous cells the jirickle cells, 
deserve special notice. 

24. Ciliated cells are characterised by possess- 
ing a bundle of very fine longer or shorter hairs or 
cilia on their free surface. These cilia are direct 
prolongations of the cell protoplasm. More correctly 
speaking, the cilia are continuous with the filaments 
or striye of the cell protoplasm. The superficial 
layer of conical cells of the epithelium in the respira- 
tory organs, the columnar cells lining the uterur, and 
oviduct, and the columnar cells lining the tubes of 
the epididymis, possess such cilia. In lower verte- 
brates the ciliated cells are much more frequently 
observed ; in Batrachia the epithelial cells lining the 
mouth, pharynx, and (esophagus are ciliated. 

While fresh in contact with the membrane which 
they line, or even after removal from it, provided the 



36 Elements of Histology. 

cells are still alive, the ciliated cells show a rapid 
synchronous whip-like movement of their cilia, the 
cilia of all cells moving in the same direction. The 
movement ceases on the death of the cell, but may 
become slower and may cease owing to other causes 
than death, such as coagulation of mucus on the 
surface, want of sufficient oxygen, presence of car- 
bonic acid, low temperature, etc. In these circum- 
stances, removal of the impediment, as by dilute 
alkalies, wdll generall}^ restore the activity of the 
cilia. Moderate electric currents and heat stimu- 
late the movement, strong electric currents and cold 
retard it. Reagents fatally affecting cell protoplasm 
also stop permanently the ciliary action. 

25. CjJoblet or clialice cells (Figs. 24, 27) are 

cells of the shape of a conical cup. The pointed part 

is directed away from the free surface, and contains a 

compressed triangular nucleus surrounded by a trace 

of protoplasm. The body of the 

=^="^-='^-%nn goblet contains mucus. This latter 

P|'| -P< £' ^ -^' - J ^i"*^! ^^ ^^ various states of for- 

^llim^^^ mation, and may at any time be 

Fig. 27.— From a Ver- poured out of the cell. Goblet 

tical Section throucrh n , i j. •-! 

the Epithelium on cclls are most commonlv met with 
the surface of the amon^jst the epithelium lining the 

mucous membrane . ^ ^ , , ^ ^ 

of the large intes- respiratory Organs, the surface 01 
^'"^* the stomach and intestines, and 

Three goblet cells are • n • i t • 

seenpourin^'oiit their especiallv HI mucous glands, m 

luucus. TliG r6st urt* "^ . . 

ordinary coiiuunar whose secretiuo- portion all cells 

cells. ® '- 

are goblet cells. 
The protoplasm of columnar cells facing a free 
surface, no matter whether in simple or stratified 
epithelium, ciliated or non-ciliated, may undergo 
such alteration as will lead to the transformation of 
the cell into a mucus-secretinfj goblet cell. This 
takes place during life, and corresjDonds to an im- 
portant function of columnar ejDithelial cells — viz. 



Epithelium. 37 

the formation of iniicus. In mucus-secreting glands 
all the epithelial cells have this function permanently, 
but in ordinary columnar epithelium only a compara- 
tively small number of the cells, as a rule, undergo 
this change, and then only temporarily : for a cell 
subject to it at one time may shorth^ afterwards 
resume the original shape and aspect of an ordinary 
protoplasmic, cylindrical, or conical epithelial cell, 
and vice versa. If ciliyted cells undergo this change, 
the cilia are generally first detached. 

It can be shown that in this change of an 
ordinary columnar epithelial cell into a goblet cell 
the interstitial substance of the cell reticulum swells 
up and increases in amount, the meshes enlarging and 
distending the body of the cell. The middle and 
upper part of the cells then change, tirst into 
mucigen, and hnally into mucin, which is eventually 
discharged, leaving in the deeper part the compressed 
nucleus surrounded by a trace of protoplasm behind 
(see Fig. 34). 

2G. Prickle cells (Fig. 25). — Amongst the 
middle and deeper la3^ers of the stratified pavement 
epithelium, such as is present in the epidermis and 
on the surface of the oral cavity and pharynx, we 
meet with a close, more or less distinct and regular 
striation, extending from the margin of one cell to 
that of each of its neighbours, by means of fine 
transverse short fibrils which, passing from proto- 
plasm to ])rotoplasm, connect the surfaces of the cells. 

27. Pigmented epithelial cells — i.e. epithelial cells 
filled with black pigment pai'ticles (crystals) — are 
found on the internal surface of the choroid and 
iris of the eyeball. 

In coloured skins, and in coloured patches of skin 
and mucous membrane, such as occur in man and 
animals, pigment in the shape of dark granules is found 
in the protoplasm of the deeper epithelial cells, as well 



38 Elements of Histology. 

as in branched cells situated between the epithelial 
cells of the deeper layers. Minute branched non- 
pig mented nucleated cells are met with in the 
interstitial or cement substance of various kinds of 
epithelium, simple and stratified — e.g. epidermis, 
epithelium of oral cavit}', cornea, etc. 

28. Epitlielial cells undergo division, and by this 
means a constant regeneration takes place. In those 
parts where the loss of the superficial layers of cells is 
conspicuous, such as the epidermis, the stratified epi- 
thelium of the tongue and oral cavity, the sebaceous 
follicles of hairs, the regeneration goes on more 
copiously than at places where no such conspicuous 
loss occurs — as, for instance, in the stomach and in- 
testines, the secreting glands, or sense organs. 

In the stratified pavement epithelium it is the 
cells of the deepest layers which chiefly divide. As 
a rule, this division takes place transversely in the 
cylindrical cells, but may also occur longitudinally (A. 
Kollmann). The epithelial cells next to the deepest 
layer of columnar cells are to a great extent the result 
of the division of the latter, and as this proceeds there 
is a orradual shiftino; of the older cells towards the 
surface and a simultaneous flattening of the cell 
protoplasm as well as the nucleus. 

29. The interstitial substance between, and the 
protoplasm of, the epithelial cells being a soft flexible 
material, the cells can change their shape and arrange- 
ment owing to pressure exerted on them by the con- 
traction or distension of the subjacent membrane. 
Thus the epithelium lining a middle-sized bronchus 
at one time apjDears composed of thin columnar cells 
in two layers ; at another, as a single layer ; or again, 
as a single layer of short columnar cells : in the first 
case the bronchus ig contracted, in the second in a 
medium state of distension, in the third much dis- 
tended. Similar changes may be noticed in the 



Epithelium. 39 

epithelium lining tlu^ bladder and the, stratum 
Malpighii. 

The interstitial substance, being a soft, semi-fluid 
substance, represents the paths through whicli granules 
and formed particles may find their way from the free 
surface into the membrane beneath, or vice versa. 
Also leucocytes pass out in certain localities from the 
membrane underneath, between and into the sul)stance 
of epithelial cells, and may Anally be discharged on to 
the free surface — e.g. in the tonsils, in the fauces and 
pharynx and larynx. Epithelial cells may in this way 
include in tlieir substance various formed particles : 
granules, fat globules, leucocytes, nuclei of leucocytes, 
etc. Besides these cell enclosures and the paranuclei 
and chromatin granules mentioned in a former para- 
graph, in some localities [e.g. stratum Malpighii of the 
ef)idermis, epithelium of the oral cavity, pharynx and 
oesophagus) the epithelial cell substance undergoes 
a partial or total change into keratinous substance, 
keratohyalin, forming a mantle around the unchanged 
cell j)rotoplasm like a capsule. 



40 



CHAPTER lY 



ENDOTHELIUM. 




30. The free surfaces of the serous and synovial 
membranes, and of those of the brain and spinal 
cord, the posterior surface of the cornea and anterior 
surface of the iris, the surfaces of tendon and tendon- 
sheaths, the lymph sinuses or lymph sacs of amphibian 
animals, the cavity of the heart, of blood-vessels 
and of lymphatic vessels, are lined with a continuous 
endothelial membrane, composed of 
a single layer of flattened trans- 
jjarent squamous cells, called endo- 
thelial cells (Fig. 28). Each 
contains an oval nucleus, situated 
as a rule excentrically. Just as in 
Fig 28 -Endothelium the case of epithelium, " the endo- 

of the Mesentery of ■,■,•■> n i ■ • 

Cat. thelial cell plates are joined by a 

The outlines of the endo- fluid or semi-fluid liomoifeneous in- 

thehal cells and tlie • • 7 7 

nucleus of the latter terstitiat or Cement substance or the 

are well shown. „ , , , . 

nature oi globulin. \\ hen examin- 
ing any of the above structures fresh, the endothelial 
cells are not, as a rule, visible, owing to their great 
transparency; but by staining the structures with a 
dilute solution of nitrate of silver, and then exposing 
them to the influence of the light, the cement sub- 
stance appears stained black, whereby the shape and 
size of the cell plates become e^■ident. By various 
dyes also the nucleus of each cell plate may be brought 
into view. 

On careful examination, and with suitable re- 
agents, it can be shown that each endothelial cell 



En DO THELIUM. 



41 



consists of a homogeneous ground 'plate. Tii it lies 
tlie nucleus, and around it is a sul)staiicf* which ap- 
pears granular, but ^vhich is of a fibrillar nature, the 
fibril he being arranged in a network, and extending 




Fig. 20.— Network of Lymphatics in the Central Teudon of the Diaphragm 
of Rabbit, prepared with nitrate of silver, so as to show the outlines of 
the Endothelial Cells formiug the wall of the Lymphatics. {Handbook.) 

a. Large I^-mphatic vessels; b, Ivinphatic capillaries ; c, apparent ends of the 

capillaries. 



in many places up to the margin of the ground 
plate. The nucleus is limited by a membrane, and 
contains a well-developed reticulum. The tibrillje of 
the cell substance appear to be connected with the 
nuclear reticulum. 

31. As regards shape, endothelial cells differ 
considerably. Those of the pleura, pericardium, peri- 
toneum, and endocardium of man and mammals are 



42 



Elemexts of Histology. 



more or less polygonal, or slightly elongated. Their 
outlines vary ; in the lining of the lymph sacs of the 
frog they are much larger, and of very sinuous out- 
line ; while those of the posterior surface of the cornea 




Fig. 30. — Onientum of Rabbit, stained with Nitrate of Silver. {Atlo.s.) 
(I. Ordiuaiy flat endothelial cells ; b, germinating cells. 



are very regular, pentagonal, or hexagonal, ha^^Ilg 
straight outlines in the perfectly normal and well-pre- 
served condition, but serrated and sinuous after they 
have been prepared with various reagents and in the 
abnormal state ; the endothelial plates lining the blood- 
vessels and lymphatic vessels (Fig. 29) are narrow 
and elongated, with more or less sinuous outlines. In 
the lymphatic capillaries the endothelial plates are 
polygonal, but their outline is serrated. 

32. As a rule, the endothelial cells are flattened — - 



Endothelium. 



4: 



i.e. scaly — but in some places they are polyhedral, 
or even short columnar. Such cells occur isolated or 
in small gi'oups, or covering large and small patches, 
nodular, \illous, or cord-like structures of the pleura 




Fig. 31.— Part of Peritoneal Surface of the Central Tendon of Diaphragm of 
Rabbit, prepared with Nitrate of Silver. (Handbook.) 

s, StoniRta; Z, lymph-channe!s ; f, tendon Inindles. The surface is covered witli 
endothelium.' The stomata are surrounded by geruunatiug endi)thelial cells. 



and omentum, on the synovial membranes, tunica 
vaginalis, testis, etc. They are especially observable 
in considerable numbers in the pleura and omentum 
(Fig. 30) of all normal subjects (in man, ape, dog, cat, 
and rodent animals) ; their number and frequency of 
occurrence are increased in pathological conditions 
(chronic inflammations, tuberculosis, cancer, etc.). 

These endothelial cells are tlie germinating endo- 
thelial cells, and they can be shown to be in an 



44 



Elements of Histology. 



active state of division. They thus produce small 
spherical lymphoid (amoeboid) cells, which ultimately 
are absorbed by the lymphatics, and carried into the 
blood system as white 1)1 ood corjiuscles. On the 




Fi.£ 



-Part of Omentum of Cat, stained with Nitrate of Silver. 



a, Feuestraj or holes ; />, tianecultB covert-a witli emloilielium. Ouiy tiie outliues 
(silver lines) of the endothelial cells are shown. 



surface of the serous membranes, especially the 
diaphragm (Fig. 31) and pleura, there exist minute 
openings, stomata, leading from the serous cavity into 
a lymphatic vessel of the serous membrane. These 
stomata are often lined by germinating cells. 

33. In the frog, germinating cells occur in great 
abundance on the mesogastrium and the part of the 
peritoneum which separates the ])eritoneal cavity 
from the cisterna lymphatica magna. This part of 



Endothelium. 45 

the peritoneum is called the septum cisternae lym- 
phaticji? magnsB, and on it occur numerous holes or 
stomata, by which a free communication is established 
between the two cavities. On the peritoneal surface 
of this septum the stomata are often bordered by 
germinating cells. In th(^ female frog, these and 
other germinating endothelial cells of the peritoneum 
(mesogastrium, mesenterium, septum cisternee) are 
ciliated. 

34. The omentum and parts of the pleura are, in 
the adult human subject, ape, dog, cat, guinea-pig, rat, 
etc., of the nature of di. fenestrated membrane {¥\g. 32), 
bands of fibrous tissue of various sizes dividing and 
reuniting, and leaving between them larger or smaller 
holes, in shape oblong or circular. These holes or 
fenestras are not covered with anything, the endo- 
thelial cells adhering only to the surfaces of the 
bands without bridging over the fenestrse. On the 
peritoneal surface of the diaphragm the endothelial 
cells possess a different arrangement from that on 
the pleural side ; on the former surface a number of 
lymph channels (that is, clefts between the bundles 
of tendon and muscle) radiate towards the middle of 
the central tendon. The endothelium of the free 
surface over these lymph channels is composed of 
much smaller cells than at the places between, so 
that the endothelium of the peritoneal surface of the 
diaphragm shows numbers of radiating streaks of 
small endothelial cells. Many of these small cells 
are not flattened, but polyhedral, and of the nature 
of germinating cells (Fig. 31). The above-mentioned 
stomata occur amongst these small endothelial cells. 



46 



CHAPTER Y. 

FIBROUS CONNECTIVE TISSUES. 

35. By the name of " connective tissues " we 
designate a variety of tissues which have in common 
with one another, that they are developed from the 
same embryonic elements ; that they all serve as sup- 
porting tissue or connecting substance, for nervous, 
muscular, glandular, and vascular tissues ; that they 
are capable of taking one another's place in the 
different classes of animals ; that in the embryo and 
in the growing normal and morbid condition one may 
be changed into the other ; that in the adult they 
gradually shade off one into the other ; and that they 
yield allied chemical products. 

Connective tissues are divided into the three great 
groups of (1) fibrous connective tissue; (2) cartilage; 
(3) bone, to which may be added dentine. Each of 
these is subdivided into several varieties, as will 
appear farther on ; but in all instances the ground 
substance, or matrix, or intercellular substance, is to 
be distinguished from tJie cells. In the fibrous con- 
nective tissue the matrix yields collagen or gelatin, 
and the cells are called connective-tissue cells, or con- 
nective-tissue corpuscles. In the cartilage the ground 
substance yields chonclrin, and the cells are called 
cartilage cells. In the third group the ground sub- 
stance contains inorganic lime salts, intimately con- 
nected with a fibrous matrix, and the cells are called 
hone cells. 

36. The fibrous coiiiiertivc tissue, or white 
fibrous tissue, occurs in the skin and mucous 



Fibrous Connective Tissues. 



Al 



membranes, in tlie serous and synovial membranes, 
in tlie membranes of the brain and spinal cord, in 
tendons and tendon sheaths, in fascite and aponeuroses, 
in the intermuscuhir tissue, and in the tissue con- 
nectino; neiirhbourim'- organs, etc. It consists of 
microscopic band-like or cylindrical bundles or fasciculi 
of exceedingly tine homogeiuous tinrils (Fig. 33), which 




Fig. 33. — Plexus of Bundles of Fibrous Tissue from the Oiuentuiu of Rat. 

«, Capillary blood-v'cSi'cl ; ^, lumiilc:^ nr Hijidhs tissue ; c tue oouuectivc-tiiiu.: 
foi'iuiscles; c/, i)lasiii i ceils. {Atlas.) 

are known as the elementary connective-tissue fibrils. 
According to the number of these the bundles differ 
in size. The bundles, and also their constituent 
fibrils, may be of very great length — several inches. 
Where the fibrous tissue forms continuous masses — 
as in tendon, fascia, aponeurosis, skin, and mucous 
membrane — the microscoj)ic bundles are aggregated 
into smaller or larger groups, the trabeciilce., and these 
are again associated into groups. The fibrils are held 
together by an albuminous (globulin), semi-fluid, 
homogeneous cement substance^ which is also present 
between the bundles forming a trabecula. 



48 Elements of Histology. 

The groups of bundles, and even the individual 
bundles, are in some localities invested with an elastic 
sheath — e.g. in the trabeculae of bundles in the 
subcutaneous tissue. 

On addincj an acid or an alkali to a bundle of 
fibrous tissue, it is seen to swell up and to become 
glassy-looking, homogeneous, and gelatinous. Sub- 
jected to boiling in water, or to digestion by dilute 
acids, the bundles of tibrous tissue vield collacjen or 
gelatin. 

37. According to the arrangement of the bundles, 
the fibrous connective tissue varies in ditierent locali- 
ties. (1) In tendons and fasciae the bundles are 
arranged j^arallel to one another. (2) In the true 
skin and mucous, serous, and synovial membranes, in 
the dura mater and tendon sheaths, the trabeculse of 
bundles divide repeatedly, cross and interlace very 
intimately with one another, so that thereby a dense 
felt-work is produced. (3) In the subcutaneous, sub- 
mucous, or subserous tissue, in the intermuscular 
tissue, in the tissue connecting with one another 
different organs or parts of the same organ — i.e. inter- 
stitial connective tissue— the texture of the tibrous 
tissue is more or less loose, the trabecul^e dividing and 
reuniting and crossing one another, but leaving between 
them larger or smaller spaces, celluhe or areola?, so 
that the tissue assumes the character of a loose 
plexus, which is sometimes called " areolar " or " cel- 
lular tissue." Such tissue can be more or less easily 
separated into larger or smaller lamelhie, or plates of 
trabecul^e. (4) In the omentum and parts of the 
pleura of man, ape, dog, cat, and some rodents, and 
in the subarachnoidal tissue of the spinal cord and 
brain, the trabecule form a fenestrated membrane, with 
larger or smaller oval or circular holes or fenestra?. 

38. The eoiiiiective -tissue cells or corpuscles 
occurring in white fibrous tissue are of several 



F/niwus C(hxXECTn'E T/ssu/:s. 



49 



varieties, {a) lii teiulon and faseiie tlie cells ai<' called 
tendon cells or tendon corpuscles ; they are flattened 




^-3^^ 



Fig. 34.— Tendon of Mouses Tail. (£. A. Schu/er.) 
a, Chains of tendon-celJ!? seen broadways ; b, the same in profile. 



nucleated protoplasmic cells of a square or oblong 
shape (Fig. 34), forming continuous rows (single files), 
situated on the 
surface of groups 
of bundles of 
fibrous tissue. 
Between these 
groups are wider 
or narrower 
channels, the in- 
t erf CISC i culn r 
lymph spaces, 
running parallel 
with the long 
axis of the ten- 
don (Fig. 35). 
The cells in each 
row are separ- 
ated from one 
another by a nar- 
row line of allju- 

minous cement substance, and the round nucleus of 
the cell is generally situated at one end, in such a 




Fig. 3.J. — From a Transveix- Section through the 
Tendons of tlie Tail of a Mouse, stained with 
gold chloride. {Handbook.) 

Several fine tendons are shown here. The darfe 
branched corpnseies correspond to albuminous 
cement substance stained with srold chloride; 
they are the channels between the bundles of 
fibrous tissue, constituting,' the tendon, and seen 
here as the clear spaces in cross section. In each 
of these channels is a row of tendon cells— not 
discernible here, the Ion? axis of these rows 
beins parallel with the long axis of the tendon. 



^o 



Elemexts of Histology. 




Fig. 36.— From the Tail of a Tadpole. 

c. Branched coDnective tissue cells ; m, 
a migratory cell. (Atlas^ 



way that in two adjacent cells of the growing tendon 
the nuclei face each other. This indicates that the 
individual cells undergo division. Corresponding to 

the martjin of each 
row, the cells j;>ossess 
minute processes. The 
cell plate is not quite 
riat, Ijut possessed of 
one, two, or even 
three membranous pro- 
jections l)y which it 
is wedged in between 
the individual bundles 
of the group to which the row of cells belongs. 

39, (fe) In the serous meuibranes, cornea, subcu- 
taneous tissue, and loose connective tissues, the cells 

are flattened transparent cor- 
puscles, eac-li witli an oblong 
flattened nucleus, and more or 
less branched and connected by 
tlifir processes. In the cornea 
they are spoken of as the 
corneal corpuscles, and are ver}' 
richly branched (Fig. 37). They 
are situated between the lamellae 
of fibrous bundles of which the 
ground substance of the cornea 
consists. 

These corpuscles are also 
situated in the interfascicular 
lymph spaces, or spaces left 
between the bundles of the 
fibrous matrix, which are cavi- 
ties in the interstitial cement, 
cementing tlie Imndles and trabecuke together (von 
Recklinghausen). In the cornea and serous mem- 
branes these spaces possess the shape of branched 




Fig. 37. — Fi-om the Cornea 
of Kitten, showing the 
Networks of the Branched 
Corneal Corpuscles. 

a. The network of their pro- 
cesses ; b, nucleus of the 
corpuscle. (Atla^.') 



Fibrous Conxecth'e Tissues. 



51 



lymph 



V 



laciinne, eacli lacuna being the home of the body of 
the cell, while the branches or canaliculi contain 
its processes. These canaliculi form the channels 
by which neighbouring lacuna? anastomose with one 
another (Fig. 38). The cell and its processes do not 
fill up the lacuna and its canaliculi, but are bathed 
in the paraplasma or fluid contained in the 
canal system. In 

loose connective tis- v^^':m^'''"'^'m 
sue the lacuna may " ^ '^ 

be of considerable 7 

size, and may contain 
several connective 
cells, which make as 
it were a lining for 
it. These in some 
places are very little 
branched, and almost 
form a continuous 
endotheloid mem- 
brane of flattened 
cells. Such is the 
subepithelial endotJie- 
lium ofDehove, occur- 
ring underneath the 
epithelium on the 
surface of the mucous 

membrane of the bronchi, bladder, and intestines. 
40. (c) In the true skin and mucous membranes 
the connecti^'e-tissue cells are also branched flattened 
corpuscles, and by their longer or shorter processes 
are connected into a network (Fig. 36). Each 
cell has a flattened oblong nucleus. As a rule, 
some of the processes are membranous prolongations 
coming ofl" under an angle from the body of the cell, 
which is then called the chief plate, the processes 
being the secondarv plates. By the latter the cell is 




g. 38.— From the Cornea of Kitten, 
stained with Nitrate of Silver, show- 
ing the Lymph-canal System. 

fl. The lacuna?, each containiugthe nucleated 
cell-body just indicated here; b, the 
canaliculi for the cell procer^ses. (Atlas.') 



52 Klemexts of Histology. 

wedged in between the bundles of the trabecula to 
which it belongs. 

This character of the cells (i.e. possession of 
secondary j)lates) is well shown Ijy the cells of the 
skin and mucous membranes, but only in a very 
limited degree by those of the cornea and serous mem- 
branes, and somewhat better by some of those of the 
subcutaneous and other loose connective tissues. 

In the skin and mucous membranes also the cells 
and their processes are bathed in the paraplasma 
contained in the interfascicular lymph spaces. 

41. The connective - tissue corpuscles hitherto 
mentioned are fixed corpuscles : they do not show 
movement. Kiihne and Rollett ascriVje to the corneal 
corpuscles a certain amount of contractility, inasmuch 
as they are said to be capable of withdrawing their 
processes on stimulation. When this ceases they 
are said again to protrude them. According to 
Strieker and Norris, they acquire contractility when 
the corneal tissue is the seat of inflammatory 
irritation. It can be shown that the connective- 
tissue cells consist, like the endothelial plates, 
of a ground plate and a fibrillar reticulated (granular- 
looking) substance around the nucleus, and extending 
beyond the ground plate into the proces.ses of the 
cell. 

42. Pigment cells. — In the cold-blooded verte- 
brates, fishes, reptiles, and amphibian animals, we 
find certain branched nucleated connective-tissue cor- 
puscles, distinguished by their size and by the proto- 
plasm both of the cell-body and processes (but not of 
the nucleus) being filled with pigment granules. The 
pigment is either grey or yellow, or more commonly 
dark brown, or even black. These cells are called pig- 
mented connective-tissue cells, or simply inijinent cells. 
They are very numerous in the skin of fishes, reptiles, 
and amphibian animals, and also around and between 



Fibrous Connective Tissues. 



53 



the blood-vessels of the serous membranes. They are 
also present in man and mammals, but then they are 
chieriy linuted to the eye-ball, where they occur in the 




Fig. 89,— Pigment Cells of the Tail of Tadpole. 

A, B, c, D represent variims states ; a heinar a cell in an uncontracted or passive 
stati'. D in a contracied or active state. 

proper tissue of the iris of all but albino and bright 
blue eyes, and in the tissue of the choroid membrane. 
In dark eyes of mammals a large number of these 
cells are found in the tissue between the sclerotic and 
choroid, as the lamina fusca, and also, but to a more 



54 Elemexts of Histology. 

limited degree, in the sclerotic. As a rule, they appear 
to be of various kinds : sucli as are flattened, large 
plates perforated l>y a number of small and large holes 
and minute clefts : such as possess a more spindle- 
shaped liudy. and loni'. thin, not very richly branched 
processes : and intermediate forms between the two. 
But on careful examination it will be seen that these 
appearances are due to different .states of contraction 
of the same kind of cells (Fig. 39). 

43. In the lower vertebrates the dark pigment 
cells show marked contractility, ina^mucli as they are 
capable of altogether withdrawing into their body the 
pigmented processes. Tn the passive state these are 
exceedino'lv numerous, anrl form a network so dense 
that the whole mass of the cells and their paraplasma 
resembles an extremely close network of pigment. 
In tlie maximum of activity the pigmented processes 
disappear, being withdrawn into the cell-body, which 
now looks like a spherical or oblong mass of black 
pigment. Between the states of passiveness and 
maximum activity there are various intermediate 
grades, in which the pigmented processes are of 
various numbers and lengths. 

41. Owing to the great number of the pigment 
cells in the skin of fishes and amphibians, the state 
of contraction of these cells materially affects the 
colour of the skin. If the dark pigment cells of a 
particular part contract, the skin of this jiarticular 
part will 1)ecome lighter and brighter, the degree of 
liijhtness and brightness depending on the degree of 
contraction of the pigmented processes by the cells. 
Briicke has shown that darkne.ss is a stimulus to the 
pigmented cells : they contract and the skin becomes 
lifdit. Sunlidit leaves the piomented cells in the 
pas.sive state, their pigmented processes numerous 
and well branched, and the skin appears therefore 
of a darker colour. If previously they have been 



Fibrous Coxnective Tissues. 



55 



contracted by darkness, on being exposed to sunlight 
they again return to tlie passive state. Tlie contrac- 
tion of the pigment cells is under the direct influence 
of the nervous system (Lister). Pouchet proved that 
the contractility of the pigment cells of the skin of 
certain fishes is intiuenced as a reflex action by the 
stimulation of the retina by light. 

45. Fat cells. — Fat cells in the ripe and 
fully-formed state are spherical, large vesicles, each 




Fig. 40. — From a Preparation of the Omentum of Guiuea-pig. {Atlas.) 
a, Artery ; v, vein ; c, young capillary lilooil-vesriel ; d, fat ceils?. 

consisting {a) of a thin protoplasmic membrane, which 
at one point includes an oval nucleus flattened from side 
to side, and (/>) of a substance, which is a fat globule 
filling the cavity of the vesicle (Fig. 40). These fat 
cells are collected together by fibrous connective 
tissue into smaller or larger groups, which in their 
turn form lobules ; these again form by means of 
thicker masses of fibrous connective-tissue lohes, and 
these are finally arranged as continuous masses. Each 
group and lobule has its afferent arteriole, one or two 



56 Elemexts of Histology. 

efferent veins, and a dense network of capillaries 
between ; each mesh of the capillary network holding 
one, two. or three fat cells [see below). Such are the 
nature and arrangement of fat or adipose tissue in 
the subcutaneous and sul)mucous tissue, in the serous 




Fig. 41. — From a Section through the adipose layer of the Skin ; showing 
Lobules of Fat-cells. Magnifying jiower, 40. {From a Photograph by 
Mr. A. Pringle.) 

and synovial membranes, in the intermuscular tissue, 
in the loose tissue connecting organs or parts of 
organs. 

It can be shown that fat cells are derived from 
ordinary connective tissue cells. In some places — 
both in the embryo and adult — the protoplasm of the 
connective-tissue corpuscles, growing in size, becomes 



Fibrous Connective Tissues. 



SI 



tilled with small fat globules, wliicb, increasing in 
number, become fused with one another to larger 
globules ; as their size thus increases the cell nucleus 
becomes shifted to the periphery ; ultimately one 
larijje fat globule tills the cell, and what is left of the 




Fig. 42. — From a Section of Lobules of Fretal Fat, showing connective-tissue 
septa with vessels (surrounding the lobules) ; the spheroidal young 
cells, many of them containing globules of fat. {Photograph, moderately 
magnified.) 

cell protoplasm surrounds this fat globule like a mem- 
branous envelope. The cell as a whole has become in 
this process many times its original size (Fig. 41). 

46. It can also be shown that where at one time 
only few isolated connective-tissue corpuscles are 
present, at another time, in the natural state of 



58 Elemexts of Histology. 

growth, and especially under very fav-ourable con- 
ditions of nutrition, the connective-tissue cells become 
increased by cell-multiplication so as to form groups ; 
these groups continue to increase in size and to be 
srraduallv furnished with their own svstem of blood- 
vessels ; the individual cells constituting the group 
become then converted into fat cells, and their pro- 
cesses are thereby lost (Fig. 42). 

Isolated connective -tissue cells situated in the 
neighbourhood of small blood-vessels are converted 
into fat cells under favourable conditions of nutrition. 

In starvation the fat cells lose their fat globule, 
tliey become smaller and contain a serous fluid, which 
may ultimately also disappear. Finally, the fat cell 
may be reduced to a small, solid, ^protoplasmic, slightly 
branched cell. 

47. In many places the fibrous connective tissue 
includes, besides the fixed cells, others which show 
amoeboid movement, u-andering cells. These are of 
various kinds, like tliose of the blood : (1) A majority 
are identical with the typical hyaline leucocytes of 
thf- blood, as regards size, shape, aspect, and 
general nature (Fig. 36, m). They wander about 
through the spaces of the fibrous tissue. They con- 
tain two or tViree nuclei. (2) Those of the second 
varietv possess a small amount of protoplasm, and one 
comparatively large nucleus : they correspond to the 
lymplwcytes mentioned in connection with the white 
blood corpuscles. The amoeboid movement of these 
cells is not so distinct as in the first variety. (3) 
Plasma cells of Waldeyer. They are larger than the 
former, less prone to migrating, being possessed of 
only slight amceboid movement, which is, however, 
sutiiiciently pronounced to be detected. They always 
contain granules, and correspond to the granular cells 
mentioned of the blood : also in regard to their predi- 
lection for acid and basic aniline dyes they may be 



Fibrous Connective Tissues. 59 

distinguished as eosinopliile or oxypliile, basophile 
or neutropliile cells. The "grnnules" in some of 
the plasma cells may change into fat globules, and 
thus the plasma cell becomes convei-ted into a fat 
cell. 

48. The wandering cells occur almost in all loose 
fibrous tissues, chiefly around or near blood-vessels ; 
they are not numerously met with in the healthy 
state, but increase greatly in the state of inflamma- 
tion of the part. Those of the larger kind — e.g. the 
granular wandering cells or plasma cells, are met with 
in certain localities onlv ; in the sub-linijual orland of 
the dog and guinea-pig they occur in numbers between 
the gland tubes or acini. They are also found in the 
mucous membrane of the intestine, in the trabecular 
of the lymphatic glands, and in the omentum. The 
" granules " of these cells under many conditions 
change into fat globules. Just like the hyaline 
leucocytes of the blood so also those of the connective 
tissues are capable of swallowing minute particles of 
extraneous matter — granules of living (bacteria) and 
non-living matter that accidentally find entrance into 
the connective tissue. These cells, when acting in 
this capacity, are called pliagocytes. 

49. Development of fibrous tissue. — Fibrous 
connective tissue is developed from embryonic connec- 
tive-tissue cells — i.e. from spindle-shaped or branched 
nucleated protoplasmic cells of the mesoblast. The 
spindle-shaped cells are met with isolated or in 
bundles, as in the umbilical cord or embryonic tendon. 
The branched cells form a network, as in the foetal 
skin and mucous membrane. In both instances the 
p)'otoplasm of the embryonic connective-tissue cells 
increases rapidly in amount, and becomes gradually 
transformed into a bundle of elementary fibrils, with 
a granular-looking: interstitial substance. The nucleus 
of the original cell finally disappears, A modification 



6o 



Elements of Histology. 



of this is when only part — generally unilateral — of 
the cell substance is converted into a bundle of con- 
nective tissue tibrils and inter-fibrillar cement sub- 
stance. A remnant of the protoplasm persists with 
the nucleus as a connective-tissue cell. 

The same modes of formation of connective tissue 
may be also observed in the achilt under normal and 
pathological conditions. 

50. Fibrous connective tissue is in most places 

associated with 
elastic fibres or 
yellow elastic 
tissue. These 
are of bright 
aspect, of vari- 
able thickness 
and length, 
branching and 
anastomosing so 
as to form net- 
works (Fig. 43). 
They are some- 
times straight, 
but more often 
twisted and 
coiled. The 
latter condition 
maybe observed 
when the tissue 
is shrunk, the former when it is stretched. They do 
not swell up in acids or alkalies, nor yield gelatin 
on boiling, but contain a chemically ditferent sub- 
stance — viz. elastin. When broken their ends 
generally curl up. 

51. Elastic fibres occur in great numbers as net- 
works extending on and between the bundles of tibrous 
tissue in the skin and mucous membranes, in the 




-From a Prei>aration of the Mesentery. 

of fibrim-; tissue; h, networks of elastic 
fibres. {Atlas.') 



F/BKOus Connect I \'E Tissues. 6i 

serous and synovial membranes, and in tlie loose in- 
terstitial connective tissues. They are not very com- 
monly met with in tendons and fasciae ; in the former 
they are seen as single fibres often twisting round the 
tendon bundles. 

Elastic fibres forming bundles, l)ut branched and 
connected into networks within the bundle, are to be 
found in large numbers in the walls of the trachea, 
l)ronchi, infundibula, and alveoli of the lung, in the 
ligamenta flava, in the ligamentum nucha? of the ox 
(in which the fibres are exceedingly thick cylinders), 
in yellow elastic cartilage {see below), in tlie mem- 
brane lining the cavity of the heart, and in the 
vascular system, particularly the arterial division. 
In the latter organs the intinia, and also to a great 
extent the media, consist of elastic fibrils densely 
connected into a network. 

52. The following are special morphological modi- 
fications of the elastic fibres : (o) elastic fenestrated 
membranes of Henle, as met with in the intima of 
the big arteries ; these are in reality networks of 
fibres with very small meshes, and the fibres unusually 
broad and Hat. {h) Homogeneous elastic membranes, 
which surround, as a delicate sheath, the connective- 
tissue trabecules in some localities — e.^. subcutaneous 
tissue, (c) Homogeneous-looking elastic membranes 
iu the cornea, behind the anterior epithelium as Botv- 
'nianHs anterior elastic membrane, and at the back of 
the cornea as elastica posterior, or Descemet's mem- 
brane ; in the latter bundles of minute fibrils haA'e 
been observed. Between the mucosa and submucosa 
of the stomach of the cat occurs an elastic membrane 
of considerable thickness, (d) Elastic trabeculae form- 
ing a network, as in the ligamentum pectinatum iridis. 
In the embryonic state the elastic fibres are nucleated, 
the nuclei beincj the last remnants of the cells from 
which the fibres develop, one cell generally giving 



2 Elements of Histology. 

oricjiii to one fibre. These nucleated fibres are called 
Henle's nucleated fibres. 

53. Special varieties of fibrous connective tissue 
are these : — 

(1) Adenoid retlcidum. This is a network of fine 
fibrils, or plates, forming the matrix of lymphatic or 
adenoid tissue. {!See Lymphatic glands.) The reti- 
culum is not fibrous connective tissue nor elastic 
tissue ; it contains nuclei in the young state, and is 
derived from a network of branched cells ; but in the 
adult state the reticulum itself possesses no nuclei. 
Those found on it do not form an essential part of it. 

(2) The iiearogUa of Virchow is a dense network 
of very fine homogeneous fibrils which form the sup- 
porting tissue for the nervous elements in the central 
nervous system. These fibrils are supposed to be 
elastic fibres (Gerlach). Embedded in, and inti- 
mately connected with, the network of these fibres 
are found branched, nucleated, flattened cell plates, 
which correspond to the fixed connective-tissue cells. 

(3) Gelatinous tissue. This occurs chiefly in the 
embiTO, being the unripe state of fibrous connective 
tissue (see above). It consists of spindle-shaped or 
branched connective-tissue cells, separated from one 
another by a homogeneous transparent mucoid sub- 
stance. It is met with in the umbilical cord and 
ill tlie cavity of the middle ear of the embryo, and in 
all places Avhere fibrous connective tissue is to be 
developed. After birth it is found in the tissue of 
the pulp of the teeth, where it persists through life ; 
in some places it is the precursor of fat tissue, its cells 
becoming: transformed into fat cells. 



63 



CHAPTER YI. 

CARTILACiE. 

54. Cartilage consists of a firm ground sub- 
stance which yields diondrin, and of cells embedded 
in it. Most cartilages (except on the articulating 
surface) are covered on their free surface with a 
membrane of tibrous connective tissue with a few 
elastic fibrils. This membrane is supplied with 
blood-vessels, lymphatics, and nerves, and is of 
essential imjiortance for the life and growth of the 
cartihige. This is the perichondriiun. There are 
three varieties of cartila^je. 

55. (1) Hyaline cartila§:e(Fig. 44).— This occurs 
on the articular surfaces of all bones ; on the borders 
of many short bones ; in the sternal part of the ribs, 
as costal cartilages : at the margin of the sternum, 
scapula, and os ileum : in the rings of the trachea, 
the cartilages of the bronchi, the septum and lateral 
cartilages of the nose ; and in the thyroid and cricoid 
cartilages of the larynx. The ground substance is 
hyaline — i.e. transparent, like ground glass, and firm. 
The cells are spherical or oval proto^^lasmic corpuscles, 
each with one or two nuclei. They undergo division, 
and although the two offsprings are at first close 
together (half moon-like in optical section), they 
gradually grow wider apart by the deposit of hyaline 
ground substance between them. The cells are con- 
tained in cavities, called the cartilage lacunce. Each 
cell generally occupies one lacuna, but, according to 
the progress of division, a lacuna may contain two. 



64 



Elemexts of Histology. 



four, six, or eight cartilage cells : the latter are those 
cases in which division proceeds at a more rapid rate 
than the deposition or formation ot hyaline ground 
substance between the cells. 

The jjart of the cartilage next to the perichon- 
drium shows most active growth; hence the cells are 
here smaller, closer together, and there is less ground 
substance. 

Each lacuna is liner] liy a delicate membrane, and, 
according to the state of the cell, is either completely 

or partially filled out bv 
it. This membrane is 
called the capsiiIe(Fig. 44). 
In many cartilages, espe- 
cially in growing cartilage, 
it is thickened by the ad- 
dition of a layer or layers 
of hyaline ground sub- 
stance. This is the most 
recently-formed j^art of 
the matrix; it stains differ- 
ently with dyes, and is dis- 
tinct from the older part 
of the ground substance. 

56. In some places, especially in articular carti- 
lage (Tillmanns Baber), bundles of fine connective- 
tissue lil>rils may Ije noticed in the hyaline ground 
substance. 

57. In some cartilages the protoplasm of the cell 
becomes filled with fat globules (Fig. 46). This fact 
may be observed in many normal cartilages ; some- 
times the fat globules become c(mfluent into one larjje 
drop, and then the cell has the appearance of a fat 
cell. In old age, disease, and deficient nutrition lime 
salts are deposited in the ground sul)stance, beginning 
from the circumference of the cell. The earthy matter 
a])})ears in the shape of opaque granules, or irregular 




Fig. 44.— Hyaline Cartilage of 
Hixiiian Trachea. 

In the hyaline ground substance are 
seen the cartilage cells enclosed in 
capsules. 



Cartilage. 




or anujular granult's. Tlie groiincl suljstance thereby 
loses its transparency, becomes o})H<jue in transmitted, 
white in re- 
flected, light, 

and, of course, / 

ver}^ hard and 
brittle. This 
process is the 
calcification of 
cartilage. It is 
also met with 
in cartilage 
that is to be 
replaced by 
bone, being the 
precursor of the 
formation of 
bone, as in the 
€mbr3'0 {see be- 
low), and at the 




Fit 



45. — From a Preparation of the Sterna 
Cartilage of a Newt. 



growing ends of 



The lacunae containing the cartilage cells anastomose 
by tine channels. 



I. •',•-•5 



long bones. 

58. The division of the nucleus of the cartilage 
cells has been observed during life by Schleicher and 
Flemming. It takes place after the 
mode of karyokinesis. The lacunie _<«U.,/ , 

of the cartilage are not isolated 
cavities, but are connected with one 
another by fine channels (Fig. 45), 
so that the ground substance is 
easily permeable by the current of 
nutritive fluid. These channels and 
lacunae form an intercommunicating 
system, and are connected with the 
lymphatics of the perichondrium 
(Budge). Formed matter, as pig- 
ment granules, red and white blood 




Fig. 40.— Three Car- 
tilage Cells filled 
with Fat Droplets. 
From the hyaline 
cartilage of the 
nasal septum of 
Guinea-pig. 



66 



Elements of Histology. 



a, o" o::S, 



o 



corpuscles, and pus corpuscles, may also find its way 
into the channels and lacunae of the cartilage from 
the perichondrium. 

At the borders of articular cartilage, where this 
is joined to the synovial meml)rane and to the capsule 
of the joint, the cartilage cells are more or less branched, 
and pass insensibly into the branched connective tissue 
cells of the membrane. In fcetal hvaline cartilacre 
many of the cells are spindle-shaped or branched. 

59. Ju the cartilage separating the bone of the 
apophyses from the end of the diapbysis of tubular 
bones there is a peculiar hyaline cartilage, known as 
the intermediate or ossifying cartilage. Its cells are 
arranged in characteristic vertical rows, owing to 

the continued division 
^11 ,jg of the cells in a trans- 

verse direction. 

Cartilages, or parts 
of cartilages, in which 
the cells are very 
closely placed, owing 
to tlie absence, or 
scanty deposit and 
formation, of ground 
substance, are called 
jKi.rencliyiiiatous or cel- 
hdar cartilacje. 

60. (2iFibro-car- 
tilagre. or connective- 
tissue cartilage, occui-s 
as the intervertebi-al 
discs, as the inter- 
articular cartilages, sesamoid cartilages, and as the 
cartilat{e forminc( the marmn of a fossa »lenoidalis. 
It consists of fibrous connective tissue arranged in 
hundles, and these again in layers. The ground sub- 
stance of this cartilage is said to yield chondrin and 







■O 






O 



^ <S Q ^ 






o. 



€/^ 



^ 



• Fig. 47. — Fibro-Cartilage of an Inter- 
vertebral Ligament. {Atlas.) 

Showing the bundles of fibrous tissue and 
rows of cartilage cells. 




Cartilage. 67 

not gelatin. Between the strata of the fibrous bundles 
are rows of more or less flattened oval protoi)lasmic 
nucleated cells, each invested in a deticate capsule 
(Fig. 47). They are less flattened than the cells of 
tendon, and the capsule dis- 
tinguishes the two. Where 

fibro-cartilage passes into %^^ ^^ ^ ; -«»^5-C7 
tendinous tissue the two WC 
kinds of cells pass insen- if^ 
sibly into one another. 5^^^^M_ 

61. (3) Yellow, or ^iS^^K^i?) 
ela«>tic cai'tilag:e. this ^ji^?^?r^i^K:''^ii^^^o 
variety is also called reti- ^p ''^-^^^^^^i 
cular ; it occurs in the epi- •^, ^^.;''®^^ TO 
glottis, in the pinna of the ^ -■--«--—. ^ 
external ear, in the Eus- 
tachian tube, in the car- 

tilacrps of AVn\bp7-rr and ^ig. 4S.— From a Section through 

iiiages or » iisueig ana the Epiglottis. {AtUs.) 

Santorini in the larynx. «^ perichondrium; &, networks of 

In the early stages this eig^c^fltois sun-ounding the car- 
kind is hyaline. Gradually 

numbers of elastic tibrils make their appearance, 
growing into the cartilage matrix from the peri- 
chondrium in a more or less vertical direction, and 
branching and anastomosin^r with one another. The 
final stage is reached when the ground substance is 
permeated by f/^e/ise neiicorJxs of elastic Jibrils (Fig. 48), 
so arranged that spherical or oblong spaces are left, 
each of which contains one or two cartilage cells, 
surrounded by a smaller or larger zone of hyaline 
ground substance. 




68 



CHAPTER VII. 

BONE. 

62. BoxE, or osseous substance, is associated with 
several other soft tissues to form a bone in the ana- 
tomical sense of the word. 

(a) The periosteiiiii. — Except at the articular 
surfaces, and where bones are joined with one another 
bv liiraments or cartilao;e, all bones are covered with a 
vascular membrane of fibrous connective tissue. This 
is the periosteum. It consists in most instances of 
an outer fibrous layer, composed of bundles of fibrous 
tissue densely aggregated, and an inner, or osteogenetic 
layer, which is of loose texture, consisting of a mesh- 
work of thin l^undles of fibrous tissue, in which 
numerous hlood-vessels and many protoplasmic cells 
are contained. The blood-vessels form hj their capil- 
laries a network. The cells are spheroidal or oblong, 
each with one spherical or oval nucleus. They have 
to form bone-substance, and are therefore called the 
osteoblasts (Gegenbaur). 

(b) Tlie carlilag-e is hyaline cartilage, and its 
distribution on and connection with bone have been 
mentioned on pp. 63 and 64. 

63. (c) The marrow of l>oiie is a soft \'ascular 
tissue, filling up all spaces and cavities. It consists 
of a very small amount of fibrous tissue as a matrix, 
and in it are embedded numerous blood-vessels and 
cells. The few afierent arterioles break up into a 
dense network of capillaries, and these are continued 
as plexuses of veins, characterised by their compara- 



Bone. 69 

lively large size and exceedingly thin walls. The 
cells are of the same size, aspect, and shape as the 
osteoblasts of the osteogenetic tissue, and they are 
called marrow cells. 

In origin and structure, the tissue of the osteo- 
genetic layer of tlie periosteum and tlie marrow are 
identical. In the embryo, the marrow is derived 
from an ingrowth of the osteogenetic layer of the 
periosteum {see below), and also in the adult the two 
tissues remain directly continuous. As will be shown 
later, the marrow at the growing ends of the bones 
is concerned in the new formation of osseous substance 
in the same way as the osteogenetic layer of the peri- 
osteum is in that of the surface ; and in both tissues 
the highly vascular condition and the cells (osteo- 
blasts of the osteogenetic layer, and marrow cells of 
the marrow) are the important elements in this bone 
formation. Marrow is of two kinds, according to 
the condition of the cells. If many or most of these 
are transformed into fat cells, it has a yellowish aspect, 
and is called yellow marroio ; if few or none of them 
have undergone this change, it looks red, and is called 
red marroiD. In the central^ or marrow, cavity of the 
shaft of tubular bones, and in the spaces of some 
spongy bones, the marrow is yellow ; at the ends of 
the shaft, in the -spongy bone substance in general, 
and in young growing bones it is red. 

Some of the cells, especially those of red marrow, 
the erythrohlasts, are the elements from which nor- 
mally vast numbers of red blood corpuscles are 
formed, as has been mentioned on a former page. 

In marrow, particularly in red marrow, we meet 
with large multinucleated cells, called inyeloplaxes of 
Robin. They are derived by overgrowth from ordin- 
ary marrow cells, and are of importance both for 
the absorption as also for the formation of bone 
[see below). According to Heitzmann, Malassez, and 



70 



Elements of HistoloCjY. 



others, they also have to do witli the formation of 
blood-vessels and blood corpuscles. NuQierous eosino- 
phile cells are present in the marrow, 

64. The matrix of osseous substance is dense 
plexiform fil^rous connective tissue, i.e. a tissue yield- 
ing- gelatin on boiling. The cement substance between 
the fibrils is petrified, owing to a deposit of insoluble 
inorganic lime salts, chiefly carbonates and phosphates. 
These can be dissolved out by strong acids (hydro- 
chloric) and are thereby converted into soluble salts. 
Thus the orijanic matrix of osseous substance — called 
ossein — may be obtained as a soft flexible material, 
easily cut. 

In young bone the matrix or ossein is a plexus of 
trabecuLe of fibrous tissue (v. Ebner), and in it are 
also a few elastic fibres to be noticed. 

The bone substance is in the adult state generally 
lainellated, the lamellse being of microscopic thinness. 
Between every two lamellae are numbers of isolated, 
flattened, oblong spaces — the hone lacnnce (Fig. 49), 

which anastomose 
by numerous fine 
canals with one 
another, and also 
with those of the 
next lamella above 
and below (Fig. 50). 
The appearances are 
very similar to those 
presented by the 
lacunse and canali- 
culi containing the 
corneal corpuscles 
as described in 
Chapter V. 

The bone lacunte and their canaliculi are the 
lymph-canalicular system of osseous substance, for they 




Fig. 49. — Osseous Lanieihe ; oblong branched 
bone lacun;e and canaliculi between them. 
{Atlas.) 



Bone. 7 1 

are in open and free communication with the lymphatic 
vessels of the marrow spaces and of the Haversian 
canals. 

65. In the bone matrix, each lacuna contains also 
a nucleated protoplasmic cell, called the hone celi, 
which, however, does not fill it completely. In the 




Fig. 50. — From a Transverse Section through Compact Bone, showing 
systems of concentric lamelliB (with bone corpuscles between) around 
Haversian canals. (From a photogram by Mr. Pearce.) 



young state the cell is branched, the branches passing 
into the canaliculi of the lacunae ; but in the old state 
only traces of the original nucleated cell and very few 
processes can be detected ; this with its lacuna and 
canaliculi is called a bone corpuscle. 

66. Accordinsf to the arrano^ement of the bone 
substance, we distinguish compact from spongy sub- 
stance. The former occurs in the shaft of tubular 



72 Elemexts of Histology. 

bones and in the outer layer of flat and short bones. 
Its lamell?e are arranged as : («) concentric or Haversian 
lamella ., directly surrounding the Haversian canals 
(Fig. 51). These are narrow canals of varying lengths 
pervading the compact substance in a longitudinal 




a 



P'ig. 51.— Compact Bone Substance in Cross-section. (Atlas.) 

a. Concentric lamellae arranged around the Haversian canals, cut across; 6, in- 
termediate or ground lamellia The bone lacuna? are seen between the bone 
lamellas. 

direction, and anastomosing with one another by 
transverse or oblique branches. The Haversian canals 
near the marrow cavity are larger than those near 
the periosteum. In fact, those next to the marrow 
cavity become gradually enlarged by absorption of 
the concentric lamellse, until finally they are fused 
with the marrow cavity. Each Haversian canal con- 
tains a blood-vessel, one or two lymphatics, and a 
variable amount of marrow tissue. These canals open 
both into the marrow cavity and on the outer surface 
into the osteogenetic layer of the periosteum, and 
they form the means by which the latter remains in 
continuity with the marrow. Each canal is surrounded 



Bone. 73 

by a series of concentric bone la?7iellcf, tvith the bone 
corpuscles between thein, and this is a system of con- 
centric lanielhe. Near the external surface of the 
compact substance the number of lamellae in each 
system is smaller than in the deeper parts, {b) 




^'^^^mm^g 



Fig. 51a. — Sharjipy's fibres amongst the iiisterstitial lamella; of a transverse 
section of the human humerus ; the fibres run in a vertical direction, 
and surround spaces wliicli contain the bone-cells. {After KolUker, I.) 

Between these systems of concentric lamellae are the 
intermediate or ground lamelhe ; they run in various 
directions, and in reality fill the interstices between 
the systems of the Haversian or concentric lamellae. 
Near the external surface of long bones they have pre- 
eminently a direction parallel to the surface. These are 
the circumferential lamellce of Tomes and de Morgan, 
The ground lamellae are the earliest to be developed, 
being the matrix of the first-formed spongy bone, 
and they are the last to disappear where bone is 



74 Elements of Histology. 

melted clown in the marrow cavity. The concentric 
lamellfe, on the other hand, are the last to be formed 
where spongy bone is converted into compact bone, 
and they are the tirst to become absorbed where com- 
pact bone is reduced again to spongy bone, as near 
the central marrow cavity. The lamellae of compact 
bone are perforated by perpendicular petrified fibres, 
the perforating fibres of Sharpey. They form a con- 
tinuity with the fibres of the periosteum, from which 
they are developed, through the lamellae of osseous 
substance deposited by the osteogenetic layer of the 
periosteum (Fig. 51a). 

67. Spongy- bone substance occurs in the end of 
the shaft, in the apophyses, in short bones, and in the 
diploe of flat bones. The cavities or meshes of the 
spongy substance are called Haversian spaces or can- 
celli ; they intercommunicate with one another, and 
are filled with marrow, which in the vouncf and grow- 
inij state is fjenerallv of the red varietv. The firm 
parts form spicules and septa, called hone trahecuUt, 
of varying length and thickness, and are composed of 
lamellae of bone substance. 

According to the arrangement of the trabeculse, 
the spongy substance is a uniform honeycombed sub- 
stance, or appears longitudinally striated, as in the 
end of the shaft. In the latter case the marrow 
spacas are elongated and the trabeculse more or less 
parallel, but anastomosing with one another by 
transverse Ijranches. 

68. Development of bone.— Bone is developed 
in the embryo, and continues to be fonned also after 
birth as long as bone grows, either in the cartilage 
or, independently of this, directly from the osteo- 
genetic layer of the periosteum. The former mode 
is called endodiondral, or intracartilagino^is: the latter 
periosteal^ or inter me mhranous formation. 

All the bones of the limbs and of the vertebral 



Bone. 7 5 

column, the sternum, and the ribs, and the bones 
forming the base of the skull, are preformed in the 
early em])ryo as solid hyaline cartilage, covered with 
a membrane identical in structure and function with 
the periosteum, which at a later period it represents. 
This cartilage is eventually replaced by bone — 
endochondral hone. The tegmental bones of the 
skull, the bones of the face with the lower jaw, 
except the angle, are not preformed as cartilage at 
all. Only a membrane identical with the future 
periosteum is present, and underneath and from it 
the bone is gravlually deposited — i-)eriosteal hone. The 
same deposit of periosteal bone takes place on all 
bones, no matter what their origin, and this deposi- 
tion of layer after layer of bone by the osteogenetic 
layer of the periosteum represents the groivtli of the 
hone in thickness. 

69. EiKlochoiiclral foriiiatioii. — The stage 
next to the one (1) in which we have solid hyaline 
cartilage covered with periosteum is the following : 
(2) Starting from the "centre, or point, of ossifica- 
tion," and proceeding in all directions, the cartilage 
l)ecomes permeated by numbers of channels (cartilage 
channels) containing prolongations (periosteal pro- 
cesses of Virchow) of the osteogenetic layer of the 
periosteum — i.e. vessels and osteoblasts, or marrow 
cells. This is the stage of the vascidarisation of the 
cartilage. In the next stage (3) the cartilage border- 
ing on these channels grows more transparent, the 
lacun{3e becoming enlarged and the cartilage cells 
more transparent. The latter gradually break down, 
while the intercellular trabeculse become calcified; 
the lacume, by absorption of the calcified trabeculfe, 
fusiuff witli the cartilaoje channels. These latter 
thereb}^ become transformed into irregidar cavities, 
which are bordered by trahecuhe of calcified cartilage. 
The cavities are the primary marroiv cavities, and 



76 



Elements of Histology. 



they are filled witli \\\^ jjrimary or 





j\4 '^'-^-f'^/'i',--, ^-- ■ 




Fig. 52. — Longitudinal Section through the entire 
Foetal Humerus of a Guinea-];)ig. 

fl, Periosteum ; 6, hyaline cartilage of the epiphysis ; 

c, intennediate cartilage at the end of the shaft ; 

d, zone of calcification ; t, i>eriostealbone, spongy ; 
/, endochondral bone, spongy. 



tilage gradually assumes the appear 



cartilage marroiv 
— i.e. blood-ves- 
sels and osteo- 
blasts, derived, 
as stated above, 
from the osteo- 
genetic layer of 
the periosteum. 
(4) The osteo- 
blasts arrange 
themselves by 
active multipli- 
cation in a special 
layer on the sur- 
face of the calci- 
fied cartilajje 
trabeculse pro- 
jecting into and 
bordering the 
primary marrow 
cavities. The 

osteoblasts form 
hone substance — 
osseous matrix 
and branclied 
bone corpuscles 
— and as this 
proceeds, the cal- 
cified cartilage 
trabecules become 
gradually en- 
sheathed and 
covered icitli a 
layer of osseous 
substance. Thus 
the original car- 
ance of a spongy 



Bone. 7 7 

substance, in wliicli the cavities (primary marrow 
cavities) arc tilled with the primary marrow, and 
are of considerable size, while the trabecuhe bor- 
dering them are calcified cartilage covered with 
layers of new bone. The marrow cells, or osteo- 
blasts, continue to deposit bone substance on tlie 
free surface of the trabecul?e, while the calcified 
cartilage in the centre of the trabeculte gradually 
becomes absorbed. 

70. The nearer to the centre of ossification, the 
more advanced is the process — i.e. the more bone and 
the less calcified cartilage is found constituting the 
trabecuhe, and the thicker the latter. At the " centre 
of ossification," i.e. whence it started, the process is 
farthest advanced ; away from it, it is in an earlier 
stage. At this period of embryo life, between the 
centre of ossification and a point nearer to the ex- 
tremity of the shaft of a long bone, all stages described 
above may be met with — viz. between the solid 
unaltered hyaline cartilage at the end of the shaft 
and the spongy bone with the unabsorbed remains of 
calcified cartilage in the middle of the shaft all 
intermediate stages occur (Fig. 52). 

71. After birth, and as long as bone grows, we 
find in the end of the shaft, and also in the epiphysis, 
a continuation of the process of endochondral forma- 
tion described above. In fact, all bones preformed 
in the embryo as cartilage grom) in length before and 
after birth by endochondral formation of new bone. 
The hyaline cartilages at their extremities, the carti- 
lage of the epiphysis, the intermediate cartilai^e at 
the end of the shaft, are the cartilages at the expense 
of which the new bone of the epiphysis and of the 
end of the shaft respectively are formed by the marrow 
(blood-vessels and marrow cells or osteoblasts) in 
contact with the cartilage. As long as this cartilage 
continues to grow, so long is there new formation of 



78 



Elemexts of Histology. 



bone by the marrow encroaching on it, or, in other 
words, so long is there growth in length of the shaft. 
When at a certain period of adidt life the growth 
of the intermediate cartilage has come to an end, the 
cartilage is completely replaced by the spongy bone 








y^^M 





m:\\b « i (f^,^m rt^ Q)% /fiT 



■* \i* it) 






'W 



Fig. 53. — From a Transverse Section tlirough the Tibia of Foetal Kitten. 

a. Fibrous layer of the periosteum; b, osteogenetic Inyer of the periosteum; 
c. periosteal bone; d, calcifled cartilage not covered yet by bone; below this 
layer the tralieculte of calcified cartilage covered with plates of bone — 
sbaded darkly in the figure ; e, boundary between periosteal and endochondral 
bone. iAtlas.) 



Bone. 



79 



of the end of the shaft, and this is not capable of 
further lengthening. 

72. Following the development of a tubular bone 
after the above mentioned stage 4, we find that the 
spongy bone once formed is not a permanent structure, 




Fig. 54.— From a Section through the Intermediate Cartilage of Femur of a 
Foetus. Low magnifjing power. {From a photogrcqjh by Mr. A. 
Pringle.) 

a, intermediate cartilajsre ; b, cartilage of the eiiiiihysis ; c, spongy bone of 
epiphysFs ; d, spongy bi>ne at the end of the shaft. 

but becomes gradually absorbed altogether, and this 
process also starts from the points of ossification. 
Thus a f;rc\dual enlargement and ultimate fusion of 
the marrow cavities of the spongy endochondral bone 



8o Elements of Histology. 

into one continuous cavity takes place. This repre- 
sents the rudiment of the future central marrow 
cavity of the shaft. Simultaneously with, or some- 
what previous to, this absorption of the endochondral 
bone, new bone of the nature of spongy hone is 
deposited directly hy tlie osteogenetic layer of the 
periosteum on the outer surface of the endochondral 
hone. This also commences at the centre of ossifica- 
tion, and proceeds from here gradually to further 
l^oints. This is the tirst rudiment of the periosteal 
hone of the shaft (Figs. 52, 53). It is formed without 
the intervention of cartilage directly by the osteo- 
blasts of the osteogenetic layer. And as fresh masses 
of osteoblasts become developed l)y division, new 
layers of spongy bone are formed by the change of 
the former into bone matrix and bone cells, and the 
old trabecular become increased in thickness. In the 
meshes or Haversian spaces of this new spongy 
periosteal bone the same tissue is to be found that 
constitutes the osteogenetic layer of the periosteum, 
the one being derived from, and continuous with, the 
other. 

In these Haversian spaces concentric lamellai of 
bone substance become subsequently formed by the 
osteoblasts, while at the same time the Haversian 
spaces, being narrowed in by the deposit of the con- 
centric lamellae, are transformed into the Haversian 
canals. The original spongy bone represents, there- 
fore, the ground substance (primary, or ground lamella?), 
in which, or rather in the spaces of which, the secondary 
deposit of the concentric lamella} or Haversian 
systems of bone lamellae takes place, by which deposit 
the spongy bone becomes transformed into compact 
bone. This process is farthest advanced in the 
middle of the thickness of the shaft, and least near 
the periosteum. When this compact bone is again 
absorbed — e.g. that next the medullary cavity of the 



Bone. 



8r 



sliaft of a long bone— tlie concentric lamella? are first 
absorbed, the Ha- 



be- 
way 
and 



versian canal 
ing in this 
widened out 
again transformed 
into a Haversian 
space. 

While, then, 
the bone first de- 
posited by the peri- 
osteum is of a 
spongy character, 
and gradually be- 
comes transformed 
into comi3act_, the 
reverse is ""oing on 
at the same time 
near the marrow 
cavity, inasmuch 
as compact bone is 
here changed into 
spongy bone, and 
this ultimately dis- 
a23pears and be- 
comes absorbed by 
the mari'ow. 

73. At birth 
all the primary en- 
dochondral bone «. 
has already disap- 
peared by absorp- 
tion from the centre 
of the shaft, and 
the bone present is 
all of periosteal origin 
shaft 




Fig. 55. — From a Longitudinal Section 
Femur of Rabbit, through the part in 
which the intermediate cartiLige joins 
the end of the shaft. {Atlas.) 

a, Intermediate cartilage; 6, zone of calcified 
cartilage ; c, zone in which the calcified tra- 
heculEB of cartilage become gradiiRlly in- 
vested in osseous substance, shaded light in 
the figure; the spaces between the tral>e- 
cula3 contain marrow, and the cai>illar.v 
blood-vessels are seen here to end in loops ; 
d, in this zone there is more bone formed; 
the greater amount the farther away from 
this zone. 



At the extremity of the 
however, tlie spongy bone is all endochondral 

G 



82 Elements of Histology. 

bone, and it continues to grow into the interme- 
diate cartilage as stated above, so long as the 
bone grows as a whole (Fig. 55). Of course the 
parts of this spongy bone nearest to the centre 






'^' 




\% 



^^§)^ 



Fig. 5(3. — Small mass of Boiie Substance in the Periosteum of the Lower 
Jaw of a Human Foetus. [Atlas.) 

tt, Osteou'enetic liiyer of periosteum ; l>. luuliiuiicle.ired giuiit cells, inyeloiil.ixes. 
Tbe one in the midcile of the upper margin is an osteoclast, whereas the 
smaller one at the left upper corner appears concerned in the fornntion of 
bone. Above c the osteoiihist cells become surrounded by osseous substance 
and thus become converted into bone cells. 

of the shaft are the oldest, and ultimately dis- 
appear by absorption into the central medullary 
cavity. In the epiphysis the spongy bone is also 
endochondral bone, and its formation is connected 
with the deep layer of the articular cartilage, but 
more so with the hyaline cartilage separating the 
epiphysial spongy bone from the intermediate carti- 
lao-e (see c of Fisj. oi). 

Underneath the periosteum and on the surface of 
the spongy endochondral bone at the extremity of the 
shaft, the periosteal bone is represented only by a 



Bone. 



83 



thill liiyer, extending as far as the periosteum reaches 
— e.g. to tlie margin of the articular cartilage. 

74. liiteriuoiiibrsiiioiis format ion. — All 




Fig. 57.— From a Longitudinal Section through the Spongy Bone of Shaft, 

near the intermediaiy cartilage, of Foetal Kitten, showing the formation 

of osseous substance on tlie calcilied cartilage. {Atlas.) 

a, Mhitow space, with bluud-vcssei ; 6, caicifled cartilage, covered with isolated 

or confluent zoues of new osseous substance, consisting of fibrillated bone 

matrix, bone lacuna, and in it a bone cell. 



84 



Elements of Hjstologv. 




Fig. 58. — From a Lolly itudiual Section 
of Femur of Rabbit, close to the 
intermecliate cartilage. 

a, Calcified cartilage, next to the inter- 
mediate cartilage; 6, calcified carti- 
lage covered with thin layer of 
bone ; c, uiari'ow spaces containing 
osteoblasts, forming bone on the 
calcified cartilage; d, niyeloplaxes 
(chondroclastsj. 



bones not preformed in 
the embryo as cartilage 
are developed directly 
from the osteogenetic 
layer of the periostemii in 
the manner of the i^eri- 
osteal bone described on 
p. 80. Here also the new 
l)one is at first spongy 
bone, which in its deeper 
or older layers gradually 
becomes converted into 
compact bone. 

In all instances dm'ing 
embryonic life and after 
birth the growth of a 
bone in thickness takes 
place after the manner of 
periosteal or intermem- 
hranous hone ; this is at 
first spongy, but is gra- 
dually converted into 
compact bone. 

75. All osseous sub- 
stance is formed in the 
embryo and after bii th by 
the osteoblasts, or marrow 
cells (Gegenbaur, Wal- 
deyer) : each osteoblast 
oivino: orioin to a zone 
of osseous matrix, and re- 
maininof in the centre of 
this as a nucleated ^yo- 
toplasmic remnant, which 
gradually becomes 
branched and transformed 
into a bone cell. The 



Bone. 85 

osseous matrix is at first a soft fil)nllar tissue, but is 
gradually and uuiformh^ impregnated with lime salts. 
This impregnation always starts from the centre of 
ossification (Fig. 57). 

76. Wherever in the embryo or adult, in health 
or disease, absorption of calcified cartilage or of osseous 
substance is going on, we meet witli the multi- 
nucleated large protoplasmic cells called the myelo- 
plaxes of Robin. K()lliker showed them to be import- 
ant for the absorption of bone matrix, and called 
them therefore osteoclasts (Fig. 5Q). For cartilage they 
ma}" be called chondroclasts ( Fig. 58). When concerned 
in the absorption we find these myeloplaxes situated 
in smaller or larger pits, which seem to have been 
produced by them; these absorption pits or lacunae on 
the surface of l)ones are called Howships lacunce. 
They invariably contain numbers of osteoclasts. It 
can, however, be shown that myeloplaxes are also 
concerned in the formation of bone by giving origin 
to a number of new osseous zones with their bone 
cells. In the earliest stages of development of the 
ftetal jaw" this process is seen with great distinctness 
(Fig. 56). 

77. Dentine forms the chief part of a tooth. It 
consists of a petrified matrix in which are numbers of 
perpendicularly arranged canals — the dentinal tubes — 
containing the dentinal fibres. It is in some respects 
similar to bone, although diftering from it in certain 
essentials. It is similar inasmuch as it is developed 
in like manner by some peculiarly transformed 
embryonic connective tissue — viz. by the tissue of the 
embryonic tooth papilla — and inasmuch as cells are 
concerned in the production both of the petrified 
matrix (impregnated with lime salts) and of the 
processes of the cells contained in its canals — the 
dentinal fibres. The details of structure and distri- 
bution will be described in connection with the teeth. 



86 



CHAPTER V]II. 

XOX-STRIPED MUSCULAR TISSUE. 

78. This tissue consists of nucleated cells, which, 
unlike amoeboid cells, are contractile in one definite 
direction, becoming' shorter and thicker diirinc; con- 
traction. 

The cells are elongated^ spindle-shaped, or band-like 
(Fig. 59), and drawn out at eacli extremity into a 
lonuer or shorter, sfenerallv single, but occasionally 




Fig. 59.— Xon-striped Muscular Fibres, isolated. (Atlas.) 

The cross-markings indicate corrugations of the elastic sheath of the individual 

fibres. 

branched, tapering process. Each cell includes an 
oval nucUAis, which is flattened if the cell it belongs 
to is flattened. The cell substance is a pale, homo- 
geneous-looking or longitudinally striated substance. 

During extreme contraction the nucleus may be- 
come more or less plicated, so that its outline becomes 
wavv or zicj-zag. 

It lias been shown by Klein in certain preparations 



Non-striped Muscular Tjssue. 87 

— e.y. the non-striped muscle cells of the mesentery of 
tlie newt — that each muscle cell consists of a delicate 
elastic shentJi, inside of which is a bundle of minute 
fibrils which cause the longitudinal striation of the cell. 
These fibrils are the contractile portion ; and they are 
contractile towards the nucleus, with whose intra- 
nuclear reticulum they are intimately connected. 
AVhen the cell is contracted its sheath becomes trans- 
versely corrugated (Fig. GO). 

79. The non-striped muscular cells are aggregated 
into smaller or larger bundh>^ by an interstitial alV)U- 




Fig. 60.— Xon-stiipL'<l Muscular Cell of Mesenteiy of Xewt. {Atlo.s.) 

Sliowin:,' several places whei'e the muscular substance appears cuntracted, 
thickened. At these places the corrugations of the sheath are mariced. 

minous homogeneous cement substance, the cells being 
imbricated with their extremities. The bundles may 
form a plexus, or they may be aggregated by fibrous 
connective tissue into larger or smaller groups, and 
these again into continuous masses or membranes. In 
the muscular coat of the bladder of the frog, in the 
choroidal portion of the ciliary muscle, in the arrector 
pili, in the muscular tissue of the scrotum, very well 
marked plexuses of bundles of non-striped muscular 
cells may l)e met with. In the muscularis mucosae of the 
stomach and intestines, in the outer muscular coat of 
the same organs, in the uterus, bladder, etc., occur 
continuous membranes of non-stri})ed muscular tissue. 

When the muscular cells form larger bundles they 
are more or less pressed against one another, and 
therefore in a cross-section appear of a polvgonal 
outline. 

80. Non-striped muscular tissue is found in the 



88 Elements of Histology. 

following places : In the muscularis mucosae of the 

oesophagus, stomach, small and large intestine ; in the 

outer muscular coat of the lower two-thirds or half 

of the human oesophagus ; in that of the stomach, small 

and large intestine ; in the tissue of the pelvis and 

outer capsule of the kidney ; in the muscular coat of 

the ureter, bladder, and urethra ; 

a *^ in the tubules of the epididymis, 

f%^*^-^ in the vas deferens, vesiculfe 

^ ^ ., ^ ^ >eminalis and j^rostate ; in the 

^. , , 9 ^ - corj^ora cavernosa and spongiosa ; 

■"''" ' ' .^ , _ ill the tissue of the ovary and in 

' . . the broad ligament : in the mus- 

x^ -^ cular coat of the oviduct, the 

uterus and vagina ; in the pos- 

Fig.61.-From a Transverse terior part of the Wall of the 
Section through Bundles \y^r.\^r.^ . infhp Inrcrp and cimnll 

of Non-striped Muscular ^racnea , mine large ana small 

Tissue of the Intestine, bronchi, in the alveolar ducts 

'^%^l^l^Jt'. c'uT^, and infundibula of the lung ; in 

cor^cie"^of%=he'flga?l the pleura pulmonalis (guinea- 

?{:^''irinre.^'^ril!e''et pig) ; in the peritoneum of the 

ceii"""(4itol)"'^ """'"^^ frog and newt, in the upper part 

of the upper eyelid, and in the 

fissura orbitalis ; in the sphincter and dilator 

pupilliTe, and the ciliary muscle ; in the capsule 

and trabecular of the spleen, and the trabecular of 

some of the lymphatic glands ; in the arrectores 

pilorum, and sweat glands of the skin, the tunica 

dartos of the scrotum ; in the tissue of the nipple of 

the breast ; in the larcfe ducts of the sali^'arv and 

pancreatic glands ; and in the muscular coat of the 

gall bladder, the hepatic and cystic duct. The aorta 

and the arteries have a large amount of non-striped 

muscular tissue, the veins and lymphatics less. 

81. As regards length, the muscular cells vary 
within considerable limits (from ^\-^ to 0-5 millimeter), 
those of the intestine, stomach, respiratory, urinary. 



NoN-STKiPED Muscular Tissu/-:. 89 

and genital organs being very long as compared with 
those of the blood-vessels, which are sometimes only 
twice or thrice as long as they are broad, and at tlie 
same time branched at their extremities. 

Non-striped muscular tissue is richly supplied with 
blood-vessels, the capillaries forming oblong meshes, 
though their number is not so great as in striped 
muscle. The nerves of non-striped muscle are all 
derived from the sympathetic ; their distribution and 
termination will be described in a future chapter 



90 



CHAPTER IX. 

STRIPED MUSCULAR TISSUE. 



82. The striped muscular tissue is composed of 
long cylindrical fibres, some measuring in length as 




Fig. 02.— Striped Muscular Fibres of the Tongue of a Guinea-pig, of which 
the blood-vessels have been injected with carmine gelatine. Owing to 
the contracted state of the niuscular tibres the capillaries are much 
twisted and wavy ; in several places tlie " safety receptacles " are well 
show n. (From a microplwto. , moderatehi magnified.) 

mucli as 1.^-2 inches, others are much shorter; their 
thickness varies between ^-^o ^^ e^o ^^ ^^^ inch. The 



Striped Muscular Tissue. 91 

til:) res are regularly transversely striated, and are 
therefore called the striped oi' striated muscular fil)res 
By fibrous connective tissue they are grouped together 
so as to form larijer or smaller bundles — muscular 
fasciculi ; the connective tissue surrounding the 
bundles is called the perimT/sium ; while the delicate 
connective tissue passing from the perimysium into 
the bundle, and separating the individual muscular 
fibres from one another, is called the endomysium. 
The perimysium is the carrier of the larger vascular 
and nervous branches, while the endomysium contains 
the capillaries and the terminal nerves. The capil- 
laries form very rich networks with elongated meshes, 
and are always situated between the individual 
muscle fibres. The capillaries and veins appear very 
wav^y and twisted in the contracted bundles, and 
straighter in the uncontracted bundles (Fig. 62). The 
small vessels are provided here and there with j)eculiar 
saccular dilatations, which act as a sort of safety 
receptacle for the blood when, during a sudden 
intense contraction, it is pressed out from some of 
the capillaries. 

83. Each muscular fibre during contraction be- 
comes shorter and thicker. In the living uninjured 
muscular tibres, sjDontaneously or after the application 
of a stimulus, a contraction starts at one point and 
passes over the whole muscular fibre like a wave — 
contraction vxive — the progress of which is noticeable 
by the thickening rapidly shifting along the fibre, the 
part behind resuming its previous diameter. 

84. A striped muscular fibre consists of (1) a 
delicate hyaline elastic sheath, the sarcolenima, and 
(2) the rnuscniar contents. It is the structure of the 
latter which has given origin to a variety of theories, 
owing to optical difficulties in examining fresh and 
living fibres, and owing to the varied changes it is 
liable to undergo when acted upon by many reagents. 



92 



Elemexts of Histology. 



jMJS8S»i»i*9f^^§i^f/ 



;i^6siJ^aS 



1; . 




»S24? ji ;t5J 


t " vC^S 



In the following we shall adopt the view enunciated 
by Rollett during recent years ; we think that his 
conclusions are based on extensive observations and 
study of muscular fibres in vertebrates and inverte- 
brates under the best conditions, and his conclusions 
harmonise best with the classical observations of 
Bowman, Briicke, Cohnheira, and Engelmann, and 

with observations which can 
g ---.,„.,,,,.,,.,,, 3 be verified by careful study 
f of fresh muscular fibres. 

S5. The contents of a mus- 
cular fibre consist of two prin- 
cipal parts (Figs. 63, G4) : {a) 
the fihrillce, or rhabdia of 
Kiihne ; and (h) the sarco- 
plas'/ii or intertibrillar sub- 
stance, a hyaline or faintly 
granular substance, having 
resemblances to protoplasm, 
and acting as the matrix for 
the tibrilhe. The fibrillar ex- 
tend in a longitudinal direc- 
tion parallel to the long axis 
of the muscular fibre, and they 
are grouped together into 
bands, strands, or tubes, called 
the muscle columns ; the latter 
larger groups. The sarco- 
plasm fills up all interstices between the groups of 
the muscle columns, between the columns of each 
group, and between the fibrillfe of each column. The 
amount of sarcoplasm between the groups of columns 
is generally greater than between the columns of each 
group. During growth and regeneration of mus- 
cular fibres in the adult the collections of nucleated 
sarcoplasm on the surface —i.e. underneath the sarco- 
lemma — become conspicuously increased in vertebrate 






Fig. 63. — Part of a Muscular 
Fibre of Geotruxjes sylva- 
ticus, showing its compo- 
sition of fibrillit. {Rollett.) 

I, Intermediate disc (Krause's 
membrane) ; s, sarcous ele- 
ments. 



are aorgresfated 



into 



Striped Muscular Tissue. 



93 



muscular tibres, both in number and size ; and they are 

the material from which muscular fil^rilhe are formed. 

Special collections of nucleated 

sarcoplasm are found at the 

termination of the motor nerve 

tiljre in the muscular fibre [see 

below). 

On observing a cross section 
through fresh or well-preserved 
muscular fibres, the sarcoplasm 
is seen as transparent lines sub- 
dividing the muscular contents, 
which appear dim like ground 
glass, into small more or less 
polyhedral areas, the areas of 
Cohnheim. These areas are the 
cross-sections of the muscular 
columns, and are therefore made 
up of a number of granules, 
the optical cross-sections of the 
constituent fibrillae. The mus- 
cular columns appear aggre- 
gated by larger accumulations 
of sarcoplasm into larger or 
smaller groups ; and between 
the groups the sarcoplasm is 
again greater than between the 
fibrillae of each column, and in 
this respect there exists the 
greatest variety between the 
different animals. In the per- 
fectly fresh condition tlie 
amount of sarcoplasm between 
the fibrilhe of a column is 
in some cases insignificant, 
and almost appears absent from place to place. 

Tlie sarco[)lasm shows also other differences of 



A'— 




\ 



jL 



Fig. 64. — Mu>;cul;ir Fibre, 
stained with hitmatoxy- 
lin, of Staphylinuscaesa- 
reus. {liollett.) 

I, Interniefliate disc (Krause's 
membrane or Dobie's 
layer); L, secondarj' disc 
(placed witliiii tlie lateral 
disc ur Floi-'el's layer) ; 
T, tranverss disc (sarcoiis 
eleiiieats); x, nucleus of 
muscle corpuscle. 



Q4 Elements of Histology. 

distribution ; in the muscular libres of many insects 
it generally forms a cylindrical accumulation in the 
centre of the muscular fibres, containing spherical 
nuclei ; from it thinner septa pass between the groups 
of muscular columns. In vertebrate muscular fibres 
the sarcoplasm forms small plate-like or angular col- 
lections on the surface of the muscular contents — i.e. 
immediately under the sarcolemma. These collections 
include spherical, or more generally oval, nuclei, and 
are called the muscle corpuscles. The whole sarco- 
plasm must be considered as a sort of protoplasmic 
basis, and the muscle corpuscles as the nucleated accu- 
mulations of it. 

86. Each hbrilla shows along the whole length of 
the muscular fibre regular alterations, as regards both 
aspect and thickness of its sul)stance, and accordingly 
can be considered as consisting of different portions 
following each other endwise, and repeating them- 
selves uniformly and in regular manner throughout 
the whole length and thickness of the muscular fibre. 
These portions are the sarcous elements of Bowman, 
dim, homogeneous rods or prisms forming the chief 
parts ; between each tw^o successive sarcous elements 
of the saQie fibrilla, at equal distance, is a dark granule, 
sometimes double, to whicli the end of each sarcous 
element is joined by a thin bridge. In the fresh state 
the sarcous elements are prisms, and those of con- 
tiguous fibrilla?, almost touch each other at their sides, 
so that little or no sarcoplasm intervenes between 
them here ; but when the sarcous elements shrink 
— e.g. after death or after hardening reagents, or 
sometimes even duriiig life and during contraction — 
they are more or less hourglass-shaped, and are 
separated by thin layers of sarcophism from those 
of contiguous fibrillse. The bridge by which each end 
of a sarcous element is joined to the granule being 
much thinner than the latter, there is more sarco- 



Sir IP /CD Muscular Tissue. 



95 



granules of the 




plasm present in the layer containing the bridge; 
and since the sarcoplasm is more transparent than 
either the sarcous elements or the 
fibrilla^ the 
nmscnlar libre 
as a whole 
shows a con- 
s p i c u o u s 
transparent 
layer or disc 
between each 
layer of the 
dark granules 
and each layer 
of the sarcous 
elements. This 
causes the 
transverse 
striation. The 
layer of the 
dark granules 
corresponds to 
tlie line of 
Dohie, or the 
line of Amici, 
or the inter- 
mediate disc of 

Engelmann, or the yneinhrane of Krause. The 
layer or disc of sarcoplasm in which the bridges 
are placed, which join the sarcous elements to 
the granules of the intermediate disc, is the lateral 
disc. The layer or disc of sarcous elements corre- 
sponds to the transverse disc. In many muscular 
fibres of insects, notably in those of the crab (Ruther- 
ford), there occurs in each fibrilla witliin the lateral 
disc a short rod-like thickening midway between the 
sarcous element and the dark granule ; the layer or 




E 



Fis. 



05.— Striped Muscular Fibres of the Water 
Beetle (Hydropliilns). {Atlas.) 

Sarcoleiuraa; b, Krause's menibrane. The sarcous 
eliiiient^; are well seen. In a the oblong nuclei of 
tlie muscle corpuscles nre shown. In b the sarco- 
lennua has become unnaturally raised from the mus- 
cular contents. The contractile discs are M^ell 
shown : so also are the sarcons elements. 



96 



Elements of Histology. 




y^-\ 





disc of these rods or grannies forms 
the secondary disc, or the Layer of 
Flcigel. 

cS7. A typical niuscnlar fibre shows 
then, owing to the differentiation of 
each fibrilla into the above portions, 
the following layers in regular 
alternation throughout the thickness 
of the fibre : (1) 27ie dark inter- 
mediate disc, Dobies line, or Kraiise's 
membrane ; (2) the transparent 
lateral disc ; (3) the dim transverse 
disc of sarcous elements. Then fol- 
lows another transparent lateral disc, 
and then again the intermediate 
disc. 

As stated above, in some fibres 
the line of Dobie is a double row 
of granules, and the transparent 
lateral disc contains a line of granules, 
Flugel's layer. 

The intermediate disc appears to 
be intimately connected with the 
sarcolemma ; hence Krause gave it 
the name of a membrane. When a 
muscular fibre contracts during life, 
or when it shrinks after death, the 
sarcolemma shows regular bulgings 
between each two Krause's mem- 
branes ; at these latter the sarco- 



Fig. 66. — Three Fibrilke of Crab's Muscle, showing 
the successive stages from complete relaxation 
(?•) to complete contraction (t). (From Rtither- 
foi'd's " .'itructui-e and Contraction of Striped 
Muscular Fibre.") 

b — 610, The various appearances of the sarcous ele- 
ments; d—(l9, the appearances of Dol>ie's granules ; 
/, Flogel's granules ; c, clear layer (lateral disc) 
between Flogel's granules and end of sarcous 
elements. 



STK/r/lD Ml'SCULAR TiSSi'E. 



97 



lemma is drawn in. The part of a muscular fihn; 
between two neighbouring Krause's membranes and 
the corresponding portion of the sarcolemma is 





Fij;-. t)7. — Semi-schematic representation of portions of Fibrils of Crab's 
Muscle, showing the appearances of the fibrillar segments in the 
several stages from complete relaxation at a to complete contraction 
at F. (After Eutherjord.) 

A.— &, Bowman's sarcous elements ; i, intermediate discs, comprising d, granules 
of Dobie ; /, granules of Fli5?el ; c, clear layer between it and end of sarcous 
element (lateral disc), b, I''frst stai,'e of contraction ; the clear layer be- 
tween Dobie's granules and Fliiiirers' granules on the one side, and Fliigel's 
granules and the end of the sarcous elements has disappeared. F, complete 
contraction, showing sarcous elements comjiletely shortened : accumulation 
of chromatic sulistauce at the ends, leaving the intervening shaft clear— 
Hansen's median disc. 

H 



yS Elements of Histology. 

spoken of as a muscular conipaitment of Krause 
{See Fig. 65, a). 

The lateral disc contains in some muscular fibres 
{see above) a layer of granules or rods, the secondary- 
disc, or Flogels layer ; but each of these granules or 
rods is ioined to a granule of the 
. 51 i intermediate disc, or Dobie's 

^^^ |! I layer, on the one hand, and to 

1 1 \ the end of a sarcous element on 

,- »* \ the other ; so that in reality it is 

vL 11 I a thickening of the bridges con- 

V^ "-^ I necting the ends of a sarcous 
Vl \\ I element to the granule of the 
V 11 I intermediate disc. 
^\\ • The transverse disc, or the 

- '* \ laver of sarcous elements, shows 



m 



VV^ \ hardening, or after treatment 
^\\ \ "^^'i^^ reagents, a median trans- 
w\ 5 verse transparency, due to the 



in muscular fibres during con- 
traction (.y^e below) or after 

1.1 

\\\\8 substance of the sarcous ele- 
"Wfi ments being here thinner, as 
IllW i^'-Pi^tioned above. This corre- 
Fig. GS.-Primitive Mus- ^ponds to the median disc of 
euiar Fibriiia; from the Hensen. Eutlierford, however, 
Si'-^^S'f- ^''■^'"' pointed out that this appear- 
ance is due to the stainable or 
chromatic substance of each sarcous element accumu- 
lating at the ends (Figs. 66 and 67). 

In muscular fibres treated with alcohol, the con- 
nection between the sarcous elements and the rest of 
the fibrillse is not recognisable ; hence the muscular 
fibre seems split up into discs, apparently not con- 
nected with one another {see Fig. 60). 

The reticulation described by ^Nlelland, ^Marshall, 
and others is due to coagulation of the sarcoplasma 



Striped Muscular Tissue. 



99 



brought about by certain hardening reagents ; the 
sarcoplasma between the granules of the layer of 
Dobie or Krause would thus form a reticulated disc 
extendinoj transversely across the muscular fibre, and 
to it are joined lines of coagulated sarcoplasma ex- 
tending longitudinally between the sarcous elements 
of the tibrill^ (Fig. 69). 

8''^. During contraction the transverse striation of 
the tibre becomes much narrower, the different discs 
becoming thinner in the 
long, broader in the trans- 
verse direction of the fibre. 
In the naturally contracted 
portion of a muscular fibre 
— i.e. at the point of the 
passage of the contraction 
wave — the stripes alter their 
character, inasmuch as at 
the end of the transverse 
and lateral discs the fibres 
become darker, while the 
middle of the discs of sarcous 
elements becomes lighter. 
Whether the former change 
— i.e. of the lateral discs — 
is due to compression, while 

the latter — i.e. of the sarcous elements —is due to an 
imbibition with water squeezed out of the sarcoplasma 
in the lateral discs, as is maintained by Engelmann, 
has not been fully established. Rutherford, on the 
other hand, points out, what appeal^ a good explana 
tion of this phenomenon — ^-iz. of the so-called re- 
versal of the stripes during contraction — that during 
contraction the chromatic substance of the sarcous 
elements, together with Flogel"s granules and Dobie's 
granules, forms one shortened mass ; hence the darkness 
of these portions in each fibrilla. We reproduce 




Fig. 69.— striped Muscular Fibres 
in Cross-section. {Altos.) 

Each fibre is limited by the sarco- 
lemiiia ; the luuscular substance 
is differentiated into Cohnheim's 
areas. 



loo Elemexts of Histology. 

here from Rutherford drawinus illustrating these 
points (Figs. 66 and 67). 

Rollett considers, with Briicke, Kolliker, Engel- 
mann, and many others, that the fibrillar are the 
contractile parts : while Klihne, Ramon y Cajal, and 
others, are inclined to think that the sarcoplasma — 
which Kiihne calls sarcoglia— is the contractile part, 
while the fibrillse — i.e. the rhabdia of Kiihne — or 
rather the sarcous elements, are elastic elements. 

The differentiation into intermediate, lateral, and 
transverse discs, possessing the above-named different 
structure and optical properties, produces the trans- 
verse striation of the muscular fibres ; but it must 
be also added that a fibre, though homogeneous but 
moniliform (by shrinking or naturally so), would 
show a transverse striation (Haycraft). 

89. In the embryo the muscular tibres are 
developed from spindle-shaped nucleated cells (Remak, 
Weissmann. Kulliker). One spindle-shaped cell with 







"^--^.s^* 



Fig 70. — Striped Muscular Fibre of the Diaphragm of a 
Guinea-pig. {Atlas.) 

The muscle corpuscles are much increased iu size aud numbers ; tbey are 
probably used here for the new formation of muscular substance. 

an oval nucleus grows rapidly in length and thickness, 
its nucleus divides repeatedly, and the offspring 
become shifted from one another as the cell continues 
to grow in lengtli. Tlius a ]<»ng spindle-shaped mass 
of sarcoplasma, with iiunierous nuclei, is the result. 



Striped Muscular Tissue. ioi 

Tliis sarcoplasiiia in the middle of the cell becomes 
converted into fibrilhe, and this formation continues, 
while the sarcoplasma as a whole increases. The 
muscle corpuscles of the adult fibres are remains of 
this sarcoplasma (Fig. 70). 

At all times in adult life, when muscular fibres 
increase in thickness, as, for instance, when muscle 
is kept at constant work, this increase is due to 
increase of sarco})lasma, and joart-conversion of this 
into fibrillin. 

Paneth described in fishes, amphibia, birds, and 
mammals a mode of new formation of muscular 
fibres which supplements the one above described. 
While in the embryo the first muscular fibres develop 
from spindle-shaped cells in the manner stated above, 
muscular fil^res are also newly formed from spherical 
or oval cells — sarcoplasts ; in the interior of these 
cells, the protoplasm is converted into contractile 
substance, which is capable of enlarging and elon- 
gating, and becoming converted into striped muscular 
fil)res. According to Kdlliker and Weissmann, 
muscle fibres divide longitudinally also, so that one 
fibre is capable of giving origin to a bundle of thin 
fibres each of which continues to increase in thickness 
[see muscle spindles below). 

90. The striped muscular fibres, taken as a whole, 
are, as a rule, spindle-shaped, becoming gradually 
thinner towards their ends. They are branched in 
some exceptional cases — e.g. in the tongue ; here the 
extremities of the muscular fibres, passing into the 
mucous membrane, become richly branched previous 
to their terndnation amongst the connective-tissue 
fibres of the mucosa. 

91. Muscular fibres terminate in tendons, either 
by the whole fibre passing into a bundle of connective- 
tissue fibrils (Fig. 71), or by the fibre ending abruptly 
with a Ijlunt, conical end, and becoming here fixed to 



102 



Elements of Histology. 



from one 



end 



FS 




a bundle of cuunective-tissue tibrils. TJie individual 
fibres have only, as has been mentioned above, a 
limited lensth : so that, following an anatomical bundle 
to the other, we tind at many points 
along the fasciculus some muscle fibres 
terminating, others originating. This 
takes place in the following way : the 
contents of a fibre suddenly terniinate, 
while the sarcolemma, as a fine thread, 
becomes interwoven with the fine con- 
necti\'e tissue between the muscular 
fibres. Manv muscles contain peculiar 
spindle-shaped enlargements ; these are 
the muscle buds of Kolliker or the 
inascle spindles of Kiihne ; each spindle 
is a bundle of fine striped muscular 
til ires formed bv lencjth division of a 
mother fibre, and enclosed within a 
thickened connective - tissue sheath, 
which sheath is continuous with the 
laminated connective - tissue sheath 
(Henle's sheath) of nerve fibres — ^in 
fact, the sjfiiidles occur at the entrance 
of certain nerves into the muscle bundle 
[see nerve endings). 

92. Tlie striped muscular fibres of 
the heart (auricles and ventricles) and 
of the cardiac ends of the large veins 
(the pulmonary veins included) differ 
from other striped muscular fil)res in 
the following respects : — -(1) They 
possess no distinct sarcolemma. (2) 
Their muscle corpuscles are in the centre of the 
fibres, and more numerous than in ordinary fibres. 
(3) They are very richly branched, each fibre giving 
oft" all along its course short branches, or continually 
dividinir into smaller fibres and forming a close 



/ 



Fig. 71. — Two 
Striped Mus- 
cular Fibres 
passing into 
Bundles of Fi- 
brous Tissue. 
(Handbook.) 

(Termination in 
Tendon.) 



Striped Muscular Tissue. 



ro3 



network (l^'ig. 72). A transverse section tlirough a 
bundle of such fil)res shows, therefore, their cross- 
sections irregular in shape and size. (4) Each nucleus 
of a muscle corpuscle occupies the centre of one 
lU'isuiatic portion ; each fibre and its branches thus 
appear composed of a single row of such prismatic 
portions, and they seem separated from one another — - 
at any rate in an 
early stage — by a 
septum of a trans- 
parent substance. 

93. Some mus- 
cular fibres are 
either markedly 
pale or markedly 
red (Ranvier) ; in 
the former {(ijj. 
quadratus lumbo- 
rum, or adductor 
magnus femoris of 
rabbit) the trans- 
verse stria t ion is 
more distinct, and 
the muscular cor- 
puscles less nume- 
rous, than in the ^ ' 
latter (ejj. semi- 
tendinosus of rabbit, 
diaphragm). Here 
the longitudinal 
striation appears very distinct, but these differences 
are not constant in the same fibres of other animals 
or of man (E. jMeyer). 

94. Briicke has shown that striped muscular 
fibres are doubly refractive, or anisotropous, like 
uniaxial positive crystals (rock crystal), the optical 
axis coincidini; with the lonsc axis of the fibres. The 




Z.— striped Muscular Fibres of the 
Heart. 

A, Showinfe' tlie liniuching of the fll)res and their 
anastomosis in networks; b, part of a thin 
filire, highly mairnifled, showing the raouili- 
forni primitive flbrillae; c, one inimitive 
tibrilla more highly magnified. 



I04 Elements of Histology. 

sarcoplasiiia is isotropous, tlie tibrilhr alone being 
anisotropoiis ; of these the sarcous elements were the 
first recognised by Briicke to be doubly refractive. 
They are, however, not the ultimate optical elements, 
but must be considered as composed of disdiaclasts, 
the real doubly refractive elements (Briicke). 



lo; 



CFI AFTER X. 



THE HEART AXD BLOOD-VESSELS. 



95. (a) The heart consists of an outer serous 
covering, tJie visceral pericardium or exocard, an 
inner lining, the endocardium, and Ijetween the two 
the muscular suh- 
stance (Fig- 73). 
Underneath the 
pericardium is a 
thin layer of con- 
nective tissue called 
the subpericardial 
tissue. 

The free surface 
of both the peri- 
cardium and endo- 
cardium has an en- 
dothelial covering, 
like other serous 
membranes — i.e. a 
single layer of trans- 
parent nucleated cell 
plates of a more or 
less polygonal or 
irregular shape. The 
groundwork of these 
two membranes is 
tibrous connective 
tissue, forming a 

dense texture, and in addition there are many elastic 
fibres arranged as networks. Capillary blood-vessels, 




Fit 



73. — Transverse Section through 
Auricle of the Heart of a Child. 



the 



a, Endotbelium lining the endocardium; h, en- 
docardium; c, muscular bundles cut trans- 
versely ; d, muscular bundles cut longitudi- 
nally ; e, pericardial covering ;/,endotlieliuui. 



io6 Elements of Histology. 

lymphatic vessels and small Ijranclies of nerve li))res 
are met with in the pericardial layer. The sub- 
pericardial tissue consists of trcibecula^ of tibrous 
connective tissue, which are continuous with the 
intermuscular connective tissue of the muscular wall 
of the heart. The former contains in many places 
groups of fat cells. 

96. On the free surface of the papillary muscles, 
in some parts of the surface of the trabeculse carnese, 
and at the insertion of the valves, the endocardium is 
thickened by tendinous connective tissue. Each valve 
is covered with a prolongation of the endocard, but 
the main body of the valve is dense tibrous connective 
tissue ; on the surface of this connective-tissue matrix 
is a somewhat looser connective tissue, containing 
also a few elastic fibres. 

All the corda3 tendineie and the \alves are of course 
co\ ered on their free surfaces with endothelium. 

Special tracts of uiuscle fibies occur in the sub- 
endocardial tissue. 

The fibres of Furkinje are peculiar beaded fibres 
occurrinor in the subendocardial tissue in some mam- 
mals — e.g. the sheep and the horse — and birds (not in 
man). They are thin, transversely striped, muscular 
fil^res possessed of local thickenings ; the central part 
of each thickening is a continuous mass of protoplasm, 
with nuclei at regular intervals, as is the case with 
some skeletal muscular fibres of insects. These 
beaded fibres of Purkinje must not be confused with 
the inuscle spindles of Kiihne. 

97. The muscular fibres forming the proper wall 
of the heart, the structure of which has been described 
in the previous chapter, are grouped in bundles 
separated by vascular fibrous connective tissue. In 
the ventricles the bundles are aggregated into more 
or less distinct lamella?. 

Like other striped muscular fi'hres, those of the 




Heart and Blood-vessef.s. 107 

wall of the iieart are richly supplied with blood-vessels 
and lymphatics. The endocardium and valves have 
no blood-vessels of their own, but the pericardium 
possesses its own 
system of Idood- , '•.-^n C"^ '~^\ "^^v - — ~ /'^^ --^ 

tics form a peri- Wi ;j_j^' -.==^^=.^^i^ 

cardial and an ^^^^ _j;_^ _ ^.^^s^ """^^^^^^'^^ 

endocardial net- ^^^ fe— .^^ .=^^=s. "^^ 

work connected g ^--^ss - _ ^^ 

with the lym- 
phatics of the 
muscular tissue 
of the heart ; here 
there are lym- 
phatic clefts be- 
tween the mus- 
cular bundles, 
and also net- 
works of tubular 

1 1 X- fig. 74.— i^roin a xransverse eectiou tiii< 

i_) inpuaiicb. ^jjg Inferior Mesenteric Artery of the Pig. 

Jg, inenerve <>, Endothelial lining; ?, elastic intinia; m, muscular 
l>.^Ti-./-l-.«c. ,^^ ■*-!.« media; a, adventitia with numerous elastic 

Dianciies Oi ine Ulinls, cut in transverse section. (Af/a.s.) 

l^lexus cardiacus 

torm rich plexuses. In connection with some of them 
are found numerous collections of ganglion cells or 
ganglia. These are very numerous in the nerve 
plexus of the auricular septum of the frog's heart 
(Ludwig, Bidder), and in tiie auriculo-ventricular 
septum of the frog (Dogiel). In man and mammals 
numerous ganglia are found on the auricular nerve 
branches, chiefly at the point of junction of the large 
veins with the heart, Remak's ganglia, and at the 
boundary between the auricles and the ventricles, 
Bidder's ganglia. 

91). (b) The artoi-ieN (Fig. 74) consist of : («) an 



Fig. 74. — From a Transverse Section thiuugh 



[o8 



Elemexts of Histology. 



endotheliaJ laijer lining the lumen of the vessel ; (6) an 
intima^ consisting of elastic tissue ; (c) a media, con- 
taining a large proportion of non-striped muscular cells 
arranged chiefly in a transverse, i.e. circular manner ; 
and [d) an adventitia composed chiefly of fibrous 

connective tissue, with 
an admixture of net- 
works of elastic fibres. 

(«) The endothelium 
is a continuous single 
layer of flattened elon- 
gated cell plates. 

(6) The intima in 
the aorta and larcje 
arteries is a very com- 
plex structure, consist- 
ing of an innermost 
layer of fibrous connec- 
tive tissue, which is the 
" inner longitudinal 
fibrous layer " of Re- 
mak, outside of which 
^^^ is a more or less longi- 

\^\ *~^^^^^^" tudinally arranged elas- 

tic membrane. This is 
laminated, and com- 
posed of fenestrated 
elastic meinhranes of 
Henle. {See page 61.) 
The larger the arte^^y 
the thicker the intima. 
In microscopic arteries 
the intima is a thin 
fenestrated membrane, the fibres having distinctly a 
longitudinal arranfjement. 

(c) The media is the chief layer of the wall of the 
arteries (Fig. 75). It consists of transversely arranged 




/ 



^ 



"^>*isa^> 



Fis. 



-Transverse Section through 
a Microscopic Artery and Vein m 
the Epiglottis of a Child. {Atlas. ) 

A, The artery, showing the nucleated en- 
dothelium, the circular muscular 
media, aud at a the fibrous-tissue ad- 
ventitia: V, the vein, showing the 
same layers ; the media is very Inuch 
thinner than in the arterv. 



Heart and Blood-vessels. 109 

clastic laniellse (fenestrated membranes and networks 
of elastic tibres), and between thern^ smaller or larger 
Ijundles of circularly arranged muscular cells. The 
larger the artery the more elastic tissue is there 
present in the media, the smaller the artery the more 
muscular tissue. In microscopic branches of arteries 
the media consists almost entirely of circular non- 
striped muscle cells with only few elastic fibres, 

100. In the last branches of the microscopic 
arteries the muscular media becomes discontinuous, 
inasmuch as the (circular) muscular cells are arranged 
not as a continuous membrane, but as groups of small 
cells (in a single layer) in a more or less alternate 
fashion. 

When the media contracts, the intima is thrown 
into longitudinal folds. 

The aorta has, in the innermost and in the outer- 
most parts of the media, numbers of longitudinal 
and oblique muscle cells. According to Bardeleben, 
all large and middle-sized arteries have an inner 
longitudinal muscular coat. 

101. Between the media and the next outer la3'er 
there is^ in larger and middle-sized arterieS; a special 
elastic membrane, the elastica externa of Henle. 
(d) The adventitia is a relatively thin fibrous con- 
nective-tissue membrane. In large and middle-sized 
arteries there are numbers of elastic fibres present, 
especially in the part next to the media ; they 
form networks, and have chiefly a longitudinal 
direction. 

The larger the artery the more insignificant is 
the adventitia as compared ^^•ith the thickness of 
the media. 

In microscopic arteries (Fig. 76) the adventitia 
is represented by thin l)undles of fibrous connective 
tissue and branched connective-tissue cells. 

Large and middle-sized arteries possess their own 



I lO 



Elements of Histology. 



system of blood-vessels (vasa 
chiefly iu the adventitia and 
vessels and lymphatic clefts are 
these coats, 
102. (c) 



vasorum), situated 

media: lymphatic 

also present in 



771 i.e 



fli 



^1 m 



11 



r^ 



3 



u 



'^ 



The veiiisi differ from the arteries in 
the greater thinness of their wall. The 
intima and media are similar to those 
of arteries, only thinner, both abso- 
lutely and relatively. The media con- 
tains in most A^eins circularly arranged 
muscular fibres ; they form a continu- 
ous layer, as in the arteries, and there 
is between them generally more fibrous 
connective tissue than elastic. The 
adventitia is usually the thickest coat, 
and it consists chiefly of fibrous con- 
nective tissue (Fig. 75). The smallest 
veins — i.e. before passing into the 
capillaries — are composed of a lining 
endothelium, and outside this are de- 
licate bundles of connective tissue 
forming an adventitia. The valves 
of the veins are folds, consisting of the 
endothelium lining the surface, of the 
whole intima, and of j^art of the mus- 
cular media. 

103. There are many veins that 
have no muscular fibres at all — e.g. 
vena jugularis (interna and externa), 
the vena -ubclavia, the veins of the bones and retina, 
and of the membranes of the brain and cord. Those 
of the gravid uterus have only longitudinal muscular 
fibres. The vena cava, azygos, hepatica, spermatica 
interna, renalis and axillaris, possess an inner circular 
and an outer longitudinal coat. The vena iliaca, 
cruralis, poplitea, mesenterica, and umbilicalis possess 
an inner and outer longitudinal and a middle circular 



n I fl J<te' i 



Fig. 76.— ilinnte 
Slicroscopic Ar- 
tery. {Atlas.) 

e, Endotheliaru ; i. 
intima; m, mus- 
cular media.com- 
posed of a siDgk- 
layer of circu- 
larly - arranged 
non-striped nius- 
cular cells; a, ad- 
ventitia. 



Heart axd Blood-vessels. iir 

muscular coat. Tlie intiina of the vena? pulmonales 
in man is connective tissue containing circular bundles 
of non-striped muscular cells (Stieda). 

104. The trunk of the venie pulmonales and 
ven?e cavre possesses striped muscular fibres, these 
being continuations of the muscular tissue of the 
auricles. 

105. Hoyer showed that a direct communication 
exists between arteries and veins witliout the inter- 
vention of capillaries— as in the matrix of the nail, 
in the tip of the nose and tail of some mammals, in 
the tip of the fingers and toes of man, in the margin 
of the ear lobe of dog and cat and rabbit. 

In the cavernous tissue of the genital organs 
veins form large irregular sinuses, the wall of 
which is formed by fibrous and non-striped muscular 
tissue. 

lOG. (d) The capillary blood-vessels are 
minute tubes of about a^oVo ^^ Wiro *^^ ^'^ inch in 
diameter. Their wall is a single layer of transparent 
elongated endothelial plates, united by thin lines of 
cement sidistance (Fig. 77). Each cell has an oval 
nucleus ; in fact, the wall of the capillaries is merely 
a continuation of the endothelial membrane linins: 
the arteries and veins. 

In some places the capillaries possess a special 
adventitia made up of branched nucleated connective- 
tissue cells (hyaloidea of frog, choroidea of mammals), 
or of an endothelial membrane (pia mater of brain 
and cord, retina and serous membranes), or of adenoid 
reticulum (lymphatic glands, His). 

The smallest capillaries are found in the central 
nervous system, the largest in the marrow of bone. 
The capillaries form networks, the richness and 
arrangement of which vary in the different organs, 
according to the nature and arrangement of the 
elements of the tissue (Fig. 78). 



1 12 



Elements of Histology 



107. If capillaries are abnormally distended, as 
ill inflammation, or otherwise injured, the cement 



fc^'<-r 




Fig. 77.- From a Preparation of the Peritoneum, stained ^vitli 
Nitrate of Silver. (Handbook.) 

a, Entlotlieliuin on the free surface of the membrane ; h, capillary blood sessels 
in the membrane ; their wall is a layer of eQclotbelium. 




Fig. 78.— Young Fat Tissue of the Omentum, its Blood-vessels injected. 
n. Artery ; b, vein ; r, network of capillariei?. {Handbook.) 

substance between the endothelial plates is liable to 
o-ive way in tlie shape of minute holes, or stigmata, 



Heart and Blood-vessels. 



i»3 



\\ liicli in;iyl>econie lur^er holes, or *•^(J'/y<^(^^ Tlie passage 
of red bloofl cori)uscles (diapedesis) and the migration 
of wJiite corpuscdes in inflammation through the un- 
broken capillaries and small veins occur through 
these stigmata and stomata. 

108. Yoiiii^: and g^row iiig^ capillaries, Ijoth 
of normal and pathological tissues, possess solid thread- 
like shorter or longer nucleated protoplasmic processes 
(Fig. 79), into which the canal of the capillary is 




Fig. 70. —From a Pi-eparation of Omentum of Rabbit, after staining with 
Xitrate of Silver. {Atkis.) 

V, Minute vein ; a, solid protoplasmic prolongations of the wall of a capillary, 
connected with connective-tissue corpuscles ; c, solid young bud. 

gradually prolonged, so that the thread becomes con- 
verted into a new capillary branch. Such growinor 
capillaries are capable of contraction (Strieker). 
All blood-vessels, arteries, veins, and capillaries. 



114 



Elements of Histology 



d fibrous connective-tissue 



both in the embryo and 



ill their early .stages, both ill embryonal and adult 
life, are of the nature of minute tubes, the wall of 
which consists of a simple endothelial membrane. In 
the case of the vessel becoming an artery or vein, 
cells are added to the outside of the endothelium, 
thus forming the material for the development of 
the elastic, muscular, and 
elements of the wall. 

109. In the first ;• 
in the adult, the vessel is re^jresented by solid nucle- 
ated protoplasmic cells, spherical, elongated, spindle- 
shaped, or bran- 
ched — vasofor- 
iiiative cells. 
Such cells may 
be isolated and 
indej)endent of 
any pre-existing 
vessel, or they 
ma}^ be solid 
prot opl as mic 
outgrowths of 
the endothelial 
wall of existing 
capillarv vessels 
(Fig. 80). In 
both cases they 
become hollowed 
out by a process 
of vacuolation ; 
isolated vacuoles 
appear at first, 
but tliev oradu- 
ally become Oion- 
iiuent, and thus a young vessel is formed, at first 
very irregular in outline, but gradually acquiring 
more and more of a tulnilar form. In the case of 




so. — Developing Capillary Blood-vessels from 
the Tail of Tadpole. {Atlas.) 

V, Capillary vein with clumps of pigiueat in the 
■wait :«, nucleated protoplasmic sprouc ; /.solid 
anastomosis between two neighbouring capil- 
laries. 



Heart and Blood-vessels. 



11^ 



ail isolated cell, its protoplasmic processes grow l)y 
degrees to th(! nearest capillary, to the wall of which 
they become fixed, and the cavity of the cell finally 
opens through such processes into that of the capillary 
vessel. 

The islets or cysts of blood that appear early in the 
area vasculosa of the embryo are due to vacuolation of 




Fig. SI.— Cells from inesoblast of chick's blastoderm undergoing develop- 
ment into blood-vessels in the area vasculosa. (Handbook.) 

", Cavitj- of cell; b, cell wall ; /, cells not yet hollowed out ; d, hlood corpuscles. 



spherical or elongated vasoformative cells of the meso- 
blast, the islets or cysts being composed of a central 
portion which are blood corpuscles, at first white, then 
red, and a joeripheral protoplasmic nucleated envelope, 
the future vascular wall. The central nucleated blood 
cells develop by a process of endogenous division from 
the original cell protoplasm. The blood cysts, at first 
isolated, afterwards become connected by protoplasmic 
processes with other cysts or other vasoformative cells, 
ultimately forming a network of vessels (Fig. 81). 

The. wall of young capillaries is granular-looking 
})rotoplasm (the original cell substance), and in it 



ii6 Elements of Histology. 

are disposed, in uiore or less regular fashion, oblong 
nuclei, derived Ijv multiplication from the nucleus of 
the orkdnal cell. In a later stai:e. a differentiation 
takes place in the protoplasmic wall of the capillary 
into cell plates and cement substance, in such a way 
that each of the above nuclei appertains to one cell 
plate, which now represents the linal stage in the 
formation of the capillary. Both in the embryo and 
in the adult a few isolated nucleated protoplasmic cells, 
or a few protoplasmic solid processes of an existing 
capillary, may by active and continued growtli give 
origin to a whole set of new capilkries (Strieker, 
Aftanasieff". Arnrild. Klein, Balfour, Ranvier, Leboucq). 



I T 



CHAPTER XI. 



THE LYMPHATIC VESSELS. 



110. The larg^e lymphatic trunks, such as the 
thoracic duct, and the lymphatic vessels passing to and 
from the lymphatic glands, are thin-walled vessels, 




Fig. 82. — Lymphatic Vessels of the Diaphragm of the Dog, stained with 
Nitrate of Silver. (Atlofi.) 

The eadothelium foniiin',' tlie wall of tlie lymphatics is well shown ; 
V, valves. 

siaiilar in structure to arteries. Their lining endo- 
thelium is of the same character as that of an artery, 
and so are the elastic intima and the media with its 
circular muscular tissue ; but these latter are very 
much thinner than in an artery of the same calibre. 



ii8 



Elements of Histology 



a 



Tlie ach entitia is an exceedingly thin connective- 
tissue membrane with a few elastic fibres. Tiie 
valves are semi-lunar folds of the endothelium and 
intima, 

111. The lyiiipliatics in the tissues and organs 
form rich plexuses. They are tubular vessels, the 
wall of which is, like that of a capillary blood-vessel, 

a single layer of endothelial 
plates (Fig. 82). The lym- 
phatic is often many times 
wider than a blood capillary. 
Tlje endothelial plates are elon- 
gated, but not so long as in a 
Ijlood capillary, with more or 
less sinuous outlines : but this 
depends on the amount of 
shrinking of the tissue in which 
tlie vessel is embedded : when 
there is no shrinking in the 
tissue or in the vessel, the out- 
lines of the cells are more or 
less straight. 

The lymphatics are sup- 
ported by the tibrous connective 
tissue of the surrounding tissue, 
which does not, however, form 
part of their wall 

112. The outline of the 

vessel is not straight, but more 

or less moniliform, owing to 

Fig. 83. -From silver-stained tlie slight dilatations present 

specimen of the mesentery l^elow and at the senii-lnnar 

of tne fro*" 

o. Artery; %. perivascular VfdceS: thcSC are folds of the 

iffendoibHiar'vaa "'"'''^ endothelial wall, and they are 

met with in great numbers. 

The vessel apjiears slightly dilated innnediately be- 

vond the valve — that is, on the side farthest from 




LvMPffAT/c Vessels. 119 

the peripliery, or rootlet, whence the current of 
lymph starts. 

il3. Tracing the lymphatic vessels in the tissues 
and organs towards their rootlets, we come to more or 
less irregularly-shaped vessels, the wall of which also 
consists of a single layer of polygonal endothelial 
])lates; the outlines are very sinuous. These are the 
IjimpJtatic capUJaries ; in .some places they are mere 
clefts and irregular sinuses, in others they have more 
the character of a tube, but in all instances they 
have a complete endothelial lining, and no valve.s. 

Sometimes a blood-vessel, generally arterial, is 
ensheathed for a shorter or longer distance in a 
lymphatic tube, which has the character of a lym- 
l»hatic capillary ; these are the perivascular hjm- 
pliatics of His, Strieker, and others (Fig. 83). 

114. The rootlets of the lyiiiphatic!^ are situ- 
ated in the connective tissue of the different origans 
in the shape of an intercommunicating system of 
crevices, clefts, spaces, or canals, existing between the 
bundles, or groups of bundles, of the connective tissue. 
These rootlets are generally without a complete endo- 
thelial lining, but are identical with the spaces in 
which the connective-tissue corpuscles are situated ; 
N\here these are branched cells anastomosing by their 
processes into a network — such as the cornea, or 
serous membranes — we tind that the rootlets of the 
lymphatics are the lacunse and canaliculi of these cells 
— the typical lymph- canalicular system of von 
Recklinghausen (Fig. 84). The endothelial cells 
forming the wall of the lymphatic caj^illaries are 
directly continuous with the connective cells situated 
in the rootlets. In tendons and fascife the minute 
lymphatics lie between the bundles, and have the 
shape of continuous long clefts or channels ; in 
striped muscular tissue they have the same character, 
being situated l^etween the muscular fibres. 



I 20 



Elements of HjsroLOGV. 



The passage of plasma from the minute arteries 
and capiUarv blood-vessels into the lymph-rootlets 
situated in the tissues, and thence into the lymphatic 




Fig. S4- From silver-stained preparation of the Central Tendon of the 
Rabbit's Diaphragm, showing the direct connection of the Lyniph- 
canalicular System of the Tissue with the Lymphatic Capillaries. 

a. LympUatlc vessel; h, lymphatic capillary lined wich "sinuous' endotheliom. 

(Handbook.) 

capillaries and lymphatic vessels, represents the natural 
current of Ivmph irrigating the tissues. 

115. Lymph cavities. — In some cases the lym- 
phatic vessels of a tissue or organ are possessed of, or 
connected with, irregularly-shaped large sinuses, much 
wider than the vessel itself : these cavities are the 
lymph sinuses, and their wall is also composed of a 



Lymphatic Vessels. 



I 2 I 



single layer of more or less polygonal endothelial 
plates with very sinuous outlines. Such sinuses are 
found in connection with the subcutaneous and sub- 
mucous lymphatics, in the diaphragm, mesentery, liver, 
lungs, etc. On the same footing — i.e. as lymph 
sinuses — stand the comparatively large lymph cavities 
in the body, such as the subdural and subarachnoidal 
spaces of the central nervous system, the synovial 
cavities, the cavities of the tendon-sheaths, the cavity 
of the tunica vaginalis testis, the pleural, pericardial, 
and peritoneal cavities. In batrachian animals — e.g. 
frogs — the skin all over the trunk and extremities is 
separated from the subjacent fascipe and muscles by 
large bags or sinuses — the subcutaneous lynipJi sacs. 
These sinuses are shut 
off from one another 
by septa. Between the 
trunk and the extremi- 
ties, and on the latter, 
the septa generally 
occur in the region of 
the joints. In female 
froiifs in the mesoo-as- 
trium smaller or larger 
cysts lined with cili- 
ated endothelium are 
sometimes found. Be- 
hind the peritoneal 
cavitv of the fros:, on 
each side of the ver- 
tebral column, exists a 
similar large lymph si- 
nus, called the cisterna 
lyniphatica magna. 

116. The lymph cavities are in all instances in direct 
communication with the lymphatics of the surround- 
ing parts by holes or open mouths (stomata), often 




Fi; 



. 8.J. — Stuinata, lined witli Gennina- 
ting Endothelial Cells, as seen froni 
the Cisternal Surface of the Septuni 
Cisternal I.yniphatici« Magnai of the 
Frog. (Hundboolc.) 



122 



Elements of Histology. 



surrounded by a special layer of polyLedral endothe- 
lial cells — germinating cells (Figs. 85, %^). Such 
stomata are numerous on the peritoneal surface 
of the central tendon of the diaphragm, in which 
are found straight lyn)ph channels between the tendon 
bundles, and these channels communicate by nu- 
merous stomata with 
the free surface. A 
similar arrangement 
exists on the costal 
pleura, the omentum, 
and the cisterna Ivm- 
phatica magna of the 
frog. {See Chapter 
IV.) 

117. The serous 
uieiiibraiies con- 
sist of endothelium 
upon a layer of 
fibrous tissue with 
networks of line 
elastic fibres : they 
contain networks of 
])lood capillaries and numerous lymphatic vessels 
arranged in (superficial and deep) plexuses. Plexuses 
of lymphatics are very numerous in the pleura costalis 
— or rather, intercostalis — in the diaphragm and pleura 
pulmonalis. They are important in the process of 
absorption from the pleural and peritoneal cavity 
respectivelv. Lymph and lymph corpuscles, and other 
solid particles, are readily taken uj:) by the stomata 
{see Fig. 31) and brought into the lymphatics. Here 
the respiratory movements of the intercostal muscles, 
of the diaphragm, and of the lungs respectively, pro- 
duce the result of the action of a pump. 

118. There exists a definite relation between the 
lymphatics on the one hand and the epithelium on the 




Fig. 86. — Endotheliuia ami Stomata of tlie 
Peritoneal Surface of the Septum Cis- 
ternse Lj-mpbaticte Magnge of the Frog. 
{Hawlhook.) 



Lymphatic Vessels. 123 

other, wliieli covers the mucous membranes and lines 
the various glands, and also between the endothelium 
covering serous membranes and that lining their vessels 
and lymph cavities — namely this: the albuminous semi- 
fluid cement substance {see former chapters) between 
the epithelial or endothelial cells is tlie path by which 
fluid and formed matter passes between the surfaces 
and the lymph-canalicular system — i.e. the rootlets of 
the lymi)liatics. 

119. L.yiiii>li taken from the lymphatics of difl^er- 
ent regions differs in composition and structure. That 
from the thoracic duct contains a large number of 
colourless or white corpuscles (lymph corpuscles), each 
of which is a protoplasmic nucleated cell similar in 
structure to a white blood corpuscle. They are of 
various sizes, according to the stage of ripeness. The 
smaller lymphocytes contain one, some of the larger con- 
tain two and three nuclei corresjDonding to the typical 
leucocytes. The latter show more pronounced amoeboid 
movement than the former. Also "granular " oxyphile, 
basophile, and amphophile cells are met with amongst 
the leucocytes. A few red corpuscles are also met 
with. Granular and fatty matter is present in large 
(|uantities during and immediately after digestion. 

In the frog (and also in other lower vertebrates — 
e.g. reptiles) there exist certain small vesicular lymph 
cavities, about an eighth of an inch in diameter, 
which show rhythmic pulsation ; they are called lym^^li 
hearts. On each side of the os coccygis and under- 
neath the skin is a pulsating posterior lymph heart. 
The anterior lymph heart is oval, and is situated on 
each side of the processus transversus of the third and 
fourth vertebrae ; it is rather smaller than the posterior 
one. Each lymph heart has afferent lymphatics, by 
which it is in open communication with the lymph- 
atics of the periphery, and from it passes out an efferent 
vessel which opens into a large vein (a l)ranch of the 



124 



Elements of Histology. 



sciatic and jugular veins resiDeetively). A valve 
allows Ivmpli to flow out of the lymph heart into 
the vein, but pre\'ents regurgitation of blood from 




Fig. 87. — Developing Lyinph-capillaries in the Tail of Tadpole. {Atlas.) 
a, Solid nucleated protoplas iiic branches not yet hollowed out. 



the vein. The i?iternal surface of the lymph hearts 
is lined with an endothelium like the lymph sacs, and 
in their wall they possess plexuses of striped, branched, 
muscular fibres. The nerve fibres terminate in these 
striped muscular fibres in the same manner as in those 
of other localities. (Ranvier.) 



L YMPHA TIC Vessel s. 125 

12U. Lvm})liatic vessels are developed and newly 
formed under normal and pathological conditions in 
precisely the same way as blood-vessels. The accom- 
panying woodcut (Fig. 87) shows this very well. AVe 
have also here to do with the hollowing out of (con- 
nective tissue) cells and their processes previously 
solid and protoplasmic. 



126 



CHAPTER XII. 

FOLLICLES OR SIMPLE LYMPH fiLAXDS. 

121. Under this name ^ve include the blood glands, 
or the conglobate gland substance of Hewson, His, 
and Henle. or the lymph follicles (Kolliker, Huxley, 
Liischka). The ground sul)staneeof all lymph glands, 
simple as well as compound (see below), is the lymph- 
atic or o.denoid tissue, or leucocvtocrenous tissue. 
Like all other gland tissue, it is supplied with a rich 
network of capillaries derived from an afferent 
artery, and leading into ett'erent veins. 

122. The elements constituting this tissue are : — 
(«) The adenoid reticnlura (Fig. 88), a network 

of tine homogeneous fibrils, with numerous plate-like 
enlargements. 

(b) SiiiaU, transparent, fljif, endotlteloid cell phites, 
each with an oval nucleus. These cell plates are fixed 
on the reticulum, of which at first sight they seem 
to form part. Their oval nucleus especially ap[)ears 
to belong to a nodal ])oint — i.e. to one of the 
enlargements of the reticuluni : l>ut bv continued 
shaking of a section of any lymphatic tissue, the oval 
nuclei and their cell plates can be got rid of, so that 
onlv the n^riculum is left, without any trace of a 
nucleus. 

(c) Lymph rorpiLScles completely fill the meshes of 
the adenoid reticulimi. These can, however, be easily 
shaken out. They are of different sizes ; some^the 
young ones — are small cells, with a comparatively 
large nucleus ; others — the ripe ones — are larger, 
have a distinct protoplasmic cell body, with one or 



S/MFLK Lymphatic Glands. 



127 













two nuclei. Ill all lyini)hatic tissues, be they part <jt" 
a simple or ot" a compound lymph glantl, certain parts 
are ot" greater transparency than others, due to the 
lymph cells 

being larger .. .. 1. '^\ J 

and in a state 
of division, as 
indicated by 
the various 
phasesofmito- 
tic division of 
their nucleus 
( F 1 e ni m i n g, 
Heilbrunn). 
These parts 
form, there- 
fore, centres 
of germina- 
tion, and con- 
stitute what 
are spoken 
of as yenn 
c e litres, or 

germ nodules (Flemming). The germ centres are 
not permanent structures. 

123. The adenoid tissue occurs as : 

(1) Diffuse adenoid tissue, without any detinite 
arrangement. This occurs in the subepithelial layer 
of the mucous membrane of the nasal fossae and 
trachea, in the mucous membrane of the false vocal 
cords and the ventricle of the larynx, in the posterior 
})art of the epiglottis, in the soft palate and tonsils, 
at the root of the tongue, in the pharynx, in the 
mucosa of the small and large intestine, including the 
villi of the former ; and in the mucous membrane of 
the nasal cavity and vagina. 

{'!) Cords, cijUnders, ov [xitclf-^ of adenoid tissue; 




Fig. SS. — Adenoid Reticulum shaken out ; most of 
the Lymph corpuscles are removed. From a Lym- 
phatic Gland. {Atlo^.) 

a, Reticulum ; c, capillary blood-vessel. 



128 



Elements of Histology 



ill the omentum and pleura, and in the spleen 
(^[alpigliian corpuscles). 

(3) Lymph follicles, i.e. oval or spherical masses 
more or less well detined ; in the tonsils, at the root 
of the tongue, in the u[)per part of the pharynx 
(phar3'nx tonsil), in the stomach, small and large 




Fig. 89. — Lyinphangial Nodules, in the Omentum of a Guinea-pig, developini: 
in connection with lymph vessels. {Klein's " Lymphatic Sydevi.") 

A, Perilymphangial nodule: a. lymph vessel; b, lymphoid tissue: c, its enclo- 
thelial wall; t', Tilood capillaries: b: endolyraphanarial structure: a, vein ; 
b, artery; c, capillaries ; d, perivascular lymph vessel ; e, lymphatic tissue; 
/, endothelial wall of the lymph vessel. 



intestine ; in the nasal mucous membrane, in the 
large and small bronchi ; and in the spleen (Mal- 
pighian corpuscles). 

Most of these masses of adenoid tissue mentioned 
hitherto are developed in the wall or even in the 
cavity of a lymph vessel or lymph sinus as pei'i- and 
endo-lymphanr/ial nodules ; in the former case the 
lymph tissue remains surrounded for a smaller or 



Simple Lymphatic Glands. 



129 



l;ir<,^u' part of its periphery by a lymph siuus formini^ 
l)art of a network of lyin[>li tubes (Fig. 89, a and b). 
124. The tonsils (Fig. 90) are masses of lymph 
follicles anil diflfase adenoid tissue covered with a thin 
mucous membrane, which penetrates in the shape of 






• ■•'.**,■•'.'. 




;'-'^i',\ 










/■' -^ ■^'^^^: --' III 

Fig. 90.— Vertical Sectiun through part of the Tuiisil of Dog. {AUo.s.) 

e. Stratified pavement epitbelluni covering tbe free surface of the raucous 
membrane. The tissue of the mucous membrane is infiltrated wiih adenoid 
tissue. /, lymph follicles ; m, raucous gland of tbe submucous tissue. 

longer or shorter folds into the substance within. 
Numbers of mucus-secreting cjlands situated outside 
the layer of lymph follicles discharge their secretion 
into the pits (the crypts) between the folds. The free 
surface of the tonsils and the crypts is covered or 
lined with similar stratified epithelium to that which 
lines the oral cavity. Xumbers of lymph corpuscles 



130 Elements of Histology. 

constantly, in the perfectly normal condition, migrate 
through the epithelium on to the free surface, and are 
mixed with the secretions (mucus and saliva) of the 
oral cavity. The so-called mucous or salivary cor- 
puscles of the saliva, taken from the oral cavity, are 
such discharged lymph corpuscles (Stohr). They 
become swollen up by the water of the saliva, and 
assume a spherical shape. They finally disintegrate. 

Similar relations, only on a smaller scale, obtain 
at the root of the tongue. 

The pJuirynx tonsil of Luschka, occurring in the 
upper part of the pharynx, is in all essential respects 
similar to the palatine tonsil. Owing to large parts 
of the mucous membrane of the upper portion of the 
pharynx being covered with ciliated columnar epi- 
thelium, some of the cryptr: in the pharynx tonsil are 
also lined w4th it. 

125. The lenticular g-laiitl*^ of the stomach are 
single lymph follicles. 

The solitary glands of the small and large 
intestine are single lymph follicles. 

The agniinated g-lands of the ileum are groups 
of lymph follicles. The mucous membrane containing 
them is much thickened by their presence. These 
groups of follicles are called a Peyer^s ixitcli or a 
Peyers gland (see Intestine). 

126. In most instances the capillary blood-vessels 
form in the lymph follicles meshes, arranged in a more 
or less radiating manner from the periphery towards 
the centre ; around the periphery there is a network 
of small veins. A larger or smaller portion of the 
circumference of the follicles of the tonsils, pharynx, 
intestine, bronchi, etc., is surrounded by a lymph 
sinus leading into a lymj)hatic vessel. (See above.) 
The lymphatic vessels and lymph sinuses in the 
neighbourhood of lymphatic follicles or of diffuse 
adenoid tissue are almost always found to contain 



Simple Lymphatic Glands. 131 

numerous lymph corpuscles, thus indicating that 
these are produced by the adenoid tissue and absorbed 
by the lymphatics. 

r27. The tliyiiiiiH ^laiid consists of a frame- 




'* ■" =« to '^ " 

Fig. 91.— Section through the Thymus Gland of a Fcetus. 

a. Fibrous tissue between the follicles; &, cortical portion of the follicles 
c, medullary portion. 



work and the gland substance. The former is fibrous 
connective tissue arranged as an outer capsule, and 
in connection with it are septa and trabeculae passing 
into the gland and subdividing it into lobes and 
lobules, which latter are again subdivided into the 
follicles (Fig. 91). The follicles are very irregular 
in shape, most of them being oblong or cylindrical 
streaks of adenoid tissue. Near the capsule they are 
well defined from one another, and present a polygonal 
outline ; farther inwards they are riiore or less fused. 
Each shows a central transparent medulla (germ centre) 
and a peripheral less transparent cortex (Watney). 



132 



Elements of Histology. 



At tlie places where two follicles are fused with one 
another the medulla of both is continuous. The matrix 
is adenoid reticulum, the fibres of the medullary part 
being coarser and shorter, those of the cortical portion 
of the follicle liner and longer. The meshes of the 
adenoid reticulum in the cortical part of the follicles 
are filled with lymph corpuscles like those occurring in 
the adenoid tissue of otlier organs, but in the medul- 
lary part they are fewer, and the meshes are more or 
less completely occupied by the enlarged but more 
transparent cells : in many of these mitotic division of 
the nucleus occurs. These conditions cause the neater 
transparency of the medulla and represent the germ 
centres above mentioned. Amongst the laro-e cells of 

the medullary portion, 
some are coarsely granu- 
lar and include more 
than one nucleus ; some 
are even multinucleated 
giant cells. 

128. Amongst the cells 
of the medulla occur also 
larger or smaller, more 
or less concerTErically arranged nucleated protoplasmic 
ijiasses. which are the concentric bodies of Hassall 
(Fig. 92). They are met with even in the early 
stages of the life of the thymus, and cannot there- 
fore be connected with the involution of the gland, 
as maintained by Afanassief, according to whom 
the concentric corpuscles are formed in blood-vessels 
which thereby become obliterated. According to 
Watney they are concerned in the formation of blood- 
vessels and connective tissue. 

The lymphatics of the interfollicular septa and 
trabecular always contain numbers of lymph corpuscles. 
The blood capillaries of the follicles are more richly 
distributed in the cortex than in the medulla, and 





Fig. 92. — Two Concentric or Hassall's 
Corpuscles of the Thymus. Foetal 
Gland. 



S/MPf-F. LvMriiAric Glands. 133 

they radiate from the periphery towards the central 
parts. 

129. After birth the thymus begins to undergo 
involution, leading to the gradual disappearance of 
the greater portion of the gland, its place l)eing taken 
by connective tissue and fat. But the time when 
the involution is completed varies within very wide 
limits. 

It is not unusual to find in persons of tifteen to 
twenty years of age an appreciable amount of thymus 
tissue. According to Waldeyer, about 60 per cent, of 
adults examined had still a portion of thymus gland 
left. In some animals— e.^. guinea-i)ig — the involu- 
tion of the gland even in the adult has not made much 
progress. In the thymus of the dog Watney found 
cysts lined with ciliated epithelial cells. 



134 



CHAPTER XTII. 

COMPOUND LYMPHATIC GLAXDS. 

130. The compound or true lymphatic glands are 
nodules, generally of an oblong shape, directly inter- 
]>olated in the course of lymphatic vessels. Such are 
the mesenteric, portal, bronchial, splenic, sternal, 
cervical, culntal, popliteal, inguinal, lumbar glands. 
Afferent lymphatic vessels anastomosing into a plexus 
open at one side (in the outer capsule) into the 
lymphatic gland, and at the other (the hilum) emerge 
from it as a plexus of efferent lymphatic tubes. 

131. Each true lymphatic gland is enveloped in a 
fibrous capsule which is connected with the interior 
and the hilum by traheculcn and septa of connective 
tissue. The trabeculse havincj advanced a certain 
distance, about one-third or one-fourth, towards the 
centre, branch into minor trabecular, which in the 
gland anastomose with one another so as to form a 
plexus with small meshes. Thus the peripheral third 
or fourth of the gland is subdivided by the septa and 
trabeculte into relatively large spherical or oblong 
compartments, while the middle portion is made up of 
relatively small cylindrical or irregularly-shaped com- 
partments (Fig. 93). The former region is the cortex^ 
the latter the meduUa of the gland. The compart- 
ments of the cortex anastomose with one another and 
with those of the medulla, and these latter also form 
one intercommunicating system. 

The fibrous capsule, the septa and trabecuhe are 
tlie carriers of the vascular trunks ; the trabeculse 
consist of fibrous connective tissue and of a certain 



Compound Lymphatic Glands. 



135 



amount of non-striped nuiscular tissue, which is con- 
spicuous in some animals — e.g. pig, calf, rabbit, 
guinea-pig^but is scanty in man. 

Sometimes coarsely granular connective-tissue cells 
(plasma cells) are present in considerable numl^ers in 
the trabecuhe. 

132. The com})artments contain masses of adenoid 




Fig. 03.— From a Vertical Section through a Lj-mphatie Gland, the 
Lymphatics of which had been injected. {Atlas.) 

c, Outer capsule, with lymphatic vessels in section; «, corticallymph follicles; 
around them are the cortical lymph sinuses; b, medulla; injected lymph 
sinuses between the masses of adenoid tissue. 

tissue, without being completely filled with it. Those 
of the cortex contain oval or spherical masses — the 
lymph follicles of the cortex ; those of the medulla 
cylindrical or irregularly-shaped masses — the medullary 
cylinders. The former anastomose with one another 
and with the latter, and the latter amongst them- 
selves, a condition easily understood from what has 
been said above of the nature of the compartments 
containing these lymphatic structures. The follicles 



136 



Elements of Histology. 



and medullary cylinders consist of adenoid tissue with 
germ centres of exactl}^ similar character to that 
described in the previous chapter. And this tissue 
also contains the last ramifications of the blood- 
vessels — i.e. the last branches of the arteries, a rich 
netwoik of capillary blood-vessels, and the first or 
smaller branches of the veins. The capillaries and 
other vessels receive also here an adventitious envelope 
fiom the adenoid reticulum. 

133. The cortical follicles and the medullaiy 

cylinders do not 
completely fill out 
the compartments 
made for them by 
the capsule and 
trabecular respec- 
tively, but a nar- 
row peripheral 
zone in each com- 
jmrtment is left 
free; these are the 
lymphatic sinuses. 
In the cortex they 
are spoken of as 
the cortical (Fig. 
94), in the medulla 
as the medullary J 
lyinj)h sinuses 

(Fig. 95). The 
former is a space 
between the outer 
surface of the cor- 
tical lymph follicle 
and the corre- 
sponding part of the capsule or cortical septum, the 
latter between the surface of a medullary cylinder 
and the trabecuhe. From what lias been said of the 




n 






eT?:^'^^ 




Fi 



04.— Fnnii a Section tlninigli a Lyiiiiiliatic 
Gland. (Atlas.) 

Outer caisiile; s, cortical lyiiii>li sinus; a, 
adenoid tissue of cortical follicle. Numerous 
nuclei, indicating lynijiL corpuscles. 



Com POUND Lymphatic Glands. 



137 



relation of the compartments, it follows that the 
cortical and medullary lymph sinuses form one inter- 
communicating system. These are not empty free 
spaces, but are filled with a coarse reticulum of fibres, 
much coarser than the adenoid reticulum ] to it are 
attached large transparent cell plates — endotheloid 




Fig. 95. — From a Section Uirough the Medulla of a Lymphatic Gland. 

a, Transition of the medullary cylinders of adenoid tissue into the cortical 
follicles; 6, lymph sinuses occupied by a reticulum; c, fllirous tissue trabe- 
culae ; d, medullary cylinders. 

plates. In some instances (as in the calf) these cell 
f)lates of the medullary sinuses contain brownish 
pigment granules, which give to the medulla of the 
gland a dark brown aspect. In the meshes of the 
reticulum of the sinuses are contained lymph cor- 
puscles, the majority of which consist of a compara- 
tively large protoplasmic body and one or two nuclei ; 



138 Elements of Histology. 

they show lively amoeboid movement ; a few small 
lymphocytes are also amongst them. 

The surface of the trabeculse facing the lymph 
sinuses is covered with a continuous layer of endothe- 
lium (von Recklinghausen), and a similar endothelial 
membrane, but not so complete, can be made out on 
the surface of the cortical follicles and the medullary 
cylinders. The endotheloid plates, applied to the 
reticulum of the sinuses, are stretched out, as it 
were, between the endothelial membrane covering 
the surface of the trabecular on the one hand and 
that covering the surface of the follicles and cylinders 
on the other. 

In the mesenteric glands of the pig the distribu- 
tion of cortical follicles and medullary cylinders is 
almost the i-everse from that of other glands and in 
other animals : the cortical part having the arrange- 
ment of cylinders of adenoid tissue and trabeculai, 
while the medulla shows lymph follicles and longer 
septa between them. 

134. The afferent lymphatic vessels having entered 
the outer capsule of the gland, and having formed 
within the capsule a dense plexus, open directly into 
the cortical lymph sinuses. The medullary lymph 
sinuses, on the other hand, lead into lymphatic vessels, 
which leave the gland at the hilum as the efferent 
vessels. 

Both afferent and efferent vessels are supplied 
with valves. 

135. The course of the lymph through a lymphatic 
gland is this : From the afferent vessels, situated in 
the capsule, the lymph flows into the cortical lymph 
sinuses, from these into the medullary sinuses, and 
from these into the efferent lymphatics. Owing to 
the presence of the reticulum in the lymph sinuses the 
current of the lymph will flow very slowly and with 
difficulty, as if through a spongy Alter. Hence a 



Compound Lympi/atic Glands. 139 

large number of formed corpuscles, pigment, inflam- 
matory or other elements, passing into the gland from 
the afferent vessels are easily arrested and deposited 
in the sinuses, and are there readily swallowed by the 
amre'boid corpuscles lying in the meshes of, or de- 
posited on the reticulum. 

Passing a stream of water by way of the afferent 
lymph vessels through the gland, the contents of the 
meshes of the reticulum of the sinuses — i.e. the 
lymph corpuscles — are of course the first things 
washed out (von Recklinghausen), and on continuing 
the stream some of the lymph corpuscles of the 
follicles and cylinders are also washed out. Probably 
also by the normal lymph-stream passing from the 
minute arteries and capillary blood-vessels of the 
adenoid tissue (follicles and medullary lymph 
cylinders) into the lymph sinuses, lymph cells are 
drained, as it were, from the follicles and cylinders 
into the sinuses. The amoeboid movement of these 
cells will greatly assist their passage into the sinuses. 
From here the cells are carried away by the lymph 
current into the efferent lymph vessels, and are ulti- 
mately carried into the big lymph-trunks discharging 
into the big veins — i.e. into the circulating blood — as 
white blood corpuscles. 



I40 



CHAPTER XIY. 



NERVE FIBRES. 



136. The nerve fibres conduct impulses to or 
from the tissues and organs on the one hand, and the 
nerve centres on the other, and accordingly we have 
to consider in each nerve fibre the peripheral and 




Fig. 9(3.— From a Transverse Section tlirough the Sciatic Nerve of Dog. 

ep, Epineurium ; }). periueuriuni ; n, nerve filires coustituting a nerve bundle in 
cross-section ; /, fat tissue surroundiug the nerve. {Athig.) 

central termination and the conducting part. The 
latter, i.e. the nerve fibres proper, in the cerebro- 
spinal nerves are grouped into bundles, and these 
afifain into anatomical nerve branches and nerve 
Each anatomical cerebro-spinal nerve con- 



trunks 



Nerve Fibres. 141 

sists, therefore, of bundles of nerve fibres (Fig. 96). 
The general stroma b}^ which these bundles are held 
together is fibrous connective tissue called the epi- 
neurium (Key and Retzius) ; this epineurium is the 
carrier of the larger and smaller blood-vessels with 
which the nerve trunk is supplied, of a plexus of 
lymphatics, of groups of fat cells, and sometimes of 
numerous plasma cells. 

137. The nerve bundles or faiiiculi (Fig. 97) vary 
in size according to the number and size of the nerve 
fibres they contain. They are well defined by a 
sheath of their own, called perineurium (Key and 
Retzius). This perineurium consists of bundles of 
fibrous connective tissue arranged in lamella?, every 
two lamella? being separated from one another by 
smaller or larger Ijmiph spaces, which form an inter- 
communicating system, and anastomose with the 
lymphatics of the epineurium wdience they can be 
injected. Between the lamella, and in the spaces, 
are situated flattened endotheloid connective-tissue 
corpuscles. 

The nerve bundles are either simple or compound. 
In the former the nerve fibres are not subdivided 
into groups within the bundle, in the latter the 
bundles are subdivided by thicker and thinner septa 
of fibrous connective tissue connected with the peri- 
neurium. When a nerve bundle divides — as when a 
trunk repeatedly branches, or when it enters on its 
peripheral distribution — each branch of the bundle 
receives a continuation of the lamellar perineurium. 
The more branches the perineurium has to supply, 
the more reduced it becomes in thickness. In some 
of these minute branches the perineurium is reduced 
to a single layer of endothelial cells. When one of 
these small bundles breaks up info single nerve 
fibres, or into small groups of them, each of these has 
also a continuation of the fibrous tissue of the 



142 



Elemexts of Histology. 



perineurium. In some places this perineural con- 
tinuation is only a very delicate endothelial membrane 
as just mentioned, in others it is of considerable 
thickness, and still shows its lamellated nature. Such 




Fig. 07.— Transverse Section through a Xerve Bundle in 
the Tail of Mouse. i^AtUs.) 

p. Perineurium ; c, endoneurium separating the medullated nerve fibres 
seen in cross-section ; i, lymph spaces in the perineurium; i, lymph spaces 
in the endoneurium. 



a lamellated sheath of single nerve fibres, or o a 
small group of them, represents what is called a 
He /lie's sheath. 

138. The nerve fibresarehekl together or separated 
respectively within the bundle by connective tissue, 
called the endoneurium (Fig. 97 j. This is a homo- 
geneous crround substance in which are embedded 
tine bundles of fibrous connective tissue, and con- 
nective-tissue corpuscles, and capillary blood-vessels 
arranged so as to form a network with elongated 
meshes. Between the perineurium and the nerve 
fibres are found here and there lymph spaces ; similar 
spaces separate the individual nerve fibres, and have 
been injected by Key and Retzius. The endoneural 
lymph spaces communicate with those of the peri- 
neural sheath. 



A^ER VE Fibres . 143 

When nerve trunks anastomose so as to form a 
plexus — e.g. in the brachial or sacral plexus — there 
occurs a division, an exchange and re-arrangement 
of nerve bundles in the branches. A similar con- 
dition obtains in the ganglia of the cerebro- spinal 
nerves. Nerve trunks and nerve branches passing 
through a lymph cavity, such as the subdural spaces, 
or the subcutaneous lymph sacs, or the cisterna lym- 
phatica magna in the frog, receive from the serous 
membrane an outer endothelial covering. 

139. Most of the nerve fibres in the bundles of 
the cerebro-spinal nerves, with the exception of the 
olfactory nerve, are meduUatecl nerve fibres. These 
are doubly - contoured smooth cylindrical fibres, 
varying in diameter between ttoVo ^^ more and 
iToooo ^^ ^^^ inch. Within the same nerve, and 
even wdthin the same nerve bundle, there occur 
fibres which are several times thicker than others, 
and it is probable that they are derived from different 
sources ; this, for instance, is very conspicuous in the 
vagus nerve (Gaskell, Fig. 98). Schwalbe has shown 
that the thickness of the nerve fibre stands in a 
certain relation to the distance of its perijihery from 
the nerve centre and to its functional activity. 

A medullated nerve fibre in the fresh condition is 
a bright glistening cylinder, showing a dark double 
contour. Either spontaneously after death, or after 
reagents — as water, salt solution, dilute acids — or 
after pressure and mechanical injury, the outline of 
the nerve fibre becomes irregular; smaller or larger 
glistening dark-bordered droplets and masses appear, 
and gradually become detached. These droplets and 
masses are called myeline droplets^ and are derived 
from the fatty substance or myelin constituting the 
medullary sheath or white substance of Schwann (see 
below). When a nerve fibre within the bundle under- 
goes degeneration during life, either after section of 



144 



Elemexts of Histology. 



the ner\'e or after other pathological changes, or in 
the natural course of its existence (S. Maver), the 
medullarv sheath is the first to undergo cliange ; it 
breaks uj) into similar smaller or larger globules or 




Fig. 98. — From a Transverse Section through the Vagus Xerve, showing in 
the nerve bundles nerve fibres (in cross-section) which differ markedly 
in size, some being much larger than others. (Photo., highly imignified.) 



particle-, whicli gradually l)ec'ome granular and 
absorbed. Later also the axis cylinder dwindles 
away, and only the neurilemma with the nucleated 
corpuscles persist. 

140. Each medullated nerve fibre (Figs. 99, 101) 
consists of tlie following parts : {a) the central axis 
cylinder, axon or neuraD:on. This is the essential 
part of the fibre, and is a cylindrical or band-like. 



Nerve Fibres. 145 

pale, trans|>ureiit structure, which in certain locali- 
ties (near the terminal distribiiiion, in tlie olfactory 
nerves, in the centj'al nervous system), and especially 
after certain reagents, shows itself composed of very 
fine homogeneous or more or less beaded tibrilhe — the 
elementary or jjriniitive Jibrillfe (Max Schultze) — held 
together by a small amount of a faintly gianular in- 
terstitial substance The longitudinal striation of 
the axis cylinder is due to its being composed of 
primitive librillcV. The thickness of the axis C3dinder 
is in direct proportion to the thickness of the whole 
nerve tibre. The axis cylinder itself is enveloped in 
its own hyaline more or less elastic sheath — the axi- 
lemma (Kiihne), composed of neurokeratin. 

1-1:1. (b) The medidlarij sheath, or myeline sheath, 
or white substance of Schwann, is also called the 
medulla of the nerve fibre. This is a olisteninff 
bright fatty substance surrounding the axis cylinder, 
as an insulating hollow cylinder surrounds an electric 
wire. The medullary sheath gives to the nerve fibre 
its double or dark contour. Between the axis cylinder 
and the medullary sheath there is a small amount of 
albuminous fluid, which appears greatly increased 
when the former, owing to shrinking, stands farther 
apart from the latter. 

142. (c) The sheath of Scliicann, or the neurileinma, 
closely surrounds the medullary sheath, and forms the 
outer boundary of the nerve fibre. It is a delicate 
structureless membiane. Here and there between 
the neurilemma and the medullary sheath, and 
situated in a depression of the latter, is an oblong- 
nucleus, surrounded by a thin zone of protoplasm. 
These nucleated corpuscles are the nerve corpuscles 
(Fig. 99), and are analogous to the muscle corpuscles, 
situated between the sarcolemma and the striated 
muscular substance. They are not nearly so numerous 
as the muscle corpuscles. 
K 



146 



Eleisients of Histology 




143. The neurilemma presents at certain definite 
intervals annular constrictions — the nodes or constric- 
tions of Rani-ier (Figs 99, 100, 101) — and at these 

nodes of Ranvier the medullary 
sheath, but not the axis cylinder and 
its special sheath, is suddenly inter- 
rupted, and sharply terminates at 
the constriction. The neurilemma 
is at the same time thickened by 
annular permanent, folds (see b in 
Fig. 101). The portion of the nerve 
fibre situated between two nodes is 
the internodal segment. Each in- 
ternodal seojment has orenerallv one, 
occasionally more than one, nerve 
corpuscle. The medullary cylinder 
of each internodal segment is made 
up of a number of conical sections 
(Fio-. 101, A) imbricated at their ends 

¥W 99. -Two Nerve - ^ . 

Fibre's, showing the (Schmidt, Lantermann ; and each 

such section is again made uj) of a 

large number of rod-like structures 

(Fig. 102) placed vertically on the 

been dissolved axis cvlinder (MacCarthy). 
away. The deeply- „ - , ^ 1 

ihese rods are, however, con- 
nected into a network. The net- 
work itself is verv likelv the neuro- 
keratin of Ewald and Kiihne, where- 
as the interstitial substance of the network is 
probably the fatty substance leaving the nerve 
fibre in the shape of myeline droplets, when pres- 
sure or reagents are applied to the fresh nerve 
fibre. 

144. Medullated nerve fibres without any neuri- 
lemma, and consequently without any nodes of 
Ranvier, with a thick more or less distinctly laminated 
medullary sheath, form the entire white substance of 



nodes or constric 
tions of Ranvier 
and the axis cy- 
linder. The me- 
dullary sheath has 



stained oblong 
nuclei indicate the 
ner\'e corpuscles 
within the neuri- 
lemma. (Atlas.) 



Ner I'E Fibres. 



147 



the brain and spinal cord. In these organs, in the 
hardened and fresh state, numerous nerve fibres may 
be noticed, whicli show 

more or less regular f(iil//'i///(' l|-i N^I/f^PI 

varicosities, owing to ((allllamlmru il/^^ h 

local accumulations of /: M lUlnf/rnwi !Wm% 

fluid between the axis /J l////tl W^lJ ///j > ^^^^ 

cylinder and medullary jl B ni f'lJ'/^^iJf'liHwV^ 

sheath. These are 
called varicose nerve 




B \\\l^ 



Fig. 101.— Medullated Xerve 
Fibres. 

A, Medullated nerve fibre, show- 
ing the subdivision of tlie 
medullary sheath into cylin- 
drical sections imbricated with 
their ends ; a nerve corpuscle 
with an oval nucleus is seen 
between tlie neurilemma and 
the medullary sheath, b, me- 
dullated nerve fibre at a node 
or constriction of Kanvier ; the 
axis cylinder passes uninter- 
ruptedly from one se.L'inent 
into the other, but the medull- 
ary s sheath is interrupted. 
(Key. and Retzius.) 




Fig. 100.— Medullated Xerve Fibies, after 
staining with nitrate of silver. {Key 
and Retzius.) 

rt. Axis cylinder; h, Ranvier's constriction. 

fibres. They occur also in 
the branches of the sympa- 
thetic nerve. 

The nerve fibres of the 
optic and acoustic nerve are 
medullated, but without any 
neurilemma ; they are there- 
fore without any nodes of 
Ranvier. Varicose fibres are 
common in them. 

145. Medullated nerve 
fibres occasionally in their 
course divide into two me- 
dullated fibres. Such divi- 
sion is very common in 



148 



Elements of Histology. 



medullated nerve libres supplying striped muscular 
tissue, especially at or near the point of entrance 
into the muscular fibres. (See below.) But also 
in other localities division of nerve fibres may be 
met witli. Tlie electric nerve of the electric fishes 

— e.g. malapterurus, gym- 
notus, silurus — shows such 
divisions to an extraor- 
dinary degree, one huge 
nerve fibre dividinc; at 
once into a bundle of 
minute fibres. Division 
of a medullated fibre 
takes place generally at 
a node of Ranvier. The 
branches taken together 
are generally thicker than 
the undivided part of the 
fibre, but in structure 
they are identical with 
the latter. 

146. When medul- 
lated nerve fibres ap- 
proach their peripheral 
Medullated xen-e Fibres, termination, they change 

A, B. Showinc on a surface view the i x • 1 

reticulated nature of the medullary SOOner Or later, inasmUCh 
sheath; c, two nerve fibres showintr ±a • in 1 ji 

the axis cylinder, the medullary aS their meOUJlary Slieath 
sheath with their vertically-arranged i i i i 

minute rods, and the delicate neuri- SUCluenlV CeaSCS ; and UOW 
lemma or outer hyaline sheath. i ' 77 

{.Atlas.) Ave have a non-meam- 

lated or grey (trans- 
parent) nerve fibre of Remak. Each of these consists 
of an axis cylinder, a neurilemma, and between the 
two a nucleated nerve corpuscle from place to place. 
Xon-medullated nerve fibres alwavs show the fibrillar 
nature of their axis cylinder. The olfactory nerve 
branches are entirely made up of non-meduUated 
nerve fibres. In the branches of the sympathetic 




A^ER I 'E Fibres. 



149 



most tilnes arc iiou-medullated. Non-medullated 
til)res do not show Raiivier's constrictions. Bundles of 
non-medullated fibres are grey, bundles of medullated 
Hbres are white, when viewed in reflected light ; the 
former being without medullary sheath allo'.v light to 








Fig. 103. — View of the anterior surface of Gold-stained Cornea of Guinea- 
pig, showing the rich distribution of the terminal nerve tibrilhe and 
their ramifications in the anterior epithelium of the cornea. {Photo., 
highly magnified.) 



pass through them, while the latter owing to their 
medullary (fatt}') sheath reflect light strongly. 

In the extra-vertebral course of many branches 
of the cerebro-spinal nerves — e.g. those supplying the 
limbs, the wall of the chest and abdomen — there occur 
non-medullated fibres generally in small groups ; 



ISO 



Elements of Histology. 



these fibres are considered to be derived from the 
sympathetic system, haviiii;' joined the cerebro spinal 
nerves by the grey portions of the rami communi- 
cantes (Gaskell). Tiie non medullated fibres near their 
terminal distribution always undergo repeated divi- 
sions. They form plexuses, large fibres branching 
into smaller ones, and these again joining. Gener- 




Fig. 104. — Dendritic terminations— Demlrons of Xerve Fibres. Transverse 
section of the optic lobe of a binl prepared by Golgi's method. (R. y 
Cajal. from Quain.) 

a, Optic fibres; ft, c, rf, e, dendrons of same in the diifereiit layers of the optic 
lobe ; 6 and 7 are the sixth and .seventh layers respectively of the organ. 



ally at the nodal points of these plexuses there are 
triangular nuclei, indicating the corpuscles of the 
neurilemma. 

147. Finally the non-medullated nerve fibres leav- 
ing tlie plexuses ultimately lose their neurilemma and 
l)reak up into tlieir constituent small bundles and 
even single primitive nerve fihrillce, which occasion- 
ally show regular varicosities (Fig. 105). Of course, 
of a neurilemma or the nuclei of the nerve corpuscles 
there is nothing left. The bundles of primitive fibrils 



Nerve Fibres. 



T51 



and also single fibrils branch and interlace, whereby a 
more or less dense dendritic ramification — avhoriHa- 
tion or (/c?irfywi— is produced (Fig. 104). The indivi- 




Fig. 105. — Nerve Fibres of tlie Cornea. 

a, Axis cylinder near the anterior epithelium of the cornea splitting up into 
its constituent primitive flbrillaj ; &, primitive flbrillae. 



dual fibrils of the dendron are straight or twisted, and 
often provided with smaller or larger terminal knobs. 
In some localities — e.g. in the grey matter of the 
central nervous system — the number of fibrils con- 



152 



Elements of Histology. 



stituting a dendron is large, and hence the dendron 
is conspicuous, in other localities the number of tibrils 
is relatively scanty — e.g. in the anterior epithelium 
of the cornea — and hence the arborising character 
of the dendron is not very conspicuous (Fig. 103). 




Fig. 106. — Intra-epitlielialXerve-teriniuation in the Anterior Epithelium of 
the Cornea, as seen in an oblique section. (Handbook.) 

a. Axis cylindei' ; b, sub-epithelial nerve flbrillie ; c, iutra-epithelial i-amiflcatiou ; 
d, epithelial cells. 



Pronounced dendrons are found in the nerve termin- 
ation in muscle and tendon (the endplates) in the 
branched processes (dendrites) of the ganglion cells 
in the central nervous system, as will be described 
and illustrated later. 

In the skin, cornea and mucous membranes, 
the peripheral termination — ■ i.e. the primitive 
fibrils and their ramitications. are intra-epithelial 
(Fig. lOG), i.e. they are situated in the stratum 
Malpighii of the epidermis, in the epithelial parts of 



NeR VE FlBR ES. 



153 



the hair follicle, in the anterior epithelium of the 
cornea, or in the epithelium of the mucous mem- 
branes. The primitive nerve fibrils lie in the inter- 
stitial substance between the epithelial cells, and some 
of them have been observed to end with minute 




Fig. 107. — From gold-stained cornea of frog, showing the numerous beaded 
line nerve fibrils and the branched corneal corpuscles. [Photo., highly 
magnified.) 



knobs in the cell substance itself close to the 
nucleus (Pfitzner, Macallum). 

148. Tracing then a nerve fibre, say one of com- 
mon sensation, from the periphery towards the centre, 
we have isolated primitive fibrils or their ramifications ; 
they form by aggregation simple axis cylinders, which 
vary in thickness according to the number of their 



154 Elemexts of Histology. 

constituent primitive til)rils. These axis cylinders 
then become invested bv neurilemma and nuclei, and 
form plexuses. By association they form larger axis 
cylinders, and these form typical non-medullated nerve 
fibres with neurilemma, and with the nuclei of nerve 
corpuscles (Fig. 106). Lastly, if a medullary sheath 
makes its appearance between the neurilemma and 
the axis cylinder of each fibre we get a rneduUated 
nerve fibre. 



155 



CHAPTER XV. 

PERIPHERAL NERVE-ENDINGS. 

149. In the preceding chapter we referred to the 
termination of the nerves of common sensation, .as iso- 
lated primitive fibrillre, and as ramifications and den- 
drons of these in the epitlielium of the skin and mucous 
membranes, in the anterior epithelium of the cornea, 
and in the grey matter of the central nervous system. 
Besides these there are other special terminal organs 
of sensory nerves, probably concerned in the per- 
ception of some special quality or quantity of sensory 
impulses. These are all connected with a meduUated 
nerve fibre, and are situated not in the epithelium 
of the surface but in the tissue, at greater or lesser 
depth. Such are the corpuscles of Pacini and Herbst, 
the end-bulbs of Krause in the tongue and con- 
junctiva, the genital end-corpuscles or end-bulbs in 
the external genital organs, the corpuscles of Meiss- 
ner or tactile corpuscles, in the papillae of the skin 
of the volar side of the fingers, the touch-cells of 
Merkel, the end-corpuscles of Grandry, in the beak 
and tongue of the duck. 

150. The Paciiiisiii corpuscles. — These are 
also called Yater's corpuscles. They occur in large 
numbers on the subcutaneous nerve fibres of the jDalm 
of the hand and foot of man, in the mesentery of the 
cat, along the tibia of the rabbit, in the genital organs 
of man (corpora cavernosa, prostate). Each corpuscle 
is oval, more or less pointed, and in some places 
(palm of the human hand, meseutery of the cat) 
easily percej)tible to the unaided eye, the largest 



'56 



Elemexts of Histology. 



beino; about T.^rrtli of an incli Ioiijt; and ^th of an 
inch broad ; in other places they are of microscopic 
size. Each possesses a stalk, to which it is attached, 
and which consists of a single medullated nerve fibre 
(Fig. 108), differing froin an ordinary medullated 

nerve fibre merely in the 
fact that outside its neuri- 
lemma there is present a 
thick laminated connec- 
tive-tissue sheath. This 
is the sheath of Henle 
— continuous with the 
perineural sheath of the 
nerve branch with which 
the nerve fibre is in con- 
nection. This medullated 
nerve tibre within its 
sheath possesses generally 
a very wavy outline. The 
corpuscle itself is com- 
posed of a large number 
of lamella, or capsules, 
more or less concentric- 
ally arranged around a 
central elongated or cylin- 
drical clear space. This 
space contains in its axis, 
from the proximal end — 
i.e. the one nearest to the stalk — to near the opposite 
or distal end, a continuation of the nerve tibre in the 
shape of a simple axis cylinder. But this axis cylinder 
does not fill out the central space, since there is 
all round it a space left filled with a transparent 
substance, in which, in some instances, rows of 
spherical nuclei may be perceived along the margin 
of the axis cylinder. At or near the distal end of the 
central space the axis cylinder divides in tico or 




Fig. lOS. — Pacinian Corpuscle, from 
the Mesentery of Cat. 

a, Medullated nerve fibre : b. concen- 
tric capsules. 



Per ipher a l Ner ve-endings. 



^57 



more branches, and these terminate in pear-shaped, 
oblong, spherical, or irregularly-shaped granular- 
looking enlargenients. 

151. The concentric cajjsules forming the corpuscle 
itself are disposed in a different manner at the peri- 
phery and near the central space 

from that in which they are dis- 
posed in the middle parts, in the 
former localities being much closer 
together and thinner than in the 
latter. On looking, therefoi-e, at 
a Pacinian corpuscle in its longi- 
tudinal axis, or in cross-section, 
we alwaj^s notice the striation 
(indicating the capsules) to be 
closer in the former than in the 
latter places. Each capsule con- 
sists of — (rt) a hyaline, probably 
elastic, ground substance, in which 
are embedded here and there (b) 
fine bundles of connective- tissiie 
fibres; (c) on the inner surface 
of each capsule, i.e. the one 
directed to the central axis of the 
Pacinian corpuscle, is a single 
layer of nucleated endotJielifd plates. 
The oblong nuclei A'isible on the 
capsules at ordinary inspection are "• ^'"^''" u\;^a\vay.'''^ ^''''^ 
the nuclei of these endothelial 
plates. There is no fluid between the capsules, but 
these are in contact with one another (Huxley). 
Neighbouring capsules are occasionally connected 
with one another by thin fibres. 

152. In order to reach the central space of the 
corpuscle, the medullated nerve fibre has to perforate 
the capsules at one pole ; thus a canal is formed 
in which is situated the medullated nervQ fibre, and 




Fig. 109.— Herbst's Cor- 
puscle, from the 
Tongue of Duck. 



1:^8 



Elements of Histology. 



as such, and in a very wavy condition, it reaches the 
proximal end of the central space. This part of the 
nerve fibre may be called the intermediate part. The 
lamellae of the sheath of Henle pass directly into the 
peripheral capsules of the corpuscle. 

Immediately before entering the central space, 
the nerve fibre divests itself of all pirts except the 
axis cylinder, which, as stated above, passes into 
the central space of the Pacinian corpuscle. In some 
cases a minute artery enters the corpuscle at the 
pole, opposite to the nerve fibre ; it penetrates the 
peripheral capsules, and supplies them with a few 
capillary vessels. 

loo!^ The corpuscles of Horbst are similar to 
the Pacinian corpuscles, with this difference, that they 
are smaller and more elongated, that the axis cylinder 
of the central space is bordered by 
a continuous row of nuclei, and 
tliat the capsules are thinner and 
more closely placed (Fig. 109). 
This applies especially to those near 
the central space, and here between 
these central capsules we miss the 
nuclei indicatinii the endothelial 
plates. Such is the nature of 
Herbst's corpuscles in the mucous 
membrane of the tongue of the 
duck, and to a certain degree also 
in tliose of the rabbit, and in ten- 
dons. 

154. The tactile corpuscles, 
or corpuscles of ^leissuer, oc- 
cur in the }>apilhe of the corium of 
the volar side of the fingers and toes 
apes ; they are oblong, straight, or 
In man they are about —t, to 




Fig. IIO'.— Tactile Cor- 
puscle of Meiss- 
ner from the Skin 
of the Human 
Hand. (£. FiscUr 
awl W. Flemming.) 

Showing the convolu- 
tions of the nerve 
fibre. 



in man and in 
slightly folded. 



1 

3 



pf an inch long, and 



5 00 



to 



-i- of 

2 ^^ 



an inch broad. 



Per ip/fER A L Ner ve-endings. 



159 



They are connected with a medullated nerve fibre — 
generally one, occasionally, V)ut rarely, two — with a 
sheath of Henle, The nerve fibre enters the corpuscle, 
but usually before doing so it winds lound the cor- 
puscle as a medullated fibre once or twice or oftener, 
and its Henle's sheath becomes fused with the fibrous 
capsule or sheath of the tactile corpuscle. The nerve 
fibre ultimately loses its medullary sheath and pene- 
trates into the interior of the corpuscle, where the axis 
cylinder branches ; 
its branches retain 
a coiled course all 
along the tactile cor- 
puscle (Fig. 110), 
anastomose with one 
another, and ter- 
minate in slight en- 
largements, pear- 
shaped or cylindrical. 
These enlargements, 
according to ]Merkel, 
are touch-cells. The 
matrix, or main part 
of the tactile cor- 
puscle consists, be- 
sides the fibrous 
sheath with nuclei 
and numerous elastic 

fibres, of fine bundles of connective tissue, and 
number of nucleated small cf-lls. 

155. The end-bulbs of Krauze. — These occur 
in the conjunctiva of the calf and of man, and are 
oblong or cylindrical minute corpuscles situated in 
the deeper layers of the conjunctiva, near the corneal 
margin. A medullated nerve fibre, with Henle's 
sheath, enters the corpuscle (Fig. 111). This possesses 
a nucleated capsule, and is a more or less laminated 




Fig. 111. — End-bulljof Kraii.sc. 

Medullated nerve fibre : b, caiisule 
corpuscle. 



)f the 



of a 



i6o 



Elemexts of Histology. 



(in man more granuLir-looking) structure, numerous 
nuclei being scattered between the lamina?. Of the 
nerve fibre, as a rule, only the axis cylinder is pro- 
longed into the interior of the corpuscle. Occasion- 
ally the medullated nerve fibre passes, as such, into 
the corpuscle, being at the same time more or less 
convoluted. Having passed to near the distal ex- 
tremity, it l)ranches, and terminates with small 
enlargements (Krause, Longworth, Merkel, Key and 
Retzius). 

The end-hidbs in the genital organs, or the genital 
corpuscles of Krause, are similar in structure to the 
simple end-bulbs. They occur in the tissue of the 
cutis and mucous membrane of the penis, clitoris, and 
vagina. 

156, The €ori>ii«irIe«» of Graiidry, or tou.ch 
corpuscles of Merkel, in the tissue of the papill?e in 
the beak and tongue of birds, are oval or spherical 
corpuscles of minute size, possessed of a very delicate 
nucleated membrane as a capstile. aud consisting of a 
series (two, three, four, or more; of large, slightly- 
flattened, granular-looking, transparent cells, each 
with a spherical nucleus, and arranged in a vertical 





71 A B -^ C 

Fig. 112. — Corpuscles of Grandry in the Tongue of Duck, {Iz2uierdo.) 

A, Composed of three cells : b. composed of two cells ; c, showing- the develop- 
ment of a Grandry's corpuscle from.tlie epithelium covering the papilla, p; 
e, epithelinra ; 'i, nerve fibre. 

row (Fig. 112). A medullated nerve fibre enters the 
corpuscle from one side, and losing its medullary 



Per ipheral Ner ve-endings. 



i6[ 



sheatl), the axis cylinder brandies, and its branchlets 
terminate, according to some (Merkel, Henle), in the 
cells of the corpuscle (touch cells of Merkel) ; accord- 
ing to others (Key and Retzius, Ranvier, Hesse, 
Izquierdo), in the transparent substance between the 
touch cells, thus forming the '• disc tactil " of Ranvier 
or the " Tastplatte " of Hesse. Neither theory seems 
to us to answer to the facts of the case, since we find 




Fig. 113.— Bundles of Non-striped Musenlar Tissue surrounded by 
Plexuses of Fine Xerve Fibres. (Hamlbook.) 



that the branchlets of the axis cylinder terminate, 
not in the touch cells, nor as the disc tactil, but with 
minute swellings in the interstitial substance between 
the touch cells, in a manner very similar to what is 
the case in the conjunctival end-bulbs. According to 
IMerkel, single or small groups of touch cells occur in 
the tissue of the papilhe, and also in the epithelium, 
in the skin of man and mammals. 

157. In Jirtieiilatioiis — e rj. the knee-joint of 
the rabbit — Xicoladoni described numerous nerve 
branches, from which fine nerve fibres are given off. 
Some of these terminate in a network, others on 
blood-vessels, and a third group enter Pacinian cor- 
puscles. Krause described in the synovial membranes 

L 



l62 



Elements of Histology 



of the joints of the human fingers medullated nerve 
fibres whicli end in peculiar tactile corpuscles, called 
by him '^ articular nerve corjiuscles.'" 

158. The nerve branches snpplyiiig^ non- 
striped ninsenlar tissue are derived from the 
sympathetic system. They are composed of non- 
medullated fibres, and the branches are invested 

in an endothelial 

c 5 sheath (perineu- 

^\"^ \ \\ \ » rium). The 

branches divide 
into single or 
small groups of 
axis cylinders, 
which reunite 
into a plexus — 
the ground 
plexus of Ar- 
nold. Small 
fibres coming oflf 
from the plexus 
supply the in- 
dividual bundles 
of non - striped 
muscle cells, and 
they form a 
plexus called 
the intermediary 
lilexus (Fig. 
113). The fibres 
joining this plexus are smaller or larger bundles 
of primitive filu'illa? ; in the nodes or the points 
of meeting of these fibres are found angular nuclei. 
From the intermediate plexus pass oft' isolated or 
small groups of primitive fibrillar, which pursue 
their course in the interstitial substance between 
the muscle cells; these are the intermuscular 




Fig. 114. — Termination of Nerves in Xon-striped 
Muscular Tissue. {Atlas.) 

a, 3Cou-inPduUated flltre of the iutermediary plexus; 
b, fine intermuscular flbrils ; c, nuclei" of mus- 
cul;ir cells. 



Peri p HER a l Ner i 'e-end/xgs. 



163 



According to Frankenliaiiser 



and 
the 
the 
the 



fibrils (Fig. lU) 

Arnold, tlicy give oti' tiner tihrils, ending in 
nucleus (or nucleolus). According to Elischer, 
primitive fibrils terminate on the surface of 
nucleus with a minute swellinij. 

In many localities there are isolated ganglion cells 
in connection with the intermuscular tibres. 

159. The nerves of blood-vessels are derived 
from the sympathetic, and they terminate in arteries 
and veins in essentially the same way as in non- 
striped muscular tissue, being chiefly present in those 




Fig. 115. — Plexus of Fine Xon-iiiedullated Xerve Fibres .surrounding 
Capillary Arteries in the Tongue of Frog, after staining Avith chloride 
of gold. (Handbook.) 

a, Blood-Tessel ; 6, connective tissue corpuscles ; c, thick non-medullated fibres 
rf, plexus of fine nerve fibres. 



parts (media) which contain the non-striped muscular 
tissue. But there are also fine non-medullated nerve 
fibres, which accompany capillary vessels — capillary 
arteries and capillary veins — and in some places they 
give off elementary fibrils, which form a plexus 
around the vessel (Fig. llo). In some localities the 



1 64 



Elements of Histology. 



vascular nerve brandies are provided witli small 
groups of ganglion cells. 

160, In striped muscle of man and mammals, 
reptiles and insects, the termination of nerve fibres 



•^^^mfi'ID^-i^i-'K 




•^•^>^' 



4 



Fig. 116. — Nerve-endings in Striped Muscular Fibres. (Kindly lint by 
Professor Kiiline.) 
A, In fresh muscular fibre of Lacerta, x ^^ ; b, in gold-stained muscular fibre 
of lacerta, X ^^•, c, in gold-stained muscular fibre of flog, x ^-Y- ! 
m, medullated nerve fibre ; t, termination of axis cylinder underneath the 
sarcolemma of the muscular flv>re. 

takes place, according to the commonly accepted view 
of Iviihne, in the following manner (Fig. 116) : — A 
medullated nerve fibre, enclosed within a lamellated 
sheath (Henle's sheath) divides at a node of Ranvier, 
each branch — a medullated nerve fibre — enters under a 
variable angle a striped muscular fibre, the neurilemma 



Periphera l Ner ve-endings. 

becoming fused with the 
sarcolemuia, and the nerve 
fibre, either at tlie point 
of entrance or immediately 
afterwards, loses its medul- 
lary sheath, so that only the 
axis cylinder, with its axi- 
lemma, })asses on, and then 
forms on the sui'face of the 
muscular substance a ter- 
minal arborisation or den- 
dron, which is called the 
nerve endpJate. Each axon, 
on entering, gives off by 
division several branches 
like antlers : in amphibia 
these branches are rodlike, 
long, and of the form of 
baj^onets ; in mammals they 
are crooked, hook-like. In 
all instances, however, the 
divisions are unsymmetri- 
cal. In many cases the 
arborisation of the endplate 
is embedded in a granular 
mass of protoplasm con- 
taining oblong nuclei. This 
nucleated protoplasm is 
identical with the substance 
of the sarcoglia, or the 
sarcoplasm mentioned on a 
former page. When the 
muscular fibre contracts, 
this endplate naturally as- Fig. 117.— Muscle Spindle of the 
sumes the shape of a pro- ^'^l^^it treated with gold chio- 

t J i iide. (Kolliker, II.) 

mmence — Boyere s nerve „^ ^^^^,.^ q^,,,^ terminating' iu the 

Oiinoi'^if ^^'npl^ mnQpnlnr middle p;iit of the spiiidlt- us a 

lUOUlil. JLaCil mUbCUiai spiral endiDg of fine Hbrils. 




i66 



Elements of Histology. 



libre has at least one nerve endplate, but occa- 
sionally has several in near pioximity. Each end- 
plate is generally supplied by one nerve fibre, some- 
times, however, by two. The contraction wave 
generally starts from the endplate. The muscle 




Fiy;. lis. — Termiuation of ilediillated Nerve Fibres in Tendon, near the 
Insertion of the Striped Muscular Fibres. (Golgi.) 

The nerve fibres terminate in peculiar arborising eudplates of primitive 
fibrillae 



huds of KoUiker or muscle spindles of Kiihne 
(mentioned on a former page) contain numerous 
medullated nerve fibres with lamellated Henle's 
sheath, and these nerve fibres terminate in the 
same manner, namely, by means of nerve endplates 
(Fig. 117). In these endplates the fine nerve fibres 
have a sj^iral arrangement (Ruffini). These are con- 
sidered to be sensorv end-organs. According to Kol- 
liker, from the primary nerve ending of the mother 
fibre — i.e. of the undiWded portion of the spindle — 
grow out the ner\e endings for the thin daughter 
fibres. 



PeRIPHERA L NeR I 'E- EN DINGS. 



167 




.-a 



Besides this iutra-musciilar termination, tliere 
is a plexus of tine nev\e fibres, many of them 
said to terminate with free ends, situated outside 
the sarcolemma — i.e. intermnscuh\r ; such free ends 
are described by Beale, Kolliker, Krause, and 
others. Kolliker and Arndt consider these intermus- 
cular fibres 

as sensory ,.:^:v -- :^ 

nerves, 

161. Ten- 
dons are sup- 
plied w i t h 
special nerve 
endings, 
studied by 
Sachs, Rol- 
lett, Gempt, 
Rauber, and 
particularly 
G olgi, whose 
work on this 
subject is ex- 
tensive. These terminations are most numerous near 
the muscular insertion. They are of the follow- 
ing kinds : — («) A medullated nerve fibre branches 
repeatedly, and the axis cylinder, after having lost 
the medullary sheath, breaks up into a small plate 
composed of a dendritic ramification of fine primi- 
tive nerve fibrils (Fig. 118). Owing to the number of 
the fibrilla3 and their repeated crossing, it is difiicult to 
say whether the appearances as shown in Fig. 119 cor- 
respond to a real network or to a dendron. This end- 
plate is occasionally embedded in a granular-looking 
material, and thereby a similar organ as the nerve end- 
plate in muscular fibres is produced (Fig. 119). (6) In 
the tendons of man and many mammals Golgi has shown 
that nerve fibres terminate in peculiar spindle-shaped 



Fig. 119. — One of the Teriniual Ramitk-atioiis of the 
previous figure, more highly magnified. 

rt, Medullated nerve fibre ; ft, apiiareutly reticulated 
endplate. {Golgi.) 



i68 




Vj^I 



<. 



I 



Fig. 120. — Two Tendon Spindles of Golgi in tlie rabliit, sliowing the distri- 
bution and spiral terniination ol' the nerve fibres ou the spindles. {After 
K oil Her.) 



Per I pn ERA l Ner ve-en dings. 



169 



enlargements of tendon Ijundles (Fig, 120). These 
tendon spindles of Golgi consist each of two, three, or 
more tendon bundk's within a common sheath ; a 
bundle of fine medullated nerve fibres enters the 




Fig. 121.— Termination of Metlnllated Nerve Fibres in Tendon. {Golgi.) 

a, End-lnilbs with couvoliited lueclullatecl nerve fibre ; b, end-bulb similar to a 
Herlist's corpuscle. 

spindle, their axis cylinders break up into primitive 
fibril he, which are arranged as a network and as 
spiral fibrillar. (c) A medullated nerve fibre ter- 
minates in an end-lmlb (Fig. 121), similar to those of 
the conjunctiva, or of a Herbst's corpuscle. 



170 



CHAPTER XVI. 

THE SPINAL CORD. 

1 G2. The spinal cord is enveloped in three distinct 
membranes. Tiie outermost one is the dura mater. 
This is composed of more or less distinct lamellag of 
fibrous connective tissue with the flattened connective- 
tissue cells and networks of elastic fibres. The outer 
and inner surface of the dura mater is covered with a 
layer of endothelial plates. 

163. Next to the dura mater is the extremely 
delicate arachnoid membrane. This also consists of 
bundles of fibrous connective tissue. The outer 
surface is smooth and covered with an endothelial 
membrane facing the space existing between it and 
the inner surface of the dura mater ; this space is the 
subdural lyniph space. The inner surface of the 
arachnoidea is a fenestrated membrane of trabeculse 
of fibrous connective tissue, covered on its free 
surface — i.e. the one facing the sub-arachnoidal lympli 
space — with an endothelium. 

164. The innermost memVjrane is the pia mater. 
Its matrix is fibrous connective tissue, and it is lined 
on its outer surface with an endothelial membrane. 
Also the inner surface facing the cord j)roper has an 
endothelial lining, but this is not as complete and 
continuous as that of its outer surface. Between 
the arachnoid and pia mater extends, from the fenes- 
trated portion of the former, a spongy f)lexus of 
trabeculse of fibrous tissue, the surfaces of the 
trabeculse being covered Avith endothelium. By this 



Sr/NA L Cord. 



lyr 



spongy tissue — tho snh-araclinoidal tissue (Key and 
Ketzius) — the subarachnoidal space is subdivided into 
a labyrinth of areohe. On each side of the cord, 
between the anterior and posterior nerve roots, 


















-•_» j^f J 

" -^■'^v*! 








Fig. 12-2.— Transverse section tlirougli the Cervical Cord of aeliild, 2 years 
old, sliowing well the anterior wliite commissure and the numerous 
nieduUated fibres passing horizontally through the grey matter (col- 
laterals) from and to the white columns. {Weigcrt.) 

z, Tract of Goll ; B, tract of Burdach ; l, tract of Lissauer. 



extends a spongy fibrous tissue, called ligamentuni 
denticidatiiin, between the arachnoidea and pia. By 
it the sub-arachnoid al space is subdivided into an 
anterior and posterior division. 

165. The subdural and sub-arachnoidal spaces do 
not communicate with one another (Luschka, Key 
and Retzius). 



^7 



Elements of Histology. 



The dura mater, as well as the arachnoid, sends 
prolongations on to the nerve roots ; and the sub- 
dural and sub-arachnoidal spaces are continued into 
the lymphatics of the peripheral nerves. 



li.C, 




Fig. 123a. — Transverse section of the Spinal Cord in tlie Cervical region- 
{M icrophotog raph of Weigcrt-Pal specimen.) 

p. E. c, Postero-extenial column ;C.g., postero-niedian column or colmnu of 
GoU ; p. u., the issuing posterior root ; L. c. lateral column : a. f., anterior or 
ventral Assure. The white matter is more deeply stained than the more 
central grey. 



All three membranes contain their own system of 
blood-vessels and nerve fibres. 

166. The cord itself (Fig. 122) consists of an outer 
or cortical part composed of medullated nerve fibres : 
the ichite matter, and an inner core of grey matter. 
On a transverse section through the cord the 



Spinal Cord. 



17.3 



contrast of colour between the white mantle and the 
grey core is very conspicuous. The relation between 
the white and grey matter differs in different parts ; 
it gradually increases in favour of the former as we 



P.E.C. 



L.H. 




L.C 



A.F. 



Fig. 123b. — Section of the Spinal Cord in the Dorsal region. 
{Micropliotograph of a IVeigert-Pal specimen.) 

Note the small aiii<iunt nf grey matter wbich project? iHterally at level L. h. to 
fonu a lateral liorn. Xote, too. at tbe same level on the median side of tbe 
posterior born a deflnite mass, forming Clarke's columns. The lettering is 
as in the section through cervical region. 



ascend from the lumbar to the upper cervical portion 
(Figs. 123a, 123b, 123c). The grey matter presents 
in every transverse section through the cord more or 
less the shape of a capital H ; the projections being the 
anterior and posterior horns or cornua of grey matter, 
and the cross-stroke being the grey commissure. 



174 Elements of Histology. 

In the centre of this grey commissure is a cylindrical 
canal lined with a layer of columnar epithelial cells ; 
this is the central canal ; the part of the grey commis- 
sure in front of this canal is the anterior, the rest the 
posterior, grey commissure. The shape of the whole 
figure of the grey matter differs in the different 
regions, and this difference is brought about by the 
breadth and thickness of the grey commissure as also 
of the grey horns themselves. In a section through 
the cervical region the grey commissure is long and 
thin ; in the dorsal region it becomes shorter and 
thicker ; and in the lumbar region it is comparatively 
very short and thick. Besides this, of course, the 
relative proportions of grey and white matter, as 
mentioned before, indicate the region from which the 
particular part of the cord has been obtained. In the 
lower cervical and lumbar regions where the nerves of 
the brachial and sacral plexus leave or join the cord 
respectively, this latter possesses a swelling, and the 
gre}^ matter is there increased in amount, the swelling 
being in fact due to an accumulation of grey matter, 
with which additional numbers of nerve fibres become 
connected ; but the general shape of the grey matter 
is retained. 

167. The cornua of the grey matter are generally 
thickest in the line of the grey commissure : they 
become thinned out into anterior and posterior edges 
respectively, which are so placed that they point 
towards the antero-lateral and jDostero-lateral fissures. 
The anterior horns are in all parts thicker and project 
less than the posterior, and therefore the latter reach 
nearer to the surface, becoming attenuated and passing 
into the posterior nerve roots. 

There is generally a third projection of grey 
matter — the lateral horn (see Fig. 123 b). This is, 
however, conspicuous only in the upper two- thirds 
of the thoracic cord. 



Spinal Cord. 



175 



1G8. The white matter is composed chiefly of 
medulhited nerve fibres riuiiiin<,^ a lon.<;itudinal course, 
and therefore, in a transverse section through the 
cord, appear in cross-section. They are arranged into 




Fij 



123c.— Section through the Spinal Cord in the Sacral region. 
(Microphotogr((2^h of a Weigert-Pal speciinen.) 



Tlie lighter stained trrey matter is larpe in amount compared with the darker 
white matter. The tips of tlie posterior horns and around the central canal 
are very lightly stained owing to the presence of much substantia tjclatinosa. 
Many niedullated fibres are seen traversing the anterior horns. 



cokimns, one anterior, one lateral, and one posterior 
column for each lateral half of the cord, the two 
halves being separated by the anterior and posterior 
median longitudinal fissure. The anterior median 
fissure is a real fissure extending in a horizontal 



176 Elements of Histology. 

direction from the surface of the cord to iiPAir the 
anterior grey commissure. It contains a prolongation 
of the pia mater and in it large vascular trunks. The 
posterior fissure is not in reality a space, but is tilled 
up by neuroglia. It extends as a continuous mass of 
neuroglia in a horizontal direction from the posterior 
surface of the cord to the posterior grey commissure. 
The exit of the anterior or motor nerve roots and 
the entrance of the posterior or sensitive nerve roots 
are indicated by the anterior lateral and posterior 
lateral fissures respectively. These are not real fissures 
in the same sense as the anterior median fissure, but 
correspond more to the posterior median fissure, 
beinof in reality filled up with neuroglia tissue, into 
which extends a continuation from the pia mater 
with laro-e vascular trunks. The white matter 
between the anterior median and anterior lateral 
fissure is the anterior column^ that between the 
anterior lateral and posterior lateral fissure is the 
lateral column, and that between the posterior 
lateral and posterior median fissure is the j^osterior 
column. 

169. Besides the septa situated in the two lateral 
fissures respectively, there are other smaller septa, 
neui^oglia and prolongations of the pia mater, which 
pass in a horizontal and radiating direction into the 
white matter of the columns, and these are thus sub- 
divided into a number of smaller portions ; one such 
big septum is sometimes found corresponding to the 
middle of the circumference of ont; half of the cord. 
This is the median lateral fissure, and the lateral 
column is subdivided by it into an anterior and 
posterior division. 

Similarly, the anterior and posterior columns may 
be subdivided into a median and lateral division 
(Figs. 123 a and 125). 

170. Some of these various subdivisions bear 



Spinal Cord. 



177 



definite names (Tiirk, Charcot, Goll, Flechsig, 
Gowers) : — 

{ct) The median division of the anterior column is 
called the direct or uncrossed pyramidal tract, being 




Fig. 124. 



-Scheme of the subdivision of the White Cohimns. 
Fleschsig and Kahler, from KolUker, II.) 



{After 



P V, Direct pyramidal tract of anterior white column ; v g, ventral ground tract 
of anterior white column ; a L,antero-lateral tract of lateral column. Gowers's 
tract; s r, remainder of antero-lateral part of lateral column; k s, direct 
cerebellar tract of lateral column ; p s, crossed pyramidal tract of lateral 
column.; H a, tract of Burdach of posterior white column ; G, tract of Goll in 
posterior column. Grey matter, grey commissure around central canal, 
anterior and posterior roots left unshaded. 



a continuation of that part of the anterior pyramidal 
tract of the medulla oblongata [see below) that does 
not decussate in the medulla. 

(h) The lateral division of the anterior column is 
the ventral or anterior ground tract. 

(c) The direct cerebellar fasciculus or tract is the 
superficial portion of the postero-lateral column ; it is 

M 



lyS Elements of Histology. 

a direct continuation of the white matter of the 
cerebellum. 

{d) The posterior division of the lateral column 
inside the cerebellar fasciculus is called the crossed 




Fig. 125 — Section of Spinal Cord, one half of wliicli (left) shows the tracts 
of the white matter ; and the other half (right) shows the grouping of 
the ganglion cells in the grey matter (semidiagrammatic) . {After 
Sherrington, from Kirke's " Physiology.") 

7, 10, 9, and 3 are tracts of descending deseneration ; 1,4, 6, and 8 of ascending 
degeneration ; 1. tract of CtoH; 2, tract of Burdach; 3, comma tract; 4, tract 
of Lissauer ; all these belong to the posterior white column ; 6, direct cere- 
bellar tract ; 7, crossed pyramidal tract ; 8, tract of Gowers ; 9, descending 
antero-lateral trace ; 10, direct pyramidal tract. 



pyramidal fasciculus or tract, being a continuation 
of the decussated part of the anterior pyramidal tract 
of the medulla oblongata. 

(e) The lateral division of the posterior column, 
with the exception of a small peripheral zone, is the 
cuneiform or cuneate Jasciculus, or the tract of 
Burdach, 



Spinal Cord. 



179 




This part is connected directly witli the median 
bundle of the posterior nerve roots, or rather by the 
numerous collaterals passing off from the posterior 
root fibres. 

(y') Tiie median division of the posterior column 
is called the J'ascicidus or tract of G oil. 

(g) The tract or fasciculus of Lissauer (Fig. 125) 
is a small mass of 
white fibres situated 
between the outer su- 
perficial portion of the 
tract of Burdach and 
of the direct cerebellar 
tract, and close to the 
posterior lateral fis- 
sure. 

In addition to 
these, a narrow mass 
of fibres in the depth 
of the tract of Bur- 
dach, near the grey 
commissure, represents 
a separate group, called 

the comma-shaped tract : and the superficial mass of 
white matter in the anterior half of the lateral column, 
which is called the anterolateral ascending tract of 
Gotcers {see Fig. 124). 

These various divisions can be traced from the 
meduUata oblongata into the cervical, and more or less 
into the dorsal part of the cord ; but farther down 
many of them, like the direct cerebellar tract and the 
tract of Goll, are lost as separate tracts, except the 
crossed pyramidal fasciculus. 

Experiments have been made which demonstrate 
that these different tracts are physiologically of very 
different character. According to a well-established 
law — the AVallerian law — each nerve fibre has its 



Fig. 12(3. — From a transverse section 

"through a most peripheral part of 

the White Matter of the Cord. {Atla^.) 

c. Special peripheral collection of neu- 
roglia ; w, white matter with the medul- 
lated nerve fibres shown in cross section, 
and nenroglia between them. 



So 



Elements of Histology. 



nutritive centre in the ganglion cell with which it is 
connected, and if a nerve fibre is cut, that part which 
remains connected with the nutritive centre does not 
degenerate, while that part severed from the centre 
degenerates. Consequently, if by cutting the cord at 




Fig. 127. — Stellate Neuroglia Cells of Golgi, with nimieroxis ramifying pro- 
cesses ; from the cord of ox. {EdlliJcer, II.) 



a particular level some fibres i-emain intact above the 
section but degenerate below, they show descending 
degeneration ; they have their nutritive centre above 
the section and are jDrobably eflferent fibres. On the 
other hand, those fibres w^hich degenerate above, but 
remain intact below the section, show ascending 
degeneration ; they have their nutritive centre below 
the section and are probably aflerent fibres. 

By means of Weigert's method it has been 



Spinal Cord. i8r 

possible to show (Weigert) not only that the nerve 
fibres constituting tlie white cohimns are grouped iu 
different tracts but that in the embryo they obtain 
their medullary sheath at different but definite periods. 



. / 




Fig. 12S. — Longitudinal section through the Lateral White Column of the 
Cord of the Ox, showing the axis cylinders of the meduUated nerve 
fibres, numerous fine longitudinal and transverse fibrils of the neu- 
roglia, and tlie stellate neuroglia cells of Golgi. {After Kolliker, II. 
Highly magnified.) 



Now in this way it has been made probable that 
the tracts marked in the figures in the above-named 
divisions of the anterior and lateral columns contain 
partly efferent, partly afferent fibres, while almost 
the whole of the fibres of the posterior columns are 
afferent ; see exolanation of figures, 



1 82 Elements of Histology. 

171. Structure of the cord. — The most im- 
portant and fundamental facts which have been 
brought to light within recent 3"ears concerning the 
intimate structure of the white and grey matter and 
of the mutual relations of the different parts and the 
different elements of the cord, the brain, the medulla, 
and the symj^athetic system, are due to various new 
methods of histological examination, as also to the 
experimental methods of section of the cord and nerve 
roots in the living, and observing the after-effects as 
exhibited by degeneration of nerve tracts. As regards 
the histological methods, Weigert and Pal's method of 
staining medullated nerve fibres of the cord, INIarchi's 
method of distinguishing between degenerated and 
healthy medullated fibres, and, above all, Golgi's 
silver method, by which nerve fibres and ganglion 
cells can be easily traced in their finest ramifications, 
have been the means of o^Dening uji an almost new 
field of accurate inquiry concerning all parts of the 
central nervous system as well as of the special senses. 
Golgi's silver method has enabled himself, and, to a 
very conspicuous degree, Ramon y Cajal and Kolliker, 
to bring to light facts concerning the intimate struc- 
ture of the central nervous system, the ganglia, and 
the sense organs, which stand out in respect of 
clearness and trustworthiness. Other histologists, 
Lenhossek, Eetzius, and others, have by this method 
also been enabled to contribute important facts. 

172. The ^-oiiiid substance (Fig. 126) of both 
the white and grey matter — i.e. the stroma in 
which nerve fibres, nerve cells, and blood-vessels are 
embedded — is a peculiar kind of connective tissue, 
which is called by Yirchow neuroglia and by 
Kolliker supporting tissue. It consists of three 
diffeient kinds of elements : [a) a homogeneous trans- 
parent semi-fluid iiwtrio:, which in hardened sections 
appears more or less granular ; {}>) a network of very 



Spinal Cord. 



183 



delicate fibrils — npurotjlia fibrils — which are similar 
in some respects, but not quite identical with elastic 
fibres. In the columns of the wliite matter the 







p.m. 



Cty.o. 




a.c. 



Fig. 129.— Cross-section of the central part of the Spinal Cord from tlie 
Lumbar region of an Adult, showing the central canal, its lining epithe- 
lium surrounded by neuroglia, forming the central grey nucleus, 
(After Schdfer.) 

/.a., Anterior median fissure; p.m.c, posterior white column ; ff.c, anterior 
white comniissure. 



fibrils extend chiefly in a longitudinal direction, in 
the gi'ey matter they extend uniformly in all 
directions, and in the septa between the columns 



184 



Elements of Histology. 



they extend for the most part radially, (c) Richly 
branched nucleated cells intimately woven into the 
network of neuroglia fibrils. These cells are the 
neuroglia cells or glia cells. Golgi was the first to 
show that though richly branched they do not anasto- 
mose with one another. The sweater the amount of 



^^%f|^NiS»/ 



1^ 



* 




Fig. 1:30a.— Cross-section tlii-ongh 
central canal of tlie cord, 
sbowiug the lining epithe- 
lium, from a child of sis. 
(After Schdfer.) 



Fig. 130b.— CUiated Epithe- 
lium lining the central 
canal of the cord in a 
child of six, more highly 
magnified than in Fig. 
130a. {After Scha/er.) 



neuroglia in a particular part of the white or grey 
matter, the more numerous are these three elements 
(Figs. 127 and 128). 

In both the white and grey matter the neuroglia 
has a very unequal distribution ; but there are certain 
definite places in which there is always a considerable 
amount — a collection, as it were, of neuroglia tissue. 
These places are : («) underneath the pia mater — 
i.e. on the outer surface of the white matter : here 
most of the neuroglia fibrils have a horizontal 
direction ; near the grey matter there is a greater 
amount of neuroglia between the nerve fibres of the 
white matter than in the middle parts of this latter : 
in the septa between the columns and between the 



Spinal Cord. 



18: 



divisions of columns of white matter ; at the exit of 
the anterior and the entrance of the posterior nerve 
roots. 

(6) A considerable accumulation of neuroglia is 
present immediately around the epithelium lining the 




Fig. 131.— Central C'aual of the Cord of a Child, 1^ year old ; the cells of 
ependyina are well shown, with their long filamentous processes. 
{Kdlliker, II.) 



central canal ; this mass is cylindrical, and is called 
the central grey nucleus of KoUiker (Fig. 129). The 
epithelial cells lining the central canal are conical, 
their bases facing the canal, their pointed extremity 
being drawn out into a fine filament intimately inter- 
woven with the network of neuroglia fibrils. In the 
embryo and young state (Figs. 130a and 130b), the 
free base of the epithelial cells has a bundle of cilia, but 
in the adult they are lost amongst the epithelial cells 



1 86 



Elements of Histology 



lining the central canal : some show in i:)reparations 
stained after Golgis method processes of extreme 
length (Fig. 131). 

(<?) Another considerable accumulation of neuroglia 
exists near the dorsal end of the posterior grey horns, 
as the suh-^tnntia gdotinos<i of Rolando. 

173. The white uiatter (Fig. 132) is composed, 
besides neuroglia, of medullated nerve fibres varving 
veiy much in diameter, and forming the essential and 

chief part of it. They 







possess an axis cy- 
linder and a thick 
medullary sheath 
more or less lamin- 
ated, but are devoid 
of a neurilemma and 
its corpuscles. Of 
course, no nodes of 
Ranvier are observ- 
able. In specimens 
of white matter of 
the posterior co- 
lumns, Avhere the 
nerve fibres have 
. been isolated by teas- 
ing after hardening, many fine' medullated libres are 
met with which show the varicose appearance mentioned 
in a former chapter. The medullated nerve fibres, 
or rather the matrix of their medullary sheath, con- 
tains neurokeratin. The nerve fibres of the white 
matter run chiefly in a longitudinal direction, and 
they are separated from one another by the neuroglia. 
Here and there in the columns of white matter are 
seen connective-tissue septa with vessels, by which 
the nerve fibres are grouped more or less distinctly 
in divisions. 

174. Although most of tiie nerve libres con- 



Fig. 132. — From a transverse section 
through the White Matter of the CorcL 

Showing thetransversely-cat medullated nerve 
fibres, the neuroglia between them with 
two branched neuroglia cells. (Atlas.) 



S/'/NAL Cord. 187 

stituting the columns of white matter are of a 
longitudinal direction — i.e. passing upwards or down- 
wards between the grey matter of the cord on the one 
hand and the brain and medulla oblongata on the 
Other — there are nevertheless a good many medul- 
lated nerve fibres and groups of nerve fibres which 
have an oblique or even horizontal course. 

Thus : (1) The anterior median fissure does not reach 
the anterior grey commissure, for between its bottom 
and the latter there is the lohite commissure {see Fig. 
129). This consists of bundles of medullated nerve- 
fibres passing in a horizontal or slightly oblique 
manner chiefly between the grey matter of the anterior 
horn of one side and the anterior white column, in- 
cluding the direct pyramidal tract, of the opposite side. 
This anterior white commissure is in respect of 
position a continuation of the decussation of the 
pyramidal tract in the lower part of the medulla 
oblongata. As mentioned above, this latter passes 
down the cord as the crossed pyramidal tract in the 
inner part of the postero-lateral column. From this 
it follows that the fibres of the pyramidal tract of the 
medulla ultimately all cross over to the opposite side 
of the cord. The majority do this in the pyramidal 
decussation of the medulla, the minority descend in 
the cord as the direct pyramidal tract, but its fibres 
gradually along the cord cross over by the anterior 
white commissure. 

(2) The medullated nerve fibres constituting the 
anterior roots of the spinal nerves leave the cord at 
and about the antero-lateral fissure; the fibres pass 
mostly in a somewhat oblique, some also in a hori- 
zontal direction through the white matter of the cord, 
and each of them originates, some sooner, some later, 
as the axon or axis cylinder process of a ganglion 
cell of the anterior grey horn. This is the fate of 
most of the anterior root fibres — that is to say, they are 



1 88 Elements of Histology. 

primarily tlie axons of ganglion cells of the anterior 
grey horn of the same side ; this axon becomes 
invested with a medullary sheath, and as an efferent 
meduUated nerve fibre passes out through the anterior 
nerve roots. It is, however, probable that some of 
these fibres are axis-cylinder processes or ax^ns of 
ganglion cells of the anterior horn of the opposite 
side, and as such pass through the anterior commis- 
sure, while a small number of anterior root fibres can 
be traced into the posterior grey horn, where they are 
evolved as the axis cvlinder or axon of a sfanglion 
cell of this part of the grey matter. 

As will be mentioned presently, the grey matter 
of the cord contains, in the dorsal or thoracic portion 
(between the seventh cervical and second or third 
lumbar nerve), a special column of ganglion cells — 
Clarke's column ; the axon of some of these cells 
appears to pass through the anterior grey horn to 
join the anterior root fibres. 

But according to Fleclisig, with whom Kolliker 
agrees, the axons of most of the ganglion cells of 
Clarke's column pass in a horizontal direction from 
the grey matter into the lateral white column, where 
they pursue their course as longitudinal fibres towards 
the cerebellum, thus forming the fibres of the direct 
cerebellar tract. 

(3) The posterior roots. The medullated nerve 
fibres constituting the posterior roots are branches of 
the axis-cylinder process of the ganglionic cells of the 
spinal ganglion ; they enter the cord as small bundles 
by the postero-lateral fissure, betw^een the lateral and 
posterior columns of white matter, in a slightly 
slanting direction, and at the same time turned more 
towards the posterior column of white matter. Now 
the fibres of the posterior roots may be roughly 
grouped into a lateral and mediau bunale, the former 
containing predominantly fine medullated fibres, the 



Spinal Cord. 189 

latter predominantly larger niedullated fibres ; the 
former as well as th(^ latter, after their entry into the 
cord, sooner or later divide, each into an ascendiny 
and a descending medullated fibre. The ascending 
and descending fibres resulting from the division of 
the fibres of. the Literal bundle form part of and 
pursue their longitudinal course in that portion of the 
posterior white column which lies next to the posterior 
grey horn and the lateral white column, and which 
is known as Lissauer's tract or Lissauer's bundle {see 
Fig. 122). The ascending and descending medullated 
fibres resulting from the division of the fibres of the 
median bundle also following a longitudinal course 
are distributed principally over, and form part of, the 
white matter of the posterior columns (Burdach's and 
GoU's tract). Some of these fibres are said, however, 
to enter directly into the grey matter of the posterior 
horn and to terminate there. 

(4) All medullated fibres constituting the dififerent 
columns of white matter and descendinof or ascending 
respectively in the cord send out at numerous levels 
horizontal fibres which enter or pass out from the 
grey matter. The discovery of these fibres by Golgi 
and II anion y Cajal by means of the silver method 
constitutes a fundamental advance in our knowledoe 
of the minute anatomy and physiology of the cord. 
These horizontal fibres which branch ofi' from, or join 
respectively, the fibres constituting the different tracts 
of the white matter are called collaterals {see Figs. 
122 and 123 c). The collaterals give off branches 
themselves. By means of the collaterals and their 
branches numerous connections are formed between 
the longitudinal fibres of the white columns on the 
one hand and the grey matter on the other. The 
collaterals terminate, or originate respectively, near 
and around nerve cells in all jjarts of the grey matter 
hy means of arborisations or dendrons (Fig. 133). 



igo 



Elements of Histology. 



175. As mentioned just now, collaterals are not 
limited to any one tract of the white columns, and are 
not limited to any particular level, but are given off 

or pass into re- 
spectively the 
longitudinal fibres 
constituting the 
white columns in 
general and at 
level 
which 
of the 
made. 




e ^' e r y 

through 

sections 

cord are 

Figs. 122 and 123c 



give a 



good 
presentation 
these facts. 



re- 

of 



F o 1 lowi ng, 
then, the longi- 
tudinal medul- 
lated fibres con- 
stituting those 
tracts of white 
matter, which 

were described 
above as descend- 
ing fibres (show- 
ing descending de- 
generation) — e.g. 
the direct pyra- 
midal tract, the 
crossed pyramidal 
tract, the inner 
portion of the an- 
terior part of the lateral column — -it is seen that 
at many points each sends out horizontal colla- 
terals which enter the grey matter and terminate 



Fig. 133. — Collaterals passing from fibres of 
posterior column into the grey matter, and 
teiTuinatiug at « by dendrons. From the cord 
of a newlj'-born child. {After Kolliker, II.) 



Spina l Cor d. 191 

there as arborisations or dendrons close to, or around, 
ganglion cells ; and similarly the longitudinal medul- 
la ted fibres constituting those tracts of white matter 
spoken of above as ascending tracts — e.g. the tract of 
Goll, of Burdach, of Lissauer, the dii-ect cerebellar 
tract and the superficial parts of the anterior portion 
of the lateral column (Gowers's tract) — are connected, 
brought into relation, by means of collaterals and 
their dendrons, with the grey matter and with the 
ganglion cells situated in the latter. The bundles of 
fine nerve fibres, so conspicuous in every horizontal 
section, passing in a horizontal manner from the 
posterior columns through and around the suhstantia 
gelatinosa of Rolando of the posterior grey horn, are 
bundles of collaterals given off by the longitudinal 
fibres of the posterior columns. 

176. The grey matter of the cord contains the 
same kind of neuroglia as the white matter — viz. neu- 
roglia fibres and neuroglia cells ; the fibres do not, 
however, form longitudinal networks as in the white 
matter — due to the peculiar (longitudinal) arrange- 
ment of the nerve fibres — but are distributed more or 
less as a uniform network ; every section, therefore, 
be it longitudinal or transverse, shows the glia fibrils 
cut transversely, obliquely and longitudinally. The 
glia cells are the same in size and in their numerous 
branched processes as in the white matter. 

In this matrix of neuroglia are embedded nerve 
cells or o-anolion cells and nerve fibres and their 
ramifications. The ganglion cells are all possessed of 
several processes, and are therefore multipolar ; they 
differ in respect (ci) of position, {b) of size, (c) of 
the structure, distribution and connections of their 
processes. 

177. (a) ill respect of position, the nerve cells 
form groups and aggregations which, in the longitu- 
dinal axis of the grey matter^ are more or less 



192 Elements of Histology. 

discontinuous, so tliat to each particular spinal nerve 
or segment corresponds a more or less separate mass. 
The following groups can be distinguished on each 
side (Fig. 125) : — 

(1) The centro-lateral group, situated in that part 
of the anterior cornu which is in contact with the 
ventral portion of the lateral column ; 

(2) The dorso-Jateral grotip, also situated laterally 
in the anterior cornu immediately behind or dorsal ly 
to the tirst-named group ; 

(3) The ventro-median group, situated in the 
foremost portion of the anterior cornu where this is 
in contact with the anterior column ; 

(4) The dorso-Tiiedian group, immediately behind 
the former — i.e. next the anterior white commissure. 

(5) As mentioned above, that portion of the grey 
matter which projects laterally between the anterior 
and posterior cornu of each side and about midway 
(Figs. 122 and 125) — i.e. the lateral cornu — -contains 
in the upper two-thirds of the thoracic cord groups of 
ganglion cells which represent the cells of the lateral 
horn, but they are present only as scattered ganglion 
cells in the corresponding portion of the grey matter 
above and below the proper lateral horn (Waldeyer). 

(6) Throughout the thoracic cord there is present 
a conspicuous group of ganglion cells, which groujD is 
in cross-section of a rounded or oval shape ; this is the 
2)osterior vesicular column of Clarke or Stilling's group^ 
and is situated at about the same level as the group 
of cells in the lateral horn ; but while this latter is 
lateral, the column of Clarke is situated medially, 
and it has to be added that it really belongs more 
to the base of the posterior cornu. These two groups 
5 and 6 belong therefore to the middle region of the 
grey matter. 

(7) The posterior cornu contains in all parts 
only scattered cells not definitely grouped. Like those 



Spinal Cord. 193 

mentioned in the anterior cornu and the middle 
region of the grey matter. Also in the substantia 
gelatinosa of Rolando occur solitary ganglion cells. 
Amongst the cells of the posterior cornu the so- 
called marginal cells of Waldeyer and Lissauer 
deserve special mention ; they are situated at the 
margin of the posterior horn, or rather of the sub- 
stantia gelatinosa, where this is in contact with the 
dorsal and lateral columns of white matter. The 
marginal cells are long and spindle-shaped and 
different from most other cells of the posterior cornu 
in their being possessed of a distinct axon or axis- 
cylinder process. 

178. {h) In respect of size the ganglion cells 
show considerable differences ; the biggest cells are 
those of the anterior cornu mentioned as groups 1, 
2, and 3 ; the cells of these groups measure about 
70 — 130yu in diameter ; while those of group 4, dorso- 
median group of the anterior horn, are considerably 
smaller, 30 — 80 ^ ; between these two sizes are the 
cells of the lateral horn and of Clarke's column, 
while those of the posterior cornu, with few 
exceptions, are comparatively small cells. 

179. (c) 111 respect of structHre each gan- 
glion cell possesses a vesicular nucleus with a promi- 
nent nucleolus, and the substance of the cell is in all 
cases, when examined in the fresh state or in suitably 
prepared specimens, of the nature of a more or less 
fibrillated substance, between which a finely granular 
matrix can be recognised (M. Schultze). The fibrillse 
are grouped in bundles, and appear continuous and 
radiating from around the nucleus towards and into 
the fibrillated processes ; around the nucleus the 
fibrillEB appear more or less concentrically arranged. 
In the anterior cornu the ganglion cells contain 
normally pigment granules grouped near and around 
the nucleus (Klonne and Midler) {see Fig. 134). 



194 



Elements of Histology. 



Between the fibrill?e constituting the substance 
of the ganghon cells are found masses of granules 
(distinct from the just-mentioned pigment) which 
take the stains well : these are the chromatic granules 
of Nissl. In some ganglion cells they are distinct 




Fig 134. — Section tlirougli the Lower Lumbar Cord of Man. After a pre- 
paration of Klonne and Mailer in Berlin. {Kdlliker, 11.) 

^y, White lateral column in cross-section ; g, grey matter of anterior liorn, 
showing ganglion cells with pigment granules, and many meduUated nerve 
fibres. 



and conspicuous, in others less so. The presence of 
these chromatic granules indicates, it is suggested, a 
phase or phases of normal activity of the ganglion 
cells, whereas their disappearance and absence cor- 
responds to a pathological state of diminished or 
abnormal function. 

180. The most important differences,^ however. 



Spinal Cord. 



195 



are noticed on the ganglion cells with regard to the 
nature and coniKM^tioniS of their processes. 

As mentioned on a previous page, all ganglion 
cells of the cord are multipolar ; amongst the processes 




Fig. 133. — Isolated Ganglion Cell of the Anterior Horn of the Human 
Cord. (Gerlach, in Strieker's " Manual of Histology.") 

o, Axis cylinder process; 6, pitrinenr.. The braucUed dendrites of the ganalion 
cell break up into the fine arborisation shown in the upper part of the 
figure. 



into which the substance of the cells is continued 
there is one, occasionally two, which become sooner 
or later the axis cylinder of a medullated nerve 
fibre ; this is the axon or neuraxon of the ganglion 



196 



Elements of Histology. 



cell (Fig. 135). Such an axon is seen to come otf 
from each of the ganglion cells of the anterior cornu 




Fig. 136. —Isolated Multipolar Gauglioii Cell ;of the Grey Matter of 
the Cord. {Gerlacli, in Strieker's Manual.) 

The dendritically-branclied processes (dendrites) break up into the flue 
arborisation into which is seen to pass a fine nerve fibre and its ramiflca- 
tion derived from a posterior nerve rf)Ot fliire. 

and of Clarke's column, and of some cells in the 
posterior cornu. The axon of most of the anterior 



Spina l Cord. 1 9 7 

cells is continued as the axis-cylinder process of a 
medullated nerve fibre passing out as an anterior 
root fibre. The axon of other cells in the anterior 
cornu, as also to a lesser extent of the posterior 
cornu (including those of the substantia gelatinosa), 
does not, however, pass into anterior root fibres, but 
becomes the axon of longitudinal medullated nerve 
fibres forming part of the lateral, and to a lesser 
extent the anterior, columns of white matter. 

These important facts were discovered by Golgi 
and Ramon y Cajal, and were confirmed by KoUiker. 
According to Golgi and Ramon y Cajal, axis-cylinder 
processes or axons of ganglion cells from all parts of 
the grey matter may pass into the anterior commissure. 

Cells of this character — i.e. possessing axons 
which pass as longitudinal medullated fibres into the 
white columns — are Kolliker's " Tract cellsJ^ 

181. Another very striking fact discovered by Golgi 
and by Ramon y Cajal is this : that the axon of the 
ganglion cells ramifies. In some, like those cells of 
the anterior cornu, whose axon passes into an anterior 
root fibre, the axon for some distance gives off few 
or no branches (Golgi's group A). In other cells, like 
those of the posterior cornu, the axon is much 
branched and its fibres are lost in the grey matter 
(Group b). The former are considered by Golgi as 
motor, the latter as sensory cells. 

Besides the axon, all ganglion cells in all parts of 
the grey matter possess more or less numerous pro- 
cesses which, owing to their rich and dendritic 
branching and their distinctly fibrillated nature, are 
the protoplasmic or branched processes, or the den- 
drites (Fig. 136). In the cells of the anterior cornu, in 
those of Clarke's column and of the lateral horn, the 
dendrites are numerous and distinctly arborescent ; 
they are less numerous in the cells of the posterior cornu ; 
thicker branches give off laterally smaller branches, 



198 



Elements of Histology 



which by euntinut'il raniiticatioii become greatly attenu- 
ated and ultimately resolve themselves into arbores- 
cent terminations or dendrons (Fig. 136). 

While the dendrites and their terminal dendrons 
of most of the ganglion cells are distributed in the 
grey matter, Golgi has proved that of some cells 
some of the dendrites pass into and are distributed 
amongst the nerve fibres of the white columns, a 




S' 



'F 



Fig. 137. — From the Lateral Horn of the Cervie<il CoM of the Ox. Highly 
magnified. (KoUiker, II.) 

s, Lateral colanin of white matter in cross-section ; F, fine dendrites of the 
ganglion cells penetrating into the white cc^ituran. 



fact wliieh Kolliker has emphasised, and whicli par- 
ticularly holds good for the cells of the lateral horn 
in the cervical cord of the ox. (Fig. 137.) 

182. Besides the ganglion cells, their axons, den- 
drites and dendrons, the grey matter contains nerve 
fibres of a ditierent origin and connection. As 
mentioned on a former page collaterals of longitu- 
dinal fibres of all white tracts enter, or pass out 
respectively from the grey matter : here they ramify 
and terminate 1)V arborisations or dendrons, wliicli 



Spinal Cord. 



199 



are either interiningliiig with, or surrounding the 
arl>orising dendrons of the dendrites of ganglion cells 
or surround the hody of the ganglion cells. Owing to 
the great number of such collaterals, as mentioned 
on a former page, 
their arborisations 
or dendrons form a 
considerable por- 
tion of the grey 
matter. 



Sherrington sug- 



gests 



W.W 




the term of 
synapsis {avv and 
(tTr-w) as indicating 
the contiguous but 
not continuous re- 
lation of the arbo- 
rising terminations 
of axons surround- 
ing the arborising 
dendrites or the 
body of a ganglion ■m\^ 
cell. Such synapsis 
would then occur 
everywhere in the 
central nervous sys- 
tem (cord, brain, 

medulla, Sympa- t^ig- 137A.-Scheme of the Elements of the Conl 

, . ' T concerned in Reflex Actions. Longitudinal 

thetlC ganglia, re- view. (Kdlliker,II.) 

where .s- rj, Ganglion cell of a spinal ganglion ; s, sen- 
sory flhre coming from the periphery; sth, 
division of a posterior root fibre into sa, an 
ascending and descending fibre; sc, collaterals 
of same passing to motor ganglion cells, m ; 
m ('•, motor (anterior) root fibres being axons of 
anterior nerve cells. 



tina, etc. ) 
neuraxons and their 
collaterals of a near 
or distant ganglion 



cell arborise ( ter- 

minate) around dendrites or the cell body of a 

ganglion cell. 

A second, also considerable, portion of the grey 



200 



Elements of Histology. 



— L/i<? 



ns 



matter is made up of dendrons, the developing fibres 
of which are not collaterals but are direct con- 
tinuations of longitudinal fibres of the white columns; 
thus the descending branches of posterior root fibres 
terminate in this way in the grey matter, many of 

the main fibres of the 
anterior and particularly 
the lateral columns pass 
into or pass from the grey 
matter, and after a shorter 
or longer course, either on 
the same side or after 
crossing through the an- 
terior or posterior com- 
missure terminate as den- 
drons around ganglion 
cells or intermingle with 
the arborisations of den- 
m IV drites of ganglion cells. 
The manner of the most 
probable connections and 
actions of the grey matter 
of the cord are illus- 
trated by the accom- 
panying diagrams (Figs. 
137a and 137b), copied 
from Kolliker. 

Before the introduc- 
tion of the method of 
Weigert, and its modifi- 
cation by Pal (by which 
the medullary sheath of 
nerve fibres is stained), 
it was unknown that the o'rev matter of the cord 
contains medullated nerve fibres to any large extent. 
By the above methods, if successfully applied to the 
examination of suitablv stained sections of the cord. 




miv 



Fig. 137e.— Scheme of the Con- 
duction of Inipiilses in Volun- 
tary Movement. (Kolliker, II.) 

2>s, Fibres of the crossed pyramidal 
tract in the cord ; these fibres had 
crossed (pyramidal crossing) m 
the medulla ; collaterals of these 
fibres pass into and terminate 
in the grey matter of the cord : 
p o, fibres of the direct pyramidal 
tract in the cord, collaterals cross 
in the cord ; m, nerve cells in the 
anterior grey horns; 7?i. if, axons 
of same forming the fibres of the 
motor (anterior) roots. 



Spinal Cord. 201 

it is shown that tlie grey matter contains a really 
astonishing number of medullated nerve fibres, run- 
ning singly or in small bundles, horizontally and 
obliquely. All the above collaterals, as also the 
continuations of the fibres passing from the white 
columns into the grey matter, or vice versd, are 
medullated fibres {see Figs. 122 and 123a). 

183. The large vascular branches enter the white 
matter of the cord from, or pass out by way of the pia 
mater, being invested in neuroglia continuous with 
the tissue of the pia mater. By continued division 
they resolve themselves into fine branches, which pass 
into, or pass from, the network of capillaries. 

The capillaries are more abundant and form a 
more uniform network in the grey than in the 
white matter. In the latter most of them have a 
course parallel to the nerve fibres, i.e. longitudinally. 
The blood-vessels and the orano^lion cells are ensheathed 
in lymph spaces (perivascular and pericellular spaces). 



202 



CHAPTER XVII. 

THE MEDULLA OBLONGATA OR SPIXAL BULB. 

184. As the cervical portion of the spinal cord 
passes into the medulla oblongata its parts alter in 
position and relation. It is possible, to a large 
extent, to recognise in the bulb, regions which 
correspond to different areas of the cord. Many of 
the cord areas are, however, lost in the bulb, and on 
the other hand, many new areas appear. 

185. The anterior or ventral fissure is continued 
as far as the bulb extends. The posterior or dorsal 
fissure of the cord is also continued for a certain 
distance along the medulla, but this widens out in the 
upper part of the bulb into the lower end of i\\e foui^th 
ventricle. The line of origin of the anterior roots of 
the spinal cord is continued into the medulla, being 
marked out by the exit of the roots of the hypoglossal 
nerve. In the upper portion of the medulla this line 
of origin develops into a marked fissure. The shallow 
groove existing dorsally between the postero-median 
and postero-external columns of the cord is even better 
marked in the bulb, and divides the funiculus gracilis 
(median) from the funiculus cuneatus (external). 
The postero-lateral groove into wliicli the posterior 
roots pass to the cord is continued up as the external 
boundary of the funiculus cuneatu.s and the internal 
boundary of yet another longitudinal projection, 
leading u]3 to a prominence, the tubercle of Rolando. 
In the upper portion of the cervical cord there project 
from the lateral columns the roots of the spinal 



Med ul la Oblo nga ta . 



203 



accessory nerve. The line of origin of these roots is 
continued up along the lateral surface of the bulb and 
there arise successively along this line the roots of 




Fig. 138.— Section through the Lower Eud of the Pyramidal Decussation. 
The section is slightly distorted. {Microphotograph of section stained 
with aniline Nue-blacl-.) 

A. F., Anterior or ventral Assure lying obliquely on accountiof fibres passing from 
crossed pyramidal tract on left side to anterior column on risht ; p. k., pos- 
terior Assure ; i. f., corresponds to septum l)etweenGoirs columnand postero- 
external column : p. li., posterior root of first cervical nerve ; on the left side 
at level a. h. the anterior horn is separated from rest of grey matter. The 
substantia gelatinosa at tip of posterior horn is increased, and the angle 
between the posterior horns is greater than below. 



the spinal accessory, the vagus, and the glosso- 
jyharyngpxd. At the junction of the bulb with the 
pons the seventh nerve passes out in the same line, and 
passing through the substances of the pons \\\q fifth 
nerve possesses a corresponding origin. 



204 



Elements of Histology. 



186. It will be found most convenient in order 
to determine the relation of the different regions in 
the bulb with those of the cord, to examine the 
appearances presented by successive sections of the 




Fig. 139.— Section thi'ougli the Upper Part of the Pyramidal Decussation 
in the Medulla Oblongata. {Microphotograph of a Weigert-Pal specimen.) 

A.F., Remains of anterior Assure; the dark mass immediately above consists 
of the decussating pyramidal fibres ; at the level A. H. is a light mass on 
either side represeatinff the remains of anterior liorn; at tue level c. c. in 
the middle line is the grey matter round the central canal ; the posterior 
nuclei are not clearly distinguishable. 



bulb, cut in a dorso-ventral direction, and com- 
mencing at a level immediately above the cervical 
spinal cord. 

187. The region of the pyraiiiiclal decus- 
sation (Figs. 138 and 139). — In this region the fibres 



Mrd ul l a Ob long a ta . 



205 



of the crossed pyramidal tract, lying in the dorsolateral 
portion of the cord, take on an oblique course and, 
passing across the middle line, again resume their direct 
course in what would correspond in the cord to the 



P.F. 




•c.c 




S D. 



M. 



A.F. 



Fig. 140.— Section through the Medulla Oblongata at the level of the 
Sensory Decussation. {Photograph of a Weigert-Pal specimen.) 

The section has not involved the olives ; the pyramids are completely formed 
and project at p, and extend inwards as far as the level sr, meeting in the 
middle line. At level of c.c. on middle line is the central canal, and at a 
short distance from this are seen numerous fibres arching round and decus- 
sating on middle line at level s.u. ; k, lies between funiculi gracilis and 
cuneatus. 



anterior or ventral column. In their passage across to 
the other side of the medulla these fibres separate oft' 
the head of the anterior horn so that the grey matter 
of the cajnit lies in the anterior area disconnected 
from the main mass of the grey matter. The angle 
formed by the median boundaries of the two posterioi^ 



2o6 Elements of Histology. 

horns increases very considerably, so that these horns 
come to lie more transversely across each half of the 
medulla than was the case in the cord. There 
develop also from this inner margin of the posterior 
horns, in the iij)per part of the pyramidal decussation, 
certain protuberances of grey matter ; a median mass 
projecting into the funiculus gracilis and known as the 
mideus of the funiculus gracilis Rud a more externally 
situated mass, projecting into the funiculus cuneatus, 
and known as the nucleus of the funiculus cuneatus. 
The substantia gelatinosa at the tip of the posterior 
horn also becomes more conspicuous and causes the 
medulla to project in this region, forming the funiculus 
uf Rolando. Higher up this projection becomes even 
more conspicuous and is known as the tubercle of 
Rolando. In the region of the pyramidal decussation 
the substantia gelatinosa of Rolando is separated from 
the surface by a longitudinal mass of medullated fibres 
which pass to the origin of the fifth nerve. This mass 
of fibres is spoken of as the ascending root of the 
fifth nerve. 

188. The region between the npper end 
of the pyramidal cleenssation and the 
eouiniencenient of the olives (Fisf. 140). — In 
this region the central canal is seen to lie more 
posteriorly corresponding to its gradual approach 
towards the posterior surface. The p3Tamids oc- 
cupy well defined positions on the ventral side 
of the bulb immediately abutting on the anterior 
fissure and bounded laterally by the fibres of the 
hypoglossal nerve coursing from the nucleus of the 
twelfth, across the medulla. There is to be seen lying 
in the lateral region between the substantia o^latinosa 
of Rolando and the fibres of the twelfth, a mass of 
cells, which correspond to some extent to the more 
dorsal portion of the separated anterior horn, but 
which in part is to be regarded as a new formation. 



Medulla Oblongata. 207 

This mass of cells is spoken of as the lateral 
HKc/f'us. It is to be noticed tliat the ])Osterior white 
matter is gradually undergoing absorption, being 
invaded by the grey matter of the corresponding 
nuclei. The grey matter of these nuclei gradually 
becomes more marked, the nucleus of the funiculus 
gracilis early absorbing the white matter of the 
column and lying quite close to the surface. The 
nucleus of the funiculus cuneatus lies rather more 
deeply, but is gradually invading the white substance. 
The central portion of the medidla becomes broken 
up, and fibres are seen passing in an arched manner 
from the nucleus gracilis mainly, and, to some extent, 
from the nucleus cuneatus towards the middle line. 
These arched fibres on reaching the middle line, 
for the most part bend longitudinally, and thus form 
a mass of fibres lying dorsal to the pyramids, and 
spoken of, higher up, as the inter-olivary layer. This 
decussation of fibres passing from the gracile and 
cuneate nuclei is sometimes referred to as the supei'ior 
or sensory decussatior. 

189. The region of the lower portion ol 
the olives (Fig. 141). — A few millimetres higher up 
than the last section the olives are seen to be distinctly 
formed, though they have not reached their greatest size 
and though the central canal is still closed. The central 
canal has at this level approached yet more closely to 
the posterior suiface. Each lateral half of the bulb 
may be more or less distinctly marked off into three 
areas : a median area lying between the middle line 
and the roots of the twelfth nerve as they coui^e across 
the bulb from the hypoglossal nucleus : a lateral area, 
lying between the roots of the twelfth and those of the 
eleventh, which issue more laterally ; and an area, 
posterior to the eleventh roots, which may be called 
the posterior area. The lateral nucleus lies in the 
dorsal portion of the lateral area. The main 



2o8 



Elements of Histology. 



mass of tlie olive lies 
of the lateral area. Imt 



in the ventral portion 

two additional masses, 



S.G. 



XI. 




N 3. A. 



M.H. 




Fig. 1-tl. — Section through the Medulla Oblongata at level of commence- 
ment of Olives. {Microphotograph of a specimen stained with aniline 
hlue-hlack.) 

The central canal is not yet opened out, and is at level of x.s. a. : the posterior 
grey matter is arranged iu three masses, >'. g., nucleus gracilis, x.c, nucleus 
ciineatus, and s. g.. the substantia gelatinosa of Rolando: with respect to 
grey matter round central canal, that at level x. s. a, has cells forming 
nuclei of the xi, that at level x. h. forming nuclei of xii ; xi is placed 
against the line of issue of the spinal accessory, xii against hyi>oglossal ; 
the grey matter lying slightly beneath surface at level l.x. is the lateral 
nucleus; o, is at level of the twisted dark 1>and, the olive; the large light 
areas at level of p are the pyramids : the area more dorsal at level R. f. is the 
reticular formation, in the middle line of which is the raphe (.above a. f. i. 



similar in structure to the olive, may also be 
seen, one lying in the lateral area, dorsal to the 
main olive, kno^vn as the dorsal accessory olives 
and the other lying in the median area, separated 



Medulla Oblongata. 209 

from the iimin olive by the roots of the liypoglossal 
nerve and known as the menial accessory olive. The 
more central ]»ortion of the section is seen to be 
broken np by til)res passing horizontally, separating 
others which are proceeding longitudinally; and yet 
other strands are to be noticed intersecting both of 
these. Nerve cells are scattered through this area, 
and more conspicuously in its lateral portions, and 
these nerve cells with attendant neuroglia may be 
regarded as representing the much ditiiised grey 
matter of the ventral horn which was separated by 
the decussation of the pyramidal fibres. This broken 
tissue is spoken of as the reticular formation, the more 
lateral portion, which appears darker on account of the 
nerve cells being more numerous, being referred to as 
the grey reticular formation, and the central j^art as the 
■?r/n"<e reticular formation. In the middle line, wdi ere 
the reticular formations of either side are continuous, 
the decussation of the fibres coursing transversely, and 
the presence of many fibres running in a dorso- ventral 
direction, give a somewhat peculiar appearance to 
the reticular region. The narrow^ intermediate band 
is called the raphe, and it contains a larger proportion 
of nerve cells than the remainder of the median 
reticular formation. The lateral nucleus is still 
prominent at this level, the substantia gelatinosa 
of Rolando and the ascending root of the fifth are 
also seen. This latter is gradually becoming separated 
from the surface by a band of fibres running longi- 
tudinally but somewhat obliquely wdiicli represents 
the commencement of the resti/orm body or inferior 
peduncle of the cerehelhua. The longitudinal fibres 
lying outside the lateral nucleus represent the upward 
continuation of the direct cerebellar tract and these 
fibres gradually pass into the restiform body. Fibres 
are seen proceeding in a ventral direction from 
the raphe, originating in part from cells of the raphe 




2IO Elemests of Histology. 

but having some connection proljably with the nuclei 
gracilis and cuneatus, and these fibres passing from 
the anterior fissure encircle the pyramids and olives 
and pass towards the commencing restiform bodies. 
These fibres are spoken of as external arcuate fibres. 
There is to be seen at about this level for the first 
time a somewhat compact bundle of longitudinal fibres 
lying between the central canal and the substantia 
jjelatinosa, though consideraljlv nearer the former. 
This bundle is surrounded by grey matter, with 
the cells of which the fibres are connected. The 
fibres of the bundle mainly pas^s out with the roots 
of the glossopharyngeal nerve and it therefore has been 
called the ascending root of the glossopharyngeal : 
the names /'rtSC2C?//?/6' solitarius and respiratory bundle 
are sometimes applied to the same tract. In addition 
to the nerve cells already referred to other important 
masses of cells are now to be seen distinctly. («) llie 
nucleus of the tvnelfth nerve. This consists of a group 
of nerve cells representing, probably, the most dorsal 
portion of the separated anterior horn, lying slightly 
ventral to the central canal. The cells are multipolar 
and vary in size from 40-70 yu, and the neuraxons of 
these cells, after a somewhat irregular course, become 
the fibres of the hypoglossal nerve. The fibres on each 
side pass in a ventro-lateral direction across each half 
of the medulla and issue i'rom the groove lying 
immediately lateral to the pyramids. (6) The nucleus 
of the eleventh nerve. It must be noted that the 
eleventh, tenth, and ninth nerves pass off' at different 
levels from a group of cells longitudinally continuous. 
This group of cells can be spoken of as the combined 
nucleus of the spinal accessory (more correctly the 
bulbar accessory), the vagus and tlie glossopharyngeal. 
It is not possible to define precisely the divisions 
of the nucleus corresponding to each nerve. In 
the region of the medulla we are now describing, 



Medulla Oblongata. 211 

liowever, the roots belong to the spinal accessory nerve. 
Here the nucleus, consisting of a mass of somewhat 
spindle-shaped cells, oO-l:0/.i long and 12-20/li wide, 
occupies a position dorsal to the twelfth nucleus and 
adjacent to the central canal. From this nucleus 
tiljres may be traced passing laterally across each half 
of the medulla, and emerging from the l)ulb between 
the restiform body and the olive, ic) The nucleus of 
the funiculus gracilis, {d) TJie nucleus of the funiculus 
cuneatus. There may be seen external to this nucleus 
an isolated mass of cells, this is to be regarded as 
an accessory cuneate nucleus. (e) The lateral 
nucleus. 

190. The region of the iiiiddle of the loAver 
half of the fourth ventricle (Fig. 142). — At this 
level the central canal has opened out into the fourth 
ventricle. This fourth ventricle is furnished with a 
lining membrane, consisting of columnar cells (which 
may be ciliated), resting upon neuroglia. This lining 
membrane is spoken of as the ependyma. With the 
opening out of the central canal the gracile and cuneate 
nuclei have retreated from their median position and 
come to lie in the dorso-lateral region. The two gracile 
nuclei therefore are separated from one another by the 
width of the fourth ventricle. The nucleus of the 
twelfth nerve lies now in the median position at the 
dorsal surface, and in this locality a slight bulging 
into the ventricle exists which corresponds to the 
funiculus teres. Lateral to the nucleus of the twelfth 
lies the combined nucleus of the eleventh, tenth and 
ninth, here corresponding to the vagus nerve. The 
restiform Vjody has increased in size and has now 
largely absorlied the direct cerebellar tract. The 
olives are also much more prominent, and have 
here reached their full development. These bodies 
each consist of a lamina of grey matter folded back 
upon itself, enclosing a space filled with white 



212 



Elements of Histology. 



matter. The convex portion of the fold corresponds to 
the external protuberance. This lamina has, in addition 
to the main fold, numerous secondary longitudinal 



N V. 



N H 
R. 




A.V. 



"\ X. 



\ 






■(,? 




'V-^--^' 



Xli 



Fig. 142. — Section throufrli the Medulla Oblongata at level of middle of 
Olives. {Microphotograph of a specirueii stained rvith aniline llue-black.) 

B lies over the raphe ; a mass of grey matter just beneath x. h. is nucleus of the 
xiith, beneath y. v. is nucleus of the xth : beneath x. g. and y. c. are the 
nuclei of the fasciculi gracilis and cuneatus ; c. k. lies atrainst the light 
mass of the restiform body, slightly deeper at level a. v, is the ascending vth ; 
X is placed against the issuing x., and running down towards xii, from 
nucleus of the xiith are the fibres of the xiith : y. a. is against grey matter 
forming the nuclei of the external areiform fibres : the olive is seen lateral 
to the roots of xiith as a deeply stained undulating band ; a part is separated 
on the dorsal side (the dorsal olive) and a small part lies on median side of 
roots of xiith (the median accessory olive i ; at level of c. R.and immediately 
beneath f.s. is a light circular area, the fasciculus solitarius; the grey 
matter lying at level of x and a little below the surface is the lateral nucleus. 



folds, so that in transverse section it presents the 
appearance of a Avavy Ijand of grey matter passing 
from the formatio reticularis towards the surface, 



Med ulla Oblonga ta. 213 

and then arching back it continues its wavy course 
towards the region from which it started. Inter- 
nally there pass into the interior of the olive tracts 
of white fibres which radiate outwards towards the 
concave surface of the lamina. The lamina itself is 
composed largely of neuroglia, broken by nerve fibres 
passing across, there are also present many multi- 
polar nerve cells. These cells possess axis-cylinder 
processes which possibly pass down into lateral 
columns of the cord and become connected with 
motor cells in the grey matter. They are themselves 
connected with nerve fibres which, springing originally 
from the cells of Purkinje in the cerebellum, course 
through the restiform body and, becoming cerebello- 
olivary fibres in the medulla, pass across the opposite 
olive. It may also be that the olives are connected 
by longitudinal fibres with the cerebral hemispheres. 

It is possible to classify to some extent the 
numerous fibres passing transversely across the 
medulla in this region. 

Somewhat lower than the transverse section 
we are at present considering were decussating 
fibres from the gracile and cuneate nuclei, called 
internal arcuate fibres, forming the inter-olivary layer. 
With the development of the restiform body and the 
olives, other fibres proceeding transversely become 
prominent. The external arcuate fibres may be 
held to comprise three minor groups. («) Those 
passing from the raphe and encircling the pyra- 
mids and olives. Amongst these fibres in the 
upper part of the bulb are a mass of nerve cells 
known as the nucleus arciformis. (6) Fibres passing 
from the lateral tract into the restiform body. These 
are largely the more superficial of the fibres of the 
direct cerebellar tract. (c) Fibres passing dorsally 
from the gracile and cuneate nuclei to the restiform 
body of the same side. These fibres are also spoken 



2 14 Elements of Histology. 

of as superficial dorsal arcuate fibres. In adrlition 
to the so-called arcuate fibres there are other fibres 
which have a somewhat arched course, but which are 
best separated into a distinct class, and spoken of as 
cerehello- olivary fibres. These include a majority of 
the fibres forming the restiform body. They pass 
from the restiform body either laterally to the ascend- 
ing root of the fifth, or to some extent intersecting it, 
and proceed towards the dorsal lamina of the olive. 
Most of the fibres then penetrate the grey matter 
(a few perhaps becoming lost therein), and passing 
into the white core of the olive emerge at the olivary 
peduncle and proceed to the raphe. The more 
dorsal of these fibres passing from the restiform body 
do not intersect the olive ; the more ventral pass 
round the olive (and are hence regarded by some as 
external arcuate fibres), and entering between the 
olive and pyramid pass to the raphe. Having 
crossed the raphe these fibres either bend longitudi- 
nally or pass to the olivary grey matter. The 
longitudinal fibres Ivino^ between the olives in the 
ventral portion of the formatio reticularis are known 
as the inter-olivary layer. This diffuse column of 
fibres becomes more distinct higher up, and is then 
known as the fillet or lemniscus. In the posterior 
part of the formatio reticularis near the raphe, a 
fasciculus of longitudinal fibres is gradually becoming 
more distinct. This is known as the posterior longi- 
tudinal bundle, and is to be regarded as representing 
a part of the anterior or ventral column of the cord. 
The hypoglossal nucleus lies now on the floor of 
the ventricle, and external to it lies the nucleus oj 
the vagus. The cells forming this nucleus may be 
divided into two groups, a more median and a more 
lateral. The median group consists of the larger cells. 
In addition to this superficial nucleus there lies in 
the formatio reticularis, midway between the fibres 



Med ulla Obl onga ta. 215 

of the twelfth aiul clcveiitli nerves, a second nucleus 
known as the nucleus amhijaus or motor nucleus oj 
the tentli. Fibres from this nucleus pass dorsally to- 
wards the main vagus nucleus, and issue with the 
vagus roots. Fibres from the fasciculus solitarius 
also pass out with the vagus. The vagus fibres thus 
have three centres of origin. 

A section taken somewhav higher than that just 
considered would show the issue of the glosso- 
pharyngeal nerve. A majority of the fibres of 
the fasciculus solitarius pass out with the glosso- 
pharyngeal, running first towards the main nucleus, 
and then turning back and coursing with the fibres 
of the ninth nerve. There are also to be seen at 
this level, rather more distinctly than in the lower 
section, lying somewhat external to the fasciculus 
solitarius, and near to the grey matter corresponding 
to the nucleus gracilis, some scattered longitudinal 
bundles of fibres, which are connected with the 
auditory nerve, and are known as the asceruJimj root 
of the eighth. 



2l6 



CHAPTER XVIII. 

CONTINUATION OF THE MEDULLA OBLONGATA 
THROUGH THE PONS VAROLII AND THE REGION OF 

THE CRURA. 

191. Tliereg:ioii of the iiii<l<1loof the fourth 
veiitriele (Fig.14.3). — Adorso-ventral section passing 
through that part of the fourth ventricle across which 
the striae acusticse course would be somewhat below 
the precise middle of the ventricle, but may be con- 
veniently considered first. Such a section would not 
involve the pons varolii and would probably just 
miss the exit of the sixth nerve. In such a section 
the upper part of the diminishing olive would be 
seen still. The formatio reticularis occupies the 
median portion of each half, and, laterally, the resti- 
form body is here at its maximal size. Coursing 
ventro-laterally with respect to the restiform body 
are seen the higher roots of the ninth nerve ; on the 
median side of this there appears the ascending root 
of the fifth. On the median side of the dorsal portion 
of the restiform body are seen longitudinal fibres 
belonging to the ascending root of the eighth nerve, 
and lying somewhat dorsal to this are nerve cells 
belonging to the same nerve. The dorsal edge of 
the section appears to be composed of transverse 
dbres coursing from the raphe round the restiform 
body and directed towards the exit of the eighth 
nerve. These are the stance aciisticd'. 

Lying on the ventrolateral side of the restiform 



Medulla Oblongata. 



2 I 7 



body is a mass of nerve cells connected with the 
fibres of the acoustic nerve and called the ventral 
ganglion of the eighth. A section taken slightly 
higher would involve the pons and show some slight 




Fig. 143.— Part of a transverse section of the Medulla Oblongata through 
the exit of the Auditory Nerve. (Micropliotograph of a IVeigert-Fal 
specimen.) 

The section is slightly obliiiiie, ;uid lience at the level d the cochlear nerve 
(N. c.) is seen dividing into ascending (the more median) and descending (the 
more lateral) divisions. The half-moon-shaped mass, dark in C(dour at level 
C. E., is the restiform body. The dark mass lying in centre of the photograph 
at level of v is the ascending root of the fifth nerve. The lighter substance 
at level of D lying mainly on inner side of the cochlear nerve is the ventral 
ganglion, the cells of the tulierculum acusticum are in the lighter substance, 
rather above the level of D, and lateral to the cochlear nerve. s.R;, lateral 
portion of stri® acusticae. 

changes when compared with the section just described. 
The most conspicuous difference in the higher section 
consists in the presence of a prominent mass of 
transverse fibres passing across on the ventral aspect 



2iS ELEME^rs OF Histology. 

and breaking up the pyramids into smaller bundles. 
The auditory nerve is to be seen issuing as before, and 
on the median side of tlie eighth a second nerve, the 
seventh, passes out. It must be remembered that 
neither the sixth nor the seventh nerves pass by direct 
dorso-ventral courses outwards. The seventh nerve 
originates from a nucleus lying in the formatio 
reticularis midway between the ventral acoustic 
nucleus and the raphe, and at about the same level 
as the nucleus. The libres from the facial nucleus at 
first pass dorsally and then turn longitudinally and 
pass for a short distance upwards, becoming involved 
in the nucleus of the sixth. After a short upward 
course they turn back again towards the lower region 
of the bulb, and, takimj o^raduallv a more ventral 
direction, finallv emerije near the exit of the eio'hth 
nerve. There also pass out with the facial nerve 
fibres derived from the hinder portion of the nucleus 
of the third nerve. These fibres sujDply the orbicu- 
laris palpebrarum and frontalis muscles. The nerxe 
cells composing the nucleus of the seventh are about 
40-60/i in size, their neuraxons are directed dorsally 
to form the nerve fibres of the facial nerve. 

A mass of grey matter is also seen lying slightly 
median, and ^■entral to the seventh nucleus. This 
mass of grey matter contains nerve cells, and is known 
as the superior or little olive. This, in adults, is about 
4-5 mm. in lengtli, but is better developed in lower 
animals. The cells are similar to those of the olive, 
about 30— tO/z in diameter, with neuraxons and much- 
branching dendrites. Another mass of cells is to 
be made out on the ventro-median aspect of the 
superior olive. This is known as the trapezoid 
nucleus. Fibres may be seen proceeding from the 
ventral nucleus of the eighth, and passing on the 
ventral side of the superior olive and the trapezoid 
nucleus. These fibres constitute the trapezium., 



Med ulla Obl onga ta. 219 

and form the most tlorsal portion of the transverse 
fibres of the pons. 

The connection of tlie auditory nerve with its 
different origins is now to be described. There are 
three main nuclei from which origin takes place : — 
(a) the ventral or accessory nucleus lying near the 
place of exit of the nerve, and, from its resemblance 
to a spinal ganglion^ sometimes called the acoustic 
ganylion ; (b) a mass of cells lying on the floor of the 
fourth ventricle, midway between the restiform body 
and the median furrow, called the dorsal median 
nucleus ; and (c) a mass of cells lying near the 
ascending root of the eighth, between the median 
nucleus and the restiform body, but somewhat deeper 
than' the former, called the dorso-lateral nucleus or 
nucleus of Deiters. The ventral nucleus is really 
divisible into two ; a more lateral portion and the 
main ventral nucleus. The lateral portion forms the 
tuherculum acusticum. The eighth nerve can be 
seen to consist of two parts, one part passes to the 
median side of the restiform body, the other to the 
lateral aspect. The former is called the vestihidar 
nerve, and the latter the cochlear nerve, corresponding 
to the destination of these two divisions. The 
cochlear nerve has finer fibres than the vestibular, 
the fibres of the former being 1-2*5^, those of the 
latter 2-4^, The fibres of both nerves divide, like 
a spinal posterior root fibre, into an ascending and 
descending branch after enterins; the medulla. The 
ascending branches of the cochlear nerve pass to 
the ventral nucleus, the descending branches to both 
the tuberculum acusticum and the ventral nucleus. 
From the ventral nucleus fibres pass as already 
stated into the trapezium and become connected in 
part with the cells of the superior olive and the 
nucleus trapezoides. The cells of the tuberculum 
acusticum, and partly also those of the ventral nucleus, 



220 



Elements of Histology. 



originate the fibres composing the strua acusticce. 
(Fig. 152.) The fibres, therefore, coursing round the 




'^m 




FiK. 144. 



-.•Section through the .Sixth Nucleus aud Genu of Seventh. 
(Pliotograph of a Weigert-Pal preparation.) 



The lower half constitutes the hulk of the pons proper, with laterally the middle 
peduncles; the two syuiinetriCHl dark masses at level F are the longitudinal 
fibres of tbe fillet ; on the left side and lateral to the fillet is seen a darkish 
mass with a lighter centre, the .-uperior olive. The floor of the fourth ven- 
tricle forms tbe median part of the upper edge, two symmetrical light masses 
beneath vi are the vith nuclei. Fibres from the inner side are seen passing 
downwards near the middle line, these are the fibres of the vith. The 
fibres of the viith are seen passing apparently from the outer side of the 
vith nucleus on the left side. The nucleus of the viith lies on dorsal side of 
the olive. The darkest tissue Ijing beneath v and at level a constitutes the 
somewhat scattered fibres of the ascending root of vich. The genu of the 
viith is between the nucleus of vith and the median sulcus and Is better 
seen in the enlargement of this region. (Pig. 145). 



restiform body, though apparently the continuation of 
the cochlear nerve, are really the neuraxons of cells of 



Med ul la Obl onga ta . 



221 



the tuberculuni acusticum and ventral nucleus, wliich 
are connected with the terminal arborescences of 
fibres composing the cochlear nerve. The vestibular 

N.A. G.F. 



F.N. i 




A N 



Fig. 145.— Section througli the Nucleus of the Sixth, being a part more 
highly magnified of Fig. 144. {Microphotograph of a Weigert-Pal 
specimen.) 

The letters x.a., g. f.. aud r. lie over the cavity of the fourth ventricle, r lies 
ahove the raphe. A dark circular patch a little below g. f. corresponds to 
the genu of tlie viith nerve, x. a. lies above a circular light area wlaich is 
the nucleus of tlie vith. F. N. lies against the lower end of a darkly stained 
mass of fibres which can he dimly traced round the nucleus of the vith 
towards the outer side of the genu of vii. This corresponds to the facial 
nerve just before it issues from the medulla. Fibres are seen passing from 
inner side of vith nucleus towards a. n., the fibres of the vith nerve. 



nerve fibres also divide, 



ascending and descending 
branches become 



on entering the bulb, into 

branches. These different 

connected with the cells of the 



2 22 ElEMF.XTS of HlSTOLOGV. 

clorso-inedian nucleus, Deiters's nucleus, and the 
cells around the ascending root of the eighth. As 
regards the further course of the stria? acusticse, these 
bundles show many fibres passing vertically into 
the central mass of the bulb or the tegmentum^ 
as it is termed ; other fibres of the striES acusticse 
decussate at the raphe, some pass thence towards 
the superior olive and turn longitudinally, others 
pass towards the restiform body. 

192. Region of iiiicleiis of seveiitli nerve. 
The nucleus of the seventh extends towards the mid- 
brain, almost to the upper limit of the nucleus of the 
sixth. A section taken through the junction of the 
upper and middle thirds of the fourth ventricle would 
pass through Vjoth these nuclei, showing the appearance 
seen in Fig. 14 4-. The fibres here are seen passing 
from the nucleus of the seventh towards that of 
the sixth, which is seen on the floor of the fourth 
v^entricle. Towards the inner side of this a more or 
less prominent mass of fibres of the seventh turn 
longitudinally, forming the genu of the seventh 
(Fig. 145), and there are seen laterally fibres about 
to pass out of the bulb, belonging to this same nerve. 
The nucleus of the sixth or abducens nerve consists 
of multipolar cells, about 40-50 fx in diameter. The 
neuraxons of these cells pass from the median side 
ventrally towards the pons and run through this 
Avitli an oblique backward course so as to issue at 
the lower edge of the pons in line with the roots 
of the twelfth. The nucleus is connected with the 
superior olive by a bundle of fibres, which is called 
the pedicle of the superior olive. Other connections 
exist with the pyramidal bundles and the posterior 
longitudinal bundle. 

193. The region of the upper end of the 
fourth ventricle. (Fig. 146.) — A section through 
the nuclei of the fifth nerve would show the 



Med ul la Ob long a ta . 



22 



characters uf a transverse section in this region. The 
origins of the fifth seen in this section consist of 
two more or less distinct masses of cells, the outer 
being described as the sensory nucleus, the inner 

Vs 




Fit 



140. — SectioL chrough the Nucleus of the Fifth Nerve. 
graph of a Weigert-Fal preparation.) 



{Microphofo- 



Below is seen a small part of the pons proper, and at p are fibres passing circuni- 
ferentially towards tbe pons. At level F is a dark mass on left side of 
middle line of section, the fillet (above this and near the centre of the micro- 
pbotoeraph) at level s. o. is tbe superior olive. At level x. and beneath vm. 
and vs. are tbe two nuclei of the vth ; from these and between these, at level 
T, are seen fibres passing downwards towards the pons fibres— these form the 
vth nerve. 



as the motor nucleus. From these masses of cells 
nerve fibres are seen to pass in a ventro-lateral 
direction to the fifth nerve. The more exact origin 
of this nerve may be now referred to. In the first 



2 24 Elements of Histology, 

place the nerve consists of two parts, the motor and 
the sensory divisions. Tlie sensory divisioit proceeds 
from the Gasserian ganglion, and, on reaching the 
deeper layers of the pons, the different fibres divide into 
ascending and descending portions, like an ordinary 
sensory nerve. The descending portions form a 
bundle of fibres, the so-called ascending root of the 
fifth, which has been referred to in most of the regions 
already described. This can be traced down distinctly 
as far as the pyramidal decussation. The bundle 
diminishes in amount on tracing it downwards, 
and is always associated with a mass of grey matter 
lying on the median side, the substantia gelatinosa. 
In this substantia gelatinosa are cells round which 
the fibres of the '' ascending " root form arborescences. 
At the level of the exit of the fifth these cells of 
the substantia gelatinosa are more evident, and are 
referred to as the chief sensory nucleus. The 
ascending branches of the bifurcating sensory root 
])ecome connected with the cells of the chief nucleus. 
From the cells lying in the substantia gelatinosa 
against the " ascending " fifth along its whole length 
there pass, towards the middle line, arched fibres, 
which cross the raphe, then become longitudinal 
in their course and enter the fillet. On their 
way towards the upper part of the brain these fillet 
fibres of the fifth give off numerous collaterals which 
are connected with cells in the reticular formation. 
The motor root sjDrings from the motor nucleus. This 
occupies the position somewhat of an upward con- 
tinuation of the seventh nucleus. It consists of large 
multipolar cells (50-70/.f) having, however, blunt, 
unbranched processes. The fibres forming the motor 
root are partially decussated, so that the root on one 
side is composed of fibres derived from the motor 
nuclei of both sides. There are connections between 
the motor and sensory nuclei which may furnish the 



Med ul l a Ob long a ta. 225 

path for reriex masticatory action. There must 
also exist connections with fibres of the pyramidal 
system. Passing dorsally between the two nuclei 
are seen fibres which turn longitudinally and form 
a small tract traceable, upwards, about as far as the 
anterior corpora quadiigemina. This is known as the 
" descending " or cerebral root of the fifth. It will 
perhaps be well to describe its course here. In 
the region of the posterior corpora quadrigemina it 
lies near the dorsal angle of the superior cerebellar 
peduncle and dorso lateral to the outer angle of the 
posterior longitudinal bundle. It is separated from 
this bundle by a mass of pigmented cells, known 
as the substantia fer rug inea (Fig. 147). The "des- 
cending " root can be traced upwards as a bundle 
of large fibres aoainst which lies scattered round or 
spindle-shaped nerve cells, less deeply pigmented than 
those of the substantia ferruginea. Passing to the 
level of the anterior corpora quadrigemina, the root 
can be seen for some distance, lying at the edge of 
the grey matter surrounding the Sylvian aqueduct 
and near the upper end of the anterior corpora 
quadrigemina it becomes lost. Returning to other 
structures seen at the level of the exit of the fifth 
nerve, it will be well to refer to the appearance 
now presented by the fillet. 

In the middle of the fourth ventricle the fillet 
consists of a mass of longitudinal fibres lying on either 
side near the middle line and separating the formatio 
reticularis from the transverse fibres of the pons. 
In the sub-pontine region the fillet fibres lie between 
the olives, forming the inter olivary layer. In the 
upper portion of the fourth ventricle the fillet on 
either side divides into two masses, one part lying 
between the superior olive and the middle line, 
forming the median fillet, the other lying dorsal to 
the superior olive and known as the lateral fillet. 
p 



2 26 Elements of Histology. 

The fibres of the median fillet are derived originally 
from the nuclei of the funiculi gracilis and cuneatus 
as well as from the nuclei of the vagus, glasso- 
pharviigeal. ami ^■r^tilal^;^l■ nerve. The lateral fillet 
probably originates (Ij from fibres of the trapezium, 
passing from the ventral acoustic ganglion of the 
ojiposite side and, therefore, connected with the 
cochlear root of the eighth; (2) from the superior 
olives on both sides and, higher ui>, from a collection of 
cells in the course of the lateral fillet, known as the 
nucleus qftJie lateral jillet j (3) from longitudinal fibres 
lying against the superior olive, which increase in 
ntmiber on proceeding upwards; (4) possibly, from 
fibres derived from the striae acusticae, which have 
passed ventrally into the tegmentum and turned into 
the tract of the"^ fillet. 

The ^jo/is proper is made up of numbers of 
transverse fibres passing laterally from the middle 
peduncles of the cerebellum on one side to that 
on the other. In crossing ventrally upon what is the 
continuation of the substance of the bulb these fibres 
divide the pyramids into groups of longitudinal fibres. 
The more dorsal of these transverse fibres (those 
lying immediately adjacent to the upward con- 
tinuation of the formatio reticularis) are known 
by the special name of the trapezium. Amongst the 
transverse fibres of the pons are numerous scattered 
masses of grev matter with which manv of the 
loncjitudinal fibres become connected. 

194. The reg^ioii of tlie posterior coi*pora 
qiiadri^eiiiina and upper part of tlie poii^>. 
— The first section taken is immediately below (distal) 
the posterior corpora quadrigemina. The fourth 
ventricle has here narrowed to form the commence- 
ment of the aqueduct of Sylvius. Surrounding the 
channel is the ependyma enveloped on all sides by 
a considerable thickness of ^rex matter. In that 



Med ulla Obl onga ta . 



227 



portion lying on the ventral side maybe seen masses 
of cells foi-mini: the commencement of the nuclei of 



S.C.P IV. I. IV. V. S.C.P. 



P.L.B 




L.F 



M.F 



Fig. 147. — Section throu<:li the Pons Varolii immediately below the 
Posterior Corpora Quadrigemina. {Fhotograph of a U'eigert-Pal 
specimen.) 

The main mass of the section forms the fibre? of the pons (P). The two large 
dark masses in the upiier part (under >s. c. p. », the lower ends meeting in 
middle line, are the superior cerebellar peduncles or lirachia conjunctiva. 
The area included between their lower halves forms tbe teirmentum. Tbe 
iiuadrangular space lielow i is the Sylvian aiiueduct. Decussating in the 
valve of Vieussens above are seen fibres of the ivth nerve, the two small dark 
masses below iv being the main trunks lying obli.iuely. Lying a short 
distance below the aqueduct at p. l. b. are two dark comma-shaped masses, 
the posterior longitudinal bundles. The twu elongated dark masses one 
lying against l. f.. the ntlier passing l)etween the pons fibres and the superior 
cerebellar peduncles opposite M. f. are the lateral and median fillets. The 
darkish mass lying below v, just on the median side of the upper part of 
the peduncle is the descending root df vth. 

the fourth nerve. Lying again ventral to thi.s grey 
matter are two prominent longitudinal bundles on 



2 28 Elements of Histology. 

either side of the middle Une, tapering towards the 
lateral region. These are the posterior longitudinal 
bundles. Near the lateral tapering end of these 
bundles may be seen the desceitdiag root of the fifth 
nerve, separated by a mass of cells forming the 
substantia femiginea or locus cceruleus. Lying to 
the median side of the root of the fifth may be 
seen bundles of white fibres pa^^sing into the superior 
nieduUary velum or valve of Vieussens, decussating 
here (Fig. 1J:7) and issuing literally as the fourth 
nerve. Lying again ventrally and laterally to the 
posterior longitudinal bundles, and separated from 
them by what is an upward continuation of the 
reticular formation, are the upward prolongations 
of the superior cerebellar peduncles or brachia 
conjunctiva. There at the level of the nuclei of 
the fifth nerve, in section, two semicircular masses 
lie immediately lateral to the side of the fourth 
ventricle. Passing upwards, they gradually take 
a more venti-al position till, as in the present 
section, they commence to fuse in the middle line. 
At a short distance externally and ventrally to the 
superior cerebellar peduncle is seen another band 
of longitudinal fibres. This band is of considerable 
thickness between the peduncle and the lateral surface, 
then passing ventrally it narrows somewhat^ and 
widens again to a fairly broad band lying on the dorsal 
side of the pons proper. This is the fillet or lem- 
niscus, the lateral portion witli nerve cells forming 
its nucleus being the lateral fillet, that portion lying 
adjacent to the pons being the median fillet. Ventrally 
to this again is the substance of the pons proper, 
having the characters described in ^ 193. 

A section slightly higher would pass through the 
posterior corpora quadrigemina. Here, there would 
appear two protuberances, dorso - laterally to the 
aqueduct. The lateral fillet forms connections with 



Medulla Oblongata. 229 

these bodies. Tlie pons pioper is here soinewliat 
smaller, the up])er limit being appruuched. The two 
superior cerebellar peduncles gradually lessen in width, 
their lateral extensions disappearing by degrees. The 
nucleus of the fourth nerve consists of a mass of large 
multipolar cells lying in the grey matter on the 
ventral side of the aqueduct and near the middle line, 
and reaching from the upper to almost the lower 
extremity of the posterior corpora quadrigemina. 
The fibres from these cells take a somewhat oblique 
backward course to the lower limit of the posterior 
corpora quadrigemina where they decussate, as already 
described. In the region of the posterior cor[)ora 
quadrigemina the posterior longitudinal bundle is 
very prominent. The basal ends of the ependyma 
lining the aqueduct are frequently continued into a 
set of fine fibres which pass through the grey matter 
(and even beyond) and give a radially striated 
appearance to the region adjacent to the aqueduct. 

195. The region ot llie anterior eorpora 
quadrigemina and the cinra eei ebri. — 
At this level (Fig. 148) the pons has disappeared, 
and its position is occupied by two well-marked 
protuberances on the ventral side, spoken of as 
the crura cerebri. Lying dorsally to the crus on 
each side is a broad band of black pigmented 
cells, forming the substantia nigra. The grey 
matter around the aqueduct is considerable, the 
posterior longitudinal bundle is somewhat less con- 
spicuous than below and forms a narrow band 
lying at the ventral edge of the central grey matter. 
Large nerve cells lie in the ventral portion of this 
grey matter, forming the nuclei of the third nerve, the 
fibres of which can be seen passing ventrally in many 
bundles. In the middle line between these roots 
a well-marked raphe is visible. Lying midway 
between the central grey matter and the substantia 



230 



Elements of Histology 



nigi'a is a large mass of cells, known as the red 
nucleus. In man this nucleus consists of cells vary- 
ing in size from 20-7 5yu. These nuclei have some 




R.N 



Fi< 



14S.— Section through the Anterioi- Corpora Quadrlgemina. 
graj^li of a Weigert-Pal preparation.) 



{Photo- 



The section is somewhat oblique, lieing slightly higher on the right side than 
the left. The symmetrical projections above are the anterior corpora quadrl- 
gemina. The openiii!.' between them is the Sylvian aqueduct. Tlie lighter 
substance around this is the grey matter surrounding the iter. The darker 
masses forming tlie lower Ijoundary of this L'rey matter arranged in discrete 
areas on right side are the posterior longitudinal bundles, lyins in which are 
cells forming the nucleus of the third nt- rve. The bundles of fibres passing 
in an arched manner downwards from the third nucleus are the fibres of the 
third nerve. At level r. x. on right side is a large dark mass lyin.L' in a still 
darker patch, having the tibres of the third passing throusrh its median 
region. This is the commencement of the red nucleus, which is not yet 
evident on the left side, where a corresponding dark mass consists of the 
decussated fibres of the suiierior cerebellar peduncle. On the left side lying 
below and laterally to this mass and light in shade is the substantia nigra, 
this forms the base of a projection (the cms cerebrii, in which the fibres of 
• thepyramids and other fibres pass longitudinally. The dark band somewhat 
arched passing upwards to the anterior corpus quadrigeminum from the dark 
mass of the superior cerebellar peduncle is the fillet. 



Medulla Oblongata. 231 

connection with the superior cerebellar peduncles, 
which terminate liere in their uj)\vard course. 
Laterally, the tillet is seen passing dorsally towards 
the prominent <niferior corpus quadrigeminum. A 
small portion of the brachiuiii of the latter may also 
be seen. The ujjward continuation of the reticular 
formation corresponds to the mass between the ventral 
aspect of the central grey matter and the substantia 
nigra, and is called the tegmeiituni. The locus 
coeruleus is no longer seen, but the descending fifth 
is still apparent. 

Structure of the anterior corpus quadrigeiidnurn. 
Externally there is a thin layer of white matter about 
30-40)1/ in thickness. This is known as (a) the 
stratum zonale. The white fibres in this layer pass 
through the superior brachium from the optic tracts. 
From the layer many fibres enter the inner layers, 
and in them form dendritic ramifications, {h) The 
stratum cinereum. In this layer are numerous cells, 
whose neuraxons pass inwards, (c) The stratum alho- 
cinereum. externum. This layer contains numerous 
small and large cells and nerve fibres. The nerve 
fibres enter the layer largely from the optic tract by 
the superior brachium. A considerable amount of de- 
cussation of these fibres occurs on the median side with 
those of the opposite corpus quadrigeminum anterius. 
(d) The stratum cdbo-<-inereuin internum. (Stratum 
lemnisci.) This layer is subdivided into three minor 
layers : (a) the fillet layer, formed from a continua- 
tion of the dorsal part of the median fillet and from the 
lateral fillet ; (/3) a layer of grey matter ; (y) a layer 
of arched filjres bordering the central grey matter 
and decussating in the middle line. All these layers 
are pervaded by radial fibres passing from the central 
grey matter. 

The optic lobes of birds have been more fully 
examined as regards the various layers and their 



232 Elements of Histology. 

connections. Dilierent authors divide these structures 
in various different layers. Adopting Kulliker's 
description, a vertical section may be regarded as 
showing^(l) a superficial layer of fibres from the optic 
tract ; (2) and (3) layers of grey matter or molecu- 
lar layers : in (2) the optic nerve fibres form their 
dendritic ramifications ; (4) a layer of white fibres 
arranged in a kind of lattice work ; (5) an inner layer 
of white fibres in which course the cerebral visual 
fibres ; (6) a layer of grey matter lying against the 
ependyma of the ventricle of the optic lobes. The 
connections of the cells and fibres of this layer have 
been established by Golgi's method by Ramon y Cajal 
and V. Gehuchten. 

In the corjDora quadrigemina important con- 
nections are made by the fillet fibres. Some of these 
connections have already been referred to (s$193). Tlie 
fillet fibres in their upward course give ofl' collaterals 
which ramify or actually terminate themselves in the 
cells of the nucleus of the lateral fillet. Many of the 
fillet fibres terminate in dendritic ramifications in 
the cells of the posterior corpora quadrigemina, many 
others pass into the anterior. The cells of the lateral 
nucleus originate fibres which pass possibly towards the 
cerebrum; some, however, descend towards the superior 
olive. Some of the fibres entering both corpora 
quadrigemina decussate dorsally and pass to the 
opposite corpora. There may also be some connection 
amongst the fillet fibres with those of the superior 
cerebellar peduncle. 

The nucleus of the third nerve has been described 
as consisting of many various groups of cells. It is to 
be regarded as mainly one nucleus, extending through 
the whole length of the anterior corpus quadri- 
geminum and somewhat above it. It consists of a 
main mass with two less distinct masses : a dorso- 
lateral with larsre cells, and a dorso-median with 



Med ul l a Ob l onga ta. 233 

smaller cells. At 3ts cerebral end there is a central 
mass having large cells. It has been suggested that 
the dorso-niedian group of small cells supplies the 
internal muscles of the eye (sphincter, ciliary). The 
nucleus is presumably connected with the pyramidal 
tracts. Arborescences around cells of the third 
nucleus are to be seen in new-born animals, and the 
fibres forming them may be followed to the raphe, 
crossing here and coursing ventrally. Connections 
also exist with the posterior longitudinal bundle. 
This bundle is to be regarded as the upward 
continuation of part of the anterior column of the 
cord, forming short longitudinal commissures It is 
associated with the hypoglossal nucleus, tho>e of the 
vago-accessory, the fifth and the acoustic (vestibular 
branch). Connections also exist with the sixth, 
fourth, and third nuclei. The posterior longitudind 
bundle furnishes, therefore, commissural connections 
between the different eye muscles. Connections 
of the third nucleus also exist with the optic 
nerves. 

The hracJiia passing to the corpora quadrigemina 
are spoken of as the superior or anterior and the 
inferior or posterior. The fibres of the superior pass 
to the lateral corpus geniculatum and to the 
occipital tract. The fibres of the inferior brachium 
are connected with the median corpus geniculatum 
and possibly may pass through the tegmentum by 
the internal capsule to the temporal region. 

That portion of a transverse section through the 
region of the corpora quidrigemina which projects 
ventrally into the two crura is sometimes S[)oken 
of as the crusta, being separated from the remainder 
(tegmentum) of the region ventral to the aqueduct by 
the substantia nigra. The crusta contains, in addition 
to the fil)res derived from the pyramids which occupy 
a central portion in each crus, other fibres derived 



23 4 Elemexts of Histology. 

from the pons. Those on the median side pass to 
the frontal region, those on the lateral portion 
to the temporal and occipital regions. Some fibres 
on the median side are derived from the median 
fillet. 



235 



CHAPTER XIX. 

THE CEREBRUM AND CEREBELLUM. 

196. The structure of the dura mater, araclinoidea, 
and pia mater of the brain is simihir to that of the 
same membranes of the cord. 

As has been shown by Boehm, Key and lletzius, 
and others, the deeper part of the dura contains 
peculiar ampullated dilatations connected with the 
capillary l)lood- vessels, and forming in fact the roots 
of the veins. 

The glanduhe Pacchioni^ or arachnoidal villi of 
Lnschka, are composed of a spongy connective tissue, 
prolonged from the sub-arachnoidal tissue and covered 
with the arachnoidal membrane. These prolongations 
are pear-shaped or spindle-shajDed, with a thin stalk. 
They are pushed through holes of the inner part of 
the dura mater into the venous sinuses of this latter, 
but are covered with endothelium. Injected material 
passes from the sub-arachnoidal sjiaces through these 
stalks into the villi. Tlie spaces of their spongy 
substance become thereby filled and enlarged, and 
finally the injection matter enters the venous sinus 
itself. The pia cerebralis is very rich in blood-vessels, 
like that of the cord, which pass to and from the 
brain substance. The capillaries of the pia mater 
possess an outer endothelial sheath. The plexus 
choroideus is covered with a layer of polyhedral 
epithelial cells, which are ciliated in the embryo and 
in the young subject. 

197. As was mentioned of the cord, so also in the 



236 Elements of Histology. 

brain the subdural lymph space does not commu- 
nicate with the sub-arachnoidal spaces or with the 
ventricles (Luschka, Key and Retzius). Nor does 
there exist a communication between the sub- 
arachnoidal space and a space described by His to 
exist between pia mater and brain surface, but 
doubted by others. The relations between the cere- 
bral nerves and the membranes of the brain and 
the lymph spaces of both, are the same as those 
previously described in the case of the cord and 
the spinal nerves. 

The pia mater ])asses with the larger blood-vessels 
into the brain substance by the sulci of the cerebrum 
and cerebellum. 

In the white and grey matter of the brain we find 
the same kind of supporting tissue that we described 
in the cord as neuroglia. In tlie brain also it is 
composed of a homogeneous matrix, of a network of 
neuroglia fibrils, and of branched, flattened neuroglia 
cells, called Deit^rss cells. 

In the white matter of the brain the neuroglia 
contains between the bundles of the nerve fibres 
rows of small nucleated cells ; tliese form s})ecial 
accumulations in the bulbi olfactorii, and in the 
cerebellum. Lymph corpuscles may be met with 
in the neuroglia, especially around the blood-vessels 
and ganglion cells. 

All the ventricles, including the aqueductus Sylvii, 
are lined witli a layer of neuroglia, being a direct 
continuation of that lining the fourth ventiicle, 
and this again being a direct continuation of the 
central grey nucleus of the cord. Like the central 
canal of the cord, also, the ventricles are lined 
with a layer of ciliated columnar, or short columnar 
epithelial cells. 

The blood-vessels form a denser capillary net- 
work in the grey than in the white matter ; in the 



Cerebrum and Cerebellum. 237 

latter the network is pre-eminently of a longitudinal 
arrangement, i.e. parallel to the long axis of the 
bundles of the nerve fibres. In the grey cortex of 
the hemispheres of the cerebrum and cerebellum, 
many of the capillary blood-A'essels have an arrange- 
ment vertical to the surface, but are connected 
with one another by numerous transverse branches. 

The blood-vessels of the brain are situated in 
spaces, perivascular lymph spaces, traversed by fibres 
passing between the adventitia of the vessels, and 
the neuroglia forming the boundary of the space. 
There are no separate lymphatic vessels in the grey 
or white substance. 

198. The white iiiaftei* consists of medullated 
nerve fibres, which like those of the cord possess no 
neurilemma or nuclei of nerve corpuscles, and no 
constrictions of Ranvier. The nerve fibres are of 
very various sizes, according to the locality. Divisions 
occur very often. When isolated the fibres show the 
varicosities mentioned in the cord. 

The grey iiiattei* consists, like that of the cord 
and medulla, of a basis of neuroglia in which are 
embedded nerve cells. The dendritic ramifications 
from the nerve cells, with medullated and non- 
medullated nerve fibres, form a large proportion also 
of the grey matter. 

With regard to the structure of the ganglion cells 
of the brain and medulla, what has been mentioned 
of the ganijlion cells of the cord holds good as to 
them. Like the former, those of the medulla and 
brain are situated in pericellular lymph spaces 
(Obersteiner). 

199. We now proceed to consider in detail the 
structure of the different parts of the cerebellum and 
cerebrum. 

The cerebelliiiii is composed of laminated folds, 
or convolutions, and these again are composed of 



238 



Elements of Histology 



secondary folds, each of which consists of a central 
tract of white matter covered with grey matter. The 
tracts of white matter of neisfhhourinfr convolutions of 
one lobe or division join, and thus form the principal 
tracts of wdiite matter. 

The white matter of the cerebellar hemisphere is 




Fig. 149. — Photograiu through the grey matter of the cereliellmn of tlie 
dog, showing the hiyer of Purkinje's ganglion cells with their dendrites 
ramifying in the grey cortex. {Lov magnification.) 



connected (a) with the medulla oblongata by the 
corpus restiforme, this forming the inferior peduncle 
of the cerebellum ; (6) with the cerebrum by the 
processus cerebelli ad cerebrum, this forming the 
superior peduncle ; and (r) with the other cerebellar 
hemisphere by the tracts connecting with the pons 



Cerebrum and Cerebellum. 239 

varolii ; these are the pedunculi cerebelli ad pontem, 
or the middle peduncles. 

200. On a vertical section through a lamina of the 
cerebellum (Fig. 149), the following layers are seen: {a) 
the pia mater covering the general surface, and pene- 
trating with the larger blood-vessels into the superficial 
substance of the lamina ; (6) a thick layer of cortical 
grey matter ; (c) the layer of Purkinje's ganglion 
cells ; {d) the nuclear layer ; and (e) the central white 
matter. 

201. The layer of ganglion cells of Purkinje is 
the most interesting layer ; it consists of a single row 
of large multipolar ganglion cells, each with a large 
vesicular nucleus. Each possesses also a thin axis- 
cylinder process, directed towards the depth, the 
cell sending out in the opposite direction — i.e. towards 
the surface — a thick process which soon branches 
like the antlers of a deer, the processes being all very 
long-branched and pursuing a vertical course towards 
the surface ; sooner or later they all break up into 
the fine nervous network of the grey cortex. The 
longest processes reach near to the surface. The 
layer (6) above mentioned — i.e. the cortical grey 
matter — is in reality the terminal nerve network 
for the branched processes of the ganglion cells of 
Purkinje. San key maintained, before the adoption of 
more modern methods of research, that in the human 
cerebellum there are also small multipolar ganglion 
cells connected with the processes of Purkinje's cells. 

202. The connections and distributions of the 
different cells of the cerebellum have been exhibited 
to a considerable extent by the labours of observers 
who have followed the methods of Golgi. A 
scheme of the main points on these results is 
shown in Figs. 150 and 151. Fig. 150 indicates 
the appearance represented in a section across a 
lamina. Fig. 151 corresponds to a section taken in 



240 



Elements of Histology. 



the direction of a lamina. 
Purkinje first, they are 
extensive dendritic ramification, viewed transversely, 



Considering the cells of 
seen to possess a very 




'\^jn\ 



i~Ta 



■ml 



Fig. 150.— Scheme of the Connectiou of the Cells in the Superficial Grey 
Substance of the Cerebellum. (After KoUiker.) 

p, Xeuraxons of Purkinje's cells with collaterals : k, tendril-like fibres with k^ 
their terminations; gU glia cells; /, nio^s fibres; m, small cells of the 
molecular layer; vi^, larare cells of the same layer (basket cells) forming 
synapses round Purkinje's cells, 3A-; gr, cells of the nuclear layer witli 
neuraxons passing into molecular layers, here turning horizontally and 
giving a punctated appearance in cross-section ; n, the luxuriant branching 
of a Gblgi's cell of the second type. 

passing through the whole thickness of the molecular 
layer, as the cortical grey matter is sometimes called. 
This ramification is less extensive viewed in the longi- 
tudinal section of a lamina (Fig. 150). The neuraxon 



Cerebrum and Cerebellum. 



241 



passes throu,<;li the uucle;ir layer oblkjuely, giving off 
collaterals which to some extent re-enter the molec- 
ular layer, then the axon passing fiom the nuclear 
layer enters the central white matter. There are also 
seen in the molecular layer other fairly conspicuous 




Fig. 151.— Longitudinal Section of the Grey Substance of the Ceiebelliun. 
{After Kolliker.) 

The restricted branching of the cells of Purkinje (v) is seen. Tbe nuclear 
cells below are seen sending axons upwards inio the luoleciilar layer which 
divide dichotomously, and run longitudinally. 



cells (m'), which are termed backet cells. These cells 
have dendrites Avhich ramify amongst those of the 
Purkinje's cells, and a neuraxon which gives off 
collaterals, and these again form arborescences around 
the Purkinje cells. Other smaller cells [in) have 
])rocesses all of which i-amify in the neighbourhood of 
the cell. On the border line between the nuclear and 
molecular layers may be seen large multipolar cells 

Q 



242 



Elements of Histology 



(sometimes spoken cf as Goh/i's* cells), which exhibit 
a dendritic ramification in the nuclear laj^er, and in 
which the neuraxon, on entering the molecular layer, 




Ne - 



Fig. 152.— From a Transverse Section through the Edge of the Restiform 
Body, PC, and the Tuberculuia Acustieum of the new-born Cat. 
{Gofgi. Kolliker, II.) 

Xe, Xerve fibres of the coclilear nerve : Ne', the same fibres passing round the 
peduncle ; c, collaterals : T, large ganglion cells of the tuberculinu ; n, their 
axons becoming fibres of the stria? acustica'. 



divides up not far from the main cell. In the nuclear 
layer are numerous small cells (fjr), the dendrites 
dividing verv near to the cells, the neuraxons. 



* Though referred to frequently as ^^ cells of Golgi,'''' these 
are more correctly described as "alls of the, second tt/pe of Golgi.'" 
Some authors use the term "cells of Golgi" to refer to neu- 
roglia cells. 



Cerebrum and Cerebellum. 243 

however, pass into the iiiolecuhir hiyer and bifurcate 
longitudinally (Fig. 150) at various levels. The so- 
called "molecular" condition of the cortical grey matter 
is largely due to the appearance of these fibres being 
cut across as well as to the sections of the processes 
of the cells of Purkinje. The central white matter 
shows other fibres than those representing the 
neuraxons of the Purkinje cells (Fig. 151). One set 
of these terminate in arborescent tufts in the nuclear 
layer, and are referred to as moss fibres {/). Another 
set pass into the molecular layer and break up on 
connection with the dendrons of the cells of Purkinje. 
These are spoken of as tendril fibres. These two 
sets of fibres are to be regarded as conducting to the 
grey matter of the cerebellum. In addition to the 
proper nerve cells already described, may be seen 
neuroglia cells (gl). These are also present in the 
central white matter (Fig. 152). 

20.3. The structure of the cerebral con- 
volutions in g-eneral. — In a vertical section 
through a cerebral convolution one is able to see with 
the naked eye a central core of white matter sur- 
rounded by a cap of grey or reddish-grey matter, 
which again, on careful observation, can be seen to 
consist of several alternate strata of lighter or 
darker substance. The exact appearance of these dif- 
ferent layers varies in different parts of the cerebral 
hemispheres. 

In general, a vertical section of a convolution 
shows three main layers : (1) a superficial molecular 
layer, (2) a layer of pyramidal cells, (3) a layer of 
poly mor pilous cells. These layers are subdivisible into 
several others in different parts of the hemispheres 
(Fig. 153). 

204. Structure of the cerebral convolu- 
tions in the reg^ion of the Rolandic fissure. — 
In this region one can distinguish six layers, showing 









Fig. 153.— Vertical Section through tlie Grey Cerebral Cortex in the 
Parietal Region. (KoUikcr, II.) 

a, .Superficial white layers : 6, onter layer of small pyramidal cells: c, outer 
laver of large pyramidal cells; d, inner layer of small pyramidal cells ; e, 
inner layer of large pyramidal cells ; /, polymorphous cells. 




Sir. zon. 



c.s.c. 



R.F. 
Fig. 154. — For description see next page. 



246 Elements of Histology. 

different characters. Superficially is the stratum 
zonale or moJecidar layer (a), then the outer layer of 
small 2^y'i'<^'i>^^d^^ cells {b), then (c) the outer layer of 
large pyramidal cells, followed by (cZ) the inner layer 
of small iiyramidal cells, then (e) the inner layer of 
large lyyramklal cells, and, adjacent to the white 
matter (/"), the layer of polymorphous cells. These 
cells are, to some extent, separated into vertical 
columns by intercolumnar bundles of nerve fibres. 
There are also, running horizontally, following the 
contour of the gyrus, other more or less defined 
bundles of fibres. Some of these run in the super 
ficial molecular layer ; two other bands are disposed 
tan^fentially, in the pyramidal cell layer, the more 
superficial being the band of Vicq d'Azyr or Geunari, 
the deeper that of Baillarger. In general, the 
neuraxons of the cells descend towards, and finally, 
pass into the white matter (Fig. ISt). There are 
some cells in the cortex which do not conform to 
this rule. Amongst the pyramidal cells may be 
found cells known as Martinotti's cells, from which 
the neuraxons ascend towards the superficial molec- 
ular layer. Cells known as Golgi's cells are also 
to be found, with neuraxons passing towards 
the surface and dividing up not far from the 
cell. The general relation of the different cells and 
fibres is sliown in the accompanying scheme (Fig. 15-i) 



Description o/Fig. 154 [-f- --15). 

Fie. 154.— Scheme of the Connection of the Cells of the Cerebral Cortex. 
{After KoUiker.) 

Pj, Pi, Smaller aud larger pyramidal cells, the neuraxons passing downwards 
on their way to the inner capsule ; P3, pyramidal cells forming a termination 
in tlie corpus striatum ; at level M a cell of Martinotti with neuraxon passing 
upwards and terminating in stratum zonale ; at level G a Golgi cell (2nd order) 
with much-branched neuraxon immediately aliove it ; Ac, association 
cell, on inner side of G is a cell (Cc) with neuraxon passing into corpus 
c-allosum : C.S.C., a cell of corpus striatum with neuraxon passing into cortex ; 
R.F.. a fibre from the fillet passing up into the cortex, one of Ramon y 
Cajal's fibres ; Str. zon., stratum zonale, or superficial white layer. 




Fig. 155. — Pyramidal Cell of the Cortex of the Brain, its axon giving off 
unmerous collaterals. {Kollilcr, II,) 







Fig. 156. -Fascia Dentata and adjoining part of C-nim Amnionis of Human 
Embryo. (Aft'^r KoUiker.) 

^^■'.^'ifL^^iK^^S'^^^^^ bundle, an accessory bundle pasMnsr out to the rights • 
^^f. ■. ""i-'? ''■*^"'" radwtuni of fascia dentata: «. cell with ascendiiis axon 
(cell of Martinott.) : Pi/r.. pyramidal cells; F, flml.ria: K. nuclear laNer 



Cerebrum and Cerebellum. 249 

from Kolliker. The pyramidal cells have a conspicuous 
apical process, which passes vertically, giving off 
lateral processes, and forms a system of dendrites in 
the superficial molecular layer. Other dendritic 
ramifications occur closer to the cell and the neuraxon 
passes towards the white matter, giving off collaterals 
as it traverses the grey substance (Fig. 155). Some of 
the pyramidal cells (Cc) have neuraxons which pass to 
the opposite hemisphere in the corpus callosum, and 
not towards the inner capsule, through which a large 
number of the neuraxons course. Some pyramidal 
cells again probably have their neuraxons ter- 
minating in connection with cells of the corpus 
striatum (P'*). The connections of a cell of Marti- 
notti are seen (M), and those of a Golgi cell (G). 
Fibres conducting towards the cortex are repre- 
sented by (1) Ramon y Cajal's fibi-es (R.F.), passing 
from the fillet and subdividing in the cortex ; 
(2) fibres from cells of the corpus striatum (C.S.C.) 
passing up into the grey matter of the cortex in a 
similar manner. 

205. Structiii-e of the liippocaiiipus major 
and the fascia deiitata (Fig. 156). 

The hippocampus as it projects into the ventricle 
is invested beneath the ependyma with a layer of 
wdiite fibres called the alveus. Lying against the 
alveus are pyramidal cells, the neuraxons of which 
pass into it ; the conspicuous apical process passes 
through a large ):»ortion of the thickness of the hippo- 
campus, giving it a radiate appearance (the stratum 
radiatum), and forming a dendritic ramification above 
this in the stratum lacunosum. Tracing the sub- 
stance of the hippocampus towards the fascia dentata, 
these pyramidal cells become less conspicuous and are 
not to be regarded as forming any definite layer in 
this region. The fascia dentata has externally a 
superficial layer or stratum zonale into which pass the 



250 



Elements of' Histology. 



dendritic ramifications of a layer of small cells, the 
stratum (jranuJosum. From these small cells 
neuraxons pass to the central substance of the fascia 




olfc. 



Fig. 157. — Diagram of the Probable Connections of Cells and Fibres in the 
Olfactory Bulb. {After Schafer.) 

olf.c, Sensory cells of tlie olfactor.v epithelium ; olf.n., deepest layer of the liulb 
composed of the olfactory nerve fibres which are prolonsed from the olfac- 
tory cells ; f//., olfactory shjiueruli, containing dendrons of hoth the olfactory 
nerve fibres and the mitral cells; mc, mitral cells; tx. their axons ; J4.fr., 
nerve fibres of tlie bulb becoming continuous with the olfactory tract. 



dentata, and from this also many so called "moss 
fibres " issue, passing to the granular layer [Mf 
and 31/"). 

206. Structure of tlie oHaetory bulb (Figs. 
157 and 158). — A vertical section through the olfac- 
tory bulb indicates considerably more development 
on the side lying against the cribriform plate than 



Cerebrum and Cerebellum. 



251 



on the dorsal side. Passing from the surface lying 
on the ethmoid bone, one can make out the following 
la3^ers : (1) Bundles of olfactory nerve fibres; (2) the 
zone of olfactory glomeruli ; (3) a layer pervaded 




Fig. 158.— From the Olfactory Bulb of a Mouse 24 days old. {Highly 
magnified. Golgi. KoUiker, II.) 

C, Collaterals ; C;^ glomeruli ; M, mitral cells; J/', large brush cell ; .172, small 
ditto ; n, neuraxon. 

by many irregular fibres, giving it the character of 
a molecular layer, and containing the so-called ^nitral 
nerve cells ; (4) a nuclear layer composed of small 
cells ; (5) a layer of longitudinal nerve fibres ; (6) 
the neuroglia forming the central substance. The 



252 Elements of Histology. 

connection of these mitral cells is indicated in Figs. 157 
and 158. One or two processes pass horizontally and 
an axis-cylinder process passes through the nuclear 
layer towards the layer of longitudinal nerve fibres. 
One conspicuous process passes towards the glomeruli 
and, entering one of the masses, forms a dendritic 
clump. Similarly axons from the olfactory cells in the 
nose pass to these glomeruli and form dendritic clumps. 
These glomeruli are definite localities where connec- 
tions are established between cells of the olfactory 
bulb and the olfactory mucous membrane. 



25. 



CHAPTER XX. 



THE CEREBRO SPINAL GANGLIA. 



207. The ganglia connected with the posterior 
roots of the spinal nerves, and with some of the 
roots of the cere- 
bral nerves — Gas- 
serian, otic, genic- 
n 1 a t e, ciliary, 
Meckel's ganglion, 
the ganglia of the 
branches of the 
acoustic nerve, the 
submaxillary gan- 
glion, etc. — possess 
a capsule of fibrous 
connective tissue 
continuous with the 
epineurium of the 
afferent and efferent 
nerve trunks (Fig. 
159). The interior 
of the ganglion is 
subdivided into 

smaller or larger 
divisions, contain- 
ing nerve bundles 
with their perineu- 
rium, or larger and 
smaller groups of 

c'an.a'lion cells In Fig- 1j9— Spinal Ganglion of the Lumbar 

^, ° . , '■ ,. Region of a Puppy. {KoUiler, II.) 

the spinal ganglia c, Ganglion with its cells and their axons; Bp, 
fVlpop latter ^''^^ posterior; Ita, anterior branch ; M, motor ; S, 




are 



sensory root. 



254 



Elements of Histology. 



generally disposed about the cortical part, whereas 
the centre of the ganglia is chiefly occupied by 
bundles of nerve fibres. 

208. The ganglion cells differ very greatly in size — 




YVj.. Ii30.— Transverse Section of the Spinal Cord of a Chick of the 9th day 
of incubation. {Afttr Ramon y Cajal, from Quain's " Aimtomy.") 

A, Axons— anterior root fibres— issuing from large ganglion cells of anterior 
horn. C : B, posterior root fibres passing from the bipolar ganglion cells (/), O 
of the spinal arangliou into the posterior white column Z>. where they bifur- 
cate to become longitudinal ; e,f,g, collaterals from these fibres : b, fibres of 
anterior white column in cross-section. 



some being as big, and bigger, than a large multipolar 
ganglion cell of the anterior horn of the cord, others much 
smaller (Fig. 162). Each cell has a large oval nucleus, 
including a network with one or two large nucleoli. 



Cerebrospinal Ganglia. 



255 



Its substance shows a distinct fibrillation. Each cell 
of the spinal ganglia in man and mammals is }inipolar 
(Fig. 1G2), tiask- or pear-shaped, and invested in a 
hyaline cajisule, lined with a more or less continuous 




Fig. 161. — From a Longitudinal Section tlirougli the Gasseiian Ganglion of 
the Calf. {Koinier, //.) 

layer of nucleated endothelial cell plates. The single 
process of the ganglion cell is finely and longitudi- 
nally striated, and is an axis-cylinder process. Im- 
mediately after leaving the cell body it is much 
convoluted (Retzius) ; it is then covered with a 
medullary sheath, and so becomes a medullated nerve 
fibre. The capsule of the ganglion cell is continued 
on the axis cylinder process, and, farther on, on the 



256 



Elements of Histology. 



meclullated ner\'e fibre, as the neurilemma ; the 

endothelial plates of the capsule pass into the nerve 




Fig. 1(32. — Large and Small 
Ganglion Cell of the Ganglion 
Gasseri of RabVdt. (A'ei/ and 
Retzhts.) 

The axis cylinder, after leaving the 
cell, becomes convoluted and 
transformed into a medullated 
nerve filire. which divides into 
two medulLited fibres. 



Fig. 163.— Lsolated Ganglion Cell 
of Spinal Ganglion of Toad. 
{Key and Retzius.) 

The axis cylinder process becomes 
transformed into a medullated 
nerve fibre. The capsule of the 
cell IS prolonged as the neu- 
rilemma of the nerve fibre. 



corpuscles linin^ the neurilemma, their number greatly 
diminishing (Fig. 162). 

209. In the rabbit this medullated nerve fibre at 
its first node of Ranvier, which is not at a great dis- 
tance from the ganglion cell, divides into two medul- 
lated nerve fibres in the shape of T ; one branch 



Cer ebr 0-spina l Ga ngl I a. 257 

passes to the cord as a posterior root fibre, the other 
to the peripher}^ (^ig- 1(^3). In man, this T-shaped 
division has also been observed by Retzius, but, 
though liighly proljable, it cannot be said to have 
been actually pro\ed that in rabbit or man every 
axis-cylinder process shows this T-shaped division. 
Retzius obser\'ed this T-shaped division also in the 
Gasserian, geniculate, and ^■agus ganglia in man. 

The ganglion cells are not unipolar in all cerebral 
ganglia ; in the ciliary and optic ganglia there are 
ganglion cells which are multipolar. 

210. Numerous ganglia of microscopic size are to 
be found in the submaxillary (salivary) gland : they 
are of ditferent sizes, and are in reality ganglionic 
enlargements of larger or smaller nerve bundles. 
Each ganglion is invested in connective tissue con- 
tinuous with the perineurium, and the ganglion cells 
are unipolar, and of the same nature as those described 
above, each cell being possessed of an axis-cylinder 
process, which becomes soon a nerve fibre. At the 
back of the tongue there are similar small micro- 
scopic ganglia. 



R 



258 



CHAPTER XXI. 



THE SYMPATHETIC SYSTEM. 



211. The sympathetic nerve branches exactly re- 
semble the cerebro-spinal nerves in their connective- 
tissue investments (epi-, ])eri-, and endoneurium)^ and 






Fig. 164.— Sympathetic Nerves. (Atlas.) 



A, Small Imndle invested in an endothelial sheatli, iierineurium ; b, one 
raediillated and three non-medullated nerve flbres of various sizes; the 
largest shows division ; c, two varicose nerve flbres. 

in the arrangement of the fibres in bundles (Fig. 164, a). 
Most of the nerve fibres in the bundles are non- 
medullated or Remak's fibres (Fig. 164a), each being 
an axis cylinder invested in a neurilemma, with 



5 J -MP A TH E TIC SyS TEM. 



259 



oblong nuclei indicative of nerve corpuscles (Fig. 
1G4, b). But there are some meJullated nerve fibres 
to be met with in each bundle, at least, of the 
hirger nei"ve trunks. These in some cases show 
the medullary sheath more or less discontinuous, 
and "with a vari- 



cose outline (Fig. 
lG-1, c), owing to 
a uniform local 
accumulation of 
fluid between it 
and the axis cyl- 
inder. The small 
or microscopic 
bundles of nerve 
fibres possess an 
endothelial (peri- 
neural) sheath. 
The small and 
large branches 
always form 
plexuses. 

212. The gan- 
glia of the sym- 
pathetic chain 
(Fig. 16 5)— lateral 
gancjlia, as also 
the further sym- 
pathetic ganglia 
— the collateral 
ganglia like the 










' - t-'^^ ;^;"' ^^;> /r.% ■ 







Fig. 164a.— Cross-Section through part of Branch 
of the Splenic Nerse of the Ox, showing 
bundles of non-medullated or Remak's fibres 
in cross-section ; the nerve fibres being com- 
posed of fibrillK appear granular in cross- 
section ; the nuclei here shown belong to the 
neurilemma of the fibres. {Kolliker, II.) 



semilunar and the 

cardiac ganglia, and the peripheral ganglia, like those 
on and in the abdominal viscera, are microscopic 
in size, but possess in a general way the same structure 
as the cerebro-spinal ganglia. The ganglion cells are 
bipolar, or more commonly multipolar. Such are the 



26o 



Elements of flisroLOGV. 



microscopic ganglionic enlargements on many of the 
sympathetic nerve l)ranclies in the thoracic and 
abdominal organs. 

Thev occur in some organs very numerously — e.g. 
,■7,,^,,^ alimentary canal, 

urinary bladder (Fig. 
166 and Fig. 167), 
respiratory organs, 
salivary glands — and 
are of all sizes, from 
a few ganglion cells 
placed between, or 
laterally to, the nerve 
tibres of a small bundle, 
to oval, spherical, or 
irregularly - shayyed 
masses of ganglion 
cells placed in the 
course of a large nerve 
bundle, or situated at 
the point of anasto- 
mosis of two or more 
nerve branches ( Fig. 
167). 

213. The fjanglia 
in connection with the 
plexuses of nerve 
branches of the heart, 
the cjanwlia in the 
plexus of non-medul- 
lated nerve tibres ex- 
isting between the 
longitudinal and cir- 
cular coat of the exter- 
nal muscular coat in 
the aliuientary canal, known as the plexus myen- 
tericus of Auerbach, the ganglia in the plexus of 




fig. 165.— Sixth Ganglion Thoracicuni of 
the Left Sympathetic of the Rabbit. 
(KoUiker, //.) 

Re, Rami communicantes ; S, lirauch of 
sranslion containing two coarser and 
several finer fibres: Spl, srlanchnicus ; 
T, sympathetic trunk; 3, ganglion cells. 



Si -MPA THE TIC SVS TEM. 



26t 



nerve Blanches of tlie submucous tissue in the 
aliiuent;iry canal, known as Meissner's plexus (Fig. 
172), the ganglia in the nervous plexuses in the 




Fig. 166.— Group of Ganglion Cells interposed in a Bundle of Sympa- 
thetic Xerve Fibres ; from the Bladder of Rabbit. (Handbook.) 

outer wall of the Vjladcler, in the bronchial wall, and 
in the trachea, and lastly the ganglia in connection 




Fig. 1G7. — Small Collection of Ganglion Cells along a small Bundle of 
Sympathetic Nerve Fibres in the Bladder of Rabbit. {Atlas.) 

Each gangliou cell possesses a capsule. Tlie substance of the ganglion cell is 
prolonged as the axis cylinder of a nerve flljre. 

with the nerves supplying the ciliary muscle of the 
eye, all belong to the sympathetic .system. 



262 



Elements of Histology 



The ganglion cells (Fig. 170) are of very different 
sizes, each possessing a large oval or spherical nucleus 
with one or two nucleoli. Their sliape is spherical or 
ova], flask -shaped, club-shaped, or pear-shaped ; they 




Fig. 168.— Microscopic Ganglion in the Submaxillary GlaudofDog. i^AtUs.') 

c. Connective tissue surrounding tlie ganglion : g, tlie ganglion cells with their 
capsule ; n, nerve fibres. 

possess either one, two, or more processes, being uni-, 
bi-, or multipolar. The cell is invested in a capsule 
lined with nucleated cells, both being continued on 
the processes as neurilemma and nerve corpuscles 
respectively. 

214. By the aid of Golgi"s method it has been 
definitely established (Golgi, Ramon y Cajal, Retzius) 



Sympathetic System. 263 

that, like the ganglion cells in the cord, the cells in 
the ganglia of the sympathetic system possess one 
axis - cylinder process, axon or nenraxon, which 
remains unramified (R^Diun y Cajal, Van Gehuchten, 




Fig. 100.— Plexus of Auerbacli iu Rectum of Toad. {Atlas.) 
n. Xerve branches ; g, ganglion cell. 

L. Sala. Von Lenhossek, Kolliker), though sometimes 
it is possessed of nodose swellings (Fig. 171). It 
passes into the periphery as a non-medullated 
fibre (as, for instance, the non-medullated fibres 
passing from the lateral ganglia of the sym- 
pathetic back to the spinal nerves as the grey 
ramus communicans) ; or as a medullated fibre 
(as for instance, the medullated fibres passing from 
the ciliary ganglion into the ciliary nerves). The 



264 



Elements of Histology. 



2)ost-ganglionic fibres of Langley are fibres which 
originate as the neuraxon of a sympathetic gan- 
glion cell (in the lateral, collateral or peripheral 
ganglia, as the case may be), and hence pass into 

muscle (wall of 
intestine, blood- 
vessels, the viscera). 
The ganglion cells 
in the microscopic 
peripheral ganglia 
are also multipolar, 
although there oc- 
cur amongst them 
bi- and unipolar 
cells (Ramon y 
Cajal, Dogiel, Kol- 
liker). 

Besides the 
neuraxou or axon 
the sympathetic 
ganglion cells pos- 
sess ramifying pro- 
cesses - — dendrites, 
which resolve them- 
selves like those of 
the cells of the grey 
matter of the cen- 
tral nervous system 
into fine fibres, 
some of them form- 
ing more or less 
distinct arborisa- 
tions or dendrons 
(Fig. 171). An 
interesting relation exists between the medullated 
nerve fibres which pass into a sympathetic gan- 
glion from a spinal nerve [motor fibres passing from 




Fig. 170.— Synipatlietic Gauglion Cell of Man. 
(Key and Itetzius.) 

The arnnarlion cell ii^ iiniltiiiolar : each proce.-s re- 
ceiving a iieiirileiunia from the eapsiile of the 
cell beeouies a iion-inediiUated aerve fibre. 



Sv^'ifPA THE TIC SyS TEM. 



265 



anterior roots, as also sensory fibres from the j)osterior 
roots and spinal ganglia], as, for instance, those 
passing from the motor roots by the white rami com- 
miinicantes into the 
lateral and farther 
into the collateral 
ganglia, i.e. the 
free - i/anc/ lionic 
fibres of Langley ; 
these fibres ter- 
m i n a t e (Van 
Gehuchten, L, 

Sal a, Dogiel, Von 
Lenhossek) as fine 
ramifications be- 
tween and around 
the ganglion cells, or 
they form curious, 
more or less dense, 
convolutions and 
plexus surrounding 
the body of the 
ganglion cell — 
circ II m c ellul a r 
plexus^ as is shown 
in Fig. 173 (Kol- 
liker). 

215. By the 
observations of 
Beale, Arnold, Axel, 
Key and Retzius, it 
was known that in 

the ganglion cells of the sympathetic nerves of the 
frog, the ganglion cell substance passes on as a straight 
neuraxon wdiich continues its course peripherally as a 
non-medullated nerve fibre surrounded by a nucleated 
sheath or neurilemma — continued from the capsule of 




Fig. 171. — Three Multipolar Ganglion Cells 
with their Axon, n. From the Ganglion 
Semilunare of Dog one day old. {Kolliker, 
II.) 



266 



Elements of Histology. 



the ganglion cell. This straight process is entwined by 
a thin spiral fibre which, farther away from the body of 
the irancvlion cell, is a medullated fibre ; it ramifies 
on the substance of the ganglion cell (Fig. 174). 




Fig. 172. — Group of Ganglion Cells from the Plexus of Meissner of a Puppy ; 
amongst them a Multipolar and several Unipolar Cells. (Kolliker, II.) 



Arnold, then Ehrlich and further Retzius (the last 
two by ibjection of methylene blue into the blood- 
vessels of the living frog) have shown this spiral fibre 
(stained blue) to terminate on and around the sub- 
stance of the ganglion cell as an arborisation ; a 
condition which occurs in many parts of the central 
nervous system (anterior grey cornu, cerebellum, 
sympathetic ganglion cells, previously mentioned, 



SVMPATHETIC SvSTEM. 



267 



etc.), that is to say, the l)odj of a ganglion cell 
becomes surrounded and ensheathed as it were by a 
dendron of an afferent nerve fibre, the dillerence being 




Fig. 173.— Circunicellular Plexus 
from tlie Gauglioii Cervieale 
Supremuin of Calf. (KoUiker, 
II.) 




Fig. 174. — Sympathetic Ganglion 
Cell of Frog, showing the 
straight process and the spiral 
fibre ; the latter becomes a 
metlullated fibre, {Key and 
Eetzius.) 



tliat in the sympathetic cells of the frog this afferent 
(inedullated) fibre entwines as the spiral fibre the 
efterent axon (non-mednllated) of the ganglion cell. 



26S 



CHAPTER XXri. 

GEXERAL COXSIDERATIOXS AS TO THE ANATOMICAL 
COXSTITUTIOX AND NATURE OF THE NERVOUS 
SYSTEM. 

216. We are now in a position to summarise the 
general structure and relation of the constituent 
parts of the nervous system. 

The nervous system consists of nerve cells or 
ganglion cells and of nerve fibres — the cells forming 
the centres, the fibres the conducting paths. The 
ganglion cells form an integral part of the central 
nervous system — brain, medulla, and cord — as also of 
the ganglia of the sympathetic and of the peripheral 
collections and special nerve end-corpuscles in the 
various viscera and in the sense organs. The ner%e 
fibres, on the other hand, are all, as far as at present 
known, axons or neuraxons — that is to say, pro- 
longations of the substance of the ganglion cells : by 
these axons near and distant centres, or ganglion 
cells, are brought in relation to one another, as also 
by the peripheral terminations of the axons with 
muscles, skin, mucous membranes, glands, etc. The 
whole nervous svstem mav be considered as consistincr 
of a collection of units (Ramun y Cajal), each such unit 
being called a neuron (Waldeyer). A neuron, then, 
is a ganglion cell with all its processes, axon or axons, 
and dendrites — be they short or long — as well as all 
the ramifications and terminations of such axons and 
dendrites. While of many parts of the nervous 




SPINAL OAN&LION CELL 



MUITI POLAR CELL 
OF ANT. HORN 



1 SMN 



Fie. 175.— Sr-heme of Relationship of Cells and Fibres of Brain and Cord, 
° prepared by Halliburton and Mott. (From Kirke's " Physiology.") 

AB, Middle line tlirough brain medulla and cord; pyr. ijyraniidal ganglion cell 
of the cerebral cortex in the Uolandic area ; ax, axon of this same gangl on 
cell, a collateral of this axon passes in the cr)rpus callosum (c. call.) to 
terminate in the cortex of the other cerebral hemisphere ; c.stk., is the corpus 
striatum : K.a.c, s-'anulion cell in the cerebral cortex (nerve unit of associa- 
tion of Cajali, around which arborises an axon coming from a ganglion cell 
of the optic thalamus ; o.th., thalamus opticus ; f, mesial hllet ; s.g., nucleus 
gracilis of the meduUa ; i. a., axon ..f a ganglion cell in the nucleus f-'rac Us. 
passing to the other side as an internal arcuate hbre; v, ganglion cell ot 
Purkinje in the corte.x of cerebellum ; p.ax., its axon ; g.m., succession ot 
cell stations (units) in the erey matter of the cord to the optic thalanu. 




qc.fi,lc. Leu. 



clcuo ocuIoTaoLorU'.S 



1 T Cbrtci CCrcV: 



Ficr 176.— Diagram of the probable Connections and Relations of the Optic 
Xerve Fibres between the Ganglion Cells of the Retina and the Cortex 
Cerebri. {After Schdfcr.) 

Between the ganffliou cells of the retina and the lateral corpus geniculatum 
or anterior corpus quadrit:eminura respectively is the rirst neuron ; between 
the corpus nuadritrennnum anterius and the nucleus oculomotorms is a 
second neuron, so also between the lateral corpus ireniculatum and the cortex 
cerebri ; between the nucleus oculomotorius and the cortex cerebri on the 
one hand and the axons of the tranarlion cells of the nucleus oculomotorms 
by the nerve tibres constituting the ocuhiraotor nerve terminating in the 
muscles supplied by this on the other hand is a third neuron. 



Of the Nervous System. 271 

system the constituent units or neuronic are under- 
stood and traced out, tliere are other parts in which 
the constituent neurons have not been as yet fully 
worked out. Of the former it has been established 
by the new methods that the older theory as to 
anatomical continuity between different parts of the 
nervous system — i.e. the units or neurons — is not 
correct ; but, on the contrary, that the processes 
(axons as well as dendrites) of one ganglion cell form 
only contact with those of others, as also with peri- 
pheral organs, ivifhout direct contimdty (Fig. 175). 
Thus, for instance, it has been shown that there 
exists no direct or uninterrupted continuity between 
a motor (pyramidal) ganglion cell, say of the limb 
centres in the grey cortex of the brain, and the nerve 
fibres which terminate as motor end-plates or 
dendrons in the muscles of the limbs, but that the 
whole of this path is made up of a succession or chain 
of neurons or units ; and similarly beginning with a 
dendritic nerve termination in the epithelium of the 
skin of the limbs up to the arborising termination of 
nerve fibres in the sensory centres of the grey cortex 
of the brain, we have no anatomical continuity, but a 
succession or chain of units or neurons. 

In each case, a ganglion cell with its axon, in- 
clusive of its collaterals, and its dendrites, is possessed 
of arborisations or dendrons which do not form con- 
tinuity with, but are only in close contiguity to, the 
arborising axons, or dendrites respectively* of another 
unit or neuron (synapsis). A further point that 
has been established is this, namely, all nerve fibres, 
be they medullated or non-medullated, afferent or 
efferent fibres, be they of a relatively short course 
— e.g. those beginning and ending within the central 
nervous system — or do they extend over long dis- 
tances like those passing out from, or passing into, 
the cord, medulla, and brain as spinal and crainial 



272 Elements of Histology. 

nerves respectively, are, in reality, axons or direct 
prolongations of the substance of ganglion cells, 
which, after a longer or shorter course, terminate 
as arl>orisations or dendrons in the periphery or in 
the central nervous system, as the case may be. 

217. We will illustrate, by selecting a few from 
the many known examj)les, the nature and extent 
of such neurons : — 

(1) A motor neuron of the grey cortex cerebri con- 
sists of the following parts (Fig. 175) : («) the cell body 
of a pyramidal ganglion cell ; (6) its dendrites, with 
their arborisations in the grey cortex ; {c) the axon 
given off as the median basilar process and its col- 
laterals becoming medullated nerve fibres of the white 
substance of the cortex, passing further through the 
internal capsule, the pons, the anterior pyramidal 
tract of the medulhi, the direct or crossed pyramidal 
tract of the cord, and forming the tinal arborisations 
or dendrons of them and their collaterals in the 
anterior cornu around the body and dendrites of the 
ganglion cells in the grey matter of the cord. 

(2) A motor neuron of the grey anterior cornu 
of the cord consists of : («) a ganglion cell in the 
anterior grey cornu of the cord ; (6) its dendrites 
terminatinix in f^itu as arborisations or dendrons; 
(«:) the axon passing out as a medullated nerve fibre 
through the anterior root, and further through a 
spinal nerve, and terminating finally in the periphery 
in a striped muscle fibre as a dendron — i.e. the nerve 
end-plate. 

(3) A sensory neuron : (a) a ganglion cell of the 
spinal ganglia ; {h) the afferent nerve fibre — i.e. the 
distal portion of the T-shaped division of the axon, 
coming from the periphery — e.g. the skin — by way of 
a medullated nerve fibre of a spinal nerve ; in the skin 
it terminates or originates either in or around special 
nerve end-corpuscles or as ramifying fibrillae in the 



Of the A^F.Ri'ous System. 



273 



epithelium of tlie smface ; (c) the efferent fibre — 
i.e. the proximal branch of the axon of the spinal 



•/•if"'^^^Nkf^)i /V---"-' 





Fig. 177.— Diagrniu showing the Mode of Termination of Sensory Nerve 
Fibres in 1, the auditory, 2, the gustatory, and 3, the tactile sense 
organs of vertebrata. Each of these represents one sensory neuron. 
(After Retzius,frorii Qnuin.) 



ganglion cell passes into the cord as a medullatecl 
fibre by way of a posterior root and farther into the 



274 



Elemexts of Histology 



posterior white colunni ; it or its collaterals finally 
enter into the grey matter of the cord or pass on into 

the nucleus gracilis of the 
bulb, terminating as dendrons 
around or close to a ganglion 
cell (body or dendrites) in 
such grey matter (Fig. 175). 

(4) A neuron of a special 
sense (Figs. 177, 178): (a) 
the fjcinolion cell in the san- 
glion cell laj^er of the retina ; 
(J)) its dendrites terminating 
as arborisations or dendrons 
in the inner molecular layer ; 
(c) the axon passing out in 
the opposite direction and 
forming a fibre of the nerve 
fibre layer and further pass- 
ing into the optic disc and 
optic nerve as a niedullated 
fibre, pursuing its course as 
such through the chiasma and 
optic tract, and terminating, 
finally, in an arborisation 
around cells in the corpus 
geniculatum or the anterior 
corpus quadrigeminum (Fig. 
176). 




Fig. ITS. — Diagram of the Ar- 
rangement of the Sensory 
Xerve Fibres in the Olfactory 
Organ and Bixlb. {After 
Eetzius, from Quain.) 

n, Neuraxon : (il. glomerulus in 
the olfactory bulb. This repie- 
seuts two consecutive neurous. 



275 



CHAPTER XXIII. 



THE TEETH. 



218. A HUMAN tootll, 

sists (Fig. 17!)) of (a) the 

(b) the denfine forming 
tiie bulk of the whole 
tooth, and surrounding 
the pulp cavity both of 
the crown and fangs, 

(c) the pulp cavity, and 
{d) the ceinent, or crusta 
petrosa. The cement 
covers the outside of the 
dentine of the fang or 
fangs, the enamel covers 
the dentine of the crown. 
The cement is covered 
on its outside by dense 
fibrous tissue acting as 
a 27eriosteuni to it, and 
is fixed by it to the 
inner surface of the 
bone forming the wall 
of the alveolar cavity. 

219. The enamel 
(Fig. 180) consists of 
thin microscopic pris- 
matic elements, the 
enamel prisms placed 
closely, and extending 
in a vertical direction 



adult and milk-tooth, con- 
enamel covering the crown, 




Fiji 17*> — Loii„Mtu(linal Section 
till oUj^h the Piceniolai Tooth of Cat. 
{Waldeyer, in Strieker's Manual.) 

a, Enamel ; 6, dentine ; c, crusta petrosa; 
c/ande, periosteum ;/, bone of alveolus. 



276 



Elements of Histology. 



from the surface to the dentine. When view^ed in 
transverse section, the enamel prisms appear of a 
hexagonal outline, and are separated by a very fine 
interstitial cement substance. The outline of the 
enamel prisms is not straight, but wavy, so that the 
prisms appear varicose. The prisms are aggregated 





Fig. ISO.— Enamel Prisms. (Kdllikc,:) 
A, In longitiuliual view ; B.in eross-section. 



into bundles, which are not quite parallel, but more 
or Jess slightly overlap one another. On a longitudinal 
section through a tooth, the appearance of alternate 
light and dark stripes in the enamel is thus produced. 
Besides this there are seen in the enamel dark hori- 
zontal curved lines, the brown parallel stripes of 
Retzius, probably due to inequalities in the density of 
the enamel prisms produced by the successive forma- 
tion of layers of the enamel. The enamel consists 
of lime salts — phosphate, carbonate, and fluoride of 
calcium — with corresponding magnesium salts. 

In young teeth the free surface of the enamel 
is covered with a delicate cuticle (the cuticle of 
Nasmyth), a single layer of non-nucleated scales. 
In adult teeth this cuticle is wanting, having been 
rubbed off. 



Teeth. 



^11 



220. The €l«'iitiii«» is tlic principal part of the hard 
substances of the tooth, it forms a coniph^te invest- 
ment of tlie pnl[) cavity 
of the crown and fang, 
being sUghtly thicker in 
the former than in the 
latter region. The den- 
tine is composed of (Fig. 
181): (l)a homogeneous 
matrix ; this is a re- 
ticular tissue of fine 
tibrils impregnated with 
lime salts, and thus re- 
sembling the matrix of 
bone ; (2) long fine 
canals, the dentinal 
canals or tithes, passing 
in a more or less spiral 
manner, and vertically 
from the inner to the 
outer surface of the 
dentine. These tubes 
are branched ; they 
open in the pulp cavity 
with their broadest part, 
and become smaller as 
they approach the outer 
surface of the dentine. 
Each canal is lined with 

a delicate sheath — the Fig. ISl.— From a Section through a 
7 ,• 7 7 ,7 T •! Canine Tooth of Man. (Waldeyer, in 

dentinal, sheath. ^ Inside Strieker's Mamud.) 

the tube is a fibre, the ((.Crustapetrosa, with large bone corpus- 
7 ,• 7 /•/ T 1 ties; b, interglobular substance: c, 

dentinal JlOre, a solid dentinal tubules. 

elastic fibre originatinsf 

with its thickest part at the pulp side of the dentine 
from cells lining the outer surface of the pulp, and 
called odontoblasts. 




278 



Elements of Histology. 



On the outer surface of tlie dentine, both in the 
region of the enamel and crusta petrosa, the dentinal 
tubes pass into a layer of intercommunicating irregular 
branched spaces, tlie interglohular spaces of Czermak, 




Fi"^. 18'2.— From Section through the Pulp and Dentine of Tooth of Guinea- 
pig. {Photograph, highly magnified.) 

Pulp tissue with vessels in cross-section; o, odontoblasts; d, dentine acci- 
' dentally detached from odontoblasts. 

or the granular layer of Purkinje. These communi- 
cate with spaces existing between the bundles of 
enamel prisms of the crown, as well as with the bone 
lamina of the crusta petrosa of the fang. The inter- 
o-lobular s})aces contain each a branched nucleated cell. 
The dentinal fibres anastomose with the processes of 
these cells. The inrrempntal lines of Salter are lines 
more or less parallel to the surface, and are due to 



Teeth. 



279 



imperfectly calcilied dentine— the inter (jlohuhir anb- 
stance of Czerniak. The lines of Schreger are curved 
lines parallel to the surface, and are due to the optical 
eflect of simultaneous curvatures of dentinal fibres. 




Fig. 183.— Early Development of Tooth. (Photograph Inj ^[,•. A. Pringle.) 

l.Tonfrue in cross-section ; 2, bone of jaws; 3, rudiment of enamel organ and 
tooth papilla, the former still connected with the surface epithelium. 



221. The eeiiieiit is osseous substance, being 
lamellated bone matrix with bone corpuscles. There 
are no Haversian canals. 

222. The pulp is richly supplied with blood- 
vessels, forming networks, and extending chiefly in 
a direction parallel to the long axis of the tooth. 
Xumerous medullated nerve fibres forming plexuses 
are met with in the pulp tissue ; on the outer surface 



2 So Elements of Histology. 

of the pulp they become non-mediillated fibres, and 
probably ascend in the dentinal tubes. The matrix of 
the pulp is formed by a transparent network of richly 
branched cells, similar to the network of cells forming 
the matrix of gelatinous connective tissue. 

223. On the outer surface of the pulp — i.e. the 
one in contact ^vith the inner surface of the dentine — 
is a layer of nucleated cells, which are elongated, more 
or less columnar. These are the odontoblasts proper 
(Fig. 182). Between them are wedged in more or less 
spindle-shaped nucleated cells, the outer or distal pro- 
cess of which passes into a dentinal fibre. The odonto- 
blasts proper are concerned in the production of the 
dentinal matrix, according to some by a continuous 
growth of the distal or outer part of the cell and a 
petrification of this increment, according to others 
by a secretion by the cell of the dentinal matrix. 
Waldeyer, Tomes, and others consider the odonto- 
blasts proper concerned in the production both of the 
dentinal matrix and dentinal iibres. The odontol)lasts 
proper and the spindle-shaped cells are continuous 
with the branched cells of the pulp matrix. 

224. Devolopiiieiit of teetli. — The first rudi- 
ment of a tooth in the embryo appears as early as the 
second month. It is a solicl cylindrical prolongation 
of the stratified epithelium of tlie surface into the 
depth of the embryonic mucous membrane. Along the 
border of the jaws the epithelium appears thickened, 
and the sul>jacent mucous membrane forms there a 
depression — the primitive dental groove. Into this 
groove the solid cylindrical prolongation of the surface 
epithelium takes place. This prolongation is the 
Y\\([\mQ\\t oi the enamel organ. While continuing to 
grow- towards the depth, it soon broadens at its deepest 
part, and the surrounding vascular mucous membrane 
condenses at the bottom of the prolongation as the 
rudiment of the tooth papilla. While the distal part 



& 



Teeth. 



28r 



of the enamel organ continues to grow towards the 
depth, it grtidually embraces the tooth ])apilla in the 
shape of a cap — the enamel caj) (Fig 183). During 
this time the connection between the surface epithe- 




Fh 



184. — From a Section tlirough the Tooth and Lower Jaw of Fatal 
Kitten. 



a, Epithelium uf the free surface of the gum {b, the raucous membrane of same; 
c, spongy bone of jaw: rf, papilla of tooth; e, odontoblasts:/, dentine; </, 
enamel ; h, membrane of Nasmy th ; /, enamel cells ; j, middle layer of enamel 
organ; A, outer layer of enamel organ. 



Hum and the enamel cap becomes greatly thinned out 
and pushed on one side, owing to the growth of the 
enamel cap and papilla taking place chiefly to one side 
of the original dental groove. 

225. The enamel cap (Fig. 184) is composed of 
three strata — an inner, middle, and outer stratum. 
The inner stratum is a layer of beautiful columnar 
epithelial cells — the enamel cells; they were originally 



2«2 



Elements of Histology 



continuous with tlie deep layer or the columnar cells 
of the surface e[jithelium. The middle stratum is the 
thickest, and is of great transparency, owing to a 







a 



\\ '■ 



Fig. 185.— From a Vertical Section through Foetal Tooth of Dog. (^Atlos.") 

a. Spindle-shaped cells of tbe tooth pulp; b, the layer of O(lontol)lasts : c, the 
ludst recently formed layer of dentine; cl, older dentine; d, the layer of 
enamel cells; C'J, the enamel ; e, outer cells of enamel organ ; /, tissue of the 
tooth sac. 



transformation of the middle layer of the epithelial 
cells into a spongy gelatinous tissue, due to accumu- 
lation of fluid between the epithelial cells of this 



Teeth. 283 

layer, and to a reduction of their substance to thin 
nucleated plates, apparently branched. The outer 
stratum consists of one or more layers of polyhedral 
cells, continuous on tlie one hand with the surface 
epithelium by the bridge of tlie rudiment of the 
enamel organ, and on the other Nvitli the enamel cells. 

226. The foetal tooth papilla is a vascular em- 
bryonic or gelatinous tissue ; on its outer surface a 
condensation of its cells is soon noticeable into a more 
or less continuous stratum of elongated or columnar 
cells, the odontoblasts. 

227. Both the dentine and enamel are developed 
in connectiou with the odontoblasts and the enamel 
cells (Fig. 185) ; the former produce the dentine 
on their outer surface, while the latter, i.e. the 
enamel cells, deposit the enamel on their inner 
surface ; thus it happens that the enamel is in 
close contact with, and on the outside of, the 
dentine. The dentine and enamel are de]josited 
gradually and in layers. At first they are soft 
tissues, showino- a vertical differentiation corre- 
sponding to the individual cells of the enamel cells 
and odontoblasts respectively. Soon lime salts are 
deposited in them, at first imperfectly, but afterwards 
a perfect petrification takes place. The layer of most 
recently formed enamel and dentine is more or less 
distinctly marked off from the more advanced layer, 
the most recently formed layer of the enauiel being 
situated next to the enamel cells, that of the dentine 
next to the odontoblasts (Fig. 186). The amount 
of enamel and dentine formed is always greatest 
in the upper part, i.e. that corresponding to the 
future crown. The milk teeth, while continuing 
to grow, remain buried in the mucous membrane 
of the gum, till after hirth their proper time 
arrives, when by active growth and enlai'gement 
they break through the gum. During this process 



:84 



Elements of Histology. 



the enamel of the crown remains co\'ered, i.p. carries 
with it the inner stratum of the enamel organ only, 
i.e. the enamel cells (Fig. 186, ec) ; these, at the 
same time as the surface of the enamel increases. 




Fig. 18(3.— From a Section through the developing Tooth of Kitten. 
(Photograph, higTibj magnified.) 

p, Pulp of the tooth papilla; o, layer of odontoblasts ; d, dentine ; e, enamel ; ec, 
enamel cells; w, middle layer of enamel organ; oit, outer layer of enamel 
organ. 

become much flattened, and, finally losing their nuclei, 
are converted into a layer of transparent scales, the 
membrane or cuticle of Ncismyth (Fig. 18-4, It). 

228. Long before the milk tooth breaks through 
the gum, there appears a solid cylindrical mass of 
epithelial cells extending into the depth from the 
orifdnal connection between the enamel organ and the 



Teeth. 285 

epitlielium of tlie surface of the gum mentioned above. 
This new epitheh'al outgrowth represents the germ for 
the enamel organ of the permanent tooth ; but it 
remains stationary in its growth till the time arrives 
for the milk tooth to be supplanted by a permanent 
tooth. Then that rudiment undergoes exactly the 
same changes of growth as the enamel organ of the 
milk tooth did in the first j^eriod of foetal life. A 
new tooth is thus formed in the depth of the alveolar 
cavity of a milk tooth, and the growth of the former 
in size and towards the surface gradually lifts the 
latter out of its socket. 

Mummery has shown that the dentine contains 
petrified fibres and traljecuhe, which are direct con- 
tinuations of the pulp tissue, and are comparable to 
the fibres of Sharpey in bone, 



286 



CHAPTER XXIV. 

THE SALIVARY GLANDS. 

229. The salivary glands, according to tlieir 

structure and secretion, are of the following kinds : — 

(1) True salivnrif (Fig. 187), s^?'o?<5, or albuminous 




^v~^^^/i'!u 



Fig. 187. — From a Section througli a Serous or True Salivary Gland ; part 
of the Human Submaxillary. {Atlas.) 

a. The gland alveoli, lined with the alhuniinous " salivary cells " ; b, intralobular 
duct cut transversely. 

glands, such as the parotid of man and mammals, 
the submaxillary and orbital of the rabbit, the sub- 
maxillary of the guinea-pig. They secrete true, thin, 
watery saliva. 



Salivary Glands, 



287 



230. (2) Jfncons (/lands. Of these there are several 
varieties. In the first phxce, there is the picre mucous 
gland (Fig. 188), represented by the subUiigual gland 
of tlie guinea-pig and many of the simple buccal glands 
of the mouth. In the next place^ the secreting 




Fig. 188.— From a Section through the Orhital (mucous) Gland of Dog. 
Quiescent State. (Heidenkain.) 

The alveoli are lined witli trans^iiarent " mucous cells," and outside these are the 
demilunes of Heidenhain. 



alveolus may contain other cells than true mucous 
cells (mucous (/lands ivith deniilunes). There may be 
comparatively few of this second variety of cell in the 
alveolus, and such cells may have an entirely peripheral 
position in the alveolus, and, being thus adapted in shape 
to the globular character of the alveolus, may become 
flattened between the basement membrane and more 
centrally disposed mucous cells, so that in section they 
have the appearance of half-moon-sha])ed masses, 
and are hence called dem.ilutie cells. The alveolus 
may contain few of these demilune cells, as in the 
orbital or submaxillary gland of the dog (Fig. 188), or 



288 



Elements uf Histology 



a more or less complete ring of such cells may exist, 
as in the submaxillary gland of the cat (Fig. 190). 
Finally, this second variety of cell may be so largely 




Fig. 1S9.— Section tliruugli a Pure Mucous Gland in the Resting State. The 
nuclei are seen flattened at the iieripliei-y of the alveoli. The cells are 
not deeply stained. There are no demilune cells. (Microphotograph.) 



represented as to cause the gland to be described as 
belonging to a separate variety — mixed glands. 

231. (3) Mixed salivary, muco-salivary, or sero- 
mucoiis glands. Here some alveoli may be entirely 
serous, some may belong to one of the varieties of 
so-called mucous glands. Sometimes the alveoli may 
contain both serous and mucous cells similarly 
situated around the lumen, so that we may have 
actually a mixed salivary alveolus (Fig. 191). It 
is justitiable to assume that demilune cells really 



Salivary Glands. 



289 



represent occasional serous cells present in a mucous 

alveolus, and these cells occupy a peripheral position. 

In addition to the three salivary glands— parotid, 

submaxillary, and sublingual — there are in some 




Fig. 190.— Section througli the Submaxillary Gland of Cat. The alveoli are 
in nearly all cases surrounded by a dark rim, composed of demilune 
cells. More deeply-stained masses consisting of ducts are also seen. 
{Microphotograph. ) 

cases, as in the rabbit and the guinea-pig, two minute 
additional glands, one intimately joined to the parotid 
and the other to the submaxillary, and both of the 
nature of a mucous gland. These are the superior and 
inferior admaxiUary glands. 

232. The framework. — Each salivary gland 
is enveloped in a fibrous connective-tissue capsule, 
in connection with which are fibrous trabeculse and 



290 



Elements of Histology 



septa in the interior of tJie gland, h\ which the sub- 
stance of the Latter is subdivided into lobes, these 
again into lobules, and these finally into the alveoli 
or acini. The duct, large vessels and nerves pass 




Fig. 191.— Section tlirougb a Human Submaxillary Gland. Nearly all the 
alveoli consist of albuminous cells. There is also to be seen a fairly 
large number of somewhat larger and less deeply-stained alveoli which 
consist largely of mucous cells. (Microphotograph.) 

to and from the gland by the hilum. The connective 
tissue is of loose texture, contains elastic filjres, and, in 
some instances more, in others less, numerous lymphoid 
cells. In the sublingual gland they are so numerous 
that they form continuous rows between the alveoli. 
The connective-tissue matrix between the alveoli is 
cliieHy rejDresented by fine bundles of fibrous tissue 
and branched connective-tissue corpuscles. 



Sal/vanv Glands. 291 

•1X\. Tlio 4lii<'l*!i. — Following the chief duct of 

tlio ij;l;in(l thi'oiii;h tho liilum into tlio interior, we s(;e 
that it divides into several larne branches, according 
to the number of lobes ; each of these takes up several 
branches, one for each lobule. Following it into the 
lobule, the branch is very minute, and is seen to take 
up several more minute tubes ; all these tubes within 
the lobule are the intrnlohidar chiefs or the salivari/ 
tubes of Pliiiger ; the bigger ducts being the inter- 
lohu^ar, and, further, the interlobar ducts. Each of 
the latter consists of a limiting membrana propi-ia, 
strengthened, according to the size of the duct, by 
thicker or thinner trabecuhe of connective tissue. In 
the chief branches there is present in addition non- 
striped muscular tissue. The interior of the duct is 
a cavity lined with a layer of colunmar epithelial cells. 
In the largest branches there is, outside this layer and 
inside the membrana propria, a layer of small poly- 
hedral cells. 

234. The intralobular cliicts, or the salivary 
tubes of Pliiiger, have each a distinct lumen or cavity, 
which is lined with a single layer of columnar epithe- 
lium, and outside this is a limiting mend)rana propria. 
Each of the lining epithelial cells has a s})herical 
nucleus in about the middle ; the outer half of the 
cell substance shows very marked longitudinal stria- 
tion, due to more or less coarse tibrilljc (see Fig. 187). 
The inner half — i.e. the one bordering the lumen — is 
granular, or oidy very faintly striated. The outline 
of these salivary tubes is never smooth, but irregular — 
i.e. the diameter of the tube varies from place to ])lace. 

Not in all salivary glands do the epithelial cells 
of the intralobular ducts show this coarse Hbrillation 
in the outer part of their substance — e.g. it is 
not })resent in the sublingual gland of the dog or 
the guinea-pig. 

235. The ends of the branches of the salivary 



292 Elements of Histology. 

tubes are connected with the secreting parts of the 
lobule — i.e. the acini or alveoli. These always very 
conspicuously differ in structure from the salivary 
tubes. 

The last part of the duct which is in immediate 
connection with the alveoli is the intermediate pcwt, 
this being interposed, as it were, between the alveoli 
and the salivary tube with librillated epithelium. The 
intermediate part is much narrower than the salivary 
tube, and is lined with a single layer of very flattened 
epithelial cells, each ^vith a single oval nucleus ; the 
boundary is formed by the membrana propria, con- 
tinued from the salivary tube. The lumen of the 
intermediate part is much smaller than that of the 
salivary tube, and is generally lined with a fine hyaline 
membrane, with here and there an oblong nucleus 
in it. 

At the point of transition of the salivary tube 
into the intermediate part there is generally a sudden 
diminution in size of the former, and the columnar 
cells of the salivary tube are replaced by polyhedral 
cells ; this is the neck of the intermediate part , In 
some salivary glands, especially in the mucous, this 
neck is the only portion of the intermediate part 
present — e.g. in the submaxillary and orbital glands 
of the dog and cat, and in the sublingual of the 
rabbit. In others, especially in the serous salivary 
glands, as the parotid of man and mammals, the sub- 
maxillary of the rabbit and guinea-pig, and in the 
mixed salivary — as the submaxillary and sublingual 
of man — there exists after the neck a long inter- 
mediate part, which gives off several shorter or longer 
branches of the same kind, all ending in alveoli. 

236. The alveoli or aeiiii are the essential or 
secreting portion of the gland ; they are flask-shaped, 
club-shaped, shorter or longer cylindrical tubes, more 
or less wavy or, if long, more or less convoluted ; many 



Salivary Glaxds. 293 

of them are branclied. Generally several open into 
the same intermediate part of a salivary tube. The 
acini are much lari^er in diameter than the inter- 
mediate ])art. and slightly larger, or about as large as 
the intralobular ducts. But there is a difference in 
this respect between the acini of a serous and of 
a mucous salivary gland ; in the former the acini 
are smaller than in the latter. 

The membrana propria of the intermediate duct 
is continuous with the membrana propria of the 
acini. This is a reticulated structure, being in reality a 
basket-shai)ed network of hyaline branched nucleated 
cells (Boll). The lumen of the acini is minute in the 
serous, but is larger in the mucous glands ; it is in 
both glands smaller during secretion than during rest. 

237. The epithelial cells lining the acini are called 
the saUi-ary cells — they are of different characters in 
the different salivary glands, and chiefly determine the 
nature of the gland. The cells are separated from one 
another by a fluid albuminous cement substance, 
(i.) In the serous or true salivary glands, as parotid of 
man and mammals, submaxillary of rabbit and guinea- 
pig, the salivary cells form a single hiyer of shorter or 
longer columnar or pyramidal albuminous cells, com- 
posed of a reticulated protoplasm, and containing a 
spherical nucleus in the outer part of the cell, (ii.) 
In the mucous glands, such as the sublingual of the 
guinea-pig, or the admaxillary of the same animal, the 
cells lining the acini form a single layer of goblet- 
shaped mucous cells, such as have been described 
above. Each cell consists of an inner principal part, 
composed of a transparent mucoid substance (contained 
in a wide-meshed reticulum of the protoplasm), and of 
an outer small, more opaque part, containing a com- 
pressed and flattened nucleus. This part is drawn 
out in a fine extremity, which, being curved in a 
direction parallel to the surface of the acinus, is 







294 Elements of Histology. 

imbricated on its neighbours. In the case of tlie sub- 
maxillary and orljital glands of the dog and the sub- 
lingual of the rabbit, there exist, in addition to and 
outside of the mucous cells lining the acini, but within 

the membrana 
propria, from 
place to place 
crescentic 
1 > -r^ masses, being 
the demilunes of 
-. /: ^l) ': Q, Ileidenhain, or 

; \; . ' Tl ■' ^^ the crescents of 

■ • .' ^' , '7 . ^^- • ^ J ji>:; Gianuzzi (see 
'i-^i-J- 'l-:'^ ' -^ -f Fig. 188). Each 
^ ^^ "^ V, _ '^ is composed of 

>' '- A il-' -■;^^^ :: ^"1 several polyhe- 
dral granular- 



r--'(vi 



f 






\VT 




^ - . -> ^ , •„^.-v lookmor cells, 

\^>§^' ^ -^-r- ■ O ^^- each with a 

Fig. 192.— From a Section through the Orbital spherical IIU- 

Gland of Dog, after prolonged electrical Stimu- „i„„„ . j.i,p ppil^ 
lation. The acini are lined with small granular ^it;u^5 , tiic ccjio 

cells. (Lavdovsid.) " at the margin 

of the crescent 
are, of course, thinner than those forming the middle. 
Heidenhain and his pupils, Lavdovski and others, 
have shown that, during prolonged exhausting 
stimulation of the submaxillary and orbital of the 
dog, all the lining cylindrical mucous cells become 
ref)laced by small polyhedral cells, similar to those con- 
stituting the crescents, while at the same time the acini 
become smaller (Fig. 192). These observers maintain 
that this change is due to a total destruction of the 
mucous cells, and a replacement of them by new ones, 
derived by multiplication from the crescent cells. This 
is improbable, since during ordinary conditions of secre- 
tions there is no disappearance of the mucous cells as 
such ; they change in size, becoming larger during 



Salifakv Glands. 295 

secretion, and tboir contonts are converted into perfect 
mucus. It is prol)able that, on prolonged exhaustive 
stimulation, the mucous cells collapse into the small 
cells, seen by Heidenliain and his pupils. 

238. (iii.) The acini of the sublingual of the dog 
are again different in structure both from those of the 
submaxillary of the dog and of the sublingual of the 
guinea-pig, for the acini are there lined either with 
mucous cells or with columnar albuminous cells, or 
the two kinds of cells follow one another in the same 
alceolus. 

This gland is a sort of intermediate form between 
the sul)lingual of man and the submaxillary of man 
and ape (Fig. 191). These are the mixed or muco- 
salivary glands. In these the great number of acini 
are serous— ■i.e. small — with small lumen, and lined 
with albuminous cells, whereas there are always present 
a few acini exactly like those of a mucous gland. The 
two kinds of acini are in direct continuity with one 
another. In some conditions there are only very few 
mucous acini to be met with within the lobule — -so few 
sometimes that they seem to be altogether absent ; in 
others they are numerous, but even under most 
favourable conditions they form only a fraction of 
the number of the serous acini. In the sublingual of 
man they are much more frequent, and for this reason 
this gland possesses a great resemblance to the sub- 
lingual of the dog. 

What appear to be crescents in the mucous acini 
of the human gland are an oblique view of albuminous 
cells lininof the acini at the transition between the 
mucous and serous part of the same gland-tube. 

239. The columnar salivary cells lining the acini 
of the submaxillary of the guinea-pig in some condi- 
tions show two distinct jjortioiis : an outer homogeneous 
or slightly and longitudinally striated substance, and 
an inner, more transparent, granular-looking part, and 



296 



Elements of Histology. 



in this respect the cells resemble those of the pancreas. 
{See pp. 330-2.) 

240. Langley has shown (Fig. 193) that during 
the period preparatory to secretion the cells lining 
the acini of the serous salivary glands become en- 
larged and tilled with coarse granules : during 
secretion these granules become used up, so that the 






Fig. 193. — Acini of Serous Gland. (Langley.) 
A, At rest ; B, first stage of secretion ; c, prolonged secretion. 



cell-substance grows more transparent, beginning from 
the outer part of the cell and gradually advancing 
towards the lumen of the acini. These granules may 
be seen in the fresh gland, but reagents very rapidly 
destroy them. Salivary glands hardened by the 
usual reagents, though not themselves showing the 
granules, may, however, present appearances corre- 
sponding to the removal of the granules from the 
outer zone of the alveolus. It is found that in 
such cases the outer zone stains more deeply 
(Fig. 102), an appearance frequently met with in the 
pancreas. 

AYhen the outer part of the alveolus is devoid 
of granules, the alveolus is said to be active or 
partially exhausted; when the granules reach practi- 
cally to the outermost part of the cells, the alve- 
olus is said to be resting. Under normal conditions 



Salivary Glands. 297 

secretion in the salivary glands never approaches ex- 
haustion, though in the pancreas it is not uncommonly 
the case. 

241. Blood-vossels and lyiiiplialics.— The 

lobules are richly supplied with blood-vessels. The 
arteries break up into numerous capillaries, which 
with their dense networks surround and entwine the 
acini. Between the interalveolar connective tissue 
carrying the capillary blood-vessels and the membrana 
ju'opria of the acini exist lymi^h spaces surrounding 
the greater part of the circumference of the acini 
and forming an intercommunicating system of spaces. 
They open into lymi-iliatic vessels accomjoanying tlie 
intralobular ducts, or at the margin of the lobule 
directly empty themselves into the interlobular 
lymphatics. The connective tissue between the lobes 
contains rich plexuses of lymphatics. 

242. The iierve-braiiclies form plexuses in the 
interlobular tissue. In connection with them are 
larger or smaller ganglia (Fig. 168). They are very 
numerously met with in the submaxillary, but are 
absent in the parotid. Some ganglia are present in 
connection with the nerve-branches surrounding the 
chief duct of the suljlingual gland. 

Pfliiger maintains that the ultimate nerve fibres 
are connected with the salivary cells of the acini in 
man and mammals, but this remains to be proved. 



298 



CHAPTER XXV. 

THE MOUTH, PHARYNX AND TONGUE. 

2-43. The jflaiids.— Into the cavity of the 
mouth and pharynx open very numerous minute 
glands, which, as regards structure and secretion, 
are either serous or mucous. The latter occur in 
the depth of the mucous membrane covering the 
U[)S, in the ]:)uccal mucous membrane, in that of the 
hard palate, and especially in that of the soft palate 
and the uvula, in the depth of the mucous membrane 
of the tonsils, at the Ijack of the tongue, and in the 
raucous membrane of the pharynx. The serous 
glands are found in the back of the tongue, in close 
])roximity to the parts containing the special organs 
for the perception of taste — the taste goblets or buds 
(see below). All the glands are very small, but 
when isolated the}^ are perceptible to the unaided eye 
as minute whitish specks, as big as a pin's head, or 
bigger. The largest are in the lips, at the back of 
the tongue and soft palate, where there is something 
like a grouping of the alveoli around the small branches 
of the duct, so as to form little lobules. 

244. The chief duct generally opens with a narrow 
mouth on the free surface of the oral cavity ; it 
passes in a vertical or oblique direction through the 
superficial part of the mucous membrane. In the 
deeper, looser part (submucous tissue) it branches 
in two or more small ducts, which take up a number 
of alveoli. Of course, on the number of minute ducts 
and alveoli depends the size of the gland. 



Mouth, Pharyxx and Tongue. 



299 



In man, all ducts are lined with a single layer of 
columnar epitliclial cells, longer in the larger than 
in the smaller ducts ; in mammals the epithelium 
is a single layer 
of polyhedral cells. 
No fibril lation is 
noticeable in the 
epithelial cells. At 
the transition of the 
terminal ducts into 
the acini there is 
occasionally a slight 
enlargement, called 
the infundibuhtm ; 
here the granular- 
looking epithelial 
cells of the duct 
change into the co- 
lumnar transparent 
mucous cells lining 
the acini. 

245. The acini 
of these glands are 
identical with those 
of the mucous glands 
described above (Fig. 
194) — e.g. the sub- 
lingual gland as regards size, tubular branched nature, 
the lining epithelium, and lumen. 

In some instances (as in the soft palate and 
tongue) the duct neir the opening is lined with 
ciliated columnar epithelium. The stratified epithelium 
of the surface is generally continued a short distance 
into the mouth of the duct. 

246. The serous glands at the root of tlie 
tongue (von Ebner) differ from the mucous chiefly 
in the epithelium, size, and lumen of the acini. These 




Fig. 194. — Part of a Lobule of a Mucous 
Gland iu the Tongue of Dog. {Atlas.) 

«, Gland tubes (alveolii viewed in various 
directions : they are lined with transparent 
■'mucous ceils" ; d, duct lined with small 
polyhedral cells. 



300 Elements of Histology. 

are of exactly the same nature and structure as those 
of the serous or true salivary glands. 

247. Saliva obtained from the mouth contains 
numbers of epithelial scales detached from the surface 
of the mucous membrane, groups of bacteria and 
micrococci, and lymph corpuscles. Some of these are 
in a state of disintegration, while others are swollen 
up by the water of the saliva. In these there are 
contained numbers of granules in rapid oscillation, 
called Brownian molecular movement. 

248. The mucous nionibrane lining the cavity 
of the mouth consists of a thin membrane covered 
on its free surface with a thick stratified pavement 
epithelium, the most superficial cells being scales, 
more or less changed into horn. 

Underneath the epithelium is a somewhat dense 
feltwork of fibrous connective tissue, with numerous 
elavstic fibrils in networks. This part is the corium or 
mucosa, and it projects into the epithelium in the 
shape of cylindrical or conical papilla. 

According to the thickness of the epithelium, the 
papillae differ in length. The longest are found where 
the epithelium is thickest — e.g. in the mucosa of the 
lips, soft palate, and vivula. 

Numerous lymph corpuscles are found in the 
mucosa of the palate and uvula. Sometimes they 
amount to diffuse adenoid tissue. The deeper part of 
the mucous membrane is the suhmucosa. It is looser 
in its texture, but it also is composed of fibrous con- 
nective tissue with elastic fibrils. The glands are 
here embedded ; adipose tissue in the shape of groups 
of fat cells or continuous lobules of fat cells are here 
to be met with. The large vascular and nervous 
trunks pass to and from the sub mucosa. 

249. Striped uiiiscular tissue is found in 
the submucosa. In the lips, soft palate, uvula, and 
palatine arches it forms a very conspicuous portion : 



Mouth ^ Pharynx and Tongue. 



301 



namely, the sphincter orbicularis, with its outrunners 
into the mucous membrane of the lips, the muscles of 
the })alate, uvula (levator and tensor palati), and the 
arcus palato-pharyngeus and palato-glossus. 

250. The last branches of the arteries break up in 




Fig. 195.— Section through the Tongue of Cat ; the Blood-vessels injected. 
The lower part of the figure shows the injected muscular tissue, in the 
middle part the mucous membrane with large vessels ; the ui)per part 
shows the papillae filiformes, with their capillary blood-vessels. 
(Photograph by Mr. A. Priiuilc.) 



a dense capiUary net 1 cork on the surface of the mucosa, 
and from it loops ascend into the papillae. Of course, 
fat tissue glands and muscular tissue receive their 
own supply. There is a very rich i^lexus of veins in 
the superficial part of the mucosa. They are con- 
spicuous by their size and the thinness of their wall. 



302 Elements of Histology. 

Tlie lymjohatics form networks in all layers of the 
mucosa, including the papilla^. The large efferent 
trunks are situated in the submucosa. The last out- 
runners of the nerve-hranches form a j^^^^ris of notv- 
meduUated fibres in the superficial layer of the mucosa, 
whence numerous primitive fihrilUe. ascend into the 
epithelium to form networks. Meissner's tactile cor- 
puscles have been found in the papillae of the lips and 
in those of the tongue. 

251. In the pharynx the relations remain the 
same, except in the upper or nasal part, where we 
find many places covered with columnar ciliated 
epithelium. As in the palatine tonsils, so also here, 
the mucosa is infiltrated with difiiise adenoid tissue, 
and with lymph follicles in great numbers. This forms 
the pJuiryngeal tonsil of Luschka. 

In the palatine tonsil and in the pharyngeal tonsil 
there are numerous crypts leading from the surface 
into the depth. This is due to the folding of the in- 
filtrated mucosa. Such crypts are, in the pharynx, 
sometimes lined all through with ciliated epithelium, 
although the parts of the free surface around them 
are covered with stratified pavement epithelium. 

252. The tongue is a fold of the mucous mem- 
brane. Its bulk is made up of striped muscular tissue 
(genio-, hyo-, and stylo-glossus ; according to direction: 
longitudinalis superior and inferior, and transversus 
lingupe). The lower surface is covered with a delicate 
mucous membrane, identical in structure with that 
lining the rest of the oral cavity, whereas the upper 
part is covered with a membrane, of which the mucosa 
projects over the free surface as exceedingly numerous 
fine and short hairdike processes, the papiUct jilijormes, 
or as less numerous, isolated, somewhat longer and 
broader mushroom-shaped papiUce fungiformes. The 
papilla?, as well as the pits between them, are covered 
with stratified pavement epithelium. Each has numbers 



MOUTH^ F/fARVNX AND ToNCUE. 



;o3 



of minute secondary papillne. Their substance, like 
the mucous membrane of the tongue, is made up of 
fibrous connective tissue. Tlie mucous membrane is on 
the whole thin, and is firmly and intimately connected 



/*»»!». 




Fig. 196. — Section through the Papilla Foliata of Rabbit, showiug the Taste 
Buds amongst the Epithelium. In the depth are Imndles of muscular 
libres and glands. Magnifying power, 40. {Photograph by Mr. A 
Pringlc.) 

with the fil3rous tissue forming the septa between the 
muscular bundles of the deeper tissue. It contains 
large vascular trunks, amongst which the plexus of 
veins is very consj^icuous (Fig. 195). On the surface of 
the mucosa is a rich network of capillary blood-vessels, 
extending as complex loops into the papillse. Lym- 
phatics form rich plexuses in the mucosa and in the 
deep muscular tissue. Adipose tissue is common 



104 



Elements of Histology. 



between the muscular bundles, especially at the back 
of the toncfue. 

253. There are two varieties of glands present in 
the tongue, the mucous and serous. The latter occur 
only at the back, and in the immediate neighbourhood 




Fig. 197.— Section through Taste Organ (Papilla Foliata.) From same 
preparation as Fig. 196, more magnitied, to show the taste buds. 
{Photogrcq^h by Mr. A. Pringle.) 



of the taste organs ; the mucous glands are chiefly 
present at the back ; but in the human tongue there 
are small mucous glands (glands of Xuhn) at the tip. 
All the glands at the back are embedded between the 
bundles of striped muscular tissue, and thus the move- 
ments of the tongue have the effect of squeezing out 
the secretion of the glands. About the 



glands 



Mouth, Pharynx and Tongue. 305 

numerous nerve bundles are found connected with 
minute ganglia. 

At the root of the tongue the mucous membrane is 
much thicker, and contains in its mucosa numerous 
lymph follicles and diffuse adenoid tissue. Thus 
numerous knob-like or fold-like prominences of the 
mucosa are produced. There are also minute pits or 
crypts leading into the depth of these prominences. 

254. The psipilltii! circiiiiivallatae are large 
papill?e fungiformes, each surrounded by a fold of the 
mucosa. They contain taste goblets or buds — i.e. the 
terminal taste organs. At the margin of the tongue, 
in the region of the circumvallate papillae, there are 
always a few permanent folds, which also contain taste 
goblets. In some domestic animals these folds assume 
a definite organisation — e.g. in the rabbit there is an 
oval or circular organ composed of numbers of parallel 
and permanent folds, jiainlla foliata (Fig. 196). 

255. The papillae fungiformes of the rest of the 
tongue also contain in some places a taste goblet. But 
most of the taste goblets are found on the papilla? circum- 
vallatae and foliatse. In both kinds of structures the 
taste goblets are placed in several rows close round 
the bottom of the pit, separating, in the papillae 
circumvallatae, the papillae fungiformes from the fold 
of the mucosa surrounding it : in the papilla foliata 
the pits are represented by grooves separating the 
individual folds from one another. 

256. The taste jfoblets or taste buds are 
barrel- or llask-shaped structures (Fig. 197) extending 
in a vertical direction through the epithelium, from the 
free surface to the mucosa. Each is covered with flat- 
tened, elongated epithelial cells, forming its periphery ; 
these are the tegmental cells. The interior of the goblet 
is made up of a bundle of spindle-shaped or staff-shaped 
taste cells. Each includes an oval nucleus, and is 
drawn out into an outer and an inner fine extremity. 

u 



;o6 



Elements of Histology. 



The former extends to the free surface, projecting just 
through the mouth of the goblet, and resembles a tine 
hair ; the latter is generally y)ranched, and passes 
towards the mucosa, where it probably becomes 
connected with a nerve fibre. The mucosa of these 
parts contains rich plexuses of nerve fibres. 

Accordmtr to Eetzius the meduUated nerve fibres 




Pig. 198.— Ending of Nerve Fibres in and around Taste Buds of Rabbit. {G. 

SetziiiSffrom Quain.) 
n, Xerve fibres; 5. taste bud ; i, iutrabulbar ramification of nerve fibrils; p, 

peribulbar ramification of nerve fibrils ; s, sulcus between two adjacent folds 

of the papilla f oliata. 

entering from the mucosa lose their medullary 
sheath and continue their course, either as peribulbar 
ramifications between the tegmental cells, or as iutra- 
bulbar fibres between and amongst the taste cells. 
Both sets of fibres terminate with free knoblike 
endings (Fig. 198). 

Into the pits surrounded by taste goblets open the 
ducts of the serous glands only (von Ebner). 



3° 7 



CHAPTER XXVI. 

THE (ESOPHAGUS AND STOMACH. 

257. I. Tlic €BSO|>liag^ii§. — Beginning with the 
cesophagiis, and ending with the rectum of the large 
intestine, the wall of the alimentary canal consists of 
an inner coat or mucous membrane, an outer or 
muscular coat, and outside this a thin fibrous coat, 
which, commencing with the cardia of the stomach, is 
the serous covering, or the visceral peritoneum. 

The epithelium lining the inner or free surface of 
the mucous membrane of the oesophagus is a thick, 
stratified, pavement epithelium. 

In Batrachia, not only the oral cavity and 
pharynx, but also the oesophagus, are lined with 
ciliated columnar epithelium. 

The mucous membrane is a fibrous connective- 
tissue membrane, the superficial part of which is 
dense — the mucosa; this projects, in the shape of 
small papillae, into the epithelium. 

The deeper, looser portion of the mucous membrane 
is the suh mucosa ; in it lie small mucous glands, the 
ducts of which pass in a vertical or oblique direction 
through the mucosa, in order to open on the free 
surface. In man these glands are comparatively 
scarce ; in carnivorous animals (dog, cat) they form 
an almost continuous layer (Fig. 199). 

258. Between the mucosa and submucosa are 
longitudinal bundles of non-striped muscular tissue. 
At the beginning of the oesophagus they are absent, 
but soon make their appearance — at first as small 



3o8 



Elements of Histology. 



bundles sejDarated from one another by masses of con- 
nective tissue ; but lower down, about the middle, 
thej form a continuous stratum of longitudinal 
bundles. This is the miiscularis mucosce (Fig. 200). 







re-^^*^ 








—^^n 









Fig. 199.— From a Longitudinal Section througli the Mucous Membrane of 
the ffidopliagus of Dog. {Atlo.s.') 

c, Stratified pavement epithelium of the surface; m, muscularis mucosa; 
between the two is the mucosa ; g, mucous irlands ; d, ducts of same. 

Outside the submucosa is the muscularis externa. 
This consists of an inner thicker circular and an outer 
thinner loncjitudinal coat. And outside this is the 
outer, or limiting, fibrous coat of the oesophagus. In 
man the outer muscular coat consists of non-striped 
muscular tissue, except at the beginning (about the 
upper third, or less) of the oesophagus, which is 
composed of the striped variety ; but in many 



(Esophagus. 



309 



mammals almost the whole of the external muscular 
coat, except the part nearest the cardia, is made up of 
stripe* I tihres. 

259. The large vessels pass into the submucosa, 




Fig. 200. — Ti'ansverse Section through the (Esophagus of a Newly-born 
Child. {Photograph. Lovj magnification.) 

1, Stratified epillieliura of the inner surface; 2, mucosa containing cross-cut 
hundles of non-striped muscle, muscularis raucoss ; 3, outer muscular coat. 

whence their liner branches pass to the surface parts. 
The superficial part of the mucosa and the papillae 
contain the capillary networks. The outer muscular 
coat and the muscularis mucosae have their own 
vascular supply. 

There is a rich plexus of lymphatics in the mucosa, 
and this leads to a plexus of larger vessels in the 
submucosa ^Teichmann). The nerves form rich 



3IO Elements of Histology. 

plexuses in the outer fibrous coat ; these plexuses 
include numerous ganglia. A second plexus of non- 
medullatecl fibres lies between the longitudinal and 
circular muscular coat ; a few ganglia are connected 
with this plexus. In the submucosa are also plexuses 
of non-medullated fibres. Now and then a small 
ganglion is connected also with this plexus. 

260. II. The istoniacli. — Beginning with the 
cardia, the mucous membrane of the stomach is covered 
with a single layer of beautiful thin columnar epithelial 
cells, most of which are mucus-secreting goblet cells. 
On the surface of the mucous membrane of the stomach 
open numerous fine ducts of glands, placed very closely 
side by side. These extend, more or less vertically, as 
minute tubes, into the depth of the mucous membrane. 
In the pyloric end, where the mucous membrane 
presents a pale aspect, the glands are called the i^yloric 
glands : in the rest of the stomach, the mucous 
membrane presents a reddish or red-brown appearance, 
and here the glands have a different character. This 
second variety of gland is typical of the cardiac end 
of the stomach as distinct from the pyloric, and hence 
is described as the cardiac gland. 

261. The part of the mucous membrane containing 
the glands is the mucosa ; outside this is a loose 
connective tissue containing the large vessels — this 
is the submucosa. Between the two, but belonging to 
the mucosa, is the muscularis mucosce, a thick stratum 
of bundles of non- striped muscular tissue, arranged 
in most parts of the stomach as an inner circular and 
an outer longitudinal layer. The tissue of the mucosa 
contains the gland tubes, arranged more or less in 
small groups. Between them is a delicate connective 
tissue, in which the minute capillary blood-vessels 
pass in a direction vertical to the surface. Numerous 
small l)undles of non-striped muscular fibres pass from 
the muscularis mucosae towards the surface — up 



Stomach. 



;ii 



to near the epitheliuin of the surface — forming 
longitudinal muscular sheaths, as it were, around 
the gland tubes. 

The plicce villos?e of the suj)erficial part of the 




Fig. 201.— Cardiac Glands. 

A, Under a low power ; d, duct ; n^ neck, b, part of the fundus of a gland tube 
under a high power ; Pi parietal cells ; c, chief cells. 



mucosa contain fibrous connective tissue and numerous 
lymphoid cells. 



312 Elements of Histology. 

262. The car<liac g'laiicls (Fig. 201) are more 
or less wavy tubes, extending down to the mnscularis 
mucosae. The dee}) part is broader than the rest, and 
is more or less curved, seldom branched. This is the 
-fundus of the gland ; near the surface of the mucosa 
is the thinnest part of the tube ; this is the neck. 
Two or three neighbouring glands may join and open 
into a short cylindrical duct. The duct is lined with 
a layer of columnar ej)ithelial cells, continuous and 
identical wdth that covering the free surface between 
contiguous glands. The duct may be really represented 
by a shallow depression from the surface ; it is then 
more usual to speak of the mouth of the gland. 

263. The epithelium covering the surface consists 
of mucous cells. The outer two-thirds stain very 
slightly as a rule, the nucleus is oval and situated in the 
inner third of the cell, where the cell substance stains 
more deeply. At the base of these cells more deeply 
staining rejjlacement cells may be seen. The neck 
and fundus of the cardiac gland is made up of two 
kinds of cells. The first variety occupies in general a 
more central position around the lumen, the cells are 
as a rule very indistinct in their outlines, the nucleus 
is in the outer half of the cell and usually somewhat 
shrunken. These cells are usually spoken of as the 
central, i-)ei')tic, or c/n'e/ cells. The shape of these cells 
is cubical or short columnar. The other variety of 
cell is characterised by a more peripheral position — at 
any rate, in the fundus of the gland, their outlines are 
much more distinct ; the nucleus is oval and situated 
in the centre of the cell. These cells may impinge on 
the lumen at the neck of the gland, where they are 
most numerous ; in the fundus they are scattered and 
placed between the investing membrane and the 
central cells. These cells are spoken of as jjarietcd, 
oxijntic, or ovoid cells. The cardiac glands may 
present appearances showing the secretion in the 



Stomach. 



13 



condition of granules in the cells. Granules are 
observable ])oth in the parietal and central cells ; 
they are more conspicuous and more easily j^reserved 
in the latter. 

264. The pyloric g^laiids (Fig. 202).— Thec^t^c^ 







iM 




Fig. 202.— Vertical Section through the Pyloric Region of the Gastric 
Mucous Membrane. (Microphotogrcq^h.) 

The wide funnel-shaped mouths are seen at the level M, the twisted ends cut 
across in various planes at level f; the darkish band at level m.m. is the 
niuscularis mucosse ; s.m., submucous layer. 

of each pyloric gland is several times longer than that of 
the cardiac. The duct of the former occupies in some 
places as much as half of the thickness of the mucosa, 
whereas that of the latter does not exceed, in the 
fundus of the stomach or in the cardia, more than one- 
fourth or one-fifth of the thickness. 



314 Elements of Histology. 

The epithelium lining the duct of the pyloric 
glands is similar to that of the free surface. Several 
tubes open into one duct by a short neck. The 
fundus or tube is much convoluted and generally 
branched. It is lined by only one variety of cell, 





Fig. 203. — From a Section throngli the Transition of the Pj'lorus into the 
Duodenum. (Micwphotograjyh. Lov: poicer.) 

a. Duodenal mucous membrane with villi ; ft, pyloric mucosa with lymph 
follicles ; c, Brunner's glauds directly continuous with the pyloric glands. 



which bears some resemblance to the central cell of 
the cardiac glands. It is difficult to make out any 
appearance of granules either in the fresh or hardened 
condition. 

265. Between the mucous membrane with cardiac 
glands and the pyloric end of the stomach with pyloric 



Stomach. 315 

glands there is a narrow intermediate zone, in which 
the cardiac ghxnds appear ])y degrees to merge into 
the pyloric glands. That is to say, the short duct of 
the former gradually eloDgates, the gland tubes get 
shorter in proportion and convoluted, their lumen 
gradually enlarges, and the parietal cells become fewer 
and ultimately disappear. 

266. The mucosa contains isolated lymph follicles, 
the so-called glandular lenticulares (Fig. 203). 

The spaces between the glands themselves and 
between the glands and the muscularis mucosfe are 
filled up by a delicate connective tissue somewhat 
condensed immediately around the tubes. Leucocytes 
are plentiful in the meshes of this network. One 
particular variety of leucocyte, the so-called basophile 
cell, may under certain conditions be very conspicuous. 

267. The submucosa is of very loose texture, and 
enables the mucosa to become easily folded in all 
directions. 

268. The muscular coat is very thick, and consists 
of an outer longitudinal and an inner thicker circular 
stratum of non-striped muscular tissue. Numerous 
oblique bundles are found in the inner section of the 
circular stratum. 

Tiie gland tubes are ensheathed in a network of 
cajnllary blood-vessels derived from the arteries of 
the submucosa. This network forms on the surface 
a special dense horizontal layer, from which the venous 
branches are derived. The outer muscular coat and 
the muscularis mucosae possess their own vascular 
supply. 

269. The lymphatics form a network in the 
mucosa near the fundus of the glands. Into this 
plexus lead lympathics wdiich run longitudinally 
between the glands ; they anastomose with one 
another freely, and extend to near the inner surface 
(Loven). Another plexus is found in the submucosa. 



3i6 Elements of Histology. 

Between the longitudinal and circular stratum of 
the outer muscular coat, and extending parallel to the 
surface, is a plexus of non-medullated nerve branches 
with a few ganglia in its nodes. This corresponds to 
the flexus of Auerhach of the intestine, and is destined 
for the outer muscular coat. A second plexus of non- 
medullated nerve branches with ganglia also extending 
parallel to the surface lies in the submucosa. This 
corresponds to the p/e^^s of Meiasner of the intestine, 
and is destined for the muscularis mucosae and the 
mucosa. 

According to Ralje, the gastric gland tubes in the 
horse are surrounded by a rich plexus of nerve fibres, 
terminating in peculiar spindle-shaped cells. 



M 



CHAPTER XXVII. 



THE SMALL AND LARGE INTESTINE. 



270. The epithelium covering the inner or free 

surface of the mucous membrane of the small and 

large intestine is a single layer of columnar cells, their 

protoplasm more or less distinctly longitudinally 

a 



/ 




Fig. 204. — Epithelium covering the Surface of a Villus of Small Intestine. 

(Atlas.) 
a. Striated free border ; b, goblet cell. 

fibrillated ; their free surface appears covered with 
a vertically and finely striated free border (Fig. 204). 
Many cells are goblet cells. Underneath the epithe- 
lium is a basement membrane, the sub-epithelial 
endothelium of Debove. 

As in the stomach, so also in the small and large 
intestine, the mucosa is connected with the outer 
muscular coat by a loose-textured fibrous subrnucosa, 
in which lie the large vascular trunks, and in many 
places larger or smaller groups of fat cells and lymph 
corpuscles. Between the mucosa and subrnucosa, but 



3i8 Elements of Histology. 

belonging to the former, is a layer of non-striped 
muscular tissue, the muscularls inucosce. This is in 
many places composed of inner circular and outer 
longitudinal bundles, but there are a good many 
places, especially in the small intestine, where only a 
layer of longitudinal bundles can be made out. 

The tissue of the mucosa is similar in structure 
to adenoid tissue (Fig. 205), consisting of a reticular 




Fig. 205. — From a Longitudinal Section through a Villus of the Small 

Intestine. 

«, Epithelium of the surface; ft, non-striped muscular fibres. Immediately 
underneath the epithelium is a basement membrane with oblong nuclei ; the 
tissue of the villus is made up of a reticulum of cells ; in its meshes are 
lymph corpuscles. 

matrix with flattened large nucleated endotheloid 
cells and numerous lymph corpuscles. These are 
either small lymph corpuscles like leucocytes, or they 
are somewhat larger and filled with coarse granules 
— plasma cells. The mucosa of the small and large 
intestine contains simple gland tubes, the cryiJts or 
follicles of Lieberkilhn (Fig. 206) ; they are placed 
vertically and closely side by side, extending from the 
free surface, where they open, to the muscularis 
mucosae. These glands possess a large lumen, and are 
lined with a single layer of columnar epithelial cells, 
many of them goblet cells. 

271. In the small intestme the mucosa projects 
beyond the surface as numerous longer or shorter, 
cylindrical, conical, or leaf-shaped villi (Fig. 206). 
These are, of course, covered with the columnar 



Small and Large Intestine. 



319 



epithelium of the general surface, and their tissue is the 
same as that of the mucosa — i.e. adenoid tissue (Fig. 
207) — with the addition of: {a) One or two central wide 
chyle (lymph) vessels (Fig. 209), their wall being a 
single layer of endothelial plates. {b) Along these 




'V mM'^ 



Fig. 206.— From a Vertical Section tlirougli a Fold of the Mucous Mem- 
brane of the Jejunum of Dog. (Atlas.) 

c, Mucosa, coutaining the crypts of Lieberkilbn, and projecting as the villi; 
in, muscularis mucosae ; s, submucosa. 

chyle vessels are longitudinal bundles of non-striped 
muscular tissue, extending from the base to the apex of 
the villus^ terminating in connection with the cells of 
the basement membrane — i.e. the sub-epithelial endo- 
thelium, (c) A network of capillary blood-vessels ex- 
tending over the whole of the villus close to the 
epithelium of the surface (Fig. 208). This capillary 
network derives its blood from an artery in about the 
middle or upper part of the villus. Two venous 
vessels carry away the blood from the villus. 



320 



Elements of Histology. 



The Lieberkiihn's crypts open between the bases 
of the villi. 

About the base of the villi of the small intestine, 








Fig. 207. — Transverse Section through Villus of Small Intestine of Dog. 
(B.e.idzn'ho.in.) 

Showing the columnar epithelium lining the free surface, the adenoid tissue 
forniini-' the groundwork ; amongst the lymph cells of this adenoid tissue 
there are numerous large cells filled with fat-droplets ; the central lacteal as 
also the capillary blood-vessels are shown cut across. 

and about the base of the plicae villosas of the stomach 
(p. 311), there exist amongst the epithelium of the 
surface peculiar goblet-shaped groups of epithelial 
cells, which, as AYatney has shown, are due to local 
multiplication of the epithelial cells. 

272. Lymph follicles occur singly in the submucosa, 



Small and Large Intestine. 



321 



and extend witli their inner part or summit through 
the muscularis mucosie into the mucosa to near the 
internal free surface of the hitter (Fig. 209). These 
are the solitary lymph foUicIes of the small and large 
intestine ; in the latter they are larger than in the 
former. 

Agminated glands, or Peyers ylands, are larger or 
smaller groups of lymph follicles, more or less fused 
with one another, 
and situated with 
their main part in 
the submucosa, 
but extending 
with their summit 
to the epithelium 
of the free surface 
of the mucosa 
(Fig. 210). In the 
lower part of the 
ileum these 
Peyer's glands are 
very numerous. 
The epithelium 
covering the sum- 
mits of these 

lymph follicles is invaded by, and more or less 
replaced by, the lymph corpuscles of the adenoid 
tissue of the follicles (Watney), similar to what 
is the case in the tonsils [see par. 124). Isolated 
]vmph corpuscles are met witli amongst the epithelium 
also of other parts of the intestine — e.g. the epithelium 
covering the villi (Fig. 204). 

The outer muscular coat consists of an inner thicker 
circular and an outer thinner longitudinal stratum of 
non-striped muscular tissue. 

In the large intestine, in the " ligamenta," only the 
longitudinal layer is present, and is much thickened. 

V 




Fig. 20s.— From a Vertical Section through the 
Siual] Intestine of Mouse ; the blood-vessels 
are injected. (Atlas.) 

The networks of the capillaries of the villi are well 
shown. 



;22 



Elements of Histology. 



273. The blood-vessels form sepaiate systems of 
capillaries for the serous covering, for the outer mus- 
cular coat, for the muscularis mucosa?, and the richest 
of all for the mucosa with its Lieberkiihn's crypts. 
The capillary network of the villi is connected with 
that of the rest of the mucosae (Fig. 208). 




Fig. 209.— From a Section through a part of a Human Peyers Patch, 
showing the distribution of tlie lynijihatic vessels in the mucosa and 
submucosa. (Frey.) 

a. Villi, with central chyle vessel ; b, Lieberkiihn's crypts: c, region of muscu- 
laris mucosEB : /, lymph follicle ; g, network of lymphatics around the lymph 
follicle; I, lymphatic network of submucosa: k, efferent lymphatic" trunk. 



The chyle vessel, or vessels of the villi, commence 
with a blind extremity near the apex of the villi. 
At the base the chyle vessel becomes narrower and 
empties itself into a j^lexus of lymphatic vessels and 
sinuses belon^inor to the mucosa, and situated be- 
tween the crypts of Lieberkiihn (Fig. 209). This 



Small and Large Intestink. 



323 



network is the same both in the small and large 
intestine, as is also that of the lymphatics of the 
submucosa with which the former communicates. The 
lymph follicles are generally surrounded with sinuous 
vessels of this plexus. The efferent trunks of the 




Fig. 210. — Cross section tlinnmh tiie C;t'cuiu of Rabbit, sliowiiig a Fever's 

ratch. ' ■ 

(!, >[iicous membrane; b. summits of the lymph follicles reaching the free 
surface; c, body of the lymph folliclfs iu the submucous tissue: d, outer 
muscular coat. {PItoto. Loic Maynijication.) 



submucous plexus, while passing through the outer 
muscular coat in order to reach the mesentery, take 
up the efferent vessels of the plexus of the lymphatics 
of the muscular coat. 



324 Elements of Histology. 

L'74. The cliyle, composed of granules and fat 
globules of different but minute sizes, passes from the 
inner free surface of the mucous membrane of the 
small intestine through the epithelium into the spaces 




Fig. 211.— Vertical Section through the Mucous Membrane of the large 
Intestine. {Micropliotograph.) 

Some six elands are shown occupying almost the full height of the photograph. 
Ihe luiuen of the ^land is large, the glands being hardened in the distended 
condition. The epii helium lining is seen to include a very large number of 
roundish, clear, and but slightly staining cells, these being goblet cells. 
The nucleated cells of the sub-epithelial reticular tissue are seen between the 
glands. 



of the reticulum of the villi, and from here into 
the central chyle vessels. The plasma-corpuscles 
in the reticulum of the matrix may, and sometimes 
do, take up chyle globules : but it is a mistake to 
ascribe to these lymph cells an important role in 



Small and Large Intestixe. 



3^5 



passing chyle gloljules from the epitheliuin into the 
central chyle vessel (Fig. 214). 

Owing to the peripheral disposition of the 
capillaries in the villi, and owing to the greater 
tilling with blood of the capillaries during digestion, 



.p ^^ 



^. 









■.ch 



.^ 



i.i 



r-/..''/t?'*» 



^r 



N '^. 






#M^ 



r**** 



















Fig. 212. — From a Horizontal Section through the Mucous Membrane of 
Large Intestine of Pig, showing the gland tubes of Lieberkiihn in 
cross-section, their lining columnar epitlielium with numerous goblet 
cells amongst them. Between the gland is the tissue of the mucosa. 
(Photo. Moderately magnified.) 



the villi are thrown into a state of turgescence during 
this period, in consequence of which the central chyle 
vessels are kept distended. Absorption is thus 
greatly supported. The contraction of the muscular 
tissue of the villi and of the muscular coat of the in- 
testine greatly facilitates the absorption and discharge 
of the chyle. 



326 Elemenis of Histology. 

275. The non-medullated nerves form a rich 
plexus, called the i^lexus myentericus of Auerhach 
(Fig. 215), with groups of ganglion cells in the 
nodes ; this plexus lies between the longitudinal and 
circular muscular coat. Another plexus connected 




%% 



Fig. 213. — Transverse Section through the Human A]ipendix Verniiforiuis ; 
showing the mucous membrane with the densely arranged glands of 
I.ieberkiilin, the subuiucous layer with the cross-cut large vessels, and 
the outer muscular coat covered by the peritoneal layer. {Photo. 
Low poicer.) 



with the former lies in the submucous tissue ; this 
is the plexus of Meissner, with ganglia. (Fig. 172.) 
In both plexnses the branches are of a very variable 
thickness ; they are groups of simple axis cylinders, 
held together by a delicate endothelial sheath. 



Small and Large Intestine. 



3^7 










Fig. 214.— Part of a Villus filled with Chyle, from the intestine of a puppy- 
four days old. (ReidenJui.in.) 

rt, Epithelium of surface of villus; b, tissue filled with chyle globules. 



rMmmM^ 



^... 



Fig, 215. — Plexus Myentericus of Auerbaeh of the small intestine of a 
newly-born child. (Atlas.) 

The minute circles and ovals indicate sranglion cells. 



.28 



CHAPTER XXVITI. 

THE GLANDS OF BRUNNER AND THE PANCREAS. 

276. At the passage of the pyloric end of the 
stomach into the diiodeniini (Figs. 'JOS, 216), and in the 



P.G. 










<^- ;;-sO^U^T,f^ 




MM. 



M.C. 

Fig. 216.— Section througli the Gastro-duodeiialJunction. (Microphotograph.) 

A bandisseen runninf,' across from m.m. to m.m., the muscularis mucosa?. In 
tlie suljimicoiis coat beneath on the right side are seenBrunuers glands, 
B.G. In the mucous coat pyloric ghands are seen on left side, p.g. ; villi, v., 
and crypts of Lieberkuhn, c.l., on right side. A small piece of muscular coat 
is seen at Ji.c. 



Glands of Brunwkk. 



329 



first part of tlie latter, is a continuous layer of gland 
tissue in the submucosa, composed of convoluted, more 
or less branched tubes grouped into lobules, and 
permeated by bundles of non-striped muscular tissue. 




^» 



M 



fti»^ 



Fig. 217. — Section tlirougli Pancreas of Cat. {Micropliotogrwph.) 

Three lobules are cut across. In the middle of the small lobule on the right a 
lighter patch is seen; this is an interlobular clump. Similar clumps are 
seen on the other lobules. 



outrunners of the muscularis mucosae. These are the 
glands of Brunner. Numerous thin ducts lined with 
a single layer of columnar epithelial cells pass through 
the mucosa and open with the crypts of Lieberkiihn 
between the bases of the villi. The gland tubes of 
Brunner's glands are identical in structure tvith the 
pyloric glands, with ichich they form a direct ana- 
tomical continuity. 



35^ 



Elements of Histology. 



111. The pancreas (Fig. 217) is in most respects 
identical in structure with a serous or true salivary 
gland. The distribution of the blood-vessels and 
lymphatics, and the arrangement of the connective 
tissue, so as to separate the ghmd tissue in lobes and 
lobules, with the corresponding inter- and intra-lobular 




Fig. 218. — From a Section through Pancreas of Dog. {Atlas.') 

a. Alveoli (tuhes) of the gland; the liuin? cells show an outer homogeneous 
and an inner granular-looking portion ; d, minute duct. 

ducts, are simihxr in both cases. The epithelium lining 
the latter ducts is only faintly striated, not by any 
means so distinctly as in the salivary tubes. The 
alveoli or acini are much more elongated than is the 
case in the serous salivary glands, and in section the 
tubular character of the alveoli is marked (Fig. 218). 
The intermediate part of the duct leading to the 
alveolus resembles the ductule of the salivary gland. 
The cells of the alveolus are somewhat pyramidal, and 
show in specimens hardened by ordinar}^ reagents an 
outer more deeply staining zone varying in width. 



Pancreas. 



331 



and an inner less deeply staining area (Fig. 218). 
Tiiis lighter zone represents the part of the cell in 
which tlie secretory grannies are collected (Fig. 
219). The outer more deeply staining zone may 




Fig. 219.— Section througli Pancreas. { Micro-photograph of specimen 
hardened in osrnic acid.) 

Several alveoli are seen, the darker masses in the centre of each being accumu- 
lations of secretory granules. 



sometimes show a radial striation. In some animals 
the cells lining the ductule appear to be continued as 
an internal lining into the alveolus. These constitute 
the so-called centro-acinous cells of Lancjerhans. 
There are also to be seen in the pancreas of most 
animals masses of cells possessing no alveolar arrange- 
ment, staining less deepl}"", but having large oval 



2>2>^ 



Elements of Histology. 



nuclei, which masses lie here and there between 
the alveoli. These groups of cells are very well 





":^.. '^L.- ^ 







Fig. 220. — Seetior. through the Pancreas of Cat. (Micropliotograph.) 

In the central lobule is seen a large, slightly-stained mass, which is an inter- 

tiihiilar clump. 



supplied witli blood-vessels, and are spoken of as 
intertiihii.lar chimjj.'i, or iiiteralveolar cell islets (see 
Fig. 220). 



333 



CHAPTER XXIX. 



THE LIVER. 




/ 




278. The outer surface of the liver is covered with 
a delicate serous membrane,, the peritoneum, which, 
like that of other abdominal organs, has on its free 
surface a layer of 
endothelium. It 
consists chiefly of 
fibrous connective 
tissue. 

At the liilum 
or porta hepatis 
this connective 
tissue is continued 
into the interior, 
where it joins the 
connective tissue 
of the GJisson's 
ccqysuh, or the in- 
terlobular connec- 
tive tissue (con- 
nective tissue of 
the portal canals). 
This tissue is 
fibrous, and more 
or less lamellated ; 
by it the substance 

of the liver is subdivided into numerous, more or less 
polyhedral, solid lobules or acini (Fig. 221), each 
about 2V of than inch in diameter. According to 



-A 



^s 



Fig. 221.— From a Section through the Liver of 
Pig. Five lobules are shown. " They are well 
separated from one another by the inter- 
lobular tissue. {Atlas.) 

.*, Interlobular connective tissue, containing the 
interlobular blood-vessels, i.e., the branches of 
the hepatic artery and portal vein. and the inter- 
lobular bile ducts ; i, intralobular or central 
vein. 



334 



Elements of Histology 



whether the interloltular tissue forms complete 
boundaries or not, the acini appear well defined from 
one another (pig, ice-bear), or more or less fused (man 
and carnivorous animals and rodents). 

AVithin each acinus there is only very scanty 
connective tissue, in the shape of extremely delicate 




Fig. 222.— From a Vertical Section through the Liver of Rabbit ; the blood- 
vessels and bile-vessels injected. i^Atlo.s.) 

a. Interlobular veins sun-ounded by interlobular bile ducts ; these latter take 
up the network of fine intralobular bile capillaries ; the mesbes of this net- 
work correspond to the liver cells ; h, Intraloliular or central vein. 



bundles and flattened connective-tissue cells. Occa- 
sionally, esjDecially in the young li\'er, lymph cells are 
to be met with in the acini and in the tissue between 
them. 

279. The vena portie having entered the hilum 
gives off' rapidly numerous branches, which follow the 
interlobular tissue in which they are situated, and 
they form rich flexuses around each ac.invs : these 
are the interlohdar veins (Fig. 222). Xumerous 



LlVEK. 



335 



large 



capillary blood-vessels are derived from these veins. 
These capillaries pass in a radiating direction to the 
centre of tlie acinus, at the same time anastomosing 
with one another by numerous transverse branches. 
In the centre of the acinus the capillaries become 
confluent into one 



vein, the cen- 
tral or intralohular 
vein. The intralo- 
bular veins of se- 
veral neighbouring 
acini join so as to 
form t\iQ sublohular 
veins, andthe-e lead 
into the efterent 
veins of the liver, 
or the hepatic veins, 
which finally pass 
into the vena cava 
inferior. 

280. The sub- 
stance of each acinus 
— i.e. the tissue 




Fig. 223. — From a Lobule of the Liver of 
Rabbit, in Avhicli blood- and bile-vessels had 
been injected, more highlv magnified than 
in Fig. 222. (Atlas.) 

b, Bile capillaries between the liver cells, which 
are well shown as nucleated polj'gonal cells, 
each with a distinct reticulum ; c, capillary 
blood-vessels. 



between the capillary blood-vessels — is composed of 
uniform polygonal protoplasmic epithelial cells, of 
about jQ^j-yth of an inch in diameter ; these are the 
liver cells. Owing to the peculiar, more or less 
radiating, arrangement of the capillaries, the liver 
cells appear to form columns or cylinders, also more 
or less radiating from the periphery towards the centre 
of the acinus. The cells contain particles of glycogen 
in various amounts. According to Brunton and 
Delepine, the amount gradually increases in the 
rabbit's liver after a meal, and reaches its maximum 
between the third and eighth hour. They also contain 
pigment granules, which, being derived from the 
disintegration of haemoglobin in the spleen, include 



336 Elements of Histology. 

iron. Each liver cell shows a more or less fibrillateJ 
protoplasm (Kupfer), and in the centre a spherical 
nucleus with one or more nucleoli. 

The liver cells are joined by an albuminous cement 
substance, in which are left fine channels ; these are the 
hile capillaries (Figs. 223 and 2'2-i). In a successfully 
injected preparation the liver cells appear separated 
everywhere from one another by a bile capillary, and 
these form for lite ivhole acinus a continuous inter- 
cominunicating network of minute channels. Where 
the liver cells are in contact with a capillary blood- 
vessel, there are no bile capillaries. 

281. At the margin of the acinus the bile capil- 
laries are connected with the lumen of minute tubes ; 
these jDOssess a membrana propria and a lumen lined 
with a single layer of transparent polyhedral epithelial 
cells. These are the small interlobular hile ducts 
(Fig. 222). Their epithelial cells are in reality 
continuous with the liver cells. These ducts join 
and form larger interlobular hile ducts, lined with 
more or less columnar epithelium. The first part of 
the bile duct lined with polyhedral cells corresponds 
to the intermediary part of the ducts of the salivary 
glands. The interlobular bile ducts form networks 
in the interlobular tissue. Towards the hilum they 
become of great diameter, and their wall is made up 
of fibrous tissue, and in it are bundles of non-striped 
muscular cells. Small mucus-secreting glands are in 
their wall, and open into their lumen. 

The wall of the hepatic duct, and of the gall 
bladder, are merely exaggerations of a large bile duct. 

282. The hepatic artery follows in its ramification 
the interlobular veins. The arterial branches form 
plexuses in the interlobular tissue, and they supply 
the capillary blood-vessels of the interlobular connective 
tissue, and especially of the bile ducts. The capillary 
blood-vessels of the bile ducts join so as to form 



Liver. 



337 



small veins, wliicli finally empty themselves into 
the hepatic veins. The anastomoses between the 
capillary blood - vessels, derived from the arterial 
branches, and the capillary blood-vessels of the acini, 




Fig. 224.— From a Section tlirougli the Liver of Rabbit, of which the bile 
ducts had been injected ; showing the distribution of the bile capillaries 
and their branchlets between the liver cells. (Fhotograpli. Moderately 
magnified.) 

are insignificant (Cohnheim and Litten). The serous 
covering of the liver contains special arterial branches 
— rami capsulares. Networks of lymphatics — deep 
lymphatics — are present in the interlobular connective 
tissue, forming plexuses around the interlobular blood- 
vessels and bile ducts, and occasionally forming a 
perivascular lymphatic around a branch of the hepatic 
vein. Within the acinus, the lymphatics are repre- 
w 



^T,S Elements of Histology. 

sented only by spaces and clefts existing between the 
liver cells and capillary blood-vessels ; these are the 
intralohidar lymphatics (Macgillivray, Frey, and 
others). They anastomose at the margin of the 
acinus with the interlobular lymphatics. 

In the capsule of the liver is a special network 
of lymphatics called the superficial lyinphatics. 
Numerous branches pass between this network and 
the interlobular lymphatics. 



539 



CHAPTER XXX. 

THE ORGANS OF RESPIRATION. 

283. I. The larynx — The supporting frame- 
work of the larynx is formed by cartilage. In the 
epiglottis the cartilage is elastic and reticulated — i.e. 
the cartilage plate is perforated by numerous smaller 
and larger holes. The cartilages of Santorini and 
Wrisbergii, the former attached to the top of the 
arytenoid cartilage, the latter enclosed in the aryteno- 
epiglottic fold, are also elastic. The thyroid, cricoid, 
and arytenoid cartilages are hyaline. All these are 
covered with the usual perichondrium. 

A small no lule of elastic cartilage is enclosed in 
the front part of the true vocal cord. This is the 
cartilao^e of Luschka. 

The mucous membrane lining the cavity of the 
larynx (Fig. 225) has the following structure : — 

The internal or free surface is covered with 
ciliated stratified columnar epithelium : the most 
superficial cells are conical cells with cilia on their 
free surface ; then between the extremities of these 
cells are wedged in spindle-shaped and inverted 
conical cells. Numerous goblet cells are found 
amongst the superficial cells. The two surfaces of 
the epiglottis and the true vocal cords are covered 
with stratified pavement epilheli^im. 

Underneath the epithelium is a basement mem- 
brane separating the former from the mucous mem- 
brane proper. 

284. Themucojs membrane is delicate connective 



;4C 



Elements of Histology. 



tissue with numerous lymph corpuscles. In the pos- 
terior surface of the epiglottis, in the false vocal cords, 
and especially in the ventricle of the larynx, this 








7n — 







\ ^^^ >- ^ ^ 

In ^-S2> ^^*'.\ 



„H(^ 



Fig. 225.— From a Longitudinal Section through the Ventricle of the Larvnx 
of a Child. (Atlas.) 

a, True vocal cord ; b, false vocal cord ; c. nodule of elastic cartilage (cartilage 
of Luschka): d, ventricle; I, lymphatic tissue ; m, bundles of the thyro- 
arytenoid muscle in transverse section. 

infiltration amounts to diffuse adenoid tissue, and 
even to the localisation of this as lymph follicles. 
In both surfaces of the ej^iglottis, and in the true 
vocal cords, the mucosa extends into the stratified 
pavement epithelium in the shape of minute papillae. 

In the lower part of the larynx the mucous mem- 
brane contains bundles of elastic fibres connected into 



Larvnx.\ 



341 



networks, antl running in a longitudinal direction. 
Those elastic fibres are found chieHy in the superficial 
parts of the mucous membrane. Tn the true vocal 




X 40. {Photograph by Mr 



Fig. 226. — Section through Trachea of Foitus. 

A. Pringle.) 

1, Ciliated columnar epithelium of internal surface; 2, mucous membrane with 
its glands ; ?,, cartilage ; 4, outside this the thyroid gland. 



cords the mucosa is entirely made up of elastic fibres 
extending in the direction of the vocal cords. 

285. The deeper part of the mucous membrane is 
of loose texture, and corresponds to the submucosa ; 
in it are embedded numerous mucous glands, the 
ducts of which pass through the mucosa and open on 
the free surface. The alveoli of the glands are of the 
nature of mucous alveoli — i.e. a considerable lumen 
lined with a layer of mucous goblet cells. There are, 



342 



Elements of Histologw 



however, also alveoli lined with columnar albuminous 
cells, and such as have Ijoth side by side, as is the case 



i^t^-^'iVmrr/r-^i^'-r-i-'. 



g»y'.;?j7-^[7f^| 











m 



•^ 



wn 



V. 



iV^ 







^^ 



I 



Fig. 227.— From a Longitudinal Section tlirougli the Trachea of a Child. 

{Atlas.) 

a. Stratified columnar ciliated epitheMum of the internal free surface: ft, base- 
ment nienihrane ; c, mucosa ; d. networks of longitudinal elastic tihres ; the 
oval nuclei bL-tween them indicate connective-tissue corpuscles; e, sub- 
mucous tissue containing mucous glands; /, large blood-vessels; g, fat 
cells ; h, hyaline cartilage of the tracheal rings. 

in the sublingual dand of the dof?. The ciliated 
epithelium of the surface in some places extends also 
for a short distance into the ducts. The true vocal 
cords have no mucous glands. 

The Ijlood-vessels terminate with the capillary net- 



Trachea. 343 

work in the superficial — i.e. &u)>epithelial — layer of 
the mucosa ; where tliersj are papilla; — i.e. in the 
epiglottis and true vocal cords — these receive a loop 
of capillary blood-vessels. The lymphatics form super- 
ficial networks of fine vessels and deep submucous 
networks of large vessels. These are of enormous 
width and size in the membrane of the anterior surface 
of the epiglottis. The finer nerves form superficial 
plexuses of non-medullated fibres, some of which ter- 
minate, according to Luschka and Boldyrew, as end 
bulbs. Taste buds have been found in the epithelium 
of the posterior surface of the epiglottis (V( rson, 
Schofield, Davis), and also in that of the deeper parts 
of the larynx (Davis). 

286. II. The trachea — The trachea is very 
similar in structure to the lower part of the larynx, 
from which it differs merely in possessing the rings 
of hyaline cartilage, and in containing, in the posterior 
or membranous portion, transverse bundles of non- 
strijoed mnscrdar tissue, extending horizontally between 
the ends of the rings. Its com])onent parts are (Figs. 
226,227, 228):— 

{a) a stratified columnar ciliated epithelium ; 

{Jj) a basement membrane ; 

(c) a mucosa, with the terminal networks of capil- 
lary blood-vessels, and infiltrated with adenoid tissue ; 

{d) a layer of longitudinal elastic fibres connected 
into networks ; 

(e) a loosely textured submucous tissue, contain- 
ing the large vessels and nerves and small mucous 
glands. Occasionally the gland or its duct is em- 
bedded in a lymph follicle. 

287. III. The bronchi and the lung: 

The bronchi ramify within the lung dendritically 
into finer and finer tubes. The finest branches are 
the terminal bronchi. In the bronchi we find, instead 
of rings of hyaline cartilage, as in the trachea, larger 



344 



Elements of Histology. 



and smaller oblong or irregularly-sliaped plates of 
hyaline cartilage distributed more or less uniformly 
in the circumference of the wall. Towards the small 
microscopic bronchi these cartilage plates gradually 
diminish in size and number. The epithelium, the 







Fig. 228.— From a Section througli the Traclieal Mucous Membrane of a 
Newly -born Child. {Photo. Highly magnified.) 

e. Ciliated columnar epithelium ; amongst the ciliated cells are numerous 
goblet cells ; m, mucosa ; </, acini of mucous glands. 

basement membrane, the sub-epithelial mucosa, and 
the layer of longitudinal elastic fibres, remain the 
same as in the trachea. The submucous tissue con- 
tains small mucous glands. 

288. Between the sub-epithelial mucosa and the 
submucosa is a continuous layer of circidar non- 
striped muscular tissue. In the smaller microscopic 



Bronchi and Lung. 345 

bronchi this layer is one of the most conspicuous. By 
the contraction of tlie circuhir muscular coat the 
mucosa is placed in longitucliiuil folds. 

The state of contraction and distension of the 
small bronchi bears an important relation to the aspect 
of the epitheliuui, wliich appears as a single layer of 
columnar cells in the distended bronchus, and as 
stratified when the bronchus is contracted. 

The distribution of the blood-vessels is the same 
as in the trachea. Lymph follicles are met with in 
the submucous tissue of the bronchial wall in animals 
and man. 

The lymphatic networks of the bronchial mucous 
membrane are very conspicuous. Those of the sub- 
mucous tissue — i.e. the peribronchial lyniphatics — 
anastomose with those surrounding the pulmonary 
blood-vessels. 

Pigment and small particles can be easily absorbed 
through the cement substance of the epithelium into 
the radicles of the superficial lymphatics, whence they 
pass readily into the (larger) peribronchial lymphatics. 

In connection with the nerve branches in the 
bronchial wall are minute ganglia. 

289. Each terminal bronchiole branches into 
several wider tubes called the alveolar ducts., or 
infundibula ; each of these branches again into several 
similar ducts. All ducts, or infundibula, are closely 
beset in their whole extent with spherical, or, being 
pressed against one another, with polygonal vesicles — - 
the air cells or cdveoli — opening by a wide aperture 
into the alveolar duct or infundibulum, but not com- 
municating with each other. The infundibula are 
much wider than the terminal bronchioles, and also 
wider than the alveoli. 

290. All infundibula with their air cells, belonging 
to one terminal bronchiole, represent a conical struc- 
ture, the apex of which is formed by the terminal 



346 



Elements of Histology. 



bronchus. Such a conical mass is a lobule of the 
lung, and the whole tissue of the lung is made up of 
such lobules closely aggregated, and arranged as lobes. 
The lobules are separated from one another by deli- 
cate fibrous connective tissue : this forms a continuity 




Fig. 229. — From a Section through the Lung of Cat, stained with nitrate of 
silver. {Atlas.) 

a, Infun(iil>ulum or alveolar duct in cross-section ; b. groups of polyhedral 
cells lining one part of the infundibulum, the rest being lined with fliittened 
transparent epithelial scales ; c, alveoli lined with flattened epithelial 
scales ; here and there between them is seen a polyhedral trranular epithelial 
cell. 

with the coDiieetive tissue accompanying the bronchial 
tubes and large vascular trunks, and with these is 
traceable to the hilum. On the other hand, the inter- 
lobular connective tissue of the superficial parts of the 
lung is continuous with the fibrous tissue of the 



Brlwchi axd Lung. 347 

surface called the pleura pulmonalis. This membrane 
contains numerous elastic libres, and on the free 
surface is covered with a hiyer of endothelium. 

In some instances (guinea-pig) the pleura pulmo- 
nalis contains bundles of non-striped muscular tissue. 

The lobes of the lung are separated from one 
another by large septa of connective tissue— the liga- 
menta pulmonis. 

291. The teriiiiiial bronchi contain no cartilage 
or mucous fflands in their wall. This is made up of 
three coats : («) a delicate epithelium — a single layer 
of small jxjhjhedral (jranular-Jooking cells ; (h) a 
circular coat of non-striped muscular tissue ; and (c) 
a tine ad\entitia of elastic fibres, arranged chiefly as 
longitudinal networks. 

292. Tracing the elements constituting the wall 
of a terminal bronchiole into the infundibula and air 
cells (Fig. 229) we find the following changes : {«) the 
polyhedral granular-looking epithelial cells forming 
a continuous lining in the terminal bronchiole are 
traceable into the infundibulum only as larger or 
smaller groups : between these groups of small poly- 
hedral granular-looking cells large, flat, transparent, 
homogeneous, nucleated, epithelial scales make their 
appearance. The farther away from the terminal 
bronchiole, the fewer are the groups of polyhedral 
granular-lookinf; cells. In all infundibula. however, 
the transparent scales form the chief lining. This 
becomes still rnoie marked in the air cells. There the 
small polyhedral granular-looking cells are traceable 
only singly, or in groups of two or three (Elens), the 
rest of the cavity of the fir cells being lined with the 
large transparent scales. 

In the foetal state all cells lining the infundibula 
and air cells are of the small polyhedral granular- 
looking variety (Kuttner). With the expansion of 
the lungs during the first inspiration many of these 



348 



Elements of Histology. 



cells change into the large transparent scales, in order 
to make up for the increment of surface. A lung 
expanded ad maximum shows much fewer or none of 
the small polyhedral cells ; while a lung that is col- 
lapsed shows them in groups in the infundiljula, and 
isolated or in twos or threes in the alveoli. 




Fig. 230.— Network of Capillary Blood-vessels surrounding the Alveoli of 
the Human Lung. (Photograph by Mr. A. Pringle.) 



293. (b) The circular coat of non-striped muscular 
tissue of the terminal bronchiole passes as a continuous 
circular coat — but slightly thinner — on to the alveolar 
ducts or infundibula, in their whole extent, but not 
beyond them, i.e. not on to the air cells. 

(c) The adventitia of elastic networks is continued 
on the infundibula, and thence on the air cells, where 



Bronchi and Lung. 349 

it forms an essential part of the wall of the alveoli, 
being its framework. 

Amongst the network of elastic fibres forming the 
wall of the alveoli is a network of branched connec- 
tive-tissue cells, contained as usual in similarly-shaped 
branched lacun?e, which are the radicles of the lym- 
phatic vessels. 

294. The blood-vessels and lyiiipliatics. — 
The branches of the pulmonary artery and veins are 
contained within the connective tissue separating the 
lobes and lobules, whence they can be traced into 
their finer ramifications towards the infundibula and 
air cells. Each of these latter is surrounded by a sort 
of basket-shaped dense network of capillary blood- 
vessels (Figs. 230 and 231). The capillary networks 
of adjacent alveoli are continuous with one another, 
and stand in communication on the one hand with a 
branch of the pulmonary artery, and on the other with 
branches of the pulmonary vein. The branches of 
the bronchial artery belong to the bronchial walls, 
which are supplied by them with capillary networks. 

The lacunse and canaliculi in the wall of the 
alveoli, mentioned above, are the rootlets of lymphatic 
vessels, which accompany the pulmonary vessels, and 
form a network around them ; these are the deep 
lymphatics, or the "perivascular lympJtatics. They are 
connected also with the networks of lymphatics sur- 
rounding the bronchi, i.e. the peribronchial lymphatics. 
The rootlets of the superficial air cells empty them- 
selves into the siib-j)leural j^le.mis oflymj^hatics., a rich 
plexus of large lymphatics with valves. All these 
lymphatics lead by large trunks into the bronchial 
lymph glands. 

295. Between the flattened transparent epithelial 
cells lining the alveoli are minute openings, stomata 
(Fig. 229), leading from the cavity of the air cells into 
the lymph lacunae of the alveolar wfiU. These stomata. 



350 



Elements of Histology. 



are more distinct during expansion, i.e. inspiration, 
than in the collapsed state. Inspiration, by its ex- 
panding the lungs, and consequently also the lym- 
phatics, greatly favours absorption. Through these 
stomata, and also throuirh the interstitial cement 




Fig. 231.— Injected Lung of Cat. (Photograph.) 



substance of the lining epithelium, formed particles 
— such as soot particles of a smoky atmosphere, 
pigment artificially inhaled, cellular elements, such 
as mucous or pus corpuscles, bacteria, etc. — find their 
way into the radicles of the lymphatics, thence into 
the perivascular and sub-pleural lymphatics, and finally 
into the bronchial glands. 

The cellular elements just mentioned, containing 
particles of soot, are spoken of as " dust cells." 



.53 



CHAPTER XXXI. 



THE SPLEEX. 



296. The capsule enveloping the spleen is a 
serous membrane — the peritoneum. It is a connec- 







c i 

0* '0 , 



Tig. 232.— From a Vertical Section through the Spleen of Ape. (Atlas.) 

a. Capsule; b, rrabeculEe; c. Malpighian corpuscle: d, artery ensheathed in a 

Malpit'hian corpuscle ; e, pulp tissue. 

tive-tissue membrane with networks of elastic fibres, 
and covered on its free surface with an endothelium. 



v5D- 



Elemexts of Histology. 



The deep part of the capsule contains bundles of non- 
striped miLscuIar tissue forming plexuses. In man 
the bundles are relati\ely thin, but in some mammals 
- — e.g. dog, pig, horse — they are continuous masses 
arranged sometimes as a deep longitudinal and a 
superficial circular layer (Fig. 232). 

In connection with the capsule are the trahecuhe- 
(Fig. 232). These are microscopical, thicker or thinner 
cylindrical bands branching and anastomosing, and 
thus making a framework in which the tissue of 
the spleen is contained. Towards the hilum the 
trabeculye are larger, and they form there a continuity 
with the connective tissue of the hilum. They are 
the carriers of the large vascular branches. The 
trabecul^e in the human spleen consist chieflv of 



fibrous tissue with an admixture of longitudinal 

non-striped muscu- 
lar tissue. This is 
more pronounced in 
the dog, horse, pig, 
guinea-pig, in which 
the trabeculae are 
chiefly composed of 
non-striped muscu- 
lar tissue. Folio v\-- 
ingasmalltrabecula 
after it is given off 
from a larger one, 
we tind it branch- 
ing into still smaller 
ones, winch ulti- 
mately lose them- 
selves amongst the 
spleen tissue called 




Fig. 233.— From a Section through the Pulip 
of the Spleen of Pig. ( Atlas. ) 

a. Last outrunners of the muscular trabecule ; 
b, flattened cells forming the honevcomhed 
matrix of the pulp: in the meshes of this 
matrix are contained lymphoid cells of various 
sizes. 



of the 



elements of that part 
spleen pulp (Fig. 233). 

Tlie meshes of the network of the trabecular are 
filled up with the parenchyma. This consists of two 



Spleex. 353 

kinds of tissues : {a) the Malpighian corpuscles ; and 
(Jj) the pulp tissue. 

297. The .llal|ii;:liiaii corpuscles are masses 
of adenoid tissue connected with the branches of the 
splenic artery. Following the chief arterial trunks as 
they pass in the big trabeculfe towards the interior 
of the spleen, they are seen to give off numerous 
smaller l>ranches to the spleen parenchyma ; these are 
ensheathed in masses of adenoid tissue, which are 
either cylindrical or irregularly-shaped, and in some 
places form oval or spherical enlargements. These 
sheaths of adenoid tissue are traceable to the end of 
an arterial branch ; and in the whole extent the 
adenoid tissue or ^Malpighian corpuscle is supplied b}^ 
its artery with a network of capillary blood-vessels. 

298. The rest of the spleen parenchyma is made up 
of the pulp. The matrix of this is a honeycombed, 
spongy network of fibres and septa, which are the 
processes and bodies of large, flattened, endotheloid 
cells, each with an oval nucleus. In some, es^^ecially 
young, animals, some of these cells are huge and 
multinucleated. The spaces of the honeycombed tissue 
are of different diameters, some not larger than a blood 
corpuscle, others large enough to hold several. All 
spaces form an intercommunicating system. The 
spaces contain nucleated lymph corpuscles, more or 
less connected with and. derived from the cell plates 
of the matrix. But they do not fill the spaces, so 
that some room is left, large enough to allow blood 
corpuscles to pass. 

The spaces of the honeycomljed pulp matrix are in 
communication, on the one hand, with the ends of the 
capillary blood-vessels of the Malpighian corpuscles, 
and, on the other, they open into the venous radicles 
or sinuses (Fig. 234), udiich are oblong spaces lined 
with a layer of more or less polyhedral endothelial cells. 
These sinuses form networks, and lead into the large 



354 



Elements of Histology. 



venous branches passing in the big trabeculse to the 
hihun. The venous sinuses in man and ape possess a 
special adventitia formed of circular elastic fibrils. 
Not all arterial branches are ensbeatlied in 




-AL 



Fig. 234. — From a Section through the Spleen of a Guinea-pig ; the blood- 
vessels had been injected. {Atlas ) 

a, Artery 'of Malpighian corpuscle; h. pulp; hetween its cells are the minute 
blood-ctiannels opening into c, the radicles of the veins. 



Malpighian corpuscles; some few fine arterial branches 
open directly into the veins of the pulp matrix, being 
invested in a peculiar reticular or concentrically 
arranged cellular tissue (not adenoid). These are the 
capillary sheaths of Schweigger Seidel. 

299. The blood passes then from the arterial 
branches through the capillaries of the ^Malpighian 



Spleex. 355 

corpuscles, whence it travels into the labyrinth of 
minute spaces in the honeycombed pulp matrix ; 
thence it passes into the venous sinuses, and finally 
into the venous trunks. The current of blood on its 
passage through the pnlp tissue becomes, therefore, 
greatly retarded. Under these conditions numerous 
red blood-corpuscles appear to be taken up by the 
cells of the pulp, some of which contain several 
in their interior. In these corpuscles the blood discs 
become gradually broken up, so that finally, only 
granules and small clumps of blood pigment are left 
in them. The presence of blood pigment in the 
corpuscles of the pulp is explained in this way ; and 
it is therefore said that the pulp tissue is a destroyer of 
red blood-corpuscles. 

The pulp tissue is most probably the birthplace of 
colourless blood-corpuscles; and according to Bizzozero 
and Salvioli it is also the birthplace of red blood- 
corpuscles. 

The hjmphatics form plexuses in the capsule 
(Tomsa, Kyber). These are continuous with the plexus 
of lymphatics of the trabecul^e : and these again with 
the plexus of lymphatics in the adventitia of the 
arterial trunks. 

Xon-meduUated nerve fibres have been traced along 
the arterial branches. 



356 



CHAPTER XXXII. 

THE KIDNEY, URETER AXD BLADDER. 

300. A. The framework. 

The kidney possesses a thin investing capsule com- 
posed of fibrous tissue, more or less of a lamellar 
arrangement. Bundles of fibrous tissue pass with 
blood-vessels between the deeper part of the capsule 
and the parenchyma of the periphery. According 
to Eberth, a plexus of non-striped muscle cells is 
situated underneath the capsule. 

The ureter entering the hilum enlarges into the 
pelvis of the kidney, and with its minor recesses or 
prolongations forms the calices. Both the pelvis and 
the calices are limited by a wall which is a direct con- 
tinuation of the ureter. The internal free surface is 
lined with stratified transitional epithelium. Under- 
neath the epithelium is a fibrous connective- tissue 
membrane (the mucosa), containing the networks of 
capillary blood-vessels and fine nerve fibres. Outside 
the mucosa and insensibly passing into it is the 
loose-textured submucosa, with groups of fat cells. 
There are present in the submucosa bundles of 
non-striped muscular tissue, continued from the 
ureter, in the shape of longitudinal and circular 
bundles. 

In the pelvis of the kidney of the horse small 
alands (simple or branched tubes), lined with a single 
layer of columnar epithelial cells, have been observed 
by Paladino, Sertoli, and Egli. The last-named 
mentions also that in the pelvis of the human kidney 



Kidney, Ureter and Bladder. 357 

there are gland-tubes similar in structure to sebaceous 
follicles. 

301. The large vascular trunks enter, or pass from 
the tissues of the calices into the parenchyma of the 
kidney between the cortex and medulla, and they are 
accompanied by bundles of fibrous connective tissue 
and a few longitudinal bundles of non-striped muscular 
tissue, thereby separating the individual Malpighian 
pyramids. 

The parenchyma itself contains ver}^ scanty fibrous 
connective tissue, chiefly around the Malpighian cor- 
puscles and around the arterial vessels, especially in 
the young kidney. In the jDapilhe there is relatively 
a great amount of fil>rous tissue. On the surface of 
the papillae (facing the calices) there is a continuous 
layer of tibrous tissue, and this on its free surface 
is covered with stratified transitional epithelium. 

The parenchyma of the kidney consists entirely of 
the urinary tubules and the intertubular blood-vessels, 
and there is an interstitial or intertubular connective- 
tissue framework in the shape of honeycombed hyaline 
membranes with flattened nucleated branched or 
spindle-shaped cells. The meshes of the honeycomb are 
the spaces for the urinary tubules and blood-vessels. 

302. B. The pareiicliyma. — I. The urinary 
tubules (Fig. 235). — In a transverse or longitudinal 
section through the kidney we notice the cortex, the 
houndary layer of Ludwig and the papillary j)ortions, 
the last terminating in the conical ^;«^?j<7/rti in the cavity 
of the calices. 

The boundary layer and the papillary portion 
form the medulla. A papilla with the papillary 
portion and boundary layer, continuous with it, 
constitutes a MalpiyJiian pyramid. The medulla of 
the human kidney contains about a dozen of such 
Malpighian pyramids. 

303. The cortex contains vast numbers of 



358 



Elements of Histology. 




Fig. 235. — Diagram showing the course of the Uriniferous Tubules in the 

difterent parts of the cortex and medulla. {Atla&,) 

(For description of this Fig. see foot of next page.) 



Kidney, Uri:ti:r and Bladder. 359 

convoluted tubules with their c.ecal origin in the 
Malpighian corpuscles ; this is the lahnrinth separated 
into numerous divisions of ecjual breadth by regulai-ly- 
disposed straight stria? originating a sliort distance 
from the outer capsule, and ratliating towards the 
boundary layer through which they pass. Each of 
these stria3 is a bundle of straight tubules, and 
represents a mednUary ray. The boundary layer 
shows a uniform vertical striation, in which opa(pie 
and transparent strife alternate with one another. The 
opacpie stria^ are continuations of the medullar}^ I'ays, 
the transparent striae are bundles of blood-vessels. 

The papillary portion is uniformly and vertically 
striated. 

Tracing a medullary ray from the boundary layer 
into the cortex, it is seen that its breadth gradually 
diminishes, and it altogether ceases at a short distance 
from the outer capsule. A medullary ray is, con- 
sequently, of a conical shape, its apex being situated 
at the periphery of the cortex, its base in the 
boundary layer. Such a pyramid is called a pyramid 
of Ferrein. 

304. All urinary tubules commence as convoluted 
tubules in the part of the cortex named the 
labyrinth, but not in the medullary rays, with a 
Cfecal enlargement called a Malpighian corpuscle^ and 
terminate — having previously joined with many other 
tubules into larger and larger ducts— at one of the 
many minute openings or mouths at the apex of a 
papilla. On their way the tubes several times alter 
their size and nature. 



Ai Cortex limited on it* free surface hy the capsule; a, subcapsular layer not 
containing Malpitfliian corpuscles ; a' inner stratum of cortex without 
Malpighian corpuscles ; b, lioundary layer : c. papillary part next the 
boundary layer; 1, Bowman's capsule; 2, neck of capsule; 3, proximal con- 
voluted tube; 4, spiral part; 5, descending limb of Henle's loop-tube; 6, 
the loop itself ; 7, 8, and 9, the ascending linil) of Henle's loop-tube ; 10, the 
irreu'ular tubule ; 11, the distal convoluted tul)ule ; 12, the first part "f the 
collecting tube; 13 and U, larger collecting tube; in the papilla itself, not 
represented here, the collecting tube joins others, and forms the duct. 



360 



Elements of Histology 



From \X> >tart to it^ end there is a continuous 
fine memhrana propria forming the boundary wall 
of the urinary tubule, and this memhrana propria is 
lined with a single layer of ejnthelial cells differing in 




Fig. 236. — From a Section through the Cortical Substance of the Kidney 
of a human Foetus, showing a 3Ialpighian corpuscle. (HandbooJ:.) 

a.Glomemlu* ; 6. tissue of the glomerulus : c. epithelium covering the glomer- 
ulus ; d, flattened epithelium lining Bowmans capsule ; e, the capsule itself ; 
/, uriniferous tubules in cross section. 



size, shape, and structure from place to place : in 
the centre of the tubule is a lunifn, differing in size 
according to the size of the tubule. 

305, (1) Each Mcdpigldan corpuscle (Fig. 236) 
is composed of the capsule — the <-apsv.le of Bou-man — 
and the glomerulus, or Malpighian tuft of capillary 
blood-vessels. 

The capsule of Bowman is a hyaline membrana 
propria, supported, as mentioned aljove, by a small 
amount of connective tissue. On its inner surface 



Kidney, Ureter and Bladder. 361 

there is a continuous layer of nucleated epithelial 
cells, in the young state of polyhedral shape, in the 
adult state squamous. 

The glomerulus is a network of convoluted 
capillary blood-vessels separated from one another 
by scanty connective tissue, chiefly in the shape 
of a few connective-tissue corpuscles. The capil- 
laries are grouped together in two to five lobules. 
The whole surface of the glomerulus is lined with 
a delicate membrana propria, and a continuous layer 
of nucleated epithelial cells, polyhedral, or even 
columnar in the young, squamous in the adult state. 
The membrana propria and epithelium dip in, of 
course, between the lobules of the glomerulus, and 
represent in reality the visceral layer of the capsule 
of the Malpighian corpuscle, the capsule of Bowman 
being the parietal layer. The glomerulus is connected 
at one pole with an afferent and efferent arterial vessel, 
the former being the larger of the t^vo. 

Between Bowman's capsule and the glomerulus 
there is a space, the size of which difiers according 
to the state of secretion, being chiefly dependent on 
the amount of fluid present. 

The Malpighian corpuscles are distributed in the 
labyrinth of the cortex only, with the exception of a 
thin peripheral layer near the outer capsule, and a 
still thinner layer near the boundary layer. The 
Malpighian corpuscles near the boundary layer are 
the largest, those near the periphery the smallest ; in 
the human kidney their mean diameter is about -^^-^ 
of an inch. 

306. (2) On the side opposite to that where the 
afferent and efferent arterioles join the glomerulus, 
the capsule of Bowman passes through a narrow neck 
into the cylindrical urinary tubule in such a way 
that the membrana propria and epithelium of the 
capsule are continued as the membrana proj^ria and 



36; 



Elements of Histology 



lining epithelium of the tubule respectively, an<l 
the space between the ca[)sule of Bowman and 




"@t,;;,;^. :.:;:^V ,Cr^^^^ 




Fig. 237. — From a Vertical Section througli tlie Kidney of Dog, showing 
jiart of the labyrintli ami the adjoining medullary ray. {Atlas.) 

a. Capsule of Bowman ; tlie capillaries of the glomerulus are arranged in 
lobules; n, neck of capsule; b, irregular tubule; c, proximal convoluted 
tubules ; d, collecting tube ; e, part of the spiral tubule : /, portion of the 
- ascending limb of Henle's loop-tube ; d, e,f, form the meduliarj- ray. 



the glomerulus becomes the cavity or lumen of the 
urinary tubule. 

307. (3) After it has passed the neck, the urinary 
tubule becomes convoluted ; this is the joroximal con- 



K/DXKV, Ureter axd Bladder. 363 

vohded tubule (Fig. 237). It is of considerable length 
and is situated in tlie labyrinth. It has a distinct 
lumen, and its epithelium is a single layer of polyhedral 
or short, columnar, angular, or club-shaped cells, each 
with a spherical nucleus. These cells commence gene- 
rally at the neck, but in some animals — e.g. in the 
mouse — they already have begun in the ]N[alpighian 
corpuscle. The outer part of the cell protoplasm — i.e. 
next the membrana propria — is distinctly striated, 
owing to the presence of rod-shaped fibrils (Heiden- 
hain) vertically arranged. The inner part of the cell 
substance — i.e. between the nucleus and the inner 
free matgin — appears granular. Epithelial cells the 
protoplasm of which possesses the above rod-shaped 
tibrils will in the following paragraphs be spoken of 
as fibrillated cells. 

The proximal convoluted tuVje appears sometimes 
thicker than at other times : in the first case, its 
lumen is smaller, but its lining epithelial cells are 
distinctly more columnar. This state is probably 
connected with the state of secretion. 

308. (4) The convoluted tube passes into the 
spiral tuhule (Schachowa). This differs from the 
former in being situated not in the labyrinth, but in 
a medullary ray, in which it forms one conspicuous 
element, and in not being convoluted, but more or 
less straight, slightly wavy, and spiral. Its thickness 
and lumen are the same as in the former : its 
epithelium is a single layer of polyhedral cells, with 
distinct indication of tilirillation. 

309. (5) Precisely at the line where the cortex 
joins the boundaiy layer, the spiral tube becomes, 
suddenly greatly reduced in thickness ; it becomes at 
the same time very transparent ; its lumen is distinct; 
its membrana propria is now lined with a single 
layer of scales, each with an oval llattened nucleus. 
This altered tubule is the descending loop-tube of 



364 Elements of Histology. 

Henle, and it pursues its course in the boundary 
layer as a straight tuljule, in the continuation of the 
medullary ray. 

In aspect and size this part of the urinary 
tul)ule resembles a capillary blood-vessel, but differs 
from it inasmuch as, in addition to the lining laver 
of flattened epithelial cells, it possesses a membrana 
propria. 

31u. (6) The so-constituted descending Henle's 
loop-tube passes the line between the boundary layer 
and papillary portion, and having entered this latter, 
pursues its course for a short distance, when it sharply 
bends backwards as the looi) of Henle's tube ; it now 
runs back towards the boundary layer, and precisely 
at the point of entering this becomes suddenly enlarged. 
Up to this point the structure and size of the loop are 
exactly the same as those of the descending limb. 

311. (7 and 8) Having entered the boundary layer 
it pursues its course in this latter to the cortex in a 
more or less straiglit direction within the medullary 
ray as the ascending loop-tube. Besides being bigger 
than the descending limb and the loop, its lumen is 
comparativelv smaller, and its lining epithelium is a 
layer of polyhedral, distinctly librillated epithelial 
cells. The tube is not quite of the same thickness all 
along the boundarv layer, but is broader in the inner 
than in the outer half ; besides, the tube is not quite 
straight, but slightly wavy or even spiral. 

(9) Having reached the cortex, it enters this as 
the cortical part of the ascending loop-tube, forming 
one of the tubes of a medullary ray ; it is at the same 
time narrower than in the boundary layer, and is 
more or less straiiiht or wavv. Its lumen is verv 
minute, its lining cells are flat polyhedral witli a 
small flattened nucleus, and there is an indication of 
librillation (Fig. 237). 

(10) Sooner or later on its way in the cortex in 



Kidney^ Ureter and Bladder. 365 

a medullary ray it leaves this latter to enter the 
labyrinth, where it Avinds between the convoluted 
tubes as an angular irregular tubule (Fig. 237). Its 
shape is very irregular, its size alters from place 
to place, its lumen is very minute, its epithelium a 
layer of polyhedral, pyramidal, or short columnar cells 
— according to the thickness of the tube ; each cell 
possesses a flattened oval nucleus next to the lumen, 
and a very coarsely and conspicuously tibrillated 
protoplasm. 

312. (11) This irregular tubule passes into the 
distal convoluted tubule or intercalated tubule of 
Schweigger Seidel. This forms one of the convoluted 
tubes of the labyrinth, and in size, aspect, and 
structure is identical with the proximal convoluted 
tubule. 

(12) The distal convoluted tube passes into a 
short, thin, more or less curved or wavy collecting 
tubule, lined with a layer of transparent, flattened, 
polyhedral cells ; this is still contained in the 
labyrinth. 

(13) This leads into a somewhat larger straight 
collecting tube, lined with a layer of transparent poly- 
hedral cells and with distinct lumen. This tube 
forms part of a medullary ray, and on its way to the 
boundary layer takes up from the labyrinth numerous 
curved collecting tubules. 

(14) It then passes unaltered as a straight collect- 
ing tube through the boundary layer into the papillary 
portion. 

313. In this part these tubes join under acute 
angles, thereby gradually enlarging. They run in a 
straight direction towards the apex of the papilla, 
and the nearer to this, the fewer and the bigger they 
become. These are the ducts or tubes of Bellini. 
They finally open on the apex into a calix. The lumen 
and the size of the lining epithelial cells — namely, 



;66 



Elements of Histology. 



i.^j-'-r-.-^-^^^^a^ 




Fig. 23S. — Diagram of the Vessels 
of the Kidney. {Ludicig, in 
Strieker's Manual.) 



whether more or less co- 
lumnar — are in direct re- 
lation to the size of the 
coUectinQ' tube. The sub- 
stance of the epithelial 
cells is a transparent pro- 
toplasm, and the nucleus is 
more or less oval. 

314. In many places 
nucleated cells, spindle- 
shaped or branched, can be 
traced from the membrana 
propria of the tubule be- 
tween the lining epithe- 
lium ; and, in some cases, 
even a delicate nucleated 
membrane can be seen 
lininor the surface of the 
epithelium next the lumen. 
In the frog, the epithelium 
lining, the Malpighian cor- 
puscles, and the exceed- 
ingly long neck of the 
urinary tubule, are pos- 
sessed of lonij hlamentous 
ciHa, rapidly moving during 
life. In the neck of some 
of the urinary tubules in 
mammals there is also an 
indication of cilia to be 
noticed. 



«/, Interlobular artery ; vi, interlobular 
vein : g. glomerulus of Malpighian 
corpuscle; vs. vena stellata; ar, 
arteriiB rectas : rr, vena; rects ; ob, 
Imndle of arteria; rectae: rb. bundle 
of venffi rectse ; rp, network of vessels 
around the nioutti of the ducts 
at the apex of the papillK. 



K/DN/:v, Ureter and B [.adder. 



367 



Heideiihaiii lias sliown tliat indigo-sulphate of 
sodium, injected into the circulating blood of the dog 
and rabbit, is excreted through certain parts of tlie 
urinary tubules only — viz. those which are lined with 






r V: '-'v yf. 



P 



t 



"-^^k:-^ ■-'V.v. ■■^•■-^■^ "^ -'"-S:' 

.■>»•/ -J . .,- '/• -. . ^. 

* •.■■•• '■% .. ■ . . (. , « ,, 

/ * .1 •' 1' 



Fig. 239. — Vertical Section through the entire Kidney (injected) of a Rat. 
{Photo. Low Power.) 

(I, Cortex ; b, papilla ; c, boundary layer. 

"fibrillated^' epithelium. He maintains that this 
excretion is effected through the cell substance ; but, 
in the case of carmine being used as pigment, I have 
not found the excretion to take place through the 
substance of the epithelial cells, but through the 
homogeneous interstitial or cement substance between 
the epithelial cells. 

315. 11. The blood-vessels. (Figs. 238 and 239). 



568 Elements of Histology. 

The large branches of the renal artery and vein 
are situated in the submucous tissue of the pelvis, 
and they enter, or pass out respectively from, the part 
of the parenchyma corresponding to the junction of 
the cortex and boundary layer, where they follow a 
more or less horizontal course, and give off, or take up 
respectively, smaller branches to or from tlie cortex 
and medulla. 

(1) In the cortex the arterial trunks give off to 
the cortex small branches, which singly enter the 
lahijrinth in a direction vertical to the surface of the 
kidney. These are the interlohidar arteries. Each of 
these, on its way towards the external capsule of the 
kidney, gives off, on all sides of its circumference, 
shorter or longer lateral branches : these are the 
afferent arterioles for the Malpighian corpuscles, each 
one entering a Malpighian corpuscle and breaking up 
into the capillaries of the glomerulus. 

On their way towards the external capsule, the 
arteries become greatly reduced in size, and finally 
enter the capillary network of the most peripheral 
part of the cortex ; but some of these arterioles may 
be also traced into the outer capsule, where they 
become connected with the capillary networks of this 
latter. The efferent vessel of a Malpighian glome- 
rulus at once breaks up into a dense network of 
capillary blood-vessels, which surround in all direc- 
tions the urinary tubules of the labyrinth. This 
network is continuous with that of the capillaries of 
the medullar}^ I'ays, the meshes being here elongated, 
and the capillary blood-vessels, for obvious reasons, 
more of a straight arrangement. The capillaries of 
the whole cortex form one continuous network. 

316. The veins which take up the blood from this 
network are arranged in this manner : — ^There are 
formed venous vessels underneath the external 
capsule, taking up like rays on all sides, minute 



Kidney, Urkter and Bladder. 369 

radicles connected with the capillaries of the most 
peripheral ^Axt of tlie cortex. These are the venoi 
steUata; ; they pass into the labyrinth of the cortex, 
where they follow a vertical course in company with 
the interlobular arteries. On tliis passage the}?" com- 
municate with the capillaries of the labyrinth, and 
ultimately open into the large venous branches 
situated between cortex and boundary layer. 

317. (2) In the medulla. From the large arterial 
trunks short branches come off, w^hich enter the 
boundary layer, and there split up into a bundle 
of minute arterioles, which pass in a straight direc- 
tion vertically through the boundary layer into the 
papillary portion. These are the arterim recUt 
(Fig. 238). The number of vessels of each bundle 
is at the outset increased by the efferent vessel of 
the Malpighian corpuscles nearest to the boundary 
layer. 

On their way through the boundary layer, and 
through the papillary portion of the medulla, 
these arterioles give off the capillary netw^ork for 
the urinary tubules of these parts, the network, 
for obvious reasons, possessing an elongated arrange- 
ment. 

From this network originate everywhere minute 
veins, which on their way towards the cortical margin 
increase in size and number ; they form also bundles 
of straight vessels — vence rectca — and ultimately enter 
the venous trunks situated between the boundary 
Jayer and cortex. 

The bundles of the arterise rectae and venae rectse 
form severally, in the boundary layer, the transparent 
striae mentioned on a previous page as alternating 
with the opaque striae, these latter being bundles of 
urinary tubules. 

At the apex of each papilla there is a network of 
capillaries around the mouth of each duct. 



J) / 



Elements of Histology. 



318. The outer capsule of the ki(hiey contains a 
network of capillary blood-vessels ; the arterial 
branches leading into them are derived from two 
sources : («) from the outrunners of the interlobular 




Fig. 240.— From Transverse Section through Urinary Bladder of Dog. 
{Photo. Low Pov:er.) 

a, Inner surface of folded mucous membrane, covered with stratified transitional 
epithelium ; b, raucous membrane : c, outer coat of non-striped muscle. 



arteries of the cortex, and (b) from extra-renal arteries. 
The veins lead [a) into the vena? stellatie, and (b) into 
extra-renal veins. 

The li/mpJtatic vessels form a plexus in the capsule 
of the kidney. They are connected with lymph spaces 
between the urinary tubes of the cortex. The large 
blood-vessels are surrounded by a plexus of lym- 
phatics, which take up lymph spaces between the 



KlDNKV, UrKTER and B LADDER. 37 1 

urinary tubules, both in the cortex and the boundary 
layer. 

oil*. The ureter is lined with stratified transi- 
tional e]>itlieliam. Underneath this is the mucosa, 
a connective-tissue membrane with capillary blood- 
vessels. The submucosa is a loose connective tissue. 
Then follows a muscular coat composed of non- 
striped muscular tissue, arranged as an inner and 
outer longitudinal and a middle circular coat. Then 
follows an outer limiting thin tibrous coat or adventitia. 
In this last have been observed minute cjanfjlia in 
connection with the nerve-branches. 

320. The bladder is similar in structure, but 
the mucous membrane and muscular coat are very 
much thicker. In the latter, which consists of non- 
striped fibres, can be distinguished an inner circular, 
a middle oblique, and an outer longitudinal stratum. 
The last is best developed in the fundus (Fig. 2-10). 

Xumerous sympathetic ganglia, of various sizes, 
are found in connection with the nerve-branches 
underneath the adventitia (peritoneal covering), and 
in the muscular coat (F. Darwin). The epithelium 
lining the bladder is stratified transitional, and it 
greatly varies in the shape of its cells and their 
stratification, according to the state of expansion of 
the bladiler. 



172 



CHAPTER XXXIII. 

THE xMALE GENITAL ORGANS. 

321. (1) The testis of man and mammals is en- 
veloped in a capsule of white fibrous tissue, the tunica 
adnata. This is the visceral layer of the tunica 
vaginalis. Like the parietal layer, it is a serous 
membrane, and is therefore covered with endo- 
thelium. Minute villi are occasionally seen pro- 
jecting from this membrane into the cavity of 
the tunica vaginalis. These villi are generally 
covered with germinating endothelium. Inside the 
tunica adnata, and firmly attached to it, is the 
tunica cdbnginea, a fibrous connective-tissue mem- 
brane of lamellar structure. Towards the posterior 
maro-in of the human testis its thickness increases, 
and forms there (Fig. 241) a special accumu- 
lation — in cross section more or less conical, with 
posterior basis — the mediastinum testis, or corpus 
Highmori. 

Between the tunica adnata and tunica albuginea 
is a rich plexus of lymphatics, which, on the one hand, 
takes up the lymphatics of the interior, and on the 
other leads into the efferent vessels that accompany 
the vas deferens. 

The testis of the dog, cat, bull, pig, rabbit, etc., 
have a central corpus Highmori ; that of the mole, 
hedgehog, and bat a peripheral one ; while that of 
the rat and mouse have none (Messing). 

322. The framework. — From the anterior 
margin of the corpus Highmori spring numerous 



Male Genital Organs. 



373 



septa of connective tissue, which, passing in a radiat- 
ing direction towards the alhuginea, with which tliey 
form a continuity, sul)divide the testis into a large 



a^ 







Fig. 241.— Passage of Convoluted Seminiferous Tubules into Straight 
Tubules and into the Rete Testis. {Mihalkovics, Quain's " Anatomy.") ^ 
a, Seminiferous tubules ; b, fibrous tissue : c, rete testis. 

number of more or less conical compartments, or 
lobules, the basis of which is situated at the tunica 
albuginea, the apex at the corpus Highmori. Kolliker 



374 Elements of Histology. 

mentions that non-striped muscular tissue occurs in 
these se[)ta. 

From these septa thin connective-tissue lamellte 
pass into the compartments, and they form the 
supporting tissue for the blood-vessels, and also 
represent the interstitial connective tissue between 
the seminal tubules. 

This intertubular or interstitial tissue is distinctly 
iamellated, the lamella? being of different thicknesses, 
and consisting of thin bundles of fibrous connective 
tissue — arranged more or less as fenestrated mem- 
branes — and endotheloid connectixe plates on their 
surface. Between the lamella? are left spaces, and 
these form, through the fenestra? or holes of the 
lamellae, an intercommunicating system of lymph 
spaces — being, in fact, the rootlets of the lymphatics 
(Ludwig and Tomsa). 

AVithin the lamellae are found peculiar cells, 
which are much larger than lymph cells, and which, 
in some instances {e.g. guinea-pig), include pigment 
granules. They contain a spherical nucleus. In man, 
dog, cat, sheep, especially in the boar, these cells form 
large, continuous groups — plates and cylinders — and 
the cells are polyhedral, and exactly similar to epithe- 
lial cells. They are separated from one another within 
the grouj:) by a thin interstitial cement substance. 
Their resemblance with epithelium is complete. They 
are remnants of the epithelial masses of the Wolffian 
body of the fcetus. 

323. The seminal tiibiile!^ (Fig. 242). — 
Within each compartment, above mentioned, lie 
numerous seminal tubules, twisted and convoluted 
in many ways, and extending from the periphery to 
near the corpus Highmori. The tubules, as a rule, 
are rarely branched ; but in the young state, and 
especially towards the periphery, branching is not 
uncommon. 



Male Genital Organs. 



375 



Each seminal tubule consists of a membrana 
propria, a lining epith(4iuin, and a lumen. The 
membrana propria is a hyaline membrane, with oval 
nuclei at regular intervals. In man it is thick and 
lamellated, several such nucleated membranes being 




Fig. 242.— Section of parts of three Seiniuiferous Tubules of Rat. 
(£. A. ScMfer.) 

a, "With the spermatozoa least advanced in development; &, more, and c, most 
advanced. Between the tubules are strands of interstitial cells. 



superimposed over one another. The lumen is in 
all tubes distinct and relatively large. The lining 
epithelium, or the seminal cells, differ in the adult 
in ditferent tubules, and even in different parts of 
the same tubule, being dependent on the state of 
secretion. 

324. Before puberty all tubules are uniform in 
this respect, being lined with two or three layers of 
polyhedral epithelial cells, each with a spherical 



376 



Elements of Histology. 



nucleus. After puberty, however, the following 
different t3qies can be distinguished. 

(a) Tubules or parts of tubules similar to those 
of the young state — viz. several layers of polyhedral 
epithelial cells lining the menibrana propria. These 
are considered as («) the outer and ih) the inner 
seminal cells. The former are next to the membrana 




Fk 



'243 



-From a Section through the Testis of Dog, showing portions of 
three seminal tubules. {Atlas.) 

j», Seminal epithelial cells and mimerous small cellt- loosely arranged ; B, small 
cells or sperniatohlasts becoming converted into spermatozoa; c, groups of 
these in a further stage of development. 

propria ; they are ])olyhedral in shape, transparent, 
and the nucleus of many of them is in the process 
of karyomitosis or indirect division (see par. 8) ; 
in some the nucleus is oval transparent, but containing 
a distinct network. The inner seminal cells generally 
form two or three layers, and are more loosely con- 
nected with one another than the outer seminal cells, 
and therefore possess a more rounded appearance. 



Male Genital Oh cans. 377 

Between these a nucleated reticuluiii of fine fibres 
is sometimes noticed, the i^erm reticulum of von 
Ebner. But this is merely a supporting tissue, and has 
nothing to do with the germination of the cells or the 
spermatozoa (Merkel). The inner seminal cells show 
very abundantly the process of indirect division of the 
nucleus, almost all being seen in one or another phase 
of it. 

325. The division of the inner seminal cells yields 
numerous small spherical cells ; these lie nearest the 
lumen, and are very loosely connected vi^ith one 
another. It is these which are transformed into 
spermatozoa, and hence are appropriately called 
spermatoblasts (-t'ig. 242). 

Amongst the seminal cells, especially of cat and 
dog, are found occasionally, but not very commonly, 
large multinuclear cells, the nuclei of which are also 
in one or other stage of karyomitosis. 

(b) The innermost cells — i.e. the spermatoblasts — - 
become pear-shaped, the nucleus being situated at the 
thinner extremity, becoming at the same time flattened 
and homogeneous (Fig. 24.')). The elongation of the 
spermatoblasts gradually proceeds, and in consequence 
of this we find numerous elongated, club-shaped 
spermatoblasts, each with a flattened nucleus at the 
thin end. These are the young spermatozoa, the 
nucleated extremity being the head. 

(c) At the same time these young spermatozoa 
become grouped together by an interstitial granular 
substance, in peculiar fan-shaped groups : in these 
groups the head — i.e. the thin end containing the 
flattened homogeneous nucleus — is directed towards 
the inner seminal cells, while the opposite extremity 
is directed into the lumen of the tube. Meanwhile 
the inner seminal cells continue to divide, and thus 
the groups of young spermatozoa get more and more 
buried, as it were, between them. 



378 Elements of Histology. 

326. The original cell-body of the spermatoblasts 
goes on elongating until its protoplasm is almost, but 
not quite, used to form a rod-shaped middle -piece 
(Schweigger Seidel) of the spermatozoa; from the 
distal end of this, a thin long hair-like filament, called 
the tail., grows out. Where this joins the end of the 
middle piece, there is present, even for some time 
afterwards, a last remnant of the granular cell-body of 
the original spermatoblast. Some of the inner seminal 
cells not used for the formation of spermatozoa dis- 
integrate and yield the granular substance between 
the spermatozoa of the groups, and also between these 
latter. 

When the granular interstitial substance holding 
together the spermatozoa of a group has become dis- 
integrated, the spermatozoa are isolated. \\'hile this 
development of the spermatozoa goes on, the inner 
seminal cells continue to produce spermatoblasts, some 
of which are converted into spermatozoa. 

327. Spermatozoa (Fig. 24-4). — Fully formed 
spermatozoa of man and mammals consist of a homo- 
geneous flattened and slightly con\-ex-concave head 
(the nucleus of the original spermatoblast), a rod- 
shaped middle 2nece (derived directly from the cell- 
body of the spermatoblast), and a long hair-like tail. 
While living, the spermatozoa show very rapid oscilla- 
tory and propelling movement, the tail acting as a 
Hagellum or cilium ; its movements are sj^iral. 

In the newt there is a tine spiral thread attached 
to the end of the long, curved, spike-like head, and by 
a hyaline membrane it is fixed to the middle piece ; it 
extends beyond this as the tail. Also in the mam- 
malian and human spermatozoa, a similar spiral thread, 
closely attached to the middle piece, and terminating 
as the tail, has been observed (H. Gibbes). 

328. The seminal tubules of each lobule pass into 
a short straight tubuU-. the vas rectum. This is 



Male Genital Organs. 



379 



narrower than tlie seminal tubule, and is lined with a 
single layer of polyhedral or short columnar epithelial 
cells. The vasa recta form, in the corpus Highmori, 
a dense network of tubular channels, which are irregu- 
lar in diameter, being at one place narrow clefts, at 




Fig. 244. — Various Kinds of Spermatozoa. 

A, Spennatr)zoon of guinea-pig not yet completely ripe; b, the same seen side- 
ways, the head of the spermatozoon is flattened from side to side; c, 
spermatozoon of h(jrse ; d, spermatozoon of newt. 



another wide tuljes, but never so wide as the seminal 
tubules ; this network of channels is the rete testis. 

329. (2) The epidid.vnii«». — From the rete testis 
we pass into the rasa eferentia, each being a tube 
wider than those of the rete testis, and each leading 
into a conical network of coiled tubes. These are the 
coiii vascalosi. The smn total of all the coni vasculosi 
forms the globus major or head of the epididymis. 

330. The vasa efferentia and the tubes of the coni 



•So 



Elements of Histology. 



vasculosi are about the size of the seminal tubules, 
but, unlike them, are lined with a layer of beautiful 
columnar epithelial cells, with a bundle of cilia (Fig. 
245). Outside these is generally a layer, more or 
less continuous, of small polyhedral cells. The sub- 
stance of the columnar cells 
is distinctly longitudinally 
tibrillated. The membrtaia 
propria is thickened by the 
presence of a circular layer 
of non - striped muscular 
fibres. The rest — i.e. the 
globus minor, or tail of the 
epididymis — is made up of 
a continuation of the tubes 
of the globus major, the 
tubes diminishing gradually 
in number by fusion, and 
thereby at the same time 
becoming larger. The 

columnar epithelial cells, 
facing the lumen of the 
minor, are possessed of cilia 




Fig. 245.— Tubule of the Epi- 
didymis in cross-section. 

The wall of the tubule is made up of 
a thick layer of roncentrically ar- 
ranged n(tn-:<triped muscular tissue, 
a layer of columnar epithelial cells 
witii extraoi'diuarily lonsr cilia pro- 
jecting into the lumen of the tube. 



tubes of the globus 
of unusual length. 

The tubes of the epididymis are separated from one 
another by a larger amount of connective tissue than 
those of the testis. 

The tubes of the organ of Giralde, situated in the 
beginning of the funiculus spermaticus, are lined with 
columnar ciliated epithelium. So is also the pedun- 
culated hydatid of Morgagni attached to the globus 
major, 

331. The seminal tubules and the tubes of the 
epididymis are surrounded by a rich network of 
capillary blood-vessels. Between the tubes of the 
testis and epididymis are lymph spaces, forming an 
intercommunicating system, and emptying themselves 



Male Genital Organs. 381 

into the superficial networks of lymphatics — i.e. 
those of the albuginea ; the arrangement of these 
networks is somewhat (liferent in the testis and 
epididymis. 

332. (3) Vas ^leferciis and vesiciila? seiiii- 
iiales. — The tubes of the globus minor open into the 
vas deferens. This is, of course, much larger than 
the former^ and is lined with stratified columnar 
epithelium. Underneath this is a dense connective- 
tissue mucosa, containing a rich network of capillary 
blood-vessels. Beneath this mucosa is a thin sub- 
mucous tissue, which in the ampulla is better de- 
veloped than in other parts, and therefore allows the 
mucous membrane to become folded. Outside the 
submucous tissue is the muscular coat, which consists 
of non-striped muscular tissue, arranged as an inner 
circular and an outer longitudinal stratum. At the 
coQimencement of the vas deferens there is in addition 
an inner longitudinal layer. There is finally a fibrous 
tissue adventitia. This contains longitudinal bundles 
of non-striped muscular tissue, known as the cremaster 
internus (Henle). A rich plexus of veins — plexus 
pampiniformis — and a rich plexus of lymphatic trunks, 
are situated in the connective tissue of the spermatic 
cord. The plexus spermaticus consists of larger and 
smaller nerve-trunks, with which are connected small 
groups of ganglion cells and also large ganglionic 
swellings. 

333. In the vesiculce semiiiales we meet with 
exactly the same layers as constitute the wall of the 
vas deferens, but they are thinner. This refers espe- 
cially to the mucosa and the muscular coat. The 
former is placed in numerous folds. The latter con- 
sists of an inner and outer longitudinal and a middle 
circular stratum. The orano-lia in connection with the 
nerve trunks of the adventitia are very numerous. 

334. In the ductus ejacidatorii we find a lining of 



382 Elements oe Histology. 

columnar epithelial cells ; outside of this is a delicate 
mucosa and a muscular coat, the latter consisting of 
an inner thicker longitudinal and an outer thinner 
circular stratum of non-striped muscular tissue. 

When passing into the vesicula prostatica the 
columnar epithelium is gradually rejDlaced by stratified 
pavement epithelium. 

335. (4) The prostate inland. — Like other 
glands, the prostate consists of a framework and the 
gland tissue proper or the parenchyma. 

The framework, unlike that of other glands, is 
essentially muscular, being composed of bundles of 
non-striped muscular tissue, with a relatively small 
adndxture of fibrous connective tissue. The latter 
is chietlv limited to the outer capsule and the thin septa 
passing inwards, whereas the non-striped muscular tis- 
sue surrounds and separates the individual gland alveoli. 

336. The pareiicliyiiia consists of the chief 
ducts, which open at the base of and near the colli- 
culus seminalis, and of the secondary ducts, minor 
brandies of the former, which ultimately lead into the 
alveoli. These are longer or shorter, wavy or con- 
voluted branched tubes with numerous saccular or 
club-shaped branches. The alveoli and ducts are 
limited by a membrana propria, have a distinct lumen, 
and are lined with columnar epithelium. In the 
alveoli there is only a single layer of beautiful 
columnar epithelial cells, the substance of which is 
distinctly and longitudinally striated. In the ducts 
there is an inner layer of short columnar cells, and an 
outer one of small cubical, polyhedral or spindle- 
shaped cells. 

At the mouth of the ducts the stratified pavement 
epithelium of the pars prostatica of the urethra passes 
a short distance into the duct. 

The alveoli are surrounded by dense networks of 
capillary blood-vessels. 



Male Genital Organs. 383 

In the pei-iplieral portion of the gland numerous 
ganglia are inter[)Osed in the rich plexus of nerves. 
Also Pacinian corpuscles are to be met with. 

337. (T)) TIk' iii-<'tlirsi. — The mucous membrane 
of the male uiethra is lined with simple columnar 
epithelium, except at the commencement— the pars 
prostatica — and at the end — the fossa navicularis — 
where it is stratified pavement epithelium. 

The mucous membrane is fibrous tissue with very 
numerous elastic fibres. Outside of it is a muscular 
coat composed of non-striped muscular tissue, and 
arranged as an inner circular and an outer longi- 
tudinal stratum, except in the pars prostatica and pars 
membranacea, where it is chiefly longitudinal. In the 
latter portion the muscular bundles pass also into the 
mucous membrane, where they follow a longitudinal 
course between large veins arranged in a longitudinal 
plexus. These veins empty themselves into small 
etTerent veins. This plexus of large veins with the 
muscular tissue between represents a rudiment of a 
cavernous tissue (Henle). 

The mucous membrane forms peculiar folds sur- 
rounding the lacunas Morgagni. There are small 
mucous glands, lined with columnar epithelium, 
embedded in the mucous membrane ; they open into 
the cavity of the urethra and are known as Littre's 
glands. 

338. (6) The ^landfi» of Cowper. — Each gland 
of Cowpei" is a large compound tubular gland, which, 
as regards structure of ducts and alveoli, resembles a 
mucous gland. The wall of the chief ducts possesses 
a large amount of longitudinally arranged non-striped 
muscular tissue. The epithelium lining the ducts is 
composed of columnar cells. The alveoli possess a 
large lumen and are lined with columnar mucous 
cells, the outer portion of the cell being distinctly 
striated (Langerhans). In the cell the reticulum is 



384 Elements of Histology. 

also distinct. In this respect the alveoli completely 
resemble those of the submaxillary of the dog, but 
there are no real crescents in the alveoli of Cowper's 
gland. 

339. (7) Tlie corpus «ipoiig'io«^iiiii. — The cor- 
pus spongiosum of the urethra is a continuation of 
the rudimentary corpus cavernosum above-mentioned 
in connection with the pars membranacea of the 
urethra. It is essentially a plexus of large veins 
arranged chiefly longitudinally, and leading into 
small efferent veins. Between the laro^e veins are 
bundles of non-striped muscular tissue. The capillary 
blood-vessels of the raucous membrane of the urethra 
open into the veins of the plexus. The outer portion 
of the corpus spongiosum, including the bulbus 
urethn^, shows, however, numerous venous sinuses, 
real caverna?, into which open capillary blood- 
vessels. 

340. The glaiis penis is of exactly the same 
structure as the corpus spongiosum. The outer 
surface is covered with a delicate fibrous tissue 
membrane, ^^•hich on its free surface bears minute 
papillae, extending into the stratified pavement epi- 
thelium. At the corona glandis exist small sebaceous 
follicles, the glands of T3^son ; they are continued 
from the inner lamella of the prepuce, where they 
abound. The papilla? of the glans contain loops of 
capillary blood-vessels. Plexuses of non-medullated 
nerve fibres are found underneath the epithelium of 
the surface of the glans. With these are connected 
the end bulbs described in a former chapter as the 
genital nerve-end corpuscles. 

341. (8) Tlie corpora cavernosa penis. — 
Each corpus cavernosum is enveloped in a fibrous 
capsule, the albuginea, made up of lamellae of fibrous 
connective tissue. Numerous Pacinian corpuscles 
are met with around it. The matrix of the corpus 



Male CiEnital Okgans. 385 

cavernosiun consists of trabecular of fibrous tissue, 
between wliicli pass bundles of non-striped muscular 
tissue, all in different directions. Innumerable 
cavernie or sinuses, intercommunicating with one 
anotlier, are present in this matrix, capaljle of such 
considerable repletion that in the maximum degree 
of this state the sinuses are almost in contact, and 
the trabeculaj compressed into very delicate septa. 
The sinuses are lined with a single layer of flattened 
endothelial plates, and their wall in many places is 
strengthened by the bundles of non- striped muscular 
tissue. The sinuses during erection become filled 
with blood, being directly continuous with capillary 
blood-vessels. These are derived from the arterial 
branches which take their course in the above tra- 
beculae of the matrix. The blood passes from the 
sinuses into small efferent veins. But the blood 
passes also directly from the capillaries into the 
efferent veins, and this is the course the blood takes 
under passive conditions, while during erection it 
passes chiefly into the above sinuses. 

342. In the peripheral part of the corpus caver- 
nosum there exists a direct communication between 
the sinuses and minute arteries (Langer), but in the 
rest the arteries do not directly communicate with 
the sinuses except through the capillary blood- 
vessels. In the passive state of the corpus caver- 
nosum, the muscular trabecular forming part of the 
matrix are contracted, and the minute arterial 
branches embedded in them are therefore much 
coiled up ; these are the arterise helicina3. 



;S6 



CHAPTER XXXIY. 



THE FEMALE (GENITAL ORGANS. 



343. (1) The ovary (Fig. 24G). — In tlie ovary, 
as in other glands, the framework is to be dis- 
tinguished from 
the parenchyma. 
In the part of 
the ovary next 
to the hilum there 
are numerous 
blood-vessels, in 
a loose fibrous 
connective tissue, 
with numerous 
longitudinal bun- 
dles of non-striped 
muscular tissue 
directly contin- 
uous with the 
same tissues of 
the lioamentum 
latum. This por- 
tion of the ovary 
is the zona vas- 
culosa (Wal- 
deyer). All parts 
of the zona vas- 
culosa — i.e. the 
bundles of tibrous 
connective tissue, 
the blood-vessels, and the bundles of non-striped 
muscular tissue— are traceable into"; the parenchyma. 

















Fig.: 246.— Vertical Section through Ovary of 

half -grown Cat. {Atlas. ) 
fi, Albuginea; the geminal epitlieliuia i3 not 
distinguishable owing to the low power under 
which the section is supposed to be viewed; 0, 
layer of smallest Graaflan follicles and ova; c, 
medium-sized follicles ; d, layer of large follicles ; 
e, zona vasculosa 



Female Gexital Organs. ^87 



O" 



The stroma of this latter, however, is made up 
of bundles of shorter or longer transparent spindle- 
shaped cells, each with an oval nucleus. These 
bundles of spindle-shaped cells form, by crossing 
and interlacing, a tolerably dense tissue, in which 
lie embedded in special distribution the Graafian 
follicles. Around the lai-ger examples of the latter 
the spindle shaped cells form more or less con- 
centric layers. In the human ovary bundles of 
librous tissue are also met with. 

The spindle-shaped cells are most probably a 
young state of connective tissue. 

Between these bundles of spindle-shaped cells 
occur cylindrical or irregular streaks or groups of 
polyhedral cells, each with a spherical nucleus ; they 
correspond to the interstitial epithelial cells men- 
tioned in the testis, and they are also derived from 
the fcetal Wolffian body. 

344. According to the distribution of the Graafian 
follicles, the following layers can be distinguished in 
the ovary : — 

{a) The albuginea. This is the most peripheral 
layer not containing any Graafian follicles. It is 
composed of the bundles of spindle-shaped cells, in- 
timately interwoven. In man, an outer and inner 
longitudinal, and a middle circular, layer can be made 
out (Henle). In some mammals an otiter longi- 
tudinal, an inner circidar, or slightly oblique layer 
can be distinguished in the albu2:inea. 

The free surface of the albuginea is covered with 
a single layer of polyhedral, or short columnar 
granular-looking epithelial cells, the germinal 
epithelium (Waldeyer). This epithelium, in its 
shape and aspect, forms a marked contrast to the 
transparent, flattened, endothelial plates covering 
the ligamentum latum. 

345. [h) TJie cortical layer (Schron). — This is a 



;88 



Elements of Histology 




% 



mBmmm 




layer containing the smallest Graafian follicles, either 
aggregated as a more or less continuous layer (cat and 
rabbit), or in small groups (human), separated by the 
stroma. These follicles are spherical or slightly oval, 
of about Y-u\,o inch in diameter, and each of them is 
limited by a delicate raemhrana propria. Inside of 
this is a layer of flattened, trans- 
parent, epithelial cells, each with an 
oval, flattened nucleus ; this is the 
membrana granulosa. The 'space 
within the follicle is occupied by, 
and filled up with, a spherical cell — 
the ovum cell, or ovum. This is 
composed of a granular-looking pro- 
toplasm, and in this is a big spherical, 
or slightly oval, nucleus — the germinal 
vesicle. The substance of this is either 
a fine reticulum, limited by a delicate 
membrane, with one or more nucleoli 
or germinal spots, or it is in one of 
the phases of indirect division or 
karyomitosis, thus indicating division 
of the ovum. 

346. (c) From this cortical layer to 

the zona vasculosa we find embedded 

the stroma isolated Graafian follicles of various 

increasino- from the former to the latter. 



Fig. 247.— A small 
Graafian Follicle, 
from the Ovary of 
Cat. {Atlas.) 

The follicle is lined 
with a layer of 
colunmar epithe- 
lial cells — the 
lueinbrana granu- 
losa. The ovum 
fills out the cavity 
of the follicle; it 
is surrounded by 
a thin zona pellu- 
cida, and it in- 
cludes a germinal 
vesicle or nucleus 
with the intra- 
nuclear reticulum. 



m 

sizes 



The 



1 

2 



biggest follicles measure in diameter about 
Those of the middle laj^ers are of me- 



inch 



In them we find inside 
the membrana granulosa, 
layer of transparent, co- 
The ovum, larger than in 
the small cortical follicles, fills out the cavity of the 
follicle, and is limited by a thin hyaline cuticle — the 
zona peUncida. This appears as an excretion of the 
cells of the membrana granulosa. The protoplasm of 



dium size (Fig. 247). 
the membrana propria 
made up of a single 
lumnar, epithelial cells. 



Female GEyiTAL Organs. 



3S9 



tlie OMiiii is tibrillateil. The part siuTOunding the 
germinal vesicle is more ti-auspaient, and stains 
ditlerently in osniic acid than the peripheral part. 
The big nucleus, or germinal vesicle, is limited by a 
distinct membrane, and inside this meml^rane is a 
reticulum ^vith 
generally one 
big nucleolus 
or germinal 

0J)Ot. 

Between 
these medium- 
sized follicles 
and the small 
follicles of the 
cortical layer 
we lind all in- 
termediate de- 
grees as regards 
size of the fol- 
licle and the 
ovum, and es- 
pecially as re- 
gards the shape 
of the cells of 
the merabrana 
granulosa, the 
intermediate sizes of follicles being lined by a granu- 
losa made up of a layer of polyhedi-al epithelial 
cells. 

347. The deeper Graafian follicles — i.e. those 
that are to be regarded as big follicles — contain an 
o\um, occasionally two or even three ova, which is 
similar to that of the previous follicles, except that it 
is larger, and its zona pellucida thicker. The ovum 
does not fill out the whole ca^-ity of the follicle, since 
at one side, between it and the membrana granulosa, 




Fii:. 248.— Large Graafian Follicle of the Ovan" ot 
Cat. 

The follicle is limited by a capsule. the thecafolliculi ; 
tlie lueiubraDa granulosa is composed of several 
layers of epithtlial cells. The ovum with its distinct 
1) valine zona pellucida is emliedded in the epithelial 
cells of the discus proligerus. The cavity of the 
follicle is filled with fluid, the liciuor foUiculi. 



390 Elements of Histology. 

there is an albuminous riuid, tljc ludiment of the 
liquor folliciili, 

348. The largest or most advanced follicles are of 
great size, easily visible by the naked eye, and con- 
tain a large quantity of this liquor folliculi (Fig. 248). 
In fact, the ovum occupies only a small part of the 
cavity of the follicle. The ovum is big, surrounded 
by a thick zona pellucida, is situated at one side, sur- 
rounded by the discus proligerus. This consists of 
layers of polyhedral cells, except the cells immediately 
around the zona pellucida, which are columnar. The 
ovum with its discus proligerus is connected with the 
membrana granulosa. This latter consists of stratified 
pavement epithelium, forming the entire lining of the 
follicle. The outermost layer of cells is columnar. 
The membrana propria of these big follicles is 
strenothened bv concentric lavers of the stroma 
cells, and this represents the tunica fibrosa (Henle) 
or outer coat of the follicle — theca folliculi externa. 
Xumerous blood capillaries connected into a network 
surround the big follicles. 

In those follicles that contain a greater or smaller 
amount of the liquor folliculi we notice in the fluid a 
variable number of detached granulosa cells in various 
stages of vacuolation, maceration, and disintegration. 

349. In connection with the medium-sized and 
large Graafian follicles are seen occasionally smaller 
or larger solid cylindrical or irregularly-shaped out- 
oTowths of the membrana o'ranulosa and membrana 
propria ; they indicate a new formation of Graafian 
follicles, some containing a new ovum. When these 
side branches become by active growth converted into 
larger follicles, they may remain in continuity with 
the parent follicle, or may be constricted off alto- 
gether. In the first case, we have one large follicle 
w^itli two or three ova, according as a parent follicle 
Itg-s given origin to one or two new outgrowths. 



Female Genital Organs. 391 

Amongst the epithelial cells constituting the 
stratified niembrana granulosa of the ripe follicles 
we notice a nucleated reticulum. 

Many follicles reach ripeness, as far as size and 
constituent elements are concerned, long before 
puberty, and they are subject to degeneration ; but 
this process of degeneration involves also follicles of 
smaller sizes. 

350. Before menstruation, generally one, occasion- 
ally two or more of the ripe follicles become very 
hyperh?emic. They grow, in consequence, very rapidly 
in size ; their liquor folliculi increases to such a degree 
that they reach the surface of the ovary ; finally — 
i.e. during menstruation — they burst at a superficial 
point ; the ovum, with its discus proligerus, is ejected, 
and brought into the abdominal ostium of the oviduct. 
The cavity of the follicle collapses, and a certain 
amount of l)lood, derived from the broken capillaries 
of the wall of the follicle, is effused into it. The 
follicle is converted into a corpus luteum by an active 
multiplication of the cells of the granulosa. New 
capillaries with connective-tissue cells derived from 
the theca folliculi externa gradually grow into the 
interior — i.e. between the cells of the granulosa. This 
growth gradually fills the follicle, except the centre ; 
this contains blood pigment in the shape of granules, 
chiefly contained in large cells, and a few new blood- 
vessels,^tlie blood pigment being the remains of the 
original blood eflused into the follicle. But, ulti- 
mately, all the pigment disappears, and a sort of 
gelatinous tissue occupies the centre, while the peri- 
phery — i.e. the greater part of the follicle — is made 
up of the hypertrophied granulosa, with young capil- 
lary vessels between its cells. The granulosa cells 
undergo fatty degeneration, becoming filled with 
several small fat globules, which gradually become 
confluent into a big globule. In this state the corpus 



392 Elements of Histology. 

luteum is complete, and has reached the height of its 
progressive growth. The tissue is then gradually 
al)Sorbed, and cicatricial tissue is left. When this 
shrinks it produces a shrinking of the corpus luteum. 
This represents the last stage in the life of a Graafian 
follicle. The corpus luteum of Graafian follicles, of 
which the ovum has been impregnated, grows to a 
much larger size than under other conditions, the 
granulosa becoming by overgrowtli much folded. 

351. Development of tlie ovary and Oraa- 
Han follicles.— The germinal epithelium of the sur- 
face of the foetal ovary at an early stage undergoes 
rapid multiplication, in consequence of which the epi- 
thelium becomes greatly thickened. The vascular 
stroma of the ovary at the same time increases, and 
permeates the thickened germinal epithelium. The 
two tissues, in fact, undergo mutual ingrowth, as is the 
case in the development of all glands — namely, the 
epithelial or glandular part sutlers mutual ingrowth 
with the vascular connective- tissue stroma. 

In the case of the ovary, larger and smaller 
islands or nests (Balfour) of epithelial cells are thus 
gradually diflferentiated ofi' from the superficial epi- 
thelium. These nests are largest in the depth and 
smallest near the surface. They remain in connec- 
tion with one another and with the surface for a 
considerable period. Even some time after birth 
some of the superficial nests are still connected with 
the surface epithelium, and with one another (Fig. 
249). These correspond to the ovarial tubes (Pfiiiger). 
While in the rabbit these nests are solid collections, 
in the dog they soon assume the character of tubular 
structures (Pfiiiger, Schafer). The cells constituting 
the nests undergo multi})lication (by karyomitosis), 
in consequence of which the nests increase in size, 
and even new nests may be constricted off from old 
ones {see also above). 



Female Genital Organs. 



193 



3.")2, At the earliest stages we notice in the 
germinal epithelium some of the cells becoming en- 
larged in their cell body, and especially their nucleus : 
these represent the primitive ova. AVhen the ger- 
minal epithelium undergoes the thickening above men- 
tioned, and when this thickened epithelium separates 




Fig. 240. — From a Vertical Section tlirough Ovary of a Xewly-borji Child. 
{Wo.ldeyer, in Strieker's Manual.) 

a, Germinal epithelium ; 6, ovarian tube ; c. primitive ova ; d, longer tubes be- 
coming consiricted off into several Graafian follicles; e, large nests; /, 
iso'ated finished Graafian follicles ; ^, blood-vessels. 

into the nests and ovarial tubes, there is a continued 
formation of primitive ova — i.e. cells of the nests 
undergo the enlargement of cell-body and nucleus 
by which they are converted into primitive ova. 
Like the other epithelial cells, tlie primitive ova 
of the nests and ovarial tubes undergo division into 
two or even more primitive ova after the mode 



394 Elements of Histology. 

of karyomitosis (Balfour). Thus each nest contains 
a series of ova. 

353. The ordinary small epithelial cells of the 
nests and ovarial tubes serve to form the membrana 
granulosa of the Graafian follicles. According to the 
number of ova in a nest or in an ovarial tube, a sub- 
division takes place in so many Graafian follicles, 
each consisting of one ovum with a more or less 
complete investment of small epithelial cells — i.e. a 
membrana granulosa. This subdivision is brought 
about by the ingrowth of the stroma into the nests. 

The superficial nests being the smallest, as above 
stated, form the cortical layer of the small Graafian 
follicles ; the deeper ones give origin to larger follicles. 
Thus we see that the ovum and the cells of the 
membrana granulosa are derived from the primary 
germinal epithelium ; all other parts — membrana 
})ropria, theca externa, stroma, and vessels — are de- 
rived from the foetal stroma. 

There is a ofood deal of evidence to show that ova 
and Graafian follicles are, as a rule, reproduced after 
birth (Pfliiger, Kolliker), although other observers 
(Bischofi", Waldeyer) hold the opposite Adew. 

3.54. (2) Till' oviduct. — The o\nduct consists of 
a lining epithelium, a mucous membrane, a muscular 
coat, and an outer fibrous coat — the serous covering, 
or peritoneum. The epithelium is columnar and 
ciliated. The mucous membrane is much folded ; it 
is a connective-tissue membrane with networks of 
capillary blood vessels. In man and mammals there 
are no proper glands present, although there are seen 
appearances in sections which seem to indicate the 
existence of short gland tubes ; but these appear- 
ances are explained by the folds of the mucous 
membrane. The muscular coat is composed of non- 
striped muscular tissue of a pre-eminently circular 
arrangement \ in the outer part there are a few 



Female Gexital Orgaxs. 395 

oblique aiul longitudinal bundles. The serous cover- 
ing contains numerous elastic tii)ril~^ in a connective- 
tissue matrix. 

355. (3) The uterus. — The epithelium lining 
the cavity of the uterus is a single la^'er of columnar 
cells, each with a l)undle of cilia on their free sur- 
face. These are very easily detached, and therefore 
difficult to tind in a hardened and preserved specimen. 
But in the fresh and well-preserved human uterus 
(Friedlander), as well as in that of mammals, the 
cells are distinctly ciliated. The whole canal of the 
cervix is in the adult lined with ciliated epithelium, 
but in children, according to Lott, only in tlie upper 
half. The surface of the portio vaginalis uteri is, 
like that of the vagina, covered with stratitied pave- 
ment epithelium. 

356. The mucous membrane of the cervix is 
diflerent from that of the fundus. In the former 
it is a fibrous tissue possessed of permanent folds — 
the palma? plicatoe. Few thin bundles of non-striped 
muscular tissue penetrate into these from the outer 
muscular coat. Between the palma? plicata? are the 
openings of minute gland-tubes, more or less cylin- 
drical in shape. They possess a membrana propria 
and a distinct lumen lined with a single layer of 
columnar epithelial cells, which, according to some 
observers, are ciliated in the newly-born child, but, 
according to Friedlander, are alwavs non-ciliated. 
Goblet cells are met with amongst the lining e^rti- 
thelium. Several observers (Kolliker, Hennig, Tyler 
Smith, and others) maintain the existence of minute, 
thin, and long vascular papilhe projecting above the 
general surface of the mucous membrane in the lower 
})art of the cervix ; these apparent papilla? are, how- 
ever, only due to sections through the folds of the 
mucous membrane. The mucous membrane of the 
fundus is a spongy plexus of tine bundles of fibrous 



396 Elements of Histology. 

tissue, covered or lined respectively with numerous 
small endothelial plates, each with an oval flattened 
nucleus. The spaces of this spongy substance are 
lymph spaces, and contain the glands and the blood- 
vessels (Leopold). 

357. The glands — glaiKliilii' iitei'iiiSB — are 
short tubular glands lodged in the mucous mem- 
brane and opening into the uterine cavity. During 
puberty their number and their size increase con- 
siderably, new glands being formed by the ingrowth 
of the surface epithelium into the mucous membrane 
(Kundrat and Engelmann). During menstruation, 
and especially during pregnancy, they greatly increase 
in length. They are more or less wavy and branched 
at the bottom. A delicate membrana propria forms 
the boundary of the tube ; a distinct lumen is seen 
in the middle, and this is lined with a single layer 
of ciliated columnar epithelium (Allen Tliomson, 
Nylander, Friedliinder, and others). 

358. Durino- menstruation the thickness of the 
mucous membrane increases, the epithelium of the 
surface and of the greater part of the glands being 
destroyed by fatty degeneration, and linally altogether 
detached. Afterwards its restitution takes place from 
the remnant in the depth of the glands. But accord- 
ing to J. Williams and also Wyder, the greater part 
of the mucous membrane, in addition to the epithe- 
lium, is destroyed during menstruation. 

The muscular coat forms the thickest part of the 
wall of the uterus ; it is composed entirely of the non- 
striped variety. 

In the cornua uteri of mammals the muscular 
coat is generally composed of an inner thicker circular 
and an outer thinner longitudinal stratum, a few 
oblique bundles passing from the latter into the 
former. In the human uterus the muscular coat is 
composed of an outer thin longitudinal, a middle thick 



FiiMAr.E Gkxital Okgaxs. 397 

layer of ciivular bundles, and an inner thick one of 
oblique and circular bundles. Within these layers 
the bundles form plexuses. 

359. The arterioles in the cervix and their 
capillaries are distinguislied by the great thickness of 
their wall. The mucous membrane contains the 
capillari/ netioorks. These discharge their blood into 
veins situated in the muscular coat. Here the veins 
are very numerous and arranged in dense j^lexuses, 
those of the outer and inner stratum beinof smaller 
than those of the middle stratum, where thev corre- 
spond to huge irregular sinuses, the bundles of 
muscular tissue of the muscular coat giving special 
support to these sinuses. Hence the plexus of venous 
sinuses of the middle stratum represents a sort of 
cavernous tissue. 

360. The lympliaties are very numerous ; in 
the connective tissue of the muscular coat are lymph 
sinuses and lymph clefts forming an intercommuni- 
cating system ; they take up the lymph sinuses of the 
mucous membrane above mentioned, and on the other 
hand lead into a plexus of efferent lymphatic vessels 
with valves, situated in the subserous connective tissue. 

The nerves entering the mucous membrane are 
connected with ganglia. According to Lindgren, 
there is in the mucous membrane a plexus of non- 
medullated nerve fibres which, near the epithelium, 
break up into their constituent primitive fibrill^. 

361. (4) Tlie vag-iiia — The epithelium lining 
the mucous membrane is a thick, stratified pavement 
epithelium. The superficial part of the mucous mem- 
brane — i.e. the mucosa — is a dense, fibrous connective 
tissue with numerous networks of elastic fibres ; it 
projects into the epithelium in the shape of numerous 
long, simple or compound papillae, each with a single 
or complex loop of capillary blood-vessels. The 
mucosa with the covering epithelium projects above 



398 Elements of Histology. 

the general surface in the shape of longer or shorter, 
conical or irregular, pointed or blunt, permanent 
folds — the rugse. These contain a plexus of large 
veins, between which are bundles of non-striped 
muscular tissue ; hence they resemble a sort of 
cavernous tissue. 

Outside of the mucosa is the loose submucosa, 
containing a second venous plexus ; its meshes are 
elongated and parallel to the long axis of the vagina. 
Outside of the submucous tissue is the muscular coat, 
consisting of an inner circular and an outer longitu- 
dinal stratum of non-striped muscular tissue. Oblique 
bundles pass from one stratum into the other. From 
the circular stratum bundles may l^e traced into the 
submucosa and mucosa. A layer of fibrous tissue 
forms the outer boundary of the wall of the vagina, 
and in it is the most conspicuous plexus of veins, the 
plexus venosus vaginalis. This plexus also contains 
Wndles of non-striped muscular tissue, and therefore 
resembles a cavernous tissue (Gussenbaur). It is 
not quite definitely ascertained whether or not there 
are secreting glands in the mucous membrane of the 
vagina. Yon Preuschen and also Hennig described 
tubular glands in the upper part of the fornix and in 
the introitus vagina?. 

The lymphatics form plexuses in the mucosa, sub- 
mucosa, and the muscular coat. The first are small 
vessels, the second are larger than the third and 
possess valves. The efferent vessels form a rich 
plexus of large trunks with saccular dilatations in 
the outer fibrous coat. 

'J'here are in the mucous membrane solitary lymph 
follicles and difi'use adenoid tissue (Loevenstein). 

Numerous ganglia are contained in the nerve 
plexus belonging to the muscular coat. 

End bulbs in connection with the nerve fibres of 
the mucosa have been mentioned in Chapter XV. 



Female Genital Organs. 399 

362. (5) TIk' iirrllira. -^The structure of the 
female urethra is siinihir to that of the male, except 
that the lining epithelium is a sort of stratified 
transitional epithelium, the superficial cells being 
short, columnar, or club-shaped ; underneath this layer 
are several layers of polyhedral, or cubical cells. 
Near the orificium externum the epithelium is 
stratified ]3avenient epithelium. 

The muscular coat is composed of an inner longi- 
tudinal, and an outer circular, layer of non-striped 
muscular tissue. 

363. (6) Tlie iiyiiiplise, clitorif^, aii<l vcsti- 
biiliiiii. — These are lined with thick stratified epi- 
thelium ; underneath is a fibrous connective-tissue 
mucous membrane, extending into the epithelium in 
the shape of C3^1indrical pajjill^e with capillary loops 
and nerve endings (end bulbs). The nympha^ contain 
large sebaceous follicles, but no hairs. 

The nymphse contain a plexus of large veins with 
bundles of non-striped muscular tissue ; hence it 
resembles a cavernous tissue (Gussenbaur). The 
corpora cavernosa of the clitoris, the glans clitoridis, 
and the bulbi vestibuli, corresjjond to the analogous 
parts in the penis of the male. The glands of 
Bartholin correspond in structure to the glands of 
(Jowper in the male. 



400 



CHAPTER XXXV. 

THE MAM M A R Y r; L A X D . 

364. This, like other glands, consists of a frame- 
work and parenchyma. The former is lamellar fibrous 
connective tissue subdividing the latter into lobes and 
lobules and containing a certain amount of elastic 
fibres. In some animals (rabbit, guinea-pig) there are 
also small bundles of non-striped muscular tissue. 
From the interlobular septa tine bundles of fibrous 
tissue with branched connective-tissue corpuscles pass 
between the alveoli of the gland substance. The 
amount of this interalveolar tissue varies in difterent 
places, l3ut in the active gland is always relatively 
scanty. 

Migratory or lymph corpuscles are to be met with 
in the interalveolar connective tissue of both active 
and resting glands. In the latter they are more 
numerous than in the former. According to Creighton, 
they are derived, in the resting gland, from the epi- 
thelium of the o'land alveoli. Granular large vellow 
(pigmented) nucleated cells occur in the connect! v% 
tissue, and also in the alveoli of the resting' 
o^land, and Creio:hton considers them both identical, 
and derived from the alveolar epithelium. And 
according to this author, the production of these cells 
would constitute the principal function of the resting 
gland. 

The large ducts as they pass from the gland to the 
nipple acquire a thick sheath, containing bundles 
of non-striped muscular tissue. These latter are 



jlfA MM.l K ) ' GlANP. 



401 



derived from tlie bundles of non-striped muscular 
tissue present in the skin of the nipple of the ])re;ist. 

The small ducts in the lolniles of the gland tissue 
possess a membrana propria, and a lining — a single 
layer of longer or shorter columnar epithelial cells. 

The terminal branches of the ducts — i.e. just 




Fig. 2oO.— From a Section through the JIamniary Gland of Cat in a late 
stage of pregnancy. {Atlas.) 

a. Epithelial cells lining tlie gland-alvedli, seen iu profile; b, the same, seen 
from the surface. Many epithelial cells coutiiiu an oil globule. In the cavity 
of some of the alveoli are milk globules and granular matter. 



before these latter pass into the alveoli — are lined ^vith 
a single layer of flattened pavement epithelium cells ; 
they are analogous to the intermediate portion of the 
ducts of the salivary glands [see Chap. XXIII.). 

365. Each of these terminal branches divides and 

takes up several alveoli (Fig. 250). These are wavy 

tubes, saccular or flask-shaped. The alveoli are 

larger in diameter than the intralobular ducts. Each 

A A 



40 2 Elements of Histology. 

alveolus in tlie active gland has a relatively large 
cavity, varying in different alveoli ; it is lined with a 
single layer of polyhedral, granular-looking, or short 
columnar epithelial cells, each with a spherical nucleus ; 
a membrana propria forms the outer limit. This 
membrana propria, like that of the salivar}^, lachrymal 
and other glands, is a basket-work of branched cells. 

In the active gland each epithelial cell is capable 
of forming in its interior one or more smaller or larger 
oil globules. These may, and generally do, become 
confluent, and, pressing the nucleus towards one side 
of the cell, give to the latter the resemblance of a fat- 
cell. The oil globules linally pass out from the cell 
protoplasm into the lumen of the alveolus, and 
represent now the milk globules. The cell resumes its 
former solid character, and commences again to form 
oil globules in its protoplasm. The epithelial cells, 
as long as the secretion of milk lasts, go on again and 
aerain forming: oil orlobules in the above manner 
without being themselves destroyed (Langer). The 
milk globules, when in the lumen of the alveoli, are 
enveloped in a delicate cuticle — the albumin mem- 
brane of Ascherson, which they receive from the cell 
protoplasm. 

According to the state of secretion, most epithelial 
cells lining an alveolus may be in the condition of 
forming oil globules, or only some of them ; and 
according to the rate in which milk globules are 
formed and carried away, the alveoli differ in the 
number of milk globules they contain. 

According to Schmid, the epithelial cells, after 
having secreted milk globules for some time, finally 
break up, and are replaced by new epithelial cells 
derived by the division of the other still active 
epithelial cells. 

366. The resting gland — i.e. the gland of a non-preg- 
nant or non-suckling individual — contains, compara- 



Ma.umakv Gland. 403 

tivfly sj»eal<iii,i,% few alveuli, but a great <leal of tilnous 
connective tissue ; the alveoli are all solid cylinders, 
containing within the limiting nieinbrana propria 
masses of polyliedral granular looking epithelial cells. 
During pregnancy these solid cylinders undergo mul- 
tiplication, elongation, and thickening, owing to the 
rapid division of the constituent epithelial cells. 

Finally, when milk secretion commences, the cells 
occupying the central part of the alveolus undergo the 
fatty degeneration just like the peripheral cells, but 
they — i.e. the central cells — are eliminated, while the 
peripheral ones remain. The central cells are the 
cohstrum corpj'.sries, and consequently they are found 
in the milk of the first few days only. 

3G7. Ordinary milk contains no colostrum corpus- 
cles, ])ut only milk globules of many various sizes, from 
the size of a granule to that of a globule several times 
as big as an epithelial cell of an alveolus of the milk 
gland. These large drops are produced by fusion of 
small globules after having passed out of the alveoli. 
Each milk globule is an oil globule surrounded, as 
stated above, by a thin albuminous envelope — Ascher- 
son's membrane. The small bits of granular substance 
met with here and there are probably the remains of 
broken-down protoplasm of epithelial cells, 

3G8. Each gland alveolus is surrounded V^y a dense 
network of' capWarij Wood-vessels. The alveoli are 
surrounded by hjmpJi spaces like those in the salivary 
glands (Covne), and these spaces lead into aetiKorks of 
hjiiii)lifdic vessels of the interlobular connective tissue. 



404 



CHAPTER XXXVI. 

THK SKIN. 

369. The skin consists of the following layers 
(Fig. 252) : — (1) The epidermis; (2) the corium, or 
cutis vera, with the papilla? : (3) the subcutaneous 
tissue, with the adipose layer or the adipose tissue, 

370. (1) The epidermis (Fig. 25), in all its 
constituent elements, has been minutely described in 
Chapter III. Its thickness varies in different parts, 
and is chiefly dependent on the variable thickness of 
tlie stratum corneum. This is of great thickness in 
the palm of the hand and the sole of the foot. The 
stratum Malpigliii fits into the depressions between 
the papilla? of the corium as the interpapillary pro- 
cesses. The i^resence of prickle cells, of pigment 
granules, and of branched interstitial nucleated cells, 
etc., has been mentioned in Chapter III. 

There occur in the stratum ]Malj)ighii migrator}- 
cells of granular aspect ; they appear to migrate from 
the papillary layer of the corium into the stratum 
IMalpighii (Biesiadecki). 

In the coloured skin — p.g. of the negro — pigment 
granules are abundant in the cell substance of the 
stratum Malpigliii, especially in the deeper layers ; 
but there is present an almost continuous layer of 
pigment in the superficial layers of the stratum 
corneum (Fig. 251). 

371. (2) The coriiiiii is a dense feltwork of 
bundles of fibrous connective tissue, w^ith a large 
admixture of networks of elastic fibres. From the 



Sa'/iv. 



405 



surface of the coriuui project small conical or cylin- 
drical papilla'.. These are best developed in those 
parts where the skin is thick — e.g. volar side of 
hand and foot, scalp, lips of mouthy etc. Between 




Fig, 261. — From Vertical Section througli Epidermis of Skin of Finger of 
Negro. (Photo. Moderate magnification.) 

a, Surface of stratum corneura, much pijjiuented; ft, stratum corneum ; e, 
stratum Maliiighii, containing pigment ni its cells; (?, corinm with papilhe 
extending into the stratum Malpigliii. 



the surface of the coriuni and the epidermis there 
is a basement membrane. Migratory cells, with and 
without pigment granules in their interior, are met 
with, especially in the superficial part of the corium ; 
they, as well as the fixed or branched connective- 
tissue corpuscles (see par. 40), and other structures, as 
vessels and nerves, lie in the interfascicular spaces. 



4o6 



Elements of Histology. 



372. (3) The supei^cial part of the subcuta- 
iieoii«» tissue insensibly merges into the deep part of 
the corium ; it cjiisistsof bundles of fibrous connective 
tissue aggi-egated into trabeculse crossing one another 
and interlacing in a complex manner. Numerous 











Fig. 252. — ^Vertical Section through the Skin of Human Finger. 

fl. Stratum comeuin : h, stratum lucidtim ; c. stratum Malpighii ; d, Meissner's, 
or tactile corpuscle ; e, blood-vessels cut across ; /, sudoriferous canal or 
duct. 

elastic fibres are attached to these trabeculse. It con- 
tains groups of fat cells, in many places arranged as 
more or less continuous lobules of fat tissue, foinning 
the stratum adiposam. These lobules are separated 
by septa of fibrous connective tissue : their structure 
and development, and the distribution of the blood- 
vessels amongst the fat cells, have been described 
(Fig. 41, and on pp. 55 and 56). The deep part of the 
subcutaneous tissue is loose in texture, and contains 
the large vascular trunks and big nerve branches. 
373. The superficial part of the subcutaneous 



tissue, or, as sonic liavc it, the deep part of the 
coriiiin, contains the sudoriparous or stveat (jlaiuh. 
Each gland is a single tube coiled up into a dens"^ 
mass of about -^^ of an inch in diameter — in some 
places, as in the axilla, reaching as much as six times 
this size. From each gland a duct — the sudori- 
ferous canal — passes through the corium in a slightly 
wavy and vertical direction towards the epidermis ; 
it penetrates more or less spirally through the inter- 
pajjillary process of the stratum Malpighii and the 
rest of the ej)idermis, and appears with an open mouth 
on the free surface of the skin. 

The total number of sweat glands in the human 
skin has been computed by Krause to be over two 
millions ; but it varies greatly in different parts of the 
body, the largest number occurring in the palm of 
the hand, the next in the sole of the foot, the next 
on the dorsum of the hand and foot, and the smallest 
in the skin of the dorsum of the trunk, 

374. The sudoriferous canal and the coiled tube 
possess a distinct lumen ; this is lined with a delicate 
cuticle, especially marked in the sudoriferous canal 
and in the commencement of the coiled tube. In the 
epidermis the lumen bordered by this cuticle is all 
that is present of the sudoriferous canal. It receives 
a continuation from the deep layers of the stratum 
Malpighii and from the basement membrane ; the 
former is the lining epithelium, the latter the limiting 
membrana propria of the sudoriferous canal. The 
epithelium consists of two or three layers of small 
polyhedral cells, each with a spherical or oval nucleus. 

375. The structure of the sudoriferous canal is, 
then, a limiting membrana propria, an epithelium 
composed of two or three layers of polyhedral cells, an 
internal delicate membrane, and, finally, the central 
cavity, or lumen. 

The first part — about one-third or one-fourth — 



4o8 



Elements of Histology. 



of the coiled tube (Fig. 253) is of the same stnu-ture, 
and is directly continuous with the sudoriferous canal, 
with which it is identical, not only in structure, but 
in size. The remainder of the coiled tube — i.e. the 
distal part — is larger in diameter, and differs in these 
essential respects, that its epithelium is a single layer 




Fig. 253. — From a Section tlirough Human Skin, showing the sweat gland 
tubes cut in various directions. {Atlas.) 

u, First part of the coiled tuljs seen in longitudinal section ; b, the same seen 
in cross-section ; c, distal part seen in longitudinal section ; d, the same 

seen in cross-section. 

of transparent columnar cells, and that tliere is 
between this and the limiting merabrana propria a 
kfjjer of non-striped muscle cells (Kolliker) arranged 
parallel with the long axis of the tube. In some 
places, as in the palm of the hand and foot, in the 
scrotum, tlie nipple of the breast, the scalp, Init 
especially in the axilla, this distal portion of the coiled 
tube is of \evy great length and breadth, and its 
epithelial cells contain a variable amount of granules. 
It appears to me that the cells resemble in this 
respect those of the serous salivary glands and the 



S/c/x. 409 

chief cells of the gastric ghmds (Langley), inasmuch 
as they produce in their interior hirger or siualler 
granules which are used up during secretion, from the 
periphery towards the lumen. 

376. The ceriiiiiiiioiis g-laiids of the meatus 
auditorius externus are of the same structure as the 
distal portion just described, except that the inner 
part of the cell protoplasm of the epithelium contains 
yellowish or brownish pigment, found also in their 
secretion — i.e. in the w^ax of the ear. 

Around the anus there is an elliptical zone, in the 
skin of which are found large coiled gland tubes — the 
circiim-anal glands of A. Gay — which are identical in 
structure with the distal portion of the sweat gland- 
tubes. 

377. The sweat gland develops as a solid cylin- 
drical outgrowth of the stratum Malpighii of the 
epidermis, which gradually elongates till it reaches 
the superficial part of the subcutaneous tissue, where 
it commences to coil. The lumen of the tube is of 
later appearance. The membrana propria is derived 
from the tissue of the cutis, but the epithelium and 
muscular layer are both derived from the original 
outgrowth of the epidermis. 

378. The liaii'-follicles (Fig. 254).— The skin 
almost everywhere contains cylindrical yb/Zic^es, planted 
more or less near to one another, and in groups. In 
each of them is fixed the root of a hair ; that part of 
the hair which i^rojects beyond the general surface of 
the skin is the slia/t. 

A very few places contain no hair follicles, such, 
for instance, as the volar side of the hand and foot, 
and the skin of the penis. 

Tn size, the hairs and hair-follicles differ in dif- 
ferent parts. Those of the scalp, the cilia of the eye- 
lids, the hairs of the axilla and pubic region, those of 
the male whiskers and moustache, are coarse and 



4TO 



Elemexts of Histology. 



thick, while the hairs of other places — e.fj. the outer 
surface of the eyelids, the inside of the arm and fore- 
ann, etc. — are very minute ; but as regards structure, 
they are all very much alike. 

379. A complete hair and hair-follicle — that is, 







trO 






Fig. 254.— Longitudinal Section through a Human Hair. (Atlas.) 

1, Epidermis; 2, moutli of hair follicle: 3. sebaceous follicle; 4, musculus 
arrector pili ; 5, papilla of hair ; 6, adipose tissue. 

the papillary hair of Unna — shows the following 
structure : — 

The hair-foUide. Each hair-follicle commences on 
the free surface of the skin with a funnel-shaped 
opening or movJlt : it |;asses in an ohlique direction 



throiiiili the corium into the subcutaneous tissue, in 
whose middle strata — i.e. in the stratum adiposum — 
it terminates with a sli^itly enlarged extremity, with 
which it is invaginated over a relatively small fungus- 
shaped papiUa. This latter is of tibrous tissue, con- 
taining numerous cells and a loop of capillary blood- 
vessels. 

Minute hairs do not reach with their follicles to 
such a depth as the large coarse hairs, the former not 
extending wnerallv much farther than the deep part 
of the corium. Degenerating and imperfect hairs (see 
below) also do not reach to such a depth as the perfect 
large hair follicles. In individuals with " woolly "* 
hail' — e.g. the negro race (C. Stewart), and in animals 
with *' woolly " hair, such as the fleece of sheep — the 
deep extremity of the hair-foHicle is curved, sometimes 
even slightly upwards. 

380. The structure of a liair-folliele is as follows 
(Fig. 255) : There is an outer coat composed of fibrous 
tissue : this is the fibrous coat of the liair-sac. It is 
merely a condensation of the surrounding fibrous 
tissue, and is continuous with the papilla at the 
extremity of the hair-follicle. About the end of the 
hair-follicle, or sometimes as much as in the lower 
fourth, there is inside of this tibrous layer of the hair- 
sac a single contintious layer of transversely or circu- 
I a rhj-ar ranged spimUe-sliaped ceUs, each with an oval 
flattened or staff"- shaped nucleus, completely resembling, 
and generally considered to be, non-striped muscle- 
cells. Inside of this layer of the hair-sac is a glassy- 
looking, hyaline, basement membrane, which is not 
very distinct in minute hairs, but is suthciently con- 
spicuous in large adult hair-follicles. This glassy 
membrane, as it is called, is a direct continuation of 
the basement membrane of the surface of the corium, 
and it can be traced as a delicate membrane also over 
the surface of the hair-papilla. 



412 



Elements of Histology. 



381. Next 
rootsheath, the 




to the glassy membrane is the outer 
most conspicuous part of the hair- 
follicle. It consists of a thick stratified epithelium of 
exactly the same nature as the stratum Malpighii of 

the epidermis, 
I '. ,. — ^i^-,^ _ with which it 

is directly con- 
tinuous, and 
from which it 
developed. 



IS 

In the outer 
root - sheath the 
layer of cells 
next to the glassy 
membrane is 
columnar, just 
like the deepest 
layer of cells in 
the stratum Mal- 
pighii ; then fol- 
low inwards seve- 
ral layers of poly- 
hedral cells; and, 
finally, flattened 
nucleated scales form the innermost boundary of the 
outer root -sheath. The stratum granulosum of the 
stratum Malpighii is not continued beyond the mouth 
of the hair-follicle, but there it is generally very marked. 
The outer root-sheath becomes greatly attenuated at 
the papilla — in fact, it is there continuous with the 
cells constituting the hair-bulb. 

382. The centre of the hair-follicle is occupied by 
the root of the hair, which terminates with an enlarged 
extremity — the Itair-hulb ; this grasps the whole 
papilla. The hair-bulb is composed of polyhedral 
ei)ithelial cells, separated from one another by cement 
substance, and continuous with the cells of the ex- 



Fig. 255. — Cross-section through a Hiunau Hair 
and Hair- follicle. 

«, ^farrow of liair; h. cortex of hair; c, cuticle of 
hair ; d, Huxley's layer of inner root-sheath ; e, 
Henle's layer of inner root-sheath ; /. outer root- 
sheath ; g, glassy Jiienibrane; /(, fibrous coat of hair- 
sac ; i, lymph spaces in the same. 



Sa'/n. 4 1 3 

tremity of tlie outer root-sheatli, from wliicli they 
originate in the first instance ; just over the papilla 
there is a special row of sJiort cohunnar cells, which 
are in an active state of multiplication, in consequence 
of which new cells are constantly being formed over 
the papilla. As a result of this there is a gradual 
pushing outwards, within the cavity of the hair- 
follicle, of the cells previously formed ; these cells 
form the hair itself. Nearest to the papilla all the 
cells of the hair are polyhedral, farther outwards — i.e. 
towards the surface of the skin — they become more 
elongated and spindle-shaped, and constitute the cells 
of the hair-substance ; except in the very centre of the 
hair, where they remain polyhedral, so as to represent 
the cells of the marrow of the hair, and in the peri- 
phery of the hair, where they remain more or less 
polyhedral, so as to form the inner root-sheath. 

383. The root of the liair, except at the hair- 
bulb, shows the following parts : The substance of the 
hair, the cuticle, and the inner root-sheath. The 
substance of the hair is composed of the hair -fibres — 
i.e. long thin fibres, or narrow long scales, each com- 
posed of hyaline horny substance, and possessed of a 
thin staff-shaped remnant of a nucleus. These are 
held together by a certain amount of interstitial 
cement substance. Towards the bulb they gradually 
change into the spindle-shaped cells above mentioned. 
They can be isolated by strong acids and alkalies. In 
pigmented hairs there occur numerous figment 
(jranules between the hair-fibres, but also diffused 
pigment in their substance. The same is noticed with 
reference to the hair-bulb — namely, pigment granules 
being present in the intercellular cement, and pig- 
ment also in the cell substance. In the centre of 
many hairs is a cylindrical marroiv, containing 
generally one row of ])olyhedral cells, which are, to a 
great extent, filled with air. 



414 



Elements of Histology. 



a I 




•384. On the surface of the haii--substance is a thin 
cuticle, a single layer of horny non-nucleated hyaline 
scales arranged more or less transversely ; they are 
imljiicated, and, according to the degree of imbrica- 
tion, the cuticle shows more or less marked projec- 
tions, which give to the circumference 
of the hair the appearance of minute 
teeth, like those of a saw. 

385. The inner root-sheath in 
well-formed, thick hairs is very dis- 
tinct, and consists of a delicate cuticle 
next to the cuticle of the hair ; then 
an inner, or Huxley's, layer, which 
is a single, or sometimes double, layer 
of horny cubical cells, each with a 
remnant of a nucleus ; and, finally, 
an outer, or HenleJs, layer — a single 
layer of non-nucleated horny cubical 
cells. 

The shaft of the hair (Fig. 256), 
or the part projecting over the free 
surface of the skin, is of exactly the 
same structure as the root, except that 
it possesses no inner root-sheath. 
386. As mentioned above, at the hair-bulb the 
polyhedral cells constituting this latter gradually pass 
into the different parts of the hair — i.e. marrow-sub- 
stance, cuticle, and inner root-sheath — and the con- 
tinual new production of cells over the jmpilla causes a 
gradual progression and conversion of the cells, and a 
corresponding growth in length of the hair. 

Pigmented hairs, as mentioned above, contain pig- 
ment granules between — i.e. in the interstitial sub- 
stance cementing together — the hair-fibres, and diffuse 
pigment in their substance. According to the amount 
of these pigments, but especially of the interstitial 
pigment granules (Pincus), the colour of the hair is 



Fig. -2.56. —Longitu- 
dinal View of the 
Shaft of a Pig- 
mented Human 
Hair. 



ilarroAV of 
b, fibres of 
substance ; 
cuticle. 



hair ; 

liaii- 

c. 



Sa'/x. 



415 



of a greater or lesser dark 
is oliieHy ditlVise pigment, 
neither the one nor the 
other pigment is present : 
in grey there is air at least 
in the superficial layers of 
the hair substance, besides 
absence of pigment. 

Sleek hairs are circular, 
curly oval, in cross-section. 
Sleek hairs are implanted 
with their h a i r - b u 1 b 
straight ; in curly hairs the 
hair-bulb forms a more or 
less pronounced hook. This 
is the cause for the more 
or less si)iral twisting of 
the hair-shaft of curly hairs 
during its growth outwards. 

387. Xew formation 
of liair (Fig. 257). — 
Every hair, be it fine and 
short or thick and long, 
\mder normal conditions, 
has only a limited exist- 
ence, for its hair-follicle, 
including the papilla, sooner 
or later undergoes degener- 
ation, and subsequent to 
this a new papilla and a 
new hair are formed in its 
place. What happens is 
this — the lower part of the 
hair-follicle, including the 
papilla and hair-bulb, de- 
generate and are gradu- 
ally absoi'bed. Then there 



tint, in red luiirs there 
In white or albino hairs 






fe''i'l't.:->.? -^ 





Fig. 257. — From a section through 
Human Scalp, showing a degen- 
erating hair. (Atlas.) 

a. Epidermis ; b, hair ; c, outer root- 
sheath of hair follicle ; d, sebace- 
ous follicle; f, arrector pili ; /, 
cyst grown out of the outer root- 
sheath; g, hair-kuob ; h, new out- 
growth of the outer root-sheath ; 
/, new papilla. 



4i6 Elements of Histology. 

is left only the uj^per part uf the follicle, and in the 
centre of this is the remainder — i.e. non-degenerated 
portion — of the hair-root. The fibres of this are at 
the extremity fringed out and lost amongst the cells 
of the outer root-sheath of the follicle. This repre- 
sents the hair-knoh (Henle). Xow, from the outer 
root-sheath a solid cylindiical outgrowtli of epithelial 
cells into the depth takes place ; against the extremity 
of this a new papilla is formed. In connection with 
this new papilla, and in the centre of that cylindrical 
outgrowth, a new hair-bulb and hair are formed, and 
as the latter gradually mows outwards towards the 
surface, it lifts, or rather pushes, the old hair — i.e. 
the hair-knob — out of the follicle. The outer part of 
the follicle of the old hair persists. 

Thus we find in all parts of the skin where hairs 
occur complete or j^apillarv hairs side by side with 
degeneratincT hairs or hair-knobs. 

388. Developiiieiit of liair. — In the human 
fcetus the liair-follicles make their first appearance 
about the end of the third m.onth, as solid cylindrical 
outgrowths from the stratum INIalpighii. This is the 
rudiment of the outer root-sheath. After having pene- 
trated a short distance into the corium, this latter 
becomes condensed around it as the rudiment of the 
hair-sac. and at the distal extremity forms the papilla 
2:rowinc( against the outer root sheath and invajicin- 
ating it. On the surface of the papilla a rapid mul- 
tiplication of the epithelial cells of this extremity of 
the outer root-sheath takes place, and this forms the 
hair-bulb, by the multiplication of whose cells the hair 
and the inner root-sheath are formed. As growth 
and multij^lication proceed at the hair bulb, so the 
new hair, with its pointed end, gradually reaches the 
outer surface. It does not at once penetrate the 
epidermis, but remains growing and burrowing its 
wav for some time in the stratum corneum of the 



Sa'/.v. 



417 



epidermis in a more or less horizontal direction, till it 
finally lifts itself out of this beyond the free surface. 

3iS9. In many mammals occur, amongst ordinary 
hairs, special large hairs, with huge hair-follicles 
planted deeply into the subcutaneous tissue ; such 




Fig. 25S.— Section througli the «kiii nf tlie Lip of a Rabbits Mouth. 
(Fhotorjraph. Loiv power.) 

Small ordinary hair-follicles, one hirge tactile hair and hair-follicle. Tlie dark 
thick hoiindarj- is the tissue of the hair-sac. the clear parts in.side are the 
masses of blood spaces, the dark line next to the hair itself is the outer 
root-sheath. 



are the big hairs in the skin about the lips of the mouth 
in the dog, cat, rabbit, guinea-pig, mouse and rat, etc. 
These are the tactile hairs (Fig. 258). Their hair-follicle 
possesses a thick hair-sac, in which are contained large 
sinuses intercommunicating with one another and 
with the blood system ; these sinuses are separated 
B B 



41 8 Elemexts of Histology. 

\)\ trabecul?e of non-strined muscular tissue, and 
represent, therefore, a cavernous tissue. The papilla 
is large, and so is the outer root-sheath and the 
hair-root in all its parts. There are vast numbers of 
nerve-fibres, distributed and terminating amongst the 
cells of the outer root-sneath (Arnstein). 

390. With each hair- follicle are connected one or 
tvro sehaceous foUirles. These consist of several fiask- 
shaped or oblong alveoli, joined into a common short 
duct opening into the hair-follicle near the surface — 
i.e. that part called the neck of the hair-follicle. 

The alveoli have a limiting membrana propria ; 
next to this is a layer of small polyhedral, granular- 
looking epithelial cells, each with a spherical or oval 
nucleus ; next to this, and filling the entire cavity of 
the alveolus, are large polyhedral cells, each with a 
■-spherical nucleus : the cell substance is filled with 
minute oil globules, between which is left a sort of 
honeycombed reticulated stroma. The cells nearer to 
the centre of the alveolus are the largest. Towards 
the duct they become shrivelled \\\} into an amorphous 
mass. The duct itself is a continuation of the outer 
root-sheath. 

As multiplication goes on in the marginal layer of 
epithelial cells — i.e. those next the membrana proprise 
— the products of this multiplication are gradually 
shifted forward towards the duct, and through this 
into the neck and rnoutli of the hair-follicle, where 
they constitute the elements oi sehuin. 

There is a very characteristic misproportion be- 
tween the size of the hair-follicle and that of the 
sebaceous gland in the embryo and newly-ljorn, the 
.sebaceous cjland Ijeing there so larije that it forms the 
most conspicuous part, the minute hairs (lanugo) 
being situated, as it were, in the duct of the sebaceous 
follicle. 

391. In connection with each hair-follicle, espe- 



Sa'/jv. 



419 



daily where they are of good size — as in the scalp — 
there is a bundle, or rather group of bundles, of non- 
sti-iped muscular tissue ; this is tlie arrector pili. It is 
inserted in the liaii--sac near the bulbous portion of the 







Fig. 259. — Vertical Section through the Human Xail and Nail-bed. 

a. Stratum Malpigbii of uail-bed; I), stratum .arrauulosuin of uail-bed • c Aeev 
layers of nail sulistaucc ; d, superfieiallayers of same. ' ' 

hair- follicle, and passes in an oblique direction towards 
the surface of the coriuni, grasping, as it were, on its 
way the sebaceous follicle, and terminating near the 
papillary layer of the surface of the corium. The 
arrector pili forms with the hair-follicle an acute 
angle — this latter being planted into the skin in an 



42 o Elements of Histology. 

oblique direction, as mentioned above — and conse- 
quently, when the arrector contracts, it has the effect 
of raising the hair-follicle and hair (cutis anserina — 
"goose's skin '), and of making the hair assume a 
more upright position (causes it, as we say, to " stand 
on end "). At the same time, it compresses the 
sebaceous follicle, and thus facilitates the discharge of 
the sebum. 

392. The corium of the scrotum, of the nipple of 
the breast, of the labia pudendi majora, and of the 
penis, contains numbers of bundles of non-striped 
muscular tissue (Kolliker), independent of the hairs ; 
these run in an oblique and horizontal direction, and 
form plexuses. 

393. The nails (Fig. 259).— We distinguish the 
hody of the nail from the free margin and from the 
root ; the body is the nail proper, and is fixed on to 
the nail-bed, while the nail-root is fixed on the nail- 
matrix — i.e. the posterior j)art of the nail-bed. The 
nail is inserted, with the greater part of its lateral and 
wdth its posterior margin, in the nail-groove, a fold 
by which the nail-matrix passes into the surrounding 
skin. 

394. The substance of the nail is made up of a 
large number of strata of homogeneous horny scales — 
the nail-cells — -each with a staff-shaped remnant of a 
nucleus. 

The corium of the nail-bed is higlily vascular : it 
is firmly fixed by stifi" bands of fibrous tissue on the 
subjacent periosteum ; it is covered with a stratum 
]\Ialpighii of the usual description, except that the 
stratum irranulosum is absent in the nail-matrix, but 
is present in a rudimentary state in the rest of the 
nail-bed. The nail itself rej^resents the stratum 
lucidum, of course of exaggerated thickness, situated 
over the stratum Malpighii of the nail-bed. There 
is no stratum corneum over the nail. 



The stratum Malpighii and coriuni of the nail-bed 
are placed into permanent minute folds, and the nail 
possesses on its lower surface corresponding linear 
indentations. 

395. In the foetal nail-bed the stratum Malpighii 
is covered with the usual stratum lucidum and stratum 
corneum, but the former is the larger : by a rapid 
multiplication of the cells of the stratum Malpighii, 
and a conversion of its superficial cells into the scales 
of the stratum lucidum. the fcetal nail is produced. 
At this early stage the nail is covered by stratum 
corneum. By the end of the fifth month the nail 
marcrin breaks throuijh this stratum corneum. and bv 
the seventh month the greater part of tlie nail has 
become clear of it. 

306. Till' bIood-ves«»eIs of the »kiii. — The 
blood-vessels are arranged in diflerent system < for the 
different parts of the skin (Tomsa) : — 

{(() There is. fir^^t, the vascular sy.stem of the 
adipose tissue, diflering in no way from the dis- 
tribution of blood-vessels in fat tissue of other places. 

(6) Then there is the vascular system of the hair- 
follicle. The papilla has a capillary loop, or rather 
a minute arteriole, a capillary loop, and a descending 
vein, and the fibrous ti.ssue of the hair-sac possesses 
capillaries arranged as a network with elongated 
meshes, with its afferent arteriole and eflerent vein. 

(c) The sebaceous follicle has its afferent arteriole 
and eflerent vein, and capillary networks surrounding 
the alveoli of the gland. The arrector pili and other 
bundles of non-striped muscular tissue possess capil- 
lary networks \\ ith elongated meshes. 

(d) The sweat glands have an afferent arteriole, 
from which proceeds a veiy rich network of capil- 
laries, twining and twisting round the gland-tube. 
The duct possesses its separate aff'erent arteriole and 
capillaries, forming elongated meshes. 



42 2 Elements of Histology. 

(e) The last arterial branches are those that reach 
the surface of the corium, and there break up into a 
dense capillarv network with loops for the papillae. 
In connection with these capillaries is a rich plexus of 

veins in the superficial layer of the corium. 




Fig. -260. —Skin of the Web of Frog of which the lymphatics had been in- 
° jected, showing the dense plexus of lympliatic vessels. {Photograph. 
Lov: poi'-er.) 

(/) In the nail-bed are dense networks of capil- 
laries, with loops for the above-named folds. 

397, The lysiipliatics (Fig. 260). — There are net- 
works of lymphatic vessels in all strata of the skin ; 
they are, more or less, of horizontal expansion, with 
oblique branches passing l^etween them. Their wall 
is a sinfde laver of endothelial cells, and some of them 
possess valves. Those of the surface of the corium 



Sa'/x. 4-3 

take up lyiuplKitics of the papilla?. The subcutaneous 
lymphatics are the biggest. The fat tissue, the sweat- 
glands, and the hair-follicles possess their own lym- 
phatic clefts and sinuses. The interfascicular spaces 
of the corium and subcutaneous tissue are directly 
continuous with the lymphatic vessels in these parts. 

398. The iierve^». — The nerve-branches break up 
into a dense plexus of fine nerve fibres in the super- 
ficial layer of the corium. This plexus extends hori- 
zontally, and gives ofi" numerous elementary fibrils 
to the stratum Malpighii, in which they ascend verti- 
cally and in a more or less wavy fashion towards the 
stratum lucidum (Langerhans, Podkopaefi", Eberth, 
Eimer, Ranvier, and others). According to some, 
they teraiinate with a minute swelling ; according to 
others, they form networks ; according to more 
recent observations, some of the fibrils terminate 
also in the substance of the deep epithelial cells {see 
Chap. XIV.). 

The subcutaneous nerve-branches of some places 
— palm of hand and foot, and skin of penis — give 
off' single niedullated nerve fibres, terminating in a 
Pacinian corpuscle, mentioned in a former chapter. 
In the volar side of the fingers and toes there occur 
in some of the papillfe of the corium the tactile or 
Meissner's corpuscles, each connected with one or two 
meduUated nerve fibres, as described in a previous 
chapter. The outer root-sheath of the hair-follicles 
contains the terminations of fine nerve fibres, in the 
shape of primitive fibrillte (Jobert, Bonnet, and 
Arnstein). According to Jobert, the nerve fibres 
entwine the hair-follicle in circular turns. The 
tactile hairs possess a greater supply of nerves than 
the ordinary hair-follicles. 



424 



CHAPTEE XXXVII. 

THE CONJCXCTIVA AXD ITS GLANDS. 

399. (1) The eyelids (Fig. 261).— The outer 
layer of the eyelids is skin of ordinary description : 
the inner is a delicate, highly vascular membrane — 
the conjunctiva palpehrcn. This includes a firm plate 
— the tarsal plate. — which is not cartila^re, but very 
dense, white, fibrous tissue. In it lie embedded the 
Meibomian glands. These extend in each eyelid in a 
vertical direction from the distal margin of the tarsal 
plate to the free margin of the eyelid : in the posterior 
angle of this margin lies the opening or mouth of each 
of the Meibomian glands. 

The duct of a Meibomian gland is lined with a 
continuation of the stratified pavement epithelium, 
lining the free margin of the lid : it passes in the 
tarsal plate toward its distal margin, and takes up on 
all sidi-s sliort minute ducts, each of which becomes 
enlarged into a spherical, saccular, or llask-shaped 
alveolus. This is identical in structure and secretion 
icith the alveoli of the sebaceous follicles of the skin. 

400. The conjunctival layer is separated from the 
subcutaneous tissue of the skin layer of the eyelid by 
the bundles of the sphincter nrbicidaris — striped mus- 
cular tissue. Some bundles of this extend near the 
free margin of the lid, and represent what is known 
as the musculus ciliaris Riolani. This sends bundles 
around the mouth of the ^Meibomian ducts. 

401. At the anterior angle of the free margin of 
the lid are the evelashes or cilia, remarkable for their 



Conjunctiva and its Glands. 



425 



thickness and rapid reproduction. Xear the cilia, Viut 
towards the ^leiboniian ducts, open the ducts of 



.9 










\iT&, 



- ^® "P^^- 



yh 









*:■$• 



Y-^ 






K. 



"=S^ 











Fig. -261.— Vertical Section through the Upper Eyelid. (Waldeger.) 

1 CoDfunetiva • 2, skin ; 3. permanent folds of the conjunctiva ,- 4, bundles of 

' the sphincter orbicularis; 5, eyelashes : 6. mouth of the gland of ilohl ; 7, 

duct of the Meibomian gland : >, tarsal gland>. 

peculiar large glands — the glands of Mold. Each of 
these is a wavy or spiral tul>e, pa^^sing in a vertical 



426 Elements of Histology. 

direction from the margin of the lid towards its distal 
part ; it comjdetely coincides in structure with the 
large portion of a sweat gland — i.e. that part contain- 
ing a columnar epithelial lining, and between this and 
the membrana propria a longitudinal layer of non- 
striped muscular cells. 

The free margin is covered, as mentioned above, 
with stratified pavement epithelium, into which the 
mucous membrane extends in the shape of minute 
papillae. In the conjunctiva palpebral the epithelium 
is a thin stratified pavement epithelium ; there are 
no papilhe, but the sub-epithelial mucosa — that is, the 
layer situated between the epithelium of the surface 
and the tarsal plate — contains a dense network of 
capillary blood-vessels. 

402. Passing from the eyelids on to the eyeball, 
we have the continuation of the conjunctiva palpebrse 
— i.e. the fornix conjunctivae — -and, further, the con- 
junctiva fixed to the sclerotic, and terminating at the 
margin of the cornea — the conjunctiva l)ul])i. The 
epithelium covering the conjunctiva fornicis and con- 
junctiva bulbi is stratified epithelium, the superficial 
cells being short columnar ; next to the fornix the 
superficial cells are beautiful columnar, and the 
mucosa underneath the epithelium is placed in regular 
folds (Stiedn, Waldeyer). Towards the cornea the 
epithelium of the conjunctiva assumes the character 
of stratified pavement epithelium, and minute papillae 
extend into it fi-om the mucosa. 

403. The mucous membrane is fibrous tissue, con- 
taining the networks of capillary blood-vessels. 

Into the fornix lead minute mucous glands, em- 
bedded in the conjunctiva fornicis; they are the glands 
of Krause. Similar glands exist in the distal "portion 
of the tarsal plate. 

404. The blood-vessels of the conjunctiva 
terminate as the capillary network of the su])erficial 



Conjunctiva and its Glands. 427 

layer of the mucosa, and as capillaiy networks for the 
Meibomian glands, Krause's gland, etc. Around the 
corneal margin the conjunctival vessels are particu- 
larly dense, and loops of ca})illaries extend from it 
into the very margin of the cornea. 

405. The lyiii|>liafic«» form a superficial and 
deep network. Both are connected by short branches. 
The deep vessels are possessed of valves. The super- 
ficial plexus is densest at the limbus cornese, and they 
are in direct connection with the interfascicular lymph 
clefts, both of the sclerotic and cornea. In the 
margin of the lid the superficial lymphatics of the skin 
anastomose with those of the conjunctiva. 

Lymph follicles occur in groups in the conjunctiva 
of many mammals about the inner angle of the eye. 
In the lower eyelid of cattle they are very conspicuous, 
and known as the glands of Bruch. They are also 
well marked in the third lid of many mammals. 

According to Stieda and Morano, isolated lymph 
follicles occur also in the human conjunctiva. 

406. The nerves are very numerous in the con- 
junctiva ; they form plexuses of non-medullated fibres 
underneath the epithelium. From these plexuses fine 
fibrils pass into the epithelium of the surface, between 
whose cells they terminate as a network (Helfreich, 
Morano). End bulbs of Krause occur in great 
numbers in man and calf. They have been mentioned 
in a former chapter. 

407. (2) The lacliryiiial g-laiids are identical 
in structure with the serous or true salivary glands. 
The arrangement of the connective-tissue stroma, the 
nature and structure of the ducts — especially of the 
intralobular ducts— and alveoli, the distribution of 
blood-vessels and lymphatics, are exactly the same 
as in the true salivary glands. Reichel has found 
that the epithelial cells lining the alveoli are well 
defined, conical or cylindrical, transparent, and slightly 



428 Elements of Histology. 

granular during rest ; but during secretion they grow 
smaller, more opaque and more granular, their outlines 
are not well defined, and the nucleus becomes more 
spherical and placed more centrally. 

408. In most mammals there is in the inner angle 
of the eye, and closely placed against the surface of 
the eyeball, a gland called Harder's (jiand. Accord- 
ing to Wendt, this is either a true serous gland, like 
the lachrymal — as in the ox, sheep, and pig — or it is 
identical in structure with a sebaceous gland, as in 
the mouse, rat, and guinea-pig ; or it consists of two 
portions, one of which (white) is identical with a 
sebaceous, while the other (rose-coloured) is a true 
serous gland ; such is the case in the rabbit and hare 
According to Giacomini, a rudiment of Harders gland 
exists also in the ape and man. 



429 



CHAPTER XXXVIII. 

CORNEA, SCLEROTIC, LIGAMENTUM PECTINATUM AND 
CILIARY MUSCLE. 

400. T. The roriiea (Fig. 262) of man and many 
mauiDials consists of the following layers, counting 
from front to back : — 

(1) The epithelium of the anterior surface [see 
Fig. 26). This is a very transparent, stratified pave- 
ment epithelium, such as has been described in par. 
22. It is directly continuous with the epithelium of 
tlie conjunctiva, but it is more transparent; in dark 
pigmented eyes of mammals the epithelium of the 
conjunctiva is also pigmented. In these cases the 
pigment, as a rule, does not pass beyond the margin 
of the cornea. 

410. (2) Next follows a homogeneous elastic mem- 
brane, Bowman^s 'ineinhrane, or elastica anterior. It 
is best shown in the human eye, but is present, even 
though only rudimentary, in the eye of mammals. 

(3) Then follows the ground suhstaiice, or sub- 
stantia propria, of the cornea. This is composed of 
iamelhe of bundles of fibrous connective tissue. 
Neiofhbourinor lamellse are connected with one another 
by oblique bundles. 

The fibre bundles within each lamella run parallel 
to the surface of the cornea, but may cross one 
another under various angles. 

In the anterior layer of the ground substance some 
of the bundles pass through several lamellae in an 
oblique manner ; they represent the librse arcuatse. 



43° 



Elements of Histology. 



The fibrils within the bundles, and the bundles, 
and the lainelhv of bundles are held together by an 

interstitial, albu- 
;g7 niinous, semi-fluid ce- 
ment sul)stance, which, 
like other similar in- 
tei'stitial substances, 
belono's to the globu- 
lins, and is soluble in 
10 per cent, saline 
solution (Schweigger 
Seidel). A few elastic 
tibrils are seen here 
and thei'e. Between 
the lamellae are left the 
lacunas and canal iculi 
for the branched, flat- 
tened, nucleated, cor- 
neal corpuscles^ de- 
scribed in a previous 
chapter (Figs. 37, 38). 
They anastomose with 
one another within the 
same plane, and also, 
to a limited degree, 
with those of neigh- 
bouring planes. 

411. (4)Thenieni- 
l>i'aiia Desceiiioti, 
or elastica posterior, 
is a resistant elastic 
membrane, conspic- 
uous by its thickness 
in all corne?e, 

(5) The posterior 
surface of this mem- 
l^rane is covered with 




Fig. 2(32. — From a Vertieal Section 
through the Membranes of the Eve of a 
Child. {Atlas.) 

a. Cornea; b, sclerotic : c. \v\> ; d, processus 
ciliaris; e, ligameunnn pectinatiiui : /, 
ciliary imisck", Its meridional bundles; n 
choroid membrane; h. retina of the nra 
serrata; i, sphincter piipilla^ in cross- 
section. 



Cornea. 431 

a mosaic of ])eautit'vil pohjijomd endotlielidJ ceUs^ 
eacli with an oval nucleus — the endotheliuiii of 
Descemet's membrane. Under stimulation these 
cells contract. At first they appear slightly and 
numerously branched, but gradually their processes 
become longer and fewer, and ultimately they are 
reduced to minute clumps of nucleated protoplasm, 
each with a few long processes. 

There are no blood-vessels in the normal cornea, 
except in fretal life, when there is underneath the 
anterior epithelium a plexus of capillaries. 

The lymphatics are represented as the intercom- 
municating lymjih-canalicular system — i.e. the lacun?e 
and canaliculi of the corneal corpuscles ; and in con- 
nection with these are lymph channels lined with a 
continuous endothelium and containing; the nerve 
bundles. 

412. The nerves (Figs. 103, 105, 106) are distri- 
buted as the nerves of the anterior layers, and as 
those of the Descemet's membrane. The first form 
rich plexuses of tibrillated axis cylinders, with trian- 
gular nodal points (Cohnheim), in the anterior layers 
of the ground substance ; from this plexus pass 
obliquely through Bowman's membrane short branches 
— the rami perforantes (Kfilliker) — and these imme- 
diately underneath the epithelium break up into their 
constituent primitive fibrils, the latter coming off 
the former brush-like (Cohnheim). These primitive 
fibrilhe ultimately ascend into the anterior epithelium 
(Hoyer, Cohnheim, and others), where they branch, 
and nearly reach the free surface. They always run 
between the epithelial cells, and are connected into 
anet\Aork. According to some observers, they ter- 
minate w^ith free ends, pointed or knobbed : but 
according to others these apparent free ends are 
not in reality free endings (Figs. 107, 263 and 
264). 



43 2 



Elemests of Histology 



413. The nerves of Descemet's membrane form 
also a j^lexus of non-medullated fibres in the posterior 
lavers of the o-round substance : from them come 
off vast numbers of primitive fibrilla?, running a more 




Fi'^'. 263. — From a Horizontal .Section through the Gokl-stained Cornea of 

" Rabbit ; the corneal (branched) cells are faintly indicated, but the 

nerve tibrillse are well marked, also their lateral branchlet.s, terminating 

apparently with a minute knob. {Photograph. Moderate magnification.) 

or less straight and long course, crossing one another 
often under right angles : they give off very fine 
fibrils, which are closely associated with the corneal 
corpuscles, without, however, really becoming con- 
tinuous wdth their protoplasm. 

414. II. The sclerotic consists of lamella? of 
tendinous tissue. The bundles of fibrous tissue are 
opaque as compared with those of the cornea, although 



SCLEKDl^IC. 



433 



they pabs insensibly into them. There are lymph 
clelts bet^veen the lamella? and trabeculse, and in 
them lie the flattened connective-tissue corpuscles, 
which, in the dark eyes of some mammals only, contain 




Fig. 264. — From the same preparation as in ijrecediiig tigiue, shuwing tlie 
tine Nerve Fibrils jiassing along the processes and bodies of the 
branched corneal corpuscles. (Pliotograph. Moderate magnification.) 

pigment granules. Numerous elastic fibrils are met 
with in the inner layers of the sclerotic. 

415. Between the sclerotic and choroid membrane 
is a loose fibrous tissue, which acts also as the sup- 
jjorting tissue for the blood-vessels passing to and from 
the choroid. The part of this loose tissue next 
to the sclerotic, and forming part, as it were, of 
the sclerotic, contains, in dark eyes of mammals, 
numerous pigmented connective-tissue corpuscles ; it 
c c 



43+ Elements of Histology. 

i« then called lamina Jusca. The rest — i.e. next 
to the choroid membrane — is the supra-choroidal 
tissue. 

416. There H re blood-vessels in the sclerotic, whicli 
belong to it ; they are arterioles, capillaries, and 
veins : in addition to these are the vascular branches 
passing to and from the choroid. 

417. III. The li»Jiiii«*iitiii" pec tiiiatuiii 
iridic [see Fig. 262) is a conical mass of spongy tissue 
joining hrndy the cornea and sclerotic to the iris and 
ciliary processes. It forms an intimate connection, on 
the one hand, with the junction of cornea and sclerotic, 
and on the other, withtliat of the iris and ciliary pro- 
cesses. This ligament is composed of trabeculse and 
lamella? of stiff elastic fibre-, forming a continuity, on 
the one hand, with the lamina Descemeti of the cornea 
and the elastic fibres of the sclerotic, and on the other 
with the tissue of the ciliary border of the iris. The 
trabecular anastomose, so as to form a honeycombed 
plexus, and the spaces in this plexus are lined 
with a layer of flattened endothelial cells, directly 
continuous with the endothelium of Descemet's mem- 
brane on the one hand, and with the layer of endo- 
thelial cells covering the anterior surface of the iris 
on the other band. In some mammals, the sjiaces 
in the ligamentum pectinatum near the iris are 
very considerable, and are called the spaces of 
Fontana. 

The interlamellar and interfascicular lymph 
spaces of the sclerotic form an intercommunicating 
system. 

The nerves form a dense plexus of non-medullated 
fibres in the tissue of the sclerotic (Helfreich). 

At the point of junction of the cornea and sclerotic, 
but belonging to the latter, and in the immediate 
neii^hbonrhood of the ligamentum pectinatum iridis, 
is a circular canal — the canal of Sclilemni ; this is 



Ciliary Muscle. 435 

lined with (nidotheliuin, and is considered Ijy some 
(Schwalbe) as a lymphatic canal ; Ijy others (Leljer) 
as a venous vessel. 

418. IV. The <'iliar.v muscle (Fig. 2G-J), or 

tensor choroideie, is tixed to this ligamentum pecti- 
natum ; it is composecl of bundles of non-striped 
muscular tissue. This muscle consists of two parts : 
{a) one of circular bundles nearest to the iris — this 
is the portio Miilleri ; {h) the greater part is composed 
of radiating bundles, passing from the ligamentum 
pectinatum in a meridional direction for a consider- 
able distance backwards into the tissue of the choroid 
membrane. It occupies the space between the liga- 
mentum pectinatuDi, sclerotic, ciliary processes, and 
the adjoining portion of the choroid membrane. 
The bundles of the muscle are arranged more 
or less in lamellpe ; within each lamella they form 
plexuses. 

A rich plexus of non-medullated nerve fibres, with 
groups of ganglion cells, belongs to the ciliary muscle. 



436 



CHAPTER XXXIX 

IRIS, CILIARY PROCESSES AND CHOROID. 

419. I. The ii'is consists of the following layers : — 

(1) The endothelium of the anterior surface : trans- 
parent, flattened, or polyhedral cells, each with a 
spherical or slightly oval nucleus ; in dark-coloured 
eyes of man and mammals brown pigment granules 
are contained in the cell substance, 

(2) A delicate hyaline basement membrane : it is 
continuous throucjh the trabecule of the lisramentum 
pectinatum with the membrana Desceraeti of the 
cornea. 

(3) The substantia propria : this i-, the ground 
substance ; it consists of fibrous connective tissue in 
bundles, accompanying the blood-vessels, which are 
very numerous in the tissue of the iris. Many 
connective-tissue corpuscles are found in the sub- 
stantia propria : they are more or less branched, and 
many of them CDntain, in all but albino and blue 
eyes, yellowish-brown pigment granules. The depth 
of the colour varies according to the number of these 
pigmented connective-tissue cells, and to the amount 
of the pigment granules present in them. 

(4) A hyaline delicate basement membrane limits 
the substantia propria on the ])osterior surface ; this 
is an elastic membrane, and is continued over the 
ciliary processes and choroid as the lamina vitrea. 

420. (5) The last layer is the epithelium of the 
posterior surface : this is a layer of polyhedral cells, 
filled with dark pigment granules, except in albinos, 



JRIS. 



437 






where there are no pigment granules This enchj- 
theliuiu is called the uvea, or iapetum nigrum. The 
interstitial cement substiince 
between the cells is not pig- 
mented, but transparent. 

The name "uvea" is some- 
times applied to the whole of the 
iris, ciliary processes, and choroid 
membrane. 

In blue eyes the posterior 
epithelium is the only pigmented 
part of the iris, and so it is 
also in new-born children, whose 
iris appears blue. In all cases 
where the iris appears blue, 
this is due to the dark back 
— i.e. the pigmented epithelium 
of the posterior surface — being 
viewed throutjh a dull layer — 
i.e. the substance of the iris. 

421. Near the pupillary 
border the posterior section of 
the substantia propria contains 
a broad layer of circular bundles 
of non-striped muscular tissue : 
this is the spliincter pupiUct. 
In connection with this are 
bundles of non-striped mus- 
cular fibres, passing in a radi- 
ating direction towards the 
ciliary margin of the iris : these 
are the bundles of the dila- 
tator pupiUc(;, forming a sort of 

thin membrane near the posterior surface of the 
iris (Henle and others). At the ciliary margin 
the bundles take a circular direction and form a 
plexus (Ivanoff). 




Fi-; 



I - vessels 



I injected) uf the Iris and 
Choroid Membrane of the 
Eye of a Child. {Kolliker, 
after Arnold.) 

a, Capillaries of the choroid ; 
b, era serrata; c, iilood- 
vessels connected with, d, 
those of the ciliary pro- 
cesses, and with e, those 
of the iris; /, capillary 
network of the pupillary 
sphincter. 



43^ Elements of Histology. 

422. The blood-vessels (Fig. 265) of the iris 
are very numerous. The arteries are derived from 
the eirculus arteriosus iridis major, situated at the 
ciliar}" margin of the iris, and from the arteries of 
the ciliary processes. These arteries run in a radi- 
ating direction towards the pupillary margin, where 
they terminate in a dense network of capillaries for 
the sphincter pupilla?. But there are also numerous 
capillary blood-vessels of a more or less longitudinal 
direction near the posterior surface of the iris. The 
veins accompany the arteries, and both are situated 
in the middle stratum of the substantia propria. 

In the sheath of the Ijlood -vessels are lymplt clefts 
and lympli sinuses; there appear to be no other 
lymphatics. 

423. The nerve fibres are very numerous 
(Arnold, Formad), and in the outer or ciliary portion 
of the iris form a rich plexus, from which are derived : 
[a) networks of non-medullated fibres for the dilator 
pupilla3 : (h) a network of fine non-medullated fibres 
for the anterior surface ; and (c) a network of non- 
medullated fibres for the sphincter pupilhe. 

The capillary blood-vessels are also accompanied 
by fine nerve fibres (A. Meyer), and, according to 
Faber, there exist ganglion cells in these nerve net- 
works. 

424. TI. The miliary processes are similar in 
structure to the iris, except, of course, that they do 
not ])0ssess an anterior endothelium or an anterior 
basement membrane. The suhstantia propria is 
fibrous tissue with elastic fibres and numerous 
branched cells, pigmented in dark (but not in blue) 
eyes. The posterior basement membrane is very 
thick, and is called the lamina vitrea ; in it may be 
detected bundles of fine fibrils. It possesses perma- 
nent folds arranged in a network (H. Muller). The 
inside of it is covered with a layer of pigmented poly- 



Ciliary Processes. 



439 



licdral v\\\\\\v\\w\\\^W\(^ inpotu))i nigriDii : the cells are 
polygonal when viewed from the surface. The in- 
divkliial cells are separated by thin lines of a trans- 
parent cement substance. This pigmented epithelium 
is covered with a layer of transparent columnar 



%M 




Y'v^. 2(i(l — Fi-()iii a Vertical Section thr()uc;li the Ciliary Processes of the 
Ox's Eye. {Atlas.) 

u. Fil)roiis tissue with iiigiiiented cells; 6, loose niirons tissue fciniiiiiLr the 
proiier ineiiihi-ane of the ciliary process ; c. iiigiiieiited epithelium rovermg 
the posterior sui-fac-e of the ciliaiy process; (/, epitheloid cells, lorniiug the 
j>ars ciliaris rctiiuv covering the l)ai-l\ of the ciliary jirocesses; e, Zonula 
Zinnii, with laindles of lilircs. 

epitheloid cells, each w^ith an oval nucleus. These are 
closely fixed on the tapetum nigrum, and are the 
continuation of the retina over the ciliary processes : 
this is thenars ciliaris retince (Fig. 266). 

425. The arterial branches for the ciliary processes 



440 Elements of Histology. 

and muscle are cliieliy derived from the ciivulus 
arteriosus iridis major, and fnrn a dense network of 
capillaries for the former ; eacli ciliar}^ process pos- 
sesses a conical group of capillaries (Fig, 'l^o). 

426. III. The €lioi"oi<l membrane consists — 
counting from outwards, i.e. from the sclerotic, in- 
wards, i.e. towards 
.,.'"%•.. ,,-. the retina — of the fol- 

'^■^^!-0^'' ''^''^0^.. lowing layers :^ 

iiii^^^^'.'fi^^^ ^^^^"^^^h^: ( 1 ) The membrana 

'^0''^''y.!f^^:-' ■:|M^-%... " supra- choroidea. This 
vi^^^^^j.v^^'^^li^ ..•;jU5:^Sl?^ i'^ ^ Continuation of 

■^i^-^i}lv^^0^ •••■^'^v;^^''" the sclerotic, with 

which it is identical 

Fjir -ly^-, — Pimneuted Connective-tissue . ^•, 

"cells of the Choroid Coat. (Atlos.^ lU structure ; the spaCCS 

between its lamellae are 
lined with endothelium, and represent lymph spaces 
(Schwalbe). 

(2) Next follows an elastic layer which contains 
networks of elastic fibres, the branches of the arteries 
and veins, and, in its outer portion, pigmented cells 
(Fig. 267). 

427. (3) Then follows the membrana chorio-capil- 
laris, a dense network of capillary blood-vessels em- 
bedded in a tissue containing numerous branched and 
unbranched pigmented and unpigmented connective - 
tissue cells. 

(4) The lamina vitrea ; and, finally, 

(5) The tapetum nigrum, or the pigmented epithe- 
lium, which, however, is considered part of the retina. 
In the reofion of the ora serrata of the retina — i.e. 
next to the ciliary processes — also this zone of the 
choroidea is lined with a layer of transparent, 
columnar, epitheloid cells, representing the jDars 
ciliaris retinte. 

428. The arteriae ciliares breves and recurrentes, 
situated in the outer part of the choroidal tissue, form 



Choroip. 441 

iiltiniatcly tlx' tlciisc networks of capillaries fof the 
cliorio-capillai-ies. The veins derived from this pass 
into the outer part of the choroid, where they anasto- 
mose so as to form the peculiar large veins, which are 
called the vente vorticosse. 

In the eyes of some animils (cat, dog, sheep, ox) 
there exists a special layer of cells (cat, dog) or 
fibres (herbivora), which, owing to its capability of 
reflecting a great deal of light, is called the tapetum 
hicidnm or me iibrana versicolor of Fielding. This 
layer when present is situated between the stroma 
of the choroid (laver 2) and the membrana chorio- 
capillaris (layer 3). 



442 



CHAPTER XL. 

THE LENS AND VITREOUS BODY. 

429. (1) TIk* lens consists of a thick, firm, elastic 
capsule and of the lens substance. The former shows 
fine longitudinal strijB, and diminishes in thickness 
towards the posterior pole of the lens. The surface 
of the capsule facing the anterior surface of the lens 
substance is lined with a single layer of pol^^hedral, 
granular-looking, epithelial cells, each with a spherical 
or oval nucleus. This epithelium stops as such at the 
margin of the lens, where its cells, gradualh'^ elongat- 
ing, pass into the lens fibres. The nuclei of these lie 
in a curved plane belonging to the anterior half of the 
lens : this is the nuclear zone. The lens substance 
consists of the lens fibres. These are band-like, hexa- 
gonal in transverse section ; their outline is beset with 
numerous fine ridges and furrows, which in neigh- 
bouring fibres, fitting the one into the other, form a 
firm connection between the fibres (Valentin, Henle, 
Kolliker, and others). The fibres of the peripheral 
portion are broader and thicker, and their substance 
is less firm than those of the centre — i.e. of the lens 
nucleus. The substance of the lens fibres is finely 
granular and delicately and longitudinally striated. 

430. The lens fibres (Fig. 268) are arranged in 
concentric lamelLie, each consisting of a single layer of 
fibres joined by their broad surfaces. Each fibre is 
slightly enlarged at the extremities ; and in each 
lamella the fibres extend from the anterior to the 
posterior surface. Their extremities are in contact 



ViTRF.ous Body. 



443 



with the ends of the fibres of the sjinie lamelhi in tlie 
siUiires, or the rays of the so-called lens stars. In 
the lens of the newly-born child, the stars of both 
anterior and ])Osterior lamellae possess three such rays, 
while in the adidt each of these rays has secondary 
rays. Tn these rays there is a homogeneous thin layer 
of an albuminous cement substance ; a similar sub- 
stance in minute quantity is also present between the 
lamellve, and in it occur smaller or larger clefts and 
channels, which evidently carry the nutritious fluid for 
the lens fibres. 

431. (:2) The vitreous bo<ly is a fluid substance 
enclosed in a delicate hyaline capsule — the memhrana 
hyaloidea. This membrane, at 

tlie margin of the fossa patel- 
la ris of the vitreous body — i.e. 
the fossa in wliich the lens is 
lodged — and without covering 
this fossa, passes as the zonula 
ciliaris, or zonula Zinnii, or 
suspensory ligament of the lens, 
to tlie margin of the latter, to 
whicli it is firmly adhering. So 
it adheres also to the surface of 
the ciliary processes. The zonula 
Zinnii is hyaline and firm, and 
is strentjthened bv numbers of 
bundles of minute stifl' fibrils. 

Between the suspensoi y liga- 
ment of the lens, the margin of the lens and of the 
fossa patellaiis is a circular lymph space, called the 
canalis Petiti. 

Beneath tlie membrana hyaloidea are found iso- 
lated nucleated granular-looking cells (the sub-hyaloid 
cells of Ciaccio), possessed of amoeboid movement 
(Ivanofl). 

432. The substance of the corpus vitreum appears 




i ,:^'^>)^j ■^^)/ A jj^ - - 



Fig. 2(iS. — From a Section 
through the Lens of Dog. 
(Atlus.) 

Sliciwing four lamellse ; in 
each the component lens 
filires are cut across ; they 
appear as flattened hexa"- 
u'ons. 



444 Elements of Histot.ogy 

didereiitiuted by clefts, conct-ntric in the })Hripberal, 
radiating in the central part (Briicke, Hannover, 
Bowman, Ivanoff, Schwalbe). But these do not con- 
tain an}' distinct membranous structures (Stilling, 
IvanofF, Schwalbe). 

The canalis hyaloideus, or canal of Stilling, extends 
from the papilla nervi optici to the posterior capsule 
of the lens, and is lined with a continuation of the 
membrana hyaloidea. 

433. In the substance of the corpus vitreum occur 
isolated nucleated cells, possessed of amoeboid move- 
ments, and some contain vacuoles, indicating com- 
mencinjj desfeneration. Thev are all identical with 
white blood-corpuscles (Lieberklihn, Schwalbe). 

Fine V)undles of fibrils are occasionally seen in the 
substance of the vitreous body. 



445 



CHAPTER XLT. 



THE RETINA. 




±iJj±ULH 



SMAlAAl~---{ 



-A 



434. The retina (Fig. 269) consists of the follow- 
ing layers, counting from inwards towards the choroid 
membrane : — (1) 
The membrana li- 
mit ans interna, 
wliich is next to 
the membrana hya- 
loidea of the vi- 
treous body ; (2) 
the nerve fibre 
layer ; (3) the layer 
of c(anglion cells ; 
(4) the inner gi-an- 
ular or inner mole- 
cular layer ; (5) the 
layer of inner 
nuclei ; (6) the 
outer granular, or 
outer molecular, or 
internuclear layer : 
(7) the layer of 
outer nuclei; (8) 
th e m em br ana 
limitans externa ; 
(9) the layer of 
rods and cones ; 
and (10) the pig- 
mented epithelium of the retina, or the tapetum 
nigrum mentioned above (p. 439), which forms, at the 



^ ,- o . 
; o oo 



o ^3 Oa 
3 3 o a tt_ 




5-— 771 



Fi<r. 269. — From a Transverse Section through 
tlie Eye of Sheep ; peripheral portion of 
retina. (Atlas.) 

a. Inner parr of sclerotic ; b, supra-choroidal 
Cpigmeiited) lamellse; c, d. layers of choroid 
C'lat; e. pigmented epithelium of retina; /, 
hiyer of rods ; jr, cones ; 7i, layer of outer nuclei ; 
i," outer molecular layer; j, layer of inner 
nuclei ; k. inner molecular layer ; I, layer of 
Kanglion cells, •with the radial or Muller's 
fibres between ; jh, layer of nerve fibres. 



446 



Elemexts of Histology. 



same time, the inner lining epithelium of the choi-oid 
membrane. 

435. From this arranixement are excepted (n) the 





mm. 

\-J} f-fC-, ^r ^ ; 




Fig. 270.— Diagram of the Ner- Fi^ 
voiis Elements of the Retina. 



•271.— Diagram of the Connective- 
Tissue Substance of the same. 



« xro,.-<> fihrps ■ 1 •'in^'lion ceUs:4, inner molecular layer; 5. inner nuclear 
- ';lver:^6.omermole6u^rl^y^ riourernuclearlaver ; 8. membranahmitans 
externa ; 9, rods and cones. (Jfojc Schultze.) 

papiUa nervi optici, (b) the macula lutea and fovea 

centralis retinae, and (c) the ora serrata of the retina. 

(a) The papilla nervi optici, or the blind spot of 



Retina. 447 

the retina, represents the entrance of tlie optic nerve 
fibres into the retina; thence, as from a centie, they 
spread out in a radiating direction into the sancer- 
sliaped retina, of which they form the internal layer. 
No other elements of the retina are present at the 
papilla, except a continuation of the limitans interna. 
At the papilla nervi optici the arteria and vena 
centralis nervi optici also enter, and spread out with 
their branches in the inner layers of the retina. A 
large lymph space is also found there. 

(6) The macula lutea and fovea centralis will be 
considered after the various layers of the retina have 
been described. 

(c) At the ora serrata all circular and nuclear 
elements of the retina — except the pigmented epithe- 
lium — and the nerve fibres, come to an end ; but the 
limitans interna, with its peculiar radial or Miiller's 
fibres, is continued over the ciliary processes in the 
shape of columnar epitheloid nucleated cells men- 
tioned above : this is the pars ciliaris retime. 

436. Structure of the layers of the retina (Figs. 
270, 271). 

(1) The iiieiiibraiia liiiiitaii!^ iiiteriia is 
composed of more or less }jolygonal areas, which are 
the ends or bases of pyramidal, finely-striated fibres 
— the radial fibres of JlilUer. Each radial fibre passes 
from the limitans interna in a vertical direction 
through all lavers to the limitans externa, and on its 
way gives off numerous lateral branchlets, fibrils and 
membranes, which anastomose with one another so as 
to form a honeycombed stroma or matrix for all 
cellular and nuclear elements of the retinal layers. 
In the nerve fibre layer the radial fibres are thickest, 
this being, in fact, the pyramidal basis ; in the inner 
nuclear layer each possesses an oval nucleus. 

437. (2) The layer ol nerve fibres. — The 
optic nerve fibres at their entrance into the eyeball 



448 



Elements of Histology. 



lose their medullary sheath, and only the transparent 
axis cylinder is prolonged into the retina. In man, 
medullated nerve fibres in the retina are very excep- 
tional : in the rabbit there are two bundles, whose 
libres retain their medullary sheath in the retina 




Fk 



jectiou of Retina of Dog. \\Aflei 
" Anatomy.") 



Cajal, from Quain's 



u. Cone rtbre ; h, rod fibre aud nucleus ; c, d, bipolar cells ■with inner nuclei, with 
vertical ramifications to receive the knobbed ends of the rod fibres, e,f, with 
flattened ramifications for the arborising ends of the cone fibres ; g. gan- 
glion cell sending an axon to the outer molecular layer; /), spongioblast ; 
1, nerve fibres passing to the outer molecular layer ;], centrifugal nerve fibres 
passing into, and terminating in, inner molecular layer : m, nerve fibres 
passing toinner molecular layer ; n, ganglion cells ; a, outer molecular layer; 
B, inner molecular layer; c, nerve fibre layer. 

(Bowman). The nerve fibres remain grouped in 
bundles in the retina, and even form plexuses. For 
obvious reasons, the number of nerve libres in the 
nerve fibre lay^n* diminishes towards the ora serrata. 

438. (3) Tlie layer of g^sin^l ion cells. — There 
is one stratum of these cells only, except in the 
macula lutea, where they form several strata. Each 



Retina. 



449 



cell is multipolar, and possessed of a lar^e nucleus. 
One process is directed inwards and Ijeconies the 
axon, being a fibie of the nerve fibre layer. Several 
branched processes or dendrites pass from the opposite 
side of the cell into the next outer layer — i.e. the 
inner molecular layer. 

From the researches of Eamon y Cajal, it is clear 




Fig.273. — From the Retina of Dog. i^Afttr Ca}al,fTom Quaiiis ''Anatomy. 

A, Small amacrine (spougiuhlast) of the inner molecular layer : c, large ganglion 
cell ; /,g,h, i, small ganglion cells arborising in the inner molecular layer. 



that the dendrites terminate by arborisations or den- 
drons in the next or inner molecular layer (see Figs. 
L'72, 27:3, and 274). 

The ganglion ceils are separated from one another 
by the radial fibres of Miiller. 

439. (4) The inner nioleciilai' layer is a 
fine and dense reticulum of fibrils, with a small 
amount of granular matter between. The fibrils are 
connected with lateral branchlets of the radial fibres 
of ^luller. This layer is, on account of its thickness, 
a conspicuous part of the retina. In lower vertebrates 
it a])pears stratified. 

As mentioned just now, it contains the terminal 
arborisations of the dendrites of the ganglion cells. 

440. (5) The inner nnrlear layer contains in 
a honeycombed matrix of a hyaline stroma numerous 
nuclei, in two. three, or four layers. In the am- 
phibian retina these form a larger number of layers. 
Some oblong nuclei of this layer belong, as has been 
mentioned above, to the radial fibres of Miiller. 

D D 



45° 



Elements of Histology 



Js^ext to the molecular layer are small nuclei belonging 
to flattened branched cells (Vintschgau). the spongio- 
hh.sts of W. Miiller. These cells have been shown 
by Golgi's method to be possessed of rich arborisations, 
^vhich extend horizontallv into the outer and inner 




Fig. 274— Section of Retina of Bird. {After Cajal,/rom (^uain's ^'Anatomy."\ 

A, B. Large sponsioljlasts of inner nuclear layer; c. small spongioblast; d. 
bipolar cell of inner nuclear layer wirh a and b arborising in inner mole- 
cular layer and also terminating at k at the limitans externa ; f, g, rod and 
cone nuclei ; H, i, cells with arborisations in outer molecular layer ; j, radial 
fibre of Muiler. 



molecular layers (see Fig. 272). Ramon y Cajal 
desicrnates them as amacrines. But the ofreat 
majority of the nuclei of this layer are slightly oval, 
with a reticulum in their interior. Each belongs to 
a spindle-shaped cell, with a small amount of proto- 
plasm around the nucleus : it is, in fact, a bipolar 



Retina. 451 

ganglion cell (Max Scliultze), of which ono i)rocess (the 
innei") ))asses as a fine varicose fibre into the inner 
molecular layer, where it terminates as a delicate den- 
dron, while the other or outer process passes into the 
next outer layer of the retina — i.e. the outer molecu- 
lar layer, to terminate here by a rich arborisation or 
dendron (Fig. 272). 

(6) Tlie outer iiiolenilai* layer is of the same 
structure as the inner molecular layer- — i.e. a fine 
reticulum of fibrils — but is considerably tliinner than 
the latter. It also contains the dendrons of cells 
inside and outside it (Fig. 272). 

441. (7) The outer uuclear layer contains, in 
a honeycombed matrix, a large number of oval nuclei. 
In the retina of man and mammals these nuclei are 
always present in considerably greater numbers or 
layers than those of the inner nuclear layer, but in 
the amphibian animals the reverse is the case. They 
are smaller than the nuclei of the inner nuclear layer, 
and show often a peculiar trans^'ersely-ribbed differ- 
entiation of their contents (Henle, Krause). The 
honeycombed matrix of this layer is in connection 
with lateral branchlets of the radial fibres of Miiller, 
with which it forms a sort of limiting delicate mem- 
brana propria at the outer surface of the layer; 
this is 

442. (8) The liuiltaus externa — The nuclei of 
the outer nuclear layer next to this limitans externa are 
connected, in the retina of man and mammals, with 
the cones, while the nuclei farther inwards from the 
limitans externa are connected with the rods. In 
both instances the connection is established throuorh 
holes in the limitans externa. Each nucleus of 
the outer nucleai- layer is, in reality, that of a 
spindle-shaped cell with a minute amount of proto- 
plasm ; this is prolonged outwards, as the outer part 
of the rod- or cone-fibre, to become connected with a 



452 Elements of Histology. 

rod or cone respectively, while inwards it passes into 
a longer, more conspicuous fibre, the inner part of the 
rod- or cone-fibre (Fi,cj. 272). According to Ramon 
y Cajal, the cone-fibre terminates as a flat dendron 
in contact witli the tufty arborisation of the outer 
process of the cells of the inner nuclear layer— f 6". in 
the outer molecular layer : the rod-fibre on the other 
hand terminates in the outer moleculai- layer as a 
small knob (Fig. 272) in tlie outer dendron of the 
same cells 

443. (*.)) The rods and cones. — Each rod is 
of cylindrical shape, Avith rounded or conical outer 
extremity : it con.sists of an outer and inner member, 
joined by linear cement. Its substance is bright and 
glistening, and that of the outer member is composed 
of the neurokeratin of Kiihne and E^vald. In the 
fresh state the outer member shows a more or less fine 
and longitudinal striation, due to longitudinal fine 
ridges and furrows (Hensen, Max 8chultze). After 
certain reagents, such as serum, liquor potass^e, the outer 
rod-member disintegrates into numerous transverse, 
thin, homogeneous-looking discs (Hannover). The 
inner member in tlie human rods is slightly broader 
than the outer : it is pale or tinely and longitudinally 
striated, and contains in many instances a peculiar 
lenticular structtire : in the human and mammalian 
retina this is aljsent. but in its stead is a mass of 
lono-ittidinal fibrils (^fax ►"^cliultze). The inner member 
passes through a hole in the limitans externa, and 
becoming thiniif-r. represents the outer part of the 
rod -fibre. 

4-4-1:. Each cone is composed of an outer, short, 
pointed, conical member, and an inner larger member 
with convex surface : this is the hody of the cone. 
The outer member of the cone separates under certain 
conditions also into thin transverse discs. The body 
of the cone is longitudinally and finely striated. The 



Rktina. 



453 



outer extremity of tlic body 
birds, reptiles, and amphibia 
contains a spherical corpuscle 
of red, orange, yellow, green, 
or even Ijlue colouration. 

The cones are shorter than 
the rods, the pointed end of 
the former not reaching much 
farther than the junction be- 
tween the outer and inner 
members of the rods. 

In the macula lutea and 
fovea centralis of man and 
most mammals there are pre- 
sent cones only, and towards 
the peripheral portion of the 
retina they gradually decrease 
in numbers ; in the peripheral 
part there are only rods. But 
in birds the cones exceed the 
rods everywhere. 

In the bat and mole the 
macula lutea possesses no 
cones, and in the owl, rat, 
mouse, guinea-pig and rabbit 
they are few and small. 

445. The outer members 
of the rods (only) show in 
the fresh and living state a 
peculiar ditiuse purplish colour 
(Leydig, Boll, Kiihne) : this is 
the visual purple or Rhodopsin 
of Kiihne. When exposed to 
sunlight it passes through 
red, orange, and yellow, and 
finally disappears altogether 
— becomes bleached. There is 



of the cones in many 








Fig. 275. — Vertical Section 
through Ketiiia of Frog. 
(Atlas.) 

a. Pigmented epitbeliiim of 
retina or tapetum nigrum; 
5, outer nieml>ers of rods, 
those of cones l)etween them ; 
c, inner mem tiers of rods and 
cones; d, liniitaus externa; 
e, outer nuclei ;/, outer mole- 
cular layer ; </, inner nuclei ; 
/(, inner molecular layer ; i, 
nuclei of ganglion cells; j, 
nerve fibres; the pyramidal 
extremities of the radial 
fibres arc well shown. 



454 Elements of Histology. 

no visual purple in tlie rods of Rhinolophus hipposi- 
deros, fowl and pige )n : in those retinae in which the 
cones contain coloured globides {ses above) the sur- 
rounding rods are wanting in the visual purple. 

The visual purple stands in an intimate relation to 
the pigmented epithelium of the retina, since a retina 
regains its visual purple after bleaching, when replaced 
on the pigmented epithelium (Kiihne). This holds 
good, of course, onlv within certain limits. 

•446. (10) The pij?iiiL'iite<l epitlieliiiiii (Fig. 
275), or tapetum nigrum, is composed of polygonal 
protoplasmic cells, which, when viewed from the 
surface, appear as a mosaic, in which they are 
separated from one another by a thin layer of cement 
substance. Eacli cell shows an outer non-pigmented 
part, containing the slightly flattened oval nucleus, 
and an inner part next to the rods and cones, 
which is full of pigmented crystalline rods 
(Frisch). Tliis part is prolonged into numerous 
tine fibrils, each containing a row of the pig- 
mented particles, and these fibrils pass between the 
outer members of the rods, to which they closely 
adhere, and which in reality become almost entirely 
ensheathed in them (M. Schultze). Each cell supplies 
a number of rods with these fibrils. Sunlight causes 
a protrusion of these fibrils from the cell body, whereas 
in the dark they are retracted (Kiihne), in a manner 
similar to what takes place in pigmented connective- 
tissue cells. {See par. 43.) The tint of this pigment 
is darker in dark than in light eyes. It is bleached 
by the light in the presence of oxygen (Kiihne), but it 
persists in the absence of oxygen ( Mays ). 

447. The macula lutea (Fig. 276) of man and 
ape contains a diffuse yellow pigment, between the 
elements of the retina (M. Schultze). In man and 
most mammals, as mentioned above, there are 
hardly any rods here, but cones only ; these are 



Retina. 



455 



longer than in other parts, and in the fovea centralis 
tliey are longest, and, at the same time, very thin. 
Since there are only cones here, the nuclei of the 
outer nuclear laj^er are limited to a very few layers 
(generally about two) next to the membrana limitans 




Fig. 276. — From a Vertical Section through the Macula lutea and Fovea 
centralis. (Diagram by Max Schultze.) 

a. Nerve fibre* : b, ganarlion cells ; c. Inner molecular layer : d, inner nuclei ; 
e, outer molecular layer ; /, coue-flbres with their outer nuclei ; g, cones. 



externa. For this reason, the rest of the outer nuclear 
layer is occupied by the cone-Hbres only, which in the 
fovea centralis pass in a slanting, or almost horizontal, 
direction sideways into the outer molecular layer. The 
ganglion cells fi)rm several strata in the macula lutea. 
In the fovea centralis are present the cones (very long 
and thin), the limitans externa, the few nuclei repre- 
senting the outer nuclear laj^er, a thin continuation of 
the inner molecular layer, and the limitans interna. 
448. In the embryo, the primary optic vesicle 



456 Elements of Histology. 

becomes invaginated so as to form the optic cup, 
which consists of two layers — an outer, giving origin 
to the pigmented epithehum : and an inner, the retina 
proper. In this Jatter the rods and cones, with their 
hbres and the nuclei of the outer nuclear layer, are 
represented by columnar epithelial cells (the sensory 
epitlieJium), while all the other layers — i.e. the outer 
molecular, inner nuclear, inner molecular layer, gan- 
glion cells, nerve fibres, and limitans interna — are re- 
presented by a separate layer : Briickes tunica nervea 
or Henle's stratum nerveum. 

449. The blood-vessels of the retina. The 
branches of the arteria and vena centralis of the optic 
nerve can be traced into the retina in the layer of 
nerve fibres and ganglion cells, while the capillaries 
connecting the arteries with the veins extend as far as 
the outer molecular layer. 

The lyiiipliatics of the retina exist as perivas- 
cular lymphatics of the retinal veins and capillaries 
(His). Lymph channels are present in the ner\e fibre 
layer. 

450. The lamina eribrosa is the part of the 
sclerotic and choroid membrane through which the 
optic nerve filires have to pass in order to reach the 
papilla nervi optici. In the optic nerve the fibres are 
grouped in larger or smaller groups — not bundles in 
the sense of those present in other nerves and sur- 
rounded by perineurium {see Chapter XI Y.) ; these 
groups are surrounded by septa of connective tissue, 
^nd they pass through corresponding holes of the 
sclerotic and choroid. 

451. The optie nerve possesses three sheaths, 
composed of fibrous connective tissue : an outer, or 
dural : a middle, or arachnoidal ; and an inner, or 
pial, sheath — all continuations of the membranes of 
the brain. The pial sheath is the perineurium, the 
optic nerve being comparable to a compound nerve- 



Retina. 457 

bundle {see Chapter XIY.). The dural slieath of 
the optic nerve, at its entrance into the lamina 
cribrosa, jiasses into the outer strata of the sclerotic, 
while the arachnoidal and pial sheaths pass into the 
inner strata of the sclerotic. Outside the dural sheath 
is a lymph space— the supravaginal sj>ace : and also 
between these various sheaths are lymph spaces — the 
subdural or sub vaginal space of Schwalbe, and the 
subarachnoidal space. The supravaginal and suit- 
vaginal spaces anastomose with one another (Michel). 
452. Around the sclerotic is a lymph space limited 
bv a tiVji'ous membrane — the Tenonian co.ps.ii.le : the 
space is called tlie Tenonian space. The supravaginal 
space anastomoses with this Tenonian space, and into 
it pass also the lymph clefts in the suprachoroidal 
tissue (Schwalbe), by means of the lymph canalicular 
system of the sclerotic (Waldeyer). The snpra- 
choroidal lymph spaces communicate also with the 
subarachnoidal space of the optic nerve. 



458 



CHAPTER XLII. 

THE OUTER AXD MIDDLE EAR. 

453. The meatus auditorius externus is lined with 
a delicate skin, in structure identical with, but thinner 
than, the skin of other parts. The ceruminous 
glands have been mentioned and described before. 
The cartilage of the auricula and its continuation into 
the meatus auditorius externus is elastic cartilage. 

454. The in em bran a tyinpani sej^arating the 
outer from the middle ear has for its matrix a firm 
stratum of stiff trabecuhe of fibrous connective tissue, 
with numerous elastic fibrils and elastic membranes. 
This is the middle and chief stratum of the membrane : 
outwards it is covered with a delicate continuation of 
the skin of the meatus auditorius externus, and inwards 
M'ith a continuation of the delicate mucous membrane 
lining the cavum tympani. In the middle stratum of 
the membrana tympani the trabecule^ radiate more or 
less from the junction of the manubrium mallei with 
the membrane ; but towards the periphery many are 
also arranged in a circular direction. The former 
belong to the outer, the latter to the inner, portion of 
the middle stratum. 

The mucous membrane lining the tympanic surface 
of the memljrane is delicate connective tissue, covered 
with a single layer of polyhedral epithelial cells. 

The blood-vessels form capillary networks for all 
three layers — i.e. a special network for the skin layer, 
a second for the middle stratum, and a third one for 
the mucous layer ; the lymphatics are also arranged in 



Outer and Mmni.E Ear. 459 

this way. An intercommunicating system of lym- 
phatic sinuses and ck^fts (Kessel) is left between tlie 
trabeculiu. The non-medullated nerve fibres form 
plexuses for the skin and mucous layer ; from these 
pass ott' fine fibrils, which form a sub-epithelial net- 
work, and from this the tilji'ils pass into the epithelium. 

455. The tuba E:ii«itsicliii is lined with a 
uuicous meml)rane, which is a continuation of that 
lining the upper part of the phar^'nx, and therefore, 
like it, is covered on its inner or free surface with 
columnar ciliated epithelium. As in the pharynx, so 
also here, we find a good deal of adenoid tissue in the 
mucous membrane. 

The cartilage of the tuba Eustachii in the adult 
approaches in structure the elastic cartilages of other 
parts. 

456. The caviiiii tympaiii, including the cellulte 
mastoidese and the surface of the ossicula auditus, is 
lined with a delicate connective-tissue membrane. Its 
free surface is covered with a single layer of poly- 
hedral epithelial cells in the following regions : on 
the promontory of the inner wall of the cavity, on the 
ossicula auditus, on the roof of the cavity, and in the 
cellulae mastoidea3 ; in all other parts it is columnar cili- 
ated epithelium, like that lining the tuba Eustachii. 

457. The three ossicula auditus are osseous 
substance covered with periosteum, which is covered 
with the delicate mucosa just described. The liga- 
ments of the bones are, like other ligaments, made up 
of straight and parallel bundles of tiV)rous connective 
tissue. The articulation surface of the head of the 
malleus, of the incus, of the extremity of the long 
process of the incus, and of the stapes, are covered 
with hyaline (articular) cartilage. 



460 



CHAPTER XLTII. 

THE INTERNAL E A K. 

458. The osseous labyrinth consists of the vesti- 
bule, prolonged on one side into the cochlea, and on 
the other into the three semicircular canals, each of 
which possesses an am^^ulla at one extremity. The 
vestibule shows two divisions — the fovea hemispherica 
next to the cochlea, and the fovea hemi-elliptica next 
to the semicircular canals. The cochlea consists of 
two and a half turnings twisted round a bony axis — the 
modiolus. From this a bony lamina extends towards 
the outer wall for each turn, but does not reach it : 
this is the lamina spiralis ossea. It extends through 
all turns, and it subdivides tlie cavity of each turn 
into an upper passage, or scala vestibuli, and a lower, 
or scala tympani. At the top of the cochlea the two 
seal* pass into one another by the helicotrema. The 
scala vestibuli opens into the fovea hemispherica, 
while the scala tympani at its commencement — i.e. 
at the proximal end of the first turn — would be in 
communication, by the fenestra rotunda, with the 
cavum tympani, were it not that this fenestra rotunda 
is closed by a membrane — the secondary membrane. 

459. The semicircular canals start from, and return 
to, the fovea hemi-elliptica of the vestibule. 

The fenestra ovalis leads from the cavum tympani 
into the vestibule — its hemispheric division ; and this 
fenestra ovalis is, in the fresh condition, filled out by 
a membrane, in which the basis of the stapes is fixed, 
the circumference of this being nearly as great as that 
of the fenestra. 



Internal Ear. 461 

460. Tilt' osseous labyi-inth in all parts consists of 
ordinary osseous suUstaiice, with the usual periosteum 
lining its outer surface and its inner cavities. These 
cavities contain the albuminous fluid called perilymph. 
But they ;ire not tilled out by this, since, in each of 
the two divisions of the vestibule, in each of the 
semicircular canals, and in the cochlea, is a mem- 
branous structure, analogous in shape to the corre- 
sponding division of the labyrinth. These membranous 
structures possess a cavity filled with the same albu- 
minous fluid as above, called the endolymph. These 
structures are disposed thus : in the fovea hemispherica 
is a spherical sac, called the saccule ; in the fovea 
hemi-elliptica is an ellij^tical sac, the lUi^icle ; in each of 
the three semicircular canals is a membranous semi- 
circular tube, which jiossesses also an ampulla corre- 
sponding to the ampulla of the bony canal. 

461. In the cochlea is a membranous canal, tri- 
angular in cross-section — the scala media or cochlear 
duct — -which also twists two and a half times from the 
basis to the apex of the cochlea, and is placed against 
the end of the lamina spiralis ossea so as to occupy a 
position between the peripheral part of the scala vesti- 
buli and scala tympani. 

462. The different divisions of the menil)ranous 
labyrinth are connected - with one another in this 
manner : the three semicircular (membranous) canals 
open into the utricle ; this does not form a direct con- 
tinuity with the saccule, but a narrow canal comes off 
both from the saccule and utricle ; the two canals 
join into one minute membranous tube situated in the 
aqueductus vestibuli. At its distal end it enlarges 
into the saccus endolymphaticus, situated in a cleft of 
the dura mater, covering the posterior surface of the 
petrous bone. The saccule is in communication with 
the cochlear canal, or scala media, by a short narrow 
tube — the canalis reuniens of Reichert. Thus the 



462 Elements of Histology. 

cavity of the whole membranous labyrinth is in 
direct communication throiigliout all divisions, and it 
represents the inner lymphatic space of the labyrinth. 
There is no communication between the perilymph 
and endolymph, and the cavity of the membranous 
labyrinth stands in no direct relation to the cavum 
tympani, since the fenestra ovalis and fenestra rotunda 
both separate the perilymphatic space, or the cavity 
of the bony labyrinth, from the cavum tympani. The 
vibrations of the membrana tynjpani, transferred by 
the ossicula auditus to the fenestra ovalis, directly 
affect, therefore, only the perilymph. The fluctuations 
of this pass from the vestibule, on the one side, 
towards and into the perilymph of the semicircular 
canals ; and on the other side, through the scala 
vestibuli, to tlie top of the cochlea, then by the heli- 
cotrema into the scala t3^mpani, and find their conclu- 
sion on the membrana secundaria closing the fenestra 
rotunda. On their way they affect the membrane of 
Reissner, which separates the scala media from the 
scala vestibuli, and also the membrana basilaris separ- 
ating the scala media from the scala tympani ; the 
vibrations of these membranes affect the endolymph, 
and therefore tlie nerve-endings {see below). 

463. Sti'U€tiire of seiiiicirciilai* canals, 
utricle and saccule. — The memhranous semi- 
circular canals are fixed by stiff bands of fibrous 
tissue to the inner periosteum of the one (convex) 
side of the osseous canal, so that towards the concave 
side there is left the space for the perilymph. A 
similar condition obtains with regaid to the saccule 
and utricle, which are fixed by the inner periosteum 
to one side of the bony part. 

The structure of the wall is the same in the semi- 
circular canals, utricle and saccule. The above-men- 
tioned fibrous ligaments of the periosteum form an 
oute7' coat ; inside this is a glassy-looking tunica 



I.XTEKNAL Ear. 



463 



propria. At one side (the one away from the bone) 
this tunica propria forms numerous papillary projec- 
tions. The internal surface of the membrane is 
covered with a single layer of polyhedral epithelial cells. 

464. Each of the branches of the nervns vestibuli 
— i.e. one for the sac- 
cule, one for the utricle, 
and three for the three 
ampullae — possesses a 
ganglionic swelling. The 
nerve - branch, having 
passed through the mem- 
branous wall, enters 
special thickenings of 
the tunica propria, on 
that part of the mem- 
branous wall next to the 
bone : in the saccule and 
the utricle the thicken- 
ing is called macula 
acustica, in the ampullae 
crista acustica ( Fig. - 7 7) 
(M. 8chultze). This 
thickenin*^ is a lar^je 
villous or fold-like pro- 
jection of the tunica 
})ropria, into which pass 
the nerve fibres of the 
several branches. These 
tibres are all meduUated nerve fibres, and, ascending 
towards the internal or free surface of that pro- 
jection, form a plexus. In this plexus are in- 
terspersed numerous nuclei. From the medullated 
fibres pass oS minute bundles or primitive fiVjrillse, 
which enter the epithelium that covers the free 
surface of the projection. 

465. This epithelium is composejcl of a laver of 




Fig. 277.— From a Transverse Section 
through the Macula acustica of the 
Utricle of the Labyrinth of Guiuea- 
pig. {Atlas.) 

a, Medullated nerve fibres, forming plex- 
uses ; b, nuclei of the membrane ; c, 
sensory epithelium (diagrammatic); the 
spindle-shaped sensory cells possess 
long auditory hairs projecting between 
the conical epithelial cells beyond the 
free surface. 



464 



Elements of Histology. 



columnar or conical cells, between which are wedged 
in spindle-shaped cells ; V^oth kinds possess an oval 
nucleus. According to Max Schultze and others, each 
of the spindle-shaped cells is connected by its inner 
process with the nerve fibrillse coming from under- 
neath : whereas, towards and beyond the free surface, 




Fig. 278. — Xerve Terminations in the Epithelium of tlie Macula acustica. 
The nerve fibres form denclrons in the epithelial layer. (After 
Betzius, from Quain.) 



its outer process is prolonged into a long, thin, stiff, 
auditory hair. Max Schultze, therefore, calls the 
columnar cells epithelial; the spindle-shaped ones, 
sensory. 

Retzius, on the other hand, maintains that, in the 
case of fishes at any rate, the epithelial cells are those 
which are connected each with a bundle of nerve 
fibrillse, and that each sendi^ <jut over the internal free 



iNTKRXAr, Ear. 465 

surface almiidle of iiiie stiff" hairs — the auditory hairs. 
The spindle-shaped cells of Max Schultze, according 
to this theory, are only supporting cells. The free 
surface of the epithelium is covered with a homo- 
geneous cuticle, perforated l)y holes which correspond 
to the epithelial cells and the auditory hairs. 

By Golgi's method Retzius has, however, obtained 
evidence (Fig. 278) which shows that fine nerve 
fibres terminate by arborisations or dendrons amongst 
the epithelial cells (Fig 177). 

On the internal surface of the macula and crista 
acustica are found the oUAithx., rhombic crystals, and 
amorphous masses, chiefly of carbonate of lime, em- 
bedded in a gelatinous or granular-looking basis. 

\^^>. The coc'lilca (Fig. 279), as has been men- 
tioned above, consists also of a bony shell and a 
membranous canal, the former surrounding the latter 
in the same way as the bony semicircular canal does 
the membranous — i.e. the latter is fixed to the outer 
or convex side of the for-mer. The difference between 
the cochlea and the semicircular canals is this, that in 
the cochlea there is a division of the perilymphatic 
space by an osseous projection — the lamina spiralis 
ossea — and bv the scala media into two scalse, viz. the 
(upper) scala vestibuli and the (lower) scala tympani. 

467. In the osseous modiolus are numerous 
parallel canals for bundles or groups of the fibres of 
the cochlear branch of the auditory nerve : these 
canals open into the porus internus, in which lies a 
large c^ansflion connected with the nerve. 

Coo 

The nerve bundles are situated in the canals of the 
modiolus, and opposite the lamina spiralis ossea are 
connected with ganglionic masses — composed of bipolar 
ganglion cells — called the ganglion spirale of Corti. 
From this ganglionic mass the nerve fibres (all niedul- 
lated) can be traced into the lamina spiralis ossea, in 
which they form rich plexuses extending to its outer 

E E 




Fig. 279.— From a Vertical Section through the Cochlea of Ear of Guinea- 
pig, seen in the long axis of the Modiolus. (Atlas.) 

a, Scala vestibuli ; b, scala tympani ; c, srala media ; d, membrana tectoria ; e, 
cells of Claudius ; /, upper outer angle of scala media ; g, region of outer 
hair cells nn membrana basilaris : /*, membrane of Reissner; ?, epithelium 
linintr «ulcus spiralis (internus) ; j, tunnel of Corti's arch ; k. stria vascularis ; 
?, ligamentum ppirale : ?», crista spiralis; n, nerve Hbres in lamina spiralis 
ossea • o gansliun spirale; p, nerve fibres in modit)lus ; q. channels in bone 
containing blood-vessels ; r, masses of bone in modiolus ; s, outer bony 
capsule. 



Internal Ear. 467 

margin — l.p. as far as the membrana basilaris of the 
scala media {see below). 

-4G(S. From the margin of the himina spiralis ossea 
to the external bony shell extends the membrana basi- 
laris (Fig. 279), forming the lower and chief wall of 
the scala media, while the upper wall of the canal is 
formed by the membrane of Reissner, extending 
under an acute an^le from near the marcrin of the 

O o 

lamina spiralis ossea to the outer bony shell. 

On a transverse section through the scala media 
we see the following structures : — 

469. (1) Its outer Avail is placed close against 
the periosteum lining the internal surface of the bony 
shell ; it consists of lamellar fibrous tissue, with 
numerous stitf elastic bands, and is the vestibular 
part of a peculiar ligament — the ligamentuTti spirale 
(Kulliker) — semilunar in cross-section, and with its 
middle angular })rojection tixed to the outer end of 
the membrana basilaris. 

470. (2) Its inner wall is represented by an 
exceedingly delicate membrane — the membrane of 
Reissner : this is also its upper wall, extending under 
an acute angle from the upper outer angle of the scala 
media to the lamina spiralis ossea. But here it is not 
tixed on the osseous substance, but on a peculiar pro- 
jection on this latter — the crista spiraUs (Fig. 279, m) 
— which is a sort of tissue intermediate between tibrous 
and osseous tissue, and is added to the vestibular 
surface of the lamina spiralis ossea. This crista spiralis 
has on one surface — i.e. that directed towards the 
scala media — a deep sulcus, called the sulcus spiralis, 
or sulcus spiralis internus ; so that of the crista 
.spiralis there are two labia to be distinguished — the 
labium vestibulare and the labium tympanicum ; the 
former being the upper, the latter the lower, boundary 
of the sulcus s})iralis (Fig. 279). 

471. (3) The lower wall of the scala media 



468 Elemexts of Histology. 

is the memhrana hasilaris, extending in a straight 
line betAveen the labium tynipanicum of the crista 
spiralis and the above-mentioned projection of the 
ligamentum spirale. The scala media is lined on its 
whole internal surface with epithelium, this only 
being derived from the epithelium forming the wall 
of the auditory vesicle of the embryo, peculiarly 
modified in certain places. The scala tympani and 
scala vestibuli are likewise lined with a continuous 
layer of flattened cells — an endothelium, which on 
the lower or tympanic surface of the mernbrana 
basilaris is somewhat modified, being composed of 
cjranular-lookinof irre^cnlar cells. 

472. As regards the scala media, the epithelium 
lining its internal surface is of the following aspect :— 
Starting with the lower outer angle — i.e. Avhere the 
mernbrana basilaris is fixed to the ligamentum spirale 
— we find a single layer of polyhedral or short 
columnar transparent cells, lining this outer angle — 
the cells of Claudius ; ascending on the ligamentum 
spirale, the cells become shorter, more squamous ; as 
such they are found over a slight projection on the 
outer wall — i.e. the ligamentum spirale accessorium — 
caused by a small blood-vessel, the vas prominens. 

473. Then we come to the stria vascularis, 
lining nearly the up[)er two-thirds of the outer 
wall of the scala media. It consists of a layer of 
columnar and spindle-shaped epithelial cells, between 
which extend capillary blood-vessels from the liga- 
mentum spirale, and in some animals (guinea-pig) 
clumps of pigment granules are found between 
them. 

474. Then we pass from the upper angle of the 
scala on to the membrane of Eeissner. This consists 
of a homogeneous thin mernbrana propria, covered on 
its outer vestibular surface with a layer of flattened 
endothelium, and on its inner surface — i.e. that facing 



Internal Ear. 469 

the scala media — with a layer of less flattened, smaller, 
poljdiedral epithelial cells. 

475. We come next to the vestibular labium of 
the crista spiralis, on which are found cylindrical 
horizontal projections anastomosing with one another : 
these are the auditor y teeth (Huschke). The epi- 
thelium of Reissner's membrane is continued into the 
grooves and pits between the auditory teeth as small 
polyhedral cells, but over the teeth as large, flattened, 
squamous cells, which, passing on, line the sulcus 
spiralis and cover also the tympanic labium of the 
crista spiralis. Xow we arrive at the membrana 
basilaris, on which the epithelium l)ecomes modified 
into the organ of Corti. 

476. The me 111 bra 11 a basilaris consists of a 
hyaline basement membrane, on which the organ of 
Corti is fixed : underneath this is the tunica propria^ 
a continuation of the tissue of the ligamentum spirale, 
composed of fine parallel stiff fibrils (Hannover, 
Henle) stretched in a very regular and beautiful 
manner in the direction from the ligamentum spirale 
to the crista spiralis (Nuel). On the tympanic side 
there is also a hyaline basement membrane. The 
endothelial cells covering this on the tympanic surface 
haA'e been mentioned above. 

477. The org:aii of Corti (Fig. 280). — Passing 
outwards from the epithelium lining the sulcus sjiiralis, 
we meet with small polyhedral epithelial cells in the 
region of the termination of the lamina spiralis ossea, 
next which are columnar-looking cells — the inner 
supporting cells ; next to these is the inner hair-cell — 
a columnar, or conical, epithelial cell, with a bundle 
of stitf hairs, or rods, extending beyond the surface. 
The inner hair-cells form a sina^le file alonsr the whole 
extent of the two and a half turns of the scala media. 

478. Xext to the inner hair-cell is the inner rod, or 
inner pillar, of Corti, and next to this the outer rod, 



470 



Elements of Histology 



or outer -pillar, of Corti. Each forms a single file for 
the whole extent of the two and a half turns of the 
scala media. The two rods are inclined towards one 
another, and in contact with their upper extremity, 




Fig. 2S0.— Organ of Corti of the Cochlea of Guinea-pig. (Atlas.) 

a. Outer rod or pillar of Corti : b, inner rod or pillar of Corti ; c, tunnel of 
arch of Corti ; d, oucer hair-cells ; e, inner hair-cell ; /, outer supporting cells 
containing fat globules; g, inner supporting cells; /*, cells of Claudius; 
i, epithelial cells lining the sulcus &i>iralis internus ; j. nerve fibres ; fc, part 
of crista spiralis. 

or head : whereas the opposite extremity, the foot, 
rests under an acute angle on the membrana basilaris, 
on which it is firuily fixed. The rest of the rod is a 
slender, more or less cylindrical, piece — the body. The 
outer rod is larger and longer than the inner, the 
latter being slightly bent in the middle. Owing to 
the position of the rods, the two files form an arch — 
the arch of Corti. Between it and the corresponding 
part of the basilar membrane is a space— the tunnel 
of the arch, triangular in cross-section. 

479. The substance of the rods, or pillars, of Corti 
is bright, highly refractive, and slightly and longitu- 
dinally striated. 

The head of the inner rod is triangular, a short 
process extending inwards towards the inner hair-cell, 
a long process extending outwards over the head 
of the outer pillar. Outwards, the triangular head 
possesses a concave surface grasping the convex 
surface of tiie head of the outer rod. This latter 



Internal Ear. 471 

possesses a process directed outwards, which is tirnily 
applied to the outer process of the head of the inner 
rod, the two together forming part of the niein))rana 
reticularis {see below). 

The relation in size between the outer and inner 
rods is such that the head of one outer rod fits into 
those of about two inner rods. 

480. At the foot, each rod has, on the side 
directed towards the tunnel, a granular, nucleated 
mass of protoplasm, probably the remnant of the 
epithelial cell from which the lower half of the rod is 
derived ; the upper part sometimes has a similar 
nucleated remnant, proving that this also has been 
formed b}^ an ei3ithelial cell, so that each rod is in 
reality derived from two epithelial cells (Waldeyer). 

481. Next follow^ three or four rows of outer hair - 
cells, similar in size and structure to the inner hair- 
cells. Each of the outer hair-cells seen in a section 
belongs to a file of hair-cells, extending on the mem- 
brana basilaris along the whole extent — i.e. two and 
a half turns — of the scala media. Each hair-cell 
possesses an oval nucleus and a number of stifl: 
rods, or hairs, disposed in the shape of a horseshoe in 
the outer jjarb of the free surface of the cell. 

Four, and even five, rows or files of hair-cells 
(Waldeyer), arranged in an alternating manner, are 
found in man. 

The outer hair-cells are also called the cells of 
Corti ; they are conical, and more or less firmly con- 
nected with a nucleated spindle-shaped cell — the cell 
of Deiters. The two cells are more or less fused to- 
gether in their middle part (Nuel). The cell of Corti 
is fixed by a branched process to the membrana 
basilaris, while the cell of Deiters sends a process 
towards the surface, where it joins the memhjrana 
reticularis {see below). 

482. Farther outwards from the last row of outer 



472 



Elemexts of Histology. 



hair-cells are columnar epithelial cells, called the outer 
supporting cells of Hensen : they form the transition 




•s 



5f •- 



f^ Si 



ss 

S 5 



i i §t 



^•3 



^ CO ... 



Internal Eak. 473 

to the epitlu'lium lininij tlie outer angle of the scala 
media — i.e. to the cells of Claudius. 

In the guinea-pig, the outer suppDi-ting cells 
include fat globules. 

483. The iii€»<lullat<'d nerve fibres, which we 
traced in a former page to the margin of the lamina 
spiralis ossea, form rich plexuses in this, and pass 
through holes in it, in order to reach the organ of 
Corti on the membrana basilaris. Looking from the 
surface on this part, we notice a row of holes— the 
habenula perforata of Kolliker — a little to the inside 
of the reofion of the inner hair-cells. Numerous 
primitive fibrillse pass there among small nucleated 
cells situated underneath the inner hair-cells : these 
are the granular cells. Some of these nerve tibrillse 
— the inner bundle of spiral nerve fibres — become 
connected with the inner hair-cells; while others — 
the three outer bundles of spiral fibrils (^Waldeyer) — 
pass, between the inner rods of Corti, right through 
the tunnel ; and, further, penetrating between the 
outer rods of Corti, they reach the outer hair-cells, 
with which they become connected (Gottstein, Wal- 
deyer). (Fig. 281.) 

484-. In connection wdth the outer process of the 
head of the inner and outer rods of Corti, mentioned 
above, is an elastic hyaline membrane — the lamina 
or membrana reticularis. It extends outwards over 
the organ of Corti to the supporting cells of Hensen, 
and possesses holes for the tops of the outer hair-cells 
and their hairs. The parts of this membrane between 
the heads of the rods of Corti and between the outer 
hair-cells appear of the shape of narrow phalanges — 
phalanges of Deiters. A cuticular membrane extends 
from the head of the inner rods of Corti inwards to 
the inner supporting cells : it possesses holes for the 
tops of the inner hair-cells. 

485, From the vestibular labium of the crista 



474 Elements of Histology. 

spiralis to the outer hair cells of the organ of Corti 
extends a peculiar tibrillated membrane ^the tnem- 
brana tectoria. By means of it the sulcus spiralis 
internus is bridged over, and so converted into a 
canal. 

486. As we ascend towards the top of the cochlea, 
all parts in the scala media decrease gradually in size. 
The organ of Corti, being of an epithelial nature, 
possesses no blood-vessels. From the anatomical 
relations of the organ of Corti, it appears most 
probable that the pillars, or rods, of Corti act as the 
supporting tissue, or framework, around which the 
other elements are grouped : and it seems likely that 
the hair-cells, with their rod-like hairs projecting 
freely into the endolymph, are the real sound-per- 
ceiving elements of the organ of Corti. Their connec- 
tion with the terminal tilirilhv of the nerves points in 
the same direction. 

As indicated on p. 460, all structures of the scala 
media, described in the foregoing pages, form an 
uninterru[)ted succession through all the turns of 
the cochlea. 



I 



475 



CHAPTER XLIV. 

THE NASAL MUCOUS MEMBRANE. 

487. The lower part of the nasal cavity is lined 
with a mucous membrane which has no relation to 
the olfactory nerve, and therefore is not connected 
with the organ of smell. It is covered with a strati- 
fied, columnar, ciliated epithelium of exactly the same 
nature as that of the respiratory passages — e.g. the 
larynx and trachea. Large numbers of mucus-secret- 
ing goblet cells are met with in it. Below the epi- 
thelium is a thick hyaline basement membrane, and 
underneath this is a mucosa of fibrous tissue, with 
numerous lympli corpuscles in it. In many places 
this infiltration with lymph corpuscles amounts to 
diffuse adenoid tissue or to perfect lymph follicles. 

488. The mucosa contains in its most superficial 
layer the network of capillaries, but in the rest it 
includes a rich and conspicuous plexus of venous 
vessels. 

In the deeper parts of the mucous membrane — 
i.e. in the submucosa — are embedded smaller and 
larger glands, the ducts of which pass through the 
mucosa and open on the free surface. Some of the 
glands are mucous ; others are serous. In some cases 
{e.g. guinea-pig) almost all glands are serous, and of 
exactly the same nature as those of the back of the 
tongue. In some places the mucous membrane is 
much thicker than in others, and then it contains 
larger glands, and between them bundles of non-striped 
muscular tissue. 



476 



Elements of Histology. 



489. In the upper or olfartory i'eg:ioii (Fig. 282) 
of the nasal cavity the mucous membrane is of a 
different tint, Ijeing more of a brownish colour; it 




Fig. 2S-2.— From a Section throiigli the Ulfactorj- Region of Guinea-pig. 

{Atlas.) 

a. Thick olfactorv epithelium; b, thin olfactory epithelium; c, ciliated non- 
olfactorv einthelium ; d. bone. The transverse sections of the olfactory 
nerve bundles and the tubular glands of Bowman are well seen. 



contains the ramifications of the olfactory nerve, and 
is the seat of the organ of smell. 

490. The free surface is covered with a columnar 



Nasal Mucous Membrane 



All 



cpitlicliuin, composed of tlie followirg kinds of cells 
(Fig. 283):— 

(«) A superficial layer of long coluniiiar, or rather 
conical, epithelial cells, each with an oval nucleus. In 



or 




iMjlJ j I IJ ill ,1/ 



!i|ipij|i]|i,!,i;jji|,|fir|!i!j||]pi^^^ 




Fig. 283.— From a Vertical Section tlirongh the Olfactory Mucous Mem- 
brane of Guinea-pig. {Atlas.) 

a, Epithelial cells; ?^, eensory or olfMctory cells; c, deep epithelial cells; d, 
bundles of olfactory uerve fibres; e, the alveoli of serous (Bowniau's) 
glands. 

some places the free surface of these cells is covered 
with a bundle of cilia, similar to the superficial cells 
of the respiratory j^ai-t of the nasal cavity ; in most 
places, however, the cilia are absent ; the former 



47 



Elements of Histology. 



condition obtains in those places which are in close 
proximity to the respiratory region. 

[h) Between the epithelial cells extend spindle- 
shaped cells, each with a spherical, or very slightly 




Fig. 284.— From a Vertical Section through Olfactory Membrane of Guinea- 
pig. {Photo. Moderate inagnijicat ion.) 

a, Olfactorv epithelium ; b, mucous membrane with blood-vessel and glands ; c 
oliactoiy nerve fibres cut longitudinally. 



oval, nucleus — the sensory cells (Max Schultze). 
Each cell sends one broad process towards the free 
surface, over which it projects in the shape of a small 
bundle of shorter or longer rods : whereas a line 
varicose filament passes from the cell body towards 
the mucosa, and, as shown first by M. Schultze, be- 
comes connected with a fibrilla of the plexus of the 
olfactory nerve fibres. 



Nasal Mucous Membrane. 



A19 



(c) In some places there i.s a deep layer of epithe- 
Hal celh^ each "svitli a spliorical rjiicleus of an inverted 
conical shape, their pointed extremity passing be- 
tween the other cells just mentioned and their broad 
basis resting on the basement membrane (Fig. 283), 



/' 



\ 




. '.x^. 




Fig. 285. — Transverse Section through the Lower Part of the Nasal Septum, 
showing the (bilateral) Organ of Jacobson in cross section. {Photo. 
Loic poicer.) 

1, Cartilage extending above and iiartially around tlie organ ; -J. cavity of 
the tuljular organ, showing on its nit-sial wall olfactory epithelium, on its 
lateral wall cohnnnar eiutheliuni ; 3, cavernous tissue in the lateral wall. 



Von Brunn has shown that there is on the free 
surface of the epithelium a sort of cuticle — a 
delicate limitans externa. 

491. The mucous membrane is of loose texture, 
and contains a rich plexus of bundles of olfactory 



4S0 Elements of Histology. 

nerve fibres, extending chiefly in a direction parallel 
to the surface (Fig. 284). Each nerve fibre is non- 
meduUated — i.e. is an axis ( ylinder composed of minute 
or primitive til)rilhe. and invested in a neurilemma with 




Fig. 286.— Section tlirough the Front Part of Nasal Septum of Rabbit, 
showing the bilateral organ of Jacobson in transverse section. The 
tube of the organ of Jacobson is lined on its mesial wall with olfactory 
epithelium. (Photo. Loiv pov:er.) 

g. Glands extendiug from the upper part of the septum to the junction of the 
mesial and lateral wall of the organ of Jacol'son ; c, rartilage extending as a 
nearly complete capsule around each organ of Jacobson. The lateral wall of 
the organ contains cavernous tissue. 

the nuclei of the nerve corpuscles. Near the surface 
tlie fibres of the plexus ai-e thin, and they split up 
into the constituent fibrils which are directly con- 
tinuous with the fine varicose processes of the sensory 
cells above named (Fig. 178). 

492. The blood-vessels supply with capillary net- 



Nasal Mucous Mi'Imbrane. 



481 



works the superficial part of the mucous membrane 
and the numerous glands. These are tlie (/lands of 
llownKut, extending through the thickness of the 
mucous membrane. They are tubes, slightly branched, 




Fig. 287.— From the same yeetiou througli the Organ uf Jaeobsou as in the 
preceding figure, more magnified. (Photo.) 

c, (';irtila,i,'c of mesial wall ; cf., cavernous tissue of lateral wall. The mesial will 
is lined with thick olfactory epithelium. 



and gradually enlarging towards their distal end ; in 
some parts they are more or less straight. In struc- 
ture they are identical with serous glands, possessing 
a minute lumen, and being lined with a layer of 
columnar albuminous cells. The duct is a very fine 
canal ; it is that part of the gland which is situated 
in the epithelium of the free surface ; it passes ver- 
tically through this, and consists of a fine limiting 

F F 



482 Elements of Histology. 

membrane, the continuation of the membrana propria 
of the gland tube, and a layer of very flattened epi- 
thelial cells. 

493. There is a definite relation between the 
size and number of the l3undles of the olfactory nerve 
fibres, the thickness of the olfactory epithelium, and 
the length of the gland tubes. The size and number 
of the bundles of the nerve fibres are determined 
by the thickness of the epithelium — i.e. by the 
number of the sensory cells ; the number and thick- 
ness of the olfactory nerve bundles determine the 
thickness of the mucous membrane, and the thicker 
this is, the longer are the inlands of Bowman. 

494. The org-aii of Jacobsoii (Figs, 'l^^'d. 
286, 287) is a minute tubular organ present in 
all mammals, and, as has been shown by Dursy 
and Kolliker, also in man. In mammals it is a 
bilateral tube, compressed from side to side, and 
situated in the anterior lower part of the nasal 
septum. Each tube is supported by a hyaline 
cartilage, in the shape of a more or less f)lough- 
shaped capsule — the cartilage of Jacohsoa — and 
opens in front directly into the nasal furrow (guinea- 
pig, rabbit, rat, etc.); or it leads into the canal 
of Stenson (dog), which passes through the canalis 
naso-palatinus, and opens immediately behind the 
incisor teeth on the palate. In all instances, how- 
ever, it terminates posteriorly with a bliud extremity. 

495. The cavity of the tube is lined with stratified 
columnar epithelium, which on the lateral wall is 
ciliated in the guinea-pig and dog, and non-ciliated in 
the rabbit. The median wall — i.e. the one next to 
the middle line — is lined with olfactory epithelium 
identical with that of the olfactory region of the nasal 
cavity. Branches of olfactory nerve fibres also pass 
into the median wall, and behave in exactly the same 
manner as in the olfactorv rejjfion. Numerous serous 



Nasal Mucous Membrane. 483 

glands — belonging ehietiy to the i^pper and hnver 
wall — open into the cavity of the organ of Jacobson. 

In the lateral wall there is in many instances a 
plexus of veins, extending iii a longitudinal direction, 
and between the vessels are Imndles of non-striped 
muscular tissue, thus constituting a sort of cavernous 
tissue. 



4«4 



CHAPTER XLV. 

THE DUCTLESS G L A X D S. 

496. I. The liypopliy«»i!^ cerebri. — The upper 
or smaller lobe belongs to the cential nervous system. 
The lower or larger lobe is surrounded by a librous 
capsule, which sends numerous minute septa into the 
interior. These split up into numerous trabeculfe of 
librous tissue, which, by di^dding and reuniting, form 
a dense plexus, with smaller and larger, spherical or ob- 
long, or even cylindrical spaces — the alveoli. In these 
lie spherical or oblong masses of epithelial cells. These 
epithelial cells are columnar, j^yramidal, or polyhedral, 
each with an oval or spherical nucleus. Between the 
epithelial cells of the same group are found here and 
there small branched or S23indle-shaped cells, with a 
small flattened imcleus. In some of the groups or 
alveoli of epithelial cells is a cavity, a sort of lumen, 
filled with a homogeneous gelatinous substance. 

The interalveolar connective tissue contains a 
network of capillaries. Between the alveoli and the 
interalveolar tissue there are lymph sinuses, like those 
around the alveoli of other glands — e.g. the salivary 
o-lands. 

497. II. The lliyroid gland (Fig. 288).— The 
framework of this gland is in many respects similar 
to that of other glands, there being an outer fibrous 
capsule, thicker and thinner septa, and finally the fine 
trabecular forming the septa between the gland alveoli. 
These are closed vesicles of a sjjherical or oval shape, 
and of various sizes. Each vesicle is lined with a 



o 



Due TL ESS Gl a XDS. 



4B: 



^ 44^#i^^ .^ 




single layiM- of polylicdral ov c »luimi;ir <'[)itli('lial cells, 
each with a spherical or oval nucleus. There is a 
cavity, which differs in size according to the size of 
the vesicle. It contains, and is more or less filled 
with, a homogeneous, viscid, albuminous fluid — the 
so-called colloid. In this often occur degenerating 
nucleated lymph corpuscles ^ 

and coloured Mood corpuscles 
(Baher). 

498. The vesicles are 
surrounded by networks of 
blood capillaries. In the 
connective-tissue framework 
lie networks of lymphatics ; 
between the framework and 
the surface of the vesicles are 
lymph sinuses lined with 
endothelium (Baber). The 
large and small lymphatics 
are often filled with the 
same colloid material as the 
vesicles, and it is probable 
that this colloid material is 

and 



%.. 



I 



// d 



Fi.i,M'8.S. — Fi-Din a Section through 
the Thyroid Gland of Dog. 

((, Epitheliiam lining the vesicles; 
h, coll{ lid contenr s of the vesicles; 
c. lymphatic tilled with the same 
material as the vesicles ; cl, 
tlbrous tissue between the gland 
vesicles. 



the 



discharged 



carried away by 

into the circu- 



produced in the vesicles 
lymphatics, to be finally 
lating blood. 

499. Its formation in the vesicles is probabh^ due 
to an active secretion by the epithelial cells of the 
vesicles, and to a mixture with it, or maceration by 
it, of the effused blood mentioned above. In some 
instances Bal)er found the amount of blood effused 
into the cavity of the vesicles very considerable, and 
hence it is justifiable to assume that the destruction of 
red blood corpuscles forms one of the functions of the 
thyroid gland. 

" 500. III. The supra-venal bodies (Fig. 289). 
— The supra-renal body is envelojDed in a fibrous cap- 



486 



Elements of Histology 



sule ; in connection with this are septa and trabeculae 

Y-)assing inwards, 
and the}^ are ar- 
ranged differently 
the cortex and 
the 




@ a ., ^ t o O^^S) * • .'?o-fe- <^ 



...e 




P'ig. 2S;\ — From a Vertical 8eetioii tlirougli 
The Supra-renal Bod}' of JVIan. {Eberth, in 
Stricl-er's Manual.) 

1, Cortical sulistance : 2,mP(iullary part ; a, outer 
capsule; />, zona glonierulosa ; r. zona fascicu- 
lata; d, zona reticularis; e, medulla: /, large 
vein. 



m 
in 

of the 
will be 
sently. 
The 



medulla 
gland, as 
seen pre- 

cortex of 
the n;land consists 
of an outer, middle, 
and inner zone, ail 
three being di- 
rectly contin n o u s 
with one anothei-. 
The outer one is 
the zona rjlomerv- 
losa ; it contains 
numerous sphe- 
rical, or, more com- 
monly, elongated, 
masses of epithelial 
cells. The cells 
are polyhedral or 
cylindrical, each 
with a spherical or 
oval nucleus. In 
some animals — as 
the dog, horse — 
the cells are thin 
and columnar, and 
arranged in a 
t ran s verse man ner. 
Occasionally a sort 
of lumen can be 



discerned in some of these cell masses. 



Ductless Glands. 487 

501. Next follows the middle zone, or zona 
fascicvlata. Tliis is the most conspicuous and 

broadest part of the whole gland. It consists of 
vertical columns of polygonal epithelial cells, each 
with a spherical nucleus. The cell substance is trans- 
parent, and often contains an oil globule. The columns 
anastomose with their neighbours. Between the 
columns are tine septa of connective tissue carrying 
blood capillaries. 

Between the cell columns and the connective septa 
are seen here and there lymph spaces, into which lead 
fine channels, grooved out between some of the cells of 
the columns. 

502. Next follows the inner zone, or zona reticu- 
laris, composed of smaller or larger groups of poly- 
hedral cells, with more or less romided edges. These 
cell groups anastomose with one another. The indi- 
vidual cells are slightly larger, and their substance is 
less transparent than those of the zona fasciculata. In 
the human subject tliey are slightly pigmented. 

503. In the medulla we find cylindrical streaks 
of very transparent cells ; the streaks are separated by 
vascular connective tissue. The cells are polyhedral, 
columnar, or branched. These cell streaks anasto- 
mose with one another and are directly continuous 
with the cell groups of the zona reticularis of the 
cortex. 

504. The cortex is richly supplied with dense 
networks of caj)illary blood-vessels ; their meshes are 
polyhedral in the outer and inner zone, elongated in 
the middle zone, or zona fasciculata. In the medulla 
numerous plexuses of veins are met with. In the 
centre of the supra-renal body lie the large efferent 
venous trunks. In the capsule (Kolliker, Arnold), 
and in the connective tissue around the central veins, 
are plexuses of lymphatic tubes with valves. The 
nerves are very numerous and composed of non- 



/ 



4SS Elemexts of Histology. 

medullated fibres ; in the medulla they form rich 
plexuses. In connection with these and with those of 
the outer capsule are smill ganglia (Holm, El)9rth). 

505. IV. The g^laiidiila coccygea and 

iiiter-rarotic-a. — The lirst of these is a minute 
corpuscle situated in front of the apex of the os 
coccygis, and was discovered by Luschka. The 
glandula carotica of Luschka (ganglion inter-caro- 
ticum) is of exactly the same structure as the 
glandula coccygea. 

506. Its framework is of about the same nature 
as that of other glands — a fibrous capsule and inner 
fibrous septa and trabecular. The septa and trabeculae 
contain in some placs-s bundles of non striped muscular 
tissue (Sertoli). 

507. The spaces of the framework are occupied by 
the parenchyma. This consists of spherical or cylin- 
drical masses of cells connected into networks. The 
individual cells are polyhedral epithelial cells, each 
with a spherical nucleus. According to Luschka, in 
the newly-born child they are ciliated. In the centre 
of each of the cell masses lies a capillary blood-v^essel, 
much convoluted and wavy. 

Numerous non-medullated nerve fibres forming a 
plexus are situated in the framework of the gland. 



I X D E X 



Alxlneens, 222 
Absorption {see Lymphatics) 
Accessory nucleus, 210 
Achruiiiatin, 11 
Acini of glands, 292 

of liver, 333 

of pancreas, 330 

Acoustic ganglion, 219 
Adenoid reticulum, 62, 126 

tissue, 126 

A' 1 maxillary glands, 289 
Adveutitia of arteries, 108 

of capillaries. 111 

of veins, 110 

lymphatic vessels, 118 

Agminated glands, 130 
Air cells, 345 
Alje nasi, 63 
Albuginea of ovary, 3S7 

of testis, 372 

Albumin membrane of Ascherson, 

402 
Albuminous cells, 293 
Alloplasmatic organs, 6 
Alveolar ca\'ity, 275 

ducts, 345 

Alveoli of glands, 292 

of lung, 345 

of pancreas, 330 

Alveus, 249 
Amacrines, 450 
Amitotic division, 12 
Amwboid corpuscles, 4 

■ movement, 4, 5, 24, 58 

Amphophile cells, 27 

Ampulla, 460 

Anterior column of cord, 17<'> 

corpus quadrigeminura, 231 

grey commissure. 174 

horn of cord, 173 

lateral tract, 179 

nerve-roots from cord, 187 

white commissure, 187 

Aorta, 109 
Aponeurosis, 47 
* 



of spinal 



Aqueduct us Sylvii, 220 

vestibuli, 461 

Arachnoid membrane 

cord, 170 

of brain, 235 

Arachnoidal villi, 235 

Arborisation, 151 

Arenate fibres of medulla, 213 

Areolar tissue, 48 

Arrector pili, 419 

Arteriaj ciliares breves, 440 

recurrentes, 440 

helicinte, 385 

rectse, 369 

Arteries, 108 
Arterioles, Afferent, 55 

of uterus, 397 

Articular cartilage, 63, 82 

nerve-corpuscles, 161 

Arjiienoid cartilage, 339 
Ascending degeneration, 180 

loop-tube, 364 

root of glosso-pharyngeal nerve, 

210 

of the eighth nerve, 215 

of the fifth nerve, 224 

Aster stage in nucleus, 15 
Attraction sphere, 9 
Auditory hairs, 464 

nen'e. Origin of, 217 

, Division of, 219 

teeth, 469 

Auerbaoh's plexus, 326 

Auricle of heart, 107 

Aiiriculo-ventricular valves, 106 

AxUemma, 145 

Axis cylinder, 144 

process of sympathetic 

ganglion cell, 263 
Axon, 144 



Bartholin's glands, 399 
Basement membranes of skin, 405 



490 



Elements of Histology. 



Basilar membrane of cochlea, 46ft 

Basket cells of cerebellum, 241 

Basophile cells, 27 

Bellini's ducts, 305 

Bile-duets, 330 

Bile capillaries, 336 

Bilirubin, 23 

Bioblasts, 9 

Bladder, S7, 371 

Blastoderm of chick, 2 

Blood, 19 

corpuscles, 19 

, their origin, 2S 

cysts, 115 

islets, 115 

glands of His, 126 

platelets of Bizzozero, 27 

-vessels, 105 

Bone, 6S 

cartilage, 6S 

cells, 71 

corpuscles, 71 

, Development of, 74 

trabecultf , 74 

Bowman's capsule, 360 

elastica anterior, 42!' 

glands, 481 

membrane, 429 

sarcous elements, 94 

Brachia, 233 

Brain membranes, 235 

structure, 243 

Bronchi, 343 

BrowTiian molecular movement. 

300 
Bruch, Glands of, 427 
Briicke's elementary organisms, 5 

oikoid and zooid, 22 

tunica nervea, 456 

Brunner's glands, 328 
Buccal glands, 298 
Bulbus olfactorius, 250 
Biitsclili's nuclear spindle, 15 



Calcification of bone, So 

of cartilage, 65 

• of dentine, 283 

Calices of kidney, 356 
Canal of Schlemm, 434 

of Stenson, 482 

of Stilling, 444 

Canalis hyaloideus, 322, 444 

Petiti, 443 

reuniens, 461 

Canaliculi in bone, 70 

in cartilage, 65 

Capillaries of marrow-bone, 111 



Capillaries of nerve system, 111 
Capillary bile-ducts, 336 

blood-vessels. 111 

• lymphatics, 119 

network in mucosa, 801 

sheaths, 354 

Capsule of Bowman, 360 

of ganglion cells, 255 

of Glisson, 333 

of kidney, 356 

of the spleen, 351 

Cartilage, 63 

, Articular, 64 

capsule, 64 

cells, 63 

, Elastic, 67 

, Fibrous, 66 

, Hyaline, 63 

, Lacun*, 63 

of Jacobson, 482 

of Luschka, 339 

Cavernous tissue in tactile liairs, 
418 

in organ of Jacobson. 483 

tissues in genital oigans, 384 

Cavities of tendon sheaths, 121 
Cavum tympani, 459 
Cell enclosures, 9 

protoplasm, 7 

Cells, 5 

, Muscular, of blood-vessels, 88 

, of intestine, 88 

, of respiratory organs, 88 

-, of stomach, 88 

, of urinary organs, 88 

in tadpole's tail, 50 

of Claudius, 468 

of Corti, 471 

of Deiters, 236. 471 

of Golgi, 242 

of Martinotti, 246 

of Purkinje, 239 

Cellulai mastoide*, 4.59 
Cellular tissue, 48 
Cement of teeth, 279 

substance, 30 

of endothelium, 40 

of epithelium, 30 

of fibrous tissue, 47 

Central canal, 185 

grey nucleus, 185 

Centroacinous cells, 331 
Centrosome, 9 
Cerebellum, 237 
Cerebrum, 243 
Ceruminous glands, 409 
Cer\ix of uterus, 395 
Chalice cells, 36 
Chondrin, 46, 63 



l.VDEX. 



491 



Chondroclasts, S:'> 

Choroidal portion of ciliary muscle, 

87 
Choroid lueinbrane, 440 
Chromatic granules in ganglion 

cells, 1H4 
Chromatin, 11 
Chromosomes, 11 
Chyle, S-M 

vessels, 31i> 

Ciliary muscle, 435 

nerves, 43S 

processes, 438 

Cilia, 404 
Ciliated eells, 3o 
Circulus arteriosus in iris, 438 
Circumanal glands, 409 
Circumcellular plexus, 265 
Cisterna lymphatica magna, 1-21 
Clarke's columns, H»2 
Cleavage of ovum, 2 

of white blood corpuscles, 25 

Clitoris, 309 

Cochlea, 465 

Cohnheim's areas, 93 

Colloid, 4S5 

Colostrum corpuscles, 403 

Coloiu-ed blood corpuscles, 19 

Colourless blood corpuscles, 23 

Columnar epithelial cells, 30 

Commatract, 179 

Commissure, Grev, of spinal cord, 

173 

, Wliite, of spinal cord, 187 

Compound lymphatic glands, 134 
Concentric bodies of Hassall, 132 

lamellie, 72 

Cone fibre, 451 
Cones of retina, 452 
Coni vasculosi, 379 
Conjunctiva, 424 

blood-vessels, 426 

bulbi, 426 

lymphatics, 427 

nerves, 427 

palpebrse, 424 

Connective tissue, 46 
Contractility of corneal corpuscles, 

52 

of pigment cells, 54 

Contraction of muscle, 99 

wave, 99 

Convolution of brain, 243 

in nucleus, 13 

Corda? tendinete, 106 
Cords of adenoid tissue, 127 
Coriuni, 404 
Cornea, 50, 429 
nerves in, 431 



Corneal cells, 50 

corpuscles, 50, 430 

Cornuain cord, 173 
Cornua uteri, 396 
Corpora cavernosa, 384 

geniculata, 270 

quadrigemina, 226 

striata, 249 

Corpus callosum, 249 

Highmori, 372 

luteum, 391 

restiforme, 209 

spongiosum, 384 

Corpuscles, Malpighian, 353, 359 

of blood, 20, 23 

of bone, 71 

of connective tissue, 48 

of Grandry, 160 

of Herbst, 158 

of lymph, 123 

of Meissner, 158 

of muscle, 94 

of nerve, 145 

■ of Pacini, 155, 423 

of Vater, 155 

, Tactile, 158, 423 

Corti's arch, 470 

cells, 471 

ganglion, 465 

organ, 469 

rods, 469 

Cortical layer of ovary, 387 

lymph-sinus, 136 

Costal cartilages, 63 

pleui-a, 122 

Cowper's glands, 383 
Cremaster internus, 381 
Crenate blood corpuscles, 21 
Crescents of Gianuzzi, 294 
Cricoid cartilage, 339 
Crista acustica, 338 

spiralis, 342, 347 

Crus cerebri, 229 

, Crusta of, 233 

Crusta petrosa, 463 
Crypts, 129 

of Lieberklihn, 318 

Cuticle of Xasmyth, 284 
Cutis anserina, 420 

■ vera, 404 

Cystic duct, SS 
Cytogenous tissue, 126 
Cytoplasm, 7 



Deiters' cells, 236, 471 

phalanges, 473 

Demilunes of Heideuhain, 



294 



492 



Elements of Histology, 



Dendrite, 197 
Dendron, 151 
Dentinal canals, 277 

fibres, 277 

sheaths, 277 

tubes, 85 

Dentine, So 

Descemet's membrane, ijl, 430 

Diapedesis. 113 

Diaphragm, 44, 122 

Diaster stage in nucleus, 16 

Diffuse adenoid tissue, 127 

Dilatator puiiiUte, 437 

Direct division, 12 

"Disetactil," 161 

Discus p>roligerus, 390 

Disdiaclasts, 104 

Dispireme, IG 

Distal convoluted tubes, 365 

Division, Remak's mode of, 12 

Doyere's nerve-mount, 165 

Ductless glands, 484 

Ducts of pancreatic gland, 330 

of salivary gland, 291 

Ductus ejaculatorii, 381 
Dui-a mater, 170 
Dural sheath, 457 



Ear, External, 458 

, Internal, 460 

Ectoplasm, 8 
Eosinophile cells, 27 
Efferent lymphatics, 138 

medullated nerve-fibres, ISS 

veins, 56 

Elastic fenestrated membrane of 

Henle, 61 
Elastin, 60 
Electric nerve, 14S 
Eleidin, 33 
Elementary fibrill*, 145 

fibrils, 47 

organisms, 5 

Enamel, 275 

cap, 281 

cells, 281 

organ, 280 

• prisms, 275 

End-bulbs of Krause. 159 

Endocardium, 105 

Endochondral formatio of bone, 

75 
EndoljTQph, 461 
Endolympliangial nodules, 128 
Endomysium, 91 
Endoneurium, 142 
Endoplasm, 8 



Endothelial cells, structure, 40 

membrane, 40 

Endothelium, 40 

Endotheloid ceU-plates, 126 

Energid, 6 

Engelmann's intermediate disc, 

95 
Ependvma, 211 
Epidermis, 33, 404 
Epididvmis, 379 
Epiglottis, 67, 339 
Epineurium. i41 
Epithelial cells, 30 

, Division of, 38 

, Regeneration of. 38 

Epithelium, 30 
Ergastic structures, 6 
Erythi-oblasts, 28 
Eustachian tube, 459 
External arcuate fibres, 213 
Eyeball, 426 

lashes. 424 

lids, 424 



Fascise, 48, 49 
Fascia dentata, 249 
Fascicles, 91 
Fasciculus cuneatus, 178 

of Goll, 179 

of Lissauer, 179 

pjrramidal, 177 

Fat cells, 55 

and starvation, 58 

Fenestra ovalis, 460 

rotunda, 460 

Fenestrated membrane, 45, 48 

of Henle, 61 

Fertilisation of ovum, 2 

Fibrfe arcuat«, 213 

Fibres. Connective tissue, 46 

, Elastic tissue, 60 

of muscle, 86, 91 

of nerves, 140 

of Puikinje, 106 

Fibrillie of connective tissue, 47 

of muscle, 92 

of nerve, 145 

Fibro-cartilage, Q() 

Fibrous tissue development, 59 

Fillet, 225 

Fissura orbitalis, 88 

Fissure of Rolando, 243 

Fissures of spinal cord, 175 

of medulla, 202 

Foetal tooth papilla, 280 
Follicles, Hair, 409 
, Lieberklihn's, 318 



Index. 



493 



Follicles, Lyinpb, 12ti 

, 8ebac»'oiis, 418 

, Thyiuus, 131 

Fornix conjunctivae, 426 

vatdna?, 3'.»S 

Fossa glenoidalis, 66 

navicularis, 383 

IKJtcllari.s, 443 

Fovea centralis, 455 

hemielliptica, 460 

hemispherica, 460 

Fuhilus of peptic gland, 312 
Funiculus cuneatus, 202 
gracilis, 202 



Gall-bladder, 336 

Ganglia, Cerebro-spinal, 253 

, Svmpathetic, 25tt 

Ganglion ceUs, 191, 239, 243, 253 
Gasserian ganglion, 253 
Gelatinous tissue, 62 
Geniculate ganglion, 270 
Genital coq>uscles of Krause, 160 

end-corpuscles, 1 55 

organs (male), 372 

(female), 386 

Germ reticulum of von Ebner, 377 
Germinating cells, 44 

endothelial cells, 43 

epithelium, 387 

spots, 1, 388 

vesicle, 1, 388 

Giralde's organ, 380 
Gland, Prostate, 382 
Glunds. agminated, 130, 321 

, Bartholini, 399 

, Bionchial, 349 

, Brunner, 328 

, Buccal, 298 

, Carotic, 488 

, Ceruminous, 409 

, Coccygeal, 4SS 

, Harder, 428 

, Krause, 426 

, Laclirymal, 427 

-. Lieberkiihn's, 318 

. Littre's, 383 

, Lymphatic, 126, 134 

. Meibomian, 424 

. Mohl, 425 

, ilucous, 287, -298 

. Peptic. 312 

. Pever, 321 

, Pyloric, 313 

, Salivary, 286 

, Sebaceous, 418 

, Serous, 286, 299 



Glands, Solitary, 130 

, Submaxillary, 286 

-: , Sweat, 407 

, Thynuis, 131 

, Thyroid, 484 

Glandulie agminat^e, ISO 

lenticulares, 315 

Pacchioni, 235 

uteri nte, 396 

Glans clitoridis, 399 

penis, 384 

Glassy membrane, 411 
Glissons capsule. .333 
Globulin, 21 
Globus major, 380 
Glomeruli. 251, 360 
Glycogen, 9, 23, 335 
Goblet cells. 36 
Golgi's eeUs, 242 

method, 182 

tendon spindles, 167 

Goll's tract, 179 
Graafian follicles, 388 
Grandry's corpuscles, 160 
Granular leucocytes, 26, 58 
Granules in blood, 27 
Granulosa, membrana, 388 
Grey commissure, 174 
Ground lamelhe, 73 

plexus of Arnold, 162 

substance, 46 

Growing capillaries, 113 



Habenula X'erforata, 473 
Hajmatin, 23 
Haematoidiu, 23 
Hsematoplasts, 27 
Hiemin crystals, 23 
H*nioglobin, 22 

cnstals, 23 

Hah-, 414 

bulb, 412 

, Development of, 416 

fibres, 413 

foUicles, 409 

knob, 416 

, Marrow^ of, 413 

, Xew formation of, 415 

l>apilla. 411 

, Root of. 413 

sheath of, 412 

sac. 411 

, Shaft of, 414 

Harder's gland, 428 
Haversian canals, 72 

lamellie, 72 

spaces, 74 



494 



Elements of Histology. 



Heart anrl blond-vessels, 105 

Helicotrenia, 469 

Henle. Fenestrated membranes of, 

•51. lOS 

, Fibres of, 62 

, Sheath of, 142 

. Stratum nervemii of, 456 

, Tulies of, 364| 

Hensen's cells, 472 

median disc, 9S 

Hepatic cells, 335 

duct, 336 

lobules, 333 

veins, 335 

Herbst, Corpuscles of, 158 
Hilum of lymph glands, 134 

of salivarj- glands, 291 

of spleen, 352 

Hippocampus, 249 

Homogeneous elastic membranes, 

61 
Howship's lacunse, 85 
Huxley's layer, 414 
Hyaline cartilage, ii3 

leucocyte, 26 

Hyaloid membrane, 443 
Hyaloplasm, 7 
Hypophysis, 484 



Ileum, 321 

Incremental lines of Salter, 278 

Incus, 459 

Indirect division, 13 

Infundibula, 88 

of bronchiole, 345 

of gland, 299 

Inner molecular layer, 449 

nuclear layer, 449 

Interarticular cartilages, 66 
Interfascicular spaces, 49 
Interglobular spaces of Czermnk. 

278 
Interlobar ducts, 291 
Interlobular bile-ducts, 336 

connective tissue of liver, 333 

ducts, 291 

Intennediate cartilage, 66 

disc, 96 

plexus, 162 

zone, 315 

Intermembranous formation of 

bone, S3 
Intermuscular fibrils, 163 
Internal arcuate fibres, 213 

cajjsule of brain, 233 

Intervertebral discs, 66 
Intestine, Large, 317 



Intestine, Small, 317 
Iiitima of arteries, 108 
Intralobular bile-capillaries, 336 

veins, 335 

Intranuclear network, 11 
Iiis, 436 

. Blood-vessels of, 438 

; Lymph-clefts of, 438 

, Lymph-sinuses of, 438 

, Nerve-fibres of, 438 



Jacobson's organ, 482 



Karyokinesis, 13 
Karyomitosis, 13 
Karyoplasm, 11 
Keratin, 33 
Kidney, 356 

, Afferent arterioles of, 368 

blood-vessels, 367 

glomerulus, 360 

lymphatics, 370 

parenchyma, 357 

vessels, 367 

Killliker's muscle buds, 102, 166 

muscle spindle, 102 

osteoclasts, 85 

tract cells, 197 

Kilhne's nerve-ending in muscle, 
164 

rhabdia, 92 

rhodopsin, 453 

sarcoglia, 100 



Labia pudendi majora, 420 
Labium tymjianicum, 467 

vestibulare, 467 

Labyrinth, Osseous, 460 
Lachrj'mal glands, 427 
Lacunfe Morgagni, 383 

of bone, 70 

of cartilage, 63 

— — of lymphatics, 51 
Lamellai of bone, 70 

of cornea, 429 

of lens, 442 

Lamina cribrosa, 456 

elastica of cornea, 429 

fusca, 434 

reticularis, 473 

spiralis ossea, 460 

vitrea, 438 

Langerhans' gi'anular layer, 34 



Index. 



495 



Larvnx, 330 r 
Lateral fillet, 228 

horn, 174 

nucleus, 211 

tract, 175 

Lemniscus, 214 
Lens. 442 

tibres, 442 

stars, 443 

Lenticular plands, l.iO 
Lencajmia, 20 
Leucocyte, 23 
Leucocj-tosis, 20 
Leucopenia, 20 
Ligamentuni denticulatum, 171 

latum, 386 

pectinatum, 434 

pulmonis, 347 

spirale, 4(57 

suspensory of lens, 443 

Liniitans, externa, 451 

interna, 447 

Lines of Salter, 278 

of Schreger, 279 

Liquor folliculi, 390 

sanguinis, 19 

Littre's glands, 388 
Liver, 333 

, Vessels of, 335 

Lobes of pancreas, 330 

of salivary gland, 200 

of thymus gland, 131 

of lung, 346 

Lobules of liver, 333 

of lung, 346 

of salivary glands. 290 

of thymus gland, 131 

Locus ccenileus, 228 
Lung, 346 

blood-vessels, 349 

Ivmphatics, 349 

Lymph, 123 

Lvmphatic capillaries. 119 

^— clefts, 119 

glands, 126, 134 

rootlets, 119 

sinuses, 120 

tissue, 62, 126 

vessels, 117 

Lymphatics, 117 

in mucosa, 302 

Lymph-canal system in cornea, 51 

-canalicular system, 119 

cavities. 120 

corpuscles, 123 

follicles, 126 

hearts, 123 

Lymphocyte, 25, 58, 123 
Lymiihoid cells, 25 



Macula acustica, 463 

lutea, 454 

Malleus, 459 

Malpighian corpuscles of kidney, 
359 

of spleen, 353 

pyramids of kidney, 357 

stratum of skin, 33 

Mammary gland, 401 
Manubrium mallei, 459 
Marchi's method, 182 
Marrow of bone, 68 
Matrix of osseous substance, 70 
^Meatus auditorius extemus, 458 
Meckel's ganglion, 253 
Media of arteries, 108 
Median fillet, 228 

lateral fissure, 176 

^fediastinum testis, 372 
Medulla oblongata, 202 

of gland, 134 

Medullary cylinders, 135 

lymph-sinus, 136 

ray, 359 

sheath of nerve-fibres, 145 

Medullated nerve-fibres, 143 
Meibomian glands, 424 
Meissner's corpuscles, 158, 423 

plexus, 261, 266, 326 

Membrana basilaris, 469 

• chorio capillaris, 441 

Descemeti, 430 

granulosa, 388 

hyaloidea, 443 

reticularis, 473 

secundaria, 460 

supra-choroidea, 434 

tectoria, 474 

tympani, 458 

Membrane of Krause, 96 
Mesencephalon, 229 
Mesentery, 122 
Mesogastrium, 45 
Metakinesis, 15 
Microcytes, 20 
Microsomes, 9 
Migratory cells. 44 
Milk, 403 

• globules. 402 

tooth, 283 

Mitoina, 11 
Mitral cells, 251 
Modiolus, 465 
Monaster, 15 
Motor ganglion cells, 197 
Moss fibres, 243 
Movement of cilia, 35 
Mucin, 37 
Mucosa, 300 



496 



Elements of Histology. 



Mucosa, Lymph follicles of, 128 
Mucous cells, 2'.)3 

glands, 2Sr, 298 

membrane, 300 

Miico-salivary glands, 288 
Mucus, Formation of, 36 
Miiller's fibres, 447 

muscle, 435 

Muscle bundles, 87, !)1 
— — buds, 102 

cells, 86 

column, 92 

corpuscles, 94 

libres, 86, 90 

librillEe, 92 

sheath, 87 

spindle, 102 

tissue, Striped, 90 

. Non-striped, 86 

Muscular compartments, 98 
Muscularis externa, 308 

mucosEe, 308 

Musculus ciliaris Riolani, 424 
Myeloplax, 7, 85 
Myeloplaxes of Robin, 85 



Xail, 420 

cells, 420 

groove 420 

substance, 420 

Xasal mucous membrane, 475 

sei)tum, 63 

Nerve bundles, 141 

corpuscles, 145 

end plate, 16o 

endings, 155 

fibres, 140 

plexus, 143, 150 

unit, 268 

Network of fibrill*, 153, 167 
Neurilemma, 145 
Neuroglia, 182 

cells, 184 

fibrils, 183 

of Virchow, 182 

• tissue, 62 

Neuraxon, 144 

Neuron, 268 

Neurokeratin, 146 

Neutropliile cells, 27 

Nipple, 401 

Non-medullated nerve-fibres, 148 

Nuclear layer in bulbus olfae- 

torius, 251 
membrane, 11 

substance, 11 

zone, 442 



Nucleoli, 11 
Nucleoplasm, 11 
Nucleus, .Structure of, H 
Nucleus ambiguus, 215 

arciformis, 213 

cuneatus, 206 

gracilis. 206 

Nuclei, Inner, of retina, 449 

, Outer, of retina, 451 

Nymphae, 399 



Odontoblasts, 277, 280 
0']sophagus, 307 
Olfactory bulb, 250 

cells, 478 

glomeruli, 251 

nerves, 148, 480 

Olivary bodies, 206, 207 

nucleus, 207 

Omentum of cat, 44 

of frog, 122 

of guinea-pig, 45 

of rat, 45 

, Structure of, 48 

Optic chiasma, 270 

lobes, 231 

nerve, 456 

nerve-fibres, 447 

tract, 270 

■ vesicle, 455 

Ora serrata, 447 
Organ of Corti, 469 

of Giralde, 380 

of Jacobson, 482 

Ossein, 70 

Osseous labyrinth of ear, 460 

lamella;, 70 

substance from osteoblasts, 85 

Ossicula auditus, 459 

Ossifying cartilage, 77 
Osteoblasts forming bone, 84 
Osteoclasts, 85 
Osteogenetic layer, 68 
Otoliths, 339 
Oval nucleus, 41 
Ovary, 386 

, Development of, 392 

, Lymphatics of, 282 

, Nerves (jf, 282 

Oviduct, 394 
Ovum, 1, 388 
Oxyntic cells, 312 
Oxj-phile cells, 27 



Pacinian corpuscles, 155 
Palate, 298 



Index. 



497 



Palmiii plicata\ 305 
Pallicbni', 4-24 
Pancreas, 330 
Papilla oircimivallata, 305 

liliJormis, 30-' 

foliata, .•i05 

fmi^iformis, 302 

iiervi optiri, 44t) 

Papillary hair ofUiiiia, 410 

muscle, ItiC. 

Paraglobiilin, 22 
Paraiiuck'i, IS 
Paraplasm, 51 
Parenchyma of kidney, 357 
Parenchymatous cartilage, 66 
Parietal cells, 312 

Pars ciliaris retiuic, 430 

niembranacea, 3S3 

prostatica, 383 

Pedunculated hydatid of .Alor- 

gagni, 380 
Pedunculus cerebelli, 238 
Penis, 384 

corpora caveinosa, 3S4 

nerve-endings, IGO 

Peptic glands, 312 
Peribronchial lymphatics, 340 
Pericardial cavity, 121 
Pericellular space, 201 
Pcrichimdriuni, ti3 
Perilymph, 401 
Perilynjphangial nodules, 128 
Perimysium, 01 
Perineurium, 141 
Periosteal bone, 75 

f(jrmation, 84 

j)tocesses of Virchow, 75 

Periosteum, 68 

Peripheral nerve-endings, 155 
Peritoneal cavity, 121 
Peritoneum, 41 
Perivascular lymphatics, 110 

lymph spaces, 201 

Peyer's ulands, 321 

- - pat'rh, 130 
Phagocvtes, 25, 50 
Pharynx, 208 

tonsil, 302 

Pia mater, 170, 235 
Pial sheath, 456 
Pigment cells, 52 
Plasma, 10 

cells, 50 

Pleura pulmonalis, 347 
Pleural cavities, 121 
Plexus choroideus, 235 

myentericus, 326 

Meissner, 326 

venosus vaginalis, 308 



Plica} villosa?, 311 
Polar bodies, 18 
Pons Varolii, 226 
Porta, hepatis, 333 
Portio iMiilleri, 435 

vaginalis uteri, 305 

Posterior nerve roots from spinal 

cord, 188 
Postganglionic libres, 2r)4 
Pricganglionic fibres, 265 
Prickle cells, 37 
Primitive dental groove, 280 

tibrilhe, 15U 

fibrils, 02 

ova, 393 

Prostate, 382 
Protoblast, 6 
Protoplasm, 1, 7 

, ^5tructure of, 7 

Protoplasmic memlirane, 55 
Proximal convoluted tubule, 362 
Pulp tissue, 270 

Purkinje's ganglion cells, 239 
Pyloric glands, 313 
Pyramid of Ferrein, 350 
Pyramidal decussation, 204 

tracts, 177 



Rami capsulares, 337 

Ranii'm y Cajal's discoveries, 182, 

180, 440, 450 
Ranvier's constrictions, 146 

nodes, 146 

Raphe, 209 

Red blood corpuscles, 20 
Red nucleus, 230 
Reissner's membrane, 46 
Eemak's fibrous layer, 108 

nerve-fibre, 148 

Rete Malpighii, 33 

mucosum, 33 

testis, 370 

Reticular cartilage, 67 

formation, 200 

Restiform body, 200 
Retina, 445 

, Blind spot of, 446 

, Blood-vessels of, 456 

, Ganglion cells of, 448 

, Lymphatics of, 456 

Rhabdia of Kiihne, 92 

Rhodopsin of Kiihne, 453 

Rods and cones, 452 

Rollett's secondary substance, 

03 
Rosette stage in nucleus, 13 
Rugse, 30S 



49S 



Elements of Histology. 



Rutherford's scheme of ir.uscle 
contr.iction, 99 



Saccules, -k52 

Saccus endolvmphaticus, 461 

Saliva, 300 

Salivary cells, 293 

• glands, 2S6 

. Blood-vessels of. 297 

, Ducts of, 291 

. Lobes of, 290 

: Lobules of, 290 

, Lnnphatics of. 297 

, Xenes of. 297 

Sarcode of Dujardin, .j 
Sarcoglia, 100 
Sareolemma, 91 
Sarcoplasma, 92 
Sarcoplasts, 101 
Sarcous elements, 94 
Scala tAiupaui, 465 

vestibuli, 335, 465 

Schultze's protoplasm, 5 
Schwann's cells. 5 
Sclerotic, 432 
Scrotum, S7 
Sebaceous follicles, 41S 
Semicircular canals, 462 
Seminal cells, 375 

tubules, 374 

Sensory decussation, 207 

end-organs in muscle, 166 

in tendon, 16S 

ganglion cells, 197 

Septum cistenise lymphatiese. 45 
Serous glands, 2S6, 299 

membranes, 122 

Sesamoid cartilages, f>*^ 
Sharpevs perforating fibres, 74 
Sheath" of Henle, 142 

of Schwann, 145 

Simple axis cylinders, 153 

Ivmphatic glands, 126 

Skin, 404 

-, Blood-vessels of, 421 

, Lymphatics of, 422 

. Nerves of, 423 

Solitarv glands. 130 

lymph follicles, 321 

Spaces of Foutana, 434 
Spermatoblasts, 377 
Spermatozoa, 37S 
Sphincter pupillae, 437 
Sphincters, SS 
Spinal accessor^-, 203 

conl, 170 ! 

grey matter, 191 



.Spinal cord white matter, 186 
Spiral fibre. 267 

tubule, 363 

Spireme, convolution, 13 
Spleen, 3jl 

, Capsule of, 351 

, L^Tiiphatics of, 355 

, Xerve-tibres of, 242, 355 

. Parenchyma of, 352 

, Pulp o.^'353 

. Red blood corpiLScles of, 2S 

, Trabecule of, 352 

Spongioblast, 450 

Spongioplasm, 7 

Spong'y bone substance, 74 

Squamous epithelial ceils, 32 

Sternal cartilage, 63 

Stigmata, 112 

Stomach, 310 

Stomata, 112, 121, 349 

Stratified columnar epithelium, 35 

pavement epithelium, 32 

Stratum adiposmn. 406 

cinereum, 231 

comeum, 33 

■ glomerulosum, 251 

granulosum, 34, 250 

lacunosum, 249 

lemnisci, 231 

liicidum, 33 

Malpighii, 33 

optieum, 232 

radiatum, 249 

zonale, 231 

Strife acusticte 220 

Stria vascularis, 468 

Stroma, 22 

Subarachnoidal spaces, 121, 170 

tissue, 171 

Subcutaneous lymphatics, 422 

tissue, 406 

Subdural spaces, 121, 170 
Subendocardial tissue, 105 
Subepithelial endothelium of De- 

l)Ove, 51 
Subhyaloid ceUs, 443 
Submaxillary ganglion . 253 
Submucosa, 300 
Submucous lymphatics, 121 
Subpericardial nerve branches, 107 

ti.ssue, 106 

Substantia ferruginea, 225 

gelatinosa, iS6 

nigra. 229 

Subvaginal space, 457 
Sudoriferous canal. 407 
Sulcus hippocampi, 249 
spiralis, 467 

Superior pedunculus cerebelli, 22S 



Index. 



499 



Suprachoroiilal tissue, 434 
.Suprarenal bodies, 480 
Supravaj^iiial space, 457 
Suspt'usory ligament, 443 
Sweat glan< Is, 407 
Sympathetic system, "258 
Synapsis, ]9f> 
Synovial cavities, 121 



Tactile eurpuscles, 1-38, 423 

hairs, 417 

Tapetuni nigrum, 43!>, 454 
Tarsal plate, 424 

Taste buds, 305 

cells, 305 

goblets, 305 

Teeth, 275 

cement, 279 

develoimient, 280 

pulp. 279 

Tegmental cells, 305 
Tegmentum, 231 
Teichmann's crystals, 23 
Tendon cells, 49 

spindles, 167 

Temlons, 49 
Tendril fibres, 243 
Tenoniau capsule, 457 

space, 457 

Tensor choroidete, 435 
Ternainal bronchi, 347 
Testis, 372 
Thoracic duct, 117 
Thymus fullicles, 131 

■ gland, 131 

Thyroid cartilage, 63 

gland, 484 

Tongue, 302 

, Serous glands of, 304 

Tonsils, 129 

Touch-cells of Merkel, 161 

corpuscles of Merkel, 169 

Trabecule carne*, 106 

of lymphatics, 134 

of sjileen, 352 

Trachea, 343 

Tracts of white matter in cord, 17 
Tract cells, 197 
Transitional epithelium, 35 
Transverse disc, 95 
Trapezoid nucleus, 218 
Trapezium, 218, 226 
Tuba Eustachii, 459 
Tubercle of Rolando, 202 
Tnberculuni acusticum, 219 
Tubes of epididymis, 379 
Tunica adnata, 372 



Tunica albuginea, 37 

dartos, 88 

fibrosa. .390 

prnpriii, 4i>9 

• vaginalis, 372 

Tyson's glands, 384 



Ureter, 371 
Urethra, Female, 399 

, Male, 383 

Urinary tubules, 361 
Uterus, 395 
Utricle, 462 
Uvea, 437 



Vagina, 397 

Varicose nerve-fibres, 147 

Vas deferens, 381 

rectum, 378 

Vasa etferentia, 379 
Vascularisation of cartilage, 75 
Vater's corpu.scles, 155 
Veins, 110 

, Intima of, 110 

, Media of, 110 

of the bones, 110 

Veins of the l)rain, cord, gravid 
uterus, membranes, and retina, 
110 

, Valves of, 110 

Vena axillaris, azygos, cava, cru- 
ralis, hepatica, intima, iliaca, 
mcsenterica, jtoplitea, I'enalis, 
spermatica, and umViilicalis, 110 

jugularis, and subclavia, 110 

Venae rectie, 369 

stellatfce, 370 

vorticosse, 441 

Venous radicles, 353 

sinuses, 353 

Ventricle, Fourth, 211 
Ventricles, 106 
Ve.sicula; seminales, 381 
Vestibulum of labyrinth, 460 
Virchow's crystals, 23 
Visceial pericardium, 105 

peritoneum, 333 

Visual purple, 453 
Vitreous body, 443 



Wandering cells, 58 
Weigert's method, 182 
White blood corpuscles, 23 



500 



Elements of Histology. 



White commissure, 187 

fibrous tissue, 40 

substance of brain, 237 

of cord, ISiJ 

of Sclnvann, 145 

Wolffian body, 374, 3S7 

Wreath arrangement of nucleus, 14 



Yellow elastir cartilai 



Yellow elastic tissue. 00 



Zona fasciculata, 487 

glomerulosa, 486 

pel In ei da, 1, 388 

reticularis, 487 

vasculosa, 386 

Zonula ciliaris, 443 
Zinnii, 443 



I'rintedbyC'AssKLL & Company. LnnTED. La Belle Sau\aye, Louilon, E.G. 



\ 



K67*^ 
1698 



lamdb