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QUAIN'S

ELEMENTS OF ANATOMY

EDITED BY

EDWARD ALBERT SCHAFER, LL.D., F.R.S.

PROFESSOR OF PHYSIOr.OCVY AND HISTOLOGY IN UNIVERSITY COLLEGE, LONDON,

GEORGE DANCER THANE,

PROFKSSOR OF ANATOMY IN UNIVERSITY COLLEGE, LONDON.

IN THREE VOLUMES.

VOL. IIL — PART IV.

SPLANCHNOLOGY.
By professor E. A. SCHAFER, F.R.S.

AND

PROFESSOR JOHNSON SYMINGTON, M.D.

PROFESSOR OF ANATOMY [N C^UEEN's COLLEGE, BELFAST.

ILLUSTRATED BY 337 ENaRAVINGS.

CciUlj (irBition.

LONGMANS, GREEN, AND CO.

31) PATEUNOSTEK ROW, LONDjON

NEW YORK AND BOMBAY

1898.

■ \f , r II ; 1 f I' I

BIBLIOGKAPHICAL NOTE.

Nmth ErUtivn, 2 Vols., 8vo. November, 1882; Vol. I. Reprinted March, 1884;
October, 1887. Vol. II. Reprinted December, 1883 ; April, 1887.

Tenth Edition, edited by E. A. Sch'dfer and G. D. Thane, in 8 separately issued
Parts and an Appendix, 1890-6.

Vol. III., Part IV., first separate issue January, 1896; Reprinted ivith additions
and emendations in Text and Figures on pp. 79, 174, 181, 229, October, 1898.

ADVERTISEMENT TO THE TENTH EDITION.

The successive Editions of Di". Jones Quain's *' Elements of Anatomy ''
were, up to the Fourth inclusive, published under the superintendence of
the original author. At his death the duty of editing- the Fifth Edition,
which was published in 1845, was undertaken by Mr. Richard Quain, then
Professor of Anatomy, and b}' Dr. William Sharjjey, who occupied the chair
of General Anatomy and Physiology in University College. On that
occasion extensive changes were made throughout the work, and a great
part was rewritten. This applies especially to the General and Visceral
Anatomy, edited by Sharpey, in which that distinguished Anatomist and
Histologist published many valuable original observations. Indeed from
this time for 35 years the influence of Sharpey was conspicuous throughout
this part of the work, which was frequently referred to as " Quain and
Sharpey's Anatomy."

In the Sixth Edition the place of Mr. Richard Quain was taken by
Mr. G. V. Ellis, his successor in the chair of Anatom}^ in University College;
Shai*pey editing as before the General Anatomy and the Descriptive
Anatomy of the Viscera.

In the Seventh Edition, which was published in 1867, while the General
Anatomy continued to be edited by Sharpey, the whole of the Descriptive
and Visceral Anatomy was taken in hand by Dr. Allen Thomson, Professor
of Anatomy in the University of Glasgow, and by Dr. John Cleland, then
Professor in Galway, now the successor of Allen Thomson in Glasgow.
This portion of the work was in great measure recast by Cleland, and many
new figures from the facile pencil of Allen Thomson were added.

The changes in the Eighth Edition, which was published in 1876, and
was the first appearing under the auspices of the present publishers, were
still greater. On this occasion most of the Descriptive Anatomy was under-
taken by Dr. Allen Thomson, who also contributed a chapter on Embryology,
while the account of the Brain and Spinal Cord was placed under the editor-
ship of Dr. W. R. Gowers. The section on General Anatomy and the
chapters on the Thoracic, Abdominal and Pelvic Organs, and the Organs of
the Senses, were again edited by Sharpey, with the assistance of one of the

IV ADVERTISEMENT TO THE TENTH EDITION.

present Editors (Professor Schafer), much of this part of the work being
re-written and many new illustrations introduced.

In 1882 the Ninth Edition was published under the editorship of
Dr. Allen Thomson, Mr. E. A. Schafer, then AssistantProfessor of Physiology
in University College, and Mr. G. D. Thane, the successor of Ellis in the
chair of Anatomy. Dr. Allen Thomson undertook the revision of the
chapter on Embryology. Professor Thane re-edited the Descriptive Anatomy;
while the General Histology and the Special and Minute Anatomy of the
Yiscera, including the Brain and Spinal Cord, fell to Professor Schafer.

The preparation of the present Edition was commenced in 1890 by
Professors Schafer and Thane. It was decided to entirely remodel the
work, to increase the size of the page and the number of illustrations, and
to publish the several parts separately as they might be got ready for press :
each part being thus a special treatise on the particular subject denoted by
its title, and the whole being intended to form collectively a complete text-
book and work of reference in Anatomy. With this end in view a copious
Bibliography has been provided for each subject, and the illustrations have
been greatly multiplied. Many have been re-drawn upon a larger scale to
suit the page, and man}^ original figures have been added, other illustrations
having been copied from various monographs and standard works. Little
of. the original book now remains beyond the title, greater alterations having
been made in this than in any previous Edition since 1845.

The first parts to appear (1890) were those on Embryology (Professor
Schafer), and Osteologj^ (Professor Thane). In 1891 the General Anatomy
or Histology (Professor Schafer) ; and in 1892 the Arthrology, Myology and
Angeiology (Professor Thane) were published. In 1893 the Brain and
Spinal Cord made its appearance, and in the following year the Organs of the
Senses, both the work of Professor Schafer. A part dealing with the Nerves,
undertaken by Professor Thane, was published this summer, and a final
part, containing the Anatomy of the Digestive, Eespiratory, Urinary and
Generative Organs has now been added, thus completing the work. In
this part the anatomical descriptions have been allotted to and in many
cases entirely re-written by Dr. J. S^^mington, Professor of Anatomy in
Queen's College, Belfast, while the histological portion of the Splanchnology
has been re-edited by Professor Schafer. A chapter on Superficial Anatomy
will appear in the form of an Appendix, under the joint editorship of
Professor Thane and Mr. E. J. Godlee, M.S., Professor of Clinical Surgery
in University College.

The publication in separate parts will, it is hoped, be found convenient
to students and others using the work. The parts have been arranged so
as to facilitate their being bound up into volumes, although each part is
complete with Table of Contents and Index. Most of the labour of

ADVERTISEMENT TO THE TENTH EDITION. V

preparing the Index, which also partakes of the nature of a Glossary, has
fallen to Mr. T. W. P. Lawrence, M.B., F.R.C.S., Curator of the Museum
in Universit}^ College, who has devoted much time and attention to rendering
this important addendum as complete as possible.

The new illustrations in the first and third volumes have mostly been
executed by Mr. J. T. Balcomb, who has taken a large amount of pains to
meet the requirements of the Editors. The illustrations of the bones and
other new figures in the second volume have been engraved by Mr. C.
Butterworth, from drawings by Mr. Donald Gunn, Mr. T. W. P. Lawrence,
and Professor Thane.

The Editors are indebted to Mr. R. J. Smith for kindly looking through
many of the proofs of the final part.

JDccemher, 1S95.

COA^TENTS OF VOL. III., PART IV.

THE ORGANS OF DIGESTION.

PAGE

The Mouth i

The Toxgue 3

Mucous Membrane .... 4
Foramen caecum and Thyro-glossal

Duct 8

Glands ...... 9

Muscular Substance .... 9

The Palate 11

Hard Palate 11

Soft Palate 13

The Salivary Glanl.s . . . 15

Parotid Gland 15

Submaxillary Gland . . . . 16

Sublingual Gland . . . • i?

Structure 17

Mucous Alveoli . . . .19

Serous Alveoli . . . 20

Ducts ..... 21

The Teeth 24

Special Characters .... 26

Permanent Teeth . . . 26
Homologies . . . -29

Milk-teeth 30

Structure ...... 30

Pulp. 30

Dentine ..... 32

Enamel . . . . . 34

Grusta Petrosa or Cement . . 36

Varieties of Dentine . ■ • Z7

Development of Teeth • • ■ 37

Changes in the Dental Lamina . 40

Formation of Dentine . . 44

Formation of Enamel . . . 45

Formation of Cement . . 46

Dental Sacs 47

Formation of Alveoli ... 48
Eruption of the Milk-teeth . . . 49
Development of the Permanent Teeth 49
Eruption of the Permanent Teeth . 51
Histoiical Account of the Develop-
ment of the Teeth . . • ■ 53

Thk Phakyn.k 57

Na.sal Part 57

Oral Part 59

Tonsils 59

Laryngeal I'art .... 61

.Structure and Attachments . . . 61

Structure of the Mucous Membrane . 62

The (Esoi'hagu.s 64

The Acdo.me.v 68

The Pekitoneu.vi 69

The Stomach 71

Variations in Positioti . . . . 71

Cardiac Orifi'.e . .... 72

I'ylorus . . . . . 72

Dimensions ..... 75

•Structure 76

The SiQ-iAKcn— continued.

Gastric Glands .
The Smaxl Intestine
Structure .
Valvulae conniventes
ViUi
Glands
Duodenum
Jejunum and Ileum
Meckel's Diverticulum
The Large Intestine
Structyre .
Caecum

Vermiform Appendix
Ileocolic or Ileo-caecal Val
Colon
Rectum
Anal Canal
The Liver

Dimensions and Weight

Fissures

Ligaments and Omentum

Position with regard to

and Thoracic Parietes
Excretory Apparatus

Hepatic Duct

Gall-bladder .

Cystic Duct .

Common Bile-duct
Liver in the Infant
Structure .

Portal Vein .

Hepatic Veins .

Hepatic Cells

Biliary Ducts
The Pancreas .

ORGANS OF RESPIRATION
AND VOICE.

page

•

. 7S
. 86

. 86

. SS

• 89

100

102

103

105

108

109

dvo

III

116

[21

121

124

Abdomina

125

127

128

129

130

132

. .

132

133

. .

139

The Larynx

Thyroid Cartilage

Cricoid Cartilage

Arytenoid Cartilage

Cornieula Laryngis .

Cuneiform Cartilage.-, .

Epiglottis ....

Peculiarities according to Age and Sc.x

Ligaments and Joints

Interior .....

Vocal Cords ....

Piima Glottidis ....

Ventricles ....

Mucous Membrane

Muscles .....
The Tiiachea and Bkonchi
The Mediastinum Tuohacis

146

147
148
148
149
149
14..,
149
15'
15-:
154
15'
'5'
'5'
15.S
i6j
160

Vlll

CONTENTS OF PART IV.

Okgans of Respieation and Voice—

continued.
The PLETJRiE

The Lungs

Roots ......

Dimensions and Physical Properties
Condition in the Foetus
Minute Structure

Bronchial Tubes .
Pulmonary Alveoli .

PAGE

169

174
176
180
181
181
181
183

THE URINARY ORGANS.

The Kidney

Structure

Excretory Apparatus

Tubuli Uriniferi .

Bloodvessels
The Feetees .
The Ueinae,y Blabdee

Ligaments .

Peculiarities in Shape
according to Age .

Interior

Structure .

and

Position

189
192
193
195
201
204
206
211

212

2X2
213

REPRODUCTIVE ORGANS.

The Testes and Acces.sory Steuctuees 218

Spermatic Cord . . . . 218

Inguinal Canal . . . .218

Scrotum . . . . . . 219

Testicles . . . . . .221

Structure of Testicles . . . . 222

Tunica albuginea . . . 222

Seminiferous Tubules . . . 224

Spermatozoa .... 225

Epithelium of Seminiferous

Tubules . . ... 226

Interstitial Tissue . . . 230

Ducts of Testicles . . . . 230

Tubuli Recti .... 230

Rete Testis 230

Vasa Efferentia .... 230

Canal of Epididymis . . . 231

Vas Deferens .... 232

Vas Aberrans . . . . 233

Organ of Giraldes .... 234

Seminal Vesicles 234

Ejaculatory Ducts .... 235

The Penis . . ... . . 236

Corpora Cavernosa .... 239

Corpus Spongiosum . . . . 241

Reproductive Organs — The Penis

—

continued, PAGE

Male Urethra . . . . . 24.'?

Prostatic Portion .

243

Membranous Portion

246

Spongy Portion .

246

Cowper's Glands

247

Prostate Gland .

■ 247

The Vulva or Pudendum .

253

Mons Veneris

253

Labia Majora .

253

Labia Minora

254

Clitoris ....

255

Erectile Tissue .

255

Uro-genital Space .

256

Glands of Bartholin .

256

The Female Urethra

258

The Hymen and Vagina

. 258

The Uterus

260

Cavity ....

262

Position ....

262

Ligaments ....

263

Structure

264

Periodic Structural Changes

267

Peculiarities according to Age

268

The Fallopian Tubes .

269

The Ovaeies

271

Peculiarities according to Age

272

Epithelium and Stroma ,

273

Graafian Follicles

275

Structure of Ovarian Ovum

279

Structure of Corpora lutea .

280

Parovarium

282

The Mammaey Glands .

285

Nipple ....

285

Structure ....

286

Varieties ....

290

Milk

291

THE DUCTLESS GLANDS.

The Spleen 292

Accessory Spleens . . . . 296

Structure 296

Splenic Pulp 299

Malpighian Corpuscles . ... 298

The Supearenal Capsules . . . 302

Structure ..... 303

Function ...... 305

The Thymus Gland .... 307

The Thyroid Body . . . . 311

The Parathyroids . . . -315

The Carotid and Coccygeal Glands 317

The Peritoneum 319

Omenta . . . , . . 322

OEGANS OF DIGESTION.

BV E. A. SCHAFER AND J. SYMINGTON.

The digestive apparatus consists of the alimeutaiy canal, the teeth, and various
glands, the secretions of which are discharged through ducts opening into the canal.

The alimentary canal commences at the mouth and terminates at the anus. Its
total length is, on an average, about thirty feet.

The part situated in the head, neck, and thorax is comparatively straight, and
measures from its commencement at the opening into the mouth to its termination
in the stomach about 15 to 18 inches. The rest of the canal lies in the abdomen
and pelvis. If this portion extended in a straight line from the oesophageal opening
of the stomach to the anus, it would not exceed in length the part above the
diaphragm ; but in consequence of its convoluted and tortuous course, it is nearly
twenty times as long.

The part of the alimentary canal which lies above the diaphragm consists of the
mouth, throat, and gidtct ; while that contained in the abdomen and pelvis consists
of the stomach, and the small and large intestines. Numerous small glands are
situated in the wall of the alimentary canal, some in its mucous membrane, and
others in its submucous tissue. The larger glands, the ducts of which open into the
canal, are the salioarij glands and the liver and pancreas. The ducts of the salivary
glands open into the mouth, and those of the liver and -pancreas into the upper part
of the small intestine. Below and behind the tongue the alimentary canal is joined
by the wind-pipe. Since the respiratory tract is developed much in the same way
as a gland by an outgrowth from the ventral wall of the fore-gut and remains
permanently connected with it, the alimentary canal and respiratory organs are often
grouped together as the gaslro-pulmonary system.

THE MOUTH.

The cavity of the mouth opens anteriorly on the face by a transverse aperture
called the rima oris, while posteriorly it communicates with the pharynx through the
fauces {isthmus faucium). This cavity is divided into two parts, an outer and an
inner, by the alveolar arches and teeth (see fig. 1). The outer part (veslilndunt
oris) is Vxjunded externally by the lips and cheeks, and internally by the teeth and
gums, covering the outer aspect of the alveolar processes of the upper and lower
jaws. The roof and floor of the vestibule are formed by the reflection of the
mucous membrane of the lips and cheek inwards to the alveolar processes, which
it joins about the level of the middle of the fangs of the teeth. The exten-
sion of the vestibule upwards and downwards external to the gums may be called
the superior and inferior alveolo-la trial sulci. Each of these sulci is interrupted in
the middle by a small vertical fold of the mucous membrane called the framum
lahii. The fold connecting the upper lip with the gum is larger than that of the
lower lip. Tiie vestibulum oris receives on each side the secretion of the parotid
gland. The inner portion of the mouth (cavitm oris) lies within the concavity of
the alveolar arches, and is bounded above by the palate, while in its floor is situated
the tongue. It receives the secretions of the submaxillary and sublingual glands.

vol,, nr., I'T. 4. u

ORGAKS OF mGESTION.

When the teeth of the upper and lower jaws are in contact, the vestibule of the
mouth communicates with the cavity of the mouth proper merely by the narrow

10-—,.

11-

Fig. 1. — Coronal section of mouth behind the second molar teeth. (J. S. ) Natural size.

1, nasal fossa ; 2, maxillary antrum ; 3, cavum oris ; 4, superior alveolo-labial sulcus ; 5, vestibulum
oris ; 6, buccinator muscle ; 7, inferior alveolo-labial sulcus ; 8, sublingual gland ; 9, duct of Wharton ;
10, superior lingualis muscle ; 11, inferior lingualis ; 12, genio-glossus ; 13, genio-hyoid ; 14, mylo-
hyoid ; 15, anterior belly of digastric ; 16, platysma.

clefts between the teeth and a somewhat larger opening placed behind the last molar
tooth and in front of the ramus of the jaw.

Fig. 2. — Three papilla from the lip, with the blood-vessels injected. (Toldt.)

Fig. 3. — Part of a small mucous gland of the mouth. (Klein.)
a, alveoli ; d, duct

The lips and cheeks are composed externally of skin, and internally of mucoug
membrane, between which are included muscles, vessels, and nerves fully described in

THE TONGUE. 3

other parts of this work, areolar tissue, fat, and numerous small glands. The free
border of the lips is protected by a dry mucous membrane, which becomes continuous
with the skin, is covered with numerous minute vascular papillae (fig. 2), and is
highly sensitive. In some of these papillae nerve end-bulbs, approaching in character
to tactile corpuscles, are found.

Numerous small racemose glands (JahM glands) open on the inner surface of the
lips near the oral aperture. They are situated between the mucous membrane and
the orbicularis oris muscle.

Other small glands {buccal glands) lie between the buccinator muscle and the
mucous membrane of the cheek. Two or three, larger than the rest, found between
the masseter and buccinator muscles, and opening by separate ducts near the last
molar teeth, are called the molar glands. The secretion of these glands is under-
stood to be mucus ; whether it has any of the specific properties of saliva is not
known. Small sebaceous glands occur on the outer part of the red border of the lips.

The posterior part of the cheek contains a pad of fat surrounded by a well-defined
capsule (see Vol. II., Part 2, p. 293).

Immediately within the lips and cheeks are the denied arches, consisting of the
teeth, gums, and alveolar borders of the maxillte. The gums {gingiva-) are composed
of dense connective tissue, cohering very closely with the periosteum of the alveolar
processes, and covered by a red and highly vascular mucous membrane, which is
smooth in its general surface, but is beset with fine papillae in the immediate
vicinity of the teeth.

The mucous membrane of the mouth is lined by scaly stratified epithelium, the
cells of the deeper layers of which are united by intercellular bridges like those of
the rete Malpighii of the epidermis.

THE TONGUE.
The tongue is a muscular organ, situated in the floor of the mouth and in the
anterior Avail of the oral portion of the pharynx. It consists of a main portion or

Pig. 4.— COROKAL SECTION OF TIIK I.OWKR PART OF THE KAOK AT THK IHTUMUH OF Till'. FAUOKS. (.J. S. ) §

1, pharynx ; 2. lev iter palati ; 3, palato-glossus ; 4, glands of soft i)alate ; .'>, intern.il pterygoid ;
6, rarriuH of lower jaw ; 7, rnaK'<eter ; 8, stylo-gloH:su.s ; 9, Keptuin lingua; ; 10, liyo-glo.ssiis ; 11, Kub-
maxillary gland ; 12, rnylo-hyoid ; 13, digastric ; 14, gcnio-glo.ssuH ; 1.'), genio-liyoid ; 10, platjHnia

body, an anterior free extremity or lip, and a lower fixed part or root, which is
attached to the lower jaw and hyoid bone. Its upper or dorsal surface, which is

1(2

OEGANS OF DIGESTION".

covered iu its entire extent hj mucous membrane, is convex from before backwards,
and from side to side, with a slight median depression. This surface is in relation
with the hard and soft palate, the posterior wall of the pharynx, and the upper part
of the anterior surface of the epiglottis (see fig. 18). The under surface is tree
and covered with mucous membrane in its anterior part only, the larger and
posterior portion of this aspect not being fi-ee, but connected by various muscles
with the lower jaw, hyoid bone, and styloid process. Here also enter its blood-
Fig. 5. — View of the under surface of the

ANTERIOR FART OF THE TONGUE AND OP THE
SUBLINGUAL PORTION OF THE FLOOR OF THE

MOUTH. (Modified from Testut.) (J. S. )

On the left side part of the mucous mem-
brane of the tongue has been removed, and also
some fibres of the inferior lingualis muscle, in
order to expose the ranino artery, the lingual
nerve, and the glands of Blandin.

1, glands of Blandin ; 2, lingual nerve ; 3,
ranine artery ; 4, frjenum linguae ; 5, orifice
of Wharton's duct ; 6, ranine vein, seen
through the mucous membrane ; 7, mucous
membrane covering sublingual gland.

vessels and nerves. The tongue has a
free rounded border at its anterior
extremity or tip, and at the sides as far
back as the last molar tooth, where the
border gradually disappears.

Mucous membrane. — On the
under surface of the tongue the
mucous memWrane is smooth and thin,
and in the middle line is raised into a
prominent vertical fold, the fnenum
linguce. In front of the frsenum the
ranine vein can be distinctly seen on
each side through the mucous mem-
brane, and close to it lies the ranine
artery. Further out a shght fold of
--'--- the mucous membrane, plica flmlyriata,

with its free edge notched (see fig. 6),
passes from near the tip backwards and outwards. This fold is better marked in
the foetus and child than in the adult ; and, according to'Gegenbaur, it is a vestige

6 — T

-; 3

^-5

■^t^^^T'Ti'^

Fig. 6.

-Under surface op the tongue of a new-borm
CHILD. (From Gegenbaur. )

of the under-tongue of the lemurs. From the
under surface of the tongue the mucous mem-
brane is reflected towards the inner aspect of
the lower jaw, forming the sublingual portion
of the floor of the mouth. The deep groove
between the tongue and the alveolar process
of the jaw may be termed the aheolo-liyigual
sulcus. On each side of the lower and anterior
part of the frsenum linguse there is a distinct papilla, at the apex of which is the
.orifice of the duct of the submaxiflary gland (fig. 5. 5). From this point outwards
and backwards for about an inch-and-a-half the mucous membrane is raised into a
ridge by the sublingual gland. On this ridge are the openings of small ducts from
the sublingual gland (fig. 5, 7).

III. genio
glossus

THE TONGUE.

The dorsal surface of the toDgue, from its mode of development and the structure
of its mucous membrane, presents a natural division into an anterior and a posterior
portion. These two portions are frequently separated in the adult by a median
recess, the foramen ccccinu, and a shallow groove {sulcus ierminalis, His) passing
from this outwards and forwards on each side.' The anterior portion, forming about
two-thirds of the upper or dorsal surface, has its mucous membrane thin, closely
adherent to the muscular tissue below, and provided with numerous small eminences
named papillfe. These are also found upon the tip and borders, where, however,
they gradually become smaller, and towards its under surface they disappear. The
mucous membrane on the posterior third of the tongue differs considerably from that
covering its anterior two-thirds. It is thicker, smoother, and less adherent, and in

Fig. 7. — Papillary surface of the tongue, with the fauces and tonsils. (From Sappey. )

1, 2, circumvallate papillfe ; behind 2, the foramen csecum ; 3, fungiform papilhc ; 4, filiform and
conical papillte : 5, transverse and oblique ranges ; 6, mucous glands and lymphoid follicles at the base
of the tongue and in the fauces ; 7, tonsils ; 8, tip of the epiglottis ; 9, median glosso-epiglottic fold of
frxnum epiglottidis.

place of papilla?, is studded with numerous mucous glands and lymphoid follicles.
The latter are often called the Umjual tonsils. Three folds of the mucous mem-
brane, one median and two lateral, named the glosso-epiglottic folds, pass backward
from the base of the tongue to the epiglottis. Between these folds arc the two
glosso-epiglottic fossoe or sinuses. Further forward the mucous membrane is joined
on each side by the anterior palatine arch, behind which it is continuous with the
mucous membrane covering the tonsils. Except in the neighbourhood of the
circumvallate papillae the papillary surface of the tongue is devoid of glands, but
they occur abundantly at the base, sides, and under surface of the organ, and are
in structure similar to those which occur elsewhere in the mouth (fig. .3).

The papillae found on the anterior two-thirds of the tongue arc of three
kinds, circumvallate, fungiform, and coniral, varying both in size and form, hut all
of them visible to the naked eye ; they themselves, like the rest of the mucous

' For their developmental significance, sec Vol. I., Part 1, Kmbryology, p. 102.

OKGANS OF DIGESTION.

membrane of the tongue and mouth generally, are covered with closely set, micro-
scopic secondary papillae hidden under the, epithelium, which correspond with those
of the skin, and are each occupied by a long loop of capillary blood-vessels.
Lymphatics also originate within the papillse and pass as elsewhere in the mouth
into a superficial plexus in the mucous membrane, from which again the lymph is
conveyed away by valved vessels seated in the submucous tissue.

The circumvallate jiapillcB (fig. 7, 1, i2), from 7 to 12 in number, are found at
the union of the middle and posterior thirds of the tongue, arranged in two lateral

Fig. 8. — Vertical section

PAPILLA FROM THE CALF.

diameters.

OF CIRCUMVALLATE

(Engelmann.) 25

A, the papilla ; B, the surrounding wall. The
figure shows the nerves of the papilla spreading
towards the surface, and towards the taste-buds
which are imbedded in the epithelium at the sides ;
in the sulcus on the left the duct of a gland is seen to
open.

rows, which run obliquely backwards and
inwards towards a median papilla, like the
arms of the letter V. Not unfrequently there are two papillse in the middle line.
They are situated in cup-like depressions of the mucous membrane, and have the
shape of a truncated cone, of which the smaller end is attached to the bottom of the
cavity, and the broad flattened base appears on the surface (fig. 8). They are, there-
fore, surrounded by a circular trench (fossa), around which again is a slight annular
elevation of the mucous membraue (vallum). In some of them there is found a
central depression. The ducts of one or more serous glands open into the trench of
each circumvallate papilla (fig. 8, d ; fig. 9, M). The stratified epithelium covering
the papilla vallata is thick, and completely conceals the minute secondary papilla.

Taste-buds are found forming a zone around the sides of these papillae, and in
mm and some animals upon the opposed wall of the vallum (fig. 9). Their struc-

Fig. 9. — Section of circumvallate papilla,
HUMAN. The figure includes one

SIDE OF THE PAPILLA AND THE ADJOIN-
ING PART OF THE VALLUM. (Magnified
150 diameters. ) (Heitzmann. )

E, epithelium ; G, taste-bud ; C, corium
with injected blood-vessels : M, gland with
duct.

ture is given in the part of this
work dealing with the sense organs
(Vol. III., Part 3, pp. 148-151).

The fungiform papilhe, more
numerous than the last, are small
rounded eminences scattered over
the middle and fore part of the
dorsum of the tongue (fig. 7, 3) ;
but they are found in greater num-
ber and closer together at the apex
and near the borders. They are

easily distinguished in the living tongue owing to their deep red colour. They are

narrow at their points of attachment, but are gradually enlarged towards their free

extremities, which are blunt and rounded (fig. 10).

The conical papilke are the most numerous of all, as well as the smallest. They

are minute, conical, tapering, or cylindrical eminences, which are densely set over

THE TONGUE.

the greater part of the dorsum of the tongue (fig, 7, 4), but towards the base
gradually disappear. They are arranged in lines diverging from the raphe, at first

Fig. 10. — ^EtriO.V OF FUNGU'oKM PAPILLA, HUMAN, WITH THE BLOOD-VESSKLS INJECTED. (Heitzmann.)

E, epithelium ; C, corium ; L, lymphoid tissue ; M, muscular fibres of tongue.
Fig. 11. — A FUNGIFORM PAPILLA WITH THE BLOOD-VESSELS INJECTED. (After Toiltl and Bowman. )
a, artery ; v, vein ; c, capillary loops of simple papilke in the neighbourhood, covered by the
epithelium ; d, capillary loops of the secondary papillae ; e, epithelium.

in an oblique direction, like the two ranges of papillae vallate, but gradually becom-
ing transverse towards the tip of the tongue. At the sides they are longer and more
slender, and arranged in parallel rows, perpendicular to the border of the tongue.

Fig. 12. — KpcrioN of two fii.ifok.m i'a-
PiLL.K, HUMAN. (Heitzmann.)
ly, epithelium ; C, corium ; L, lymphoid
tissue ; M, muscular fibres of tongue.

Fig. 1."}. — Two filifokm pai'Ill.i-:, one with

KI'JTHKLIUM AND WITH THE UI.OOD-
VI-«SEI.H I.SJECTED, THK OTHER WITHOUT.

?jf) diamct<:r8. (Aft<;r Todd and J5ow-
man.)

p, the substance of the papillie divided at tlieiruiipcr cxtromities into .secondary jiapilln; ; n. art(!iy,
and V, vein, wmnected by cajiillary loops ; ^:, epithelial covering, laminated between tin; papillie, bui
extended into hair-like processes, /, over the secondary pa))illa;.

/'■vi

8 ORGANS OF DIGESTION.

The secondary papillae T^'hich are borne by some of the conical papillee are
peculiar both in containing a number of elastic fibres, giving them greater firmness,,
and in the character of their epithelial covering, which forms a separate horny-
process over each secondary papilla, greater in length than the papilla which it
covers (figs. 12 and 13). Over some of the papillse these processes form a pencil of
fine fibres, as shown in fig. 13 ; hence the name " filiform " which has been applied
to these papillse.

The papillary surface of the tongue is supplied abundantly with nerves, some
of which terminate in end-bulbs, and a few in tactile corpuscles. In the fungiform

Fk. 14.

-Tongue of rabbit, showing the situation of

THE PAPILL^i FOLIATJ?, 2).

papillee the nerves are large and numerous ; but
they are still more abundant, and of greater size^
in the circumvallate papillae, where they are chiefly
distributed in the neighbourhood of the taste-buds
(fig. 8).

The papillfp, besides being the parts chiefly
concerned in the special sense of taste, also possess, in a very acute degree, tactile
sensibility ; and the conical and filiform papillge, armed with their denser epithelial
covering, serve a mechanical parpose, in the action of the tongue upon the food, as
is well illustrated by the more developed form which these papillse attain in many
carnivorous animals.

In some animals {e.rj., rabbit) there is present on each side of the tong'ue, about opposite
the ends of the V formed by the line of papillae vallatEe, an oval ag'gregation of transversely

Fig. 15. — Vertical section of

PAPILLA FOLIATA OF THE
RABBIT, PASSING ACROSS THE

FOLi^. (Ranvier.)

]), central lamina of the co-
rium ; v, section across a vein,
which traverses the whole lengih
of the folia ; p', lateral lamina
in which the nerve-fibres run ;
g, taste-bnd ; Wj sections of nerve-
bundles ; a, serous gland.

placed ridges or laminte with
intervening furrows, which i&
termed the pajnlla fullata
(fig. 14). The ridges are
covered with a thick stratified
epithelium, and in this epithe-
lium at their sides are em-
bedded numerous taste-buds
(fig. 1.5). There is no definite
papilla foliata in the human
tongue, but in a situation

similar to that in which the papilla foliata of animals occurs the mucoua membrane often

exhibits a number of low ridges, and is beset with taste-buds.

Foramen caecum and thyro-glossal duct. — The foramen csecum is a median
recess, variable in size and sometimes absent, which is situated just behind the
median circumvallate papilla. According to His, it represents the apex of a V-
shaped depression, which is formed by the development of the tongue from an
anterior median process (tuberculum impar), and two lateral and posterior promi-

THE TONGUE. \)

nences, which grow forwards at the sides of the tuberculum impar. According to
the same authority, the foramen caecum indicates the position of the epitheh"al
outgrowth from which the median portion of the thyroid gland has b^en formed.
As the thyroid recedes from the tongue it becomes connected with the foramen
caecum by a long narrow tube — the tlvjro-gJossal dvcf. The upper part of this duct
may persist as a canal {ductus linffvalis) leading from the foramen caecum downward
to the hyoid bone. Kanthack, on the other hand, holds that no intrinsic connec-
tion exists between the development of the tongue and that of the thyroid body.
He states that the foramen csecum is often absent, and when present passes back-
wards near the surface and never dips down towards the basi-hyoid. In none out of
one hundred adults that he examined did he find any trace of a lingual duct, and
out of sixty f(X^tuses, varying in age from two and-a-half to eight months, he never
observed the foramen caecum to extend downwards to the hyoid bone.

Glands. — The mucous membrane of the tongue is provided with numerous
small glands (lingual glands), collected principally about the posterior part of its
upper surface, near the papillae vallate and foramen ceecum, into which last the
ducts of several open. These glands have usually been supposed to secrete mucus,
but it has been ascertained that some of them, especially those which open in the
trenches around the papillte vallatas, and at other parts where taste-buds occur,
yield a serous secretion (Ebner). Other small glands arc found also beneath
the mucous membrane of the borders of the tongue. There is, in particular, a
group on the under surface of the tongue on each side near the apex called the
glands of Bland in (see fig. 5). They are there aggregated into a small oblong mass,
out of which several ducts proceed and open in a line on the mucous membrane.
^Nlost of the glands are acino-tubular.

The mucous membrane of the tongue, at least its posterior part, is largely com-
posed of retiform or lymphoid tissue, which is collected at numerous points into the
denser nodular masses known as follicular glands, or lymphoid follicles. The
blood-vessels and lymphatics of this part of the membrane are numerous and large,
but the papillae on its surface are comparatively small, and are completely concealed
l>y the thick superjacent epithelium. Here and there the mucous membrane ex-
hibits recesses or crypts (fig. 16,/), either simple or surrounded by smaller ones
which open into them. The walls of these recesses are generally studded with
lymphoid nodules ; and they receive many of the ducts of the mucous glands.

Mnscnlar substance. — -The substance of the tongue is chiefly composed of
muscular fibres running in various directions. Many belong to muscles which enter at
its base and under surface, and attach it to other parts : these are called ihQ extrinsic
mvscles of the tongue (hyo-glossus, chondro-glossus, genio-glossus, palato-glossus,
stylo-glossus), and are elsewhere described. Others which constitute the intrinsic or
proper muscles, and are placed entirely within the substance of the organ, will be
here more particularly noticed. They are as follows : —

The superficial lingual muscle consists mainly of longitudinal fibres, placed
near the upper surface of the tongue, immediately beneath the mucous membrane,
and is traceable from the apex of the organ backwards to the hyoid bone (fig. 17, 10 ;
fig. 10, Is). The individual fibres do not run the whole of this distance, but are
attached at intervals to the submucous and glandular tissues. I'lic entire layer
l)ecome8 thinner towards the base of the tongue, near which it is overlapped at the
sides by a thin plane of oblique or nearly transverse fibres derived from the palato-
glossus and hyo-glossus muscles.

Tlie inferior lingual muscle consists of a roimded muscular band, extending
along the under .surface of the tongue from base to apex, and lying outside the
genio-glossus, between that muscle and the hyo-glossus (fig. 17, 0). Posteriorly,
Horne (jf its fibres an; lost in the suljstaiice of the tongue, and others reach the hyoid

OEGANS OF DIGESTION.

bone. In front, having first been joined, at the anterior border of the hyo-glossus
muscle, by fibres from the stylo-giossus, it is prolonged beneath the border of the
tongue as far as its point.

The transverse muscular fibres of the tongue (fig. 17,2 • fig. lio,tr) form together
with the intermixed fat a considerable Dart of its substance. They are found in the

Fig. 16. — Longitudinal vertical section of thk tongue, lip, &c. (From Kolliker and Arnold. )

m, symphysis of tLe lower jaw"; d, incisor tooth ; 7;, hyoid bone ; g h, genio-hyoid muscle ; g,
gei)io-liyo-glossus spreading along the whole of the tongue ; t r, transverse muscle ; I s, superior longi-
tudinal muscle ; g I, lingual glands ; /, lymphoid crypts ; e, epiglottis ; /, section of the lip and labial
glands ; o, cut fibres of the orbicularis oris ; I m, levator luenti.

interval between the upper and lower longitudinal muscles, and they are interwoven
extensively with the other muscular fibres. Passing outwards from the median
plane, where they take origin from a fibrous septum (fig. 17, 3), they reach the
dorsum and borders of the tongue. In proceeding outwards, they separate, and the
superior fibres incline upwards, forming a series of curves with the concavity upwards.

Fig. 17.' — Coronal section of the tongue

ABOUT THE MIDDLE OF ITS LENGTH, LEFT
HALF SEEN FROM BEHIND. (W. KraUSe. )

1, papillaj on the dorsal surface ; 2, trans-
verse muscular fibres ; 3, septum linguae ; 4,
genio-glossus ; f>, lanine artery; 6, inferior ]in-
gualis ; 7, hyo-glossus ; 8, vertical muscular
fibres; 9, stylo-glossus ; 10, sui^erficial Jiogual
muscle.

The fibres of the palato-glossus muscle
are stated by Zaglas and Henle to be
continuous with fibres of the transverse
set.

Vertical fibres (external perpen-
dicular muscle of Zaglas), decussating
with the transverse fibres and the in-
sertions of the genio-glossus (fig. 17, 8),
form a set of curves in each half of the
tongue with their concavity outwards,

and extending down and out from the dorsum to the under surface of the border, so

that those which are outermost are shortest.

THE PALATE. 11

Examined in transverse sections, the muscular fibres are seen to be arranged so as to render
the substance divisible into an outer part or cortex and an internal or niedullavy jmrt. The
fibres of the cortex are principally long-itudinal, derived superiorly from the lingualis
superior, further outwards from the hyo-glossus, on the side from the stylo-glossus, and
beneath this from the lingualis inferior. They ensheath the medullary part on all sides
except inferiorly. where the genio-glossi muscles enter it between the inferior linguales. In
the medullary part are found, embedded in fat, the decussating fibres of the transverse
muscle passing across, the genio-glossi radiating upwards and ovitwards, and the vertical
muscles arching downwards and outwards. In addition to the movements which may be
given to the tongue by the extrinsic muscles, this organ is capable of being curved upwards,
downwards, or laterally by its cortical fibres, it is flattened by the vertical fibres, and its
margins are again drawn together by the transverse whilst the two last mentioned, acting
together, would tend to lengthen the organ.

The septaiu of the tongaie is a fchiti fibrous partition ^yhicli extends forwards
from the hyoid bone to the tip, and divides one half of the mednllary part of the
tongue from the other, but does not penetrate into the corte.x.

Vessels and nerves. — The arteries of the tongue are derived from the
lingual, with some small branches from the facial and ascending pharyngeal. The
veins empty their contents into the internal jugular trunk.

The nerves of the tongue (exclusive of branches from the sympathetic nerves)
are five, viz., the lingual branch of the fifth pair, which supplies the papillae and
mucous membrane of the fore part and sides of the tongue to the extent of about
two-thirds of its surfoce with common sensibility ; the chorda tijmpani, which
accompanies the lingual to the tongue and probably serves as the nerve of taste to
a corresponding area of the mucous membrane ; the lingual branch of the glosso-
pharyngeal, Avhich sends filaments, both sensory and gustatory, to the mucous
membrane at the base of the tongue, and especially to the papillae vallata3 ; the
superior laryngeal, which distributes a few sensory branches in the neighbourhood of
the epiglottis ; and lastly, the hg[)oglossal nerve, which is distributed to the muscles.
Microscopic ganglia exist upon the expansions of the glosso-pharyngeal nerve,
especially in the neighbourhood of the papillae vallatge and papilltB foliatae, and they
have also been found in the sheep and calf upon the gustatory division of the fifth.

Lymphatics. — The chief lymphatic trunks accompany the ranine vessels, and
after traversing one or two small lymphatic glauds, seated on the hyo-glossus
muscle, pass into the deep cervical glands. Others pass through the mylo-hyoid
muscle to the submaxillary lymphatic glands.

The detailed description of the blood-vessels will be found in Vol. II., Part 2, and of the
nerves in Vol. III., Part 2.

THE PALATE.

The roof of the mouth is formed by the palate, which consists of two portions ;
the fore part being named the hard palate and the back part the soft palate. As a
whole, the jiahite is concave from before backwards, and also from side to side.

The hard palate is bounded in front and at the sides by the alveolar arches and
gums, and is distinguished from the soft palate by having an osseous framework,
already described (see Vol. II., Part I). It is covered by periosteum and
mucous membrane, these two structures being firmly connected together. In front
the mucous membrane is thick, dense, rather pule, and corrugated, but it becomes
thinner, smoother, and of a deeper colour behind. The corrugations of the mnccius
membrane — palatal rug(z — may be divided into the longitudinal and the ti'aiis-
verse. lu the middle line there is a longitudinal ridge or rai)lie, ending behind the
interval between the two mesial incisors in a small eminence, t\\Q papilla palalina or

Fig. 18. — Median section of the head and neck. (Braune.) |
1, sphenoidal sinus ; 2, lateral recess of pharynx ; 3, pharyngeal orifice cf Eustachian tube ; 4,
anterior arch of atlas ; 5, soft palate ; 6, body of axis ; 7, oral portion of pharynx ; 8, epiglottis ; 9,
arytenoid muscle ; 10, cricoid cartilage ; 11, trachea ; 12, oesophagus ; 13, origin of innominate artery
from aorta ; 14, genio-glossus muscle ; 15, genio-hyoid muscle ; 16, mylo-hyoid muscle ; 17, platysma ;
18, hyoid bone ; 19, thyroid cartilage ; '20, cricoid cartilage ; 21, isthmus of thyroid body ; 22, sterno-
hyoid; 23, sterno-thyroid ; 24, left innominate vein; 25, manubrium sterni.

THE PALATE.

!;*^-

incisive pad. This papilla corresponds to the anterior paUitine fossa, and receives
the terminal filaments of the naso-palatine and anterior palatine nerves. Two small
blind recesses, one on either side, are sometimes found upon it. They represent the
lower part of the naso-palatine foi'amina or canals of Stensen, which in many
animals lead fi-om the mouth into the nose. The transverse rugse, generally about
five or six in number, vary considerably in their development. They are much

Fig. 19. — View of the soft palate and

ISTHMIS FACCIUM FROM BEFORE. (J. S.)

1, soft palate ; 2, its raphe ; 3, uvula ; 4,
anterior, and 5, posterior pillar of fauces ; 6.
tonsil ; 7, posterior wall of pharynx ; 8. dorsum
of tongue.

better marked and more regular in the
foetus (Gegeubaur). In the adult the
ridges are often broken up into several
small eminences.

The soft palate {velum pendulum
palati) is formed by a duplication of
mucous membrane, including muscular
fibres and numerous glands. It ex-
tends from the hard palate backwards
and downwards between the nasal and
oral portions of the pharynx, and ends
below in a free border, which in the
middle is prolonged as a conical pro-
cess, the uvula, while at the sides it is
continuous with the posterior pillar of
the fauces. As a rule it is about 10 to
12mm. in thickness, nearly half of
which is due to the glandular tissue
situated between the muscles and the
mucous membrane of the anterior or
under surface of the velum. Tliis . -, . :. ---'-"'^

membrane, which is visible from the

mouth, is thinner and redder than that of the hard palate, but like it, is covered
with a scaly stratified epithelium. The median ridge or raphe, which is continued
backwards from the hard palate to the base of the uvula, indicates the original
separation of the palate into two lateral halves. The posterior or upper surfsice of
the soft palate is convex and continuous in front with the floor of the nasal fossa;.
This surface is covered with ciliated columnar epithelium, while on the under aspect
and free margin the epithelium is scaly and stratified.

On both surfaces of the velum are found numerous small compound glands.
Thay part cularly abound on the under surface, where tiiey form almost a complete
layer under the mucous membrane ; they are also very abundant in the uvula.

In the new-born child the whole posterior surface is covered with ciliated epithelium,
V)Ut this becomcH HubKCfiucntly replaced V)y squamous ; the epithelium of the trland-duutn,
however, retains in many instances its ciliated character (Klein).

The miLscles of the >^oft palate are described in Vol. II., I'art 2.

14 ORGANS OF DIGESTION.

KECENT LITEEATUBE OF THE MOUTH, TONGUE, AND PALATE.

Allen, Harrison, The palatal rugce in man, Pi-oceedings of the Acad, of Nat. Science of Phila-
delphia, 1888.

Breglia, A., Nota anatomica sulla capacitd del cavo huccale, Progresso med., Napoli, 1891.

rusari, R. et Panasci, A., Demonstration des terminaisons des nerfs dans les glandes
sinuses cle la langue des mammiferes, Verhandl. des x. internal., medic. Kongresses, Berlin, ISl'O,
Bd. ii., Abt. i ; Sulle terminazioni ncrvose nella mucosa e nelle ghiandole sierose della lingua dei
mammiferi, Atti della r. accademia delle scienze di Torino, vol. xxv., 1890.

G-aupp, E., Anntomische Untersuchungen ilher die Nervenversorgung der Mund- und Nasen-
Iwhlendrilsen der WirheHiere, Morph. Jahrbuch, Bd. xiv., 1888.

Geg-enbaur, C, Die Ganmenfcdten des Menschen, Morph. Jahrbuch, Bd. iv., 1879 ; Beitrdge zur
Morphologie der Zunge, Morph. Jahrbuch, Bd. xi., 1886 ; Zur Phylogenese der Zunge, Morph.
Jahrb., Bd. xxi., 1894.

Grillet, H., Po/rticularites anatomiques du fi'ein cle la Uvre superieiire, Annales de la policlin. de
Paris, 1892.

Gmelin, Ztir Morphol. der Papilla vallata u. foliata. Arch. f. mikr. Anat., Bd. xl., 1892.

Hintze, K. , Ueb. die Entioickelung der Zungenpapillen heim Menschen, Inaug. Diss., Strassburg,
1890.

His, "W., Anatomie menschl. Emhryonen. iii., 188.5, p. 97 ■ Der Tractus thyreo-glossus und
seine Beziehi.ingen zum Zungenbein, Arch, fiir Anatomie, 1891.

Kanthack, A. A., The Thyreo-glossal duct. Journal of Anatomy and Physiology, vol. xxv, 1891.

Marshall, C. F., Thyro-glossal duct or " Canal of His," Journal of Anatomy and Physiology,
vol. xxv, 1891.

Merkel, F., Handhuch der topograpkischen Anatomie, 1 Bd., 1885 ; Jacohson' sche Organ und
Papilla palatina heim Menschen, Anatom. Hefte, i., 1892.

Pod-wisotzky, Anatomische Untersuchungen ilher die Zungendriisen des Menschen u. der
SaugctJiiere, Inaug. Diss., Dorpat, 1878.

S-wrain, Die Balgdrilsen am Zungengrunde und deren Hypertrophie, Archiv. f. klin. Med.,
Bd. xxxix., 1886.

Suzanne, G., Recherclics anatomiques sur le plancher cle la houche avec etude anatomique et
pathogeniqtie sur la grenouillitte commune ou suhlingucde, Arch, de Physiol., 1887.

Waldeyer, W., Ucbcr den harten Gaumen, Corr. Bl. d. anthrop. Ges. (Vers. U m, 1892).

THE SALIVARY GLANDS.

The saliva, which is poured into the mouth, and there mixed with the food
durinff mastication, is secreted by three pairs of glands, named from their respective
situations, parotid, submaxilkiri/, and suhlinf/i/al. Agreeing in their general physical
characters and structure, these glands differ in their size, form, and position.

The Parotid Gland. — The parotid (fig. 20, 2^) is the largest of the three
salivary glands. It lies on the side of the face, in front of the ear, and extends
deeplyinto the space behind the ramus of the lower jaw. Its weight varies from
five to eight drachms (20 to 30 grammes).

Its outer surface is convex and lobulated, and is covered by the skin and fascia,
and partially by the platysma muscle. It is bouTided above by the zygoma, below
bv a line drawn backwards from the lower border of the jaw to the sterno-raastoid

Fig. 20. — Sketch of a superficial

DISSECTION OF THE FACE, SHOWING
THE POSITION OF THE PAROTID
AND SUBMAXILLARY GLANDS. (Allen

Thomson.) -?.

p, parotid gland ; p', socia paro-
tidls ; d, the duct of Stensen before it
perforates the buccinator muscle ; a,
transverse facial artery ; n, n, branches
of the facial nerve emerging from below
the gland ; /, the facial artery passing
out of a groove in the submaxillary
gland and ascending on the face ; sm,
superficial portion of the submaxillary
gland.

muscle, and behind by the ex-
ternal meatus of the ear, the
mastoid process, and sterno-
mastoid muscle. Its anterior
border, which lies over the
ramus of the lower jaw, is
more irregular, and stretches
forwards to a vai'iable extent
on the ma-sseter muscle. It is
from this anterior border of the
gland that the excretory duct
pa.sses off; and there is fre-
quently found in connection with the duct, and lying upon the masseter muscle, a
small process or a separated portion of the gland (//), which is called (jJandula socia
1)arotidi8. On trying to raise the deeper part of the parotid gland from its position,
it is found to extend far inwards, between the mastoid process and the ramus of the
jaw, towards the bas'^ of the skull, and to be intimately connected with several
deep-seated parts. Thus, above, it reaches into and occupies the posterior part of
the glenoid cavity ; behind and below, it touches the digastric muscle, and rests on
the Btyloid process and styloid muscles ; and, in front, under cover of the ramus of
the jaw, it advances a certain distance between the external and internal pterygoid
muscles.

The internal carotid artery and internal jugular vein are close to the deep surface
of the gland. The external carotid artery, accompanied by the temporo-niaxillary
vein, passes through the parotid gland, and in that situation divides into the
temporal and internal maxillary arteries, the former soon giving off its auricular a,nd
transverse facial branches. The gland is also traversed by the facial nerve, which

16 OEGATs^S OF DIGESTION,

divides into branches within its substance, and it is pierced by branches of the great
auricular nerve, while the auriculo-temporal nerve ascends beneath its upper and
posterior part.

The parotid duct, named also Stensen's duct {d. Stenommius), appears at the
anterior border of the gland, about one finger's breadth below the zygoma, and runs
forwards over the masseter muscle, accompanied by the socia parotidis, when that
accessory portion of the glaud exists, and receiving its duels. At the anterior
border of the masseter, the duct (d) turns inwards through the fat of the cheek and
pierces the buccinator muscle ; and then, after running for a short distance obliquely
forwards beneath the mucous membrane, opens upon the inner surface of the
cheek, by a small orifice on a papilla opposite the crown of the second molar tooth
of the upper jaw. Its direction across the face may be indicated by a line drawn
from the lower margin of the concha of the ear to a point midway between the
red margin of the lip and the ala of the nose. The length of the Stenonian duct
is about two inches and a half (62 mm.), and its diameter rather less than ^th of
an inch (3 mm.). At the place where it perforates the buccinator, its canal is as
large as a crowquill, but at its orifice it is smaller than in any other part, and will
■only admit a fine probe.

Blood-vessels and nerves. — The vessels of the parotid gland enter and leave
it at numerous points. The arteries are derived directly from the external carotid,
and from those of its branches which pass through or near the gland. The veins
correspond. The lymphatics join the deep and superficial set in the neck ; and there
are often one or more lymphatic glands embedded in the substance of the parotid.
The nerves come from the sympathetic plexus on the external carotid artery, and
also from the facial, the auriculo-temporal and great auricular nerves. In the dog
and cat it has been experimentally shown that the parotid derives its cerebro-spinal
nerve-supply from the glosso-pharyngeal, through the lesser superficial petrosal nerve
and the otic ganglion, the fibres finally passing to the gland by a branch of the
auriculo-temporal.

Vaeieties. — An instance is recorded by Gruber of a remarkable displacement of the
parotid on one side ; the whole giand being situated on the masseter muscle as if it were an
enlarged socia parotidis (Virchow's Archiv, xxxii.). Its absence has also been recorded by
Poirier (Bulletins de la societe anat. de Paris, 1888).

The submaxillary gland.— The submaxillary gland (fig. 4, 11 ; fig. 20, sm), the
next in size to the parotid, is of a spheroidal form, and weighs about 2 or 2| drachms
(8 to 10 grammes). It is situated immediately below the base and the inner surface
■of the inferior maxilla, and above the digastric muscle. In this position (fig. 4, 11)
it is covered by the skin, fascia, and platysma myoides, and its inner surface rests on
the mylo-hyoid, hyo-glossus, and stylo-giossus muscles ; above, it corresponds with a
depression on the inner surface of the jaw-bone ; and it is separated behind from the
parotid gland merely by the stylo-maxillary ligament. The facial artery, before it
mounts over the jaw-bone, lies in a deep groove upon the back part and upper border
■of the gland ; while the vein is placed on the superficial surface of the gland.

The duct of the submaxillary gland, named "Wharton's duct {d', fig. 21), which is
about two inches (50 mm.) in length, leaves the main gland posteriorly, together with
a thin process of the glandular substance, and passing round the posterior border of
the mylo-hyoid muscle {pih), runs forwards and inwards above that muscle, between
it and the hyo-glossus and genio-glossus, and beneath the sublingual gland, to
reach the side of the frsenum linguEe. Here it terminates, close to the duct of the
opposite side, by a narrow orifice, which opens at the summit of a soft papilla
(fig. 5, 5) seen beneath the tongue. The obvious structure of this gland is like that

THE SALIVARY GLANDS.

of the parotid ; but its lobes are larger, its surrouuding areolar web is finer, and its
attachments are not so firm. Moreover, its dact has much thinner coats than the
parotid duct.

Blood-vessels and nerves. — The blood-vessels of the submaxillary gland are
branches of the facial and lingual arteries and veins. The nerves include those
derived from the submaxillary ganglion, and through this from the chorda tympani,
from the lingual branch of the inferior maxillaiy (and in rare cases from the mylo-
hyoid branch of the inferior dental nerve), and from the sympathetic. »

Vaeieties. — Griiber (Tirchow's Archiv. Bd. cii.) has recorded a case of complete absence
of both submaxillary glands.

The saiblingual gland. — The sublingual gland (fig. 1, 8, and fig. 21, si), the
smallest of the salivary glands, is of a narrow oblong shape and weighs scarcely one
drachm (4 grammes). It is situated along the floor of the mouth, where it forms a
ridge between the tongue and the gums of the lower jaw, covered only by the mucous
membrane. It extends from the fr^enum lingnas in front, where it is in contact
with the gland of the opposite side, obliquely backwards and outwards for rather
more than an inch and a half. On its inner side it rests on the genio-glossus ;

Fig. 21 . — View of the right submaxillary and

SUBLINGUAL GLANDS KROil THE INSIDE. (Alien

Thomson. )

Part of the right side of the jaw, divided from the
left at the symphysis, remains ; the tongue and its
muscles have been removed ; and the mucous mem-
brane of the right side has been dissected off and hooked
upwards so as to esjwse the suldingual glands ; s m,
the larger superficial part of the submaxillary gland ;
/, the facial artery passing through it ; s m', deep
portion jjrolonged on the inner side of the mylodiyoid
muscle m h ; s I, is jdaced below the anterior large part
of the sublingual gland, with the duct of Uartliolin
partly shown ; « V, placed above the hinder small end
of the gland, indicates one or two of the ducts per-
forating the mucous membrane ; d, the papilla, at which the duct of Wharton opens
the incisor teeth : d', the commencement of the duct ; /<, the hycid bone ; n, the lingual
it is the submaxillary ganglion.

in front
nerve ;

behind
close to

below, it is sui)ported by the mylo-hyoid muscle {mh), which is interposed between
it and the nuiin part of the submaxillary gland ; and it is here in close contact
with the Whartonian duct, with the accompanying deep portion of the last-named
gland, and also with the lingual branch of the fifth nerve.

The lobules of the sublingual gland are not so closely united together as
those of the other salivary glands, and the ducts from many of them open separately
into the mouth, along the lidge which indicates the position of the gland. These
ducts, named ducts of Rivinus, are from eight to twenty in number. Some of
them open into the duct of Wharton. One, longer than the rest (which is
occasionally derived in part also from the submaxillary gland), runs along the
Whartonian duet, and opens either with it or very near it ; this has been named the
duct of Bfi.rlhdiiih but it is inconstant in its occurrent-o (Chievitz, Suzanne).

Blood-vessels and nerves. — The blood-vessels of this gland arc supplied
by the sublingual and submental arteries and veins. The nerves are numerous,
and are derived from the lingual branch of the fifth, the chorda tympani and the
sympathetic.

STRUCTURE OP THE SALIVARY GLANDS

These glands are constructed on the compound racemose type (see Vol. I.,
Part ii., p. 39!)). Their ducts (traced backwards), after branching a certain number

VOL. IT., I'T. 4. 0

ORGANS OP DIGESTION.

of times, terminate in fine ramuscules, into which the alveoli open. The alveoli of
the salivary glands do not always present the form usually regarded as typical of the
alveoh of a compound racemose gland. They are sometimes dilatations of the

Fig. 22. — Diagram of the construc-
tion OF A LOBirLE OF A TUBULO-
KACEMOSE (acINO-TUBULAr) MUCOUS

GLAND. (From KoJliker.)

a, duct ; h, a t ranch of the duct ;
c, alveoli as they lie together in the
gland ; d, the same separated, showing
their connection as an irregular tube.

extremities of the duct beset
with saccular enlargements, some-
times more tubular and even somewhat convoluted without marked sacculation
(fig. 22) (acino-tubular variety), but there is no essential difference between the two
forms, transitions being met with between them. The alveoli are enclosed by a
basement membrane, which is not complete as in some glands, but forms a basket-
Fig. 23. MeMBRANA propria of two alveoli ISOLATED.

(Heidenhain, after Lavdovsky. )

The preparation is taken from the orbital gland of the dog,,
which is similar in structure to a mucous salivary gland.

like investment to the alveolus, the flattened cells
which form it being ramified and united together
by their branches (fig. 23). There is, however, in
addition a delicate homogeneous substance occupy-
ing the meshes between the cells (see the left-hand alveolus in fig. 23). The cells
of the basement membrane are said to send inwards processes to form a susten-
tacular network amongst the alveolar cells.

The alveoli are united by the blood-vessels and a small amount of loose connective

Fig. 24. — Section op part op the human
SUBMAXILLARY GLAND. (Heidenhain.)

To the right of the figure is a group of
mucous alveoli, to the left a group of serous
alveoli.

tissue into lobules, and these again by
a larger quantity of the same tissue
into larger lobules. A considerable
amount of connective tissue also ac-
companies the blood-vessels and duct,
in their ramifications through the
gland. The connective tissue, where
it is in larger amount, is lamellar in
character (Klein), and it contains,,
besides the ordinary flattened cells, a
certain number of granular plasma -cells
and lymph-corpuscles, with fat cells
occasionally.
The alveoli of the salivary glands may be divided into two classes, according to
the nature ol^ their secretion : — those of the one kind yielding a ropy secretion
characterised by containing mucin, and those of the other kind, a thinner more
watery secretion, sometimes containing a considerable amount of serum-albumin, so-

THE SALIVARY GLANDS.

that thfe secretion coagulates on being heated. The two kinds of alveoli may
accordingly be distinguished as mucous and serous or albuminous (Heideuhain) ;
they differ from one another both in appearance and in the nature of their secreting
cells. In some cases an alveolus may contain mucous and serous cells side by side.

The human parotid and that of all mammals is composed of serous alveoli, and
the sublingual gland of mucous alveoli, but in man the submaxillary is a mixed
gland, containing both kinds of alveoli, although the serous are the more numerous
(tig. 24:). In the dog and most other animals it is purely a mucous gland, and
in the rabbit and guinea pig it is purely a serous gland. Similar differences have
already been noticed (p. D) in the small glands of the tongue. According to
Bermann a gland of tubular structure and furnishing a mucous secretion may
also be found attached to the submaxillary in man, and opening into Wharton'rj
duct. In the guinea-pig and rabbit there are small fiat mucous glands of tubular
structure connected both to the parotid and submaxillaiy, one to each, and sending

25. — Sections of thf survaxit.lary gland op the doo.
PERIOD OK ACTiviTT. (Ranvier )

In A, most of the celts of the alveoli are large and clear, being fille4 with the material for secretion
(in this ease, mucigen) which obscures tlieir iirotoplasm, hut some of the cells are small and proto-
plasmic, forming a crescentic group seen in most nf the alveoli.

In B, the accumulated material (mucigen) is discharged from the miicin-secreting cells, which appear
in consequence shrunken and less clear. Both the cells and the alveoli are much smaller, and the ijro-
toplasm of the cells is now more apparent. The marginal cells of Gianuzzi are enlarged.

c, "crescent" cells ; ff, mucus-secreting cells ; I, lumen of alveolus.

their ducts to open into the ducts of those glands ( a thna.r illaiies, Khiu). Similar
tubular glands have boon described in various othei- anini-dls, ;ind, as above men-
tioned, also in man. Thoy are most frcfjuently found in connection with the
submaxillary, where they form usually a glandular mass dii-tinguishable to the
naked eye, and termed by Ranvier the ralro-lingual (jUinil. Ranvier states, how-
ever, that he has not found this in the rabbit, hare, horse and sheep, or in man, but
it occurs constantly in all other animals examined.

Mucous alveoli. — In the mucous glands and mucous alveoli of mixed glands
most of the alvef)lar cells, when the gland is in the inactive (condition, appear large,
clear, and almost sphcroidul in shape, and nearly fill the alveoli, which are distended
by the cells (right-hand side of fig. 24). The nucleus of each cell. is in the pare of
the cell next to the basement membrane, against which it is generally flattened, and
thecfills may cause the basement membrane to l)e bulged out opposite to them. In
preparations hardened in alcohol the cells are finely granular, ami with the exception
of the part around tlie niifileus are scarcely stained by carmine (fig. 2"), A).

When the ceils of the nmcous alveoli are isolated, they not nnfr(i|iicntly exhibit

(; 2

ORGANS OF DIGESTION

processes, one from the base of each cell : the projection is flattened and overlaps the
base of a neighbouring cell (Kolliker). The peculiar clear appearance of these cells
is due to the accumulation within them of mucin (or of a substance " mucigen '"
from which mucin is formed). When i'ragments of the fresh mucous glands are
examined in solutions of salt of a certain strength, it may be seen that the clear
material which is accumulated within the cells is in the form of minute globules
(Langley). AVhen swollen by the addition of water, these run together, and the cell

Fig. 26. — Isolated jiucin-secreting cells from the

SUBMAXILLARY GLAND OF A DOG. (Langley.)

a and h, isolated in 2 p. c. salt solution ; a, from
loaded gland ; h, from discharged gland ; a' , b' , similar
cells after treatment with dilute acid.

then appears distended with clear secretion, with
threads of protoplasm intersecting it (see fig.
26).

Besides the " mucin cells " there are met
with in most alveoli of these glands, cells of a
different character, which from their position
may be named ''marginal cells." In some
mucous glands, e.g., the submaxillary of the cat,
they form an almost complete outer layer, next to the basement membrane, and
enclosing the mucin-cells, but in the dog's submaxillary gland they occur only in
small semilunar masses {lunulrc or crescents of Gianuzzi) at the bottom of the
alveoli, flattened up between the basement membrane and the mucin-cells (flg. 25, A ;
fig. 28, s). These marginal cells are small and granular, and stain deeply with
carmine and hasmatein.

If the mucous glands are stimulated to secretion, the mucin-cells become
gradually smaller and less clear, their contents being exuded in the form of mucus,
which first fills the cavity of the alveolus and then passes on into the duct. At the
same time the cells are easily stained with carmine and their nuclei are no longer

Fig. 27. — Alveoli of serous glands. A, at rest. B, after a short pertod of activity.
C, after a prolonged period of iCTiviTY. (Langley.)

flattened, but assume a more rounded form and central position (fig. 25, B). If the
gland be strongly urged to activity, as by prolonged stimulation of its cerebral
nerves, the mucin-cells may undergo still more profound alterations, and may even,
according to Heidenhain, become partially or wholly disintegrated, but probalily the
cell is normally never destroyed. It is possible, however, that, in extreme salivation,
some of the mucin-cells are occasionally destroyed, but whether the marginal cells
multiply and become filled with secretion, and thus serve to replace the mucin-cells
which are lost is doubtful, for it is rare to find evidence of cell-division during
functional activity of the gland.

Serous alveoli. — In the serous glands and serous alveoli of mixed glands, the
cells, in the inactive condition of the glands, are in the fresh condition and in osmic

THE SALIVxVRY GLANDS.

preparations seen to be packed full of distinct granules, of an albuminous nature,
which obscure their nuclei (Laugiey). The granules are imbedded in the proto-
plasm of the cells and the latter almost completely fill the alveoli, scarcely any
lumen being discernible (tig. 27, A).

After ii short period of activity the granules are found to have disappeared in
the outer part of the cell, the inner part being still distinctly granular, and some
of the granules are apparently free within the lumen of the alveolus, now becoming
distinct (tig. 27, B). With more prolonged activity (fig. 27, C; the clear outer
part increases in extent, and the granules are found only in the part of the cell which
is clcse to the lumen, and in those parts which are contiguous to the adjacent cells
(corresponding perhaps to fine capillary clefts which pass from the cavity of the
alveolus between the cells). The nuclei have now become distinct, and the cells are
smaller. We may suppose therefore that the granules, which no doubt contain the
specific elements of the secretion, are formed by or from the protoplasm of the
cells during rest, and are discharged into the lumen and dissolved during activity.
Probably however even during activity new granules are constantly being formed

Fig. 28. — Section of the submaxillaky

GLAND OF THE DOO, SHOWING THE
COMMENCEMENT OP A DUCT IN THK

ALVKOLi. Magnified 425 dia-
meters. (E. A. S.)

rt, one of the alveoli, several of which
are in the section shown grouped around
the commencement of the duct, d' ; a' , an
alv«.olus, not opened by the section ; b,
basement membrane in section ; c, inter-
stitial connective tissue of the gland ; (/,
section of a duct which has passed away
from the alveoli, and is now lined with
characteristically-striated columnar c-lls ;
g, semilunar group of darkly- stained cells
at the periphery of an alveolus.

and passed onwards towards the
lumen. According to Langley,
the three processes of growth of
the clear protoplasm, conversion
of this into granules, and dis-
charge of these into the lumen, are all proceeding simultaneously in different parts
of the cell during activity.

In glands which have been hardened in alcohol the granules are no longer seen,
their place being occupied by a clear substance which does not stain Avith carmine.

Ducts. — Tn the serous glands, and serous parts of mixed glands, the first or
inlercalurij part of the duct which conveys the secretion from the alveoli is narrow,
and lined with clear flattened cells with elongated nuclei. After a longer or shorter
course, tin's part passes by a somewhat narrower neck, lined with cubical cells with
small nuclei, into the intralobular ducts (Klein).

In the mucous glands the intercalary ducts are also lined (fig. 28, d') with clear
cells continuous with the cells of the alveoli, but flattened against the basement
membrane so as to leave a considerable lumen.

This first part of the duct is generally shorter than the corresponding part in
the serous glands, and is regarded by Klein as representing only the part by him
termed the "neck"; more probably, however, it must be looked upon as repre-
senting both parts, although they are not here so clearly differentiated. The
intercalary part of the ducts is described by Klein as being lined, within the

OEGANS OF DIGESTION.

epithelium, by a special delicate nucleated membrane, which in some animals is
continued into the intralobular ducts.

lu the next or iutraloiular part of the duct (fig. 28, d) the character of the
epithelium changes abruptly, the cells becoming large and columnar or conical, the

Fig. 29. — Section op alveoli of sublingual gland, human, pre-
pared BY GOLGl's SILVER CHROMATE METHOD. (E. Muller. )

I, lumen, stained, showing lateral diverticula proceeding between
and also into the cells of the alveoli ; h, diverticula penetrating into
" crefcents. "

rounded or truncated apex being directed towards the
lumen of the tube. Each cell contains a spherical nucleus
near the centre (fig. 28). The part of the cell next
the lumen of the duct is granular in character, whereas
the part nearest the basement membrane is finely striated
longitudiually. This striated appearance is most distinct
in the ducts of the submaxillary gland ; it is due to the
presence of a rod-like or fibrillar structure in that part of
the cell.

The lumen of the ducts is continued directly into the
alveoli, and its course tliere can be traced both by injec-
tion and in preparations stained by the silver chromate
method. By the latter method it has been shown that diverticula extend between
the cells of the alveoli, and minute channels are also traceable for a short distance
into the protoplasm of the cells. In the mucous alveoli a special diverticulum of
the lumen passes to each crescent of Gianuzzi, and ramifies within this between and
perhaps partly within its component cells (figs. 29, 30).

The larger ducts acquire a coating of fibrous and elastic tissue outside the
basement membrane, and, except in those of the sublingual gland, a few plain

Fig. 30. — Tkrminal nerve-fibrils in an alveolus of thb
SUBMAXILLARY GLAND OF THE DOG. (Gr. Retzius. ) Chroiuate
of silver method.

The extension of the lumen into the crescents of Gianuzzi is
also slio«n.

muscular fibre-cells are also to be found. The
columnar epithelium is here double, a second row
consisting of somewhat smaller cells lying outside,
and fitting between, the elongated cells which are
continuous Avith those of the smaller ducts.

Vessels and nerves. — The blood-vessels of
the salivary glands are numerous, and form a close capillary network outside the
basement membrane both of the alveoli and the ducts.

The lymphatics commence in the form of lacunar clefts between and around
the alveoli, lying closer to these than do the networks of blood-capillaries
(Gianuzzi). The issuing lymphatics accompany the blood-vessels and ducts.

The nerves are large and numerous, and many of them exhibit minute ganglia,
especially those in the dog's submaxillary. There are fewer in the human sub-
maxillary gland, and no gangha in the parotid (Klein). Some of them have been
observed to end in Pacinian corpuscles of a simple kind (Krause). Many, no doubt,
supply the blood-vessels, Avhich they are knoAvn to influence. Most of them, however,
appear to end in the secreting alveoli. 'J'hese they reach for the most part as non-

THE SALIVARY GLANDS. 23

medullated fibres, and, after piercing the basement membrane, end in an open
arborescence of the finest varicose fibrils, ramifying between and around the cells of
the alveoli (fig. 30).

RECENT LITERATURE OP THE SALIVARY GLANDS.

Berkeley, H. J., The intrinsic nerves of the suhmaxillarij [/land of Mus viusculus, Johns
Hopkins' Hd^p. Rep., vol. v., 1894.

Eermann, Ueher d. Zusammensctzung der Gliindula aiihmax., d-c, Wiiizburg, 1878.

Biedermann, Zur Histologic und Physiologic der Schleimsef.rction, Sitzungsbeiichte tier Kaiserl.
Akademie tier Wissensch. zu Wieii, Math. Katurwiss. Klasse, Abt. iii., 1894.

Bizzozero, Gr., und Vassalo, G., Ueber die Er~eugung uml die physiotogische Regeneration der
Driisenzclhn hei den iSdugetieren, Virchow's Archiv, Bd. ex., 1887.

earlier, The so-called "hibernating glatid" of the hedqehog, Journ. of Auat. and Plivsiol.,
xxvii., 1893.

Chievitz, J. H. , Bcitrdgc zur Entivickelungsgeschichte der Spcichcidrilscn, Arch. f. Anat. und
Physiol.. Anat. Alth., 1885.

Flemming', "Walter, Ueber Ban und Einthcilung der Drilsen, Arch. f. Anat. u. Physiol.,
Anat. Abthlg., 1S88.

Frenkel, Moise, Sur les modifications da tissu conjonctif des glandcs et en particul icr de la
glande suus-iii<i.i:iUaire, Anat. Anzeiger, Jalirg. viii., 1893.

van Gehuchten, A., Lc mecanismc de la secretion, Anat. Anzeig., Bd. vi., 1890.

Gruber. W., t'dngeiiitaler Manyel heider Glcniduke submaxiUares, Virchow's Archiv, cii., 1885.

Kamocki, Utber die EntwicM. der Bernmnn' schcn tubuloscii Driisen, Intern. Monatschr. f. Anat.,
Bd. i., 1884.

Klein, E., Histological Notes, Quart. Journ. of Micr. Science, xxi., 1881 ; On the hjtnphatic
syntcia and the minute structure of the scdirary glands and pancreas. Ibid., xxii., 1882.

Korolkow, P., Die Nervenendigungcn in den Speicheldriisen, Anatom. Anz., Jahrg. vii., 1892.

KultscMtzky, N., Zur Lehre v. feineren Ban der Spjeiclieldrilsen, Zeitschr. f. wiss. Zool, Bd.
xli., 1885.

Langley, J. N., On the histology of the mucous salivary glands, and on the behaviour of their
mucous coiiftitnents, Journ. of Physiol., vol. x., 1889.

Laserstein, Sigfried, Ueber die Anfdngr der Absonderungswege in den Speicheldriiseii uud im
Panlrcas, Arch. f. d. ges. Physiol., Hd. Iv., 1893.

Liist, Joseph Heinrich, Ucher den feineren Bau Schlei/n-sezernierendir Drilsenzellen, nebst
Benifrkunyen iiber dca Sekrctionspro:ess, Anat. Anzeiger., Jahrg. iv., 1889.

Loewenthal, N., Zur Kenntnis der Glandula subnmxillaris einiger Sdugetiere, Anat. Anzeiger,
hii. ix., 1894 ; Historisrhe-kritische i\cti': ii. d. Glandula submax., Ibid, Bd. x., 1895 ; and Arch. f.
mikr. Anat., I'.d. xl., 1892.

Mayer, S., Adenologische Mitteilungen, Anat. Anzeig., Bd. x., 1895.

Muller, Erik, Zvr Anatomic der Speicheldriisen, Nordiskt med. Aikiv, 1893.

Nicolas, A., tjonlribvtion d I'etude des cellules g/andulaires, Le protoplasma des elements des
gfondes album incuses. Archives de physiologie normale et pathologique, Annee xxiv., 1892.

Paulsen, Ed., Bemerkungen iiber Sekretion und Bau der Schlcimdrilscn, Archiv ftir niikrohkop.
Anatoiuie, liand xxviii., 1886.

Poirier, Paul, Absence des parotides, Bulletins de la Societe anatoniique de Paris, Annee Ixiii.,
1888.

Ranvier, L., Etude anatomique des glandes connues sous les noms de sous maxillaire et sub-
lingualc chez les niammifiires. Archives de jjhysiologie, Annee xviii., 1886 ; Les membranes
muquiuses et le systi:me ylandulaire, Journal de micrographie, t. x. ; Le mecanismc de la secretian,
Ibid., t. xi., 1887.

Retzius, Gustaf, Uehei- die Anfdngc der Drilsengdnge und die Nerveneniligungen in den
Speirheldriixen des Mundex, Biolog. Untereuch. , N. F. iii., 1892.

Bicard, A., De quelques rapports anutomiques de la glande sous-maxilluire. Bull. See. Anat ,
Paris ^^'^'■*-

Seidenmann, M., Belt, zur Micro2)hy8iologie der Schlcimdriisen, Internat. Alonatschr. f. .\iiat.
u. Physiol., Bd. x., 1893.

Soli^er, Bernh., Zar Kenntniss der secern irendenZellen der Glandula subviaxillnris des Mtnscheu,
Anat. .ViiZf-igf-r, 1'.<1. ix., 1894, and " Nachtrng", in the same.

Steiner, Hermann, Ucher das Ejnthel der A usfuhrungsgdnge tkr grosscren Driisen, des
Mnixrhr,,, Archiv I. mikr. Anat., Bd. xl., 1892.

Zumstein, J. J., Ueber die Unta-kieferdriiseii einiger Sdugcr, 1891.

OKGANS OF DIGESTION".

THE TEETH.

In the human subject as in the great majority of mammals the dentition is
difhyodont, that is two sets of teeth make their appearance in the course of hfe, of
which the first comprehends the temporary or milk teeth, while the second is the
'permanent set.^ The temporary teeth are twenty in number, ten in each jaw, and
the permanent set consists of thirty-two, sixteen above and sixteen below.

The human dentition is also heterodont ; the teeth, instead of all having the
same form Qiomodont condition), differ considerably in their size, shape, and
function. The twenty temporary teeth consist of four incisors, two canines, and
four multicuspids or molars above and below. The thirty-two permanent teeth are
four incisors, two canines, four bicuspids or premolars, and six molars in each jaw.
There are no bicuspids among the temporary teeth, the eight deciduous molars
preceding eight bicuspids of the permanent set. The relative position and arrange-
ment of the different kinds of teefch may be expressed by the following formuJaj^
which also exhibit the relation between the two sets in these respects : — "

Temporary teeth j ?PP®^'
-^ •' ( Lower

MO. CA. IX.

-2 ] 2
2 12

MO. BI. CA. IX.

IN. CA. MO.

2 12

= 10
= 10

IX. CA. BI. MO.

Permanent teeth /yPP^^ I l I I I
\ Lower 3 2 12 2

Or they may be written more simply thus : —

(2.1.2

Milk teeth - —

2.1.2

16 i

-32

Permanent teeth

As the typical mammalian dentition is In^, C, , Pm^, and MO3 on each side of each jaw, it
follows that three pairs on each side are suppressed in man. Not unfrequently one or more of

Fig. -31. — Lower aspect of superior dental

ARCH AND HARD PALATE. (Mlihlf eitsr. )

these normally suppressed teeth appear,
sometimes in a well developed condition,
but much more frequently they are rudi-
mentary. From the position these super-
numerary teeth occupy it is probable that
the missing teeth are the second incisor and
the first and fourth premolars (A. Wilson).

The curve occupied by the teeth of

the upper jaw is elliptical, and of the

lower parabolic. It is not broken by

any interval or diastema as is the case

in most mammals. The span of the

upper dental arch is rather larger

than that of the lower one, so that

the teeth of the upper jaw slightly overlap those of the lower, both in front

and at the sides. While there is a slight diminution in the height of the crowns

of the teeth from the incisors backwards to the wisdom-teeth, there is in man

' The three permanent -molars are by some regarded as belonging to the /rs< dentition, since they
do not take the place of any of the milk teeth, but are formed independently in a backward extension of
the dental germ.

THE TEETH.

no abrupt change of level along the range. lu consequence of the large pro-
portionate breadth of the upper central incisors, the other teeth of tlie upper
jaw are thrown somewhat outwards, so that in closure of the jaws the canines and
bicuspids come into contact partly with the corresponding lower teeth, and partly

Fis

2. — Upper aspect of lower uektal arch axd body of lower jaw. (Mulilreiter.)

with those next following ; and in the case of the molars, each cusp of the upper
lies behind the corresponding cusp of the lower teeth. Since, however, the upper

Fig. 3.3. — Labial aspect of the right half

OF THE two IjKNTAL ARCHES To SHOW THE
RELATION BETWEEN THE UPPER AND LOWER

TEETH. (Zuckerkaiull. )

molars and especially the wisdom-teeth
are smaller than those below, the dental
ranges terminate behind nearly at the
fame point in both jaws (see figs. 38
and 34;.

Ill Europeans the upper incisors project
in front of the lower incisors, but it has
been shown by Turner that in some, at
least, of the Australian aVjorifrines this is
not the case, the cutting edges of the lower
incisors projecting- as far forwards as those of the upper.

It is well known that the teeth of certain races are larger in relation to the general
stature of the individual than in others. Flower has investigated this question so far as the
premolars and molars are concerned. He has constructed a driitul iiidr.r by comparing the
distance between the anterior surface of the first jiremolar and the posterior surface of the
wisdom-tooth with the banio-naml htngth of the skull. He divides the various races

Fig. 3i. — LlNOLAL ASPECT OF THE LEFT
HALF OK THE TWO DENTAL ARCHES.

(Zuckerkandl.;

according to their dental index into
vi'icriuhint. vitnoihinf, and mftjadont.
The microdont section contains the
white races, the meswlont the Mon-
((olian or yellow races, and the mega-
dont the black races, including the
Australians.

In consequence of the curve of the dental arch, such terms as anterior,
r>08terior, internal and external, when used in the description of the surfaces of the

ORGANS OF DIGESTION.

teeth, are liable to lead to confusion, to obviate which special names must be
employed. The surface of a tooth directed towards the lips or cheek is therefore
called labial or buccal, and that towards the tongue the lingual, while the terms
proximal and distal are used to represent the surfaces that would look towards and

Fig. 35. — Vertical section of premolar of
CAT. 15 DIAMETERS. ( Waldeyer. )

c, is placed in the pulp- cavity, opposite
the cervix or neck of the tooth ; the part
above is the crown, that below is the root
(fang). 1, enamel with radial and concen-
tric markings ; 2, dentine with tubules and
incremental lines ; 3, cement or crusta
petrosa, with bone corpuscles ; 4, dental
periosteum ; 5, bone of lower jaw.

away from the median plane were
the teeth arranged in a straight
line passing outwards from the
mesial incisor.

A tooth consists of three por-
tions, viz., one which projects above
the gums and is named the body or
croum, another fixed in the alveolus
or socket, the root, consisting of a
fang or fmigs — and a third, inter-
mediate between the other two, and,
from being more or less constricted,
named the neck. The size and form
of each of these parts vary in the
different kinds of teeth.

The roots of the teeth are
accurately fitted to the alveoli of
the j'aAvs, m which they are im-
planted. Each alveolus is lined
by periosteum {denial periosteum,
fig. 35, 4), which also invests the
contained tooth as high as the
neck, and is blended above with the
dense tissue of the gums. The
fangs of all the teeth taper from the
cervix to the point, and this form together with their accurate adjustment to the
alveolus has the effect of distributing the pressure during use over the whole socket,
and of preventing it from unduly bearing on the point of the fang, through which
the blood-vessels and nerves enter.

SPECIAL CHARACTERS OP THE TEETH.

The Permakext Teeth. — The incisors (fig. 36), eight in number, are the four
front teeth in each jaw, and are so named from being adapted for cutting or
dividing the food. Their crowns are chisel-shaped (c), and have a sharp horizontal
cutting edge, which by continued use is bevelled off behind in the upper teeth, but
in the lower ones is worn down in front, where it comes into contact with the over-
lapping edges of the upper teeth. Before being subjected to wear the horizontal
edge of each incisor is marked by three small prominent points, separated by two
slight notches (fig. 36, d). The labial surface. of the crown is slightly convex, both
from above downwards, and from side to side. The hngual surface is concave.

THE TEETH.

especially from above downwards, and presents a prominence termed tlie laml
ridge or ciiujulum. The proximal and distal surfaces are triangular with the base
at the gum, and the apex towards the cutting edge. The fang is long, single,
conical and compressed at the sides, where it sometimes, though rarely, presents a
slight longitudinal furrow (as in c). The lower incisor teeth are placed vertically
in the jaw, but the corresponding upper teeth are directed obliquely forwards. The
upper incisors are, on the whole, larger than the lower ones. Of those in the upper
jaw the mesial incisors are the larger ; but in the lower jaw the mesial incisors are
the smaller, and are, indeed, the smallest of all the incisor teeth. The cingulmn is

fig. 36. — Imisor teeth ok the ui>ier aku lower

JAWS.

«, front view of the upper and lower mesial incisors ;
h, front view of the upper and lower lateral incisors ;
f, lateral view of the upper and lower nie.sial inci&ovs,
showing the chisel shape of the crown ; a groove is seen
marking slightly the fang of the lower tooth ; r/, the
ujiper and lower mesial incisor teeth lefore they have
been worn, showing the three points on the cutting
«dge.

absent in the lower incisors, but sometimes
in the upper lateral incisors, and less Ire-
quently in the upper mesial incisors, it is
developed into a distinct lingual cusp (fig. :^7).
The canine teeth (fig. 38), four in
number, are placed one on each side, above
and below, next to the lateral incisors.
They are larger and stronger than the
incisor teeth. The crown is thick and
conical, its labial surface decidedly convex, and the lingual concave. It may be
compared to that of a large incisor tooth the angles of which have been removed,
so as to leave a single central point or cusp, whence the name cuspidate applied to
these teeth. The point always becomes worn down by use. The fanf/ of the canine
teeth is single, conical, and compressed at the sides : it is longer than the fangs of

Fig. .37. — «, b, c, lin(}i;ai> surface «v lppkr incisor teeth show-
ing VARIATIONS I.N FORM ; I.N a THE CINGL'I.U.M IS WELL MARKED.

(Zuckerkaiidl.)

any of the other teeth, and is so thick as to cause a
prominence of the alveolar arch.

The upper canines, popularly called the ei/e-fee//t, are
larger than the lower, and in consequence of this, as well
as of the greater width of the upper rang(! of incisors,
they are thrown a little farther outwards than the lower
ones. On the lingual surface of the upper canine a well-marked ridge pius.scs from
the apex of the cusp to the cingulum, where there is frequently a distinct tubercle.
The lower c-inine has neither a liugiial ridge nor cingulum. The root of the u])per
canine is almost invariably single, while that of the lower is often bifid at its a])e.\.
In the dog-tribe, and in tiie cnmivora generally, these teeth acquii-e a great size,
and are fitted for 8eiz;ing and killing prey, and for gnawing atid tearing it when
taken a.s food.

The bicuspids ffig. :'>'.)), also c-.alied premottirs, are four in each jaw ; they are
shorter and smaller than tlie canines, next to which th(!y are placed. The crown is
compressed proxiiiio-distaliy, and both its labial and lingual surfaces an; convex
Tlie grinding surface sliewK two cus])H — a large labial and a smaller linguiil —

ORGANS OF DIGESTION.

separated by a deep fissure. The fang is compressed in the same directioa
as the crown, and is grooved on its proximal and distal surfaces so as tO'

Fig. 38. — Canine tooth of the upper jaw.
a, front view ; h, lateral view, showing the long fang grooved on the side.

shew a tendency to be divided into a labial and a lingual
portion.

The upper bicuspids differ very considerably from the lower,

and while in the latter there is a decided distinction between

the first and second, in the case of the two upper bicuspids

there is but little difference. The labial surface of the crown

J ^ of the first upper bicuspid has a vertical ridge passing from

its apex upwards towards the neck ; this ridge is bounded by

two lateral depressions (see a, fig. 39). The lingual surface of the crown is smaller

and more convex both longitudinally and transversely than the labial aspect. It

Fig. 39. — First bicuspid iooth of the upper and lower jaws.

a, labial view ; h, lateral view, showing the lateral groove of the fang,
and the tendency in the upper to division.

has usually two roots, a labial and a lingual ; sometimes
only one, and more rarely three, two labial and one lingual.
In the second upper bicuspids the labial and lingual surfaces
are nearly equal, and the labial ridge is indistinct, while the
fang is more frequently single than in the first bicuspid.
The lower bicuspids are smaller than the upper ones, their
cusps are less deeply divided, and the lingual surface is
much less convex than the labial. In the upper bicuspids
the two cusps are separated by a deep fissure, while in the
lower they are united by a low ridge. The lower bicuspids
have generally single roots, but occasionally the root is
divided into a labial and a lingual fang. The first lower
sometimes only one cusp distinctly marked, viz. the labial, and in
that case it approaches in figure to a canine tooth. The second bicuspid is larger

Fig 40.— First molar tooth of the upper and lower jaws.
Tliej- arc viewed from the buccal aspect.

than the first, and its lingual cusp is nearly as prominent as the
labial one, whereas in the first bicuspid the lingual cusp is much
smaller.

The molar teeth (fig. 40), true or large molars, or grinders, are
twelve in number, and are arranged behind the bicuspid teeth,
three on each side, above and below. They are distinguished by the
large size of the crown, and by the great width of its grinding
surface. The first molar is the lai'gest, and the third is the smallest,
in each range, so as to produce a gradation of size in these teeth.
The last of the range, owing to its late appearance through the gum,
is called the ivisdom-tooth. The croivns of the molar teeth are low
and cuboid in their general form. Their labial and lingual surfaces
are convex, but the proximal and distal surfaces are flattened.
The grinding surface is nearly square in the lower teeth, and rhomboidal in the
upper, the corners being rounded off ; it bears four or five trihedral tubercles or

bicuspid has

THE TEETH.

cusps (whence the name muUicuspuiati), separated from each other by a crucial
depressiun.

The crown of the first upper molar bears four cusps, situated at the angles of
the masticating surface : of these the proximo-lingual is the largest, and is usually
connected with the labio-distal cusp by a low oblicjue ridge. This tooth has
occasionally a fifth cusp situated on the lingual side of the proximo-hngual cusp ;

Fig- 41. — (jRINDIXG SURFACE OF TI]E UPPER MOLARS.

(ZuckerkaniU. )

A, on right side ; tlie first molar has four cusps, and the second and
third three each.

B, another set from the left side, with the same number of cusps as in
A, except that a small additional cusp is seen on the lingual side of the
proximo-lingual cusp of the first molar. The third molar i.s larger than
the second.

ihis additional cusp is small, and rarely, if ever, reaches the
grinding surface. The second upper molar is generally

described as having four cusps, but according to Zuckerkandl and Rose there are
often only three. Zuckerkandl found four cusps in 45-G per cent, of Europeans,
the cusps being reduced to three in .34-4 per cent., while in the lower races four
cusps were found in 73-5 per cent. Rose's results agree essentially with those of
Zuckerkandl. In the upper wisdom-tooth the two lingual cusps are usually blended.
The crowns of the lower molars, which are larger than those of the upper, have
five cusp.>, the additional one being placed between the two distal ones, and

Fig. 42.— Grlsding surface of the luweii molars on left side. (Zuckerkandl.)

In this series the first molar has five cusps, the second 4, and the third 4, and the
teeth diminish in size from the fir.st to the third.

rather to the outer side. Not nnfrequently the second molar has only
four cusps, but this reduction in the number of cusps rarely affects the
firsS and third molars. The third mohir is usually as large as and
sometimes even larger than the second. The fcuigs of the molar teeth
arc multiple. In the first and second molars of the upper jaw the
fangs are three in number, viz. two labial and one lingual ; the labial fan<'-s are
short, divergent, and directed towards the antrum of the superior ma.\illa, while
the lingual fang is larger and longer and directed towards the palate, its distal
border extending as far back as the labio-distal fang. The first and second
molars of the lower jaw have each two broad compressed fangs, one proximal
and the other distal ; they are grooved on the faces that are turned towards each
other as if each consisted of two fangs fused together. In the wisdom-teeth of
both jaws the fangs are often collected into a single irregular, CDiiical mass, which
is either directed backwards in the substance of the jaw, or curved irregularly ; this
composite fang sometimes shows traces of subdivision, and there are occasionally
two fangs in the lower teeth and three in the upper.

TFoMOLOoiK.s oi' TJIK TKETH. — Two main views are held as to the phylo^'eny of tlie
inulticuHpidate teeth of various mammals, such as the molars in man. According" to Rdso and
others these teeth are formed by the fusion of a number of orig-inally simple cones, such as
are found in the Ileptilia. The evidence offered in support of this view is mainly embryo-
log^ical. On the other hand. Copy and Osborn, from a study of the teeth in a larg-e .«eries of
t(Mn\\ mammals, hold that the primitive form of mammalian molar was a sing-le cone, to which
all the other cusps have V)een successively added.

In fishes, amphibia, and reptilia, in place of two series of teeth such as occur in mammals,
there is throujfhout life a constant succession of series which replace one another from behind
forwards. There can be little doubt that the two series, milk and permanent, of mammals
reprcHcnt a part, at least, of the successive series of reptilian teeth. .Some considerable amount

ORGANS OF DIGESTION.

of discussion has of late years taken place as to which of the two dentitions is the primary,
for although in higher mammals the milk dentition is the first to appear, in marsupials it
appears to be absent ; and it has hence been inferred that it is really only of secondary
development. The most recent researches seem, however, to show that the milk dentition is-
represented in a rudimentary form even in marsupials, and it would further appear that in
excep'~.ional instances in higher mammals, and in man, a third, and even a fourth, series of
teeth may be produced in connection with persistent remains of the dental lamina, behind
and lateral to the permanent teeth ; this being an apparent reversion to the reptilian con-
ditions of dental succession. For a full discussion of these and other points in connection
with the homologies of the teeth, see Schwalbe, " Ueber Theorien der Dentition," VerhandL
d. anat. Gesellschaft, Anat. Anzeiger, lS9i.

The Milk-teeth (fig. 43). — The temporaiy or milk-teeth are distinguished
from the permanent by the marked bulging of the crown close to the neck, so that

Fig. 43. — Milk teeth of the right

SIDE OP THK UPPER AND LOWER JAWS.

a, the incisors
the molar teeth.

b, the canines ; r.

the latter shews a well-marked
constriction. The temporary in-
cisors and canine teeth resemble
those of the permanent set in
their general form, but they are
of smaller dimensions, and all
th^ir characteristic markings are
much less decided, especially
those in the canines.
The temporary molars are lar gcr than the bicuspids which succeed them. The
hinder of the two is much the larger, being, indeed, the largest of all the milk-teeth.
The first upper milk molar has only three cusps, two labial and one lingual ; the
second has four. The first lower temporary molar has four cusps, and the second
five, of which in the latter case three are labial. The fangs of the temporary molars
resemble those of the permanent set, but they are smaller and are more divergent
from the neck of the tooth.

STRUCTURE OP THE TEETH.

On making a section of a tooth, it is found to be hollow within (fig. 44). The
form of the cavity bears a general resemblance to that of the tooth itself ; it occupies

Fig. 44. — Sections op an incisor and molar tooth.

the interior of the crown, and extends along each
fang, at the point of which it opens by a small
orifice. In the incisor teeth the cavity is pro-
longed above into two tapering canals, which proceed
one to each corner of the crown ; in the bicuspid
and molar teeth it advances a short distance into
each cusp. In the case of a root formed by the
of two or more fangs, each division has a separate canal prolonged to its

blending-

Pulp of the teeth. — The central cavity of a tooth is called the jndp-cavitij ,
because it is occupied by a soft, highly va&cular, and sensitive substance, called the
dental pulp. This pulp (fig. 45, F) consists of jelly-like connective tissue containing-
cells, blood-vessels and nerves, and fine fibres. The fibres appear to be formed from
processes of the cells : according to Rose they are not collagenous, although a few

THE TEETH.

bundles of ordinary collagenous connective tissue fibres may accompany the blood-
vessels and nerves. The cells are partly disseminated in the matrix, and partly form
a stratum at the surface of the pulp, where, during the formation of dentine, they are
elongated, somewhat like the cells of columnar epithelium (see fig. ().3, c, p. 44).
but after the dentine is completely formed they become flattened like the osteoblasts
under the periosteum of bone. These superficial cells {odontoblasts, fig. 45, Od, Od^)
send processes into tubules in the dentine, to be afterwards noticed, of which more
than one may come from the same cell. The filaments within the tubules were first
noticed by J. Tomes, and are known as Tomes' fibres. The arteries and nerves,
which are derived from the internal maxillary and fifth pair respectively enter by

Fig. 4."). — Section across the root of a youno tooth showino its pulp in situ. (Rose.) saq.

/', pulp ; V, V, veins ; A, A, arteries ; N, nerve-bundles ; Od, columnar odontoblasts still
depositing dentine ; Od^, flattened odontoblasts, which have ceased to form dentine.

the aperture at the point of each fang. The vessels form a capillary network
beneath the superficial cells ; the nerves end in fine non-medullated fibrils, which
arc distrilnited abundantly at the surface of the pulp and run up between the
superficial cells, but they have not been traced into the dentinal tubules.

Weil haH described a clear layer (haxiil layer') under the odontoblasts, pervaded with
fibreH. which he rej^ards a.s derived from the odontoblasts. It is, however, somewhat
uncertain whether the layer dfiseribed is not an artefact, due to the shrinking of the main
mass of the pulp from the layer of odontoblasts. It is only seen iu the crown of the
teeth. No lymphatics have been seen in the pulp.

Hard tissues of the teeth.— The hard part of a tooth is composed of tlu'ce
di.stiuct substances, — viz., thi; j)roper dental substance, ivory or dentine, the enamel^

ORGANS OF DIGESTION.

and the cement or crusta petrosa. The dentine constitutes by far the larger portion :
the enamel is found only upon the* exposed part or crown ; and the cement covers
with a thin layer the surface of the faug.

The dentine (Owen) resembles bone in its general aspect and chemical
constitution, but is not identical with it in structure.

The dentine of human teeth is composed of 28 parts per cent, of animal, and 72 of earthy
matter. The former is resolved into gelatin by boiling. The composition of the latter.

46. — Section of a tooth across the crown. (Raiiber. ) f

a, dentine, the tubules cut longitudinally ; a', the same cut obliquely ; a", the same cut across ;
c, enamel, showing contour lines (5) ; d, d, portions of the pulp cavity extending into the cusps, with
the dentinal tubes converging horizontally towards them (1).

according to Bibra, is as follows, viz., phosphate of lime 6(i'7 per cent., carbonate of lime 3'.3,
phosphate of magnesia and other salts, including a trace of fluoride of calcium, 1'8. Berzelius
found .5"3 carbonate of lime.

The dentine is penetrated throughout by fine tubes {dentinal tubes), which being
nearly parallel, give it a striated aspect (figs. 46, 47). When a thin section of a

Fig. 47. — Section or the same tooth
ACROSS THE FANG. (Rauber.) 8

a, pulp cavity ; b, dentine ; c, cement ;
1, incremental lines ; 2, granular layer.

macerated tooth, prepared by
grinding, is viewed under the
microscope by transmitted light,
the solid substance, or matrix, is
transparent and apparently homo-
geneous, while the tubes, being (in
a dried specimen) filled with air,
are dark ; but when seen with reflected light on a dark ground, the latter appear
white ; in these respects they resemble lacunae and canaliculi of bone.

The dentinal tubules open at their inner ends into the pulp-cavity, which has
accordingly very numerous minute orifices over the whole surface. Thence they
pass in a radiated manner through every part of the ivory towards its periphery.
In the upper part of the crown they have a vertical direction ; buc towards the
sides, and in the neck and root, they become gradually oblique, then horizontal, and

THE TEETH.

are finally even inclined downwards towards the point of the fang. The tubules
describe in their course two or three gentle curves (primari/ curvatures, fig. 35),
and each is besides twisted throughout its whole length into numerous fine spiral
turns, which follow more closely one upon another ; these are the secondarij curva-
tures (fig. 48). In form a tubule may accordingly be likened to the thread of a
corkscrew, stretched so that the turns are drawn far apart, and their breadth
proportionally diminished (Welcker).

The tubes are only slightly divergent as they pass towards the surface ; and, as
they occasionally divide dichotomously, and at first without being much diminished
in size, they continue to occupy the substance of the dentine at almost equal
distances, and their nearly parallel primary curvatures produce, by the manner in
which they reflect the light, un appearance of concentric undulations in the dentine,

Fig. 48. — Section of fang, parallel to the dentinal
TUBULES (human canine). Magnified 300 diameters.
(Wuldeyer.)

1, cement, with large bone lacunae and indications of
lamellffi ; •!, granular layer of Purkinje (interglobular
space.s) ; 3, dentinal tubules.

which may be well seen with a low magnifying
power (Sckreger's lines). The average diameter
of the tubules at their inner and larger end is
O-Ou.3.5 mm., and the distance between adjacent
tubules is commonly about two or three times
their width. From their sides, numerous im-
measurably fine branches are given off, which
penetrate the hard intertubular substance, where
they either anastomose or terminate blindly.
These lateral ramuscules are more abundant in
the fang. Xear the periphery of the ivory the
tubules, which by division and subdivision have
become very fine, terminate imperceptibly by
free ends.

The tubules have each a proper wall (dentinal
sheath of Neumann) independent of the inter-
tubular matrix, but intimately adhering to it.
By steeping sections of decalcified dentine in
strong hydrochloric acid, the matrix is destroyed,
and the mcmljranous tubes, which consist of a
more resisting material (probably elastic substance), remain behind. Rose states
that these sheaths, which are formed of dentinal matrix which calcifies either late or

Fig. 49. —Sections op dentinal tubules. (After Fraenkel.)
a, cut acro8.s ; b, cut obliquely. (About 30(J diameters.)

not at all, anastomose freely, and that it is their anastomoses which
have been often taken for that of the tubules themselves.

In the temporary, and sometimes even in the permanent teeth,
the tubules are constricted at short intervals, so as to present a
monililorm character. The terminal branches of tiibides are
occasionally .seen to pass on into the cement which covers the fang, and to commu-
nicate with canalif-uli procecditig from tiie characteristic lacinuje found in that
OHsi'Ous layer. Tubules have likewise been observed by Tomes and others passing
into the enamel in the teeth of marsupial animals, and in a less marked degree,

VOL. III., PT. 4. jj

34.

OEGANS OF DIGESTIOX,

in human teeth. In this case they pass, not into the enamel prisms, but into the
inter-prismatic substance.

The intertuljular sithsta?ice is translucent. The animal matter which remains
after the earth has been removed by an acid, may be torn into laminge (Sharpey),

Fig. 50. — Vertical section of the upper part of an
INCISOR TOOTH. (From KoUiker. ) Magnified 7 dia-
meters.

a, the pulp-cavity ; h, dentine ; c, arched incremental
lines ; d, cement ; e, enamel, with bands indicating the direc-
tion of the ranges of fibres ; /, coloured lines of the enamel.

parallel with the internal surface of the pulp-cavity,
and therefore across the direction of the tubules.
It has been shown by Ebner and Mummery that
the matrix contains iine fibrils like those of the
matrix of bone. These fibrils are not themselves
calcified but are enveloped in the calcified inter-
fibrillar substance, and, according to Mummery,
are continuous with fibrils of the dental pulp.

The laminated structure is an indication of the
deposition of dentinal substance in successive strata
in the process of formation of the tooth — the
lamime corresponding with the shape of the pulp-
surface at successive stages of the process. Not
unfrequsntly lines, varying in number and breadth,
are seen in sections of the dry tooth, conforming in
direction with the lamination just spoken of {^incre-
mental lines, Salter, fig. 50, c). They are caused
by the drying of imperfectly calcified dentine,
which shows little cavities bounded by, and therefore receiving their figure from,
minute nodules or globules of dentine, and hence named interglobular spaces (fig.
51, c). The interglobular spaces, and the globules surrounding them, vary in size

Fig. 51. — A small portion op the dentine with
interglobular spaces. (From Kolliker.) 350
diameters.

c, portion of incremental line formed by the inter-
globular spaces, which are here filled up by the trans-
j)arent material used in mounting the siDecimen.

within wide limits. A layer, in which they
are very fine — gramdar lager (fig. 48, 2) — is
not uncommonly found towards the outer
surface of the dentine.

The enamel is that hard white covering

which encrusts and protects the exposed

portion or crown of a tooth. It is the

hardest of all the dental tissues, but is gradually worn down by ]3rotracted use. It

is thickest on the grinding surface and cutting edge of the teeth, and becomes

gradually thinner towards the neck, where it ceases.

According to Bibra, it contains of earthy constituents 96'5 per cent., viz., phosphate of
lime with traces of fluoride of calcium 89'8, carbonate of lime 4:'4, phosphate of magnesia and
other salts 1-3, and of animal matter only 3"5 per cent. Berzelius, however, gave the
proportion of carbonate of lime as 8, and of animal matter as only 2 per cent.

THE TEETH.

The enamel is made up entirely of veiy hard and dense microscopic columns or
prisms, arranged closely together, side by side, and set by one extremity upon the

Fig. 52. — Section of part of the crown of a tooth,

PARALLEL WITH TliE GEKERAL SET OF THE ENAMEL

PRISMS. (Rauber. ) S-sa.

a, pointed projection of dentine ; b, tubules extending
from the dentioe into the enamel ; c, enamel prisms ; d, prisms
cut across ; e. cuticle of the enamel.

subjacent surface of the dentine (fig. 52). The

columns are disposed in ranges, which, on the

grinding surface, are set vertically, but on the sides

of the crown get more horizontal. Near the

dentine the prisms cross one another in the alternate

ranges, but become parallel as they approach the

surface of the tooth. An eflFect of radial alternate

light and dark stripes is obtained (^as in fig. 50)

(A. Retzius). A series of concentric lines is

likewise to be seen crossing the enamel fibres :

these are termed coloured lines from their brown

appearance. According to Ebner, these are

produced by some of the inter-prismatic spaces

becoming in the dried tooth filled with air.

Minute fissures not unfrequently e.xist in the

deep part of the enamel, which run between clusters of the prisms down to the

surface of the dentine (fig. 53, c) ; and other much larger and more evident fissures

Fig. 53.

-Thin section of the enamel and a part of the dentine.
(From Kblliker.) 350 diameters.

a, cuticle of the enamel ; h, enamel-fibres or columns with fissures
between them and cross striae ; c, clefts in the enamel communicating
with the extremities of some of the dentinal tubules {d).

are often observed leading down from the depressions or
crevices between the cusps of the molar and premolar teeth.
The unworn surface of the enamel is finely striated.

The enamel-columns (fig. 52) have the form of solid six-
sided pri.sms. Their diameter is ordinarily about 0"005 mm.
They are marked by frequent dark transverse shadings,
which are usually ascribed to the existence of shallow con-
Btrictions along the fibres. Althougli this may be in })art
the cau.se, it is not improbable that the transverse markinos
are largely the result of tlie manner in which the prisms arc
built up in successive stages by the cells which produce them,
each marking representing the termination of a stage. The
inner ends of the prisms are implanted in minute hexagonal
depressions on the surface of the dentine ; whilst the outer
ends are free, and present, when examined with a high
magnifying power, a tes.selated appearance (fig. 54, B), The
prisms are united by a small amount of a substance which
api>earH similar to the intercellular substance of an epithelium, but is
calcified. In marsupials and some rodents there are regular canalicuii
interprismatic substance.

])erhap3
in tin's

D 2

ORGANS OF DIGESTION,

When submitted to the action of dilute acids, the enamel is almost entirely-
dissolved, and J eaves scarcely any discernible traces of animal matter. The centre

Fig. 54. — Enamel-prisms. (From Kblliker.) 350 diameters.

A, fragments and single columns of the enamel, isolated by the action of hydrochloric acid.

B, surface of a small fragment of enamel, showing the hexagonal ends of the prisms.

of the prisms is first dissolved, showing this part to be less firmly calcified than the
periphery. After exposure for a short time to the action of an acid, the enamel of

Fig. 55. — Section op the fang of a tooth

SHOWING dentine AND CEMENT TOGETHER
WITH THE DENTAL PERIOSTEUM. (RoSe. )
200
1 •

Ep., nests of epithelial cells within the
dental peiiosteum which are the remains of the
epithelial sheath of Hertwig ; 0., osteoblasts
which have formed the cement ; K., lacuna of
the cement ; /., granular layer of the dentine ;
D, dentine.

newly formed or still growing teeth
may be broken up, and its structural
elements more easily distinguished. In
broken enamel prisms thus treated a
longitudinally striated structure has
been described (Annell).

It is further found, on treatment
with acid, that a very thin membrane
(enamel cuticle, Nasmytlis membrane)
entirely covers the enamel of unworn
teeth upon its outer surface (figs. 52,
53). This membrane forms a protective
covering to the enamel. It is of an
epithelial and horny nature, and with-
stands prolonged boihng as well as the action of acids and other re-agents. It is
formed of short flattened prisms which are the remains of the last formed portions
of the enamel prisms, and which have remained uncalcified. After the action of
nitrate of silver, it exhibits markings like those seen in a pavement epithelium.

The crusta petrosa or cement is the third substance which enters into the
formation of the teeth. This is a layer of true bone, slightly modified in structure,

THE TEETH.

and investing that part of the dentine which is not protected by the enamel. It
covers the whole fang, towards the lower end of which it becomes gradually thicker,
and is specially developed at the apex, and along the grooves of the compound
fangs. As life advances, the cement generally grows thicker, especially near the
point of the fang, where it sometimes blocks up the orifice leading to the pulp-
cavity.

The crusta petrosa is lamellar in structure, and contains lacunas and canaliculi
resembling those of bone but larger and more irregular (fig. 55, K). Where the
cement is very chick it may contain Haversian canals. On the milk teeth the
cement is thinner, and contains fewer cells. Perforating and decussating fibres,
similar to those of ordinary bone, occur in the cement. It is covered externally
by the dental periosteum, by means of which it is firmly fixed into its bony socket.

VARIETIES OF DENTINE.
Certain varieties of hard tissue are liable to be formed in the pulp-cavity of a tooth after
the regular production of the dentine is completed. The two chief kinds hitherto described
are the following : —

1. Osteodentine (Owen). — This is a hard substance which sometimes becomes deposited
within the pulp-cavity, somewhat resembling bone in structure. It is traversed by canals,

Fig. 56. — LOXGITCDINAI, SECTION OF INCISOR TOOTH SHOWING DENTINE OF

REPAIR. Slightly magnified. (Reduced from Salter.)

d. d'. denuded
secondary deiitine.
dentine.

surfaces of dentine ; r, r.
Two or three incremental

corresponding deposits of
lines are observed in the

which contain blood-vessels and pulp-tissue, and may be surrounded
by concentric lamellae like the Haversian canals of bone. From these
canals numerous tubules radiate, larger than the canaliculi of bone,
resembling, in this respect, and also in their mode of ramification, the
tubes of the dentine. It may or maj' not coalesce with the previously
formed dentine.

2. Secondary dentine. Dentine of repair (Salter). — When the
outer surface of the dentine becomes denuded at any place, so that the
peripheral ends of the tubules are there exposed, as may happen
in the crown from injury or wear of the enamel, or at the cervix
from continued friction and abrasion of the cement, a deposition of
dentinal matter occurs on the inner surface of the dentine exactly
coiTcsponding in position and extent with the area occupied by
the central ends of the exposed tubules. Many of the affected
tubules become subsequently filled up by a deposit of hard matter
within them, so that on section both the secondary dentine and
the corresponding part of the primary dentine appear clearer
and more transparent than the remainder of the dentinal substance
(see fig. rA',).

When the surface- injury has been considerable, the dentine
of repair is largely in excess, and may in such cases completely
cavity.'

fill up the pulp-

DEVELOPMENT OF THE TEETH.-
The first trace of the tei.'th appears during the sixth week of intra-uterine life (in
embryo.s of 11 mm. to 12 mm. long) in the l"orm of a longitudinal thickening of the
epithelium of the mouth along the line of the future jaw. The thickening in
question is produced by multiplication of the deeper-lying cells of the epithelium,
and in some animals, e.g., ruminants, is marked by a prominence raised above the
general level of the epithelial surface. A i)rominence is found in the human

' In mm't animaJH other kinds of dentine arc found ; for a description of these, and other details
regarding the structure and developfnent of the teeth of vertebrates, the student is referred to the
"Manual of Dental Anatomy," by C. S. Tomes, F.ll.S.

^ The following account of the develoijment of the teetJi is mainly baaed upon the descriiition given
hy Roue.

OEGANS OF DIGESTION.

embryo for a very short time, and at one point only of the jaw, Nevertheless
it is considered by Eose of great morphological importance, as representing a

Fig. 57. — Figures (from C. Rose's models) showing four successive stages in the development

OF THE DENTAL LAMINA AND TOOTH GERMS OF THE MILK TEETH OF THE UPPER JAW. OnLY THE
BUCCAL EPITHELIUM AND THE EPITHELIAL STRUCTURES OF THE TOOTH GERMS ARE REPRESENTED,
AND EVERYTHING IS SHOWN AS SEEN FROM ABOVE.

1. From an embryo 25 mm. long. — d.l., dental lamina ; M., aperture of mouth.

2. From an embryo 40 mm. long. — M., mouth; l.f., reverse of labio-dental furrow; d.l., dental
lamina ; p., mould for papilla of milk canine ; p^, mould for papilla of second milk molar.

3. From an embryo 115 mm. long. — L., epithelial layer of upper lij) ; l.f., reverse of labio-dental
furrow ; d.l., dental lamina ; m.i.^, epithelial rudimentof first milk incisor ; ni.i.'^, m.c, m.m.^, in.m.^,
epithelial rudiments of second milk incisor, and of milk canine, and first and second molars resijectively.

4. From an embryo 180 mm. long. — m.i.^, m.i.", m.c, m.m.^, and m.m.', as before ; m.^, rudi-
ment of first permanent molar.

vestige of the primitive larval epithelial teeth which occur in fishes and amphibians.
The longitudinal epiblastic thickening grows into the mesoblast, as a strand
of cells which is at first semicircular in section, and the mesoblast encloses

THE TEETH.

it in a continuous groove ; for there is at first no indication of the formation of
separate teeth. The strand in question has been called the "dental lamina"
(Zahnleiste) : it is also known as the " common enamel germ," because some of its
cells are concerned in the production of the enamel of the teeth. But it is not
merely a dental germ, for before long (embryo of 17 mm., or seventh week) it is
found that the originally simple strand of cells is separating longitudinally into
two. One of these, the outer, or labial, which dips vertically into the embryonic
jaw, becomes hollowed out from the surface to form the labio-dental furrow,
and may accordingly be termed the lahio-dentcd strand, whilst the other, lingual or
inner part, takes at first a vertical and then an inward (lingual) direction, and is the
actual tract of cells in connection with which the teeth of both dentitions subsequently

Fig. 58. — Palatine surface of the model

WHICH IS SHOWN FROM ABOVE IN FIG. 57. 3.

P, palate ; L, upper lip ; d.Lf., labio-dental
furrow ; d.f., dental furrow.

become developed. The name dental
lamina, or common dental germ^ should
therefore be retained for this portion
of the original strand of epiblast cells
alone. The separation of the two
strands begins in front and extends
gradually backwards : it is not com-
plete until the eleventh or twelfth week.
The dental lamina, when thus separated
from the labio-dental strand, forms a
flat band of cells (fig. 57, 1, d.l.) con-
nected by one edge with the epithelium
lining the mouth, whilst the other, or
free edge, projects almost horizontally
inwards {i.e., tongue-wards) in the
substance of the embryonic jaw. Sub-
sequently, however, as the milk teeth
develop, it takes a vertical direction.
Over the line of its attachment to the
epithelium of the mouth there is a shal-
low furrow, the dental farrow (fig. ,')8,
^/./.), which is at first rather outside (or

on the labial side of) the most prominent part of the jaw, but gradually comes to lie
further inwards. At about nine weeks (embryo of 25 mm.) the free border of the
dental lamina begins to exhibit ten enlargements in each jaw corresponding in situa-
tion to the ten milk teeth. At ten weeks (embryo of 32 mm.) these enlargements
show a moulding on one of their surfaces (upper in the upper jaw and lower in the
lower) (fig. 57, 2,p.,p.^), and the adjacent mesoblast fits against this moulded surface
and l)ecomes differentiated into the form of a papilla, which thus at once begins to
have the shape of the crown of the future tooth, being simple in the incisors and
multiple in the molars.- The papillic have all appeared by eleven and a half weeks,
and the enlargements of the dental lamina, which are now very evident, grow around

' " Dental gerrn " is UHed insbiad of the former expression "enamel germ," because tlie cells in
^|iie«tion not only form enamel, but also appear to determine the formation of dentine (tjy the mesoblast
celJH in contact with themj (see p. 4fJ,i.

^ In the canines, however, the papilla is at first double, not single. It has been suggested that this
is i>robably an indieaticn of the ori;,'inally premolar character of these teeth.

ORGANS OF DIGESTION.

and gradually invest the papillae at their sides also. The dentine and pulp of the-
milk teeth are formed from these papillae, whilst the enlargements of the dental
lamina which invest them form special dental germs for those teeth, to which also'
they furnish the enam.el.

In the meantime the dental lamina has grown further inwards (tongue-wards)
beyond these prominent special dental germs, which appear now as ten rounded
masses of cells attached to the labial side of the flat common dental lamina " like
swallows' nests built against a board " (fig. 57, 3). The common dental germ
extends backwards in the substance of the jaw a short distance behind the last
of these special dental germs for the milk-teeth. This backward extension of
the dental lamina is not directly connected with the buccal epithelium. At
about seventeen weeks (embryo of 18 centimeters long) it shows another

Fig. 59. — Gingival surface of the

MODEL WHICH IS SHOWN FROM
ABOVE IN FIG. 57, 4.

P., palate ; L., upper lip ; l.d.f.,
labio-dental furrow ; d.f., dental fur-
row ; d.l., prominence caused by dental
lamina with its enlargements.

enlargement, which is the special
germ of the first permanent
molar, and, in connection with
this enlargement, the corre-
sponding papilla soon makes its
appearance (fig. 57, 4, m^). Behind
this again the dental lamina is
continued backwards into the gum
as a thin flat band of epithelium.
About four months after birth an
enlargement for the second per-
manent molar appears, and the
corresponding papilla at six
months, and about the third year
the enlargement for the third
permanent molar, or wisdom-
tooth, begins to be visible in a
still further backward extension
of the dental lamina, and its
papilla is seen about the fifth year.
Meanwhile, important changes have been occurring in the dental lamina, in the
attachments of the special germs to it, and in the special germs themselves.

Changes in the dental lamina. — The changes in the common dental lamina
consist in the formation of numerous apertures of irregular size and form, with the
result that from a complete flat band of cells it becomes partly atrophied and changed
into a cribriform tract (fig. 63), so that in transverse sections of the jaw it appears to
be broken up into separate portions (fig. 64). This is, however, not the case,
although the lamina is pierced with apertures so as to be almost reticular in
character. This atrophic change begins in front about the seventeenth week, and
gradually extends backwards, but the most posterior part is still complete (non-
cribriform) at the time of birth, and even for some time after. Moreover, at
certain points the reticulation is absent, viz., on the lingual side of and slightly
lateral to the special germ of each milk-tooth, and at these points the dental lamina

THE TEETH.

41.

again undergoes a thickening. These thickenings become the special enamel germs
for the teeth of succession of the second dentition. In connection with each one a
papilla becomes formed in the same Avay as for the milk teeth, but by no means

Fig. 60. — Sagittal section through the first lower milk molar of a human embryo
30 MM. long. (Rase.) ^^^.

Lh.L., labio-dental lamina, here separated from and well in advance of the dental lamina;
Z.L., placed over the shallow dental furrow, points to the dental lamina, which is spread out below to
form the enamel germ of the future tooth ; P.]).. bicuspidate papilla, cajjped by the enamel germ ;
Z.S., condensed tissue forming dental sac ; M.E., mouth-epithelium.

simultaneously, for the germs of the permanent incisors and canines are formed,
along with their papillae, at about the twenty-fourth week (embryo of 30 cm,),
whereas the enlargements of the dental lamina, which are eventually to form the
enamel organs of the first and second premolars, are not visible until the twenty-

^"""^S^^^^^

Fig. 61.

-SiMir.
I.

AR SECTION THROUGH THE CANINE TOOTH OF AN EMIIKYO 40 MM. LONG.

(Rose.) J-7^.
F., labiodental furrow. The other lettering as in Fig. 60.

ninth and thirty-third weeks respectively, and the corresponding papillse are not
formed until the tenth and eighteenth months after birth.

Changes in the connection between the special dental germs and the
common dental germ. — Tlie special dental germs are ut first simply enlurgenients
of the common germ which grow out on its lingual side. They soon become
globular, and rapidly in(;rease in size, and are then connected by a l)r()ad tract of
cells with the common germ. This connactimj shand gi-adually gets thinner and

ORGANS OF DIGESTION.

flatter, and, like the common dental lamina itself, becomes cribriform, so that in
sections there appear to be breaches of its continuity. Its connection, however,

Fig. 62. — Section through

THE GERM OP THK FIRST
MILK MOLAR OF A OOW's
FCETUS 47 MM. LONG.

(Rose.) s.ao.

p., bicuspidate papilla ;
Z.S., dental sao ; M.E.,
mouth-epitlielium ; Z. W. , its
thickening over the dental
germ, characteristic of Rumi-
nantia ; S.£., enamel epi-
thelium; S.P., enamel pulp.

with the common dental
germ, and through this
with the buccal epithe-
lium on the one hand
and the germ of the
corresponding tooth of
the secondary dentition
on the other hand, long
persists. As with the
common lamina, this
atrophic process begins
in connection with the
frontteeth,and gradually
extends backwards, so
that at birth the con-
necting bands of the milk incisors are almost completely broken up, whilst that of
the second milk molar is still uninterrupted. The common dental lamina and the

Fig. 63. — Section of second milk incisor of
AN embryo 30 centimeters long. Thk

EPITHELIAL STRUCTURES ONLY ARE REPRE-
SENTED. (From a model by C. Rose.)
cl.f., dental furrow in the buccal epithelium ;
d.L, dental lamina now become cribriform ; p.,
siDace occupied by the papilla ; d. , dentine ;
en., enamel of the developing tooth ; en.oj:,
enamel organ, its surface cribriform ; a.d.,
adamantoblasts ; r., reticular tissue ; and o.e.,
outer epithelium of the enamel organ. '

bands connecting the special dental
germs with it thus become ultimately
broken up into separate fragments or
islands of dental epithelium of varying
size and form. Such " islands " are
frequently seen in the infant near the
surface of the gum, as pearl-like masses
or nests, the so-called " glands of
Serres." K"ormaUy they have no
functional importance, and gradually
entirely disappear ; but, abnormally,
they may give rise to cysts and other new formations, and in some cases fragments of
dentine, and even more or less complete teeth, may become developed from them.

THE TEETH. 43

Changes in connection with the special dental germs. — The special
dental germs are at first masses of rounded or polyhedral epithelial cells, but the
outermost layer early shows a tendency to be columnar. This becomes pronounced
as soon as the papilla begins to make its appearance, and now while the cells which
immediately rest upon the papilla become long, regular prismatic columns, the central
cells of the germ develop processes, fluid being at the same time secreted between
them. The result is the formation of a reticular tissue, which to the naked eye has
the appearance of a jelly, to which the name of enamel-fmlp has been applied
(fig. 64, S.P.). The more peripheral cells do not participate in this change, but
remain polyhedral or become cubical and flattened {outer e^iamel epithelium) ; they

-^jhe:

J.U —

^ ^VvTs^ V ^ -_^ -^'^ ' no

^.V

Fig. 64. — Section of the first 3iilk incisor of a human embryo 30 ckntimetkrs long.
Frontal section through lower jaw. (Rose.)

D.K., papilla; Od., odontoblaste ; K., bone of the alveolar process of the jaw ; H.E.a., S.K.i.,
outer and inner layers of the enamel organ ; S.P., enamel pulp ; Z.F., dental furrow ; M.E.. mouth-
epithelium ; Z.L., remains of dental lamina ; V.B., cell bridge, connecting this with tooth germ;
E.L., resen'e germ for the permanent tooth ; J.l.ll., germ of second milk incisor cut obliquely across.

pass gi-adually into the long columnar prisms which invest the papilla. These
prisms are the cells which form the enamel fibres, and which determine by their
presence the production of dentine by the superficial cells of the papilla. They may
be termed the encund-cells or adamantohlasis ; they form the mmibrana adamanlimn
of I'urkinje, The whole epithelial dental germ thus transformed is known as the
enamel organ (oryanon adamantiiKe of Purkinje). These changes begin in the
milk incisors at about 14 weeks. At about 20 weeks (embryo of 24 cm.) the first
traces of calcification are visible in the form of a simultaneous deposit of enamel
and of dentine upon the crown of the central incisors. The outer enamel epithelium
now begins to grow out into the surrounding connective tissue in the form of
epithelial sprouts, and Ixifore long there seem to be breaches of continuity between

ORGANS OF DIGESTION.

these sprouts ; hut, acoording to Eose, the enamel-pulp is uever invaded by vascular
connective tissue, as has been sometimes described.

Changes in the meantime have been occurring in the dental papillae. These are
composed at first of undifferentiated mesoblast ; but their more superficial cells —
those which are immediately in contact with the columnar epithelium of the special
dental germs — early become elongated, and abut by their distal end against that
epithelium, whilst the other end is tapered, and may be branched like the other cells
of the embryonic connective tissue. It is from this superficial layer of cells — which
in sections have a palisade-like appearance — that the dentine becomes gradually
formed, and they have accordingly received the name of odontoMasts. There is
nothing of the nature of a membrane — the so-called memhrana preformativa —
between the adamantoblasts and the odontoblasts, but the two layers abut at first the
one against the other.

Meanwhile the whole tooth-germ — papilla and enamel organ — has become in-
cluded within a vascular membrane of connective tissue which is known as the
dejital sac.

Formation of the dentine. — The odontoblasts, either by secretion or, as some
think, by direct transformation of the peripheral end of each cell, form a layer of
dentinal matrix immediately at the surface of the papilla at its apex, or if it have
more than one cusp, then at the apex of each cusp. This layer is at first uncalcified.

Fig. 65.— Section of developing jjentine from the

INCISOa TOOTH OF A YOUNG RAT. (E. A. S.)

a, outer layer of fully formed dentine ; h, uncalci-
fied matrix, with one or two nodules of calcareous
matter near the calcified part ; c, odontoblasts send-
ing processes into fche dentine ; d, pulp. The section
is stained with carmine, which colours the uncalcified
matrix, but not the calcified part.

and is probably the structure which used ta
be described as membrana preformativa.
Griobules of calcareous matter soon begin to appear in it. They are at first isolated,,
but by further deposition of lime salts they become more or less blended into a con-
tinuous calcification, which thus forms the first cap of dentine. In the meanwhile
the odontoblasts have formed a second layer of uncalcified matrix within the first
one, and calcification proceeds in this as in that. In like manner a succession of
layers become formed, each one extending laterally rather further than its pre-
decessor, and thus iu teeth where there are at first separate deposits for diflPerent
cusps these become ultimately blended, or as each successive layer is calcified its
calcareous deposits blend with that of the preceding and more superficial layers. In.
places this blending remains incomplete, portions of the dentinal matrix remaining
uncalcified between the successive layers ; and in a macerated tooth these portions
get destroyed, and cleft-like spaces arise. Since these are bounded by calcified
deposit which has been originally laid down in globules, they present a knobbed out-
line, and are known as interglobular spaces.

As the odontoblasts form the successive layers of dentine in the manner above
described, they retire gradually towards the centre. But whilst thus retiring they
leave in situ, in the layers of forming dentine, filamentous processes of cell-proto-
plasm, themselves provided with finer side-processes, and the dentinal matrix
becomes formed and moulded around these processes, leaving them within tubes
which become dentinal tubules, whilst the processes of the odontoblasts become the
fibres of Tomes. The same cell continues to spin out such a filament in this manner
as long as the formation of dentine continues, each tubule being thus completed in

THE TEETH.

its whoie leogth from a single odontoblast. In many cases two or more processes
are connected with each cell at first, and these coalesce as the cell recedes, the main,
branches of the dentinal tubules being thus formed.

The other cells of tbe dental papilla which are not immediately concerned in the
formation of dentine become, a^! the tooth approaches completion, the cells of the
dental pulp.

Formation of the enamel. — The prismatic fibres which compose the enamel
of the teeth appear to be formed by the direct agency of the ends of the adamanto-
blasts which abut against the dental papilla. In connection with each of these cells
at the end in question a finely globular deposit occurs (Annell), which stains with
osmic acid and resembles keratiu in its extreme resistance to the action of mineral

^ % '*" str.tnt.

Ui)

JZ:;-'ii.itt*ittsiife^

,i:J-^-v-

Fig. 66. — Part of the enamel organ of the canine of a young kitten. (Rose.) ^^K

d., superficial layer of dentine ; e., newly forniing enamel stained black by osiiiic acid ; T.. Tomes'
processes from the r.damantoblasts, ad. ; str.int., stratum intermedium of the enamel organ; p., branched
cells of the enamel pulp.

acids (enamel droplets, v. Spee). The layer which is thereby formed, and which is
not yet calcified, is outside the main body of the adamantoblast-s — although a process
from each adamantoblast extends into it as a tapering fibre {process of Tomes) — and
it is usually produced simultaneously with the first layer of uncalcified deutine
against which it is applied. Before long it undergoes calcification, and the first
layer of enamel is then complete. After a time the adamnntoblasts yield a second
layer of keratin-like material, and from this after calcification has invaded it, another
stratum f)f (;nan)('l is formed, and so on. As witli the dentine, the formation of enamel
aj)[)ear8 first at tlie apex of each cusp, so that there are at first as many caps as
<-us[>s. "Whilst these changes are being effected, the adamantoblasts gradually retire
as the successive layers of the enamel are being produced by them, and this gradual
shifting goes on as long as the formation of enamel continues — that is to say, until
the crown of the tooth is completed. By this time the euanjci jnilp has grcatlj'

ORGANS OF DIGESTION.

diminished, and in fact almost disappeared, and the remainder of the enamel organ
forms a thin epithelial cap over the crown, which soon disappears on the emergence
of the tooth beyond the gum. But besides this epithelial cap, and underneath it,
there is a very thin membrane, which is more persistent, and covers the crowns of
the teeth for some little while after their emergence (fig. 52, e, e). This is NasmytKs
membrane, or the enamel cuticle, and, according to v. Brunn, it is the last formed
keratinous layer of enamel which has remained uncalcified.

cul. e.riy. d, od.

m^-:-:

ep'-sJi^r-^

Fig. 67. — Longitudinal section op the lower part of a growing tooth, the crown of which
IS formed, showing the extknsion of the layer op adamantoblasts beyond the crown to

MARK off the LIMIT OP FORMATION OP THE DENTINE OP THE ROOT. (RoSe. )

j>., pulp ; od., odontoblasts ; d., dentine ; en., enamel ; ad., adamantoblasts, continuous below
with, ep.sch., the epithelial sheath of Hertwig.

Fig. 68. — Section similar to that shown in pig. 67, but from a tooth more advanced

IN GROWTH.

ep. sh., epithelial sheath ; ep.' sJi'., remnants of this, overlying dentine of fang.

It has usually been considered (Tomes, AValdeyer and others) that the enamel prisms are
formed by direct calcification m situ of the inner ends of the adamantoblasts, the outer
nucleated end growing- jixz/v' 2^f/.s.??i with the extent of the inner end which has thus been
converted into enamel. But a different view has been taken by some authorities, viz. that
the layer of adamantoblasts sheds out the substance within w^hich calcareous matter is sub-
sequently deposited ; the enamel prisms being formed therefore rather as a secretion from the
adamantoblasts than by transformation /» situ. This is supported by the readiness with
which the adamantoblasts separate from the enamel, but on the other hand it is more difficult
if it is accepted to account for the fact that the enamel prisms take the exact diameter and
shape of the adamantoblasts. The view seems to me to be corroborated by appearances seen
in sections which have been placed at my disposal by Mr. J. L. Williams, which show a
well-marked layer of highly refractive globules imbedded in a fibrinous-looking matrix lying
between the adamantoblasts and the already formed strata of enamel.

Formation of the cement. — The roots of the teeth are gradually formed
shortly before the time for the emergence of the crowns beyond the gum, but they

THE TEETH.

are not completed until long- after the crowns have come through. They are deter-
mined in their form —moulded, as it were — by a growth of the epithelium of the
dental germ, which extends in the form of a fold, the so-called epifhelial sheath,
(fig. 67) towards the future apex of each fang (v. Brunn). On the inner or papilla
surface of this sheath odontoblasts form dentine, as in the crown, and thus the
root is gradually produced. The epithelial sheath becomes gradually atrophied and
ultimately broken up into isolated portions, which may be seen occasionally, even in
the adult, as epithelial islands, in the connective tissue of the dental periosteum
(fig. 55;.

C. Tomes has shown that an epithelial sheath is formed in the same manner, even in the
teeth of animals (r.f/., Taturia) in which the dental germ produces no enamel at all.

After the formation of the dentine of the root has begun, the vascular tissue of
the dental sac begins to break through the epithelial sheath near the crown, and
forms a layer of bone-forming tissue at the surface of the newly-deposited dentine.
The osteoblasts of this tissue deposit layers of true bone, with osteogenic fibres,
lacunEe, and canaliculi, upon the surface of the dentine of the root, and these layers
form the cement of the fang. The very apex of each fang, which is the last part to
be produced, is formed wholly of cement, for the epithelial sheath which determines
the formation of dentine, never extends quite as far as the permanent apex.

In some animals the cement of the teeth is preceded by the formation of cartilage, which
becomes ossified as in the endochondral fomiation of bone (Magitot, v. Brunn). According to
Magitot, in animals such as ruminants in which the cement covers the crown, a special
cartilaginous " cement organ " is developed for the production of this cement. It is question-
able, however, whether the cartilaginous tissue which gives origin to this cement is sufficiently
specialized to deserve a distinct name.

The dental sacs are well seen in the jaw of an infant a few months old, before
the eruption of the teeth. They are represented at this state in fig. G9. They

Fig. 69. — The dental sacs exposed in

THE J.tW OF A CHILD AT BIRTH.

rt, the left half seen from the inner .side ;
b, the right half shown from the outer side ;
part of the bone has been removed so as to
expose the dental sacs as they lie below the
gum ; the lower tij,'ure shows the sacs of the
milk teeth and the first permanent molar,
exposed by removing the Ijone from the
outside ; the upper figure shows the same
from the insi'ie, together with the sacs of
the permanent incisor and canine teetli
adhering to the gum.

consist of an outer fibro-vascular
coat connected with the periosteum,
and an inner highly vascular layer
with a little jelly-like tissue inter-
posed between the two. The inner
coat is lined with the epithelium of
the enamel organ to be hereafter described.

from the flental arteries which coui-.se along the base of the sacs, and partly from
those of the gums. Their extreme vascularity doubtless has relation to the nutrition
of the enamel organ.

At birth the crowns of all the milk incisors and canines arc fairly advanced in
calcification. The separated cusps of the milk molars have also bl(;iided, and the
calcification of the first permanent molar i.s just beginning in the form of separate

Theii' blood-vessels are derived ]iartly

ORGANS OF DIGESTION.

caps for each cusp, one of which has usually appeared at birth, and the others follow
shortly after. These, however, do not run together until six months after birth.

The germs of the permanent incisors and canines are visible to the naked eye at
birth, lying behind and slightly lateral to the corresponding milk-teeth ; but there
is no trace as yet either of the premolars or of the second permanent molar. The
last-mentioned makes its appearance between four and six months after birth, the
papilla of the first premolar about the tenth month, and that of the second premolar
about the eighteenth month. At two years, when the second milk molars are
just coming through the gum, the crown of the first permnneut molar is finished,
but there are still only isolated cusps on the* second permanent molar of the upper
jaw, and none on the second permanent molar of the lower jaw. In the premolars
also the (two) cusps are still separate at this time.

The various phases in the formation of the teeth occur almost simultaneously in
the corresponding teeth of both jaws.

Fig. 70. — Different stages in the formation of a molar tooth with two fangs. (From Blake.

1, the distinct caps of dentine for five cusps in the earliest stage of formation ; in 2, and the
remaining figures, the crown is downwards ; in 2 and 3, the formation of the crown having proceeded
as far as the neck, a bridge of dentine stretches across the base of the tooth-pulp ; and in 4. the
division of the fangs is thus comjjleted ; in 5, 6, and 7, the extension takes place in the fangs.

Formation of the alveoli. — All the tooth germs are at first included in a
common trough or groove, which encloses the whole dental lamina and the adjacent
connective tissue. This begins to be formed at about 14 weeks (embryo of
11| cm.). Bony septa subsequently become formed and subdivide the trough into
loculi, but even at birth these septa are incomplete, and up to this time, and even
later, both the milk tooth and the corresponding permanent tooth germ are enclosed
in the same loculus. As the fangs become developed the loculi deepen and also
become subdivided to form separate cavities for the teeth of both first and second
dentition. Around the milk-teeth they become narrowed to form alveoli which

Fig. 71. — Diagram (after Welckek)

SHOWING ON THE LEFT SIDE THE
ORDER, AND ON THE RIGHT SIDE
THE TIME (IN MONTHS) OF APPEAR-
ANCE OF THE MILK TEETH OF THE

ui-PER JAW. (Rauber. )

closely invest the roots ; but
although the whole of the de-
veloping tooth is at one time
embedded in the cavity of the
alveolus, the bone never com-
pletely closes over it, an aperture
being always left over the crown,
through which the dental sac is
connected by soft tissues with
the surface of the gum. In the same way, when the teeth of the second dentition
become invested within alveoli, these always have a narrow opening through which
the so-called gvhernacuhmi deniis, a band of connective tissue containing remains
of the common dental lamina, passes.

THE TEETH.

Eruption of the millc-teeth. — The ernption of the teeth does not occur in
regular success iou from behind forwards, and by a gradual and continuous process,
but in batches, with intervals of repose between the successive batches. The follow-
ing shows the most usual time of eruption (C. S. Tomes). The first to appear are
the lower central incisors, at six to nine months. Their eruption is rapid, and is
completed in about ten days ; then follows a resting period of two or three months,
after which the upper incisors appear, both central and lateral. Then, after a rest
of a few months, come the lower lateral incisors and the first molars ; then, after
four or five months, the canines, and finally, about the second year, the second
molars.

Table of Eruption of the Milk-Teetii.

Lower central incisors G to 9 months.

Upper incisors 8 to 10 months.

Lower lateral incisors and first molar.-!. . . 15 to 21 months.

Canines " . . 10 to 20 months.

Second molars 20 to 24 months.

Development of the permanent Teeth.— Ten permanent teeth in each jaw

ni.

IV.

Fi.;. 72. — Sketches showing tie rel.\tions op the temporary and permanenp dental sacs and
TEETH. (After Blake, with some additions. )

The lower parts of the first three figures, which are somewhat enlarged, represent sections of the
lower jaw through the alveolus of a temporary incisor tooth: a, indicates the sac of the permanent
tooth ; c, its pedicle ; h, the .sac nf the milk tooth or the milk tooth itself ; a', b' , indicate the bony
recesses in which the permanent and temiiorary teeth aie lodged, and c', the canal hy which that of tiie
former leails to the surface of the bone behind the alveolus of the temporary tooth. The fourth and fiftii
figures, which are nearly of the natural size, show the same relations in a more advanced stage, in IV.,
previou.sto the change of teeth, in V., when the milk-tooth has fallen out and the permanent tooth
begins to ri.ic in the jaw ; c, the orifice of the bony canal leading to the place of the permanent tooth.

succeed the milk-teeth, and si.x are superadded further ])aclv in the jaw. It will be
convenient to treat first of the ten anterior teeth or tacih of succession.

The sacs and i)ulps of these teeth have their foundations laid before birth in
the way already described. It will be remembered that behind and lateral to each
milk-follicle there is found about the sixteenth week a thickening of the common
dental lamina Tpp. 40, 41, and fig. 04, E.L.), and this forms the enamel-germ of the
corresponding permanent tooth. Thoy are ten in number in each jaw, and arc
formed successively from before backwards. These germs soon elongate and recede
into the substance of the gum behind the germs of the milk-teeth. In the mean-
time, a papilla is f<jrmed at the bottom of each enamel germ (that for the central
incisor appearing first) and the germs become each enclosed within a dental sac, the
sac of the permanent tooth adhering to the b.ick of that f<.r the temporary tooth.

vol,. III., I'T. 4. li

ORGANS OF DIGESTION.

The bone of the jaw not only forms a cell for the reception of the milk sac^
but ultimately also a small posterior recess or niche for the permanent tooth-sac, with
which the recess keeps pace in its growth. In the lower jaw, to which our descrip-
tion may now, for convenience, be confined, the permanent sac is at length found at
some distance below and behind the milk-tooth ; the sac for the permanent tooth
acquiring at first a pear-shape, and being then connected with the gum by a solid
pedicle of fibrous tissue (fig. 72, I., II., c). The recess in the jaw {a') has a similar
form, drawn oat into a long canal for the pedicle, which opens on the edge of the
jaw, by an aperture behind the corresponding milk-tooth. The permanent tooth is.
thus separated from the socket of the milk-tooth by a bony partition, which, as Avell
as the root of the milk-tooth just above it, becomes absorbed as the crown of the
permanent tooth rises through the gum. When this has proceeded far enough, the
milk-tooth becomes loosened, falls out or is removed, and the permanent tooth takes.

Fig. 73. — Part of the lower jaw of a child of three or four years old, showins the

RELATIONS OP THE TEMfOKART AND PERMANENT TEETH.

The specimen contains all the milk-teeth of the right side, together with the incisors of the left ;
the inner plate of the jaw has been removed, so as to expose tlie sacs of all the permanent teeth of the
right side, except the eighth or wisdom-tooth, which is not yet formed. The large sac near the ramus
of the jaw is that of the first permanent molar, and above and behind it is the commencing rudiment of
the second molar.

its place. The absorption of the dental substance commences at or near the ends of
the fangs, and proceeds upwards until nothing but the crown remains. The cement
is first attacked, and then the dentine ; but the process is similar in the two tissues.
The change is not produced merely by pressure, but, as in the case of the absorj)tion
of bone, through the agency of multi-nucleated absorbing cells or osteoclasts,,
developed at the time, and applied to the surface of the fang. The sockets begin to
be formed around the neck of the tooth as soon as the crown projects, and are formed
simultaneously with the developing fangs.

The six posterior (or superadded) permanent teeth, that is, the three permanent
molars on each side, do not come in the place of other teeth. They arise from
successive extensions of the common dental lamina carried backwards in the jaw
behind the milk-teeth.

The part of the common lamina posterior to the last temporary molar long
continues unobliterated, and from it there becomes developed at about the seven-
teenth week of embryonic life a special enamel germ which forms the rudiment of
the first permanent molar tooth (fig. 57, 4, ni^). After a long interval, viz., about the
fourth month after birth, the germ for the second permanent molar tooth appears
in the dental lamina, which is now projecting backwards from the neck of that for
the first molar. After another long interval, during which the sac of the first
permanent molar and its contained tooth have acquired great size, and that of the

THE TEETH.

second molar has also advanced considerably in development, the same changes once
more occur and give rise to the sac and papilla of the wisdom-tooth (third year).
The subsequent development of the permanent molar teeth takes place within their
sacs just like that of the other teeth. In exceptional instances, a fourth molar may
be formed in like manner in a further backward extension of the dental lamina.

After all the teeth of the second dentition are thus formed, the dental lamina
generally ceases to form more special enamel germs and gradually atrophies in the
manner already described. But in I'are instances a third series of germs make their
appearance postero-lateral to the teeth of the second dentition, and a third complete
series of teeth may result therefrom.

Calcification begins first in the anterior permanent molar teeth. Its order and

Fig. 74. — Diagram from Welckkr, snowiNO on the left side the (juder, and on the right

SIDE THE TIME (iN YEARS) OF APPEARANCE OF THE PERMANENT TEETH OF THE UPPER JAW.

(Rauber. )

periods may be thus stated : First molar, one cusp shows calcification at birth, the
rest soon after birth ; central incisor, lateral incisor, and canine, about six months
after birth, the central incisors first, the canines last ; bicuspids, two years or more ;
second molar, two years ; third molar, or wisdom-tooth, about twelve years.

Eruption of the permanent Teeth. — The time at which this occurs in
regard to each pair of teeth in the lower jaw is exiiibited in the subjoined table.
The corresponding teeth of the upper jaw appear somewhat later : —

Molai-, first (> years.

Incisors, central 7 ,,

„ lateral ..... 8 „

Bicuspids, anterior . , . . . '-^ „

„ posterior 1" ,,

Canine.s . . . , . . J 1 to 12 ,,

Molar;?, second . . . . ]2 to 1'.) „

„ third (or wisdom) . . . 17 to 25 „

It is just before tiie shedding of the temporary incisors— /.e., about the sixtli

ORGANS OF DIGESTION.

year, that there is the greatest number of teeth in the jaws. At that period there
are all the milk-teeth, and the crowns of all the permanent set except the wisdom-
teeth, making forty-eight (see fig. 75).

Dnring the growth of the teeth the jaw increases in depth and length, and
undergoes changes in form. In the child it is shallow, but it becomes much deeper
in the adult. In the young subject the alveolar arch describes almost the
segment of a circle ; but in the adult the curve is semi-elliptical. The increase
which takes jjlace in the length of the jaw arises from a growth behind the
position of the milk-teeth, so as to provide room for the three additional

Fig. 75. — The teeth of a child op six tears, with the calcified parts of the perjianent teeth
EXPOSED. (After Henle, and modified from nature, A. T.)

The whole of the teeth of the right side are shown, together with the three front teeth of the left
side : in the upper and lower jaws the teeth are indicated as follows : — 1, milk-teeth — i, inner or iirst
incisor ; i', outer or second incisor ; c, canine ; m, first molar ; m', second molar. 2, permanent-teetli —
I, inner or first incisor ; I', outer or second incisor ; C, canine ; B, first bicuspid ; B', second bicuspid ;
M', the first molar, which has passed through the gums ; M^, the second molar, which has not yet risen
above the gums ; the third molar is not yet formed.

teeth on each side belonging to the permanent set. At certain jseriods in
the growth of the jaws there is not sufficient room in the alveolar arch for tlie
growing sacs of the permanent molars ; and hence the latter are found enclosed in
the base of the coronoid process of the lower jaw, and in the maxillary tuberosity of
the upper jaw, but they afterwards successively assume their ultimate position as the
bone increases in length. The space taken up by the ten anterior permanent teeth
very nearly corresponds with that which had been occupied by the ten milk-teeth ;
the difference in width between the incisors of the two sets being compensated for
by the smallness of the bicuspids in comparison with the milk-molars to which they
succeed. Lastly, the angle formed by the ramus and body of the lower jaw differs
at different ages ; thus it is obtuse in the infant, approaches nearer to a right
angle in the adult, and again becomes somewhat obtuse in old age (see Vol. II,
p. 78).

THE TEETH. 53

Historical. — The first complete account of the development of the teeth was pfiven by
Goodsir {Edln. Med. and Sn?-//. Junrnal, 1838), who described the formation of a groove in the
mucous membrane of the jaw, the formation of special depressions in this groove corresponding
to the milk-teeth, the appearance of papillaa within these, the enclosure of the papilla within
follicles covered by membrane, and finally the time and mode of eruption of the several
teeth.

Goodsir's results, which, so far as they went, were fairly accurate, were obtained from
specimens which had been badly preserved, and in which the epithelium, which is now
regarded as the imi^ortant element in tooth formation, had become detached in consequence of
maceration.

The views of Goodsir prevailed until 1863, when Kolliker (Gewebelehre) clearly showed the
important part taken by the involution of the Malpighian layer of the epithelium of the jaw
in the formation both of the common and of the special enamel germs. (This had been already
pointed out by Marcusen (Bull, de I'Acad. de Petersbourg, 184!)) and by Huxley (in fishes and
reptUes, Quar. Jour, of Mier. Set., 18.53), but was nevertheless not generally accepted.) Kolliker's
results were confirmed and extended by the work of Waldeyer, Kollmann, Magitot, C. S. Tomes,
and others. Baume first pointed out the independent origin of the teeth of succession from the
common dental lamina ; previous observers had followed Kolliker (and Goodsir) in ascribing the
origin of their germs to the special germs of the milk-teeth. Pouchet and Chabry were the first
to describe the common origin of the labio-dental furrow and the common dental lamina.
Finally, the most important details regarding the origin of the human teeth are to be met
with in the works of Magitot and Legros and of Rose. Rose's account is based upon
sections of the jaw of embryos of various ages, from which he has constructed models shewing
several stages of development in a strikingiy objective form ; figui'es of some of these models
have here been reproduced.

RECENT LITERATURE OP THE TEETH.

d'Ajutolo, Gr., Quinta dentizione in un fanciuUo di dodici anni, Bologna, 1893.

Albrecht, P., Ueh. ziceiivurzeliye Eck- u. Schneidezahiie beiin Menschen, Ceiitralbl. f. Chirurgie,
1885 ; Uch. das sccJischneidczahnige Gebisse bcim nonnalcn Menschen, Ibid.

Andrevrs, R. R., 'J'he origin of the dental fibril. New York Mclical Record, v<.l. .K.xxii, 1887 ; On
the fornwtion and calcification of the enamel, Verhandl. des 10 internat. niedicin. Kongresses zu
terlin, 1890, Bd. v. Abt. 14 ; The fornuition of enamel, Internat. Dental Journ. vol. xii, 1891.

Annell, G-., Zur Kcnntniss der zahnbildenden Geiocbc, Biol. Unters. lierausg. von G. Retziu.s, ii,
1882.

Azonlay and Regnault, Des diverses formes des dents incisivcs sirperieurs, Bull. Soc.
d'Anthrop. , Paris, 1893.

Balkwill, F. H., Soles on swne morphological dental irregularities in some of the skulls of the
museum of the Roijal College of Sur/eons of England, British Journal of Dental Science, 1891.

Ballowitz, E., Das Schvielzorgan der Edentaten, Arch. f. mikr. Anat., Bd. xv, 1892.

Barillet, A., Des anomalies dentaii'es de nombrc. Union mM. du Nord-Est, Reims, 1893.

Bateson, W. , On numerical variation in teeth icith a discussion of the conception of homology,
Proc. Zool. Sue., London, 1892.

Baume, R., Odont. Forschungen, 1 Theil. Ftrsuch einer Enticicklungsgcsch. d. Gebisses, Leipzig,
18S2.

Beauregard, H., Consid. sur I. deux dentitions d. mammif, C. r. d. I. soc. biol., 1885.

Berten, f'eb. Anomalien der Zahnstcllung, Pbys. nied. Gcsellsch. zu Wiirzburg, 1893.

Betty, E. Cr., A criliccd examination of the teeth of several races, including one hundred and
fifty inoandhuiltlers, tL-c, Dental Review, Chicago, 1890.

Black, Gr. v.. The Periosteum and Peridental Membranes, Dental Review, Chicago, vol. i, 1886.

Bourgrois, L. F. , Elude anatomique et pathologique sur le sinus maxillaire dans les rapports
aver I, s dents, Lilk-, 18S6.

Brownlie, J. R., On certain mummy teeth, Journal of the British Dental Association, 1886.

von Brunn, A. Ueber die Ausdehnung des Schmelzorgancs und seine liedeutung fur die Zahn-
bibliitig, Arcliiv f. niikroskop. Anitoniie, Bd. xxix, 1887 ; Ueber Membrana praformativa und
L'vticiila dentis, Anatoin. Ar.zeiger, Jahrg. iii, 1888 ; Beitrdge zur Kenntniss der Zahneiitwickelung,
Arcliiv f. niikro.skop. Anat., lid. xxxviii, 1891.

Busch, Die Ueberzahl und Unterzahl in den Zdhnen des mr.nschlichcn Gebisses mit EinscIUuss

■ der sogenannten Dentitio tertia, Deutsche .Monats.sclirift fiir Zahnheilkunde, 1887 ; Ueber die Deutung

des MUchgehisses, Verhandl. d. deutKch. odont. Gcsell., IM. iv, 1892 ; Ueber Vcrschmclzung und

Verwnchsung der Zdhne des Milchgebisses und des blcibenden Gebisses, Vhldgn. d. deutscli. odontol.

Gc8ol!.H<,-h., IM. V, 1893.

Canalis, Pietro, HuUo sviluppo dei denti nei m/immifcri, Anatoin. Anzeiger, Jahrg. i, 1886.

Cleland, J., Tlie rcUitvm of incisors to compound teeth, British Medical Journal, 1893; On the
dev'l . of the molar teeth of tlve elephant, with remarks on the dental series, IJriti.sli A.s.soc. lveiJortn,
1893.

54 OEGANS OF DIGESTION.

Cope, E. D., Onthetrituhercular molar in human dentition, Journal of Morphology, iii, 1S89 ; The
mechanical causes of the dtvelojrinent of the hard parts of the mammalia, Jouni. of Morph., iii, 1889.

Debierre, Ch.. et Pravaz, J., Contributions d Vodontogenie, Archives de physiologie, 1886.

Dieblein, W., Ueher Zahnwcchsel, <L-c., Anat. Anzeiger, Bd. x, 1895.

Dunog-ier, Douhle heterotopic de la dent de sagesse. Sec. de med. et de chir. de Bordeaux, 1893.

von Ebner, V. , Histologie der Zdhne mit Einschluss dcr Bistogencse, aus Scheff, Handb. der
Zahnlieilk., Wien, 1890 ; Strittige Fragen ilber den Bau des Zahnschmelzes, Sitzungsberichte d. kaiserl.
Akad. d. Wissensch, zu Wien, 1890.

Edwards, H. H. , The missing incisors in man, Journ. Brit. Dent. Assoc, vi, 1885.

Ellenberger und Eaum, Ein Bcitrag zu dem Ka2ntel: Zahnreteritione7i unci Zahnrudimente,
Archiv f. Anat. n. Physiol., iinatom. Abt., Jahrg. 1892.

Pauton Touvet, K,., Considerations sur les anomalies des dents humaines, Paris, 1882.

Feuoliel, Odontologische Schddelmessungen, Deutsche Monatsschr. f. Zabnheilkunde, 1893.

Fleischmann, A., Die Grundform der Baclczahne iei Siiugetieren uvd die Homologie dcr
einzclnen Hoclcer, Sitzungsb. der kgl. preuss. Akad. der Wissensch, 1891, Nos. 39 and 40.

Flesch, M., Ein Fall angeborener Zahnbildung, Aiaatom. Anz. , viii, 1892.

Flower, W. H., On the development and succession of the teeth in the Marsuvi-''la, Phil. Trans.
1867 ; Remarks on the homologies and notation of the teeth of the mammalia, Journ. of Anat. and
Phys., vol. iii, 1869 ; On the size of the teeth as a character of race, Journal of the Anthropological
Institute, vol. xiv, Nov., 1884.

Freund, Paul, Beitrdge zur Entwichclungsgeschichte der Zahncmlagen bei Nagethieren, Archiv f.
mikroskoi?. Anat., Bd. xxxix, 1892.

Gmria, P. M. , Formazione gemellata bilatende dci denti incisivi superiori meclii, Boll, accad.
med., Genova, 1893.

G-rasset, Louis, Becherches sur la distribution mathdmatique des jmsmes de Vemail dentaire,
Intern. Monatsschr. f. Anat. nnd Physiol., Bd. viii, 1891.

G-rosscourth, Ein ilberzdhliger Zahn, Deutsche Monatsschr. f. Zahnheilkunde, 1890.

Halarz, H. , Seltener Fall ciner Zohnentwickelungsanomalie, Allgem. Wien. med. Certral-
Zeltung, 1894.

Hancock, J. L., The tendency of the root of the lower canine teeth of man toward bifurcation.
North American Practitioner, Chicago, 1890.

Herrmann, Eine Milchzahnanomcdie, Deutsch. Monatsschr. f. Zahnheilkunde, 1891 ; Resorption
und Ausstossen der zxceiten Molaris durch Weisheitszahji ; unci 3dilchzahnanomalie, weitere Bcobach-
t'ungeii, tCr., Deutsche Monatsschr. f. Zahnheilk., 1893.

Hertwig, O., Ueber d. Bau u. d. Entiuicki. d. Placoidschuppen u. d. Zdhne d. Selachier,
Jena Zeitschr. , Bd. viii, 1874 ; Ueber d. Zahnsystemd. Amphibien, Arch. f. mikr. Anat., Bd. xi, 1874.

Hesse, Zur Topographic des Gebisses, Deutsche Monatsschr. f. Zahnheilkunde, 1890.

Hollander, Dcmonst^xiticn einiger pathologischer Kieferprdparate unci einiger Zahnanomalicn,
VerhandJg. d. deutsch. odontol. Gesellsch., 1890 ; Ueb. Anomalien des Kiefers und Zahnstcllung,
Munchener Sitzungsber. , 1891.

Kaftan, F., Stelluvgsanomcdien pcrmancnter Zdhne, Die zahntechnische Reform, xii, 1892.

Kirk, K., Malformation of the incisor Teeth, Journ. of Anat. xviii, 1884.

Kiikentlial, Willy, Einige Bemerkungen ilber die Sdugetierbezdhnung, Anatom. Anz., Jahrg. vi,
1891 ; The dentition of Didelphys, a Contribution to the Embryology of the dentition of Marstipials,
Observations on the dentition of Mamyncds (translated from the Anatom. Anz.), Annals and Magazine
of Natural History, vol. ix, 1892 ; Ueber den Ureprung unci die Entwickeluiig der Sdugctier zdhne,
Jenaische Zeitschr. f. Naturwissenschaft, Bd. xxvi, 1892.

Lataste, Fernand, Des deux dentitions, de lait on permanente, des mammiferes, quelle est la
dentition primitive, Cornptes rendus de la societe de Biol., serie ix, t. v.

Latliam, V. A., Histology of the teeth; notes on methods of preparation, Journ. of Micr. and
Natur. Sci., naw series, vol. ii, 1889.

Leclie, Wilhelm, Studien iibcr die Enticickelung des Zahnsystems iei den Sdugctiere, Morph.
Jahrb., Bd. xix, 1892, and Bd. xx, 1893.

Lepkowski, W., Bcitrag zur Histologic des Dentins mit Angabe einer ncucn 31ethode, Anatom.
Anz., Jahrg. vii, 1892.

Ijippscliitz, Eine seltene Zahnanomalie, Deutsche Monatsschr. f. Zahnheilk., xi, 1893.

Liivi, Ridolfo, Note on the development of tvisdom teeth, Brit. Asisoc. Reports, 1889; Sur le clevel.
de la dent de la sagesse, Arch, ital, de biol., t. xxi, 1894.

Livy, J., On the periods of eruption of the permanent teeth as a test for age, British Medical
Journal, August, 1885.

Magitot, E., Traite des anomcdies clu sysieme dentaire, Paris, 1877; Des lois de la dentition,
Journ. de I'anat., 1883 ; Sur les deux dentitions des mammiferes, C. r. d. 1. soc. biol., 1888.

IiTaliieu, E., Contribution d Vetude de la premiere dentition {Evolution dentaire, ses accidents),
These, Paris, 1893.

Malassez, L., Sur la structuo'e du gubernacidum dentis tt la theorie piaradentaire, Comptes
rendus hebdom. de la societe de biologie, serie viii, 1887.

Malm, Robert, Bau und Entinckelung tier Molaren bei Mus und Arvicola, Morpholog. Jahrb.,
Bd. xvi, 1890.

Marchand, Schacdel mit uberzahligem Schneidezahn am Boden der Nasenoffnung, Anatomischer
Anzeiger, 1888.

Monteg-azza, P., II terzo molare nclle rc(zze umane, Rendicont. Instit. Lombard., 2 ser., torn, xi ;
also in Zool. Anz., 1880.

THE TEETH. 55

Montig-el, Ucb. zicei Fdllc von sdtcncr Dcnt'itlonsanomalie {drittc Dentition), Deutsche. Jlonats-
scLritt f. Zahnheilkunde, 18S8.

Morgrenstern, Mich., Untcrsuclningen iiher den Ursprung der bleibenden Zdhnc, Leipzig, 1886 ;
Ncue ['nttrsuchiiur/cn iiher die Entwickelunc/ des Zahnheins und dcs Schmelzes, Verhandl. des 10.
iiiternat. medicin. Kongresses zu Berlin, 1890, Bd. v, Abt. xiv ; Vcler das Vorhommen von Nerven
in den hartcn Zahnsuhstanzen, Deutsche Monatssch. f. Zahnheilkunde, Jahrg. x, 1892, and xiii, 1895.

Morgrenstern, T., Bcitrag zur Ilistologie der Membrana Eboris, Oester.-ungar. Yierteljahrs-
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Muhlreiter, E., Ancdomie dcs mcnschlichen Gcbisses, Leipzig, 1891.

Mummery, J. H., Some points in the structure and development of dentine, Philosoph. Trans, of
the Rov. Soc. of Lend., vol. clxxxii, sec. B, 1891 ; The basal layer of Weil, Journ. Brit. Dent. Ass.,
1S92. "

Osbom, H. F., The evolution of the mammaUan molar teeth to and from the tritubercular
tjipe, American Xaturalist, vol. xxii ; Tlie history and homologies of the hwman molar cusps, Anatom.
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Parreidt, J., Die Breite der oberen ccntralen Schneidezithne beim, m,annliclicn und weiblichen
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Anzeiger, Bd. ix, 1894.

Quilford, S. H. , Eine Zahnanomalie, Wien. med. "Wochenschr. , 1883. (Absence of teeth.)

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Robertson, W. G. Aitchison, On the relation of nerves to odontoblasts and on the growth of
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Roetter, F. , Ueber Entiuickelung und Wachstuni der Schneidezdhne bci Mus mttsculus, Mor-
pholog. Jahrb., Bd. xv, 1889.

Rose, Ueber die Entivickeluvg dcs mcnschlichen Gcbisses, Verhandl. der deutschen odontologisclien
<jresellscl)aft, Bd. iii, 1891 ; Utber die Entwichelung der Zdhne dcs Menschen, Archiv f. mikroskop.
Anat., Bd. xxxviii, 1891 ; Uebcr das menschliche Gebiss, Verhandl. der Anat. Grcsellsch. auf der 5
Versamm]., 1891 ; Ueber die Entstehung und Formabdnde^ningen der mcnschlichen Molaren, An^t. Anz.,
Jahrg. vii, 1892 ; Ueber die Zahncntioickclung der Beuteltiere, Anat. Anz., Jahrg. vii, 1892 ; Ueber
rudimentdre Zahnanlagen der Gattung Manis, Anat. Anz., Jahrg. vii, 1892 ; Beitrdge zur Zahnent-
■uickelung der Edentaten, Anat. Anz., Jahrg. vii, 1892 ; Ueber die v. Koclisehe Versteinerungsmethode,
Anat. Anz., Bd. vii, 1892 ; Uebcr die ZahnleisteunddieEischwicle der Sauropsiden, Auat. Anz., Jahrg.
vii, 1892 ; Uebcr dicerstc Anlage der Zahnlciste beim Menschen, Anat. Anz., Jahrg. viii, 1892 ; Ucb'r
die Verwachsung von retinirten Zdhnen mit clem Khfcrknochcn, Anat. Anz., Jahrg. viii, 1892 ; Ueber
die Zahnentwickelvng von Chamcdcon, Anat. Anz., Jahrg. viii, 1892 ; Zur Ilistologie der Zahnpulpa,
Deutsche Monat.sschrift f . Zahnheilkunde, Jalirg. x, 1892 ; Uebcr die Nervenendigungen in den Zdhnen,
Deutsche ]\[onats.schrift fiir Zahnheilkunde, Jg. xi, 1893; Ueber die Nicht-Existenz der sogcnannten
WtU'schen Basalschicht der Odontoblasten, Anat. Anz., .Jg. viii, 1893 ; Uebcr den Zahnbau und Zahn-
v.cchsel von Elephas indicus, Morphol. Arheiten, Bd. iii, 1893 ; Uebcr die Zahnentwickelung der
Crocodile, .Moqihol. Arbeiten, Bd. iii, 1893 ; Contributions to the liidogcny and histology of bones and
■ hjntal tissues, translated by Hanitscb, Dental Cosmos, Philadelphia, vol. xxxv, 1893 ; Ucb. die
.'chmelzlosen Zahnrudimente des 31enschen, Verhandlg. d. doutiseh. odontol. Gesellsuli., iv, 1893 ;
I'e. d. Zahnentwickl. der Fischc, Anat. Anzeiger, Bd. ix, 1894 ; Ueber die Zahnentwickelung der
Kreuzotter, Viperaberus, L., Anat. Anzeiger, Bd. ix, 1894.

Rosenberg', E., Ueber Umformungen an den Incisiven der zweiten Zahngeneration des MenscJien,
Morph. Juhrl*. xxii, Wjr,.

Ryder, J. A., On the mecJutnical genesis of tooth forms, Proc. of tlie acad. of sci. of Philadfdphia,
1S78 and 1879.

Sag'emehl, M., Die Uebcrzahl und Unterzahl in den Zahlcn des menschliche Gcbisses mit
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Schaffer, Josef, Uebci' Iloux'sche Handle in mcnschlichen Zdhnen, Sitzungsb. der kais. Aka<l. der
\\'i.s.s<;n(-f:li. Abt. iii, VA. xcix, 1890.

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<)CKt<,-rr. -iin;.'ar. Vierteijabrsschr. f. Zahnheilk., 1890.

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1-87.

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h'ilkiiMde, 1887.

Schmidt, W., Ueb. Grotsenverhdllnisse der Zdhne, Zahntcchnischc Reform, xii, 1892.

56 ORGANS OF DIGESTION.

Schwalbe, G-., Ueber Zalmenticickelung unci Zalimoechsel, (Naturwiss, med. Yei\ in Stras.sbiirg;
i. E.), Wierier kliiiische Wocbensclirift, 1893 ; Ueber eine seltene Anomalie des Milcligebisses beini
Menschen und Hire Bedeutung ficr die Lehre von den Bentitionen, Morphol. Arb., Bd. iii, 1894 ;
Ueber Thcorien der Dentition, Verbdlg. d. anatom. Gesellsch., 1894.

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Odont. Soc, Nov. 1893.

Smith., "Wilberforce, The teeth often Sioux Indians, Joiirn. Anthrop. Institute, xxiv, 1894.

Somm.er, Carl, Zur Tlistologie des Zahnschmehes, Jahrb. f. Zahnheilk., Bd. vii.

V. Spee, F., Ueber die ersten Vorgdnge der Ablagerung des Zahnschmelzes, Anatom. Anz., Jahrg. ii^
1887.

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^Ylss(nschaften, 1890.

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1878 ; A Manual of Dental Anatomy , 4tb edition, 1894.

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Vhomme, L'Anthropologie, 1892.

' Troitzky, De la deuxieme dentition ou de I'apparition des premieres grosses rnolaires dans soil
raptpiort aiec la troisieme dentition, c'est-d-dire avec Ic remplacement des dents du lait par les dents
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Turner, W., The relation of the alveolar form of cleft palate to the incisor teeth and the inter-
maxillary bone, Journ. Anat., xix, 1885 ; The relations of the dentary arcades in the crania cf
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Virchow, B,., Retention, Heterotypic und Ueberzahl von Zdhnen, Verhandl. d. Berliner
anthropol. Gesellscbaft, 1886.

Weil, Xi. A., Zur Histologie der Zahnpidpa, Deutscbe Monats¥clirift fiir Zahnbeilkunde, Jabrg. v,
1887 ; Doppclseitige Zwillingsbildung der mittleren oberen Schieidczdhne, Anat. Anz., viii,"1893, and
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"Wells, A. L., Osseous union of two teeth, Journ. Brit. Dental Asso3,, 1892.

Werner, Ueb. die Zapfcnzdhne des Menschen, Inaug. Diss., Mtincben, 1892.

"Wilson, A., Tlic Premolars in Man, Journal of British Dental Association, 1887.

"Windle, B. C. A., and Humphreys, J., Extra Ctisps on the Human Teeth, Anatom. Anzeiger,
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Wortman, Jacob L., The comparative anatomy of the teeth of the Vertebrata, American
System of Dentistry, vol. i, 1886.

Zsigmondy, Otto, Ueber die Verdnderungen des Zahnbogens bei der zaeiten Dentition, Archiv-
f. Anat. u. Physiol., Anatom. Abt., 1890.

Zuckerkandl, E., Ueb. Zahnretention, und Ueb. rudimentdre Zdhne, Wiener med. Jabrblicher
1885 ; Ueber das epithcliale Rudiment eines vierten Mahlzahnes beim Menschen, Sitzungsb. der k.
Akad. der Wissensch. in Wien, 1891 ; Anatomic der Mundhohle nvit besonderer Berucksichtigung
der Zdhne, Wien, 1891.

THE PHARYNX. 57

THE PHARYNX.

The pharynx (figs. 7G, 77, 78 aud 80) extends from the base of the skull to the
lower border of the sixth cervical vertebra, where it terminates by becoming con-
tinuous with the oesophagus. It lies in front of the lower part of the basilar process
of the occipital bone and the upper six cervical vertebva3 and behind the nasal
cavities, mouth, and larynx. It may therefore be divided into three parts, viz.,
uasal, oral, and laryngeal. The solt palate projects backwards and downwards into
it, and during the act of- deglutition is drawn upwards and backwards against its
posterior wall, so as to completely separate the nasal from the oral portion. In all,
seven openings lead into the cavity of the pharynx, viz., above the velum, the two
posterior nares {choame) and the two Eustacliian tubes, and below the velum, from
above downwards, the orifices leading into the mouth, larynx, and oesophagus.
The pharynx is about five inches (li centimeters) in length. Its transverse
diameter is considerably greater than its antero-posterior. Its widest part is
opposite the laryngeal aperture, below which it rapidly contracts like a funnel
towards its termination, where it is narrowest.

The nasal part of the pharynx {iiaso-pharijnx or post-nasal space) is an air
cavity irregularly cubical in shape, which cannot be obliterated by muscular action,
although its floor can be raised and depressed by the muscles of the soft palate. Its
anterior wall shows the posterior edge of the nasal septum with the posterior naies,
one on either side. In the posterior wall the mucous membrane is thickened and
thrown into a number of folds, chiefly vertical in direction. As these folds contain
a considerable quantity of lymphoid tissue they are often called the j;/^«ry;?^m? tonsil.
A well-marked recess of the mucous membrane, known as the 'pharyngeal bursa
(recessus j)hartjnr)ei(s medius), which is constant in the foetus and young subject, and
is occasionally present in the adult, extends from just below the pharyngeal tonsil
upwards in the middle line as far as the pharyngeal tubercle.

This recess was regarded by Luschka (Der Schlundkopf d. Mensohen, 1868, p. 26) as a
rudiment of the invagination from which is developed the anterior part of the pituitary body.
This idea is r-ow generally abandoned in favour of the view that it is connected with the
formation of the pharyngeal tonsil. Killian (Morph. Jahrb., Bd. xiv, 1888, p. 618), liowever,
has shown that the pharyngeal tonsil may exist in the human foetus aud also in aniniaLs
without any traces of a pharyngeal bursa.

The opening of the Eustachian tuhe appears as a vertical cleft, or as a funnel-
shaped opening, in the lateral wall, and is bounded behind by a prominence — the
cushion of the' Eustachian orifice — containing the cartilage of the tube. Between
this prominence and the posterior wall of the pharynx there is a deep recess passing
backwai'ds and outwards. It is known as the lateral recess of the phari/nx (fossa of
RosenmiUler). This recess represents the upper part of the pharyngeal portion of the
second visceral ck-ft, the Eustachian tube Ijcing formed from the first cleft. From
the cushion of the Eustachian orifice the mucous ineinhranc forms a vertical fold,
the ^;//ca salpmyo-2)h(iryn(jea, passing downwards on the side wall of the pharynx
behind the posterior palatine arch.

When the levatores palati are contracted, the upper surface of the soft palate
presents a convex eminence behind each posterior naris, called the levator cushion.
This is occasionally seen in the dead body.

The average capacity of the nasal part of the pharynx is said to be 14 cubic
centimeters. Its transverse diameter in front of the Eustachian orifices is about
22 mm. ; between the Eustachian cushions it varies considerably — on an average it
is about ir> mm. The distance from the lower part of the posterior edge of the
na.sal septum to the posterior wall of the pharynx is lo mm.

Fig. 76. — Median section of the head and neck. (Braune.) |
1, spLeDoidal sinus ; 2, lateral recess of pharynx ; 3, pharyngeal orifice of Eustachian tulie ; 4,
anterior arch of atlas ; 5, soft palate ; 6, body of axis ; 7, oral portion of pharynx ; 8, epiglottis ; 9,
arytenoid muscle ; 10, cricoid cartilage ; 11, trachea ; 12, cesophagus ; 13, origin of innominate artery
from aorta ; 14, genio-glossus muscle ; 15, genio-hyoid muscle ; 16, mylo-hyoid muscle ; 17, platysma ;
18, hyoid bone ; 19, thyroid cartilage ; 20, cricoid cartilage ; 21, isthmus of thyroid body ; 22, sterno-
hyoid ; 23, sterno-thyroid ; 24, left innominate vein ; 25, manubrium stcrni.

THE PHARYNX.

The oral part of the pharynx is situated below the soft palate and above
the level of the larynx. Owing to the mobility of its walls it is very variable in form
and size. In front it commnnicates with the mouth through the isthmus of the
fauces, and below this opening it is bounded anteriorly by the posterior part of the

Fig. 77.— Horizontal section through nasal cavities and nasal portion of niAuvxx, seen

FROM above. (.1. S.) I

], anterior naris ; 2, septal cartilage; 3, vomer; 4, inferior concha; 5, inferior meatus; 6,
maxillary antrum ; 7, posterior naris ; 8, Eustachian tube ; 9, tensor palati ; 10, levator paiati ;
11, internal carotid artery; 12, lateral recess of pharynx ; 13, rectus anticus major; 14, pliaryngcal
tousiL

dorsum of the tongue. On its lateral wall there is a somewhat triangular recess
bounded ]>y two folds of mucous membrane, called the anferior and posterior
palatini ardias. Both these folds are connected above with the soft palate, and
diverge as they pass downwards. Tlie anterior arch joins the tongue and foi-ms tlio
lateral boundary of the isthmus of tiic fauces, while the posterior one gradually
disapfKjars on the side wall of the pharynx.

The tonsils (totisi/he, arni/f/dake) aie two prominent l)odies situated in the recess
between the anterior and posterior palatine arclies. 'J'hey ai'e usually from 20 to
2'» mm. in vertical extent, reaching from the soCt palate above to the le\'el of the toj)
of the epiglottis below; they measure about jr* mm. from before backwards and
rather less than this from within outwards, Vjut they vary much in dilferent indi-
viduals. The free inner surface of the tonsil has a variable number of slit-like or

ORGANS OF DIGESTION.

rounded orifices which lead into recesses or crypts in the substance of the tonsil
(fig. 78, 16 ; fig. 79). The outer surface is connected with the inner aspect of the
superior constrictor of the pharynx, external to which is the internal pterygoid muscle.
Both the external and internal carotid arteries lie fully an inch external and posterior
to the tonsil. The tonsils extend downwards as low as the angle of the jaw, but they
cannot, even when enlarged, be felt from the surface of the neck at this point.

Above the tonsil there is frequently a recess directed upwards and backwards,
and called the fossa svpra-tonsillaris. It is considered by His to be the remains of
the lower part of the second visceral cleft. The fold of mucous membrane covering
this recess is named j7?'/c« triangularis.

Vessels and iiei?ves. — Arteries. — These structures receive a very large supply
of blood from various arteries, viz., from the tonsillar and palatine branches of the

Fig. 78. — Horizontal section through the mouth, pharynx, &o., jfst above the teeth of

THE lower jaw. ThE SECTION IS A'lEWED FROM ABOVE. (J. S. ) §

1, Body of axis ; 2, ramus of lower jaw ; 3, orbicularis oris ; 4, buccinator ; 5, masseter ;
6, internal pterygoid ; 7, stylo-glossns ; 8, stylo-pharyngeus ; 9, digastric and stylo-liyoid ; 10, rectus
capitis anticus major ; 11, longus colli; 12, sublingual gland, anil on its inner side Wharton's duct ;
13, aperture oY Wbarton's duct ; 14, muscular substance of tongue; 15, tip of uvula; 16, tonsil
(somewhat enlarged) ; 17, root of tongue ; 18, epiglottis ; 19, posterior palatine arch ; 20, anterior
palatine arch ; 21, parotid gland ; 22, external carotid artery ; 23, internal jugular vein ; 24, hypo-
glossal nerve ; 25, vagus ; 26, internal carotid artery ; 27, pharyngeal veins ; 28, lymphatic gland.

facial artery, the descending palatine of the internal maxillary, the ascending
pharyngeal and the dorsal artery of the tongue. From these arteries fine branches
and capillaries are distributed abundantly to the lymphoid tissue and follicles and
to the papillse of the mucous membrane which lines the recesses. The veins are
numerous, and enter the tonsillar plexus on its outer side. The nerves come from
the glosso-pharyngeal nerve, and from the fifth. Lymphatics are abundant, and
surround the follicles with a close plexus ; they eventually pass into the superior
deep cervical lymphatic glands.

Structure. — The tonsils are composed of a spongy connective tissue infiltrated
with lymphoid cells, which are collected at frequent intervals into nodules or
follicles, in which the lymphoid tissue is denser than elsewhere. These nodules, as
in other situations where they occur, represent germinating centres in which the

THE TONSILS. 61

lymphoid cells are most rapidly multiplying. Extending* inwards from the sui-face
are tubular or clel't-like crypts, which are liued with stratified epithelium similar to
that of the surface, and the walls of which are beset with lymphoid nodules. Into
these crypts mucous glands open, but these are not very numerous. The lymphoid
cells are constantly passing in large numbers through the epithelium, to become free
at the surface and on the crypts of the tonsils (Stohr) ; in this way they pass into
the mouth and mix with the saliva to form the so-called salivary corpuscles.

The laryngeal part of the pharynx is situated behind the entire extent
of the larynx. Its length is ecpial to thai of the nasal and oral parts combined. lu
the upper part of its anterior wall is the superior aperture of the larynx. On either

Fig. 79. — Section thuougii one of the crvpts of the tonsil, magnifiei/. (Stohr.)
f, stratified epithelium of general surface, continued into crypt; /, /, follicles or nodules of
lympjioid ti.ssue ; opposite each nodule or germ-centre numbers of lymph-cells are passing into and
through the epithelium ; s, s, masses of cells wliich have thus escaped from the tonsil to mix with the
saliva as salivary corpuscles.

side of this is a longitudinal groove called the ainus pyriformis, which represents the
remains of the fourth visceral cleft (His).

Opposite tjie laryngeal aperture the transverse diameter of the pharynx is about
3-6 cm. Below this opening the anterior and posterior walls of the pliarynx are in
contact, but the transverse diameter undergoes only a very slight diminution as far
down as the cricoid cartilage, behind which it rapidly contracts so that at its
termination it is only about 12 to IG mm.

Varieties. — The principal variations of the pharynx arc duo to the abnormal persistence
of the vi.-ceral clefts or irrcKulariticH in their position. Various cases of this kind have been
flcHcribfcd as pharyngeal diverticula or cervical fistuliu (for literature, see von KosLanecki).

Structure and attachments,— The walls of the pharynx are formed from
witliin outwards of a mucous membrane, a layer of fibrous tissue called the pharyn-
(jml aiioncjirfms, a mu.scular coat, and another layer of fibrous tissue, which with
that covering the buccinator muscle, is called hucco-pharijiKjeal fuHcia (see Vol. II,

6a ORGANS OF DIGESTION.

p. 307). The pharyngeal aponeurosis is thin and lax below, but becomes thicker
and denser above, where it is attached to the posterior part of the sphenoid bone
and passes outAvards to the petrous portion of the temporal bone and on to the
Eustachian tube. It is strengthened in the middle line by a strong band descending

Fig. 80. — Horizontal section op the larynx and

LARYNGEAL PART OK PHARYNX. (J. S. )

], thyroid cartilage; 2, thyroarytenoid muscle; 3,
lateral crico- arytenoid muscle ; 4, arytenoid cartilage ; 5,.
rima glottidis ; 6, arytenoid muscle ; 7, cavity of laryngeal
part of pharynx ; 8, inferior constrictor of pharynx.

between the recti antici muscles from a part of
the basilar process of the occipital bone, which
often presents a marked tubercle.

Behind, the bucco-pharyngeal fascia is con-
nected by a very loose areolar tissue to the
prevertebral fascia, covering the bodies of the
cervical vertebra and the muscles which rest upon them. At the sides it has similar
connections with the styloid process and its muscles, and with the sheaths of the
large vessels and nerves of the neck.

The attachments and relations of its muscular coat are described in Vol. H,
Part ii. Its mucous membrane is continuous at the several apertures with those of
the adjacent cavities.

Structure of the mucous membrane of the pharynx. — The mucous
membrane of the pharynx is formed by connective tissue, provided with low
papilla and covered by epithelium, which is stratified over the greater part of the
cavity, but ciliated in the upper or naso-pharynx. The back of the soft palate also
has a covering of stratified epithelium in the adult, althoug'li in the foetus it is
ciliated. Cihated epithelium has been described in some of the gland ducts both here
and in other parts of the pharynx in the adult. Numerous racemose mucous glands
occur under the mucous membrane ; they are especially abundant above, near the
Eustachian tube, but they are found in all parts. Lymphoid tissue is also abundant
m the upper pare and back of the pharynx ; a large collection of lymph-follicles
stretches across the back of the cavity between the orifices of the Eustachian tubes
(pharyngeal tonsil). This is apt to become hypertrophied in children, and to block
those orifices, and even the posterior nares.

RECENT LITERATURE OF THE PHARYNX AND TONSILS.

Albrecht, P., Ueber die morph. Bedeutung der Pharynxdivertikel, Centralblatt f. Chirurgie,
1885.

Anderson, The morphology of the tongue and pharynx, Journ. of Anat. and Physiol., vol. xv, 188].

Bickel, Ue. d. Ausdehnung u. d. Zusammenhang d. lymph. Gewebes in der Eachengegend. Arch.
f. path, anat., 1884.

Bo-wles, R. L., Observations upon the mammalian pharynx, with especial reference to the
epiglottis, Journ. of Anat. and Physiol., vol. xxiii, 1889.

Brosike, Ueber cinen Fall von Dirertikel der Seitenicand dcs Pharynx in Communication mit der
Tuba Evstachii, Arch. f. path. Anat., Bd. xcviii.

Donelan, J., Supernumerary Tonsils, Brit. Med. Journ., 1890.

Drews, E.., Zellvcrmehrung i. d. Tonsilla paJatina, Arch. f. mikr. Anat., Bd. xxiv, 1884.

Fisclier, M. , Ueber die angeborenen Formf elder des Rachens, Inaug. Diss., Wiirzburg, 1892.

Grulland, G. L., The development of adenoid tissue loith special reference to th» tonsils and
thymus, Reports of Lab. Roy. Coll. Phys , Edin., vol. iii, 1891.

His, W., Anatomiemenschl. Embryonen, Leipzig, 1885.

Kastsclienko, Vas Schicl'sal der embryonalen Schundspalten bei Sdugithicren, Arch. f. mikr.
Anat., Bd. xxx, 1888.

Killian, Ueber die Bursa unci Tonsilla pharyvgea, Morph. Jahrb., 1888. .*

IIECEXT LITERATURE OF THE PHARYNX AXD TONSILS. 63

Kircher. I'thr Divcrtikclhilduiui in der Tula Eustachii des MenscJien, Leipzig, 18S7.

von Kostanecki, Kasimir, Zur Kenntniss des Pharijnxdiverticidum des Menschcn ink
h'-fotjderer Beriicl-sichti/jun'j der Bivertikelbildungea im Nascurachenraum, Arch. f. path. Atiat., lid.
cxvii.

Mancloire, Depressions et dircrticules pharyngis. Bull. Soc. anat., Paris, 1892.

Piersol, Gr. A., L'eber die Eatwickelang der cruhry. Schlundspalten und ihrer Derivate bei
Sdu'irthiiren. Zeitscb. f. wisseiisch. Zoologie, Bd. Ivii.

Poelchen, B., Zur Anatomie des Nasenrachenrauvies, Archiv f. path. Anat., BJ. cxix, 1890.

Potiquet, La bourse pharyngienne dc Luschka, Res. de laryngologie, .x, 18S9.

Betterer, E., Origine et evolution des amygdules cliez les mammiferes, Journ. de ranatoinie,
Annee xxiii. 1SS8 ; Dn tissu, angiotheVud des amygdcdes et les plaques de Peyer, Memoires de la
societe de biologie, 1892.

Rieffel, H., Sur les rapports des amygdales avcc les vaisseaux carotldiens, Paris, 1893.

Kuckert, J., Der Pharynx als Sprarh und Schluckapparat, Munchen, 1882.

Schwabach, Ucbcr die Bursa pharyn-gexi. Arch. f. inikr. Anat., Bd. xxix, 1887.

Stdhr. Ph., Ucber Mandela u. Balgdriiusen, Arch. f. path. Auat. Bd. xcvii, 1884.

Stuart, Anderson, and M'Cormick, Alexander, Tlic positionof the Epiglottis in sioalloicing,
Journ. of Anat. and Physiol., vol. xxvi, 1SL)2.

Suchannek, H. Bcitrdgc zur noriii. v.. path. Anit. des Eachengeiaolbes, Ziegler u. Nauwerck,
Beitriige zur path. Anat.. iii, 1888 ; Auatoinisvhe Beilrdje zur Frage uber die sog. Bursa pharyngea,
ZeJtsch. f. Obrcnheilk., x'ix, 1888—89.

Symins-ton, J., On nares and epiglottis, Proc. of t'.ie Anat. Society, Journ. of Auat. and Physiol.,
ToL xxiii, 1SS9.

Tornwaldt, Ueber die Bedeutung der Bursa 'pharyngea, u.s.iv., Wiesbaden, 1885.

"Waldeyer, Beitrdge zur norm. u. vcrgl. Anutomie des Pharynx mit besondercr Beziehung auf
den Sch/in;/u-Lg, Sitz. d. k. pr. Akad. der Wissensch. zu IJerlin, 1886.

Wheeler, Pharyngocelc and dilatation of the pharynx, Dubl. Journ. Jled. Science, 1886.

Zaufal, Die Plica salpingo-jiharyngea. Arch. f. Ohrenheilkunde, Bd. xv.

Za-warykin, Th., Ueber das Epithd. der Tonsillcn, Anatom. Anz., Jahrg. iv, 1839.

Zuckerkandl. O., Zur Frage der Blutung nach Tonsillotomie, Wiener med. Jahrb., 1887.

OKGANS OF DIGESTION.

THE (ESOPHAGUS.

The oesophagus or gullet is the part of the alimentary canal leading from the
pharynx to the stomach. Ic commences at the level of the lower border of the
cricoid cartilage, opposite the disc between the sixth and seventh cervical vertebra,
and passes downwards through the lower part of the neck into the thorax. In this
cavity it lies in the superior and posterior mediastina, and after piercing the
diaphragm, it ends opposite the tenth o" eleventh dorsal vertebra by opening into
the stomach.

The length of the oesophagus is about nine or ten inches (26 centim.). It is of
smaller diameter than any other division of the alimentary canal, its narrowest part
being at the commencement behind the cricoid cartilage ; it is also slightly constricted
in passing through the diaphragm, but, below that, widens into the stomach. It is
usually flattened from before backwards, so that its lumen appears as a transverse
slit (fig. 81), but occasionally it is rounded with the cavity stellate in form (fig. 82).

Fig. 81. — Horizontal section of trachea, oescphagtjs, and thyroid body. (J. S.,
1, CBSophagus ; 2, cavity of trachea ; 3, cartilaginous ring of tracLea ; 4, thj'roid body ; 5, inferior
thyroid artery ; 6, recurrent laryngeal nerve.

Fig. 82. — Horizontal sectiom op the (ESOpriASus and thoracic aorta at the level of the

9th dorsal vertebra. (J. S.)

1, oesopbagus ; 2, thoracic aorta ; 3, thoracic duct ; 4, vena azygos major receiving a tributary from
the left side ; 5, i)ody of vertebra : 6, pleura ; 7, diaphragm.

When empty its greatest diameter is about 20 mm., and when moderately distended,
so that it acquires a cyhndrical form, its diameter varies from 18 to 24 mm. It is
not quite straight in its direction, but has three slight curvatures. One of these is
an antero-posterior flexure, corresponding with that of the vertebral column in the
neck and thorax. The other two are shght lateral curves ; for the oesophagus,
commencing in the median line, inclines to the left side as it descends to the root
of the neck ; thence to the fifth dorsal vertebra it gradually resumes the median
position ; and finally, it deviates again to the left, at the same time coming forward
towards the oesophageal opening of the diaphragm. After piercing the diaphragm,
it turns abruptly towards the left side to join the stomach.

Relations. — In the lower cervical and upper dorsal region the oesophagus is
applied to the anterior surface of the spine, being connected with it and with the
lougus colli muscle by loose areolar tissue ; opposite the middle dorsal vertebrse the
thoracic duct passes obliquely upwards from right to left behind it, and then ascends
on its left side ; in its lower third the oesophagus is placed in front of the aorta. In
the neck the oesophagus lies close behind the trachea (projecting about a quarter of

THE (ESOPHAGUS.

an inch to the left of that tube), and the recurreut hiryngeal nerve ascends on each
side in the angle between them (see fig. 81) ; on each side is the common carotid
artery and also a part of the thyroid body, but as the oesophagus inclines to the
left side, it is in more immediate connection with the left carotid. In the thorax
the oesophagus is successively covered in front by the lower part of the trachea, by
the commencement of the left bronchus, and by the pericardium and the diaphragm.
The aorta, except near the diaphragm, where the oesophagus is in front of the vessel,
lies to the left, and the vena azygos major to the right and behind ; the pneumo-
gastric nerves descend in close contact with its sides, and form a plexus around it,
the left nerve proceeding gradually to the front, and the right nerve retiring behind
it. In the superior mediastinum the left pleura lies close to its left side, while lower
down in the posterior mediastinum the right pleura is in relation with its right side,
and often extends inwards slightly behind it. Lastly, just before it pierces the
diaphragm the oesophagus is in contact with both pleura?.

'^S^/^

STRUCTURE OF THE CESOPHAGUS.

The walls of the gullet arc composed of three coats ; viz., an external or
muscular, a middle or areolar, and an internal or mucous coat. Outside the

Fig. 83. — .Section of the human cesophagus.

(From a drawing by V. Horsley.) Moderately magnified-

The section is transverse, and from near the middle
of the gullet, a, fibrous covering ; b, divided fibres
of the longitudinal muscular coat ; c, transverse
muscular fibres ; d, sub-raucous or areolar layer ; c,
muscularis mucosa; ; /, mucous membrane, with vessels
and part of a lymphoid nodule ; 'j, laminated epithelial
lining ; /*, mucous gland ; i, gland duct ; r/t', striated
muscular fibres cut across.

muscular coat there is a layer of areolar
tissue, with well marked elastic fibres.

The muscular coat consists of an
external lonfjitudinal layer (seen in section in
fig. 83, l) and an internal circular layer (c).
This twofold arrangement of the muscular
fibres prevails throughout the whole length
of the alimentary canal ; but the two layers
are here much thicker, more uniformly dis-
posed, and more evident than in any other
part, except quite at the lower end of tiic
intestine. The external or lo7i(/itudmal Hhvcs
are disposed at the commencement of the tube

in three l)ands, one in front and one on cacii side. The lateral bauds are coii-
tinuouH above with the inferior constrictor of the pharynx ; the anterior arises from
the back of the cricoid cartilage afc the prominent ridge between the posterior
crico-arytenoid muscles, and its fibres spread out on each side of the gullet as they
descend, soon blending with those of the lateral ])undleB to form a continuous
layer around the tul)e. The direction of many of the fibres is at first slightly
oblique, but towards the lower end it is more directly longitudinal. The internal
or circutar fibres arc separated above by the fibres of the lateral longitudinal bands
from those of the inferior constrictor of the pharynx. The rings which they form
anmnd the tube have a horiz(^ntal direction at its upper and lower part, but in the
intervening sjjacc are slightly obIi(|UC. At the lower end both layii's of fihrcH
Ix'conie continuous with those of the stomach.

VOL. III., I'T. 4. K

66 ORGANS OF DIGESTION.

The muscular coat of the upper end of the oesophagus is of a well marked red
colour, and consists wholly of striped muscular fibres ; these are gradually replaced
by plain muscular fibres, so that these are almost the only ones found in the lower
half of the tube. A few striped fibres may, however, be found even at the lower
end, and in some animals they preponderate throughout the whole length of the tube.

The longitudinal fibres of the oesophagus are sometimes joined by a broad band of smooth
muscle, passing from the left pleura, and sometimes also by another from the left bronchus.
According to Cunningham, the former is almost constantly present, and the latter very
frequently.

The areolar or submucous coat is placed between the muscular and mucous
coats, and connects them loosely together. It exceeds the mucous membrane con-
siderably in thickness, tad in it are contained the mucous glands (fig. 83, h), which
open on the mucous membrane.

The mucous membrane is of firm texture, and is paler in colour than that of
the pharynx or stomach. From its loose connections its outer surface is freely
movable on the muscular tunic ; and under ordinary circumstances the mucous
lining is thrown into longitudinal folds or rugte, which are in mutual contact. These
folds disappear on distension of the canal.

Minute papillee (/) are seen upon the mucous membrane, and the whole is covered
with a thick stratified scaly epithelium. In the embryo for a certain period the
oesophagus is lined by columnar ciliated epithelium (Neumann), patches of which
may persist even to the time of birth (Klein).

The small compound racemose or tubulo-racemose glands, named ceso})hagml
glands, which are for the most part seated in the submucous tissue, are specially
numerous at the lower end of the tube. A few of the smallest are situated in the
substance of the mucous membrane. The cells of these glands are columnar. Their
ducts are usually surrounded by collections of lymphoid tissue as they pass through
the mucous membrane.

The mucous membrane is bounded next to the submucous coat by longitudinally
disposed plain muscular fibres, which, imperfect above, form a continuous layer
towards the lower end of the tube {muscularis mucoscc, e).

Duplicity of the oesophagus in part of its extent, without other abnormality, has been
recorded (Blaes, quoted by Meckel).

Vessels and nerves. — The arteries of the oesophagus consist of a series of
small vessels derived from the inferior thyroid, descending thoracic aorta, left
inferior i^hrenic, and coronary of the stomach ; these branches anastomose together.
The veins pass to the inferior thyroid, azygos, and coronary of stomach; the
submucous veins at the lower part of the oesophagus form a free communication
between the portal and systemic veins, and become dilated in cases of obstruction
to the circulation through the liver. The lymphatics go to the inferior deep
cervical and posterior mediastinal glands. The nerves are derived from the
recurrent laryngeals, vagi, and sympathetic. The blood-vessels have for the most
part a longitudinal arrangement. There are separate networks for the mucous
membrane, the muscularis mucosEe and the muscular coat, and the glands and fat
lobules which are met with in the submucosa have each their capillary plexus.
Lymphatics are found in both the submucous and mucous coats, those of the latter
commencing as in the mouth and pharynx within the papillse. A small amount of
lymphoid tissue is also present, and may be accumulated into lymphoid nodules,
especially in the neighbourhood of the ducts of the mucous glands. Both here and
in the pharynx the alveoli of the mucous glands are invested by sinus-like lymphatic

THE (ESOPHAGUS. 67

vessels (Kitld). The nerves form a gangliated plexus between the two layers of the
muscular coat, as in other parts of the alimentary canal, but it is characterised by
the comparatively large size of the groups of ganglion-cells and of the cells
themselves, and also by the fact that it contains, besides non-medullated fibres, a
large number of raedullated nerve-fibres (derived from the pneumo-gastric nerves).
Each of these fibres in passing a ganglion is joined by a non-medullated fibre
derived from one of the cells of the ganglion, a T-shaped junction being formed, as
in the case of the nerve-fibres passing through the posterior-root ganglia. The
medullated fibre then passes on and branches, and is finally distributed in terminal
arborisations (motor end-organs) in the striped muscular fibres (Rauvier). The non-
medullated fibres are distributed chiefly to the plain muscular tissue. There is also
a gangliated plexus in the submucous tissue, from which fibres pass to the glands,
and to the muscularis mucosa?, whilst others penetrate between the deeper layers of
the stratified epithelium and end in an open arborisation of varicose fibrils between
the cells (G. Retzius).

EECENT LITERATURE OF THE CESOPHAGUS.

Big-grs, Gr. P., Diverticulum of the ccsophagus, Proc. New York Path. Soc. , 1S91-92.

Brosset, J., Des vices de conformrition de V assoi^harje, Lj'on medical, 188'.'.

Chavasse, T. F., On a case of pressure diverticulum of the wsoplatfjus, Trans. Patli. Soc.
LondoD, xlii, 1891.

Coakley, C. S., The arrangement of the muscular fibres of the ocsophtyus, Researches from tlie
Loorais Labor., Univ. ot: the City of New York, 1892.

Dobrowolski, Z., Lympjhknotchcn in tier Schleimhaut der Speiserohre, des Mugens, d-c, Beitr.
zur pathol. Anatomic u. allg. Pathologic, Bd. xvi, 1894.

Flesch, Max, Uc/jer Bczichungcn zicischen Lymphfollikeln und secernicrenden Driisen im
(Esophagus, Anatom. Anz. , Jahrg. iii, 1888.

Juvara, E., Sur un mitsclc diaphragmatico-cesophagien, Bull. .soc. anat., Paris, 1894.

Klaus, Gr., Der hindliche (Esophagus, d:c., Inaug. l)iss., Miinchen, 1890.

Laimer, E., Bcitrag zur Anatomic des (Esophagus, Wien. med. Jahrb., 1884.

Mayer, S., Die Membrana peri-a'sophagealic, Anat. Anz., viii, 1892.

Rubeli, O., Ueber den (Esophagus des Menschcn und der Haustierc, Archiv if. wisscnscli. u.
prakt. Ticrheilkunde, Bd. xvi, 1890.

Shattock, S. G., Congenital atresia of the wsophagus, Trans. Path. Soc, xli, 1890.

Strahl, H., Beitrdge zur Kentnniss des Bancs des (Esophagus, Arch. f. Anat. u. Physiol., Anat. '
Abth., 1889.

Tetens, J., Ein Beitrag zur Lehve von dem (Esophagus-Diicrticulum, Kiel, 1889.

Willett, E., Atresia of (esophagus, Trans. Path. Soc, 1893.

) 2

OKGANS OF DIGESTION.

THE ABDOMINAL VISCEEA.

As that part of the digestive canal which is found beneath the diaphragm, and
consists of the stomach and intestines, is situated within the cavity of the aMomen,
and occupies, together with the Hver and pancreas, by far the greater part of that
cavity, the general topographical relations of the abdominal viscera may here be
qriefly explained.

THE ABDOMEN^.

The abdomen is the largest cavity in the body, and is lined by an extensive and
complicated serous membrane, named the perito7ieum. It is subdivided into two
parts : an upper or larger part, the abdomen, properly so called ; and a lower or
pelvic part. The limits between these portions of the cavity are marked by the brim
of the true pelvis.

The abdomen proper differs from the other large cavities of the body in being
bounded mainly by muscles and fascia (described in Vol. II., pt. 2.) instead of
more or less rigid osseous walls, so that it can readily vary in its capacity according
to the condition of its contained viscera. Its walls are pierced by several apertures,
such as the several diaphragmatic openings for the aorta, vena cava and oesophagus,
and the femoral rings and inguinal canals. In the median fibrous substance of
the anterior wall lies the umbilical cicatrix. The cavity is of an irregularly oval
form with the long axis directed from above downwards and having its transverse
diameter usually greater than its antero-posterior. It extends under cover of the
lower ribs and costal cartilages as high as the vault of the diaphragm, and below it
is bounded laterally by tbe iliac fossse, between which at the pelvic inlet it becomes
continuous with the cavity of the pelvis. The posterior Avail of the abdomen is
formed by the bodies of the lumbar vertebra with the psoas and quadratus
lumborum muscles on either side. In consequence of the forward projection of the
lumbar vertebra there is a considerable hollow on either side of the spine ; so that in
a horizontal section the abdominal cavity appears somewhat kidney-shaped. The

Fig. 84.— Outline of the front of the abdomen,

SHOWING THE DIVISION INTO REGIONS.

1, epigastric legion ; 2, umbilical ; 3, hypogastric ;
4, 4, right and left hypochondriac ; 5, 5, right and left
lumbar ; 6, 6, right and left iliac.

walls of the pelvic cavity are mainly osseous,
but its floor is formed by the integument, fat,
fascige, and muscles, and has certain apertures
which are usually closed, but can be opened for
the passage of the genito-urinaiy products and
the contents of the rectum.

For the purpose of enabling reference to be
made to the situation and condition of contained
organs, the aMomen proper has been artificially
subdivided into certain regions which are
separated from one another by imaginary hori-
zontal and sagittal planes passing through the
abdomen, the edges of these planes being indicated by lines drawn upon the surface
of the abdomen. By this plan the abdomen is divided into nine regions (fig. 84),
the boundaries and contents of which will be described in the Appendix to this
work.

THE ABDOMINAL VISCERA. 69

THE PERITONEUM.

The peritoneum or serous membrane of the abdominal cavity is by far the most
extensive and complicated of the serous membranes. Like the others it may be
considered to form a shut sac, but in the female the two Fallopian tubes open at
their free extremities into its cavity. The parietal layer is connected with the fascia
linino; the abdomen and pelvis by means of areolar tissue (subperitoneal) ; it is more
firmly adherent along the middle line of the body in front, as well as to the under
surface of the diaphragm. The visceral layer, which is thinner than the other,
afifords a more or less complete covering to most of the abdominal and pelvic
organs. The folds of the peritoneum are of various kinds. Some of them
constituting the mesmteries connect certain portions of the intestinal canal with
the posterior wall of the abdomen ; they are, the mesentery properly so called for the
jejunum and ileum, the transmrse and sigmoid tneso-colon, and the meso-rectum.
Other folds connected with the stomach are called omenta ; they are the great
omentum or epiploon, the small omentum., and the g astro -splenic omentum. Lastly,
certain reflexions of the peritoneum from the walls of the abdomen or pelvis to
viscera which are not portions of the intestinal canal are named ligaments ; such
are the ligaments of the liver, spleen, uterus, and bladder.

The further account of the peritoneum will be deferred until the abdominal
viscera have been described.

RECENT LITEKATURE OP THE ABDOMINAL PORTION OF THE ALIMENTARY
CANAL IN GENERAL, AND OP THE PERITONEUM.

Anderson, R. J., Tlie peritoneum in man and animals, Dublin Journ. of Med. Science, 1SS3.

Anderson, W. , A plea for uniformity in the delimitation of tlie regions of the abdomen, Jonrn.
An.'it. and Phys., vol. xxvi, 1892.

Anderson, "W. , and Makins, Gr. H., The planes of subperitoneal and subplcural connective
tissue, Journ. Anat. and Pliys., vol. xxv, 1890.

Baginsky, Adolf, Untersuchunrjen ilber den Darmkancd des menschlichen Kindes, Virchow's
Arch, fiir pathol. Anat., Bd. Ixxxix.

Ballantyne, J. W., The relations of the abdominal viscera in the infant, Edinburgh Medical
Journal, July, 1891.

Born, Hermann, Ein seltener Fall von angeborener Atrcsie und Durchtrennung des Darmrohres
mit entwickelungsgcschichtlich-intercssanten Vcrhdltnisscn am Peritoneum, Archiv f. Anat. u. Physiol.,
Anatora. Abt., Jahrg. 1887.

Brossike, G., Uebcr intraabdominale {retroj)eritoneah) Hernien utid Bauchfelltaschcn, nehst
finer IhtrsVlhing dcr Entwickelung peritonealtr Formationcn, Berlin, 1891.

Cunningrham, D. J., Delimitation of the regions of the abdomen, Journ. of Anat. and Phj's. ,
1S9-J, an.l Tr. of the R. Acad, of Medicine of Ireland, vol. xi, 1893.

Dexter, S., The anatomy of the peritoneum, New York, 1892.

Farabeuf, Arret d' evolution de Vintestine, Progres medical, 1885, and Piidl. soc. anat., Pari.s, 1885.

Flesch, Max, liemerhungen ilber die Beziehungcn des Bauchfclls zur vorderen IFand der llarn-
blasf, Anat. Anzeii^er, Jahrg. iii. 1888.

fraser, A., A case of comphte transposition of the tlioracic and abdominal viscera, Trans, of tiie
Roy. Acad, of Mc-d. of Ireland, vol. v, 1895.

Froxnont, Henri P., Contributions a I'anatomie topograph iqite de la jwrtion sous-diaphrag-
matif/un du tuhf dl /islif, Lille, 1890.

Griffith, J. Wardrop, A case of transposition of tlie thoracic and abdominal viscera. Journal
Anat. and Phys., vol. xxvi, 1891.

Hasse, C, Ucber die liewegungen der Zwerchfelles und ucber den Einjluss derselben auf die
Unterleihsurgdve, Arch. f. Anat. und Phys., Anat. Alith., Jahrg. 1886.

Henke, W., iJer liaum der Dauchliohlc des Menschen und die Vcrteilung der Eingexoeide in
demiielljei,, Archiv f. Anat. u. Physiol., Anatoni. Abt., Jahrg. 1891.

Jones, C. H., OhHervations on the omentum, especially its blood-vessels, lllustr. Med. News,
London, vol. i, 1888.

Jonnesco, Organs de digestion, in I'oirier, Anatomic, Paris, 1895.

Jonnesco et Juvara, Anatmnie des ligaments de I'appendirc vermiculaire ct dc la fusscllc ilea-
uj>iiiiid\iiilii'ir<\ I'ronri'H nied., 1894.

Klaatsch, H. , Zur Morithobxjie der Mesenterialhildungen am Darmbinal der Wirbclthicre,
Mor|.h. Jahrb., l!d. xviii, 1892.

Le/ishaft, P., fJeber die /icdcutung der Bauchpresse fiir die Erhallung der llauchciwjeweide in
Hirer L<ige, Anal. Anzeiger. 1888,

70 ORGANS OF DIGESTION.

Liockwood, C. B., On the devdopment cf the great omentum and iransccr&e colon, Proe. Royal
Society of London, vol. sxsv. 1883 ; Hunter lan lectures on hernia, London, 1889.

ISIetteiilietmer, H., Eln Beitrag zur topographischea Anatomic der Brust- Bauch- uiid Bccken-
hohl". des neugehorenen Kindes, Morpli. Arbelten, iii. 1893.

Perignon, L., Etude sur le d-eveloppernent du peritoine dans ses rappiorts avec Vevolututn dji tuhe
digestif et de ses annexes, Paris, 1893.

RoUeston, H. D., The fossae round the caecum, and the position of the vermiform appendix,
with sptecial reference to retro-pteritoneal hernia, Proc. of the Anatom. Soc. of Grt. Brit, and Ireland,
Joum. of Anat. and Physiol., vol. xxvi, 1891.

Smitli, W. 'Wilberforce, Delimitation of the regions of the abdomen, Joam. of Anat. and
Piys. , vol. xxvii, 1892.

SyminglorL, J., Tfte topographical anatomy of the child, 1887 ; TIce relations of the peritoneum
to the descending colon in the human subject, Jonrn. of Anat. and Physiol., vol. xxvi, 1892.

Toldt, C, Bau und Wacltsthumsverdndei-ungen der Gel'rose des menscMichen Barmlcanales,
Denksch. d. k. Alcad. der "Wissensct. , Wien, Bd. Ivi, 1889 ; Die Darmgekrose und Netze im gesetz-
mdssigen und irn gesetzwidrigen Zustand, Ibid. ; Ueher die Geschichte der Mescnterien, Vhdlgn. d.
Anat. Ges., Anat. Anzeiger, 1893 ; Ueher die massgehenden Gesichtspmnlcte in der Anatomic des
Bauchfells und der Gelcrose, Denkschr. d. Akad. d. Wiss , Wien, 1893.

Treves, F., The anatomy of the intestinal canal and peritoneum in man, Hiinterian lectures, 1875.

Wartlin, A., A case of situs viscerum inversus^ New York Med. Journ., vol. lix.

THE STOMACH.

The stomach is a dilated portion of the ahmentary canal situated between the
termination of the oesophagus and the commencement of the small intestine. In
shape it is somewhat pyriform, with the larger end ov fundus directed upwards and
backwards on the Mt side, and the smaller and lower end turned to the right. It
may be divided into a main or cardiac part, the long axis of which is directed
from above downwards, forwards, and a little to the right, and a much smaller
pyloric part, which passes nearly horizontally from left to right. Of its two open-
Fig. 85. — Diagrammatic octlises of

THE EMPTY (A) AXK DISTENDED (B)
STOMACH, SEEN FKOJI THE FRO.VT.

M dotted line represents the median
plane. The -f indicates pusition on back
of organ of pyloric oritice.

ings the one, by which food

entei-s from the cesophagus, is

situated to the right of the fundus,

and is named the cardiac orifice

or cardia, the other, by which it passes into the duodenum, and which is placed on

a lower level and more forwards and to the right, is the pi/loric orifice, which is

bounded internally by a circular constriction, sometimes also marked externally,

called the pijlorus. The stomach has two surfaces, called anterior and posterior,

and two borders, termed the great and small (greater and lesser) curvatures.

Variations in position. — The stomach varies greatly in size, position, direction,
and relatiijiis under norma! physiological conditions, such as the condition of its
muscular wall, whether relaxed or contracted, the degree of its distension, and the
state of neighbouring organs.

"When the stomach is empty it lies in the left hypochondrium and left half of
the epigastric region, its pyloric end being situated in or near the median plane

Fig. 86. — DiAGBAMJIATIC OUTLINE OF THE STOMACH, AS SEEN FROM
BEHIND. (Ilis.) \

a, grejit curvature ; h, small curvature ; c, left end, great cul-
de-sac, or fundus ; d, small cul-de-sac, or antrum Jjylori ; o,
cesophageal orifice or cardia ; p, pyloric extiemity.

under cover of the liver at the level of the last dorsal
or first lumbar vertebra. The empty stomach is
often described a.s hanging vertically, with its sur-
faces anterior and posterior ; but it always presents
some degree of obliquity from above downwards
and forwards, and not unfrequently it is more nearly horizontal than vertical, this
direction being associated with a distended state of the small intestine, which pushes
the lower part of the stomach upwards and forwards. Although usually flattened so
as to present two surfsic^iS and two borders, it is sornetinies found contracted into a
f-ylindrical form. This is especially the case towards the region of the pylorus, where
its circular muscular fibres are best develofxjd.

As the stomach is distended its fundus fills up the left cupola of the diaphragm,
pushing the left lobe of the liver towards the right side, and tilting up the apex of
the heart, while the lower part of the great curvature lies so as to come in contact
with the anterior abdominal wall below the left f;ostal wall and the liver, and not
unfrequently to enter tli(; left lumbar and unil^ilical regions. The distension of the
stomach is also af;corapanied by a movement of the pylorus towards the right side,

ORGANS OF DIGESTION",

SO that this orifice of the stomach is often found under the liver close to the neck of
the gall bladder, and two or three inches to the right of the median plane. This
movement of the pylorus to the right side is accompanied by one of rotation, so
that the orifice, which in the empty stomach is directed towards the right side,
looks backwards, and the pylorus is concealed from the front by the dilated pyloric
portion of the stomacho This part of the stomach moves more freely to the right

Fig. 87. — Horizontal section of abdomen op boy aged six tears, at the level of the cardiac

ORIFICE. (J. S.)

a, disc between tenth and eleventh dorsal vertebrEe ; 6, diaphragm divided at the level of its
cesophageal opening ; c, aorta ; d, cardiac orifice, behind this the stomach lies in direct contact with the
diaphragm. The spleen is normally more completely covered with peritoneum at this level.

than the pylorus itself, so that a blind recess is gradually formed to the right of a
sagittal plane passing through the pylorus. This is often called the antrum pylori
or small cul-de-sac.

Cardiac Orifice. — The opening by which food enters the stomach from the
cesophagus is called the carcUa, or cardiac orifice. Owing to its connections with the
oesophagus and diaphragm, the cardiac orifice is the most fixed part of the stomach.
It is situated at the level of the body of the 10th or llth dorsal vertebra,
in front and to the left side of the aorta, and behind a notch in the posterior
surface of the left lobe of the liver. It lies, on an average, about 4 or 5 inches
posterior to the interval between the ensiform process and the inner end of the 7th
left costal cartilage. It appears from the researches of Braune and v. G-ubaroff that
the cardiac orifice may have a valvular action independent of its muscular fibres.
Thus, after dividing the thorax horizontally some distance above the diaphragm,
and filling the stomach w4th fluid by injecting from the cut end of the oesophagus,
they found that the gastric contents were retained, although the oesophagus was not
ligatured. After piercing the diaphragm the oesophagus turns somewhat abruptly
to the left side to open into the stomach, and it is probable that when the stomach
is distended this bend is increased so as to obstruct the return of its contents into
the oesophagus.

Pylorus. — From what has already been said regarding the movements of the
stomach, it is evident that the position of the pylorus in relation to the
anterior surface of the abdomen must vary considerably. As a rule, both in the
empty and in the distended state of the stomach it is overlapped in front by the
liver, which thus separates it from the abdominal wall. "When the stomach is empty
the pylorus is in, or close to, the median plane, and an inch or so below the ensiform

THE STOMACH.

process ; but, as already mentioned, it is found two or three inches to the right
of the median plane when the stomach is distended. Occasionally the pylorus
lies directly against the abdominal wall, just below the liver. The position
of the pyloric orifice can be recognized by a slight constriction on the outer
surface of the organ, and also by a thickening of the wall, which can be
readily felt by taking it between the thumb and fore-finger. The closure of
this opening is produced by the contraction of the circular muscular fibres,
which are well developed in this situation, and form a distinct projection
towards the orifice. This contraction at the pylorus is sometimes associated with
a similar condition of the muscular fibres of the stomach for an inch or more
from the pylorus, while the rest of the stomach is dilated. Viewed from its
duodenal side the closed pylorus presents some resemblance to the external os
Fig. 88. — Section through py-loric part op

STOMACH AND COMMENCEMENT OP DUODENUM,
FROM A SPECIMEN HARDENED IN SITU. (J. S. ) 1

a, a, a, longitudinal folds of the mucous mem-
brane in pyloric part of stomach ; b, section of
mucous membrane ; c, circular muscular fibres of
stomach, the longitudinal fibres are just visible to
the naked ej'e as a narrow line external to the
circular fibres ; p, duodenum ; p, pyloric orifice.

uteri, but the opening is stellate or
rounded. When the stomach and duo-
denum are distended and dried the open-
ing of the pylorus is usually circular, about half an inch in diameter, and bounded
by an annular projection. When distended and hardened with alcohol the annular
fibres at the orifice appear in section as a sharply marked band of considerable
thickness, producing a sharp prominence of the mucous membrane into the interior.

Borders. — The borders of the stomach are termed the small and great curva-
tures. They give attachment to folds of peritoneum, between the layers of which
bloodvessels and lymphatics reach the organ. The small curvature is readily
recognized by its giving attachment to the small or (jastro-hqmtic omentum. It
passes from the cardiac orifice at first downwards and a little to the left, and then
turns somewhat abruptly to the right, to end at the upper border of the pyloi'us.
Near this opening it often has one or two depressions with intervening convex pro-
minences. The great curvature is four or five times as long as the small, and consists
of an upper, a left, and a lower portion. Traced from the oesophageal orifice it will be
found to pass to the left, forming an upwardly directed convexity, where it encircles
the upper part of the fundus. On the left side of the fundus it first passes nearly
straight downwards, and then turns to the right to end at the ])ylorus. The lower
part of the great curvature forms a convexity directed downwards ; it gives attach-
ment to the great or f/astro-colic omentum, and usually has the transverse colon just
below it. Towards tlie pylorus its general curve may be interrupted by one or two
depressions.

Surfaces. — The surfaceH of the stomach are usually termed anierior and posterior,
but as already mentioned, the anterior surface looks inoi-e or less upwai'ds and the
pofiterior downwards. Usually flattened when the stomach is empty, they l)ecome
ajnvex on distension, so that in this condition the distinction between the borders
and surfaces of the organ is ill-defined, IJehind the cardiac orifice there is a small
area of the stomach which is uncovered by peritoneum, and lies in direct contact with
the diaphragm (see fig. 87;, and also often with the upper part of thi; left supra-
renal capsule. The reflection of the peritoneum at the boundari(!S of this area from
tlie Rtoma^ili to the diapliragm is called the f/as/ro-phrenic //'//amenl. With this
exception both surfaces of the stomach are entirely covered by peritoneum. On tiie

ORGANS OF DIGESTION.

posterior aspect near the left part of the great curvature the gastro- splenic omentum
is attached.

The anterior surface of the stomach is in contact with the under surface of the
left lobe of the liver and the diaphragm ; also, when distended, with the anterior

Fig. 89. — YiEW OF THE STOMACH IN SITU AFTER REMOVAL 01 THE LIVER AND THE INTESTINE (EXCEPT
THE DUODENUM AND COMMENCEMENT OF JEJUNUM). (Testut.)

A, diai)liragm ; B, B', tlioracico-abdominal parietes ; C, right kidney -with c, its ureter ; D, right
sui^rarenal capsule ; E, left kidney with e, its ureter ; F, spleen ; Q, G', aponeuroses of the transverse
abdominal muscles ; H, right quadi-atus lumborum muscle ; H', left ditto ; I, right psoas magnus and
parvus muscles ; I', left ditto ; K, oesophagus : L, stomach ; M, duodenum ; N, jejunum ; the position
of the duodeno-jejunal junction behind the stomach is indicated by dotted lines. 1, termination of oeso-
phagus ; 2, great curvature of stomach ; 3, small curvature ; 4, fundus ; 5, antrum pylori ; 6, pyloric end ;
7, right vagus nerve ; 8, left ditto ; 9, thoracic aorta ; 9', abdominal aoria-;,-10y-inferior phrenic artery ;
11, cceliacuxis ; 12, hepatic artery ; 13, riglitgastro- epiploic ; 14, coronary artery ; 1,5, splenic artery ; 16,
16', superior mesenteric artery and vein ; 17, inferior mesenteric artery ; 18, spermatic arteries ; 19, gall
bladder ; 20, cystic duct ; 21, hepatic duct ; 22, inferior vena cava ; 23, portal vein ; 24, sympathetic cord.

abdominal wall and the quadrate lobe of the liver. Occasionally the transverse colon
is found in front of the stomach.

Posteriorly the stomach is in relation with the diaphragm, the spleen, the left
suprarenal capsule, the upper end of the left kidney, the pancreas, and the splenic
flexure of the colon. It is separated from the duodeno-jejunal junction and some
convolutions of the small intestine by the transverse mesocolon. The pyloric portion
of the stomach exhibits a tendency to sacculation owing to constrictions due to local
contractions of the muscular fibres. One or more of these constrictions are often
found on both the great and the small curvatures, but they seldom extend all round
the stomach, and can generally be obliterated by full distension. Occasionally, how-

THE STOMACH.

ever, a constriction occurs which is of a more permanent character, ami partially
divides the stomach into two parts (hour-giass form).

Dimensions. — These vary greatly in different subjects, and also according to the
state of distension of the organ. When moderately filled its length, measured from
the top of the fundus to the lowest part of the great curvature, is about 10 to 12
inches, and its diameter at the widest part from 4 to 5 inches. The distance

Fig. &0. — View of the liver, duodenum, pancreas, spleen, &c. The greater part of the

STOMACH HAS BEEN REMOVED TO SHOW ITS POSTERIOR RELATIONS ; ITS POSITION IS INDICATED BY
A DOTTED OUTLINE. (Tcstut. )

A, inferior surface of liver ; B, riglit kidney ; C, C", right and left suprarenal capsules : D, left
kiilney ; E, jjancreas ; F, upper jjart of stomach ; G-, .spleen ; H, duodenum with a, h, c, (f, its four
jxjrtions ; I, jejunum ; K, duodeno-jejunal junction ; 1, lower end of (r;soi)hagus ; 2, pyloric orifice ; 3,
codiac axi.s ; 4, coronary artery ; f>, hepatic artery ; (J, lohus Spigelii of liver ; 7, 7', splenic ves.sels ; 8,
left gastro-epiploic ; 9, right ga.stro-epiploic ; 10, .suj)crior mesenteric vessels ; 11, portal vein ; 12,
hepatic duct ; l-'i, cystic <luct ; 14, gall bladder: l.'j, left crus of diaphragm; 16, aorta; 17, inferior
vena cava ; 18, inferior mesenteric vessels ; 19, 19', spermatic vessels.

between its two orifices varies fi'om 3 to C inches. It weighs, when freed from other
parts, about 4\ ounces in the male and somewhat less in the female (fllendinning)
(al>oiit 200 grammes, Diiroy). Its capacity is, on an average, about 5 pints (IJrinton)
(2 to y litn;s).

Variations according to age. — In the new-born child the stomach is small
and usually empty. Its general form and position are very similar to that of the
empty and contracted stomach in the adult, but in consequence of the large size of
the left lobe of the liver the whole of its anterior Htirfac(! is covered by this organ.
When it becomes distended the movement of its pyloric portion towards the right
Hide is proljably imj)eded by the large size of the liver.

ORGANS OF DIGESTION.

BTRUCTUEE OF THE STOMACH.

The stomach has four coats, named, in order from without inwards, the serous,
muscular, areolar or submucous, and mucous tunics (fig. 91).

The external or serous coat (s), derived from the peritoneum, is a thin,
smooth, transparent, and elastic membrane, which closely covers the entire viscus,
excepting along its two curvatures, and a small area near the cardiac end. Along
the line of these curvatures the attachment is looser, leaving an interval occupied
by the larger blood-vessels.

The second, or muscular coat, is composed of plain muscular tissue, forming

Fig. 91.

-SECTION THROUGH THE COATS OF THE STOMACH.

Diagrammatic. (Mall. )

m., mucous membrane; e., epithelium; d., orifice of gland
duct; m.m., muscularis mucoste ; sm., submucous coat; cm.,
circular muscular layer ; l.m., longitudinal muscular layer ; s.,
serous coat.

three sets of fibres, disposed in layers, and named,
from their direction, the longitudinal, the circular,
and the oblique fibres.

Tlie first or outermost layer consists of the longi-
tudinal fibres (fig. 91, l.m., fig. 92, a), which are in
direct continuity with those of the oesophagus. They
spread out in a radiating manner from the cardiac
orifice, and are found in greatest abundance along the
curvatures, especially the lesser one. On the anterior
and posterior surfaces they are very thinly scattered,
or scarcely to be found, but towards the pylorus are
well marked and form a thick uniform layer, which,
passing over the pylorus, becomes continuous with the
longitudinal fibres of the duodenum.

The second set consists of the circular fibres
(fig. 91, cm., fig. 92, b) which form a complete layer
over the whole extent of the stomach. They com-
mence by small and thinly scattered rings at the
extremity of the great cul-de-sac, describe larger and
larger circles as they surround the body of the stomach
at right angles to its curved axis, and towards the
pyloric end again form smaller rings, and at the same
time become much thicker and stronger than at any
other point. At the pylorus itself they are gathered
into a thick bundle (fig. 88, in section), which forms, within a circular fold of
mucous membrane, a well-marked projection — the pijloric sphincter. Some of the
circular fibres appear to be continued from those of the oesophagus, spreading from
its right side.

The innermost muscular layer is incomplete, and consists of the oblique, fibres
(fig. 92, c). These are continuous with the circular fibres of the gullet, on the
left of the cardiao orifice, where they form a considerable stratum ; from that place
they descend obliquely upon the anterior and posterior surfaces of the stomach,
where they spread out from one another, and, taking the direction of the circular
fibres, gradually disappear on the greater curvature.

The submucous coat of the stomach is a distinct layer connecting the muscular
and mucous coats (fig. 91, s.m.). It consists of areolar tissue, in which occasional

THE STOMACH.

fat-cells may be found ; and it is the seat of division and passage of the blood-
vessels.

The internal coat or mucous membrane is a smooth, soft, rather thick and
pulpy membrane, which in the fresh state has generally a somewhat pink hue owing

,^^':

E-:.<#-ii#'ssa

,:-■ P

Fig. 92. —Sketch of the ar-

R.^\GEMKNT OF THE FIBRES IN
THE MUSCULAR COAT OF THE

STOMACH. (Allen Thomson. )

A, e.xteraal layei- of longitu-
dinal fibres, as seen from the
outside ; B, middle layer of cir-
cular fibres as seen on removing
the longitudinal layer ; C, oblique
filtres exposed by removing some
of the fibres of the circular layer,
the cut edges of which are seen
below the small curvature.

c, the cardiac end ; p, the
pyloric end ; in A are shown the
stronger longitudinal fibres pass-
ing along the small and large cur-
vatures, and all round the pyloric
end, and radiating from tJie end
of the gullet over the front (and
back) of the stomach ; in B, the
nearly uniform layer of circular
fibres, in two sets crossing each
other very obliquely at o, and at
the cardiac end becoming con-
centric to the centre of the great
cul-de sac ; in C, the oblique
fil)res, oh, oh' , which form a con-
tinuation of the circular fibres of
the gullet (cb), and spread from
the left side of the cardia,
gradually merging into the deeper
circular fibres, with which finally
they entirely blend.

to the blood in its capillary
vessels. In infancy the
vascular redness is more
marked.

The mucous membrane
is thickest in the pyloric
region, and thinnest in the
great cul-de-sac. It always
Ijecomes thinner in old age.

It is connected with the
muscular coat by means of
the intervening submucous
layer so loosely as to allow
of considerable movement
or displacement. In con-
sequence of this, and of the

want of elasticity of the mucous membrane, the internal surface of the stomach,
when that organ is in an empty or contracted state, is thrown into numerous
convoluted ridges, rugrn, which are produced by the wrinkling of the mucous,
together with the areolar coat, and are entirely obliterated by distension of the

78 ORGANS OF DIGESTION.

stomach. These folds are most evident along the greater curvature, and have a
general longitudinal direction.

On examining the gastric mucous membrane closely with the aid of a simple
lens, it is seen to be marked throughout, but more plainly towards the pyloric
extremity, with small depressioDS which have a polygonal figure, and vary from
about 0"12 to 0"2o mm. across, being larger and more oblong near the pylorus.
They are the enlarged mouths or ducts of the tubular glands with wliich the mucous
membrane of the stomach is beset (fig. 91).

Towards the pyloric region of the stomach these depressions are larger and
deeper, and their margins are elevated into pointed processes, which resemble,
especially in vertical section, rudimentary villi, but the perfect forms of those
appendages exist only in the small intestine, and make their appearance in the
duodenum, immediately beyond the pylorus (fig. 91).

Epithelium of the surface. — The thick stratified epithelium of the oesophagus
passes abruptly at the cardia into a simple layer of columnar epithelium, which
completely covers the inner surface of the stomach, and extends to a variable
distance into the mouths of the gastric glands. The transition of the stratified
into the columnar epithelium occurs quite suddenly, the lowermost columnar cells
of the stratified epithelium passing into the single columnar layer of the gastric
surface, and all the other layers of the stratified epithelium ceasing abruptly.

The epithelial cells of the surface of the stomach differ in some respects from
the columnar epithelium of the intestine. They are more elongated in form, and

Fig. 93. — Epithelium of the surface of the stomach examined fkesh
(Heiclenhain). Highly magnified.

in inactive conditions of the organ they exhibit two parts, the
attached end of the cell being granular, the free part — that turned
towards the cavity of the organ — occupied by a clear, muco-
albuminous substance (mucigen). Moreover, there is no striated border as in the
intestinal cells. The clear substance swells and is discharged from the cell during
digestion, leaving empty the part of the cell which contained it, and a similar change
is produced by water and various other reagents. Between the smaller ends of the
columnar cells, small, round, or oval cells occur, sometimes in small nests (Watney).

Gastric glands. — ;As was first shown by Sprott Boyd, the surface of the stomach
within the depressions above mentioned is dotted with small round apertures, which
are the openings of minute glandular tubules, placed perpendicularly to the surface.
On making a vertical section of the membrane, and submitting it to microscopic
examination, it is seen to consist almost entirely of these small tubules, arranged
parallel with each other (fig. 91). Each mouth or duct, together with the tubules
which open into it, constitutes a r/astric gland.

Some of the glands may be simple, consisting of a single tubule throughout, but
most are cleft into two or three tubules, or even, by the branching of these, eventually
into six or eight. The glands have externally a basement membrane, composed of
flattened cells joined edge to edge, and with processes which on the one side join the
retiform tissue of the mucous membrane, and on the other side, more delicate, extend
in amongst and support the enclosed epithelium cells.

Two kinds of glands are distinguished, which differ from one another both in
the character of the enclosed cells, and, it is believed, in the nature of their secre-
tion. Those of the one kind (fig .94) are simpler in structure than the others,
and being found most numerously in the pyloric region, they have been named
pyloric glands. These are distinguished by the large size and depth of the gland-
mouth as compared with the tubules which open into it, and by the character of

THE STOMACH.

the epithelium lining the tubules. The mouth of the gland is lined throughout
by an epithelium which is continuous with and similar to the columnar epithelium
which covers the general surface of the stomach. But in the tubules of the gland
the lining cells are shorter and more cubical, and are uniformly finely granular
throughout ; moreover, they are filled with secretion of a different nature from that of
the surface epithelium.

Amongst the cells of these glands there are occasionally found others which are
characterised by becoming darkly stained with osmic acid (Nussbaum). They have

'Ji. — A PYLORIC GLAND, FROM A SECTION OP THE COO'S

STOMACH. (El)stein. )
?/i, moutli ; n, neck ; tr, a deep portion of a tubule cut transversely.

Fig. 95. — A CAKDIAC GLAND OF SIMPLE FOKM, FROM THE BAT's STOMACH. (Langley. )

Osmic acid preparation, c, columnar epithelium of the surface ; ??., neck of the gland with central
and parietal cells ; /, base or fundus, occupied only by principal or central cells, which exhibit granules
accumulated towards the lumen of the gland.

been supposed to represent the jjarietal cells of the cardiac glands (see below), but
this is probably not the case.

In the glands of the second kind (figs, fl], Dr>, 90)— which may be termed, from
the portion of the stomach where they occur most numerously, the cardiac (jlaiuh *
(fundua n lands o^ Jleidenhain, oxynlic^ (jiands of Langley) — the mouth, or part
lined with epithelium like that of the surface, is comparatively short, and into it
open two, three, or more tubules, which are lined throughout and almost filled with
short columnar or polyhedral cells ; these cells are in most respects similar to the

* This name lias, however, been also applied to certain glands situated close to the rardia which
contain no parietal cells. These glamls were first fiescribed in the Kangaroo (Schiifer and Wiii'anis,
Proc. Zooi. Soc, Londrui, .Jan. 18, 187*>), and they iiavc since been shown to occur in man and all
inammals nvleltnann, Jnaug. Diss., Kostoek, 1889), .See also (Jjipel, Vergleich. mikr. Anat. der
Wirbelthien-, Jena, \H'.iC,).

t From d^us, acid ; since they contain tlic cells which are Iielieved to produce the acid of the gastric
•ecretion.

OUGANS OF DIGESTION.

secreting cells of the pyloric glands, out are much more coarsely granular. They
were termed by Heidenhain the pindpal cells of the glands ; they are also known
as the central cells. Between these cells and the basement membrane of the tubule
other cells of a different nature are interpolated in the cardiac glands. These are the

Fig. 96. A CARDIAC GLAND FROM THE DOG's

STOMACH. (Klein and Noble Smiths.)
Highly magnified.

d, duct or mouth of the gland ; h, base
or fundus of one of its tubules. On the
right the base of a tubule more highly mag-
nified ; c, central cell ; p, parietal cell.

superadded, parietal, or oxyniic cells.
They were long thought to be the
only cells of the cardiac glands, and
were on that account known as

THE LUMEN
SILVER. (E.

Fig. 97. — A GASTRIC GLAND
SHOWN BY CHROMATE 0

Muller. )

The cells are not represented, but the ex-
tension of the lumen into the network
surrounding the parietal cells is well shown.

"peptic cells," a term which must
now be entirely discarded.

The parietal cells are rather more
closely arranged in the neck of the
gland than elsewhere. They usually cease abruptly at the upper part of the neck, but
occasional cells may be found under the columnar epithelium of the mouth or
even of the general surface. In the human stomach they are only absent from the
glands which are quite near the pylorus.

THE STOMACH.

In some animals (porpoise, pig) the parietal cells lie each in a special pit formed by baes-
ment membrane, and communicating with the rest of the gland only by a narrow orifice. In
the glandular stomach of birds they line secondaiy tubules which lead out of the main tubule,
this alone being lined by jirincipal cells. In the frog and other amphibia the cardiac glands

Fig. 9S. — Cross-section of cardiac

GLANDS FROM THE HUMAN STOMACH,
SHOWING THE CONDITION OF THE

CELLS DURING FASTING. (Bohm and
V. Davidoff.) ^^

c, centr.il cell ; I, lumen of gland ;
p, parietal cell ; t, connective tissue
between glands.

have only parietal or oxyntic cell? >
the principal cells being altogether
absent, but glands containing cells
which are similar in appearance and
function to the principal cells of the
stomach are found in the oesophagus.

The parietal cells have a finely
granular appearance in the fresh
condition, but in the gland hardened
in alcohol are much darker and more
granular-looking. This appearance

is due, according to Klein, not to the presence of actual granules within the cells, but to the
existence of a close and uniform intracellular network (fig. 9(i). They are more readily'
stained than the principal cells.

Fine intercellular passages extend from the lumen of the gastric glands between the
lining epithelium celk, and in the case of the cardiac glands these passages pass to the parietal
cells and invest them with a pericellular network (E. Miiller) (fig. 97).

Pig. 99. — CbCSS-SECTION op cardiac glands from the human stomach, showing the CONDITION OF

THE cells during DIGESTION. (liiihrn and v. Davidolf.) ^-j-i!
(References as in Fig. 98. )

'ITie cells of the gastric glands undergo changes during the functional activity of the
organ which are Ktrictly compai-iible to the changes that have been described in the cells of the
KerouH salivary glands. The principal cells of the cardiac glands are enlarged and almost fill
the lumen of the tubule in the intervals of digestion, and in this so-called '• resting" or " loa<led "
w>ndJtion they are in some animals granular throughout, wliih; in oth(!rH there is a small outer
w>ne clear of granules. IJut they become Hinallcr and distinctly differentiated into two zones
during a^jtivity, some of the g^ranuled becoming disHolved and discharged with the secretion,

Vol hi., VI. 4. 0

OKGANS OF DIGESTION.

and the rest tending towards the lumen of the gland so as to leave the outer half or third of
the cell clear of granules (fig. 95). After digestion has ceased the outer parts of the cells
become again partially or wholly occupied by granules (Langlej')- On the other hand the
parietal cells of the cardiac glands are smaller during fasting, and are then angular in form
(fig. 98). During digestion, on the other hand, they becom-e enlarged and more spheroidal,
bulging out the tunica propria of the glands (fig. 99).

Heideaihain first showed that both the central cells and the parietal cells undergo a change
of size during digestion, becoming at first enlarged and subsequently shrinking to less than
their volume during rest. The changes occur later in the parietal than in the central cells.

The secreting cells of the pyloric glands undergo changes which are similar to those of the
central cells of the cardiac glands (Ebstein).

Between the glands and at their base the mucous membrane consists of delicate
connective tissue with retiform lymphoid tissue in small amount.

A thin layer of plain muscular tissue {muscularis mtccosce, fig. 91, vi.m.) bounds

Fig. 100. — Section through the

COATS OP THE STOMACH TO
SHOW THE ARRANGEMENT OP
THE PRINCIPAL BLOOD-VES-
SELS, (Mall.)

On the right side of the figure
the glandular and muscular ele-
ments are shown ; on the left only
the blood-vessels. It will be seen
that the principal vessels are in
the submucous tissue, and that
from these, branches are distrib-
uted to the mucous membrane and
to the muscular coat.

the mucous membrane ex-
ternally, separating it from
the submucous tissue. It
consists of more than one
stratum (an outer longitu-
dinal and an inner circular),
and is better marked in
some animals than in man.
Offsets pass from it between
the gastric glands towards
the surface of the mucous
membrane.

Lymphoid Follicles.
— The stomachs of young
persons sometimes present
a mamillated aspect, due
to little elevations of the
surface, which are pro-
duced by local accumula-
tions of lymphoid tissue, and somewhat resemble the solitary follicles of the
intestine in appearance. The lymphoid accumulations in question are situated
amongst the glands, and do not extend into the submucous tissue ; they are
not so distinctly circumscribed as those of the intestine, but fade off into the
surrounding retiform tissue. They are most numerous near the junction of the
stomach and small intestine (Watney). They vary in development in different
individaals, and are sometimes not to be found at all.

Vessels and Nerves. — The stomach is a highly vascular organ. Its arterial
branches, derived from all three divisions of the coeliac axis, reach the stomach

THE STOMACH.

8:5

between the folds of the peritouenm, and form, by anastomosing together, two
principal arterial arches, which are placed along its two curvatures. Their branches
pass through the muscular coat (to which in passing they give off some arterioles)
and divide into smaller vessels in the submucous areolar tunic, where they also
freely anastomose, and whence they are distributed to the mucous me mbrane and to
the muscular layers. The arterial branches (fig. 101, a) which enter the mucous
membrane, pass between the tubuli, ramifying freely in a radial manner ; here
they form a plexus {(I) of fine capillaries upon the walls of the tubules ; and from
this plexus larger vessels pass into a coarser capillary network around the mouths of
the glands. The veins, fewer in number than the arteries, arise from the latter
network, and take an almost straight course (c, c) through the mucous membrane
between the glands and join to form a plexus of larger vessels near the bases of the
glands. From this plexus branches pass off, which, after piercing the muscularis
mucosae and forming a wide venous plexus in the submucous tissue, return the

Fig, 101. — Plan op the blood-ves.?els of the mucous membranf, of the stomach.
(Modified froiu Brinton.)

«, small arteries passing to break up into the fine capillary network, d, between the glands ; />,
coarser capillary network around the mouths of the glands ; c, c, veins passing vertically downwards
from the superficial network ; e, larger vessels in the suljmucosa.

Pig. 102. — LVSIPHATICS OF THE HUMAN GASTRIC MUCOUS MEMBRANE, INJECTED (frOm Loven).

The tubules are only faintly indicated ; a, muscularis mucoste ; I), plexus of fine vessels at base of
glands ; c, plexus of larger valved lymphatics in submucosa.

residual blood into the splenic and superior mesenteric veins, and also directly
into the vena portaj. These veins, as well as other tributaries of the vena })orta,
have a particularly \vell-marked muscular coat, and contain numerous valves
(Ilochstetter).

'J'he lymphatics are very numerous. As shown by Lovcn, they arise in the
mucous memljrane dig. 102) by a dense network of lacunar spaces, situated between
and amongst the gland-tubuli, which, as well as the blood-vessels, in many paits
tliey enclose in sinus-like dilatations. Near the surface of the membrane the lymph
is collected into vessels which form loops or j)os,sess dilated extrenn'ties : these
vessels are less superlir;ial than *Jie blood capillaries. At the deeper part of the
mucous membrane the interglandular lymphatics pass into a jilexns of fine
vesKcls (//j, imm(;diately underlying the tubular glands ; tlicii i)i(!iriiig tlw;
rau.scularis mucosae (a), they form a coarser, nicjre deeply-seated network (() in the

(i 2

ORGANS OF DIGESTION.

submucous coat, the vessels of this network being provided with valves. Thence
efferent lymphatics proceed, and, piercing the muscular coats, follow the direction of
the blood-vessels beneath the peritoneal investment, and traverse lymphatic glands
found along the two curvatures of the stomach.

The tierves, which are large, consist of the terminal branches of the two pneumo-
gastric nerves, belonging to the cerebro-spinal system, and of offsets from the
sympathetic system, derived from the solar plexus. The left pneumo-gastric nerve

Fig. 103. — View of the pylorus and duodenum from
BEFORE. The stomach and duodenum have been

DISTENDED AND HARDENED IN SPIRIT, AND THE GREATER
PART OP THE STOMACH THEN CUT AWAY. (Slightly

altered from Luschk a.) 5

12, the twelfth dorsal vertebra and rib ; 1, 3, 4, 5, trans-
verse processes of the tirst, third, fourth, and fifth left lumbar
vertebrae ; 2, that of the second on the right side ; a, a, the
abdominal aorta above the cceliac axis and also near the
bifurcation ; m, superior mesenteric artery ; v, v, the vena
cava above the renal veins and near the bifurcation ; p, placed
on the first part of the duodenum, points to the pyloric
orifice seen from the side next the stomach, of which a small
part is left connected with the intestine ; d, on the descend-
ing part of the duodenum, indicates the termination of the
common bile-duct and the pancreatic duct ; d', the ascending
Ijart of the duodenum ; j, the commencement of the jejunum.
(This is represented as drawn over to the left, instead of
curving forward, as is actually the case.)

descends on the front, and the right upon the back of the stomach, and both
nerves are here composed almost entirely of non-medullated nerve-fibres. Numerous
small ganglia have been found by Eemak and others on both the pneumo-gastric and
sympathetic twigs. The nerves form gaugliated plexuses (like the plexuses of
Auerbach and Meissner) of the intestine, both between the layers of the muscular
coat and in the submucous coat. From these plexuses nerve-fibrils proceed to the
muscular tissue and to the mucous membrane.

The Pylorus. — While there is no special apparatus at the cardiac orifice of the
stomach for closing the passage from the oesophagus, the opening at the pyloric

Fig. 104. — Section through pyloric part op

STOMACH AND COMMENCEMENT OF DUODENUM,
FROM A SPECIMEN HARDENED IN SITU. (J. S. ) \

a, a, a, longitudinal folds of the mticous mem-
brane in pyloric part of stomach ; b, section of
mucous membrane ; c, circular muscular fibres of
stomach : the longitudinal fibres are just visible to
the naked eye as a narrow line external to the
circular fibres ; d, duodenum ; p, pyloric orifice.

end, leading from the stomach into the
duodenum, is provided with a sphincter
muscle. On looking into the pyloric end
of a distended stomach, the mucous membrane is seen projecting in the form
of a circular fold, called the pylorus, leaving a correspondingly narrow opening.
Within this fold are circular muscular fibres, belonging to the general system
of circular fibres of the alimentary canal, which are here collected in the form of
a strong band, whilst the longitudinal muscular fibres and the peritoneal coat
pass over the pyloric fold to the duodenum, and do not enter into the forma-
tion of the sphincter (fig. 104, p ; fig. 105). Externally the pylorus may be
easily felt, like a thickened ring, at the right end of the stomach, where also a

THE STOMACH. 85

slight external constriction is visible. Internally its opening is usually circular,
and even when the stomach is artificially distended after death it measures less than

Fig. 105. —Diagrammatic view in perspective of a portion

OF THE COATS OF THE STOMACH ANT) DUODENUM, INCLUDING

THE PYLORUS. (Allen Thomson.)

g, the innei' surface of the gastric mucous membrane ; rj',
section of the mucous membrane with the pyloric gastric
glands ; v, the villous surface of the mucous membrane of
the duodenum ; i, section of the same with the intestinal
glands or crypts of Lieberkiihn : j) P, the ridge of the pyloric
ring, with a section of its component parts ; mi, doep or cir-
cular layer of muscular fibres : these are seen in the section to
form the pyloric sphincter ; mc, external or longitudinal layer of muscular fibres ; s the serous
covering. '

half an inch (12 mm.) across, so that it is the narrowest part of the whole alimentary
canal.

Occasionally the orifice is oval, and it is often placed a little to one side.
Sometimes the circular rim is imperfect, and there are found instead two crescentic
fulds, placed one above and the other below the passage (Huschke) ; and, lastly,
there is occasionally but one such crescentic fold.

When the sphincter is contracted the longitudinal fibres covering it are bowed
inwards, and these, if they contract at the same time that the sphincter muscle
relaxes, will tend to dilate the orifice.

RECENT LITERATURE OF THE STOMACH.

Aufschnaiter, O., Die Muslcelhuut d. menschl. Magcns, Sitzungsb. d. Wiener Akad., Bd ciii
1894.

Bizzozero, G., Ucljei- die schlauchformigen Driisen des Magcndarmlanah und die Bc-.ichnigeii
ihres Epithets zu dem OberHachenepithel der i^'chleimhaut, Ai-chiv f. mikroskop. Anat., I'.d xxxiii
1889 ; Bd. xl, 1892; and Bd. xlii, 189-3.

Capparelli, Andrea, Die nervosen Endigungen in der Magcnschlcimhaut, Biolog. Centralbl.,
1891.

Contejean, Ch., Sur les fonctions des cellules des glandes gasiriques. Archives de physiol.
norm.ib; ct [latholog., 1892.

Golgri, C. , 8ijr la fine organisation drs glandes peptiques des mammiferes, Arch, italiennes de
biologic, t. xxi, 189:5.

GubaroflF, A v., f'eber den Verschliiss des mensc/ilichen Magens an der Cardia, Arcliiv f.
AriaViiii. u. riiysiol., Anatom. Abt., Jahrg. 1886.

Hamburg-er, Ernst, Britrdge znr Kenntniss der Zellen in den Magendrilscn, Archiv fiir
mikroskop Anat., l!d. xxxiv, 1889.

Lang-endorff, O. , und Laserstein, S., Die feineren Ahsonderungsvcge der Magmdrusen,
Aich. f. d. gfcs. Physiol., lid. Iv, 1891.

Lesshaft, P., Ueber die Loge des Magens und ueber die Beziehungen si incr Form und seiner
Fuiirtioii. Arch. f. pathol. Anat., 1882.

Martins, F. , Ucber O'rfjsse, Lage u. Bcweglichkeit d. gtsvnden u. Iranlen vicvschi. Magens,
Wiener njcd. IJIattor, xvii, 1894.

Miiller, E. , Zur Kfinitniss dxr Labdriisen der MagenscIdcimhatU, Biolog. Forens. Forhandl.,
SUwkholm. 1891-92, Jahig. iv.

V. Openchowski, Th., Ueber die gesammte Innervation des Magens, Deutsche mcdicin.
WiK.'hcns<;h., 1889.

Ost, A., Beitrdge zur Bcstimmung der (Joparitnt des Magens, Di.ss., Dorpat, 1891.

Pilliet, A., Sur I'ivotulion des cellules glanduluires de Icstoniac chcz I'homme it les vtrtcbn's,
Journal de ranatoiiiie, 1887.

Beynier et Soulig^oux, Direction de Vestomac, Bull. soc. anat., Paris, 1891.

Schmidt, M., Zv, d/r Anatomie drs Magens tim. Libcnden und der Diagnose der Dihit'tlio
rtii/riru/i, l'.<.rliner kliiiihche WochenK-lirift, .lalirg. xiii, ]8«(i.

Stein, C, Ueber das Ver/iulten des liivdegrvebcs zu din dcfomoyp/u n Zi//in tier M(ig< ndrusen,
Mitl<;il. auH i\. embryo). IiiKtit. dor Universitiit Wien, 1892.

Windle, B. C. A., On t/ic saceulation oj the human stovuich, Proc. of the liiiiiiingliiiiu Pliilosopli.
Soc., vol. V, IviSO.

86 OEGANS OF DIGESTION.

THE SMALL INTESTINE.

The small intestine commences at the pylorus, and, after many convolutionSj
terminates in the large intestine. It measures, on an average, about 22 feet in
length in the adult, and becomes gradually narrower from its upper to its lower end.
Its convolutions occupy the middle and lower parts of the abdomen, and also
frequently descend into the pelvis.

The small intestine is divided into three portions, which have received different
names. The first ten or twelve inches immediately succeeding to the stomach, and
comprising the widest and most fixed part of the tube, is called the duodenum.
This part is further distinguished by its close relation to the head of the pancreas,
and by the absence of a mesentery. The remainder, which is arbitrarily divided
into an upper two-fifths called the jejunum, and a lower three-fifths called the ileum, is
very convoluted and movable, being connected with the posterior abdominal wall by
a long and extensive fold of peritoneum called the mesentery, and by numerous
blood-vessels and nerves. Although there is no distinct line of demarcation between
the jejunum and the ileum, yet the portion of the small intestine included under
these two names gradually undergoes certain changes in structure and appearance
fi'om above downwards, so that the upper end of the jejunum can readily be
distinguished from the lower part of the ileum.

STRUCTURE OF THE SMALL INTESTINE.

The small intestine, like the stomach, is composed of four coats, viz., the serous
or peritoneal, muscular, areolar, and mucous.

The external or serous coat almost entirely surrounds the intestinal tube in the
whole extent of the jejunum and ileum, leaving only a narrow interval behind,
where it passes off and becomes continuous with the two layers of the mesentery.
The line at which this takes place is named the attached or mesenteric dorder of the
intestine. The duodenum, on the other hand, is but partially covered by the
peritoneum.

The muscular coat consists of two layers of fibres ; an outer longitudinal, and
an inner or circular set. The longitudinal fibres constitute an entire but com-
paratively thin layer, and are most obvious along the free border of the intestine.
The circular layer is thicker and more distinct.

j The muscular tunic becomes gi'adually thinner towards the lower part of the
small intestine. It is pale in colour, and is composed of plain muscular tissue, the
cells of which are of considerable length. The progressive contraction of these
fibres, commencing in any part of the intestine, and advancing in a downward
direction, produces the peculiar vermicidar or jjeristaltic movement by which the
contents are forced onwards through the canal. In the narrowing of the tube the
circular fibres are mainly concerned, the longitudinal fibres tending to produce
dilatation (Exner) ; and those found along the free border of the intestine may have
the effect of straightening or unfolding its successive convolutions. There is a
gangiiated plexus of nerve-fibres and a network of lymphatic vessels between the
two muscular layers.

The submucous coat of the small intestine is a layer of areolar tissue of a
loose texture, which is connected more firmly with the mucous than with the
muscular coat. "Within it the blood-vessels ramify before passing to the mucous
membrane, and there is a gangiiated plexus of nerve-fibres and a network of large
lymphatic vessels.

THE SMALL INTESTINE.

The iuteraal coat or mucous membrane is characterised by the finely flocculent or
shaggy appearance of its inner surface, resembling the pile upon velvet. This appear-

Fig. 106. — Diagram showing thk position op thk rnoRAcic and abdominal organs.
(llauher alter LuscJika.)

1, Lower borrler of tlic riglit lung ; 2, the same of the left lung ; ',', liver, ri;;I)t lobe ; 4, liver, left
lol)c ; 5. BUHjjcnsory ligament of the liver ; fi, fundus of gail-iiladder ; 7, cai'dia of stomach ; 8, fundus
ofhtomach ; 9, lower border of stomach ; 10, iiotition of pylorus ; 11, cicsum ; 12, vermiform apiiendix ;
13, ascending wlon ; 14, right flexure of colon ; If), transverse colon ; IG, iiosition of left flexure of
colon ; 17, descending colon ; 18. portion of sigmoid colon, concealed by 19, coiivolutiiins of the small
int«!«tine ; 20, termination of ileum, ascending from left to right ; 21, ijladder, distended, partly
covered by peritoneum ; 22, the part of the bladder which i« not covered by peritoneum.

ance i« due to the surface being thickly covered wiMi minute proccgses named vil/i. It is
one of the most vuHCuiar membranes in the liody, :ind is naturally (^f a reddisii

ORGANS OF DIGESTION.

colour in the upper part of the small intestine, but is paler, and at the same time
thinner, towards the lower end. It is lined with columnar epithelium throughout
its whole extent, and next to the submucous coat is bounded by a layer of plain
muscular tissue {miiscularis mucosa) ; between this and the epithelium the sub-
stance of the membrane, apart from the tubular glands which will be afterwards
described, consists mainly of retiform tissue which supports the blood-vessels,
nerves, and lymphatics (lacteals), and encloses in its meshes numerous lymph-
corpnscles.

Fig. 107. — Portion of small intestine distendel

WITH alcohol and LAID OPEN TO SHOW THE

VALVDL.E conniventes. (Brintoii.)

ValvulsB conniventes. — The mucous
membrane, in addition to small efFaceable
Ibids or rngge, possesses also permanent
folds, which cannot be obliterated, even
when the tube is forcibly distended.
These permanent folds are the valvulm
conniventes or valves ofKerlcrmg. They are crescentic projections of the mucous mem-
brane, placed transversely to the axis of the bowel and following one another closely.
The majority of the folds do not extend more than about one-half or two-thirds
round the interior of the tube, but it has been shown by Brooks and Kazzander that
some form complete circles, and others spirals. The spiral forms may occur singly
or in groups of two or three. They generally extend a little more than once round
the bowel, but in rare cases may go round two or three times. At their highest
point they project inwards for about a third of an inch. Some of the valvulge
conniventes are bifurcated at one or both ends, and others terminate abruptly.
Each consists of a fold of mucous membrane, that is, of two layers placed back to

Fig. 108. — Small portion of the surface of

THE mucous membrane OF THE SMALL IKTES-

TINE. (Rauber.) -^
1, mouths of lirypts of Lieberkiilin ; 2, villi.

back, and united together by submucous
areolar tissue. They contain no part of
the circular or longitudinal muscular
coats. Being extensions of the mucous
membrane, they serve to increase the
absorbent surface to which the food is
exposed.
The valvulae conniventes are not uniformly distributed over the various parts of
the small intestine. There are none quite at the commencement of the duodenum ;
a short distance from the pylorus they begin to appear ; beyond the point at which
the bile and pancreatic juice are poured into the duodenum they are very
large, regularly crescentic in form, and placed so near to each other that the
intervals Detween them are not greater than the breadth of one of the valves ; they
continue thus through the rest of the duodenum and along the upper half of the
jejunum ; below that point they begin to get smaller and farther apart, and finally,
towards the middle or lower end of the ileum, having gradually become more
irregular and indistinct, sometimes even acquiring a very oblique direction, they
altogether disappear.

The villi, peculiar to the small intestine, and giving to its internal surface

THE SMALL INTESTINE.

_ fpitlidium of

till IIS.

connective tis-
sue of villus.

cpitheliuiii of
c ill us.

»^ r/oblet cell.

cri/pt of
Lieherkiikn.

connective tis-
sue at base of
[/lands.

musculai-is
mucosce.

the velvety appearance already
spoken of, are small processes of
the mucous membrane, which
are closely set on every part of

Fig. 109. — Section uf the human
intestinal mucous membrane
(': child), showing three villi
with crypts op lleberkuhn.
(Bohm and v. Davidoff. ) -*^

the inner surface over the valvulte
conniventes, as well as between
them.

Their length varies from
0"u mm. to 0*7 mm., or some-
times more. They are largest
and most numerous in the
duodenum and jejimum, and
become gradually smaller, and
fewer in number in the ileum.
According to Rauber, they are
short and leaf-shaped in the
duodenum, and as the gut is
followed downwards they become
gradually longer and thinner, so
that they are tongue-shaped in
the jejunum, and filiform in
the ileum. Occasionally two or
three are connected together at their base. In the upper part of the small
intestine there are from 10 to 18 villi in a square millimeter, and in the ileum from
8 to 14 in the same space. This would give about i millions altogether (Krause).

Fig. 110. — Part of a section
through a villus of the
Doo, highly magnified.
(R. Heidcnhain.)

m, 771, muscular fibres ; I, I', I",
lymijli-corpuscles ; U, blood-ves-
sels ; c, branf^hed connective tissue
corpuscles, covering the reticular
fibres. Theeiiithelium of the villus
is not represented.

Chaput describes the villi
as l>eintf so closely arranged as
to be separated merely by
narrow clefts into which the
crypts of Lieberkiihn open.
This may be the case in the
empty condition of the in-
testine, but when it is dis-
t/-nded they are necessarily
more separated from one
another as usually described.

A villus consists of a
prolongation of the proper
mucous membrane. It is
'overed by columnar epi-
Lhelium (lig. Ki'.);, and en-

ORGANS OF DIGESTION.

closes a network of blood-vessels, one or more lymphatic vessels (lacteals), and a few
longitudinal plain muscular fibre-cells, these being all supported and held together by
retiform lymphoid tissue. Under the epithelium is a basement membrane composed of
flattened cells, which on the one hand are connected with the branched cells of the
retiform tissue, and on the other hand send processes between the epithelium-cells.
Nervous fibrils penetrate into the villi from the plexus of Meissner, and form arbori-
zations throughout their whole substance (fig. 130, p. 99). Each villus receives, as a
rule, one small arterial twig, which runs from the submucous coat through the mus-

Fig, 111. — Magnified view of the

BLOOD-VESSELS OF THE INTESTINAL

VILLI. (Sharpey. ) ;

The drawing was taken from a pre-
Ijaration injected by Lieberkiihn, and
shows, belonging to each villus, a small
ai'tery and vein with the intermediate
capillary network.

cularis mucosae to the base of the
villus, and then up the centre to
near the middle of the villus,
where it begins to break up into a number of capillaries (fig. 111). These
form near the surface, beneath the epithelium and hmiting membrane, a fine
capillary network, from which the blood is returned for the most part by one
or two venules, wiiich in man commence near the tip of the villus, and pass
down to its base to join the venous plexus of the mucous membrane, whence
the blood is conveyed to the large veins of the submucosa. The general
arrangement of the vascular supply of the villi varies considerably in diflFerent
animals.

Fig. 112. — Cross section op a villus of
THE cat's INTESTINE. (Highly magni-
fied.) (E. A. S.)

€, columnar epithelium ; //, goblet cell,
its Tiiucus is seen partly exuded ; I, lymph -
corpuscles between the epithelium cells ; b,
basement membrane ; c, blood-capillaries ;
m, section of plain muscular fibres ; c.l.,
central lacteal.

The lacteal lies in the centre of
the villus (figs. 112, 113, 114), and
is in the smaller villi usually a single
2 vessel, with a closed and somewhat

expanded extremity, and of con-
siderably larger diameter than the
According to the observations of Teich-
mann, there are never more than two intercommunicating lacteals in a single
villus in the human subject (fig. 113, h) ; but both he and Frey found a copious
network in the villi of the sheep. Like the lymphatics elsewhere, the lacteals in
the villi are bounded by a delicate layer of flattened epithelial cells. These are
connected with the branched cells of the tissue of the villus (fig 110, c), and
these again with the flattened cells which form the basement membrane ; from
the latter, prolongations extend between the epithelium-cells towards the surface.

The muscular tissue within the villus was discovered by Briicke ; it consists
of a thin stratum of plain fibre-cells disposed longitudinally around the lacteal ;
on being stimulated in animals they produce an obvious retraction of the villus.

capillaries of the blood-vessels around.

THE SMALL INTESTINE.

This muscular tissue is a prolongation from the musculoris mucosa. The fibre-
cells at the sides and towards the end of the villus pass from the lacteal to be

-Injected lacteal vessels in two villi dp tiii; iir^iAN intestine.
100 DIAMETERS. (Teicliiiianii. )

The lacteals are represented as filled with white substance and the blood-vessels with dark, n, h,
the lacteal vessels, single in one villus and double in the other ; c, the horizontal lacteal vessels with
which those of the villi communicate ; d, the blood-vessels, consisting of small arteries and veins with
capillary network between.

Fig. Hi. — Vertical section oe the intestinal mucous membrane of the rabbit.
(Slightly altered from Frey.) ^^

Two villi are represented, in one of which the dilated lacteal alone is shown, in the other the lijood-
vcssels and lacteal are both seen injecteJ, the lacteal white, the blood-vessels dark : a, the lacteal
vessels of the villi ; a', horizontal lacteal, which they join ; h, capillary blood-vessels in one of the
villi ; c, small artery ; d, vein ; e, the epithelium covering the villi ; r/, tubular glands or crypts of
Lieberkiibn, some divided down the middle, others cut more irregularly ; ?', the submucous layer.

A, cross section of three tubular glands more highly magnified.

attached to the basement membrane (fig. IK), m. m.) ; usually their attacliinent to
this is forked, a connective tissue corpuscle filling up the interval (Watuey).

A. B.

Fig. 115. — Columnar ei-itiiklicv cells "e the rabbit's intestine. (E. A. S.)

A. Two cells isolated after maceration in very weak chromic acid. They are much vacuolated,
and one of them (2) has a fat-gloiiulc attached near its end ; the striated border («<;•.) is well seen, and
the bri},'ht <li«k separating this from the cell-protophiHin ; n, nucleus with intranuclear network ; a, ii
thinned out wing-like jjrfijection of the cell which ijrobably fitted between two adjacent cells.

15. A row of columnar cells from an iotcstinal villus of the rabbit, atr, striated bordci' ; tr. .smaller
cells of the nature of lymph-corpuscles, between the epithelium cells.

Columnar epithelium cells (figs. Kil), 1 \-l, W'y) cover not only the villi Imt iilso
the rcHt of the Kurfuce of the intestine, and extend into the tuljulai' glands. Their
general characters have already beeu described under the head of " Epithelium" (see
Vol. I., Part 2, }.]). J'J:J, riOO).

OKGANS OF DIGESTION".

ep sbf

They are set upon the surface of the basement membrane often by a somewhat
flattened extremity. There is never any continuity between their attached
extremity and the branched corpuscles of the retiform tissue of the villus, such
as has often been supposed to exist ; on the contrary, the epithelium separates
with the greatest readiness from the subjacent tissue, and almost always with a
simple truncated extremity, sometimes pitted but never much branched. Between

Fig. 116. — Section of part of a rat's

VILLUS DURING ABSORPTION OF FAT.

(E. A. S.) Osmic acid preparation.
Highly magnified.

ep, epithelium, filled with fatty particles ;
str, striated free border ; c, lymph-cor-
puscles in the tissue of the villus, containing
fatty particles ; c', others between the epi-
thelium cells ; I, central lacteal, containing
chyle and disintegrating leucocytes.

the epithelium cells are leucocytes
in variable number, but most nu-
merous in the lower part of the
intestine and near the lymphoid
follicles. They often show indica-
tions of division by karyokinesis.
They may lie free in small (lymph)
spaces between the columnar cells.

There is frequently a well-marked
layer of granular eosinophil cells im-
mediately below the epithelium of
the villi (Hardy).
Amongst the ordinary epithelium cells are others (fig. 112, g), the outer half
of which is filled with mucigen, and in some this has become discharged as
mucus from the cell, and the free end is ruptured (goblet cells, see Vol. I.,
Part 2, p. 200). The number of cells containing mucus varies much in different
animals, and perhaps, under different conditions, in the same animal. There are
comparatively few in the glands of the small intestine. The epithelial cells are
in all probability the primary agents in promoting the absorption of the food
materials from the interior of the gut, and the seat of the retrograde processes of

Fig. 117. — Section op frog's intestine during absorp-
tion OF FAT. (E. A. S.) Osmic acid preparation.
Highly magnified.

ep, epithelium ; str, its striated border ; I, lacteal ;
c, c, lymph-corpuscles containing fine fatty particles.
The fatty particles in the epithelium cells are coarse in the
peripheral and fine in the central zone of each cell.

metabolism which the products of digestion
undergo during absorption. Most food materials
cannot be traced in microscopic specimens, but
fatty substances, from their property of becom-
ing stained with osmic acid, can be to some extent followed. The examination of
such specimens taken during digestion of a meal containing fat shows the
epithelium cells turbid with oil-droplets in their interior ; and in some animals
(frog, rat), at a subsequent stage amoeboid cells within the tissue of the villus
appear pervaded with similar but finer fatty particles, and eventually the central
lacteal becomes filled with these. It is probable that the amoeboid lymph-corpuscles

THE SMALL INTESTINE.

which are found so abundantly within the tissue of the vilhis, and even amongst
the epithelium-cells of the surface, play an important part in the transference of
such particles from the epithelium-cells to the lacteal, for at certain stages of fat
absorption they contain abundant fatty particles, and the large amount of lymphoid
tissue in the lower end of the small intestine seems to be related to a greater power
of absorption in that part of the gut. In the transference of carbon particles
in the lungs from the interior of the alveoli to the lymphatics, which at least in
part is due to the activity of amoeboid cells, we have an analogous process.

In other animals (dogs) the absorption of fat appears to occur in a fluid form,
and here we see darkly stained streaks extending from the inter-epithelial spaces
to the borders of the central lacteal.

It has been denied by Heidenhain that the lymphoid cells of the intestine contain fatty
particles during fat absorption : he states that the particles within them which are stained
black by osmic acid are not fatty but albuminous, being insoluble in ether. This is, however,

Fig. 119. — Lymphoid or retiform tissue op the intestinal mucous membrane of the siilep
(from Fre^. Magnified 400 diameters.

Cross section of a small fragment of tlie mucous membrane, including one entire crypt of Lieber-
kiihn and parts of several others : a, cavity of the tubular glands or crypts ; /', one of the liidng
epithelial cells ; c, the lymphoid or retiform spaces, of which some are empty, and others occupied by
lymph-cells as at d.

not correct. !Many of the particles which the lymph-cells contain durinj,"- fat absorption
unquestionably dissolve in ether and other solvents of fat, although there are some cells which
contain particles which are undissolved by those re-a;.ronts. These may be of an albuminous
nature, or they may still be fatty, but so modified by the action of the osmic acid as to have
been nmdered insoluble in ordinary fat solvents. In the frojj, where absorption proceeds
more slowly, and can be more easily traced, no fat is to be seen anywhere but in tlie eiiithelium
cells, in the leucocytes, and in the lacteals. In the guinea-pig also, as Heidenhain has himself
shown, amoeboid cells take up the whole of the absorb;;!! fat, after it has traversed the epithe-
lium. In other animals absorption may take place so rapidly that the absorbed fat, after being
finely divided and modified in the epithelium cells, may be set free between them without all
being immediately taken up by leucocytes. Eventually, however, most of it appears to be
removed by these cells. The agency of the epithelium cells in fat absorption has been denied
(Watney, Zawarykin), but on entirely insufficient grounds, for the absorbed fat is very easily
shown within those cells.

Glands. — Two kinds of small secreting glands open on the inner surface of the
intestine, viz., the crypts of Lieberkiiliu, and Urunner's glands, the last being
jx.'cniiar to the duodenum. \\\ addition to these, numerous lymphoid nodules are
found, which are either scattered and isohitcd (solitary glands) or colle(;ted into
patches (Teyer's glands).

Tlie crypts of Lieberkuliu, the smallest but iiKjst numerous of these glandular
structures, are found in every part of the wnflll intestine, opening on the surface

ORGANS OF DIGESTION,

between the villi (figs. 109, 114, 118, 119). They consist of minute tubes, closed
at their attached extremity, which is slightly enlarged, and placed more or less per-
pendicularly to the surface, upon which they open sometimes two or three together.
The crypts of Lieberkiihn vary in length from 0*2 to 0*3 mm., and their diameter is
about 0*04 mm. They are longest in the duodenum. The walls of the tubes are
formed of a basement membrane, lined with a columnar epithelium (fig. 119), the
deepest cells of which — those, that is to say, at the fundus of the glands, are in
some animals filled with granules (Paneth). Goblet-cells occur here and there
amongst the ordinary cells.

Althoug-li it is usually believed that mucus-secreting or goblet cells may be formed from
any of the columnar epithelium cells of the intestine, it would appear from the observations
of Bizzozero, that the granules of the cells of the gland-fundus are mucigen -granules, and that
it is these cells which give rise to the goblet cells not only of the glands themselves but also
of the surface epithelium of the mucous membrane and villi. In this process they become
gradually shifted in position, their place being taken by other cells formed by a process of

Fig. 120. — Section through the com-
mencement OF the duodenum at
the pylorus. (Klein.)

V, villi ; h, apex of a lymphoid
nodule ; c, crypts of Lieberkiihn ; m,
muscularis mucosae ; s, secreting tubes
of Brunner's glands ; d, ducts of pyloric
glands of stomach ; g, tubes of these
glands cut across in mucous membrane ;
t, deeper lying tubes situated in sub-
mucous tissue, and corresponding with
Brunner's glands of the intestine.

cell-division at the base of the glands .
While this seems to be the mode of
production of the goblet or mucus-
producing cells, the ordinary co-
lumnar cells appear to be formed
near the mouths of the glands,
where karj^okinetic figures are com-
mon (they are very rare on the villi
themselves), and to become shifted
along the villi as any of the columnar
cells of those organs become de-
stroyed.

Brunner's glands are small compound acino-tubular glands, which exist in the
duodenum, -where they are most numerous at the upper end, in general occupying
thickly a space extending from one to two inches beyond the pylorus. A few of
them are said also to be found quite at the commencement of the jejunum. They
are imbedded in the submucous coat, and may be exposed by dissecting off the
muscular coat from the outside of the intestine. They may extend partly into
the mucous membrane between the crypts of Lieberkiihn. In structure they
somewhat resemble the small glands which are found in various parts of the lining
membrane of the mouth and elseAvhere, each consisting of a number of tubular
alveoli, connected by the terminal ramifications of the duct, which latter penetrates
the muscularis mucosse, and opens upon the inner surface of the intestine. The
ducts open either between the crypts of Lieberkiihn or in some cases into the bases
of the crypts (Schafi'er). In sections through the pylorus the glands of Brunner
appear like direct continuations of the pyloric glands of the stomach (Watney),
which they closely resemble in structure, but they are somewhat more complicated
and more deeply seated.

The solitary glands are soft, white, rounded, and slightly prominent bodies
0"6 mm. to 3 mm. in diameter, which are found scattered over the mucous

THE SMALL INTESTINE.

mem^jrane in every part of the small intestine. They are found as well at the
mesenteric as at the free border, both between and upon the valvule conniventes,
and are rather more numerous in the lower portion of the bowel. These so-called

Fig. 12L — Section of a solitary ^

GLAND OF THE SMALL INTESTINE.

(Cadiat. )

c, c, villi, partially depriveJ of
their epithelium ; d, crypts of Lieber-
kiihn ; a. solitary glaml composed of
retiform lymphoid tissue, which has
become partly broken away in pre-
paring the section ; h, epithelium
covering the apex or cupola of the
follicle ; e, c, muscularis mucosie ;
/, submucous coat.

glands are in structure similar
to the lymphoid nodules of
various parts already described,
consisting of clumps of dense
retiform tissue, the meshes of
which are closely packed with
lymph-corpuscles, and per-
vaded by fine capillaries.
They are here and there

united at the sides with the surrounding lymphoid tissue, but are at most points
distinctly marked off from it, partly owing to the fact that their supporting
retiform tissue becomes closer and finer, partly owing to their being surrounded
by a rich plexus of lymphatic vessels ; or they even hang, as it were, into a lymphatic

s?^^.

Fijr. 122.

-A SMALL PATCH OF PeYEr's GLANDS FROM THE ILEUM.

Slightly magnified (Boehm).

(or lacteal) sinus, which may entirely surround the
nodule, except next the inner surface of the intestine.
The epithelium over the nodule often has a large
number of lymph-corpuscles between the epithelial
cells. The base of the nodule or follicle is situated in
the submucous tissue ; but it extends upwards, through
the muscularis mucosfe, into the mucous membrane,
causing a bulging of this towards the interior of the
gut (as in fig. 124, d d). The prominent part of the
follicle sometimes has villi upon it, and, placed around
very ii-regularly, arc seen the moutlis of the crypts of
Lieberkiilin.

The agminated glands or glands of Peyer
(who described them in ](;77) are groups oi' patches
of lymphoid nodules. The groups have an oblong
figure (fig. 122), and vary from half an incli to two
or even four inches in length, and from half an inch "'

to about an inch in width (12 mm. to 120 mm. long

and ]2 mm. to 20 mm.bnjad). 'I'hey are plac,(!d lengthways in the intestine! at tliiit
part of the tube most distant from the mesentery ; and hence, to oljtain the best
view of them, the bowel should be opened by an incision along its attached i)order.

Tlie lymphoid nodules which by their aggregation make up a Pcyer's paich arc
in almost all respects similar to the solitary glands above described. As a rule, their

ORGANS OF DIGESTION.

surface is free from villi, and the crypts of Lieberkiihn are collected in circles
around theiu. Fine blood-vessels are distributed abundantly on the exterior of the

Fig. 123. — Portion ov an injected Peter's
PATCH (from Kblliker). Magnified.

The drawing was taken from a prepira-
tion made by Frey of the intestine of the
rabbit. It represents the fine capillary net-
work spreading from the surrounding blood-
vessels into the interior of three lymphoid
nodules.

follicles, and give off still finer capil-
lary branches, which, supported by
the retiform tissue, are disposed
principally in lines converging to
the centre (fig. 123).

The lacteal plexuses, which are
abundant in the whole extent of
the intestine, are especially rich
where they surround the follicles of
Peyer's glands (fig. 124), often
forming sinuses around them, as in
the case of the solitary follicles
above described.
In all, from twenty to thirty of these oblong patches may in general be found ;
but in young persons dying in health as many as forty-five have been observed.

Fig. 124. — Vertical section of a portion of a patch op peter's glands, with the lacteal
VESSELS injected (after Frey). 32 diameters.

The specimen is from the lower part of the ileum : a, villi, with their lacteals left white ; h, some of
the tubular glands ; c, the muscular layer of the mucous membrane ; d, cupola or projecting part of the
rtodule ; e, central part ; /, the reticulated lacteal vessels occupying the lymphoid tissue between
the nodules, joined above by the lacteals from the villi and mucous surface, and passing below into g,
the reticulated lacteals under the follicles, which again pass into the latge efferent lacteals, g' ; i, part
of the muscular coat.

They are larger and placed at shorter distances from each other in the lower part of
the ileum ; but in the upper portion of that intestine and in the lower end of
the jejunum the patches occur less frequently, become smaller, and are of a nearly
circular form ; they may, however, be discovered occasionally in the lower portion of

THE SMALL INTESTINE.

the duodenum Still smaller irregularly shaped clusters of these follicles are

sometimes found scattered throughout the intestine.

The glands of Peyer are best marked in the young sni^ject. After middle life

they become less obvious, and disappear almost completely in advanced a-e their

remams being often indicated by dark colouration of the mucous membrane." '

Vessels and Nerves of the
small intestine.— The branches of
the mesenteric artery, having reached
the attached border of the "intestine,
pass round its sides, dividing into
numerous ramifications, and frequently
anastomosing at its free border. Most
of the larger branches run immediately
beneath the serous coat ; they then

i»^/-^

Fig. 125.— Section of small intestine with blood-vessels injected. (Hoitzmann )

.uii:HL;c2';?t;tc;L~'"'^ "^"^^' "■ ""^^"- ''''-' '' "^^^^'^^'•' ^"^ ^' '-^'^"^'-^

Fi-. 126.— Section tuuoloji i-aut op a Peyeu's patch shovvinq the Lv.MrHATics injected.

(Moditieil from Hcitzuiaiin.)
r, villi ; ALV, muscularis mucosre ; P, lymplioid follicles ; iW, mucous membrane ; T, circular and
in\hKtion """"" '"'"^ ' ^'' I'""*""^'^' ^■•'y''- '^^'^ ^Tl'ts of Liebcrkuhn are socu

pierce the muscular coat, supi)lying it with a few vcsselo as they pass, and ramify
in the submucous areolar layer, so as to form a close network. From this
smaller vessels pass into the mucous coat. Some of these are the arteries of the
villi, already described. Others pass to the mucous membrane and supply a
network of capillaries surrounding its glands. Other branches again pass into the
Jnuw;ular coat from the vessels of the submucosa. The fine capillaries of the
mu«<;ular coat are arranged in two layers of oblong meshes, which correspond in

VOL. in., IT. i.

ORGANS OF DIGESTION,

direction with the longitudinal and circular muscular fibres. The veins accompany
the arteries, with which they correspond in general distribution.

Fig. 127. — Lymphatic plexus {I) and nervous plexus (n) in the muscular coat of the intestine

(Auerbach).

The lymphatics of the intestine (lacteals) may be conveniently distinguished as
those of the mucous membrane aud those of the muscular coat. Those of the

Fig. 128. — Plexus of Auerbach between the two layers of the muscular coat of the
intestine. (Cadiat. ) Chloride of gold preparation.

mucous membrane form a copious plexus (figs. 124, 126), Avhich receives the central
vessels of the villi, and pervades both the mucous and submucous layers — in
the latter being of considerable size, and forming, as before mentioned, a close plexus

THE SMALL INTESTINE.

Fig. 129. — Plexus op Meissner, from the

SUBMUCOUS LAYER OK THE INTESTINE.

(Catliat.) Chloride of gold prepara-
tion.

a, a, ganglia ; b, b, cords of plexus ; c, a
small blood-vessel.

01- a sinus around the base of each
lymphoid folHcIe. Another set of
lymphatics hes under the peritoneal
coat, and is especially developed
along a narrow strip at the
attachment of the mesentery. In
the muscular coat the main plexus
is situated between the circular and
longitudinal layers of fibres (fig.
127, I) ; and there are likewise close
plexuses threading the whole thick-
ness of the muscular wall. These
lymphatics of the muscular coat are
in complete continuity with those of
the mucous membrane, and pass
into larger vessels at the mesenteric
border, Avhich again run into the
lacteal vessels of the mesentery.

The nerves of the small intes-
tine are chiefly deri^•ed from the

superior mesenteric plexus. This plexus is formed by nervous branches from the
coeliac plexus, the semilunar ganglion, and from the vagus nerve. The plexus and

Hg. 130.— Nerve-endings in the small in-
testine OF THE GUINEA-I-IG. (Cajal. )
Silver chromate preparation.

a, b, c, d, small nerve cells belonging to the
intergjandular plexus of the mucous membrane ;
e, /, coiTcsponding cells belonging to the nerve-
plexus of the villi ; M, nerve-fibres belonging
to the plexus of Meissner, distributed to the
niuscularis mucosae.

plexiform branches into which it divides
cling at first very closely to the larger
divisions of the superior mesenteric
iirtery, and, dividing similarly with
the ramifications of the arteries, the
branches of the nerves, retaining still a
wide plexiform arrangement, pass on-
wards to the dilferent parts of the
intestine between the two folds of the
mesentery, and finally, separating some-
what from the blood-vessels, reach the
intestine in very numerous branches,
t<) be distributed in its coats. Passing

first between tiie longitudinal and circular layer of the muscular coat, they hero
form a close gangliated [)lexu8 throughout the whole extent of the intestine (fig. 127, n,
us exhibited under a low [uwer ; also fig. I'JH). This, which is known as the plexus

B 2

loo OKGANS OF DIGESTION.

of Auerhach, or the plexus myentericus, and which is principally composed of non-
medullated fibres, gives off fine branches to the muscular substance, these first
forming a smaller plexus amongst the muscular fibres. Other larger branches pass
between the circular bundles of fibres to reach the submucous layer, where they form
a second gangliated plexus {plexus of Meissner, fig. 129), the threads of which are
much finer than those of the intermuscular plexus.

The cords of these plexuses contain two kinds of nerve-fibres, both non-
meduUated. Those of the one kind pass through the ganglionic enlargements,
giving off collateral fibres which ramify around the nerve-cells : they probably
take origin in the prevertebral or other more central ganglia. Those of the other
kind are finer and more numerous ; they are processes of the cells of the ganglionic
enlargements and are probably partly passing to their distribution in the muscular
layers or in the mucous membrane respectively ; partly serving to connect
neighbouring ganglia with one another.

From Meissner's plexus nerve-fibres pass to be distributed to the muscular layer
of the mucous membraue, breaking up into fine fibrils, which take the direction of
the fibre-cells of this layer, whilst other fine fibrils form ramifications in the proper
tissue of the mucous coat and villi (fig. 130), and, according to some authors, send
branches into the epithelium penetrating between the columnar cells. Upon these
ramifications in the mucous membrane and villi, and also upon the ramifications
which are distributed to the muscular layers, small cells are found which are thought
to be of nervous nature. Similar cell -like enlargements occur on the terminal
plexuses within the salivary glands and pancreas (Drasch, Cajal). According to
Berkeley the nerves end both between the muscular fibres and within the villi by
small pear-shaped or globular dilatations.

SPECIAL CHAEACTEBS AND RELATIONS OF THE SEVERAL PARTS OP THE

SMALL INTESTINE.

Duodenum. — This is the shortest and widest part of the small intestine. In
length it measures about 10 to 12 inches (250 to 300 mm.), and in diameter from
one-and-a-half to two inches (35 to 50 mm.). In its course it describes a single large
curve, which, when the stomach is empty, forms an almost complete ring, its termina-
tion in the jejunum being only a little to the left of its commencement (Braune).
Distension of the stomach, and the consequent movement of the pylorus towards the
right side, makes the curve of the duodenum U-shaped rather than annular. The
curve of the duodenum lies in a coronal plane, except at its two extremities which
are directed forwards. The concavity embraces the head of the pancreas.

It has no mesentery, and is covered only partially by peritoneum. Its muscular
coat is comparatively thick, and its submucous layer towards the pylorus is the seat
of the glands of Brunner, already described. The common bile duct and the
pancreatic duct open into this part of the intestinal canal.

The duodenum may be divided, for the purpose of anatomical description, into
four parts.

The first or superior portion is the most variable part, as its length and direction
depend upon the position of the pylorus. When the stomach is empty it is fully
two inches long, and extends from the j)ylorus to the right in contact with the
quadrate lobe of the liver, and then backwards beneath the neck of the gall-bladder,
where it bends sharply downwards to join the second part. If the stomach be fully
distended, the commencement of the first part of the duodenum is moved towards
the right side, while its termination remains stationary, so that its direction is then
almost directly backwards, while its length is diminished to an inch, or even less.
Its anterior surface is covered entirely by peritoneum, but its posterior aspect only
in the neighbourhood of the pylorus.

THE SMALL INTESTINE.

101

Above and in front of it are the liver and gall-bladder. Its close relation to the
latcer is indicated by the fiict that it is often stained by the exudation of bile a feu-
hours after death. Behind it are the portal vein, the gastro-duodenal artery, and
the common bile-duct. The neck of the pancreas lies behind and to its inner side.

The second or descending portion is about three inches long. It commences
just below the neck of the gall-bladder, opposite the right side of the first lumbar

Fig. 131. YlF.W OF THE LIVER, DUODENUM, PANCREAS, SPLEEN, &C. ThE GKKATER PART OF THE

STOMACH HA.S BEEN REMOVED, E-XPOSINQ ITS POSTERIOR RELATIONS. (Tcstut.)

A, inferior surface of liver ; B, right kidney ; C, C, right and left suprarenal capsules ; D, left
kidney ; E, pancreas ; F, upper part of stomach ; G, spleen ; H, duodenum with a, b, c, d, its four
portions ; I, jejunum ; K, duodeno-jejunal junction ; 1, lower end of cesophagus ; 2, pyloric orifice ;
3, CjtfA'iHC axis ; 4, coronary artery ; 5, iiepatic artery ; 6, lobus Spigelii of liver ; 7, 7', splenic vessels ;
8, left ga.stro- epiploic artery ; 9, right gastro-epiploic artery ; 10, superior mesenteric vessels ; 11, portal
vein ; 12, hepatic duct; 13, cystic duct ; 14, gall bladder ; 15, left crus of diaphragm ; 10, aorta ; 17,
inferior vena cava ; 18, inferior mesenteric vessels ; 19, 19', spermatic vessels.

vertebra, and passes down to the level of the body of the third or fourtli lumbar
verteljra, where it turns sharply inwards to join the third part. Its anterior surface
iwually gives attachment to the transverse meso-colon, and is entirely covered by
pf^ritoneum, with the exception of the small iuterval between the two layers of the
meso-colon. This small uncovered area is sometimes consideralily increased, owing
to the transversa.' colon being here destitute of a meso-colon, and separated from the
duo<Ienum by areolar tLs.sue only. Above the traiisvei'.se colon the anteiior surface is
in contar;t with the liver. The posterior surface has no jjcritoneal cAcring, l)ut is
connected by areolar tissue to' the right kidney and its vessels and the inferior vena

102 OEGANS OF DIGESTION.

cava. There are considerable variations in tlie relations of the second part of the
duodenum to the right kidney. According to Cunningham, they are probably
due rather to variations in the position of the kidney than of the duodenum.
As a rule, the duodenum comes in contact with the kidney a little above
its hilum, and reaches down to about the level of its lower end. To the
left is the head of the pancreas (see fig. 131), which adapts itself to the shape of
the intestine on that side, and, according to Verson, some of the longitudinal fibres
of the gut are intercalated amongst the contiguous lobes of the gland. The common
bile-duct descends behind the left border of this part of the duodenum, and the
pancreatic duct accompanies it for a short distance. On opening into this part of
the duodenum, the valvulse conniventes appear numerously, and a downwardly
projecting papillary eminence of the mucous membrane is found immediately below
one of these, about four inches from the pylorus, on the inner and back part of the
intestine, at the apex of which is seen the common orifice of the biliary and
pancreatic ducts.

The third or transverse portion of the duodenum is between two and three
inches long. Beginning on the right of the third or fourth lumbar vertebra, it
crosses over to the left side, with a slight upward inclination, and ends to the
left of the aorta by curving upwards to join the ascending or terminal part
of the duodenum. Its anterior surface is covered by peritoneum at its commence-
ment, but near the median plane it becomes separated from the anterior layer of
the mesentery by the superior mesenteric vessels which groove its anterior surface.
Behind, it lies against the inferior vena cava and the aorta. On the right side its
posterior surface is uncovered by peritoneum, but towards the left the posterior layer
of the mesentery is prolonged upwards behind it for a variable distance. Above it
is the head of the pancreas.

The fourth or ascending portion (Treves) is about two inches long. It passes
upwards on the left side of the aorta as high as the upper border of the second
lumbar vertebra, where it turns abruptly forwards to join the jejunum, forming the
duodeno -jejunal flexure. It is covered in front and on the left side by the peritoneum,
which often forms on its left side one or two peritoneal pouches called the duodeno-
jejunal fossEe, and it lies immediately behind the transverse meso-colon, which
separates it from the stomach. It rests on the left psoas muscle, the inner edge of
the left kidney is sometimes slightly overlapped by it, and near its upper end the
left renal vein passes behind it.

The upper end of this part of the duodenum is maintained in position by a
strong fibrous band descending from the left crus of the diaphragm, and the tissue
around the coeliac axis. This band, which is better marked in the foetus and young
child than in the adult, contains plain muscular fibres, and is called the musculus
suspensorius duodeni. In subjects in which the intestines are large and dilated
the curve of the duodenum may descend to the level of the iliac crest, but, owing
to the support given by the band alluded to, its terminal extremity maintains a
nearly uniform position.

As a rule, the second, third and fourth parts of the duodenum together form a
U-shaped bend, with the concavity looking upwards, but occasionally the third part
passes across the front of the vertebral column, with a considerable degree of
obliquity, giving rise to the V-shaped type of duodenal curve. In these cases the
distinction between the third and fourth parts is not well marked.

Jejunum and Ileum. — The jejunum, originally so called from its having
been supposed to be empty after death, follows the duodenum, and includes the
upper two-fifths of the remainder of the small intestine, while the succeeding three-
fifths constitute the ileum, so named from its numerous coils and convolutions.
Both the jejunum and the ileum are attached to the posterior abdominal wall by an

THE LARGE INTESTINE. 103

extensive fold of peritoneum termed the mesentery. This mesentery, although
greatly frilled out in front to correspond in length with the jejunum and ileum
to which it gives support, is attached posteriorly by a comparatively short border
(about sis inches), which extends from the left side of the second lumbar vertebra
obliquely across the third part of the duodenum, aorta, inferior vena cava, and right
psoas muscle to the right iliac fossa, where it ends. The length of the mesentery,
measured from the parietal attachment to the intestine, varies, being longer about
the middle than at either end of the bowel. The average length, according to
Treves, may be taken as eight to nine inches. Lockwood found that up to the age
of forty years it rarely exceeded eight inches, but after this period of life longer
mesenteries occurred with greater frequency. Between the two layers of the
peritoneum forming the mesentery are placed, besides some fat, numerous branches
of the superior mesenteric artery and vein, together with nerves, lacteal vessels, and
lymphatic glands. The convolutions of the jejunum tind ileum occupy parts of the
middle and lower zones of the abdomen, and a variable number of loops lie in the
pelvis. The jejunum lies above and to the left of the ileum, but the coils are so
irregular that the position of any individual loop affords but little clue to the part
of the intestine to which it belongs. The terminal portion of the ileum is more
fixed in position than the other parts of the jejuno-ileum. It generally passes
outwards and upwards from the cavity of the true pelvis across the right psoas
muscle to join the large intestine, being united to the psoas by the lower part of
the mesentery, which here is usually very short.

The character of the intestine gradually changes from its upper to its lower end,
so that portions of the jejunum and ileum, remote from each other, present certain
well-marked dilFerences of structure. Thus, the ileum is narrower ; its coats are
thinner and paler ; the valvulae conniventes are small, and gradually disappear towards
its lower end ; the villi are shorter ; and the groups of Peyer's glands are larger and
more numerous. The diameter of the jejunum is about one inch and a half, that of
the ileum about one inch and a quarter. A given length of the jejunum weighs
more than the same of the ileum.

Meckel's diverticulum. — In about one in fifty subjects a pouch or diverticulum
is given off from the main tube of the ileum. Its average position above the ileo-
colic opening is about 43 inches, but it has been found to vary from 11 to 120
inches. It usually comes off from the ileum on the side opposite to the attachment
of the mesentery. As a rule, it is from two to three inches in length, and about the
same calibre as the bowel from which it arises. The origin of this diverticulum is
probably connected with the persistence of a part of the vitelline duct of early foetal
life. It is not to be confounded with hernial protrusions of the mucous membrane,
which may occur at any point.

Variations with agre and sex. — Treves found the average length of the small intestine
in the new-bom child to be 9 feet 5 inches, and he estimates that it grows about 2 feet during
the first month of extra-uterine life and a similar amount in the second month, but after this
periofl its rate of growth is very variable. Treves gives the average length of the small
intestine in the adult female as 10 inches longer than that of the male ; but Rolssen, from
measurements on German subjects, found it about 2 feet longer in the male.

THE LARaB INTESTINE.

The large intestine extends from the tcrminat'on of the ileum to the anus.
It is divided into the ccccum (with the vermiform appendix), the colon and the
rectum; and the colon is again subdivided, according to its direction, into four
parts, eallod the asceyiding, transverse, and descending colon, and the sir/moid colon
or Jlexure.

104

ORGANS OF DIGESTION".

The length of the large intestine is usually about 5 or 6 feet ; being about one-
fifth of the whole length of the intestinal canal. Its diameter, which for the most
part greatly exceeds that of the small intestine, varies at different points and under
different conditions, from 2j inches to less than an inch. It diminishes gradually

Fig. 132.— Diagram showing the position of the thoracic and abdominal organs.
(Rauber after Lusclika.)

1, Lower border of the riglit lung ; 2, the same of the left lung ; 8, liver, right lobe ; 4, liver, left
lobe ; 5, suspensory ligament of the liver ; 6, fundus of gall-bladder ; 7, cardia of stomach ; 8, fundus
of stomach ; 9, lower border of stomach ; 10, position of pylorus ; 11, cacum ; 12, vermiform appendix ;
13, ascending colon ; 14, right flexure of colon ; 15, transverse colon ; 16, position of left flexure of
colon ; 17, descending colon ; 18, portion of sigmoid colon, concealed by 19, convolutions of the small
mtestme ; 20, termination of ileum, ascending from left to right ; 21, bladder, distended, partly
covered by peritoneum ; 22, the part of the bladder which is not covered by peritoneum.

from its commencement at the caecum to its termination at the anus, excepting that
there is a well-marked dilatation of the rectum just above its lower end.

THE LARGE INTESTINE.

105

In outward form, the greater part of the large intestine differs remarkably from
the small intestine ; for, instead of constituting an even cylindrical tube, its surface
is thrown into numerous sacculi, marked off from each other by intervening constric-

--^^

Fig. 133. — Transverse colon, empty and contracted. (Drawn by G. C. R. Harbinson. )
a, inferior longitudinal band ; h, one of the saccules ; c, appendices cpiploicae.

tions, and arranged in three longitudinal rows which are separated by three strong
flat bands of longitudinal muscular fibres (fig. 133). It can also be distinguished
by its appendices epiploicse (see below), which are not found in connection with the
small intestine.

STRUCTUEE OF THE LARGE INTESTINE.

The large intestine has four coats, like those of the stomach and small intestine,
namely, the serous, muscular, submucous, and mucous.

Fig. 134. — OCTLINK SKETCH OF A SECTION OF THE

ASCENDING COLON (Allen Thomson). ^

s, serous covering ; »', s', reflection of this at the
attached border forming a short wide mesocolon between
the folds of which the blood-vessels are seen passing to
the colon ; a, one of the appendices epiploicic hanging
from the inner border ; I m, indicates at the free border
one of the three bands formed by the thickening of the
longitudinal muscular coat ; the dotted line continued
from the margins of these l^inds reiire.sents the rcmniiuler
of the longitudinal muscular coat; and the thick line
within it, marked c m, represents the circular muscular
layer ; rn, the mucous membrane at the flattened i)art ;
r, the crescentic bands or indentations which divide the
sacculi.

The serous coat is for the most part
similar to that of the small int(.'fitine, except
that, along the colon and npper })art of the
rectum, it is j)roloriged into numerous little

prcjjections, which enclose a certain amount of fat, and arc termed appendices
epvplokie.

106

ORGANS OF DIGESTION.

The muscular coat, like that of the other parts of the intestinal canal, consists
of external longitudinal and internal circular fibres.

The longitudinal fibres, although found in a certain amount all round the intes-
tine, are, in the cseoum and colon, more thickly collected into three remarkable flat
longitudinal bands (fig. 134, Im ; fig. 133, a). These bands, sometimes called the
ligaments of the colon, are about 12 mm. wide, and 1 mm. thick ; they commence
upon the csecum, at the attachment of the vermiform appendix, and may be traced
along the whole length of the colon as far as the commencement of the rectum,
where they form the two bundles which pass down, one on its anterior and the
other on its posterior surface. One of these bands, the posterior, is placed
along the attached border of the intestine ; another runs along its anterior

— exjitlielhun.

lumen of
gland.

goUet cell.

Fig. 135. — Section op the mucous mem-
brane OP THE COLON, MAN. (Bolim

and V. Davidoff.) -^ao

interglanduktr
tissue.

border, and, in the transverse
colon, corresponds with the
attachment of the great omen-
tum ; whilst the third band (inner
or inferior) is found on the inner
border of the ascending and
descending colon, and on the
under border of the transverse
colon. It is near the course
of this third band that the
appendices epiploicse are most of
them attached (fig. 134, a).
Measured from end to end, these
three bands are shorter than the
intervening parts of the tube ;
and the latter are thus thrown
into the sacculi already men-
tioned : accordingly, when the
bands are removed by dissection,
the sacculi are entirely effaced,
and the colon, elongating con-
siderably, assumes the cylindrical
form. The transverse constric-
tions seen on the exterior of the
intestine, between the sacculi,

appear on the inside as sharp ridges separating the cells, and are composed of all

the coats. In the vermiform appendix the longitudinal muscular fibres are disposed

in a uniform layer.

The circular muscular fibres form only a thin layer over the general surface of

the csecum and colon, but are accumulated in large numbers between the sacculi.

In the rectum, especially towards its lower part, the circular fibres form a very thick

and powerful muscular layer.

The submucous or areolar coat resembles in all respects that of the small

intestine.

The mucous membrane diifers from that of the small intestine in being smooth

and destitute of villi. Viewed with a lens, its surface is seen to be marked all over

by the orifices of numerous tubular glands (crypts of LieberJcilhn) (fig. 1 35), resembhng

those of the small intes-tine, but longer and more numerous, and further distinguished

areolar tissue
of mucous
membrane.

THE LARGE INTESTINE.

107

from them by the large number of mncns-cells which they contain. Indeed in
some animals all the cells of these glands may be found to be filled with mucus

Fig. 130.— Glands of the large intestine. Magnified (from Heidenhain and Klose).
a, of the rabbit ; h, of the dog. c, transverse section of a gland of the dog.

cpHhelium

of surface.

lymphoid cells
conceiitrieally
arranged.

gland

area of multi-
jilication of
lymphoid cells.

"uhmucosa.

Fig. 137. — Si'-oiroN tiikol'oii a tioiA'rwa oi.and of the large intestine of man.
(Bohrn and v. Davidofr. )

(fig. ino, a) ; in others every filLernatocell presents this character (fig. l;U'>, /^ r), the
cells between being of the ordinary columnar kind. If the glands are stimulated

108

OEGANS OF DIGESTION.

to active secretion the mucus is discharged and all the cells assume the appearance
of ordinary columnar epithelium-cells (Klose).

Scattered over the whole large intestine lymphoid nodules are found, similar to
the solitary glands of the small intestine. They are most numerous in the csecum
and its vermiform appendix ; being placed closely all over the latter.

The epithelium which covers the general surface of the mucous membrane is of

Fig 138. — BLOOD-VESSEtiS OF LARGE INTESTINE AS SEEN IN VK.R-

TicAL SECTION (Kolliker).
a, artery passing xip from submucosa ; c, vein arising from
capillary plexus, b, which surrounds the mouths of the glands.

the columnar kind, and in every respect similar to
that of the small intestine. As in the stomach the
mucous membrane consists of areolar connective
tissue with a certain amount of retiform tissue, and is
bounded next the submucous coat by a layer of plain
muscular fibres {muscularis mucoscc), which sends
prolongations up between the glands to be attached
to the basement membrane near the surface, in the
same way as in the villi of the small intestine.

Vessels and Nerves. — In the large intestine
an arrangem.ent of capillary plexuses and venous
radicles obtains, similar to that which has been
described in the stomach (fig. 138). The arrange-
ment of the lymphatics is also nearly the same.

Nervous plexuses similar to those of the small intestine are also found in the
muscular and submucous coats of the large intestine.

SPECIAL CHABACTERS AND RELATIONS OF THE DIFFERENT PARTS
OF THE LARGE INTESTINE.

The CiECUM. — The iniestinum ccacum, or cajmt ccBcum coli, is that part of the large
intestine which is situated below the entrance of the ileum (fig. 132, 11). Its
length is about 2|- inches, and its breadth about three inches ; it is the widest part
of the large intestine.

The cgecum is situated in the right iliac fossa, in front of the ilio-psoas muscle
and immediately behind the anterior wall of the abdomen above the outer half
of Poupart's ligament. It is covered by the peritoneum in front, below and at
the sides ; behind, the peritoneum is usually reflected from the bowel on to the
iliac fascia at the level of the ileo-colic opening, or even still higher up, so that
the posterior surface is entirely invested. In about 5 p.c, however, the reflection
occurs at a lower level, in which ca?es the upper part of the posterior surface
is uncovered and connected with the iliac fascia by areolar tissue. There is no
meso-c£ecum.

In the foetus the c^cum is conical in form, and its apex gives attachment to a
slender process called the vermiform appendix. The three longitudinal bands of the
large intestine are united at the root of the appendix, but on the csecum they diverge,
one passing up the anterior surface, another on the inner side, and a third on the
postero-external aspect. This, the infantile type of caecum, may persist in the adult,
Treves found it in two out of one hundred adult subjects. In the great majority of
cases, however, the walls of the caecum begin, even before birth, to grow at unequal
rates. The anterior and right walls grow more rapidly than the posterior and left
ones, so that the attachment of the vermiform appendix is no longer situated at the

THE LARGE INTESTINE.

109

lower end, but is found on the inner and posterior aspect of the caecum. The three
bands, however, are still found to unite at the root of the appendix. The free,
rounded and usually blunt lower end of the csecum thus comes to be formed by the
expanded saccule situated between the anterior and postero-external bands. In the
third month of foetal life the caecum is situated near the median plane just below the
liver, and in the process of development it normally passes downwards and to the
right, in fi'ont of the second part of the duodenum and the kidney towards the right
iliac fossa. In the 6th month it lies opposite the lower end of the kidney, and at birth
it has usually attained it3 adult position. This process of descent of the crecum is
liable to be arrested in any part of its course. On the other hand the caecum is
sometimes unusually long and movable, and its free extremity may project down into
the true pelvis or even pass across the median plane to the left side. It has been

Fi^'. 139. — Antero-external

WALL OF CJICUM AND
COMMENCEMENT OF AS-
CENDING COLON REMOVED
TO SHOW ILEO-COLIC ORI-
FICE, &c. From a speci-
men HARDENED IN SITU.

(Drawn by G. C. R.
Harbinson.)

a, lower end of ileum ;
b, its mesentery ; c, r, c;ecum ;
(/, oritice of vermiform appen-
dix ; e, ileo-colic orifice ; /,
upper or ileo-colic segment of
its valve ; [/, lower or ileo-
ciecal segment ; h, ascending
colon.

found rotated on its
long axis so that the
ileum, after passing be-
hind the caecum, opened
on its right side.

Coming oS' from the
inner and back part of
the cascum, a little below
the ileo-colic opening is
a narrow, round, and
tapering portion of the
intestine, named the
appendix cccci, or vermi-
form appendix. The width of this process is usually about 0 mm., and its
average length 92 mm. (Herry), but it varies considerably ; thus, Berry found
it, in two out of 100 cases, only 31 mm. in length, and Kansshoff has recorded
one 230 mm. long. It varies considerably in its position, but will generally be
found passing from behind the caecum either upwards and to the left behind
the ileum and mesentery in tlie direction of the spleen (Treves), or downwards
and to the left so as to lie on the brim of the pelvis or even project into that
cavity. Sometimes it is situated entirely behind the caecum, and in this posi-
tion may be quite fiee or firmly bound down to the peritoneum. It has a
peritoneal fold, the mcso-ajipendix, containing its vessels and nerves and attached
to above half the length of the appendix, the distal ])ortioii being generally
quite free and entirely surrounded by peritonwim. The vermiform iip])endix is
usually hollow as far as its extremity ; and its cavity communicates with that of

ORGANS OF DIGESTION.

the csecum by a small orifice, sometimes guarded by a valvular fold of mucous
membrane.

According to the results of Ribbert's observations the cavity of the vermiform
appendix exhibits a distinct tendency to undergo obliteration. Thus out of 400
cases examined by him 99 or nearly 25 p.c. had the lumen of the process more or
less obliterated. In 50 p.c. of the obliterated cases its distal fourth only, and in
3.5 p.c. the whole process was closed, while the remainder showed intermediate
stao-es. This tendency to obliteration increased with age. Lafforgue did not find
such a large proportion of cases showing this tendency, thus out of 200 cases only
7 p.c. belonged to this category. In 3 p.c. the obliteration was total, in 3 p.c. it
Avas closed for a distance of 1 cm. and in 1 p.c. from 2 to 3 cm.

Ptibbert has also investigated the length of the appendix at different periods of
life. At birth its average length is 34:*4 m.m., by the 10th year it has increased to
90 mm., during the next 10 years it grows slowly, being at the 2Cth year 97.5 mm.
lono-. After this period it gradually diminishes in length, thus from 20 to 30 to

Fig. 140. — Section through the lower end

OF THE ILEUM, THE ILEO- COLIC VALVE, THE
C^CUM, AND ASCENDING COLON, TO SHOW
THE RELATION OP THE TERMINATION OF
THE ILEUM TO THE C.KCUM. ThE ANTERO-
EXTERNAL WALL OF CiECUM REMOVED IN
FIG. 139 IS REPRESENTED AS IN SITU. (J. S. )

a, an tero- external wall of c^cum ; h, cavity
of ileum ; c, lower or ileo-ceecal segment of
ileo-colic valve ; cZ, upper or ileo-colic segment ;
f, frcenum on right side of ileo-colic opening ;
/, ascending colon ; g, vermiform appendix with
its mesentery ; K, h, h, peritoneum.

95 mm. ; from 30 to 40, 87"5 mm. ;
ii'om 40 to 60, 85 mm. ; and the
average in subjects over 60 is 82 "5 mm.
Eibbert found considerable individual
variations ; in one middle-aged male it
was 210 mm., and in a child 5 years
old 120 mm. He estimates the length
of the appendix as compared with the
whole of the large intestine as 1 to 10
in the new-born, andl to 20 in the adult.

So far as is known, this appendix is peculiar to man and certain of the higher apes, and to
the wombat ; but in some animals, as in the rabbit and hare, the distal part of the csecum,
being diminished in diameter and thickly studded with lymphoid follicles, may represent a
condition of the appendix.

Ileo-colic or ileo-caecal orifice and valve. The lower end of the ileum passes
upwards and to the right, being at first internal to and then behind the cascum, and
terminatss by opening into the posterior part of the large intestine at the junction
of the csecum and ascending colon (see figs. 139 and 140).

The orifice is generally situated opposite a point on the anterior abdominal wall
from 1 to 2 inches internal to and a little above the anterior superior iliac spine. When
the colon is opened it appears as a transverse or slightly oblique slit about half an
inch in length. This opening is guarded by a valve composed of two segments or
folds which project into the large intestine. This is the ileo-colic or ileo-ccccal valve :
it is also called the valve of Bauhin and the valve of Tulpius, although Fallopius
had described it before either of those anatomists. The upper of the two segmentG

THE LARGE INTESTINE. Ill

(see fig. 140) is horizontal, and the lower and larger obli(jue. At each end of the
aperture these folds coalesce, and are then prolonged as a single ridge on each side
for some distance round the cavity of the intestine, forming the frceiia or retinacula
of the valve. The opposed surfaces of the valvular folds which look towards the
ileum, and are continuous with its mucous surface, are covered like it with villi ;
while their otlier surfaces, turned towards the large intestine, are smooth and
destitute of villi. In the 5th month of fuetal life both surfaces of the ileo-colic valve
possess villi, but by the 9th month the villi on the colic aspect of the valve are
represented by only a few stunted processes (Langer).

Each segment of the valve consists of two layers of mucous membrane, continuous
with each other along the free margin, and including between them, besides the sub-
mucous areolar tissue, a number of muscular fibres, continued from the circular
fibres of the ileum and of the large intestine. The longitudinal muscular fibres and
the peritoneal coat take no part in the formation of the valve, but are stretched
across it uninterruptedly from one intestine to the other ; if these be removed and
gentle traction be made upon the ileum the valve will gradually become less pro-
minent, and may ultimately disappear by being unfolded and drawn out of the colon.
The function of the ileo-colic valve is to prevent the intestinal contents passing from
the large into the small intestine. Its valvular action is independent of muscular
contraction as air or fluid forced into the large intestine in the cadaver does not
generally find its way into the ileum. It is probable that the distension of the
caecum presses the walls of the ileum against one another much in the same way as
the urine is prevented from passing from the bladder into the ureters.

Dcbierre {Lijon Mhlical, Nov., 1885) made a series of experiments to determine the
competency of this valve by injecting-, per rectum, air or water with the intestines in situ,
and he found that it permitted these to pass from the large to the small intestine in the
proportion of about 2 out of 3. ^\'ben competent, however, it resisted the pressure of a
column of water from 3 to 4 metres in height, the large intestine finally rupturing- without
a drop of fluid having passed through the ileo-colic orifice. He considered that in the cases of
incompetency the ctecal segment of the valve was shorter than the colic, while in the others
it was as long or longer.

Birmingham has recorded a case of absence of the ileo-colic valve, and Struthers has
described several specimens in which the valve was imperfectly developed.

Various peritoneal folds and fossae occur in the region of the coacum, vermiform
appendix, end of ileum and commencement of ascending colon, but anatomists are
by no means agreed as to their frequency or nomenclature. The following state-
ment is based mainly upon the observations of Lockwood and RoUeston.

Ileo-colic fossa, situated in the angle between the ileum and the commencement of
the ascending colon and bounded in front by the ileo-colic fold {superior ileo-ccecal
fold of Treves).

Ileo-ccecal fossa, behind the junction of the ileum and the ciccum. It may
extend upwards behind the a.scending colon nearly as high as the right kidney and
duodenum. The mouth of this fossa is below, and is bounded in front by the ileo-
caecal fold {bloodless fold of Treves).

Sub-cmcal fossa, placed directly behind the caecum. Its fundus may pass
upwards behind the ascending colon. It is less frequently met with than the other
fossae.

The vermiform appendix may be concealed within one of these pouches and
firmly attached to its walls, constituting what is termed hernia of the appendix, lb
is veiy probable that the cases described as examples of absence of the appendix were
of this nature with the mouth of the fossa closed.

CoLOX. — The ascending colon is continuous with the caecum at the level of
the ileo-colic opening. It pas^su.s upwards through the right lumbar iuto the hypo-

113

ORGANS OP DIGESTION.

chondriac region until it comes in contacfc with the inferior surface of the right
lobe of the liver external to the gall-bladder. Here it bends forwards and to the
left as the hepatic flexure. The ascending colon is smaller than the c«cum, but
larger than the transverse colon. It is overlaid in front by some convolutions of
the ileum, and is bound down firmly by the peritoneum which passes over its anterior

Fig. 141.— TkANSVERSE section through the abdomen of a FCETUS ?>i INCHES LONG. (J. S.)

D.G., descending colon ; P, peritoneum ; K, left kidney ; V, body of vertebra.

Fig. 142.— Transverse section through abdomhn of a nine months foetus. (J. S.)
D.C., descending colon; Ps, psoas muscle; Q.L., quadratus lumborum ; E.S., erector spinas;
L v., lumbar vertebra.

surface and its sides, and generally leaves an interval in which its posterior surface
is connected by areolar tissue with the fascia covering the quadratus lumborum
muscle, and with the front of the right kidney. In some cases, however, the peri-
toneum passes nearly round it and thus forms a distinct though very short meso-
colon.

The transverse colon extends from the hepatic flexure in the right hypochon-

Fig. 143. — Transverse section

THROUGH the ABDOMEN OF A
MALE ADULT. (J. S. )

References as in Fig. 142.

i\fc pj. .'/-^/'-'■'l ^^-—-—^ — ^ drium to the splenic flexure in

' I \\ -■-^^li^^7'?^'^'^\ fr^\ ^^® ^^^^ hypochondrium ; be-

h\ %'"■■-- ''^^^^^^ (^^-^ ■' r^ifi^ / tween these two points it

\^\^---^=:^P^^^ forms a loop usually directed

\^\/^fe^^p>r^^A,'=^^^''^^VT downwards and forwards. As

^, ^"^^^^^^^^^S^r^^- £^!sr-'''' ■^'^ /a ^^® transverse colon is con-

\ ^\l^ ^7^=^^-'-^h=<^'C\i'^ siderably longer than the

\^v\^ \<2_( ^-^'^ "^ c^~J!%J^ transverse diameter of the

2. \ "'***^^5:<0-X^\ ^ ^.^J'^^ =" abdomen, and possesses a long

meso-colon, its position is
liable to considerable varia-
tions. It generally crosses the abdomen above the level of the umbilicus, but may
reach considerably lower.

Above, the transverse colon is in contact with the under surface of the liver, the
gall-bladder, the great curvature of the stomach and the lower end of the spleen. It
is covered in front by the great omentum. On the right side it crosses in front of
the second part of the duodenum to which it may be united by areolar tissue or
attached by a short peritoneal fold. In the rest of its course it has behind it some

THE LARGE INTESTINE. 113

of the convolutions of the jejunum and ileum to the left of the second part of the
duodenum. The two layers of the transverse meso-co/on are attached to its upper
border, and after investing the colon they become continuous with the great
omentum. The part of the transverse meso-colon which is often found in front of
the duodenum is formed entirely by the great sac, while that to the left of the
duodenum is derived from both great and small sacs.

The descending colon is continuous with the left extremity of the transverse
colon by a sudden bend named the splenic flexure, which is higher up and farther
back in the left hypochondrium than the hepatic flexure in the right hypochondrium.
At this bending there is found a fold of peritoneum, the costo-colic or phreno-colic
ligament, which stretches with a lunated free border to the colon from the diaphragm
opposite the tenth or eleventh rib. As was pointed out by Haller, it supports the
spleeu although unconnected with that organ, and may be termed " sustentaculum
lienis." From the splenic flexure the colon descends in contact with the outer
border of the left kidney. At the lower end of the kidney it usually turns inwards
a little and then descends near the outer border of the psoas muscle to the iliac fossa
where it joins the sigmoid colon. In a young foetus (see fig. 141) the descending
colon has a relatively long meso-colon which is attached to the abdominal wall
intei'nal to the kidney, and passes outwards in front of that organ to join the colon.
This meso-colon is obliterated before birth (see fig. 142), probably by a blending of
its posterior layer with the peritoneum in front of the kidney. After foetal life the
descending colon is generally covered by peritoneum on its anterior and outer sur-
faces, the posterior and inner surfaces being uncovered.

Occasionally, especially when the colon is empty, the peritoneum lies behind the
outer part of the posterior surface (see fig. 143), but the existence of a distinct
descending meso-colon is rare.

The sigmoid colon may be defined as that part of the colon which is attached
to the left iliac fossa from the iliac crest to the brim of the true pelvis. In front of
the crest of the ilium it is continuous with the descending colon ; from this point it
usually passes downwards, forwards, and somewhat inwards for two or three inches,
approaching the anterior abdominal wall internal to the anterior superior iliac spine.
This part generally lies in close relation with the fascia in front of the iliacus and is
covered by peritoneum on its anterior and lateral aspects only. The rest of the
sigmoid colon is generally very movable, being provided with a long meso-colon
which is attached transversely in front of the psoas, and becomes continuous
internally near the bifurcation of the common iliac artery with the meso-rectum.
This portion may be termed the sigmoid loop or the sigmoid flexure proper. It is
very variable in its length and position, and frequently forms with the first part of
the rectum an omega loop (Treves). In many cases it forms a loop hanging down
int<^j the true pelvis ; if the bladder or rectum is distended it is pushed out of the pelvis
and may curve upwards as high as the umbilicus, and even in rare cases touch the
liver (Treves). Occasionally this loop lies in the iliac fossa in front, and to the outer
side of the first part of the sigmoid colon. When its mesocolon is short it simply
passes downwards and inwards across the iliac fossa, usually entirely covered in front
by the convolutions of the small intestine. The average length of its meso-colon is
about 3 inches. On turning upwards the sigmoid loo|) and its meso-colon the
mouth of a peritoneal pouch is sometimes seen, which is called the inler-sigmoid
fossa. It is somewhat funnel-shaped and extends upwards a variable distance in the
direction of the left ureter.

The Rectum. — The lowest part of the large intestine {intestinum rectum) extends
from the sigmoid loop of the colon to the anal canal. It is situated entirely
within the true pelvis to the pfjstcrior wall of which it is attached. Jt is continu(jus
at the pelvic brim near the left sacro-iliac articulation with the sigmoid flexure, and

VOL. III., PT. 4. I

Fig. 144. — Median section of the pelvis and its viscera in an adult male. (J. S.) |.

The bladder contained about 3 oz. of nrine and there were some fgeces in the lower part of the
rectum. 5th L.V., body of 5th lumbar vertebra; S, on body of 2nd sacral vertebra; P.S., pubic
symphysis; R.R., rectum; P.R., plica dextra recti; A.C., anal canal with its longitudinal folds of
mucous membrane— the columns of Morgagni. The tissues between the anal canal and the coccyx
constitute the ano-coccygeal body. I.S., internal sphincter ; E.S., external sphincter ; L.A., levator
ani ; E..C., recto-coccygeus muscle ; Bl., bladder ; P, pi, P^, prostate gland, P, its middle lobe,
between P and P', the common ejaculatory duct ; M., membranous part of urethra ; S. , spongy part of
urethra; C.G., corpus cavernosum ; Gr., glans penis; B., bulb of corpus spongiosum; B.C., bulbo-
cavemosus muscle ; F., supra-pubic pad of fat ; F^, retro-pubic pad ; 'p, peritoneum.

:dliJl

THE LARGE INTESTINE. Il5

passing downwards, backwards, and to the right, usually reaches the middle line
opposite the third piece of the sacruift. This is generallj' called the first part of the
rectum. At the third sacral vertebra it changes its direction, and curving forwards
and downwards as far as the lower end of the prostate gland forms the second part
of the rectum which is continuous below with the anal canal.

The first part of the rectum, about 5 or 4 inches long, is covered by peritoneum,
and attached by a fold of this membrane called the meso-redum to the front of the
sacrum. Some convolutions of the small intestine, or a loop of the sigmoid colon,
usually lie against its anterior aspect. In the male a distended bladder will push the
intestines upwards and come in contact with it, while occasionally in the female the
uterus touches it. On its left side are the ureter and the branches of the internal
iliac artery.

The second part of the rectum, 3 or 4 inches in length, is only partially covered
by peritoneum. It has no meso-rectum, and its posterior surface is entirely uncovered
by the peritoneum. At its commencement it is covered in front and at the sides,
but the peritoneum gradually leaves the lateral surfaces, and is finally reflected from
the anterior aspect on to the bladder about an inch above the prostate gland. In
passing from the rectum to the bladder the peritoneum forms a cul-de-sac, the recto-
vesical pouch, which is bounded above on each side by a lunated fold of the serous
membrane of which the left is almost always the larger {posterior false ligaments of
the bladder). Distension of the bladder and rectum tends to draw up the peritoneum
and thus diminish the depth of the recto-vesical pouch. The posterior wall of this
part of the rectum lies from above downwards on the lower part of the sacrum, the
coccyx and the ano-coccygeal body. The anterior wall, which is longer and more
curved than the posterior, is in contact with the recto-vesical pouch of peritoneum, a
triangular area at the base of the bladder with its lateral boundaries, the vasa
deferentia and the vesiculae seminales, and the prostate gland. Opposite the prostate
gland it turns downwards and backwards to end in the anal canal, not unfrequently
forming below the prostate a short blind recess (see fig. 144). In the female the
second part of the rectum is in relation with the pouch of Douglas and the posterior
vaginal vv'all. Sometimes the sigmoid flexure is displaced towards the right iliac
fossa, and the first part of the rectum descends in the pelvis in front of the right
half of the sacrum.

Variatioxs according to Age. — The rectum is straighter, more vertical, and
relatively larger in the infant than in the adult.

Stractnrc of the rectum. — The rectum differs in some respects from the rest
of the large intestine in the arrangement of both its muscular and mucous coats.

The muscular coat is thick ; the external or longitudinal fibres are found
all round the bowel, but are collected chiefly into two bundles, one on the anterior
and the other on the posterior aspect. The longitudinal fibres being rather shorter
than the other coats give rise to sacculations, which are chiefly situated at the sides
of the rectum. The circular fibres are well developed and form thick bundles at the
constrictions between the sacculations (Otis). A pair of small bands of plain
muscular tissue, which arise from the front of the second and third coccygeal
vertebra;, and are also connected with the pelvic fascia, pass with a slight downward
inclination to the posterior part of the anal canal (see fig. 144), and become inter-
mingled with its loiighudinal fibres. They are known as the recto-coccygeal muscles.

The mucous membrane of the rectum is thicker, redder, and more vascular
than that of the colon ; and it moves more freely upon the muscular coat. When
the rectum is empty and contracted it exhibits numerous folds, most of which are
obiit<;rated by distension. Several transverse or oblique folds are, however, of a
more permanent character, and have been designated "valves of the rectum"
(Houston) or "plicae recti." One of tliesC; usually the largest, is situated on

I 2

116

ORGANS OF DIGESTION.

the right side opposite the reflection of the peritoneum from the rectum to the
bladder, and ■o'as named by Kohh'ausch the " plica transversalis recti." There
are generally two other folds, both on the left side, one about an inch above, and the
other about the same distance beloAv, the fold on the right side. From the position
and projection of these folds they may more or less impede the introduction of
instruments. The dilatation of the rectum between the anal canal and the lowest
of these folds is called the rectal ampulla. (For the appearance of these folds on
rectal inspection with the body in the genu-pectoral position, see Otis, " The
Sacculi of the Rectum," Leipzig, 1887.)

The anal canal and its muscles. — The terminal portion of the alimentary
canal, which is surrounded by the sphincters of the anus, may be termed the anal
canal. It is an antero-posterior slit in the pelvic floor ; its lateral walls being in
opposition, it differs in this respect from the lower part of the rectum, which when
empty appears as a transverse slit (fig. 145). The anal canal is directed downwards

Fig. 145. A TRANSVERSE AND NEARLY

VERTICAL SECTION OP ADULT MALE
PELVIS ; THE SECTION PASSED FROM
ABOVE DOWNWARDS AND SLIGHTLY

BACKWARDS. Life size. (J. S.)

B. , cavity of bladder ; V. D. , vas
deferens ; S. V. , seminal vesicle ; K,,
second part of rectum ; A.Q., anal canal ;
L. A., levator ani; I.S., internal sphincter
of anus ; E. S. , external sphincter of
anus.

and backwards, and measures
fully an inch in length when the
rectum is empty, but is shorter
when the rectum is distended.
Its antero-posterior extent is
from half to three-quarters of an
inch (see fig. 144). It is bounded
behind by the ano-coccygeal body,
and at the sides by the fat of the
ischio-rectal fossse. Its anterior
relations diflPer in the two sexes ;
in the male the bulb of the
corpus spongiosum lies a little
in front of it, while in the
female it is separated from the vulval opening, and the lower end of the vagina
by the perineal body.

In the skin around the anus and about a centimeter from its margin is a circular
zone of large sweat glands which are known as the circumanal glands. At the anus
the epidermis is continued for a short distance into the aperture, but becomes
gradually thinner and finally is replaced by the columnar cells of the mucous
membrane. The crypts of Lieberklihn do not appear immediately; there is a
narrow zone of mucous membrane destitute of glands.

The mucous membrane of the anal canal is thrown into 4 or 5 longitudinal
folds on each side which were named by Morgagni the columns of the rectum.
These folds contain longitudinal muscular fibres (apparently part of the muscu-
laris mucosae) which terminate both superiorly and inferiorly in elastic tissue
(Treitz).

The muscles which close the anal canal are the internal and external sphincters

LITERATURE OF THE INTESTINES. 117

and the levatores ani. The external sphincter and the levator ani will be found
described in Vol. II. pt. 2.

The internal sphincter is a pale muscle, composed of non-striped fibres, which
surrounds the entire length of the anal canal. It is of nearly uniform thickness,
about 4 mm., in its entire extent, and ends almost abruptly above, where it
becomes continuous with the much thinner circular fibres of the rectum.

Vessels and Nerves of the Kectum and Anal Canal. — The arteries of the
rectum spring from three sources, viz., the superior hamorrhoidal from the inferior
mesenteric, the middle Jmmorrhoidalixom. the internal iliac, and the inferior hcemor-
rhoidal from the pudic artery. Of these the most important is the superior hgemr)r-
rhoidal. It is a single vessel which descends in the mesc -rectum, and then divides
into two branches which form loops, one on each side of the rectum, with the con-
vexity of the loop directed downwards. From these loops several branches arise which
pass downwards, pierce the muscular coat, and run in a longitudinal direction under
the mucous membrane, and anastomose freely with one another. In the anal canal
they lie in the longitudinal folds of the mucous membrane and reach as far as the
verge of the anus. The arrangement of the veins is somewhat similar ; they com-
mence in little dilatations at the lower end of the anus, ascend beneath the mucous
membrane for aljout three inches, where they communicate with one another to form
the haemorrhoidal plexus, and then pierce the muscular coat by 6 or 6 openings,
and pass upwards to the superior haemorrhoidal vein, which forms the beginning of
the inferior mesenteric trunk. According to Quenu, the haemorrhoidal plexus
communicates freely with the tributaries of the inferior hiemorrhoidal, but only
slightly with those of the middle haemorrhoidal.

The lymphatics enter some glands placed in the hollow of the sacrum (see
Vol. I r., Pt. 2, p.- 051).

The nerves are very numerous, and are derived from both the cerebro-spinal and
the sympathetic systems. The former consist of branches derived from the sacral
nerves, and the latter of offsets from the inferior mesenteric and hypogastric plexuses.
Experiments upon animals have shown that the longitudinal muscular fibres of the
rectum are supplied with motor fibres from the anterior roots of certain of the sacral
nerves (2nd and 3rd, and in part the 1st in the dog), which nerves also supply inhibitory
fibres to the circular coat, whereas the fibres of the hypogastric plexus which supply
the circular muscular tissue with motor fibres, are derived from white rami com-
municantes of the anterior roots of certain of the lumbar nerves, which join the
sympathetic chain and lose their medullary sheath before passing to their distribution
in the muscular coat. Pilliet has noted the presence of Pacinian corpuscles upon
some of the nerves distributed to the anal mucous membrano.

EECENT LITERATURE OF THE INTESTINES.

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Toldt, C, Die Fcn-mhildung d. menschl. Blinddarmes u. die Valv. Coli, Sitz. der Wiener Akad.,
Bd. ciii., 1894.

Tomarkin, E., Lieberkilhn'sche Krypten und ihre Bezichungen zu den Follikeln beim Meerschwein-
chen, Anat. Anzeiger, Jg. viii., 1893.

Tuffler, Conformation exterieure et vaisseaux du ccecum, Bulletins de la societe anatomique de
Paris, Annee Ixi., lS8t5.

TJhlyarik, "E. and Tolti, L., Ueher die histologische Sti'uktur der Diinndarmzottcn und iiber
Fettresorption, Aus dem physiolog. Institut der k. Ungar.Yeterinar-Lehranstalt zu Budapest, Mathemat.
u. naturwissenschafte Berichte aus [Jngarn, Bd. vi., 1887-88.

"Windle, B. C. A., Notes on an abnormal arrangement of the large intestine, Journ. of Anat. and
Phys., vol. XX.

Young:, R. Bruce, Abnormal disposition of the colon. Journal Anat. and Phys. vol. xix. , 1884.

Zuckerkandl, E., C'eber die Obliteration des Wuriufortsatses beim Menschen, Anat. Hefte, B. iv.,
1894.

THE LIVER. 121

THE LIVER.

The liver is the largest glaud in the body, aud dj far the most bulky of
the abdomiual viscera. Its shape is liable tc ocnsiderable variations, but is
essentially that of a right-angled triangular prisitx, with the right angles rounded
off. If the upper part of the abdomen be supposed to be occupied by a cuboidal
mass divided into two by a cut passing from its upper left edge to its lower right
one, the position aud shape of the liver will be represented by the upper and right
half of this mass. The liver has live surfaces, viz., anterior, posterior, superior,
inferior, and right. The anterior and posterior surfaces are triangular, one of their
angles, which is situated above and on the right side, being rounded off, while the
remaining two are acute, and placed one above and on the left side, the other below
and on the right.

Dimensions and Weight. — The greatest vertical extent of the liver is near its
right surface, where it measures, on an average, from five to seven inches. This
diameter gradually diminishes from right to left, the organ ending on the left side
in a thin sharp border. Its greatest transverse diameter is usually one or two inches
more than the corresponding vertical one, but is sometimes less. The antero-
posterior diameter is greatest on the right side of the vertebral column, and just
above the right kidney ; here it measures from four to six inches. In front of the
vertebral column its antero-posterior extent is considerably reduced, being in the
median plane only about two-and-a-half to four inches. The ordinary bulk of the
liver is 90 to 100 cubic inches, and its average weight between 50 and 60 ounces.
According to the facts recorded by Reid, the liver weighed, in 43 cases out of 82,
between 48 and 58 ounces in the adult male ; and, in 17 cases out of 36, between
40 aud 50 ounces in the adult female. It is generally estimated to be equal to about
l-36th of the weight of the whole body ; but in the foetus, and in early life, its
proportionate weight is greater. Thus at birth it is about 1-1 8th of the body
weight.

Vierordt (Anatom. Daten u. Tabellen) prives the following approximate numbers for the
adult : — Weigrht, male l,o7'J g., female 1,520 g. ; volume, 1,720 cubic cent. ; length, 320 mm. ;
eagittal diameter, 200 mm.

The specific gravity of the liver is between 1"05 and 1'06 ; in fatty degene-
ration this is reduced to 1'03, or even less.

The liver is solid to the touch, but easily torn. Its colour is a dull reddish-
brown, with frequently a dark purplish tinge along the anterior margin. During
life it is probably softer than after death, as when hardened in situ it shows
impressions for all the viscera that are in contact with it.

The liver is divided into two unequal lobes, a right and a left, and on the
under and posterior surfaces of the right lobe are three secondary lobes, named the
lobe of tS/zifjeliun, the caudate or tailed lobe, and the quadrate lobe.

The right and left lobes are separated from each other on the under surface by
the umbil ical fmmre (fig. 147, uf), and on the posterior surface by its prolongation,
the Jissure for the ductus venosus (f.d.v.). On the anterior aud upper surfaces the
only indication of a separation between them is the line of attachment of the fold of
peritoneum, termed the falciform or broad lifjaiiipnl, except below, where the
umbilical fissure is prolonged upwards on the anterior surface for a short distance,
Uirm'iu'^ this umbilical notch (i\<!;. 146). The right lobe is much lai'ger and thicker
than the left, which is very variable in extent, and ordinarily constitutes only about
one-fifth or one-sixth of the entire gland.

Surfaces. — I'he anterior (fig. 146) is fr(M|uently the largest of all the surfaces.
It 1.-, iiiuuulh aud tiiaiigiihir, and united witli the upper and right surfaces by

122

ORGANS OF DIGESTION.

rounded borders, but separated from the under surface by a sharp margin, which
can often be felt in the living body. This surface is formed by both the right and
left lobes, the separation between which is indicated by the umbilical notch and the
attachment of the falciform ligament. To the right of the umbilical notch the
lower margin of this surface presents an excavation situated over the fundus of the
gall-bladder. The peritoneum covers the whole of the anterior surface, except along
a narrow line between the two layers of the above-named ligament.

The posterior surface (fig. 147) is triangular, very uneven, only partially covered
by peritoneum, and not so distinctly marked off from the under surface as is the
anterior. It includes :— 1. A portion of the left lobe which lies immediately in front
of the cardia, and abuts against the anterior wall of the omental sac. The upper
part (fig. 147, C), which is in contact with the cardia, is concave, but the remainder

Fig. 146. — Anterior surface of the liver. (J. S.)
K, right lobe ; L, left lobe ; B, fundus of gall-bladder ; C, round ligament of liver.

forms a considerable protuberance {onwiial hiberosity, t.o.) projecting over the lesser
curvature of the stomach. This posterior surface of the left lobe passes with
a gradual slope into the under surface. 2. The Spigelicm lobe {lolulus S'lngelii, L.S.)
and the caudate lohe {L.G.). The latter is a narrow ridge prolonging the Spigelian
lobe towards the under surface of the right lobe. It runs behind the portal fissure,
and lies immediately above the foramen of Winslow. The Spigelian lobe is
separated from the left lobe by the fissure of the ductus venosus, and from the
posterior surface of the right lobe by the fossa for the vena cava. Its free surface
looks directly backwards, and is nearly vertical and slightly concave from side to
side. Superiorly it slopes over towards the upper surface of the organ, while its
inferior border is divided by a notch into a right part, which joins the caudate lobe,
and a left portion, ending in a small tubercle (tuber 2^apiUare, His). The Spigelian
lobe is opposite the tenth, and eleventh dorsal vertebrse. It rests against the
diaphragm, the two opposing surfaces being covered by peritoneum belonging to the
lesser sac. Behind its upper left hand corner the lower end of the oesophagus passes
obliquely into the cardia. Lower down behind the left border is the end of the
tnoracic aorta, separated, however, from the liver by the diaphragm. 3. A strip

THE LIVER.

123

of the right lobe 2| to 3 inches broad ; convex for the most part, except for
a small depression at its lower and mesial corner, which receives the right snpra-renal
capsule {imprcssio supra-renalis, i.sr.). In consequence of the separation of the
layers of the coronary ligament, this surface of the right lobe (fig. 147, X) is not
covered by peritoneum except at its right extremity. It rests against the ascending
part of the diaphragm, and superiorly passes gradually into the upper surface.
Inferiorly it is separated by a sharp margin from the renal impression on the under
surface. This margin is sloped obliquely downwards and outwards, following
the line of the eleventh and twelfth ribs. The mesial border often projects over the
inferior vena cava.

The upper surface of the organ is smooth, covered by peritoneum and

R.L

'''*lsl^5&*

Fig. 147. — Thk liver of a young sdbject, sketched from below and behind. (The drawing has
been made hy Mr. Wesley from a cast prepared under the direction of Prof. His of Leipzig.) A

.ff. /«., rigiit lobe; LL., left lobe; L.S., lobe of Sjiigeliiis ; L.C., caudate lobe; L.Q., quadrate
lobe; p, jjortal fissure; u.f., umbilical fissure ; /.(/.r., fissure of the ductus venosus ; ;).bl.y gall-
bladder ; v.c.i., vena cava inferior ; %.(j., impression on the under surface ot the left lol)e corresponding
to llie stomach ; C, j)Osition of the cardia ; t.o., projection of the posterior surface of the left lobe against
the lesser omentum (tuber omentale, His); i.e., im2)ressio colica ; i.r., impressio renalis ; i.sr.,
impressiosu]jra-renalis ; i.d., impressio duodenalis ; ^', j'", 1^"*) l>*, lines of reflection of the 2)eritoneum ;
A', surface of the liver uncovered by peritoneum.

exactly moulded to the under surface of the diaphragm. Near the median plane it
'_Mvc8 attachmenc to the falciform ligament. It has two rounded convex ])ortions
-eparated by a shallow concavity coriespondiug to tiie situation ot the heart. The
right convexity is much larger and more prominent than the left one.

The under surface is concave, uneven, and looks downwards, backwards,
and to the left. It is invested with peritoneum everywhere except where the gall-
bladder (fig. Wl.y.hl.) is adherent to it, and at the jiortal fissure {p), where the fold
of peritoneum termed the lesser omentiun, wliieh enclo.^-s tiie blood-vessels and
'lijcts of the viscuH, comes oU', atid passes to the smaller curvature of tlie stomacli.
The under surface of the left lobe (i.f/.)i8 moulded over the subjacent cardiac part of
if)e stomach, and over that part of the anterior hurfacc of the stomach which is
next to the lesser curvature.

124

OKGANS OF DIGESTION.

The under surface of the right lobe may be regarded as divided by the fossa
which lodges the gall-bladder {fossa sen inipressio vesicalis) into two unequal
portions. Of these the lateral is by far the larger, and is mainly occupied by two
large shallow concave impressions, one situated anteriorly being produced by the
hepatic flexure of the colon {impressio coUca, i.e.), the other and posterior one being
caused by the right kidney {im^jressio renalis, i.r.). These two impressions
are separated from one another by a low ridge. At the mesial border of the renal
impression is a third narrow and but slightly marked impression, corresponding to
the descending part of the duodenum {mpressio duodenalis, id.).

The mesial of the two parts into which the fossa of the gall-bladder subdivides
the under surface of the right lobe is somewhat rectangular and oblong, having the
antero-posterior diameter greater than the transverse ; it is known as the quadrate
Me {L.Q.). It is immediately over the pyloric end of the stomach and the

Fig. 148.— Coronal section op part of thorax and abdomen of female child, aged one year

AND TEN MONTHS. TuE LIVER IN THE INFANT IS RELATIVELY LARGER THAN IN THE ADULT.

(J. S.)

R.L., right lung ; L.L., left liiDg ; R.A., right auricle of heart ; R.V., rij,ht ventricle, distended with
lujectiou ; S, stomach, empty and contracted ; P, pylorus, situated in the median plane just beneath the
longitudinal fissure of liver ; D, first part of duodenum in contact with quadrate lobe of liver ;
Gr. B. , gall-bladder, which was full of bile.

commencement of the duodenum, and when these are distended they impress upon
the surface of the quadrate lobe a slight concavity. It is bounded on the left by
the umbilical fissure, and behind by the transverse or portal fissure.

The right surface is convex from before backwards, and often slightly
convex from above downwards. It unites with the upper, anterior, and posterior
surfaces by rounded borders, but is separated below from the under surface by a
sharp edge.

Fissures. — The transverse or portal fissure (fig. 147, |?) is the most important,
because it is here that the great vessels and nerves enter, and the hepatic duct
passes out. It lies transversely between the quadrate lobe in front and the caudate
and Spigelian lobes behind, and meets the longitudinal fissure nearly at right angles.

The longitudinal fissure, between the right and the left lobes, is divided into two
parts by its junction with the transverse fissure. The anterior part {u.f.), named

THE LIVER. 125

the wnlnlical fis^yrp, contains the umbihcal vein in the foef'i?; and the remnant of
that vein in the adult, wliich then constitutes the round hgamcnt. It Ues between
the quadrate and left lobes of the liver, the substance of which often forms a bridge
{pons hcpatis) across the fissure, so as to convert it partially or completely into a
canal. The posterior part {f.d. v.) is named VdQ fissure of the ductus venosus ; it is
situated between the lobe of Spigelius and the left lobe, and lodges the ductus
venosus in the foetus, and in the adult a sbnder cord or ligament into which that
vein is converted.

The fissure or fossa of the vena cava {v. c. i.) is situated at the back of the liver
between the Spigelian lobe and the right lobe, and is separated from the transverse
fissuie by the caudate lobe. It is at the upper part of this fossa that the blood
leaves the liver by the hepatic veins, which end here in the vena cava. As in the
case of the umbilical fissure, the substance of the liver in some cases unites around
the vena cava, and encloses that vessel in a canal.

The transverse and umbilical fissures are on the under surface of the liver ; the
fissure of the 'ductus venosus and that for the vena cava are on the posterior
surface.

Ligaments and Omentum. — The ligaments of the lirer are, with one
exception, only reflections of serous membrane. Thus the name coronari/ ligament is
given to the reflection of peritoneum around the somewhat triangular portion of the
posterior surface of the liver (fig. 147, JT), which is here immediately adherent to the
diaphragm. These reflections are continued at either end into a fold — the right
and left lateral ligaments, of which the left is the longer and more distinct, the risrht
being sometimes scarcely perceptible. Another of these so-called ligaments is the
falciform, h'oad, or suspensory ligament, a wide thin membrane, formed of two
cohering layei"s of peritoneum continuous behind with the upper layer of the
coronary and left lateral ligament respectively. By one of its margins it is
connected with the under surface of the diaphragm, and with the sheath of the
right rectus muscle of the abdomen as low as the umbilicus ; by another it is
attached along the upper and anterior surfaces of the liver ; the remaining margin is
free, and contains between its layers the round ligament, a dense fibrous cord, the
remnant of the umbilical vein of the foetus, which ascends fi'om the umbilicus
within the lower edge of the falciform ligament, and enters the longitudinal fissure
on tlie under surface.

In addition to the folds called ligaments, the liver gives attachmcTitto two Liyers
of peritoneum, which pass between the liver and stomach, and form the gastro-
hepatic or lesser omentum. This is attached to the transverse fissure of the liver,
and the posterior part of the longitudinal fissure, or the fissure of the ductus
venosus, and near its right free border encloses between its two layers the bile-duct,
port-il vein, hepatic artery, lymphatics, and nerves.

Position with regard to the abdominal and thoracic parietes. — The
liver occupies the right hypochondriac and epigastric regions, extending also
frequently into the left hypochondriac and right lumbar. In almost the whole of
it8 extent it is separated from the surface of the body by the lower ribs and costal
cartilages, but in the subcostal angle a small part of the anterioi- surface lies directly
behind the abdominal wall. Above it is accurately adapted to the vault of the
diaphragm, and the right lobe reaches higher beneath the ril)s than the left,
corresj)onding thus with the more elevated position of the diaphragm on the right
si'le. The liver is separated by the diaphragm from the concave base of the right
Inng, the thin margin of which descends a short distance between the thoracic wall
and the solid niftss of the liver.

The right surface is protected by the seventh to the 11th ribs, and the anterior
surface hy the fifth, sixth, seventh, eighth, and ninth costal cartilages, with tlie

126

OEGANS OF DIGESTION".

anterior parts of the corresponding ribs, and by the cnsiform cartilage, the
diaphragm, of course, being interposed. The upper limit of the liver may be
indicated on the anterior wall of the chest by a line which crosses the median plane
at the lower end of the body of the sternum. On the right side this line must be
extended outwards and slightly upwards, so that in the mammary line it is near" the
upper edge of the fifth rib, from which point it descends towards the seventh rib in
the mid-axillary line. On the left side the line passes nearly horizontally outwards,
being slightly overlapped by the heart.

Its lower limit on the right side practically coincides with the lower edge of the
thoracic wall as far inwards as the tip of the ninth costal cartilage. About this
point the line representing its lower edge passes upwards and to the left, to near the
tip of the eighth costal cartilage. It is then continued in the same direction
across the left costal cartilages, to meet the left end of the upper limit at an acute
angle.

The situation of the liver is modified by the position of the body, and also by the
movements of respiration. Thus, in the upright or sitting position it descends
to just below the lateral margin of the thorax, but in the recumbent posture ascends
half an inch or an inch higher up, and is entirely covered by the ribs, except
a small portion opposite the sub-costal angle. During a deep inspiration the liver

Fig. 149. — Sketch of a portion of the under sur-
face OF THE LIVER, SHOWING THE ARRANGEMENT
OF THE VESSELS IN THE PORTAL FISSURE. (Gr. D. T. )

a, hepatic artery ; p, portal vein ; d, bile-duet ;
g.hl, gall-bladder; 2^ ^ P^, lines of reflection of the
peritoneum.

also descends below the ribs, even in the
recumbent posture, and in expiration
retires up behind them. In females it is
often permanently forced downwards below
the costal cartilages, owing to the use of tight
stays ; sometimes it reaches nearly as low as
the crest of the ilium, and in many such cases its convex surface is indented from
the pressure of the ribs.

The position of the liver is also affected by the condition of its neighbouring
organs. Thus, when the intestines are distended and the abdomen prominent, the
liver is pushed upwards, and its vertical extent diminished, while when these are
empty and the abdominal wall retracted, the liver is compressed from before
backwards, and the inferior surface is nearly in the same plane as the posterior.
Again, with the distension of the stomach the left lobe of the liver is pushed over
towards the right side.

Vessels and Nerves.— The two vessels by which the liver is supplied with
blood are the hepatic artery and the portal vein. The hepatic artery (fig. 149),
a branch of the coeliao axis, is small in comparison with the organ to which it is
distributed. It enters the transverse fissure, and there divides into a right and left
branch for the two principal lobes.

By far the greater part of the blood which passes through the liver — and in this
respect it differs from all other organs of the human body — is conveyed to it by a
large vein, the portal vein, or vena portse (fig. 149). This vein is formed by the
union of the veins of the stomach, intestines, pancreas, and spleen. It enters the
transverse fissure, or porta hepatis, and, like the hepatic artery, there divides into
two principal branches.

The hepatic artery and portal vein, lying in company with the bile-duct, ascend

THE LIVER. 127

to the liver between the layers of the gastro-hepatic omentum, in front of tlie
foramen of Winslow, and thus reach the transverse fissure. In this course the
bile-duct is to the right, the hepatic artery to the left, and the large portal vein
behind the other two. They are accompanied by numerous lymphatic vessels and
nerves. The branches of the three vessels accompany one another in their course
through the liver nearly to their termination, and are surrounded for some distance
by an areolar investment, the so-called capsule of Glisson, which is prolonged into
the interior of the organ.

The hepatic veins, which convey the blood away from the liver, pursue through
its substance an entirely different course from the other vessels, and pass out at its
posterior surface, where, at the upper part of the fossa already described, they end
by two or three principal branches, besides a number of smaller ones, in the vena
cava inferior.

The lymphatics of the liver, large and numerous, form a deep and a superficial
set. Their mode of origin and their course will be afterwards described.

The nerves are derived partly from the coeliac plexus, and partly from the
pneumogastric nerves, especially from the left pneumogastric. They enter the liver
supported by the hepatic artery and its branches, along with which they may be
traced in the portal canals.

Excretory Apparatus. — The excretory apparatus of the liver consists of the
hepatic duct, the cystic duct, the gall-bladder, and the common bile-duct.

The hepatic duct, formed by the union of a right and left branch, which
issue from the bottom of the transverse fissure and unite at a very obtuse angle,
descends to the right, within the gastro-hepatic omentum, in front of the vena
portEB, and with the hepatic artery to its left. Its diameter is about ^th of an inch
(•4 mm.), and its length nearly two inches (one inch only, according to Luschka).
At its lower end it meets with the cystic duct, descending from the gall-
bladder, and the two ducts uniting together at an acute angle form the common
bile-duct.

The gall-bladder (fig. 147, g.bl.), is a pear-shaped membranous sac, 3 or 4
inches (lo to 100 mm.) long, about an inch and a half (35 mm.) across its widest
part, and capable of containing from 8 to 12 fluid-drachms (30 to 50 cub. cent.).
It is lodged obliquely in the fossa before mentioned on the under surface of the
right lobe, with its large end or fundus, which projects beyond the anterior border
of the liver, directed forwards, downwards, and to the right, whilst its necJc is
inclined in the opposite direction. Its upper surface is attached to the liver by
areolar tissue. Its under surface and fundus are covered by the peritoneum,
which is reflected over them from the surface of the liver. In rare cases the
peritoneum completely surrounds the gall-bladder, which is then suspended by
a sort of mesentery l^om the under surface of the liver. The fundus generally
touches the abdominal parietes immediately beneath the margin of the thorax,
opposite the nintii costal cartilage. It is, however, subject to considerable varia-
tions. Thu.s, if the liver be small, or the gall-bladder empt-y, it often fails
to reach the abdominal wall. In cases of distension of the stomach it may be
displaced to the right. The gall-bladder rests below on the commencement of the
transverse colon ; and, farther back, it is in contact with the duodenum, and some-
times with the pyloric extremity of the stomach. The neck, gradiiaJly narrowing, is
curved like the letter 8, and then, becoming much constricted, and changing its
general direction altogether, it bends downwards and terminates in the cystic duct.

The gall-bladder is supplied with blood by the cystic artery, a branch of tho
right division of the hepatic artery, along which vessel it also receives nerves from
the ca;liac plexus. The cystic veins empty themselves into the vena portae.

128 OKGANS OF DIGESTION.

The cystic duct is about an inch and a half in length (35 mm., Luschka),
and only about -^th of an inch wide (2*3 mm., Krause). It runs backwards,
downwards, and to the left, and unites with the hepatic duct to form the common
bile-duct.

The common bile-duct, ductus communis choledochus, about \ of an inch
(5'6 mm. to 7*5 mm,, Krause) in width, and nearly three inches (about 70 mm.)
in length, conveys the bile into the duodenum. It passes downwards and back-
wards, continuing the course of the hepatic duct, between the layers of the gastro-
hepatic omentum, in front of the vena portge, and to the right of the hepatic artery.
Passing behind the first part of the duodenum it reaches the descending portion
and continues downwards on the inner and posterior aspect of that part of the
intestine, covered by or included in the head of the pancreas, and for a short
distance in contact with the right side of the pancreatic duct. Together with that
duct, it then perforates the muscular wall of the duodenum, and, after running
obliquely for three quarters of an inch between its coats, and forming an elevation
beneath the mucous membrane, it becomes somewhat constricted, and opens by a
common orifice with the pancreatic duct on the inner surface of the intestine,
near the junction of the second and third portions of the duodenum, and three or
four inches beyond the pylorus, as already described.

Liver in the Infant. — The liver is relatively much larger in the new-born
child than in the adult. Indeed, at birth, it occupies nearly one half of the
abdominal cavity. The left lobe, as compared with the right, is distinctly larger
than in the adult, and often reaches to the left, so as to come in contact with
the lateral wall of the abdomen on that side, presenting in this position a distinct
left surface. In such cases Ballantyne describes the anterior surface as being
more nearly quadrilateral than triangular. According to this authority, the
anterior surface of the liver in the new-born infant corresponds in its vertical extent
in the median plane with the last four dorsal and upper two lumbar vertebras, and its
lower border is within 2 cm. of the umbilicus. Its vertical extent increases from
left to right, the lower edge of the right surface coming within 1 cm. or 1-5 cm. of
the right iliac crest.

Varieties. — The liver is not subject to great or frequent deviation from its ordinary
form and relations. It has been found without any division into lobes. On the other hand,
Soemmerring- has recorded a case in which the adult liver was divided into twelve lobes, and
similar cases of subdivided liver (resembling that of some animals) have been now and then
observed by others. A detached portion, forming a sort of accessory liver, is occasionally
found appended to the left extremity of the gland by a fold of peritoneum containing blood-
vessels. The upper surface sometimes shows longitudinal furrows, which are occupied, when
the organ is in situ, by folds of the diaphragm. These have been attributed to tight lacing,
but, according to Turner, they are found almost as frequently in males as in females, and
are probably congenital. Various cases have been described of unusual mobility of the liver
in women with flaccid and often pendulous abdominal walls (see Landau, Die Wanderleher
wid der Hdngehauch der Frauen, 1888).

The gall-bladder is occasionally wanting, in which case the hepatic duct is much dilated
within the liver, or in some part of its course. Sometimes the gall-bladder is irregular in
form, or is constricted across its middle, or, but much more rarely, it is partially divided in
a longitudinal direction. Purser (Trans. Acad. Med., Ireland, Vol. V.) has recorded a case in
which there were two distinct gall-bladders, each having a cystic duct which joined the
hepatic duct. The gall-bladder has been found on the left side (Hochstetter, Arch. f. Anat.,
1886) in subjects in which there was no general transposition of the thoracic and abdominal
viscera. Direct communications by means of small ducts (named hepato-cystic), passing
from the liver to the gall-bladder, exist regularly in various animals ; and they are sometimes
found, as an unusual formation, in the human subject.

The right and left divisions of the hepatic duct sometimes continue separate for some
distance within the gastro- hepatic omentum. Lastly, the common bile-duct not unfrequently
opens separately from the pancreatic duct into the duodenum.

THE LIVER.

129

STRUCTUKE OP THE LIVER.

The liver is covered externally by a serous coat derived from the peritoneum.
This, with its folds and so-called ligaments, has already received notice. In its
general structure it resembles other serous membranes, but no stomata have as yet
been described in it. Connecting the serous coat to the glandular substance, and
also present where the serous coat is absent, is a layer of areolar tissue, which
is described as the areolar or fibrous coat of the organ. Its inner surface is
connected with the delicate areolar tissue which lies between the hepatic loDuies.
Opposite the transverse fissure, where it is greatly increased in amount, it invests
the entering and issuing vessels and duct, forming for them a loose but strong
sheath of areolar tissue, which surrounds all their branches as they ramify through
the organ, becoming more and more delicate, until it becomes continuous with the
areolar tissue between the lobules. To this investment of areolar tissue, which
encloses the three vessels above mentioned, and their branches, the name capsule of
Glisson has been applied, and the canals through the liver substance which ai-e
occupied by those vessels and their " capsule " have been termed portal canals.
At the back of the liver, where there is no serous coat, the areolar coat is also

Fi^

150. — Section of a portal canal (E. A. S.).
Magnified.

«, branch of hepatic artery ; v, branch of portal vein ;
d, bile-duct ; /, I, lymijhatics in the areolar tissue of Glisson"s
cap.sule which enclo.ses the ves.sel.s.

considerably thickened, and it here invests the
hepatic veins as they issue from the organ to
open into the vena cava inferior. These veins
and their tributaries are also invested in their
cour.se through the liver by areolar tissue con-
tinuous with that of the areolar coat, but it is
very small in amount, and binds the hepatic
veins clo.sely to the glandular substance, so that
in section of these hepatic canals in the dead
liver the vein always remains patent, whereas in
section of the portal canals the looseness of the

areolar tissue investing them, and the large relative amount of this tissue, enables
the branches of the portal vein to collapse, and this is their usual condition when
seen in section, if empty of blood. Both the portal and the hepatic canals conduct
lymphatic vessels, which discharge their lymph into lymphatic glands, situated
respectively at the transverse fissure and behind the organ.

Hepatic lobules. — The proper substance of the liver, which has a mottled
aspect when closely observed, is compact, but not very firm. It is easily cut
or lacerated, and is not unfrequently ruptured during life from accidents in Avhich
other j)art8 of the body have escaped injury. When the substance of the liver is
torn, the broken surface is not smooth, but coarsely graimlar, the liver being
composed of a multitude of small lobules (fig. 151), which vary from V^itli to J,tli of
an inch in diameter (1 — 2 millimeters).

These lobules in some animals, as in the pig and camel, are completely isolated
one from another by areolar tissue continuous with the fibrous coat of the liver, and
with the capsule of (ilisson ; but in tbe iniman subject and in most animals,
although very distinguishable, they are confluent in a part of their extent.

The loljules of the liver have, throughout its substance, in general the polyhedral
form of irregularly compressed spheroids, but on the surface they are flattened and

VOL. III. I'T. 4, '^

130

ORGANS OF DIGESTION.

angular. They are all compactly arranged around the sides of branches (suhloiiilar)
of the hepatic veins (fig. 151), each lobule resting, by a smooth surface or base, upon
the vein, and being connected with it by a smaU venous trunklet {intralobular),
which begins in the centre of the lobule, and passes out from the middle of its base,
to end in the larger subjacent vessel. If one of the sublobular veins be opened (as
in the figure), the bases of the lobules may be seen through the coats of the vein,
which are here very thin, presenting a tesselated appearance, each little polygonal
space representing the base of a lobule, and having in its centre a small spot, which
is the mouth of the intralobular vein (/).

Each lobule consists of a mass of cells penetrated from the circumference to the

d a

Fig. 151. — Section of a portion of liver passing longitudinally through a considerable hepatic
VEIN, FROM THE PIG (after Kiernan). About 5 Diameters.

H, hepatic venous trunk, against which the sides of the lobules are applied ; h, h, h, three
sublobular hepatic veins, on which the bases of the lobules rest, and through the coats of which they
are seen as polygonal figures ; i, mouth of the intralobular veins, opening into the sublobular veins ;
i', intralobular veins shown passing up the centre of some divided lobules ; c, c, walls of the hepatic
venous canal, with the polygonal bases of the lobules.

Fig. 152. — Longitudinal section of a portal canal, containing a portal vein, hepatic artery, and
hepatic duct, froji the pig (after Kiernan). About 5 diameters.

P, branch of vena portje, situated in a portal canal, formed amongst the lobules of the liver ;
p, p, larger branches of portal vein, giving off smaller ones named interlobular veins ; there are also
seen within the large portal vein numerous orifices of interlobular veins arising directly from it ;
a, hepatic artery ; d, biliary duct ; at c, c, the venous wall has been partially removed.

centre by a close network of blood-capillaries, as well as by the minute capillary
commencements of the bile-ducts, with the intervention of little other tissue. For
convenience of description, the disposition of the vessels of the liver may be con-
sidered first.

Blood-vessels. — The portal vein and hepatic artery, accompanied by the
emerging biliaiy ducts, enter the liver at the transverse fissure. AYithin the liver
the branches of these three vessels lie together in the portal canals.

The portal vein subdivides into branches which ramify between the lobules,
anastomosing freely around them, and are named inierlobular or peripheral veins
(fig. 153,^;). The branches of these pass into the lobules at their circumference,

THE LIVER.

131

and end in the capillary network, from which the intralobular or central veins take
origin. Within the portal canals the branches of the portal vein receive small
veins which are returning blood distributed by branches of the hepatic artery.

The hepatic artery terminates in three sets of branches, termed vaginal,
capsular, and interlobular. The vaginal branches ramify within the portal canals,

Fig. 153. — Diagrammatic representation of two hepatic luuules (E. A. S. )

The left-hand lobule is represented with the intralobular vein cut across ; in the right-hand one the
section takes the course of the intralobular vein, p, interlobular branches of the portal vein; /;, intra-
lobular branches of the hepatic veins ; s, sublobular vein : c, capillaries of the lobules. The arrows
indicate the direction of the course of the blood. The liver-cells are only represented in one jmrt
of each lobule.

supplying the walls of the ducts and vessels, and the accompanying connective
tissue. The capsular branches appear on the surface of the liver spread out on the
fibrous coat, accompanied by their veins. The interlohular branches accompany the
interlobular veius, but are much smaller ; they supply blood to the walls of these and

Fio. 154. — Capillary network of

THE LOBULES OF THE RABBIt's

LIVER (from Kolliker). About
40 Diameters.

The figure is taken from a very
successful injection of the hepatic
veins made by Harting ; it shows
nearly the whole of two lobules, and
parte of three others : p, portal
branches running in the interloliular
«pace8 ; h, hepatic veins radiating
from the centre of the lobules.

the accompanying bile-ducts ;
it is doubtful if they transmit
any blood directly to the capil-
lary network of the lobules.

The capillary network P ^'■

of the lobules is very clcse,

HO that commonly the interval between two vessels is not greater than the diameter
of two liver cells (figs, 1 .'>?>, 154, ]");')). Moreover, the vessels are comparatively
large (0-01 mm,), and in specimens in which they have been filled with transparent
injection, can be seen, not only to pass in a radiating manner, as before described,
between the intra- and inter-lobular veins, but also in the human subject to be
c<jntiuued from one lobule to another,

K 2

132

OEGANS OF DIGESTION.

The capillaries are accompanied by a small amount of fine connective tissue
of a retiform or reticular character, the fibrils of which are densely felted, and when
stained give the appearance of a close lattice-work. This is far better developed in
some animals than in man. Characteristic of this tissue is the presence of a large
number of stellate cells (Kupffer), which appear to be applied to the blood-capillaries.
This reticular tissue occurs more abundantly at the centre and surfaces of the
lobule, near the intralobular and interlobular veins, than elsewhere ; it forms a
delicate framework to the vascular and glandular structures. In the connective

Fig. 155. — Cross section of a lobule of the human liver, in which the capillary network

BETWEEN THE PORTAL AND HEPATIC VEINS HAS BEEN FOLLY INJECTED {from SappCj). 60
DIAMETERS.

1, sectiou of the intralobulai" or central vein ; 2, its smaller branches collecting blood from the
capillary network ; 3, interlobular or peripheric branches of the vena portse with their smaller
ramifications passing inwards towards the capillary network in the substance of the lobule.

tissue accompanying the interlobular veins there are numerous granular connective
tissue cells.

The hepatic veins commence in the centre of each lobule by the convergence
of its capillaries into the single independent intralobular or central vein (figs.
153, h, and 155, 1), as already stated. These minute intralobular veins open at
once into the sides of the adjacent sublolular veins (fig. 153, s), which are of
various sizes, and join to form larger vessels, ending at length in hepatic venous
trunks, which receive no intralobular veins. Lastly, these venous trunks, con-
verging towards the posterior surface of the liver, and receiving in their course other
sublobular veins, terminate in the vena cava inferior, as already described. In this
course the hepatic veins and their successive ramifications are unaccompanied by any
but lymphatic vessels. Their coats are thin ; the sublobular branches adhere
closely to the lobules, and even the larger trunks have but a slight areolar investment
connecting them to the substance of the liver. Hence, as already explained, the
divided ends of these veins are seen upon a section of the liver as simple open
orifices, the thin wall of the vein being surrounded closely by the solid substance of
the gland.

The hepatic cells. — The interstices between the blood-vessels are, as before
said, almost entirely filled by the hepatic cells. These are of a compressed spheroidal
or polyhedral form, having a mean diameter of from 0"017mm. to 0*022mm. They
possess no cell membrane. Collectively they are yellowish, but, seen singly, are
oolourlesSj with a variable number of yellow or brown pigment granules in their

THE LIVER.

133

protoplasm. Their substance appears granular, and they contain each a clear round
nucleus, with intra-nuclear network and one or two nucleoli. Sometimes two
nuclei are to be found in a cell ; this is frequently the case in the rabbit. In many
cases, especially with a fatty diet, the cells are found to have large or small fat-
globules in their interior ; this fatty deposit is usually more abundant ia the cells
which are near the periphery than in those near the centre of the lobule. When
isolated in the fresh condition they are said to exhibit slow changes of form. The
liver-cells are packed between and around the vessels, and in sections made at right
angles to the intralobular veins, appear as if radiating from the centre of the
lobules towards their circumference. They form a continuous network, or sponge-
work, the more obvious openings in which are the spaces occupied by the blood-
capillaries. The walls of the latter are not everywhere in contact with the liver

Fig. 156. — Hepatic cells from the liver op a dog 14 hours after a full meal. (Heidenhain.)

a, with glycogenic deposit ; b and c, after its solution. In c the network of protoplasm which
remains is finer than in b, and imparts a somewhat granular appearance to the cells. The external
layer of the protoplasm contains no glycogen.

cells, but are separated from them in parts by a cleft-like lymphatic space, which is
only imperfectly marked off" by the flattened and stellate connective tissue cells
before mentioned (p. 132).

The hepatic cells frequently contain glycogen, especially after a heavy meal of
starchy matters. It occurs in globules or in irregular amorphous masses within
them (Heidenhain), and when abundant reduces the protoplasm of the cell to
the condition of an open network, which becomes very distinct after solution of
the glycogen (fig. I'tG). When these masses of glycogen are not present the
pi'otoplasm exhibits, after hardening, a more finely reticulated appearance (Klein,
Langley).

Commencement of the ducts. — When a thin section of the hardened tissue is
examined under a high ])ower of the microscope, minute apertures may occasionally
be observed between the op])Osed sides of adjacent liver-cells. These are the sections
<jf fine intercellular passages (bUc-canalicuU), which form a close network (figs. \hl,
l.">8) between and around the individual cells, much finer and closer than the blood-
capillary network, from the branches of which they run apart. These passages are
the commencements of the biliary ducts, into which at the circumference of the
lobule they open. They may be injected from the trunk of the l)ile-duct, at
least in the outer parts of the lobule (fig. l')?). It is uncertain whether they
have a proper wall, or if they are merely channels grooved out between the
hepatic cells.

To demonstrate the intercellular network throughout the whole extent (if the
lobules, TMirzons/xzewsky employed a method of niiturid injection. He introduced a
saturated wat<-ry .solution of pure sulpli-indig(jiate of stjda, in repeated doses, into the
circulation of dogs and suf;king-pigH, by the jugular vein ; and in an lioui- and

134

ORGANS OF DIGESTION.

a half afterwards the animals were killed, and the blood-vessels either Avashed out
with chloride of potassium, introduced by the portal vein, or were injected with
gelatine and carmine. In specimens prepared in this way the fine network of bile-
ducts throughout each lobule is filled with blue, while the intervening cells remain
free from colour. By kiUing the animals sooner after the injection, the blue
colouring matter was found within the hepatic cells, thus demonstrating that it was
through their agency that the canals were filled. They may also be shown by the
chromate of silver method.

From the observations of Pfliiger and of KupflPer, it would appear that the

Fig. 157. — Section of a liver-lobule wiTn the blood-vessels akd ducts injected. (Cadiat.)

h, b, interlobular veins ; a, intralobular vein ; c, interlobular bile-ducts, with wbich the bile
canaliculi from the lobule are connected. The canaliculi have only become injected in the peripheral
parts of the lobule.

relation between the hepatic cells and the bile-canaliculi is even more intimate than
has been generally supjDosed. For both by the methods of artificial and of natural
injection, they have demonstrated the existence of vacuoles within the cells
communicating by exceedingly minute intracellular channels with the adjoining
bile-canaliculi (see fig. 159). These observations have since been confirmed by
others, but it is not known whether the channels and vacuoles in question are
permanent structures, or whether they are only formed at the moment of secretion.

In the lower vertebrates and in the embryos of birds and mammals the liver
is a tubular gland, composed of branching tubules nearly filled with the glandular
cells of the organ (fig.^160), and with narrow lumina (biliary canahculi), directly

THE LIVER.

135

coutiniidus witJi the ducts. The biliary canaliculi do not anastomose nor form a
netAvork in the embryo (fig. 160), and in some mammals, e.g., mouse, Retzius was
unable to find evidence of a network, even in the adult state, although in others

Fig. loS. — Section of rabbit's liver with the ixtek-

CELLCLAR NETWORK OF BILE-CANALICOLI INJECTED.

HiGHLV MAGNIFIED (Hering).
Two or three layers of cells are represented ; b, b,
blood capillaries.

(dog, man) it i.s sufficiently obvious. In all
animals the bile-caualiculi are separated by
at least a portion of a liver-cell from the
nearest blood capillaries.

A different account of the structure of the
liver of the lower vertebrata and of the embryo
bird and mammal is given by Shore and Jones
(Journ. of Physiology, vol. x.).

Structure of the ducts. — The minute
ramifications Ijetween the lobules have walls
composed of fibrillar connective tissue, within
which is a basement membrane, and a lining
of short columnar epithelium. According to
Heidenhain they also possess both longitudi-
nally and circularly disposed muscular cells

in their wall. As they pass into the lobules, the columnar epithelium becomes shorter
and flatter, the tube at the same time branching both laterally and terminally,
and becoming much reduced in size, so that only a very small lumen is left. The
basement membrane is no longer complete, and the intercellular bile passages open
A B

Fig. \i)'.i. — Sketches illustkatino the mode of commencement of the bile-canaliculi within the
LIVER-CELLS (Heidcnhain after Kupffer).

A. Canaliculi of the rabbit's liver artificially injected from the hepatic duct with Berlin blue
solution. The intercellular canaliculi are seen to give off minute twigs, which penetrate into the liver-
cells, anil there terminate in vacuole-like enlargements.

K. From a frog's liver naturally injected with sulph-indigotate of soda. A similar apijearance is
obtained, but the communicating twigs are ramified.

directly into the minute ducts, the hepatic cells abutting against tlie flattened
epithelium of the latt* r.

In the portal canals, where they are somewhat larger, the ducts present numerous
openings on the inner surface, which are scattered irregularly in the larger ducts,
but in the subdivisions are arranged in two longitudinal rows, one at each side of

136

ORGANS OF DIGESTION.

the vessel. These openings were formerly supposed to be the orifices of mucous
glands ; but, while the main ducts are studded with true mucous glands of lobulated
form and with minute orifices, the openings now referred to belong to saccular and
tubular recesses, which are often branched and anastomosing, and may be beset all
over with cfecal projections (Theile). The larger bile-ducts have areolar coats, contain-
ing abundant elastic tissue, and a certain amount of plain muscular tissue disposed
both longitudinally and circularly. They are lined with columnar epithelium.

In the duplicature of peritoneum forming the left lateral ligament of the liver,
and also in the two fibrous bands which sometimes bridge over the fossa for the
vena cava and the fissure of the umbilical vein, there have been found biliary ducts
of considerable size which are not surrounded with lobules. These aberrant duds,
as they are called, were described by Ferrein, and afterwards by Kiernan ; they
anastomose together in form of a network, and are accompanied by branches of the
vena portge, hepatic artery, and hepatic vein. They represent portions of hepatic

Fig. 160. — From a chromate of

SILVER PREPARATION OF THE
LIVE 11 OP A SIX months'

FCETUS. (G. Retzius.)

The bile-canaliculi are repre-
sented black. It is seen that at
this stage of development they do
not anastomose. They appear to
give minute offsets, which end
between and within the liver-
cells in small enlargements.

substance which were pre-
sent at an early period of
development, but have sub-
sequently become atrophied.
Iiymphatics of the
liver. — Lymphatics are
seen in the prolongations
of aiisson's capsule between the lobules (interlobular lymphatics), where ^they
accompany the blood-vessels, and in some cases surround and enclose them. They
originate from the lymphatic spaces around the capillaries of the lobules (p. 133).
They unite into larger vessels, which run along the portal canals (fig. 150, 1 1), and
emerge at the portal fissure. Other lymphatic vessels accompany the branches of the
hejjaUc veins, also conveying lymph from the perivascular lymphatics of the lobules.
There is further a close subperitoneal plexus on the surface of the organ, which
on the upper surface communicates, through the ligaments of the liver, with the
thoracic lymphatics, and on the under surface with the lymphatics of Glisson's capsule.
In the pig's liver lymphoid follicles have been noticed by Kisselew and
Chrzonszczewsky, in connection with the interlobular lymphatics.

Nerves of the liver.— The liver receives nerves from the left pneumogastric
and from the solar plexus of the sympathetic. The branches of the pneumogastric
reach the organ between the two layers of the small omentum and enter at the
portal fissure. The sympathetic branches also enter the portal fissure, accompanying
the hepatic artery : some branches also accompany the portal vein. The termi-
nations of the nerves within the liver have been investigated by Berkeley, who
describes them as ending in fine terminal arborizations, showing varicosities,
especially at their extreme endings, and as being distributed to the walls of
the blood-vessels and biliary ducts, and also between the hepatic cells of the
lobules. According to this author, they follow the course of the biliary canalicuh.
Korolkow has studied the nerve-endings in the liver of the pigeon by the methylene

THE LIVER.

137

blue method. He describes the nerves which enter the hver and accompany the
vessels and ducts to the intervals between the lobules as both medullated and non-
medullated. Of these, the latter are distributed almost exclusively to the arteries
and veins, whereas the former enter the lobules, and, losing their medullary sheaths,
run at first along the trabeculEe of hepatic cells, and finally end by ramifying between
and over the cells (fig. IGl).

Structure of the Gall-bladder. — Besides the peritoneal investment and the
mucous lining, the gall-bladder possesses an intermediate muscular and connective
tissue coat, of considerable strength. This consists mainly of bands of dense shining
white fibres, which interlace in all directions. Intermingled with these are plain

Fig. 161. — Plexus of NERVE-FiaKiLS within a hepatic lobule of the pigeon; methylene blue

METHOD. (Korolkow.)

a a, axis-cylinders of nerve-fibres, passing between the cell-trabeculiE of the lobule, c : h h, fibiils
ramifj'ing over the cells of the trabeculie.

muscular fibres, which have principally a longitudinal direction, but some run
transversely. This coat forms the framework of the organ, and supports the larger
blood-vessels and lymphatics. The nerves form a gangliated plexus within it ;
partly also immediately beneath the serous coat (L. Gerlach).

The mncons membrane which after death is generally strongly tinged with bile,
is elevated upon its inner surface into vry numerous small ridges, whicli, uniting
together into meshes, leave between them depressions of difTei'ent sizes, and of various
polygonal forms. This gives the interior of the gall-bladder an alveolar aspect,
similar to what is seen on a smaller scale in the vesiculaj seminales. These alveolar
intervals become smaller towards the fundus and neck of the gall-l)ladder, and at the
bottom f)f the larger ones other minute depressions, which maybe seen with a simple
lens, lead into numerous mucous I'ecesses. The whole of the mncous membrane is
covered by columnar e[)ilhelium, and it secretes an abundanc^e of viscid mucus.
The blood-Tcssels form a close network near the surface of the mucous membrane,
and there is also a fine lymphatic plexus in the mucous meimbrane, cominnniLjating
with a network of lar''er vessels in the serous coat

138 OEGAKS OF DIGESTION.

At the places where the neck of the gall-bladder curves on itself there are strong
folds of its mucous and areolar coats projecting into the interior.

In the cystic duct the mucous membrane is elevated internally in a similar
manner into a series of cresceatic fol's, which are arranged in an oblique direction,
and succeed closely to each other, so as to present very much the appearance of a
continuous spiral valve. When distended, the outer surface of the duct appears to
be indented in the situation of these folds, and dilated or swollen in the intervals
so as to present an irregularly sacculated or twisted appearance. In the structure of
its wall the cystic duct resembles Che gall-bladder.

EECENT LITERATURE OP THE LIVER.

Berkley, Henry J., Studies in the Mstology of the liver, 1. Ttie intrinsic nerves, Anat.
Anzeiger, Jg. viii. , 1893.

Braum, H. , Die morjjhologisch-histologischen Verdnderungen in den ruhenden und thdtiyen
Leberzellen, Deutsche Zeitschr. fiir Tiermedicin, Band xii., 1886.

Brunton, T. Lauder and Delepine, Slieridan, On some of the variations obseried in the
rahhit's liver under certain physiological and patliohgical circumstances, Proc. of the Roy. Soc,
vol. 1., 1892.

Cavassani, E., Ueher die Verdnderungen der LeherzeUen wdhrencl der Reizung d. Plex.
cceliacus. Arch. f. d. gesammte Physiologie, Bd. Mi., 1894.

Cunning-ham, D. J., Delimitation of the regions of the abdomen, Part II., Topography of
the viscera. Jonr. Anat. and Phys., vol. xxvii., 1893.

Delepine, S. . Contribution to the study of the vertebrate liver. Proceed, of the Roy. Soc, 1891,
vol. xlix.

Disse, J., Ueber die Lymphbahnen der Sdugetierleber, Archiv f. mikroskop. Anat., Bd. xxxvi.,
1890.

Paure, J. L. , L'appareil suspenseur du foie, (to.; Quelques points de I' anatomic du canal
cystique. Bull. soc. anat., Paris, 1892.

Prenkel, Moise, Du tissu conjonctif dans le lobule Mpatique de certains mammiferes, Comptes
rendus hebdom. de la soc. de biol., 1892.

Gebergr, A., Weber die Gallengdnge in der Sdugetierleber, Internat. Monatsschr. f. Anat. u. Physiol.,
Bd. X., 1893.

Hartmann, H., Quelques points de Vanatomle tt de la chirurgie des voies iiliaires, Bull. soc.
anat., Paris, 1891.

Hertz, P., Abnormitdlen in der Lage und Form der Bauchorgane, 1894.

Hoeppe, H., Muskeln und Klappen in den Wurzeln der Ffortader, Archiv f. Anat. u. Physiol.,
Jahrg. 1890, Physiolog. Abt., Supplement Band.

Korolkow, P., Ueber die Nervenendigungen in der Leber, Anat. Anzeiger, Jahrg. viii., 1893.

Krause, Kudolf, Beitrdge zar Eistologie der Wirbeltierlcber, Arch. f. mikrosk.Anat., Bd. xlii.,
1893.

liahousse, E., Contribution d Vitude dcs modifications morphologiques de la cellule Mpatique
pendant la secretion. Archives de biologic, tome vii., 1887.

Landau, Die Wdnderleber und die Hdngebauch der Frauen, 1885.

Macallum, A. B., The termination of nerves in the liver. Quarterly Journ. of Microscop.
Science, vol. xxiv., 1887.

Mall, F., Das reticuUrte Gewebe u. seine Bezichwngen z. d. Bindcgewebsfibrillen, Abhandl. d.
k. Sachs. Gesellsch., xvii., 1891.

Oppel, Albert, Ueber Gittei-fasern der menschlichen Leber und MHz, Anatom. Auz., Jahrg. vi.,
1891.

Pilliet, A., Contribution d Vdtude des espaces partes du foie chez quelques vertebris, Journ. de
I'anatomie, annee xxv., 1889.

Ketzius, Grustav, Ueber die Gallenhapillaren und den Driisenbau der Leber, Biol. Unter-
suchungen, N. P., Bd. iii., 1891, and iv., 1892.

Eex, H., Beitrdge zur Morphologic der Sdugerleher, Morphol. Jahrbuch, Bd. xiv., 1888.

Kolleston, H. D., Abnormal vascular supply to the liver, Journ. of Anat. and Physiol.,
vol. xxiv. ,1889 ; Specimens of livers with anomalies in their lobulation, Pr. Anat. Soc. Gt. Brit, and
Ireland, Journ. Anat. and Physiol., vol. xxvii., 1893.

Sabourin, Ch., Recherches sur I'anatomie normale et pathologique de la glande biliaire de
I'hommc, Paris, 1888.

Shore, Thomas "W., Notes on the origin of the liver, Journ. of Anat. and Physiol., vol. xxv., 1891.

Shore, T. W., and Jones, H. L., On the structure of the vertebrate liver, Journ. of
Physiol., vol. x., 1889.

Stocquart, Alfr., Note sur le poids et des dimensions dufoie chez l' enfant, Internat. Monatsschr.
f. Anat. u. Physiol., Bd. viii., 1891.

Symington, Johnson, On certain physiological va7'iations in the shape and position of the liver,
Edinburgh Med. Joiu-n., Feb., 1888.

Thomson, A., Some variations in the anatomy of the human liver, Joui-n. Anat. and Phys.,
vol. xix., pt. iii., 1885.

THE PANCREAS.

139

THE PANCREAS.

The pancreas (fi^u'. 102) is a long gland of a reddish cream colour and
irregularly prismatic shape, which lies across the posterior wall of the abdomen,
behind the stomach, and opposite the first and second lumbar vertebrae. Its right
end is the larger and is termed the head ; from this arises a short and slightly con-
stricted necli-. whi-ch connects the head with the body. The body passes to the left,
its free extremity or tail touching the spleen.

The pancreas varies considerably, in different cases, in its size and weight. It is usually
5 or G inches (120 — loO mm.) long, and from half an inch to an inch iu thickness. The

Fig. 162. — AxTEKiuK Aspect of the pancreas, t&c, drawn by G. C. R. IIakhinson, from a specimen

PREPARED BY HARDENING THE ABDOMINAL VISCERA IN SITU BY THK INJECTION OF A 1 P.C.

Solution of chromic acid. (J. S.)

H.H.H., head of pancreas ; C. . its neck ; B.B. , its body ; A., anterior surface of tlie body ; I., its
inferior surface ; O.T., omental tuberosity near right end of body ; 2nd, 3rd, 4th, corresijonding parts of
the duodenum ; J., jejunum ; 11. A., hepatic artery; (i., gastric artery ; S.P., splenic artery; (i.D.,
gastro-duodenal artery; H.P.I)., superior pancreatico-duodenal artery; S.V., splenic vein; I.M.,
inferior mesenteric vein ; 8.M.V., superior mesenteric vein ; P.V., jjortal vein ; M.D., bile duct.

weig'ht of the gland, according to Krause and Clendenning, is usually from 2] to iii oz. ((IC to
102 grammes) ; Vjut Meckel has noted it as high as G oz., and .Socmmerring as low as \h oz.
Its Bi)ecific gravity is TOIG.

The head (fig. 1(;2, II) of the pancreas forms a disc-sliaped mass flattened from
before backwards, and lying in the concavity formed by the second, tliii-d, and fourth
parts of the duodenum, to wliich it is closely united. The superior mesenteric
vessels are in contact with the anterior surface near its left border, while near its
lower end it is crossed by the tran.sverse colon and its mcso-colon. Tlic superior
and inferior pancreatico-duodenal vessels pass down in front of the head a short

140

ORGANS OF DIGESTION.

distance from its right and left borders respectively. Posteriorly it lies upon the
inferior vena cava, the left renal vein and the aorta. The common bile duct
passes down behind it, and is generally received into a groove or canal in its
substance.

The 72ecJcofthe pancreas (fig. 162, C) is about an inch long. It springs from the
upper part of the anterior surface of the head and turns upwards, forwards, and to
the left to join the body. In its course it passes in front of the termination of the
superior mesenteric vein and the commencement of the vena portse. At its attach-
ment to the head it is gi'ooved on its right side by the gastro-duodenal and superior
pancreatico-duodenal arteries. The first part of the duodenum lies against its

vm—

Fig. 16.3. — View of the abdominal tiscera from behind, after removal of the spinal column,

THE ■^'HOLE OF THE POSTEIIIOR WALL OF THE ABDOMEN AND THE KIDNEYS AND SUPRA-RENAL

CAPSULES, THE PERITONEUM BEING LEFT (this and the next figure are taken from Prof. His'
models). ^

P, pancreas : P', its head : d, duodenum ; st, stomach ; spl, spleen ; R.L., right lobe of the liver ;
L.S., Spigelian lobe ; v.c.i., vena cava inferior ; ^J.r., portal vein ; h, common bile duct ; i.r., imj)res-
sion for the right kidney on the posterior surface of the liver ; the situation of the two kidneys is well
shown by the corresponding impressions in the cast : asc. col., clesc. col., ascending and descending
colon ; 2Jt, back of the peritoneum ; m, line of attachment of the mesentery ; VIII, IX, X, XI, the
con-esponding ribs ; il, ilium.

anterior and right aspect, and the pylorus often touches it when the stomach is
distended.

The hody and fail together (fig. 162, B) are four or five inches long. After
crossing from the right side in front of the aorta the body curves backwards in its
course to the left, and close to the spleen the tail turns sharply upwards and backwards.
The body is prismatic in form and has three surfaces, anterior, posterior, and inferior.
The inferior surface is narrow but better marked on the left than on the right side.
The surfaces, like those of the liver, are moulded to the adjacent organs.

The anterior surface is concave, looks upwards as well as forwards, and is covered
by the stomach, the lesser sac of the peritoneum intervening. At its right extremity
it often forms a well-marked prominence called the omental tuberosity (His).

THE PANCKEAS.

141

The posterior surface lies in front of the aorta, the origin of the superior
mesenteric artery, the pillars of the diaphragm, the splenic vein, the left kidney and
its vessels, and the left suprarenal capsule.

The inferior surface is narrow and rests upon the duodeno-jejunal flexure, and
frequently also upon some convolutions of the jejunum and upon the transverse
colon near its left end.

The superior border lies in relation with the coeliac axis, the hepatic branch of
this trunk passing to the right just above it, while on the left side the splenic artery
in its tortuous course to the spleen grooves it.

At the anterior border the two layers of the transverse meso-colon separate, the
anterioi- layer ascending in relation with the anterior surface of the pancreas, whilst
the posterior layer passts backwards in contact with the inferior surface. The
posterior surface is thus devoid of peritoneum.

Fig. 164. — The pancreas and adjoining visceua from before. /,

The liver, the stomach, the greater part of the small intestine, and the transverse colon liave been
removed. P, pancrea.s ; d, duodenum; d.j., duodeno-jejunal flexure; above the duodenum, and
between it and the head of the jjancreas are seen the bile-duct, portal vein, and hepatic artery ; asc.
col., dine. coL, ascending and descending colon ; .ipl., spleen ; r.l:, l.k., right and left kidneys; .s.r..
s.r', right and left suprarenal capsules ; pt, peritoneum at the back of the abdominal cavity ; 7«, Hue
of reflection of thi; mesentery ; the line of reflection of the transverse mesocolon is seen along the lower
edge of the pancreas and crossing the duodenum.

The tail of the pancreas is in contact with the lower part of the inner surface of
the spleen.

The principal excretory duct, called the pancreatic duct or canal of Wirsung,
runs tliroagh the entire length of the gland from left to right, buried entirely in its
substance. Commencing by the union of the small ducts derived from the groups
of lobules composing the tail of the pancreas, and receiving in succession at various
angles and from all sides the ducts from the body of the gland, the canal of Wirsung
pursues a nearly straight course in the axis of the gland until it reaches the neck.
Here it turns obliquely downwards, backwards, and to the right through the neck
and head, gradually ap])roa(;liing the ])osterior surface of the latter. Near its
termination it comes in contact with the left side of the common bile duct, which it
accompanies to the second part of the duodenum. As it traverses the head of the
irancreas it is joined by numerous branches, one of which coming from the lower
part of the head is larger than the others. The bile and pancreatic ducts placed
side by side, pass very obliquely through the muscular and areolar coats of the

142 OEGANS OF DIGESTIONS.

intestine, and terminate, as already described, on its internal surface, by a common
orifice, situated near the junction of the second and third portions of the duodenum,
between three and four inches below the pylorus. The pancreatic duct, with its
branches, is readily distinguished within the glandular substance, by the very white
appearance of its thin fibrous walls. Its widest part, near the duodenum, is from
Jg-th to ith of an inch in diameter, or nearly the size of an ordinary quill. It is
lined by a remarkably thin and smooth membrane, which near the termination of
the duct may present a few scattered recesses.

Varieties of pancreas and its ducts. — Symington (Journal of Anatomy and Physiology,
1885) described a case in which, the upper part of the second portion of the duodenum was
encircled by a ring of pancreatic tissue. A somewhat similar case has been recorded by
G-enersich (Verhandl. x. Internat. Med. Congress, 1890). The tail of the pancreas is sometimes
bifid ; and the part of the head lying behind the mesenteric vessels may be separate from the
remainder of the gland, and form what is called the lesser i^ancreas.

Various examples of an accessory pancreas have been described. They occur most fre-
quently in the wall of the upper part of the jejunum, more rarely in the wall of the stomach
(see Zenker, Nehetijiancreas in der Barmwand, Arch. f. path. Anat., Bd. xxi.).

Accessory duct, or duct of Santurini. Occasionally the main duct gives off at the neck
an accessory duct, which passes to the right and opens into the duodenum about an inch
above the common opening of the bile and main pancreatic ducts. This accessory duct is
occasionally found of large size, and evidently serving as the principal channel for the
passage of the pancreatic secretion into the duodenum, the lower part of the duct of Wirsung
being small. On the other hand the accessory duct may not open into the duodenum, but
terminate in the upper and right part of the head in small branches. In such cases its
contents must pass from right to left, and be discharged into the duct of Wirsung.

Schirmer {Beitrag ziir GescMclde und Anat. des Pancreas, Basel, 1893), has investigated
the arrangement of the ducts of the pancreas in 105 specimens. In fifty-six of these the
duct of Santorini arose from the main duct, and opened into the duodenum upon a papilla
situated above the common orifice of the bile and pancreatic ducts. In nineteen the duct of
Santorini, although well developed, did not open into the duodenum. In four there was
only one pancreatic duct, and that the upper, the common bile-duct opening by itself lower
down. In none of his specimens did he meet with an example of an arrangement described
by Claude Bernard, in which there were two ducts running thi-oughout the whole length of
bhe gland.

The variations of the pancreatic ducts are of interest in connection with the mode of
development of the pancreas. From the observations of Zimmermann and Hamburger it
appears that in the human subject the pancreas is formed from two distinct outgrowths from
the wall of the duodenum. One of these, the smaller, is in close relation with the duodenal
end of the common bile-duct ; the other, which is situated nearer the pylorus, is much larger,
and forms the greater part of the pancreas. About the sixth week of embryonic life the two
processes join, and their contained ducts subsequently communicate with one another. The
portion of the upper duct on the duodenal side of the point of union grows less rapidly than
the lower duct. It becomes the duct of Santorini, while the lower duct, with the peripheral
portion of the upper one, forms the main channel for the pancreatic secretion, and is
generally known in the adult as the main pancreatic duct, or canal of Wirsung.

Structure. — The pancreas belongs to the class of acino-tubular glands. In its
general characters it closely resembles the salivary glands, but it is somewhat looser
and softer in its texture than those organs, the lobes and lobules being less compactly
arranged.

The ducts are lined with a simple layer of long columnar epithelium, the cells
becoming shorter and more cubical in the smaller ducts. They do not exhibit any
well-marked longitudinal striation like that met with in the duct-cells of some of the
salivary glands. The ultimate branches of the ducts which are connected with the
alveoli {inteixalary ducts), are much narrowed, and are lined with flattened cells,
looking spindle-shaped in optical section. The alveoli of the gland are distinctly
tubular, and somewhat convoluted. In the inactive condition of the gland, and
during the earlier stages of activity, the alveoli are almost completely occupied by
the secreting cells, scarcely any lumen, being visible. Moreover the middle of the

THE PANCREAS.

143

alveolus is in the dog and some other animals occupied by spindle-shaped cells
{centro-acinar cells, fig. 165) which according to Langerhans are continuous with
the epithelium-cells of the intercalary ducts.

The secreting cells of the pancreas have a very characteristic appearance. They

^^^'^

Group of cells : -^^ ^

probably an (P 1 fo, -^ <-.

Comiective
tissue. '

Centro-acinar
cell.

^)?, ^0^v pC*® ^^1 Ce

Larger duct. i

I""-

ntro-acinar

Commencement
_ of duct.

Inner zone of
'alveolar cells.

Fig. 1C5. — Section of human pancreas, (licilim and Davidoff.) Ail'.

frequently, if not constantly, contain, besides the ordinary nucleus, a paranuclei! s
(Xebenkern), a spherical mass, staining more readily than the rest of the proto-
plasm, and said to be formed by extrusion of material from the nucleus (Gaule,
Nicolaides). In shape they are columnar, in some parts approaching the polygonal
form, and they show very distinctly, even in the loaded condition of the gland, two

A, B,

Fig. 166. — An alvkulus ok the uaijdit's pancreas.

A., (luring rest, the cells loaded with granules, and the inner zone, a, large, and the outer zone, h,
narrow.

B., after a/;tivity, the inner zone small, and the outer zone large and distinctly striated. The cell
outlincH are also now visible, c, lumen of alveolus ; d, basement membrane. {Kiihne and Lea.)

parts or zones ; an inner granular zone next th(^ liiincu, and an outer clear and fiiKily-
fitriated zone next the Ijasement membrane (figs. 1 ('..") and 1 (id).

When the gland is stimulated to activity tlie cells at first enlarge and bulge the
basement membrane ; subsequently the gi'anulcs of the inner zone become fewer in
number and aggregated near the lumen, and the outer clear zone extends over the
greater part of the cell (lleidenhain, Kiihne and Lea (fig. 1(JG)). It is stated by

144

ORGANS OF DIGESTION,.

Ogata that these zymogen granules are formed from the paranucleus, but the state-
ment requires confirmation.

Fig. 167. — Origin op the ducts op the pancreas, as shown by the chkomate of silver

METHOD. (E. Miiller. )

A, duct cut longitudinally, lined l)y columnar epithelium giving off laterally the intercalary or
lobular ductules, rn, to the alveoli, l. The manner in which these commence within the alveoli is
shown under a higher power in B.

Various observers, after forcing injections into the alveoli of the pancreas
backwards from the duct, have seen fine intercellular canaliculi, comparable to those

Fig. 168. — Section op pancreas of

armadillo, showing several

alveoli and one of the INTER-

alveolar cell-isleis. (v. d.

Harris. )

The alveolar cells are much more

elongated here than in man and in

most animals.

of the liver, passing from
the lumen of an alveolus
between the secreting cells.
These can also be shown by the
use of Grolgi silver chromate
method (fig. 167, A), and with a high magnifying power, the canahculi can be seen
penetrating not only between the cells of the alveoli, but even into the interior of the
individual cells (fig. 167, B).

LITERATURE OF PANCREAS. 145

Connective tissue ; interalveolar cell-islets. — The connective tissue of the
gland, af cerforming a sort of external investment, penetrates between its lobes or lobules
conveying the blood-vessels to all parts. They are not, however, everywhere equally
numerous, for some acini are not surrounded by the capillary network. On the
other hand, in certain parts of the interalveolar tissue collections of small cells
{interalveolar cell-islets, figs. 165, 168) are met with, which are permeated with a very
close network of large convoluted capillaries. The cells in question are like the cells
met with in the carotid and coccygeal glands, but their meaning is entirely
unknown. They are very characteristic of the pancreas, being apparently always
present in it.

Blood-vessels, lymphatics, and nerves. — The arteries of the pancreas
are derived from the splenic and hepatic divisions of the coeliac axis, and from the
inferior pancreatico-duodenal Iranch of the superior mesenteric. Its veins are
tributaries of the splenic and superior mesenteric, and therefore belong to the portal
system. The lymphatics pass to some of the neighbouring coeliac glands. Their
arrangement within the pancreas is similar to that found in the salivary glands.

The nerves are derived from the solar plexus, and accompany the arteries to the
organ. They are almost exclusively non-medullated and have minute ganglia on
them as they traverse the gland. Besides these ganglia, small cells, apparently of
nervous nature, are found upon the nerves, near their distribution to the epithelium-
cells of the alveoli, over and between which they ultimately ramify.

EECENT LITERATURE OF THE PANCREAS.

Assmann, E., Zur Kenntniss der Panh-eas, Vircliow's Archiv f. path. Anat., Bd. cxi., 1888.

Cajal, S. Ramon y, and Sala Claudio, Terminacidn de los nervios y tubas ylandulares del
2xcncreas de los vertebrados, Barcelona, 1891.

Dogriel, S., Zur Frage ilber die Ausfiihrunr/sgdnge des Panlcreas des Mcnschen, Arcb. f. Anat. u.
Entwickelungsgesch., 1893.

£berth, C. J., and Miiller, K. , Untersuchungen iiler das Pancreas, Zeitsclir. f. wissenscli.
Zoologie, Bd. liii.

Genersich, Anton, Seltene Anomalie des Pancreas, 10th International Medical Congress, 1890,
Bd. xi.

Hamburgrer, Ove, Zur Entwickelung der Bauchspeicheldriise des Mcnschen, Anat. Anzciger,
Bd. vii., 1892.

Herzen, A., Le jeHne, le pancreas et la rate, Arch, de physiol. norm, et pathol., 5sdr. t. vi., 1891.

liagruesse, 13., Hur la formation des Hots de Langerhans dans le pancrias, C. R. soc. bid. , t. v. ,
1893.

Nicolaides, R., Ucber die mihroslcopischen Erscheinungen der Pancreaszellen bci der Sckretion,
Centralbl. f. Physiol., No. xxv., 1889.

Nicolaides, E. , und Melissinos, C, Untersuchungen iiber einige intra- u. extra-nvcJeare
Ochilde im Pankreas der Sdugetiere auf ihrc Beziehung zu dtr Sekrciiun, Archiv f. Anat. u. Piiy.siol. ,
Physiol. Abt., Jahrg. 1890.

Schirmer, A. M. , Beitrag zur Geschiehte und Anatomic des Pancreas, Ba.sel, 1893.

Stoss, Zur /yntuickdungsyeschichte des Pancreas, Anat. Anzeiger, Dec, 1891.

Symin^on, J., Notes on a rare abnormality of the pancreas, Journal Anat. and Phys., vol. xix.,
1885.

Trolard, P., Note sur la direction de la rate et du pancrias chez le foetus et chez Venfant,
Cornptes rondiis liclidoni. de la soc. de biol., serie ix., t. iv., 1892.

Ver Eecke, A., Modifications de la cellule pancriat I que pendant Vactiviti sicritoire, Arch, de biol.,
t. xiii., 1893.

Zimmermann, Jkhonstruklionen einea menschlichen Embryos, Vcrhaudlun^uu der Anat. Qesoll-
Bchaft, Berlin, 1889.

▼m. iir., PT 4.

OEGANS OF KESPIEATION AND VOICE,

By E. a. SCHAFER AND J. SYMINGTON.

The organs of respiration and voice comprise the larynx, trachea, and troncM,
and the lungs, with their serous investments, named the loleurm.

The respiratory organs are developed as a median oiitgrowth from the ventral
wall of the fore-gut, and this primitive connection between the alimentary canal and
the respiratory apparatus is maintained in the adult, the upper end of the air-passage
opening on the anterior wall of the pharynx. Below, this median air-tube divides
into two lateral branches, one for each lung, while its upper part is modified to
form the organ of voice. In the majority of mammals the windpipe opens above
into the nasal part of the pharynx, the anterior boundary of the orifice (the
epiglottis) projecting upwards behind the soft palate. This is not the case, how-
ever, in the human subject, either during intra-uterine or extra-uterine life.

THE LARYISrX, OR ORGAK OF VOICE.

The larynx is placed at the upper and fore part of the neck, where it forms a
considerable prominence in the middle line. It lies between the large vessels of the
neck, and below the tongue and hyoid bone. It is covered in front by the skin and
cervical fascia along the middle line, and on each side also by the sterno-hyoid,
sterno-thyroid, and thyro-hyoid muscles, by the upper end of the lateral lobe of the
thyroid body, and by a small part of the inferior constrictor of the pharynx.
Behind, it is separated from the 4th, 5th and 6th cervical vertebrae by the laryngeal
part of the pharynx and the prevertebral muscles. Above, it opens into the cavity of
the pharynx, and below, into that of the trachea.

Its dimensions, according to Sappey, are, on an average of eight males and eight
females, as follows : —

Vertical diameter, measured from the upper border of the thyroid cartilage to the
lower border of the cricoid, 44 mm. in the male and 36 in the female ;

Transverse diameter, represented by the distance between the posterior borders of
the thyroid cartilage, 43 mm. in the male and 41 in the female ;

Antero-posierior diameter, measured from the most prominent part of the anterior
border of the thyroid cartilage to a line uniting its posterior borders, 36 mm. in the
male and 26 in the female.

The larynx consists of a framework of cartilages, articulated together, and
connected by elastic membranes or ligaments, two of which, projecting into the
interior of the cavity, are named the true vocal cords, being more immediately
concerned in the production of the voice. It possesses special muscles, which move
the cartilages one upon another, and modify its form and the tension of its ligaments,
and it is lined by a mucous membrane, continuous above with the mucous
membrane of the pharynx and below with that of the trachea.

CABTILAGES OF THE LARYNX.

The cartilages of the larynx (figs. 169a, and 169b) consist of three single' and
symmetrical pieces, named respectively the thyroid cartilage, the cricoid cartilage,
iind the cartilage of the epiglottis, and of three pairs, namely, the two arytenoid

CARTILAGES OF THE LARYNX.

147

cartilarjes, the cornicida laryngis, and the cuneiform carfilages. In all there are nine
distinct pieces, but the cornicula and cuneiform cartilages are very small. Only
the thyroid and cricoid cartilages are visible on the front and sides of the larynx ;
the back of the cricoid cartilage, surmounted by the arytenoid cartilages, and these
again by the cornicula, are seen behind ; whilst the epiglottis is situated in front of,
and the cuneiform cartilages on each side of, the upper opening.

The thyroid cartilage, the largest, consists of two flat lateral plates, which are
united in front at the isthmus, and form an angle of about 90° with one another like
the letter Y, most prominent at the upper part. This angular projection is
subcutaneous, and is much more marked in the male than in the female,
being named in the former i\iQ 2}omum Adami. The two symmetrical halves, named
the ake, are somewhat quadrilateral in form. Of each half the anterior border
is the shortest, the pomum Adami being surmounted by a deep thyroid notch (see
fig. 1G9a). The free posterior border is thickened and vertical, and is prolonged

Fig. 169a. — Front view op the laryngeal cartilages and ligaments. (Sappey.)

1, hyoid bone ; 2, its large cornua ; 3, its small cornua ; 4, th3rroid cartilage ; 5, thyro-liyoid
membrane; 6, lateral tliyro-hyoid ligament, containing the car<«7a//o triticea, 7; 8, cricoid cartilage;
i*, crico thyroid membrane ; 10, lateral crico-thyroid ligaments ; 11, uppermost ring of trachea.

Fig. 169b. — Back view of the laryngeal cartilages and ligaments. (Sappey.)
1, thyroid cartilage; 2, cricoid cartilage; 3, arytenoid cartilages; 4, their nuiscular i)rocesses;
5, a ligament Itetter marked than usual, connecting the lower cornu of the thyroid with tlie l)ack of
the cricoid cartilage ; 6, upper ring of the trachea ; 7, epiglottis ; 8, ligament connecting it to the
angle of the thyroid cartilage. The cornicula are seen surmounting the arytenoid cartilages.

upwards and downwards into two processes or cornua ; it gives attachment to the
fitylo-pharyngeus and palato-pharyngeus muscles. The upper and lower borders
have each a well-marked concavity close to the cornu ; otherwise the u|)per is
ajnvex, and the lower nearly straight. The flattened external surface of each ala
is marked by an indistinct oblique line or ridge (flg. 16i)A), which, commencing
above at the posterior part of the superior border in a slight prominence called
the superior tubercle, passes downwards and slightly forward, and ends at the lower
border in an inferior tulterrle, so as to mark off tlu; anterior three-fourths of the sur-
face from the remainder. This line gives attachment below to the sterno-thyroid, and

L 2

148 OKGANS OF EESPIEATION AND VOICE.

above to the thyro-hyoid muscle, whilst the small smooth surface behind it gives
origin to part of the inferior constrictor of the pharynx, and affords attachment, by
means of areolar tissue, to the thyroid body. On their internal surfaces the alse
are smooth and slightly concave. Of the four cornua, all of which bend inwards,
the two superior or great cornua (fig. 169), pass upwards with sometimes a slight
backward curve, and terminate each by a blunt extremity, which is connected, by
means of the lateral thyro-hyoid ligament, to the tip of the corresponding great
cornu of the hyoid bone (fig. 169a, 2). The inferior or smaller cornua, which are
somewhat thicker but shorter, are directed slightly forwards, and, on the inner
aspect of the tip, show a smooth surface, for articulation with a prominence on
the side of the cricoid cartilage.

Occasionally there is a f orameu in the ala of the thyroid cai-tilage situated near the upper
part of its posterior border ; an abnormal branch of the superior laryngeal artery passes
through it. In the infant the isthmus of the thyroid cartilage differs from the two al«
in being less opaque and more flexible.

The cricoid cartilage (fig. 169a, 8), which is shaped like a signet ring, is thicker
and stronger than the thyroid. It is deep behind (fig. 169b, 2), where it is expanded
into a squarish plate or lamina, measuring' in the male about an inch from above
downwards ; but in front it forms a narrow ring or arch, with a vertical measure-
ment of only one-fourth or one-fifth of an inch. Corresponding with this, the
superior 'border, which is markedly elevated behind, descends with a deep concavity
in front below the thyroid cartilage ; while the inferior border is horizontal, and
connected by membrane to the first ring of the trachea. The posterior elevated part
of the upper border is slightly depressed in the middle line, and on the sides of this-
depression are the elongated oval facets for articulation with the arytenoid
cartilages. These facets are slightly convex, and they look outwards as well as
upwards. The external surface of the cartilage is convex and smooth in front and
at the sides, where it affords attachment to the crico-thyroid muscles, and behind
these to the inferior constrictors of the pharynx ; in the middle line posteriorly is a.
slight vertical ridge to which some of the longitudinal fibres of the oesophagus are-
attached. On each side of this ridge is a broad depression occupied by the posterior
crico-arytenoid muscle, outside which is a small fiat, oval, and slightly raised surface
for articulation with the inferior cornu of the thyroid cartilage. The internal
surface is covered throughout by the mucous membrane of the larynx. At its lower
border the cricoid is circular, but higher up the cartilage is somewhat compressed
laterally, so that the passage through it is here elliptical.

The arytenoid cartilages (fig. 169b, 3) are two in number, and symmetrical in
form and position. They may be compared in shape to irregular three-sided
pyramids, and they rest by their bases on the posterior and highest part of the
cricoid cartilage, while their somewhat curved apices approach one another. Each is
about half an inch high and one quarter of an inch wide. Of the three faces the
posterior is broad, triangular, and concave from above downwards, lodging part of
the arytenoid muscle. The anterior, or external, has a transverse ridge situated at
about the junction of its lower and middle thirds ; above and below this the surface
is concave. The false vocal cord is attached near the inner end of the ridge, and the
thyro-arytenoideus is inserted into the depressions and outer part of the ridge. The
internal surface, which is the narrowest of the three, and slightly convex, is nearly
parallel with that of the opposite cartilage, and is covered by the laryngeal mucous
membrane. The anterior and posterior borders, which limit the internal face, are
nearly vertical, whilst the external border, which separates the anterior from the
posterior surface, is oblique.

The base of each arytenoid cartilage is slightly hollowed, having towards its outer
part a smooth concave surface for articulation with the cricoid cartilage. Two of its-

CAllTILAGES OF THE LARYNX. 149

angles are remarkably prominent, viz., one external, short, and rounded, which
projects backwards and outwards, and into which the posterior and the lateral
crico-aryfcenoid muscles are inserted {muscular p-ocess) ; the other anterior, which is
more pointed, and forms a horizontal projection forwards, to which the corre-
sponding true vocal cord is attached {vocal ^^rocess).

The aj)ex curves backwards and a little inwards, and terminates in a blunt point,
which is surmounted by the corniculum laryngis.

A small cartilaginous nodule (sesamoid cartilage) is sometimes found at the outer side of
the arytenoid near the tip, embedded in the perichondrium.

The cornicula laryngis, or cartilages of Sautorini, are two small yellowish
cartilaginous nodules of a somewhat conical shape, which are articulated with the
summits of the arytenoid cartilages (fig. 169b), and serve, as it were, to prolong them
backwards and inwards. They sometimes form part of the arytenoid cartilages.

The cuneiform cartilages, or cartilages of Wrisberg, are two very small,
soft, yellowish, cartilaginous bodies, placed, one on each side, in the fold of the
mucous membrane which extends from the summit of the arytenoid cartilage to the
epiglottis. They have a conical form, with the base directed upwards. They
occasion small elevations of the mucous membrane, a little in advance of the
cornicula, with which, however, they are not directly connected.

These cartilages are very frequently absent, especially in the white races of mankind, but
according to Gibb are always present in the negro.

The epiglottis (fig. 1G9b, 7) is a median lamella of yellow cartilage, shaped
somewhat like an obovate leaf, and covered by mucous membrane. It is placed in
front of the superior opening of the larynx, projecting, in the ordinary condition,
upwards immediately behind the base of the tongue.

The cartilage of the epiglottis is broad and rounded at its upper free margin, but
below it becomes pointed, and is prolonged by means of a long, narrow, elastic
band (the thyro-ejvfjlottic ligament) to the deep angular depression between the alae
of the thyroid cartilage, to which it is attached behind and below the median notch.
Its lateral borders, which are convex and turned backwards, are only partly free, the
lower parts being enveloped in the aryteno-epiglottic folds of mucous membrane.
The anterior or lingual surface is free only in its upper part, where it is covered by
mucous membrane. Lower down, the membrane is reflected from it forwards to the
base of the tongue, forming three folds or frtenula, the middle and lateral glosso-
epiglottic folds. This surface is also connected below with the posterior surface of
the hyoid bone by a median elastic structure named the hyo-epiglottic ligament.
The posterior or laryngeal surface, which is free in the whole of its extent, is
concavo-convex from above downwards, but concave from side to side ; the convexity
projecting backwards into the larynx is named the tubercle or cushion. The
epiglottis is closely covered by mucous membrane, on removing which the yellow
cartilaginous lamella is seen to be pierced by numerous little pits and perforations, in
which are lodged small glands, which open on the surface of the mucous membrane.

Structure of the cartilages of the larynx. — The epiglottis, the cornicula
laryngis, and the cuneiform cartilages are composed of elastic or yellow fibro-
cartilage, and have no tendency to ossify. The apices of the arytenoid
cartilages are also formed of elastic fibro-cartilagc, but the greater part of these, as
well as the cricoid and thyroid cartilage, are composed of hyaline cartilage,
resembling generally that of the costal cartilages, like which, they are very prone to
ossification as life advances.

Peculiarities of the larynx according to age and sex. — In the ffctus
the larynx is considerably higher in relation to the vertebral column than in the

150

ORGANS OF RESPIRATION AND VOICE.

adulfc. Thus, in the sixth month of foetal life the upper end of the epiglottis
is opposite the anterior arch of the atlas and the lower border of the cricoid
cartilage, at the level of the middle of the body of the fourth cervical, the vs^hole
larynx being thus fully two vertebri» higher than in adult life. Until puberty the
larynx gradually descends, by which time it has attained its adult position. This
descent of the larynx is, therefore, independent of the special increase in size of the
organ occurring at puberty, and appears to be associated with the growth in a vertical
direction of the facial part of the skull, which is relatively very small in the foetus.

Up to the age of puberty the larynx is similar in the male and female, the
chief characteristics at that period being the small size and comparative slightness of
the organ, and the smooth rounded form of the thyroid cartilage in front. In the
female these conditions are permanent, excepting that a slight increase in size takes
place. In the male, on the contrary, at the time of puberty, remarkable changes
rapidly occur, and the larynx becomes more prominent and more perceptible at the
upper part of the neck. Its cartilages become larger, thicker, and stronger, and the
alse of the thyroid cartilage project forwards in front so as to form at their union

Fig.

Portion"

B C

170. — Views op thyroid, cricoid, and arytenoid cartila«es partially ossified.
OSSIFIED SHADED. (Chievitz.)
The relative proportions of the three cartilages are not kept in this figure.

A, thyroid cartilage, with inferior cornu and adjacent part of ala ossified ; B, cricoid cartilage
ossified at upper part ; C, arytenoid almost completely ossified.

with one another the prominent ridge of the pomum Adami. ' At the same time, the
median notch on its upper border is considerably deepened. In consequence
of these changes in the thyroid cartilage, the distance between its angle in front and
the arytenoid cartilages behind becomes greater, and the vocal cords are necessarily
lengthened. Hence the dimensions of the glottis, which, at the time of puberty,
undergo an increase of about one-third only in the female, are nearly doubled in the
male, and the adult male larynx becomes altogether one-third larger than that of the
female.

Taguchi found that the average distance from the upper border of the thyroid
cartilage to the lower border of the cricoid, measured in the median plane, was in
39 males 4*8 cm. and in 33 females 3-8 cm.

Ossification of tlie cartilag-es of the laryiix. — At about twenty years of age
ossification usually begins in the thyroid and cricoid cartilages, and a few years later in the
arytenoids. In the thyroid cartilage ossification takes place first near the inferior cornu, and
this is speedily followed by the appearance of a median nucleus in the angle between the
alee ; from the lower cornu the ossification extends along the inferior and posterior borders,
and thence spreads through the ala. The cricoid cartilage first becomes ossified at its upper
border on each side, near the arytenoid and thyroid articular facets, and the bony masses of
the two sides soon become united across the back of the ring ; the lower border remains
cartilaginous for some time longer. The arytenoid cartilages become ossified from below
upwards. The ossification begins somewhat earlier and proceeds more rapidly in the male
than in the female. (J. H. Chievitz, Arch. f. Anat., 1882.)

LIGAMENTS OF THE LARYNX. 151

The cricoid and the arytenoids are the most primitive of the laryngeal cartilages, being found
in connection with the air-pas^^ages of certain of the amphibia, and also in the reptilia, while
the thyroid and the epiglottis, at least in a well-developed condition, are peculiar to mammals.
The thyroid cartilage represents the ventral remains of the skeleton of two pairs of visceral
arches (4th and 5th), united by a median plate. In the ornithorhynchus these five parts of
the thyroid can be recognized as distinct elements, but in the higher mammalia they are more
or less blended. In man the two cornua of each ala represent ununited parts of the two
arches, while the peculiarities in appearance and structure of the isthmus as compared with
the al£e indicate the median portion uniting the arches. According to Dubois the epiglottis
represents a chondrification in the submucosa of the glosso-laryngeal fold, the cartilao-es of
Wrisberg being fomied in a similar manner in the false cords, i^egenbam- maintains, how-
ever, that the epiglottis is an independent element of the skeleton, derived from the sixth pair
of visceral arches, and according to Goppert, the cartilages of Wrisberg are formed from the
lateral processes of the primitive epiglottis. Small cartilaginous nodules are sometimes found
behind or between the arytenoids, which are the rucliments of the pro-cricoids.

LIGAMENTS AND JOINTS OF TH2 LARYNX.

The larynx is connected with the hyoid bone by a broad membrane, and at the
sides of this by two round lateral ligaments. The thyro-hyoid membrane, or
middle thyro-hyoid ligament (fig. 169a, 5), is a broad, fibrous, and somewhat
elastic membrane, which passes up from the whole length of the superior border
of the thyroid cartilage to the hyoid bone, where it is attached to the posterior and
upper margin of the obliquely inclined inferior surface. Owing to this arrange-
ment, the top of the larynx, when drawn upwards, is permitted to slip within the
circumference of the hyoid bone, between which and the upper part of the thyroid
cartilage there is found a small synovial bursa. The thyro-hyoid membrane is thick
where subcutaneous towards the middle hue, but at the sides becomes thin and loose,
and is covered by the thyro-hyoid muscles. Behind is the epiglottis, with the
mucous membrane of the base of the tongue, separated, however, by adipose tissue
and mucous glands. This ligament is perforated by the superior laryngeal artery
and nerve of each side. The lateral thyro-hyoid ligaments (fig. 1G9a^ GJ, placed
at the posterior limits of the thyro-hyoid membrane, are two rounded yellowish
cords, which pass up from the superior cornua of the thyroid cartilage, to the
extremities of the great cornua of the hyoid bone. They are distinctly elastic, and
there is frequently enclosed in each a small oblong cartilaginous nodule, which has
been named carlilago triticea ; sometimes this nodule is bony.

The thyroid and cricoid cartilages are connected together by a membranous
ligament and synovial articulations. The crico-thyroid membrane(fig. 1G9a, 9)is
divisible into a median and two lateral portions. The median portion, broad below
and narrow above, is a strong, triangular, yellowish ligament, consisting chiefly of
elastic tissue, and is attached to the contiguous borders of the two cartilages. Its
anterior surface is convex, is partly covered by the crico-thyroid muscles, and is
cro.ssed horizontally by a small anastomotic arterial arch, formed by the junction of
the crico-thyroid branches of the right and left superior thyroid arteries. The
lateral portions are fixed on each side along the inner edge of the upper border of the
cricoid, close under the mucous membrane ; they become much thinner above, where
they are continuous with the inferior thyro-arytenoid ligaments.

The crico-thyroid articulations, between the inferior cornua of the thyroid
cartilage and the sides of the cricoid, are two small but distinct joints, having each a
ligamentous capsule and a synovial membrane. The prominent oval articular
surfaces of the cricoid cartilage are directed ui)wards and outwards, while those of
the thyroid cartilage look in the opposite direction. The capsular fibres form
a stout Vjand behind the joint. The movement allowed is of a rotatory description,
tlie axis of rotation passing transversely through the two joints. In addition,
a slight glidiug movement forwards and backwards may occur.

152 ORGANS OF RESPIRATION AND VOICE.

The superior thyro-arsrfcenoid ligaments consist of a few slight fibrous
fasciculi, contained within the folds of mucous membrane forming the false vocal
cords hereafter to be described, and are fixed in front to the angle between the alse
of the thyroid cartilage, somewhat above its middle, and close to the attachment of
the epiglottis ; behind, they are connected to the inner part of the ridges on the
anterior surface of the arytenoid cartilages. They are continuous above with
scattered fibrous bundles contained in the aryteno-epiglottic folds.

The inferior thyro-arytenoid ligaments are formed of fine closely arranged
elastic fibres, which are attached in front to the middle of the angle between the alse
of the thyroid cartilage, and behind to the anterior projection of the base of the
arytenoid cartilages. The inner edge of each ligament is free and sharply defined
between those attachments, and, covered by the mucous membrane, forms the true
vocal cord of its own side. In other directions these ligaments are less sharply
defined, for in their outer part they spread out both above and below as they pass
backwards. Above, the fibres of the ligament lie near the upper surface of the
projecting fold of mucous membrane which bounds the rima glottidis, and become
gradually merged into the elastic tissue of that membrane. Below, the inferior
thyro-arytenoid ligament passes in continuity with the lateral crico-thyroid
ligament, so that it may be described as an upward extension of this ligament, and
the vocal cord may be stated to be formed by the superior free edge of the crico-
thyroid membrane.

The crico-arytenoid articulations are surrounded by a series of thin capsular
fibres, which, together with a loose synovial membrane, serve to connect the convex
elliptical articular surfaces on the upper border of the cricoid cartilage with
the concave articular depressions on the bases of the arytenoid cartilages. The
articular surface on the arytenoid cartilage is longer from before back than from side
to side ; so that its long axis crosses that of the corresponding surface on the
cricoid, and a part of the latter surface is in every position of the arytenoid
left uncovered (Henle). The movements allowed are of two kinds, viz. : — 1. a
lateral gliding movement from within out or vice versa, the arytenoid cartilage being
bodily moved away from or towards its fellow ; 2. a rotating movement on a nearly
vertical axis, the vocal processes being inclined inwards or outwards (as well as
somewhat downwards or upwards). A combined rotating and gliding movement
may also occur. The ordinary position of the arytenoid, when the larynx is at rest,
is on the outer part of the articular surface on the cricoid. There is a strong
crico-arytenoid ligament, arising from the cricoid, and inserted into the inner
and back part of the base of the arytenoid cariilage.

The summits of the arytenoid cartilages and the cornicula laryngis are
sometimes united by a synovial joint, but most frequently by connective tissue
forming a sort of syndesmosis.

INTERIOR OF THE LARYNX.

The cavity of the larynx is divided into an upper and a lower compartment by
the comparatively narrow aperture of the glottis, or o-ima glottidis, the margins of
which, in their anterior two-thirds, are formed by the lower or true vocal cords ; and
the whole laryngeal cavity, viewed in transverse vertical section (fig. 171) thus
presents the appearance of an hour-glass. The upper compartment, often called
the vestibule, communicates with the pharynx by the superior ajoerture of the
larynx, and contains immediately above the rima glottidis the ventricles (s), with
their pouches or saccules {s'), and the upper ov false vocal cords. The lower compart-
ment passes inferiorly into the tube of the windpipe without any marked con-
striction or limitation between them. The whole of the interior of the larynx is
lined by mucous membrane.

INTERIOR OF THE LARYNX.

153

The superior aperture of the larynx, when open, is triangular, wide in front
and narrow behind, the lateral margins sloping obliquely downwards and backwards.
It is bounded in front by the epiglottis (fig. 173, A, e, and fig. 174, «), behind by
the summits of the arytenoid cartilages (fig. 173, B, a) and cornicula (s), with the
angular border of mucous membrane crossing the median space between them, and
on the sides by two folds of mucous membrane, the aryte,no-e2ngloiiic folds, which,
enclosing a few ligamentous and muscular fibres and the cuneiform cartilages

Fig. 171. — A.NTi;iaoii ualf of a coronal section through the larynx near its middle.

(Allen Thomson.)

1, upper division of the laryngeal cavity ; 2, central portion ; 3, lower division, continued into 4,
trachea ; e, the free part of tlie epiglottis ; e', its cushion ; //, gi'eat cornu of the Iiyoid bone ;
Id, thyro-hyoid memljrane ; t, thyroid cartilage ; c, cricoid cartilage ; r, first ring of the trachea ;
tn, thyro-aryteuoid muscle ; rl, inferior thyro-arytenoid ligament in the membrane of the true vocal cord
at the rima glottidis ; «, the ventricle ; above this, the superior or false cords ; s', the sacculus or
pouch opened on the right side by carrying the section further forward.

Fig. 172. — View of the interior op the right half of the larynx. (Sappey.)

1, ventricle ; 2, superior, and 3, infei'ior vocal cord ; 4, arytenoid cartilage covered by mucous
memijrane ; f), arytenoid muscle cut across ; 6, slope of crico-thyroid membrane leading up to inferior
vocal cord ; 7, 8, sections of cricoid; 9, its upper border; 9', its lower border; 10, section of
thyroid ; 11, upper part of larynx ; 12, 13, glandular prominence in ary. -epiglottic fold ; 14, 16,
epiglottis ; \;>, fat between it and the thyro-hyoid membrane ; 17, section of epiglottis ; 18, section of
hyoid bone ; 19, 20, trachea.

(fig. 17:5, B, ?/•), pass forwards fi-om the tips of the arytenoid cartilages and cornicuia
to the lateral margins of the epiglottis (fig. 174, 8, \), lOj.

In studyinjr the form of the laryngeal cavity and its apertures, it is well to become
aciuaintf^l with the ai)rM;aranceH which they present on examination durinj,' life by means of
the larynf,'Oi"COpe, and with the relations of these to the anatomical structure. On thus
examininjf the superior afXirture, tlierc arc seen on each side two rounded elevations
(fig. 173, A, B, *, w), corresj>ondinj.' respectively to the cornicula and the cuneiform cartilages ;

154

ORGANS OF RESPIRATION AND VOICE,

while in the middle line in front there is a tumescence of the mucous membrane on the lower
part of the epiglottis, named the tubercle or cushion of the ejpiglottis (e).

When the superior aperture is closed during the act of deglutition, it presents,
according to Anderson Stuart, a T-shaped fissure. The transverse limb of the
T is slightly curved, with the convexity forwards, and is bounded in front by the
epiglottis, and behind by the aryteno-epi glottic folds. The vertical limb of the
T is represented by a median fissure, extending from the epiglottis in front to the
interarytenoid fold behind, and bounded at the sides by the arytenoid cartilages.

On looking down through the superior opening of the larynx, the glottis or rima
glottidis (fig, 173, and fig. 174, c) is seen at some distance below, in the form of a
long narrow fissure running from before backwards. It is situated on a level with
the lower part of the arytenoid cartilages, and is bounded by the true vocal cords.
Above the glottis another pair of projecting folds is seen, the superior or false

Fig. 173. — Threk lakyngoscopic views op

THE SUPERIOR APERTURE OF THE
LARYNX AND SURROUNDING PARTS IN DIF-
FERENT STATES OP THE GLOTTIS DURING

LIFE. (From Czermak.)

A, the glottis during the emission of a
high note in singing. B, in easy or quiet
inhalation of air. C, in the state of widest
possible dilatation, as in inhaling a very
deep breath. The diagrams A', B', C have
been added to Czermak's figures to show in
horizontal sections of the glottis the position
of the vocal ligaments and arytenoid car-
tilages in the three several states represented
in the other fiigures. In all the figures, so
far as marked, the letters indicate the parts
as follows, viz. : I, the base of the tongue ;
e, the upper free part of the epiglottis ; e',
the tubercle or cushion of the epiglottis ;
p h, part of the anterior wall of the pharynx
behind the larynx ; in the margin of the
aryteno-epiglottidean fold w, the swelling of
the membrane caused by the cuneiform
cartilage ; s, that of the corniculum ; a,
the tip of the arytenoid cartilages ; c ■y, the
true vocal cords or lips of the rima glottidis ;
c V s, the superior or false vocal cords ; be-
tween them the ventricle of the larynx ;
in C, t r is placed on the anterior wall of the
receding trachea, and h indicates the com-
mencement of the two bronchi beyond the
bifurcation, which may be brought into view in this state of extreme dilatation.

vocal cords, which are much less projecting than the inferior. Between the superior
and inferior vocal cords the sinus or ventricle is seen as an elongated depression
(fig. 174, V).

The superior vocal cords or ventricular bands, also called the false vocal
cords, because they are not immediately concerned in the production of the voice,
are prominent rounded folds of mucous membrane enclosing very numerous glands
which form somewhat arched projections, immediately above the corresponding
ventricle (fig. 174, h). The latter is seen on looking down into the laryngeal cavity,
the superior vocal cords (fig. 173, cvs,) being further apart than the inferior {cv).

Wylie showed (Edin. Med. Journal, 1866) that when the false vocal cords are simply
approximated and air is injected into the larynx from below, they prevent the exit of the air,
and he held that the closure of the glottis in def secation and vomiting is mainly effected by
the apposition of the false cords. His experiments have been confirmed by Brunton and
Cash.

VOCAL CORDS.

155

The inferior or true vocal cords, the structures by the vibration of which tlio
sounds of the voice are produced, bound the anterior two-thirds of the aperture

Fig. 174. — Perspective view of

OPENINft INTO THE LARYNX

BEHIND. (Allen Thomson.)

THE PHARYNGEAL
FROM ABOVE AND

The superior aperture has been much dilated ; the
glottis is in a moderately dilated condition ; the wall of
the pharynx is opened from behind and turned to the
sides. 1, body of the hyoid bone ; 2, small cornua ; 3,
great cornua ; 4, cornua of the thyroid cartilage ; 5,
membrane of the pharynx covering the jjosterior surface
of the cricoid cartilage ; 6, gullet ; 7, trachea ; 8, pro-
jection caused by the cartilage of Santorini ; 9, the
same belonging to the cartilage of Wrisberg ; 10,
aryteno- epiglottic fold ; 11, cut margin of the wall
of the pharynx ; a, free part of the epiglottis ; «', its
lower pointed part ; a", the cushion ; b, eminence on
each side over the sacculus or pouch of the larynx : h',
the ventricles ; c, the glottis ; the lines on each side
point to the vocal cords.

of the glottis, corresponding with the thyro-
arytenoid h'gaments (fig. 1 74, c) . The mucous
membrane covering them is so thin and
closely adherent as to show the yellowish
colour of the ligaments through it. They are
situated at the inner and free edge of a mass
of tissue triangular on coronal section (fig.
171). One surface of this mass looks up-
wards, and forms the floor of the ventricle,
another looks downwards and inwards, and
bounds the lower division of the laryngeal cavity, while the third is external.

A small nodule of elastic cartilage {cartilage of Luschlca) is found in the anterior
and inferior part of the vocal cord (Klein) (fig. 177, c).

Taguchi gives the following data for the determination of the position of

Fig. 175. — AnTEHIOK A.S1'ECT ok TUVKOID CARTILAOE to show P0INT.S OPPOSITFj WHIOH THE TRUE
AND FAL3K VOCAL COKD.S ARE ATTACHED. (Tnguchi.)

«, bottom of thyroid notch ; c and d, opposite attachment of false vocal cords ; h, ojipositc attach-
ment of true vocal cordH.

Fig. 176. — Horizontal .section of the larynx and larvnoeal part of pharynx, (J. S.) \

1, thyroir] cartilapte ; 2, tliyro-arytenoid muscle ; 3, lateral crico-arytenoid muscle ; 4, arvtenoid
cartilage ; Ti, rima giottidis ; G, arytenoid muHclc ; 7, cavity of laryngeal part of pharyn.x ; 8, inferior
constrictor of pharynx.

156 OEGANS OF EESPTEATION AND VOICE.

the true and false vocal cords in the undisi,ected body. The true vocal cords are
attached to the thyroid cartilage, close to one another, in the male 8" 5 mm. and in
tlie female 6*5 below the bottom of the median notch on the upper border of
the thyroid cartilage. The false vocal cords are 4 mm. apart at their anterior
attachment, and 2'5 mm. higher than the true cords (see fig. 175).

The rima glottidis, an elongated aperture, situated, anteriorly, between the
inferior or true vocal cords (pars vocalis), and, posteriorly, between the bases of the
arytenoid cartilages {pars respiratoria), forms a long narrow slit, slightly wider in
the centre when nearly closed, as in the production of the voice, and opening
out to a triangular form in the pars respiratoria (fig. 173, A'). When moderately
open, as in easy respiration, its shape is that of a long triangle, the pointed
extremity being directed forwards, and the base being behind, between the arytenoid
cartilages (fig. 173, b') ; in its fully dilated condition it is lozenge-shaped (the
posterior sides being formed by the inner sides of the bases of the arytenoid
cartOages), while the posterior angle is truncated (c'). The rima glottidis is
the narrowest part of the interior of the larynx ; in the adult male it measures about
23 mm., or nearly an inch, in an antero-posterior direction, and 6 or 8 mm. across at
its widest part, which may be dilated to nearly 12 mm. In the female, and
in males before the age of puberty, its dimensions are less, its antero-posterior
diameter being about 17 mm., and its transverse diameter about 4 mm. The vccal
cords are about 15 mm. long in the adult male and 11 mm. in the female.

The ventricles or sinuses of the larynx (fig. 171, s, and fig. 174, V) are
narrower at their orifice than in their interior. The outer surface of each is
covered by the upper fibres of the corresponding thyro-arytenoid muscle.

The small recesses named the laryngeal 'pouches (fig. 171, s'), lead from the
anterior part of the ventricles upwards, for the space of half an inch, between the
superior vocal cords inside and the thyroid cartilage outside, reaching as high as the
upper border of that cartilage, and nearly to the level of the aryteno-epiglottic
folds. The pouch, which is of variable size, is conical in shape^ and curved shghtly
backwards. Its opening into the ventricle is narrow, and k; generally marked by
two folds of the lining mucous membrane. Numerous small mucf&us glands, sixty or
seventy in number, open into its interior, and it is surrounded 'lj|'- a quantity of fat.
Externally to the fat, this little pouch receives a fibrous investment, which is
continuous below with the superior vocal cord. Over its laryngeal side and upper
end is a thin layer of muscular fibres {compressor sacculi laryngis, aryiczno-
epiglottideus inferior, Hilton) connected above with those found in the aryteno-
epiglottic folds. The upper fibres of the thyro-arytenoid muscles pass over the
cuter side of the pouch, a few being attached to. its lower part. The laryngeal
pouch is suppHed abundantly with nerves, derived from the superior laryngeal.

THE MUCOUS MEMBEANE AND VESSELS OF THE LABYNX

The laryngeal mucons membrane is thin and of a pale colour. In some
situations it adheres intimately to the subjacent parts, especially on the epiglottis,
and still more in passing over the true vocal cords, on which it is very thin and most
closely adherent. About the upper part of the larynx, above the glottis, it is
extremely sensitive. In and near the aryteno-epiglottic folds it covers a quantity
of loose areolar tissue, which is liable in disease to infiltration, constituting oedema
of the glottis. Like the mucous membrane in the rest of the a.L-passages, that of
the larynx is covered in the greater part of its extent with a columnar ciliated
epithelium, by the vibratory action of which the mucus is urged upwards. The
cilia are found higher up in front than on each side and behind, reaching in the
former direction as high as the widest portion of the epiglottis, and in the other

MUCOUS MEMBRANE OF THE LARYNX.

157

directions only to a line or two above .he superior vocal cords : above these points
the epithelium loses its cilia, and assumes a stratified squamous form, like that of
the pharynx and mouth. Upon the true vocal cords also the epithelium is
squamous, although both above and below them it is columnar and ciUated. Patches
of stratified squamous epithelium are found also dotted here and there in the ciliated
tract above the glottis, especially on the under (posterior) surface of the epiglottis, the
inner surface of the arytenoid cartilages, and at the free border of the superior vocal
cord. Bodies which are to all appearance similar to the taste-buds which occur in
coonection with the mucous membrane of the tongue (Vol. III., Pt. 3) are here and
there found imbedded in this stratified epithelium (but not over the vocal cords).

The lining membrane of the larynx is provided with numerous glands, which
secrete an abundant mucus, and the orifices of which may be seen almost everywhere

Tig. 177.— Vertical section through the ventricle of the lakynx of a child. (Klein.)
a, stratifieil epithelium over true vocal cord ; b, ciliated epithelium over false vocal cord ; c, nodule
of elastic cartilage (cartilage of Luschka) ; d, ventricle ; I, lymphoid tissue ; m, bundles of thyro-
arytenoid muscle, cut acros.s.

Fig. 178. — P0.STER10R VIEW OF the nerves of the larynx. (Sappey.)
], superior laryngeal nerve ; 2, its external branch ; 3, 4, 5, branches to the mucous membrane of
the larynx ; (>, filaments uniting the left superior and inferior laryngeal nerves ; 7, the same on the
right side, cut ; 8, 8, inferior laryngeal nerves ; 9, branch to the posterior crico-arytenoid musoles ;
10, branch to the arytenoid ; 11, 12, branches passing to the lateral cricoarytenoid and the thyro-
arytenoid mu-scles.

excepting upon and near the true vocal cords. They abound particularly upon the
epiglottis, in the substance of which arc found upwards of fifty small compound glands,
some of them perforating the cartilage. Between the anterior surface of the epiglottis,
the iiyoid bone, and the root of the tongue is a mass of yellowish fat, erroneously
named the epiglottic gland, in or upon which some small glands may exist. Another
collection of glan,ds is placed within the fold of mucous membrane in front of each
arytenoid cartila,,^', from which a series may be traced forwards, along the corre-
sponding superior vocal cord. The glands of the laryngeal pouches have already
been noticed.

Vessels and Nerves of the Larynx. — The arteries of the laryn.v are derived
from the superior tliijroid, a branch of the external carotid, iind from the inferior

158

ORGANS OF EESPIHATION AND VOICE.

thyroid, a branch of the subclavian. The veins join the superior, middle, and
inferior thyroid veins. The lymphatics are divisible into two sets, upper and lower.
The upper pierce the thyro-hyoid membrane and join glands near the bifurcation
of the common carotid artery ; the lower pass through the crico-thyroid membrane,
and end either in one or two small glands often found in front of that membrane,
or in some inferior laryngeal glands at the side of the lower part of the
larynx. Their mode of distribution resembles that in the trachea. The nerves
are supplied from the sujnrior larynyeal and inferior or recurrent laryngeal branches
,of the pneumo-gastric nerves, joined by branches of the sympathetic. The superior
laryngeal nerves supply the mucous membrane and the crico-thyroid muscles, and
also, in part, the arytenoid muscle. The inferior laryngeal nerves supply, in part,
the arytenoid muscle, and all the other muscles, excepting the crico-thyroid.

The superior and inferior laryngeal nerves of each side communicate with each
other in two places, viz., at the back of the larynx, beneath the pharyngeal mucous
membrane, and on the side of the larynx, under the ala of the thyroid cartilage.
Numerous ganglion- cells are found on the branches, both on those which enter the

Fig. 179. — Intraepithelial nerve-terminations in the larynx. (Gr. Retzius.)

Silver-cbromate preparation.
The section is taken at a place where the ciliated epithelium passes into stratified.

muscles, and also underneath the mucous membrane. End-bulbs are also described
in the mucous membrane which covers the posterior or laryngeal surface of the
epiglottis (Lindemann). Other nerve-bundles enter the epithelium, within which
they end in arborisations of fine fibrils (fig. 179).

The further details of the distribution of the vessels and lymphatics will be
found in Vol. II., Pt. 2, and of the nerves in Vol. III., Pt. 2.

muscijES of the laetnx.

Besides certain extrinsic muscles elsewhere described — viz., the sterno-hyoid,
omo-hyoid, sterno-thyroid, and thyro-hyoid muscles, together with the muscles
of the supra-hyoid region, the middle and inferior constrictors of the pharynx, and
the stylo-pharyngeus and palato-pharyngeus, all of which act more or less upon the
entire larynx — there are other muscles which move the different cartilages upon one
another, and modify the size of the apertures and the state of tension of the vocal
cords. These intrinsic muscles are the crico-thyroid, the posterior crico-arytenoid,
the lateral crico-arytenoid, the thyro-artjtenoid, the arytenoid, and the cmjtetw-
epiglottic, together with certain other slender muscular fasciculi. All these muscles,
except the arytenoid which 'crosses the middle line, are in pairs.
^^^ ^ The crico-thyroid muscle (fig. 180, A, 14) is a short, thick, triangular muscle

S^*'"'^'^^seen on the front of the larynx. Its attachment below, to the cricoid cartilage,
^., extends from the median line a considerable way backwards, and its fibres passing
>r upwards and outwards, diverging slightly, are fixed above to the inferior border of

N the thyroid cartilage, and to the anterior border of its lower cornu. The latter

^ portion of the muscle, the fibres of which are nearly horizontal, is usually distinct

from the rest. Some of the superficial fibres are almost always continuous with the
inferior constrictor of the pharynx. The muscles of the two sides are somewhat

MUSCLES OF THE LARYNX.

159

separate from one another in the middle Hne in front, leaving an interval which is
triangular, with the base upwards. The crico-thyroid membrane is here exposed.

Action. — The anterior part of the muscle contracting will approximate the cricoid and
thyroid cartilages in front. In this action the thyroid is fixed by the extrinsic muscles, and
the anterior part of the cricoid rotating- on the axis which unites the articulations between
the cricoid and the lower coruua of the thyroid is drawn upwards, and the part behind
the crico-thyroid joints is depressed, and with it the arytenoid cartilages, so that the vocal
cords are thus put on the stretch. This stretching of the vocal cords is still fui-ther assisted
by the action of the oblique fibres, which, acting from the cornu of the fixed thyroid, draw
the cricoid caitilage backwards. It is found, also, that with electric excitation of this muscle
the anterior part of the cricoid is raised towards the thyroid. Paralysis of these muscles is
accompanied by inability to produce high tones of the voice.

The posterior crico-arytenoid muscle (fig. 180, B, 1), situated behind, arises
from the broad depression on the corresponding half of the posterior surface of the
cricoid cartilage, and its fibres, converging upwards and outwards, are inserted into

Fig. 180. — Muscles of the larynx. (Sappey.)
A, as shown in a view of the larynx from the right side.
1, hyoid bone ; 2, 3, its cornua ; 4, right ala of thyroid cartilage ; 5, posterior part of the same
separated by oblique line from anterior part ; 6, 7, superior and inferior tubercles at ends of oblique
line ; 8, upper cornu of thyroid ; 9, thyro-hyoid ligament; 10, cartilage trlticea ; 11, lower cornu of
thyroid, articulating with the cricoid ; 12, anterior part of cricoid ; 13, crico-thyroid membrane ;
14, crico-thyroid mu.scle ; 15, posterior crico-arytenoid muscle, partly hidden by thyroid cartilage.
B, as seen in a view of the larynx from behind.
1, posterior crico-arytenoid ; 2, arytenoid muscle ; 3, 4, oblique fibres passing around the edge of the
arytenoid cartilxtge lo join the thyro-arytenoid, and to form the aryteno-epiglottic, 5.

the outer angle of the base of the arytenoid cartilage, behind the attachment of the
lateral crico-arytenoid muscle. The upper fibres are short, and almost horizontal ;
the middle are the longest and run obliquely ; whilst the lower or external fil)rGs arc
nearly vertical. Near their insertion the upper fibres are blended with the lower
fibrcH of the arytenoideus.

Aftion. — The posterior crico-arytenoid muscles draw the outer angles of the arytenoid carti-
la^fes backwards and inwards, and thus rotate the anterior or vocal processes outwards, and widen
the rima glottidis. Acting with the iatf^ral crico-arytenoid muscles, they approximate the
vocal cords (KanthackJ. They may also draw the arytenoid cartilages apart. They come into

160

ORGANS OF RESPIRATION AND VOICE.

action during' deep inspiration. If paralysed, the lips of the glottis approach the middle line,
and come in contact during each inspiration, so that severe dyspnoea may be produced.
Expiratory efforts, however, are not impeded, and vocalization is unaffected.

Variety. — In connection with the posterior crico-arytenoid muscle may be mentioned an
occasional small slip in contact with its lower border viz., the kerato-cricoid muscle
of Merkel. It is a short and slender bundle, arising from the cricoid cartilage uear its lower
border, a little behind the inferior cornu of the thyroid cartilage, and passing obliquely
outwards and upwards to be inserted into that process. It usually exists on one side only.
Turner found it in seven out of thirty-two bodies. ' It is not known to be of any physiological
significance. (Merkel, Anat. und Phys. des menschl. Stimm-und Sprach-organs, Leipzig, 1857;
Turner in Month. Med. Journal, Feb. 1860.)

The lateral crico-arytenoid muscle (fig. 182, cr.ar.Iat.), smaller than the
posterior, is in a great measure hidden by the ala of the thyroid cartilage. It lies
along the sloping upper border of the
cricoid cartilage, from which it arises,
its origin extending as far back as the
articular surface for the arytenoid. Its

Fig. 181. — Outline of the right half op the cartilages of the larynx as seen prom the

INSIDE, WITH THE THYRO-ARYTENOID LIGAMENT, TO ILLUSTRATE THE ACTION OP THE CRICC-THYROID

MUSCLE. (Allen Thomson. )

t, thyroid cartilage ; c, cricoid cartilage ; a, right arytenoid cartilage ; a', its vocal process ;
s, corniculum ; c v, the thyro-arytenoid ligament ; the position of the lower cornu of the thyroid
cartilage on the outside of the cricoid is indicated by a dotted outline, and r indicates the point or axis
of rotation of the cricoid cartilage on the cornu of the thyroid ; c « A, a line in the principal direction of
action of the crico-thyroid muscle ; cap, the same of the posterior crico-arytenoid muscle.

Fig. 182. — Side view op the larynx after removal op the right ala op the thyroid cartilage.

(S. G. Shattock.)
h,_ body of hyoid bone, cut ; e, epiglottis ; th, cut surface of right ala of thyroid cartilage ; cr, front
of cricoid cartilage, the articular facet for the inferior cornu of the thyroid is seen posteriorly ; th.ar,
th.ar, fibres of the thyro-arytenoid (outer portion) passing from the thyroid in front to the arytenoid
behind ; th.ar', others arising from the crico-thyroid membrane ; another considerable mass of fibres is
seen arising from the same parts, and passing at first obliquely and afterwards nearly vertically upwards
as the thyro-epiglottic muscles, <A.ep. ; «A. an 7/t, small thyro-arytenoid ; th.ar.m', a small slip of the
same muscle passing into the false vocal cord; cr.ar.Iat, lateral crico-arytenoid; cr.ar.p, posterior
crico-arytenoid ;_ r.ar.ep, right aryteno-epiglottic muscle near its origin ; l.ar.ep, left aryteno-
epiglottic near its insertion; l.ar.ep', portion of the same inserted into the corniculum; /, fat;,
s, saccule covered by mucous glands.

fibres pass backwards and upwards, the anterior or upper ones being necessarily
the longest, and are attached to the muscular process of the arytenoid cartilage
and to the adjacent part of its anterior surface.

MUSCLES OF THP: LARYxXX. 161

This muscle is covered interually by the lateral part of the crico-thyroid
membrane, and externally at its anterior part by the upper part of the crico-thyroid
muscle. The upper part is in close contact, and, indeed, is always more or
less blended with the thyro-arytenoid, and a few of its fibres are continuous round
the outer side of the arytenoid cartilage with the arytenoideus muscle.

Action. — These muscles, drawing the muscular processes of the arytenoids forwards and
downwards, rotate the vocal processes inwards, and approximate the vocal cords. They thus
act antagonistically to the posterior crico-arytenoids.

If both posterior and lateral crico-arytenoids be thrown into action simultaneously, the
arytenoids will not undergo rotation, but will be drawn inwards, and the glottis will thus bo
narrowed.

The thjrro-arytenoid muscle consists of two portions, one external situated
immediately within the ala of the thyroid cartilage, and one internal lying in close
contact with the vocal cord. Sometimes these are described as distinct muscles
under the names external and internal thyro-arytenoid (Henle), but the separation
between them has to be effected by artificial means. The inner portion of the
muscle is triangular in section corresponding with the vocal fold which it occupies ;
the outer is laterally compressed and extends both above and below the inner
portion. Each contains both antero-posterior and oblique fibres.

Inner portion. — The antero-posterior fibres of the internal portion arise
in the lower half of the angle formed by the alee of the thyroid cartilage,
a few even from a nodule of firmer tissue (cartilage of Luschka) in the
anterior part of the vocal cord itself ; and, passing backwards in a slight curve
with the concavity inwards, are attached behind to the vocal process along
its whole length, and to the adjacent part of the outer surface of the arytenoid
cartilage. They are joined internally by short fibres, which arc attached in front to
the vocal cord, and behind to the vocal process of the arytenoid {jjortio ary-vocalis
of Ludwig) ; and externally they are contiguous with the antero-posterior fibres of
the external portion. The oblique fibres of the internal portion pass from the
sloping portion of the crico-thyroid membrane below the vocal cord proper (in its
anterior third), upwards, outwards, and somewhat backwards, passing between the
antero-posterior fibres, and over the ventricle of Morgagni, to end in the tissue of the
false vocal fold.

Outer portion (fig. 182). — The fibres of the external portion arise in front from
the thyroid cartilage, close to the origin of the internal portion, and from the
crico-thyroid membrane ; from here they in part pass backwards to be inserted into
the lateral border and muscular process of the arytenoid cartilage, in part
obliquely upwards towards the aryteno-epiglottidean fold, some which are more
vertical in direction passing in a thin layer around the ventricle of Morgagni and
the sacculus, to end in the false vocal fold. The portion of this muscle which
extends towards the epiglottis is often described as a separate muscle under the name
of thyro-epiglottideau (fig. 182, th.ep). It resembles the crico-arytcnoideus
lateralis in having some of its fibres continuous with those of the arytenoideus.

Action. — The bundles of the thyro-arytenoid muncle, differing as they do in direction and
in fKtints of attachment, must differ also in their action, if separately called into play. The
antero-posterior fibres will tend to draw forwards the arytenoid, and with it the posterior part
of the cricoid cartilage, rotating the latter upwards, and antagonising the action of the
crico-thyroid, the effect being to relax the vocal cords. But if the latter be kei)t stretched
and approximated by the action of other muscles, those fibres of the inner portion which are in
close contact with the vocal cord may serve to modify its elasticity and consistc^ice, while the
fibres which constitute the portio ary-vocalis may serve, as Ludwig has pointed out, to tighten
the parts of the cord in front of their attachment, and to slacken the j)art3 behind. The
vertical fibres of the muscle which extend from the slojiing part of the crico-thyroid
membrane across the base of the vocal fold, and over the ventricle into the false vocal cord,
must, when they cfjntract, render ihe free edge more prominent. Finally, the fibres which
are inwjrted into the muscular process and outer surface of the arytenoid will tend to draw

VOL. III., I'T 4. H

162 ORGANS OF RESPIRATION AND VOICE.

forwards and rotate inwards the arytenoid cartilage, and those which pass up into the
aryteno-epicclottidean folds may assist in depressing the epiglottis.

If the thyro-arytenoid muscles are paralysed, the lips of the glottis are no longer parallel,
but are curved with the concavity towards one another, and a much stronger blast of air is
required for the production of the voice.

Santorini described three thyro-arytenoid muscles, an inferior, a middle, and a suj)erior.
The latter is not always present. The inferior thyro-arytenoid muscle of Santoriui comprises
most of the antero-posterior bundles ; the middle thyro-arytenoid, the oblique bundles of the
external portion. The fibres of the superior fasciculus, when present, arise nearest to
the notch of the thyroid cartilage, and are attached to the upper base of the arytenoid
cartilage (fig. 182, tli.ar.m.'). This is named by Soemmering the small thyro-arytenoid, whilst
the two other portions of the muscle constitute the great thyro-arytenoid of that author.

Arytenoideus muscle. — When the mucous membrane is removed from the
back of the arytenoid cartilages, a thick band of transverse fibres is laid bare
(fig. 180, B, 2), and on the dorsal surface of this are seen two slender decussating
oblique bundles (3, 4).

The transverse and oblique fibres are often described as separate muscles
(arytenoid and aryteno-epiglottic), but the two sets of fibres are intimately blended.
Most of the anterior or ventral fibres pass straight across between the arytenoid
cartilages, and are attached to about the outer half of the concave surface on the
back of each. The dorsal fibres can be traced into the lateral walls of the larynx,
the uppermost fibres to the cartilages of Santorini, the intermediate fibres run
partly independently and partly with the uppermost fibres of the thyro-arytenoidei
into the inner and outer walls of the saccules of the larynx, forming the so-called
aryteno-epiglottidean muscles, and the lowest fibres blend at the level of the true
vocal cords with the thyro-arytenoid and lateral crico-arytenoid muscles.

Action. — The arytenoid muscle draws the arytenoid cartilages together, and, from the
structure of the crico-arytenoid joints, this approximation, when complete, is necessarily
accompanied with depression. If the muscle is paralysed, the intercartilaginous part of the
glottis remains patent, although the membranous lips can still be approximated.

The superior aperture of the larynx has been generally supposed to be closed during
the act of deglutition by the descent of the upper free end of the epiglottis as a lid over the
opening. Prom observations made by Stuart and McCormack ( The position of the epiglottis in
swallowing. Jour. Anat. and Phys., vol. xxvi.), it has been shown that this is not the case, the
epiglottis projecting upwards in close contact with the base of the tongue. According
to Stuart (On the mechanism of the closure of the larynx, Proc. Roy. Soc. London, 1892), it is
effected by the two arytenoid cartilages being drawn together and also forwards, so that their
upper ends are brought in contact with the posterior surface of the epiglottis. These
movements of the arytenoid cartilages are produced by the contraction of the arytenoid and
thyro-arytenoid muscles.

It is remarked by Henle that the muscles " which lie in the space enclosed by the laminse
of the thyroid cartilage, and above the cricoid, may be regarded in their totaKty as a kind of
sphincter, such as is found in its simplest form embracing the entrance of the larynx in
reptiles." In the human larynx there is a marked predominance of adductor over abductor
fibres (acting upon the vocal cords).

THE TRACHEA AND BRONCHI.

The trachea is that part of the common air passage of both lungs, which com-
mences above at the larynx and divides below into two smaller tubes, right and left
bronchi, one for each lung.

The trachea has a median position in the neck and thorax, and extends from the
lower border of the cricoid cartilage of the larynx, on a level with the lower part
of the sixth or upper part of the seventh cervical vertebra, into the upper part of the
thorax, where it is crossed in front and on the left side by the arch of the aorta and
then bifurcates into the two bronchi at about the level of the disc between the fourth
and fifth dorsal vertebras. It usually measures from 4 in. to 4| in. (10 to 11 cm.)
in length, and from | in. to 1 in. (2 to 2| cm.) in width ; but its length varies
according to the position of the neck. It is usually stated on the authority of Aeby
that the trachea gradually increases in calibre from above downwards, but according

THE TRACHEA.

163

to Braune and Stahel it presents a series of alternate dilatations and contractions.
Thus it is smallest at its commencement ; from this point it gradually increases
until about midway between its two ends, from here it diminishes to within about
3 cm. of its bifurcation towards which it aofain enlarges. Its averasfe diameter is

Fig. 1S3. — Horizontal section of trachea, cesopha-

GUS, AND thyroid BODY. (J. S. ) \

1, cesophagus ; 2, cavity of trachea ; 3, cartilaginous
ring of trachea ; 4. thyroid body ; 5, inferior thyroid
artery ; 6, recurrent hiryngeal nerve.

greater in the male than in the female. As

the trachea passes obliquely downwards and

somewhat backwards it gradually recedes

from the anterior surface of the neck in its

course towards the thorax. If the face be

directed forwards the distance from the upper end of the trachea to the top of the

sternum is about 2 to 3 in., and this is increased by fully an inch when the head is

thrown back. In fi-ont and at the sides the trachea is rendered cylindrical, firm.

Fig. 184. — Outline showing the general form of the

LARYNX, TRACHEA, AND BRONCHI, AS SEEN PROM

BEFORE. (Allen Thomson.) 3

k, the great cornu of the hyoid bone ; e, epiglottis ;
t, superior, and t', inferior cornu of the thyroid cai'tilage ;
c, middle of the cricoid cartilage ; t r, the trachea, showing
sixteen cartilaginous rings ; b, the right, and h', the left
bronchus. In this and also in the succeeding figure the
right bronchus is represented as somewhat more horizontal
than is usually described (see p. 164).

and resistant, by a series of cartilaginous rings ;
these, however, are deficient behind, so that the
posterior portion is flattened and entirely mem-
branous (fig. 183). Near its bifurcation the
trachea is somewhat expanded laterally.

Peculiarities according to age. — In the
fcetus the trachea is flattened before and behind, its
anterior surface being even somewhat depressed ; the
ends of the cartilages touch ; and the sides of the
tube, which now contains only mucus, are applied to
one another. The effect of respiration is at first to
render the trachea open, but it still remains somewhat
Hattene<I in front, and only later becomes convex. In
consequence of the hi^'h position of the larjoix in the
infant the cervical part of the trachea is relatively
longer at this period of life than in the adult, but
this increase in length is somewhat diminished by a
higher position of the manubrium sterni. The point
of Vjifurcation of the trachea is generally about a
vertebra higher at birth than in the adult. In an
infant six months old the trachea will admit a tube
4 mm. in diameter ; at two years one of i> mm. ; and
at six years one of 6 or 7 mm. Ossification of its car-
tilaginous rings usually commences in the male at
aVxiUt forty years of age, and in the female about .sixty
(Chievitz).

Bielations of the trachea to neighbouring parts. — The windpipe is nearly
everywhere invested l;y a loose areolar tissue, ahouiidiiig in clastic fibres, and is very
moveable on the surrounding parts. J>oth in the neck and thorax, it rests behind
against the gullet, which iuLerveues between it and the vertebral column, but

M 2

164

ORGANS OF EESPIRATION AND VOICE.

towards its lower part projects somewhat to the left side. The recurrent laryngeal
nerve ascends to the larynx on each side in the angle between these two tubes.

In the neck the trachea is situated between the common carotid arteries ; at its
upper end it is embraced by the lateral lobes of the thyroid body, the middle part
or isthmus of which lies across it just below the larynx. It is covered in front by
the sterno-thyroid and sterno-hyoid muscles, between which, however, there is left
an elongated lozenge-shaped interval in the middle line : this interval is covered in
by a strong process of the deep cervical fascia, while, more superficially, another
layer not so strong crosses between the sterno-mastoid muscles. The inferior

Fig. 185. — Outline showing the general form op the

LARYNX, trachea, AND BRONCHI, AS SEEN FROM

BEHIND. (Allen Thomson.) i

Ji, great cornu of the hyoid bone ; t, superior, and t',
inferior cornu of the thyroid cartilage ; e, the epiglottis ; a,
points to the back of both the arytenoid cartilages, which
are surmounted by the cornicula ; c, the middle ridge on
the back of the cricoid cartilage ; t r, the posterior mem-
branous part of the trachea ; h, b', right and left bronchi :
their relative direction, as shown in this figure, is not that
most frequently met with.

thyroid veins and the arteria thyroidea ima,
when that vessel exists, also lie upon its anterior
surface below the isthmus of the thyroid body ;
while just above the level of the upper edge of
the sternum the innominate artery is occasionally
found crossing obliquely in front of it.

In the thorax, the trachea is covered by the
manubrium sterni, together with the sterno-
thyroid and sterno-hyoid muscles and the re-
mains of the thymus gland ; behind these, by
the left innominate vein, then by the com-
mencement of the innominate artery and left
carotid, which pass round to its sides ; and
lastly by the arch of the aorta and the deep
wSiTiTn-^ cardiac plexus of nerves. Placed between the
^m-G^-l\^) two pleurge, the trachea is contained in the
superior mediastinum, and has on its right side
the pleura and pneumo-gastric nerve ; on the
left side are the arch of the aorta, the left carotid
and subclavian arteries and the left recurrent
laryngeal together with some cardiac nerves.

The right and left bronchi (figs.
184, 185, b, V) proceed each to the root of
the corresponding lung, and then undergo division. Previous to this they exactly
resemble the trachea on a smaller scale ; being rounded and firm in front and at the
sides, where they are provided with imperfect cartilaginous rings, and flattened and
membranous behind. The right bronchus is larger than the left, the area of a
section at right angles to the long axis of the right bronchus being in the proportion
of 100 to 78 for a corresponding section of the left bronchus. It is also more nearly
vertical so that on looking down the windpipe towards the bifurcation, the right
bronchus appears to be a more direct continuation of the trachea than the left.
This is, however, by no means constantly the case. Further it differs from the left
in giving off on its outer side about | in. to 1 in. from its origin a branch which
passes to the upper lobe of the right lung. As this branch comes off above the
place where the right pulmonary artery crosses the bronchus it is called epartmal,

STRUCTURE OF THE TRACHEA AND BRONCHI.

165

the continuation of the bronchus below this branch being called hyparterial. On
the left side there is no eparterial branch and the bronchus passes downwards and
outwards for about two inches before giving off" any branches (see p. 177 and fig. 195),

The right bronchus is embraced above by the vena azygos major, which hooks
forwards over it to end in the vena cava superior. The right vagus descends behind
it. At the root of the lung the eparterial branch is above the pulmonary artery,
the hyparterial part is crossed close to its origin by the pulmonary artery and
lower down the superior pulmonary vein gets in front of it. The left bronchus
inclines downwards and outwards beneath the arch of the aorta to reach the root of
the left lung where the left pulmonary artery lies first in fi'ont of and then above it.
It crosses over the front of the oesophagus and the descending aorta. Close to the
hiluni of the lung the upper left pulmonary vein is in front of it.

The combined sectional area of the two bronchi is about one-fifth greater than
that of the trachea.

The distribution of the branches of the bronchi within the lungs will be
descrited in connection with those organs.

STRUCTURE OF THE TRACHEA AND BRONCHI.

Trachea. — The trachea consists of an elastic framework of incomplete cartila-
ginous rings or hoops united by fibrous tissue, and at one part by plain muscular
tissue. It is lined throughout by a mucous membrane, and provided with glands.

e'fP'Se

Fig. 186. — I/jXOITCW.VAL SECTION OF THK HCMAN TRACHEA, INCLUDING PORTIONS OK TWO CARTILAGINOUS

RINGS. (Klein and Noble Smith.) Moderatkly magnified.

a, ciliated epithelium ; h. basement membrane ; c, superficial part of the mucous membrane, con
taining the sections of numerous capillary blood-vessels and much lymphoid tissue ; d, deeper part of
the mufous membrane, consisting,' mainly of elastic fibres ; e, submucous areolar tissue, containing the
lar((er blood-vessels, small mucous glands (their ducts and alveoli are seen in section), fat, &c. ; /,
fibrous tissue investing and uniting the cartilages ; y, a small ma.ss of adipose tissue in the fibrous layer ;
!•, cartilage.

The cartilages are from sixteen to twenty in number. Each forms a curve of
rather more than two-thirds of a circle, resembling the letter C (fig. 183). The depth

166

ORGANS OF RESPIRATION AND VOICE.

from above downwards is three or four millimeters, and the thickness 1 mm. The
outer surface of each is flat, but the inner is convex from above downwards, so as to
give greater thickness in the middle than at the upper and lower edge. The cartilages
are held together by strong fibrous tissue, which is elastic and yielding to a certain
extent, and not only occupies the intervals between them, but is prolonged over
their outer and inner surfaces, so that they are, as it were, imbedded in the tissue.

The cartilages terminate abruptly behind by rounded ends, but the fibrous tissue
is continued across between them, and completes the tube behind : it is here looser
in its texture.

The first or highest cartilage, which is connected by the fibrous membrane with
the cricoid cartilage of the larynx, is broader than the rest, and often divided at one
end. Sometimes it coalesces to a greater or less extent with the cricoid or with the
one below. The lowest cartilage, placed at the bifurcation of the trachea, is
peculiar in shape ; its lower border being prolonged downwards, and at the same
time bent backwards so as to form a curved projection between the two bronchi.

Fig. 187. — A PART OP THE SECTION REPRESENTED IN
THE PRECEDING FIGURE MORE HIGHLY MAGNIFIED.

(Klein and Noble Smith.)

The letters represent the same parts as in that figure.

The cartilage next above this is slightly
widened in the middle line. Sometimes
the extremities of two adjacent cartilages are
united, and not unfrequently a cartilage is
divided at one end into two short branches,
the opposite end of that next it being like-
wise bifurcated so as to maintain the
parallelism of the entire series. The use of
these cartilaginous hoops is to keep the wind-
pipe open, a condition essential for the free
passage of air into the lungs.

Within the fibrous membrane at the
posterior flattened part of the trachea, is a
continuous pale reddish layer of unstriped
muscular fibres, which pass across, not only
between the ends of the cartilages, but also
opposite the intervals : they doubtless serve to narrow the tube by approximating
the ends of the cartilages. Those opposite the hoops are attached to the extremities
of the latter, and encroach also for a short distance upon their inner smface.
Outside the transverse fibres are a few fasciculi having a longitudinal direction.

The submucous tissue consists of loose areolar tissue which serves to connect the
mucous membrane with the fibrous layer and the cartilaginous rings. It contains
mucous glands and a quantity of adipose tissue is often found in it.

The mucous membrane is smooth and of a pale pinkish white colour
in health, although when congested or inflamed, it becomes intensely purple
or crimson. It contains a considerable amount of lymphoid tissue. Underneath the
epithelium is a basement membrane (figs. 186, 187, b), well marked in the human
trachea, through which nerves and processes from the subjacent connective tissue
eeUs here and there pass into the epithelium. Throughout the mucous membrane
a number of fine elastic fibres are found, but in the deeper parts the elastic fibres
are very large and numerous (d). Along the posterior membranous part, they are
more abundant thaa elsewhere, and are there collected into distinct longitudinal

STRUCTURE OF THE TRACHEA.

167

bundles, which produce visible elevations or flutings of the mucous membrane.
These bundles are particularly strong and numerous opposite the bifurcation of the
trachea.

The epithelium consists of a layer of long columnar ciliated cells, often very
irregular at their fixed end, where they are impressed by smaller cells, between
which they penetrate to reach the basement membrane. The cilia serve to drive
the mucous secretion upwards towards the larynx. Between these ciliated cells, are
found others, also elongated ; they are prolonged at one end towards the surface, whilst
the other end, which is not unfrequently forked, reaches to the subjacent membrane.
These intermediate cells secrete mucus, which is to be seen in them in various
stages of formation, and some of them are to be seen converted into goblet-cells by
the extrusion of their mucinoid contents (6g. 188). A few lymph corpuscles are
also found amongst the epithelial cells, as in other epithelia.

The trachea is provided with numerous small mucous (/lands. The largest are
situated at the back part of the tube, either close upon the outer surface of the
fibrous layer, or occupying little recesses formed between its meshes. Smaller
glands ai'e found between the cartilaginous rings, upon and within the fibrous
membrane, and still smaller ones close beneath the mucous membrane. Thev are

Fig. 188. — Ciliated tpithelium cells from the trachea op

THE KABBIT ; HIGHLY MAGNIFIED. (E. A. S. )

m', VI-, m?, mucus -secreting cells, lying between the ciliated
cells, and seen in various stages of mucin-formation.

racemose glands, and their cavities are lined hj a
columnar epithelium : the excretory ducts pass through
the muscular layer and the mucous membrane, on
the surface of which their orifices are perceptible.

Vessels and Nerves. — The arteries of the
trachea are principally derived from the inferior thy-
roid. The larger branches run for some distance
longitudinally, and then join a superficial capillary
plexus with polyhedral meshes. The veins enter the \ \

adjacent plexuses of the thyroid veins. A rich plexus of in.^ vb m-

lymphatics may readily be injected in the mucous

membrane and submucous tissue, but the lymphoid follicles, so common in the
alimentary mucous membrane, and also in the walls of the smaller bronchi, are
rarely present. "When found it is generally surrounding the ducts of the glands
as they pass through the mucous membrane. The nerves come from the trunk
and recurrent branches of the 2meumo-gastric, and from the sympathetic system.
There are said to be numerous ganglia upon them, especially outside the muscular
layer at the back of the tube.

In the dog, cat, sheep, and rabbit, the upper half of the trachea is said to be
supplied chiefly by the superior laryngeal nerve, through the anastomosis between
the superior and inferior nerves in the larynx (Kandarazi).

Bkonx'III. — The general structure of the undivided portions of the l)ronchi
corresponds with that of the trachea in every particular. Their cartilaginous i-ings,
which resemble tho.se of the trachea in being imperfect behind, are, however, sliortcr
and naiTower. The number of these rings on the right side varies from six to eight,
whilst on the left the number is from nine to twelve.

The bronchi are sujiplied by the bronchial arteries and veins, and the nerves are
from the same source as those of the lower part of the trachea.

168

ORGANS OF RESPIRATION AND VOICE.

THE MEDIASTINUM THORACIS.

The o-reater part of the thorax is occnpied by the lungs, each of which is invested
by a serous membrane, i\xQ pleura. The right and left pleural cavities are separated

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THE LUNGS AND PLEURA. 169

by a median partition called the mediastinum. This consists of a layer of pleura
on each side, with the heart, great vessels, pericardium, and other structures inter-
posed. The interval between the right and left pleura, which is occupied by the
structures referred to, is known as the mediastinal space. The whole mediastinum
is subdivided into the following parts: — The middle mediastinum, which is co-
extensive with the pericardium ; the anterior mediastinum, the part in front of the
pericardium ; ihQ posterior mediastinum, the part behind the pericardium ; and the
sujierior mediastinum, which is situated above the pericardium, and extends upwards
as far as the root of the neck.

The superior mediastinum may be considered as bounded below by a plane
passing from the lower border of the body of the fourth dorsal vertebra behind to
the junction of the manubrium with the body of the sternum in front. Its upper
limit corresponds with the superior aperture of the thorax. In front are the
manubrium and the lower ends of the sterno-hyoid and sterno-thyroid muscles ; and
behind are the upper four dorsal vertebr;e and the lower ends of the longus colli
muscles.

It contains the trachea, oesophagus and thoracic duct ; the whole of the arch of
the aorta, the innominate artery, and the thoracic parts of the left common carotid
and subclavian arteries ; the innominate veins and upper part of the superior vena
cava ; the plirenic and pneumo-gastric nerves, the left recurrent, and the cardiac
nerves ; and the cardiac lymphatic glands and remains of the thymus gland.

The anterior mediastinum is narrow in its upper half, the two pleurse coming
nearly or quite into contact behind the second piece of the sternum. Below it is
a little broader, the left pleura receding from its fellow, and is bounded in front by
the sternum, sometimes also by the fifth and sixth, and a small portion of the
seventh left costal cartilages, and by the triangularis sterni muscle ; behind it is the
pericardium. The enclosed space contains only some areolar tissue, and in its lower
part two or three small lymphatic glands (anterior mediastinal glands).

The middle mediastinum is the enlarged central portion of the partition, con-
taining in addition to the pericardium with its contents (viz., the heart, the arch of
the aorta, the trunk of the pulmonary artery and the lower half of the superior
vena cava), the phrenic nerves and accompanying vessels, the arch of the azygos
vein, and the roots of the lungs with the bronchial lymphatic glands.

The posterior mediastinum is the part between the pericardium, the dia-
phragm, and the roots of the lungs in front, and the spine behind (from the lower
border of the fourth dorsal vertebra downwards). It contains between its pleural
layers the descending thoracic aorta ; the a3sophagus with the pneumo-gastric
nerves, the azygos veins, the thoracic duct and the posterior mediastinal lymphatic
glands.

THE LUNGS AND PLEURA.

The lungs occupy by far the larger part of the cavity of the chesi, and in health
are always in accurate contact with the internal surface of its wall. Each lung
is attached at a comparatively small part of its flattened inner or mesial surface by a
part named the root. In other directions the lung is free, and its surface is closely
covered by a serous membrane, which is reflected at the root to the corresponding
side of the thorax, and named the (right or left) pleura.

THE PLEURA.

The pleurae arc two serous sacs quite distinct from each other. Each consists
of a visceral and 'd parietal portion, between which is the pleural cavity containing a
very small quantity of fluid, merely suflicient to lubricate the opposing surfaces.
The viscera] portion (j)leura2mlmonaiis) covers the lung and extends into the fissures

170

OEGANS OF EESPIEATION AND VOICE.

between its lobes ; and the parietal portion lines the ribs and intercostal spaces
(pleura costalis), covers the upper convex surface of the diaphragm (iihura dia-
jjhragmatis), enters into the formation of the mediastinum (?j/e?^m mediastmalis), and
extends upwards into the neck {ijJeura cervicalis).

At the root of each lung the visceral and parietal portions of the corresponding
pleura are continuous with one another ; and at the lower border of the root is a
fold of the serous membrane, the two layers of which are continuous above with
those in front of and behind the root of the lung. It extends vertically along the
inner surface of the lung down to the diaphragm, to which it is attached by its
extremity ; this fold is named ligamentum latum 2Julmonis.

Fig. 190. — Horizontal section o thorax of man, aged 57, immediately above the bifurcation

OF the trachea, seen from 4B0VE. (J. S.) i

TJ.L., upper lobe of right lung ; tj.p., l.l., upper and lower lobes of left lung ; r.b., l.b., origin of
right and left V)ronchi, in this specimen the termination of the trachea was lower than usual ; a, arch
of aorta ; d.a., descending aorta ; d, obliterated ductus arteriosus ; n, left recurrent laryngeal nerve ;
L.G., lymphatic glands ; other letters as in fig. 189.

Along the mediastinal aspect of eacli pleura there descends a ligamentous band, an offshoot
of the prevertebral fascia, attached above to the bodies of the cervical and first dorsal vertebrge
and below to the pericardium and central tendon of the diaphragm. These bands, the " sus-
pensory ligaments of the diaphragm " of Teutleben, embrace the roots of the lungs, and in a
measure serve to fix both these and the other parts to which they are attached below.

Relations. — The costal portion of the pleura lines the inner surface of the ribs
and intercostal spaces and posteriorly passes over the heads of the ribs and the
gangliated cord of the sympathetic on to the sides of the bodies of the dorsal
vertebra, where it becomes continuous with the posterior part of the mediastinal
pleura, while in front it is reflected backwards to join the anterior part of the
mediastinal pleura. This anterior line of reflection varies at different levels, and
also shghtly on the two sides. Oj^posite the mauubrium sterni it may be repre-
sented by a line passing from the sterno-clavicular articulation downwards and

THE PLEURA.

171

inwards to meet the pletira of the opposite side at the upper edge of the body of the
Btemum. From this point the two pleurse are in dose contact down to the level of
the upper border of the fifth costal cartilage, where they tend to separate from one
another. On the right side the line of reflection contiaues nearly straight down to
the lower end of the body of the sternum, where it begins to turn outwards. On the
left side, according to Luschka, it normally diverges from the median line at the
npper border of the fifth costal cartilage, so that at the level of the sternal end of the
filth costal cartilage it is 1*5 cm., at the sixth 2 cm., and at the seventh 3-5 cm.
external to the left border of the sternum. Xot unfrequently, however, the lateral
deviation of the left pleura opposite the lower end of the .^cemum is not so marked

Fij. 191. — HoBIZOFTAL SZCnOS of the THOBAX op a ILkS, ACED 57, AT IHB LETRL OF THE BOOTS OF
THE LCSS«, SEES FKOIf ABOVE. 'J. S. , |

L, 8., superior and inferior lobes of longs ; e, eparterial bronchns ; A.y., anterior mediastiniim ;
B.P.C., ri^t pleural caritj ; p.c, pericardial earitr ; a. a., asceodiog aorta ; p.a., polm<Hiai7 artery :
K.P.A., ita right branch ; B.p.r., l.p.t.. right and left polmonaiy reins: a.t., azjgos major rdn ;
other letters as in fig. 18d.

a« described by Luschka, Thus, Sick, in seventeen out of twenty-three adolts, fonnd
the reflection of the pleura at the level of the sternal end of the fifth costal cartilage
was either behind the sternum or at its left edge. This was also the case in ten
out of the twenty-three at the sixth cartilage and in nine of them at the seventh
costal cartilage. Brooks' oheervations also support this view. In four out of seven
casf^ in which the pleura was quite healthy he found the reflection was entirely
'f>ehind the sternum, while in one it was at the left edge of this bone. He also
states that in all the cases the two pleura? were close to one another as far down as
the ensiform cartilage, so that the area of pericardium uncovered by the pleura was
reduced to a minimum.

The lower border of the costal pleura is reflected on to the diaphragm opposite a
line [>a%sing from the lower end of the sternum outwards behind the seventh costal

n-z

OEGANS OF EESPIRATION AND VOICE.

cartilage nearly as far as its rib ; here it leaves the seventh cartilage, and continuing
to pass obliquely downwards and backwards, crosses the eighth, ninth, tenth, and
eleventh ribs, and reaches the twelfth rib near its vertebral end. If the twelfth rib
be very short the whole of its anterior surface may be covered and the pleura pass
as low as the transverse process of the first lumbar vertebra (Pansch). When the
rib is well developed it is seldom in contact with the pleura external to its inner
half. On the lateral wall of the chest the pleura will generally be found rather
lower on the left than on the right side. Luschka estimates that in the midaxillary
hne the pleura reaches to the lower border of the ninth rib on the right side and to
the loAver border of the tenth on the left. The inferior limit of the pleura does not

Fig. 192. — Horizontal section op thorax of a man, aged 67, immediately above the pulmonary

VALVES, AND THE RIGHT AURICULAR APPENDIX, SEEN EROM ABOVE. (J. S.) §

3', third costal cartilage ; s.i., superior and inferior lobes of lungs ; p, on right anterior pulmonary-
valve ; R, tip of right auricular appendix ; L, left auricular appendix; l.a., left auricle ; a, b, c,
branches of right pulmonary arteiy and vein and of right bronchus ; l.p.c, left pleural cavity; other
letters as in iig. 189.

extend to the attachment of the diaphragm, but leaves a portion of the circumference
of this muscle in contact with the costal parietes. Owing to the height of^ the
diaphragm on the right side (corresponding to the greater convexity of the liver)
the right pleural sac is shorter than the left ; it is at the same time wider, as the
pericardium does not pass so far to the right as to the left of the median plane.

The upper part of the pleura, together with the apex of the corresponding lung,
rises dome-like into the root of the neck forming the pleura cervicalis. It reaches
from one to two inches above the anterior end of the first rib and half an inch to
one and a-half inches above the clavicle, but not higher than the neck of the first
rib. The subclavian artery, as it arches outwards, lies in a groove on its inner and
anterior aspect a little below its highest point. Externally it comes in contact with
the scalenus anticus and medius.

THE PLEUR.^.

173

A small slip of muscle arising- from the transverse process of the last cervical vertebra is
described b.v Sibson as expanding- into a dome-like aponeurosis or fascia, which covers or
strengthens" the pleural cul-de-sac, and is attached to the whole of the inner edge of the
first rib.

The mediastinal portions of the two pleural sacs constitute, as already described,
the lateral Ijoundaries of the mediastinal space. The layers forming the sides of the
anterior mediastinum pass backwards from the sternum to the pericardium in close
i-elation with one another except below, where a triangular interval is sometimes
found between them. At the front of the pericardium the two layers separate, each
passing round its own side of the pericardium to the front of the root of the corre-

Fig. 193. — Horizontal section of the thorax of a man, aged 57, at the level op the nipples,

SEEN FROM ABOVE. (J.S.) J

n, nipple; m, middle lobe of right lung; r.a., riglit auricle; R.v., right ventricle; l.a., left
auricle ; l.v., left ventricle ; R. P.v., right posterior valve of aortic orilice ; r.p.c, right pleural cavity ;
other letters as in fig. 189.

sponding lung, where it becomes continuous with the visceral pleura. This part of
the pleura is often termed 'perkardial ; it is the lateral limit of the middle medias-
tinum. The phrenic nerve courses to the diaphragm between it and the pericardium.
The pleura which goes from the side of the vertebral column to the back of the i-oot
Tjf the lung bounds the posterior mediastinum. On the right side it lies in relation
with the vena azygos major, the right vagus, and the oesophagus ; on the left side
with the descending aorta, and low down with the oesophagus. The two pleura)
are here united by an interpleural ligament passing behind the oesophagus and in
front of the aorta. At the level of the superior mediastinum the pleura passes back-
wards from the anterior to the posterior chest wall without being reflected over the
lungs. On the right side it covers the right innominate vein and superior vena
cava, the innominate artery and the right phrenic and vagus nerves, and the

174 ORGAKS OF RESPIRATION AND VOICE.

trachea ; and on the left the oesophagus and thoracic duct, the left common carotid
and subclavian arteries, and the corresponding phrenic and vagus nerves.

In certain situations the surface of the parietal pleura directed towards the
pleural cavity is not in contact with the visceral pleura, two portions of parietal
pleura being in apposition. The part of the pleural cavity bounded in this way by the
parietal pleura is called the supplemental or complemental pleural space. This space
varies in its extent according to the condition of the lungs, being diminished in
inspiration and increased during expiration ; but in all probability it cannot be
completely obliterated even by forcible inspiration. It is found on both sides
between the chest wall and the diaphragm, and on the left side between the chest
wall and the pericardium, opposite the lower part of the body of the sternum. It
is best marked posteriorly, as here the costal and diaphragmatic portions of the
pleura are in contact from about the tenth to the twelfth rib.

Structure. — The pleura possesses the usual characters of serous membranes.
The costal part is the thicker, and may be easily raised from the ribs and intercostal
spaces. It is strengthened here by a layer of subserous areolar tissue of considerable
thickness. On the pericardium and diaphragm the pleura is thinner and more firmly
adherent ; but it is thinnest and least easily detached upon the surface of the lungs.
A difference is also noticeable in the character of the superficial epithelial layers, for
while on the pleura cosialis this consists of the ordinary flattened cells, on the pleura
pulmonalis the cells are less distinctly flattened and more granular and polyhedral,
but they become flattened out when the lung is distended (Klein). Lymphatic
vessels are abundant in and beneath the pleura as in other serous membranes, and
they communicate in many parts, by means of stomata, with the cavity of the
membrane. In the pleura costalis the stomata are only found over the intercostal
spaces, not over the ribs (Dybkowsky).

Beneath the serous covering there is placed a thin layer of subserous areolar
tissue mixed with a large number of elastic fibres. It is continuous with the areolar
tissue in the interior of the lung, and has been described as a distinct coat under the
name of the second or deeper layer of the pleura. In the lungs of many animals,
such as the Hon, seal, and leopard, this subserous layer forms a very strong
membrane, composed principally of elastic tissue ; in others, as the guinea-pig, a
network of plain muscular fibres is found, which have a general radiating direction
from the apex (Klein). A close plexus of lymphatic vessels is also met with in this
sub-pleural tissue : these vessels communicate on the one side by means of stomata
with the pleural cavity, and on the other, as will be afterwards noticed, with a net-
work of similar vessels in the inter-alveolar septa of the lungs. A uniform network
of capillary veins covers the surface of the lung underneath the pleura. They are
supplied with blood from the venules of the superficial pulmonary lobules, but they
also receive some blood from the bronchial vessels. They are less closely arranged
than the blood-vessels of the pulmonary alveoli, and are thus, as well as by their
position, easily distinguishable from them in specimens of injected lung.

THE LUNGS.

Each lung is irregularly pyramidal or conical, with the base downwards (fig. 194).
The broad, concave base is of a semilunar form, and rests upon the arch of the
diaphragm. It is bounded by a thin margin, which is received in the angle between
the ribs and the diaphragm, and reaches much lower down behind and at the outer
side than in front. The apex is blunt, and, as already mentioned, reaches into the
root of the neck, above the first rib, where it is separated from the first portion of
the subclavian artery by the pleural membrane. The apex is generally marked by
a groove where the subclavian artery crosses it. The outer surface, which moves
upon the thoracic parietes, is smooth, convex, and of great extent, corresponding

THE LUNGS.

17i

with the arches of the ribs and costal cartilages. The iiiner surface is concave, and
in part adapted to the convex pericardium. The posterior border is rounded, and is
received into the deep groove formed by the ribs at the side of the vertebral column ;
measured from above downwards, it is the longest part of the lung. The anterior
border is thin and overlaps the pericardium, forming a sharp edge, which, opposite
the middle of the sternum, is separated during inspiration from the corresponding
margin of the opposite lung only by the two thin layers of the mediastinal septum.
Upon the inner surface, somewhat above the middle of the lung, and considerably
nearer to the posterior than the anterior border, is the hilum or fissure, where the
bronchi and great vessels enter the lung. These structures form the root of the lung.
The left lung is divided into two lobes by a long and deep fissure, which can be
traced on the surface of the lung from the upper and posterior part of the hilum
upwards and backwards on the inner surface, and reaches the posterior border at
about the level of the fourth rib ; the fissure then passes obliquely downwards and
forwards over the outer surface to the lower border, which it joins near its anterior

Fig. 194. — View of the lungs from before, drawn from the models of His.
a, b, c, upper, middle, and lower lobes of the right lung ; d, c, upper and lower lobes of the left lung.

end. This part of the fissure is somewhat more oblique than the adjacent ribs ; thus,
beginning at the fourth rib it gradually leaves it to gain the inner surface of the
fifth rib, which it finally crosses to reach the sixth costal cartilage a little below the
apex of the heart. From tlie lower border of the lung the fissure can be seen to
pass up the inner surface to the lower part of the hilum. The fissure extends from
the surface deeply into the lung, reaching close to the hilum, and practically dividing
the lung into two distinct parts. The upper lobe is the smaller. It forms the apex,
the whole of the anterior border, and the greater part of the concavity for the heart.
To the lower and larger lobe belong the greater part of the thick posterior border
and almost the wjjole of the diaphragmatic surface except a small area in front. The
highest part of the lower lobe is found at the posterior border of the lung, where it
usually reaches to the fourth rib.

In the right lung there are two fissures dividing it into three lobes, called upper,
middle, and lower. One of these fissures closely corresponds in its position and
direction with the one on the left side, except that it is rather more vertical, and joins
the lower border of the lung farther outwards. It may l>e regarded as the main

176 ORGANS OF EES PI RATION AND VOICE.

fissure, and separates the lower lobe from both the upper and middle lobes. The
additional fissure is seen on the outer surface to pass from the main fissure nearly
horizontally inwards and join the anterior border at the level of the fourth costal
cartilao-e. From this border it can be traced on the inner surface backwards to the
hilum. Like the main fissure it extends deeply into the lung, and it almost
completely cuts ofE the middle from the upper lobe.

Varieties. — Irregularities in the number and position of the lobes of the lung are not
very uncommon. Absence of a lobe owing to its non-development is very rare, but cases of
its partial union with the adjacent parts of the lung owing to defective formation of the
fissures are often seen. Accessory lobes often result from Assuring of the primary ones. An
accessory lobe on the right side situated below the root of the lung, and apparently corre-
sponding to the lobus impar of various mammals, has been frequently observed. Several cases
have also been recorded of an accessory lobe above the root of the lung, which was constricted
at its base by the vena azygos major.

In spite of its comparatively small size, it appears not improbable, from the researches of
Aeby, which will be afterwards more fully referred to, that the middle lobe of the right lung
is the morphological equivalent of the whole upper lobe of the left lung, and that the upper
lobe of the right lung is not represented on the left side.

The left lung has a deep notch in its anterior border, into which the apex of the
heart (enclosed in the pericardium) is received. Besides these differences the right
lung is shorter than the left, owing to the diaphragm rising higher on the right side
to accommodate the liver, whilst the left lung is the narrower, owing to the heart
and pericardium encroaching on the left half of the thorax. On the whole, how-
ever, as is seen on a comparison of their weights, the right is the larger of the two
lungs.

At the summits and posterior borders the extent of the lungs corresponds with
that of the pleural sacs which contain them, but in front and below the relation is
variable, inasmuch as the anterior margins below the level of the third or fourth
costal cartilages pass forwards most completely between the mediastinal and costal
pleurae during inspiration, and retire to a variable degree from between them in
expiration ; and in like manner the inferior margins descend, during inspiration,
between the costal and diaphragmatic pleuras ; probably at no time do they ever
descend completely to the line of reflection between those membranes.

The lower edge of the right lung usually extends to the sixth rib in the
mamillary line, to the eighth in the midaxillary, and to the tenth in the post-scapular
line. The left lung is often nearly a rib lower than the right.

In consequence of the notch in the lower part of the anterior border of the left lung, an
area of the heart, on the left side of the median plane, is uncovered by lung. This area,
which is of importance clinically, is often called the area of prsecordial dulness, or the area
of superficial cardiac dulness. It is irregularly triangular in shape, the three fixed points
being, (a) one at midstemum opposite the fourth costal cartilages, iV) another at the apex
beat, (e) a third at midsternum at the junction of the body of the sternum with the ensi-
form cartilage. The line joining the first two of these points is irregularly curved with
the convexity directed upwards and outwards. The line joining the second with the third
point is slightly curved with the convexity directed downwards and to the right. At the
inner part of its lower border cardiac dulness frequently merges in hepatic dulness.

EooTS OF THE LuNGS. — The root of each lung is composed of the bronchus or
sub-division of the air-tube, and the large blood-vessels, together with nerves,
lymphatic vessels, and glands, connected together by areolar tissue, and enclosed by
the reflection of the pleura.

The roots of the lungs are situated at the level of the bodies of the fifth, sixth,
and seventh, and often also the eighth, dorsal vertebras. The root of the right lung
lies behind the superior vena cava and part of the right auricle, and below the azygos
vein, which arches over it to enter the superior cava. That of the left lung passes
below the arch of the aorta, and in front of the descending aorta. The phrenic
nerve descends in front of the root of each lung, and the pneumogastrio nerve

THE LUNGS.

behind, whilst the h'gamentum latum pulmonis is continued from the lower border.
The bronchus, together with the bronchial arteries and veins, the lymphatics, and
lymphatic glands, are placed on a plane posterior to the great blood-vessels, whilst
the pulmonary veins are in front of the arteries. The pulmonary plexuses of nerves
lie on the anterior and posterior aspect of the root, beneath the pleura, the posterior
plexus being the larger of the two.

On the right side the undivided portion of the bronchus is usually altogether
above the right pulmonary artery ; on the left side the undivided portion of the
bronchus, which is considerably longer than on the right side, extends to below the

ep-. r.bi

d.h1

Fig. 195. — Sketch showing the lower end ok the trachea, its division into the two kronchial

TRUNKS, AND THE COURSE AND CUIEK BRANCHES OF TIIKSE WITHIN THE LUNGS FHOM BEFORE

'^after Aeby).
a, upper, h. middle, c, lower, lobe of tbe right lung ; //, upper, c', lower lobe of the left lung :
r.p., rigiit pulmonary artery; l.p., left artery; 7:hr., right bronchial trunk; /./;)•., left bronoiiial
trunk ; ep., on the right side, eparterial branch supplying the upper lobe ; r./(.', first ventral hypar-
terial bronchus supplying the middle lobe on the riglit side, the upper lobe on the left ; v.h.-, v.h.\
v.h.*, the remaining ventral hyparterial brandies distributed in the lower lobe on each side ; d.h.^,
d.h^, d.h.^, d.h.*, the four dorsal hyparterial branches distributed on both sides in the posterior and
inner part of the lower lobe ; h, accessory bronclius arising close to the first dorsal hyparterial bronchus
on the right side, and rejnesenting the one which supplies the azjgos lobe in some animals. The
main branches of the pulmonary vessels are distributed like the bronchi. Within the lung the arterial
trunks run behind the bronchial branches, the venous trunks in front.

level of the left pulmonary artery, which crosses it. On both sides the pulmonaiy
veins are below the corresponding arteries.

DiSTPJiu-riox OF THE BRONCHI wiTiiix TifE ujxos. — As already mentioned,
the right bronchus gives off a brnnch near its origin which is distributed in
the upfxjr lobe of the lung (fig. V.)'), cp). This branch, which comes oft" above the
place where the right pulmonary artery crosses the bronchus {eparlcridl branch), is
not represented on the left side in man, and it is hence inferred by Aeby that the
lobe of the lung to which it is distributed is also absent on the left side, and that
the upper lobe of the left lung is in reality the homologue of the middle lobe
of the right lung. All the other branches of the right bronchus, and all the

VOL, III., I'T. 1. "

178

OKGAjMS of HESPIRATION AND VOICE.

branches of the left bronchus, come off below the place where the corresponding-
pulmonary artery crosses the air-tube (Jiyparterial).

In many animals the bronchi, instead of dividing, as in man they appear to do,
into nearly equal branches at the root of the lung, pass down in the form of
main trunks towards the extremity of the lower lobe, giving off branches at
intervals in two directions, viz., dorsally and ventrally. The character of the
ramification of the hyparterial bronchial trunk as it is continued in the lung is
therefore bipinnate and not dichotomous. In addition to these two rows of dorsal
and ventral branches, accessory branches are occasionally met with coming off from
the main trunk in its passage through the lower lobe. These usually arise from
the front, and are intermediate in position between the dorsal and ventral series.

Fig. 196. — Cast op the interioe of the trachea and bronchi, with tileir chief ramifications

WITHIN THE LUNG. ( Aeby. )

This cast sliows a type of division frequently met with, the right bronchus being almost in continua-
tion of the line of the trachea.

a, eparterial branch ; h, c, hyparterial branches (central and dorsal).

generally taking origin near one or other of these. Of the accessory bronchi the
only one that claims especial notice is that which arises near the second ventral
branch of the right bronchial trunk, and which in some animals (monkeys) supplies
a special small lobe placed mesially behind the pericardium, and termed by Owen the
azygos lobe. In some animals well-developed eparterial branches arise from both
bronchi, and supply corresponding lobes in the two lungs. This arrangement repre-
sents the bilaterally symmetrical type of bronchial distribution. In some (sheep,
ox), the eparterial bronchus to the right upper lobe springs directly from the
trachea ; and a similar condition has in rare cases been met with in the human subject.

THE LUNGS.

179

In the human hing the same character of bronchial ramification can be made out
(figs. 195, 196, 197). From the continuation of the bronchus four dorsal and as
many ventral hyparterial branches are given oif in succession in each lung. Of these
the ventral or outer are much the larger, and the first ventral branch supplies the
middle lobe of the right and the upper lobe of the left lung. But the subordination
of the branches to the trunk becomes obscured in consequence of the size of the
ventral branches, which are as large in most cases as the trunk itself ; the latter

Pip. 197. — Cast op tiik tXTKUioii of the trachea and bronchi, with tiikik chikf ramifications

WITHIN THE LUNGS. (Aeby. )

This oast shows a type of division less frequent tlian tiie last, the right ami left bronchi licing at
about a right angle with one another.

a, cjKirterial branch ; b, ventral hyparterial branches ; // accessory (azygos) branch ; c, dorsal
hyparterial branches.

can nevertheless be detected pursuing with but little deviation a course towards the
posterior and lower extremity of the inferior lobe.

According to Ifasse the larger branches of the bronchi distributed to the upper
lobe of the left lung and the upper and middle lobes of the right lung are directed out-
wards, upwards, and forwards ; while those of the lower lobes of both lungs pass
downwards, inwards, and backwards. These directions agree with the movements of
the chest walls, which in their upper and anterior jiarts expand in an upward,
forward, and outward direction, while below the descent of the diaphragm increases
the chest cavity in a direction downwards and inwards.

N 2

180 ORGANS OF RESPIRATION AND VOICE.

On the whole there is a gradual increase in the combined sectional area of the
system of air-tubes in proceeding from the lower end of the trachea to the termina-
tions of the bronchial tubes in the lungs ; the increase being only interrupted at one
point, namely, immediately below the origin of the first branches which are given off
from the bronchial trunks. The combined sectional area is here no greater than the
sectional area at the lower end of the trachea, although the combined area of the
undivided bronchi is distinctly greater than this. (C. Aeby, Der Bronchialbaum
der Saugethiere und de> Menschen, Leipzig, 1880.)

Dimensions of the lungs. — The lungs vary much in weight according to the
quantity of blood they may happen to contain, as well as from other causes.
The weight of both lungs together, as generally stated, ranges from 30 to 48 ounces,
the more prevalent weights being found between 36 and 42 ounces (1,300 grammes
in the male and 1,023 grammes in the female, according to W. Krause). The
proportion borne by the right lung to the left is nearly that of 22 ounces to 20,
taking the combined weight of the two at 42 ounces (682 to 618 grammes, taking
the combined weight as 1,300). The lungs are not only absolutely heavier in the
male than in the female, but appear to be heavier in proportion to the weight of the
body.

Their extreme length in the male is 271 mm. for the right and 298 mm. for the
left lung ; in the female 216 mm. and 230 mm. respectively. TLe extreme outer
and posterior diameters of the right and left lungs respectively are in the male
203 mm. and 176 mm., and in the female 176 mm. and 162 mm. The transverse
diameter at the base is in the male 135 mm. (right) and 129 mm. (left), and in the
female 122 mm. (right) and 108 mm. (left). These numbers are also taken from
Krause (quoted by Vierordt).

Physical properties. — The substance of the lung is of a light porous spongy
texture, and, when healthy, is buoyant in water : but in the foetus, before respira-
tion has taken place, and also in certain cases of congestion, collapse, or consolida-
tion from disease, the entire lungs, or portions of them, sink in that fluid. The
specific gravity of a healthy lung, as found after death, varies from 0-345 to 0*746.
When the lung is fally distended its specific gravity is 0*126, whilst that of the
pulmonary substance, entirely deprived of air, is 1*056 (Krause). When pressed
between the fingers, the lungs impart a crepitant sensation, which is accompanied by
a peculiar noise, both effects being caused by the air contained in the tissue. On
cutting into the lung, the same crepitation is heard, and there exudes from the cut
surface a reddish frothy fluid, which is partly mucus from the air-tubes and air-
cells, and partly serum of blood, rendered frothy by the admixed air.

The pulmonary tissue is endowed with great elasticity, in consequence of which
the lungs collapse to about one-third of their bulk when the thorax is opened.
Owing to this elasticity also, the lungs, if artificially inflated out of the body,
contract to their previous volume when the air is again allowed to escape.

In infancy the lungs are of a pale rose-pink colour, which might be compared to
blood-froth ; but as life advances they become darker, and are mottled or variegated
with spots, patches, and streaks of dark slate-colour, which sometimes increase to
such a degree as to render the surface almost uniformly black.

The dark colouring-matter found in these streaks is in the form of granules and collec-
tions of granules, frequently not enclosed in cells : it is deposited in the interstitial areolar
tissue mostly near the surface of the lung, and is not found so abundantly in the deeper
substance. It exists sometimes in the air-cells, and on the coats of the larger vessels. Its
quantity increases with age, and is said to be less abundant in females than in males. In
persons who follow the occupation of miners, more especially colliers, the lungs are often
intensely charged with black matter. The black substance seems mainly to consist of
particles of carbonaceous substance. It is found also in the bronchial glands ; indeed, it

THE LUNGS.

181

appears to be taken up in la:-.u-e measure b,v the lymphatics. In exceptional cases the adult
lungs e'xhibit only very slight streaks of pigment.

Condition in the Toetus and changes after birth. — In the foetus the kings
contain no air, and consequently sink in water. They undergo very rapid and
remarkable changes after birth, iu consequence of the commencement of respiration :
these affect their size, position, form, consistence, texture, colour, and weight, and
should be carefully studied, as furnishing the only means of distinguishing between
a still-horn cliild and one that has respired.

1. Position, size, and form. — In a foetus at the full period, or in a still-boru
child, the lungs, comparatively small, lie packed at the back of the thorax, and do
not entirely cover the sides of the pericardium ; subsequently to respiration they
expand, and completely cover the pleural portions of that sac, and are also in contact
with almost the whole extent of the thoracic wall, where it is covered with the
pleural membrane. At the same time their previously thin sharp margms become
more obtuse, and their whole form is less compressed.

2. Consistence, texture, and colour. — The introduction of air and of an increased
quantity of blood into the foetal lungs, which ensues immediately upon birth,
converts their tissue from a compact, heavy, granular, yellowish-pink, gland-like
substance, into a loose, light, rose-pink, spongy structure, which, as already
mentioned, floats in water. The changes thus simultaneously produced in their
consistence, colour, and texture, occur first at their anterior borders, and proceed
backwards through the lungs : they, moreover, appear in the right lung a little
sooner than in the left.

3. Weight. — The absolute weight of the lungs having gradually increased from
the earliest period of development to birth, undergoes at that time, from the quantity
of blood then poured into them, a very marked addition, amounting to more than
one-third of their previous weight : for example, the lungs before birth weigh about
one ounce and a half, but after complete expansion by respiration they weigh as
much as two and a half ounces. The relative iveight of the lungs to the body,
which at the termination of intra-uterine life is about 1 to 70, becomes, after
respiration, on an average about 1 to 35 or 40 ; a proportion which is not materially
altered through life. The specific gravity is at the same time changed from I'OoG to
about -342.

MINUTE STRUCTURE OF THE LUNGS.

Fig. 198. — Diagram of the exdixg of a uku.n-
CHIAL TUBE (W. S. Miller).

B, termination of tube in V, vestibule, by means
of which it communicates with the atria, A ; S,
air-sac, opening out of atrium, and beset with air-
cells, C ; P, pulmonary arteriole , T, pulmonary
Ten u If.

Termination of the bronchi ; struc-
tnre of the bronchial tubes. — The

principal divi.sions of the bronchi, as they
pass into the lungs, divide into tubes of
less calibre, and these again subdivide in
succession into smaller and smaller tubes,
often distinguished as lironrhia, Jjronchioles,
or bronchial tubes, which, diverging in
all directions, never anastomose, but ter-
minate Beparat<;ly. 'Wa larger branches
pass oft' at acute angles, but the more
remote and smaller ramifications spring

183

ORGANS OF RESPIRATION AND VOICE.

less acutely. After a certain stage of subdivision each bronchial tube, reduced to a
small size (about 0'2 mm.), is termed a lobular or respiratory hroncMole (Kolliker),
and its walls become beset here and there with small hemispherical saccules, termed

deb

Pig. 199. — Portion op a transversk section of a bronchial ture, tiuman (6 mm. in liameter)
(F. E. Schultze). Magnified 30 diameters,

a, cartilage and fibrous layer with mucous glands, and, in the outer pai't, a little fat ; in the
middle, the duct of a gland opens on the inner surface of the tube ; b, annular layer of involuntary
muscular fibres ; c, elastic layer, the elastic fibres in bundles which are seen cut across ; d, columnar
ciliated epithelium.

air-cells, or alveoli. Each lobular bronchiole ends in a so-called vestibule, out of which
open dilatations, which have been termed atria by Miller. Each atrium is continued
into two or more blind diverticula, which have us-ually been known as infundibula,

d. c b a

Fig. 200.— Section of a smail bkowchial tube (4 mm. in diameter) prom the pig's lung
(F. E. Schultze). Magnified 240 diameters.

a, fibrous layer ; 6, muscular layer ; c, mucous membrane in longitudinal folds, with numerous
longitudinally running elastic fibres cut across ; d, ciliated epithelium ; /, surrounding alveoli.

but are termed air-sacs by Miller : their walls are completely covered with air-cells,
which are also found on the walls of the atria (fig. 198).*

Within the lungs the air-tubes are not flattened behind like the bronchi and
trachea, but form completely cylindrical tubes. Hence, although they contain the
same elements as the larger air-passages, they are reduced gradually to a state of

* Fig. 198 and the accompanying description are taken from W. S. Miller, Journ. of Morph.,
vol. viii., and have been introduced in reprinting this Part in August, 1898.

THE LUNGS.

188

greater tenuity, but possess certain peculiarities of structure. Thus, the cartilages
no longer appear as imperfect rings rnnniug only upon the front and lateral surfaces
of the air-tube, but ^re disposed over all sides of the tubes in the form of irregularly
shaped plates and incomplete rings of various sizes. These are most developed at
the points of division of the bronchia, where they form a sharp concave ridge
projecting inwards into the tube. They may be traced, becoming rarer and rarer
and more reduced in size, as far as bronchia one miUimeter in diameter. The fibrous
coat extends to the smallest tubes, becoming thinner by degrees, and degenerating
into areolar tissue. In it are mucous glands which send their ducts to open on the
mucous membrane. These occur most numerously in the larger tubes ; in those
which measure less than 1 mm. they are rarely if ever found. The mucous memhrane,
which extends throughout the whole system of air-passages, is also thinner than in
the trachea and bronchus, but it retains its ciliated columnar epithelium (figs. 199,
200, d). The longitudinal bundles of elastic fibres (c, in the transverse sections) are
very distinct in both the large and small bronchia, and may be followed by dissection
as far as the tube can be laid open, and by the microscope into the smallest tubes.
The muscutar fibres, which in the trachea and bronchi are confined to the back
part of the tube, surround the bronchial tubes with a continuous layer of annular
fibres, lying inside the cartilaginous plates (&) ; they are found, however, beyond
the place where the cartilages cease to exist, and appear as irregular annular fasciculi
even in the smallest tubes.

Pulmonary alveoli. — At the point where the small bronchial tubes lose their
cylindrical character, and begin to be beset with air-cells, their structure also
gradually undergoes a change. The muscular layer almost disappears, the longitu-

Fig. 201. — Section of I'Akt of cats lung, .stainkd with nituatk of silver (Klein and Noble

Smith). HiOHLV magnified.

The sraali granular and the large flattened cells of the alveoli are shown. In the middle is a section
of a lobular bronchial tube, with a patch of the granular pavement epithcliuin-cells on one side.

dinal elastic bundles are broken up into an interlacement of elastic tissue, which
siirround.s the mouths of the air-cells and the walls of the infuudibula, and
the columnar ciliated epithelium gives place to a stratum of non-ciliated cells. The
change in the character of the epitlielium first occurs in the lobular bronchioles,
•where patches of small pavement epithelium-cells begin to appear amongst the

184 ORGANS OF EESPIRATION AND VOICE.

ciliated cells, especially in the neighbourhood of the air-cells upon the walls
of these tubes. At the end of the lobular bronchiole, near the atrium, all the
cells which line the wall of the tube are of the non-ciliated pavement variety.
But the air-cells themselves, both those which are scattered over the respiratory
bronchioles and those which cover the infundibula, as well as intermediate portions
of the infundibula which occur here and there between the air-cells, possess an
epithelium of a peculiar character. The cells of this epithelium are of two kinds,
viz. : — 1, large, thin, very dehcate cells, irregular in size and shape, lying over the
blood-vessels, but also in many cases extending over the interstices between them ;
and, 2, small, flat, polygonal, nucleated cells, which lie singly or in small groups
of two or three cells, between the others, and always in the interstices of the capillary
network. These are similar to the cells which are found in patches in the lobular
bronchioles. If the lung is greatly distended they also become flattened out.

In the foetus the alveoli are entirely lined with small granular pavement cells, but with
the distension which follows upon the first respiratory efforts most of the cells become trans-
formed into the large thin epithelial elements above described.

The walls of the alveoli, which mainly consist of an indistinctly fibrillated
connective tissue, with corpuscles scattered here and there, are • supported and

Fig. 202. — Portion of the outer surface
OF THE cow's LUj^^a (from KoUiker, after
Harting). Magnified 30 diameters.

a, pulmonary vesicles filled artificially
■with wax ; b, the margins of the smahest
lobules or infundibula.

strengthened by scattered and coiled
elastic fibres, especially numerous
near their orifices, in addition to
which, according to some authori-
ties, there is likewise an intermixture
of muscular fibre-cells. A number
of leucocytes, mostly granular and
eosinophil, are usually to be found
free in the air-cells and smaller bronchial tubes : not unfrequently they contain
carbonaceous particles. By the migration of these cells into the pulmonary tissue,
the carbon particles may be conveyed into the substance of the lung and thence
into the lymphatics and bronchial glands.

The air-cells in the natural state are always filled with air. They are readily
seen on the surface and in a section of a lung which has been inflated with air and
dried ; also upon portions of foetal or adult lung injected with mercury or wax:
(fig. 202, a, a). In the lungs of some animals, as of the lion, cat, and dog, they are
very large, and are distinctly visible on the surface of the organ. In the adult
human lung their most common diameter is about 0*25 mm. (y^ inch), but it varies
from 0*1 mm, to 0*4 mni. ; they are larger on the surface than in the interior, and
largest towards the thin edges of the organ : they are also very large at the apex of
the lung. Their dimensions go on increasing from birth to old age, and they
are larger in men than in women. In the infant the diameter is usually under
0"12 mm.

The whole lung has a lobulated structure best seen in the foetus, where the lungs,
not yet distended with air, present very mach the appearance of compound race-
mose glands. The infundibula may be regarded as corresponding to the smallest or
ultimate lobules of such a gland. They produce the appearance of polygonal areas
enclosing groups of six or eight air-cells which are seen at the surface of the lung.

THE LUNGS.

18:

(fig. •2\)2). The infundibula are grouped iuto larger or secondary lobules, and these
again into yet larger divisions. The various lobules are united and separated by
connective tissue in variable amount, more between the larger and less between the
smaller groups. From the mutual compression to which they are subjected the
lobules are bounded by flattened sides, and they are compactly fitted to each other
and to the larger air-tubes and vessels of the lungs.

Blood-vessels, lymphatics, and nerves of the lungs. Pulmonary
vessels. — The branches of the pidmonanj artery accompany the bronchial tubes,
but in their remote ramifications ihey subdivide more frequently, a branch passing
to each atrium, and being distributed to the capillary network of all the infundibula
which open out of it (fig. V^S, P). The venules commence on the outer border
of the air-sacs, and course independently of the arterioles. The main arterial

Fig. 203. — Section of injected lung, iNr;LuwNo several contiguous alveoli (F. E. Schultze).

Highly magnified.
a, a, free edge.s of alveoli ; '■, r, jiartitions between neighbouring alveoli, .seen in .section ; b small
arterial tn-anch giving off capillaries to tlie alveoli. The looping of the vessels to either side of the
partitions is well e.xhibite'J. Between the capillaries is seen the homogeneous alveolar wall with nuclei
of connective tissue corpuscles and elastic fibres.

trunk runs down immediately behind the main bronchial trunk, giving off corre-
sponding branches as it proceeds. They ramify without anastomoses, and the
arterioles which pass to the atria send small branches about i)-())ir> mm. {-jxho inch)
in diameter between the air-cells, partially encircling their mouths (fig. 203, b). From
these vessels the capillary network arises, and covers each alveolus, passing in the
interalveolar septa between the adjacent air-cells. As was pointed out by Rainey, the
capillary network in these partitions is single in the lungs of man and mammalia, the
capillaries winding through the septa from one alveolus to the other, although in the
lungs of amphibia and reptiles the capillary network of each ah-eolus is distinct.

The capillaries are fine, and the network they form 8(j clo.se that the meshes are
scarcely wider than the vessels themselves. They arc very superficial, being covered
only by the thin layer of tesselated epithelium above mentioned, and in the parti-
tions between contiguous alveoli the vessels of the network project on either side in
an arched or loop-like manner into the cavities of the alveoli (fig. 20;>), The
mucous membrane of the Ijronchi-il tubes, especially near the air-cells, is partly
supplied with blood from branches of the pulmonary artery.

186 ORGANS OF EESPIRATION AND VOICE.

The radicles of the pulmonary veins arise from the capillary network of the
alveoli and from that of the smaller bronchial tubes. Their radicles are collected in
the septa between the infundibula, apart from the terminations of the arteries and
bronchioles. The branches of these veins which arise from the infundibula near
the surface of the lung run alone for a certain distance through the substance of
the organ. They finally either join some deeper vein which is passing towards the
hilum, or they remain superficial, forming a wide-meshed plexus near the surface
of the lung, finally tending towards the hilum to join the larger veins near the root
of the lung. The veins from the more deeply lying infundibula form frequent
communications, and finally coalesce into large branches, which ultim.ately accom-
pany the bronchial tubes and arteries, coursing as a rule in front of the bronchial
tubes, and thus proceed to the root of the lung. In their course together through
the lung the artery is usually found above and behind a bronchial tube, and the vein
below and in front.

The pulmonary vessels diflFer from the systemic in regard to their contents,
inasmuch as the arteries convey dark blood, whilst the veins carry red blood. The
pulmonary veins, unlike the other veins of the body, are not more capacious than
their corresponding arteries ; indeed, according to Winslow, Santorini, Haller, and
others, they are somewhat less so. These veins have no valves. The arteries of
different secondary lobules are usually independent, the veins fi'eely anastomose.

Bronchial vessels. — The bronchial arteries and veins, which are much smaller
than the pulmonary vessels, carry blood for the nutrition of the lung. The
bronchial arteries, from one to three in number for each lung, arise from the aorta,
or from an intercostal artery, and follow the divisions of the air-tubes through the
lung. They are ultimately distributed in three ways : (1) many of their branches
ramify in the bronchial lymphatic glands, the coats of the large blood-vessels, and
in the walls of the bronchial tubes, supplying an outer capillary plexus with trans-
verse meshes to the muscular coat, and an inner plexus with close longitudinal
meshes to the mucous membrane, which in the lobular bronchioles is continuous
with that supplied by the pulmonary artery ; (2) others form plexuses in the inter-
lobular areolar tissue ; (3) branches pass to the surface of the lung beneath the
pleura, and join the network of pulmonary venous capillaries which is found there.

The bronchial veins have not quite so extensive a distribution in the lung as
the bronchial arteries, since part of the blood carried by the bronchial arteries is
returned by the pulmonary veins. The superficial and deep bronchial veins unite at
the root of the lung, opening on the right side into the large azygos, and on the left
usually into the left upper azygos vein.

According to Zuckerkandl it is not only at the extremities of the bronchial tubes that the
blood brought by the bronchial arteries is returned by the pulmonary veins, but in other parts
small bronchial veins open into pulmonary branches ; and even veins which receive branches
from the larger bronchia, from the bronchial glands, and from the posterior surface of the
pericardium, empty their contents partly into the great trunks of the pulmonary veins.

A few small branches of the intercostal arteries also pass to the pulmonary pleui'a and
surface of the lung through the ligamentum latum pulmonis (Turner).

Iiymphatics. — The alveolar lymphatics of the lung take origin from lymphatic
capillaries in the interalveolar septa, and those near the surface of the lung come into
connection w^ith the subpleural lymphatic plexus, previously mentioned (p. 174).
They join to form vessels which accompany the branches of the pulmonary artery
and vein, running on the walls of those vessels in twos or threes, connected by
numerous cross branches, and in some cases almost completely surrounding the
blood-vessel.

Other lymphatics, which may be distinguished as bronchial, originate in
plexuses in the mucous membrane of the bronchial tubes. Hence they pass

LITEEATURE OF TKE RESPIRATORY ORGANS. 187

through the muscular coat to form another plexus in the fibrous layer, where they
are most numerous on the side opposite the accompanying branch of the pulmonary
artery. Here they are not unfrequently found to enclose nodules of lymphoid tissue.
The branched connective tissue corpuscles and cell-spaces with which the lymphatics
are in connection at their origin, send processes upwards to the inner surface of the
air tubes and alveoli, between the epithelial cells (like the pseudostomata of the
serous membranes). Lymphoid tissue is found, according to Arnold, in various
parts, viz., under the pulmonary pleura ; in the perivascular and peribronchial
tissue ; in the bronchial wall, and around the alveolar passages.

At the root of the lung the superficial and deep lymphatics unite into a few
anastomosing trunks before entering the bronchial lymphatic glands.

Nerves. — The nerves of the lung come from the anterior and posterior pt/l-
)nonarij ptexuscs, which are formed chiefly by branches from the pneumo-gastric
nerves, joined by others from the sympathetic system. The fine nervous cords
enter at the root of the lung, and follow the air-tubes. According to Remak, whose
account has been confirmed and added to by the more recent observations of
Stirling and others, they include both white fibres, derived in all probability from
the vagus, and grey filaments proceeding from the sympathetic, and have ganglion-
cells, both singly and in groups, upon them in their course. In the lower verte-
brates (frog, newt) the nerves are chiefly distributed to a layer of plain muscular
tissue, which is everywhere found taking part in the composition of the relatively
simple pulmonary wall (Stirling). Berkeley has described the nerve-endings in
mammals as forming a plexus of fine fibrils with interspersed stellate cells such as
have been noticed in many glands and mucous membranes. The ultimate ending
appeal's to be in open arborisations upon and between the alveoli.

BECENT LITERATURE OF THE RESPIRATORY ORGANS.

V. Beregrszaszy, Beitrag zur Anatomie und Phy siolorjie dcs Kchllcopfs, Arcliiv f. d. gesammte
Physiol., Bd. Ixvi., 1889.

Berkeley, H. J., The intrinsic imlmonarij nerves in mammalia, Johns Hopkins Hosp. Rep.,
vol. v., 1894.

Bowles, R. L., Observations upon the mammalian pharynx ivith especial reference to the
epiglottis, Jour. Anat. and Phys. , vol. xxiii., 1889.

Bradford, J. Hose, The innervation of the pulmonary vessels, Proceed, of the Roy. See.,
vol. xlv., 1889.

Bradford, J. Rose, ami Dean, H. P., The pidmonary circulation, Journ. of Physiol, xvi.,
1894.

Braune, W. , und Stahel, H., Uthcr das Verhaltniss der Lwngen zii den Bronchcn, Arch. f.
Anatomic u. Physiol., Anat. Abth., 1886.

Brooks, St. John, On the relations of the pleura to the sternum and costal cartihujes, Trans, of
the Roy. Acad, of Med. in Ireland, vol. vii., 1889.

Brunton, T. Ii., antl Cash, J. T., 'The valvular action of the larynx, Jour. Anat. and Phys.,
vol. xvii., 188:'.

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DaUa Rosa, L., Beitrdge zur Kasuistik und AJorjjhologie der Varieldten dcs menschlichcn
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Dubois, Eug:., Zur Morphologic des Larynx, Anatom. Anzeiger, Jahrj;. i., 1886.

Ewart, William, The bronchi and 'pulmoruiry blood-vessels, their anatomy and nomen-
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Exner, Signn., iJie Innervation des Musculus cricothj/reoideus, Arch. f. path. Anat., Rd. cxxxi.

Fag'an, P. J., The arrangement of the branches of the right l)ronchus arid their relations to the
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Frankel, B., Studien zur feineren Anatomic des Kehlkopfs. 1. Das ^timmhand, seine
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Haynes, J. 8., The relation of the heart and Invgs to the anterior chest wall as determined by
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18S OEGANS OF RESPIKATION AND VOICE.

Hasse, C. , Ber Bern der Lunge cles Menschen, heclingt durch die Bewegung der Brushvande hei
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Kelilko'pfes im gcsunden, und kranhen Zustande, Archiv f . path. Anat. , Bd. cxviii.

Howes, Gr. B. , Rabbit with an intra-narial epiglottis, ivith a suggestion concerning the
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1888, u. Arch. f. mikr. Anat., Bd. xxxii., 1888.

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THE URINARY ORGANS.

By E. a. SCHAFER axd J. SYMINGTON.

The urinary organs consist of the ludneys, the glands by which the urine is
secreted, and the ureters, bladders and urethra, serving for its reception and
evacuation.

THE KIDNEYS.

Tlie kidneys, two in number, are deeply situated in the loins, lying one on each
side of the vertebral column, ac the back part of the abdominal cavity, and behind

Fig. 204. — OUTLINK VIEW OK THK KIUNKYS KKOM IlKIIINI), CONSTIIUCTKI) FKOM A SERIES OV UOKIZONTAL
SECTIONS THROUOH THE TRUNK OK AN ADULT MALK. (J. S. )

K.K., I, K., riKht and left kidneys ; k.s., outer border of erector sijintc muscle ; q.l., outer border
of quadratiLS lumborum luuscle ; i.e., iliac crest ; V.V., dotted line to kIiow lower limit of costal pleura.

the y)eritorienm. 'J'lio upper and grcat(T j)art of (sacl/ kidney is situated in the
hyp^jchondriac and epigastric regions, but the lower end usually extends into the

190

THE URINAEY ORGANS.

adjacent portions of the lumbar and umbilical regions. They are on a level with
the last dorsal and the upper two or three lumbar vertebras (fig. 204), the right
kidney being usually a little lower than the left, probably in consequence of the
vicinity of the great right lobe of the liver. They are maintained in this position
by their vessels, by a quantity of surrounding loose areolar tissue, which usually

Fig. 205. — The urinary organs op the female from behind (Henle).

R, right kidney ; U, commencement of the ureter ; A, aorta, Ar, right renal artery, Vc, vena cava ;
Vr, right renal veia ; Vu, urinary bladder ; Ua, commencement of urethra. 3

contains much fat (capsula adiposa), and by the tonicity of the muscles of the
abdominal wall.

The kidneys measure about four inches (100 mm.) in length, two-and-a-half
inches (60 mm.) in breadth, and one-and-a-quarter or one-and-a-half in thickness.
The left is usually longer and narrower and a little heavier than the right. The
weight of the kidney is usually stated to be about four-and-a-half ounces in the male,
and somewhat less in the female. Yierordt gives 277 g. as the weight of the two
kidneys together in the male. The specific gravity is about 1-050.

THE KIDNEYS.

'191

Form and relations. — The surface of the kidney is smooth and of a deep red
colour. It is bean-shaped, and possesses two surfaces, an anterior looking' forwards
and outwards, and a posterior backwards and inwards ; two borders, an outer, which
is convex, and an inner, concave ; and two somewhat enlarged convex extremities,
upper aud loirer. Its long axis is directed from above downwards and slightly
outwards. The posterior surfaces of the two kidneys lie against the abdominal
wall and are nearly identical in their relations, but the connections of their
anterior or visceral surfaces diifer on the two sides. The posterior surface,
embedded in areolar and adipose tissue and uncovered by peritoneum, rests upon the
last rib and sometimes, more particularly on the left side, also upon the eleventh
rib ; the diaphragm ; the anterior layer of the lumbar aponeurosis covering the
quadratus lumborum, and the psoas, these two muscles intervening between the
kidney and the transverse processes of the first and second lumbar vertebrae. The
pleura descends behind tha upper part of the kidney, separated, however, from
it by the diaphragm. Below the twelfth rib the last dorsal, ilio-iuguinal and

Fig. 206.— DIA'iRA.M TO ILLUSTRATE THE RELATIONS OF THE KIDNEYS, AS SEEN FROM BEFORE. (J. S. )

A, ri^ht kidney ; S, area for right suprarenal cajwule, non-peritoneal ; L, area for liver, peritoneal ;
D, area for second part of duoJeiuini, non-peritoneal ; C, area for ascending colon and hepatic flexure
of colon, non-peritoneal ; 3.1., area for convolutions of jejuno-ileum, peritoneal. B, left kidney ;
S, area for left suprarenal capsule, non-peritoneal ; St, area for stomach, peritoneal ; Sp, area for
spleen, peritoneal ; C, area for splenic flexure and descending colon, non -peritoneal ; J. I., area for
convolutions of jejuno-ileum, jjeritoneal ; P, area for pancreas, non-peritoneal.

ilio-hypogastric nerves pass outwards behind it. The anterior surface of the right
kidney is covered on its upper and outer part by peritoneum whicli intervenes
between it aud the large renal impression on the liver. Near its inner border the
second part of the duodenum descends in contact with it, while more externally it is
crossed by the commencement of the transverse colon ; both those portions of the
intestine are destitute of peritoneum posteriorly. The lower end of the right
kidney is again covered by peritoneum. Tiie anterior surface of the left kidney is
crossed transversely, just above the level of the hilum, by the pancreas and the
splenic vessels. Above this there is usually u small area covered by the stomach,
the lesser sac of the peritoneum intervening. Jielow the pancreas it is separated
from some coils of the small intestine by the peritoneum. The upper end of the
right kidney is capped by the right suprarenal (;a[)sule aiul the liver, and that of the
left kidney by its capsule and the s])leen. The lou)er ends of the kidnejs are
generally smaller than the uf)per. 'J'hey reach on an average to within about 2 inches
of the iliac crest. The outer border of the right kidney is covered in about its
iipfxip two-thirds by the liver, and the left kidney in its upper half or more by the
spleen. The ascending colon on the right side and the splenic flexure and descending

192 THE UEIISTARY ORGANS.

colon on the left are found at the lower and outer parts of the right and left
kidneys respectively. The inner border presents about its middle third a vertical
fissure termed the Mlum, which is bounded by anterior and posterior lips. The
direction of the hilum varies considerably in different subjects and even on the two
sides in the same individual, but as a rule it looks more forwards than towards
the middle line, and not unfrequently the posterior lip reaches as far forwards
as the anterior one.

D. J. Cunningham has shown that the kidneys when hardened in situ present
facets corresponding to the viscera with which they are in contact, and the posterior
surfaces also have slight depressions opposite the last rib, and the transverse
processes of the upper two lumbar vertebrae .

Varieties. — The kidneys sometimes vary from their normal form, being either longer and
narrower, or shorter and more rounded. The characteristic foetal lobulation may persist in
the adult. Occasionally one kidney is very small, while the other is proportionately enlarged.
Upward displacement is very uncommon, but they are often found lower than normal, lying
more or less entirely in the iliac fossa, or with their lower ends projecting into the true
pelvis. Numerous cases are recorded of absence of one kidney, most frequently the left.
The single kidney is usually enlarged, but not invariably. The occurrence of an additional
kidney is extremely rare, the supernumerary organ is placed either in front or on one side of
the vertebral column or in the pelvic cavity.

Instances are now and then met with in which the two kidneys are joined by their lower
ends across the front of the great blood-vessels and vertebral column. The conjunct organ
has usually the form of a horse-shoe. Sometimes two united kidneys are situated on one or
other side of the vertebral column in the lumbar region, or, but much more rarely, in the
cavity of the pelvis.

The kidney may be movahle owing to the laxity of its areolar and adipose capsule, or in
rare cases floating, when it has a more or less distinct mesonephron, and the peritoneum moves
with the organ. These conditions occur much more frequently in connection with the right
than the left kidney.

Structure. — The kidney is surrounded by a proper fibrous coat, which forms a
thin, smooth, but firm investment, closely covering the organ. It consists of dense
areolar tissue, with numerous fine elastic fibres, and can easily be detached from the
substance of the gland, to which it adheres by minute processes of connective
tissue and vessels. Underneath the capsule in the human kidney is an incomplete
layer of plain muscular fibres.

On splitting open the kidney by a longitudinal section, from its outer to its
inier border, the fissure named the hilum (fig. 207, h, Ti) is found to extend some
distance into the interior of the organ, forming a cavity called the sinus of the
kidney (s). This is enclosed on all sides except at the hilum by the solid substance
of the organ ; and is lined by an inward prolongation of the fibrous coat. The
solid part consists of cortical and medullary substance ; the latter being arranged in
separate conical masses named pyramids of Malpighi with their broad bases
(b, h) directed towards the surface, and their points towards the sinus, where they
form prominent papilke. The pyramids are embedded in the cortical substance,
which separates them from each other, and encloses them everywhere except at the
papillas, which emerge from it and project into the sinus.

The external or cortical substance («) is situated immediately within the fibrous
capsule, and forms the superficial part of the organ throughout its whole extent to
the depth of about 4 mm., and moreover sends prolongations inwards (septula
renum or columnce Bertini) between the pyramids as far as the sinus and bases of
the papillae. It is of a nearly uniform light crimson-brown appearance, and is soft
and easily lacerated in directions vertical to the surface. The medullary portion of
the kidney is more dense than the cortical, and is distinctly striated, owing to its
consisting of small diverging uriniferous tubes, and to its blood-vessels being
arranged in a similar manner. There are generally more than twelve pyramids, but

THE KIDNEYS.

193

theiv number is inconstant, varying from eight to eighteen. Towards the papillae
the pyramids are of a lighter colour than the corticaf substance, but at their base
they are usually purplish and darker.

Excretory apparatus. — On squeezing a fresh kidney which has been split
open, a little urine will be seen to drain from the papillte by fine orifices on their
surface. The secretion is carried away and conveyed into the bladder by the ureter.
This long tube on being traced up to the kidney is seen to be somewhat eidarged,
and then to expand as it enters the hilum, into a large funnel-shaped dilatation
named the pelvis (fig. 208, Pj. This, within the sinus, divides usually into three,
but sometimes only two primary tubular divisions, and these at length end in a
larger number of short, truncated but comparatively wide branches named caliccs or
inftduUbula, which receive the papilla into their wide mouths and are attached

Fig. 207. — Plan of .v i.oxgiti-dinal section THRoron thk pklvis and substance of the nionr
KIDNEY. One-half the natural size.

<i, the cortical f?ubstance ; h, h, broad part of two of the pyrainiils of Malpiglii ; c, c, the ilivisions
■of the pelvis named calices, or infundibula. laid ppen ; c', one of the.se unopened ; d, d. .summit of the
pyramids or papillje projecting into calices ; e, e, section of the narrow part of two pyramids near tJie
calices; p, pelvis or enlarged i>ortion of the ureter within the kidney ; ii, the ureter ; s, the sinus ; h,
the liilum.

Fig. 208. — Cast of the interior of the upper end of the ureter. (Henlc.)

P, pelvis ; U, ureter.

around the bases of those prominences from which, of course, they catch the
issuing urine.

A single calix often surrounds two, sometimes even three papillae, which are in
that case united together ; hence, the calices are in general not so numerous as the
papillae. The spaces between the calices are occupied by a considerable amount of
fat, imbedded in which are seen the main branches of the renal vessels.

Like the rest of the ureter, the pelvis and greater part of the calices consist of
three coats, viz., a strong external fibrous and elastic tunic, which becomes
continuous around the bases of the papillae with that part of the proper coat of the
kidney which is continued into the sinus ; secondly, a thin internal mucous coat,
which, or at least its epithelium, is reflected over the summit of each papilla ; and
thirdly, between these two, a double layer of muscular fibres, longitudinal and
circular. The longitudinal fil)res are lost near the extremity of the calix, })ut the
circular fibres, according to Ilenic, foi'm a continuous circular muscle round the
papilla where the wall of the calix is attached to it.

VuL. III., I'T. 4. o

194

THE UKINARY ORGAIS'S.

The pyramidal masses found in the adult kidney indicate the original separa-
tion of this gland into lobules in the earlier stages of its growth. Each of these

Fig. 200. — Diagram OF a section through pakt

OF THE KIDNEY PARALLEL TO THE MEDULLARY

TUBULES. (Testut. )

a, papillarj' zone ; h, boundary zone ; c, cortical"
zone. 1, apex of papilla ; 2, capsule ; 3, clear
strite of boundary zone, formed by tubules of
medulla ; 4, dark strife of boundary zone formed'
by vasa recta ; 5, vascular arches ; 6, medullary
rays ; 7, labyrinth ; 8, interlobular vessels ; 9,^
Malpighian corpuscles ; 1 0, subcapsular layer.

primitive lobules is in fact a pyramid
surrounded by a proper investment of
cortical substance, and is analogous to
one of the lobules of the divided Mdney&
seen in many mammals. As the human
kidney continues to be developed, the
adjacent surfaces of the lobules coalesce
and the gland becomes a single mass ;
the contiguous parts of the originally
separate cortical investments, being-
blended together, form the partitions-
between the pyramids already described.
Moreover, npon the surface of the
kidney even in the adult, after the
removal of the fibrous capsule, faintly
marked furrows may be traced on the
cortical substance, opposite the intervals
in the interior between the several Malpighian pyramids ; and not nnfrequently
instances occur in w^hich a deeper separation of the original lobules by grooves-
remains apparent in the adult kidney.

Fig. 210. — Diagram of the course of thic tubules in a uni-ptramidal kidney, such, as that'

OF the rabbit. (Toldt. )

«, Malpighian bodies ; h, first convoluted tubule j c, d, looped tubule of Henle ; e, second convoluted,
tubule ; /, collecting tube ; g, ducts of Bellini.

THE KIDNEYS.

195

Tnbuli uriniferi. — On examining the summit of one of the papilla carefully,
especially with the aid of a lens, a number of small orifices may be seen varyino- in
diameter from 0'06 to 0'12 mm. They are frequently collected in large numbers
at the bottom of a slight depression or foveoJa found near the summit of the papilla,
but most commonly the surface is pitted over with about a score of small depressions
of this sort. On tracing these minute openings into the substance of the pyramids.

Fig. 211. — Diagram of the couuse of two ukiniferous tubules. (Klein.)

A, cortex ; B, bouiKlary, zone C, papillary zone of the medulla ; a, a', .su])erficial ami deep layers of
cortex, free from glomeruli. For the explanation of tlic numerals, see the text (p. 197).

they are discovered to be the mouths of small tubes or ducts, the nriniferons tubes
before mentioned, wliich thus open upon the surface of the several papillae into the
interior of the calices.

As these tubules pass up into the pyramidal sulistance, they bifurcate again and
again at very acute angles, their successive branches running close together in
straight and slightly diverging lines, and they continue thus to divide and subdivide
until they reach the sides and bases of the pyramids, whence they pass, greatly
augmented in number, into the cortical substance. In the cortical part the straight
tubules belonging to a Malpighian pyramid are continued for some way, in several

0 2

196

THE URINAEY ORGANS.

oTOups or bundles, the tubules in the centre of which approach nearer the surface
than those at the sides. These bundles are known as the medullary rays (fig. 209, 6)

Kg. 212.— Three malpxghian corpuscles and ukiniferous laBULES of a young mammal showing

THREE STAGES OF FORMATION OP THE LOOPED TUBULES, AND THE ADHERENCE OF THE BEGINNING
OF THE SECOND CONVOLUTED TUBES TO THE MALPI6HIAN CORPUSCLES. (Golgl.)

of the cortex, and the cortical substance between and around them is termed, on
account of the intricate arrangement of its tubules, the labyrinth of the cortex (7).
The part of the pyramid which is nearest the cortical substance contams^ a
number of pencil-like bundles of small blood-vessels, which originating from arterial

THE KIDNEYS.

197

and venous arches at the junction of cortex and medulla, dip into the pyramid, and
thus commence the separation of its tubules into the bundles which are continued
into the cortex as the medullary rays. The portion of the pyramid which is thus
broken up is termed the hoimdary zone (fig. 20i), h).

Course of the tubules. — Each tube commences in the labyrinth of the cortical
substance by a spherical dilatation enclosiug the vascular Malpighian tufts to be
afterwards described.

Emerging from this dilatation (fig. 211, 1), which is known as the capsule (2), the
tubule is at first convoluted and wide {Jirstconvohded tuhule, 2, 3), but on approaching
the medullary ray it becomes nearly straight with a slight tendency to a spiral
{spiral iubide of Schachowa, 4). At the junction of cortex and medulla the spiral
tube rapidly narrows and passes straight down through the boundary zone towards
the apex of the pyramid (5). After a shorter or longer course, however, it loops
upwards again (6) becoming enlarged in the boundary zone (7), but somewhat smaller
again above this (8, 9) where it pass'es again up the medullaiy ray. The part of
the uriniferous tube which thus dips down towards the papilla and turns upwards
again is known as the looped tuhide of Henle. On emerging from the medullary ray
the tubule is characterized by great irregularity of outline {irregular fubtile, 10)

Fig. 213.

-Diagram showing severat. phases of development of the uuiniferous tubule.

«iokM.)

before again becoming convoluted (swon^Z ro«ro'2.!/ff/ tubule, 11). Finally this last
is connected with one of the collecting tubules of the medullary ray by a small
jundioncd tubide (12), and the rollecHng tubes (13, 14, 15) uniting with one another,
as already noticed, become gradually larger as they pass to open as excretory tubes at
the summit of the papilla (fig. 210).

Accordinff to the obsei-vations of Golgi, the Malpi^'-hian corpuscle of each uriniferous tube
is alwaj's intimately adherent to a part of the tube near the commencement of the second
convoluted tubule (fig. 212). and has retained this adhesion from its earliest appearance in the
embryo, when the tube is an S-shaped projection from the collecting tube. For of the three limbs
of the S, the lowermost embraces the glomerulus, and forms the Malpighian corpuscle : the
middle one develops into the first convoluted tube, and all the parts of the tube of Henle
f including the spiral and irregular tubes) while the upper part of the S forms the second con-
voluted and junctional tubes (figs. 212, 21H).

Structure of the tubules. — The tulniles consist in every case of a basement
membrane and epithelium, but the character of the latter as well as the size of the
tubes varies considerably in the dillerent f)artK.

The capsule (fig. 21G, a) is lined by a layer of flattened cells, which is
reflected over the contained tuft of blood-ve.ssel.s, dipi)ing between the separate
bunches of which tliis is composed. This layer is much more easily recognized in
the foetus and young subject than in the adult (fig. 215). At the commencement

198

THE UEINARY ORGANS.

of the convoluted tu'oule and sometimes, as in the mouse, even in the part of the
Malpighian corpuscle nearest the tubule, the epithelium becomes cubical. It has
been stated by Hassall (various mammals), and by Klein (mouse) that the epithelium
here is provided with cilia, but the statement requires confirmation. In lower
vertebrates, as in the frog, the existence of ciUa in this place has long been known.

The first convoluted tubule has an epithelium of a peculiar character (Heiden-
hain). The part of the cell which encloses the nucleus is composed of ordinary
granular-looking protoplasm, but the part next to the basement membrane is
chiefly made up of straight or nearly straight rods or fibrils placed vertically
to the basement membrane and extending a variable distance towards the

Fig. 214. — Portions op kidney tubules (isolated). (Cadiat. )
a, large collecting tubule ; b, loop of Henlo.

lumen (figs. 216, 217), but usually occupying the greater
parb of the cell, although there is always a stratum of
homogeneous or granular substance bounding the cell
towards the lumen. The nucleus is spherical. The cells
are with difficulty separated from one another, at least in
some animals {e.ff., dog), owing to their possessing lateral
ridge-like processes (fig. 217, e ; fig. 218) which interlock
with one another (Schachowa).

The spiral tubiile of Schachowa is the continuation of
the convoluted tubule into the medullary ray, and possesses
a similar epithelium (fig. 216, e). Towards its termination,
however, the cells become shorter and less distinctly fibril-
lated, but split up more completely at their borders, into
ridges with intervening furrows, especially in the part of the
cell next to the basement membrane, so that the cells bear
somewhat the aspect of columns deeply fluted at their base.
Between these fluted cells, others of clearer aspect are found
fitting in, and having an expanded base which extends partly
underneath them. According to Schachowa they are present
also in the convoluted tubules proper.

In the narrow tube which forms the descending limb of
Henle's loop, the epithelium is quite low, and flattened
against the basement membrane. The protoplasm is clear
and the nucleus prominent. The ridge-like processes at
the base of the cells are said not to be altogether absent even here.

The loop of Henle has an epithelium similar in character to that of the descending
limb.

In the ascending limb of the looped tubule the epithelium again takes on the
character which is exhibited in the first convoluted and spiral tubes, but the cells
are rather smaller, the lumen of the tube relatively larger, and the intracellular
rods not so long as in those tubes. The cells of this segment are sometimes set
obliquely so as to overlap one another. In the human subject they contain brown
pigment-granules (Klein). This tubule is apt to exhibit a spiral character. It is
divisible into three parts, viz., a lowermost tapering part, a part in the boundary
zone (fig. 211, 7, 8) which is the largest, and a part in the cortical zone (9) which
is narrow and has strongly rodded epithelium, and may be looked upon as the
commencement of the next tubule.

In the irregular tubules the rod-like structure of the cells is very distinct
(fig. 216, b). The cells are very unequal in size, the irregularity of the tubules

THE KIDNEi^S.

199

beino- thus compensated, and the lumen reudeiel nearly the same throughout.
The nucleus is oval. These tubules are said to lack a basement membrane.

The second convoluied tubule (infercalan/ tube, Schweigger-Seidel) is like the firsi
in size, but has a different kind of epithelium. The cells, which are rather long.

Fig. 21:). — vSectio.v op coutical srBSTANca of

KtDXEY : HC.M.IS KlEl'US. HiGHLY MAG-

KIFIED. (Klein.)

a, glomerulus with blood-vessels not lully
ileveloped ; b, connective tissue between the
blood-vessels: c", epithelium covering it continuous
with d, flattened epithelium lining Bowman's
capsule ; /, /, convoluted tubes.

with a relatively large nucleus, present
a peculiar highly refractive appearance,
and where they rest on the membrana
propria, the protoplasm exhibits pro-
jections which fit between those of
neighbouring cells.

The Junctional tubule, which unites
the last-named to the collecting tubes,
is narrow, but its lumen is relatively
large. It is lined by clear flattened

or cubical cells ; but between them some cells are found which are similar in
appearance to the cells which line the segment just described.

Pig. 216.— Tubules kkom a section of tiik i>og's kii»xev. (Kluin and Noble Smith.)
a, Capsule, enclosing the glomerulus ; n, neck of the ca))8ule ; c, c, convoluted tnbulcs ; b,
irregular tubul-s ; d, collecting tube ; e, e, spiral tubes ; /, part of the ascending limb of llenie s loops
here (in the medullary ray) narrow.

The collecluKj tulm, which arc characterised by tlieir straight course and
veiy di.stinct lumen (fig. 210, d), are lined by a clear cubical epithelium, the cells
of which are at first somewhat irregular, but become longer and more regular as
the tubes approach the papilla.

200

THE UEINARY OKGANS.

In the larger collecting or excretory tubes (ducts of Bellini) the form of the
cells is typically columnar, modified only by the form of the surface which they
cover. In these largest tubes the basement membrane is said to be absent, the
epithelium cells resting directly upon the connective tissue.

Fig. 217. — To ILLUSTRATE THE STRUCTURE OF THE EPITHELIUM OF THE CONVOLUTED TUBULES

(from Heidenhain).

d, section of a convoluted tubule from the rat, showing the unaltered protoplasm occupying a-
circular area around the nucleus of each cell ; «, h, c, isolated cells fi'om the convoluted tubules of the
rat ; e, isolated cells from the dog's kidney, viewed from the inner surface, and showing the irregular
contour of the i^rotoplasm ; /, isolated cells from the newt, showing the rods and the homogeneous
cuticular layer ; g, longitudinal optical section of part of a convoluted tubule from the dog's kidney.

The characters of the ejDithelium in the several parts of a uriniferous tube may
be thus concisely stated, viz., clear flattenecl cells in the capsule, the descending
part of Henle's loop and the loop itself ; granular -looYing rodded epithelium with

Fig. 218. — Portion of a convoluted tube froj: the kidney, showing the irregularly fluted
OUTLINES OF THE CELLS. (Lanclauer. )

fluted interlocking borders in the convoluted tubules, the spiral tubules, the
ascending limb of Henle's tubule, and in the irregular tubule ; clear cubical or
columnar cells in the junctional tubule, the collecting tubules, and the ducts of
BeUini.

Klein describes a very delicate nucleated membrane lining the tubules within the epithe-
lium, in all the tubes except the descending limb of Henle's loop, and in the loop itself.

THE KIDNEYS.

201

Blood-vessels. — The kidneys are highly vascular, and receive their blood from
the renal arteries, which are very large in proportion to the size of the organs they
supply. Each renal artery divides into four or five branches, which, passing in at
the hilum, between the vein and ureter, may be traced into the sinus of the kidney^
where they lie amongst the infundibula, together with
which they are usually embedded in a quantity of fat. ^'s-

Penetrating the substance of the organ between the
papillae, the arterial branches enter the cortical sub-
stance which intervenes between the pyramids of
Malpighi, and proceed in this, accompanied by a
sheathing of areolar tissue, and dividing and sub-
dividing, to reach the bases of the pyramids, where
they form arterial arches between the cortical and
medullaiy parts, which however are not complete, and
in this respect differ from the freely anastomosing
venous arches which accompany them. From the

Fig. Il'.i. — .Mai-i'Ighian coupusclk from thic RAnnii's kidnky : nitkatk of .sinvhr i-kkpahation.

HtGIILY MACNIFIKI). (Ludwig. )

V, vaB afferenB, Bhowing its epithelial lining : at v', the transverse muscular fibres are also seen ; r,
▼iiB efferens ; a, a, basement membrane of capsule with epithelioid maikiiigs, i)assing at h into that of
the commencing uriniferous tubule.

Pig. 220. — I)IA«RAM OK THF, DISTRIBUTION OF TIIK HI.OOD-VESSKLS IN TIIK KIDNKY (flOm Ludwig).

ai,ai, interlobular arteries ; vi, vi, interlobular veins ; ;/, a glomerulus ; vx, stellate vein; ar, vr,
arteriifc et vena- recta.- forming pencil-like bundles, ah, vh ; rii, venous plexus in the papillie.

arches peripheral branches {arlernr. inlerlobulares (fig. t'M), ai)) are given off, which
paH8 outwards bet.\vcen the medullary rays and amongst the convoluted tubulcis,
pursuing a nearly straight course towards the surfa(;e of tlie organ. As tiiey proceed

202

THE URINARY ORGANS.

they give off at intervals short and usually curved branches (arterice glomeruJorum)
which proceed without further division to the dilated ends of the uriniferous tubules.
Within the capsule the small artery {vas adferens) breaks up into a larger number
of capillary vessels which have a convoluted arrangement, and are closely held
together by connective tissue to form a spheroidal vascular tuft, the glomerulus of
Malpighi. A vein {yas efferens) smaller than the artery, emerges from the glome-
rulus close to the point where the artery enters ; but, instead of joining with other
small veins to form larger venous trunks, as is the case in other. organs, the efferent
vessel divides into branches after the manner of an artery, and from these arises a
dense network of capillaries which everywhere ramify over the walls of the urin-
iferous tubules (fig. 221), the meshes of the network being polygonal amongst the
convoluted tubules and elongated amongst the tubules of the medullary rays. But
the efferent vessels from the lowermost glomeruli break up wholly into pencils of
straight vessels (pseud-ajiericc redcB (fig. 220, vr : fig. 223, ef) ) which pass directly

Kg. 221. — Diagram showikg the rklation of the ukinifkeous tubules to the blood-vessels (after

Bowman).

a, one of the interlobular arteries ; a', afferent artery passing into the glomerulus ; c, capsule of the
glomerulus ; t, convoluted tube ; e', e', efferent vessels which subdivide in the plexus p, surrounding
the tube, and finally terminate in the interlobular vein, e,

Fig. 222. — Lobules of glomerulus of riu's kidnev. (Ludwig. )

into the boundary layer of the medulla, and there supply the continuation down-
wards of the meciullary rays into the pyramid.

The renal arteries o:ive branches likewise to the capsule of the kidney which anastomose
vsrith branches of the lumbar arteries, and that so freely that Ludwig was able partially to
inject the kidneys of a dog from the aorta after the renal arteries had been tied.

The blood is conveyed from the cortex of the kidney by veins {venm interlohulares)
. which accompany the interlobular arteries, and join the convex side of the venous
arches which lie between the medulla and cortex, and also by veins which lie close
beneath the capsule of the organ, and take origin by the convergence of minute
venous radicles, so as to present a stellate appearance {venm stellukc). These vessels,
which receive blood from the capsule of the kidney, pass inwards through the
cortex and also join the venous arches.

With the exception of the blood brought by the false arterise rectse the blood
supply of the medulla is to a great extent independent of that of the cortex,
although of course the capillary network is continuous throughout. The pyramids
are chiefly provided with blood by branches which come off directly from the
concave side of the arterial arches, and passing down into the boundary layer of
the medulla there divide to form bunches or pencils of parallel or slightly diverging
minute vessels {arterim redcB, fig. 220, ar), which by alternating with the bundles of
uriniferous tubules which are passing up to the cortex to form the medullary rays,
produce the characteristic streaked appearance of this part of the pyramid (see
fig. 209).

THE KIDNEYS.

203

The Ions: meshed capillary network which is supplied by the arterige rectfe
is coiitinued down to the apex of the papilla. Here the veins of the pyi-amid
commence in a close plexus of small venous radicles surrounding the excretory
ducts near their orifices (fig. 220, vp). Passing outwards towards the base of the
pyramid, and receiving lateral branches at acute angles from its capillary network,
the same veins become collected together into pencils, the vessels of which (veme
recta;) are intermixed with the arterige rectee, and unite into vessels which open into
the concave side of the venous arch.

The venous trunks thence proceed, in company with the arteries, through the
cortical septula between the pyramids, to the sinus of the kidney. Joining

Uig. 223. — InJECTKD GLOMERULUS FROM THK INNER PAP.T 01." THK CORl'ICAL SUfiSTANfJF, OF TIIK HOUSES

KIDNEY. 70 DIAMETERS (froiii Kijlliker after IJowinan).
a, interlobular artery ; af, afferent vessel ; m, m, convoluted vessels of the gloiuerulus ; ef, effereut
ressel ; 6, its subdivision in the medullary substance.

Fig. 224. — Section across a papili^a of the kidnev. (Cadiat )
a, ducts of Bellini ; h, c, d, tubes of Henle, ascending and descending ; c,f, blood-capillarics.

together, they escape from the hilum, and ultimately form a single vein, which lies
in front of the artery, and ends in the inferior vena cava.

Lymphatics.— The lymphatics of the kidney are numerous, consisting of a
superliciul riet forming a plexus in the fibrous capsule, and of deep lymphatics wliich
issue from the hilum with the blood-vessels. Ludwig and Zawarykin showed
that there exists a network of fntely intercommunicating lymphatic spaces between
the tubules, in communication both with the; lym])hatics of the surface and those
which issue with the blood-vessels at the hilum. They are most abuiidiint in the
cortical suljstance.

Nerves.— The nsrvcs which have been traced into the kidneys are small. They
com<; immediately from the renal plerm and the /essar .yi/anrhuir nerves, and contain
filaments derived from both the sympathetic and cerebro-spinal systems. They may

204 THE URINARY ORGANS.

be traced accompanying the arteries as far as their finer branches, and some fibrils'
ramify over and amongst the uriniferous tubules, but it is uncertain how they end.

Intertubular stroma. — Between the tubules and vessels of the kidney,
although they are disposed closely together, a small amount of interstitial connective
tissue is found. It has a more fibrous character in the vicinity of the chief
ramifications of the blood-vessels, and also around the Malpighian corpuscles, and
the tubes of the medullary substance. It is more abundant in the neighbourhood
of the papillffi than in other parts of the kidney substance (fig. 224).

THE URETERS.

The ureters are the two tubes which conduct the urine from the kidneys into-
the bladder. The dilated commencement of each called the pelvis, which is partly
situated in the sinus of the kidney, and into which the calices pour their contents,
has already been described. Towards the lower end of the hilum of the kidney
the pelvis becomes gradually contracted, and opposite the lower end of the gland
assuming the cylindrical form receives the name of ureter.

The ureters measure from fourteen to sixteen inches in length ; their ordinary
width is that of a goose-quill. They are frequently, however, dilated at intervals,
especially near the lower end. The narrowest part of the tube, excepting its orifice,.
IS that contained in the walls of the bladder.

Each ureter passes at first obliquely downwards and inwards to enter the cavity
of the true pelvis, and then turns forwards and inwards to reach the base of the bladder.
In its whole course it lies close behind the peritoneum, and is connected to neighbour-
ing parts by loose areolar tissue. Superiorly it rests upon the psoas muscle and i&
crossed very obliquely from within outwards by the spermatic vessels which descend
in front of it. The right ureter passes close to the outer side of the inferior vena
cava, and often gets in front of this vessel. Lower down the ureter passes either
over the common iliac or the external iliac vessels, behind the tei'mination of the
ileum on the right side, and behind the sigmoid colon on the left. Descend-
ing into the pelvis it lies beneath the layer of peritoneum forming the corre-
sponding posterior false ligament of the bladder, and reaching the side of the
bladder near the base (fig. 227, u), runs downwards and forwards in contact
wath it, below the obliterated hypogastric artery, and is crossed upon its inner
side in the male by the vas deferens {%) which passes down between the ureter
and the bladder. In the female the ureter runs along the side of the cervix uteri
and upper part of the vagina. According to HoU at the level of the origin of the
obturator, vesical, and uterine arteries it begins to describe a bow-shaped curve
three and three-fifths of an inch long, which extends to the bladder. This curved
portion is crossed at the level of the external os uteri by the uterine artery which is-
separated from the ureter by a venous plexus. Here it lies three-fifths of an inch
external to the cervix. It then passes on to the side wall of the vagina and near
where it pierces the bladder lies between this organ and the anterior vaginal wall.

Having arrived at the base of the bladder about two inchss apart from one
another the ureters enter its coats, and running obliquely through them for about
three-quarters of an inch, open at length upon the inner surface by two narrow
and oblique slit-like openings. When the bladder is distended these openings are
situated about an inch-and-a-half from the urethral orifice, and about the same
distance from one another. This oblique passage of the ureter through the vesical
walls, while allowing the m'ine to flow into the bladder, has the eflFect of preventing-
its reflux.

Varieties. — Sometimes there is no funnel-shaped expansion of the ureter at its upper end
into a pelvis, but the calices unite into two or more narrow tubes, which afterwards coalesce

THE URETERS.

205

to form the ureter. Occasionally the separation of these two tubes continues lower down
than usual, and even reaches as low as the bladder, in which case the ureter is double. In
rare ea?es a triple ureter has been met with. Several instances are recorded in which a
supernumerary ureter, proceeding from the upper part of the kidney, opened directly into the
urethra.

The rij^ht ureter has been seen passimj: behind the inferior vena cava, and then turning:
forwards between that vessel and the aorta (Hochstetter, Morph. Jahrb.. xxi, (J30).

In instances of long-continued obstruction to the passage of the urine, the ureters may
become enormously dilated.

Strnctnre. — The walls of the ureter are pinkish or bluish white in colour.
They consist of an external fibrous coat, a middle coat of plain muscular tissue, and
a mucous lining. The muscular coat possesses two layers of longitudinal fibres and a
middle circular layer.

The mncoTis membrane, thin and smooth, presents a few longitudinal folds when
the ureter is laid open. It is composed of areolar tissue which becomes gradually
loose towards the muscular coat, but there is no marked distinction into mucous and
submucous layers. It is prolonged above to the papilla of the kidney, and below
becomes continuous with the lining membrane of the bladder. The epithelium
(fig. 225) IS of a peculiar character, like that of the bladder. It is stratified, con-

Fig. 225.

-Epithelium from the pelvis op the human kidney. (KolUker. ) 350 piameters.
A, different kinds of epithelial cells separated ; B, the same in situ.

sisting of four layers (fig. 225, b, in section), in the uppermost of which the cells
are somewhat cubical, with depressions on their under surface, which fit upon the
rounded ends of a second layer of pear-shaped cells ; then follow two layers of
rounded or oval cells, with processes extending down to the mucous memlmine. This
description of the shape of the epithelium cells applies to them as they occur in the
empty condition of tlie duct, but in the distended state the superficial cells are
flattened out, and the pear-shaped and oval cells are much shorter. All the cells are
connected by "cell-bridges" with one another as in a stratified epithelium. The
superficial cells usually have two nuclei, and are believed to divide by " amitosis."
The deeper cells multiply on the other hand by karyokinesis.

A few small mucous glands have occasionally been described at the upper end of
the ureter and in the renal pelvis, but they appear not to be present in man.
Epithelial downgrowths are occasionally found both here and in the urinary bladder,
and these may occasionally have been taken for glands (v. Brunn). Mucus is
however secreted by the lining epithelium. Lymphoid nodules have been met with
in the mucous membrane of the jjelvis of the kidney.

Vessels and Nerves. — The ureter is supplied with blood from small branches of
the renal, tlie .sijcrmatk, the inlernal iliac, and tlie inferior vesical arteries. The
\eins end in various neighbouring vessels. The nerves come from the inferwr
ifU'HenUrric, apermalic, and hi/potjaHlric p/f.ntMs. They form plexuses in the outer
and muscular coats containing a few ganglion-cells.

THE URINARY ORGANS.

THE URUSTARY BLADDER.

The urinary bladder (vesica urinaria) is a hollow receptacle for the urine, having
an average capacity of about a pint when moderately filled, but capable of being-
distended to a considerably greater degree.

The average capacity of the bladder is often stated to be greater in the female than
in the male ; and, no doubt, instances of very laige female bladders are not unfrequent ;
but these have probably been the result of unusual distension : in the natural condition,
according to Luschka and Henle, the female bladder is decidedly smaller than that of the male.

The size, shape, and position of the bladder and its relations to neighbouring
parts vary according to the degree of distension of its cavity, and also, when empty,

,.'''" ^.,^ Fig. 226. — Diagram of median section of empty diastolic

/■' _, ...___ ~^^-., BLADDER AND ADJACENT PART OF URETHRA. (J. S. )

/ /'' _,. '"'..^ \, A, anterior limb of bladder ; P, its posterior limb ; U, urethra.

Tlie clotted lines show the changes in the shape of the bladder
during its distension.

according to the condition of its muscular coat,
whether contracted or relaxed. When empty and
relaxed (in diastole) it lies deeply in the pelvis, and
in a vertical median section its cavity, with that of
the adjacent portion of the urethra, is Y-shaped, the
stem of the Y being formed by the urethra, and its
two limbs by the bladder. Of the two limbs the
anterior is the longer, and is directed upwards

and forwards, while the shorter posterior limb passes backwards and upwards.

The empty diastolic bladder has three surfaces — a superior, Avith its concave

-Lateral view of the viscera op the male pelvis (K Quajn ) \

The left hip-bone has been disarticulated from the sacrum, the spinous process oi the ischium cut
through, and the pubis divided to the left of the symphysis ; a, bladder ; h V, rectum ; c, mem-
branous 23art of the urethra ; d, section of the left corpus caveruosum ; e, bulb of the spongy body of
the urethra ; /, Cowper's gland ; g, section of the body of the pubis ; h, sphincter ani muscle ; i, part
of the left vas deferens ; m, articular surface of the sacrum ; «, divided spine of the ischium ;
o, coccyx ; p, prostate gland ; r, r, peritoneum ; r', recto-vesical pouch ; u, left ureter ; v, left
vesicula seminalis.

upper aspect covered by peritoneum, an anterior, lying above the pubo-prostatic
ligaments, and behind the pubic symphysis, and a posterior, which is in relation

THE BLADDER.

207

with the rectum, vasa defereutia, and vesiculfe seminales in the male, and the
cervix of the uterus and upper ]iart of the vao-ina in the female. Both the anterior
and posterior surfaces are micovered by peritoneuna.

On the other hand, when the bladder is empty and contracted (in systole) the
two limbs of its cavity are much shortened, its mucous membrane is thrown into

Fig. 228. — Vektical median section of the pelvis of an adult male subject. (Braune.) ^

1st s, body of Ist sacral vertebra; p. s., pubic symphysis; Bl., bladder; ii, R, r, rectum;
P, p, prostate; p', middle lobe of prostate ; F, retro-pubic pad of fat ; i>a., bulb ; p. c, peritoneal
cavity ; j. i., convolutions of jejuno-ileuni.

numerous folds, its muscular coat is greatly thickened, and its superior aspect is
rounded and convex. As the relaxed ])ladder is ^n-adually filled with urine it
oxp>an<ls chiefly in an upward direction, its superior sui-face hein*^ separated from
the anterior and ])0:sterior surfaces, and becomins^ convex towards tiie peritoneal
cavity. "When moderately filled it is still contained within the pelvic cavity, and
has a rounded form (fi{?. 'I'll, a), but when completely distended it rises above the
brim of the pelvis, and becomes egg-shaped ; its larger end, which is called the

'308

THE URINARY OEUANS.

hase, ov fundus, being directed downwards and backwards towards the rectum in the
male and the vagina in the female ; and its smaller end, or summit, resting against
the lower part of the anterior wall of the abdomen. Immediately in front of
the base is the portion which joins the urethra, and is often named the cervix,
or neclc. When the bladder is excessively distended (fig. 229) it may rise into
the abdomen nearly as high as the umbihcus, and it also sinks somewhat in
the pelvis, pushing the prostate and lower end of rectum downwards and back-
wards. The long axis of the distended bladder varies in difterent cases, being
modified by the degree of distension of the bladder itself, as- well as that of

Fig. 229. Median section of the i'Elvis
OF AN ADULT MALE SUBJECT. (Riidinger. )

L. body of 5th lumbar vertebra ; s, body of
1st sacral vertebra ; v, s, pubic symphysis ; p,
prostate ; b, bulb of corpus spongiosum ; u,
urethra ; b, umbilicus ; A, peritoneum. The
reflection of the peritoneum from the anterior
abdominal wall on to the bladder is higher than
normal.

the rectum and other portions of
the intestine that may be in relation
Avith it. In a section of Braune's (see
fig. 228), in which the bladder was
moderately distended, it is almost hori-
zontal, while in one by Elidinger (see
fig. 229), in which the bladder was
greatly distended, it is rather more
nearly vertical than horizontal. While
in the male the longest diameter of
the moderately distended bladder is
directed from its base to its summit,
in the female the transverse diameter is
the longest;

Connections and Relations. —
While freely movable in all other direc-
tions, the bladder is fixed to the walls
of the pelvis in the neighbourhood of
the urethral orifice, its mucous and muscular coats being here continuous with those
of the prostatic portion of the urethra, while its fibrous investment is connected with
the pelvic wall by bands of fibrous tissue, called the true ligaments of the bladder
(see Vol. II., Pt. 2). It is supported, moreover, by strong areolar connections with
the rectum and prostate or uterus and vagina, according to the sex, in a slighter
degree by the two ureters, the obliteratrd hypogastric arteries, and the urachus, by
numerous blood-vessels, and, lastly, by a partial covering of the peritoneum, Avhich,
in being reflected from this organ in different directions, forms duplicatures, named
i\\Q, false ligaments of the bladder.

The antero-inferior or pubic surface is entirely destitute of peritoneum, and is
in apposition with the redo-vesical fascia, the symphysis and body of the pubis, and,
if the organ be full, the lower part of the anterior wall of the abdomen. It is con-
nected to these parts by loose areolar tissue. The lower part of this surface, close
to where it joins the prostate, is attached to the back of the pubis by two strong
bands of the recto-vesical fascia, named the anterior true ligaments. This surface of
the distended bladder may be punctured just above the pubis without wounding the
peritoneum.

THE BLADDER.

209

The superior or abdominal surface is entirely free, aiul covered everywhere by
the peritoneum, which in the male is prolonged also for a short distance upon the
base of the bladder. In the male this surface is often in contact with the sigmoid
loop of the colon, and in the female with the uterus, as well as, in both sexes, with
convolutions of the small intestine. Beneath the peritoneum, in the male, a part of
the vas deferens is found on each side of the hinder portion of this surface.

The summit is connected to the anterior abdominal wall by a tapering median
cord, named the umchus, which is composed of fibrous tissue, mixed at its base with
plain muscular fibres, which are prolonged upon it from the bladder. This cord,
becoming narrower as it ascends, passes upwards fi'om the apex of the bladder

T I I

Rl/

jPr/

JS':pr.

Fig. 230.— Median section of the velvis of a nkwlt-born male child. (Disse.)

V.l.'c, body of 5th lumV)ar vertebra ; V.s.v, body of .'Jtb sacral vertebra ; Sy, pubic symphysis ;
Ret, rectum (distended) ; Prt, peiitoneum ; Bspr, pnevesical cleft ; Pro, placed just below median
lobe of prostate ; Lf, longitudinal muscular fibres of rectum ; 1, s^jhiucter ani int.

between the linea alba and the peritoneum, to reach the uml)ilicus, wliere it
becomes blended with the dense fibrous tissue found in that situation.

The urachns, which forms in the early ffjetal state a tubular connection between the
urinary bladder and the allantois. preserves, according to Luschka. vestiges of its original
condition in the foi-m of a long interrupted cavity, with irregularities and dilatations,
lined with epithelium similar to that of the bladder, and sometimes communicating by a fine
opening with the vesical cavity.

As during distension the summit of the bladder rises more rapidly than the
peritoneum is detached from the anterior abdominal wall, a peritoneal pouch,
gradually increasing in depth, is formed between the top of the bladder and the
anterior abdominal wall. It is generally estimated that, even in extreme distension,
the l>ladder is seldom uncovered by peritoneum for more than two inches above the
pubic symphysi.s.

The sides of the bladder, when tin's orgiin is empty, are \ery iiai-nnv, but when
it is distended they are rounded and prominent, and are each of them crossed
obliquely by the cord of the obliterated hypogastric artery, which is connected
posteriorly with the superior vesical artery, and runs forwards and upwards to the
umbilicus, approaching the urachus above the summit of the bladder. IJehind and
VOL. m., IT. 4. 1-

210

THE UPJNARY ORGANS.

above this cord the side of the bladder is covered with peritoneum, but below and in
front of it the peritoneum does not reach the bladder, which is here connected to
the sides of the pelvic cavity by loose areolar tissue containing fat, and, near
its anterior and lower part, by the broad expansion from the recto-vesical fascia,
forming the lateral true ligament. The vas deferens crosses obliquely the hinder
part of this lateral surface, from before backwards and downwards, and turning
over the obliterated hypogastric artery, descends on the inner side of the ureter,
to the base of the bladder (fig. 232).

Fig. 231. — Median section of the pelvis of a male child 7 months old. Bladder naturally
DISTENDED WITH URINE. Natural size. (J. S.)

P, peritoneum ; s. p., pubic symphysis ; b, bladder; R, rectum; h, bulb of corpus spongiosum. In
this specimen the distance from the umbilicus to the top of the pubic symphysis was 7 cm., and the
vertical extent of the bladder in contact with the anterior abdominal wall and uncovered by peritoneum
was 3 cm.

The anterior and lateral surfaces of the bladder, between the anterior and lateral
true ligaments of the bladder below and the peritoneum above, are connected with
the neighbouring structures by loose areolar tissue, an arrangement which obviously
must facilitate the movements of the bladder. The space occupied by this tissue is
sometimes termed the cavum prce,vesicale, or cavum Retzii.

The base or fundus (fig. 232) is the widest part of the bladder. It is directed
downwards as well as backwards, and differs according to the sex in its relations to
other parts. In the male it rests against the second portion of the rectum, and is
covered superiorly for a short space by the peritoneum, which, however, is imme-
diately reflected from it upon the rectum, so as to form the recto-vesical pouch
(fig. 227). Below the line of reflection of the serous membrane the base of the

THE BLADDEE.

211

bladder is adherent to the rectum by dense areohir tissue over a triangular area
bounded at the sides by the vasa deferentia and vesicuhe seniinales (hg. 2ij2), while
in front, its apex reaches the prostate gland. It is in this triangular space, which,
in the natural state of tiie parts, is by no means so large as it appears after tliey
ai-e disturbed in dissection, and seldom measures more than an inch from base to
apex, that the bladder may be punctured from the rectum without injury to the
peritonemn. In the female the base of the bladder is of less extent, and does not

Fig. 232. — Bask of the male bladder,

PROSTATE, &C., IN THE MALE. (J. S.)

b1, part of base covered by peri-
toneum, separated by a dotted line from
a triangular space left uncovered by that
membrane; u, ureter; s. v., seminal
vesicle; e. v., ejaculatory duct ; p, pros-
tate; M. , membranous part of urethra;
B, bulb; c. s., corpus spongiosum; c. G.,
Cowper's gland.

reach so far back in the pelvis as
in the male, for it rests against
the fi'ont of the neck of the uterus
and the upper part of the ante-
rior wall of the vagina, both of
which organs inter\'ene between
it and the rectum. This part of
the bladder is connected with the
vagina and cervix uteri by loose
areolar tissue, and above it there
is a shallow utero-vesical pouch
of peritoneum. In both sexes
the vesical orifice of the urethra
is usually the lowest part of the
bladder in the erect ])osture. It
is generally situated about an
inch behind the middle of the
pubic symphysis.

Disse (Merkel u. Bonnet, Anato-
mische Hefte, i) found that the
distance of the orifice from the con-
juf^ate of the pelvic inlet in seven
arlult males varied from 44 mm. to
<i.'j mm., while in women it was
placefl more deeply in the pelvis,
being, on an average, 60 mm. beiow
the pelvic inlet.

Ligaments of the bladder. — The true ligaments of the bladder, four in numbcf",
two anterior and two lateral, all derived from the rccto-vesical portion of the pelvic
fascia, are described in Vol. II., Pt. 2.

The/a/.s/? liiianwilH, or peritoneal folds, are described as live in number. Two
of tiieni, nam(;d poslerm false ligaments or reclo-veHkal folds, run forwai'ds in
the male along the sides of the rectum to the posterior and lateral aspects of the
bladder, and bound the sides of tiie recto-vesical cul-de-sac. In the female these
jKJStcrior folds pass forwards from the sides of the uterus, and are comparatively
small. The two lalortU false ligaments extend from the iliac foss.-c to the sides of
the bladder, which they join at the level ol' the obliterated hypogastric arteries.
The aumrior false ligament {I itjamentum suspensorium) is the portion of peritoneum

r 2

213 THE UEmARY ORGANS.

which descends from the umbilicus on the nrachus and obhterated hypogastric
arteries to the summit of the bladder.

Peculiarities in Shape and Position according to Age. — In the newly-
born child the bladder is much higher than in the adult. Thus, its urethral
orifice is at the level of the upper border of the pubic symphysis, and the anterior
surface of the bladder, entirely uncovered by peritoneum, lies against the anterior
abdominal wall, opposite about the lower two-thirds of the space between the pubes and
the umbilicus (fig. 230). If the bladder be empty, its cavity in a median section shows
a long anterior limb passing from the urethral orifice upwards and forwards towards the
umbilicus, but there is no indication of a posterior limb such as has already been
described in the adult. If the bladder be distended, it usually has an ovoid form, with
the large end of the oval directed downwards and backwards. The bladder is
commonly described as being at this age an abdominal organ, but, as a rule, only
one-half of it lies above the plane of the pelvic inlet. After birth the bladder
rapidly descends into the pelvis, and acquires a more rounded form when con-
tracted. In an infant three and a half months old, .with the bladder contracted,
the peritoneum was reflected from the anterior abdominal wall on to the bladder
10 mm. above the pubic symphysis, the distance from this point to the umbilicus
being 48 mm. Again, in a boy, aged five years, in which the bladder was also
contracted, the peritoneum passed on to the back of the pubic symphysis before
being reflected on to the bladder (Symington). According to Disse, the vesical
orifice of the urethra sinks rapidly from birth up to the beginning of the third year,
then slowly until the commencement of the ninth year, when it remains stationary
until puberty, at which period it again slowly descends until it gains its adult
position.

Interior of the bladder. — On opening the bladder, its internal surface is
found to be lined by a smooth membrane, which is comparatively loosely attached
to the other coats, so that in the empty condition of the organ it is nearly every-
where thrown into small wrinkles or ruga, which disappear as soon as the bladder is
distended. Besides these, the interior of the bladder is often marked by reticular
elevations or ridges, corresponding with fasciculi of the muscular coat.

At the lower part of the bladder is seen the orifice leading into the urethra,
around which the mucous membrane is corrugated longitudinally. Immediately
behind the urethral opening, at the lower part of the fundus, is a smooth triangular
surface, having its apex turned forwards, which, owing to the firmer adhesion of the
mucous membrane to the subjacent tissue, never presents any rugse, even when the
bladder is empty. This surface is named the trigone {trigonum vesicm, Lieutaud) ;
at its postero-superior angles are the orifices of the two ureters, situated in a
distended bladder about an inch and a half from each other, and nearly the same
distance from the antero-inferior angle, where the bladder opens into the urethra.
When the bladder is contracted, this area is diminished in size.

The orifices of the ureters, presenting the appearance of oval slits, are directed
obliquely forwards and inwards : they are united by a curved elevation, convex
in front, which extends generally outwards and backwards beyond them, and which
corresponds in position with a muscular band which joins them together and to the
neck of the bladder. Proceeding forwards from opposite the middle of this is
another slight elevation of the mucous surface, named the uvula vesica,, which
extends to the posterior margin of the urethral orifice. In the female the trigone is
small and the uvula indistinct. In the male the uvula lies a little in advance of
the middle lobe of the prostate, and is sometimes prolonged on the posterior wall of
the prostatic portion of the urethra as far as the verumontanum. It is produced by
a thickening of the submucous tissue. In its natural state this may contribute to
the more perfect closure of the orifice of the bladder.

THE BLADDER. 213

BTRUCTURE OF THE BLADDER.

The bladder is composed of a serous, a muscular, a submucous, and a mucous
coat, and supplied with numerous blood-vessels and nerves.

The serous or peritoneal coat is a partial covering, investing only the posterior
and upper half of the bladder, and reflected from it npon the surrounding parts in
the manner already described in detail.

The muscular coat consists of unstriped muscular fibres, which are described
as forming layers, the outer of which consists of bundles of fibres more or less
longitudinal, and the next of fibres more circular in disposition ; while beneath this
is another imperfect longitudinal layer.

The external long itucUnal fibres (fig. 2;33, a, b, c) are most distinctly marked on
the anterior and posterior surfaces of the bladder. Commencing in front at the
neck of the organ, from the pubes in both sexes {musculi puho-cesicales), and, in
the male, from the adjoining part of the prostate gland, they may be traced
upwards along the anterior surface to the summit of the bladder ; and they may
likewise be followed down over the posterior surface and base to the under part
of the neck of the bladder, where they become attached to the prostate in the
male, and to the front of the vagina in the female. Upon the sides the superficial
fasciculi run more or less obliquely, and often intersect one another ; in the male
they reach the prostate. At the summit a few are continued along the urachus.
The longitudinal fibres taken together constitute what has been named the detrusor
urincB muscle, but, according to Griffiths, these fibres " do not form a separate
muscle, and have not a separate function."

The so-called circular fibres furm a thin and somewhat irregular reticulated
layer distributed over the body of the bladder, having various appearances in
different bladders. Their course may in general be looked upon as transverse, but
for the most part throughout the upper two-thii"ds of the bladder they cross one
another in very oblique bands : towards the lower part of the organ they assume a
more circular course, and upon the fundus and trigone form a tolerably regular
layer. Close to and around the urethral orifice, in immediate connection with the
prostate in the male, they are often described as forming a thick band of circular
fibres, which has been named the sji/a'/icter vesiccc. According to GriifiLhs, there is,
however, no thickening of the muscular fibres in this situation to justify the term of
sphincter.

The third stratum of fibres, still more deeply situated, and which might be
termed internal longitudinal, was first described by Ellis, who distinguished it as
"submucous." It is thin, and its bundles have a reticular arrangement, but with a
general longitudinal direction. At the trigone the inner bands of muscular fibres
are united together and to the mucous membrane by dense areolar tissue, while
they are separated from the external longitudinal fibres by a thin layer of loose areolar
tissue.

The muscular coat of the bladder forms bo irregular a covering that, when the organ is
much distended, intervals arise in which the walls are very thin ; and, should the internal or
mucous lining protrude in any spot through the muscular bundles, a sort of hernia is pro-
duced, which may go on increasing, so as to form what is called a vesical sacculus, or
ujtpciidix venicw, the bladder thus affected being termed succulatvd. Hypertrophy of the
muscular fasciculi, which is liable to occur in stricture of the urethra or other affections
impeding the issue of the urine, gives rise to that condition named the fanciculdtid bladder,
in which the interior <>i the organ is marked by strong reticulated ridges or columns, with
intervening depressions.

Next to the muscular coat, between it and the raucous menibruno, but much
more intimately connected with tlie latter, is a well-murked layer of areolai- tissue,

214

THE UmNARY OKGATS'S.

Fig. 233. — Dissections showisr the course of the muscular, fibres of the blapder (Allen
Thomson, after Pettigrew, and from nature), g.

A. From the front.

On the right side the superficial fibres are shown ; on the left the deep or circular fibres chiefly are
displayed, a, on the right side, the median and most superficial bands of the longitudinal fibres, in
which a slight decussation of fibres is seen : a', those divei'ging somewhat ; a", the lowest, which pass
much more obliquely ; the attachment of the longitudinal fibi-es to the prostate is shown ; on the left
side, c, the upper, c', the middle, c", the lowest set of circular or deejier fibres ; at s, the thickest and
most transverse sets of these fibres forming the sphincter ; p, right half of the prostate, the left
half having been removed ; u, the nrachus, into which some of the longitudinal fibres are seen
prolonged.

B. From the back.

On the right side the superficial fibres are displayed ; on the left the deeper fibres of the same
kind or intermediate fibi-es, and some of the circular fibres ; h, h, the median, most superficial and
strongest bands of longitudinal fibres on the right side ; h' , the more diverging set of fibres near the
middle of the bladder ; h", the most divergent fibres which surround the entrance of the ureters ; on
the left side, c, c', and c", indicate the deeper circular fibres passing round at various levels, and
crossing with the deeper diverging fibres posterioi-ly ; s, the most ti-ansverse fibres at the neck forming
the sphincter ; u, the urachus ; ur, the ureters ; the left half of the prostate has been removed to
show the sphincter ; v, part of the right vas deferens and vesicula seminalis.

C. From the left side.

The anterior and iDosterior superficial fibres are seen running from below upwards, crossing each
other by their divergence on the side of the bladder, and are indicated by the same letters as in the
preceding figures ; at c, a portion of the anterior longitudinal fibres has been removed so as to expose
th'j deeper circular fibres.

THE BLADDER. £15

the rascnlfir or submucous coat. Tbis submucous areolar layer contains a large
number of tine coiled tibres of elastic tissue.

The mucous membrane of the bladder is soft, smooth, and of a pale rose colour.
It is continuous above with the lining membrane of the ureters and kidneys, and
below with that of the urethra. Neither here uor in the ureters is the mucous
membrane provided n'ith a muscularis mucosfe. It adheres loosely to the muscular
tissue, and is thus liable to be thrown into wrinkles, except at the trigone, where
it is always more even. Ifc is covered with a (transitional) stratified epithelium
(fig. 234), similar to that of the ureters. The cells vary much in form according
to the condition of distension of the bladder, for in the distended organ they are
flattened out so as to cover a larger surface, while in the empty condition of the
bladder they are of less diameter and proportionately higher. Many of the super-
ficial cells contain two nuclei. The deeper cells divide by karyokinesis, and the newly
formed cells take the place of others which are thrust towards the surface. There are
no definite glands in the bladder, but in some places there are solid dowu-growths

Fig. 234. — Epithelium ok tho ukinary i!Lai>I)i;r.
a, superficial : h, iiiteniiciliate ; and c, deep laj'cr of cells, partly doulile.

of the deeper epithelium cells into the muoous membrane, which have sometimes
been described as true glands.

Vessels and nerves. — Arteries. — The f^vperior vesical arteries proceed from
the remaining pervious poi-tious of the hypogastric arteries ; in the adult they appear
as direct branches of the internal iliac. The inferior vesical arteries are usually
derived from the anterior division of the internal iliac. In the female the uterine
arteries also send branches to the bladder. The neck and base of the organ appear
to be the most vascular jxirtions. The veins form large plexuses around the neck,
f-ides, and baso of the ])laddcr ; they eventually ])ass into the internal iliac veins.
The lymphatics follow a similar course. Nerves. — The nervous supply of the
bladder is bilateral, each half having its own nerves. On each side the nerves are
derived from two sources, viz. : — (a) from the third, tho fourth, and sometimes the
necond sacral nerves : these fibres, which are known as the pelvic splanchnics
(Gaskell), consist almost entirely of fine medullated nei'ves, and pass from the sacral
spinal nerv'es directly to the pelvic plexus without going through the gangliated cord
of the sympathetic ; (t)) from the hyjxujaslric ple.nis (f the siimpatlielic : these fibres
are nearly all non-medullatfjd. Tiiey arise from the upper lumbar nerves, and reach
the hypogastric plexus through the aortic plexus and the inferior mesenteric ganglion.
Both sets unite in the pelvic plexus, which contains numerous ganglia, and the fibres
which go from the plexus to the bladder are mainly, if not (entirely, non-m(!dullated.
According to v. Z';issl, tlie pelvic, sphinelinics supply only the longitudinal fibres of
the bladder, but Griffiths found that stiniulati(jn of the peripheral cut ends of these
nerves produced contraction of the entire nmscular coat on the same side. Thess

216 THE URmARY ORGANS.

nerves also contain sensory fibres from the bladder. Stimulation of the peripheral
cut ends of the hypogastric fibres causes feeble contraction of the corresponding half
of the bladder (Langley), and if the bladder be previously contracted it causes rapid
relaxation (Griffiths). The hypogastric plexus also contains sensory fibres, which
probably reach the spinal cord through the twelfth dorsal and first and second
lumlar nerves.

RECENT LITERATURE OF THE URINARY ORGANS.

Adami, J. G-., and Day, J. L., Two cases of complete double ureter, Montreal Med. Journal,

1893-94.

AschoflF, L., Eln Beitrag zur normal, u. pathol. Anatomic der i'chleimhaut der Harnicege,
U.S.W., Virch. Arch. f. path. Anat., Bd. cxxxviii., 1894.

Earth, P., Recherches sur la structure de I'uretere humain, These, Nancy, 1894.

Berkeley, Henry J., The intrinsic nerves of the hidney. Bull. Johns Hopkins Hospital, v, iv.

Bianchi-Mariotti, Gr. B., Ricerche sull 'histoloyia normalc dclV uretere, Atti e rendic. ace. med.
chirurg. Perugia, v. ix., 1893.

Birmingham, A., Peculiar horse-shoe kidney, Trans, of the Roy. Acad, of Med. in Ireland,
1894. Siriiple unilateral {siymoidj kidney. Trans, of the E,oy. Acad, of Med. in Ii-eland, vol. viii.,
1890.

Bradford, J. Eose, The innervation of the renal hlood-vcsscls, Proceed, of the Roy. Soc. ,
vol. xlv., and Journal of Physiol., vol. x., 1889.

Brovrn, Macdonald, Variations in the 2^osition and dei-elopment of the kidneys, Journ. of
Anat. and Physiol., vol. xxviii., 1894.

Brunn, A. v., Ueber druscndhnUche Bildungen in der Schleimhaut des- Nierenbeckens des
Ureters und der Harnblase beim Menschcn, Arch. f. mikrosk. Anat., Bd. xli., 1393.

Cabot, A. T., Observations upon the anatomy and surgery of the ureter, The American Journal of
the Medical Sciences, 1892.

Cuccati, Giov., Nuove osservazioni intorno al distribuimento e alia terminazione deUe fibre
nervci nella vescica urinaria in alcuni anfibi, rettili e mammiferi, Memorie della r. accademia delle
scienze dell' istituto di Bologna, 1889.

Cunning-ham, D. J., The form of the spleen and of the kidneys, Journal Anat. and Phys., vol.
xxix., 1895.

Disse, J., Beitra./e zur Kcnntniss der Spaltriiiime des Menschcn, iv. Der Blasenspaltraum bei
Kindcrn und sein Verhdltniss zuni Cavum Ilctzii, Arch. f. Anat., Supplement, 1889 ; Untersuchungen
uber die Lage der rncnschlichen Harnblase und ihre Verdnderungen, im Laufe des Wachstuma,
Anatom. Hefte, 1891 ; Ueber die V eranderungen der Epithelien in der Niere bei der Harnsekretiun,
Anatom. Hefte, ii. , and Yerhandl der Anat. Gesellsch., 1892.

Disselhorst, E.. Der Harnleiter der Wirbcltiere, Anat. Hefte, Bd. iv., 1894.

Dogiel, A. S., Zur Frage iiber das JSpithel. der Harnblase, Archiv f. mikroskop. Anat.,
Bd. x.xxv., 1890.

Dwight, T., Case of absence of the right kidney, Jour. Anat. and Phys., vol. xxiz., 1894.

V. Pischer-Benzon, L., Beitrag zur Anatomic und (Etiologie der beweglichen Niere, Kiel,
1887.

Flesch, M., Bemcrkungcn fiber die Beziehungen des Bauchf ells zur vorderen Wand der Harnblase,
Anat. Anzeiger, 1888.

Golgi, C, Rend. d. r. accad. d. Lincei, t. v.

Goluhew, "W. S., Ueber die Blutycfdsse in der Niere der Sdugetiere und des Menschen, Internat.
Monatsschr. f. Anat. u. Physiol., Bd. x., 1893.

Griffiths, Joseph, Observations on the urinary bladder and urethra. The Journ. of Anat. and
Physiol., vol. xxv., 1891.

Gruber, W., Hautiger Isthmus einer Hufeisenniere, Vircli. Arch. f. path. Anat., Bd., ciii.

Halasz, Heinrich, Niere mit doppeltem Ureter, Anat. Anzeiger, Bd. ix., 1894.

Hamburger, 0., Ueber die Entwickelung der Sdtigetierniere, Archiv f. Anat. u. Physiol.,
1890, Anatom. Abt. , Supplement- Band.

Hedinger, Heinrich, Ueber den Bau der 3Ialpighi schen Gefdssknduel der Niere, Breslau,
Inaug. Dissert., 1883.

Hepburn, D., Floating kidney. Jour. Anat. and Phys., vol. xix., 1885.

HoU, M. , Zur Topographic des iveiblichen Harnleiters, Wien. med. Wochensch., 1882.

James, Ernest W., Congenital absence of right kidney and suprarenal capsule, Brit, Med.
Joiu-nal, 1893, vol. ii., p. 579.

Kostjurin, S. D., Das glatte Muskelgewebe der Nieren und seine Bedeutung als Harnleiter ,
Aichiv f. experimentelle Pathologic und Pharmakologie, Bd. xxv., 1888.

Howden, E. , Case of misplaced kidney with undescended testicle and rudimentary vas deferens
on the same side, Jour. Anat. and Phys., vol. xxi, 1887.

Kruse, A., Demonstration von Fallen abnormer Lage und Gestalt der Nieren, Deut. med.
Wochensch., 1890.

Kruse, Walther, Ein Beitrag zur Histologic der gewundenen Harnkandlchen, Vii'cliow's Archiv
f. path. Anat., Bd. cix., 1887.

Lindner, Ueber die Wandernicre der Frauen, Berli;i, 1888,

RECENT LITERATDRE OF THE UlUNARi^ ORGAXS. 217

Little, Jolin Fletcher, The depth of the cortex of the kidney, Proceed, of the Anatom. Soc. of
Gt. Britain, Journ. of Anat. and Physiol., 1888.

Mackey, E., iioUtary kidney in a child, Brit. Mel. Jour., 1887. vol. ii., p. 626.

M'Gee, R*:poH upon the distance of the lower end of the kidney from the crest of the ilium,
Trans, of the Roy. Acad, of Med. in Ireland, vol. i.\., 1891.

Mahon. R. B., Abnormal arrangement of the kidney and its vessels, Jour. Anat. and Phvs
vol. xxiii., 1889. •' '

Menzies, W. F., Ttoo cases of single kidney, Jour. Anat. and Phys., vol. xxi., 1887.

Manca, G., Rapport cntre Ics poids des reins ct Ic pnds et la supcrfcie du corps chez les chiens,
Arch. ital. de biol., t. xxi. 1894 (abstract of a paper in Atti d. R. Accad. d. so. d. Torino).

Noel, J., Absence congmitale du rein et dc rurctire du cote droit chez une fcmme de 62 ans, Bull,
60c. anat., Paris, 1892.

Newman, D., On malposition of the kidneys, Glasgow Med. Journ., 1883.

Nussbaum, M., Zur Kenntnis der Niercnorganc, Ai-chiv f. mikroskop. Anatomie, Band xxvii.

Pilliet, Sphincter interne de la vessie, Bull. soc. anat., Paris, 1892.

Kichmond, W. Stephenson, Abnormxd ureters. Jour. Anat. and Phys., vol. xix., 1884.

Rothstein, T., Zur Kenntnis des Nierenepilhcls, Biol. Foren. Fdrhandl., Stockholm, 1891.

Bussel, J. C, Note on a peculiar shaped kidney. Jour. Anat. and Phys., vol. xLx., 1885.

Spencer, H. R., The distance of the lower margin of the kidney from the iliac crest in the infant
at birth. Jour. Anat. and Phys., vol. xxvi.

Steig-er, R., Beitrage zur Histologic der Xiercn, Virchow's Archiv f. path. Anat., Bd. civ.

Syming-ton, J., On the position of the empty and distended bladder in the male child, Edin". Med.
Journ., April 1885 ; The topographical anatomy of the child {position of bladder), 1887.

Takahasi, S., Beitrage zur Kenntnis der Lage der fotalcn und kindlichen Harnblase, Archiv f. ■
Anat. u. Physiol., Anatom. Abt., Jahrg. 1888.

Thompson, "W. H., Horse-shoe kidney, The Dublin Journal of Med. Sci., August, 1889.

Thomson, A., Second annual repoi-t of the Committee of Collective Investigation of the
Anatomical Society of Great Britain and Ireland for the year 1890 — 91, Distance of the lower margin
of the kidney from the iliac crest, Jour. Anat. and Phys., vol. xxvi.

Tweedy, H. C, Case of single unilateral kidney, Jour. Anat. and Phys., vol. xxviii., 1894.

Waldeyer, Ueber die sogenannte Urettrscheide, Verhand. der Anat. Gesellsch. Anat. Anzeiger
1892. ^ ^ '

Zuckerkandl, E., Ueba- den Fixationsappjarat der jS'ieren, Wien. med. Jahrbuch, 1883.

KEPKODUCTIVE OEGANS.

By B. a. SCHAFER asb J. SYMINGTON.

I. IN THE MALE SEX.

TJndee this head are included — 1, the testes with their ducts and coverings ;
and, 2, the urethra, with certain accessory parts, such as the prostate and Cowper's
glands. The urethra in the male is at once the outlet for the urine from the
bladder and the products of secretion from the sexual glands. Extending from the
neck of the bladder to the extremity of the penis, it is surrounded in its first part
by the prostate gland, and there receives the excretory ducts of the testes and
vesiculge seminales ; its second parb passes through the triangular ligament of the
perineum ; and its third and longest part passes along the perineum and penis,
surrounded by the corpus spongiosum,

THE TESTES AND THEIR ACCESSORY STRUCTURES.

The testes or testicles, the two glandular organs which produce the spermatozoa,
are situated in the pouch of integument termed the scrotum, each being suspended
by its own spermatic cord.

The spermatic cord. — The parts which form this cord are the excretory duct
of the testis, named the vas deferens, the spermatic artery and veins, lymphatics,
nerves, and connecting areolar tissue. Besides this last the cord has several
coverings in common with the testis. The structures mentioned come together to
form the cord at the internal or deep abdominal ring, and, extending through the
abdominal wall obliquely downwards and towards the middle line, escape at the
superficial or external abdominal ring, whence the cord descends over the front of
the pubis into the scrotum.

The inguinal canal. — By the term inguinal canal is understood the space
occupied by the spermatic cord as it passes through the abdominal wall. It extends
from the deep to the superficial abdominal ring, and is about an inch and a half in
length. In the upper part of this course the cord has the fascia transversalis behind
it, and is covered in front by the lower fibres of the internal oblique and transversalis
muscles ; lower down it lies in front of the conjoined tendon of these muscles, the
fibres of which have arched inwards over it, and its cremasteric covering is in contact
anteriorly with the aponeurosis of the external oblique muscle. The inguinal canal
is therefore said to be bounded posteriorly by the fascia transversalis above and the
conjoined tendon below, and anteriorly by fibres of the transversalis and internal
oblique muscles above, and the aponeurosis of the external oblique muscle below ;
while its floor is formed by the curving backwards of Poupart's hgament, and its
roof by the apposition of the layers of the abdominal wall and the arched fibres of
the internal oblique and transversahs muscles.

As it enters the inguinal canal, the cord receives a covering from the infundibuli-
form fascia, a thin layer continuous with the fascia transversalis, and prolonged
down from the margin of the deep abdominal ring ; within the canal it receives a
covering from the cremaster muscle and its layer of fascia ; and as it emerges from
the canal there is added superficially to this, the intercolumnar fascia prolonged
from the margin of the superficial abdominal ring.

THE SCROTUM AND SPERMATIC CORD. 219

The scrotum. — The scrotum forms a purse-like investment for the testes and
part of the spermatic cords. Its condition is liable to some variation according to
the state of the health and other circumstances ; thus it is short and corru^uated in
robust persons and under the effects of cold, but becomes loose and pendulous in
persons of weak constitution, and under the relaxing influence of heat. A superficial
division into two lateral halves is marked by a slight median ridge, named the
raphe, extending forwards to the under side of the penis, and backwards along the
perineum to the margin of the anus.

The coverings of the cord and testis in the scrotum may be enumerated
from without inwards as follows, viz., the slcin, and the darios iissiie, the
tntercolumnar fascia, the cremaster muscle and fascia, and the infundibuliform fascia,
which is united to the cord by a layer of loose areolar tissue ; lastly, the special
serous membrane of the testis named the tunica vaginalis, which forms a close
sac, of which one part lines the scrotum and the other closely envelopes the
testis.

1. The skin of the scrotum is very thin, and is of a darker colour than that of
the body generally ; it is commonly thrown into rugje or folds, which are more or
less distinct according to the circumstances already mentioned. It is furnished
with sebaceous follicles, the secretion from which has a peculiar odour, and it is
covered over with thinly scattered curled and flattened hairs, the bulbs of which
may be seen or felt i:hrough the skin when the scrotum is stretched. The superficial
blood-vessels are also readily distinguished through this thin integument.

2. Immediately beneath the sldn of the scrotum there is found a thin layer of a
peculiar loose reddish-brown tissue, endowed with contractility, and named the
dartos tunic. This subcutaneous layer is continuous with the superficial fascia of
the groin, perineum, and inner side of the thighs, but assumes a ditJerent structure,
and is entirely free from fat. The dartoid tissue, which is more abundant on the
fore part of the scrotum than behind, forms two distinct sacs, for the corresponding
testes, united together along the middle line so as to establish a median partition
named the septum scroti, which is adherent below to the deep surface of the raphe.
and reaches upwards to the root of the penis. The dartos is very vascular, and
owes its contractile properties to the presence of a considerable amount of unstripcd
muscular tissue (Kolliker).

3. The intercolumnar or spermatic fascia, a very thin and transparent but
relatively firm layer derived from the tendon of the external oblique muscle of the
abdomen, is attached above to the margins of the external ring, and is prolonged
downwards upon the cord and testis. It lies at first beneath the superficial fascia,
and lower down beneath the dartos, and it is intimately connected with the layer
next mentioned.

4. The cremasteric layer is composed of scattered bundles of striped muscular
fibres, connected together into a continuous covering by intermediate areolar
membrane. The red muscular portion, which is continuous with the lower border
of the internal oblique muscle of the abdomen, constitutes the cremaster muscte, and
the entire covering is named the cremasteric fascia. By the action of the cremaster
the cord is shortened and the testicle is raised towards the abdomen.

5. The infundibuliform fascia, continuous above with W\q fascia transversalis
and situated immediately beneath the cremasteric fascia, invests the cord completely,
and is connected below with the posterior part of the testicle and the outer surface
of its serous tunic. On forcing air beneath the infundibuliform fascia, a quantity
of loose and delicate areolar tissue is seen to connect its deep surface with the vas
deferens and spermatic blood-vessels, and to form lamellne between them. This
areolar tissue is continuous above with the subserous areolar tissue found beneath
the peritoneum on the anterior wall of the abdomen ; below, it is lost upon tlie back

220 MALE REPRODUCTIVE ORGANS.

of the testicle. Together with the infandibuliform fascia, it forms the fascia propria
of Astley Cooper.

Lying amongst this loose areolar tissue, in front of the upper end of the cord, there is often
seen a fibrous band, which is connected above with the pouch of peritoneum found opposite
the upper end of the inguinal canal, and which passes downwards for a variable distance
along the spermatic cord. Occasionally it may be followed as a fine cord, as far as the upper
end of the tunica vaginalis ; sometimes no trace of it can be detected. It is the vestige of a
tubular process of the peritoneum, which in the foetus connects the tunica vaginalis with the
general peritoneal membrane. The testicle is placed within the abdomen during the greater
part of foetal life ; but at a period considerably pi-ior to its escape from the abdominal cavity,
a pouch of peritoneum already extends down into the scrotum. Into this pouch, or processus
raginalis 2}fi'itoncBi, the testicle projects from behind, supported by a duplicature of the serous
membrane, named the intsorcJtium. Sooner or later after the gland has descended into the
scrotum, the upper part or neck of this pouch becomes contracted and finally obliterated, from
tlie internal abdominal ring down nearly to the testicle, leaving no trace but the indistinct
fibrous cord already described, while the lower part remains as a closed serous sac surrounding
the testicle, and which is thence named the tunica vaginalis.

In the female foetus an analogous pouch of peritoneum descends for a short distance along
the lound ligament of the uterus, and has received the appellation of the canal of NucTi. Of
this traces may almost always be seen in the adult.

The neck of the processus vaginalis sometimes becomes closed at intervals only, leaving a
series of sacculi along the front of the cord ; or a long pouch may continue open at the upper
end, leading from the abdominal cavity into the inguinal cansJ. In other instances, the
peritoneal process remains altogether pervious, and the cavity of the tunica vaginalis is thus
made continuous with that of the laeritoneum. In such a case of congenital defect, a portion
of intestine or omentum may descend from the abdomen into the inguinal canal and scrotam,
and constitute what is named a congenital hernia. Lastly, one or both testes may remain
permanently within the abdomen, or their descent may be delayed till after puberty, when it
may occasion serious disturbance. Retention of the testes in the abdomen (cryptorchismus)
is, in many instances, the accomiianiment of arrested development of the glandular structure ;
it is, however, a peculiarity which may be present without impotence.

In a few mammals, as the elephant, the testes remain permanently within the abdomen ;
in a much larger number, as the rodentia, they only descend at each period of rut. The
complete closure of the tunica vaginalis is peculiar to man, and may be considered as connected
with his adaptation to the erect posture.

6. The tunica vaginalis. — This tunic forms a shut sac, of which the opposite
free surfaces are in contact with each other. Like the serous membranes in general,
of which it presents one of the simplest forms, it may be described as consisting of
a visceral and a pa7ietal portion. The visceral portion, tunica vaginalis testis, closely
invests the greater part of the body of the testis, as well as the epididymis, between
which parts it is depressed in the form of a pouch (digital fossa), and lines their
contiguous surfaces, and it adheres intimately to the proper fibrous tunic of the
gland. Along the posterior border of the gland, where the vessels and ducts enter
or pass out, the serous coat, having been reflected, is w^anting. This portion of the
serous covering frequently presents villous prolongations on the borders of the
epididymis and upper end of the testis ; these processes, sometimes of considerable
length, are covered in some places with cylindrical, in others with layers of flat
epithelium.

The parietal or scrotal portion of the tunica vaginalis is more extensive than
that which covers the body of the testis ; it reaches upwards, sometimes for a
considerable distance, upon the spermatic cord, extending somewhat higher on the
inner than on the outer side. It also reaches downwards below the testicle, which,
therefore, appears to be suspended at the back of the serous sac, when this latter is
distended with fluid ; a fold, or so-called ligament, being left projecting at the lower
end of the epididymis (fig. 235,/).

Vessels and nerves of the scrotum and spermatic cord. — The arteries
are derived from several sources. The two external pudic arteries, branches of
the femoral, reach the front and sides of the scrotum, supplying the integument and

THE TESTICLES.

2'Zl

Jartus ; the superficial per inml branch of the internal pudic artery is distributed to
the back part of the scrotum ; aud, lastly, more deeply seated than either of these
is a branch given from the epigastric artery, named cremasteric, which is chiefly
distributed to the cremaster muscle, but also supplies small branches to the other
coverings of the cord, and by its ultimate divisions anastomoses with the other
vessels. The artery of the vas deferens, a long slender vessel derived from the
superior or inferior vesical, accompauies the tube in its whole length. The veins
accompany the arteries. The veins of tlie cord form the spermatic or pampiniform
plexus elsewhere described. The lymphatics of the scrotum pass into the inguinal
lymphatic glands.

The nervea also proceed from various sources. The ilio-infjuinal, a branch
of the lumbar plexus issuing by the external abdominal ring, supplies the iutega-
ment-s of the scrotum ; this nerve is joined also by a filament from the ilio-
hypoiiastric branch of the same plexus : sometimes two separate cutaneous nerves
come forward through the external ring. The two superficial perineal branches of
the pudic nerve accompany the artery of the same name and supply the inferior and
posterior parts of the scrotum. The inferior pmJemlal, a branch of the small sciatic
nerve, joins with the perineal nerves, and with them is distributed to the sides and
lower part of the scrotum. Lastly, the genital branch of the (/enito-crurcd nerve,
reaching the spermatic cord at the internal abdominal ring, passes with it through
the inguinal canal, and supplies the fibres of the cremaster muscle, besides sending
a few filaments to the other deep coverings of the cord and testicle.

THE TESTICLES.

The testicles, the principal reproductive glands (S.'Su/xos, opx^), are suspended
obliquely in the scrotum by means of the cord and membranes already described ;

Fig. 235. — The left tunica vaginalis opened, showino

THE TESTIS, EPIDIDYMIS, &C., FROM THE OUTER SIDK

(Allen Thomson. )

p, p, cut edges of the parietal layer of the tunica vagi-
nalis drawn aside ; t, body of the testis ; e, e', epididymis ;
/, a fold of the tunica vaginalis passing from the body of the
testis to the side. In the upper part of the figure the tunica
vaginalis has been dissected off at the place of its rertectiou
on the cord to show v d, the vas deferens, and g, the organ
i)f Girald^s ; (i,the three small nodules of this organ enlargetl
about ten times, and showing the remains of tubular struc-
ture within them ; h, hydatid of Morgagni, or appendix of
the testicl'i.

they are usually placed at unequal heights, that
of the left side being lower than the other.
They are of an ovoid form, but are slightly
compressed laterally, so that they have two
Homewhat flattened sides or faces, an upper and
a lower end, an anterior and a posterior border.
They are about an inch and a half (37 mm.)
long, an inch and a quarter (28 mm.) wide from
back to front, and nearly an inch (24 mm.)
thick from side to side. The weight of each
varies from three-quarters of an ounce to an
ounce do to 24*.5 grammes, W. Krause).

The front and sides of the testiw, together
with the upper and the lower ends, are free, smooth, and closely invested l»y
tunica vaginalis. 'J'he posterior border is attached to the spermatic cord, and

the
it is

222 MALE REPHODUCTIVE ORGANS.

here that the vessels and nerves enter or pass out. When the testis is suspended in
its usual position, its upper end is directed obliquely forwards and outwards, as well
as upwards, whilst the lower, which is rather smaller, has the opposite direction.
It follows from this that the posterior or attached border is turned upwards and
inwards, and the outer flattened face slightly backwards.

Attached to the posterior border of the gland, and resting also on the neighbour-
ing portion of its outer face, is a long narrow body, the epididymis, which forms part
of the excretory apparatus of the testicle, and is principally composed of the
convolutions of a long tortuous canal or efferent duct, to be presently described. Its
upper extremity, larger than the lower, projects forwards on the upper end of the
testis, and is named the head or globus major (fig. 235, e) ; the lower, which is more
pointed, is termed the tail or globus minor {e') ; whilst the intervening portion is
named the body. The convex surface of the epididymis and the thin anterior border
are free, and covered by the tunica vaginalis. The concave surface, or that directed
towards the testis, is also free, except at the upper and lower ends, and invested by
the same tunic, which here forms a pouch between the epididymis and the outer face
of the testicle, and nearly surrounds the epididymis, except along its posterior
border, which is united to the gland by a duplicature of the serous membrane,
containing numerous blood-vessels. At its upper and lower extremity, the
epididymis is attached to the testis by fibrous tissue and a reflection of the tunica
vaginalis, the globus major also by the efferent ducts of the testis.

At the back of the testis and epididymis, beneath the fascia propria, opposite
the lower two-thirds of the testis, is a considerable amount of unstriped muscular
tissue, the inner muscular tunic of Kolliker.

On the front of the globus major, somewhat to the outer side, there are usually
found one or more small pedunculated bodies covered by an extension of the tunica
vaginalis and formed mainly by connective tissue and blood-vessels. These are the
hydatids of Morgagni. They are commonly regarded as remains of part of the foetal
structure termed Miiller's duct. One of them, of a more regularly pyriform shape,
and more constant than the rest, lies closely between the head of the epididymis and
the testis.

This has been thought, but as it would appear on insufficient evidence, to be the homologue
of the ovary in the male sex (Fleischl, Kiause). Its surface is ciliated, and a canal lined by
ciliated epithelium and opening into the cavity of the tunica vaginalis is sometimes contained
within it.

STRUOTUEE OF THE a?ESTIS.

The testis is enclosed in a strong capsule, the tunica albugiuea. This is a
dense unyielding fibrous membrane, of a white colour, and of considerable thickness,
which immediately invests the soft substance of the testis, and preserves the form of
the gland. It is composed of bundles of fibrous tissue, which interlace in every
direction. The outer surface is covered by the tunica vaginalis, except along the
posterior border of the testis, where the spermatic vessels pass through and the
two extremities of the epididymis are attached.

In the interior, the fibrous tissue of the tunica albuginea is prolonged from the
posterior border for a short distance into the substance of the gland, so as to form
within it an incomplete vertical septum, known as the cor^pus Highmori, and named
by Astley Cooper mediastinum testis. It extends from the upper nearly to the
lower end of the gland, and it is wider above than below. The firm tissue of which
it is composed is traversed by a network of seminal ducts, and by the larger blood-
vessels of the gland, which are lodged in channels formed in the fibrous tissue.

From the front and sides of the corpus Highmori numerous slender fibrous

THE TESTICLE.

223

cords and imperfect septa of connective tissue are given off in radiating directions
and are attached by their outer ends to tlie internal surface of the tunica albuo-inea

Fig. 236. — TR.ixsvERSE section through the right testicle and the tunica vaginalis.
(Modified from KoUiker. )

fi, seminiferous tubes, converging at b, to the mediastinum ; c, rete testis ; d, vasa efferentia ;
(, epididymis ; /(, section of vas deferen.s ; t, tunica albuginea, sending septa into the body of the
testis ; c.v., cavity of tunica vaginalis.

at different points, thus incompletely dividing the glandular substance int(j lobules.
According to Kolliker, plain muscular fibres are prolonged upon these septula.
The whole internal surface of the tunica albuginea is covered by a multitude of

Fig. 237. — Plan of a vertical .section ok the testicle, snowiNa tiie arrangement oir the uucts.

The true length ami diameter of the ducts have been disregarded in this as well as in the preceding
figure, a, a, tubuli seminiferi coiled up in the separate lobes ; Ij, vjisa recta ; c, rete vascuiosum ;
>l, va«a efferentia ending in the coni vasculosi ; e, /, '/, convoliiteil canal of the epididymis ; h, van deferens;
t, i, section of the back jart of the tunica albuginea with fibrous processes running between the lobes.

fine blood-vessels, wliioh are branches of the spermatic artery and veins, and are
held together by a delicate areolar web. Similar delicate ramifications of vessels

224

MALE KFPRODUCTIVE ORGANS.

are seen on the various fibrous offsets of the mediastinum, upon which the blood-
vessels are thus supported in the interior of the gland. This vascular network,
together with its connecting areolar tissue, constitutes the tumca vasculosa of

Astley Cooper. . , . , .

Seminiferous tubules. — The glandular substance of the testis which is
included in the fibrous framework formed by the albuginea, the mediastinum, and
the trabeculge, is a mass of convoluted tubules known as the tubuli seminiferi,
which are somewhat loosely connected together by areolar tissue into the lobes or
lobules above mentioned. Of these lobes there are some 100 to 200 (Krause) or more ;
they are of unequal size, the middle ones being the larger, and are imperfectly

lohuli testis

ry^- 'caput epididymis

-^ — rete testis
epididymis

tubuli recti

vas deferens

Fig. 238. — Section through the testis and epididymis. (Bohm and v. DavidofF.)

separated from one another, the septa being incomplete. In each lobe are two,
three, or more seminiferous tubules closely convoluted, and here and there branched,
especially at their anterior or distal extremity, where, in a cortical zone near the
albuginea, they are stated to communicate frequently laterally with one another.
It is not difficult to unravel the tubules for some distance, for their walls are
moderately strong, and their diameter (0*2 mm.) large compared with those of other
tubular glands, such as the kidney. Their length is estimated to be on an average
rather greater than two feet (60 cm.) and their number between 800 and 90O
(Lauth). They have a smooth contour, but this is interrupted at intervals by
small bulgings, which are more numerous near the commencement of a tubule than
near its termination. The walls of the seminiferous tubules are composed of several
layers of flattened cells. Of these only the innermost layer is complete, being
formed of epithelioid cells closely united edge to edge into a basement membrane.
This is strengthened by the other layers, which, however, exhibit intervals between
the flattened cells which compose them, these intervals becoming very marked in
the outermost layers. In consequence of their being thus formed of several layers,
the walls of the tubules have a concentrically striated appearance in cross-section.

THE TESTICLE.

225

The tubules are occupied by an epithelium which consists of several irregular
layers of cells, amongst which the semuuil filaments or spermatozoa may be observed
in different stages of development (%. 239). In different tubules of the same testis
and even in parts of the same tubale the condition of development of the spermatozoa
may be very various, and the epithelium presents corresponding differences both in
the number of its layers and the appearance of the cells.

Fig. 239. — Section of parts of three seminifeuous tubules of the rat. (E. A. S., from a
preparation by Mr. A. Fraser.) Magnified.
«, with the spermatozoa least advanced in development ; b, more advanced ; c, containing fully
rleveloped spermatozoa. Between the tubules are seen strands of interstitial cells with blood-vessels
and lymph-spaces.

Structure of the spermatozoa. — A spermatozoon is a minute filiform particle

about 0"05.!i mm. long, consisting of three parts : a micleiis or Jwid, a middle piern

or bodij, and a s|iontaneously vibratile tail. In man the head is of a flattened oval

t
Fig. 2411. — Human spermatozoa (Retzius).

], in profile, the tail not represented ; 2, viewed on the flat ; h, head ; c, middle-
piece ; d, tail ; c, end-piece of the tail.

shape, appearing pointed when seen in profile and with a depression on
each flattened surface. A minute bar])-like projection has been described
at its extremity (T)owdeswell) ; this is however much more apparent in d

some animaLs. The head stains intensely with nuclear djes, and is
mainly formed of chromatin (nuclein). It is about (/•004r) mm. long,
<f()02.j mm. broad, and 0"0015 mm. thick. In certain animals it is
invested with a clear mantle termed the head-cap (Schweigger-Seidel),
but this is not easily apparent in man in the completed stage. The
hea^l also varies greatly in other respects in different animals, its shape
and siz'! beiriL'" charactei'istic for each species.

The middle piece oi- body of the spermatozoon is nearly cylindrical
in man. It is about O'OOf; mm. long and less than O'OOl mm. in
diameter. It is difficult to make out any structure in it in man, but in some
animals (mouse, rat), a spiral thread can be seen closely coiled around its
periphery, whilst through its centre a filament passes which appears to be a
prolongation of a central filament within the tail and which cuds close under
the ba«e of the nucleus or head in a globular enlargement known as the tvimbial
(jlobule or fjlobuloid body.

VOL. III., IT. 4. Q

226 MALE EEPEODCCTIVE ORGANS.

The tail is about 0'045 mm, long, and finer than the middle piece. It tapers
towards the extremity. Near its termination it becomes abruptly finer and its
terminal sixth {end-piece of Retzius) is an extremely delicate fibre, which under
certain circumstances can be seen to be composed of three or more of the finest
possible fibrils. This end-piece is apparently a direct combination of the central
filament of the tail, which is elsewhere invested by a sheath, but is here bare. The
distinction between sheath and central filament cannot be made out in the human
spermatozoon. In some animals (newt) an undulating membrane with a fine fibre
running along its free margin is attached spirally by one border along the whole
length of the tail (Leydig) : a similar membrane has been described in man
(Gibbes, "W. Krause, v. Bardeleben). The motion of the spermatozoon is a forward
one produced by a spirally lashing movement of the tail, similar to the movements

fibrils of axial filament fibrils of marginal fi,la7nent

point of head .

fibril of axial filament

marginal fibril. . . .f4 -7l^^#^ ..._ end piece of tail

enlargement of axial
filament in head
{globidoid body) .

body

marginal fibril .
axial fibres ....
undulatory membrane

~ I _ membrane of tail

Fig. 241. — Diagram of a Spermatozoon. (Bolim and v. DavidolF. ) All the parts here shown have
not been made out in the human speimatozoon.

of the cilia of zoospores of bacilli. It may last under favourable conditions for
several days after discharge (4 to 9 days, Piersoll).

Several varieties of human spermatozoa have been described, differing from one another
chiefly in size. Some are occasionally found which are very much larger than usual
("07.5 mm. long and 'OO.o.o mm. broad). According to the observations of K. v. Bardeleben
(Verhandl. d. Anat. Gesellsch., 1891), founded partly on his own preparations, partly on those
of E. M. Nelson, the head of the human spermatozoon consists of several portions, viz., spear,
head-cap, and a main part divided into anterior and posterior portions. The .yjcar, the
existence of which appears to be rather doubtful, is described as an immeasurably fine process
unsymmetrically placed, which may be twice as long as the head. Its tip is recurved and
hooklike. At its base is an elongated particle staining more deeply than the rest. The
7tead-caj) is clear and very delicate. The anterior 2^art of the head is clear, the 'posterior
part cross striated. A protoplasmic fringe extends from the anterior part to the body of the
spermatozoon. Within the head is a clear refractive particle {(ilohvlohl), not staining with
ordinary dyes. A short neck unites the head to the body or middle 2nece of the spermatozoon.
Both this and the tail (except the end-piece of Retzius) have a frilled membrane along one
side: the tail has a special membrane on the opposite side. The tail contains a central
filament which extends through the body and head and may be traced even into the spear.

Structure of the epithelium of the seminiferous tubules. — Of the cells
forming the epithelium of the seminiferous tubules, there are, in most tubules, three
several kinds, differing in situation, in size, and in structure. Those of the first
kind, which are termed the ouier or liiimg cells (.'<permafoffonia) form the outermost
zone. They are cubical or somewhat flattened cells disposed in a single regular
layer next to the basement membrane of the tubule. In some tubules one of these
cells may here and there be seen to be elongated and to project between the cells
of the next zone, where it comes into connection with a group of developing
spermatozoa. Indications of kaiyokinetic division are also met with in the cells
of this layer in certain tubules (fig. 212, 6). In the early foetal condition the

THE TESTICLE.

227

spermatogonia are the only cells found in the tubule. The ceils of the next zone
become formed from them by karyokinetic division.

The cells of the second kind, intermediate or spermafoqenk cpUs (sperm afocysfs of
some authors), form a middle or intermediate zone in the tubules. They nrc laro-e
clear cells with conspicuous nuclei, the latter invariably exhibiting some stage of
karyokinesis. They lie one, two or more deep, varyiug in different tubules according
to the condition of development of the spermatozoa, and the thickness of the layer
they form varies accordingly. AVhen two or more deep, the groups of developing
spermatozoa and the elongated spermatogonia with which the groups are connected
penetrate between tiiem and tend somewhat to break the continuity of the layer.

Fig. 242. — Diagram exhibiting the cycle of phases of spermatogenesis in the rat. (E. A. S.)

(This diagram is cliiefly founded upon the drawings of H. II. Brown.)

a, lining epithelium cells, seen dividing in 6 ; a', sustentacular cells ; b, spermatogenic or mother-
cells, with skein-like nuclear filaments : there cells are seen activel}' dividing in ;> ; c, sjiermatoblasts,
forming an irregular column or clump in 6, 7, 8, and 1, and connected to sustentacular cell, a', in
2, .3, 4, and !j. in 6, 7, and 8 advanced spermatozoa of one croj) are seen between columns of spermato-
Jflasts of the next crop, s', parts of the spermatoblasts which disappear when the sjiermatozoa arc fully
formed ; s, seminal granules, probably resulting from the disintegration of s' ; a", in 1 and 'J. are
nuclei of su.stentacular cells, which are probably becoming extruded.

These spermatogenic cells, which are originally derived from the spermatogonia,
themselves give origin by two or more stages of karyokinetic division to the cells of
the next layer or spermatoblasts, but some of the cells resulting from the first
division are not converted into spermatoblasts. These remain as a layer of sperma-
togenic cells, ready in due time to produce by further division the next crop of
spermatoblasts.'

The third kind of cell in the seminiferous tubule is the spermatoblast. The
spermalofj/asts (xpermafids of some authors) are derived as just stated from division
of the spermatogens or sperraatocysts, and on the other hand are directly trans-

' According to Brown all the spermatogenic cells or Hpcrmatocysts are converted, after division,
into si>ermatobla«tH, and fresh Kpermatocysts are jiroduccd for the next crop of siiermatoblustH by
4iTiBiou of Home of the lining cella or spermatogonia.

o 2

228 MALE EEPRODUCTIVE ORGANS.

formed into spermatozoa: hence they were termed by H. H. Brown, yow^g spcrmalozon.
They form in most tubules an innermost zone of small closely packed grannlar-
looking and ill-defined cells, which appear blended into a continuous mass (fig. 239, c) -,
they are, however, not so blended, but are quite discontinuous. Their nuclei are
small and do not stain deeply with reagents : they show no signs of proliferation.
In some tubules these cells are already becoming elongated (fig. 239, a), and in the
various tubules of the same testis every stage of transformation is met with between
them and the fully developed spermatozoa. As this transformation proceeds they
are seen to collect into definite groups (fig. 239, b) which penetrate between the cells
of the intermediate layer, and become connected with and imbedded in cells of the
outer layer {susteniacular cells) which elongate to receive them (fig. 242). These
snstentacular cells in all probability subserve a nutritive function for the developing
spermatozoa. When the development is approaching completion the group of
spermatozoa moves again towards the middle of the tubule, the connection with the
ouier layer becoming gradually longer and more attenuated until finally the heads
of the fully developed spermatozoa form a complete zone next to the lumen of the
tubnle, into which their tails project, being bent sharply round and extending for a
short distance along the course of the tubule (fig. 239, c ; 242, 1, a).

"While this gradual transformation of spermatoblasts into spermatozoa is going
on in a tubule, a fresh crop of spermatoblasts is being formed in the same tubule to
take the place of those thus transformed. This crop is formed as before by
proliferation of the spermatogenic cells which have remained next to the lining
layer,^ and hence it happens that in the same tubule at least two phases of develop-
ment of spermatozoa or of spermatoblasts are constantly to be seen. But after the
complecion of one crop of spermatozoa, the spermatoblasts, which are to become
transfoi'med into the next crop, remain quiescent until the first crop has been dis-
charged. The spermatogenic cells divide at first each into two, and thus form a
first generation. This division takes place by what is termed by Flemming the
" heterotypical form " of karyokinesis, the split chromosomes long remaining con-
nected at their ends, and the stage of metakinesis being greatly prolonged. During
the dyaster phase a second longitudinal splitting occurs, and the daughter-nuclei
again divide immediately, without entering into a resting condition, and without a
further splitting of the chromosomes, to form the nuclei of the ceils of the third
generation. The cells of this third generation have, therefore, only half the
typical number of chromosomes in their nuclei, and these are the cells which become
transformed into spermatoblasts. In the final division, therefore, it appears that
the number of chromosomes, or chromatic segments of the nucleus, becomes, by
failure of the usual longitudinal cleavage, reduced to one half the number usual in
the cells of the particular species of animal under observation. The resulting
nuclei, therefore, of the spermatoblasts resemble, in this respect, the nucleus of the
ovum after extrusion of the second polar globule, and it is only on the conjunction
of the two within the fertilized ovum that the typical number of chromosomes is
re-established.

The process of reduction of chromosomes in the final division of the spermatic cells was
first shown by 0. Hertwig to occur in Ascaris, and it has since been established for the
salamander (by Flemming) and some other animals. It has been thought to be of general
occurrence, but this cannot as yet be regarded as conclusively proved, especially in mammals,
in which the observation of the number and changes of the chromosomes is extremely difficult.

Transformation of the spermatoblasts into spermatozoa. — The fully
formed spermatoblasts, or spermatids, are small, granular cells, with round nuclei.

^ Or which have been formed by a new karyokinetic division of the spermatogonia (see note od
previous page).

THE TESTICLE.

229

lu developing into spermatozoa, these become elongated. The nucleus alters in
shape and passes towards one end of the cell, where it forms the head of the
spermatozoon. Within the protoplasm a filament begins to form, soon growing out
beyond the rest of the cell as the tail. The protoplasm of the ceil pai'tly remains to
form the body or middle piece ; partly becomes detached and disintegnited, as the
maturation of the spermatozoon is completed.

CItanjvs in the tiucleus. — The nucleus of the spermatoblast is at first spherical.

Fig. '243. Phases of transformation of a

SPERMATOBLAST OU SPERMATID INTO A SI'ER-

ATOZOON IN TUE RAT. (H. H. Urown. )

with a somewhat faint outline. It
shows the usual network of a resting
nucleus, but has comparatively little
tendency to stain with dyes (poor in
chromatin). As development proceeds
it becomes at first oval, then conical,
then greatly elongated and compressed,
so that no structure can be seen within
it. In the meantime its chromatin
becomes increased, and finally forms a
dense mass, which gradually takes on

the shape and position of the head of the future spermatozoon.
f'ha/ijcs ill fhv proiopJasnt. — AY i thin the body of the
nucleus various structures can be made out (Moore), viz.

cell but near the
the archoplasm,

clear or nearly clear portion of the protoplasm (which muy contain a vacuole).

I'i^'. "244. — Folk stares in the Iievklop-

MEST ok SPEKMATOBLASrs OR SPERMATIDS

INTO SPERMATOZOA (Lenliossek).

The tail filaraeut is seen to be counected
with the (double) ceiitrosonie ot the spermatid,

the so-called cJiromatic bodij, a small

mass of darkly staining material

close to the nucleus and probably a

detached portion of its chromoplasm,

and the centrosomc, which is usually

double (fig. 244, a, h). As the nucleus

passes towards the inner end of the

cell, with its pointed end projecting

Ijeyond the general circumference,

and the base directed towards the

centre of the cell, the body of the cell

becomes elongated, assuming first an

oval and then a pear shape, witli

the nucleus emVjcdded in the smaller

end of the pear. In connec^tion

with tlie centroKome, a thread —

axial Jilamcnt — begins to appear

in the protoplasm, and is soon seen to emerge from the (ipposite or larger end

of the pear-8hap(;d cell, the protoplasm ot which is [irobabiy continued over it.

330 MALE REPRODUCTIVE ORGANS.

This filament is the rudiment of the " tail," and g-radnally elongates. It is not clear
how the head-cap is formed, but probably from nucleoplasm, this being perhaps
itself covered by clear protoplasm. The spermatozoon is now developed, but the
middle piece is still large and pyritbrm, and its peripheral portion forms a projection
which partly encircles the tail (fig. 243). The projection in question disappears in
the further course of development, being partly absorbed into the rest of the middle
piece and into the tail, partly becoming detached and disintegrated. It contains
some deeply staining granules, which are found? mingled with the spermatozoa when
these are set free {spermatic granules).

Interstitial tissue of the testicle. — The tissue which connects the semi-
niferous tubules is in some respects peculiar. It consists of fine fasciculi and
laminae of areolar tissue, these being covered by and partly composed of fiattened
epithelioid cells. Between the laminge and fasciculi are large cleft-like spaces,
containing lymph, and almost everywhere enclosing the basement membrane of
the tubules. If these spaces are injected by the puncture-method, the injecting
fluid flows away by the lymphatics of the spermatic cord. It is found to penetrate
between the incomplete outer layers of the membrane of the tubules, but is arrested
by the innermost layer.

'i'he blood-vessels are conducted at first along the trabeculse, andfi'om these they
pass into the angular interstices between the tubules. Here they are supported by
the areolar tissue, and accompanied and often completely surrounded by tracts of
peculiar epithelium-like polyhedral cells somewhat like the cortical cells of the
suprarenal capsules, and, like these, often containing yellowish granules. They are
known as the interstitial cells of the testis, and have been regarded as specially
modified connective tissue cells (plasma-cells, Waldeyer), or as epithelial cells derived
from the Wolffian body (Klein), but until their development has been fully traced,
nothing certain with regard to their nature can be stated. In sections of the foetal
testis, the cells in question are noc distinguishable from the other cells of the develop-
ing intertubular connective tissue. Similar cells are met with in the stroma of the
ovary.

The capillaries form a close network over the walls of the seminiferous
tubules.

The nerves of the testis appear not to be provided with ganglia, as is the case
with most of the visceral nerves, nor have they been traced into the interioi" of thb
seminiferous tubules, but they ramify over the tubules and many are distributed
to the blood-vessels.

Ducts of the testis. — As the convoluted tubuli seminiferi approach the medi-
astinum testis they unite, as before said, with one another at acute angles into a
smaller number of tubes which have a less flexuous course, and at length become
nearly straight. Close to the mediastinum they taper into short, straight tubes
(tubuli recti), of smaller diameter than the seminiferous tubes, and differing from
them in the character of their epithelium (fig. 245). This, in the straight tubules,
is a single layer of flattened or cubical cells continuous with the outer or lining cells
of the seminiferous tubes. The basement membrane is also continued on to the
straight tubules.

The straight tubules open into a network of vessels which lies in the fore part of
the mediastinum, and was named by Haller, rete vasculosum testis (fig. 245, c).
'I'he tubes composing the rete have no proper walls, but are merely channels in the
fibrous stroma, fined by flattened epithelium. Their diameter is greater than that of
the tubuli recti. The secretion from the testis is accumulated in the rete testis, and
is conducted to the upper and back part of the testis, whence it is conveyed away
by h\\Q efferent tubules, or vasa efferentia. These are from twelve to fifteen, or

THE TESTICLE.

231

sometimes tv\-enty in number ; they perforate the tunica albuginea beneath the
globus major of the epididymis, of which they may be said to form a part, and in
the convoluted canal of which they ultimately terminate. On emer"-ino- from the
testis, these vasa efferentia are straight, but, becoming more convoluted as they
proceed towards the epididymis, they form a series of small conical masses, the
bases of which are turned in the same direction, and which are named coiii vasculosi

Fij. 245. — Passage of convolutkk seminiferous tubules into straight tubulks, and op these
INTO the rete testis. (Mihalkovics.)

fi, seminiferous tubules ; h, fibrous stroma continued from the mediastinum testis ; c, rete testis.

Fig. 24G. — Docts of the testicle ixjected with mercury. (From ILilier. )
a, body of the testicle ; b, tubuli in the interior of the gland ; r, rete vasculosum ; d, vasa
efTerentia terminating in the coni vasculosi ; e, f, ;/, convoluted canal of the epididymis ; A, vas
deferens a.scending from the globus minor of the epididymis.

(figs. 237, 240). They are about O'T) mm. in diameter. The large.st of the cones is
about 14 mm. long, and when unrolled, each i;? found to consist of a single coiled
duct, varying from 150 mm. to 200 mm. in length, and the diameter of which
gradually decreases from the testis to the epididymis (ITuschke). Opposite the
globus major these separate efferent vessels open, at intervals which, in the un-
ravelled tube, are found to be about 75 mm. in length, into a single canal or duct,
the intervening and snl).sf;r|U(;iit convolutions of which constitute the epididymis itself.
The canal of the epididymis (fig. 240, e,f,!j) is disposed in very numerous (ioils,
and extends from the globus major downwards to the globus minor or tail, where,
turning upwards, it is continued on as the van deferens. When its complicated
flexuosities are unrolled, it is found to be twenty feet CO or more metres) in
length. The smallest windings are supported and held together by fine areolar

232

MALE REPRODUCTIVE ORGANS.

tissue ; but, besides this, numerous incomplete, transverse, fibrous partitions arn
interposed between larger masses of the coils, which have been named the Johes of
the epididymis. The canal of the epididymis is, at its commencement, about,
0'4 mm. ia diameter, but diminishing as it proceeds towards the globus minor, it is
about 0'27 mm., after which it again increases in size, and becomes less deeply cou-
voluted as it approaches the vas deferens. Its coats, which are at first thin, become
thicker in its progress.

The vasa eflPerentia have a layer of circular muscular fibres, to which in the tube
of the epididymis is added an external longitudinal layer, both being relatively thin.

Fig. 247. — Injected testis, epididymis, and a'AS
DEFERENS. (From Kolliker, after Arnold. ) j.

a, body of tbe testicle ; b, lobules ; c, vasa recta ;
d, rate vasculosum ; e, vasa eff'erentia ; /, coni
vasculosi ; g, epididymis ; h, vas deferens ; i, vas
aberrans ; in, branches of the si3erniatic artery
passing to the testicle and eiDididymis ; n, ramitica-
tion in the testis ; o, arterj' of the vas deferens ;
2), its nninn with a twig of the spermatic artery.

The epithelial hning cells are columnar in
form, and are ciliated, the ciha being long,
and causing by their movement a current
towards the vas deferens. In the epidi-
dymis the cells are greatly elongated, in
the vasa efferentia they are shorter ; in
the lower part of the epididymis the cilia
disappear. Between the fixed ends of the
columnar cells other smaller cells are met
with.

The vas deferens (fig. 247, h), or
excretory duct of the testis, forms the con-
tinuation upwards of the convoluted canal
of the epididymis. It commences at the
lower end of the epididymis, and, at first rather tortuous but afterwards becoming
straight, it ascends upon the inner side of the epididymis, and along the back of the
testicle, separated from both, however, by the blood-vessels passing to and from the
gland. Continuing then to ascend in the spermatic cord, the vas deferens accom-
panies the spermatic artery, veins and nerves, as far as the internal abdominal ring.
Between the testicle and the external ring its course is nearly vertical : it lies
behind the spermatic vessels, and is readily distinguished by its hard cord-like feel.
It then passes obliquely upwards and outwards along the inguinal canal, and reach-
ing the inner border of the internal abdominal ring, it leaves the spermatic vessels
(which extend to the lumbar region), and turns suddenly downwards and inwards
into the pelvis, crossing over the external iliac vessels, and turning round the outer
or iliac side of the epigastric artery. Running beneath the peritoneum, it reaches
the side of the bladder (fig. 249), upon which it descends, curving backwards and
downwards to the hinder surface of that viscus, and finally passes forwards to the
base of the prostate gland. In its course within the pelvis, it crosses over the cord
of the obliterated hypogastric artery, and lies to the inner side of the ureter.
Beyond this point, where it ceases to be covered by the peritoneum, it is attached to
the coats of the bladder, in contact with the rectum, and gradually approaching its
fellow of the opposite side. Upon the base of the bladder, the vasa deferentia are
situated between two elongated receptacles, named the seminal vesicles (fig. 249, s.v.) ;
and, close to the base of the prostate, each vas deferens ends by joining with the

THE TESTICLE.

233

duct from tlie corresponding seminal vesicle on its outer side to form one of the
•common seminal or ejaculatory ducts (fig. 249, e.d,).

The vas deferens measures about a foot in length (300 mm.) ; but when
-extended and unravelled, about half as much again, or even more than this. In
the greater part of its extent it is cylindrical or slightly compressed, and has an
average diameter of about 2'5 mm., with a lumen of 0"7 mm. ; but towards its
termination, beneath the bladder, it becomes enlarged and sacculated, forming the
ampuUa of Henle, and resembling in sliape and structure a part of the seminal

248. — Section across the commencement of the

VAS DEFERENS. (Klein.)

a, epithelium ; h, mucous memljrane ; c, d, e.

inner, middle, and outer layers of the muscular coat ;

f, bundles of the internal cremaster muscles ; </,

section of a blood-vessel.

vesicle. Previously to its junction with the
duct of that vesicle, it again becomes
naiTOwed into a smaller and straight cylin-
•drical canal. The walls of the vas deferens
•are very dense and strong, and feel hard to
the touch, owing to the large proportiou
their thickness bears to the inner cavity of
the tube. In the sacculated portion the
passage is much wider, and the walls are
thinner in proportion. Small simple and
"branched tubular glands beset the mucous
membrane of this portion of the duct (Henle).

Besides an external areolar investment,
and an internal mucous membrane, the vas
deferens is provided with an intermediate
thick muscular tunic, of a deep yellowish
colour. This coat consists of two layers

of plain fibres, an outer of longitudinal and an inner of cii'cular fibres (fig. 248, d, e).
In addition, near the commencement of the tube is an internal longitudinal stratum,
extremely thin, and constituting not more than |th of the muscular coat (fig. 248, c);
in the ampulla, the inner longitudinal fibres are absent.

The lining membrane exhil)its on its surface three or four longitudinal ridges,
and, besides this, in the sacculated portion of the duct, it is marked by numerous finer
i-ugae which enclose irregular polylicdral spaces, resembling in this alveolar character
the lining membrane of the seminal vesicles. The epithelium is of the cohunnar
kind, and not ciliated. As in the epididymis, there is a deeper layer of small cells
between the columnar cells.

According to Steiner the epithelium may be ciliated in parts, or it may show a character
(•imilar to that of the ureter and bla<lder.

Vas aberrans.— This name was applied by Haller to a hm^ narrow tube, or diverticulum
ffig. 247, i), discovered by him, and almost invariably met with, which leads oif from the
lower part of the canal of the epididymis, or from the commencement of the vas deferens, and,
becoming tortuous and convoluted, is rolled up into an elongated mass which extends upwards
for an inch or more amongst the vessels of the si)ermatic cord, where the tuln; ends liy a
closed extremity. Its length, when it is unravelled, ranges from about two to twedve or
fourteen inches : and its width increases towards its blind extremity. Sometimes tliis
iliverticulum is branched, and occasionally there arc^ two or more such aberrant ducts. Its
structure ajipears to be similar U> that of the v!w deferens. Its origin is j)robal>ly connected
with the Wolllian duct of the f(i;tus, but the exact mode of its formation ami its ollice are
unknown. Luschka states tliat occasionally it docs not communicate with the canal of tlio
epididymis, but appears to be a simple serous cyst.

234

MALE EEPRODUCTIVE ORGANS,

Eoth has described other small blind vasa aberrantia lying along the epididymis and
connected with the rete testis.

Orgaji of Giraldes The small body thus named is situated in the front of the cord

immediately above the caput epididymis (see fig. 235, rj). It consists usually of several small
irregular masses containing convoluted tubules lined with columnar ciliated epithelium, and
is scarcely to be recognised until the surrounding connective tissue has been rendered
transparent by re-agents. It has also received the name of paracUdijnus (Waldeyer). Its
tubules appear to be vestiges of part of the Wolffian body.

The seminal vesicles are two membranous receptacles, situated, one on each
side, upon the base of the bladder, between it and the rectum. When distended, they
form two long- sacculated bodies, somewhat flattened on the side next the bladder, to

Fig. 249. ^Base of the male bladder,

THE prostate GLAND, THE ROOT OF
THE PENIS, &C. (J. S. )

b1, part of base covered by peri-
toneum, separated by a dotted line from
a triangular space left uncovered by that
membrane ; u, ureter ; s. v. , seminal
vesicle ; e. d. , ejaculatory duct ; p, pros-
tate ; M., membranous part of urethra ;
B, bulb ; c. s., corpus spongiosum ; c. o,.,
Cowpers gland.

which they are firmly attached, and
convex on their posterior surface ;
they are widened above and
narrow below (fig. 249, S. v.).
Their length is usually about two
inches (50 mm.), and the greatest
breadth about half an inch
(12'5 mm.); but they vary both in
size and shape in different indi-
viduals, and also on the two sides.
Their upper obtuse extremi-
ties are separated widely from
each other, but anteriorly they
converge so as to approach the
two vasa deferentia, which run
forwards to the prostate between
them. With the vasa deferentia
thus interposed, they occupy the
two diverging sides of the tri-
angular portion of the base of
the bladder, which lies upon the
rectum, and is bounded behind
by the line of reflexion of the
peritoneum at the extremity of
the recto-vesical pouch. The
seminal vesicles themselves also rest upon the rectum, but are separated from it by a
layer of the recto-vesical fascia, which attaches them to the base of the bladder.

The sacculated appearance of the seminal vesicles is owing to their peculiar
formation. Each consists of a tube somewhat coiled and repeatedly doubled on
itself, and invested by dense fibrous tissue. When unrolled, this tube is found to
be from four to six inches long, and about the width of a quill. Its upper
extremity is closed, so that it forms a long cul-de-sac ; but there are generally, if

THE SEMINAL VESICLES. 235

not always, several longer or shorter branches or diverticula connected with it, which
also end by closed extremitieb (fig. 249). Inferiorly the seminal vesicle becomes
straight and narrowed, and ends opposite the base of the prostate by uniting on its
inner side, at an acute angle, with the narrow termination of the corresponding vas
deferens to form a single canal, which is the common seminal or ejaculatory duct.

The vesiculae seminales receive branches from the inferior vesical and middle
Jucmorrlioidal arteries and veins. The nerves belong to the sympathetic system, and
come from the hypogastric plexus.

In structure, the seminal vesicles resemble very closely the adjoining sacculated
portions of the vasa defereutia. Besides an external investment, connected with the
recto-vesical fascia, and containing vessels of considerable size, lymphatics, and
gangliated nervous cords, they have a muscular coat and a mucous membrane. Tlif^
muscular layers are thin compared with those of the vas deferens, and consist
of two layers, an outer of longitudinal, and an inner of circular fibres. A
considerable amount of plain muscular tissue is found covering the posterior
surface and extending transversely between the two vesicles. There are also longi-
tudinal fibres traceable over the vesicles from those of the bladder (Ellis, Henle).
The mucous membrane is traversed by very many fine rugso, which form an alveolar
structure resembling that seen in the gall-bladder, but deeper and enclosing much
finer meshes. The epithelium of the vesicles is columnar with a deeper layer of
small polyhedral cells.

The ducts of the testis serve as receptacles or reservoirs for the semen, as is jjroved by a
microscopic examination of their contents ; but, this is not usually the case with the seminal
vesicles : it is probable that they secrete a peculiar fluid which is incorporated with the semen.

The common seminal or ejaculatory ducts, two in number (fig. 249, e.d.)^
are formed on each side by the junction of the narrowed extremities of the corre-
sponding vas deferens and vesicula seminalis, close to the base of the prostate gland.
From this point they run forwards and downwards, at the same time approaching
each other, and then pass side by side through the prostate between its middle and
two lateral lobes. After a course of nearly an inch, during which they become
gradually narrower, they end in the floor of the prostatic portion of the urethra by-
two small slit-like orifices placed on the verumontanum, one on each prominent
margin of the opening of the prostatic utricle (fig. 261, d). For a short distance
the ejaculatory ducts run in the substance of the walls of the utricle.

The coats of the common seminal duct, as compared with those of tlie vns
deferens and vesicula, are very thin. The muscular coat consists of an outer thin
circular and an inner longitudinal layer, the outer longitudinal fil)res blending
with the muscular tissue of the prostate. The strong areolar tunic almost
entirely disappears after the entrance of the ducts between the lobes of the prostate^
but muscular fibres may be traced into the prostatic portion. The mucous membrane
becomes gradually smoother as it passes into that of the urethra. Its epithelium is
like that in the seminal vesicles and vas deferens. According to Henle, the
muscular fibres of the duct as it passes through the prostate are separated from one
another by blood-vessels, and form the t,rabecula3 of a layer of cavernous tissue.

These ejaculatory ducts convey the fluid contained in the seminal vesicles and
vasa deferentia into the urethra. Their canal gradually narrows as they approach
their termination, where the diameter is reduced to 0*5 mm.

Vessels and nerves of the testis. — The testicle and its excretory a]>paratu&
rec.'ive blood-vessels and nerves from sources which are dilferent from those giving
the vascular and nervous supply to the coverings of those parts.

Arteries. — The Hpermatk artenj, or proper artery of the testicle, is a shinder and
remarkably long branch, which arises from the abdominal aorta, and passing dowi>

236 MALE REPEODUCTIVE ORGAKS.

the posterior abdominal wall reaches the spermatic cord, and descends along it to
the gland. In early foetal life its course is much shorter, as the testis is then situated
near the part of the aorta from which the artery arises. As the vessel approaches
the testicle, it gives off small branches to the epididymis, and then divides into others
which perforate the tunica albuginea at the back of the gland, and pass through the
corpus Highmori ; some spread out on the internal surface of the tunica albuginea,
whilst others run between the lobes of the testis, supported by the fibrous processes
of the mediastinum. The smallest branches ramify on the delicate membranous
septa between the lobes, before supplying the seminiferous tubes.

The vas deferens receives from one of the vesical arteries a long slender branch
which accompanies the duct, and hence is named the artery of the vas deferens. It
ramifies in the coats of the duct, and reaches as far as the testis, where it anasto-
moses with the spermatic artery.

Veins. — The spermatic veins commence in the testis and epididymis, passing out
at the posterior border, where they unite into larger vessels, which freely communi-
cate with each other as they ascend along the cord, and form \X\q pampiniform^ plexus.
Ultimately two or three veins follow the course of the spermatic artery into the
abdomen, where they unite into a single trunk [spermatio vein), that of the right
side opening into the inferior vena cava, and that of the left into the left renal vein.

Lymphatics. — The lymphatics accompany the spermatic vessels and terminate
in the lumbar lymphatic glands, which encircle the large blood-vessels in front of the
vertebral column. As previously stated, they begin from intercommunicating lymph
spaces which occupy the intervals between the tubuli seminiferi.

Nerves. — The nerves are derived from the sympathetic system. The sijermatic
plexus is a very delicate set of nervous filaments, which descend upon the spermatic
artery from the renal and aortic plexuses. Some additional filaments, which are
very minute, come from the hypogastric plexus, and accompany the artery of the
vas deferens.

THE PENIS.

The j)enis is composed principally of erectile tissue, arranged in three long
•somewhat cylindrical masses, which are enclosed in fibrous sheaths, and are united
together so as to form a three-sided prism which receives a covering from the
general integument. Of these masses, two, named corpora cavernosa penis, placed
side by side, form the principal part of the organ, whilst the other, situated beneath
the two preceding, surrounds the canal of the urethra, and is named corpus
■cavernosutn ureihrm or corpus spongiosum.

The penis is attached at its root to the symphysis of the pubes, and to the pubic
arch ; in front it ends in an enlargement named the glans, which is structurally
■similar to and continuous with the corpus spongiosum. The intermediate portion or
hody of the penis, owing to the manner in which its three component parts are
united together, has three somewhat flattened and grooved sides and three rounded
borders : the upper side is named the dorsum. The glans penis, Avhich is slightly
compressed above and below, has at its extremity a vertical fissure forming the
■external orifice of the urethra {meatus urinarius) ; its base, which is wider than the
body of the penis, is hollowed out to receive the narrowing extremities of the
corpora cavernosa ; its border is rounded and projecting, and is named the corona
glandis, behind which is a constriction of the penis named the cervix. The median
fold of integument connecting the glans below the urethral orifice to the inferior
border of the penis is named thQfrce?ium of theprepiuce.

The integument of the penis, which is continued from that of the pubes and
•scrotum, forms a simple investment as far as the neck of the glans. Here it
is doubled up in a loose fold, the prepuce ov fore- shin. The inner layer of this fold

THE PENIS.

237

is firmly attached behind the cervix ; and from thence the integument, becoming
closely adherent, is continued forwards over the corona and glans, as far as the
orifice of the urethra, where it meets with the mucous membrane of the urethra.

Fig, 2.0O.— Mki.ia.s skotioh of male i-klvih, i'KNIh, and scrotum. (J. S.) I
CO., cori,08 cavernoHun. ; s, corpus 8i>ongio«uni ; u, its bulb ; «, [art forming tho glann penis. For
the othtr IctU'ring, m.c p. 114,

288

MALE REPRODUCTIVE ORGANS.

Upon the body of the penis the skin is thin, free from fat, and, in the anterior
two-thirds of its length, from hairs also ; in these respects differing remarkably from

Fig. 251. — Transverse section passing

FKOM ABOVE UOWNWARDS AND BACK-
WARDS THROUGH PUBIC SYMPHYSIS,
ROOT OF PENIS, AND SKIN OF PERI-
NEUM. (J.S. ) \.

P.S., xjubic syniphjisis ; i.r., inferior
ramus of pubi.'s (the ramus of the ischium
and the ischial tuberosity are j)03terior
to the plane of this section) ; c.p. , crus
penis ; b, bulb of corpus spongiosum ;
I.e., ischio-cavernosus muscle ; B.C., bulbo-
cavernosus muscle ; p. v., superficial ijeri-
neal vessels and nerves ; s. of p., skin
of perineum ; d.v. , dorsal vein of penis
Avith an artery and a nerve on each side.

that on the pubes, which is thick,
covers a large cushion of fat, and,
after puberty, is beset with hairs :
the skin of the penis is moreover
very movable and distensible, and
is of a darker colour than the skin
generally. At the free margin
of the prepuce the integument
changes its character, and ap-
proaches that of a mucous mem-
brane, being red, thin, and moist.
Numerous sebaceous glands are
collected round the cervix of the penis and corona glandis ; they are named the
glands of Tyson, or glandulcB odoriferce, their secretion having a peculiar odour.

Upon the surface of the glans the integument again changes its character ;

Fig. 252. — Root op the penis attached to the rami op
THE PUBES AND ISCHIUM (from Kobelt). |.

a, a, ejaculator urinse muscle covering the bulb of
the spongy body of the urethra, with at e, poste-
riorly, a median notch ; b, h, anterior slips of the bulbo-
cavernosus muscle passing round the sides of the corpora
cavernosa ; c, c, crura of the penis, with an oval dila-
tation or bulb of the corpus cavernosum; d, d, ischio-
cavernosi or erectores penis muscles ; /, corpus spongiosum
uretliraj.

it contains no glands, but is beset with large
vascular and nervous papillae, and it adheres
most intimately and immovably to the spongy
tissue of the glans.

Beneath the skin, on the body of the penis,
the ordinary superficial fascia is very distinct ;
it is continuous with that of the groin, and
also with the dartos tissue of the scrotum.
Near the root of the organ there is a
dense band of fibro-elastic tissue, named the
suspensory ligament, lying amongst the fibres
of the superficial fascia ; it is triangular in
form ; its anterior border is free, its upper border is connected with the fore part
of the pubic symphysis, and below it runs down upon the dorsum of the penis.

THE PENIS.

2:39

The integnmeuts of the penis are supplied with blood by branches of the dorsal
artery of the jienis and external jnalic ; the veins join the dorsal and external pa die
reins. Their nerves are derived from the dorsal and internal saperjicial perineal
branches of the pialic nerves.

The corpora cavernosa form the principal part of the body of the penis. They
are two cylindrical bodies placed side by side, flattened on their median aspects,
and closely united and in part blended together along the middle line in the
anterior three-fourths of their length ; whilst at the back part, in contact with the
symphysis pubis, they separate from each other in the form of two bulging and then
tapering processes named crura, which, extending backwards, are attached to the
pubic and ischial rami, and are invested by the erectores penis or ischio-cavernosi
muscles. The enlarged portions at the root, named by Kobelt the hulhs of the corpora
cavernosa., attain a much greater proportionate development in some quadrupeds
than in man. Iii front, the corpora caveruosa are closely bound together into a

Fig. 2r>3. — Traxsverse section of the glans penis in a distended state, h an inch behind the

MEATUS. (J. S.)

1, glans peiiLs ; 2, prepuce ; 3, urethra ; A, frtenuiu of the prepuce.

Fig. 254. — TrANSVEKSE section ok the glans penis in a distended state, 5 of an inch BEHINIi

THE MEATUS. (J. S.)

1, glaus penis ; 2, prepuce ; 3, urethra ; 5, corpus spongiosum ; 6, corpus cavernosum.

Fig. 255. —Transverse section of the bodv of the pknis in the distended state (altered from

Henle).

The outer outline indicates the integument surrounding the deeper parts ; the erectile tissues of tlie
corpora cavernosa and the seirtum pectiniforme are shown in section ; u, placed on the section of the
spongj- body, below the urethra ; v, the single dorsal vein ; a, the dorsal artery, and n, the nerve of
oae side.

blunt conical extremity, which is covered by the glans penis and firmly connected
to its base by fibrous tissue.

The under surface of the united cavernous bodies is marked l)y a longitudinal
groove, in which is lodged the corpus spongiosum. Tiie upper or anterior surface
is also marked with a slight median groove in which the dorsal vein of the penis
is situated, and near the root is attached to the pubes by the suspensory ligament.

Structure. — The median septum between the two corpora cavernosa is thick
and complete near the root of the penis ; but further forward it becomes thinner,
and only imperfectly separates their cavities, for it exhibits, parti(;ularly towards
the anterior extremity, numerous clefts, extending from the dorsal to the urethral
edge, and admitting of a free communication between the erectile tissue of the two
fides. From the direction of these slits, the intermediate white portions of the
fieptum resemble somewhat the teeth of a comb, and hence the partition has received
the name of seplurn pectiniforme.

The external fibrous investment of the cavernous structure is white and dense,
from one to two millimetres thick, and very strong and elastic. It is composed
for the most part of longitudinal bundles of shining white fibres, with numerous
well-developed elastic fibres, enclosing the two corpora cavernosa in a common

240

MALE EEFEODUCTIVE ORGANS.

covering ; and internal to this, each corpus cavernosum is surrounded by a layer of
circular fibres, which enter into the formation of the septum.

From the interior of the fibrous envelope, and from the sides of the septum,,
numerous lamellae, bands, and cords, composed of fibrous elastic and plain muscular
tissue, and named trabecu/ce, pass inwards, and run through and across the cavity in

Fig. 256. -- Section of erectile'

TISSUE OF PENIS IN A NON-DIS-
TENDED CONDITION (Cadicit).

a, trabeculse of connective tissue
with many elastic fibres and bundles
of plain muscular tissue cut across (c) ;.
b, venous simces.

all directions, thus subdividing-

it into a multitude of inter-
stices, and giving the entire
structure a spongy character.

The trabeculse, whether
lamelliform or cord-like, are
larger and stronger near the
circumference than along the
centre of each cavernous body,
and they also become gradually
thicker towards the crura.
The interspaces, conversely,,
are larger in the middle than near the surface ; their long diameter is, in the latter
situation, placed transversely to that of the penis : and they become larger towards
the forepart of the penis. They are occupied by venous blood, being in reahty large

Fig. 257. — Portion of the erectile tissue.
OF the corpus cavernosum magnified,

SHOWING THE AREOLAR STRUCTURE AND-
THE VASCULAR DISTRIBUTION (frOm J.

Miiller).

a, a small artery supported by the larger
trabeculcB, and branching oiit on all sides ;
c, the tendril-like arterial tufts or helicine
arteries of Miiller ; d, the areolar structure
formed by the finer trabeculse.

cavernous veins, and are lined by a
layer of flattened epithelium similar
to that lining other veins.

The intertrabecular spaces thus-
form a labyrinth of intercommuni-
cating venous areolae divided by th-e
trabecular tissue, and opening freely
from one corpus cavernosum to the
other through the septum, especially
in front. The blood is carried away
from these spaces by two sets of veins, the one set joining the prostatic plexus and
pudendal veins ; the others passing into the dorsal vein. Of these last some issue
from between the corpus cavernosum and the spongy body of the urethra, encircling
the penis nearly at right angles, while others pass more directly into the dorsal vein
from the upper surface.

The principal arteries of the corpora cavernosa are the cavernous branches of the
pudic arteries (profundas penis), of the right and left sides ; but the dorsal artery of

THE PENIS.

241

the penis also sends small twigs through the fibrous sheath of the corpora cavernosa,
along the upper surface, especially in the fore part of the penis. Within the*
cavernous tissue, the numerous branches of arteries are supported by the trabeculae
in the middle of which they run, and terminate in branches of capillary minuteness
which open into the intertrabecular spaces ; some of the arterial twigs project
into the spaces, and form peculiar curling and somewhat dilated vessels, which

Fig. 258. -Part of a section of one of the corpora cavernosa, iniected from the peep arterv of

THE penis (Henle).

On the left is seen the fibrous tissue ; at *, a section of the arteria profiinchi penis.

were named by .J. iliiller, heUcine arteries. These are usually bound down by small
librous bands (fig. 259,* *;, and it appears to be due to this circumstance that these
projecting vessels acquire a looped or toi'tuous aspect when distended with injection.
The helicine arteries are most abundant in the posterior part of the corpora
cavernosa, and are found in the corresponding part of the corpus spongiosum also ;

Fig. 259. — Helicine arteries with their sheaths,
AS seen with a low power (Henle).

A and li, from the corpus cavernosura penis : D, from
the corpus spongiosum urethrfe ; C, transverse section
of one of the helicine arteries ; in this and the other
figures the smaller lateral prolongations of the arterial
ve.s.sels into the sheath are shown ; * *, fasciculi of
connective tissue passing oft' from the summit of two of
the sheaths.

but they have not been s^een in the glans
penis. They are more distinct in the human
subject than in animals, where they are often
missed. Small capillary branches pass from
rhem to supply the tissue of the enclosing
-heath.

In addition to the blood which passes
into the venous spaces from the capillary
network of the sheath and trabeculge some
.small arteries are said by C. Langer to open
directly into the larger venous spaces.

The corpus spongiosum urethrae com-
mences below lIk; LriuiiLiiiliir liLiaiiiciit of the

jjcrineum, where it is placed between the diverging crura of thf corpora cavernosa,
and .somewhat behind their point of junction. The enlarged and rounded posterior
extremity is named the bulb, and projects backwards somewhat beyond the urethra.
It extends forwards a.s a cylindrical, or slightly tapering body, lodged in the groove
on the under side of the united cavernous bodies, as far as their blunt conical
anterior extremity, over which it expands ho as to form the glans penis already
described. In the whole of this extent it encloses the urethra.

VOL. III., pt. 4. *

242

MALE EEPEODUCTIVE ORGANS.

The posterior bulbous part, or hulh of the urethra, varies in size in different
•subjects. It receives an investment from the triangular ligament on which it rests,,
and is embraced by the ejaculator urinje, or bulbo-cavernosus muscle. The posterior
extremity of the bulb exhibits, more or less distinctly, a subdivision into two lateral
portions or lobes, separated by a slight furrow on the lower surface, and by a slender
fibrous partition within, which extends for a short distance forwards ; in early
infancy this is more marked. It is above this part that the urethra, having pierced
the triangular ligament, enters the bulb, surrounded obliquely by a portion of the
spongy tissue, named by Kobelt the colliculus Uilbi, from which a layer of venous

Fig. 260. — Section of the corpus spon-
giosum INJECTED FROM ITS ARTERT
(Henle).

1, fibrous tunic of the corpus spon-
giosum ; 2, mucous membrane of the
urethra ; 3, section of a lacuna of the
mucous membrane ; 4, section of an
artery.

erectile tissue passes back upon
the membranous and prostatic
portions of the urethra to the
neck of the bladder, lying closely
beneath the mucous membrane.
At first the urethra is nearer the
upper than the lower part of the
corpus spongiosum, but it soon
gains and continues to occupy
the middle of that body.

According- to the observations of Retterer, which are founded mainly upon a study of
the development of the organ, the gians penis is only formed as to the part immediately
encircling the urethra by true corpus spongiosum, the greater portion being developed
from integumental tissue, which has become very vascular and cavernous, and which
has united with the anterior ends both of the corpora cavernosa and of the corpus
spongiosum ; the vascular connection with the latter being however by far the most
complete.

Structure. — This is essentially the same as that of the corpora cavernosa, but
with a much less developed fibrous framework. Like the corpora cavernosa, it is
distended with blood during erection, but it never acquires the same rigidity. The
fibrous tunic (fig. 260, 1) is much thinner, is less white in colour, and contains more
elastic tissue; the trabeculae are finer and more equal in size ; the areolse are smaller,
more uniform, and directed for the most part with their long diameter in the line of
that of the penis ; in the glans, the meshes are smallest and most uniform. Plain
muscular fibres immediately surround the canal of the urethra, and also form part of
the external coat of the spongy substance.

Blood-vessels. — Arteries. — A considerable artery derived from the infernal
pudic enters the bulb on each side, and supplies the greater part of the spongy body,
sending branches as far as the glans penis, but this part is chiefly supplied by
branches from the arteria dorsalis. Besides these, there is another but much smaller
branch of the pudic artery, entering the bmlb on the upper surface, about an inch
from its posterior extremity, and running forwards in the corpus spongiosum to the
glans (Kobelt). The arteries open into the venous spaces chiefly if not entirely by
the intervention of capillaries. Veins issue from the glans and adjoining part of
the spongy body, to end in the vena dorsalis penis ; those of the rest of the spongy
body for the most part pass backwards through the bulb, and end in the prostatic

THE URETHRA. 243

and mdic venous plexuses; some emerge from beneafcli the corpora cavernosa,
anastomose with their veins, and end partly in the cuianeous veins of the penis and
scrotum, and partly in the pud ic and obturator veins.

The lymphatics of the penis form a dense network on the skin of the glans
and prepnee, and also underneath the mucous lining of the urethra. They pass
chiefly into the inguinal glands. Deep-seated lymphatics are also described as
issuiug from the cavernous and spongy bodies, and passing under the pubic arch
with the deep veins, to join the lymphatic plexuses in the pelvis.

The nerves of the penis are derived from the dorsal and superficial perineal
branches of the pudic nerve and from the hypogastric plexus of the sympathetic.
The former are distributed to the skin and mucous membrane, the latter entirely
to the cavernous and spongy bodies. Simple and compound end-bulbs (genital
corpuscles) occur numerously on the nerves of the penis, and Pacinian bodies have
been found on the nerves of the glans (see Vol. I., Part 2, p. 338).

URETHKA OF THE MALE.

The male urethra extends from the neck of the !)Iadder to the extremity of the
penis. Its total length when moderately stretched is about 8| inches (20.4 cm.),
but it varies with the length of the penis, and the condition of that organ. Except
during the passage of urine or semen the walls of the canal are in close apposition,
the outline of the urethral cleft being vertical in the glans penis, transverse in the
body of the penis, and crescentic about the middle of the prostatic part. Its
diameter when moderately distended differs at different parts, as will be stated more
particularly hereafter. The tube consists of a continuous mucous membrane,
supported by an outer layer of submucous tissue connecting it with the several parts
through which it passes. In the submucous tissue there are, throughout the whole
extent of the urethra, two layers of plain muscular fibres, the inner fibres disposed
longitudinally, and the outer in a circular direction. The urethra may be divided
into two parts, a urinary and a uro-yenitcd. The urinary portion is about half an
inch in length and extends from the vesical orifice to the openings of the common
ejaculatoiy ducts. The uro-genital part, as its name implies, serves as a channel
for both the urine and the spermatic fluid. It comprises the remaining and much
the longer division of the urethra.

More commonly, however, the urethra is described under the three divisions of
the prostatw, membranous or musctdar, and spongy ov pende portions.

1. The first, or prostatic portion, is the part which passes through the prostate
gland. It is about Ij inches in length, is the widest part of the canal, and is wider
in the middle than at either end : at the neck of the bladder its diameter is nearly
one-third of an inch, in the next part it widens a little, so as to be rather more than
this (in old persons nearly half an inch), farther on it diminishes, until, at its
inferior limit, it is smaller than at its commencement. Its direction is vertical or
very nearly so. Though enclosed in the firm glandular su])stance, it is more dilatable
than any other part of the urethra ; but immediately at the neck of the bladder, it
is much more resistant. The transverse section of the urethra, as it lies in the
prostati,', is curved with the convexity forwards.

The lining meml^rane of the prostatic portion of the urethra is thrown into
longitudinal folds, when not distended by fluid. Towards the neck of the bladder,
a slight elevation on the posterior surface passes back into the uvula vcsicte. Somewhat
in advance of this, and continued from it along the floor (posterior wall) of the passage,
projects a narrow median ridge, about three quarters of an inch in length, and one
eighth of an inch in its greatest height ; this ridge gradually rises into a peak, and
sinks down again at its anterior or lower end ; it is formed by an elevation of the

R 2

244

MALE KEPEODUCTIVE ORGANS.

mucous membrane and subjacent tissue. This is the crest of the urethra {crista
nrethrce), which also receives the names of colUculus seminalis, caput gallinaginis and
verumontanum. On each side of this ridge the surface is shghtly depressed, so as to
form a longitudinal groove, named the prostatic sinus, the floor of which is pierced
by numerous foramina, the orifices of the prostatic ducts. Through these a viscid
fluid oozes out on pressure ; the ducts of the middle lobe open above the urethral

Fig. 261. — The lowek part of the

BLADDER AND THE PROSTATIC,
MEMBRANOtTS, AND BULBOUS PARTS
OF THE URETHRA OPENED FROM

ABOVE. (Allen Thomsou. )

A portion of the wall of the bladder
and the anterior jiart of the prostate
gland have been removed, the corpora
cavernosa jjenis have been sepai-ated
in the middle line and turned to the
side, and the urethra -has been slit
up ; the bulb is left entire below, and
upon and behind it the glands of
Cowper with their ducts have been
exposed, t, placed in the middle of
the trigonum vesicse ; «, ic, oblique
apertures of the ureters ; from these
an elevation of the wall of the bladder
is shown running down to u v, the
uvula vesicae ; I, the longitudinal
muscular fibres of the bladder passing
down upon the prostate ; s v, the
circular fibres of the sphincter ; p,
the glandular j)art of the prostate ;
p', the prostatic ijortion of the urethra ;
from the uvula vesicae a median ridge
is seen descending to the caput gal-
linaginis, in which s indicates the
opening of the prostatic utricle, and
d, that of one of the ejaculatory
ducts ; m, the commencement of the
membranous portion of the urethra ;
b, the bulb of the spongy body ; b',
the bulbous part of the urethra ; c,
one of Cowper's glands ; c d, c d,
course and orifice of its duct lying
upon the bulb, and passing forward
between the spongy body and the
urethra, into which along with its
fellow it opens ; c c, one of the corpora
cavernosa.

crest, and some others open below it. The prostatic urethral mucous membrane is
covered by a laminated epithelium like that of the bladder.

At the fore part of the most elevated portion of the crest, and exactly in the
middle line, is the orifice of a blind recess, upon or within the lateral margins of
which are placed the slit-like openings of the common seminal or ejaculatory ducts,
one at each side. This median opening leads into the prostatic utricle, which has
been named also sinus pocularis, vesicula prostatica or uterus masculinus. It was
first described by Morgagni, and corresponds with the vagina and uterus in the
female, its prominent lateral lips being supposed to represent the hymen.

The vesicle forms a cul-de-sac running upwards or backwards, for a distance of
from a quarter to half an inch (6 to 12 mm.). Its orifice forms a longitudinal cleft
about 2 or 3 mm. in length, but the vesicle increases somewhat in diameter towards its
farther end or fundus. The narrow portion runs in the urethral crest, and its
fundus lies behind and beneath the middle lobe, and in some cases reaches to the
posterior surface of the prostate gland. Its parietes, which are distinct, and of

THE URETHRA.

2i5

some thickness, are composed of fibrous tissue and mucous membrane, together with
a few muscular fibres, and enclose on each side the ejaculatory duct ; numerous

Pig. 262. — Mklian section of thk malk pklvls ani> ukethka. (J. S.) 2

Bi,., bJa/lder ; i-.s., pubic HymphyBis ; v., f;it ; i', i-', prostate ; bu, bulb of corjiuH spongiosum • m,
membranouH portion of urethra ; h, spongy portion ; o, glaus penis. For other references see p. lit

246 MALE REPEODDCTIVE ORGANS.

jsmall ramified and convoluted glands open on its inner surface. The epithelium is
columnar and is by some authors stated to be ciliated. There are small glands
opening into its cavity near the entrance into the urethra. The caput gallinaginis
contains some -n-ell-marked erectile and plain muscular tissue, and it has been
supposed that this eminence, when distended with blood, may offer an obstacle to
the passage of the semen backwards into the bladder.

2. The membranous portion of the urethra comprises the part between the
apex of the prostate and the bulb of the corpus spongiosum. It is three quarters of
an inch (18 mm.) long, but about half an inch of its posterior surfixce is covered by
the bulb of the corpus cavernosum which projects backwards over it. This
membranous portion is the narrowest division of the urethra. In the middle its
diameter is one-fifth of an inch (5 mm.) : at the end not quite so much. It is
directed downwards and slightly forwards beneath the pubic arch, the anterior
slightly concave surface being distant nearly an inch from the pubic symphysis,
leaving an interval, occupied by the dorsal vessels and nerves of the penis, by
areolar tissue, and some muscular fibres. Its posterior convex surface is turned
towards the rectum. It lies between the two layers of the triangular ligament, and
both these fibrous membranes are prolonged upon it, the one backwards and the
other forwards. Between these two layers the urethra is surrounded by erectile
tissue, by some veins, and also by plain muscular tissue, and the fibres of the com-
pressor urethrte muscle. On each side are Cowper's glands. The plain muscular
fibres of this portion of the urethra are continued over the outer and inner surfaces
of the prostate into the muscular fibres of the bladder posteriorly, aud into those of
the spongy portion of the urethra anteriorly (Hancock).

3. The spongy portion of the urethra, by far the longest and most variable in
length and direction, includes the remainder of the canal, or that part which is
surrounded by the erectile tissue of the corpus spongiosum. Its length is about six
inches (1 50mm.). The direction of the spongy portion of the urethra varies in different
parts of its course and under different conditions. Thus it inclines forwards and
downwards for a short distance in front of the superficial layer of the triangular
ligament, and then turns forwards and somewhat upwards to about the middle of
its length, Avhere in the flaccid condition of the penis it usually bends sharply
downwards to the external meatus. During erection of the penis or when this
organ is drawn forwards, as in passing a catheter, this temporary curve is obliterated
and the spongy part is straight from the external meatus to the neighbourhood of
the bulb. The part contained within the bulb, sometimes distinguished as the
Imlhous portioti, or sinus, is somewhat dilated. The succeeding portion, as far as the
glans, is of uniform diameter, being intermediate in this respect between the bulbous
and membranous portions. The cross section of its canal appears like a transverse
slit. The canal of the urethra in the glans has, on the contrary, when seen in a
cross section, the form of a vertical slit ; in this part, which is from one-third to
halt an inch in length, the canal is again dilated, forming what is named the

fossa navicularis.

Lastly, at its orifice, which is a vertical fissure from one-fifth to one-fourth of an
inch (5 to 6 mm.) in extent, and bounded by two small lips, the urethra is again
contracted and reaches its narrowest dimensions. From the resistant nature of the
tissues at its margin, this opening does not admit so large a sound or catheter as
even the membranous portion of the canal.

The mucous membrane of the urethra possesses a lining of epithelium, of
which the superficial cells are long and columnar, except for a short distance (5 to
8 mm.) from the orifice, where they are squamous, and where the subjacent
membrane is beset with papillse. The epithelium rests on a basement membrane.
Outside the mucous membrane there is a layer of convoluted vascular structure, and

THE PROSTATE GLAND. 247

external to that a double layer of plain muscular fibres, the inner disposed
longitudinally and the outer circularly, separating it from the proper substance of
the spongy body.

The whole lining membrane of the urethra, except near the orifice, is beset with
small racemose mucous glands and follicles, commonly named the fjlands of
Litfre, the ducts of which pass obliquely forwards through the membrane. They
vary much in size and in the extent to which their cavities are ramified and
sacculated, some being quite simple. Besides these there are larger recesses or
lacwuii, opening by oblique orifices turned forwards, or down the canal. These are
most abundant along the floor of the urethra, especially in its bulbous part. One
large and conspicuous recess, situated on the upper surface of the fossa navicularis,
is named the lacuna ma(jna. A median fold of the membrane rising from the inferior
surface of this part of the urethra has been named the mh'c of the fossa navicularis.

Stratified concrements like those met with in the prostate (see below) are also found in old
subjects in the glandular recesses of the urethra (Robin and Cadiat;.

Cowper's glands. — In the bulbous portion of the urethra, near its anterior end,
are the two openings of the ducts of Cowper's glcmds. These small glandular
bodies (fig. 261, c) are seated above the bulb, behind the membranous portion of
the urethra, between the two layers of the triangular ligament, the inferior layer
supporting them against the urethra. The arteries of the bulb pass above, and the
transverse fibres of the compressor urethrtu beneath these glands. They ibrm two
small firm rounded masses, about the size of peas, and of a deep yellow colour.
They are compound racemose glands, composed of several small lobules held
together by a firm investment. This latter, as well as the walls of the ducts,
contains muscular tissue. The epitheHum of the acini consists of clear columnar
cells, with a reticular protoplasm, staining like the cells of mucous glands. The
ducts are lined with cubical epithelium. The ducts unite outside each gland to
form a single excretory duct (tig. 2G1, c ^Z). These ducts run forward near each
other for about an inch or an iuch-and-a-half, first in the spongy substance and
then beneath the mucous membrane, and terminate in the floor of the bulbous
part of the urethra by two minute orifices opening obliquely. The glands secrete
a viscid fluid, the use of which is not known ; they appear to dimiiiish in old af^e ;
sometimes there is only one present, and it is said both may be absent.

Occasionally there is a third {glandular body in front of and between Cowiier's glands ;
this has been named the anfcrtnr prcxtate or iiiitr-jn-nxtatic (lUind.

The muscles in conrection with the urethra and penis have been already described with
the muscles of the perirntum in Vol. II.. Part 2,

PROSTATE GLAND.

The prostate gland (figs. 262, 203, 204) is an organ connected with both the
urinary and male genital ducts, but it primarily belongs to the latter, being one
of the accessory male organs of generation. It atrophies in the adult after the
t€8ticles arc excised, and when these organs are removed in infancy it remains un-
developed. In animals it enlarges, like the testicles, dui-ing the breeding season.

It i.s a firm, glandular, and muscular body, comparable in size and shape to a
chestnut, situated in the pelvis, and traversed by the first part of the urethra and
by the common ejaculatory ducts. It has a base, an apex, an anterior, a posterior
and two lateral surfaces. The base is situated immediately below the neck of the
bladder, while the uiici' is above the superior layer of the triangular ligament. Its
pOKkrioT surface, which is flat and larger than the anterior, lies against the second
part of the rectum so that it can readily be felt by passing the finger into that
organ. The anterior surface is convex and is jjlaced about half-an-iiich behind the
lower part of the pubic symphysis from which it is separated by some fat, a plexus

248

MALE REPRODUCTIVE ORGANS.

of veins and the pubo-prostatic ligaments. The lateral surfaces are convex and:
prominent, and are covered by the anterior portions of the levatores ani muscles,
which pass backwards on each side from the pubis and the superior layer of the
triangular ligament and embrace the sides of the prostate, but are separated from
the gland by a plexus of veins. The urethra passes through the prostate from its
base to its apex in the median plane and rather nearer the anterior than the posterior
surface, being generally about a quarter of an inch (6mm.) from the former and

Fig. 263. — Horizontal section of male pelvis passing through the prostate gland at its

JUNCTION WITH THE BLADDER. ThE RECTUM WAS DISTENDED WITH F^CES. (J. S. ). \

P. s., pubic symphysis ; o. i, obturator intei-nus muscle ; L. A., levator ani muscle ; p. v., prostatic"
plexus of veins ; f, retro-pubic pad of fat ; u, upper part of prostatic urethra ; r, anterior wall of rectum ;,
VD., vas deferens ; s. v. , seminal vesicle.

nearly half an inch (12mm.) from the latter. The prostate is also pierced by the
two common ejaculatory ducts which enter at a median depression situated at
the upper part of the posterior surface and, passing downwards and forwards in

Fig. 264. — Transverse section of the prostate gland through
THE middle. (Allen Thomson.)

■M, the urethra into which the eminence of the caput gallinaginis
rises from below ; s, the utricle cut through ; d e, the ejaculatory
ducts ; m, superiorly, the deep sphincter muscular fibres ; m, lower
down, intersecting muscular bands in the lateral lobes of the
prostate ; p, glandular substance.

close contact with one another, open on the posterior
wall of the prostatic portion of the urethra. In a
median section (fig. 262) the prostate is therefore seen to be divisible into three
parts, one in front and two behind the urethra. Of the two posterior portions,
one lies above and in front, and the other below and behind, the channel for the
ejaculatory ducts.

The prostate is usually described as consisting of three lobes, two lateral and one
median. The lateral lohes form the great mass of the gland and are united with ons'

THE PROSTATE GLAND.

249-

another in front of the urethra, and also behind the urethra below the ejaculatory
ducts. The middle lobe lies behind the upper portion of the urethra, below the apical
portion of the trigone of the bladder and above the common ejaculatory ducts. At
the sides it passes without any hue of demarcation into the lateral lobes. This
part of the prostate is of considerable surgical interest since, when enlarged, it
may seriously interfere with micturition. Its title to be regarded as a distinct
" lobe " is disputed. Sometimes it projects backwards, as a rounded prominence,
between the bladder and the vasa deferentia, but, according to H. Thompson, this only
occurs when it is pathologically enlarged. According to J. Griffiths it contains, in
some subjects, glandular tissue, the ducts of the glands being distinguishable from
those of the lateral lobes by opening on the posterior surface of the upper part of
the prostatic urethra in and near the middle line. In other cases neither glandular
tissue nor ducts are present in this position. The prostatic part of the urethra
receives not only the openings of the seminal and prostatic ducts, but also, as has
already been more particularly described, that of a small blind recess, called the
sinus pondaris or jnvsia tic idricle, which passes backwards in close relation with the
ejaculatory ducts.

Size and Weight. — The longest diameter of the prostate is the transverse
which measures near the base of the organ about one and a half inches (oG mm.), its
vertical extent is about one and a quarter inches (30 mm.), and its antero-posterior
nearly three-quarters of an inch (18 mm.) These diameters, however, are liable to
alteration according to the condition of the bladder and rectum. Thus distension
of the bladder tends to diminish its vertical extent, while a dilatation of the lower
part of the rectum will compress the organ from before backwards, and increase its
vertical and transverse diameters. Its average weight may be estimated, according
to H. Thompson, at about four and a half to four and three-quarter drachms
(•20'5 grammes, Bischoff).

Structure. — The prostate gland is covered externally by a dense fibrous coat,
which is continuous with the recto-vesical fascia, and with the superior layer of the

Fig. 26.*^. — Section op some of the gland-tubes
OF THE prostate. (Heitzmaiin).

M, muscular tissue ; E, epithelium ; C, concretions.

triangular ligament. This fibrous cap-
sule, which includes much plain muscular
tissue, is divisil)le into two layers, be-
tween which the prostatic plexus of
veins is enclosed (Adams). From the
capsule trabeculae extend through the
gland towards the colliculus seminalis.
Th^' glandular substance is associated
with a large quantity of plain muscular
tissue, which forms the principal part of
the stroma of the organ. This muscular
tissue forms an external layer below the
fibrous capsule, and extends everywhere
through the glandular substance : there
is also a strong layer of circular fibres
continuous posteriorly with those of the
blarlder, and in front with the thin layer surrounding the membranous part of the
urethra. The part of the prostate in front of the urethra is almost entirely
muscular ; in the hinder part the muscular substance is in greatest quantity near
the bladder.

'^<-

'^^^'S^^^^^

250 MALE KEPKODUCTIVE OJIGAKS.

The glandular substance is spongy and yielding ; its colour is reddish grey, or
sometimes of a brownish hue. It consists of numerous tubular alveoli, which unite
into a smaller number of excretory ducts. The epithelium is shortly columnar or
vertical throughout, and there is a second layer of small cells next to the basement
membrane. In the upper part of the gland the acini are smaller and more saccular ;
in the middle and lower parts the tubes are longer and convoluted at their ends.
The capillary bloodvessels form a close network, as in other similar glands, on the
ducts and acini, and the different portions of the gland are united by areolar tissue,
and supported by processes of the deep layer of the fibrous capsule and by the
muscular stroma. The ducts open by from twelve to twenty or more orifices upon
the floor of the urethra, chiefly in the hollow on each side of the collioulus seminalis.

Vessels and Nerves. — Arteries. — The prostate is supplied by branches of
the vesical, hcmiorrlioidal, and imdic arteries. Its veins form a plexus imbedded
in the fibrous covering round the sides and front of the gland, which is highly
developed in old subjects. The veins communicate in front with the dorsal vein
of the penis, and behind with branches of the internal iliac vein. Lymphatics
ramify with the veins, between the two layers of the fibrous capsule. The nerves,
which are derived from the hypogastric plexus, consist of both meduUated and non-
medullated fibres, and are interspersed with ganglion cells. Pacinian bodies have
also been observed on the superficial nerves.

Secretion. — Examined after death, the prostatic fluid has a milky aspect, due to the
admixture of a large number of epithelial cells, but probably, during life, it is more trans-
jaarent. It is not a mucou.s secretion but, according to Adams, the fluid has an acid reaction,
and presents, under the microscope, numerous granules, epithelial cells and nuclei. Some of
the granules are composed of lecithin (Fllrbringer, Jena. Sitzungsb., 1881).

Peculiarities according- to ag-e. — The prostate is very small at birth and it remains
comparatively so until puberty, when in common with the other generative organs it under-
goes a considerable increase in size. Thus, according to Gross, it weighs at birth 13 grains,
-at the 4th year 23 grains, at the 12th 43 grains, at the 14th 58 grains, and at the 20th
260 grains (17 grammes).

The glandular tissue of the prostate is developed by epithelial outgrowths from the
posterior wall of the urethra at the sides of the orifices of the primitive genital ducts, both
Mtillerian and Wolfiian (Griffiths). These gland tubules grow outwards to form the lateral
lobes of the prostate, and by their extension forwards and inwards, may meet in the median
plane in front of the urethra. The amount of gland tissue in front of the urethra is very
small in the child, and in some cases it is not developed in this situation at any period of
life. Grifliths considers that the median lobe, when present, is not formed by a fusion of the
lateral lobes behind the urethra, but arises independently by median outgrowths from the
upper part of the posterior wall of the urethra. The prostate exhibits a marked tendency to
iindergo enlargement in old age, and its tubules frequently contain small laminated bodies
which gradually become calcified (fig. 265, <?.).

RECENT LITERATURE OP THE MALE REPRODUCTIVE ORGANS.

Arthaud, Etude sur le testicle senile, Paris, 1885.

Ballo-witz, Emil, Zu7' Zehre von dcr Strulctur dcr Spermatozoen, Anatom. Anzeiger, Jahrg. i.
1886 ; Untcrsuchimfjen ilher die Strulctur der Spermatozoen, zugleich cin Beitrag zur Lelire vom
feineren Bau der kontraktilen Eltmente, Arch. f. mikrosk. Anat., Bd. xxxii. 1888 and Zeitschr. f.
wissenscli. Zoologie, Bd. 1., 1890 j Las Betzius'sche Endstilck der Sdugetiere-Spermatozoen, Inter-
nationale Monatsschr. f. Anat. u. Physiol., Bd. vii. 1890 ; Die innere Zusammensetzung dcr
Spermatozoenknpfes der Sdugetiere, Centralbl. f. Physiol., Bd. v., 1891 ; Weitere Beohachtungen uber
den feineren Bau der Sdugetier spermatozoen, Zeitschr. f. wissensch. Zoologie, Bd. lii., 1891 ; Die
Bedcidung der Valentin' schen Querbdnder am, Spermatozoenkopfe der Sdugetiere, Archiv f. Anat. u.
Physiol., Anatom. Abt., Jahrg. 1891.

Bardeleben, Karl v., Ueber den feineren Bau der menschlichen Spermatozoen, Verhandl. der
anatom. Gesellsch. , Anat. Anz., 1891 ; Ueher Spermatogencse bei Sdugetieren, besonders beim
Mcnschen, Verhandl. der anatom. Gesellsch., Anat. Anz., 1892.

Benda, C, Die neuestcn Puhlikationen aufdem Gebiete der Samenlelire, Internat. Centralbl. f. d.
Physiol, u. Pathol, d. Ham- u. Sexual- Organe, Bd. i. ; Untersuchimgcn Ilher den Bau des funk-
tionierendcn Samenkandlchens einiger Sdugetiere und Folgerungen fur die Spermatogenese diescr
Wirbeltierklasse, Axchiy t. mikroskop. Anat. . Bd. xxx., 1887 ; -Die Entioickelung des Sdugetierhodens,
Verhandl. d. anatom. Gesellsch., Anat. Anz., 1889; Neue Alitteilun gen uber die Entwickclung der
{jenitaldriisen und uber die Metamorphose der Samenzellen, Verhandlgn. d. physiol. Ges. zu Berlin,

RECENT LITERATURE OF THE MALE REPRODUCTIVE ORGAN?, 251

1891-92 ; Ueha' die Histiogenesc dcs Sauropsidcnsper^natozoons, Yerhandl. der anatoni. Gesellscb.,
Anat. -Anz., 1892 ; Anatomie des Gcachlcchtsapparatcs, Klinisch. Handb. d. Harn- u. ij-exualoTgane v. W.
Ziilzer, Leipzig, 1894; Zur S]icrmato[/e>iese u. Hodcnstructur der WirbeUhiere, Anat. Anzeiger, 1887

Simar, lleclurches sur la disiribution dcs vaisseaux spermatiques chcz Us mammifercs et chez
rhomme. Journal de Tanatomie, xxiv, 1S8S.

Biondi, Die Enticickl. der Spcrmatozoiden, Arch. f. mikr. Anat., 1885. and in Arcli. p. I. sci.
med., ISS'! ; Uutcrsiichungen hctreffend da- Spenaatoc/cnese, Arch. f. Anat. u. Phys., 1885.

Blomfield, The devel. of the spermatozoa of Ildix and Jlaua, Quart. Jouru. of Micr. Sci., 1881.

Boas, J. E. O., Zur Morphologie der Bcgaltungsoryane der amniotcn Wirbeltierc, Morpholog.
Jahrb., Bd. xvii., 1S91.

Bramann, Bcitr. zur Lehre von dcni Descensus Testicidorian, dc., Arch, f . Anat. u. Physiol., 1884.

Brauer, August, Zur Kerintniss der Spermatojenese von Ascaris ine<jalocephala , Arch. f. mikrosk.
Anat., 1x1. xlii., 1893.

Brazzolo, Floriano. Riccrchc sulla istolo'jia normalc e patologica del testicolo, Memorie della
R. Accademia delle scienze dell' Istituto di Bologna, t. ix, 1888.

Bro-wn, H. H., On spermatogenesis in the rat. Quarterly Journal of Micr. Sci., 1882.

Czerny, Adalbert, Das Giraldes'sche Grgan, vach Untersuchuxgcn an Kaninchcn, Ilundcn und
Katzcn, Archiv furmikroskop. Anat., Bd. xxxiii., 1889.

Debierre, C, et Pravaz, J., Contribution a V elude du muscle crenuistcr, du guhevnaculam
testis ct f/( i/iigration tisticidaire, Lyon medical, vol. Hi., 1886.

Dog-iel, A. S. , Die Nervenendigungen in der Ilaut der dussercn Genitalorgane dcs Mcnschcn,
Arch. f. mikr. Anat., Bd. xli., 1893.

V. Ebner, V. , Zur Spermatogenese bci den Sdugeticren, Arcliiv fiir mikroskopische Anatomie,
Bd. xxxi., 1887 ; Nachtrag "'zur Spermatogenese bei den Sdugeticren," Ibid.

Eng-lisch, Ucbcr Anat. u. Path. d. C'owper'schen Dr'uscn, Wiener med. Jahrb., 1885.

Falcone, Sullc terrnin. nerrose ml testicolo, Monit. zool. ital., 1894.

Ferrari, Carlo, Sidla spermatogcnesi nei mammiferi, Memorie della R. Accademia delle scienze di
Bologna, 18S9.

Flemming-, W., Weitcre Beobacldungen iiber die Entivicklung der Spcrmatosonun bei Salamandra
marido."", Archiv f. mikroskop. Anat., Bd. xxxi., 1887.

Frankenstein, J., Beitrag zur normalen und pathulogischcn A natomic dcs Pra'pmtiuni Penis,
Diss., Freiburg i. B., 1891.

Griffiths, Joseph, Observations on the anatomy of the prostate, Journ. of Anat., vol. xxiii.,
1889 ; Observations on the function of the j)rostate gland in man and the lower animals, Journ. of
Anat., vol. xxiv,, 1889 ; The structural changes observed in the testicles of aged persons. Journ. of
Anat., vol. xxvii., 1893 ; Observations of the appendix of the testicle and on the cysts of the epididymis,
ilie rasa effercntia, and the rete testis, Journ. of Anat. vol. xxviii. , 1893 ; Varieties of hydrocele of
the tunica vagincdis testis and some anomalous states of the processus vaginalis, Journ. of Anat.,
vol. xxviii., 1894; Observations on the urinary bladder and urethra, Journ. of Anat., vol. xxv,,
1891, and vol. xxix, 1895 ; Retained testes in man and in the dog. Journal of Anat., xxviii., 1894;
The condition of the testes and prostate gland in eunuchoid persons. Journal of Anat., xxviii., 1894.

Henkingr, H., Ucbcr Reduliionsteilung der Chromosomen in den Samenzdlen von Insektcn,
liiternat. Monatsschr. f. Anat. und Physiol., Bd. vii., 1890.

Hermann, Friedrich, Bcitrdge zur Histologic des Hodens ; and Die postfotale Ilistiogenese des
Ilodms der Maus bis zur Pubertdt, Archivr f. mikroskop. Anat., Bd. xxxiv.

Hertwig-, Oskar, Vtrgleich der Ei- und Samcnbildung bei Nematoden, Archiv f. mikroskop,
Anat., IM. xx.w'i., 1890.

Jarisch, A., I'eber die Schlagadern des menschlichen Hodens, Berichten des nat.-wiss. Yercines zu
Innsbruck, 188'j.

Jensen, O. S., Recherches sur la spermatogenhe, kxch. de biol., 1883 ; Ueber die Strvktur der
Samenkbrper der Sdugeticren, Vbgeln und Amphibien, Anatoniischer Anzeiger, Jahrg. i., 188(5 ;
Untersuchun'/en iibcr die SamenkOrpjcr der Sdugetiere, Vogel und Amphibien, Arch. f. mikroskop.
Anat., Bd. xxx., 1887.

Klaatsch, Ueber d. Descensus Tcsticnlorum, Morph. .Lahrb., 1890.

Kolossow, A., Beitrag zur Lehre von der Entwickelung der Samenfddcn bei Sdugeticren, Ccntralb.
f, d. inedicin. Wissensch., 1888.

V. Korotneff, A., lidtrdge zur Spcrmatologie, Archiv i. mikroskop. Anat., Bd. xxxi., 1888.

Elrause, W., Zum Spiralsaum der Samenfddcn, Biol. Centralbl. 1881 ; and Int. IMonatss'.lir. fiir
Anat. u. riivsiol., 1885.

V. la Valette St. Georg-e, Spermatologlsche Bcitrdge, Archiv f. mikroskop. Anatomie,
lid. xxviii., lS>5f; : and Archiv f. mikrokop. Anat., J'xl. xxx., 1^87.

Liockwood, C. B., The development and tranaition of the testis, normal and abnormal. Jour.
Anat. ami Phys., vol. xxi. and vol. xxii., 1887 k 1888.

Marchand, JlechercheB sur les lympluitiques des teguments dcs organrs genilaux de I'hoinmc,
Bull. HOC. anat., Paris, 1889.

Mermet, P. Des valvules anomales du pripuce. Bull. soc. anat., Paris, 1894.

Moore, J. E. S., Mammalian spermatogenesis, Anat. Anzeiger, Jahrg. viii., 1893 ; On the
germinal blastema and the nature of the so (•ailed ''Reduction Division" in the cartilaginous fishes,
.Anat. Anzfci;,'(;r, Bd. ix.,1894; Some points in the sjiermatogcncsis of muvimalia, Intcrnat. Monatsschr.
f, Anat. u. Physiol.. iJd. xi., 1894,

Sloullin, E. Hansen, A contribution to the morphology of the jtrostate. Journal of Anat.
and I'L)«iol., vol. xxix., 1895.

25^ MALE REPRODUCTIVE ORGANS.

Muller, Vitalis, Ueher die Entwickelungsgeschichte und feinere Anatomic der Bartholiii 'schen
und Ooivper' schen Drilsen des Menschen, Archiv f. raikroskop. Anat., Bd. xxxix., 1892.

Nag-el, W., Ueher die Entwickelung des Urogenitalsy stems des iJ/cwscAe/i, Archiv f. mikroskop.
Anat., Bd. xxxiv., 1889.

Nakasima, K., Beitrdge zur Kenntniss der Prostata, 1886.

Nelson, E. M. , Some observations on the human spermatozoon, Journal of the Qiiekett Microscop.
Club, London, 1888.

Niessing-, Greorgr, Untersuchvngen iibcr die EntwirMung und den feinstcn Bau der Samenfdden
einiger Sdugetiere, Verhandl. der physik. mediciu. Gesellsch. zu Wurzburg, 1888.

Oudemans, J. Th., Die uccessorischen Geschlechtsdrilsen der Sdugetiere, Verhandl. v. d. hoIJ.
Maatschappig der Wetenschappen, 1892.

Piersol, G. A., The structure of spermatozoa, especially those of Amphiuma tridactylum,
University Med. Magazine, Philadelphia, vol. i., 1888 ; Duration of m,otion of human spermatozoa, Anat.
Anzeiger, Jahrg. viii., 1893.

Planner, B.. v., Ueher das VorJcommen von N erven- Endkorperchen in der mdnnlichen Harn-
rohre, Archiv f. mikroskop. Anat., Bd. xxxi., 1889.

Ploetz, A. J., Die Vorgange in derti Froschhoden unter dem Einjluss der Jahres'cit, Archiv f,
Anat. u. Physiol., Physiolog. Aht. 1890.

Poirier, P., Anatomic de I'epididyme, Ic vas du rete, kystes spermatiqiics, Verhandl. des internat.
nied. Congr.. Berlin, Bd. ii., 1890.

Prenaut, A., Sur un point de la structure dutuhe siminif^rc chez Ics mammiferes, Comptes rendus
hebd. de la societe de biologie, serie viii., 1887 ; liccherches sur la signification des iUments du
tuhe sdminifere adulte des mammiferes, Internationale Monatsschrift ftir Anatomie, Bd. iv.,1887 ; Etudes
sur la structure du tube seminifire des mammifhres. Bull. d. 1. soc. des sciences de Nancy, 1887 ; Note
sur la structure des spennutozoides cJiez I'homme, (Comptes rendus hebd. de la socieie de biologie,
fcerie ix., 1888 ; Contribution a, I'hisiogenese du tube seminifere, Internationale Monatsschrift fiir
Anatomie, Bd. vi., 1889 ; Sur he signification de la cellule accessoire du testicule et sur la comparaison
morphologique des elements du testicule et de I'ovaire, Journ. de I'anat. , 1892.

Q,uelliot, Des vesicules seminales, &c., These, Paris (contains a bibliography).

Kath, Otto v., Ueher die Bedeutung der amitotischen Kernteilung im Hoden, Zool. Anz.,
Jahrg. xiv.. 1891 ; Beitrdge zur Kenntniss der Spiermatogencse von Salamandra maculosa, Zeitschr.
f. wissensch. Zool., Bd. Ivii., 1893.

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Retterer, Note sur la vuleur morphol. du gland des mamimifcres, Mem. de la soc. de biol., 1890 j
Sur le developpement du p4nis et du clitoris chez le fcetus humain, Journ. de I'anat., 1892.

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1892.

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beim Menschen, Munchen, 1883.

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Jahrg. vii., 1892.

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Tourneux, Les restesdu corps de T\'olffchezl'adulte, Bull. sc. du Nord, 1882 ; Sur le developpement
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"Waldeyer, Ueber Bau u. Entwickl. d. Samenfdden, Anat. Anzeiger, 1887.

Weil, Ueher den Descensus Testiculorum, &c., Prager Zeitschr. f. Heilkunde. 1884.

Ziegler, Ccntrihution a I'dtude de la circulation veineuse de la prostate, These, Bordeaux, 1893,

THE EXTERNAL GENITALS.

2 5. -J

REPRODUCTIVE ORGANS IN THE FEMALE.

The genital organs in the female consist of a pair of glands called the ovaries,
and of certain passages leading from the peritoneal cavity to the exterior. These
passages may be divided into a pair of lateral ducts, the Fallopian tubes, and a single

Fig. 266. — DiAGR.\M OF FEMALE GENITAL PASSAGES. Modified from Henle. (J. S.)

0., ovarj- ; p"., parovarium ; F.T., Fallopian tube ; p'., pavilion at fimbriated end of Fallopian tube ;
A., amijulla of Fallopian tube ; i., isthmus of Fallopian tube ; F., fundus of uterus ; b., cavity of body of
uterus; i.e., os uteri internum ; c, cavity of cervix of uterus ; e.g.. os uteri externum ; va., vagina ;
H., hymen ; c, orifice of urethra ; v., vestibule ; N., labium minus ; l.m.. labium majus ; p., pudendal
or vulval cleft. The passage from u. to p. constitutes the uro-genital space.

median passage, which consists of three main portions named from above downwards
the uferifs, ragina, and uro-genital space, or vulval cleft. Fig. 200 shows diagram-
matically the general relations of these parts. The structures which bound the
uro-genital space constitute the external genitals, while those above the hymen are
the internal genitals.

THE EXTERNAL GENITALS.

The vnlva, or pudendum, is a general term for the external genitals
(fig. 208). It includes the mans Veneris, the labia mrijora and minora, the clitoris,
and the hynun. The urethra may also be described in connection with these parts.

The mons Veneris is an eminence formed by a mass of areolar and adipose
tissue coverf;d l^y skin provided with numerous hairs. It is situated in front of the
upjK-r yturt of tin: pubic symjihysis.

The labia majora are two rounded folds of skin extending dowuAvards and
backwards from the mons to within about an inch of the aims. Each labium
has an outer convex surface, resembling ordinary skiu, covered with haii-s, and an

254

FEMALE REPRODUCTIVE ORGANS.

inner smooth surface of a pinkish colour, which hes against the opposite labium.
Within the substance of the fold there is found, besides fat, vessels, nerves, and
glands, a tissue resembling that of the dartos in the scrotum of the male, to which
the labia majora correspond. The labia majora, by their contact, generally conceal
the other parts of the external genitals 3 not unfrequently, however, in old persons

Fig- 267. — View of the female organs op generation from behind, the vagina being cbt open

AND its walls TURNED ASIDE. (Sappev.) J.

1, ovaries ; 2, Fallopian tubes ; 3, 4, 5, their fimbriated extremities (4 points to the ostium abdomi-
nale) ; 6, ovarian fimbria ; 7, ligament of the ovary ; 8, 9, broad ligaments ; 10, uterus ; 11, its
vaginal portion ; 12, os uteri ; 13, lateral and posterior walls of vagina reflected ; 14, its anterior wall ;.
15, edge of hymen ; 16, orifice of urethra ; 17, vestibule ; 18, Dymj)h0e ; 19, clitoris ; 20, labia majora.

the labia minora project forwards between the labia majora so as to be visible
externally.

The laMa minora, or nymphae, are two narrow pendulous folds of skin, one
on the inner surface of each labium ma jus. From their attached borders they
extend downwards, having their outer surfaces in contact with the labia majora, and
their inner surfaces against one another. Anteriorly each labium divides into two
branches, the upper of which joins the prepuce of the clitoris, and the other its
glans. Posteriorly the labium minus may end by gradually blending with the inner
surface of the labium majus, but in some cases it can be traced backwards until it
becomes continuous with a transverse fold of skin situated at the anterior edge of
the perineum, and known as the fourcheUe. The nymphas and fourchette resemble
one another and differ from the labia majora in being devoid of fat. In young

THE EXTERNAL GEXITALS.

255

subjects the labia minora are of a rosy-red colour, and look like a mucous membrane,
but as age advances they become darker in colour and more like skin.

The clitoris, the homologue of the penis, is an erectile organ composed of two
corpora cavernosa and a rudimentary glans. It diifers from the penis in being
much smaller, and in not being traversed by a urethra. The corpora cavernosa are
separated behind where they constitute the crura of the clitoris, but they unite in
front to form its body. Each crus is firmly attached to the inner aspect of the
pubic arch superficial to the triangular ligament, and is covered by the ischio-
cavernosus or erector clitoridis muscle. In the body of the clitoris the two corpora

Fig. 26S. — View of external genitals of

ADULT FE.MALE, WITH THIGHS ABDUCTED,
AND LABIA MAJORA AND MINORA SEPARATED.

(J. S.)

1, labium majus ; 2, labium minus ; 3, pre-
putium clitoridis ; 4, vestibule ; 5, h.ymen ; 6,
fourchette ; 7, vaginal orifice ; 8, base of perineal
body ; 9, opening of duct of gland of Bartholin ;
A., anus. Dotted line to show position of outlet
of ligamentous pelvis ; G.s., great sacro-sciatic
ligament ; p. a., pubic arch ; c. , coccyx.

cavernosa • are closely united by their
flattened inner surfaces, the fibrous
septum between them {septum pec-
liniforme) being incomplete. The
body is fixed by a small suspensory
ligament to the ft-ont of the symphysis
pubis, ft'om which point it extends
downwards and backwards for about an
inch and a half. Its extremity is sur-
mounted by a small glans composed of
spongy erectile tissue. The glans is
imperforate, highly sensitive, and sur-
rounded superiorly by a membranous
fold, like the prepuce of the penis, while
below it gives attachment to a small
frsenum. The prepuce and fi*£enum
are continuous with the labia minora.

Erectile tissue. — All the parts of
the vulva are abundantly supplied with
blood-vessels, and in certain situations

there are maases composed of venous

plexuses or erectile tissue, corresponding

to those found in the male. Besides the corpora cavernosa and glans clitoridis
just referred to, there are two oval masses of erectile tissue, the hidhi vestibiili (figs.
2C!j and 270, a). Each bulb is about an inch long, and lies in the side wall of the
uro-genital space a little above the nympha? and superficial to the triangular liga-
ment. The bulbs are rallier pointed at their upper extremities and rounded below ;
their inner aspects are partially covered by mucous membrane, while on the outer
side they are embraced by the fibres of the bulbo-cavemosus muscle. Together
they are equivalent to the bulb of the urethra in the male, which, it will be remem-
bered, shows traces of a median division. In front of the bipartite bulb of the
vestibule is a smaller plexus on each side, the vessels of which are directly continuous
with those of the bulbi vestibuli behind, and of the glans clitoridis in front. This
ifl the pars intermedia of Kobelt, and is regarded by liim as corresponding with the

B56

past C)f

r.?DUCIlTE OBGAXS.

: :rs iducb lies bdcween tiie bulb and Uie

Ik- —: -re-it:;

en.

t^r^T 7-f _

•w
an- tike

Ik- 1:

((¥k«B KidssJS.)) i.

Ite l&B?i]-'i(€5gffik fawe ¥^9 iBJeGtei. ant tte ^m sid ■mgase wKmikKaas kns feooK navveil ;

¥%. 2P8L — Skissnr

"flia

Errrjs-iLi oS'Sjuk? is rsM. tesllle.

^in. and ilsie de^er pail b^ mneaiK memlns _ : ~
maeoos mianbiane d. the meliliiai and TagnuL ^- :
sqpaiatii^ ^jn ftom nmoooB memJhBane nms ± :
^^tsraslncfcirardb cm eadi side aloii^ file baeec^rirf :
to idle cmer s^eek of fbe Isass oi the hjinea. T t
i@ddi^ in cs^osir, is coiPgi@d h^ a seal^ ^iIIi^Gecizi.
able nnmber of moooos ei]rpis cr fiiDides, and vi::
and odotODs sibelanQe. ^^^^laceoos ^and^ asss :
upon the labia majaca and minoRu fine, dovcj
a^@ct of th@ labia majcsa^ hat none on ibe labia i:. l
Ibe ^tHHds cif BaHboli^ or of Dnvcinsj (%. ^C
^bndsintheniale,ai»t»oieddiyh-ydbv, roiniii :
half anindiin JtbelgM^e^dSameter, lod^ied one ::.
cf the vagina and b@aealh the inferior lajer c:
dneiiSL, vfaieb are Itsng; and sample^ opak one «» ^i>:^ f :
naiicnlam. bj the s^ of the Tag:inal ori3c€, in il^
biMder «^ the hjmai and the lal^nm nunos ~ r -
€f thes? dnels; aie too anall to be d^dnctlT : - _ _

1? -wiib the

: : :' r ':ne

ra <m the inn«-

- -- roOowper's

THE EXTERNAL GENITALS.

257

Blood-vessels. — Arteries. — The outermost parts of the vulva are supplied by
the superficial pud ic and perineal arteries ; the deeper parts and all the erectile tissues
receive branches from the internal pudic arteries as in the male. The veins also in a
great measure correspond ; there is a dorsal vein of the clitoris receiving branches
from the glaus and other parts as in the male ; the veins of the bulbus vestibuli pass
backwards into the vaginal plexuses, and are connected also with the obturator

Fig. 271. — Transverse section passing from above downwards and slightly uackwards through

THE ANTERIOR PART OF THE PELVIS OF A WOMAN AGED 54 YEARS : SEEN FROM THE FRONT. (J. S. ) \

B. Bla-lder, cut across about half-an-inch in front of urethral orifice, r ; e, external urinary meatus,
formeil a vertical slit on a slight prominence ; A, opening of left ureter ; v.C, vulval cleft ; u, anterior
wall of urethra ; v. b., vestibular bulb; c, crus clitoriilis ; n.c, bulbo-cavernosus muscle; i.o., iscliio-
cavernosus muscle; l.m., labium majus ; l.mi., labium minus; p.a., pubic arch; o.i., obturator
intemus muscle ; x., on triangular ligament ; p., pelvic fascia.

vein.s : above they communicate with the veins of the pars intermedia, those of the
corprjra cavernosa and the glans of the clitoris, and also with the vena dorsalis. The
lymphatics accompany the blood-vessels.

Nerves. — IJesides sijmpathetic branches, which descend along the arteries,
especially for the erectile tissues, there are other nerves proceeding from the lumbar
and sacral plexu.ses ; those from the former being branches of the genito-crural, and
those from the latter of the inferior pudendal and inlernal pudic nerves, which last
sends comparatively large branches to the clitoris. They terminate in the clitoris in
Ijcculiar tactile corpuscles (see Vol. I., Part 2, p. oiiH).

VOL. III., PT. 4. *

258 FEMALE KEPEODUCTIVE OKGAXS.

THE FEMALE URETHRA.

The female urethra is short as compared with that of the male sex, and corre-
sponds to the part of the male urethra which extends from the bladder to the open-
ings of the ejaculatory ducts. It is about an inch and a half in length, and is
directed from above downwards and forwards anterior to and parallel with the
vagina, with which its posterior wall is intimately blended. It is closed, except
during micturition, by the apposition of the anterior and posterior walls. The
transverse diameter of the closed tube is about a quarter of an inch, but the tube is
capable of great distension, so that the index finger can" be passed through it without
causing any permanent incontinence (Berry Hart). The external orifice or meatus
urinarius appears as a vertical sHt with shghtly prominent edges (see fig. 268, e),
situated about an inch behind the glans clitoridis, immediately in front of the
entrance to the vagina and below the lower edge of the pubic symphysis. The upper
opening of the urethra is at the neck of the bladder.

Structure of the urethral wall. — The mucous membrane is whitish, except
near the orifice ; it is raised into longitudinal folds, which are not entirely obliterated
by distension, especially one which is particularly marked on the lower or posterior
surface of the urethra. Near the bladder the membrane is soft and pulpy, with
many tubular mucous glands. Lower down these increase in size and lie in groups
between the longitudinal folds ; and immediately within and around the orifice, the
lips of which are elevated, are several larger and wider crypts.

The lining membrane is covered with a stratified scaly epithelium, but near the
bladder it becomes transitional. The submucous areolar tissue contains numerous
elastic fibres. Outside this there is a highly vascular structure, in which are many
large veins. Between layers of the triangular ligament, the female urethra is
embraced by the fibres of the compressor urethra? muscle.

The vessels and nerves of the female urethra are very numerous, and are
derived from the same sources as those of the vagina.

THE HYMEN.

The hymen is a thin fold of mucous membrane, which is situated at the vulvo-
vaginal orifice, and narrows this opening so that it will usually only admit the little
finger. It is generally described as forming an annular fold, which is much broader
behind than in front ; but the fold is compressed from side to side, and has its free
edge directed downwards so that the opening is a vertical slit bounded by lateral
lips, the inner surfaces of which are in close apposition (Cullingworth). In rare
cases the hymen forms a complete partition between the vagina and vulva, giving
rise to the condition known as " imperforate hymen." It has been described as
occasionally cribriform, and even in some cases as entirely absent. The small
rounded elevations called caruncvM myrtifm'mes, found in women who have borne
children, are probably the remains of the hymen. The vaginal surface of the
hymen shows a few folds continuous with the rugse of the vagina. This fact is
considered by Budin to favour his view that the hymen is vaginal in its origin.
Others hold that it is of vulval origin, as in various cases of absence of the vagina
the hymen has been found well developed.

THE VAGINA.

The vagina is a dilatable membranous and muscular passage, extending from the
vulva to the uterus, the neck of which is embraced by it. It passes with a slight
curve from above downwards and forwards, usually nearly parallel with the plane of
the pelvic inlet, but tending to become more horizontal with a distended bladder,
and more vertical when the lower part of the rectum is loaded. The ends of the
vagina are somewhat narrower than the middle part ; the lower end, which is the

THE UTERUS.

259

^wKm^^M"

narrowest, is H -shaped on transverse section, the middle part is flattened from before
backwards, so that its anterior and posterior walls are ordinarily in contact with
each other (see fig. 272). At its upper end it is rounded, and expands to receive tlie
vaginal part of the neck of the uterus. The vagina reaches higher up on the cervix
uteri behind than in front, so that the uterus appears to be inserted into its anterior
wall. The anterior wall of the vagina is about 2h inches (6 centimeters) in
length, and the posterior 3| inches (8-5 centimeters). In front the vagina is in
relation with the bladder and urethra, its anterior wall being connected by loose
areolar tissue with the bladder, but intimately blended with the urethra. The

Fig. 272. — Coronal section of pel-
vis OF FEMALE AGED 54 PASSING
THROCGH BLADDER, VAGINA,
AND PERINEAL BODr. (J. S. )

B., brim of true pel%'is ; it., ischial
tuberosity ; o. i. . obturator intemus ;
O.F., obturator fascia; l.a., levator
ani ; p. b., jierineal body; a.w.,
anterior vaginal wall ; bl., trigone
of bladder. The transverse black
line below a.w. represents the cavity
of the vagina.

posterior vaginal wall is
usually covered in about its
upper fourth by the perito-
neum, and below this is
loosely attached to the ante-
rior wall of the rectum. At
the sides it is enclosed be-
tween the levatores ani
muscles (fig 272).

Structure. — The walls
of the vagina are composed

from within outwards of a mucous membrane, a muscular and a fibrous coat. They
are thickest in front, in thf vicinity of the urethra, which indeed may be said to be
imbedded in the anterior wall of the vaginal pa.ssage ; in other situations they are
thinner. The vagina is firmly connected by areolar tissue to the neck of the bladder,
and only loosely to the rectum and levatores ani muscles ; at the upper end as just
stated, for about a fourth part of its length, its posterior surface receives a covering
from the peritoneum, which descends in the form of a cul-de-sac thus far between
the vagina and the rectum.

Externally the vagina is covered 1)y a coat of dense areolar tissue, and beneath
this its walls are composed of unstriped muscle, which is not distinctly separable
into strata, but is composed chiefly of fibres iaternally circular and externally longi-
tudinal. Round the tube a layer of loose erectile tissue is found, which is most
marked towards the vulva.

At its lower end, the vagina is embraced by striated muscular fibres, which con-
stitute the sphmcler vagintp, already described.

On the inni'r siirfam of the vagina, anteriorly and posteriorly, a slightly elevated
riflge extends from the lower end upwards in the middle line, forming the cohimns
of the vofjhm, or cohonmn rwjarum. Numerous dentatcd transverse ridges, called
riiyfr, are also observed, particulaily in persons who have not b rne children,
running at right angles from the columns. These columns and rugae
evident near the entrance of the vagina and on the anterior surface, and
■!x;come less marked, and disappear towards its upper end.

'^^^ ^V Am "-^ m V'^s-^^^

Murr^

arc most
gradually

c 2

260 FEMALE EEPEODUCTIVE OEGANS.

The mucous membrane, besides the columns and rugae, is provided with
microscopic papillae, and is lined with a stratified scaly epithelium. Mucous glands
are stated by Yeith to be usually absent altogether, but one or two may occasionally
be met with.

Vessels and nerves. — The vagina is largely supplied with vessels and nerves.
The arteries are derived from branches of the internal iliac, viz. the vaginal, internal
pudic, vesical, and uterine. The veins correspond ; but they first surround the
vagina with numerous branches, and form at each side a plexus named the vaginal
plexus. The nerves are derived from the hypogastric plexus of the sympathetic,
and from the fourth sacral and pudic nerves of the spinal system ; the former are
traceable to the erectile tissue.

THE UTERUS.

The uterus or womb {matrix, varepov), is a hollow muscular organ with very
thick walls situated in the pelvic cavity between the rectum and the urinary
bladder. The Fallopian tubes, extending from each upper angle of the uterus to
their ovarian opening, conduct the ovum from the ovary to the uterine cavity. In
the case of pregnancy the uterus receives the ovum, retains and supports it during
the development of the foetus, and expels it at the time of parturition. During
gestation the uterus undergoes a great enlargement in size and capacity, as well as
important structural changes.

In the fully developed virgin condition, which is that to which the following
description mainly applies, the uterus is a somewhat pear-shaped body flattened
from before backwards, free above, and connected below with the vagina into which
its lower extremity projects. Its average dimensions are three inches (7'5 centimeters)
in length, two inches (5 centimeters) in breadth at its upper and wider part, and
nearly an inch (2"5 centimeters) in thickness ; it weighs from 7 to 12 drachms
(33 to 41 grammes). It is usually described as possessing a fundus, body, and neck.

The fundus is the broad convex upper end of the body, which projects upwards
from between the points of attachment of the Fallopian tubes (fig. 274). The
body gradually narrows as it extends from the fundus to the neck ; its sides are-
nearly straight ; its anterior and posterior surfaces are both somewhat convex, but
the latter more so than the former. At the points of union of the sides with the
rounded superior border are two projecting angles with which the Fallopian tubes
are connected, the round ligaments being attached a little before, and the ovarian
ligaments behind and beneath them : these three parts are all included within the
peritoneal duplicature of the broad ligaments (fig. 274). The neck or cervix uteri,
narrower and more rounded than the rest of the organ, is about an inch in length ;.
it is continuous above with the body, and becoming somewhat smaller towards its
lower extremity projects into the anterior part of the upper end of the tube of the-
vagina, which is united all round with the substance of the uterus, but extends-
upwards to a greater distance behind than in front. The cervix may be divided
into three parts, upper, middle, and lower, according to their relation to the vagina.
The upper and middle parts lie respectively above and opposite the attachments of
the vaginal walls, while the lower portion projects free towards the cavity of the
vagina being entirely below the line of union of the uterine and vaginal walls. The-
lower end of this, the vaginal part of the cervix, has a transverse aperture by which
its cavity opens into the vagina (figs. 273, 274) ; this is variously named os ute)'i, os:
uteri externum, and (from a supposed resemblance to the mouth of the tench fish)
OS tincce. It is bounded by two thick lips, the posterior of which is the thinner
and longer of the two, while the anterior, although projecting less from its vaginal
attachments, is lower in position, so that when the tube is closed both lips come
into contact with the posterior wall of the vagina. These borders or lips are smooth

THE UTEKtJS.

261

'-iliiM^Ui,\,k

Fig. 273. — Median section ok the pelvis of a female aged ahout 30 years. (J. S.) ^

l8t 8., VxKly of 1st Kacral vertebra ; v.s., pubic symphysis ; ii., J)iadfler ; u., uretlira ; ut., uterus ;
K.O., external os uteri ; v»., utero-sacral b'ganients which are united witli one another on iiostcrior aspect
of uterus; v., vagina ; a. F., anterior vaginal fornix; i-. f., posterior vaginal fornix; ii., hymen;
K., rectum ; a.c, anal canal ; L.Jiin., lal>iiim minus ; L.Maj., labium majus ; c, clitoiis ; m., fat of
inons Veneris; v., peritoneum ; p.u., jtcrineal body ; a.c.b., anococcygeal body.

This section was made after hardening the body by the injection of a 1 p. c. solution of chronuc acid,
and the (iistension of the abdominal vessels with this fluid proiiablydcp-esscd somewhat the pelvic viscera.

262

FEMALE REPEODUCTIVE ORGANS.

in the nullipara, but after parturition they frequently become irregular, and. are
sometimes fissured or cleft.

The peritoneum covers the upper end or fundus of the uterus, and also the
anterior surface of the body. Anteriorly, at about the union of the body with the
cervix it is reflected on to the bladder, forming the utero-vesical ])omh. The
anterior aspect of the cervix is thus uncovered by peritoneum, and it is connected
with the bladder by loose cellular tissue. The posterior surface of the .body and
upper part of the cervix is covered by peritoneum, and below this level the membrane
passes on to the posterior wall of the vagina, which thus separates the lower part of
the back of the cervix from the peritoneum. From the sides of the uterus the
peritoneum is prolonged outwards in the form of duplicatures named the broad
ligaments.

Cavity of the uterus. — The walls of the uterus are of great thickness, and the
cavity is thus proportionately much reduced in size. The part within the body is

Fig. 274. — Diagrammatic view of the uoiERUS and its appendages, as seen from behind. (A. T.) |.

The uterus and upper part of the vagina have been laid open by removing the posterior wall ; on the
left side the Fallopian tube, round ligament, and ovarian ligament have been cut short, and the broad
ligament removed ; w, the fundus of the uterus ; c, the cervix opposite the os internum ; the triangular
shape of the uterine cavity is shown, and the dilatation of the cei'vical cavity with the rugse termed
arbor vitEe ; v, upper part of the vagina ; od, Fallopian tube or oviduct ; I, round ligament ; lo,
ligament of the ovary ; o, ovary (here represented with its long axis horizontal although in the natural
position within the body it is oblique or nearly vertical) ; i, wide outer part of the right Fallopian tube ;
/ i, its fimbriated extremity ; po, parovarium ; /;, one of the hydatids frequently found connected with
the broad ligament.

triangular (fig. 274), and flattened from before backwards, so that its anterior and
posterior walls touch each other (fig. 273). The base of the triangle is directed
upwards, and is convex towards the interior of the uterus. The cavity, narrowing
gradually, is prolonged into its two superior angles, at each of which it leads by a
minute foramen into the narrow canal of the Fallopian tube. At the junction of
the body and the neck, the cavity is slightly constricted, and thus forms what is
sometimes named the internal orifice (os uteri internum, isthmus vel ostium uteri) ;
this opening is often smaller than the os externum, and is of a circular form. That
portion of the cavity which is within the neck is tubular and shghtly flattened
before and behind ; it is somewhat dilated in the middle, and opens inferiorly into
the vagina by the os uteri externum. Its inner surface is marked by two longitu-
dinal ridges or columns, which run, one on the anterior, the other on the posterior
wall, and from both of which rugse are directed obliquely upwards on each side, so
as to present an appearance which has been named arbor vitcB uterina, or palnuB
plicated (fig. 274) : this structure is most strongly marked anteriorly.

Position of the uterus. — The question as to the normal position of the
uterus is one that has given rise to much controversy, and regarding which very

THE UTERUS.

P.63

contradictory statements have been made. The uterus does not occupy any definit(!
fixed position, but possesses a considerable range of mobility, the chief factors thai,
influence its position being the intra-abdominal pressure, and the condition of the
bladder and rectum. In the nullipara, with the bladder empty, the whole uterus is
inclined forwards (anteverted), and the body is also bent upon the cervix (anteflexed),
the body of the uterus lying upon the bladder. As the bladder becomes filled the
body and fundus are pushed upwards and backwards, until, if the bladder be fully
distended and the rectum empty, the upper part of the uterus may come to lie near
the sacrum, and the long axis of the organ be directed from above downwards and
forwards nearly parallel with that of the vagina. As a rule there are no intestines
in the pouch between the uterus and the bladder, these two organs lying in close

Ohliteratedhypo-
gastric artery.

Fig. 275. — View of the female pelvic viscera fkom above.

U, uterus ; B, bladder.

(v. Bardeleben andHaeckel.)

contact. Occasionally however, especially in women who have borne children, the
upper part of the uterus points somewhat backwards, and the utero-vesical pouch is
occupied by some portion of the intestine. The uterus generally deviates to one or
other side, this lateral displacement usually affecting the body more than the cervix.
Ligaments of the nterus. — The reflection of the peritoneum from the uterus
to the bladder is called the ulero-rcsical fold or sometimes the anterior lif/amenl of
Ihe uterus. Posteriorly, as we have already seen, the ])eritoneum passes from the
uterus on to the upper part of the vagina before being reflected backwards to the
rectum, thus forming a recto-vaginal ligament. The peritoneal recess situated in
front of the rectum, and behind the cervix of the uterus and the upper part of the
vagina is usually termed the j^ouch of Dovfjlas. 'I'his pouch is bounded on each side
by a semilunar fold of the peritoneum, which joins the upper part of the cervix
uteri in front and extends backwards on the side of the rectum towards the sacrum.
This fold contains a variable amount of fibrous tissue and some nou-striped
muscular fibres forming the utero-mcral liijament.

264 FEMALE REPRODUCTIVE ORGANS.

The broad ligaments (fig. 274) are formed on each side by a fold or double
layer of the peritoneum, which is directed laterally from the anterior and
posterior surfaces of the uterus, to be connected with the sides of the pelvic cavity.
Between the two layers of the serous membrane are placed the Fallopian tube, the
round ligament of the uterus, the ovary and its ligament, the parovarium, and
numerous blood-vessels, lymphatics, and nerves with fibres spreading from the
superficial muscular layer of the uterus. The Fallopian tube is situated at the
upper border of a special fold of the broad ligament sometimes termed the meso-
salpinx. This fold is attached to the main part of the broad ligament close to the
ovary and its ligament. It is narrow internally, but broadens as it passes outwards.
The parovarium is enclosed within its two layers between the ovary and the outer
part of the Fallopian tube. This fold is thin, its serous layers being separated by only
H small quantity of areolar and muscular tissue. The ovary and its ligament are
situated in a special extension from the posterior part of the broad Kgament. The liga-
ment of the ovary is merely a dense fibro-areolar cord, containing some uterine mus-
cular fibres, and measuring from an inch to an inch-and-a-half in length, which
extends from the lower end of the ovary to the upper angle of the uterus, which
it joins immediately below and behind the point of attachment of the Fallopian tube.

The round ligaments are two flat, cord-like bundles of fibres, about four or
five inches in length, attached to the upper angles of the uterus, one on either side,
immediately in front of the Fallopian tube. As each ligament proceeds upwards,
outwards, and forwards towards the internal abdominal ring it raises the anterior
layer of the broad ligament into a more or less prominent fold. After having
passed, like the spermatic cord in the male, through the inguinal canal, it reaches
the fore part of the pubic symphysis, where its fibres expand and become united with
the substance of the mons Veneris. Besides areolar tissue and vessels, the round
ligaments contain, chiefly in their inner third, plain muscular fibres, which are
prolonged into them from the outer muscular layer of the uterine wall. Each
ligament also receives a covering from the peritoneum, which, in the young subject,
projects in the form of a tubular process for some distance into the inguinal
canal ; this, which resembles the processus vaginalis originally existing in the same
situation in the male, is named the canal of Nuck ; it is generally obliterated in the
adult, but is sometimes found even in advanced life.

STRUCTUEE OF THE UTERUS.

The walls of the uterus consist of an outer serous covering, an inner mucous
membrane, and thick intermediate muscular substance. The serous covering or
peritoneal layer has been already referred to.

The thick middle part of the wall of the uteims is of firm consistence : being
mainly composed of plain muscular fibres of small size, 0'23 mm. in length, in the
nnimpregnated uterus, but greatly enlarged in the gravid state. These fibres
interlace closely with each other, but are disposed in bundles and layers, and are
intermixed with areolar tissue, a large number of blood-vessels and lymphatics, and
some nerves'. The areolar tissue is more abundant near the outer surface. The
arrangement of the muscular fibres is best studied in the uterus at the full period
of gestation, in which the bundles become augmented in size. They may be
referred to three sets of which the two more external may be regarded as
corresponding with the muscular coat of other hollow viscera, whereas the internal
is an immensely hypertrophied muscularis mucosce, and will accordingly be described
with the mucous membrane.

Muscular coat. — The external layer of the muscular coat forms a thin
superficial sheet immediately beneath the peritoneum, and incomplete strata situated
more deeply. A large share of these fibres, beginning as longitudinal bands at the

THE UTERUS. 265

•cervix, arch transversely and obliquely over the fundus and adjoining part of the
body of the organ, and pass on each side into the broad ligament. Of these some
converge at either side towards the commencement of the round ligaments, along
■which they are in part prolonged to the groin ; others pass off to the Fallopian
tubes, and strong transverse bands from the anterior and posterior surfaces are
•extended iuto the ovarian ligaments. Other fibres run back from the cervix uteri
beneath the utero-sacral folds of the peritoneum. The inner layer of the muscular
•coat, which is also thin, is composed of fibres which are found chiefly on the back of
the uterus, and stretch over the fundus and towards the sides, running somewhat
iiTegularly between the ramifications of the blood-vessels. The muscular coat proper
seldom exceeds 6 mm. in thickness altogether, but it is not easy to assign its limits
exactly, for there is little or no submucous areolar tissue forming a distinct coat as in
most of the hollow viscera. But the place of ramification of the blood-vessels before
they pass into the mucous membrane serves to determine the boundary between the
muscular layer of the mucous membrane and the muscular coat proper (J. Williams).

Mucous membrane. — The mucous membrane of the uterus is characterized by
the enormous hypertrophy of the muscular layer proper to it — the muscularis
mucosa ; indeed it is this which forms the greater part of the thickness of
the uterine wall. The presence of this mass of plain muscular tissue in it confers a
distinct character on the outer part of the membrane, so that in sections it is
distinctly differentiated from the inner part or corium.

Muscularis mucosse. — This consists of bands of fibres which are disposed with
■comparative regularity in its upper part, being arranged there in numerous
concentric rings round the openings of the two Fallopian tubes, the widest circles of
the two series meeting from opposite sides in the middle of the uterus. In the
lower part of the body, and in the cervix the internal fibres run more transversely.
They form the so-called sphincters of the os internum and os externum. At the
neck, however, there are also longitudinal fibres within the transverse.

Corium. — As regards its inner part or corium the mucous membrane lining the
•cavity of the body differs greatly from that of the cervix, a distinct line of
demarcation separating the two parts at the isthmus.

The mucous membrane of the 'body of the uterus is smooth, except during the
menstrual period, and iu the unimpregnated state is entirely devoid of ridges ; it is
of a peculiar soft spongy consistence, and of a dull, reddish colour.

Under the microscope it appears composed in great measure of small, rounded,
spindle-shaped, or irregular cells imbedded in a homogeneous ground-substance
and with but few connective tissue fibres apparent (fig. 276). According to
Leopold there are, however, numerous fibres, and they form a spongework with
lymphatic spaces in the meshes. The inner surface is everywlicre covered by
<;olumnar ciliated epithelium, and is beset, but somewhat sparingly, by the orifices
of the uterine glands (fig. 277). These, which were discovered by Sharpey, are
simple tubes bounded by a basement membrane and lined with ciliated cok;mnar
cells like those covering the inner surface. They pass usually obliquely and often
with an irregular or convoluted course into the deeper part of the mucous membrane,
and there terminate by blind, sometimes forked extremities, which are situated
amongst the bundles of the muscularis raucosic. Towards their extremities the
uterine glands are entirely filled by cells (fig. 277, V), but in the greater part of their
•extent they have a distinct lumen.

The mucous membrane of the cervix is much firmer and more fibrous than that of
the body. Between the ruga) of the arbor viUx there are numerous siiccular and
tubular glands. In the lower part of the cervix the mucous membrane is beset with
vascular papillae, and the epithelium is stratified, but in the upper half or more the

266

FEMALE REPRODUCTIVE ORGANS.

epithelium is columnar and ciliated like that of the body. The glands, which are
short, with a large lumen, are everywhere lined with columnar ciliated epithelium,
even where the epithelium of the surface is stratified. Besides the follicular glands
there are almost constantly to be seen the so-called ovula Nalothi, clear yellowish
vesicles of variable size, but visible to the naked eye, embedded in the membrane.
These probably arise from closed and distended follicles ; but their exact nature is
still doubtful.

During pregnancy the mucous glands of
the cervix secrete a considerable quantity
of tenacious mucus, which effectually closes
the passage downwards from the uterine
cavity.

The surface of the os uteri is covered,
like the vaginal portion, with stratified
epithelium, which conceals the vascular
papillse. It is destitute of glands.

The arrangement of the muscular fibres
both of the muscular coat proper and of the
muscularis mucosae is more regular and more
easily made out in the uterus of the lower

150..
1

Fig. 276. — Section op the uterine mucous membrane parallel to the surface (Henle). '-|2.
1, 2, 3, glands (the epithelium has fallen out from 2) ; 4, a blood vessel.

Fig. 277.— Section of the mucous membrane of the human uterus from near the fundus (adapted
by J. C. Ewart from a figure from J. Williams).
a, epithelium of inner suface ; &, 6, uterine glands ; c, interglandular connective tissue ; d, part of
the muscularis mucosae with the ends of the glands, some of which, V , are entirely filled by epithelium
cells. This specimen was prepared from the uterus of a young woman who was accidentally killed three
or four days before the expected appearance of the menstrual flow, and the mucous membrane and
glands are therefore in the hypertrophied condition which precedes menstruation.

mammals (below Primates), which possess a bi-cornel uterus consisting of two long tubular
portions, which unite below before opening into the vagina. A section across one of the
horns of such a uterus is represented in fig. 278, from which it will be seen that the fibres of
the muscularis muccsse (on.vi.) run almost entirely in a transverse or circular direction, and
are imperfectly separated by an areolar layer (a.) containing the large bloodvessels of the
organ from the inner thin layer of circular fibres of the muscular tunic proper (cm.'). Outside
these are seen the stout bundles of the outer or longitudinal muscular layer (l.m.), and most
externally is the peritoneal or serous coat (.s\).

THE UTERUS.

267

Periodic structural changes in the uterus. — The changes which accompany
menstruation and gestation may be shortly indicated here.

At each successive recurrence of mensiniaiion a complete removal of the super-
ficial part of the mucous membrane takes place by a process of softening and
molecular disintegration which commences, along with the menstrual discharge,
close to the cervix, or at the os internum, and advances progressively towards the
fundus during the remaining days of the flow of blood (J. Williams). Previous to
this change, there is a greatly increased general vascularity of the parts, and the
mucous membrane becomes very much thicker. The process of disintegration
reaches as far as the inner fibres of the muscularis mucosiB ; and the haemorrhage
is the direct result of the destruction and open condition of the small vessels.

The process of restoration of the uterine membrane, which begins even before
the cessation of the menstrual flow, proceeds in the same order, from the lower end

Fig. 278. — Transverse VEEXiCAii section

OF THE WALL OF ONE OF THE CORNCA
UTERI OF THE RABBIT. (E. A. S.)

s, serous layer; I. m., longitudinal fibres of
the muscular coat; c. m., circular fibres of
the same ; «, areolar tissue with large blood-
vessels ; m. m., muscularis mucoste ; 7)2.,
mucosa, with coiled glands.

upwards to the fundus, and consists in
a very rapid proliferation of the cells
and nuclei which occupy the inter-
stices of the inner muscular fibres,
and among which are embedded the
deepest parts of the uterine glands
The whole of the destroyed epithelial
structure both of the glands and of
the general surface is renewed from
the epithelium of these parts of
the glands. The epithelial regenera-
tion is very rapid, and the inner sur-
face is already covered again with ^g
epithelium very shortly after the
menstrual flow has ceased, but the
original thickness of the mucous membrane is not at once attained, the growth in
thickness progressing gradually up to the time of the next menstruation, and
with it the gi'owth in length and the intricacy of the uterine glands. The lining-
membrane of the cervix does not participate in the changes referred to.

In ijeatalmi more extensive alterations ensue. The weight of the organ increases
from about one ounce to a pound-and-a-lialf or even three pounds. Its colour
becomes darker, its tissue less dense and its muscular bundles more evident. A
very great increase takes place in the muscular tissue, this increase being mainly the
result of the enlargement of the already existing elements, the cells becoming
enlarged to the extent of from seven to eleven times in length, and from two to five
times in breadth (Kollikerj. A formation of new colls is also said to occur mainly
in the innermost layers (but whether by proliferation of pre-existing cells or other-
wise is not stated;, and to continue until the sixth month of pregnancy, when
it cea8<js. The round ligaments become enlarged, and their muscular structui-e more
marked ; the broad ligaments are encroached upon by the intrusion of tbe growing

£68

FEMALE REPRODUCTIVE ORGANS.

uterus between their layers. The mucous membrane and the glands of the body
•of the uterus at first undergo an enlargement very similar to that which precedes
menstruation, and they subsequently become the seat of peculiar changes, more
particularly described under Development (Vol. I., Part 1). The blood-vessels
and lymphatics are greatly enlarged, and it is observed that the arteries become
exceedingly tortuous as they ramify upon the organ. The nerves also undergo
considerable increase in size.

After parturition, the uterus gradually but rapidly diminishes till it nearly regains
the size and structure of the unimpregnated condition. During this change the
enlarged muscular fibres undergo fatty degeneration and are said to become subse-
quently absorbed, while a new set of fibre-cells is developed. After the first pregnancy,

Pig. 279. — Outlines of moulds op the utekine cavity in diffeeent states (after F. Guyon).

Natural size.

A, in a virgin of 17 years of age ; B, in a woman of 42 years who had not borne children ; C, in a
■woman of 35 years who had borne children ; h, cavity of the body ; c, that of the cervix ; i, the
isthmus or os internum ; o, os externum ; t, passage of the upper angle into the Fallopian tube.

however, the organ never regains its original virginal character. In those who have
had children its weight usually remains from two to three ounces (102-117 grammes,
Vierordt) ; its cavity is larger (fig. 279, C) ; the os externum is wider and more
rounded, and its margins often puckered or fissured ; the arteries remain much
more tortuous, and its muscular fibres and layers more defined than in the virgin.

Peculiarities according to ag'e. — In the newly-born infant the neck of the uterus is
larger than the body, and also much firmer. There is no fundus, the upper end of the uterus
not forming a convex prominence between the attachments of the Fallopian tubes. The
cavity is narrow, there is no distinct internal os and it tapers above on both sides so as to present
an approach to the two-horned form prevalent in animals. The arbor vitse is very distinct
and reaches to the highest point of the cavity. At this period the uterus is usually from an
inch to an inch-and-a-quarter in length. It grows but slightly from birth until near puberty,
at which period it undergoes a rapid and marked increase in size. This growth is especially
marked in the body, which at the same time acquires a firmer consistence, while its mucous
membrane becomes smooth. The cavity remains comparatively narrow in all women who
liave borne no children (fig. 279, b), while in those who have been pregnant it is widely
triangular (c). In old age the uterus atrophies : it becomes paler in colour and harder in
texture, and its external os frequently becomes diminished in size.

Varieties. — The uterus is subject to numerous congenital defects or malformations
especially in connection with abnormal conditions of the other genital organs. Amongst

THE FALLOPIAN TUBES. 269

those involving the uterus may be mentioned its more or less complete absence, the occui-rence
of one 01- two horns at its upper part, and the presence of two distinct cavities. Such cases
are obviously due to an imperfect development of one or both Miillerian ducts or their
incomplete fusion (see Development, Vol. I., Pt. 1). Occasionally the uterus retains its
infantile condition after puberty.

Vessels and nerves. — The arteries of the uterus are four in number, viz., the
right and left ovarian (which correspond to the spermatic of the male) and the uterine.
Their origin, as well as the mode in which they reach the uterus and ovaries, has been
described in Vol. IL, Pt. 2. They are remarkable for their frequent anastomoses,
and also for their singularly tortuous course. After passing a short distance into
the thickness of the uterine wall they divide into branches, which penetrate the
muscular tissue of the mucous membrane, supplying it with capillaries, and then
pass towards the inner portion of the membrane and open into a network of large
capillaries which pervades the tissue in that situation, and is especially developed
near the surface and around the glands. In the cervix, however, and especially in
the vaginal portion, the arteries, which in this situation possess walls of considerable
thickness, after entering the mucous membrane, divide into a number of small
branches which pass directly towards the surface and open into the capillary
network there present, from which loops pass into the papillse. The veins
correspond with the arteries ; they are very large, and form plexuses of sinus-like
vessels, with thin walls in immediate contact with the uterine tissue. The lymphatics
commence according to Leopold as cleft-like spaces in the mucous membrane, and
there are also well-marked lymphatic vessels extending as a plexus through the
whole thickness of the membrane (Hoggan). These open into plexuses of vessels in
the muscularis mucosas and muscular coat proper ; and these again are in communica-
tion with valved vessels beneath and in the serous covering.

The nerves are derived from the inferior hypogastric plexuses, the spermatic
plexuses, and the third and fourth sacral nerves. They consist of both medullated
and non-medullated fibres, and in animals small ganglia have been observed in the
submucous tissue, connected with the non-medullated fibres.

THE FALLOPIAN- TUBES.

The two Fallopian tubes may be considered as ducts of the ovaries (oviducts)
since they serve to convey the ova from these glands into the uterus. They differ,
however, from the ducts of all the other glands in the body in being detached from
the organs whose secretions they convey. They are enclosed in the free margin of
the broad ligaments in the whole of their extent, except at their inner ends, where
they pierce the uterine wall. Traced from the uterus, to the superior angles of
which they are attached, they are found to pass almost horizontally outwards, for a
distance of from half an inch to an inch, until they reach the side walls of the
pelvis, against which they ascend, frequently in a tortuous manner, in front of their
corresponding ovaries and then arch backwards above these glands and internal to
their suspensory ligaments (fig. 280). Finally they turn downwards so that the
fimbriae are opposite the inner surfaces and posterior borders of the ovaries. Some
convolutions of the small intestine are often situated above and internal to the
right Fallopian tube, while the sigmoid loop of the largo intestine may have a
similar relation to the left one. The average length of the tubes is from four to five
inches (120 ram.), and, as a rule, the right one is a little longer than the left.

Each tube may be divided into an isthmus, an ampulla, a neck, and a fimhriated
extremity. The isthmus corresponds to about the inner third of the tube, it is
straight, round and cord-like, and has a diameter of 2 mm. to 3 mm. Its lumen
communicates with the uterine cavity by an orifice which will barely admit a hog'a
bristle. From this opening its cavity enlarges as it passes outwards but only very

270

FEMALE REPRODUCTIVE ORGANS.

gradually. The ampulla extends from the isthmus to the neck, and forms rather
more than one half of the total length of the tube. It differs from the isthmus in
its larger size, in being less firm to the touch and by its tortuous course. This part
of the tube increases in size from the isthmus to the neck, and its average diameter
is 6 mm. to 8 mm., while in many cases it will admit, in the greater part of its
length, a No. 6 to No. 8 catheter. Ballantyne and Williams found that the orifice
at the neck of the tube, or ostium abdominale, was physiologically closed in tubes
removed during life, while in specimens obtained Irom the post mortem room
it was somewhat gaping. When moderately distended it has a diameter of

Broad ligament

ti - l/raclms.

Obliterated Tiypo-
yastric artery.

Fia

280. — Pelvic organs of the female, viewed prom above, (v. Bardeleben & Haeckel.)
U, uterus ; B, bladder.

8 or 4 mm. The ovarian end of the tube expands in a trumpet-shaped manner
from the neck to enclose a space called the wfunclibulum or pavilion, and is
then prolonged into a number of irregular processes called /m&nVe, hence the term
fimlriated extremity. From its irregular torn appearance it was named by the
ancient anatomists morsus diaholi. The fimbrise vary considerably in number, size,
and complexity. The larger ones have numerous smaller processes attached to their
edges, and their inner surfaces present folds continuous with those lining the
pavilion. One of the fimbriae, which is longer than the others, is attached to the
upper end of the ovary. This, the ovarian fimbria, has a longitudinal groove leading
from the pavilion to the ovary, and bounded at its sides by secondary fimbrise.
In some cases this fimbria does not reach the ovary, but is attached to it by a
ligament.

Peculiarities according- to age. — In the new-born child the Fallopian tubes are not
situated entirely in the cavity of the true pelvis, their outer ends lying in the iliac fossse.
The ampuUary part of the tube shows one to three spiral twists, and the edges of the ovarian
fimbria are not fringed. In old age the tubes tend to become narrower and straighter, and
their muscular coat atrophies.

THE OVAKIES. 27 L

Varieties. — A pedunculated cyst, known as the liiidatid of Morfjagni, apparently peritoneal
in oriorin. is frequently found attached to one of the fimbriaj or to the tube itself. A second
smaller fimbriated opening not unfrequently occurs at a short distance from the main one.
Congenital absence of a part or the whole of a tube occasionally occurs.

Structure. — Beneath the external or peritoneal coat the walls of the tube
contain, besides areolar tissue, plain muscular fibres, arranged in an external longi-
tudinal and an internal circular layer. The submucous tissue contains, like that of
the uterus, multipolar ganglion cells. The mucous membrane lining the tubes is
thrown into longitudinal plicae, which are broad and numerous in the wider part of
the tube, and in the narrower part are broken up into very numerous arborescent
processes : it is continuous, on the one hand, with the lining membrane of the

Fig. 281. — Section of the isthmus of the Fallopian tube ; human. (E.A.S. )

uterus, and at the other end of the tube with the peritoneum ; presenting an
example of the direct continuity of a mucous and serous membrane, and making the
peritoneal cavity in the female an exception t* the ordinary rule of serous cavities,
?>.. of being perfectly closed to the exterior. The epithelium in the interior of the
Fallopian tube is, like that of the uterus, columnar and ciliated ; the inner surface
of the fimbrije is also provided with cilia. On their outer or serous surface it passes
into the pavement epithelium of the peritoneal membrane. It does not appear
that there are glands, as was at one time supposed, in the mucous membrane lining
the Fallopian tubes, although the appearances of the folds of mucous membrane may
simulate tabular glands (fig. 281).

THE OVARIES.

The ovaries are two somewhat, flattened oval bodies, which are placed one on
each side of the pelvis, and connected with the posterior layer of the broad ligament
of the uterus. The weight of each is about 100 gi-ains (7 grammes on the average
aaxjrding to Puech, but varying from 5"2r> to 10 grammes), and they usually
mea.sure about one inch and a half in length (.36 mm.), three quarters of an inch in
breadth ClHmm.), and nearly half an inch (12 mm.) in thickness, Ijiife tlieir size is
variable.' The exact position of the ovary is by no means uniform, and opinions are

' Krause gives rather larger dimenHionH for the virf,'in fviz. : lcnf,'t!i, 41 -.02 mm.; breadth,
20-27 mm. ; thickneBH, 10-11 mm. ; volume, 4-5 c.c. ) than for women of .35 to 40 who have borne
children (length, 27-41 mm. ; breadth, 14-16 mm. ; thickness, 7-9 mm. ; volume, 2-5 c.c.).

273 FEMALE EEPEODUCTIVE OEGANS.

divided as to the condition which is to be regarded as normal. According to His^
Waldeyer, and the majority of recent observers, the ovary in the adult nullipara is-
placed against the side wall of the pelvis with its long axis vertical, in the erect position
of the body. Kolliker, however, describes it as lying obliquely in the pelvis with its
long axis parallel with the external iliac vessels, and Hasse, while admitting that the
ovary may be considered as normally occupying the position described by His, believes
that it is frequently drawn towards the uterus by the plain muscular fibres contained in
the broad ligament, so that its long axis is then directed obliquely downwards and
inwards. Adopting the account given by His as representing the usual position of
the ovary, we may describe it as presenting two surfaces, a mesial and a lateral, two-
borders, an anterior and a posterior, and two extremities, an upper and a lotver.
The mesial surface is free and covered to a variable extent by the fimbriated end
of the Fallopian tube and the adjacent portion of the meso-salpinx. Some convolu-
tions of the jejuno-ileum are often found on the inner side of the right ovary, and
the sigmoid loop of the large intestine may have a similar relation to the left ovary.
The lateral surface is also free and lies against a more or less distinct peritoneal
depression on the side wall of the pelvis termed the fossa ovarii. This depression
is generally situated a little below the level of the external iliac vessels, and is often
bounded below and behind by the ureter. The posterior border is free, convex, and
turned somewhat inwards towards the rectum. Like the mesial surface it is
covered partially by the fimbriated end of the Fallopian tube. The anterior border
is straighter than the posterior, it gives attachment to the broad ligament between
the two layers of which is the hihmi, where the bloodvessels and nerves enter the
ovary. The Fallopian tube ascends in front of this border. To its upper extremity
.is attached the ovarian fimbria of the Fallopian tube, and also a peritoneal fold,
termed the ligamentum suspensorium ovarii or ligamentwn infundibido-pelvicum,
which passes downwards from the brim of the pelvis and contains the ovarian
vessels and nerves. The Fallopian tube bends backwards at the upper end of the
ovary. The lower end of the ovary is generally narrower than the upper, and is
attached to the uterus by the hgament of the ovary. This extremity does not
normally reach the floor of the pelvis, so that the ovary is suspended against the
side wall of the pelvis.

Peculiarities according- to age. — In the young foetus the ovary lies in front of the-
psoas muscle near the kidney and having the Fallopian tube on its outer side. From this-
position it gradually passes downwards and inwards, so that at birth it lies at the brim of the
pelvis with its lower and inner end projecting slightly into the pelvis, and its upper and outer-
part in the iliac fossa. During foetal life the ovary is long and narrow, but soon after birth
it becomes more oval in form. Until puberty its surface is smooth, but after the process of
ovulation is fully established it tends to become uneven. This is due to the laceration of the-
surf ace by the rupture of the Graafian follicles and the cicatrizations that occur in connection
with the closui-e of the openings. In old age the ovary undergoes atrophy, becoming more
fibrous and less vascular.

"Varieties. — The above description of the position and relations of the ovaries is based upon
the examination of adult nuUiparse, with the bladder empty and the uterus anteflexed and ante-
verted. The ovaries, however, are not firmly fixed in any one place, and even in the same
individual their position is liable to vary according to the condition of the other pelvic organs.
Thus, if the uterus be moved upwards and backwards, by distention of the bladder or other
causes, the ovaries will be displaced backwards towards the sacrum. His found that in cases
of lateral deviation of the uterus the ovary on the side towards which the uterus lies is
vertical, while the lower end of the opposite ovary is drawn towards the median plane by the
ligament of the ovary, so that its long axis becomes oblique. Waldeyer, however, has recorded
a case in which the ovary on the side opposite to the uterine deviation maintained its vertical
position against the side wall of the pelvis, apparently on account of the ligament of the
ovary being longer than usual on that side. As a rule the ovary on the side towards which
the uterus is displaced is distinctly higher than the one on the opposite side. Thus in a
specimen of Waldeyer's, the one ovary had its upper end 1 cm. below the level of the external
iliac vein, and the other ovary reached as high as the upper border of the corresponding vein.

THE OVARY.

273

Walderer states that he has not seen any cases, such as Hasse describes, where a normal ovary
lies in contact with the uterus.

Absence of one or both ovaries is extremely rare. Occasionally the ovary retains its
infantile form until adult life. It is very uncommon to find it remaining in its primitive
position near the kidney, but sometimes in place of descending into the pelvis it takes a

Fig. 282. — Section of the ovary of the
CAT. (Schrbn. ) ^5

1, outer covering and free border of the
ovary ; 1', attached border ; 2, the central
ovarian stroma, presenting a fibrous and
vascular structure ; 3, peripheral stroma ;
4, blood-vessels ; 5. Graafian follicles in their
earliest stages lying near the surface ; 6, 7, 8,
more advanced follicles which are imbedded
more deeply in the stroma ; 9, an almost
mature follicle containing the ovum in its
deepest part ; 9', a follicle from which the
ovum has accidentally escaped ; 10, corpus
luteum.

similar course to that of the testicle.

passing into the inguinal canal and even

through the external abdominal ring to

the labiimi majus. "WTien enlarged it frequently becomes prolapsed, passing downwards and

inwards behind the uterus, so that when both ovaries are enlarged they may meet near the

median plane.

Structure of the Ovary.

The ovary consists of a stroma, in which are embedded Graafian follicles con-
taining ova. The stroma is composed of a peculiar connective tissue with blood-
vessels, nerves, and plain muscular fibres, and it has an outer epithelial covering.

'y^

■^

■^^f d

■^•^■^Ymi'

Fig. 283. — POKTION OF THE SECTION OF THE PTIEPARED CAT's OVARY, REPRESENTiil) iN THE PRECEDINO
FIGURE, MORE HIOHLY MAGNIFIED. (Schron.)

1, epithelium and outer covering of the ovary ; 2. fibrous stroma ; 3, 3', less fibrous, more .super-
ficial stroma ; 4, blood-vessels ; 5, small Graafian follicles near the surface ; 6, one or two more deeply
placed ; 7, one farther developed, enclosed ]>y a prolongation of the fibrous .stroma ; 8, a follicle farther
advanced ; 8', another which is irregularly compressed ; 9, part of the large.st follicle ; a. tunica
granulosa ; h, discus proligerus ; c, ovum ; d, germinal vesicle ; c, germinal spot.

Epithelium and stroma. — The external surface of the ovary is of a whitisli
colour, and in early life is comparatively smooth and even ; but in later life
becomes more uneven and is marked by pits and scars. It is covered by an epi-

VOL. III. PART 4. T

274

FEMALE KEPEODUCTIVE ORGANS.

thelium which diflFers from that of the peritoneum in being composed of pyrif orm or
columnar cells ; and the surface has a dull appearance as compared with the shining
smoothness of the serous membrane. A distinct line of demarcation exists around
the attachment of the ovary, where the two kinds of epithelium pass into each other
(Waldeyer). This ovarian epithelium is the remains of the germinal epitheUiim from
which both the ova and the other cells within the Graafian follicles have been
developed in the embryo. Here and there are occasionally to be seen amongst the
ordinary epithelium-cells, others which are much enlarged and of a spherical form.
These are primitive ova, similar to those from which the permanent ova are formed

Germinal Epithelium.
• Tunica albuginea.
Small Graafian follicle.
Ovum.

Memhrana granulosa
of a large follicle.

Fig. 284. — Section of part or the ovary of a toting girl. (v. Bohm and Davidoff.) l|a

in the foetus and young subject, but it is doubtful whether the formation of ova from
cells of the germ-epithelium proceeds further in the adult.

Within the epithelium a firm layer of fibrous tissue encloses all the deeper parts.
This has been compared to the dense fibrous covering of the testicle, and thence
named tunica alluginea ovarii, but without sufficient reason, for it is not a distinct
tunic, and is in fact no more than a condensed part of the ovarian stroma.

The stroma is chiefly composed of a fine connective tissue, in which the cells,
many of which are spindle-shaped, are remarkably abundant and distinct. Besides
the spindle-shaped cells, others are met with which closely resemble the interstitial

THE OVAEY.

a75

cells of the iutertubular substance of the testis. Like these, they have a polyhedral
or irregular shape and often a yellowish colour, ai>d they are chiefly found ac-
companying the blood-vessels, although in older ovaries they may be very extensively
diffused throughout the stroma. The stroma also contains elastic tissue, and is
permeated by blood-vessels, which are large towards the hilum and in the centre of
the ovary where the tissue is more fibrous, and become gradually smaller towards the
surface. Along these blood-vessels in the deeper part of the ovary bands of muscular
fibres run, having entered from the broad ligament ; but it is uncertain whether
they extend into the more superficial parts of the ovarian stroma. According

Fig. 285. — Section of the ovary of a

NEWLY-BORN CHILD. HlGHLY MAGNI-
FIED. (Waldeyer.)

a, Ovarianor germinal epithelium ; b,
formation of an ovarian tube ; e, c, pri-
rjordial ova lying in the germ epithelium ;
</. (/, longer tube becoming constricted so
as to form nests of cells ; c, c, larger
nests ; /, distinctly formed follicle with
ovum and epithelium ; [/, <j, blood-
vessels.

to some authorities the spindle-
shaped cells which characterize
the ovarian stroma are also of
a muscular nature. There is a
general radial disposition of the
bands of stroma from the hilum
towards tlie surface.

Graafian follicles. — Im-
mediately under the superficial

covering of the ovary there is a layer of stroma somewhat different from the deeper
parts, and which is so uniformly spread over the organ as to have received the
name of cortical layer. This is particularly obvious in the ovaries of some animals
(figs. 282, 283, 5) and of young children, in whom this layer is comparatively thick,
and to the naked eye its appearance is granular from the* accumulation in it of an
immense number of closely set small vesicles, constituting the early condition of the
ovarian or Graafian follicles with their contained ova. Embedded more deeply in
the substance of the ovary are seen other larger and less numerous follicles of varying
size, the largest being also the most deeply seated. The very largest, however, which
are approaching maturity, eventually reach the surface again, owing to then- being
gradually more and more distended with fluid, and may there be seen projecting
somewhat, in the form of clear vesicles, from one-twentieth to one-sixth of an inch
in diameter. When these are punctured or ruptured a drop of clear fluid (Jiquor
follkuli) escapes, carrying with it the minute ovum surrounded by an accumulation of
the epithelium-cells of the follicle, known as the discus proligenis. Eupturc of a
Graafian vesicle, or it may be of more than one, occurs in healthy females at or before
every successive menstrual period. After the discharge of its contents, the empty
and collapsed Graafian follicle becomes filled with a peculiar reddish- yellow tissue
and constitutes a body termed corpus hiteiim. .Should pregnancy occur, this body
undergoes a considerable development, which is maintained during the greater part
of the time of utero-gestation. But in the unimpregnated female the corpus luteum
begins to retrograde within ten or twelve days after its commencement, and
8'^>on shrinks and ultimately disappears. Other follicles, especially before and
after the child-bearing period, may after advancing to a certain stage of development
undergo a retrograde metamorphosis, their contents becoming broken up and

T 2

276

FEMALE EEPRODUCTIYE OFvOANS.

liquefied and their walls collapsed and converted into a non- vascular homogeneous
membrane. Follicles in this condition are not at all infrequent in the deeper parts
of the ovary (fig. 286, 1).

In addition to Graafian follicles in various stages of development and retrogression, there
may also occasionally be seen in sections of the adult ovary and constantly in that of the-
young subject, cords or tubes composed of rounded or polyhedral cells, sometimes with
developing ova imbedded amongst the other cells (fig. 286, h). These cords may be in con-

Fig. 286. — Section of the ovary of an adult bitch. (Waldeyer. ) ^-

a, germ-epithelium ; i, egg-tubes ; c, c, small follicles ; d, more advanced follicle ; e, discus-
proligerus and ovum ; /, second ovum in the same follicle (this occurs but rarely) ; g, outer tunic of the
follicle ; h, inner tunic ; i, membrana granulosa ; Ic, collapsed retrograded follicle ; I, blood-vessels ;
m, m, longitudinal and transverse sections of tubes of the parovarium ; y, involuted portion of the
germ-epithelinm of the surface ; z, place of the transition from jperitoneal to germinal or ovarian
epithelium.

tinuity with the germinal epithelium or they may be altogether cut off from it. Others occur
which are partially constricted into rounded nests of cells by growth of the stroma across the
cords, and similar nests or groups are found entirely separated, and with or without a developing'
ovum in the centre. It is from such nests of cells that the Graafian follicles have become
developed.

Structure of the Graafian follicles. — The smallest Graafian follicles have no
proper wall. They consist merely of a single layer of cells, immediately investing
the contained ovum (fig. 284). In section, the cells are flattened and look spindle-
shaped in the human subject, and not very unlike the cells of the ovarian stroma, so-

THE OVARY.

277

that they have been thought to be derived from those cells ; but the observations
of Balfour and others upon the lower animals tend to confirm the view which
-was first taken by Waldeyer that, like the ova themselves, the epithelium-cells of
the follicles are originally derived from the germinal epithelium. These smallest

Fig. 287. — Figures showing VARiors stages in the development of the Graafian follicles in

THK RABIilT. HlUHLY MAfiNIFIED. (E. A. iS. )

A, From a section of the ovary of a youns,' m.liljit, sliowing the " egg- tubes of Pfluger conmiuous
with the germinal epithelium of the surface, from wliinli they are develoiied somewhat after the manner
of tubninr glands. Some of the egg-tubes contain primitive ova. B, primitive Graafian follicles derived
from the hroaking up of an egg-tube. C, a (jiaafian folliile within whii'.li the ijcrmanent ovum \u\£
now become liistinct. The follicle has only a single layer of epithelium. D, a larger follicle in which
there are two distinct layers of epithelium, but the inner layer is formed of flattened cells. E, a
larger but still quite young follicle in which the inner layer of cells as well as the outer is composed
of columnar epithelium. Figs. 15, C, D, and E are taken from .sections of ovaries more advanced in
development than A.

follicles are very numerous, especially in the young subject ; indeed, it has been
computed that in the ovaries of a female child at birth there cannot be fewer than
70,000 of tliem. If this is the ca.se, a large proportion must degenerate and dis-
appear without coming to maturity. Their size is about ,,',,,th of an inch
('2-'} mm.).

278 FEMALE REPRODUCTIVE ORGANS.

In follicles which are a little larger, and situated somewhat more deeply in the-
stroma, the epithelium-cells, although still in a single layer, are no longer flattened
but cubical (fig. 287, c) ; a membrana propria or basement membrane can be detected,,
and the layer of stroma next to the follicle is beginning to be somewhat differentiated
from the rest so as to form a special fibrous wall to the follicle. In others again a
second layer of cells is beginning to be formed or may be found entirely formed
within the first, and of the two layers thus produced, one immediately invests the
ovum, and the other lines the wall of the follicle (fig. 287, d). The former is the
beginning of the discus proligerus, and the latter of the memh^ana granulosa. The
cells of both layers soon become columnar (fig. 287, e).

In. follicles which are still larger, fluid is seen to be accumulated between the two
layers of cells, and thus to distend the follicle. This collection of fluid is absent at
one part, generally that which is directed away from the surface of the ovary, so
that here the cells which surround the ovum are in continuity with those which line
the follicle, and the ovum is thus in a manner attached at this place to the wall of
the follicle (see fig. 283). In the largest follicles the chief difference in the contencs
of the follicle consists in the far greater accumulation of the liquor foUiculi, and in
the multiplication of the epithelium-cells — both those which Une the follicle (mem-
brana granulosa) and those which invest the ovum (discus prohgerus) — so that each
of these parts consists, in large follicles, of several layers of cells, mostly rounded or
irregular, but columnar next to the wall of the follicle and the exterior of the ovum
respectively.

The larger follicles have a very distinct wall, which is continuous with and
derived from the stroma of the ovary, and is separable into two parts, an inner
containing the ramifications of the capillary blood-vessels, which are abundantly
distributed to the larger follicles, but nowhere penetrate amongst the epithelium,
cells ; and an. outer part more fibrous, in which the larger branches of the blood-
vessels of the follicle run. In both layers of the follicular wall, the cells are similar
to those of the general stroma, interstitial cells occurring abundantly ; but it is
uncertain whether there are any cells present of the nature of muscular fibres. The
smaller blood-vessels running round the follicle from its deepest part, and minutely
sub-divided on its inner surface, converge towards a point near the middle of the
most projecting part, called the stigma. This marks the spot where the rupture
of the vesicle ultimately occurs, when fully matured.

Each Graafian follicle usually contains only a single ovum ; but occasionally^
though seldom, two ova, and very rarely three, are observed in the same follicle.
The structure of the ovum has already been described in Yol. I., pt. 1 ; but for
the sake of completeness the description of the human ovum may be here repeated.

Structtire of the ovarian ovum. — The human ovum resembles that of all other
mammals (with the exception of monotremes) in its minute size. Immediately
before the time of its discharge from the Graafian follicle of the ovary in which it
has been formed, it is a small spherical vesicle measuring about xkr^^ i^^ch ("2 mm.)
in diameter, and is just visible as a clear speck to the naked eye. When
examined with the microscope, it is found to be invested by a comparatively thick,
clear covering. This, when the centre of the ovum is exactly focussed, has the
appearance in optical section of a clear girdle or zone encircling the ovum (fig. 288),
and was hence named zona pellucida by von Baer (1827). But on more careful
examination with higher magnifying powers, and especially by the examination of
sections, there is not much difiiculty in making out the existence of striae passing
radially through the membrane (fig. 289, zpi). On this account, and especially since a
similar radially striated membrane forms a characteristic part of the investment of~
the ovum in many animals belonging to widely different classes, it is more convenient,
in place of the name zona pellucida, which has been exclusively used to designate^

THE OVARY,

279

this investment in mammals, to employ the more general term zona radiata, or to
speak of it simply as the striated membrane of the ovum.

The zona radiata of the luammalian ovum is sufficiently tough to prevent the
escape of the contents of the ovum, even when subjected to a considerable amount
of pressure. If, however, the pressure be excessive, the tunic splits, and the soft
contents are extruded (fig. 288, h). The strife in the membrane are believed to
be minute pores, and are supposed, while the ovum is yet within the Graafian
follicle, to permit the passage of granules of nutrient material into the interior of
the ovum. After the ovum is discharged from the follicle, the spermatozoa may
perhaps find their way into the ovum through these pores. According to Retzius

Fig. 288. — Ovarian ovum of a mammal. (Allen Thomson.)

a, an entire ovum, viewed under pressure ; the granular cells have been removed from the outer
surface, the germinal vesicle is seen in the yolk substance within ; h, the external coat or zona burst by
increased pressure, the yolk protoplasm and the germinal vesicle having escaped from within ; c, germi-
nal vesicle more freed from the yolk substance. In all of them the macula is seen.

Fig. 289. — Ovum of a mammal; highly magnified, semi-diagrammatic. (E. A. S.)

zp, zona pellucida, showing radiated structure ; vi, vitellus, round which a delicate membrane is
seen ; yv, germinal vesicle ; gs, germinal spot.

the protoplasm of the ovum is united with the follicle-cells by fibres which pass
through the pores of the zona.

Immediately sun-oundinff the zona radiata, as the ovum lies within the mature Graafian
follicle, is a thin stratum of granular substance, probably deposited upon the exterior of the
ovum by the innermost cells of the discus prolis^erus, which immediately encircle the ovum
within the follicle. When the Graafian follicle bursts and the ovum is set free, this granular
material appears to imbibe water, and, as is specially noticeable in the ovum of the rabbit,
swells up into a clear gelatinous envelope, which has been termed, from a possible homology
with the white of the bird's egg, the all/umcn. But in the mammal this structure has not
the nutritive importance to the embryo which is possessed by the corresponding formation
in the bird, and it disappears during the passage of the ovum down the Fallopian tube.

The substance of the ovum within the tunica radiata is known as the vitellus
or yolk (fig. 289, vi). It is a soft semi-fluid substance, composed mainly of proto-
plasm, which is filled with globules and granules (yolk-granules) of different
sizes, but all small, and possessing a high index of refraction, E.xamined in the
fresh condition, the protoplasm between the granules looks perfectly clear and
structureless, but after treatment with suitable reagents, it may be seen to consist of
a fine reticulum, which is especially fine and close near the periphery of the ovum,
and also around the germinal vesicle, at which places the yolk-gramiles are in less
amount than elsewhere. The substances which occur within an ovum other than

280

FEMALE REPEODUCTIVE ORGANS.

the nucleus and protoplasm, may, as in cells generally, be collectively desigaated
" deutoplasm " ; they are regarded as furnishing a supply of nutrient matter to the
protoplasm during the earlier stages of development.

Embedded in the protoplasmic vitellus, usually eccentrically, is a large spherical
nucleus, which was termed by its discoverer, Purkinje, the germinal vesicle} This,
which is about ^^o^h inch ('05 mm.) in diameter, has all the characters of a nucleus
of a cell. It consists of a nuclear membrane (fig. 289, gv) enclosing a clear material
or matrix, embedded within which may be seen strands of karyoplasm, enclosing
one or more well-marked nucleoli. Frequently there is but one nucleolus, which is
then large and prominent, and has received the name of germinal spot {macula ger-
minativa, Wagner, 1835).

There is some doubt whether, before fertilization, there is another membrane (yitelline
membrane) enclosing the vitellus within the zona radiata. The evidence of the presence of
such a membrane is by no means clear, although its existence has been maintained by very
competent observers (v. Beneden, Balfour).

Structure of the corpora lutea. — The corpora lutea are produced after the
rapture of the G-raafian follicles and the escape of their contents by what may-

.^^^^^''-•.. \r''^'^,

^-"^^^^^^^•.^

Fig. 290. — Three stages in the formation of the corpus luteum in the mouse. (Sobotta.)

A, commencing ingrowth of the vascular tissue of the theca f olliculi into the hypertrophied follicular
epithelium ; a, vascular ingrowth ; thi, theca or wall of follicle ; /c, follicular epithelium.

B, a further stage in which the vascular ingrowths of the theca converge towai'ds a central cavity.
Between the ingrowths or trabeculee the follicular epithelial cells, which are undergoing rapid
multiplication, appear as if disposed in columns. I, ileucocytes amongst the follicular cells ; he, surface
epithelium of the ovary.

0, a further stage, the columns being now narrower and the trabeculse more numerous.

^ Purkinje discovered the germinal vesicle in the bird's ovum in 1825 ; that of mammals was first
noticed by Coste in 1833.

THE OVAKV.

281

pel haps be most correctly described as a process of hypertrophy, i.e., growth of the
walls of the empty follicles. The hypeitrophied follicular wall becomes thrown into
plaits or folds which as they increase in extent occupy more and more of the cavity
of the empty follicle, until this has become entirely filled. The hypertrophy is
usually described as the result of the proliferation of the polyhedral interstitial
stroma-cells, which as already stated occur in the wall of the follicle in abuudance,
and there is in addition a considerable development of blood-vessels, which run,
accompanied by fibrous tissue, into the folds into which the wall of the follicle is

Fig. '291. iloRE ADVAKCED COR-
PUS LUTEUM OF THE MOUSE,
KHOWISC. ITS FOKMATION COM-
PLETED. (^Sobotta. )

The central cavity is now occu-
l>ied by jelly-like connective tissue
and the converging trabecule anas-
tomose with one another so as some-
what to break up the columnar
axrangement of the luteal cells.

thrown, giving off capil-
laries which ramify abun-
dantly in the folded wall.
But according to the obser-
vations of J. Sobotta upon
the mouse, the main part
of the thickening is due to
a simple hypertrophy of
the epithelium-cells of the
membraua granulosa, into
which vascular processes of
the wall of the follicle grow

and amongst which a certain number of leucocytes penetrate (fig. 290). Meanwhile
the irregular cleft-like space which now alone represents the cavity of the follicle, as
well as the opening resulting from the rupture of the follicle and by which its cavity
communicated with the surface, become occupied by a sort of jelly-like connective
tissue, which constitutes a kind of hilum for the follicle. To this central fibrous
band the strands of fibrous tissue which accompany the blood-vessels in the folds of
the hypertrophied wall of the corpus luteum converge. At the same time the plaited
disposition of the wall becomes in great measure obscured, so that a section of a
corpus hiteum, when advanced in development (fig. 291), exhibits a fibrous frame-
work having a radial disposition, with the intervals between the radiating trabeoulse
occupied by a tissue which is almost wholly composed of large yellowish cells.
Amongst these cells are numerous cleft-like spaces (lymphatic), and except for the
fact that the columnar disposition is less distinct and that the capillary blood-
vessels come more closely into relationship with the cells of the tissue, the structural
appearances ai'e not unlike tliose which are met with in the cortical part of the
suprarenal capsule.

The corpus luteum is at first sharply marked oil" by the theca folliculi
from the surrounding ovarian stroma, but after a time its limits are less well
defined from the neighbouring parts of the stroma, into which it may be said
gradually to merge and in this way to disappear. Tiie result is tliat, as age
advances, the stroma of the ovaries, at least in some animals, becomes gradually
pervaded with cells like those of the corpora hitca.

Vessels and nerves of the ovaries. — Arteries. — The ovaries are most directly

282

FEMALE KEPRODUCTIVE ORGANS.

supplied by the ovarian arteries, analogous to the spermatic in the male, which
anastomose freely by an internal branch with the termination of the uterine arteries.
Sometimes this anastomotic branch is so large that the ovary seems to be supplied
almost entirely by the uterine artery. The ovarian artery always sends numerous
branches to the Fallopian tube. The smaller arteries penetrate the ovary along its
attached border, pierce the proper coat, and run in flexuous parallel lines through its
substance. The veins correspond, forming a plexus near the ovary named i\iQ pam-
piniform plexus. The nerves are derived from the ovarian plexus ; and also from the
uterine nerves, which invariably send offsets to the Fallopian tubes. The nerves are

Two FIGURES EXHIBITING A COMPARISON BETWEEN PARTS OF THE GENERATIVE ORGANS IN THE TWO-
SEXES (from Farre, after Kobelt).
Fig. 292. — Adult ovary, parovarium and Fallopian tube.

«, a, Epoophoron (parovarium) formed from the upper part of the Wolffian body ; h, remains of the
uppermost tubes, sometimes forming hydatids ; c, middle set of tubes ; d, some lower atrophied tubes ;.
e, atrophied remains of the Wolffian duct ; /, the terminal bulb or hydatid ; h, the Fallopian tube,
originally the duct of Miiller ; i, hydatid attached to the extremity ; I, the ovary.

Fig. 293. — The adult testis and epididymis.

a, a, convoluted tubes in the head of the epididymis developed from the upper part of the WolflBaa
body ; h and /, hydatids in the head of the epididymis ; c, coui vasculosi ; d, vasa aberrantia ; A,,
remains of the duct of Miiller with i, the hydatid of Morgagni, at its upper end ; I, body of the testis.

said by Gawronsky to penetrate even amongst the epithelium cells of the membrana
granulosa of the Graafian follicles.

Parovarium. — The organ so named by Kobelt, or the organ of Rosenmilller,.
who first described it, is a structure which can usually be brought plainly intO'
view by holding against the light the fold of peritoneum between the ovary
and Fallopian tube (see fig. 292, a, l, c, d). It consists of a group of
scattered tubules lying transversely between the Fallopian tube and ovary, lined
with epithelium, but having no external openings. The tubules converge towards
their ovarian end, but remain separate there, while at the other they are more or
less distinctly united by a longitudinal tube which is sometimes of considerable size,
and prolonged for some distance downwards in the broad ligament. Its more
developed form in some animals, as the cow and pig, constitutes the dud of
Gartner. The origin of this vestige of a foetal structure is referred to under Develop-
ment (Vol. I. part 1, p. 120). Here it is sufficient to state that it corresponds
essentially to the epididymis of the male. "Vestiges corresponding to the organ of
Giraldes of the male are also sometimes to be detected in the adult female, in the
shape of tubular remnants, situated in the broad ligament nearer to the uterus-
than the parovarium. These constitute the paroophoron of Waldeyer ; the organ of
Rosenmiiller constituting the epoophoron.

KECEXT LITERATUKE OF THE FEMALE REPRODUCTIVE ORGANS. 28$

RECENT LITERATURE OF THE FEMALE REPRODUCTIVE ORGANS.

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Ballantyne, J. W., The labia minora and hymen, Edin. Med. Journal, 1888 ; The relations of
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infajit, Teratologia, Juh% 1894.

Ballantyne, J. W., and Williams, J. D., The histology and pathology of the Fallopian tubes,
Brit. Med. Journal, vol. i, 1891.

Bandl. L., l/eber die normale Lage und das normcde Verhalten des Uterus, u. s. w., Arch. £.
Gynakologie, Bd. xxii, 1883.

Barbour, A. H. F., Early contributions of anatomy to obstetrics, Edin. Med. Jour., 1888 ;
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V. Bardeleben, Karl, l/eber die Lage der weiblichen Beckenorgane, Verliandl. der Anatom..
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Barnes, Fancoiirt, On Hermaphroditism, British Gynaecological Journal, August, 1888.

Carrard, H., Beitrag zur Anatomic und Pathologic der kleinen Labien, Zeitschr. f. Geburtsh. u,
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Charpy, A., La position de Vutirus, Midi medical, Toulouse, 1892.

Cullingrworth, Charles J., A note on the anatomy of I he hymen and of the posterior commissure
of the vulva, Journ. of Anat. and Physiol., vol. xxvii, 1893.

Dohrn, "R., Die Bildungsfehler des Hymens, Zeitschr. f. Geburtsh. u. Gynakol., Bd. xi.

Diilirssen, Alfred, Beitrag zur Anatomie, Physiologic und Pathologic derPortio vaginalis uteri,
Archiv f. Gynakologie, Bd. xli., 1891.

Duval, Mathias, Be la regendration de ^epithelium des comes ut6rines apr^s la parturition,
Comptes rendus de la societe de biologic, 1890.

Fischel, "W., Ueber das Vorkornmen von Resten des Wolff' schen Ganges in der Vaginalportion,
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Frommel, Beitrag zur Histologic der Eileiter, Mtinchener medicinische AVochenschrift, Jahrg. xxxiii.

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Hart, D. Berry, A further contribution to the structural anatomy of the female pelvic floor,
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Hasse, C, Die Wanderung des menschl. ^^ic^-, Zeitschr. f. Geburtsh. u. Gyuiik., Bd. xxii, 1891.

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Edinburgh : Trans, of the R. Soc. of Edinburgh, vol. xxxv, 1890.

V. Herff, O., Ue. d. feineren Verlauf der Nerven im Eierstocke des Menschcn, Zeitschr. f.
Geburtsh. u. Gynak., Bd. xxiv, 1892.

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of London, 1890.

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Uterusmusculatur, Freunus Gynak. Klinik, 18S4.

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Akad. d. Wi.ssen., 1894.

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Anat., Bd. xx.\vi, 1890.

Kiersnowski, A., ZurJlegen. d. Uterus'pithels, Anat. Hefte, Bd. iv, 1894.

Kleinwachter, L., Zur Anatomie und Pathologie des Vestibulum vaginae, Prager med.
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with rema/rka on the to-called " Transverse Hermaphroditism," Cleland's Memoirs and Memoranda,
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Miiller, Vitalis, Ueber die Entwickelungsgeschichte und feinere ylnatomie der Bartholin^ schen
und Cowper' gchen I)ru»en des Mensclien, Arch, f , mikro.skop, Anat., Bd. xxxix, 1892,

Na^el, W,, Beitrag zur Anatomie geaundcr und kranker Ovaricn, Archiv fiir Gynakologie, Bd.xxxi,
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^84 FEMALE EEPRODUCTIVE ORGANS.

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Mcnschen, Arch, fiir Gynak., Bd. xliv, 1893.

Pozzi, S. , De la bride musculaire du vestibule chez la femme et de Vorigine de I'hyme^i, Gaz. med.
de Paris, 1884.

Kanney, A. L. , The topographical relations of the female pelvic organs, Amer. Jour, of Obstetrics,
1883.

Batterer, E., Sur Vorigine du vagin de la femme, Mem. de la soc. de biologie, Sdrie ix, t. iii,
1891 ; Sur la morphologic et revolution de Vipithilium du vagin des mammiferes, Ibid., 1892.

Riese, H. , Die feinsten Nervenfascrn und ihre Endigungen im Ovarium der Sdugetiere und des
2Ienschen, Anatom. Anz., Jahrg. vi, 1891.

Robinson, Arthur, The p)osition and peritoneal relations of the mammalian ovary, Journ. of
Anat. and Physiol., vol. xxi, 1887.

Scli-wryzer, A-vnold, Zur Anatomic der Lageverdnderungen des Uterus, Arch. f. Gynakol., Bd.
41, 1891.

Shattock, S. Gr., A specimen of incomplete transverse hermapliroditism in the female, &c.. Trans,
of the Path. Soc, vol. xli, 1890.

Solbotta, Beitrdge zur vergleichenden Anatomic und Entivickelungsgeschichte der Uterusmuscii-
latur, Arch. f. microsk. Anat., Bd. xxxviii, 1891 ; Ueber die Bildung d. Corp. hit. bei der Maus, Anat.
Anzeiger, x, 1895.

Soulig-oux, Ch., Arthres et veincs de Vuterus et de I'ovaire, Bull, de la soc. anat., Paris, 1894.

Stonham, C, Case of perfect uterus masculinus with perfect Fcdlopian tubes and testes in the
broad ligament, complex or vertical hermap)h7'oditism, Trans, of the Path. Soc. of London, vol. xxxix,
1888.

Stratz, C. H., Die normale Lage des Uterus, Zeitschrift fiir Geburtshiilfe und Gynakologie, Bd. xiii.

Sutton, Bland, The glands of the Fcdlopian tubes and their function, Brit. Med. Journ., 1888 ;
On the nature of the hymen. The British Gynecological Journal, 1888.

Syming-ton, J., A contribution to the normal anatomy of the female pelvic organs, Edin. Med.
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the female genitals, Edinburgh Med. Journ., vol. xxxii ; On the viscera of a femcde chimpanzee,
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Anatomy and Phys., Oct., 1888.

Testut, L., Sur la position normale de Vidirus, Bull, de la soc. anat. de Paris, t. Ixix, 1894.

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Tscliaussow, M., Ueber die Lage des Uterus, Anatom. Anzeiger, Jahrg. ii., 1887.

Veitii, Eranz, Vaginalepithd und Vaginaldrilsen, Virchow's Archiv f. path. Anat., Bd. cxvii,
1889.

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Beschreibung eines frontalen Gefrierschnittes des Uterus gravidus in situ, Bonn, 1892.

"Wassilieff, H., Betreffend die Mudimente der Wolff'' schen Gauge beim Weibe, Arch. f. Gyna-
■kologie, Bd. 22.

Webster, J, Clarence, The nerve-endings in the labia minora and clitoris, ^^c, Edin. Med.
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Williams, John, On the circulation in the uterus, with some of its anatomical and pathological
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Windle, B. C. A., Hermaphroditism, Birmingham Medical Review, Aug., 1886.

THE MAMMAKY GLANDS.

285

MAMMARY GLANDS.

The mammary glands (mammre), which yield the milk in the female, are accessory
parts to the reproductive system. They give a name to a large class of animals
(Mammalia) which are distinguished by the possession of these oi-o-ans. When
fully developed in the human female, they form, together with the integuments and
a considerable quantity of fat, two hemispherical or conical eminences (the breasts)
placed one at each side on the front of the thorax. A little below the centre of
each breast, on a level with the fourth rib, or slightly lower, projects a smalL
cylindrical or conical body named the nipple {mamiUa), which points somewhat
upwards and outwards. Each gland is situated in the superficial fascia, and extends,
in a vertical line passing through its nipple, from the second to the sixth or seventh
rib, and in a horizontal line, through the same structure, from a little internal to.

Fig. 204. — Dis?;ectiox of the lower half of the fkmale jiamma durino the period of lactation

(from Luschka). g

«, ffl, a, undissected part of the mamma ; 1, tlie mamilla ; 2, areola; 3, subcutaneous masses of
fat ; 4, loculi in the connective tissue which supports the glandular substance ; 5, three lactiferous
ducts ijassing towards the mamilla where they open ; 6, one of the sinuses or ampullse ; 7, some of
the glandular lobules which have been unravelled ; 7', others massed together.

the lateral border of the sternum opposite the fourth costal cartilage to the fifth
intercostal space opposite the mid-axillary line,i and measures some A\. inches
(112 mm.) from above down ; about 5 inches (128 mm.) across ; and about 2 inches
{iiX mm.) thick. The average weight of each gland in the virgin is from 150 to
200 granmies ; in the nursing woman from 400 to oOO grammes (Testut).

Stmctnre of the nipple. — The surface of the nipple is dark, and around it
there is a coloured circle or areola, within which the skin is also of a darker tinge
than elsewhere. In the virgin, these parts are of a rosy pink colour, differing somc-
wliat according to the complexion of the individual, but they are always darker in
women who have borne children. Even in the second month of the first j)regnancy,
the areola begins to enlarge and acquire a darker tinge ; these changes go on

' The lateral extension of the mammarv gland given above is based upon the observations of
Stiles, Edin, Med. Journal, 1892.

;£86 FEMALE KEPRODUCTIVE ORGAJNS.

increasing as gestation advances, and are regarded as signs to be relied on in
judging of suspected pregnancy. After lactation is over, the dark colour subsides,
but never entirely disappears. The skin of the nipple is marked with many
wrinkles, and is covered with papillse ; besides this, it is perforated at the tip by

Fig. 295. — Transverse section of the nipple. (Testut, after cle Sinety.)

rt, sections of galactophorous ducts, with, e, columnar epithelium ; h, connective tissue ; m, m' , plain
-muscular fibres cut longitudually and transversely respectively ; v, bloodvessels.

numerous foramina, which are the openings of the lactiferous ducts ; and near its
base, as well as upon the surface of the areola, there are scattered rounded elevations,
which are caused by the presence of well-marked sebaceous glands with branched
ducts four or five of which open on each elevation. The sudoriparous glands of
the areola are also large and much convoluted, but there are no sudoriparous glands
in the nipple proper nor are there any hair follicles here. The tissue of the nipple
contains a large number of vessels together with much plain muscular tissue, and its
papillge are highly sensitive ; it becomes firmer and more projecting from mechanical
excitement, a change caused by contraction of the muscular fibres, which form
concentric circles round the base of the nipple and radiating bands running from
base to apex.

Structure of the mamma. — The mamma is composed of glandular tissue,
supported by a connective tissue stroma in which the blood-vessels, lymphatics and
nerves ramify. It also comprises a greater or less amount of adipose tissue. The
relative amount and distribution of these constituents varies considerably according
to the age of the individual, and whether the gland is, has been, or has not been,
functionally active. In the adult nullipara the gland is usually a firm conical mass
with its apex at the nipple. This part is called the corpus mammce. ; from it peri-
pheral processes extend in various directions. Under the nipple and areola the
stroma is entirely devoid of fat, but towards the circumference a few fat lobules may
be embedded in it. The anterior surface of the gland is convex, but uneven, owing
to the presence of numerous irregular processes passing towards the skin, with which

THE MAMMARY GLANDS.

287

eome of them are united by bands of connective tissue, the so-called ligameah of
Cooper. Lobules of fat occupy the intervals between these processes. The posterior

Pig. 296. — HoKIZONTAL SECTION OF THE MAMMARY
GLAND AT THE LEVEL OF THE NIPPLE IN A NULLI-
PAROUS FEMALE AGED 27 YEABS. (StileS.) \

The specimen was kept for 2 days in a 5 p. c.
solution of nitric aciil, then washed in water and
preserved in methylated spirit.

N, nipple ; s, skin ; l.c, ligament of Coopei
connecting a process of the gland with the skin ;
p. p, peripheral processes ; f.l., fat lobules ; p.m,
pectoralis major muscle.

surface of the gland is flat or slightly con-
cave, and muchmoreeven than the anterior,
as the corpus mammae is bounded here by a
smooth compact layer of gland tissue.
Delicate glandular processes do, however,
extend from this aspect into the retro-
mammary tissue, reaching close to the
subjacent muscles and even, according to
Heidenhain, passing into the pectoralis
major. The upper and inner portion of
this surface, comprising about two-thirds
of its whole extent, lies upon the pectoralis
major; external to this muscle the posterior
surface rests on the axillary fascia which
separates it from the serratus magnus, and
lower down it is in relation with the digi-
tations of the serratus magnus and external
oblique which arise from the fifth and
sixth ribs (Stiles). The edges of the
mamma are not sharply defined as, at its
peripheiy, the corpus mammae breaks up
into numerous irregular processes which
branch and unite to form a reticular
formation enclosing lobules of fat. The
stroma of the peripheral 5)rocesses, where
the gland tissue ceases, becomes directly
continuous with the connective tissue
framework of the adjacent fat lobules.
At puberty the gland appears on external
examination to be well developed, but it
really consists mainly of stroma and excre-
tory ducts, the true secreting acini Ijeing
few in numVjer. During lactation the
gland tissue proper undergoes a marked
development, and the stroma is relatively
reduced in amount, so that on section the
gland presents to the naked eye a close

resemblance to a salivary gland. After the period of functional activity is ended
the gland returns by a process or involution to its resting stage, but it does not
regain the appearances it exhil>ited before pregnancy. Tiius the corpus mammae
IB less distinct, and its stroma is looser and contains numerous fat lobules, while

ass

FEMALE EEPEODUCTIVE ORGANS.

the peripheral processes are larger and have a more extensive distribution. A layer
of fat of greater or less thickness is now found between the gland and the deep fascia.

Fig. 297. — Horizontal section of the mam-
mart GLAND AT THE LEA'EL OP THE NIPPLE-
IN A MULTIPARA, AGED 40. ThE SPECIMEN
WAS TREATED IN THE SAME WAY AS THAT

SHOWN IN FIG. 296. (Stiles.) i

M.s, sinus or ampulla of milk duct ; r.m.p,
retromammary fat ; other letters as in fig. 296.

After the menopause the appearance
of the gland varies according to the
general condition of the subject. Thus
in thin women it forms a somewhat
flattened disc which comes into close-
relation both with the skin and the
subjacent muscles, while in obese
women the mamma is composed mainly
of fat, the stroma investing the paren-
chyma forming a wide open mesh work,,
except in the immediate vicinity of the^
nipple.

The glandular substance of the'
mamma consists of numerous distinct
lobes, twelve to twenty in number, held
togetlier by firm intervening fibrous or
areolar tissue, and having adipose tissue-
penetrating between them. Each of
these lobes is provided with an excre-
tory duct, and is subdivided into smaller
lobes, and these again into the lobules,
which are beset with the alveoli, Eachi
lobe is practically a distinct gland,,
although the lobes come into close-
contact with one another. Sometimes,,
besides the principal lobes, small acces-
sory lobes or glands are met with near'
the base of the nipple. The lobules are ■
separated from one another in the human
subject by a large quantity of areolar-
tissue (fig. 298). The interlobular tissue-
contains numerous plasma-cells. The
substance of the lobules is of a pale^
reddish cream-colour, contrasting with:
the adjacent fat, and is rather firm.
The excretory ducts, named the galado-
phorous ducts, are, like the lobes, about
twenty in number ; they converge-
towards the areola, beneath which they
become considerably dilated, especially
during lactation, so as to form ampullcR'
or sinuses about 12 mm. long and 6 ram. wide (fig. 294, 6), which serve as smalL
temporary reservoirs for the milk. At the base of the nipple all these ducts, again
reduced in size, are assembled together, those in the centre being the largest, and;

P.M..

THE MAMMARY GLANDS.

289

then proceed, side by side, suiTounded by areolar tissue and vessels, and without
communicating with each other, to the summit of the mamilla, where they open
by separate orifices ; these orifices are seated in little depressions, and are smaller
than the ducts. The walls of the ducts are composed of areolar tissue, with lougi-

Fig. 298.— Section of jiAMMARy gland of woman during lactation. (Testut, after de Sinety.)
a, lobule of gland ; h, acini lined by cubical epitlielium ; c, duct ; t, connective tissue stroma.

tudinal and circular elastic fibres but without muscular tissue. The membrana
propria of the alveoli is described as consisting of a homogeneous membrane having
stellate and anastomosing cells upon its inner surface next to the epithelium.

Fig. 299. — Alveoli of the mammary gland of the bitch under different conditions of activity.

(Heidenhain.)

a, h. soction througli the middle of two alveoli at the commencement of lactation, the epithelium
ccIIh being s<;en in profile ; c, part of the wall of an alveolus in a similar condition with the epithelium
cells seen flat ; d, an alveolus in full secretory activity.

Fioth the alveoli and the ducts are lined with a simple layer of epithelium, which
is flattened in the alveoli and in the lobular ducts ; cubical in the larger ducts and
columnar in the excretory ducts and ampullaa. Near the external openings on the
nipple it becomes scaly stratified.

The epithelium differs in its appearance accoi-ding to the state of activity of the
gland. When entirely inactive the alveoli are very small, and the epithelium cells

VOL. MI,, IT. \. C

290 FEMALE EEPRODUCTIVE 0EGANS„

small and granular. At the commencement of lactation the alveoli enlarge and
become distended with clear secretion (fig. 299, a, h) ; the cells are flattened out
against the membrana propria and contain fat globules of varying size and in the
fluid contents of the. alveoli besides similar fat globules, some of which have a
partial surrounding of protoplasm, a few uni- or multi-nucleated granular cells are
seen. During full activity the cells become cubical or even columnar, but are
irregular in size and exhibit indications of division and of budding off into the
interior of the alveoli (fig. 299, d). By the breaking down of parts of the cells
which have thus become free in the alveoli the constituents of the milk appear to be
formed, the fat globules which were present within the cells becoming suspended in
the fluid of the alveoli as milk globules, and the albuminous constituents of the cells
becoming dissolved and forming the casein and other proteid substances of the milk}

There is a rich network of blood-capillaries investing the alveoli, and the alveoli
are surrounded by sinus-like lymphatics, as in other racemose glands.

In the adult male the mammary gland and all its parts exist, but quite in a
rudimentary state, the gland itself measuring only from half to three-quarters of an
inch across, and one-sixth of an inch thick. Occasionally the male mamma,
especially in young subjects, enlarges and gives out a thin watery fluid ; and, in
rare cases, it has secreted milk.

Blood-vessels, Lymphatics, and Nerves. — The arteries which supply the
mammary glands are the long thoracic and some other branches of the axillary artery,
the internal majmnary, and the subjacent iniercostals. The veins have the same
denomination. Haller described a sort of anastomotic venous circle surrounding
the base of the nipple as the circulus venosus. The lymphatics within the
mammary gland form plexuses in the connective tissue around the alveoli and ducts.
There are also lymphatics which accompany the blood-vessels in the gland, and, as
elsewhere, the smaller blood-vessels have usually a single accompanying lymphatic
vessel of much larger calibre than the artery itself, while the sheaths of the larger
vessels contain two or three lymphatics (Stiles). These perivascular lymphatics
communicate freely with those around the lobules and ducts of the gland. In addition
to the intramammary lymphatics there are four other sets of vessels connected with
the mammary lymphatic system, viz., cutaneous, subareolar of Sappey, circummam-
mary, and retromammary. The lymphatics from the inner part of the gland pass with
the perforating branches of the internal mammary artery to join the small sternal
glands situated along the course of this vessel. On the outer side of the gland the
vessels are much larger and unite to form two or three principal trunks which pass to
lymphatic glands in the axilla. The nerves proceed from the anterior and lateral
mte'cos fa? cutaneous branches. They pass partly to the glandular substance and blood-
vessels, partly to the skin. In the nipple many of them end in tactile corpuscles
n'ithin the papillse, and some of those in or near the areola enter Pacinian corpuscles.

Varieties. — Entire absence of botli glands and nipples is very rare ; a few such instances,
however, are recorded in othei-wise normally developed individuals. Thus Wylie met with a
case in a woman, aged twenty-one years. A small mole existed where the right nipple is
normally situated. Batchelor describes a similar condition in an adult female, but in this
instance the usual position of each nipple was occupied by a small area of pigmented skin.
In a boy three-and-a-half years old J. Hutchinson found complete absence of both mammary
glands, associated with absence of hair and an atrophic condition of the other integumentary
appendages. Absence of one mammary gland is almost as uncommon as that of both, and is
usually associated with an imperfect development of the thoracic wall on the same side. The
glands themselves may be well formed, but the nipples absent. Such cases are of interest in
connection with the fact that in the ornithorhynchus there are no nipples, the mammary
secretion being discharged on to a plane surface ; further in the development of the

* This is the view wliich was taken by R. Heidenhain (Hermann's Handbuch der Physiologie, BJ. v., )
but it is doubtful if it is really correct. For a critical account of this and other views which have been
taken as to the changes in the cells which accompany secretion, see article, "Secretion of Milk,"
Text-book of Physiology, edited by E. A. Schafer, vol. i., 1898. [Note added August, 1898].

THE MAMMARY GLAXDS. .291

mammarj gland the papillary elevation of the skin giving rise to the nipple is secondary to
the epithelial do'migrowth from which the gland itseff is formed.

In the majority of mammals more than two glands are normally present, indeed in some
of the Insectivora there are as many as eleveu pairs. It has been shown by O. Schultze that
in the embryo of various mammals, such as the cat. rabbit, and mole, a line of thickened
epithelium is formed on each side of the trunk extending from the axilla downwards and
inwards to the groin. It is in this situation that the mammary glands are usually developed
in polymastic mammals, and in the great majority of cases of additional glands in the human
subject they are found in a corresponding position and may be designated axillary, pectoral,
abdominal, inguinal or vulval mammaj. The supernumerary mammary structures are usually
represented by the nipple only, but in some cases the glandular tissue is well developed and
may be functionally active. Most of the cases of additional mamma3 appear, on one or both
sides, just below and internal to the normal pair. The largest number of additional glands
that has hitherto been recorded is eight. In this instance, which was described by Xeugebauer
in a woman aged twenty-three, there were three pairs of nipples above the ^normal
ones, and one pair below. It is probable that in this case, as Roger Williams suggests,
the two nipples below the normal pair did not represent a pair of glands, but ^single
examples of two pairs, as the right one was some inches higher up than the left. If such
be the case there were representatives of six pairs of glands in this woman. Ammon
has described a case of three additional pairs of nipples in a man aged twenty-two
years. One pau- was placed above the normal nipples on the anterior folds of the axilla?,
another near the lower margin of the chest wall, and the lowest on the anterior wall
of the abdomen above the level of the umbilicus. Bardeleben concludes from his most
recent investigations that the normal pair of glands represents a persistence of the sixth pair
counting from above downwards. Various cases of mammary glands appearing in the axilla
during pregnancy have been regarded as examples of excessive development of the cutaneous
glands of that region, or of a more or less complete separation of that process of the normal
gland which extends into the axilla. A few cases have been recorded of mammary glands
(mtiniw(P crri/fiea-) being found over the acromion process, on the upper iJart of the thigh, or
even on the back. Sometimes two or more nipples occur on one gland.

Milk. — The milk is characterized by containing an immense number of fat-globules of
varying size but averaging from ,^-jgth to 5fij3th of an inch in diameter. They appear to be
coated with an exceedingly thin investment of albuminous substance, probablj' casein, which
prevents them from running together into larger drops, but when this is dissolved by the
addition of an acid, they readily blend with one another. Rarely there is a more distinct

Fig. 300. — CoxsTiTUEXTS OF THE COLOSTRUM. (Ueiclenliaiii. )

a, b, colostrum-corpuscles with tine and coarse fat globules respectively ;
c, d, e, pale cells devoid of fat globules.

envelope of granular substance, occasionally containing a nucleus,
and free nuclei have also been described as existing to a small extent
in the milk.

The mammary gland before and during the first two or three days after parturition yields
a small amount of a turbid fluid termed the culoatruiii. This contains besides milk -globules
xingle and in groups, amoeboid cells, containing small or large fat-globules, either ck sely
packed within the cell, or but few in numVjer, and sometimes absent altogether : in the latter
case permitting the nucleus to be visible (fig. SOO). These amoeboid cells are known as the
'■ colostrum-corpuscles " (" granular corpuscles" of Donne) : they occur either not at all or but
very rarely, when the gland is in full activity. It is uncertain whether they originate as
separated epithelium cells of the alveoli, or whether they are emigrated white corpuscles.

Development of the Mammary Gland. — The first sign of the gland shows itself at
the end of the second month in the human embi-yo in the shape of a thickening and
downgrowth of the rete muccsum of the epidermis at the site of the future nipple. The
thickening spreads laterally so as to correspond with a small area (mammary area)
which wjon becomes sunk below the general surface. From the tli!i;kened rete mucosum of
this area sfM.-cial outgrowths of the epithelium into the cutis vera occur, one for each of the
lobes of the future gland. These outgrowths, as with other racemose glands, become branched,
and their branches end in enlargements. The formation of these sprouts goes on until birth,
but the develoi)ment of glandular alveoli from them does not occur until the aj)i)roach of
pulx,-rty in the female, and in the male not at all. The projection of the nipple from the rest
of the mammary area does not begin until about the first year after birth ; within it a large
amount of plain muscular tissue becomes formed. The remaindtir of the mammary area
l>ecomeH the areola.

'JTie subsef^uent growth of the gland is comparatively tardy. At the third or fourth yt;ar
of infancy, there is little or no difference in male and female children. The fuller develop-

n 2

■Z2Z RECENT LITERATURE OF THE MAMMARY GLANDS.

ment of the gland in the female occurs only towards puberty. It is probable that during the
later period of pregnancy, not only do the alveoli increase in size, but new alveoli may bud
laterally from the pre-existing ones, and that after lactation some of the alveoli may become
atrophied and disappear.

EECENT Iiia?EBATURE OF THE MAMMARY GLANDS.

Altmann, R., Ueher die Inaetivitdtsatrophie der tveihlichen Brustdriise, Virch. Arch. f. path.
Anat., Bd. cxi., 1888.

Ammon, O., Einige Bcmerlcungin hetreffend das Vorkommen der uberzdhligen Bi-ustwarzen und
die Richtuvg der Korperhaare auf der Brust, Mitgetheilt in R. Weidersheim : Der Bau des Menschen
als Zeugniss fur seine Vergangenheit, 1893.

V. Bardeleben, El., Die Hilufigkeit iiherzdMiger Brustwarzen {Hyperthelie) besonders beim
Manne, Verhand. der anat. Gesellscbaft, Anat. Anz., 1891 ; Ueber 600 neue Fcdle von Hyperthelie
bei Mdnnern, Verhand. d. anat. Gesellsch., Anat. Anz., 1892 ; Weitere Untersuchungen ilber die
Hyperthelie bei Mdnnern, Anat. Anzeiger, 1892, No. 3 ; 3Iassenuntersuchungen iiber Hyperthelie
beim Mann, 4. Beitrag zur HypertTidiefrage, Verhand. d. anat. Gesellsch., Anat. Anz., 1893.

Basch., Karl, Beitrdge zur Kenntnis des menschlichen Milchapparats (1) Zur Anatomie und
Physiologie der Bruf>tu-arze, Archiv f. Gynakol., Bd. xliv.

Batchelor, H. T., Absence ofmammce in a woman, Brit. Med. Journal, 1888, vol. ii., p. 876.

Brush., E. F., The mammary gland. New York Medical Record, No. 13, 1887.

Coen, Edmondo, Beitrdge zur normalen und paihologi.fchen Histologie der Milchdruse,
Ziegler's Beitrage zur pathologischen Anatomie und Physiologie, Bd. ii., 1887.

Creiglitoii, Contrib. to the physiol. and piathol. of the breast, London, 1878.

Evelt, E., Ein Fall von Polymastie beim Mann, Arch. f. Anthropologie, Bd. xx., 1891.

Hausemann, D., Polymastie, Verhandl. d. Berliner Gesell. f. Anthropologie, 18S9.

Hennigr, C, Ueber menschliche Polymastie und ilber Uterus bicornis. Arch. f. Anthropologie,
Ed. xix., 1890.

Kolessnikow, Die Histologie der Brustdriisen in der Kuh, Virch. Arch. f. path. Anat., 1877.

Marcacci, H musculo areolo-capezzolare, Giorn. d. r. accad. di med. di Torino, 1883 ; Le muscle
areolo-mamelonnaire, Arch. ital. de biologic, iv. ,3.

Middendorp, H. "W., Die Injection der Mamma, Internat. Monatssch. f. Anat. und Phys.,
Bd. iv., 1887.

Mori, A., Sulle variazioni di struttura della ghiandola mammaria durante la sua attivitd, Lo
Sperimentale, Firenze, 1892.

MLoullin, The memh'ana propria of the mammary gland, Joum. of Anat. and Physiol., 1881.

Neugebauer, F. L., Eine bisher einzig dastehende Beobachtung von Polymastie mit 10 Brust-
warzen, Centralbl. f. Gynakologie, 1886.

Nissan, Ueber das Verhalten der Kerne in den Milchdriisenzellen, Arch. f. mikr. Anat., 1886.

Partsch, Ueber d. feineren Bau der Milchdricse, Diss., Breslau, 1880.

Puech., Les mammelles ct leur anomalies, Progres med., 1885.

Saefftigen, Anat. des glandes lactifhres pendant la p6riode de lactation, Bull, de I'acad. imp. d©
St. Petersbourg, 1881.

Scliultze, O., MilchdriisenentwicTcelung und Polymastie, Sitzungsberichte d. Wiirzburger phys.
med. Gesellscbaft, viii., 1892 ; Ueber die erste Anlage des Milchdriisenapparates, Anat. Anzeiger,
viii., 1892 ; Beitrag zur Entwic/celungsgeschichte der Milchdrilsen, Verhaadl. d. phys. med. Gesellscbaft
zu Wiirzburg, xxvi., 1893.

De Sinety, Surle died, et Vhistol. comp. de la raamelle, M(^m. de la soc. de biol., 1877.

Stiles, Harold J., The surgical anatomy of the breast and axillary lymphatic glands, Edin.
Med. Journal, 1892.

Steinhaus, J., Die Morphologieder Milchabsonderung, Arch. f. Anatom. u. Physiol., Physiol. Abt. ,
1892, Suppl. Bd.

Sutton, J. Bland, Supernumerary mammce and nipples in m.an, monkeys, cows, itc. The American
Joum. of the Med. Sciences, vol. xcvii., 1889.

Talma, Beitrag zur Histogenese der weibl. Brustdriise, Arch. f. mikr. Anat., 1882.

Testut, L., Note sur un cas de mamclle crurale observ6 chez la femme. Bull, de la society
d'anthropologie de Paris, tome ii., 1891 ; and Trait6 d' Anatomie, t. iii., Paris, 1894.

Proramel, Zur Histologie und Physiologie der Milchdriise, Centralbl. f. Gynakologie, 1891.

Truman, E. B., The colostrum corpuscle of human milk. Lancet, 1888, vol. ii.

■Williams, Roger, Polymastism with special reference to mammce erraticoe and the development
of neoplasms from supernumerary mamma/ry structures, Jour. Anat. & Phy^., vol. xxv., 1891 ;
Mammary variations per defectum. Ibid.

Wylie, "W., Case of entire absence of both mammce in a female, aged twenty-one years, Brit.
Med. Journal, 1888, vol. ii., p. 235.

THE DUCTLESS GLANDS.

By E. a. SCHAFER and J. SYMINGTON.

The reraaining organs to be described all belong to the class of bodies known as
ductless glands. Some of these, such as the lymphatic glands, have been described
in the General Anatomy (Vol. I., Pt. 2) ; others, such as the solitary and agminated
glands, the pituitary body and the pineal gland, with the viscera to which they are
structurally connected. There remain to be uoticed here the spleeM, the suprarenal
capsules, the thi/mas (jland, the thyroid hodij with the parathyroids, and the small
vascular nodules termed carotid and coccyyml ylands.

THE SPLEEN.

The spleen (figs. 301 and 304) is a soft, highly vascular and easily distensible
organ of a dark purplish colour. It is placed obliquely behind the stomach, its upper
and inner end being in the posterior part of the epigastric region, while the lower,
outer and larger portion is in the left hypochondrium. Its long axis, which on an

Fig. 301. — Horizontal section oi' the abuoiien of an adult male at the level of the lower

IKjRDEIi OF the BOUY OF THE TWELFTH DORSAL VERTEBRA, SEEN FROM ABOVE. NEARLY t,. (J. S. )

L,K, left kidney ; d.d, diaphragm ; b.c, left suijrarcnal capsule ; 8. V, splenic vein ; St, stomach ;
O.H.O, ga.stro-splenic omentum : Z<. .S, lesser sac of the peritoneum.

average measures five to six inches, nearly corresponds with that of the lower ribs,
and the organ usually extends from the level of the eighth rib above to the eleventh
V)elow. It is the largest of the ductless glands.

Surfaces and borders. — When hardened in situ the spleen has, according to
runniiigham, tlie shape of an irregular tetrahedron, with its apex above and its base
below. Its four surfarjes are termed phrenic, renal, yaslric, and basal. Of these the
phrenic is large and convex, and h'es against th'; diaphragm. In the gieater part of
its extent it looks upwards, backwards, and to the left, but near its ujjper end some-

294

THE DUCTLESS GLANDS.

what inwards. It is separated from the eighth, ninth, tenth, and eleventh ribs not
only by the peritoneum and the diaphragm, but also in part of its extent by the left
pleura and lung. The left lobe of the liver is occasionally found to extend back-
wards and to the left between the upper part of the phrenic surface and the
diaphragm. The renal surface is generally flat, and narrower than the gastric, and
does not reach so high as either the gastric or phrenic surfaces. Above, it generally
touches the suprarenal capsule, and in the rest of its extent is in relation with the
outer aspect of the left kidney. It looks inwards and downwards. The gastric
surface is concave, and looks forwards and inwards. In the great part of its extent

Fig. 302. — View of the abdominal viscera from behind, after removal op the spinal column,

THE WHOLE OP THE POSTERIOR WALL OP THE ABDOMEN AND THE KIDNEYS AND SUPRARENAL

CAPSULES, THE PERITONEUM BEIN3 LEFT (this and the D«xt figure are taken from Prof. His'

models). |

P, pancreas ; P', its head ; d, duodenum ; st, stomach ; spl, spleen ; R.L., right lobe of the liver ;
L.S., Spigelian lobe ; v.c.i., vena cava inferior ; p.r., portal vein ; b, common bile duct ; i.r., imj>res-
sion for the right kidney on the posterior surface of the liver ; the situation of the two kidneys is well
shown by the corresponding impressions in the cast; asc. col., desc. co^. , ascending and descending
colon ; pt, back of the peritoneum ; m, line of attachment of the mesentery ; VIII, IX, X, XI, the
corresponding ribs ; il, ilium.

it lies against the posterior surface of the stomach, but towards its lower end it
touches the tail of the pancreas. This surface presents, parallel with and near its
inner border (see fig. 304), a long fissure, or, more frequently, a series of depressions,
termed the Mlum, through which the vessels and nerves enter the spleen, and around
which the peritoneum is reflected from the surface of the organ. The upper and
inner extremity of the spleen is directed inwards, and reaches to within about an
inch of the left side of the vertebral column, usually opposite the body of the eleventh
dorsal vertebra. The lower and outer end is blunt, and presents a triangular area,
which may be termed the iasal surface (Cunningham). It lies against the tail of
the pancreas, the splenic flexure of the colon and the costo-colio ligaments. Of

THE SPLEEN.

295

the borders of the spleen the anterior, situated between the gastric and phrenic
surfaces, is the most prominent, and is usually marked near its lower end by one or
two notches. Traced from its inner end, it is seen to curve outwards with the
convexity of the curve upwards. This part of the anterior border reaches forwards
and upwards between the diaphragm and the stomach nearly as high as the fundus of
the stomach. Towards the left side this border turns downwards and somewhat
forwards, being in close contact with the chest wall near the mid-axillary line and
opposite the eighth, ninth, and tenth ribs. It generally terminates in a prominent
angle. The inner border lies slightly internal to the hilum, and separates the gastric
and renal surfoces. The 2)oste7ior border is between the renal and phrenic surfaces.
In some cases it is very well marked, dipping slightly inwards between the diaphragm

Fig. 303. — The pancreas and adjoining viscera from before, i

The liver, the stomach, the greater part of the .small intestine, and the transverse colon have been
removed. P, jjancreas ; d, duodenum ; d.j., duodeno-jejunal flexure ; above the duodenum, and
between it and the head of the pancreas are seen the bile duct, portal vein, and liepatic artery ; asc.
col., desc. col., ascending and descending colon ; spL, spleen ; r.k., l.k., right and left kidneys ; s.r.,
s.r' , right and left suprarenal capsules ; ipt, peritoneum at the back of the abdominal cavity ; m, line
of reflection of the mesenterj ; the line of reflection of the transverse mesocolon is seen along the lower
edge of the pancreas and crossing the duodenum.

and the kidney. It is inclined downwards and outwards opposite the lower border
of the eleventh rib. A loxrei' border separates the phrenic and basal surfaces.

ILelation to peritoneum. — The spleen is almost entirely covered by peri-
toneum which is firmly connected with its capsule. It also gives attachment to two
peritoneal folds — the gastro-splenic omentum and the lieno-renal ligament. The
gastro-splenic omentum consists of two layers of peritoneum, which pass from the
front of the hikini of the spleen forwards and outwards to the posterior surface of
the stomach near its left border. If the outer of these layers be traced over the
spleen it will be found to cover the gastric surface to the left of the hihim, the
phrenic surface and the posterior part of the renal surface. It is then reflected on
to the kidney, forming the posterior layer of the lieno-renal ligament. The inner
layer of the gastro-splenic omentum is derived from the lesser sac, and is continued
into the anterior layer of the lieno-naial ligament, iielow, the two layei's of the
gastro-splenic omentum are continuous with the gastro-colic omentum. The
splenic vessels pass to the spleen between the layers of the lieno-renal ligament.

296 THE DUCTLESS GLANDS.

The spleen varies in magnitude more than any other organ in the body ; and this
not only in different subjects, but, as may be ascertained by percussion, in the same
individual under different conditions. On this account it is difficult or impossible
to state what are its ordinary weight and dimensions. In the adult it may vary in
weight from 100 grammes to 300 grammes, the average being about 170 grammes ;
it generally measures 120 to 130 mm. (five or six inches) in length, and the breadth
of the phrenic surface is 70 to 80 mm. ; its volume varies enormously, but
usually does not exceed 200 to 300 cub. cent. After the age of forty the average
weight gradually, diminishes. In intermittent and some other fevers the spleen is
much enlarged, reaching below the ribs, and often .weighing as much as 18 lbs.
to 20 lbs.

Accessory spleens. — Small detached roundish nodules are occasionally found in the
neighbourhood of the spleen similar to it in substance. These are commonly named accessory
or supplementary spleens {j<i)lencult, liencvli). One or two most commonly occui-, but a greater
number, and even up to twenty-three have been met with. They are small rounded masses

Fig. 304. — The spleen of an infakt five days old, hardened in situ by the chloride of
ZINC method. Drawn from a model prepared by A. F. Dixon.

Gr, gastric surface ; R, renal surface ; B, basal surface : A, anterior border ; A.T, anteto-internal
or inner boi-der ; P.I, posterior or postero-internal border; l.B.A, internal basic angle; A.B.A,
anterior basic angle ; H. bihim.

varying from the size of a pea to that of a walnut. They are usually situated near the lower
end of the spleen, either in the gastro-splenic omentum or in the great omentum.

Spleen in the infant. — The spleen is relatively slightly larger in the new-born child
than in the adult, but the peculiarities in the infant are mainly due to the large size of the
liver and suprarenal eapsule. The under surface of the left lobe of the liver is normally in
contact with it at bii-th, and, according bo Ballantyne, the hepatic area of the spleen is larger
than any of the other surfaces. The same observer suggests that the renal surface in the
new-bom infant is more appropriately named the suprarenal, as this organ lies in contact
with it and separates it in almost the whole of its extent from the kidney.

STKUCTT7EE OF a?HE SPLEEN.

The spleen has two membranous investments — a serous coat derived from the
peritoneum, and s^ fibrous coat {tunica jjropria). The soft substance {pvlf) of the
organ is supported by a reticular framework of fibrous and muscular bands
{trahecuM).

The serous coat is thin, smooth, and firmly adherent to the tunica propria
beneath. It closely invests the surface of the organ, except at the places of its
reflection to the stomach and diaphragm, and at the hilum.

The tunica propria (fig. 305, a), much thicker and stronger than the serous
coat, is whitish in colour and highly elastic. It is continuous with the trabecular

THE SPLEEN.

297

structure within. Along the hilum this coat is reflected into the interior of the
spleen, in the form of large trabeculse, supported and enclosed by which run the
blood-vessels and nerves ; so that these are ensheathed by prolongations of the

Fig. 305. — Vertioal section of a small superficial portion of the human spleen (from Kolliker).

Magnified with a low power.
A, peritoneal and fibrous covering ; b, trabecular ; c c, Malpighian corpuscles, in one of which an
artery is seen cut transversely, in the other longitudinally ; d, injected arterial twigs ; e, spleen-pulp.

fibrous coat. These sheaths ramify with the vessels which they include, as far as
their finer subdivisions, and are connected with numerous trabecular processes
which pass into the interior from the whole inner surface of the fibrous coat. The
aiTangement of the sheaths and trabecule may be easily displayed in the spleen of

Fig. .306. — Thin section of spleen-pulp, highly magnified, showing the mode of origin of a

small vein. (E.A.S.)
V, the vein, filled with blood-corpuscles, which are in continuity witii others, Jil, filling up the
interstices of the retiforin tissue of the pulp, kip the blood-corpuscles have been omitted from the
figure, and the blanched cells are better seen ; w, wall of the vein. The shaded bodies amongst tiie red
bloo<l-corpu8cles are ijale corpuscles.

the ox by pressing and washing out the pulp from a thick section ; and then
they are seen to form a close reticulation through the substance. Thus, the fibrous
coat, the sheaths of the vessels, and the trabeculaj, all of a highly elastic nature,
constitute a distensible framework, which contains in its interstices or areola the

298

THE DUCTLESS GLANDS.

red pulp. These fibrous structures are composed of interlaced bundles of areolar
tissue containing a large amount of fine elastic tissue, and a few plain muscular
fibre-cells. In the spleen of the pig, the dog, and the cat, and to a smaller extent
in that of the ox and sheep, there is a far more abundant admixture of muscular
tissue, and this tissue exhibits a regular rhythmic contractility (Roy).

The pulp of the spleen is of a dark reddish-brown colour : when pressed out
from between the trabeculse it resembles grumous blood, and, like that, acquires a
brighter hue on exposure to the air. In fact, what is thus pressed out 'from the
dead spleen is mainly clotted blood.

When a thin section which has been treated with dilute solution of potash
is examined under the microscope the pulp is seen to be everywhere pervaded

•\'*=^j

Fig. 307. — Eeticulum op spleen pulp shown by silver-chromate method. The capillaries op a
Malpighian corpuscle are also seen. (Oppel.)

1, Malpighian corpuscle ; 2, part of its reticulum ; 3, condensed reticulum around margin of
corpuscle ; 4, more open tissue outside this ; 5, 6, connective tissue of artery ; 7, capillaries of
Malpighian corpuscle ; 8, reticulum of pulp immediately investing arteriole.

by a reticulum of fine fibres continuous with the tissue of the trabeculaa. These
fibres are in the natural condition covered over and concealed by branched con-
nective-tissue corpuscles, which are of various forms and sizes ; in some parts little
but the intercommunicating branches remaining, in other parts the cells being
larger and flatter and in closer connection (fig. 306, p). These corpuscles, which
may be termed the reticular cells of the pulp, contain each a round or oval nucleus,
like connective-tissue cells generally : and, in teased-out preparations of the fresh
spleen substance it is not uncommon to find within them yellowish pigment
granules of various sizes. In the young subject the nuclei of many of these cells
have been noticed to be multiple, or to be beset with prominences as if budding.
The interstices between the sus tentacular cells are, in sections of the hardened organ,,
always found to be occupied by blood (fig. 306, U), white corpuscles occurring in
rather larger proportion than in ordinary blood, especially in the neighbourhood of

THE SPLEEN.

299

the Malpighiau corpuscles to be immediately described. In close relation to the
branched or flattened cells of the pulp, and occupying some of the smaller interstices
between them, rounded, unbranched cells are seen {sj)Iee?i-ceUs), larger than white
blood-corpuscles, but otherwise much resembling them. These cells are amoeboid,
and, like the fixed cells of the pulp, often contain both red blood corpuscles in
yarious stages of disintegration, and clumps of pigment granules. Some observers
have noted the presence of nucleated red corpuscles (similar to those found in
marrow) both in the splenic pulp and in the blood of the splenic vein.

Bohm and v. DavidofE describe tubular spaces within the pulp of the human spleen, lined by
a " rodded " epithelium like that in the convoluted tubes of the kidney, but they leave the
nature of these spaces unelucidated.

Blood-vessels. — The splenic artery and vein, alike remarkable for their great
proportionate size, having entered the spleen by six or more branches, ramify in its
interior, enclosed within the trabecular sheaths already described.

The smaller branches of the arteries have an adventitia derived from the
trabeculae, and pass into the proper substance of the spleen, dividing into small

Fig, 308.-

-S3IALL ARTERY FROM THE DOG's SPLEEN WITH MaLPIGHIAN CORPUSCLES ATTACHED.

10 Diameters. (Kolliker. )

tufts of arterioles arranged in pencils (fig. 308). But before they thus terminate,,
the adventitious fibrous coat which is prolonged over them from the trabeculge
becomes transformed Into lymphoid tissue, which forms a comparatively thick sheath
along each. This lymphoid sheath is abruptly dilated here and there into small
oval or spheroidal enlargements, measuring on an average OSC) mm. in diameter, but
varying in size from much smaller than this up to 1 mm., and closely resembling
the lymphoid follicles met with in the intestine and elsewhere. These lymphoid
expansions may be seen on the surface of a fresh soction of the organ as light-
coloured spots scattered in the dark substance composing the pulp, and have been
long noticed and described as the Malpigliiau corpuscles of the spleen (fig. W^), c c,
fig. .308). In some cases the corpuscle is d(!velo])ed upon one side only of the arterial
wall, upon which it then appears to be sessile ; whilst in other instanciis — and this
is ihe most frequent in the human subject — the expansion takes place all round the
circumference of the vessel, Ijy which it then appears to be pierced. In either case
the artery sends off radiating branches to be distributed in the Malpighian
corpuscle.

300 THE DUCTLESS GLANDS.

As just stated, the Malpighian corpuscles are localised expansions of the
lymphoid tissue of which the external coat of the smaller arteries of the spleen is
formed, and have apparently been produced by increased multiplication of lymph-
cells at the spots in question. The reticulum of the tissue is comparatively open,
being almost absent towards the centre of the corpuscle : at the confines it becomes
closer ; there is, however, no distinct boundary separating it from the retiform
tissue of the pulp. The meshes are densely packed with lymphoid corpuscles, and
the tissue is traversed by capillaries.

The small arteries, after leaving the Malpighian corpuscles, terminate in capillary
vessels, which soon lose their tubular character, the cells which compose their wall
becoming partially separated ft'om one another by elongated clefts ; those at the
extremity of the capillary have branching processes and are united by these with
the branched connective-tissue cells of the pulp. In this manner the blood can flow
directly into the interstices of the pulp tissue. The veins, which form a network
of intercommunicating spaces within the pulp, commence in the same manner as the
capillaries terminate ; that is to say, the layer of flattened cells which lines and
mainly composes their walls, on being traced back, loses its epithelioid character,
and the cells, becoming thickened and spindle-shaped and their nuclei prominent,
are found to be separated here and there from each other, and to be connected by
processes with the cells of the pulp (fig. 306). The small veins take a different
■course from the arteries, for they soon pass to the trabeculse and are conducted upon
and within these, fr*eely joining and anastomosing ; whereas the arteries appear to
have few or no anastomoses within the substance of the organ.

The small veins within the pulp of the human spleen often exhibit peculiar
transverse markings. These are produced by fine elastic fibres of the reticulum,
which encircle the vessels. Structures which have been described as " ellipsoids,"
which are in fact condensations of the reticular tissue of the spleen pulp not loaded
with leucocytes as in the Malpighian corpuscles, are often found encircling the
terminations of the arterioles. They are stated by Miiller (bird) and Whiting (cat)
to be surrounded by a special vascular sinus, but this is denied for the cat by Carlier.

From the description above given, it would appear that the blood in passing
through the spleen is brought into immediate relation with the elements of the pulp,
and no doubt it undergoes important changes in the passage ; in this respect
resembling the lymph as it passes through the lymphatic glands. Two modifica-
tions which are probably effected in it may be here pointed out. In the first place
the lymphoid tissue ensheathing the arteries, together with that composing the
Malpighian corpuscles, would appear like the same tissue in the lymphatic glands,
and other parts, to be the seat of the production of pale blood corpuscles. At the
circumference of this tissue, these may pass into the interstices of the pulp, and so
into the blood. It is found, in fact, that the blood of the splenic vein is extremely
rich in pale corpuscles. In the second place, red blood-corpuscles may be taken up
by the pulp-cells, their colouring matter being transformed into pigment. The
splenic cells have, indeed, been noticed, when examined on the warm stage, to take
red corpuscles into their interior. Finally, if it be the case that nucleated red
corpuscles occur normally in the spleen, it is probably also a seat of formation of
coloured blood corpuscles.

The lymphatics of the spleen form two systems, a trabecular and a perivascular.
The vessels belonging to the former system run in the trabeculte and are in com-
munication with a superficial network in the capsule. The perivascular lymphatics
take origin in the interstices of the lymphoid tissue which ensheaths the smaller
arteries, and which forms the Malpighian corpuscles ; they do not, therefore, at
first form distinct vessels. When these are seen they commonly run in pairs, one
•on either side of an artery, uniting over it by frequent anastomoses, and sometimes

THE SPLEEN. 301

partially or wholly enclosing it. At the hilum the two sets of lymphatics join one
another and proceed along with the main blood-vessels, and ultimately pass into
lymphatic glands at the back of the abdomen.

The nerves, derived from the solar plexus, surround and accompany the splenic
artery and its branches. They are most probably distributed to the vessels and
plain muscular tissue of the framework.

RECENT LITERATURE OF THE SPLEEN.

Ballantyne, J. W., The relations of the ahdominal viscera in the infant, Edinburc'h Med. Jour.,
July, 1891.

Bannwarth, l'nt(rsuchungen Uher die Mih, Archiv f. raikroskop. Anat.. BJ. xxxviii., 1891.

Bdhm & V. Davidoff, Handbuch der Histologie, Leipzig, 1895.

Cunningham, D. J., On the form of the spleen and the kidneys, Jouin. of Anat. and Physiol.,
vol. xxix. , 1895.

earlier, The minute structure of the reticulum in the cat's spleen, Journ. of Anat. and Physiol.,
voL ssix.. 1895.

Denys, Note preliminaire surla structure de la rate et sur la destruction dc globules rouges qui
s^opdre normalcmciit a I'interieur de cet organe. Bulletin de I'acadomie r03'ale de medecinc de
Belgique, 1888.

Eliasberg-, Miron, Experivientelle Untersuchungen uher die Bluthildung in der Mih der
Saugetiere, Dorpat. luaug. Diss., 1892.

Fusari, Romeo, Sul modo di distrihuirsi delle fibre ncrvose nel parenehima della milza, Monitore
zoologio italiano, anno iii. , 1892.

Hoyer, H., Ueher den Bau der Milz, Morphol. Arbeit., Bd. iii., 1893.

V. Koelliker, A., Die Nerven der Milz und der Nieren und die GallcncapiUaren, Sitzgsber. d.
WilTzb. phys.-med. Ges., 1893.

V. Kupffer, C, Ueber die Entwichdung der Milz und Pancreas, Miinch. med. Abhandl.,
Munchen, 1892.

Lagriiesse, E., Le tissu spUnique et son d4veloppement, Anatom. Anz., Jabrg. vi., 1891.

Oppel, A., Ueber Gitterfasern der menschl. Leber u. Milz, Anat. Anz., Jahrg. vi., 1891.

Toldt, Zur Anatomic der Milz, Wiener med. Wochensch., 1889.

:303

THE DUCTLESS GLANDS.

SUPRARENAL CAPSULES.

The suprarenal bodies or capsules (capsulm atraMlarice, seu rems succenturiafi
of old anatomists), also frequently termed " adrenals," are two flattened bodies,
each of which surmounts the corresponding kidney (fig. 309). They are both

Fig. 309. — Front view of the eight kidney and sitprarenal body of a
FULL GROWN FQSTUs. (Allen ThoiBson. )

This figure shows the lobulated form of the fcetal kidney, r ; v, the renal
vein and artery ; u, the ureter ; s, the suprarenal capsule, the letter is
placed near the sulcus in which the large veins {v') are seen emerging from
the interior of the organ.

situated in the epigastric region, one on each side of the
vertebral column. They differ from one another in shape
and also in their relations. The right capsule has a
flattened triangular form, one surface called anterior looks
forwards and outwards, and the other, the posterior, back-
wards and inwards, while the angles are directed upwards,
downwards and outwards. The anterior surface has a furrow,
called the Idlum, which passes horizontally a little below the
upper border and vertically near the inner border. At the
union of these two parts of the fissure the capsular vein emerges from the organ.
The area above and internal to the fissure is depressed and forms about one-third
of the anterior surface. The inner part of this area lies behind the inferior vena
cava, and the upper part is in direct contact with the liver. The outer and larger

Fig. 310. — Anterior surface of
the suprarenal capsules,
modified from Rolleston.
(J. S.)

A, right capsule, s, c, i, its supe-
rior, external and inferior angles ;
a, area in direct contact with liver ;
&, area behind inferior vena cava ;
c, area, below and external to the
fissure^ covered by the peritoneum
and the liver exceirt near the inferior
angle where it comes in contact with
the duodenum ; d, fissure on ante-
rior surface ; /, vein.

B, left capsule, s, its superior
angle ; d, fissure on anterior sui-
face ; /, vein ; L. R, left renal vein ;
L.S, left spermatic vein.

portion of the anterior surface is covered by the peritoneum, which separates it
from the liver, except a small area near the inferior angle, which sometimes lies
against the duodenum. The posterior surface also has a depression dividing it
into two parts, one of these, the upper and larger, lies against the diaphragm, and
is bounded below by an elevation projecting into the groove between that muscle
and the kidney ; the lower and smaller area is in contact with the kidney.

The left suprarenal capsule is slightly larger than the right. It does not
project so much above its corresponding kidney, but is prolonged downwards along
the upper half of its inner border. Looked at from the front, its outline is
crescentic, the concavity of the crescent being directed downwards and outwards
towards the kidney. The anterior surface lies in contact with the upper end of the
renal surface of the spleen and the stomach near its cardiac orifice, while its lower
half is crossed by the pancreas and the splenic vessels. It has a groove passing

THE SUPRARENAL CAPSULES.

303

downwards and forwards, at the lower end of which the suprarenal vein emerges.
The posterior surface is divided into two parts by a prominent vertical ridge, the

Fig. 311. — Section of the suprarenal body. (Allen Thomson.)

A vertical section of the suprarenal body of a foetus, twice the natural size, showing
the lower notch by which it rests on the summit of the kidney (?•), and the anterior
notch by which the suprarenal vein {v) issues, together with the distinction between
the medullary and cortical substance.

area mesial to the ridge looking inwards and backwards and resting
upon the left crns of the diaphragm and the lateral area outwards as
well as backwards against the kidney.^

The suprarenal capsules measure from 1\ in. to 2| in. (30 mm.
to GO mm.) from above downwards and about Ij in. (30 mm.) from
side to side ; their thickness is from |th in. to -\ in. (4 mm. to G mm.),
the left being usually thicker than the right. The weight of each in the adult
is about 1 drachm (4 grammes), the left being slightly the heavier. They are
nearly as large at birth as in adult life.

Structure. — Besides a covering of areolar tissue mixed frequently with much

Fig 312. — Vertical section of scprarenal boi>v ; human. MAfiNiFiED. (Kliertli.)
1, cortical suljstancc ; 2, medullary substance : a, capsule ; h, '/.oiia glonierulosa ; c, zona fasciculata
d, zona reticulariH ; e, groups of medullary cella ; /, section of a large vain.

V\g. 313. — Section of the cortex of the doo's suprarenal. (IJohni and v. DavidolF.)
a, fibrouH covering ; h, zona glomerulosa ; c, zona fasciculata ; d. zona reticularis.

' The above description is based largely upon the account of these organs givo:i by II. D. Rollestor
^Journal of An.'iUiniy and rhysiology, vol. xxvi ).

304

THE DUCTLESS GLANDS.

fat, the suprarenal capsules have a thin fibrous investment. On the exterior their colour
is yellowish or brownish-yellow. When cut into (fig. 311) they are seen to consist,
of two substances : one, external or cortical, of a deep yellow colour, firm and
striated, and forming the principal mass of the organ ; the other, internal or
meclullary, in the adult of a dark brownish-black hue, and so soft and pulpy that-
some anatomists have erroneously described a cavity within it.

The fibrous coat (figs. 312, 313, a), which is distinguishable into an outer
looser and an inner firmer part, is so intimately connected with the deeper parts
that it cannot be removed without lacerating the subjacent structure. Its deeper
layers contain plain muscular cells, at least in some animals : it is continuous with
the septa which enter into the formation of the substance of the organ.

The cortical part of the suprarenal body, examined in a section with a low magni-
fying power (fig. 312, 1 ; fig. 313), is seen to consist of a fibrous stroma, in which are
embedded column-hke, intercommunicating groups of cells (c). The groups measure
on an average T^th inch (-036 mm.) in diameter, and are arranged vertically to the
surface of the organ. In the deepest part of the cortex, however, the colour is darker,
and the columnar arrangement is lost, the stroma being more equally distributed {d) ;
and immediately beneath the fibrous coat there is another narrow zone in which the
stroma encloses what in section look like rounded or oval spaces occupied by groups
of cells, which are really the outer ends of the columnar groups above mentioned {h).
These inner and outer layers have been named respectively zona reticularis and zojia
(jlomerulosa, and the term zona fasciculata is applied to the main part (c) ; but the
transition from one of these parts to another is in man not sudden nor indicated by
any sharp line of demarcation.

The cells which form the groups and columns of the cortical substance are

Fig. 314. — Cells and cell-groups from the outermost later of the cortical substance of the

SUPRARENAL BODY. HiGHLY MAGNIFIED. (Eberth. )
Fig. 315. A SMALL PORTION OF THE MEDULLARY PART OF THE SUPRARENAL CAPSULE Oi' THE OX

(Eberth.) Highly magnified.

polyhedral in form (fig. 314) : their protoplasm is -finely reticular, and not
unfrequently contains yellowish oil globules. The cells vary from '0125 mm. to
'02 mm. in diameter.

In some animals (horse, dog, cat), the spaces of the zona glomerulosa are occupied
by regularly arranged long columnar cells, set around a sort of lumen, and looking
not unhke part of a glandular tube (fig. 313, I). In man, however, most of the cells
of this part are polyhedral, like those of the other zones.

The medullary part (fig. 312, 2) of the suprarenal capsule is marked off from
the cortical part by a layer of loose connective tissue. In the thinner parts of the
adult organ there is no medullary part, and the layer of connective tissue referred
to is found separating the deep surfaces of two opposed portions of the cortical part ;
but in the young state the distinction of cortical and medullary portions probably

THE SUPRARENAL CAPSULES. 305

extends throughout the whole gland. The medullary part is pervaded by. large
venous capillaries, which receive the whole of the blood which has passed through
the orgau. These venous capillaries are supported by the fibrous stroma, which
also contains, especially in man, a number of bundles of plain muscular cells
disposed parallel to the course of the larger veins, and forming a complete invest-
ment to the issuing suprarenal vein (v. Brunn). The general arrangement of the
stroma is reticular ; in its meshes are enclosed groups of cells (fig. 315), which ditfer
from those of the cortex in being more irregular in form, larger in size, of a clearer
aspect, and destitute of oil-globules. They are frequently highly vacuolated.
Moreover they become stained of a deep brown colour by solutions of bichromate
of potasli, whereas the cortical cells are but slightly tinged by that re-agent.

In some animals the medullary cells contain a large amount of reddish-brown pig-ment,
which marks the medulla off sharply from the cortex, but this is not generally the case in the
human subject, the deep colour of the medulla being chiefly due to the blood within its
numerous vessels.

Varieties. — One or both capsules may be absent, although this is very rarely the case.
Accessory suprarenal capsules are occasionally met with varying in size from a pin's
head to that of a large pea. The smaller ones have no medullary substance, but the large ones
jiossess a medulla (RoUeston). The accessory capsules are generally found near or upon the
capsule itself and united to it by connective tissue. Sometimes they are partially embedded
in the kidney or liver, and Marchaut has found them in the broad ligament of the uterus,
and Schmorl on the spermatic vessels near the inguinal canal.

Arteries and veins. — Tlic suprarenal bodies receive arteries from three
sources, viz., Irom the aorta, the phrenic and the renal arteries. All these arteries
break np into small branches before entering the capsule. The veins, which pass out
from the centre, are usually united into one for each organ. The right vein enters
the inferior vena cava immediately, while the left, after a longer course, terminates
in the left renal vein.

The small arteries, entering from the surface, run in the septa parallel to the
columns, frequently anastomosing together, and surrounding each group of cells
with a fine capillary network. From these capillaries the blood is continued
into the medulla, where it is collected into the large venous capillaries already
mentioned. The chief efferent vein emerges at the hilum. According to
Pfaundler, none of the vessels in the suprarenals have any coat other than the
endothelium.

Lymphatics run in the trabeculaB of the cortical substance and are connected
with cleft-like spaces between the trabeculas and the cell-columns, and even with fine
clefts between the cells within the columns (Klein). They communicate with
efferent valved lymphatics both in the fibrous coat and in the medulla, where they
are very numerous, forming an especially close plexus around the central vein.

Nerves. — The nerves, which are exceedingly numerous, are derived from the
.iilar j/lexus of the sympathetic and from the renal plexuses. According to
JJergmann some filaments come iVom the phrenic and iineinuo-fiastric nerves. They
are made up mainly of medulhited fibres of different sizes, and they have many small
ganglia upon them before entering the ofgan. The nerves are especially numerous
on the lower half and inner border. Tliey ramify between the cells of the cortex,
where they are especially abundant in the zona glomerulosa. In the medulla they
are connected with numerous small ganglion-cells, and are distiibufed to the blood-
ves.sels and amongst the glandular cells.

Function. — Removal of the HUprarenal bodies in animals is speedily followed by symj)toma
of extreme muscular i>rostration and, witliiti a very few days, by death (IJrown-Sc'cjuard,
]>ii»f;). iJiseaHc of the organs is usually accompanied by the a])pcaraiicci of l)r()ii/.ed patcln-s on
various |»arts of the skin and mucous membranes (Addison, iNu")^, ami the syniptoms in ad-

VOL. III.. VT. i. S

806 THE DUCTLESS GLANDS.

vanced disease are similar to those resulting from removal. The watery extract of the medulla
of the capsules contains a (non-proteid) substance which produces when injected even in
minute quantities into the blood-vessels of an animal, a g'reat aug-mentation of the contraction
of the muscular tissue of the heart and arteries, and prolongs the contractions of the skeletal
muscles (Oliver and Schllfer, 1894).

RECENT LITERATURE OF THE SXJPRARENALS.

Alexander, Carl, Untersuchungcn ucbcr die Nehennieren unci Hire Beziehimgcn zum Ncrrcn-
system, Beitrage ziir patliologischen Anatomie und zur allgemeinen Pathologie, Bd. xiv., 1891.
Arren, L., Esaai sur les capsules surrenales, These, Paris, 1894.

Biesmg, Karl, Ueher die Nehennieren und den Sympathious bei Anencephalen, Bonn, G.
Georgi, 1886.

Brandt, Alexander, Ueher den Zusammenhang der Glandula suprarencdis 7nit dem Parovarium
resp. der Epididymis hei Hilhnern, Biolog. Gentralbl., Bd. ix., 1889.

Canalis, P., Contribution a Vetude du developpement et de la patJtologie des cajosules surrenales,
Internationale Monatsscbrift flir Anatomie, Bd. iv.

earlier, E. W., Note on the structure of the suprarenal body, Anat. Anzeiger, Jg. viii., 1893.
Chiari, H. , Zur Kenntniss der aecessorischen Nehennieren des Menschen, Ztschr. f. Heilk.,
Prague, 1884.

Dogiel, A. S., Die Nervencndigungen in den Nehennieren der Saiigetiere, Arcli. f. Anat. u.
Physiol., Anat. Abth., 1894.

Dostoiewsky, G., Ein Bcitrag zur milcroshopischen Anatomie der Nehennieren hei Sdugethiercn,
Arcliiv fiir niikroskopische Anatomie, Bd. xxvii.

Fusari, Romeo, Sulla terminazione delle fibre nervose nelle capsule surrenali dei mavimiferi,
Atti della R. Accad. delle Scien. di Torino, vol. xxvi. 1890-91 ; Be la terminaison des fibres nervei(,ses
dans les capsules surrenales des mammiferes, Archives italiennes de biologie, t. xvi., 1891.

Gruarneri, J., et Magini, J., Studie sulla fina struttura delle capsule suprarenali. Atti della R.
Accademia dei Lincei, 1883 ; Etudes sur la fine structure des capsules surrenales, Archives italiennes
de biologie, tome x. , 1888.

Janosik, J., Bemerkungen iiher die Entwichelung der Nebenniere, Arcb. f. mikr. Anat., 1883.
LieTbmann, Arthur, Ueher die Nehennieren und den Symp)athicus hei Hemicephalen, Bonn,
1886.

Magnus, Kich., Ueher das anatomische Verhalten der Nehennieren, der Thyreoidea imd Thymus
und des SyjnjKitMeus bei Hcmiceplialen, Konigsberg, 1889.

Manasse, Paul, Uber die Beziehungen der Nehennieren zu den Venen und dem venosem Kreislauf,
Arch. f. path. Anat., Bd. cxxxv., 1894.

Iffiarchand, Beitrage zur Kenntniss der normaZsn und palhologischen Anatomie der Glandida
carotica unci der Nehennieren, Internat. Beitrage zur -wissenschaftl. Medicin, Virchow Festschrift,
Bd. i., 1891 ; Ueher accessorische Nehennieren im Ligamentum latum, Virch. Arch. f. jjath. Anat.,
Bd. xcii.

Martinotti, C, Contribute cdlo studio delle capsule s%trrencdi, Ann. di freniatr., 1891-92, v. iii. ;
and Giorn. d. r. accad. d. med. d. Torino, 1892.

Mattel, Sulle fibre muscolari liscie delle capsule soptrarencdi cdlo stato normcde e patologico,
Giornale della R. Accademia di Medicina di Torino, anno xlix., 1887.

Michael, Zum VorJcommen aecessorischen Nehennieren, Deutsches Archiv flir klinische Chirurgie,
Bd. xliii., 1888.

Minot, C. S., Morphdogy of the suprarenal capsides, Proc. Amer. Assoc, for the Adv. of Science,
vol. xxxiy.

Oliver, Gr. and Schafer, E. A., On the physiological action of extract of the suprarencd
ccqjsules. Journal of Physiology, 1894 and 1895.

Pfaundler, Zur Anat. der Nebenniere, Sitzungsb. der Wiener Akad., 1892.

Pilliet, A. H., Capsule surrenale sous la, capsule fibreuse du rein droit, Bull, de la soc. anat. de
Paris, annee 68.

Kabl, Hans, Die EntivicJcelung und Struktur der Nehennieren hei den Vogeln, Archiv f.
mikroskop. Anatomie, Bd. xxxviii., 1891.

KoUeston, H. D., Note on the anatomy of the swprarencd bodies. The Journ. of Anat. and
Physiol., vol. xxvi., 1892 ; The Gulstonian Lectures on the sii'prarencd bodies, Brit. Med. Jour.,
1895, vol. i.

Solg'er, R., Anatom. Einleitiing: Ilarnapparat, Nebenniere, Klin. Hdb. d. Harn- und SexuaJorg,
von. W. Zidzer, Leipzig, 1894.

Stilling-, H., Zur Anatomie der Nehennieren, Virchow's Archiv f. path. Anat., Bd. cix., 1887.
Weldon, W. E. K., On the suprarencd bodies of vertebrata, Quart. Jour. Micr. Science, 1885.
Zander, E.., Ueher funktionelle und cicnctische Beziehungen der Nehennieren zu anderen Organen,
spczicll zum Grosshirn, Beitr. z. pathol, Anat, v. £. Ziegler, Bd. vii., 1890.

THE THYMUS GLAXD.

307

THE THYMUS GLAND.

The thymus gland or body is a temporary organ which reaches its greatest size
at about the end of the second year of Hfe, after which period it ceases to grow,
and is gradually reduced to a mere vestige. Its function is not fully understood,
although it is probable that it is in some way connected with the elaboration of the
blood in infancy. "When examined in its mature state in an infant under two years
of age, it appears as a narrow elongated glandular-looking body, situated partly in
the thorax, and partly in the lower region of the neck (fig. 316) : below, it lies in

Fig. 316. — The thymus in a ciiilh hv six sionths. (Sappey.)

A. .Situation, form and relations of the gbiud. 1, liglifc IoIjc ; 2, left lobe ; 3, median furrow ; 4,
lung, .soinewliat everted ; 5, internal mammary vein ; ('), thyroid liody ; 7, inferior, 8, middle thyroid veins ;
9, common carotid artery ; 10, internal jugidar vein ; 11, pneumo-gastric nerve. I!. Right lolie of the
thymus after removal ot' its envelope ; 1, its apex ; 2, its hase ; .'5, thin outer border ; J, thick inner
border. (J. The gland iiuravelled, showing the lobules, 3, group<'il around a centra! cord ; 4, the central
cord or .strand of councctive tis.sue,. connecting the lobules.

the superior and aiiteri(n' mediastinal spaces close behind the sternum as far down
as the fourth rilj-cartilage, and in front of the great vessels and pericardium ; above,
it extends upwards upon the trachea in the neck as high as tlie lower border of the
thyroid body, being covered ?jy the stcrno-hyoid and sterno-thyroid muscles. Its
colour is gi-eyish, with a pinkish tinge ; its consistence soft and pulpy, and its
surface apjcirs distinctly lobulated. It consists of two lalyral lobes, which touch
eadi other along the middle line, and are of a nearly symmetrical long pyramidal
form, though genei-ally unc'iual in size, sometimes the left, and at oth(!i' times the
right lobe being the larger of the two. An inlcruydldle lobe often exists between the
two lateral ones, and occasionally the whole body forms a single mass.

X 2

308

THE DUCTLESS GLANDS.

Externally the gland is in contact with the pleura, near the internal mammary
artery, and higher up (in the neck), with the sheath of the carotid artery. The
dimensions of the thymus vary according to its stage of development. At birth it
measures rather more than two inches (60 mm.) in length, an iach and a half
(37 mm.) in width at its lower part, and about one quarter or one third of an inch
^g — 8 mm.) in thickness. Its weight at this period was found by Testut, on an
average of twenty cases, to be 5 grammes.

At piiberty the tlivmus is generally rediiced to a mere vestige which, has entirely lost its
original structure, and consists of brownish tissue occupying part of the superior mediastinum.
Occasionally it is still found in good condition at the twentieth year : but generally only
traces of it remain at that time, and these are rai'ely discoverable beyond the twenty-fifth or
thirtieth yeai'.

Structure. — The lateral lobes of the thymus gland are each invested by a thin
capsule of areolar tissue, which sends partitions into the gland between the lobules :
on its outer surface the cap.sule is covered by a layer of flattened cells. Each lobe

Fig. 317. — From a sectiox of the xHTMrs of a child. (E. A. S.)

c, cortex of a lobule partly separated into nodules by the trabesulas, tr. ; b, h, blood-vessels and
c, c, connective tissue corptiscles in the medulla.

consists of numerous polyhedral lolndes, connected by a more delicate intervening
areolar tissue. These primary lobules are made up of a number of small nodules or
follicles (fig. 317), one to two millimeters in diameter. Each follicle is composed
of a central part or medulla, and an external larger part or cortex. The cortex is
in many respects similar in structure to an ordinary lymphoid follicle, such as
those of the tonsils or of Peyer's patches in the intestine : consisting, like these, of
retiform tissue composed of a fine reticulum of fibres, the meshes beiug filled with
lymphoid cells {ihymus corpuscles). At the surface of the follicle the retiform tissue
is somewhat closer, so as to form a species of capsule for it. In some animals these
capsules coinpletely enclose the follicles, but in others, including man, several follicles
may be imited towards the centre of the lobule (see fig. 317), which is then com-
monly of softer consistence than the other parts, and apt to break down if not
perfectly fresh, so as to give the deceptive appearance of a centi-al cavity.

In the medulla, the retiform tissue is coarser and the lymphoid cells fewer ; but
it contains here and there nests of cells which have a concentric structure, and are
known as the concentric corpuscles of Hassall. They vary in size from 0*025 mm. to
three times that diameter, or more ; the larger ones (compound corpuscles) often
contain smaller ones in their interior (fig. 318).

THE THYMUS GLAND. 309

Each nest is composed of an envelope of keratinized epithelium-like cells enclosing
a central mass, formed of one or more granular cells. Cells like those in the centre
of the nest are also found, unenclosed, in the retiform tissue of the follicle, and
occasionally attain a large size fgiant-cells). The concentric corpuscles are vestiges of
the original epithelial tube which is found in the developing thymus (see Vol. I., Pt. J,

Fig. 318. — Part of the medulla of a thyml's oland showing the reti-

Cl'LUM, THE LYMPHOID CELLS OR THYJIUS CORPUSCLES AND TWO CONCEN-
TRIC CORPUSCLES. (Cadiat. )

p. 111). According to some authorities the thymus corpuscles
are also of epithelial {i.e., hypoblastic) origin, and are not derived
as has usually been believed, from the surrounding raesoblastic
tissue. Small portions of thymus tissue are constantly found,
according to Kohn, in association with the thyroid and para
thyroids. Schaffer describes in the thymus nucleated red Ijlood
corpuscles like those met with in bone-marrow.

The retrogressive development of the gland is accompanied by an increase in the
interstitial connective tissue, which also invades the follicles. In this tissue plasma-
cells become accumulated, and then appear to be eventually transformed into fat-
cells, the normal structure of the thymus liecoming gradually obliterated. It has
been shown, however, by Waldeyer, that even in advanced age not only can the
original shape of the thymus be distinctly made out, but that in addition there are
constantly to be found traces of its original structure in the form of small masses
of thymus corpuscles and even of concentric corpuscles.

Vessels and Nerves. — The arteries of the thymus are derived from various
sources, viz., from llie infenial mammarij, the inferior and sieptrior thuroitl, the
subclavian and carotid arteriea. Their branches penetrate to the follicles, where
they form a plexus which surrounds the cortex and from which capillaries converge
towards the medulla. In some animals these vessels loop back towards the cortex,
but in others they open into an inner vascular circle which lies just within the
lx)undai7 of the medulla. The veins, for the most part, open into the left
iimominate vela.

The lymphatics are large. According to the observations of His on the calf, the
larger bUjod-xessels passing to the centre are each accompanied by two or more
lymphatic trunks. These arise from an interlobular plexus, Avhich again is in
connection with vessels which suiTound and enclose the individual follicle;^ without
penetrating them fas in those of the intestine).

The nerves arc very minute. Haller thought that they were partly derived from
the phrenic nerves, but according to Cooper, no filaments from these nerves go into
the gland, although they reach the investing capsule, as does also a l)ranch from the
descendens hypogloasi. Small filaments, derived from the jmeumo-yastric and Hijmpa-
fhetic nervea, descend, on the thyroid body, to the upper part- of the thymus.
SynipatJK-tif: n* ives also reach the gland ahjng its various arteries.

RECENT LITERATURE OF THE THYMUS GLAND.

Beard, J., The ilrrdopmeid and iirnhiililc fnnilMn <>f the l/i.i/miiH, Aii.it. An/.ci^^cr, I'd. ix,, 1894.

Capobianco, Contrib. ii In nwrphoL da thi/mun, Arcli. ital. <le bid., .vvii., 189'2.

Flemming'. W., Die Zellvcrimkrumj in d. Lymp/idriinen u. verwand. (Jr<jancn, tic, Arch. f.
iiiikr. Ariat/., xxiv,, IHH!).

O-ulland, 77" f/nr/oprarnt of fii/ipoKc timm wiik rHppruil reffmirc to t/ic lom'd and thymus,
lAhor. |{<;i.'.rt", <,f tli<; K. CuW. «f I'liyni'-iiinH of Kdiiiljiir^li, vol. iii., 18!)1.

Mon^uidi, C, Sulla jilandoln limo, raniia, 1885.

3X6 THE DUCTLESS GLA.NDSi

Schaffer Josef, Ucber das VorJcommen eosinophiler Zcllen in clef menscfdichen TJiymUB
Centralbl f d medicin. Wissensch., 1891: Uebe7' den feineren Bern der Thymus und deren Bezie-
Imnq zur BlutMldung, Sitzungsb. d. K. Akad. d. Wisseusch., Wien, Bd. cii., 1893 ; KrUische
Bemerkungen uber einige neuere Thymusarheiten, Intern. Monatsschr. f. Anat. u. Physiol., J3d. xi.,
1 SQ4

Waldeyer, Lie Euckbildung der Thymus, Sitzungsb. d. Kgl, preuss. Akad. der Wisseusch. zu

Berlin, 1890.

Watney,!!., The minute anatomy of the Thymus, FluL Tmns., 1882.

Zoja, Gr., Sidla permanenza delta glandola timo nei fanckilU e negli adolescenti, Boll, scientif.,

vii No. 1, e R. Instituto Lombardo, 1885.

THE THYROID BODY.

811

THE THYROID BODY.

The thyroid body is a highly vascular organ consistiDg of two lateral lohcs generally
nnited towards their lower ends by a transverse portion named the isthmus. Viewed
as a whole it is convex on its external and anterior aspects forming a rounded pro
jection upon the trachea and larynx. It is covered by the sterno-hyoid, omo-hyoid,
and sterno-thyroid muscles, the last-mentioned being in close contact with the
lateral lobes. The sterno-cleido-mastoid muscles also overlap it. Its deep surface is
concave where it rests against the trachea and larynx, and external to these structures
and the recurrent laryngeal nerves its lateral lobes extend backwards to the sides of
the pharynx and oesophagus. In consequence of the deviation of the oesophagus to
the left side the lower end of the left lateral lobe lies slightly in front of that struc-
ture. The lateral lobes also pass outwards in front of the common carotid arteries,
the carotid sheaths intervening. Each lateral lobe is somewhat conical in form with
the apex upwards, and extends from the fifth or sixth ring of the trachea to the side
of the thyroid cartilage of which it covers the inferior cornu and adjacent portion of

Fig. 319. — Horizontal section of traciiea, (esophagus', and TnyRoiR body. (J. S. )

1, i-e.sophagu.s ; 2, cavity of trachea ; 3, cartilaginous riug of traclica ; 1, tiiyroi'l body ; 5, inferior
thyroid artery ; 6, recurrent laryngeal nerve.

Fig. 320.-

-Sketch showing the form and position of the thyroid body.
half the natural size.

(.Vllcn Thomson.) One

The larynx and surrounding ii.irts .are viewed from before ; on tlio riglit side tlio muscles covering
the th\Toi(l body are rctaineil, on the left side they are removed ; h, hyoid bone ; th, right thyro-hyoid
muscle ; o h, omo-hyoid ; .sh, sterno-hyoid ; st, .sterno-thyroid ; o, crico-thyroid membrane ; tr, trachea ;
CB, fcsoidiagus ; t, right lobi; of the thyroid body ; t', the left lobe ; (', the isthmus ; ft, the fibrous or
iniiHcular band termed levator thyroidem, which is more rarely found in the middle lino or to the right
side, and which existed in the ca-c from which tiie figure was taken.

the al;i. The transverse portion or isthmus commonly lies across the second, thh'd
and fourth rings of the trachea, but is veiy inconstant in si/.c, shape, and position.
From the uppfM' part of the i.sLlimns or from the adjacent portions of one of the lobes
a slender conical process called the pi/ramid or middle lobn often proceeds upwards to
the hyoid bone to which it is attached by fibrous or muscular tissue (fig. 31(1). The
thyroid gland is connected to the trachea and laryn.v by fibrous tissue so that it
follows the movements of thwic organs. In front the pretracheal fascia (xtends

313

THE DUCTLESS GLANDS.

from the isthmus and adjacent portions of the lateral lobes upwards to the front of
tlie cricoid cartilage and the lower border of the thyroid cartilage, forming a some-
what indistinct anterior ligament of the gland. Further, each lateral lobe is attached
by a firm band of fibrous tissue, the lateral ligament, to the side of the cricoid
cartilage and the first two or three rings of the trachea.

Size, weight, and colour. — Each lateral lobe measures about two inches
(50 mm.) in length, an inch and a quarter (80 mm.) in breadth, and three quarters
of an inch (18 mm.) in thickness at its largest part which is below its middle ;
the right lobe is usually a little wider and longer than the left. The isthmus
measures nearly half an inch (12 mm.) in breadth and from a quarter to three
quarters of an inch in depth.

The weight of the thyroid body is ordinarily rather more than an ounce (30 to
40 g.). It is generally larger in females than in males, and appears in many of the
former to undergo a periodic increase about the time of menstruation. It varies
a good deal in size and occasionally undergoes enormous enlargement.

Its colour is usually of a dusky brownish red, but sometimes of a yellowish hue.

Fig. 2>'21. A THYROID GLAND SHOWING BIFURCATION OF THK LOWER END OF PYRA-UID PROCESS. ONE

PART GOING TO EACH LATERAL LOBE. (After C. F. Marshall.)

Fig. 322. — A THYROID GLAND AVITH PYRAMIDAL PROCKSS ATTACHED TO LEFT LOBE OF GLAXD, ISTHMUS

ABSENT. (After G. F. Marshall.)

Fig. 323. — A THYROID GLAND, WITH BOTH PYRAMIDAL PROCESS AND ISTHMUS ABSENT. (After C. F.

Marshall. )

Varieties. — As a rule the two lateral lobes are approximately equally well developed, but
occasionally they are very unequal in size and in rare cases one lateral lobe may be entirely
absent. The isthmus varies greatly in size and not unfrequently it is absent or fused with
one or other of the lateral lobes. Observers differ considerably as to the frequency with
which a pyramidal process occurs. Thus Streckeisen met with it in 104 out of 153 cases, or
nearly 68 per cent., while Marshall only found it in 24 out of 60 cases, or 40 per cent. It is
usually attached below to the isthmus on the left side of the median plane, but it may join
one of the lateral lobes, and above it is connected with the hyoid bone. Out of the 104
specimens in which the pyramidal process was present .5.5 were glandular up to the hyoid
bone, in 12 the process was connected to that bone by fibrous tissue, and in 2 by muscle. The
muscular fasciculi which are occasionally found to descend from the hyoid bone to the thyroid
gland or its pyramidal process are known as the levator (jlnnfluhc tlujvoidece (fig. 320). The fibres
are most frequently derived from the thyro-hyoid muscle, but occasionally they are independent.
In one of Marshall's cases there were two pyramidal processes, while in another a single
process divided into two parts, one for each lateral lobe. Accessory thyroids may be formed
by transverse division of the p3rramidal process into several separate masses, more rarely they
are found in relation with the lateral lobes. Small glandular masses, resembling in structure
the thyroid are also frequently found in front of and above the hyoid bone.

Structure. — The texture of this organ is firm, and to the naked eye appears
coarsely granular. It is invested by a thin transparent layer of dense areolar tissue

Viy/>^^ss.*«s«^

THE THYROID BODY. 313

which connects it with the adjacent parts, and imperftctly separates its substauce
iuto small lobules of irregular ibrm and size.

"When the organ is cut into, a yellow glairy fluid {colloid) escapes from the cut
surface. Imbedded in its substance are multitudes of closed vesicles (tig. o24), which
are held together in groups or imperfect lobules by areolar tissue. The size of the
vesicles varies from •o4.") mm. to l* mm., so as to be visible to the naked eye. They
are spherical, polyhedral, or flattened in shape. The wall of each vesicle consists of
a simple layer of cubical or columnar epiihelium-cells which, according to Langen-
dorff, are of two kinds, viz.:— those which are actually secreting the material of the
contents of the vesicles (colloid cells) and others {reserre cells) which may take the

Fig. 324. — Section of the thyroid gland
OF A CHILI). (E A. S. )

Two eoinplete vesicles and portions of others
are lepresenttJ. The vesicles are filled with
colloid which, in this case, also occupied the
interstitial spaces. In the middle of one of
the spaces a blood-vessel is seen cut obliquely,
and close to it is a plasma-cell. Betv/een the
cubical epithelium cells, smaller cells like
lymph-corpuscles are seen here and there.

place of some of the colloid cells

which become detached or mingled

with the secretion. Both Langen-

dorff and Hiirthle agree in stating

that the secretion is formed partly

by exudation from the cells an

partly by the complete transformation of some of the cells into colloid substince.

According to Baber there is no basement membrane to the vesicles.

The vesicles may contain, besides the characteristic yellow glairy fluid, detached
e})ithelium-cells, white blood-corpuscles which seem to have migrated into the cavities,
and also red blood-corpuscles in various stages of disintegration and decolourization,
but whether these last arc accidental or normal constituents is still undecided.

In the interstitial connective tissue of the gland there occur a number of cells
similar to the " plasma-cells " of Waldeyer (" parenchyma-cells," Baber). The spaces
(areohvj of this tissue and the lymphatic vessels may be filled with the same colloid
substance as that which occupies the vesicles. The blood-vessels and lymphatics are
conducted to the vesicles in the interstitial tissue, but the lymphatic vessels do not come
into such intimate relations with the walls of the vesicles as the blood-capillary net-
work, the vessels of which are in close contact with the epithelium and may even
project between the epithelium-cells.

Occasionally small bodies detached from the main mass of the thyroid are found,
iiaving all the structure of the normal thyroid (nccessonj IJn/roids).

One of the most frequent pathological changes to which the thyroid body is
subject consists in the accumulation within its vesicles of colloid substance : in
certain forms of goitre it distends them to an enormous degree, llomoval of the
thyroid produces myxnedema.

in the foetus, and during early infancy, this organ is relatively larger than in
after-life ; its proportion to the weight of the body in the new-born infant being
that of 1 to 24i» or 4iM», whilst at the end of three weeks it becomes only 1 to IKio,
and in the adult 1 to 1X00 (Krause). In advanced life the thyroid body is liable to
become indurated, and frequently contains eartliy deposit ; its vesicles also attain a
very large si/f.

Vessels and nerves. — 'i'he arteries of the thymid body arc tiic si/jicrior and
inferior lliijroids of eacli side, to whicii is sometimes added a liftli vessel, the llujroidea

SJ4 THE DUCTLESS GLANDS

ima. The arteries are remarkable for their large relative size, and for their frequent
and large anastomoses ; they terminate in a capillary network upon the outside of
the vesicles. The veins, which are also large, ultimately form plexuses on the sur-
face, from which a superior, middle, and inferior thyroid vein are formed on each
side. The superior and middle thyroid veins open into the internal jugular ; the
inferior veins issue from a plexus formed in front of the trachea, and open into the
innominate veins. The lymphatics of the thyroid body form numerous and large
anastomosing trunks, both at the surface of the organ and throughout its substance ;
they originate, according to the observations of Frey, in the connective tissue which
unites the gland-vesicles, with the cavity of which they appear not to be in
communication. Hiirthle has however by using intermittent pressure succeeded in
causing injection-material to pass into the vesicles from the lymph-paths. The
lymphatics may contain colloid substance, similar to that found within the vesicles
(Baber). This appears to pass between the epithelium cells into the interstitial
connective tissue and so into the lymphatics.

The nerves are derived from the middle and inferior cervical ganglia, of the
sympathetic. They accompany the blood-vessels. According to Anderson there are
no ganglion-cells in their course. Their branches extend close to the base of the
epithelium cells.

PAEATHYROIDS (GLANDULE PAIIATHYIIOIDE2E.)

Under the name of parathyroids Saudstrom described (in LS80) a pair of small
glandular masses, constant in occurrence in man and other mammals, and always
lying in close proximity to the lateral lobes of the thyroid body (fig. 325, p, p') They
vary in size from 3 mm. to 15 mm. in diameter, being on the average about 6 mm.
They are usually flattened, and their colour is reddish-brown, somewhat like that of
the thyroid itself. In structure, however, they differ from the thyroid proper, being
composed not of hollow vesicles but of solid masses of epithelium-like cells (which
sometimes appear in sections as if arranged in anastomosing columns) with numerous
convoluted blood-vessels between them (fig 326). Connected with the cell-masses
there are frequently lymph-follicles. They diff'er completely in structure from the
normal thyroid and are not therefore to be confounded with the accessory thyroids
which have just been mentioned. These bodies have undoubtedly been previously
noticed (by Eemak, Yirchow, and others), but their importance, as shown by their
constancy of occurrence, was not recognised nor were they systematically described.
Since the appearance of Sandstrom's account, their structure was independently
described by Baber (in 1881), and more recently several observers have directed their
attention to these bodies. According to Gley they represent embryonic portions of
the true thyroid, and if left after the removal of the latter, they are able to develop
further and to take on the functions of the main organ, and it is thus he accounts
for the failure to obtain in some animals the usual effects of thyroidectomy. It is
however denied by Edmunds that they develop into thyroid tissue proper under these
circumstances, although they appear as stated by Gley to undergo hypertrophy if left
after removal of the thyroid, and to act to some extent vicariously for it.

Kohn, who has made a careful investigation of the structure of these bodies and
their relations to the main part of the thyroid, states that there is one parathyroid
("outer epithehal body") constantly to be met with in mammals on the lateral
surface of each lateral lobe of the thyroid and another on the mesial surface of each
lateral lobe (" inner epithelial body ") (see fig. 325, p, p'). Associated in position
with these bodies there is, at least in some animals, almost constantly to be met
with a small mass of "adenoid " tissue, which has all the structural characLeristics of

THfi PAKAtHYKOli)S.

.SI5

thymus tissue, including the well-known epithelial nests (concentric corpuscles), and
which tends to blend insensibly with the neighbouring interstitial tissue of the thyroid
(fig. 32,'), h). According to Prenant, again, the tissue of the parathyroids is similar in
general structure and appearance to that of the carotid glands, and is not embryonic
thyroid tissue. This author states that it takes origin from the fourth inner branchial
cleft of the embryo, from which also part of the thymus and the lateral rudiments

6 —

Fig. 325. — Transverse .SECTION OF THE LEFT LOBE OF THE THYROID OP. V TWO-MONTHS KITTEN. (Koha.) ^-^
a, thyroid tissue ; h, h, tliymus tissue ; p, p, inner and outer parathyroid bodie.s.

Fig. 326. — P.\RT OF THE OUTER PARATHYROID REPRESENTED IN THE PRECEDING FIGURE, MORE HIGHLY

M.IGNIFIED. (Kohn.) =^^

The figure shows the columns of epithelium-like cells with intervening vascular septa of which the
parathyroid i.s composed, m, m, cells undergoing mitotic division.

of the thyroid are derived Cde Meuron, see Vol. I., Part 1, p. Ill), whereas the
main part of the thymus and the carotid gland are derived from the third cleft.

RECENT LITERATURE OF" THE THYROID AND PARATHYROIDS.

Andersson, O., Die Ncrvcn dcr ScJiilddrilsc, Biol. Fiireningens Forhaudl., Stockholm, Dd. iv.,
lS'.)l-'.)2 ; Znr Kcnntmnnd. Movph. d. f-childdrUse, Arch. f. Anat. u. Physio!., Anat. Alith., 1894.

Baber, E. Cresswell, Jlescarclics on the minute structure of the thi/mid y/Kud, Phil. Trans.,
1S8I.

Berkeley, H. J., 7'hc intrinsic nerves of the thyroid (jlaiid in the do;/, Johns Hopkins Ho.sii.
Ilcp., vol. v., ]H'.)i.

Berry, J., Hunpemory ligaments of the thyroid gland, Proceed, of the Anatoni. Soc. of (xt.
Britain, 1887,

Biondi, /ScHru'i zur Histol^ffic, Physiologic und Chirurgie der Schilddrilse, Vcrhandi. dos
iritcrnat. iir.dicin. Kongresscs zu Berlin, 1890, ]5d. iii., Aht. vii. ; Oontributo aUo studio della
'jl/indol'i tiroide, Coniin fatti alia viii adunanza della Soc. Itali. di chir. en Roma, 1892.

Brooks, W. K. , On the origin of the thyroid gtand, I!ull. .Johns Hopkins Hosji. , vol. iv

Christiani, H., /ttjn/ir/fuis nur I'aiiatomie rt Im phi/slo/ogie drs gliindex ct glandule-i thyrol-
dicHius rhcz le rat, Arch, do iMiysiol., t. v., 1893 ; Dea jlundalcs Uiyroldicrmca chcz la souria et k
aarapa'jnol, Ibid.

316 THE DUCTLESS GLANDS.

Crisafulli, E., Nervi della glandola tiroide, Biilletino mens, della acad. di scienz. nat. in Catania,
1892.

Edmunds, "W. , Experiments on the thyroid and parathjroid c/lands, Proc. Physiol. Soc, Jouni.
of PJaysiol., vol. xviii., 1895.

Freund, Die Beziehung der Schilddruse zu den weiblichen Geschlectorganen, Deut. Zeitsch. f.
Cliirnrgie, 1883.

Gaudier, Henri Joseph., Anatomic de la glande thjroide, Lille, 1891, These.

Gley, E., Glande et glandules thyroides du chien, C. r. d. la soc. de biolog., t. v., 1893.

Gley, E., et Phisalix, C, Sur la nature des glandules thyroidiennes da chien, 0. r. soc. de
biolog., t. v., 1893 ; Sur la fonction deti glandules thyroides, Atti de' XI congresso medico inteniat.,
lloma, 1894, vol. ii.

His, Wilhelm, Der Tractus thyreoglossus und seine Bezlehungen zuni ZungenOein, Avcliiv f.
Anat. u. Physiol., Anatom. Abt. , Jahrg. 1891.

Horsley, "V., Die Function der Schilddrilse, Festchrift R. Virchow gewidmet, Bd. i. , 1891.

Hilrtlile, K., Beitrdge zur Kenntniss des Secretionsvorganges in der Schilddrilse, Arch. f. d.
ges. Phys., Bd. Ivi., 1894.

Kadyi, Ueher access. Schilddrilsenldpjxhen in der Zimgenieingegend {Glandula praehyoidcs et
suprahyoides), Archiv f. Anat. u. Physiol., Anat. Abth., 187;9.

Kanth.ack, A. A., The Thyreo-glossal Duct, Journ. of Anat. and Physiol., vol. xxv., 1891.

Koh.n, A., Studien il. d. Schilddrilse, Arch. f. mikr. Anat., Bd. xliv. , 1895.

Lang-endorff, O., Aeltere und neuere Ansichten ilher die Schilddrilsen, Liologisches Centralblatt,
ix., 1889 ; Beitrdge zur Kenntniss der Schilddrilse, Ai-chiv f. Anat. u. Physiol., Pbysiolog. Abt.,
Jahrg., 1889.

liindemann, "W., Zur Fraqe ilher die Innervation der Schilddrilse, Vorlaufige Mitteil., Centralbl.
f. allgemeine Pathol, und patholog. Anat., Bd. ii., 1891.

Lustig-, Alessandro, Contribution a la connaisfance de Vhistogenhse de la glande thyrioide,
Archives italiennes de biologie, tome xv., 1891.

Madelung-, Anatomisches u. chirurgisohes il. d. Gland, thyroid, access., Arch. f. klin. Chir'urg.,
xxiv., 1879.

Marshall, C. F. , Thyreo-glossal duct or canal of His, The Journ. of Anat. and Physiol.,
vol. xxvi., 1891 ; Variations in the form of the thyroid gland in man, Journ. Anat. and Phys.
vol. xxix., Jan., 1895.

Mayer, Sigmund, Zur Lehre von der Schilddruse und Thymus hei den Amphibien, Anatom.
Anzeiger, Jahrg. iii., 1888.

Mertens, P., Zur Kenntniss der Schilddriise, Diss., Gottingen, 1891.

Podack, M., Beitrag zur Histologie und Function der Schilddriise, Inaug. Dissert., Konigsberg
i. Pr., 1893.

Prenant, A., Contribution a Vetiide du devcloppemcnt organique et histologique du thymus, dc la
glande thyroid e et de la glande carotidicnne, La Cellule, t. x., 1894.

Kibbert, Ueber die Regeneration des Schilddriisengewebes, Virchow's Archiv f. path. Anat., Bd.
cxvii., 1889.

Riviere, A., Contribution ci l' etude anatomique du corps thyroide et des goitres. These, Lyon,
1893.

Sacerdotti, Sui nervi della tiroide, Atti d. r. Accad. d. sc. d. Torino, xxix, 1893.

Sandstrom, I., Om en ny Kortel Iws menniskan och atskilliga ddggdjur, Upsala, Lakarcfor.
Fdrhandl., 1880 (Abstr. in Schmidt's Jahresb., 1880).

Schonemann, Hyp)ophysis und Thyroidca, Virch. Arch. f. path. Anat., 1892.

Sebileau, Le capsule et les ligaments du corps thyroide, Bull. soc. anat., Paris, 1888.

Staelin, A., Zur Kasuistik der accessor ischen Schilddriise, Jahib. d. Hamburger Staats-
krankenanstalten, iii, 1891-92.

Streckeisen, Beitrdge zur Morphologic der Schilddrilse, Virch. Arch. f. path. Anat., 1886.

Waldeyer, Beitrdge zur Anatomic der Schilddruse, Deutsche Medizinal-Zeitung, Jahrg. viii.

"Weibgen, K., Zur Morphologic der Srhilddriise des Menschen, Miinchen, 1891.

White, "W. Hale, On the naked-eye and microscopical variations of the human thyroid body,
Proceed, of the Roy. Med. and Chirurg. Soc. of London, 1888.

Wolf, Kudolf, Ein Fall von accessorischen Schilddrilsen, Archiv fur klinische Chirurgie,,
Bd. XXXV., 1889.

Vfyss, H. v., Uebcr die Bcdoutung der Schilddrilse, Correspondenzblatt fur Schweizer Acrzte,
1889.

Zielinska, Marie, Beitrdge zur Kenntniss der normahn und striun'Osen Schilddruse des
Menschen und des Hundcs, Arch. f. path. Anat.^ Bd. cxxxvi.j 1894.

THE CAHOXri) GLAXD.

317

THE CAROTID AND COCCYGEAL GLANDS.
The carotid glands {glanchd(n carDtim-) are small bodies situated just above
the bifurcation of the common carotid arterj on each side, and between its internal

Fig. 327.— Section nhar the bifurcation op the common carotid artery, passing through the
CAROTID GLAND. (.Marcliaiul.) Somewliat magnified.
ci, ce, internal and external carotid arteries cut across ; gl c, carotid gland ; rj, Ijlood-vcs.-els ;
/, interstitial connective tissue of gland ; I, glandular lobules or nodules.

Fig. .328, — Section of part of the carotid gland, human, showing the epithelium-like cells
OF which the glandular nodules are composed. (Scbaper. ) Highly magnified.
Numerous blood-vessels are seen in section among the gland-cells.

Fig. 329.— Diagrammatic view of the disposition of the i)Loi)d-\ eshels in a nodule of the

carotid gland. (Schaijcr.)
a, art<;riole erit<;riii;,' nodule ; v", vfiiis leavint; nodule ; v', veins in connective tissue around nodule ;
t, enlar(,'cd caj^ilJary within noilule ; A, ej)ith<liuni-like <ells of the «land ; c, r, boundary of nodule
abutting uiMi lyiii|)lisi»aceH ; d, iiiteiHtitial cuiinc.live tissue of gland.

318

THE BUCTLESS GLANDS.

and external brancheg. They are enveloped in connective tissue which also passes
into their substance, subdividing them into small nodules. Each nodule is com-
posed of a mass of polyhedral epithelium-like cells, amongst which are distributed
numerous wide and tortuously-disposed blood-capillaries, the cells being in close
contiguity to the walls of the capillaries. These small organs somewhat resemble in
minute structure the parathyroids just described ; they are also similar in character
to the vascular islets of the pancreas. Their origin is very similar to that of the
parathyroid bodies, except that they are developed from the third inner branchial
cleft, whereas, as already mentioned, the parathyroids take origin from the fourth
cleft. The physiological relations of these bodies are unascertained.

The coccygeal gland {glandula coccygea, Luschka), is a small organ at most
2*5 mm. in diameter, sometimes broken up into 3 to 6 smaller corpuscles, placed

Fig. 330. — Section of an ir-
regular NODULE OF THE
COCCYGEAL GLAND. (Ser-
toli.) -Sf-
Tlie .section shows the fibrous
covering of the nodule, ths
blood-vessels within it and the
polyhedral cells of which it is
constituted.

'^ immediately in front of
the apex of the coccyx
and receiving branches of
the middle sacral artery.
It resembles very closely
in minute structure the
carotid glands, being com.-
** ->;->■"'" ~^~ ' -^ ^" posed of masses and

columns of polygonal cells,
amongst \\hich Eberth has noticed nests of cells similar to the concentric corpuscles
of the thymus. The gland-cells closely invest the blood capillaries, which are
numerous and tortuous, and here and there show dilatations upon their course. The
gland is subdivided into nodular portions by ingrowths of the investing connective
tissue which conducts numerous nerves to the glandular part of the organ. Luschka
described the gland as rich in ganglion-cells and compared it in this respect with
the pituitary body, but this has not been confirmed by later observers. The mode
of development and the function of this body are not known.

LITEBATUKE OP THE CABOTID AND COCCYGEAL GLANDS.

Arnold, J., Uehcr d. Struchir dcr Steissdriisen, Arch, f. path. Anat. xxxii., 1865, xxxv., 1866,
xxxvii., 1867; Ueber d. Structur d. gavr/l. intercar..^ Arch. f. path. Anat., xxxiii., 1865.

Eberth, In Strieker's Ilandbuch der Gexvebelchre, Bd. i., pp. 209 — 21.3.

Heppner, Uehcr d. feineren Bau der Glandula carotica, Arch. f. path. Anat., xlvi., 1869.

Krause, W., Anatomischo Untersuchungcn, Hannover, 1860.

Luschka, W., Steissbeindrilse oder Nervendrilse des Beelens, Arch. f. path. Anat., xviii., 1860 ;
Der Hirnanhang u. die Stcissdrilse des Menscken, Berlin, 1860 ; Anatomic d. menscJd. Beekens, 1864 ;
Ueber die driisenartlrje Natur des sogencmnten Ganglion intcrcccroticum, Arch. f. Anat. u. Phys., Anat.
Abth., 1862.

Marchand, Beitr. zur Kenntniss d. normal, u. pathol. Anat. der Glandtda carotica u. d. Nchcn-
nieren, Festschr. z. R. Virchow, Bd. i., Berlin, 1891.

Pfortner, Unters. ii. d. Ganglion interearot. u. d. Ncbcnnicren, Zeitschr. f. ration. Med., xxxiv., 1869.

Prenant, A., Contrib. a I'etude du devcloppcnient nrejaniqiie et histoloejique du thymus, de la
glande thyroide et de la glande caroticUenne, La Cellule, t. x., 1894.

Schaper, Beitr. ~. Histologic der Glandida carotica, Arch. f. mikr. Anat., Bd. xl., 1892.

Sertoli, Ueber die Structur der Stcissdrvse des Menscken, Arch. f. path. Anat., xlii. , 18fc'8.

Stieda, Unters. ii. d. Enticickl. d. Glandula thymus, Glandida thyroidea u, Glandula carotica,
Le'pzig, 1881.

Stilling, Du ganglion intercarotidien, Rec. inaug., Lausanne, 1892.

THE PERITONEUM.

By J. SYMINGTON.

The abdominal viscera having been described, as well as the disposition of the
peritoneum in relation to each of them, it remains to give an account of that
membrane in its whole extent, and to trace its continuity over the various parts
which it lines or covers.

The peritoneum lines the whole of the anterior abdominal wall, except along a
narrow line extending from the umbilicus upwards to the diaphragm, and corre-
sponding to the interval between the two layers of the falciform ligament of the liver.

fovea frnwraViH

l."i„. '.V.'A.—SlV.SS FROM nF.niNW op the lower I'AKT OV the anterior AIJJJOMINAL WALL ANI> OF
" ' THE ULAKDEK. (G. D. T., aftCT JoCSHcl. )

This peritoneal fold is usually attached to the ubdominal wall slightly to the riglit
of the median plane. For a short distance above the pubis the peritoneum is loosely

THE PERITONEUM.

connected with the abdominal wall, so that when the bladder becomes distended with
urine the serous membrane is detached from the lower part of the abdominal wall. This,
however, can only occur to a limited extent, since the peritoneum as it passes upwards

towards the umbilicus becomes gradually more
firmly adherent to the abdominal wall. In
cases of great distension of the bladder an area
above the pubic symphysis, two inches in ver-
tical extent, may be uncovered by peritoneum.
Between the anterior wall of the pelvis
and the umbilicus the peritoneum is raised
into five vertical iblds, with intervening
depressions, by certain structures which con-
verge towards the umbilicus. These folds are
a median one, caused by the urachus, and two
lateral, on each side, formed by the obliterated
hypogastric artery and the deep epigastric
artery (see fig. 331). The depression on the
outer side of the deep epigastric artery cor-

Fig. 332 A. — Diagrammatic outline of a supposed section of the body, showing the inflections

OF THE peritoneum IN THE FEMALE. (Alleil TllOinSGD.) i

The upper part of the section is a little to the right of the median plane in the body, throngh the
qnadrate and Spigelian lobes of the liver : below these it is supposed to be median : I c, placed above the
diaphragm opposite to the coronary ligament of the liver ; I, liver ; I', lobe of Spiegel ; s, stomach ; c,
transverse colon ; i, small intestine ; pa, pancreas ; a, aorta ; d, duodemim ; v, urinary bladder ; u,
uterus ; r, rectum ; r', its lower i^art opened ; v a, vagina ; p, p, the parietal peritoneum lining the
front and back of the abdominal cavity. The line representing the inflections of the greater sac of the
peritoneum will be traced from the neighbourhood of I c, where it passes from the diaphragm to the
upper surface of the liver, over the upper and lower surfaces of that organ, forming the ivont of gh, the
gastro-hepatic omentum, over the front of the stomach down to o', the outer layer of the great omentum ;
thence jiassing back to the vicinity of the pancreas, and descending again as the upper layer of the trans-
verse mesocolon. After enclosing the colon it returns as the lower layer of the transverse mesocolon,
m c, to the root of the mesentery, m ; it now forms the mesentery and incloses the small intestine,
returning to the posterior wkll of the abdomen, whence it passes over the rectum, r, descends into the
recto-vaginal pouch, vf, covers the back and front of the uterus and the bladder partially, and regains
the anterior abdominal wall above the pubis. In connection with the lesser sac of the peritoneum, w
marks the position of the foramen of Winslow as if seen beyond the section ; the lesser sac, with the
cavity of the omentum, is shaded with horizontal lines, and is marked o o ; round this space the line of
the peritoneum may be traced from the diaphragm over the lobe of Spiegel, to the back of the gastro-
hepatic omentum, thence behind the stomach and down into the great omentum ; it then ascends to the
pancreas, which it covers, and thence reaches again the diaphragm,

Fig. 332 B is a sketch of part of a section similar to that of A, but showing a condition more com-
monly found in the adult, according to which the two layers of the mesocolon are continuous with the
posterior pair of the Inyers of tlic great omentum.

TPIE PERITONEUM. 3^1

responds to the iuternal abdominal ring, that internal to the artery to Hesselbach's
triangle, while the one below Ponpart's ligament is opposite the femoral ring.
The signiticance of these pouches will be found described in connection with the
anatomy of the groin (see separate Appendix).

After lining the anterior wall of the abdomen, the peritoneum passes round on
each side to the lumbar and iliac regions, where it meets with the right and left
portions of the large intestine. On the right side it completely invests the esecum
and its vermiform appendix, and it also provides the latter with a mesentery. Higher
up it covers the ascending colon in front and on the outer side, the remaining part
of the circumference of the bowel being usually uncovered.

Leaving the right colon, the peritoneum gives a scanty covering to the lower
part of the anterior face of the right kidney and adjoining third portion of the
duodenum where that intestine comes down from behind the transverse mesocolon ;
lower down it continues over muscles and vessels to the root of the mesentery,
proceeds forwards to form the rigiit layer of that fold, passes round the jejunum
and ileum, affording them their peritoneal coat, and returns back to the vertebrae,
thus completing the mesentery on the left side. The membrane now passes in front
of the lower portion of the left kidney to the left colon, which it invests much in
the same manner as the right, and is then continued over the lateral wall on the left
side to the front again, thus completing a horizontal circuit round the abdomen.
Although the descending colon is usually uncovered behind and on its inner side,
yet occasionally it is entirely invested by peritoneum and provided with a mesocolon.
The frequency, however, with which a descending mesocolon occurs has l)een much
exaggerated.

Where the colon forms its sigmoid loop it is completely invested by peritoneum,
which attaches it by a comparatively free and moveable sigmoid mesocolon to the
fascia of the left iliac fossa.

From this part, and from the lower end of the mesentery the peritoneum is con-
tinued into the pelvis. It there invests the upper part of the rectum completely,
forming a mesorectum behind. Lower down the membrane gradually quits the
intestine, first behind, then at the sides, and finally in front, whence it is reflected
on the base and upper part of the bladder in the male, and forms here the recto-
vesical pouch, the mouth of which is bounded by a crescentic fold on each side,
named plica semilunaris. From the apex of the bladder the peritoneum passes on
to the nrachus as already described. In the female the peritoneum passes from the
lectum to the upper part of the vagina, and over the posterior surface, the fundus,
and upper part of the anterior surface of the uterus, whence it goes to the bladder.
The reclo-vaginal pouch (pouch of Douglas), like the recto-vesical, is bounded above
by its semilunar folds, and the uterine peritoneum forms at the sides the broad liga-
ments of the uterus, along the upper iDorder of which the Fallopian tubes receive
from it a serous covering ; at their fimbriated openings the peritoneum is con-
tinuous with the mucous membrane lining the tubes.

The peritoneum, on being traced to the upper part of the abdomen, is found to
line the vault of the diaphragm, adhering moderately to the muscular and firmly to
the tendinous part, and continuing down behind as far as the hinder surface of the
liver and the oesophageal opening. It then passes forwards on to the liver, forming
the falciform, coronary, and lateral ligaments of that organ, already specially
described.

Turning round the anterior border it passes back on tin; under surface ; but, after
covering tlje quadrate lobe, and arriving at the transverse fissure, it meets with a
peritoneal layer from behind, and in association with it, stretches from the liver to
the stomach, to form the lesser omentum, as will be presently explained. To the
right of this part it invests the gall-bladder more or less completely, and the under

VOL. III. I'T. 4. If

S22

THE PERITONEUM.

surface of the right lobe of the liver, covers anteriorly the adjacent part of the
duodenum, and passes to the upper end of the right kidney, forming here a slight
fold, named he2Mto -renal ligament. It then invests the hepatic flexure of the colon
and reaches the right colon, on which it has been already traced. To the left of the
longitudinal fissure the peritoneum invests the whole of the left lobe of the liver, and
stretches out as the long left lateral ligament above and beyond the oesophageal
opening. It then passes down over that opening and covers the front and left side

Fig. 333. — Front view of the viscera of the upper part of the abdomen in a child. (Henle.)

The liver is drawn upwards in order to sbow its under surface and the small omentum, together
with the entrance of the foramen of Wiuslbw. into which a probe is passed.

A, quadrate lobe of liver ; S, left lobe ; D, right lobe ; Lt, ligamentum teres with its peritoneal
covering forming the falciform ligament ; V, stomach ; Ct, transverse colon ; D', duodenum ; 1, small
omentum ; 2, part of great omentum ; 3, right part of small omentum, its anterior layer being divided
to show its contents, viz., Ah, hepatic artery ; Vp, portal vein ; Dch, common bile- duct ; Dh, hepatic
duct ; and Dc, cystic duct ; 4, peritoneum reflected from the liver over the upper part of the right
kidney, or hepato-renal ligament.

of the gullet, spreads over the left end of the stomach, where it passes oflF to invest
the spleen, forming a duplicature named the gastro-splenic ligament, or g astro-splenic
omentum, for it is connected below with the great omentum, and often reckoned as
a part of it. "When the membrane passes from the diaphragm to the stomach it
forms a small duplicature to the left of the oesophagus, named the gastro-phrenic
ligament; it extends also as a generally stout and well-marked fold (the costo- or
phreno-colic liga7neni) from the diaphragm opposite the tenth and eleventh ribs
to the splenic flexure of the colon, then j^asses over the splenic flexure, and reaches
the left kidney and descending colon, where it has been already described.

Omenta. — The arrangement of the remaining part of the peritoneum — that

THE PERITONEUM. 823

betweeu the stomach, liver, and transverse colon — is somewhat complex, in conse-
quence of the membrane forming in this situation a second and smaller sac, which
communicates towards the right with the general cavity by a narrow throat, named
t\iQ foramen of Winslmo. This passage, which readily admits two fingers, is situated
behind the bundle of hepatic vessels which stretches between the liver and duodenum ;
behind the orifice is the inferior vena cava ; above is the caudate lobe of the liver ;
and its lower boundary is formed by the duodenum and a curve of the hepatic
artery. From this opening the lesser sac spreads out to the left behind the general
or main sac of the peritoneum. It covers a part of the posterior abdominal wall,
but in front and below it is applied to the back of the main sac, to which it adheres
except where the stomach is interposed. Moreover, it indents, as it were, the back
of the main sac, and between the stomach and colon protrudes into it in the form of
a great pouch — the bag of the omentum, — which thus has a double coat, formed by
the apposition of the membranes of both sacs. To trace this arrangement more
particularly : suppose a fingei- pushed into the foramen of AVinslow, and the thumb
brought to meet it from before, to the left of the hepatic vessels ; the membrane
held between is double ; its anterior layer (from the greater sac) turns round the
hepatic vessels into the foramen, and then belongs to the lesser sac. The double
membrane, so constituted, is the small or gastro-hepatic omentum. From the
point indicated it may be followed to the transverse fissure of the liver, where its
laminae separate, the anterior, which has already been traced from above, spreading
on the adjacent part of the liver, the posterior covering the Spigelian lobe, where
it will be again met with. The attachment of the combined layers continues back-
wards from the left end of the transverse fissure along the fissure of the ductus
venosus to the diaphragm on which it runs a short way to reach the oesophagus,
where the anterior lamina covers the end of that tube in front and on the left, and
the posterior lamina invests it on the right and behind. From this point, as far as
the pylorus, the small omentum is attached to the lesser curvature of the stomach,
where its laminee separate — one covering the anterior and the other the posterior
surface of the organ — but meeting again at the great curvature, they pass down in
conjunction to a variable distance before the small intestine to form the anterior
jjart of the great omental sac, and then turn up to form its posterior wall. Meeting
next with the transverse colon, the two laminae separate, and enclose that intestine,
ijutmeet again behind it to form the transverse mesocolon. This extends back to the
anterior border of the pancreas, from which its inferior layer passes backwards over
the inferior surface of this organ and then turns downwards over the posterior wall
of the abdomen, and forms the mesentery, where it has been already recognized.
The superior layer, on the other hand, which, as will be understood, belongs to the
lesser sac, covers the front of the pancreas, the coeliac artery and its main divisions,
the upper part of the left kidney, and the portion of the diaphragm between the
aortic and caval orifices, and may extend to the left end of the pancreas and gastric
surface of the spleen, partially investing the latter organ and forming part of the
gastro-splenic omentum. It then goes forward on the Spigelian lobe to the trans-
verse fissure, and the line of attachment of the lesser omentum of which it then
becomes the posterior layer. More to the right the layer in question passes over the
vena cava, and continues into the general jK-ritoneum beyond the i'uramen of Wins-
low. The gastric and hepatic arteries, especially the former (Husclike), may raise
the membrane into folds which project into the cavity.

From the description given it will be understood that, as the sides or walls of
the great omental bag consist of two peritoneal layers, its whole thickness (in its
usually empty and collapsed state) will comprehend four layers. But although the
bag may be inflated in its whole extent in the infuntile twdy, its sides afterwards
cohere, and it becomes impervious in its lower part. Fat, moreover, accumulates

y 2

324

THE PERITONEUM.

between its laminse ; long siender branches also pass down into it from the gastro-
epiploic vessels.

The part of the membrane just described, which is attached to the great curva-
ture of the stomach and transverse colon, and which is connected also with the
gastro-splenic ligament (or omentum), is usually named the great or gastro-colic
omentum. This may reach the hepatic flexure and pass a certain way down on the
right colon, and this part has been distinguished by Haller and others as the omentum
coUcum. The great omentum (proper) usually reaches lower down at its left border,
and it is said that omentum inguinal hernife are more common on the left side.

Fig. 334. DiAORAM OF A HORIZONTAL SECTION THROUGH THK ABDOMEN AT THE LEVEL OF THE

FORAMEN OF WINSLOW. (R. J. Godlce. )

LI first lumbar vertebra ; 12, 11, 10, &c., successive ribs ; r, rectus muscle ; eo, external oblique ;
Id latissimus dorsi ; spi, serratus posticus inferior ; i, intercostal muscles ; cs, erector spinje ; ms,
multifidus spinw ; pn, psoas ; d, diaphragm.

Ao aorta ; V.C, inferior vena cava ; C A, coronary artery ; S A, splenic ai-tery ; S V, splenic vein ;
S splenic vessels cut as they enter the spleen ; H A, hepatic artery ; P V, portal vein ; B D, common

bile duct.

L liver • L T, ligamentum teres or round ligament of the liver ; St, stomach ; Sp, spleen ; P,
iiancreas ; K, kidney ; L S, large sac of peritoneum ; S S, small sac ; S 0, small omentum ; G S 0,
gastro-splenic omentum ; F W, foramen of Winslow ; PI, pleura.

The peritoneum is represented by a thick dark line. It can lie traced from the middle line anteriorly,
where it is seen investing the round ligament of the liver and forming the commencement of the falci-
form ligament, along the light side of the abdominal wall, over the front of the right kidney, to the
inferior vena cava where it forms the posterior boundary of the foramen of Winslow ; from the latter
spot the small bag extends over the pancreas and left kidney nearly as far as the spleen, and then is
reflected backwards along the back of the small omentum to the front of the foramen ; here becoming
large bag again, it turns round the hepatic vessels, foi-ms the anterior layer ot the small omentum,
covers the front of the stomach, forms the gastro-splenic ligament or omentum as it is reflected on to
the spleen, which it invests almost completely, and is thence continued along the diaphragm and
fibdominal wall back to the middle line.

The description now given of the relation of the omentum to the mesocolon
agrees with the appearances most frequently seen in the adult subject, the exterior
(here also posterior) layer of the great omentum being described as separating from
the layer within, belonging to the omental sac, w^hen it reaches the transverse colon
so as to pass behind or below that viscus, and as proceeding thence backwards to the
abdominal wall as the posterior or lower layer of the transverse mesocolon. In the
young foetus, however, two layers of peritoneum pass from the greater curvature of
the stomach upwards and backwards to the posterior abdominal wall forming the
raesogastrium, and the transverse colon possesses an independent mesocolon. Sub-

THE PERITONEUM.

3^5

sequeuLly the posterior layer of the mesogastrium fuses with the anterior layer oi
the transverse mesocolon (see Development, Vol. I., Pt. I., p. lo7). Occasionally
in the child, and even in the adult, tliese layers remain distinco.

Fig. 335. — Transverse section through the abdomen of a KOiTus 3;^ inches long. (J. S. )
V, body of luniliar vertebra ; K, left kidney ; D.C., deicendiug colou ; P, peritououm.

Various peritoneal fossee or pouches are often found on the posterior wall of the
abdomen. They are of importance surgically on account of the fact that portions

S. F,

Fig. 336. — View ov intek-sigmoid fossa. The pelvis h.\s been iuvided in a (xikonal plane

OPPOSITE THE BOTTOM Ot THE KEI'TO-VKSICAL POUCH, ANI> THE SIGMOID LUOP HAS BEEN TUKNE1»
UPWARDS AND TO THE RIGHT, (JenilCHCO. )

D. C, descending colon ; S. F., sigmoid colon ; R. , rectum covered l)y peritonemu : li', rectum un-
covered by peritoneum ; R. V. , recto- vesical fold of the iieritoneum ; S. A., brandies of the sigmoid
artery ; L, U., left ureter ; I. V., external iliac artery and vein ; H. A., obliterated hypogastric artery.

of the intestine are liable to become lodged in them, giving rise to letro-peritoneal
herniai.

Several of these fossaj are found in relatioti with the caacuin and have already
been descriljed (see j». Ill ). Another fossa, the i/iler-fiif/moul, is very commonly met
with during the fifth and sixth months of fmtal life. This recess is funnel-shaped and
ofjens below, behind the root (jf the mesentery of the sigmoid colon. It extends
upward for a variable distiince along the course of the ureter. In the young foetus (see
tig. 3;joj the descending colon is connected by a relatively long mesentery to the

326

THE PERITONEUM.

posterior abdominal wall near the median plane. The posterior layer of the
descending mesocolon soon unites with the peritoneum in front of the kidney, but
internal to this organ the fusion of the two layers of peritoneum does not occur so
readily, hence the formation of a tubular recess, which communicates below with
the general peritoneal cavity. This fossa is only occasionally met with, in a well
developed condition, in the adult. Several fossse, duodenal and duodeno-jejunal, are

IDF

LC A

Fig. 337. — SHJERIOE AKI) INPEEIOE DUODENAL FOSSiE. ThE TKAKSVEKSE COLON AND THE GREAT
OlIENTUM HAVE BEEN TURNED UPWARDS AND THE CONVOLUTIONS OF THE JEJUNO-ILEUM TO THE

RIGHT SIDE. (.Tonnesco.)

J, upi^er end of jejunnni ; M, the mesentery ; D, terminal or 4tli part of duodemim ; S D F,
superior duodenal fold of peritoneum ; S F, superior duodenal fossa ; IDF, inferior duodenal fold ;
I F, inferior duodenal fossa ; I M V, inferior mesenteric vein ; L C A, left colic artery.

sometimes present near the termination of the duodenum. According to Jonnesco
there are five varieties of fossse met with in this region ; viz., inferior duodenal,
superior duodenal, retro-duodenal, para-duodenal, and duodeno-jejunal. The most
frequent of these fossae, inferior duodenal, lies on the outer side of the terminal part
of the duodenum and has its orifice above. It is bounded anteriorly by a thin fold
of peritoneum, which is attached to the posterior abdominal wall along a vertical
line to the left of the duodenum, while on the right side it is attached to the
duodenum. This fold possesses an upper, free and somewhat crescentic margin. In
other cases the fossa, superior duodenal, has its orifice directed downwards, or these
two fossse may both occur in the same subject (see fig. 837).

For the recent literature of the Peritoneum, see pp. 69, 70.

INDEX AND GLOSSARY TO VOL. IIL, PT. IV.

Abdomen, 68
Abdominal mammce, 291

regious, 68

surface of bladder, 209

viscera, 68
Aberrant biliary ducts, 136
Accessory bronchi, 178

liver, 128

lobes of lung, 1 76

mammae, 291

pancreas, 142

pancreatic duct, 142

spleen, 296

suprarenal capsules, 305

thyroids, 312, 313
Adamantobla.sts {a5d/j.as, adamant ; GKacrrSs,

germ), 43, 45, 46
Adams on prostatic secretion, 250
Admaxillary glauus, 19
Adrenals {ad, near to ; renes, kidiiey.s), 302
Aeby on calibre of trachea, 162

eparterial bronchial tube, 177
morphology of pulmonary lobes, 176
Agminated glands, 95
Air-celLs of lung, 181
Ala (wing) of tliyroil cartilage, 147
Albumen of ovum, 279
Albuminous or serous alveoli, 19
Alimentary canal, i

literatui'e of, 69
Alveolar pas.sage, 181

Alveoli {alveolus, small liollow or bowl), dental,
formation of, 48

of foetal lung, 184

of lung, 181, 183

mammary, 288

mucou.s, 19

of parotid gland, 19

of salivary glands, 18, 22

serous or albuminous, 19, 20

of sublirjgual gland, 19
Alveolo-labial sulci, i
Alveolo-lingual sulcus, 4
Ampliibia, dentition of, 29

larval epithelial teeth of, 38

]>ulmonary capillaries of, 185
Anipulla (flask-shaped ves.sel) of Fallopian tube,
269, 270

rectal, 116

of van 'lelcrens, 233
Anipullse of galact'.|ihiirciMs ducts, 2S8
Amygdala; 'almonds), 59
Anal canal, 1 16
Anteprcttatic gland, 247
Ant mm pylori, 72
AniiH (nngj, 1 16

Apex of lung, 174

of prostate, 247
Appendices e|.iploic;e (^nhKoov, omentum), 105
Appendix cseci, 109

vermiform, 103, 106, 108, 109, in, 321
of lower animals, no

vesicas, 213
Aponeurosis, pharyngeal, 61
Arbor vitae uterina, 262, 268
Arches, arterial, of kidneys, 201

dental, 3, 24, 52

palatine, 59

venous, of kidney, 201
Archoplasm(apx<^J, chief; ■KKa.Tffoo, I form), 229
Area, mammary, 291

of prsecordial dulness, 176
Areolaj (small open sprices) of thyroid bod}-, 313
Areola (dim. of area, halo), 285
Areolar coat of large intestine, 106
of liver, 129
of resuphagiis, 66
of small intestine, 86
of stomach, 76
Arnold on lymphoid tissue of lung, 1C7
Arterial arches of kidney, 201
Arteries or Arterj"-, of bladder, 215

of bronchi, 167

of bronchia, 186

of corpus spongiosum, 242

of dental pulp, 31

of female urethra, 258

of gall-bladder, 127

helicine, 241

he))atic, 126, 130, 131

of kidney, 201

of lar;;e intestine, 108

of larynx, 157

of lung, 185

of mammary glanil, 290

of cesophngus, 66

of ovary, 281

of pancn-as, 145

of parotid gland, 16, 22

of penis, 239, 240

of pleura, 174

of prostate, 250

of rectum, n7

of scrotum and s|iermMtii; cord, 220

01 seminal vesicles, 235

of small intestine, 90, 97

of spleen, 299

of stomach, 82

of sublingual gland, 17, 22

ot submaxillary gland, 17, 22

of suprarenal capsules, 305

of testis, 235

^■zs

IxVDEX AXD GLOSSARY TO VOLUiSIE III., PART IV.

Arteries or Artery — conlliiucd.

of thymus, 309

of thyroid bod}', 313

of tongue, 1 1

of tonsil, 60

of trachea, 167

of ureter, 205

of uterus, 268, 269

of vagina, 260

of vulva, 257
Arteri.e glomerulorum, 202

iuterlobulares of kidney, 2Ci

rectse, 202
Articulation, crico-arytenoid, 152

crico-thyroid, 151
Aryteno-epiglottic folds, 152

muscle, 156, 158, 162
Arytenoid {apiraiva, vessel with spout ; sIjos,
form) cartilage, 146, 148, 150

muscle, 158, 162
Ascaris, chromosomes in sjierniatic cells of, 228
Atrium (forecourt, hall) of pulmonary iniundi-

bula, 181
Auerbach, plexus of, 100
Australians, dental index of, 25

incisors of, 25
Axial filament of spermatoblast, 229
Axillary mammee, 291
Azj'gos {6.(^vy6s, unyoked) lobe, 178

Babek on thyroid vesicles, 313
Bag of omentum, 323
Balfour on Graafian follicles, 277
Ballantyne on liver of infant, 12S

ostium abdominale, 270

spleen of infant, 296
Bands, muscular, of colon, 106, 108
Bardeleben on mammary glands, 291

spermatozoa, 226
Bartholin, duct of, 17

glands of, 256
Basal layer of dental jiulp, 31
ridge of incisor teeth, 27
surface of sjdeen-, 293
Base of bladder, 208, 210

lung, 174

prostate, 247
Bauhin, valve of, no
Baume on development of teeth, 53
Bellini, ducts of, 200
Bergmann on nerves of suprarenal.--, 305
Berkeley on Meissner's ple.Kus, 100

nerves of liver, 136
lung, 187
Bermaun on submaxillary gland, 19
Berry on vermiform appendix, 109
Bibra on dentine, 32

enamel, 34
Bicuspid {bis, twice ; cuspis, point) teeth, 24,

27. 30. 51 .
Bile-canaliculi, 133

Bile-duct, common, 100, 102, 127, 12S, 140, 141
Biliary ducts, 133, 135
aberrant, 136
Birds, parietal cells otj 81
Birmingham on ileo-C£Ecal val\L', iii
Bizzozero on goblet-cells, 94
Bladder, 189, 206, 321

bloodvessels of, 215

interior of, 212

fasciculated, 213

Bladder — contiiiued.
glands of, 215

ligaments of, false, 115, 208, 211
true, 208, 210, 211
literature of, 216
lymphatics of, 215
mucous membrane of, 212, 213, 215
nerves of, 215

]ieculiarities of, according to age, 212
relations of, 208
sacculated, 213
structure of, 213
urethral oriiice of, 211, 212
Biandin, glands of, 9
Bloodless fold, iii

Bloodvessels. See Arteries, Veins.
Body, chromatic, 229
of epididymis, 222
globuloid, 225, 226, 229
of i)anerias, 139, 140
of penis, 236

of spermatozoon, 225, 226, 229
thyroid. See Thyroiu Body.
of tongue, 3
of tooth, 26

of uterus, 260, 265, 268
l>ohm on S])lenic pulp, 299
Border, mesenteric, 86
ISoundary zone, 197
Braune on cardia, 72
trachea, 163
Breast, 285
Broad ligament of liver, 121, 125

uterus, 262, 2h4, i.67, 321
Bronchi {^poyxo^, from lip^xou, I drink : the
Greeks believed that liquids passed, not
into the cesopliagns, but into the air-
tube), 146, 162, 164, 176
accessory, 178
bloodve.ssels of, 167
distribution of, in lung, 177
literature of, 187
in lower animals, 178
lymphatics of, 167
nerves of, 167
structure of, 167
termination of, 181
Bronchia, 181

Bronchial cartilages, 163, 167
tubes, 181

bloodvessels of, 1C6
cartilages of, 182
coats of, 182
lymphatics of, 186
mucous membrane of, 182
muscular tissue of, 183
nerves of, 187
ramifications of, iSi
structure of, 181
Bronchioles, 181

lobular or respiratory; 181, 183
Bronchus, epai-terial branch of. 164, 177, 17S

hyparterial branches of, 178
Brooks on pleurae, 171

valvulse conniventes, 5:8
Brown on spermatogenic cells, 227
Brunn on enamel cuticle, 46
Brunner's glands, 93, 94, ico
Buccal glands, 3
Bucco-pharyngeal fascia, 61
Budin on hymen, 258
Bulb of urethra, 241, 242

INDEX AND GLOSSARY TO VOLUME III., PART IV.

■6->\)

Piiilbi vestibuli, 255

Halbous portion ol uretliin, 246

I'lulbs of corpora cavernosa, 239

l»ursa (jSiVffi, liiile, bag), jiliMryiigi-al, 57

C^CUM (sc. intesthnim, blind bowel), 103, loS,
321
descent of, loS
infantile type of, 108
Cilices of kidney, 193
( iiinel, hepatic lolni.es of, 129
Canal or Canals, alimentary, I
alimentary, liter.iture of, 69
aual, 116
of e|pididviiiis, 231
hepatic, 129
inguinal, 21S
of Muck, 220, 264
portal, 129
of S tense n, 13
of Wirsung, 141
Canaliculi, liiliary, 133

pancreatic, 144
Canine teeth, 24, 27, 30, 49. 51
Capillaries, hepatic, 131
Capsula adiposa, 190

Capsulae atr-ibiliaria; s. renes succenturiati, 302
Cajtsular braurhes of hciiatic artery, 131
Capsule of Glisson, 127, 129
of kidney, 190, 192, 202
supiarenai. i>ee Supkarenal capsule.
of uriniferous tubule, 197
C:iput cecum coli, 108

gailiuaginis, 244, 246
Cardia (KopSia, stomach), 71, 72
Cardiac glands, 79
orifice, 71, 72
Carlier on ellipsoids, 300
Carotid gland, 293, 317

literature of, 318
Caitilage or cartilages, arytenoid, 146, 148, 150
bronchial, 163, 167, 182
cricoid, 146, 148, 150
cuneiform, 147, 149, 153
of epiglottis. 146, 149
of larynx, 146

inor|ihology of, 1 5 1
ossification of, 1 50
structure of, 149
of Lnschka, 155, 161
of Santorini, 149
iliyroid, 146, 147, 150
tracheal, 163, 165
of Wrisberg, 149
Cartilago triticea (iri^tCMOT, wheat), 1 51
(J.ininculsB myrtifonnes {caruncula, little piece
of Hesh : myrtum, myrtle-berry), 258
Cat, development of mamma; of, 291
marginal cells of, 20
nerves of trachea of, 167

of parotid of, 16
spleen of, 298
supiarenai ot, 304
Caudate lobe (cawlu, tail), 121, 122
Cavum oris (cavity of mouth), i
prajvesicale, 210
Ketzii, 210
Celj-islctfl, iiileralveolar, of pancrciis, 145
(Jell-nests of ovary, 276
Cells, central, of gastric glands, 80
centro-acinar, of pancreas, 143
colloid, 313

Cg[\s— ^continued.
enamel, 43
goblet, 92, 94, 107
hepatic, 132

intermediate, of seminiferous tubules, 227
interstitial, of ovarian stroma, 274, 278, 281

of testis, 230
lining, of seminiierous tubules, 226
mniginal, of gastric glands, 20
mucin, 20

oxyutic. parietal or supei added, of gastrio
glands, 80
• pancreatic, 142
peptic, 80

principal, of gastric glands, So
reserve, 313

reticular of splenic pulp, 298
spermatogenic, 227

sustentacula!- of seminiferous tulmles, 22S
Cement, 32, 36, 46

organ, 47
Central cells, 80

Centro-acinar cells of pancreas, 14^
Centrosome [Kfvrpov, centre of circle ; aufxa,

body), 229
Cervical fistulre, 61

pleura, 170, 172
Cervix (neck) of blaijdcr, 20S
of penis, 236
of uterus, 260, 265, 268
Chabry on development of teetli, 53
Chaput on villi, 89
Cheeks, 2
Choanai (x"""'?. melting j>ot, deriv. fr. x^^*

pour), 57
Chromatic body, 229
Chromosomes of spermatoblasts, 228
Chrzonszczewsky on bile-ducts. 133

on hepatic lymphatics, 136
Cingulum (girdle), 27
Circiilus venosus, 290
Circum-anal glands, 116
Circumvallate papillre, 5, 6
Cleft, vulval, 253, 256

visceral, 57, 60, 61
Clitoris (KAeiTopts), 253, 255
Coccygeal gland, 293, 317
literature of, 318
Collecting tubes, 197, 199
Colliculus (little hill) bulbi, 242

seminalis, 244
Colloid iK6K\a, glue ; fUus, form) cells, 313

fluid, 313
Colon (k&jAoj'), 103, III

ascending, 103, in, 321
descending, 103, 113, 321, 322, 324
ligaments of, 106
sigmoid, 103, 113, 321
transverse, 103, 112, 323
Colostrum, 291
Colostrum-corpuscles, 291
Coloured lines of enamel, 35
Columnie IJertini, 192

rugarum, 259
Columns of enamel, 35, 43, 45
of rectum, 116
of vagina, 259
Common bile-duct, 100, 102, 127, 12S, 140, 14I
dental germ, 39, 40, 41, 48, 50
enamel germ, 39
seminal duct, 233, 235, 244
Compressor sacculi laryngis, 150

330

INDEX AND GLOSS AEY TO VOLUME III., PART lY

Concentric corpuscles of Hassall, 308, 315, 318

Coni vasculosi, 231

Conical papillse, 5, 6

Connecting strand of dental gevms, 41

Convoluted tubules, 197, 198, 199

Cooper on nerves of thymus, 309

ligaments of, 287
Cope on phylogeny of teeth, 29
Cord, spermatic. See Spkrmatic Cord.
Cords, vocal, false, 152, 154

true, 146, 152, 154, 155, 157
Cornicula (little horns) laryngis, 147, 149,152,153
Cornua (horns) of thyroid cartilage, 147, 148
Corona glandis, 236
Coronary ligament, 125, 321
Corpora cavernosa [cavarnosus, full of cavities)
clitoridis, 255
penis, 236, 239

structure of, 239
Corpus cavernosum urethrse, 236

Highmori, 222

luteum (yellow body), 275
structure of, 280

mammse, 286

spongiosum, 236, 241
bloodvessels of, 242
structure of, 242
Corpuscles, concentric of Hassall, 30S, 315, 318

genital, 243

Malpighian, of kidney, 197
of spleen, 299

salivary, 61

tactile, 8, 117, 243, 250, 257, 290

thymus, 308
Cortex of kidney, 192

labyrinth of, 196

of muscle-substance of tongue, II

of suprarenal capsules, 304

of thymus-follicles, 308
Cortical zone of testis, 224
Costal pleura, 170, 174
Costo-colic ligament, 113, 322
Cow, Gartner's duct of, 282
Cowper's glands, 218, 246, 247
Crem aster {Kpefxdoc, suspend) muscle, 219
Cremasteric fascia, 219
Crescents of Gianuzzi, 20
Crest of urethra, 244
Cricoid («p//cos, ring ; elSos, shape) cartilage, 146,

148, 150
Crico-arytenoid articulations, 152

ligament, 152

muscle, lateral, 158, 160
posterior, 158, 159
Crico-thyroid articulations, 151

membrane, 151

muscle, 158
Crista (crest) iirethrre, 244
Crown of tooth, 26, 27, 28. 29, 30, 34
Crura (cms, leg) of clitoris, 255

of corpora cavernosa, 239
Crusta petrosa (stony crust), 32, 36
Cryptorchismus {Rpvirrds, hidden ; opx^s, tes-
ticle), 220
Crypts of Lieberkiihn, 93, 106

of mucous membrane of tongue, 9

of tonsil, 60, 61
Cul-de-sac, small, of stomach, 72
Cuneiform [cuneus, wedge ; forma, shape) car-
tilages, 147, 149, 153
Cunningham on muscles of oesopliagus, 66

relations of kidney and duodenum, 102

Cunningham on renal impressions, 192
Curvatures of dentinal tubes, 33

oesophagus, 64

stomach, 71, 73
Curve of dental arches, 24, 52
Cushion of epiglottis, 149, 154

Eustachian orittce, 57
levator, 57
Cuspidate teetli, 27
Cusps {cuspis, point), 27, 28, 29, 30

dental, of different races, 29
Cuticle, enamel, 36, 46
Cystic duct, 127, 128, 138

Dartos (5apT(iy, flayed ; ^ipo>, flay) tunic, 219
Davidoff on splenic pulp, 299
Debierre on ileo-csecal valve, 1 1 1
Deglutition, larynx during, 162
Dental arches, 3, 24, 52

fun"ow, 39

germ, common, 39, 40, 41, 48, 50
special, 40, 41, 43, 49, 50

index, 25

lamina, 39. See also Dental germ, com-
mon.

papillffi, 39, 41, 44

periosteum, 26, 37, 47

pulp, 30, 40, 45

sac, 44, 47, 50
Dentinal sheath, 33

substance, intertubular, 34, 44

tubes, 32, 44
Dentine, 31, 32, 40, 43, 44

of repair, 37

secondaiy, 37

varieties of, 37
Dentition, 24, 29

changes in jaws during, 52
Descending colon, 103, 113
Descent of csecum, 109

of ovary, 273

of testis, 220
Detrusor urinaj, 213
Deutoplasm {^evTfpo^, second ; TrAajTco, I form),

280
Development of teeth, 37, 49

historical account of, 53
Diaphragmatic pleura, 170, 174
Diastema (Siao-Tjj^a, interval), 24
Digestion, organs of, i
Digital fossa, 220

Diphyodont (Sk/jw^s, double ; oZovs, tooth) den-
tition, 24
Discus proligerus, 275, 278
Disse on vesical orifice of urethra, 211, 212
Diverticula, j)haryngeal, 61
Diverticulum (by-path, diverto, turn away),

Meckel's, 103
Dog, fat-absorption in, 93

marginal cells of, 20

nerves of, parotid of, 16
trachea of, 167

salivary alveoli of, 19

spleen of, 298

suprarenal of, 304
Dorsum penis, 236
Douglas. poiTch of, 263, 321
Dubois on laryngeal cartihiges, 151
Duct or Ducts of Bartholin, 17

of Bellini, 200

bile, common, ico, 102, 127, 128, 140, 14I

IXDEX AND GLOSSARY TO VOLUME III., PART IV.

.331

IJuct or Ducts — continued.

biliary, 133. 135
aberrant, 136

common seminal, 233, 235. 244

cystic, 127, 128, 138

ejaculatory, 233, 235, 244

galactophorous, 2S8

of Gartner, 2S2

hepatic, 127, 128

hepato-cystic, 12S

intercalary, of ]iancreas, 142

salivary glands, 21

intralobular of salivary glands, 21, 22

pancreatic, 100, 102, 140, 141
accessory, 142

parotid, 15, 16

prostatic, 244

ofRivinus, 17

ofSantorini, 142

of serous glands, 21

of Stensen, 16

of sublingual giand, 4, 17

of submaxillary gland, 4. 16, 17, 22

of testis, 230

thyro-glossal, 8

of Wharton, 16, 17
Ductless glands, 293
Ductus communis choledochus, 12S

lingualis, 9

Stenonianus, 16

venosu.s, fissure of, 121, 125
Duodenal fossa, inferior and superior, 326
Duodeno-jejunal flexure. 102

fo.ssfe, 102, 326
Duodenum (duodeni, twelve ; the first twelve
finger-breadths of the intestine), 86, 100, 128,
142, 321, 322
Duverney, glands of, 256

Eberth on coccygeal gland, 318
Ebner on coloured lines of enamel, 35

dentinal substance, 34
Edmunds on parathyroids, 314
EfTerent tubules of testis, 230, 232
Egg-tubes, 277

Ejaculatory duct, 233, 235, 244
Elephant, testis of, .-^20
Ellipsoids, 300
Enamel, 31, 34, 40, 45

cells, 43

columns or prisius, 35, 43, 45

cuticle, 36, 46

droplets, 45

epithelium, outer, 43

germ, conjnion, 39

oigan, 43

P>ilp, 43
End-bulbs, 3, 8, 158, 243
End-piece of sperniato^^oon, 226
Eparterial [int, upon) branf^h of l)ronchus, 164,

177. 178
Epididymis (M, upon ; SiSv/xos, testicle), 222,

231, 282
Epiglottic gland, 157
Epiglottis 'Jnl, upon;, 146, 149
cartilage of, 146, 149
position of, in swallowing, ifiz
tubercle or cushion of. 149, 154
Epithelial bodie.*, outer and inner, of tliyroid,
3'4

Epithelial sheath of dental germ, 47

teeth, larval, 38
Epithelium, germinal, 274

enamel, outer, 43
Epoophoron (fVi, upon: wSu, egg; cfx'ou. carry),

282
Erectile tissue of vulva, 255
Eruption of milk-teeth, 49

permanent teeth, 51
Europeans, dental cusps ol, 29

position of incisors of, 25
Eustachian orifice, cushion of, 57

tubes, 57
Excretory tubes, uriniferous, 197, 200
Extrinsic tongue-muscles, 9
Eye-teeth, 27

FALClFor.M ifalx, sickle ; forma, shape) liga-
ment, 121, 125, 321
Fallopian tubes, 253, 264, 269, 321
literature of, 283
mucous membrane of, 271
peculiarities of, according to age, 270
position of. 269
structure of, 271
varieties of, 271
Fangs of teeth, 26, 27, 28, 29, 30, 37, 47
Fascia, bucco-pharyngeal, 61
cremasteric, 219
infundibuliform, 219
intercolumnar, 219
propria of spermatic cord, 220
spermatic, 219
Fasciculated bladder, 213
Fat, absorption ot, 92

Fat-pad of cheek, 3 ,

Fauces, i

isthmus of, i, 59
Ferrein on aberrant biliary ducts, 136
Fibres of Tomes. 31, 44
Fibrous coat of kidney, 192
liver, 129
jirostatc. 249
spleen, 296

suprarenal capsule, 304
testis, 222
Filament, axial, of spermatozoon, 229
Filaments, seminal, 225
Filiform papillae, 8
Fimbria, ovarian, 270
Fimbriae (threads, fringe), 270
Fimbriated extremity of Fallopian tube, 269,

270
Fishes, dentition of, 29

larval epithelial teeth of, 38
Fissure or Fissures, of ductus vcno.sus, 121, 125
if liver, 124

longituilinal, of liver, 124
of lung, 175
portid, 124

transverse;, of liver, 124
umbilical, 121, 125
of vena cava, 125
Fistula, cervical, 61
Flexure, dnodeno-jfjnnal, IC2
hepatic, 112, 322
sigmoid, 103, 113, 115
splenic, ii2, 113, 322
Floating kidney, 192
Flower, dental index of, 25

;382

INDEX AND GLOSSARY TO VOLUME IIL, PART IV.

Fold or Folds, of aual canal, 1 16

aryteno-epiglottic, 153

bloodless, iii

glosso-epiglottic, 5, 149

ileo-csecal, 11 1

ileo-colic, iii

of oesophageal inucous membrane, 66

of peritoneum, 6g

recto- vesical, 211

of rectum, 115

utero-vesical, 263
Follicles, Graafian. Sec Graafian follicles.

lymphoid. See Lymphoid follicles.

spleen, 299

of thymus gland, 308
Foramen caecum (blind), 5, 8

of Wiuslow, 323
Foramina, naso-palatine, 13
Fore-skin, 236

Fossa (trench or ditcb) or Fosste, of cii-cum vallate
papillae, 6

digital, 220

duodenal, superior and inferior, 326

duodenal -jejunal, 102, 326

glosso-epiglottic, 5

ileo-caecal, iii

ileo-colic, 1 1 1

iutersigmoid, 113, 326

navicularis urethrse, 246
valve of, 247
vulvae, 256

ovarii, 272

par.i-duodenal, 326

jieritoneal, 11 1, 325

I'etio-duodenal, 326

of Rosenmiiller, 57

subeaecal, 1 1 1

supra-tonsillaris, 60

of vena cava, 125

vesicalis, 124
Fourohette, 254

Foveola {fovea, small pit) of renal papilla, 195
Freuum (bridle) of ileo-csecal valve, 1 10

labii, I

lingUiB, 4

of prepuce, 236, 255
Frey ou lacteals of sheep, 90

lymphatics of thyroid, 314
Frog, cilia in uriniterons tubules of, 19S

cardiac glands of, 81

i'at-absorptioii in, 92
F'undus (cup) of bUidder, 208, 210

of gall-bladder, 127

glands, 79

of stomach, 71

of uterus, 260, 26S
Fungiform {fungas, mushroom, fungus ; forma,

shape) papillae, 5, 6
Furrow, dental, 39

Galactophokous (^aAa, milk; (pipca, carry)

ducts, 2S8
Gall-bladder, 127, 321

lymphatics of, 137

nerves of, 137

structure of, 137

varieties of, 128
Gartner's duct, 282
Gastric glands, 78

secretion, 81

surface of spleen, 293

Gastro-colic omentum, 73, 125, 324
Gastro-hepatic omentum, 73, 125, 323
Gastro-phrenic ligament, 73, 322
Gastro- pulmonary system, i
Gastro-splenic ligament, 322

omentum, 69, 74, 295, 322, 323
Gawronsky on nerves of ovary, 282
Gegenbaur on laryngeal cartilages, 151

on plica fimbriata, 4
Genital corpuscles, 243
Genitals, external, 253

internal, 253
Germ, common dental, 39, 40, 41, 48, 50
enamel, 39

special dental, 40, 41, 43, 49, 50
Germinal epithelium, 274

spot, 280

vesicle, 280
Gianuzzi, crescents of, 20
Gibb on cartilages of Wrisberg, 149
Gingivae (gums), 3
Giraides, organ of, 234, 282
Gland or Glands, admaxillary, 19

agminated, 95

of alimentary canal, i

ante-prostatic, 247

of Bartholin, 256

of bladder, 213

of Blandin, 9

of bronchial tubes, 182
^ of Brunner, 93, 9j, 100

buccal, 3

cardiac, 79

carotid, 293, 317

of cervix uteri, 266

circum-anal, 116

of circumvallate papillae, 6, 9

coccygeal, 293, 317

of Cowjier, 218, 246, 247

ductless, 293

of Duverney, 256

epiglottic, 157

fundus, 79

of gall-bladder, 137

gastric, 78

labial, 3

of large intestine, 106

of laryngeal pouches, 156

of larynx, 157

lingual, 9

of Littre, 247

mammary. See Mammary gland.

molar, 3

of mouth, I, 3

mucous, 19

of liver ducts, 136

of nipple and areola, 286

of oesophagus, 66

oxyntic {H'^s, acid), 79

parotid, 15

of penis, 238

of Peyer, 93, 95

of pharynx, 62

prostate, 218, 247

pyloric, 78

retrolingual, 19

salivary, 15

literature of, 23
structure of, 17

serous, 19

of Serres, 42

of small intestine, 93

INDEX AXD GLOSSARY TO VOLUME III., PART IV.

333

Glanil or GlatiJs — conti/uitd,

of soft palate, 13

solitar}-, 93, 94

of stomach, 78

sublingual, 15, 17

submaxillary, 15, 16

of thymus. See Thymus olaxd.

of tongue, 5, 9

of tonsil, 61

of trachea, 166, 167

of Tyson, 23S

of ureter, 205

of urethra, 247, 25S

uterine, 265, 267, 26S

of uterus masculinus, 246

of vagina, 260

of vas deferens, 233

of vulva, 256
Glandula coccygea, 31S

socia parotidis, 1 5
Gland ulse caroticae, 317

odoriferse, 23S

]iarathyroidea;, 314
Glans clitoridis, 255

penis, 236
Gley on parathyroids, 314
Glisson, capsule of, 127, 129
Globule, terminal, 225
Globuloid body, 225, 226, 229
Globus major, 222

minor, 222
Glomerulus (dim. of glo?nus, skein), 202
Glosso-epiglottic folds, 5, 149

fossae, 5

sinuses, 5
Glottis (■yXuTTis, mouth-piece of musical pipe),

152, 154
Glycogen, 133

Goblet-cells, 92, 94, 107, 167
Goppert on laryngeal cartilages, 151
Golgi on uriniferous tubules, 197
Goodsir on development of teeth, 53
Graafian follicles, 273, 275, 281
fibrous wall of, 278
structure of, 276
Granular layer of dentine, 34
Granules, spermatic, 230
Griffiths on muscular coat of bladder, 213

on middle lobe of prostate, 249, 250

on pelvic splanchnics, 215
Grinders. 28

Gross on weight of prostate, 250
Gubaroff on cardia 72
Gubemaculum (rudder) dentis, 48
Guinea-pig, fat-absorption in, 93

salivary alveoli of, 19

subserous layer of pleura of, 1 74
Gullet, I, 64
Gums, 3

Hard palate, 1 1

Hare, vermiform appendix of, no
Hassall on capsule of uriniferous tubules,
198
concentric corpuscles of, 308, 315, 318
Hasse on position of ovaiy, 272

ramification of bronchi, 179
Head of epididymis, 222

pancreas, 139

Hpennatozooti, 225, 229
Headcai) of 8[)ermatozoon, 225, 226, 230

Heidenhaiu on bile-ducts, 135
fat-absorption, 93
mammary gland, 2S7
salivary secretion, 20
Helicine (eAi^, spiral) arteries, 241
Henle, on capacity of bladdei-, 206
ejaculatory duct, 235
looped tubule of, 197, 198
on muscles of laryn.K, 162
Hepatic artery, 126, 130, 131
canals, 1 29
capillaries, 131
cells, 132
duct, 127, 12S
flexure, 112, 322
lobules, 129
veins, 127, 132
Hepato-cystic ducts, 12S
Hepato-renal ligament, 322
Hertwig on reduction of chromosomes in sper-
matic cells, 22S
Heterodont (erepos, different ; oSuvs, tooth) den-
tition, 24
Hilum (mark of attachment on cuni ave side of
bean) of kidney, 192
of lung, 175
of ovary, 272
of spleen, 293
of suprarenal capsule, 302
His on foramen caecum, S

fossa supra-tousillaris, 60
lymphatics of thynms, 309
position of ovary, 272
Historical account of dental develoi)inent, 53
Holl on ureter, 204
Homodont {&fj-6s, same ; oSovs, tooth) dentition,

24
Homologies of teeth, 29
Horse, suprarenal of, 304
Horse-shoe kidney, 192
Hour-glass stomach, 75
Hiirthle on thyroid body, 313, 314
Hydatid {hydatis, water-coloured gem) of Mor-

gagni, 222, 271
Hymen {i/ixiiv, membrane), 253, 25S
Hyo-epiglottic ligament, 149
Hyparterial {uit6, below) branches of bronchus,
178

Ileo-cxboal or ileo-colic fold, 1 1 1

fossa. III

orifice, no

valve, 1 10
Ileum {fXK(u>, wind about), 86, 102, 321
Imperforate hyniiMi, 258
Impressio (impression) colica, 124

duodenali.s, 124

renalis, 124

suprarenal is, 123

vesicaiis, 124
Incisive pad, 13

Incisor (incido, cut) teeth, 24, 26, 30, 49. 51
Incremental lines, 34
Index, dental, 25
Infundibula, ])ulmonary, iSi

renal, 193
Infundibiiliform fascia, 219
Inl'undibulum (funnel) of Fallopian tube, 270
Inguinal {ingueii, groin) canal, 218

mumiiije, 291

334

INDEX AND GLOSSARY TO VOLUME III., PART IV.

Insectivora, mammary glands of, 290
Intei'-alveolar cell-islets of pancieas, 145
Intercalary ducts of pancreas, 142
salivary, 21
tube of kidney, 199
Intercolumnar fascia, 219
Interglobular spaces, 34, 44
Interlobular brauclies of hepatic artery, 131

portal veins, 130
Intel-mediate cells of seminal tubes, 227
Interpleural ligament, 173
Intersigmoid fossa, 113, 326
Interstitial cells of ovary, 274, 278, 281

testis, 230
Intertubular dentinal substance, 34
Intestine, large, i, 103

blood-vessels of, 108
divisions of, 108
lymphatics of, 108
mucous membrane of, 106
nerves of, 108
structure of, 105
small, I, 86

age and sex variations of, 103
blood vessels of, 97
divisions of, 100
glands of, 93

lymphatics of, 88, go, 96, 98
mucous membrane of, 87
nerves of, 99
structure of, 86
villi of, 89
Intestines, literature of, 117
Intestinuni (gut) caecum (blind), 108

rectum (straight), 113
Intralobular or central hepatic veins, 130, 131,
132
salivary ducts, 21, 22
Intrinsic tongue-muscles, 9
Irregular tubule of kidney, 197, 19S
Islands of dental epithelium, 42, 47
Isthmus of Fallopian tube, 269
fauciurai i, 59
of thyroid body, 311, 312

cartilage, 147, 148
uteri, 262
Ivory, 31

Jaws, changes in, during dentition, 52
Jejunum (empty), 86, 102, 321
Jonnesco on peritoneal fossae, 326
Junctional tubule, 197, 199

Kanthack on foramen caecum, 9
Kazzander on valvulae conniventes, 88
Kerato-cricoid muscle, 160
Kerkring, valves of, 88
Kidneys, 189, 321, 322, 323

bloodvessels of, 201

capsule of, 190, 192, 202

excretory apparatus of, 193

floating, 192

hilum of, 192

lobules of, 194

lymphatics of, 203

moveable, 192

muscular fibres of, 192

nerves of, 203

Kidneys —continued.
stroma of, 204
structure of, 192
varieties of, 192
Kiernan on aberrant biliary ducts, 136
Killian on pharyngeal bursa, 57
Kisselew on hepatic lymphatics, 136
Klein on capsule of uriniferous tubules, 198
intercalary salivary ducts, 21
lining membrane of uriniferous tubes,

200
parietal cells, 81
Kohn on parathyroids, 314

tliynius tissue, 309
KoUiker on development of teeth, 53

position of ovary, 272
Korolkow on nerves of liver, 136
Krause on size of ovary, 271
Kupffer on bile-canaliculi, 134

Labia (lips) mnjora, 253

minora, 253, 254
Labial glands, 3
Labio-dental strand, 39
Labyrinth of renal cortex, 196
Lacteals {lac, milk), 88, 90, 96, 98
Lacuna (hollow) magna, 247
Lacunae, urethral, 247
Lafforgue on vermiform appendix, 1 10
Lamina (layer, plate), dental, 39. See also

Dental gekm, common.
Langendorfl on cells of thyroid, 313
Langer on bloodvessels of penis, 241
Langerhans on centro-acinarcells of pancreas, 143
Langley on salivaiy seci'etion, 21
Larval epithelial teeth, 38
Laryngeal pouches, 156

cartilages, 146, 149, 150
morphology of, 151
part of pharynx, 57, 61
Larynx (Xdpvy^), 146
bloodvessels of, 157
cartilages of, 146, 149, 150
during deglutition, 162
in foetus, 149
interior of, 152
joints of, 151

laryngoscopic appearances of, 153
ligaments of, 151
literature of, 187
lymphatics of, 15S
mucous membrane of, 156
muscles of, 158
nerves of, 158
at puberty, 150
saccules of, 152
sexual differences of, 150
superior aperture of, 153, 162
ventricles or sinuses of, 152, 154, 156
vestibule of, 152
Lateral recess of pharynx, 57
Layer, basal, of dental pulp, 31

granular, 34
Leopard, subserous layer of pleura of, 174
Leopold on uterine mucous membrane, 265
Levator cushion, 57

glandulae thyroidese, 312
Lieberkiihn, crypts of, 93, 106
Lienciili [lien, spleen), 297
Lieno-renal ligament, 295

INDEX AND GLOSSARY TO VOLUME III., TART IV.

335

Ligament or Ligaments, of bladder, false, 115,
20S, 211
true, 20S. 210, 211
broad, of liver, 121, 125

of uterus, 262, 264, 267, 321
of colon, 106
of Cooper, 287
coi'onaiy, 125, 321
costo-colic, 113, 322
crico-arytenoid, 152
falciform, 121, 125, 321
gastro-plirenic, 73, 322
gastro-splenie, 322
hepato-rcual, 322
hyo-epiglottic, 149
interpleural, 173
of larynx, 151
lieuo-renal, 295
of liver, 125. 321
of ovaiy, 264, 272
phreno-colic, 113, 322
recto-vaginal, 263
round, of liver, 125

of uterus, 264, 267
suspensory, of clitmis, 255

of diaphragm, 170

of liver, 125

of penis, 238
thyro-arytenoid, 152
thyro-epigiottic, 149
thyrohyoid, 151
thyroid body, 312
utero-sacral, 263
of uterus, 263
of viscera, 69
Ligamentum infundibulo-pelvicum, 272
latum pulmonis, 170, 177
suspensorium ovarii, 272

vesica, 211
Liues, coloured, of enamel, 35
incremental, 34

oblique of thyroid cartilage, 147
of Schreger, 33
Lingual glands, 9

muscle, external perpendicular, 10

inferior, 9

superficial, 9

transverse, 10

vertical, 10
tonsils, 5
Lining cells of seminiferous tubules, 226
l,ion, subserous layer of pleura of, 174
I.ips, 2

Liquor folliculi, 275, 278
Literature of alimentary canal, 69

carotid gland, 318

coccygeal gland, 318

female reproductive organs, 283

intestines, 117

liver, 138

male reproductive organs, 250

mammary gland, 292

mouth, tongue and palate, 14

<.«soi»hagus, 67

pancreas, 145

jiarathyroids, 315

]>eritoneum, 69

jiharynx and tonsil, 62

res pi rato ry oiga n s, 187

salivary glands, 23

spleen, 301

stomach, 85

Literature — continued.

suprarenals, 306
teeth, 53
thymus, 309
thyroid, 315
urinary organs, 216
Litti'e, glands of, 247
Liver, i, 121

accessory, 128
bloodvessels of, 126
excretory apparatus of, 127
fissures of, 124
of infant, 12S
ligaments of, 125, 321
literature of, 138
of lower animals, 134
lymphatics of, 127, 136
nerves of, 127, 136
structure of, 129
Lobe or Lobes, azygos, of lung, 178
caudate, of liver, 121, 122
of epididymis, 232
liver, 121

mammary gland, 2S8
lung, 175, 177, 178
accessory, 176
prostate, 248
quadrate, of liver, 121, 124
of Spigelius, 121, 122
thymus, 307
thyroid, 311
Lobular bronchiole, 181, 1S3
Lobules, hepatic, 129
of kidney, 194

testis, 223, 224
thymus, 307
Lobulus Spigelii, 121, 122
Lobus impar (uneven, odd), of lung, 176
Lockwood, on mesentery, 103
peritoneal fossae, 1 1 1
Longitudinal fissure of liver, 124
Looped tubule, 197, 198
Loven on lymphatics of stomach, 83
Ludwig on Ij-niphatics of kidney, 203
Lungs, 146, 169, 174
alveoli of, 181, 1S3
bloodvessels of, 185
dimensions of, 180
distribution of bronchi in, 177
of foetus, 181, 184
literature of, 187
lobes of, 177, 178
lymfihatics of, 186
nerves of, 187

physical properties of, l8o, 181
root of, 169, 175, 176
structure of, iSi
Lunulfe (dim. of luua, moon), 20
Luschka on bladder, 206
cartilage of, 155, 161
on jdiaryngeal bursa, 57
pleura, 171, 172
urachus, 209
vas aberraiis, 233
Lym[ihatii',s of bladder, 215
bronchi, 167
bioncliial tubes, 186
gall-bladder, 137
kidney, 203
laige intestine, io8
larynx, 158
liver, 127, 136

336

INDEX AND GLOSSARY TO VOLUME 111., PART IV.

Lvmjjhatics — continiocd.
lungs, 1 86

mammary gland, 290
cesophagLis, 66
pancreas, 145
parotid gland, 16
penis, 243
]ileura, 174
prostate, 250
rectum, 117
salivary glands, 22
scrotum, 221

small intrstine, 88, 90, 96, 98
spleen, 300
stomach, 83
suprarenals, 305
testis, 230, 236
thymus, 309
thyroid, 313, 314
tongue, 6, II
tonsil, 60
trachea, 167
uterus, 265, 26S, 269
vulva, 257
Lymphoid follicles of large intestine, 108

liver, 136

lungs, 187

pharj'nx, 62

small intestine. See Solitary
Glands and Peyer's Glands.

spleen, 299, 300

stomach, 82

tongue, 5, 9

tonsil, 60

trachea, 167

ureter, 205

Macula germinativa (germinal spot), 2S0
McCormick on epiglottis in swallowing, 162
Magitot on cement organ, 47
Malpighi, glomerulus of, 202

pyramids of, 192, 194
Malpighian corpuscles of kidney, 197

spleen, 299
Mamma (breast), 285
Mammee erraticse. 291
Mammals, typical dentition of, 24
Mammary area, 291
gland, 285

bloodvessels of, 290

development of, 291

in lactation, 287, 290

literature of, 292

lobes of, 2S8

lymphatics of, 290

of male, 290

nerves of, 290

in pregnancy, 291

structure of, 206

supernumerary, 291

varieties in, 290
Mammilla (teat), 285
Marginal cells, 20
Marshall on thyroid gland, 312
Marsupials, dentinal tubules of, 33, 35

dentition of, 30
Matrix, dental, intertubular, 34, 44
Meatus (passage) urinarius, 236, 258
Meckel's diverticulum, 103

Mediastinal pleura, 170

space, 109
Mediastinum {per medium iensum, stretched
throughout the middle), anterior, 169

middle, 169

posterior, 169

superior, 169

testis, 222

thoracis, 168
Medulla of thymus follicles, 308
Medullary part of muscle-substance of tongue,
II

rays, 196

substance of kidney, 192

supra-renal capsule, 304
Megadont [fieyas, large ; oBovs, tooth) races, 25
Meissner, plexus of, 100
Membrana adamantinse, 43

granulosa, 278, 281

preform ativa, 44

propria of Graidian follicles, 278
Membrane, crico-thyroid, 151

of Nasmyth, 36, 46

striated, 279

thyro-hyoid, 151

vitelline, 280
Membranous portion of urethra, 243, 246
Menstruation, uterus during, 267
]\lesenteric border, 86

Mesentery [fxecrov, middle ; evrepov, entrail — the
word signifying any of the abdominal con-
tents and not onl}' the bowel), 69, 86, 103,
321
Meso-appendix, 109
Meso-colon, ascending, 112

descending, 113

sigmoid, 69, 113, 321

transverse, 69, 112, 113, 323
Mesodont [fiearos, middle ; oSovs, tooth) races, 25
Meso-gastrium {yaffr-fip, belly), 324
Meso-nephron (i'e(pp6s, kidney), 192
Meso-rectum, 69, 115, 321
Mesorchium {opx's, testicle), 220
Meso-salpinx {ad\in'y^, trumpet), 264
Microdont (/xiKpds, small ; o5ous, tooth) races, 25
Middle-piece of spermatozoon, 225, 226, 229
Milk, 291
Milk-teeth, 24, 29, 30, 33, 37, 40

eruption of, 49
Molar glands, 3

{molo, grind) teeth, 24, 28, 30, 40, 49, 50, 5 r
Mole, development of mammae of, 291
Mongolians, dental index of, 25
Monkey, azygos lobe of, 178
Mons Veneris, 253
Morgagni, hydatid of, 222, 271
Morphology of laryngeal cartilages, 151
Morsus diaboli (devirs-ldte ; name of tiie plant,
Scabiosa succiia, to the root of which the ex-
tremity of the Fallopian tube was likened), 270
Mouse, corpus luteum of, 281

spermatozoa of, 225
Mouth, I

literature of, 14
Moveable kidney, 192
Mucigen, 20
Mucin-cells, 20
Mucous alveoli, 19

Mucous membrane of bladder, 212, 213, 215
of bronchial tubes, 182
of Fallopian tube, 271
of gall-bladdei-, 137

ES'DEX AND GLOSSARY TO VOLUME III., PART IV.

337

S6, 87

Mucous membrane — continued.
of gums, 3
of hard palate, 1 1
of large intestine, 105, 106
of larj"ux, 1 56
of lips, 3
of mouth, 3
of oesophagus, 66
of pharynx, 62
of rectum, 115
of small intestine,
of soft palate, 13
of stomach, 76. 77
of tongue, 4
of trachea, 166
of ureter, 193, 205
of urethra, 246, 258
of uterus, 264, 265, 267, 268
of vagina, 259
of vulva, 256
Mucus cells, 92, 94, 107
Miiller on ellipsoids, 3CX3
AInlticuspidate {muUi, many ; cuspis, point)

teeth, 29
Mummery on dentinal substance, 34
Muscle or Muscles, arytenoid, 15S, 162
aryteno-epiglottic, 158, 162
cremaster, 219
crico-arytenoid, lateral, 158, 160

posterior, 158, 159
crico-thyroid, 158
kerato-cricoid, 160
of larynx, 158

lingual. See Lingual muscle.
recto-coccygeal, 1 1 5
thyro-arytenoid, 158, 161
thyro-epiglottidean, 161
of tongue, 9
Muscular bands of colon, 106, loS
coat of bladder, 213

large intestine, 105, 106
oesophagus. 65
rectum, 115
small intestine, 86
stomach, 76
ureter, 193, 205
fibres of bile-ducts, 135

bronchial tubes, 1S3
kidney, 192
pleura, 173, 174
spleen, 298
trachea, 166
process of arytenoid cartilage, 149
substance of piostate, 249
tongue, II

uterus, 264, 267, 268
tunic, inner, of testis, 222
Muscularis mucosae of large intestine, 108
oesophagus, 66
small intestine, 88, 91
stomach, 81
uterus, 264, 265
Musculi ))ubo-vesicales, 213
MuBculus suBpensorius duodeni, 102

NxiiEa (nostrils), posterior, 57
Nasal part of pharynx, 57
Xa.smyth'8 membrane, 36. 46
Naso-pahitine for;uiiiii.i, 13
Na-so-pharynx, 57

VOL. IIL J'T. 4.

Neck of bladder, 208

Fallopian tube, 269, 270
gall-bladder, 127
pancreas, 139, 140
spermatozoon, 226
tooth, 26, 30
uterus, 260, 265, 268

Nerves of bladder*, 215
bronchi, 167
bronchial tubes, 1S7
deutal pulp, 31
female urethra, 25S
gall-bladder, 137
kidney, 203
large intestine, 108
larynx, 158
liver, 127, 136
lungs, 187

mammary gland, 290
oesophagus, 66
ovary, 282
papillae of tongue, 8
pancreas, 145
parotid gland, 16
penis, 239, 243
prostate, 250
rectum, 117
salivary glands, 22
scrotum, 221
seminal vesicles, 235
small intestine, 99
spleen, 301
stomach, 82, 84
sublingual gland, 17
submaxillary gland, 17
suprarenal ca])sules, 305
testis, 230, 236
thymus, 309
thyroid, 314
tongue, 8, 1 1
tonsil, 60
trachea, 167
ureter, 205
uterus, 268, 269
vagina, 260
vulva, 257

Newt, spermatozoa of, 226

Nipple, 285, 290, 291

Notch, thyroid, 147
umbilical, 121

Nuck, canal of, 220, 264

Nucleus of ovum, 280
spermatozoon, 225

Nymphse, 254

Oblique line of thyroid cartilage, 147
Odontoblasts {dSovs, tooth; &Kaar6s, gcrm\ 31,

(Esophageal glands, 66

(Esophagus [oXaui, carry ; <\)ay(iv, eat), 64, 322.

323
literature of, 67
mucous membrane of, 66
nerves of, 66
struiluie of, 65
vessels of, 66
Ogata on zymogen granules, 144
Omental tul)cro.sity of liver, 122
pancreas, 140

338

INDEX AKD GLOSSARY TO VOLUME III., PART IV.

Omentum (contraction of operimentuTti, coverlet)
bag of, 323

colicum, 324

of foetus, 324

gastro-colic, 73, 324

gastro-hepatic, 73, 125, 323

gastro-splenic, 69, 74, 295, 322, 323

great, 69, 73, 324

small, 69, 73, 125, 321, 323
Oral part of pharynx, 57, 59
Organ or Organs, cement, 47

of digestion, i '

enamel, 43

of Giraldes, 234, 282

reproductive. See Reproductive Organs.

respiratory, 146

literature of, 1S7

of Rosenmiiller, 282

urinar}', 188

literature of, 216

of voice, 146
Organon adamantine, 43
Orifice, cardiac, 71, 72

common, of bile and pancreatic ducts, 102

of Fallopian tube, 270

i]eo-c3ecal or ileo-colic, no

of larynx, superior, 153, 162

pyloric, 71, 84

of ureter, 212

urethral, of bladder, 211, 212
externa], 236, 256

of uterus, external, 260, 266, 2G8
internal, 262, 268

of vagina, 256
Oriiithorhynchus, thyroid cartilage of, 151
Os tincae (tench's mouth), 260
Os uteri externum, 260, 266, 268

internum, 262, 268
Osborne on phylogeny of teeth, 29
Osteoclasts {offTeov, bone ; K\a.a>, break in pieces),

50
Osteodentine, 37

Ostium (mouth) abdominale, 270

uteri, 262
Ova, 273, 274, 278
Ovarian fimbria, 270
Ovary, 253, 264, 271

bloodvessels of, 281

cell-nests of, 276

descent of, 273

Graafian follicles of, 273, 275

ligament of, 264

nerves of, 282

peculiarities of, with age, 272

position of, 272

stroma of, 273, 275

structure o , 273

varieties of, 272
Oviducts, 269
Ovula Nabothi, 266
Ox, bronchi of, 178

spleen of, 298
Oxyntic (o|vs, acid) cells, So

glands, 79

Pacinian corpuscles, 22, 117, 243, 250, 290
Pad, incisive, 13
Palatal rugse, 1 1

VtHdiiB {pcdatus, roof of mouth), 11
hard, il

Palat e — continued.

literature of, 14

soft, 13, 57
Palatine arches, 59

Palmse plicatse (folded palm -branches), 262
Pampiniform (jyampinus, tendril ; forma, shape)

plexus, 221, 236, 282
Pancreas {wav, all ; np^as, flesh, glandular flesh),

I, 139, 323
accessory, 142
bloodvessels of, 145
lesser, 142
literature of, 145
lymphatics of, 145
nerves of, 145
structure of, 142
varieties of, 142
Pancreatic canaliculi, 144
cells, 142

duct, 100, 102, 141, 142
accessory, 142
Papilla (nipple) or Papillie, of cervix uteri,
265
circumvallate, 5, 6
conical, 5, 6
dental, 39, 41, 44
filiform, 8
foliatse of rabbit, 8
fungiform, 5, 6
of glans penis, 238
kidney, 192, 193
labial mucous membrane, 3
nipple, 286

cesophageal mucous mem-
brane, 66
palatina, 11

of pharyngeal mucous meni'
brane, 62
tongue, 5, 9

secondary, 6, 8
vaginal mucous membrane,
260
Paradidymis {irapd, by the side of ; SiSvf^LoSf

testicle), 234
Para-duoden;d ibssa, 326
Paranucleus, 143
Parathyroids, 293, 314

literature of, 315
Parenchyma-cells of thyroid, 313
Parietal cells, 80
Paroophoron (Trapd, by the side of ; aiSv, egg ;

(pepoj, carry), 282
Parotid {irapd, beside ; ovs, ear) duct, 15, 16
gland, IS _

alveoli of, 19
varieties of, 16
Parovarium (irapd), 282
Pars intermedia of bulb of vestibule, 255
respiratoria, 156
vocalis, 156
Parturition, uterus after, 268
Passage, alveolar, 181
Patch, Peyer's, 95
Pavilion, 270
Pectoral mammte, 291
Pelvic portion of abdomen, 68
Pelvis (basin) of kidney, 193, 204
Penile portion of urethra, 243, 246
Penis (Latin, akin to ireos, and so connected
with oTTviw, marry), 236
bloodvessels of, 239, 240
corpora cavernosa of, 236, 239

IXDEX AND GLOSSARY TO VOLUJ^IE III., PART IV.

331)

Peuis — continued.

corpus spongiosum of, 236, 241

lymphatics of, 243

nerves of, 239, 243
Peptic cells, So
Pericardial pleura, 173, 174
Periosteum, dental, 25, 37, 47
Peritoneal coat of bladder, 213

fossa; or pouches, iii, 325
Peritoneum {irfpiTeivte, stretch all over), 68, 69,

. 319

fossre of, III

literature of, 69
Permanent teeth, 24, 26, 29, 41, 49, 51
eruj^tion of, 51
superadded, 50
Peyer's glands, 93, 95

patch, 95
Pfaundler on vessels of su])rarenals, 305
Pfliiger on bile-canaliculi, 134
Pharyngeal aponeurosis, 61

bursa, 57

diverticula, 61

tonsil, 57, 62
Pharynx (<pdpvy^, throat), 57

attachments of, 61

Uteratuie of, 62

mucous membrane of, 62

sti'ucture of, 61
Phrenic surface of spleen, 293
Phreno-colic ligament, 113, 322
Phylogeny of mammalian teeth, 29
Pig, duct of Gartner of, 2S2

hepatic lobules of, 1 29
lymphatics of, 136

parietal cells of, 81

spleen of, 298
Pigeon, nerve-eudiugs in liver of, 136
Pleura (irAei/pa, rib), 146, 168, 169

bloodvessels of, 174

cervicalis, 170, 172

costalis, 170, 174

lUaphragmatis, 170, 174

lymphatics of, 1 74

mediastinalis, 170

muscular fibres of, 174

pericardial, 173, 174

pulmonalis, 169, 174

structure of, 174
Plexus of Auerbach, 100
Meissuer, 100
myentericus, 100
pampiniform, 221, 236, 282
spermatic, venous, 221
Plica fimbriata (fringed fold), 4

salpiugo-pharyngea, 57

semilunaris, 321

trarisversalis recti, 116
Plicae recti, 115

Polymastic (ttoAus, many ; fiavrSs, breast) mam-
mals, 291
Pomum Adami (Adam's apple, properly ^otmjww
viri, Adami being a mistranslation of Arabic
adam, man, vir), 147, 150
PoDH (bridge) hepatis {hepur, liver), 125
Porpoise, parietal cells of, 81
Porta (gate) hepatis, 126
Portal canals, 129

fissure, 124

vein, 126, 130
Portioaiy-vocalisof thyro-ary tcnoid mtiscle, 161
Post-nasal space, 57

Pouch of Douglas, 263, 321

recto- vaginal, 321

recto-vesical, 115, 210, 321

utero-vesical, 211, 262, 263
Pouches, laryngeal, 156

peritoneal, iii, 325
Pouchet on development of teeth, 53
Pregnancy, uterus during, 267
Premolar teeth, 24, 27
Prenant on parathyroids, 315
Prepuce {prccputmm, akin to Trpoirocrdiut' =
aKpow6(r6ioi/, extremity of penis), 236

of clitoris, 255
Principal cells, So
Prisms of enamel, 35, 43, 45
Process, muscular, of ar} tenoid cartilage, 149

of Tomes, 45

vocal, of arytenoid cartilage, 149, 152
Processus vaginalis peritontei, 220
Prostate (TrpoiaTafiai, stand before) gland, 2iS,
247

anterior, 247

bloodvessels of, 250

literature of, 250

lobes of, 248

lymphatics of, 250

nerves of, 250

peculiarities of, according to age, 250

secretion of, 250

structure of, 249
Prostatic ducts, 244

portion of urethra, 212, 243

sinus, 244

utricle, 244, 249
Pseud-artei'iae recta;, 202
Pubic surface of bladder, 20S
Pudendum (pudeo, feel shanie), 253
Puech on weight of ovary, 271
Pulmonary alveoli, 181, 183
of foetus, 184

pleura, 169, 174

veins, 186
Pulp-cavity, 30, 32, 37
Pulp, enamel, 43

splenic, 296, 298, 300

of teeth, 30, 40, 44
Purser on double gall-bladder, 128
Pyloric glands, 78

orifice, 71, 72, 84

sphincter, 76, 84
Pylorus (irv\up6s, gate-keeper), 71, 72, 76, 84
Pyramid of thyroid body, 311
Pyramids of ilalpighi, 192, 194

Quadrate lobe, 121, 124

Quenu on haiiaorrhoidal plexus, 117

Rabbit, development of mamma; of, 291
hepatic cells of, 133
innervation of trachea of, 167
papilla foliata of, 8
salivary alveoli of, 19
vermiform ap]ien(lix of, no
Rainey on pulmonary capillaries, 185
Rimitication of bronchi, 177
Ransshotfon vermiform ap|i(Midix, 109
{{aiivier on retro-lingual gland, 19
Rajihe (^ai^ij, seam) of palate, II, 13
scrotum, 219

34-0

INDEX AND GLOSSARY TO VOLUME III., PART IV,

Rat, fat-absorption in, 92

spermatozoa of, 225
Rauber on villi, 89
l.'ays, medullary, 196
Recess, lateral, of pharynx, 57
Recessus pharyngeus niedius 57
Rectal ampulla, 116
Recto-coccygeal muscles, 115
Recto-vaginal ligament, 263

pouch, 321
Recto-vesical folds, 211

pouch, 115, 210, 321
Rectum (sc. intestinum, straight bowel), 103,
106, 113, 321
bloodvessels of, 117
columns of, 116
folds of, 115
lymphatics of, 117
nerves of, 117
structure of, 115
valves of, 115

variations of, with age, 115
Regions of abdomen, 68
Rnid on liver- weight, 121
Runal surface of spleen, 293
Repair, dentine of, 37
Keproductive organs, female, 253
literature of, 283
male, 218

literature of, 250
Reptilia, teeth of, 29

pulmonary capillaries of, 185
Keserve cells, 313
Respiratory bronchiole, iSi
organs, 146

literature of, 187
Rete (net) vasculosum testis, 230
Reticular cells of splenic pulp, 298
Retinacula (restraining bands) of ileo-csecal

valve, no
Retro-lingual gland, 19
Retro-duodenal {retro, behind) fossa, 326
Ketterer on glans penis, 242
Retzius on biliary canaliculi, 135

on o'vum, 279
Ribbert on vermiform appendix, no
Ridge, basal, of incisor teeth, 27
Rima (cleft) glottidis, 152, 154, 156

oris, I
Rivinus, ducts of, 17
Rodents, enamel of, 35

testes of, 220
Rolleston on peritoneal fossfe, in
Rolssen on length of small intestine, 103
Root of lung, 169, 175, 176
tongue, 3

tooth, 26, 27, 28, 46
Rose on dental cusps, 29

dentinal sheaths, 33
enamel-pulp, 44
larval epithelial teeth, 38
phylogeny of teeth, 29
Rosenmiiller, fossa of, 57

organ of, 282
Both on vasa aberrantia, 234
Round ligament of liver, 1 25

uterus, 264, 267
JLagsn (wrinkles) of bladder, 212
hard palate, 1 1
oesophagus, 66
scrotum, 219
stomach, 77

Rugae of vagina, 259
Ruminants, cement-organ of, 47

Sac, dental, 44, 47, 50
Sacculated bladder, 213
Saccules of larynx, 152
Sacculi of large intestine, 105, 106

rectum, n5
Sacculus, vesical, 213
Salamander, chromosomes of spermatic cells of,

228
Saliva (spittle), 15
Salivary corpuscles, 61
glands, I, 15

alveoli of, 18, 22
literature of, 23
structure of, 17
secretion, 20
Sandstrom on parathyroids, 314
Santorini, cartilages of, 149
duct of, 142

on thyro-arytenoid muscle, 162
Schaffer on corpuscles of thymus, 309
Schirmer on pancreatic duct, 142
Schultze on development of mamrare, 29c
Schreger's lines, 33

Scrotum (by transposition from scortum, skin).
218, 219
bloodvessels of, 220
lymphatics of, 221
nerves of, 221
septum of, 219
skin of, 219
Seal, subserous layer of pleura of, 174
Secondary dentine, 37
Secretion, gastric, 81

salivary, 20
Seminal duct, common, 233, 235, 244
filaments, 225
vesicles, 234

bloodvessels of, 235
nerves of, 235
structure of, 235
Seminiferous tubules, 224

epithelium of, 226
Septula renum, 192

Septum pectlniforme (partition, from sepio,
hedge in ; pecten, comb ; forma, shape),
239, 255
scroti, 219
of tongue, II
Serous alveoli, 19, 20
ducts of, 21
coat of bladder, 213, 215
large intestine, 105
liver, 129
small intestine, 86
spleen, 296
stomach, 76
Serres, glands of, 42
Sheath, dentinal, 33

epithelial, of dental germ, 47
Sheep, bronchi of, 178

innervation of trachea of, 167
lacteals of, 90
spleen of, 298
Shore on structure of liver, 135
Sibson on muscle of cervical pleura, 173
Sick on pleurae. 171

Sigmoid (C, a form of the letter alyixa, sigma j
tlSos, shape) colon, 103 113

INDEX AND GLOSSARY TO VOLUME III.. PART IV

341

Sigmoid flexure, 103, 113, 115

meso-colon, 69, 113, 321
Sinus (hollow) of kidney, 192

pocularis {poculum, cup), 244, 249

prostatic, 244

pyriformis, 61

of urethra, 246
Sinuses of galactophorous ducts, 288

glosso-epiglottic, 5

of larynx, 154, 156
Sobotta on corpora lutea, 281
Soemmering on thyro-arytenoid muscle, 162
Soft palate, 13, 57
Solitary glands, 93. 94
Space, mediastinal, 169

post-nasal, 57

uro-genitai, 253, 256
Spaces, interglobular, 34, 44
Spear of spermatozoon, 226
Special dental germs, 40, 41, 43, 49, 50
Spermatic cord, 218

blood-vessels of, 220
coverings of, 219

fascia, 219

granules, 230

plexus, venous, 221
Spermatids, 227, 228

Spermatoblasts {a-irepfxa, semen : P^acTrduw,
grow), 227, 228

chromosomes of, 228
Spermatocysts, 227
Spermatogenic cells, 227
Spermatogonia {vitepfta ; yiyvonai, be bom),

226
Spermatozoa (Cv"") animal), 225, 228

development of, 228

literature of, 250

structure of, 225
Sphincter {ff<piyyct>, bind) ani, internal, 117

of pylorus, 76, 84
uterine orifices, 265

vaginae, 259

vesica, 213
Spigelius, lobe of, 121, 122
Spiral tubules of kidney, 197, 198
Spleen (o-wX^j'), 293, 322, 323

accessory, 296

bloodvessels of, 299

cells, 299, 300

of infant, 296

literature of, 301

hTnphatics of, 300

nerves of, 301

structure of, 296
Splenculi, 296
Splenic flexuie, 112, 113, 322

pulp, 296, 298, 300
Spongy portion of urethra, 243, 246
Spot, germinal, 280
Stahel on trachea, 163
Steiner on epithelium of vaa deferens, 233
Stensen, canals of, 13

duct of, 16
Stigma (iTTlyfia, puncture), 278
Stirling on pulmonary nerves, 187
Stomach (<n6yua.xoi, gullet), I, 71, 322, 323

bloodvessels of, 82

dimensions of, 75

f lands of, 78
iterature of, 85
lymphatics of. 83
mucous membrane of, 77

Stomach — contiuued,
nerves of, 84
structure of, 76
variations in position of 7 1
of, with age, 75
Straight tubules, 230
Strand, connecting, of dental erms, 41

labio-deutal, 39
Streckeisen on thyroid, 312
Striated membrane, 279
Stroma ((rrpufjia, bed) of kidney, 204
of mammary gland, 286
of ovary, 273, 274

cortical layer of, 275
Struthers on ileo-cnecal valve, 1 1 1
Stuart, A., on aperture of larjmx, 154
epiglottis in swallowing, 162
Sub-caecal fossa, iii
Sublingual gland, 15, 17

alveoli of, 19
ducts of, 4, 1 7
structure of, 17
vessels an<l nerves of, 17, 22
Sublobular hi'patie, veins, 130, 132
Submaxillary gland, 15, 16
alveoli of, 19
ducts of, 4, 16, 17, 22
structure of, 17
vessels and nerves of, 17, 22
Submucous coat of bladder, 213, 215
oesophagus, 66
large intestine, 105, 106
small intestine, 86
stomach, 76
Succession, teeth of, 49
Sulcus (furrow) alveolo-labial, i
alveolo-lingnal, 4
terminalis, 5
Summit of bladder, 208, 209
Superadded permanent teeth, 50
Supra-renal capsules, 293, 302
accessory, 305
bloodvessels of, 305
function of, 305
literature of, 305
lymphatics of, 305
nerves of, 305
structure of, 303
varieties of, 305
Suspensorj' ligament of clitoris, 255
liver, 125
ovary, 272
penis, 238
ligaments of diaphragm, 170
muscle of duodenum, 102
Sustentacular cells of seminiferous tubules, 22S
Sustentaculum lienis (support of spleen), 113

Tablk of eruption of milk-teetli, 49

permanent teeth, 51
Taguchi on vocal cords, 155
Tail of epididymis, 222

pancreas, 139, 140, 142
spermatozoon, 225, 226, 229, 230
Taste-buds, 6, 8, 157
Teeth, i, 24

alveoli of, 48
bicuspid, 24, 27, 30, 51
canine, 24, 27, 30, 49, 51

342

INDEX AND GLOSSARY TO VOLUME III., PART IV.

Teeth — continued.

conditiou of, at birth, 47, 51

cuspidate, 27

development of, 37, 49

hard tissues of, 31, 44, 45, 46

homologies of, 29

incisor, 24, 26, 30, 49, 51

larval epithelial, 38

literature of, 53

molar, 24, 28, 30, 40, 49. 50, 51

multicuspidate, 29

permanent, 24, 26, 29, 41, 49, 51

premolar, 24, 27

pulp of, 30, 40, 45

special characters of, 26

structure of, 30

of successiou, 49

superadded permanent, 50

temporary or milk, 24, 29, 30, 33, 37, 40,

49
wisdom, 28, 29, 51
Teichmann on lacteals, 90 ^

Temporary teeth, 24, 29, 30, 33, 37, 40

eruption of, 49
Terminal globule, 225
Testis (testicle), 218, 221

bloodvessels of, 223, 235
coverings of, 219
descent of, 220
ducts of, 218, 230
interstitial tissue of, 230
literature of, 250
lymphatics of, 230, 236
nerves of, 230, 236
structure of, 222
tubules of, 224, 226, 230
Testut on weight of tliyimis, 308
Thompson on prostate, 249
Throat, i
Thyro-aryteuoid ligaments, 152

muscle, 158, 161
Thyro-epiglottic ligament, 149
Thyro-epiglottidean muscle, 161
Thyro-glossal duct, 8
Thyro-hyoid ligaments, 151

membrane, 151
Thyroid body, 293, 311

accessory, 312, 313
bloodvessels of; 313
of foetus and infant, 313
ligaments of, 312
literature of, 315
lymphatics of, 313, 314
nerves of, 314
structure of, 312
varieties of, 312
Thyroid (dvpeos, shield) cartilage, 146, 147, 150

notch, 147
Thymus corpuscles, 308

Thymus [Ov/xos, the plant thymus, to the corymbs
of which, probably, the gland was
likened) gland, 293, 307
bloodvessels of, 309
follicles of, 308
literature of, 309
lymphatics of, 309
nerves of, 309
structure of, 308
Tip of tongue, 3
Tomes on epithelial sheath, 47
fibres of, 31, 44
process of, 45

Tongue, 3

bloodvessels of, 11

glands of, 9

literature of, 14

lymphatics of, 1 1

mucous membrane of, 4

muscular substance of, 9

nerves of, 1 1

septum of, II
Tonsillse or Tonsils, 59

bloodvessels of, 60

lingual, 5

literature of, 62

lymphatics of, 60

nerves of, 60

pharyngeal, 57, 62

structure of, 60
Tooth. See Teeth.

Trabeculse {trahs, beam) of corpoi'a cavernosa,
240

of spleen, 296
Trachea {dpr-r)pia Tpax^ra, rough artery, so nanied
from the irregularity of surface due to the
cartilages, compared with the smoothness
of a bloodvessel, dprripia Ae7a, smooth
artery), 146, 162

bloodvessels of, 167

cartilages of, 163, 165

of fcetus and infant, 163

lymphatics of, 167

mucous membrane of, 166

muscular fibres of, 166

nerves of, 167

structure of, 165
Transverse fissure, 124
Treves on infantile type of ceecum, loS
length o( mesentery, 103

small intestine, 103
Trigone (trigonus, three-cornered), 212,

213
Trigonum vesicffi, 212
Tube or Tubes, bronchial. See Bronchial

TUBES.

collecting, 197, 199

dentinal, 32, 44

Eustachian, 57

excretory uriniferous, 197, 200

Fallopian, 253, 264, 269

intercalary, 199

uriniferous, 192, 195, 197
Tuber (swelling) papillare, 122
Tubercle of epiglottis, 149, 154

of thyroid cartilage, inferior, 147
superior, 147
Tuberculum impar, 8
Tuberosity, omental, of liver, 122

of pancreas, 140
Tubules of kidney, convoluted, 197, igS, 199

irregular, 197, 198

junctional, 197, 199

looped, 197, 198

spiral, 197, 198

of testis, efferent, 230, 232
seminiferous, 224

epithelium of. 226

uriniferous, 192, 195, 197

epithelium of, 197

Tubuli recti (straight tubules), 230

uriniferi, 195
Tulpius, valve of, 1 10
Tunic, dartos, 219

inner muscular, of testis, 222

IXDEX AND GLOSSARY TO VOLUME III., PAllT IV.

343

Tunica albuginea {albugo, whiteness) testis. 222
ovarii, 274
propria, ot spleen, 296
vaginalis, 219, 220

testis, 220
vasculosa, 224
Turner, on furrows of liver, 128

on position of incisor teeth, 25
Tyson, glands of, 23S

Umbilical fissure. 121. 125
notch, 121
vein, 125
Urachus {ovpaxos\. 209

Ureters {ovpriTTipes, fr. ovpov, urine ; rripfo),
keep), 1S9, 193. 204
nerves of, 205
orifices of, 212
structure of, 205
varieties of, 204
vessels of, 205
Urethra [ovp-ndpa, fr. ovpov, uriiie\ 1S9
of female, 253, 258
ol male, 218, 243

bulbous portion <>f, 246
membranous portion of, 243, 246
mucous membrane of, 246
prostatic portion of, 212, 243
sinus of, 246
spong}' or penile portion of, 243,

246
vesical orifice of, 211, 212
Urinary blaiUler, 1S9, 206

meatus, external, 236, 258
organs, 189

literature of, 216
portion of urethra, 243
Uriniferous tubules, 192, 195

stnicture of, 197
Uro-genital space, 253, 256
portion of urethra, 243
Uteiine glands, 265, 267, 268
Utero-sacral ligament, 263
L^tero-vesical fold, 263

pouch, 211, 262, 263
Uterus (uter, leather bag or bottle), 253, 260,
321
bloodvessels of, 268, 269
cavity of. 262, 268
after child-beaiing, 268
during gestation, 267
ligaments of, 263, 321
l}Tnphatics of, 265, 268, 269
during menstruation, 267
inasculinus, 244

mucous membrane of, 264, 265, 267, 268
nerves of, 268, 269
lifter partuiition, 268
peculiarities of, according to age, 268
position of, 262
structure of, 264
varieties of, 268
! of virgin, 260

Utricle, prostatic, 244, 249
Uvula (itfw, bunch of giapes) 13
vesicae, 212

Vagina (sheath), 253, 25S, 327
bloodvi-ssels ol, 260
columns of, 259

Vagina — contimu-d.

nerves of, 260

structure of, 259
Vallum (rampart), of circumvallate papillae, 6
Valve or Valves of Bauhin, no
of fossa navicularis, 247
ileo-colic or ileo-ca?cal, no
of Kerkring, 88
of rectum, 115
of Tulpius, 1 10
Valvulre conniventes (vahahc, folding doors ;

connivco, shut together), 88
Vas (vessel) aberrans, 233

adferens of glomerulus, 202

efferens of glomerulus, 202

deferens, 231, 232
structure of, 233
Vasa efterentiii of testis, 230, 232
Veins of bladder, 215

of bronchi, 167

of bronchial tubes, 186

of corpus spongiosum, 242

of gall-bladder, 127

hepatic, 127, 132

interlobular portal, 130
of kidney, 202

intralobular or central hejiatic, 130, 131, 132

of large intestine, loS

of larynx, 158

of lungs, i8t>

of mammary gland, 290

of cesophagus, 66

of ovary, 282

of pancreas, 145

of parotid glantl, 16, 22

of penis, 239, 240

portal, 126, 130

of prostate, 250

of rectum, 117

of scrotiim and spermatic cord, 221

of seminal vesicles, 235

of small intestine, 90, 98

of spleen, 299

of stomach, 83

of sublingual gland, 17, 22

sublobular hepatic, 130, 132

of submaxillary gland, 17, 22

of suprarenal capsules, 305

of testis, 236

of thymus, 309

of thyroid, 314

of tongue, II

of tonsil, 60

of trachea, 167

of ureter, 205

of urethra of female, 258

of uterus, 269

of vagina, 260

of vulva, 257
Veith on glands of vagina, 260
Velum (sail or curtain) ])endulum ])alati, 13
Vena cava, fossa or fissure of, 125
Verne interlobulares of kidney, 202
recta-, 203
stellata-, 202
Venous arches of kidney, 201
Ventricles of larynx, 152, 154, 156
A'ermiform (vermis, worm ; Jurina, sliape) ap-
pendix, 103, 106, 108, 109, III, 321
of lower animals, no
Verson on connection of <luodcniini anil jmti-
creas, 102

344

INDEX AND GLOSSARY TO VOLUME TIL, PAET IV.

Verunioutauum {veru, spear ; inontanus, moun-
tain), 244
Vesica urinaria (urinary bladder), 206
Vesical orifice of urethra, 211, 212

sacculus, 213
Vesicle, germinal, 280
Vesicles, seminal, 234

of thyroid body, 313
Vesicula prostatica, 244

Vessels. See Arteries, Veins, LvMrHATics.
Vestibule of larynx, 152
mouth, I
vulva, 256
Villi {villus, tuft of haij-), 87, 89, ill
Viscera, abdominal, 68

ligaments of, 69
Visceral clefts, 57, 60, 61
Yitelline membiaue, 280
Vitellus (yolk), 279
Vocal cords, false, 152, 154

true, 146, 152, 154, 15s, 157

process, 149, 152
Voice, organs of, 146

literature of, 187
Vulva {vulva, womb), 253

bloodvessels of, 257

lymphatics of, 257

mucous membrane of, 256

nerves of, 257
Vulval cleft, 253, 256

mammse, 291

Waldeyer on Graafian follicles. 277
on position of ovary, 272
on thymus, 309

WeU on basal layer of dental pulp, 3 1

Wharton's duct, 16, 17

Whiting on ellipsoids, 300

Williams on formation of enamel, 46
on ostium abdomiuale, 270

Winslow, foramen of, 323

Wirsung, canal of, 141

Wisdom-teeth, 28, 29, 51

Womb, 260. See also Uterus.

Wrisberg, cartilages of, 149

Wylie on vocal cords, 154

Yolk, 279
Yolk-granules, 279

Zahnleistb (dental lamina), 39
Zawarj'kin on lymphatics of kidney, 203
Zeissl on pelvic splanchnics, 215
Zimmermann and Hamburger on pancreas, 142
.Zona fasciculata, 304

glomerulosa, 304

pellucida, 278

radiata, 279

reticularis, 304
Zone, boundary, 197

cortical, of testis, 224
Zuckerkandl on dental cusps, 29

on pulmonary veins, 1S6

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